A quantitative study of enterotoxin production by sheep milk staphylococci

Of 124 staphylococcal strains isolated from sheep milk, 78 produced enterotoxin A, B, C, or D when evaluated by an enzyme-linked immunosorbent assay. Enterotoxins A and D, elaborated by 44 and 43 strains, respectively, showed the highest incidence. Enterotoxin production by coagulase-negative strains (one Staphylococcus cohnii, three S. epidermidis, five S. haemolyticus, and four S. xylosus) was detected. Linear and logarithmic-logarithmic regressions of optical density on enterotoxin concentration yielded the best-fitting equations for enterotoxin quantitation. A significantly higher incidence of enterotoxin producers and significantly higher levels of enterotoxins produced were recorded for coagulase-positive, thermostable nuclease-positive, hemolysis-positive, or mannitol-positive strains. Mannitol utilization was the best test for discriminating between enterotoxigenic and nonenterotoxigenic staphylococci.     

Characteristics of rhamnan isolated from preparations of Pseudomonas aeruginosa lipopolysaccharides

A polysaccharide isolated from the degraded lipopolysaccharides of P. aeruginosa serogroup O7 (Lányi--Bergan classification) was characterized by liquid chromatography, acid hydrolysis, and 1H and 13C NMR spectroscopy. It has molecular mass 15,000 and represents mainly a rhamnan of the structure----2)-alpha-D-Rha-(1----3)-alpha-D-Rha-(1----3)-alpha-D-Rha-(1 ----, identical to the structure of O-specific polysaccharides of Pseudomonas aeruginosa pvs morsprunorum and cerasi. Some minor constituents, such as glucose, mannose, an unknown sugar, and phosphate, are found in the polysaccharide preparation as well. Distribution of the rhamnan in some other P. aeruginosa serogroups is discussed and its identity to the common polysaccharide antigen of P. aeruginosa is suggested.     

Model studies at mechanical aortic heart valve prostheses--Part I: Steady-state flow fields and pressure loss coefficients

In a 3:1 scaled model of the human aorta models of the Omniscience, Bj?rk-Shiley Convexo-Concave, Bj?rk-Shiley Monostrut, Medtronic-Hall, Duromedics (Hemex) and the Saint Jude Medical heart valve prostheses are studied in steady flow representing the systolic peak flow phase. Detailed flow visualization experiments show flow separations at all inner ring surfaces as well as at most of the occluders. The resulting stagnation areas increase the risk of thrombus accumulation. Flow separations also stimulate vortex formation and turbulent mixing at the downstream jet boundaries and thus may intensify blood damage by turbulent shear stresses. The different influences of struts and occluder guides on the flow around the occluders are discussed. The effects of the individual valve components on the flow fields are analyzed and correlated with the resulting pressure losses.     

Purification of the growth-related protein p25 of the Ehrlich ascites tumor and analysis of its isoforms

1. Two of the three isoforms of the growth-related protein p25 of the Ehrlich ascites tumor have been purified to homogeneity by giant two-dimensional polyacrylamide gel electrophoresis. 2. Antibodies raised against the isoform p25/1 react also with isoforms p25/2 and p25/3. 3. Limited tryptic digestion of p25/1 and p25/2 resulted in similar oligopeptide patterns. Corresponding oligopeptides of both isoforms have identical amino acid sequences. 4. The isoforms p25/2 and p25/3 are phosphorylated derivatives of unphosphorylated p25/1. The phosphorus is bound to serine and a further unknown phosphorylation site.     

Stretch activated ion channels in ventricular myocytes

Patch-clamp recordings from ventricular myocytes of neonatal rats identified ionic channels that open in response to membrane stretch caused by negative pressures (1 to 6 cm Hg) in the electrode. The stretch response, consisting of markedly increased channel opening frequency, was maintained, with some variability, during long (>40 seconds) stretch applications. The channels have a conductance averaging 120 pS in isotonic KCl, have a mean reversal potential 31 mV depolarized from resting membrane potential, and do not require external Ca⁺⁺ for activation. The channels appear to be relatively non-selective for cations. Since they are gated by physiological levels of tension, stretch-activated channels may represent, a cellular control system wherein beat-to-beat tension and/or osmotic balance modulate a portion of membrane conductance.Abbreviations SACs stretch-activated channels - HEPES 4-(2-hydroxyethyl)-1-piperazine-ethanesulfonic acid     

Effects of traces of rare earth elements on the protozoanBlepherisma and on mice

The growth of the protozoanBlepherisma is stimulated by Lanthanum (La) at concentrations as low as 0.32 ppm. In mice Yttrium (Y) and Ytterbium (Yb) are absorbed, accumulated, and metabolized. Both rare earth elements (RE) exhibit a high affinity for teeth and bones, accumulation occurs and metabolism is slow. In the livers of RE-exposed mice, concentrations are variable. The liver is apparently capable of absorbing and discharging RE in a manner depending on metabolic activity. The main route of discharge for ingested REs is the alimentary canal. Exposure of pregnant mice to RE leads to rapid placental transfer of RE; 14.1% of the total amount of RE administered was detected in newborn mice. Young, developing organisms appear to be especially susceptible to RE accumulation.     

