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Biomedical subjects

D B Archer

Publications and source records attributed to D B Archer.

At least 199 records · Page 11Linked to original sources
PubMed1979

Long-term review of injuries to the lacrimal drainage apparatus.

A series of 57 patients with injuries to the proximal lacrimal drainage apparatus was reviewed to assess the long-term sequelae. The lower canaliculus was involved in 33 patients, the upper in ten, and both upper and lower in twelve, while the common canaliculus and lacrimal sac were each involved in one patient. It was found that either the upper or the lower canaliculus could cope independently with basal lacrimal secretions and that patients with at least one canaliculus intact had no symptoms under normal conditions. In seven patients with lower canalicular lacerations it was found that spontaneous functioning fistulae had developed nasal to the site of canalicular obstruction. The management of canalicular lacerations is discussed and it is recommended that the function of an intact canaliculus should not be jeopardized by surgical manipulations in an attempt to repair a damaged fellow canaliculus.

Adolescent↗
PubMed1979

Vitreous body oxygen tension following experimental branch retinal vein obstruction.

We obstructed either temporal or nasal superior and inferior retinal veins on one eye of rhesus monkeys with xenon photocoagulation. This resulted in large areas of nonperfused retina adjacent to normal retina in the same eye. Intraretinal neovascularization (new vessels in the retina) developed following the absorption of retinal hemorrhage and edema. We used microelectrodes to measure and compare vitreous body oxygen tensions over the nonperfused and over the normal retinal areas. There was no significant difference between the oxygen tension measurements in the same eye.

Animals↗
PubMed1978

The nature and location of Acholeplasma laidlawii membrane proteins investigated by two-dimensional gel electrophoresis.

The high resolution, two-dimensional electrophoresis system for the separation of proteins described by O'Farrell, (O'Farrell, P.H. (1975) J. Biol. Chem. 250, 4007--4021) has been modified for the separation of Acholeplasma laidlawii proteins. Reproducible protein patterns have been obtained from A. laidlawii cell, membrane and soluble protein preparations. The isoelectric focusing of membrane proteins was greatly improved by removing the bulk of the membrane lipid before solubilizing the protein. A. laidlawii peripheral membrane proteins were removed from the membrane by low ionic strength washing and by treatment with EDTA. The effect of an exhaustive EDTA treatment and a rapid, warm EDTA treatment were compared. By comparing the protein patterns obtained in these ways it was possible to distinguish two separate groups of peripheral membrane proteins and one integral membrane protein group. The peripheral membrane proteins which were removed from the membrane at low ionic strength (group I) were also insoluble in Triton X-100, whereas additional peripheral membrane proteins extractable by subsequent EDTA treatment (group II) were soluble in Triton X-100. Exterior-facing membrane proteins were distinguished from the interior-facing ones by lactoperoxidase-catalyzed iodination of intact cells and membranes. Group I peripheral membrane proteins faced the cell interior whereas group II proteins faced the cell exterior. We counted approximately 320 individual whole cell proteins. Of these, about 140 were membrane associated and a maximum of 40 proteins were iodinated after iodinating intact cells. A. laidlawii was also grown in the presence of NaH232PO4 and whole cell proteins were separated by two-dimensional gel electrophoresis. One membrane protein and two soluble proteins were labelled.

Acholeplasma laidlawii↗
PubMed1977

Chitin biosynthesis in protoplasts and subcellular fractions of Aspergillus fumigatus.

The biosynthesis of chitin has been obtained in broken mycelia and protoplasts of the fungus Aspergillus fumigatus. The specific activity of chitin synthase (EC 2.4.1.16) in a membrane preparation from protoplasts derived from the hyphal tips of A. fumigatus was 26.8-fold greater than that of the chitin synthase in broken mycelia, indicating that the active chitin synthase is located primarily in a membrane-bound site at the hyphal tip. Polyoxin D was a potent competitive inhibitor of the enzyme, having Ki 5.2 +/- 0.8 micron with respect to the natural substrate UDP-N-acetyl-D-glucosamine, which has Km 1.58 mM.

Anti-Bacterial Agents↗
PubMed1977

Aetiological survey of visually handicapped children in Northern Ireland.

A survey of visually h,ndicapped children in Northern Ireland identified 486 subjects aged 0 to 20 years on January 1, 1976, with a corrected visual acuity of 6/18 or less in the better eye. The prevalence of visual handicap was 81/100,000 of the population with an estimated ascertainment rate of 80%. Genetically determined diseases accounted for 51% of the cases. Birth hypoxia secondary to prenatal and perinatal complications was the second most important aetiological factor contributing towards visual handicap.

Adolescent↗
PubMed1976

Effect of the lipid composition of Mycoplasma mycoides subspecies capri and phosphatidylcholine vesicles upon the action of polyene antibiotics.

(1) The effects of filipin and amphotericin methyl ester upon the K+ efflux from Mycoplasma mycoides subsp. capri and egg lecithin sonicated vesicles were investigated. Both the nature of the sterol and the composition of the membranes affected the sensitivity to each polyene antibiotic. (2) M. mycoides subsp. capri containing ergosterol was much more sensitive to amphotericin methyl ester than cells containing cholesterol. Cholesterol-containing cells were about twice as sensitive to filipin as the ergosterol-containing cells. These results were confirmed with phosphatidylcholine vesicles. (3) At 2 degrees C the filipin sensitivity of M. mycoides subsp. capri was independent of the membrane cholesterol content and the sensitivity towards amphotericin methyl ester decreased when the membrane cholesterol content was increased, in contrast to the results at 20 degrees C. (4) At 2 degrees C, sterol-free egg lecithin vesicles became very sensitive to both filipin and amphotericin methyl ester and the presence of cholesterol in the vesicles did not increase the sensitivity further. At high concentrations of cholesterol (greater than 30 mol%), the polyene antibiotic sensitivity, particularly towards amphotericin methyl ester, was greatly reduced.

Amphotericin B↗
PubMed1976

Submacular choroidal circulation.

A neoprene latex and pigment mixture was injected into the choroidal blood vessels of human cadaver eyes. When peripheral resistence was normal, a single arteriole filled a single lobule of the choriocapillaris drained by mulitple surrounding venules. The choridal veins interconnected and an increase in the peripheral resistance caused by elevation of the venous pressure resulted in filling of contiguous lobules in a retrograde manner through the venules that normally drain them.

Aged↗
PubMed1975

Modification of the membrane composition of Mycoplasma mycoides subsp. capri by the growth medium.

Mycoplasma mycoides subsp. capri was grown in different media. The amounts of the lipids in these media were varied, resulting in altered lipid compositions of the cells. Lowering the amounts of cholesterol in the media resulted in less cholesterol incorporation into the cell lipid, with a concomitant decrease in the amount of phospholipid. The changes in the phospholipid/cholesterol ratio in the mycoplasmas were very small compared with the large changes in the amounts of cholesterol which occurred when the cholesterol content in the medium was altered. Changes in the amounts of glycolipid and glyceride in the cell lipid also resulted from alterations of the cholesterol concentration in the media. Under these conditions cell with reduced cholesterol contents were more sensitive to lysis by digitonin. No changes were observed in the polyacrylamide gel electrophoretic pattern of cellular or membrane proteins when the cholesterol was replaced by other sterols.

Bacterial Proteins↗