bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantitation of Ultrastructural Twenty‐Four‐Hour Changes in Pineal Nuclear Dimensions
Authors: Lew G.M. , Washko K. , Quay W.B.
Published: February 2007

An ultrastructural stereological analysis was made of the nucleus in pinealocytes of 28 male Fischer rats sampled at seven times in a light:dark 12:12 photoperiod cycle. Comparisons of the data from the seven times, in relation to daily means, showed variations in mean nuclear cross‐sectional surface area of ±16%, and in mean nuclear perimeter of ±10%. Peaks in both nuclear dimensions occurred at the middle of the light period and were coincident with the presence of elaborate nuclear configurations and deep indentations. At 2330 and 0430 (1 and 6 h after lights off) nuclear folding was generally less complex. Mitochondria were found in close association with the nuclear folds. Forty percent of nucleoli were marginated at all of the sampling times, except at 1130 (l h after lights on) and at 2330 (l h after lights off), when 50% and 35%, respectively, were marginated.
Relative Efficacy of Melatonin and 5‐Methoxytryptamine in Terms of Their Antigonadotrophic and Counterantigonadotrophic Actions in Male Syrian Hamsters
Authors: Reiter Russel J. , Holtorf Anke , Champney Thomas H. , Vaughan Mary K.
Published: February 2007

Antigonadotrophic and counterantigonadotrophic activities of melatonin and 5‐methoxytryptamine (5‐MT) were quantitatively compared in male Syrian hamsters. In long day conditions, the daily afternoon administration of either 5, 15, 25, 50, 100 or 200 μg melatonin induced testicular regression within 10 wk; under the same circumstances, only the 200‐μg dosage of 5‐MT was able to suppress testicular weights. Thus, 5‐MT appears to have about one‐tenth the antigonadotrophic action of melatonin in the male Syrian hamster. In short days, the subcutaneous implantation of either 50 or 100 μg melatonin (every 2 wk in beeswax) prevented testicular regression whereas it required much larger doses of 5‐MT (1 mg every 2 wk in beeswax) to achieve the same counterantigonadotrophic action. In terms of both their antigonadotrophic and counterantigonadotrophic effects, hamsters seem to be more sensitive to melatonin than to 5‐MT.
Differential Responsiveness of the Reproductive System of Blind or Melatonin‐Treated Male Hamsters to Injections of Gonadotrophin‐Releasing Hormone (GnRH) and/or Prolactin
Authors: Blask David E. , Leadem Christopher A. , Stockmeier Craig A.
Published: February 2007

The combination of pituitary grafts and daily injections of gonadotrophin‐releasing hormone (GnRH) completely prevents gonadal atropy in blind (BL) and melatonin (Mel)‐treated male hamsters. In order to avoid potential problems associated with the use of pituitary grafts and further define the interactions between prolactin (PRL) and GnRH in preventing reproductive regression, we injected various doses of each hormone either alone or in combination into BL or Mel‐treated male hamsters. In another experiment, BL hamsters received either weekly beeswax implants of estradiol benzoate (EB) (1 mg) alone or EB implants in combination with daily injections of GnRH (2 μg). In each experiment the hamsters were BL and/or treated with hormones for 10 wk. Either GnRH (8 fig) or PRL (5 μg) per d partially prevented gonadal atrophy in BL hamsters. However, increasing doses of GnRH plus PRL wre more effective than either hormone alone in preventing gonadal atrophy. The combined effect of these hormones was greater than the algebraic sum of their individual effects. Injections of either GnRH or PRL alone resulted in a significant maintenance of gonadal and accessory organ size in Mel‐treated animals. The combination of GnRH and PRL resulted in virtually complete maintenance of testicular weight while the accessory sex organs remained atrophic. The combined effect of these hormones was equivalent to the algebraic sum of their individual effects. The treatment of BL animals with EB implants with or without GnRH did not prevent reproductive regression in spite of elevated serum PRL levels. In conclusion, the effects of GnRH and PRL were synergistic in BL hamsters and additive in Mel‐treated animals. The data suggest that there is a differential responsiveness of BL v. Mel‐treated hamsters to the individual as well as the combined actions of GnRH and PRL.
Interdependent Effects of the Ionophore A23187 and Serum on the Serotonin N‐Acetyltransferase Activity of Cultured Chick Pineal Glands
Authors: Wainwright S. D. , Wainwright Lillian K.
Published: February 2007

Marked effects of the ionophore A23187 on the cycle of N‐acetyltransferase (NAT) activity in cultured chick pineal glands were observed under three conditions of illumination. However, the effects were qualitatively and quantitatively dependent on the batch of fetal calf serum used in the medium and time of explanation into culture. lonophore increased the level of NAT activity remaining in glands exposed prematurely to light regardless of the serum used. The ionophore suppressed the “spike” in cyclic GMP content of glands cultured in the dark, and extended the period of maximum cyclic GMP content of glands under diurnal illumination.
Morphometric Analysis of the Synaptic Ribbons and Nerve Vesicles of the Cat Pineal Gland After Electrical Stimulation of the Superior Cervical Ganglia
Authors: González Gabino , Alvarez‐Uria Manuel
Published: February 2007

