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Biomedical subjects

R L Cooper

Publications and source records attributed to R L Cooper.

At least 163 records · Page 9Linked to original sources
PubMed1981

The Arden grating acuity: effect of age and optical factors in the normal patient, with prediction of the false negative rate in screening for glaucoma.

The Arden contrast sensitivity was investigated in normal persons, cataract eyes, and glaucoma patients with only plates 6 and 7 of the Arden grating set. The mean score of 90 normal eyes on plate 6 was 9.50 +/- 2.29 and on plate 7 it was 9.44 +/- 2.32. The mean scores of patients with early cataract were 14.51 +/- 2.99 on plate 6 and 13.74 +/- 3.26 on plate 7. Several patients with cataract missed the grating on plate 7. Mydriasis and miosis did not affect contrast sensitivity in normal eyes. Mydriasis significantly improved contrast sensitivity in patients with early cataract. In patients with glaucoma enlargement of the pupil from a miotic state to near normal size significantly improved contrast sensitivity. It is predicted that if plate 6 and 7 are used in mass screening for glaucoma in the elderly, there will be a false negative rate of 83% for plate 6 and 52% for plate 7. A false positive rate of 17% is predicted.

Adolescent↗
PubMed1981

Regeneration of retinal limiting membranes after chorioretinal biopsy in dogs.

After chorioretinal biopsy in dogs, obtained without vitreous loss, accessory glial cells and fibroblasts filled the defect between cortical vitreous and bare sclera. The proliferating glial cells laid down a new basement membrane which was complete both on the internal and external aspects of the defect. After biopsy complicated by vitreous loss, however, cellular proliferation failed to re-establish complete internal and external limiting membranes, and new formed fibroblastic tissue extended into the vitreous. To our knowledge, this is the first report to describe effective regeneration of the internal limiting membrane of the retina in any species. These findings suggest that when vitreous loss can be avoided, healed chorioretinal biopsies are unlikely to lead to delayed pathological complications.

Animals↗
PubMed1980

Vasopressin and conditioned flavor aversion in aged rats.

The effect of lysine vasopressin on the performance of young-adult and old rats subjected to a conditioned flavor aversion procedure was studied. Young rats maintained an aversion to a 0.1% saccharin solution significantly longer than did older rats. Treatment with lysine vasopressin ( 1 microgram/kg) during the recovery period prolonged the aversion in both age groups. A single injection of lysine vasopressin prior to the aversion procedure significantly reduced the age difference in extinction. These observations support the hypothesis that age-dependent changes in endogenous vasopressin synthesis or secretion underlie some of the behavioral deficits observed in old animals.

Aging↗
PubMed1980

Macular oedema and retinal branch vein occlusion.

The visual prognosis of patients suffering from retinal branch vein occlusion complicated by macular oedema is assessed in relation to the degress of capillary fallout. Extensive retinal capillary fallout associated with macular oedema was found to confer a poor visual prognosis in a series of 89 patients followed for an average time of 14 months. If the degree of capillary fallout associated with marular oedema was minimal, the visual prognosis was considerably improved.

Capillaries↗
PubMed1980

Mass screening of glaucoma and other eye disease using the Arden grating test.

The Arden grating test of visual function has been used for mass screening for glaucoma in Western Australia over the past year. A brief description of the test is given. Comparison is made between the Arden grating test scores, tonometry and optic disc cupping. Other eye diseases detected with this method of screening are outlined. An attempt is made to establish the proportions of false positives and negatives using this method.

Adult↗
PubMed1980

Effects of centrally and systemically administered L-tyrosine and L-leucine on ovarian function in the old rat.

The effects of centrally and systemically administered L-leucine and L-tyrosine on ovarian function were studied in the old female rat. Systemically administered L-tyrosine reinstated regular vaginal cycling and ovulation, whereas systemically administered L-leucine did not. When administered centrally, through an indwelling cannula in the medial preoptic area, neither L-tyrosine nor L-leucine altered the ovarian or vaginal condition of the old female. When these females were subsequently treated with L-dopa, both systemic and central application were found to reinstate ovarian cycles. Potential mechanisms of action at the level of CNS monoaminergic neurotransmission are discussed.

Aging↗
PubMed1980

Medical correlates and diabetic retinopathy screening.

