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At least 865 records · Page 48Linked to original sources
PubMed2003

Absorptive activity of calcium in the isolated cecal epithelium adaptively increased by 2 week's feeding of difructose anhydride III in rats.

We compared net Ca absorption and Lucifer Yellow (LY), a paracellular passage dye, permeability in the epithelium isolated from the rat small intestine, cecum, and colon after feeding with control and difructose anhydride (DFA) III diets for 14 days using the Ussing chamber system. Feeding of DFA III increased net Ca transport and LY passage in the cecal but not in small intestinal or colonic epithelium. Ability of paracellular Ca passage via Tight-junction (TJ) in the cecum was changed adaptively by feeding of DFA III. Changes in microbial fermentation may affect the functional changes of Ca transport in cecal epithelium itself.

Animal Feed↗
PubMed2001

American Society of Microbiology 101st General Meeting. 20-24 May 2001, Orlando, FL, USA.

The application of sophisticated molecular biology, genetics and genomics has made possible the advanced analyses of microbial genes, the topology of DNA and chromosomes, and insight into the regulation of gene expression during all stages of the life cycle of microbes, both in vitro and in vivo. The struggle to control contagious pathogens continues world wide amidst resistance emergence to many classes of antimicrobial agents. Many hospital, research and community labs are applying themselves to a more thorough understanding of the molecular basis of this resistance. New drugs which improve on predecessor agents were presented. The following classes of antimicrobial agents were represented: quinolones, cephems, macrolides and natural products. New target opportunities against both lethal (essential) gene targets and virulence targets were presented throughout the conference. In addition, increasing attention to the involvement of microbial life forms in immune function and dysfunction were described in numerous presentations.

Anti-Bacterial Agents↗
PubMed2001

Combating Gram-positive pathogens: emerging techniques to identify relevant virulence targets.

Recent progress in microbial genome sequencing, along with functional genomics technologies based on gene expression, proteomics and genetics have facilitated the identification of significant numbers of Gram-positive virulence genes. These genes represent a novel and heterogeneous class of targets for antimicrobial drug development. This review will concentrate of the contribution of two functional genomics technologies, in vivo expression technology (IVET) based on gene expression and signature-tagged mutagenesis (STM), a genetics based technology to the identification of virulence genes in Gram-positive pathogens.

Journal Article↗
PubMedDate not supplied

Reprogramming the phagocytic pathway--intracellular pathogens and their vacuoles (review).

Phagocytic immune cells (particularly macrophages and neutrophils) take up and digest particles that have invaded our bodies. In doing so, they represent a very early line of defence against a microbial attack. During uptake, the particles are wrapped by a portion of the phagocyte's plasma membrane, and a new endocytic compartment, the phagosome, is formed. The typical fate of a phagosome is its fusion with lysosomes to yield a phagolysosome in which the particle is digested. Recent data show that some 'intracellular microorganisms' that can cause severe illnesses (tuberculosis, leprosy, legionnaire's disease and others) manage to reprogramme the host phagocytes not to deliver them to the lysosomal compartment. This probably results in increased survival of the pathogens. The analysis of the composition of such 'novel' compartments and research on the molecular mechanisms underlying the microbial interference with host cell functions are likely to yield important insights into: (1) which endocytic/phagocytic compartments phagocytes employ to handle ingested material in general; (2) how some pathogenic microorganisms can reprogramme the phagocytic pathway; and possibly (3) how infections caused by these microorganisms can be treated more effectively. Here, some studies are presented analysing which compartments intracellular pathogens inhabit and how microbes might be able to reprogramme their host cells.

Animals↗
PubMed2001

Novel engagement of CD14 and multiple toll-like receptors by group B streptococci.

