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At least 163 records · Page 9Linked to original sources
PubMed1995

Food intake, nutrient utilization and water turnover in the lesser mouse-deer (Tragulus javanicus) given lundai (Sapium baccatum).

Voluntary food intake, digestibility and water turnover were determined in adult Malaysian lesser mouse-deer (Tragulus javanicus) given unlimited access to lundai foliage (Sapium baccatum). Daily dry matter (DM) intake was 42.4 g/kg metabolic live mass (M0.73) or 3.7% M. Digestible energy intake was 853 kJ/day (571 kJ metabolisable energy per M0.73), calculated to be used with 79% efficiency. Apparent digestibility (%) of organic matter was 83.8, crude fibre 63.7, acid detergent fibre 60.5, neutral detergent fibre 72.1 and crude protein 65.0. Urinary excretion of the purine derivative, allantoin, was 0.05 mg/g digestible DM intake suggesting rumen microbial yield efficiency may be lower than in other ruminant species. Total water intake was 182 ml/M0.82. The body-water content of the fed mouse-deer, from tritiated water dilution, was 77% M, consistent with a very lean carcass. Turnover of body water was 17% per day. The mouse-deer produced relatively dry, well-defined faecal pellets.

Allantoin↗
PubMed2006

Benthic bacterial and fungal productivity and carbon turnover in a freshwater marsh.

Heterotrophic bacteria and fungi are widely recognized as crucial mediators of carbon, nutrient, and energy flow in ecosystems, yet information on their total annual production in benthic habitats is lacking. To assess the significance of annual microbial production in a structurally complex system, we measured production rates of bacteria and fungi over an annual cycle in four aerobic habitats of a littoral freshwater marsh. Production rates of fungi in plant litter were substantial (0.2 to 2.4 mg C g(-1) C) but were clearly outweighed by those of bacteria (2.6 to 18.8 mg C g(-1) C) throughout the year. This indicates that bacteria represent the most actively growing microorganisms on marsh plant litter in submerged conditions, a finding that contrasts strikingly with results from both standing dead shoots of marsh plants and submerged plant litter decaying in streams. Concomitant measurements of microbial respiration (1.5 to 15.3 mg C-CO2 g(-1) of plant litter C day(-1)) point to high microbial growth efficiencies on the plant litter, averaging 45.5%. The submerged plant litter layer together with the thin aerobic sediment layer underneath (average depth of 5 mm) contributed the bulk of microbial production per square meter of marsh surface (99%), whereas bacterial production in the marsh water column and epiphytic biofilms was negligible. The magnitude of the combined production in these compartments (approximately 1,490 g C m(-2) year(-1)) highlights the importance of carbon flows through microbial biomass, to the extent that even massive primary productivity of the marsh plants (603 g C m(-2) year(-1)) and subsidiary carbon sources (approximately 330 g C m(-2) year(-1)) were insufficient to meet the microbial carbon demand. These findings suggest that littoral freshwater marshes are genuine hot spots of aerobic microbial carbon transformations, which may act as net organic carbon importers from adjacent systems and, in turn, emit large amounts of CO2 (here, approximately 870 g C m(-2) year(-1)) into the atmosphere.

Bacteria↗
PubMed1963

Alcohol-soluble protein of microorganisms.

Pine, Martin J. (Roswell Park Memorial Institute, Buffalo, N.Y.). Alcohol-soluble protein of microorganisms. J. Bacteriol. 85:301-305. 1963.-In two microbial systems, new protein synthesis has been reported to take place at the expense of a disappearing alcohol-soluble protein fraction. Studies were made to characterize the fraction and assess its storage function in Escherichia coli. Synthesis of the fraction does not cease promptly on sulfur depletion but overshoots initially and maintains a preferential rate of turnover. The fraction is probably of heterogeneous composition. It does not disappear during starvation but interacts with acid-insoluble metaphosphate accumulating in high levels as a peculiar consequence of sulfur deficiency. Solubility interactions with proteins of cell extracts are demonstrable with a number of polyanions, including teichoic acid. It is concluded that previous studies of transformations of microbial alcohol-soluble proteins are artifactitious.