A systematic ophthalmological, medical, and biochemical screening of a rural population of diabetics in Western Australia is being carried out. A team of ophthalmologists, physicians, and paramedical personnel establish regional screening centres on a voluntary basis at weekends. Every attempt is made to locate and examine all known diabetics. All patients are given a thorough ophthalmic examination including standard multiple field colour fundus photography. Thorough physical examination includes assessment of cardiovascular and neurological status. Biochemical parameters include random blood sugar, urine analysis, serum creatinine, glycosylated haemoglobin, cholesterol, and high density lipoprotein. A detailed questionnaire and interview is carried out to assess the historical degree of control and the patient's knowledge of the control and management of diabetes. The sample now comprises an unselected population of 400 diabetics living in rural areas and allows comparison of areas which have scarce medical services with centres that are well supplied with medical practitioners. Incidence of retinopathy varies from 25 to 36 per cent of the diabetic population. Positive correlations of retinopathy have been found with duration, age, hypertension, level of control assessed biochemically at the time of examination, presence of ischaemic heart disease, peripheral neuropathy, and renal disease. Smoking also correlates positively. The data provide a baseline by which attempts to alter diabetic knowledge, management, and control may be measured in follow-up studies.

Adolescent↗
PubMed1979

Induced ovulation in aged female rats by L-dopa implants into the medial preoptic area.

Direct placement of L-dopa into the medial preoptic area (MPOA) of aged pseudopregnant or constant vaginal estrous female rats resulted in a reinitiation of vaginal cycles and ovulation. Similar treatment with L-dopa in the dorsomedial septum or cortex was ineffective. Direct placement of leucine into any of the three brain regions did not have an effect on ovarian function. Intermittent treatment with L-dopa to MPOA was found to reinstate and maintain vaginal cycles in constant estrous females only when administered on the day of vaginal estrus of successive cycles. These findings support the hypothesis that age-dependent disturbances in ovarian function may be initiated by changes in neurotransmitter metabolism within the central nervous system.

Age Factors↗
PubMed1979

Passive radiotelemetry of intraocular pressure in vivo: calibration and validation of continual scleral guard-ring applanation transensors in the dog and rabbit.

Continual monitoring of intraocular pressure (IOP) by passive radiotelemetry, with a miniature scleral applanating device, mounted in a haptic contact lens (applanating transensor) is reported in the rabbit and dog. Several prototype transensors were calibrated in vivo in the rabbit and dog; a consistent linear output was obtained for each eye, although reproducibility of the slope between eyes over a period of time was less than ideal. Accuracy of determination of IOP was found to be better for the rabbit and will have to be improved before the instrument can be applied to the human. Multiple regression analysis of calibration studies in six rabbits established that the transensor output was not significantly affected by the small changes in body temperature and atmospheric pressure encountered during the study. Continual scleral tonometry with a standard Mackay-Marg tonometer showed that ocular rigidity has a significant effect on calibration curves, in contradistinction to standard Mackay-Marg corneal tonometry. A time-dependent decay in tonometer readings was more evident in canine eyes with low ocular rigidity. Since the transensor is also a guard-ring applanating device, calibration may be necessary for individual eyes and species.

Animals↗
PubMed1978

Influence of the thyroid gland on ovarian function in the aging rat.

The effects of underfeeding and manipulation of the thyroid axis on ovarian function were determined in young and old rats. The depressant effect of reduced food intake on ovarian cycling in young females was potentiated by chemical thyroidectomy, while young anestrous, underfed rats cycled when their diet was supplemented with thyroid extract. These observations iindicate that cycling aberrations in underfed rats may occur secondarily to an altered thyroid state. To determine if thyroid state influences ovarian function in old animals, constant estrous (CE) rats were underfed or chemically thyroidectomized. All underfed rats eventually cycled, while the response to chemical thyroidectomy alone, though still effective, was less dramatic. Realimented CE animals eventually returned to a pattern of constant vaginal cornification. Underfeeding had no effect on ovarian function in old recurrently pseudopregnant females however, these rats responded to thyroid treatment with renewed cycling. 4-6 (YC) 10-12 (PEP) month old females entered a persistent vaginal estrous condition when fed low doses of thyroid extract with their ad libitum diet. When the thyroid supplemented diet was discontinued, YC females resumed regular cycling, whereas the vaginal smear in 40% of the PEP rats remained cornified. Cycling could be restored in YC-thyroid induced CE rats by electrochemical stimulation of the medial preoptic area. These date suggest that senile deviations from normal cycling in the aging reproductive system may be affected by alterations in the thyroid state.

Aging↗