Group B streptococcus (GBS) imposes a major health threat to newborn infants. Little is known about the molecular basis of GBS-induced sepsis. Both heat-inactivated whole GBS bacteria and a heat-labile soluble factor released by GBS during growth (GBS-F) induce nuclear translocation of NF-kappaB, the secretion of TNF-alpha, and the formation of NO in mouse macrophages. Macrophages from mice with a targeted disruption of MyD88 failed to secrete TNF-alpha in response to both heat-inactivated whole bacteria and GBS-F, suggesting that Toll-like receptors (TLRs) are involved in different aspects of GBS recognition. Immune cell activation by whole bacteria differed profoundly from that by secreted GBS-F. Whole GBS activated macrophages independently of TLR2 and TLR6, whereas a response to the secreted GBS-F was not observed in macrophages from TLR2-deficient animals. In addition to TLR2, TLR6 and CD14 expression were essential for GBS-F responses, whereas TLR1 and TLR4 or MD-2 did not appear to be involved. Heat lability distinguished GBS-F from peptidoglycan and lipoproteins. GBS mutants deficient in capsular polysaccharide or beta-hemolysin had GBS-F activity comparable to that of wild-type streptococci. We suggest that CD14 and TLR2 and TLR6 function as coreceptors for secreted microbial products derived from GBS and that cell wall components of GBS are recognized by TLRs distinct from TLR1, 2, 4, or 6.

Animals↗
PubMed2000

Morphological changes associated with the development of the rumino-reticulum in growing lambs fed different rations.

Morphological changes associated with rumino-reticular development was compared in two groups of SA Mutton Merino lambs (n = 12) fed different diets at 3-5 weeks, 17-19 weeks and 31-33 weeks of age. Diet groups were identified as MMH or MHH according to the sequence at which the full-milk replacement (M) or hay (H) diet were fed to the lambs over the three study phases (phases I, II and III) preceding each age period. Prominent differences in the morphology (size and volume) and function (pH, proteolytic activity and microbial population) of the rumino-reticulum were observed in indicator lambs (n = 2) killed at every age period and also between milk-fed and hay-fed lambs. The size of the rumino-reticulum was rudimentary at 3-5 weeks of age and remained underdeveloped in lambs at 17-19 weeks of age which had received a full-milk replacement diet during phase II. One lamb, slaughtered at 3 weeks of age, showed a large distended rumen with severe sloughing of the surface cells of the stratum corneum. The size of the rumino-reticulum increased in size (2 x) in lambs which were fed hay relative to the milk-fed lambs during phase II and reached adult proportions in all lambs at 31-33 weeks of age. Ultrastructural examination showed that rumen papillae were more developed in lambs fed hay during phase II when compared to those of milk-fed lambs. Rumen papillae were best developed in phase III lambs.

Aging↗
PubMed2002

Emerging evidence that molecules expressed by mammalian tissue grafts are recognized by the innate immune system.

The innate immune system existed prior to the emergence of adaptive immunity in sharks and higher vertebrates. Homologues of many mammalian innate immune-system elements such as the toll-like receptors exist in species as distant as Drosophila. Selective pressure has led to the development of highly conserved, soluble, and cell-surface receptors that recognize functionally essential molecules shared by microbial pathogens. It is thought that molecular patterns that exquisitely distinguish pathogenic cells from mammalian cells are recognized. Therefore, it would seem unlikely that innate immune-system elements should recognize mammalian tissues. However, there is increasing evidence to suggest that this is the case and that innate immunity promotes rejection of transplanted mammalian tissues, particularly those from other species (xenografts). Evidence for innate recognition of mammalian grafts, the nature of this recognition, and the bi-directional interactions between innate and adaptive immunity that contribute to graft rejection are discussed in this review, with the emphasis on nonvascular xenografts.

Animals↗
PubMedDate not supplied

[CD1 pathway and NK T cell activation to glycolipid antigens from Mycobacterium tuberculosis].

