摘要:

The incidence of primary liver cancer in the countries of tropical Africa is the highest in the world. There is a growing belief that the relatively high prevalence of hepatocellular carcinoma in Nigeria may have a multiple chemical factor etiology in such forms as food contaminants, herbal teas, and environmental chemicals. Major chemical toxins and carcinogens that have been identified so far in the tropical environment include sapotoxin, cycasin, mushroom toxin, capsaicin, oxalic acid, prusslc acid, fluorooleic acid, N‐nltroso compounds, aflatoxin, palmotoxin, pyrrolizidine alkaloids, quinine, DDT, and cyclamate.

ISSN:0098-4108    

DOI:10.1080/15287397809529691

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

To clarify the effect of subacute manganese feeding on serotonin and mineral metabolism, Wistar rats were separated into two groups and fed two different diets, one a normal diet and another a manganese‐supplemented diet. After 3 wk on these dietary regimens, the rats on the manganese‐supplemented diet manifested the following abnormalities: blood pressure was decreased, brain serotonin was decreased, aromatic L‐amino‐acid decarboxylase activity in the brain was decreased, and manganese levels in heart, lung, and kidney were increased, whereas sodium, potassium, magnesium, and calcium levels in the brainstem were decreased.

ISSN:0098-4108    

DOI:10.1080/15287397809529692

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

A pharmacokinetic study was conducted to determine the fate of dioxane in rats at doses equivalent to those given in toxicological studies conducted previously. The results show that the fate of dioxane in rats is markedly dose‐dependent because of a limited capacity to metabolize dioxane to ß‐hydroxyethoxyacetlc acid (HEAA). The pharmacokinetic data collected in support of these conclusions include plasma concentration‐time curves for dioxane given to rats iv at dose levels of 3–1000 mg/kg and for an inhalation study of 50 ppm dioxane vapors for 6 h. The plasma curves at low doses by each route were linear with half‐life values of about 1 h. As the dose was increased above 10 mg/kg the plasma clearance rate decreased, the fraction of the dose excreted as HEAA decreased, and the fraction of the dose excreted as dioxane per se in the urine and expired in the breath increased. These data could be described by a one‐compartment open system model with parallel first‐order (urinary and pulmonary excretion) and Michaelis‐Menten (metabolism) elimination kinetics. At saturation, the maximum velocity of metabolism of dioxane to HEAA was about 18 mg/kg • h. Multiple daily oral doses of 1000 mg/kg, but not 10 mg/kg, were excreted more rapidly than equivalent single doses, indicating that at high daily doses dioxane induced its own metabolism. The correlation of the dose‐dependent fate of dioxane with the results of toxicological studies in rats supports the conclusion that there is an apparent threshold for the toxic effects of dioxane that coincides with saturation of the metabolic pathway for its detoxification.

ISSN:0098-4108    

DOI:10.1080/15287397809529693

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

1,2,4,5‐Tetrachlorobenzene (TCB), an intermediate in several industrial processes, was administered in the diet to dogs at 5 mg/kg • d for 2 yr, followed by a 20‐mo recovery phase. The animals were examined periodically for toxicity; the concentration of TCB in the plasma and fat was measured during the 2 yr of exposure and 20 mo of recovery. After 18 mo of exposure, all clinical chemistry parameters were normal; however, after 24 mo, serum alkaline phosphatase activity and total bilirubin levels were slightly elevated in the dogs dosed with TCB. Both clinical chemistry parameters returned to normal levels within 3 mo of the cessation of exposure. After the 20‐mo recovery, gross and histopathologic examination of tissues revealed no morphological changes considered related to the ingestion of TCB. A t the end of 2 yr of exposure, TCB had reached 98 and 97% of the calculated steady‐state concentrations in fat and plasma, respectively. TCB was eliminated from the fat and plasma with half‐life values of 111 and 104 d, respectively. Although there were only small differences in the approach to steady state, differences in the rate of elimination of TCB from fat and plasma resulted in dramatic changes in the fat/plasma ratio of TCB throughout the entire study.

ISSN:0098-4108    

DOI:10.1080/15287397809529694

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

The principal cyanogenic glucoside in cassava is linamarin (2‐hydroxyisobutyronitrile‐ß‐D‐glucoside). Addition of pure linamarin to a diet based on 10% vitamin‐free casein did not affect the weight gain of rats. However, as expected, the animals that received the casein diet supplemented with methionine gained more weight than those that received the unsupplemented diet. The amount of thiocyanate ion excreted in the urine by the animals that received linamarin was higher than that excreted by the animals that did not receive linamarin at both levels of dietary methionine. The plasma thiocyanate concentration was also higher for linamarin‐fed animals than for animals that did not receive linamarin. Higher plasma thiocyanate levels were associated with a lower percentage uptake of radioiodine by the thyroid.

