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Biomedical subjects

D Kirby

Publications and source records attributed to D Kirby.

At least 19 recordsLinked to original sources
PubMed1999

Psychosocial predictors of delay of first sexual intercourse by adolescents.

This investigation predicted adolescents' delay of intercourse onset from attitudes, social norms, and self-efficacy about refraining from sexual intercourse. Age, gender, ethnicity, and parental education were also examined as predictors and moderators of the relationships among the 3 psychosocial determinants and onset. The participants (N = 827), part of a cohort initially surveyed in the 9th grade, reported at baseline that they had never engaged in intercourse. The multivariable proportional hazards regression model suggested that adolescents with more positive attitudinal and normative beliefs, as well as those with a parent who graduated from college, were less likely to engage in intercourse in the follow-up period (up to approximately 2 years). Interventions that include an objective to delay onset may benefit from addressing psychosocial determinants, especially attitudes and norms about sexual intercourse.

Adolescent↗
PubMed1999

Short-term impact of safer choices: a multicomponent, school-based HIV, other STD, and pregnancy prevention program.

This study evaluated the effectiveness of the first year of Safer Choices, a theoretically based, multicomponent HIV, STD, and pregnancy prevention program for high school youth. The study featured a randomized trial involving 20 schools in California and Texas, with a cohort of 3,869 ninth-grade students. Students who completed both the baseline and the first follow-up survey approximately seven months later were included in the analysis (n = 3,677). Safer Choices enhanced 9 of 13 psychosocial variables including knowledge, self efficacy for condom use, normative beliefs and attitudes regarding condom use, perceived barriers to condom use, risk perceptions, and parent-child communication. Safer Choices also reduced selected risk behaviors. Specifically, Safer Choices reduced the frequency of intercourse without a condom in the three months prior to the survey, increased use of condoms at last intercourse, and increased use of selected contraceptives at last intercourse.

Adolescent↗
PubMed1999

Reflections on two decades of research on teen sexual behavior and pregnancy.

During the past 20 years, both researchers and program developers made great progress in their efforts to reduce adolescent unprotected sex and prevent teen pregnancy. Research studies are now more likely to employ experimental designs with random assignments, to have large sample sizes with adequate statistical power, to measure actual sexual and contraceptive behaviors, to measure longer term effects, to employ proper statistical methods, and to report results in an unbiased manner. As a result of this body of research, large advances have occurred in our understanding of: 1) the incidence of teen pregnancy, and its consequences; 2) the effects of improving adolescent knowledge, increasing access to contraception, and improving parent/child communication; and 3) the characteristics of effective programs. The on-going evaluation of sex and HIV education programs coupled with creativity and perseverance on the part of program developers led to two groups of effective programs--sex and HIV education programs that reduce sexual risk-taking behavior, and youth development programs that reduce teen-age pregnancy and childbearing.

Adolescent↗
PubMed1999

The impact of condom availability [correction of distribution] in Seattle schools on sexual behavior and condom use.

OBJECTIVES: Ten Seattle high schools made condoms available through vending machines, baskets in school clinics, or both. This study measured the number of condoms that students obtained and subsequent changes in sexual behavior and condom use. METHODS: Schoolwide surveys were administered in spring 1993 and in spring 1995, before and during the condom availability program. These data were compared with data from nationally representative surveys administered at the same time. RESULTS: Seattle students obtained an average of 4.6 condoms per year, the vast majority from baskets and very few from vending machines. Relative to the national samples, the percentage of Seattle students who had ever had sex remained stable after the program began; current sexual activity decreased significantly; and the percentage of sexually experienced students who used a condom the last time they had sex decreased significantly, particularly in the 5 schools with baskets of condoms in clinics. CONCLUSIONS: Making condoms available in Seattle schools enabled students to obtain relatively large numbers of condoms but did not lead to increases in either sexual activity or condom use.

Adolescent↗
PubMed1999

Sexually transmitted diseases, unintended pregnancy, and adolescent health promotion.

