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Biomedical subjects

G G Gum

Publications and source records attributed to G G Gum.

At least 37 records · Page 2Linked to original sources
PubMed1983

Dose response of topical pilocarpine-epinephrine combinations in normotensive and glaucomatous Beagles.

Dose responses to single-dose loadings with a placebo (0.50% methylcellulose) and 1%, 2%, 3%, 4%, and 6% pilocarpine combined with 1% epinephrine were determined in normotensive and glaucomatous Beagle dogs. All combinations of pilocarpine and 1% epinephrine significantly (P less than 0.007) reduced pupil size and intraocular pressure in the normotensive and glaucomatous-treated eyes at most measurement times, as compared with base-line (predrug) values, untreated fellow eyes, and placebo-treated eyes. There were no significant (P less than 0.11 or greater) contralateral effects on pupil size and intraocular pressure by unilateral pilocarpine-epinephrine instillations as compared with base-line values or placebo-treated eyes.

Animals↗
PubMed1983

Effects of phacoemulsification and extracapsular lens removal on corneal thickness and endothelial cell density in the dog.

Twenty-one dogs were used to study the effects of phacoemulsification and extracapsular lens removal on corneal endothelium and corneal thickness. Specular microscopy revealed preoperative cell morphology and cell densities similar to man. After surgery endothelial cell counts significantly decreased 22% (central) and 13% (periphery) with phacoemulsification and 34% (central) and 31% (periphery) with extracapsular lens removal. Corneal thickness increased with both procedures. Endothelial cell pathology included cellular enlargement, increased pleomorphism, and focal cellular degeneration. Phacoemulsification time did not correlate with the degree of cell loss. Dog corneal endothelium responds to surgical trauma in a manner similar to man and maintains a functional monolayer via cellular enlargement and migration. The dog, therefore, represents a good animal model for the study of corneal endothelial disease in man.

Animals↗
PubMed1982

Effects of alpha chymotrypsin on the canine eye.

Injection of 150, 500, or 750 U of alpha chymotrypsin into the posterior chamber of clinically normal Beagles resulted in changes in intraocular pressure and iridocyclitis. In the 6 eyes treated with 500 or 750 U, lens subluxation occurred in 4 eyes, retinal detachment in 1 eye, retinal degeneration in 1 eye, and optic nerve degeneration in 6 eyes. Scanning electron microscopic changes included dose-related zonulolysis and zonulary remnants within the aqueous humor outflow pathways. Ultrastructural changes by transmission microscopy of the optic nerve degeneration revealed loss of axoplasm and organelles and disruption of the myelin sheaths. Retinal and optic nerve changes may represent the direct toxic effects of alpha chymotrypsin and/or the indirect effects of increased intraocular pressure.

Animals↗
PubMed1982

Episcleral venous pressure in normotensive and glaucomatous beagles.

Episcleral venous pressure was measured by a noninvasive method with a modified force-displacement transducer in six laboratory-quality normotensive and 12 glaucomatous beagles. The dogs were anesthetized by ketamine-xylazine, acepromazine-ketamine, and halothane. Simultaneous intraocular pressure (IOP) and blood pressure were recorded. The mean episcleral venous pressures in normotensive beagles were 11.4 to 11.6 mm Hg with the three methods of anesthesia; in the glaucomatous beagles the mean episcleral pressures were 10.6 to 12.5 mm Hg. There were no significant differences in episcleral venous pressure (p less than 0.19 and greater) and blood pressure (p less than 0.53 and greater) between the normotensive and glaucomatous beagles. IOP was significantly different between the normotensive and glaucomatous beagles anesthetized with acepromazine-ketamine (mean IOP, 23.4 and 34.2 mm Hg, respectively; p less than 0.02) and halothane (mean IOP, 19.9 and 27.4 mm Hg, respectively; p less than 0.001) but not significant with anesthesia with ketamine-xylazine (mean IOP, 26.0 and 37.8 mm Hg, respectively; p less than 0.12). Episcleral venous pressure is unchanged as the disease progresses in the glaucomatous beagle.

Anesthetics↗
PubMed1981

Tonometry in glaucomatous globes.

