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41.
The sporophyte-gametophyte junction in Acaulon muticum is composed of the sporophyte foot, the surrounding gametophyte vaginula, and an intervening placental space. At an early stage of development the foot has a large basal cell, characterized by extensive wall ingrowths beginning at the lowermost tip of the basal cell and extending along its tangential walls. Sporophyte cells in contact with the basal cell develop ingrowths on their outer tangential walls and on radial walls in contact with the basal cell. All sporophyte cells at this stage are characterized by numerous mitochondria, strands of endoplasmic reticulum, and dictyosomes, particularly in the cytoplasm adjacent to areas of extensive wall development. Plastids typically contain abundant starch reserves. As development proceeds, wall ingrowths become more extensive on all walls in the sporophyte foot but are never found on the upper wall of the basal cell in contact with the remainder of the sporophyte. Plastids in the foot contain fewer starch reserves later in development. Wall ingrowths are not visible in the cells of the gametophyte vaginula until well after extensive development has occurred in the sporophyte foot. Stacks or layers of endoplasmic reticulum are characteristic of the cells of the gametophyte vaginula, along with numerous mitochondria, dictyosomes, and well-developed plastids. Starch reserves typically are less abundant in cells of the gametophyte. The early development of extensive wall elaborations in the cells of the sporophyte foot, and particularly in the basal cell, may favor the rapid movement of water and nutrients from the gametophyte into the sporophyte at a time when rapid development in this minute, ephemeral moss is critical. 相似文献
42.
Ursula Kües Anna M. Tymon Wendy V. J. Richardson Georgiana May Paul T. Gieser Lorna A. Casselton 《Molecular & general genetics : MGG》1994,245(1):45-52
We have identified the seven genes that constitute the A43 mating-type factor of Coprinus cinereus and compare the organisation of A43 with the previously characterised A42 factor. In both, the genes that trigger clamp cell development, the so-called specificity genes, are separated into and loci by 7 kb of noncoding sequence and are flanked by homologous genes -fg and -fg. The specificity genes are known to encode two classes of dissimilar homeodomain (HD1 and HD2) proteins and have different allelic forms which show little or no cross-hybridisation. By partial sequencing we identified a divergently transcribed HD1 (a1-2) and HD2 (a2-2) gene in the A43 locus. a2-2 failed to elicit clamp cell development in three different hosts, suggesting that it is non-functional. a1-2 elicited clamp cells in an A42 host that has only an HD2 gene (a2-1) in its locus, thus demonstrating that the compatible A mating interaction is between an HD1 and an HD2 protein. The A43 locus contains three specificity genes, the divergently transcribed HD1 and HD2 genes b1-2 and b2-2 and a third HD1 gene (d1-1) that was shown by hybridisation and transformation analyses to be functionally equivalent to d1-1 in A42. An untranscribed footprint of a third A42 HD1 gene, c1-1, was detected between the A43 b2-2 and d1-1 genes by Southern hybridisation. 相似文献
43.
The three known classes of eukaryotic telomeres share the requirement for an RNA template in their replication. This RNA-templated replication is subject to species-specific differences, such as telomere length and its regulation, which suggest that telomeres may have acquired different additional functions in different organisms. Centromeres show less conservation than do telomeres. 相似文献
44.
45.
四种动物病毒的细胞培养及血凝检测的比较研究李天宪,赵林,罗怡珊,冯锋(中国科学院武汉病毒研究所,武汉430071)关键词细小病毒,细胞培养,细胞病变,血凝试验云豹肠炎病毒(LPV)、水貂肠炎病毒(MEV)、犬肠炎病毒(CPV)和猫泛白细胞减少症病毒(... 相似文献
46.
Retha R. Newbold Rita B. Hanson Wendy N. Jefferson 《In vitro cellular & developmental biology. Animal》1994,30(8):519-528
Summary Although estrogens have been shown to stimulate a variety of morphologic and biochemical changes in the uterus in vivo, no
clear consistent demonstration of similar responses in vitro have been made; thus, a defined organ culture system using the
immature mouse uterus was established to study the possibility of demonstrating estrogenic responses in vitro. Uterine tissue
from immature outbred mice (17 to 24 days of age) were cut crosswise in 1-mm3 coins and cultured in a defined medium in the absence of serum, phenol red, or growth factor supplements. Diethylstilbestrol
(DES), a synthetic estrogen, was added to the media at doses ranging from 1 to 100 ng/ml. The effect of DES on uterine cell
proliferation was assessed by morphologic changes in uterine epithelial and stromal cells, increase in number of epithelial
cells per unit basement membrane, increase in height of luminal epithelial cells, and [3H]thymidine incorporation. Functional changes were determined by measuring the amounts of the estrogen-inducible uterine protein,
lactoferrin, that was localized in the epithelial cells and secreted into the media, and the localization of the estrogen
receptor in the cultured tissues. Results indicate that under the described conditions of culture, estrogens like DES can
induce morphologic and biochemical responses in the uterus that are similar to those seen in vivo. This organ culture system
will aid in the investigation of various mechanisms involved in the hormonal regulation of growth and differentiation of estrogen
target tissues. 相似文献
47.