Bacterial Proteins↗
PubMed1989

Microbial influences on urinary polyamine excretion.

We determined diamines, polyamines, their monoacetylated conjugates and some of their catabolites in urines of healthy persons during decontamination of the gastrointestinal tract and patients with urinary tract infections. The compounds were also measured after in vitro incubation of urines from healthy persons and patients. During decontamination the urinary excretion of total putrescine decreased by a small amount. This fall was for the greater part accountable to monoacetylated putrescine. Free putrescine levels were increased in urines of patients with urinary tract infections, decreased after therapy, and increased after incubation of the pretherapeutical samples. Total cadaverine decreased during decontamination and increased during recontamination. The changes were partly accountable to monoacetylated cadaverine. Free cadaverine levels of patients with urinary tract infections were normal and did not change after therapy. These data show that, under normal conditions, a small part of monoacetylated putrescine and a considerable part of monoacetylated cadaverine originate from the gastrointestinal tract, and that urinary tract infections lead to an increase of free putrescine. The microbial synthesis of putrescine in the gastrointestinal- and urinary tracts, should therefore be taken into account for the interpretation of urinary putrescine levels as a parameter for body cell turnover.

Adult↗
PubMed1985

Nature and significance of microbial cometabolism of xenobiotics.

Microbial cometabolism, i.e. "transformation of a non-growth substrate in the obligate presence of a growth substrate or another transformable compound" (Dalton and Stirling 1982) is a whole-cell phenomenon physiologically based on coupling of different catabolic pathways at the cellular level. It is frequently observed in transformation of xenobiotic non-growth substrates by individual microbial species. Transformation processes of this type are usually mediated by appropriate non-specific enzymes of the peripheric cellular metabolism able to modify a variety of substances other than their natural substrates. The precise mechanisms of coupling between metabolism of xenobiotic non-growth substrates and of particular additional carbon substrates may be different depending on the substrates and the microbial species involved. However, experimental data indicate that the primary function of the respective additional carbon substrates is to supply either energy, cofactors or metabolites for the different cellular events involved in the transformation process (e.g. uptake of the xenobiotic non-growth substrate, functioning of appropriate degradative enzymes of the peripheric cellular metabolism). Cometabolism of xenobiotics involves nothing special or novel from the standpoint of biochemistry. On the contrary, there are numerous examples where the turnover of particular natural compounds by certain aerobic or anaerobic microorganisms is essentially based on coupling of different catabolic pathways at the cellular level by transfer of hydrogen (i.e. reducing power) and/or energy between two or more enzymatic reactions. Synthetic chemicals which resist total degradation by individual microbial species may undergo mineralization due to complementary catabolic sequences mediated by certain multispecies microbial associations with cometabolic transformations being the initial steps. Although taking place in certain natural habitats (e.g. rhizospheres, sewage), microbial cometabolism of xenobiotics in natural ecosystems occurs with slow rates since the respective cometabolizing populations are generally small and will not increase in number or biomass in response to the introduced chemicals. However, under conditions of axenic microbial cultures, high concentrations of biomass, and appropriate substrate mixtures cometabolism of synthetic chemicals may be a useful technique of considerable practical importance to accumulate biochemical products at high yields. In addition, cometabolic capabilities of wild-type microorganisms may serve as a tool for the construction of microbial strains with a new degradative potential for recalcitrant xenobiotic compounds.

Aerobiosis↗
PubMed2001

Linking the composition of bacterioplankton to rapid turnover of dissolved dimethylsulphoniopropionate in an algal bloom in the North Sea.

