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A Abdelfattah

Publications and source records attributed to A Abdelfattah.

5 recordsLinked to original sources
PubMed2000

Cloning and expression of the Wnt antagonists Sfrp-2 and Frzb during chick development.

The Wnt genes are known to play fundamental roles during patterning and development of a number of embryonic structures. Receptors for Wnts are members of the Frizzled family of proteins containing a cysteine-rich domain (CRD) that binds the Wnt protein. Recently several secreted frizzled-related proteins (Sfrps) that also contain a CRD have been identified and some of these can both bind and antagonise Wnt proteins. In this paper we report the expression patterns of the chick homologues of Frzb, a known Wnt antagonist, and Sfrp-2. Both genes are expressed in areas where Wnts are known to play a role in development, including the neural tube, myotome, cartilage, and sites of epithelial-mesenchymal interactions. Initially, Sfrp-2 and Frzb are expressed in overlapping areas in the neural plate and neural tube, whereas later, they have distinct patterns. In particular Sfrp-2 is associated with myogenesis while Frzb is associated with chondrogenesis, suggesting that they play different roles during development. Finally, we have used the early Xenopus embryo as an in vivo assay to show that Sfrp-2, like Frzb, is a Wnt antagonist. These results suggest that Sfrp-2 and Frzb may function in the developing embryo by modulating Wnt signalling.

Amino Acid Sequence↗
PubMed1999

Mechanisms of GDF-5 action during skeletal development.

Mutations in GDF-5, a member of the TGF-beta superfamily, result in the autosomal recessive syndromes brachypod (bp) in mice and Hunter-Thompson and Grebe-type chondrodysplasias in humans. These syndromes are all characterised by the shortening of the appendicular skeleton and loss or abnormal development of some joints. To investigate how GDF-5 controls skeletogenesis, we overexpressed GDF-5 during chick limb development using the retrovirus, RCASBP. This resulted in up to a 37.5% increase in length of the skeletal elements, which was predominantly due to an increase in the number of chondrocytes. By injecting virus at different stages of development, we show that GDF-5 can increase both the size of the early cartilage condensation and the later developing skeletal element. Using in vitro micromass cultures as a model system to study the early steps of chondrogenesis, we show that GDF-5 increases chondrogenesis in a dose-dependent manner. We did not detect changes in proliferation. However, cell suspension cultures showed that GDF-5 might act at these stages by increasing cell adhesion, a critical determinant of early chondrogenesis. In contrast, pulse labelling experiments of GDF-5-infected limbs showed that at later stages of skeletal development GDF-5 can increase proliferation of chondrocytes. Thus, here we show two mechanisms of how GDF-5 may control different stages of skeletogenesis. Finally, our data show that levels of GDF-5 expression/activity are important in controlling the size of skeletal elements and provides a possible explanation for the variation in the severity of skeletal defects resulting from mutations in GDF-5.

Amino Acid Sequence↗
PubMedDate not supplied

[Designation of symptoms in mental disorder].

In the author's opinion, language and clinical facts in psychiatry are misused and it is hypothesized that many malfunctions of psychiatric practise are symptomatic. It is indeed very hard to modelise mental illness: what terms should be chosen and how should they be articulated? Considering the complexity of the relationship between language, ideas and memory, an empirical and experimental approach has been chosen; working out structures of concepts isomorphic to psychiatric reality, either from observed phenomena or from words. In our view, language skills are sufficient to build these sophisticated models, and language skills can be trained as can be trained sensorimotor skills. Experimenting psychiatric language in using their encyclopedic knowledge will allow staff members to teach themselves and will have a heuristic value in changing their beliefs about reality. These experiments have been undertaken for a year and an half, in a general psychiatry ward, in a ward for retarded and autistic adults and in a rehabilitation ward. Rigour and perseverance are required but these experiments seem particularly promising.

Adult↗