Circadian and Ultradian Glucocorticoid Rhythmicity:Implications for the Effects of Glucocorticoids on Neural Stem Cells and Adult Hippocampal Neurogenesis

Total glucocorticoid hormone levels in plasma of various species, including humans, follow a circadian rhythm that is made up from an underlying series of hormone pulses. In blood most of the glucocorticoid is bound to corticosteroid-binding globulin and albumin, resulting in low levels of free hormone. Although only the free fraction is biologically active, surprisingly little is known about the rhythms of free glucocorticoid hormones. We used single-probe microdialysis to measure directly the free corticosterone levels in the blood of freely behaving rats. Free corticosterone in the blood shows a distinct circadian and ultradian rhythm with a pulse frequency of approximately one pulse per hour together with an increase in hormone levels and pulse height toward the active phase of the light/dark cycle. Similar rhythms were also evident in the subcutaneous tissue, demonstrating that free corticosterone rhythms are transferred from the blood into peripheral target tissues. Furthermore, in a dual-probe microdialysis study, we demonstrated that the circadian and ultradian rhythms of free corticosterone in the blood and the subcutaneous tissue were highly synchronized. Moreover, free corticosterone rhythms were also synchronous between the blood and the hippocampus. These data demonstrate for the first time an ultradian rhythm of free corticosterone in the blood that translates into synchronized rhythms of free glucocorticoid hormone in peripheral and central tissues. The maintenance of ultradian rhythms across tissue barriers in both the periphery and the brain has important implications for research into aberrant biological rhythms in disease and for the development of improved protocols for glucocorticoid therapy

The mechanisms of amniote photoperiodism: from deep-brain photoreceptors to rhythmic epigenetics

Seasonal reproduction is a strategy conserved across nature. The duration of light (photoperiod) regulates the reproductive molecular control within the Hypothalamic-Pituitary-Gonadal Axis of seasonal species, and supplementary cues fine-tune the exact timing of breeding. In recent years, epigenetic mechanisms have been shown to be involved in an array of circannual rhythms, including reproduction. The aim of this thesis was to explore the molecular reproductive neuroendocrine processes that underlie the onset of reproduction in two summer-breeding animal models, the Japanese quail (Coturnix japonica) and the Siberian hamster (Phodopus sungorus). In birds, light penetrates the skull and is detected by deep-brain photoreceptors (DBPs) within the hypothalamus, stimulating the photoperiodic reproductive response. However, the identity of these DBPs is unclear to this day. In the present thesis, the expression of two photoreceptors, Vertebrate-Ancient Opsin (VA Opsin) and Neuropsin (OPN5), was repressed through adeno-associated viral injection, and the breeding response was monitored in control and treated birds maintained under short-days (SD), or long-days (LD) for 2, 7 or 28 days. The data revealed that both opsins may be involved in seasonal reproduction in the Japanese quail, and that OPN5’s role includes modulating gonadal sensitivity to gonadotropins during breeding. It was also found that hypothalamic OPN5, GNRH and DNAmethyltransferase (Dnmt) expression increases at embryonic day 14 in this species. In addition, higher global methylation levels were found in the pituitary gland of adult LD quail, compared to SD. In the Siberian hamster, two studies were conducted to investigate the effect of triiodothyronine (T3) on the photoperiod-dependent regulation of reproductive physiology and hypothalamic DNA methyltransferase enzyme expression in both males and females. Two weeks of daily T3 injections induced gonadal growth in SD males, but not in females. Female SD hamsters, but not males, were found to express lower levels of de novo Dnmts compared to LD individuals. However, exogenous T3 did not affect hypothalamic Dnmt expression in neither males or females. The data indicated sex differences in the gonadal response to T3, as well as in the regulation of hypothalamic DNA methyltransferase expression. It is likely that female Siberian hamsters require additional cues to initiate reproductive processes. The studies presented allowed for an exploration of reproductive mechanisms in both an avian and a mammalian model, including the role of epigenetic processes in seasonal breeding. Future studies are required to elucidate the precise mechanisms of DBPs, as well as identify downstream targets of maintenance and de novo Dnmts

