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Biomedical subjects

A C Shah

Publications and source records attributed to A C Shah.

At least 37 records · Page 2Linked to original sources
PubMed1989

Six month follow-up of fourteen victims with short-term exposure to chlorine gas.

Fourteen cases, 5 with pre-existing COAD, exposed to up to 30 p.p.m. chlorine gas in an accidental leakage, were followed up clinically, radiologically and by spirometry at 2 weeks, 4 weeks, 8 weeks and 6 months. All the patients were asymptomatic by 2 weeks and did not reveal any radiological abnormality. The FVC, FEV1 and FVC observed/predicted improved at 4 weeks (p less than 0.05, p less than 0.05, p less than 0.01) and the improvement in FEF0.25-0.75 reached statistical significance (p less than 0.05) at 6 months. The mean improvement in FVC was 0.84 l and FEV1 was 0.6 l at 4 weeks. The 5 patients with pre-existing COAD did not show any evidence of additional lung damage. The observations have been consistent with acute tracheobronchitis with trends towards complete recovery.

Adult↗
PubMed1988

Simultaneous radiotherapy and chemotherapy with 5-fluorouracil and cisplatin for locally confined squamous cell head and neck cancer.

Fifty-four patients with previously untreated or minimally treated locally confined (MO) squamous cell carcinoma of the head and neck were treated with chemoradiotherapy employing multiple courses of simultaneous radiation, cisplatin, and a 4-day 5-fluorouracil infusion. Twenty-eight patients subsequently underwent definitive surgery, and 26 were treated without surgical resection. Of the 54 patients, 51 were ultimately rendered disease free by this combined modality protocol. The projected relapse-free survival rate for the entire cohort is 71%, with a median relapse-free survival time greater than 17 months. Thirteen patients who had tumors that were technically operable did not undergo surgery after achieving a complete response to induction chemoradiotherapy. Only 1 of these patients experienced subsequent local failure. Although the treatment-associated mucositis and local failure. Although the treatment-associated mucositis and myelosuppression were significant, this chemoradiotherapeutic protocol offers a significant chance of relapse-free survival for all patients with locally confined disease and merits comparison with more standard treatment approaches.

Adult↗
PubMed1987

Mass transport in dissolution kinetics. I: Convective diffusion to assess the role of fluid viscosity under forced flow conditions.

The quantitative influence of viscosity on dissolution kinetics is assessed under laminar flow conditions by utilizing a convective diffusion model for drug dissolution. Functional dependency of three types of viscosity inducing agents is established with respect to the parameters of fluid flow rate, diffusivity, and solubility. Studies of aqueous solutions of sucrose and of glycerol demonstrate that the decrease in dissolution rate of ethyl p-aminobenzoate is related to the decrease in solute diffusivity in these solutions, whereas the solubility change in the glycerol solutions has an additional independent simultaneous effect. Dissolution in hydroxypropyl cellulose solutions remains constant under fixed fluid flow conditions because of the negligible effect of the polymer upon the drug diffusivity. A change in fluid flow rate, however, alters the dissolution rate and correlates quantitatively with the rate of shear in the convective diffusion model. The interpretation of the effect of viscosity on dissolution kinetics with the convective diffusion model explains these phenomena quantitatively in terms of the fundamental mass transport processes.

Cellulose↗
PubMed1987

Mass transport in dissolution kinetics. II: Convective diffusion to assess role of viscosity under conditions of gravitational flow.

Dissolution kinetics was studied in a laminar flow cell, through which aqueous solutions of increasing viscosity flowed under the force of gravity, in order to help elucidate the mechanism of drug dissolution. The viscosity was varied by addition of either hydroxypropyl cellulose, sucrose, or glycerin. The dissolution data were evaluated quantitatively in terms of a convective diffusion model for dissolution. It was demonstrated that the decrease in dissolution rate of a test compound due to viscosity in the polymer solution occurs primarily because of a decrease in the rate of shear over the dissolving surface. In solutions of sucrose or glycerin, the decrease in dissolution rate due to viscosity results because of a decrease in the diffusivity of the solute in addition to the decreased rate of shear. Also, the model accounts for the increase in solubility in the glycerin solution. Thus, the influence of viscosity on dissolution depends on whether the viscosity-inducing agent primarily affects only the flow properties of the liquid, or whether it affects diffusivity (i.e., a "micro" viscosity effect, in addition to the flow properties).

