Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P01189 (beta-endorphin)
 21,003 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Melanin was measured by a spectrophotofluorometric method in the brains of albino rats from birth to 20 months of age. The concentration of brain melanin increased from Day 1 until adult levels were reached at 1 month. Between 1 and 20 months of age no significant differences were found in brain melanin. Daily injections of alpha-MSH, MIF-I, melatonin, or diluent did not consistently alter the concentration of brain melanin and a high (40%) protein diet did not appear to increase it. After concurrent injections of alpha-MSH and theophylline, an initial elevation of the level of melanin in the brain of newborn rats was found beginning at Day 8 but by age 1 month the values had returned to control levels. The results show that the largest changes in the concentrations of melanin in the brains of rats occur with age during the first month after birth.
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PMID:Rat brain melanin at different ages and after various treatments. 52 60

Melanin was measured in various parts of the rat brain by a spectrophotofluorometric assay. This method could detect natural, Sepia melanin as well as melanin synthesized from L-DOPA. Contrary to published expectations of other investigators, measurable amounts of melanin were found in the brain of albino as well as pigmented rats. The highest concentrations of melanin occurred in the pons-medulla and midbrain, but all regions within the blood-brain barrier contained greater concentrations than samples from many other tissues in the body. No significant change in the melanin content was found after various endocrine manipulations such as removal of the pituitary, pineal, adrenals, thyroid, testes, or ovaries, exposure to constant illumination or darkness, and daily injection for 5 weeks of alpha-MSH, Pro-Leu-Gly-NH2 (MIF-I) or melatonin. As expected, retinal tissue from black-hooded rats contained extremely high levels of melanin whereas that from albino rats contained no melanin. It is thought that the presence of melanin in the brain of albino and pigmented rats may have a function which is still unknown.
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PMID:Melanin in the rat brain. 102 Dec 12

The secretion of most pituitary hormones is under the control of feedback mechanisms. The feedback control of alpha-melanophore-stimulating hormone (alpha-MSH) from melanotrope cells is controversial. The possible existence of an autofeedback exerted by alpha-MSH or other POMC-derived peptides on melanotrope cells of the amphibian Xenopus laevis has been investigated. alpha-MSH or its potent agonist 4-norleucine,7-D-phenylalanine-alpha-MSH has no effect on the release of radiolabeled POMC-derived peptides or immunoreactive beta-endorphin from superfused neurointermediate pituitary lobes. Melanin concentrating hormone, previously reported to have an alpha-MSH-like effect on melanophores, did not affect alpha-MSH secretion. Neurointermediate lobe superfusate, which contains a mixture of POMC-derived peptides, failed to affect the secretory activity of melanotropes. It is concluded that in X. laevis the secretory activity of melanotropes is not under the control of short-term autofeedback mechanisms involving alpha-MSH or other POMC-derived peptides.
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PMID:Analysis of autofeedback mechanisms in the secretion of pro-opiomelanocortin-derived peptides by melanotrope cells of Xenopus laevis. 133 Aug 8

Administration of monosodium glutamate (MSG) in the neonatal period renders the rat to be alpha-MSH deficient later in life. In this study rats received MSG in their neonatal period and were examined at the age of 60 days. alpha-MSH caused hypothermia, potentiated induced hypothermia, blocked paradoxical behavioral thermoregulation, improved performance in the Morris water tank, but had no effect on pain threshold. Melanin only caused an increase in pain threshold. It is suggested that the differential effect of alpha-MSH and melanin is governed by the dopaminergic system.
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PMID:The facilitative effects of alpha-MSH and melanin on learning, thermoregulation, and pain in neonatal MSG-treated rats. 168 21

