1,720,982 research outputs found
Possible tributyltin-calmodulin interaction in morpho-functional alterations of ascidian phagocytes
No full textThis paper addresses studies on the rearrangement of cytoskeletal components occurring in phagocytes of the colonial ascidian Botryllus schlosseri during phagocytosis and their alteration induced by sublethal concentrations of the immunotoxic tributyltin (TBT). Incubation with TBT lead to change in phagocyte morphology due to depolymerisation of microfilaments and microtubules. Calmodulin is able to restore amoeboid shape, microtubule and microfilament polymerisation, and activity of the membrane-bond Ca2+-ATPase, but never the phagocytosis index. A direct TBT-calmodulin interaction establishing intracellular Ca2+ homeostasis, following a pattern of saturation, is suggested, even though other interactions with cytoskeletal components cannot be excluded
Are tributyltin-induced cytoskeletal alterations mediated by interaction with calmodulin?
No full textTributyltin chloride (TBTC), a powerful antifouling biocide, acts as immunosuppressant in Vertebrates, since it causes lymphocyte depletion, impairs phagocytosis, decreases the activity and the number of polymorphonuclear leukocytes. In the colonial ascidian Botryllus schlosseri we observed irreversible and significant decrease in yeast phagocytosis at sublethal dose (10 μM) associated with considerable changes in the shape of phagocytes which withdraw their pseudopodia and become spherical in relation to structural damage to cytoskeletal components. Subsequent and prolonged washes in sea water never succeed in restoring the amoeboid shape, suggesting an irreversible interaction between TBTC and cytoskeletal components. However, phagocytes do not change their morphology when 80 μg/ml calmodulin (CaM) are added tgether with 10 μM TBTC. In these cytoskeletal alterations the F-actin undergoes an extensive depolymerization resulting in the absence of fluorescence labelling by phalloidin-FITC. Analogously, microtubules are not recognizable as single filaments with anti-alpha-tubulin immunofluorescence although the centrosome is not affected. In the presence of increasing CaM concentrations in the incubation medium we observed that microtubules form an aster beginning from the concntration of 20 μg/ml CaM. At 80 μg/ml thin microtubules are rebuilt in pseudopodia and the amoeboid shape of the phagocytes is restored. At the same concentration only scattered spots of F-actin are observed corresponding with the adhesion plaques. Microfilaments appear only beginning from 120 μg/ml CaM and therefore they are more vulnerable than microtubules. Experiments with isodynamic mixtures of TBTC and specific CaM inhibitor, i.e. chlorpromazine (CPZ) and N-(6-aminohexyl)-5-chloronaphtalene-1-sulfonamide (W7), reveal a combined effect of antagonism. On the other hand, similar experiments with thapsigargin, a specific inhibitor of CaM-dependent Ca2+-ATPase show an effect of potentiation. We think that TBTC can interact on the same CaM receptor sites of CPZ and W7 in a Ca2+-CaM hydrophobic region. This interaction may induce a conformational change which prevents the regulative activity of CaM on Ca2+-ATPase. Consequently, the cell Ca2+ homeostasis is deeply altered. An excess of intracellular Ca2+ accumulate which, together with the inhibition of CaM-dependent kinases, produce an extensive cytoskeletal disaggregation.
(This work was supported by grants of the italian C.N.R. and M.U.R.S.T. "Sistema Lagunare Veneziano"
Ghrelin, an endogenous ligand for the growth hormone-secretagogue receptor, is expressed in the human adrenal cortex
No full textGhrelin is an endogenous ligand of the growth hormone secretagogue receptor (GHS-R), which was originally isolated from rat stomach. Ghrelin and GHS-R are also expressed in several peripheral tissues, including adrenal glands, and this prompted us to study ghrelin expression and ghrelin-binding site localization in the human adrenal cortex, and the possible effect of this peptide on corticosteroid-hormone secretion. Reverse transcription-polymerase chain reaction (RT-PCR) and radioimmune assay (RIA) showed sizeable expression of ghrelin mRNA and protein in six human adrenal cortexes. Autoradiography evidenced abundant [125I]ghrelin binding sites in the adrenal zona glomerulosa and outer zona fasciculata. However, ghrelin (10(-6) M) did not significantly affect either basal or agonist (ACTH and angiotensin-II)-stimulated early and late steps of steroid-hormone synthesis from adrenocortical slices (as measured by quantitative high pressure liquid chromatography). Since zona glomerulosa is the cambium layer involved in the growth maintenance of adrenal cortex, the present coupled RT-PCR, RIA and autoradiographic findings could suggest the involvement of ghrelin in the autocrine-paracrine regulation of human adrenal growth
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Adrenomedullin stimulates angiogenic response in cultured human vascular endothelial cells: Involvement of the vascular endothelial growth factor receptor 2
No full textIn recent years, evidence has accumulated that many endogenous peptides play an important regulatory role in angiogenesis by modulating endothelial cell behavior. Adrenomedullin (AM), one such factor, was previously shown to exert a clearcut proangiogenic effect in vitro when tested on specialized human endothelial cells, such as HUVECs and immortalized endothelial cell lines. In the present study we used normal adult vascular endothelial cells isolated from human saphenous vein to analyze in vitro the role of AM, related to both early (increased cell proliferation) and late (differentiation and self-organization into capillary-like structures) angiogenic events and their relationship with the vascular endothelial growth factor (VEGF) signaling cascade. The results indicated that also in this endothelial cell phenotype AM promoted cell proliferation and differentiation into cord-like structures. These actions resulted specific and were mediated by the binding of AM to its AM1 (CRLR/RAMP2) receptor. Neither the administration of a VEGF receptor 2 (VEGFR-2) antagonist nor the downregulation of VEGF production by gene silencing were able to suppress the proangiogenic effect of AM. However, when the experiments were performed in the presence of SU5416 (a selective inhibitor of the VEGFR-2 receptor at the level of the intra-cellular tyrosine kinase domain) the proangiogenic effect of AM was abolished. This result suggests that in vascular endothelial cells the binding of AM to its AM1 receptor could trigger a transactivation of the VEGFR-2 receptor, leading to a signaling cascade inducing proangiogenic events in the cells
