Genomic structure and transcriptional regulation of grass carp calmodulin gene

A fish calmodulin (CaM) gene was characterized for the first time in grass carp. The CaM gene is about 12-Kb in size with identical intron/exon organization as that of mammalian CaM genes. When compared to mammalian counterparts, the 5′-promoter region of grass carp CaM gene contains a TATA box and has a much lower GC content and CpG dinucleotide frequency. Interestingly, the 5′-promoter of carp CaM gene is AT-rich with multiple IRS elements and putative binding sites for Pit-1, Sp1/Sp3 and AP1. Using luciferase reporter assay, a potent silencer region was identified in the distal region of grass carp CaM promoter. Besides, the CaM promoter activity could be upregulated by IGF but suppressed by PACAP, forskolin and over-expression of Sp1 and Sp3. These findings, taken together, indicate that grass carp CaM gene does not exhibit the typical features of housekeeping genes and its expression is under the control of hormone factors, presumably by coupling with the appropriate signaling pathways/transcription factors.postprin

Neurokinin B and reproductive functions: 'KNDy neuron' model in mammals and the emerging story in fish

In mammals, neurokinin B (NKB), the gene product of the tachykinin family member TAC3, is known to be a key regulator for episodic release of luteinizing hormone (LH). Its regulatory actions are mediated by a subpopulation of kisspeptin neurons within the arcuate nucleus with co-expression of NKB and dynorphin A (commonly called the 'KNDy neurons'). By forming an 'autosynaptic feedback loop' within the hypothalamus, the KNDy neurons can modulate gonadotropin-releasing hormone (GnRH) pulsatility and subsequent LH release in the pituitary. NKB regulation of LH secretion has been recently demonstrated in zebrafish, suggesting that the reproductive functions of NKB may be conserved from fish to mammals. Interestingly, the TAC3 genes in fish not only encode the mature peptide of NKB but also a novel tachykinin-like peptide, namely NKB-related peptide (or neurokinin F). Recent studies in zebrafish also reveal that the neuroanatomy of TAC3/kisspeptin system within the fish brain is quite different from that of mammals. In this article, the current ideas of 'KNDy neuron' model for GnRH regulation and steroid feedback, other reproductive functions of NKB including its local actions in the gonad and placenta, the revised model of tachykinin evolution from invertebrates to vertebrates, as well as the emerging story of the two TAC3 gene products in fish, NKB and NKB-related peptide, will be reviewed with stress on the areas with interesting questions for future investigations.postprin

Novel pituitary actions of TAC3 gene products in fish model: Receptor specificity and signal transduction for prolactin and somatolactin α regulation by neurokinin B (NKB) and NKB-related peptide in carp pituitary cells

TAC3 is a member of tachykinins, and its gene product neurokinin B (NKB) has recently emerged as a key regulator for LH through modulation of kisspeptin/GnRH system within the hypothalamus. In fish models, TAC3 not only encodes NKB but also a novel tachykinin-like peptide called NKB-related peptide (NKBRP), and the pituitary actions of these TAC3 gene products are still unknown. Using grass carp as a model, the direct effects and postreceptor signaling for the 2 TAC3 products were examined at the pituitary level. Grass carp TAC3 was cloned and confirmed to encode NKB and NKBRP similar to that of other fish species. In carp pituitary cells, NKB and NKBRP treatment did not affect LH release and gene expression but up-regulated prolactin (PRL) and somatolactin (SL)α secretion, protein production, and transcript expression. The stimulation by these 2 TAC3 gene products on PRL and SLα release and mRNA levels were mediated by pituitary NK2 and NK3 receptors, respectively. Apparently, NKB- and NKBRP-induced SLα secretion and transcript expression were caused by adenylate cyclase/cAMP/protein kinase A, phospholipase C/inositol 1,4,5-triphosphate/protein kinase C and Ca(2+)/calmodulin/Ca(2+)/calmodulin-dependent protein kinase II activation. The signal transduction for the corresponding responses on PRL release and mRNA expression were also similar, except that the protein kinase C component was not involved. These findings suggest that the 2 TAC3 gene products do not play a role in LH regulation at the pituitary level in carp species but may serve as novel stimulators for PRL and SLα synthesis and secretion via overlapping postreceptor signaling mechanisms coupled to NK2 and NK3 receptors, respectively.postprin

