Whitening,thallus decay and fragmentation in Gracilaria chilensis associated with an endophytic amoeba

Whitening of Gracilaria chilensis, accompanied by tissue softening and thallus fragmentation, was found to be associated with the presence of an endophytic amoeba. Although the symptoms developed originally in green mutant thalli, subsequent infections in the laboratory also affected normal, wild-type G. chilensis. Ultrastructural evidence indicates that the amoebae perforate the host cell walls of both cortical and medullary cells and digest their protoplasm. Feeding by the amoeba appears to involve both phagocytosis and enzymatic digestion of the host tissue. Destruction of the host tissue resulted in large cavities first, followed by thallus fragmentation. No other organism was found during the early stages of thallus invasion by the amoeba, although bacteria may appear once the amoeba reaches the inner tissues of the host.     

Osmotic Stress-Induced Polyamine Accumulation in Cereal Leaves : II. Relation to Amino Acid Pools

Arginine decarboxylase activity increases 2- to 3-fold in osmotically stressed oat leaves in both light and dark, but putrescine accumulation in the dark is only one-third to one-half of that in light-stressed leaves. If arginine or ornithine are supplied to dark-stressed leaves, putrescine rises to levels comparable to those obtained by incubation under light. Thus, precursor amino acid availability is limiting to the stress response. Amino acid levels change rapidly upon osmotic treatment; notably, glutamic acid decreases with a corresponding rise in glutamine. Difluoromethylarginine (0.01-0.1 millimolar), the enzyme-activated irreversible inhibitor of arginine decarboxylase, prevents the stress-induced putrescine rise, as well as the incorporation of label from [¹⁴C]arginine, with the expected accumulation of free arginine, but has no effect on the rest of the amino acid pool. The use of specific inhibitors such as α-difluoromethylarginine is suggested as probes for the physiological significance of stress responses by plant cells.     

Cortisol binding in human breast cancer: Correlation with antitumor immunity

Summary The intensity of cortisol binding was measured in the cytosol fraction of the primary tumor obtained from 50 patients with stage I and II breast cancer. The state of cellular antitumor immunity of the same patients was investigated by the tube leucocyte adherence inhibition (LAI) test, performed with peripheral blood leucocytes 1–2 days preoperatively. It was found that the intensity of tumor cortisol binding correlates negatively with LAI values. Patients with high cortisol binding in their tumors have low LAI values, while low tumor cortisol binding is associated with higher antitumor immunity. The results suggest that high cortisol binding in the tumor might inhibit the tumor recognition process and/or the cellular immune defense mechanism and thus facilitate cancer development.     

Studies on the time course and rate-limiting steps in the activation of adenylate cyclase in rat liver by cholera toxin.

Cholera toxin stimulates adenylate cyclase in rat liver after intravenous injection. The stimulation follows a short latent period of 10min, and maximum stimulation was attained at 120min. Half-maximal stimulation was achieved at 35min. In contrast with this lengthy time course in the intact cell, adenylate cyclase in broken-cell preparations of rat liver in vitro were maximally stimulated by cholera toxin (in the presence of NAD+) in 20min with half-maximal stimulation in 8min. Binding of cholera toxin to cell membranes by the B subunits is followed by translocation of the A subunit into the cell or cell membrane, and separation of the A1 polypeptide chain from the A2 chain by disulphide-bond reduction, and finally activation of adenylate cyclase by the A1 chain and NAD+. As the binding of cholera toxin is rapid, two possible rate-limiting steps could be the determinants of the long time course of action. These are translocation of the A1 chain from the outside of the cell membrane to its site of action (this includes the time required for separation from the whole toxin) or the availability of NAD+ for activation. When NAD+ concentrations in rat liver were elevated 4-fold, by the administration of nicotinamide, no change in the rate of activation of adenylate cyclase by cholera toxin was observed. Thus the intracellular concentration of NAD+ is not rate-limiting and the major rate-limiting determinant in intact cells must be between the time of toxin binding to the cell membrane and the appearance of subunit A1 at the enzyme site.     

THE ANATOMY OF THE PISTILLATE INFLORESCENCE AND FLOWER OF CASUARINA VERTICILLATA LAMARCK (CASUARINACEAE)

The pistillate inflorescence of Casuarina verticillata is described as consisting of a primary axis bearing whorls of bracts with a cymule in the axil of each bract of the more central whorls. Each cymule consists of an atepallate, two-carpellate, syncarpous floret and two, lateral, once-lobed bracteoles. A “peripheral intercalary” meristem, in which divisions are primarily periclinal, forms a meshwork beneath the bracts from early development and moves the connate bracts centrifugally around the cymules and extends and binds the bracts, and to some extent the bracteoles, of the fertile part of the inflorescence together. Each bract receives a single trace; each cymule receives two traces. Each bundle extension of a cymule trace supplies: 1) a branch which joins its counterpart to become the anterior common carpellary bundle; 2) a second branch which joins its counterpart to become the posterior common carpellary bundle; and 3) a central branch which supplies a lateral bracteole. Within each floret, each common carpellary bundle provides a dorsal carpellary bundle, two ventral carpellary bundles (fertile anterior carpel) or one common ventral bundle (sterile posterior carpel). The ventral bundle-supplies join and form a single placental bundle which lies in the gynoecial septum, and which, in turn, supplies the two ovules in the anterior carpel. Whether the inflorescence is a simple racemose or a condensed cymose type cannot be determined from this species alone. The function of the sclerenchymatous, enclosing bracteoles and connate bracts is discussed.     

