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Host Organism (host + organism)
Selected AbstractsEvasion of innate and adaptive immune responses by influenza A virusCELLULAR MICROBIOLOGY, Issue 7 2010Mirco Schmolke Summary Host organisms have developed sophisticated antiviral responses in order to defeat emerging influenza A viruses (IAVs). At the same time IAVs have evolved immune evasion strategies. The immune system of mammals provides several lines of defence to neutralize invading pathogens or limit their replication. Here, we summarize the mammalian innate and adaptive immune mechanisms involved in host defence against viral infection and review strategies by which IAVs avoid, circumvent or subvert these mechanisms. We highlight well-characterized, as well as recently described features of this intriguing virus-host molecular battle. [source] Listeria monocytogenes response regulators important for stress tolerance and pathogenesisFEMS MICROBIOLOGY LETTERS, Issue 1 2001Birgitte H. Kallipolitis Abstract Environmental sensing by two-component signal transduction systems is likely to play a role for growth and survival of Listeria monocytogenes both during transmission in food products and within a host organism. Two-component systems typically consist of a membrane-associated sensor histidine kinase and a gene regulatory protein, the response regulator (RR). We have identified seven putative RR genes in L. monocytogenes LO28 by PCR using degenerate oligonucleotide primers. By insertional inactivation we obtained data suggesting that three of the putative RRs contribute to the pathogenicity of L. monocytogenes in mice. Strikingly, the mutants that were attenuated in virulence also had a decreased ability to grow in the presence of various stress conditions potentially encountered in an infection process. Thus, our data point to a connection between the ability of the putative two-component systems to sense and respond to certain environmental stimuli, and the virulence of L. monocytogenes. [source] The role of host organism, transcriptional switches and reporter mechanisms in the performance of Hg-induced biosensorsJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2004M. Harkins Abstract Aims:, The purpose of this study was to comprehensively compare the response of nine biosensors capable of being induced by Hg. Induction by Hg was based upon the insertion of merR, merB, zntA and zntR promoter genes. LuxCDABE or lucFF reporter genes expressed luminescence, and host organisms were Escherichia coli, Vibrio anguillarum and Pseudomonas fluorescens. The role of transcriptional switches, reporter mechanism and host organism was to be investigated. Methods and Results:, All biosensors were subjected to the same assay conditions. Sensors had their own individual growth characteristics and response to the doses of Hg tested. Maximum bioluminescence response was induced by concentrations of Hg between 2·5 nm and 5 ,m. E. coli pRB28 was found to detect levels of Hg as low as 1·6 nm and yet was capable of operating in a concentration range of up to 12·5 ,m. Conclusions:, The response of the sensors demonstrated their suitability for analysis under environmentally relevant concentrations. The sensitivity of the sensors, the optimum range and the expediency of the assay could not be related to a single sensor trait. It may be concluded that biosensor performance is dependent on more than one of the single factors studied. Significance and Impact of the Study:, The results show that comparative testing of sensors is an important step in evaluating the relevance and performance of biosensors prior to routine environmental application. [source] REGULAR PAPERS Unusual stable isotope fractionation patterns observed for fish host,parasite trophic relationshipsJOURNAL OF FISH BIOLOGY, Issue 3 2001J. K. Pinnegar Trophic relationships between four taxa of fish parasite (Cestoda, Nematoda, Isopoda, Copepoda) and their hosts (Gasterosteus aculeatus, Merlangius merlangus, Boops boops, Platichthys flesus) were investigated using stable isotopes of carbon and nitrogen. ,15N differences between parasite and host were unlike those conventionally observed among consumers and their diets. In no case were parasites enriched in 15N with respect to the host organism; endoparasites were significantly and consistently depleted. In no case were parasites enriched in 15N with respect to the host organism; endoparasites were significantly and consistently depleted. [source] A New Biological Matrix for Septal OcclusionJOURNAL OF INTERVENTIONAL CARDIOLOGY, Issue 2 2003CHRISTIAN JUX, M.D. The ideal septal occluder scaffold should promote the healthiest and most complete healing response possible while eventually facilitating the full resorption of the material, leaving "native" tissue behind. An excellent