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M Mehta

Publications and source records attributed to M Mehta.

At least 37 records · Page 2Linked to original sources
PubMed1992

Effect of stimulus contrast on simultaneous steady-state pattern reversal electroretinogram and visual evoked response.

We studied the effect of stimulus pattern contrast on the simultaneously recorded pattern reversal electroretinogram (PERG) and pattern reversal visual evoked response (PVER) at 5 check sizes. The stimulus contrast ranged from 24 to 95% in 6 steps of 0.1- or 0.15-log unit increments. PERG amplitude showed a linear increase with an increase in pattern contrast at all check sizes. PVER amplitude showed an increase up to a certain pattern contrast, but was saturated upon further increase in stimulus contrast at all check sizes. The PERG amplitude-check size function curve showed a flattened, inverted-U shape only with the highest contrast and low-pass filter shape or flat shape with lower contrasts. The PVER amplitude-check size function curve showed an inverted-U shape (bandpass filter shape) at all contrasts. These characteristics to the changes in contrast and the spatial frequency tuning suggest that PVER is processed in a different location of visual pathway than PERG.

Adult↗
PubMed1991

Methods for in vitro skin absorption studies of a lipophilic toxin produced by red tide.

The penetration and distribution of [3H]PbTx-3 into pig skin was determined using in vivo and in vitro methods. The dose used in each topical study was 0.3-0.4 micrograms/cm2 skin, with dimethylsulfoxide as the vehicle. In the in vivo study, mean cutaneous absorption after 48 h (expressed as percentage of the dose) was 11.5% (n = 3). In the in vitro study, mean cutaneous absorption after 48 h was 1.6% (n = 12), when based on accumulation of radioactivity in receptor fluid, or 9.9% when based on receptor fluid and dermis. [3H]PbTx-3 readily penetrated through the epidermis into the dermis, reaching maximal dermal accumulation at 4 h (9.1% in vivo and 18% in vitro). At 24 h, the amount in the dermis decreased to 2.3% and 15% in vivo and in vitro, respectively and at 48 h the amount in the dermis decreased to 8.2% in vitro. These results demonstrate the important role of the dermis as a reservoir for a lipophilic compound in both in vivo and in vitro percutaneous absorption studies.

Administration, Topical↗
PubMed1991

Pharmacokinetic evaluation of drug interactions with zidovudine. I: Probenecid and zidovudine in monkeys.

Pharmacokinetic evaluation of a drug interaction between zidovudine (AZT) and probenecid was conducted in monkeys. Six animals received 20 mg/kg of AZT as single intragastric (ig) and iv doses in the absence and presence of 50 mg/kg of probenecid administered ig. Plasma concentrations of AZT and its 5'-glucuronide metabolite (AZTG) were quantitated for 12 h by HPLC. Amounts of AZT and AZTG in urine were also measured, as were probenecid plasma concentrations. Non-compartmental methods were used to obtain pharmacokinetic parameters for AZT and AZTG. In the presence of probenecid, the total clearance of AZT decreased by 50%, renal clearance decreased, and elimination half-life increased. The volume of distribution at steady-state and systemic bioavailability of AZT were not significantly altered by probenecid. The areas under the plasma concentration-time curves and terminal half-lives of AZTG were increased, and renal clearances of AZTG were decreased. The alterations in AZT and AZTG pharmacokinetic parameters are consistent with inhibition of metabolism and renal tubular secretion by probenecid. Since AZT was administered by both oral and iv routes, clearance, volume of distribution, and bioavailability parameters were independently determined. Based on data reported for humans on the zidovudine-probenecid interaction, monkeys appear to be appropriate animal models for the evaluation of zidovudine drug interactions.

Animals↗
PubMed1991

In vitro penetration of tritium-labelled water (THO) and [3H]PbTx-3 (a red tide toxin) through monkey buccal mucosa and skin.

