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C A van der Heijden

Publications and source records attributed to C A van der Heijden.

At least 19 recordsLinked to original sources
PubMed1991

Chronic inhalation toxicity and carcinogenicity study of methyl bromide in Wistar rats.

The toxicity and carcinogenicity of methyl bromide (MeBr) were studied in male and female Wistar rats exposed by inhalation to 0, 3, 30 or 90 ppm MeBr 6hr/day, 5 days/wk for 29 months. After 13, 52 and 104 wk ten rats/sex/group were killed to provide interim information. Body weights, clinical signs, haematology, biochemistry and gross and microscopic pathology were studied. Mortality was increased by wk 114 in the 90-ppm group. Body weights in males and females of the 90-ppm group were lower than those of the controls throughout the study. Increased incidences of degenerative and hyperplastic changes of the nasal olfactory epithelium were observed in all exposed groups, the incidences being positively correlated with the MeBr concentration; the nasal lesions did not progress appreciably with time. Exposure to 90 ppm MeBr was associated with an increased incidence of lesions in the heart (thrombi, myocardial degeneration), and with hyperkeratosis in the oesophagus and forestomach. Data on site, type and incidence of tumours in the various groups did not indicate carcinogenic activity of MeBr.

Administration, Inhalation↗
PubMed1991

Role of genotoxicity assays in the regulation of chemicals in The Netherlands: considerations and experiences.

This paper discusses genotoxicity testing and data interpretation as applied in The Netherlands in the context of the regulation of chemicals. Guidelines were first formulated in 1981 and their use evolved in practice, on the basis of increasing experience at the national and international levels. The distinction between in vitro assays to detect intrinsic genotoxic properties and in vivo assays as a subsequent phase to show the realization of this potential in an intact organism has always been a cornerstone of the Dutch approach. Several critical aspects of the use of short-term genotoxicity tests in sequential schemes are discussed, such as their predictivity for carcinogenicity, the limited database concerning the performance of short-term in vivo assays, the relevance of devising separate strategies to test for possible carcinogenicity and germ cell mutagenicity, and the use of short-term tests to discriminate between genotoxic and non-genotoxic carcinogens. Examples are given of how short-term tests contributed to the toxicological evaluation of chemicals in The Netherlands.

Animals↗
PubMed1990

Chronic toxicity and carcinogenicity of bis(tri-n-butyltin)oxide (TBTO) in the rat.

In a 106-wk toxicity and carcinogenicity study, groups of 60 male and 60 female weanling Wistar rats were fed 0, 0.5, or 50 mg bis(tri-n-butyltin)oxide (TBTO)/kg diet. In males, feed consumption was increased in all treated groups and increased water consumption occurred at 5 and 50 mg/kg. During the second year, body weight decreased in the 50-mg/kg males, while the females in that group showed no weight gain. Excess mortality was confined to the 50-mg/kg group towards the end of the study. Haematological changes, comprising anaemia, lymphocytopenia and thrombocytosis were noted mainly at the high-dose level. Also, signs of decreased kidney function and increased plasma enzyme activities (alanine aminotransferase, aspartate aminotransferase and alkaline phosphatase) were noted. No effects on serum hormone concentrations (thyrotropin, follicle stimulating hormone, luteinizing hormone or insulin) were observed, except for a decrease in the free thyroxin:thyroxin ratio in both sexes at the high-dose level. Higher serum IgM and IgA levels were present at 50 mg/kg, while, in females, IgG was decreased. At 50 mg/kg, the ovaries, adrenals, spleen (females), heart (males), pituitary, liver and kidneys were increased in weight, but the thyroid weight was decreased in females. The total tin concentrations in liver and kidneys showed a dose relationship and, in general, the concentrations were similar after 1 and 2 yr. Non-neoplastic histological alterations after 1 yr consisted of a decrease in the cell height of the thyroid follicles in all dose groups, with a reduced number of psammoma bodies at 50 mg/kg, a decrease in splenic iron content at 5 (females only) and 50 mg/kg, and a slight bile-duct activation. After 2 yr, only the thyroid changes were still present. In addition, at 2 yr, vacuolation and pigmentation of the proximal tubular epithelium and nephrosis were enhanced at 50 mg/kg. The incidence of benign tumours of the pituitary was significantly elevated and enhanced at 0.5 and 50 mg/kg. At 50 mg/kg increases in pheochromocytomas in the adrenal medulla and in parathyroid adenomas (males) were noted, while adrenal cortical tumours were decreased (males). There was a low, non-dose-related incidence of pancreatic carcinoma. Other tumour rates were in line with control data. It is concluded that lifetime feeding of 50 mg TBTO/kg diet induces toxicity in various organ systems. An increase in some common tumours was found at the high dose, probably due to hormonal or immunological changes.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenal Cortex Neoplasms↗
PubMed1988

