Melatonin as adjunctive therapy in the treatment of periodontitis associated with obesity.

AIMS: To study the effect of adjunctive systemic administration of melatonin to standard mechanical periodontal therapy in obese rats with experimental periodontitis. MATERIALS AND METHODS: In 42 Wistar rats with an initial body weight of 180 g., half (n = 21) were fed with a high-fat diet to induce obesity. In both obese and normal-weight groups, experimental periodontitis was subsequently induced through oral gavages with a combination of Porphyromonas gingivalis and Fusobacterium nucleatum. Both groups were randomly allocated to either no treatment or periodontal treatment consisting on standard mechanical debridement, with either adjunctive chlorhexidine or melatonin. Outcomes were evaluated by the changes in clinical parameters (probing depth modified gingival index, plaque dental index and bleeding on probing [BOP]), in bone resorption and in the levels of biomarkers in plasma and in gingival tissue (inflammatory cytokines, insulin, leptin, osteocalcin, osteopontin, plasminogen activator inhibitor-1, intercellular adhesion molecule 1, E-selectin and lipids). RESULTS: In the obese-periodontitis group, adjunctive melatonin administration resulted in reduced gingival inflammation and BOP, with significant reductions in probing depth and enhanced bone repair demonstrated by micro-CT (15% reduction in alveolar bone destruction) when compared with the same group treated with adjunctive CHX or the normal-weight rats with either melatonin or CHX. In this melatonin-treated obese-periodontitis group, a significant impact on biochemical biomarkers was also demonstrated in both gingival and plasma samples, when compared with the other groups, with significant reductions in pro-inflammatory cytokines. CONCLUSIONS: Adjunctive melatonin therapy significantly reduced alveolar bone loss and exerted a protective anti-inflammatory effect mainly in those experimental animals affected by the co-morbidity of periodontitis and obesity.

Citrus essential oils inhalation by mice: Behavioral testing, GCMS plasma analysis, corticosterone, and melatonin levels evaluation.

The use of orange essential oils (EOs) as a complementary treatment is very common in Brazilian popular culture. The levels of melatonin (MEL) and corticosterone (CORT) hormones were investigated simultaneously, by the Luminex™ immunoassay system in mice plasma, after Citrus aurantium and Citrus sinensis EOs inhalation for 30 min. The plasma was analyzed by headspace through gas chromatography coupled to mass spectrometry for investigation of the EO components. Mice were submitted to behavioral testing to research anxiolytic-like, sedative, and antidepressant-like effects. The inhalation of atmosphere obtained from vaporization of 10% solution of this Citrus EO separately did not affect MEL or CORT plasma levels; that is, the MEL and CORT levels did not present variation in function of the EO in the schedule used. On the other hand, the imipramine positive control used altered the level of MEL as expected. The EO constituents were detected in plasma at different ratios that is present in inhaled EO. Behavioral tests showed that the inhalation of 10% C. sinensis EO presents an anxiolytic-like and sedative effect. Thus, C. sinensis EO can be a valuable tool for treatment of the anxiety disturbs, apparently without interference with MEL and CORT physiological levels.

Do chronic myeloid leukemia patients with late "warning" responses benefit from "watch and wait" or switching therapy to a second generation tyrosine kinase inhibitor?

In the latest recommendations for the management of chronic-phase chronic myeloid leukemia suboptimal responses have been reclassified as "warning responses." In contrast to previous recommendations current guidance advises close monitoring without changing therapy. We have identified 198 patients treated with first-line imatinib, with a warning response after 12 months of treatment (patients with a complete cytogenetic response but no major molecular response [MMR]). One hundred and forty-six patients remained on imatinib, while 52 patients changed treatment to a second generation tyrosine kinase inhibitor (2GTKI). Changing therapy did not correlate with an increase in overall survival or progression-free survival. Nevertheless, a significant improvement was observed in the probability of a MMR: 24% vs. 42% by 12 months and 43% vs. 64% by 24 months (P = 0.002); as well as the probability of achieving a deep molecular responses (MR(4.5) ): 1% vs. 17% and 7% vs. 23% by 12 and 24 months, respectively (P = <0.001) .The treatment change to 2GTKI remained safe; however, we have observed a 19% of treatment discontinuation due to side effects. We have observed an improvement of molecular responses after changing treatment to 2GTKI in patients with late suboptimal response treated with imatinib first line. However, these benefits were not correlated with an improvement of progression free survival or overall survival.