The algal osmolyte, dimethylsulphoniopropionate (DMSP), is abundant in the surface oceans and is the major precursor of dimethyl sulphide (DMS), a gas involved in global climate regulation. Here, we report results from an in situ Lagrangian study that suggests a link between the microbially driven fluxes of dissolved DMSP (DMSPd) and specific members of the bacterioplankton community in a North Sea coccolithophore bloom. The bacterial population in the bloom was dominated by a single species related to the genus Roseobacter, which accounted for 24% of the bacterioplankton numbers and up to 50% of the biomass. The abundance of the Roseobacter cells showed significant paired correlation with DMSPd consumption and bacterioplankton production, whereas abundances of other bacteria did not. Consumed DMSPd (28 nM day(-1)) contributed 95% of the sulphur and up to 15% of the carbon demand of the total bacterial populations, suggesting the importance of DMSP as a substrate for the Roseobacter-dominated bacterioplankton. In dominating DMSPd flux, the Roseobacter species may exert a major control on DMS production. DMSPd turnover rate was 10 times that of DMS (2.7 nM day(-1)), indicating that DMSPd was probably the major source of DMS, but that most of the DMSPd was metabolized without DMS production. Our study suggests that single species of bacterioplankton may at times be important in metabolizing DMSP and regulating the generation of DMS in the sea.

Alphaproteobacteria↗
PubMed1979

Preferential digestion of basement membrane collagen by an enzyme derived from a metastatic murine tumor.

The specificity of human skin collagenase and of an enzyme from an invasive tumor were studied by using types I, II, III, IV, and V (AB) collagen as substrates. Human skin collagenase degraded types I, II, and III collagen, producing the characteristic 3/4 and 1/4 cleavage products, but failed to degrade type IV or V collagen. Collagenase prepared from the invasive tumors showed maximal activity after trypsin treatment. The tumor enzyme degraded type IV (basement membrane) collagen, producing fragments consistent with a single cleavage site but did not attack types I, II, III, and V collagen. Because type IV collagen prepared by pepsinization of placenta was also digested, it is likely that cleavage of type IV collagen by the tumor collagenase occurs within a largely helical domain. A type IV collagenase could play a significant role in tumor metastases and in normal tissues where basement membrane turnover takes place.

Animals↗
PubMed2001

Infection control measures to limit antimicrobial resistance.

Increasing antimicrobial resistance has resulted in a rapidly decreasing array of therapeutic options for infections in the critical care setting. Reports of reduced susceptibility to vancomycin in Staphylococcus aureus raise the possibility of patients being infected with a virulent pathogen for which most antibiotics are ineffective. Infection control methods to contain resistance, exclusive of antimicrobial restrictions, focus on surveillance to identify carriers of resistant organisms, prevention of nosocomial infections, adequate hand hygiene, isolation of patients who harbor resistant organisms, and the use of barrier techniques such as gowns and gloves. Surveillance using clinical isolates alone is inadequate for the identification of the majority of patients who carry resistant organisms. However, it is unclear what intensity of surveillance is needed to control the spread of these organisms in the intensive care unit in nonoutbreak situations. Attempts at eradicating carriage are often unsuccessful when there is extranasal colonization with methicillin-resistant S. aureus. Transmission of resistant organisms is primarily the result of transient contamination of healthcare workers' hands. Adequate handwashing, isolation of carriers, and barrier techniques are all necessary for containing resistance within the intensive care unit, however, compliance with these measures can be compromised by high staff turnover and heavy workload.

Anti-Bacterial Agents↗
PubMed2006

Short term oral minocycline treatment of meibomianitis.

AIM: To evaluate the clinical impact, aqueous tear parameters, and meibomian gland morphology in patients with primary meibomianitis before, during, and 3 months after a course of oral minocycline. METHODS: 16 patients were prospectively enrolled, 11 male and five female (mean age 69 years old). Each patient received routine clinical evaluations before, after 3 months therapy, and at 6 month study follow up visit. The clinical appearance, tear volume, flow and turnover, evaporation, Schirmer I test, meibomian gland dropout, lissamine green staining, and bacteriology wer evaluated. RESULTS: Improvement was observed in clinical signs of meibomianitis at the second and third visits. Microbial culture findings improved. Decreased aqueous tear volume and flow, and increased evaporation rate range at 35-45% relative humidity (RH) (p < 0.05) were also detected. Other related tear parameters did not change. Meibomian gland dropout showed no improvement. CONCLUSIONS: 3 months of oral minocycline resulted in clinical improvements in all meibomianitis signs that persisted for at least 3 months after discontinuation despite decreased aqueous tear volume and flow with increased evaporation (35-45% RH). However, there was improvement in the turbidity of secretions. Short term minocycline therapy probably has efficacy in the management of meibomianitis that extends beyond eradication of bacteria.

