Biomedical subjects

P B Johnson

Publications and source records attributed to P B Johnson.

At least 19 recordsLinked to original sources

PubMed2006

Selective laser trabeculoplasty: predictive value of early intraocular pressure measurements for success at 3 months.

AIM: To determine the predictive value of the 2 week post-selective laser trabeculoplasty (SLT) intraocular pressure (IOP) by comparing it to the 4 week and 3 month values. METHODS: A retrospective chart review of eyes that underwent SLT between 2001 and 2004 was performed. The primary outcome measure was IOP. Demographic and medical data were collected for correlational analysis. RESULTS: 132 eyes of 95 patients were identified, none was excluded. Of the eyes that exhibited a decrease in IOP of >1 mm Hg at 2 weeks postoperatively, 99.24% continued to show a lowered IOP at the 4 week and 3 month visits. For these patients, the Pearson's r value between 2 weeks and 4 weeks was 0.708 (p value = 0.01) while the r value between 2 weeks and 3 months was 0.513 (p value = 0.01). CONCLUSIONS: The 2 week visit post-SLT predicted the 4 week and 3 month visits if the 2 week visit demonstrated a decrease in IOP. These findings suggest that those patients who had a decreased IOP at 2 weeks and are at their goal IOP may not need to be screened until 3 months postoperatively.

Aged↗

PubMed2001

Gender, weight concerns, and adolescent smoking.

This study examined the beliefs that adolescents' hold regarding smoking and weight. In particular, this study examined the relationship between smoking status and self-perceptions of body weight. In addition, it examined gender and age differences in adolescent male and female smokers' beliefs about smoking and weight control. Analyses were conducted on the telephone interview responses of 1,200 adolescent smokers and nonsmokers between the ages of 12 and 17. Chi-square analyses were utilized for univariate comparisons, and logistic regression for multivariate comparisons. Results revealed gender and age differences in perceptions of body weight. In addition, female smokers were more likely than male smokers to adhere to the belief that smoking controlled weight. While no relationship was observed between males' perceived weight and their smoking status, females who perceived themselves to be either overweight or underweight were more likely to smoke. Findings suggest a gender bias in processing social/environmental cues linking smoking and weight control.

Adolescent↗

PubMed2000

Age-related differences in adolescent smokers' and nonsmokers' assessments of the relative addictiveness and health harmfulness of cigarettes, alcohol, and marijuana.

The present work was undertaken to determine how general beliefs about various substances and substance use behaviors change during adolescence. Secondary analyses were carried out on the telephone interview responses of 1,200 adolescent smokers and nonsmokers between the ages of 12 and 17. The specific beliefs regarding which substances were hardest to stop using and which were the most harmful to one's health by smoking status and age were compared using Chi-squared analyses for univariate comparisons, and polytomous logistic regression for multivariate analyses. Results revealed that the youngest cohort believed that marijuana was the substance most difficult to stop using while the oldest cohort believed that cigarettes were the hardest to stop using. A similar pattern was observed regarding which substance was the most harmful to one's health. While smokers believed that cigarettes were both the hardest to stop using and the most harmful, nonsmokers were divided between cigarettes and marijuana as the hardest to stop using, and indicated that marijuana, rather than cigarettes, were most harmful. Results are discussed in terms of their implications for substance abuse prevention and the development of relative risk assessments.

Adolescent↗

PubMed2000

The relationship between adolescent smoking and drinking and likelihood estimates of illicit drug use.

Using data from a recent national survey of adolescent substance use, the present work examined whether adolescents with different patterns of alcohol and cigarette use differed in their estimates of the likelihood they would use an illegal drug in the future. While nonusers of either substance were the most likely to indicate that they would never use drugs in the future, users of both substances were the most likely to indicate that they would use drugs. In addition, while users of both were most likely to indicate that they were likely to use illegal substances, only-smokers were more likely than only-drinkers to indicate that they were likely to use such substances in the future. Results are discussed in terms of the gateway theory of drug sequencing and cognitive precursors of experimentation with illegal substances.

