Close correlation of streptococcal DNase B (sdaB) alleles with emm genotypes in Streptococcus pyogenes

DNase B is a major nuclease and a possible virulence factor in Streptococcus pyogenes. The allelic diversity of streptococcal DNase B (sdaB) gene was investigated in 83 strains with 14 emm genotypes. Of the 15 alleles identified, 11 alleles carried only synonymous nucleotide substitutions. On the other hand, 4 alleles had a non-synonymous substitution other than synonymous substitutions, resulting in the substitution of a single amino acid. The distribution of each allele was generally emm genotype-specific. Only sdaB7 was found in both emm2 and emm4. The promoter region was highly conserved and DNase B protein was similarly expressed in all alleles.     

Involvement of DNase gamma in the resected double-strand DNA breaks in immunoglobulin genes

Somatic hypermutation (SHM) of immunoglobulin variable (V) region genes occurs in the germinal center (GC) B cells during immune responses, depending on activation-induced cytidine deaminase (AID). SHM is associated with resected double-strand DNA breaks (DSBs) which were shown to occur specifically in rearranged V regions in the GC B cells and CD40-stimulated B cells expressing AID. So far, endonucleases responsible for the DSBs have not been identified. Here we show that DNase gamma, a member of DNase I family of endonucleases, is expressed in GC B cells and CD40-stimulated B cells. Overexpression of DNase gamma in the mutation-competent Ramos B-cell line resulted in a marked increase in the resected but not blunt DSBs in the V region. Conversely, a selective DNase gamma inhibitor, DR396, suppressed the generation of the resected DSBs. These results suggest that DNase gamma is involved in the generation of resected DSBs associated with SHM.     

Expression of vascular endothelial growth factor (VEGF) and its cognate receptors in human pheochromocytomas

Pheochromocytomas are well-vascularized tumors, suggesting that a potent angiogenic factor may be involved in the mechanism of their formation. As vascular endothelial growth factor (VEGF) is a potent mitogen for vascular endothelial cells, here we have investigated the mRNA and protein expression of VEGF and the mRNA expression of its two receptors (Flt-1 and Flk-1/KDR) in pheochromocytomas tissue. An increase in VEGF mRNA (mainly isoforms VEGF(121) and VEGF(165)) and in VEGF protein expression were observed by semi-quantitative RT-PCR and Western blot, respectively, compared to normal adrenomedullary tissue. Flk-1/KDR, and Flt-1 levels of mRNA were also increased markedly in tumors and correlated with levels of VEGF mRNA. Therefore, we speculate that upregulation of VEGF expression and its receptors might be important in the pathogenesis of pheochromocytomas.     

The role of circulating precursors in vascular repair and lesion formation

The accumulation of smooth muscle cells (SMCs) plays a principal role in atherogenesis, post-angioplasty restenosis and transplantation-associated vasculopathy. Therefore, much effort has been expended in targeting the migration and proliferation of medial smooth muscle cells to prevent occlusive vascular remodeling. Recent evidence suggests that bone marrow-derived circulating precursors can also give rise to endothelial cells and smooth muscle cells that contribute to vascular repair, remodeling, and lesion formation under physiological and pathological conditions. This article overviews recent findings on circulating vascular progenitor cells and describes potential therapeutic strategies that target these cells to treat occlusive vascular diseases.     

Bioinspired Surface Layer for the Cathode Material of High‐Energy‐Density Sodium‐Ion Batteries

Cathode materials are usually active in the range of 2–4.3 V, but the decomposition of the electrolytic salt above 4 V versus Na⁺/Na is common. Arguably, the greatest concern is the formation of HF after the reaction of the salts with water molecules, which are present as an impurity in the electrolyte. This HF ceaselessly attacks the active materials and gradually causes the failure of the electrode via electric isolation of the active materials. In this study, a bioinspired β‐NaCaPO₄ nanolayer is reported on a P2‐type layered Na_2/3[Ni_1/3Mn_2/3]O₂ cathode material. The coating layers successfully scavenge HF and H₂O, and excellent capacity retention is achieved with the β‐NaCaPO₄‐coated Na_2/3[Ni_1/3Mn_2/3]O₂ electrode. This retention is possible because a less acidic environment is produced in the Na cells during prolonged cycling. The intrinsic stability of the coating layer also assists in delaying the exothermic decomposition reaction of the desodiated electrodes. Formation and reaction mechanisms are suggested for the coating layers responsible for the excellent electrode performance. The suggested technology is promising for use with cathode materials in rechargeable sodium batteries to mitigate the effects of acidic conditions in Na cells.     

