Studies on the submicrosomal fractions of bovine oligodendroglia: Lipid composition and glycolipid biosynthesis

Oligodendroglia were isolated from bovine brain, and a crude, microsomal fraction obtained from cell homogenates was subfractionated into myelin (MP), plasma membranes (PM), Golgi (GF), smooth (SER) and rough (RER) endoplasmic membranes using discontinuous-sucrose gradient centrifugation. The submicrosomal fractions were characterized by ultrastructural examination and analysis of the specific organelle markers. The myelin and plasma membrane rich fractions contained characteristically the highest amounts of the lipid with lower mole percentages of total phospholipids and phosphatidylcholine, and higher concentrations of phosphatidylethanolamine (+plasmalogens), cholesterol and galactolipids. Considerable amounts of the typical myelin galactolipids (galacto-cerebrosides, sulfatides and monogalactosyl diglycerides) were also found in the Golgi fraction (GF). The GF fraction had the greatest enrichment of glycolipid-forming galactosyltransferases, and the distribution of these enzymes correlated well with that of the Golgi marker enzymes. The results give evidence that intracellular Golgi apparatus of oligodendroglia is rich in the myelin-specific lipids, and suggest its involvement in the synthesis and processing of myelin lipids.     

Billingen (Lower Arenig/Lower Ordovician) acritarchs from the East European Platform and their palaeobiogeographic significance

Billingen (Lower Arenig/Lower Ordovician) sediments of the St. Petersburg region, northwest Russia and the Leba area, northern Poland of the East European Craton yield acritarch assemblages, which are largely homogenous though displaying minor compositional differences that probably reflect a gradient from inner to outer shelf environments. Comparison with coeval acritarch microflora from the Yangtze Platform, South China, shows an overall similarity between Baltoscandian and South Chinese phytoplankton. The widespread uniformity in the fossil microphytoplankton may be related to the extensive global 'evae' sea-level transgression, which characterized the Billingen time. This suggests that during the Tremadoc through early Arenig times, acritarch assemblages displayed essentially an undifferentiated cold-water and oceanic character along the whole margin of Perigondwana in the South, as well as on the South Chinese and Baltic platforms, at middle latitudes (Mediterranean oceanic Realm). Despite this overall similarity, however, some typical taxa of the high-latitude Mediterranean Province (Arbusculidium, Coryphidium and Striatotheca) occur in South China, but are absent in Baltica. This discrepancy is explained as caused by differences in climatic and physiographic conditions that prevailed at the two palaeocontinents at this time. The inferred pattern of oceanic circulation during the Lower Ordovician is consistent with the palynological evidence of a prevailing warmer climate in Baltica than in South China, although the two palaeocontinents occupied the same palaeolatitudinal position.     

Ultrastructural cytochemical studies of plasma membrane phosphatase activities during the HeLa S3 cell cycle.

Alkaline phosphatase (AP), 5'-nucleotidase (5'N), Mg2+-activated ATPase (Mg-ATPase) and Ca2+-activated ATPase (Ca-ATPase) were studied in sychronized HeLa S3 cells with cytochemical methods and electron microscopy. It was found that AP activity, as determined by the deposition of lead phosphate reaction product (r.p.) was most active in mitotic (M), early and middle G1 cells, less active in late G1 and almost undetectable in S phase cells. Most AP enzyme activity was found to be associated with undulations (mainly microvilli) of the plasma membrane. Fluctuations and the redistribution of 5'N were also observed; the reaction for 5'N was positive in all phases of the cell cycle studied, it was strongest in M cells and in the majority of middle G1 cells. Mg-ATPase activity was present in the plasma membranes of cells throughout the cell cycle, but did not show noticeable fluctuations in activity and distribution. Ca-ATPase activity appeared in plasma membranes and in limited areas of cell nuclei but was evident only in S phase cells. The results of the present study confirm and extend previous biochemical observations and indicate that changes in membrane phosphate activities are associated with enzyme activity redistributions within the plasma membrane during the HeLa S3 cell cycle.     

Ultrastructural localization of cytoplasmic phosphatases in preimplantation mouse embryos.