Sanford D. Eigenbrode Anthony M. Shelton Wendy C. Kain Harry Leichtweis Terry D. Spittler 《Entomologia Experimentalis et Applicata》1993,69(1):41-50
S-ethyldipropylthiocarbamate (EPTC) applied as a soil treatment or over-the-top spray on cabbage plants (Brassica oleracea L.) caused the leaves to turn ‘glossy’ for as long as 30 days. EPTC-induced glossy plants were damaged significantly less
than untreated plants by diamondback moth,Plutella xylostella (L.), imported cabbage worm,Pieris rapae (L.), and cabbage looper,Trichoplusia ni (Hbn.). Reductions in damage were equivalent to those obtained from treatment with permethrin. When used in combination with
permethrin, EPTC provided additive control of damage by these pests. Our calculations show EPTC-induced resistance to be cost-effective.
This use of EPTC has several limitations, however. Younger plants (<9 leaves) were killed or injured by the herbicide. The
growth of older plants was not affected, but plants did not become glossy for ca. 10 days after they were treated with EPTC.
The crop must be protected with insecticides until the plants are mature enough to treat with EPTC, and until treated plants
become glossy. In addition, since the glossy trait is only effective against first instar larvae, populations of later instars
on glossy plants must be reduced with an application of insecticide. Finally, EPTC formulations are water-soluble and can
be washed away from the plants by heavy rains and irrigation, which may make this use of EPTC impractical in some situations.
Where its use is practical, and the indicated precautions are taken, EPTC-induced resistance could reduce dependence on chemical
insecticides and reduce selection for insecticide resistance in diamondback moth. 相似文献
48.
Albert A. Schinzel Wendy P. Robinson Franz Binkert Toni Torresani Edmond A. Werder 《Human genetics》1993,92(2):175-178
A 13 1/2 year-old girl with short stature and very few Turner stigmata revealed 45,X/46,XX mosaicism with 90%–100% 46,XX cells in three sequential blood lymphocyte cultures. Molecular investigation of the parental origin of her X chromosomes revealed homozygosity for paternal X markers and an absence of maternal markers. Luteinizing hormone response to growth hormone releasing hormone was increased. Impaired gonadal function and shortness of stature in this case could be a result of the mild mosaicism with a 45,X cell line and/or is a consequence of the paternal-only origin of her X chromosomes. 相似文献
49.
Richard Darley Alan Morris James Passas Wendy Bateman 《Cancer immunology, immunotherapy : CII》1993,37(2):112-118
The cell-surface expression of major histocompatibility (MHC) antigens and the adhesion molecule intercellular adhesion molecule 1 (ICAM-1) is essential for target cell recognition by T lymphocytes. The expression of both classes of molecule is induced by various cytokines, notably interferon (IFN). Since transforming growth factor (TGF) has been recently reported to antagonise HLA-DR induction by IFN we have examined, using a number of murine and human cell lines, the effect of TGF on IFN-induced MHC class I and class II and ICAM-1 expression. All of the cell lines tested expressed elevated class I MHC following IFN treatment. Class II MHC induction was seen on most but not all of the cells, the exceptions being among a panel of human colorectal carcinoma cell lines. A striking difference between cells of different origin was noted in the response to TGF. TGF was found to antagonise IFN-induced class I and class II MHC expression on C3H 10T1/2 murine fibroblasts, early-passage BALB/c mouse embryo fibroblasts, a murine oligodendroglioma cell line, and on MRC5 human fibroblasts and two human glioblastoma cell lines. Class II MHC was much more strongly inhibited (sometimes completely) than class I MHC. TGF also inhibited induction of class I MHC expression by IFN. However, TGF did not inhibit class I or class II MHC induction by IFN in any of the nine colorectal carcinoma cell lines, although two of five of the lines tested were growth-inhibited by TGF. On the other hand, human ICAM-1 induction by IFN was not affected by simultaneous treatment with TGF in any of the cell lines. The down-regulation of IFN-induced MHC antigens by TGF is not, therefore, the result of a general antagonism of IFN. Retinoic acid has recently been reported to induce ICAM-1 expression on human tumour cells. We have confirmed this observation on MRC5, and the two human glioblastoma cell lines, however six colorectal carcinoma cell lines tested did not respond. In contrast to IFN-induced ICAM-1 expression, retinoic-acid-induced ICAM-1 expression was inhibited by TGF on two of the three responsive lines. 相似文献
50.
Martina Ferraguti Sergio Magallanes Jéssica Jiménez-Peñuela Josué Martínez-de la Puente Luz Garcia-Longoria Jordi Figuerola Jaime Muriel Tamer Albayrak Staffan Bensch Camille Bonneaud Rohan H. Clarke Gábor Á. Czirják Dimitar Dimitrov Kathya Espinoza John G. Ewen Farah Ishtiaq Wendy Flores-Saavedra László Zsolt Garamszegi Olof Hellgren Dita Horakova Kathryn P. Huyvaert Henrik Jensen Asta Križanauskienė Marcos R. Lima Charlene Lujan-Vega Eyðfinn Magnussen Lynn B. Martin Kevin D. Matson Anders Pape Møller Pavel Munclinger Vaidas Palinauskas Péter L. Pap Javier Pérez-Tris Swen C. Renner Robert Ricklefs Sergio Scebba Ravinder N. M. Sehgal Manuel Soler Eszter Szöllősi Gediminas Valkiūnas Helena Westerdahl Pavel Zehtindjiev Alfonso Marzal 《Global Ecology and Biogeography》2023,32(5):809-823