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PubMedDate not supplied

Ectodermal ablation of the third branchial arch in chick embryos and the morphogenesis of the parathyroid III gland.

The parathyroid glands have been classically considered to be derivatives of the third and fourth pharyngeal pouches in most species, including humans. Furthermore, the presence of neural crest-derived cells in the parathyroid glands connective tissue has been apparently established. However, our previous studies have provided a new hypothesis on the origin of these glands in human and chick embryos. To determine the origin of the parathyroid III (P3) gland, ectoderm of the third branchial arch was cauterized in chick embryos at Hamburger and Hamilton's stage 19 (embryonic day 3). Cauterization of the ventral half of the ectoderm was followed by the non-formation, on the same side, of the P3 gland. When the dorsal half of the ectoderm was cauterized, both the right and left P3 glands formed. Our observations suggest that the ectoderm of the ventral half of the third branchial arch is necessary for the organization of the P3 gland.

Animals↗
PubMed2001

Craniofacial tissues including tooth buds in fetal hypohidrotic ectodermal dysplasia.

OBJECTIVE: Hypohidrotic ectodermal dysplasia (HED) comprises defects in hair, teeth, and sweat glands. Disturbances in other ectodermal tissues have been associated with the condition. Our objective was to examine ectodermal craniofacial structures histologically in a fetus with HED and to compare the findings to similar structures in normal control fetuses. MATERIALS AND METHODS: A male fetus diagnosed with HED was therapeutically aborted in the 15th week of gestation. One male and two female healthy fetuses were used as normal controls. All fetuses were examined with parental consent, and had comparable sizes. Their bone maturation stage in the hand was identical. Tissue blocks from the craniofacial region were excised from all fetuses and prepared for histological analysis (formalin fixed, stained with toluidine blue or Alcian blue). The tissues examined were: tooth buds, skin and skin appendages, oral mucosa including minor salivary glands, major salivary glands, lacrimal glands, and adenohypophysis. RESULTS: Fewer tooth buds, minor salivary glands, and hair follicles were observed in the HED fetus as compared to controls. The structures of the epidermal components in the developing HED organs were loose and disorganised. The adhesion between the ectodermal and mesenchymal organ components in the HED fetus seemed to be disturbed.

Ectodermal Dysplasia↗
PubMed2001

Hypohidrotic ectodermal dysplasia: dental features and carriers detection.

Ectodermal dysplasia is a heterogeneous condition characterized by affected ectodermal structures, among which the teeth and skin with its derivatives (hair sweat glands) are the most frequent. The aim of this work is to present the analysis of dental traits in five families (affected boys and their mothers) with hypohidrotic ectodermal dysplasia (HED), and to evaluate the importance of orofacial and dental findings in the determination of female HED gene carriers. Hypodontia (oligodontia) was found in all the patients. The mothers, gene carriers, had either hypodontia or a reduced size of teeth with a particular morphological, peg shape. In patients with hypohidrotic ectodermal dysplasia the deciduous second molar teeth were mostly affected by taurodontism. The characteristic dental finding in heterozygous females of the mandibular peg shaped incisors and canines, as well as of hypodontia or peg shaped upper lateral incisors can be used as a reliable criterion for the detection of HED gene carriers.

Adult↗
PubMed2005

Three successive generations of women with anhidrotic/hypohidrotic ectodermal dysplasia.

We describe the findings of anhidrotic/hypohidrotic ectodermal dysplasia in three successive generations of a family. All three women had variable alopecia, anhidrosis, hypodontia and malar hypoplasia. Chromosomal studies revealed a defect of the 2q12 region in all three patients. Previous studies have reported rare cases of autosomal dominant ectodermal dysplasia associated with defects in the 2q11-13 region1. These rare disorders are characterized by common anomalies of at least two elements of the ectoderm and its appendages--namely, the skin, teeth, hair, nails and sweat glands. These patients also frequently have chronic dental problems with early loss of teeth and recurrent lung, ear and nose infections secondary to a defect in mucous membrane function. The majority of reported cases of ectodermal dysplasias have historically been X-linked recessive, but our findings indicate that an autosomal version may be more prevalent than previously thought.

Adult↗
PubMed1991

Cell commitment and cell interactions in the ectoderm of Drosophila melanogaster.

