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Biomedical subjects

J K Haseman

Publications and source records attributed to J K Haseman.

At least 181 records · Page 10Linked to original sources
PubMedDate not supplied

Structure and control of a cell-cell adhesion complex associated with spermiation in rat seminiferous epithelium.

Spermiation, the release of late spermatids from the Sertoli cell, is disrupted by a number of toxicants. Control of the spermiation process, and the proteins that interact to adhere mature spermatids to Sertoli cells, is poorly understood. In these studies we used immunohistochemistry, coimmunoprecipitation/Western blotting, and mass spectrometry to refine an earlier model of sperm adhesion proposed by our laboratory. We have identified specific proteins linked together as part of a multiprotein complex, as well as several additional proteins (cortactin, ERK1/2, and 14-3-3 zeta) that may be functioning in both structural and signal transduction roles. The current and prior data suggest that protein phosphorylation is central to the control of spermiation. We also present and characterize an in vitro tubule culture system that allowed functional testing of the spermiation model by pharmacologic manipulation, and yielded data consistent with the importance of protein phosphorylation in spermiation.

Animals↗
PubMedDate not supplied

No evidence of carcinogenicity of D-mannitol and propyl gallate in F344 rats or B6C3F1 mice.

Chronic toxicity and carcinogenicity studies were conducted on D-mannitol and propyl gallate in F344 rats and B6C3F1 mice. Groups of 50 rats and 50 mice of each sex were maintained on diets containing either 0, 2.5 or 5.0% D-mannitol or 0, 0.6 or 1.2% propyl gallate for 103 wk. D-Mannitol had no effect on survival or mean body weight of rats and mice, and feed consumption was approximately the same in control and treated groups in each species. Gastric fundal gland dilation occurred at a higher incidence in treated female rats than in controls. A mild nephrosis characterized by focal vacuolization of the renal tubular epithelium was observed in an increased incidence in treated mice. No significant increase in tumour incidence was observed in any of the treated groups in comparison with the corresponding controls. Survival of rats and mice given propyl gallate was similar to that of the controls. Mean body weights were lower in chemically exposed animals, and more so for females. Male rats exposed to propyl gallate showed an increased incidence of hepatic cytoplasmic vacuolization and suppurative inflammation of the prostate gland. Tumours of the preputial gland, islet-cell tumours of the pancreas, and phaeochromocytoma of the adrenal gland occurred at a significantly (P less than 0.05) higher incidence in the low-dose male rats. Malignant lymphoma occurred with a positive trend in male mice (control 1/50, low dose 3/49 and high dose 8/50), and the incidence in the high-dose group was significantly (P less than 0.05) higher than in the control group. However, since the incidence in the control group was much less than the historical control rate (36/398 or 9%) in this laboratory, this apparent increase was not considered to be related to propyl gallate administration. Under the conditions of these studies, neither D-mannitol nor propyl gallate was considered to be carcinogenic to F344 rats or B6C3F1 mice of either sex.

Administration, Oral↗
PubMedDate not supplied

Carcinogenesis bioassay in rats and mice fed diets containing 2-biphenylamine hydrochloride.

Diets containing 0.1 or 0.3% 2-biphenylamine hydrochloride were fed to groups of 50 Fischer 344 rats and 50 B6C3F1 mice of each sex for 104-106 weeks. Mean body weights of high-dose rats of both sexes and of low-dose male rats were slightly lower than those of controls. No significant differences in survival times were observed between dosed and control groups. In dosed male rats there was a compound-related increased incidence of kidneys with inflammatory cells and interstitial fibrosis. No tumors in dosed rats were associated with the chemical. Mean body weights of high-dose male mice were slightly lower than those of controls, and survival of high-dose male mice was also significantly (P less than 0.01) reduced relative to controls. Hemangiosarcoma of the circulatory system occurred in female mice with a statistically significant (P less than 0.001) positive trend. The observed incidences of hemangiosarcoma were 0/49 (0%), 1/50 (2%), and 7/50 (14%) in controls, low- and high-dose groups, respectively. In individual group comparisons, the incidence in the high-dose group was significantly (P less than 0.01) higher than that in the controls. The hemangiosarcoma seen in female mice were quite rare with only 6/816 (0.7%) previously seen in controls at the same laboratory and no more than 3 in any group of 50. Hemangiosarcoma also occurred in male mice with a statistically significant positive trend (P = 0.04 by a life table test), with incidences of 0/50 (0%), 2/50 (4%), and 3/50 (6%), in control, low-dose and high-dose groups, respectively. The development of hemangiosarcoma in the high-dose male mice might have been curtailed by the significantly reduced survival time in this group.

