Ovules play a central role in plant reproduction, generating the female gametophyte within sporophytic integuments.When fertilized, the integuments differentiate into the seed coat and support the development of the embryo and endosperm. Mutations in the AlNTEGUMENTA (ANT) locus of Arabidopsis have a profound effect on ovule development. Strong ant mutants have ovules that fail to form integuments or a female gametophyte. Flower development is also altered, with a random reduction of organs in the outer three whorls. In addition, organs present in the outer three floral whorls often have abnormal morphology. Ovules from a weak ant mutant contain both inner and outer integuments but generally fail to produce a functional female gametophyte. We isolated the A N T gene by using a mutation derived by T-DNA insertional mutagenesis. A N T is a member of a gene family that includes the floral homeotic gene APETALA2 (AP2). Like AP2, ANT contains two AP2 domains homologous with the DNA binding domain of ethylene response element binding proteins. A N T is expressed most highly in developing flowers but is also expressed in vegetative tissue.Taken together, these results suggest that ANT is a transcription factor that plays a critical role in regulating ovule and female gametophyte development. I NTRODU CTI ONA unique element of plant reproduction is the alternation of generations between a diploid sporophyte and a haploid gametophyte. Ovules are fundamentally involved in this aspect of the plant life cycle due to their role in generating the female gametophyte or embryo sac. Ovule development has been proposed to occur in four distinct phases . The first phase involves the initiation of the ovule primordia from the carpel placenta. During the second phase, the specification of ovule identity occurs. This is followed by the formation of spatially defined pattern elements within the developing ovule in the third phase. The final phase involves morphogenesis to form the mature ovule. In angiosperms, morphogenesis results in ovules that consist of a nucellus enclosed by one or two integuments and a supporting stalk, the funicuIus, which attachcs the ovule to the placenta (Bouman, 1984;Reiser and Fischer, 1993). The megasporocyte is produced within the nucellus and undergoes meiosis to produce four megaspores (megasporogenesis). A single surviving megaspore will undergo megagametogenesis to produce the female gametophyte (Willemse and Van Went, 1984;Mansfield et al., 1990;Reiser and Fischer, 1993).Little is known about the molecular basis of ovule development. Recently, severa1 laboratories have taken a genetic To whom correspondence should be addressed approach to understand the genetic circuitry used in the developing ovule and to identify potential communication between the diploid ovule and the haploid female gametophyte. A number of sporophytic mutants have been identified in Arabidopsis that specifically affect the ovule and/or the female gametophyte. In belll (bell) plants, ovules lack an inner integument, the outer in...

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Many different techniques for stenting bifurcation lesions are based on lesion locations, angiographic appearances, and types. Rigorous geometrical models have not been developed to give consistent descriptions. This study presents a rigorous geometrical analysis of vessel bifurcations to understand problems associated with tubular stents in order to help optimize stent placements. A 2-D bifurcating geometrical model of the side branch vessel (SB) angulations to the main vessel (MV) was analyzed and examined: (a) side branch exposed stent length (SBExpSt), (b) the side branch horizontal distance of the stent overhang (SBStOvH) into the MV, (c) side branch longitudinal axis of the ostial opening (SBLongOp), (d) the "saddle gap" at the ostium of branch to the wall of the MV. Formulas for SBExpStent, SBStOvH, SBLongOp, and saddle gap were derived. Results showed a curvilinear relation between the SBExpStent, the SBStOvH, and the SBLongOp to the SB angulations (θ). The relationship between saddle gap and the MV diameter also appears to be curvilinear. From the graphs, an acceptable ostial branch vessel stent coverage occurs between 70 • and 90 • ; for a 3 mm diameter SB at 70 • , the SBExpStent = 1.1 mm, SBStOvH = 1.03 mm, and SBLongOp = 3.05 mm were calculated. From the geometrical analysis, SB angulation should be considered before the stents are placed at bifurcating vessels, regardless of the different methods or types of vessels. Stent protrusion and/or incomplete coverage should be calculated at the bifurcating areas, especially at SB angulations <70 • .