biocompatibility of the scaffold tissue is a prerequisite for quick, complete, and firm ingrowth of the device, optimizing outcomes and minimizing the potential for complications. Intestinal collagen layer (ICL) is a highly purified (acellular) bioengineered type-1 collagen derived from porcine submucosa. It is gradually resorbed by the host organism and subsequently replaced by the host tissue. CardioSEAL® occluders were modified by substituting the conventional polyester fabric for an intestinal collagen layer (ICL). Percutaneous transcatheter closure of interventionally created atrial septal defects was performed in lambs using these modified occluders. A complete pathomorphological investigation including histology was carried out after 2, 4, and 12 weeks follow-up. Standard CardioSEAL implants served as a control group. After 2 weeks in vivo the devices were already covered completely by neo-endothelium. Compared with the conventional synthetic scaffold, ICL devices showed a quicker endothelialization, decreased thrombogenicity, and superior biocompatibility with no significant cellular infiltration observed in the histology of explants with ICL fabrics. After 3 months in vivo the collagen layer remained mechanically intact, but began to show the first histological signs of mild disintegration, gradual resorption, and remodeling. In conclusion, short-term results from preliminary in vivo experiments using a bioengineered collagen matrix as the occluder tissue scaffold showed excellent biocompatibility. This resulted in superior overall results: quicker endothelialization, a decreased thrombogenicity, and decreased immunological host response. (J Interven Cardiol 2003;16:149,152) [source] Cell-free expression and selective isotope labelling in protein NMRMAGNETIC RESONANCE IN CHEMISTRY, Issue S1 2006David Staunton Abstract Isotope labelling is a very powerful tool in NMR studies of proteins and has been employed in various ways for over 40 years. 15N and 13C incorporation, using recombinant expression systems, is now commonplace because heteronuclear experiments assist with the fundamental problems of peak resolution and assignment. The use of selective labelling for peak assignment has been restricted by the scrambling of isotope label through metabolic pathways within the expression host organism. The availability of efficient cell-free expression systems with low levels of metabolic conversion allow the increasing use of selective isotope labelling as a tool in protein NMR. We describe two examples, one where a selective labelling scheme can identify backbone amide peaks from unassigned 1H15N HSQC and HNCO spectra of a 84 residue protein, and another where a specific backbone amide in a 198 residue construct of the ninth and tenth Type III repeats from human fibronectin can be labelled and rapidly identified using a simple HSQC experiment. Copyright © 2006 John Wiley & Sons, Ltd. [source] Role of drug metabolism in drug discovery and developmentMEDICINAL RESEARCH REVIEWS, Issue 5 2001Gondi N. Kumar Abstract Metabolism by the host organism is one of the most important determinants of the pharmacokinetic profile of a drug. High metabolic lability usually leads to poor bioavailability and high clearance. Formation of active or toxic metabolites will have an impact on the pharmacological and toxicological outcomes. There is also potential for drug,drug interactions with coadministered drugs due to inhibition and/or induction of drug metabolism pathways. Hence, optimization of the metabolic liability and drug,drug interaction potential of the new chemical entities are some of the most important steps during the drug discovery process. The rate and site(s) of metabolism of new chemical entities by drug metabolizing enzymes are amenable to modulation by appropriate structural changes. Similarly, the potential for drug,drug interactions can also be minimized by appropriate structural modifications to the drug candidate. However, the optimization of the metabolic stability and drug,drug interaction potential during drug discovery stage has been largely by empirical methods and by trial and error. Recently, a lot of effort has been applied to develop predictive methods to aid the optimization process during drug discovery and development. This article reviews the role of drug metabolism in drug discovery and development. © 2001 John Wiley & Sons, Inc. Med Res Rev, 21, No. 5, 397,411, 2001 [source] Substrate specificity of three cytochrome c haem lyase isoenzymes from Wolinella succinogenes: unconventional haem c binding motifs are not sufficient for haem c attachment by NrfI and CcsA1MOLECULAR MICROBIOLOGY, Issue 1 2010Melanie Kern Summary Bacterial c -type cytochrome maturation is dependent on a complex enzymic machinery. The key reaction is catalysed by cytochrome c haem