Biomedical subjects

B A Weissman

Publications and source records attributed to B A Weissman.

At least 55 records · Page 3Linked to original sources

PubMed1989

Corneal ulcers associated with disposable hydrogel contact lenses.

Four patients developed corneal ulcers associated with the use of disposable extended-wear hydrogel contact lenses. Bacteria were recovered from corneal ulcers in three of the patients. Three patients discarded their contact lenses after ten or more days of extended wear; the corneal ulcers in these patients developed toward the end of the wearing cycle. The fourth patient removed her contact lenses every two days for cleaning and disinfection and discarded them for a new pair on a weekly basis. Improper lens hygiene was noted in only one patient. All corneal ulcers responded to antibiotic treatment. In three patients visual acuity returned to normal, but scarring of one patient's cornea resulted in a visual acuity of 20/60.

Adult↗

PubMed1989

Microbial analysis of contact lens care systems contaminated with Acanthamoeba.

We analyzed bacterial and fungal contamination within the contact lens care systems of ten patients who had Acanthamoeba detected within their care systems. Seven patients had Acanthamoeba keratitis, one had Pseudomonas keratitis, and the remaining two were asymptomatic. Gram-negative bacteria were found in all ten care systems, and Pseudomonas was found in six. Bacillus species, the only gram-positive bacteria isolated, were found in five systems. Fungi were isolated in six care systems. The use of homemade saline and the two-cup method of peroxide disinfection were associated with microbial contamination. Acanthamoeba organisms were found only in contact lens cases or solutions that also had bacterial and in many cases fungal contamination, suggesting that the presence of bacterial and fungal contamination within the contact lens care system may be an important element for the survival and growth of Acanthamoeba.

Acanthamoeba↗

PubMed1989

Behavioral and neurochemical effects of the serotonin (5-HT)1A receptor ligand spiroxatrine.

The effects of spiroxatrine, a putative antagonist with selectivity for the serotonin (5-HT)1A receptor, were compared with compounds believed to function as agonists at the 5-HT1A receptor. Schedule-controlled responding of pigeons was maintained under a multiple 30-response fixed-ratio (FR), 3-min fixed-interval (FI) schedule or under a schedule in which responding was suppressed by electric shock ("conflict" procedure). Under the multiple schedule, spiroxatrine (0.3-1.0 mg/kg) decreased FR responding but did not affect FI responding; responding was decreased in both schedule components at 3.0 mg/kg. When administered alone, buspirone, a compound believed to produce its anxiolytic effects through 5-HT1A agonist actions, produced effects similar to those of spiroxatrine; in combination, the two drugs produced greater effects than when either was administered alone. As with 5-HT1A agonists such as buspirone and 8-hydroxy-2(di-n-propylamino)tetralin (8-OH-DPAT) in the pigeon, spiroxatrine (0.01-1.0 mg/kg) increased punished responding. Spiroxatrine and buspirone were potent inhibitors of [3H]8-OH-DPAT binding to pigeon cerebral membranes with IC50 values in the nM range. Neurochemical analyses of metabolite changes produced by spiroxatrine in pigeon cerebrospinal fluid showed buspirone-like effects, with increases in MHPG, DOPAC and HVA at doses that decreased 5-HIAA levels. Spiroxatrine dose-dependently blocked the behavioral effects of the dopamine agonist piribedil indicating that, like buspirone, it also is a potent dopamine antagonist. Spiroxatrine most likely functions as an agonist at the 5-HT1A receptor. As with buspirone, however, spiroxatrine has a prominent dopamine antagonist component.

8-Hydroxy-2-(di-n-propylamino)tetralin↗

PubMed1989

Stacking samples while measuring oxygen transmissibility of hydrogel contact lenses.

It is necessary to measure several samples with different thicknesses of the same material to be able to determine a value for the oxygen permeability (Dk incm2 ml O2/s ml mm Hg) of that material. Some current contact lens materials are not available in multiple thicknesses, but it might be possible to "stack" several samples of the same thickness as an alternative procedure. This study demonstrates that measurements of Dk for one particular midwater-content hydrogel (Methafilcon, a nominally 55% water-content ionic material) give statistically indistinguishable results whether single samples of various thicknesses (Dk = 20.52 x 10(-11)) or thinner stacked samples to attain similar thicknesses (Dk = 20.05 x 10(-11)) are used in this measurement.

Contact Lenses, Hydrophilic↗

PubMed1989

Four cases of keratoconus and posterior polymorphous corneal dystrophy.

We examined four young men with keratoconus and posterior polymorphous corneal dystrophy. All four patients showed central corneal steepening and irregularity, and large areas of irregular polymorphous opacification at the level of Descemet's membrane (in at least one cornea of each patient), which are consistent with posterior polymorphous dystrophy.

Adult↗

PubMed1989

Cancellation of the boundary and edge effects by choice of lens thickness during oxygen permeability measurement of contact lenses.

