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Biomedical subjects

R W Rice

Publications and source records attributed to R W Rice.

At least 19 recordsLinked to original sources
PubMed1995

Cytotoxicity and genotoxicity of wood drying condensate from Southern Yellow Pine: an in vitro study.

We tested condensates from Southern Yellow Pine for potential cytotoxicity and genotoxicity in CHO-WBL and human peripheral blood lymphocytes (PBL) in the absence of S-9 activation. Cytotoxicity was evaluated by the Trypan blue exclusion assay, mitotic index (MI) and proliferative rate index (PRI). Genotoxicity was measured by the chromosome aberration (CA) assay and sister chromatid exchange (SCE) analysis. Both cytotoxic and genotoxic effects were observed. Laboratory-generated Southern Yellow Pine condensate reduced the viability of CHO-WBL cells. The number of viable cells was roughly inversely proportional to dosage over a range of 100% to 31% in treated groups, in both experiments, as compared to 2.6 x 10(5) (100%) in the control. The MI data in both CHO cells and PBL also showed an inverse correlation. The highest scorable dose limited by toxicity was determined to be 1 ml of Southern Yellow Pine condensate in 10 ml total of medium. Lastly, a dose response curve was observed in CHO cells, as well as in PBL, using the CA assay and also with the SCE analysis. The present findings corroborate the results from Ames testing and represent the only information currently available on the genotoxic potential of these chemicals.

Animals↗
PubMed1995

Eastern white pine wood-drying condensate induced cytotoxicity and genotoxicity in human peripheral blood lymphocytes in vitro.

Condensate from eastern white pine, one of the commercially most important species of tree in the northeastern United States, was treated for potential cytotoxicity and genotoxicity in human peripheral blood lymphocytes in the absence of S-9 activation. Cytotoxicity was evaluated by mitotic index (MI) determination and proliferative rate index. Genotoxicity was measured by the chromosome aberration (CA) assay and sister chromatid exchange (SCE) analysis. Both cytotoxic and genotoxic effects were observed with laboratory-generated eastern white pine condensate. The MI data showed an inverse correlation between the MI and treatment dosage. A dose response curve was observed using the CA assay and also with the SCE analysis. The present findings thus corroborate the results from Ames testing and represent the only information currently available on the cytotoxic and genotoxic potential of these chemicals.

Cell Division↗
PubMed1988

The effects of grapefruit pectin on patients at risk for coronary heart disease without altering diet or lifestyle.

Dietary intake of cholesterol has been linked to coronary heart disease. The effect of grapefruit pectin (Citrus paradisi) on plasma cholesterol, triglycerides, very low-density lipoprotein cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and the low-density lipoprotein:high-density lipoprotein cholesterol ratio was studied. The study design was a 16-week double-blind, crossover (placebo or pectin) using 27 human volunteers screened to be at medium to high risk for coronary heart disease due to hypercholesterolemia. The study did not interfere with the subjects' current diet or lifestyle. Grapefruit pectin supplementation decreased plasma cholesterol 7.6%, low-density lipoprotein cholesterol 10.8%, and the low-density lipoprotein:high-density lipoprotein cholesterol ratio 9.8%. The other plasma lipid fractions studied showed no significant differences. We conclude that a grapefruit pectin-supplemented diet, without change in lifestyle, can significantly reduce plasma cholesterol.

Adult↗
PubMed1988

Grapefruit pectin inhibits hypercholesterolemia and atherosclerosis in miniature swine.

