Cranial irradiation alters neuroinflammation and neural proliferation in the pituitary gland and induces late-onset hormone deficiency.

Cranial radiotherapy induces endocrine disorders and reproductive abnormalities, particularly in long-term female cancer survivors, and this might in part be caused by injury to the pituitary gland, but the underlying mechanisms are unknown. The aim of this study was to investigate the influence of cranial irradiation on the pituitary gland and related endocrine function. Female Wistar rat pups on postnatal day 11 were subjected to a single dose of 6 Gy whole-head irradiation, and hormone levels and organ structure in the reproductive system were examined at 20 weeks after irradiation. We found that brain irradiation reduced cell proliferation and induced persistent inflammation in the pituitary gland. The whole transcriptome analysis of the pituitary gland revealed that apoptosis and inflammation-related pathways were up-regulated after irradiation. In addition, irradiation led to significantly decreased levels of the pituitary hormones, growth hormone, adrenocorticotropic hormone, thyroid-stimulating hormone and the reproductive hormones testosterone and progesterone. To conclude, brain radiation induces reduction of pituitary and reproduction-related hormone secretion, this may due to reduced cell proliferation and increased pituitary inflammation after irradiation. Our results thus provide additional insight into the molecular mechanisms underlying complications after head irradiation and contribute to the discovery of preventive and therapeutic strategies related to brain injury following irradiation.

Melanin-Concentrating Hormone and Its MCH-1 Receptor: Relationship Between Effects on Alcohol and Caloric Intake.

BACKGROUND: Reward and energy homeostasis are both regulated by a network of hypothalamic neuropeptide systems. The melanin-concentrating hormone (MCH) and its MCH-1 receptor (MCH1-R) modulate alcohol intake, but it remains unknown to what extent this reflects actions on energy balance or reward. Here, we evaluated the MCH1-R in regulation of caloric intake and motivation to consume alcohol in states of escalated consumption. METHODS: Rats had intermittent access (IA) to alcohol and were divided into high- and low-drinking groups. Food and alcohol consumption was assessed after administration of an MCH1-R antagonist, GW803430. Next, GW803430 was evaluated on alcohol self-administration in protracted abstinence induced by IA in high-drinking rats. Finally, the effect of GW803430 was assessed on alcohol self-administration in acute withdrawal in rats exposed to alcohol vapor. Gene expression of MCH and MCH1-R was measured in the hypothalamus and nucleus accumbens (NAc) in both acute and protracted abstinence. RESULTS: High-drinking IA rats consumed more calories from alcohol than chow and GW803430 decreased both chow and alcohol intake. In low-drinking rats, only food intake was affected. In protracted abstinence from IA, alcohol self-administration was significantly reduced by pretreatment with GW803430 and gene expression of both MCH and the MCH1-R were dysregulated in hypothalamus and NAc. In contrast, during acute withdrawal from vapor exposure, treatment with GW803430 did not affect alcohol self-administration, and no changes in MCH or MCH1-R gene expression were observed. CONCLUSIONS: Our data suggest a dual role of MCH and the MCH1-R in regulation of alcohol intake, possibly through mechanisms involving caloric intake and reward motivation. A selective suppression of alcohol self-administration during protracted abstinence by GW803430 was observed and accompanied by adaptations in gene expression of MCH and MCH1-R. Selective suppression of escalated consumption renders the MCH1-R an attractive target for treatment of alcohol use disorders.

Making pituitary hormone-producing cells in a dish [Review].

The hypothalamic-pituitary system is essential for maintaining life and controlling systemic homeostasis. The functional disorder makes patients suffer from various symptoms all their lives. Pluripotent stem cells, such as embryonic stem (ES) cells and induced pluripotent stem (iPS) cells, differentiate into neuroectodermal progenitors when cultured as floating aggregates under serum-free conditions. Recent results have shown that strict removal of exogenous patterning factors during the early differentiation period induces rostral hypothalamic-like progenitors from mouse ES cells. The use of growth factor-free, chemically defined medium was critical for this induction. The ES cell-derived hypothalamic-like progenitors generated rostral-dorsal hypothalamic neurons, in particular magnocellular vasopressinergic neurons. We subsequently reported self-formation of adenohypophysis in three-dimensional floating cultures of mouse ES cells. The ES cell aggregates were stimulated to differentiate into both non-neural head ectoderm and hypothalamic neuroectoderm in adjacent layers. Self-organization of Rathke's pouch-like structures occurred at the interface of the two epithelia in vitro. Various pituitary endocrine cells including corticotrophs and somatotrophs were subsequently produced from the Rathke's pouch-like structures. The induced corticotrophs efficiently secreted ACTH in response to CRH. Furthermore, when engrafted in vivo, these cells rescued systemic glucocorticoid levels in hypopituitary mice. Our latest study aimed to prepare hypothalamic and pituitary tissues from human pluripotent stem cells. We succeeded in establishing the differentiation method using human ES/iPS cells. The culture method is characterized by replication of stepwise embryonic differentiation. Therefore, these methods could potentially be used as developmental and disease models, as well as for future regenerative medicine.

