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Biomedical subjects

L Hall

Publications and source records attributed to L Hall.

At least 217 records · Page 12Linked to original sources
PubMed1977

Murphy's glue.

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Canada↗
PubMed1976

Synthesis of ribosomal RNA during the mitotic cycle on the slime mould Physarum polycephalum.

1. An isotope dilution technique has been used to analyze the synthesis of metabolically stable nucleic acids during the mitotic cycle in surface plasmodia of the slime mould Physarum polycephalum. Microplasmodia that had been labelled with [3H]uridine were used to prepare a surface culture, after a period of growth long enough to ensure that radioactivity was present only in tRNA, rRNA and DNA. The synthesis of rRNA or nuclear DNA during the growth of the surface plasmodium was then followed by measuring the specific activity of the nucleic acid. 2. Synthesis of rRNA during the mitotic cycle shows the following characteristics: (a) it is low during the immediate period of nuclear division, (b) synthesis is then continuous throughout interphase and (c)the rate of synthesis increases 5-6-fold between the beginning and end of interphase. These results are discussed in relation to the pattern of replication of the genes for rRNA. 3. Approximately 80% of the nuclear DNA replicates during the first 90 min of the mitotic cycle; completion of replication, however, occupies the remainder of interphase.

Cell Nucleus↗
PubMed1975

Ribosomal RNA genes in the amoebal and plasmodial forms of the slime mould Physarum polycephalum.

1. The degree of homology between ribosomal RNA isolated from microplasmodia and amoebae of the slime mould Physarum polycephalum has been determined by competive hybridisation of the RNA from the two sources to homologous DNA in solution. The extent of competition was measured both by hybridisation to saturation and by following the kinetics of hybrid formation. In each case competition was found to be 100%, indicating that the ribosomal RNAs from the two, quite different vegetative forms of the organism exhibit a high degree of homology and are probably transcribed from the same genes. 2. The relationship between the amount of nuclear DNA that codes for ribosomal RNA (rDNA) and ploidy has been investigated in three strains of P. polycephalum which exhibit a 1:2:5 variation in the amount of DNA per nucleus. Ribosomal RNA saturation values were determined by hybridisation to DNA isolated from prophase nuclei of plasmodia. The proportion of rDNA was found to be constant at 0.16--0.18% of the total genome in the three strains.

Amoeba↗
PubMed1975

Preliminary studies on the toxicity and metabolism of palladium and platinum.

Preliminary data are given on the LD50 of PdCl2 following different routes of exposure and on the LD50 of PtCl4 following intravenous exposure. The retention, tissue distribution, and excretion of 103Pd and 191Pt in rats was determined following oral, intravenous, intratracheal, and inhalation exposure. The highest retention for both 103Pd and 191Pt was obtained following intravenous dosing, and the lowest retention occurred after oral dosing. Following a single oral dose, almost all of the 103Pd and 191Pt was excreted in the feces due to nonabsorption, whereas after intravenous dosing, similar quantities were excreted in both the urine and feces. Tissues containing the highest concentrations of these metals were the kidney, spleen and liver. Following intravenous dosing of pregnant rats, a small amount of 103Pd and 191Pt was found in the fetuses.

Administration, Oral↗
PubMed1971

Virus-specific proteins synthesized in encephalomyocarditis virus-infected HeLa cells.

The in vivo synthesis of encephalomyocarditis-specific proteins was studied by labeling the viral proteins with radioactive amino acids under conditions where host-protein synthesis was almost completely inhibited. To assure recovery of all proteins, intact cells were lysed in hot 1% sodium dodecyl sulfate. These lysates were analyzed by quantitative high-resolution electrophoresis on sodium dodecyl sulfate-polyacrylamide gels. This technique allowed the detection and estimation of the molecular weight of 15 virus-specific polypeptides: A, 100,000; B, 90,000; C, 84,000; D, 75,000, D1, 65,000; E, 56,000; epsilon, 40,000; F, 38,000; alpha, 34,000; beta, 30,000; gamma, 23,000; G, 16,000; H, 12,000; I, 11,000; and delta, 9,000. Pulse-chase experiments, in conjunction with cyanogen bromide and tryptic mapping of the isolated polypeptides, indicate that at least three primary gene products (A,F,C), with a cumulative weight of about 220,000, are generated during translation of the RNA genome. Chains A and C then undergo post-translational cleavages, while F remains uncleaved. The proteins generated by the cleavage of A include all of the capsid chains (alpha, beta, gamma, delta, epsilon). Those generated by the cleavage of C include D and E. The chains alpha, beta, gamma, delta, E, F, G, H, I, with a cumulative molecular weight of about 230,000, are stable and are produced in about equimolar amounts. A model for the synthesis of, and a cleavage sequence that accounts for, all of the viral polypeptides is proposed.

Amino Acids↗
PubMed1970

Serum creatine phosphokinase levels in pigs reacting abnormally to halogenated anaesthetics.

Serum levels of creatine phosphokinase (CPK) were estimated in pigs. Among those known to react abnormally either to halothane alone or to halothane and suxamethonium most had very high levels of CPK. Twenty-four hours after five minutes' anaesthesia with halothane and oxygen a sustained, pronounced rise in the serum CPK occurred in some pigs-principally but not exclusively in the abnormal reactors. Estimation of the serum level of CPK may be a useful screening test for an abnormal hyperpyrexial response to halothane.

Anesthesia, Inhalation↗