Somatostatin inhibits dendritic cell responsiveness to Helicobacter pylori

Somatostatin is a regulatory peptide found in abundance in the stomach. We have previously shown that somatostatin is required for IL-4-mediated resolution of Helicobacter pylori gastritis. In the current study, we hypothesize that somatostatin acts directly on antigen-presenting cells in the stomach to lessen the severity of gastritis. To test this hypothesis, we first show that CD11c+ dendritic cells are present in the infected tissue of mice with H. pylori-induced gastritis. Pretreatment of bone marrow-derived dendritic cells with somatostatin results in decreased IL-12 production, and lower splenocyte proliferation induced by H. pylori-stimulated dendritic cells. Furthermore, octreotide, a somatostatin analogue, is more potent than somatostatin in suppressing IL-12 release by H. pylori-stimulated dendritic cells through an NF-kappaB-independent pathway. In addition, IL-4 stimulates somatostatin secretion from dendritic cells. In conclusion, somatostatin inhibits dendritic cell activation by H. pylori; a possible mechanism by which IL-4 mediates resolution of gastritis. We suggest that octreotide may be effective in treating immune-mediated diseases of the stomach.     

Positive and negative regulation of the gamma-secretase activity by nicastrin in a murine model

Nicastrin is a component of the gamma-secretase complex that has been shown to adhere to presenilin-1 (PS1), Notch, and APP. Here we demonstrate that Nicastrin-deficient mice showed a phenotype that is indistinguishable from PS1/PS2 double knock-out mice, whereas heterozygotes were healthy and viable. Fibroblasts derived from Nicastrin-deficient embryos were unable to generate amyloid beta-peptide and failed to release the intracellular domain of APP- or Notch1-Gal4-VP16 fusion proteins. Additionally, C- and N-terminal fragments of PS1 and the C-terminal fragments of PS2 were not detectable in Nicastrin-null fibroblasts, whereas full-length PS1 accumulated in null fibroblasts, indicating that Nicastrin is required for the endoproteolytic processing of presenilins. Interestingly, cells derived from Nicastrin heterozygotes produced relatively higher levels of amyloid beta-peptide whether the source was endogenous mouse or transfected human APP. These data demonstrate that Nicastrin is essential for the gamma-secretase cleavage of APP and Notch in mammalian cells and that Nicastrin has both positive and negative functions in the regulation of gamma-secretase activity.     

Quercitol and osmotic adaptation of field-grown Eucalyptus under seasonal drought stress

This study investigated the role of quercitol in osmotic adjustment in field-grown Eucalyptus astringens Maiden subject to seasonal drought stress over the course of 1 year. The trees grew in a native woodland and a farm plantation in the semi-arid wheatbelt region of south Western Australia. Plantation trees allocated relatively more biomass to leaves than woodland trees, but they suffered greater drought stress over summer, as indicated by lower water potentials, CO₂ assimilation rates and stomatal conductances. In contrast, woodland trees had relatively fewer leaves and suffered less drought stress. Plantation trees under drought stress engaged in osmotic adjustment, but woodland trees did not. Quercitol made a significant contribution to osmotic adjustment in drought-stressed trees (25% of total solutes), and substantially more quercitol was measured in the leaves of plantation trees (5% dry matter) than in the leaves of woodland trees (2% dry matter). We found no evidence that quercitol was used as a carbon storage compound while starch reserves were depleted under drought stress. Differences in stomatal conductance, biomass allocation and quercitol production clearly indicate that E. astringens is both morphologically and physiologically 'plastic' in response to growth environment, and that osmotic adjustment is only one part of a complex strategy employed by this species to tolerate drought.     

Ultrastructural and autoradiographic observations of hamster cheek pouch epithelium grown in vitro.

Epithelial outgrowths from hamster cheek pouch explants were cultured for varying periods of time up to 22 days. Growth of the epithelial sheets was monitored, employing colcemid for demonstrating mitotic activity and tritiated thymidine for DNA synthesis. Mitoses and thymidine uptake were observed among epithelial outgrowths at a considerable distance form the original explant. The epithelial nature of the growing cell sheets was confirmed, employing electron microscopic techniques. The cells exhibited the presence of tonofilaments, desmosomes, ribosomes, Golgi, mitochondria, and rough endoplasmic reticulum. The cultured explants were treated with cyclic nucleotides in order to investigate their modulatory effects on epithelial cell differentiation. Dibutyryl cAMP induced marked mitotic inhibition (46.3%) in our assay, which was increased to 57% with the addition of theophylline. Dibutyryl cGMP showed only a mild (5%) stimulatory effect on mitotic activity. Dibutyryl cAMP enhanced keratinization in the epithelial cell outgrowths with the biogenesis of keratohyalin granules, whereas dibutyryl cGMP did not produce any observable alterations.     

