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Biomedical subjects

A Rowe

Publications and source records attributed to A Rowe.

At least 55 records · Page 3Linked to original sources
PubMed1992

Development of the spatial pattern of retinoic acid receptor-beta transcripts in embryonic chick facial primordia.

Retinoic acid causes a range of embryonic defects, including craniofacial abnormalities, in both birds and mammals and is believed to have a number of roles in normal development. We have previously shown that the distribution of retinoic acid receptor-beta (RAR-beta) transcripts is spatially restricted within the neural-crest-derived upper beak primordia of the chick embryo. We have now used in situ hybridisation to trace the distribution of RAR-beta transcripts during the migration of cranial neural crest cells and during formation of these primordia. RAR-beta transcripts were present in a subset of migrating neural-crest-derived cells in the head of the stage 10 embryo. These cells were situated in pathways followed by cells that migrate from the neural crest overlying the posterior prosencephalic/anterior mesencephalic region of the developing brain. Cells containing RAR-beta transcripts accumulated around the developing eyes and in the regions of the ventral head from which the upper beak primordia later develop. We mapped the distribution of RAR-beta transcripts as the facial primordia were forming, with particular reference to the development of the maxillary primordia. We found that these form in a region of the ventral head that includes the boundary between regions of high and low levels of RAR-beta transcripts. The boundary between these two groups of cells persisted as the maxillary primordia developed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

A member of the chicken RXR family of nuclear receptors activates transcription in response to retinoic acid.

The chicken cRXR nuclear receptor is a member of the steroid/thyroid hormone receptor superfamily. In this paper we show that cRXR can transactivate gene expression in response to retinoic acid, but that its sensitivity to retinoic acid is lower than that of the hRAR-beta receptor. We have also compared the ability of cRXR and hRAR-beta to respond to a panel of other retinoids. Unlike hRAR-beta, cRXR failed to respond to the naturally occurring retinoid 3,4-didehydro-retinoic acid or to the synthetic retinoid TTNPB, both of which share the ability of retinoic acid to induce digit duplications when locally applied to chick limb buds.

Animals↗
PubMed1991

A member of the RXR nuclear receptor family is expressed in neural-crest-derived cells of the developing chick peripheral nervous system.

Retinoic acid (RA) affects differentiation and morphogenesis in various developmental systems and is believed to act through nuclear RA receptors that belong to the steroid/thyroid hormone family of ligand-binding transcription factors. Three closely related receptors, RAR-alpha, -beta and -gamma, with distinct expression patterns, have been identified and a fourth receptor, hRXR-alpha, which responds to RA but which has low homology to RAR-alpha, -beta and -gamma, was recently discovered. Here we report the isolation of a cDNA clone encoding a chicken homologue of hRXR-alpha (cRXR) and show that a cRXR transcript of 2.5 kb is expressed in a range of embryonic chick tissues. By in situ hybridization to sections from stage 24 and stage 27 chick embryos, we show that cRXR transcripts are expressed at high levels in the liver and in elements of the developing peripheral nervous system derived from the neural crest, including dorsal root ganglia, cranial ganglia, enteric ganglia and peripheral nerve tracts. At stage 16, in the posterior trunk region, cRXR transcripts are expressed by cells in the neural crest and in neural crest cells migrating into the sclerotome, indicating that neural crest cells express cRXR transcripts before overt differentiation into peripheral nervous tissue. This distribution suggests a novel role for RA in the developing peripheral nervous system, mediated by cRXR. In addition, it identifies cRXR as a marker for a specific population of neural-crest-derived cells.

Amino Acid Sequence↗
PubMed1991

Retinoic acid treatment alters the distribution of retinoic acid receptor-beta transcripts in the embryonic chick face.