Melatonin and the metabolic syndrome: physiopathologic and therapeutical implications.

Metabolic syndrome (MS) patients exhibit sleep/wake disturbances and other circadian abnormalities, and these may be associated with more rapid weight increase and development of diabetes and atherosclerotic disease. On this basis, the successful management of MS may require an ideal drug that besides antagonizing the trigger factors of MS could also correct the disturbed sleep-wake rhythm. Melatonin is an effective chronobiotic agent able to change the phase and amplitude of circadian rhythms. Melatonin has also significant cytoprotective properties preventing a number of MS sequelae in animal models of diabetes and obesity. A small number of controlled trials indicate that melatonin is useful to treat the metabolic and cardiovascular comorbidities of MS. Whether the recently introduced melatonergic agents (ramelteon, agomelatine, tasimelteon) have the potential for treating sleep disorders in MS patients and, more generally, for arresting the progression of disease, merits further investigation.

Laser microperforated biodegradable microbial polyhydroxyalkanoate substrates for tissue repair strategies: an infrared microspectroscopy study.

Flexible and biodegradable film substrates prepared by solvent casting from poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) solutions in chloroform were microperforated by ultraviolet laser ablation and subsequently characterized using infrared (IR) microspectroscopy and imaging techniques and scanning electron microscopy (SEM). Both transmission synchrotron IR microspectroscopy and attenuated total reflectance microspectroscopy measurements demonstrate variations in the polymer at the ablated pore rims, including evidence for changes in chemical structure and crystallinity. SEM results on microperforated PHBHV substrates after cell culture demonstrated that the physical and chemical changes observed in the biomaterial did not hinder cell migration through the pores.

TP53 Abnormalities and MMR Preservation in 5 Cases of Proliferating Trichilemmal Tumours.

Proliferating trichilemmal tumours (PTT) are defined by a benign squamous cell proliferation inside a trichilemmal cystic (TC) cavity. A possible explanation of this proliferative phenomenon within the cyst may be molecular alterations in genes associated to cell proliferation, which can be induced by ultraviolet radiation. Among other genes, alterations on TP53 and DNA mismatch repair proteins (MMR) may be involved in the cellular proliferation observed in PTT. Based on this assumption, but also taking into account the close relationship between the sebaceous ducts and the external root sheath where TC develop, a MMR, a p53 expression assessment and a TP53 study were performed in a series of 5 PTT cases, including a giant one. We failed to demonstrate a MMR disorder on studied PTT, but we agree with previous results suggesting increased p53 expression in these tumours, particularly in proliferative areas. TP53 alteration was confirmed with FISH technique, demonstrating TP53 deletion in most cells.

Melatonin effect on plasma adiponectin, leptin, insulin, glucose, triglycerides and cholesterol in normal and high fat-fed rats.

Melatonin effect on body weight progression, mean levels and 24-hr pattern of circulating adiponectin, leptin, insulin, glucose, triglycerides and cholesterol were examined in rats fed a normal or a high-fat diet. In experiment 1, rats fed a normal diet were divided into two groups: receiving melatonin (25 µg/mL drinking water) or vehicle for 9 wk. In experiment 2, animals were divided into three groups: two fed with a high-fat diet (35% fat) and melatonin (25 µg/mL) or vehicle in drinking water for 11 wk, while a third group was given a normal diet (4% fat). At the end of experiments, groups of eight rats were killed at six different time intervals throughout a 24-hr period. Melatonin administration for 9 wk decreased body weight gain from the 3rd wk on without affecting food intake. A significant reduction in circulating insulin, glucose and triglyceride mean levels and disrupted daily patterns of plasma adiponectin, leptin and insulin were observed after melatonin. In high fat-fed rats, melatonin attenuated body weight increase, hyperglycemia and hyperinsulinemia, as well as the increase in mean plasma adiponectin, leptin, triglycerides and cholesterol levels. The high-fat diet disrupted normal 24-hr patterns of circulating adiponectin, insulin and cholesterol, the effects on insulin and cholesterol being counteracted by melatonin. Nocturnal plasma melatonin concentration in control and obese rats receiving melatonin for 11 wk attained values 21-24-fold greater than controls. The results indicate that melatonin counteracts some of the disrupting effects of diet-induced obesity in rats.

