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Biomedical subjects

R L Cooper

Publications and source records attributed to R L Cooper.

At least 181 records · Page 10Linked to original sources
PubMed1977

"Blow-in" fracture of the orbit with partial visual loss and choroidal folds.

Choroidal fold formation caused by "blow-in" fracture of the orbit is described. Rapid and almost complete recovery of vision followed removal of the bone fragments compressing the globe. The findings in this case support the conclusions of recent animal experiments on the pathogenesis of choroidal folds. Congestion of the choroid and adhesions to Bruch's membrane are probably prerequisites for folds to form, and folds are aligned perpendicular to a force applied to the eye.

Adult↗
PubMed1977

Infective keratitis in soft contact lens wearers.

Eight cases of infective keratitis are reported in wearers of soft contact lenses. Four of them had normal eyes and were wearing lenses on a continual basis. One was wearing a lens continually for therapeutic reasons. Three others were wearing lenses daily or intermittently. The four latter cases were using contaminated lens solutions. Two of the continual lens wearers lost vision to the point of blindness. A significant factor in their bad outcome was the fact that both lived in areas remote from adequate ophthalmic services. Serratia liquefaciens was implicated in one case. This is thought to be the only reported case of corneal abscess due to this organism in the past 16 years. S. marcescens was grown in another case from the lens solutions and carrying case.

Adult↗
PubMed1977

Radio telemetry of intraocular pressure in vitro.

A guard ring pressure transensor, using the principles of surface applanation, was used to transmit intraocular pressure (IOP) from a cadaver canine eye. The transensor consisted of a passive resonant coil/capacitor combination, made pressure sensitive by the movement of a small ferrite plate which acted as its applanating surface. Oscillation induced in the transensor by a remote grid dip oscillator (GDO) was monitored by a digital frequency counter (DFC). The resonant frequency of oscillation in the transensor bore a linear relationship to the in vitro IOP in three separate experiments (coefficient of determination for linear regression, r2 equals 0.90). These data indicate that radio telemetry is feasible, using a miniature applanating passive radio telemetric device for continual monitoring of IOP.

Animals↗
PubMed1976

On the visual disturbances associated with massive basal aneurysms.

When massive basal aneurysms compromise the anterior visual pathways the resulting disturbances of vision are diverse and a firm clinical diagnosis is difficult. Because of the rarity of the condition, a critical analysis of the visual defects was made in five personally studied patients with large anterior basal aneurysms in an effort to clarify the clinical features of the disorder. These observations were related to those reported in larger series of patients by Jefferson and Bull. This study gives support to the opinion that the commonest visual defect seen with massive basal aneurysms is impairment of visual acuity, followed next in frequency by bitemporal hemianopia, and then by junction scotoma.

Adult↗
PubMed1976

Reinstatement of vaginal cycles in aged female rats.

Old constant estrous and young cycling control rats were injected with L-dopa, 200 mg/kg, for a period of 14 days. L-Dopa reinstated vaginal cycling in the old rats and it did not affect the vaginal cycling in young rats. Likewise, 200 mg/kg of L-tyrosine reinstated vaginal cycling. The effect of L-dopa on old rats was blocked by pimozide, by high doses of MK-486 and Ro 4-4602, and by fusaric acid. High doses of phenoxybenzamine or L-propranolol did not alter the L-dopa effect on old rats. A low dose of MK-486 or Ro 4-4602 increased the efficacy of L-dopa in reinstating vaginal cycling. These results suggest that L-dopa reinstates vaginal cycling in old rats by stimulating dopamine receptors. The possibility that a simultaneous stimulation of norepinephrine alpha and beta receptors and/or a decrease of central nervous system serotonin is necessary for this effect is discussed.

Aging↗
PubMed1975

Age-dependent changes in hippocampal theta.

The hippocampal theta rhythm in rats exhibited an age-dependent slowing in modal frequency. However, the theta rhythm of young rats with chronic respiratory infections showed a similar slowing. Respiratory disease-free hamsters also exhibited an age-dependent slowing of modal frequencies. These findings emphasize that the health status of the animal must be examined carefully in order to establish an age-dependent slowing in hippocampal rhythm.

Age Factors↗
PubMed1974

Restricted diffusion in biophysical systems. Experiment.