Endocrine dysfunction and follow-up outcomes in patients with pituitary abscess.

OBJECTIVE: Endocrine dysfunction caused by pituitary abscess (PA) and its outcomes have not been fully studied. This study aims to investigate endocrine dysfunction and outcomes in patients with PA. METHODS: Eight patients (3 males and 5 females) with PA were identified for collecting clinical, hormone, and therapeutic data before and after long-term follow-up lasting 12 to 116 months (median, 25 months) since the first hospitalization, which was regarded as the baseline time. All patients' pituitary and respective target gland functions were evaluated. Six patients had acute onset (less than 1 month), and the other 2 patients had chronic onset (more than 6 months). Five patients underwent surgical therapy, and the other 3 patients underwent conservative therapy. The factors associated with endocrine outcome were analyzed as well. RESULTS: At baseline, the release of 91.7% (22 of 24 total) of pituitary tropic hormones was impaired, but 59.1% (13 of 22) had normalized by the last follow-up. Male gender, acute onset mode, and normal baseline prolactin level seemed to be the factors that favored tropic hormone normalization, whereas surgical operation was not. Two patients received provocative test suggesting decreased reserves of both somatotrophin and prolactin or only somatotrophin. Only 1 patient suffered from permanent diabetes insipidus. CONCLUSION: The production of almost all pituitary tropic hormones was impaired with PA in the present study, but production of nearly 60% percent of the hormones normalized during follow-up of >1 year. A chronic abscess state may be the most important factor associated with permanent hormone deficiency.

The vertebrate diencephalic MCH system: a versatile neuronal population in an evolving brain.

Neurons synthesizing melanin-concentrating hormone (MCH) are described in the posterior hypothalamus of all vertebrates investigated so far. However, their anatomy is very different according to species: they are small and periventricular in lampreys, cartilaginous fishes or anurans, large and neuroendocrine in bony fishes, or distributed over large regions of the lateral hypothalamus in many mammals. An analysis of their comparative anatomy alongside recent data about the development of the forebrain, suggests that although very different, MCH neurons of the caudal hypothalamus are homologous. We further hypothesize that their divergent anatomy is linked to divergence in the forebrain - in particular telencephalic evolution.

Dynamic pituitary hormones change after traumatic brain injury.

OBJECTIVE: To study the dynamic changes of pituitary hormones in traumatic brain injury (TBI) and to correlate the severity and neurological outcome. PATIENTS AND METHODS: Dynamic changes in the pituitary hormones were evaluated in 164 patients with TBI on day-1, day-7, day-14, day-21, and day-28 post injury. Admission TBI severity and long-term outcome were assessed with Glasgow Coma Scale (GCS) score and Glasgow Outcome Scale (GOS) score. The pituitary hormonal changes were correlated with TBI severity and outcome. RESULTS: Of the 164 patients included in the study, pituitary dysfunction was found in 84 patients and in the remaining 80 patients pituitary function was normal. Most of the pituitary hormone deficiencies observed resolved over time; however, a significant proportion of patients had pituitary dysfunction at one month post injury. The hormones associated with poor outcome included growth hormone, thyrotropic hormone, and gonadotropic hormone. CONCLUSION: Dynamic changes of pituitary hormones in patients with TBI may reflect the severity of injury and also determine the outcome. Deficiency of growth hormone, gonadotropic hormone, and thyrotropic hormone can adversely affect neurological outcome.

Signal transduction mechanisms for autocrine/paracrine regulation of somatolactin-α secretion and synthesis in carp pituitary cells by somatolactin-α and -ß.

