Search PubMed⌕ Search

Biomedical subjects

A Martin

Publications and source records attributed to A Martin.

At least 793 records · Page 44Linked to original sources
PubMed1981

Who should decide?

Explore the source record for details and available documents.

Decision Making↗
PubMed1981

Extended solubility approach: solubility parameters for crystalline solid compounds.

A method is suggested to obtain solubility parameters for crystalline solid compounds involving a quadratic equation based on the original Scatchard-Hildebrand solubility expression. The geometric mean delta 1 delta 2, of the Hildebrand approach is replaced by w12 = K delta 1 delta 2, and log alpha 2/(V2 phi 2(2)/2.3RT) is regressed against delta 1 in a second-degree power series for parabens and benzoic acid in a series of normal alcohols. The method provides reasonable solubility parameters for the solid solutes and affords a convenient calculation of the solubility of drugs in a homologous series of solvents.

Benzoates↗
PubMed1981

Influences of matrixes on nylon-encapsulated pharmaceuticals.

The preparation and properties of nylon microcapsules containing three different matrixes (formalized gelatin, calcium alginate, and calcium sulfate) are described. Microcapsules containing each matrix were dense and free flowing and could be made of very small diameter by controlling the stirring speed during nylon formation. The preparation of microcapsules containing calcium alginate employed freeze-drying procedures. Lyophilization was not necessary with the formalized gelatin and calcium sulfate systems. Various representative drugs (anionic, cationic, nonionic, quaternary, and amphoteric compounds) were used in the formulation studies. The effects of pH, matrix, and encapsulated species on retention of drug in the microcapsules are described. In addition, the surface morphology of the microcapsules was examined using scanning electron microscopy.

Capsules↗
PubMed1981

Extended Hildebrand Solubility Approach: methylxanthines in mixed solvents.

The solubility profiles of theobromine, theophylline, and caffeine at 25 degrees were examined in binary solvent systems including dioxane-formamide, water-polyethylene glycol 400, and glycerin-propylene glycol. Theobromine solubility was studied in dioxane-water mixtures, a solvent system that was investigated earlier for the solubility of theophylline and caffeine. Solubilities were calculated in these polar systems by a regression method, based on an extension of the Hildebrand-Scatchard equation of regular solution theory. A linear relationship between the mixed solvent solubility parameter, and dielectric constant, epsilon, was introduced earlier and was confirmed in the present study. In addition, it was observed that a regression of log (activity coefficient) on epsilon in a second or higher degree polynomial provides reasonable solubility values for the methylxanthines in mixed solvents. A direct regression of molal or mole fraction (but not molar) solubility against delta 1, epsilon, or against volume percent of one or the other solvent in a binary solvent mixture provided a suitable measure of solubility for these crystalline drugs in mixed polar solvents. The drug's solubility parameter as determined from peak solubility in mixed polar solvents varied somewhat, depending on the specific solvent system employed. It is suggested that a drug may exhibit one (or more) solubility parameters in nonpolar solutions and multiple solubility parameters in polar systems. The extended solubility approach serves for the back-calculation of solubilities in mixed solvent systems, even though the solubility parameter of the solute may vary from one solvent system to the next.

Caffeine↗
PubMed1981

Extended Hansen solubility approach: naphthalene in individual solvents.

A multiple regression method using Hansen partial solubility parameters, delta D, delta p, and delta H, was used to reproduce the solubilities of naphthalene in pure polar and nonpolar solvents and to predict its solubility in untested solvents. The method, called the extended Hansen approach, was compared with the extended Hildebrand solubility approach and the universal-functional-group-activity-coefficient (UNIFAC) method. The Hildebrand regular solution theory was also used to calculate naphthalene solubility. Naphthalene, an aromatic molecule having no side chains or functional groups, is "well-behaved', i.e., its solubility in active solvents known to interact with drug molecules is fairly regular. Because of its simplicity, naphthalene is a suitable solute with which to initiate the difficult study of solubility phenomena. The three methods tested (Hildebrand regular solution theory was introduced only for comparison of solubilities in regular solution) yielded similar results, reproducing naphthalene solubilities within approximately 30% of literature values. In some cases, however, the error was considerably greater. The UNIFAC calculation is superior in that it requires only the solute's heat of fusion, the melting point, and a knowledge of chemical structures of solute and solvent. The extended Hansen and extended Hildebrand methods need experimental solubility data on which to carry out regression analysis. The extended Hansen approach was the method of second choice because of its adaptability to solutes and solvents from various classes. Sample calculations are included to illustrate methods of predicting solubilities in untested solvents at various temperatures. The UNIFAC method was successful in this regard.

