Prospective Evaluation of Genetic Variation in Platelet Endothelial Aggregation Receptor 1 Reveals Aspirin-Dependent Effects on Platelet Aggregation Pathways.

Genetic variation in the platelet endothelial aggregation receptor 1 (PEAR1) gene, most notably rs12041331, is implicated in altered on-aspirin platelet aggregation and increased cardiovascular event risk. We prospectively tested the effects of aspirin administration at commonly prescribed doses (81, 162, and 324 mg/day) on agonist-induced platelet aggregation by rs12041331 genotype in 67 healthy individuals. Prior to aspirin administration, rs12041331 minor allele carriers had significantly reduced adenosine diphosphate (ADP)-induced platelet aggregation compared with noncarriers (P = 0.03) but was not associated with other platelet pathways. In contrast, rs12041331 was significantly associated with on-aspirin platelet aggregation when collagen and epinephrine were used to stimulate platelet aggregation (P < 0.05 for all associations), but not ADP. The influence of PEAR1 rs12041331 on platelet aggregation is pathway-specific and is altered by aspirin at therapeutic doses, but not in a dose-dependent manner. Additional studies are needed to determine the impact of PEAR1 on cardiovascular events in aspirin-treated patients.

Wearing a Wetsuit Alters Upper Extremity Motion during Simulated Surfboard Paddling.

Surfers often wear wetsuits while paddling in the ocean. This neoprene covering may be beneficial to upper extremity movement by helping to improve proprioceptive acuity, or it may be detrimental by providing increased resistance. The purpose of this study was to evaluate the effects of wearing a wetsuit on muscle activation, upper extremity motion, heart rate, and oxygen consumption during simulated surfboard paddling in the laboratory. Twelve male, recreational surfers performed two paddling trials at a constant workload on a swim bench ergometer both with and without a wetsuit. Kinematic data and EMG were acquired from the right arm via motion capture, and oxygen consumption and heart rate were recorded with a metabolic cart and heart rate monitor. Wearing a wetsuit had no significant effect on oxygen consumption or heart rate. A significant increase in EMG activation was observed for the middle deltoid but not for any of the other shoulder muscle evaluated. Finally, approximate entropy and estimates of the maximum Lyapunov exponent increased significantly for vertical trajectory of the right wrist (i.e. stroke height) when a wetsuit was worn. These results suggest that a 2mm wetsuit has little effect on the energy cost of paddling at lower workloads but does affect arm motion. These changes may be the result of enhanced proprioceptive acuity due to mechanical compression from the wetsuit.

Impact of porcine maternal aerobic exercise training during pregnancy on endothelial cell function of offspring at birth.

The purpose of this investigation was to test the hypothesis that maternal exercise training during pregnancy enhances endothelial function in offspring at birth. Six-month-old gilts (n = 8) were artificially inseminated and randomized into exercise-trained (n = 4) and sedentary groups (n = 4). Exercise training consisted of 15 weeks of treadmill exercise. The thoracic aorta of offspring were harvested within 48 h after birth and vascular responsiveness to cumulative doses of endothelium-dependent (bradykinin: 10-11-10-6 M) and independent (sodium nitroprusside: 10-10-10-4 M) vasodilators were assessed using in vitro wire myography. Female offspring from the exercised-trained gilts had a significantly greater endothelium-dependent relaxation response in the thoracic aorta when compared with the male offspring and female offspring from the sedentary gilts. The results of this investigation demonstrate for the first time that maternal exercise during pregnancy produces an enhanced endothelium-dependent vasorelaxation response in the thoracic aortas of female offspring at birth.

Effects of exercise on endothelium and endothelium/smooth muscle cross talk: role of exercise-induced hemodynamics.

