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Biomedical subjects

K Green

Publications and source records attributed to K Green.

At least 325 records · Page 18Linked to original sources
PubMed1977

The public health implications of ethnomedical practices.

The public health implications of ethnomedical practices are extensive. In particular, there is the need to research the cultural and social behaviour patterns relevant to health care in order to utilise aspects of ethnomedical practices within a comprehensive health care system. To exploit the positive aspects of the ethnomedical practices successfully, health education for the consumers (the population) and the producers (the health workers) must be developed. Because of the limited resources of most developing countries and as a part of the movement away from "industrialized medicine", a large number of health auxiliary workers, including ethnomedical practitioners, need to be trained and deployed to develop and maintain this new health care system.

Community Health Workers↗
PubMed1977

Corneal endothelium bicarbonate transport and the effect of carbonic anhydrase inhibitors on endothelial permeability and fluxes and corneal thickness.

Unidirectional fluxes of bicarbonate across the corneal endothelium were determined. A net flux of bicarbonate from the stromal to aqueous-facing surface was demonstrated. Under conditions of carbonic anhydrase inhibition the net bicarbonate flux was reduced by 54 percent and the passive water permeability of the endothelium was increased. Experiments with the specular microscope demonstrated an increased rate of corneal swelling under conditions of carbonic anhydrase inhibition. Attempts to identify H+ as the cation moving with the bicarbonate ion to maintain electroneutrality were not successful because of the impossibility of sustaining a differential H+ concentration difference across the endothelium.

Animals↗
PubMed1976

Decreased rate of metabolism induced by a shift of the double bond in prostaglandin F 2alpha from the delta5 to the delta4 position.

The synthesis of an isomer of prostaglandin F 2alpha,9alpha,11alpha,15(S)-trihydroxyprosta-4-cis,13-transdienoic acid is described. The metabolism of this compound in the rat has been investigated. The rate of degradation by beta-oxidation was slowed down considerably. Thus 10-20% of the injected isomer was excreted in the urine unchanged indicating a longer half-life in the circulation than for prostaglandin F 2alpha. More over 2% was excreted as C20 metabolites, 11-18% as C18 metabolites and 8-15% as C16 metabolites. This relative resistance to degradation by beta-oxidation is of considerable biochemical and pharmacological interest.

Animals↗
PubMed1976

Electrophysiological and anatomical effects of cetylpyridinium chloride on the rabbit cornea.

The effects of cetylpyridinium chloride on the trans-corneal potential difference and the surface anatomy of the cornea have been examined. Concentrations of cetylpyridinium chloride from 0.21 mM to 2 mM were used for either 1 or 2 minute exposure times on the in vitro and in vivo cornea for the electrophysiology studies. The potential difference of the in vitro cornea showed a concentration and exposure-time dependent decrease, the in vivo cornea shows a qualitatively similar behaviour although quantitatively less. The fall in potential difference is preceeded by a hyperpolarization. The scanning electromicroscopy reveals a loss of microvilli and microplicae as well as surface pitting, with some exposure of cells underlying the superficial epithelium. These changes occur in a dose-dependent manner. The effect of cetylpyridinium chloride on the cornea is to enhance the permeability of the superficial cells by destroying the cell membranes and causing lysis of the cells.

Action Potentials↗
PubMed1976

Physiological function of regenerating endothelium.

A defined area, 4 mm. diameter, cryothermal injury was created on a rabbit cornea. Corneal thickness was measured at four distances from the limbus to the center of the cornea during the swelling phase after endothelial damage, and during the recovery period. Rapid initial swelling was followed by a period of stable maximum thickness over 24 hours. More swelling occurred centrally than peripherally. Eight days after injury the peripheral cornea regained normal thickness, and the central portion was normal thickness after 10 to 12 days. Histological examination of corneal endothelium showed that early migration of cells into the denuded area occurred 6 hours after injury. By 2 days, most of the denuded area was covered by endothelial cells, although the cells were large and irregular. The number of normal cells increased, and of irregular cells decreased, over the next five days, until two weeks after freezing all cells had a normal appearance. The recovery of physiologic endothelial function lags behind the histologic recovery by about four to five days, indicating that recovery of the normal endothelial permeability is possibly related to the status of the cellular junctions rather than covering of the posterior surface by cells per se.

Animals↗
PubMed1976

Chlorampenicol retention on, and penetration into, the rabbit eye.

The retention of the antibiotic chloramphenicol on, and penetration into, the rabbit eye has been compared following administration in two vehicles. Samples were taken of both aqueous humor and a washing fluid applied to the conjunctival surface and the concentration of 14C-chloramphenicol determined. Greater tear film and aqueous humor drug concentrations, which are effective against many organisms, were found with a vehicle which enhanced retention time on the ocular surfaces.

Animals↗
PubMed1976

Corneal membrane water permeability as a function of temperature.

Osmotically driven water flow across the corneal epithelium and endothelium has been measured as a function of temperature. For both membranes deviations from a single straight-line relationship are found in a logarithmic plot of hydraulic conductivity against 1/T. Both membranes show a high (14 to 16 kcal per mole) apparent activation energy at temperatures between 23 degrees C. and 5 degrees C. At higher temperatures, between 23 degrees C. and 37 degrees C., the apparent activation energy falls to 5.7 and 9.3 kcal per mole for the epithelium and endothelium, respectively. The low value for the apparent activation energy for water crossing the epithelium and endothelium at normal corneal temperatures presumably reflects water passage through water-filled channels.