ISSN:0098-4108    

DOI:10.1080/15287397809529695

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Biochemical studies were performed on blood and lung tissue of squirrel monkeys(Saimiri sciureus)following acute exposure to 0.75 ppm ozone (O3) for 4 h/d for 4 consecutive days. One group of animals was sacrificed at the end of the last exposure day and another group was sacrificed 4 d later after the last exposure. Evidence was sought for oxidation‐induced changes known to occur in rodents when high levels of O3are inhaled. A significant increase in red blood cell membrane fragility was observed, as well as significant decreases in red blood cell glutathione and erythrocyte acetylcholinesterase; however, the red blood cell enzymes, lactic acid dehydrogenase (LDH), and glucose‐6‐phosphate dehydrogenase (G6PDH) were not changed significantly. Lung tissue analysis showed that lipid peroxidation was markedly increased and tissue vitamin E levels were significantly decreased. The tissue enzymes G6PDH, glutathione reductase, and LDH significantly increased in activity. No significant changes were seen in either Superoxide dismutase or maliç acid dehydrogenase. The results of this experiment indicate that O3, or reaction products resulting from O3‐tissue interaction in the lung, pass the air‐blood barrier and are capable of producing biochemical changes in blood as well as in lung tissue.

ISSN:0098-4108    

DOI:10.1080/15287397809529696

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Nitrogen dioxide (NO2) is both edematogenic and cytotoxic to the lung. Preexposure to NO2protects against mortality from formation of excessive pulmonary edema (tolerance) and, depending on the preexposure schedule, may or may not protect against the cytotoxic effects of NO2in the lung. Measurement of DNA synthesis in hamster lung was used to study the question of whether the more subtle cytoiogical injury induced by NO2is mediated by a system that also exhibits tolerance. It was found that when hamsters are preexposed daily to 10 ppm NO2, they develop tolerance for normally lethal concentrations of NO2, are protected against further cytoiogical injury from 10 ppm NO2, but are not protected from the cytotoxic effects of NO2at concentrations greater than 10 ppm. Animals exposed weekly to 10 ppm NO2are not protected from further cytoiogical injury induced by weekly exposures to 10ppm NO2, but do develop tolerance for lethal concentrations of NO2. Thus, the data indicate that induction of tolerance to NO2does not necessarily protect the cell populations of the lung from the cytotoxic effects of NO2.

ISSN:0098-4108    

DOI:10.1080/15287397809529697

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

A testing procedure is described for the assessment of the toxicological response (e.g., acute toxcity or mutagenicity) of any combination and number of chemical, physical, and biological agents, with no more effort for a particular combination than for a single agent. The method provides a simple, sensitive, and quantitative index of synergism, antagonism, and additivity, and it has been demonstrated experimentally in rats by determining the acute lethality of combinations of cadmium, mercury, and lead salts. In a combination of two metal salts, the dose of one metal of the pair was fixed at or near the no‐effect level while the dose of the second metal was Increased until the entire dose‐response curve was obtained. To evaluate interactions of the three metals, the previous pair of metals were kept fixed at their combined extrapolated LD1 level, and the third metal was increased. The statistical treatment of the data employed a computer program that did not involve probit transformations, but rather the approximate linear relationship between the fractional response and the logarithm of the dose.

ISSN:0098-4108    

DOI:10.1080/15287397809529698

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

The effect of exposure to a sublethal concentration (0.30 mg/l) of mercuric chloride on the activities of alkaline phosphatase, acid phosphatase, amylase, trypsin, and pepsin has been examined at intervals of 7, 15, and 30 d in the digestive system of a teleost fish,Channa punctatus. Inhibition of the activities of all these enzymes was noted after the first week of treatment. Treatment of the fish for 15 d resulted in marked increases in the activities of all the enzymes. A slight fall in enzyme activity was recorded after 30 d, but the overall activity was higher than in control fish.

ISSN:0098-4108    

DOI:10.1080/15287397809529699

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Radioimmunoassay (RIA) data on concentrations of circulating steroids in normal prepubertal and adult male and female humans, chimpanzees, rhesus monkeys, rats, mice, and hamsters have been collated from the literature. Few reports include data for both sexes, for age groups, or for more than one species. In selecting references for inclusion in the tables, efforts were made to choose data only from RIA procedures that were adequately validated. A number of similarities can be found by reviewing the tables. Levels of estradiol appear somewhat similar for humans, chimpanzees, and rhesus monkeys of both sexes. Among the notable differences are the levels of estradiol and progesterone in primates and rodents, the apparently high level of aldosterone in mice, and the patterns of progesterone secretion in mice and rats. All values in the tables have been converted to picograms for easy comparison between steroids and species. Data for humans are fairly complete, but there is a significant lack of information for several other species.

ISSN:0098-4108    

DOI:10.1080/15287397809529700

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor