Prevalencia de parasitosis intestinal en la población infantil de una zona rural del Ecuador / Prevalence of intestinal parasitosis in the child population of a rural area of Ecuador

En la actualidad las investigaciones entorno a la calidad de vida desde la salud, son de vital importancia a nivel mundial, puesto que la identificación de los factores que desencadenan ciertas patologías prevalentes sirven para actuar y mejorar las condiciones de vida; en específico en este trabajo nos referiremos al grupo infantil y la parasitosis pediátrica, la misma que genera índices de anemia, peso bajo, entre otros. El propósito fue identificar la prevalencia de parásitos intestinales en escolares de 6 a 12 años en poblaciones rurales, de la ciudad de Paute, Ecuador. Se realizó una investigación de tipo cuantitativa, descriptiva y transversal, se trabajó con 608 niños pertenecientes a zonas rurales de Paute, el análisis coprológico fue mediante el método convencional, se reportó número de parásitos por campo. Esta investigación fue desarrollada bajo el permiso de un Comité de Bioética. Se analizaron 608 muestras coproparasitarias, obteniéndose una significancia estadística con respecto al sexo, los varones presentaron una prevalencia de parasitismo (14,63%) sobre las mujeres (8,88%), el parásito con mayor prevalencia es la Entamoeba histolytica. La prevalencia de parasitosis infantil en el sector rural de Paute, Ecuador es de 23,52%, siendo mayor en varones, el parásito más frecuente es la E. histolytica(AU)

Currently, the research about life's quality from a health's point of view has received tremendous attention around the world, because the identification of the facts that start a variety of prevalent pathologies are being used to improve life conditions. In this work we try the child group and its pediatric parasitosis, that produce anemia, low weight, and others. The purpose was to recognize the prevalence of intestinal parasites in scholar children from 6 to 12 years old in marginal populations of the city Paute, Ecuador. A quantity type of investigation was made, descriptive and transversal, using a population of 608 children from the rural population of Paute, the coprological analysis was using conventional methods, number of parasites were reported. This research was developed under the permission of the Bioethics Committee. 608 coproparasites samples were analyzed, getting a significative statistic in reference to sex. Boy's samples show a prevalence of parasitism (14,63%) in girls' samples (8,88%), the more prevalent parasite is Entamoeba Histolytica. The prevalence of children's parasitosis in the rural sector of Paute, Ecuador is 23,52% being more affected boys than girls. The most frequent parasite is E. Histolytica(AU)

Fos immunoreactivity in the suprachiasmatic nuclei of golden hamsters bearing an ectopic pituitary graft.

Young male golden hamsters, made hyperprolactinemic by a pituitary graft under the kidney capsule, were exposed to a light pulse (1,000 lx/30 min) at Zeitgeber time (ZT) 18. Controls included hamsters receiving a sham graft (muscle). Fos immunoreactive cells were counted in both suprachiasmatic nuclei (SCN) of each animal, using an image analyzer system. The Fos immunoreactivity (Fos-ir) of the ventrolateral and dorsomedial SCN regions was greater in the pituitary-grafted hamsters. Indeed, light induced the greatest response in grafted animals in both SCN regions. However, the SCN of pituitary-grafted hamsters in the absence of light showed the lowest Fos-ir in both regions. The results support the occurrence of a dual effect of hyperprolactinemia on Fos-ir in the SCN of hamsters at ZT 18, with inhibition of Fos expression in the absence of light and potentiation of early gene expression when animals were exposed to a light pulse.

Age-dependent changes in 24-hour rhythms of catecholamine content and turnover in hypothalamus, corpus striatum and pituitary gland of rats injected with Freund's adjuvant.

