Daily hyperhydration effect on electrolyte deficiency of endurance-trained subjects during prolonged hypokinesia

The aim of this study was to evaluate the effect of a daily intake of fluid and salt supplementation (FSS) on the deficiency of electrolytes, which is characterized by higher rather than lower plasma concentration of electrolytes during prolonged hypokinesia (HK) (decreased number of km taken per day). Forty long distance runners aged 22-25 yr with a peak VO2 65.4 mL min(-1) kg(-1) with an average 14.2 km d running distance were selected as subjects. They were equally divided into four groups: 1) unsupplemented control subjects (UCS); 2) unsupplemented hypokinetic subjects (UHS); 3) supplemented hypokinetic subjects (SHS), and 4) supplemented control subjects (SCS). During the investigation of 364 d, groups 2 and 3 maintained an average running distance of less than 4.7 km per day, groups 1 and 4 did not experience any modification in their normal training routines and diets. During the preexperimental period of 60 d and during the experimental period of 364 d urinary excretion of electrolytes and concentrations of sodium, potassium, calcium, and magnesium in plasma were determined. Whole blood hemoglobin, hematocrit index, plasma osmolality, and plasma protein concentration were measured. In the UHS plasma concentration of electrolytes and urinary excretion thereof, fluid elimination, hematocrit, whole blood hemoglobin, plasma osmolality, and plasma protein concentration increased significantly (p < 0.05) when compared with the UCS, SCS, and SHS groups. In the SHS plasma concentration of electrolytes and urinary excretion thereof, fluid excretion, whole blood hemoglobin, hematocrit, plasma osmolality, and plasma protein concentration decreased when compared with the UHS and increased insignificantly when compared with the UCS and SCS groups. It was concluded that FSS may be used to prevent or minimize electrolyte deficiency in endurance-trained volunteers during prolonged restriction of muscular activity.     

Visualization of the cysteinyl-phosphate intermediate of a protein-tyrosine phosphatase by x-ray crystallography

Protein-tyrosine phosphatases (PTPs) are signal transduction enzymes that catalyze the dephosphorylation of phosphotyrosine residues via the formation of a transient cysteinyl-phosphate intermediate. The mechanism of hydrolysis of this intermediate has been examined by generating a Gln-262 --> Ala mutant of PTP1B, which allows the accumulation and trapping of the intermediate within a PTP1B crystal. The structure of the intermediate at 2.5-A resolution reveals that a conformationally flexible loop (the WPD loop) is closed over the entrance to the catalytic site, sequestering the phosphocysteine intermediate and catalytic site water molecules and preventing nonspecific phosphoryltransfer reactions to extraneous phosphoryl acceptors. One of the catalytic site water molecules, the likely nucleophile, forms a hydrogen bond to the putative catalytic base, Asp-181. In the wild-type enzyme, the nucleophilic water molecule would be coordinated by the side chain of Gln-262. In combination with our previous structural data, we can now visualize each of the reaction steps of the PTP catalytic pathway. The hydrolysis of the cysteinyl-phosphate intermediate of PTPs is reminiscent of GTP hydrolysis by the GTPases, in that both families of enzymes utilize an invariant Gln residue to coordinate the attacking nucleophilic water molecule.     

Outcomes following mechanical ventilation in children undergoing bone marrow transplantation

Between 1976 and 1992, 869 patients <19 years of age underwent BMT at the University of Minnesota for a variety of malignant and non-malignant disorders. One hundred and ninety-six required mechanical ventilation (MV) at some time from the start of pre-BMT cyto reduction through the first year following BMT. Reasons for MV included respiratory compromise, upper airway management and non-pulmonary indications for respiratory support. In multivariate models, underlying diagnosis, receipt of HLA-mismatched marrow and the presence of acute graft-versus-host disease (aGVHD) were independent predictors of the need for MV. Indication for MV, underlying diagnosis, and presence of aGVHD were independent predictors of successful extubation. Overall survival at 2 years was 14% among MV patients and 52% among non-MV patients. While the need for MV during BMT reduces the overall likelihood of survival, 40% of children who required MV were successfully extubated; 35% of these extubated patients were long-term survivors. This outcome is better than that reported for adult BMT patients requiring respiratory support, who show survival of <5% at 6 months following BMT. Our data suggest extrapolation of outcome data from adult to pediatric patients is not appropriate and aggressive care of pediatric patients requiring respiratory support is not futile.     

Recent developments in the hammerhead ribozyme field

Developments in the hammerhead ribozyme field during the last two years are reviewed here. New results on the specificity of this ribozyme, the mechanism of its action and on the question of metal ion involvement in the cleavage reaction are discussed. To demonstrate the potential of ribozyme technology examples of the application of this ribozyme for the inhibition of gene expression in cell culture, in animals, as well as in plant models are presented. Particular emphasis is given to critical steps in the approach, including RNA site selection, delivery, vector development and cassette construction.     

Ion-pair high-performance liquid chromatography for determining disaccharide composition in heparin and heparan sulphate

Rats deficient in vitamin A express low levels of P4502C7 mRNA in the liver. Administration of all-trans retinoic acid (at-RA) or growth hormone (GH) to deficient animals only partially restored the expression whereas the combined treatment returned the P4502C7 mRNA levels to that observed in normal rats. That a retinoid is the predominant inducer of P4502C7 at the cellular level is evident from studies performed with primary hepatocytes, but it became clear that GH is a prerequisite for the vitamin A effect in vivo. The at-RA induction of P4502C7 mRNA in primary rat hepatocytes was inhibited by ketoconazole, an inhibitor of P450 activity, and by cycloheximide, blocking ongoing protein synthesis. In contrast, the at-RA induction of RAR-beta2 mRNA was not affected by any of these compounds. This could indicate previously not recognized mechanisms of at-RA action. Interestingly, at-4-oxo-RA, an at-RA metabolite formed by a P450 catalyzed reaction, also induced P4502C7 mRNA. Induction of P4502C7 mRNA by the retinoic acid receptor (RAR) selective agonist TTNPB indicated that this pathway is preferred over the retinoid X receptor (RXR) pathway. In addition, analysis of RA metabolites in liver cell extracts revealed the formation of several as yet unidentified metabolites. The formation of some of these metabolites was inhibited by ketoconazole and they could therefore constitute potential inducers of CYP2C7. We suggest that metabolism of at-RA, possibly by a P450 enzyme, is an important step in the at-RA induction of P4502C7.     

Effects of midazolam on the differentiation of murine myeloid leukemia cells

The effects of midazolam (MID) on the in vitro growth and differentiation of two murine myeloid leukemia WEHI 3B (JCS) and M1 cells were studied. MID inhibits the proliferation of both M1 and JCS cells in a dose-dependent manner. At the concentration of 10 micrograms/ml, MID was found to induce both monocytic and granulocytic differentiation of the JCS but not M1 cells. Induction of morphological differentiation of the JCS cells was also associated with the enhanced expression of the differentiation antigens Mac-1, F4/80, and Gr-1 for the cells. Results from mRNA phenotyping experiments also indicated that the expression of tumor necrosis factor (TNF-alpha) and neutrophil-specific J11d differentiation marker was significantly upregulated in MID-treated JCS cells. In addition, the phagocytic activity of MID-treated JCS cells was increased towards opsonized yeast cells. Results from this investigation suggested that MID may be used as an inducer for further study on the mechanisms of differentiation in these myeloid leukemia cells.