Parental Influences on Physical Activity and Screen Time among Preschool Children from Low-Income Families in Brazil.

Background: Children from low-middle income countries (LMIC) are disproportionately affected by obesity, and low physical activity (PA) and high screen time (ST) are major contributors. Parents are key influencers on children's PA and ST, yet, no study has investigated relationships between parenting practices and children's PA and ST in LMIC families. This study examined parental influences on PA and ST among preschool-aged children from low-income families in Brazil. Methods: Parents completed a validated, culturally adapted interviewer-administered survey assessing child ST and parenting practices. Child sedentary time, total movement, and energetic play were measured by accelerometery. Results: Data were available on 77 parent-child dyads [mean age 4.6 years (standard deviation = 0.8), 53% male, and 41% mixed-race]. Parenting practices associated with greater PA were use of PA to reward/control behavior (rho = 0.34-0.49), limiting or monitoring ST (rho = 0.30), explicit modeling/enjoyment of PA (rho = 0.24), verbal encouragement for PA (rho = 0.30), and importance and value of PA (rho = 0.24-0.38; p < 0.05). Parenting practices associated with higher ST were rules around active play indoor (rho = 0.23), use of ST to reward/control behavior (rho = 0.30), exposure to screens (rho = 0.40), and explicit modeling/enjoyment of ST (rho = 0.50; p < 0.05). Conclusion: Recognized parenting practices such as explicit modeling of PA and ST, monitoring and limiting ST, and rules and restrictions about PA and ST are associated with young children's PA and ST in low-income Brazilian families. The findings identify potential targets for family-based interventions to promote healthy lifestyle behaviors and prevent childhood obesity.

Psychometric properties of instruments to measure parenting practices and children's movement behaviors in low-income families from Brazil.

BACKGROUND: Childhood obesity has increased remarkably in low and middle-income (LMIC) countries. Movement behaviors (physical activity, screen time, and sleep) are crucial in the development of overweight and obesity in young children. Yet, few studies have investigated the relationship between children's movement behaviors and parenting practices because validated measures for use among families from LMIC are lacking. This study evaluated the psychometric properties of previously validated measures of young children's physical activity, screen time, and sleep and parenting practices, translated and culturally adapted to Brazilian families. METHODS: A total of 78 parent-child dyads completed an interviewer-administered survey twice within 7 days. Child physical activity, sedentary time and sleep were concurrently measured using a wrist-worn accelerometer. Internal consistency and test-retest reliability was assessed using McDonald's Omega and Intraclass Correlation Coefficients (ICC's). Concurrent validity was evaluated by calculating Spearman correlations between parent reported child behaviors and accelerometer measured behaviors. RESULTS: Seventeen of the 19 parenting practices scales exhibited acceptable internal consistency reliability (Ω ≥ 0.70). Test-retest reliability ICC's were acceptable and ranged from 0.82 - 0.99. Parent reported child physical activity was positively correlated with objectively measured total movement (rho= 0.29 - 0.46, p < .05) and energetic play (rho= 0.29 - 0.40, p < .05). Parent reported child screen time was positively correlated with objectively measured sedentary time; (rho = 0.26, p < .05), and inversely correlated with total movement (rho = - 0.39 - - 0.41, p < .05) and energetic play (rho = - 0.37 - - 0.41, p < .05). Parent reported night-time sleep duration was significantly correlated with accelerometer measured sleep duration on weekdays (rho = 0.29, p < .05), but not weekends. CONCLUSIONS: Measurement tools to assess children's movement behaviors and parenting practices, translated and culturally adapted for use in Brazilian families, exhibited acceptable evidence of concurrent validity, internal consistency, and test-retest reliability.

Cross-Cultural Adaptation of Instruments Measuring Children's Movement Behaviors and Parenting Practices in Brazilian Families.

