A coherent pattern among social behavior, blood pressure, corticosterone and catecholamine measures in individual male rats

Behavioral and physiological responses of 18 chronically cannulated male TMD-S3 rats were assessed during various social interactions with conspecifics, both with and without the possibility for physical contact (social vs. psychosocial stimulation). Response magnitudes (behavior, blood pressure, plasma catecholamines) depend upon both the social environmental requirements (offense, defense, psychosocial stimulus following defense) and individual characteristics. The more competitive males generally reacted with higher responses of blood pressure and catecholamines than more passive rats. In addition, these competitive males had higher baseline levels of noradrenaline. The present experiment shows that male rats differ in the individual sympathetic tone and reactivity in relation to their behavior in a social environment.     

Early smoking initiation and associated factors among in-school male and female adolescents in seven African countries

Objective

This report examines the prevalence and common correlates of early smoking initiation among male and female school children across seven African countries.

Method

The total sample included 17,725 school children aged 13 to 15 years from nationally representative samples in seven African countries. Univariate and multivariate analyses were conducted to assess the relationship between early smoking initiation, health compromising behaviours, mental distress, protective factors and socio-economic status variables.

Results

Overall 15.5% had experienced smoking initiation before age 14, with the percentages 20.1% among boys and 10.9% among girls. In multivariable analysis, early smoking initiation was among boys associated with ever drunk from alcohol use (OR=4.73, p=0.001), ever used drugs (OR=2.36, p=0.04) and ever had sex (OR=1.63, p=0.04). Among girls, it was associated with higher education (OR=5.77, p=0.001), ever drunk from alcohol use (OR=4.76, p=0.002), parental or guardian tobacco use (OR=2.83, p=0.001) and suicide ideation (OR=2.05, p=0.02).

Conclusion

The study found a high prevalence of early smoking initiation among 13–15 year-olds in seven African countries. Various risk factors have been identified in boys and girls who initiate smoking before age 14, forming a distinct risk group in this setting. Specific interventions are needed for boys and girls in the preteen years, before smoking initiation.     

The relationship between health status and blood pressure in urban African Americans.

African Americans have higher rates of hypertension and poorer health status than their white counterparts. This study assessed the relationship between health status, cardiovascular risk factors, and measured blood pressure. Free blood pressure screenings were performed at businesses and organizations located in west Baltimore. All individuals with cardiovascular risk factors were offered health education. Also, participants with a measured blood pressure of > or = 140/90 mm Hg were referred for free medical treatment. Participants completed a questionnaire that included demographics, cardiovascular risk factors, the Medical Outcomes Study SF 36, and two tests on cholesterol and heart disease knowledge. A total of 1389 African-American men and women were screened; 20% were found to have high normal blood pressure and 31% had stage 1 hypertension or higher. Those with hypertension reported lower physical functioning and poorer general health than those without high blood pressure. When compared with US normative data, participants reported higher levels in vitality and physical and emotional role functioning, more bodily pain, and poorer general health, but they were similar in physical functioning, social functioning, and mental health. Preliminary data suggest that hypertension does have an effect on health function.     

Sleep and stressor exposure in relation to circadian rhythms in catecholamine excretion.

12 healthy male volunteers spent 64 h of continuous waking under strictly controlled environmental conditions (light, food, drink, activity) in isolation from the external world. Before and after the vigil the subjects slept in the laboratory. An additional group of five participated only during day time and spent the intervening night period asleep at home. Measurements were carried out in 3 h intervals except for sleep periods. Shortly before the circadian trough and peak of adrenaline excretion respectively, the subjects were exposed to a performance stressor. Results from the vigil showed a very pronounced circadian rhythm for adrenaline excretion but none for noradrenaline excretion. For adrenaline, night-time sleep reduced excretion levels, causing an even more pronounced circadian pattern. For noradrenaline, night-time sleep caused a drop in excretion giving the impression of a circadian rhythm. These and previous results led to the conclusion that the excretion of adrenaline exhibits a self-sustained rhythm while a rhythm in noradrenaline excretion is found only when caused by external synchronizers such as sleep-wake alternation. No difference in magnitude of stress response between peak and trough was observed for any of the catecholamines. Night-time (trough) exposure completely obliterated the circadian rhythm of adrenaline excretion for the duration of the exposure. It was concluded that the normal pronounced night-time trough of adrenaline cannot be due to unavailability of adrenaline in the medulla. With respect to sleep deprivation, no effect was found on excretion levels during waking, during sleep, or in response to the stressor as deprivation progressed. Finally, there was also found to be a close temporal covariation between adrenaline excretion and both rectal temperature and self-rated fatigue (neg.).     

