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At least 127 records · Page 7Linked to original sources
PubMed1980

Effect of tensile mechanical stress on the synthesis of metalloproteinases by rabbit coronal sutures in vitro.

The application of a continuous tensile mechanical stress (30 g) to explants of coronal sutures from newborn rabbits (1-2 days) produced increases in enzyme activity of 33.7% for collagenase, 95.2% for gelatinase, and 35.9% for NMP III over a 4-day culture period. All three activities were in latent form and required activation with either 4-APMA or trypsin. The increases in enzyme activities were not accompanied by an alteration in the degradation of structural proteins. This was due to the ability of the cells to synthesize an inhibitor (mol wt 29,000 daltons) which complexed the increased quantities of enzyme. This necessitated a substantial stimulation of inhibitor production because there was still a residue of free inhibitory activity in the media of stressed cultures after 4 days. We previously showed using the same model system that coronal sutures respond to tensile mechanical stress by a two-fold increase in collagen synthesis. The present data suggest that when the priority of the cell population is the synthesis of structural proteins, the inhibitor, in addition to preventing the hydrolysis of newly synthesized peptides, also maintains matrix degradation at normal turnover levels.

Animals↗
PubMed2005

Radiocesium storage in soil microbial biomass of undisturbed alpine meadow soils and its relation to 137Cs soil-plant transfer.

This study focuses on radiocesium storage in soil microbial biomass of undisturbed alpine meadow sites and its relation to the soil-to-plant transfer. Soil and plant samples were taken in August 1999 from an altitude transect (800-1600m.a.s.l.) at Gastein valley, Austria. Soil samples were subdivided into 3-cm layers for analyses of total, K(2)SO(4)-extractable and microbially stored (137)Cs. Microbial biomass was measured by the fumigation extraction method, and fungal biomass was quantified using ergosterol as biomarker molecule. In general, the quantity of (137)Cs stored in the living soil microbial biomass was relatively small. At the high-altitude meadows, showing high amounts of fungal biomass, microbially stored (137)Cs amounted to 0.64+/-0.14kBqm(-2) which corresponds to about 1.2-2.7% of the total (137)Cs soil inventory. At lower altitudes, microbial (137)Cs content was distinctly smaller and in most cases not measurable at all using the fumigation extraction method. However, a positive correlation between the observed soil-to-plant aggregated transfer factor, microbially stored (137)Cs and fungal biomass was found, which indicates a possible role of fungal biomass in the storage and turnover of (137)Cs in soils and in the (137)Cs uptake by plants.

Austria↗
PubMed1987

Flavin catabolites: identification and quantitation in human urine.

Riboflavin is the primary flavin excreted in human urine but significant amounts of 7 alpha-hydroxyriboflavin and lesser amounts of 8 alpha-hydroxyriboflavin are present and reflect tissue microsomal oxidations. A newly found flavin catabolite of an 8 alpha-sulfonyl type may reflect intake and/or turnover of such thioether-linked flavin as occurs in monoamine oxidase. Additionally, lesser amounts of 10-hydroxyethylflavin (indicative of intestinal microbial action on the vitamin) and traces of lumiflavin (arising from photodecomposition) constitute part of the remaining flavin, which acutely reflects level of intake.

Adult↗
PubMed1984

Laboratory calibrations of the [h]adenine technique for measuring rates of RNA and DNA synthesis in marine microorganisms.

The nucleic acid synthesis rates of several marine phytoplankton and bacteria grown in chemostat and batch cultures were measured by using [H]adenine. The [H]adenine synthesis rates showed excellent agreement with the known rates of synthesis estimated from chemical RNA and DNA data. Under certain conditions, RNA turnover and ATP pool compartmentalization produce inaccuracies in synthesis measurements made with [H]adenine. However, accurate measurements of the rates of microbial RNA and DNA synthesis can be made in any environmental situation provided a few simple precautions are observed. First, time course experiments are recommended. Second, experiments should be conducted for periods long enough to avoid problems arising from disequilibria of internal ATP pools. Finally, exogenous [H]adenine should remain in the medium over the length of the time course.

Journal Article↗
PubMedDate not supplied

[Applicability of the new law of State and Regional Agreement on management of swimming pools].

The Authors carried out a survey on private and public managers of 80 Italian swimming pools to evaluate the hygienic aspects and safety of the swimming pools. Participants were submitted to a set of questions about the modifications recently brought to the Act on management of the swimming pools during 2003. The study showed a poor knowledge about the hygienic-safety parameters, in particular of chlorine doses, range of temperature and frequency of daily turnover of the swimming pool water. The respect of chemical-physical parameters is necessary not only to assure an adequate microbial control of the water, but also to reduce the production of irritant and potentially toxic substances. The Authors pointed out the need of greater attention to hygienic aspects in order to reduce health risks, deriving from an uncorrected application of the laws, and to provide a greater comfort to the users of swimming pools.

