Incompatibility of the Cad plasmid from Yersinia pestis with plasmids of the IncFI group

The relation of Yersinia pestis calcium dependence plasmid (pCad) to known Inc FI (F'lac, R386, pOX38) and IncFV (F0lac) plasmids has been studied. Evidence that plasmid pCad of Yersinia pestis belongs to FI incompatibility group is presented.     

Plasmid content in Yersinia pestis strains of different origin

Plasmid content in 242 Yersinia pestis strains from various natural plague foci of the U.S.S.R. and other countries was studied. Of these strains, 172 (71%) were shown to carry three plasmids described previously of about 6, 45-50 and 60 MDa, respectively. Twenty strains (8%) from different foci harboured additional cryptic plasmids, most often of about 20 mDa in size. Plasmid pPst displayed considerable constancy of its molecular mass. On the contrary, size variations of pCad (45-49 MDa) and, especially, pFra (60-190 MDa) were found. Molecular mass of these plasmids correlated with the host strain origin.     

Water Balance in Cucumis Plants, Measured by Nuclear Magnetic Resonance, I

In this paper we demonstrate the study of plant water balanceby the non-invasive measurement of tissue water content andwater flow using proton nuclear magnetic resonance (NMR). Sapvelocity and flux were measured independently in the presenceof an excess of stationary tissue water. The instrumentationdescribed allows automated and unattended measurement of flow-and water content-variables in a well-defined region of theplant over periods of several days, with a time resolution betweensuccessive measurements of c. 5 s. Using this apparatus theeffect of changes in light intensity (day/night rhythm) andrelative humidity on stem tissue water content as well as onthe velocity and flux of xylem sap in the stem were investigatedin a cucumber plant. The results are in agreement with predictionsfrom a simple model for plant water balance, which is basedon water potential, flow rate and resistance to flow. As longas only transpiration is varied, flow rate and water content(or potential) are affected in opposite ways as demonstratedin this paper. In contrast, the model predicts that changesin uptake (resulting from changes in, for example, root resistance)will induce changes in water content and flow in the same direction.An experimental verification of this prediction is given ina subsequent paper, where, in addition, the NMR results arecompared to those obtained with a dendrometer. Key words: Water balance model, Cucumis sativus L., flow, water content, NMR, water balance measurement     

TASTE GROUP THRESHOLDS AND SENSORY EVALUATION OF SPANISH WINE VINEGARS

Wine vinegar is a product obtained from wine acidification which contains at least 5% by wt. of acetic acid, in general without any additives or colorings.
Aspects studied in this work include: the determination of the taste group thresholds (geometric mean of the individual best-estimate thresholds "BET") of two different acids (citric and acetic acids) in aqueous solution and spanish vinegars produced from table and sherry wines. The results obtained suggest that wine vinegar can be considered something more than just an acidulant agent.
In order to evaluate differences among wine vinegars, discriminant tests for twenty-five spanish vinegars (sherry, table and flavored vinegars) were applied. Six of the twelve attributes freely chosen by assessors allowed grouping of the spanish wine vinegars according to their sensory aspects.     

Arginine deprivation in KB cells: I. Effect on cell cycle progress

When exponentially growing KB cells were deprived of arginine, cell multiplication ceased after 12 h but viability was maintained throughout the experimental period (42-48 h). Although tritiated thymidine ([(3)H]TdR) incorporation into acid-insoluble material declined to 5 percent of the initial rate, the fraction of cells engaged in DNA synthesis, determined by autoradiography, remained constant throughout the starvation period and approximately equal to the synthesizing fraction in exponentially growing controls (40 percent). Continous [(3)H]TdR-labeling indicated that 80 percent of the arginine-starved cells incorporated (3)H at some time during a 48-h deprivation period. Thus, some cells ceased DNA synthesis, whereas some initially nonsynthesizing cells initiated DNA synthesis during starvation. Flow microfluorometric profiles of distribution of cellular DNA contents at the end of the starvation period indicated that essentially no cells had a 4c or G2 complement. If arginine was restored after 30 h of starvation, cultures resumed active, largely asynchronous division after a 16-h lag. Autoradiographs of metaphase figures from cultures continuously labeled with [(3)H]TdR after restoration indicated that all cells in the culture underwent DNA synthesis before dividing. It was concluded that the majority of cells in arginine-starved cultures are arrested in neither a normal G1 nor G2. It is proposed that for an exponential culture, i.e. from most positions in the cell cycle, inhibition of cell growth after arginine with withdrawal centers on the ability of cells to complete replication of their DNA.     

