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Biomedical subjects

R L Harris

Publications and source records attributed to R L Harris.

At least 91 records · Page 5Linked to original sources
PubMed1976

Inhibition of wool follicle DNA synthesis by mimosine and related 4(1H)-pyridones.

The in vitro incorporation of [3H]thymidine has been examined in thin slices of sheep skin. Most of the radioactivity (88%) was incorporated into the bulb cells of the wool follicles, and the technique is therefore suitable for the study of some aspects of wool follicle DNA synthesis. The effect of mimosine and a number of related 4(1H)-pyridones on [3H]thymidine incorporation into sheep skin slices was examined. Mimosine was shown to inhibit the incorporation at a concentration of 0-2 mM. At this concentration, the incorporation of [3H]uridine or [14C]leucine was not affected. The inhibition of [3H]thymidine incorporation was time dependent, 2 h of incubation being required for maximal inhibition of DNA synthesis, and was readily reversible by removal of mimosine from the incubation medium. The 3-hydroxyl-4-oxo function of the pyridone ring appears to be directly involved in DNA synthesis inhibition. The amino acid side chain is not a toxophoric centre, but changes in its polarity have been shown to affect the inhibitory activity. The results suggest that the primary action of mimosine on the inhibition of wool biosynthesis in vivo is the inhibition of follicle bulb cell DNA synthesis and consequently of cell division.

Animals↗
PubMed1976

A model for deposition of fibers in the human respiratory system.

A mathematical model for estimating lung deposition of fibers is described. It is based on the aerodynamic behavior of thin straight rods. Predicted deposition values for rods of various equivalent aerodynamic diameters and lengths, for each of three tidal volumes and for each of three respiratory system compartments are reported.

Bronchi↗
PubMed1975

Investigation of the transport of metals and orthophosphate away from a sewage treatment plant outfall.

The distribution of O2, chlorophyll a, alkalinity, phosphate, Ca, Mg, Mn, Fe, Cu, Zn, Cd and Pb has been measured in the discharge plume of the large sewage treatment plant on Back River, Maryland. The concentrations of phosphate and the trace metals decrease downstream more rapidly than can be accounted for by conservative dilution. Solubility calculations suggest that saturation with respect to phosphate or oxyhydroxide phases could limit the mobility of phosphate, Fe, Mn, and Pb. For Cu, Zn, and Cd, saturation is not a feasible control mechanism, and other processes such as biofixation or adsorption are probably involved.

Alkalies↗
PubMed1975

Visual acuity improvement in eyes with corneal scars fitted with contact lenses.

The vision of 190 eyes of 130 patients with corneal scars was tested with contact lenses, of which 166 eyes subsequently were fitted with contact lenses. Over 75% of all eyes with corneal scars showed a visual acuity improvement to 6/12 or better. All eyes with a nebular or macular corneal scar and an initial visual acuity of 6/60 or better improved to 6/12 or better. The visual acuity of 77% of the eyes fitted with contact lenses, compared to the visual acuity of 36% of the same eyes obtained with spectacle lenses, improved to 6/12 or better.

Adolescent↗
PubMed1975

Effect of enrichment procedure upon auxotroph recovery in Escherichia coli K-12.

Proline-requiring auxotrophs are recovered preferentially after mutant enrichment procedures (e.g., penicillin) which perturb the cell envelope, but not after procedures (e.g., thymineless death) which affect other cellular targets. This probably stems from effects of penicillin and similar antibiotics upon proline metabolic and transport enzymes associated with the cell envelope.

Escherichia coli↗
PubMed1975

The influence of fibre shape in lung deposition-mathematical estimates.

Inhaled fibres deposit by sedimentation, diffusion, impaction, and interception in airways of the respiratory system. Long straight fibres may exhibit periodic motiion with ordered orientation in those airways having laminar flow. We assume that irregular fibres are randomly oriented in airways. Mathematical models based on respiratory system architecture, respiratory airflow, and mathematical expressions for deposition mechanisms have been developed to predict deposition in respiratory compartments of fibres in ordered orientation and of various fibre confirgurations in random orientations. The size and shape characteristics of chamber aerosols generated with U.I.C.C. asbestos specimens have been determined. Combinations of the chamber aerosol data with mathematical estimates of deposition suggest that fibre shape as well as size influences the magnitude of deposition in pulmonary spaces. For size distributions such as those of the U.I.C.C. asbestos chamber aerosols, the mathematical models predict pulmonary spaces deposition for straight fibres in ordered orientation about twice as great as for irregular fibres in random orientation.

Aerosols↗
PubMed1973

Ethanol administration and the relationship of malonyl-coenzyme A concentrations to the rate of fatty acid synthesis in rat liver.

1. The effect of ethanol on liver fatty acid synthesis was studied in vivo in 24h-starved and ;meal-fed' rats (i.e. fed for 3h per day and not ad libitum). 2. In the fed animal (3)H(2)O was incorporated into fat at a rate of 0.46mumol of C(2) units/min per g wet wt. of liver. Administration of either ethanol (3.2g/kg) or equicaloric amounts of glucose had no effect on the rate of (3)H(2)O incorporation into lipid. 3. In the 24h-starved animal, administration of the same dose of ethanol produced an increase in the rate of (3)H(2)O incorporation from 0.06 to 0.12mumol of C(2) units/min per g fresh wt. after 3h whereas [malonyl-CoA] increased from 0.006 to 0.009mumol/g. Glucose given in amounts equicaloric to ethanol was significantly more lipogenic, increasing both the (3)H(2)O incorporation from 0.06 to 0.20mumol of C(2) units/min per g and the malonyl-CoA content from 0.006 to 0.013 mumol/g wet wt. at 3h. 4. The decrease in the redox state of free cytoplasm NAD or NADP couples or the changes in content of citrate, glucose 6-phosphate and pyruvate of liver after ethanol administration had no measurable effect on the rate of fatty acid synthesis in vivo. 5. Under the conditions of the experiments there was no significant difference, among any of the groups, in the activity of liver fatty acid synthetase measured in vitro. A double-reciprocal plot of the rate of (3)H(2)O incorporation and the total tissue malonyl-CoA concentrations showed a striking relationship. It has been concluded that the rate of fatty acid synthesis in vivo is determined principally by the V(max.) of fatty acid synthetase and the concentration of free malonyl-CoA. 6. It has also been concluded that under the conditions of the present study, the synthesis of fatty acids de novo is unlikely to be an important factor in the increased liver lipid content associated with ethanol administration.

Acetyl-CoA Carboxylase↗