PubMed Health⌕ Search

Biomedical subjects

P H Francis

Publications and source records attributed to P H Francis.

5 recordsLinked to original sources
PubMed1994

Bone morphogenetic proteins and a signalling pathway that controls patterning in the developing chick limb.

We show here that bone morphogenetic protein 2 (BMP-2) is involved in patterning the developing chick limb. During early stages of limb development, mesenchymal expression of the Bmp-2 gene is restricted to the posterior part of the bud, in a domain that colocalizes with the polarizing region. The polarizing region is a group of cells at the posterior margin of the limb bud that can respecify the anteroposterior axis of the limb when grafted anteriorly and can activate expression of genes of the HoxD complex. We dissect possible roles of BMP-2 in the polarizing region signalling pathway by manipulating the developing wing bud. Retinoic acid application, which mimics the effects of polarizing region grafts, activates Bmp-2 gene expression in anterior cells. This shows that changes in anteroposterior pattern are correlated with changes in Bmp-2 expression. When polarizing region grafts are placed at the anterior margin of the wing bud, the grafts continue to express the Bmp-2 gene and also activate Bmp-2 expression in the adjacent anterior host mesenchyme. These data suggest that BMP-2 is part of the response pathway to the polarizing signal, rather than being the signal itself. In support of this, BMP-2 protein does not appear to have any detectable polarizing activity when applied to the wing bud. The pattern of Bmp-4 gene expression in the developing wing bud raises the possibility that BMP-2 and BMP-4 could act in concert. There is a close relationship, both temporal and spatial, between the activation of the Bmp-2 and Hoxd-13 genes in response to retinoic acid and polarizing region grafts, suggesting that expression of the two genes might be linked.

Amino Acid Sequence↗
PubMed1986

Structurally related Bacillus thuringiensis delta-endotoxins display major differences in insecticidal activity in vivo and in vitro.

Many strains within the 22 serotypes of Bacillus thuringiensis produce crystal delta-endotoxins with slight differences in their insecticidal toxicity spectrum in vivo. Since the basis of this specificity is unknown, we chose to compare the activity of delta-endotoxins from three strains: B. thuringiensis var. kurstaki HD-1, var. aizawai HD-249 and var. thuringiensis HD-350, both in vivo and on insect cell lines in vitro. Immunoblotting with antisera to activated var. kurstaki P1 lepidopteran toxin revealed antigenic cross-reaction with the 130 X 10(3) Mr toxin of var. aizawai, and with polypeptides of 130 and 138 (X 10(3)) Mr from var. thuringiensis. In addition, crystals from var. kurstaki and var. aizawai contained an antigenically related 63 X 10(3) Mr protein that did not cross-react with antisera to the 130 X 10(3) Mr component. Bioassays on Pieris brassicae larvae (Lepidoptera) and Aedes aegypti larvae (Diptera) indicated that the 130 X 10(3) Mr protein of var. kurstaki, and the 138 plus 130 X 10(3) Mr components of var. thuringiensis killed only P. brassicae, while the 130 X 10(3) Mr protein of var. aizawai and the 63 X 10(3) Mr proteins of var. aizawai and var. kurstaki were toxic to both P. brassicae and A. aegypti. Activation of the 130 and 138 (X 10(3)) Mr proteins of the three varieties of B. thuringiensis with insect gut proteases yielded active products of 50-60 (X 10(3)) Mr. Assay of these products on a range of lepidopteran and dipteran cell lines revealed very different toxicity spectra: var. kurstaki killed only one lepidopteran line, var. thuringiensis killed two lepidopteran lines, while var. aizawai was cytolytic to all of the lepidopteran and most of the dipteran cell lines tested, reflecting its broader spectrum in vivo. Thus we have shown that antigenic cross-reaction of B. thuringiensis delta-endotoxins does not necessarily imply a similar toxicity spectrum in vivo or in vitro.

Bacillus thuringiensis↗