We studied the effect of dietary grapefruit pectin on plasma cholesterol and the development of atherosclerosis in 18 miniature swine. Pigs were randomized to one of three diets: no added fat (I), added fat/cellulose (II), and added fat/pectin (III). Plasma cholesterol was measured monthly. Arteries were examined for atherosclerosis at the termination of the experiment. Pectin supplementation of an added fat diet resulted in a significantly lower average plasma cholesterol than did cellulose supplementation (168 mg/dl vs. 249 mg/dl, p less than 0.05). The pectin-fed pigs also developed less atherosclerosis of their aortas (1.1% vs. 7.0%, p less than 0.05) and coronary arteries (2.9% vs. 26.2% cross-sectional narrowing, p less than 0.05). Plasma cholesterol levels correlated with the severity of aortic (r = 0.836) and coronary artery (r = 0.735) atherosclerosis. We conclude that dietary grapefruit pectin supplementation inhibits hypercholesterolemia and appears to be proportionately protective against atherosclerosis.

Animals↗
PubMed1986

Transfer of hepatitis B virus by contaminated reusable needle electrodes after electrodesiccation in simulated use.

Reusable needle electrodes have been standard for electrodesiccation procedures commonly done by dermatologists. This study investigates the risk of transmission of hepatitis B virus by such electrodes during simulated use with electrodesiccation. Sterile needle electrodes were inoculated with either purified hepatitis B surface antigen (HBsAg+) concentrate or serum positive for both HBsAg and deoxyribonucleic acid (DNA) polymerase activity (a measure of infectious and replicating hepatitis B virus), followed by simulated use for electrodesiccation at various settings and rinsing of the tip with negative serum. The rinse serum was then assayed for HBsAg, DNA polymerase activity, and the presence of viral particles by electron microscopy. HBsAg could be transferred through the electrodesiccation procedure at all settings used. Although DNA polymerase activity was negative in the rinse serum, electron microscopy demonstrated transfer of HBsAg forms and complete virus. These results suggest a potential risk of spread of hepatitis B virus by reusable needle electrodes for electrodesiccation.

Electrocoagulation↗
PubMed1980

Supraorbital development in chimpanzees, macaques and baboons.

Macroscopic and histological parameters are considered in an analysis of bone formation in the supraorbital region of macaques (Macaca mulatta), baboons (Papio cynocephalus anubis), and chimpanzees (Pan troglodytes verus). Results indicate that post-natal osteogenesis of the supraorbital segment of the frontal bone in these primates occurs as a cyclic phenomenon that coincides wth dental eruption patterns.

Animals↗
PubMed1979

Craniofacial growth in olive baboons (Papio cynocephalus anubis): browridge formation.

The examination of a developmental series of skulls of olive baboons has led to the generation of a model for browridge formation. Evidence in support of the model comes from surface configuration of browridge bone as studied by scanning electron microscopy, histology of the bone by the analysis of thin sections and by measurements that reflect both depositional cycles in browridge bone and the biomechanics of mastication. The model relates sudden changes in the biomechanical system caused by the tooth eruption cycle to cyclical changes in the formation of browridge bone. We suggest that browridge bone is added during periods of peak stress caused by the positive response of the masticatory muscles to relatively sudden reduction of their biomechanical efficiency.

Animals↗
PubMed1978

Abolition of plasma growth hormone response to stress and of the circadian rhythm in pituitary-adrenal function in female rats with preoptic-anterior hypothalamic lesions.

The chronic effects of lesions placed in the medial or lateral preoptic-anterior hypothalamic area (PO-AHA) on plasma growth hormone (GH) and corticosterone (cpd B) responses to stress, non-stress levels of these hormones and somatic growth were studied in adult female rats. Responses to 3-min immobilization--blood withdrawal stress uere tested at 2 and 11 weeks and to 3-min ether--blood withdrawal at 5 weeks after surgery. Non-stress plasma GH levels were further assessed in serial blood samples collected at 4-h intervals during a 24-h period at 15 weeks, and cpd B levels were studied similarly for a 44-h period at 22 weeks. Rats with lateral PO-AHA lesions showed normal GH suppression and cpd B elevation in response to both stress procedures. In contrast, neither stressor suppressed plasma GH levels in rats with medial PO-AHA lesions, but both produced normal increments in cpd B. The 24-h mean non-stress level of plasma GH in the group with medial lesions was higher and that of the group with lateral lesions was lower than those of controls. Cpd B levels were reduced during the 44-h study, and circadian rhythmicity was abolished in rats with medial lesions. The group with lateral lesions showed normal rhythmicity in plasma cpd B levels, Linear growth was not affected in either lesioned group. The GH findings suggest that the medial but not lateral PO-AHA is essential for stress-induced inhibition of GH secretion and that this region may exert a tonic inhibitory influence on non-stress GH secretion. The data also suggest that the medial PO-AHA is importantly involved in producing the circadian rhythm in pituitary-adrenal function.

