920 resultados para Hair Follicle Bulge
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A chemical test previously described for the diagnosis of pregnancy was applied to the study of the excretion of gonadotropin in the urine during menstrual cycle. The chemical test is based on the selective adsorption by kaolim of the reducing substances biologically related to urinary gonadotropin. The active substance when acidified to pH 4.0 is adsorbed by the kolin and eluated with O.1N sodium hydroxide. The alkaline solution is treated by Somogyi's copper reagent and the excess not reduced is titrated by 0.005 N sodium thiosulfate. Gonadotropin is quantitatively addorbed by kaolin at pH 4.0 and eluated by alkaline solution as previously demonstrated by the A. (1). In the present paper the complete menstrual cycle was studied daily. It was observed that normally there are two distinct maxima of excretion. This study is based on 11 normal cycles (24-30 days) and 34 abnormal ones. Normal cycles showed a intramenstrual estrogens elimination from 200 to 260 mice units determinated by the Allen - Doisy full estrus smear test. The abnormal cycles belonging also to normal women showed much less estrogen excretion (14 to 25 mice units) Table II). In those cases with decreased estrogen excretion no fall in the curve after 14 th. day was observed. The A. suggest that the peaks of gonadotropin excretion is not related to the oculation but possibly due, the first one, to the follicle stimulating hormone and the second to the luteinizing hormone of hormone stimulating of the inerstitial tissue.
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Fidena adnaticornis n. sp. is described from female specimens. It closely resembles Fidena besckii (WIED. ), 1828 and indeed more closely Fidena soledadei (LUTZ), 1911. It can be distinguished from both by the antenna which are so close together that the distance between their basis is less that the width of the first antennal segment; also by the prevalence of yellow hairs on the coxae. In F. soledadei and chiefly in F. besckii the antennae an evidently more separated; they have also few yellow hairs limited to the base extremity of the coxae with prevalence of brown or black hairs. In F. besck the prealar hairs are predominantly yellow ones and there exist yellow hair around the edge of the scutellum, which does not occours in F. adnaticorn and in F. soledadei. In the abdomen the following areas, covered by whit hairs are more extensive in F. besckii: the mid row of white patches on the sternites is more conspicuous and involves the fifth segment; on the sternites instead of stripes the hairs form bands somewhat broader at the middle the respective segment, they may even form triangles with the base as with as the whole segment. Both cotypes of F. soledadei have the hairs damages but, at least, in the 1+2 sternites the areas covered by the white hairs see to be larger than in F. adnaticornis; they have also a higher frons: index : = 2.9.
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Our work is on the isolation from brazilian soil of the perfect stage of Microsporum gypseum, Nannizzia gypsea, Stock., 1963, using cut sterilized children hair as bait.
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Organs developing as appendages of the ectoderm are initiated from epithelial thickenings called placodes. Their formation is regulated by interactions between the ectoderm and underlying mesenchyme, and several signalling molecules have been implicated as activators or inhibitors of placode formation. Ectodysplasin (Eda) is a unique signalling molecule in the tumour necrosis factor family that, together with its receptor Edar, is necessary for normal development of ectodermal organs both in humans and mice. We have shown previously that overexpression of the Eda-A1 isoform in transgenic mice stimulates the formation of several ectodermal organs. In the present study, we have analysed the formation and morphology of placodes using in vivo and in vitro models in which both the timing and amount of Eda-A1 applied could be varied. The hair and tooth placodes of K14-Eda-A1 transgenic embryos were enlarged, and extra placodes developed from the dental lamina and mammary line. Exposure of embryonic skin to Eda-A1 recombinant protein in vitro stimulated the growth and fusion of placodes. However, it did not accelerate the initiation of the first wave of hair follicles giving rise to the guard hairs. Hence, the function of Eda-A1 appears to be downstream of the primary inductive signal required for placode initiation during skin patterning. Analysis of BrdU incorporation indicated that the formation of the epithelial thickening in early placodes does not involve increased cell proliferation and also that the positive effect of Eda-A1 on placode expansion is not a result of increased cell proliferation. Taken together, our results suggest that Eda-A1 signalling promotes placodal cell fate during early development of ectodermal organs.
