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Journal Article 2004; 25(3): 219-222 PubMed PMID: 15349089 Citation  Keywords:  Animals, Estradiol:pharmacology, Female, Hypothalamus:enzymology, Rats, Rats, Wistar, Sexual Maturation:physiology, Synaptic Transmission:drug effects,.   

OBJECTIVES: To determine the hypothalamic activity of nitric oxide synthase (NOS, the enzyme involved in the synthesis of nitric oxide NO) during sexual maturation in prepubertal (15 days old) and peripubertal female rats (30 days old) as well as the effect of estradiol administration on this neurotransmitter system.

METHODS: Hypothalamic samples containing the anterior preoptic and medial basal areas (APOA-MBH) were homogenized with HEPES 20 mM, pH = 7.4 and NOS activity was determined in APO-MBH after 10 minutes of incubation by the conversion of 14C arginine to 14C citrulline.

RESULTS: The hypothalamic concentration of NOS is significantly higher in peripubertal than in prepubertal rats. Treatment with EB increased significantly the activity of the enzyme in both groups compared with control and the increases was similar at both ages.

CONCLUSIONS: These results clearly demonstrated that the hypothalamic NOS activity increases in peripubertal rats as compared with prepubertal animals. Estradiol has a similar stimulatory effect on hypothalamic NOS activity at both ages of sexual maturation, indicating that the increase in NOS during sexual maturation is connected with the peripubertal increase of estradiol rather than an increase in the sensitivity of the enzyme to the ovarian hormone....

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Journal Article 2004; 25(3): 196-200 PubMed PMID: 15349085 Citation  Keywords:  Acute Disease, Animals, Corticosterone:blood, Encephalomyelitis, Autoimmune, Experimental:blood, Male, Rats, Rats, Wistar, Testosterone:blood, Time Factors,.   

OBJECTIVES: Experimental autoimmune encephalomyelitis (EAE) was induced to investigate the levels of circulating total testosterone (TT) and the possible association of corticosterone with the steroid-producing capacity of the testes.

SETTING AND DESIGN: We determined gonad weights, serum TT and corticosterone levels during the development of EAE in male rats.

METHODS: Active EAE was induced in young male Wistar rats by injection of whole myelin in complete Freund's adjuvant. All the rats were weighted and monitored daily for clinical signs and blooded during different phases of the disease. Serum TT was measured by radioimmunoassay and circulating corticosterone was determined using a competitive enzyme immunoassay. Also testes and seminal vesicles were removed to determine their weights.

RESULTS: Seminal vesicle weights and serum TT levels diminished during the acute stage of the disease in all EAE rats and then they began gradually to increase, reaching the normal values at the post-recovery phase. Concomitantly a significant increase in serum corticosterone levels was observed during the acute EAE and the post-recovery phase was accompanied by a decline in corticosterone levels.

MAIN FINDING: Our results indicated an inverse correlation between serum TT and corticosterone levels during the acute EAE. Moreover, the diminution of TT was not a consequence of an alteration of the testes induced by anti-myelin antibodies neither contributed by apoptosis of testis cells by exposure to corticosterone.

CONCLUSIONS: The negative correlation between corticosterone and TT levels associated to EAE may be relevant in understanding the association of the endocrine system and the development of autoimmune demyelinating diseases....

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Comparative Study 2004; 25(1-2): 115-118 PubMed PMID: 15159694 Citation  Keywords:  Animals, Atrophy:prevention & control, Male, Melatonin:physiology, Organ Size, Pineal Gland:physiology, Rats, Rats, Wistar, Thymus Gland:pathology,.   

OBJECTIVES: The purpose of this study was to investigate the effects of pinealectomy and pinealectomy plus melatonin administration on thymus weight and histology in adult Wistar-albino rats.

METHODS: The animals were divided into three groups. Group I and Group II were designated as control (sham-pinealectomized) and pinealectomized rats, respectively. They received 10% ethanol (0.1 ml per day s.c.) alone. The rats in Group III were pinealectomized and daily injected with melatonin (3 mg/kg/0.1 ml 10% ethanol per day s.c.) commencing on the day seven after surgical operation. Injections were applied for two months.

RESULTS: The thymus atrophied and its weight decreased after pinealectomy (p<0.001). The cortico-medullary boundary could not be distinguished and in the thymus induced a loss of lymphoid elements, increased number of phagocytic macrophages and enlarged blood vessels. Melatonin prevented the thymic involution.

CONCLUSIONS: These results suggest that pinealectomy decreases thymus weight and that long-term administration of melatonin restores thymus weight to normal levels....

