Biomedical subjects

J Harezlak

Publications and source records attributed to J Harezlak.

5 recordsLinked to original sources

PubMed2005

Simple fitting of subject-specific curves for longitudinal data.

We present a simple semiparametric model for fitting subject-specific curves for longitudinal data. Individual curves are modelled as penalized splines with random coefficients. This model has a mixed model representation, and it is easily implemented in standard statistical software. We conduct an analysis of the long-term effect of radiation therapy on the height of children suffering from acute lymphoblastic leukaemia using penalized splines in the framework of semiparametric mixed effects models. The analysis revealed significant differences between therapies and showed that the growth rate of girls in the study cannot be fully explained by the group-average curve and that individual curves are necessary to reflect the individual response to treatment. We also show how to implement these models in S-PLUS and R in the appendix.

Biometry↗

PubMed2001

A placebo-controlled trial to evaluate immunomodulatory effects of paricalcitol.

Calcitriol has shown a benefit in various small uncontrolled studies of ex vivo immune function. We hypothesized that paricalcitol, a new vitamin D derivative, will have a positive effect on the immune system with minimal adverse effects on calcium homeostasis. Thirty-one hemodialysis patients not administered vitamin D because of low intact parathyroid hormone (PTH) levels were randomized to placebo or 4 microg of paricalcitol intravenously with the hemodialysis session three times weekly for 12 weeks. Effects on in vivo and ex vivo assessments of immune function were evaluated. All patients achieved the target dose of paricalcitol. Twenty patients were anergic at the start of the study; 4 of 11 patients in the paricalcitol group and 0 of 9 patients in the placebo group converted to reactive (P = 0.09). The in vivo response to standard hepatitis B booster vaccine and in vitro proliferation and release of interleukin-2 (IL-2), IL-6, tumor necrosis factor-alpha, and interferon-gamma from stimulated lymphocytes were not different between the groups. In contrast to clinical immune effects, paricalcitol increased serum calcium levels and decreased PTH and bone alkaline phosphatase levels (all P < 0.05). However, hypercalcemia was infrequent. In vitro experiments showed that paricalcitol led to greater dose-dependent thymidine uptake than calcitriol in lymphocytes isolated from either dialysis patients or control subjects. Paricalcitol has a tendency toward improving delayed hypersensitivity reactions, but did not have other proimmune effects. However, as expected, paricalcitol had significant effects on calcium homeostasis compared with placebo. Thus, patients with low PTH levels are unlikely to experience the proimmune effects of vitamin D therapy without more profound and potentially adverse oversuppression of PTH.

Adult↗

PubMed2001

Sexual behavior among adolescent women at high risk for sexually transmitted infections.

BACKGROUND: The temporal pattern of partners and sexual encounters may be key factors in the acquisition and transmission of sexually transmitted diseases (STDs). Behavior among adolescent women is of particular interest because they frequently have the highest prevalence and incidence of infection. GOAL: To examine coital diary data collected during a 7-month longitudinal study of young women at high risk of STDs and to describe their sexual behaviors, with particular attention to issues of partner sequence and overlap. STUDY DESIGN: A 7-month longitudinal study of young women infected with or having a sexual contact infected with Neisseria gonorrhoeae, Chlamydia trachomatis, or Trichomonas vaginalis attending the STD clinic or one of four neighborhood adolescent health clinics. Data were collected at enrollment and at 1, 3, 5, and 7-month follow-up visits. Coital diaries were kept between visits. RESULTS: The average frequency of coital events was 0.94 per week. The median number of sexual partners during the follow-up period was one, and overlapping of partnerships was an uncommon occurrence. The number of days between the last coital event of a current relationship and the first encounter of a new relationship differed for those choosing a new partner (mean, 20.6 days) and those who returned to a previous partner (mean, 7.9 days; P < 0.001). CONCLUSION: Although at high risk for STDs, high-risk behavior was not common among the study population. Partner choice and the behavior of these partners may be more important elements than personal high-risk behavior in accounting for the high prevalence of sexually transmitted infections among inner-city adolescent women.

Adolescent↗

PubMed2001

Behavior problems in children before first recognized seizures.

OBJECTIVE: It is not known when behavior problems begin in children with epilepsy. The purposes of this study were to: 1) describe the rates of behavior problems in children before their first recognized seizure, 2) determine the differences in behavior problems between children with a first recognized seizure and their healthy siblings, and 3) identify the seizure variables early in the course of the condition that are associated with behavior problems before the first recognized seizure. METHODS: The sample was 224 children (4-14 years old) with a first recognized seizure and their 135 healthy siblings. As part of a larger study, computer-assisted structured telephone interviews were conducted with mothers to measure child and sibling behavior problems. Behavior problems were measured using the Child Behavior Checklist. Frequencies, t tests, correlational analysis, and multiple regression were used to analyze data. RESULTS: Higher than expected rates of behavior problems in the 6 months before the first recognized seizure were found in the total seizure sample, with 32.1% being in the clinical or at-risk range. Rates were highest in children who had previous events that were probably seizures, with 39.5% in the clinical or at-risk range. Children with seizures had significantly higher Total, Internalizing, Attention, Thought, and Somatic Complaints problem scores than their nearest-in-age healthy siblings. Within the seizure sample, variables significantly associated with behavior problems after adjusting for research site, child sex, child age, and socioeconomic status (as represented by primary caregiver's education) were interactions of previously unrecognized seizures with gender and epilepsy syndrome/type of seizures. CONCLUSIONS: Children with previously unrecognized seizures are already at increased risk for behavior problems at the time of their first recognized seizure. These findings are consistent with the hypothesis that in some children, epilepsy is a pervasive condition that includes both seizures and behavioral problems.

Adolescent↗

PubMed2000

Cumulative experience with Haemophilus ducreyi 35000 in the human model of experimental infection.

BACKGROUND AND OBJECTIVES: To study Haemophilus ducreyi pathogenesis, the authors developed an experimental model of infection in human volunteers. The authors analyze their cumulative experience with strain 35000 in the model and calculate the papule and pustule formation rates for estimated delivered doses (EDDs) ranging from 1 cfu to 100 cfu. STUDY DESIGN: Sixty-five volunteers were included in the analysis. A total of 139 sites were available for calculation of the papule formation rate, and 117 sites were available for calculation of the pustule formation rates. RESULTS: The effect of EDDs and probabilities of papule formation and the pustule formation were dose-dependent. Increasing the EDD resulted in a higher probability of papule and pustule formation. CONCLUSION: H ducreyi is highly infectious for humans. Inoculation of an EDD of 1 cfu causes a papule formation rate of 50%. Pustule formation rates are approximately 50% for 27 cfu and 90% for 100 cfu.

Adult↗