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Biomedical subjects

M Marcus

Publications and source records attributed to M Marcus.

At least 145 records · Page 8Linked to original sources
PubMed1983

A temperature sensitive mutant of a Chinese hamster cell line exhibiting high chromosomal breakage.

A temperature sensitive mutant exhibiting a very high level of chromosomal aberrations has been isolated from the Chinese hamster cell line E36. The chromosome aberrations, which include chromosome and chromatid breaks, multiradial configurations, dicentrics, and pulverizations, start to appear 1 h after a shift in temperature from 34 degrees C to 40.5 degrees C. The rate of sister chromatid exchange is not increased in this mutant. Analysis of somatic cell hybrids indicates that the mutation in this temperature sensitive mutant is dominant.

Animals↗
PubMed1983

Electrophysiologic tests in assessment of senile macular degeneration.

Twelve patients with macular disease were studied. Mean age at the beginning stages of the disease was 61.75 years. They were examined by biomicroscopy, fluorescein angiography, and electrophysiological tests (ERG, EOG, VEP). No relevant correlation could be found between the routinely administered and evaluated ERG and EOG tests and the clinical stage of the disease. The VEP proved a more sensitive means of evaluating macular function in our patients. The possibility of the VEP's being of prognostic importance is raised.

Aged↗
PubMed1982

Newborn intensive care and neonatal mortality in low-birth-weight infants: a population study.

We examined the neonatal mortality rates of low-birth-weight infants (501 to 2250 g) born between 1976 and 1978 in three kinds of hospitals in New York City: those with newborn-intensive-care units (Level 3), those with capabilities for the care of most premature infants (Level 2), and those without any special facilities for premature newborns (Level 1). Among 13,560 singleton low-birth-weight infants, the adjusted neonatal mortality rate for Level 3 hospitals was 128.5 per thousand live births - significantly lower (P less than 0.001) than the rates for both level 2 (168.1) and Level 1 units (163.0). The association of level of care with mortality could not be accounted for by differences between groups in social or demographic status, in prenatal care, or in medical complication of pregnancy. We infer that birth at a Level 3 center lowers neonatal mortality in low-birth-weight infants. However, only 34 per cent of the patients in this study were born in such units.

Critical Care↗
PubMed1982

Isolation by a replica-plating technique of Chinese hamster temperature-sensitive cell cycle mutants.

Isolation of a wide variety of temperature-sensitive (ts) cell cycle mutants in mammalian cells has previously proved to be a very difficult task. The various procedures used for the isolation of such mutants included a mutant enrichment step based on exposure of the cells to the restrictive temperatures in order to kill the growing wild-type cells with agents that kill DNA-synthesizing cells. Hence, these methods favored the isolation of ts mutants that do not lose viability rapidly at the restrictive temperatures. We have treated cells of the Chinese hamster established cell line E36 with the mutagen ethyl-methane-sulfonate (EMS) and used a replicating technique that we developed to screen the ts mutants for growth. This technique enabled us to recover all its mutants for growth including the ts cell cycle mutants. Screening of the ts cell cycle mutants among the ts mutants for growth was performed by the flow microfluorimetry technique and the premature chromosome condensation technique. Our results show that 1.3% of the survivors of the mutagenic treatment are ts mutants for growth. Six of 84 ts mutants analyzed were found to be ts cell cycle mutants. They include ts mutants arrested in phases G1, S, and G2. Many of the ts mutants for growth including the ts cell cycle mutants arrested in S and G2 lose viability very fast when incubated at the restrictive temperature. As a consequence they could not have been isolated by any method that includes a mutant enrichment step based on the exposure of the cells to the restrictive temperature.

Animals↗
PubMed1982

Kinetic assay of beta-hydroxybutyrate in plasma with a COBAS-BIO centrifugal analyzer.

An enzymic rate method for measuring beta-hydroxybutyrate in plasma by use of beta-hydroxybutyrate dehydrogenase (EC 1.1.1.30) was adapted to the Roche COBAS-BIO centrifugal analyzer. Optimum reagent composition and reaction conditions were determined, to provide increased sensitivity and accuracy. Use of magnesium ions increased sensitivity. Comparison of results with those of a manual enzymic endpoint method involving perchloric acid protein-free filtrates of whole blood showed excellent correlation (r = 0.996). The method has good within-run and day-to-day precision. Linearity of the standard curve extends to 5000 mumol of beta-hydroxybutyrate per liter. The assay can be completed in less than 5 min and requires 15 microL of plasma and minimal reagent volumes.

3-Hydroxybutyric Acid↗
PubMed1982

The bioavailability of two commercial preparations of allopurinol tablets.