Human interferon omega (omega) binds to the alpha/beta receptor.

It was proposed that human interferon omega (omega) binds to the interferon alpha/beta receptor but not to the interferon gamma receptor. However, since no studies were performed to provide direct evidence for this hypothesis, we carried out cross-linking experiments and saturation binding assays between a 32P-labeled human interferon-alpha (Hu-IFN-alpha) and unlabeled Hu-IFN-alpha A, -beta, -gamma, and -omega. These assays demonstrated that Hu-IFN-alpha A, -beta, and -omega, but not Hu-IFN-gamma, were able to block binding of 32P-labeled Hu-IFN-alpha A to human cells. These results indicate that Hu-IFN-omega binds to the alpha/beta receptor.     

Expression and regulation of UDP-glucuronate: neolactotetraosylceramide glucuronyltransferase in the nervous system

Sulfoglucuronyl glycolipids (SGGLs) are temporally and spatially regulated molecules present in the nervous system during its development. The characteristics of the rat brain enzyme glucuronyltransferase involved in the biosynthesis of SGGLs have been described. The enzyme catalyzes the transfer of glucuronic acid (GlcA) from UDP-GlcA to terminal galactose of the neolacto (type 2) series of glycolipids to form beta 1-3-linked glucuronyl neolacto glycolipids. The enzyme was highly specific for the neolacto series of acceptor glycolipids, neolactotetraosylceramide (nLcOse4Cer), neolactohexaosylceramide (nLcOse6-Cer), and neolactooctaosylceramide (nLcOse8Cer) and was different from the drug-inducible phenol:GlcA transferase. Considerable activity of GlcA transferase was present in the adult rat cerebral cortex, even though SGGLs almost completely disappeared from the cortex by postnatal day 15. In the cerebellum, although levels of SGGLs increased with development, the specific activity of GlcA transferase declined. The results indicated that GlcA transferase was not a regulatory enzyme controlling the expression of SGGLs. Measurements of the levels of nLcOse4Cer and nLcOse6Cer in these neural tissues indicated that the availability of these precursors may regulate the differential expression of SGGLs seen previously. GlcA transferase was significantly reduced in the cerebellar Purkinje cell degenerating murine mutant (pcd/pcd), which is consistent with the loss of SGGLs in the cerebellum of this mutant and specific association of these glycolipids with Purkinje cells.     

A monoclonal antibody that detects a specific human neutrophil antigen involved in phorbol myristate acetate- and formyl-methionyl-leucyl-phenylalanine-triggered respiratory burst.

A mouse IgM mAb termed P1E3 was raised against resting human peripheral blood neutrophils and has been shown to recognize a cell-surface Ag with an apparent molecular mass of 155 kDa, as assessed by immunoprecipitation analysis. In addition to the main 155-kDa protein, an additional band of about 210 kDa was also recognized by P1E3 in Western blot analysis. Sequential immunoprecipitation assays showed that the Ag recognized by P1E3 differed from the CD29 and CD45 Ag. However, sequential immunoprecipitation assays carried out with two distinct anti-CD15 mAb and P1E3 showed that P1E3 reacted with CD15 or with a CD15-like Ag. P1E3 stained strongly resting human peripheral blood neutrophils, hardly reacted with peripheral blood monocytes and did not react with PBL and platelets, as assessed by immunofluorescence flow cytometry. P1E3 inhibited the respiratory burst induced by PMA or FMLP, but not the oxidative response induced by Con A or the calcium ionophores A23187 or ionomycin. Furthermore, P1E3 inhibited the activation of the Na+/H+ antiporter in response to PMA or FMLP and the phosphorylation of a protein of about 50 kDa in response to PMA. However, preincubation of neutrophils with P1E3 did not affect the increase in cytosolic free calcium concentration induced by FMLP. These data suggest that the Ag recognized by P1E3 may play a role in modulating the activation of the respiratory burst induced by PMA or FMLP, and that P1E3 seems to affect protein kinase C-mediated signal transduction mechanisms coupled to the induction of the respiratory burst.     

Differential expression of heat shock proteins in Drosophila embryonic cells following metal ion exposure

Drosophila embryonic cells were exposed to a number of metal ions that have been previously reported to act as teratogens in mammalian systems, including some known to induce heat shock (stress) proteins in a variety of model systems. This study examined the effects of these ions both on differentiation of muscles and neurons and on the induction of heat shock proteins. Metals such as arsenate, cadmium, and mercury all inhibited neuron and/or muscle differentiation in Drosophila embryonic cultures, while they also induced the entire set of heat shock proteins. Two metal ions, nickel and zinc, were shown to induce only the 22-and 23-K proteins, a pattern similar to that seen in “classical” teratogens reported previously. None of the metals tested induced only the 26-and 27-K proteins. These results suggest that there exist different regulatory mechanisms responsible for the heat shock response.