Adolescent↗

PubMed1999

Euphorbia hirta leaf extracts increase urine output and electrolytes in rats.

Euphorbia hirta is locally used in Africa and Australia to treat numerous diseases, including hypertension and edema. The diuretic effect of the E. hirta leaf extracts were assessed in rats using acetazolamide and furosemide as standard diuretic drugs. The water and ethanol extracts (50 and 100 mg/kg) of the plant produced time-dependent increase in urine output. Electrolyte excretion was also significantly affected by the plant extracts. The water extract increased the urine excretion of Na+, K+ and HCO3-. In contrast, the ethanol extract increased the excretion of HCO3- decreased the loss of K+ and had little effect on renal removal of Na+. Acetazolamide, like the water extract, increased urine output and enhanced the excretion of Na+, K+ and HCO3-. The high-ceiling diuretic, furosemide, increased the renal excretion of Na+ and Cl-; but had no effect on K+ and HCO3- loss. This study suggests that the active component(s) in the water extract of E. hirta leaf had similar diuretic spectrum to that of acetazolamide. These results validate the traditional use of E. hirta as a diuretic agent by the Swahilis and Sukumas.

Acetazolamide↗

PubMed1999

The moderating effects of gender and ethnicity on the relationship between effect expectancies and alcohol problems.

OBJECTIVE: Research has demonstrated that alcohol outcome expectancies moderate the relationship between psychological states such as stress and negative affect and alcohol use. This study examined whether the relationship between expectancies and alcohol problems would be moderated by gender and ethnicity. METHOD: Using a household survey format, personal interviews were conducted with Puerto Rican and Irish American men and women. The final sample consisted of 412 (231 male) Puerto Ricans and 476 (252 male) Irish Americans. Alcohol expectancies were measured with the Effects of Drinking Alcohol Scale. All subjects resided in the New York metropolitan area. The original study was designed to compare the drinking behaviors and alcohol-related beliefs of groups with varied drinking practices and distinct drinking beliefs. RESULTS: Both gender and ethnicity moderated the links between aggressive and self-control expectancies and drinking problems. For example, anticipated loss of control from drinking was more negatively related to Puerto Rican and female alcohol problems than it was to Irish and male problems. CONCLUSIONS: The present findings suggest that whether an outcome expectancy is associated with more alcohol problems depends upon the particular meaning of the outcome. This meaning, in turn, depends upon an individual's particular sociocultural perspective which is associated with such personal characteristics as gender and ethnicity.

Adult↗

PubMed1999

Cultural and familial influences that maintain the negative meaning of alcohol.

OBJECTIVE: The purpose of this overview is to highlight the ways that cultural and familial factors may buffer children and adolescents from initiating alcohol use. METHOD: This article uses the findings from studies of black and Hispanic adolescent and adult alcohol use to identify potentially important cultural and familial variables that buffer these groups from early alcohol use and misuse, abuse or dependence. RESULTS: We begin with the notion that negative beliefs regarding alcohol and its effects protect young children from early alcohol involvement. We then consider how, for blacks and Hispanics, family structure, parent-child interaction patterns and value orientations function to maintain these negative belief schemas, thereby protecting children and adolescents from involvement with alcohol. CONCLUSIONS: We conclude by emphasizing the importance of studying "nonmainstream" groups who are more likely to abstain from alcohol use. In doing this, research can more easily identify those family practices that produce the negative beliefs about alcohol consumption and thereby prevent early experimentation and adolescent alcohol abuse.

Adolescent↗

PubMed1998

The relationship between ethnicity, gender and alcohol consumption: a strategy for testing competing models.

AIM: This study tested mediator, moderator and main effects models to determine the pattern of relationships between ethnicity, gender, temperament, and alcohol use. DESIGN: A large-scale survey was employed. Respondents were interviewed in their homes. Participants were 523 Puerto Rican and 490 Irish American adults residing in the New York metropolitan area. MEASURES: Quantity and frequency of alcohol consumption were assessed with standard measures, and recent drinking problems with the substance abuse module of the Composite International Diagnostic Instrument. FINDINGS: Rather than supporting a complex, nested model, the findings supported a main effects model and indicated that each of the three predictors was related to one or more drinking measure. While gender strongly influenced each drinking behavior, ethnicity only influenced frequency, and temperament only influenced recent drinking problems. CONCLUSIONS: The results support previous studies indicating consistent male-female drinking differences while highlighting a statistical strategy for comparing competing models of ethnic drinking behavior.

