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Biomedical subjects

R G Jacob

Publications and source records attributed to R G Jacob.

At least 37 records · Page 2Linked to original sources
PubMed1991

Effects of dose, gender, and level of physical activity on acute metabolic response to nicotine.

The acute thermogenic effect of nicotine was examined in cigarette smokers under conditions of rest and two levels of low-intensity physical activity comparable to that normally engaged in by sedentary adults. Male and female smokers (n = 10 each) each received 0 (placebo), 7.5, 15, or 30 micrograms/kg nicotine via measured-dose nasal spray once every 30 min for 90 min, with each dose presented on a separate occasion. After each dose presentation, subjects engaged in 10 min of rest or low-intensity activity at 30 or 60 watts (W) using a bicycle ergometer. For males, results indicated that expenditure attributable to nicotine was more than twice as large during 60-W activity compared with rest, while that during 30-W activity was intermediate. For females, expenditure attributable to nicotine was generally similar to that of males during rest and 30-W activity but was significantly lower during 60-W activity, indicating an apparent "inverted-U" relationship with activity intensity. The enhanced effect of nicotine was specific to energy expenditure, since heart rate showed dose-dependent changes that were generally similar regardless of activity level. These findings confirm a mediating influence of physical activity level on the acute metabolic effect of nicotine, especially in males, and may have implications for explaining individual differences in body weight changes due to tobacco smoking and cessation.

Adult↗
PubMed1991

Social phobia: Axis I and II correlates.

The presence of Axis I and Axis II disorders in 71 social phobic patients was examined. Generalized anxiety disorder was the most common secondary Axis I disorder, followed by simple phobia. Avoidant personality disorder and obsessive-compulsive personality disorder were the most common Axis II diagnoses, and 88% of the sample exhibited features of these 2 personality styles. Subjects with additional Axis I diagnoses were more anxious and depressed than those with no additional Axis I disorder. Social phobics with additional Axis II disorders were more depressed but not more anxious than those with no Axis II diagnosis. Furthermore, those with an additional Axis I disorder had higher scores on measures of neuroticism, interpersonal sensitivity, and agoraphobia. The prevalence and impact of additional Axis I and II disorders on the etiology, maintenance, and treatment outcome for persons with social phobia are discussed.

Adult↗
PubMed1991

Neither awake nor sleep blood pressures better predict target-organ effect.

We sought to assess the strengths of commonly used ambulatory blood pressure (ABP) parameters as predictors of transmitral flow/velocity ratio (E/A) and the dimensions that govern the left ventricular (LV) mass index. ABP, E/A, and LV dimensions were assessed in 47 subjects, with inclusion of 45 in the final data analysis. The results of four weekly (96 h total) ABP studies were averaged for each subject. No single ABP parameter immerged as a "best predictor." Furthermore, casual blood pressures taken at the beginning of the echo examination had predictive strength for LV mass which was similar to that of the ambulatory data. In the present study, neither awake nor sleep ABPs differed significantly with respect to correlations with indices of LV structure.

Adult↗
PubMed1990

Behavioral performance effects of nicotine in smokers and nonsmokers.

Performance on finger-tapping and handsteadiness, tasks opposite in response requirements, was compared between male smokers and nonsmokers (n = 10 each) on two occasions, once following intake of nicotine (15 micrograms/kg) by measured-dose nasal spray and once following placebo. Compared with nonsmokers, smokers had significantly greater increase in finger-tapping speed due to nicotine. On the other hand, smokers tended to have improved performance on handsteadiness (i.e., less involuntary movement) due to nicotine, while nonsmokers had impaired performance, although this difference was not significant. Nicotine-induced changes in performance on each task were inversely related, suggesting specificity of the behavioral effects of nicotine depending on task demands, rather than a generalized effect. These effects of nicotine on behavioral performance may be important in understanding the reinforcing value of nicotine intake, and differences in effects as a function of smoking history may suggest chronic adaptation to nicotine.

Adult↗
PubMed1990

Perception and hedonics of sweet and fat taste in smokers and nonsmokers following nicotine intake.

Nicotine's effects on reducing perception and/or hedonics of sweet and fat taste may lead to less intake of sweet tasting, high-fat foods by smokers, helping to explain their generally lower body weights. Smokers and nonsmokers (n = 10 males each) rated perception (intensity and sensitivity) and hedonics (liking) of sweet/fat taste in milk samples varying both in sucrose (0, 5, 10, 20% w/w) and fat (0.1, 3.5, 11.7, 37.6% w/w) concentration on two occasions, once following intermittent presentation of nicotine (15 micrograms/kg) via measured dose nasal spray and the other following placebo. Nicotine significantly reduced perceived intensity of fat but not sweet taste and had no effect on sensitivity to either taste. There was no effect of nicotine on hedonics of sweet/fat taste. On the other hand, although there were no differences between smokers and nonsmokers in perception of sweet or fat, hedonics of sweet/fat taste was reduced in smokers regardless of nicotine or placebo intake. Thus, nicotine may acutely decrease fat taste perception without influencing sweet/fat hedonics, while long-term exposure (i.e., being a smoker) may produce chronically decreased taste hedonics without altering perception.