The aim of this review is to analyze the current state of our knowledge about cell surface molecules involved in glycolipid antigen presentation, named CD1 family. These proteins constitute a third class of antigen-presenting molecules. CD1 molecules develop diverse important immune functions in host defenses against microbial infections. In recent years these proteins have been involved in the generation of cell-mediated immune response against Mycobacterium tuberculosis. Here, we analyze relevant roles of CD1 proteins and glycolipid antigen-specific T cells.

Antigens, Bacterial↗
PubMedDate not supplied

[Spore germination and mycelial growth of streptomycetes at different humidity levels].

This study is the first to show the ability of streptomycetes to develop at a very low humidity level. All of the streptomycetes studied produced growth at low humidity (aw 0.86 and 0.67). This capacity was most markedly pronounced in Streptomyces odorifer, whose spores were capable of germinating, and mycelial germs increased in length, at the air humidity aw 0.50. The formation of lateral branches (mycelium branching) at this humidity was noted only in single S. odorifer germs and only after 72 h of incubation. Study of streptomycete growth on an agarized medium with different osmotic pressures, created by various glycerol concentrations in the medium, showed that, at aw 0.67, the spores of all the streptomycetes studied germinate, producing mycelial germs but not microcolonies. The ecological significance of mycelial prokaryotes in soil microbial communities that develop and function under conditions of extremely low humidity is discussed.

Culture Media↗
PubMed2006

Gene therapy for chronic granulomatous disease.

Chronic granuloniatous disease (CGD) is a rare inherited imnunodeficiency characterized by recurrent, often life threatening bacterial and fungal infections due to a functional defect in the microbial-killing activity of phagocytic neutrophils. If regular care and conventional therapy fail, tile disease can be cured by bone marrow transplantation. This treatment is, however, only available to patients with human leukocyte antigen-identical sibling or matched unrelated donors. One therapeutic option for patients lacking suitable donors is the genetic modification of autologous hematopoietic stem cells. This review discusses the developments that have led to the realization of a successful gene therapy protocol for the correction of CGD.

Bone Marrow Transplantation↗
PubMed1985

Mycobacterial antigen-specific human T-cell clones secreting macrophage activating factors.

Macrophage activating factor (MAF) is produced by antigen-stimulated lymphocytes and activates macrophages for antimicrobial function. The capacity of individual microbial antigens to evoke and regulate this response has been explored using an affinity purified antigen (TB68) of Mycobacterium tuberculosis in combination with T-cell cloning. Four helper/inducer clones are described which responded strongly to this antigen. Three were specific, proliferating only to TB68 antigen and antigenic preparations containing this antigen. However, one of these clones (68.1) did not proliferate to BCG and PPD which contained the TB68 antigen. In addition, another clone, 68.13, also proliferated to other antigenic preparations which did not contain the TB68 antigen. Taken together, these data indicate the presence of several epitopes in the affinity-purified TB68 antigen. All the clones produced MAF, which enhanced H2O2 production in U937 cell lines and conventional macrophages matured from monocytes. Thus, T-cell clones proliferating to a mycobacterial antigen constitutively secrete lymphokines that activate macrophages to antimicrobial immunity.

Antigens, Bacterial↗
PubMed1998

Human myelomonocytic cells express an inhibitory receptor for classical and nonclassical MHC class I molecules.

Leukocyte activation can be negatively regulated by inhibitory receptors specific for MHC class I molecules. While one inhibitory receptor, Ig-like transcript 2 (ILT2), is expressed by all lymphoid and myelomonocytic cell types, other receptors display a more selective tissue distribution. Here we characterize an inhibitory receptor, termed ILT4, which is selectively expressed in monocytes, macrophages, and dendritic cells (DCs), binds classical class I molecules and the nonclassical class I molecules HLA-G, and transduces negative signals that can inhibit early signaling events triggered by stimulatory receptors. ILT4 may control inflammatory responses and cytotoxicity mediated by myelomonocytic cells and may modulate their Ag-presenting functions, focusing immune responses to microbial challenges and avoiding autoreactivity.

