An investigation of the interactions of the allosteric modifiers of pyruvate kinase with the enzyme from Carcinus maenas hepatopancreas

Appropriate low dosages of vincristine stimulate megakaryocytopoiesis and produce thrombocytosis. In this study of the thrombocytotic action of vincristine, administration of a single dose of 0.1 mg/kg to rats produced an increase in megakaryocyte concentration, diameter and 24 h [3H]thymidine labelling index. Transfusion of one body equivalent of platelets from normal donors prevented stimulation of megakaryocytopoiesis by vincristine whereas platelets from vincristine-treated donors did not. These results suggest that vincristine stimulates megakaryocytopoiesis by altering the functional role of circulating platelets in the regulation of thrombopoiesis.     

Influenza virus hemagglutinin: hydrodynamic properties and molecular weight

Following acute alcohol administration (80-160 mg/100 g body weight) histamine levels of rat brain cortex and thalamus were elevated and histidine decarboxylase activity was decreased. The effect was less pronounced after chronic alcohol treatment (15% v/v in drinking water for 4 weeks). In the striatum there was no change in the metabolic pattern of histamine. Histamine-N-methyltransferase was unaffected in either case. Depolarisation-induced release of histamine was inhibited by alcohol in the hypothalamus, thalamus and cortex. The results indicate that ethanol affects the histamine metabolism and release processes in the histaminergic pathway of the brain.     

Use of linear proportional chambers for small-angle synchrotron radiation scattering in solutions of biopolymers

The results of applying linear position sensitive proportional counters to diffuse small-angle synchrotron radiation scattering to biopolymer solutions are presented. Synchrotron radiation of the VEPP-3 storage ring (Institute of Nuclear Physics, Novosibirsk) was used. On the basis of small-angle scattering curve obtained from protein pepsinogen it has been shown that the exposure is about 100 times less than with conventional X-ray technique.     

Occurrence of somatostatin and insulin immunoreactivities in the stomach of sea bass (Dicentrarchus labrax L.): light and electron microscopic studies

Somatostatin (SST)- and insulin (INS)-immunoreactive (ir) cells were identified in the gut of sea bass (Dicentrarchus labrax) by immunofluorescence double staining and peroxidase-antiperoxidase (PAP) techniques for light microscopy and by immunogold method for electron microscopy using antisera to mammalian and fish peptides. SST-14 and SST-25 immunoreactivities coexisted in cells mainly located among the mucous neck cells of the gastric glands. Preabsorption controls showed that some SST-25- and, possibly, some SST-14-like peptides appeared in these cells. Immunoreactivity to fish INS, but not to mammalian INS (mINS) or insulin-like growth factor I (mIGF-I), was observed in all the SST-ir cells. The preabsorption controls suggest a cross-reaction of the fish INS antisera with SST-containing or type I cells. These cells displayed ovoid or round secretory granules with fibrous, medium electron-dense or homogeneous osmiophilic materials. Some gastric cells (type II) with round secretory granules of variable electron density, which were gold immunolabeled with bonito INS but not with mINS, mIGF-I, or SST antisera, were also found. INS-related peptide in type II cells of the sea bass stomach is suggested.     

Role of the Rab3A-binding domain in targeting of rabphilin-3A to vesicle membranes of PC12 cells

Rab3A is a small GTPase implicated in the docking of secretory vesicles in neuroendocrine cells. A putative downstream target for Rab3A, rabphilin-3A, is located exclusively on secretory vesicle membranes. It contains near its C terminus two C2 domains that bind Ca2+ in a phospholipid-dependent manner and an N-terminal, Rab3A-binding domain that includes a Cys-rich region. We have determined that the Cys-rich domain binds two Zn2+ ions and is necessary but not sufficient for efficient binding of rabphilin to Rab3A. A minimal Rab3A-binding domain consists of residues 45 to 170 of rabphilin. HA1-tagged Rab3A and a green fluorescent protein (GFP)-rabphilin fusion were used to examine the roles of Rab3A and of rabphilin domains in the subcellular localization of these proteins. A Rab3A mutant (T54A) that does not bind rabphifin in vitro colocalized with the GFP-rabphilin fusion, indicating that Rab3A targeting is independent of its interaction with rabphilin. Deletion of the C2 domains of rabphilin reduced membrane association of GFP-rabphilin but did not cause mistargeting of the membrane-associated fraction. However, disruption of the zinc fingers, which drastically reduced Rab3A binding, did not reduce membrane association. These results suggest that the C2 domains are required for efficient membrane attachment of rabphilin in PC12 cells and that Rab3A binding may act to target the protein to the correct membrane.