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Biomedical subjects

K Green

Publications and source records attributed to K Green.

At least 217 records · Page 12Linked to original sources
PubMed1985

Ocular blood flow after experimental alkali burns and prostaglandin administration.

Ocular blood flow was determined using radioactive strontium 85 microspheres after an alkali (sodium hydroxide [NaOH]) burn to the eye. With 20 microL of NaOH, blood flow was significantly increased in the iris, ciliary processes, and choroid from two through four hours. This correlated well with the sustained increase in intraocular pressure (IOP) seen after a 20-microL burn. A 50-microL burn increased blood flow at one hour, but it returned toward normal levels beyond two hours. In general terms, there appeared to be a meaningful correlation between IOP changes and altered blood flow following ocular alkali burns. The blood flow changes paralleled those occurring after the topical application of prostaglandins and supported the concept that ocular blood flow dynamics are mediated by prostaglandins.

Alkalies↗
PubMed1985

The penetration of detergents into adult and infant eyes: possible hazards of additives to ophthalmic preparations.

In studies of surfactant penetration into the eye, radiolabelled detergent was found to penetrate the rabbit cornea, to accumulate readily in ocular tissues and to be released slowly. Repeated applications led to increasing binding of the detergent. Permeability, ocular and systemic uptake and retention were all greater in juvenile than in adult rabbits. Preliminary tests of the effects of surfactants on ocular cells in vitro using concentrations found in vivo, suggest that some low-level effects might occur, particularly in juveniles.

Age Factors↗
PubMed1985

Interaction between ophthalmic drugs and intraocular lenses.

We evaluated the in vitro interaction between commonly used ophthalmic drugs and a series of intraocular lenses to determine if the lenses could act as a drug reservoir in the eye. Lenses examined included anterior and posterior chamber lenses as well as iris plane lenses. Assessment of lens uptake was made by immersing the lens for nine days in a radioactive drug solution with a concentration equal to that found in the anterior chamber one hour after drug administration. No evidence of drug uptake was found for any lens immersed in epinephrine, norepinephrine, dexamethasone, or chloramphenicol.

Absorption↗
PubMed1985

Pharmacological modification of corneal endothelial intracellular pH, intracellular electrical potential difference, and corneal swelling and deswelling rates.

Rabbit corneal endothelial intracellular pH and electrical potential difference were measured using radioactive tracer techniques. A variety of drugs and chemicals were used to modify specific aspects of cell membranes in order to determine, in this steady state system, whether a close relationship existed between intracellular pH and potential. Corneal swelling and deswelling rates were also determined in the presence and absence of the drugs. Longer times of immersion of tissue with drugs (3 hours) tended to provide more support for a link between intracellular pH and the inability of the cornea to maintain a constant thickness. Drugs that altered corneal thickness without altering either intracellular pH or potential difference presumably acted on extracellular pathways. No conclusive evidence was obtained for a direct link between intracellular pH and the intracellular electrical potential difference of the endothelial cell.

Acid-Base Equilibrium↗
PubMed1985

Development and validation of a measure of dental patient satisfaction.

As part of the Washington State Dental Auxiliaries Project, a 42-item measure of patient satisfaction with dental care was developed. The measure is comprised of 13 subscales: dentist-patient relations, technical quality of care, access, patient waiting time, cost, facilities, availability, continuity, pain, auxiliaries performing expanded duties, staff-patient relations, staff technical quality of care, and office atmosphere. The measure was developed from a set of 52 items included in a questionnaire administered to the patients of private dental practices in Washington state. Usable questionnaires were returned by 30.8% of patients receiving questionnaires in 1979, 40.1% in 1980, and 34.0% in 1981. Factor analysis plus categorization of items by a panel of professionals were used initially to group items into subscales. Contribution to internal consistency was the final criterion for an item's inclusion in a subscale. Internal consistency of subscales ranged from 0.44 to 0.80. The concurrent validity of subscales was assessed by relating patient satisfaction to characteristics of the dental practices. The following statistically significant relationships between subscales and criterion variables were observed: dentist-patient relations and percent of patients seen by the dentist; access and number of weeks appointments must be booked in advance; patient waiting time and actual patient waiting time; continuity of care and percent of patients seen by the dentist; auxiliaries performing expanded duties and delegation to auxiliaries; and staff technical quality and percent of hygienist restorations with satisfactory quality. Each relationship was in the expected direction.

