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Biomedical subjects

N Webb

Publications and source records attributed to N Webb.

At least 19 recordsLinked to original sources
PubMed1998

Covariation in regulation of affinity for branchial zinc and calcium uptake in freshwater rainbow trout.

The possible coupling between regulation of the affinities for branchial Zn and Ca influx was investigated in juvenile rainbow trout Oncorhynchus mykiss acclimated to relatively hard fresh water ([Ca]=1.0 mmol l-1). The Km for branchial Ca influx was manipulated experimentally by exposing the fish to 2.3 micromol l-1 waterborne Zn for a total of 28 days. This procedure resulted in rapidly increased Km values for both Ca and Zn influx, an effect that remained through the experimental period. There was a significant linear correlation (r=0.88, P<0.02) between Km values for Ca and Zn measured at the same time points. Zn exposure caused progressively increasing maximum rate of transport, Jmax, values for Zn relative to the control value, but there was little, if any, effect on Jmax for Ca. These results support the idea of a shared transport site for Zn and Ca at the apical membrane of the gill epithelium and suggest that there is a certain degree of coregulation of branchial Zn and Ca uptake in rainbow trout. Removal of Ca from the water resulted in a large (six- to 24-fold) increase in affinity (decreased Km) for Zn influx and a modest (1.1- to 1.8-fold) increase in Jmax for Zn. Thus, Ca is a competitive inhibitor of Zn influx. In water lacking Ca, the Km for Zn in Zn-acclimated fish was no different from that of the control fish, suggesting that the Ca2+/Zn2+ transporter was regulated to improve Ca uptake.

Adaptation, Physiological↗
PubMed1996

Developing a plan for primary health care facilities in Soweto, South Africa. Part I: Guiding principles and methods.

The new political era in South Africa offers unique opportunities for the development of more equitable health care policies. However, resource constraints are likely to remain in the foreseeable future, and efficiency therefore remains an important concern. This article describes the guiding principles and methods used to develop a coherent and objective plan for comprehensive primary health care facilities in Soweto. The article begins with an overview of the context within which the research was undertaken. Problems associated with planning in transition are highlighted, and a participatory research approach is recommended as a solution to these problems. The article goes on to describe how the research methods were developed and applied in line with the principles of participatory research. The methods were essentially rapid appraisal techniques which included group discussions, detailed checklists, observation, record reviews and the adaptation of international and local guidelines for service planning. It is suggested that these methods could be applied to other urban areas in South Africa and elsewhere, and that they are particularly appropriate in periods of transition when careful facilitation of dialogue between stakeholders is required in tandem with the generation of rapid results for policy-makers.

Community Health Planning↗
PubMed1996

Developing a plan for primary health care facilities in Soweto, South Africa. Part II: Applying locational criteria.

This article is the second of a two-part series describing the development of a ten-year plan for primary health care facility development in Soweto. The first article concentrated on the political problems and general methodological approach of the project. This second article describes how the technical problem of planning in the context of scanty information was overcome. The reasoning behind the various assumptions and criteria which were used to assist the planning of the location of facilities is explained, as well as the process by which they were applied. The merits and limitations of this planning approach are discussed, and it is suggested that the approach may be useful to other facility planners, particularly in the developing world.

Catchment Area, Health↗
PubMed1995

Routine omentectomy is not required in children undergoing chronic peritoneal dialysis.

A routine omentectomy is recommended in children commencing chronic peritoneal dialysis, but is not routine practice in adults. We reviewed the outcome of 66 catheters (57 straight and 9 spiral) inserted into 38 patients (median age 7.8 years, 12 patients under 2 years) over a period of 4.8 years. The aim of the study was to determine whether an omentectomy affects the incidence of catheter blockage or peritonitis. Mean catheter life was 6.8 months (range 0.2-28 months). Fifteen are still in situ, and 14 were removed electively (transplantation). Blockage occurred in 1/22 catheters inserted after an omentectomy, compared with 10/44 inserted without an omentectomy (absolute risk reduction with omentectomy = 0.18). Blockage was more frequent with spiral catheters (4/9 vs 7/57; p < 0.05). Thirty-seven catheters were associated with one or more episodes of peritonitis. Peritonitis was not significantly more frequent after omentectomy. We conclude that a routine omentectomy is not routinely indicated in children commencing chronic peritoneal dialysis. Eleven omentectomies are required to prevent two omental blockages (1/0.18), and secondary omentectomy after blockage is a straightforward procedure. Spiral catheters conferred no benefit in this study. Omentectomy does not influence the incidence of peritonitis.

Adolescent↗
PubMed1985

Radioiodinated 1-(diethylaminopropyl)-4-phenylpiperazine: a potential brain imaging agent.

The preparation of radioiodinated 1-(diethylaminopropyl)-4-phenylpiperazine, an analog of HIPDM, and its tissue distribution in rats are described. The precursor undergoes facile electrophilic radioiodination with radionuclides of iodine at the no-carrier-added level to give isolated yields in the 69-85% range. Biodistribution studies indicate that the radiochemical is well extracted by the brain (1.68-1.79% ID) and activity is substantially retained for 4 h (greater than 67%). Brain-to-blood ratios during the 0.25-4.0 h period were 15-23:1. The brain uptake and retention as well as the high brain-to-blood ratios suggest the potential use of this agent for regional cerebral blood flow imaging.

Animals↗