A chemically defined medium for the culture of mature oligodendrocytes

A new chemically defined medium consisting of equal parts of Dulbecco modified Eagle's and Ham's F-12 media supplemented with insulin, sodium selenite, putrescine, and D+ galactose, which allows the long-term survival of mature oligodendrocyte pure cultures, is described. Immunohistochemical staining has shown that over 90% of the cells become positive for myelin proteins shortly following subculture. Contaminating astrocytes (2%) do not survive in this medium. Biochemical data have indicated that these purified oligodendrocytes express 2'3'-cyclic nucleotide 3'-phosphohydrolase and UDP-galactose ceramide galactosyltransferase activities. Electron microscopical examination revealed that the oligodendrocytes were mostly of medium-dark type and appeared to be identical to cells cultured in serum-containing medium. The ability to maintain pure oligodendrocyte cultures in such a defined medium will allow investigations concerning exogenous and endogenous factors involved in oligodendrocyte metabolism.     

Arylneuraminidase activity of Pseudomonas aeruginosa does not degrade natural substrates such as human respiratory mucins.

The culture supernatant from a single Pseudomonas aeruginosa strain has been reported to show neuraminidase activity, leading to the speculation that this bacterium may use this enzyme as a virulence factor to act on host macromolecules. In order to extend this finding, we have examined the activity of concentrated P. aeruginosa culture supernatants and cells on synthetic and natural substrates containing sialic acid, such as human respiratory mucins. Four P. aeruginosa strains showed some activity on the synthetic substrate 4-methylumbelliferyl-alpha-D-N-acetylneuraminic acid but failed to liberate N-acetylneuraminic acid from six different natural substrates. Attempts to induce enzyme production by use of human respiratory mucins in the culture medium were also unsuccessful. The supernatants also showed N-acetyl-beta-D-glucosaminidase-like activity on a synthetic substrate but did not liberate N-acetylhexosamines from natural substrates. We conclude that the neuraminidase-like activity observed in P. aeruginosa can be defined as an arylneuraminidase and that the possession of a neuraminidase active on natural substrates is not a common attribute of P. aeruginosa strains.     

Insulin protects brain tissue against focal ischemia in rats.

The influence of insulin on the infarct volume due to middle cerebral artery (MCA) occlusion was investigated in rats. A small dose of insulin (1 unit/kg) was injected i.p. just after MCA occlusion. The infarct areas were measured by planimetry from brains perfused with 2,3,5-triphenyltetrazolium-chloride (TTC) 48 h after the occlusion. Systemic variables were measured before and at various times after ischemia. The comparison between insulin-treated (n = 14) and control (n = 13) rats provided evidence that insulin significantly reduced the infarct volume due to MCA occlusion. As insulin minimally and transiently decreased blood glucose, the present results suggest that insulin exerts a beneficial effect directly on the central nervous system.     

腹部外科常见感染性疾病的病原菌及药敏试验研究

为了了解本地区本医院腹部外科感染性疾病病原菌的构成比和药物敏感率的变化,指导临床用药,我们采用美国BD公司生产的6B和7D两种增菌瓶采集标本和培养细菌,并用该公司生产的生化板和药敏板,对1994～1996年269例常见的普外科感染性疾病患者的手术标本进行前瞻性的细菌培养和药敏试验研究.     

Recognition of Lewis x derivatives present on mucins by flagellar components of Pseudomonas aeruginosa

