A simple and very efficient method for generating cDNA libraries

5-Noncoding sequences have been tabulated for 211 messenger RNAs from higher eukaryotic cells. The 5'-proximal AUG triplet serves as the initiator codon in 95% of the mRNAs examined. The most conspicuous conserved feature is the presence of a purine (most often A) three nucleotides upstream from the AUG initiator codon; only 6 of the mRNAs in the survey have a pyrimidine in that position. There is a predominance of C in positions -1, -2, -4 and -5, just upstream from the initiator codon. The sequence CCAGCCAUG (G) thus emerges as a consensus sequence for eukaryotic initiation sites. The extent to which the ribosome binding site in a given mRNA matches the -1 to -5 consensus sequence varies: more than half of the mRNAs in the tabulation have 3 or 4 nucleotides in common with the CCACC consensus, but only ten mRNAs conform perfectly.

Compilation and analysis of sequences upstream from the translational start site in eukaryotic mRNAs

Small synthetic molecules called growth hormone secretagogues (GHSs) stimulate the release of growth hormone (GH) from the pituitary. They act through the GHS-R, a G protein-coupled receptor whose ligand has only been discovered recently. Using a reverse pharmacology paradigm with a stable cell line expressing GHS-R, we purified an endogenous ligand for GHS-R from rat stomach and named it "ghrelin," after a word root ("ghre") in Proto-Indo-European languages meaning "grow." Ghrelin is a peptide hormone in which the third amino acid, usually a serine but in some species a threonine, is modified by a fatty acid; this modification is essential for ghrelin's activity. The discovery of ghrelin indicates that the release of GH from the pituitary might be regulated not only by hypothalamic GH-releasing hormone, but also by ghrelin derived from the stomach. In addition, ghrelin stimulates appetite by acting on the hypothalamic arcuate nucleus, a region known to control food intake. Ghrelin is orexigenic; it is secreted from the stomach and circulates in the bloodstream under fasting conditions, indicating that it transmits a hunger signal from the periphery to the central nervous system. Taking into account all these activities, ghrelin plays important roles for maintaining GH release and energy homeostasis in vertebrates.

https://www.physiology.org/doi/pdf/10.1152/physrev.00012.2004

Ghrelin: Structure and Function

Prolactin is a protein hormone of the anterior pituitary gland that was originally named for its ability to promote lactation in response to the suckling stimulus of hungry young mammals. We now know that prolactin is not as simple as originally described. Indeed, chemically, prolactin appears in a multiplicity of posttranslational forms ranging from size variants to chemical modifications such as phosphorylation or glycosylation. It is not only synthesized in the pituitary gland, as originally described, but also within the central nervous system, the immune system, the uterus and its associated tissues of conception, and even the mammary gland itself. Moreover, its biological actions are not limited solely to reproduction because it has been shown to control a variety of behaviors and even play a role in homeostasis. Prolactin-releasing stimuli not only include the nursing stimulus, but light, audition, olfaction, and stress can serve a stimulatory role. Finally, although it is well known that dopamine of hypothalamic origin provides inhibitory control over the secretion of prolactin, other factors within the brain, pituitary gland, and peripheral organs have been shown to inhibit or stimulate prolactin secretion as well. It is the purpose of this review to provide a comprehensive survey of our current understanding of prolactin's function and its regulation and to expose some of the controversies still existing.

/pdf/prolactin-structure-function-and-regulation-of-secretion-3w4x6fqbg3.pdf

Prolactin: Structure, Function, and Regulation of Secretion

Isolation of a novel 38 residue-hypothalamic polypeptide which stimulates adenylate cyclase in pituitary cells

A peptide has been isolated from ovine hypothalamus which, at 1 x 10(-9)M, inhibits secretion in vitro of immunoreactive rat or human growth hormones and is similarly active in vivo in rats. Its structure is H-Ala-Gly-Cys-Lys-Asn-Phe-Phe-Trp-Lys-Thr-Phe-Thr-Ser-Cys-OH The synthetic replicate is biologically active.

