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Biomedical subjects

M Weiss

Publications and source records attributed to M Weiss.

At least 505 records · Page 28Linked to original sources

Identification of 5 alpha-androstane-3 alpha,17 alpha-diol in adrenal venous plasma of female possum (Trichosurus vulpecula).

Two hitherto unidentified C19 steroids were isolated from adrenal venous blood plasma of female possum (Trichosurus vulpecula). They were 5 alpha-androstane-3 alpha,17 alpha-diol and its isomer 5 beta-androstane-3 alpha,17 alpha-diol. The compounds were isolated and identified by fractionation on paper chromatograms and HPLC, followed by gas chromatography-mass spectrometry after conversion to trimethylsilyl ethers. In adrenal venous plasma the concentrations of the 5 alpha-isomer ranged from 24-71 micrograms/100 ml, 47.5 +/- 7.7 (mean +/- SEM) and of the 5 beta-isomer 1.5-9.3 micrograms/100 ml, 5.6 +/- 1.6 (mean +/- SEM). In peripheral plasma only the 5 alpha-derivative was detectable, the highest concentration being 0.97 microgram/100 ml. The reduced steroids were not detected in the plasma of a male possum, confirming previous in vitro evidence that reduced steroids are products of the adrenocortical special zone which is found only in the female.

Adrenal Glands↗

The role of radiation therapy in the management of childhood craniopharyngioma.

Between 1965 and 1986, 31 children were treated for craniopharyngioma at the Children's Hospital of Philadelphia. Total removal was attempted in all patients. Some patients received radiation therapy following subtotal removal. Of the patients whose first resection was subtotal, five received radiation and seven did not. Four of the 5 patients who were radiated (80%) are stable (median 89 months, range 42-155 months) and one recurred at 42 months, failed salvage with total removal, and subsequently died of disease. Of the seven who were not irradiated, all had recurrences (median 12 months, range 3-192 months) and one died of disease. Nineteen patients initially had total removal and none received adjuvant radiation. One patient died postoperatively. Of the 18 remaining patients, 6 had recurrences (median 24 months, range 7-100 months) and 12 (66%) are stable (median 42 months, range 9-133 months). One of these stable patients died of endocrine complications 24 months after initial surgery. Fourteen of the 31 patients recurred. Two died with recurrence and one required no further treatment. Eleven had second resections following initial surgical removal. Seven of these 11 went on to receive radiation and four did not. All seven who were radiated are stable (median 33 months, range 1-228 months); whereas 1 of the 4 who were not radiated recurred again at 18 months. This patient had a third resection followed by radiation therapy and is now stable at 20 months. After initial surgery (and before radiation, when given) 26 of 31 patients had panhypopituitarism, 4 had partial deficits, and 1 was normal. Severe diencephalic syndrome, loss of visual acuity, and intellectual deficits were no more frequent in patients treated with total removal, subtotal removal, and in patients who received radiation. We conclude that radiation has an important role following subtotal removal and for salvage treatment after initial surgery. Aggressive attempt at total removal does result in prolonged progression-free survival in some patients. Extensive resections may result in significant mortality and endocrine morbidity. This review suggests that subtotal removal and radiation results in outcomes at least as favorable as treatment with total removal alone.

Adolescent↗

Fibrin formation and platelet activation in patients with myocardial infarction and normal coronary arteries.

Coronary spasm is the mechanism most often postulated to explain the rare combination of myocardial infarction and angiographically normal coronary arteries, although the reported evidence for its role is circumstantial rather than conclusive. Whereas the importance of thrombosis in myocardial infarction is uncontested in the presence of significant coronary artery disease, there is little in vivo evidence for thrombosis in angiographically normal coronary arteries. Among 11 consecutive patients with acute myocardial infarction undergoing thrombolytic therapy with recombinant tissue plasminogen activator (rtPA) 3.2 +/- 0.7 h after onset of chest pain, and angiography 10.2 +/- 4.5 days later, three young men had normal coronary arteries. Their cases are documented electrocardiographically, enzymatically and angiographically. Mean plasma levels of fibrinopeptide A (FPA) and beta-thromboglobulin (BTG) were clearly elevated before and during rtPA therapy: FPA 52 +/- 41 ng ml-1, BTG 257 +/- 46 ng ml-1. They did not differ significantly from corresponding mean plasma levels in the eight patients with severe coronary artery disease: FPA 67 +/- 66 ng ml-1, BTG181 +/- 75 ng ml-1. We conclude that fibrin formation and platelet activation are probably equally important in the early hours of myocardial infarction, whether or not significant coronary artery disease is present.