Adolescence is a critical period in the development of sexual behaviors that may lead to acquiring sexually transmitted diseases (STDs), including human immunodeficiency virus (HIV), and to unintended pregnancy. Understanding adolescent sexual behavior is essential for understanding adolescents' risk of pregnancy and STD/HIV infection and for planning and evaluating health promotion activities. This chapter reviews the sexual behaviors and psychosocial factors associated with STDs and unintended pregnancy among adolescents as well as school-, community-, and clinic-based interventions designed to reduce risk behaviors and promote adolescent sexual health.

Adolescent↗
PubMed1999

Sexuality and sex education at home and school.

This article reviews numerous studies of parent-adolescent communication about sexuality and 30 studies of sexuality and HIV education programs. Although parent-adolescent communication about sexuality has increased during the last few decades, both the occurrence and the quality of this communication could still be greatly improved. There does not exist a clear simple relationship between greater parent-adolescent communication and less adolescent risk-taking behavior, but both adults and youth believe it is important anyway. Sexuality and HIV education programs do not increase any measure of sexual activity, but some of them with ten common characteristics do reduce sexual risk-taking, either by delaying or reducing sexual behavior or increasing condom use. Thus, these programs can be an effective component in a larger initiative to reduce HIV, other STDs, and unplanned pregnancy in adolescence.

Adolescent↗
PubMed1998

Optical Monitoring of Cerebral Hemodynamics and Oxygenation in the Neonatal Piglet

> Objective: Optical spectroscopy can monitor changes in cerebral oxyhemoglobin (HbO), deoxyhemoglobin (Hb), and total hemoglobin (HbT = Hb + HbO). The purpose of this study was to identify which one of these three optical variables would be the best correlate of cerebral hemodynamics and oxygenation accompanying different physiological conditions known to affect cerebral perfusion pressure and oxygenation. Methods: Eleven anesthetized and ventilated newborn piglets were subjected to: 1) hyperoxic hypercapnia, 2) asphyxia from room air, 3) hypertension, 4) hypotension, and 5) cerebral venous congestion. Optical measurements were recorded continuously along with carotid blood flow (CaBF) measured by the transit time Doppler technique and arterial hemoglobin oxygen saturation (SaO2) measured by pulse oximetry. Results: A good positive HbT-CaBF correlation was recorded during hypercapnia (r = 0.816), asphyxia (r = 0.846), hypertension (r = 0.72), and hypotension (r = 0.95), where as negative correlation was recorded during venous congestion (r = -0.91). A good positive correlation HbO-SaO2 was recorded during asphyxia (r = 0.842) and hypotension (r = 0.86), whereas no HbO-SaO2 agreement occurred during hypercapnia (r = 0.23), hypertension (r = 0.19), and venous congestion (r = 0.34), when SaO2 did not change at all. A good positive HbO-SaO2 correlation was recorded during hypercapnia (r = 0.84), hypertension (r = 0.91), and hypotension (r = 0.94), suggesting a high HbO dependence on changes in CaBF. Conclusions: We demonstrated that none of the optical variables (Hb, HbO, HbT) alone can be used as a correlate of cerebral hemodynamics and oxygenation over a broad range of cerebral perfusion pressure and oxygenation. However, all three variables combined (i.e. optical patterns) strongly reflect the changes in cerebral hemodynamics and oxygenation accompanying those physiological conditions. These and similar patterns could potentially serve as a reference model for future studies in the human fetus where "gold standard" correlation methods do not exist.

Journal Article↗
PubMed1998

Optical Brain Monitoring of the Cerebrovascular Effects Induced by Acute Cocaine Exposure in Neonatal Pigs.