Effect of aging on 24-hour pattern of stress hormones and leptin in rats.

This work analyzes the 24-hour changes of hypothalamic-pituitary-adrenal (HPA) axis activity and leptin release in aged rats. Three- and 22-month-old male Wistar rats were killed at 6 time intervals during a 24-hour cycle (n=8-10 rats/group). Aging augmented plasma ACTH while it decreased plasma and adrenal gland corticosterone levels. Plasma and adrenal corticosterone levels attained high levels during all the scotophase, concomitantly with the maxima in ACTH levels, whereas in aged rats only a brief plasma corticosterone peak at the early scotophase and no time of day variations of adrenal corticosterone were observed. Aging augmented circulating leptin, with a significant interaction "agextime" in the factorial ANOVA, i.e. only in young rats time of day changes were significant, with the lowest values of leptin at the middle of the light period and higher values at night. When plasma leptin was expressed on body weight basis, the age-related differences became not significant but the daily pattern of plasma leptin found in young rats persisted. Plasma and adrenal corticosterone levels correlated significantly with plasma ACTH only in young rats. Likewise, plasma leptin correlated with plasma corticosterone only in young rats. These changes can be attributed to a disrupting effect of aging on the homeostatic mechanisms modulating HPA activity and leptin release.

Obesity and periodontitis: An experimental study to evaluate periodontal and systemic effects of comorbidity.

BACKGROUND: Obesity and overweight have been associated with periodontitis. This study aims to evaluate periodontal and systemic effects of this association in a validated experimental model. METHODS: Twenty-eight male Wistar rats were randomly divided into four groups: 1) control group (Con) (fed with standard diet); 2) high-fat diet group (HFD) (fed with a diet containing 35.2% fat); 3) control group with induced periodontitis (Con-Perio); and 4) HFD group with induced periodontitis (HFD-Perio). To induce periodontitis, oral gavages with Porphyromonas gingivalis ATCC W83K1 and Fusobacterium nucleatum DMSZ 20482 were used. Periodontal outcomes were evaluated by inflammatory parameters, periodontal probing depth (PD), and modified gingival index (MGI). Systemic effects were evaluated by measuring levels of inflammatory cytokines, insulin, adiponectin, and leptin using multiplex immunoassays and levels of visfatin, resistin, lipid profiles, transaminases, and plasma endotoxin using colorimetric tests and the glucose tolerance test. RESULTS: Clinical parameters (PD and MGI) were significantly increased (P < 0.05) in the induced periodontitis groups compared with controls. The HFD-Perio group demonstrated significantly higher PD compared with Con-Perio group. Lipid profiles, cytokines, and adipocytokines showed significantly elevated levels in the HFD-Perio group compared with the other groups. Similarly, glucose levels in the HFD-Perio group were significantly higher (P < 0.05) than in the HFD group, and hepatic damage parameters demonstrated a tendency toward higher levels in the HFD-Perio group. CONCLUSION: Obesity and periodontitis demonstrated a comorbidity effect on both systemic inflammatory and metabolic dysregulation biomarkers, with increased glucose, dyslipidemia and hepatic damage.

Immune response after experimental allergic encephalomyelitis in rats subjected to calorie restriction.

Male Lewis rats (6 weeks-old) were submitted to a calorie restriction equivalent to 33% or 66% of food restriction. Fifteen days later, groups of 7 animals were injected with complete Freund's adjuvant plus spinal cord homogenate (SCH) to induce experimental allergic encephalomyelitis (EAE) or with complete Freund's adjuvant alone. EAE was defined solely on clinical grounds. Rats were assessed daily for clinical signs of EAE and were killed on day 15 after immunization. Both diet and SCH injection diminished body weight significantly. In contrast to rats receiving a normal diet or a 33% calorie-restricted diet, rats subjected to severe calorie restriction did not exhibit clinical signs of EAE. Concomitantly with the lack of disease manifestation, 66% of calorie-restricted rats injected with SCH showed significantly less splenic and lymph node mitogenic response to concanavalin A (Con A) and a higher splenic response to lipopolysaccharide. Fewer splenic, lymph node and thymic CD4+ cells, greater numbers of splenic and lymph node CD8+ and CD4+- CD8+ cells, and fewer splenic T, B and T-B cells, and lymph node and thymic B and T-B cells were observed. There was impaired interferon (IFN)-gamma production occurred in the three examined tissues. The results are compatible with the view that the acute phase of EAE can be curtailed by severe calorie restriction, presumably through impaired IFN-gamma production.

