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At least 19 recordsLinked to original sources
PubMedDate not supplied

Embryonic development of the head and neck: part 2, the branchial region.

The embryology of the branchial (pharyngeal) region is reviewed in terms of the embryonic pharynx, branchial apparatus and derivatives, tongue, larynx, and trachea. Derivatives of the branchial pouches, grooves (clefts), and arches are analyzed in relation to each other and to the first arch syndrome. Other common head and neck defects attributable to abnormal development of the branchial region are also discussed, particularly those defects involving the incomplete degeneration or the abnormal migration of branchial tissues.

Branchial Region↗
PubMedDate not supplied

Retinoic acid alters hindbrain Hox code and induces transformation of rhombomeres 2/3 into a 4/5 identity.

It has been suggested that Hox genes play an important part in the patterning of limbs, vertebrae and craniofacial structures by providing an ordered molecular system of positional values, termed the Hox code. Little is known about the nature of the signals that govern the establishment and regulation of Hox genes, but retinoic acid can affect the expression of these genes in cell lines and in embryonic tissues. On the basis of experimental and clinical evidence, the hindbrain and branchial region of the head are particularly sensitive to the effects of retinoic acid but the phenotypes are complex and hard to interpret, and how and if they relate to Hox expression has not been clear. Here we follow the changes induced by retinoic acid to hindbrain segmentation and the branchial arches using transgenic mice which contain lacZ reporter genes that reveal the endogenous segment-restricted expression of the Hox-B1 (Hox-2.9), Hox-B2(Hox-2.8) and Krox-20 genes. Our results show that these genes rapidly respond to exposure to retinoic acid at preheadfold stages and undergo a progressive series of changes in segmental expression that are associated with specific phenotypes in hindbrain of first branchial arch. Together the molecular and anatomical alterations indicate that retinoic acid has induced changes in the hindbrain Hox code which result in the homeotic transformation of rhombomeres (r) 2/3 to an r4/5 identity. A main feature of this rhombomeric phenotype is that the trigeminal motor nerve is transformed to a facial identity. Furthermore, in support of this change in rhombomeric identity, neural crest cells derived from r2/3 also express posterior Hox markers suggesting that the retinoic acid-induced transformation extends to multiple components of the first branchial arch.

Animals↗
PubMed1992

Hox codes and positional specification in vertebrate embryonic axes.

We have compared the ways in which vertebrate Hox genes are used in the patterning of three distinct embryonic contexts, the branchial region, the somites, and the limb. We have identified common features of the three systems, but have suggested on the basis of their differences (in both embryological properties and use of Hox genes) that it is better to consider each as an independent system for regional specification. Nevertheless, there are sufficient common features to expect that exploitation of the distinct experimental advantages of each system will provide important insights to the mode of operation of the others.

Animals↗
PubMed1978

Thyroglobulin biosynthesis in a larval (ammocoete) and adult freshwater lamprey (Lampetra planeri Bl.).

1. The biosynthesis of 18-19S thyroglobulin has been studied in a larval and adult freshwater lamprey (Lampetra planeri Bl.). 2. In vivo and in vitro experiments have been performed by injecting into the coelomic cavity or by incubating branchial region labeled constituents of Tg of higher vertebrates (125I, [3H]leucine and various [3H]carbohydrates). 3. Larvae (ammocoetes) and adults incorporate all labels into thyroglobulin (18-19S Tg), containing a small proportion of labeled T3 and T4, as identified by paper chromatography, and very minute amounts of stable iodine. 4. In adults, the biosynthesis of 18-19S Tg proceeds much more rapidly and the labels are incorporated in higher percentage than in larvae. 5. The demonstration of the biosynthesis of the specific thyroid protein, 18-19S Tg, in larvae indicates that the biochemical mechanism of hormonogenesis is present in larval endostyle before the morphological differentiation of thyroid cells and follicles occurring during metamorphosis. 6. Some 18-19S Tg is apparently stored in the endostyle.

Aging↗
PubMed1976

Three-dimensional anatomy of the 8-day mouse concepts: a study by scanning electron microscopy.