Lactate and catecholamine responses in male and female sprinters during a Wingate test

A total of six male and six female sprinters at the same national competition level and aged 18–20 years performed a force/velocity test and a 30-s supramaximal exercise test (Wingate test) on 2 different days, separated by a maximal interval of 15 days. The maximal anaerobic power (W _max) was determined from the force/velocity test, and the mean anaerobic power (W) from the Wingate test. Immediately after the Wingate test, a 5-ml venous blood sample was drawn via a heparinized catheter in an antebrachial vein for subsequent catecholamine (adrenaline and noradrenaline) analysis. After 5 min recovery a few microlitres of capillary blood were also taken for an immediate lactate determination. Even expressed per kilogram lean body mass,W _max andW were significantly lower in women. The lactate and adrenaline responses induced by the Wingate test were also less pronounced in this group whereas the noradrenaline levels were not significantly different in men and women. Above all, very different relationships appeared between lactate, adrenaline, noradenaline and W according to sex. Thus, as reported by other authors, the adrenergic response to a supramaximal exercise seemed to be lower in women than in men. Nevertheless a different training status between the two groups, even at same national competition level, could not be excluded and might contribute, at least in part, to the gender differences observed in the present study.     

Attitudes toward using condoms and condom use: difference between sexually abused and nonabused African American female adolescents

Rates of many sexually transmitted diseases remain higher among adolescents than among any other age group. The associations between abuse experiences and risky sexual behaviors suggest that exploring the relationships between adolescents' abuse history and condom use beliefs and behaviors is warranted. Females (N = 725) attending an adolescent clinic reported demographic characteristics, beliefs about condom use, sexual behaviors, and sexual abuse or molestation history. Those reporting sexual abuse or molestation (23%) were more likely to think condoms interfered with sexual pleasure and less likely to think condoms were important to partners. They also reported more unprotected vaginal sex and more lifetime sex partners. Beliefs were correlated with condom use consistency, number of lifetime partners, and number of unprotected sex experiences. The greater levels of behavioral risk among those reporting abuse suggest greater risk for acquisition and transmission in abused female adolescents. The authors discuss hypotheses to inform future research and intervention.     

Central catecholamine depletion, vasopressin, and blood pressure in the DOCA/NaCl rat

To determine whether impaired arginine vasopressin (AVP) release occurs when DOCA-NaCl hypertension is prevented following chemical sympathectomy with 6-hydroxydopamine (6-OHDA), male Sprague-Dawley rats treated with intraventricular injections of 6-OHDA (250 micrograms X 2) or Merlis solution received deoxycorticosterone acetate (DOCA) implants (100 mg/kg) and drank 0.5% saline. Systolic blood pressure in the 6-OHDA-treated DOCA/NaCl group (139 +/- 4 mmHg) was lower (P less than 0.001) than in the Merlis-DOCA/NaCl group (183 +/- 7 mmHg). 6-OHDA treatment produced widespread catecholamine depletion throughout the central nervous system, including the supraoptic and paraventricular nuclei, the cells of which are known to produce AVP, but hypothalamic, pituitary, and plasma AVP levels were similar in both experimental groups, the latter values averaging 1.5-2 times those of controls. Both groups of rats suppressed AVP secretion appropriately when water loaded. Such suppression, however, had no effect on blood pressure in the hypertensive animals and, furthermore, administration of the AVP antagonist d(CH2)5Tyr(Me)AVP produced small decrements in mean blood pressure of both groups that were not significantly different from responses seen in control normotensive rats. These data demonstrate that 6-OHDA does not prevent DOCA-NaCl hypertension by decreasing AVP levels and suggest that AVP is not necessary for the maintenance of hypertension in this model.     

