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Biomedical subjects

C A Snyder

Publications and source records attributed to C A Snyder.

70 records · Page 4Linked to original sources
PubMed1981

Behavioral changes in mice following benzene inhalation.

Although benzene is an important occupational health hazard and a carcinogen, the possibility that behavioral changes may forewarn of the later-occurring hematological changes has not been investigated. A time-sampling protocol was used to quantify the occurrence of 7 categories of behavior in the homecage following daily 6-hr exposures to two strains of adult mice (CD1 and C57BL/6J). The behavioral categories were stereotypic behavior, sleeping, resting, eating, grooming, locomotion, and fighting. The inhalation exposures were designed to reflect occupational exposure. Dynamic vapor exposure techniques in standard inhalation chambers were employed. Exposure to 300 or 900 ppm benzene increased the occurrence of eating and grooming and reduced the number of mice that were sleeping or resting. The responses to benzene of both the CD1 and the C57 strains were similar. The positive findings with benzene inhalation indicate the utility of behavioral investigations into the toxicology of inhaled organic solvents. The methods described herein illustrate an objective observation of animal behavior that is capable of documenting toxicity and of guiding detailed follow-up studies aimed at mechanism of action.

Animals↗
PubMed1980

Inhalation carcinogenesis by dimethylcarbamoyl chloride in Syrian golden hamsters.

The comparative carcinogenicity of dimethylcarbamoyl chloride (DMCC) was studies in male, Syrian Golden Hamsters by inhalation. Hamsters were exposed to 1ppm and the exposure periods were 6 hours per day, 5 days per week for the lifetime of the animals. Fifty-one percent of the hamsters developed carcinomas of the nasal tract. Morphologically, all of these tumors were classified as squamous cell carcinomas. In comparing the response of rats and hamsters at 1 ppm DMCC, the rat seems to show increased sensitivity and the percentage of tumor yield is almost doubled, with the tumors appearing much earlier in rats than in hamsters. However, the remarkable tumor yield in both species indicates the potent carcinogenic effects of DMCC.

Animals↗
PubMed1979

Peptic ulcer in Rwanda, Africa: influence of geography and dietary habits.

There are areas of Africa with an extremely high incidence of peptic ulcer disease, while most of Africa has a low incidence of ulcer disease. The reason for this variation is unknown. Thirty-three patients with peptic ulcer disease in Rwanda, Africa, were studied in an attempt to determine why they had ulcer disease. High basal acid studies (mean of 10.3 mq per hour) were found in the patients with duodenal peptic ulcers. The males predominated over the females and the Batutsi predominated over the Bahutu in having much more peptic ulcer disease. The male population and patients with ulcers had the custom of eating only one large meal per day. There is a definite correlation between the incidence of peptic ulcers among certain tribes and going for long periods without eating.

Adolescent↗
PubMed1977

An extraction method for determination of benzene in tissue by gas chromatography.

An extraction procedure has been developed for the determination of benzene by gas chromatography in tissues following inhalation. Results are reproducible using very small quanities of sample (0.05 g for tissue and 0.02 ml for blood). The procedure has been applied to the analysis of blood and tissue of A.K.R. mice following a single exposure to levels similar to those that may be found in industrial hygiene atmospheres.

Animals↗
PubMed1977

Benzene toxicity: a critical evaluation: analytical techniques.

The choice of any procedure for analysis involves consideration of a number of factors and is best resolved by professional judgment. In general, techniques that require the fewest steps for sample preparation give the best results and instrumentation should be selected with this in mind. In recent times, the most successful determinations of benzene have used nonvisible spectrophotometry and gas chromatography. These techniques provide good sensitivity and require minimal sample preparation. Spectrophotometric methods are best used where there are few interfering compounds and therefore they are adequate for determinations of benzene in air, water, some industrial gases, and simple solvent mixtures. The development of Fourier transform interfacing has greatly improved the sensitivity of spectrophotometers and allows for improved accuracy using small samples. This has been especially realized in the direct analysis of gases by infrared spectrophotometry. The usefulness of gas chromatography lies in its ability to separate components in a mixture before analysis. For this reason, gas chromatography is the technique of choice for determining benzene in complex gaseous or liquid mixtures and biological systems. The development of microcircuitry has improved detector response as well as reduced the costs of most instruments. This, combined with the availability of prepacked columns, has made the gas chromatograph a standard instrument in even small laboratories.

