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Biomedical subjects

R F Brown

Publications and source records attributed to R F Brown.

At least 73 records · Page 4Linked to original sources
PubMed1983

A repeated dose study of the toxicity of inhaled 2-chlorobenzylidene malononitrile (CS) aerosol in three species of laboratory animal.

The repeated dose inhalation toxicity of 2-chlorobenzylidene maloninitrile (CS) was investigated in male mice, rats, and guinea-pigs. Exposure was 1 h X day-1 for 120 days surviving animals being killed approximately 1 year after the start of exposure. Excess mortality was noted in the high dose groups of all three species but at exposure concentrations below 30 micrograms X 1(-1) mortality varied little between the control and test groups. Death during the experiment was related to concentration of exposure rather than total dose (Ct). No case of a dose-response relationship between tumours in a particular site, and total dose of CS was noted.

Aerosols↗
PubMed1983

The histopathology of rat lung following short term exposures to mixed oxides of nitrogen (NOx).

The histopathology of rat lung after exposure to high concentrations of mixed oxides of nitrogen (NOx) has been studied. Considerable damage was observed, which initially took the form of 'thickening' and 'blebbing' of the alveolar epithelium and disruption of type II pneumocytes. These early changes were attributed to the direct effect of the oxidant action of NOx. There then followed a latent period of approximately 6 h after which the development of oedema of the interstitium and alveolar septum was observed. Clinical observations and the results from light and electron microscopical examination suggested that the lung damage caused by exposure to 518 parts/10(6) NOx for 5 min was greater than that caused by 1435 parts/10(6) for 1 min. This was not supported by the findings from light microscopy where similar damage was observed at both dose levels. These results suggest that such exposures might pose a risk of lung damage to man.

Animals↗
PubMed1980

Identifiable pharmacokinetic models: the role of extra inputs and measurements.

Single input, single output experiments can result in nonunique solutions for the rate constants to a linear compartmental model used to describe the pharmacokinetics. Where a finite number of solutions exists, a priori knowledge has to be used to distinguish between the solutions. Where there is a infinite number of solutions, assumptions have to be made about the values of some rate constants in order to obtained a unique solution for the other. This paper considers such experiments and determines whether either the addition of an extra input (simultaneously with the first input) or the taking of an extra measurement would result in a unique solution. It is found that perturbing a second input can be useful, but only if the perturbation is of different shape from the first input. Measurements of drug in urine and metabolite in plasma are generally not helpful in resolving identifiability of the drug dynamic model. If a radioactive tracer is used, through, the second measurement (for example, by externally scanning the radioactivity of the liver) can prove useful, but only if the gain of the measuring device is known.

Administration, Oral↗
PubMed1980

Chlorpropamide inhibition of excision repair and postreplication repair of ultraviolet damage in Chinese hamster ovary cells.

Chlorpropamide, an oral hypoglycemic agent, was tested for effects on excision repair and postreplication repair of ultraviolet (UV) damage of DNA in CHO-K1 cells. The technique used to measure excision repair involved isopycnic centrifugation of density- and isotopically-labeled DNA. Alkaline sucrose gradient sedimentation was used to monitor postreplication repair. Administration of chlorpropamide at 250 and 1000 microgram/ml after exposure of cultures to 254-nm UV reduced excision repair to 79 and 67%, resp., of control. Post-irradiation treatment with the drug at 1000 microgram/ml inhibited the postreplication gap-filling mechanism almost as effectively as did 2 mM caffeine. The hypoglycemic agent was also found to reduce UV cell survival but did not appear to alter the rate of semiconservative replication. These results suggest that chlorpropamide inhibition of repair processes may potentiate the effects of known mutagenic hazards and may also be responsible for the increased incidence of chromosome aberrations in patients treated with the drug.

Animals↗
PubMed1979

Ultrastructure of rat lungs following exposure to aerosols of dibenzoxazepine (CR).

Three groups of 18 animals were exposed respectively to the following large doses of dibenz (b.f)-1:4 oxazepine (CR) aerosols, 78,200,140,900 and 161,300 mg/min/m3. Animals were killed at intervals from 15 min to 2 days, and the lungs examined macroscopically, by electron microscopy and conventional histology. There were no deaths during or after exposure. Macroscopically the lungs from all rats appeared normal. Microscopically there were a few areas of mild congestion, haemorrhage and emphysema, but there was little variation between the different groups. Electron micrographs revealed some morphological alteration of the epithelium and endothelium but only occasional changes in the interstitium. The alterations took the form of "ballooning" of the endothelium with isolated foci of swelling and thickening of the epithelium. Interstitial oedema was observed in one animal only which was exposed to the highest concentration. The effects appeared similar in all groups, and are thought to be transient. The results of this investigation suggest that even high doses of CR aerosols cause minimal damage to the lung, and the structural alterations which do occur are believed to be due to the stress to which the animals were subjected during the exposure period.

Aerosols↗
PubMed1976

Stimulation of food intake in horses by diazepam and promazine.

In two adult horses doses of 0.02-0.03 mg/kg diazepam, intravenously, increased 1 hr intake 54-75% above control levels. Intake was stimulated when the diet was a high grain, calorically dense one and also when the diet was a high fiber, calorically dilute one. Two young rapidly growing weanling horses showed an even more pronounced stimulation of intake. Following diazepam 1 hr intake was increased 105-240% above control lelvels. Promazine at a dose of 0.5 mg/kg also stimulated intake in adult horses, but not as markedly as did diazepam. A transquilizer and a neuroleptic appear to have a stimulatory eff upon short-term intake in horses.

Age Factors↗
PubMed1976

Enzyme activity in human scars, hypertrophic scars and keloids.

Biopsies from non-hypertrophic and hypertrophic scars and from normal skin have been studied histochemically for activities of nicotanamide adenine dinucleotide diaphorase, lactate dehydrogenase, acid phosphatase, beta-D glucuronidase and alkaline phosphatase. The activities of all enzymes studied except alkaline phosphatase were found to be increased in hypertrophic scars as compared with non-hypertrophic scars and normal skin.

Acid Phosphatase↗
PubMed1975

The utilization and efficacy of pelvimetry.

Data from non random groups of deliveries with some identical clinical factors were compared and certain conclusions are suggested. Most x-ray examinations which cause significant fetal exposure are pelvimetries. There appears to be no uniform set of indications for performing pelvimetry. Instead, the criteria seem to vary from hospital to hospital and even from physician to physician within the same hospital. A normal pelvimetry gives the physicina little confidence that a cesarean section will not be necessary. The duration of labor is not significantly altered by pelvimetry in those cases needing a cesarean section for cephalopelvic disproportion or following unsuccessful oxytocin stimulation.

Cesarean Section↗
PubMed1973

Isoindole.

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Chemical Phenomena↗