Relationship of blood pressure status,dietary factors and serum electrolytes of in-school adolescents in Ilishan-Remo,Ogun State,Nigeria

BackgroundGlobally, rising blood pressure is of public health concern as it is a major cause of cardiovascular diseases (CVDs), and preventable death. This study accessed the relationship of blood pressure status, dietary factors and serum electrolytes among in-school adolescents in Ilishan-Remo, Ogun State, Nigeria.MethodsA cross-sectional survey of 488 secondary school students (aged 10–19 years). Blood pressures were assessed using auscultatory method and questionnaires were used to obtain food frequency and 24-hour dietary recall data. Blood samples from volunteers were used for serum sodium and potassium assays.ResultsThe mean systolic blood pressure (SBP) increased with age, irrespective of gender. The prevalence of elevated blood pressure and hypertension among participants were 19.3% and 10.5%, respectively, with males and females having similar pattern. Dietary factors like addition of table salt to already prepared foods, higher intake of eggs, and lower intake of vegetables were associated with the development of elevated blood pressure among the adolescents. The estimated mean dietary intakes (mg/person/day) of sodium and potassium were 2289±938.7 and 1321±603.8, respectively, with majority consuming far higher (for sodium – 80%) or far below (for potassium – 95%) recommendations. The mean serum sodium (138.0±18.3 mmolL^-1) and potassium (3.06±1.1 mmolL^-1) were similar across genders. A significant (p<0.05) negative relationship exists between serum potassium and SBP.ConclusionsThe blood pressure status of the adolescents studied are of great concern and are somewhat negatively influenced by poor dietary and lifestyle practices. They require prompt intervention to slow down the development of CVDs in the future.     

Changes in blood pressure,heart rate and blood constituents during heat exposure in men with elevated blood pressure

Summary Although the vascular volume response of hypertensive men during exercise has been rather well characterized, the effect of resting heat exposure in this patient population has not been examined. This was done in the present report in seven men with high blood pressure (BP) (i. e., diastolic pressure>12 kPa (90 mmHg) upon initial interview) and 5 normotensive control subjects. 50 min after each subject had consumed an amount of water equal to 1% of his body weight, he reclined on a cot. 10 min later the subject was carried into an environmental chamber equilibrated at Tdb=45 C, Twb=28 C. Free-flowing venous blood samples were obtained from a cubital vein, and BP and heart rate were measured, before the heat exposure and at 15 min intervals during the experiment. Within 30 min systolic, diastolic and mean BP of the high BP subjects had decreased to normal levels; no BP changes were detected in normotensive subjects. Accompanying this depressor response was an exaggerated elevation in plasma glucose concentration. No alterations were found with haematocrit, plasma osmolality or electrolytes, or total protein and albumin. The data suggest that heat exposure may have been more stressful for the subjects with high BP than for their controls. This finding implies that phasic depressor responses may be as important as phasic pressor episodes in the aetiology of established essential hypertension.Training Grant HL07050 from the National Institutes of Health supported this project     

Longitudinal association of sleep-disordered breathing and nondipping of nocturnal blood pressure in the Wisconsin Sleep Cohort Study