Expressão de genes associados à obesidade em testículos e esperma de ratos sujeitos a restrição calórica e administração de GLP-1

Caloric restriction (CR), due to its negative energy balance and GLP-1, for being an incretin, constitute two weight loss protocols that remain poorly investigated, particularly its impact on male reproductive function, whose proper functioning depends on a balanced energy homeostasis. That energy homeostasis has been related to genes linked to energy metabolism control, namely the obesity-related genes (ORGs), such as fat mass and obesity associated (FTO), melanocortin-4 receptor (MC4R), glucosamine-6- phosphate deaminase 2 (GNPDA2) and transmembrane protein 18 (TMEM18). Thus, this project aimed to use an animal model to study the potential of CR and GLP-1 administration in the regulation of those ORGs expression in testes and sperm of Wistar rats and verify if there is an impact on sperm quality. Firstly, we observed that CR promoted a lower weight gain and a decrease in insulin resistance. On the other hand, GLP-1 administration, beyond the expected increase in active GLP-1 levels, did not promote any change in glucose metabolism, hormonal profile and consequently in body weight. Furthermore, CR promoted an increase in sperm head defects, while the GLP-1 administration improved sperm morphology. Regarding the ORGs we observed the presence of FTO, MC4R and TMEM18 transcripts in rat testes and identified those transcripts, for the first time, in rat sperm. Additionally, we identified, for the first time, the presence of GNPDA2 transcripts in rat testes and sperm. The corresponding proteins were also identified in rat testes, being that they all presented distinct cellular locations. CR and GLP-1 administration promoted an increase in the expression of the ORGs in testes, however in spermatozoa the expression was not altered. We also identified the presence of NFE2L2 (encodes for an important antioxidant transcription factor) transcripts in rat testes and sperm and verified that their abundance is increased, in testes, by CR and GLP-1 administration. Then we explored, individually, the role the ORGs at the testicular and sperm levels, namely in the response to CR and GLP-1 administration and we obtained some clues related to the potential involvement of each of the ORGs in the male reproductive function. Overall, we were able to perceive that CR and GLP-1 administration promoted a general association of all ORGs with an improvement in oxidative status both in testes and sperm.A restrição calórica (CR), pelo seu balanço energético negativo e o GLP-1, por ser uma incretina, constituem dois protocolos de perda de peso, que permanecem pouco investigados, principalmente no que toca ao seu impacto na função reprodutiva masculina, cujo correto funcionamento depende de uma homeostase energética equilibrada. Essa homeostase energética tem sido relacionada a genes ligados ao controlo do metabolismo energético, nomeadamente os genes relacionados à obesidade (ORGs), como gene de obesidade e de massa de gordura associada (FTO), recetor de melanocortina-4 (MC4R), glucosamina-6-fosfato desaminase 2 (GNPDA2) e proteína transmembranar 18 (TMEM18). Assim, este projeto teve como objetivo utilizar um modelo animal para estudar o potencial da CR e da administração de GLP-1 na regulação da expressão desses ORGs nos testículos e esperma de ratos Wistar e verificar se há impacto na qualidade espermática. Primeiramente, observamos que a CR promoveu menor ganho de peso e diminuição da resistência à insulina. Por outro lado, a administração de GLP-1, além do esperado aumento nos níveis de GLP-1 ativo, não promoveu qualquer alteração no metabolismo da glucose, no perfil hormonal e consequentemente no peso corporal. Para além disso, a CR promoveu um aumento nos defeitos da cabeça dos espermatozoides, enquanto a administração de GLP-1 melhorou a morfologia espermática. Em relação aos ORGs, observamos a presença de transcritos de FTO, MC4R e TMEM18 em testículos de ratos e identificamos esses transcritos, pela primeira vez, em esperma de ratos. Além disso, identificamos, pela primeira vez, a presença de transcritos GNPDA2 em testículos e esperma de ratos. As proteínas correspondentes também foram identificadas em testículos de ratos, sendo que todas apresentavam localizações celulares distintas. A CR e a administração de GLP-1 promoveram um aumento na expressão dos ORGs nos testículos, porém no esperma a expressão não foi alterada. Também identificamos a presença de transcritos de NFE2L2 (codifica para um importante fator de transcrição antioxidante) em testículos e esperma de ratos e verificamos que sua abundância é aumentada nos testículos, pela CR e administração de GLP-1. Em seguida, exploramos, individualmente, o papel dos ORGs nos níveis testicular e espermático, nomeadamente na resposta à CR e à administração de GLP-1 e obtivemos algumas pistas relacionadas com o envolvimento potencial de cada um dos ORGs na função reprodutiva masculina. No geral, pudemos perceber que as duas intervenções promoveram uma associação geral de todos os ORGs com uma melhoria no estado oxidativo dos testículos e esperma.Mestrado em Bioquímic

