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Biomedical subjects

G E Barnes

Publications and source records attributed to G E Barnes.

At least 19 recordsLinked to original sources
PubMed1995

Nitric oxide and choroidal blood flow regulation.

PURPOSE: Nitric oxide (NO) has been found to be an endothelial-derived relaxing factor mediating the vasodilatation that results from the stimulation of muscarinic endothelial receptors. It also has been identified as a putative neurotransmitter of parasympathetic origin in choroidal perivascular autonomic fibers. The authors investigated a potential role of NO in choroidal blood flow (ChBF) regulation. METHODS: Local ChBF in the tapetal region of 26 anesthetized cats was measured by laser Doppler flowmetry. Cats were infused through the femoral vein with increasing dosages of acetylcholine (ACh); N omega-nitro-L-arginine (NNL-A), a specific inhibitor of NO synthesis; L-arginine; and D-arginine. ChBF and mean arterial pressure (MAP) were continuously recorded. RESULTS: Infusion of 20 micrograms/minute ACh induced a 68% increase in ChBF despite a 9% decrease in MAP. Infusion of 16 mg/minute NNL-A attenuated the ACh-induced increase in ChBF by 46% and increased MAP by 40%. Infusion of different dosages of NNL-A without prior administration of ACh caused ChBF to fall below and MAP to rise above baseline in a dose-dependent fashion. Infusion of L-arginine prior to ACh infusion enhanced by 27% the ACh-induced increase in ChBF, whereas D-arginine had no effect on this increase. CONCLUSIONS: These findings suggest the presence of a local vasodilatory cholinergic mechanism in the choroid, inducing the release of NO. They also suggest that release of NO in the choroid may maintain basal blood flow to this tissue.

Acetylcholine↗
PubMed1994

The relative performance of diverse measures of alcohol abuse and dependence in a community sample.

There is broad diversity among the ways in which alcohol abuse and/or dependence are defined and operationalized by researchers. In a community survey of 1,257 adult males and females, eight different measures of alcohol abuse or dependence were used. For analysis, each measure was dichotomized at its usual cutoff point. A factor analysis of distance scores between pairs of measures gave only one interpretable factor representing drinking patterns and social problems. Sensitivity and specificity were calculated for each measure with respect to abuse or dependence, as measured by the DIS-III-R. High maximum levels of drinking and social problems were moderately sensitive and specific to DIS-III-R. These relationships varied, though, for subgroups of age and gender. DSM-III-R alcohol abuse and dependence are widely respected variables but relatively expensive to measure. Alternative approaches for various survey purposes are discussed. Measures to be regarded as alternatives to the DIS-III-R are found to perform better in that role in samples limited by age and gender.

Adolescent↗
PubMed1994

The reliability and construct validity of two measures of addictive personality.

Gossop and Eysenck developed a subscale of the EPQ that discriminates between drug addicts in treatment and nonaddicts. They called this scale the Addiction Scale (AS). Previously, MacAndrew developed an Alcoholism Scale (MAC) by comparing alcoholics and nonalcoholic psychiatric patients' responses on the MMPI. In the present report both scales were completed by 615 men and 642 women as part of the Winnipeg Health and Drinking Survey, a longitudinal study of personality and health. The reliability of both scales is quite low, .64 for the AS and .57 for the MAC. Correlations with other personality measures indicate that the MAC is more associated with extraversion-related characteristics whereas the AS is more associated with neuroticism-related factors. The AS was not associated with the level of smoking, and the MAC was correlated with smoking for men only. Both scales were significantly correlated with various drinking measures, and the correlations were slightly higher for the MAC.

Adult↗
PubMed1994

Local choroidal blood flow in the cat by laser Doppler flowmetry.