The appearance and localization of the cytoplasmic phosphatases [acid phosphatase (AcPase) as a marker of lysosomes, TPPase as a marker of the Golgi apparatus, and NDPase (IDPase) as enzymatic marker of the endoplasmic reticulum (ER)] were cytochemically studied on the ultrastructural level in secondary oocytes and in preimplantation mouse embryos. The detectable AcPase activity, located on the inner surface of the membrane delimiting some cytoplasmic vacuoles (lysosomes and autophagic vacuoles), appears at the eight-cell stage and grows pregressively stronger up to the blastocyst stage. Golgi-associated reaction for TPPase was detectable in oocytes, dropped in one-cell embryos and became negative in the two-cell embryos. The reaction for TPPase and IDPase was present in plasma membranes of oocytes and early embryos and appeared in the delimiting membrane of some cytoplasmic vesicles in eight-cell embryos. Some activity of IDPase was found in small segments of the ER at the morula and blastocyst stage. The observed results suggest that the lysosomes are the first organelles in early embryos showing activity of the marker enzymes of the phosphatase type, while the activity of other marker enzymes is mainly concentrated in the plasma membrane of blastomeres. It cannot be excluded, however, that positive reaction for TPPase and IDPase in the plasma membrane results from nonspecific action of other phosphatases.     

Cyrtocrinids (Echinodermata,Crinoidea) from Upper Jurassic Štramberk‐type limestones in southern Poland

Abstract: A systematic account of highly diverse cyrtocrinid faunules from Upper Jurassic strata of ?tramberk type (Oxfordian–Tithonian) in southern Poland (Polish Carpathians) is presented. Fourteen taxa (Phyllocrinus malbosianus, Ph. stellaris, Ph. sp., Psalidocrinus armatus, Sclerocrinus compressus, S. polonicus sp. nov., Hemicrinus aff. kabanovi, Ancepsicrinus parvus gen. et sp. nov., Tetracrinus baumilleri sp. nov., Eugeniacrinites alexandrowiczi, E. cf. moravicus, E. sp., Eudesicrinus gluchowskii sp. nov. and Hemibrachiocrinus tithonicus sp. nov. are described and illustrated. Representatives of the genus Eudesicrinus, previously recorded only from the Lower Jurassic, are here shown to extend into the uppermost Jurassic. Other cyrtocrinids considered are common in Jurassic/Cretaceous strata across Europe. In the present faunules, isocrinid (Isocrinida), comatulid (Comatulida) and roveacrinid (Roveacrinida sensu Rasmussen, inclusive of Saccocoma) crinoids are associated.     

Quantitative immunogold study of increased expression of metallothionein-I/II in the brain perivascular areas of diabetic scrapie-infected mice

Quantitative immunogold procedure was used to study the distribution of metallothionein I/II (MT-I/II) at the ultrastructural level in the perivascular areas, including microvascular endothelial cells (ECs) and astrocytes with their perivascular end-feet, in brains of scrapie-infected hyperglycemic (diabetic) and normoglycemic (non-diabetic) mice. Samples of the fronto-parietal cortex obtained from diabetic and non-diabetic scrapie-infected, as well as from non-infected (control) SJL/J mice, were processed for immunocytochemical examination. In control mice, the labelling of the ECs was of low intensity, restricted to few immunogold particles in the cytoplasm. More intense labelling was present in the cytoplasm of astrocytic perivascular processes and perikarya, where it was associated with endoplasmic reticulum and fibrils. A few immunosignals were also present inside the nuclei of astrocytes. In diabetic mice the labelling of the EC cytoplasm was slightly increased, whereas in the cytoplasm of perivascular processes and pericarya of astrocytes, including their nuclei, there was significant enhancement of labelling. In these cells the density of immunosignals was highest in the areas of cytoplasm containing bundles of fibrils. In non-diabetic, scrapie-infected mice the intensity of immunolabelling was higher than in control mice but slightly lower than in diabetic mice. These results are similar to those in Alzheimer’s disease reported by other authors, and suggest that neurodegenerative diseases as well as metabolic stress enhance the metallothionein expression in perivascular regions of brain cerebral cortex, predominantly in astrocytes.