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Biomedical subjects

S Hamilton

Publications and source records attributed to S Hamilton.

At least 91 records · Page 5Linked to original sources
PubMed1988

Fatty acid activation of protein kinase C: dependence on diacylglycerol.

The kinetics of activation of protein kinase C by oleic acid have been reinvestigated, using highly purified preparations of the rat brain and bovine spleen enzymes. Activation of both enzymes by oleic acid is enhanced dramatically by diolein, contrary to previous reports. In the presence of 9.7 microM diolein, the concentrations of oleic acid required for half-maximal activation are 5 microM and 9 microM for the rat brain and bovine spleen enzymes respectively, indicating that the system is much more sensitive to activation by fatty acids than previously recognized. Both enzymes also exhibit a pronounced lag in the activation at low concentrations of oleic acid. The kinetics of activation are very similar to those reported by Hannun et al. (J. Biol. Chem 260, 10039-10043), who characterized the activation of the rat brain enzyme by mixed micelles containing Triton X-100, phosphatidylserine and diolein.

Animals↗
PubMed1988

Characterization of the sulfonylurea receptor on beta cell membranes.

Specific, high affinity sulfonylurea receptors were characterized on membranes of an insulin-secreting hamster beta cell line (HIT cells). Saturable binding of the sulfonylurea, [3H]glyburide, was linear up to 0.8 mg/ml membrane protein. Scatchard analysis of equilibrium binding data at room temperature indicated the presence of a single class of saturable, high affinity binding sites with a Kd of 0.76 +/- 0.04 nM and a Bmax of 1.09 +/- 0.13 pmol/mg protein, n = 9. The insulin secretory potency of glyburide, glipizide, tolbutamide, tolazamide, and carboxytolbutamide was compared to the ability of these ligands to displace [3H]glyburide from the sulfonylurea receptor. Tolbutamide, tolazamide, and glipizide demonstrated reasonable agreement with ED50 values of 15 microM, 3 microM, and 30 nM and Ki values of 25.3 microM, 7.2 microM, and 45 nM, respectively. The inactive tolbutamide metabolite, carboxytolbutamide, at the highest concentration tested, only partially displaced [3H]glyburide from the receptor and was a very poor secretagogue. At 37 degrees C the affinity of [3H]glyburide binding, Kd = 2.0 nM, was similar to the ED50 of 5.5 nM when the free glyburide concentrations were corrected for binding of the drug to albumin. These studies suggest that sulfonylureas initiate their biologic effect through a high affinity, specific interaction with sulfonylurea receptors on the beta cell membrane.

ATP-Binding Cassette Transporters↗
PubMed1988

Precursor amino acid concentrations in normal weight bulimics and normal controls.

1. CNS serotonergic neurotransmission has been implicated in the control of appetitive behavior. The ratio of plasma tryptophan (TRP) to other large neutral amino acids (LNAA) is believed to regulate CNS serotonin (5-HT) synthesis. 2. After an overnight fast, plasma TRP ratios were determined in 23 normal weight bulimics and 7 normal controls. 3. All subjects were assessed for mood disorder using a SADS interview and Beck Depression ratings. 4. There was no significant difference in TRP ratios between bulimics and normal controls. TRP ratios in depressed bulimics were not significantly different from those of nondepressed bulimics. 5. Potential abnormalities in CNS serotonergic function in bulimics are not reflected in decreased baseline TRP ratios. Further investigation of the dynamic serotonergic system may prove fruitful. 6. Reduced availability of tryptophan for conversion to serotonin is not likely to be the postulated biological abnormality common to both depression and bulimia.

Adult↗
PubMed1988

Chronic stress and coping styles: a comparison of male and female undergraduates.

Male and female coping behaviors were compared in order to test the theory that men use instrumental coping strategies more frequently than women, who are thought to use emotion-focused coping solutions. We interviewed 51 female and 39 male first-year undergraduates by telephone three times a week for 8 weeks, using an inventory developed for 28 chronic stressors. Analyses of variance were used to test gender differences in frequency of daily stressors, concomitant perceptions of stress, and utilization of problem-solving behaviors. The majority of analyses showed no gender differences. The implications of these findings are discussed in light of cultural expectations.

Adaptation, Psychological↗
PubMed1988

Esophageal leiomyoma arising in an epiphrenic diverticulum.

A 32-year old woman was found at surgery to have an esophageal leiomyoma arising within an epiphrenic diverticulum. These uncommon conditions may rarely occur together, causing difficulty in diagnosis of the leiomyoma. Other neoplasms may also arise in an epiphrenic diverticulum and should be borne in mind in this situation.