BACKGROUND: Little information is available on the circadian sequela of an immune challenge in the brain of aged rats. To assess them, we studied 24-hour rhythms in hypothalamic and striatal norepinephrine (NE) content, hypothalamic and striatal dopamine (DA) turnover and hypophysial NE and DA content, in young (2 months) and aged (18-20 months) rats killed at 6 different time intervals, on day 18th after Freund's adjuvant or adjuvant's vehicle administration. RESULTS: Aging decreased anterior and medial hypothalamic NE content, medial and posterior hypothalamic DA turnover, and striatal NE concentration and DA turnover. Aging also decreased NE and DA content in pituitary neurointermediate lobe and augmented DA content in the anterior pituitary lobe. Immunization by Freund's adjuvant injection caused: (i) reduction of DA turnover in anterior hypothalamus and corpus striatum; (ii) acrophase delay of medial hypothalamic DA turnover in old rats, and of striatal NE content in young rats; (iii) abolition of 24-h rhythm in NE and DA content of neurointermediate pituitary lobe, and in DA content of anterior lobe, of old rats. CONCLUSIONS: The decline in catecholamine neurotransmission with aging could contribute to the decrease of gonadotropin and increase of prolactin release reported in similar groups of rats. Some circadian responses to immunization, e.g. suppression of 24-h rhythms of neurointermediate lobe NE and DA and of anterior lobe DA were seen only in aged rats.

Effect of parasympathetic decentralization on interferon-gamma release from rat submandibular lymph nodes in vitro.

The aim of this study was to examine the regulation of interferon (IFN)-gamma release by cells from submandibular lymph nodes of rats subjected to a unilateral parasympathetic decentralization by severing the ipsilateral chorda tympani 7 days earlier. Cells obtained from contralateral sham-operated submandibular lymph nodes were employed as control. Parasympathetic decentralization of lymph nodes resulted in significantly less IFN-gamma release as compared to that found in innervated lymph nodes. Mitogens (lipopolysaccharide, concanavalin A) stimulated IFN-gamma release in cells derived from the innervated lymph nodes only. The muscarinic agonist metacholine decreased IFN-gamma release in cells derived from innervated lymph nodes. At the highest concentration employed (10(-4) M), metacholine suppressed the stimulatory effect of mitogens on IFN-gamma release in cells of innervated lymph nodes while the muscarinic antagonist atropine (10(-8) - 10(-4) M) lacked to affect IFN-gamma release. Addition of nicotine (10(-5) - 10(-3) M) failed to modify IFN-gamma release. The results support the occurrence of significant effects of local parasympathetics in modulating IFN-gamma release by submandibular lymph nodes.

Changes in substance P content at the hypothalamic-pituitary axis during the Wallerian degeneration of peripheral sympathetic neurons after superior cervical ganglionectomy in male rats: effect of hyperprolactinemia.

The effects of Wallerian degeneration of the peripheral sympathetic neurons projecting to the hypothalamus on the mechanism of interaction between prolactin and substance P (SP) were examined. The effects of superior cervical ganglionectomy (SCGx) on SP content in various hypothalamic regions and in the hypophysis were evaluated in control and hyperprolactinemic rats. Male rats that received pituitary transplants at the age of 5 days and age-matched sham-operated controls were used. Pituitary grafting significantly increased circulating values of prolactin, as did SCGx. In hyperprolactinemic rats, SCGx partially decreased plasma prolactin levels. Neonatal hyperprolactinemia decreased SP content in the anterior (AH) and posterior (PH) hypothalamus and in the median eminence (ME), but increased it in the mediobasal hypothalamus (MBH). Acute SCGx significantly increased SP in the MBH, PH, and ME. SCGx in hyperprolactinemic animals further increased SP content in MBH. In the ME and Ah, SCGx in pituitary grafted rats decreased SP content as compared with the controls. In the pituitary gland (PG), SCGx only decreased SP content in hyperprolactinemic, but not in control rats. An interaction between peripheral nor-adrenergic neurons and prolactin to regulate SP within the hypothalamus was positive in the MBH, AH, ME, and PG, but not in the PH. These data indicate the existence of interactive mechanisms between prolactin and the peripheral sympathetic neurons to regulate SP content at the hypothalamic-pituitary axis. Interrelationships between prolactin and SP were also observed.

In vitro pituitary prolactin, growth hormone and follicle stimulating hormone secretion during sexual maturation of female rats primed with melatonin.