Chlorine↗
PubMed1989

[Gas chromatographic analysis of the S. mutans product spectrum from glucose turnover].

In addition to other acids lactate was detected as prevailing end product in glucose containing broth of 8 S. mutans strains. The total acid amounts differed depending on the microbial origin. Further quantitative and qualitative differences existed between acidic products of the pH-stat controlled reaction with glucose as substrate and defined germ suspensions. S. mutans LM 7 showed the most strongly heterofermentative pathway.

Chromatography, Gas↗
PubMed1997

Stream periphytic biodegradation of the anionic surfactant C12-alkyl sulfate at environmentally relevant concentrations.

The effects of continuous exposure to C12-alkyl sulfate on a periphytic microbial community were determined in an 8-week stream mesocosm study. C12-alkyl sulfate concentrations ranged from environmentally relevant (< 10-20 micrograms/liter) to unrealistically high concentrations (> 1500 micrograms/liter). Endpoints evaluated included turnover rates, bacterial cell density, heterotrophic mixed amino acid uptake, and fatty acid profile evaluations. Predosed periphyton demonstrated a mean turnover rate for C12-alkyl sulfate of 0.08/hr. During the 8-week dosing period, a significant increase in mean turnover rates was observed in streams dosed with > or = 61 micrograms C12-alkyl sulfate/liter, despite a 10 degrees C drop in stream temperature. A significant correlation between turnover rate and C12-alkyl sulfate concentration was also observed. While bacterial cell density increased during the study, it was determined that the biodegradation acclimation to C12-alkyl sulfate was not biomass-specific. Likewise, bacterial activity generally increased over the study, but it did not correlate with either biodegradation or bacterial cell density. Lastly, phospholipid fatty acid profiles indicate that a shift in the microbial community occurred in the high-dose stream as opposed to the control stream. This study demonstrates that C12-alkyl sulfate is rapidly degraded and induces a biodegradative acclimation response at environmentally relevant concentrations.

Amino Acids↗
PubMed1984

Diel production and microheterotrophic utilization of dissolved free amino acids in waters off southern california.

Diel patterns of dissolved free amino acid (DFAA) concentration and microheterotrophic utilization were examined in the spring and fall of 1981 in euphotic waters from the base of the mixed layer off the southern California coast. The average depths of the isotherms sampled were 19.2 m for spring and 9.0 m for fall. Total DFAA levels were generally higher in the spring than in the fall, 18 to 66 nM and 14 to 20 nM, respectively. Two daily concentration maxima and minima were observed for total DFAAs as well as for most individual DFAAs. Maxima were usually measured in the mid-dark period and in the early afternoon; minima were typically observed in early morning and late afternoon. Bacterial cell numbers reached maximal values near midnight in both seasons. These increases coincided with one of the total DFAA maxima. The second total DFAA maximum occurred in early to midafternoon, during the time of maximum photosynthetic carbon production and rapid dissolved amino acid utilization. Microbial metabolism (incorporation plus respiration) of selected H-amino acids was 2.7 to 4.1 times greater during the daylight hours. DFAA turnover times, based on these metabolic measurements, ranged between 11 and 36 h for the amino acids tested, and rates were 1.7 to 3.7 times faster in the daylight hours than at night. DFAA distributions were related to primary production and chlorophyll a concentrations. Amino acids were estimated to represent 9 to 45% of the total phytoplankton exudate. Microheterotrophic utilization or production of total protein amino acids was estimated as 3.6 mug of C liter day in spring and 1.9 mug of C liter day in the fall. Assimilation efficiency for dissolved amino acids averaged 65% for marine microheterotrophs.

Journal Article↗
PubMed1991

Effects of dietary energy level and protein source on nutrient digestion and ruminal nitrogen metabolism in steers.

Four Simmental steers with ruminal, duodenal, and ileal cannulas were used to examine effects of dietary forage: concentrate ratio and supply of ruminally degradable true protein on site of nutrient digestion and net ruminal microbial protein synthesis. Steers (345 kg) were fed ammoniated corn cob (high forage; HF)- or corn cob/ground corn/cornstarch (low forage; LF)-based diets supplemented with soybean meal (SBM) or a combination of corn gluten meal and blood meal (CB). Diets were fed at 2-h intervals with average DM intake equal to 2.2% of BW. Feeding LF vs HF increased (P less than .05) OM digestion (percentage of intake) in the stomach, small intestine, and total tract. Efficiency of microbial CP synthesis (EMCP; g of N/kg of OM truly fermented) decreased (P less than .05) for LF vs HF (24.1 vs 26.8), but microbial N and total N flows to the small intestine were similar (P greater than .05) between energy levels (average 112 and 209 g/d, respectively). Total N flows to the small intestine were 13.1% greater (P less than .05) for CB than for SBM because of increased (P less than .05) passage of nonmicrobial N. Feeding SBM vs CB increased (P less than .05) EMCP (27.3 vs 23.3) and microbial N flow to the small intestine (127.5 vs 112.5 g/d), but these increases were not likely due to increased ruminal concentrations of ammonia N (NH3 N). Decreased (P less than .05) incorporation of NH3 N into bacterial N and slower turnover rates of ruminal NH3 N for SBM vs CB suggest that direct incorporation of preformed diet components into cell mass increased when SBM was fed. Results of this study suggest that the inclusion of ruminally degradable protein in the diet may increase the supply of products from proteolysis and that this can increase EMCP and microbial protein flow to the small intestine.

