Journal of craniofacial genetics and developmental biology. Supplement最新文献

The palatal shelf medial edges of day 8 (Hamburger-Hamilton [HH] stages 32-33) and day 9 (HH stage 35) embryonic chicks were surgically disrupted in ovo and in vitro in an attempt to discover if the naturally cleft chick palate could be induced to fuse experimentally. At HH stages 32-33 (day 8) the chick palatal shelves were apart at the time of in ovo operation. Consequently, their medial edges did not fuse but rather underwent embryonic would healing with re-epithelialisation (which often formed needle track invaginations), but no signs of inflammation or scar or scab tissue formation. Conversely, at HH stage 35 (day 9) the palatal shelves are in contact at the time of in ovo operation and so underwent fusion. The extent of palatal fusion depended upon the extent of initial medial edge epithelial disruption. Fusion did not spread from the operated sites to adjacent unoperated areas, where the palatal shelves were in contact with each other. Occasional epithelial seams were formed, but these persisted and did not undergo cell death. There was no evidence of inflammation or scar or scab tissue at the operated sites. Abnormal bony and muscular blastemae appeared in the continuity zones of these experimentally intact chick palates. Mortality was high for embryos operated upon in ovo. Palatal shelves explanted from HH stages 32, 33, and 35 chick embryos and cultured in vitro with their medial edges in contact did not fuse unless their medial edge epithelia were surgically disrupted, in which cases fusion always occurred regardless of the stage of the explanted shelves.(ABSTRACT TRUNCATED AT 250 WORDS)

Some general principles of syndromic growth and development useful for cephalometric studies are set forth under the headings of bone age determination, limitations of radiographic assessment in syndromic dysmorphism, dysharmonic maturation and patterned dysmorphism, primary growth deficiency of prenatal onset, asymmetric dysmorphism, problems in diagnostic homogeneity, and problems in ascertainment bias.

There is increasing evidence that hemifacial microsomia (HFM), Goldenhar syndrome (GS), and oculoauriculovertebral dysplasia (OAV) are part of a spectrum within a single entity. In support of this thesis are the family studies that have suggested that isolated microtia (M) may represent the mildest form of the condition [Kaye et al, 1979; Rollnick and Kaye, 1983]. Vertebral malformations are pathognomonic of OAV, but they have also been described in HFM and GS. In this investigation we studied the frequency and type of cervical spine malformations in HFM, GS, OAV, and M. Our findings show that the frequency of cervical spine malformations in HFM and M was greater than values for a normal population. This further supports the probable association between HFM, GS, OAV, and M. Fusions were the most prevalent cervical spine malformation encountered. The study also included analysis of the cranial base and craniovertebral junction.

The core problem in craniofacial development is regional specification of cell-specific gene expression. Regional specification is also referred to as pattern formation or spatial organization. During early embryogenesis, regional specification is possibly operant following blastula, and is apparent during gastrulation and thereafter during embryonic and fetal stages of development. Current interdisciplinary approaches toward understanding embryonic development incorporate a number of scientific approaches including those of recombinant DNA technology. Three major advances have significantly enhanced the utility of so-called "genetic engineering," including the discovery of restriction nuclease enzymes that cleave DNA sequences at specific sites; the discovery of DNA ligase enzymes that facilitate ligation and annealing of DNA sequences to one another, so as to facilitate the joining of foreign DNA sequences with host DNA; and the discovery of effective techniques for the introduction of foreign DNA sequences into previously refractory organisms. The present discussion analyzes the problem of regional specification of ameloblast-specific gene expression as a paradigm for utilizing recombinant DNA technology in studies of normal and abnormal craniofacial development.

The complex rotation process of the mandible during growth is elucidated by longitudinal roentgencephalometric analyses, using metallic implants as fixed references. Contrasting development of face and mandibular shape is described in three subjects. In the so-called long face syndrome, development is characterized by increasing inclination of the mandible during growth with only moderate remodeling. In the subjects with juvenile rheumatoid polyarthritis and mandibulofacial dysostosis, the increase in mandibular inclination is moderate. However, the mandibular corpus rotates backward to an extreme extent within the more stable soft tissue matrix, giving rise to the characteristic development of angular notching with an extended angular process at the lower border.

Agent Orange (AO), a phenoxyherbicide, and dioxin, an impurity found in AO, are considered clastogens, mutagens, and teratogens in plants and animals. AO has come under suspicion in humans following claims that it causes chromosome damage and birth defects in offspring of exposed individuals. No well-designed epidemiological studies are available to support this conclusion. Of ten exposed individuals studied for chromosome breaks and sister chromatid exchange frequencies, eight were ascertained because they had children with congenital defects. No consistent pattern of anomalies was observed. Five children had neurologic deficit, one child had a central nervous system anomaly, and one child was affected with glaucoma. Although all individuals studied had normal karyotypes, a statistically significant increase in chromosome breakage was observed in exposed males compared to their unexposed wives and children; sister chromatid exchange frequency was not increased.

Agnathia-holoprosencephaly (A-H) is a developmental field complex involving a graded series of defects in the jaws, mouth, tongue, ears, eyes, and brain. Two general groups can be recognized: agnathia with holoprosencephaly (more severe) and agnathia without holoprosencephaly (less severe). This report describes three new cases of agnathia without holoprosencephaly and reviews the recent literature. By combining published cases with those ascertained through a survey of genetic centers in the United States, it appears that there have been at least 24 occurrences of A-H in the past 25 years. An inductive defect of the prechordal mesoderm that also affects neural crest cells is presented as the cause for this developmental field complex. Because of the etiologic heterogeneity associated with developmental field defects, the genetic counselor must provide a wide range of recurrence risks when dealing with the A-H complex.