Novel functional role of NK3R expression in the potentiating effects on somatolactin α autoregulation in grass carp pituitary cells

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Activin/follistatin system in grass carp pituitary cells: Regulation by local release of growth hormone and luteinizing hormone and its functional role in growth hormone synthesis and secretion

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Dual role of insulin in spexin regulation: Functional link between food intake and spexin expression in fish model

Spexin (SPX), a neuropeptide discovered by the bioinformatics approach, has been recently identified as a satiety factor in a fish model. However, the functional link between feeding and SPX expression as well as the signal transduction for SPX regulation are totally unknown. In this study, we used goldfish as a model to examine the functional role of insulin as a postprandial signal for SPX regulation in bony fish. In goldfish, feeding could elevate plasma levels of glucose, insulin, and SPX with concurrent rises in insulin and SPX messenger RNA (mRNA) expression in the liver. Similar elevation in SPX mRNA level was also observed in the liver and brain areas involved in appetite control in goldfish after intraperitoneal injection of glucose and insulin, respectively. In parallel experiments with goldfish hepatocytes and brain cell culture, insulin signal induced by glucose was shown to exert a dual role in SPX regulation, namely (1) acting as an autocrine/paracrine signal to trigger SPX mRNA expression in the liver and (2) serving as an endocrine signal to induce SPX gene expression in the brain. Apparently, the peripheral (in the liver) and central actions of insulin (in the brain) on SPX gene expression were mediated by insulin receptor (to a lesser extent by insulin-like growth factor I receptor) coupled to mitogen-activated protein kinase kinase 3/6/p38 mitogen-activated protein kinase and phosphatidylinositol 3-kinase/Akt/mammalian target of rapamycin but not mitogen-activated protein kinase kinase 1/2/extracellular signal-regulated kinase 1/2 cascades. Our findings indicate that an insulin component inducible by glucose is present in the liver of the fish model and may serve as the postprandial signal linking food intake with SPX expression both in the central as well as at the hepatic level.postprin

Pituitary adenylate cyclase activating polypeptide as a novel hypophysiotropic factor in fish

Pituitary adenylate cyclase activating polypeptide (PACAP) is a novel member of the secretin-glucagon peptide family. In mammals, this peptide has been located in a wide range of tissues and is involved in a variety of biological functions. In lower vertebrates, especially fish, increasing evidence suggests that PACAP may function as a hypophysiotropic factor regulating pituitary hormone secretion. PACAP has been identified in the brain-pituitary axis of representative fish species. The molecular structure of fish PACAP is highly homologous to mammalian PACAP. The prepro-PACAP in fish, however, is distinct from that of mammals as it also contains the sequence of fish GHRH. In teleosts, the anterior pituitary is under direct innervation of the hypothalamus and PACAP nerve fibers have been identified in the pars distalis. Using the goldfish as a fish model, mRNA transcripts of PACAP receptors, namely the PAC1 and VPAC1 receptors, have been identified in the pituitary as well as in various brain areas. Consistent with the pituitary expression of PACAP receptors, PACAP analogs are effective in stimulating growth hormone (GH) and gonadotropin (GTH)-II secretion in the goldfish both in vivo and in vitro. The GH-releasing action of PACAP is mediated via pituitary PAC1 receptors coupled to the adenylate cyclase-cAMP-protein kinase A and phospholipase C-IP3-protein kinase C pathways. Subsequent stimulation of Ca 2+ entry through voltage-sensitive Ca 2+ channels followed by activation of Ca 2+-calmodulin protein kinase II is likely the downstream mechanism mediating PACAP-stimulated GH release in goldfish. Although the PACAP receptor subtype(s) and the associated post-receptor signaling events responsible for PACAP-stimulated GTH-II release have not been characterized in goldfish, these findings support the hypothesis that PACAP is produced in the hypothalamus and delivered to the anterior pituitary to regulate GH and GTH-II release in fish.published_or_final_versio