STUDY OBJECTIVES: The association of sleep-disordered breathing (SDB) and blunting of normal nocturnal lowering of blood pressure (BP) (nondipping) has only been examined cross-sectionally. The purpose of this study is to investigate whether SDB is prospectively associated with nondipping. METHODS: The longitudinal association between SDB and incident nondipping was examined in a subsample of 328 adults enrolled in the Wisconsin Sleep Cohort Study who completed 2 or more 24-hour ambulatory BP studies over an average of 7.2 years of follow-up. SDB identified by baseline in-laboratory polysomnography was defined by apnea-hypopnea index (AHI) categories. Systolic and diastolic nondipping was defined by systolic and diastolic sleep-wake BP ratios > 0.9. All models were adjusted for age, sex, body mass index at baseline and follow-up, smoking, alcohol consumption, hypertension, sleep time, length of follow-up time, and antihypertensive medication use. RESULTS: There was a dose-response increased odds of developing systolic nondipping in participants with SDB. The adjusted odds ratios (95% confidence interval) of incident systolic nondipping for baseline AHI 5 to < 15 and AHI > or = 15, versus AHI < 5, were 3.1 (1.3-7.7) and 4.4 (1.2-16.3), respectively (P trend = 0.006). The adjusted odds ratios (95% confidence interval) of incident diastolic nondipping for corresponding SDB categories were not statistically significant: 2.0 (0.8-5.6) and 1.3 (0.2-7.1). CONCLUSIONS: Our longitudinal findings of a dose-response increase in development of systolic nondipping of BP with severity of SDB at baseline in a population-based sample provide evidence consistent with a causal link. Nocturnal systolic nondipping may be a mechanism by which SDB contributes to increased cardiovascular disease.     

Risky and Protective Contexts and Exposure to Violence in Urban African American Young Adolescents

Contexts of risk for and protection from exposure to violence were identified and the relation of exposure to violence to delinquent behaviors and symptoms of trauma was examined. Using the Experience Sampling Method (ESM), the immediate daily experience of risky and protective contexts was examined. One hundred sixty-seven African American 6th-, 7th-, and 8th-grade children from urban neighborhoods carried watches and booklets for 1 week. Structural equation modeling supported the hypotheses that more time in risky contexts and less time in protective contexts was related to more exposure to violence. Exposure to violence partially mediated the relation of time in protective and risky contexts to delinquent behaviors, assessed with the Juvenile Delinquency Scale and the Child Behavior Checklist, and distress levels, assessed by a posttraumatic stress disorder (PTSD) score.     

Physiological correlates of peer victimization and aggression in African American urban adolescents

This study examined physiological correlates (cortisol and α-amylase [AA]) of peer victimization and aggression in a sample of 228 adolescents (45% male, 55% female; 90% African American; M age = 14 years, SD = 1.6 years) who participated in a longitudinal study of stress, physiology, and adjustment. Adolescents were classified into victimization/aggression groups based on patterns with three waves of data. At Wave 3, youth completed the Social Competence Interview (SCI), and four saliva samples were collected prior to, during, and following the SCI. Repeated-measures analyses of variance with victimization/aggression group as the predictor, and physiological measures as outcomes, controlling for time of day, pubertal status, and medication use revealed significant Group × SCI Phase interactions for salivary AA (sAA), but not for cortisol. The results did not differ by sex. For analyses with physical victimization/aggression, aggressive and nonaggressive victims showed increases in sAA during the SCI, nonvictimized aggressors showed a decrease, and the normative contrast group did not show any change. For analyses with relational victimization/aggression, nonaggressive victims were the only group who demonstrated sAA reactivity. Incorporating physiological measures into peer victimization studies may give researchers and clinicians insight into youth's behavior regulation, and help shape prevention or intervention efforts.     

Prenatal glucocorticoid exposure alters hypothalamic–pituitary–adrenal function and blood pressure in mature male guinea pigs

