A regulação do lobo anterior da hypophyse por um hormonio testicular, especialmente sob o ponto de vista morphologico

The authors summarize the results of former works, based on the technics of parabiosis. After parabiotic union of two infantile rats, normal + castrate, the normal fellow enters into precocious puberty in about 7 days (Kallas). In the case of pairs: castrated male + normal female, the implants of testicles, or injection of maceration or aqueous extracts of testis in the castrated fellow, prevents the induction of early puberty in the normal female. In the case: castrated female + normal female, no inhibiting effect is provoked by that treatment. There is therefore a testicular hormone that regulates the hypophysis. After castration, this gland manifests a hyper-function and shows histological alterations, the chief character of these being the appearing in the anterior lobe, of the so-called castration cells, probably originated from basophile cells. Implants or injections of testis material prevent those alterations. This is a useful test; the effect is controlled by estimating the castration cells in the microscopic field. The testicular hormone that regulates the anterior lobe is probably another one, quite different from that which regulates the accessory genitalia. On account of the facts and experiments, it may be assumed that this new hormone is elaborated by the germinal epithelium of the testicles.

The role of the hypothalamic kisspeptin/GPR54 system in the control of GnRH neurons

Summary : The hypothalamus represents less than 1 % of the total volume of the brain tissue, yet it plays a crucial role in endocrine regulations. Puberty is defined as a process leading to physical, sexual and psychosocial maturation. The hypothalamus is central to this process, via the activation of GnRH neurons. Pulsatile GnRH secretion, minimal during childhood, increases with the onset of puberty. The primary function of GnRH is to regulate the growth, development and function of testes in boys and ovaries in girls, by stimulating the pituitary gland secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Several factors contribute to the timing of puberty, including sex and ethnicity, genetics, dietary intake and energy expenditure. Kisspeptins constitute a family of small peptides arising from the proteolytic cleavage of metastin, a peptide with 54 amino acids initially purified from human placenta. These kisspeptins were the subject of much attention following their discovery because of their antimetastatic properties, but it was more recently that their determining role in the reproductive function was demonstrated. It was shown that kisspeptins are ligands of a receptor, GPR54, whose natural inactivating mutation in humans, or knockout in the mouse, lead to infertility. GnRH neurons play a pivotal role in the central regulation of fertility. Kisspeptin greatly increases GnRH release and GnRH neuron firing activity, but the neurobiological mechanisms for these actions are unknown. Gprotein-coupled receptor 54, the receptor for kisspeptin, is expressed by GnRH neurons as well as other hypothalamic neurons, suggesting that both direct and indirect effects are possible. In the first part of my thesis, we investigated a possible connection between the acceleration of sexual development induced by leptin and hypothalamic metastin neurons. However, the data generated by our preliminary experiments confirmed that the commercially available antibodies are non-specific. This finding constituted a major drawback for our studies, which relied heavily upon the neuroanatomical study of the hypothalamic metastinergic pathways to elucidate their sensitivity to exogenous leptin. Therefore, we decided to postpone any further in vivo experiment until a better antibody becomes available, and focused on in vitro studies to better understand the mechanisms of action of kisspeptins in the modulation of the activity of GnRH neurons. We used two GnRH-expressing neuronal cell lines to investigate the cellular and molecular mechanisms of action of metastin in GnRH neurons. We demonstrated that kisspeptin induces an early activation of the MAP kinase intracellular signaling pathway in both cell lines, whereas the SAP/JNK or the Akt pathways were unaffected. Moreover, we found an increase in GnRH mRNA levels after 6h of metastin stimulation. Thus, we can conclude that kisspeptin regulates GnRH neurons both at the secretion and the gene expression levels. The MAPK pathway is the major pathway activated by metastin in GnRH expressing neurons. Taken together, these data provide the first mechanism of action of kisspeptin on GnRH neurons. Résumé : L'hypothalamus est une zone située au centre du cerveau, dont il représente moins de 