Amino Acids↗
PubMed1981

On the insensitivity of sheep to the almost complete microbial destruction of dietary choline before alimentary-tract absorption.

1. Injection of [Me-14C]choline into sheep indicated that the small amount of phosphatidylcholine present in abomasal digesta was largely (69%) of non-dietary or ruminal origin. 2. Long-term feeding of [Me-3H]choline to sheep produced insignificant labelling of plasma phosphatidylcholine, indicating that more than 99% of the choline body pool was of non-dietary origin. 3. In contrast, when rats were fed with [Me-3H]choline for similar periods, 18-54% of the tissue phosphatidylcholine was derived from dietary choline. 4. The loss of [14C]choline and 32P from the plasma phosphatidylcholine after a single injection of these isotopes indicated a markedly slower turnover of choline in the sheep compared with the rat. This observation, coupled with a lack of liver glycerophosphocholine diesterase, provides an explanation for the insensitivity of the sheep to an almost complete microbial destruction of dietary choline before alimentary-tract absorption.

Abomasum↗
PubMed1999

Use of biochemical indices in the mediterranean environment: comparison among soils under different forest vegetation.

In the present study, soil biomass activity, organic carbon storage, and turnover times were compared in adjacent mediterranean biotopes with different forest vegetation, to analyze the effects of litter diversity and soil management protocols on microbial decomposition rates. Samples of forest soil from four vegetation types were collected at depths of 0-20 and 20-40 cm in the 'Tenuta Presidenziale di Castelporziano' Reserve on the Tyrrhenian coast, near Rome (Italy). The samples were incubated under standard laboratory conditions (-33 kPa water tension, and 30 degrees C), in order to compare the microbial activity independently of temperature and humidity. The CO2-C accumulation curves over a 28-d incubation period showed substantially different kinetics between the samples; in particular, soils with above-ground diversity were characterised by high mineralization activity when compared with those sampled under monospecific vegetation. For all the sites, statistically significant linear correlation was observed between nitrogen concentration and potentially mineralizable carbon (r = 0.97), and microbial biomass carbon (Cmic) to total organic carbon (Corg) ratio and the microbial metabolic quotient q(CO2) (r = -0.96). The q(CO2), indicator of the stability of ecosystems, was enhanced by plant diversity, while the Cmic:Corg ratio was reduced.

Biomass↗
PubMed1987

Ecophysiological adaptations of anaerobic bacteria to low pH: analysis of anaerobic digestion in acidic bog sediments.

The dynamics of anaerobic digestion were examined in the low-pH sediments of Crystal Bog in Wisconsin. The sediments (pH 4.9) contained 71% organic matter and the following concentrations of dissolved gases (micromoles per liter): CO2, 1,140; CH4, 490; and H2, 0.01. The rate of methane production was 6.2 mumol/liter of sediment per h, which is slower than eutrophic, neutral sediments. Microbial metabolic processes displayed the following pH optima: hydrolysis reactions, between 4.2 and 5.6; aceticlastic methanogenesis, 5.2; and hydrogen-consuming reactions, 5.6. The turnover rate constants for key intermediary metabolites were (h-1): glucose, 1.10; lactate, 0.277; acetate, 0.118; and ethanol, 0.089. The populations of anaerobes were low, with hydrolytic groups (10(6)/ml) several orders of magnitude higher than methanogens (10(2)/ml). The addition of carbon electron donors to the sediment resulted in the accumulation of hydrogen, whereas the addition of hydrogen resulted in the accumulation of fatty acids and the inhibition of hydrogen-producing acetogenic reactions. Strains of Lactobacillus, Clostridium, and Sarcina ventriculi were isolated from the bog, and their physiological attributes were characterized in relation to hydrolytic process functions in the sediments. The present studies provide evidence that the pH present in the bog sediments alter anaerobic digestion processes so that total biocatalytic activity is lower but the general carbon and electron flow pathways are similar to those of neutral anoxic sediments.

