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Biomedical subjects

M Steiner

Publications and source records attributed to M Steiner.

At least 415 records · Page 23Linked to original sources
PubMed1982

Detailed analysis of estrous-related changes in wheel running and self-stimulation.

Previous studies have demonstrated that a number of behaviors change their probability of occurrence during the estrous cycle. Wheel running is known to show estrous-related changes while reports upon intracranial reinforcement (self-stimulation, ICS) have been equivocal. The present studies examined both behaviors to further resolve the underlying behavioral determinants of these estrous effects. Data for wheel running and intracranial self-stimulation behaviors of adult female Holtzman rats were collected nightly on a minute by minute basis across the estrous cycle. It was found that: (a) both behaviors showed significant estrous-related changes in frequency; (b) the two behaviors occurred in discontinuous episodes (bursts) during the dark phase of the diurnal cycle; and (c) of three burst parameters (number/session, average length, rate of response), number proved the best predictor of estrous-related behavioral change. Burst number may reflect an important motivational parameter underlying estrous-related changes in behavior.

Animals↗
PubMed1982

Synthetic byproducts of tocopherol oxidation as inhibitors of platelet function.

Vitamin E and its fully oxidized form tocopherol quinone are known inhibitors of platelet aggregation. Previous results from our laboratory have shown that the quinone was approximately equal in effectiveness to vitamin E. A recent report of a far greater inhibitory activity of the quinone produced by nitric acid oxidation of vitamin E prompted this investigation. Our studies show that the unusually high inhibition of platelet aggregation, release and cyclooxygenase activity associated with nitric acid oxidized vitamin E is due to byproducts of the oxidation process and not due to tocopherol quinone. Treatment of vitamin E acetate, a substance of mild effect on aggregation and arachidonate metabolism of platelets, with nitric acid did not produce tocopherol quinone but exerted as potent an inhibition as oxidized vitamin E. We conclude that nitric acid oxidation is unsuitable for preparation of tocopherol quinone unless the latter is carefully isolated. Oxidation with permanganate proved to be an alternate method without these difficulties.

Arachidonic Acid↗
PubMed1982

Platelet-associated complement C3 in immune thrombocytopenic purpura.

Platelet-associated C3 (PA-C3) was measured with a quantitative immunofluorescence assay. With this assay, PA-C3 levels were determined for 78 normal volunteers, 30 patients with immune thrombocytopenic purpura (ITP), and 20 patients with nonimmune thrombocytopenias. Platelet-associated IgG (PA-IgG) levels were also measured with our standard quantitative immunofluorescence assay. All patients with nonimmune thrombocytopenias and ITP in remission had normal PA-C3 levels. Twenty-four patients with active ITP were classified into 3 groups: 9 (38%) with increased PA-IgG and normal PA-C3 levels, 10 (42%) with elevated PA-C3 and PA-IgG levels, and 5 (20%) with increased PA-C3 values only. A direct correlation was found between PA-C3 and PA-IgG levels. PA-IgG levels were higher in the group of patients with elevated PA-C3 levels than in those with normal values. Platelet survival studied showed reduced survival times of 1.5--2.5 days for the 5 patients with elevated PA-C3 levels only. Elevated PA-C3 levels returned to normal in 7 ITP patients whose platelet counts increased in response to corticosteroid therapy or to splenectomy. Therefore, PA-C3 and PA-IgG assays can be used to identify patients with ITP, to follow their response to therapy, and to classify them into immunologic subgroups similar to red cell classification by Coombs' testing in immune hemolytic anemia.

Adolescent↗
PubMed1981

Vitamin E changes the membrane fluidity of human platelets.

The in vitro addition of alpha-tocopherol to human platelets was evaluated by measuring fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene-labeled platelets and platelet membranes. The fluorescence anisotropy was decreased compared to non-vitamin E-loaded control platelets at temperatures less than 24--27 degrees C but was increased above 27 degrees C. The curve relating temperature to this parameter remained monophasic in alpha-tocopherol-enriched platelets but exhibited a steeper slope, indicative of increased flow activation energy. The latter was linearly related to platelet alpha-tocopherol levels. A possible role of membrane proteins in the mechanism of this change was suggested by the increased anisotropy which liposomes prepared from platelet membrane lipids displayed when they were located with alpha-tocopherol. This modulation of 'apparent membrane microviscosity' by alpha-tocopherol may play a role in the normal effect of this vitamin on human cells.

