Modeling the contraction of the pelvic floor muscles

We performed numerical simulation of voluntary contraction of the pelvic floor muscles to evaluate the resulting displacements of the organs and muscles. Structures were segmented in Magnetic Resonance (MR) images. Different material properties and constitutive models were attributed. The Finite Element Method was applied, and displacements were compared with dynamic MRI findings. Numerical simulation showed muscle magnitude displacement ranging from 0 to 7.9 mm, more evident in the posterior area. Accordingly, the anorectum moved more than the uterus and bladder. Dynamic MRI showed less 0.2 mm and 4.1 mm muscle dislocation in the anterior and cranial directions, respectively. Applications of this model include evaluating muscle impairment, subject-specific mesh implant planning, or effectiveness of rehabilitation.     

Rapid multiplication of Sapium sebiferum Roxb. by tissue culture

Multiple shoots formation and elongation was induced from stem explants of Sapium seedlings on media containing cytokinins. Leaf explants produced callus on a medium containing cytokinins, auxin, casein hydrolysate and coconut milk, which could be induced to form multiple shoots on transfer to a medium lacking casein hydrolysate, coconut milk and auxin. Rooting of isolated shoots by treatment with an auxin mixture (indole-3-acetic acid, indole-3-butyric acid and indole-3-propionic acid) and transfer of the plantlets to field have also been successful.     

The biochemistry of angiosperm pollen development

Recent work concerning the regulation of pollen and pollen tube development at the biochemical level in angiosperms has been reviewed, commencing with the microspore immediately after meiosis and terminating with the entry of the pollen tube into the embryo sac. Some of the topics that have been considered are, (1) the role of the tapetum in pollen development, (2) gene activity in the microspore and pollen grain prior to anthesis, (3) DNA synthesis in the microspore and pollen tube, (4) the types of RNA and protein synthesized in the pollen tube including the biochemistry of the vegetative and generative nuclei and finally, (5) the interactions between pollen and pistil after pollination.     

Genes expressed in the male gametophyte of flowering plants and their isolation

Recombinant cDNA libraries to poly(A)RNA isolated from mature pollen of Zea mays and Tradescantia paludosa have been constructed. Northern blot analyses indicate that several of the clones are unique to pollen and are not expressed in vegetative tissues. The majority, however, are expressed both in pollen and vegetative tissues. Southern hybridizations show that the pollen specific sequences in corn are present in one or a very few copies in the genome. By using several of the clones as probes, it was found that there are at least two different groups of mRNAs with respect to their synthesis. The mRNAs of the first group represented by the pollen specific clones are synthesized after microspore mitosis and increase in concentration up to maturity. The second group, exemplified by actin mRNA, begins to accumulate soon after meiosis, reaches its maximum by late pollen interphase, and decreases thereafter. Although the actin mRNA and the pollen specific mRNAs studied show very different patterns of initiation of synthesis and accumulation during pollen development, the rates of decline of these mRNAs during the first 60 minutes of germination and pollen tube growth in Tradescantia are similar and reflect the previously observed declines in rates of protein synthesis during this period.     

The distribution of ionic calcium in the tissues of the gynoecium ofAntirrhinum majus

Summary The distribution of ionic calcium in the tissues of the gynoecium ofAntirrhinum majus flowers has been studied using the glyoxal bis (2-hydroxy-anil) staining procedure.The highest concentration of ionic calcium is found in the cells of the placenta and the cells lining the inner ovary wall. The cells of the ovule are comparatively low in calcium, and there is no higher concentration of calcium in the region of the micropyle and embryo sac. The cells of the stigma contain less calcium than those of the placenta, but almost the same as the cells of the ovule. The stigmatoid tissue and surrounding parenchyma in the style contain a low amount of calcium, lower than that found in the ovule and stigma. The relevance of these data to the growth and chemotropism of pollen tubes is discussed.This study was made possible by a grant from the Brown-Hazen Fund of Research Corporation and by Grant GB 3243 from the National Science Foundation. The technical assistance of Miss Annabelle M. Birrow is gratefully acknowledged.     

Optimization of conditions for in situ hybridization and determination of the relative number of ribosomes in the cells of the mature embryo sac of maize

Summary We have initiated experiments to understand the molecular regulation of embryo sac development in flowering plants by a study of ribosome synthesis and accumulation. Because of the very small size of the embryo sac and the large volume of ovule tissue it is embedded in, in situ hybridization with nucleic acid probes is presently the only practical method for such molecular measurements on individual cells of the embryo sac. Methods of tissue preparation, sectioning and screening of ovules for embryo sac containing sections, in situ hybridization using a ribosomal mRNA probe, and staining were optimized. Relative densities of silver grains for individual cells of the mature maize (W22) embryo sac were determined from in situ hybridizations. The silver grain counts are directly related to the numbers of ribosomes. Volumes of individual cells were determined by confocal microscope image analysis, and this permitted the calculation of the relative total numbers of ribosomes in individual cells of the embryo sac and nucellus. The central cell has a volume 260 times that of a nucellar cell at the micropylar end of the ovule, 15 times that of the egg cell, 30 times that of a synergid, and 130 times the volume of an antipodal cell. The mature maize embryo sac has 20 or more antipodal cells. The central cell has approximately 200 times the number of ribosomes as are present in a nucellar cell, about 7 times as many ribosomes as are in the egg cell, 14 times as many ribosomes as in each synergid, and about 80 times the ribosome content of individual antipodal cells. The data are discussed with respect to the utilization of the ribosomes following fertilization in the early embryo and endosperm.     

Somatic embryogenesis and plants from zygotic embryos of coconut (Cocos nucifera L.) in vitro

Complete plants were grown from zygotic embryos cultured on Y3 basal liquid medium supplemented with coconut milk, BA and NAA. Explants from stem, leaf and rachilla of mature coconut trees turned green and swelled on Y3 semi-solid basal media supplemented with 2,4-D, K, NAA, BA and activated charcoal. Callus was initiated in explants from the subapical regions of the stem on Y3 basal medium supplemented with 2,4-D (4.52×10²M). Globular embryo-like structures were obtained when this callus was subcultured to auxinless medium. Root formation was obtained from leaf explants on Y3 basal medium containing citric acid, ascorbic acid and 2,4-D (4.52×10² M). Globular embryo-like structures were also obtained directly from leaf explants on a Y3 basal medium supplemented with 2,4-D (2.26×10² M). Callus isolated from rachilla explants on Y3 basal medium containing 2,4-D(4.52×10² M), formed nodular structures when transferred to medium with 2,4-D (2.3×10¹ M). These nodules developed roots from the base of the nodular growth whereas from the upper portion shoots were observed on Y3 basal liquid medium.Abbreviations K kinetin - BA Benzyl adenine - 2,4-D 2,4-Dichlorophenoxyacetic acid - NAA Naphthalene acetic acid - CM Coconut milk - IAA Indole acetic acid - 2iP N⁶-r-r-dimethyl allyl amino purine NCL Communication No. 3471