Adolescent↗
PubMed1990

Metabolic effects of nicotine after consumption of a meal in smokers and nonsmokers.

The thermogenic effect of nicotine intake after calorie consumption was investigated to determine if nicotine influences metabolic response to a calorie challenge. Smokers and nonsmokers (10 males in each group), matched for body weight, age, and physical fitness, each participated in four sessions that involved consuming a liquid calorie load (4.77 kcal/kg body wt) or water, followed by nicotine (15 micrograms/kg body wt) or placebo via nasal spray every 20 min for 2 h. Energy expenditure was significantly increased above baseline resting metabolic rate (RMR) over the 2 h by nicotine alone (6.5% of RMR, p less than 0.01). However, the combined effect of nicotine after calorie load (20.1% of RMR, p less than 0.001) was not significantly greater than the effect of calorie load alone (18.4% of RMR, p less than 0.001). Smokers and nonsmokers did not differ in baseline RMR or in response to nicotine or calorie load. These results confirm the thermogenic effect of nicotine but suggest that the effect of nicotine after calorie consumption is less than additive.

Administration, Intranasal↗
PubMed1990

Cardiovascular effects of nicotine during physical activity and following meal consumption.

1. In two separate studies using healthy male smokers as subjects, the acute cardiovascular effects of a measured dose of nicotine (15 micrograms/kg) were examined in conjunction with light physical activity and following consumption of a meal, conditions typical of nicotine intake via smoking. 2. Increases in heart rate and systolic blood pressure attributable to nicotine were similar during rest, physical activity, and following eating, demonstrating additivity with the cardiovascular effects of activity and a caloric load. Diastolic blood pressure was less affected by nicotine. 3. These results indicate that cardiovascular activity is acutely increased following nicotine (smoking) regardless of other influences on the cardiovascular system. Such effects may help explain increased risks of acute cardiac abnormalities due to smoking.

Adolescent↗
PubMed1989

The effect of nicotine on energy expenditure during light physical activity.

The metabolic effects of nicotine have been implicated in the relation between smoking and lower body weight. This study examined whether the nicotine-induced increase in the metabolic rate observed at rest is also present during physical activity. We compared the energy expenditure of 10 male smokers receiving nicotine (15 micrograms per kilogram of body weight) with that of 10 male smokers receiving placebo on two occasions, each including a period of rest and a period of exercise on a modified bicycle ergometer at workloads designed to simulate and standardize light daily activity. All had abstained from cigarette smoking the night before the study. The excess energy expenditure attributable to nicotine was more than twice as great during exercise (difference between groups, 0.51 kJ per kilogram per hour, or 12.1 percent of the metabolic rate at rest; P less than 0.001) than during rest (0.23 kJ per kilogram per hour, or 5.3 percent of the metabolic rate at rest; P less than 0.05). In contrast, the expenditure was not affected by placebo during exercise or rest in the smokers or in a comparison group of 10 non-smokers, indicating that smoking status has no long-term metabolic effect in the absence of short-term nicotine intake. We conclude that the relatively small metabolic effect of nicotine when the subject is at rest is enhanced during light exercise. Our data also suggest that the weight gain that often follows smoking cessation may be influenced not only by nicotine intake but also by the level of physical activity a smoker typically engages in while smoking.

Adult↗
PubMed1989

Chronic and acute tolerance to the heart rate effects of nicotine.

Tolerance to the effects of nicotine reflects physiological adaptation and may be related to the development and persistence of smoking behavior. However, little is known about tolerance to nicotine in humans, in part due to methodological difficulties. This study examined chronic and acute tolerance to nicotine's effect on heart rate (HR) using a measured-dose nasal spray nicotine procedure. Eight "Light" smokers (less than 20 cigarettes per day) and ten "Heavy" smokers (greater than or equal to 20 per day) participated in two sessions on separate days in which they received four administrations (1 every 20 min) of a high nicotine dose (15 micrograms per kg body weight, equivalent to a typical cigarette) or a low nicotine dose (7.5 micrograms/kg) while HR was monitored during the 5 min following each administration. Compared with Light smokers, Heavy smokers had significantly smaller HR responses to the high dose, indicating greater chronic tolerance, but there was no difference between groups in response to the low dose. Acute tolerance to HR response across the four 5-min periods was not observed with either dose. However, subsequent examination of HR response in the first 2 min following each dose administration did suggest acute tolerance, particularly for the low dose, as this more acute HR response declined from the first to the last administration. These results demonstrate chronic and, to a lesser extent, acute tolerance to HR effects of nicotine and suggest that both may be dose dependent.

Adult↗
PubMed1989

The Social Phobia and Anxiety Inventory: concurrent validity with a clinic sample.