The permeability coefficients (Kp) for tritium-labelled water (THO) were determined in human and monkey skin, and monkey buccal mucosa. Kp of human skin (0.47 x 10(-3) cm/h) correlated favorably with previous reports. Kp of hydrated monkey skin for THO (0.77 x 10(-3) cm/h) was not significantly different (P greater than 0.05) from Kp of hydrated human skin (0.88 x 10(-3) cm/h). Kp of monkey buccal mucosa for THO (6.15 x 10(-3) cm/h) was significantly greater than that for monkey skin. Penetration and disposition of [3H]PbTx-3 into layers of monkey buccal mucosa and skin was determined. [3H]PbTx-3 (5-7 microCi) dissolved in 2 ml of water was applied to epithelial/epidermal surface (2.8 cm2) at zero time. The relative percent dose recovered from the upper layers of buccal mucosa (epithelium) and skin (epidermis) varied, but at each time interval was less than 2.5% of the dose. At most of the time intervals (2-24 h), a larger percent of the dose was recovered from the inner layer of the buccal mucosa (lamina propria) than from the inner layer of skin (dermis). After 24 h, as much as 34 or 13% of the dose was recovered from lamina propria or dermis, respectively. At each time interval studied, less than 2% of dose of [3H]PbTx-3 penetrated into the receptor fluid which bathed the inner surfaces of the lamina propria or dermis. The results of this study demonstrate that monkey buccal mucosa is more permeable than skin to THO and PbTx-3.

Administration, Topical↗
PubMed1991

Best's macular dystrophy with a macular hole.

The occurrence of a macular hole with Best's dystrophy is an extremely rare finding with only one reported case in the literature. We wish to report two cases with typical Best's dystrophy in one eye and a macular hole in the contralateral eye. In one case the Pattern Reversal VER (PVER) was also recorded and graphed as an amplitude-check size function curve. The PVER changes in this case were grossly subnormal in both the eyes, suggesting a significant degree of bilateral macular impairment. This implies that a significant amount of functional impairment occurs at the vitelliform stage itself, though how this stage progresses to a macular hole is unclear.

Adult↗
PubMed1991

Retinal function in birdshot retinochoroidopathy.

The electroretinograms (ERGs) of 15 patients with birdshot retinochoroidopathy varied from super-normal to non-recordable, depending upon the severity and the stage of the disease. The abnormal ERGs were characterized by a disproportionate decrease of the b-wave amplitude compared with the a-wave amplitude, demonstrating the negative (-) type response. This distinct ERG pattern has not been observed in any other type of uveitis or chorioretinitis, and appears specific to birdshot retinochoroidopathy. ERG findings indicate that in birdshot retinochoroidopathy the neural layers of the retina are more diffusely and severely involved than the receptor-retinal pigment epithelium-choroid complex. In the most advanced stage, the patients becomes night blind with a non-recordable ERG, a situation that is essentially the same as retinitis pigmentosa, except that pigmentation is conspicuously absent in the fundus.

Adult↗
PubMed1991

Behavioral training for mothers of mentally handicapped children: teaching of self-help skills.

Deficits in self help skills are an inevitable problem with the mentally handicapped. The acquisition of self-help skills, learned effortlessly by more intelligent children, is a crucial aspect of the overall development of the mentally handicapped child. In the present study, thirty seven mothers of mentally handicapped children aged between 3 1/2 and 8 years, with an IQ of less than 70, were trained in behavioral techniques such as shaping, task analysis, prompting, and modelling, to develop independent self-help functioning in their children. The self-help areas were toileting, feeding, bathing, washing, and dressing. Thirty two per cent of mothers reported complete skill learning. The problems encountered in the course of training and the subsequent evaluation of its efficacy are discussed.

Adult↗
PubMed1990

Simultaneous pattern reversal ERG and VER recordings. Effect of stimulus field and central scotoma.

The effects of the sizes of the stimulus field and of an artificially created central scotoma on simultaneously recorded pattern-reversal electroretinogram (P-ERG) and pattern-reversal visual-evoked response (P-VER) were investigated. With an increase in the stimulus field from 4 degrees X 4 degrees to 12 degrees X 12 degrees, the amplitude of the P-ERG increased steadily. The amplitude of the P-VER also showed an increase up to a stimulus field of 6 degrees X 6 degrees or 8 degrees X 8 degrees, but showed no increase with further expansion of the stimulus field. A central scotoma, created by placing a square of black paper at the center of the 12 degrees X 12 degrees stimulus field, was increased from 4 degrees X 4 degrees to 10 degrees X 10 degrees by 2-degree increments. Amplitudes of both the P-ERG and the P-VER decreased with increasing central scotoma size. The P-VER decreased significantly with a 4 degrees X 4 degrees central scotoma. Although both the P-ERG and the P-VER were influenced by the overall stimulus field and the central scotoma, there was a distinct difference in their behavior. The P-VER showed saturation above a certain stimulus field size and, with a central scotoma of 4 degrees X 4 degrees, much more reduction than the P-ERG, suggesting that the P-VER depends more on the macular area than does the P-ERG. The P-ERG also exhibited a substantial macular dependency, which, however, was not as great as that of the P-VER. The greater macular dependency of the P-VER compared to the P-ERG, as observed in our study, reflects the larger anatomic representation of the macula at the higher visual level.