Childhood obesity is a global problem, disproportionately affecting children in low-to-middle income countries (LMIC). Despite this evidence, no previous study has adapted instruments measuring children's movement behaviors and associated parenting practices for use in LMIC families. This study reports the results of a cross-cultural adaptation of previously validated measures of children's movement behaviors and parenting practices in economically disadvantaged Brazilian families. Study 1 involved translation of the instruments from English to Portuguese. A team of translators (fluent in both English and Portuguese) and researchers followed established procedures for translating measurement scales, identifying problematic items, and reaching consensus on discrepancies. Study 2 involved cognitive interviews with 24 parents from urban and rural North-eastern Brazil addressing the format, content, and clarity of the items. Half the parents provided feedback on the first 33 items of the questionnaire, with the remaining parents providing feedback on the final 29 items. Notes were recorded during the interview and parents' feedback summarized in a report. In the translation and back-translation, 15 discrepancies were identified. These were mostly due to multiple Portuguese words having the same meaning in English. The research team discussed these discrepancies and consensus was reached to ensure that the concepts depicted in the Portuguese version were consistent with the English version. In the cognitive interviews, parents identified minor problems with item comprehension resulting in minor adaptations to response options, recall period, and format of the questionnaire. The process of translation and cognitive interviews conducted in Brazilian families resulted in an appropriate cultural adaptation of scales measuring children's movement behaviors and parenting practices. Future studies should evaluate the validity and reliability of the measures in LMIC families.

Parental influences on screen time and weight status among preschool children from Brazil: a cross-sectional study.

BACKGROUND: Little is known about the influence of parental attributes and parental screen time behaviours on pre-schooler's screen time and weight status in low-to-middle income countries. The purpose of this study was to examine the relationships between parental screen time, parental self-efficacy to limit screen time, child screen time and child BMI in preschool-aged children in Brazil. METHODS: Three hundred eighteen parent-child dyads from Caruaru, Brazil completed a survey measuring sociodemographic data, weekday and weekend screen time, and parental self-efficacy for limiting screen time. Height and weight were measured and used to derive BMI and BMI percentile. Observed variable path analysis was used to evaluate the relationships between the parental and child variables. RESULTS: Analyses were conducted for screen time on weekdays and weekend days. Parental screen time was positively associated with child screen time, either directly (weekdays = ß = 0.27, p < 0.001, weekends = ß = 0.24, p < 0.001) or indirectly through reduced self-efficacy to limit child screen time (weekdays = ß = - 0.15, p = 0.004, weekends = ß = - 0.16, p = 0.004). After controlling for household income, parental occupation, and parental BMI, greater child screen time on weekends, not weekdays, was associated with higher child BMI percentile (ß = 0.15, p = 0.006). CONCLUSIONS: Parental screen time and self-efficacy to limit screen time are important influences on child screen time and weight status in pre-schoolers from Brazil. Reducing parental screen time and increasing parental confidence to limit screen time may be effective strategy to prevent overweight in Brazilian pre-schoolers.

Decision Trees for Detection of Activity Intensity in Youth with Cerebral Palsy.

PURPOSE: To develop and test decision tree (DT) models to classify physical activity (PA) intensity from accelerometer output and Gross Motor Function Classification System (GMFCS) classification level in ambulatory youth with cerebral palsy (CP) and compare the classification accuracy of the new DT models to that achieved by previously published cut points for youth with CP. METHODS: Youth with CP (GMFCS levels I-III) (N = 51) completed seven activity trials with increasing PA intensity while wearing a portable metabolic system and ActiGraph GT3X accelerometers. DT models were used to identify vertical axis (VA) and vector magnitude (VM) count thresholds corresponding to sedentary (SED) (<1.5 METs), light-intensity PA (LPA) (≥1.5 and <3 METs) and moderate-to-vigorous PA (MVPA) (≥3 METs). Models were trained and cross-validated using the "rpart" and "caret" packages within R. RESULTS: For the VA (VA_DT) and VM DT (VM_DT), a single threshold differentiated LPA from SED, whereas the threshold for differentiating MVPA from LPA decreased as the level of impairment increased. The average cross-validation accuracies for the VC_DT were 81.1%, 76.7%, and 82.9% for GMFCS levels I, II, and III. The corresponding cross-validation accuracies for the VM_DT were 80.5%, 75.6%, and 84.2%. Within each GMFCS level, the DT models achieved better PA intensity recognition than previously published cut points. The accuracy differential was greatest among GMFCS level III participants, in whom the previously published cut points misclassified 40% of the MVPA activity trials. CONCLUSIONS: The GMFCS-specific cut points provide more accurate assessments of MVPA levels in youth with CP across the full spectrum of ambulatory ability.

Physical Activity, Obesity Status, and Blood Pressure in Preschool Children.