The pulsed-gradient spin echo nuclear magnetic resonance (PGSENMR) technique was used to measure restricted diffusion of water in three types of animal tissue: human blood plasma and red cells; rat and rabbit heart; rat and rabbit liver. Characteristic lengths (L) for restriction of diffusion are estimated from dependence on the measuring time. Limitations on the range of observable restrictive lengths (1.5-15 mum) are discussed.The decrease in diffusivity due to 1 mum alumina powder (volume fraction = 0.18) in glycerin/water mixtures agrees with the Wang theory assuming spherical particles and no hydration. The characteristic length (L approximately 4 mum) is larger than the particle size (1 mum) or separation (1.8 mum). Comparison of the diffusivities in tissues at short diffusion times with the Wang theory indicates some bound or trapped water.For packed red blood cells, a restriction (L approximately 2.3 mum) was attributed tothe red cell membrane. A permeability p approximately 0.014 cm/s may be estimated from the decrease in diffusivity. Average values of diffusivity ratio in heart were: 0.36 +/- 0.02 for rat; and 0.26 +/- 0.03 for rabbit; and in liver: 0.25 +/- 0.01 for rat; 0.25 +/- .04 for 10-day old rabbit; and 0.195 +/- 0.03 for 2-yr old rabbit. A restriction (L approximately 2.7 mum) in rat liver probably results from the mitochondria.

Aluminum↗
PubMedDate not supplied

Umbilical cord serum levels of thromboxane B2 in term infants of women who participated in a placebo-controlled trial of low-dose aspirin.

OBJECTIVE: Our aim was to quantify thromboxane B2 (TXB2) in umbilical cord serum of term infants of nulliparous, low-risk women who were randomly assigned to either placebo or low-dose (60 mg) aspirin (ASA) on a daily basis from 24 weeks' gestation through delivery as part of a randomized clinical trial for prevention of preeclampsia. METHODS: Umbilical cord sera from 230 singleton, term infants whose mothers were involved in our low-dose ASA trial were assayed for TXB2, the stable metabolite of thromboxane A2, without knowledge of treatment or outcome data. The data were related to assigned treatment group, longitudinal pattern of maternal serum TXB2 levels, and other maternal and newborn characteristics. The data also were analyzed according to whether or not maternal serum levels of TXB2 at 29-31, 34-36, and delivery were reduced > or =50% compared to values prior to initiation of the trial. RESULTS: Umbilical cord TXB2 levels (ng/ml, mean +/- SE) were significantly lower at term in the ASA group (36.1 +/- 3.3, n = 111) than in the placebo group (56.6 +/- 5.7, n = 119; P = 0.002). Umbilical cord TXB2 levels were correlated to those in maternal serum at delivery in the ASA group (r = 0.3441; P = 0.0005) but not in the placebo group (r = 0.0626; P = 0.53). Regardless of assigned treatment group, infants whose mothers had a > or =50% longitudinal reduction in serum TXB2 had lower umbilical cord TXB2 levels (39.2 +/- 3.6, n = 114) than infants whose mothers had <50% reductions in TXB2 (54.6 +/- 5.9, n = 116; P = 0.027). Birthweights of these infants correlated inversely (r = 0.1678, P = 0.017) with maternal serum TXB2 at delivery but not to umbilical cord TXB2 levels; the best correlation between birthweight and maternal serum TXB2 was noted in pregnancies assigned to receive placebo (r = -0.2558, P = 0.009). CONCLUSIONS: Umbilical cord serum levels of TXB2 1) are reduced in instances of long-term maternal ingestion of ASA, 2) correlate well with maternal serum levels of TXB2 at delivery when there is evidence for consistent maternal use of ASA, but 3) do not correlate with maternal serum TXB2 levels when there is no evidence for frequent maternal ingestion of cyclooxygenase inhibitors. These data suggest that the capacity for platelet production of TXA2 in fetal and maternal compartments are regulated independently. Finally, there is an inverse relationship between maternal serum TXB2 levels at delivery and birthweight of newborn infants that is most evident among the pregnancies assigned to placebo and also among pregnancies in which there was little evidence to suggest a pattern of cyclooxygenase inhibitor use during pregnancy.