The three-dimensional anatomy of the 8-day mouse concepts was studied by scanning electron microscopy aided by microdissection within the microscope specimen chamber. Attention was given to the relationship of the extra-embryonic membranes and their subtended compartments and particular emphasis was placed on the 'inverted' condition of the embryo at this stage of development. The main points brought forth in this study are: (1) the five basic brain segments are discernible on the basis of surface contour; (2) the cervical fold, extending from the ventrum of the metencephalon to the somatopleure, forms a partition which separates the branchial region from the rest of the amniotic space; (3) the procephalic membrane bifurcates in a vertical plane to form the splanchnopeure and somatopleure lateral to the forebrain, and it bifurcates horizontally to form the dorsal and ventral coverings of the pericardial coelom; (4) the anttrum of the pericardial-peritoneal canal opens into the lateral coelom posterior to the cervical fold; (5) the midgut of the embryo is delineated laterally by longitudinal grooves connecting the foregut and hindgut antra; (6) embryonic ectoderm in the neural-fold region is formed by a single layer of pseudostratified columnar cells; (7) the allantois is hollow near its base and the inner surface is formed by a discontinuous layer of squamous cells; (8) blood islands in the extra-embryonic mesoderm form a ring of bulges around the middle of the exocoel. Other structures such as the ectoplacental cavity, the ectoplacental cone and the parietal capsule are also described.

Animals↗
PubMed1976

[Biosynthesis of thyroglobulin in an adult lamprey, Lampetra planeri (Bloch)].

Thyroglobuline (Tg) biosynthesis has been studied in an adult fresh water lamprey Lampetra planeri (Bloch), by injection in coelomic cavity or by in vitro incorporation in follicles of branchial region of various radioactive labels: 125I-, 3H-leucine, 3H-mannose, 3H-galactose, N-acetyl mannosamine and 3H-N-acetylglucosamine. Labelling by all theses substances, present in Tg of mammals, proceeds efficiently in two hours. It has been demonstrated that the cyclostome studied synthetizes a 18 S iodinated glycoprotein analogous to Tg of higher vertebrates by its molecular size. It contains all the same hexose and N-acetyl derivatives of these in its sugar moiety and the same iodinated aminoacids. Purified 18 S Tg of the lamprey has been prepared; it is very poor in iodine (127I) and has a very low T3 and T4 content.

Acetylglucosamine↗
PubMed1978

[Transfer of behavior patterns through transplantation of systems of neuroanatomic structures in amphibian larvae. II. Xenoplastic transplantation of hind brain systems between Xenopus laevis (Daud.) as well as Hymenochirus boettgeri (Torn.) and Triturus vulgaris].

By replacing parts of the neural plate (prospective medulla oblongata) of Triturus vulgaris by neural ectoderm of Xenopus laevis larval chimaeras were obtained, which showed donorlike rhythmical movements of distinct parts of the visceral musculature according to the place of implantation. Especially the branchial region with its external gills showed rhythmical movements and is the special object of this investigation.

Amphibians↗
PubMed1992

Expression of Hox 2.1 protein in restricted populations of neural crest cells and pharyngeal ectoderm.

A polyclonal antibody, alpha Hox 2.1a, was used to localize Hox 2.1 protein in presumptive neural crest cells and nodose ganglion of 8.5-10.0 day p.c. mouse embryos. The following results were obtained: (1) The nodose placode, in its epithelial state, first expresses Hox 2.1 protein at 9.0 d.p.c. By 9.5 d.p.c. presumptive migrating neuroblasts between the nodose placode and ganglion primordium also express Hox 2.1 protein. (2) At 9.5 d.p.c., presumptive crest cells lateral to the cephalic cardinal vein and within pharyngeal arches 4 and 6 are immunoreactive for alpha Hox 2.1a. In the arch 6 region, positive cells extend medially to a mesenchymal cell population on the lateral aspect of the foregut wall. (3) At 10.0 d.p.c., Hox 2.1 protein expression in putative crest cells is restricted to the arch 6 cell population. A similar staining pattern is seen using alpha Hox 2.1a with chick embryos. Comparison with the chicken embryo suggests that the Hox 2.1 positive cells in the pharyngeal arch and those on the lateral aspect of the foregut in the mouse embryo correspond to the caudalmost subpopulation of the circumpharyngeal crest (Kuratani and Kirby: Am. J. Anat. 191:215-227, 1991; Anat. Rec. 234:263-280, 1992). These results are consistent with a role for Hox 2.1 in pattern formation in the caudalmost region of the vertebrate head.