Adult↗
PubMed1988

Medial talo-calcaneal coalition. Case report.

Medial talo-calcaneal coalition is an uncommon developmental anomaly consisting of a bony projection arising from the postero-medial aspect of the sustentaculum tali, which may articulate with another bony projection from the medial aspect of the talus. Fibrous, cartilaginous or bony ankylosis may occur. It usually presents in adolescents, and causes pain following exercise. It may cause a lump, and can predispose to flat foot and early osteoarthrosis. This condition is easily overlooked on routine views of the ankle, and may require oblique views and tomography for its detection and clarification.

Adolescent↗
PubMed1987

Primary non-obstructive megaureter in adults.

Primary non-obstructive megaureter is rarely first diagnosed in adult life. The clinical and radiographic findings in 11 adults presenting with this condition are reviewed. The commonest complaint was pain. In all cases the diagnosis was suggested by intravenous urography, which was usually the initial diagnostic test. Confirmation was aided chiefly by micturating cystography and retrograde pyelography. Cystoscopy was normal. The radiologist can make an early diagnosis in this condition, which requires no treatment, in the absence of complications.

Adult↗
PubMed1987

Increased intrinsic pumping of intestinal lymphatics following hemorrhage in anesthetized sheep.

The return of fluid and protein to the bloodstream by the lymphatic circulation may play an important role in reconstituting intravascular volume following hemorrhage. In this study, we have defined the lymph-flow changes that occur in cannulated mesenteric lymphatics following a 25% blood loss in anesthetized sheep and investigated the effects of hemorrhage on the intrinsic contractile activity (lymph pumping) of these vessels in vivo using a new model system. The removal of 25% of the calculated blood volume resulted in increases in lymph flow over a 6-hour period, with peak changes to 3.5 times the prebleed levels. Systemic arterial pressures dropped to roughly 50% of control values immediately following the bleed and returned to control in 3 hours. To directly assess the effects of hemorrhage on lymphatic pumping, a segment of intestinal lymphatic was isolated from all lymph input and supplied with fluid from a reservoir. While there was no net pressure driving fluid through the duct, a transmural distending pressure was applied to the vessel, which stimulated resting lymphatic contractions and fluid pumping. A 25% blood loss resulted in increased activity of the lymph pump; up to 6 times more fluid was propelled through this "isolated" vessel in vivo than in similar preparations in sheep that were not bled (p less than 0.01). Measurements of fluid pulse pressures in this preparation indicated increased pumping frequency and/or force after hemorrhage compared with prebleed levels. We conclude that lymphatic contractile activity is stimulated after a blood loss independent of changes in lymph formation and speculate that this mechanism may play an important role in the reexpansion of the vascular space.

Animals↗
PubMed1987

Surgical treatment of acne scars.

Dermatologists and their plastic surgical colleagues treating acne vulgaris and its sequelae have an effective arsenal of anti-acne preparations to inhibit and avoid many of the long-term, cosmetically deforming effects of severe inflammatory acne. It is incumbent upon the physician participating in the care of the early and late sequelae of acne vulgaris to provide timely surgical therapy for those lesions requiring surgical drainage, extraction, or scar revision, while maintaining appropriate medical therapy for those areas of the skin still at risk to develop active disease.

Acne Vulgaris↗
PubMed1987

Skin morphology and function.

Proper understanding of the cause, nature, and treatment of diseases affecting the skin requires an intimate knowledge of the anatomy and physiology of normal as well as pathologic skin. This article thus lays the groundwork for the discussions of specific pathologic conditions that follow in this issue.

Adipose Tissue↗
PubMed1985

Profile of the oppositely acting enantiomers of the dihydropyridine 202-791 in cardiac preparations: receptor binding, electrophysiological, and pharmacological studies.

Receptor binding, electrophysiological, and inotropic effects of the pure dihydropyridine enantiomers (+)S202-791 and (-)R202-791 were studied in cardiac preparations. The KI for (+)S202-791 binding correlated with the ED50's for an increase in contractile force and an increase in calcium current, the latter effect occurring at depolarized as well as resting holding potentials. The KI for (-)R202-791 binding was much lower than the IC50's for inhibition of calcium current measured at holding potentials of -80 or -90 mV and a negative inotropic effect, but correlated closely with the IC50 for inhibition of calcium current measured at -30 mV. Thus, (+)S202-791, is a voltage independent calcium channel activator and (-)R202-791 is a voltage dependent calcium channel inhibitor.

Animals↗
PubMed1985

Pelvic digit.

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Humans↗