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Biomedical subjects

R M Cooper

Publications and source records attributed to R M Cooper.

At least 73 records · Page 4Linked to original sources
PubMed1984

2-Deoxyglucose uptake and histologic changes in rat thalamus after neocortical ablations.

2-Deoxy[14C]glucose (2-DG) uptake was examined in pentobarbital-anesthetized rats that 3 days to 2 years earlier had sustained large posterior neocortical ablations. At 2 weeks postoperatively 2-DG uptake was pronounced in those thalamic nuclei with cortical projection zones included in the ablated region. At shorter postoperative intervals (3 to 4 days) there appeared to be no increases in 2-DG uptake in these thalamic nuclei and at longer postoperative intervals (greater than 1 month) increases were only discernible in calcified sites. Both temporal and spatial postoperative variations in 2-DG uptake were found to coincide almost perfectly with glial cell proliferation and staining in the affected regions.

Animals↗
PubMed1984

2-Deoxyglucose uptake in the thalamus of awake rats after neocortical ablations.

Local, temporary or permanent depressions and elevations in 2-deoxy[14C]glucose (2-DG) uptake were observed in the brains of unanesthetized, freely moving rats that 3 days to 1 year earlier had sustained large unilateral posterior neocortical ablations. Some of the differences in metabolic activity between the normal and damaged hemispheres, in both cortical and subcortical regions, were attributed to cell death and gliosis, and surgical trauma. In addition, it appeared that certain metabolic changes provided a physiologic correlate of diaschisis, a temporary impairment in function which von Monakow hypothesized to occur in neurons denervated by a lesion. We concluded that the 2-DG technique is a useful tool for examining the widespread effects of brain damage, and that when employed in the manner exemplified by this and a previous study, the technique can disentangle the changes in neural activity which occur after brain damage from the changes in glial activity which accompany them.

Animals↗
PubMed1981

Trimethoprim-sulfamethoxazole therapy for infective endocarditis.

A man with stenosis of the aortic valve acquired endocarditis after abdominal surgery. Klebsiella pneumoniae and Acinetobacter calcoaceticus were cultured from his blood. The blood cultures remained positive despite intravenous gentamicin and cephalothin to which the organisms were sensitive in vitro. Ultimately, the blood was sterilized by a combination of gentamicin and trimethoprim-sulfamethoxazole taken orally. The course of the patient was complicated by cardiac arrest and pericardial tamponade caused by a valve ring abscess and a dissecting mycotic aneurysm of the coronary sinus of Valsalva. Aortic valve replacement and right coronary artery bypass were performed. A prolonged course of trimethoprim-sulfamethoxazole was given postoperatively, and the patient has had no evidence of recurrent infection after five years. Trimethoprim-sulfamethoxazole, in combination with other antibiotics, has been successfully used to treat other patients with bacterial endocarditis and thus may be an alternative for patients in whom conventional therapy has failed.

Acinetobacter Infections↗
PubMed1979

Pharyngeal colonisation by Neisseria gonorrhoeae and Neisseria meningitidis in black and white patients attending a venereal disease clinic.

Pharyngeal colonisation by Neisseria gonorrhoeae and Neisseria meningitidis was studies in 2000 patients attending a venereal disease clinic. Of these patients, 64% were white and 36% were black. The incidence of gonococcal infections was highest in the period from June to August. The incidence of genital or rectal infections or both was higher in the black patients. Pharyngeal colonisation by gonococci was present in 1.3% of the patients. There was no significant associations between pharyngeal colonisation and the pharyngeal symptoms, race, sex, or marital state of the patients. Pharyngeal colonisation was more frequent in patients with gonococcal infections at other sites. However, in 40.7% of the patients with pharyngeal colonisation, the pharynx was the only culture-positive site. There was no significant difference in the auxotypes or in the antibiotic susceptibility of the pharyngeal and the rectal-genital isolates except in the susceptibility to spectinomycin. Our findings do not indicate that gonococci isolated from the pharynx differ significantly from gonococci isolated from rectal or genital sites. It was notable that meningococcal colonisation of the pharynx was significantly more frequent in the white patients. This may be a genetically determined phenomenon.

Adult↗
PubMed1979

Meningococcal colonisation misdiagnosed as gonococcal pharyngeal infection.

