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Biomedical subjects

A Martin

Publications and source records attributed to A Martin.

At least 757 records · Page 42Linked to original sources
PubMed1983

Are biopsy forceps helpful in the endoscopic evaluation of ulcer diameter?

A hand-made papier-mâché stomach model with hollowed-out ulcers was employed for evaluating the accuracy in estimating ulcer diameters by means of endoscopy. The opened biopsy forceps were also used as a reference marker. Ten endoscopists with various degrees of experience were involved in the study. All the endoscopists underestimated the ulcer diameters; the use of the forceps, resulted in an improvement, in particular in the case of the comparatively inexperienced endoscopists. A stomach model may be helpful in the subjective assessment of the endoscopists' ability to estimate ulcer size.

Biopsy↗
PubMed1983

Epidemiologic health study of workers in an aluminum smelter in British Columbia. Effects on the respiratory system.

A health survey was carried out on all white males in an aluminum smelter in British Columbia. The survey consisted of a medical-occupational questionnaire, spirometry, chest radiography, and environmental monitoring. We have compared the results of a respiratory survey in 713 workers in the office and casting department with no significant exposure to air contaminants (control workers) with those of 797 potroom workers: 495 who spent more than 50% of their working time in the potroom (high exposure) and 302 workers who spent less than 50% of their working time in the potroom (medium exposure). Potroom workers (high) had a significantly greater prevalence of cough and wheeze than did those in the control group, and they had significantly lower mean forced expiratory volume in one second and maximal midexpiratory flow rate than did those in the control group after adjustment had been made for differences in age, height, and smoking habits. Potroom workers (medium) had a slightly greater prevalence of respiratory symptoms and lower lung function than did workers in the control group, but the differences were not significant. We were unable to demonstrate potroom asthma. The levels of total fluoride, gaseous fluoride, particulate fluoride, sulphur dioxide, and total particulates found in the potroom at the time of the study were below the currently accepted threshold limit values, but the levels of benzo-alpha-pyrene were high.

Adult↗
PubMed1983

Antitumor activity of cell walls from Brucella abortus.

The ip inoculation of inactivated Brucella abortus, strain B19 R, protected mice against a subsequent graft of an ascites lymphoma. The bacterial components responsible for this effect were investigated. Centrifugation supernatants of sonicated bacteria supposed to contain mainly cytoplasmic products did not offer protection against the lymphoma. Cell walls (CW's) prepared by enzyme digestion of pellets of lysed bacteria and checked for purity by electron microscopy prolonged survival of mice and induced cytotoxic macrophages in their peritoneal cavities. CW peptidoglycan (PG) did not seem to play an important part in this effect. Enzyme digestion of CW, in particular by lysozyme, was found to reduce a PG characteristic component (diaminopimelic acid) without altering CW antitumor activity. Conversely, a purified PG preparation did not influence tumor growth. Extraction of CW by an ether:water mixture did not alter its antitumor activity, while incubation in NaOH abolished its activity almost completely. All CW preparations were found to elicit hypersensitivity reactions in Brucella-infected animals.

Animals↗
PubMed1982

Impaired glycosylation in liver microsomes of orotic-acid-fed rats.

In rats fed orotic acid, the incorporation in liver subcellular fractions of sugars injected intraperitonealy is altered only for mannose, but not for fucose or galactose. Direct determinations of several glycosyltransferases are done in smooth and rough microsomes: fucosyl-, glactosyl-, N-acetylglucosaminyltransferase activities are at quite similar levels in normal and fatty livers. By contrast, sialyltransferase activity is increased (+50%) in smooth microsomes of fatty livers, while mannosyltransferase activity is inhibited by 30%. These alterations are not caused by interfering reactions (pyrophosphatases or proteases). For the mannosyltransferase activity, the inhibition is found in the dolichylphosphorylmannose intermediates. Kinetic studies suggest that there is deficiency of both enzyme and endogenous dolichyl phosphate.

Animals↗
PubMed1982

Inhibition by valproic acid of pyruvate uptake by brain mitochondria.

