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Biomedical subjects

P Meisel

Publications and source records attributed to P Meisel.

At least 55 records · Page 3Linked to original sources
PubMed1981

[Photodynamic injuries of erythrocytes during illumination with blue light in patients with icterus neonatorum].

In a prospective study the influence of intermittent phototherapy (with and without riboflavin substitution) on red blood cells of newborns was examined in vivo. Hemoglobin concentration and hematocrit values did not differ significantly between treated patients and untreated controls. However, after illumination during 24 h (real exposure time 12 h) with a highly effective NC 400-04 Narva lamp, we found a completely reversible decrease of the mean erythrocyte diameters. The changes were statistically significant at the 8th day of life and disappeared up to the 16th day after birth. Riboflavin administration immediately before starting the phototherapy was able to prevent this phenomenon. The glutathione reductase activity (method by BEUTLER) was not affected, neither by phototherapy alone nor by riboflavin administered additively. As a conclusion of our results we would like to recommend a general riboflavin substitution in newborns after phototreatment.

Erythroblastosis, Fetal↗
PubMed1980

Effect of theophylline on the riboflavin-sensitized photodegradation of bilirubin in vitro.

Under in vitro conditions, theophylline accelerates the rate of bilirubin photodestuction sensitized by riboflavin, but does not do so in absence of this dye. The effect depends on the concentrations of theophylline and/or riboflavin, on the bilirubin/albumin ratio, and seems to implicate bilirubin unbound to serum albumin. Possible causes of the theophylline action and clinical implication regarding thephototherapy of neonatal jaundice are discussed.

Bilirubin↗
PubMed1980

Kinetics of self-sensitized and riboflavin-sensitized photodegradation of bilirubin.

Kinetics of self-sensitized or riboflavin-sensitized photodestruction of bilirubin in albumin containing solutions follows equations of the Stern-Volmer type, which resemble expressions of enzyme catalyzed reactions. The dependence of quantum yields of bilirubin decay on substrate concentration, bilirubin/albumin ratio, and riboflavin concentration is estimated and described in terms of such equations. The ratios of kinetic constants obtained in this way are discussed and related to clinical experiences regarding the phototherapy for the treatment of neonatal hyperbilirubinaemia.

Bilirubin↗
PubMed1979

[Behavior of the erythrocyte glucose-6-phosphate dehydrogenase in patients with functional thyroid disorders and in hyperthyroxinemic rats].

This paper deals with the activity of glucose-6-phosphate dehydrogenase in patients with hyper- and hypothyroidism as well as in hyperthyroxinaemic rats. The activity of glucose-6-phosphate dehydrogenase is enhanced in red blood cells of hyperthyreotic patients and hyperthyroxinaemic animals. The activity will be decreased to normal range in patients by administration of antithyreotic drugs, such as thiamazole. Patients with hypothyroidism exhibit decreased enzymatic activity. It is suggested that thyroid hormones stimulate the HMP-shunt in red blood cells as a defence mechanism against additional oxidative stress.

Animals↗
PubMed1978

[Determination of residual bilirubin binding capacity in the serum of newborn infants using bromphenol blue].

In serum specimens collected from premature infants the residual bilirubin binding capacity was determined by a direct spectrometric method using bromphenol blue. The bindingin capacity determined in this way is strongly correlated to the serum bilirubin level. Changes in binding capacity are shown during the first 16 days of life. Experiments on model sera show the dependence of binding capacity for bromphenol blue on the ratio albumin/bilirubin. The results are discussed with respect to the urgency of blood exchange transfusions preventing danger of kernicterus.

Bilirubin↗
PubMed1978

Photodegradation of bilirubin as enhanced by photosensitizers in vitro.

Photosensitizers such as methylene blue or riboflavin enhance the rate of bilirubin photodegradation in vitro. This effect is studied with respect to dose-response and time-response relationships, the influence of concentrations of bilirubin and albumin, and the oxygen consumption. The results are discussed in view of the probability that the effects described also occur in vivo and that riboflavin supplementation to neonates could improve the phototherapy of neonatal hyperbilirubinaemia.