OBJECTIVE: To examine the combined effects of physical activity and weight status on blood pressure (BP) in preschool-aged children. STUDY DESIGN: The sample included 733 preschool-aged children (49% female). Physical activity was objectively assessed on 7 consecutive days by accelerometry. Children were categorized as sufficiently active if they met the recommendation of at least 60 minutes daily of moderate-to-vigorous physical activity (MVPA). Body mass index was used to categorize children as nonoverweight or overweight/obese, according to the International Obesity Task Force benchmarks. BP was measured using an automated BP monitor and categorized as elevated or normal using BP percentile-based cut-points for age, sex, and height. RESULTS: The prevalence of elevated systolic BP (SBP) and diastolic BP was 7.7% and 3.0%, respectively. The prevalence of overweight/obese was 32%, and about 15% of children did not accomplish the recommended 60 minutes of daily MVPA. After controlling for age and sex, overweight/obese children who did not meet the daily MVPA recommendation were 3 times more likely (OR 3.8; CI 1.6-8.6) to have elevated SBP than nonoverweight children who met the daily MVPA recommendation. CONCLUSIONS: Overweight or obese preschool-aged children with insufficient levels of MVPA are at significantly greater risk for elevated SBP than their nonoverweight and sufficiently active counterparts.

d-f hybridization and quantum criticality in weakly-itinerant ferromagnets.

We investigate the unusual magnetic, thermodynamic and transport properties of nearly-critical, weakly-itinerant ferromagnets with the general formula UTX, where T=Rh, Co and X=Ge, Si. As a unique feature of these systems, we show how changes in the V(df) hybridization, which controls their proximity to a ferromagnetic instability, determine the evolution of the ground state magnetization, M(0), the Curie temperature, T(C), the density of states at the Fermi level, N(E(F)), the T(2) resistivity coefficient, A, and the specific heat coefficient, γ. The universal aspect of our findings comes from the dependence on only two parameters: the transition metal T(d) bandwidth, W(d), and the distance between the T(d) and U(f) band centers, C(T(d)) - C(U(f)). We discuss our results in connection to data for URh(1-x)Co(x)Ge.

Association of the intronic polymorphism rs891512 (G24943A) of the endothelial nitric oxide synthase gene with hypertension in Chilean type 2 diabetes patients.

We investigated two single nucleotide polymorphisms of the NOS3 gene in type 2 diabetic patients (n=93) and healthy non-diabetic controls (n=76) and their relationship with smoking habits, body mass index, hypertension and dyslipidemia. Results showed that eNOS polymorphism rs891512 (G24943A) is associated with hypertension in Chilean individuals (p<0.05).

Advanced pubertal status at age 11 and lower physical activity in adolescent girls.

OBJECTIVE: To examine the relationship between pubertal timing and physical activity. STUDY DESIGN: A longitudinal sample of 143 adolescent girls was assessed at ages 11 and 13 years. Girls' pubertal development was assessed at age 11 with blood estradiol levels, Tanner breast staging criteria, and parental report of pubertal development. Girls were classified as early maturers (n = 41) or later maturers (n = 102) on the basis of their scores on the 3 pubertal development measures. Dependent variables measured at age 13 were average minutes/day of moderate to vigorous and vigorous physical activity as measured by the ActiGraph accelerometer. RESULTS: Early-maturing girls had significantly lower self-reported physical activity and accumulated fewer minutes of moderate to vigorous and vigorous physical activity and accelerometer counts per day at age 13 than later maturing girls. These effects were independent of differences in percentage body fat and self-reported physical activity at age 11. CONCLUSION: Girls experiencing early pubertal maturation at age 11 reported lower subsequent physical activity at age 13 than their later maturing peers. Pubertal maturation, in particular early maturation relative to peers, may lead to declines in physical activity among adolescent girls.

Incidence of tuberculosis among a cohort of tuberculin-positive refugees in Australia: reappraising the estimates of risk.