Animals↗
PubMed2004

Functional gene diversity analysis in BTEX contaminated soils by means of PCR-SSCP DNA fingerprinting: comparative diversity assessment against bacterial isolates and PCR-DNA clone libraries.

Developments in molecular biology based techniques have led to rapid and reliable tools to characterize microbial community structures and to monitor their dynamics under in situ conditions. However, there has been a distinct lack of emphasis on monitoring the functional diversity in the environment. Genes encoding catechol 2,3-dioxygenases (C23O), as key enzymes of various aerobic aromatic degradation pathways, were used as functional targets to assess the catabolic gene diversity in differentially BTEX contaminated environments by polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP). Site specific PCR-SSCP fingerprints were obtained, showing that gene diversity experienced shifts correlated to temporal changes and levels of contamination. PCR-SSCP enabled the recovery of predominant gene polymorphs, and results closely matched with the information retrieved from random sequencing of PCR-DNA clone libraries. A new method for isolating strains capable of growing on BTEX compounds was developed to diminish preselection or enrichment bias and to assess the function of predominant gene polymorphs. C23O abundance in isolates correlated with the levels of BTEX pollution in the soil samples analysed. Isolates harbouring C23O genes, identical to the gene polymorph predominant in all contaminated sites analysed, showed an unexpected benzene but not toluene mineralizing phenotype whereas isolates harbouring a C23O gene variant differing by a single point mutation and observed in highly polluted sites only, were capable, among some other isolates, to mineralize benzene and toluene, indicating a catabolically determined sharing of carbon sources on-site. The PCR-SSCP technique is thus a powerful tool for assessing the diversity of functional genes and the identification of predominant gene polymorphs in environmental samples as a prerequisite to understand the functioning of microbial communities.

DNA Fingerprinting↗
PubMed2004

Protein targeting to endosomes and phagosomes via FYVE and PX domains.

Phosphatidylinositol 3-phosphate (PI3P) is generated on early endosomal and phagosomal membranes by PI 3-kinases. This lipid serves important regulatory functions in phagocytosis, endocytic traffic, receptor signalling and microbial killing through the recruitment and activation of a number of effector proteins. Almost all of these effectors contain FYVE or PX domains, functional protein modules which are conserved from yeast to mammals. Structural information is available regarding the binding of FYVE and PX domains to PI3P. The two domains are highly different, but they have in common that clusters of basic residues mediate ligand binding through interactions with the phosphate groups of PI3P. Most proteins that contain FYVE or PX domains serve as regulators of endocytic membrane trafficking, whereas others function as regulators of phagosome maturation, signal transduction, microbial killing and other cellular activities of relevance for the immune system.

Animals↗
PubMed2002

Microbial enzymes involved in carbon dioxide fixation.

This review focuses on the enzymes involved in two microbial carbon dioxide fixation pathways, the Calvin-Benson-Bassham cycle and the reductive tricarboxylic acid cycle. The function, structural features, and gene regulation of microbial ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco), a key enzyme of the Calvin-Benson-Bassham cycle, is described. Some recent findings on Rubisco from archaea and Rubisco-like proteins are also outlined. In the final section, biochemical features of the key enzymes in the reductive tricarboxylic acid cycle are reviewed.

Journal Article↗
PubMedDate not supplied

Effect of IP6 on human neutrophil cytokine production and cell morphology.

Inositol hexaphosphate (IP6) has anti-cancer properties, but recently other extracellular functions have been observed for IP6, including enhancing superoxide production and phagocytosis by neutrophils in the presence of microbial stimuli. This study investigated other inflammatory functions of IP6 on adherent neutrophils. The effect of IP6 on the release of IL-8, tumour necrosis factor (TNF-alpha) and IL-6 by neutrophils attached to either plastic or laminin for up to 6 hours in response to stimulation with lipopolysaccharide or N-formyl-Met-Leu-Phe (fMLP) was investigated. An increase in IL-8 secretion by stimulated cells occurred in the presence of IP6. The incubation of cells attached to laminin with IP6 alone (100-250 BM) did not effect cell morphology, but in the presence of 10(-7) M fMLP altered cell shape. A direct effect of IP6 on cell function was to trigger a sustained assembly of F-actin. Thus, exposure of neutrophils to low levels of IP6 appears to modulate selective neutrophil functions.

