Effect of exercise on protein metabolism in humans as explored with stable isotopes

Exercising for 3.75 h on a treadmill at 50% VO2 max in the fed state induced an increased excretion of 71 mg nitrogen/kg over the 18 h after exercise. However, measurements of the time course of changes in 13CO2 excretion from ingested [1-13C]leucine indicated that all of this increased nitrogen production occurs during the exercise period. Because of the reduced renal clearance and slow turnover of the urea pool, urea excretion lags behind urea production. Measurements of nitrogen flux from the plateau labeling of urinary ammonia achieved by repeated oral doses of 15N-labeled glycine indicated that the nitrogen loss resulted from an increase in protein degradation and a decrease in protein synthesis. Further studies with [1-13C]leucine indicated that a 2-h treadmill exercise induced an increase in the nitrogen loss from 5.4 to 16 mg . kg-1 . h-1 measured with a primed constant infusion of [1-13C]leucine. This resulted from a fall in whole-body protein synthesis. Glucose given at the rate of 0.88 g . kg-1 . h-1 depressed the rate of whole-body protein degradation and appeared to suppress the exercise-induced increase in nitrogen excretion. When leucine oxidation rates were measured at increasing work rates, a linear relationship between percentage of VO2 max and leucine oxidation was observed up to 89% VO2 max when 54% of the flux of leucine was oxidized. These changes may involve nonmuscle as well as muscle tissue. Thus the source of the increased nitrogen losses is probably liver. In muscle, protein degradation is actually decreased judged by methylhistidine excretion, whereas in liver, protein degradation may be increased. Also the fall in whole-body protein synthesis may reflect changes in nonmuscle tissues because in running rats protein synthesis in muscle is maintained. As far as leucine metabolism is concerned, because the increase in leucine oxidation occurs when leucine and its keto acid concentration falls, exercise must specifically activate the 2-oxoacid dehydrogenase.     

The Effect of Formaldehyde on Tissue Lipids and on Histochemical Reactions for Carbonyl Groups

Histcchemical and chemical evidence indicates that formaldehyde combines with unsaturated lipids at the double bond. The resulting complex contains a free carbonyl group which probably originates from the formaldehyde. The reaction occurs over a wide pH range, and takes place in the absence of oxygen or moisture. The reaction product is visualized by the Schiff reagent, and by the Ashbel-Seligman procedure. In the plasmal procedure, when performed on formalin-treated material, the reaction has the same significance as the pseudo-plasmal reaction, i.e. it denotes the presence of double bonds. The Ashbel-Seligman technic seems to be more sensitive to this complex than the Schiff reagent and shows it more markedly than it does the true plasmals and the atmospherically oxidized unsaturated compounds.     

Differential Staining of Acidic Tissue Components by the Improved Bi-Col Method

Technical particulars of the Bi-Col method for differentiating strongly acidic from weakly acidic compounds are described. The method can be applied to tissue sections which should preferably be fixed in Carnoy's fixative, and to strips of glass fiber paper.     

Percutaneous coronary intervention with adjunctive abciximab and clopidogrel in a patient with chronic idiopathic thrombocytopaenic purpura

The use of the antiplatelet agents abciximab and clopidogrel is now accepted therapy in percutaneous coronary intervention. We present a case in which these agents were used in a patient with idiopathic thrombocytopaenic purpura and a platelet count of 40x10(9)/l undergoing primary multivessel coronary stenting. This case shows that unstable coronary syndromes can occur in patients with thrombocytopaenia and that antiplatelet agents may be used safely in this context.     

A Forward Genetic Screen in Zebrafish Identifies the G-Protein-Coupled Receptor CaSR as a Modulator of Sensorimotor Decision Making

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Isolation and characterization of a spontaneously arising long-lived line of human keratinocytes (NM1)

Summary The long-lived keratinocyte line, NM1, was isolated from the epidermis of a pool of foreskins obtained from apprently, normal neonates at the time of circumcision. Cultures were initiated in Dulbecco’s minimal essential medium containing 20% fetal bovine serum, 0.4 μg/ml hydrocortisone, 10⁻⁹ M cholera, toxin, and 10 ng/ml epidermal growth factor using mitomycin C-treated 3T3 cells as a feeder layer. Unlike normal keratinocytes which survive for only 150 generations these cells have been in culture for more than a year and have been carried for more than 400 doublings. The cells seem to follow a pathway, of growth and differentiation that is very similar to normal keratinocytes. Cytokeratin fibrils, intercellular attachments, and cornified envelopes were observed. The keratin polypeptides isolated from the NM 1 cells were similar to those previously described in normal cultured, cells; the presence of profilaggrin and involucrin was demonstrated by sodium dodecyl sulfate electrophoresis and immunoblotting with monoclonal antibodies specific to these proteins. The NM 1 cells showed a reduced dependency on 3T3 feeder cells but did not form tumors when placed into athymic nude mice. Screening of the cells for SV40, BK, HPV 16, and HPV 18 viruses was negative. The NM1 cells showed trisomy of chromosome 8. The long-lived nature of these cells makes them a valuable model for studying growth and differentiation of kerationocytes.