Edge and boundary effect correction factors have been proposed to modify the oxygen transmissibility and permeability values obtained by polarographic measurement of contact lenses. These two correction factors are opposite in sign: the boundary effect causes oxygen transmissibility and permeability to be underestimated; the edge effect causes the reverse. Two methods are used to define lens thickness values where the two effects should be quantitatively equal and therefore cancel for both rigid gas permeable and hydrogel contact lenses.

Contact Lenses↗

PubMed1989

Pseudomonas corneal ulcer after use of extended-wear rigid gas-permeable contact lens.

We report a bacterial corneal ulcer that occurred in a patient who had worn extended-wear rigid gas-permeable contact lenses on a 1-week cycle for 9 months. Pseudomonas aeruginosa was cultured not only from the corneal ulcer but also from the contact lens solutions, suggesting that the patient had been noncompliant with care procedures. To our knowledge, this is the first report of a bacterial corneal ulcer associated with use of a rigid gas-permeable contact lens on an extended-wear basis.

Atropine↗

PubMed1988

Differential regulation of mu-opiate receptors in heroin- and morphine-dependent rats.

Rats made dependent on heroin and morphine exhibit both qualitative and quantitative differences in the characteristics of radioligand binding to mu-opioid receptors in the central nervous system. In brain membranes prepared from control animals, [3H]dihydromorphine (DHM) binding was best described by a two-site model, while in morphine-dependent rats, [3H]DHM binding was best described by a single-site model. In contrast, [3H]DHM binding to membranes from heroin-dependent animals was best described by a two-site model, with an increased density of the high-affinity, and no change in the low-affinity population compared to controls. Furthermore, both the number of binding sites for [3H]DAGO (a ligand that selectively labels a population of high-affinity mu-opiate receptors) and the sensitivity of [3H]DHM to sodium ions was increased in heroin; but not in morphine-dependent rats. These studies demonstrate that opiate receptors are differentially regulated in heroin- and morphine-dependent animals. Such neurochemical changes in mu-opiate receptors may underlie differences in the behavioral and pharmacological profiles of heroin and morphine reported in man.

Animals↗

PubMed1988

Bacillus keratitis associated with contaminated contact lens care systems.

We examined two soft contact lens wearers who developed keratitis associated with Bacillus contamination of their contact lens care systems. Patient 1 developed a corneal ulcer caused by B. subtilis, and Patient 2 demonstrated multiple, diffuse, punctate corneal epithelial opacities associated with B. cereus contamination in the contact lens and lens case compartment. The contact lens cases of both patients contained Bacillus spores that survived multiple heat disinfection treatments. Three different contact lens chemical disinfection systems used for the minimum recommended time failed to kill the Bacillus organisms.

Adult↗

PubMed1988

Oxygen transmissibility, thickness, and water content of three types of collagen shields.

Oxygen transmissibility, thickness, and water content were measured for three types of collagen shields: six of each type designed to dissolve in 12, 24, and 72 hours. Oxygen transmissibility was measured by a polarographic method at 35 degrees C and was found to be 17.9, 17.3, and 23.8 x 10(-9) cm mL O2/s mL mm Hg, respectively. Thicknesses were measured with an electronic gauge, and the central thicknesses of the 12-hour shields were found to be significantly greater (mean thickness, 0.19 mm) than the central thicknesses of the other two types (0.15 mm each). Water content, as measured by a hand refractometer, was found to be about 63% for all three types of shields, and no statistically significant differences were found. These measurements indicate that collagen shields behave like 63% water-content hydrogel contact lenses (oxygen permeability estimated at 27 x 10(-11) cm2 mL O2/s mL mm Hg) with regard to oxygen transmission.

Collagen↗

PubMed1988

Cryptococcosis of the nasopharynx in mice and rats.

An attempt to infect the upper respiratory tract of mice and rats with various bacteria and fungi by intranasally instillation was performed. Cryptococcus neoformans was the only agent to invade the tissue. The infection was limited to the nasopharynx, a phenomenon which probably indicates the presence of a specific chemotaxis or receptor.

Animals↗

PubMed1988

Open-eye corneal swelling secondary to hydrogel contact lens wear.

Three hydrogel contact lenses of measured oxygen transmissibility (Dk/L = 20, 12, and 6 x 10(-9) cm ml O2/s ml mm Hg, respectively) were used to induce central corneal swelling as measured by optical pachometry in five human subjects under open-eye conditions (8 h wear). Both contact lenses with higher Dk/L values induced mean central corneal swelling of about 1.5%. The lower Dk/L lens induced a mean central corneal swelling of 2.2%. However, statistical analysis of the differences in central corneal swelling between the lens-wearing and the control eyes indicates that swelling induced by the higher Dk/L lenses is not identical, and indicates that even a Dk/L of 20 x 10(-9) is insufficient to reduce corneal swelling to zero. This suggests that the "critical oxygen tension" (COT) could be in excess of 20 to 40 mm Hg, but not necessarily as high as 70 mm Hg.

Adult↗

PubMed1988

In situ oxygen transmissibility of rigid gas-permeable contact lenses.

