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Biomedical subjects

S Charles

Publications and source records attributed to S Charles.

At least 55 records · Page 3Linked to original sources
PubMed1983

Ocular hypothermia: anterior chamber perfusion.

The anterior chambers of 27 rabbit eyes were perfused at constant pressure with room temperature (25 degrees C) or cooled (11 degrees C) balanced salt solution at constant flow rates of 4.8 ml/min or 8.5 ml/min. Intraocular temperature changes in the anterior chamber, anterior vitreous, mid vitreous, and posterior vitreous and on the retina surface were monitored with an intraocular thermocouple probe. Perfusion of the anterior chamber of the pigmented rabbit eye with cooled fluid significantly reduced the temperature of the anterior chamber and anterior vitreous and even that of the retina. Both an increase in the rate of perfusion and a lowering of the perfusion temperature enhanced the cooling effect. The observed decrease in temperatures returned to approximately normal 4 minutes following the cessation of perfusion.

Animals↗
PubMed1982

A single mechanism for the stimulation of insulin release and 86Rb+ efflux from rat islets by cationic amino acids.

The mechanisms by which cationic amino acids influence pancreatic B-cell function have been studied by monitoring simultaneously (86)Rb(+) efflux and insulin release from perifused rat islets. The effects of two reference amino acids arginine and lysine were compared with those of closely related substances to define the structural requirements for recognition of these molecules as secretagogues. Arginine accelerated (86)Rb(+) efflux and increased insulin release in the absence or in the presence of 7mm-glucose. Its effects on efflux did not require the presence of extracellular Ca(2+) or Na(+), but its insulinotropic effects were suppressed in a Ca(2+)-free medium and inhibited in an Na(+)-free medium. Among arginine derivatives, only 2-amino-3-guanidinopropionic acid mimicked its effects on (86)Rb(+) efflux and insulin release; citrulline, guanidinoacetic acid, 3-guanidinopropionic acid and guanidine were inactive. Norvaline and valine also increased (86)Rb(+) efflux, but their effect required the presence of extracellular Na(+); they did not stimulate insulin release. Lysine as well as the shorter-chain cationic amino acids ornithine and 2,4-diaminobutyric acid accelerated (86)Rb(+) efflux in a Ca(2+)- and Na(+)-independent manner. Their stimulation of insulin release was suppressed by Ca(2+) omission, but only partially inhibited in an Na(+)-free medium. The uncharged glutamine and norleucine increased the rate of (86)Rb(+) efflux in the presence of glucose, only if extracellular Na(+) was present. Norleucine slightly increased release in a Ca(2+)- and Na(+)-dependent manner. The effects of lysine on efflux and release were not mimicked by other related substances such as 1,5-diaminopentane and 6-aminohexanoic acid. The results suggest that the depolarizing effect of cationic amino acids is due to accumulation of these positively charged molecules in B-cells. This causes acceleration of the efflux of K(+) ((86)Rb(+)) and activation of the influx of Ca(2+) (which triggers insulin release). The prerequisite for the stimulation of B-cells by this mechanism appears to be the presence of a positive charge on the side chain of the amino acid, rather than a specific group.

Amino Acids↗
PubMed1982

Retinopathy following jejunoileal bypass surgery: report of a case.

Vitamin A deficiency associated with retinopathy and night blindness was observed in a patient 4 yr after jejunoileal bypass. Upon further investigation, a multiple vitamin deficiency state was established. Daily supplementation with 30 000 units of vitamin A resulted in normal levels of vitamin A and retinol-binding protein. The patient's night blindness improved, but his retinopathy remained unchanged as demonstrated by fluorescein angiography. We conclude that patients who have undergone jejunoileal bypass should be supplemented with vitamin A since the vitamin A deficiency is preventable and the retinopathy associated with the deficiency may not be totally reversible.

Adult↗
PubMed1981

The natural history of diabetic extramacular traction retinal detachment.

There is a difference of opinion concerning the advisability of surgery for extramacular fraction retinal detachment (EMTRD) in diabetic patients before development of macular detachment. Ninety-nine eyes with EMTRD of 84 diabetic patients observed without surgery had a detachment rate of 13.8% in one year. This rate compares favorably with the reported 30% to 47% failure rate for diabetic eyes subjected to vitrectomy.

Diabetic Retinopathy↗
PubMed1981

Pneumatic intraocular microscissors.

Intraocular microscissors were developed based on a vitreous cutter-like actuation and control by the console and foot pedal. They are right angled for resection of periretinal membranes and 20 gauge for compatibility with the vitrectomy system.

Diabetic Retinopathy↗
PubMed1981

The microretinal retractor.

A retractor was developed for the scleral buckling portion of a vitrectomy under the operating microscope. The right-angled handle reduces hand fatigue and keeps the assistant's hand away from the operative field. The nonslotted blade prevents tissue prolapse into the operative field.

Humans↗
PubMed1981

Endophotocoagulation.

A system was developed for transvitreal application of photocoagulation using a fiberoptic probe attached to a portable xenon arc coagulator (endophotocoagulation, EPC). The system is activated by a footswitch, and the probe tip is positioned near the retina after performing a pars plana vitrectomy. This technique can be used to treat posterior retinal breaks, stop retinal bleeding, coagulate retinal neovascularization, apply scatter retinal photocoagulation in certain diabetic eyes, treat some of the ciliary processes in eyes with neovascular glaucoma, and enlarge the pupil in eyes with iris neovascularization and miosis. Endophotocoagulation was used in 169 eyes for one or more of these indications and found to be safe and reliable.

Glaucoma↗
PubMed1981

Intravenous amiodarone in the treatment of various arrhythmias following cardiac operations.

In a group of 95 patients having cardiac operations with extracorporeal circulation, intravenous (IV) amiodarone, administered in doses of 2.5 to 5 mg/kg, was used in the treatment of various perioperative arrhythmias. Conversion to sinus rhythm was achieved in 55 (61%) of 90 patients with supraventricular arrhythmias, the other patients showing a satisfactory slowing of their heart rate. Total suppression and control was obtained in 18 patients with persistent ventricular extrasystoles associated with various supraventricular arrhythmias. Amiodarone was administered in five patients with life-threatening ventricular arrhythmias resistant to other antiarrhythmic agents: Suppression was obtained in one of two patients with recurrent ventricular tachycardias and control was achieved in three patients with repetitive ventricular tachycardia and ventricular fibrillation, allowing the effective use of intra-aortic balloon counterpulsation (IABP) needed for hemodynamic support. Seven patients experienced minor side effects such as nausea or flushing. No complete atrioventricular (AV) block was noted. Significant hypotension occurred at the end of the IV injection in 17 (18%) patients. In all but five patients, hypotenion was transient, without clinical complications. In the five others, adrenergic drugs in four cases and IABP in one case were necessary. Those five patients had marked cardiomegaly with poor myocardial contractility. IV bolus injection of amiodarone seems prohibited in such patients; constant infusion would be preferable.

Adult↗