Photosensitivity of the isolated pigment epithelium and arachidonic acid metabolism: preliminary results.

The administration of 0.1-0.5% of ethanol produces a slow increase in the transepithelial potential (TEP) of about 2 mV in the bovine pigment epithelium (RPE) under ordinary room lighting.

The possible role and treatment of deficient microcirculation regulation in age-associated memory impairment.

The assumption that all mental activity is accompanied by changes in blood flow to the activated areas of the brain implies that precisely controlled mechanism of regulation are in operation. Part of the regulatory mechanisms would involve the dilation of arterioles. Experimental studies have shown that aged or damaged cerebral arterioles lose their responsiveness to vasodilators which presumably activate nitric oxide (EDRF).

The potentiating effects of ethanol on the blue light depolarization of the retinal pigment epithelium.

The retinal pigment epithelium (RPE) is the site of two major effects of ethanol. In humans, ethanol produces a slow damped oscillation in the steady electrical potential of the eye, which is generated primarily by the RPE. It has also been shown that ethanol potentiates the reversible, depolarizing effect of blue light on the transepithelial potential (TEP) of the isolated RPE.

The effects of retina-derived factors on the electrical and ultrastructural properties of the bovine pigment epithelium.

The transepithelial potential (TEP) and short circuit current (SCC) of the bovine retina pigment epithelium (RPE) were monitored throughout a 3hr period. Application of retina-derived factors to the apical side of the preparation resulted in a stabilization of the TEP and SCC, followed by a secondary rise in both electrical parameters. The late, secondary rise could be eliminated or reduced by the administration of cycloheximide suggesting a dependence upon protein synthesis.

Hemoprotein(s) mediate blue light damage in the retinal pigment epithelium.

In order to elucidate the mechanisms of blue light damage on ocular tissues, the transepithelial transport, electrical characteristics and ultrastructural properties of irradiated isolated bovine retinal pigment epithelium (RPE) were investigated. Blue light (430 nm) irradiation at 20 mW/cm2 significantly reduced the transepithelial potential and short circuit current of RPE. During blue light exposure, a decrease in chloride transport was observed, and this decrease appeared to be closely coupled to changes in the electrical properties of the pigment epithelium.

Modification of leucine transport across bovine pigment epithelium by metabolic stress.

The transport of leucine in the apical-to-basal (retina to choroid) direction across the isolated bovine retinal pigment epithelium is mediated predominantly by the L amino transport system at low carrier (10 microns) concentrations. There is no evidence of an active or facilitated transport system operating in the opposite direction. The identification of the L system is based on the lack of sodium dependence, specific inhibition of leucine transport by 2-aminobicyclo-(2,2,1)-heptane-2-carboxylic acid (BCH), and the demonstration of trans-stimulation.

Effect of disodium cromoglycate (DSCG) and antihistamines on postirradiation cerebral blood flow and plasma levels of histamine and neurotensin.

In an attempt to elucidate mechanisms underlying the irradiation-induced decrease in regional cerebral blood flow (rCBF) in primates, hippocampal and visual cortical blood flows of rhesus monkeys were measured by hydrogen clearance, before and after exposure to 100 Gy, whole-body, gamma irradiation. Systemic blood pressures were monitored simultaneously. Systemic arterial plasma histamine and neurotensin levels were determined preirradiation and postirradiation.

The action of factor Xa on peptide p-nitroanilide substrates: substrate selectivity and examination of hydrolysis with different reaction conditions.

Kinetic parameters for the action of bovine Factor Xa (EC 3.4.21.

Transport of acidic amino acids by the bovine pigment epithelium.

The regulation of acidic amino-acid transport across the retinal pigment epithelium is of particular interest since glutamate and possibly aspartate have been identified as putative neurotransmitters in the retina, at the level of the photoreceptor cell. The present study, designed to measure the rate of acidic amino-acid transport across the mammalian pigment epithelium (PE), shows that there is a net transport of both glutamate and aspartate in the retina to choroid direction (R-C), with the R-C unidirectional flux of glutamate being substantially larger than the corresponding aspartate flux. The R-C and C-R fluxes of glutamate were found to be inhibited by ouabain.

Disodium cromoglycate, a mast-cell stabilizer, alters postradiation regional cerebral blood flow in primates.

Early transient incapacitation (ETI) is the complete cessation of performance during the first 30 min after radiation exposure, and performance decrement (PD) is a reduction in performance at the same time. Supralethal doses of radiation have been shown to produce a marked decrease in regional cerebral blood flow in primates concurrent with systemic hypotension and a dramatic release of mast-cell histamine. In an attempt to elucidate mechanisms underlying the radiation-induced ETI/PD phenomena and the postradiation decrease in cerebral blood flow, primates were given the mast-cell stabilizers disodium cromoglycate (DSCG) or BRL 22321 (Beecham Pharmaceuticals, Research Division) before exposure to 100 Gy whole-body gamma radiation.

Determination of bovine retinal melatonin with HPLC-EC.

Unlabelled: Bovine retinae, devoid of pigment epithelium, were assayed for endogenous melatonin using high-performance liquid chromatography with electrochemical detection (HPLC-EC). A method of extracting the more polar biogenic amines and metabolites was employed, allowing for direct injection of retinal supernatants into the chromatographic column.

The Results: 1) confirm the presence of melatonin in the bovine retina; 2) provide a "benchmark" of 3.

The effect of diet on inherited retinal dystrophy in the rat.

The rate of photoreceptor cell degeneration was significantly retarded in albino rats afflicted with inherited retinal dystrophy by merely changing the food supply from a commercial lab chow to a well defined diet. The data suggest that female dystrophic rats may benefit somewhat more from this dietary manipulation than the males. A well defined fat-free diet was less successful than a standard defined diet in retarding the rate of retinal degeneration.

In situ kinetics of glucose transport across the blood-retinal barrier in normal rats and rats with streptozocin-induced diabetes.

Glucose transport across the blood-retinal barrier (BRB) was investigated in situ by means of a modification of the single-injection technique developed for studying transport across the blood-brain barrier. A retinal uptake index was calculated from the fractional extraction for 14C-glucose divided by the fractional extraction for the 3H2O reference. The use of the Eadie-Hofstee transformation to determine the Km of carrier-mediated transport revealed at least two transport systems for the unidirectional glucose flux across the BRB.

Transport of 3-O-methylglucose in isolated rat retinal pigment epithelial cells.

The uptake of 3-O-methylglucose in isolated rat retinal pigment epithelial cells exhibits complex kinetics as revealed by a plot of the Lineweaver-Burke transformation of the Michaelis-Menten equation. Conventional analysis of the linear portion of the double-reciprocal plot yields a Km of 7 . 69 mM and a Vmax of 1 .

The effect of induced diabetes on the electroretinogram components of the pigmented rat.

The fast and slow components of the electroretinogram (ERG) of the pigmented rat were observed 2, 4, and 19 weeks after the induction of diabetes by streptozotocin. The diabetic state was confirmed by measures of serum and urine glucose and the appearance of polydipsia and polyuria. There was no apparent effect on the b-wave of the ERG in the diabetic animals at the 2- and 4-week periods of observation; however, at 19 weeks the form of the intensity-amplitude curve differed from that of the controls.