Adult↗
PubMed1985

Effect of oxygen free radical products on rabbit iris vascular permeability.

Oxygen free radicals and their products are known to be elaborated by inflammatory cells during the 'respiratory burst'. Xanthine oxidase combined with hypoxanthine was injected into the anterior chamber of rabbit eyes. This combination is known to result in the production of oxygen free radicals. Iris fluorescein angiography performed 2 h and 24 h following injection of xanthine oxidase and hypoxanthine into the anterior chamber resulted in increased iris vascular permeability. The increased permeability was not modified by either of the prostaglandin inhibitors naproxen or aspirin nor by the free radical scavenger D-penicillamine. This study demonstrates that iris vascular permeability, and possibly blood-aqueous barrier permeability is increased following exposure to chemically generated oxygen free radicals. It is possible that the increased iris vascular permeability that occurs during ocular inflammatory processes may in part be mediated by oxygen free radical products. This model may be useful in developing therapeutic modalities directed at preventing the damaging effect of oxygen free radical products, and this may be of benefit in reducing the untoward effects of ocular inflammatory disorders.

Animals↗
PubMed1985

The effect of naproxen on the ocular inflammatory response following extracapsular lens extraction in rabbits.

Naproxen effects on the ocular inflammatory response following extracapsular lens extraction were studied in rabbits. Twelve hours before surgery, rabbits were given 20 mg of a 5 mg/ml naproxen suspension by gavage. A maintenance dose of 10 mg naproxen 3 times per day was started on the day of lensectomy and continued throughout the entire observation period. Phakic and aphakic control rabbits received no drug suspension. Central corneal thickness and intraocular pressure measurements were determined pre-operatively, at 4 and 24 h post-operatively and every 24 h thereafter. Four groups of rabbits, sacrificed at 24, 48, 72, and 168 h after lensectomy, had anterior chamber paracentesis performed for PMN (polymorphonuclear leucocyte) counts and determination of protein content. A 5th group had both paracentesis and iris-ciliary body excision for PGE2 assay at 24 h. No parameter was significantly altered by the naproxen regimen compared to untreated rabbits.

Animals↗
PubMed1985

Drug effects on the hydraulic conductivity of the isolated rabbit ciliary epithelium.

Three aspects of hydrostatically driven volume flow across the isolated rabbit ciliary epithelium have been examined. (1) Hydraulic conductivity was increased in a dose-dependent manner by amiloride, but not by furosemide, indicating that amiloride may interfere with junctional permeability. The absence of a furosemide effect suggests that regulation of passive fluid movement may be independent of net ionic fluxes of either chloride or bicarbonate. Ethacrynic acid had no effect on hydraulic conductivity at concentrations below 10(-2) M. At 10(-2) M, hydraulic conductivity was decreased, suggesting that fluid pathways may be linked to ionic pathways. (2) Successive in vivo daily treatments with adrenergic agonists result in changes in the intraocular pressure response. Dose-effect curves to in vitro agonists from eyes pre-treated on successive days indicate that isoprenaline caused a lack of response in hydraulic conductivity after 3 d of in vivo treatment, adrenaline caused responses after 2 d which were about half of those found on day 0, while phenylephrine and noradrenaline had no influence on hydraulic conductivity. These data suggest that beta-agonists cause a deactivation or desensitization of some moiety which is coupled with regulation of hydraulic conductivity in a manner similar to that seen for the beta-receptor-coupled adenylate cyclase. (3) While cyclic GMP was without effect, various modifiers of cyclic GMP activity increased hydraulic conductivity. Alteration of cellular cyclic GMP levels appears to exert some regulation over ciliary epithelial permeability.

Amiloride↗
PubMed1985

The effect of retrobulbar epinephrine injection on ocular and optic nerve blood flow.

