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Biomedical subjects

K Green

Publications and source records attributed to K Green.

At least 109 records · Page 6Linked to original sources
PubMed1992

A 10-year longitudinal study of untreated mucogingival defects.

A study was conducted to observe the changes in areas with untreated mucogingival defects over a 10-year period. The results in this group after 4 years were previously published. Upon entering dental school, a group of 39 freshman dental students were assessed for plaque index, gingival index, probing depth, and width of keratinized gingiva in 112 sites of inadequate keratinized gingiva. Eighteen of the original 39 participants were reassessed for the same parameters in 64 sites after 10 years. The results revealed that 22 sites showed a slight increase in keratinized gingiva, 32 were unchanged, and 10 sites showed a slight decrease in keratinized gingiva. The mean width of keratinized gingiva at the beginning of the study was 1.73 +/- 0.542 mm and was 2.01 +/- 0.864 mm after 10 years. This represented a small, but statistically insignificant, increase in the width of keratinized gingiva. The Plaque Index and Gingival Index of this group at baseline and at 10 years indicated a high level of oral hygiene and gingival health. It was concluded that in the absence of gingival inflammation, areas with small amounts of keratinized gingiva may remain stable over long periods of time.

Dental Plaque Index↗
PubMed1992

Influence of vehicle and anterior chamber protein concentration on cyclosporine penetration through the isolated rabbit cornea.

The transcorneal penetration of cyclosporine A has been determined from each of three vehicles across isolated cornea into simulated aqueous humor containing either 50 mg % protein (0.5 mg/ml; as found in a normal eye) or 5000 mg % protein (50 mg/ml; as found in an inflamed eye). Cyclosporine entered the corneal epithelium and stroma/endothelium as well as passed through the cornea from an alpha cyclodextrin vehicle. Entry into the epithelium and stroma/endothelium occurred from an ointment vehicle with limited detectable anterior chamber penetration using 50 mg % protein solution in the anterior chamber. From corn oil vehicle, cyclosporine penetrated across the cornea with a permeability equal to that of alpha cyclodextrin vehicle. The concentration of cyclosporine in both corn oil and ointment vehicles is 8 times greater than that in alpha cyclodextrin vehicle resulting in a flux from corn oil vehicle about 7 or 8 times greater than that seen after alpha cyclodextrin vehicle. The amounts retained in the cornea, however, were relatively low after corn oil compared to cyclodextrin. The penetration of cyclosporine from either the cyclodextrin vehicle or ointment was at least doubled in the presence of 5000 mg % protein in the simulated aqueous humor relative to that seen in 50 mg % protein. This data indicates that the (presumed) absorption and binding of drug by the excess protein in the simulated aqueous humor may have removed free cyclosporine from the solution and sustained a high concentration gradient of free solute across the cornea.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Chemical restraint of Weddell seals (Leptonychotes weddellii) with a combination of tiletamine and zolazepam.

A 1:1 combination by weight of tiletamine hydrochloride and zolazepam hydrochloride was administered to 30 adult Weddell seals (Leptonychotes weddellii) in doses varying from 100 to 300 mg. Full immobilization was achieved in 16 seals, moderate sedation in seven and light sedation in seven. Three animals died; two were fully immobilized and one was moderately sedated prior to death. The drug combination was considered satisfactory, although its usefulness was limited by the lack of chemical antagonists when complications were encountered in immobilized animals.

Animals↗
PubMed1992

Role of toxic ingredients in silicone oils in the induction of increased corneal endothelial permeability.

Silicone oils may induce pathological changes in corneas or retinas by unknown mechanisms but the effects are probably related to certain specific components. Low molecular weight compounds have been implicated in the induction of toxic tissue reactions. Several of these components, that occur as contaminants or by-products in crude silicone oils, were tested for their ability to alter corneal endothelial permeability. In vitro inulin/dextran permeability was measured after one week of in vivo exposure to a non-toxic oil to which various low molecular weight components were added. At least 75% of the anterior chamber volume was replaced with oil +/- additives. A long-chain silanol-terminated polydimethylsiloxane (1000 cps) at 2 mg/ml, tetramethyl-ammonium siloxanolate (a catalyst) at 1 mg/ml and a mixture of a series of linear compounds (MM through MD10M) each at 10 mg/ml all caused a large corneal endothelial permeability increase. A mixture of two short-chain silanol-terminated compounds was less damaging, as was a mixture of a cyclic series. Evidently certain compounds can induce toxic effects on the corneal endothelium whereas other compounds are much less toxic. The linear series and the catalyst, that induce corneal endothelial changes, have been shown to occur in silicone oils.

