RESUMEN

Wastewater and urine generated on the International Space Station (ISS) will be processed to recover pure water using vapor compression distillation (VCD). To verify the long-term reliability and performance of the VCD Urine Processor Assembly (UPA), life testing was performed at the Marshall Space Flight Center (MSFC) from January 1993 to April 1996. Two UPAs, the VCD-5 and VCD-5A, were tested for 204 days and 665 days, respectively. The compressor gears and the distillation centrifuge drive belt were found to have operating lives of approximately 4800 h, equivalent to 3.9 years of operation on ISS for a crew of three at an average processing rate of 1.76 kg/h (3.87 lb/h). Precise alignment of the flex-splines of the fluids and purge pump motor drives is essential to avoid premature failure after about 400 h of operation. Results indicate that, with some design and procedural modifications and suitable quality control, the required performance and operational life can be met with the VCD/UPA.

Asunto(s)

RESUMEN

Oxidation of mitochondrial DNA might be responsible for the persistence of structural and functional abnormalities of mitochondria in alcoholics after cessation of ethanol intake. Ethanol (4g/kg) was administered to mice, and DNA was isolated 3 h later from liver homogenates and mitochondria. Ethanol resulted in a 25% decrease of GSH in liver homogenates without increase in GSSG, oxidized proteins and 8-OHdG, respectively. In contrast, the content of carbonyls (23 +/- 1 vs 9 +/- 1 nmol/mg protein) and the extent of oxidation of DNA (49 +/- 8 vs 17 +/- 3 8-OHdG/10(5) dG) were significantly increased in mitochondria. Depletion of GSH with diethyl maleate also resulted in a 2-3 fold increase in the oxidation of proteins and DNA in mitochondria exclusively. Oxidation of DNA and low GSH together with the lack of DNA repair enzymes may result in permanent damage to the mitochondria of alcoholic subjects.

Asunto(s)

RESUMEN

Glutathione monethyl ester (GSHE) is though to deliver glutathione (GSH) directly and intact into cell cytosol and therefore might have therapeutic potential in states of GSH deficiency. To better understand the disposition of GSHE, the pharmacokinetics of GSHE and GSH were compared in rats. Fifteen min after an i.v. dose of 5 mmol/kg GSHE, the plasma concentration of GSHE was 7.2 +/- 1.2 mmol/l and the plasma concentration of GSH had increased from 0.009 +/- 0.002 to 2.5 +/- 0.3 mmol/l. The areas under the plasma concentration time curves of GSH were identical after either the administration of GSHE or GSH, but the mean residence time of GSH in plasma was significantly longer after GSHE. The concentration of GSHE in liver reached a peak of 0.66 +/- 0.09 mumol/g. Intrahepatic concentrations of cysteine and GSH increased from 53 +/- 15 to 319 +/- 41 nmol/g and from 5.5 +/- 0.4 to 7.8 +/- 1.5 mumol/g, respectively, and remained elevated for 2 hr. Similar increases occurred after administration of GSH. However, the concentrations of cysteine and GSH peaked earlier and had returned to baseline by 2 hr. Qualitatively similar results were obtained in rats pretreated with L-buthionine-[S, R]-sulfoximine that partially inhibits GSH synthesis. GSHE added to rat plasma at a concentration of 10 mM was hydrolyzed to GSH at a rate of 0.1 mumol/min. Our data indicate that GSHE is not readily taken up by the liver, but is hydrolyzed by esterases in plasma and thereby gradually releases GSH in the extracellular space.(ABSTRACT TRUNCATED AT 250 WORDS)

Asunto(s)