Three cases of pharyngeal gonorrhoea were misdiagnosed in patients harbouring meningococci which failed to utilise maltose in CTA medium. The microbiological identity of the isolates was established by other means. Although meningococci giving atypical reactions to carbohydrate utilisation tests occur only rarely, the possibility of a misdiagnosis of gonorrhea, and its social and legal repercussions, should be considered.

Adult↗
PubMed1978

Reversal set formation in the visually decorticate rat.

Rats given large visual cortex lesions demonstrated a simultaneous task reversal deficit previously reported to follow more extensive cortical ablation. However, no deficit appeared in an operant discrimination that deemphasized visuospatial cues, and the simultaneous task deficit vanished when translucent eye occluders were applied to eliminate spatial, but not intensity, cue use. Because the lesion subjects showed an impairment only when visuospatial cues were available and relevant to correct reversal performance, they seemed hindered by their incompetent processing of visuospatial information. The results are interpreted as support for spatial rather than learning approaches to visual cortex function.

Animals↗
PubMed1978

Cryoactivation and tryptic activation of blood 'prorenin' in normal man and animals.

Plasma and serum of healthy subjects apparently contain a precursor form of renin, or 'prorenin,' which can be activated by the ice-cold temperature at which samples are customarily handled for prolonged periods in laboratories and blood banks. The effect of such prior cryoactivation for 9 days at 4 degrees C is to increase subsequent plasma renin activity (PRA) at 37 degrees C by 108 +/- 16.3% (mean +/- SE) over the nonactivated control value (P less than 0.001). At a lower temperature (-4 degrees C), the cryoactivation effect is considerably greater than at 4 degrees C. Cryoactivation is not obliterated by the prefreezing of plasma, or reduced by inclusion of bacteriostats. Nor is it attributable to any detectable reduction in angiotensinase activity. In rats, cryoactivation at 4 degrees C is much lower than in humans, suggesting a marked species difference either in prorenin concentration or in the rapidity of its spontaneous conversion after blood collection. Trypsin at near optimal concentrations also consistently activates human plasma prorenin, whether at 4, 23, or 37 degrees C indicating that cold is not an essential concomitant of tryptic activation. In excess, the magnitude of which varies among individuals, trypsin at first produces activation and later a decline in PRA, probably due to degradation of the reactants (prorenin, renin, angiotensinogen) and of the initial product (angiotensin I). The identity of angiotensin I in activated and control plasmas can be established by specific radioimmunoassay, and bioassay. Our data indicate that tryptic activation involves little direct production of angiotensin I but rather converts prorenin, thereby enhancing the angiotensin generating capacity of the plasma renin system itself. Tryptic activation in plasma of anaesthetized dogs is lower than in humans, but higher than in conscious or anaesthetized rabbits in whom the effect appears to be slight. In anaesthetized rats there is virtually no tryptic activation, which is in line with the results by cryoactivation. Since the renin--angiotensin systems of dogs, rabbits, and rats have been extensively studied in experimental models of human hypertension, these observed departures from human levels of cryoactivation and tryptic activation of prorenin deserve further investigation.

Adult↗
PubMed1976

Striate cortex ablation and spatial vision.

Normal and visually decorticate rats were trained to orient to a luminous target. All subjects reached the same criterion of orientation accuracy, but operated subjects required more training and exhibited greater response latency throughout testing. To determine if visually decorticate subjects located the target according to the retinal position of its image, or only by sampling luminous flux density at different points in space, field-displacing wedge prisms were placed before the subjects' eyes to laterally displace the retinal locus of the target image without affecting luminous flux information. Prism imposition shifted orientation toward the virtual target position for all subjects. In a second study, translucent plastic was place over the subjects' eyes to disrupt the retinal topography and location of the target image while again leaving luminoux flux unaffected as a potential cue. All animals showed a dramatic and complete disruption of target localization once the diffusing material was applied. The data were considered as support for the hypothesis that 'spatial' vision survives visual decortication.

Animals↗
PubMed1976

Effects of pretectal lesions on rats wearing light-diffusing occluders.

The study provides behavioral evidence that the pretectal region of the subcortical visual system primarily mediates responses to diffuse rather than to patterned light stimuli: pretectal lesions induced greater transoperative deficits in performance of a light-dark discrimination task for rats wearing light-diffusing occluders than for non-occluded animals. Pretectal lesions also produced less transoperative disruption in animals trained to perform a pattern discrimination task (horizontal vs. vertical stripes). These results are precisely the opposite of those which follow ablation of visual cortex.

Animals↗