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PubMed1998

Preponderance of slightly deleterious polymorphism in mitochondrial DNA: nonsynonymous/synonymous rate ratio is much higher within species than between species.

We estimated synonymous (dN) and nonsynonymous (dS) substitution rates for protein-coding genes of the mitochondrial genome from two individuals each of the species human, chimpanzee, and gorilla. The genes were analyzed both separately and in a combined data set. Pairwise sequence comparisons suggest that the dN/dS rate ratios are about 5-10 times higher in within-species comparisons than in between-species comparisons. This result is confirmed by a more rigorous likelihood ratio test, which rejected the null hypothesis that the dN/dS rate ratios are identical within and between species. The likelihood models account for the genetic code structure, transition/transversion rate ratio, and codon usage bias and are expected to produce more reliable results than the commonly used contingency test. Separate analyses of different genes show that the dN/dS rate ratios are higher within species than between species for all 13 mitochondrial genes, with the difference being statistically significant for all except three small or slowly evolving genes. Furthermore, in conserved genes, nonsynonymous rates within species tend to be higher than the between-species rates by a greater proportion than in fast-changing genes. Our findings confirm and extend earlier results obtained from smaller data sets and suggest the operation of slightly deleterious mutations throughout the mitochondrial genome in the hominoids. Implications of the results for evolutionary studies and, in particular, for studies of the origin of modern humans, are discussed.

Adenosine Triphosphatases↗

PubMed2003

A recent polyploidy superimposed on older large-scale duplications in the Arabidopsis genome.

The Arabidopsis genome contains numerous large duplicated chromosomal segments, but the different approaches used in previous analyses led to different interpretations regarding the number and timing of ancestral large-scale duplication events. Here, using more appropriate methodology and a more recent version of the genome sequence annotation, we investigate the scale and timing of segmental duplications in Arabidopsis. We used protein sequence similarity searches to detect duplicated blocks in the genome, used the level of synonymous substitution between duplicated genes to estimate the relative ages of the blocks containing them, and analyzed the degree of overlap between adjacent duplicated blocks. We conclude that the Arabidopsis lineage underwent at least two distinct episodes of duplication. One was a polyploidy that occurred much more recently than estimated previously, before the Arabidopsis/Brassica rapa split and probably during the early emergence of the crucifer family (24-40 Mya). An older set of duplicated blocks was formed after the monocot/dicot divergence, and the relatively low level of overlap among these blocks indicates that at least some of them are remnants of a larger duplication such as a polyploidy or aneuploidy.

Arabidopsis↗

PubMed1992

Toxicology and Carcinogenesis Studies of g-Butyrolactone (CAS No. 96-48-0) in F344/N Rats and B6C3F1 Mice (Gavage Studies).

g-Butyrolactone is an intermediate in the synthesis of polymers used as film formers in hair sprays, blood plasma extenders, and clarifying agents in beer and wine. Toxicology and carcinogenesis studies were conducted by administering g-butyrolactone (greater than 97% pure) in corn oil by gavage to groups of F344/N rats and B6C3F1 mice of each sex, 5 days per week for 16 days, 13 weeks, and 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, Drosophila melanogaster, and Chinese hamster ovary cells. 16-Day Studies: Groups of five rats of each sex received doses of 0, 75, 150, 300, 600, or 1,200 mg of g-butyrolactone per kg of body weight and groups of five mice of each sex received doses of 0, 87, 175, 350, 700, or 1,400 mg/kg. All male and female rats given 1,200 mg/kg and one male rat given 600 mg/kg died within 3 days. The mean body weight gain of female rats given 600 mg/kg was significantly lower than that of the controls. Mean body weight gains of the other female dose groups and all male dose groups were similar to those of the controls. All of the male and four female mice receiving 1,400 mg/kg died during the studies. Mean body weight gains of dosed mice were generally similar to those of the controls. Rats receiving 600 or 1,200 mg/kg and mice receiving 350 mg/kg or more became inactive or recumbent with irregular respiration following dosing. 13-Week Studies: Groups of 10 rats of each sex received doses of 0, 56, 112, 225, 450, or 900 mg of g-butyrolactone per kg of body weight and groups of 10 mice of each sex received doses of 0, 65, 131, 262, 525, or 1,050 mg/kg. One female and all male rats given 900 mg/kg died during the studies. The final mean body weight and mean body weight gain of male rats receiving 450 mg/kg were significantly lower than those of the controls; final mean body weights and body weight gains of all female rat dose groups were similar to those of the controls. There was an increased incidence of focal inflammation of the nasal mucosa in rats administered g-butyrolactone. Three male mice and one female receiving 1,050 mg/kg died from g-butyrolactone toxicity during the studies. The mean body weight gain and final mean body weight of high-dose male mice were lower than those of the controls; the mean body weight gains and final mean body weights of dosed female mice were similar to those of the controls. No lesions related to the administration of g-butyrolactone occurred in mice of either sex. 2-Year Studies: The doses administered to groups of 50 animals per sex were 0, 112, and 225 mg ofg-butyrolactone per kg of body weight for male rats; 0, 225, and 450 mg/kg for female rats; and 0, 262, and 525 mg/kg for male and female mice. Body Weight and Survival in the 2-Year Studies: The mean body weights of male rats administered g-butyrolactone were similar to those of the controls throughout the study. The mean body weight of high-dose females was lower than that of the controls after week 5 and was 10% to 20% lower than that of the controls throughout the second year. The survival of high-dose male rats was slightly higher than that of the controls (control, 24/50; low-dose, 27/50, high-dose, 32/50) due primarily to a lower incidence of mononuclear cell leukemia in the high-dose group (16/50, 15/50, 9/50). The survival of dosed females was similar to that of the controls (28/50, 27/50, 28/50). The mean body weights of dosed male mice were lower than those of the controls throughout the study, but the differences in mean body weights decreased when male mice were housed individually at week 67. The final mean body weights of dosed male mice were 6% lower than that of the controls. Mean body weights of dosed female mice were also lower than those of the controls throughout the study, and the final mean body weights were from 14% to 17% lower than that of the controls. The survival in high-dose male mice was significantly lower than that of the controls (35/50, 30/50, 12/50) due to bite wounds and fighting in high-dose males recovering from the sedative effects of g-becovering from the sedative effects of g-butyrolactone. The survival of female dosed mice was similar to that of the controls (38/50, 34/50, 38/50). Neoplasms and Nonneoplastic Lesions in the 2-Year Studies: No increased incidences of neoplasms or nonneoplastic lesions in male rats were related to the administration of g-butyrolactone for 2 years. In female rats, negative trends were observed in the incidences of cysts (42/50, 35/50, 23/50) and fibroadenomas of the mammary gland (22/50, 14/50, 6/50) and in cysts of the pituitary pars distalis (25/49, 13/37, 11/48). These decreases were considered to be related to g-butyrolactone administration. Increased incidences of proliferative lesions, primarily hyperplasia, of the adrenal medulla in low-dose male mice were associated with g-butyrolactone administration (pheochromocytoma, benign or malignant: 2/48, 6/50, 1/50; hyperplasia: 2/48, 9/50, 4/50). The incidence of hepatocellular neoplasms in both dose groups of male mice was lower than the incidence in the controls (hepatocellular adenoma or carcinoma: 24/50, 8/50, 9/50). Genetic Toxicology: g-Butyrolactone was not mutagenic, with or without exogenous metabolic activation (S9), in Salmonella typhimurium strains TA98, TA100, TA1535, and TA1537, nor did it induce sex-linked recessive lethal mutations in germ cells of male Drosophila melanogaster when administered in feed or by injection. Positive results were obtained, however, in cytogenetic tests with Chinese hamster ovary cells; g-butyrolactone induced sister chromatid exchanges and chromosomal aberrations in trials conducted in the presence of S9 activation. Conclusions: Under the conditions of these 2-year gavage studies, there was no evidence of carcinogenic activity of g-butyrolactone in male F344/N rats given 112 or 225 mg/kg or in female F344/N rats given 225 or 450 mg/kg in corn oil. There was equivocal evidence of carcinogenic activity of g-butyrolactone in male B6C3F1 mice based on marginally increased incidences of adrenal medulla pheochromocytomas and hyperplasia in the low-dose group. The sensitivity of the study in male mice to detect a carcinogenic effect was reduced by the low survival of the high-dose group associated with fighting. There was no evidence of carcinogenic activity of g-butyrolactone in female B6C3F1 mice given 262 or 525 mg/kg in corn oil. A decreased incidence of hepatocellular neoplasms in dosed male mice and decreased incidences of mammary gland fibroadenomas and cysts and pituitary cysts in female rats were associated with the administration of g-butyrolactone. Synonyms: Dihydro-2(3H)-furanone (8CI) (9CI), 1,2-butanolide, butyrolactone, 1,4-butanolide, 4-butyrolactone, 4-hydroxybutanoic acid lactone, g-hydroxybutyric acid cyclic ester, g-hydroxybutyric acid lactone, g-lactone 4-hydroxy-butanoic acid, butyric acid lactone, butyryl lactone, 4-hydroxybutyric acid lactone, tetrahydro-2-furanone, 4-butanolide, 4-deoxytetronic acid, g-hydroxybutyrolactone

Journal Article↗

PubMed1993

Domains within the mammalian ornithine decarboxylase messenger RNA have evolved independently and episodically.

