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Biomedical subjects

M L Chiu

Publications and source records attributed to M L Chiu.

42 records · Page 3Linked to original sources
PubMed1983

Equimolar proportions of somatic-type core histones in chromatin of spermatogonia.

[3H]Leucine incorporation into histones of seminiferous epithelial cells of hypophysectomized rats was used to calculate the molar proportions of the core histones of spermatogonia. The molar proportions H3:H2B:(H2A + protein A24):H4 are 1:1:1:1, viz. identical with those reported by others for somatic cells. Similar results were obtained when molar proportions of histones of seminiferous epithelial cells from immature rat testis (predominantly populated with spermatogonia) were determined by the dye-binding method. These data are relevant to mechanisms for the replacement of some of the core histones by variants during the primary spermatocyte stages.

Animals↗
PubMed1982

Molar proportions and relative rates of synthesis of histones in rat testis.

The molar proportions and relative rates of synthesis of histones in normal and hypophysectomized rat testis seminiferous epithelial cells were determined. After hypophysectomy the molar proportions of histones H1, H2B and (H2A + protein A24) in seminiferous epithelial cells of rat testis increased while their corresponding variants TH1-x, TH2B-x and X2 decreased, but the molar proportions of major-class histones (i.e., sum of subfractions) remained relatively constant and similar to the proportions in somatic cells. The apparent molar proportions of the labeled histones, determined immediately after 2-h periods of [3H]leucine incorporation, were much higher relative to H4 than the proportions of total histones determined by dye binding. The values, however, approached the molar proportions of total histones when rats were killed 11 days after the [3H]leucine injection. Two-dimensional gel electrophoresis confirmed that the high initial molar proportions relative to H4 by [3H]leucine incorporation were not due to the possible contamination by highly-labeled non-histone proteins. The specific activity of histone H4 relative to the specific activity of DNA, determined immediately after 3-h periods of [3H]leucine and [14C]thymidine incorporations was similar to the value when rats were killed 13 days after the injections. It is proposed that histones of seminiferous epithelial cells are synthesized disproportionally relative to H4 and in excess of the quantities required for polynucleosome assembly. The excess histones are subsequently displaced or degraded slowly.

Animals↗
PubMedDate not supplied

In vitro killing kinetics and postantibiotic effect of josamycin and other macrolides on several bacteria.

The antimicrobial activity [minimal inhibitory concentration (MIC) and killing kinetics] and postantibiotic effect (PAE) of different concentrations (MIC and 10 x MIC) of josamycin, erythromycin, midecamycin and azithromycin on Streptococcus pneumoniae, Staphylococcus aureus and Escherichia coli were studied in vitro. The MIC and killing kinetics were determined by standard methods. The PAE was measured after 1 h exposure to the drugs, which were removed by diluting the culture 1,000-fold. All tested macrolides had their lowest MIC against S. pneumoniae, and the most active against S. aureus was josamycin. In killing kinetics, using 10 x MIC, the macrolides exhibited a bactericidal effect against S. pneumoniae and E. coli, with reductions of 3 log10 in colony-forming units per milliliter with respect to the initial inoculum, while a bactericidal effect was not observed for S. aureus. The PAEs were concentration dependent, the greatest PAEs being obtained with S. pneumoniae. Although lower, the PAEs induced on E. coli were significant when high concentrations of the drug were tested. The assayed macrolides showed both more activity and PAEs on S. pneumoniae.

Anti-Bacterial Agents↗