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Comparative Study 2004; 25(1-2): 102-108 PubMed PMID: 15159692 Citation  Keywords:  Adaptation, Physiological, Animals, Circadian Rhythm:radiation effects, Darkness, Light, Male, Photoperiod, Photoreceptor Cells:radiation effects, Pineal Gland:radiation effects, Rats, Rats, Wistar,.   

OBJECTIVE: This study was aimed to examine the pineal gland of rats exposed to constant light and darkness at light and electron microscopic level.

DESIGN: For this purpose 18 male Wistar rats were used. Animals were divided into three groups. Rats in group I (Control) were kept under 12 hrs light: 12 hrs dark conditions. Rats in group II were exposed to constant darkness, while rats in group III were exposed to constant light for 6 weeks. At the end of the experiment, all animals were killed by decapitation. The pineal glands of rats were removed, then processed for light and electron microscopy.

RESULTS: In our study, extensive number of pinealocytes was observed in the structure of pineal gland of rats exposed to constant darkness and some of the observed pinealocytes were determined to contain double nucleoli. Furthermore, mitochondria and lipid droplets in the cytoplasm of pinealocytes were increased and rough endoplasmic reticulum sacs were enlarged in this group. Whereas, in rats those exposed to the constant light, a decrease in pinealocyte intensity was associated with increase in the connective tissue between parenchymal cells. Additionally, mitochondria and lipid droplets in the cytoplasm of cells were decreased.

CONCLUSIONS: It was observed that the pinealocyte cell activity of rats exposed to constant darkness was increased but decreased in rats exposed to constant light....

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Comparative Study 2004; 25(1-2): 70-74 PubMed PMID: 15159686 Citation  Keywords:  Animal Feed, Animals, Antioxidants:physiology, Brain:metabolism, Dose-Response Relationship, Drug, Iodides:administration & dosage, Liver:metabolism, Lung:metabolism, Male, Melatonin:physiology, Oxidative Stress:physiology, Rats, Rats, Wistar, Schiff Base.   

OBJECTIVES: Administration of iodides to animals, living in iodine-deficient areas, can induce necrosis and fibrosis of the thyroid gland. It is believed that structural and functional changes of the thyroid may be related to oxidative processes. Increased lipid peroxidation levels were reported in murine thyroid glands after high doses of iodine. Melatonin (MEL) is believed to exert its effects via electron donation to directly detoxify free radicals, such as, e.g., the highly toxic hydroxyl radical. In numerous reports related to the antioxidative action of MEL, the authors have considered the protective ability of this hormone against peroxidation of lipids. The goal of the study was to evaluate oxidative processes and the protective role of MEL in three organs of the rat (the liver, the brain, and the lungs) during treatment with different doses of iodide.

MATERIAL AND METHODS: Schiff's bases (SB) concentrations (a parameter of oxidative stress) were measured in liver, lung and brain homogenates of male Wistar rats. The animals received iodides in their diet in the following concentrations, for 2 weeks: Group 1--Controls (standard normal-iodine diet, containing approx. 0.7 mg of kalium iodide per kg; KI/kg); Group 2--diet containing 0,25 mg KI/kg; Group 3--diet with 4,0 mg KI/kg; Group 4--diet with 8,0 mg KI/kg. Group 5--standard normal-iodine diet and MEL alone in a dose of 1 mg/kg BW i.p. at 3.00 pm, every day for two weeks. Subsequent three groups (6-8) received KI in their diet in doses as above, respectively, together with MEL.

RESULTS: We noted increased levels of SB in the lungs and in the liver, when compared to those observed in controls. We also found decreased SB concentrations in liver and lung homogenates after an administration of MEL but--unexpectedly--the level of SB increased in the group with the highest dose of iodine in diet in lung homogenates. Increased levels of Schiff's bases suggest that iodine is involved in oxidative processes not only in the thyroid but also in other tissues, and MEL protects against the iodine-induced oxidative stress.

CONCLUSION: Our results confirm the differences in lipid peroxidation among the examined organs. These alterations can possibly be related to different sensitivity rates of examined tissues to oxidative damage....

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Journal Article 2003; 24(6): 435-439 PubMed PMID: 15073571 Citation  Keywords:  2-Amino-5-phosphonovalerate:pharmacology, Age Factors, Animals, Dizocilpine Maleate:pharmacology, Excitatory Amino Acid Antagonists:pharmacology, Hypothalamus:drug effects, Injections, Intraventricular, Male, Prolactin:metabolism, Rats, Rats, Wistar, Rece.   

OBJECTIVE: To investigate the effects of N-methyl-D-aspartate (NMDA) receptor antagonists on restraint-induced release of prolactin (PRL) in male Wistar rats of different ages.

