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Biomedical subjects

A R Davidson

Publications and source records attributed to A R Davidson.

At least 55 records · Page 3Linked to original sources
PubMed1987

Sarcoidosis of the stomach.

A 25-year-old housewife presented with an 8-month history of epigastric pain, vomiting and weight loss. This was found to be due to sarcoidosis of the stomach. Her condition improved remarkably on steroids.

Adult↗
PubMed1985

Action of surface-active agents on arylsulfatase-C of human cultured fibroblasts.

Arylsulfatase-C is a microsomal membrane-bound enzyme with unusual biochemical and genetic properties. Whether it is a single enzyme hydrolyzing different sterol sulfates or a complex of enzymes, with each enzyme hydrolyzing a specific substrate, has not been resolved. Its locus has been mapped to the human X chromosome but appears to escape inactivation. As a first step to clarify its biochemical properties, a systematic search was undertaken for a suitable detergent that can release this enzyme from human cultured fibroblast membranes in a form that is biologically active and electrophoretically mobile. Four non ionic (Triton X-100, Nonidet P-40, Digitonin, and saponin) and four amphoteric (lysolecithin, Zwittergent, Miranol, and Chaps) detergents were studied. At 1% concentration, they released more than 80% of the activity into a low-speed supernatant fraction, except for Saponin which had no effect. With Triton X-100 and Miranol representing the two groups of detergents, significant release occurred only when the detergent concentrations exceeded their respective critical micelle concentrations, thus indicating that arylsulfatase-C is an integral membrane protein. The apparent molecular weight of the detergent-enzyme complex, ascertained by gel filtration, was 85,000 in the presence of Triton X-100 and 335,000 in the presence of Miranol. However, only the preparation solubilized by Miranol (and Chaps, to a lesser degree) permitted migration of the enzyme in nitrocellulose acetate during electrophoresis at pH 7.0, while the enzyme extracted with all other detergents remained at the origin. Therefore, the amphoteric detergent, Miranol, appears to fulfill the requirements for further characterization of the membrane-bound arylsulfatase-C in human cultured fibroblasts.

Arylsulfatases↗
PubMed1985

Amount of information about the attitude object and attitude-behavior consistency.

The synthesis of two separate lines of inquiry--research on information integration and longitudinal studies of attitudes--prompted the hypothesis that the degree of consistency between attitudes and behavior will increase as a function of the amount of information available about the attitude object. The hypothesis was tested in three separate longitudinal studies, ranging in length from 4 days to 4 months, that investigated the following behaviors: voting for candidates for political office, voting for two social policy election initiatives, and having an influenza vaccination. In support of the hypothesis, in each study, amount of information moderated the consistency between attitudes and behavior; and the significance of this relation remained even after controlling for the effects of a number of other potential moderators, including prior direct behavioral experience with the attitude object and attitude certainty. Consistent with previous research, direct behavioral experience was also a determinant of attitude-behavior consistency, and for the behavior of having an influenza vaccination, this relation was independent of the effect of amount of information. The discussion focuses on the interrelation among moderators of attitude-behavior consistency and on the theoretical implications of the findings.

Adult↗
PubMed1984

A comparison of three social-psychological models of attitude and behavioral plan: prediction of contraceptive behavior.

We compared the predictive validities of three prominent models of attitudes and behavioral decisions: Rosenberg's instrumentality-value model, Fishbein's belief-evaluation model, and Beach's adaptation of subjective expected utility theory. Seventy female undergraduates rated each of the models' components and reported their attitudes and behavioral plans toward using three different methods of contraception. With the traditional across-subjects prediction procedure, the Rosenberg model generally accounted for 5-25% less variance in subjects' attitudes and behavioral plans than the Fishbein an Beach models, which were not different. With a within-subject prediction procedure, the Rosenberg model was again the least accurate, and the Fishbein and Beach models had similar predictive accuracy. As hypothesized, within-subject predictions were more accurate than across-subjects predictions. The relatively poor performance of the Rosenberg model was attributable to the instrumentality component. In addition, we found that the Beach model could be simplified with no appreciable loss in predictive accuracy. Finally, a subject's personal normative beliefs emerged as a strong independent predictor of behavioral plan.

Adult↗
PubMed1983

Predicting contraceptive behavior from attitudes: a comparison of within- versus across-subjects procedures.

Within- versus across-subjects procedures for predicting behavior from attitudes were contrasted. Each procedure requires a comparison among attitudes in order to generate a prediction; the comparison is either among the same attitudes held by different people (across subjects) or among different attitudes held by the same person (within subject). It was hypothesized that the within-subject model provides a more adequate explanation of behavior from attitudinal constructs and, hence, more accurate prediction of behavior from attitudes than does the across-subjects model. To test this view, a sample of 349 married couples was administered a questionnaire containing measures of three attitudinal components--affect, cognition, and conation--toward each of four contraceptive methods--oral contraceptives, IUD, diaphragm, and condoms. Contraceptive behavior was assessed 1 year later. In support of the hypothesis, the within-subject predictions bore a significantly stronger relation to the behavioral criteria than did the across-subjects predictions. This effect was consistent for each of the three components of attitude, for the prediction of behavior and behavioral intention, for male and female respondents, and for a variety of contraceptive behaviors. In addition, both the within- and the across-subjects analyses demonstrated a clear rank ordering in the predictive validity of the three attitudinal components: Conation was a better predictor of behavior than was affect, which, in turn, was better than cognition.

Affect↗
PubMed1981

Preoperative use of antibiotics.