Cellulose↗
PubMed1987

Evaluation of reversible polymorphic phase transitions by thermal analysis.

Crystalline states of 1,2-dihydro-6-neopentyl-2-oxonicotinic acid, an investigational antidiabetic drug, were evaluated by thermal analyses. Two polymorphs were detected for the drug, Form I (m.p. 193 degrees C) and Form II (m.p. 196 degrees C). Interconversion of the polymorphs upon cyclic solid-melt transitions provided confirmation of the crystal forms. Solidification of the melt was observed to occur either at 162 or 182 degrees C with the formation of Form I or Form II crystals, respectively. Form I underwent partial conversion to Form II upon heating at 10 degrees C min-1 when nucleating crystals of Form II were present in the sample. Differential scanning calorimetry (DSC) thermograms were recorded for different lots of the drug, solvent-recrystallized samples, and a series of known mixtures of Form I and II polymorphs. The study illustrates the usefulness of cyclic heat-cool studies to characterize polymorphic crystal forms of drugs.

Crystallization↗
PubMed1986

Chemoradiotherapy as initial management in patients with squamous cell carcinoma of the head and neck.

Thirty-nine previously untreated or minimally treated patients with squamous cell carcinoma of the head and neck were entered onto a chemoradiotherapy protocol employing multiple courses of simultaneous radiation therapy, cisplatin, and a 4-day 5-FU infusion. Thirty-eight patients were evaluable for response and toxicity. Twenty-three patients underwent surgical resection midway through this therapy and 11 (48%) were pathologically free of disease. Thirty-five of the 38 patients (92%) were ultimately rendered disease-free by this combined modality protocol. Thirty-one patients remain disease-free, with a projected 2-year disease-free survival of 74%. Although the treatment-associated mucositis and myelo-suppression were significant, this chemoradiotherapeutic approach is promising and merits further study.

Actuarial Analysis↗
PubMed1985

Combination chemotherapy prior to definitive local therapy in squamous cell carcinoma of the head and neck.

30 patients with locally advanced squamous cell carcinoma of the head and neck were given chemotherapy with methotrexate, bleomycin and cis-Platinum prior to planned definitive surgery and/or radiation therapy. Chemotherapy was well tolerated and 90% of patients responded. Of 14 initially unresectable patients, 6 became operable after chemotherapy. After definitive therapy 70% of patients were considered complete responders, and 43% of the entire cohort remain disease-free. All partial responders have died. Patients receiving chemotherapy, surgery and radiation had a significantly greater likelihood of achieving a complete response than those receiving chemotherapy and radiation alone. Although this initial chemotherapy is highly active in this disease its contribution to ultimate survival is unclear. Overall treatment success is determined by the results of definitive therapy.

Adult↗
PubMed1985

Flow volume loops.

Explore the source record for details and available documents.

Forced Expiratory Flow Rates↗
PubMed1981

A genetic study of some Gujarat populations.

A study of gene frequencies at 24 loci and their phenotypes in four castes of Gujarat indicates their general alignment with other populations of western India. There is distinct genetic heterogeneity among them, which appears to be maintained by an endogamous breeding structure. The presence of some marker alleles suggests appreciable African influence in at least one of the castes, but other explanations are possible.

Blood Proteins↗
PubMed1980

Membrane transport of alkyl homologs: role of fluid flow in aqueous diffusion region.

Passive drug transport across a membrane involves the resistances in series offered by the membrane and the liquid layer immediately adjacent to it. The liquid layers generally are referred to as unstirred aqueous diffusion layers, suggesting that solute transport across these layers occurs solely by molecular diffusion. In accord with convective diffusion theory, recent studies showed that the transport from either a dissolving surface or a membrane surface depends not only on molecular diffusion but also on fluid convection inthe liquid adjacent to the membrane. Membrane permeation rates were determined for a series of alkyl p-aminobenzoates, and the results correlated with a model comprised of membrane diffusion and convective diffusion in the adjacent liquid region.

Aminobenzoates↗