1 du volume total. La puberté est la période de transition entre l'enfance et l'age adulte, qui s'accompagne de transformations somatiques, psychologiques, métaboliques et hormonales conduisant à la possibilité de procréer. La fonction principale de la GnRH est la régulation de la croissance, du développement et de la fonction des testicules chez les hommes, et des ovaires chez les femmes en stimulant la sécrétion de l'hormone lutéinisante (LH) et de l'hormone folliculostimulante (FSH) par la glande hypophysaire. Plusieurs facteurs contribuent au déclanchement de la puberté, y compris le sexe et l'appartenance ethnique, la génétique, l'apport alimentaire et la dépense énergétique. Les Kisspeptines constituent une famille de peptides résultant de la dissociation proteolytique de la métastine, un peptide de 54 acides aminés initialement purifié à partir de placenta humain. Ces kisspeptines ont fait l'objet de beaucoup d'attention à la suite de leur découverte en raison de leurs propriétés anti-metastatiques, et c'est plus récemment que leur rôle déterminant dans la fonction reproductive a été démontré. Les kisspeptines sont des ligands du récepteur GPR54, dont la mutation inactivatrice chez l'homme, ou le knockout chez la souris, conduisent à l'infertilité par hypogonadisme hypogonadotrope. Les neurones à GnRH jouent un rôle central dans le règlement des fonctions reproductrices et la kisspeptine stimule l'activité des neurones à GnRH et la libération de GnRH par ces neurones. Toutefois, les mécanismes neurobiologiques de ces actions ne sont pas connus. Dans la première partie de ma thèse, nous avons étudié le lien potentiel entre l'accélération du développement sexuel induite par la leptine et les neurones hypothalamiques à metastine. Les données générées dans cette première série d'expériences ont malheureusement confirmé que les anticorps anti-metastine disponibles dans le commerce sont aspécifiques. Ceci a constitué un inconvénient majeur pour nos études, qui devaient fortement s'appuyer sur l' étude neuroanatomique des neurones hypothalamiques à metastine pour évaluer leur sensibilité à la leptine exogène. Nous avons donc décidé de focaliser nos travaux sur une étude in vitro des mécanismes d'action de la kisspeptine pour moduler l'activité des neurones à GnRH. Nous avons utilisé deux lignées de cellules neuronales exprimant la GnRH pour étudier les mécanismes d'action cellulaires et moléculaires de la metastine dans des neurones. Nous avons ainsi pu démontrer que la kisspeptine induit une activation précoce de la voie f de signalisation de la MAP kinase dans les deux lignées cellulaires, alors que nous n'avons observé aucune activation de la voie de signalisation de la P13 Kinase et de la SAP/JNK. Nous avons en outre démontré une augmentation de l'expression de la GnRH par la stimulation avec la Kisspeptine. L'ensemble de ces données contribue à élucider le mécanisme d'action avec lequel la kisspeptine agit dans les neurones à GnRH, en démontrant un effet sur l'expression génique de la GnRH. Nous pouvons également conclure que la voie de la MAPK est la voie principale activée par la metastine dans les neurones exprimant la GnRH.

Two Studies on the Interplay between Social Preferences and Individual Biological Features

Biological features and social preferences have been studied separately as factors influencing human strategic behaviour. We run two studies in order to explore the interplay between these two sets of factors. In the first study, we investigate to what extent social preferences may have some biological underpinnings. We use simple one-shot distribution experiments to attribute subjects one out of four types of social preferences: Self-interested (SI), Competitive (C), Inequality averse (IA) and Efficiency-seeking (ES). We then investigate whether these four groups display differences in their levels of facial Fluctuating Asymmetry (FA) and in proxies for exposure to testosterone during phoetal development and puberty. We observe that development-related biological features and social preferences are relatively independent. In the second study, we compare the relative weight of these two set of factors by studying how they affect subjects’ behaviour in the Ultimatum Game (UG). We find differences in offers made and rejection rates across the four social preference groups. The effect of social preferences is stronger than the effect of biological features even though the latter is significant. We also report a novel link between facial masculinity (a proxy for exposure to testosterone during puberty) and rejection rates in the UG. Our results suggest that biological features influence behaviour both directly and through their relation with the type of social preferences that individuals hold.