Basic surgical research has demonstrated that bacterial infection is a function of the dose of bacteria times virulence over resistance of the host. This risk of infection can be lowered by the use of preoperative antibiotics. Preoperative use of antibiotics has few if any complications. However, one can not use preoperative antibiotics as a replacement for good surgical technique and sound surgical principles.

Anti-Bacterial Agents↗
PubMed1980

Erythrocytotoxicity induced by cancer chemotherapeutic agents. In vitro studies of osmotic fragility and methaemoglobin generation.

Increased osmotic fragility and methaemoglobin generation in vitro have resulted from the exposure of normal human erythrocytes to numerous cancer chemotherapeutic agents. These findings offer a possible explanation for the earlier, consistent clinical observation of the rapid development of anaemia, during consolidation therapy, in children with acute lymphoblastic leukaemia in remission.

Adult↗
PubMed1976

The relation of psychological, social, and economic variables to fertility-related decisions.

To test a recent model of social behavior, a questionnaire was designed and administered to 270 married women in a midwestern city. A stratified random sample was obtained, comprising a 2 X 3 factorial design (Catholic vs. Protestant and high vs. middle vs. low socioeconomic status). It was hypothesized that an individual's intention to engage in a fertility-related behavior would be highly correlated with (a) her beliefs about the consequences of performing that behavior weighted by the value of those consequences, and/or (b) her beliefs about what relevant others think she should do and her motivation to comply with those others. The data strongly supported this hypothesis for each of three different behaviors. Analysis of variance revealed a significant religious differential for intentions to have a two-child family (Catholics were less likely to intend to have a two-child family than Protestants). This differential was further examined in terms of the proposed model of behavior.

Attitude↗
PubMed1976

Early unconjugated hyperbilirubinaemia after paracetamol overdosage.

A rapid increase of predominantly unconjugated bilirubin in the blood -- which was not due to haemolysis -- was observed in 38 of 60 patients who had taken an overdose of paracetamol. Studies in the rat given an overdose of the drug showed that within 24 hours there was a striking reduction in the activity of bilirubin glucuronyl-transferase and the content of cytochrome P.450 in the liver. It is suggested that such early damage of the hepatic endoplasmic reticulum contributes to the hyperbilirubinaemia of paracetamol poisoning.

Acetaminophen↗
PubMed1975

Carcinoid myopathy. Serotonin-induced muscle weakness in man?

A myopathy, which improved with cyproheptadine hydrochloride therapy, developed in a patient with carcinoid syndrome of ten years' duration. Biopsy examination revealed advanced atrophy of type II muscle fibers, with type I fiber preponderance. Many of the small fibers had degenerated. Carcinoid myopathy may be due to excess circulating serotonin.

Adult↗
PubMed1975

Histopathological changes in the liver following a paracetamol overdose: correlation with clinical and biochemical parameters.

The histological appearances of the liver damage occurring after a paracetamol overdose are described in liver biopsies from 104 patients, of whom 38 developed fulminant hepatic failure. Confluent centrilobular necrosis of varying extent was followed by rapid disappearance of necrotic cells, leaving areas of reticulin collapse and a usually mild inflammatory reaction. The histological recovery in even the most severe cases was remarkable, and only one of the 17 survivors whose initial biopsy showed the pattern of interlobular bridging necrosis had appreciable residual fibrosis in a follow-up biopsy taken after 1 yr. A quantitative estimate was made of the amount of surviving liver parenchyma using a morphometric technique and the hepatocyte volume fraction (HVF) in biopsies performed within 10 days of the overdose correlated well with the clinical course and both the maximal prolongation of the prothrombin time and the peak plasma bilirubin concentration in the first 10 days. An HVF value (normal 85 +/- 5 per cent.) of less than 40 per cent. in a biopsy taken within 10 days of the overdose was found only in patients who died. However, HVF measurements on biopsies from three survivors taken later than 10 days after the overdose shows that survival is possible below this critical level.

Acetaminophen↗
PubMed1974

Mesentericocaval "jump" graft in management of portal hypertension: experience with 24 cases.

A series of 24 patients with cirrhosis have undergone mesentericocaval shunt operations for the relief of portal hypertension. Overall the results have been satisfactory. Four of the five patients treated as an emergency and 17 of the 19 who had the operation two to six weeks after haemorrhage had been controlled left hospital alive and well. Separation of the patients into three categories according to the findings of clinical and biochemical tests, however, showed that subsequent survival was satisfactory for patients in categories A and B but that all four patients in category C had died within one year after surgery. Assessment at three months showed that in three patients moderate hepatic encephalopathy had developed.Evidence that the shunt remains patent was shown by a low incidence of repeated gastrointestinal haemorrhage and a marked diminution in variceal size in 18 of the 19 cases examined serially. Radiographic techniques for confirming shunt patency were compared and cannulation of the graft via the femoral vein was found to provide a reliable and rapid means of assessment.

Adult↗
PubMed1974

Dopamine and serotonin metabolism in hepatic encephalopathy.

Patients with stupor or coma from fulminant hepatic failure were found to have high cerebrospinal fluid concentrations of homovanillic acid (HVA) and 5-hydroxyindole acetic acid (5-HIAA), metabolites of dopamine and serotonin respectively. Excessive amounts of their precursors-phenylalanine and tyrosine and free tryptophan-were found in the patients' plasma. Methionine, which participates in dopamine degradation, was also much increased. Similar disturbances were found in patients suffering an acute exacerbation of chronic encephalopathy. These abnormalities would be consistent with other evidence of an increased turnover of serotonin and possibly dopamine in the brain during hepatic encephalopathy.

Acetaminophen↗