Physical activity, exercise training, and fitness are associated with decreased cardiovascular risk. In the context that a risk factor "gap" exists in the explanation for the beneficial effects of exercise on cardiovascular disease, it has recently been proposed that exercise generates hemodynamic stimuli which exert direct effects on the vasculature that are antiatherogenic. In this review we briefly introduce some of the in vitro and in vivo evidence relating exercise hemodynamic modulation and vascular adaptation. In vitro data clearly demonstrate the importance of shear stress as a potential mechanism underlying vascular adaptations associated with exercise. Supporting this is in vivo human data demonstrating that exercise-mediated shear stress induces localized impacts on arterial function and diameter. Emerging evidence suggests that exercise-related changes in hemodynamic stimuli other than shear stress may also be associated with arterial remodeling. Taken together, in vitro and in vivo data strongly imply that hemodynamic influences combine to orchestrate a response to exercise and training that regulates wall stress and peripheral vascular resistance and contributes to the antiatherogenic impacts of physical activity, fitness, and training.

Effects of chronic nitric oxide synthase inhibition on endothelium-dependent and -independent relaxation in arteries that perfuse skeletal muscle of swine.

The purpose of this investigation was to test the hypothesis that chronic N(G)-nitro-l-arginine methyl ester (l-NAME) treatment produces differential effects on conduit artery and resistance arteriole relaxation responses to endothelium-dependent and -independent vasodilators in arteries that perfuse skeletal muscle of swine. To test this hypothesis, conduit skeletal muscle arteries and second-order skeletal muscle (2A) arterioles were harvested from 14 Yucatan swine that were chronically administered l-NAME and from 16 controls. In vitro assessments of vasorelaxation to increasing doses of acetylcholine (ACH), bradykinin (BK), and sodium nitroprusside (SNP) were performed in both conduit and 2A arterioles. l-NAME treatment produced a significant reduction in both BK and ACH relaxation responses in the conduit arteries. In contrast, the relaxation response and/or sensitivity to SNP were significantly greater in the intact, but not denuded, conduit arterial rings from chronically l-NAME-treated swine. There were no significant effects of chronic l-NAME treatment on vasodilation of skeletal muscle arterioles. These findings suggest (1) that unlike arterioles, skeletal muscle conduit arteries do not functionally compensate for a lack of NO through the upregulation of alternative vasodilator pathways; (2) that the greater relaxation response in conduit arteries of chronically l-NAME-treated swine to SNP can be explained by alterations to the endothelium.

Effects of posture on shear rates in human brachial and superficial femoral arteries.

Shear rate is significantly lower in the superficial femoral compared with the brachial artery in the supine posture. The relative shear rates in these arteries of subjects in the upright posture (seated and/or standing) are unknown. The purpose of this investigation was to test the hypothesis that upright posture (seated and/or standing) would produce greater shear rates in the superficial femoral compared with the brachial artery. To test this hypothesis, Doppler ultrasound was used to measure mean blood velocity (MBV) and diameter in the brachial and superficial femoral arteries of 21 healthy subjects after being in the supine, seated, and standing postures for 10 min. MBV was significantly higher in the brachial compared with the superficial femoral artery during upright postures. Superficial femoral artery diameter was significantly larger than brachial artery diameter. However, posture had no significant effect on either brachial or superficial femoral artery diameter. The calculated shear rate was significantly greater in the brachial (73 +/- 5, 91 +/- 11, and 97 +/- 13 s(-1)) compared with the superficial femoral (53 +/- 4, 39 +/- 77, and 44 +/- 5 s(-1)) artery in the supine, seated, and standing postures, respectively. Contrary to our hypothesis, our current findings indicate that mean shear rate is lower in the superficial femoral compared with the brachial artery in the supine, seated, and standing postures. These findings of lower shear rates in the superficial femoral artery may be one mechanism for the higher propensity for atherosclerosis in the arteries of the leg than of the arm.

Skeletal muscle intracellular PO(2) assessed by myoglobin desaturation: response to graded exercise.