Ectodysplasin regulates hormone-independent mammary ductal morphogenesis via NF-κB.

Ductal growth of the mammary gland occurs in two distinct stages. The first round of branching morphogenesis occurs during embryogenesis, and the second round commences at the onset of puberty. Currently, relatively little is known about the genetic networks that control the initial phases of ductal expansion, which, unlike pubertal development, proceeds independent of hormonal input in female mice. Here we identify NF-κB downstream of the TNF-like ligand ectodysplasin (Eda) as a unique regulator of embryonic and prepubertal ductal morphogenesis. Loss of Eda, or inhibition of NF-κB, led to smaller ductal trees with fewer branches. On the other hand, overexpression of Eda caused a dramatic NF-κB-dependent phenotype in both female and male mice characterized by precocious and highly increased ductal growth and branching that correlated with enhanced cell proliferation. We have identified several putative transcriptional target genes of Eda/NF-κB, including PTHrP, Wnt10a, and Wnt10b, as well as Egf family ligands amphiregulin and epigen. We developed a mammary bud culture system that allowed us to manipulate mammary development ex vivo and found that recombinant PTHrP, Wnt3A, and Egf family ligands stimulate embryonic branching morphogenesis, suggesting that these pathways may cooperatively mediate the effects of Eda.

The neuropeptide Y Y1 receptor regulates leptin-mediated control of energy homeostasis and reproductive functions.

The orexigenic neurotransmitter neuropeptide Y (NPY) plays a central role in the hypothalamic control of food intake and energy balance. NPY also exerts an inhibition of the gonadotrope axis that could be important in the response to poor metabolic conditions. In contrast, leptin provides an anorexigenic signal to centrally control the body needs in energy. Moreover, leptin contributes to preserve adequate reproductive functions by stimulating the activity of the gonadotrope axis. It is of interest that hypothalamic NPY represents a primary target of leptin actions. To evaluate the importance of the NPY Y1 and Y5 receptors in the downstream pathways modulated by leptin and controlling energy metabolism as well as the activity of the gonadotrope axis, we studied the effects of leptin administration on food intake and reproductive functions in mice deficient for the expression of either the Y1 or the Y5 receptor. Furthermore, the role of the Y1 receptor in leptin resistance was determined in leptin-deficient ob/ob mice bearing a null mutation in the NPY Y1 locus. Results point to a crucial role for the NPY Y1 receptor in mediating the NPY pathways situated downstream of leptin actions and controlling food intake, the onset of puberty, and the maintenance of reproductive functions.

Molecular characterization and phenotypic expression of mutations in genes for gonadotropins and their receptors in humans.

Gonadotropin hormones undergo important dynamic changes during life. Their rise during puberty stimulates gonadal steroid secretion, triggering the development of secondary sexual characteristics and the acquisition of fertility. The full spectrum of possible mutations and polymorphisms in the human gonadotropins and in their receptor genes has been described in recent years. Patients harboring these mutations display a very wide range of phenotypes affecting all aspects of the reproductive axis. An important insight provided by the careful study of these patients lies in the striking gender differences in the phenotypes associated with a given mutation. As a result, the careful study of these rare patients has allowed us to better define the respective roles of luteinizing hormone and follicle-stimulating hormone in normal human pubertal development and in the achievement of full fertility potential in either males or females. In this work, we describe briefly the known mutations in the genes for both gonadotropins and their receptors, and discuss their genotype/phenotype correlations in light of these important gender differences.

Heparan sulfate 6-O-sulfotransferase 1, a gene involved in extracellular sugar modifications, is mutated in patients with idiopathic hypogonadotrophic hypogonadism.

