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Biomedical subjects

S Levin

Publications and source records attributed to S Levin.

At least 37 records · Page 2Linked to original sources
PubMed2000

Sports participation and health-related behaviors among US youth.

OBJECTIVE: To examine the relationship between sports participation and health-related behaviors among high school students. DESIGN: Cross-sectional design using data from the 1997 Centers for Disease Control and Prevention Youth Risk Behavior Survey. PARTICIPANTS: A nationally representative sample of 14,221 US high school students. MAIN OUTCOME MEASURES: Prevalence of sports participation among males and females from 3 ethnic groups and its associations with other health behaviors, including diet, tobacco use, alcohol and illegal drug use, sexual activity, violence, and weight loss practices. RESULTS: Approximately 70% of male students and 53% of female students reported participating on 1 or more sports teams in school and/or nonschool settings; rates varied substantially by age, sex, and ethnicity. Male sports participants were more likely than male nonparticipants to report fruit and vegetable consumption on the previous day and less likely to report cigarette smoking, cocaine and other illegal drug use, and trying to lose weight. Compared with female nonparticipants, female sports participants were more likely to report consumption of vegetables on the previous day and less likely to report having sexual intercourse in the past 3 months. Among white males and females, several other beneficial health behaviors were associated with sports participation. A few associations with negative health behaviors were observed in African American and Hispanic subgroups. CONCLUSION: Sports participation is highly prevalent among US high school students, and is associated with numerous positive health behaviors and few negative health behaviors.

Adolescent↗
PubMed2000

Moment expansions in spatial ecological models and moment closure through Gaussian approximation.

We describe the dynamics of competing species in terms of interactions between spatial moments. We close the moment hierarchy by employing a Gaussian approximation which assumes that fluctuations are independent and distributed normally about the mean values. The Gaussian approximation provides the lowest-order systematic correction to the mean-field approximation by incorporating the effect of fluctuations. When there are no fluctuations in the system, the mean equations agree with the Gaussian approximation as the fluctuations are weak. As the fluctuations gain strength, they influence the mean quantities and hence the Gaussian approximation departs from the mean-field approximation. At large fluctuation levels, the Gaussian approximation breaks down, as may be explained by the bimodality and skewness of the fluctuation distribution of the partial differential equation.

Animals↗
PubMed2000

The association between severity of sanction imposed for violation of tobacco policy and high school dropout rates.

This investigation explored the association between severity of sanctions imposed on students resulting from tobacco policy violation and the event dropout rate in South Carolina public high schools. The study employed a cross-sectional design (n = 132). Surveys were mailed to school principals to assess tobacco policy and sanctions for violation. Severe sanctions were categorized as those resulting in the student being denied onsite instruction, such as out-of-school suspension or expulsion. General linear regression models adjusting for SES, ethnicity, and rural/urban status, tested for an association between event dropout rate and severity of sanction imposed. The mean dropout rate in 1998 for high schools in South Carolina was 2.58% (+1.74). Suspension at first violation and expulsion were associated with lower dropout rates. Suspension at second violation was not associated with dropout behavior while suspension at third violation was associated with higher dropout rates. Results from the study provide preliminary evidence that severe sanctions imposed for violation of tobacco policy may help reduce high school dropout rates.

Adolescent↗
PubMed1999

Nucleation and relaxation from meta-stability in spatial ecological models.

We study a model for competing species that explicitly accounts for effects due to discreteness, stochasticity and spatial extension of populations. If a species does better locally than the other by an amount epsilon, the global outcome depends on the initial densities (uniformly distributed in space), epsilon and the size of the system. The transition point moves to lower values of the initial density of the superior species with increasing system size. Away from the transition point, the dynamics can be described by a mean-field approximation. The transition zone is dominated by formation of clusters and is characterized by nucleation effects and relaxation from meta-stability. Following cluster formation, the dynamics are dominated by motion of cluster interfaces through a combination of planar wave motion and motion through mean curvature. Clusters of the superior species bigger than a certain critical threshold grow whereas smaller clusters shrink. The reaction-diffusion system obtained from the mean-field dynamics agrees well with the particle system. The statistics of clusters at an early time soon after cluster-formation follow a percolation-like diffusive scaling law. We derive bounds on the time-to-extinction based on cluster properties at this early time. We also deduce finite-size scaling from infinite system behavior.