Animals↗
PubMed1978

Somatostatin content of the median eminence in female rats with lesion-induced disruption of the inhibitory control of growth hormone secretion.

These experiments were designed to determine whether brain lesions which elevate nonstress plasma levels of GH and disrupt stress-induced suppression of GH secretion in female rats affect the median eminence content of somatostatin. Some rats received lesions in the medial or lateral preoptic-anterior hypothalamic area (PO-AHA), while others received anterior hypothalamic cuts. Sham-operated and intact rats served as controls. GH and somatostatin were measured by RIA. Medial but not lateral PO-AHA lesions caused elevated nonstress plasma GH levels at 2, 14, 17, and 23 weeks after surgery, but normal levels were obtained at autopsy at 27 weeks. These lesions compromised GH responses to stress at 14 and 23 weeks. Rats with anterior hypothalamic cuts showed elevated nonstress GH levels at 17, 23, and 27 weeks after surgery and loss of the GH response to stress at 14 and 23 weeks. Median eminence content of somatostatin was reduced approximately 80% in rats with medial PO-AHA lesions or anterior cuts. Whereas medial PO-AHA lesions were associated with normal body length and weight and evidence of estrogen secretion, anterior hypothalamic cuts produced increased linear growth and body weight and signs of functional castration. These results suggest that the effects of lesions which cause prolonged elevation of nonstress GH levels and disruption of the GH stress response are due to interference with somatostatin neurons located in the medial PO-AHA. Somatostatin content of the median eminence seems to depend largely on connections originating in or traversing the medial PO-AHA.

Animals↗
PubMed1977

A scanning electron microscopic and x-ray microanalytic study of cell surface material during amphibian neurulation.

Treatment with lanthanum (La3+) after fixation in phosphate (PO4-3)-buffered glutaraldehyde results in the deposition of a cell surface material (CSM) primarily on the developing urodele amphibian neural axis. X-ray probe microanalysis indicates that calcium (CA2+) levels are considerably higher in the neural fold region. La3+ displaces Ca2+ from negatively-charged moieties on biological membranes. Once bound, La3+ likely interacts with residual phosphate(s) resulting in deposition of CSM. Elemental X-ray microanalysis shows CSM contains mostly lanthanum and phosphorus. The high level of regional La3+ binding is correlated with inherently greater Ca2+ levels in the developing neural axis.

Ambystoma↗
PubMed1976

Evidence for a free-running circadian rhythm in pituitary-adrenal function in blinded adult female rats.

To study the eyes' role in maintaining the circadian rhythm in pituitary-adrenal function, 24-h patterns of corticosterone levels were compared in intact and blinded adult female rats. Rats were blinded by optic enucleation at approximately 80 days of age. Nonstress plasma corticosterone levels were determined fluorometrically in serial blood samples obtained from a tail vein at 4-h intervals for 44-h periods, 3 and 10 weeks after surgery. At 3 weeks after surgery, blinded and intact rats demonstrated comparable rhythms in corticosterone levels. At 10 weeks, steroid fluctuations in individual blinded rats still had an approximate 24-h periodicity. However, these fluctuations were no longer synchronized with the light-dark cycle or with those of other rats. These findings suggest that rats blinded as adults have a free-running pituitary-adrenal circadian rhythm.

Animals↗