"即连即铸"的奥钢联连铸技术

1前言 生产率和作业率方面的收益以及可能性调整的灵活性是提高钢铁工业竞争力的关键因素.     

An effect of voltage on binding of Na+ at the cytoplasmic surface of the Na(+)-K+ pump

This work utilizes proteoliposomes reconstituted with renal Na(+)-K(+)-ATPase to study effects of electrical potential (40-80 mV) on activation of pump-mediated fluxes of Na+ or Rb+ (K+) ions and on inhibitory effects of Rb+ ions or organic cations. The latter include guanidinium derivatives that are competitive Na(+)-like antagonists (David, P., Mayan, H., Cohen, H., Tal, D. M., and Karlish, S.J.D. (1992) J. Biol. Chem. 267, 1141-1149). Cytoplasmic side-positive diffusion potentials significantly decreased the K0.5 of Na+ at the cytoplasmic surface for activation of ATP-dependent Na(+)-K+ exchange but did not affect the inhibitory potency of Rb+ (K+) or any Na(+)-like antagonist. Diffusion potentials did not affect activation of Rb(+)-Rb+ exchange by Rb+ ions at the cytoplasmic surface and had only a minor effect on Rb+ activation at the extracellular surface. Previously, we proposed that the cation binding domain consists of two negatively charged sites, to which two K+ or two Na+ ions bind, and one neutral site for the third Na+ (Glynn, I. M., and Karlish, S.J.D. (1990) Annu. Rev. Biochem. 59, 171-205). The present experiments suggest that binding of a Na+ ion in the neutral site at the cytoplasmic surface is sensitive to voltage. By contrast, binding of Rb+ ions at the extracellular surface of renal pumps appears to be only weakly or insignificantly affected by voltage. Inferences on the identity of the charge-carrying steps, based on experiments using proteoliposomes, are discussed in relation to recent evidence that dissociation of Na+ or association of K+ ions, at the extracellular surface, represent the major charge-carrying steps.     

Influence of high titers of maternal antibody on the serologic response of infants to diphtheria vaccination at three, five and twelve months of age

Diphtheria antitoxin was determined in serum from 44 pregnant women, of whom 26 had received one injection of diphtheria toxoid during pregnancy. Their infants were vaccinated with a combined diphtheria-tetanus vaccine at 3, 5 and 12 months of age. This vaccination schedule has been used in Sweden since 1986, replacing the old schedule of vaccination at 3, 4.5 and 6 months of age originally designed for diphtheria-tetanus-pertussis vaccine, which had not been used after cessation of general vaccination against pertussis in 1979. Serum samples from the infants were obtained at 3, 7 and 18 months of age. After 2 injections infants of mothers with high antitoxin titers, > or = 0.1 IU/ml, tended to have lower antitoxin titers than infants of mothers with low antitoxin concentrations (P = 0.067). All children had, however, antitoxin above the minimum protective level of 0.01 IU/ml. Median antitoxin titers were 1.6 IU/ml in both groups after the third booster injection. Four infants of mothers who had been vaccinated during pregnancy and who had titers of > or = 0.4 IU/ml did not reach the 0.1 IU/ml level after 2 injections: all 4 responded with high antitoxin titers after the third dose. Thus all infants were primed by 2 doses of vaccine, irrespective of maternal antibody concentration. The repressive effect of maternal antibody on titers noted after 2 doses was no longer observed after the third, booster dose.     

Sequence-specific methylation of the mouse H19 gene in embryonic cells deficient in the Dnmt-1 gene