The effect of retrobulbar epinephrine administration on ocular and optic nerve blood flow was studied in phakic and aphakic rabbit eyes using a radioactive microsphere (85Sr) technique. One hour before blood flow determination, 10 microliter of a 0.2% (base) epinephrine bitartrate solution was administered to the right eye of each experimental rabbit by the retrobulbar route. For control rabbits, 10 microliter of saline was injected retrobubarly. Blood flow measurements were determined for the iris, scrap[ed ciliary processes, choroid, retina, and optic nerve. Neither optic nerve nor ocular blood flow was altered by this dose which is approximately the dose used in retrobulbar injections in humans.

Animals↗
PubMed1985

Decreased intraocular pressure and aqueous humor turnover rate during longitudinal ocular studies in the rabbit.

One group of 5 pigmented rabbits, during a period of 10 weeks, and two groups of 8 albino rabbits, during 16 weeks, showed a fall in aqueous turnover rate and outflow facility of about 30%. A fall in intraocular pressure also occurred of about 10 mm Hg. The biochemical correlative mechanism, systemic and/or local, is conjectural (reduction of "stress"; homeostasis). Empirically a parallel completely untreated control group should accompany any longitudinal study group in order to differentiate these temporal trends from experimental effects.

Animals↗
PubMed1985

Alterations in ocular and optic nerve blood flow during intraocular surgery in aspirin pretreated rabbits.

The effect of intraocular surgery on ocular and optic nerve blood flow was determined in rabbits either untreated or pretreated with aspirin. Surgery was either extracapsular lens extraction through a 100 degrees corneal incision or a sham-operation in which a 45 degrees corneal incision was performed and the lens left in place. In both cases, the incisions were not sutured and the intraocular pressure remained zero for one hour. A (85Sr) radioactive microsphere technique was used to measure blood flow in the iris, scraped ciliary processes, retina, choroid, and optic nerve. In rabbits not receiving aspirin pretreatment, blood flow was statistically increased in all portions of the eye, except the retina and optic nerve, studied for sham-operated eyes, and in the iris and optic nerve in the lens extraction group. In rabbits pretreated with aspirin, blood flow remained at normal levels. These results are consistent with the hypothesis that prostaglandins released during ocular surgery cause increased ocular tissue blood flow.

Animals↗
PubMed1985

Ocular fluid dynamics response to topical RU486, a steroid blocker.

A steroid antagonist applied to one eye of 18 young pigmented rabbits during a 10-week period caused a statistically significant fall in IOP, but no statistically significant nor clinically relevant change in the rate of aqueous humor turnover. The pressure change is therefore ascribed to an alteration in outflow channels. No changes occurred in a parallel group of 5 animals in which one eye was treated with vehicle and the contralateral eye was untreated. The drug effects became evident after two weeks of application, suggesting that a slow turnover pathway is involved.

Administration, Topical↗
PubMed1985

Marihuana-derived material: biochemical studies of the ocular responses.

Some biochemical factors of the iris-ciliary body of the rabbit have been examined for effects induced by water-soluble marihuana-derived material (MDM). Adenylate cyclase activity and sensitivity to beta-adrenergic agonists were unchanged, as measured 4 hours after MDM administration in vivo. Magnesium-dependent and anion-sensitive, but not sodium-potassium, ATPase activities were inhibited 6 hours after MDM administration in vivo, although they were unaffected by in vitro incubation. Topical administration of a potent substance P antagonist had no effect on the time course or magnitude of intravenous MDM-induced ocular effects in rabbit. Intravenously administered sugars antagonized the effects of MDM on intraocular pressure. A variety of drugs which display a range of biochemical effects varying from beta-adrenergic receptor agonism, to alteration of glycoprotein residues were employed. None of the agents employed, ranging from cAMP modifiers to protein synthesis blockers, had any effect on the MDM-induced response. It is apparent that the mechanism underlying the ocular hypotensive effect of MDM does not reside in mediation through adenylate cyclase, ATPase or substance P, but rather through a mechanism mediated by terminal sugar moieties on the molecule. The data suggest that modification of the surface membrane glycoprotein residues on the ciliary epithelium can induce marked alterations in aqueous humor flow rate.

