Exercise rapidly increases eukaryotic elongation factor 2 phosphorylation in skeletal muscle of men

Protein synthesis in skeletal muscle is known to decrease during contractions but the underlying regulatory mechanisms are unknown. Here, the effect of exercise on skeletal muscle eukaryotic elongation factor 2 (eEF2) phosphorylation, a key component in protein translation machinery, was examined. Eight healthy men exercised on a cycle ergometer at a workload eliciting ∼67% peak pulmonary oxygen consumption     with skeletal muscle biopsies taken from the vastus lateralis muscle at rest as well as after 1, 10, 30, 60 and 90 min of exercise. In response to exercise, there was a rapid (i.e. < 1 min) 5- to 7-fold increase in eEF2 phosphorylation at Thr56 that was sustained for 90 min of continuous exercise. The in vitro activity of skeletal muscle eEF2 kinase was not altered by exercise indicating that the increased activity of eEF2 kinase to eEF2 is not mediated by covalent mechanisms. In support of this, the increase in AMPK activity was temporally unrelated to eEF2 phosphorylation. However, skeletal muscle eEF2 kinase was potently activated by Ca²⁺–calmodulin in vitro , suggesting that the higher eEF2 phosphorylation in working skeletal muscle is mediated by allosteric activation of eEF2 kinase by Ca²⁺ signalling via calmodulin. Given that eEF2 phosphorylation inhibits eEF2 activity and mRNA translation, these findings suggest that the inhibition of protein synthesis in contracting skeletal muscle is due to the Ca²⁺-induced stimulation of eEF2 kinase.     

Effect of perioperative blood transfusion on recurrence of colorectal cancer

The aim of the present study was to examine the outcome of 517 patients undergoing curative surgery for colonic and rectal cancer, and to compare the recurrence and mortality rates in transfused and non-transfused groups of patients. The two groups were evenly matched for age, sex, Dukes' stage and histological differentiation. There were significantly more rectal tumours in the transfused group (P less than 0.01), but the distribution of colonic lesions did not differ. Life table analysis revealed that the transfused patients had a 20 per cent greater probability of recurrence at 5 years (P less than 0.005) and there were 16 per cent more cancer related deaths (P less than 0.01). Even when all rectal cancers were excluded, a similar trend was seen for the colonic lesions: a 24 per cent greater probability of recurrence at 5 years (P less than 0.025) and 15 per cent more cancer related deaths (P less than 0.02). We conclude that blood transfusion may be associated with increased mortality and recurrence in patients undergoing curative surgery for colorectal cancer.     

Updating McKusick: an educational exercise for medical students

An educational module is described in which first-year medical students were assigned different entries from the 1983 edition of McKusick's Mendelian Inheritance in Man to revise and update. Following review and discussion in small group sections, the entries were reproduced to provide each student with an updated compendium of the selected genetic disorders. The important principles of Mendelian inheritance could be readily illustrated by the entities assigned to each discussion group. Students learned to use the library and how to understand and integrate clinical and experimental papers. More than half the students reported spending 11-20 h to complete the assignment and reviewed from six to ten articles in detail. The caliber of the entries was found to be significantly correlated with the time students reported they spend on the exercise, but not with the number of papers reviewed, prior knowledge of the disease entity, the frequency of dictionary usage, or undergraduate exposure to genetics.     

Renal allograft rejection: induction and function of adhesion molecules on cultured epithelial cells.