Animals↗
PubMed1992

A brief history of ocular toxicology.

The background leading to the need for ocular toxicity testing is reviewed. Awareness of side effects of various categories of drugs (e.g., steroids and cataracts) has provided impetus for examination of many categories of compounds including ocular drugs, cosmetics and household chemicals. The standard test (Draize) used for many years in the evaluation of ocular toxicity of many chemicals is being modified or replaced by other procedures. Modifications include volume and/or concentration reductions. Replacements include the use of in vitro systems of either freshly isolated tissues, tissue cultured cells, or non-living systems. The relative predictability of each approach is evaluated with the conclusion that only in vivo testing (albeit using low doses and low volumes) can reflect the full spectrum of potential responses. Each in vitro methodology has at least one drawback relative to in vivo test procedures.

Animals↗
PubMed1992

Ocular toxicity of subconjunctival gentamicin.

The subconjunctival injection of commercial gentamicin, given either as a single dose or as repeated injections, caused a hyperemic conjunctival response. Simultaneously there was a toxic myopathy induced in the extraocular muscles. The overall response, followed with light microscopy, occurred as a focal infiltrate of polymorphonuclear leukocytes with progression over a few days to a mononuclear cell infiltrate that accompanied fiber degeneration. Injections of each ingredient of commercial gentamicin individually showed that only gentamicin caused the muscle response; methylparaben, EDTA, and sodium bisulfite were without effect. The pH of the solution was eliminated as a contributing factor as was osmolarity of the injection. Increasing recognition is being given to post-operative complications caused by the prophylactic subconjunctival injection of gentamicin following cataract, and other intraocular surgery. The present data offer a mechanistic explanation for many of these toxic findings.

Animals↗
PubMed1992

Corneal endothelial toxicity of dapiprazole hydrochloride.

A new adrenergic antagonist designed for topical use to induce pupillary miosis has been tested for direct toxicity on isolated rabbit corneal endothelium. Dapiprazole hydrochloride was perfused across endothelia in the specular microscope at concentrations from 1.25 micrograms/ml to 1000 micrograms/ml. No toxicity was observed, as determined by corneal thickness determinations over a 3 hour perfusion period, until concentrations greater than 125 micrograms/ml were reached. At 250 micrograms/ml a swelling rate of 17.8 microns/hour occurred, and at 500 micrograms/ml the swelling rate was 17.1 microns/hour; with 1000 micrograms/ml inducing a swelling rate of 23.3 microns/hour. It is evident that the drug concentration that reaches the endothelium after topical application has no toxic effect on the cornea, and that the drug should only be used as directed and not used as an anterior chamber perfusate.

Adrenergic alpha-Antagonists↗
PubMed1992

Intraocular gas effects on corneal endothelial permeability.

We examined the effects of intraocular gases on the permeability of the rabbit corneal endothelium to inulin and dextran. Volumes of air (0.16 ml), sulfur hexafluoride (SF6) (0.08 ml), and octafluoropentane (C3F8) (0.04 ml) were infused into the anterior chamber at constant intraocular pressure so that all volumes were equal after expansion. The inulin/dextran permeability was statistically decreased by infusion with Ringer, while air caused an 8.4% increase in dextran permeability but no effect on inulin flux. These small effects were of no biological significance. SF6 caused a 16% and 13% increase in inulin and dextran permeability, respectively, while C3F8 caused an 18% increase in both inulin and dextran permeability. Longevity of gas in the anterior chamber appears important in delineating the deleterious effects. The gases per se do not appear toxic but rather disrupt normal physiologic function through physical process.

Air↗
PubMed1992

Perfluorocarbon liquid effects on corneal endothelial permeability.