lyase (CCHL) that usually forms two thioether bonds to attach haem b to the cysteine residues of a haem c binding motif (HBM) which is, in most cases, a CX2CH sequence. Here, the HBM specificity of three distinct CCHL isoenzymes (NrfI, CcsA1 and CcsA2) from the Epsilonproteobacterium Wolinella succinogenes was investigated using either W. succinogenes or Escherichia coli as host organism. Several reporter c -type cytochromes were employed including cytochrome c nitrite reductases (NrfA) from E. coli and Campylobacter jejuni that differ in their active-site HBMs (CX2CK or CX2CH). W. succinogenes CcsA2 was found to attach haem to standard CX2CH motifs in various cytochromes whereas other HBMs were not recognized. NrfI was able to attach haem c to the active-site CX2CK motif of both W. succinogenes and E. coli NrfA, but not to NrfA from C. jejuni. Different apo-cytochrome variants carrying the CX15CH motif, assumed to be recognized by CcsA1 during maturation of the octahaem cytochrome MccA, were not processed by CcsA1 in either W. succinogenes or E. coli. It is concluded that the dedicated CCHLs NrfI and CcsA1 attach haem to non-standard HBMs only in the presence of further, as yet uncharacterized structural features. Interestingly, it proved impossible to delete the ccsA2 gene from the W. succinogenes genome, a finding that is discussed in the light of the available genomic, proteomic and functional data on W. succinogenes c -type cytochromes. [source] Autoinduction and signal transduction in the regulation of staphylococcal virulenceMOLECULAR MICROBIOLOGY, Issue 6 2003Richard P. Novick Summary The accessory genes of Staphylococcus aureus, in-cluding those involved in pathogenesis, are controlled by a complex regulatory network that includes at least four two-component systems, one of which, agr, is a quorum sensor, an alternative sigma factor and a large set of transcription factors, including at least two of the superantigen genes, tst and seb. These regulatory genes are hypothesized to act in a time- and population density-dependent manner to integrate signals received from the external environment with the internal metabolic machinery of the cell, in order to achieve the production of particular subsets of accessory/virulence factors at the time and in quantities that are appropriate to the needs of the organism at any given location. From the standpoint of pathogenesis, the regulatory agenda is presumably tuned to particular sites in the host organism. To address this hypothesis, it will be necessary to understand in considerable detail the regulatory interactions among the organism's numerous controlling systems. This review is an attempt to integrate a large body of data into the beginnings of a model that will hopefully help to guide research towards a full-scale test. [source] Near-atomic resolution analysis of BipD, a component of the type III secretion system of Burkholderia pseudomalleiACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 9 2010M. Pal Burkholderia pseudomallei, the causative agent of melioidosis, possesses a type III protein secretion apparatus that is similar to those found in Salmonella and Shigella. A major function of these secretion systems is to inject virulence-associated proteins into target cells of the host organism. The bipD gene of B. pseudomallei encodes a secreted virulence factor that is similar in sequence and is most likely to be functionally analogous to IpaD from Shigella and SipD from Salmonella. Proteins in this family are thought to act as extracellular chaperones at the tip of the secretion needle to help the hydrophobic translocator proteins enter the target cell membrane, where they form a pore and may also link the translocon pore with the secretion needle. BipD has been crystallized in a monoclinic crystal form that diffracted X-rays to 1.5,Å resolution and the structure was refined to an R factor of 16.1% and an Rfree of 19.8% at this resolution. The putative dimer interface that was observed in previous crystal structures was retained and a larger surface area was buried in the new crystal form. [source] Structure and biochemical characterization of an adenylate kinase originating from the psychrophilic organism Marinibacillus marinusACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 8 2009Milya Davlieva Adenylate kinases (AKs; EC 2.7.4.3) are essential members of the NMP kinase family that maintain cellular homeostasis by the interconversion of AMP, ADP and ATP. AKs play a critical role in adenylate homeostasis across all domains of life and have been used extensively as prototypes for the study of protein adaptation and the relationship of protein dynamics and stability to function. To date, kinetic studies of psychrophilic AKs have not been performed. In order to broaden understanding of extremophilic