Pituitary hormones can act locally via autocrine/paracrine mechanisms to modulate pituitary functions, which represents an interesting aspect of pituitary regulation other than the traditional hypothalamic input and feedback signals from the periphery. Somatolactin, a member of the growth hormone (GH)/prolactin (PL) family, is a pleiotropic hormone with diverse functions, but its pituitary actions are still unknown. Recently, two SL isoforms, SLα and SLß, have been cloned in grass carp. Based on the sequences obtained, recombinant proteins of carp SLα and SLß with similar bioactivity in inducing pigment aggregation in carp melanophores were produced. In carp pituitary cells, SLα secretion and cell content were elevated by static incubation with recombinant carp SLα and SLß, respectively. These stimulatory actions occurred with a parallel rise in SLα mRNA level with no changes in SLß secretion, cell content, and gene expression. In contrast, SLα mRNA expression could be reduced by removing endogenous SLα and SLß with immunoneutralization. At the pituitary cell level, SLα release, cell content, and mRNA expression induced by carp SLα and SLß could be blocked by inhibiting JAK2/STAT5, PI3K/Akt, MEK1/2, and p38 MAPK, respectively. Furthermore, SLα and SLß induction also triggered rapid phosphorylation of STAT5, Akt, MEK1/2, ERK1/2, MKK3/6, and p38 MAPK. These results suggest that 1) SLα and SLß produced locally in the carp pituitary can serve as novel autocrine/paracrine stimulators for SLα secretion and synthesis and 2) SLα production induced by local release of SLα and SLß probably are mediated by the JAK2/STAT5, PI3K/Akt, and MAPK signaling pathways.

Anterior pituitary morphology and hormone production during sustained critical illness in a rabbit model.

Prolonged critical illness is hallmarked by striking alterations in the somatrope, thyrotrope, and lactotrope axes, the severity of which is associated with the risk of morbidity and mortality. The exact role of the pituitary gland in these alterations is unknown. We studied the impact of sustained critical illness on pituitary morphology and hormone production in a standardized rabbit model of prolonged (7 days) burn injury-induced critical illness. In healthy and prolonged critically ill rabbits, we determined pituitary weight, size, morphology and orientation of the somatrope, lactotrope and thyrotrope cells and the pituitary expression of GH, PRL, and TSH at gene and protein level. The weight of the pituitary gland was unaltered by 7 days of critical illness. Also, spatial orientation and morphology of the GH, PRL, and TSH producing cells remained normal. In prolonged critically ill rabbits GH mRNA levels were higher and PRL mRNA levels were lower than in healthy controls, whereas TSH mRNA was not affected. The sizes of GH, PRL, or TSH producing cells and the pituitary content of GH, PRL, and TSH proteins were unaltered. In conclusion, in this rabbit model of prolonged critical illness, the morphology of the pituitary gland and the pituitary GH, PRL, and TSH content was normal. The alterations in pituitary hormone mRNA levels with sustained critical illness are compatible with altered hypothalamic and peripheral regulation of pituitary hormone release as previously suggested indirectly by responses to exogenous releasing factors.

Birthdating studies reshape models for pituitary gland cell specification.

The intermediate and anterior lobes of the pituitary gland are derived from an invagination of oral ectoderm that forms Rathke's pouch. During gestation proliferating cells are enriched around the pouch lumen, and they appear to delaminate as they exit the cell cycle and differentiate. During late mouse gestation and the postnatal period, anterior lobe progenitors re-enter the cell cycle and expand the populations of specialized, hormone-producing cells. At birth, all cell types are present, and their localization appears stratified based on cell type. We conducted a birth dating study of Rathke's pouch derivatives to determine whether the location of specialized cells at birth is correlated with the timing of cell cycle exit. We find that all of the anterior lobe cell types initiate differentiation concurrently with a peak between e11.5 and e13.5. Differentiation of intermediate lobe melanotropes is delayed relative to anterior lobe cell types. We discovered that specialized cell types are not grouped together based on birth date and are dispersed throughout the anterior lobe. Thus, the apparent stratification of specialized cells at birth is not correlated with cell cycle exit. Thus, the currently popular model of cell specification, dependent upon timing of extrinsic, directional gradients of signaling molecules, needs revision. We propose that signals intrinsic to Rathke's pouch are necessary for cell specification between e11.5 and e13.5 and that cell-cell communication likely plays an important role in regulating this process.

Insulin-like growth factor as a novel stimulator for somatolactin secretion and synthesis in carp pituitary cells via activation of MAPK cascades.