Adult↗

PubMed1998

Possible precursors of gender drinking differences.

This study explored the responses of sixth graders to a recently developed alcohol expectancy scale and a drinking attitude question. While factor analyses yielded the same "positive" and "negative" factors previously identified in scale construction, no significant gender differences were observed on scale items or factors. However, sixth grade males responded more favorably than their female counterparts to the general attitude item regarding alcohol consumption. Results also revealed that while male attitudes were related significantly to whether they reported observing adult intoxication in the home, female attitudes were not. Results are discussed in terms of their implication for the origins of initial male-female drinking behavior differences.

Adolescent↗

PubMed1997

Visual control of hand-reaching movement: activity in parietal area 7m.

The activity of single neurons was studied in parietal area 7m while monkeys performed an instructed-delay reaching task to visual targets under normal light conditions and in darkness. The task was aimed at assessing the influence of vision of hand position on the neural activity of 7m related either to static posture and movement of the hand or to eye position in the orbit. The results show the existence of preparatory, movement-related and postural activity for the control of reaching, all of which are strongly modulated by vision. The activity of many 7m neurons, otherwise insensitive to pure visual stimuli, seems to reflect complex interactions between gaze angle and hand position in the visual field.

Animals↗

PubMed1997

Premotor and parietal cortex: corticocortical connectivity and combinatorial computations.

The dorsal premotor cortex is a functionally distinct cortical field or group of fields in the primate frontal cortex. Anatomical studies have confirmed that most parietal input to the dorsal premotor cortex originates from the superior parietal lobule. However, these projections arise not only from the dorsal aspect of area 5, as has long been known, but also from newly defined areas of posterior parietal cortex, which are directly connected with the extrastriate visual cortex. Thus, the dorsal premotor cortex receives much more direct visual input than previously accepted. It appears that this fronto-parietal network functions as a visuomotor controller-one that makes computations based on proprioceptive, visual, gaze, attentional, and other information to produce an output that reflects the selection, preparation, and execution of movements.

Animals↗

PubMed1997

Combination of hand and gaze signals during reaching: activity in parietal area 7 m of the monkey.

The role of area 7 m has been studied by recording the activity of single neurons of monkeys trained to fixate and reach toward peripheral targets. The target was randomly selected from eight possible locations on a virtual circle, of radius 30 degrees visual angle from a central target. Three tasks were employed to dissociate hand- from eye-related contributions. In the first task, animals looked and reached to the peripheral target. In a second task, the animal reached to the peripheral target while maintaining fixation on the central target. In the third task, the monkey maintained fixation on peripheral targets that were spatially coincident with those of the reaching tasks. The results show that cell activity in area 7 m relates, for some cells to eye position, for others to hand position and movement, and for the majority of cells to a combination of visuomanual and oculomotor information. This area, therefore, seems to perform an early combination of information in the processing leading from target localization to movement generation.

Animals↗

PubMed1997

Alcohol-use-related problems in Puerto Rican and Irish-American males.

This study compared the alcohol-use-related problems of Puerto Rican and Irish-American men: groups sometimes considered at "high risk" for the development of such problems. It was found that Irish-American men had higher lifetime prevalence rates in the following areas: excessive intake, tolerance and/or dependence, physical or psychological problems associated with alcohol misuse, and social and/or occupational problems associated with alcohol misuse. Results are discussed in terms of Puerto Rican and Irish-American risk status and the importance of appropriate comparisons in studies focused on culture/ethnicity and alcohol consumption.

Adult↗

PubMed1996

Cortical networks for visual reaching: intrinsic frontal lobe connectivity.