Animals↗
PubMed1999

Beta-adrenergic agonists regulate cell membrane fluctuations of human erythrocytes.

1. Mechanical fluctuations of the cell membrane (CMFs) in human erythrocytes reflect the bending deformability of the membrane-skeleton complex. These fluctuations were monitored by time-dependent light scattering from a small area ( approximately 0. 25 microm2) of the cell surface by a method based on point dark field microscopy. 2. Exposure of red blood cells (RBCs) to adrenaline (epinephrine) and isoproterenol (isoprenaline) resulted in up to a 45 % increase in the maximal fluctuation amplitude and up to a 35 % increase in the half-width of the amplitude distribution. The power spectra of membrane fluctuations of control and treated cells revealed that adrenaline stimulated only the low frequency component (0.3-3 Hz). Analysis of the dose-response curves of beta-adrenergic agonists yielded an EC50 of 5 x 10-9 and 1 x 10-11 M for adrenaline and isoproterenol, respectively. Propranolol had an inhibitory effect on the stimulatory effect of isoproterenol. These findings show a potency order of propranolol > isoproterenol > adrenaline. 3. The stimulatory effect of adrenaline was a temporal one, reaching its maximal level after 20-30 min but being abolished after 60 min. However, in the presence of 3-isobutyl-1-methylxanthine, a partial stimulatory effect was maintained even after 60 min. Pentoxifylline and 8-bromo-cAMP elevated CMFs. However, exposure of ATP-depleted erythrocytes to adrenaline or 8-bromo-cAMP did not yield any elevation in CMFs. These findings suggest that the beta-agonist effect on CMFs is transduced via a cAMP-dependent pathway. 4. Deoxygenation decreased CMFs and filterability of erythrocytes by approximately 30 %. The stimulatory effect of isoproterenol on CMFs was 2.2-fold higher in deoxygenated RBCs than in oxygenated cells. 5. Exposure of RBCs to adrenaline resulted in a concentration-dependent increase in RBC filterability, demonstrating a linear relationship between CMFs and filterability, under the same exposure conditions to adrenaline. These findings suggest that beta-adrenergic agonists may improve passage of erythrocytes through microvasculature, enhancing oxygen delivery to tissues, especially under situations of reduced oxygen tension for periods longer than 20 min.

Adenosine Triphosphate↗
PubMed1999

[Operative laparoscopy in pregnancy].

The development of laparoscopic surgery in gynecology and general surgery has greatly advanced over the past decade, and recently has been successfully performed in pregnancy. In the English literature we found that of the 518 cases reported (mean age 32 years) the most common was for cholecystectomy (45%), followed by operations on the adnexae (34%), appendectomy (15%) and others (6%). To these we add 3 cases of cholecystectomy and 1 of an adnexal tumor. Of all the reported cases, 33% were performed in the 1st trimester, 56% in the 2nd and 11% in the 3rd. This review demonstrates a definite trend to laparoscopy in pregnancy. It appears to be safe when performed by experienced surgeons, but further studies addressing safety of laparoscopic surgery during pregnancy are needed to reach definitive conclusions.

Adult↗
PubMed1999

Weight-related attitudes and behaviors in fourth grade American Indian children.

OBJECTIVE: American Indian children have a high prevalence of obesity, yet little is known about weight-related attitudes and the prevalence of dieting in this population. This study assessed weight concerns, body size perceptions, weight reduction attempts, and weight loss methods in fourth grade American Indian children. RESEARCH METHODS AND PROCEDURES: Participants (n = 304) attended one of eight schools in the Pathways Feasibility Study. Question and answer choices were read to children by trained staff, and children marked their own answers. RESULTS: Thirty-eight percent of the children reported that they had tried to lose weight. The most common strategy for weight reduction was exercising more. Girls were more likely than boys to be dissatisfied with their body size (48% of girls vs. 34% of boys desired a slimmer body size; 22% of girls vs. 15% of boys desired a larger body size; p<0.001). Children who had tried to lose weight were more likely to indicate that the size they most desired and the most healthy size were smaller than their perceived size (p<0.001). Children who reported trying to lose weight were also more likely to want to be skinnier and to be unhappy about their weight than were children who did not report trying to lose weight (p<0.001 for both). DISCUSSION: We conclude that weight loss attempts and weight-related concerns are prevalent in American Indian children at a young age.

