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Biomedical subjects

D Sharp

Publications and source records attributed to D Sharp.

34 records · Page 2Linked to original sources
PubMed1979

Dissociation of active from immobility components of sexual behavior in female rats by central 6-hydroxydopamine: implications for CA involvement in sexual behavior and sensorimotor responsiveness.

Ovariectomized female rats were given a hormone treatment (2 X 8 micrograms/kg estradiol benzoate) that normally supports only low levels of lordosis responding and no soliciting behavior in tests with sexually active males. When subjected to an intraventricular 6-hydroxydopamine (6-OHDA) procedure (with pargyline pretreatment) that produced 85% and 95% depletions of caudate dopamine and cortical norepinephrine respectively, these females exhibited a dramatic increase in the intensity and frequency of lordotic responding but no soliciting behavior over 3 weekly tests. The increase in lordosis was not due to a drug- or stress-induced release of adrenal progesterone, since dexamethasone suppressed the progesterone levels, as documented by radioimmunoassay, but not the higher receptivity of 6-OHDA treated females. In other ovariectomized females given a hormone regimen (2 X 50 micrograms/kg estradiol benzoate plus 500 micrograms progesterone) that supported maximal levels of lordosis and soliciting, the same 6-OHDA treatment prolonged the average duration of lordosis while actually decreasing the incidence and duration of soliciting. The hypothesis is put forward that the differential effects of interfering with catecholamine, and more likely dopamine function on the soliciting and lordosis components of female sexual behavior might best be understood as a dissociation between mutually antagonistic behavior patterns such that responsiveness involving active orientation and forward locomotion is suppressed, whereas responses requiring immobility are augmented.

Animals↗
PubMed1979

Intestinal bacterial metabolism of protein and bile acids: role in pathogenesis of hepatic disease after jejuno-ileal bypass surgery.

Jejunal bacterial colonization and intestinal metabolism of bile acids and protein by bacteria have been investigated in 12 patients with abnormal liver histology following jeujno-ileal bypass surgery for obesity. Aerobic and/or anaerobic colonic flora was present in jejunal aspirates from 8 of 12 bypass patients, but in none of the controls. Intestinal protein metabolism and bile acid deconjugation (measured by urinary indican excretion and 14C-glycocholic acid breath test) was significantly enhanced in bypass patients. Intestinal bacterial overgrowth, with abnormal intestinal metabolism by bacteria of ingested nutrients and bile acids, could contribute to hepatic disease after bypass surgery via the production of endogenous hepatotoxins.

Adult↗
PubMed1979

Radiation-induced mitotic and meiotic aneuploidy in the yeast Saccharomyces cerevisiae.

A number of genetic systems are described which in yeast may be used to monitor the induction of chromosome aneuploidy during both mitotic and meiotic cell division. Using these systems we have been able to demonstrate the induction of both monosomic and trisomic cells in mitotically dividing cells and disomic spores in meiotically dividing cells after both UV light and X-ray exposure. The frequency of UV-light-induced monosomic colonies were reduced by post-treatment with photoreactivity light and both UV-light- and X-ray-induced monosomic colonies were reduced by liquid holding post-treatment under non-nutrient conditions. Both responses indicate an involvement of DNA-repair mechanisms in the removal of lesions which may lead to monosomy in yeast. This was further confirmed by the response of an excision-defective yeast strain which showed considerably increased sensitivity to the induction of monosomic colonies by UV-light treatment at low doses. Yeast cultures irradiated at different stages of growth showed variation in their responses to both UV-light and X-rays, cells at the exponential phase of growth show maximum sensitivity to the induction of monosomic colonies at low doses whereas stationary phase cultures showed maximum induction of monosomic colonies at high does. The frequencies of X-ray-induced chromosome aneuploidy during meiosis leading to the production of disomic spores was shown to be dependent upon the stage of meiosis at which the yeast cells were exposed to radiation. Cells which had proceeded beyond the DNA synthetic stage of meiosis were shown to produce disomic spores at considerably lower radiation doses than those cells which had only recently been inoculated into sporulation medium. The results obtained suggest that the yeast sustem may be suitable for the study of sensitivities of the various stages of meiotic cell division to the induction of chromosome aneuploidy after radiation exposure.

Aneuploidy↗
PubMed1979

Detection of mitotic and meiotic aneuploidy in the yeast Saccharomyces cerevisiae.

