Unexpected expression of a unique mixed-isotype class II MHC molecule by transfected L-cells

Class II (Ia) major histocompatibility complex (MHC) molecules are heterodimeric integral membrane proteins composed of non-covalently linked alpha and beta glycoprotein chains. Studies of both normal cells and L-cell transfectants have shown that neither alpha- nor beta-chains are found on the cell surface alone, and that alpha beta dimers are required for membrane expression. In both mouse and man, several distinct non-allelic alpha and beta genes exist. Analysis of Ia molecules by immunoprecipitation and two-dimensional gel electrophoresis has demonstrated apparently selective association of particular pairs of the various alpha- and beta-chains to form the expressed class II isotypes I-A and I-E (mouse) or DQ, DP and DR (human). Because the various alpha- or beta-chains encoded by distinct loci exist in many allelic forms within a species, such specific pairing suggests a special role for isotypically conserved regions of each chain in the association process. In attempting to localize such putative assembly-controlling regions using the technique of DNA-mediated gene transfer, various combinations of murine alpha and beta genes were introduced into L-cells. Here we report the unexpected observation, following transfection, of mixed-isotype (Ad beta Ea/k alpha) molecules on the L-cell membrane and document that the formation of this pair is strongly influenced by allelic polymorphism of the A beta chain.     

A unique colour and polarization vision system in mantis shrimps

The apposition compound eyes of mantis shrimps (stomatopods) are divided into three sections, the dorsal and ventral hemispheres and the midband. Many ommatidia of both hemispheres, and all those in the midband, sample the same narrow band in space. The function of the morphologically distinct midband region is not clear, but new evidence suggests that it may be adapted in a unique manner for colour and polarization vision. A series of carotenoid colour filters screen the photopigment and potentially provide a tetrachromatic input for contrast-enhanced vision or true colour vision. The filters are blocks of coloured droplets (red, orange, yellow, purple, pink or blue) within the rhabdoms of two rows of midband ommatidia. The arrangement of tiered microvilli in two other midband rows suggests that they provide a unique form of polarization vision.     

Direct relationship between urinary prostaglandin E and sodium excretion in essential hypertensive patients

Summary Urinary prostaglandins (PGEs and PGFs), sodium and potassium were measured in 17 essentially hypertensive patients. Significant positive correlations were found between a) PGEs secreted in 24 h and sodium excreted in 24 h, b) the ratio PGEs/U_NaV before and PGEs/U_NaV after volume expansion and c) the ratio Na/K and urinary PGEs. It was suggested that renal PGEs, potent natriuretic and diuretic substances, play an important homeostatic role in the extracellular fluid regulation, and consequently in long-term control of the arterial blood pressure.     

Action of Corynebacterium parvum on the activity of glycosidases and proteases of peritoneal macrophages in the mice]

Glycosidase and peptidase of non-treated Mouse peritoneal macrophages were characterized. The enzymatic activities of Corynebacterium parvum stimulated Mouse macrophages were compared to those of macrophages obtained from non-treated animals. All the enzymatic activities, but beta-C-galactosidase, were higher in stimulated Mouse macrophages.