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History Variables (history + variable)
Selected AbstractsHatching fraction and timing of resting stage production in seasonal environments: effects of density dependence and uncertain season lengthJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 3 2001M. Spencer Many organisms survive unfavourable seasons as resting stages, some of which hatch each favourable season. Hatching fraction and timing of resting stage production are important life history variables. We model life cycles of freshwater invertebrates in temporary pools, with various combinations of uncertain season length and density-dependent fecundity. In deterministic density-independent conditions, resting stage production begins suddenly. With uncertain season length and density independence, resting stage production begins earlier and gradually. A high energetic cost of resting stages favours later resting stage production and a lower hatching fraction. Deterministic environments with density dependence allow sets of coexisting strategies, dominated by pairs, each switching suddenly to resting stage production on a different date, usually earlier than without density dependence. Uncertain season length and density dependence allow a single evolutionarily stable strategy, around which we observe many mixed strategies with negatively associated yield (resting stages per initial active stage) and optimal hatching fraction. [source] Interpreting Urine Drug Tests: Prevalence of Morphine Metabolism to Hydromorphone in Chronic Pain Patients Treated with MorphinePAIN MEDICINE, Issue 7 2008Ajay D. Wasan MD ABSTRACT Objective., Pain medicine practitioners frequently use urine drug testing (UDT) to monitor adherence to opioid therapy. It can be difficult to interpret a result as normal or abnormal in relation to which opioid compounds are expected to be found in the urine. We investigated whether hydromorphone may be a metabolite of morphine normally appearing in UDT of patients prescribed morphine. Design., This is a retrospective case-control study of urine toxicology results in pain patients taking only morphine. Inclusion criteria included urine results positive for morphine only (controls) or morphine and hydromorphone (cases). Demographic and medical history variables, and any history of aberrant drug behavior were recorded and related to the presence or absence of hydromorphone in the urine. Results., Hydromorphone was present in 21 of 32 cases (66%), none of whom had a history of aberrant drug behavior. Positive cases occurred more frequently in women, in those taking higher daily doses of morphine, and in those with higher urine morphine concentrations (P < 0.05). Only morphine urine concentration was a significant predictor of the hydromorphone metabolite in a logistic regression model (P < 0.05). Conclusions., Hydromorphone is likely a minor metabolite of morphine, normally appearing in the UDT of patients taking morphine. This finding assists in determining whether a UDT result is normal or abnormal, and subsequently whether a patient is compliant with opioid therapy. This observation should be confirmed by a prospective study in a controlled environment. Variables such as gender, morphine dose, morphine urine concentration, and genetic determinants of morphine metabolism should be investigated further. [source] Substance use disorders among adolescents with bipolar spectrum disordersBIPOLAR DISORDERS, Issue 4 2008Benjamin I Goldstein Objective:, We set out to examine the prevalence and correlates of substance use disorders (SUD) in a large sample of adolescents with bipolar disorder (BP). Methods:, Subjects were 249 adolescents ages 12 to 17 years old who fulfilled DSM-IV criteria for bipolar I disorder [(BPI), n = 154], or bipolar II disorder [(BPII), n = 25], or operationalized criteria for BP not otherwise specified [(BP NOS), n = 70], via the Schedule for Affective Disorders and Schizophrenia for School-Aged Children (K-SADS). As part of the multi-site Course and Outcome of Bipolar Youth study, demographic, clinical, and family history variables were measured via intake clinical interview with the subject and a parent/guardian. Results:, The lifetime prevalence of SUD among adolescents with BP was 16% (40/249). Results from univariate analyses indicated that subjects with, as compared to without, SUD were significantly less likely to be living with both biological parents, and that there was significantly greater lifetime prevalence of physical abuse, sexual abuse, suicide attempts, conduct disorder, and posttraumatic stress disorder among subjects with SUD. Subjects with SUD reported significantly greater 12-month prevalence of trouble with police, and females with SUD reported significantly greater 12-month prevalence of pregnancy and abortion. Significant predictors of SUD in a logistic regression model included living with both biological parents (lower prevalence), conduct disorder and suicide attempts (increased prevalence). In logistic regression analyses controlling for demographic differences and conduct disorder, SUD remained significantly associated with trouble with police, whereas the association of SUD with pregnancy and abortion was reduced to a statistical trend. The prevalence of SUD was not significantly different among child- versus adolescent-onset BP subjects. Conclusions:, SUD among adolescents with BP is associated with profound hazards including suicide