Administration, Oral↗
PubMed1977

Extractable collagenase and carcinogenesis of the mouse skin.

Collagenolytic activity has been demonstrated in the early phase of chemical carcinogenesis of mouse skin following 3-methylcholanthrene application dropwise in acetone or painted on the skin in benzene. In addition very high levels of collagenase could be detected in mouse skin papillomas and carcinomas. In all the tissues investigated, collagenase activity was extracted from the 6000 X g sediment of tissue homogenates with 5 M urea in 50 mM Tris-HCl buffer, pH 7.5. After dialyzing the extract, the enzyme was precipitated with ammonium sulfate and the activity determined against 14C-collagen substrate in solution. This procedure was found suitable for the detection and estimation of collagenase activity in skin tissues with high turnover of collagen and thus offers an attractive alternative to tissue culture methods.

Animals↗
PubMed1986

The role of ciliate protozoa in nutrition of the ruminant.

The effects of ciliate protozoa on the ruminal ecosystem, digestion in different parts of the gut, the nature of nutrients available for absorption and their effects upon the nutrition and productivity of their host are reviewed. Compared with fauna-free ruminants, the presence of ciliate protozoa results in a more stable ruminal fermentation, higher levels of ammonia, reduced numbers of bacteria, as well as changes in dry matter (%), liquid volume and turnover rate of ruminal contents. Associated with these differences in the rumen are higher ruminal and total tract digestion of organic matter and fiber in faunated animals. A reduction in net microbial synthesis and an increase in dietary protein degradation in the rumen results in the flow of protein to the small intestine being lower in faunated ruminants. The major nutritional effect of the ciliate protozoa is to change the ratio of protein to energy in the nutrients absorbed, with faunated animals having lower protein and higher energy availabilities compared with ciliate-free ruminants. Of the nutrients available for absorption, the ciliates have no consistent effect on the proportions of volatile fatty acids or amino acids. However, there is evidence that hydrogenation of lipids is increased, as is the supply of choline, and that the bioavailability of copper is reduced by the presence of ciliates. Defaunation of young growing ruminants that are fed high energy diets, containing low levels of ruminal nondegradable protein, results in increased growth rate and feed efficiency. It is unlikely, with the possible exception of wool growth, that there are other situations in which defaunation will be beneficial; and it is more likely to be detrimental to animal productivity. It remains to be determined whether manipulation of the types of ciliate protozoa in the rumen could improve animal performance. Information for this review was largely derived from comparisons of faunated and fauna-free animals. However, it is indicated that there are large differences in protozoa numbers and types between naturally faunated individuals in the same flock or herd, and that the effects of such variations on their host's nutrition are unknown.

Animal Nutritional Physiological Phenomena↗
PubMed1988

Influence of pH on microbial hydrogen metabolism in diverse sedimentary ecosystems.

Hydrogen transformation kinetic parameters were measured in sediments from anaerobic systems covering a wide range of environmental pH values to assess the influence of pH on hydrogen metabolism. The concentrations of dissolved hydrogen were measured and hydrogen transformation kinetics of the sediments were monitored in the laboratory by monitoring hydrogen consumption progress curves. The hydrogen turnover rate constants (kt) decreased directly as a function of decreasing sediment pH, and the maximum hydrogen uptake velocities (Vmax) varied as a function of pH within each of the trophic states. Conversely, the half-saturation concentrations (Km) were independent of pH. The steady-state hydrogen concentrations were at least 2 orders of magnitude lower than the half-saturation constants for hydrogen uptake. Dissolved hydrogen concentrations were at least fivefold higher in sediments from eutrophic systems than from oligotrophic and dystrophic systems. The rates of hydrogen production determined from the assumption of steady state decreased with sediment pH. These data indicate that progressively lower pH values inhibit microbial hydrogen-producing and -consuming processes within sedimentary ecosystems.

