Age-related alterations in the cardiovascular responses to acute exercise in males and females: role of the exercise pressor reflex.

Autonomic adjustments of the cardiovascular system are critical for initiating and sustaining exercise by facilitating the redistribution of blood flow and oxygen delivery to meet the metabolic demands of the active skeletal muscle. Afferent feedback from active skeletal muscles evokes reflex increases in sympathetic nerve activity and blood pressure (BP) (i.e., exercise pressor reflex) and contributes importantly to these primary neurovascular adjustments to exercise. When altered, this reflex contributes significantly to the exaggerated sympathetic and BP response to exercise observed in many cardiovascular-related diseases, highlighting the importance of examining the reflex and its underlying mechanism(s). A leading risk factor for the pathogenesis of cardiovascular disease in both males and females is aging. Although regular exercise is an effective strategy for mitigating the health burden of aging, older adults face a greater risk of experiencing an exaggerated cardiovascular response to exercise. However, the role of aging in mediating the exercise pressor reflex remains highly controversial, as conflicting findings have been reported. This review aims to provide a brief overview of the current understanding of the influence of aging on cardiovascular responses to exercise, focusing on the role of the exercise pressor reflex and proposing future directions for research. We reason that this review will serve as a resource for health professionals and researchers to stimulate a renewed interest in this critical area.

Microstructural and mechanical insight into atherosclerotic plaques: an ex vivo DTI study to better assess plaque vulnerability.

Non-invasive microstructural characterisation has the potential to determine the stability, or lack thereof, of atherosclerotic plaques and ultimately aid in better assessing plaques' risk to rupture. If linked with mechanical characterisation using a clinically relevant imaging technique, mechanically sensitive rupture risk indicators could be possible. This study aims to provide this link-between a clinically relevant imaging technique and mechanical characterisation within human atherosclerotic plaques. Ex vivo diffusion tensor imaging, mechanical testing, and histological analysis were carried out on human carotid atherosclerotic plaques. DTI-derived tractography was found to yield significant mechanical insight into the mechanical properties of more stable and more vulnerable microstructures. Coupled with insights from digital image correlation and histology, specific failure characteristics of different microstructural arrangements furthered this finding. More circumferentially uniform microstructures failed at higher stresses and strains when compared to samples which had multiple microstructures, like those seen in a plaque cap. The novel findings in this study motivate diagnostic measures which use non-invasive characterisation of the underlying microstructure of plaques to determine their vulnerability to rupture.

Diffusion tensor imaging and arterial tissue: establishing the influence of arterial tissue microstructure on fractional anisotropy, mean diffusivity and tractography.

This study investigates diffusion tensor imaging (DTI) for providing microstructural insight into changes in arterial tissue by exploring how cell, collagen and elastin content effect fractional anisotropy (FA), mean diffusivity (MD) and tractography. Five ex vivo porcine carotid artery models (n = 6 each) were compared-native, fixed native, collagen degraded, elastin degraded and decellularised. Vessels were imaged at 7 T using a DTI protocol with b = 0 and 800 s/mm2 and 10 isotopically distributed directions. FA and MD were evaluated in the vessel media and compared across models. FA values measured in native (p < 0.0001), fixed native (p < 0.0001) and collagen degraded (p = 0.0018, p = 0.0016, respectively) were significantly higher than those in elastin degraded and decellularised arteries. Native and fixed native had significantly lower MD values than elastin degraded (p < 0.0001) and decellularised tissue (p = 0.0032, p = 0.0003, respectively). Significantly lower MD was measured in collagen degraded compared with the elastin degraded model (p = 0.0001). Tractography yielded helically arranged tracts for native and collagen degraded vessels only. FA, MD and tractography were found to be highly sensitive to changes in the microstructural composition of arterial tissue, specifically pointing to cell, not collagen, content as the dominant source of the measured anisotropy in the vessel wall.

Role of prostaglandins in spinal transmission of the exercise pressor reflex in decerebrated rats.

Previous studies found that prostaglandins in skeletal muscle play a role in evoking the exercise pressor reflex; however the role played by prostaglandins in the spinal transmission of the reflex is not known. We determined, therefore, whether or not spinal blockade of cyclooxygenase (COX) activity and/or spinal blockade of endoperoxide (EP) 2 or 4 receptors attenuated the exercise pressor reflex in decerebrated rats. We first established that intrathecal doses of a non-specific COX inhibitor Ketorolac (100 µg in 10 µl), a COX-2-specific inhibitor Celecoxib (100 µg in 10 µl), an EP2 antagonist PF-04418948 (10 µg in 10 µl), and an EP4 antagonist L-161,982 (4 µg in 10 µl) effectively attenuated the pressor responses to intrathecal injections of arachidonic acid (100 µg in 10 µl), EP2 agonist Butaprost (4 ng in 10 µl), and EP4 agonist TCS 2510 (6.25 µg in 2.5 µl), respectively. Once effective doses were established, we statically contracted the hind limb before and after intrathecal injections of Ketorolac, Celecoxib, the EP2 antagonist and the EP4 antagonist. We found that Ketorolac significantly attenuated the pressor response to static contraction (before Ketorolac: 23 ± 5 mmHg, after Ketorolac 14 ± 5 mmHg; p<0.05) whereas Celecoxib had no effect. We also found that 8 µg of L-161,982, but not 4 µg of L-161,982, significantly attenuated the pressor response to static contraction (before L-161,982: 21 ± 4 mmHg, after L-161,982 12 ± 3 mmHg; p<0.05), whereas PF-04418948 (10 µg) had no effect. We conclude that spinal COX-1, but not COX-2, plays a role in evoking the exercise pressor reflex, and that the spinal prostaglandins produced by this enzyme are most likely activating spinal EP4 receptors, but not EP2 receptors.