adaptation, the kinetic parameters of adenylate kinase from the psychrophile Marinibacillus marinus were examined and the crystal structure of this cold-adapted enzyme was determined at 2.0,Å resolution. As expected, the overall structure and topology of the psychrophilic M. marinus AK are similar to those of mesophilic and thermophilic AKs. The thermal denaturation midpoint of M. marinus AK (321.1,K) is much closer to that of the mesophile Bacillus subtilis (320.7,K) than the more closely related psychrophile B. globisporus (316.4,K). In addition, the enzymatic properties of M. marinus AK are quite close to those of the mesophilic AK and suggests that M. marinus experiences temperature ranges in which excellent enzyme function over a broad temperature range (293,313,K) has been retained for the success of the organism. Even transient loss of AK function is lethal and as a consequence AK must be robust and be well adapted to the environment of the host organism. [source] The first structure of a cold-adapted superoxide dismutase (SOD): biochemical and structural characterization of iron SOD from Aliivibrio salmonicidaACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 2 2009Hege Lynum Pedersen Superoxide dismutases (SODs) are metalloenzymes that catalyse the dismutation of the superoxide radical anion into O2 and H2O2 in a two-step reaction. The crystal structure of the iron superoxide dismutase from the cold-adapted and fish-pathogenic bacterium Aliivibrio salmonicida (asFeSOD) has been determined and refined to 1.7,Å resolution. The protein has been characterized and compared with the closely related homologous iron superoxide dismutase from the mesophilic Escherichia coli (ecFeSOD) in an attempt to rationalize its environmental adaptation. ecFeSOD shares 75% identity with asFeSOD. Compared with the mesophilic FeSOD, the psychrophilic FeSOD has distinct temperature differences in residual activity and thermostability that do not seem to be related to structural differences such as intramolecular or intermolecular ion bonds, hydrogen bonds or cavity sizes. However, an increased net negative charge on the surface of asFeSOD may explain its lower thermostability compared with ecFeSOD. Activity measurements and differential scanning calorimetry measurements revealed that the psychrophilic asFeSOD had a thermostability that was significantly higher than the optimal growth temperature of the host organism. [source] Strategy for selecting and characterizing linker peptides for CBM9-tagged fusion proteins expressed in Escherichia coliBIOTECHNOLOGY & BIOENGINEERING, Issue 3 2007Mojgan Kavoosi Abstract The influence of linker design on fusion protein production and performance was evaluated when a family 9 carbohydrate-binding module (CBM9) serves as the affinity tag for recombinant proteins expressed in Escherichia coli. Two bioinformatic strategies for linker design were applied: the first identifies naturally occurring linkers within the proteome of the host organism, the second involves screening peptidases and their known specificities using the bioinformatics software MEROPSÔ to design an artificial linker resistant to proteolysis within the host. Linkers designed using these strategies were compared against traditional poly-glycine linkers. Although widely used, glycine-rich linkers were found by tandem MS data to be susceptible to hydrolysis by E. coli peptidases. The natural (PT)xP and MEROPSÔ-designed S3N10 linkers were significantly more stable, indicating both strategies provide a useful approach to linker design. Factor Xa processing of the fusion proteins depended strongly on linker chemistry, with poly(G) and S3N10 linkers showing the fastest cleavage rates. Luminescence resonance energy transfer studies, used to measure average distance of separation between GFP and Tb(III) bound to a strong calcium-binding site of CBM9, revealed that, for a given linker chemistry, the separation distance increases with increasing linker length. This increase was particularly large for poly(G) linkers, suggesting that this linker chemistry adopts a hydrated, extended configuration that makes it particularly susceptible to proteolysis. Differential scanning calorimetry studies on the PT linker series showed that fusion of CBM9 to GFP did not alter the Tm of GFP but did result in a destabilization, as seen by both a decrease in Tm and ,Hcal, of CBM9. The degree of destabilization increased with decreasing length of the (PT)xP linker such that ,Tm,=,,8.4°C for the single P linker. Biotechnol. Bioeng. 