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Biomedical subjects

A Sessions

Publications and source records attributed to A Sessions.

11 recordsLinked to original sources
PubMed2001

Reversal of diastolic plateau in partial testicular torsion.

Testicular torsion is a urologic emergency. The ability of color and power Doppler sonography to diagnose partial testicular torsion definitively remains uncertain. We present a case in which color Doppler findings were indeterminate and the diagnosis of partial testicular torsion was made on the basis of spectral waveform analysis. The characteristic findings in the spectral waveform were asymmetry between the 2 testes, with a higher intratesticular resistance index on the affected side, and reversal of the diastolic plateau on the affected side.

Adolescent↗
PubMed2001

Differential expression of members of the annexin multigene family in Arabidopsis.

Although in most plant species no more than two annexin genes have been reported to date, seven annexin homologs have been identified in Arabidopsis, Annexin Arabidopsis 1-7 (AnnAt1--AnnAt7). This establishes that annexins can be a diverse, multigene protein family in a single plant species. Here we compare and analyze these seven annexin gene sequences and present the in situ RNA localization patterns of two of these genes, AnnAt1 and AnnAt2, during different stages of Arabidopsis development. Sequence analysis of AnnAt1--AnnAt7 reveals that they contain the characteristic four structural repeats including the more highly conserved 17-amino acid endonexin fold region found in vertebrate annexins. Alignment comparisons show that there are differences within the repeat regions that may have functional importance. To assess the relative level of expression in various tissues, reverse transcription-PCR was carried out using gene-specific primers for each of the Arabidopsis annexin genes. In addition, northern blot analysis using gene-specific probes indicates differences in AnnAt1 and AnnAt2 expression levels in different tissues. AnnAt1 is expressed in all tissues examined and is most abundant in stems, whereas AnnAt2 is expressed mainly in root tissue and to a lesser extent in stems and flowers. In situ RNA localization demonstrates that these two annexin genes display developmentally regulated tissue-specific and cell-specific expression patterns. These patterns are both distinct and overlapping. The developmental expression patterns for both annexins provide further support for the hypothesis that annexins are involved in the Golgi-mediated secretion of polysaccharides.

Amino Acid Sequence↗
PubMed2000

Cell-cell signaling and movement by the floral transcription factors LEAFY and APETALA1.

LEAFY (LFY) and APETALA1 (AP1) encode unrelated transcription factors that activate overlapping sets of homeotic genes in Arabidopsis flowers. Sector analysis and targeted expression in transgenic plants were used to study whether LFY and AP1 can participate in cell-cell signaling between and within different layers of the floral meristem. LFY signaled equally well from all layers and had substantial long-range action within layers. Nonautonomous action of LFY was accompanied by movement of the protein to adjacent cells, where it directly activated homeotic target genes. In contrast, AP1 had only limited nonautonomous effects, apparently mediated by downstream genes because activation of early target genes by AP1 was cell-autonomous.

Arabidopsis↗
PubMed1999

The Arabidopsis thaliana MERISTEM LAYER 1 promoter specifies epidermal expression in meristems and young primordia.

The Arabidopsis thaliana MERISTEM LAYER 1 (ATML1) gene is expressed in the epidermis of developing embryos and shoot meristems. To identify regulatory sequences necessary for epidermis-specific expression, three fusions of overlapping ATML1 genomic sequences to the GUS reporter gene were introduced into Arabidopsis plants. All fusion genes conferred epidermis-specific expression of both GUS mRNA and protein activity but varied in both the timing and relative levels of expression, suggesting partial redundancy of ATML1 regulatory elements. This study defines L1-specific regulatory sequences that are sufficient to direct foreign gene expression in a layer-specific manner.

Arabidopsis↗
PubMed1998

Patterning the floral meristem.

Flowers are reproductive structures unique to the angiosperms. Flowers, which develop from small mounds of cells called floral meristems, show a number of universal patterns such as the arrangement of organs of different type along the floral axis. However, other conserved patterns, such as floral asymmetry, are merely conserved within different subgroups. This review discusses the emerging picture of early operating developmental mechanisms, which pattern floral meristems along the radial and dorsiventral axes, and of later-acting ones, which pattern tissue differentiation within floral organs.

Body Patterning↗
PubMed1997

ETTIN patterns the Arabidopsis floral meristem and reproductive organs.

ettin (ett) mutations have pleiotropic effects on Arabidopsis flower development, causing increases in perianth organ number, decreases in stamen number and anther formation, and apical-basal patterning defects in the gynoecium. The ETTIN gene was cloned and encodes a protein with homology to DNA binding proteins which bind to auxin response elements. ETT transcript is expressed throughout stage 1 floral meristems and subsequently resolves to a complex pattern within petal, stamen and carpel primordia. The data suggest that ETT functions to impart regional identity in floral meristems that affects perianth organ number spacing, stamen formation, and regional differentiation in stamens and the gynoecium. During stage 5, ETT expression appears in a ring at the top of the floral meristem before morphological appearance of the gynoecium, consistent with the proposal that ETT is involved in prepatterning apical and basal boundaries in the gynoecium primordium. Double mutant analyses and expression studies show that although ETT transcriptional activation occurs independently of the meristem and organ identity genes LEAFY, APETELA1, APETELA2 and AGAMOUS, the functioning of these genes is necessary for ETT activity. Double mutant analyses also demonstrate that ETT functions independently of the 'b' class genes APETELA3 and PISTILLATA. Lastly, double mutant analyses suggest that ETT control of floral organ number acts independently of CLAVATA loci and redundantly with PERIANTHIA.

Amino Acid Sequence↗
PubMed1983

Differentiation-related differences in the plasma membrane phospholipid asymmetry of myogenic and fibrogenic cells.

We have determined the asymmetric distribution of two aminophospholipids phosphatidylethanolamine and phosphatidylserine in the plasma membrane of chick embryo fibroblast and myoblasts. Right-side-out membrane preparations were incubated with two different amidating reagents, trinitrobenzenesulfonate and isethionylacetimidate, under nonpenetrating conditions. Inside-out membranes were incubated with trinitrobenzenesulfonate. In fibroblasts, the similar plateau values suggested that 35% of the phosphatidylethanolamine and 20% of the phosphatidylserine is externally disposed. These values agree with previous measurements on fibroblast plasma membranes. In myoblasts, however, labelling plateaux were achieved which suggested that 65% of the phosphatidylethanolamine and 45% of the phosphatidylserine is externally disposed. This represents a 2-3-fold increase in potentially fusogenic lipids on the external leaflet of the plasma membrane. This unique distribution of aminophospholipids in myoblasts extends through the stage of development during which myoblasts become competent to fuse and form myotubes in culture. Two inferences may be drawn from these results. First, the external concentration of aminophospholipids in myoblasts is enriched significantly over that of fibroblasts or erythrocytes. This orientation may contribute to its fusion competence. Second, although large amounts of externally disposed aminophospholipid may be necessary for myoblast fusion, they do not confer fusion competence.

Agglutination↗