Ornithine decarboxylase (ODC) is the first enzyme in the polyamine biosynthetic pathway. We have studied the evolutionary history of the mammalian ODC mRNA, focusing on the rate of accumulation of sequence divergence within specific subregions of the molecule. The phylogenetic relationships among the mRNAs from several mammalian species, including two mouse species, rat, hamster, and human, were determined based upon the numbers of synonymous substitutions in pairwise comparisons of mRNA coding regions. The separation times for the mRNAs were very similar to those for the corresponding species, suggesting that ODC is encoded by orthologous genes in the different species. Analysis of divergence patterns in four subregions, or domains, of the mRNA (the 5'-untranslated region, the coding region, and two domains of the 3'-untranslated region) showed that the domains have evolved in a noncoordinate fashion. Furthermore, evolution of each subregion has been episodic, with periods of both rapid and slow sequence divergence. We suggest that the episodic pattern of ODC mRNA evolution may indicate the existence of selection pressures that were exerted in a time- and domain-specific manner during mammalian speciation.

Amino Acid Sequence↗

PubMed2003

Silent DNA: speaking RNA language?

The sequence of silent DNA in the human genome (intergenic spacers, introns and synonymous codon positions of protein-coding genes) was found here to have the higher thermostability of corresponding RNA/RNA and RNA/DNA duplexes as compared with randomized sequence. This difference increased with elevation of GC content. The revealed effect was not due to correlation of RNA/RNA and RNA/DNA thermostabilities with thermostability of the DNA/DNA duplex, which, on the contrary, was lower than in the randomized sequence and lagged behind the elevation of GC content. The same picture was observed in the genomes of other warm-blooded vertebrates but not in the lower organisms. This finding suggests that RNA-RNA and RNA-DNA interactions could be involved in the putative function of silent DNA.

Animals↗

PubMed1997

NTP Toxicology and Carcinogenesis Studies of Butyl Benzyl Phthalate (CAS No. 85-68-7) in F344/N Rats (Feed Studies).

Butyl benzyl phthalate is a plasticizer added to polymers to give flexibility and softness. It is used extensively in polyvinyl chloride and in cellulose plastics, polyvinyl acetate, polysulfides, and polyurethane. Butyl benzyl phthalate was nominated as part of a class study of phthalates. Previous studies of butyl benzyl phthalate by the NTP (1982a) resulted in chemical-related mortality in male rats beginning at about 14 weeks of exposure and, thus, were inadequate for evaluating carcinogenicity in male rats. The companion studies revealed a marginal increase in leukemia in female rats and no evidence of carcinogenicity in B6C3F1 mice. Consequently, the present evaluations were conducted only in F344/N rats. Male and female F344/N rats were given butyl benzyl phthalate (at least 97% pure) in feed for 10 weeks, 26 weeks, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, L5178Y mouse lymphoma cells, cultured Chinese hamster ovary cells, mouse bone marrow cells, and Drosophila melanogaster. 10-WEEK MODIFIED MATING STUDY IN RATS: Groups of 15 male F344/N rats were given 0, 300, 2,800, or 25,000 ppm butyl benzyl phthalate (equivalent to average daily doses of approximately 20, 200, or 2,200 mg butyl benzyl phthalate/kg body weight) in feed for 10 weeks. All rats survived to the end of the study. The final mean body weight and body weight gain of the 25,000 ppm group were significantly less than those of the controls. Feed consumption by the 25,000 ppm group was less than that by the controls at the end of the study. A few minimal hematology changes occurred in the 25,000 ppm male rats. There was some evidence of a minimal anemia characterized by a decreased erythrocyte count and increases in mean cell hemoglobin and platelet count. The absolute and relative prostate gland weights of the 25,000 ppm males were significantly less than those of the controls. Degeneration of the seminiferous tubule germinal epithelium was observed in all males from the 25,000 ppm group. The absolute right cauda, right epididymis, and right testis weights of the 25,000 ppm males were significantly less than those of the controls. The epididymal spermatozoal concentrations in 2,800 and 25,000 ppm males were significantly less than that in the controls. Although 10 females mated to 25,000 ppm males were initially found to be sperm positive, none of these females were pregnant at necropsy. The fertility indices of males and females in the 25,000 ppm group were significantly lower than those of the controls. The maternal body weights of females mated to 300 and 2,800 ppm males were similar to those of females mated to control males. There were no significant differences in litter data between the controls and the 300 and 2,800 ppm groups. 26-WEEK STUDY IN RATS: Groups of 15 male F344/N rats were given 0, 300, 900, 2,800, 8,300, or 25,000 ppm butyl benzyl phthalate in feed for 26 weeks. Dietary levels of 300, 900, 2,800, and 8,300 ppm delivered average daily doses of approximately 30, 60, 180, and 550 mg butyl benzyl phthalate/kg body weight. The final mean body weight and body weight gain of the 25,000 ppm males were significantly less than those of the controls. Except for the 25,000 ppm males, feed consumption by all exposed groups was similar to that by the controls. An exposure-related macrocytic responsive anemia was present in the 25,000 ppm group at all time points. Additionally, minimal erythrocyte count decreases occurred sporadically in the 2,800 and 8,300 ppm groups at various time points. Reticulocyte counts were increased on days 60 and 90. Increases in mean cell hemoglobin and mean cell hemoglobin concentrations occurred in the 8,300 and 25,000 ppm rats. The absolute right cauda, right epididymis, and right testis weights and the sperm concentration of 25,000 ppm males were significantly less than those of the controls. The incidences of hypospermia and of atrophy of the seminiferous tubule in the testis and of hypospermia in the epididymis in 25,000 ppm males were significantly greater than those in the in the controls. Degenerative changes of the testis and epididymis in the 25,000 ppm males were qualitatively and quantitatively similar to those observed in males in the 10-week modified mating study. 2-YEAR STUDY IN RATS: Groups of 60 male F344/N rats were given 0, 3,000, 6,000, or 12,000 ppm butyl benzyl phthalate (equivalent to average daily doses of approximately 120, 240, or 500 mg butyl benzyl phthalate/kg body weight), and groups of 60 female F344/N rats were given 0, 6,000, 12,000, or 24,000 ppm butyl benzyl phthalate (equivalent to average daily doses of approximately 300, 600, or 1,200 mg/kg) in feed for 2 years. Survival, Body Weights, and Feed Consumption: Survival of all exposed groups of male and female rats was similar to that of the controls. Mean body weights of the 12,000 ppm males and 24,000 ppm females were less than those of the controls throughout most of the study. Feed consumption by the females exposed to 24,000 ppm was less than that by the controls at the beginning of the study, but was similar to that by the controls by week 6. Hematology and Hormone Assays: In general, hematology changes were sporadic and minor. At 6 months, a minimal decrease in erythrocyte count and an increase in mean cell hemoglobin, similar to that which occurred in the 26-week study, occurred in male rats in the 12,000 ppm group. In female rats, a decreased hematocrit value occurred at 15 months in the 24,000 ppm group. There was also a mild decrease in triiodothyronine concentrations in the 24,000 ppm females at 6 and 15 months and at the end of the study. Pathology Findings: of pancreatic acinar cell adenoma and adenoma or carcinoma (combined) in 12,000 ppm males were significantly greater than those in the controls. The incidences of adenoma and of adenoma or carcinoma (combined) in 12,000 ppm males exceeded the ranges of historical controls from NTP 2-year feed studies. One carcinoma was observed in one 12,000 ppm male, and two adenomas were observed in 24,000 ppm females. At 2 years, the incidence of focal hyperplasia of the pancreatic acinar cell in 12,000 ppm males was significantly greater than that in the controls. At 2 years, transitional epithelial papillomas in the urinary bladder were observed in one control female and in two 24,000 ppm females. The incidence of this neoplasm exceeded the range of historical controls from NTP 2-year feed studies. The incidence of transitional epithelial hyperplasia in 24,000 ppm females was significantly greater than that in the controls. The absolute right kidney weight of 12,000 ppm females and the relative right kidney weights of all exposed groups of males and of 24,000 ppm females were significantly greater than those of the controls at the 15-month interim evaluation. The severities of renal tubule pigmentation in 12,000 ppm males and in 24,000 ppm females were greater than those in the controls at 15 months and 2 years. At 2 years, the incidences of kidney mineralization in 6,000 and 24,000 ppm females were significantly less than that in the controls, and the severity was decreased in exposed females. The incidence of preputial gland adenoma or carcinoma (combined) in 12,000 ppm male rats was significantly less than in the controls, and the incidences occurred with a negative trend. GENETIC TOXICOLOGY: Results from in vitro mutagenicity tests with butyl benzyl phthalate were uniformly negative. No mutagenic response was obtained in any of several strains of Salmonella typhimurium treated with up to 11,550 mg/plate butyl benzyl phthalate, with or without S9 metabolic activation enzymes. Negative results were also obtained in in vitro studies of mammalian cell systems with and without S9. No induction of trifluorothymidine resistance in L5178Y mouse lymphoma cells or sister chromatid exchanges and chromosomal aberrations in cultured Chinese hamster ovary cells were observed. These assays also were conducted with and without S9. No significant increase in sex-linked recessive lethal mutations was observed in germ cells of male Drosophila melanogaster after administration of butyl benzyl phthalate either in feed or by injection. In contrast to the negative results obtained in vitro and in Drosophila, butyl benzyl phthalate gave positive responses in two in vivo studies with mice. Results of a mouse bone marrow sister chromatid exchange test were positive at sample times of 23 and 42 hours, but no confirmatory test was conducted. Chromosomal aberrations were induced in bone marrow cells of male mice sampled 17 hours after intraperitoneal injection of 5,000 mg/kg butyl benzyl phthalate. CONCLUSIONS: Under the conditions of this 2-year feed study, there was some evidence of carcinogenic activity of butyl benzyl phthalate in male F344/N rats based on the increased incidences of pancreatic acinar cell adenoma and of acinar cell adenoma or carcinoma (combined). There was equivocal evidence of carcinogenic activity of butyl benzyl phthalate in female 344/N rats based on the marginally increased incidences of pancreatic acinar cell adenoma and of transitional epithelial papilloma of the urinary bladder. Exposure of rats to butyl benzyl phthalate in feed for 2 years resulted in focal hyperplasia in the pancreas in male rats and in transitional epithelial hyperplasia in the urinary bladder of female rats. Synonyms: A13-14777; BBP; 1,2-benzenedicarboxylic acid butyl phenylmethyl ester (9CI); benzyl n-butyl phthalate; n-butyl benzyl phthalate; butyl phenylmethyl 1,2-benzenedicarboxylate; NCI-C54375; phthalic acid benzyl butyl ester (8CI) Trade names: Palatinol BB; Santicizer 160; Sicol 160; Unimoll BB