2007;98: 599,610. © 2007 Wiley Periodicals, Inc. [source] Crystallization and preliminary X-ray diffraction analysis of BipD, a virulence factor from Burkholderia pseudomalleiACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 8 2006M. J. Knight Burkholderia pseudomallei, the causative agent of melioidosis, possesses a protein-secretion apparatus that is similar to those found in Salmonella and Shigella. A major function of these secretion systems is to secrete virulence-associated proteins into target cells of the host organism. The BipD gene of B. pseudomallei encodes a secreted virulence factor that is similar in sequence and most likely functionally analogous to IpaD from Shigella and SipD from Salmonella. Thus, the BipD protein is likely to be a component of a type III protein-secretion system (TTSS) in B. pseudomallei. Proteins in the same class as BipD, such as IpaD and SipD, are thought to act as extracellular chaperones to help the hydrophobic translocator proteins enter the target cell membrane, where they form a pore and might even link the translocon pore with the secretion needle. There is evidence that the translocator proteins also bind an integrin which stimulates actin-mediated insertion of the bacterium into the host-cell membrane. Native BipD has been crystallized in a monoclinic crystal form that diffracts X-rays to 2.5,Å resolution. BipD protein which incorporates selenomethionine (SeMet-BipD) has also been expressed and forms crystals which diffract to a higher resolution of 2.1,Å. [source] Biogeography of bacteria associated with the marine sponge Cymbastela concentricaENVIRONMENTAL MICROBIOLOGY, Issue 3 2005Michael W. Taylor Summary Recent debate regarding microbial biogeography has focused largely on free-living microbes, yet those microbes associated with host organisms are also of interest from a biogeographical perspective. Marine eukaryotes and associated bacteria should provide ideal systems in which to consider microbial biogeography, as (i) bacteria in seawater should be able to disperse among individuals of the same host species, yet (ii) potential for adaptation to particular hosts (and thus speciation) also exists. We used 16S rDNA-DGGE (denaturing gradient gel electrophoresis) to examine geographic variability in bacterial community composition in the marine sponge Cymbastela concentrica. Denaturing gradient gel electrophoresis banding patterns (and phylogenetic analysis of excised DGGE bands) indicated different communities in Cymbastela concentrica from tropical versus temperate Australia. In contrast, communities were very similar over a 500-km portion of the sponge's temperate range. Variation in bacterial community composition was also considered with respect to ocean current patterns. We speculate that the divergent communities in different parts of the sponge's range provide evidence of endemism attributed to host association, although variation in environmental factors such as light and temperature could also explain the observed results. Interestingly, bacterial communities in seawater varied much less between tropical and temperate locations than did those in C. concentrica, supporting the concept of widespread dispersal among these free-living microbes. [source] Telotroch formation, survival, and attachment in the epibiotic peritrich Zoothamnium intermedium (Ciliophora, Oligohymenophorea)INVERTEBRATE BIOLOGY, Issue 3 2008Laura R.P. Utz Abstract. Aspects of the life cycle of the peritrich ciliate Zoothamnium intermedium, an epibiont on calanoid copepods in the Chesapeake Bay, were investigated using host and epibiont cultures. Experiments were designed to characterize the formation, survival, and attachment of free-swimming stages (telotrochs) and to assess whether telotrochs preferentially attach to primary (Acartia tonsa and Eurytemora affinis) or alternate hosts from the zooplankton community (the rotifer Brachionus plicatilis, barnacle nauplii, polychaete larvae, and a harpacticoid copepod). The results showed that telotroch formation started 2 h after the death of the host, with >90% of the zooids leaving the host carapace within 7 h. Formation of telotrochs was triggered only by the death of the host, failing to occur when the host was injured or unable to swim. Telotrochs failed to attach to non-living substrates and survived for only 14 h in the absence of host organisms, suggesting that members of Z. intermedium are obligate epibionts. Attachment success decreased with telotroch age, indicating that colonization success in nature may strongly depend on the ability to find a suitable host in a short period of time. Individuals exhibited no preferences in colonizing juvenile or adult stages of A. tonsa or E. affinis. While telotrochs were able to colonize barnacle nauplii and the harpacticoid copepod in the absence of individuals of A. tonsa or E. affinis, they did not attach to the rotifers or polychaete larvae. Telotrochs preferentially colonized individuals of A. tonsa when in the presence of other non-calanoid host species. [source] The role of host organism, transcriptional switches and reporter mechanisms