Association of thrombospondin of endothelial cells with other matrix proteins and cell attachment sites and migration tracks

Different biochemical and cytochemical techniques were applied to characterize the sites of localization of thrombospondin in cultured endothelial cells. The results obtained by [35S]methionine labeling, immunoblotting, immunoprecipitation, fluorescence microscopy, ultracytochemistry, immunogold labeling, and silver enhancement experiments revealed that thrombospondin secreted by endothelial cells is structurally organized together with proteoheparan sulfate in spherical granules at the cell surface. These granules are about 100 to 300 nm in size. Heparin or enzymatic degradation with heparitinase, but not with ABC lyase, release thrombospondin from the cell surface. Fibronectin is expressed in the extracellular matrix of endothelial cells in a fibrillar organization, clearly distinct from the punctate pattern of thrombospondin on the cell surface. Furthermore, secreted thrombospondin is highly enriched together with fibronectin and proteoheparan sulfate in cell attachment sites and in cell migration tracks. In cell migration tracks proteoheparan sulfate more clearly resembles the fibrillar distribution pattern of fibronectin, whereas thrombospondin reveals a rather monodisperse pattern. The obtained data suggest preferential sites of interaction between thrombospondin and heparan sulfate proteoglycans on the cell surface and a participation of thrombospondin in cell adhesion and cell migration.     

Formation of double-walled microtubules and multilayered tubulin sheets by basic proteins

Some basic proteins enable microtubule protein to form special assembly products in vitro, known as double-walled microtubules. Using histones (H1, core histones) as well as the human encephalitogenic protein to induce the formation of double-walled microtubules, we made the following electron microscopic observations: (1) Double-walled microtubules consist of an "inner" microtubule which is covered by electron-dense material, apparently formed from the basic protein, and by a second tubulin wall. (2) The tubulin of the second wall seems to be arranged as protofilaments, surrounding the inner microtubule in a helical or ring-like manner. (3) The surface of double-walled microtubules lacks the projections of microtubule-associated proteins, usually found on microtubules. (4) In the case of protofilament ribbons (incomplete microtubules), H1 binds exclusively to their convex sides that correspond to the surface of microtubules. Zn2+-induced tubulin sheets, consisting in contrast to microtubules of alternately arranged protofilaments, are covered by H1 on both surfaces. Furthermore, multilayered sheet aggregates appeared. The results indicate that the basic proteins used interact only with that protofilament side which represents the microtubule surface. In accordance with this general principle, models on the structure of double-walled microtubules and multilayered tubulin sheets were derived.     

Carnivora: primary structure of the hemoglobins from ratel (Mellivora capensis)

The erythrocytes of adult ratel contain two hemoglobin components, with two alpha- and one beta-chains. In this paper, their complete amino acid sequences are presented. The two alpha-chains differ in one residue at position 34 (Ala----Val) only. The primary structure of the chains was determined by sequencing the N-terminal regions (45 steps) and the tryptic peptides after their isolation from the digests by reversed-phase high-performance liquid chromatography. The alignment of these peptides was deduced from homology with other carnivora globins. The alpha-chains show 21 and the beta-chains 11 exchanges compared with human globin chains. In the alpha-chains, one heme- and two alpha 1/beta 1 contacts are exchanged. In the beta-chains there are three exchanges which involve one alpha 1/beta 1-, one alpha 1/beta 2- and one heme-contact. Between the ratel hemoglobin and those of carnivora a high degree of homology was found.     

Enzymatic resynthesis of the "reactive site" bond in the modified aprotinin derivatives [seco-15/16]aprotinin and [Di-seco-15/16,39/40]aprotinin

On incubation of [di-seco-15/16,39/40]aprotinin with human plasmin, porcine pancreatic kallikrein or bovine or porcine trypsin in neutral or slightly alkaline solutions [seco-39/40]aprotinin is slowly formed with enzymatic resynthesis of the reactive-site bond 15/16. With chymotrypsin, however, further degradation of [di-seco-15/16,39/40]aprotinin takes place without enzymatic resynthesis. The apparent rate constants for the synthesis of [seco-39/40]aprotinin with kallikrein and trypsin have been determined and indicate that the bond-forming reaction is 10-200-fold slower with [di-seco-15/16,39/40]aprotinin than with [seco-15/16]aprotinin. The newly formed [seco-39/40]aprotinin has similar kinetic constants for the complexation with its cognate enzymes as aprotinin, indicating that any distortion of the secondary binding region due to cleavage of the Arg39-Ala40 bond does not seriously influence binding and affinities.