Journal Article↗

PubMed2004

Low frequency of deafness-associated GJB2 variants in Kenya and Sudan and novel GJB2 variants.

A large proportion of non-syndromic autosomal recessive deafness (NSARD) in many populations is caused by variants of the GJB2 gene. Here, the frequency of GJB2 variants was studied in 406 and 183 apparently unrelated children from Kenya and Sudan, respectively, with mostly severe to profound non-syndromic deafness. Nine (2.2 %) Kenyan and 12 (6.6 %) of the Sudanese children only were carriers of variants within the coding sequence of the GJB2 gene. Variants in the 5'-adjacent region were detected in further 115 individuals. A total of 10 novel variants was recognized, among them four variants in the adjacent 5'-region of the GJB2 coding exon 2 (g.3318-6T>A, g.3318-15C>T, g.3318-34C>T, g.3318-35T>G), a 6 base-pair deletion (g.3455_3460del [p.Asp46_Gln48delinsGlu]), a variant leading to a stop codon (g.3512C>A [p.Tyr65X]), synonymous variants (g.3395C>T [p.Thr26], g.3503C>T [p.Asn62], g.3627A>C [p.Arg104]), and one non-synonymous variant (g.3816C>A [p.Val167Met]). In addition, the previously described variants g.3352delG (commonly designated 30delG or 35 delG), g.3426G>A [p.Val37Ile], g.3697G>A [p.Arg127His], g.3774G>A [p.Val153Ile], and g.3795G>A [p.Gly160Ser] were identified. With the exception of g.3318-34C>T and g.3352delG, all variants occurred heterozygously. For most of the variants identified in the Kenyan and Sudanese study population, a causative association with NSARD appears to be unlikely. Compared to many other ethnic groups, deafness-associated variants of the coding region of GJB2 are rare in Sudan and Kenya, suggesting a role of other genetic, or epigenetic factors as a cause for deafness in these countries.

Age of Onset↗

PubMed1988

NTP Toxicology and Carcinogenesis Studies of Rotenone (CAS No. 83-79-4) in F344/N Rats and B6C3F1 Mice (Feed Studies).

Toxicology and carcinogenesis studies of rotenone (more than 98% pure), a pesticide, were conducted in B6C3F1 mice and F344/N rats for 14 days, 13 weeks, and 2 years. Results of the Fourteen-Day Studies: In the 14-day studies (dietary rotenone concentrations of 0-600 ppm in the first 14-day studies and 0-4,800 ppm in the second 14-day studies), rough hair coats and dose-related decreases in mean body weight gain were observed in rats. Rats fed diets containing rotenone at concentrations of 1,200 ppm or higher lost weight. No compound-related toxic effects were observed in mice. Results of the Thirteen-Week Studies: In the 13-week studies (concentrations of 0-1,200 ppm rotenone in feed for rats and 0-50,000 ppm for mice), compound-related effects included lower body weight gain in rats at 150 ppm or more; and bone marrow atrophy and inflammation and hyperplasia of the forestomach in male rats at 300 ppm or more and in female rats at 150 ppm or more. These findings were used to establish the dietary concentrations of rotenone for the 2-year studies. Experimental Design for the Two-Year Studies: Two-year studies of rotenone were conducted by administering diets containing 0, 38, or 75 ppm rotenone to groups of 50 F344/N rats of each sex for 103 weeks. Groups of 50 B6C3F1 mice of each sex were administered diets containing 0, 600, or 1,200 ppm rotenone on the same schedule. The estimated average amount of rotenone consumed per day was 1.7 mg/kg or 3.5 mg/kg for low dose or high dose rats and 115 mg/kg or 250 mg/kg for low dose and high dose mice. Survival and Mean Body Weight in the Two-Year Studies: Survival of control and dosed rats was similar (male: control, 22/50; low dose. 31/50; high dose, 30/50; female: control, 27/50; low dose, 32/50; high dose, 31/50). Mean body weights of dosed and control male rats were comparable. Mean body weights of high dose female rats were 5%-9% lower than those of the controls between weeks 58 and 88. Survival of high dose male mice was significantly greater than that of the controls (male: 29/50; 36/50; 47/50; female: 37/50; 42/50; 45/50). Final mean body weights of dosed mice were lower than those of the controls by 8%-13% for males and 17%-24% for females. Neoplastic Effects in the Two-Year Studies: Parathyroid gland adenomas were observed in 1/41 control, 0/44 low dose, and 4/44 high dose male rats. The historicalincidence of this uncommon tumor in untreated control male rats in NTP studies is 4/1,314 (0.3%). Because these tumors are rare and because the highest incidence ever seen in a control group is 1/50, the increase in these tumors may have been related to rotenone administration. The incidence of subcutaneous tissue fibromas, fibrosarcomas, sarcomas, myxosarcomas, or neurofibrosarcomas (combined) in low dose female rats was greater (P<0.05) than that in the controls (0/50; 5/50; 3/50). These tumors were combined because of their possible common histiogenic origin from fibroblasts or undifferentiated mesenchymal cells. The incidence of those tumors in the low dose females was greater than the historical rats at this laboratory (9/337, 3% +/- 1%) and throughout the Program (50/2,021, 2% +/- 2%). Because of the lack of a significant dose-related trend and because statistical significance was attained only by combining tumors of differing morphology, the subcutaneous tissue tumors in female rats were not considered to be chemically related. The incidences of these tumors in dosed male rats were not significantly different from that in the controls. Hepatocellular adenomas or carcinomas (combined) occurred in male mice with a negative (P<0.02) trend, and the incidence in the high dose group was lower than that in the controls (12/47; 12/49; 1/50). Because this low rate of combined liver tumors is unusual, this decrease may have been related to rotenone administration. Subcutaneous tissue fibromas, sarcomas, fibrosarcomas, or neurofibrosarcomas (combined) in male mice occurred with a significant (P<0.05) negative trend (8/49; 4/50; 2/50). The incidence in the high dose group was signignificant (P<0.05) negative trend (8/49; 4/50; 2/50). The incidence in the high dose group was significantly lower than that in the controls by the life table test (P=0.01). Genotoxicity: Rotenone was not mutagenic when tested according to a preincubational protocol with Salmonella typhimurium strains TA100, TA1535, TA1537, and TA98 with or without metabolic activation by rat or hamster liver S9. Rotenone induced forward mutations in the mouse L5178Y/TK± lymphoma assay without activation; it was not tested in the presence of S9. Results of tests with rotenone in Chinese hamster ovary cells were negative for induction of sister chromatid exchanges (SCEs) in the absence of exogenous metabolic activation (at concentrations at which the chemical was very toxic), equivocal for SCEs in the presence of rat liver S9 (due to a nonrepeatable positive response when tests were conducted up to toxic concentrations), and negative for chromosomal aberrationsin both the presence and absence of metabolic activation. Data Audit: An audit of the experimental data was conducted for the 2-year studies of rotenone. No data discrepancies were found that influenced the final interpretations. Conclusions: Under the conditions of these 2-year feed studies, there was equivocal evidence of carcinogenic activity of rotenone for male F344/N rats, as indicated by an increased incidence of parathyroid gland adenomas (uncommon tumors). There was no evidence of carcinogenic activity in female F344/N rats fed diets containing 38 or 75 ppm rotenone. There was no evidence of carcinogenic activity for male or female B6C3F1 mice fed diets containing 600 or 1,200 ppm rotenone for 2 years. The decreased incidence of liver neoplasms in male mice may have been related to the administration of rotenone. Synonym: 1,2,12,12a-tetrahydro-8,9-dimethoxy-2-1-methylethenyl)-[1]benzopyrano[3,4-b]furo2,3-h][1]benzopyran-6(6H)-one Trade Names of Formulations: Derrin; Derris; Tubatoxin; Nicouline; Prentox; Noxfish; Rotocide; Barbasco; Cube Root; Haiari; Dactinol