Aspartame: review of recent experimental and observational data.

In this report the neurotoxicity of aspartame and its constituent amino acids aspartic acid and phenylalanine is reviewed. The adverse reactions ascribed to the consumption of aspartame-containing products, as reported in the U.S.A., are discussed and placed in perspective with the results of recent behavioural studies in humans and animals. The issue of common intake levels associated with proposed uses of aspartame is addressed. In brief, the following conclusions can be drawn: When aspartame is consumed at levels within the ADI-limit of 40 mg/kg body wt, there is no significant risk for an aspartate-induced neurotoxic effect in the brain. When aspartame is consumed at levels within the ADI-limit by normal subjects or persons heterozygous for phenylketonuria (PKU) the resultant plasma phenylalanine concentrations are practically always within the normal postprandial range; elevation to plasma concentrations commonly associated with adverse effects has not been observed. Persons suffering from phenylketonuria (PKU-homozygotes) on a phenylalanine-restricted diet should avoid consumption of aspartame. PKU-homozygotes on the (less strict) phenylalanine-liberalized diet should be made aware of the phenylalanine content of aspartame. In the available behavioural studies in humans with acute dosing, no adverse effects were observed. Long-term studies on behaviour and cognitive function in (sensitive) humans are lacking. Analyses of adverse reaction reports made by consumers in the U.S.A. have not yielded a specific constellation of symptoms clearly related to aspartame that would suggest a widespread public health hazard associated with aspartame use. Focussed clinical studies are now being carried out in the U.S.A.; the results should provide additional evidence concerning the interpretation of the reports on adverse reactions ascribed to aspartame. In the regulation of admitted uses for aspartame the possibility of intake levels exceeding the ADI-limit in some groups of consumers should be a point of attention.

Animals↗
PubMed1987

Evaluation of the genetic and embryotoxic effects of bis(tri-n-butyltin)oxide (TBTO), a broad-spectrum pesticide, in multiple in vivo and in vitro short-term tests.

