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Biomedical subjects

B Michiels

Publications and source records attributed to B Michiels.

10 recordsLinked to original sources
PubMed2001

Lower incidence of the upper respiratory tract infections among general practitioners as compared to their patients.

A retrospective cohort study suggest that general practitioners (GPs) run a significant reduced risk (more then 50%) to develop an upper respiratory tract infection (URTI) with fever compared to their patients. This difference can't be explained by variables such as gender, age, children and particularly young children, vaccination against influenza, presence of chronic illness or allergies, medication taken on a regular basis, smoking habits and regular physical exercise.

Adult↗
PubMed1999

Selection models and pattern-mixture models for incomplete data with covariates.

Most models for incomplete data are formulated within the selection model framework. This paper studies similarities and differences of modeling incomplete data within both selection and pattern-mixture settings. The focus is on missing at random mechanisms and on categorical data. Point and interval estimation is discussed. A comparison of both approaches is done on side effects in a psychiatric study.

Biometry↗
PubMed1999

Analysis of incomplete public health data.

The problem of dealing with missing values is common throughout statistics and is very prominent with epidemiologic data in the broad sense. Not only do data collection procedures break down, but subjects may be lost to follow up, or simply withdraw their consent without further providing a reason for doing so. In this paper, we review a framework for handling incomplete studies, and then concentrate on a specific case. It comes from a complex health interview survey, conducted in Belgium in 1997, where different types of missingness arise at various levels of the hierarchical sampling procedure.

Belgium↗
PubMed1990

Experimental diabetes impairs rat embryo development during the preimplantation period.

Congenital malformations and early fetal losses are still the main complications of diabetic pregnancy. Whether the diabetic state affects the early embryo development during the preimplantation period is not known. To understand better the early steps of embryo growth, we collected the embryonic structures from the uterine horns of pregnant diabetic rats on day 5 of pregnancy. Diabetes was induced by streptozotocin (50 mg/kg) injection, 7, 14 or 21 days before mating. The morphological analysis revealed a lower rate of blastocysts (72% of all structures) and an increased rate of morulae (19.5%) in diabetic rats, compared to control animals (86.7 and 7.9% respectively). Hence, diabetic rats had fewer blastocysts (5.5 +/- 2.9 per rat) and more morulae (1.5 +/- 1.7) than control animals (7.2 +/- 2.7 and 0.66 +/- 1.2 respectively). Moreover, blastocysts from diabetic rats had fewer nuclei (26.9 +/- 7.3 per blastocyst) than blastocysts from control animals (31 +/- 6.1). In another set of experiments, subdiabetogenic doses of streptozotocin were administered. In rats injected with 25 mg/kg, neither the glycaemia, nor the morphological aspects of the embryos, nor the number of blastocyst nuclei differed from the control animals. In the animals receiving 35 mg/kg, the glycaemia was increased to approximately twice the control group value. However, the embryonic morphology and the nuclei counting of the blastocysts were similar to those of the fully diabetic group injected with 50 mg of streptozotocin. These results show that experimentally induced diabetes, even of a rather mild degree, affects the embryo development during the preimplantation period. The recovered embryos appear less mature and less developed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Co-culture of two-cell rat embryos on cell monolayers.

Monolayers of 2 different populations of uterine cells and of fetal fibroblasts were evaluated for the support of rat embryo development in vitro. Compared to controls, cultures performed in Earle's buffered saline solution (EBSS) alone, the cleavage rate of 2-cell embryos to the 4-cell stage was significantly increased when the embryos were cocultured for 24 h with mixed uterine stromal and myometrial cells (70.7 vs. 56.0%; P less than 0.01). Coculture of 2-cell embryos with either uterine epithelial-stromal or stromal-myometrial cells in medium TC 199 (M199) for 24 h significantly increased the cleavage rate to the 4-cell stage compared to controls in the same medium (respectively, 78.3 and 77.6 vs. 49.9%; P less than 0.01). The development was not improved when fibroblasts were used as feeder cells. After 48 h, the proportion of 4-cell embryos showing cellular fragmentation was significantly decreased in the presence of either epithelial-stromal or stromal-myometrial cells in M199 compared to controls (respectively, 18.4 and 20.0 vs. 43.8%; P less than 0.01). Coculture in EBSS or with fibroblasts failed to prevent embryo degeneration. In one coculture with stromal-epithelial cells in M199, 6/11 embryos proceeded beyond the 4-cell stage, two of them reaching the 8-cell stage. No embryo developed beyond that stage in our study. Although considerable efforts remain necessary to achieve further growth, these results suggest that coculture offers promise as a means of supporting the in vitro development of rat embryos.

Animals↗
PubMed1990

Decreased inner cell mass proportion in blastocysts from diabetic rats.

Late morulae and blastocysts were recovered from streptozocin-induced diabetic pregnant rats and individually examined for numbers of inner cell mass (ICM) cells and trophectoderm (TE) cells. Compared with embryos collected from control rats, exposure to maternal diabetes significantly decreased mean ICM cell number of blastocysts recovered on day 5 of gestation, but the TE population of these embryos remained unaffected. The mean ICM proportion was therefore significantly lower than that of control embryos. These differences were not observed between the two groups of morulae collected on day 5, suggesting that the distinctive susceptibility of the ICM was expressed after blastocyst formation. On day 6, a significant inhibitory effect of diabetes was observed on the growth of both ICM and TE cells, but because the reduction was more severe in the ICM than in the TE, the mean ICM proportion of these blastocysts was again significantly lower than in control embryos. A linear quadratic relationship was obtained between the numbers of ICM cells of individual blastocysts and their respective numbers of TE cells in each of the two experimental groups. However, the slope of the curve was slower in the diabetic group than the control group. The disturbed ICM cell growth in the blastocysts from diabetic rats was found to be associated with a significantly increased incidence of cell death predominantly located in the ICM. Because it is known that excessive reduction of the ICM is incompatible with normal embryogenesis after implantation, our results suggest that the differential sensitivity of ICM and TE cells in preimplantation blastocysts may contribute to the pattern of postimplantation defects described in diabetic pregnancies.

Animals↗
PubMedDate not supplied

Missing data perspectives of the fluvoxamine data set: a review.

Fitting models to incomplete categorical data requires more care than fitting models to the complete data counterparts, not only in the setting of missing data that are non-randomly missing, but even in the familiar missing at random setting. Various aspects of this point of view have been considered in the literature. We review it using data from a multi-centre trial on the relief of psychiatric symptoms. First, it is shown how the usual expected information matrix (referred to as naive information) is biased even under a missing at random mechanism. Second, issues that arise under non-random missingness assumptions are illustrated. It is argued that at least some of these problems can be avoided using contextual information.

Data Interpretation, Statistical↗