Signal transduction mechanisms mediating secretion in goldfish gonadotropes and somatotropes

The intracellular signal transduction mechanisms mediating maturational gonadotropin and somatotropin secretion in goldfish are reviewed. Several major signaling mechanisms, including changes in intracellular [Ca2+], arachidonic acid cascades, protein kinase C, cyclic AMP/protein kinase A, calmodulin, nitric oxide, and Na+/H+ antiport, are functional in both cell types. However, their relative importance in mediating basal secretion and neuroendocrine-factor-regulated hormone release differs according to cell type. Similarly, agonist- and cell-type-specificity are also present in the transduction pathways leading to neuroendocrine factor-modulated maturational gonadotropin and somatotropin release. Specificity is present not only in the actions of different regulators within the same cell type and with the same ligand in the two cell types, but this also exists between isoforms of the same neuroendocrine factor within a single cell type. Other evidence suggests that function-selectivity of signaling may also result from differential modulation of Ca2+ fluxes from different sources. The interaction of different second messenger systems provide the basis by which regulation of maturational gonadotropin and somatotropin release by multiple neuroendocrine factors can be integrated at the target cell level.published_or_final_versio

Factors associated with spontaneous stone passage in a contemporary cohort of patients presenting with acute ureteric colic. Results from the MIMIC Study (A Multi-centre cohort study evaluating the role of Inflammatory Markers in patients presenting with acute ureteric Colic)

Objectives There is conflicting data on the role of white blood cell count (WBC) and other inflammatory markers in spontaneous stone passage in patients with acute ureteric colic. The aim of the study was to assess the relationship of WBC and other routinely collected inflammatory and clinical markers including stone size, stone position and Medically Expulsive Therapy use (MET) with spontaneous stone passage (SSP) in a large contemporary cohort of patients with acute ureteric colic. Subjects and Methods Multi‐centre retrospective cohort study coordinated by the British Urology Researchers in Surgical Training (BURST) Research Collaborative at 71 secondary care hospitals across 4 countries (United Kingdom, Republic of Ireland, Australia and New Zealand). 4170 patients presented with acute ureteric colic and a computer tomography confirmed single ureteric stone. Our primary outcome measure was SSP as defined by the absence of need for intervention to assist stone passage. Multivariable mixed effects logistic regression was used to explore the relationship between key patient factors and SSP. Results 2518 patients were discharged with conservative management and had further follow up with a SSP rate of 74% (n = 1874/2518). Sepsis after discharge with conservative management was reported in 0.6% (n = 16/2518). On multivariable analysis neither WBC, Neutrophils or CRP were seen to predict SSP, with an adjusted OR of 0.97 [95% CI 0.91 to 1.04, p = 0.38], 1.06 [95% CI 0.99 to 1.13, p = 0.1] and 1.00 [95% CI 0.99 to 1.00, p = 0.17], respectively. Medical expulsive therapy (MET) also did not predict SSP [adjusted OR 1.11 [95% CI 0.76 to 1.61]). However, stone size and stone position were significant predictors. SSP for stones 7mm. For stones in the upper ureter the SSP rate was 52% [95% CI 48 to 56], middle ureter was 70% [95% CI 64 to 76], and lower ureter was 83% [95% CI 81 to 85]. Conclusion In contrast to the previously published literature, we found that in patients with acute ureteric colic who are discharged with initial conservative management, neither WBC, Neutrophil count or CRP help determine the likelihood of spontaneous stone passage. We also found no overall benefit from the use of MET. Stone size and position are important predictors and our findings represent the most comprehensive stone passage rates for each mm increase in stone size from a large contemporary cohort adjusting for key potential confounders. We anticipate that these data will aid clinicians managing patients with acute ureteric colic and help guide management decisions and the need for intervention