The influence of in vivo melatonin administration on in vitro pituitary follicle stimulating hormone (FSH), growth hormone (GH) and prolactin secretion, as well as the possible influence of dopamine (DA) were evaluated in prepubertal (31-day-old), pubertal (33-day-old) and adult female rats at diestrus phase of the sexual cycle. The in vitro pituitary hormone secretions were evaluated at basal rate for the first hour of incubation only, in Krebs Ringer phosphate (KRP) (I1) and after a second hour of incubation with KRP (I2) or with KRP+DA (I2 plus DA). I1PRL secretion was significantly higher in 33-day-old control and melatonin treated (MEL) rats as compared to I2 periods. However, in 31-day-old rats I1 secretion was higher than in the I2 or I2+DA periods, in MEL rats. In vitro GH secretion was significantly higher at I1 than during I2 periods in the control 31- and 33-day-old groups, but not in MEL rats. The only significant effect of DA was the elevation of GH in prepubertal MEL rats. In vitro FSH release was increased by melatonin in 31- and 33-day-old female rats. No differences in PRL, GH and FSH secretion were found in adult rats. In conclusion, the results show that melatonin effects upon in vitro pituitary gland activity are reproductive-stage-dependent modifying the secretory capacity of the lactotrop, gonadotrop and somatotrop during prepubertal and pubertal ages but not in adult rats studied at a quiescent phase of the sexual cycle.

Aging-induced changes in 24-h rhythms of mitogenic responses, lymphocyte subset populations and neurotransmitter and amino acid content in rat submaxillary lymph nodes during Freund's adjuvant arthritis.

In young (two months) and aged (18 months) male rats injected s.c. with Freund's adjuvant or adjuvant's vehicle 18 days earlier, 24-h variations in mitogenic responses, lymphocyte subsets and monoamine and amino acid content were examined in submaxillary lymph nodes. Mitogenic responses to concanavalin A (Con A) and lipopolysaccharide (LPS) were higher during the light phase of daily photoperiod. Old rats exhibited a suppressed or impaired mitogenic response to Con A but not to LPS. Acrophases of 24-h rhythm in lymphocyte subset populations in submaxillary lymph nodes were: 18:37-19:44h (B cells), 09:00-10:08h (T and CD4(+) cells) and 12:19-15:58h (CD8(+) cells). Aging augmented B cells and decreased T, CD4(+) and CD8(+) cells. Significant correlations were found between Con A activity and T cells, between lymph node 5HT content and B, T and CD8(+) lymphocytes, and between lymph node 5HT and taurine and GABA content. Aging increased lymph node 5HT content but did not modify NE content. Lymph node concentration of aspartate, glutamate and taurine was higher at night while that of GABA attained peak values at late afternoon. Old rats injected with Freund's adjuvant showed a higher mean value (glutamate) and smaller amplitude (glutamate, taurine) than their respective young controls. The results further document the effects of aging on the chronobiology of the immune system.

Effect of superior cervical ganglionectomy on 24-h variations in hormone secretion from the anterior hypophysis and in hypothalamic monoamine turnover during the preclinical phase of Freund's adjuvant arthritis in rats.

The effect of superior cervical ganglionectomy (SCGx) on 24-h rhythms of circulating adrenocorticotropic hormone (ACTH), growth hormone (GH), prolactin and luteinizing hormone (LH) and of hypothalamic noradrenaline content and dopamine and serotonin turnover, was assessed in rats 3 days after administering Freund's complete adjuvant. In sham-operated rats, Freund's adjuvant injection increased serum ACTH without affecting its diurnal rhythmicity. SCGx, performed 10 days earlier, suppressed 24-h rhythmicity and augmented mean values of circulating ACTH. A depressive effect of immunization on GH release was found in both sham-operated and SCGx rats. GH concentrations did not exhibit diurnal rhythmicity and decreased after immunization. Time-of-day-related changes in serum prolactin were significant for all examined groups, except for SCGx-immunized rats. Freund's adjuvant administration augmented prolactin secretion. Daily changes in serum LH concentration and a decrease after immunization were found in both sham-operated and SCGx rats. SCGx: (i) counteracted inhibition of daily variations of noradrenaline content in medial hypothalamus of Freund's adjuvant-injected rats; (ii) decreased anterior hypothalamic dopamine turnover and augmented it in the medial hypothalamus; (iii) lowered amplitude of serotonin turnover rhythm in medial hypothalamus. The data indicate that several early changes in levels and 24-h rhythms of circulating ACTH and prolactin, and in hypothalamic noradrenaline content and dopamine and serotonin turnover, were modified by a previous SCGx in Freund's adjuvant-injected rats.