Cloning of the locus encoding synthesis of an outer membrane protein (Omp2) of the calcium dependence plasmid of Yersinia pestis (Lehmann, Neumann)

The genetic locus of Yersinia pestis encoding synthesis of a 46-kDa heat-inducible outer membrane protein (Omp2) was cloned into pBR322 plasmid. The Omp2 was shown to be analogous to previously described YopH and Yop2b proteins. The fifth HindIII fragment of 48-MDa calcium dependence plasmid pCad358 mediates production of 31- and 28-kDa proteins, irrespective of orientation of the insertion. A 31-kDa polypeptide seems to correspond to the YopJ described elsewhere. The maps of BamHI and HindIII of pCad358 region studied differed from those described for pCD1 plasmid of Y. pestis KIM. The products encoded by genes from the fragment cloned in the Pgm+ background give rise to considerable growth of Y. pestis within mouse peritoneal macrophages but were not sufficient to cause lethal infectious process.     

Enzymatic decomposition of pectin in the presence of amino acids and proteins]

The influence of amino acids--glycine, alpha-alanine, lysine, phenylalanine, serine, methionine, cysteine, tryptophan, aspartic acid and asparagine--and proteins--chick egg albumin and autolysate of Aspergillus niger biomass--on the disintegration of beet pectine by the Asp. niger enzymic preparation was investigated. This process was shown to depend on the chemical composition and concentration of amino acids and the protein nature. All the tested amino acids, except tryptophan, at doses of 0.0001 to 0.5% stimulated the activity of pectolytic enzymes. The effect of proteins was different: Asp. niger autolysate showed no essential influence and egg albumin inhibited pectine disintegration.     

The effects of afterload and stimulation delay on the slow force response in the heterogeneous myocardium

The results of numerical simulations and physiological experiments that assessed the dependence of the intramyocardial slow force response under an afterload in the heterogeneous myocardium are described. Muscle duplexes of our design were used as the simplest experimental and theoretical models of the heterogeneous myocardium. It is shown that the degree of the slow force response increases with an afterload and the time of the stimulation delay between the elements of the duplex. This effect is explainable by an increase in the time of the mechanical interaction between the duplex elements in the isometric phase of contraction. This leads to changes in individual contractility, the configuration of the action potential, and the kinetic characteristics of intracellular calcium in cardiomyocytes of interacting muscles.     

Production of endothelial progenitor cells obtained from human Wharton's jelly using different culture conditions

Endothelial progenitor cells (EPC) participate in revascularization and angiogenesis. EPC can be cultured in vitro from mononuclear cells of peripheral blood, umbilical cord blood or bone marrow; they also can be transdifferentiated from mesenchymal stem cells (MSC). We isolated EPCs from Wharton's jelly (WJ) using two methods. The first method was by obtaining MSC from WJ and characterizing them by flow cytometry and their adipogenic and osteogenic differentiation, then applying endothelial growth differentiating media. The second method was by direct culture of cells derived from WJ into endothelial differentiating media. EPCs were characterized by morphology, Dil-LDL uptake/UEA-1 immunostaining and testing the expression of endothelial markers by flow cytometry and RT-PCR. We found that MSC derived from WJ differentiated into endothelial-like cells using simple culture conditions with endothelium induction agents in the medium.     

Genistein binding protein targets in dental pathogens

Oral pathogens have created a menace in recent years due to biofilm formation and antimicrobial drug resistance. The current treatment strategy works well with antibiotics. However, constant use of antibiotics creates a selective pressure, which increases adaptability of the pathogens. Therefore, it is of interest to analyze the potential targets of genistein in dental pathogens using computer aided prediction tools.