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Biomedical subjects

J M Hayes

Publications and source records attributed to J M Hayes.

At least 37 records · Page 2Linked to original sources
PubMed1997

Carbon isotopic fractionation associated with lipid biosynthesis by a cyanobacterium: relevance for interpretation of biomarker records.

For the cyanobacterium Synechocystis UTEX 2470, grown photoautotrophically to a logarithmic stage of growth, the total lipid extract is depleted in 13C by 4.8% relative to average biomass. Depletions observed for acetogenic (straight-chain) lipids range from 7.6 (hexadecanoic acid) to 9.9% (a C16 n-alkyl chain bound in a polar-lipid fraction), with a mass-weighted average of 9.1%. Polyisoprenoid lipids fall into two isotopic groups, with phytol, diplopterol, and diploptene depleted by 6.4-6.9% and bishomohopanol (produced from the extracts by the preparative degradation of bacteriohopanepolyol) depleted by 8.4%. Analysis of the pattern of depletions indicates that two carbon positions in each C5 biomonomer leading to polyisoprenoid products are probably depleted in 13C relative to average biomass. The depletion of bacteriohopanepolyol relative to other polyisoprenoids can be ascribed to changes that occur over the life of each cell: (1) the 13C content of carbon flowing to lipid biosynthesis decreases as the cell size increases and (2) a greater proportion of the bacteriohopanepolyol which, unlike other polyisoprenoids, is present mainly in the cytoplasm rather than in membranes and is synthesized when cells are larger. Chlorophyll a is depleted relative to average biomass by O.7%. Given the observed depletion of 13C in phytol, the heteroaromatic, chlorophyllide portion of chlorophyll must be enriched in 13C by 2.7%. This enrichment is large relative to that in chlorophyllides produced by eukaryotes and may be related to a parallel enrichment of 13C in cyanobacterial glutamic acid. As in many previous investigations of cyanobacterial lipids, long-chain n-alkanes (C22-C29) are found in the extracts. They are, however, enriched in 13C relative to biomass and have isotopic compositions suggesting that they are contaminants of petrochemical origin. Available results indicate that cyanobacterial lipids will be depleted relative to dissolved CO2 that has served as a carbon source by 22-30% and that a wider range of depletions will be characteristic of eukaryotic products. The absence of long-chain n-alkanes in cyanobacteria reduces the possibility that petroleum ever formed from pre-eukaryotic sedimentary debris.

Acetic Acid↗
PubMed1997

Coordinated systems of community-based health care delivery: a vehicle for health care reform.

The need for health care reform in this country continues to be high on the public agenda. Deficits in the access of United States citizens to needed health care services continues, despite recent efforts at health care reform. In addition, the health status of children in this country is of paramount concern. Significant threats to the health of this nation's children have spurred several proposals for reducing the cost of health care while improving the quality of outcomes. A sample of these proposals is analyzed. An example of a health care program which exemplifies one such proposal for health care reform is then discussed. Findings of a recent research project that is relative to the benefits of such a program are provided.

Adolescent↗
PubMed1997

Consistent fractionation of 13C in nature and in the laboratory: growth-rate effects in some haptophyte algae.

The carbon isotopic fractionation accompanying formation of biomass by alkenone-producing algae in natural marine environments varies systematically with the concentration of dissolved phosphate. Specifically, if the fractionation is expressed by epsilon p approximately delta e - delta p, where delta e and delta p are the delta 13C values for dissolved CO2 and for algal biomass (determined by isotopic analysis of C37 alkadienones), respectively, and if Ce is the concentration of dissolved CO2, micromole kg-1, then b = 38 + 160*[PO4], where [PO4] is the concentration of dissolved phosphate, microM, and b = (25 - epsilon p)Ce. The correlation found between b and [PO4] is due to effects linking nutrient levels to growth rates and cellular carbon budgets for alkenone-containing algae, most likely by trace-metal limitations on algal growth. The relationship reported here is characteristic of 39 samples (r2 = 0.95) from the Santa Monica Basin (six different times during the annual cycle), the equatorial Pacific (boreal spring and fall cruises as well as during an iron-enrichment experiment), and the Peru upwelling zone. Points representative of samples from the Sargasso Sea ([PO4] < or = 0.1 microM) fall above the b = f[PO4] line. Analysis of correlations expected between mu (growth rate), epsilon p, and Ce shows that, for our entire data set, most variations in epsilon p result from variations in mu rather than Ce. Accordingly, before concentrations of dissolved CO2 can be estimated from isotopic fractionations, some means of accounting for variations in growth rate must be found, perhaps by drawing on relationships between [PO4] and Cd/Ca ratios in shells of planktonic foraminifera.