Adenosine Triphosphatases↗
PubMed1985

Blood flow in aphakic rabbit eyes after sub-chronic glaucoma drug treatment.

Ocular blood flow was measured in aphakic rabbit eyes using a radioactive microsphere technique following sub-chronic three times a day treatment with one of the following drugs: ecothiophate iodide (0.125%), pilocarpine (4%), epinephrine (2%), norepinephrine (2%) or timolol (0.5%). The results show that regional ocular blood flow was statistically normal after this treatment regimen compared to both normal and aphakic control eyes. Ecothiophate did statistically increase choroidal blood flow and, although not statistically significant, other drugs did induce trends which may be relevant to drug use.

Animals↗
PubMed1985

An electrophysiologic study of rabbit ciliary epithelium.

Microelectrode recordings from cells in rabbit ciliary epithelium have been made in vitro. Ionophoresis of Lucifer Yellow dye from microelectrodes during measurements of potential confirmed that the recordings were intracellular. Dye passed from the impaled cells into adjacent cells in both the nonpigmented and pigmented layers of the epithelium. Electrical coupling between epithelial cells also was observed. The mean (+/- SD) values of the potential measured across the basolateral membranes of the nonpigmented cells was -65 +/- -15 mV (n = 77); the mean value of the input resistance at this intracellular recording site was 37 +/- 28 M omega (n = 17). The membrane potential was reduced by raising the concentration of extracellular potassium but unaffected by changes in the concentrations of sodium, chloride, or bicarbonate ions. After a period of deprivation of extracellular potassium, the cells hyperpolarized without a measurable change in membrane resistance when potassium was restored to the bathing solution; this transient response to potassium was abolished by preincubation with ouabain or by bathing the epithelium in a solution lacking sodium. It was concluded that the ciliary epithelial cells are permeable to potassium but exhibit only a low permeability to sodium, chloride, or bicarbonate ions; that the cells possess an electrogenic Na/K pump; and finally, that all of the cells in the epithelium function as a syncytium.

Animals↗
PubMed1985

Effect of hematoporphyrin derivative on rabbit corneal endothelial cell function and ultrastructure.

Hematoporphyrin derivative (HpD) is a systemically administered photosensitizing agent that may be of value in the treatment of solid tumors. When corneal endothelial cells were perfused in the specular microscope with HpD and exposed to a 25-W incandescent light at 5 cm (5.5 mW/cm2) there was anatomic disruption of corneal endothelial cells and swelling of the corneal stroma. Perfusion with 0.2 microliter/ml (1.0 microgram/ml) HpD and 5 min exposure to light resulted in a corneal swelling of 71 +/- 4 microns after 3 hr, whereas perfusion with 0.2 microliter/ml HpD and a 1-min exposure to light resulted in a corneal swelling of 36 +/- 4 microns after 3 hr. Perfusion with 0.2 microliter/ml HpD with no light exposure resulted in a corneal swelling of 22 +/- 4 microns after 3 hr. Inclusion of 100 micrograms/ml catalase in the perfusion solution resulted in a significant 38% reduction of the corneal swelling. The inclusion of either 100 micrograms/ml superoxide dismutase, 15 mM D-mannitol, 5 mM ascorbic acid, 1/4% DMSO, 50 microns EDTA, 50 microns DETAPAC, 10 mM L-histidine, or 1 mM sodium azide did not modify the corneal swelling induced by the photosensitization reaction. Perfusion of corneal endothelial cells with 2 microliters/ml (10 micrograms/ml) HpD and exposure to 25-W incandescent light for 5 min resulted in swelling of mitochondria, the appearance of vacuoles in the cytoplasm, and rapid corneal swelling. The data suggests that corneal endothelial cells can be damaged by hydrogen peroxide generated by the dismutation of superoxide anion produced during the photoreaction. Superoxide anion itself and hydroxyl-free radical do not appear to participate in causing the endothelial cell damage. The role of singlet oxygen remains somewhat unclear. The data suggests that further in vivo studies should be performed to delineate precautions that should be taken to protect the corneal endothelium during photoradiation therapy.

Animals↗