The anatomical substrates of reaching to visual targets were studied in monkeys (Macaca nemestrina) by combining behavioural neurophysiology and neuroanatomy. An instructed-delay reaching task was used to characterize the arm-related regions of the dorsolateral frontal cortex. This task revealed gradients of signal-, set- movement- and position-related activity along the rostrocaudal extent of the frontal lobe. The frontal mesial projections to these physiologically defined gradients were studied through anatomical methods based on the retrograde transport of distinguishable tracers. The tangential distribution of the cells of origin of these projections displayed a gradient-like arrangement similar to that defined physiologically in their terminal territory. These mesial projections to the dorsolateral frontal cortex may therefore be considered part of a cortical network wherein connections make only a limited contribution to the integration of different sources of information for the control of reaching movements. Further combination of such information must occur within each given cortical region by intrinsic local connections.

Animals↗

PubMed1996

The self-generated alcohol expectancies of Puerto Rican drinkers and abstainers.

Using data from an epidemiological study of mainland Puerto Rican drinking, this work compares the self-generated alcohol expectancies of Puerto Rican drinkers and abstainers. While positive expectancies are more characteristic of drinkers, especially "heavy drinkers," negative expectancies are more characteristic of abstainers, especially lifetime abstainers. Results are discussed in terms of the cultural influences on alcohol expectancies and the positivity bias in alcohol expectancy research.

Adult↗

PubMed1995

GABA-immunopositive neurons in rat neocortex with contralateral projections to S-I.

The callosal projection is traditionally believed to be exclusively excitatory in function. A new method combining lectin-conjugated colloidal gold for retrograde tracing with immunofluorescence for GABA was used to investigate this question. The large majority of neurons retrogradely labeled after injections of tracer into contralateral S-I were GABA-negative cells in layers II-VI. However, GABA-positive neurons projecting to contralateral S-I were also seen. The majority of double-labeled cells were only weakly labeled with tracer; they were located both in superficial and deep cortical layers and represented at least 1% of all retrogradely labeled neurons. Neurons double-labeled for both tracer and GABA in upper layers were found mainly within the central patch of callosally projecting neurons, whereas those in deep layers were scattered throughout contralateral cortex.

Animals↗

PubMed1995

Analgesic effect of Irvingia gabonensis stem bark extract.

Irvingia gabonensis is used medicinally in most parts of tropical Africa for the treatment of a number of ailments. In West Africa the Mende tribe of Sierra Leone uses the stem bark to relieve pain. In order to establish a pharmacological rationale for the traditional use of this plant as a remedy for pain, the water and ethanol extracts of the powdered stem bark were screened for analgesic activity and compared with standard analgesic drugs. The water extract and morphine protected the mice from heat-induced pain. In contrast, the ethanol extract and metamizole sodium showed very low level of analgesic activity in this test. However, using tail pressure as a source of pain, the water and ethanol extracts, metamizole sodium and morphine offered protection to the mice against pain stimuli. Morphine and the water extract were more potent as analgesic agents in heat than non-heat pain test. The analgesic effects of the water extract and morphine were blocked by a non-selective opioid receptor antagonist, naloxone in both tests, whereas the analgesic effects of the ethanol extract and metamizole sodium were not antagonized by the same dose of the opioid antagonist. The data presented in this study suggest that the active principle(s) in the water extract has analgesic profile similar to that of the narcotic analgesic and the ethanol extract might contain compound(s) that behave like non-narcotic analgesic agent. These findings provide for the first time the pharmacological basis for the folkloric use of Irvingia gabonensis in the relief of pain.

Analgesics↗

PubMed1994

Negative affect, alcohol expectancies and alcohol-related problems.

Using data from the first epidemiological study of mainland Puerto Rican drinking, the authors explore the relationships between negative affect, alcohol expectancies and drinking problems. Results revealed that the co-occurrence of depressed mood and drinking problems was strongly moderated by alcohol expectancies. More specifically, the co-occurrence was strongest among those Puerto Ricans who most expected alcohol to elevate their mood. Findings are discussed in terms of their explication of the co-morbidity of depressive symptomatology and alcohol abuse.

Adolescent↗