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Biomedical subjects

E Marcus

Publications and source records attributed to E Marcus.

At least 19 recordsLinked to original sources
PubMed1994

Interaction of melittin with lipid membranes.

Interaction of melittin with lipid membranes was studied systematically with respect to its adsorption onto membranes, its effect on membrane leakage and fusion, and micellization at various melittin/lipid ratios. It was found that melittin has a strong affinity for adsorption onto lipid membranes. The analysis of the measured electrophoretic mobilities by use of a Gouy-Chapman double layer theory, shows that melittin is adsorbed onto the phosphatidylserine membrane several times more than the phosphatidylcholine membrane. However, it was observed that the phosphatidylcholine membrane is more susceptible to membrane leakage, vesicle fusion and micellization at a lower level of melittin adsorbed than the phosphatidylserine membrane. For small unilamellar phosphatidylcholine vesicles in 0.1 M NaCl, membrane leakage started at melittin to lipid ratio of 1:2000, a large increase in the rate of membrane leakage occurred at a ratio of about 1:500 or higher, membrane fusion occurred at a ratio of 1:200, and membrane micellization at a ratio of 1:10. On the other hand, for small unilamellar phosphatidylserine vesicles, the respective concentrations of melittin to result in membrane leakage, vesicle fusion, and membrane micellization were several times higher. Surface pressure measurements of lipid monolayers showed that the increase in surface pressure of the phosphatidylcholine monolayer due to the presence of melittin in the subphase solution was greater than that for the phosphatidylserine monolayer at any melittin concentration in the subphase solution. These experimental results indicate that melittin tends to be adsorbed on the surface of the negatively charged phosphatidylserine membrane due to the electrostatic binding so that the melittin molecule can stay out more on the surface of the membrane, while melittin appears to be adsorbed more into the hydrophobic membrane core for the electrically neutral phosphatidylcholine membrane.

Adsorption↗
PubMed1992

Effect of exercise training on glomerular filtration rate of mice with various degrees of renal mass reduction.

We studied the effect of repeated heavy physical activity on glomerular filtration rate (GFR) in healthy, uninephrectomized and experimentally uremic mice. Exercise consisted of running uphill in the inner surface of a rotating cylinder in ideal environmental temperature. In the control groups, no extra physical activity was imposed. In sham-operated and nephrectomized mice, GFR rose significantly following training. By contrast, GFR did not change significantly in the exercised mice with experimental renal failure 24 h following the last exercise session. During the same period, no significant change was observed in GFR of any of the control groups. Following training in each experimental group, mean aortic blood pressure as well as fractional kidney weight (kidney weight/body weight) were not different from the respective controls. Our results indicate that the capacity to augment GFR by physical training is dependent upon the amount of remaining functional renal tissue.

Animals↗
PubMed1990

Minisatellite DNA profiles: rapid sample identification in linkage analysis.

Locus-specific minisatellite probes detect multiple alleles with heterozygosities of greater than 90% when hybridised to HinfI and AluI restriction digests of human DNA. We have hybridised 4 of these probes to a panel of DNAs digested with 6 of the restriction enzymes which commonly reveal di-allelic polymorphisms in the human genome. All 6 enzymes detected multiple resolvable alleles with at least 1 of the 4 minisatellite probes tested, thus providing a rapid and efficient means to check family relationships and paternity on filters already being used for linkage analysis.

Blotting, Southern↗
PubMed1985

Prevalence of mitral valve prolapse in normal children.

Although echocardiography has become the standard noninvasive method of diagnosing mitral valve prolapse, the diagnostic criteria have been established without clearly defining the range of normal patterns for mitral valve closure. The current study reports the analysis of mitral valve closure patterns in 193 children (aged 5 days to 18 years) making scheduled visits for well child care who were screened by history and physical examination to exclude structural heart disease. Mitral valve systolic leaflet position was analyzed for the appearance of any portion of either leaflet superior to the plane of the anulus. Superior systolic motion was noted in 13% of the overall study group; this pattern was uncommon in infants but more frequent in older children, with a prevalence of 35% in the 10 to 18 year age group. There was no statistically significant difference between male and female children at any age. The prevalence of superior systolic motion decreased markedly if consideration was given to its presence in more than one echocardiographic view (1%) or to displacement of the coaptation point of the mitral valve leaflets (0.5%). Superior systolic motion occurs with such frequency in normal children as to call into question the reliability of this pattern of mitral valve closure as a standard for the diagnosis of mitral valve prolapse. More restrictive diagnostic criteria which consider the degree of leaflet displacement or its presence in multiple echocardiographic views may be necessary to identify those subjects whose mitral valve closure patterns truly fall outside the range of normal.

Adolescent↗
PubMed1983

Concentration and composition of plasma proteins in wild mammals.

Total protein concentrations from a variety of wild mammalian species were measured by the Lowry and Biuret techniques and compared with results obtained or derived by refractometry. Values obtained with the Lowry method were the highest and certain derived refractometry results, the lowest. It is suggested that the Biuret method provides the most acceptable values but that care should be exercised in using the correct standard. The percentage composition of plasma from 22 species of wild mammals is also presented and the observations discussed with relation to methodology and A/G ratio.

Animal Population Groups↗
PubMed1983

Single-dose amoxicillin therapy of uncomplicated pediatric urinary tract infections.

Forty-nine ambulatory children between 2-1/2 and 12 years of age with acute, clinically uncomplicated urinary tract infections caused by susceptible organisms were randomized to receive a single dose of amoxicillin based on weight or a 10-day course of amoxicillin therapy (conventional therapy). Patients receiving single doses of amoxicillin had a cure rate of 63%, which compares unfavorably with the cure rate of 92% in patients given conventional therapy. A failure of single-dose therapy predicted underlying radiologic abnormalities with a sensitivity of 60% and a specificity of 58%, making it a poor screening test for detecting those patients at risk for renal parenchymal damage. The antibody-coated bacteria assay had no predictive value in separating upper and lower tract disease, although it may predict underlying radiologic abnormalities. The data indicate that the response to single-dose amoxicillin therapy fails to separate upper from lower tract disease reliably and has a limited role in predicting response to conventional antimicrobial therapy.

Acute Disease↗
PubMed1975

An evaluation of electroencephalographic monitoring for carotid study.

Continuous electroencephalogram (EEG) monitoring was used during 213 carotid endarterectomies in 157 patients to identify cerebral ischemia. General anesthesia was used for all patients. An intraluminal shunt was not used routinely, but was inserted in 23 operations when EEG abnormalities associated with ischemia appeared. EEG changes occurred in 31 operations (14.5 percent). Four patterns of abnormal recordings were identified and are discussed. Six patients developed ischemic EEG changes in association with hypotension during endarterectomy. In two of these patients changes appeared with a blood pressure drop of only 20 mm. Hg below preoperative levels. Four patients with internal carotid artery back pressures of 75 to 100 mm. Hg developed EEG abnormalities which disappeared after shunt insertion. Our experience emphasizes the value of continuous EEG monitoring in detecting inadequate cerebral perfusion.

Aged↗