The relationship between skeletal muscle intracellular PO(2) (iPO(2)) and progressive muscular work has important implications for the understanding of O(2) transport and utilization. Presently there is debate as to whether iPO(2) falls progressively with increasing O(2) demand or reaches a plateau from moderate to maximal metabolic demand. Thus, using (1)H magnetic resonance spectroscopy of myoglobin (Mb), we studied cellular oxygenation during progressive single-leg knee extensor exercise from unweighted to 100% of maximal work rate in six active human subjects. In all subjects, the Mb peak at 73 ppm was not visible at rest, whereas the peak was small or indistinguishable from the noise in the majority of subjects during progressive exercise from unweighted to 50-60% of maximum work rate. In contrast, beyond this exercise intensity, a Mb peak of consistent magnitude was discernible in all subjects. When a Mb half saturation of 3.2 Torr was used, the calculated skeletal muscle PO(2) was variable before 60% of maximum work rate but in general was relatively high (>18 Torr, the measurable PO(2) with the poorest signal-to-noise ratio, in the majority of cases), whereas beyond this exercise intensity iPO(2) fell to a relatively uniform and invariant level of 3.8 +/- 0.5 Torr across all subjects. These results do not support the concept of a progressive linear fall in iPO(2) across increasing work rates. Instead, this study documents variable but relatively high iPO(2) from rest to moderate exercise and again confirms that from 50-60% of maximum work rate iPO(2) reaches a plateau that is then invariant with increasing work rate.

Genetic benefits enhance the reproductive success of polyandrous females.

Although it is generally accepted that females can gain material benefits by mating with more than one male, the proposal that polyandry provides genetic benefits remains controversial, largely because direct experimental support is lacking. Here, we report the results of a study testing for genetic benefits to polyandry in the pseudoscorpion Cordylochernes scorpioides. In an experiment that controlled for male mating experience and the number of spermatophores accepted by a female, twice-mated females received either one sperm-packet from each of two different males (the "DM" treatment) or two sperm-packets from a single male (the same male or "SM" treatment). Over their lifetime, DM females gave birth to 32% more offspring than did SM females, primarily because of a significantly reduced rate of spontaneous abortion. This result could not be attributed to male infertility nor to lack of sexual receptivity in males paired with previous mates. Spermatophore and sperm numbers did not differ between males presented with a previous mate and males paired with a new female. Because SM and DM females received the same quantity of ejaculate, it was possible to eliminate material benefits as a contributor to the enhanced reproductive success of DM females. The reduction in embryo failure rate achieved by DM females is most consistent with the genetic incompatibility avoidance hypothesis, i.e., that polyandry enables females to exploit postcopulatory mechanisms for reducing the risk and/or cost of fertilization by genetically incompatible sperm. This study, which rigorously controlled for material benefits and excluded inbreeding effects, demonstrates that polyandry provides genetic benefits that significantly enhance female lifetime reproductive success.

Intended pregnancies and unintended pregnancies: distinct categories or opposite ends of a continuum?

PIP: This article examines the entity of intended and unintended pregnancy. Results provided a strong evidence of bias. The reason for this bias may be due to an increased pressure for women to give a socially desirable response. This problem suggested three potential courses of action, such as: a combination of traditional cross-sectional studies with intendedness and wantedness values, improvement of retrospective measurements, and development of model predictors of reporting bias. With regards to the affective dimension, the positive and negative extremes may not be located on the same continuum; that is, positive and negative feelings coexist, hence producing ambivalence. Consequently, researchers should continue their efforts to expand approaches to these concepts and improve the ways of measuring them in future studies.^ieng

Polyandrous females discriminate against previous mates.