Heavy Metal-Activated Synthesis of Peptides in Chlamydomonas reinhardtii

In this study, we have addressed the capacity of the green alga Chlamydomonas reinhardtii to produce metal-binding peptides in response to stress induced by the heavy metals Cd²⁺, Hg²⁺, and Ag⁺. Cells cultured in the presence of sublethal concentrations of Cd²⁺ synthesized and accumulated oligopeptides consisting solely of glutamic acid, cysteine, and glycine in an average ratio of 3:3:1. Cadmium-induced peptides were isolated in their native form as higher molecular weight peptide-metal complexes with an apparent molecular weight of approximately 6.5 × 10³. The isolated complex bound cadmium (as evidenced by absorption spectroscopy) and sequestered (with a stoichiometry of 0.7 moles of cadmium per mole of cysteine) up to 70% of the total cadmium found in extracts of cadmium-treated cells. In Hg²⁺-treated cells, the principal thiol-containing compound induced by Hg²⁺ ions was glutathione. It is possible that glutathione functions in plant cells (as it does in animal cells) to detoxify heavy metals. Cells treated with Ag⁺ ions also synthesized a sulfur-containing component with a charge to mass ratio similar to Cd²⁺-induced peptides. But, in contrast to the results obtained using Cd²⁺ as an inducer, these molecules did not accumulate to significant levels in Ag⁺-treated cells. The presence of physiological concentrations of Cu²⁺ in the growth medium blocked the synthesis of the Ag⁺-inducible component(s) and rendered cells resistant to the toxic effects of Ag⁺, suggesting competition between Cu²⁺ and Ag⁺ ions, possibly at the level of metal uptake.     

Comparison of proteins expressed on secretory vesicle membranes and plasma membranes of human neutrophils

Secretory vesicles are neutrophil intracellular storage granules formed by endocytosis. Understanding the functional consequences of secretory vesicle exocytosis requires knowledge of their membrane proteins. The current study was designed to use proteomic technologies to develop a more complete catalog of secretory vesicle membrane proteins and to compare the proteomes of secretory vesicle and plasma membranes. A total of 1118 proteins were identified, 573 (51%) were present only in plasma membrane-enriched fractions, 418 (37%) only in secretory vesicle-enriched membrane fractions, and 127 (11%) in both fractions. Gene Ontology categorized 373 of these proteins as integral membrane proteins. Proteins typically associated with other intracellular organelles, including nuclei, mitochondria, and ribosomes, were identified in both membrane fractions. Ingenuity Pathway Knowledge Base analysis determined that the majority of canonical and functional pathways were significantly associated with proteins from both plasma membrane-enriched and secretory vesicle-enriched fractions. There were, however, some canonical signaling pathways that involved proteins only from plasma membranes or secretory vesicles. In conclusion, a number of proteins were identified that may elucidate mechanisms and functional consequences of secretory vesicle exocytosis. The small number of common proteins suggests that the hypothesis that secretory vesicles are formed from plasma membranes by endocytosis requires more critical evaluation.     

Hairy cell leukemia: kinetics and intercellular relationships of cells in leukemic colonies grown in a semisolid medium

We examined cellular relationships and cytokinetics of hairy cells in colonies formed in an in vitro cloning system. Cells in small colonies and at the periphery of larger ones were separated by wide, irregular intercellular spaces. Cells in the core of large colonies were elaborately intertwined by their cytoplasmic processes and so densely packed that their intercellularity was greatly reduced. Cell labeling with 3H-thymidine revealed indices ranging from less than 1% to 35%. The combination of autoradiography with a stain for tartrate-resistant acid phosphatase showed that the enzyme was not expressed by cells in S-phase. The cellular relationships of hairy cells in colonies grown in this system closely mimic those of their in vivo counterparts in the spleen and bone marrow.     

Ultraviolet Radiation on Innate Immunity and Growth of Broad-Snouted Caiman (Caiman latirostris): Implications for Facilities Design

Sunlight is a key environmental factor in almost all ecosystems, and it is necessary for many physiological functions. Many vertebrates require ultraviolet (UV) radiation to perform different physiological processes. Artificial light is used to supplement UV in captive animals, through appropriate photoperiods and UV wavelengths. Previous studies reported that repeated exposure to artificial UV radiation may cause damage to the immune system. Taking into account the importance of UV effects and the serum complement system, the relationship between them was investigated. The study lasted 90 days and was carried out in plastic chambers. Ninety six broad‐snouted caiman (C. latirostris) were assigned to four treatment groups with two replicates each: total darkness (TD), 8 hr per day (8 hr) and 16 hr per day (16 hr) of artificial UV/visible light exposure, and normal photoperiod of natural light (NP). Snout–vent length was measured to determine animal growth. Hemolytic assays were performed to evaluate the effects of artificial UV/visible light, TD, and NP on the serum complement system. Results showed that animals grew more in the NP group. The capacity of C. latirostris serum to hemolyze sheep red blood cells was higher in the NP group than when they are maintained in constant light–dark cycles (8 and 16 hr) or in TD. These data demonstrate that artificial UV should be considered as a potential hazard for captive crocodilians if it is not properly managed, and this should be taken into account in the general design of facilities for reptilian husbandry. Zoo Biol 31:523‐533, 2012. © 2011 Wiley Periodicals, Inc.