Animals↗
PubMedDate not supplied

Is Far a Hox mutation?

The mouse First arch mutation, Far, causes a severe syndrome of craniofacial defects described previously. All of the known defects are derived from the anterior first arch, and to a very small extent, the dorsal second arch. Recently Far has been shown to be closely linked to Ulnaless on chromosome 2, and therefore in the vicinity of the Hox-4 gene cluster. This paper reports the results of several studies focused on the development origin of the most consistently expressed dominant effect caused by Far, an abnormal major bifurcation of the maxillary nerve. Nerve-stained whole-mount preparations of day 12 embryos showed that in Far mutants the maxillary nerve appears to have a central wedge missing from the normal single-stalked fan shape, and that the nerve defect in Far/Far and +/Far may be equally severe. The effect of retinoic acid on the development of the maxillary nerve was tested. Maternal treatment with 5 mg/kg retinoic acid on day 9 of gestation had no detectable effect on the maxillary nerve of +/Far embryos, and similar treatment with a teratogenic dosage (20 mg/kg) on day 8 or 9 produced no Far-like maxillary nerve defects in genetically normal embryos. The neural crest cells that give rise to nerves and mesenchyme of the first arch originate from specific rhombomeres, discrete segments of the developing head. The rhombomeres of 15 embryos at the 14-23 somite stages, of which 75% are expected to be +/Far or Far/Far, were examined. There was no detectable defect in segmentation or morphology of the rhombomeres compared with controls. The significance of ectopic cartilage in the palate of Far/Far mutants in relation to nerve bifurcation was explored. In histological studies, five out of six Far/Far day-15 fetuses had a rod of ectopic cartilage lateral to the posterior palate, running parallel to, and morphologically similar to, Meckel's cartilage, and lying between the two trunks of the abnormally bifurcated maxillary nerve. None of six +/Far day-15 fetuses examined had detectable ectopic cartilage in this region. We hypothesize that the maxillary nerve defects in Far mutants may be explained by the presence of an ectopic precartilaginous blastema that does not always further develop into detectable cartilage. The ectopic cartilage found in Far/Far resembles the epibranchial cartilage expressed in more posterior branchial arches and in the first arch of lower organisms, and therefore may represent an atavistic posteriorization of the anterior first arch in Far mutants.(ABSTRACT TRUNCATED AT 400 WORDS)

Abnormalities, Multiple↗
PubMed1975

Bilateral symmetrical maldevelopment of external and middle-ear cleft with pharyngeal and soft palate defects.

An unusual combination of first and second arch anomlies is presented. This has resulted in absent middle and external ears with gross naso- and oropharyngeal defects. A brief reference is made to the embryology of this region to explain the anatomical and functional defects. Vascular abnormality during the peri-gestational period is suggested as a possible cause and a conservative line of treatment has been followed with good result.

Audiometry↗
PubMed1977

Facial and visceral arch development in the mouse embryo: a study by scanning electron microscopy.

The morphogenesis of the face and visceral arch region were studied by scanning electron microscopy in 63 mouse embryos between 8 and 13 days post coitum. The developmental stages were determined by reference to Theiler's (1971) scheme for the categorization of the normal stages of development. After the cervical fold is formed (stage 12) the mandibular primordium appears (stage 13) followed by the primordia of arches II and III (stage 14 with arch IV forming last (stage 15). Arches II, III and IV regress in reverse order, with no evidence that a cervical sinus pouch is formed. Placodes of the sensory ganglia from cranial nerves 7, 9 and 10 are formed in the first, second and third visceral grooves respectively. Formation of the external auditory meatus and its surrounding tubercles were also observed. Morphogenesis of the upper face is dominated by the midsagittal grove, which extends into the stomatodeum; and by the medial nasal, lateral nasal and maxillary processes. The temporal changes in shape and the interrelationships of the structures mentioned are described in detail.