A number of genetic systems are described which involve the use of the yeast Saccharomyces cerevisiae. The systems may be used to detect the production of aneuploid cells produced during both mitotic and meiotic cell division in the presence of genetically active chemicals. During mitotic cell division, monosomic colonies (2n - 1) may be detected by plating upon selective medium. Increases in such monosomic colonies are produced by exposure of cells to a number of chemical mutagens such as ethyl methane-sulfonate and mitomycin C. More importantly, monosomic colonies are also induced by nonmutagens such as sulfacetamide and saccharin, which suggests that such chemicals are capable of inducing aneuploidy (aneugenic) in the absence of mutagenic activity. Genetic analysis of aneuploid colonies produced on nonselective medium indicate that at least a proportion of the monosomic colonies were the result of mitotic nondisjunction. During meiotic cell division, disomic cells (n + 1) produced by chromosome nondisjunction may be detected by plating on selective media. The frequency of disomic cells has been shown to increase after exposure to p-fluorophenylalanine.

Aneuploidy↗
PubMed1978

Selective enhancement of the lordotic component of female sexual behavior in rats following destruction of central catecholamine-containing systems.

Ovariectomized female rats received two intraventricular injections of 200 microgram of 6-hydroxydopamine (6-OHDA), a treatment which produced 66% depletion of telencephalic norepinephrine and 53% depletion of telencephalic dopamine. Compared to vehicle-injected controls, 6-OHDA-treated animals showed increased lordosis scores when treated with ovarian hormones. This effect was potentiated by additional treatment with 100 mg/kg alpha-methyl-p-tyrosine (AMT), a catecholamine synthesis inhibitor. Besides showing increased frequency and intensity of lordosis, animals treated with both 6-OHDA and AMT retained the lordotic posture significantly longer after the male dismounted than animals given either treatment alone or vehicle controls. The enhancement of lordosis following CA depletion was not prevented by a series of dexamethasone treatments which caused a marked suppression in adrenal steroid (corticosterone) levels. This suggests that normal adrenal function is not a prerequisite for the observed enhancements. It was concluded that the lordotic response is inhibited by the activity of a catecholamine system. Soliciting behavior (hop-darting) was not enhanced by any treatment, suggesting that catecholamine activity has an inhibitory influence on the stop component of sexual behavior, but not on the whole copulatory pattern.

Animals↗
PubMed1977

The endothelium: roles in thrombosis and hemostasis.

The renewed interest in endothelial function is based partly on success with tissue culture of endothelial cells. Endothelium functions primarily in the control of blood vessel wall permeability and in the provision of a blood-compatible lining surface. Recent findings indicate that endothelial cells are active metabolically in ways that may help prevent thrombosis. Endothelium actively degrades several different vasoactive compounds that circulate in blood and that can serve as platelet-aggregating agents. Endothelium also contains an inhibitor of platelet function and an activator of plasminogen, both of which can be released from the cell in response to appropriate stimuli. While intact endothelium functions primarily in prevention of thrombosis, damaged endothelium can contribute greatly to thrombus formation. Release of prostaglandins, adenine nucleotides, and other intracellular components from damaged endothelium can enhance platelet aggregation. Damaged endothelium may not function effectively in removal of vasoactive agents and may not release effective quantities of the inhibitor of platelet function or the activator of plasminogen. Altered endothelium exhibits tissue-factor activity, which can activate the extrinsic blood coagulation-system cascade. Finally, altered endothelial cells may contract and expose basement membrane to blood, thus enhancing thrombosis.

Blood Coagulation↗
PubMed1970

A comparison of monovalent Hong Kong influenza virus vaccine with vaccines containing only pre-1968 Asian strains in adult volunteers. A report to the Medical Research Council Committee on Influenza and other Respiratory Virus Vaccines.

A total of 1601 adult industrial workers were vaccinated with either monovalent inactivated vaccine of the Hong Kong strain of influenza A virus, or with polyvalent vaccine containing only pre-1968 Asian viruses. Serological investigations on a random sample of volunteers showed that 53/56 (95%) given Hong Kong vaccine developed a significant rise in specific haemagglutination-inhibiting antibody; final titres were 1/48 or greater in 39 (70%) and the GMT (geometric mean titre) was 96.5. After polyvalent Asian vaccine, 40/67 (60%) also produced antibody against Hong Kong virus, but only 21 (31%) had final titres of 1/48 or above, and the GMT rose only to 14.1. An intranasal spray of the Hong Kong vaccine in addition to injected Asian vaccine gave no additional increase in antibody.Each type of vaccine stimulated a recall of pre-existing antibody against Asian viruses. The possible significance of heterologous responses to the two vaccines is discussed.The incidence of clinical influenza in the trial population was sporadic, and the infection rates were too low to allow any accurate estimate of the protective efficiency of the two vaccines.

Adolescent↗
PubMed1969

Linguistic structure and transposition.

Transfer of a learned discrimination along the size dimension was studied in groups of American and African tribal children. The language spoken by the African children contains an asymmetry in the expression of size comparisons that is not present in English. Contrary to theories of linguistic mediation of choice behavior, transfer choices were not related to the differing linguistic patterns; however, initial choices and post-test descriptions of choices were so related.

Child↗
PubMedDate not supplied

Behind the wall.

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Delivery of Health Care↗