> Objective: The purpose of this study was to assess the direct effects of cocaine on cerebral blood flow and oxygenation in newborn piglets using optical spectroscopy. Optical spectroscopy is capable of monitoring changes in cerebral oxyhemoglobin, deoxyhemoglobin, and total hemoglobin continuously, noninvasively, and in real time. Methods: Five anesthetized and ventilated newborn piglets were injected intravenously with 1 mg/kg cocaine through a central venous catheter over 60 seconds. Cerebral blood flow and oxygenation were assessed by optical spectroscopy and standard physiologic monitoring: mean arterial pressure, carotid blood flow, cerebrovascular resistance, and arterial hemoglobin oxygen saturation (by pulse oximetry). Results: Cocaine induced a profound increase in cerebrovascular resistance, a decrease in carotid blood flow, and a decrease in mean arterial pressure and heart rate. Cerebrovascular changes were detected readily by optical spectroscopy (i.e. a decrease in cerebral oxyhemoglobin was associated with an increase in deoxyhemoglobin). The hypotensive response augmented the cerebral vasoconstriction effect on carotid blood flow. A good correlation existed between the changes in carotid Doppler blood flow and total hemoglobin in each animal and for all animals combined. Peripheral arterial hemoglobin oxygen saturation measured by pulse oximetry remained normal throughout the experiment. Conclusions: The cause for the apparent idiosyncratic hypotensive response to intravenous injections of cocaine is uncertain and requires further investigation. Our study clearly demonstrates that optical spectroscopy might become an extremely useful tool for monitoring cerebral hemodynamics and oxygenation in cocaine-exposed fetuses and infants.

Journal Article↗
PubMed1997

Anxiolytic activity of NPY receptor agonists in the conflict test.

This investigation examined receptor subtype specificity and possible modulation by GABAa receptor ligands of NPY-induced behavioral responses to stressful stimuli. First, a series of NPY receptor agonists were examined for their potential effects on punished responding in a conflict test modified for incremental shock. NPY, peptide YY (PYY) and NPY Y1 receptor agonists [Leu31,Pro34]-NPY and [Gly6, Glu26,Lys26,Pro34]-NPY produced increases in punished responding in the conflict test. No significant effects on unpunished responding were noted. The pattern of responding was similar to that observed with the benzodiazepine agonist chlordiazepoxide. Neither pancreatic peptide (PP) nor the Y2 agonists NPY13-36 or [Glu2,32,Ala6,Dpr27,Lys28]-NPY significantly altered punished or unpunished responding. Of significance, the atypical Y1 agonist [Cys7,21,Pro34]-NPY produced negligible effects on punished responding, consistent with the presence of a subclass of Y1 receptors. Second, the anxiolytic effects of NPY were subjected to treatments that block actions at the GABAa receptor complex. The increase in punished responding produced by NPY was not altered by administration of the benzodiazepine antagonist flumazenil and only partially blocked by the picrotoxinin receptor ligand isopropylbicyclophosphate (10 and 15 microg/kg). These findings further support the hypothesis that the pharmacologic substrates for the anxiolytic-like actions of NPY may be mediated by the Y1 receptor subtype and suggest that these actions are independent of either the benzodiazepine or picrotoxinin binding sites of the GABA/benzodiazepine receptor complex.

Animals↗
PubMed1997

Electrophysiological actions of neuropeptide Y and its analogs: new measures for anxiolytic therapy?