Effect of local sympathectomy on 24-h changes in mitogenic responses and lymphocyte subset populations in rat submaxillary lymph nodes during the preclinical phase of Freund's adjuvant arthritis.

Wistar male rats received a bilateral superior cervical ganglionectomy or sham-operation and 10 days later were injected with Freund's complete adjuvant or its vehicle. Two days later, rats were killed at six different time intervals throughout a 24-h cycle. The mitogenic effect of lipopolysaccharide (LPS) and concanavalin A (Con A) and the relative size of lymphocyte subset populations were measured in submaxillary lymph nodes. Cells from sympathectomized lymph nodes showed a lower response to Con A. Freund's adjuvant injection decreased amplitude of daily rhythm in Con A response, an effect prevented by denervation. Generally, ganglionectomy increased Con A response at the early phase of arthritis. Acrophases for Con A and LPS effect occurred at early afternoon and did not change after ganglionectomy. Administration of Freund's adjuvant caused a 10-h advance in acrophase of LPS mitogenic activity, an effect prevented by ganglionectomy. Significant 24-h rhythms were observed in relative size of lymph node B and T cells. Denervation augmented amplitude of rhythm in B cells in adjuvant's vehicle-injected rats. As far as T lymphocyte subsets, acrophases occurred at the afternoon (CD4(+) and CD4(+)-CD8(+) cell types) or at night (CD8(+) cell types). Immunization augmented amplitude of 24-h rhythms in CD4(+)-CD8(+) cells regardless of innervation whereas denervation counteracted the suppression of daily rhythm in CD8(+) cells seen in arthritis. The results indicate that some of the changes seen in 24-h organization of immune responses in lymph nodes at an early phase of arthritis are modified by severing the local sympathetic nerves.

Effect of chronic hyperprolactinemia on daily changes of glutamate and aspartate concentrations in the median eminence and different hypothalamic areas of male rats.

The 24h changes of glutamate (GLU) and aspartate (ASP) were studied in the median eminence (ME) and hypothalamic areas. It was analyzed whether prolactin may change their daily patterns. The hypothalamic concentration of these amino acids was measured by high-performance liquid chromatography (HPLC) with fluorometric detection. Plasma prolactin levels increased over the 24h light-dark cycle after pituitary grafting compared to controls, and its circadian rhythm was disrupted. In controls, aspartate and glutamate in the hypothalamic areas studied followed a specific daily variation or showed no rhythmicity. In the median eminence, hyperprolactinemia seem to phase advance the aspartate or glutamate peaks from 16:00 to 12:00. In the mediobasal hypothalamus, hyperprolactinemia altered daily changes of aspartate and significantly decreased its concentration. Also, it seems to delay the nocturnal glutamate peak compared to controls. In the posterior hypothalamus, hyperprolactinemia did not change aspartate and glutamate concentrations and their daily changes, although it increased the glutamine concentration. These data show the existence of 24h changes of amino acid concentration in three of the hypothalamic regions studied. Increased plasma prolactin levels differentially affected these patterns depending on the hypothalamic area analyzed.

Effect of melatonin treatment on 24-h variations in responses to mitogens and lymphocyte subset populations in rat submaxillary lymph nodes.

Wistar male rats were injected s.c. with melatonin (30 microg) or vehicle, 1 h before lights off, for 11 days. Ten days after beginning melatonin treatment, rats received Freund's complete adjuvant or its vehicle s.c., and after 2 days, they were sacrificed at six different time intervals throughout a 24-h cycle. The mitogenic effect of lipopolysaccharide (LPS) and concanavalin A (Con A), the activity of ornithine decarboxylase (ODC) and the relative size of lymphocyte subset populations were measured in submaxillary lymph nodes. In control rats, the mitogenic effects of LPS and Con A and ODC activity peaked during the afternoon. Injection of Freund's adjuvant induced a 10-h shift in the diurnal rhythm of the mitogenic effect of LPS to attain maximal values at night. Melatonin pretreatment blunted the daily variations in the mitogenic activity of Con A or LPS and, when given to Freund's adjuvant-injected rats, augmented mesor and amplitude of diurnal rhythm in ODC activity. Maxima in B cell number occurred at night whereas those of T and B-T cell number occurred during the afternoon. During the early phase of immunization tested, the number of B cells augmented and the amplitude of its diurnal rhythmicity increased both after immunization and following melatonin pretreatment. Maxima of 24-h rhythms in CD4+ and CD4+/CD8+ cell populations occurred during the afternoon while those of CD8+ cells occurred at late night. Melatonin significantly augmented CD4+ cell number and decreased CD8+ cell number; it therefore augmented the CD4+:CD8+ ratio. The results suggest that pretreatment with a pharmacological dose of melatonin exerts immunomodulating effects at an early, preclinical, phase of Freund's adjuvant-induced arthritis in rats.

