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E A Laws

Publications and source records attributed to E A Laws.

7 recordsLinked to original sources
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↗
PubMed1986

Method for Assessing Heterogeneity in Turnover Rates within Microbial Communities.

A method is presented for determining both the average turnover rate and the standard deviation of the average turnover rate of the adenine nucleotide (AN) pool within a population of microorganisms. The method requires the calculation of the initial slope and curvature of a plot of AN specific activity versus time following the introduction of [H]adenine. An analysis of noise-corrupted data indicated that the method is capable of detecting a lack of uniformity in the turnover rate when the coefficient of variation of the turnover rate exceeds 39%. An analysis of field data revealed a significant lack of uniformity in the turnover rates of microbial communities in a marine sediment sample and freshwater pond but no significant nonuniformity in the turnover rates of microbial communities in a seawater sample and in a second freshwater pond. Although the method has been applied only to the analysis of AN turnover rates, it is applicable to any intracellular pool for which a suitable radioactive precursor exists.

Journal Article↗
PubMed1983

Pharmacokinetics and tolerance of single intravenous doses of cefotetan disodium in male Caucasian volunteers.

Cefotetan, a third generation cephalosporin, in doses of 0.25, 0.5, 1.0 and 2.0 g was administered intravenously as the disodium salt to ten healthy male Caucasian volunteers and its pharmacokinetics and tolerance determined. The elimination half-life was 3.3 h. The drug was 88% plasma protein bound and 67% was recovered unchanged in the urine. HPLC and bioassay techniques for cefotetan plasma-concentration determinations gave virtually identical results. Cefotetan was well tolerated although half of the volunteers experienced transient mild to moderate diarrhoea. It is concluded that the pharmacokinetic disposition of cefotetan is similar in Caucasian and Japanese subjects and that the long elimination half-life, lack of detectable metabolism and high urinary excretion will result in plasma and urine concentrations in excess of the MIC of sensitive bacteria on a twice daily dosing regime.

Adult↗
PubMed1977

The effect of clofibrate on glucose tolerance, insulin secretion, triglycerides and fibrinogen in patients with coronary heart disease.

The effects of clofibrate treatment have been monitored in a double-blind cross-over study conducted in 16 male patients with coronary heart disease. Most had latent diabetes mellitus with elevated and delayed insulin release after i.v. glucose administration. Blood glucose and insulin levels were measured during repeated i.v. glucose tolerance tests in each patient and serum triglyceride and plasma fibrinogen were estimated at intervals. Clofibrate treatment significantly lowered fasting blood glucose levels (p less than 0.01) and improved the glucose tolerance (p less than 0.01). Fasting plasma insulin levels and those at 30 min after glucose loading were reduced (p less than 0.05). Serum triglycerides (p less than 0.01) and plasma fibrinogen levels (p less than 0.05) were lowered during the treatment period. The change in k-value (glucose utilization) did not correlate to changes in triglyceride or fibrinogen. This study confirms the beneficial effect of clofibrate therapy on abnormal glucose tolerance observed by other workers. It is suggested that clofibrate acts by reducing peripheral insulin resistance.

Adult↗