Neuropeptide Y (NPY) has neuromodulatory actions on multiple brain functions including endocrine, behavioral, and circadian processes. Behavioral studies suggest that NPY is a potent anxiolytic; however, little is known about how NPY affects general arousal and/or attention states. The present study evaluated the effects of NPY on spontaneous brain activity as well as auditory processing by using electrophysiological measures. Electroencephalographic (EEG) and event-related potentials (ERPs) were obtained in awake animals after intracerebroventricular administration of NPY (1.0, 3.0 nmol) and two of its analogs, active at Y1 (1.0, 3.0 nmol) and Y2 (1.0, 3.0 nmol) receptor sites. NPY was found to produce dose-related effects on electrophysiological measures. Spectral analyses of the EEG revealed that NPY produced slowing of delta activity (1-2 Hz) in the frontal cortex and high frequency theta activities (6-8 Hz) concomitant with a speeding up of low frequency theta (4-6 Hz) in cortex, hippocampus, and amygdala. At higher doses (3.0 nmols) in addition to shifts in frequency, EEG power was also significantly reduced in all frequencies (0.5-50 Hz) in cortex, and in the higher frequencies (8-32 Hz) in the amygdala. The Y1 and Y2 agonists had a somewhat different profile of EEG effects than the parent compound. At the 1 nmol dose both agonists were found to produce selective depressions in power in the hippocampus. The 3.0 nmols dose of the Y1 agonist produced decreases in EEG stability, an effect commonly produced by anxiolytic drugs, whereas the Y2 agonist produced increases in EEG stability in cortex and amygdala. Auditory processing, as assessed by ERPs, was affected most significantly in the frontal cortex where dose-dependent decreases in the N1 component of the ERP, a finding also commonly seen after anxiolytics, was found. Y1 and Y2 agonists were also found to significantly reduce the amplitude of the N1 component of the ERP but less so than the parent compound. The electrophysiological and behavioral profiles of NPY and the Y1 agonist resembles those of anxiolytics such as ethanol and benzodiazepines. Taken together these data suggest that electrophysiological measures of the actions of this peptide system may represent a new potentially useful assay for the development of anxiolytic drugs.

Amygdala↗
PubMed1997

The safer choices project: methodological issues in school-based health promotion intervention research.

Randomized trials of school-based health promotion programs present unique design and analytical issues not widely discussed in the research literature. This article describes the Safer Choices study--a school-based program for prevention of HIV, other sexually transmitted diseases, and pregnancy--to illustrate critical methodological issues involved in large-scale, school-based intervention trials, particularly those evaluating interventions with a school-wide focus. The issues presented are: 1) comparability of the intervention and control groups even when few units are randomized; 2) factors that affect the decision to use a cohort or cross-sectional design; and 3) appropriate analysis strategy when the unit of randomization and intervention is at the school level, but observations are at the student level.

Adolescent↗
PubMed1997

An impact evaluation of project SNAPP: an AIDS and pregnancy prevention middle school program.

OBJECTIVES: A theory-based curriculum designed to delay the onset of intercourse and increase use of condoms was implemented in the classrooms of six Los Angeles middle schools. METHODS: The curriculum activities were very interactive, emphasized skill building, and were implemented by well trained peer educators, including young HIV-positive males and teen mothers. To evaluate the impact of the curriculum, 102 classrooms of students were randomly assigned to receive either the existing curriculum or the existing curriculum plus the intervention curriculum. Students completed confidential questionnaires before program implementation, five months later, and 17 months later. A total of 1,657 students completed both the baseline and 17-month follow-up questionnaires. RESULTS: Analyses of these data revealed that the curriculum significantly increased knowledge, significantly improved only two out of 21 attitudes or beliefs, and did not significantly change sexual or contraceptive behaviors. CONCLUSIONS: Well implemented programs that are based on upon theory, use interactive activities, and utilize well-trained peer educators do not always change important sexual attitudes and behaviors among middle school youth.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Safer Choices: a multicomponent school-based HIV/STD and pregnancy prevention program for adolescents.

Given the serious consequences of HIV infection, other STDs, and pregnancy among teens, professionals must develop and evaluate new approaches to reduce risks associated with adolescent sexual behavior. The Safer Choices intervention is a comprehensive, theoretically based program designed to reduce risk behaviors and increase protective behaviors to prevent HIV, other STDs, and pregnancy among high school adolescents. The program includes five components: a School Health Promotion Council involving administrators, school staff, students, parents, and community members; curriculum and staff development activities; school environment activities designed and implemented by a team of peer educators; parent education activities; and school-community linkage activities. The School Health Promotion Council is responsible for planning and overseeing program implementation. This article describes the theoretical framework, process for intervention development, and key intervention strategies used in Safer Choices.

Adolescent↗