Pineal-adrenal gland interactions in search of an anti-stressogenic role for melatonin

The multiple functions of the pineal gland have been collectively interpreted as constituting a general anti-stressogenic role. The adrenal glands play a central role in maintaining homeostasis. The major neuroendocrine consequence of long-term stress is elevated circulating glucocorticoid levels. In this study, the effect of chronic, oral hydrocortisone treatment on pineal biochemistry was investigated in male Wi star rats of the albino strain. The results show that seven days of oral hydrocortisone treatment endows the pineal gland with the ability to increase melatonin synthesis in organ culture. The increase is accompanied by a rise in NAT activity, cyclic AMP levels and enhanced specific binding to the pineal B-adrenergic receptors. It appears that hydrocortisone sensitizes the pineal gland to stimulation by B-adrenergic agonists. thus rendering the pineal more responsive to B-adrenergic agonists. Further studies were directed at demonstrating an anti-stressogenic function for the pineal gland by investigating whether the principal pineal indole, melatonin. could protect against the deleterious effects of elevated. circulating drocortisone levels. The results show that chronic, oral hydrocortisone treatment significantly increases liver tryptophan pyrrolase activity. The catabolism of tryptophan by tryptophan pyrrolase is an important determinant of tryptophan availability to the brain, and therefore, brain serotonin levels. The findings show that melatonin inhibits basal and hydrocortisone-stimulated liver tryptophan pyrrolase apoenzyme activity in a dose-dependent manner. This inhibition suggests that melatonin may protect against excessive loss of tryptophan from circulation and against deficiencies in the cerebral serotinergic system which are associated with mood and behavioural disorders. It was shown that another deleterious effect of chronic hydrocortisone treatment is a significant increase in the number of glutamate receptors in the forebrain of male Wistar rats. The increase in receptor number observed in this study is probably due to an increase in the synthesis of glutamate receptors and is associated with a marked reduction in the affinity of the glutamate receptors for glutamate. possible to demonstrate an receptor number or the For practical reasons, it was not effect of melatonin on either glutamate affinity of glutamate receptors for glutamate in rat forebrain membranes. In view of the neurotoxic effect of glutamate in the eNS, the functional significance of recently described glutamate receptors in the pineal gland was investigated. The results show that 10-4 M glutamate significantly inhibits the isoprenaline-stimulated synthesis of N-acetylserotonin and melatonin in organ culture when the pineal glands were pre-incubated with glutamate for 4 hours prior to stimulation with isoprenalin and when glutamate and isoprenaline were administered together in vitro. GABA, a glutamate metabolite could not mimic the decrease in isoprenalinestimulated melatonin, and it is likely that the observed effects were directly attributed to glutamate. Incubation of the pineal gland with 10-4 M glutamate in organ culture did not affect HIOMT activity in pineal homogenates, but significantly elevated both basal and isoprenaline-stimulated NAT activity. It was concluded that glutamate only inhibits melatonin synthesis in intact pineal glands and not in pineal homogenates. The present study has provided further support for an interaction between the pineal and the adrenal glands. There is an ever increasing likelihood that melatonin is an anti-stressogenic hormone and that the pineal gland may have a protective role to play in the pathology of stress-related diseases