Aminobiphenyl Compounds↗
PubMedDate not supplied

Lesions of the urinary tract produced in Fischer 344 rats and B6C3F1 mice after chronic administration of 11-aminoundecanoic acid.

11-Aminoundecanoic acid, the monomer of nylon 11, was toxic to the urinary tract of both male and female B6C3F1 mice and Fischer 344 rats, when administered in the diet at 7500 or 15 000 ppm for 103-104 weeks. Dose-related effects included a decrease in mean body weight gain and in survival for male rats and for mice of each sex; increased incidence of hyperplasia of the transitional epithelium of the kidney in rats of each sex; increased incidence of calcification of the kidney in the female rats; increased incidence of hyperplasia of the urinary bladder in male rats; and mineralization of the kidney in mice of each sex. Transitional cell carcinomas of the urinary bladder of the male rat occurred with increased frequency in the high-dose group (control, 0/48; low-dose, 0/48; high-dose, 7/49). Additional evidence for carcinogenicity in the male rat was seen in the liver, where an increased frequency of neoplastic nodules was found in the treated animals (controls, 1/50; low-dose, 9/50; high-dose, 8/50). Therefore, under the conditions of these studies, 11-aminoundecanoic acid was carcinogenic for male Fischer 344 rats, inducing transitional cell carcinomas in the urinary bladder and neoplastic nodules in the liver. The test chemical was not demonstrated to be carcinogenic for female Fischer 344 rats or for B6C3F1 mice of either sex.

Amino Acids↗
PubMedDate not supplied

A reexamination of false-positive rates for carcinogenesis studies.

False-positive rates in the National Cancer Institute/National Toxicology Program (NCI/NTP) two-year carcinogenesis bioassay are examined. Previous studies that have reported high (20-50%) false-positive rates for these bioassays are reviewed. The decision rules used in many of these earlier investigations are far different than the procedures actually employed by the NCI/NTP in the interpretation of bioassay data. Data from 25 recent NTP feeding studies are examined, and the statistical significance of observed tumor increases are compared with the final interpretations regarding the carcinogenic effects of the chemicals under study. Based on this examination, a more realistic decision procedure is formulated. It is shown that under the assumption of a statistical decision rule which appears to mimic more closely the scientific judgment process, the actual overall false-positive rate in NCI/NTP bioassays appears to be no greater than 7% to 8%.

Animals↗
PubMedDate not supplied

Patterns of tumor incidence in two-year cancer bioassay feeding studies in Fischer 344 rats.

Patterns of tumor incidence in 25 of the National Toxicology Program's (NTP's) two-year cancer bioassay feeding studies in Fischer 344 rats were investigated. It was found that the overall frequencies of statistically significant (P less than 0.01) increases and decreases in organ-specific tumor incidence in treated groups relative to controls were approximately the same. The decreases were due primarily to mammary gland fibroadenomas in females (which were clearly associated with decreased weight gain in the treated groups) and leukemia/lymphoma in both sexes (which were frequently associated with increased liver tumor incidences in the treated groups). A clear explanation for this latter association was not apparent. The increased tumor incidences in the treated groups relative to controls were due primarily to liver neoplastic nodules. Treated animals of either sex had slightly (but significantly) improved overall survival relative to controls. The intra- and inter-laboratory variability in control tumor incidence frequently exceeded what one would expect to find by chance alone. This investigation helps explain the decreased tumor incidences observed in many NTP feeding studies. It also indicates that attention should be directed toward the determination of underlying mechanisms responsible for the negative correlation between the incidences of liver tumors and leukemia/lymphoma.

Animals↗
PubMedDate not supplied

Reproductive endpoints in general toxicity studies: are they predictive?

The ability to use necropsy and in-life vaginal cytology data from 90-d general toxicity studies to predict the outcome of more definitive reproductive toxicity tests was evaluated using data from 18 compounds tested by the National Toxicology Program. Sperm motility and vaginal cytology evaluations (SMVCE) were performed at the end of 90-d toxicity studies. When these same compounds were tested in the definitive Reproductive Assessment by Continuous Breeding (RACB) design, 13 of the 18 compounds were classified the same way by both tests. The different conclusions for five compounds can be explained by differences in dose used or in endpoints evaluated. We conclude that reproductive-system necropsy data from general toxicity studies can provide a valuable preliminary indication of the likely reproductive toxicity of the compound under study.