Animals↗
PubMed1976

Anomalies of the first branchial cleft.

Eleven cases of first branchial cleft duplication anomalies are classified into types I and II. Type I defects are associated with the first cleft and are duplication anomalies of the membranous external auditory canal. Type II defects are associated with the first cleft and first and second arches, and, as such, are associated with defects of the membranous external auditory canal and cartilaginous elements. Microscopical examination of tissue in type I anomalies shows a cyst lined by skin without adnexal structures and without cartilage. Type II anomalies usually contain all elements. Misdiagnosis, infection, and recurrences are common with these lesions. Clinically, they may drain through the neck and external auditory canal. Surgical excision must be complete or there will be recurrence. The facial nerve must be identified and protected during the excision.

Adolescent↗
PubMed1976

Carcinoma arising in a branchial cleft cyst.

A patient is presented who was found to have invasive squamous cell carcinoma arising in the epithelial lining of a lateral cervical cyst which had been present for more than 40 years. Radical neck dissection was performed, and metastases were found in a single cervical lymph node. A critical review of cases of branchiogenic carcinoma reported over the past quarter-century yielded no more than three others which meet the criteria for diagnosis of this entity established by Martin, Morfit, and Ehrlich in 1950.

Adult↗
PubMed1978

Genetic aspects of the BOR syndrome--branchial fistulas, ear pits, hearing loss, and renal anomalies.

A pedigree of branchio-oto-renal dysplasia (the BOR syndrome) is reported, including the documentation by serial audiometric studies of the onset and rapid progression of hearing loss in the twin sister of an affected child. The literature on this syndrome is analyzed to derive some figures for use in genetic counseling of such families. Branchio-oto-renal dysplasia is an autosomal dominant disorder in which affected individuals may have preauricular pits, lachrymal duct stenosis, hearing loss, branchial fistulas or cysts, structural defects of the outer, middle, and inner ear, and renal anomalies, which may range from mild hypoplasia to complete absence. Not all features of the syndrome are expressed in all carriers of the gene, but few carriers lack all the features, and the pits, branchial clefts, and hearing loss, are frequently expressed. Those offspring of affected persons who have pits or fistulas are likely (about 80%) to have hearing loss of varying degrees of severity. A minority of heterozygotes (about 7%) may have hearing loss without pits or fistulas. The risk of severe renal malformation is probably fairly low. Whether families that show dominant inheritance of pits, clefts, and deafness without renal anomalies represent variants of the BOR syndrome or a separate entity (the BO syndrome), is still not clear. At present, any individual with preauricular pits and branchial clefts deserves both otologic and renal investigation.

Abnormalities, Multiple↗
PubMed1992

Branchio-oto-renal syndrome: further delineation of an underdiagnosed syndrome.

We report on a woman who was diagnosed with branchio-oto-renal (BOR) syndrome after 2 pregnancies complicated by oligohydramnios due to renal hypoplasia and agenesis. Both babies died neonatally of pulmonary hypoplasia. Histopathology of the temporal bones of the second child showed marked immaturity of the middle ear cleft, ossicles, facial nerve and canal, and cochlear nerve. Maternal renal ultrasound study was normal although intravenous pyelography indicated renal hypoplasia. The frequency of BOR syndrome among cases of recurrent fetal renal hypoplasia/dysplasia or agenesis is unknown, and parental renal ultrasonography may not identify a heritable renal defect. Investigations should include a family history, and examination of relatives to look for preauricular pits, lacrimal duct stenosis, and branchial fistulae and/or cysts. Hearing studies and IVP may be indicated.

Abnormalities, Multiple↗
PubMed1992

Long-term evaluation of a child with the branchio-oculo-facial syndrome.

We report on the 12-year development of a child with branchio-oculo-facial syndrome who was initially referred at age 5 months. Of note is his normal intelligence, regular class placement, hypernasal speech, and continued growth along the third centile. The importance of serial observations of patients with rare genetic disorders is emphasized.

Abnormalities, Multiple↗