The 1988-1989 NASA Space/Gravitational Biology Accomplishments

This report consists of individual technical summaries of research projects of NASA's space/gravitational biology program, for research conducted during the period May 1988 to April 1989. This program is concerned with using the unique characteristics of the space environment, particularly microgravity, as a tool to advance knowledge in the biological sciences; understanding how gravity has shaped and affected life on Earth; and understanding how the space environment affects both plant and animal species. The summaries for each project include a description of the research, a list of the accomplishments, an explanation of the significance of the accomplishments, and a list of publications

Advances in comparative endocrinology : vol. VIII

Ponències presentades al 10th Congress of the Iberian Association of Comparative Endocrinology (AIEC), celebrat a la Universitat Jaume I, els dies 23 al 25 de setembre de 2015Les diverses comunicacions presentades al 10è Congrés de la Asociación Ibérica de Endocrinología Comparada (23-25 setembre 2016, Castelló) s'agrupen en aquest volum. Les intervencions han aportat els darrers avenços en àrees científiques com ara reproducció, metabolisme, estrés, resposta immune, creixement, mineralització i pigmentació...Las diversas comunicaciones presentadas en el 10º Congreso de la Asociación Ibérica de Endocrinología Comparada (23-25 septiembre 2016, Castellón) se agrupan en este volumen. Las intervenciones han aportado los últimos adelantos en áreas científicas como por ejemplo reproducción, metabolismo, estrés, respuesta inmune, crecimiento, mineralización y pigmentación...The present volume of Advances in Comparative Endocrinology collects the contributions of the participants at the 10th Congress of the Iberian Association of Comparative Endocrinology (AIEC). Eighteen years after the foundational meeting of our Association in Peñíscola, the return of this Congress to Castellón highlights the growing success of this initiative to foster the research and scientific development in the field of comparative endocrinology developed in the Iberian Peninsula. AIEC meetings have proven to be a way to keep in contact among research groups with common interests. Some of the participants in this last meeting were also present in the foundational one, others members came after and keep assisting every time. As one of the aims of AIEC has been to encourage students to participate, we are particulary proud of those young students and doctors from the first editions that have gained more permanent positions and continue participating in the AIEC meetings with new students

The role of melatonin and the pineal gland in the photoperiodic control of reproduction and smoltification in Salmonid fish

The timing of seasonal events in salmonids is thought to be controlled by endogenous circannual rhythm(s) which are entrained by the seasonally-changing daylength. This thesis investigates the role of the pineal gland in the perception of the photoperiodic zeitgeber and the subsequent transmission of this information to the brain through neural or hormonal pathways. Melatonin biosynthesis by isolated rainbow trout pineal glands was shown to exhibit a differential response to graded photic or thermal stimuli. In vitro experiments were carried out at 10±0.50 C as this provided optimum melatonin levels for radioimmunoassay analysis together with a pineal longevity of up to 14 days. By incorporating a variety of light intensities into the light/dark cycle, the salmonid pineal gland was shown to synthesise significantly different levels of melatonin even when light levels varied by only 0.5 lux. Early work on the salmonid pineal suggested it was unresponsive to red light, having a spectral sensitivity which peaks between 500 and 550 nm, this study has revealed that the pineal is also capable of responding to wavelengths between 660 to 800 nm, at which pineal reception was previously thought to be severely limited. No endogenous rhythm of melatonin secretion was observed within the isolated rainbow' trout pineal gland. Both Atlantic salmon and Atlantic halibut pineals exhibited elevated levels- of melatonin in response to the dark phase, however, they also appeared capable of maintaining this rhythm in the absence of external stimuli. This provides the first evidence that the daily rhythm of melatonin production in these species is controlled by an endogenous circadian oscillator located within the pineal II gland. The pinealectomy technique developed during the course of this thesis successfully abolished the diel rhythm of melatonin secretion and, together with an enucleation procedure, enabled the pineal to be identified as the predominant source of the dark phase melatonin in Atlantic salmon and rainbow trout. However, the lateral eyes did contribute significantly to plasma melatonin levels in both species. Long term experiments, involving pinealectomy and/or implantation of melatonin, were used to investigate the role of the pineal gland in the timing of rainbow trout maturation and smoltification in Atlantic salmon. Pineal removal at the summer or winter solstices did not significantly alter the timing of smoltification. However, significantly higher blood serum osmolarities following seawater challenge tests were observed in smolts implanted with melatonin. This, together with a significant growth increase shown by salmon parr within 1 month of implantation, indicates that melatonin may directly affect the development of salmonids through either a physiological response or by influencing the entrainment of endogenous rhythms. The increased growth observed in the implanted parr is also thought to be responsible for the unimodal population distribution and high percentage of S1 smolts within this group. Investigations into the role of the pineal gland in the timing of spawning in rainbow trout found that pineal removal at the summer solstice caused a 6 week delay in spawning time compared to intact fish. However, no clear effects on spawning time were observed when pineal removal, with or without melatonin implantation, was performed to coincide with the change from long to short daylengths which is known to advance spawning times. Although no significant effect in spawning times was observed between groups, the 4 month spawning period of the pinealectomised group compared to 1 month in the shampinealectomised fish also suggested that pineal removal may have caused a desynchronisation in spawning time. Pinealectomy and/or implantation did not alter egg size or fecundity, but plasma calcium levels were shown to be significantly lower in the pinealectomised trout over the spawning period. To summarise, the pineal gland and melatonin play a significant role in salmonid development. It is suggested that melatonin can influence biological systems through a direct physiological action while the pineal gland may synchronise . circannual events through the photoneuroendocrine transduction of seasonal environmental information

