Hemolysis associated with 25% human albumin diluted with sterile water--United States, 1994-1998.
(17/15056)
Since 1994, a shortage of 5% human albumin, a product used off-label during therapeutic plasma exchange (TPE), has existed in the United States. Because of this shortage, hospital pharmacists may prepare 5% solution of human albumin by diluting 25% human albumin with 0.9% NaCl or, when sodium load is a concern, 5% dextrose. However, if sterile water alone is used as the diluent, the osmolarity (tonicity) of the albumin solution is reduced and may cause hemolysis in recipients. This report describes two of 10 episodes of hemolysis (one fatal) among persons who received 25% human albumin diluted with sterile water and emphasizes that sterile water alone should not be used to dilute albumin. (+info)
Effects of nicorandil on experimentally induced gastric ulcers in rats: a possible role of K(ATP) channels.
(18/15056)
The anti-ulcer effects of nicorandil [N-(2-hydroxyethyl)nicotinamide nitrate ester] were examined on water-immersion plus restraint stress-induced and aspirin-induced gastric ulcers in rats, compared with those of cimetidine. Nicorandil (3 and 10 mg/kg) given orally to rats dose-dependently inhibited the development of acid-related damage (water-immersion- and aspirin-induced gastric lesions) in the models. Cimetidine (50 mg/kg, p.o.) also had anti-ulcer effects in the same models. However, in the presence of glibenclamide (20 mg/kg, i.v.), an antagonist of K(ATP) channels, nicorandil did not inhibit the formation of gastric lesions. Nicorandil (10 mg/kg) given intraduodenally (i.d.), like cimetidine (50 mg/kg), significantly reduced the volume of the gastric content, total acidity and total acid output in the pylorus ligation model. Glibenclamide reversed the changes caused by i.d. nicorandil. I.v. infusion of nicorandil (20 microg/kg per min) significantly increased gastric mucosal blood flow, without affecting blood pressure and heart rate, but the increase in the blood flow was not observed after i.v. treatment with glibenclamide (20 mg/kg). These results indicate that nicorandil administered orally to rats produces the anti-ulcer effect by reducing the aggressive factors and by enhancing the defensive process in the mucosa through its K(ATP)-channel-opening property. (+info)
Binding of a substrate analog to a domain swapping protein: X-ray structure of the complex of bovine seminal ribonuclease with uridylyl(2',5')adenosine.
(19/15056)
Bovine seminal ribonuclease (BS-RNase) is a unique member of the pancreatic-like ribonuclease superfamily. The native enzyme is a mixture of two dimeric forms with distinct structural features. The most abundant form is characterized by the swapping of N-terminal fragments. In this paper, the crystal structure of the complex between the swapping dimer and uridylyl(2',5')adenosine is reported at 2.06 A resolution. The refined model has a crystallographic R-factor of 0.184 and good stereochemistry. The quality of the electron density maps enables the structure of both the inhibitor and active site residues to be unambiguously determined. The overall architecture of the active site is similar to that of RNase A. The dinucleotide adopts an extended conformation with the pyrimidine and purine base interacting with Thr45 and Asn71, respectively. Several residues (Gln11, His12, Lys41, His119, and Phe120) bind the oxygens of the phosphate group. The structural similarity of the active sites of BS-RNase and RNase A includes some specific water molecules believed to be relevant to catalytic activity. Upon binding of the dinucleotide, small but significant modifications of the tertiary and quaternary structure of the protein are observed. The ensuing correlation of these modifications with the catalytic activity of the enzyme is discussed. (+info)
A novel strategy for the preparation of liposomes: rapid solvent exchange.
(20/15056)
During the preparation of multi-component model membranes, a primary consideration is that compositional homogeneity should prevail throughout the suspension. Some conventional sample preparation methods pass the lipid mixture through an intermediary, solvent-free state. This is an ordered, solid state and may favor the demixing of membrane components. A new preparative method has been developed which is specifically designed to avoid this intermediary state. This novel strategy is called rapid solvent exchange (RSE) and entails the direct transfer of lipid mixtures between organic solvent and aqueous buffer. RSE liposomes require no more than a minute to prepare and manifest considerable entrapment volumes with a high fraction of external surface area. In phospholipid/cholesterol mixtures of high cholesterol content, suspensions prepared by more conventional methods reveal evidence of artifactual demixing, whereas samples prepared by rapid solvent exchange do not. The principles which may lead to artifactual demixing during conventional sample preparation are discussed. (+info)
A model of the transition state in the alkaline phosphatase reaction.
