Functional insulin-like growth factor I receptors are expressed by neural-derived continuous cell lines.

High affinity insulin-like growth factor I (IGF-I) receptors are expressed by two human neural derived cell lines, SK-N-SH and SK-N-MC. Specific [125I]IGF-I binding to crude membranes was 23.4% for SK-N-SH and 10.7% for SK-N-MC, with 50% inhibition of binding by unlabeled IGF-I between 0.6-0.7 nM. Scatchard analysis of crude membrane binding was linear, whereas Scatchard analysis after wheat germ agglutinin purification of the receptor became curvilinear. The IGF-I receptor alpha-subunits of SK-N-SH have an apparent Mr of 126K, whereas that for SK-N-MC is 132K. Despite these differences in alpha-subunit structure both cell lines demonstrate IGF-I-induced autophosphorylation of their own beta-subunits as well as specific IGF-I induced tyrosine kinase activity, suggesting normal coupling between the ligand-binding alpha-subunit and the tyrosine kinase-containing beta-subunit. Furthermore, IGF-I stimulated iododeoxyuridine uptake in both SK-N-SH and SK-N-MC in a dose-dependent manner, suggesting that these cells may be used to study the role of IGF-I action on neural tissues.

Mortality in the Jerusalem 70-year-olds longitudinal study: does nifedipine have a role?

BACKGROUND: Short-acting nifedipine was found to be associated with increased mortality in elderly patients in some studies. METHODS: We examined effects of long-acting nifedipine in a longitudinal study of Jerusalem 70 year olds (448 participants). RESULTS: After follow-up of 6.5 years (1990-1996) 70 subjects died. We examined the effects of baseline variables on total mortality. Hypertensives had higher mortality than normotensives, 21.2% versus 13.8%, p = 0.01. Diuretic-treated patients (n = 72), mostly hypertensive (n = 71), had significantly higher mortality than non-diuretic-treated patients (n = 375), 45.5% versus 14.1%; p < 0.001. Although nifedipine-treated patients had a higher prevalence of coronary heart disease diagnosis than diuretic-treated patients (52% versus 35%), their relative risk of mortality was 0.8 (CI 0.4-1.4) of that of diuretic-treated patients. A multiple logistic regression model, including gender, systolic blood pressure, creatinine, cholesterol, diagnosis of congestive heart failure, cardiovascular arrest, diabetes, previous myocardial infarction, physical activity, nifedipine, other calcium channel and beta blockers and diuretics, found only serum creatinine and diuretic therapy associated with total mortality, p = 0.004 and p < 0.02, respectively. When interaction terms were added to account for drug combinations, diuretic therapy lost significance, but the combination of diuretics and beta blockers (probably representing a more severe form of hypertension) became significant, p = 0.03. CONCLUSION: Long acting nifedipine is not associated with increased mortality in elderly hypertensives.

The effect of caffeine ingestion on physical performance after prolonged exercise.

The purpose of this study was to determine the effect of caffeine ingestion on physical performance after prolonged endurance exercise. Twenty three trained male volunteers participated in a 40-km march and were divided into two groups, matched for caffeine clearance rate and aerobic capacity. The experimental group ingested, prior to the march, a caffeinated drink at a dose of 5 mg.kg-1 body mass and at the 3rd and 5th h of marching an additional drink at a dose of 2.5 mg.kg-1 body mass. The control group ingested a drink of equal volume at the same times. Upon termination of the march each subject performed a cycle ergometer test at an intensity of 90% maximal oxygen consumption. Time to exhaustion and rate of perceived exertion (RPE) were recorded. Blood samples were drawn predrink, at the 3rd and 5th h of marching and immediately after the cycle ergometer test, and were analysed for caffeine, free fatty acids (FFA), lactate and glucose levels. Plasma FFA levels increased during the march (p less than 0.05), with no significant difference between groups. Lactate levels increased in the experimental group (p less than 0.05), with no significant change in the control group. Glucose levels did not change significantly in either group. After the cycle ergometer test, lactate levels were significantly higher in the experimental, as compared to the control group (3.77 +/- 0.33 vs 2.52 +/- 0.35 mmol.l-1, respectively). There was no significant difference between treatments in the time to exhaustion on the cycle ergometer, but RPE was different (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)