Animals↗
PubMedDate not supplied

Unique renal tubule changes induced in rats and mice by the peroxisome proliferators 2,4-dichlorophenoxyacetic acid (2,4-D) and WY-14643.

Peroxisome proliferators are non-mutagenic carcinogens in the liver of rodents, acting both as initiators and promoters. The National Toxicology Program (NTP) conducted a study of several peroxisome proliferators (PPs), including Wyeth (WY)-14643 as a prototypical PP and 2,4-dichlorophenoxyacetic acid (2,4-D) as a weak PP, in Sprague-Dawley rats. B6C3F1 mice, and Syrian hamsters. In the kidney, an unusual change was observed in the outer stripe of the outer medulla, especially in rats treated with 2,4-D or WY-14643. This change was characterized by foci of tubules that were partially or completely lined by basophilic epithelial cells with decreased cytoplasm and high nuclear density. Changes typical of chronic nephropathy such as interstitial fibrosis or basement membrane thickening were not associated with these foci. Results of immunohistochemical staining for catalase and cytochrome P-450 4A in the kidney indicated increased staining intensity in renal tubular epithelial cells primarily in the region where the affected tubules were observed: however, the altered cells were negative for both immunohistochemical markers. Ultrastructurally, affected cells had long brush borders typical of the P3 tubule segment. The most distinguishing ultrastructural change was a decreased amount of electronlucent cytoplasm that contained few differentiated organelles and, in particular, a prominent reduced volume and number of mitochondria; changes in peroxisomes were not apparent. In addition to the lesion in rats, mice treated with the highest dose of 2,4-D, but not WY-14643, manifested similar renal tubular changes as seen by light microscopy. Neither chemical induced renal tubular lesions in hamsters. Hepatocellular changes characteristic of PPs were present in all 3 species treated with WY-14643, but not 2,4-D. These results indicate that the rat is the species most sensitive to the nephrotoxic effects of PPs and there is a site specificity to this toxicity related to areas of PP-related enzyme induction. Although 2,4-D is considered a weak PP for the liver, it was the most effective at inducing renal lesions, indicating that the toxic potency of various PPs will depend on the target organ.

2,4-Dichlorophenoxyacetic Acid↗
PubMedDate not supplied

A retrospective analysis of background lesions and tissue accountability for male accessory sex organs in Fischer-344 rats.

Because the paired lobes (ventral, dorsal, lateral, and anterior) of the rat prostate have not been consistently sampled in many carcinogenicity and toxicity studies, comparison among different investigations has been compromised. The lack of specific site identification for prostatic lesions further lessens the value of incidences reported. We present here the lobe-specific incidences and degree of severity of background prostatic, seminal vesicular, and ampullary glandular lesions in 1768 control Fischer-344 rats from 35 recent National Toxicology Program 2-year carcinogenicity and toxicity studies conducted in 4 laboratories. The dorsal and lateral lobes were combined and considered the dorsolateral lobe where inflammation, epithelial degeneration, mucinous cysts, and edema were observed. Inflammation in the dorsolateral lobes was significantly associated with pituitary gland adenoma whose prolactin was suggested to play an important role in pathogenesis of prostatic inflammation. Epithelial degeneration, epithelial hyperplasia, inflammation, edema, and adenoma were conspicuous in the ventral lobes. Inflammation and edema occurred in the anterior lobes (coagulating glands). Inflammation, dilatation, epithelial hyperplasia, edema, and adenoma were observed in the seminal vesicles. Inflammation was also present in the ampullary glands. We suggest an optimal embedment and trimming method in rat prostate and seminal vesicle to ensure adequate, consistent sampling.

Animals↗
PubMedDate not supplied

An alternative perspective: a critical evaluation of the Waddell threshold extrapolation model in chemical carcinogenesis.