Age-dependent effect of Freund's adjuvant on 24-hour rhythms in plasma prolactin, growth hormone, thyrotropin, insulin, follicle-stimulating hormone, luteinizing hormone and testosterone in rats.

The effect of Freund's adjuvant administration on 24-hour changes of plasma prolactin, growth hormone (GH), thyrotropin (TSH), insulin, follicle-stimulating hormone (FSH), luteinizing hormone (LH) and testosterone were studied in young (2 months) and aged (18 months) male Wistar rats. Rats were injected s.c. with Freund's adjuvant or adjuvant's vehicle and, 18 days later, they were killed at 6 different time intervals throughout a 24-hour cycle to measure circulating hormone levels by specific RIAs. Young rats receiving adjuvant's vehicle exhibited significant time-of-day-dependent variations in plasma TSH, LH and testosterone, with maximal levels at 1300 h, 0100 h and 1700 h, respectively. Prolactin and insulin levels, analyzed globally in a factorial ANOVA, showed significant time-of-day changes with maximal levels at 1300 - 1700 h and 2100 h, respectively. The daily rhythms in plasma LH and testosterone found in young rats were not longer observed in Freund's adjuvant-injected rats, while as far as TSH, a second peak was observed at 0100 h after Freund's adjuvant administration. Twenty-four hour rhythms in circulating TSH, LH and testosterone were blunted in old rats receiving either Freund's adjuvant or its vehicle. Aged rats exhibited significantly higher circulating levels of prolactin, and lower levels of GH, TSH, FSH and testosterone. The results indicate that secretion of prolactin, GH, TSH, FSH and testosterone are age-dependent, as are the responses of TSH, LH and testosterone to Freund's adjuvant administration.

Differential effect of interferon-gamma injection on mitogenic responses in sympathetically denervated submaxillary lymph nodes of rats.

This study aimed to assess the effect of interferon (IFN)-gamma treatment on mitogenic responses in submaxillary lymph nodes in the presence or absence of local sympathetic nerves. Adult male rats were subjected to a unilateral superior cervical ganglionectomy and to a contralateral sham-operation. Seven days later, rats received five i.p. daily injections of human IFN-gamma (10(5) U.I./kg) or saline. On the day after the last injection, rats were killed at six different times throughout a 24-h cycle and the mitogenic effect of lipopolysaccharide (LPS) and concanavalin A (Con A) was assessed in single-cell suspensions of lymph nodes. In vehicle-treated rats, proliferation responses to LPS in innervated lymph nodes did not show time-of-day variations while those in denervated lymph nodes attained a maximum at 17:00 h. Following IFN-gamma administration, a promoting effect of LPS mitotic response was detected at 01:00 h at the innervated side only. As far as the mitogenic responses to Con A, proliferation in innervated lymph nodes of vehicle-treated controls attained a maximum at 09:00 h. Such a daily variation in response to Con A was not detectable at the denervated side. IFN-gamma treatment increased significantly Con A activity by promoting a greater mitogenic response at 01:00 h. Sympathetic denervation of lymph nodes brought about a shift in the maximum in number of cells per mg of lymph node from 21:00 to 13:00 h. After IFN-gamma treatment, maxima in cell number occurred at 05:00 h at both the innervated and denervated side. The results indicate that IFN-gamma effects in rat submaxillary lymph nodes are under substantial modulation by local sympathetic nerves.

Effect of prenatal melatonin on the gonadotropin and prolactin response to the feedback effect of testosterone in male offspring.