(21/15056)
A high resolution crystal structure of Escherichia coli alkaline phosphatase in the presence of vanadate has been refined to 1.9 A resolution. The vanadate ion takes on a trigonal bipyramidal geometry and is covalently bound by the active site serine nucleophile. A coordinated water molecule occupies the axial position opposite the serine nucleophile, whereas the equatorial oxygen atoms of the vanadate ion are stabilized by interactions with both Arg-166 and the zinc metal ions of the active site. This structural complex supports the in-line displacement mechanism of phosphomonoester hydrolysis by alkaline phosphatase and provides a model for the proposed transition state in the enzyme-catalyzed reaction. (+info)
Faecal composition after surgery for Hirschsprung's disease.
(22/15056)
Diarrhoea and perianal excoriation occur frequently after the endorectal pull-through operation for Hirschsprung's disease. A new method of faecal analysis was performed on 3-day stool collections in 17 postoperative Hirschsprung patients and in 14 normal children, in order to define the faecal abnormality and to establish the cause of perianal excoriation in these patients. Loose stools in postoperative patients were deficient in dry solid content and contained an excess of extractable faecal water. This also had a raised electrolyte concentration, particularly with respect to sodium. Total daily output of faecal water was normal. Formed stools from postoperative patients were also deficient in drysolids but had a normal extractable water content. Excess extractable faecal water, the main abnormality of loose stools in these patients, is the result of abnormal water absorption from the distal colon. Perianal excoriation in these patients is most closely associated with the concentration of sodium in faecal water. (+info)
The structure of an entire noncovalent immunoglobulin kappa light-chain dimer (Bence-Jones protein) reveals a weak and unusual constant domains association.
(23/15056)
Monoclonal free light chains secreted in immunoproliferative disorders are frequently involved in renal complications, including a specific proximal tubule impairment, Fanconi's syndrome. The latter is characterized in most cases by intracellular crystallization including a light-chain variable-domain fragment which resists lysosomal proteases. Bence-Jones protein (BJP) DEL was isolated from a patient with myeloma-associated Fanconi's syndrome. The crystal structure of this human kappa immunoglobulin light-chain noncovalent dimer was determined using molecular replacement with the structure of molecule REI, as the variable domain, and that of BJP LOC as the constant domain. To our knowledge, DEL is the first complete kappa BJP structure described to date. The R-factor is 20.7% at 2.8 A resolution. The BJP DEL dimer was compared with other light-chain dimers and with Fab fragments with a kappa light chain. Although the domain-folding pattern was similar, the relative positions of the constant domains differed. BJP DEL showed a noncanonical quaternary structural arrangement which may be attributable to the poor CL-CL affinity and lack of an interchain disulfide bridge, combined with the conformational editing effect of the crystal-packing forces. Our results suggest that, in the absence of a disulfide bridge, most BJP CLs are probably mobile in solution. This may explain their high susceptibility to proteases and the absence of naturally occurring crystals for these dimers. Furthermore, these findings of an unusual quaternary structure of an immunoglobulin light-chain association extend our knowledge about the large and highly diverse structures of the immunoglobulin superfamily. (+info)
Hydrogen peroxide on the surface of Europa.
(24/15056)
Spatially resolved infrared and ultraviolet wavelength spectra of Europa's leading, anti-jovian quadrant observed from the Galileo spacecraft show absorption features resulting from hydrogen peroxide. Comparisons with laboratory measurements indicate surface hydrogen peroxide concentrations of about 0.13 percent, by number, relative to water ice. The inferred abundance is consistent with radiolytic production of hydrogen peroxide by intense energetic particle bombardment and demonstrates that Europa's surface chemistry is dominated by radiolysis. (+info)