In a recent Perspective article (Toxicologic Pathology 31: 260-262, 2003) Waddell asserts that he has developed a log linear extrapolation model that can demonstrate a threshold and resolve for once and for all the uncertainies associated with low dose cancer risk extrapolation. However, his method essentially forces, rather than demonstrates, a threshold, and has many serious flaws that result in significant under-estimation of low dose risk. It would be a serious mistake for the scientific community to adopt Waddell's log linear extrapolation model for chemical carcinogenesis risk assessment.

Animals↗
PubMedDate not supplied

Prediction of rodent carcinogenesis: an evaluation of prechronic liver lesions as forecasters of liver tumors in NTP carcinogenicity studies.

The National Toxicology Program (NTP) developed the chronic 2-year bioassay as a mechanism for predicting the carcinogenic potential of chemicals in humans. The cost and duration of these studies has limited their use to small numbers of selected chemicals. Many different short-term methods aimed at increasing predictive accuracy and the number of chemicals evaluated have been developed in attempts to successfully correlate their results with evidence of carcinogenicity (or lack of carcinogenicity) are assessed. Using NTP studies, the effectiveness of correlating prechronic liver lesions with liver cancer encompassing multiple studies using mice (83 compounds) and rats (87 compounds). These lesions include hepatocellular necrosis, hepatocellular hypertrophy, hepatocellular cytomegaly, bile duct hyperplasia, and hepatocellular degeneration, along with increased liver weight. Our results indicate that pooling 3 of these prechronic data points (hepatocellular necrosis, hepatocellular hypertrophy, and hepatocellular cytomegaly) can be very predictive of carcinogenicity in the 2-year study (p < 0.05). The inclusion of increased liver weight as an endpoint in the pool of data points increases the number of rodent liver carcinogens that are successfully predicted (p < 0.05), but also results in the prediction of increased numbers of noncarcinogenic chemicals as carcinogens. The use of multiple prechronic study endpoints provides supplementary information that enhances the predictivity of identifying chemicals with carcinogenic potential.

Administration, Oral↗
PubMedDate not supplied

Development and viability of offspring of male mice treated with chlorinated phenoxy acids and 2,3,7,8-tetrachlorodibenzo-p-dioxin.

Male C57BL/6 mice were given feed containing various concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) such that their diets contained daily doses of approximately 40 mg/kg 2,4,-D, 40 mg/kg 2,4,5-T, and 2.4 micrograms/kg TCDD (group II); 40 mg/kg 2,4-D, 40 mg/kg 2,4,5-T, and 0.16 microgram/kg TCDD (group III); or 20 mg/kg 2,4-D, 20 mg/kg 2,4,5-T, and 1.2 micrograms/kg TCDD (group IV). Controls (group I) were given a diet with only the corn oil vehicle added to the feed. At the conclusion of an 8-wk dosing period, treated males cohabited with untreated virgin C57BL/6 female mice. Females were randomly assigned either to undergo teratological examination at 18 d of gestation, when the fetuses were examined for external, visceral, and skeletal malformations, or to be segregated and allowed to deliver their pups. Live and dead offspring and birth weight were recorded and viability was monitored until postnatal d 21. In both cases, development and survival of offspring in the test groups, whose sire had been treated with the mixture of phenoxy acids and TCDD, were not significantly different from those in the control group, whose sire had received untreated feed.

2,4,5-Trichlorophenoxyacetic Acid↗
PubMedDate not supplied

Effects of antioxidants apocynin and the natural water-soluble antioxidant from spinach on cellular damage induced by lipopolysaccaride in the rat.

Oxidative damage plays a key role in septic shock induced by the endotoxin lipopolysaccaride (LPS) by enhancing the formation of reactive oxygen species such as superoxide anion radicals, peroxides, and their secondary product, malondialdehyde, especially in the liver. In this study, histopathologic changes in several organs were compared among groups of male Wistar rats that had been injected with LPS following prophylactic pretreatment with either of 2 antioxidants, a group that had been injected with LPS without pretreatment with antioxidants, an untreated control group, and groups that had been injected with either of the 2 antioxidants only. The antioxidants used were a water-soluble natural antioxidant from spinach (NAO) and the NADPH oxidase inhibitor apocynin. Hematoxylin-and-eosin-stained slides were prepared, and lesions were semiquantitatively scored. Exposure to LPS alone was associated with multifocal hepatocellular necrosis and acute inflammation, thymic and splenic lymphoid necrosis, ocular retinal hemorrhage and acute endophthalmitis, adrenal medullary vacuolation and necrosis and acute inflammation, and decreased adrenal cortical cytoplasmic vacuolation (consistent with depletion of steroidal hormone contents). Results indicated that pretreatment with both antioxidants for 8 days reduced, in some organs, the necrotic and inflammatory changes associated with the LPS challenge. These findings suggest a potential therapeutic application for these antioxidants in clinical sepsis.

