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Biomedical subjects

S M Podos

Publications and source records attributed to S M Podos.

At least 109 records · Page 6Linked to original sources
PubMed1983

Topical nylidrin and aqueous humor dynamics in rabbits and monkeys.

Topical administration of nylidrin hydrochloride lowered intraocular pressure in both albino rabbits and cynomologus monkeys. The maximum decrease occurred two hours following drug application and was unilateral. The response lasted four hours in monkeys and at least six hours in rabbits. Outflow facility, episcleral venous pressure, and aqueous humor flow measured by fluorophotometry were unaltered in both species. In rabbits in the treated eyes, ocular blood flow was increased, and anterior and posterior chamber ascorbate concentrations were unchanged. The mechanism of IOP reduction appears to be increased aqueous humor outflow via uveoscleral outflow routes that are not pressure dependent.

Administration, Topical↗
PubMed1983

Topical timolol and the nursing mother.

A 34-year-old nursing woman with elevated intraocular pressure voluntarily and without our knowledge applied 0.5% timolol maleate twice daily to her right eye. A milk sample 1.5 hours after administration of drug showed a much higher level of timolol (5.6 ng/mL) than a plasma sample drawn at the same time (0.93 ng/mL). Three control milk specimens showed no measurable levels of timolol. The patient's milk sample 12 hours after her last timolol dose contained 0.5 ng/mL of timolol. On the basis of our calculations, timolol should be used with caution by nursing mothers.

Administration, Topical↗
PubMed1983

The effect of topically administered carbonic anhydrase inhibitors on aqueous humor dynamics in rabbits.

Repeated topical administration of 2.5% trifluormethazolamide, a halogenated derivative of methazolamide, resulted in a unilateral decrease in intraocular pressure in rabbits. Mean (+/- S.E.M.) baseline intraocular pressure (19.8 +/- 2.1 mm Hg) was significantly (P less than .05) decreased 30 minutes (16.1 +/- 2.2 mm Hg) and 60 minutes (15.8 +/- 2.7 mm Hg) after drug administration. Trifluormethazolamide did not alter outflow facility. Aqueous humor flow calculated from the tonographic data was reduced 44% and flow measured by fluorophotometry was reduced 29%. Topical delivery of trifluormethazolamide decreased the level of carbon dioxide in the aqueous humor in the treated eye in a manner similar to that observed after systemic administration of carbonic anhydrase inhibitors. Topical administration of 10% acetazolamide did not decrease intraocular pressure. However, topical administration of either trifluormethazolamide or acetazolamide before oral administration of water resulted in a blunting of the water-induced ocular hypertensive response.

Acetazolamide↗
PubMed1983

Long-term results of valve implants in filtering surgery for eyes with neovascular glaucoma.

Filtration surgery was performed with a pressure-sensitive, unidirectional valve implant in 79 eyes with neovascular glaucoma. The device consisted of an open Supramid tube (outside diameter 0.58 mm) sealed to a Silastic tube with a slit valve. The Supramid tube was inserted at the corneoscleral limbus 1 to 4 mm into the anterior chamber. The Silastic portion was located under a scleral flap. Of the 79 eyes, 53 had postoperative intraocular pressures less than or equal to 24 mm Hg after a mean follow-up period of 23.7 +/- 10.9 months. Bleb revision for external scarring was required in ten of these 53 eyes and postoperative medical therapy was required in 26. The valve implant failed to control intraocular pressure in 26 of the 79 eyes. Failure was secondary to scarring of the external bleb in 18 eyes and to closure of the internal Supramid tube in five eyes. Mortality during the follow-up period was high: 12 of the 53 successfully treated patients and five of the unsuccessfully treated patients died.

Adolescent↗
PubMed1983

Flicker threshold and pattern VEP latency in ocular hypertension and glaucoma.

Latency of the pattern visual-evoked potential (PVEP) was measured in 24 ocular hypertensive (OHT) patients, eight open-angle glaucoma (OAG) patients, and 37 control subjects. The PVEP stimulus was a 2.3 cycle/degree sinusoidal grating, counterphase-modulated at 1 Hz. Field size was 9 degrees and mean luminance 1.7 log ft-lamberts. For 22 of the 32 patients, a psycholphysical measure of dynamic contrast sensitivity at 8 Hz (DRC) was obtained with a 4 degrees diameter stimulus, by determining the mean value for the contrast sensitivities to a homogeneous flickering field and to a 1.2 cycle/degree counterphase-flickering grating. Patient DRC values were compared with previously published control data from 21 subjects. Mean PVEP latencies of both the OHT and the OAG patients were greater than normal (P less than 0.001), with the OAG value larger than the OHT value (P less than 0.001). Mean DRCs were lower than normal (P less than 0.002) for both patient groups, with the OAG value lower than the OHT value (P less than 0.025). DRC correlated with PVEP latency for these patients (r = -0.66, P less than 0.001).