PURPOSE: To develop a procedure using a noninvasive technique that will allow the investigation of choroidal blood flow (ChBF) regulation in discrete regions of the cat eye. Validation of this procedure will provide a method to study intrinsic, neural, and pharmacologic factors that regulate regional ChBF. METHODS: The technique to measure ChBF is based on laser Doppler flowmetry. However, in contrast to conventional laser Doppler flowmetry, which uses fiber-optic probes in direct contact with the tissue to deliver the laser beam and detect the scattered light, with this technique the beam is delivered through a fundus camera and the scattered light is detected in the retinal image plane of the camera. Measurements were made in 34 anesthetized cats under conditions that would ensure that the flow measured represented ChBF in the choriocapillaris: the laser beam was aimed at retinal intervascular sites in the tapetal region of the fundus; the Doppler shift power spectrum of the light scattered by the red blood cells had the shape and frequency range typical for a microvascular bed; and the recorded flow did not decrease by more than 5% when the cat was given 100% O2 to breathe for 4 minutes. The responses to various physiologic and pharmacologic stimuli were tested and compared with those obtained from retinal vessels. RESULTS: Intravenous infusions of acetylcholine increased ChBF in a dose-response fashion, whereas sympathetic nerve stimulation at various frequencies decreased ChBF as predicted by previous studies. By comparison, retinal blood flow was negligibly affected by these two stimuli. In contrast to retinal blood flow, ChBF was unaffected by diffuse luminance flicker. ChBF was found to be pulsatile. The mean of the pulsatile component of ChBF represented approximately 34% of mean ChBF, a value similar to those derived from ChBF measurements in minipigs and retinal blood flow in the cat. CONCLUSIONS: This study demonstrates that laser Doppler flowmetry is a valid technique for obtaining local, noninvasive, and continuous recordings of relative ChBF. Tested under steady-state conditions for blood pressure, heart rate, and acid-base balance, ChBF is stable for long periods of time, allowing the investigation of the effect of various physiologic stimuli and pharmacologic agents on this flow.

Acetylcholine↗
PubMed1990

New leupeptin analogues: synthesis and inhibition data.

Syntheses of several tripeptide analogues of leupeptin containing C-terminal argininal, lysinal, or ornithinal units are presented. The synthetic analogues were tested as inhibitors of trypsin, plasmin, and kallikrein. (Benzyloxycarbonyl)-L-leucyl-L-leucyl-L-argininal (2a) was significantly less effective as an inhibitor of trypsin and plasmin activity than leupeptin. (Benzyloxycarbonyl)-L-leucyl-L-leucyl-L-lysinal (2e) and (benzyloxycarbonyl)-L-leucyl-L-leucyl-L-ornithinal (2i) display different inhibition characteristics than (benzyloxycarbonyl)-L-leucyl-L-leucyl-L-argininal (2a). While (benzyloxycarbonyl)-L-leucyl-L-leucyl-L-argininal (2a) showed moderate inhibition of all three enzymes tested, (benzyloxycarbonyl)-L-leucyl-L-leucyl-L-lysinal (2e) was less effective as an inhibitor of trypsin and plasmin activity. Of the three enzymes tested, (benzyloxycarbonyl)-L-leucyl-L-leucyl-L-ornithinal (2i) showed significant inhibition of kallikrein activity only. Modifications made in the composition and sequence of the P2 and P3 amino acids also resulted in variations in the inhibitory activity of the analogues. In general, plasmin showed a strong preference for inhibitors which contain an L-phenylalanyl-L-leucyl or an L-leucyl-L-valyl unit in the P2 and P3 positions.

Amino Acid Sequence↗
PubMed1990

Predicting marijuana use among adolescents.

The present paper (1) contrasts the prevalence of marijuana use and involvement with marijuana among 194 delinquent and 405 nondelinquent adolescents, (2) examines the utility of an expanded version of Jessor and Jessor's (1977) problem behavior model in predicting adolescent marijuana use, and (3) tests the relative importance of the predictors of marijuana use. Personality variables that were added to the Jessor problem behavior model included: (1) stimulus reducing - augmenting, (2) ego strength, (3) anxiety, and (4) field dependence. Results showed that delinquents reported using marijuana more often than nondelinquents. In the multiple regression analyses the expanded model explained a slightly greater percentage of the variance in adolescent marijuana use than the Jessor and Jessor model. Of the added personality variables, the Vando (1969) Reducer--Augmenter dimension seemed to be a particularly significant predictor. In addition, reducing--augmenting seemed to be a better predictor of involvement with marijuana than several previously used personality and demographic variables since it replaced these in the final regression equation. Perceived environment variables measuring pressure from friends to use marijuana and friends as models for marijuana use were the best predictors of marijuana use.

Adolescent↗
PubMed1988

Symptoms of depression in a Canadian urban sample.

The prevalence and correlates of symptoms of depression in a Canadian urban sample were examined. A random sample of 524 respondents completed the CES-D scale and a variety of sociodemographic questions. In this Sample, 15% of the males and 19% of the females had scores above the depression cut-point of 16 on the CES-D scale. These rates were very similar to results reported in various U.S. centres. Symptoms of depression were most common among the younger, less educated, and those employed in trades and farming. Depression was lowest in the older, more educated, the married and those employed in professional and management roles. Taken as a whole the set of sociodemographic predictors explained 11% of the variance in symptoms of depression.

Adult↗
PubMed1985

Mental health professionals' knowledge in the field of caring for chronic mental disorders.