Acetophenones↗
PubMedDate not supplied

The utility of multiple-section sampling in the histopathological evaluation of the kidney for carcinogenicity studies.

In a recent review of 379 carcinogenicity studies in rodents conducted under the auspices of the National Cancer Institute and, later, the National Toxicology Program (NTP), the kidneys were the third most frequent site for chemical-related neoplasia. While some potent carcinogens induced high incidences of renal neoplasms with shortened latency in Fischer-344 (F-344) rats or B6C3F1 mice, other usually nonmutagenic compounds produced marginally increased incidences of renal neoplasms that were difficult to interpret. As an aid to the interpretation of 16 recent studies, additional kidney sections from rats or mice were prepared and examined microscopically. The remaining pieces of formalin-fixed kidney were embedded and sectioned at intervals of 1 mm (rats) or 0.5 mm (mice) to produce an additional 6-8 (rats) or 4-6 (mice) H&E-stained sections per kidney per animal for microscopic examination. The average number of additional sections per animal was similar between dosed and control groups to avoid sampling bias. The supplemental evaluation of these additional kidney sections was clearly useful in determining potential renal carcinogenicity in male F-344 rats in these NTP studies. Of the 13 studies in male rats in which step-sections of kidney were evaluated, the supplemental data demonstrated conclusively an association between chemical administration and renal tubule hyperplasia, adenoma, or both in 9 studies. For 3 chemicals, the evidence of an association with renal proliferative lesions in male rats remained uncertain. In contrast, the supplemental evaluation of step-sections was less useful for female rats, male mice, and female mice, largely because such evaluations generally revealed few if any additional neoplasms. For these sex-species groups, there were only two instances, both involving male mice, in which the additional data confirmed an association with kidney neoplasia.

Adenoma↗
PubMedDate not supplied

Toxicology and carcinogenesis studies of ozone and ozone 4-(N-nitrosomethylamino)-1-(3-pyridyl)-1-butanone in Fischer-344/N rats.

The purpose of this study was to evaluate the toxicity and potential carcinogenicity or cocarcinogenicity of ozone exposure in rats. Fischer-344/N (F-344/N) rats were exposed 6 hr/day, 5 days/wk, to 0, 0.12, 0.5, or 1.0 ppm ozone by inhalation for 2-yr and lifetime exposures. The cocarcinogenicity study included subcutaneous administration of 0, 0.1, or 1.0 mg/kg body weight of 4-(N-nitrosomethylamino)-1-(3-pyridyl)-1-butanone (NNK) and inhalation of 0 or 0.5 ppm ozone to male rats. NNK was administered by subcutaneous injections 3 times per week for the first 20 wk with ozone inhalation exposure. The ozone inhalation exposure was for 2 yr (104 wk), including the first 20 wk of NNK treatment and continuing for 84 wk after the last NNK injection. Ozone exposure caused a concentration-related increase in inflammation of the centriacinar region of the lung. There was also increased fibrosis and an extension of the bronchiolar epithelium in these centriacinar regions to involve the proximal alveoli. There was no increased incidence of neoplasms at any site, including the lung, that was associated with ozone exposure. Rats administered 1.0 mg/kg body weight NNK alone had an increased incidence of bronchiolar/alveolar neoplasms, but this effect was not enhanced by ozone exposure. Ozone exposure for 2 yr and lifetime was associated with site-specific toxic alterations in the nasal passage and lung similar to those previously described for short-term exposures. While there was significant attenuation of the pulmonary lesions as compared to short-term exposures, lesions persisted in the lifetime study and there was evidence of a mild progressive fibrosis. We conclude that under the conditions of these studies: (a) ozone exposure is not carcinogenic to either male or female F-344/N rats, (b) ozone does not enhance the incidence of pulmonary neoplasms in F-344/N rats exposed to a known pulmonary carcinogen (NNK), and (c) mild site-specific toxic lesions characteristic of ozone exposure persist in the nasal passage and lung throughout the lifetime of the rat with continued ozone exposure.

Administration, Inhalation↗