Animals↗
PubMed1976

Interaction of adrenergic antagonists with prostaglandin E2 and tetrahydrocannabinol in the eye.

Both alpha- and beta-adrenergic antagonists have been utilized in an atempt to discern the site of action of prostaglandin (PG) and tetrahydrocannabinol (THC) in the eye. Both alpha- and beta-adrenergic antagonists (alpha-antagonists, phentolamine and phenoxybenzamine; beta-antagonists, propranolol and sotalol) cuased a dose-dependent reduction in intraocular pressure and blood pressure and increased total outflow facility. The results are consistent with the concept that both alpha- and beta-adrenergic receptors are present in the anterior uvea and that vasomotor tone is essential to the maintenance of normal intraocular pressure. No antagonist reduced the PG-induced elevation of intraocular pressure unless the blood pressure was severely lowered. All antagonists inhibit the normal PG-induced increase in total outflow facility, indicating that these agents protect the blood-aqueous barrier from breakdown without altering the vasodilatory response to PG. All antagonists reduced the fall in intraocular pressure produced by THC by approximately 50 per cent, except for sotalol which completely abolished the intraocular pressure fall. Only the alpha-adrenergic antagonists prevented the THC-induced increase in total outflow facility. The results indicate that true outflow facility may well be regulated exclusively by alpha-receptors. The data are consistent with the effect of THC being primarily a vasodilation of the efferent blood vessels of the anterior uvea. The partial inhibition by alpha-adrenergic antagonists may also suggest a lesser role of THC on the afferent vessels.

1-Propanol↗
PubMed1976

Dextran uptake into, and loss from, corneas stored in intermediate-term preservative.

This investigation demonstrates that dextran passes into rabbit corneas stored in M-K medium prior to corneal transplantation. An equilibrium between dextran in the cornea and in the M-K medium is reached at about 24 hours. Post-keratoplasty dextran efflux is rapid with about 70 to 75 per cent being lost within one to three hours and 99 per cent being lost in 12 hours.

Animals↗
PubMed1976

Effect of brinolase on corneal endothelium.

We investigated Brinolase, a substance producing enzymatic zonulysis, for effects on the physiological and anatomical function of the corneal endothelium in the specular microscope. Concentrations of 100 C2 units/ml perfused for ten minutes did not appear to damage the corneal endothelium. Longer perfusions or higher concentrations possibly produced alterations in the physiological functions of the endothelium, but no significant anatomic change was demonstrated. Longer perfusion times with high concentrations (1,600 C2 units/ml) resulted in the formation of holes which perforated the corneal stroma.

Animals↗
PubMed1976

Stromal sodium binding after glycosaminoglycan digestion.

The glycosaminoglycans of isolated rabbit corneal stroma, clamped between two lucite plates at near normal hydration, were digested with testicular hyaluronidase in saline solution. After equilibration with 0.9 per cent saline solution alone the sodium and chloride content of the stroma was determined. Chloride was in equilibrium with both normal and hyaluronidase-treated stroma, allowing use of the Donnan calculation for excess or bound sodium to be made. Normal stromas contained 200 mEq. bound sodium per kilogram of dry weight calculated from the Donnan calculation; hyaluronidase-treated stromas contained 110 mEq. bound sodium per kilogram of dry weight. The data show that about half of the bound sodium in the corneal stroma is on nonsaccharide binding sites. Quantitative verification of the loss of glycosaminoglycans was performed.

Animals↗
PubMed1976

Hydrostatic pressure effects on deswelling of de-epithelialized and de-endothelialized corneas.

The effects of varying hydrostatic pressure on the thinning rate of preswollen de-epithelialized or de-endothelialized corneas has been determined in the specular microscope. The appropriate membrane was removed, the cornea given access to Ringer to swell, and then fluid exchange at that surface blocked with oil. De-epithelialized corneas thin more slowly as hydrostatic pressure on the posterior surface is increased, until fluid movement ceases at 60 to 70 mm. Hg. Fluid movement can occur, therefore, against a considerable hydrostatic pressure. De-endothelialized corneas thin at a higher rate as hydrostatic pressure is increased; this effect is probably a mechanical one with increasing pressure forcing fluid out across the epithelium.

Animals↗
PubMed1976

Effects of mechanical agitation on endothelial function of preserved corneas.

Corneas from adult albino New Zealand rabbits were stored in either MK medium or moist chambers at 4 degrees C. for 18 to 24 hours. During that time, half the corneas from each group were agitated for 8 hours to simulate the motion that might occur during long-distance shipment. The corneas were then placed in specular microscopes and perfused for 4 hours with a modified Krebs-Ringer solution at 34 degrees C. Serial measurements of corneal thickness made during temperature reversal showed that agitation had no effect on endothelial viability of corneas stored in either solution. Electron microscopy of selected corneas confirmed this finding.

Animals↗
PubMed1976

Corneal water and electrolyte content following storage in moist chamber and MK medium.

Rabbit corneas were subjected to MK-medium or moist-chamber storage for periods up to 7 days. Sodium, potassium, and chloride concentrations and hydration were measured. The hydration of corneas stored in MK medium was less than that of those stored in moist chambers. The sodium concentration of MK corneas remained stable for up to 7 days; the potassium concentration, however, decreased with increasingly longer periods of storage. Chloride concentrations quickly equilibrated with the high chloride level of MK medium. The concentration of sodium and chloride in moist chamber-stored corneas fell with progressively longer storage periods. Potassium showed an initial decrease in concentration followed by an increase in concentration that paralleled, and equilibrated with, the increasing acqueous humor concentration.

Animals↗