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At least 127 records · Page 7Linked to original sources
PubMed1999

Fraction of electrons consumed in electron acceptor reduction and hydrogen thresholds as indicators of halorespiratory physiology.

Measurements of the hydrogen consumption threshold and the tracking of electrons transferred to the chlorinated electron acceptor (f(e)) reliably detected chlororespiratory physiology in both mixed cultures and pure cultures capable of using tetrachloroethene, cis-1, 2-dichloroethene, vinyl chloride, 2-chlorophenol, 3-chlorobenzoate, 3-chloro-4-hydroxybenzoate, or 1,2-dichloropropane as an electron acceptor. Hydrogen was consumed to significantly lower threshold concentrations of less than 0.4 ppmv compared with the values obtained for the same cultures without a chlorinated compound as an electron acceptor. The f(e) values ranged from 0.63 to 0.7, values which are in good agreement with theoretical calculations based on the thermodynamics of reductive dechlorination as the terminal electron-accepting process. In contrast, a mixed methanogenic culture that cometabolized 3-chlorophenol exhibited a significantly lower f(e) value, 0.012.

Chlorobenzoates↗
PubMed2000

Evidence for microbial Fe(III) reduction in anoxic, mining-impacted lake sediments (Lake Coeur d'Alene, Idaho).

Mining-impacted sediments of Lake Coeur d'Alene, Idaho, contain more than 10% metals on a dry weight basis, approximately 80% of which is iron. Since iron (hydr)oxides adsorb toxic, ore-associated elements, such as arsenic, iron (hydr)oxide reduction may in part control the mobility and bioavailability of these elements. Geochemical and microbiological data were collected to examine the ecological role of dissimilatory Fe(III)-reducing bacteria in this habitat. The concentration of mild-acid-extractable Fe(II) increased with sediment depth up to 50 g kg(-1), suggesting that iron reduction has occurred recently. The maximum concentrations of dissolved Fe(II) in interstitial water (41 mg liter(-1)) occurred 10 to 15 cm beneath the sediment-water interface, suggesting that sulfidogenesis may not be the predominant terminal electron-accepting process in this environment and that dissolved Fe(II) arises from biological reductive dissolution of iron (hydr)oxides. The concentration of sedimentary magnetite (Fe(3)O(4)), a common product of bacterial Fe(III) hydroxide reduction, was as much as 15.5 g kg(-1). Most-probable-number enrichment cultures revealed that the mean density of Fe(III)-reducing bacteria was 8.3 x 10(5) cells g (dry weight) of sediment(-1). Two new strains of dissimilatory Fe(III)-reducing bacteria were isolated from surface sediments. Collectively, the results of this study support the hypothesis that dissimilatory reduction of iron has been and continues to be an important biogeochemical process in the environment examined.

Culture Media↗
PubMed2000

Germination-induced bioluminescence, a route to determine the inhibitory effect of a combination preservation treatment on bacterial spores.

In this work, we have used spores of Bacillus subtilis that specifically induce bioluminescence upon initiation of germination as a rapid, real-time monitor of the effects of preservative treatments on germination. Using this tool, we have demonstrated that the combination of mild acidity (pH 5.5 to 5.0), lactic acid (0. 5%), and a pasteurization step (90 degrees C for 5 min) results in enhanced inhibition of spore germination compared with the effects of the individual treatments alone. Inhibition by the combination treatment occurred as a result of both direct but reversible inhibition, entirely dependent on the physical presence of the preservative factors, and permanent, nonreversible damage to the L-alanine germination apparatus of the spore. However, we were able to restore germination of the preservative-damaged spores unable to germinate on L-alanine by supplementing the medium with the nonnutrient germinant calcium dipicolinic acid. The demonstration that simple combinations of preservative factors inhibit spore germination indicates that food preservation systems providing ambient stability could be designed which do not adhere to the strict limits set by commonly accepted processes and which are based on precise understanding of their inhibitory action.

Alanine↗
PubMed2001

Relationship of hydrogen bioavailability to chromate reduction in aquifer sediments.

