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Biomedical subjects

D C White

Publications and source records attributed to D C White.

At least 163 records · Page 9Linked to original sources
PubMed1980

Lumbar extradural injection pressures in pregnant women. An investigation of relationships between rate of infection, injection pressures and extent of analgesia.

Before the induction of labour in 34 pregnant women 1.5% lignocaine 10 ml was injected into the lumbar extradural space at constant rates between 0.143 and 0.333 ml s-1. Injection pressures and residual pressures were recorded and the extent of analgesia to pinprick was assessed. No significant correlation was found between the rate of injection and injection pressures or residual pressures over the range investigated. Analgesia was significantly more extensive on the side dependent during injections, but there was no significant correlation between the overall extent of analgesia and the rate of injection, injection pressures or residual pressures in the extradural space. It is concluded that there is no advantage from rapid extradural injections.

Adolescent↗
PubMed1980

Topography of the lumbar epidural space. A study in cadavers using injected polyester resin.

Polyester resin was injected into the epidural space of fresh-adult cadavers to study the shape of the lumbar epidural space and the spatial relationship between the dura mater and vertebral canal. In most of the anatomical preparations the shape of the lumbar dural sac was distinctly triangular and in some cases a dorso-median fold of the dura was apparent. These observations support the explanation suggested by others to account for the midline translucency seen in contrast radiological examination of the lumbar epidural space. Factors which may influence the shape and dimensions of the lumbar epidural space are discussed. It is suggested that these anatomical observations may have clinical significance in the practice of lumbar epidural analgesia.

Adult↗
PubMed1980

Characterization of benthic microbial community structure by high-resolution gas chromatography of Fatty Acid methyl esters.

Fatty acids are a widely studied group of lipids of sufficient taxonomic diversity to be useful in defining microbial community structure. The extraordinary resolution of glass capillary gas-liquid chromatography can be utilized to separate and tentatively identify large numbers of fatty acid methyl esters derived from the lipids of estuarine detritus and marine benthic microbiota without the bias of selective methods requiring culture or recovery of the microbes. The gas-liquid chromatographic analyses are both reproducible and highly sensitive, and the recovery of fatty acids is quantitative. The analyses can be automated, and the diagnostic technique of mass spectral fragmentation analysis can be readily applied. Splitless injection on glass capillary gas chromatographic columns detected by mass spectral selective ion monitoring provides an ultrasensitive and definitive monitoring system. Reciprocal mixtures of bacteria and fungi, when extracted and analyzed, showed progressive changes of distinctive fatty acid methyl esters derived from the lipids. By manipulating the environment of an estuarine detrital microbial community with antibiotics and culture conditions, it was possible to produce a community greatly enriched in eucaryotic fungi, as evidenced by scanning electron microscopic morphology. The fatty acid methyl esters from the lipids in the fungus-enriched detritus showed enrichment of the C(18) dienoic and the C(18) and C(20) polyenoic esters. Manipulation of the detrital microbiota that increased the procaryotic population resulted in an absence of large structures typical of fungal mycelia or diatoms, as evidenced by scanning electron microscopy, and a significantly larger proportion of anteiso- and isobranched C(15) fatty acid esters, C(17) cyclopropane fatty acid esters, and the cis-vaccenic isomer of the C(18) monoenoic fatty acid esters. As determined by these techniques, a marine settling community showed greater differences in bacterial as contrasted to microeucaryotic populations when compared with the microbial communities of benthic cores.

Journal Article↗
PubMed1980

Fluorometric determination of adenosine nucleotide derivatives as measures of the microfouling, detrital, and sedimentary microbial biomass and physiological status.

Adenosine, adenine, cyclic adenosine monophosphate (AMP), AMP, nicotinamide adenine dinucleotide, adenosine diphosphate, and adenosine triphosphate (ATP) were recovered quantitatively from aqueous portions of lipid extracts of microfouling, detrital, and sedimentary microbial communities. These could be detected quantitatively in the picomolar range by forming their 1-N-etheno derivatives and analyzing by high-pressure liquid chromatography with fluorescence detection. Lipid extraction and subsequent analysis allowed the simultaneous measurement of the microbial community structure, total microbial biomass with the quantitative recovery of the adenine-containing cellular components, which were protected from enzymatic destruction. This extraction and fluorescent derivatization method showed equivalency with the luciferin-luciferase method for bacterial ATP measurements. Quick-freezing samples in the field with dry ice-acetone preserved the ATP and energy charge (a ratio of adenosine nucleotides) for analysis at remote laboratories. The metabolic lability of ATP in estuarine detrital and microfouling communities, as well as bacterial monocultures of constant biomass, showed ATP to be a precarious measure of biomass under some conditions. Combinations of adenosine and adenine nucleotides gave better correlations with microbial biomass measured as extractable lipid phosphate in the detrital and microfouling microbial communities than did ATP alone. Stresses such as anoxia or filtration are reflected in the rapid accumulation of intracellular adenosine and the excretion of adenosine and AMP into the surrounding milieu. Increases in AMP and adenosine may prove to be more sensitive indicators of metabolic status than the energy charge.

Journal Article↗
PubMed1980

Effects of grazing by estuarine gammaridean amphipods on the microbiota of allochthonous detritus.

