摘要:

Abstract:Pineals from neonatal rats born to alcohol‐fed mothers had lower unstimulated serotonin‐N‐acetyltransferase activity (NAT) and responded less to isoproterenol, vasoactive intestinal polypeptide, or desmethylimipramine challenge than did pineals from pups born to normal or pair‐fed mothers. Group differences disappeared after the first week of life. Reduced NAT activity is coincident with elevated glucocorticoids in these pups. In contrast to these effects of chronic in utero ethanol exposure, acute ethanol addition to normal adult pineals in organ culture enhanced ISO but not VIP stimulation of NAT activity. The results suggest that the neonatal pineal is more affected by ethanol‐induced activation of the adrenocortical axis during gestation than by the direct effect of ethanol on membrane

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1995.tb00140.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract:Effects of season, environmental temperature, and photoperiod on plasma melatonin concentrations were studied in the goldfish, Carassius auratus. When goldfish were reared under natural conditions, melatonin levels at mid‐dark exhibited seasonal changes, with higher levels obtained in June and September than in December and March. When fish were kept under light: dark (LD) cycle of 12: 12 at 5, 15, or 25°C during March‐April, temperature‐dependent increases in melatonin levels at mid‐dark were observed. When animals were maintained under LD 16: 8 or LD 8: 16 in combination with temperature changes (5, 15, and 25°C) during January‐February, the duration of nocturnal elevation in melatonin was controlled by the length of the scotophase while the amplitude was influenced by environmental temperature. These results indicate that plasma melatonin profiles in the goldfish exhibit seasonal changes that are regulated by both photoperiod and

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1995.tb00141.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract:To monitor pineal function in the Djungarian hamster (Phodopus sun‐gorus), we measured the urinary excretion of the melatonin metabolite 6‐sulpha‐toxymelatonin (aMT6s) at 3‐hr intervals by radioimmunoassay. Hamsters maintained in either long photoperiod (LP, LD 16: 8) or short photoperiod (SP, LD 8: 16) showed marked daily rhythms in aMT6s excretion, with elevated levels during the dark phase. In both photoperiods, we found large interindividual differ‐ences, mainly in the amplitude of the signal. However, the amplitude as well as the duration of nocturnal aMT6s excretion was higher in SP than in LP. Light ex‐posure at night (180 mW/m2, 30 min) caused a decrease in aMT6s excretion, indicating that the pineal gland is the major source of urinary aMT6s. Moreover, there was a significant correlation between nocturnal pineal/plasma melatonin contents and 24‐hr aMT6s excretion. We conclude that, measurements of aMT6s provide a valid and quantitative index of pineal melatonin synthesis in this hamster species. As an advantage in determining pineal melatonin contents, this approach will al‐low noninvasive long‐term studies of individual animals under varying environ

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1995.tb00142.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract:Prenatal photoperiod influences postnatal prolactin secretion and the timing of reproductive development in male red deer reared from birth in a constant equatorial photoperiod (12: 12 light: dark). The present trial investigated whether a similar phenomenon occurs in female red deer. Female deer whose mothers had been exposed for the last 14 weeks of gestation to long (group L, 18: 6 light: dark) or short day length (group S, 6: 18 light: dark) were kept from birth in constant equatorial day length with food available ad libitum. Both groups showed similar live‐weight gain to 90–100 weeks of age. Blood samples taken once or twice weekly were analyzed for progesterone and prolactin. Progesterone concentrations indicated that there was no difference between the groups in the timing of the first incidence of ovarian (luteal) activity, which occurred at a normal or late age for natural puberty (67 weeks or older). Only one individual per group exhibited normal repeated luteal cyclicity since there was a high incidence of irregular or abnormal luteal function. Plasma prolactin concentrations at birth were higher in group L than group S (P<0.001). Thereafter, although the mean and peak values did not differ significantly between the groups, there was a significant difference in the pattern of secretion; deer in group L showed significant clustering of prolactin peaks (P<0.01) at a mean age of 48 weeks, whereas deer in group S showed a random distribution of peaks. Therefore, for female red deer raised in constant equatorial photoperiod, prenatal long day lengths did not advance timing of puberty. However, the long‐term pattern of prolactin secretion tended to be synchronized by long but not by short day lengths experienced prena

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1995.tb00143.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract:In the past several years we demonstrated that the pineal neurohormone melatonin has immunoenhancing properties and can counteract the immunodepres‐sion that may follow acute stress, drug treatment, and viral diseases or aging. Sev‐eral laboratories have subsequently confirmed and extended our findings. It soon appeared evident that T‐derived cytokines constitute the main mediators of the im‐munological effect of melatonin. We have recently found a high affinity (Kd: 346 |Mp 24 pM) binding site for125I‐melatonin on T‐helper‐type 2 lymphocytes in the bone marrow. Activation of this putative melatonin receptor, with both physiologi‐cal and pharmacological concentrations of melatonin, resulted in an enhanced pro‐duction of interleukin‐4 (IL4), which in turn acted on bone marrow stromal cells and induced the release of hematopoietic growth factors. This melatonin‐cytokine cascade showed the remarkable capacity of rescuing hematopoietic functions in mice treated with cancer chemotherapeutic compounds without interfering with the anticancer action of these agents. The very low concentration (0.1 nM) at which melatonin is active may well reflect a physiological function of endogenous melatonin. The pineal gland has been, in fact, reported to signal the blood forming system. The evidence of IL4 involvement is relevant to our understanding of many melatonin effects and may be part of a pineal‐immune axis involving also Th 1 cy‐tokines. The ability of rescuing hematopoiesis against the toxic action of cancer chemotherapeutic compounds and the presence of high‐affinity IL4 receptors on human tumors provide a further promising rationale for t