The relative bioavailability of two commercial preparations of 100 mg and 300 mg allopurinol tablets was examined in two groups of 16 healthy human subjects, one for each dosage level. Serum concentrations of allopurinol and its major metabolite, oxypurinol, were measured using a competitive protein-binding assay. After single doses of allopurinol, no significant differences between brands were revealed in the resultant serum levels of the drug or the metabolite, or in the relevant pharmacokinetic parameters. Serum oxypurinol levels were higher and more persistent than those of the parent drug. A comparison of the serum concentration profiles after 100 mg and 300 mg doses suggests that allopurinol absorption in humans may be dose dependent.

Absorption↗
PubMed1981

Vitamin B12.

Explore the source record for details and available documents.

Animals↗
PubMed1981

Transthoracic resistance in human defibrillation. Influence of body weight, chest size, serial shocks, paddle size and paddle contact pressure.

Successful defibrillation depends on delivery of adequate electrical current to the heart; one of the major determinants of current flow is transthoracic resistance (TTR). To study the factors influencing TTR, we prospectively collected data from 44 patients undergoing emergency defibrillation. Shocks of 94-450 J delivered energy were administered from specially calibrated Datascope defibrillators that displayed peak current flow, thereby permitting determination of TTR. Shocks were applied from standard (8.5-cm diameter) or large (13 cm) paddles placed anteriorly and laterally. First-shock TTR ranged from 15-143 omega. There was a weak correlation between TTR and body weight (r = 0.45, p less than 0.05) and a stronger correlation between TTR and chest width (r = 0.80, p less than 0.01). Twenty-three patients who were defibrillated using standard 8.5-cm paddles had a mean TTR of 67 +/- 36 omega (+/- SD), whereas 21 patients who received shocks using paddle pairs with at least one large (13 cm) paddle had a 21% lower TTR of 53 +/- 24 omega (p = 0.05, unpaired t test). Ten patients received first and second shocks at the same energy level; TTR declined only 8%, from 52 +/- 19 to 48 +/- 16 omega (p less than 0.01, paired t test). In closed chest dogs, shocks were administered using a spring apparatus that regulated paddle contact pressure against the thorax. Firmer contact pressure caused TTR to decrease 25%, from 48 +/- 22 to 36 +/- 17 omega (p less than 0.01, paired t test). Thus, human TTR varies widely and is related most closely to chest size. TTR declines only slightly with a second shock at the same energy level. More substantial reductions in TTR and declines only slightly with a second shock at the same energy level. More substantial reductions in TTR and increases in current flow can be achieved by using large paddles and applying firm paddle contact pressure.

Animals↗
PubMed1981

Eliminating mycoplasmas from contaminated cell cultures.

Mycoplasmas are bothersome contaminants in cell cultures. Cells derived from various sources are subject to contamination and although many procedures have been suggested to eliminate the contaminating mycoplasmas, there is no simple, rapid and effective method for eliminating them. We have devised a method for the selective killing of mycoplasmas based on the differences between the nucleic acid metabolism of mycoplasmas and that of tissue culture cells. Whereas the nutritional requirements of mycoplasmas for nucleic acid precursors can be met by purine and pyrimidine bases, mammalian cells do not incorporate the free bases. The approach was to selectively incorporate the free base analogue 5-bromouracil (5-BrUra) into the mycoplasmas followed by photosensitization of the DNA containing 5-BrUra by low concentrations of the fluorochrome 33258-Hoechst. Such treatment renders the mycoplasma DNA very susceptible to breaks induced by visible light. The unusually high A + T content in mycoplasma DNA makes these organisms suitable candidates for the induction of breakage by the combined action of 5-BrUra, 33258-Hoechst and light because 33258-Hoechst has a high affinity for A + T base pairs and an even higher affinity for A-BrUra base pairs. We report that Mycoplasma hyorhinis and Acholeplasma laidlawii contaminating Chinese hamster cells were selectively killed by our technique, and cured clones of cells were easily obtained from the treated cell cultures. The technique proved efficient in curing BHK-21 and RAG cells from unknown contaminating mycoplasmas suggesting that this technique could be generally applied to eliminate contaminating mycoplasma strains from mammalian cell culture.

Animals↗
PubMed1980

Stability of vitamin B12 in the presence of ascorbic acid in food and serum: restoration by cyanide of apparent loss.

Ascorbic acid in varying amounts was added to food and serum samples and heated at 37 C. Vitamin B12 was then measured by radioimmunoassay and microbiologically using several extraction methods. B12 values in a cottage cheese meal were lower than controls when concentrations of ascorbic acid greater than but not equal or less than 0.5 mg/ml were added and if KCN was not used during extraction, but when 70 micrograms/ml KCN was added after ascorbic acid exposure B12 was quantitatively recovered. Serum B12 was variably decreased by lesser concentrations of ascorbic acid but was also quantitatively restored by increasing KCN concentration during extraction. In the absence of KCN in the extraction step some loss of B12 at 100 C was observed; the loss was greater with added ascorbic acid. Our results indicate that previous reports on B12 loss in the presence of ascorbic acid are artifacts of the methods used. In view of these in vitro findings B12 destruction by ascorbic acid in vivo seems highly improbable.

Ascorbic Acid↗