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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.
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Eggs of Manduca sexta contain four well-characterized protein derived from hemolymph: vitellogenin and lipophorin (very high density lipoproteins); microvitellogenin, a 26,000 dalton female-specific protein lacking lipid and carbohydrate, and insecticyanin, a blue biliprotein composed of four identical 22,000 dalton subunits. In addition, eggs contain a large store of triacyl glycerols. It has been shown that vitellogenin and lipophorin are actively taken up by follicles in vitro. The lipid components of these two proteins together account for only 10% of egg lipid. The follicle actively sequesters intact high density lipophorin, which, inside the oocyte, is stripped of much of its neutral lipid and two molecules of apolipophorin III. On the other hand, low density lipophorin donates diacylglycerol to the oocyte without its protein components being sequestered. Most of the egg lipid is transported from the fat body by a shuttle system involving low density lipophorin.
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We have identified C7orf11, which localizes to the nucleus and is expressed in fetal hair follicles, as the first disease gene for nonphotosensitive trichothiodystrophy (TTD). C7orf11 maps to chromosome 7p14, and the disease locus has been designated "TTDN1" (TTD nonphotosensitive 1). Mutations were found in patients with Amish brittle-hair syndrome and in other nonphotosensititive TTD cases with mental retardation and decreased fertility but not in patients with Sabinas syndrome or Pollitt syndrome. Therefore, genetic heterogeneity in nonphotosensitive TTD is a feature similar to that observed in photosensitive TTD, which is caused by mutations in transcription factor II H (TFIIH) subunit genes. Comparative immunofluorescence analysis, however, suggests that C7orf11 does not influence TFIIH directly. Given the absence of cutaneous photosensitivity in the patients with C7orf11 mutations, together with the protein's nuclear localization, C7orf11 may be involved in transcription but not DNA repair.
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During 1985, 50,356 children and adolecents from 105 public schools of Belo Horizonte, Minas Gerais State were questioned about or examined for head lice (Pediculus capitis). The mean prevalence of pediculosis, obtainde from the questionnaires and sometimes confirmed by head inspections, was 7.7% or else 10.2% when adjusted to 38,311 respondents. Current and past infestations combined - within a period of three months before survey - revealed a total prevalence of 57.4%. Significant differences were observed among socioeconomic levels, and grades of school age. The more prevalent categories among the factors studied were: sex - femal: 9.2% (P<0.001); ethnic group - white: 10.0% (P<0.001); hair length - long: 9.5% (P<0.05); year age-group - 1-5 years: 19.2% (P<0.001), with a peak in the 5th year (21.3%).
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In cases of highly inflammatory dermatophytosis in humans, it is important to identify the possible source of animal transmission in order to prevent recurrence, family outbreaks or rapidly progressing epidemics. A survey of dermatophytes in pets during a 14-month period in Switzerland revealed, in addition to Microsporum canis, two different species of the Trichophyton mentagrophytes complex, Arthroderma benhamiae and Arthroderma vanbreuseghemii, all causing inflammatory dermatophytoses. Arthroderma benhamiae was only and frequently isolated from guinea pigs. Arthroderma vanbreuseghemii was isolated mainly from European short hair cats, but also from dogs and in one case from a pure-bred cat. Ninety-three percent of the cats carrying A. vanbreuseghemii were hunters and all had skin lesions. In contrast, cats with skin lesions that were strictly indoors were found to be almost exclusively infected by M. canis. Therefore, it can be suspected that infection with A. vanbreuseghemii occurred during hunting and that the natural source of this dermatophyte is either soil or an animal other than the cat, most probably a rodent.
