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Biomedical subjects

M Lai

Publications and source records attributed to M Lai.

5 recordsLinked to original sources
PubMed1979

Effects of thyroxine on postnatal cell acquisition in the rat brain.

The effects of treatment with L-thyroxine (3 micrograms by subcutaneous injection daily from birth) on cell acquisition in the rat brain were studied during the first 3 postnatal weeks. In the forebrain, thyroxine has no effect on cell proliferation in the first 6 days, but it causes decreased cell acquisition from 12 to 21 days so that cell number becomes significantly reduced. Estimates of cell proliferation kinetics and of cell death in the lateral ventricular subependymal layer show no apparent abnormality. In the cerebellum, treatment from birth leads to increased cell proliferation during the first week: in comparison with controls, the rate of [3H]thymidine incorporation into DNA, thymidine kinase activity, and the number of cells both in the major germinal site (external granular layer: EGL) and in the whole cerebellum are elevated. This initial effect of thyroxine appears by day 3 and is short-lived, being no longer evident after day 6. The build-up of cell numbers in the EGL at day 6 seems to be related to a preceding, transient retardation of cell migration from this layer rather than to an acceleration of cell replication, since cell cycle parameters are normal. From day 12 the rate of [3H]thymidine incorporation into DNA is severely reduced in treated rats. Advancement of cellular differentiation rather than increased cell death in the EGL appears to be involved in this phenomenon.

Aging↗
PubMed1979

Heteroduplex analysis of the sequence relationships between the genomes of Kirsten and Harvey sarcoma viruses, their respective parental murine leukemia viruses, and the rat endogenous 30S RNA.

The sequence relations between Kirsten murine sarcoma virus (Ki-SV), Harvey murine sarcoma virus (Ha-SV), and a rat endogenous 30S RNA were studied by electron microscope heteroduplex analysis. The sequence relationships between the sarcoma viruses and their respective parental murine leukemia viruses (Kirsten and Moloney murine leukemia viruses), as well as between the two murine leukemia viruses, were also studied. The only observed nonhomology feature of the Kirsten murine leukemia virus/Moloney murine leukemia virus heteroduplexes was a substitution loop with two arms of equal length extending from 1.80 +/- 0.18 kilobases (kb) to 2.65 +/- 0.27 kb from the 3' end of the RNA. It is believed that this feature lies in the env gene region of the viral genomes. The Ha-SV and Moloney murine leukemia virus genomes (respective lengths, 6.0 and 9.0 kb) were homologous in a 1.0 +/- 0.05-kb region at the 3' end and possibly over a 200-nucleotide region at the 5' ends; otherwise, they were nonhomologous. Ha-SV and Ki-SV (length, 7.5 kb) were homologous in the first 4.36 +/- 0.37-kb region from the 3' end and in a 0.70 +/- 0.15-kb region at the 5' end. In between, there was a nonhomology region, possibly containing a short (0.23-kb) region of partial or total homology. The heteroduplex analysis between rat endogenous 30S RNA and Ki-SV shows that there are mixed regions of sequence homology and nonhomology at both the 5' and 3' ends. However, there is a large (4-kb) region of homology between Ki-SV and the rat 30S RNA in the center of the genomes, with only a small nonhomology hairpin feature. These studies help to define the regions of homology between the Ha-SV and Ki-SV genomes with each other and with the rat endogenous 30S RNA. These regions may be related to the sarcoma genicity of the viruses. In particular, the 0.7-kb region of homology of Ha-SV with Ki-SV at the 5' ends may be related to the formation of a 21,000-dalton phosphoprotein in cells transformed by either virus.

Animals↗
PubMed1977

Aqueous humor ascorbate concentration and open-angle glaucoma.

The mean value for aqueous concentration in 35 patients with open-angle glaucoma was 22.4 +/- 12.9 mg/100 ml. The mean value for aqueous ascorbate in four patients with uncomplicated senile cataract was 11.55 +/- 3.01 mg/100 ml. The results indicate that the majority of open-angle glaucomatous eyes do not involve a deficiency of ascorbate, and suggest that ascorbate has no therapeutic value in the management of primary open-angle glaucoma. The magnitude of aqueous ascorbate variation among glaucoma eyes is probably related to the factors that influence the patency of trabecular meshwork, not the metabolic activity of the ciliary processes.

Animals↗