Algorithms↗
PubMed1996

Patellar tilt in total knee arthroplasty.

Eighty-nine consecutive primary total knee arthroplasties performed for osteoarthrosis were evaluated to determine the effect of patellar thickness, alignment, joint line, patellar height, type of patellar prosthesis, and length of follow-up on patellar tilt. Preoperatively, 62% of the patellae were tilted neutrally and 38% tilted laterally on standard 45 degrees Merchant-view radiographs. At 3-week follow-up, 52% were neutral, 32% tilted laterally and 16% tilted medially. At the most recent follow-up (mean 36 months), 41% were neutral, 46% tilted laterally and 13% tilted medially. Five (5.6%) required reoperation for patellar complications. Change in joint line, in alignment, and in patellar height had no effect on postoperative patellar tilt. Patients who required a lateral release had postoperative patellar tilt measurements that were not statistically different from those who did not require a lateral release. Metal-back domed patellae were more likely to tilt laterally than all-polyethylene domed patellae; however, the metal-back patellae had a longer mean follow-up (41 months) compared with the all-polyethylene patellae (27 months). The positive correlation between preoperative patellar thickness and postoperative patellar tilt was statistically significant. The negative correlation between change in patellar thickness and postoperative patellar tilt also was statistically significant. Finally, postoperative medically tilted patellae moved toward neutral with time and laterally tilted patellae not only remained laterally tilted but also the tilt increased with time.

Aged↗
PubMed1995

Performance and optimization of a combustion interface for isotope ratio monitoring gas chromatography/mass spectrometry.

Conditions and systems for on-line combustion of effluents from capillary gas chromatographic columns and for removal of water vapor from product streams were tested. Organic carbon in gas chromatographic peaks 15 s wide and containing up to 30 nanomoles of carbon was quantitatively converted to CO2 by tubular combustion reactors, 200 x 0.5 mm, packed with CuO or NiO. No auxiliary source of O2 was required because oxygen was supplied by metal oxides. Spontaneous degradation of CuO limited the life of CuO reactors at T > 850 degrees C. Since NiO does not spontaneously degrade, its use might be favored, but Ni-bound carbon phases form and lead to inaccurate isotopic results at T < 1050 degrees C if gas-phase O2 is not added. For all compounds tested except CH4, equivalent isotopic results are provided by CuO at 850 degrees C, NiO + O2 (gas-phase mole fraction, 10(-3)) at 1050 degrees C and NiO at 1150 degrees C. The combustion interface did not contribute additional analytical uncertainty, thus observed standard deviations of 13C/12C ratios were within a factor of 2 of shot-noise limits. For combustion and isotopic analyses of CH4, in which quantitative combustion required T approximately 950 degrees C, NiO-based systems are preferred, and precision is approximately 2 times lower than that observed for other analytes. Water must be removed from the gas stream transmitted to the mass spectrometer or else protonation of CO2 will lead to inaccuracy in isotopic analyses. Although thresholds for this effect vary between mass spectrometers, differential permeation of H2O through Nafion tubing was effective in both cases tested, but the required length of the Nafion membrane was 4 times greater for the more sensitive mass spectrometer.

Alkanes↗
PubMed1995

Terminal Proterozoic reorganization of biogeochemical cycles.

The Proterozoic aeon (2,500-540 million years ago) saw episodic increases in atmospheric oxygen content, the evolution of multicellular life and, at its close, an enormous radiation of animal diversity. These profound biological and environmental changes must have been linked, but the underlying mechanisms have been obscure. Here we show that hydrocarbons extracted from Proterozoic sediments in several locations worldwide are derived mainly from bacteria or other heterotrophs rather than from photosynthetic organisms. Biodegradation of algal products in sedimenting matter was therefore unusually complete, indicating that organic material was extensively reworked as it sank slowly through the water column. We propose that a significant proportion of this reworking will have been mediated by sulphate-reducing bacteria, forming sulphide. The production of sulphide and consumption of oxygen near the ocean surface will have inhibited transport of O2 to the deep ocean. We find that preservation of algal-lipid skeletons improves at the beginning of the Cambrian, reflecting the increase in transport by rapidly sinking faecal pellets. We suggest that this rapid removal of organic matter will have increased oxygenation of surface waters, leading to a descent of the O2-sulphide interface to the sea floor and to marked changes in the marine environment, ultimately contributing to the Cambrian radiation.