Biological Cr(VI) reduction was studied in anaerobic sediments from an aquifer in Norman, Okla. Microcosms containing sediment and mineral medium were amended with various electron donors to determine those most important for biological Cr(VI) reduction. Cr(VI) (about 340 microM) was reduced with endogenous substrates (no donor), or acetate was added. The addition of formate, hydrogen, and glucose stimulated Cr(VI) reduction compared with reduction in unamended controls. From these sediments, an anaerobic Cr(VI)-utilizing enrichment was obtained that was dependent upon hydrogen for both growth and Cr(VI) reduction. No methane was produced by the enrichment, which reduced about 750 microM Cr(VI) in less than six days. The dissolved hydrogen concentration was used as an indicator of the terminal electron accepting process occurring in the sediments. Microcosms with sediments, groundwater, and chromate metabolized hydrogen to a concentration below the detection limits of the mercury vapor gas chromatograph. In microcosms without chromate, the hydrogen concentration was about 8 nM, a concentration comparable to that under methanogenic conditions. When these microcosms were amended with 500 microM Cr(VI), the dissolved hydrogen concentration quickly fell below the detection limits. These results showed that the hydrogen concentration under chromate-reducing conditions became very low, as low as that reported under nitrate- and manganese-reducing conditions, a result consistent with the free energy changes for these reactions. The utilization of formate, lactate, hydrogen, and glucose as electron donors for Cr(VI) reduction indicates that increasing the availability of hydrogen results in a greater capacity for Cr(VI) reduction. This conclusion is supported by the existence of an enrichment dependent upon hydrogen for growth and Cr(VI) reduction.

Anaerobiosis↗
PubMed2003

Stimulating the in situ activity of Geobacter species to remove uranium from the groundwater of a uranium-contaminated aquifer.

The potential for removing uranium from contaminated groundwater by stimulating the in situ activity of dissimilatory metal-reducing microorganisms was evaluated in a uranium-contaminated aquifer located in Rifle, Colo. Acetate (1 to 3 mM) was injected into the subsurface over a 3-month period via an injection gallery composed of 20 injection wells, which was installed upgradient from a series of 15 monitoring wells. U(VI) concentrations decreased in as little as 9 days after acetate injection was initiated, and within 50 days uranium had declined below the prescribed treatment level of 0.18 micro M in some of the monitoring wells. Analysis of 16S ribosomal DNA (rDNA) sequences and phospholipid fatty acid profiles demonstrated that the initial loss of uranium from the groundwater was associated with an enrichment of Geobacter species in the treatment zone. Fe(II) in the groundwater also increased during this period, suggesting that U(VI) reduction was coincident with Fe(III) reduction. As the acetate injection continued over 50 days there was a loss of sulfate from the groundwater and an accumulation of sulfide and the composition of the microbial community changed. Organisms with 16S rDNA sequences most closely related to those of sulfate reducers became predominant, and Geobacter species became a minor component of the community. This apparent switch from Fe(III) reduction to sulfate reduction as the terminal electron accepting process for the oxidation of the injected acetate was associated with an increase in uranium concentration in the groundwater. These results demonstrate that in situ bioremediation of uranium-contaminated groundwater is feasible but suggest that the strategy should be optimized to better maintain long-term activity of Geobacter species.

Acetates↗
PubMed2003

Diversion of electron flow from methanogenesis to crystalline Fe(III) oxide reduction in carbon-limited cultures of wetland sediment microorganisms.

Electron flow in acetate-limited cultures of wetland sediment microorganisms was diverted from methane production to Fe(III) reduction in the presence of crystalline Fe(III) oxides at surface area loadings equivalent to that of amorphous Fe(III) oxide. The results indicate that inferences regarding the ability of microbial Fe(III) oxide reduction to compete with other terminal electron-accepting processes in anoxic soils and sediments should be based on estimates of bulk microbially available surface site abundance rather than assumed thermodynamic properties of the dominant oxide phase(s) in the soil or sediment.

Electron Transport↗
PubMed2005

Evidence for aceticlastic methanogenesis in the presence of sulfate in a gas condensate-contaminated aquifer.

The anaerobic metabolism of acetate was studied in sediments and groundwater from a gas condensate-contaminated aquifer in an aquifer where geochemical evidence implicated sulfate reduction and methanogenesis as the predominant terminal electron-accepting processes. Most-probable-number tubes containing acetate and microcosms containing either [2-(14)C]acetate or [U-(14)C]acetate produced higher quantities of CH(4) compared to CO(2) in the presence or absence of sulfate.(14)CH(4) accounted for 70 to 100% of the total labeled gas in the [(14)C]acetate microcosms regardless of whether sulfate was present or not. Denaturing gradient gel electrophoresis of the acetate enrichments both with and without sulfate using Archaea-specific primers showed identical predominant bands that had 99% sequence similarity to members of Methanosaetaceae. Clone libraries containing archaeal 16S rRNA gene sequences amplified from sediment from the contaminated portion of the aquifer showed that 180 of the 190 clones sequenced belonged to the Methanosaetaceae. The production of methane and the high frequency of sequences from the Methanosaetaceae in acetate enrichments with and without sulfate indicate that aceticlastic methanogenesis was the predominant fate of acetate at this site even though sulfate-reducing bacteria would be expected to consume acetate in the presence of sulfate.

Acetates↗
PubMed2006

Geobacter lovleyi sp. nov. strain SZ, a novel metal-reducing and tetrachloroethene-dechlorinating bacterium.