Arizona↗
PubMed1999

Local frequency dependence and global coexistence.

In sessile organisms such as plants, interactions occur locally so that important ecological aspects like frequency dependence are manifest within local neighborhoods. Using probabilistic cellular automata models, we investigated how local frequency-dependent competition influenced whether two species could coexist. Individuals of the two species were randomly placed on a grid and allowed to interact according to local frequency-dependent rules. For four different frequency-dependent scenarios, the results indicated that over a broad parameter range the two species could coexist. Comparisons between explicit spatial simulations and the mean-field approximation indicate that coexistence occurs over a broader region in the explicit spatial simulation.

Ecosystem↗
PubMed1999

Randomized clinical trial comparing the efficacy of mandibular implant-supported overdentures and conventional dentures in diabetic patients. Part III: comparisons of patient satisfaction.

STATEMENT OF PROBLEM: There is insufficient evidence to indicate the functional superiority of mandibular implant-supported overdentures to justify their use in edentulous patients. PURPOSE: This study compared the benefits perceived by patients who received a new maxillary denture and a mandibular conventional denture (CD) and an implant-supported overdenture (IOD). METHOD: New maxillary and mandibular dentures were delivered to 89 diabetic denture wearers with clinically acceptable metabolic control who treated their diabetes either with insulin (IT) or without insulin (NIT). Of the 89 patients, 37 received maxillary and mandibular CDs and 52 received a maxillary CD and an IOD. Two questionnaires with categorical responses were used; the first contained 13 questions to ascertain a patient's absolute assessments of original dentures at entry and study dentures at 6- and 24-months after treatment completion; the second questionnaire had 11 questions that assessed the relative change perceived by patients with study dentures. Of the 78 patients who completed the posttreatment (PT) assessments at 6 months, 68 patients provided longitudinal data for questionnaire I and cross-sectional data for questionnaire II. In addition, 46 patients (18 CD and 28 IOD) also provided PT assessments at 24 months. RESULTS: Both mean scores and percentage distributions of longitudinal data for questionnaire I showed perceptual improvements with both types of study dentures. Improvements were higher in the IOD than in the CD group. Mean scores failed to show any significant differences between the 2 treatment groups. The only significant difference was found in the change in percentage distributions for perceptual chewing ability in favor of the IOD group. Even this advantage was lost at 24 months. With the comparative questionnaire, a higher percentage of patients in the IOD group than in the CD group perceived improvements with study dentures from their original dentures in chewing ability, chewing comfort, and denture security. However, mean differences were statistically significant in favor of the IOD group only for chewing ability and less difficulty to chew hard foods. CONCLUSION: The mandibular implant-supported overdenture offers same advantage in terms of perceived chewing function over the conventional denture.

Aged↗
PubMed1999

Validity and reproducibility of a food frequency interview in a Multi-Cultural Epidemiology Study.