Estimates of the lifetime risk of tuberculosis have varied widely and may not be applicable in all current settings. The aim of this study was to measure the incidence of reactivation of latent tuberculosis in a cohort of 15,489 predominantly Southeast Asian refugees aged 12 yr and over who arrived in Sydney, Australia during the period 1984 to 1994 and who had a clear chest X-ray on arrival. Tuberculin skin test (TST) reaction size and the presence of a BCG scar were recorded at entry. Incident cases of tuberculosis, occurring before June 1998, were identified by record linkage analysis with confirmatory review of case notes. There were 122 cases of tuberculosis over an average 10.3 yr of follow-up (crude annual incidence, 76.2/100,000). There was a linear increase in risk with increasing TST reaction size above 10 mm. The risk, and the relation of risk to TST reaction size, were unrelated to BCG scar status. Among those whose initial TST reaction was >/= 15 mm, the annual incidence rate in the first 3 yr was 213 (95% CI, 150 to 300) per 100,000 person-years and in the subsequent 10 yr the rate averaged 122 (95% CI, 90 to 165) per 100,000 person-years. The observed rates are similar to those estimated in the general population of the United States in the 1950s and 1960s. Further data on the prognosis of tuberculosis and the effects of isoniazid preventive therapy in Southeast Asian migrants to Western countries are required to inform policy and practice for the prevention of tuberculosis in this population.

[New classification and diagnostic criteria for diabetes mellitus]. / Nueva clasificación y criterios diagnósticos de la diabetes mellitus.

The new Classification and Diagnostic Criteria for Diabetes Mellitus (DM), prepared by a group of experts from the American Diabetes Association is presented and analyzed. On an etiopathogenic basis, it designates Insulin Dependent and Non Insulin Dependent as Type 1 and Type 2 respectively. It specifies DM having specific known causes. It maintains Gestational Diabetes and Glucose Intolerance and adds the Impaired Fasting Glucose Condition. It recommends fasting plasma glucose for search and diagnosis, and lowers the level to > or = 126 mg/dl instead of > or = 140 mg/dl, due to its association with chronical complications of DM. It maintains the diagnostic criteria of random and post charge glycemia > or 200 mg/dl. It does not alter the glucose intolerance figure (140-200 mg/dl in OGTT) and introduces fasting abnormality > or = 110 and < 126 mg/dl. It encourages the search with fasting glucose every 3 years in individuals aged over 45, and at more frequent intervals in younger individuals with high risk factors. Analysis of the report allows to conclude that, although the classification does not introduce any significant change in daily clinical use, its pathogenic orientation makes future innovations possible. The preferential use of fasting glucose > or = 126 mg/dl for diagnosis of DM has theoretical basis and practical advantages. Identification of individuals with impaired fasting glucose allows to detect, in a simple manner, a high risk group in which to start preventive measures. However, there is a percentage of cases which are not diagnosed by fasting glycemia, but are diagnosed by OGTT, therefore the latter should not be discarded.

Cloning of a complementary DNA encoding an Ambystoma mexicanum metallothionein, AmMT, and expression of the gene during early development.

We have used a polymerase chain reaction strategy to isolate a metallothionein (MT) cDNA from the amphibian Ambystoma mexicanum (axolotl). This cDNA is 875-bp long and encodes a 60 amino acid protein, AmMT, typical for family 1 MTs. It contains 20 cysteine (Cys) residues that can be aligned with those of other vertebrate MTs. The overall structure of the protein is unique among vertebrates in having only two amino acid residues before the first Cys at the amino-terminal end. Northern analyses showed that AmMT is expressed throughout embryogenesis, giving rise to three mRNA species of 650, 750, and 1,600 nucleotides (nt). The 750 and 1,600 nt transcripts appear to result from differential use of polyadenylation signals, whereas the 650 nt RNA could arise from deadenylation of the 750-nt transcript. Both the 750- and 1,600-nt RNAs were presented in embryos before the mid-blastula transition (MBT). After the MBT, the 750-nt RNA was replaced by the 650-nt RNA which was gradually degraded to undetectable levels in post-neurulation embryos. Levels of the 1,600-nt transcript increased at gastrulation and reach a maximum in Stage 30 embryos. In adult animals, levels of the 750-nt RNA were high in liver and testes, and very low in lung, gut, skin, and oviducts, whereas levels of the 1,600-nt transcript were similar and moderately elevated in all tissues examined. In contrast, in Xenopus laevis, Northern analysis did not detect XIMT-A mRNA in embryos before late neurulation (Stage 24). XIMT-A mRNA levels then increased sharply in Stage 36 hatched embryos at levels similar to those found in adult livers. These results show that AmMT presents a unique expression pattern among metazoans being transcribed as two transcripts differing in the length of their 3' untranslated regions, the levels of which vary during embryogenesis and in adult tissues.

