Variation in Discosauriscus austriacus (Makowsky, 1876) from the Lower Permian of the Boskovice Furrow (Czech Republic)

Two genera and four species of discosauriscids, Discosauriscus potamites, D. pulcherrimus, Letoverpeton austriacum and L. moravicum , have previously been described from the Boskovice Furrow in Moravia. These laxa were differentiated primarily on the basis of proportional differences of the skull together with other morphological characters.
Excavations at two localities in the Boskovice Furrow have produced new, relatively abundant, skeletal material. The specimens are preserved three-dimensionally. In order to evaluate the differences in skull proportions, 17 variable characters on 70 skulls were measured. Statistical analysis demonstrates the existence of several morphological trends in the shape of the skull. However, no trend permits the division of this set of specimens into two clearly differentiated groups. The morphological differences used previously to define genera and species seem to be incorrect. Pending the discovery of distinct morphological differences, the Moravian discosauriscids can be considered as belonging to only one taxon: Discosauriscus austriacus (Makowsky, 1876).     

D- AND L-STEREOISOMERS OF ALLYLGLYCINE: CONVULSIVE ACTION AND INHIBITION OF BRAIN L-GLUTAMATE DECARBOXYLASE

DL-Allylglycine was resolved into the L- and D-stereoisomers using hog kidney acylase. Both isomers were active as convulsants after administration to mice. The dose of D-allylglycine required to induce convulsions was greater than that of the L-isomer. Studies on the concentration of the two isomers in brain suggest that the lower effectiveness of D-allylglycine is partially due to its slower penetration into the brain through the blood-brain barrier. Both isomers of allylglycine inhibited brain glutamate decarboxylase in vitro to approximately the same extent, however, in vivo L-allylglycine inhibited the enzyme more strongly than the D isomer. Concentrations of allylglycine which caused a significant inhibition of L-glutamate decarboxylase in vivo were ineffective in inhibiting the enzyme in vitro. Oxidation products derived from L- or D-allylglycine by the action of either L- or D-amino acid oxidase caused an almost complete inhibition of the enzyme in vitro. It is suggested that a common intermediate derived from the two isomers (possibly 2-keto-4-pentenoic acid) is responsible for the in vivo inhibition of L-glutamate decarboxylase and possibly also for the induction of convulsions.     

Collagen formation by fibroblasts of the chick embryo dermis

This investigation has sought to determine the relation between collagen fiber and fibroblast during fibrogenesis. Toward this end the surfaces of chick fibroblasts grown under in vitro conditions have been examined with the electron microscope after fixation in OsO(4). Supplementary information has been obtained from thin sections of fibroblasts fixed in situ during phases of fiber production. The evidence provided by these studies and by various conditions of the experiments indicates that the unit fibrils of collagen form in close association with the cell surface. They were never observed within the cell. When these unit fibrils form in bundles it appears as though templates of some nature, possibly coinciding with stress fibers within the cell cortex, influence the polymerization of the fibrils out of material available at the cell surface. From here the fibrils and bundles of them are shed into the intercellular spaces and there grow to limited diameters by accretion of materials from the general milieu.