摘要:

Bastianelli E, Pochet R. Calbindin‐D28k, calretinin, and recover in immunoreactivities in developing chick pineal gland. J. Pineal Res. 1994: 17: 103–111.AbstractCalbindin‐D28k, calretinin, and recoverin, three intracellular calcium‐binding proteins belonging to the troponin C/calmodulin superfamily, were immunohistochemically localized in chick pineal during development [from embryonic day 16 (E16) to postnatal day 14 (P14)]. At E18, only calretinin immunoreactivity could be detected in nuclei from follicular pinealocytes. With development, calretinin immunoreactivity expanded from nucleus to cytoplasm, and calretinin immuno‐positive cell number increased. At P14 almost all pinealocytes were calretinin positive. Calbindin‐D28k immunoreactivity was not detected before E20. During development, many follicular and parafollicular pinealocytes became strongly calbindin‐D28k positive, reaching a peak both in intensity and in number at P7; thereafter their number decreased. In addition to pinealocytes, neuron‐like cells appeared calbindin‐D28k positive at E20 and calretinin positive at P7. Recoverin, a myristoylated protein isolated from vertebrate photoreceptor and which might participate in the inactivation of the phototransduction cascade, was transiently expressed in follicular and parafollicular pinealocytes from P1 to P14 with a maximal expression at P7. This transitory expression may coincide with a transitory light sensitivity period in chick pinealocytes, before complete maturity of

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1994.tb00120.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Sirotkin AV. Direct influence of melatonin on steroid, nonapeptide hormones, and cyclic nucleotide secretion by granulosa cells from porcine ovaries. J. Pineal Res. 1994; 17: 112–117.AbstractThe release of progesterone, estradiol‐173, oxytocin, arginine‐vasopressin, cAMP, and cGMP by cultured granulosa cells isolated from porcine ovaries without and in the presence of melatonin (0. 001, 0. 01, 0. 1, 1, 10, and 100 ng/ml medium) was analyzed. It was found that melatonin is able to inhibit progesterone and stimulate estuarial secretion. Melatonin treatments significantly inhibited oxytocin release. Some inhibition of vasopressin and cAMP and significant stimulation of cGMP also resulted from melatonin treatment. The present observations suggest a direct effect of melatonin on the steroid, nonapeptide hormone, and cyclic nucleotide release from porcine ovarian

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1994.tb00121.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Fielke SI, Young IR, Walker DW, McMillen IC. Effect of two weeks of continuous light on the development of the circadian melatonin rhythm in newborn lambs. J. Pineal Res. 1994; 17: 118–122AbstractWe have investigated the effect of exposure of newborn lambs to continuous light during the first 2 weeks after birth on the subsequent development of the phase and amplitude of the plasma melatonin rhythm during the next 8 weeks. During the first 2 weeks after birth, the mean plasma melatonin concentrations were significantly lower (P<0. 001) in lambs exposed to continuous light (58 ± 15 pmol/1, n = 7) than in lambs exposed to LD 12: 12 (i. e., “normal” lighting: 189 ± 38 pmol/1, n = 9). Between 3 and 4 weeks of age, plasma melatonin concentrations during the daily light and dark periods were also significantly lower in the lambs exposed to continuous light during the first 2 weeks after birth. There was no effect of time of day on plasma melatonin in either group of lambs during the first 2 weeks after birth but between 3 and 10 weeks of age there was a significant (P<0. 001) effect of light and dark and time of day on plasma melatonin concentrations which was the same in both groups of lambs. Plasma melatonin concentrations were higher in the dark period than in the light period and between 2100 and 0700 than between 0900 and 1700 at all ages after week 2. We have therefore demonstrated that exposure of the lamb to 2 weeks of continuous light after birth results in a suppression of melatonin secretion that extends beyond the end of the exposure to continuou

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1994.tb00122.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Nelson RJ, Moffatt CA, Goldman BD. Reproductive and no reproductive responsiveness to photoperiod in laboratory rats. J. Pineal. Res. 1994; 17: 123–131AbstractLaboratory rats (Rattus norvegicus) have been traditionally considered nonphotoperiodic because reproductive function is unaffected by day length. However, at least three experimental manipulations of rats—perinatal androgen injection, per pubertal androgen implants, and peripubertal olfactory bulbectomy—have been reported to unmask reproductive responsiveness to photoperiod. The physiological means by which early testosterone treatment or olfactory bluestem affect the expression of photoperiodic were hypothesized to operate through similar underlying mechanism(s) that involved gonadotropin and prolactin blood levels. Short day lengths reduce blood levels of gonadotropins in so‐called photoperiodic rodent species. Reduced prolactin levels result in virtually all reproductively photoperiodic species housed in short day lengths. In Experiment 1, male weanling rats either were olfactory‐bulbectomized or received a sham‐procedure and housed for 10 weeks in long (LD 16: 8) or short (LD 8: 16) days. Short‐day rats reduced body mass, testicular sperm counts, and the size of their reproductive systems; olfactory bluestem amplified this inhibitory effect for some parameters including testicular and epididymal sperm counts. However, neither short days nor olfactory bluestem affected blood titers of follicle stimulating hormone (FSH) or prorating. Pelage density was also unaffected by photoperiod, but rats retained their juvenile fur color; i. e., short‐day rats remained white, but long‐day rats became yellowish. In Experiment 2, male rats were injected with testosterone at 3 days of age, then housed in long or short days until 10 weeks of age. Day length alone did not affect any experimental parameter measured in Experiment 2 except fur color; again, short‐day rats retained their juvenile fur color. Perinatal testosterone treatment combined with short day lengths suppressed reproductive organ size and function. Blood plasma concentrations of FSH, but not prolactin were reduced at 6 and 10 weeks of age by early testosterone injection. In Experiment 3, male offspring of rats born in our lab were weaned at 21 days of age and implanted with a Silastic capsule that was either empty or filled with testosterone. Animals were housed for 10 weeks in long or short days. Photoperiod did not affect reproductive organ size or function in this experiment; however, pelage color was again affected by day length. There were no significant interactions between photoperiod and hormonal treatment. Rats bearing testosterone capsules displayed reduced reproductive organ size and function. Blood levels of FSH were reduced at 6, but not 10, weeks of age in these animals. Prolactin concentrations were unaffected by testosterone treatment. Taken together, these results suggest that laboratory rats retain some vestiges of photoperiodic responsiveness, indicating that the physiological capability to measure day length is extant, but that the effects of photoperiodic regulation on reproduction are minor and probably of limited functional significance in the

