变形杆菌的耐药性及接合性R质粒的检测

本文报告了从烧伤病人感染创面分离、鉴定的35株变形杆菌的药敏试验及接合性R质粒的检测结果。35株变形杆菌双测试的6种抗菌药物都具有不同程度的耐药性。其中,对6种药物同时耐受的有26株(74.3％)。对其中的27株做了接合试验,接合性R质粒的检出率为70.4%。     

Phagocytic cell molecules that bind the collagen-like region of C1q. Involvement in the C1q-mediated enhancement of phagocytosis

C1q binds to and elicits cellular responses by several cell types, including monocytes, macrophages, neutrophils, B cells, and fibroblasts. The cell-binding domain is located within the collagen-like pepsin-resistant region of the C1q molecule (C1q tails). An affinity matrix of C1q tails coupled to Sepharose was used to select C1q-binding proteins from detergent extracts of surface-iodinated human monocytes, polymorphonuclear leukocytes, and the U937 cells. The major radiolabeled polypeptide eluted specifically from the ligand affinity column had an apparent molecular mass (Mr) of 126,000. Minor iodinated components eluted from Sepharose-tails migrated with Mr of 216,000 and 55,000. When subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions no change in the migration of any of these polypeptide bands was detected. None of these polypeptides reacted with antibodies directed against the integrins alpha 5 beta 1 (fibronectin receptor) or alpha v beta 3 (vitronectin receptor), LFA-1, or to several other cell adhesion molecules. The Mr 126,000 band was found to contain more than one polypeptide. Lectin binding properties, susceptibility to glycosidases and proteases, and immunoreactivity with the monoclonal antibody L-10, indicated that CD43 (sialophorin/leukosialin) is a component of this band. However, further data show that a monoclonal antibody, generated by immunization with the isolated Clq-binding fractions, recognizes a cell surface sialoglycoprotein distinct from CD43 and inhibits the C1q-mediated enhancement of phagocytosis in monocytes. These latter observations provide the first definitive connection between a specific phagocytic cell surface protein and a known C1q-mediated function. While these proteins contain sialic acid, binding assays and functional assays using neuraminidase-treated cells demonstrate that the functional interaction between C1q and the cell surface is not via sialic acid. The data taken together indicate either that the functional C1q receptor on phagocytic cells is a multi-subunit complex or that multiple proteins can interact with the fragment of C1q containing the cell-binding domain, at least one of which is involved in the C1q-mediated enhancement of phagocytosis.     

Location-dependent variations in the material properties of the anterior cruciate ligament.

Our recent anterior drawer studies in human cadaveric knees [Guan and Butler, Adv. Bioengng 17, 5 (1990); Guan et al., Trans. orthop. Res. Soc. 16, 589 (1991)] have suggested that anterior bundles of the anterior cruciate ligament (ACL) develop higher load-related material properties than posterior bundles. This was confirmed when we reevaluated the axial failure data for these bundle-bone specimens from an earlier study [Butler et al., J. Biomechanics 19, 425-432 (1986)]. The purpose of this study was to determine, in a larger data set, if anteromedial and anterolateral bundles of the anterior cruciate ligament exhibit significantly larger load-related material properties than the posterior ligament bundles. Seven ACL-bone units from seven donors (the three tissues from the original study plus four new ones) were subdivided into three subunits, preserving the bone insertions. The subunits were failed in tension at a constant strain rate (100% s-1) and four material properties were compared within and between donors. The anterior bundles developed significantly larger moduli, maximum stresses, and strain energy densities to maximum stress than the posterior subunits. Moduli for the anterior vs posterior subunits averaged 284 MPa vs 155 MPa, maximum stresses averaged 38 MPa vs 15 MPa, and strain energy densities averaged 2.7 N m cc-1 vs 1.1 N m cc-1, respectively. No significant differences were found, however, among strains to maximum stress or between any of the other properties for the two anterior subunits. These results are important to the design of ligament replacements and suggest new experiments designed to distinguish in vivo force levels in these ACL bands, a possible reason for the material differences.     

Studies on the isolation of penicillin acylase from Escherichia coli by aqueous two-phase partitioning

A method of enzyme release and aqueous two-phase extraction is described for the separation of penicillin acylase from Escherichia coli cells. Butyl acetate, 12% (v/v), treatment combined with freeze-thawing gives up to 70% enzyme release. For polyethylene glycol (PEG) + phosphate two-phase extraction systems the enzyme purity and yield were rather low. Modified PEG, including PEG-ampicillin, PEG-aniline, PEG-phosphate, and PEG-trimethylamine, were synthesized and used in aqueous two-phase systems; PEG-trimethylamine is the most satisfactory. A system containing 12% (w/w) PEG4000, 8% (w/w) of which is PEG-trimethylamine, with 0.7M potasium phosphate at pH 7.2, resulted in the enzyme selective partition being greatly enhanced by charge directed effects. Possible mechanisms for the separation process are discussed. (c) 1992 John Wiley & Sons, Inc.     

