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Biomedical subjects

G Ostermann

Publications and source records attributed to G Ostermann.

At least 73 records · Page 4Linked to original sources
PubMed1983

Central alpha 1-adrenoceptors and cardiovascular control in normotensive and spontaneously hypertensive rats.

Intracerebroventricular (i.c.v.) injections of AR-C 239 (30 micrograms/kg), a selective alpha 1-adrenoceptor blocking drug, did not modify the heart rate in normotensive control (without pretreatment), bilaterally vagotomized and beta blocked rats and in spontaneously hypertensive (SH) bilaterally vagotomized rats. Intracisternal (i.c.) administrations of AR-C 239 (30 micrograms/kg) however decreased the heart rate in normotensive beta blocked and in SH bilaterally vagotomized rats. The differential effect on heart rate of i.c.v. versus i.c. administration of AR-C 239 suggests a brainstem localization of the alpha 1-adrenoceptors involved. The binding of [3H]prazosin was significantly higher in homogenates from whole brain and in membranes from the cerebral cortex and hypothalamus of SH rats as compared to normotensive rats. In addition, the binding of [125I]BE 2254, a new iodinated radioligand of high specific radioactivity used to characterize alpha 1-adrenoceptors, was significantly increased in membranes from the NTS of SH rats. These results suggest that central alpha 1-adrenoceptors localized in the brainstem and in the hypothalamus and the cortex play a role in the control of vagal tone in normotensive rats and of sympathetic activity in SH animals. Thus, it is postulated that central alpha 1-adrenoceptors may participate in either the genesis or the maintenance of genetic hypertension.

Adrenergic alpha-Antagonists↗
PubMed1983

Studies on the stimulation of human blood platelets by semi-synthetic platelet-activating factor.

"Saturated" and "unsaturated" platelet-activating factor (PAF) obtained from ratfish liver oil were proved to exert potent stimulation on human blood platelets. Using 0.025 to 1.0 mumol/1 PAF a dose-dependent platelet aggregation in platelet-rich plasma was observed. During PAF-induced irreversible aggregation a 9 to 40% release of platelet bound serotonin occurred. The specific effect of PAF, however, seems to be limited to induce reversible aggregation since second wave of aggregation and serotonin release were suppressed by a combination of acetylsalicylic acid and an ADP scavenging system. Incubation of PAF for 30 min in plasma resulted in a 90% loss of its platelet aggregating power. Subthreshold concentrations of PAF enhanced the platelet aggregation triggered by suboptimal concentrations of ADP, epinephrine, or collagen. Vice versa non-aggregating concentrations of ADP, epinephrine, collagen, Ca-ionophore A 23,187, or arachidonic acid amplified PAF-induced platelet aggregation. The synergistic effect of PAF and other stimuli of blood platelet activation can be partly interpreted as a stimulating effect of PAF on the metabolization of arachidonic acid.

Adenosine Diphosphate↗
PubMed1983

Possible role of alpha 1- and alpha 2-adrenoceptors in the modulation of the sympathetic component of the baroreflex.

In anaesthetized and bilaterally vagotomized dogs, reflex bradycardia elicited by intravenous injection of noradrenaline was facilitated by AR-C 239, a new alpha 1-adrenoceptor blocking drug and inhibited by the alpha 2-adrenoceptor antagonist, yohimbine. Both alpha-blocking drugs were administered into the vertebral artery. In another group of bilaterally vagotomized dogs, unilateral electrical stimulation of the carotid sinus nerve induced a frequency-dependent decrease in mean blood pressure solely mediated through the sympatho-inhibitory component of the baroreflex. Administration of the alpha 1-adrenoceptor blocking drugs, AR-C 239 and prazosin (5 micrograms/kg) into the vertebral artery decreased basal mean blood pressure and increased depressor responses to the carotid sinus nerve stimulation, whereas the intracisternal injection of phenylephrine (30 micrograms/kg), a preferential alpha 1-agonist, increased mean blood pressure but inhibited the hypotension resulting from electrical stimulation. In addition, the injection into the vertebral artery of yohimbine (100 micrograms/kg), an alpha 2-adrenoceptor blocking agent which caused no change in mean arterial pressure, inhibited the decrease in the sympathetic component. In conclusion, these results suggest the possible participation of the two types of alpha-adrenoceptors in the modulation of the sympathetic component of the baroreflex: alpha 1-adrenoceptor stimulation could inhibit, whereas alpha 2-adrenoceptor activation facilitates the reflex activity in the sympathetic fibres.

Animals↗
PubMed1982

The effect of diamide (azodicarboxylic acid-bis-dimethylamide) on sulfhydryl group content, proteins, and the location of phosphatidylethanolamine in human blood platelets.

Treatment of human blood platelets with the thiol-oxidizing agent, diamide, causes rapid oxidation of glutathione and alterations in aggregation and release reaction. Moreover, cross-linking of proteins was observed. Three high molecular weight bands of 200 - 240 X 10(3) daltons and a band of 66 X 10(3) daltons were involved in this process. After reduction with dithiotreitol the normal pattern was received. In contrast to the erythrocyte, the cross-linking of platelet proteins was not accompanied by a reorientation of phosphatidylethanolamine in the membrane. Also a considerably smaller effect of diamide on platelet protein sulfhydryl group content was measured.