Currently, the pig species is regarded as the most likely organ donor for human xenotransplantation in the future. However, it cannot be granted that the pig will be the optimal species of choice. We have studied human anti-sheep antibodies in comparison with anti-pig antibodies. The anti-sheep lymphocytotoxic and hemagglutination titers were in the range 8 to 128 and 2 to 32, respectively, in single individuals, which were considerably lower than the anti-pig titers of these individuals. Perfusion of sheep kidneys with human blood reduced the anti-sheep xenoantibody titers to zero as measured by lymphocytotoxic, hemagglutination, and sheep aortic endothelial cell antibody binding assays. The perfused kidneys showed generalised depositions of human IgM and C3c in the vascular tree and focal depositions of C1q and fibrin. Obliteration of capillaries by human platelets and polymorphonuclear cells were observed. Total neutral glycolipid fractions were isolated from sheep intestinal, pancreatic, and kidney tissues. By using a chromatogram binding assay, a monoclonal anti-Forssman antibody identified a single compound with five sugar residues in all organs. Several glycolipid bands were stained in all organs by the Gal(alpha)1-specific lectin I-B4 from Griffonia (Bandeiraea) Simplicifolia. A human AB serum pool showed staining by both IgG and IgM antibodies of the Forssman and Gal(alpha)1-terminating components as well as some other, not structurally identified, components. The Forssman and Gal(alpha)1-reactivity in human sera could be eliminated by immunoadsorption using Forssman and Gal(alpha)1-3Gal-immunoadsorbent columns, respectively. Immunostaining of sheep kidney tissue sections showed the presence of Gal(alpha)1-terminating epitopes by immunoperoxidase and immunogold silver staining techniques. Proximal convoluted tubules showed a strong staining, while thin loops of Henle, collecting ducts, urothelium, and vessels showed a weaker staining. Distal convoluted tubules and thick loops of Henle were completely negative. In summary, human serum contains anti-sheep xenoantibodies reacting mainly with the Forssman and Gal(alpha)1-determinants in sheep tissues and the anti-sheep antibody titers are lower than the corresponding anti-pig titers.     

BID: a novel BH3 domain-only death agonist

The BCL-2 family of proteins consists of both antagonists (e.g., BCL-2) and agonists (e.g., BAX) that regulate apoptosis and compete through dimerization. The BH1 and BH2 domains of BCL-2 are required to heterodimerize with BAX and to repress cell death; conversely, the BH3 domain of BAX is required to heterodimerize with BCL-2 and to promote cell death. To extend this pathway, we used interactive cloning to identify Bid, which encodes a novel death agonist that heterodimerizes with either agonists (BAX) or antagonists (BCL-2). BID possesses only the BH3 domain, lacks a carboxy-terminal signal-anchor segment, and is found in both cytosolic and membrane locations. BID counters the protective effect of BCL-2. Moreover, expression of BID, without another death stimulus, induces ICE-like proteases and apoptosis. Mutagenesis revealed that an intact BH3 domain of BID was required to bind the BH1 domain of either BCL-2 or BAX. A BH3 mutant of BID that still heterodimerized with BCL-2 failed to promote apoptosis, dissociating these activities. In contrast, the only BID BH3 mutant that retained death promoting activity interacted with BAX, but not BCL-2. This BH3-only molecule supports BH3 as a death domain and favors a model in which BID represents a death ligand for the membrane-bound receptor BAX.     

Routine use of ultrasound 24 hours before laparoscopic cholecystectomy can predict the need for intraoperative cholangiogram: results of a 12-month prospective audit

Progressive supranuclear palsy (PSP) is a progressive degenerative extrapyramidal disease that often masquerades as Parkinson's disease (PD). Similar to PD, dysphagia frequently complicates the course of PSP. Because there is only one published report characterizing dysphagia in PSP, we reviewed the neurologic features and dynamic videofluoroscopic swallowing function study results in 10 dysphagic PSP patients. Abnormalities during multiple stages of ingestion were recorded in each patient. Uncoordinated lingual movements, absent velar retraction or elevation, impaired posterior lingual displacement, and copious pharyngeal secretions were noted in all patients. Tongue-assisted mastication, noncohesive lingual transfer, excessive oral bolus lingual leakage to the pharynx prior to active transfer, vallecular bolus retention, abnormal epiglottic positioning, and hiatal hernias were noted in at least half of the cohort. Although ingestion abnormalities in PSP are similar to those previously reported in PD, the number of studied patients and observed differences were too few to clearly differentiate the two diseases.     

Late cytomegalovirus disease in marrow transplantation is predicted by virus load in plasma

Late occurrence of cytomegalovirus (CMV) disease after day 100 after bone marrow transplantation has become an increasing problem; whether a quantitative measurement of CMV DNA in plasma by polymerase chain reaction (P-PCR) could be predictive of such disease was investigated. In a prospective study, 117 subjects undergoing allogeneic marrow transplantation were followed for 120 days with weekly CMV blood cultures, with day 35 bronchoalveolar lavage CMV cultures, with weekly CMV P-PCR, and with clinical follow-up for an additional 1-2 years. Despite preemptive ganciclovir, CMV disease occurred in 9% of subjects, with a median time of onset of 176 days. Quantitative CMV P-PCR was associated with the late development of CMV disease (P = .01). Of 43 subjects with positive P-PCR results, 23% developed CMV disease, but no disease occurred in the 74 subjects with negative P-PCR (P < .001), despite the fact that 22% had CMV isolated from lung lavage fluid and 32% had CMV isolated from blood.