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RESUMEUne consommation excessive et chronique d'alcool est associée à une augmentation significative de la morbidité et de la mortalité. L'identification de marqueurs biologiques fiables, permettant de mettre en évidence une consommation excessive et chronique, présente donc un intérêt certain pour prévenir les conséquences néfastes de l'abus d'alcool. L'approche couramment employée consiste à mesurer les marqueurs biologiques indirects dans le sang, tels que les marqueurs hépatiques dont l'augmentation peut résulter d'une consommation chronique et excessive d'alcool. Cependant, leur valeur diagnostique est souvent limitée par leur manque de sensibilité et/ou de spécificité et leur combinaison est généralement recommandée pour améliorer le diagnostic. A ce jour, il n'existe pas de marqueur biologique permettant le diagnostic fiable d'une consommation chronique et excessive d'alcool.L'objectif principal de cette thèse était d'évaluer la pertinence de l'éthylglucuronide (EtG), un métabolite direct de l'éthanol présentant la particularité d'être incorporé dans les cheveux, comme marqueur d'une consommation chronique et excessive d'alcool. Dans un premier temps, une revue de la littérature a permis de dresser un état des lieux de l'usage de l'EtG et d'identifier les axes de réflexion. L'EtG s'est révélé être un marqueur efficace pour identifier une consommation chronique et excessive d'alcool. Cependant, l'absence de seuil de positivité fiable et une méconnaissance des facteurs influençant l'incorporation de l'EtG dans les cheveux ont été mises en évidence. Afin d'investiguer ces différents points, deux études ont été conduites : (1) une étude chez le rat pour tenter de comprendre les facteurs influençant l'incorporation de l'EtG dans les cheveux et étudier la relation entre la quantité d'alcool administrée et la concentration d'EtG mesurée dans les cheveux; et (2) une étude clinique afin de déterminer les performances diagnostiques de l'EtG comme marqueur d'une consommation excessive et chronique d'alcool. Une méthode analytique sensible et sélective par chromatographic gazeuse couplée à la spectrométrie de masse en tandem a été développée et appliquée à l'analyse de l'EtG dans les cheveux.Le sang semblait jouer un rôle majeur dans l'incorporation de l'EtG dans les poils. Son incorporation n'était pas influencée par la pigmentation. La concentration d'EtG mesurée dans les poils de rats reflétait la dose d'éthanol administrée. De plus, la mesure de l'EtG dans les cheveux humains a démontré de très bonnes performances diagnostiques pour détecter une consommation excessive et chronique d'alcool. Les performances diagnostiques de l'EtG surpassaient celles des marqueurs hépatiques usuels seuls ou combinés. L'EtG n'était pas influencé par l'âge, le sexe ou l'indice de masse corporelle. Un seuil de positivité de 25 pg/mg permettait de détecter les consommateurs à usage nocif avec une grande fiabilité. Un seuil de positivité de 9 pg/mg permettait de détecter les consommateurs à risque.SUMMARYChronic and excessive alcohol consumption is associated with a significant increase of morbidity and mortality. The identification of a reliable biomarker to detect chronic and excessive alcohol consumers would be valuable to prevent alcohol's harmful effects. The combined analysis of 2 or more hepatic biomarkers, which are known to be increased following sustained alcohol consumption, is usually applied to enhance the diagnostic performance in identifying chronic and excessive alcohol consumers. However, their diagnostic value is often limited by their lack of