The separation of neural from epidermal progenitor cells in the ventral neuroectoderm of Drosophila is thought to be mediated by cellular interactions. In order to verify the occurrence of regulatory signals and to test the neurogenic capabilities of cells from various regions of the ectoderm, we have carried out homotopic and heterotopic transplantations of single ectodermal cells. We found that cells from any of the tested regions, with the exception of the proctodeal anlage, are capable of developing as neuroblasts following their transplantation into the ventral neuroectoderm. These neurogenic capabilities are gradually distributed. Cells from the procephalic and ventral neurogenic regions exhibit maximal capabilities, as shown by their behavior in heterotopic transplantations. However, the two neurogenic regions differ from each other in that no epidermalising signals can be demonstrated to occur within the procephalic neuroectoderm, whereas such signals are strong within the ventral neuroectoderm; in addition, neuralising signals from neighbouring cells seem to be necessary for neuroectodermal cells to develop as neuroblasts. Other ectodermal regions whose cells exhibit weaker neurogenic capabilities are, in decreasing order of capability, the dorsal epidermal anlage, the anterolateral region of the procephalic lobe, comprising the anlage of the pharynx, and the anterior pole of the embryo, corresponding to the anlagen of the stomodeum and ectodermal anterior midgut. We assume that, during development in situ, the neurogenic capabilities of all these cells are suppressed by inhibitory signals, which are released upon heterotopic transplantation into the neuroectoderm. A community effect which prevents groups of dorsal epidermal cells from taking on a neural fate upon their transplantation into the ventral neuroectoderm, is shown.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

[Cell differentiation of the head ectoderm in mouse embryos in vitro].

Cell differentiation has been studied in the explants of head ectoderm of 8, 9 and 10 day old mouse (CBA) embryos and of head epidermis of 13 day old embryos. Pieces of ectoderm were taken from the temporal region. It was established by indirect immunofluorescence that within 10, 15 and 20 days of cultivation spheroids with keratins or crystallins in some groups of fibres formed in the head ectoderm explants from 9 and 10 day old embryos. When cultivating the regions of head epidermis from 13 day old embryos, spheroids formed with keratin only in their cells. The data obtained suggest that there appear to be two clones of cells determined to the synthesis of keratins or crystallins in the head ectoderm of early mouse embryos. During embryogenesis, the number of cells determined to the synthesis of keratins appears to increase in the regions not related to the eye area. At the same time, the clone of cells determined to the synthesis of crystallins appears to be eliminated.

Animals↗
PubMedDate not supplied

[Compatibility of chick embryo eye anlagen with the ectoderm of the early amphibian gastrula in vitro].

Eye vesicles were isolated from the early chick embryos (stage 9+ after Hamburger and Hamilton, 1951) and combined with the Rana temporaria early gastrula ectoderm (EGE) in vitro. The tissues were jointly incubated in medium 199 diluted twice with deionized water at 22 +/- 1 degree for 7-8 days or the eye vesicles were removed from the EGE ectoderm within 16-18 h. At the joint long-term incubation of these tissues, a toxic effect of the chick embryonic tissues on the EGE cells was noted. In none of the experiments, the inducing effect of the eye vesicle on the EGE was found. Similar data were obtained when the EGE was jointly cultivated with the brain (stage 9-10) and retina (stage 15) of chick embryos. The brain of the chick embryos at stage 15 exerted a weak neuralizing effect on the EGE. In the control experiments, the eye vesicles explanted with the chick embryonic ectoderm remained viable till the end of cultivation but no lentoids formed in the ectoderm. The absence of lens-inducing effect at the joint cultivation of the chick embryonic eye vesicles with the EGE is considered as a result of disturbance of the synthesis or secretion of the corresponding agents rather than a sequence of the species "incompatibility" of the inductor and reacting tissue. Hence, the use of "xenogenic" tissue recombinants is not justified when analyzing the lens-inducing activity of the eye vesicles.

Animals↗
PubMed1983

[Experimental study of the effect of the ectoderm on the chondrogenic differentiation of the mesoderm of the mouse embryo limb in vitro. Results of a histological analysis].

