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Biomedical subjects

R D Richards

Publications and source records attributed to R D Richards.

At least 19 recordsLinked to original sources
PubMed1991

Prevention of selenite cataract by vitamin C.

Studies have been conducted to determine the efficacy of vitamin C in the prevention of cataracts induced by selenite. Administration of the latter to rat pups results in the development of advanced cataracts within 5 days. Treatment with ascorbate had a significant preventive effect. The observations indicate that selenite cataract is due to an oxidative stress to the lens. In addition, the findings are in conformity with our view that ascorbate functions as an anticataractogenic substance.

3,4-Methylenedioxyamphetamine↗
PubMed1988

Ascorbic acid and the eye lens.

Exposure of mice to hyperbaric oxygen leads to an inhibition of the mitotic activity in the germinative epithelium of the lens. This is followed by an eventual development of cataracts. Cataracts have also been observed in human beings treated with hyperbaric oxygen for different afflictions. The lens damage and cataract formation appears to be due to in situ generation of active radicals and other active species of oxygen. These oxygen derivatives may also contribute to the multifactorial process of senile cataract formation in human beings. This hypothesis is based on in vitro experiments with rat lenses cultured in medium generating oxygen radicals, the generation of the radicals being accomplished either photochemically or enzymatically. The ability of the lens to transport rubidium and amino acids from such a medium is adversely affected. This is a recognized index of the damage to the tissue physiology. Scavengers of active oxygen species have been found to protect against this damage. Ascorbate, present in concentrations similar to that in the primate aqueous and lens, is also protective. The studies, therefore, point to an antioxidant and perhaps an anti-cataract effect of ascorbate. Pyruvate is another agent useful in this regard.

Animals↗
PubMed1987

Glaucoma.

Explore the source record for details and available documents.

Adrenergic beta-Antagonists↗
PubMed1987

Hexose monophosphate shunt in rat lens: stimulation by vitamin C.

The metabolism of glucose through the hexose monophosphate (HMP) shunt has been studied in rat lens in vitro, in the absence and presence of ascorbic and dehydroascorbic acids. Both forms of the vitamin stimulated the utilization of glucose through the HMP shunt, the stimulatory effect of dehydroascorbate being substantially greater than that of ascorbate. The stimulatory effect of ascorbate, as well as of dehydroascorbate, was antagonized by sodium iodide, and N,N-bis (dichloroethyl)-N-nitrosourea, compounds known to inhibit glutathione reductase. N-ethylmaleimide also antagonized the stimulation. These findings, therefore, suggest that the DHA/AA redox couple acts in concert with the GSSG/GSH couple in stimulating the tissue shunt activity.

Animals↗
PubMed1986

Ambulatory pulmonary arterial pressures in humans: relationship to arterial pressure and hormones.

Six healthy volunteers were studied by use of a continuous ambulatory recording technique to document the normal range and variability of pulmonary artery pressure (PAP) and to examine its relationship to systemic arterial pressure (SAP) both at rest and during standardized interventions. Vasoactive hormone levels were measured at frequent intervals. Over 8-10 h of study the mean PAP was 15.7/6.3 mmHg. Parallel changes in PAP and SAP were observed at rest and during exercise and eating. On the contrary, PAP rose and SAP fell with hypoxia, whereas smoking was associated with a rise in SAP but no change in PAP. Sympathetic nervous system activity, as gauged by plasma norepinephrine levels, may have contributed to pressure and heart rate changes during exercise and smoking, but activity of the renin-angiotensin system was not altered by any of the maneuvers. These results provide base-line information on the level of PAP and its variability in healthy volunteers under standardized conditions. Pressures within the systemic and pulmonary circuits change in parallel under some circumstances but move in opposite directions under other conditions.

Adult↗
PubMed1985

Complications associated with the use of the neodymium:YAG laser.

The neodymium:YAG laser was used in a consecutive series of 93 eyes. Diagnosis was opacified posterior capsule in 81 eyes of which 52 were pseudophakic, with cystoid macular edema and vitreous strands in eight eyes, pigmented anterior hyaloid in two eyes, opacified anterior capsular flap in one eye and vitreous strand blocking an anterior chamber tube shunt to an encircling band tube in one eye. Despite significant visual improvement and reduction of cystoid macular edema, a variety of complications were seen. These included pitting of the implant in 26 eyes and cracks in four, two of which developed a vitreitis. These occurred more frequently in our earlier cases. Also seen was elevated IOP in six eyes, pupillary block in two, vitreous face rupture in five, cystoid macular edema in four, hyphemas in four, corneal injury in two and acute peripheral retinal hemorrhage in one eye.