Azo Compounds↗
PubMed1982

Reconsideration of quantitative phospholipid analysis in human gel-filtered blood platelets.

In the literature the values for phospholipid content and the pattern of human gel-filtered platelets diverge considerably. In order to find the possible reasons for these discrepancies, the separation of plasma constituents from gel-filtered platelets and the influence of different extraction methods were reinvestigated. The critical point in phospholipid determination of platelets appeared to be the completeness of plasma lipid separation from platelets and not the extraction method. Avoiding contamination by plasma lipids the results with gel-filtered platelets correlated to that obtained with washed platelets.

Blood Platelets↗
PubMed1982

[Contact (prekallikrein) and fibrinolytic (plasminogen/antiplasmin value) system in the physiopathology of vascular complications of diabetes].

Both micro and macro-angiopathy involve interaction of blood vessel and plasma factors which may be altered in diabetes. Little is known concerning changes in contact and fibrinolysis factors as prekallikrein, plasminogen and fast antiplasmin in diabetes. We tested also the plasminogen/antiplasmin ratio in 151 diabetics and 64 normal subjects (18 to 74 years old). Our conclusion is:--the absence of correlation between the clinical characteristic of diabetes and prekallikrein level,--the decrease of plasminogen/antiplasmin ratio in complicated diabetes,--in complicated diabetes, correlation between antithrombin III, VIII factor and fibrinogen levels, perhaps, in relation with inflammation signs.

Adolescent↗
PubMed1982

[Predictive value of the exercise test for multivessel disease after initial myocardial infarction].

The extent of coronary artery disease after primary myocardial infarction is an important prognostic factor. The predictive value of exercise electrocardiography for multivessel disease was assessed by comparison with coronary angiography in a series of 100 patients. In the group of patients with primary anterior infarction (n = 48), 37.5% had positive exercise ECGs. Coronary angiography showed 62.5% single vessel disease. In multivessel disease, the sensitivity of exercise ECG was 78% and specificity 86%. The predictive value of a positive test was 78% and, for a negative test, 86%. In primary inferior infarction (n = 52), positive exercise ECGs were recorded in 48% of cases. Coronary angiography showed 48% multivessel disease. In multivessel disease, sensitivity of exercise ECG was 92% ans specificity 93%. The predictive value of a positive test was 92% and of a negative test, 93%. Therefore, exercise ECG gives a more precise prediction of the extent of coronary artery disease after primary inferior infarction than after primary anterior infarction. However, it is not an ideal guide for the choice of patient for coronary angiography because of its poor predictive value in cases of anterior infarction, and because of the high incidence of multivessel disease in patients with primary inferior infarcts. Nevertheless, it is of great prognostic value with regards to the eventual course of the coronary disease.

Adult↗
PubMed1979

[Cardiac manifestations of pheochromocytoma. Anatomo-clinical study].

Cardiomyopathy induced by catecholamines, first demonstrated in the animal is also observed in clinical medecine either after infusion by vasopressor drugs or during the course of pheochromocytoma. The clinical presentation is varied and may often deceive: acute coronary insufficiency, arrhythmia, heart failure, and, above all, cardiogemic shock. The authors emphasise the importance of considering the diagnosis of "adrenergic myocarditis" in such situations as well as in cases of pheochromocytoma, for which the only cure is ablation of the tumour.

Adrenal Gland Neoplasms↗
PubMed1979

[Preparation of human platelets without the use of anticoagulants and study of the effect of Catt on aggregation].

A method for the preparation of human blood platelets is presented which substitutes the use of anticoagulants by a gelfiltration for the removal of plasma calcium from native blood. In a second step the platelets are separated from the gel filtered blood by a centrifugation on a Ficoll density gradient. The anticoagulant-free platelets reveal an intact morphological feature and a normal aggregation behaviour in response to different aggregation inducers. It was found that in ADP-induced aggregation monophasic aggregation is shifted to a biphasic one by increasing concentrations of extracellular calcium.

Blood Platelets↗
PubMed1976

[Effects of a fully balanced synthetic diet on physical efficiency (author's transl)].

Nutrition with Biosorbin MCT and Biosorbin forte had no disadvantageous effect in any single case. There are no hidden risks if controlled by suitable tests to see whether the fluid supply is satisfactorily adjusted in the individual case. Subjective assessment from a felling of thirst is unreliable. Clinically and ergospirometrically there is an increase in capacity in almost all groups after taking the diet. This is all the more clear if the simultaneous reduction in body weight is taken into account. A direct effect of the elementary constituents of the diet is clearly recognizable. As a result of being rapidly absorbed and metabolized there are immediately available as energy suppliers and delay the threatening fall in efficiency. In almost all subjects an improvement in respiratory economy was achieved, the body weight approached the ideal weight and the relative efficiency improved.

Adult↗