Journal Article↗

PubMed2006

Human cytomegalovirus (HCMV) UL139 open reading frame: Sequence variants are clustered into three major genotypes.

Human cytomegalovirus (HCMV) infects a number of organs and cell types, leading to the hypothesis that HCMV disease and tissue tropism may be related to specific sequence variability. This study examined the genomic variability of a new polymorphic locus in HCMV, UL139 open reading frame (ORF). Detailed analysis showed that a large number of nucleotide insertions and non-synonymous substitutions occurred in the UL139 ORF, particularly in the 5' half, using the Toledo strain as the reference sequence. The UL139 variants were not distributed randomly, but were clustered clearly into three major groups: G1 (G1a, G1b, and G1c), G2 (G2a, G2b), and G3. In this study, it was found that the predicted UL139 product shared sequence homology with human CD24, a signal transducer modulating B-cell activation responses, and the sequences in G1c contained a specific attachment site of prokaryotic membrane lipoprotein lipid. The precise definition of UL139 genotypes and its putative function would be helpful in understanding better HCMV.

Amino Acid Sequence↗

PubMed1993

Genetics of insulin action.

Insulin action is highly likely to be primarily genetically determined (given a permissive or facilitative environment, for example sufficient calorie availability), as shown by variations in ethnic distribution, evidence for familial transmission and genotypic responses to experimentally induced metabolic stresses. Further, it is likely that the genetic predisposition to insulin resistance is closely linked to (or perhaps synonymous with) the predisposition to develop overt NIDDM. Alternatively, in the development of diabetes, the genetic basis for insulin resistance may be necessary, but not sufficient, requiring a second major gene for beta-cell vulnerability (e.g. exhaustion, deterioration of function, amyloid deposition). The future examination of the genetics of insulin action depends in large measure on the method of assessment of insulin action that is selected and its consistent application to individuals, families and populations. The phenomenological approaches currently being used to describe and define insulin resistance could be identifying many different disorders, all leading to an apparent decrease or impairment of insulin action compared with that in 'normals'. Selection of any method for determining the presence of insulin resistance, together with selection of the threshold for 'present versus absent' is, at best, difficult. It is further complicated by the frequent association of insulin resistance with a wide range of disturbances, including hypertension, dyslipidaemia and glucose intolerance--the insulin resistance 'syndrome'. A number of possible loci and candidate genes controlling insulin action have been studied, and most have been ruled out as the probable underlying cause of the majority of cases of defective insulin action. Among those genes that are unlikely to be determinants of insulin resistance (except in a few rare cases of mutations) are those for insulin, the insulin receptor, glucose transporters and the genes for many specific enzymes. While these are unlikely to be responsible for insulin resistance, such potential genetic defects cannot be fully excluded using present methods. Direct gene sequencing of polymerase-chain-reaction amplified DNA may be the ultimate approach to identifying the critical defects underlying insulin resistance. Other candidate genes regulating insulin action are likely soon to come forth, such as those controlling the generation and function of the intracellular mediators of insulin action.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1991

Molecular evolution of hemagglutinin genes of H1N1 swine and human influenza A viruses.

The hemagglutinin (HA) genes of influenza type A (H1N1) viruses isolated from swine were cloned into plasmid vectors and their nucleotide sequences were determined. A phylogenetic tree for the HA genes of swine and human influenza viruses was constructed by the neighbor-joining method. It showed that the divergence between swine and human HA genes might have occurred around 1905. The estimated rates of synonymous (silent) substitutions for swine and human influenza viruses were almost the same. For both viruses, the rate of synonymous substitution was much higher than that of nonsynonymous (amino acid altering) substitution. It is the case even for only the antigenic sites of the HA. This feature is consistent with the neutral theory of molecular evolution. The rate of nonsynonymous substitution for human influenza viruses was three times the rate for swine influenza viruses. In particular, nonsynonymous substitutions at antigenic sites occurred less frequently in swine than in humans. The difference in the rate of nonsynonymous substitution between swine and human influenza viruses can be explained by the different degrees of functional constraint operating on the amino acid sequence of the HA in both hosts.

Amino Acid Sequence↗

PubMed2005

Variation in the pattern of synonymous and nonsynonymous difference between two fungal genomes.

The proportion of synonymous nucleotide differences per synonymous site (p(S)) and the proportion of nonsynonymous differences per nonsynonymous site (p(N)) were computed at 1,993,217 individual codons in 4,133 protein-coding genes between the two yeast species Saccharomyces cerevisiae and Saccharomyces paradoxus. When the modified Nei-Gojobori method was used, significantly more codons with p(N) > p(S) were observed than expected, based on random pairing of observed p(S) and p(N) values. However, this finding was most likely explained by the presence of a strong negative correlation between the number of synonymous differences and the number of nonsynonymous differences at codons with at least one difference. As a result of this correlation, codons with p(N) > p(S) were characterized not only by unusually high p(N) but also by unusually low p(S). On the other hand, the number of codons with p(N)>p(S) (where p(S) is the mean p(S) for all codons) was very similar to the random expectation, and the observed number of 30-codon windows with p(N) > p(S) was significantly lower than the random expectation. These results imply that the occurrence of a certain number of codons or codon windows with p(N) > p(S) is expected given the nature of nucleotide substitution and need not imply the action of positive Darwinian selection.

Codon↗

PubMed1988

NTP Toxicology and Carcinogenesis Studies of Trichloroethylene (CAS No. 79-01-6) in Four Strains of Rats (ACI, August, Marshall, Osborne-Mendel) (Gavage Studies).