Resistance to Onchocerca volvulus: differential cellular and humoral responses to a recombinant antigen, OvMBP20/11.

Persons putatively immune (PI) to Onchocerca volvulus (Ov) infection were identified in Ecuador on the basis of epidemiologic, clinical, and parasitologic findings. Immune responses of PI subjects to a recombinant onchocercal protein, OvMBP20/11, were determined and compared with those of a comparable infected (INF) group from the same Ov-endemic area. PI subjects had significantly less antibody reactivity to this molecule; however, not all INF subjects had an antibody response. IgG1 and IgG4 were the predominant IgG subclasses induced to this molecule, and the amount of IgG1 produced was the only significant difference between the PI and INF groups. In contrast to the antibody responses, proliferative responses to OvMBP20/11 were significantly higher in PI than in INF subjects. Cytokine analysis of peripheral blood mononuclear cell culture supernatants revealed that INF subjects produced significantly more interleukin-10 in response to OvMBP20/11 than did PI subjects. This antigen induced few other cytokines, and there were no differences between study groups.

Isotype-specific characterization of antibody responses to Onchocerca volvulus in putatively immune individuals.

Isotype/subclass-specific antibody responses to adult Onchocerca volvulus extract (OvAg) were assessed by both ELISA and immunoblotting for a group of putatively immune individuals (PIs, n = 29) from a hyperendemic area in Ecuador and for a group of infected individuals (INFs, n = 470) from the same regions. As a group, the PIs have been previously shown to possess lower levels of OvAg specific IgG1, IgG2, IgG3 and IgG4 than INF's but semi-quantitative analysis revealed that the relative proportions of these subclasses differs between the two groups. The IgG of the PI group contained a higher proportion of IgG3 and a lower proportion of IgG4 than the INF group. The frequency distribution of IgG3 responses was similar for the PI and INF groups. The frequency distributions for IgG1, IgG4 and IgE were significantly different between the PI and INF groups. A subgroup of the PIs were identified from frequency distributions and multivariate plots of individual isotype responses as having antibody responses (mainly IgG4) possibly indicative of cryptic infection. High IgE responses were exclusive to INF individuals, and a rare response type of high IgG3 with negligible levels of other isotypes/subclasses was seen only in the PI group. However, the majority of the PIs had negligible responses for all antibody classes. Immunoblots demonstrated no obvious differences in qualitative recognition between the PIs and INFs.

Structural requirements of platelet chemokines for neutrophil activation.

Using recombinantly expressed proteins and synthetic peptides, we examined the structural/functional features of the platelet chemokines, neutrophil-activating peptide-2 (NAP-2) and platelet factor 4 (PF4); that were important in their activation of neutrophils. Previous studies with the chemokine interleukin-8 (IL-8) had shown that the N-terminal region preceding the first cysteine residue was critical in defining neutrophil-activating properties. We examined whether NAP-2 and PF4 had similar structural requirements. In the Ale-glu-leu-arg (AELR) N-terminus of NAP-2, substitution of E or R abolished Ca2+ mobilization and elastase secretion. Unlike the parent molecule PF4, AELR/PF4, the hybrid formed by replacing the N-terminal sequence of PF4 before the first cysteine residue with the homologous sequence of NAP-2, stimulated Ca2+ mobilization and elastase secretion. Furthermore, the effect of amino acid substitutions in the ELR motif differed from those seen with NAP-2 in that conserved substitutions of E or R in NAP-2 abolished activity, but only reduced neutrophil activation in the hybrid. These studies show that just as with IL-8, the N-termini of NAP-2 and PF4 are critical for high-level neutrophil-activating function. Desensitization studies provided information on receptor binding. NAP-2, which binds almost exclusively to the type 2 IL-8 receptor (IL-8R), did not desensitize neutrophils to activation by IL-8 because IL-8 could bind to and activate via both type 1 and 2 IL-8R. AELR/PF4 appears to bind to both types of receptors because it desensitized neutrophils to NAP-2 activation; but was not desensitized by NAP-2, and because it desensitized to and was desensitized by IL-8. Thus, although NAP-2 and AELR/PF4 share approximately 60% amino acid homology, they have different receptor affinities. Studies were performed to define the role of the C-termini of these platelet chemokines in receptor binding. Heparin and a monoclonal antibody specific for the heparin-binding domain of PF4 both inhibited Ca2+ mobilization and elastase release, further suggesting that the C-terminus of these chemokines is important in receptor binding. Synthetic NAP-2(51-70) failed to mobilize Ca2+, whereas PF4(47-70) and PF4(58-70) induced Ca2+ mobilization and secretion of elastase at high concentrations. Pertussis toxin inhibited neutrophil activation by 40% to 50%, establishing a role for G-protein-coupled receptors such as the IL-8Rs in activation by the PF4 C-terminal peptides.(ABSTRACT TRUNCATED AT 400 WORDS)