Neuronal development is the result of a multitude of neural migrations, which require extensive cell-cell communication. These processes are modulated by extracellular matrix components, such as heparan sulfate (HS) polysaccharides. HS is molecularly complex as a result of nonrandom modifications of the sugar moieties, including sulfations in specific positions. We report here mutations in HS 6-O-sulfotransferase 1 (HS6ST1) in families with idiopathic hypogonadotropic hypogonadism (IHH). IHH manifests as incomplete or absent puberty and infertility as a result of defects in gonadotropin-releasing hormone neuron development or function. IHH-associated HS6ST1 mutations display reduced activity in vitro and in vivo, suggesting that HS6ST1 and the complex modifications of extracellular sugars are critical for normal development in humans. Genetic experiments in Caenorhabditis elegans reveal that HS cell-specifically regulates neural branching in vivo in concert with other IHH-associated genes, including kal-1, the FGF receptor, and FGF. These findings are consistent with a model in which KAL1 can act as a modulatory coligand with FGF to activate the FGF receptor in an HS-dependent manner.

Long-term follow-up of four patients with Langer-Giedion syndrome: clinical course and complications.

Long-term observations of individuals with the so-called Langer-Giedion (LGS) or tricho-rhino-phalangeal type II (TRPS2) are scarce. We report here a on follow-up of four LGS individuals, including one first described by Andres Giedion in 1969, and review the sparse publications on adults with this syndrome which comprises ectodermal dysplasia, multiple cone-shaped epiphyses prior to puberty, multiple cartilaginous exostoses, and mostly mild intellectual impairment. LGS is caused by deletion of the chromosomal segment 8q24.11-q24.13 containing among others the genes EXT1 and TRPS1. Most patients with TRPS2 are only borderline or mildly cognitively delayed, and few are of normal intelligence. Their practical skills are better than their intellectual capability, and, for this reason and because of their low self-esteem, they are often underestimated. Some patients develop seizures at variable age. Osteomas on processes of cervical vertebrae may cause pressure on cervical nerves or dissection of cerebral arteries. Joint stiffness is observed during childhood and changes later to joint laxity causing instability and proneness to trauma. Perthes disease is not rare. Almost all males become bald at or soon after puberty, and some develop (pseudo) gynecomastia. Growth hormone deficiency was found in a few patients, TSH deficiency so far only in one. Puberty and fertility are diminished, and no instance of transmission of the deletion from a non-mosaic parent to a child has been observed so far. Several affected females had vaginal atresia with consequent hydrometrocolpos.

Congenital Myasthenic Syndromes with COLQ mutations: Long term follow-up

Congenital myasthenic syndromes (CMS) are clinically and genetically heterogeneous inherited disorders characterized by impaired neuromuscular transmission. Mutations in the acetylcholinesterase (AChE) collagenlike tail subunit gene (ColQ) cause recessive forms of synaptic CMS with end plate AChE deficiency. We report the time course of clinical manifestations in 15 COLQ-mutated patients followed from 1987 to 2010. All patients suffered from a muscle weakness with onset at birth or in childhood. Ocular and bulbar signs were found in 60% of the patients and delayed pupillary light response in 20% of our patients. EMG study demonstrated a decrement on repetitive nerve stimulation and repetitive compound muscle action potential in all patients. Clinical symptoms strongly fluctuated daily, weekly, monthly or even yearly. Severe relapses were characterized by a general motor weakness associated with pain which resolved spontaneously after a few months whereas the relapses with these symptoms and bulbar signs could last up to several years. Genetic analyses identified 16 different mutations including 9 novel ones. There was no genotype-phenotype correlation. Our study confirms the predominance of oculobulbar signs and the frequency of respiratory distress in COLQrelated CMS. At the end of the follow up of 23 years, interesting findings were (i) the spontaneous reversibility of severe relapses, some of them lasting for up to 5 years (ii) the good prognosis of COLQ-related CMS, since at the end of the follow-up 80% of patients were ambulant and 87% of patients had no respiratory trouble (iii) the efficacy of Ephedrine and, to a lesser extend, of 3-4 DAP. The triggering factors of relapses were esterase inhibitors, effort, puberty, pregnancy and delivery highlighting the importance of hormonal factors in CMS. In conclusion, patients diagnosed with unknown congenital myopathy should undergo an electrophysiological study of neuromuscular junction to identify ColQ-related CMS.