Intrapulmonary arteries respond to serotonin and adenosine triphosphate in broiler chickens susceptible to idiopathic pulmonary arterial hypertension.

This study examined factors contributing to increased vascular resistance and plexiform lesion formation in broiler chickens susceptible to idiopathic pulmonary arterial hypertension (IPAH). A diet supplemented with excess tryptophan (high-Trp diet), the precursor for serotonin, was used to accelerate the development of IPAH. Broilers fed the high-Trp diet had higher pulmonary arterial pressures than broilers fed the control diet, and plexiform lesion incidences tended to be higher (P = 0.11) in the high-Trp group than in the control group at 30 d of age. The intrapulmonary arteries were assessed for vasoconstriction in response to serotonin and adenosine triphosphate (ATP) and for activities of key metabolic enzymes for serotonin and ATP. The pulmonary artery (defined as the first major branch of the pulmonary artery inside the lung) and the primary pulmonary arterial rami (defined as the second major branch of the pulmonary artery inside the lung) both exhibited vasoconstriction in response to serotonin and ATP. This is the first study to demonstrate purinergic-mediated vasoconstriction in intrapulmonary arteries from broilers. Arteriole responsiveness did not differ between broilers fed the control diet or the high-Trp diet. Therefore, the high-Trp diet enhanced the development of IPAH but did not affect the artery's sensitivity to serotonin or ATP. Monoamine oxidase activity, responsible for the breakdown of serotonin, was severely impaired in pulmonary arteries from broilers in the high-Trp group. Accordingly, serotonin may persist longer and elicit an amplified response in broilers fed the high-Trp diet.

A kinematic and kinetic analysis of drop landings in military boots.

OBJECTIVE: The purpose of this study was to examine knee valgus in drop landings during three different footwear conditions and to examine the ground reaction forces exhibited during the drop landing in the three different footwear conditions. METHODS: Sixteen male and female Reserve Officer Training Corps (ROTC) university undergraduate cadets (21 +/- 3 yrs, 79 +/- 12 kg, and 172 +/- 10 cm) volunteered to participate in the study. Kinematic data were collected while participants performed drop landings in three conditions: bare feet, tennis shoes, and issued military boots. RESULTS: Significant differences among footwear for ground reaction forces (bare feet: 1646 +/- 359%, tennis shoe: 1880 +/- 379%, boot: 1833 +/- 438%; p < 0.05) were found, while there was no significant difference in knee valgus among footwear. CONCLUSIONS: Though footwear conditions did not affect knee valgus, they did affect ground reaction forces. Participants in this study had yet to receive any military training on how to land properly from a specified height. Further research should be completed to analyze the kinematics and kinetics of the lower extremity during different landing strategies implemented by trained military personnel in order to better understand injury mechanisms of drop landings in this population. It is likely that injury prevention landing techniques would be beneficial if these were employed by the military and not just in the sporting community.

A pilot study of rhuIL-11 treatment of refractory ITP.

The objective of this research was to determine whether rhuIL-11 is an effective treatment in patients with refractory immune thrombocytopenic purpura (ITP). Platelet production is decreased in certain cases of refractory ITP. IL-11 stimulates megakaryocytopoiesis in vitro and was licensed for its clinical effects to ameliorate chemotherapy-induced thrombocytopenia. A pilot study was initiated, intending to enroll 12 patients with ITP. These patients were to receive rhuIL-11 (Neumega) at a dose of 50 microg/kg subcutaneously daily for 21 consecutive days and be observed afterward for 21 additional days. CBC with platelets were obtained twice weekly with visits and physical examinations weekly. The study was terminated after 7 patients were enrolled because of toxicity and lack of efficacy. All 7 patients had had ITP for >9 years and had failed splenectomy, intravenous gammaglobulin, corticosteroids, and a variety of other treatments. The patients at entry all had platelet counts <20,000/microl; 5 of 7 had counts <10,000/microl. The maximal median increase for any day of the study was 6,000/microl. No patient achieved a count of 30,000/microl, and only 3 patients achieved (once each) a platelet count >20,000/microl. Substantial toxicity was seen. The nadir hemoglobin decrease was a mean of 2 g/dl. rhuIL-11 was not effective at increasing the platelet count in any of these patients with refractory ITP. Toxicity was substantial. The lack of platelet response to rhuIL-11 in this study does not exclude the possibility of better effects at other doses and/or in less refractory patients.