The nerve vesicles and synaptic ribbons were quantified in the cat pineal gland after electricl stimulation of the pineal sympathetic nerve fibers. It has been shown that the bilateral electrical stimulation of the preganglionic fibers innervating the superior cervical ganglia (SCG) markedly reduces the number of dense cores of small dark vesicles (SDV) and on the other hand modifies the number and shape of the large dark vesicles (LDV). An increase in the number of the synaptic ribbons after stimulation of the SCG supports the hypothesis that the numerical reduction of dense cores of nerve vesicles in the cat pineal gland influences the level of synaptic ribbon formation.
Effects of Pinealectomy on Photoperiodic Control of Hair Follicle Activity in the Limousine Ram: Possible Relationships With Plasma Prolactin Levels
Authors: Allain D. , Ravault J. P. , Panaretto B. A. , Rougeot J.
Published: February 2007

Twelve adult Limousine rams (five pinealectomized, four sham operated, and three control) were housed under an artificial lighting regime of alternating periods of long (16L:8D) and short (8L:16D) days for 18 months, and long‐term variations in kemp follicle growth were recorded along with measurements of the plasma prolactin concentrations. In control 2nd sham‐operated rams, both parameters varied in relation to imposed lighting regime. Moult and growth of the kemp follicles occurred during each short‐day period at a time when the concentrations of prolactin were low and vice versa. Variations in the pinealectomized rams were different from those in the control or sham‐operated ones. There was no synchronous periodic kemp activity: some follicles remained active at all times, and the seasonal pattern of plasma prolactin levels disappeared. The relationship between the kemp follicle cycle and the pattern of plasma prolactin concentrations and its control by the pineal gland are discussed.
The Effect of Serotonin, N‐Acetylserotonin, and Melatonin on Spontaneous Contractions of Isolated Rat Intestine
Authors: Bubenik G. A.
Published: February 2007

A dose‐dependent increase in tone and reduction in amplitude of contractions was observed after serotonin (5‐HT) was administered to isolated segments of rat ileum, incubated in Locke's solution at 38°C. Melatonin (M) reduced the tone but not the amplitude or frequency of contractions. Addition of M (administered in doses 20 to 100 × higher than 5‐HT) relieved the spasm induced by 5‐HT. Furthermore, pretreatment with M significantly reduced the 5‐HT effect. N‐acetylserotonin (NAS) exhibited delayed but similar effects to M. Neither M nor NAS could prevent or relieve acetylcholine‐induced contractions or influence relief of intestinal contractions by adrenaline. This indicates that 5‐HT and M act via a different mechanism than that of adrenaline and acetycholine system. Serotonin muscle receptor blocker methysergide reduced 5‐HT effect but was not able to abolish it completely. As methysergide could not reduce the muscle tone and did not relieve spasm caused by 5‐HT, it is speculated that M is not acting as antagonist of 5‐HT‐ stimulatory receptors but rather as agonist of 5‐HT‐inhibiting neuronal receptors.
Dynamic Uptake of Radioactive Substance in Rat Salivary Gland Following 3H‐Melatonin Administration
Authors: Withyachumnarnkul Boonsirm , Wongprapairot Pornpimol , Trakulrungsi Wantanee
Published: February 2007

Dynamics of radioactive accumulation in rat greater salivary glfollowing systemic administration of 3H‐melatonin was studied to determine a possible action of the hormone in the gland. Progressive decline of 3H‐melatonin concentrations was found in the serum, lung, skeletal muscle, liver, kidney, salivary glduring 60 min following the administration. On the contrary, there was a progressive accumulation of radioactive substance other than 3H‐melatonin in the salivary glbut not in other tissues mentioned. The radioactivity was also progressively preferentially localized in the nuclear fraction of the glcells. These results suggest a possible direct action of melatonin derivative in rat salivary gland.
Melatonin Rhythm in Human Plasma Saliva
Authors: McIntyre Iain M. , Norman Trevor R. , Burrows Graham D. , Armstrong Stuart M.
Published: February 2007

Human plasma saliva were collected at frequent intervals throughout the night after a nocturnal challenge by exposure to 3,000 Ix of light for 1 h in the middle of the night. Melatonin, as measured by radioimmunoassay, was found to correlate highly in plasma saliva, described by a linear regression equation: y = 55x ‐ 2.6 (r = 0.90). The nocturnal melatonin rhythm in saliva was parallel to that observed in plasma. A good correlation was also observed between plasma salivary melatonin on exposure to light. Melatonin in both fluids showed a significant fall during light exposure. Levels returned to normal nocturnal values within 2 h after returning to darkness. These results indicate that salivary melatonin, although lower than plasma melatonin, may be used as an index of pineal glrelease of melatonin. It is suggested that saliva may be useful as a non‐invasive technique for obtaining data on melatonin profiles, especially in pilot‐test screening situations.
Melatonin, Cortisol, Prolactin, and Calcitonin Secretion in Primary Hyperparathyroidism Before After Surgery
Authors: Brismar K. , Werner S. , Bucht E. , Wetterberg L.
Published: February 2007

The aim of the present study was to determine the diurnal secretion of melatonin, cortisol, prolactin, calcitonin during chronic parathyroid hormone‐dependent hypercalcemia. Eight women, aged 40–76 years, with primary hyperparathyroidism (PHPT) were studied before after surgical removal of a parathyroid adenoma. The hormone concentrations in blood were determined at 08, 12, 16, 22, 02, 04, 06 h. Concomitantly, the excretion of melatonin cortisol in urine between 07–19 h 19–07 h, the clearance of calcium creatinine were measured.