Pregnant guinea pigs were treated with dexamethasone (1 mg kg⁻¹) or vehicle on days 40–41, 50–51 and 60–61 of gestation, after which animals delivered normally. Adult male offspring were catheterized at 145 days of age and subjected to tests of hypothalamic–pituitary–adrenal (HPA) axis function in basal and activated states. Animals exposed to dexamethasone in utero (mat-dex) exhibited increased hippocampus-to-brain weight ratio, increased adrenal-to-body weight ratio and increased mean arterial pressure. There were no effects on gestation length, birth weight and postnatal growth. There were no overall differences in diurnal plasma adrenocorticotropic hormone (ACTH) and cortisol profiles, though there were subtle differences during the subjective afternoon between control and mat-dex offspring. A significant decrease in initial ACTH suppression was observed following dexamethasone injection in mat-dex offspring compared to control offspring. Molecular analysis revealed significantly increased MR mRNA expression in the limbic system and particularly in the dentate gyrus in mat-dex offspring. In the anterior pituitary, both pro-opiomelanocortin (POMC) and glucocorticoid receptor (GR) mRNA levels were significantly elevated in mat-dex offspring. In conclusion, (1) repeated prenatal treatment with synthetic glucocorticoid (sGC) permanently programmes organ growth, blood pressure and HPA regulation in mature male offspring and these changes involve modification of corticosteroid receptor expression in the brain and pituitary; (2) the effects of prenatal sGC exposure on HPA function appear to change as a function of age, indicating the importance of investigating HPA and cardiovascular outcome at multiple time points throughout life.     

Plasma catecholamine and blood pressure responses to sympathetic stimulation in pithed rats.

Sympathetic stimulation in pithed rats elicits increases in blood pressure (BP) and plasma levels of catecholamines. The BP is proportional to the logarithm of the plasma norepinephrine (NE) concentration. Adrenal medullectomy diminishes slightly only the initial phase of the BP responses, whereas bretylium blocks completely the BP response and diminishes by about 70% the increase in plasma NE. Adrenal medullectomy completely prevents the increase in plasma epinephrine (Epi) and diminishes by 30% plasma NE. Plasma levels of NE appear to reflect sympathetic neuronal activity, but the NE at sympathetic nerve endings is responsible for the increase in BP. Epi released from the adrenal medulla may enhance and accelerate the initial BP response, but plays only a minor role after the first 15 s.     

Anger expression,body fat,and blood pressure in adolescents: Project HeartBeat!

This study explores the potential influence of growth, body/composition, and sexual maturity on the relation of anger expression and blood pressure in adolescents. Baseline data from Project HeartBeat! (82 boys and 85 girls, 14 years of age) examined the ability of anger expression (STAXI scale) to predict blood pressure, after controlling for the effects of ethnicity (African‐American/non‐African‐American), height, weight, percentage body fat, and sexual maturity. Blood pressures were unrelated to anger expression in models that included the above developmental variables. However, girls scoring high on healthy anger expression (“anger‐control”) had significantly lower levels of percentage body fat (P = 0.015) independent of the above factors. The literature suggests that body fat or body mass is often, though not unanimously, associated with unhealthy forms of anger expression in adolescents. Research is required into the biological, social, and behavioral origins of the association between body fat and anger expression. Height and sexual maturity, virtually ignored in this literature, should be included in future research. Am. J. Hum. Biol. 13:531–538, 2001. © 2001 Wiley‐Liss, Inc.     

Prenatal morphine exposure differentially alters learning and memory in male and female rats

The present study tested the hypothesis that exposure to morphine on prenatal days 11-18 impairs performance on tasks requiring learning and memory in adult male and female rats. In Experiment 1, a symmetrical maze was used to measure learning. In Experiment 2, an eight-arm radial maze was used to assess working spatial memory. The results of Experiment 1 demonstrated that prenatal morphine exposure reduces the time needed to complete the trials, but does not affect the accuracy of performance in male rats. In contrast, prenatal drug treatment had no effects on either the time or the accuracy of performance in female rats. In Experiment 2, both male and female morphine-exposed rats needed more time to complete regular trials (no delay) than controls; however, morphine exposure in male rats did not affect performance on tasks requiring memory, measured with delay trials, but hindered it in ovariohysterectomized (OVX) female rats. In OVX females, replacement injections of both estrogen and progesterone restored the impairment of performance on delay trials produced by prenatal morphine exposure. Thus, the present study demonstrates that prenatal morphine exposure differentially alters performance of adult male and female rats on tasks requiring learning and spatial memory.