Biomedical subjects
K Harding
Publications and source records attributed to K Harding.
Spatial regulation of homeo box gene expression in Drosophila.
1. Each of the 17 known homeo box genes shows a unique pattern of expression during early embryonic development. Thus, virtually every embryonic cell contains a unique combination of active and inactive homeo box genes. 2. These different permutations of homeo box gene expression are thought to specify unique positional values, and appear to play key roles in selecting diverse pathways of morphogenesis. 3. It has been proposed that selective patterns of homeo box gene expression involve cross-regulatory interactions. For example, it appears that homeotic genes expressed in posterior regions of the embryo (such as abd-A and Abd-B) repress the expression of those homeotic genes expressed in more anterior regions (such as Antp and Ubx). Such interactions might involve sequence-specific DNA binding and occur at the level of transcription. 4. The establishment of selective patterns of pair-rule gene expression along the anterior-posterior embryonic body axis might involve the differential regulation of these genes by a common set of transcription factors. In particular, it appears that eve and ftz show opposite responses to regulatory products that are either directly or indirectly specified by several gap genes.
Cross-regulatory interactions among pair-rule genes in Drosophila.
The pair-rule genes of Drosophila are required for the subdivision of the developing embryo into a repeating series of homologous body segments. One of the pair-rule genes, even-skipped (eve), appears to be particularly important for the overall segmentation pattern since eve- embryos lack all segmental subdivisions in the middle body region. On the basis of homeo box cross-homology we have isolated a gene, S72, which probably corresponds to eve. In embryo tissue sections S72 transcripts show a periodic distribution pattern. The eve- phenotype appears to involve altered patterns of fushi tarazu and engrailed expression. These and other findings suggest that pair-rule gene expression might involve hierarchical cross-regulatory interactions.
Spatial regulation of Antennapedia and bithorax gene expression by the Polycomb locus in Drosophila.
Transcripts encoded by six of the homeotic lethal complementation groups within the Antennapedia and bithorax gene complexes (ANT-C and BX-C) accumulate primarily in nonoverlapping regions of the embryonic central nervous system (CNS). It has been previously proposed that the maintenance of these selective patterns of expression involve hierarchical cross-regulatory interactions among ANT-C and BX-C loci. Selective expression of the ANT-C and BX-C also involves regulation by a number of unlinked genetic loci, including the Polycomb (Pc) locus. Here we show that the ANT-C and BX-C transcript distribution patterns are dramatically altered in the CNS of Pc- embryos. We discuss these altered patterns of expression in the context of different models for the spatial regulation of ANT-C and BX-C gene expression.
Homeo box gene expression in anterior and posterior regions of the Drosophila embryo.
The homeo box is a 180-base-pair coding sequence that has been implicated in the control of Drosophila development. A common feature of the nine previously reported homeo box genes is their involvement in the establishment of the segmentation pattern of the embryo. In this report we describe the isolation and properties of two additional homeo box genes, F90-2 and S67. Transcripts encoded by the two genes are detected in embryonic tissues that derive from regions near the anterior and posterior poles of the embryo, which are outside the limits of expression of known homeotic genes. These results suggest that at least some homeo box genes specify positional identity along the anterior-posterior body axis that is independent of the process of segmentation.
Spatially regulated expression of homeotic genes in Drosophila.
The sites of transcript accumulation for six different homeotic loci of the Antennapedia and bithorax gene complexes (ANT-C and BX-C) were identified within embryo tissue sections by in situ hybridization. These six loci belong to the Antennapedia class of the homeo box gene family. Transcripts encoded by each locus are detected primarily in discrete, nonoverlapping regions of the embryonic central nervous system (CNS). The regions of the CNS that contain transcripts encoded by each of these loci correspond to the embryonic segments that are disrupted in mutants for these genes. The maintenance of spatially restricted expression of each ANT-C and BX-C locus could involve hierarchical, cross-regulatory interactions that are mediated by the homeo box protein domains encoded by these genes.
Homeo box genes of the Antennapedia and bithorax complexes of Drosophila.
The Antennapedia, Ultrabithorax, and fushi tarazu genes of Drosophila melanogaster each contain a very similar protein coding sequence, the homeo box. Previously cloned homeo box sequences were used to isolate additional well conserved members of the homeo box gene family. The most strongly conserved members of the homeo box gene family map within either the Antennapedia or Bithorax gene complexes. The tissue distribution of transcripts encoded by the two rightmost homeo box genes of the Bithorax complex are compared with the iab-2 and iab-7 phenotypes.
Expression of the homeo box gene family in Drosophila.
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Silastic foam elastomer for treating open granulating wounds.
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The early--late onset distinction in DSM-III-R dysthymia.
DSM-III-R recently introduced early-late and primary-secondary subtypes of dysthymia. The present study explored the validity of the DSM-III-R early-late onset distinction by comparing early- and late-onset primary dysthymics on demographic, clinical and familial variables and short-term outcome. Compared to the late-onset dysthymics, the early-onset group had higher lifetime rates of superimposed major depressive episodes and anxiety disorders, had sought treatment significantly more frequently, had a higher rate of major affective disorders in first-degree relatives, and exhibited higher levels of depression throughout the course of a 6-month follow-up study. These data provide preliminary support for the validity of the DSM-III-R early-late onset distinction in dysthymia.
Transcripts encoded by a homoeo box gene are restricted to dorsal tissues of Drosophila embryos.
In Drosophila elaboration of positional identity along the anterior-posterior and dorsal-ventral embryonic body axes involves early zygotic gene functions that are expressed in response to maternal cues present in the unfertilized egg. Zygotic loci that are required for the specification of positional identity along the anterior-posterior body axis have been described in detail. Less is known about the zygotic loci responsible for differentiation of the dorsal-ventral pattern; however, several genes that might be involved have been identified. Zerknüllt (zen) is an example of a zygotic gene required for correct differentiation of dorsally derived embryonic tissues. On the basis of homoeo box cross homology, we have now isolated a gene, called S60, that derives from the zen region of the Antennapedia complex (ANT-C). Transcripts encoded by S60 transiently accumulate in the dorsal-most tissues of developing embryos. This pattern of expression suggests that S60 corresponds to zen. Since S60 contains a homoeo box, it is possible that differentiation of the anterior-posterior and dorsal-ventral embryonic patterns involves similar molecular mechanisms.
Journal of wound care nursing. Reach for the sky.
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New vistas in wound care. Interview by Charlotte Alderman.
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Stroke patients. A model of support.
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Accident and emergency. Dressing down the discomfort.
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