Somatolactin (SL), a member of the growth hormone/prolactin family, is a pituitary hormone unique to fish models. Although SL is known to have diverse functions in fish, the mechanisms regulating its secretion and synthesis have not been fully characterized. Using grass carp pituitary cells as a model, here we examined the role of insulin-like growth factor (IGF) in SL regulation at the pituitary level. As a first step, the antisera for the two SL isoforms expressed in the carp pituitary, SLα and SLß, were produced, and their specificity was confirmed by antiserum preabsorption and immunohistochemical staining in the carp pituitary. Western blot using these antisera revealed that grass carp SLα and SLß could be N-linked glycosylated and their basal secretion and cell content in carp pituitary cells could be elevated by IGF-I and -II treatment. These stimulatory effects occurred with parallel rises in SLα and SLß mRNA levels, and these SL gene expression responses were not mimicked by insulin but blocked by IGF-I receptor inactivation. In carp pituitary cells, IGF-I and -II could induce rapid phosphorylation of IGF-I receptor, MEK1/2, ERK1/2, MKK3/6, and p38 MAPK; and SLα and SLß secretion, protein production, and mRNA expression caused by IGF-I and -II stimulation were negated by inactivating MEK1/2 and p38 MAPK. Parallel inhibition of PI3K and Akt, however, were not effective in these regards. These results, taken together, provide evidence that IGF can upregulate SL secretion and synthesis at the pituitary level via stimulation of MAPK- but not PI3K/Akt-dependent pathways.

Signal Transduction Mechanisms for Glucagon-Induced Somatolactin Secretion and Gene Expression in Nile Tilapia (Oreochromis niloticus) Pituitary Cells.

Glucagon (GCG) plays a stimulatory role in pituitary hormone regulation, although previous studies have not defined the molecular mechanism whereby GCG affects pituitary hormone secretion. To this end, we identified two distinct proglucagons, Gcga and Gcgb, as well as GCG receptors, Gcgra and Gcgrb, in Nile tilapia (Oreochromis niloticus). Using the cAMP response element (CRE)-luciferase reporter system, tilapia GCGa and GCGb could reciprocally activate the two GCG receptors expressed in human embryonic kidney 293 (HEK293) cells. Quantitative real-time PCR analysis revealed that differential expression of the Gcga and Gcgb and their cognate receptors Gcgra and Gcgrb was found in the various tissues of tilapia. In particular, the Gcgrb is abundantly expressed in the neurointermediate lobe (NIL) of the pituitary gland. In primary cultures of tilapia NIL cells, GCGb effectively stimulated SL release, with parallel rises in the mRNA levels, and co-incubation with the GCG antagonist prevented GCGb-stimulated SL release. In parallel experiments, GCGb treatment dose-dependently enhanced intracellular cyclic adenosine monophosphate (cAMP) accumulation with increasing inositol 1,4,5-trisphosphate (IP3) concentration and the resulting in transient increases of Ca2+ signals in the primary NIL cell culture. Using selective pharmacological approaches, the adenylyl cyclase (AC)/cAMP/protein kinase A (PKA) and phospholipase C (PLC)/IP3/Ca2+/calmodulin (CaM)/CaMK-II pathways were shown to be involved in GCGb-induced SL release and mRNA expression. Together, these results provide evidence for the first time that GCGb can act at the pituitary level to stimulate SL release and gene expression via GCGRb through the activation of the AC/cAMP/PKA and PLC/IP3/Ca2+/CaM/CaMK-II cascades.

Isolation of tumour stem-like cells from benign tumours.

BACKGROUND: Cancerous stem-like cells (CSCs) have been implicated as cancer-initiating cells in a range of malignant tumours. Diverse genetic programs regulate CSC behaviours, and CSCs from glioblastoma patients are qualitatively distinct from each other. The intrinsic connection between the presence of CSCs and malignancy is unclear. We set out to test whether tumour stem-like cells can be identified from benign tumours. METHODS: Tumour sphere cultures were derived from hormone-positive and -negative pituitary adenomas. Characterisation of tumour stem-like cells in vitro was performed using self-renewal assays, stem cell-associated marker expression analysis, differentiation, and stimulated hormone production assays. The tumour-initiating capability of these tumour stem-like cells was tested in serial brain tumour transplantation experiments using SCID mice. RESULTS: In this study, we isolated sphere-forming, self-renewable, and multipotent stem-like cells from pituitary adenomas, which are benign tumours. We found that pituitary adenoma stem-like cells (PASCs), compared with their differentiated daughter cells, expressed increased levels of stem cell-associated gene products, antiapoptotic proteins, and pituitary progenitor cell markers. Similar to CSCs isolated from glioblastomas, PASCs are more resistant to chemotherapeutics than their differentiated daughter cells. Furthermore, differentiated PASCs responded to stimulation with hypothalamic hormones and produced corresponding pituitary hormones that are reflective of the phenotypes of the primary pituitary tumours. Finally, we demonstrated that PASCs are pituitary tumour-initiating cells in serial transplantation animal experiments. CONCLUSION: This study for the first time indicates that stem-like cells are present in benign tumours. The conclusions from this study may have applications to understanding pituitary tumour biology and therapies, as well as implications for the notion of tumour-initiating cells in general.

