Oxygen transport and peripheral microcirculation in long-term diabetes

The purpose of this investigation was to evaluate the impact of long-term diabetes on muscle blood flow (MBF) and oxygen transport (vO2) during exercise. Twelve male patients (58 +/- 8 years, mean +/- SD), with at least a 10-year history of diabetes controlled by insulin, and seven age-matched controls (56 +/- 5 years, mean +/- SD) participated in this study. No patient had been clinically diagnosed as having peripheral vascular disease, and on the average resting ankle/arm systolic blood pressure ratios were normal. Following a baseline period, 5 min of cycle ergometer exercises at 75 W were performed in the upright position and, after 1-hr recovery, in the supine position. Continuous vO2 was determined via breath-by-breath analysis. MBF was measured in the vastus lateralis (VL) and tibialis anterior (TA) by 133Xe clearance. In the erect position, the diabetic group (compared with the control group, respectively) exhibited significantly (P less than 0.05) lower exercise MBF [ml. (100 g.min)-1] in both VL (19 +/- 2.5 vs 30.9 +/- 2) and TA (13.7 +/- 2 vs 22.0 +/- 4), a lower steady-state VO2 (1.3 +/- 0.3 vs 1.7 +/- 0.2 liters.min-1) during exercise including the values in the last 15 sec of exercise, and greater accumulation of blood lactate (35 +/- 2 vs 22.0 +/- 2 mg/100 ml). The same trends in the data were observed during supine exercise; however, the blood pressure of the diabetics was significantly elevated during exercise when compared with that of controls. The reduced exercise MBF in the TA and VL demonstrated that impaired microvascular flow, without clinically overt peripheral vascular disease, in long-term diabetics leads to reduced oxygen delivery and exercise tolerance.     

BCR sequences essential for transformation by the BCR-ABL oncogene bind to the ABL SH2 regulatory domain in a non-phosphotyrosine-dependent manner.

BCR-ABL is a chimeric oncogene implicated in the pathogenesis of Philadelphia chromosome-positive human leukemias. BCR first exon sequences specifically activate the tyrosine kinase and transforming potential of BCR-ABL. We have tested the hypothesis that activation of BCR-ABL may involve direct interaction between BCR sequences and the tyrosine kinase regulatory domains of ABL. Full-length c-BCR as well as BCR sequences retained in BCR-ABL bind specifically to the SH2 domain of ABL. The binding domain has been localized within the first exon of BCR and consists of at least two SH2-binding sites. This domain is essential for BCR-ABL-mediated transformation. Phosphoserine/phosphothreonine but not phosphotyrosine residues on BCR are required for interaction with the ABL SH2 domain. These findings extend the range of potential SH2-protein interactions in growth control pathways and suggest a function for SH2 domains in the activation of the BCR-ABL oncogene as well as a role for BCR in cellular signaling pathways.     

Genetic Controls over Activities of Tyrosinase and Dopachrome Conversion Factor in Murine Melanocytes

We evaluated the three catalytic activities of tyrosinase and one activity of dopachrome conversion factor (DCF) in extracts made from skins of 6-day-old yellow and nonyellow mice. At least one of the catalytic activities of tyrosinase and of DCF correlate with the color of pigment being produced in the hair follicles of the mice. We use these data to evaluate existing hypotheses about the mechanism of the interacting genetic controls over melanogenesis.     

Structural and signaling requirements for BCR-ABL-mediated transformation and inhibition of apoptosis.

BCR-ABL is a deregulated tyrosine kinase expressed in Philadelphia chromosome-positive human leukemias. Prolongation of hematopoietic cell survival by inhibition of apoptosis has been proposed to be an integral component of BCR-ABL-induced chronic myelogenous leukemia. BCR-ABL elicits transformation of both fibroblast and hematopoietic cells and blocks apoptosis following cytokine deprivation in various factor-dependent cells. To elucidate the mechanisms whereby BCR-ABL induces transformation and blocks apoptosis in hematopoietic cells, we examined the biological effects of expression of a series of BCR-ABL mutants. Single amino acid substitutions in the GRB2 binding site (Y177F), Src homology 2 domain (R552L), or an autophosphorylation site in the tyrosine kinase domain (Y793F) do not diminish the antiapoptotic and transforming properties of BCR-ABL in hematopoietic cells, although these mutations were previously shown to drastically reduce the transforming activity of BCR-ABL in fibroblasts. A BCR-ABL molecule containing all three mutations (Y177F/R552L/Y793F) exhibits a severe decrease in transforming and antiapoptotic activities compared with the wild-type BCR-ABL protein in 32D myeloid progenitor cells. Ras is activated, the SHC adapter protein is tyrosine phosphorylated and binds GRB2, and myc mRNA levels are increased following expression of all kinase active BCR-ABL proteins with the exception of the Y177F/R552L/Y793F BCR-ABL mutant in 32D cells. We propose that BCR-ABL uses multiple pathways to activate Ras in hematopoietic cells and that this activation is necessary for the transforming and antiapoptotic activities of BCR-ABL. However, Ras activation is not sufficient for BCR-ABL-mediated transformation. A BCR-ABL deletion mutant (delta 176-427) that activates Ras and blocks apoptosis but has severely impaired transforming ability in 32D cells has been identified. These data suggest that BCR-ABL requires additional signaling components to elicit tumorigenic growth which are distinct from those required to block apoptosis.     

Effect of neurotensin on pancreatic function in man

The effect of neurotensin on submaximally-stimulated hepatobiliary and pancreatic secretion was studied in 6 healthy subjects. An intravenous infusion of neurotensin 1.4 ± 0.3 pmol/kg/min, designed to reproduce plasma neurotensin immunoreactivity levels within the physiological range, produced a significant increase in pancreatic bicarbonate output. Plasma concentrations of pancreatic polypeptide rose by 83 ± 16 pmol/l and were associated with a small reduction in trypsin, but no significant change in bilirubin outputs.     

Effects of specific muscle training on VO2 on-response and early blood lactate

The relationship between half time of the O2 uptake on-response (t1/2 VO2on, seconds) and early blood lactate accumulation (delta Lab, mmol.1(-1) at the onset of submaximal arm and/or leg exercise was the object of a cross-sectional study of sedentary subjects (S,n = 3), and kayakers (K, n = 8), and of a longitudinal study on 11 untrained subjects of specific arm vs. leg training. In supine arm cranking (W = 125 watts) S had an average t1/2 VO2on of 82 s and a delta Aab of 9.2 mmol.1(-1) compared to 47 +/- 7 s and 4 +/- 1.4 mmol.1(-1), respectively, for K. In longitudinal trainees shorter t1/2 VO2on was accompanied by lower Lab for the trained limbs. Specific limb conditioning in swimmers and runners resulted in shorter t1/2 VO2on. A linear relationship was observed between delta Lab and t1/2 VO2on having an intercept on the time axis at congruent to 20 s and a slope proportional to muscle mass. Trained muscles were grouped closest to the intercept indicating local acceleration of the rate of O2 transfer approaching the t1/2 VO2on for isolated perfused muscle at the onset of work. Since t1/2 VO2on, we conclude that factors distal to the capillary are specifically involved in the local training response.