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Biomedical subjects

D Davidson

Publications and source records attributed to D Davidson.

At least 253 records · Page 14Linked to original sources
PubMed1977

Cell cycle analysis in developing cercariae of Trichobilharzia ocellata (Trematoda: Schistosomatidae).

Cellular proliferation has been analyzed during cercarial development of the digenetic trematode Trichobilharzia ocellata. Prior to the tail-bud stage (about 1,000 cells), cells were actively involved in cellular proliferation. The mean cell cycle was 15.2 hr. The time for mitosis was 1.6 hr; for G1, 5.6 hr; for G2, 3.2 hr, and for the S phase, 4.8 hr. Beginning with the tail-bud stage, an increasing proportion of cells accumulate in the G1 phase. Cytological evidence of changes in the amount of cytoplasm per cell revealed that these noncycling cells were differentiating. During organ development and differentiation, the proportion of proliferating cells decreases and by the 2,000-celled stage proliferation ceases. Our results do not support a germinal lineage theory of cercarial development since none of the observed nuclear types could be unequivocally identified as belonging to the germ line.

Animals↗
PubMed1976

Lysosomal enzymes in cerebral atrophy.

In seven patients with cerebral atrophy due to pre-senile dementia and/or cerebrovascular disease, the activity of acid phosphatase in lumbar cerebrospinal fluid (CSF) was higher (p less than 0.05) than in six controls. The activity of arylsulphatase and beta-galactosidase in CSF was the same in the two groups. In the serum, the activities of acid phosphatase and arylsulphatase were the same in the two groups but the activity of beta-galactosidase was lower (p less than 0.02) in patients with cerebral atrophy.

Acid Phosphatase↗
PubMed1975

The freezing lesion. III. The effects of diphenylhydantoin on potassium transport within nerve terminals from the primary foci.

Possible mechanisms by which dephenylhydantoin (DPH) controls seizures were examined. The effects of intraperitoneal DPH on seizure discharges within epileptogenic freeze lesions were correlated with DPH action on in vitro potassium uptake within synaptosomes isolated from the same freeze foci. When in vivo DPH suppressed seizure discharges, it stimulated in vitro potassium uptake within synaptosomes incubated in a high-Kplus (10 mM) media. With 2-5 mM Naplus and 10mM Kplus, DPH stimulation of synaptosome potassium uptake was reversed by ouabain. With 50 mM Naplus and 10 mM Kplus, DPH stimulation of potassium uptake was not reversed by ouabain. In low-Kplus (0.2-5 mM) media, DPH did not affect potassium uptake even when sodium concentrations were varied at 10-100 mM. In sham-operated controls and in non-epileptogenic lesions, the effects of DPH on synaptosome potassium uptake were identical to those previously reported in normal brains. These results strongly suggest that DPH controls the epileptogenic state by stimulating potassium uptake within synaptic terminals. DPH controls the epileptogenic state by stimulating potassium uptake within synaptic terminals. DPH enhances synaptic potassium uptake by stimulating the (Naplus-Kplus) pump and a second potassium uptake process which is insensitive to ouabain.

Animals↗
PubMed1971

5-Aminouracil treatment. A method for estimating G2.

Treatment of Vicia faba lateral roots with a range of concentrations of 5-aminouracil (5-AU) indicate that cells are stopped at a particular point in interphase. The timing of the fall in mitotic index suggests that cells are held at the S - G(2) transition. When cells are held at this point, treatments with 5-AU can be used to estimate the duration of G(2) + mitosis/2 of proliferating cells. Treatment with 5-AU can also be used to demonstrate the presence of subpopulations of dividing cells that differ in their G(2) duration. Using this method, 5-AU-induced inhibition, we have confirmed that in V. faba lateral roots there are two populations of dividing cells: (a) a fast-dividing population, which makes up approximately 85% of the proliferating cell population and has a G(2) + mitosis/2 duration of 3.3 hr, and (b) a slow-dividing population, which makes up approximately 15% of dividing cells and has a G(2) duration in excess of 12 hr. These estimates are similar to those obtained from percentage labeled mitosis (PLM) curves after incorporation of thymidine-(3)H.

Mitosis↗