RESUMEN

Glutathione (GSH) plays an important role in the detoxification of reactive metabolites of oxygen and xenobiotics and as a source of cysteine. Since several clinical situations characterized by low circulating and intracellular GSH have been identified, there is a growing interest in pharmacological interventions to correct a deranged sulfhydril status. Therefore, the systemic bioavailability of orally administered GSH and glutathione monoethyl ester (GSHE) was examined in the rat. Following the intraduodenal administration of 0.5 mmol/kg of GSH and GSHE there was no significant increase in the concentrations of cysteine and GSH in plasma, but hepatic cysteine and GSH increased significantly, albeit transiently. Five mmol/kg of GSH and GSHE significantly increased circulating and hepatic cysteine and GSH. Following the administration of 0.5 and 5 mmol/kg of GSHE low concentrations of the ester were found in plasma and the liver, indicating that GSHE is not readily absorbed from the gastrointestinal tract, although it is not a substrate for gamma-glutamyl-transferase. GSHE resulted in a delayed release of cysteine and GSH compared to GSH, such that the concentrations of GSH and cysteine in liver and plasma were significantly higher 2 h after administration of GSHE than after GSH. The data indicate that the bioavailability of GSH and GSHE is low in the rat. Orally administered GSH and GSHE do not affect the circulating concentrations of GSH and cysteine unless very high doses are administered, but increase hepatic cysteine and GSH at lower doses because of the efficient extraction by the liver of cysteine originating from the breakdown of GSH and GSHE in the gut.

Asunto(s)

RESUMEN

Permanent human presence in space beyond low Earth orbit (LEO) is now technically feasible. To achieve this goal several requirements must be met, which can be summarized as: technologies, facilities, organization, vision, and will. This paper describes a recently published NASA Reference Publication, "Designing for Human Presence in Space: An Introduction to Environmental Control and Life Support Systems" that addresses how to achieve the goal of permanent human presence in space, specifically, how to design and develop environmental control and life support systems (ECLSS) for space habitats. This includes the technologies that perform the required functions, the facilities where the systems will be developed, and the organization necessary to perform the numerous tasks efficiently.

Asunto(s)

Asunto(s)

Asunto(s)

RESUMEN

We report three unrelated patients with Kenny syndrome. Clinical symptoms included severe dwarfism, with internal cortical thickening and medullary stenosis of the tubular bones, normal bone age, macrocephaly, absent diploic space, delayed closure of the anterior fontanel, and normal intelligence; two of the patients had hyperopia and papillary edema. The patients also had episodic hypocalcemic tetany and low serum levels of magnesium. In two patients the diagnosis of idiopathic hypoparathyroidism was established on the basis of undetectable serum parathyroid hormone (PTH) levels (N- and C-terminal RIAs); one of these had normal urinary cyclic adenosine monophosphate (cAMP) response to exogenous PTH. Circulating calcitonin was undetectable in either patient. In a third patient, who had abnormal body proportions, serum levels of PTH were increased in an RIA detecting predominantly intact PTH (N-RIA) and undetectable in another RIA recognizing carboxy-terminal fragments (C-RIA). Administration of PTH promptly increased urinary cAMP excretion. In this patient, serum levels of calcitonin were increased, whereas values for 25-OHD and 1,25(OH)2D were normal.

Asunto(s)

Asunto(s)

RESUMEN

Plasma levels of calcium and of parathyroid hormone (PTH) were comparable in the mothers at delivery and in nonpregnant controls; magnesium was decreased (P < 0.001) in maternal blood; and phosphate (P < 0.001), 1,25-dihydroxyvitamin D (1,25(OH)2D) (P < 0.001), and calcitonin (CT) (P < 0.01) were raised. Cord levels of calcium (P < 0.01), magnesium (P < 0.05), and CT (P < 0.01) were higher, and PTH (P < 0.01) was lower than in the maternal blood. Levels of 25(OH)D, 1,25(OH)2D, and 24,25(OH)2D lower in fetal than in maternal blood (P < 0.01) and significant linear correlations between the vitamin D metabolites examined in mothers and neonates (P < 0.001) are consistent with a diffusion barrier across the placenta and/or different affinities of binding proteins. Plasma levels of 25(OH)D and 24,25(OH)2D were significantly related (P < 0.01), suggesting precursor product type, relationships. Levels of 1,25(OH)2D higher in arterial than in venous umbilical blood (P = 0.06, sign test; P < 0.005, paired t test) suggest that the fetus participates in the synthesis of 1,25(OH)2D. Maternal PTH was significantly related to the arteriovenous difference of 1,25(OH)2D levels (P < 0.01) in cord blood, and it possibly enhances the synthesis of 1,25(OH)2D during the final stage of fetal development.

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)