Evoked Potentials, Visual↗
PubMed1983

Glucocorticoid target cells in human outflow pathway: autopsy and surgical specimens.

Target cells for glucocorticoids were found in trabeculectomy specimens obtained surgically from humans with glaucoma (primary and secondary) and from nonglaucomatous autopsy eyes using an autoradiographic technique. Specific nuclear localization of 3H-dexamethasone was found in cells of the trabecular meshwork, scleral fibroblasts, and in the endothelial lining of both Schlemm's canal and the outflow vessels. Glucocorticoids may alter the outflow facility by a direct effect on the metabolism of these cells. The autoradiographic method is suitable for studying competitors of glucocorticoid binding in small surgical specimens of human tissue involved in the outflow of aqueous humor.

Aqueous Humor↗
PubMed1982

Extended-wear aphakic soft contact lenses and corneal ulcers.

A review of 100 aphakic extended-wear soft contact lenses is presented for the period July 1980 to August 1981. Four previously successfully fitted patients with either American Optical Company's Sofcon or Cooper Laboratories' Permalens for extended wear developed corneal ulcers either directly under the lenses or shortly after removal. Three of the female patients were well controlled diabetics without retinopathy, one of whom sustained severe visual loss and neovascular glaucoma after a pseudomonas ulcer. Another patient, who had developed a Seratia marcescens ulcer 3 months later, developed metastatic carcinoma of the bowel. Special attention to diabetic aphakic patients being fitted with extended-wear soft contact lenses is suggested.

Aged↗
PubMed1981

Fluorophotometric study of epinephrine and timolol in human subjects.

The action and interaction of topical 2% epinephrine hydrochloride and 0.5% timolol maleate therapy were studied in 12 normal and 16 ocular hypertensive subjects. Measurements of intraocular pressure, outflow facility, and aqueous secretion by fluorophotometry were made. Uveoscleral outflow values were calculated. Epinephrine, applied topically twice daily for one week, resulted in a decrease in IOP of 3.3 +/- 0.9 mm Hg and an increase in outflow facility of 0.05 +/- 0.01 microL/min/mm Hg, as well as an increase in the rate of aqueous production of 0.32 +/- 0.09 microL/min. Uveoscleral outflow showed an increase of 0.83 +/- 0.23 microL/min. Timolol, applied topically twice daily for one week, reduced the IOP 3.9 +/- 1.0 mm Hg and decreased aqueous flow 0.84 +/- 0.23 microL/min, but produced no change in outflow facility or uveoscleral flow. When epinephrine and timolol are given in combination, the effects in lowering IOP may not be completely additive.

Aqueous Humor↗
PubMed1981

Dipivefrin and echothiophate. Efficacy of combined use in human beings.

In a previous study, pretreatment of rabbit eyes with echothiophate iodide prevented the ocular hypotensive effect of dipivefrin. The present masked study, using inpatient volunteers and nurse-administered drops, investigated whether a similar antagonism of action occurred in human beings. Eight volunteers received 0.25% echothiophate iodide twice a day in both eyes for three weeks. During the second week of therapy, one eye also received 0.25% dipivefrin twice a day and the contralateral eye received 2% epinephrine hydrochloride twice a day. During the third week of therapy, the eyes receiving dipivefrin and epinephrine were reversed. In four volunteers, dipivefrin plus echothiophate produced a significantly greater reduction in intraocular pressure than epinephrine plus echothiophate. As a group the eight eyes treated with dipivefrin plus echothiophate had significantly lower IOPs than the eyes treated with epinephrine plus echothiophate during the second week of therapy. Epinephrine plus echothiophate was never superior to dipivefrin plus echothiophate. Dipivefrin seemed to be effective during combination therapy with echothiophate.

Drug Therapy, Combination↗
PubMed1981

Chloride transport inhibition by piretanide and MK-196 in bullfrog corneal epithelium.

