The importance of the length of preceding birth intervals for the survival chances of young children has been established, but the debate concerning the causal biomedical or behavioral mechanisms continues. This article uses data from 17 Demographic and Health Surveys to investigate the effect of birth intervals on child mortality: Anthropometry of children, recent morbidity of children, and use of health services are examined in addition to child survival data for children born in the five years before the survey. Various methodological approaches are used to investigate the relative importance of the postulated mechanisms linking birth intervals and child survival. Short preceding birth intervals are associated with increased mortality risks in the neonatal period and at 1-6 months of age, and, to a much lesser extent, at 7-23 months of age. The effects of short birth intervals on nutritional status are rather moderate, and there is a weak relationship with lower attendance at prenatal care services. No consistent relationship exists between the length of birth intervals and other health status or health-service utilization variables. The results indicate that prenatal mechanisms are more important than postnatal factors, such as sibling competition, in explaining the causal nature of the birth interval effect.
This paper analyses the impact of the length of birth intervals on mortality and growth of young children. An attempt has been made to improve the methodology of birth interval studies and the results of an analysis of longitudinal data from a rural area in Kenya with a relatively favourable level of health are presented. It is shown that children with short retrospective or short prospective birth intervals do not run a higher risk of mortality or growth retardation than children with longer intervals, neither during the perinatal period nor during the first 2 years of life. This suggests that the socioeconomic setting, in which a birth interval study is carried out, is of ultimate importance.
Many plasmodesmata can be found in the walls of the cells of the endodermis and the pericycle of the roots. A mutual symplasmatic contact is thus established between the cells of the pericycle,endodermis and the innermost layer of the cortex.The radial walls of the endodermal cells are very thin and tend to become folded as a result of the fixation and embedding procedure. Virtually no plasmodesmata could be observed in these walls nor any striking feature which could be related to the presence of a Casparian strip.The plasmodesmata are spindle-shaped and lined by a membrane, which is a continuation of the plasmalemma. They all possess a central osmophilic strand. The pores on either end of the plasmodesmata are closed by the contact between plasmalemma and this strand. The substructure of the strand and its relationship to the endoplasmatic reticulum is discussed.Some rough calculations with respect to the role these structures may play in the process of intercellular transport are given and the significance of the plasmalemma for this type of transport is emphasized.
This paper uses data from 22 national surveys in developing countries to estimate the use of bottles for feeding of infants under 6 months of age. These data were collected in the context of the Demographic and Health Surveys programme (DHS) between 1986 and 1989. Bottle use appears to be very common in most countries. Only six of the 22 countries had levels of bottle use of less than 20 per cent, and all these countries are in sub-Saharan Africa. The policy implications are discussed briefly.
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