PURPOSE: There is limited support for the validity and reproducibility of dietary assessment in culturally diverse populations. The goal of this study was to evaluate the comparative validity and reproducibility of a Food Frequency Questionnaire (FFQ) used in the observational, multi-cultural Insulin Resistance Atherosclerosis Study (IRAS). METHODS: Women (n = 186) were approximately equally distributed by ethnicity from one urban center (African Americans and non-Hispanic whites) and one rural center (Hispanics and non-Hispanic whites). The IRAS FFQ was modified from the National Cancer Institute Health Habits and History Questionnaire to include ethnic and regional foods. Validity was assessed by comparing dietary values, including supplements, obtained from the FFQ to the average intake estimated from a series of 8 24-hour dietary recalls collected by telephone over the same 1-year period. Reproducibility was assessed among women who reported no change in their usual diet (n = 133) by comparing data from the original IRAS FFQ (in-person) with the FFQ administered for the validity study (two to four years later, by telephone). RESULTS: Correlation coefficients for validity were statistically significant for most nutrients (mean r = 0.62 urban non-Hispanic white, 0.61 rural non-Hispanic whites, 0.50 African American, 0.41 Hispanic) and did not differ among subgroups of obesity or diabetes status. The median correlation coefficient for the total sample was 0.49. Correlations were lower for women with less than 12 years of education (mean r = 0.30; median r = 0.25). The lower correlations among Hispanics was largely explained by the lower educational attainment in that sample. For reproducibility, the mean correlation for nutrients evaluated was r = 0.62 (median r = 0.63) and did not differ for subgroups. CONCLUSIONS: Although educational attainment must be considered, the IRAS FFQ appears to be reasonably valid and reliable in a diverse cohort.

Adult↗
PubMed1999

Intra-individual variation and estimates of usual physical activity.

PURPOSE: The magnitude of intra-individual variation, as determined by three methods of physical activity (PA) assessment, was estimated to determine the optimal number of repeated measures needed to reliably measure an individual's usual PA habits. METHODS: Data were obtained from 77 healthy adults enrolled in the Survey of Activity, Fitness, and Exercise (SAFE). PA was measured by: 1) Caltrac accelerometers worn 48-hours every 26 days for one year; 2) concurrent 48-hour PA records (PARs); and 3) a corresponding series of four-week PA histories (FWH). Repeated measures regression analyses were used to analyze the data. RESULTS: PA tended to be slightly higher in the summer months as compared with the winter months, but this seasonality explained little of the intra-individual variation. The intra-individual standard deviation (SD) estimated for the FWH (180 MET-min(d(-1))) was 39% of the mean annual MET-min(d(-1)), as compared with the Caltrac (163 MET-mind(d(-1)) or 9%) and PAR (259 MET-min(d(-1)) or 11%). Given the intra-individual variation, three repeated observations of the FWH, six Caltrac, or nine PAR over the course of the year were needed to achieve 80% reliability in estimation of mean annual PA. CONCLUSIONS: Intra-individual variation in PA is substantial and must be accounted for in estimates of usual PA.

Adult↗
PubMed1999

Microsurgical reconstruction of extensive scalp defects.

Large, full-thickness scalp defects represent a reconstructive challenge that has benefitted greatly from the introduction of microsurgical techniques. The authors review their experience with 16 patients with acquired defects of the scalp for which local or regional reconstructive options were unavailable. The mean age at the time of operation was 44.8 years. Nine patients underwent resection of malignant scalp lesions, followed immediately by free-flap coverage. Six patients required revision procedures for unstable scar as a result of prior trauma (2), old scalp avulsions (2), and multiple intracranial procedures (2). The remaining patient underwent replantation of an acutely avulsed scalp. The free-flap donor sites utilized included latissimus (6), scapular (3), radial forearm (2), rectus abdomnis (2), and omentum (2). Vein grafts were required in four cases. All flaps survived, although one required anastomotic revision and skin grafting for superficial loss. Additional complications were limited to seromas at two latissimus donor sites. Tumor control rates were poor, with all malignancy-associated defects having persistent disease or recurring soon after surgery. All patients eventually achieved full defect coverage. The authors conclude that microsurgical reconstruction is a reliable option for providing stable coverage of large, complex, scalp defects.

Adolescent↗
PubMed1999

Secondary school tobacco policy and prevention curricula in South Carolina.