The histological study of cultures of distal limb bud tips of 11 days old Mouse embryos and of dissociated mesoderm obtained from identical tips enabled us to demonstrate that distal bud mesoderm spontaneously differentiate into cartilage in vitro if its normal ectodermal covering is removed. If the ectoderm is present in situ or in close vicinity, the chondrogenic differentiation does not occur and mesodermal cells develop into a loose mesenchyme where numerous mitosis are observed. Experimental associations performed between limb bud mesoderm and epithelial sheets other than limb ectoderm demonstrated that the properties of this ectoderm are specific.

Animals↗
PubMed1983

A study of the properties, morphogenetic potencies and prospective fate of outer and inner layers of ectodermal and chordamesodermal regions during gastrulation, in various Anuran amphibians.

In both the ectodermal and the chordamesodermal regions of Anuran embryos, the outer layer of cells possesses epithelial properties and has the same restricted morphogenetic potencies. It is thus interchangeable between the regions, capable of epiboly and, when underlain by notochord material, of the formation of bottle-shaped cells as at the blastoporal groove, and invagination. When taken from the chordamesoderm region, this outer layer has no inducing effect on the ectoderm of the early gastrula. In normal development the outer layer of the neural plate takes an active part in forming the neural tube cavity. It gives rise to the neuroepithelial roof of the diencephalon and medulla oblongata and, when underlain by neuroblasts that develop from the inner cell layers, to ependymal cells of the brain wall. The outer layer of the notochord material is included in the epithelial layer underlying the roof of the gastrocoel - the hypochordal plate. The inner layers of these regions consist of loosely arranged cells and normally have no epithelial properties although, when taken from the ectoderm region, they may acquire such properties upon long-term contact with the environment. However they have wide morphogenetic potencies; the differences in these potencies between cells taken from the various presumptive regions being less than the differences between outer and inner cell layers in each region. Maps are provided which show the arrangement of presumptive rudiments in the ectoderm and chordamesoderm on sagittal sections through Bombina bombina embryos in early and late gastrulation.

Animals↗
PubMed1980

Differential localization of [35S] sulfate within ectodermal basement membrane in relation to initiation of chick limb buds.

This study examined the possible developmental relationship between differential amounts of glycosaminoglycans (GAG) within the ectodermal basement membrane and initiation of limb outgrowth. Chick embryos at stages 11-20 were labeled in ovo with 35SO4 and processed for autoradiography. After exposure to sulfate for 15 min. The label was localized within the surface ectoderm whereas after 3 h the label was localized within the subjacent basement membrane. The label was sensitive to chondroitinase ABC. These experiments suggest that the labeled material was ectodermally derived chondroitin sulfate. At all stages, examined, intense labeling of the basement membrane was associated with relatively undifferentiated, mitotically active tissue, e.g. limb-bud mesoderm. The labeling was less intense in regions with decreased mitotic activity, e.g. the flank. Thus, the labeling pattern of the basement membrane correlated with differential mitotic rates presumed to be associated with limb outgrowth. These observations support the hypothesis that communication between tissues of different origin resulting in altered mitotic behavior of limb and flank mesenchymal cells is facilitated by the ectodermal basement membrane.

Animals↗
PubMed1994

Mitral and aortic valve replacement in a patient with ectodermal anhydrotic dysplasia. A case report.

Ectodermal anhydrotic dysplasia is a rare, usually X-linked recessive malformation of ectodermal tissues and organs. The case of a 17-year-old boy with ectodermal anhydrotic dysplasia and concomitant combined mitral valve disease and aortic insufficiency is described. The surgical risk was considered to be high due to severe atrophia of the laryngo-pharyngeal mucosa complicating endotracheal intubation and the possibility of postoperative temperature control disturbances. Double valve replacement was performed late in the autumn, after laryngo-pharyngeal pharmacological treatment preparing for endotracheal intubation. The peri-operative course was managed without any complication related to the hereditary malformation. Our experience suggests that patients suffering from ectodermal anhydrotic dysplasia may undergo open heart surgery after appropriate preparation. Potential postoperative problems related to the hypohydrosis and impaired spontaneous temperature control could be prevented in our patient.

Adolescent↗
PubMed1995

Ectodermal dysplasia: literature review and a case report.

