Effects of age and regular exercise on muscle strength and endurance

Summary Twenty male and 20 female non-professional tennis players were classified into two different age groups (n=10 per group): young active men (30.4±3.3 years), young active women (27.5±4.3 years), elderly active men (64.4±3.7 years), and elderly active women (65.3±4.5 years). These individuals were matched (n = 10 per group) according to sex, age, height and mass to sedentary individuals of the same socio-economical background: young sedentary men (29.2±3.4 years), young sedentary women (25.6±4.4 years), elderly sedentary men (65.2 ± 3.2 years) and elderly sedentary women (65.6±4.4 years). An isokinetic dynamometer was used to measure the strength of the knee extensors and flexors (two separate occasions) and the endurance of the extensors. Vastus lateralis electromyogram (EMG) was measured concomitantly. Significant sex, age and exercise effects (P<0.001) were observed for peak torque of both muscle groups. The effect of age on extensor strength was more pronounced at high speeds where men were also able to generate larger relative torques than women.No age or sex effects were noted for muscle endurance. However, muscles of active individuals demonstrated a greater resistance to fatigue than those of sedentary individuals. In conclusion, men were found to be stronger than women, age was associated with a decrease in muscle strength, but not of muscle endurance, and tennis players were stronger and had muscles that were more resistant to fatigue than their sedentary pairs in both age groups. Although the results of this study cannot be generalized to other types of sports activities, they do give credence to the health benefits of moderate exercise in the maintenance of muscle function with age.     

A continuous-flow technique for analysis of stoichiometry and transport kinetics of gastric H,K-ATPase

A continuous-flow method was developed for determining the stoichiometry of the gastric proton pump H, K-ATPase (EC 3.6.1.36) in its hydrolysis of ATP and translocation of H⁺ and the K⁺ congener “Rb⁺. H, K-ATPase-containing vesicles which had been isolated from pig gastric mucosa were incubated at 37 °C for 2 h in 150 mM ⁸⁶RbCl, 0.5 mM ethylenebis(oxyethylenenitrilo)tetra-acetic acid and J mM 2–(N-morpholino)ethane sulphonic acid (Mes) adjusted to pH 6.1 with Tris, and then applied onto a 0.45 μm pore size cellulose acetate filter. The immobilized vesicles were perfused with 0.15 mM Mes/Tris buffer, pH 6.1, containing 150 mcholine chloride and 0.2 mM MgCl₂., After changing to a medium containing 0.1 mM ATP, the amounts and rates of H⁺ uptake, ⁸⁶Rb⁺ efflux and ATP hydrolysis were measured. The initial ratio of Rb⁺ transported to ATP hydrolysed gave values of 0.96 ± 0.26 (mean f SD, n= 28). The initial ratio of ATP-dependent Rb⁺ efflux to H⁺ uptake gave values of 0.92 + 0.28 (mean f SD, n= 28). The Mg-ATPase activity was measured in vesicles which had been incubated with choline chloride instead of RbC1. This activity was 15.8 f 8.7% (mean + SD) of the total ATPase activity in the initial fractions used for calculation of the stoichiometry. It is argued that this Mg-ATPase may be an intrinsic activity of the H, K-ATPase and that the relation between these activities is dependent on the amount of K⁺ (or Rb⁺) present in the assay. However, whether corrections were made for this Mg-ATPase or not, it had only marginal effects on the calculations of the stoichiometry of the pump. Thus simultaneous measurements of ⁸⁶Rb⁺ efflux, H⁺ uptake and ATP hydrolysis in immobilized gastric vesicles gave a stoichiometry of the pump close to a 1:1:1 ratio. These results indicate that the pump is non-electrogenic.     

Neonatal duodenum: fluid-aided US examination

In 261 infants with vomiting, 11 duodenal abnormalities were diagnosed with fluid-aided ultrasound (US). These abnormalities included duodenal obstruction, malrotation with and without associated volvulus, incomplete rotation, and duodenal stenosis. US was the initial modality used in the evaluation of vomiting in these neonates and young infants. The overall sensitivity and specificity of fluid-aided US evaluation of duodenal abnormalities were 100% and 99%, respectively. (Workup bias limits the reliability of these figures.) Fluid-aided US examination of the stomach and duodenum provided a dynamic view of duodenal rotation and anatomy, and at the very least provided a method of triaging those infants who may require surgery, upper gastrointestinal series, or follow-up US to make a definitive diagnosis.     