Trichloroethylene is an industrial solvent used primarily for vapor degreasing and cold cleaning. It was selected for study because of its industrial use and for potential for human exposure. (An estimated 3.5 million workers are exposed to trichloroethylene.) In an earlier study trichloroethylene (stabilized with epichlorohydrin and 1,2-epoxybutane) administered by gavage caused hepatocellular carcinomas in male and female B6C3F1 mice. Trichloroethylene administration did not increase the incidence of tumors in male or female Osborne-Mendel rats. However, the survival of dosed rats was reduced, thereby compromising the sensitivity of the study to detect a carcinogenic effect. The studies described in this report were conducted to compare the sensitivities of four strains of rats (ACI, August, Marshall, and Osborne-Mendel) to diisopropylamine-stabilized trichloroethylene. The results of the present studies demonstrate that long-term administration of trichloroethylene produces nephrotoxicity in four strains of rats and that the susceptibilities of these strains to the nephrotoxic effects of the chemical are similar. Because of chemically induced toxicity, reduced survival, and incomplete documentation of the experimental data, the studies are considered inadequate for either comparing or assessing trichloroethylene-induced carcinogenesis in these strains of rats. Toxicology and carcinogenesis studies of trichloroethylene (more than 99% pure, stabilized with 8 ppm diisopropylamine) were conducted by administering the chemical in corn oil gavage at doses of 0, 500, or 1,000 mg/kg per day, 5 day per week, for 103 weeks to groups of 50 male and 50 female ACI, August, Marshall, and Osborne-Mendel rats. The doses were selected on the basis of results from 13-week gavage studies in which groups of 10 male and 10 female ACI, August, and Marshall rats received daily doses or trichloroethylene (male: 125-2,000 mg/kg; female: 63-1,000 mg/kg). Doses for Osborne-Mendel rats were selected to conform with doses used in an earlier carcinogenicity study in that strain (TR-2). In the 13-week studies, male ACI and August rats receiving 2,000 mg/kg trichloroethylene and male and female Marshall rats receiving 1,835 mg/kg had final mean body weights 12%-17% lower than those of the vehicle controls. All other dose groups had body weights comparable to those of the vehicle controls. Three male August rats dosed with 2,000 mg/kg died. Histopathologic evaluation of tissues revealed no lesions attributable to trichloroethylene administration in the 13-week studies. This absence of histopathologic findings did not accurately predict the nephrotoxic effects of long-term administration of trichloroethylene to rats. Body Weight and Survival in the Two-Year Studies: In the 2-year studies, all dosed groups exhibited some reduction in mean body weights relative to the vehicle controls. Survival relative to vehicle controls was significantly reduced in 7/16 dosed groups (see page 6 of the Technical Report). Also, the survival of high dose male Marshall rats was reduced by a large number of accidental deaths. Nephrotoxicity, reduced survival, and central nervous system toxicity (characterized by sedation, loss of consciousness, tremors, and convulsions) showed that the doses of trichloroethylene selected for the 2-year studies were too high. Renal Effects in the Two-Year Studies: Trichloroethylene caused tubular cell cytomegaly in 82%-100% of all dosed animals. In addition, trichloroethylene produced toxic nephropathy (which was distinguishable from age-related nephropathy) in 17%-80% of the dosed animals. Cytomegaly, karyomegaly, or toxic nephropathy was not found in untreated or vehicle control animals. Trichloroethylene administration was also associated with increased incidences of renal tubular cell adenomas and adenocarcinomas. The incidences of renal lesions are shown in the following table (see page 7 of Technical Report). Other Pathologic Effects in the Two-Year Studies: An increased incidence of interstitial cell tumors of the testis was observinterstitial cell tumors of the testis was observed in high dose male Marshall rats (untreated control, 16/46; vehicle control, 17/46; low dose, 21/48; high dose, 32/48; P=0.002). The incidences of pheochromocytomas of the adrenal gland were significantly reduced in male ACI, female August, female Marshall, and male and female Osborne-Mendel rats. Genetic Toxicology: Trichloroethylene did not cause mutations in Salmonella typhimurium strains TA98, TA100, TA1535, or TA1537 with or without metabolic activation. In Chinese hamster ovary cells, trichloroethylene did not induce chromosomal aberrations; the results for sister chromatid exchanges were considered positive. Trichloroethylene was mutagenic to mouse L5178Y lymphoma cells in the presence of rat liver S9. Data Audit: Audits of the experimental data for these 2-year studies of trichloroethylene were conducted by the National Toxicology Program (see Appendix Q of the Technical Report). The results of the audits revealed evidence that the doses of trichloroethylene were too high. In addition, there was insufficient documentation of animal breeding, clinical observations, environmental conditions, and analytical chemistry data. Also, individual animal identification was not always verifiable. Conclusions: Under the conditions of these 2-year gavage studies of trichloroethylene in male and female ACI, August, Marshall, and Osborne-Mendel rats, trichloroethylene administration caused renal tubular cell cytomegaly and toxic nephropathy in both sexes of the four strains. However, these are considered to be inadequate studies of carcinogenic activity because of chemically induced toxicity, reduced survival, and deficiencies in the conduct of the studies. Despite these limitations, tubular cell neoplasms of the kidney were observed in rats exposed to trichloroethylene and interstitial cell neoplasms of the testis were observed in Marshall rats exposed to trichloroethylene. Synonyms: acetylene trichloride; 1-chloro-2,2-dichloroethylene; 1,1-dichloro-2-chloroethylene; ethinyl trichloride; ethylene trichloride; 1,1,2-trichloroethylene; trichloroethene Trade names of formulations: Algylen; Anamenth; Benzinol; Blacosolv; Blancosolv; Cecolene; Chlorilen; Chlorylea; Chorylen; Circosolv; Crawhaspol; Densinfluat; Dow-Tri; Dukeron; Fleck-Flip; Flock Flip; Fluate; Gemalgene; Germalgene; Lanadin; Lethurin; Narcogen; Narkogen; Narkosoid; Nialk; Perma-A-Chlor; Perm-A-Clor; Petzinol; Philex; Threthylen; Threthylene; Trethylene; Tri; Triad; Trial; Triasol; Trichloran; Trichloren; Triclene; Tri-Clene; Trielene; Trielin; Triklone; Trilen; Trilene; Triline; Trimar; Triol; TRI-plus; TRI-plus M; Vestrol; Vitran; Westrosol Target Organs & Incidences from 2-year Studies

Journal Article↗

PubMed1992

NTP technical report on the toxicity studies of Castor Oil (CAS No. 8001-79-4) in F344/N Rats and B6C3F1 Mice (Dosed Feed Studies).

Castor oil is a natural oil derived from the seeds of the castor bean, Ricinus communis. It is comprised largely of triglycerides with a high ricinolin content. Toxicity studies with castor oil were performed by incorporating the material at concentrations as high as 10% in diets given to F344/N rats and B6C3F1 mice of both sexes for 13 weeks. Genetic toxicity studies also were performed and were negative for mutation induction in Salmonella typhimurium, for induction of sister chromatid exchanges or chromosomal aberrations in Chinese hamster ovary cells, and for induction of micronuclei in the peripheral blood erythrocytes of mice evaluated at the end of the 13-week studies. Exposure to castor oil at dietary concentrations as high as 10% in 13-week studies did not affect survival or body weight gains of rats or mice (10 per sex and dose). There were no biologically significant effects noted in hematologic analyses in rats. Mild increases in total bile acids and in serum alkaline phosphatase were noted at various times during the studies in rats receiving the higher dietary concentrations of castor oil. Liver weights were increased in male rats receiving the 10% dietary concentration and in male and female mice receiving diets containing 5% or 10% castor oil. However, there were no histopathologic lesions associated with these liver changes, nor were there any compound-related morphologic changes in any organ in rats or mice. No significant changes were noted in a screening for male reproductive endpoints, including sperm count and motility, and no changes were observed in the length of estrous cycles of rats or mice given diets containing castor oil. Thus, no significant adverse effects of castor oil administration were noted in these studies. Synonyms: Ricinus Oil, oil of Palma Christi, tangantangan oil, phorboyl, Neoloid.

Journal Article↗

PubMed1995

NTP Toxicology and Carcinogenesis Studies of Diethylphthalate (CAS No. 84-66-2) in F344/N Rats and B6C3F1 Mice (Dermal Studies) with Dermal Initiation/ Promotion Study of Diethylphthalate and Dimethylphthalate (CAS No. 131-11-3) in Male Swiss (CD-1(R)) Mice.