Nyctohemeral serum prolactin calcitonin were unaffected by moderate parathyroid hormone‐dependent hypercalcemia. In contrast, serum cortisol melatonin were significantly higher during active disease than after surgical cure. Mean 24‐h variation of serum cortisol was 349 ± 34 nmol/liter vs. 223 ± 17 nmol/liter mean serum melatonin was 0.13 ± 0.04 nmol/liter vs. 0.06 ± 0.02 nmol/liter. Endogenous creatinine clearance was similar before after surgery, while the clearance of melatonin cortisol significantly increased after surgery, indicating an increased tubular reabsorption of both hormones during active disease. Fasting morning glucose concentrations were also significantly decreased after successful surgery, 6.1 ± 0.6 vs. 5.2 ± 0.5 mmol/liter. It is suggested that the relative hypercortisolism may be the cause of the glucose intolerance in primary hyperparathyroidism.

Three to 4 months after surgical cure the serum melatonin levels were significantly lower than those seen in age‐matched controls, indicating a melatonin insufficiency in patients successfully treated for PHPT. The meaning of this finding is not yet understood but might be of importance in the development of primary hyperparathyroidism.
Persistence of Photic Evoked Responses in Pineal Gland After Its Pedunculotomy Superior Cervical Ganglionectomy
Authors: Barajas‐López C. , Barrientos‐Martinez M.A. , Reyes‐Vazquez C.
Published: February 2007

The present study analyzes the participation of pineal stalk superior cervical ganglia (SCG) in the conduction of photic evoked potentials (PEP) to the pineal body (PB) in unanesthetized freely moving rats implanted with semimicroelectrodes. The PEPs were recorded in PB, lateral hypothalamus (LH), habenular complex (HC). In some rats the pineal stalk was lesioned either by electrolysis or by surgical means. Recordings were begun 3 days after electrode implantation; three recording sessions were performed before after extirpation of SCG or lesion of pineal stalk. The PEPs recorded in LH HC were characterized by 3 components (positive‐negative‐positive: PNP). The average latency of the first wave was 35.3 ± 1.7 38.8 ± 1.6 ms for LH HC, respectively. The peaks of PEPs in PB showed different polarity (NPN), the first component had a latency of 36.1 ± 1.2 ms. The PEPs persisted in all three structures after extirpation of SCG after electrolytic lesion or transection of the pineal stalk. These results show that the PEPs recorded in PB are not generated in this structure, since they persist after interrupting its connections with the rest of the central nervous system; this suggests that PEPs could be the result of electrotonic transmission from neighboring structures.
Inhibitory Actions of Pineal Indoles on Steroidogenesis in Isolated Rat Leydig Cells
Authors: Ng T. B. , Lo Louisa L. H.
Published: February 2007

The inhibition elicited by pineal indoles on testosterone production by isolated rat Leydig cells could not be overcome by a maximally active dose of luteinizing hormone (LH), and dibutyryl‐CAMP‐induced steroidogenesis was also suppressed, suggesting that the indoles did not exert their effect through an interaction with LH receptors on Leydig cells. Pregnenolone‐induced progesterone secretion was unaffected, indicating that the activity of 3P‐dehydrogenase was not altered. Methoxytryptamine (MTN) at a dose of I mM decreased progesterone‐induced 17αL‐ hydroxyprogesterone secretion by 50%, suggesting that the enzyme 17α‐hydroxylase was inhibited. The inhibition caused by other pineal indoles was either very slight or absent. MTN reduced 17α‐hydroxyprogesterone‐induced androstenedione production by 65%, methoxytryptophol (MTOL) and melatonin (MEL) by 35%, and methoxyindoleacetic acid (MIAA) and hydroxyindoleacetic acid (HIAA) by 10%, revealing an inhibition of 17–20 desmolase. The reduction of androstenedioneinduced testosterone production by MTN infers inhibition of 17‐ketoreductase activity. However, testosterone production induced by either dehydroepiandroster‐ one or androstenedione was unaffected by other indoles. The data suggest that MTN inhibited 17α‐hydroxylase, 17–20 desmolase, and 17‐ketoreductase while MEL, MTOL, MIAA, and HIAA inhibited only 17–20 desmolase. The highest potency of MTN in inhibiting enzymes on the testosterone biosynthestic pathway was reflected in its greatest inhibition of testosterone production. On the other hand, MIAA and HIAA had the lowest potency in inhibiting the enzymes and testosterone production while MEL and MTOL had intermediate potencies.
Quantitative Cytological Analysis of Functional Changes in Adrenomedullary Chromaffin Cells in Normal, Sham‐Operated, and Pinealectomized Rats in Relation to Time‐of‐day: II. Nuclear‐Cytoplasmic Ratio, Nuclear Size, and Pars Granulosa of Nucleolus
Authors: Kachi T. , Banerji T. K. , Quay W. B.
Published: February 2007

Adrenaline(A)‐ and noradrenaline(N)‐cells in the adrenal medulla of nonoperated (NO), sham‐operated (SO), and pinealectomized (PX) male rats (n = 125) were investigated by quantitative electron and light microscopy. Animals were killed at eight time points during a standardized 24‐h, light‐dark (12:12) cycle 14 days after surgery. Nuclear‐cytoplasmic (N/P) ratios, diameters of nuclei, and the frequency of nucleoli showing a large amount of pars granulosa (granulated nucleoli), were the primary characteristics studied.