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Evidence for a paracrine role of endogenous adrenomedullary galanin in the regulation of glucocorticoid secretion in the rat adrenal gland
No full textPrevious investigations have shown that rat adrenocortical cells are provided with galanin receptors, and galanin stimulates glucocorticoid secretion from dispersed cells. The present study aimed to clarify the possible role of galanin in the physiological regulation of rat adrenal secretory activity. Reverse transcription-polymerase chain reaction detected galanin mRNA expression in the adrenal medulla, but not in the cortex. Sizeable concentrations of galanin-immunoreactivity were measured by radioimmune assay only in the adrenomedullary tissue. Galanin raised norepinephrine, but not epinephrine, release from adrenomedullary tissue. Galanin immunoneutralization (obtained with concentrations of anti-galanin antibody able to block the galanin glucocorticoid secretagogue effect on dispersed adrenocortical cells) decreased basal corticosterone production from adrenal slices containing adrenomedullary tissue, without affecting that from dispersed adrenocortical cells. The beta-adrenoceptor antagonist l-alprenolol partially prevented galanin-stimulated corticosterone secretion from adrenal slices, without per se altering basal secretion. Taken together, our findings allow us to conclude that endogenous galanin, produced in adrenal medulla, is involved in the regulation of adrenocortical glucocorticoid secretion acting via a two-fold paracrine mechanism: i) direct activation of adrenocortical galanin receptors; and ii) stimulation of adrenomedullary release of catecholamines, which in turn activate beta-adrenoceptors located on adrenocortical cells
Two selective rat adrenomedullin (AM)-receptor antagonists: AM20-50 and AM24-50
No full textAdrenomedullin (AM) is a hypotensive peptide, which is produced in several organs and tissues, the functions of which it regulates in a autocrine-paracrine manner. Rat (r) and human (h) AM are 50- and 52-amino acid peptides, which differ for 2-amino acid deletions and six substitutions and contain a disulfide bridge-formed six-membered ring between adjacent cysteine residues in the 14 and 19 and 16 and 21 positions, respectively. The amidated C-terminal sequence is needed for AM to bind its receptors, and the ring structure (but not t he N-terminal sequence) seems to be required for AM to activate its receptors. Hence, we examined the effectiveness of some N-terminus and ring-lackingAM fragments as AM-receptor antagonists in the rat zona glomerulosa (ZG), whose cells are provided with abundant AM binding sites and display an AM-induced inhibition of K+-stimulated aldosterone secretion. Quantitative autoradiographic studies showed that cold rAMI-50, rAM20-50 and rAM24-50 displaced [125I]AM1-50 binding from rat ZG with the same potency and efficacy, which were significantly higher than those of hAM1-52, hAM22-52 and hAM26-52. Accordingly, rAM20-50 and rAM24-50 reversed the inhibitory effect of 10(-8) M rAMI-50 on aldosterone response of dispersed rat ZG cells to 10(-2) M K+ with significantly higher potency and efficacy than hAM22-52 and hAM26-52. Taken together, our findings confirm that CONH2-terminal AM fragments, lacking the six-membered ring structure, act as antagonists of AM receptors in the rat ZG. Moreover, they provide the first evidence that rAMI-50 and its fragments should be used in the investigations carried out in the rat
Cerebellin in the rat adrenal gland: gene expression and effects of CER and [der-Ser1]CER on the secretion and growth of cultured adrenocortical cells.
No full textCerebellin (CER) is a regulatory peptide, originally isolated from rat
cerebellum, which derives from the cleavage of precerebellin (Cbln), three types
of which (Cbln1-3) have been identified in humans and rats. CER is also expressed
in several extra-cerebellar tissues, including adrenal gland, and evidence has
been provided that CER exerts a modulatory action on human and rat adrenal gland.
Hence, we have investigated the expression of Cbln1-3 mRNAs and CER
protein-immunoreactivity (IR) in the various zones of rat adrenal glands, and the
effects of CER and its metabolite [des-Ser(1)]CER (des-CER) on the secretion and
growth of cultured rat adrenocortical cells. Reverse transcription-polymerase
chain reaction showed high and low expression of Cbln2 mRNA in zona glomerulosa
(ZG) and zona fasciculata-reticularis, respectively. Cbln1 was not expressed, and
Cbln3 mRNA was detected only in ZG. No Cbln expression was found in adrenal
medulla. Immunocytochemistry demonstrated the presence of CER-IR exclusively in
the adrenal cortex, the reaction being more intense in ZG. As expected, ACTH
(10(-8) M) markedly enhanced corticosterone secretion and lowered proliferation
rate of cultured adrenocortical cells. CER was ineffective, while des-CER exerted
an ACTH-like effect, but only at the lowest concentration (10(-10) M). Taken
together, these findings allow us to conclude that CER is expressed in rat
adrenal cortex, and to suggest that CER conversion to des-CER by endopeptidases
is needed for CER to exert its autocrine-paracrine regulatory functions
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