Modeling phasic insulin release: immediate and time-dependent effects of glucose

The cellular and molecular mechanisms of insulin secretion are being intensively investigated, yet most researchers are seemingly unaware of the complexity of the dynamic regulation of the secretion. In this article, we summarize studies of the physiology of insulin secretion performed over several decades. The insulin response of perifused islets of rats, perfused rat pancreas, or that of a human, to a square-wave glucose stimulus is biphasic, a transient first-phase response of 4- to 10-min duration followed by a gradual rise in secretion rates (second-phase response). Several hypotheses have been proposed to account for the phasic nature of insulin secretion; they are briefly discussed in this review. We have favored the hypothesis that nutrient stimulators such as glucose, in addition to a primary and almost immediate secretory signal, with time induce both stimulatory and inhibitory messages in the beta-cell, and those messages modulate the primary insulinogenic signal. Indeed, studies in the rat pancreas and in humans have demonstrated that short stimulations with glucose generate a state of refractoriness of the insulin secretion, which we have termed time-dependent inhibition (TDI). Nonnutrient secretagogues such as arginine induce strong TDI independent of the duration of stimulation. Once the agent is removed, TDI persists for a considerable period. In contrast, prolonged stimulations with glucose (and other nutrients) lead to the amplification of the insulin response to subsequent stimuli; this can be demonstrated in the perfused rat pancreas, in perifused islets from several rodents, and in humans. We have termed this stimulatory signal time-dependent potentiation (TDP). The generation of TDP requires higher glucose concentrations and prolonged stimulation; the effect is retained for some time after cessation of the stimulus. Of major interest is the observation that, while the acute insulin response to glucose is severely reduced in glucose-intolerant animals and humans, TDP seems to be intact. The cellular mechanisms of TDI and TDP are poorly understood, but data reviewed here suggest that they are distinct from those that lead to the acute insulin response to stimuli. A model is proposed whereby the magnitude and kinetics of the insulin response to a given stimulus reflect the balance between TDP and TDI. Researchers studying the cellular and molecular mechanisms of insulin release are urged to take into consideration these complex and opposing factors which regulate insulin secretion.     

Practice in epidemiologic surveillance: between the general and the specific

This study analyses the perspectives of the organization of epidemiological surveillance (ES) in two kinds of organizations. The first is a set of undifferentiated practices; the second is a set of specific practices carried out in the local health system of Ribeir?o Preto, S?o Paulo Federal State. Both organizations are described in general terms and discussed according to the view of local health professionals and professionals of the epidemiological surveillance. This study presupposes that the decentralization should be supported by discussions regarding forms of organization among the groups involved in it. The guiding concepts of this research are nuclei and field of competence and responsibility. Seventeen professionals were the subjects of this study. Eleven participants were nurses and six were managers of the municipal health department of Ribeir?o Preto. Data was obtained from documents and semi-structured interviews, which were analyzed through the method of content analysis, theme modality. The theme "the epidemiological surveillance practice: between the general and the specific" was created according to the following signification nuclei: specific and general knowledge, and collective actions.     

School height censuses are reliable and valid tools for small-area targeting of nutrition interventions in Honduras

Nutrition program planners often need information on the relative burden of malnutrition in different communities, or administrative units, to decide where best to invest limited available resources. National nutrition surveys, however, rarely provide precise, representative findings at a finer level than that of large, subnational regions. The school height census is an alternative, low-cost approach that does provide disaggregated data on growth retardation at the local level. This study assessed the reliability and validity of the school height census for small-area targeting of nutrition interventions in Honduras. Reliability was assessed by examining the stability of small-area estimates of mean height-for-age Z-score over five consecutive years from 1993 to 1997. Validity was assessed by comparing municipality-level mean height-for-age Z-score in the 2001 school height census with the same parameter estimated in an anthropometric survey of children < 5 y old conducted in representative samples in 70 municipalities 3-7 mo earlier. The study found that stable estimates of mean height-for-age Z-score could be obtained at the level of municipalities or larger (intraclass correlation coefficients > or = 0.85). The school height census estimates of mean height-for-age Z-score at the municipality level were also valid, with the reference criterion the survey results for children > or = 1 y of age (Spearman's rank correlation = 0.74). School height censuses cannot provide reliable estimates of levels of growth retardation in individual schools. Wider use of school height censuses could make it much easier to identify communities that might benefit from targeted nutrition interventions.     

Analysis of titles of research articles published in a Brazilian nursing journal

This study analyzes titles of research works published in a nursing journal in 1997 and 1998. Data were collected through forms and organized by using the EPI-INFO 6.0 computer program. The analysis was based on recent national and international literature concerning the analysis of research reports. Results, which have been disposed in tables, showed that most of the analyzed articles presented a partly adequate titles in relation to variables, studied populations and/or key words. It was concluded that the evaluation of titles in nursing research still requires more attention since a large number of databases used by researchers only publicize research work means of its titles.