We investigated the effects of perfluoro-n-octane liquid on the rabbit corneal endothelial permeability to inulin and dextran. Permeability measurements were made either after 10 minute in vitro exposure of the endothelium to 50 microliters of the test liquid or after one week exposure in vivo following injection of 50 microliters of the test fluid into the anterior chamber. Retention of the perfluorocarbon on the in vitro cornea and in the anterior chamber during the appropriate exposure time was visually verified. The corneal endothelial permeability was unchanged after either short or sub-chronic treatment with perfluoro-n-octane indicating an absence of toxicity for this substance should it reach the cornea either intraoperatively or postoperatively.

Animals↗
PubMed1992

Intraocular silicone oil effects on rabbit blood-retinal barrier permeability.

Both short- (1 week) and longer-term (7 week) studies have been made on a series of silicone oils to determine their effects on blood-retinal barrier permeability. About 25% of the vitreous humor was replaced with the test oil, and fluorophotometric determinations made after intravenous fluorescein at intervals after oil injection. The short-term studies revealed a uniform disturbance of the eye at 24 hours after oil injection that probably represents the physical disturbance of the eye during injection. For most oils the readings on day 4 and day 7 after oil injection revealed no difference between the experimental and the paired control eye. Adatomed 5000 cps oil and a Japanese 1000 cps oil caused more sustained aqueous humor fluorescein values over the first week. Longer-term studies, with two oils shown in prior studies on corneal endothelium to increase permeability and one oil that had no influence on endothelial permeability, revealed no effects on fluorescein penetration into any ocular compartment. It is apparent that the corneal endothelium offers a more sensitive paradigm for examining the toxicity of oils for predictive behavior of long-term exposure of the retina.

Animals↗
PubMed1992

The effects of intraocular gases on rabbit blood-retinal barrier permeability.

The effects of intravitreal expansile gases, sulfur hexafluoride and octafluoropropane, as well as air and needle insertion alone were assessed by iris fluorescein angiography and blood-retinal barrier permeability determination. Iris angiography, at 3 days after injection, indicated no differences between experimental and paired control eyes. Vitreous fluorophotometry on day 1, day 4 and day 7 after gas or sham injection also showed no differences between paired control and experimental eyes regardless of which experimental condition was employed. The results indicate that these gases are non-toxic to the blood-retinal barrier over a 7 day time course.

Animals↗
PubMed1992

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Acupuncture Therapy↗
PubMed1991

Immunogenicity and safety of rhesus-human rotavirus reassortant vaccines with serotype 1 or 2 VP7 specificity.

Rhesus-human rotavirus reassortants incorporating the gene expressing the VP7 surface protein of human rotavirus serotypes 1 or 2, and the remaining ten genes from rhesus rotavirus (RRV) were evaluated as candidate oral vaccines in 2-4-month-old infants. A single dose of the serotype 1 reassortant vaccine which had a titre of 10(4) plaque-forming units (p.f.u.) induced a fourfold or greater antibody response in 81% of the recipients by a combination of ELISA and neutralization assays; 51% of the vaccinees developed a neutralizing antibody response to the vaccine strain. A single dose of the serotype 2 vaccine (10(4) p.f.u.) induced a seroresponse in all vaccinees by the combination of assays whereas 67% developed neutralizing antibodies to the vaccine strain. A combination of these two vaccines (0.5 x 10(4) p.f.u. of each) induced an overall seroresponse in 95% of the recipients but only 48% and 24% response in neutralizing antibodies to serotypes 1 and 2, respectively. A trivalent combination which included the two reassortants and RRV (0.33 x 10(4) p.f.u. of each strain) induced an overall response in 82% of the vaccinees, but only 30%, 20% and 65% developed a neutralizing antibody response to serotype 1, serotype 2, and RRV, respectively. Febrile reactions on days 2-5 after vaccination were seen in 23-45% of the infants receiving the various vaccines and combinations and in 5% of the placebo group. It is concluded that rhesus-human reassortant rotaviruses may be combined with each other and with RRV as a polyvalent vaccine, but the VP7-specific neutralizing antibody responses are likely to be lower after combined vaccination than following vaccination with a single reassortant rotavirus.