Bacteria, Anaerobic↗
PubMed1999

Functional studies on dendritic cells in the respiratory tract and related mucosal tissues.

Recent reports indicate that mucosal tissues contain dendritic cell (DC) populations that exhibit phenotypic features distinct from those at more studied sites such as skin. In particular, mucosal DC populations display very rapid baseline turnover rates, which increase in response to local inflammatory stimuli. This property is likely to be central to the role of mucosal DC in surveillance of these front-line tissues for incoming microbial pathogens. As we discuss, it may also indirectly account for the "Th2 default," which is the recognized hallmark of mucosal immune system in the steady state.

Animals↗
PubMed2005

Sediment resuspension effects on the benthic microbial loop in experimental microcosms.

Sediment resuspension induced by anthropogenic disturbance is becoming a major threat of marine coastal ecosystems worldwide. The effects of sediment resuspension on the pelagic domain and on macro- and meiobenthos are well documented in the literature, whereas the effects on the benthic microbial components are nearly neglected. We have investigated the effects of sediment resuspension at two different disturbance levels on benthic bacterial abundance, biomass, and activities and on heterotrophic nanobenthos abundance in experimental microcosms. The results of our experiments pointed out that, independently from the amount of involved energy, sediment resuspension determined a general decrease of all benthic microbial components. The main effects consisted of a decreased abundance of the metabolically active bacterial fraction and of heterotrophic nanobenthos abundance. However, the amount of energy involved in sediment resuspension had differential effects on the structure and functioning of the benthic microbial loop, but only in the short term (i.e., within 36 h). Sediment resuspension had a stimulatory effect on activities of surviving bacterial cells, which, in turn, resulted in increased sediment organic C turnover rates. We hypothesize that such an effect, enhancing nutrient availability, might have relevant consequences on the trophic state of coastal marine ecosystem.

Aminopeptidases↗
PubMed1983

A neutral proteinase from human gingival fibroblasts active against the c-terminal cross-linking region of type I collagen.

An enzyme that was capable of releasing small fragments containing hydroxynorleucine from the c-terminal extra-helical region of the alpha 1 chain of reduced (tritiated) soluble type I collagen was found, along with collagenase, in medium that had been conditioned by the culture of human gingival fibroblasts (Gin-1). The enzyme was present in a latent form or forms and could be activated by treatment with either trypsin or p-hydroxymercuribenzoate. It was maximally active at neutral pH and inhibited by EDTA. It is suggested that this enzyme, acting within a region of the molecule which is of major importance in stabilizing fibrillar collagen through intermolecular cross-linking, could potentially play an important role in collagen turnover in vivo.

Cells, Cultured↗
PubMed1970

Conditional mutants of meiosis in yeast.

Three temperature-sensitive mutants, spo1-1, spo2-1, and spo3-1, were characterized with respect to their behavior in sporulation medium at a restrictive temperature. The time of expression of the functions defective in the mutants was determined by temperature-shift experiments during the sporulation process. In addition, each mutant was examined for the following: (i) its ability to undergo the nuclear divisions of meiosis; (ii) deoxyribonucleic acid (DNA), ribonucleic acid (RNA), and protein synthesis; (iii) protein turnover; and (iv) colony-forming ability after exposure to sporulation medium. Mutant spo1-1 is defective in a function which confers a temperature-sensitive period which extends over 32% of the sporulation cycle. The temperature-sensitive period of mutant spo2-1 occupies 34% of the cycle, whereas the temperature-sensitive period of mutant spo3-1 extends over 2% of the sporulation cycle. Cytological evidence indicates that all three mutants initiate but do not complete the meiotic nuclear divisions. The DNA content of sporulation cultures of mutants spo1-1 and spo3-1 did not increase to the wild-type level; DNA synthesis in spo2-1 was normal. All three strains exhibit a loss of colony-forming ability during incubation in sporulation medium at the restrictive temperature. RNA and protein synthesis and protein turnover occur in the mutants.

Adenine↗