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1995.tb00144.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract:Melatonin solutions are frequently used in human, animal, and in vitro research. Generally, fresh solutions are prepared, for fear of instability of mela‐tonin in solution. We tested the high‐performance liquid chromatography (HPLC) stability of melatonin in aqueous solutions stored room temperature, 4°C, and ‐70°C for up to 6 months. Solutions were prepared in a laminar flow hood using sterile technique, directly into sterile, pyrogen‐free glass vacuum vials for storage. Different concentrations were tested (1.0–113.0 μg/ml). There was no loss of po‐tency as assessed by HPLC, and the preparations remained sterile and pyrogen‐free. We conclude that melatonin solutions may be prepared in batches maintained in sterile, pyrogen‐free vials at 4°C or at ‐70°C until use within 6 months. This method will save on research time used for preparation of fresh solutions and will reduce the number of dose validation tests f

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1995.tb00145.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract:The growth‐inhibitory actions of the pineal hormone, melatonin, on hu‐man breast tumor cells and the possible association between this inhibition and melatonin's down‐regulation of the estrogen receptor (ER) expression were exam‐ined in the ER‐positive, estrogen‐responsive MCF‐7 human breast tumor cell line. As previously reported, melatonin dramatically inhibits the growth of these breast tumor cells and down‐regulates ER levels in these cells, suggesting that the modu‐lation of ER may be an important mechanism by which melatonin inhibits breast cancer cell growth. In the present studies, Northern blot analysis was used to ex‐amine the expression of estrogen‐regulated transcripts known to be involved in es‐trogen's mitogenic actions. Melatonin, at a physiologic concentration (10−9M), rapidly, significantly, and, in some cases, transiently elevated the steady‐state mRNA levels of growth stimulatory products such as TGFα, c‐myc, and pS2, which are normally up‐regulated in response to estrogen. Conversely, melatonin decreased the expression of other factors normally up‐regulated by estrogen, such as progesterone receptor and c‐fos. Significant stimulation of the expression of the growth‐inhibitory factor TGFβ was seen with melatonin treatment, potentially sup‐porting the concept that melatonin's growth‐inhibitory activity is mediated through the breast tumor cells’estrogen‐response pathway. The early regulation of many of these products by melatonin suggests that mechanisms more rapid than the down‐regulation of ER are important in melatonin's modulation of their ex‐pression. However, the long‐term modulation of these transcripts (12–48 hr) may be heavily influenced by melatonin's down‐regulation of ER expression. These re‐sults clearly define the need for additional in depth studies to dissect the cellular events leading t

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1995.tb00146.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract:Melatonin is widely abundant in many eukaryotic taxa, including vari‐ous animal phyla, angiosperms, and unicells. In the bioluminescent dinoflagellate Gonyaulax polyedra, melatonin is produced in concentrations sometimes exceed‐ing those found in the pineal gland, exhibits a circadian rhythm with a pro‐nounced nocturnal maximum, and mimics the short‐day response of asexual encystment. Even more efficient as a cyst inducer is 5‐methoxytryptamine (5MT), which is also periodically formed in Gonyaulax. In this unicell, the photoperiodic signal‐transduction pathway presumably involves melatonin formation, its deace‐tylation to 5MT, 5MT‐dependent transfer of protons from an acidic vacuole, and cytoplasmic acidification. According to this concept, we observe that cyst forma‐tion can be induced by various monoamine oxidase inhibitors and protonophores, that 5MT dramatically stimulates H+‐dependent bioluminescence and leads to a decrease of cytoplasmic pH, as shown by measurements of dicyanohydroquinone fluorescence. Cellular components from Gonyaulax catalyze the photooxidation of melatonin. Its property of being easily destroyed by light in the presence of cel‐lular catalysts may have been the reason that many organisms have developed mechanisms utilizing this indoleamine as a mediator of darkness. Photooxidative reactions of melatonin, as studied with crude Gonyaulax extracts and, more in de‐tail, with protoporphyrin IX as a catalyst, lead to the formation of N1‐acetyl‐N ‐formyl‐5‐methoxykynuramine (AFMK) as one of the main products. Photochemical mechanisms involve interactions with a photooxidant cation radi‐cal leading to the formation of a melatonyl cation radical, which subsequently combines with a superoxide anion. Photooxidation of melatonin represents one of several possibilities of a more general, biologically highly important property of this indoleamine to act as an extremely efficient radical scavenger, including its feature of terminating radical reaction chains by a final combination with the su‐peroxide anion. Trapping of free radicals may reflect the primary and evolutionar‐ily most anc

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1995.tb00147.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract:The ultrastructure of the pineal gland in the adult cat is described and compared with that of other mammals. Connective tissue spaces showed capillar‐ies with nonfenestrated endothelia and numerous unmyelinated nerve fibers. In the proximal region of the gland, myelinated nerve fibers coming from the anterior commissure were also found. Cat pinealocytes showed a nucleus with prominent nucleoli, a well developed Golgi apparatus, centrioles, granular endoplasmic reticulum, ribosomes, abundant microtubuli and enlarged mitochondria. Pinealo‐cytes showed several long processes with bulbous endings filled with clear vesicles and scarce “synaptic” ribbons. Pineal astrocytes and their processes were characterized by the presence of abundant fi

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1995.tb00148.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY