Cloning of Escherichia coli lacZ and lacY Genes and Their Expression in Gluconobacter oxydans and Acetobacter liquefaciens

An efficient transformation protocol for Gluconobacter oxydans and Acetobacter liquefaciens strains was developed by preparation of electrocompetent cells grown on yeast extract-ethanol medium. Plasmid pBBR122 was used as broad-host-range vector to clone the Escherichia coli lacZY genes in G. oxydans and A. liquefaciens. Although both lac genes were functionally expressed in both acetic acid bacteria, only a few transformants were able to grow on lactose. However, this ability strictly depended on the presence of a plasmid expressing both lac genes. Mutations in the plasmids and/or in the chromosome were excluded as the cause of growth ability on lactose.     

Modelling faunal responses to climatic gradients with GIS: land snails as a case study

Abstract. This study describes and exemplifies a multivariate approach based on geographical information system (GIS) technology for the analysis of faunal responses to climatic gradients. The approach is particularly suitable for the analysis of museum collections, and it combines the data reduction capabilities of multivariate techniques (ordination and classification) with GIS tools for the manipulation of geographically referenced data. The specific steps of the analysis are (1) construction of a grid covering the study area at an appropriate resolution, (2) overlaying the grid with a data base of spatially referenced species records, (3) determining the number of times each species was recorded in each cell, (4) constructing a matrix of grid cells by species where each entry indicates the number of records of a particular species in a particular cell, (5) removing cells whose total number of records is lower than some threshold (to be determined) from the matrix, (6) analysis of the reduced matrix using ordination and classification techniques, (7) construction of maps representing the results of the multivariate analyses, and (8) analysis of these maps with respect to digital maps of relevant climatological factors. The applicability of this approach was evaluated by analysing the response of the land snail fauna of Israel to regional variation in mean annual rainfall. As was expected, patterns of faunal variation were significantly correlated with underlying variation in rainfall. However, the per-unit effect of rainfall on the composition of the studied fauna was much greater in dry regions than in more rainy areas. Above 450 mm, no relationships could be detected between the observed patterns of faunal variation and rainfall. These patterns were consistent over a wide range of grid cell sizes (5–20 km), and were robust to outliers. The overall results indicate that the integration of GIS tools with standard multivariate techniques may serve as a valuable methodology for the identification and interpretation of regional patterns of faunal variation.     

Pax6 and Pdx1 form a functional complex on the rat somatostatin gene upstream enhancer

The somatostatin upstream enhancer (SMS-UE) is a highly complex enhancer element. The distal A-element contains overlapping Pdx1 and Pbx binding sites. However, a point mutation in the A-element that abolishes both Pdxl and Pbx binding does not impair promoter activity. In contrast, a point mutation that selectively eliminates Pdx1 binding to a proximal B-element reduces the promoter activity. The B-element completely overlaps with a Pax6 binding site, the C-element. A point mutation in the C-element demonstrates that Pax6 binding is essential for promoter activity. Interestingly, a block mutation in the A-element reduces both Pax6 binding and promoter activity. In heterologous cells, Pdx1 potentiated Pax6 mediated activation of a somatostatin reporter. We conclude that the beta/delta-cell-specific activity of the SMS-UE is achieved through simultaneous binding of Pdx1 and Pax6 to the B- and C-elements, respectively. Furthermore, the A-element appears to stabilise Pax6 binding.     

The wild-type allele of tonB in Escherichia coli is dominant over the tonB1 allele,encoding TonBQ160K,which suppresses the btuB451 mutation

The entire coding sequence of the tonB gene, except for nine codons at the 3′ end, was deleted from the chromosome of Escherichia coli. Introduction of the btuB451 suppressor mutant tonB1 into the chromosome of such a tonB deletion strain showed that the tonB1 allele was active as a suppressor in a single copy at 37° C and 42° C but not at 28° C. No temperature dependence was seen when FepA- or FhuA-dependent activities of the tonB1 gene product (TonB_Q160K) were tested. The btuB451 suppressor activity of tonB1 was inhibited by the simultaneous presence within the cells of the tonB ⁺ allele on a multicopy plasmid. This represents the first case of dominance among different tonB alleles. Inhibition of suppression was abolished by overexpression of the btuB451-encoded receptor protein. Competition for binding of TonB⁺ and TonB_Q150K to ExbB was excluded as the cause of dominance. Based on our data we conclude that competition for binding of TonB ⁺ and TonB_Q160K to the btuB451 gene product is the reason for the observed dominance. The implications of these findings for the mechanism of btuB451 suppression by tonB1 are discussed.     

Cytological and Physiological Reasons for the Latent Type of Infection in Sunflower Caused by Plasmopara halstedii

Lightmicroscopy was used to investigate cytological and physiological reasons for the latent type of infection of sunflowers with Plasmopara halstedii. Sections of the hypocotyl of inoculated, but healthy looking plants of compatible and incompatible host-pathotype combinations revealed vital hyphae and oospores, thus indicating an uninterrupted life cycle of the pathogen. Plants with latent infections showed enhanced cell division activities which restricted the pathogen to the cortical parenchyma. Additionally, hypersensitive reactions inhibited further growth in the pith parenchyma. In contrast, for systemic infection a successful invasion by the pathogen of the pith parenchyma of the hypocotyl and a growth of the hyphae faster than the hypersensitive reactions of the host tissue are needed.     

