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  • 1
    Electronic Resource
    Electronic Resource
    The pineal melatonin rhythm and its regulation by light in a subterranean rodent, the valley pocket gopher (Thomomys bottae) (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of pineal research 16 (1994), S. 0 
    Details
    ISSN: 1600-079X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Reiter RJ, Reiter MN, Hattori A, Yaga K, Herbert DC, Barlow-Walden L. The pineal melatonin rhythm and its regulation by light in a subterranean rodent, the valley pocket gopher (Thomomys bottae). J. Pineal Res. 1994; 16: 145–153.〈section xml:id="abs1-1"〉〈title type="main"〉AbstractThe daytime and nighttime levels of pineal N-acetyltransferase (NAT) activity, hydroxyindole-O-methyltransferase (HIOMT) activity, and melatonin were measured in adult male and female valley pocket gophers, Thomomys bottae. This species was chosen for study because it is a subterranean rodent that inhabits burrows whose openings to the surface are closed. Therefore, under field conditions it is estimated that the pocket gopher spends roughly 99% of its time in absolute darkness in underground burrows. When wild captured pocket gophers were maintained under a light dark cycle (light intensity during the day of roughly 140 μ,W/cm2), nighttime levels of pineal NAT activity and melatonin content were higher than values measured during the day; on the other hand, HIOMT activity in the pineal gland was similar in the day and at night. When pocket gophers were exposed to an extended light period (220 μW/cm2) 4 hr into the night, the rise in melatonin synthesis normally associated with darkness onset was not inhibited. Also, when gophers were acutely exposed to a light intensity of 400 μW/cm2 for 1 hr beginning 4 hr after darkness onset, neither high nocturnal levels of pineal NAT nor pineal melatonin contents were reduced. Finally, when pocket gophers were exposed to a 600 (μW/cm2 light intensity at either 4 hr or 8 hr into the dark period, pineal melatonin synthesis remained elevated at a level comparable to that measured in dark-exposed controls. The results show that under controlled laboratory conditions the pineal gland of the valley pocket gopher, a species that in its natural habitat spends about 99% of its time in absolute darkness, exhibits higher melatonin synthesis during night than during the day. While the rhythm in pineal melatonin production in the pocket gopher is clearly synchronized by the prevailing light: dark cycle, high nighttime pineal melatonin synthesis is not readily inhibited by light in the intensity range of 220 to 600μW/cm2. In terms of its relative insensitivity to light at night, the pineal gland of the valley pocket gopher resembles that of other diurnally active rodents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-079X.1994.tb00094.x
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  • 2
    Electronic Resource
    Electronic Resource
    Unusual responses of nocturnal pineal melatonin synthesis and secretion to swimming: Attempts to define mechanisms (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of pineal research 14 (1993), S. 0 
    Details
    ISSN: 1600-079X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The effect of swimming at night on rat pineal melatonin synthesis was compared with that of light exposure at night. Rats were forced to swim at 0030 hr (lights out at 2000 hr) and sacrificed by decapitation 15 and 30 min later, immediately after swimming. Other groups of animals were exposed to white light (650μW/cm2) for 15 and 30 min at same time. Swimming caused a rapid and highly significant drop in the melatonin content in the pineal gland; however, the activity of N-acetyltransferase (NAT), the supposed rate limiting enzyme in the melatonin production, was not changed. Despite the drop in pineal melatonin levels, serum concentrations of the indole remained elevated in the rats that swam. In contrast, melatonin levels in the pineal and serum of light exposed rats fell precipitously, accompanied by a significant suppression of NAT activity. Since we anticipated that the strenuous exercise associated with swimming may induce release of artrial natriuretic peptide (ANP) from the heart, which in turn could cause the release of pineal melatonin, in a second study we injected physiological saline intravenously to stretch the cardiac muscle and release ANP. Three milliliters of normal saline was injected during the day into the jugular vein of anesthetized rats that were pretreated with isoproterenol to stimulate pineal melatonin production. Animals were killed 15 min after the saline injection, and pineal NAT activity and pineal melatonin levels were measured. The saline injections caused no alteration in the elevated levels of either NAT or melatonin. These data suggest that the disparity in pineal NAT activity (which was high) and pineal melatonin (which was low), in animals swum at night, may not be caused by ANP which is released during strenuous exercise such as swimming.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-079X.1993.tb00492.x
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  • 3
    Electronic Resource
    Electronic Resource
    Melatonin suppresses osteoclastic and osteoblastic activities in the scales of goldfish (2002)
    Oxford, UK : Munksgaard International Publishers
    Journal of pineal research 33 (2002), S. 0 
    Details
    ISSN: 1600-079X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The effects of melatonin on osteoclastic and osteoblastic cells were examined using a culture system of the goldfish scale. Tartrate-resistant acid phosphatase (TRACP) and alkaline phosphatase (ALP) were used as markers of osteoclastic and osteoblastic cells, respectively. In Earle's minimum essential medium containing melatonin (10−9 to 10−5 m), activities of both enzymes in scales were significantly suppressed at 6 hr after incubation (TRACP: 10−8, 10−6, 10−5 m; ALP: 10−7 to 10−5 m), but at 18 hr only ALP activity was significantly lowered (10−8, 10−7 m). Estradiol-17ß (E2) enhanced both activities, which were significantly inhibited and brought down to the level of the controls when co-incubated with E2 and melatonin (TRACP at 6 hr: 10−9 to 10−5 m; ALP at 6 hr: 10−7 m; ALP at 18 hr: 10−8 m). Moreover, using reverse-transcription polymerase chain reaction, the mRNA expression of the estrogen receptor (ER) and insulin-like growth factor (IGF)-1, which are related to osteoblastic growth and differentiation, was decreased in the melatonin-treated scales. These results suggest that melatonin acts directly on the scale osteoclastic and osteoblastic cells where it suppresses the ALP activity via down-regulation of ER and IGF-1 mRNAs expression. This is the first report on the function of melatonin in osteoclasts and on the suppressive effect of melatonin in osteoblasts among vertebrates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1600-079X.2002.02953.x