7B2 facilitates the maturation of proPC2 in neuroendocrine cells and is required for the expression of enzymatic activity.

The prohormone convertase PC2, which is thought to mediate the proteolytic conversion of many peptide hormones, has recently been shown to interact with the neuroendocrine-specific polypeptide 7B2 in Xenopus intermediate lobe (Braks, J. A. M., and G. J. M. Martens. Cell. 78:263. 1994). In the present work we have stably transfected neuroendocrine cell lines with rat 7B2 constructs and found that overexpression of 27 kD 7B2 greatly facilitates the kinetics of maturation of proPC2, both in AtT-20/PC2 cells and in Rin5f cells. The half-life of conversion of proPC2 was reduced from 2.7 to 1.7 h in AtT-20/PC2 cells stably transfected with 27 kD 7B2 cDNA. The previously proposed "chaperone" domain was not sufficient for this facilitation event; however, a construct corresponding to the 21-kD 7B2 protein (which represents the naturally occurring maturation product) functioned well. A 7B2 construct in which maturation of 27 kD 7B2 to its 21-kD form was blocked was unable to facilitate maturation of proPC2. To correlate effects on PC2 maturation with the actual generation of PC2 enzymatic activity, a similar transfection of 21 kD 7B2 was performed using CHO cells previously amplified for the expression of proPC2. Enzymatic activity cleaving the fluorogenic substrate Cbz-Arg-Ser-Lys-Arg-AMC was highly correlated with the expression of immunoreactive 21 kD 7B2 in the conditioned medium; medium obtained from the parent cell line was completely inactive. Enzymatic activity was identified as PC2 on the basis of inhibition by the carboxy-terminal peptide of 7B2, which has previously been shown to represent a potent and specific PC2 inhibitor. Taken together, our in vivo results indicate that the interesting secretory protein 7B2 is a bifunctional molecule with an amino-terminal domain involved in proPC2 transport as well as activation.

Mechanism of the facilitation of PC2 maturation by 7B2: involvement in ProPC2 transport and activation but not folding.

Among the members of the prohormone convertase (PC) family, PC2 has a unique maturation pattern: it is retained in the ER for a comparatively long time and its propeptide is cleaved in the TGN/ secretory granules rather than in the ER. It is also unique by its association with the neuroendocrine protein 7B2. This interaction results in the facilitation of proPC2 maturation and in the production of activatable proPC2 from CHO cells. In the present study, we have investigated the mechanism of this interaction. ProPC2 binds 7B2 in the ER, but exits this compartment much more slowly than 7B2. We found that proPC2 was also slow to acquire the capacity to bind 7B2, whereas 7B2 could bind proPC2 rapidly after synthesis. This indicated that proPC2 folding was the limiting step in the formation of the complex. Indeed, sensitivity of native proPC2 to N-glycanase F digestion and inhibition of proPC2 folding supported the notion that 7B2 is not involved in the early steps of proPC2 folding, and that proPC2 must fold before binding 7B2. Under experimental conditions that prevent propeptide cleavage, 7B2 expression increased proPC2 transport to the Golgi. This increase exhibited the same kinetics as the facilitation of the removal of the propeptide. Finally, proPC2 activation could be reconstituted in Golgi- enriched subcellular fractions. In vitro, 7B2 was required for proPC2 activation at an acidic pH. Taken together, our results demonstrate that rather than promoting proPC2 folding, 7B2 acts as a helper protein involved in proPC2 transport and is required in the proPC2 activation process. We propose, therefore, that 7B2 stabilizes proPC2 in a conformation already competent for these two events.

