High prevalence of asthma in cross country skiers.

OBJECTIVES--To study the prevalence of asthma (asthma symptoms and bronchial hyperresponsiveness) in Swedish cross country skiers compared with non-skiers and monitor changes in symptoms and bronchial hyperresponsiveness during the year. DESIGN--Cross sectional study during the winter ski season and in the summer. SETTING--Six ski clubs for élite skiers (total 47) in two different areas of Sweden. SUBJECTS--42 élite cross country skiers and 29 non-skiing referents. MAIN OUTCOME MEASURES--Bronchial responsiveness, asthma symptoms, and lung function. RESULTS--Bronchial responsiveness was significantly greater and asthma symptoms more prevalent in the skiers than in the referents. There was no difference in bronchial responsiveness within either group between winter and summer. 15 of the 42 skiers used antiasthmatic drugs regularly and 23 had a combination of asthma symptoms and hyperresponsive airways or physician diagnosed asthma, or both. Altogether 33 skiers had symptoms of asthma or bronchial hyperresponsiveness. One of the referents had symptoms of asthma and bronchial hyperresponsiveness, and none used antiasthmatic drugs regularly. CONCLUSIONS--Asthma, asthma-like symptoms, and bronchial hyperresponsiveness are much more common in cross country skiers than in the general population and non-skiers. Strenuous exercise at low temperatures entailing breathing large volumes of cold air is the most probable explanation of persistent asthma in skiers.     

GENETIC AND SOCIAL INHERITANCE OF BODY AND EGG SIZE IN THE BARNACLE GOOSE (BRANTA LEUCOPSIS)

We present heritability estimates for final size of body traits and egg size as well as phenotypic and genetic correlations between body and egg traits in a recently established population of the barnacle goose (Branta leucopsis) in the Baltic area. Body traits as well as egg size were heritable and, hence, could respond evolutionarily to phenotypic selection. Genetic correlations between body size traits were significantly positive and of similar magnitude or higher than the corresponding phenotypic correlations. Heritability estimates for tarsus length obtained from full-sib analyses were higher than those obtained from midoffspring-midparent regressions, and this indicates common environment effects on siblings. Heritabilities for tarsus length obtained from midoffspring-mother regressions were significantly higher than estimates from midoffspring-father regressions. The results suggest that this discrepancy is not caused by maternal effects through egg size, nor by extra-pair fertilizations, but by a socially inherited foraging site fidelity in females.     

Lower limb skeletal muscle function after 6wk of bed rest

Berg, H. E., L. Larsson, and P. A. Tesch. Lower limbskeletal muscle function after 6 wk of bed rest. J. Appl. Physiol. 82(1): 182-188, 1997.Force,electromyographic (EMG) activity, muscle mass, and fibercharacteristics were studied in seven healthy men before and after 6 wkof bed rest. Maximum voluntary isometric and concentric knee extensortorque decreased (P < 0.05)uniformly across angular velocities by 25-30% after bed rest.Maximum quadricep rectified EMG decreased by 19 ± 23%, whereassubmaximum (100-Nm isometric action) EMG increased by 44 ± 28%.Knee extensor muscle cross-sectional area (CSA), assessed by usingmagnetic resonance imaging, decreased by 14 ± 4%. Maximum torqueper knee extensor CSA decreased by 13 ± 9%. Vastus lateralis fiberCSA decreased 18 ± 14%. Neither type I, IIA, and IIB fiberpercentages nor their relative proportions of myosin heavy chain (MHC)isoforms were altered after bed rest. Because the decline in strengthcould not be entirely accounted for by decreased muscle CSA, it issuggested that the strength loss is also due to factors resulting indecreased neural input to muscle and/or reduced specifictension of muscle, as evidenced by a decreased torque/EMG ratio.Additionally, it is concluded that muscle unloading in humans does notinduce important changes in fiber type or MHC composition or in vivomuscle contractile properties.

     

Comparison between (RS)-nipecotic acid and GABA transport in cultured astrocytes: Coupling with two sodium ions

The sodium ion dependency of the uptake of (RS)-nipecotic acid into astrocytes in primary cultures has been studied by performing kinetic analysis at different sodium ion concentrations (16–151 mM).V _max of the saturable component of the astroglial (RS-nipecotic acid uptake is clearly affected by the sodium ion concentration whereasK _m surprisingly remains unaffected. At high (RS)-nipecotic acid concentrations (50 M), uptake rates as a function of the sodium ion concentration were clearly sigmoid. This sigmoid shape was not obvious at lower concentrations of (RS)-nipecotic acid. The calculated Hill coefficients corresponding to all (RS)-nipecotic acid concentrations studied were approximately two. From these results it is concluded that (RS)-nipecotic acid uptake into astrocytes in primary cultures, like astroglical GABA uptake, requires the binding of at least two sodium ions per (RS)-nipecotic acid molecule transported.     

Comparative immunocytochemical localization of putative opioid ligands in the central nervous system

We report a detailed comparative immunocytochemical mapping of enkephalin, CCK and ACTH/beta-endorphin immunoreactive nerves in the central nervous system of rat and guinea pig. Enkephalin immunoreactivity was detected in many groups of nerve cell bodies, fibers and terminals in the limbic system, basal ganglia, hypothalamus, thalamus, brain stem and spinal cord. beta-endorphin and ACTH immunoreactivity was limited to a single group of nerve cell bodies in and around the arcuate nucleus and in fibers and terminals in the midline areas of the hypothalamus, thalamus and mesencephalic periaqueductal gray with lateral extensions to the amygdaloid area. Cholecystokinin immunoreactive nerve fibers and terminals displayed a distribution similar to that of enkephalin in many regions; but striking differences were also found. An immunocytochemical doublestaining technique, which allowed simultaneous detection of two different peptides in the same tissue section, showed that enkephalin-, CCK- and ACTH/beta-endorphin-immunoreactive nerves although closely intermingled in many brain areas, occurred separately. The distributions of nerve terminals containing these neuropeptides showed striking overlaps and also paralleled the distribution of opiate receptors. This may suggest that enkephalin, CCK, ACTH and beta-endorphin may interact with each other and with opiate receptors.