A Nd:YAG laser-microperforated poly(3-hydroxybutyrate-co-3-hydroxyvalerate)-basal membrane matrix composite film as substrate for keratinocytes.

Epithelia cultured for the treatment of ulcers, burns and for gene therapy applications require a flexible biomaterial for growth and transplantation that is adaptable to body contours. We tested several materials and found that a poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) polyester provided support for keratinocytes, although adhesion to this material proved to be suboptimal. Since epithelia adhere to the mesoderm through basal membranes, we engineered a basal membrane surrogate by preparing composites of PHBHV with basal membrane matrix (BMM). To allow cell migration into injuried areas the polyester film was micromachined to insert high-density micropores through a Nd:YAG laser ablation process. These flexible composites provided firm attachment for keratinocytes from the outer root sheath of human hair allowing keratinocyte migration through micropores. Films of microperforated PHBHV-BMM may be of use for the replacement of diseased or injured skin epithelia.

24-Hour rhythm in gene expression of nitric oxide synthase and heme-peroxidase in anterior pituitary of ethanol-fed rats.

Chronic exposure of rats to ethanol results in significant changes in pituitary hormone secretion. However, identification of the site(s) and mechanism of action of ethanol to induce these effects remains elusive. Free radical damage at the adenohypophyseal level may play a role in the decline in serum gonadotropin levels in ethanol-fed rats. Since 24-h changes in redox state occurred, we analyzed the 24-h changes in pituitary gene expression of the prooxidant enzymes nitric oxide synthase (NOS) 1 and 2, and of heme oxygenase-1 (HO-1) enzyme, and in plasma NO(2)(-) and NO(3)(-) (NO(x)) levels, in ethanol and control rats. Male rats, 35-day-old, received a liquid diet for 4 weeks. The ethanol-fed group received a similar diet to controls except for that maltose was isocalorically replaced by ethanol. Animals were killed at six time intervals during a 24-h cycle. Anterior pituitary mRNA levels encoding NOS1, NOS2 and HO-1 were measured by real-time PCR analysis. Plasma NO(x) concentration was determined by the Griess reaction. Ethanol feeding of prepubertal rats changed significantly the 24-h pattern of expression of NOS1, NOS2 and HO-1 in the adenohypophysis and augmented NOS2 and HO-1 mRNA levels. Peak values for the three enzymes in ethanol-fed rats occurred at the beginning of the scotophase (i.e., at 21:00 h). Ethanol feeding augmented mean values plasma NO(x) levels with a maximum at 13:00 h while in controls a biphasic pattern was observed, with peaks at 09:00 h and 17:00-21:00 h. One of the mechanisms by which ethanol augments oxidative damage in the adenohypophysis may include overproduction of nitric oxide and carbon monoxide.

Cadmium-induced changes in Per 1 and Per 2 gene expression in rat hypothalamus and anterior pituitary: effect of melatonin.

Chronic cadmium (Cd) administration affects the circadian release of pituitary hormones in rats. To assess whether Cd modifies expression of two major clock genes, period (Per) 1 and Per 2, in the hypothalamic-pituitary unit and to what extent the changes could be prevented by melatonin, rats were exposed to CdCl(2) (5ppm in drinking water) with or without melatonin (3 microg/mL drinking water) for 1 month and were killed at two time intervals, i.e. a the beginning of the rest span (09:00h) and at the middle of the activity span (01:00h). Hypothalamic and pituitary mRNA levels encoding Per 1 and Per 2 were measured by real-time PCR analysis. Cd treatment decreased expression of hypothalamic Per 1 gene at both time intervals, of hypothalamic Per 2 gene at 01:00h, and of adenohypophysial Per 1 and Per 2 genes at 09:00h. Melatonin administration counteracted most of the effects of Cd and augmented hypothalamic Per 2, and adenohypophysial Per 1 and Per 2 gene expression. The results indicate that Cd administered chronically in the drinking water to rats affected expression of clock genes in the hypothalamic-pituitary unit, an effect prevented by melatonin.

Experimental allergic encephalomyelitis in pituitary-grafted Lewis rats.