attempts, trouble with police, and teenage pregnancy and abortion. [source] Substance abuse in bipolar disorderBIPOLAR DISORDERS, Issue 4 2001Frederick Cassidy Background: High rates of substance abuse have been reported in the general population, with males more often affected than females. Although high rates of substance abuse have also been reported in bipolar patients, the relationship between substance abuse and bipolar disorder has not been well characterized. Methods: Substance abuse histories were obtained in 392 patients hospitalized for manic or mixed episodes of bipolar disorder and rates of current and lifetime abuse calculated. Analyses comparing sex, subtype (manic vs. mixed) and clinical history variables were conducted. Results: Rates of lifetime substance abuse were high for both alcohol (48.5%) and drugs (43.9%). Nearly 60% of the cohort had a history of some lifetime substance abuse. Males had higher rates of abuse than females, but no differences in substance abuse were observed between subjects in manic and mixed bipolar states. Rates of active substance abuse were lower in older age cohorts. Subjects with a comorbid diagnosis of lifetime substance abuse had more psychiatric hospitalizations. Conclusions: Substance abuse is a major comorbidity in bipolar patients. Although rates decrease in older age groups, substance abuse is still present at clinically important rates in the elderly. Bipolar patients with comorbid substance abuse may have a more severe course. These data underscore the significance of recognition and treatment of substance abuse in bipolar disorder patients. [source] Assessment of risk for the development of pre-eclampsia by maternal characteristics and uterine artery DopplerBJOG : AN INTERNATIONAL JOURNAL OF OBSTETRICS & GYNAECOLOGY, Issue 6 2005Aris T. Papageorghiou Objective To develop a method for the estimation of patient-specific risk for the development of pre-eclampsia by combining maternal history and uterine artery Doppler. Design Prospective multicentre observational study. Setting Antenatal clinics in seven hospitals in the UK and three overseas centres. Population Unselected women with singleton pregnancies attending for routine antenatal care. Methods Doppler studies of the uterine arteries were performed using colour flow mapping and pulsed wave Doppler at 23 weeks of gestation. The mean pulsatility index (PI) of the two uterine arteries was calculated. Doppler and maternal history variables were combined to develop a model for risk assessment. The incidence of pre-eclampsia was used to derive the prior risk for this complication. The posterior risk was derived by multiplying the prior odds with likelihood ratios (LRs) derived from independent risk factors identified from the maternal history, and the LR estimated from the heights of the frequency distributions of mean PI in affected and unaffected pregnancies. Main outcome measure Pre-eclampsia. Results There were 17,480 women recruited to the study, in which 17,319 (99.1%) of these Doppler examination of both uterine arteries were completed, and outcome data were available in 16,806 (97.0%). Pre-eclampsia occurred in 369 (2.20%) cases. Significant independent prediction of pre-eclampsia was provided by mean PI, ethnic origin, body mass index (BMI), parity, cigarette smoking, history of hypertension and family or personal history of pre-eclampsia. Models were derived allowing calculation of patient-specific risk for development of pre-eclampsia. For a false-positive rate of 25%, the detection rate of pre-eclampsia by screening using maternal history was 45.3%, with uterine artery Doppler it was 63.1% and with combined assessment it was 67.5%. Conclusions Combining risk factors in the mother's history with Doppler of the uterine arteries allows calculation of patient-specific risk for the development of pre-eclampsia. [source] The Large-Scale Structure of Semantic Networks: Statistical Analyses and a Model of Semantic GrowthCOGNITIVE SCIENCE - A MULTIDISCIPLINARY JOURNAL, Issue 1 2005Mark Steyvers Abstract We present statistical analyses of the large-scale structure of 3 types of semantic networks: word associations, WordNet, and Roget's Thesaurus. We show that they have a small-world structure, characterized by sparse connectivity, short average path lengths between words, and strong local clustering. In addition, the distributions of the number of connections follow power laws that indicate a scale-free pattern of connectivity, with most nodes having relatively few connections joined together through a small number of hubs with many connections. These regularities have also been found in certain other complex natural networks, such as the World Wide Web, but they are not consistent with many conventional models of semantic organization, based on inheritance hierarchies, arbitrarily structured networks, or high-dimensional vector spaces. We propose that these structures reflect the mechanisms by which semantic networks grow. We describe a simple model for semantic growth, in which each new word or concept is connected to an existing network by differentiating the connectivity pattern of an existing node. This model generates appropriate small-world statistics and power-law connectivity distributions, and it also suggests one possible mechanistic basis for the effects of learning history variables (age of acquisition, usage frequency) on behavioral performance in semantic processing tasks. [source] | ||||||||||