Adult↗
PubMed1990

Fracture of the carpal navicular--efficacy of clinical findings and improved diagnosis with six-view radiography.

A prospective study was conducted to determine the usefulness of clinical findings and 25-degree pronation and supination radiologic views to diagnose carpal navicular fractures. All patients presenting to the emergency department during a two-year period who fell on their outstretched hand and had pain and/or swelling in the anatomic snuffbox were evaluated initially and at two weeks. All patients received at least the standard four-view wrist radiography. If a fracture was not detected, two additional views were obtained. Ninety patients were enrolled; 54 fractures of the navicular were evident on initial four-view radiography. Thirty-six patients with a negative initial four-view radiograph had two additional views; 11 of the 36 were found to have a fracture. The other 25 patients failed to show fracture. In this series; no fractures were missed when six-view radiography was used. Anatomic snuffbox tenderness was 100% sensitive and 76% specific and had a 92% positive predictive value for carpal navicular fracture. We conclude that patients clinically suspected of carpal navicular fracture should undergo additional radiologic views if the standard four views of the wrist are negative.

Carpal Bones↗
PubMed1990

Transanal and intraperitoneal prolapse in intussusception.

An infant with intussusception who developed an unusual complication of transanal and intraperitoneal prolapse is reported. Complete venous occlusion of the intussusceptum for a prolonged period in a patient with congenital anomalous vascular supply of the colon is suggested as a mechanism responsible for rupture of the intussuscepiens.

Ascites↗
PubMed1990

Effect of optical defocus on the steady state pattern reversal visual-evoked response.

The effects of optical defocusing with convex lenses on the amplitudes of pattern reversal visual-evoked response (PVER) were investigated. With the large check size and high-contrast pattern, PVER amplitudes showed a linear decrease in response to initial defocusing up to +5 to +6 dptr. As the degree of defocus increased, the PVER amplitude, though irregular, continued to show reliable, definite responses up to +25 dptr. With the intermediate check size and pattern contrast, PVER amplitudes displayed a linear decrease, but unlike the large-check/high-contrast condition, diminished to noise level after a defocus of greater than +4 to +5 dptr. From these results, we speculate that two phases in this function curve derive from the large-check/high-contrast condition: first, the contrast- or contour-dependent phase, and, second, the luminosity/movement-dependent phase.

Adult↗
PubMed1990

A comparative study of family-based and patient-based behavioural management in obsessive-compulsive disorder.

Thirty obsessive-compulsive patients were randomly allocated to two treatment conditions. In group A a significant family member was trained to act as cotherapist at home, whereas in group B, only the patient was seen and given home assignments. All 30 patients received a similar treatment regime of systematic desensitisation, exposure, and response prevention. The family-based approach resulted in greater improvement in anxiety, depression, obsessive symptoms, and in social adjustment in occupational and household responsibilities. The personality pattern of the family members also appeared to influence outcome.

Adolescent↗
PubMed1990

Effect of endobronchial radiation therapy on malignant bronchial obstruction.

We evaluated the effect of endobronchial radiation therapy in 52 patients with malignant airway occlusion. Fifty-five endobronchial applications of the radioisotope iridium 192 were carried out. Response was assessed by change in performance status, symptom resolution, duration of symptom relief, roentgenographic reaeration, pulmonary function tests, and postimplant bronchoscopy. Thirty-three patients showed at least a one-level improvement in performance status. Of a total of 166 symptoms present prior to therapy, 131 resolved or improved. Approximately 70 percent of a patient's lifetime was rendered symptom improved or symptom free. A roentgenographic reaeration response of 30/41 (73 percent) was achieved. The average FEV1 and FVC improved from 1.5 to 2.1 L and from 2.3 to 2.9 L, respectively. Posttherapy bronchoscopy was performed between one and two months following the implant in 15 patients who agreed to undergo the procedure. Eleven (73 percent) of 15 had complete tumor regression. Major long-term complications were noted in seven patients. Endobronchial radiation, therefore, appears to be a safe and effective technique to palliate malignant airway occlusion.

Aged↗
PubMed1989

A study of psychiatrically normal children in a hospital based child guidance clinic.

A total of 1330 children who attended a hospital-based child guidance clinic in last three years were studied retrospectively. 7.37% of these were found to have no psychiatric disorder. Epilepsy and scholastic backwardness without any psychiatric disorder, together constituted 70.41% of this group. Children referred to a child guidance clinic require proper assessment to detect psychiatrically normal children who would otherwise receive unnecessary label of psychiatric disorder and treatment.

Child↗