In most animal species, particularly those in which females engage in polyandry, mate choice is a sequential process in which a female must choose to mate or not to mate with each male encountered. Although a number of theoretical and empirical investigations have examined the effects of sequential mate choice on the operation of sexual selection, how females respond to solicitation by previous mates has received little attention. Here, we report the results of a study carried out on the polyandrous pseudoscorpion, Cordylochernes scorpioides, that assessed the sexual receptivity of once-mated females presented after a lapse of 1.5 hr or 48 hr with either their first mate or a different male. Females exhibited a high level of receptivity to new males, irrespective of intermating interval. By contrast, time between matings exerted a strong effect on female receptivity to previous mates. After a lapse of 48 hr, females did not differ significantly in their receptivity toward previous mates and different males, whereas at 1.5 hr after first mating, females were almost invariably unreceptive to males from whom they had previously accepted sperm. This result could not be attributed to male size or mating experience or to male sexual receptivity. Indeed, males were as willing to transfer sperm to a previous mate as they were to a new female. This difference between males and females in their propensity to remate with the same individual may reflect a conflict between the sexes, with males seeking to minimize postcopulatory sexual selection and females actively keeping open the opportunity for sperm competition and female choice of sperm by discriminating against previous mates.

School-based health centers and adolescent use of primary care and hospital care.

PURPOSE: Little is known about the impact of school-based primary care on adolescents' use of hospital and emergency room care. METHODS: Students (grades 6-12) in nine Baltimore schools with school-based health centers and four schools without health centers were surveyed in May 1991 using an anonymous classroom questionnaire. Self-reported use of primary care services and emergency rooms and hospitalization were examined over the academic year. Logistic regression was used to assess factors influencing use of health care including the presence of a school health center. RESULTS: Students (n = 3,258) in health center schools and comparison schools reported similar rates of chronic health conditions. Students from schools with health centers were more likely to report seeing a social worker or counselor and more likely to report the use of certain health services in the past 4 years. Self-reported emergency room use (38%) and hospitalization (19%) were common. Students in schools with health centers were less likely to report hospitalization (OR = 0.80, 95% CI = 0.66-0.98). Emergency room use was also lower but only for students attending the school with a health center for more than 1 year (OR = 0.78, 95% CI = 0.62-0.99). Significant predictors of hospital care included reporting one or more chronic health condition, having health insurance, being of African-American race, or older age, and lower grade. CONCLUSIONS: Access to school-based, primary health care for adolescents was associated with increased use of primary care, reduced use of emergency rooms, and fewer hospitalizations. These findings have implications for both access to primary care and funding of school-based primary care.

Student attitudes toward school-based health centers.

PURPOSE: Little is known about student attitudes toward school-based health centers (SBHCs) or about factors that influence SBHC enrollment. METHODS: Students in 9 Baltimore schools with SBHCs and 4 schools without health centers were surveyed in May 1991, using an anonymous classroom questionnaire. SBHC enrollees, nonenrollees from health center schools, and students in schools without health centers were compared using bi-variate analyses. Logistic regression analyses identified predictors of enrollment. RESULTS: A total of 91% of enrollees supported having a SBHC compared with 89% of nonenrollees and 77% of students from non-health center schools (p < .001). Support for a variety of services (including contraceptive services) was significantly higher among enrollees and nonenrollees compared with students in non-SBHC schools. A total of 86% of enrollees rated the quality of care "satisfactory" to "excellent" and 79% rated privacy in the school health center as "satisfactory" to "excellent." The most common reason given for not enrolling was satisfaction with current provider. Independent predictors of student confidence in the privacy of SBHCs included prior SBHC use and enrollment of close peers. Predictors of enrollment included: one or more self-reported health problems; having medical assistance; attending one or more special education classes; enrollment of close peers; membership in a school club, sports team, or church organization; and being African-American. CONCLUSIONS: Students overwhelmingly supported school-based health centers. Personal experience and peer influences were important in shaping student attitudes. We found evidence of a "learning curve" gradient in student attitudes such that students with the greatest exposure to SBHCs (as measured by attending a SBHC school, enrolling in the SBHC, and using the health center) had the most favorable attitudes.

The exclusion of never-married women from Chinese fertility surveys.