A national sample of 246 Canadian mental health professionals was given a knowledge test concerning principles of care for chronic mental patients. Results showed that: (1) mental health professionals were moderately knowledgeable on this topic (mean score 66%), (2) errors made were more commonly in the direction of over-enthusiastic support for the community approach and (3) there were no differences in knowledge scores by a demographic or professional status variables included in this study.

Adult↗
PubMed1985

Cardiovascular responses to elevation of intra-abdominal hydrostatic pressure.

Intra-abdominal fluid volume and hydrostatic pressure were elevated by positive pressure infusion of Tyrode solution into the peritoneal cavity of anesthetized dogs. The compliance of the peritoneal cavity fell from 10.8 to 0.56 ml X mmHg-1 X kg-1 of body wt as intra-abdominal pressure increased from 0 to 40 mmHg. Intrathoracic pressure also increased as elevated peritoneal pressure caused diaphragmatic bulging. Cardiac output and stroke volume were reduced by 36% after an intra-abdominal pressure rise of 40 mmHg; in contrast, heart rate did not change. Flow in the celiac, superior mesenteric, and renal arteries was reduced by 42, 61, and 70%, respectively. Pressure in the femoral vein increased to 46 mmHg, while flow in the femoral artery decreased by 65%. Whole-body O2 consumption, pH, and arterial PO2 decreased as intra-abdominal pressure rose. The peritoneal cavity, with its high initial compliance, affords the body an ideal location for the temporary accumulation of small to moderate volumes of fluid during episodes of increased vascular pressure or permeability. The marked alterations in the hemodynamic properties of the cardiovascular system are indicative of the physiological changes that occur when intra-abdominal fluid accumulation becomes excessive and peritoneal pressure rises to high levels.

Abdomen↗
PubMed1985

Characteristics affecting successful outcome in the cessation of smoking.

In this study predictors of successful smoking cessation among 166 clients of a smoking cessation program were examined via multiple regression analyses. Results showed that seven significant predictors accounted for 25% of the variance in successful smoking cessation. Abstainers tended to have higher incomes, to rate pregnancy as a motivation more highly, to have made fewer previous attempts to quit, to be low on habit smoking, to crave cigarettes more in low-arousal situations, to be stimulus reducers, and to be older.

Adult↗
PubMed1984

Professional and business role orientations among practicing pharmacists.

This paper examines business and professional role orientations among practicing pharmacists. Data from pharmacists in six urban centres in Canada are examined, focusing on three questions: the co-existence of these two role orientations, the factors related to each and the relevance for actual practice behaviors. The data analyses show a lack of correlation between business and professional role orientations and their co-existence in some instances, the particular importance of work setting and current position for role orientation and beneficial practice behaviors related to high professional orientations.

Adult↗
PubMed1984

Depression in Canadian general practice attenders.

In this study, depression among patients visiting general practitioners was examined by administering a short self-report measure of depression to 1,250 patients visiting 37 general practitioners in three Canadian centres (Winnipeg, Brandon and Virden). According to scores on the CES-D scale, 66.8% of the patients were judged to be normal, 11.8% were experiencing mild depression, 13.3% moderate depression and 8.1% were experiencing fairly severe depression. Depression scores were highest among female patients, patients who lived in Winnipeg, patients who were unemployed and patients who were divorced or separated.

Adult↗
PubMed1982

Adolescent marijuana use: a review.

The adolescent marijuana literature is reviewed. Studies show that the prevalence of marijuana use is generally quite low in elementary schools. In junior and senior high samples, findings vary greatly from place to place. The prevalence of use increased dramatically during the 1970s although the use patterns may have peaked already in some areas. The use of marijuana increases with age, but some evidence suggests that a slight drop-off in use occurs near the end of high school. Female use seems to be increasing more than male use. Use seems to be somewhat more prevalent in middle- and upper-middle-class homes and in broken homes. Mixed support has been found for the hypothesis that marijuana users have parents that are more permissive. Parents of marijuana users are generally characterized as being less warm and supportive, and more inclined toward the use of drugs themselves. Peer and sibling use of marijuana seem to be particularly important predictors of adolescent marijuana use. Findings on personality characteristics of marijuana users are not extensive and are somewhat contradictory. There is some evidence that users tend to be somewhat alienated, external in their locus of control, and possibly higher on anxiety. Users are also characterized by a higher value on independence vs achievement and more positive attitudes toward marijuana use. Behavioral correlates of marijuana use include greater use of alcohol and other drugs, and poorer school performance.

Adolescent↗