[The role of platelet activating factor in the pathogenesis of asthma]

The work reviews knowledge about the function of PAF, the presupposed mediator of asthma. The PAF mediator evokes contraction of smooth muscles of respiratory passages, too in vivo as in vitro, by means of an indirect mechanism involving activated platelets which function as intermediaries. The constrictor released due to this process can be represented by histamine or a product of arachidonic acid. Mucous secretion is according to current knowledge stimulated by PAF. The PAF mediator appears to be a considerable chemotactic factor for eosinophils which by their cytotoxic effects on respiratory epithelium support the origin and development of bronchial hyperresponsiveness. PAF has an eminent effect on the growth of microvascular permeability. Antagonists of PAF inhibit some mentioned PAF effects. Their possible therapeutic utilization, excluding ketotiphen, are currently subjected to research. (Fig. 2, Ref. 17.).

[Carnosine and anserine in working muscles--study using proton NMR spectroscopy]

NMR spectroscopy was used to study carnosine and anserine metabolism in rat tissues under intensive muscle loading. Muscle loading was accompanied by the dipeptide (predominantly anserine) accumulation in muscle tissues. Preliminary per os administration of carnosine (250 mg/kg of body mass) did not increase the dipeptide content in muscle tissues but diminished the lactate content in rat muscles under intensive muscle loading.

Effects of denervation on the contents of cholesterol and membrane systems involved in muscle contraction in rabbit fast-twitch sarcotubular system

Denervated fast-twitch rabbit muscles were progressively losing their fresh weight and the yield of sarcotubular protein was increasing. The activity of Ca(2+)-ATPase was affected but very slightly, the basal Mg(2+)-ATPase and the Mg(2+)-ATPase/Ca(2+)-ATPase ratio however increased together with a simultaneous depression of the membrane-bound acetylcholinesterase activity. We did not observe any differences in density properties of sarcotubular fractions between control and denervated muscle. However, a relative enrichment in SM and H fraction could be seen after denervation with small changes in the content of the Ca(2+)-pump protein, increased levels of calsequestrin and cholesterol, mostly in the heavy and the SM fraction. After denervation the binding sites for 3H-PN-200-110 did not show any changes in receptor affinity, but the number of putative Ca(2+)-channels increased twice along with a depression of 3H-ouabain binding sites. We suggest that the denervation of fast-twitch muscle leads to the hypertrophy of the junctional sarcoplasmic reticulum and the T-system. Changes in the cholesterol content, in the number of putative Ca(2+)-channels and in Na+, K(+)-ATPase can affect the muscle contraction.