in the performance of Hg-induced biosensorsJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2004M. Harkins Abstract Aims:, The purpose of this study was to comprehensively compare the response of nine biosensors capable of being induced by Hg. Induction by Hg was based upon the insertion of merR, merB, zntA and zntR promoter genes. LuxCDABE or lucFF reporter genes expressed luminescence, and host organisms were Escherichia coli, Vibrio anguillarum and Pseudomonas fluorescens. The role of transcriptional switches, reporter mechanism and host organism was to be investigated. Methods and Results:, All biosensors were subjected to the same assay conditions. Sensors had their own individual growth characteristics and response to the doses of Hg tested. Maximum bioluminescence response was induced by concentrations of Hg between 2·5 nm and 5 ,m. E. coli pRB28 was found to detect levels of Hg as low as 1·6 nm and yet was capable of operating in a concentration range of up to 12·5 ,m. Conclusions:, The response of the sensors demonstrated their suitability for analysis under environmentally relevant concentrations. The sensitivity of the sensors, the optimum range and the expediency of the assay could not be related to a single sensor trait. It may be concluded that biosensor performance is dependent on more than one of the single factors studied. Significance and Impact of the Study:, The results show that comparative testing of sensors is an important step in evaluating the relevance and performance of biosensors prior to routine environmental application. [source] 28 Lipid composition of members of the algal class chlorarachniophyceaeJOURNAL OF PHYCOLOGY, Issue 2003J. L. Dahmen The algal class Chlorarachniophyceae is comprised of a small group of unicellular eukaryotic algae that are often characterized by an unusual amoeboid morphology. This morphology is hypothesized to be the result of a secondary endosymbiosis in which a green alga was engulfed as prey by a nonphotosynthetic amoeba or amoebaflagellate. Whereas much is known about the phylogenetic relationships of individual chlorarachniophytes to one another, and to possible ancestral host organisms in the genera Cercomonas and Heteromita, little is known about their physiology, particularly that of their lipids. In an initial effort to characterize the lipids of this algal class, seven organisms were examined for their fatty acid and sterol composition. These included Bigelowiella natans, Chlorarachnion globusum, Chlorarachnion reptans, Gymnochlora stellata, Lotharella amoeboformis, Lotharella globosa, and Lotharella sp. Fatty acids associated with chloroplast-associated glycolipids, cytoplasmic membrane-associated phospholipids, and storage triglycerides were characterized. Glycolipid fatty acids were found to be of limited composition, containing principally eicosapentaenoic acid [20:5(n-3)] and hexadecanoic acid (16:0), which ranged in relative percentage from 67,90% and 10,29%, respectively, in these seven organisms. Triglyceride-associated fatty acids were found to be similar. Phospholipid fatty acid composition was more variable. The principal phospholipid fatty acids, 16:0 (25,32%) and a compound tentatively identified as docosapentaenoic acid [22:5(n-3)] (26,35%), were found along with a number of C18 and C20 fatty acids. All organisms contained two sterols as free sterols. These were tentatively identified as 24-ethylcholesta-5,22E-dien-3b-ol (stigmasterol; 70,95%) and 24-methylcholesta-5,22E-dien-3b-ol (brassicasterol; 5,30%). [source] Quorum sensing and signal interference: diverse implicationsMOLECULAR MICROBIOLOGY, Issue 6 2004Lian-Hui Zhang Summary Quorum sensing (QS) is a community genetic regulation mechanism that controls microbiological functions of medical, agricultural and industrial importance. Discovery of microbial QS signals and the signalling mechanisms led to identification of numerous enzymatic and non-enzymatic signal interference mechanisms that quench microbial QS signalling. Evidence is accumulating that such signal interference mechanisms can be developed as promising approaches to control microbial infection and biofilm formation. In addition, these mechanisms exist not only in microorganisms but also in the host organisms of bacterial pathogens, highlighting their potential implications in microbial ecology and in host,pathogen interactions. Investigation of QS and signal interference mechanisms might significantly broaden the scope of research in microbiology. [source] The Development of the Metanephric Kidney in the PigANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 2005H. Bragulla Aims:, The metanephric kidneys of the pig are used as xenotransplants in human medicine. In order for transplants to fit within the host organisms, the subcapsular blastema and blood vessels