Two new diuretic agents, piretanide and MK-196, inhibited short-circuit current (SCC) across the isolated frog corneal epithelium. The effect is explained as an inhibition of active Cl transport. A definite decrease in SCC and an increase in electrical resistance was observed with both diuretics in concentrations as low as 10(-6) M. Piretanide, at 10(-4) M, reduced the SCC by 90%, reduced th unidirectional forward Cl flux from 0.60 to 0.28 mueq x h-1 x cm-2, and increased the resistance by 60%. There was no effect on the Cl backflux. At 10(-4) M, MK-196 reduced the SCC by 83% and increased the resistance by 72%, from 1.68 to 2.91 k omega x cm2. Replacement of Cl by SO4 in the bathing solutions resulted in a larger increase in resistance, from 1.68 to 3.80 k omega x cm2. The diuretics had no effect on active Na transport across the corneal epithelium. After the permeability of the apical side was increased by amphotericin B, the drugs could not inhibit the Cl-originated SCC. These results suggest that piretanide and MK-196 selectively inhibit active Cl transport in the cornea by blocking Cl permeability of the apical side of the epithelial cells.

Animals↗
PubMed1981

Inhibition of active transport of chloride and sodium by vanadate in the cornea.

Vanadate, an inhibitor of (Na+ + K+)ATPase, also inhibits active transepithelial Na+ and Cl- transport (measured as short-circuit current) in the isolated cornea in concentrations of 10(-4)M to 10(-3)M. The disulfonic stilbene, DIDS, does not affect the short-circuit current per se, but it prevents the inhibitory effect of vanadate on Na+ and Cl- transport. Since vanadate acts in other systems from the cytoplasmic side, it is postulated that DIDS interferes with vanadate penetration into the epithelial cells. These results also strengthen the notion of a Na-Cl co-transport system in the corneal epithelium.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1981

A visual field screening protocol for glaucoma.

In this prospective evaluation of the reliability and efficiency of an optimized visual field screening protocol for glaucoma, we tested 145 eyes (73 patients) with increased intraocular pressures to determine the location of early glaucomatous visual field defects. The field examination, which was used as a control, and protocol testing were performed on a manual Goldmann perimeter using kinetic and suprathreshold static techniques, respectively. Of the 145 eyes tested, kinetic Goldmann perimetry detected 43 eyes with glaucomatous defects. The screening protocol detected 39 defective eyes. There were four false-negative tests and one false-positive test. The false-negative rate of just under 10% was within the range predicted from earlier data. The computer-generated optimal protocols performed as predicted and provided an excellent screening technique for the detection of early glaucomatous visual field defects.

Clinical Trials as Topic↗
PubMed1980

Is phenylephrine pivalate a prodrug?

Phenylephrine pivalate has been assumed to be a prodrug devoid of important intrinsic activity because of its structural similarity to dipivefrin (dipivaly epinephrine). However, unlike dipivefrin, the pharmacologic activity of phenylephrine pivalate was not prevented by prior administration of echothiophate iodide. Rabbits pretreated bilaterally with 0.25% echothiophate for two and seven days had similar mydriasis, both in quantity and duration, after receiving 10% phenylephrine hydrochloride to one eye and 1% phenylephrine pivalate to the other eye. This as consistent with the hypothesis that the phenylephrine pivalate molecule has important alpha-adrenergic activity regardless of whether it is converted to phenylephrine.

Animals↗
PubMed1980

Filtering valve implant surgery for eyes wtih neovascular glaucoma.

We performed filtration surgery with a unidirectional, pressure-sensitive valve implant in 40 eyes with neovascular glaucoma. The device consisted of an open Supramid tube (outside diameter 0.58 mm, inside diameter 0.38 mm) sealed to a Silastic tube with a slit valve. The Supramid tube was inserted at the corneoscleral limbus 1 to 4 mm into the anterior chamber and the Silastic portion was located under a lamellar scleral flap. Twenty-seven of 40 eyes (68%) had a postoperative IOP less than or equal to 24 mm Hg with a mean follow-up of 13.8 months. Ten of these 27 eyes required postoperative medical therapy to achieve this level of IOP control. The glaucoma valve implant failed to return IOP to normal in 13 of the 40 eyes (32%), 11 of these as a consequence of scarring of the external bleb.

Adult↗
PubMed1980

Exercise-induced increase of intraocular pressure in the pigmentary dispersion syndrome.

A 32-year-old man with pigmentary dispersion syndrome had blurred vision and halos after strenuous exercise, associated with a release of pigment into the anterior chamber and increased intraocular pressure (IOP). Additionally, he had typical symptoms after emotional stress or exposure to dim illumination, and had a high IOP without angle closure during a darkroom provocative test. The exercise-induced symptoms and the increase of IOP were prevented by the use of pilocarpine 0.5% drops immediately before exercise.

Adult↗