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Biomedical subjects

R M Levy

Publications and source records attributed to R M Levy.

108 records · Page 6Linked to original sources
PubMed1978

An unusual location of an esteochondroma.

An unusual hip tumor was seen in a 13-year-old youth following a brief history of discomfort. The osteochondroma was differentiated from dysplasia epiphysealis hemimelica by its location.

Adolescent↗
PubMed1977

Genetic deficiency of the fourth component of complement (C4) in Wistar rats.

A chance observation has led to the discovery of single component complement deficiency in Wistar rats. During serial total haemolytic activity (CH50) determinations on 10 male rats, 2 were consistently found to have values 20% or less than that of the others. An additional 30 males (200--220 g) and 20 females (180--200 g) were screened for CH50 and the defect was found in 10 of the males but none of the females. Mixtures of sera of high and low haemolytic activity gave intermediate values between the two populations arguing against the presence of an inhibitor of the complement system. Single component analysis revealed the defect to reside in the fourth component of complement (C4). Highly purified human C4 completely reconstituted the haemolytic activity of the complement deficient rat serum. A linear relationship between C4 and CH50 titres was observed. Data from preliminary selective breeding experiments point toward an autosomal recessive mode of inheritance. Animals with intermediate values were observed indicating a gene dosage effect with which the heterozygote may be recognized.

Animals↗
PubMed1976

Ca2+ dependence of tension and ADP production in segments of chemically skinned muscle fibers.

Both ADP production and tension have been measured in segments of chemically skinned fibers contracting at different Ca2+ concentrations. Full mechanical activation occurred between pCa 7.00 and pCa 6.50. The total ATPase was due to both actomyosin and non-actomyosin ATPase. Actomyosin ATPase was observed at pCa 7.09 without accompanying tension. The Ca2+ dependence of tension was steeper than actomyosin ATPase. This finding implies some rate constants of the mechano-chemical cycle are Ca2+ dependent. Non-actomyosin ATPase was measured in fibers stretched beyond overlap of the thick and thin filaments. Sarcoplasmic reticulum was isolated and sarcoplasmic reticulum activity was measured in vitro under the same conditions as the single-fiber experiments. Non-actomyosin ATPase in the single fibers was found to be small compared to maximally activated actomyosin ATPase but larger than the ATPase that could be attributed to sarcoplasmic reticulum activity.

Actins↗
PubMed1976

Effect of vagotomy on anaphylaxis in the rat.

Vagatomy or atropinization protects rats from lethal anaphylaxis and histamine shock. These procedures do not significantly affect production of anaphylactic antibodies or release of histamine following induction of anaphylaxis. The response of the intestinal microvasculature during anaphylaxis is observed to consist of an early brief increase permeability followed by prolonged and irreversible damage. Cholinergic blockade abolishes the latter and markedly reduces deposition of colloidal carbon and immune complexes in the vessel. The possible relevance of these observations to development of chronic immunological vascular disease is discussed.

Anaphylaxis↗
PubMedDate not supplied

Proton nuclear magnetic resonance imaging of acute experimental cerebral ischemia.

To determine the efficacy of proton nuclear magnetic resonance (NMR) imaging in documenting acute ischemic infarction and to characterize the changes in these images during the first 24 hours following the ischemic insult, serial NMR imaging was performed in gerbils that had undergone unilateral carotid artery ligation. No significant changes in the signal intensity, T1 or T2 relaxation times were noted for either asymptomatic animals or the control hemisphere of symptomatic gerbils. There was a significant increase in T1 and especially T2 relaxation times and in both the relative signal intensity and Hf(v) for the ischemic hemisphere of symptomatic gerbils. These parameters appeared to increase linearly over 24 hours. The ischemic lesion first could be detected by NMR as early as 3 hours after carotid artery ligation, our earliest time point. The physiologic significance of these changes is discussed. These data suggest that NMR imaging may have significant diagnostic importance for acute cerebral ischemia and infarction in man.

Acute Disease↗
PubMedDate not supplied

Contrast-enhanced MR of cerebral arteritis: intravascular enhancement related to flow stasis within areas of focal arterial ectasia.

The authors present a case of probable amphetamine-induced cerebral arteritis in a 31-year-old man with AIDS, testicular carcinoma, and recurrent pneumocystis pneumonia. MR enhancement was demonstrated in areas of focal arterial ectasia, presumably due to slow flow. CT, MR, and angiographic findings were strikingly confirmed postmortem. Angiography remains essential in the diagnosis of cerebral arteritis.

Adult↗
PubMedDate not supplied

NMR imaging of acute experimental cerebral ischemia: time course and pharmacologic manipulations.

Nuclear magnetic resonance (NMR) imaging was used to evaluate the intracerebral changes over time in gerbils after unilateral carotid artery ligation. Each animal was imaged during one of three stated periods 3-28 hr after surgery and again after administration of dexamethasone, morphine, or naloxone, agents reported to affect the clinical outcome of ischemic cerebral lesions. Asymptomatic animals exhibited no differences between the occluded and control hemispheres in relative signal intensity or in T1 or T2 relaxation times, but symptomatic animals demonstrated significant differences in these parameters between hemispheres. The ischemic lesion was detected at the earliest imaging time, 3 hr after surgery. A linear increase was observed in the relative interhemispheric signal intensity in three of four intensity images and in T1 and T2 relaxation times over the 24 hr experiment. No effect was noted on any image parameter as a result of pharmacologic manipulations. The results suggest that NMR may be of significant diagnostic importance for acute cerebral ischemia and infarction in man.

Animals↗