Adult↗

Transcutaneous and liver surface PO2 during hemorrhagic hypotension and treatment with phenylephrine.

Transcutaneous PO2 (PtcO2) and liver surface PO2 (PIO2) were measured in six mongrel dogs during hemorrhagic shock, normotensive shock, and volume resuscitation. Normotension was produced during extreme hypovolemia by an infusion of phenylephrine. PtcO2 and PlO2 were compared to each other and to hemodynamic and oxygen transport variables. PtcO2 and PlO2 correlated well with cardiac index (CI) r = .71 and .86, respectively; n = 60) and with each other (r = .79; n = 60). Heart rate, mean arterial pressure (MAP), and PaO2) correlated less with PtcO2 or PlO2. During the normotensive shock period, PtcO2, PIO2, CI, oxygen delivery (DO2), and oxygen consumption (VO2) were all severely decreased, while PaO2 and MAP were normal and lactic acid concentrations were elevated. It was concluded that PtcO2 follows changes in PlO2 during hypotensive and normotensive low cardiac output shock in mongrel dogs. Low PtcO2 values are associated with low values of PlO2, DO2, VO2, and rising lactic acid concentrations in dogs. These animal data imply that low PtcO2 values encountered in clinical monitoring during anesthesia and surgery may correspond to decreased blood volume, blood flow, and PlO2.

Animals↗

First description of "Indian childhood cirrhosis" in a non-Indian infant in Europe.

The first female child of healthy German parents, breast-fed for 5 weeks, developed progressive abdominal distension due to hepatosplenomegaly at the age of 7 months and died from acute liver failure 3 months later. Histology showed destruction of liver architecture with extreme hepatocellular copper storage, characteristic of "Indian childhood cirrhosis" (ICC). The family received drinking water from a well via copper pipes. The copper level of the water was extremely elevated (430 and 5510 micrograms/l) so that exogenous copper intake during the first months of life may have induced the fatal liver disease, probably in association with an unproven genetic disposition. This is the first description of a case of ICC in a member of a non-Indian family in Europe.

Copper↗

Reduced neuroexcitatory effect of domoic acid following mossy fiber denervation of the rat dorsal hippocampus: further evidence that toxicity of domoic acid involves kainate receptor activation.

Domoic acid, an excitatory amino acid structurally related to kainic acid, has been shown to be responsible for the severe intoxication presented, in 1987, by more than one hundred and fifty people having eaten mussels grown in Prince Edward Island (Canada). Unitary extracellular recordings were obtained from pyramidal neurons of the CA3 region of the rat dorsal hippocampus. The excitatory effects of microiontophoretic applications of domoic acid and of the agonists of the two other subtypes of glutamatergic receptors, quisqualate and N-methyl-D-aspartate, were compared on intact and colchicine-lesioned sides. Similar to what has been previously found for kainate, the colchicine lesion of the mossy fiber projections induced a 95% decrease of the neuronal responsiveness to domoic acid, whereas the effect of quisqualate was unchanged and that of N-methyl-D-aspartate was only slightly decreased. These results provide further electrophysiological evidence that domoic acid is a potent agonist of kainate receptors and that it may produce its neuroexcitatory and neurotoxic effects, in the hippocampal CA3 region, through activation of kainate receptors located on the mossy fiber terminals.

Animals↗

Methylene blue potentiates vascular reactivity in isolated rat lungs.

A bolus injection of methylene blue (1 mg), a guanylate cyclase inhibitor, or aspirin (3 mg) in the isolated rat lung preparation had little or no effect on resting perfusion pressure under normoxic condition. In contrast, methylene blue markedly potentiated hypoxic vasopressor response (4-fold) when injected before or during the alveolar hypoxic stimulation. Hemoglobin also potentiated the hypoxic pressor response. Similarly, methylene blue or aspirin augmented the pressor responses to angiotensin II (0.1-1 microgram). The increased hypoxic response induced by methylene blue was immediate and sustained. Methylene blue, when added during hypoxia in the presence of aspirin, further augmented the response to hypoxia compared with the enhanced hypoxic response observed with aspirin alone. Our results suggest that, in addition to the role of cyclooxygenase products, the pulmonary vascular bed may be regulated by endothelium-dependent factors that can be antagonized directly or indirectly by methylene blue.