Ectodermal dysplasia is a group of rare inherited disorders that affect various tissues of ectodermal origin. The mode of inheritance varies among the different disorders. The most common form of ectodermal dysplasia is hypohidrotic ectodermal dysplasia (HED), which most severely affects the hair, nails, teeth, and skin. Men are more often and more severely affected than women. However, transmission is from the female carrier, who usually appears normal and unaffected. Dental treatment for these patients varies on an individual basis. This article illustrates a case of overdentures in a 7-year-old boy with HED.

Anodontia↗
PubMed1997

Ectodermal dysplasia: a review and case report.

Ectodermal dysplasia is a hereditary disease characterized by a congenital dysplasia of one or more ectodermal structures and their accessory appendages. Common manifestations include defective hair follicles and eyebrows, frontal bossing with prominent supraorbital ridges, nasal bridge depression, and protuberant lips. Intraorally, common findings are anodontia or hypodontia, conical teeth, and, consequently, generalized spacing. The patient may suffer from dry skin, hyperthermia, and unexplained high fever as a result of the deficiency of sweat glands. The present review focuses on the clinical manifestations, classifications, and diagnosis of ectodermal dysplasia. A 6-year-old girl, described in the case report, exhibited many of the manifestations of ectodermal dysplasia as well as behavioral problems and a severe gag reflex. The treatment to improve her appearance and oral function included a removable prosthesis, acid-etch-retained indirect resin composite veneers, and a fixed partial denture.

Anodontia↗
PubMed2004

Retinoic acid synthesis controlled by Raldh2 is required early for limb bud initiation and then later as a proximodistal signal during apical ectodermal ridge formation.

We present evidence for the existence of two phases of retinoic acid (RA) signaling required for vertebrate limb development. Limb RA synthesis is under the control of retinaldehyde dehydrogenase-2 (Raldh2) expressed in the lateral plate mesoderm, which generates a proximodistal RA signal during limb outgrowth. We report that Raldh2(-/-) embryos lack trunk mesodermal RA activity and fail to initiate forelimb development. This is associated with deficient expression of important limb determinants Tbx5, Meis2, and dHand needed to establish forelimb bud initiation, proximal identity, and the zone of polarizing activity (ZPA), respectively. Limb expression of these genes can be rescued by maternal RA treatment limited to embryonic day 8 (E8) during limb field establishment, but the mutant forelimbs obtained at E10 display a significant growth defect associated with a smaller apical ectodermal ridge (AER), referred to here as an apical ectodermal mound (AEM). In these RA-deficient forelimbs, a ZPA expressing Shh forms, but it is located distally adjacent to the Fgf8 expression domain in the AEM rather than posteriorly as is normal. AER formation in Raldh2(-/-) forelimbs is rescued by continuous RA treatment through E10, which restores RA to distal ectoderm fated to become the AER. Our findings indicate the existence of an early phase of RA signaling acting upstream of Tbx5, Meis2, and dHand, followed by a late phase of RA signaling needed to expand AER structure fully along the distal ectoderm. During ZPA formation, RA acts early to activate expression of dHand, but it is not required later for Shh activation.

Aldehyde Oxidoreductases↗
PubMed2006

Requirements for Endothelin type-A receptors and Endothelin-1 signaling in the facial ectoderm for the patterning of skeletogenic neural crest cells in zebrafish.

Genetic studies in mice and zebrafish have revealed conserved requirements for Endothelin 1 (Edn1) signaling in craniofacial development. Edn1 acts through its cognate type-A receptor (Ednra) to promote ventral skeletal fates and lower-jaw formation. Here, we describe the isolation and characterization of two zebrafish ednra genes - ednra1 and ednra2 - both of which are expressed in skeletal progenitors in the embryonic neural crest. We show that they play partially redundant roles in lower-jaw formation and development of the jaw joint. Knockdown of Ednra1 leads to fusions between upper- and lower-jaw cartilages, whereas the combined loss of Ednra1 and Ednra2 eliminates the lower jaw, similar to edn1-/- mutants. edn1 is expressed in pharyngeal arch ectoderm, mesoderm and endoderm. Tissue-mosaic studies indicate that, among these tissues, a crucial source of Edn1 is the surface ectoderm. This ectoderm also expresses ednrA1 in an edn1-dependent manner, suggesting that edn1 autoregulates its own expression. Collectively, our results indicate that Edn1 from the pharyngeal ectoderm signals through Ednra proteins to direct early dorsoventral patterning of the skeletogenic neural crest.