Carbon↗
PubMed1995

Carbon isotopic analysis of atmospheric methane by isotope-ratio-monitoring gas chromatography-mass spectrometry.

Less than 15 min are required for the determination of delta 13CPDB with a precision of 0.2% (1 sigma, single measurement) in 5-mL samples of air containing CH4 at natural levels (1.7 ppm). An analytical system including a sample-introduction unit incorporating a preparative gas chromatograph (GC) column for separation of CH4 from N2, O2, and Ar is described. The 15-min procedure includes time for operation of that system, high-resolution chromatographic separation of the CH4, on-line combustion and purification of the products, and isotopic calibration. Analyses of standards demonstrate that systematic errors are absent and that there is no dependence of observed values of delta on sample size. For samples containing 100 ppm or more CH4, preconcentration is not required and the analysis time is less than 5 min. The system utilizes a commercially available, high-sensitivity isotope-ratio mass spectrometer. For optimal conditions of sample handling and combustion, performance of the system is within a factor of 2 of the shot-noise limit. The potential exists therefore for analysis of samples as small as 15 pmol CH4 with a standard deviation of <1%.

Atmosphere↗
PubMed1995

Evidence for gammacerane as an indicator of water column stratification.

A new route for the formation of gammacerane from tetrahymanol is proposed; in addition to dehydration and hydrogenation, sulphurisation and early C-S cleavage are shown to be important in the pathway of formation, especially in marine sediments. Evidence is twofold. First, relatively large amounts of the gammacerane skeleton are sequestered in S-rich macromolecular aggregates formed by natural sulphurisation of functionalised lipids. Selective cleavage of polysulphide linkages with MeLi/MeI led to formation of 3-methylthiogammacerane, indicating that the gammacerane skeleton is primarily bound via sulphur at position 3, consistent with the idea that tetrahymanol (or the corresponding ketone) is the precursor for gammacerane. Second, upon mild artificial maturation of two sediments using hydrous pyrolysis, gammacerane is released from S-rich macromolecular aggregates by cleavage of the relatively weak C-S bonds. The stable carbon isotopic compositions of gammacerane and lipids derived from primary producers and green sulphur bacteria in both the Miocene Gessoso-solfifera and Upper Jurassic Allgau Formations indicate that gammacerane is derived from bacterivorous ciliates which were partially feeding on green sulphur bacteria. This demonstrates that anaerobic ciliates living at or below the chemocline are important sources for gammacerane, consistent with the fact that ciliates only biosynthesize tetrahymanol if their diet is deprived of sterols. This leads to the conclusion that gammacerane is an indicator for water column stratification, which solves two current enigmas in gammacerane geochemistry. Firstly, it explains why gammacerane is often found in sediments deposited under hypersaline conditions but is not necessarily restricted to this type of deposits. Secondly, it explains why lacustrine deposits may contain abundant gammacerane since most lakes in the temperate climatic zones are stratified during summer.

Animals↗
PubMed1995

Molecular indicators for palaeoenvironmental change in a Messinian evaporitic sequence (Vena del Gesso, Italy). II: High-resolution variations in abundances and 13C contents of free and sulphur-bound carbon skeletons in a single marl bed.