Aerospace medicine and biology: A continuing bibliography with indexes, supplement 183

This bibliography lists 273 reports, articles, and other documents introduced into the NASA scientific and technical information system in July 1978

Activation of the pro-resolving receptor Fpr2 attenuates inflammatory microglial activation

Poster number: P-T099 Theme: Neurodegenerative disorders & ageing Activation of the pro-resolving receptor Fpr2 reverses inflammatory microglial activation Authors: Edward S Wickstead - Life Science & Technology University of Westminster/Queen Mary University of London Inflammation is a major contributor to many neurodegenerative disease (Heneka et al. 2015). Microglia, as the resident immune cells of the brain and spinal cord, provide the first line of immunological defence, but can become deleterious when chronically activated, triggering extensive neuronal damage (Cunningham, 2013). Dampening or even reversing this activation may provide neuronal protection against chronic inflammatory damage. The aim of this study was to determine whether lipopolysaccharide (LPS)-induced inflammation could be abrogated through activation of the receptor Fpr2, known to play an important role in peripheral inflammatory resolution. Immortalised murine microglia (BV2 cell line) were stimulated with LPS (50ng/ml) for 1 hour prior to the treatment with one of two Fpr2 ligands, either Cpd43 or Quin-C1 (both 100nM), and production of nitric oxide (NO), tumour necrosis factor alpha (TNFα) and interleukin-10 (IL-10) were monitored after 24h and 48h. Treatment with either Fpr2 ligand significantly suppressed LPS-induced production of NO or TNFα after both 24h and 48h exposure, moreover Fpr2 ligand treatment significantly enhanced production of IL-10 48h post-LPS treatment. As we have previously shown Fpr2 to be coupled to a number of intracellular signaling pathways (Cooray et al. 2013), we investigated potential signaling responses. Western blot analysis revealed no activation of ERK1/2, but identified a rapid and potent activation of p38 MAP kinase in BV2 microglia following stimulation with Fpr2 ligands. Together, these data indicate the possibility of exploiting immunomodulatory strategies for the treatment of neurological diseases, and highlight in particular the important potential of resolution mechanisms as novel therapeutic targets in neuroinflammation. References Cooray SN et al. (2013). Proc Natl Acad Sci U S A 110: 18232-7. Cunningham C (2013). Glia 61: 71-90. Heneka MT et al. (2015). Lancet Neurol 14: 388-40