Partitioning of inorganic nitrogen assimilation between the roots and shoots of cerrado and forest trees of contrasting plant communities of South East Brasil.

Woody plants growing in cerrado and forest communities of south-east Brasil were found to have low levels of nitrate reductase activity in their leaves suggesting that nitrate ions are not an important nitrogen source in these communities. Only in the leaves of species growing in areas of disturbance, such as gaps and forest margins, were high levels of nitrate reductase present. When pot-grown plants were supplied with nitrate, leaves and roots of almost all species responded by inducing increased levels of nitrate reductase. Pioneer or colonizing species exhibited highest levels of nitrate reductase and high shoot: root nitrate reductase activities. Glutamine synthetase, glutamate synthase and glutamate dehydrogenase were present in leaves and roots of the species examined.15N-labelled nitrate and ammonium were used to compare the assimilatory characteristics of two species:Enterolobium contortisiliquum, with a high capacity to reduce nitrate, andCalophyllum brasiliense, of low capacity. The rate of nitrate assimilation in the former was five times that of the latter. Both species had similar rates of ammonium assimilation. Results for eight species of contrasting habitats showed that leaf nitrogen content increased in parallel with xylem sap nitrogen concentrations, suggesting that the ability of the root system to acquire, assimilate or export nitrate determines shoot nitrogen status. These results emphasise the importance of nitrogen transport and metabolism in roots as determinants of whole plant nitrogen status.

Operative venodilation: a previously unsuspected factor in the cause of postoperative deep vein thrombosis.

Intraoperative venodilation in veins distant from the site of operation has been shown to occur in animals and has been directly correlated with focal venous endothelial damage. This exposure of subendothelial collagen could serve as initiation sites for thrombus formation. This study tests the hypothesis that human beings (1) significant operative venodilation occurs and that it correlates with postoperative deep venous thrombosis (DVT); (2) operative venodilation can be pharmacologically controlled; and (3) this control reduces the incidence of postoperative DVT. Twenty-one patients undergoing total hip replacement had their contralateral cephalic vein continuously monitored with modified ultrasonographic instrumentation, with a continuous on-line recorder graphing venous diameter. Patients were randomly assigned to receive 0.5 mg of dihydroergotamine and 5000 U of heparin (DHE/Hep) for prophylaxis or placebo, with investigators "blinded" Postoperatively, all patients underwent ascending phlebography. Patients in whom postoperative DVT developed (11) had a mean operative venodilation of 28.9% +/- 3.93%, and those in whom DVT did not develop (10) had a mean venodilation of 11.6% +/- 1.55% (p = 0.001). Only 17% (2/12) dilating less than 20% baseline diameter had DVT compared with 100% (9/9) dilating greater than 20% of baseline diameter (p = 0.002). Patients receiving venotonic agent DHE had significantly less venodilation and DVT (p less than 0.001) compared with patients receiving the placebo. Patients who had DVT and whose veins dilated greater than 20% were older than patients who did not have DVT and whose veins minimally dilated: p = 0.04 and p = 0.07, respectively. Although there was a trend toward increased venoconstriction in patients receiving DHE/Hep (p = 0.09), there was no correlation of venoconstriction with ultimate thrombotic outcome. Maximal venodilation occurs during handling of soft tissue (muscle), and this occurs significantly sooner than maximal venoconstriction, which occurs during bone manipulation. We conclude that excessive operative venodilation is a new and important etiologic factor that leads to postoperative DVT. Operative venodilation can be pharmacologically controlled with the venotonic agent DHE. The combination DHE/Hep reduces postoperative DVT by the reduction of operative venodilation in the presence of low doses of an anticoagulant. These findings offer a new approach for predicting postoperative DVT and an object rationale for developing effective prophylaxis.