The purpose of this study was to investigate the effects of prenatal melatonin administration on the sensitivity of the androgens negative feedback effect on gonadotropin and prolactin secretion in male offspring. Male offspring of control (control-offspring) and melatonin treated (MEL-treated) (150 microg/100 g BW) mother rats during pregnancy (MEL-offspring), at infantile, prepubertal, and pubertal periods were studied. LH secretion in response to testosterone propionate (TP) in control-offspring showed the classical negative feedback effect at all ages studied. In MEL-offspring a negative response after TP was also observed in all ages studied although the magnitude of this response was altered in this group as compared to controls. FSH values were significantly lower at most ages and time points studied in MEL-offspring than in control-offspring. FSH secretion in MEL-offspring showed a delayed negative feedback action of TP injection as compared to control-offspring. This response was observed at 21 days of age in control-offspring and delayed until day 30 of life in MEL-offspring. Parallely it remain at later age in MEL-offspring than in control-offspring. Prolactin secretion in control-offspring showed increased values after TP injections from infantile to pubertal periods. This increase was blunted in MEL-offspring at 17 and 35 days of age showing significantly reduced (p<0.01; p<0.05) plasma prolactin levels. During pubertal period a prolactin positive response to TP administration was observed in MEL-offspring but with significantly lower magnitude than in control-offspring. These results indicate that prenatal melatonin exposure induced changes in the sensitivity of gonadotropin and prolactin feedback response to testosterone, indicating a delayed sexual maturation of the neuroendocrine-reproductive axis in male offspring.

Interferon-gamma release in sympathetically denervated rat submaxillary lymph nodes.

OBJECTIVE: To examine the regulation of interferon (IFN)-gamma release by cells derived from submaxillary lymph nodes of rats subjected to an acute or chronic superior cervical ganglionectomy (SCGx). METHODS: A unilateral SCGx and a contralateral sham operation were performed. Twenty hours or 7 days later cells from submaxillary lymph nodes were incubated for 24 h without any additional treatment (experiment 1), after adding lipopolysaccharide or concanavalin A (experiment 2) or after adding norepinephrine (NE, 10(-8) M; experiment 3). IFN-gamma concentration in the culture media was measured by ELISA. RESULTS: Compared to controls, cells obtained from lymph nodes at a time of degeneration of sympathetic nerve terminals released more IFN-gamma, whereas those derived from chronically SCGx lymph nodes released less IFN-gamma. Stimulation of IFN-gamma release by mitogens was detectable in the innervated or acutely denervated lymph nodes, but not in chronically denervated lymph nodes. When the effect of 10(-8) M NE on IFN-gamma release was tested, the neurotransmitter augmented cytokine release in cells prepared from chronically denervated lymph nodes only. CONCLUSION: The microenvironment provided by local sympathetic nerves is essential to enable an appropriate IFN-gamma release by submaxillary lymph node cells to occur.

Prenatal melatonin exposure influences the maturation of gonadotropin and prolactin estradiol-benzoate feedback system.

Gonadotropin and prolactin response to estrogen feedback in female rat offspring of control and melatonin treated (150 microg/100 g BW) mother rats during pregnancy (MEL-offspring) were studied at these periods: infantile, prepubertal and pubertal. In controls negative or absent LH feedback developed after estradiol benzoate (EB) injection up to 30 days of age indicating that the onset of puberty had not occurred. The positive feedback was established from day 33 on. However, in MEL-offspring the first activation of gonadotropin secretion during afternoon, 31 h after EB, was observed at 25 days of age, representing the first neuroendocrine sign of the onset of puberty. This positive response disappeared on day 30 in MEL-offspring. At 33 days of age, the LH positive response to EB was found in both groups, indicating a more advanced sexual development. In controls, this response increased at 35 days of age while in MEL-offspring it was highly depressed. FSH secretion in response to EB showed a negative feedback effect from infantile to the end of prepubertal period in both groups. The positive feedback was observed earlier in MEL-offspring (at 33 days of age) than in controls (at 35 days of age), but at this age it was absent in MEL-offspring. A positive prolactin response to EB at all ages in controls was observed. The typical pulsatility with higher values in the afternoon appeared by the first time at 30 days of age. However, in MEL-offspring no pulsatile response was observed throughout any age. These data suggest that prenatal melatonin administration altered gonadotropin and prolactin response to EB inducing precocious sensitivity during prepubertal period but depressed response during the pubertal period.

