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B R Hajratwala

Publications and source records attributed to B R Hajratwala.

13 recordsLinked to original sources
PubMed1986

Surface-tension measurements of pulmonary lavage from ozone-exposed rats.

Ozone, an important component of photochemical air pollution, has been shown to cause morphological and functional changes in the lung after acute, high-level exposure in controlled animal studies. Previous exposures of rats to 0.8 ppm ozone for 18 h showed trends toward decreased lung volumes, as well as modifications in phospholipid composition of lung lavage fluid. These results suggested that exposure to ozone may have diminished the ability of surfactant to reduce surface tension. The purpose of this pilot study was to determine if changes in the surface tension of lavaged pulmonary surfactant occur with ozone exposure. The lavage fluid from rats exposed to ozone at 0.8 ppm for 18 h had a 360% increase in protein and a 30% increase in lipid phosphorus content. Lung lavage samples from ozone-exposed rats were more potent in reducing surface tension as measured on a Wilhelmy plate balance. This difference was evident whether determined with half the total lavage or with equivalent microgram amounts of lipid phosphorus. It is concluded that at this dose and duration of ozone exposure, contrary to our hypothesis, surface-tension-lowering ability of surfactant increases and therefore does not appear to be a contributory factor in the previously observed changes in pulmonary function.

Animals↗
PubMed1985

An 'adjustable' calculator program to determine fraction of species versus pH profiles for mono-, di- or triprotic weak acids or bases.

A calculator program for TI-58/59 is presented which determines the fraction of dissociated and undissociated species of weak acids and bases, provided values for dissociation constants and pH are known. The answers are displayed in exponential notation. The calculations can be repeated at as many pH-values as required to obtain a satisfactory fraction of species versus pH profile. The program is made 'adjustable' by deleting selected program steps to accommodate calculations for mono-, di- or triprotic weak acids or bases.

Acids↗
PubMed1984

Effect of aging on hydrocortisone-polyethylene glycol 4000 and hydrocortisone-polyvinylpyrrolidone dispersions.

Dispersions containing 40% hydrocortisone were prepared by the solvent method in polyethylene glycol 4000. Dispersions in polyvinylpyrrolidone were prepared by slow evaporation of solvent (type A) and by fast evaporation of solvent (type B). These dispersions were stored at 25 degrees C for 30 d. Plots of time required for 50% (t50%) and 70% (t70%) of the hydrocortisone dispersion to dissolve (beaker method) versus time were obtained. Hydrocortisone-polyethylene glycol showed no apparent significant change in either dissolution rate, X-ray spectra, or scanning electron micrographs. Type A dispersions showed an increase in dissolution rate up to 8 d. Type B dispersions showed an initial decrease followed by an increase in dissolution rate. The initial decrease in dissolution rate of type B dispersions is due to hydrocortisone crystallizing out of the polyvinylpyrrolidone matrix. The increased dissolution for both types of polyvinylpyrrolidone dispersions was not expected and is for both types of polyvinylpyrrolidone dispersions was not expected and is explained by an increased proportion of the high-energy amorphous component, based on X-ray spectra. Other possibilities such as the presence of polymorphic forms of hydrocortisone and/or reduction in particle aggregation could not be discounted.

Chromatography, Thin Layer↗
PubMed1982

Particle size reduction by a hammer mill I: Effect of output screen size, feed particle size, and mill speed.

A hammer mill is an impact mill commonly used in pharmaceutical manufacturing for reducing particle size for a variety of drugs. Commercial grade ammonium sulfate was milled as a model powder. This salt was sieved to obtain particle size fractions with average diameters of 1.3, 0.9, and 0.72 mm which were used as feed particles. The milled material was analyzed for particle size distribution (PSD) using standard sieves. At a moderate speed (approximately 2500 rpm), the feed size did not result in a significantly changed arithmetic mean diameter, dx of milled particles. A new particle size reduction constant, k, is proposed as a result of a linear relationship between dx and output screen size, dss. As dss decreases, the PSD range of milled particles narrows; as mill speed increases (approximately 5000 rpm), dx decreases. The decrease is of a greater magnitude for larger dss (2 mm) than for a smaller dss (1 mm). At low speeds (approximately 1000 rpm), the PSD is wider compared to medium and high speeds.

Ammonium Sulfate↗
PubMed1977

Kinetics of indomethacin degradation I: Presence of alkali.

The kinetics of indomethacin degradation were followed in alkaline aqueous solutions at various temperatures between 20.1 and 40.7 degrees. The apparent first-order rate constants were evaluated from log absorbance versus time plots at lambda max 318 nm. The primary salt effect was positive. The rate constant-hydroxide-ion concentration profile was linear with a positive slope, suggesting the following rate law: kobs = k1 [OH-]. The experimental data fit the proposed reaction of degradation, I- + OH k1 leads to products, where I- = mono-dissociated indomethacin species. Activation energies and other related parameters were calculated from Arrhenius-type plots.

Alkalies↗
PubMed1977

Influence of sunscreening agents on color stability of tablets coated with certified dyes III: FD&C Yellow No. 6.

The influence of a protective coating of six sunscreening agents (glyceryl p-aminobenzoate, benzocaine, cinoxate, homosalate, n-octyl salicylate, and amyl salicylate) upon the photostability of FD&C Yellow No. 6 used to color coat tablets was studied. The alcohol film, modified sugar-, and film-coating methods were used to apply the sunscreening agents. Tablets were exposed to 1000 foot-candles of light for various times, after which reflectance measurements and visual observations were recorded. FD&C Yellow No. 6 did not follow the Kubelka-Munk equation. The order of relative stability was FD&C Yellow No. 6 greater than erythrosine sodium (FD&C Red No. 3) greater than FD&C Blue No. 1. The greatest protection against fading was afforded by benzocaine.

Azo Compounds↗
PubMed1977

Kinetics of indomethacin degradation II: Presence of alkali plus surfactant.

The kinetics of indomethacin were studied in the presence of the surfactants ethoxylated lanolin, polysorbate 80, and cetrimonium bromide under alkaline conditions at 30.3 degrees. The degradation followed apparent first-order kinetics. Plots of kobs versus surfactants; concentrations were curved with negative slopes for nonionic surfactants; but with the ionic surfactant, the plots showed a marked positive change in kobs as the surfactant concentration passed through the critical micelle concentration. Literature model systems adequately explained the data for nonionic surfactants but not for the ionic surfactant. A new set of equations was derived for each case using electrochemical potentials. The experimental data for all three surfactants fit the derived equations quite well.

Alkalies↗
PubMed1976

New generalized equations for multiple dose kinetics by i.v. injection.

New generalized equations for one compartment open model system with rapid i.v. injections for multiple dose kinetics are developed. The model assumers the first order elimination. Equations are developed for the maximum and minimum amounts of drug in body after n and infinity number of doses. The methods for calculating rate of accumulation is presented and the relationship bewteen, f (fraction of drug present in the compartment at the time of repeated dosing), t1/2 and the dosing interval, tau.

Half-Life↗
PubMed1975

Kinetics of sulfite-induced anaerobic degradation of epinephrine.

The rate constant-pH profile of the rate of sulfite-induced disappearance of epinephrine from an aqueous solution under anaerobic conditions was determined at 81 degrees in the 3.63-5.00 pH range at the ionic strength of 0.2. The profile shows a linear relationship with a positive slope. The anaerobic rate shows buffer catalysis above pH 4.4 Metabisulfite was found to be more catalytic than either bisulfite or acetone bisulfite. The concentration of epinephrine used was 5.5 times 10- minus 5 mole/liter.

Anaerobiosis↗