Melanin concentrating hormone (MCH) is a key neuroendocrine peptide which is involved in the regulation of body color in teleost fish. Antigenically similar peptides exist in higher vertebrates including rodents and man. The precise function(s) of these peptides in these higher vertebrates has yet to be fully elucidated, although regulatory roles in stress-induced or corticotropin-releasing hormone-stimulated ACTH release and/or water balance have been proposed. The salmon, rat, and human MCH cDNA clones have been isolated and sequenced. We isolated and characterized the structure of the rat MCH gene. In addition to providing the complete nucleotide sequence of this gene, we demonstrate that there is a single copy of this gene in the rat genome. The structure of the rat MCH gene indicates that the MCH mRNA is encoded by three exons. Using primer extension and RNase protection assays, the transcriptional start sites of hypothalamic MCH mRNA were determined, allowing us to define the promoter region of this gene. We also characterize the central nervous system distribution of expression of the MCH gene by Northern blot analysis, demonstrating that the MCH mRNA is found predominantly if not exclusively within the hypothalamus.
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PMID:Nucleotide sequence and tissue-specific expression of the rat melanin concentrating hormone gene. 226 Oct 81

Melanin concentrating hormone (MCH) is a heptadecapeptide, Asp-Thr-Met-Arg-Cys-Met-Val-Gly-Arg-Val-Tyr-Arg-Pro-Cys-Trp-Glu-Val, which is synthesized in the hypothalamus and secreted by the neurohypophysis of teleost fishes. This hormone exhibits both MCH-like as well as alpha-MSH (alpha-melanocyte stimulating hormone) like activity. We have examined the role of the disulfide bond for the two contrasting melanotropic activities of MCH. Nine analogues of the parent peptide were synthesized and characterized for biological activity. The disulfide ring was contracted from the 5-14 to the 7-14, 8-14, and 10-14 residues with concomitant substitution of alanine for Cys at position 5 in each of the heptadecapeptides. Similar substitutions were made in a series of MCH analogues. In addition, the following cyclic peptides also were synthesized: [Cys7]MCH, [Cys8]MCH, and [Cys10]MCH. The fish-skin bioassay is sensitive to MCH at a concentration of 10(-12) M. All ring-contracted analogues were inactive at 10(-6) M or lower concentrations; less than 1/1,000,000 compared to MCH (1.0) except [Ala5,Cys8]MCH (0.0008; 1/1250), [Cys10]MCH (0.000 09; 1/10,000), and [Cys8]MCH (0.000 001; 1/1,000,000). In the frog-skin bioassay, [Ala5,Cys10]MCH, although lacking MCH-like activity in the fish-skin bioassay, was equipotent to MCH in its alpha-MSH-like component of activity. Most other analogues were either inactive or much less active than MCH in stimulating melanosome dispersion. These results demonstrate that the disulfide bond between positions 5 and 14 is essential for the MCH-like activity since contraction of the ring generally leads to inactive peptides. Contraction of the disulfide bridge does not, however, have as great an effect on the MSH-like activity of MCH.
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PMID:Melanin concentrating hormone analogues: contraction of the cyclic structure. 1. Agonist activity. 325 25

Melanin is specifically produced in melanocytes. The pathway for melanin biosynthesis is regulated by a number of melanocyte-specific proteins, including tyrosinase and tyrosinase-related protein-1 (TRP-1, b locus protein). To understand the regulation of melanogenesis, we examined tyrosinase activities, mRNA levels of tyrosinase and TRP-1, and eumelanin and pheomelanin contents in mouse B16-F1 melanoma cells after they had been treated with some melanotropic reagents. Cholera toxin, alpha-melanocyte-stimulating hormone, and dibutyryl cyclic AMP increased tyrosinase activity and stimulated eumelanin biosynthesis. These reagents elevated intracellular cAMP levels. In contrast, 12-O-tetradecanoylphorbol 13-acetate reduced tyrosinase activity and eumelanin synthesis. In all cases, the mRNA levels of tyrosinase and TRP-1 changed in parallel with tyrosinase activity and eumelanin content. TRP-1 was induced simultaneously with tyrosinase, although its inducibility was lower than that of tyrosinase. These results suggest that the expressions of tyrosinase and TRP-1 genes are coordinately regulated by melanotropic reagents through cAMP-dependent protein kinase and protein kinase C in mouse B16-F1 cells, and that their coordinate expression causes eumelanin biosynthesis.
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PMID:Eumelanin biosynthesis is regulated by coordinate expression of tyrosinase and tyrosinase-related protein-1 genes. 768 98