DESIGN: Rats were implanted with a brain ventricular for icv injection, and with a jugular vein cannula for iv injection. Competitive NMDA receptor antagonist AP-5 and noncompetitive NMDA receptor blocker MK-801 was injected via brain cannula or vein cannula and was restrained for 3 hours. The blood sample was collected through vein cannula during the restraint. The plasma concentration of prolactin was measured by RIA.

RESULTS: The restraint-induced PRL release in the adult rat (12-weeks) was significantly suppressed by MK-801 (50 microg/rat, icv; or 5 mg/kg, iv) and was partially inhibited by pretreatment of AP-5 (50, 100 microg/rat, icv), but was not changed by systemic administration of AP-5 (10 mg/kg, iv). MK-801 (5 mg/kg, iv) prevented the restraint-induced PRL release in the peripuberal rat (45-days) and in the middle-aged rat (16-months).

CONCLUSION: Central NMDA receptors mediate restraint-induced PRL release in the male rat....

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Journal Article 2003; 24(6): 397-400 PubMed PMID: 15073563 Citation  Keywords:  Angiotensin II:analogs & derivatives, Animals, Antihypertensive Agents:pharmacology, Cell Division:drug effects, Female, Losartan:pharmacology, Pituitary Gland, Anterior:cytology, Rats, Rats, Wistar, Receptor, Angiotensin, Type 1:metabolism, Vasoconstrict.   

OBJECTIVES: The purpose of this study was to investigate the effect of angiotensin II (AII) and angiotensin IV (AIV, 3-8 fragment of AII) on the cell proliferation in the anterior pituitary of rat in vivo.

MATERIALS AND METHODS: The female adult Wistar rats, ovariectomized 10 days before experiment were injected intraperitoneally with saline, AII, AIV and AII or AIV together with losartan--the specific AT1 receptor subtype antagonist. Bromodeoxyuridine (BrDU) incorporation into anterior pituitary cell nuclei was used as the index of cell proliferation.

RESULTS: We observed the increased BrDU-labeling index (LI) in the anterior pituitary of rat treated with either AII or AIV. The proliferogenic effect of neither AII nor AIV was reversed by AT1 specific antagonist losartan.

CONCLUSIONS: AII and AIV stimulate the rat anterior pituitary cell proliferation in vivo. This action of both angiotensin peptides is connected with activation of receptor different from AT1 subtype....

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Journal Article 2003; 24(5): 350-354 PubMed PMID: 14647012 Citation  Keywords:  Animals, Anti-Bacterial Agents:pharmacology, Antioxidants:pharmacology, Female, Graft Survival, Malondialdehyde:blood, Melatonin:pharmacology, Necrosis, Ovary:metabolism, Oxytetracycline:pharmacology, Peritoneal Cavity, Rats, Rats, Wistar,.   

OBJECTIVES: To comparatively investigate the effects melatonin and oxytetracycline as antioxidants on autologous intraperitoneal ovary transplantation in rats.

SETTING AND DESIGN: 28 adult female Wistar rats with regular estrous cycles were randomly divided into four groups. Group 1 (n=7) was the control group; Group 2 (n=7) bilateral oophorectomy and intraperitoneal transplantation group; and Groups 3 (n=7) and 4 (n=7) firstly received 20 mg/kg/IP melatonin and 10 mg/kg/IP oxytetracycline., respectively and fifteen minutes after that, they had bilateral oophorectomy and intraperitoneal transplantation. Ovarian tissue and blood malondialdehyde (MDA) levels, superoxide dismutase (SOD) and glutathione peroxidase (GSHPx) levels were determined. Vaginal cytology and ovarian necrosis were histopathologically investigated. Kruskall Wallis analysis of variance was used in the statistical analysis of data.

RESULTS: Ovarian necrosis, tissue MDA and plasma MDA levels were significantly higher in Group 2 compared to the Groups 1, 3 and 4 (p<0.03). SOD and GSHPx levels were significantly lower in group 2 compared to the groups 1, 3 and 4 (p<0.03). Melatonin was found to be more effective on ovarian necrosis and tissue MDA level than the use of oxytetracycline following autologous intraperitoneal ovary transplantation (p<0.03). There was a significant positive correlation between tissue MDA level and ovarian necrosis and a very strong negative correlation between tissue MDA and SOD level (rs = +/-0.9, n=28, p=0.000).

CONCLUSION: Although both melatonin and oxytetracycline were found to be effective in autologous intraperitoneal pelvic ovary transplantation, melatonin is more effective against both the ovarian necrosis and tissue MDA level in rats....

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