Gastroesophageal reflux during sleep in asthmatic patients

To determine what relationship might exist between gastroesophageal reflux and nocturnal asthma, we studied nine patients with asthma and seven control subjects overnight in the sleep laboratory, monitoring sleep state, esophageal pH, tidal volume (including the relative contribution of rib cage and abdomen), and oxygen saturation. There were 15 episodes of gastroesophageal reflux, in three patients with asthma and four control subjects. There were no significant differences between the two groups in the number of reflux episodes, duration of the longest episode, and the percentage of reflux time. Thirteen of the 15 episodes occurred during the awake state or after movement arousal. None of the episodes caused coughing, wheezing, or changes in oxygen saturation in any of the subjects. These patients with chronic asthma did not have an increased incidence of gastroesophageal reflux at night, and reflux did not play any role in the production of their nighttime symptoms.     

Selective apoptosis within the rat subependymal zone: a plausible mechanism for determining which lineages develop from neural stem cells

During development, the output of the subventricular zone (SZ) becomes increasingly restricted, yet it still harbors multipotential progenitors. The output of the SZ could be gated by selectively eliminating inappropriately specified progenitors. Using in situ end-labeling (ISEL) to identify apoptotic cells, nearly 60% of the ISEL(+) cells in the juvenile forebrain were localized to the SZ. Of these dying cells, at least 9% could be identified as neurons, 4% as astrocytes, and 12% as oligodendrocytes. The remainder were negative for the stem cell marker nestin, as well as other markers evaluated. To test the hypothesis that committed progenitors were under selective pressures, neural stem/progenitor cells were allowed to differentiate in vitro in the presence or absence of the caspase 3 inhibitor z-DEVD-fmk. DEVD increased neuronal production 10-fold over control cultures. By contrast, the development of astrocytes and oligodendrocytes was not affected. Altogether, these data support the hypothesis that selective forces within the postnatal rat forebrain control the types of precursors that emerge from the germinal matrix. Furthermore, they suggest that different mechanisms control neuronal versus glial cell numbers.     

Lung function in children following repair of tracheoesophageal fistula.

Lung function and bronchial reactivity by methacholine challenge were studied in 24 patients seven to 18 years after repair of type I tracheoesophageal fistula. Only one patient had no abnormalities of the variables tested. Thirteen patients had obstructive airways disease, five had a restrictive defect, and 15 had a positive methacholine challenge. It is postulated that continuing subclinical aspiration of esophageal contents causes lung damage and renders the airways hyperreactive.     

Challenges in determining how child work affects child health

Credible findings from well-crafted research studies are essential in assessing the impact of child work on children's health. Researchers, however, encounter significant challenges in defining the relevant group of workers for a study and identifying an appropriate comparison group. This article describes some of those challenges and explains how choices about study and comparison groups can lead to biased research results. When selecting study groups, researchers should be aware that the impact of work on health may depend on the type and intensity of the work, and on the context in which it occurs. They should avoid drawing conclusions about the health effects of particular work situations from studies of very heterogeneous groups of workers and should not overgeneralize from studies of more homogenous groups. When choosing comparison groups, researchers should select children whose health outcomes are likely to be comparable to the outcomes working children would experience if they did not work. In particular, researchers should attempt to find children who are similar to the workers of interest on relevant non-work characteristics, including socioeconomic status and levels of parental education. In addition, they should consider the extent to which healthier children are more likely to select into the labor force as a result of decisions by parents or employers, or due to their own greater fitness. Ideally, studies of the health effects of child work should use multiple comparison groups, including children who work in relatively safe, non-strenuous occupations.     

Divergent glial fibrillary acidic protein and its mRNA in the activated supraoptic nucleus

Previous studies have shown decreased immunoreactive glial fibrillary acidic protein (GFAP) in the supraoptic nucleus (SON) when magnocellular neuroendocrine cells (MNCs) are activated by lactation or dehydration. This is thought to underlie structural plasticity of glial processes that occurs during these times. Here, we investigated how this apparent reduction in protein relates to GFAP mRNA expression in the dehydrated rat as visualized by in situ hybridization. Densitometry of silver grains in the SON revealed low levels of mRNA expression in control, 2-day dehydrated and 21-day rehydrated (R21) animals. Conversely, the SON from 7-day dehydrated (D7) subjects displayed significantly more silver grains. Thus, the pattern of GFAP mRNA expression is the inverse of what we previously observed for GFAP immunoreactivity in tissue sections of the SON. No differences in mRNA levels due to hydration state were seen in the lateral hypothalamic area, suggesting that increases in GFAP mRNA at D7 were specifically related to MNC activation. These data indicate a divergence in GFAP mRNA and protein expression in the SON.