Residential magnetic fields,wire codes,and pregnancy outcome

The relationship of measured residential magnetic fields and wire codes to pregnancy outcome was examined in data collected for a study of childhood cancer in Denver. Pregnancies in homes with measured fields above 0.2 μT or high wire codes were not more likely to end in miscarriage, low birth weight, or preterm delivery. Lack of data on potential confounders and small numbers of cases limit the study's conclusions. © 1994 Wiley-Liss, Inc.     

Measurements of birth defect prevalence: Which is most useful as a comparator group for pharmaceutical pregnancy registries?

Pharmaceutical pregnancy registries document birth defects and other complications reported in pregnancies exposed to specific medications or diseases. A baseline estimate of birth defect prevalence is necessary for comparison. To identify potential teratogenic signals, the pregnancy registry must have a comparator that most closely matches the exposed population and data collection methodology, which are characteristics that vary among the multiplicity of birth defect surveillance systems. The system that yields the most accurate prevalence data may be different from that most closely matching the pregnancy registry methods. State public health programs have highly accurate and precise statistics, but their populations are broader than those of a pharmaceutical pregnancy registry. Large collaborative databases may have a more useful covered population, but there are secondary problems related to data precision. Health care databases enroll large numbers of patients and have good information about exposures and health problems, but the data can be difficult to access and lack useful detail. Exposure‐related databases are closer in population definition and collection methods, though the presence of different diseases and exposures can be problematic. Internal comparators are likely to be most useful in formal statistical analysis, but added cost and management burden and may require significantly increased registry enrollment. There is no ideal comparator, and this must be taken into account when planning a single‐exposure or single‐disease pregnancy registry. Birth Defects Research (Part A), 2009. © 2009 Wiley‐Liss, Inc.     

Group size elicits specific physiological response in herbivores

With increasing group size, individuals commonly spend less time standing head-up (scanning) and more time feeding. In small groups, a higher predation risk is likely to increase stress, which will be reflected by behavioural and endocrine responses. However, without any predator cues, we ask how the predation risk is actually processed by animals as group size decreases. We hypothesize that group size on its own acts as a stressor. We studied undisturbed groups of sheep under controlled pasture conditions, and measured in situ the cortisol and vigilance responses of identified individuals in groups ranging from 2 to 100 sheep. Both vigilance and average cortisol concentration decreased as group size increased. However, the cortisol response varied markedly among individuals in small groups, resulting in a lack of correlation between cortisol and vigilance responses. Further experiments are required to explore the mechanisms that underlie both the decay and the convergence of individual stress in larger groups, and whether these mechanisms promote adaptive anti-predator responses.     

Gestation length in rhesus macaques (Macaca mulatta)

We describe some of the sources of variation in gestation length among rhesus macaques. the data were obtained from the timed-mating breeding program at the California Regional Primate Research Center (CRPRC). Information about approximately 700 pregnancies that resulted in spontaneous vaginal deliveries of liveborn young is presented. The average length of these pregnancies was 166.5 days. In this population, older females with higher parities had significantly longer pregnancies and significantly heavier infants than other females did. Other factors, including infant sex, month of conception, maternal reproductive history, and paternal identity, had no consistent effect upon gestation length.     

低出生体重儿乙肝疫苗免疫持久性与安全性分析

目的:研究低出生体重儿乙肝疫苗免疫持久性与安全性。方法:选择86例低出生体重儿作为研究组,另选取86例正常出生体重儿作为对照组,分别对两组接种全程酵母乙肝疫苗后的抗-HBs阳性率、抗体平均滴度进行检测,并观察不良反应的发生情况。结果:研究组与对照组接种全程乙肝疫苗后3年内的抗-HBs的有效阳性率分别是74%和72.1%(P0.05),抗体平均滴度分别是214.2 mIU/mL与210.8 mIU/mL(P0.05);6年内的抗-HBs的有效阳性率分别是82.6%和81.4%(P0.05),抗体平均滴度分别是178.6 mIU/mL与170.4 mIU/mL(P0.05)。研究组与对照组接种第1针、第2针乙肝疫苗后均未发现发热、体温波动与败血症等不良反应。结论:免疫后数年内,低出生体质量对乙肝疫苗抗体的持久性没有影响,也不影响乙肝疫苗抗体的安全性。