Actins↗
PubMed1987

Interleukin 1 and interferon-gamma: cytokines that provide reciprocal regulation of macrophage and T cell function.

Interactions between macrophages and T cells are symbiotic, since optimal functions of both cell types require interchange of soluble mediators. Upon activation, macrophages release interleukin-1 (alias lymphocyte activating factor, leukocytic endogenous mediator, and endogenous pyrogen), a family of molecules with multivarious biological effects, ranging from induction of fever and the acute phase response to lymphocyte activation and concomitant release of interleukin-2. Interleukin-2 induces activation and replication of several subsets of precursor lymphocytes, including cytotoxic T cells, lymphokine-activated killer (LAK) cells, and natural killer (NK) cells, and enhances their cytotoxic activity for tumor cells. Both interleukin-2 and leukotrienes enhance production of immune interferon (interferon-gamma) by activated T cells. Aside from antiviral activity, interferon-gamma produces a number of immunomodulatory effects, including macrophage activation (Ia induction, antimicrobial effector function, and activation of oxidative metabolism) and augmentation of NK function. Expression of Ia on accessory cell membranes is required for the initiation of many antigen-specific, T-dependent immune responses. Interferon-gamma also synergizes with a variety of microbial agents to augment macrophage tumoricidal function and enhance interleukin-1 secretion. The production of interferon-gamma appears to have a critical role in feeding back the cascade of interleukins in a loop of amplification. Both interleukin-1 and interferon-gamma modulate release of arachidonate metabolites in various cells. This cascade of cytokines, in collaboration with arachidonate oxygenation products, regulates immunity and sets the stage for many of the events underlying inflammation. Various anti-inflammatory drugs and immunopotentiators appear to act by modulating cytokine pathways.

Animals↗
PubMed2005

Root exudation, phosphorus acquisition, and microbial diversity in the rhizosphere of white lupine as affected by phosphorus supply and atmospheric carbon dioxide concentration.

White lupine (Lupinus albus L.) was used as a phosphorus (P)-efficient model plant to study the effects of elevated atmospheric CO(2) concentrations on (i) P acquisition, (ii) the related alterations in root development and rhizosphere chemistry, and (iii) the functional and structural diversity of rhizosphere microbial communities, on a P-deficient calcareous subsoil with and without soluble P fertilization. In both +P (80 mg P kg(-1)) and -P treatments (no added P), elevated CO(2) (800 micromol mol(-1)) increased shoot biomass production by 20 to 35% and accelerated the development of cluster roots, which exhibit important functions in chemical mobilization of sparingly soluble soil P sources. Accordingly, cluster root formation was stimulated in plants without P application by 140 and 60% for ambient and elevated CO(2) treatments, respectively. Intense accumulation of citrate and increased activities of acid and alkaline phosphatases, but also of chitinase, in the rhizosphere were mainly confined to later stages of cluster root development in -P treatments. Regardless of atmospheric CO(2) concentrations, there was no significant effect on accumulation of citrate or on selected enzyme activities of C, N, and P cycles in the rhizosphere of individual root clusters. Discriminant analysis of selected enzyme activities revealed that mainly phosphatase and chitinase contributed to the experimental variance (81.3%) of the data. Phosphatase and chitinase activities in the rhizosphere might be dominated by the secretion from cluster roots rather than by microbial activity. Alterations in rhizosphere bacterial communities analyzed by denaturing gradient gel electrophoresis (DGGE) were related with the intense changes in root secretory activity observed during cluster root development but not with elevated CO(2) concentrations.

Atmosphere↗