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Biomedical subjects

D C White

Publications and source records attributed to D C White.

At least 127 records · Page 7Linked to original sources
PubMed1985

Biomass and community structure of the abyssal microbiota determined from the ester-linked phospholipids recovered from Venezuela Basin and Puerto Rico Trench sediments.

Extractible phospholipid fatty acids of abyssal sediment cores from three stations in the Venezuela Basin, transects between them, and a station in the Puerto Rico Trench were analyzed to determine microbial biomass and community composition. Results were compared to abyssal sediments from an area of high-energy boundary currents in the North Atlantic, and estuarine sediments from Apalachee Bay, Florida. Venezuela Basin and Puerto Rico Trench sediments were characterize by low microbial biomass, measured as phospholipid palmitic acid. Venezuela Basin sediments of three different sedimentary regimes showed a remarkably similar microbial community structure, as characterized by fatty acid profiles. Prokaryotic organisms dominated the microbial community, and fatty acids believed to be signatures of anaerobic organisms were present in greater proportions in Venezuela Basin and Puerto Rico Trench sediments than in either the North Atlantic abyssal sediments or shallow-water estuarine sediments.

Biomass↗
PubMed1985

Fourier transform-infrared spectroscopic methods for microbial ecology: analysis of bacteria, bacteria-polymer mixtures and biofilms.

Fourier transform-infrared (FT-IR) spectroscopy has been used to rapidly and nondestructively analyze bacteria, bacteria-polymer mixtures, digester samples and microbial biofilms. Diffuse reflectance FT-IR (DRIFT) analysis of freeze-dried, powdered samples offered a means of obtaining structural information. The bacteria examined were divided into two groups. The first group was characterized by a dominant amide I band and the second group of organisms displayed an additional strong carbonyl stretch at approximately 1740 cm-1. The differences illustrated by the subtraction spectra obtained for microbes of the two groups suggest that FT-IR spectroscopy can be utilized to recognize differences in microbial community structure. Calculation of specific band ratios has enabled the composition of bacteria and extracellular or intracellular storage product polymer mixtures to be determined for bacteria-gum arabic (amide I/carbohydrate C-O approximately 1150 cm-1) and bacteria-poly-beta-hydroxybutyrate (amide I/carbonyl approximately 1740 cm-1). The key band ratios correlate with the compositions of the material and provide useful information for the application of FT-IR spectroscopy to environmental biofilm samples and for distinguishing bacteria grown under differing nutrient conditions. DRIFT spectra have been obtained for biofilms produced by Vibrio natriegens on stainless steel disks. Between 48 and 144 h, an increase in bands at approximately 1440 and 1090 cm-1 was seen in FT-IR spectra of the V. natriegens biofilm. DRIFT spectra of mixed culture effluents of anaerobic digesters show differences induced by shifts in input feedstocks. The use of flow-through attenuated total reflectance has permitted in situ real-time changes in biofilm formation to be monitored and provides a powerful tool for understanding the interactions within adherent microbial consortia.

Bacterial Physiological Phenomena↗
PubMed1985

Precision and sensitivity of the measurement of 15N enrichment in D-alanine from bacterial cell walls using positive/negative ion mass spectrometry.

Sensitive detection of cellular components from specific groups of microbes can be utilized as 'signatures' in the examination of microbial consortia from soils, sediments or biofilms. Utilizing capillary gas chromatography/mass spectrometry and stereospecific derivatizing agents, D-alanine, a component localized in the prokaryotic (bacterial) cell wall, can be detected reproducibly. Enrichments of D-[15N]alanine determined in E. coli grown with [15N]ammonia can be determined with precision at 1.0 atom%. Chemical ionization with methane gas and the detection of negative ions (M - HF)- and (M - F or M + H - HF)- formed from the heptafluorobutyryl D-2 butanol ester of D-alanine allowed as little as 8 pg (90 fmol) to be detected reproducibly. This method can be utilized to define the metabolic activity in terms of 15N incorporation at the level of 10(3)-10(4) cells, as a function of the 15N-14N ratio.

Alanine↗
PubMed1985

Microbial biomass and productivity in seagrass beds.

