Molecular and Biochemical Characterization of Three Anthocyanin Synthetic Enzymes from Gentiana triflora

Full length cDNA clones of flavonoid 3',5'-hydroxylase, dihydroflavonol4-reductase and flavonoid 3-glucosyltransferase were clonedfrom petals of Gentiana triflora. Their sequences were homologousto counterparts from other plants. Flavonoid 3',5'-hydroxylaseand flavonoid 3-glucosyltransferase were enzymatically characterizedby expressing cDNAs in heterologous expression systems. (Received May 21, 1996; Accepted June 4, 1996)     

Plant Callus: Mechanisms of Induction and Repression

Plants develop unorganized cell masses like callus and tumors in response to various biotic and abiotic stimuli. Since the historical discovery that the combination of two growth-promoting hormones, auxin and cytokinin, induces callus from plant explants in vitro, this experimental system has been used extensively in both basic research and horticultural applications. The molecular basis of callus formation has long been obscure, but we are finally beginning to understand how unscheduled cell proliferation is suppressed during normal plant development and how genetic and environmental cues override these repressions to induce callus formation. In this review, we will first provide a brief overview of callus development in nature and in vitro and then describe our current knowledge of genetic and epigenetic mechanisms underlying callus formation.     

Generation of a purely clonal defective interfering influenza virus

Defective interfering (DI) influenza viruses carry a large deletion in a gene segment that interferes with the replication of infectious virus; thus, such viruses have potential for antiviral therapy. However, because DI viruses cannot replicate autonomously without the aid of an infectious helper virus, clonal DI virus stocks that are not contaminated with helper virus have not yet been generated. To overcome this problem, we used reverse genetics to generate a clonal DI virus with a PB2 DI gene, amplified the clonal DI virus using a cell line stably expressing the PB2 protein, and confirmed its ability to interfere with infectious virus replication in vitro. Thus, our approach is suitable for obtaining purely clonal DI viruses, will contribute to the understanding of DI virus interference mechanisms and can be used to develop DI virus‐based antivirals.     

Aggregatibacter actinomycetemcomitans induces detachment and death of human gingival epithelial cells and fibroblasts via elastase release following leukotoxin‐dependent neutrophil lysis

Aggregatibacter actinomycetemcomitans is considered to be associated with periodontitis. Leukotoxin (LtxA), which destroys leukocytes in humans, is one of this bacterium's major virulence factors. Amounts of neutrophil elastase (NE), which is normally localized in the cytoplasm of neutrophils, are reportedly increased in the saliva of patients with periodontitis. However, the mechanism by which NE is released from human neutrophils and the role of NE in periodontitis is unclear. In the present study, it was hypothesized that LtxA induces NE release from human neutrophils, which subsequently causes the breakdown of periodontal tissues. LtxA‐treatment did not induce significant cytotoxicity against human gingival epithelial cells (HGECs) or human gingival fibroblasts (HGFs). However, it did induce significant cytotoxicity against human neutrophils, leading to NE release. Furthermore, NE and the supernatant from LtxA‐treated human neutrophils induced detachment and death of HGECs and HGFs, these effects being inhibited by administration of an NE inhibitor, sivelestat. The present results suggest that LtxA mediates human neutrophil lysis and induces the subsequent release of NE, which eventually results in detachment and death of HGECs and HGFs. Thus, LtxA‐induced release of NE could cause breakdown of periodontal tissue and thereby exacerbate periodontitis.     

Butyryl-CoA synthetase of pseudomonas aeruginosa —Purification and characterization

The preparation of highly purified medium chain acyl-CoA synthetase (Acid: CoA ligase, AMP-forming (EC 6.2.1.2)) from the cell extracts of $\text{Pseudomonas}\text{aeruginosa}$ is described. The enzyme is inducibly formed in the cells of the microorganism, when it is grown with butyrate as a major carbon source. The purified enzyme is homogeneous on disc gel electrophoresis. Its molecular weight is approximately 142,000, and it is possibly composed of 4 identical subunits of approximately 37,000 molecular weight and has isoelectric point of 4.3. The enzyme catalyzes the stoichiometric conversion of butyrate and CoA to butyryl-CoA in the presence of ATP and Mg²⁺. It also activates fatty acids with carbon chain lengths of 3 to 5 well, but is inactive toward fatty acids with carbon chain lengths of more than 6. The enzyme is sulfhydryl dependent and inactivated by silver and mercury compounds.     

Existence of a Novel Hemagglutinin Having No Protease Activity in Vibrio mimicus

The protease elaborated by Vibrio mimicus is known to possess hemagglutinating ability to chicken erythrocytes, the well-known HA/protease. A non-protease hemagglutinin (HA) with strong agglutinating ability towards rabbit erythrocytes was obtained from 32 hr culture supernatant of a pathogenic environmental strain of V. mimicus. This HA (V. mimicus HA: VMHA) appeared stable at relatively higher temperature and agglutinated the erythrocytes from rabbit, guinea pig and mouse but not the erythrocytes from chicken, bovine, horse and sheep. Simple sugars, metal ions and chelating agents failed to inhibit the activity of VMHA. The activity of VMHA was found to be sensitive to digestion by proteolytic enzymes including HA/protease. These results provide evidence for the existence of novel HA other than HA/protease in V. mimicus.     

Ring chromosome 15 in a mother and her children

Summary A case of ring chromosome 15 passed on to the index patient's two children is reported, and possible reasons for the infrequent records of inheritance of ring chromosome are suggested.     

MTRAP: Pairwise sequence alignment algorithm by a new measure based on transition probability between two consecutive pairs of residues

Background  

Sequence alignment is one of the most important techniques to analyze biological systems. It is also true that the alignment is not complete and we have to develop it to look for more accurate method. In particular, an alignment for homologous sequences with low sequence similarity is not in satisfactory level. Usual methods for aligning protein sequences in recent years use a measure empirically determined. As an example, a measure is usually defined by a combination of two quantities (1) and (2) below: (1) the sum of substitutions between two residue segments, (2) the sum of gap penalties in insertion/deletion region. Such a measure is determined on the assumption that there is no an intersite correlation on the sequences. In this paper, we improve the alignment by taking the correlation of consecutive residues.     

Effect of Clostridium perfringens Beta Toxin on Blood Pressure of Rats

Guanethidine treatment or adrenal medullectomy significantly inhibited the elevation in blood pressure induced by Clostridium perfringens beta toxin, and the combination of the two drastically reduced the pressure rise, to less than 19% of that in control rats. When rats were pretreated with tetrodotoxin or hexamethonium, the toxin-evoked rise was significantly inhibited. Elevation in blood pressure induced by the toxin in spinal rats tended to be less than that in control rats. When investigated by a microscopical technique, arteriolar constriction in the mesenteric vasculature was observed after the blood pressure elevation induced by the toxin reached a maximum. Blood flow in the skin decreased with an increase in blood pressure following intravenous injection of the toxin. It is concluded that beta toxin acts on the autonomic nervous system and produces arterial constriction.