Vinyl polymerization by metal complexes, 20. Initiation by vinylamine/vinyl alcohol copolymer · copper(II) systems

The polymerization of acrylonitrile (AN) and of methyl methacrylate (MMA) initiated by various copper(II) chelates was studied in the presence of carbon tetrachloride. Several vinylamine (VAm)/vinyl alcohol (VA) copolymers with different contents of NH₂ and OH bearing monomeric units were chosen as polymer ligands as well as polyvinylamine (PVAm)/poly(vinyl alcohol) (PVA) mixtures (of equal NH₂ and OH group contents as the corresponding copolymers), PVAm, and PVA. The activity of the used polymer chelates to initiate the AN and the MMA polymerization was compared at various pH values of the reaction systems. For the polymerization of MMA, the VAm/VA copolymer systems showed a higher activity than the PVAm chelate containing the same amount of NH₂ groups, contrary to the case of the polymerization of AN, where the polymerization activity showed a reverse behavior. The initiation mechanism is discussed.     

Vinyl polymerization by metal complexes, 19. Formation of copper(II) chelates of vinylamine/vinyl alcohol copolymers

Chelate formation of vinylamine/vinyl alcohol copolymers with copper(II) was studied both by the spectrophotometric and by titrimetric methods. For comparison, polyvinylamine/poly(vinyl alcohol) mixtures were also taken up for measurements. In the case of the copolymer systems, copper(II) ions were found to be coordinated exclusively by nitrogen atoms of the copolymer ligand. The complexation constants of the chelates were determined by applying the modified Bjerrum method, in neglect of the acid dissociation of hydroxy groups in the copolymers. It was found that the copolymer/Cu(II) chelates tend to be unstable with decreasing contents of NH₂ groups in the copolymers. In the homopolymer mixture systems, copper(II) ions are not coordinated by the oxygen atoms of poly(vinyl alcohol), but only by the nitrogen atoms of polyvinylamine.     

Simultaneous localization of histamine and factor VIII-related antigen in the endothelium of the human umbilical vein

Simultaneous immunoelectron microscopic localization of histamine and factor VII-related antigen was examined on the same ultrathin section of the endothelium of the human umbilical vein from full-term deliveries by means of the double-immunolabeling technique. Small gold particles demonstrating antibody reaction with histamine are preferentially located in the cytoplasmic matrix and organelles, especially in mitochondria and on the luminal membrane surface of the endothelial cells. The gold particles representing histamine immunoreactivity also located on some of Weibel Palade (WP) bodies. In contrast, large gold particles demonstrating factor VII-related antigen are concentrated preferentially on most WP bodies. Single labeling of either histamine or factor VIII-related antigen shows similar results to those of the double labeling. The present study indicates that some WP bodies are involved in storage of both factor VIII-related antigen and histamine, but others store factor VIII-related antigen only. This difference in contents of WP bodies may be induced during the development and maturation process of this inclusion. At any rate, it is reasonable to consider that WP bodies have important roles in both vascular tonus and hemostasis during the vascular obliteration.     

Effect of vitamin K2 on cortical and cancellous bones in orchidectomized young rats

OBJECTIVES: The purpose of the present study was to compare the effect of vitamin K(2) on cortical and cancellous bones in orchidectomized young rats. METHODS: Forty male Sprague-Dawley rats, 6 weeks of age, were randomized by stratified weight method into four groups with 10 rats in each group: baseline controls (BLC), age-matched controls (AMC), orchidectomy (ORX), and ORX+vitamin K(2) administration (K). Vitamin K(2) (menatetrenone) was administered subcutaneously twice a week at dose of 30 mg/kg each. The experimental period was 8 weeks, and cortical and cancellous bone histomorphometry was performed on the tibial shaft and the proximal tibia, respectively. RESULTS: Cortical area (Ct Ar) and cancellous bone volume (BV/TV) were significantly greater in the AMC group than in the BLC group. Ct Ar was significantly lower in the ORX group than in the AMC group, and cancellous BV/TV was also significantly lower in the ORX group than in the AMC group as a result of significantly increased eroded surface (ES/BS). Although Ct Ar in the ORX+K group did not differ significantly from that in the ORX group, cancellous BV/TV was significantly greater in the ORX+K group than in the ORX group, but still significantly lower than in the AMC group. This protective effect of vitamin K(2) on cancellous bone was attributable to normalizing increased ES/BS. CONCLUSIONS: Vitamin K(2) appears to act more strongly on cancellous bone than on cortical bone in ORX young rats. High dose vitamin K(2) could partially prevent the reduction of cancellous bone gain by normalizing raised bone resorption in ORX young rats.     