The genetic and embryotoxic effects of bis(tri-n-butyltin)oxide (TBTO) were evaluated in multiple in vivo and in vitro short-term tests preparatory to its potential wide use as a molluscicide in control of schistosomiasis. When tested in the rec assay in Bacillus subtilis, TBTO was not mutagenic and it did not induce reverse mutations in Klebsiella pneumoniae. Neither in the presence nor in the absecne of rat liver activation system did TBTO produce point mutations in Salmonella typhimurium strains TA1530, TA1535, TA1538, TA97, TA98 or TA100. TBTO was matagenic in strain TA100 in a fluctuation test, but only in the presence of rat liver S9 (Aroclor-induced). TBTO did not induce gene mutations in the yeast Schizosaccharomyces pombe, mitotic gene conversions in the yeast Saccharomyces cerevisiae, nor sister-chromatid exchange in Chinese hamster ovary cells in the presence or absence of rat or mouse liver S9. In the latter cells, structural chromosomal aberrations, endoreduplicated and polyploid cells were induced. TBTO did not induce gene mutations in V79 Chinese hamster cells (to 8-azaguanine-, ouabain- or 6-thioguanine-resistance) in the presence of a rat liver postmitochondrial fraction or in cell (hamster embryo cells and human and mouse epidermal keratinocyte)-mediated assays. In mouse lymphoma cells, TBTO did not induce 6-thioguanine- or BUdR-resistant mutations. As many tumour promoters inhibit metabolic cooperation between V79 Chinese hamster 6-thioguanine-resistant/-sensitive cells, TBTO was tested but showed no such activity. TBTO was examined for the induction of recessive lethal mutations in adult Berlin K male Drosophila melanogaster, either by feeding or by injection. Doses of 0.37 or 0.74 mM did not increase the number of X-linked recessive lethal mutations. An increased number of micronuclei was observed in the polychromatic erythrocytes of male BALB/c mice 48 h after a single oral dose of TBTO (60 mg/kg bw), while a lower dose (30 mg/kg bw) was ineffective. Neither of the two doses had induced micronuclei 30 h after treatment. The reproductive toxicity of TBTO was studied in NMRI mice. In a 10-day toxicity study, the LD50 and LD10 were 74 and 34 mg/kg bw, respectively. An increased frequency of cleft palates was seen in the fetuses of mice (compared with controls, 0.7%) treated orally during pregnancy with 11.7 mg/kg TBTO (7%), 23.4 mg/kg (24%) or 35 mg/kg (48%).(ABSTRACT TRUNCATED AT 400 WORDS)

Abnormalities, Drug-Induced↗
PubMed1985

Carcinogenicity study in rats with a mixture of eleven volatile halogenated hydrocarbon drinking water contaminants.

A lifetime carcinogenicity study was carried out in Wistar rats, with a mixture of the following halogenated hydrocarbons: trichloromethane, tetrachloromethane, monobromodichloromethane, trichloroethylene, tetrachloroethylene, 1,2-dichlorobenzene, 1,3,-dichlorobenzene, 1,4,-dichlorobenzene, 1,2,3,-trichlorobenzene, 1,2,4,-trichlorobenzene, 1,3,5-trichlorobenzene. From this mixture 0.22, 2.2, or 22 mg was added per liter drinking water representing concentrations being three orders of magnitude higher than found in several water wells. Most of the changes found in body weight, hematology and pathology correlated with intercurrent diseases or were in accordance with background pathology. With respect to incidence and time of occurrence of tumors, no significant differences were found between the control and the high dose group when lifespan correction was applied. Thus it is concluded that in the present study no significant toxic or carcinogenic effects are induced by lifetime exposure of rats to a mixture of volatile halogenated hydrocarbons in the drinking water.

Animals↗
PubMed1985

Induction of early lesions in the forestomach of rats by 3-tert-butyl-4-hydroxyanisole (BHA).

BHA was administered to Wistar rats at a dose level of 2% in a powdered diet for periods of 1, 2 and 4 wk. After 1 wk epithelial damage, mild hyperplasia and hyperkeratosis of the forestomach mucosa was observed. The hyperplasia and hyperkeratosis showed progression at wk 2 and 4 whereas other epithelial defects regressed. The lesions were most pronounced in the vicinity of the limiting ridge. A further 4 wk of feeding without BHA resulted in a complete regression of epithelial defects, although the hyperplastic changes were still apparent. Other rats were given 1 g BHA/kg body weight/day by gastric intubation in arachis oil for 1, 2, 4, 8, 16 or 32 days. Increased mitotic activity was observed after 1 day and mild hyperplasia after the second intubation, but inflammatory response and superficial defects were not prominent and the hyperplasia of the squamous epithelium did not appear to result from initial damage and subsequent hyper-regenerative activity. A gradual regression of the hyperplastic changes occurred after eight daily intubations. The lesions were found in the apex of the forestomach remote from the limiting ridge. It is concluded that BHA incorporated in powdered diet or given in arachis oil by oral intubation causes lesions in the rat forestomach similar to that reported for BHA given in a pelleted diet (Ito et al. J. natn. Cancer Inst. 1983, 70, 343; idem, Gann 1983, 74, 459). The hyperplastic changes in the mucosa occur rapidly and their localization is dependent on the mode of application. Following withdrawal of the BHA there was almost complete regression of the lesion, only a residual mild hyperplasia remaining after 4 wk.