Major findings include the following: 1) The frequency of low N/P ratios over a 24‐h period tended to be higher in PX animals than in controls in A‐cells, as shown in large cell profiles (P < 0.02); but such a tendency was not apparent in N‐cells. Daily mean nuclear diameters were similar among the three experimental groups. 2) The 24‐h changing pattern of phase relations in the frequency of low N/P ratio and nuclear size differed between A‐ and N‐cells in NO and SO but not in PX animals. 3) The frequency of granulated nucleoli in A‐cells was much higher in PX animals than in NO and SO animals throughout a 24‐h period (P < 0.018), especially from the late light to early dark phase (P < 0.003), and higher in A‐cells than in N‐cells generally (P < 0.0009). Pinealectomy thus caused increases in the cytoplasm and in the pars granulosa of the nucleolus in many A‐cells; changes in N‐cells were less apparent. This suggest a disturbed balance and coordination between A‐ and N‐cell systems of adrenal medulla following pinealectomy.
Purification and Characterization of DSIP‐Like Material From Ovine Pineal Glands: Possible Peptide‐Protein Interaction
Authors: Noteborn H. P. J. M. , Graf M. V. , Ernst A. , Schoenenberger G. A. , Weusten J. A. M. , Ebels I. , Salemink C. A.
Published: February 2007

The nonapeptide delta‐sleep‐inducing peptide (DSIP) has been isolated from venous blood of rabbits induced to sleep. Numerous reports have described sleep as well as extra‐sleep effects. Radiochemical and immunochemical data suggest a relationship of DSIP with the pineal gland supported by interactions of this peptide with pineal functions such as the serotonin N‐acetyltransferase activity. In order to demonstrate the natural occurrence of DSIP‐like material associated with high Mr proteins in the ovine pineal, organs were water‐extracted and fractionated by ultrafiltration and gel filtration. Radioimmunoassay (RIA) for DSIP‐like fragments of the fractions revealed considerable amounts of pineal DSIP‐like immunoreactivity (DSIP‐LI) apparently existing in small as well as large molecular forms. Acidification of large DSIP‐LI forms resulted in the elution from Sephadex G‐50 of Mr≤ 1,000 DSIP‐like material. This free DSIP‐LI form co‐eluted with the synthetic DSIP nonapeptide from μBondapak C18 on high‐performance liquid chromatography. The results, therefore, appear to indicate the presence of a (biospecific) noncovalent intermolecular interaction of DSIP (1–9) with proteins (Mr≥ 10,000) of the ovine pineal gland.
Effects of Protein Restriction, Melatonin Administration, and Short Daylength on Brain Benzodiazepine Receptors in Prepubertal Male Rats
Authors: Kennaway D. J. , Royles P. , Webb H. , Carbone F.
Published: February 2007

The possibility that there are changes in brain benzodiazepine binding sites controlled by photoperiod was investigated in two strains of male rats. The hypothesis was tested by 3H‐diazepam binding studies in various brain regions of prepubertal rats maintained in 14 or 10h of light or treated with late‐afternoon injections of melatonin (50 μg/day). Protein restriction was applied during the experiment to sensitise the animals to the treatments. Under the conditions employed, rats kept in short daylength throughout or kept on long photoperiod and given late‐afternoon melatonin injections showed evidence of delayed puberty (seminal vesicle, ventral prostate, and testis weight decreased by 45%, 55%, and 60% respectively, compared to control rats). Binding measurements were made 1 h before and 2 and 5 h after the onset of darkness in the pubertal (42‐day‐old) or experimentally prepubertal rats. In the rats of the Porton strain (for which protein restriction was obligatory for the gonadal response) there was no consistent treatment or time effects on specific binding of 3H‐diazepam to washed membranes of the hypothalamus, midbrain, or striatum. Similarly, there were no differences in the stimulation of 3H‐diazepam binding by 100 μM GABA or the inhibition of binding by 50 μM N‐acetyl 5 methoxy kynurenamine. By contrast, in Wistar rats, specific binding to midbrain membranes was reduced 5 h after dark compared to 2 h (37% saline; 20% melatonin) and the extent of stimulation by GABA in the hypothalamus was increased 5 h after darkness (35.6% to 46.7% saline; 37.4% to 50% melatonin). Melatonin treatment resulted in significantly higher specific binding in the hypothalamus 2 h after dark (10%, controd fed; 20%, protein restricted) but reduced the GABA induced stimulation of binding in the midbrain (35.5% to 25%, control fed; 33.7% to 23.5%, protein restricted). The Bmax of benzodiazepine binding to unwashed cortical P2 synaptosomal membranes has been reported to increase twofold in adult Wistar rats at mid‐dark. By contrast the Bmax of juvenile Wistar rats in this study increased only 17% (116 ± 2.4 fmol/mg protein to 140 ± 3 fmol/mg protein) between 2 and 5 h after darkness. In melatonin‐treated animals the increase in Bmax of 3H‐diazepam binding was blocked (124 ± 5 fmol/mg protein at 2 h; 127 ± 3 fmol/mg protein at 5 h) and the Kd reduced (4.5 ± 0.5 to 4.0 ± 0.2 nM). When the cortical membranes from these animals were extensively washed and analysed for binding using a single concentration of ligand (3 nM) the rise in binding during the night was still observed (430 ± 27 fmol/mg protein to 505 ± 60 fmol/mg protein), but there was no blocking effect of melatonin treatment. These results indicate that some aspects of benzodiazepine binding may be influenced by melatonin treatment during the prepubertal period in the rat.
In Vivo Effect of Melatonin and Gonadotropin‐Releasing Hormone on Testicular Function in Rana temporaria
Authors: Alonso‐Bedate Mercedes , Delgado Maria Jesus , Carballada Rosa
Published: February 2007

Studies concerning pineal‐gonadal interactions and investigations about the effect of the putative pineal hormone melatonin in male amphibians are very scarce. In this work we investigate the effects of melatonin, synthetic gonadotropin‐releasing hormone (GnRH), or both when injected in Rana temporaria males. We conclude that melatonin inhibits spermiation and spermatogonial multiplication when injected alone or with GnRH. We have been unable to find any significant differences in plasma testosterone levels when melatonin or GnRH are injected alone, but when melatonin is injected with GnRH the levels of testosterone are significantly increased. These results seem to demonstrate that melatonin could play a role in the regulation of the gonadal function in the male Rana temporaria.
On the Uptake and Incorporation of Thymidine by Cultured Chick Pineal Glands
Authors: Wainwright S.D. , Wainwright Lillian K.
Published: February 2007