Diethylphthalate and dimethylphthalate are used as phthalate plasticizers, in an extensive array of products. The chronic dermal toxicity of diethylphthalate was evaluated in male and female F344/N rats and B6C3F1 mice in 2-year studies. In a series of special studies, the tumor initiation or promotion potential of diethylphthalate or dimethylphthalate was evaluated in male Swiss (CD-1(R)) mice by an initiation/promotion model of skin carcinogenesis. The genetic toxicity of diethylphthalate and dimethylphthalate in Salmonella typhimurium and cultured Chinese hamster ovary cells was also evaluated. 4-WEEK STUDY IN F344/N RATS: Groups of 10 male and 10 female rats were dermally administered diethylphthalate at volumes of 0, 37.5, 75, 150, or 300 &mgr;L (0, 46, 92, 184, or 369 &mgr;g) applied neat, 5 days per week for 4 weeks. All male and female rats survived to the end of the study. No evidence of dermatotoxicity was observed, with no adverse clinical signs observed and no effects on weight gain or feed consumption. Relative liver weights of 300 &mgr;L males and females and 150 &mgr;L females were greater than those of controls. Relative kidney weights of 150 and 300 &mgr;L males and 150 &mgr;L females were greater than those of controls. No other adverse effects were observed in this study. 4-WEEK STUDY IN B6C3F1 MICE: Groups of 10 male and 10 female mice were dermally administered diethylphthalate at volumes of 0, 12.5, 25, 50, or 100 &mgr;L (0, 15, 31, 62, or 123 &mgr;) applied neat, five days per week for 4 weeks. One control female died before the end of the study; all other mice survived. No evidence of dermatotoxicity or other adverse clinical signs were observed, and no clear adverse effects on weight gain or feed consumption were seen. Absolute and relative liver weights of 25 and 100 &mgr;L females were greater than those of the controls. Based on these 4-week study results, doses of 0, 35, and 100 &mgr;L diethylphthalate were recommended for the 2-year mouse studies. A chronic study in male and female B6C3F1 mice at 0, 35, and 100 &mgr;L (applied neat, once per day, 5 days per week) was started and subsequently stopped after 32 weeks when significant body weight reductions were noted in treated animals (males and females, 100 &mgr;L groups: 19% lower; males, 35 &mgr;L group: 12% lower; females, 35 &mgr;L group: 10% lower than controls). Based on these body weight reductions, doses of 0, 7.5, 15, and 30 &mgr;L in 100 &mgr;L acetone were recommended for the restart of the 2-year mouse study. 2-YEAR STUDY IN F344/N RATS: Based upon the results of the 4-week study, doses of 0, 100, or 300 &mgr;L diethylphthalate (0, 123, or 369 &mgr;) were chosen for the 2-year rat study. Groups of 60 male and 60 female rats received the doses applied neat 5 days per week for 103 weeks and up to 10 animals per group were evaluated after 15 months. Survival, Body Weights, and Clinical Findings: Survival of dosed rats during the first 15 months was similar to that of controls. However, 2-year survival was significantly reduced in all groups of male rats (survival probabilities, males: 0 &mgr;L, 8%; 100 &mgr;L, 12%; and 300 &mgr;L, 12%). The mean body weights of 300 &mgr;L males were slightly less than those of the controls throughout the study. No adverse clinical signs were observed, including no evidence of dermatotoxicity. Pathology Findings: No morphological evidence of dermal or systemic toxicity was observed in male or female rats. Skin neoplasms were not observed in female rats and were only rarely observed in male rats. A high incidence of anterior pituitary adenoma occurred in all groups of male and female rats. The incidence of anterior pituitary adenomas in the 0, 100, and 300 &mgr;L groups were: males, 39/44, 41/49, 41/49; females, 38/50, 33/49, 33/48. The incidence of this benign tumor in control males (84%) exceeded the historical control mean incidence [feed controls, (28.7%)] and range (12% to 60%). Anterior pituitary adenomas were considered a primary contributing factor in the increased mortality observed in all grtor in the increased mortality observed in all groups, regardless of treatment. A dose-related decreasing trend in the incidence of mammary gland fibroadenomas was observed in female rats (21/50, 12/48, 7/50). The incidence of mononuclear cell leukemia in male rats in this study was lower than the historical incidence and may be attributable to the shortened life span of male rats. Similarly, the incidence of interstitial cell tumors of the testes was markedly decreased in all groups of males (4/50, 3/50, 8/50), relative to historical control rates (90.1&percnt;; range 74&percnt;-98&percnt;). The incidence of fatty liver degeneration was notably lower in dosed rats than in controls (males: 26/50, 8/50, 4/51; females: 23/50, 11/50, 3/50). 2-YEAR STUDY IN B6C3F1 MICE: Groups of 60 male and 60 female mice received doses of 0, 7.5, 15, or 30 μL diethylphthalate (0, 9, 18, or 37 μ) in 100 μL acetone 5 days per week for 103 weeks with a 1 week recovery period, and up to 10 animals per group were evaluated after 15 months. Survival, Body Weights, and Clinical Findings: Two-year survival of dosed mice was similar to that of controls: 43/50, 41/48, 46/50, and 43/50 (males), and 41/50, 38/51, 37/49, and 36/49 (females). Mean body weights of dosed male and female mice were similar to those of the controls throughout the study. No adverse clinical signs were observed in mice, including no gross evidence of dermatotoxicity. Feed consumption by male and female mice was similar to or up to 13% greater than that by controls. Pathology Findings: No morphological evidence of dermal toxicity was observed in male or female mice. No skin neoplasms were observed in dosed male mice. In female mice receiving 30 μL, one squamous cell carcinoma and one basal cell carcinoma were seen at the site of application. An increased incidence of liver neoplasms was observed in dosed male and female mice. The incidence of hepatocellular adenoma or carcinoma (combined) in B6C3F1 mice in the 0, 7.5, 15, and 30 μL groups were: (males) 9/50, 14/50, 14/50, and 18/50; (females) 7/50, 16/51, 19/50, and 12/50. The incidence of adenoma or carcinoma (combined) was increased in 30 μL male mice and the incidences of adenoma and of adenoma or carcinoma (combined) were increased in 7.5 and 15 μL females. A positive dose-related trend in the incidence of adenoma or carcinoma (combined) was also observed in male mice. The incidence of basophilic hepatic foci was increased in 15 μL male mice (0/50, 1/50, 9/50, 3/50). The increased incidence of liver neoplasms in this study was considered equivocal because the incidence of hepatocellular neoplasms in control and dosed males was within the historical range and because there was no clear dose-response relationship in females. No other treatment-related findings were observed in this study. 1-YEAR INITIATION/PROMOTION STUDY IN MALE SWISS (CD-1®) MICE: Groups of 50 male mice were dosed dermally with diethylphthalate or dimethylphthalate to study their effect as initiators and promoters. Diethylphthalate and dimethylphthalate were tested as initiators with and without the known skin tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). Diethyl phthalate and dimethylphthalate were tested as promoters with and without the known skin tumor initiator 7,12-dimethylbenzanthrancene (DMBA). Comparative control groups used during the study of diethylphthalate and dimethylphthalate included: vehicle control (acetone/acetone); initiation/promotion control (DMBA/TPA); initiator control (DMBA/acetone); and promoter control (acetone/TPA). Based on the incidence of skin neoplasms diagnosed histologically and the multiplicity of skin neoplasms, there was no suggestion that either diethylphthalate or dimethylphthalate was able to initiate skin carcinogenesis when chronically promoted by TPA. Further, there was no evidence that either diethylphthalate or dimethylphthalate was able to promote skin carcinogenesis in skin previously initiated with DMBA. High incidences of both squamous cell papillomas and squamous cell carcinomas occurred among the initiation/promotion control animals initiated with DMBA and promoted with TPA. All TPA-dosed groups had significantly greater incidences of dermal acanthosis, ulceration, exudation, and hyperkeratosis than controls. GENETIC TOXICOLOGY: Neither diethylphthalate (10-10,000 μ/plate) nor dimethylphthalate (33-6,666 μ/plate) induced gene mutations in Salmonella typhimurium strains TA98, TA100, TA1535, or TA1537, with or without rat and hamster liver S9. In cultured Chinese hamster ovary cells, both diethylphthalate and dimethylphthalate induced sister chromatid exchanges in the presence of S9. Neither induced sister chromatid exchanges in the absence of S9. Neither chemical induced chromosomal aberrations, with or without S9, in cultured Chinese hamster ovary cells. CONCLUSIONS: Under the conditions of these 2-year dermal studies, there was no evidence of carcinogenic activity of diethylphthalate in male or female F344/N rats receiving 100 or 300 μL. The sensitivity of the male rat study was reduced due to low survival in all groups. There was equivocal evidence of carcinogenic activity of diethylphthalate in male and female B6C3F1 mice based on increased incidences of hepatocellular neoplasms, primarily adenomas. In an initiation/promotion model of skin carcinogenesis, there was no evidence of initiating activity of diethylphthalate or dimethylphthalate in male Swiss (CD-1®) mice. Further, there was no evidence of promotion activity of diethylphthalate or dimethylphthalate in male Swiss (CD-1®) mice. The promoting activity of TPA following DMBA initiation was confirmed in these studies. Minor dermal acanthosis was observed following dermal application of diethylphthalate in male and female F344/N rats dosed for 2 years and in male Swiss (CD-1®) mice dosed for 1 year. Synonyms: Diethylphthalate (CAS No. 84-66-2): 1,2-benzenedicarboxylic acid, diethyl ester; DEP; diethyl 1,2-benzenedicarboxylate; diethyl o-phthalate; diethyl phthalate; ethyl phthalate; o-benzenedicarboxylic acid diethyl ester; phthalic acid, diethyl ester; RCRA U088 Dimethylphthalate (CAS No. 131-11-3): 1,2-benzenedicarboxylic acid, dimethyl ester; dimethyl 1,2-benzenedicarboxylate; dimethyl benzene-o-dicarboxylate; dimethyl benzeneorthodicarboxylate; dimethyl o-phthalate; dimethyl phthalate; DMP; FIFRA 028002; methyl phthalate; go-dimethyl phthalate; phthalic acid, dimethyl ester; phthalic acid methyl ester; RCRA U102

Journal Article↗

PubMed2003

Inferring nonneutral evolution from human-chimp-mouse orthologous gene trios.