Never-married women have been regularly excluded in official national surveys of fertility in China, even in light of evidence of increasing premarital sexual activity. Likewise, never-married women in the United States were consistently excluded from national fertility surveys prior to 1982 because of the perceived sensitivity of questions about contraceptive use and sexual activities. Data on sexual and fertility behavior from all women of reproductive age, regardless of marital status, can provide direct measures of sexual activity and unintended pregnancies, as well as facilitate modeling of social networks underlying the sexual transmission of diseases. China's need for such information, however sensitive, will become more difficult to ignore given increasing pressures to attend to the health needs of their never-married but sexually active population.

PIP: It is argued that exclusion of the never married from Chinese fertility surveys eliminates consideration of unintended pregnancies and sexually transmitted diseases (STDs) and factors that might indicate future changes in fertility or contraceptive use. Never married persons are important as providers of information on sexual activity and sexually transmitted diseases. Asia may replace Africa as a major transmission site for HIV infection by the year 2000. Official Chinese reports indicated 2594 HIV-infected persons in 1995, but actual numbers could be as high as 100,000 persons. Information about social networks and sexual activity can be helpful in predicting the potential for spread of HIV. Economic reforms are expected to impact on patterns of marriage and sexual behavior. Although the 1982 One-per-thousand Population Fertility Sampling Survey included married and unmarried women, it excluded women aged 15-19 years. Reproductive histories were not collected from unmarried women. The 1985 and 1987 In-Depth Fertility Surveys only collected reproductive histories among ever married women aged 15-49. The 1992 National Sex Civilization Survey of sexual behavior was limited to the currently married. The only survey of sexual activity among the never married was conducted among college students in Shanghai, but six universities refused to participate. There is no nationally representative fertility survey of the Chinese population that includes the never married. 1990 Census findings indicate that 25% of population aged 15 years or older were never married. There were 194 million never married persons aged 15-30 years in 1990, or 95% of the 205 million never married persons. The proportion of those never married is likely to increase. Lessons from Taiwan and the US indicate the difficulties in measuring premarital sexual behavior, but there are compelling reasons to collect information on sexual behavior and reproductive health.

Research on adolescent fertility.

PIP: Research on adolescent pregnancy in the US has tended to be driven more by the politically motivated agendas of funding agencies than by careful considerations of this phenomenon's psychosocial context. In the 1970s, when adolescent pregnancy was already showing a trend of progressive increase, funding agencies issued calls for papers on the adverse consequences of early parenthood and programs were designed on the basis of such pathology-oriented research. In 1978, an Office of Adolescent Pregnancy Programs was established in the Department of Health and Human Services. Starting in 1982, the National Survey on Family Growth included unmarried adolescents in its surveys, enabling the quantification of trends in premarital sex, contraceptive use, and adolescent pregnancy. Cross-national comparisons of adolescent pregnancy rates have underscored the importance of sociocultural constructions of partnerships and sexuality on the meaning of adolescent fertility. Since condom use is the most feasible acquired immunodeficiency syndrome prevention method for adolescents, researchers have been forced to assess effective strategies for engaging young people in open discussions of premarital sexuality and to refine understanding of the influence of partners, parents, peers, and community norms. Also encouraging is awareness that interventions aimed at influencing high-risk behaviors must start in middle childhood.^ieng

Demographics of adolescent sexual behavior, contraception, pregnancy, and STDs.

The demographics of fertility-related behavior of youth ages 10-18 are reviewed. Data were collected from U.S. vital statistics, and birth rates, contraceptive use, sexual behavior, number and types of sexual partners, patterns of sexual initiation and sexual intercourse, and sexually transmitted diseases were examined. Despite data limitations, the demographic profile of adolescent sexual intercourse is striking. Age clearly is the single most important predictor of sexual debut.

Television viewing and adolescents' sexual behavior.