Cultured chick pineal glands showed a marked cycle in the incorporation of thymidine into DNA. They also accumulated exogenous thymidine in one, or more, endogenous thymidine pool(s). However, there was no significant variation in ability to take up thymidine during incubation with either standard medium or media of increased thymidine content. We could not eliminate the possibility of variation in size of a quantitatively minor, but metabolically extremely important, thymidine pool which “channels” precursor directly into DNA.
Inhibition of the Catalytic Activity of Bovine Pineal Gland Hydroxyindole‐O‐ Methyltransferase (EC 2.1.1.4) by Estrone, Estradiol, Progesterone, and Testosterone but not Pteridines
Authors: Morton Dougal J. , Forbes Heather J.
Published: February 2007

The effect of pteridines and sex hormones on hydroxyindole‐O‐methyltransferase (HIOMT) catalysis was examined. Equivalent quantities of partially purified bovine HIOMT was incubated in the presence and absence of the various test substances and the results fitted to the Michaelis‐Menten equation. The pteridines (triampterene and xanthopterin) had no noticeable effect on HIOMT catalysis, while all the sex hormones examined were found to be competitive inhibitors of the enzyme with respect to the hydroxy‐substrate. Testosterone concentrations causing noticeable inhibition were above physiological while estrone, estradiol, and progesterone all caused inhibition within the physiological range; estrone was the most potent and progesterone the least potent inhibitor. The possible significance of these findings are discussed.
Effect of Pinealectomy and of Diabetes on Liver Insulin and Glucagon Receptor Concentrations in the Rat
Authors: Mellado Consuelo , Rodríguez Victoria , de Diego Juana G. , Alvarez Elvira , Blázquez Enrique
Published: February 2007

The studies described in this paper were undertaken to characterize the circulating and hepatic insulin and glucagon receptor concentrations of control (C), diabetic (Db), and pinealectomized‐diabetic (Pn + Db) rats. Compared with C rats, an increase in plasma glucose and glucagon levels and a reduction in circulating insulin concentrations in Db animals was observed; these differences were greater in Pn + Db rats. In liver membranes, insulin binding was lower in Db and in Pn + Db than in C rats, and glucagon binding was greater in Db and in Pn + Db than in C rats. The modifications in hormone binding did not reflect changes in the affinity constants. The time courses of hormone association and dissociation from liver membranes were similar in all three experimental groups. The degradation of both hormones and their receptors was similar in all three groups. These findings indicate that in either pinealectomized‐diabetic or diabetic rats there were significant changes in the circulating and liver insulin and glucagon receptor concentrations and that the changes in the circulating levels of both pancreatic hormones were more pronounced in pinealectomized‐diabetic animals. In addition, the absence in Db and in Pn + Db rats of the insulin and glucagon down‐regulation of their own receptors could further modify metabolic activities in these animals.
Melatonin Inhibits Mitotic Activity of Adrenocortical Cells In Vivo and in Organ Culture
Authors: Sewerynek Ewa , Lewiński Andrzej
Published: February 2007

The goal of this study was to examine the effects of melatonin, as well as those of melatonin and corticotropin (1–24 adrenocorticotropic hormone (ACTH); Synac‐then Depot) administered together, on the mitotic activity of adrenocortical cells in male and female mice. Melatonin was given subcutaneously once daily, in late‐afternoon injections (between 16: 00 and 18: 00) in doses of 1 μg, 10 μg, and 100 μg, and ACTH in a dose of 0. 1 mg (10 U) daily for 10 days. Additionally, the highest dose of melatonin (100 μg daily) was administered together with ACTH. The metaphase‐arrest technique using colchicine as a stathmokinetic agent was employed in the study. Melatonin, in all the examined doses, significantly decreased mean mitotic activity rate (MMAR) of the adrenal cortex in both male and female mice. Moreover, in a dose of 100 μg, melatonin suppressed the mitogenic effect of ACTH on the adrenal cortex.

Furthermore, the present study investigated the effects of melatonin (5 × 10−7M), N‐acetylserotonin (NAC‐5HT) (5 × 10−7M), and ACTH (250 mU/ml or 1,000 mU/ml) alone as well as the effect of ACTH (250 mU/ml) applied jointly with melatonin on the mitotic activity of adrenocortical cells in rat adrenal explants incubated in vitro. Both pineal indoleamines (melatonin and NAc‐5HT) significantly decreased the MMARs of adrenocortical cells. Corticotropin, as well as ACTH and melatonin applied together, also reduced the MMAR of adrenocortical cells.