Acetates↗
PubMed1990

Relationship between sensitivity and density of muscarinic receptors in single smooth muscle cells of guinea pig taenia caecum prepared under three conditions.

The relationship between the sensitivity (the pD2 value) of carbachol and the density (the total concentration of receptors) of muscarinic receptors using single cells from the guinea pig taenia caecum prepared with a mixture of crude collagenase and trypsin inhibitor, purified collagenase alone, and a mixture of purified collagenase and papain was examined. The sensitivity of the single cells prepared with a mixture of purified collagenase and papain was about 10 times more effective than that of the single cells prepared under other conditions. The dissociation constant of [3H]quinuclidinyl benzilate (QNB) and Hill's coefficient did not change in the single cells prepared under the three conditions, though the maximum binding sites were significantly greater in the cells prepared with the mixture of purified collagenase and papain than in those prepared by other means. These results suggest that the increase in the sensitivity of carbachol obtained in the single cells prepared with this mixture is due to the increase in the density of muscarinic receptors and also suggest that the effects of this enzyme mixture may be due to an increase in the incorporation of newly synthesized receptors and (or) changes in receptor turnover.

Animals↗
PubMed2003

Heterotrophic microbial activity and organic matter degradation in coastal lagoons of Colombia.

In this study we measured the community respiration and the bacterial respiration as part of the overall degradation process of organic material. Additionally, the turnover rates of the pools of dissolved free glucose and acetate as representatives of the fraction of easily degradable low molecular organic solutes were determined. The study was performed in several coastal lagoons of the "Outer Delta of the Río Magdalena" in northern Colombia. The lagoons can be separated into two groups: The first group contains highly productive brackish lagoons with chl a concentrations ranging from 62-130 micrograms/l. The second group consists of less productive freshwater lagoons with chl a between 5.5-19 micrograms/l. Turnover rates of glucose and acetate were very fast in the highly productive lagoons resulting in turnover times of less than 20 min for both compounds. In the less productive systems the cycling of glucose and acetate was much slower. Here the mean values of the turnover times were 2 hr for glucose and 1.5 hr for acetate. The rates of bacterial DNA-formation measured as thymidine incorporation differed significantly between both groups of lagoons, being very high (1.86-2.76 nmol/l/hr) in the highly productive and relatively low (0.073-0.55 nmol/l/hr) in the less productive group. Water column community respiration ranged between 122 and 16 micrograms C/l/hr with means of 88 micrograms C/l/hr in the highly and 19 micrograms C/l/hr in the less productive group. In the first group the mean values of the bacterial contribution to community respiration amounted to 37% and in the second group to 18%. The bacterial respiration was determined in an indirect way via bacterial biomass production and assuming a growth efficiency of 50%. It is discussed whether this relatively high growth efficiency allows reasonable results in both groups of lagoons.

Acetates↗
PubMed1977

Ruminal microbial yields: factors influencing synthesis and bypass.

Bacterial growth (protein production) in the rumen is typically limited by anaerobic energy supply. But the mass of bacteria produced per mole of ATP (YATP) varies markedly with turnover or growth rate of bacteria, availability of cell components, accumulation of ash or starch, and intraspecies transfer of reducing equivalents. Increased turnover rate of rumen contents appears to enhance bacterial protein production, increase ruminal acetate and methane production and increase bypass of fiber and concentrate components of the ration.

Adenosine Triphosphate↗
PubMed1996

Geotrichum candidum P-5 produces an intracellular serine protease resembling chymotrypsin.

A wide range of intra- and extracellular microbial proteases has been studied and characterized. These enzymes are mostly extracellular and in some cases they may resemble 'classical' serine proteases. As part of a programme in which the lipase and protease activities of the fungus Geotrichum candidum are being studied, an intracellular protease with an apparent chymotrypsin-like specificity was detected. The serine protease was isolated from biomass using ion-exchange and exclusion chromatography. Kinetic characterization was done using a series of synthetic substrates and inhibitors. Aprotinin-sepharose affinity chromatography was used to isolate a fraction for molecular size determination on SDS-PAGE. The purified protease, which could hydrolyse haemoglobin as protein substrate, was obtained with a 30-fold purification and a yield of 44%, but it was very unstable and rapidly lost activity. The enzyme which bound to the affinity column had a single subunit mass of 278 kDa. Kinetic analysis showed a similarity with trypsin and chymotrypsin, but tending more towards chymotrypsin in that a bulky aromatic group, e.g. phenylalanine in the P1 position, was preferred. The optimum pH was in the region of 7-8.25. Inhibition patterns indicated that the enzyme was a serine protease with no metal dependence, although it was stabilized by magnesium ions. The enzyme seems to share some properties with other intra- and extracellular microbial serine proteases. The exact function of the enzymatic activity is still unclear, but it is suggested that it may be involved with intracellular protein turnover.

Chymotrypsin↗