Breast stem cells and hormonal mechanisms in carcinogenesis

A woman's risk of breast cancer is strongly affected by her reproductive history. The hormonal milieu is also a key determinant of the course of the disease. Combining mouse genetics with tissue recombination techniques, we have established that the female reproductive hormones, estrogens, progesterone, and prolactin, act sequentially on the mammary epithelium to trigger distinct developmental steps. The hormones impinge directly on a subset of luminal mammary epithelial cells that express the respective hormone receptors and act as sensor cells translating and amplifying systemic signals into local stimuli. Local signaling is stage and age specific. During puberty, estrogens promote proliferation using the EGF family member, amphiregulin, as essential paracrine mediator. In adulthood, progesterone, rather than estrogen, is the major inducer of stem cell activation and cell proliferation of the mammary epithelium. Hormonal signaling modulates crucial developmental pathways that impinge on mammary stem cell populations, while Notch signaling, by inhibiting p63, is central to mammary cell fate determination. Cell proliferation occurs in two waves. The first results from direct stimulation of the small fraction of hormone receptor positive cells. It is followed by a second wave of progesterone-induced proliferation involving mostly hormone receptor negative cells, in which RANKL is a key mediator. A model in which repeated activation of paracrine signaling by progesterone with resulting stem cell activation promotes breast carcinogenesis is proposed.

The relationship between muscle strength and physiological age: a cross-sectional study in boys aged from 11 to 15.

OBJECTIVE: To investigate the relationships between isokinetic knee flexor and extensor muscle strength and physiological and chronological age in young soccer players. MATERIAL AND METHODS: Seventy-nine young, healthy, male soccer players (mean+/-standard deviation age: 12.78+/-2.88, range: 11 to 15) underwent a clinical examination (age, weight, height, body mass index and Tanner puberty stage) and an evaluation of bilateral knee flexor and extensor muscle strength on an isokinetic dynamometer. Participation in the study was voluntary. RESULTS: The peak torque increased progressively (by 50%) between the ages of 11 and 15 and most significantly between 12 to 14. The knee flexor/extensor ratios only decreased significantly between 14 and 15 years of age. Puberty stage was the most important determinant of the peak torque level (ahead of chronological age, weight and height) for all angular velocities (p<0.0001). Muscle strength increased significantly between Tanner stages 1 and 5, with the greatest increase between stages 2 and 4. CONCLUSION: The present study showed that isokinetic muscle strength increases most between 12 and 13 years of age and between Tanner stages 2 and 3. There was strong correlation between muscle strength and physiological age.

Mutation screening of SEMA3A and SEMA7A in patients with congenital hypogonadotropic hypogonadism.

Background:Congenital hypogonadotropic hypogonadism (HH), a rare disorder characterized by absent, partial, or delayed puberty, can be caused by the lack or deficient number of hypothalamic gonadotropin-releasing hormone (GnRH) neurons. SEMA3A was recently implicated in the etiology of the disorder, and Sema7A-deficient mice have a reduced number of GnRH neurons in their brains.Methods:SEMA3A and SEMA7A were screened by Sanger sequencing in altogether 50 Finnish HH patients (34 with Kallmann syndrome (KS; HH with hyposmia/anosmia) and 16 with normosmic HH (nHH)). In 20 patients, mutation(s) had already been found in genes known to be implicated in congenital HH.Results:Three heterozygous variants (c.458A>G (p.Asn153Ser), c.1253A>G (p.Asn418Ser), and c.1303G>A (p.Val435Ile)) were found in SEMA3A in three KS patients, two of which also had a mutation in FGFR1. Two rare heterozygous variants (c.442C>T (p.Arg148Trp) and c.1421G>A (p.Arg474Gln)) in SEMA7A were found in one male nHH patient with a previously identified KISS1R nonsense variant and one male KS patient with a previously identified mutation in KAL1, respectively.Conclusion:Our results suggest that heterozygous missense variants in SEMA3A and SEMA7A may modify the phenotype of KS but most likely are not alone sufficient to cause the disorder.