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  • 4
    Electronic Resource
    Electronic Resource
    Day-night changes in melatonin levels in different organs of the cricket (Gryllus bimaculatus) (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of pineal research 18 (1995), S. 0 
    Details
    ISSN: 1600-079X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Day-night levels of melatonin (N-acetyl-5-methoxytryptamine) were determined in different organs of adult female crickets (Gryllus bimaculatus) exposed to a 12/12 light/dark cycle, using reversed-phase high performance liquid chromatography coupled with fluorometric detection. Melatonin levels in the compound eye, brain, and palp were significantly higher during the dark period than during the light period, suggesting that a diurnal rhythm of melatonin levels exists in these organs of crickets, with a peak during the dark period. Conversely, melatonin levels were significantly higher during the light period than the dark period in the cercus, ovipositor, antenna, hind-leg and ovary. No significant day-night difference was found in the fore- and mid-legs, Malpighian tube, and digestive tube. Thus, these organs may have different melatonin-metabolizing systems compared to those found in the compound eye, brain, and palp. Differences in the phasing of the melatonin rhythm in various organs of the cricket suggest possible differences in melatonin function in these organs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-079X.1995.tb00156.x
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  • 5
    Electronic Resource
    Electronic Resource
    Retinal melatonin is not involved in corneal mitotic rhythms in the Japanese quail: Effects of formoguanamine hydrochloride and eye-lid suture (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of pineal research 21 (1996), S. 0 
    Details
    ISSN: 1600-079X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Relation between retinal melatonin and corneal mitotic rhythms in the Japanese quail was investigated in experiments manipulating the ocular physiology by treatments with formoguanamine hydrochloride (FG) and eye-lid suture. In experiment 1, we investigated the effects of FG, which is known to induce photoreceptor degeneration, on retinal melatonin and corneal mitotic rhythms. FG-treatment completely abolished the retinal melatonin rhythms in both LD 12: 12 and constant darkness (DD), but the corneal mitotic rhythm was maintained with high mitotic rate in darkness under a LD cycle and subjective night under DD. The result suggests that 1) the photoreceptor cells in the retina are the site for melatonin production and/or for the oscillator which drives the circadian rhythm in retinal melatonin, and 2) melatonin is not involved in generation of the corneal mitotic rhythm. In experiment 2, we investigated the effects of eye-lid suture, which is known to induce eye enlargement and bulgy cornea, on the retinal melatonin and corneal mitotic rhythms. Eye-lid suture abolished the corneal mitotic rhythm in both LD and DD, with a high mitotic rate being maintained throughout 24 hr. But retinal melatonin maintained its rhythm with high levels in darkness under a LD cycle and in subjective night under DD. The result suggests that 1) bulgy cornea in the sutured eye was induced by the increase in mitotic rate in the light period, and 2) disappearance of the corneal mitotic rhythm does not have a relation to retinal melatonin. These results suggest that retinal melatonin is not involved in generation of the corneal mitotic rhythm and that there are two circadian clock systems in the eye.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-079X.1996.tb00282.x
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  • 6
    Electronic Resource
    Electronic Resource
    Quantitative morphological analysis of the pituitary gland in protein-calorie malnourished rats (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 235 (1993), S. 121-125 
    Details
    ISSN: 0003-276X
    Keywords: Immunocytochemistry ; Light microscopy ; Gonadotrophs ; Somatotrophs ; Thyrotrophs ; Corticotrophs ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A quantitative analysis of the pituitary gland was conducted to ascertain the effects of protein-calorie malnutrition on the morphology of the somatotrophs, gonadotrophs, thyrotrophs, and corticotrophs. Male rats were fed a low, 8% protein diet from 20 to 50 days of age, while their age-matched controls were given a diet containing 27% protein. The hypophyses were then processed for light microscopic immunocytochemical staining using antibodies to growth hormone, the β subunits of luteinizing hormone and thyroid stimulating hormone, and adrenal corticotrophic hormone. The number of each cell type along with an evaluation of the cell, cytoplasmic, and nuclear areas was conducted using a computerized image analyzer. All of these parameters were reduced significantly in the somatotrophs as a result of the low protein diet, while in the gonadotrophs, the cell, cytoplasmic, and nuclear areas were similarly affected. Smaller cell number, cell area, and nuclear area were noted in the corticotrophs of the malnourished animals, while in the thyrotrophs, only the cell and nuclear areas were reduced. The data demonstrate that each pituitary cell type responds in a unique manner to undernutrition. © 1993 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092350112
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