A case of carcinoid tumor of the lung with focal melanin production was encountered in a 56 year old Japanese woman. The tumor was found 16 years previously by mass survey chest X-ray and had enlarged two-fold in the intervening period. The tumor consisted of a variety of tumor cells showing a spindle, polygonal and pleomorphic appearance with abundant vasculature in the stroma. All tumor cells showed argyrophilia, together with a few showing argentaffinity. Melanin-containing tumor cells were also present in parts. Ultrastructurally, most tumor cells possessed various numbers of neurosecretory granules and a few of them contained granular type melanosomes. Tumor cells were connected with desmosomes and a few of them contained tonofilament-like microfilaments. Only a few contained both neurosecretory granules and melanin. By immunohistochemistry, serotonin, met-enkephalin and beta-endorphin positive cells were observed scattered throughout the tumor. A few tumor cells positive for tyrosine hydroxylase were also detected. Additionally, most tumor cells were positive for keratin. On the basis of these findings, the tumor of the current case is a pulmonary carcinoid tumor with focal melanin production.
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PMID:Peripheral carcinoid tumor of the lung with focal melanin production. 804 98

Using antibodies that recognize either tyrosinase, tyrosinase-related protein-1 (TRP1), or tyrosinase-related protein-2 (TRP2, DOPAchrome tautomerase), the quantities of those melanogenic enzymes were analyzed in five melanoma cell lines that possess various degrees of melanin production. All cells except JB/MS-W increased melanin production four to 30 times after 4 d of melanocyte-stimulating hormone (MSH) treatment. Melanin production by JB/MS-W cells was always under background, with or without MSH treatment. There was a positive correlation between quantities and synthetic rates of those melanogenic enzymes and their melanin formation or DOPAchrome tautomerase activities. The activity of a heat-resistant melanogenic inhibitory factor was also analyzed. The results showed, surprisingly, that pigmented cells showed higher levels of melanogenic inhibitors activity. Tyrosinase activity was increased dramatically whereas the level of melanogenic inhibitor was remarkably decreased following MSH treatment. Interestingly, melanogenic inhibitor derived from JB/MS-W cells suppressed not only tyrosinase but also DOPAchrome tautomerase, another enzyme functional in melanin production. These results clearly suggest that melanin production is regulated by a subtle balance between the activities of these enzymes and other factors such as the melanogenic inhibitor.
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PMID:Pigment production in murine melanoma cells is regulated by tyrosinase, tyrosinase-related protein 1 (TRP1), DOPAchrome tautomerase (TRP2), and a melanogenic inhibitor. 842 35

The role of leptin and its receptor on the regulation of appetite and body fat was summarized. Leptin directly exerts its anorexigenic effects on arcuate nucleus via proopiomelanocortin and neuropeptide Y neurons. The anorexia and sympathetic nerve activation result in the reduction of body fat. But physiological concentrations of leptin could not reduce body fat in obese people, while genetic loss of central leptin effects induces obesity in children. Melanin concentrating hormone, orexin, and corticotropin-releasing hormone may be directly regulated by leptin. Serotonergic neurons may be separate from leptin effects. Phosphorylation of 985- and 1138-tyrosine of long-form leptin receptor activates SHP-2 and STAT3, respectively. Soluble leptin receptor concentrations in serum are negatively correlated with BMI. Clinical usefulness of leptin is now in progress.
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PMID:[Role of leptin and its receptor in the regulation of appetite and body fat]. 1126 87


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