Genetic and mutational analysis of virulence traits and their modulation in an environmental toxigenic Vibrio cholerae non-O1/non-O139 strain, VCE232

Vibrio cholerae O1 and O139 isolates deploy cholera toxin (CT) and toxin-coregulated pilus (TCP) to cause the diarrhoeal disease cholera. The ctxAB and tcpA genes encoding CT and TCP are part of two acquired genetic elements, the CTX phage and Vibrio pathogenicity island-1 (VPI-1), respectively. ToxR and ToxT proteins are the key regulators of virulence genes of V. cholerae O1 and O139. V. cholerae isolates belonging to serogroups other than O1/O139, called non-O1/non-O139, are usually devoid of virulence-related elements and are non-pathogenic. Here, we have analysed the available whole genome sequence of an environmental toxigenic V. cholerae non-O1/non-O139 strain, VCE232, carrying the CTX phage and VPI-1. Extensive bioinformatics and phylogenetic analyses indicated high similarity of the VCE232 genome sequence with the genome of V. cholerae O1 strains, including organization of the VPI-1 locus, ctxAB, tcpA and toxT genes, and promoters. We established that the VCE232 strain produces an optimal amount of CT at 30 °C under AKI conditions. To investigate the role of ToxT and ToxR in the regulation of virulence factors, we constructed ΔtoxT, ΔtoxR and ΔtoxTΔtoxR deletion mutants of VCE232. Extensive genetic analyses of these mutants indicated that the toxT and toxR genes of VCE232 are crucial for CT and TCP production. However, unlike O1 isolates, the presence of either toxT or toxR gene is sufficient for optimal CT production in VCE232. In addition, the VCE232 ΔtoxR mutant showed differential regulation of the major outer membrane proteins, OmpT and OmpU. This is the first attempt to explore the regulation of expression of major virulence genes and regulators in an environmental toxigenic V. cholerae non-O1/non-O139 strain.

Atypical presentation of Goldenher syndrome- a rare scenario

In 1952 Goldenher described a case with triad of pre auricular tags, mandibular hypoplasia and ocular (epibulbar) dermoid and described the case as Goldenger Syndrome. Exact etiology of this disease is not known. Here we present a case of Goldenher syndrome in a 5 days old newborn who presented with all the classical features except ocular involvement.   Gorlin et.al named this syndrome as oculoauriculovertebral dysplasia due to presence of additional vertebral anomalies .2 Exact etiology of this disease is not known. Most of the cases are sporadic, though autosomal recessive, autosomal dominant and multifactorial inheritance has also been suggested.2.Chromosomal analysis shows no abnormalities.3 In this report we presented a case of Goldenger Syndrome in a 5 days old newborn who presented with all the classical features except occular involvement. Journal of College of Medical Sciences-Nepal, 2013, Vol-9, No-4, 59-62 DOI: http://dx.doi.org/10.3126/jcmsn.v9i4.10239

Isolated exon 8 deletion in type 1 spinal muscular atrophy with bilateral optic atrophy: unusual genetic mutation leading to unusual manifestation?

Proximal spinal muscular atrophy (SMA) or type 1 SMA is a fatal autosomal recessive disorder usually caused by homozygous deletion of exons 7 and 8 in the survivor motor neuron (SMN) gene. Additional deletion of the neuronal apotosis inhibitory protein (NAIP) gene exacerbates the clinical severity. Isolated exon 8 deletion has been reported in a single case series of SMA types 2 and 3 and never with SMA type 1. While extraocular muscles are typically spared, there are a few case reports documenting associated external ophthalmoplegia. Optic atrophy is a hitherto unreported association of SMA. We report a 10-month-old male infant with SMA type 1 with optic atrophy due to isolated deletion of exon 8 of the SMN gene with intact exon 7 and NAIP gene.