Even though human and chimpanzee gene sequences are nearly 99% identical, sequence comparisons can nevertheless be highly informative in identifying biologically important changes that have occurred since our ancestral lineages diverged. We analyzed alignments of 7645 chimpanzee gene sequences to their human and mouse orthologs. These three-species sequence alignments allowed us to identify genes undergoing natural selection along the human and chimp lineage by fitting models that include parameters specifying rates of synonymous and nonsynonymous nucleotide substitution. This evolutionary approach revealed an informative set of genes with significantly different patterns of substitution on the human lineage compared with the chimpanzee and mouse lineages. Partitions of genes into inferred biological classes identified accelerated evolution in several functional classes, including olfaction and nuclear transport. In addition to suggesting adaptive physiological differences between chimps and humans, human-accelerated genes are significantly more likely to underlie major known Mendelian disorders.

Active Transport, Cell Nucleus↗

PubMed1990

NTP Toxicology and Carcinogenesis Studies of Glycidol (CAS No. 556-52-5) In F344/N Rats and B6C3F1 Mice (Gavage Studies).

Glycidol is a viscous liquid that is used as a stabilizer in the manufacture of vinyl polymers, as an additive for oil and synthetic hydraulic fluids, and as a diluent in some epoxy resins. NTP Toxicology and Carcinogenesis studies were conducted by administering glycidol (94% pure, containing 1.2% 3-methoxy-1,2-propanediol, 0.4% 3-chloro-1,2-propanediol, 2.8% diglycidyl ether, and 1.1% 2,6-dimethanol-1,4-dioxane) in water by gavage to groups of F344/N rats and B6C3F1 mice of each sex for 16 days, 13 weeks, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, Chinese hamster ovary (CHO) cells, Drosophila melanogaster, and the bone marrow of male B6C3F1 mice. Sixteen-Day Studies: Glycidol doses for groups of five rats or five mice of each sex ranged from 37.5 to 600 mg/kg; vehicle controls received distilled water. All rats that received 600 mg/kg died between days 3 and 13. Edema and degeneration of the epididymal stroma, atrophy of the testis, and granulomatous inflammation of the epididymis occurred in males that received 300 mg/kg. All mice that received 600 mg/kg and two males and two females that received 300 mg/kg died by day 4 of the studies. Focal demyelination in the medulla and thalamus of the brain occurred in all female mice that received 300 mg/kg. Thirteen-Week Studies: Doses for groups of 10 rats ranged from 25 to 400 mg/kg, and doses for groups of 10 mice ranged from 19 to 300 mg/kg; vehicle controls received distilled water. All rats that received 400 mg/kg died by week 2; three males and one female that received 200 mg/kg died during weeks 11-12. Final mean body weights of male rats that received 50, 100, or 200 mg/kg were 96%-85% that of vehicle controls; final mean body weights of female rats receiving the same doses were 95%-89% that of vehicle controls. Sperm count and sperm motility were reduced in male rats that received 100 or 200 mg/kg. Necrosis of the cerebellum, demyelineation in the medulla of the brain, tubular degeneration and/or necrosis of the kidney, lymphoid necrosis of the thymus, and testicular atrophy and/or degeneration occurred in rats that received 400 mg/kg. All mice that received 300 mg/kg died by week 2; deaths of mice that received 150 mg/kg occurred during weeks 4-8 for males and weeks 1-5 for females. Mean body weights of chemically exposed mice surviving to the end of the studies were generally 90%-94% those of vehicle controls. Sperm count and sperm motility were reduced in dosed male mice. Compound-related histopathologic lesions included demyelination of the brain in males and females that received 150 or 300 mg/kg, testicular atrophy in males at all doses, and renal tubular cell degeneration in male mice that received 300 mg/kg. Based on reduced survival, reduced weight gain, and histopathologic lesions in the brain and kidney in rats that received 200 or 400 mg/kg and on reduced survival and histopathologic lesions of the brain in mice that received 150 or 300 mg/kg, doses selected for the 2-year studies of glycidol were 37.5 and 75 mg/kg for rats and 25 and 50 mg/kg for mice. Body Weights and Survival in the Two-Year Studies: Mean body weights of chemically exposed male rats generally ranged from 80% to 94% of those of vehicle controls, and mean body weights of chemically exposed female rats were from 90% to 97% those of vehicle controls. Mean body weights of chemically exposed male mice were similar to those of vehicle controls; mean body weights of chemically exposed female mice were 79%-95% of those of vehicle controls. Virtually all male and female rats that received glycidol died or were killed in a moribund condition as a result of the early induction of neoplastic disease (final survival--male: vehicle control, 16/50; low dose, 0/50; high dose, 0/50; female: 28/50; 4/50; 0/50). Survival of vehicle control male rats was lower than that usually observed; however, specific causes of deaths could not be determined. The survival of male mice and low dose female mice was similar to that of vehicle controls; survival of female mice that resurvival of male mice and low dose female mice was similar to that of vehicle controls; survival of female mice that received 50 mg/kg was lower than that of vehicle controls after week 101 (final survival--male: 33/50; 25/50; 27/50; female: 29/50; 27/50; 17/50). Nonneoplastic and Neoplastic Effects in the Two-Year Studies: Chemical-related nonneoplastic lesions in both rats and mice included hyperkeratosis and epithelial dysplasia of the forestomach. Fibrosis of the spleen was also present in rats of each sex, and cysts of the preputial gland and kidney were present in male mice. Exposure to glycidol induced dose-related increases in the incidences of neoplasms in numerous tissues in both rats and mice (see summary table on page 5 of the Technical Report). In male rats, mesotheliomas arising in the tunica vaginalis and frequently metastasizing to the peritoneum were considered the major cause of early death. Early deaths in female rats were associated with the presence of mammary gland neoplasms. Genetic Toxicology: Glycidol was mutagenic in a variety of in vitro and in vivo short-term tests. Mutagenic activity was observed in S. typhimurium strains TA97, TA98, TA100, TA1535, and TA1537 exposed to glycidol with and without exogenous metabolic activation. Glycidol was positive in the absence of exogenous metabolic activation in the mouse lymphoma assay for induction of trifluorothymidine resistance in L5178Y/TK cells; it was not tested with activation. In cytogenetic tests with CHO cells, glycidol induced both sister chromatid exchanges and chromosomal aberrations in the presence and absence of exogenous metabolic activation. Glycidol induced sex-linked recessive lethal mutations and reciprocal translocations in the germ cells of male D. melanogaster exposed by feeding. The incidence of micronucleated polychromatic erythrocytes was increased in the bone marrow of male B6C3F1 mice administered glycidol by intraperitoneal injection. Conclusions: Under the conditions of these 2-year gavage studies, there was clear evidence of carcinogenic activity of glycidol for male F344/N rats, based on increased incidences of mesotheliomas of the tunica vaginalis; fibroadenomas of the mammary gland; gliomas of the brain; and neoplasms of the forestomach, intestine, skin, Zymbal gland, and thyroid gland. There was clear evidence of carcinogenic activity for female F344/N rats, based on increased incidences of fibroadenomas and adenocarcinomas of the mammary gland; gliomas of the brain; neoplasms of the oral mucosa, forestomach, clitoral gland, and thyroid gland; and leukemia. There was clear evidence of carcinogenic activity for male B6C3F1 mice based on increased incidences of neoplasms of the harderian gland, forestomach, skin, liver, and lung. There was clear evidence of carcinogenic activity for female B6C3F1 mice, based on increased incidences of neoplasms of the harderian gland, mammary gland, uterus, subcutaneous tissue, and skin. Other neoplasms that may have been related to the administration of glycidol were fibrosarcomas of the glandular stomach in female rats and carcinomas of the urinary bladder and sarcomas of the epididymis in male mice. Synonym: 2,3-epoxy-1-propanol

Journal Article↗

PubMed1993

NTP Toxicology and Carcinogenesis Studies of Benzyl Acetate (CAS No. 140-11-4) in F344/N Rats and B6C3F1 Mice Feed Studies).