Principes de la lecture critique de la littérature médicale: Illustration urologique

There has been an enormous expansion in scientific literature, especially in the area of health and medicine. At the same time the complexity of the research has increased. Through the reading of medical literature of his field of interest, the physician is in search of useful information. However, reading medical papers is very time consuming and most physicians, for their usual literature review, content themselves with the titles and the abstracts. Moreover, quality and relevancy of the publications vary greatly and the reader must be able to “separate the wheat from the chaff”. Thus the reading of literature needs selection and evaluation. As a result, physicians require critical appraisal skills. The principle of appraisal of medical literature is to assess the value of publications which will influence the medical practice of the reader. The reader has a double objective: to assess the credibility of the publications, and to define the applicability of the publication information. By following eight steps the reader is able to quickly rule out from his reading what is not valid and have an objective look at the quality of the results which are proposed to him. These eight steps comprise the assessment of the study objectives, the study design, the study factor(s), the outcome factor(s), the study population and sample, the confounding factor(s) and bias, the results with their statistical and clinical significance and the power of the study, and, lastly, the synthesis of the reader's judgment. The last word belongs to the clinician facing his patient.     

Acoustic signalling in palaeotropical bushcrickets (Orthoptera: Tettigonioidea: Pseudophyllidae): does predation pressure by eavesdropping enemies differ in the Palaeo- and Neotropics?

When producing its calling song, a male bushcricket exposes itself to predators which use this sound for localization. Male signalling therefore has to be a compromise between attracting females and avoiding predators. In this study, the calling song structure of six Malaysian bushcricket species of the family Pseudophyllidae was examined. The lowest frequency of longdistance signals in insects yet discovered is the 600 Hz produced by Tympanophyllum arcufolium. The peak frequency of all six species and three additional species, from which only handling sounds were examined, was below 12 kHz. The duty cycle (that period of time spent signalling) was low, between one and five percent in four species and more than 20 percent in the remaining two species, typical for species which rely on camouflage. None of the various types of bat avoidance behaviour observed in the neotropical Pseudophyllidae was found in the Malaysian species. This difference is discussed in regard to the possibility of different predation pressures in the Palaeo- and Neotropics.     

Plasma membranes from cardiac cells in culture. Enzymatic radio-iodination,evaluation of preparation and properties of the sarcolemma

Plasma membranes from heart (sarcolemma) were prepared by the method of Kidwai, A.M. ((1975) Methods in Enzymology (Fleischer, S. and Packer, L., eds.), Vol. XXXIA, pp. 134–144, Academic Press, New York). On many occasions the sarcolemmal fraction identified by the enzyme markers such as $\text{(}\text{Na}{}^{\mathrm{+}}\text{+}\text{K}{}^{\mathrm{+}}\text{)-}\text{ATPase}$ banded at heavier densities ($\text{3 > 1.25}\text{g/ml}$) than expected for plasma membrane ($\text{d < 1.15}\text{g/ml}$). Radio-iodination of the membrane was added as an independent marker and conditions for the reproducible preparation of the sarcolemma were studied. Cultured heart cells were enzymatically iodinated under conditions which did not affect viability and labeled primarily the sarcolemma. The distribution of radioactivity in homogenates of cultured cells on the density gradient corresponded to that of the enzymes' activity. The best sarcolemma preparation was obtained with 0.3 M KCl extraction of heart homogenates in the presence of 0.05 M pyrophosphate, especially if the salt was also present during the fractionation by density gradient centrifugation. Alterations in the density were also observed with erythrocytes and cultured liver cells' plasma membrane. The data suggests a meta-stable state of the plasma membranes due to handling or storage which could cause alterations of some of their physical properties (e.g. density).     

Flavanone synthase from Petroselinum hortense. Molecular weight, subunit composition, size of messenger RNA, and absence of pantetheinyl residue.

Flavanone synthase from irradiated cell suspension cultures of parsley was purified to apparent homogeneity. Molecular weights of about 77 000 for the enzyme and about 42 000 for the subunits were determined respectively by sedimentation-equilibrium measurements and disc-gel electrophoresis in the presence of dodecyl sulfate. A specific antiserum was prepared for the enzyme and was used in an assay for flavanone synthase mRNA activity in partially purified RNA preparations. The apparent molecular size of flavanone synthase mRNA was estimated by sucrose gradient centrifugation and gel electrophoresis under partially denaturing conditions. Values of about 17 S and Mr = 0.62 X 10(6) were obtained. The fractionation patterns suggested that flavanone synthase mRNA was homogeneous in size. All together, the results support the idea that the enzyme is composed of two subunits which are probably identical. Amino acid analysis and a microbial assay were carried out to test the possible occurrence of cysteamine, beta-alanine, and pantothenate in the enzyme. The results were negative, indicating the absence of pantetheine or a similar residue. The possible similarity in mechanism between flavanone synthase and 3-oxoacyl-(acyl carrier protein) synthase is discussed.