Somatostatin

Summary 1. Somatostatin (SRIF) exerts diverse physiological actions in the body including regulation of hormone and neurotransmitter release and neuronal firing activity. Analogs of SRIF are used clinically to treat tumors and cancers and to block the hypersecretion of growth hormone in acromegaly.2. The recent cloning of five SRIF receptor subtypes has allowed for the identification of the molecular basis of the cellular actions of SRIF. The ligand binding domains and regions involved in coupling to G proteins and cellular effector systems are being identified and the processes by which SRIF inhibits cell growth and proliferation are being established. Furthermore, subtype selective agonists have been generated which are being used to investigate the specific biological roles of each SRIF receptor subtypes.3. Such information will be useful in developing a new generation of SRIF drugs that could be employed to treat metabolic diseases, disorders of the gut, cancer and abnormalities in the central nervous system such as epilepsy and Alzheimer's disease.     

Changes in haemolymph octopamine levels associated with food deprivation in the locust, Schistocerca gregaria

ABSTRACT. Levels of octopamine in the haemolymph and locomotor activity have been measured over 24 h in fed and food-deprived adult male locusts, Schistocerca gregaria (Forskål). Locusts are predominantly diurnal, the locomotor activity of individuals with continuous access to food was higher during the photophase. The basal level of octopamine in haemolymph sampled during the first quarter of the light cycle was 7.8±1.1 pg/μl (51 nm). Depriving locusts of food at the start of the photophase for 9 h caused an increase in both the speed of movement and total activity compared to fed individuals. There was a corresponding increase in the haemolymph octopamine concentration which continued for as long as the insects were unable to feed, reaching a concentration of 20.7 ± 3.7 pg/μl (135 nM). While declining, the levels of octopamine remained higher in fed locusts for up to 4 h after replacing the food. The results are discussed in relation to the regulation of feeding behaviour and a proposed neurohormonal role of octopamine in insects.     

Inhibition of epinephrine and gonadotropic hormone induced ornithine decarboxylase activity by phenoxybenzamine in the testis of immature rat

The effect of α and β adrenergic receptor blockers on epinephrine and gonadotropic hormone induced ornithine decarboxylase (ODC) activity in the testis of immature rats was studied. Intratesticular injection with phenoxybenzamine at 15 min before treatment with epinephrine or gonadotropic hormones blocked ODC activity. Similar injection with propranolol or practolol had no effect on ODC activity. These results show that α adrenergic receptors are involved in the action of epinephrine and gonadotropic hormones in the testis.     

Accumulation of glycoprotein gonadotropin in the pituitary of juvenile rainbow trout in response to androgens and C21-steroids,including 11-steroids

Summary Effects of steroids on the accumulation of glycoprotein gonadotropin (GTH) in pituitaries of juvenile trout were investigated by means of scanning cytophotometry applied to immunocytochemical preparations, and with the use of a radioimmunoassay. Effects on other aspects of GTH-cell activity were analyzed by measuring the size of the gonadotrops and their nuclei.Progesterone added to aquarium water and methyltestosterone incorporated into the food showed a pronounced stimulatory effect on the accumulation of GTH. To a lesser extent, treatment with cortisol, cortisone, and desoxycorticosterone acetate administered to aquarium water, and 11-hydroxy-androstenedione added to the food resulted in an increase of the hypophysial content of GTH. Steroids stimulating the accumulation of GTH in the pituitary also exhibited a positive effect on GTH-cell activity as indicated by an increase in the size of gonadotropic cells. Progesterone incorporated into the food did not influence the GTH-content and the GTH-cell activity. It is suggested that the route of administration of an exogenous steroid is essential for its effect on GTH cells in trout.Comparison of GTH values reveals an excellent correlation between the data from the radioimmunoassay and those from the corresponding densitometric measurements. No correlation was observed between values of morphometrically determined GTH-cell activity and the densitometric values reflecting hypophysial GTH content.     

The effects of melatonin on neurohormonal regulation in cardiac cachexia: A mechanistic review

Heart failure (HF) is one of the prominent health concerns and its morbidity is comparable to many malignancies. Cardiac cachexia (CC), characterized by significant weight loss and muscle wasting, frequently occurs in progressive stage of HF. The pathophysiology of CC is multifactorial including nutritional and gastrointestinal alterations, immunological and neurohormonal activation, and anabolic/catabolic imbalance. Neurohormones are critically involved in the development of both HF and CC. Melatonin is known as an anti-inflammatory and antioxidant hormone. It seems that melatonin possibly regulates the neurohormonal signaling pathway related to muscle wasting in CC, but limited comprehensive data is available on the mechanistic aspects of its activity. In this, we reviewed the reports regarding the role of neurohormones in CC occurrence and possible activity of melatonin in modulation of HF and subsequently CC via neurohormonal regulation. In addition, we have discussed proposed mechanisms of action for melatonin considering its possible interactions with neurohormones. In conclusion, melatonin likely regulates the signaling pathways related to muscle wasting in CC by reducing tumor necrosis factor α levels and activating the gene expression of insulin-like growth factor-1. Also, this hormone inhibits the proteolytic pathway by inhibiting nuclear factor-κB (NF-κB), renin-angiotensin system and forkhead box protein O1 pathways and could increase protein synthesis by activating Akt and mammalian target of rapamycin. To elucidate the positive role of melatonin in CC and exact mechanisms related to muscle wasting more cellular and clinical trial studies are needed.     