The Mackay-Marg, pneumatonograph, and EMT-20 tonometers were evaluated in the eyes of glaucomatous beagles. Tonometric scale readings were compared to the manometric recordings from the anterior chamber. Tonometry was performed with manometric system closed and open to the reservoir column. The Mackay-Marg tonometer evaluated in the closed and open manometric systems was highly reliable (goodness of fit [r2] = 0.852 and 0.816, respectively) with intraocular pressures up to 50 mm Hg and somewhat lower (r2 = 0.818 and 0.740, respectively) with intraocular pressures up to 100 mm Hg. The pneumatonograph also exhibited high reliability (r2 = 0.892 [closed] and 0.806 [open]) at pressures up to 50 mm Hg and (r2 = 0.796 [closed] and 0.75 [open]) at pressures up to 100 mm Hg. The EMT-20 tonometer was the least satisfactory for the glaucomatous globe, with r2 ranging from 0.235 to 0.654.

Animals↗
PubMed1981

Inheritance of primary glaucoma in the beagle.

Primary glaucoma in the Beagle is inherited as an autosomal recessive trait. Twenty-six matings of affected x affected Beagles resulted in 77 offspring with glaucoma (38 males/39 females). Four matings of glaucomatous Beagles (1 male/3 females) x normal laboratory-quality Beagles (3 males/1 female) yielded 15 ocular normotensive Beagles (6 males/9 females). Three matings of glaucomatous Beagles (3 males/1 female) x carrier Beagles (1 male/2 females) produced 19 offspring; 8 exhibited glaucoma (2 males/6 females) and 11 were ocular normotensive (6 males/5 females).

Animals↗
PubMed1981

Evaluation of electronic tonometers in the rabbit eye.

The MacKay-Marg, pneumatonograph, and EMT-20 tonometers were evaluated in the normal rabbit eye. Tonometric scale readings were compared with the manometric recordings from the anterior chamber. Tonometry was performed with the manometric system closed and open to the reservoir column. The MacKay-Marg tonometer evaluated in the closed and the open manometric systems was highly reliable (goodness of fit (r2) = 0.958 and 0.961, respectively) with intraocular pressures (IOP) up to 50 mm of Hg and similarly (r2 = 0.949 and 0.967, respectively) with IOP up to 100 mm of Hg. The pneumatonograph also exhibited high reliability, r2 = 0.936 (closed) and 0.898 (open), at pressures up to 50 mm of Hg and r2 = 0.932 (closed) and 0.948 (open) at IOP up to 100 mm of Hg. The EMT-20 tonometer was least satisfactory for the normal rabbit eye, with r2 ranging from 0.069 to 0.171.

Animals↗
PubMed1980

An autosomal recessive blind mutant in the chicken.

A type of blindness due to lack of rods and cones in the retina was found to be controlled by a single autosomal recessive gene, rc. The mutation was first identified in the second generation descendants of a male carrying an ethyl methanesulfonate (EMS) induced chromosome translocation involving one arm of the Z sex chromosome and the long (q) arm of chromosome 3. A linkage test between the locus causing the blindness and the translocation break-point on chromosome 3 was not significant. There is no proof that the mutation was EMS induced.

Animals↗
PubMed1980

Serum hydrocortisone (cortisol) values in glaucomatous and normotensive Beagles.

Serum hydrocortisone (cortisol) values were measured by radioimmunoassay in 5 normortensive and 20 glucomatous Beagles at 1 AM, 7 AM, 1 PM, and 7 PM. Significant differences (P < 0.01) in mean serum values of cortisol occurred between glaucomatous (20.9 ng/ml) and normotensive (9.5 ng/ml) Beagles. The slightly increased serum cortisol values in glaucomatous Beagles at 1 AM and 7 AM coincided with increases in intraocular pressure of glaucomatous Beagles. However, neither the normotensive nor glaucomatous Beagles exhibited any diurnal variations in serum cortisol values.

Animals↗
PubMed1980

Aqueous humor outflow in beagles with inherited glaucoma: constant pressure perfusion.

Determination of facility of aqueous humor outflow (C), using constant pressure perfusion, was performed in vivo in normal dogs and in Beagles with inherited glaucoma at different stages of the disease process. Measurements were taken at 10 mm of Hg increments of intraocular pressure (IOP) from 10 to 50 mm of Hg IOP in the controls and to higher levels of IOP, as needed, to obtain 3 consecutive intervals in which perfusion was required in glaucomatous animals. In normal dogs, C increased slightly as IOP increased to a maximum of 0.22 at 50 mm of Hg. In glaucomatous dogs, C was significantly (P = 0.001) reduced compared with the value in the controls, with a maximum value of 0.09 at 50 mm of Hg.