sensitivity and / or specificity and their combination is generally recommended to improve diagnosis. To date, there are no reliable biomarkers available for diagnosing chronic and excessive alcohol consumption.The main objective of this research was to evaluate the relevance of EtG, a direct alcohol metabolite, as a biomarker of chronic and excessive alcohol consumption, thanks to its characteristic to incorporate into hair. First, a review of literature on the use of EtG was carried out. EtG demonstrated strong potential in detecting chronic and excessive alcohol consumption. However, the lack of reliable cutoff and the unawareness of factors that affect the EtG incorporation into hair were stressed. To investigate these points, two studies have been conducted: (1) a nonclinical study in rats to determine the factors affecting the incorporation of EtG into hair as well as to investigate the relationship between the amount of alcohol administered and the EtG concentration measured in hair; and (2) a clinical study to determine the diagnostic performance of EtG as a biomarker for the identification of chronic and excessive alcohol consumers. A sensitive and specific Gas Chromatography-Mass Spectrometry coupled to tandem Mass Spectrometry method has been developed and applied to hair EtG analysis.Bloodstream seemed to play a major role in the EtG incorporation into hair. EtG incorporation into rat hair was not affected by hair pigmentation. EtG concentration in rat hair appeared to reflect the EtG concentration in blood. Besides, EtG demonstrated strong diagnostic performance in detecting both heavy alcohol consumption and at-risk alcohol consumption, and clearly outperformed diagnostic performance of hepatic biomarkers. In contrast with hepatic biomarkers, EtG was not associated with age, gender or body mass index. A reliable cutoff value of 25 pg/mg allowed to detect heavy drinkers; a reliable cutoff value of 9 pg/mg allowed to detect at-risk drinkers.
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Ectodermal organogenesis is regulated by inductive and reciprocal signalling cascades that involve multiple signal molecules in several conserved families. Ectodysplasin-A (Eda), a tumour necrosis factor-like signalling molecule, and its receptor Edar are required for the development of a number of ectodermal organs in vertebrates. In mice, lack of Eda leads to failure in primary hair placode formation and missing or abnormally shaped teeth, whereas mice overexpressing Eda are characterized by enlarged hair placodes and supernumerary teeth and mammary glands. Here, we report two signalling outcomes of the Eda pathway: suppression of bone morphogenetic protein (Bmp) activity and upregulation of sonic hedgehog (Shh) signalling. Recombinant Eda counteracted Bmp4 activity in developing teeth and, importantly, inhibition of BMP activity by exogenous noggin partially restored primary hair placode formation in Eda-deficient skin in vitro, indicating that suppression of Bmp activity was compromised in the absence of Eda. The downstream effects of the Eda pathway are likely to be mediated by transcription factor nuclear factor-kappaB (NF-kappaB), but the transcriptional targets of Edar have remained unknown. Using a quantitative approach, we show in cultured embryonic skin that Eda induced the expression of two Bmp inhibitors, Ccn2/Ctgf (CCN family protein 2/connective tissue growth factor) and follistatin. Moreover, our data indicate that Shh is a likely transcriptional target of Edar, but, unlike noggin, recombinant Shh was unable to rescue primary hair placode formation in Eda-deficient skin explants.