Air Pollutants↗
PubMedDate not supplied

Cecal-colic adult intussusception as a cause of intestinal obstruction in Central Africa.

During a 5-year experience in Central Africa, the most common cause of 78 adult intestinal obstructions was primary adult cecal-colic intussusception (n = 43; 55%). The symptom complex of colicky abdominal pain and obstipation was present in 100% of the patients with intussusception. Operative repair in 90% of patients consisted of simple reduction of the intussusceptum. There were no known recurrences. The etiology of adult cecal-colic intussusception is unknown. Patients typically present with a 3- to 4-day history of abdominal pain, obstipation, and usually a palpable mass. Treatment is surgical reduction. Right colectomy is reserved for intestinal gangrene. We treated 43 cases during a 5-year period with only one death.

Adolescent↗
PubMedDate not supplied

Reduced IL-6 levels among individuals in Hudson County, New Jersey, an area contaminated with chromium.

Hudson County, New Jersey, was a major center for the processing of chromium ore. After processing, some of the ore residue that contained low concentrations of chromium became distributed in population centers throughout the county. There now exists concern in the county about possible health effects from chromium exposure. Our previous research suggested that immune-function assays would make useful biomarkers for chromate exposure in humans. Blood samples were drawn from 46 individuals who lived and/or worked in Hudson County and from 47 controls. Only one of the immune-associated assays performed on these samples showed any statistically significant differences between the Hudson County and control groups. The mean level of IL-6 produced by pokeweed mitogen-stimulated mononuclear cells isolated from the Hudson County group was 64% of the control value--a highly significant decrease (p<.001). There was also a significant correlation between the proliferative responses of the mononuclear cells to pokeweed mitogen and the levels of IL-6 produced by these cells. No differences were detected in the IL-6 responses that resulted from age, gender, or smoking status. The reliability of the IL-6 assay was found to be 90%. To our knowledge, there have been no reports, until now, that describe reduced production of any cytokine in individuals who are exposed to chromate.

Cell Division↗
PubMedDate not supplied

An assessment of the tumorigenic properties of a Hudson County soil sample heavily contaminated with hexavalent chromium.

During much of this century, Hudson County, New Jersey, was a major center for the processing of chromium ore. Some of the residue from this processing was used in landfills and in construction materials throughout the county and, in some cases, in highly populated areas. Given that it is widely accepted that exposure to hexavalent chromium compounds poses a risk for the development of respiratory-tract cancer, concerns were raised that individuals who worked or resided in chromium-contaminated areas might be at increased risk for the development of respiratory cancer. To address these concerns, we evaluated a Hudson County soil sample-heavily contaminated with chromium ore residue (Cr(+6) concentration at 5 895 mg/kg)-with respect to its carcinogenic potential to the respiratory tract of Sprague-Dawley rats. Groups of animals were given repeated intratracheal exposures to one of four materials: (1) Hudson County chromium-contaminated soil (CCS), (2) CCS augmented with calcium chromate (CaCrO4), (3) CaCrO4 alone, or (4) control soil. Nominal total doses of Cr(+6) for each respective group were 324 microg/kg, 7,975 microg/kg, 8,700 microg/kg, and 0.02 microg/kg. Incidences of malignant tumors and nephritis were not elevated in any group. Four primary lung tumors appeared in animals that received CCS + CaCrO4, and one primary lung tumor appeared in the group treated with CaCrO4 alone. These incidences were not significant statistically, but the rare spontaneous occurrence of these tumors in Sprague-Dawley rats suggested that they were treatment related. No primary lung tumors appeared in the control or CCS-treated groups.

Animals↗