Optimizing tillage schedule for maintaining activity of the arbuscular mycorrhizal fungal population in a rainfed upland rice (Oryza sativa L.) agro-ecosystem

Rainfed uplands in India are predominantly mono-cropped with rice (Oryza sativa L.) in the wet season (June/July to September/October) and grown under aerobic soil conditions. The remaining fallow period (winter followed by summer) of about 8-9 months leads to natural crash in the population of native arbuscular mycorrhizal fungi (AMF) in the soil. Attempts have been made to minimize this population crash by reducing soil disturbance-induced deleterious effects on native AMF activity of improperly scheduled off-season tillage, an agronomic recommendation for weed and disease (soil-borne) management, practiced by the upland farmers. On-farm (farmers' field) evaluation of effects of all suitable off-season tillage schedule combinations on rice during wet seasons of 2004, 2005, and 2006 revealed that a maximum of two off-season tillage schedules with a minimum gap of 13 weeks between them minimized the population crash of native AMF with a concomitant increase in phosphorus (P) uptake and grain yield of upland rice (variety "Vandana").

Genetic organization of pre-CTX and CTX prophages in the genome of an environmental Vibrio cholerae non-O1, non-O139 strain

The cholera toxin (CT) is a critical determinant of the virulence of epidemic Vibrio cholerae strains. The ctxAB operon encoding CT is part of the genome of a filamentous bacteriophage CTXΦ, which may integrate as a single copy or as multiple copies in the genome of V. cholerae. The CTXΦ genome is composed of RS2 (2.4 kb) and core (4.5 kb) regions. In the present study extensive genetic mapping analyses indicated that two copies of tandemly arrayed CTX prophages are integrated in the small chromosome of an environmental V. cholerae strain, VCE232, belonging to serogroup O4. Further mapping revealed that the integration of prophages has occurred in the same genetic locus of the small chromosome of VCE232 as that of V. cholerae O1 biotype El Tor strains. Interestingly, a new type of RS2-like element 3.5 kb in size was found in the CTX prophage genome in the small chromosome of VCE232. Cloning followed by sequencing of the new RS2-like element of VCE232 revealed the presence of three ORFs, which probably encode highly divergent types of phage regulatory proteins. Furthermore, the strain VCE232 also harbours two copies of a tandemly arranged CTX prophage devoid of the ctxAB genes, called pre-CTX prophage, in its large chromosome. The presence of multiple copies of diverse CTX prophages in both the chromosomes of VCE232 suggests that toxigenic environmental V. cholerae non-O1, non-O139 strains could play a role in the emergence of new epidemic clones.

Vacuolar-type H+-ATPases at the plasma membrane regulate pH and cell migration in microvascular endothelial cells

Microvascular endothelial cells involved in angiogenesis are exposed to an acidic environment that is not conducive for growth and survival. These cells must exhibit a dynamic intracellular (cytosolic) pH (pHcyt) regulatory mechanism to cope with acidosis, in addition to the ubiquitous Na+/H+exchanger and HCO3−-based H+-transporting systems. We hypothesize that the presence of plasmalemmal vacuolar-type proton ATPases (pmV-ATPases) allows microvascular endothelial cells to better cope with this acidic environment and that pmV-ATPases are required for cell migration. This study indicates that microvascular endothelial cells, which are more migratory than macrovascular endothelial cells, express pmV-ATPases. Spectral imaging microscopy indicates a more alkaline pHcytat the leading than at the lagging edge of microvascular endothelial cells. Treatment of microvascular endothelial cells with V-ATPase inhibitors decreases the proton fluxes via pmV-ATPases and cell migration. These data suggest that pmV-ATPases are essential for pHcytregulation and cell migration in microvascular endothelial cells.