A bacterial isolate, designated strain SZ, was obtained from noncontaminated creek sediment microcosms based on its ability to derive energy from acetate oxidation coupled to tetrachloroethene (PCE)-to-cis-1,2-dichloroethene (cis-DCE) dechlorination (i.e., chlororespiration). Hydrogen and pyruvate served as alternate electron donors for strain SZ, and the range of electron acceptors included (reduced products are given in brackets) PCE and trichloroethene [cis-DCE], nitrate [ammonium], fumarate [succinate], Fe(III) [Fe(II)], malate [succinate], Mn(IV) [Mn(II)], U(VI) [U(IV)], and elemental sulfur [sulfide]. PCE and soluble Fe(III) (as ferric citrate) were reduced at rates of 56.5 and 164 nmol min(-1) mg of protein(-1), respectively, with acetate as the electron donor. Alternate electron acceptors, such as U(VI) and nitrate, did not inhibit PCE dechlorination and were consumed concomitantly. With PCE, Fe(III) (as ferric citrate), and nitrate as electron acceptors, H(2) was consumed to threshold concentrations of 0.08 +/- 0.03 nM, 0.16 +/- 0.07 nM, and 0.5 +/- 0.06 nM, respectively, and acetate was consumed to 3.0 +/- 2.1 nM, 1.2 +/- 0.5 nM, and 3.6 +/- 0.25 nM, respectively. Apparently, electron acceptor-specific acetate consumption threshold concentrations exist, suggesting that similar to the hydrogen threshold model, the measurement of acetate threshold concentrations offers an additional diagnostic tool to delineate terminal electron-accepting processes in anaerobic subsurface environments. Genetic and phenotypic analyses classify strain SZ as the type strain of the new species, Geobacter lovleyi sp. nov., with Geobacter (formerly Trichlorobacter) thiogenes as the closest relative. Furthermore, the analysis of 16S rRNA gene sequences recovered from PCE-dechlorinating consortia and chloroethene-contaminated subsurface environments suggests that Geobacter lovleyi belongs to a distinct, dechlorinating clade within the metal-reducing Geobacter group. Substrate versatility, consumption of electron donors to low threshold concentrations, and simultaneous reduction of electron acceptors suggest that strain SZ-type organisms have desirable characteristics for bioremediation applications.

Acetates↗
PubMedDate not supplied

The use of unallowed excipients.

The laws governing the U.S. Food and Drug Administration (FDA) do not provide for the approval of stand-alone excipients. Current regulations do not permit the use of excipients, but allow their use. The acceptance process for excipients is slow and only recently did the FDA propose draft guidance for nonclinical studies for pharmaceutical excipients. The FDA has made four suggestions to the U.S. Pharmacopoeia concerning including excipient monographs in the National Formulary for excipients not yet allowed. This article reviews these four proposals to identify the proposal that is most appropriate.

Chemistry, Pharmaceutical↗
PubMed1989

Microcomputer processing of film radiographs.

An inexpensive image processing system, assembled from commercially available components and driven by "in-house" software, was tested as a means of processing radiographs obtained in a radiology department. In this preliminary study, the main interest was to investigate, through subjective appraisal, the ability of the system to recover the image quality of poorly exposed radiographs. Subsidiary objectives were to obtain some information regarding the specification limits of the system and its components, as well as some quantitative estimate of its advantages for clinical diagnosis. The system was used to process a set of film radiographs of an anthropomorphic chest phantom, produced under conditions that were designed to provide a wide range of image qualities. Following this, four sets of randomly ordered processed and unprocessed images were formally assessed by a group of experienced observers. Consensus opinion from the group indicated that significant improvement could be obtained through simple image processing. Some radiographs regarded as unacceptable became, after processing, acceptable to viewers.

Humans↗
PubMed2000

What perimenopausal women think about using hormones during menopause.

The purpose of this study was to improve our understanding of women's thoughts about taking hormones during menopause. Analysis of the responses of 61 perimenopausal women resulted in the identification of four categories of factors influencing women's opinions about taking hormones: perceptions of need, perceptions of risk, beliefs and values, and knowledge and information. Women used multiple cognitive processes in forming opinions about taking hormones, and the presence of conflicting factors contributed to their uncertainty. Women's references to interactions with their doctors indicated they preferred to take one of three roles in the decision making process: accepting advice, deciding together, or taking control. These findings indicate that women's decisions about hormone use take place in an arena broader and more complex than heretofore acknowledged in some studies.

Adult↗
PubMed1996

A new route of transmission for Escherichia coli: infection from dry fermented salami.