Different methods for measuring the rates of processes mediated by bacteria in sediments and the rates of bacterial cell production have been compared. In addition, net production of the seagrass Zostera capricorni and bacterial production have been compared and some interrelationships with the nitrogen cycle discussed. Seagrass productivity was estimated by measuring the plastochrone interval using a leaf stapling technique. The average productivity over four seasons was 1.28 +/- 0.28 g C m-2 day-1 (mean +/- standard deviation, n = 4). Bacterial productivity was measured five times throughout a year using the rate of tritiated thymidine incorporated into DNA. Average values were 33 +/- 12 mg C m-2 day-1 for sediment and 23 +/- 4 for water column (n = 5). Spatial variability between samples was greater than seasonal variation for both seagrass productivity and bacterial productivity. On one occasion, bacterial productivity was measured using the rate of 32P incorporated into phospholipid. The values were comparable to those obtained with tritiated thymidine. The rate of sulfate reduction was 10 mmol SO4(-2) m-2 day-1. The rate of methanogenesis was low, being 5.6 mg CH4 produced m-2 day-1. A comparison of C flux measured using rates of sulfate reduction and DNA synthesis indicated that anaerobic processes were predominant in these sediments. An analysis of microbial biomass and community structure, using techniques of phospholipid analysis, showed that bacteria were predominant members of the microbial biomass and that of these, strictly anaerobic bacteria were the main components. Ammonia concentration in interstitial water varied from 23 to 71 micromoles. Estimates of the amount of ammonia required by seagrass showed that the ammonia would turn over about once per day. Rapid recycling of nitrogen by bacteria and bacterial grazers is probably important.

Amines↗
PubMed1985

Evaluation of the Datex 'Normac' anaesthetic agent monitor.

The Datex 'Normac' infrared anaesthetic agent monitor has been evaluated for accuracy of calibration, stability and speed of response. Accuracy was assessed by comparing with a gas chromatograph calibrated using volumetric standards and was found to be very good for isoflurane and enflurane but was slightly less accurate for halothane, due to a low signal: noise ratio. The stability of the instrument was found to be exceptionally good. The response time is dependent on the sampling rate and we found that, in practice, the instrument would record the end expired anaesthetic concentration on patients breathing up to 15 breaths/minute. The instrument is compact and convenient for use in operating theatres.

Anesthesia, Inhalation↗
PubMed1985

Examination of thermophilic methane-producing digesters by analysis of bacterial lipids.

Thermophilic methane-producing digesters were examined by the analysis of lipids to determine the microbial biomass, community structure, and nutritional status of the microbes within the digesters. The digesters received a daily feedstock of cattle feed and Bermuda grass, with some digesters receiving additional supplements of propionate, butyrate, or nitrate. Microbial biomass, measured as total extractable lipid phosphate, was decreased in slurries from digesters receiving continuous addition of the fermentation intermediates propionate or butyrate as compared with slurries from control digesters receiving the feedstock alone. In slurries from digesters that received continuous addition of nitrate, the microbial biomass was higher than in the slurries from control digesters. The control digesters had ca. 2.5 x 10 bacteria per g (dry weight) as determined from total extractable lipid phosphate. Shifts in microbial community structure were observed by analysis of ester-linked phospholipid fatty acids. Statistical analysis of the patterns of phospholipid fatty acids indicated that the digesters receiving different supplements could be distinguished from the control digester and from each other. Poly-beta-hydroxybutyric acid, an indicator of metabolic stress, was detected in slurries from all the digesters. Slurries from the nitrate-amended digester had the highest concentration of poly-beta-hydroxybutyric acid, whereas slurries from the propionate-amended digester had the lowest concentration. These chemical analyses offer a quantitative means to correlate shifts in microbial biomass, community structure, and nutritional status in complex fermentation systems to the production of a specific end product.

Journal Article↗
PubMed1985

Determination of monounsaturated double-bond position and geometry in the cellular fatty acids of the pathogenic bacterium Francisella tularensis.

The nonhydroxy fatty acid composition of Francisella tularensis is reported in detail. The double-bond configuration of the monounsaturated acids has been determined by capillary gas chromatography-mass spectrometry of the derivatized fatty acids. The monounsaturated fatty acids detected, in decreasing order of abundance, were 24:1 omega 15c, 18:1 omega 9c, 22:1 omega 13c, 20:1 omega 11c, 16:1 omega 7c, 26:1 omega 17c, and 14:1 omega 7c. The fatty acid profile found in F. tularensis, in particular the double-bond positions, represents a valuable taxonomic characteristic of this pathogenic bacterium.