Estuarine gammaridean amphipods grazing at natural population density on detrital microbiota affected the microbial community composition, biomass, and metabolic activity without affecting the physical structure of the leaves. Total microbial biomass estimated by adenosine triphosphate and lipid phosphate or observed by scanning electron microscopy was greater on grazed than on ungrazed detritus. The rates of oxygen consumption, poly-beta-hydroxybutyrate synthesis, total lipid biosynthesis, and release of CO(2) from radioactively prelabeled microbiota were higher on grazed than on ungrazed leaves, indicating stimulation of the metabolic activity of grazed detrital microbes. This was true with rates based either on the dry leaf weight or microbial biomass. Alkaline phosphatase activity was lower in the grazed system, consistent with enhanced inorganic phosphate cycling. The loss of C from both total lipid and poly-beta-hydroxybutyrate of microorganisms prelabeled with C was greater from grazed than ungrazed microbes. There was a faster decrease in the C-glycolipid than in the C-neutral lipid or C-phospholipid fractions. Analysis of specific phospholipids showed losses of the metabolically stable [C]glycerolphosphorylcholine derived from phosphatidylcholine and much more rapid metabolism of the bacterial lipid phosphatidylglycerol measured as [C]glycerolphosphorylglycerol with amphipod grazing. The biochemical data supported scanning electron microscopy observations of a shift as the grazing proceeded from a bacterial/fungal community to one dominated by bacteria.

Journal Article↗
PubMed1979

The microscopic characterization of multinucleated giant cells formed on polymeric surfaces perfused with blood.

Multinucleated, foreign body giant cells were formed by the fusion of blood monocytes on polymeric membranes perfused with blood during extended extracorporeal circulation. In the current study, heparinized blood, flowing in an arteriovenous shunt in a sheep, perfused polycarbonate, polypropylene and silicone rubber membranes of a recently developed bioartificial tissue culture system. The multinucleated giant cells were studied by light, scanning electron, and transmission electron microscopy, after membrane perfusion for periods of one to two weeks. The giant cells, which were the predominant cellular components of the blood-polymer interface layer, contained from a few to more that one hundred nuclei and varied in diameter up to 400 microns. The cellular interaction with the three membrane types was similar, although fewer mononuclear cells were observed adhering to the silicone rubber membrane. The presence or absence of micropores in the membranes had no effect on the formation of giant cells, nor did the presence of foreign tissue in culture behind the microporous membranes. High blood flow rates and chronic anticoagulation with heparin permitted observation of this foreign body reaction of blood independent of thrombosis.

Animals↗
PubMed1979

Poly-beta-Hydroxybutyrate Accumulation as a Measure of Unbalanced Growth of the Estuarine Detrital Microbiota.

The procaryotic endogenous storage material poly-beta-hydroxybutyrate (PHB) can be induced to accumulate in the estuarine detrital microbiota under conditions which suggest unbalanced growth, such as limitation of a critical factor(s) in the presence of carbon and energy sources. Changes in PHB-to-lipid phosphate ratios detected in field samples can be mimicked in the laboratory with common estuarine stresses. Acute anoxia or low pH induces conditions of no growth with depression of both the synthesis and catabolism of PHB without change in the lipid phosphate. Balanced growth induced by nutrients increases the lipid phosphate, depresses PHB synthesis, and stimulates PHB catabolism, resulting in a low ratio of PHB to lipid phosphate. Unbalanced growth induced to a small extent by high salinity or much more readily by dark upland runoff water results in rapid accumulation of PHB and slowing of PHB catabolism with little change in lipid phospate. Unbalanced growth conditions result in high PHB-to-lipid phosphate ratios in the detrital microbiota.

Journal Article↗
PubMed1979

Muramic Acid assay in sediments.

An improved chromatographic assay for muramic acid which is sufficiently sensitive for marine sandy sediments is described; it involves acid hydrolysis, thin-layer chromatography, and gas-liquid chromatography.

Journal Article↗
PubMed1978

Effects of substrate biodegradability on the mass and activity of the associated estuarine microbiota.

Multiple biochemical assays of microbial mass and activities were applied to the estuarine detrital microbiota colonizing morphologically similar polyvinyl chloride needles and needles from slash pine (Pinus elliottii). Biodegradable pine needles consistently showed 2- to 10-fold higher values of extractable adenosine 5'-triphosphate, rates of oxygen utilization, activities of alkaline phosphatase and phosphodiesterase, and the mucopeptide cell wall component muramic acid than did the polyvinyl chloride needles, during a 14-week incubation in a semitropical estuary. The higher activities by the microbiota of the biodegradable substrate correlated with estimates of the microbial density from scanning electron microscopy. The microbial community associated with the nondegradable substrate showed minimal activity of beta-d-galactosidase, beta-d-glucosidase, and alpha-d-mannosidase in contrast to the biota of the degradable substrate, which showed 10- to 100-fold higher activities of these glycoesterases. These enzymes logically could be involved in catabolism of the carbohydrate polymers of the detritus. Assuming equivalent rates of predation, a surface that is also a utilizable substrate supports a three- to fivefold more active microbial population.

Journal Article↗
PubMed1978

Recovery of Poly-beta-Hydroxybutyrate from Estuarine Microflora.

Poly-beta-hydroxybutyrate (PHB) is a uniquely procaryotic endogenous storage polymer whose metabolism has been shown to reflect environmental perturbations in laboratory monocultures. When hydrolyzed for 45 min in 5% sodium hypochlorite, PHB can be isolated from estuarine detrital microflora in high yield and purified free from non-PHB microbial components. Lyophilization of frozen estuarine samples shortens the exposure time to NaOCl necessary for maximal recovery. Lyophilized samples of hardwood leaves, Vallisneria, and the aerobic upper millimeter of estuarine muds yielded PHB. The efficiency of incorporation of sodium [1-C]acetate into PHB is very high and is stimulated by aeration. PHB was not recovered from the anaerobic portions of sediments unless they were aerated for a short time. Levels of PHB in the detrital microbial community do not correlate with the microbial biomass as measured by the extractible lipid phosphate, suggesting that PHB-like eucaryotic endogenous storage materials may more accurately reflect the metabolic status of the population than its biomass.

Journal Article↗