Mannosephilic adhesins produced by some strains of motile Aeromonas reveal structural details of Salmonella lipopolysaccharide through the phenomenon of co-agglutination

Abstract Some strains of motile Aeromonas produce lectin-like adhesins, whose activity can be inhibited by d -mannose. Such strains can co-agglutinate with some strains of Salmonella . Whether or not co-agglutination occurs is dependent upon both the properties of the Aeromonas adhesin and the structure of the Salmonella lipopolysaccharide (LPS). These studies have enabled new structural information for Salmonella LPS to be deduced and have confirmed previous studies regarding the nature of the Aeromonas adhesin binding site. It is possible that the observed in vitro co-agglutination between Aeromonas and Salmonella is a reflection of an in vivo situation which could modify the virulence of either or both bacteria.     

Autolytic Activity and Butanol Tolerance of Clostridium acetobutylicum

The effects of acetone and butanol on the growth of vegetative cells and the stability of swollen-phase bright-stationary-phase cells (clostridial forms) of Clostridium acetobutylicum P262 and an autolytic deficient mutant (lyt-1) were investigated. There was little difference in the sensitivity of strain P262 and the lyt-1 mutant vegetative cells and clostridial forms to acetone. The stability of the different morphological stages was unaffected by acetone concentrations far in excess of those encountered in factory fermentations. Butanol concentrations between 7 and 16 g/liter, which are within the range obtained in industrial fermentations, increased the degeneration of strain P262 clostridial forms but had no effect on the stability of lyt-1 clostridial forms which never underwent autolysis. Vegetative cells of the lyt-1 mutant were able to grow in higher concentrations of butanol than strain P262 vegetative cells. It was concluded that there is a relationship between butanol tolerance and autolytic activity.     

Chimeric antithrombin peptide. Characterization of an Arg-Gly-Asp (RGD)- and hirudin carboxyl terminus-containing synthetic peptides

We investigated the properties of an artificial chimeric peptide that contains an Arg-Gly-Asp (RGD)-tripeptide, the versatile cell recognition signal of extracellular matrix protein components, coupled to a carboxyl-terminal fragment of the highly specific alpha-thrombin inhibitor, hirudin (residues 53-64): WGRGDSANGDFEEIPEEYL (RGD-hirudin53-64). Hirudin53-64 and RGD-hirudin53-64 inhibited the fibrinogen clotting activity of alpha-thrombin and prolonged the activated partial thromboplastin time of human plasma. In addition, both peptides afforded total protection to thrombin from trypsionolysis. Neither hirudin53-64 nor RGD-hirudin53-64 dramatically interfered with the thrombin-antithrombin inhibition reaction either in the absence or presence of added heparin. alpha-Thrombin-induced platelet aggregation was effectively inhibited by hirudin53-64 and RGD-hirudin53-64. Unlike hirudin53-64, RGD-hirudin53-64 in solution inhibited integrin-mediated endothelial cell and fibroblast cell attachment to polystyrene wells in the presence of fetal bovine serum. Collectively, our results demonstrate that RGD-hirudin53-64 has anticoagulant/antiplatelet aggregation activity attributable to its hirudin sequence and integrin-directed cell attachment activity due to its RGD site. Our results suggest that this chimeric motif may serve as a prototype for a new class of anticoagulants where an integrin-specific sequence "targets" the peptide to a cell (ultimately through the platelet integrin alpha IIb beta 3) trapped amid a thrombus with ensuing proteinase inhibition.     

Characterization of the Butyrivibrio fibrisolvens glgB gene, which encodes a glycogen-branching enzyme with starch-clearing activity.

A Butyrivibrio fibrisolvens H17c glgB gene, was isolated by direct selection for colonies that produced clearing on starch azure plates. The gene was expressed in Escherichia coli from its own promoter. The glgB gene consisted of an open reading frame of 1,920 bp encoding a protein of 639 amino acids (calculated Mr, 73,875) with 46 to 50% sequence homology with other branching enzymes. A limited region of 12 amino acids showed sequence similarity to amylases and glucanotransferases. The B. fibrisolvens branching enzyme was not able to hydrolyze starch but stimulated phosphorylase alpha-mediated incorporation of glucose into alpha-1,4-glucan polymer 13.4-fold. The branching enzyme was purified to homogeneity by a simple two-step procedure; N-terminal sequence and amino acid composition determinations confirmed the deduced translational start and amino acid sequence of the open reading frame. The enzymatic properties of the purified enzyme were investigated. The enzyme transferred chains of 5 to 10 (optimum, 7) glucose units, using amylose and amylopetin as substrates, to produce a highly branched polymer.     

Reactivity of Hg(II) with superoxide: Evidence for the catalytic dismutation of superoxide by HG(II)

Mercuric ion, a well-known nephrotoxin, promotes oxidative tissue damage to kidney cells. One principal toxic action of Hg(II) is the disruption of mitochondrial functions, although the exact significance of this effect with regard to Hg(II) toxicity is poorly understood. In studies of the effects of Hg(II) on superoxide (O) and hydrogen peroxide (H₂O₂) production by rat kidney mitochondria, Hg(II) (1–6 μM), in the presence of antimycin A, caused a concentration-dependent increase (up to fivefold) in mitochondrial H₂O₂ production but an apparent decrease in mitochondrial O production. Hg(II) also inhibited O-dependent cytochrome c reduction (IC₅₀ ≈?2–3 μM) when O was produced from xanthine oxidase. In contrast, Hg(I) did not react with O in either system, suggesting little involvement of Hg(I) in the apparent dismutation of O by Hg(II). Hg(II) also inhibited the reactions of KO₂ (i.e., O) with hemin or horseradish peroxidase dissolved in dimethyl sulfoxide (DMSO). Finally, a combination of Hg(II) and KO₂ in DMSO resulted in a stable UV absorbance spectrum [currently assigned Hg(II)-peroxide] distinct from either Hg(II) or KO₂. These results suggest that Hg(II), despite possessing little redox activity, enhances the rate of O dismutation, leading to increased production of H₂O₂ by renal mitochondria. This property of Hg(II) may contribute to the oxidative tissue-damaging properties of mercury compounds.     

The assessment of cellular proliferation by immunohistochemistry: A review of currently available methods and their applications

Summary Immunohistochemical methods using antibodies to cell cycle-related antigens may be used as a means of assessing various aspects of proliferation in tissue, and have the important advantage of preserving the spatial orientation of proliferating cells in histological sections. Currently, the most widely available antibodies for this purpose are antibodies to bromodeoxyuridine (BrdU), Ki67 and antibodies to proliferating cell nuclear antigen (PCNA). BrdU is a thymidine analogue incorporated during the S phase of the cell cycle, which can be introduced by in vivo administration or by in vitro incubation, and monoclonal antibodies are available to display its localization. Ki67 demonstrates a nuclear antigen expressed in all phases of the cell cycle, except G₀ and early G₁, but can only be applied to frozen tissue. PCNA is a nuclear antigen which is essential for DNA synthesis, two commercially available antibodies to PCNA work in paraffin-embedded tissue, but may have different staining characteristics under different conditions of fixation. The main advantages and disadvantages of these different techniques are discussed, together with their main applications to date.