The anticonvulsive drug, valproic acid, inhibits competitively the pyruvate carrier in rat brain and liver mitochondria. Due to this inhibition the oxygen consumption supported by pyruvate oxidation is also affected. In our experimental conditions, pyruvate oxidation is partially inhibited by VPA concentration as low as 0.05 mM. Valproic acid, however, is unable, even at 10 mM, to fully inhibit pyruvate oxidation. Concentrations of VPA higher than 1 mM have an uncoupling effect on mitochondrial respiration. The oxidation of other mitochondrial substrates such as isocitrate, 2-ketoglutarate, DL-3-hydroxybutyrate and succinate is uncoupled but not inhibited by VPA. The effects of VPA on mitochondrial metabolism may be related to the therapeutic and/or toxicologic properties of this drug.

Animals↗
PubMed1982

Combined water-soluble carriers for coprecipitates of tolbutamide.

A study was conducted on the influence of single and combined carriers on the dissolution rate of tolbutamide from its coprecipitates. All of the water-soluble carriers investigated enhanced the dissolution rate of tolbutamide, but the combination of 40% polyethylene glycol 6000--60% dextrose as the carrier for a 1:1 coprecipitate yielded the most rapid dissolution of tolbutamide. Other carriers used were polyethylene glycol 6000, polyethylene glycol 4000, dextrose, and mannitol, alone or combined in various proportions.

Chemical Precipitation↗
PubMed1982

Extended Hildebrand solubility approach: solubility of tolbutamide, acetohexamide, and sulfisomidine in binary solvent mixtures.

The extended Hildebrand approach for predicting solubilities of crystalline compounds in solvent mixtures was tested using tolbutamide, acetohexamide, and sulfisomidine in mixed solvents consisting of hexane-absolute ethanol and 95% (v/v) ethyl alcohol-aqueous buffer. The solubility of these drugs was determined at 25 +/- 0.2 degrees and then back-calculated using the adhesive energy term, W, to account for solute-solvent interaction. Solubilities were predicted within 13% for tolbutamide, 31% for acetohexamide, and 43% for sulfisomidine, and with considerably better accuracy in most solvent mixtures.

Acetohexamide↗
PubMed1982

Extended Hildebrand solubility approach and the log linear solubility equation.

The log linear solubility equation, log S = log Sw + sigma f, was studied in relationship to the extended Hildebrand solubility approach. It is shown that the log linear form may be derived beginning with the extended Hildebrand approach. The log linear expression gives a good linear fit for semipolar drugs in a number of water-cosolvent mixtures. It is particularly successful when the solubility parameter, delta 1, of the cosolvent is 3 or more solubility parameter units larger than the solubility parameter, delta 2, of the drug. When the cosolvent tends to solvate the drug strongly, the log linear function may even hold where the solubility parameters of the drug and cosolvent are similar. It appears, however, not to be applicable to nonpolar cosolvent systems. An interfacial model for the solubility of drugs in polar mixed solvents is based on sigma, a parameter that also figures prominently in the log linear solubility equation. When used to describe mixed solvent systems, the interfacial model applies in the region of the solubility profile (solubility versus solvent composition) where the log linear relationships hold. The extended Hildebrand solubility approach is applicable over a wide range of cosolvent composition in mixed systems from nonpolar organic solvents to water.

Aminobenzoates↗
PubMed1982

Extended Hansen approach: calculating partial solubility parameters of solid solutes.

A multiple linear regression method, known as the extended Hansen solubility approach, was used to estimate the partial solubility parameters, delta d, delta p, and delta h for crystalline solutes. The method is useful, since organic compounds may decompose near their melting points, and it is not possible, to determine solubility parameters for these solid compounds by the methods used for liquid solvents. The method gives good partial and total solubility parameters for naphthalene; with related compounds, less satisfactory results were obtained. At least three conditions, pertaining to the regression equation and the solvent systems, must be met in order to obtain reasonable solute solubility parameters. In addition to providing partial solubility parameters, the regression equations afford a calculation of solute solubility in both polar and nonpolar solvents.

Chemical Phenomena↗
PubMed1982

Extended Hildebrand solubility approach: testosterone and testosterone propionate in binary solvents.

Solubilities of testosterone and testosterone propionate in binary solvents composed of the inert solvent, cyclohexane, combined with the active solvents, chloroform, octanol, ethyl oleate, and isopropyl myristate, were investigated with the extended Hildebrand solubility approach. Using multiple linear regression, it was possible to obtain fits of the experimental curves for testosterone and testosterone propionate in the various binary solvents and to express these in the form of regression equations. Certain parameters, mainly K and log alpha 2, were employed to define the regions of self-association, nonspecific solvation, specific solvation, and strong solvation or complexation.

Chemistry, Pharmaceutical↗