https://science.sciencemag.org/content/sci/179/4068/77.full.pdf

Hypothalamic Polypeptide That Inhibits the Secretion of Immunoreactive Pituitary Growth Hormone

A 44 amino acid peptide with growth hormone-releasing activity has been isolated from a human tumor of the pancreas that had caused acromegaly. The primary structure of the tumor-derived peptide is H-Tyr-Ala-Asp-Ala-Ile-Phe-Thr-Asn-Ser-Tyr-Arg-Lys-Val-Leu-Gly-Gln-Leu-Ser- Ala- Arg-Lys-Leu-Leu-Gln-Asp-Ile-Met-Ser-Arg-Gln-Gln-Gly-Glu-Ser-Asn-Gln-Glu-Ar g-Gly -Ala-Arg-Ala-Arg-Leu-NH2. The synthetic replicate has full biological activity in vitro and in vivo specifically to stimulate the secretion of immunoreactive growth hormone. The tumor-derived peptide is identical in biological activity and similar in physiochemical properties to the still uncharacterized growth hormone-releasing factor present in extracts of hypothalamic tissues.

https://science.sciencemag.org/content/sci/218/4572/585.full.pdf

Growth hormone-releasing factor from a human pancreatic tumor that caused acromegaly.

Somatostatin, a tetradecapeptide isolated from ovine hypothalamic extracts on the basis of its ability to inhibit the spontaneous secretion of growth hormone (GH) by pituitary cell cultures, has been found to inhibit the stimulated secretion of thyrotropin (TSH) mediated by TRF(pGlu-His- Pro-NH2), 10 × [K†], or theophylline in vitro, while having no effect on the secretion of luteinizing hormone (LH) due to LRF. The spontaneous release of PRL in vitro is also inhibited by somatostatin but to a lesser extent than is the spontaneous secretion of GH. In vivo, the TRF-triggered secretion of TSH but not of PRL is suppressed by somatostatin in the estrogen-progesteronepretreated male rat. The injection of TRF leads to a greater rise in both plasma TSH and PRL in estrogen-progesterone-pretreated male rats than in untreated male rats. Somatostatin acts rapidly but reversibly to inhibit the secretion of TSH due to TRF in a dose-dependent manner. Thyroid hormones and somatostatin exhibit summation in their inhibiti...

Effects of Somatostatin on the Secretion of Thyrotropin and Prolactin

The concept of a hypothalamic neurohumoral control for anterior pituitary secretion postulates the existence of a growth hormone-releasing factor (GRF) of neuronal origin that stimulates the pituitary gland to release growth hormone (GH). Such a compound has not yet been isolated and characterized from the brain, although there is extensive physiological and biochemical evidence for its existence (reviewed in ref. 2). However, a 44-amino-acid amidated peptide having the physiological properties of GRF as well as chemical similarities was recently isolated from a human pancreatic tumour that had caused acromegaly. Two shorter biologically active fragments of 40 and 37 residues were also isolated. The synthetic replicates of these human pancreas GRF (hpGRF) peptides specifically stimulate GH release in vitro and in vivo. Assuming similarity or identity between the putative hypothalamic GRF and the tumour-derived hpGRF, we have used immunohistochemistry to search for hpGRF-like immunoreactivity in the brain. We report here that antisera against the hpGRF1-40 peptide specifically stain neuronal cell bodies in the arcuate nucleus of the primate hypothalamus, with fibres projecting to the median eminence and ending in contact with portal vessels. This topography is characteristic of a neuronal system elaborating a releasing factor. These results provide evidence that hypothalamic GRF is very similar, if not identical, to hpGRF.

Paul Brazeau

Papers

Hypothalamic Polypeptide That Inhibits the Secretion of Immunoreactive Pituitary Growth Hormone

Growth hormone-releasing factor from a human pancreatic tumor that caused acromegaly.

Effects of Somatostatin on the Secretion of Thyrotropin and Prolactin

Immunohistochemical detection of growth hormone-releasing factor in brain

Physiological roles of somatocrinin and somatostatin in the regulation of growth hormone secretion.