Animals↗
PubMed1984

[Dioxins].

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Abnormalities, Drug-Induced↗
PubMed1984

Toxicity of bis(tri-n-butyltin)oxide in the rat. I. Short-term effects on general parameters and on the endocrine and lymphoid systems.

Male and female Wistar rats were fed bis(tri-n-butyltin)oxide (TBTO) at 0, 5, 20, 80, or 320 mg/kg diet for 4 weeks. Clinical signs and decreases in feed and water consumption were observed in the 80 and 320 mg/kg groups. The serum transferase activities (alanine amino transferase and aspartate amino transferase were increased at 20 (males only), 80, and 320 mg/kg. The serum glucose and liver glycogen concentrations were lowered in the 320 mg/kg group. At 80 and 320 mg/kg the serum IgG level was reduced and IgM level was increased. Compared to controls the mean relative weight of the thymus was decreased at 20 (males), 80, and 320 mg/kg. In the groups receiving 80 or 320 mg/kg microcytic anemia was found. The white blood cell counts were decreased, due to the reduction in the number of lymphocytes in the 80 (males) and 320 mg/kg groups. The concentration of neutrophilic granulocytes was increased in the highest dose group. Histopathologic effects included a dose-related lymphocyte depletion of thymic cortex and of T lymphocytes in spleen and mesenteric lymph nodes. In the spleen also depletion of iron stores was found, and in the medullary sinuses of mesenteric lymph nodes, rosettes of erythrocytes were found around mononuclear cells; the occurrence of rosettes increased with dose from 5 to 80 mg/kg, and appeared to be the most sensitive parameter. A low incidence of areas of liver necrosis with inflammatory reaction and bile duct hyperplasia was found in the 320 mg/kg group. A viral or bacterial etiology could be demonstrated for these liver lesions, but they appeared associated with TBTO-induced ulcerative inflammation of the common bile duct as shown in an additional study. In 6-week studies exposure of male weanlings to the 0, 20, and 80 mg/kg diets, the serum insulin concentration in the treated groups was decreased, although the response to glucose challenge was unaffected. The serum thyroxin and thyrotropin (TSH) concentrations were reduced, whereas the luteinizing hormone (LH) concentration was increased in the 80 mg/kg group. The concentrations of follicle-stimulating hormone (FSH) and corticosterone were not changed. The release of LH and FSH was enhanced in the 80 mg/kg group and a tendency toward reduced release was found for TSH. Using immunocytochemistry a dose-related reduction was found in the number and staining intensity of TSH-producing cells in the pituitary, correlating with histopathologically decreased activity of the thyroid.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1984

Methylbromide: carcinogenic effects in the rat forestomach.

Methylbromide (MB) administered by oral gavage as a solution in arachis oil was carcinogenic to rats in a 90-day experiment. In 13 of 20 animals of the highest dose group, 50 mg MB/kg body wt squamous cell carcinomas of the forestomach developed. All animals of this group showed a marked diffuse hyperplasia of the epithelium of the forestomach. A less pronounced hyperplasia was observed in high and lower incidence with respectively 10 and 2 mg MB/kg body wt. The lowest dose, 0.4 mg MB/kg body wt was without effects.

Animals↗
PubMed1984

Induction of ornithine decarboxylase and augmentation of tyrosine aminotransferase activity by N-hydroxy-2-acetylaminofluorene and 2-acetylaminofluorene in rat liver. Influence of sex, retinylacetate, indomethacin, and pentachlorophenol.