Evidence against the role of alpha 1-adrenoceptor reserve in buffering the inhibitory effect of nifedipine on the contractility of canine vascular smooth muscle

The relationship between the postsynaptic alpha 1-adrenoceptor reserve and the sensitivity of vasoconstriction induced by alpha-adrenoceptor agonists to the dihydropyridine Ca2+ entry blocker nifedipine was investigated in isolated muscle strips of dog mesenteric artery (DMA) and saphenous vein (DSV). The amplitudes of the contractile responses of DMA induced by phenylephrine were the same as those in DSV in the presence and in the absence of extracellular Ca2+. The use of 3 x 10(-9) M phenoxybenzamine to irreversibly block the alpha 1-adrenoceptors revealed a marked difference in the size of the alpha 1-adrenoceptor reserve between DMA (40%) and DSV (7%). In spite of a larger receptor reserve, the contractile responses induced by phenylephrine in DMA were more sensitive to nifedipine compared with those in DSV. These results suggest that the postsynaptic alpha 1-adrenoceptor reserve in vascular smooth muscle, at least in DMA and DSV, does not play an important role in buffering the inhibitory effect of nifedipine on the contractile response to a full agonist of alpha 1-adrenoceptors. Other factors, such as the difference in the membrane depolarizing effect, the ability to utilize intracellular Ca2+ for contraction, and the possible existence of alpha 1-adrenoceptor subtypes, may contribute to the different inhibitory effects of nifedipine on these blood vessels.     

Aquatic macroinvertebrate assemblages in wetlands of Northeastern China

Hydrobiologia - Lake Malaŵi cichlids have evolved rapidly, extensively, and in some cases iteratively to fill an array of ecological niches; however, neither species richness nor trophic...     

Models and Algorithms for Hub and Spoke Locations for Emergency Service Facilities in Response to Serious Emergency Incidents

This article examines the location-allocation of emergency service facilities as a research subject. The research presents the setup of the single allocation set covering location-allocation models for emergency service facilities under strong time constraints, in view of the shortage of hub & spoke network bypass. The article also presents an extension to the single allocation set covering location-allocation model (SASCP) and the SASCP model with bypass constraints (γ-SASCP) for emergency service facilities under large-scale emergency requirements. For the two models, an improved genetic algorithm was designed and the two models were respectively solved, with the effectiveness of the algorithm verified by a specific example. The impacts of change of parameters such as time discount rate, maximum time constraints, and bypass ratio on the model's results are compared and analyzed, based on solved results by the specific example.     

A Novel Mechanism for NF-κB-activation via IκB-aggregation: Implications for Hepatic Mallory-Denk-Body Induced Inflammation

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Highlights

• •Liver Mallory-Denk-Body inducers elicited an IκBα-loss and NF-κB-activation.
• •IκBα-loss was due to its sequestration into insoluble cytoplasmic aggregates.
• •Four proteomic approaches identified 10 IκBα-interacting/aggregating proteins.
• •Nup153/RanBP2-aggregation prevented IκBα nuclear entry for ending NF-κB-activation.

     

Impact of Histone H4 Lysine 20 Methylation on 53BP1 Responses to Chromosomal Double Strand Breaks

Recruitment of 53BP1 to chromatin flanking double strand breaks (DSBs) requires γH2AX/MDC1/RNF8-dependent ubiquitination of chromatin and interaction of 53BP1 with histone H4 methylated on lysine 20 (H4K20me). Several histone methyltransferases have been implicated in 53BP1 recruitment, but their quantitative contributions to the 53BP1 response are unclear. We have developed a multi-photon laser (MPL) system to target DSBs to subfemtoliter nuclear volumes and used this to mathematically model DSB response kinetics of MDC1 and of 53BP1. In contrast to MDC1, which revealed first order kinetics, the 53BP1 MPL-DSB response is best fitted by a Gompertz growth function. The 53BP1 MPL response shows the expected dependency on MDC1 and RNF8. We determined the impact of altered H4K20 methylation on 53BP1 MPL response kinetics in mouse embryonic fibroblasts (MEFs) lacking key H4K20 histone methyltransferases. This revealed no major requirement for the known H4K20 dimethylases Suv4-20h1 and Suv4-20h2 in 53BP1 recruitment or DSB repair function, but a key role for the H4K20 monomethylase, PR-SET7. The histone methyltransferase MMSET/WHSC1 has recently been implicated in 53BP1 DSB recruitment. We found that WHSC1 homozygous mutant MEFs reveal an alteration in balance of H4K20 methylation patterns; however, 53BP1 DSB responses in these cells appear normal.