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Rates of liquid-solid mass transfer at horizontal array of cylinders resting on the base of a square agitated vessel were studied. An electrochemical technique which involves measuring the limiting current of the cathodic reduction of K3Fe(CN)6 in a large excess of NaOH supporting electrolyte was used. The mass transfer data were correlated by dimensionless mass transfer equations. Drag reducing polymers were found to reduce the rate of mass transfer at the tube array by an amount ranging from 2.4 to 21.8% depending on the operating conditions. The volumetric mass transfer coefficient (kA) at the tube array was found to be higher than that of the flat tank bottom cathode by a factor ranging from 4.24 to 9.33. The importance of the present study in the design and operation of stirred square tank reactor with a cooling system at the bottom was noted. Also the importance of the present results in designing semi-continuous tubular dialyzers was highlighted. The possibility of using the outer tube surface as a catalyst support and the inner surface as a cooler for conducting diffusion controlled reactions which need critical temperature control such as immobilized enzyme catalyzed biochemical reactions was discussed. [ABSTRACT FROM AUTHOR]

GADD45 is a multifunctional protein that is regulated by p53. p53 plays an important role in regulating DNA repair and in the response to ultraviolet light in keratinocytes. This study investigates the role of GADD45 in the response to ultraviolet B. Cell cycle analysis demonstrated that wild-type and Gadd45-deficient cells have transient G2/M arrest, but only in the wild-type cells was arrest sustained. Cdc2 kinase activity in immunoprecipitates from normal and Gadd45-deficient cells decreases after irradiation in normal cells but not in Gadd45-deficient cells. An immunofluorescent study with Cdc2 antibody demonstrated diffuse cellular fluorescence before ultraviolet irradiation in both Gadd45-deficient and wild-type cells, but upon ultraviolet irradiation only Gadd45-proficient cells showed Cdc2 sequestration in the cytoplasm. Gadd45-deficient cells also have a slower rate of nucleotide excision repair. The lack of G2/M arrest coupled with reduced DNA repair leads to a higher ultraviolet sensitivity of Gadd45-deficient cells. These results reveal that GADD45 promotes G2/M arrest via nuclear export and kinase activity of Cdc2, increases global genomic DNA repair, and inhibits cell death in keratinocytes. Thus, GADD45 plays an important role in maintaining genomic integrity in ultraviolet-exposed skin. [ABSTRACT FROM AUTHOR]

Introduction: Differences in human chorionic gonadotropin (hCG) results obtained by seven different methods were documented by analyzing dilutions of the WHO 4th International Standard (IS) and a pregnant patient''s serum.Materials and methods: Biases of +30.9 to −37.5% and +36.8 to −36.1% from the target concentration were found for the WHO 4th IS and patient sample dilutions, respectively.Results: Imprecision was calculated from replicate measurements of hCG on the different sample dilutions. Imprecision ranged from 1.0% to 18.9% and 1.1% to 5.3% for the WHO 4th IS and patient sample dilutions, respectively. Using a maximum allowable error of 12.5% for hCG measurements, we found that two instruments were so biased that their hCG measurements could not be interchanged with hCG values produced by any of the other systems.Discussion: It is ideal to use only one hCG methodology for the serial monitoring of hCG; otherwise, hCG methods should be carefully chosen to minimize inter-method bias. [Copyright &y& Elsevier]

Abstract The hypothalamus participates in the regulation of carbohydrate metabolism involving a feedback loop between the brain and the periphery in which glucose-sensitive hypothalamic areas appear to be involved. We have previously shown that a glucose injection (9 mg/kg) in the carotid artery toward the brain, in an amount that did not modify glycaemia, caused a rapid and transient increase in plasma insulin concentrations. To determine whether central insulin could influence this response, we investigated the change in central glucose-induced insulin secretion in intracerebroventricular (i.c.v) insulin-injected rats and in hyperinsulinaemic obese Zucker rats. Central glucose-induced insulin secretion was increased by 50% in i.c.v. insulin-injected rats compared to control rats. When a similar test was performed at a lower dose of glucose (3 mg/kg), a significant insulin secretion was observed only in rats submitted to a prior central insulin injection. These data indicate an increase in the brain response to glucose after insulin treatment. Using an identical lower glucose dose, we also demonstrated an enhanced brain glucose sensitivity in hyperinsulinaemic and insulin-resistant obese Zucker rats. Together, these results indicate that acute i.c.v. insulin or pathological hyperinsulinaemic state (i.e. obese Zucker rat) modulates the nervous control of insulin secretion by increasing the brain response to glucose. [ABSTRACT FROM AUTHOR]