Biomedical subjects

V Poon

Publications and source records attributed to V Poon.

3 recordsLinked to original sources

PubMed2003

GLUT4 activation: thoughts on possible mechanisms.

A family of facilitative glucose transporters or GLUTs mediates glucose uptake by cells and tissues. The glucose transporter isoform GLUT4, which is the predominant isoform expressed in mature muscle and fat tissues, is primarily responsible for the increase in glucose uptake in response to insulin stimulation. Recent work in our laboratory suggests that there are two divergent responses initiated by insulin stimulation. The first response involves the recruitment of GLUT4 transporters from intracellular reserves and their subsequent insertion into the plasma membrane. The second pathway results in an increase in the intrinsic activity of the transporters. This review will discuss evidence supporting the divergence of the two pathways regulating glucose uptake and, in particular, evidence for the increased intrinsic activity of GLUT4 in response to insulin stimulation. Inhibitors of p38 mitogen-activated protein kinase (MAPK) affected only the arm leading to the insulin-stimulated activation of GLUT4. This implicates p38 MAPK involvement in the regulation of this pathway. There is further evidence that p38 MAPK is itself recruited to the plasma membrane. The role of the phosphorylation state of the glucose transporter in response to insulin stimulation has been studied and indicates that, contrary to what might be predicted, there is actually a decrease in its phosphorylation at the plasma membrane in response to insulin. The relationship of this change to glucose uptake remains to be established. Other possible mechanisms regulating GLUT4 activity include binding of (+) or (-) modulators of its function.

Biological Transport↗

PubMed1997

Guidelines for international collaborative research.

OBJECTIVE: As the global village becomes a reality, there is an increasing need to conduct international collaborative studies in family practice. A workshop at the WONCA meeting in Hong Kong used international attendees to produce a set of guidelines for international research. METHODS: At the workshop four completed international projects, each using a different strategy, were presented so that common themes might become apparent. The themes were then discussed and guidelines emerged from the process. RESULTS: Seven guidelines emerged for consideration before embarking on an international collaborative research project in family medicine. The guidelines deal with the characteristics of the research question and the importance of communication. The need for simple, brief methods of data collection, funding and pilot testing were identified. CONCLUSION: The question must be relevant to all participants to maintain interest and measurement tools must be validated to understand the impact of cultural differences in understanding.

Communication↗

PubMed1983

Reduced solubility of short-acting soluble insulins when mixed with longer-acting insulins.

Using insulins from three manufacturers, we examined the recovery by radioimmunoassay of short-acting soluble insulin when mixed with long-acting insulin as a function of the ratio of the mixture and the time of pre-mixing. In ratios of 1:2, 1:3, and 1:5 (short- to long-acting insulin), all Novo, Nordisk, and Lilly short-acting insulins tested showed a significant loss of solubility when mixed with the respective company's long-acting insulin either for less than 75 s or for 20 min before centrifugation. In ratios of 1:1, Novo's Actrapid (regular) with Monotard (lente) and Lilly's regular with lente showed no significant loss of solubility when pre-mixed for less than 75 s, and the regular insulin also showed no significant loss when pre-mixed for 20 min. However, when Lilly's regular was mixed with either NPH or ultralente in a 1:1 ratio, a significant loss of solubility of the short-acting insulin occurred regardless of time [as was also found with Nordisk's Velosulin (regular) with insulatard (NPH)]. When Lilly regular was incubated with Lilly lente in ratios of 1:3 for less than 75 s, 20 min, 4 h, and 24 h before centrifugation, there was a progressive loss of solubility. In contrast, with the same ratios and times of pre-mixing, Lilly regular when mixed with Lilly NPH showed a rapid initial loss of solubility that plateaued by 20 min before centrifugation.(ABSTRACT TRUNCATED AT 250 WORDS)

Drug Combinations↗