Animals↗
PubMed1980

Dose-response of topical pilocarpine in the normotensive and glaucomatous Beagle.

Single-dose loading with a placebo (isotonic saline solution), and 0.5%, 1%, 2%, 3%, 4%, 6%, and 8% pilocarpine hydrochloride (pH 7.4) was evaluated in normotensive and glaucomatous Beagle dogs to determine dose response. The seven concentrations of pilocarpine significantly (P less than 0.01) reduced intraocular pressure and pupil size in the normotensive and glaucomatous-treated eyes at most time intervals as compared with baseline (pre-drug) values, untreated fellow eyes, and placebo-treated eyes. There was no significant (P greater than 0.40) contralateral effect on intraocular pressure or pupil size by unilateral pilocarpine administration as compared with base-line values or placebo-treated eyes.

Animals↗
PubMed1979

Evaluation of a soluble sustained-release ophthalmic delivery unit in the dog.

A 5-mg hydroxypropyl cellulose soluble ocular insert was evaluated by placement in the upper and the lower conjunctival and bulbar nictitating membrane fornices in normal dogs. The insert was easily placed in the conjunctival fornices, but was difficult to place in the bulbar nictitating membrane fornix. The conjunctival inserts did not produce irritation of the cornea and the conjunctiva. Placement of the inserts beneath the nictitating membrane produced local irritation and chemosis. The sites of highest to lowest retention for the insert were upper conjunctival fornix, bulbar nictitating membrane fornix, and lastly, lower conjunctival fornix. Dissolution was nearly complete in 8 hours.

Animals↗
PubMed1979

Uveoscleral flow of aqueous humor in the normal dog.

Fluorescein-labeled dextran and sodium fluorescein perfused in the posterior chamber of the normal dog eye egressed through the trabecular meshwork and intrascleral plexus, as well as posteriorly through the ciliary body into the suprachoroidal space and the sclera. Intraocular pressures of 20, 25, 30, and 60 mm of Hg did not produce detectable changes in the fluorescein-labeled dextran movement. Topical 1% atropine and 10% phenylephrine did not affect posterior passage of sodium fluorescein; 2% pilocarpine impeded posterior passage, causing an accumulation of sodium fluorescein and associated fluorescence in the anterior ciliary body.

Animals↗
PubMed1978

Effects of topical 1-epinephrine and dipivalyl epinephrine on intraocular pressure and pupil size in the normotensive and glaucomatous Beagle.

Dipivalyl epinephrine and l-epinephrine were evaluated in various concentrations in normotensive and glaucomatous Beagles. In higher concentrations, both drugs produced significant lowering of intraocular pressure. Mydriasis and some local irritation occurred. The hypotony after drug administration tended to be greater in glaucomatous than in normotensive Beagles. The glaucomatous Beagle may be a valuable biomedical model in the investigation of various pharmacologic substances.

Animals↗
PubMed1978

Pressure-volume relationships of the normal canine eye.

Changes in intraocular volume and pressure induced by Schiøtz tonometry were measured and utilized to calculate the in vivo rigidity of the normal canine eye. Rigidity was found to be dependent upon intraocular pressure (IOP) and tonometer weight; rigidity assumed a parabolic relationship to IOP, decreasing from 0.0754 at 5 mm of Hg IOP to 0.0274 at 55 mm of Hg IOP and gradually increasing to 0.0333 at 100 mm of Hg IOP.

Animals↗
PubMed1977

Tonography in the normal and glaucomatous beagle.

A standard procedure for tonography was developed in the dog. Acepromazine, ketamine, xylazine, droperidol-fentamyl, and combinations of these drugs were evaluated for effects on blood pressure, intraocular pressure, and restraint of the dog for 4 minutes of Schiotz tonography of each eye. In dogs given a cepromazine (0.5 mg/kg intravenously) and then ketamine (10.0 mg/kg intramuscularly), the mean coefficient of aqueous humor out-flow in 24 normal Beagles was 0.24 mul/mm of Hg/minute (SD +/- 0.07). Mean coefficient of aqueous humor outflow in 35 glaucomatous Beagles, between 4 months to more than 37 months old, was 0.09 mul/mm of Hg/minute (SD +/- 0.04). Coefficient of aqueous humor out-flow was less in the older glaucomatous Beagle.

Acepromazine↗