Bilirubin↗
PubMed1977

[Studies on the mechanism of action of vascular spasmolytics. 3. Effect of nitroprusside sodium, nitroglycerin, prenylamine and verapamil on the fluoride-induced contracture of the isolated coronary artery].

On isolated coronary arteries of cattle, nitroprusside-sodium, nitroglycerol, prenylamine, and verapamil were studied for their spasmolytic effects on a contracture induced by fluoride ions. With this contracture model, which is independent of extracellular calcium, nitroprosside-sodium and nitroglycerol showed strong spasmolytic action. Verapamil proved ineffective, and the effectiveness of prenylamine was strongly reduced. The results lend support to earlier findings suggesting that nitroglycerol and nitroprusside-sodium are endowed with a relaxation mechanism different from that of verapamil and analogously acting compounds.

Animals↗
PubMed1977

[Experiments on the mechanism of action of vascular spasmolytics. 4. Effect of nitroprusside sodium, nitroglycerin, prenylamine and verapamil on the calcium uptake of microsomes of the smooth bascular muscles].

Nitroprusside-sodium, nitroglycerol, and verapamil had no effect on the calcium uptake by microsomes from the carotid artery of cattle. Prenylamine reduced the passive binding and the active uptake and released already bound calcium. The basal Mg-dependendent ATPase and Ca-stimulatable Mg-ATPase were inhibited by prenylamine.

Animals↗
PubMed1976

Some properties of adenosine deaminase from vascular smooth muscle and its inhibition by various vasodilators.

Because of some uncertainties still existing about the role of adenosine deaminase in the drug-influenced adenosine breakdown, the authors isolated this enzyme from vascular smooth muscle and studied the inhibition of its activity by some vasodilating drugs. The adenosine deaminase was purified 360-fold from bovine carotid artery by means of (NH4)2SO4-precipitation, heat treatment, and gel filtration. This enzyme behaves in a similar way as preparations of the same enzyme from other tissues in respect to pH-dependence and Michaelis constant. The vascular enzyme is inhibited by dipyridamole and trapymine in a competitive manner, hexobendine and lidoflazine are without any effect. The results lead to the conclusion that the inhibition of vascular adenosine deaminase does not constitute the sole cause of the adenosine-potentiating effect of the vasodilating drugs studied.

Adenosine Deaminase↗
PubMed1976

[Experments on the mechanism of action of vascular spasmolytic agents. I. Effect nitroprusside sodium, nitroglycerine, prenylamine and verapamil on the arrested potassium contracture of isolated coronary arteries].

On the potassium contracture of isolated coronary arteries of cattle, the relaxation effected by calcium depletion can be blocked by lanthanum ions. The contracture persisting in calcium-free solution (arrested potassium contracture) is used to differentiate the sites of attack of spasmolytics. Verapamil and prenylamine are ineffective in this contracture model. By contrast, nitroprusside sodium and nitroglycerol as before act spasmolytically. Thus, both groups of drugs act through basically different sites. The findings are consistent with the hypothesis that the spasmolytic action of verapamil and prenylamine is based on a blockade of calcium influx. For nitroprusside sodium and nitroglycerol such a mechanism on the arrested potassium contracture has to be ruled out.

Animals↗
PubMed1976

[Experiments on the mechanism of action of vascular spasmolytic agents. II. Action of nitroprusside sodium, nitroglycerin, prenylamine and verapamil on the lanthanum contracture of isolated coronary arteries].

On isolated coronary arteries of cattle, lanthanum causes after preceding calcium depletion by EGTA a contracture which is independent of the presence of extracellular calcium. Nitroprusside sodium and nitroglycerol act on this contracture strongly relaxing in the same concentrations that were active on the potassium contracture. In contrast, a very low spasmolytic effect is demonstrable for verapamil on the lanthanum contracture, and prenylamine is without any statistically significant influence. Nitroprusside sodium and nitroglycerol and act by a mechanism entirely different from that of verapamil and prenylamine.

Animals↗