Cataract Extraction↗
PubMed1985

Anterior chamber tube shunt to an encircling band in the treatment of neovascular glaucoma and other refractory glaucomas. A long-term study.

Long-term follow-up results of the anterior chamber tube shunt to an encircling band (ACTSEB) procedure are reported. Thirty eyes of 28 patients with neovascular glaucoma (Group I) and five eyes with non-neovascular refractory glaucoma (Group II) underwent this procedure. In Group I, the average preoperative intraocular pressure (IOP) was 57.1 mmHg. After surgery and average followup of 25 months 96% of eyes had a successful outcome with an average IOP of 15.8 mmHg (P less than 0.001). In Group II, despite multiple glaucoma surgical procedures, the average preoperative IOP was 54 mmHg. After surgery and average followup of 20 months 80% of eyes had a successful outcome with an average IOP of 19.8 mmHg (P less than 0.01). Revisions in our surgical technique utilizing a small entry with a 25-gauge needle into the anterior chamber and use of Healon resulted in a fully formed anterior chamber by two days. Clinical and experimental evidence is presented which suggest that aqueous filters through the tube to a reservoir around the encircling band.

Adult↗
PubMed1979

Light-induced damage to ocular lens cation pump: prevention by vitamin C.

The cation pump activity of the ocular lens was damaged by exposure to light in the presence of riboflavin phosphate. The intensity of light was similar to that used for reading purposes. The observed light-induced damage was due to superoxide or its derivatives, the superoxide being produced photochemically. Such damage was attenuated by vitamin C in amounts comparable to that in the aqueous humor. Thus, a new role for the high ascorbate level present in the anterior chamber fluid and the lens has been suggested. Ascorbate in other tissues also might have this novel physiological function of protecting against damage due to superoxide and its derivatives produced during normal cellular oxidation.

Animals↗
PubMed1979

Implications of aldose reductase in cataracts in human diabetes.

Cataracts removed intracapsularly by cryoprobe technique from human diabetics were analyzed for sugars and polyols by gas liquid chromatography. The contents of sorbitol and fructose of lenses followed blood glucose levels at least up to 250 mg/dl. Studies indicate that human lens is capable of synthesizing substantial amounts of polyol pathway metabolites given exposure to high glucose levels such as are prevalent in diabetes. The synthesis of sorbitol was found to be susceptible to quercitrin, an inhibitor of aldose reductase. The implications of these findings in the formation of cataracts in diabetic individuals have been discussed.

Aldehyde Reductase↗
PubMed1979

Simulataneous occlusion of the central retinal artery and vein.

Combined CRAO/CRVO in our patients occurred with rapid visual loss, usually over a few hours, associated with evidence of inflammation and/or cellular infiltration of the retrobulbar portion of the optic nerve. The ophthalmoscopic appearance was characteristic, with papilledema and hemorrhages of various types in the posterior pole. The retina also showed ischemic changes, with a milky-white color and cherry-red macula. Fluorescein angiography, when possible, showed no retinal vascular flow, and normal choroidal flow. After six to eight weeks, optic atrophy was evident and the retinal vessels were markedly narrowed or obliterated. The macula showed typical cystic changes. Neovascularization often developed, leading to neovascular glaucoma as the end result.

Adult↗
PubMed1978

Ophthalmologic toxicity after cis-dichlorodiammineplatinum(II) therapy.

Two cases of apparent ophthalmologic toxicity which occurred during treatment with cis-dichlorodiammineplatinum(II) (DDP) are described. In the first case, a patient with testicular carcinoma developed papilledema after three courses of DDP and adriamycin therapy. In the second case, a patient with breast cancer developed retrobulbar neuritis after three courses of DDP therapy. The differential diagnosis and possible explanation for these toxic effects are discussed.

Aged↗
PubMed1975

Statistics of eye collections.

Our data show cause of death is relatively unimportant as a factor in determining if donor eyes will be used for corneal transplantation. Two factors that are important are age of donor and time of donation (weekday vs weekend). Cultures taken at time of enucleation are positive 50% of the time. Treatment with antibiotics will reduce this to 20% to 30%. Most organisms are considered nonpathogenic and probably not important, but 15% of positive cultures of eyes used for corneal transplantation (about 4% of eyes obtained) had potentially pathogenic organisms present.

Adolescent↗