Chemical Phenomena↗
PubMed1981

Controlled trial of cimetidine in acute pancreatitis.

A double-blind comparison of cimetidine and placebo has been carried-out in 60 patients with acute pancreatitis. No clear-cut benefit from cimetidine was observed, either in the whole group, or in alcohol or gallstone-associated pancreatitis.

Acute Disease↗
PubMed1981

[Kinetic parameters of a soluble purified intestinal fucosyl-transferase].

The soluble fucosyl-transferase of the rat small intestinal mucosa was purified by passing through a Sephadex G-100 column, then resolved in two isoenzymes F1 (pHi = 4,47) and F2 (pHi = 4,96) by isoelectric focusing. The use in the first step of DEAE-cellulose instead of Sephadex G-100 leads to another component F3 (pHi = 8,70). Kinetic parameters (KM et Vm) for the three isoenzymes are given. The enzymatic mechanism seems to be a bi-bi random type for the three isoenzymes, and F3 appears as the most active species.

Animals↗
PubMed1981

Biosynthesis of glycoproteins in the intestinal mucosa. II. Influence of diets.

To determine the effect of diets on the biosynthesis of glycoproteins in the intestinal mucosa, male Sprague-Dawley rats were fed, ad libitum, high-carbohydrate high-fat and high-protein diets. In in vivo methodology, the animals from each dietary group received an intraperitoneal injection of [14C]-fucose, or [14C]-galactose or [14C]-glucosamine. Incorporated radioactivity was detected in the different subcellular fractions. In in vitro methodology, five glycosyl-transferases were studied on microsomes and cell sap. In vivo, only the high-fat diet induces a decrease in the incorporation of [14C]-glucosamine in the macromolecules. In vitro, only the fucosyl-transferase activity is modified by several diets: as compared with an increase in the activity of the control with the age of the animals, high-protein diet induces a slight activation after 2 weeks of diet, while high-carbohydrate and particularly high-fat diets inhibit the enzyme activity. The inhibition is the same when high-fat diet consists of either oil mixture or triolein or oleic acid or linoleic acid and becomes significant with a supplementation rate of 10%.

Animals↗
PubMed1981

[Mechanism of lipid inhibitory effect on intestinal fucosyl-transferase in the rat].

High-fat diets decrease microsomic and soluble fucosyl-transferase activities in rat intestinal mucosa. This inhibition is not due to qualitative (pHi) or quantitative (relative activities) changes ion three isoenzymes, nor is it caused by alterations in the kinetic behaviour of these enzymes (Km, V). It is also not due to a direct effect of the fatty acids on the enzyme activities. It seems reasonable to suggest that a decreased biosynthesis of the fucosyl-transferase occurs as a result of the high-fat diets.

Animals↗
PubMed1981

[Pharmacological therapy of senile dementia in Europe and the U.S.A].

This article is a review of the pharmacotherapy of senile dementia in Europe and the United States. Neurophysiological and neuropathological studies of demented elderly have suggested that a change from the attempt to improve cerebral blood flow to the attempt to improve neuronal intermediary (glycolytic) metabolism may be more fruitful therapeutically. Clinical studies of drugs which are direct smooth relaxant vasodilators are compared with studies of drugs claimed to improve neuronal intermediary metabolism in order to test this hypothesis. Comparison of 102 clinical studies of these two types of medications finds that a significant (p less than .005) number of studies of drugs with metabolic action claim positive results than to studies of drugs with vasodilatator action alone. Three new studies addressing questions of dose and spinal fluid effects of these medications are presented. Two studies provide evidence for the superiority of 6 mg/day of dihydroergotoxine mesylate to 3 mg/kg in the elderly. One study suggests that the medication naftidrofuryl, in doses of 800 mg/day and 400 mg/day, may have similar effects.

Aged↗