Molecular analysis of the rstR and orfU genes of the CTX prophages integrated in the small chromosomes of environmental Vibrio cholerae non-O1, non-O139 strains

The ctxAB genes encoding cholera toxin, reside in the genome of a filamentous bacteriophage CTXphi. The presence of CTX prophage in non-epidemic environmental Vibrio cholerae strains is rare. The CTX prophage, the lysogenic form of CTXphi in V. cholerae, is comprised of the 'RS2' and the 'Core'. Analysis of the rstR gene present in the RS2 region of the CTX prophage revealed the presence of new alleles of the prophages in four environmental non-O1, non-O139 strains VCE22 (O36), VCE228 (O27), VCE232 (O4) and VCE233 (O27), and the CTX prophages are located in the small chromosomes. Phylogenetic analysis based on the nucleotide sequences of the rstR and orfU (present in the core) genes of these prophages placed them in a single unique cluster, which is distally located compared with that of epidemic V. cholerae O1 strains. Further analysis indicated that the genome of the prophage present in the strain VCE22 is devoid of the ctxAB genes, called pre-CTX prophage and the strain also possess the toxin-coregulated pilus protein coding gene tcpA of classical type, another important pathogenicity determining locus of the epidemic V. cholerae strains. Comparative analysis of the nucleotide sequences of the rstR and orfU genes indicated that the pre-CTX prophage of VCE22 might be the progenitor of new alleles of the CTX prophages present in these environmental strains.

Role of biomodulators and involvement of protein tyrosine kinase on stem cell migration in normal and leukaemic mice

Tyrosine kinase has an important role with regard to self-renewal and as a comitogen in the movement of stem cells out of the haemopoietic stem cell pool into the progeny pool. The present investigation has an objective to evaluate the protein tyrosine kinase (PTK) activity of bone marrow derived pluripotent cells before and after application of biological response modifiers (BRMs) in normal and leukaemic mice. The PTK activity of the cytosolic fraction of bone marrow cells has been determined by the assay kit based on per-oxidase labeled substrate analog and biotin-streptavidin expression. A consequent cell population kinetic study has also been conducted. Results showed a higher activity in the cells of leukaemic mice, which under the influence of interleukin-2 (IL-2) and the non-specific BRM sheep erythrocytes (SRBC) undergo further activation. Interferon-gamma (IFN-gamma) when administered alone showed a suppressive effect and the combination of the three manifested a resultant suppression. Corresponding migration (cell population kinetics) of the bone marrow cells (BMC) also correlated well with the PTK activity of the cells concerned. The observations indicated that the pluripotent BMCs are under regulated control of the PTK activity, which can be manipulated by selective BRMs. The data also suggested the therapeutic benefit of IFN-gamma along with chemotherapeutics against leukaemia and that of IL-2 and SRBC during bone marrow failure.

Genesis of variants of Vibrio cholerae O1 biotype El Tor: role of the CTXphi array and its position in the genome

The gene encoding cholera toxin, the principal virulence factor of Vibrio cholerae, is encoded by a filamentous, lysogenic bacteriophage known as CTXphi. The genome of V. cholerae, the host for CTXphi, consists of two chromosomes, one large and one small. Here, it is shown that localization and array of CTX prophage DNA in either the large or small chromosome of V. cholerae is likely to be one of the reasons for the emergence of O1 biotype El Tor variants isolated just before and after the V. cholerae O139 cholera outbreak in 1992. Analyses of the organization of the CTX region of the genome of pre-O139 El Tor strains revealed that these strains carry two distinct CTX prophages integrated in the small chromosome in tandem: CTX(ET), the prophage having a conserved NotI site in its repeat sequence segment which seems to be specific for the El Tor strains so far examined, followed by CTX(calc)-like genome, the prophage found in recent O139 clinical isolates from Calcutta. In sharp contrast, in post-O139 El Tor strains only one copy of the CTX(ET) prophage was found to be integrated in the large chromosome. To the authors' knowledge, the presence of CTX prophage in the small chromosome of O1 El Tor strains has not been reported previously. It is also shown that the difference in the CTX copy number and the position of the bacteriophage on the genomes of pre- and post-O139 El Tor strains have an effect on cholera toxin production. While a pre-O139 strain produced maximum cholera toxin in yeast extract/peptone medium at 30 degrees C, a post-O139 El Tor strain showed maximal yield at 37 degrees C, indicating differential regulation of cholera toxin between the strains. It appears from this study that the variation in the integration site of the CTX prophage, its copy number and the presence of diverse phage genomes in V. cholerae O1 biotype El Tor may be strategically important for generating variants with subtle phenotypic modulations of virulence factor production in this longest-ruling seventh pandemic strain.