Over the past two decades the sexual content on television has increased in frequency and explicitness but has seldom included depiction of the use of contraceptives. Concurrently, the age of initiation of heterosexual intercourse has decreased and the number of teenaged pregnancies has remained high. Are these trends related? This survey of 391 adolescents found that those who chose heavier diets of sexy television shows were more likely than those who viewed a smaller proportion of sexual content on television to have had sexual intercourse. This relationship held regardless of perceived peer encouragement to engage in sex and across race and gender groups. While causal direction is not clear from these data, the relationship suggests that either sexual activity results in increased interest in sexual content in the media and/or that viewing such content leads to sexual activity. In either case, the finding points to the need for further research and increased discussion and portrayal of the use of contraceptives on television.

Parent-child communication and adolescent sexual behavior.

Data collected over a two-year period from more than 500 teenagers and their mothers indicate that neither parental attitudes toward premarital sex nor parent-child communication about sex and contraception appear to affect teenagers' subsequent sexual and contraceptive behavior. Teenagers are often ignorant of their parents' attitudes toward sex-related issues, and they and their parents often contradict one another in describing the kinds of sex-related conversations they have had. In only two cases was a significant relationship found between communication and adolescent behavior: Girls whose mothers reported that they had discussed sex with their daughters were less likely to subsequently initiate coitus; and girls who reported that their mothers had discussed birth control with them were more likely to use effective contraceptives. However, the former association disappeared when it was the daughters who reported the communication, and the latter disappeared when it was the mothers who reported it.

PIP: Interviews conducted in 1980 and 1982 among more than 500 teenagers and their mothers indicate that neither parental attitudes toward premarital sex nor parent-child communication about sex and contraception appear to affect teenagers' subsequent sexual and contraceptive behavior. In only 2 cases was a significant relationship found between communication and adolescent behavior: girls whose mothers reported that they had discussed sex with their daughters were less likely to subsequently initiate coitus; and girls who reported that their mothers had discussed birth control with them were more likely to use effective contraceptives. These associations disappeared, however, when it was the other party who reported the communication. The analysis clearly shows that teenagers are frequently ignorant of their parents' attitudes toward sex-related issues, and parents and teenagers frequently disagree about the kinds of sex-related conversations they have had. For example 73% of the boys and 77% of the girls believe that their mothers think that only married people should have sex, whereas only 45% of the mothers of sons and 49% of the mothers of daughters report holding that opinion. Similarly, 75% of mothers with sons, but only 33% of the sons, say mothers have taught their children "things about sex"; for mothers and daughters, the comparable figures are 87% and 62%. The reason the data reveal little effect of parental attitudes or parent-child communication on either the child's subsequent initiation of coitus or his or her contraceptive behavior may be that parental communication about sex is generally so vague or so limited as to have no impact.

Oral sex in an adolescent population.

The incidence of oral sex in an adolescent population is discussed. More girls have either given or received oral-genital stimulation than have had intercourse. More boys have had intercourse than have either given or received oral-genital stimulation. Oral sex is more common than intercourse for females because they are more likely to have received oral-genital stimulation than to have either had intercourse or given oral-genital stimulation. For both sexes, fellatio is less common than is either intercourse or cunnilingus. For both sexes, oral sex is considerably more frequently reported than was the case in the Kinsey surveys.

PIP: Using data from 2 surveys conducted in a US Southern city in 1980 and in 1982, this study concludes that the incidence of oral-genital contact among teenagers is increasing. This contact is seen as a way to give and receive sexual stimulation without the necessity of birth control or the risk of pregnancy. For both white sexes, contrary to Kinsey findings, cunnilingus is more frequently reported than is fellatio. Of the nonvirgins surveyed, 69% of each sex have both given and received oral-genital stimulation; of the nonvirgins, 80% have participated in either fellatio or cunnilingus. Slightly more teenagers have given or received oral sex than have had intercourse. Using a Goodman log-linear technique, no difference between the order in which boys and girls engage in giving and receiving oral sex is found, and, for girls, cunnilingus occurs no more often than does sexual intercourse. However, boys are more likely to have had intercourse than to have given or received oral-genital stimulation, probably due to the cited minority of boys who reported that they liked giving oral-genital stimulation, and the minority of girls who reported that they enjoyed receiving it.