Treatment of susceptible rats with dopaminergic agonists that reduce prolactin release decreases both severity and duration of clinical signs of experimental allergic encephalomyelitis (EAE). To assess to what extent the presence of an ectopic pituitary (that produces an increase in plasma prolactin levels mainly derived from the ectopic gland) affects EAE, 39 male Lewis rats were submitted to pituitary grafting from littermate donors. Another group of 38 rats was sham-operated by implanting a muscle fragment similar in size to the pituitary graft. All rats received subcutaneous (s.c.) injections of complete Freund's adjuvant (CFA) plus spinal cord homogenate (SCH) and were monitored daily for clinical signs of EAE. Animals were killed by decapitation on days 1, 4, 7, 11 or 15 after immunization and plasma was collected for prolactin RIA. In a second experiment, 48 rats were immunized by s.c. injection of a mixture of SCH and CFA, and then received daily s.c. injections of bromocriptine (1 mg/kg) or saline. Groups of 8 animals were killed on days 8, 11 or 15 after immunization and plasma prolactin was measured. Only sham-operated rats exhibited clinical signs of the disease when assessed on day 15 after immunization. A progressive decrease in plasma prolactin levels was observed in pituitary-grafted rats, attaining a minimum 15 days after immunization, whereas plasma prolactin levels were increased during the course of the disease in sham-operated rats. Plasma prolactin levels were higher in pituitary-grafted rats than in sham-operated rats 1 day after immunization, but lower on days 7, 11 and 15 after immunogen injection. Further supporting a correlation of suppressed prolactin levels with absence of clinical signs of EAE, rats that were administered the dopaminergic agonist bromocriptine showed very low plasma prolactin levels and did not exhibit any clinical sign of EAE. These results indicate that low circulating prolactin levels coincide with absence of clinical signs of EAE in Lewis rats.

NMR relaxometry and imaging of water absorbed in biodegradable polymer scaffolds.

Porous substrates made of poly(3-hydroxybutyrate-3-hydroxyvalerate) (PHBHV) were prepared by a particulate leaching method. After removing the salt by extraction in water, proton nuclear magnetic resonance (NMR) relaxometry and imaging were performed on sets of PHBHV substrates immersed in phosphate-buffered solution during 3 months at different time points. Polarized optical microscopy studies were performed on thin sections, 25 and 5 mum, of the PHBHV samples. The results of NMR relaxometry showed two (1)H nuclei populations, well distinguishable on the free induction decay (FID), due to the different decay time constants, a factor of 10(2) apart. Thus, it was possible to separate the two populations, giving separate distributions of T(1) relaxation times. One population could be associated with water protons in the pores and the other to macromolecular protons. The distributions of T(1) and T(2) of the water proton shifted to lower values with increasing immersion time to a constant value after 30 days. The results obtained by NMR imaging showed an initial increase in the apparent porosity, reaching a plateau after 25 days of immersion. This increase is attributed mainly to the absorption of water in the microporosity as supported by the results of the relaxometry measurements and shown by scanning electron microscopy. The average porosity measured by NMR imaging at the plateau, 78+/-3%, is slightly higher than that determined by optical microscopy, 73+/-9%, which may be due to the fact that the latter method did not resolve the microporosity. Overall, the results suggest that at early stages after immersing the scaffolds in the aqueous medium, first 30 days approximately, NMR imaging could underestimate the porosity of the substrate.

Toxic effects of methoxychlor on the episodic prolactin secretory pattern: possible mediated effects of nitric oxide production.