SEROTONERGIC MODULATION OF BEHAVIOUR: A PHYLOGENETIC OVERVIEW

Serotonergic neurons are present in all phyla that possess nervous systems. In most of these phyla, serotonin modulates important behaviours, including feeding, sexual and aggressive behaviour. Serotonin exerts its effects by acting in three basic modes: as a classical neurotransmitter, as a neuromodulator, or as a neurohormone. In a number of invertebrate species, the neural circuitry underlying the effects of serotonin has been well characterized, whereas in vertebrates, the mechanisms by which serotonin affects behaviour are currently less fully understood. The following review examines the role played by serotonin in the generation and modulation of behaviour in successively more complex species, ranging from coelenterates to humans.     

大鼠垂体促性腺激素细胞内cAMP的改变对LHβ mRNA表达的影响

目的 分析大鼠LHβ mRNA表达的促性腺激素释放激素(GnRH)受体后信号转导机制.方法 将体外培养的大鼠腺垂体促性腺激素(GTH)细胞用cAMP的兴奋剂FSK或抑制剂SQ22536处理后,再用高频GnRH脉冲刺激,然后用实时荧光定量PCR法测定细胞LHβ mRNA的Ct值,并与空白组比较.结果 LHβ mRNA的Ct值随着GTH细胞cAMP含量的增高而显著降低,随着cAMP含量的降低而显著增高.结论 cAMP是高频GnRH脉冲刺激所引起的LHβ mRNA表达的受体后的信号转导途径.     

Structure-activity relationships of a pigment-dispersing crustacean neurohormone

This study evaluated the effects of N-terminal sequence deletion and of chemical modifications on the melanophore pigment dispersing activity of a crustacean neuropeptide (DRPH: Asn-Ser-Gly-Met-Ile-Asn-Ser-Ile-Leu-Gly-Ile-Pro-Arg-Val-Met-Thr-Glu-Ala-NH2). Sustained biological activity was not demonstrated by peptides smaller than the tridecapeptide DRPH (6-18). N-terminal extension of this peptide led to a steady increase in activity, with the DRPH (1-18) showing the maximum activity. Carboxyl group modification had no effect, but acetylation, oxidation, cyanogen bromide, and trypsin caused a decrease in activity. Phenylglyoxal modification of Arg-13 in DRPH led to a 14-fold increase in activity. It is concluded that the N-terminus and the methionine residues are important for full activity and that the phenylglyoxal-induced potentiation is due to protection of the peptide from proteolysis in vivo.     

Age-dependent response of adults of a homochrome grasshopper, Oedipoda miniata, to the dark-colour-inducing neurohormone (DCIN) of locusts

Abstract The effect of the dark-colour-inducing neurohormone (DCIN = [His⁷]-corazonin) of locusts was investigated in field-collected young and old adults of the grasshopper, Oedipoda miniata (Pallas) (Orthoptera: Acrididae). This species shows homochromy, but neither green-brown, nor phase-dependent colour polymorphism. By injecting graded doses of synthetic DCIN in 2 µL of olive oil, young adults were tested within a week of their last moult, and old adults 3.5 months later, a few weeks before natural termination of their reproductive summer diapause. Colour changes were followed for 28 days after injection. Darkening of the young adults was considerable, but their response to DCIN is more moderate than that of conspecific nymphs, by exhibiting a higher threshold, slower response and weaker maximal response. Old adults also show a clear effect, but their response is even slower and less marked than the response of the young adults. It is concluded that the response to DCIN decreases from nymphs to young adults and it is further decreasing with ageing of the adults.     

In Silico Analysis of Crustacean Hyperglycemic Hormone Family

Through multiple sequence alignment and phylogenetic analysis, the subgrouping of the crustacean hyperglycemic hormone (CHH) family was updated using the most complete, nonredundant sequence data set. All sequences from insects were clustered into a distinct subbranch with characters closer to CHH subfamily I. Several sequences that are controversial in their nomenclature and classification are discussed. The motif configuration of CHHs differs from that of molt-inhibiting hormone or gonad-inhibiting hormone in both N and C termini. These two motifs approach each other in tertiary structure models, and the motif preference reveals the critical roles of these regions in functional specificity. Two types of exon organizations of the CHH family genes were observed. Four-exon Chh genes were found in a wide range of pan-crustacean (crustacean and hexapod) taxa, except for the penaeid species, from which the 3-exon Chh genes were reported. Meanwhile, the 3-exon structure was found in the Mih gene and Moih genes from one brachyuran species. Combining gene scan skill and exon splicing rules found in this study, we define three more novel sequences from two insect genomes. The pattern of the exon-exon junction within the mature peptide segment is preserved in all CHH family members.The authors wish it to be known that, in their opinion, the first two authors should be regarded as joint first authors.