IP injection in rats of 2-acetylaminofluorene (AAF) or N-hydroxy-2-acetylaminofluorene (N-OH-AAF) resulted in a transient increase of hepatic ornithine decarboxylase (ODC) and tyrosine aminotransferase (TAT) activity. Maximal activity of ODC was observed 4 hr and of TAT 3 hr after administration of either AAF or N-OH-AAF. A lag-time of 2 hr preceded the increase of ODC and TAT activity. N-OH-AAF dependent ODC induction displayed an almost linear dose-response in the dose range up to 94.1 mumol/kg bw (body weight) when the ODC activity was measured at its maximum 4 hr after administration. Elevation of the dose N-OH-AAF to 126 mol/kg bw resulted in a lower ODC induction. Administration of doses AAF to 31.4 mumol did not change ODC activity. At doses up to 126 mumol/kg bw ODC induction increased linear. TAT induction increased linear in the dose range 15.7-94.1 mumol N-OH-AAF and 31.4-94.1 mumol AAF/kg. Lowering the dose of AAF did not result in a lower ODC or TAT activity. Judged by the effects of actinomycin D or cycloheximide administered 1 hr prior to AAF or N-OH-AAF, the in vivo induction of rat liver ODC activity by AAF and N-OH-AAF appeared to be under transcriptional control, whereas augmentation of TAT activity under influence of AAF or N-OH-AAF appeared the result of (post) translational events. Induction of ODC by AAF or N-OH-AAF was not significantly changed by indomethacin, was slightly increased by pentachlorophenol (PCP) and was synergistically enhanced by retinylacetate (RA). The increase of TAT activity was stimulated by PCP and RA. The effect of PCP indicates that N-sulfonoxy-2-acetylaminofluorene is most probably not involved in the induction of ODC. AAF appeared more effective hepatic ODC inducer in females than males and moreover more effective than N-OH-AAF in females. N-OH-AAF had stronger ODC inducing capacity in males than females. Similar observations were made with respect to TAT activity. When induction of ODC is indicative for a tumor promoting property then the data presented here suggest that tumor promotion of the complete carcinogens AAF and N-OH-AAF is not mediated by N-O-sulfation; this might be due to other metabolic conversions.

2-Acetylaminofluorene↗
PubMed1981

Short-term induction of neoplastic nodules in the rat liver. II. Study of their development and the effects of withdrawal of 2-acetylaminofluorene.

Neoplastic liver nodules were induced by a single administration of N-nitrosodiethylamine (NDEA) and selectively stimulated to growth by 2-acetylaminofluorene (2-AAF) and partial hepatectomy to provide morphological data on very early and late stages of preneoplastic development. Presumptive preneoplastic liver cells were recognizable by light and electron microscopy by 2 days after partial hepatectomy, and they developed within 2 weeks into large, solid nodules consisting of plates of 2 or 3 cell layers thick, that compressed the surrounding non-nodular tissue. The cells showed nuclei with an enlarged nucleolus, tortuously dispersed rough endoplasmic reticulum (RER) and an electron lucent cytoplasm. These features remained present throughout the first 2 weeks of growth. During this period the initially small, distinct smooth endoplasmic reticulum areas proliferated gradually. They were associated with an increasing incidence of cytoplasmic membranes whorl formation and incidentally with annulate lamellae. After withdrawal of 2-AAF the majority of the nodules regressed resulting in slowly disappearing foci of glycogen rich cells. A relatively small number of solid nodules persisted. They were characterized by large cells with a homogeneous eosinophilic cytoplasm, enlarged cells with a homogeneous eosinophilic cytoplasm, enlarged nucleoli and dispersed RER. Because these characteristics were absent in nodular cells that had reverted to normal liver cells, it is not appropriate to consider these characteristics to represent neoplastic transformation per se.

2-Acetylaminofluorene↗