Biological signals最新文献

{"title":"Electrophysiological studies of pineal photoreception in the pioneering early 60s.","authors":"Y Morita","doi":"10.1159/000109127","DOIUrl":"https://doi.org/10.1159/000109127","url":null,"abstract":"","PeriodicalId":9265,"journal":{"name":"Biological signals","volume":"6 4-6","pages":"181-3"},"PeriodicalIF":0.0,"publicationDate":"1997-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1159/000109127","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20424801","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Melatonin inhibits GnRH-induced Ca2+ mobilization and influx through voltage-regulated channels.","authors":"O Slanar,&nbsp;H Zemkova,&nbsp;J Vanecek","doi":"10.1159/000109139","DOIUrl":"https://doi.org/10.1159/000109139","url":null,"abstract":"<p><p>In neonatal rat gonadotrophs, melatonin acts through the high-affinity membrane-bound receptors to inhibit GnRH-induced [Ca2+]i increase. GnRH increases [Ca2+]i primarily by mobilization from the inositol trisphosphate-sensitive pool followed by Ca2+ influx through the voltage-sensitive channels. Melatonin inhibits the GnRH-induced [Ca2+]i increase. When added after the GnRH-induced spike, melatonin decreases [Ca2+]i in 52% of the gonadotrophs. The effect of melatonin is dependent on extracellular Ca2+ and may be mimicked by Ca2+-free medium or verapamil. When added before GnRH, melatonin inhibits the [Ca2+]i spike. This effect of melatonin is independent of extracellular Ca2+ as it persists in Ca2+-free medium. These findings indicate that melatonin blocks Ca2+ mobilization as well as Ca2+ influx in the gonadotrophs.</p>","PeriodicalId":9265,"journal":{"name":"Biological signals","volume":"6 4-6","pages":"284-90"},"PeriodicalIF":0.0,"publicationDate":"1997-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1159/000109139","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20425801","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Differential behaviour of cell membranes towards iron-induced oxidative damage and the effects of melatonin.","authors":"P L Tang,&nbsp;M F Xu,&nbsp;Z M Qian","doi":"10.1159/000109140","DOIUrl":"https://doi.org/10.1159/000109140","url":null,"abstract":"<p><p>The ability of melatonin to protect iron-induced lipid peroxidation was studied in various rat cell membranes. The concentration of cellular membrane malondialdehyde (MDA) was used as an index of induced oxidative membrane damage. Cell membranes from the brain, heart, kidney and liver of the male Sprague-Dawley rat were incubated with ferric ammonium citrate (20 microg/ml iron) alone for 3 h and concomitant with varying concentrations of melatonin ranging from 125 to 2,000 microM. The basal MDA levels of all the cell membranes were 25.0+/-1.4 (brain), 21.2+/-0.2 (heart), 10.0+/-0.9 (kidney) and 20.7+/-0.4 (liver) microM/g membrane protein, and the highest lipid peroxidation after exposure to iron occurred in the kidney (314.4%), followed by the heart (151.3%), the liver (130.4%) and the brain (121.7%). This peroxidative effect was completely (ED50 846.7 microM for the heart) and partially suppressed by melatonin (ED50 462.1 microM for the brain, 178.3 microM for the kidney and 886.6 microM for the liver). This inhibition effect on MDA production by these cell membranes was also found - except for the liver - if melatonin was used alone. These results show that the direct effect of lipid peroxidation on cellular membrane following iron exposure is markedly reduced by melatonin.</p>","PeriodicalId":9265,"journal":{"name":"Biological signals","volume":"6 4-6","pages":"291-300"},"PeriodicalIF":0.0,"publicationDate":"1997-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1159/000109140","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20425804","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Melatonin receptors in the spinal cord.","authors":"S. Pang, Q. Wan, Gregory M. Brown","doi":"10.1159/000109138","DOIUrl":"https://doi.org/10.1159/000109138","url":null,"abstract":"The pineal hormone, melatonin, plays an important role in the regulation of diurnal and seasonal rhythms in animals. In addition to the well established actions on the brain, the possibility of a direct melatonin action on the spinal cord has to be considered. In our laboratory, we have obtained data suggesting that melatonin receptors are present in the spinal cords of birds and mammals. Using radioreceptor binding and quantitative autoradiography assays with 2-[125I]iodomelatonin as the specific melatonin agonist, melatonin binding sites have been demonstrated in the rabbit and chicken spinal cords. These sites are saturable, reversible, specific, guanosine nucleotide-sensitive, of picomolar affinity and femtomolar density. The linearity of Scatchard plots of saturation data and the unity of Hill coefficients indicate that a single class of melatonin binding sites is present in the spinal cord membranes studied. The picomolar affinity of these sites is in line with the circulating levels of melatonin in these animals suggesting that these sites are physiologically