Fatty Acids↗
PubMed1985

Quantitative determination of microbial activity and community nutritional status in estuarine sediments: evidence for a disturbance artifact.

In estuarine sediments with a high degree of vertical heterogeneity in reduced substrate and terminal electron acceptor concentrations, the method of exposure of the microbiota to labeled substrates can introduce a "disturbance artifact" into measures of metabolic activity. The detection of this artifact is based on quantitative measurement of the relative rates of incorporation of [14C]acetate into phospholipid fatty acids (PLFA) and endogenous storage lipid, poly-beta-hydroxyalkanoate (PHA). Previous studies have shown that PLFA synthesis measures cellular growth and that PHA synthesis measures carbon accumulation (unbalanced growth). The "disturbance artifact" of exposure to [14C]acetate was demonstrated by comparing injection of a core with the usual or pore-water replacement or slurry techniques. Only injection of labeled substrate allowed detection of preassay disturbance of the sediment with a garden rake. The raking increased PLFA synthesis with little effect to differences in concentration or distribution of [14C]acetate in the 10-min incubation. Bioturbation induced by sand dollar feeding in estuarine sediment could be detected in an increased PLFA/PHA ratio which was due to decreased PHA synthesis if the addition of labeled substrate was by the injection technique. Addition of labeled precursors to sediment by slurry or pore-water replacement induces greater disturbance artifacts than injection techniques.

Acetates↗
PubMed1985

Isolation and partial chemical analysis of firmly bound exopolysaccharide from adherent cells of a freshwater sediment bacterium.

Cells of a freshwater sediment bacterium produced firmly bound extracellular polymers in laboratory cultures which, at the ultrastructural level, resembled those produced by natural sediment bacterial populations. Production of the exopolymers during subculture was maintained by using as a source of inoculum the population of cells which adhered to each other and to the wall of the glass culture vessel. The exopolymers were selectively released from the cells by blending and centrifugation in the presence of EDTA. Evaluation of glucose-6-phosphate dehydrogenase activity and 2-keto-3-deoxyoctonate concentration indicated that only small amounts of intracellular and cell wall components were released from the cells during exopolymer removal. Chemical analysis of the isolated crude exopolymer material indicated that it contained protein, polysaccharide, and DNA. The treatment promoted the selective isolation of firmly bound polymers from the surface of adherent cells.

Bacteria↗
PubMed1985

C15, C20, and C25 isoprenoid homologues in glycerol diether phospholipids of methanogenic archaebacteria.

The glycerol diether phospholipids of 25 monocultures of methanogenic bacteria were isolated and degraded with hydriodic acid. The resulting alkyl iodides were converted to acetate esters and alcohols which were examined using capillary gas-liquid chromatography. The presence of C20 phytanol was observed in accordance with previous studies. Soft fragmentation by chemical ionization mass spectrometry combined with selected ion monitoring enabled the detection, for the first time, of C15 and C25 isoprenologues as components of the diether phospholipids in several strains.

Archaea↗
PubMed1985

Warming blood before transfusion. Does immersion warming change blood composition?

The practice of warming blood for transfusion by immersion in a water bath has been studied. Blood, 3 days after collection, with CPD-adenine anticoagulant, was warmed at 25 degrees C, 37 degrees C and 45 degrees C for up to 2 hours. The procedure was repeated after 2 and 4 weeks' storage at 4 degrees C. Only trivial biochemical and morphological changes resulted from warming. Within these limits, immersion warming of blood appears to be a reasonable alternative to using a blood-warming coil. Other aspects of immersion warming are discussed.

Blood Chemical Analysis↗
PubMed1985

Extractable and lipopolysaccharide fatty acid and hydroxy acid profiles from Desulfovibrio species.