Effect of melatonin treatment on 24-hour rhythms of serum ACTH, growth hormone, prolactin, luteinizing hormone and insulin in rats injected with Freund's adjuvant.

The effect of melatonin injection on Freund's adjuvant-induced changes in levels and 24-hr rhythms of circulating ACTH, growth hormone (GH), prolactin (PRL), luteinizing hormone (LH), and insulin was assessed in rats. Animals received subcutaneous (s.c.) injections of melatonin (30 microg) or vehicle, 1 hr before lights off for 12 days. Ten days after melatonin treatment, they were injected with Freund's complete adjuvant or its vehicle s.c., and after 3 days, rats were killed at six different time intervals throughout a 24-hr cycle to measure the different hormones by radioimmunoassay (RIA). Following Freund's adjuvant injection, an increase in serum ACTH, with maintenance of ACTH diurnal rhythm was found. Acrophases of the ACTH rhythm varied from 13:39 to 17:12 hr and the amplitude of rhythm was augmented after immunization. In immunized rats, melatonin treatment increased the amplitude of serum ACTH rhythm. For GH, a depressive effect of immunization on circulating levels, together with absence of diurnal rhythmicity were found. Immunization augmented circulating PRL, while conserving its diurnal rhythmicity. Melatonin-injected rats showed significant diurnal variations of serum PRL after immunization only. Acrophases of the serum PRL rhythm varied from 19:37 to 22:04 hr. Immunization decreased circulating LH and suppressed its 24-hr rhythmicity pattern. The effect of immunization on LH was counteracted by melatonin injection. Acrophases of serum LH rhythm varied from 00:44 to 03:53 hr. Significant effects of immunization and time of day on circulating insulin were detected; immunization increased serum insulin levels with a shift in acrophase from early afternoon to midnight. The data indicate that several early changes in levels and 24-hr rhythms of circulating ACTH, PRL, and LH in Freund's adjuvant-injected rats were sensitive to treatment with pharmacological amounts of melatonin.

Melatonin as a time-meaningful signal in circadian organization of immune response.

Melatonin is synthesized and secreted during the dark period of the light/dark cycle. The rhythmic nocturnal melatonin secretion is directly generated by the circadian clock, located within the suprachiasmatic nuclei in mammals and is entrained to a 24-hour period by the light-dark cycle. The periodic secretion of melatonin may be used as a circadian mediator to any system that can 'read' the message. Melatonin seems to act as an arm of the circadian clock, giving a time-related signal to a number of body functions; one of these, the circadian organization of the defense of the organism, is discussed in some detail as an example.

Coexpression of glucagon-like peptide-1 (GLP-1) receptor, vasopressin, and oxytocin mRNAs in neurons of the rat hypothalamic supraoptic and paraventricular nuclei: effect of GLP-1(7-36)amide on vasopressin and oxytocin release.

This study was designed to gain better insight into the relationship between glucagon-like peptide-1 (GLP-1) (7-36) amide and vasopressin (AVP) and oxytocin (OX). In situ hybridization histochemistry revealed colocalization of the mRNAs for GLP-1 receptor, AVP, and OX in neurons of the hypothalamic supraoptic and paraventricular nuclei. To determine whether GLP-1(7-36)amide alters AVP and/or OX release, both in vivo and in vitro experimental study designs were used. In vivo, intravenous administration of 1 microg of GLP-1(7-36)amide into the jugular vein significantly decreased plasma AVP and OX concentrations. In vitro incubation of the neurohypophysis with either 0.1 or 1 microg of GLP-1(7-36)amide did not modify the release of AVP. However, addition of 1 microg of GLP-1(7-36)amide to the incubation medium increased slightly the secretion of OX. The coexpression of GLP-1 receptor and AVP mRNAs in hypothalamic supraoptic and paraventricular nuclei gives further support to the already reported central effects of GLP-1 (7-36)amide on AVP. Our findings also suggest a dual secretory response of AVP and OX to the effect of GLP-1 (7-36)amide, which most likely is related to the amount and/or the route of peptide administration.