The extractable organic matter of 10 immature samples from a marl bed of one evaporitic cycle of the Vena del Gesso sediments (Gessoso-solfifera Fm., Messinian, Italy) was analyzed quantitatively for free hydrocarbons and organic sulphur compounds. Nickel boride was used as a desulphurizing agent to recover sulphur-bound lipids from the polar and asphaltene fractions. Carbon isotopic compositions (delta vs PDB) of free hydrocarbons and of S-bound hydrocarbons were also measured. Relationships between these carbon skeletons, precursor biolipids, and the organisms producing them could then be examined. Concentrations of S-bound lipids and free hydrocarbons and their delta values were plotted vs depth in the marl bed and the profiles were interpreted in terms of variations in source organisms, 13 C contents of the carbon source, and environmentally induced changes in isotopic fractionation. The overall range of delta values measured was 24.7%, from -11.6% for a component derived from green sulphur bacteria (Chlorobiaceae) to -36.3% for a lipid derived from purple sulphur bacteria (Chromatiaceae). Deconvolution of mixtures of components deriving from multiple sources (green and purple sulphur bacteria, coccolithophorids, microalgae and higher plants) was sometimes possible because both quantitative and isotopic data were available and because either the free or S-bound pool sometimes appeared to contain material from a single source. Several free n-alkanes and S-bound lipids appeared to be specific products of upper-water-column primary producers (i.e. algae and cyanobacteria). Others derived from anaerobic photoautotrophs and from heterotrophic protozoa (ciliates), which apparently fed partly on Chlorobiaceae. Four groups of n-alkanes produced by algae or cyanobacteria were also recognized based on systematic variations of abundance and isotopic composition with depth. For hydrocarbons probably derived from microalgae, isotopic variations are well correlated with those of total organic carbon. A resistant aliphatic biomacromolecule produced by microalgae is, therefore, probably an important component of the kerogen. These variations reflect changes in the depositional environment and early diagenetic transformations. Changes in the concentrations of S-bound lipids induced by variations in conditions favourable for sulphurization were discriminated from those related to variations in primary producer assemblages. The water column of the lagoonal basin was stratified and photic zone anoxia occurred during the early and middle stages of marl deposition. During the last stage of the marl deposition the stratification collapsed due to a significant shallowing of the water column. Contributions from anaerobic photoautotrophs were apparently associated with variations in depth of the chemocline.

Animals↗
PubMed1995

Postoperative toxic shock syndrome.

We conducted a retrospective review of all cases of postoperative toxic shock syndrome (PTSS) occurring in two community hospitals from 1981-1993, during which time 390,000 surgical procedures were performed. The incidence was 0.003% (12 cases). All wounds in these 12 cases, from those with scant superficial exudates to those with gross purulence, yielded Staphylococcus aureus. All tested isolates were susceptible to methicillin or cephalothin. Patients had a mean maximal temperature of 40 degrees C. All patients had a rash, most in a truncal, "sunburn" pattern. Eleven patients had desquamation. Mean time from surgery to onset of symptoms was 4 days. All patients required vigorous fluid resuscitation. No correlation could be demonstrated between the development of toxic shock syndrome and a patient's age, sex, preoperative skin preparation or administration of antibiotics, members of the surgical team, or duration of procedure. All patients with PTSS survived. PTSS should be considered in the differential diagnosis for the acutely febrile, systemically ill postoperative patient, even when surgical wounds are deceptively benign in appearance. Early recognition and treatment of PTSS is essential for successful outcome.

Adolescent↗
PubMed1995

Arab population data on the PCR-based loci: HLA-DQA1, LDLR, GYPA, HBGG, D7S8, Gc, and D1S80.

Allele and genotype frequencies for seven polymerase chain reaction (PCR)-based DNA genetic markers were determined in an Arab sample population. The loci analyzed were HLA-DQA1, LDLR, GYPA, HBGG, D7S8, Gc and D1S80. Results were obtained from the first six loci using the AmpliType HLA-DQ alpha DNA and AmpliType PM PCR Amplification and Typing Kits. The VNTR locus D1S80 PCR product was analyzed by polyacrylamide electrophoresis and silver staining. All loci meet Hardy-Weinberg expectations. The frequency data can be used in forensic analyses and paternity tests to estimate the frequency of a DNA profile in the Arab population.

Alleles↗
PubMed1995

Postoperative toxic shock syndrome.

PURPOSE: To determine risk factors for postoperative toxic shock syndrome (PTSS), a rare, rapidly progressive, and potentially fatal syndrome associated with postoperative wound infections. Components of PTSS include fever, rash, desquamation, hypotension, and multisystem organ dysfunction. METHODS: We conducted a retrospective review of all cases of PTSS occurring in 2 community hospitals from 1981 to 1993, following 390,000 surgical procedures. RESULTS: There were 12 cases of PTSS among the procedures reviewed (0.003%). Orthopedic procedures included excision of accessory navicular and patellar realignment. Wounds ranged from those with scant superficial exudates to those with gross purulence; all cultures yielded Staphylococcus aureus. All tested isolates were susceptible to methicillin or cephalothin. Mean time from surgery to onset of symptoms was 4 days. All patients had sudden onset of fever; mean maximal temperature was 40 degrees C. All patients displayed a rash, most in a truncal "sunburn" pattern. Eleven of 12 patients desquamated. All patients required vigorous fluid resuscitation. All patients survived. No correlation could be demonstrated between PTSS and patient age, sex, preoperative skin preparation or antibiotics, members of surgical team, or duration of procedure. CONCLUSIONS: Early recognition and treatment of PTSS are essential. No risk factors for PTSS have been identified. PTSS should be considered in the postoperative, acutely febrile, systemically ill patient, though surgical wounds may be deceptively benign in appearance.