The present data suggest that melatonin may be directly involved in the inhibitory control of adrenocortical cell proliferation.
Sexually Dimorphic Effects of Melatonin on Prolactin Cell Function in Male and Female Syrian Hamsters
Authors: Blask David E.
Published: February 2007

The purpose of this study was to determine and compare the effects of chronic melatonin treatment in vivo on several aspects of prolactin (PRL) cell activity (PRL synthesis, storage, and release) in vitro in male and female Syrian hamsters. Adult male and female hamsters were maintained on long photoperiod and treated with daily late afternoon injections of melatonin (25 μg) or vehicle for 11 weeks. Melatonin treatment resulted in an 85% and 65% decrease in serum PRL levels in male and female hamsters, respectively. There was a similar 79% and 64% decrease in PRL release in vitro from pituitaries of male and female hamsters, respectively, treated with melatonin in vivo. Total stored PRL was 75% lower in male hamsters and 62% lower in female hamsters receiving melatonin. The synthesis of PRL by pituitaries from melatonin‐treated male hamsters was reduced by 65%, whereas in melatonin‐treated females it was decreased by 58%. Both nanomolar and micromolar doses of melatonin in vitro caused a modest but significant decrease (14–19%) in the amount of PRL stored in and released from normal male pituitaries without affecting synthesis. The inhibitory effects of melatonin on PRL cell function appear to be more pronounced in male than in female hamsters suggesting a sexually dimorphic response to this pineal hormone. While melatonin's PRL‐inhibitory effects appear to be exerted primarily via indirect neuroendocrine mechanisms, a secondary component of its overall regulation of PRL processing may involve direct pituitary mechanisms as well.
How Hamsters Keep Time: The 6 PM to 6 AM Light‐Sensitive Period
Authors: Alleva John J.
Published: February 2007

A recent review of the pineal literature revealed that when hamsters are exposed to 24‐hour light:dark (LD) cycles with < 12 hours of darkness (summerlike, SLD), the nightly period of pineal melatonin synthesis (PPMS) begins close to the midpoint of the dark period (“midnight”) and ends at lights‐on irrespective of the length of the dark period or time of day presented. New evidence based on the onset of behavioral estrus every 4 days indicated that the 24‐hour hamster clock controlling timing of estrus (4:30 PM) and the PPMS has a 12‐hour light‐sensitive period (LSP) set to 6 PM‐6 AM in LD 16:8 (dark 8 PM‐4 AM, SLD) by a balance in opposing actions of evening and morning light [Alleva: Pineal Research Reviews, Volume 5, Alan R. Liss, Inc., New York, 1987]. Present experiments focus on how this balance is maintained. When lights‐off was advanced to 6 PM in SLDs ranging from LD 12.5:11.5 (dark 6:15 PM‐5:45 AM) to 18:6 (dark 9 PM‐3 AM), the onset of estrus later that day was advanced in every SLD. However, when lights‐on was delayed to or beyond 6 AM, the onset of estrus was unaffected. Thus, the balance is maintained by a resistive force (blocking without a delaying action) of evening light and an advancing action of morning light. In this balancing process all evening light from 6 PM to lights‐off but only the first 5 minutes or less of morning light were involved. The advancing action of morning light was characterized in LD 13:11 and 18:6 by imposing on the night before estrus a 5:30 PM‐6:30 AM dark period scanned with a 15‐minute light pulse. Shifts in onset of estrus later that day were plotted vs. time of the light pulse. The resulting phase response curves (PRCs) were similar and comprised only an advancing curve, which rose about 10 PM, peaked at 2 AM, and returned gradually to normal at 6 AM. In contrast, a PRC obtained from LD 12:12 (dark 6 PM‐6 AM) was sinelike, comprising a 6 PM‐9 PM delaying curve followed by an advancing curve similar to those from SLD. An hypothesis based on these findings is presented to explain how hamsters would keep constant AM—PM time throughout summer.
Influence of Pinealectomy on Sexual Behavior of Normal and Monosodium L‐Glutamate‐Treated Rats
Authors: Hsu Chin , Huang Hung‐Tu , Hsu Hseng‐Kuang , Yu John Yuh‐Lin , Peng Ming‐Tsung
Published: February 2007

Subcutaneous injections of monosodium L‐glutamate (MSG) were administered, as a neurotoxin, at a dose of 4 mg/g body weight to rat pups on days 1 and 3 postnatally. Pinealectomy was performed at 6 weeks of age, and animals were allowed to mature. The intact MSG‐treated rats showed a decrease of lordosis quotient in females and a reduction of ejaculation frequency and an increase in mount frequency in males. Pinealectomy caused no significant improvement on sexual behavior of the salinetreated normal rats, but it caused a marked improvement of the sexual receptivity in MSG‐treated female rats and reinstated ejaculation in MSG‐treated males. The circulatory sex steroid levels, estrogen in females and androgen in males, were not significantly different between the intact and pinealectomized MSG‐treated groups in the respective sexes, whereas the progesterone level in females was significantly elevated in the pinealectomized MSG‐treated group compared with the intact MSG‐treated group. These findings suggest that the pineal gland plays an inhibitory role on the sexual behavior of MSG‐treated rats and the improvement of sexual behavior following pinealectomy may be dependent on certain mechanisms other than the actions of circulatory androgens or estrogens.
Histoenzymological Light and Electron Microscopic Localization of Carbonic Anhydrase in the Rat Superficial Pineal Gland
Authors: Krstic Radivoj , Nicolas Dominique
Published: February 2007

A histoenzymological method for demonstration of carbonic anhydrase (CA) was used for cryostat sections of superficial rat pineal gland. Light and electron microscopic analysis showed a high concentration of this enzyme in stellate cells, particularly heavily distributed under the organ capsule and scattered in the parenchyma, where they form a widespread three‐dimensional network. Most of the pericapillary spaces were lined by CA‐reactive cells. The reaction product, in the form of strongly electron‐dark precipitates, was localized in the cytoplasmic matrix, whereas organelles, except for some mitochondrial intracristal spaces, were CA‐negative. On the basis of localization and morphology of CA‐positive cells, we conclude that these represent glial (interstitial) cells.
6‐Sulphatoxymelatonin Production in Breast Cancer Patients
Authors: Skene Debra J. , Bojkowski Christopher J. , Currie Jane E. , Wright John , Boulter Patrick S. , Arendt Josephine
Published: February 2007