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1994.tb00123.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Esposti D, Mariani M, Demartini G, Lucini V, Fraschini F, Mancia M. Modulation of melatonin secretion by acetyl‐L‐carnitine in adult and old rats. J. Pineal Res. 1994; 17: 132–136.Abstract; Modification of melatonin synthesis and release by acetyl‐L‐carnitine (ALC) was studied in adult (2 month old) and old (24‐month‐old) male Sprague Dawley rats. When ALC was injected at 1500 into adult rats at doses of 10, 30, or 90 mg/kg, there was a remarkable increase in their pineal and serum melatonin 1 hr later. However, using the same experimental protocol acute ALC administration in old rats did not modify pineal and serum melatonin levels. ALC administered in the same dose range induced a significant increase in pineal and serum melatonin in adult rats treated at 0100 h following exposure of 30 min to bright, white light to suppress endogenous melatonin. In the same conditions, in old rats, only the higher dose (90 mg/kg) caused any noteworthy increase in melatonin pineal content while lower doses were ineffective both on serum and pineal melatonin levels. It is known that ALC affects fatty acid transport in the cells, modulates Co A, modifies neuronal transmission and reduces lipofuscin accumulation which is related to lipid per oxidation. The action of ALC on melatonin synthesis could be the result of a modulation of the neuronal transmission related to circadian pineal endocrine activity. Moreover, since both ALC and melatonin exert remarkable scavenger activity, it is possible to suppose that ALC effects in reversing certain aging processing may be due to its ability to promote melaton

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1994.tb00124.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Kennaway DJ, Hugel HM, Rowe SA. Characterization of the chicken brain melatonin‐binding protein using iodinated and triturated ligands. J. Pineal Res. 1994; 17: 137–148.AbstractThe melanoma‐binding protein in chicken brain membranes was characterized using both [125I]‐2‐iodomelatonin and [3H]‐melatonin as radioligands. Saturation studies conducted at 25°C revealed a single class of binding site with dissociation constants of 24 ± 4. 8 pM (n = 7) and 125 ± 21 pM (n = 6) for the iodinated and tritiated legends, respectively. Calculation of the affinity constant using data from kinetic experiments gave values of 2.2 ± 0.4 pM and 135 ± 15 pM for the iodinated and tritiated ligands, respectively. Competition studies showed that the rank order of inhibition of binding by melatonin analogues was similar for both radioligands (2‐iodomelatonin>melatonin>2,3‐dihydromelatonin>N‐acetyl‐5‐methoxykynurenamine>N‐acetylserotonin>5‐methoxytryptamine). The calculation of Ki, which depends upon the affinity constant, was 22 ± 4.9 pM and 129 ± 21 pM for 2‐iodomelatonin and melatonin, respectively, when the affinity constant derived from the [125I]‐2‐iodomelatonin saturation experiments was used, but 4.9 ± 1.5 pM and 33 ± 5.5 pM when the kinetically derived constant was used. When [3H]‐melatonin was used, the Ki for melatonin was 72 ± 8 pM and 20 ± 4.6 pM for 2‐iodomelatonin and melatonin. Binding of [125I]‐2‐iodomelatonin to the membranes was partially reversible at 25°C in contrast to the complete reversibility of [3H]‐melatonin. Examination of the effects of temperature on binding indicated that at 37°C both association and dissociation of both legends were accelerated. Closer examination showed that at 37°C there was a loss of approximately 40% of the [125I]‐2‐iodomelatonin binding sites and little influence upon the affinity of binding with time. By contrast, when [3H]‐melatonin was used, the affinity decreased fourfold, with only a slight change in the number of sites. If membranes were incubated at 37°C and then switched 25°C, binding increased, emphasizing the fact that the binding sites were not destroyed. Whereas there appears to be little doubt that 2‐iodomelatonin is a biologically active melatonin agonist, the binding of the radioactive form of this agonist to the putative melatonin receptor binding site is quite different from that of the endogenous ligand. This may have serious consequences in studies where receptor content is de

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1994.tb00125.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1994.tb00126.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY