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Results for “microbial function”

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At least 1,315 records · Page 73Linked to original sources
PubMed2002

Perforin-mediated CTL cytolysis counteracts direct cell-cell spread of Listeria monocytogenes.

The immune system has evolved various effector cells and functions to combat diverse infectious agents equipped with different virulence strategies. CD8 T cells play a critical role in protective immunity to Listeria monocytogenes (Lm), a bacterium that grows within the host cell cytosol and spreads directly into neighboring cells. The importance of CD8 T cells during Lm infection is currently attributed to the cytosolic niche of this organism, which allows it to evade many aspects of immune surveillance. CTL lysis of infected cells is believed to be an essential protective mechanism, presumably functioning to release intracellular bacteria, although its precise role remains to be fully defined. In this study, we examined the contribution of perforin-mediated CTL cytolysis to protective immunity against recombinant Lm capable of or defective in cell-cell spread. We found that CTL cytolysis is critical for protective immunity to Lm capable of cell-cell spread while protective immunity against spread-defective Lm is largely independent of CTL cytolysis. These results demonstrate that an important function of CTL cytolysis is to counter the microbial virulence strategy of direct cell-cell spread. We propose a model that advances the current view of the role of CTL cytolysis in immunity to intracellular pathogens.

Animals↗
PubMed2003

Identification of IFN regulatory factor-1 binding site in IL-12 p40 gene promoter.

IL-12 is a heterodimer composed of p40 and p35 and is a key cytokine that functions to protect the host from viral and microbial infections. IL-12 links the innate immune system with the acquired immune system during infection, and induces differentiation of type 1 T cells that play an important role in the eradication of microbes. The induction of the IL-12 p40 gene is regulated by NF-kappaB in the presence of IFN-gamma. IFN-gamma induces IFN regulatory factor-1 (IRF-1), which in turn induces the transcription of the IL-12 p40 gene. However, the IRF-1 binding site in the promoter region of the IL-12 p40 gene has not yet been formally determined. In the present study, we demonstrated that IRF-1 directly binds to the IL-12 p40 gene promoter and identified its binding site. The IRF-1 binding site in the promoter region of the IL-12 p40 gene is shown to be in the -72 to -58 area of the 5'-upstream region. The -63 to -61 position is the critical site within this region for the binding of IRF-1 to the IL-12 p40 gene promoter. While IFN-gamma must be present for IL-12 p40 gene induction, the p35 gene is strongly induced by LPS, even in the absence of IFN-gamma, and therefore the induction of the p35 gene is IRF-1 independent.

5' Untranslated Regions↗
PubMedDate not supplied

[Enzymatic reactions in biotechnology (48th Bach lecture)].

The paper is the 48th Bach Lecture presented under the same title. It covers the biochemical mechanisms of the biogenesis of microbial biosynthetic products, role of acetyl-CoA, function of the succinate-glycine cycle, reactions of the hexose-monophosphate pathway of carbon metabolism. The reversible action of hydrolases in enzymatic catalysis and degradation of xenobiotics are discussed. The data on redox reactions are pooled. Such modern biotechnological processes as epoxidation, synthesis of acrylamide and some monomers involved in chemical syntheses of polymers, synthesis of oligosaccharide and fluorine-containing amino acids are considered. Promising commercial applications of biocatalysis are discussed.

Biotechnology↗
PubMedDate not supplied

[Principles of developing methods for decontamination and preservation of water-containing human wastes in a mission to Mars].

Chemical and microbial safety will be one of the major functions of a closed eco-system aboard piloted interplanetary vehicle. Methods for decontamination and preservation of water-containing human wastes (WHW) should be developed on the assumption that WHW are a labile biochemical system biological and chemical processes of which are intricately dependent on preservatives, regenerative water quality, structural material off-gassing, and methods of WHW collection, storage, and management.

Decontamination↗
PubMed2004

Bacterial degradation of aromatic pollutants: a paradigm of metabolic versatility.

Although most organisms have detoxification abilities (i.e mineralization, transformation and/or immobilization of pollutants), microorganisms, particularly bacteria, play a crucial role in biogeochemical cycles and in sustainable development of the biosphere. Next to glucosyl residues, the benzene ring is the most widely distributed unit of chemical structure in nature, and many of the aromatic compounds are major environmental pollutants. Bacteria have developed strategies for obtaining energy from virtually every compound under oxic or anoxic conditions (using alternative final electron acceptors such as nitrate, sulfate, and ferric ions). Clusters of genes coding for the catabolism of aromatic compounds are usually found in mobile genetic elements, such as transposons and plasmids, which facilitate their horizontal gene transfer and, therefore, the rapid adaptation of microorganisms to new pollutants. A successful strategy for in situ bioremediation has been the combination, in a single bacterial strain or in a syntrophic bacterial consortium, of different degrading abilities with genetic traits that provide selective advantages in a given environment. The advent of high-throughput methods for DNA sequencing and analysis of gene expression (genomics) and function (proteomics), as well as advances in modelling microbial metabolism in silico, provide a global, rational approach to unravel the largely unexplored potentials of microorganisms in biotechnological processes thereby facilitating sustainable development.