The daily pattern of the major urinary metabolite of melatonin, 6‐sulphatoxymelatonin (aMT6s), was determined in women prior to having a breast biopsy. Women with malignant tumors appeared to have significantly lower 24 h concentrations of aMT6s with a decrease in the amplitude of the rhythm compared to women with benign tumors. The amount of urinary aMT6s was dependent upon the age of the subject but was not affected by either menopausal status or body mass index. However, when the women with malignant tumors were compared with a large group of normal women of the same age their aMT6s levels were not outside the normal range. The results show that a large control group and very accurate age matching are essential when investigating melatonin production in different groups of subjects.
Acute Cerebral Hemorrhage Changes the Nocturnal Surge of Plasma Melatonin in Humans
Authors: Pang Shiu Fun , Li Yi , Jiang De‐hua , Chang Beng‐shu , Xie Bing‐li
Published: February 2007

The diurnal rhythm of plasma melatonin was studied in 46 Chinese patients with acute cerebral hemorrhage. The state of consciousness of each patient was assessed clinically. The individual sites of lesion were determined by computerized tomography scanning. One to five days after stroke, blood samples were collected by venipuncture at 1000 and 1400 h in the daytime and 0200 and 0400 h at night. Plasma melatonin was extracted by dichloromethane and determined by radioimmunoassay. It was found that patients with lesions in the brain stem or in the third and lateral ventricles had melatonin levels significantly different from the other subjects in that these values were lower and lacking a nocturnal rise. These results are consistent with the presumptive retina‐pineal pathway proposed in humans. Dramatic blunting or obliteration of the nocturnal melatonin surge in the blood was also observed in some patients with lesions in the frontal lobe, fronto‐parietal lobe, parieto‐temporal lobe, and basal ganglia. These brain regions are not involved in the retina‐pineal pathway described in rodents or humans. Thus, our results suggest that brain regions other than the presumptive retina‐pineal neural pathway may play an important role in the generation and/or regulation of the diurnal production and/or secretion of pineal melatonin in humans. However, a global functional disturbance caused by cerebral hemorrhage cannot be ruled out in some cases. It should be noted that many of the lesions leading to a change in the nocturnal rise of plasma melatonin were unilateral lesions. The significance of this finding is presently unknown. In addition, patients without a nocturnal rise of plasma melatonin were mostly comatose. They had lesions in the basal ganglion, fronto‐parietal lobe, brain stem, and lateral and third ventricles. The latter findings suggest that in the brain, certain regions responsible for the state of consciousness of the individual may also be important to the dirunal rhythm of pineal melatonin secretion.
“Synaptic” Ribbons and Spherules Lacking in the Pineal Gland of the European Hamster Appear After Ganglionectomy
Authors: Masson‐Pévet M. , Pévet P.
Published: February 2007

“Synaptic” ribbons and spherules are typical organelles of the mammalian pinealocytes, that present quantitative day‐night variations parallel to pineal melatonin levels. The European hamster is a wild photoperiodic mammal whose pineal melatonin concentrations do not vary during the 24 hr light‐dark cycle. The aim of this study was thus to see if a rhythmic variation in synaptic structures was nevertheless present in this species. It was found that, in contrast to all of the photoperiodic species studied to date, the European hamster pinealocyte contains no ribbons, and virtually no spherules. Moreover, constant administration of melatonin does not result in the occurrence of these organelles; nevertheless, the pinealocytes have the potentiality to produce spherules and, to a lesser extent, ribbons, as they are observed in ganglionectomized animals and in the deep pineal of some hamsters after ablation of the superficial part of the gland. The formation of pineal synaptic structures, normally lacking in the European hamster, thus seems directly related to the noradrenergic innervation of the gland.
Influence of pineal indoleamines on the mitotic activity of gastric and colonic mucosa epithelial cells in the rat: Interaction with omeprazole
Authors: Lewiński A. , Rybicka I. , Wajs E. , Szkudliński M. , Pawlikowski M.
Published: February 2007

Lewinski A, Rybicka I, Wajs E, Szkudlinski M, Pawlikowski M. Influence of pineal indoleamines on the mitotic activity of gastric and colonic mucosa epithelial cells in the rat: Interaction with omeprazole. J Pineal Res 1991:10:104‐108.

We have investigated the effects of melatonin (Mel) and N‐acetylserotonin (NAc‐5HT) on the mitotic activity of gastric and colonic mucosa in adult male rats under basal conditions and after an administration of omeprazole (OM) (H+, K+‐ATPase inhibitor). The metaphase‐arrest technique was applied in the study. Additionally, serum gastrin levels were measured by RIA method in the OM‐treated group and in respective polyethyleneglycol (PEG)‐administered controls. We have found that: 1) OM‐treatment increased serum gastrin levels in rats; 2) OM enhanced the mitotic activity of the colonic mucosa cells, although, unexpectedly, it did not exert such an effect on the gastric mucosa cells; 3) Mel suppressed the OM‐induced increase of the colonic epithelium cell proliferation, while NAc‐5HT failed to reveal that action: 4) NAc‐5HT decreased the proliferation of gastric mucosa epithelial cells. The value of the mean mitotic activity rate (MMAR) of gastric mucosa after Mel‐treatment also decreased, but that change was not statistically significant. The obtained data are in compliance with previous results from our laboratory concerning the inhibitory effect of pineal indoleamines on the jejunal epithelium mitotic activity. The stimulatory effect of OM on the proliferation of colonic epithelium is probably mediated by OM‐induced hypergastrinaemia. The possibility of Mel interaction with intestinal gastrin receptors (a structural similarity occurs between Mel and benzotript, a specific gastrin receptor antagonist), as well as of the opposite effects of Mel and gastrin on intracellular cAMP content in the gut, are considered in the discussion of results.
Ontogeny of the pineal response to norepinephrine
Authors: Kaufman Claire M. , Menaker Michael
Published: February 2007