are crucial for the development of new nephrons to sustain the organ functions. The aim of this study is to obtain data concerning the post-natal development of metanephric nephrons in the porcine kidney. Materials and Methods:, The metanephric kidneys of six porcine fetuses with a crown-rump length ranging from 40 mm to 220 mm of eight piglets aged between 6 to 10 weeks and of three adult pigs were studied. Eight lectins as well as anti-actin and anti-myosin antibodies were used for lectin- and immunohistochemistry to study the subcapsular metanephric blastema, to visualize the blood-urine barrier in the nephrons and collecting tubules, and to study the blood vessels in both the renal cortex and marrow. Results and Conclusions:, A subcapsular metanephric blastema was still present in the kidney of 10-week-old piglets. Dense condensation of mesenchymal cells surrounded the terminal branches of the collecting ducts and showed first signs of mesenchymal-epithelial transformation. Characteristic comma-shaped and s-shaped bodies were found in and underneath the subcapsular blastema. In the fibrous renal capsule of six-week-old piglets, a first faint binding reaction of anti-actin was visible and intensified in the fibrous renal capsule in ten-week-old piglets and in adult pigs. In addition, the smooth-muscle layers of the blood vessels were stained by the anti-actin and anti-myosin antibodies. The lectins showed various affinities to the endothelium of blood vessels and to the epithelial cells lining of the capsules of the metanephric renal corpuscles, the various parts of the renal tubules, as well as the collecting tubules and the renal pelvis. The affinity of the epithelial cells to a specific lectin varies in neighbouring cells, indicating different cell activities or cell cycles. [source] Histones and histone modifications in protozoan parasitesCELLULAR MICROBIOLOGY, Issue 12 2006William J. Sullivan Jr Summary Protozoan parasites are early branching eukaryotes causing significant morbidity and mortality in humans and livestock. Single-celled parasites have evolved complex life cycles, which may involve multiple host organisms, and strategies to evade host immune responses. Consequently, two key aspects of virulence that underlie pathogenesis are parasite differentiation and antigenic variation, both of which require changes in the expressed genome. Complicating these requisite alterations in the parasite transcriptome is chromatin, which serves as a formidable barrier to DNA processes including transcription, repair, replication and recombination. Considerable progress has been made in the study of chromatin dynamics in other eukaryotes, and there is much to be gained in extending these analyses to protozoan parasites. Much of the work completed to date has focused on histone acetylation and methylation in the apicomplexans and trypanosomatids. As we describe in this review, such studies provide a unique vantage point of the evolutionary picture of eukaryotic cell development, and reveal unique phenomena that could be exploited pharmacologically to treat protozoal diseases. [source] Eicosanoid-mediated proinflammatory activity of Pseudomonas aeruginosa ExoUCELLULAR MICROBIOLOGY, Issue 12 2005A. M. Saliba Summary As Pseudomonas aeruginosa ExoU possesses two functional blocks of homology to calcium-independent (iPLA2) and cytosolic phospholipase A2 (cPLA2), we addressed the question whether it would exhibit a proinflammatory activity by enhancing the synthesis of eicosanoids by host organisms. Endothelial cells from the HMEC-1 line infected with the ExoU-producing PA103 strain exhibited a potent release of arachidonic acid (AA) that could be significantly inhibited by methyl arachidonyl fluorophosphonate (MAFP), a specific PLA2 inhibitor, as well as significant amounts of the cyclooxygenase (COX)-derived prostaglandins PGE2 and PGI2. Cells infected with an isogenic mutant defective in ExoU synthesis did not differ from non-infected cells in the AA release and produced prostanoids in significantly lower concentrations. Infection by PA103 induced a marked inflammatory response in two different in vivo experimental models. Inoculation of the parental bacteria into mice footpads led to an early increase in the infected limb volume that could be significantly reduced by inhibitors of both COX and lipoxygenase (ibuprofen and NDGA respectively). In an experimental respiratory infection model, bronchoalveolar lavage (BAL) from mice instilled with 104 cfu of PA103 exhibited a marked influx of inflammatory cells and PGE2 release that could be significantly reduced by indomethacin, a non-selective COX inhibitor. Our results suggest that ExoU may contribute to P. aeruginosa pathogenesis by inducing an eicosanoid,mediated inflammatory response of host organisms. [source] | ||||||||||||||||