Bacteria↗
PubMedDate not supplied

Electrophysiological properties of rat heart cells in vitro and in tissue culture.

Some electrical properties of right ventricles of neonatal rats and of aggregates from collagenase-dissociated cells from the same tissue are compared. The duration of the action potential does not change upon changing the stimulation frequency both in ventricles and aggregates; a decrease in temperature increases duration in both preparations to the same extent. The take-off potential and the maximal rate of rise of the action potential decrease in the same way in both preparations, while the time course of these changes is also comparable. It is concluded that the dissociation and aggregation procedure does not interfere with the membrane properties upon which the measured parameters are based; thus, aggregates are well suited for a realistic voltage-clamp analysis.

Action Potentials↗
PubMed1981

Preparation and analysis of a lung microsomal fraction from control and 3-methylcholanthrene treated rats.

In order to facilitate the homogenization of lung tissue it was previously incubated with collagenase during 30 minutes. Morphological observations were performed in order to ascertain the cell integrity. The enzymatically digested tissue was homogenized in a 0.25 M sucrose solution containing 1 mM EDTA, 3 mM imidazole (pH.7.3) and supplemented with 1 mM imipramine in order to stabilize the mitochondria, which otherwise might contaminate the microsomal fraction. The homogenate was then centrifuged and subdivided into four fractions which were analyzed for their content in protein and for the activities of so-called marker enzymes. The cytochrome P450 level was measured in both control and 3-methylcholanthrene preparations. The activities and the kinetic parameters of lung benzpyrene hydroxylase and aldrin epoxidase were measured using the lung microsomal fractions from control and previously 3-methylcholanthrene treated rats; 3-methylcholanthrene pretreatment modified the catalytiac properties of both enzymes.

Animals↗
PubMed1981

High-dose tobramycin combined with clindamycin or lincomycin in the treatment of septic peritonitis and intraabdominal sepsis.

Tobramycin in combination with clindamycin or lincomycin were used as systemic antibiotics in the treatment of 20 consecutive patients with septic peritonitis or intraabdominal sepsis, 10 of which were in septic shock. Doses were: tobramycin 1.5 mg/kg body weight every 8 hours, with prolonged dosage interval in patients with reduced renal function, clindamycin 0.9 g every 8 hours and lincomycin 1.2 g every 8 hours. Therapy was monitored by means of tobramycin serum concentration determinations and renal function tests. Eventual cure of the infection was obtained in 19 patients. In 2 of these, the effects of the antibiotics were doubtful. Side effects were observed on 8 occasions: One patient had a slight and temporary subjective hearing loss, coinciding with raised trough levels of tobramycin. Diarrhoea occurred in 3 cases and skin reactions in 3 cases. Superinfection with Candida albicans fungemia occurred in one patient. From the overall results it is concluded that the antibiotic regimen is of value in serious life-threatening infections. Although the tobramycin dose was higher than customarily used in Scandinavia at the time, 0 hour and 1 hour serum concentrations remained stable during therapy in patients whose renal function was normal at onset of therapy. Serum creatinine (S-Cr) levels in these patients were also essentially unchanged. Temporary reductions in osmolality (Osm) ratio Osm-urine/Osm-serum occurred in 11 patients despite normal S-Cr, but it was hard to attribute these impairments of renal function to tobramycin specifically. It was also doubtful whether tobramycin further aggravated renal function in those patients where it was impaired at onset of therapy. Thus, no conclusive evidence of clinically important tobramycin-induced nephrotoxicity were found. We suggest that the dosage schedule of tobramycin used in this study is applied when treating serious intraabdominal infections.

Adolescent↗
PubMed1994

Leukocyte depletion of cellular blood components.

Clinical studies have indicated that the use of leukocyte-reduced cellular blood components produced in the laboratory may prevent febrile reactions and delay or prevent alloimmunization to HLA antigens and refractoriness to platelet transfusion. Additional investigations regarding the effects of the use of leukocyte-reduced blood components were reported during the past year. A recent study in patients with hematologic malignancy that employed the commonly used bedside leukocyte-reduction filters failed to confirm a decrease in the rate of alloimmunization, except in a subgroup of patients with acute myelogenous leukemia. Another major multicenter trial confirmed the effectiveness of leukocyte-reduced blood components in the prevention of cytomegalovirus infection. The effect of allogeneic leukocytes in transfused blood on immune function in patients undergoing colorectal surgery continues to receive attention. Whereas one study failed to demonstrate an adverse effect of standard blood components on disease recurrence or survival, a second study demonstrated a marginally significant decrease in infectious complications in patients who received only leukocyte-reduced blood. Increasingly efficient leukocyte-reduction filters have been developed for cellular blood components, many of which are best suited for laboratory filtration of unstored blood. Laboratory studies indicate that prestorage leukocyte-reduction of cellular blood components does not impair erythrocyte or platelet function and will not increase the incidence of microbial contamination of blood. New methods that employ flow cytometry should enable improved quality control of blood components rendered leukocyte-reduced by the newer, more efficient filters. Finally, a cost-benefit analysis suggests that the appropriate use of leukocyte-reduction filters for acute leukemia patients may reduce the cost of health care to these patients.