An analysis of the phospholipid ester-linked and the lipopolysaccharide (LPS) fatty acids and hydroxy fatty acids of six lactate-utilizing Desulfovibrio-type sulfate-reducing bacteria (SRB) has been performed using capillary gas-liquid chromatography-mass spectrometry (GLC-MS). The concentrations of normal fatty acids were essentially similar, with the possible exception of a high content of normal fatty acids in the LPS of Desulfovibrio gigas. Determination of monounsaturated acid double bond configuration was performed by GLC-MS analysis of the derivatized fatty acids. A total of nine branched chain and eight straight chain monounsaturated fatty acids was detected in the Desulfovibrio species analyzed. The major component detected in five Desulfovibrio was the 17-carbon iso-branched monoenoic acid which showed cis unsaturation [i17:1(n-7)c] seven carbons from the terminal methyl group of the fatty acid chain. D. gigas, in contrast, contained almost no unsaturated fatty acids and was greatly enriched in iso-branched 15:0. Major differences between strains were found in the phospholipid and LPS hydroxy fatty acids. These components, in addition to the i17:1(n-7)c and other characteristic branched chain unsaturated acids, can possibly be utilized as signatures of the lactate-utilizing SRB.

Desulfovibrio↗
PubMed1984

Determination of the gram-positive bacterial content of soils and sediments by analysis of teichoic acid components.

Many gram-positive bacteria form substituted polymers of glycerol and ribitol phosphate esters known as teichoic acids. Utilizing the relative specificity of cold concentrated hydrofluoric acid in the hydrolysis of polyphosphate esters it proved possible to quantitatively assay the teichoic acid-derived glycerol and ribitol from gram-positive bacteria added to various soils and sediments. The lipids are first removed from the soils or sediments with a one phase chloroform-methanol extraction and the lipid extracted residue is hydrolyzed with cold concentrated hydrofluoric acid. To achieve maximum recovery of the teichoic acid ribitol, a second acid hydrolysis of the aqueous extract is required. The glycerol and ribitol are then acetylated after neutralization and analyzed by capillary gas-liquid chromatography. This technique together with measures of the total phospholipid, the phospholipid fatty acid, the muramic acid and the hydroxy fatty acids of the lipopolysaccharide lipid A of the gram-negative bacteria makes it possible to describe the community structure environmental samples. The proportion of gram-positive bacteria measured as the teichoic acid glycerol and ribitol is higher in soils than in sediments and increases with depth in both.

Aluminum Silicates↗
PubMed1984

Lumbar epidural injections in the treatment of sciatica.

A randomized trial of lumbar epidural injections for the treatment of acute sciatic pain was carried out. All the patients had unilateral sciatica for less than six months and had never previously been treated in hospital for their backs. The treatments used were 20 ml normal saline, 80 mg Depomedrone in normal saline made up to 20 ml, 20 ml, 20 ml 0.25% bupivacaine solution and needling with a standard Touhy injection needle into the interspinous ligament but with no injection. The patients improved at about the same rate for all four treatments. Overall, 75% of the patients improved or were cured. As some of these were in the group treated by needling of the interspinous ligament, it seems likely that the epidural injections administered achieved effects partially as a placebo and partially by virtue of the natural history of the acute sciatic syndrome.

Acupuncture Therapy↗
PubMed1984

Use of isoflurane in closed circuit. Measurement of anesthetic uptake.

A totally closed circuit is described into which a liquid volatile anesthetic is injected by a servomechanism to maintain end-tidal anesthetic concentration at a constant preset level during positive pressure ventilation. This equipment has been used to measure the uptake of isoflurane, at an end-tidal concentration of 1.55% (1.3 MAC) in the first half hour of anesthesia in 26 patients undergoing elective surgery. The rate of uptake was found to be rapid initially but became constant after 15 minutes. Uptake varied considerably, the standard deviation of the rate of uptake being approximately one third of the mean at any one time. The total uptake of isoflurane at 30 minutes was correlated with 5 anthropometric variables, body surface area, body weight, body weight 3/4, fat free body mass and fat body mass. Significant (P less than .01) correlations were found with the first four of these, the best being with surface area (correlation coefficient 0.629). No anthropometric variable provided a correlation on which anesthetic dose could be reliably predicted and we therefore conclude that administration of isoflurane in a closed circuit is best controlled in response to direct in-circuit analysis. Methods based on anthropometric variables will be inaccurate.

Adipose Tissue↗