Guaianolides and lignans from Centaurea solstitialis subs Schouwii

Aerial parts of Centaurea solstitialis subs schouwii afforded the guaianolides cynaropicrin and aguerin B and the lignans arctigenin and matairesinol. The structure of a third guaianolide previously found also in Centaurea behen was revised.     

Comparative study of G- and C-banded chromosomes of five species of Microtidae

G-banded karyotypes were compared in the following species of Microtidae: Microtus nivalis; M. cabrerae; M. arvalis and Arvicola sapidus. Previous observations on A. sapidus and A. terrestris (Díaz de la Guardia & Pretel, Caryologia 32: 183–189, 1979) were also incorporated in this study. The results show that Robertsonian translocations and pericentric inversions are common mechanisms involved in the karyotypic evolution of this group. Interspecific differences in C-banding patterns were also analyzed. Using the karyograph method (Imai et al., Am. Nat. 121: 477–488, 1983), the evolutionary distances of the karyotypes were estimated, and an attempt was made to establish a presumptive phylogenetic tree.     

Effect of pinealectomy on plasma glucose, insulin and glucagon levels in the rat

In an attempt to know the role of the pineal gland on glucose homeostasis, the blood plasma concentrations of glucose, insulin and glucagon under basal conditions or after the administration of nutrients were studied in the jugular vein of conscious pinealectomized (Pn), melatonin-treated pinealectomized (Pn + Mel) and control (C) rats. Glucose levels were smaller in C than in Pn rats, while immunoreactive insulin (IRI) concentrations were significantly greater in C than in Pn rats. Contrary to this, immunoreactive glucagon (IRG) levels were significantly greater in Pn than in C animals. Melatonin treatment of Pn rats induces an increase of IRI concentrations and a reduction in IRG levels. Similar changes were obtained when hormonal determinations were carried out in portal blood plasma. Although ether anesthesia increases circulating glucagon levels in the porta and cava veins, the qualitative changes of plasma insulin and glucagon in Pn and Pn + Mel were similar to those found in conscious rats. To determine the effects of nutrients on pancreatic hormone release, intravenous arginine or oral glucose were administered to the animals of the three experimental groups. In C rats, both glucose and IRI levels reached a peak 30 minutes after glucose ingestion, decreasing thereafter. However, in Pn rats a glucose intolerance was observed, with maximum glucose and insulin concentrations at 60 minutes, while in Pn + Mel animals, glucose and IRI concentrations were in between the data obtained with the other two groups. Furthermore, glucose ingestion induced a significant reduction of IRG levels in all the groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

A double staining method for differentiating between two classes of mycobacterial catalase in polyacrylamide electrophoresis gels

Mycobacteria produce two classes of catalase, designated T and M. Only the T-catalase also has a peroxidase-like function. When a 3,3'-diaminobenzidine (DAB) peroxidase stain was applied to polyacrylamide gel electrophoresis gels, followed by a ferricyanide negative stain for catalase, isoenzymes of T-catalase appeared as dark bands within a zone of clearing in the green background; the M-catalase appeared only as a clear zone. Heated and unheated preparations could be used to demonstrate the presence of comigrating bands of M and T. The application of the ferricyanide stain after the DAB stain of T-catalase resulted in marked intensification of the positive bands of T-catalase due to nonenzymatic, peroxide-independent reduction of the ferricyanide by the DAB product.     

Cytosine-specific DNA modification interferes with plasmid establishment in Escherichia coli K12: involvement of rglB

Summary Several chimeric pBR322/328 derivatives containing genes for cytosine-specific DNA methyltransferases (Mtases) can be transformed into the Escherichia coli K12/E. coli B hybrid strains HB101 and RR1 but not into other commonly used E. coli K12 strains. In vitro methylation of cytosine residues in pBR328 and other unrelated plasmids also reduces their potential to transform such methylation sensitive strains, albeit to a lesser degree than observed with plasmids containing Mtase genes. The extent of reduced transformability depends on the target specificity of the enzyme used for in vitro modification. The role of a host function in the discrimination against methylated plasmids was verified by the isolation of K12 mutants which tolerate cytosine methylated DNA. The mutations map in the vicinity of the serB locus. This and other data indicate that the host rglB function is involved in the discrimination against modified DNA.     

A neuraminidase from Streptococcus sanguis that can release O-acetylated sialic acids

The naturally occurring sialic acids can have different types of N- and O-substitutions, resulting in more than 20 known isomers and compounds. Most methods for the detailed study of these various sialic acids require that the molecules be first released from their alpha-glycosidic linkage. When mild acid hydrolysis is used for this purpose, significant destruction of O-substituent groups occur. On the other hand, the presence of O-substituent groups renders the sialic acid molecule partially or completely resistant to the action of the currently known neuraminidase. To circumvent this problem, we searched for a neuraminidase whose activity is not affected by O-substitution. We reasoned that because Streptococcus sanguis from the human oral cavity is continually exposed to O-substituted sialic acids, its extracellular neuraminidase might not be blocked by O-substitution. We therefore purified this enzyme 3100-fold (56% yield) using ammonium sulfate precipitation, N-(p-aminophenyl)oxamic acid-agarose affinity chromatography, and chromatography on quaternary aminoethyl (QAE)-Sephadex, sulfopropyl (SP)-Sephadex, and Sephacryl S-200. The purified preparation is free of other significant glycosidase activities and proteolytic activities. It is capable of quantitatively releasing all the O-acetylated sialic acids that we studied with the single exception of the 4-O-acetylated sialic acid of equine submaxillary mucin. The activity of the enzyme is also not restricted by the type pf sialic acid linkage or the nature of the underlying oligosaccharide. However, it has maximal activity on gangliosides only in the presence of detergents. The general properties of this enzyme are described and its substrate specificities are contrasted with those of the commonly used neuraminidase from Vibrio cholerae.     

Surface Antigens of Smooth Brucellae

Surface antigens of smooth brucellae were extracted by ether-water, phenol-water, trichloroacetic acid, and saline and examined by immunoelectrophoresis and gel diffusion with antisera from infected and immunized rabbits. Ether-water extracts of Brucella melitensis contained a lipopolysaccharide protein component, which was specific for the surface of smooth brucellae and was correlated with the M agglutinogen of Wilson and Miles, a polysaccharide protein component devoid of lipid which was not restricted to the surface of smooth brucellae and was not correlated with the smooth agglutinogen (component 1), and several protein components which were associated with internal antigens of rough and smooth brucellae. Immunoelectrophoretic analysis of ether-water extracts of B. abortus revealed only two components, a lipopolysaccharide protein component, which was correlated with the A agglutinogen, and component 1. Component 1 from B. melitensis and B. abortus showed identity in gel diffusion tests, whereas component M from B. melitensis and component A from B. abortus showed partial identity with unabsorbed antisera and no cross-reactions with monospecific sera. Attempts to prepare monospecific sera directly by immunization of rabbits with cell walls or ether-water extracts were unsuccessful. Absorption of antisera with heavy fraction of ether-water extracts did not always result in monospecific sera. It was concluded (as has been described before) that the A and M antigens are present on a single antigenic complex, in different proportions depending upon the species and biotype, and that this component is a lipopolysaccharide protein complex of high molecular weight that diffuses poorly through agar gel. Components 1, A, and M were also demonstrated in trichloroacetic acid and phenol-water extracts. With all extracts, B. melitensis antigen showed greater diffusibility in agar than B. abortus antigens. After mild acid hydrolysis, B. abortus ether-water extract was able to diffuse more readily.