The interaction of graft-infiltrating immune cells with donor parenchymal cells is an important early event in allograft rejection. This binding is stabilized by interaction of antigen-independent 'adhesion' molecules expressed on the two cell types. As the level of expression of these molecules can be altered during inflammation, a series of experiments was performed to examine the effects of the inflammatory cytokines interferon-gamma (IFN-gamma) and tumour necrosis factor-alpha (TNF-alpha) on adhesion molecules expressed by cultured human renal tubular epithelial cells. These cells constitutively expressed ICAM-1 and LFA-3. Incubation with IFN-gamma increased expression of ICAM-1 but had no significant effect on expression of LFA-3 (P greater than 0.05). Incubation with TNF-alpha increased expression of both ICAM-1 and LFA-3; IFN-gamma synergized with TNF-alpha to further augment expression of these molecules. Peripheral blood lymphocytes (PBL) showed an enhanced binding to allogeneic renal epithelial cell monolayers which had been pretreated with IFN-gamma or TNF-alpha. MoAbs specific for ICAM-1 or its ligand LFA-1 inhibited adhesion of PBL to either IFN-gamma- or TNF-alpha-pretreated renal cells. By contrast, antibodies specific for LFA-3 or its ligand CD2 only significantly blocked PBL adhesion to renal cells which had been pretreated with TNF-alpha. Combination of antibodies specific for multiple components of the adhesion systems produced greater inhibition of adhesion than was produced by any single MoAb. These results suggest that the inflammatory cytokines IFN-gamma and TNF-alpha up-regulate expression of functional ICAM-1 and LFA-3 molecules which can augment the binding of potentially graft-damaging lymphoid cells to renal tubular epithelial cells.     

Clinical findings in four children with biotinidase deficiency detected through a statewide neonatal screening program

Four children with biotinidase deficiency were identified during the first year of a neonatal screening program for this disease in the Commonwealth of Virginia. Two unrelated probands were identified among the 81,243 newborn infants who were screened. In addition, two siblings of one of these infants were found to be affected. Both probands had mild neurologic symptoms at two and four months, respectively, and the two older children had more severe neurologic abnormalities, cutaneous findings, and developmental delay at two and three years of age. However, none of the affected children had acute metabolic decompensation. Previous studies have shown that the administration of biotin to affected children can be a lifesaving procedure that can reverse acute symptoms and prevent irreversible neurologic damage. Our findings demonstrate that subtle neurologic abnormalities may appear as early as at two months of age and that developmental abnormalities may occur even in the absence of episodes of overt metabolic decompensation. Since screening and treatment are both inexpensive and effective and the incidence of the disease is well within the range of that of other metabolic diseases for which screening is performed, biotinidase deficiency should be added to the group of metabolic diseases for which screening is done in the neonatal period.     

Distribution of immunoreactive kallikrein along the rat nephron

We have used a direct radioimmunoassay to localize kallikrein along the corticomedullary axis of the rat kidney and in microdissected rat cortical nephron segments. As previously seen in rat and dog, kallikrein content was highest in the outer cortex and decreased progressively toward the papillary tip. In microdissected cortical nephron segments, the highest kallikrein content was found in the connecting tubule [176 +/- 16 (SE) pg/mm tubule length (n = 12)]. In addition, a significant amount of kallikrein was found in distal convoluted tubules [53 +/- 4 pg/mm (n = 14)], initial collecting tubules [75 +/- 10 pg/mm (n = 14)], and cortical collecting ducts [37 +/- 4 pg/mm (n = 13)]. Little or no kallikrein was found in glomeruli, proximal convoluted tubules, proximal straight tubules, and cortical thick ascending limbs. These results are compatible with a site of action of the kallikrein-kinin system in the cortical segments of the rat distal nephron.     

Effects of a single-dose pretreatment with captopril on the immediate response to nasal challenge with allergen

We performed a double-blind, placebo-controlled, crossover study using 12 subjects to determine the effects of a single 50-mg dose of captopril on the response to nasal challenge with increasing doses of allergen. Levels of kinins, histamine and N-alpha-p-tosyl-L-arginine methyl ester (TAME)-esterase activity were measured in nasal lavages, and symptom scores and the number of sneezes were recorded. Captopril had no significant effects on histamine, TAME-esterase, sneezing or symptom scores. Peak postchallenge kinin levels, however, were significantly elevated (p less than 0.05) compared to placebo, while an increase in the magnitude of the dose-response curve was of marginal significance (p = 0.058). Thus, captopril causes increases in the kinin levels in nasal secretions during the allergic response. If increased kinin levels persist or worsen with chronic therapy, it is possible that they could exacerbate allergic symptoms during repeated seasonal exposure.