Adolescent↗
PubMed1994

Soluble HLA class II concentrations in normal individuals and transplant recipients. Comparison with soluble HLA class I concentrations.

We developed an ELISA to quantify soluble HLA class II (S-HLA-II) in 702 sera obtained from normal subjects, patients with end-stage renal disease, and recipients of renal, hepatic, and cardiac transplants. Concentrations of S-HLA-II were detectable in 124 of 126 normal individuals. The distribution of normal values described a monophasic curve with a skewed distribution. In transplant recipients, there were no differences between preoperative and posttransplant values, but values in liver patients were significantly higher than in kidney patients, and values for heart patients were lowest of all groups. There were periodic variations in concentrations in individual patients, but these were unrelated to rejection, infection, or any other apparent clinical event. S-HLA-II was consistently present in the urine. All of these observations contrast with previous observations concerning soluble HLA class I (S-HLA-I) molecules, which were almost the precise reverse. It seems likely that these clear differences in S-HLA-II and S-HLA-I concentrations relate to different physiologic processes in either production, function, or elimination.

Graft Rejection↗
PubMed1994

Factors controlling precision and accuracy in isotope-ratio-monitoring mass spectrometry.

The performance of systems in which picomole quantities of sample are mixed with a carrier gas and passed through an isotope-ratio mass spectrometer system was examined experimentally and theoretically. Two different mass spectrometers were used, both having electron-impact ion sources and Faraday cup collector systems. One had an accelerating potential of 10kV and accepted 0.2 mL of He/min, producing, under those conditions, a maximum efficiency of 1 CO2 molecular ion collected per 700 molecules introduced. Comparable figures for the second instrument were 3 kV, 0.5 mL of He/min, and 14000 molecules/ion. Signal pathways were adjusted so that response times were <200 ms. Sample-related ion currents appeared as peaks with widths of 3-30 s. Isotope ratios were determined by comparison to signals produced by standard gases. In spite of rapid variations in signals, observed levels of performance were within a factor of 2 of shot-noise limits. For the 10-kV instrument, sample requirements for standard deviations of 0.1 and 0.5% were 45 and 1.7 pmol, respectively. Comparable requirements for the 3-kV instrument were 900 and 36 pmol. Drifts in instrumental characteristics were adequately neutralized when standards were observed at 20-min intervals. For the 10-kV instrument, computed isotopic compositions were independent of sample size and signal strength over the ranges examined. Nonlinearities of <0.04%/V were observed for the 3-kV system. Procedures for observation and subtraction of background ion currents were examined experimentally and theoretically. For sample/ background ratios varying from >10 to 0.3, precision is expected and observed to decrease approximately 2-fold and to depend only weakly on the precision with which background ion currents have been measured.

Carbon Dioxide↗
PubMed1994

Evidence for only minor contributions from bacteria to sedimentary organic carbon.

Because their molecular signatures are often prominent in extracts of sediments, bacteria are thought to be important contributors to petroleum source beds. It has been shown recently, however, that abundances of biomarkers do not always reflect relative contributions to sedimentary organic carbon (Corg). The contribution of photosynthetic green sulphur bacteria to sediments can be assessed effectively because the diagenetic products of distinctive carotenoids from these organisms occur widely and their biomass is isotopically labelled, being enriched in 13C. We show here that, although sediments and oils from the Western Canada and Williston basins contain prominent biomarkers of photosynthetic bacteria, the absence of 13C enrichment in the total Corg requires that the bacterial contribution is in fact minimal. Although the importance of bacterial reworking of sedimentary debris cannot be doubted, we argue that our findings, when considered in conjunction with those from other settings, suggest that bacterial biomass may commonly represent only a minor component of total Corg in carbonaceous rocks.

Canada↗