OBJECTIVES: This study evaluated the production of dry fermented salami associated with an outbreak of Escherichia coli O157.H7 infection in Washington State and California. METHODS: Facility inspections, review of plant monitoring data, food handler interviews, and microbiological testing of salami products were conducted. RESULTS: Production methods complied with federal requirements and industry-developed good manufacturing practices. No evidence suggested that postprocessing contamination occurred. Calculations suggested that the infectious dose was smaller than 50 E. coli O157:H7 bacteria. CONCLUSIONS: Dry fermented salami can serve as a vehicle of transmission for O157:H7 strains. Our investigation and prior laboratory studies suggest that E. coli O157:H7 can survive currently accepted processing methods.

Adult↗
PubMed1994

Graduate education. Creating nursing diagnoses.

Students participating in this clinical exercise learned to critically evaluate problems occurring in their practice areas. In addition, they learned ways of addressing problems through nursing diagnosis. They experienced research as they conducted surveys, calculated results, and listed characteristics. The students had the opportunity to create a product. Unfortunately, as students graduated and became busy with their new positions, they no longer pursued the academic activity of getting a diagnosis accepted by NANDA. The acceptance process seemed particularly formidable after the initial rejection. An even more serious loss exists for graduates who work in gerontological nursing--that of not having these existent problems readily identified and labeled.

Education, Nursing, Graduate↗
PubMed1999

Health expenditure and finance: who gets what?

The methods used in South Africa's first comprehensive review of health finance and expenditure are outlined. Special measures were adopted to make the process acceptable to all concerned during a period of profound political transition. The estimation of indicators of access to public sector resources for districts sorted by per capita income allowed the health care problems of disadvantaged communities to be highlighted.

Costs and Cost Analysis↗
PubMed1989

Health care technology assessment and adoption: a case study.

Today's progressive hospital and health care system managers look to new ways to retain or augment their market share and to position themselves in their service areas. Since diffusion of new technologies into health care is market driven, informed decisions on the adoption of certain emerging patient care technologies can place a health care organization in a favorable financial position. There is a compelling need for hospital management and the governing board to collaborate with their medical staff on the development of an acceptable process to quickly identify and implement appropriate new technologies into the patient care environment. This joint effort is vital to ensure the integration of sound clinical values and objectives with planned institutional business strategies. Mount Carmel Health, a multifaceted health care corporation in central Ohio, has met the challenge of managing patient needs, physician interests, and limited hospital resources by forming a unique entity within the organization for the effective assessment and adoption of the latest medical technology. The division, which is called the Advanced Treatment and Bionics Institute (ATBI), is charged with assessing the latest clinical technologies and managing a hospital's adoption of the most appropriate ones. It serves to organize and streamline the identification, acquisition, adoption, and implementation of innovative treatment technologies at Mount Carmel hospitals.

Academies and Institutes↗
PubMed1992

[Child and adolescent psychiatry--how, where, for whom? Questions on medical care and medical care research].

Regarding the question of child psychiatry--how, where, for whom? research of medical care can provide some answers, which are referred to here. However, many questions regarding epidemiology and research of structure, use and development remain open. Because of constant urgency to take action provisional situations have to be accepted, processes have to be attended to, statements have to be examined concerning their validity and theories concerning their range.

Adolescent↗
PubMed1991

[Dynamics of the lipoprotein distribution in early hypercholesterolemia characterizes the activation of cholesterol transport].

Using gradient gel electrophoresis, the levels of major classes of rabbit blood sera lipoproteins were studied over a period of 28 days. Hypercholesterolemia persisted up to the 4th day with a subsequent decrease. This was paralleled with an increase in the levels of triglyceride-rich and apoB-containing particles. The decrease of the electrophoretic mobility of low density lipoproteins correlated with an increased content of the intermediate fraction. On the 28th day after the beginning of experiment the concentration of total high density lipoproteins showed an increase. The subfractional redistribution of HDL3 and HDL2 subclasses pointed to the stimulation of the accepting process and the overall reverse cholesterol transport system. A comparison of experimental results with literary data allowed to conclude that the relative decrease of the serum cholesterol level typical of hypercholesterolemia of one month duration is due to the activation of specific and nonspecific preventive mechanisms.

Animals↗
PubMed1980

Demonstration of several sporocysts generations as a normal pattern of reproduction of Schistosoma mansoni.

A thorough study of the development of Schistosoma mansoni demonstrates that asexual reproduction within the vector-mollusc does not proceed according to the usually accepted process. Under natural conditions, daughter sporocysts are capable fo stopping production of cercariae and orienting production towards an additional generation of sporocysts, which themselves will be able to evolve in the same manner. This process intervenes without exception provided that the duration of parasitosis exceeds 40 days (at 26 degrees C). It is observed in three different american strains of S. mansoni. We believe that this is the first demonstration of the existence of several sporocysts generations as an habitual mode of reproduction in the life cycle of Digenea.

Animals↗