Benzyl acetate is used as a flavoring agent in foods, as a fragrance in soaps and perfumes, as a solvent for cellulose acetate and nitrate, and as a component of printing inks and varnish removers. The NTP previously studied the toxicology and carcinogenicity of this chemical in F344/N rats and B6C3F1 mice using the gavage route of administration and corn oil as a vehicle. Benzyl acetate increased the incidences of pancreatic acinar cell adenomas in male rats and the incidences of hepatocellular adenomas and forestomach neoplasms in male and female mice. Because of the confounding effect of corn oil on the incidences of pancreatic neoplasms and because of controversy over the use of the gavage route of administration, the NTP decided to restudy benzyl acetate using the dosed feed route of administration. In these repeat studies, male and female F344/N rats and B6C3F1 mice received benzyl acetate (at least 98% pure) in feed for 13 weeks and 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium nunnery, cultured Chinese hamster ovary cells, LS178Y mouse lymphoma cells, Drosophila melanogaster, and mouse bone marrow and peripheral blood cells. 13-WEEK STUDY IN RATS: Groups of 10 male and 10 female F344/N rats were fed diets containing 0, 3,130, 6,250,12,500, 25,000, or 50,000 ppm (0, 230, 460, 900,1,750, or 3,900 mg/kg body weight for males and 0, 240, 480, 930,1,870, or 4,500 mg/kg for females) benzyl acetate for 13 weeks. Nine male and nine female rats receiving 50,000 ppm benzyl acetate died or were killed moribund between weeks 2 and 8 of the study. The mean body weight gain and the final mean body weight of 25,000 ppm males were significantly lower (P</=0.01) than those of the control group. Feed consumption by exposed rats, except the 25,000 and S0,000 ppm males and 50,000 ppm females, was similar to that by the controls. The reduced feed consumption by 25,000 and 50,000 ppm males and 50,000 ppm females may have been due to toxicity or decreased palatability. Tremors and ataxia occurred only in the 50,000 ppm rats. These findings were first observed on day 15 in nine males and six females and continued until the end of the study. Cholesterol levels in 12,500 and 25,000 ppm females and triglyceride levels in 25,000 ppm females were lower than those in the controls. Chemical-related lesions occurred in the brain, kidney, tongue, and skeletal muscles of the thigh. Necrosis of the brain involving the cerebellum and/or hippocampus, degeneration and regeneration of the renal tubule epithelium, and degeneration and sarcolemma nuclear hyperplasia of the tongue and skeletal muscles occurred in most male and female 50,000 ppm rats. This effect was observed in the 1,000 mg/kg group in the previous gavage study (NTP, 1986). 13-WEEK STUDY IN MICE: Groups of 10 male and 10 female B6C3F1 mice were fed diets containing 0, 3, 130, 6,250, 12,500, 25,000, or 50,000 ppm (0, 425, 1,000, 2,000, 3,700, or 7,900 mg/kg body weight for males and 0, 650, 1,280, 2,980, 4,300, or 9,400 mg/kg for females) benzyl acetate. One 50,000 ppm male mouse died and one 50,000 ppm female mouse was killed moribund before the end of the study. Mean body weight gains and final mean body weights of all exposed male and female mice were significantly lower than those of the controls and the mean body weight gains decreased with increased exposure level. Feed consumption by 3,130 ppm males and all exposed females was lower than that by the controls. Tremors occurred only in females and were first observed on day 16 in three females receiving 50,000 ppm, day 94 in one female receiving 25,000 ppm, and day 93 in one female receiving 12,500 ppm. The tremors continued until the end of the study. Necrosis of the brain involving the hippocampus occurred in four 50,000 ppm mice, one male and three females. Hepatocellular necrosis also occurred in the male with brain lesions. On reexamination of the previous 13-week gavage study (NTP, 1986), a similar lesion was seen in the brain of one 1,000 mg/kg female mouse; none were seen in 1,000 mg/kg male mi male mice. The lesion was less severe than that described in the present dosed feed study. The highest dose used in the gavage study was 1,000 mg/kg compared to an estimated high dose of 7,200 mg/kg for the feed study. 2-YEAR STUDY IN RATS: The doses selected for the 2-year feed study of benzyl acetate in F344/N rats were based on lower survival, mean body weights, and feed consumption, and on increased incidences of histopathologic brain lesions in 50,000 ppm male and female rats in the 13-week study. Groups of 60 male and 60 female F344/N rats were fed diets containing 0, 3,000, 6,000, or 12,000 ppm benzyl acetate for 2 years. Survival, Body Weights, Feed and Compound Consumption, and Clinical Pathology: Survival of exposed rats was similar to that of the controls. The mean body weights of the 12,000 ppm males and exposed females were approximately 5&percnt; lower than those of the controls throughout most of the study. The feed consumption by 12,000 ppm males was slightly lower than that by the controls. Dietary levels of 3,000, 6,000, and 12,000 ppm benzyl acetate were estimated to result in average daily consumption levels of 130, 260, and 510 mg/kg body weight (males) and 145, 290, and 575 mg/kg (females). No biologically significant changes in hematology or clinical chemistry parameters were found that could be attributed to benzyl acetate administration. Pathology Findings: No compound-related increased incidences of neoplasms or nonneoplastic lesions occurred in male or female F344/N rats receiving benzyl acetate for as long as 2 years. 2-YEAR STUDY IN MICE: The doses selected for the 2-year feed study of benzyl acetate in B6C3F1 mice were based primarily on lower body weight gains and lower final mean body weights of exposed mice in the 13-week study. Groups of 60 male and 60 female B6C3F1 mice were fed diets containing 0, 330, 1,000, or 3,000 ppm benzyl acetate for 2 years. Survival, Body Weights, Feed and Compound Consumption, and Clinical Pathology: Survival of all exposed mice, except the 3,000 ppm females, was similar to that of the control groups. Survival of 3,000 ppm females was significantly higher than that of the control group. Throughout the 2-year study, the mean body weights of 1,000 and 3,000 ppm males and females were 2&percnt; to 14&percnt; lower than those of the control groups. Dietary levels of 330, 1,000, and 3,000 ppm benzyl acetate were estimated to result in average daily consumption levels of 35, 110, and 345 mg/kg (males) and 40, 130, and 375 mg/kg (females). No biologically significant changes in hematology or clinical chemistry parameters were observed in mice receiving 330,1,000, or 3,000 ppm benzyl acetate. Pathology Findings: No increase in neoplasm incidence in mice could be attributed to benzyl acetate administration in feed. This contrasts with the previous finding that administration of benzyl acetate in corn oil by gavage once daily 5 days a week for as long as 2 years was carcinogenic to mice, causing increased incidences of hepatocellular neoplasms and forestomach neoplasms. The contrast in results between the two studies may be due to differences in the dose levels used (highest dose: gavage, 1,000 mg/kg a day; feed, 360 mg/kg a day). Dose-related increased incidences or severities of nonneoplastic nasal lesions occurred in the most posterior portions of the nasal cavity in all exposed groups. The lesions occurred in the majority of the exposed mice and consisted of atrophy and degeneration, primarily of the olfactory epithelium, cystic hyperplasia of the nasal submucosal glands, pigmentation of the mucosal epithelium, and exudate accumulation. GENETIC TOXICOLOGY: Benzyl acetate was not mutagenic in Salmonella typhimurium strains TA98, TA100, TA1535, or TA1537, with or without exogenous metabolic activation (S9). However, a positive response was observed for benzyl acetate, with and without S9, in the mouse lymphoma assay for induction of trifluorothymidine resistance in L5178Y cells. No significant increases in the frequencies of sister chromatid exchanges or chromosomal aberrations occurred in cultured Chinese hamster ovary cells treated with benzyl acetate in vitro, with or without S9, and no increases in either sister chromatid exchanges or chromosomal aberrations occurred in bone marrow cells of male mice treated in vivo by intraperitoneal injection. No increase in sex-linked recessive lethal germ cell mutations occurred in male Drosophila melanogaster administered benzyl acetate in feed or by injection. Tests of benzyl acetate for induction of micronucleated erythrocytes in bone marrow and peripheral blood of mice were also negative. CONCLUSIONS: Under the conditions of these 2-year feed studies, there was no evidence of carcinogenic activity of benzyl acetate in male or female F344/N rats receiving 3,000, 6,000, or 12,000 ppm; however, rats may have tolerated higher doses. There was no evidence of carcinogenic activity of benzyl acetate in male or female B6C3F1 mice receiving 330, 1,000, or 3,000 ppm. Nasal lesions associated with benzyl acetate exposure in male and female mice included nasal mucosa atrophy and degeneration (primarily of the olfactory epithelium), cystic hyperplasia of the nasal submucosal gland, and luminal exudate and pigmentation of the nasal mucosal epithelium. In previous 2-year gavage studies (TR-250), benzyl acetate increased the incidence of acinar cell adenomas of the exocrine pancreas in male F344/N rats; the gavage vehicle may have been a contributing factor. There was no evidence of carcinogenic activity in female F344/N rats receiving 250 or 500 mg/kg a day. There was some evidence of carcinogenic activity in male and female B6C3F1 mice, indicated by the increased incidences of hepatocellular adenomas and squamous cell neoplasms of the forestomach. Synonyms: acetic acid benzyl ester, acetic acid phenyl methyl ester, (acetoxymethyl)benzene, acetoxytoluene, benzyl ethanoate, phenylmethyl acetate

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