Pseudomonas aeruginosa binds to human respiratory mucins by mechanisms involving flagellar component-receptor interactions. The adhesion of P. aeruginosa strain PAK is mediated by the flagellar cap protein, FliD, without the involvement of flagellin. Two distinct types of FliD proteins have been identified in P. aeruginosa: A type, found in strain PAK, and B type, found in strain PAO1. In the present work, studies performed with the P. aeruginosa B-type strain PAO1 indicate that both the FliD protein and the flagellin of this strain are involved in the binding to respiratory mucins. Using polyacrylamide-based fluorescent glycoconjugates in a flow cytometry assay, it was previously demonstrated that P. aeruginosa recognizes Le(x) (or Lewis x) derivatives found at the periphery of human respiratory mucins. The aim of the present work was therefore to determine whether these carbohydrate epitopes (or glycotopes) are receptors for FliD proteins and flagellin. The results obtained by both flow cytometry and a microplate adhesion assay indicate that the FliD protein of strain PAO1 is involved in the binding of glycoconjugates bearing Le(x) or sialyl-Le(x) determinants, while the binding of flagellin is restricted to the glycoconjugate bearing Le(x) glycotope. In contrast, the type A cap protein of P. aeruginosa strain PAK is not involved in the binding to glycoconjugates bearing Le(x), sialyl-Le(x), or sulfosialyl-Le(x) glycotopes. This study demonstrates a clear association between a specific Pseudomonas adhesin and a specific mucin glycotope and demonstrates that fine specificities exist in mucin recognition by P. aeruginosa.     

Thermogenesis and thermolysis during sleeping and waking in the rat

Thermogenesis (VO₂), sensible heat loss and subcutaneous back temperature were recorded simultaneously during sleeping and waking in both intact and depilated rats at Ta ranging from 21–28°C.VO₂ increased during wakefulness (W), decreased and plateaued during slow wave sleep (SWS) and then decreased 10% with each paradoxical sleep (PS) phase. Sensible heat loss, which represented about 90% of the heat production, increased and plateaued during SWS, decreased in W and generally rose abruptly (+40%) during PS. After removal of the fur the mean levels ofVO₂ and sensible heat loss were increased by 30–50% and returned to normal values within two weeks, although their variations related to stages of sleep were unchanged.These results concerning thermogenesis and thermolysis are in agreement with the variations of body temperature (brain excluded) during sleeping and waking.     

Immunoelectron microscopic localization of the M6a antigen in rat brain

The monoclonal antibody M6-7, which recognizes both native and denatured immunopurified M6a antigen, was used in the present immunocytochemical study to localize its corresponding antigen in young rat brain. Strong labelling was observed in the cerebellar molecular layer, which corresponds to heavily stained axon terminals originating from granule cells. The immunodeposit, as observed by electron microscopy, is present only on the cytoplasmic side of the presynaptic membrane and on the membrane of synaptic vesicles. In contrast, the Purkinje cells and their processes are unstained. Stained synapses are also found, although less frequently, in several other cerebral areas. The pattern of staining at these synapses is similar to that observed in the cerebellar molecular layer. It is hypothesized, on the basis of its restricted distribution in certain neuronal endings and its high homology with myelin proteolipids, that the M6a antigen revealed by the M6-7 antibody is probably involved in a specific biological function in these structures.     

Pseudomonas aeruginosa recognizes carbohydrate chains containing type 1 (Gal beta 1-3GlcNAc) or type 2 (Gal beta 1-4GlcNAc) disaccharide units.

The adhesion of Pseudomonas aeruginosa to type 1 (Gal beta 1-3GlcNAc) and type 2 (Gal beta 1-4GlcNAc) disaccharide determinants was studied in a microtiter adhesion assay and a thin-layer chromatography bacterial overlay assay. The oligosaccharides were prepared from human breast milk and human urine and were conjugated to hexadecylaniline to form neoglycolipids that were used in were used in the assays. Both the mucoid and the nonmucoid strains that were studied recognized the disaccharide determinants Sialylation of the oligosaccharides did not suppress binding in the thin-layer chromatography assay, but alpha 2-6-linked sialic acid blocked binding in the microtiter assay. The use of bovine serum albumin instead of gelatin as a blocking agent against nonspecific binding completely suppressed binding in the thin-layer chromatography assay. Isogenic nonpiliated mutants of nonmucoid strains constructed by interrupting the pilin gene retained their adhesive capacity for the disaccharide units, indicating that binding to the disaccharides was mediated by a nonpilus adhesin(s). Furthermore, two monoclonal antibodies that recognize the type 2 disaccharide determinant (Gal beta 1-4GlcNAc) partially inhibited adhesion of a pair of piliated and nonpiliated isogenic strains to mucin. This study suggests that P. aeruginosa utilizes a nonpilus adhesin(s) to bind to disaccharide units commonly found in mucins, in addition to pili and alginate, two previously described adhesins.