The pyrogenic effect of scarlet fever toxin

The scarlet fever toxin is pyrogenically active. The pyretic reaction can be inhibited with antiserum bothin vitro andin vivo. From the quantitative aspect the pyrogenicity neutralization point corresponds approximately to the equivalence point of the flocculation reaction. The transmission of tolerance with the serum of tolerant animals failed. Tolerance was of short duration; interruption of the series of toxin injections for two days resulted in complete restoration of the animal's sensitivity. It is argued on the basis of these results that although tolerance carries signs of immunological specificity it cannot be explained in terms of circulating antibodies.     

Loss of caveolin expression in type I pneumocytes as an indicator of subcellular alterations during lung fibrogenesis

 Caveolin is a major structural protein of caveolae, also known as plasmalemmal vesicles, which are particularly abundant in type I pneumocytes and capillary endothelial cells of lung parenchyma. Here we demonstrate that caveolin expression in the alveolar epithelium of rats and mini pigs is strikingly downregulated after irradiation-induced lung injury. Indirect immunoperoxidase staining with polyclonal anti-caveolin antibodies, confirmed by double fluorescence studies with type I cell-specific monoclonal anti-cytokeratin antibodies or lectins, revealed a dramatic loss of caveolin immunoreactivity in type I pneumocytes. In contrast, caveolin expression increased in endothelial cells. Immunoblotting of lung homogenates from normal and irradiated rats using specific anti-caveolin antibodies confirmed the presence of caveolin in normal tissue and its marked decrease of expression in fibrotic tissue. The loss of caveolin as an important structural protein of caveolae in alveolar epithelial cells may be an early indicator of serious type I cell injury during fibrogenesis. The increase of caveolin immunoreactivity in endothelia of blood vessels may indicate that different types of caveolae and/or different regulatory mechanisms of caveolin expression exist. Accepted: 28 May 1997     

Inhibition of lymphocyte mitogenesis by autoxidized low-density lipoprotein.

Mitogenic stimulation of lymphocytes is significantly inhibited by addition of human serum low-density lipoprotein that has undergone autoxidation, while no significant effect is seen with non-oxidized lipoprotein. The inhibition is effective for cells stimulated either by the plant lectin phytohemagglutinin or enzymatically by neuraminidase-galactose oxidase treatment. However, it is markedly attenuated when oxidized LDL is added to cells which have been triggered 24 hours earlier. Lipid extracts from oxidized LDL are similarly inhibitory, indicating that the effect is mediated by an oxidized lipid fraction.     

Microsporidal encephalitis in muskrats.

Microsporida similar morphologically to Encephalitozoon cuniculi were found in granulomatous foci in the brain of 5 of 29 wild-caught muskrats (Ondatra zibethica) held in captivity for various periods of time, but not in any of 36 free-living muskrats examined. The significance and possible source of this infection are discussed.