The primary purpose of this study was to describe tobacco control policy in secondary schools in South Carolina, and sanctions imposed on students for violation of these policies; and to explore potential associations between policies and sanctions. A secondary purpose was to explore the use of tobacco education curricula in the state. This study employed a cross-sectional design in which two surveys were mailed to all secondary schools in South Carolina (n = 437): the School Principal Questionnaire (SPQ) and the Lead Health Education Teacher Questionnaire (LHETQ). The SPQ elicited information about tobacco control policies and the sanctions imposed on violators of such policies. The LHETQ was sent to lead health education teachers to elicit information about use of packaged curricula addressing tobacco use and prevention. Over 95% of respondents reported having school policies that prohibited use of tobacco inside buildings, and explicitly prohibited the use of cigarettes for students anywhere on school grounds. Sanctions imposed for violation of tobacco policy were severe. For a second offense, nearly 68% of students were suspended out-of-school or expelled, and for a third offense, almost 28% of students were expelled. There is some evidence to suggest that more stringent policies were associated with more severe sanctions. Cessation from tobacco programs were rarely used as a sanction, and in fact, tobacco education curricula were rarely used by health education teachers. In South Carolina secondary schools, tobacco policies are prevalent. Student violators of such policies are punished by means that potentially detract from their educational experience (e.g., out-of-school suspension, expulsion). It is recommended that school administrators and school health education teachers implement tobacco cessation programs as part of appropriate sanctions for violations of school tobacco use policy.

Adolescent↗
PubMed1999

Development of a questionnaire to assess knowledge, attitudes, and behaviors in American Indian children.

One aim of the Pathways study is to improve the knowledge, attitudes, and behaviors of American Indian children in grades 3-5 regarding physical activity and diet in. This article describes the development of a culturally sensitive, age-appropriate questionnaire to assess these variables. The questionnaire was designed to be administered in the classroom in two 30-min sessions. Questions were developed to assess 4 key areas: physical activity, diet, weight-related attitudes, and cultural identity. Potential questions were written after review of relevant literature and existing questionnaires. Numerous and extensive revisions were made in response to input from structured, semistructured, and informal data collection. Questions were pretested in 32 children in grades 3-5 by using semistructured interviews. Test-retest reliability and the internal consistency of scales were examined in 371 fourth-grade children and subsequently in 145 fourth-grade children. Questions were reviewed by American Indians from the communities involved in the Pathways study several times during the developmental process. The process described here serves as one model for the development of a culturally appropriate tool to assess knowledge, attitudes, and behaviors in American Indian children.

Asian People↗
PubMed1999

Physical activity assessment in American Indian schoolchildren in the Pathways study.

The objective of the Pathways physical activity feasibility study was to develop methods for comparing type and amount of activity between intervention and control schools participating in a school-based obesity prevention program. Two methods proved feasible: 1) a specially designed 24-h physical activity recall questionnaire for assessing the frequency and type of activities and 2) use of a triaxial accelerometer for assessing amount of activity. Results from pilot studies supporting the use of these methods are described. Analyses of activity during different segments of the day showed that children were most active after school. The activities reported most frequently (e.g., basketball and mixed walking and running) were also the ones found to be most popular in the study population on the basis of formative assessment surveys. Both the physical activity recall questionnaire and the triaxial accelerometer methods will be used to assess the effects of the full-scale intervention on physical activity.

Asian People↗
PubMed1999

Pathways family intervention for third-grade American Indian children.

The goal of the feasibility phase of the Pathways family intervention was to work with families of third-grade American Indian children to reinforce health behaviors being promoted by the curriculum, food service, and physical activity components of this school-based obesity prevention intervention. Family behaviors regarding food choices and physical activity were identified and ranked according to priority by using formative assessment and a literature review of school-based programs that included a family component. The family intervention involved 3 primary strategies designed to create an informed home environment supportive of behavioral change: 1) giving the children "family packs" containing worksheets, interactive assignments, healthful snacks, and low-fat tips and recipes to take home to share with their families; 2) implementing family events at the school to provide a fun atmosphere in which health education concepts could be introduced and reinforced; and 3) forming school-based family advisory councils composed of family members and community volunteers who provided feedback on Pathways strategies, helped negotiate barriers, and explored ideas for continued family participation. For strategy 2, a kick-off Family Fun Night provided a series of learning booths that presented the healthful behaviors taught by Pathways. At an end-of-year Family Celebration, a healthy meal was served, students demonstrated newly learned Pathways activities, and certificates were presented in recognition of completion of the Pathways curriculum. Based on evaluation forms and attendance rosters, strategies 1 and 2 were more easily implemented and better received than strategy 3. Implications for developing family involvement strategies for intervention programs are discussed.

Adult↗