relevant. Autoradiography studies in the rabbit spinal cord show that melatonin binding sites are localized in the central gray substance (lamina X). In the chicken spinal cord, these binding sites are localized in dorsal gray horns (laminae I-V) and lamina X. As lamina X and laminae I-II have similar functions, melatonin may have comparable roles in the chicken and rabbit spinal cords. Moreover, in the chicken spinal cord, the density of 2-[125I]iodomelatonin binding in the lumbar segment was significantly higher than those of the cervical and thoracic segments. The densities of these binding sites changed with environmental manipulations. When chickens were adapted to a 12L/12D photoperiod and sacrificed at mid-light and mid-dark, there was a significant diurnal variation in the density (maximum number of binding sites; Bmax) of melatonin binding sites in the spinal cord. After constant light treatment or pinealectomy, the Bmax of melatonin receptors in the chicken spinal cord increased significantly in the subjective mid-dark period. Moreover, there was an age-related decrease in the 2-[125I]iodomelatonin binding to the chicken spinal cord. Our results suggest that melatonin receptors in the chicken spinal cord are regulated by environmental lighting and change with development. These receptors may play an important role in the chronobiology of spinal cord function. The biological responses of melatonin on spinal cords have also been demonstrated in vitro. Melatonin decreased the forskolin-stimulated cAMP production in the chicken spinal cord explant. Preincubation with pertussis toxin blocked the melatonin effect. Our results suggest that melatonin receptors in the chicken spinal cord are linked to the adenylate cyclase via a pertussis toxin-sensitive G protein and that melatonin binding sites in spinal cords are melatonin receptors with biological functions. These receptors may b","PeriodicalId":9265,"journal":{"name":"Biological signals","volume":"2028 1","pages":"272-83"},"PeriodicalIF":0.0,"publicationDate":"1997-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91318702","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Recent Progress of Pineal Research--40 Years After Discovery of Melatonin. Proceedings of the AsiaPacific Pineal Meeting. Hamamatsu, Japan, March 28-31, 1997.","authors":"","doi":"","DOIUrl":"","url":null,"abstract":"","PeriodicalId":9265,"journal":{"name":"Biological signals","volume":"6 4-6","pages":"181-312"},"PeriodicalIF":0.0,"publicationDate":"1997-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20478096","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Circadian oscillators in vertebrate retinal photoreceptor cells.","authors":"G M Cahill,&nbsp;M Hasegawa","doi":"10.1159/000109129","DOIUrl":"https://doi.org/10.1159/000109129","url":null,"abstract":"<p><p>Recent progress in research on retinal circadian rhythmicity is reviewed. Important advances include the discovery that circadian oscillators are present in the retinas of diverse vertebrate species, and evidence that circadian rhythmicity is generated by the photoreceptor cells. Research on the cellular and molecular mechanisms of photoreceptor circadian rhythms has revealed that expression of a subset of genes associated with photoreception, melatonin synthesis and transcriptional control are regulated by a circadian oscillator. Finally, it has been found that cAMP mimics darkness in resetting the phase of the retinal photoreceptor circadian oscillator, suggesting that it may be a component of a transduction pathway for entrainment of the oscillator.</p>","PeriodicalId":9265,"journal":{"name":"Biological signals","volume":"6 4-6","pages":"191-200"},"PeriodicalIF":0.0,"publicationDate":"1997-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1159/000109129","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20424802","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Regulation of the intracellular concentration of free calcium ions in pinealocytes of the rainbow trout and the rat.","authors":"H W Korf,&nbsp;S Kroeber,&nbsp;C Schomerus","doi":"10.1159/000109130","DOIUrl":"https://doi.org/10.1159/000109130","url":null,"abstract":"Together with cAMP, calcium ions play an important role in the regulation of melatonin synthesis in the pineal organ of all vertebrate species, irrespective of the conspicuous phylogenetic transformation of the melatonin-producing cell, the pinealocyte. Here we address the question how the intracellular concentration of free calcium ions [Ca2+]i is regulated in directly light-sensitive trout pinealocytes and in rat pinealocytes which have lost the direct light sensitivity and respond to norepinephrine. Isolated pinealocytes identified by the S-antigen immunoreaction were investigated by means of the fura-2 technique, image analysis and patch clamp recordings. Approximately 30% of the trout pinealocytes exhibited spontaneous [Ca2+]i oscillations that were not affected by light or dark adaptation of the cells. Removal of extracellular Ca2+ or application of 10 microM nifedipine caused a reversible