BACKGROUND: This work addresses the issue of whether methoxychlor (MTX) exposure may modify the ultradian secretion of prolactin through changes in the synthesis of nitric oxide (NO) induced by Nomega-nitro-L-arginine methyl ester (L-NAME) in the hypothalamic-pituitary axis. Associated changes in dopamine (DA) content in the anterior (AH), mediobasal (MBH) and posterior hypothalamus (PH) and median eminence (ME) were evaluated. METHODS: Two groups of animals (MTX and MTX+L-NAME treated) received subcutaneous (sc) injections of MTX at a dose of 25 mg/kg/day for one month. The other two groups of animals (control and L-NAME treated) received sc vehicle injections (0.5 mL/day of sesame oil), during the same period of time to be used as controls. Forty hours before the day of the experiment, animals were anaesthetized with intrapritoneal injections of 2.5% tribromoethanol in saline and atrial cannulas were implanted through the external jugular vein. Plasma was continuously extracted in Hamilton syringes coupled to a peristaltic bomb in tubes containing phosphate-gelatine buffer (to increase viscosity). The plasma was obtained by decantation and kept every 7 minutes for the measurement of plasma prolactin levels through a specific radioimmnunoassay and DA concentration by high-pressure liquid chromatography (HPLC). RESULTS: Prolactin release in animals from all experimental groups analyzed was episodic. Mean plasma prolactin levels during the bleeding period, and the absolute pulse amplitude were increased after MTX or Nomega-nitro-L-arginine methyl ester (L-NAME) administration. However MTX and L-NAME did not modify any other parameter studied with the exception of relative pulse amplitude in MTX treated rats. L-NAME administration to rats treated with the pesticide reduced mean plasma prolactin levels and the absolute amplitude of prolactin peaks. Peak duration, frequency and relative amplitude of prolactin peaks were not changed in the group of rats treated with MTX plus L-NAME as compared to either control or MTX treated rats. Whereas MTX decreased DA content in the ME and increased it in the AH, its content did not change in the MBH or PH, as compared to the values found in controls. Also, L-NAME administration decreased DA content in the ME as compared to controls. However, L- NAME administration to MTX exposed rats, markedly increased DA content in the ME as compared to either MTX treated or control rats. L-NAME administration increased DA content in the AH as compared to the values found in non-treated rats. However L-NAME administration to MTX exposed rats did not modify DA content as compared to either MTX treated or control rats. L-NAME administration did not modify DA content at the MBH nor in saline treated nor in MTX treated rats. However, the values of DA in the MBH in MTX plus L-NAME treated animals were statistically decreased as compared to L-NAME treated rats. In the PH, L-NAME administration increased DA content as compared to the values found in non-treated animals. L-NAME administration to MTX exposed rats also increased DA content as compared to either MTX treated or control rats. CONCLUSION: The results suggest the existence of an interaction between MTX and L-NAME in the modulation of the ultradian prolactin secretion at the pituitary levels. The possibility of an indirect effect mediated by changes in DA content at the ME requires further examination.

Effect of rabbit doe-litter separation on 24-hour changes of luteinizing hormone, follicle stimulating hormone and prolactin release in female and male suckling pups.

BACKGROUND: The daily pattern of nursing of the rabbit pup by the doe is the most important event in the day for the newborn and is neatly anticipated by them. Such anticipation presumably needs a close correlation with changes in hormones that will allow the pups to develop an appropriate behavior. Although a number of circadian functions have been examined in newborn rabbits, there is no information on 24-h pattern of gonadotropin release or on possible sex-related differences in gonadotropin or prolactin (PRL) release of pups. This study examined the 24-h changes of plasma luteinizing hormone (LH), follicle stimulating hormone (FSH) and prolactin (PRL) in 11 days old suckling female and male rabbits left with the mother or after short-term (i.e., 48 h) doe-litter separation. METHODS: Animals were kept under controlled light-dark cycles (16 h-8 h; lights on at 08:00 h). On day 9 post partum, groups of 6-7 female or male rabbit pups were separated from their mothers starting at 6 different time intervals in the 24 h cycle. Pups were killed 48 h after separation. At each time interval groups of male or female pups that stayed with the mother were killed as controls. Plasma, LH, FSH and PRL levels were measured by specific radioimmunoassays. RESULTS: In pups kept with their mother plasma FSH and LH maxima occurred at the first and second part of the light phase (at 13:00 and 17:00-21:00 h, respectively) (females) or as two peaks for each of the hormones (at 13:00 and 01:00 h) (males). PRL release was similar in female and male rabbit pups kept with their mother, showing a 24-h pattern with two peaks, at 13:00 and 01:00 h, respectively. Mean 24-h values of gonadotropins and PRL did not differ between sexes. Isolation of pups for 48 h augmented circulating gonadotropin and PRL levels and distorted hormone 24-h pattern to a similar extent in both sexes. CONCLUSION: Significant sex differences in 24-h changes in LH and FSH, but not in PRL, release occurred in rabbit pups kept with the doe. Separation of newborn pups from their mother augmented circulating gonadotropin and PRL levels and disrupted 24-h rhythmicity of gonadotropin and PRL release similarly in both sexes. The effect of pups' isolation can be attributed either to a modification of the circadian pacemaker or to a masking effect on some of its output overt rhythms.

Prolactin daily rhythm in suckling male rabbits.