Pitx2 deletion in pituitary gonadotropes is compatible with gonadal development, puberty, and fertility.

This report introduces a gonadotrope-specific cre transgenic mouse capable of ablating floxed genes in mature pituitary gonadotropes. Initial analysis of this transgenic line, Tg(Lhb-cre)1Sac, reveals that expression is limited to the pituitary cells that produce luteinizing hormone beta, beginning appropriately at e17.5. Cre activity is detectable by a reporter gene in nearly every LHbeta-producing cell, but the remaining hormone-producing cell types and other organs exhibit little to no activity. We used the Tg(Lhb-cre)1Sac strain to assess the role Pitx2 in gonadotrope function. The gonadotrope-specific Pitx2 knockout mice exhibit normal expression of LHbeta, sexual maturation, and fertility, suggesting that Pitx2 is not required for gonadotrope maintenance or for regulated production of gonadotropins.

Lactational exposure to hexavalent chromium delays puberty by impairing ovarian development, steroidogenesis and pituitary hormone synthesis in developing Wistar rats.

Hexavalent chromium (Cr-VI) is used in a wide range of industries. Cr-VI from chromate industries and atmospheric emissions contribute to the Cr contamination in the environment. Cr is a reproductive metal toxicant that can traverse the placental barrier and cause a wide range of fetal effects including ovotoxicity. Therefore, the goal of this study was to investigate the basic mechanisms involved in Cr(VI)-induced ovotoxicity, and the protective role of vitamin C on ovarian follicular development and function in Cr(VI)-induced reproductive toxicity using both in vivo and in vitro approaches. Lactating rats received potassium dichromate (200 mg/L) with or without vitamin C (500 mg/L), through drinking water from postpartum days 1-21. During postnatal days (PND) 1-21 the pups received Cr(VI) via the mother's milk. Pups from both control and treatment groups were continued on regular diet and water from PND-21 onwards, and euthanized on PND-21, -45 and -65. Cr(VI) decreased steroidogenesis, GH and PRL, increased FSH and did not alter LH. Cr(VI) delayed puberty, decreased follicle number, and extended estrous cycle. Spontaneously immortalized rat granulosa cells were treated with 12.5 microM (IC(50)) potassium dichromate for 12 and 24 h, with or without vitamin C pre-treatment. Cr(VI) decreased the mRNA expressions of StAR, SF-1, 17beta-HSD-1, 17beta-HSD-2, FSHR, LHR, ER alpha and ER beta. Vitamin C pre-treatment protected ovary and granulosa cells from the deleterious effects of Cr(VI) toxicity, both in vivo and in vitro. Therefore, Cr(VI) toxicity could be a potential risk to the reproductive system in developing females, and vitamin C plays a protective role against Cr(VI)-induced ovotoxicity.

Cloning of somatolactin alpha, beta forms and the somatolactin receptor in Atlantic salmon: seasonal expression profile in pituitary and ovary of maturing female broodstock.

BACKGROUND: Somatolactin (Sl) is a fish specific adenohypophyseal peptide hormone related to growth hormone (Gh). Some species, including salmonids, possess two forms: Sl alpha and Sl beta. The somatolactin receptor (slr) is closely related to the growth hormone receptor (ghr). Sl has been ascribed many physiological functions, including a role in sexual maturation. In order to clarify the role of Sl in the sexual maturation of female Atlantic salmon (Salmo salar), the full length cDNAs of slr, Sl alpha and Sl beta were cloned and their expression was studied throughout a seasonal reproductive cycle using real-time quantitative PCR (RTqPCR). METHODS: Atlantic salmon Sl alpha, Sl beta and slr cDNAs were cloned using a PCR approach. Gene expression of Sl alpha, SL beta and slr was studied using RTqPCR over a 17 month period encompassing pre-vitellogenesis, vitellogenesis, ovulation and post ovulation in salmon females. Histological examination of ovarian samples allowed for the classification according to the degree of follicle maturation into oil drop, primary, secondary or tertiary yolk stage. RESULTS: The mature peptide sequences of Sl alpha, Sl beta and slr are highly similar to previously cloned salmonid forms and contained the typical motifs. Phylogenetic analysis of Atlantic salmon Sl alpha and Sl beta shows that these peptides group into the two Sl clades present in some fish species. The Atlantic salmon slr grouped with salmonid slr amongst so-called type I ghr. An increase in pituitary Sl alpha and Sl beta transcripts before and during spawning, with a decrease post-ovulation, and a constant expression level of ovarian slr were observed. There was also a transient increase in Sl alpha and Sl beta in May prior to transfer from seawater to fresh water and ensuing fasting. CONCLUSION: The up-regulation of Sl alpha and Sl beta during vitellogenesis and spawning, with a subsequent decrease post-ovulation, supports a role for Sl during gonadal growth and spawning. Sl could also be involved in calcium/phosphate mobilization associated with vitellogenesis or have a role in energy homeostasis associated with lipolysis during fasting. The up-regulation of both Sl alpha and Sl beta prior to fasting and freshwater transfer, suggests a role for Sl linked to reproduction that may be independent of the maturation induced fasting.