Maintenance and breeding of Thrichomys (Trouessart, 1880) (Rodentia: Echimyidae) in captivity

South American histricognath rodents Thrichomys apereoides laurentius and Thrichomys pachyurus are natural hosts of Trypanosoma cruzi, agent of Chagas disease. We established breeding colonies of these species to serve as experimental models in various parasitological studies. Both species of Thrichomys have all the requirements necessary to become excellent laboratory models: they can be easily maintained in the standard laboratory conditions and breed throughout the year and they do not have any special dietary demands and can be fed by standard food pellets designed for laboratory mice. Both species produce precocious offspring that have their eyes and ears open, teeth erupted, fur well developed, and can eat solid food in the first week of life. T. a. laurentius has larger litter sizes and lower body masses at birth and weaning than T. pachyurus. Moreover, females of T. a. laurentius reach puberty earlier and with lower body mass than T. pachyurus.

A nutritional intervention study with hydrolyzed collagen in pre-pubertal Spanish children: influence on bone modeling biomarkers

Aim: The aim of the study was to investigate the influence of dietary intake of commercial hydrolyzed collagen (Gelatine Royal ®) on bone remodeling in pre-pubertal children. Methods: A randomized double-blind study was carried out in 60 children (9.42 ± 1.31 years) divided into three groups according to the amount of partially hydrolyzed collagen taken daily for 4 months: placebo (G-I, n = 18), collagen (G-II, n = 20) and collagen + calcium (G-III, n = 22) groups. Analyses of the following biochemical markers were carried out: total and bone alkaline phosphatase (tALP and bALP), osteocalcin, tartrate-resistant acid phosphatase (TRAP), type I collagen carboxy terminal telopeptide, lipids, calcium, 25-hydroxyvitamin D, insulin-like growth factor 1 (IGF-1), thyroid-stimulating hormone, free thyroxin and intact parathormone. Results: There was a significantly greater increase in serum IGF-1 in G-III than in G II (p < 0.01) or G-I (p < 0.05) during the study period, and a significantly greater increase in plasma tALP in G-III than in G-I (p < 0.05). Serum bALP behavior significantly (p < 0.05) differed between G-II (increase) and G-I (decrease). Plasma TRAP behavior significantly differed between G-II and G-I (p < 0.01) and between G-III and G-II (p < 0.05). Conclusion: Daily dietary intake of hydrolyzed collagen seems to have a potential role in enhancing bone remodeling at key stages of growth and development.

Effect of a general school-based physical activity intervention on bone mineral content and density: A cluster-randomized controlled trial.

Background: Specific physical loading leads to enhanced bone development during childhood. A general physical activity program mimicking a real-life situation was successful at increasing general physical health in children. Yet, it is not clear whether it can equally increase bone mineral mass. We performed a cluster-randomized controlled trial in children of both gender and different pubertal stages to determine whether a school-based physical activity (PA) program during one school-year influences bone mineral content (BMC) and density (BMD), irrespective of gender.Methods: Twenty-eight 1st and 5th grade (6-7 and 11-12 year-old) classes were cluster randomized to an intervention (INT, 16 classes, n = 297) and control (CON; 12 classes, n = 205) group. The intervention consisted of a multi-component PA intervention including daily physical education with at least 10 min of jumping or strength training exercises of various intensities. Measurements included anthropometry, and BMC and BMD of total body, femoral neck, total hip and lumbar spine using dual-energy X-ray absorptiometry (DXA). PA was assessed by accelerometers and Tanner stages by questionnaires. Analyses were performed by a regression model adjusted for gender, baseline height and weight, baseline PA, post-intervention pubertal stage, baseline BMC, and cluster.Results: 275 (72%) of 380 children who initially agreed to have DXA measurements had also post-intervention DXA and PA data. Mean age of prepubertal and pubertal children at baseline was 8.7 +/- 2.1 and 11.1 +/- 0.6 years, respectively. Compared to CON, children in INT showed statistically significant increases in BMC of total body, femoral neck, and lumbar spine by 5.5%, 5.4% and 4.7% (all p < 0.05), respectively, and BMD of total body and lumbar spine by 8.4% and 7.3% (both p < 0.01), respectively. There was no gender*group, but a pubertal stage*group interaction consistently favoring prepubertal children.Conclusion: A general school-based PA intervention can increase bone health in elementary school children of both genders, particularly before puberty. (C) 2010 Elsevier Inc. All rights reserved.