breakdown of the [Ca2+]i oscillations. Treatments with 60 mM KCl and nifedipine suggest that voltage-gated L-type calcium channels play a major role in the regulation of [Ca2+]i in both oscillating and nonoscillating trout pinealocytes. Experiments with thapsigargin (2 microM) revealed the presence of intracellular calcium stores in 80% of the trout pinealocytes, but their role in the regulation of [Ca2+]i remains elusive. Norepinephrine had no apparent effect on [Ca2+]i in any trout pinealocyte. In rat pinealocytes, [Ca2+]i did not show spontaneous oscillations. Norepinephrine evoked a dramatic biphasic rise in [Ca2+]i in more than 95% of the cells via stimulation of alpha1-adrenergic receptors. The response reflects a combination of calcium mobilization from intracellular, thapsigargin-sensitive calcium stores and an increased calcium influx. Voltage-gated calcium channels of the L-type are present in the rat pinealocyte membrane, but they are not involved in the norepinephrine-induced calcium response. These channels, however, mediate the increase in calcium influx which is observed in virtually all rat pinealocytes upon stimulation with acetylcholine or nicotine. The results show that the mechanisms which regulate [Ca2+]i in pinealocytes are complex and differ considerably between poikilothermic and mammalian species.","PeriodicalId":9265,"journal":{"name":"Biological signals","volume":"6 4-6","pages":"201-11"},"PeriodicalIF":0.0,"publicationDate":"1997-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1159/000109130","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20425913","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Melatonin excretion rhythms in the cultured pineal organ of the lamprey, Lampetra japonica.","authors":"M. Samejima, S. Tamotsu, K. Uchida, Y. Moriguchi, Y. Morita","doi":"10.1159/000109134","DOIUrl":"https://doi.org/10.1159/000109134","url":null,"abstract":"Pineal organ of the lamprey, Lampetra japonica, is essential to keep the circadian locomotor activity rhythm as previously reported. In this paper, we tried to show that an endogenous oscillator is located and is working in the pineal organ. When the pineal organs were excised and cultured in a plastic tube with M199 medium at 20 degrees C, melatonin secretion rhythms were clearly observed under both light-dark and continuous dark conditions. The circadian secretion of melatonin continued for more than five cycles under the continuous dark condition. This indicates that the pineal organ has an endogenous oscillator and that the melatonin secretion rhythm is controlled by this oscillator. These findings suggest the possibility that the locomotor activity rhythm of the lamprey is under the control of the oscillator in the pineal organ.","PeriodicalId":9265,"journal":{"name":"Biological signals","volume":"88 1","pages":"241-6"},"PeriodicalIF":0.0,"publicationDate":"1997-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73861663","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Growth of studies on hypusine in biological systems.","authors":"S S Cohen","doi":"10.1159/000109116","DOIUrl":"10.1159/000109116","url":null,"abstract":"","PeriodicalId":9265,"journal":{"name":"Biological signals","volume":"6 3","pages":"110-4"},"PeriodicalIF":0.0,"publicationDate":"1997-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1159/000109116","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20226361","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Two distinct pathways for intronless mRNA expression: one related, the other unrelated to human immunodeficiency virus Rev and human T cell leukemia virus type I Rex functions.","authors":"T Kiyokawa,&nbsp;T Umemoto,&nbsp;Y Watanabe,&nbsp;S Matsushita,&nbsp;H Shida","doi":"10.1159/000109119","DOIUrl":"https://doi.org/10.1159/000109119","url":null,"abstract":"<p><p>Intronless mRNAs were classified into two classes based on the sensitivities of their expression to the inhibitory effect of TAgRex, a dominant-negative mutant of the Rex protein of human T cell leukemia virus type I, and their abilities to express the genes encoded in the intron of the human immunodeficiency virus (HIV) genome. Interferon-alpha mRNA could not induce the expression of the env gene of HIV, and its expression was resistant to TAgRex. In contrast, the posttranscriptional regulatory element (PRE), necessary for the nucleo-cytoplasmic export of mRNAs of hepatitis B virus, induced expression of the chloramphenicol acetyl transferase gene located within the intron of the HIV genome. PRE-mediated expression was inhibited by TAgRex. Thus, these results suggest that there are at least two distinct pathways for intronless mRNA expression, one related to and the other unrelated to Rev and Rex functions.</p>","PeriodicalId":9265,"journal":{"name":"Biological signals","volume":"6 3","pages":"134-42"},"PeriodicalIF":0.0,"publicationDate":"1997-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1159/000109119","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20226365","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}