The endogenous lectins of the chick blastoderm are present in association with an apolipoprotein in distinct organelles and in the extracellular matrix

Summary Affinity purified preparations of the galactose-binding lectin from gastrulating chick blastoderms consist of three main polypeptides. Two of these have been identified as the 14 kD and 16 kD galactose-binding lectins. A third one migrates in SDS-PAGE gels with a relative molecular weight of 6,500±500 and has been identified as an apolipoprotein (Apo) of plasma very low density lipoproteins, Apo-VLDL-II. We have studied the localization of these polypeptides using immunofluorescence and ultrastructural immunocytochemistry with peroxidase and protein-A gold. The 14 kD lectin occurs in the intracellular yolk where it is mainly present within the electron lucent component. The 16 kD is also present in the intracellular yolk platelets, but tends to predominate in the electron-dense component. In addition, the 16 kD lectin is also present in pleiomorphic yolk-associated organelles and in the extracellular matrix. Apo-VLDL-II is also localized in the electron-lucent component of the yolk platelet and in the extracellular matrix. Our results suggest that the lectin(s) are associated with Apo-VLDL-II in the yolk platelet, and may subsequently become externalized.     

Artificial dimers of native actin: Preparation and properties in biological functions

With the aid of tartryl-bis--aminocaprylazide artificial dimers were produced from F actin from rabbit striated muscle. These derivatives will not polymerize by themselves but are able to copolymerize fully with native G actin. By modification of a single side chain per dimer, this copolymerization was completely inhibited. The dimers are able to activate subfragment I ATPase of myosin and bind to DNase I with inactivation of the enzyme in the same manner as native G actin. Within the dimer, one ADP is immobilized and will exchange against ATP extremely slowly. The dimers do not bind to the mushroom toxin phalloidin.     

Plasmids in toxic and nontoxic strains of the cyanobacteriumMicrocystis aeruginosa

The plasmid content and toxicity of nine different strains ofMicrocystis aeruginosa have been analyzed. The two toxic strains of the HUB Culture Collection were found to carry each two plasmids, pMA1 and pMA2, of 2.9 kb and 8.5 kb, respectively. In strains PCC 7813 and PCC 7820, also toxic, two different plasmids of 2.6 kb and 16 kb were detected. Hybridization experiments showed that there exists no sequence homology between the pMA plasmids and the plasmids found in the PCC strains; but the pMA plasmids hybridized to chromosomal DNA of the toxic strains PCC 7820, PCC 7813, HUB 063, and the nontoxic strain HUB 5-3. In nontoxic strains no or at most one plasmid of unstable occurrence could be detected. Only one of the toxic strains investigated, SAG 14.85 (NRC-1), contained no plasmid.     

Two auditory filter systems determine the calling behavior of the fire-bellied toad: a behavioral and neurophysiological characterization

Summary Male fire-bellied toads,Bombina bombina, are stimulated into calling by conspecific mating calls. They tend to synchronize their activity with other calling individuals, which leads to antiphonal calling. Behavioral physiological experiments revealed the existence of two different auditory filter systems which influence this acoustic behavior. One filter system is tuned to the recognition of conspecific mating calls, the other is part of a circuit that controls an acoustic jamming avoidance reaction. The two filter systems differ in several properties: filter bandwidth, threshold, and time constant. Neurophysiological recordings in the midbrain and the thalamus show that the filter characteristics can be explained by the coding properties of auditory neurons in these two brain nuclei.     

TGF-Beta inhibits the in vitro induction of lymphokine-activated killing activity

Summary Employing serum-free media, human peripheral blood mononuclear cells, and purified recombinant interleukin-2 (IL-2), conditions were observed in which the development of IL-2-driven cytotoxic activity was suppressed. The cytotoxic activity of such IL-2-generated lymphokine activated killing (LAK) was tested against natural killer-resistant cultured tumor cells (Daudi, Raji, and a glioma). LAK generation was inhibited by addition of some normal sera, normal platelets, or some tumor cells. Because recent reports have indicated that transforming growth factor-beta (TGF-beta)-like factors are often secreted by tumors and the acidic alpha granules of platelets and can be present in sera, we tested the effect of purified human TGF-beta on the activation of LAK. Our results indicated that TGF-beta is very suppressive for LAK induction, and can completely prevent both the IL-2-driven proliferation and cytotoxicity at concentrations as low as 5 ng/ml. Titrations of IL-2 and of TGF-beta indicated that the suppression is dose-dependent and can be avoided by employing higher levels of IL-2. It was also found that the suppressive effect of TGF-beta can be overcome by washing suppressed cell populations and further culture in low levels of IL-2. Collectively, these data indicate that TGF-beta can be a potent inhibitor of LAK generation under standard activation conditions, but that this effect is regulated by the relative level of IL-2 and may be overcome and/or reversed in vitro.     

Hemagglutinating and adherence properties of Staphylococcus saprophyticus: epidemiology and virulence in experimental urinary tract infection of rats

Abstract We studied hemagglutinating and adherence properties in Staphylococcus saprophyticus isolates originating from symptomatic urinary tract infections. 12/13 (92%) of strains adhered to Hep cells and 11/13 (85%) were able to agglutinate sheep erythrocytes. Adherence properties differed markedly between strains ( P < 0.0001. Two strains, one hemagglutinating and adherent and one negative for both properties were chosen for experimental urinary tract infections. Results indicate that presence of the hemagglutinin favours colonization of kidney tissue.     

Isolation of aClostridium thermocellum gene encoding a thermostable β-1, 3-glucanase (laminarinase)

Summary AClostridium thermocellum gene directing the synthesis of a thermostable -glucanase was localized on a 1.9-kb DNA fragment by subcloning intoEscherichia coli plasmid vectors. The enzyme was highly efficient in degrading glucans with alternating -1, 3- and -1,4-linkages such as lichenan and barley glucan. It was also active towards the -1, 3-glucan laminarin, but lacked activity on cellulosic substrates and -glucans. The enzyme was therefore classified as -1, 3-glucanase (laminarinase) and the corresponding gene was designatedlicA. With barley -glucan as substrate the enzyme had a pH optimum around pH 6.5 and a temperature optimum at 65°C. It was stable for several hours at 60°C in the absence of substrate.     

Structure and function of ferredoxin-NADP+-oxidoreductase

The redox-enzyme ferredoxin-NADP-oxidoreductase has been shown to be activated by light and inactivated in the dark. This review will summarize recent data concerning the biochemical characterization of the enzyme compared to its in-vivo activation. Further-more the mechanism of this activation process is discussed as a conformational change caused by the light-driven proton gradient.Abbreviations cyt cytochrome - fd ferredoxin - FNR1 large form of ferredoxin-NADP-oxidoreductase - FNRox oxidized FNR - FNRred reduced FNR - FNRs small form of FNR - FNRsq FNR-semiquinone     

Organisation and expression of a wound/ripening-related small multigene family from tomato

cDNA clones derived from a ripe tomato fruit cDNA library were used to investigate changes in the abundance of specific mRNAs in ripening fruit and wounded leaves. mRNAs related to one cDNA clone (pTOM 13) were expressed in both situations. This clone was used to identify homologous sequences in a tomato genomic library. Three groups of related clones that hybridised to the pTOM 13 cDNA insert were identified and subcloned into plasmid vectors. Genomic Southern analysis of tomato DNA using gene-specific DNA fragments isolated from the subcloned DNAs indicated that all pTOM 13 closely related genes had been isolated. RNA dot blot analysis with these DNA fragments as probes indicated differential expression of this small multigene family in leaves and fruit.