Fragmented red cells are the major cause of spuriously high platelet counts in patients with fragmented red cells when counts are obtained by automated blood cell counter

Platelet counts measured by automated blood cell counter often show spuriously high values when measuring samples contain particles of equal size to platelets. The major cause of spuriously high platelet counts in samples with fragmented red cells (FRC) is thought to be the FRC themselves. We studied the correlation between FRC and spuriously high platelet counts in 40 patients demonstrating FRC on blood smears. FRC were measured by manual hemocytometry and by flow cytometry using a monoclonal antibody against glycophorin A (GPA method). There was a significant correlation between spuriously high platelet counts and FRC by manual hemocytometry (r=0.60, p<0.001) or FRC by the GPA method (r=0.45, p<0.005). These data suggest that FRC are the major cause of spuriously high platelet counts in samples with FRC.     

Isolation,characterization and chromosomal mapping of an actin gene from the primitive red alga Cyanidioschyzon merolae

Based on the results of cytological studies, it has been assumed that Cyanidioschyzon merolae does not contain actin genes. However, Southern hybridization of C. merolae cell-nuclear DNA with a yeast actin-gene probe has suggested the presence of an actin gene in the C. merolae genome. In the present study, an actin gene was isolated from a C. merolae genomic library using a yeast actin-gene probe. The C. merolae actin gene has no intron. The predicted actin is composed of 377 amino acids and has an estimated molecular mass of 42003 Da. Southern hybridization indicated that the C. merolae genome contains only one actin gene. This gene is transcribed at a size of 2.4 kb. When Southern hybridization was performed with C. merolae chromosomes separated by pulsed-field gel electrophoresis, a band appeared on unseparated chromosomes XI and XII. A phylogenetic tree based on known eucaryote actin-gene sequences revealed that C. merolae diverged after the division of Protozoa, but before the division of Fungi, Animalia and Chlorophyta.     

Frequent occurrence of in vivo clonal expansion of CD4− CD8− T cells bearing T cell receptor αβ chains in adult humans

We have previously reported 2 cases of healthy men showing in vivo monoclonal expansion of mature CD4^? CD8^? αβ T cells. In the present study, an additional 3 adults were found to exhibit such an expansion, among a total 464 adult donors studied. These 5 individuals were otherwise physiologically normal, with no history of severe illness and autoimmune disease at the time of examination. To investigate the mechanisms of the clonal expansion, further characterization of the clonal cells was attempted. No apparent preference for usage of the Tcell receptor β chain variable region was observed in the clonal T cells. These clonal T cells showed lectin-dependent or redirected antibody-dependent cell-mediated cytotoxicities, whereas they could not lyse autologous lymphoblastoid cell lines. Failure of Fas antigen expression was not observed for any of these clones. These results suggest that clonal expansion of CD4^? CD8^? αβ T cells frequently occurs in the periphery without any T cell abnormalities.     

Angiopoietins and angiopoietin-like proteins in angiogenesis.

Vascular network formation requires several endothelial cell growth factors. These factors have a potent angiogenic effect, and their precise coordination is essential for vascular development. Among them, angiopoietins function through the Tie2 receptor, whose signaling is critical to regulate vascular stabilization and remodeling. It has been reported that the angiopoietin/Tie2 signal is involved in survival and migration of endothelial cells and regulates vascular remodeling and maintenance of vascular integrity. More recent studies demonstrate that angiopoietin/Tie2 signaling is also required for lymphangiogenesis. The authors and several other groups have identified six angiopoietin-like proteins (Angptls) containing a coiled-coil domain and a fibrinogen-like domain, both of which are characteristic of angiopoietins. Interestingly, Angptls also function in angiogenesis through regulating survival and migration of endothelial cells, although Angptls do not bind the angiopoietin receptor Tie2. Currently, Angptls are orphan ligands, but they have been reported to have pleiotropic effects not only on vascular cells but also on metabolism and tumor biology. Here, the authors review current findings relating to the roles of angiopoietins and Angptls in vascular biology and discuss molecular mechanisms relevant to these factors and angiogenesis.