Abstract: The Syrian hamster pineal displays age‐dependent changes in melatonin output measured in vitro. Between the ages of 4 and 19 days, pineal melatonin generation in response to 10 μM norepinephrine (NE) increased 34‐fold. Production of melatonin by cultured pineals from 1‐week‐old hamsters showed a clear dose responsiveness to NE: The most effective dose was 10 μM and the response declined at both higher and lower doses. When cultured pineals from 7‐day‐old animals were exposed to four cycles of NE in the medium (10 hr 10 μM NE: 14 hr 0 M NE), the melatonin output followed the driving rhythm with a rising lag time of 8 hr and a falling lag of 4 hr. This time course is consistent with the conclusion [Santana et al., 1990; Gonzalez‐Brito et al., 1990] that transcription events lead to a long lag time between the stimulus and the onset of melatonin synthesis. In the absence of exogenous NE, melatonin output from most glands dropped to undetectable levels in just over 2 days; however, even after 3 days without NE, glands could be stimulated to produce melatonin when NE was added to the medium. When incubated with 10 μM NE for 6 hr in static culture, glands from 11‐ versus 4‐day‐old neonates produced 20 times more melatonin and had over three times higher NAT specific activity. After a 15 min incubation with 10 μM NE, cAMP content was three‐fold higher in 11‐compared to 4‐day‐old pineals. Our results demonstrate that although the pineal's response to NE increases with age, its response time is invariant throughout postnatal development.
Chronic administration of melatonin induces changes in porphyrins and in the histology of male and female hamster Harderian gland: Interrelation with the gonadal status
Authors: Rodriguez‐Colunga Maria J. , Fernandez Covadonga , Antolin Isaac , Rodriguez Carmen , Tolivia Delio , Menendez‐Pelaez Armando
Published: February 2007

Abstract: In this paper, we have investigated the influence of melatonin on the histology and porphyrin content of the Syrian hamster Harderian glands. Daily afternoon injections of 25 μg of melatonin to female hamsters for 12 weeks resulted in the discontinuity of estrous cyclicity, a marked decrease in the Harderian gland intraluminal area occupied by porphyrins, and in a significant rise in the number of Type II cells. A similar decrease in porphyrins was observed after 8 weeks of ovariectomy. However, if the melatonin injections were given for only 8 weeks (without inducing gonadal atrophy), no changes were observed in the area occupied by intraluminal porphyrins, suggesting that the effects of melatonin in female Syrian hamsters might be associated with the subsequent gonadal atrophy. Castration of male hamsters induced a significant increase in porphyrins and a clear drop in the number of Type II cells. These changes were totally prevented when melatonin was administered daily from the day of castration. Our results suggest that melatonin, at least in male Syrian hamsters, plays a role in Harderian metabolism, acting directly on the Handerian secretory cells or indirectly through pituitary hormones.
Circadian and seasonal rhythms of melatonin production in mules (Equus asinus × Equus caballus)
Authors: Cozzi Bruno , Morei Giovanni , Ravault Jean‐Paul , Chesneau Didier , Reiter Russel J.
Published: February 2007

Abstract: The present study describes the patterns of melatonin production in the mule (Equus asinus × Equus caballus). Blood was sampled hourly for 24 h from eight mule mares in spring and fall. The data obtained show the presence of a circadian rhythm of production of melatonin, with highest values during the dark phase both in spring and fall. In fall the nightly rise of melatonin production begins earlier in the dark phase and reaches higher quantitative levels than in spring. The morning decline of melatonin production is similar in the two seasons. Maximal levels of nightly melatonin production in the mule are about 10× higher than those described in the horse. The results reported here indicate the persistence of brain structures able to receive and transduce environmental signals in the mule, a genetically sterile mammalian hybrid.
The effect of food deprivation on brain and gastrointestinal tissue levels of tryptophan, serotonin, 5‐hydroxyindoleacetic acid, and melatonin
Authors: Bubenik George A. , Ball Ronald O. , Pang Shiu‐Fun
Published: February 2007

Abstract: In order to investigate the effect of food deprivation on the levels of indoles in the brain and the gastrointestinal tissues, we have determined tissue levels of tryptophan (TRP), serotonin (5‐HT), 5‐hydroxyindoleacetic acid (5‐H1AA), and melatonin in the brain and the gastrointestinal tract (GIT) of mice on ad libitum diet as well as in mice deprived of food for 24 and 48 hr. The reduction of food intake 1) had no effect on TRP levels in the brain, but increased TRP concentrations in the stomach and the gut, especially in the colon; 2) decreased 5‐HT levels in the brain, but increased values in the stomach and the intestines; 3) decreased 5‐HIAA levels in the brain, but increased them in the stomach and the intestines; 4) did not change 5‐HT conversion to 5‐HIAA in the brain, stomach, and the jejunum, but increased the conversion in the ileum and colon and; 5) increased melatonin levels in all tissues investigated, particularly in the stomach and the brain. The changes of indole levels induced by food deprivation were compared to their known function in the brain and the individual segments of the GIT. A possible serotonin‐melatonin antagonism in the brain and GIT function is considered.