Designing interventions to prevent HIV-1 infection by promoting use of condoms and spermicides among intravenous drug abusers and their sexual partners.

This paper summarizes the results of a 2-day workshop to identify the most effective educational strategies to promote use of condoms and spermicides for preventing heterosexual transmission of HIV-1 virus from intravenous drug abusers (IVDA) to their steady, nonintravenous drug abusing (NIVDA) sexual partners. Representatives from health departments, drug abuse treatment centers, academic institutions, service organizations, and the community discussed issues relating to population characteristics, educational strategies and recruitment techniques. A consensus document that identifies the most effective recruitment and intervention strategies was developed. Recruitment issues include locations, recruitment targets, anticipated difficulties, and ethical considerations. The majority of workshop participants agreed that an intervention should target the couple (both IVDA and NIVDA). Intervention concerns encompass obtaining trust, maintaining participation, and identifying guidelines to maximize program impact.

PIP: Participants at a 2-day workshop convened by the University of California, Los Angeles School of Public Health in May 1988, at the request of the Contraceptive Evaluation Branch of the National Institutes of Child Health and Human Development, discussed the feasibility of interventions aimed at promoting use of condoms and spermicides among intravenous drug abusers and their sexual partners. Such interventions are crucial to child survival efforts since the major source of human immunodeficiency virus (HIV) transmission to children is from infected intravenous drug abusers. Although most intravenous drug abusers have casual sexual contacts, over 90% are in a long-standing relationship. Contraception is more likely to be used by drug addicts in casual sexual encounters than in their stable sexual relationship. Participants at the workshop reached the consensus that intervention programs should target the couple (even if 1 partner is not an intravenous drug user), use existing value systems to change behavior, have a warm and entertaining tone, and obtain community support. Among the strategies that have been effective in recruiting intravenous drug abusers and their sexual partners have been advertisements, use of sites such as family planning and community health centers, use of nonmedical service locations such as day care centers and community organizations, involvement of trained volunteers, and targeting of a high-risk housing project. Since many intravenous drug abusers are members of poor minority communities with a history of degrading contact with institutions, attention must be given to securing the trust of participants. The interventions themselves should use behavioral modification methods that leave existing values and roles intact. In general, peer group meetings are most successful in inducing a commitment to initiate and maintain new sexual behaviors.

Detection of benign cardiac fibroma on thallium-201 imaging in an adult.

A rare case of benign cardiac fibroma causing a focal defect on Tl-201 imaging in an adult patient is presented. The abnormalities on the Tl-201 scan are correlated with other studies performed on the same patient. The usefulness of the Tl-201 myocardial perfusion scan as an early, noninvasive test in cardiac workup is stressed.

Correlates of accurate knowledge of cancer.

Knowledge acquisition, although a prerequisite of preventive behavior, has been a neglected area of research. Mass communication research shows that audience characteristics explain most of the variation in knowledge acquistion. Since cancer information is mainly disseminated via the media, we hypothesized that the same audience characteristics would be related to accuracy of cancer knowledge. Bivariate and multivariate associations between the hypothesized variables and a cancer knowledge score were tested using a three-stage random sample of Los Angeles County (N = 931). Smoking status, education, degree of cancer worry, health improvement behavior, ethnicity, age, household size, and frequency of health worry were related to knowledge accuracy. An examination of the underlying dimensions of cancer knowledge revealed three beliefs about cancer: smoking causes cancer; cancer can be cured; and the environment does not cause cancer. Smoking status, ethnicity, health improvement behavior, and worry about cancer and health were associated with the belief that smoking causes cancer. The independent variables in this study were not significantly related to the other two beliefs. These results conform with the general predictions of mass communication research. We conclude that targeting of cancer information and particular uses of media could raise the general level of cancer knowledge.

Is hostility linked with affiliation among males and with achievement among females? A critique of Pollak and Gilligan.

This investigation attempted to replicate and to clarify methodologically an investigation by Pollak and Gilligan (1982). Those investigators reported sex differences in violence imagery to Thematic Apperception Test (TAT) pictures depicting affiliation and achievement situations. Pollak and Gilligan concluded that men perceive danger in situations of affiliation whereas women perceive danger in situations of achievement. It was demonstrated in the present study that Pollak and Gilligan incorrectly classified TAT cards into motivational categories, which may have resulted in incorrect inferences. In addition, their findings could not be replicated when using four different systems for classifying TAT cards into motivational categories. Other potential sources of error in their research, including a restrictive scoring scheme for hostility, unusual instructions, and failure to control for sex role in the TAT pictures, did not influence the pattern of results.