Adult↗
PubMedDate not supplied

Effects of metal cations on pituitary hormone secretion in vitro.

Increased body burdens of metal cations are known to affect adversely reproductive function in several species. The effects of these metals on gonadal function are well documented. In contrast, little is known about their possible direct effects on pituitary hormone release. The purpose of this study was to determine, in vitro, the effects of nickel, cadmium, and zinc (50 microM) on both baseline and potassium chloride (KCl)-stimulated pituitary luteinizing hormone (LH), prolactin (Prl), and thyroid-stimulating hormone (TSH) release. Anterior pituitary fragments from adult male Long-Evans rats were evaluated using a continuous-flow perifusion system. Baseline and stimulated LH releases were unaffected by nickel and zinc; however, cadmium caused an increase in baseline LH secretion. Baseline Prl release was decreased by zinc, while cadmium resulted in increased release of this hormone. Stimulated Prl release was lower during exposure to zinc but unaltered by nickel and cadmium. Following exposure to zinc, a rebound in stimulated release was noted for all three hormones measured. These results showed that the metal cations tested did have a direct effect on pituitary hormone release at a dose lower than those reported to alter testicular function in vitro. Furthermore, the changes in pituitary hormone secretion varied depending upon the metal and hormone being evaluated.

Animals↗
PubMedDate not supplied

Quantal measurement and analysis methods compared for crayfish and Drosophila neuromuscular junctions, and rat hippocampus.

Quantal content of transmission was estimated for three synaptic systems (crayfish and Drosophila neuromuscular junctions, and rat dentate gyrus neurons) with three different methods of measurement: direct counts of released quanta, amplitude measurements of evoked and spontaneous events, and charge measurements of evoked and spontaneous events. At the crayfish neuromuscular junction, comparison of the three methods showed that estimates from charge measurements were closer to estimates from direct counts, since amplitude measurements were more seriously affected by variable latency in evoked release of quantal units. Thus, charge measurements are better for estimating quantal content when direct counts cannot be made, as in crayfish at high frequency of stimulation or in the dentate gyrus neurons. At the Drosophila neuromuscular junction, there is almost no latency variation of quantal release in realistic physiological solutions, and the methods based upon amplitudes and charge give similar results. Distributions of evoked synaptic quantal events obtained by direct counts at the crayfish neuromuscular junction were compared to statistical distributions obtained by best fits. Binomial distributions with uniform or non-uniform probabilities of release generally provided good fits to the observations. From best fit distributions, the quantal parameters n (number of release sites) and p (their probability of release) can be calculated. We used two algorithms to estimate n and p: one allows for non-uniform probability of release and uses a modified chi-square (chi 2) criterion, and the second assumes uniform probability of release and derives parameters from maximum likelihood estimation (MLE). The bootstrap estimate of standard errors is used to determine the accuracy of n and p estimates.

Animals↗
PubMedDate not supplied

Catecholaminergic-serotonergic balance in the CNS and reproductive cycling in aging rats.

Treatment with the serotonin (5-HT) reuptake inhibitor zimelidine, 20 mg/kg/24 hr, SC, for 14 days increased the duration of vaginal cycles in 3 month-old Long Evans hooded rats. It induced persistent vaginal estrus in 12 of 16 ten-month-old animals, and blocked reinitiation of vaginal cycles by L-dopa in 10 of 10 twenty-month-old rats. A single injection of zimelidine at 1400 hr did not alter the vaginal smear pattern of young or middle-aged cycling females or old constant estrus females. Also, a single dose of zimelidine at 1400 hr on the day of vaginal proestrus had no effect on serum LH values in young females. The serotonergic neurotoxin 5,7-dihydroxytryptamine, 4 micrograms, injected into the ventral and dorsal raphe areas (after desipramine, 25 mg/kg IP) reinitiated vaginal cycling in 8 of 13 twenty-month-old rats. These results suggest that age-dependent changes in serotonin metabolism may contribute to the age-dependent changes in luteinizing hormone secretion which eventually lead to the cessation of ovarian function in the rat and that alterations in serotonin function are an important component of the mechanism by which treatments with catecholamine precursors reinstate ovarian function in the old female rat.

5,7-Dihydroxytryptamine↗