Animals↗
PubMed1991

Absence of drug effects on rabbit blood-aqueous barrier permeability to non-electrolytes.

The effects of either topical epinephrine, norepinephrine or pilocarpine upon the entry of non-transported radioactive solutes into the anterior or posterior chamber of pigmented rabbit eyes was examined after intravenous solute perfusion. Solutes employed were urea, thiourea, sucrose and inulin. They were infused at a rate that maintained constant plasma levels from 1 minute through 5 hours of intravenous perfusion. Anterior and posterior chamber samples were taken at either 5 minutes or 5 hours after infusion of solutes, but in either case at 1 hour after drug administration. Differences between the 5 minute and 5 hour data showed more solute entry with the passage of time, and differences were found between the rate of solute entry at both times based upon molecular size. However, while occasional statistically significant differences were found between certain drug treatments, no drug effects were noted on solute entry into the treated eye either when compared to the contralateral untreated eye or to a separate untreated control group.

Animals↗
PubMed1991

Developmental expression of intestinal surfactant-like particles in rats.

We have reported the appearance of surfactant-like particles enriched for intestinal alkaline phosphatase and phosphatidylcholine within enterocytes and in the lumen of adult fat-fed rat intestine. Because rat pulmonary surfactant decreases in abundance during the first postnatal days, we examined the developmental expression of these intestinal particles in suckling rats. Electron microscopy revealed abundant particles in 1-day-old rats within and surrounding the villus enterocytes, declining in frequency by day 14. Phosphatidylcholine content, alkaline phosphatase, sucrase-isomaltase, and lactase activity in particles peaked 1 day after birth, declining rapidly to adult levels by day 3 of life, except for sucrase, which peaked again after weaning. The postnatal developmental profile of the same brush-border-associated enzymes was totally different. Membrane fractions enriched for alkaline phosphatase and of similar density to rat surfactant-like particles were isolated from the small intestine of an amphibian (Xenopus laevis) and a fish (grass carp). Electron microscopy of the Xenopus membranes revealed unilamellar structures similar to the rat particles, but the carp membranes were of dissimilar morphology. We conclude that particles with surfactant-like properties in the rat intestine are ontogenically expressed like pulmonary surfactant; similar particles are evident only in animals with lungs.

Alkaline Phosphatase↗
PubMed1991

Roles of catalase and the glutathione redox cycle in the regulation of anterior-chamber hydrogen peroxide.

The effects of inhibition of both glutathione synthesis and of glutathione reductase and catalase activities have been determined in the regulation of hydrogen peroxide (H2O2) in the anterior chamber of pigmented rabbits. Glutathione reductase inhibition using intravitreal 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU) did not significantly alter either total glutathione or the percent oxidized glutathione fraction in the iris-ciliary body. Intravitreal buthionine sulfoximine (BSO) significantly reduced the total glutathione content of iris-ciliary body and corneal endothelium, while not altering the oxidized fraction. BCNU increased the oxidized fraction of glutathione in the aqueous humor from 22 to 63% without significantly altering total glutathione levels. BSO, however, reduced total glutathione by 70% in the aqueous humor, and the oxidized fraction doubled. Decreases in the reduced glutathione concentration caused by BSO correlate with increases in the normally stable ratio of H2O2 to ascorbate concentrations in the aqueous humor, strongly suggesting that glutathione metabolism is correlated with H2O2 regulation at endogenous levels of this oxidant. Both BSO and 3-aminotriazole (3AT) separately increased the half-time for the loss of exogenously added H2O2 from the anterior chamber. BSO increased the half-time by 77% after 10 microliters of 10 mM H2O2 was injected intracamerally, while suppression of catalase activity with 3AT increased it by only 40%. With intracameral injections of 10 microliters of either 25 or 50 mM H2O2, however, 3AT had a greater effect than BSO. The half-time values after 3AT pretreatment were 61 and 135% greater than control values at the concentrations of 25 and 50 mM H2O2, respectively; those after BSO pretreatment were at 14 and 78%. From these data we conclude that the glutathione redox system protects the anterior segment tissues from hydrogen peroxide at low concentrations of this oxidant, while catalase assumes a greater role at higher concentrations of hydrogen peroxide.

Amitrole↗