Amino Acid Sequence↗
PubMed2004

Hair and sweat glands in families with hypohidrotic ectodermal dysplasia: further characterization.

OBJECTIVES: To gather and compare clinical and histologic information from individuals affected by hypohidrotic ectodermal dysplasia (HED) and unaffected control subjects and to assess the value of these data in the diagnosis of HED. DESIGN: Volunteer subjects attending the 20th Annual Family Conference of the National Foundation for Ectodermal Dysplasia answered a questionnaire and performed a starch-iodide sweat-function test. A subset of the subjects also donated samples of hair and 4-mm punch biopsy specimens of palmar and scalp skin. Specimens from each of these tests were assessed in a blinded fashion. Analysis was performed comparing affected and control subjects for each of the following parameters: quantification of eccrine structures in the skin biopsy specimens, analysis of hair sample trichograms for hair shaft defects, and qualitative classification of starch-iodide palm-print sweat-function test results. SETTING: An international conference for families and individuals with ectodermal dysplasias. SUBJECTS: A total of 40 subjects were included in the final analysis: 15 unaffected control subjects and 25 subjects with HED. Nine affected subjects and 9 unaffected subjects donated skin biopsy specimens. MAIN OUTCOME MEASURE: This study was designed to assess the value of 4 simple tests in supporting the diagnosis of HED. RESULTS: Investigators were blinded to group during analysis of the test samples. Trichogram examination identified 3 hair shaft abnormalities, with a slightly higher prevalence in the affected group: variable shaft thickness, trichorrhexis nodosa, and pili torti. The sensitivity and specificity for each of these findings was less than 40%. Starch-iodide paper palm imprints identified a higher likelihood of diminished or absent sweat in the affected group, but this test had a low sensitivity (44%) and an imperfect specificity (93%). Examination of horizontally sectioned skin biopsy specimens from the palm were devoid of eccrine structures in a minority of affected subjects (sensitivity, 30%; specificity, 100%). In contrast, scalp biopsy specimens lacked eccrine structures in the majority of affected subjects (sensitivity, 67%; specificity, 100%). Separate analysis excluding the subjects without apparent eccrine apparatus yielded comparable numbers of eccrine ducts from control and affected groups. CONCLUSIONS: We have defined the value of simple, easily performed tests in the morphological diagnosis of HED. Noninvasive trichogram and sweat testing results can support the diagnosis of HED, but they are not sensitive or highly specific; horizontally sectioned 4-mm punch biopsy specimens of the scalp or palms that lack eccrine structures are diagnostic of HED; scalp biopsy is much more sensitive than palmar biopsy; and a scalp biopsy specimen with detectable eccrine structures suggests that a patient does not have HED.

Biopsy↗
PubMed1996

Family with autosomal dominant hidrotic ectodermal dysplasia: a previously unrecognised syndrome?

We describe a three-generation family with an autosomal dominant hidrotic ectodermal dysplasia consisting mainly of tricho- and onychodysplasia. One of the patients had supraventricular tachycardia, another had palpitations, and two others had sinus brachycardia. We consider that the clinical manifestations in this family differ significantly from those of the Clouston syndrome (their previous diagnosis) and places them in Group A, subgroup 1-3 (tricho-onychic) of the ectodermal dysplasia classification proposed by Freire-Maia and Pinheiro [1988, "Ectodermal Dysplasias"].

Adolescent↗
PubMed1987

Variable expression in ankyloblepharon-ectodermal defects-cleft lip and palate syndrome.

The ankyloblepharon-ectodermal defects-cleft lip and palate (Hay-Wells) syndrome is a rare autosomal dominant form of congenital ectodermal dysplasia. It is characterized by coarse, wiry, sparse hair; dystrophic nails; slight hypohidrosis; scalp infections; ankyloblepharon filiforme adnatum; hypodontia; maxillary hypoplasia; and cleft lip and palate. To date, 12 patients have been reported; however, the diagnosis has been questioned in 3 of these patients. We report 2 additional patients, one of whom has nasal speech but not cleft palate, in contrast to all other reported patients. This entity must be distinguished from numerous other forms of ectodermal dysplasia, especially those forms that can be associated with oral clefts and/or ankyloblepharon.

Child↗