BACKGROUND: This study describes the 24-h changes in plasma prolactin levels, and dopamine (DA), serotonin (5HT), gamma-aminobutyric acid (GABA) and taurine concentration in median eminence and adenohypophysis of newborn male rabbits. METHODS: Animals were kept under controlled light-dark cycles (LD 16:8, lights on at 08:00 h), housed in individual metal cages, and fed ad libitum with free access to tap water. On day 1 after parturition, litter size was standardized to 8-9 to assure similar lactation conditions during the experiment. Groups of 6-7 suckling male rabbits were killed by decapitation on day 11 of life at six different time points during a 24-h period. RESULTS: Plasma prolactin levels changed significantly throughout the day, showing a peak at the beginning of the active phase (at 01:00 h) and a second maximum during the first part of the resting phase (at 13:00 h). Median eminence DA concentration also changed significantly during the day, peaking at the same time intervals as plasma prolactin. A single maximum (at 13:00 h) was found for adenohypophysial DA concentration. Individual adenohypophysial DA concentrations correlated significantly with their respective plasma prolactin levels. A maximum in median eminence 5HT concentration occurred at 21:00 h whereas adenohypophysial 5HT peaked at 13:00 h. Median eminence 5HT concentration and circulating prolactin correlated inversely. In the median eminence, GABA concentration attained maximal values at 21:00 h, whereas it reached a maximum at 13:00 h in the pituitary gland. Median eminence GABA concentration correlated inversely with circulating prolactin. In the median eminence, taurine values varied in a bimodal way showing two maxima, at the second half of the rest span and of the activity phase, respectively. In the adenohypophysis, minimal taurine levels coincided with the major plasma prolactin peak (at 01:00 h). Circulating prolactin and adenohypophysial taurine levels correlated inversely. CONCLUSION: The correlations among the changes in the neurotransmitters analyzed and circulating prolactin levels explain the circadian secretory pattern of the hormone in newborn male rabbits.

Effect of litter separation on 24-hour rhythmicity of plasma prolactin, follicle-stimulating hormone and luteinizing hormone levels in lactating rabbit does.

BACKGROUND: This work describes the effect of a 48-h litter separation on 24-h patterns of plasma prolactin, FSH and LH concentration in female lactating rabbits kept under a 16:8 light-dark photoperiod (lights on at 0800 h). METHODS: Groups of 6-7 female lactating rabbits maintained with their litters or separated from them for 48 h were killed by decapitation on day 11 post-partum, at 6 different time points throughout a 24-h cycle, starting at 0900 h. Plasma levels of prolactin, FSH and LH were measured by specific double antibody radio-immunoassays. RESULTS: Plasma level of prolactin in control and separated does changed in a similar way throughout the day, showing two maxima, at 0500-0900 h and at 1700-2100 h, respectively. Litter separation significantly augmented plasma FSH and LH and disrupted their 24-h rhythmicity. CONCLUSION: Since previous studies had shown that litter separation for short periods of time augmented sexual receptivity and fertility of the doe, the changes in FSH and LH reported may influence the massive release of gonadotropin releasing hormone, LH and FSH triggered by mating or artificial insemination in litter-separated mothers.

Twenty-four-hour rhythms of mitogenic responses, lymphocyte subset populations and amino acid content in submaxillary lymph nodes of growing male rats subjected to calorie restriction.

Peripubertal male Wistar rats were submitted to a calorie restriction diet enriched in proteins and low in fat and carbohydrates for 4 weeks, and starting on day 35 of life. Mitogenic responses, lymphocyte subset populations, interferon (IFN)- gamma release and amino acid content were determined in submaxillary lymph nodes at six time intervals during the 24-h span. The diet employed completely arrested growth in growing rats. After caloric restriction, mean values of Con A response, lymph node T and CD4+ cell number and CD4+/CD8+ ratio augmented, whereas those of B cell number, IFN-gamma release and glutamine and glutamate concentration decreased. Calorie restriction modified 24-h rhythmicity of lymph node mitogenic responses to Con A and LPS, and of T, T-B, CD4+ and CD4+ -CD8+ lymph node cell subsets. It also changed the 24-h pattern of lymph node IFN-gamma release and glutamine, aspartate, glutamate and taurine lymph node content. Availability of nutrients presumably affects the mechanisms that modulate the circadian variation of immune responsiveness in growing rats.