Blood Platelets↗
PubMed1981

A specific laboratory test for the diagnosis of melancholia. Standardization, validation, and clinical utility.

Four hundred thirty-eight subjects underwent an overnight dexamethasone suppression test (DST) to standardize the test for the diagnosis of melancholia (endogenous depression). Abnormal plasma cortisol concentrations within 24 hours after dexamethasone administration occurred almost exclusively in melancholic patients. The best plasma cortisol criterion concentration, above which a DST result may be considered abnormal, was 5 microgram/dL. The optimal dose of dexamethasone was 1 rather than 2 mg. Two blood samples obtained at 4 and 11 PM after dexamethasone administration detected 98% of the abnormal test results. This version of the DST identified melancholic patients with a sensitivity of 67% and a specificity of 96%. Baseline nocturnal plasma cortisol concentrations were not useful. Abnormal DST results were found with similar frequency among outpatients and inpatients with melancholia; but they were not related to age, sex, recent use of psychotropic drugs, or severity of depressive symptoms. Extensive evidence validates this practical test for the diagnosis of melancholia.

Adolescent↗
PubMed1981

[Dental caries in the cantons of Glarus and Waadt, 4 years and 8 years after the introduction of fluordized salt].

In 1955 for the first time 90 mg of fluoride was added to 1-kg domestic salt packages in Switzerland. This dosage turned out to be too low for an effective inhibition of caries. Later the fluoride level of salt for use in households, bakeries, canteens and restaurants was raised to 250 mg/kg in the cantons of Vaud (1970) and Glarus (1975). Average numbers of DMF-teeth of schoolchildren initially and after 4 years (canton of Glarus) and 8 years (canton of Vaud) of salt fluoridation (250 ppmF) show a reduction of caries experience. Decreases failed to appear only in age classes with initially low caries experience, the latter having been due to previous distribution of fluoride tablets.

Adolescent↗
PubMed1981

Percentages of lifetime caries experience retained by eight systems of partial DMF-recording.

Eight partial recording systems were compared. Averages of D(M)FS experiences retained by the different systems ranged from 81.0 to 93.6%. The percentages of D(M)FS experience retained varied when the systems were applied on different data on caries occurrence by surfaces. Most systems gave a fairly accurate assessment of the caries reduction in Norwegian schoolchildren due to war-time dietary restrictions.

Adolescent↗
PubMed1981

Selection of donor platelets for alloimmunized patients using a platelet-associated IgG assay.

A quantitative immunofluorescence platelet-associated immunoglobulins (PA-IgG) assay was used to detect alloimmunity to platelets in 8/12 multitransfused patients and to perform platelet crossmatching in the 8 alloimmunized patients. The correct separation of multitransfused patients into alloimmune and nonalloimmune groups was substantiated with chromium-51-labeled platelet survival studies. For 5 alloimmunized patients, compatible and incompatible donor platelets were demonstrated by PA-IgG crossmatching and were confirmed by platelet survival studies. With the other 3 alloimmunized patients, only studies with 5 of these incompatible donor platelets showed markedly reduced survival times on 4 occasions. PA-Igg compatible donor platelets survived 3.5-8.7 days, while PA-IgG incompatible platelets showed survival times of 0.1-2.4 days. Overall, PA-IgG testing correctly indicated survival results on 15/17 occasions (88%), whereas platelet aggregation, serotonin release, and lymphocytotoxicity testing showed correct predictions for only 41%-59% of the survival studies. PA-IgG testing predicted which times, thus indication patients with platelet-specific alloantibodies. the PA-IgG assay provides a sensitive method to detect platelet alloantibodies and to perform platelet crossmatching, which can complement HLA typing in the selection of donor platelets for alloimmunized patients.

ABO Blood-Group System↗