Angiotensin II↗

Monitoring of fibrin generation during thrombolytic therapy of acute myocardial infarction with recombinant tissue-type plasminogen activator.

Fibrinopeptide A (FPA) is a very sensitive marker of fibrin generation in vivo. Because an imbalance between thrombogenic and thrombolytic forces may be responsible for the failure to recanalize and for reocclusion of coronary arteries, such a marker could be of eminent value during thrombolytic treatment of acute myocardial infarction. Thirty-four consecutive patients with acute myocardial infarction (peak creatine kinase level, 1,869 +/- 1,543 IU/l) were treated with 100 mg recombinant tissue-type plasminogen activator (rt-PA) 3.1 +/- 1.1 hours after onset of chest pain. Angiography 12.5 +/- 6.1 days later revealed an 81% patency rate of the infarct-related vessel. FPA plasma levels (normal, 1.9 +/- 0.5 ng/ml) were 34 +/- 46 ng/ml on admission and 93 +/- 86 ng/ml (538 +/- 674% with respect to each patient's admission level) after 90 minutes of rt-PA infusion (p less than 0.01). In patients without evidence of reocclusion (including three primary failures), FPA levels fell under continuous heparin infusion to 6.7 +/- 9.7 ng/ml (24 +/- 33%, p less than 0.01) within 30 minutes and were 3.1 +/- 2.2 ng/ml (15 +/- 15%, p less than 0.01), 1.6 +/- 1.1 ng/ml (8 +/- 10%, p less than 0.01), and 2.5 +/- 3.0 ng/ml (12 +/- 16%, p less than 0.01) 30 minutes, 9 hours, and 21 hours, respectively, after completion of rt-PA therapy. Five patients sustained intermittent or permanent coronary reocclusion after primary thrombolytic success. Their early postlytic FPA levels (13-51 ng/ml) remained high or increased again despite adequate anticoagulation. FPA allows the monitoring of fibrin generation during acute myocardial infarction and thrombolytic therapy. Despite successful recanalization, fibrin generation is increased under rt-PA administration before anticoagulation. Patients under anticoagulation with postlytic FPA levels less than 5 ng/ml or below their admission value seem to be at low risk of reocclusion for several days. FPA levels that are persistently high or that increase again despite adequate anticoagulation indicate ongoing fibrin generation. However, whether FPA can indeed be considered a useful marker of reocclusion remains to be confirmed in a larger population of patients with acute myocardial infarction.

Coronary Angiography↗

Embolization in the treatment of epistaxis after failure of internal maxillary artery ligation.

Internal maxillary artery ligation is effective in treating epistaxis. Occasionally a patient may continue to hemorrhage after this procedure. Evaluation of postoperative angiograms reveals several factors accounting for the failure of internal maxillary artery ligation. These factors include incomplete ligation of vessels, alternative dominance of vessels, and reconstitution of flow through collaterals. Eleven such patients have been successfully treated with angiography and embolization. There was one complication of skin slough in the region of the columella. Embolization is a useful modality in the management of these difficult cases.

Adult↗

Contribution of alpha- and beta-receptors to ketogenic and lipolytic effects of norepinephrine in humans.

To assess the effects of alpha- and beta-adrenergic-receptor activation on ketone body kinetics and lipolysis in humans, five groups of overnight-fasted subjects were studied. Group 1 (n = 7) received norepinephrine (NE) to activate alpha- and beta-receptors, resulting in plasma NE concentrations of 1.5 +/- 0.19 ng/ml; group 2 (n = 7) received NE plus beta-blockade; group 3 (n = 7) NE plus alpha-blockade; group 4 (n = 6) NE plus alpha- and beta-blockade; and group 5 (n = 6) saline. Plasma insulin and glucagon concentrations were maintained constant by infusion of somatostatin with insulin and glucagon replacements. Infusion of NE for 170 min resulted in an increase in total ketone body production ([3-14C]acetoacetate infusions) to 8.5 +/- 1.3 vs. 3.9 +/- 0.6 mumol.kg-1.min-1 (P less than .01) in saline controls and in an increase in plasma free fatty acids (FFAs) to 1120 +/- 102 vs. 526 +/- 115 microM (P less than .01) in controls. alpha-Blockade during NE infusion enhanced the lipolytic effect of NE, because plasma FFA increased to 1981 +/- 204 vs. 1301 +/- 146 microM after 45 min (P less than .002), and the ketogenic effect was augmented (14.3 +/- 1.7 vs. 5.6 +/- 0.9 mumol.kg-1.min-1) after 60 min (P less than .001). In contrast, beta-blockade abolished the ketogenic and lipolytic effects of NE to those observed in saline controls. Combined alpha- and beta-blockade during NE infusion was without significant effect on ketone body kinetics and plasma FFA.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

Bioavailability of trapidil tablets.