The Social Phobia and Anxiety Inventory (SPAI) is an empirically derived self-report inventory developed as a specific measure of social phobia. The current investigation included two studies. The first examined the correlation of the SPAI with daily social behavior of a clinic sample of social phobics. The results indicated that the SPAI provides a reasonable indication of the distress experienced during daily social encounters in three dimensions: behavior, cognitions, and overall distress. The second study examined the validity of the SPAI with reference to the somatic response and avoidance behavior of social phobics. The results indicated that the somatic items of the SPAI are related to the somatic response of social phobics and that performance on the SPAI is associated with avoidance behavior in an anxiety-producing task.

Adult↗
PubMed1989

Comment on Holloway and McNally's (1987) "Effects of Anxiety Sensitivity on the Response to Hyperventilation".

Holloway and McNally (1987) found that normals with high scores on the Anxiety Sensitivity Index (ASI), an instrument developed to assess beliefs regarding the adverse consequences of anxiety, reported more anxiety and more frequent and intense somatic sensations following hyperventilation than did normals with low scores on the ASI. They concluded that this result provides support for the construct validity of the ASI and thus for the construct of anxiety sensitivity. Nevertheless, we argue that (a) the developers of the ASI have conflated beliefs regarding the adverse consequences of anxiety with fear of these consequences, (b) the accumulated evidence for the construct validity of the ASI is weak, and (c) Holloway and McNally's design and analyses do not permit them to exclude the more parsimonious explanation that trait anxiety accounts for their findings. Implications for research on anxiety sensitivity are discussed.

Anxiety↗
PubMed1989

Acute effects of nicotine on resting metabolic rate in cigarette smokers.

The acute effects of nicotine on resting metabolic rate (RMR) were examined to identify a mechanism that may help explain the inverse association between smoking and body weight. Multiple administrations of two nicotine doses (moderate [15 micrograms/kg body wt] and low [7.5 micrograms/kg body wt]) and a placebo (0 micrograms) were presented to 18 male smokers via nasal-spray solution on three separate occasions while RMR was assessed by computerized open-circuit indirect calorimetry. Plasma nicotine levels confirmed the reliability of dosing. RMR increases of 6% above base line after both moderate and low doses were significantly greater than the 3% increase after the placebo. Subsequent examination of the effects of smoking a nonnicotine cigarette suggested that the small placebo effect was due to acute metabolic consequences of inhalation. These results confirm that intake of nicotine, isolated from tobacco smoke, significantly increases RMR in humans. However, the results also indicate that non-pharmacological, behavioral aspects of smoking may also contribute to acutely increasing RMR in smokers.

Adolescent↗
PubMed1988

The statistical analysis of treatment effects in 24-hour ambulatory blood pressure recordings.

This paper presents a statistical analysis of treatment effects in 24-hour ambulatory blood pressure recordings. The statistical models account for circadian rhythms, subject effects, and the effects of treatment with drugs or relaxation therapy. In view of the heterogeneity of the subjects, we fit a separate linear model to the data of each subject, use robust statistical procedures to estimate the parameters of the linear models, and trim the data on a subject by subject basis. We use a meta-analytical method to combine the results of all subjects in the study.

Activity Cycles↗
PubMed1988

Panic disorder and the vestibular system.

This article reviews the interrelationship between panic disorder and vestibular function. There is a possibility of both somatopsychic and psychosomatic interactions between panic and the vestibular system. Another possibility is that vestibular dysfunction could be associated with certain mental disorders, including panic disorder, as a nonspecific marker. Somatopsychic interactions are suggested by findings of high prevalence of vestibular dysfunction in selected patients with panic disorder, by the occurrence of "space and motion phobia" in patients with panic disorder, and by the report of anxiety and pseudoagoraphobia in some patients with a primary complaint of vertigo. Psychosomatic influences include symptoms of dizziness and increased sensitivity of the vestibular system due to anxiety or hyperventilation. Vestibular dysfunction as a nonspecific marker is discussed in the context of a review of studies of the vestibular system in schizophrenia. Before more definite conclusions can be drawn whether panic disorder is related to vestibular dysfunction in some cases, further research is needed to establish the specificity of vestibular dysfunction for panic disorder.

Agoraphobia↗
PubMed1986

Relaxation therapy for hypertension. Comparison of effects with concomitant placebo, diuretic, and beta-blocker.

We compared the effects of relaxation therapy in hypertensive patients taking placebo, a beta-blocker (atenolol, 100 mg/d), or a diuretic (chlorthalidone, 50 mg/d), and we also compared the effects of relaxation therapy with the effects of the latter two drugs alone. Blood pressures were measured not only in the relaxation therapists' office and at a hypertension clinic, but also in the patient's environment by means of 24-hour ambulatory blood pressure recordings. The effect of relaxation therapy, while statistically significant, was modest. There was no generalization of effect to ambulatory blood pressure. Atenolol was significantly more effective than relaxation in reducing both systolic and diastolic pressure. Chlorthalidone was significantly more effective than relaxation in reducing systolic but not diastolic pressure in the hypertension clinic only. The long-term effects of relaxation were independent of concomitant drug use, but within the actual relaxation sessions blood pressure dropped further during chlorthalidone than during placebo or atenolol treatment.

Adrenergic beta-Antagonists↗