Blood Component Transfusion↗
PubMed1997

[Programmed debridement, combined with jet lavage in extensive hand infections].

108 patients with a distinct infection of the hand were treated according to a protocol with serial debridements in combination with jet-lavage. In 106 patients the infection could be controlled with good functional result (79%) and normal neurological findings (85%). Microbial count in different tissues showed a significant decrease during the serial debridements.

Adolescent↗
PubMed1987

Glucan: mechanisms involved in its "radioprotective" effect.

It has generally been accepted that most biologically derived agents that are radioprotective in the hemopoietic-syndrome dose range (eg, endotoxin, Bacillus Calmette Guerin, Corynebacterium parvum, etc) exert their beneficial properties by enhancing hemopoietic recovery and hence, by regenerating the host's ability to resist life-threatening opportunistic infections. However, using glucan as a hemopoietic stimulant/radioprotectant, we have demonstrated that host resistance to opportunistic infection is enhanced in these mice even prior to the detection of significant hemopoietic regeneration. This early enhanced resistance to microbial invasion in glucan-treated irradiated mice could be correlated with enhanced and/or prolonged macrophage (but not granulocyte) function. These results suggest that early after irradiation glucan may mediate its radioprotection by enhancing resistance to microbial invasion via mechanisms not necessarily predicated on hemopoietic recovery. In addition, preliminary evidence suggests that glucan can also function as an effective free-radical scavenger. Because macrophages have been shown to selectively phagocytize and sequester glucan, the possibility that these specific cells may be protected by virtue of glucan's scavenging ability is also suggested.

5'-Nucleotidase↗
PubMed2000

Novel purification scheme and functions for a C3-binding protein from Streptococcus pneumoniae.

To isolate microbial proteins capable of binding the third component of complement (C3), we coupled the free sulfhydryl group of methylamine-inactivated C3 to a thiolSepharose matrix. This simple technique facilitated the purification of the first C3-binding protein isolated from a bacterium (Streptococcus pneumoniae). Both metastable (native) and thioester-disrupted C3 were recognized by this protein; binding of C3 was noncovalent, independent of thioester conformation, and preferential for the C3 alpha-chain. Sequencing of amino-terminal and internal peptides from the C3-binding protein disclosed a proline-rich region spanning approximately 20 amino acids and a signal peptide that had not been previously reported. The gene was isolated from a library of genomic DNA from laboratory strain CP1200 by screening with a 1200 bp PCR product amplified from degenerate oligonucleotides encoding the amino terminal sequence and the internal proline-rich sequence. The open reading frame spanned 1692 bp; all peptide sequences were identified in the translated gene product, which also contained at least three choline-binding repeats at the carboxy-terminus. The gene was conserved, and the translated protein was functionally active in pneumococcal clinical isolates of serotypes 1, 3, 4, 14, and 19F. Serum from a patient recovering from acute pneumococcal infection contained IgG antibodies specific for this protein by immunoblot. Wide conservation among clinical isolates, saturable binding of C3, and the ability to stimulate the human immune response have not previously been reported for this choline-binding protein. A similar biochemical approach should enable the identification of other C3-binding proteins in microorganisms able to elude complement-mediated host defense.

Amino Acid Sequence↗
PubMed2002

Cathelicidin anti-microbial peptide expression in sweat, an innate defense system for the skin.

The eccrine gland is one of the major cutaneous appendages and secretes sweat. Its principal function is thermoregulation during exposure to a hot environment or physical exercise. In addition to this function, we show that LL-37, a member of cathelicidin family of anti-microbial peptides, is expressed in sweat. LL-37 protein and mRNA was seen in the eccrine structures of normal human skin by immunohistochemistry and in situ hybridization. LL-37 was localized to both the eccrine gland and sweat ductal epithelial cells, whereas dermcidin, a previously described natural antibiotic in sweat, was expressed only in the gland itself. The anti-microbial activity of LL-37 and dermcidin against various bacteria in the sweat ionic environment was demonstrated by solution colony forming assay using synthetic peptides, and in sweat obtained from normal volunteers. These results indicate that cathelicidin is secreted in human sweat, has potent anti-microbial activity against both gram-positive and gram-negative bacteria, and can, after processing from the preproform, provide a barrier for protection against infection. Thus, sweat represents a unique mode of delivery for potent innate immune effector molecules in the absence of inflammation.

Amino Acid Sequence↗