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ABSTRACT : The epidermis, the outermost compartment of the skin, is a stratified and squamous epithelium that constantly self-renews. Keratinocytes, which represent the main epidermal population, are responsible for its cohesion and barrier function. Epidermal renewal necessitates a fine equilibrium between keratinocyte proliferation and differentiation. The keratinocyte stem cell, located in the basal cell layer, is responsible for epidermal homeostasis and regeneration during the wound healing process. The transcription factor p63 structurally belongs to the p53 superfamily. It is expressed in the basal and supra-basal cell layers of stratified epithelia and is thought to be important for the renewal or the differentiation of keratinocyte stem cells (Yang et al., 1999; Mills et al., 1999). In order to better understand its function, we established an in vitro model of p63 deficient human keratinocyte stem cells using a shp63 mediated RNA interference. Knockdown of endogenous p63 induces downregulation of cell-adhesion genes as previously described (Carroll et al., 2006). Interestingly, the replating of attached p63-knockdown keratinocytes on a feeder layer results in a loss of attachment and proliferation. They are no longer clonogenic. However, if the same population are replated in a fibrin matrix, extended fibrinolysis is reported, a common process in wound healing, suggesting that p63 regulates the fibrinolytic pathway. This result was confirmed by Q-PCR and shows that the urokinase pathway, which mediates fibrinolysis, is upregulated. Altogether, these findings suggest a mechanism in which the fine tuning of p63 expression promotes attachment or release of the keratinocyte stem cell from the basement membrane by inducing genes of adhesion and/or of fibrinolysis. This mechanism may be important for epidermal self-renewal, differentiation as well as wound healing. Its misregulation may be partly responsible for the p63 knockout phenotype. The downregulation of p63 also induces a decrease in LEKTI expression. LEKTI (lymphoepithelial Kazal-type serine protease inhibitor) is a serine protease inhibitor encoded by the Spink5 gene. It is expressed and secreted in the uppermost differentiated layers of stratified epithelia and plays a role in the desquamation process. When this gene is disrupted, humans develop the Netherton syndrome (Chavanas et al., 2000b). It is a dermatosis characterized by hair dysplasias, ichtyosiform erythroderma and impairment in epidermal barrier function promoting inflammation similarly as in psoriasis with inflammatory infiltrate in excess. TNFα (tumor necrosis factor alpha) and EDA1 (ectodysplasin A1) are two transmembraneprecursors that belong to the TNF superfamily, which is involved in immune and inflammation regulation (Smahi et al., 2002). We suggest that the secreted serine protease inhibitor LEKTI plays a role in the regulation of TNFα and EDA1 precursor cleavage and absence of LEKTI induces excess of inflammation. To investigate this hypothesis, we induced downregulation of Spink5 expression in rat keratinocyte stem cells by using a shSpink5 mediated RNA interference approach. Interestingly, expression of TNFα and EDA1 is modified after knockdown of Spink5 by Q-PCR. Moreover, downregulation of Spink5 induces loss of cohesiveness between keratinocytes and colonies adopt a scattered phenotype. Altogether, these preliminary data suggest that downregulation of LEKTI may play a role in the inflammatory response in Netherton syndrome patients, by regulating TNFα expression.
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Forensic scientists have long detected the presence of drugs and their metabolites in biological materials using body fluids such as urine, blood and/or other biological liquids or tissues. For doping analysis, only urine has so far been collected. In recent years, remarkable advances in sensitive analytical techniques have encouraged the analysis of drugs in unconventional biological samples such as hair, saliva and sweat. These samples are easily collected, although drug levels are often lower than the corresponding levels in urine or blood. This chapter reviews recent studies in the detection of doping agents in hair, saliva and sweat. Sampling, analytical procedures and interpretation of the results are discussed in comparison with those obtained from urine and blood samples.
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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.
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Patients with defective ectodysplasin A (EDA) are affected by X-linked hypohidrotic ectodermal dysplasia (XLHED), a condition characterized by sparse hair, inability to sweat, decreased lacrimation, frequent pulmonary infections, and missing and malformed teeth. The canine model of XLHED was used to study the developmental impact of EDA on secondary dentition, since dogs have an entirely brachyodont, diphyodont dentition similar to that in humans, as opposed to mice, which have only permanent teeth (monophyodont dentition), some of which are very different (aradicular hypsodont) than brachyodont human teeth. Also, clinical signs in humans and dogs with XLHED are virtually identical, whereas several are missing in the murine equivalent. In our model, the genetically missing EDA was compensated for by postnatal intravenous administration of soluble recombinant EDA. Untreated XLHED dogs have an incomplete set of conically shaped teeth similar to those seen in human patients with XLHED. After treatment with EDA, significant normalization of adult teeth was achieved in four of five XLHED dogs. Moreover, treatment restored normal lacrimation and resistance to eye and airway infections and improved sweating ability. These results not only provide proof of concept for a potential treatment of this orphan disease but also demonstrate an essential role of EDA in the development of secondary dentition.