Trapidil was given orally (200 mg, Rocornal dragees 100 mg) and intravenously (100 mg) to 12 healthy volunteers. Serum samples were analyzed for trapidil by HPLC. Complete bioavailability was obtained and a mean absorption time of 66.4 min was calculated using the method of curve moments.

Administration, Oral↗

Self development and self-conscious emotions.

In each of 2 studies, the mirror-rouge technique was used to differentiate children into those who showed self-recognition and those who did not. In Study 1, 27 children (aged 9-24 months) were observed in 2 experimental situations thought to differentially elicit fear and embarrassment behaviors. In Study 2, 44 children (aged 22 months) were seen in the situations of Study 1 and 3 additional contexts thought to elicit embarrassment behavior. The results of both studies indicate that embarrassment but not wariness was related to self-recognition.

Emotions↗

[Magnesium in cardiology. Fundamentals and potential indications].

The precise mechanism of magnesium effects on the heart is unknown. It may be based on calcium antagonism, prevention of vasospasm, enhancement of metabolic processes or inhibition of platelet aggregation. At present there are no established indications for parenteral magnesium administration. Probatory magnesium treatment can however be used in all tachyarrhythmias without major risk of adverse effects; in polymorphic ventricular tachycardia with QT prolongation (torsade de pointes) it can be recommended as a primary measure. Further investigations are needed to confirm the so far encouraging results of prophylactic intravenous magnesium administration in acute myocardial infarction.

Heart↗

[The osmotic gap in the diagnosis of alcoholic intoxication].

Sodium, urea, glucose and osmolality were determined in 50 hospitalized patients. Osmolality was calculated according to two different methods and compared with measured osmolality. Both methods showed equally close correlations (r = 0.87), and for clinical use we recommend the following simple formula: osmolality = 2 x sodium + glucose + urea. The two formulas studied were then used to calculate the osmolal gap (difference between measured and calculated osmolality) in 30 patients with ethanol intoxication, in order to estimate the blood alcohol concentration. For the equation: blood ethanol concentration (g/L) = osmolal gap/27 we found a very good correlation between calculated and measured ethanol levels (r = 0.95). Our data confirm previous reports that blood ethanol can be quickly and fairly exactly estimated by using the osmolal gap.

Alcoholic Intoxication↗

A light-dependent dicyclohexylcarbodiimide-sensitive Ca-ATPase activity in chloroplasts which is not coupled to proton translocation.

The early observation of light-dependent Ca-ATPase activity in chloroplast thylakoids [Avron, M. (1962) J. Biol. Chem. 237, 2011-2017] has been reinvestigated. It is demonstrated that in contrast to light-triggered Mg-ATP activity, Ca-ATPase activity is strictly dependent on delta microH+, the transthylakoid membrane electrochemical potential gradient, since (a) there is an absolute requirement for continuous illumination; (b) electron-transport mediators that catalyze proton uptake, like phenazinemethosulphate, methylviologen of ferricyanide, are essential and (c) uncouplers inhibit the activity. The Ca-ATPase activity is essentially unaffected by dithiols, but is inhibited by CF0-CF1 inhibitors including tentoxin, dicyclohexylcarbodiimide and antisera to CF1. Addition of Ca-ATP to thylakoids does not induce delta pH or delta psi (the electrical potential gradient) formation either in the light or following preillumination with dithiols, demonstrating that it is not coupled to proton translocation. It is also demonstrated that Ca-ATP or Ca-ADP does not induce a proton leak through CF0-CF1. It is concluded that the Ca-ATPase activity in chloroplast thylakoid reflects a partial reaction of ATP synthesis catalyzed by CF0-CF1, which is internally uncoupled from proton translocation but is dependent on energization by a transmembrane delta microH+.

Ca(2+) Mg(2+)-ATPase↗