Melanin-concentrating hormone-expressing neurons adjust slow-wave sleep dynamics to catalyze paradoxical (REM) sleep.

Study Objectives: Experimental studies over the last 15 years established a role in sleep of the tuberal hypothalamic neurons that express melanin-concentrating hormone (MCH). Controversies still remain regarding their actual contribution to both slow-wave sleep (SWS) and paradoxical sleep (PS also known as REM sleep) or PS alone. Methods: To address this point, we compared effects of chemogenetic activation and inhibition of MCH neurons on SWS and PS amounts and EEG rhythmic activities in transgenic Pmch-cre mice. Results: In agreement with recently reported optogenetic data, the activation of MCH neurons invariably facilitates PS onset and maintenance. Our chemogenetic experiments further disclose that the ultradian rhythm of SWS is also notably related to the activity of MCH neurons. We observed that the mean duration of SWS episodes is significantly extended when MCH neurons are inhibited. Conversely, when they were excited, SWS bouts were drastically shortened and depicted substantial changes in δ rhythmic activities in electroencephalographic recording likely reflecting a deeper SWS. Conclusions: According to these original findings, we propose that when MCH neurons are physiologically recruited, SWS depth is increased and the extinction of SWS episodes is accelerated, two joint physiological processes strengthening the probability for natural SWS to PS transition and likely facilitating PS onset.

Melanin-concentrating hormone overexpression in transgenic mice leads to obesity and insulin resistance.

Several lines of investigation suggest that the hypothalamic neuropeptide melanin-concentrating hormone (MCH) regulates body weight in mammals. Obese mice lacking functional leptin overexpress the MCH message in the fed or fasted state. Acute intracerebroventricular injection of MCH increases energy intake in rats. Mice lacking the MCH gene are lean. To test the hypothesis that chronic overexpression of MCH in mice causes obesity, we produced transgenic mice that overexpress MCH (MCH-OE) in the lateral hypothalamus at approximately twofold higher levels than normal mice. On the FVB genetic background, homozygous transgenic animals fed a high-fat diet ate 10% more and were 12% heavier at 13 weeks of age than wild-type animals, and they had higher systemic leptin levels. Blood glucose levels were higher both preprandially and after an intraperitoneal glucose injection. MCH-OE animals were insulin-resistant, as demonstrated by markedly higher plasma insulin levels and a blunted response to insulin; MCH-OE animals had only a 5% decrease in blood glucose after insulin administration, compared with a 31% decrease in wild-type animals. MCH-OE animals also exhibited a twofold increase in islet size. To evaluate the contribution of genetic background to the predisposition to obesity seen in MCH-OE mice, the transgene was bred onto the C57BL/6J background. Heterozygote C57BL/6J mice expressing the transgene showed increased body weight on a standard diet, confirming that MCH overexpression can lead to obesity.

MIF re-discovered: pituitary hormone and glucocorticoid-induced regulator of cytokine production.

The protein mediator known as macrophage migration inhibitory factor (MIF) was one of the first cytokine activities to be discovered and was described 30 years ago to be a T cell-derived factor that inhibited the random migration of macrophages. Despite the long-standing association of MIF with activated lymphocytes, the precise role of MIF in host responses remained undefined. Recent studies however, have led to the description of a pituitary mediator that appears to act as the natural, counter-regulatory hormone for glucocorticoid action within the immune system. Isolated as a product of an anterior pituitary cell line, this protein was sequenced and found to have the same structure as MIF. The major role of MIF appears to be to act at an inflammatory site or lymph node to counter-balance the inhibitory effects of steroids on the primary immune response, which must necessarily be mounted to eliminate the source of infection or tissue invasion.