Facilitation of functional compartmentalization of bone marrow cells in leukemic mice by biological response modifiers: an immunotherapeutic approach

Biological Response Modifiers (BRMs) including interleukin-2 (IL-2), interferon-gamma (IFN-gamma) and sheep erythrocytes (SRBC) protected N,N'-ethylnitrosourea (ENU) induced leukaemic mice. Two cell types from the bone marrow were isolated in density specific gradient representing two distinct compartments, the low density cells being more CD34 positive than the high density group. Investigations with the functional efficacy of such compartments revealed significant improvement of cytotoxic efficacy and phagocytic burst at the high density compartment (HDC) level. The high density compartment was found to be more responsive towards the BRMs compared to the cells of the low density compartment (LDC). It was suggested that use of BRMs in vivo can stimulate a potent functional progenitor compartmentalization in normal as well as leukaemic mice. These observations are expected to help a logistic approach towards combined BRM therapy at the clinical level.

Lipoarabinomannan from Mycobacterium tuberculosis promotes macrophage survival by phosphorylating Bad through a phosphatidylinositol 3-kinase/Akt pathway

Efforts in prevention and control of tuberculosis suffer from the lack of detailed knowledge of the mechanisms used by pathogenic mycobacteria for survival within host cell macrophages. The exploitation of host cell signaling pathways to the benefit of the pathogen is a phenomenon that deserves to be looked into in detail. We have tested the hypothesis that lipoarabinomannan (LAM) from the virulent species of Mycobacterium tuberculosis possesses the ability to modulate signaling pathways linked to cell survival. The Bcl-2 family member Bad is a proapoptotic protein. Phosphorylation of Bad promotes cell survival in many cell types. We demonstrate that man-LAM stimulates Bad phosphorylation in a phosphatidylinositol 3-kinase (PI-3K)-dependent pathway in THP-1 cells. Man-LAM activated PI-3K. LAM-stimulated phosphorylation of Bad was abrogated in cells transfected with a dominant-negative mutant of PI-3K (Delta p85), indicating that activation of PI-3K is sufficient to trigger phosphorylation of Bad by LAM. Since phosphorylation of Bad occurred at serine 136, the target of the serine/threonine kinase Akt, the effect of LAM on Akt kinase activity was tested. Man-LAM could activate Akt as evidenced from phosphorylation of Akt at Thr(308) and by the phosphorylation of the exogenous substrate histone 2B. Akt activation was abrogated in cells transfected with Deltap85. The phosphorylation of Bad by man-LAM was abrogated in cells transfected with a kinase-dead mutant of Akt. These results establish that LAM-mediated Bad phosphorylation occurs in a PI-3K/Akt-dependent manner. It is therefore the first demonstration of the ability of a mycobacterial virulence factor to up-regulate a signaling pathway involved in cell survival. This is likely to be one of a number of virulence-associated mechanisms by which bacilli control host cell apoptosis.

Effects of enoximone on quality of life

To assess whether an inotropic agent may affect quality of life in severe heart failure, a double-blind, placebo-controlled crossover study was performed in 10 patients over three periods of 3 weeks, including an initial control period of 3 weeks and periods on placebo or enoximone, 150 mg t.d.s. Quality of life was assessed by a questionnaire following initial training of patients to evaluate their symptoms after certain stresses, by visual analogue scales of symptoms, and by objective assessments during graded exercise. Daily dyspnoea score decreased from 33.2 +/- 2 (placebo) to 27.7 +/- 4 (enoximone) (P less than 0.01) and daily fatigue score decreased from 14.8 +/- 2.5 (placebo) to 12.6 +/- 2 (enoximone) (P less than 0.05). There were also significant beneficial responses in the mean daily NYHA class and in the duration of a walking test. Self-assessed global quality of life score increased from 2.7 +/- 0.6 (placebo) to 3.6 +/- 0.8 (enoximone) (P less than 0.05). It was concluded that over periods of 3 weeks, enoximone significantly improved self-assessed quality of life.