The Spirulina platensis Adenylate Cyclase Gene, cyaC, Encodes a Novel Signal Transduction Protein

A cyaC gene encoding an adenylate cyclase of the filamentouscyanobacterium Spirulina platensis was se-quenced. The predictedamino acid sequence of the C-ter-minal region of cyaC is similarto the catalytic domains of adenylate cyclases in other cyanobacteriaand eukaryotes. The sequences of other regions are similar tothose of proteins consisting of the bacterial two-componentsignal transduction system: the sensory kinase and the responseregulator. The predicted gene product of cyaC contains, fromthe N-terminal end, a receiver domain of the response regulatorprotein (Rl), a domain similar to the ETR1 of Arabi-dopsis thaliana,a transmitter domain of the sensory kinase protein, a receiverdomain of the response regulator protein (R2), and a catalyticdomain of adenylate cyclase. The cyaC gene was expressed asan affinity-tagged protein in Escherichia coli, and the recombinantprotein was purified. The purified protein had adenylate cyclaseactivity which was activated by Mn²+. The results of Westernblotting using an anti-CyaC antiserum and the S. platensis cellextract confirmed that cyaC gene is expressed in S. platensis (Received February 27, 1997; Accepted April 26, 1997)     

Amyloplast formation in cultured tobacco cells; effects of plant hormones on multiplication, size, and starch content

In BY-2 cultured tobacco cells (Nicotiana tabacum L.), depletion of 2,4-dichlorophenoxyacetic acid (2,4-D) and addition of benzyladenine (BA) caused amyloplast formation, a decrease in cell multiplication, and an increase in cell size. These changes were primarily triggered by the depletion of 2,4-D, and facilitated by the addition of BA. An increase in the starch content of BY-2 cells was always accompanied by a reduction in cell multiplication. However, when hormonal conditions were unsuitable for amyloplast formation, the starch content of the cells did not increase, even if cell multiplication was forcibly terminated by the addition of aphidicolin. This result indicates that the hormonal conditions themselves, and not the decrease in cell multiplication, induce amyloplast formation in BY-2 cultured tobacco cells.Abbreviations BA benzyladenine - 2,4-D 2,4-dichlorophenoxyacetic acid - DAPI 4,6-diamidino-2-phenylindole - DMSO dimethyl sulfoxide - NAA 1-naphthylacetic acid - PMSF phenyl methyl sulfonyl fluoride     

Concurrent changes in sinusoidal expression of laminin and affinity of hepatocytes to laminin during rat liver regeneration.

Distribution of fibronectin, laminin, and collagens type I, III, IV, and V in the lobular regions of regenerating rat liver was studied by indirect immunofluorescence. Little or no laminin was detected in sham-operated controls throughout the experimental period, while it was detected in sinusoids of regenerating liver as early as 6 h after partial hepatectomy (PH). After reaching a maximum at 24 h, it decreased and was barely detectable 6 days after PH. Changes in the other extracellular matrix (ECM) proteins were evident 3 days after PH, but not earlier than 24 h. Hepatocytes isolated from regenerating rat livers were tested in a short term assay for attachment to the substrates coated with the ECM proteins. The attachment of hepatocytes to laminin substrates increased 12 h after PH, reached a maximum at 24 h, and decreased to the control level 6 days after PH, while that of the control remained constant. The attachment to fibronectin substrates was not different between regenerating livers and controls at any time point. The attachment to collagen did not change earlier than 24 h after PH, but increased slightly 3 days after PH. Primary rat hepatocytes cultured on the substrates coated with the ECM proteins were determined for replicative DNA synthesis in response to epidermal growth factor. Both in normal liver and in regenerating liver 24 h after PH, laminin was one of the most effective substrates in supporting the responsiveness of hepatocytes to the growth stimulus. Taken together, these results suggest the importance of hepatocyte-laminin interaction during the early stage of liver regeneration possibly in growth stimulation of hepatocytes and/or maintenance of hepatocyte-specific functions.     

The significance of scirrhous gastric cancer cell lines: the molecular characterization using cell lines and mouse models

Scirrhous gastric cancer (SGC) exhibits aggressiveness of the rapid infiltrating tumor cells with abundant fibroblasts. Experimental studies using SGC cell lines have obtained useful information about this cancer. Our literature search divulged a total of 18 SGC cell lines; two cell lines were established from primary SGC and the other lines were established from a metastatic lesion of SGC. Fibroblast growth factor receptor 2 (FGFR2) and transforming growth factor-beta receptor (TβR) are linked to the rapid development of SGC. Cross-talk between the cancer cells and cancer-associated fibroblasts (CAFs) has been shown to contribute to the progression of SGC. Chemokine (C-X-C motif) receptor 1 (CXCR1) from SGC cells might be associated with the abundant CAFs in cancer microenvironments. The in vivo models established using SGC cell lines are expected to serve as a useful tool for the development of drugs such as FGFR2 inhibitors, TβR inhibitors, and CXCR1 inhibitors, which might be promising as SGC treatments. However, the number of available SGC cell lines is insufficient for the clarification of the entire biologic behavior of SGC. Since the mechanisms responsible for the characteristic aggressiveness of SGC are not fully elucidated, the establishment of new SGC cell lines could help clarify the biological behavior of SGC and contribute to its treatment.