Retinoic acid is a metabolite of vitamin A that can act as a signalling molecule in a number of developmental systems. Retinoic acid is also known to be teratogenic in mammals, causing a range of defects including abnormalities in craniofacial development. Exposure of the developing chick face to retinoic acid released slowly from a bead implanted in the wing bud results in a specific facial defect, in which outgrowth of the frontonasal mass is inhibited. This results in clefting of the primary palate and absence of the upper beak. To investigate the role of nuclear retinoic acid receptors in normal and abnormal chick face morphogenesis, we isolated chick retinoic acid receptor-beta (RAR-beta) cDNA clones and probed northern blots of RNA isolated from chick embryos at stages 22, 24 and 25 and from adults. RAR-beta transcripts of 2.8 and 3.5 kb were present in several regions of the embryo, including the facial primordia, and were also present at much lower levels in adult tissues. In situ hybridisation showed that RAR-beta transcripts were present in all of the facial primordia at embryonic stages 20, 24 and 28, but that their distribution was not uniform. Transcripts were abundant in the lateral nasal processes, at the edges and corners of the frontonasal mass and in the anterior part of the maxillary primordia. Lower levels were present elsewhere. Treatment of stage 20 embryos with retinoic acid altered the distribution of RAR-beta transcripts in the maxillary primordia, such that high levels of transcripts were present throughout, rather than being confined to the anterior part. This change was detectable at stage 24, before any alterations in the morphology of the facial primordia were apparent. By stage 28, when the morphology of the facial primordia was clearly abnormal, there were more widespread changes in the distribution of RAR-beta transcripts. These results show that RAR-beta transcripts are particularly concentrated in regions of the primordia that give rise to the upper beak, the development of which is specifically affected by retinoic acid. In addition, they demonstrate that retinoic acid can induce changes in the pattern of expression of RAR-beta transcripts in vivo.

Amino Acid Sequence↗
PubMed1991

Is 'evaluation' a dirty word?

How do we measure the important aspects of preventive health care? - what the users of the service value and what we know from experience is working. Pippa Mackeith and Ann Rowe's work at 45 Cope Street, a centre for young mothers, suggests that evaluation can be both acceptable and useful to clients, workers, managers and taxpayers.

Community Health Nursing↗
PubMed1989

Ectodermal inhibition of cartilage differentiation in micromass culture of chick limb bud mesenchyme in relation to gene expression and cell shape.

Ectoderm inhibits the formation of cartilage by chick wing bud mesenchyme in micromass culture. This suggests that the pattern of cartilage formation in the limb bud may result from a restriction of cartilage cell differentiation to the limb bud core as cells leave the progress zone. We have used in situ hybridization to investigate whether ectodermal inhibition in micromass culture occurs at the level of gene transcription. We found that ectoderm completely inhibited the accumulation of cartilage-specific type II collagen transcripts in the mesenchyme cells, whilst the level of type I collagen transcripts was unaffected. Morphometric analysis of electron micrographs revealed that inhibition of chondrogenesis in micromass culture was not preceded by cell flattening. In fact, a rounded cell shape was found not to be a prerequisite for cartilage cell differentiation in micromass.

Animals↗
PubMed1975

Composition, quaternary structure, and catalytic properties of D-ribulose-1, 5-bisphosphate carboxylase from Euglena gracilis.

D-Ribulose-1,5-bisphosphate carboxylase has been purified in one step by sedimenting extracts of autotrophically-grown Euglena gracilis into a linear 0.2-0.8 M sucrose density gradient. The resultant product was pure by the criteria of disc electrophoresis in gels polymerized from 5 or 7.5% acrylamide and sedimentation. The molecular weight of the enzyme estimated by density gradient centrifugation and electrophoresis in gels polymerized from various concentrations of acrylamide was 5.25 X 10(5). The S20,W was 16.4 S. Dissociation and polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate established that the enzyme was composed of two types of subunits (mr 50,000 and 15,000). The oligomeric structure was visualized through negative staining and transmission electron microscopy leading to a model for the quaternary structure. Although the enzyme was moderately unstable, the estimated maximal specific activity was 1.6 mumol CO2 fixed min-1 mg protien-1 at 30 degrees C and pH 8.0 Km values were 2.2 m M, 15. 1 MUM and 0.63 mM for Mg2+, ribulose 1,5-bisphosphate, and CO2, respectively, when measured under air. 6-Phospho-D-gluconate was a noncompetitive inhibitor with respect to ribulose 1,5-bisphosphate (Ki = 0.04 mM). Oxygen was a competitive inhibitor with respect to CO2 suggesting that the enzyme was also an oxygenase. The latter was confirmed by experiments showing a molar equivalence between ribulose-1,5-bisphosphate-dependent oxygen consumption and phosphoglycerate production.

Amino Acids↗