On the eye a contact lens is bathed in tear fluid, which increases its resistance to oxygen flux. For rigid gas-permeable lenses, this effect should be small during open-eye wear because a large amount of oxygen is provided by air-saturated tears that are pumped under the lens. However, under closed-eye conditions this study suggests substantial decrease in overall lens system oxygen transmissibility when lens transmissibility itself is greater than 20 x 10(-9) cm ml O2/s ml mm Hg and when the average thickness of the tear layer is greater than about 20 micron.

Contact Lenses↗

PubMed1988

Contact-lens correction of aphakic infants and children: early behavioral and VEP results.

We studied 11 infants and young children fitted with contact lenses for correction of unilateral or bilateral aphakia. The visual-acuity estimates obtained from behavioral cues (alternate-cover test and central-fixation monitoring) were compared with results obtained from pattern-reversal visual-evoked potentials (VEP). We conclude that VEP may be more sensitive than behavioral observation for monitoring the visual progress in certain aphakic children.

Aphakia↗

PubMed1987

Microbial contamination of contact lens care systems.

We examined the contact lens care systems of 100 asymptomatic patients who used hard or soft contact lenses for correction of refractive errors for the presence of bacteria, fungi, Acanthamoeba, and endotoxin. Of 100 patients, 52 had contaminated contact lens care systems. Sixteen of 126 bottles (13%) of commercial contact lens care solutions were contaminated. Contaminated commercial solutions were opened and used for a longer period of time than uncontaminated solutions. Contamination was not found in bottles of preserved commercial solutions that were opened and used for less than 21 days. All 12 bottles of homemade saline were contaminated with bacteria, and Acanthamoeba was isolated from two of these bottles. Pseudomonas was found in the care systems of 12 patients. Bacillus species, which form spores resistant to heat, were found in the care systems of seven patients. Endotoxin, which is also resistant to heat, was detected in nine of 35 care systems (26%) tested. Potential pathogens were isolated from the conjunctiva of six patients.

Adolescent↗

PubMed1987

Differential effects of heroin on opioid levels in the rat brain.

Dependence on the potent narcotic agent heroin in rats was produced by the implication of double-coated pellets. Chronic administration of this drug induced significant alterations in dynorphin B and [Met5]enkephalin-Arg6-Gly7-Leu8 (ME-RGL) levels in discrete areas of the rat brain. The level of the latter increased by 53.6% in the substantia nigra while the levels of dynorphin B increased in the globus pallidus and ventral tegmental area (188.0 and 41.8%, respectively).

Animals↗

PubMed1987

Calcium antagonist binding in cat brain tolerant to electroconvulsive shock.

Cats subjected to daily (25-30 days) electroconvulsive shock (ECS) demonstrated an elevation of their electroconvulsive threshold or tolerance to ECS. [3H] Nitrendipine binding was measured to brain regions from non-tolerant (sham shocked) and ECS tolerant cats 24 hr following the last shock. ECS produced a significant increase (45%) in the density of [3H] nitrendipine binding sites in the cerebral cortex and a significant decrease (33%) in the apparent affinity of [3H] nitrendipine in the cerebellum. No changes in binding were observed in the hippocampus. The effects of ECS were also investigated in the rat, an animal not displaying tolerance to repeated ECS. [3H] Nitrendipine binding to rat brain was measured 10 min and 24 hr following one shock (acute) or ten shocks delivered transauricularly once daily (chronic). Twenty-four hours following chronic ECS, there was a significant increase (19%) and decrease (11%) in the density, but no change in the apparent affinity of [3H] nitrendipine binding sites in the cerebral cortex and hippocampus respectively. No significant change in [3H] nitrendipine binding was observed in rat cerebellum 24 hr following chronic ECS. There were no changes in [3H] nitrendipine binding in the cerebral cortex and hippocampus 10 min and 24 hr following acute ECS. These results indicate that ECS can alter [3H] nitrendipine binding to calcium channel linked dihydropyridine binding sites in the central nervous system. It is suggested that changes in [3H] nitrendipine binding in the cat cerebellum may be involved in the development of tolerance to ECS.

Animals↗

PubMed1987

The effects of chemically and electrically-induced convulsions on [3H]nitrendipine binding in mouse brain.

The effects of chemically and electrically-evoked seizures on [3H]nitrendipine binding to voltage-dependent calcium channels in mouse brain were determined 30 and 60 min following the initiation of convulsions. While maximal electroconvulsive shock, pentylenetetrazol and strychnine exhibited either no or marginal effects, Ro 5-4864 produced a decrease (14%) in the Bmax of [3H]nitrendipine at 30 min but not 60 min. The convulsant dihydropyridine calcium channel activator, BAY K 8644, produced a significant increase in the Kd (31%) of [3H]nitrendipine at 30 min, and a significant increase in both the Bmax (21%) and Kd (28%) of [3H]nitrendipine 60 min following the initiation of convulsions. While maximal electroconvulsive shock, pentylenetetrazol and strychnine exhibited either no or marginal effects, Ro 5-4864 produced a decrease (14%) in the Bmax of [3H]nitrendipine at 30 min but not 60 min following the initiation of convulsions. These findings indicate that modulation of voltage-dependent calcium channels by certain convulsants may be important in the genesis of seizures or in post-ictal compensatory processes.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