A ketogenic drink improves brain energy and some measures of cognition in mild cognitive impairment

IntroductionUnlike for glucose, uptake of the brain's main alternative fuel, ketones, remains normal in mild cognitive impairment (MCI). Ketogenic medium chain triglycerides (kMCTs) could improve cognition in MCI by providing the brain with more fuel.MethodsFifty-two subjects with MCI were blindly randomized to 30 g/day of kMCT or matching placebo. Brain ketone and glucose metabolism (quantified by positron emission tomography; primary outcome) and cognitive performance (secondary outcome) were assessed at baseline and 6 months later.ResultsBrain ketone metabolism increased by 230% for subjects on the kMCT (P < .001) whereas brain glucose uptake remained unchanged. Measures of episodic memory, language, executive function, and processing speed improved on the kMCT versus baseline. Increased brain ketone uptake was positively related to several cognitive measures. Seventy-five percent of participants completed the intervention.DiscussionA dose of 30 g/day of kMCT taken for 6 months bypasses a significant part of the brain glucose deficit and improves several cognitive outcomes in MCI.     

BCG vaccination and pulmonary tuberculosis in Quebec

The BCG vaccination program officially set up in 1949 in the Province of Quebec has been retrospectively evaluated for the period from 1956 to 1961. Two series of age groups were studied, 0-14 and 15-29, each comprising populations of several hundred thousand. At the beginning and the end of the period, the rates of primary vaccination were, in percentages of viable births, from 40 to 47.8 and, in cumulative percentages, for the 0 to 14 year age group, from 39.98 to 53.41, and for the 0 to 29 year age group, from 29.22 to 45.98.

During this period, the ratios between the yearly rates of incidence of new cases of pulmonary tuberculosis per 100,000 in vaccinated and non-vaccinated individuals ranged from 1-2.5 to 1-3.5 within the age group 0-14 years and from 1-4.5 to 1-7 within the age group 15-29 years. When only the incidence of the more severe forms of tuberculosis is considered, the ratios ranged from 1-3.7 to 1-6.0 for the younger group and from 1-5.3 to 1-7.6 for the older one.

Mortality from pulmonary tuberculosis was practically non-existent in the vaccinated groups and decreased from 2.5 to 1.3 per 100,000 population in the non-vaccinated groups.

     

Inhibitory action of neuropeptide Y on agonist-induced responses in isolated guinea pig trachea.

The effect of neuropeptide Y (NPY) was tested on isolated guinea pig trachea. At 30 nM, NPY induced a weak but significant contractile response which was on average less than 6% of responses elicited by standard spasmogens. This myotropic action of NPY was blocked by indomethacin. In addition to its contractile activity, NPY greatly reduced the maximal response to vasoactive intestinal peptide (VIP), noradrenaline (NA), substance P (SP) and 5-hydroxytryptamine (5-HT), without affecting their pD2 values. However, NPY did not influence the response induced by histamine and carbamylcholine. Pretreatment of tracheal spirals with indomethacin (10(-6) M) abolished the NPY-evoked inhibition of VIP, SP and 5-HT responses but failed to reduce the action of NPY on NA-elicited relaxation. This latter effect was however blocked in the presence of tetrodotoxin. In conclusion, NPY inhibits responses elicited by various agonists in the guinea pig trachea. This effect seems to be mediated at both pre- and postjunctional levels. The postjunctionally mediated inhibitory action of NPY appears to be expressed especially with agents that generate prostaglandins concomitantly with inducing their response. In contrast, the NPY-evoked inhibition of NA-evoked relaxation seems to be mediated via a prejunctional mechanism.     

Attenuation of LDH-A expression uncovers a link between glycolysis, mitochondrial physiology, and tumor maintenance

Alterations in cellular metabolism are among the most consistent hallmarks of cancer. Herein we have investigated the relationship between increased aerobic lactate production and mitochondrial physiology in tumor cells. To diminish the ability of malignant cells to metabolize pyruvate to lactate, lactate dehydrogenase A (LDH-A) levels were knocked down by means of LDH-A short hairpin RNAs. Reduction in LDH-A activity resulted in stimulation of mitochondrial respiration and decrease of mitochondrial membrane potential. It also compromised the ability of these tumor cells to proliferate under hypoxia. The tumorigenicity of the LDH-A-deficient cells was severely diminished, and this phenotype was reversed by complementation with the human ortholog LDH-A protein. These results demonstrate that LDH-A plays a key role in tumor maintenance.