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41.
Shoot regeneration from mature endosperm of Passiflora foetida 总被引:1,自引:0,他引:1
Murashige and Skoog (1962) medium supplemented with 2 M 6-benzylaminopurine (BA) induced adventitious shoots on mature endosperm explants, whilst gibberellic acid (GA3) and casein hydrolysate stimulated growth and development of these shoot primordia. Plantlets were successfully weaned in vivo. These plants were found to be triploid and flowered, although fruit set was not observed. 相似文献
42.
Ali Arslan Cuillermina Almazan Hans H. Zingg 《In vitro cellular & developmental biology. Animal》1995,31(2):140-148
Summary Normal and neoplastic growth of epithelial cells depends on mutual interactions between epithelial and stromal cells. As a
tool for the study of the underlying molecular mechanisms, we have developed temperature-sensitive, nontransformed cell lines
derived from rat uterine epithelium and stroma by transfecting primary cultures with a temperature-sensitive mutant of the
SV40 large T antigen. The epithelial and stromal cell lines obtained shared relevant morphological characteristics with the
primary cells from which they were derived. Immunocytochemical analysis showed that the epithelial cell lines expressed the
intermediate filament cytokeratin, whereas the stromal lines expressed the intermediate filament vimentin. Alkaline phosphatase
activity was present in all cell lines examined. All cell lines were anchorage dependent and did not form foci. One epithelial
cell line expressed oxytocin mRNA, a gene product recently shown to be highly expressed in vivo in the uterine epithelium
at term. If grown on Matrigel, this cell line formed domelike structures, a further characteristic of its differentiated phenotype.
In an attempt to reconstitute an endometrium in vitro, epithelial cells were seeded on top of a layer of stromal cells. Paraffin
cross sections showed that this in vitro system consisted of a bilayer structure. Four to five cuboidal epithelial cells were
typically anchored atop one stromal cell, forming an endometriumlike tissue. The present in vitro system should provide a
useful model for further studies on endometrial functions and epithelial/stromal cell interactions at a molecular level. 相似文献
43.
An RNA pseudoknot is an essential structural element of the internal ribosome entry site located within the hepatitis C virus 5' noncoding region. 总被引:8,自引:2,他引:6 下载免费PDF全文
Translation of the human hepatitis C virus (HCV) RNA genome occurs by a mechanism known as "internal ribosome entry." This unusual strategy of translation is employed by naturally uncapped picornaviral genomic RNAs and several cellular mRNAs. A common feature of these RNAs is a relatively long 5' noncoding region (NCR) that folds into a complex secondary structure harboring an internal ribosome entry site (IRES). Evidence derived from the use of dicistronic expression systems, combined with an extensive mutational analysis, demonstrated the presence of an IRES within the HCV 5'NCR. The results of our continued mutational analysis to map the critical structural elements of the HCV IRES has led to the identification of a pseudoknot structure upstream of the initiator AUG. The evidence presented in this study is based upon the mutational analysis of the putative pseudoknot structure. This is further substantiated by biochemical and enzymatic probing of the wild-type and mutant 5'NCR. Further, the thermodynamic calculations, based upon a modified RNAKNOT program, are consistent with the presence of a pseudoknot structure located upstream of the initiator AUG. Maintenance of this structural element is critical for internal initiation of translation. The pseudoknot structure in the 5'NCR represents a highly conserved feature of all HCV subtypes and members of the pestivirus family, including hog cholera virus and bovine viral diarrhea virus. 相似文献
44.
Summary Excavation of 18 nests ofHarpegnathos saltator from southern India revealed an unusually complex architecture for a ponerine ant. The inhabited chambers are not deep in the ground. The uppermost chamber is protected by a thick vaulted roof, on the outside of which is an intervening space serving as isolation from the surrounding soil. In large colonies, the vaulted roof is extended into a shell which encloses several superimposed chambers. Little openings, which may be encircled by moulded flanges, occur in the upper region of the shell. The inside of the chambers is partly or completely lined with strips of empty cocoons. A refuse chamber is always found deeper than the inhabited chambers; live dipteran larvae (family Milichiidae) are typically present. These elaborate nests represent a large energetic investment, and we speculate therefore that nest emigration is unlikely in this species. Consequently, colony fission may never occur, unlike other ants where gamergates reproduce. 相似文献
45.
Abstract: cis -Methyldioxolane (CD) is a muscarinic receptor agonist. [3 H] CD has been used to label a subpopulation of muscarinic receptors described as exhibiting high agonist affinity. Pharmacological evidence suggests that the population of receptors labeled by [3 H] CD consists of m2 and/or m4 subtypes; however, no studies have directly addressed the subtype selectivity of [3 H] CD. The present study characterizes binding of this ligand to individual human receptor subtypes expressed in transfected Chinese hamster ovary cells. Results indicate that [3 H] CD binds with high affinity only to Hm2 receptors but not to all Hm2 receptors. Twenty-eight percent of Hm2 receptors bound [3 H] CD with a K D of 3.5 ± 0.5 nM. Binding was eliminated in the presence of guanosine 5'- O -(3-thiotriphosphate), indicating that the Hm2 receptors labeled by [3 H] CD are those that are associated with GDP-bound G protein. Binding of [3 H] CD by only a subpopulation of Hm2 receptors is in agreement with data generated from studies of [3 H] CD binding in mammalian brain. Because muscarinic receptors have been implicated to play a role in the pathogenesis of both Alzheimer's and Parkinson's disease, as well as the neurotoxicity of organophosphorus compounds, knowledge of the binding specificity of the muscarinic agonist [3 H] CD should aid research in these areas. 相似文献
46.
Mohamed Mandour 《BMJ (Clinical research ed.)》1994,308(6925):412-413
47.
48.
49.
Dipanwita Bhattacharya T.K. Dhar K.A.I. Siddiqui E. Ali 《Journal of applied microbiology》1994,77(2):129-133
The production of phaseolinone, a phytotoxic metabolite of Macrophomina phaseolina in infected Phaseolus mungo seeds grown on soil, was estimated by enzyme-linked immunosorbent assay and HPLC. The degree of inhibition of seed germination correlated well with the amount of toxin produced; 50% inhibition was observed at a toxin level of 2.1 μg g-1 of wet tissue. A comparison of the toxin-producing ability of nine isolates of the fungus obtained from different hosts and localities showed that the strain MPK'83 produced a significantly larger amount of the toxin, both in liquid culture and in infected seeds. The virulence of the isolates was related to their ability to produce phaseolinone. 相似文献
50.
Mohamed S. Dehlawi Amira T. Eldefrawi Mohyee E. Eldefrawi Nabil A. Anis James J. Valdes 《Journal of biochemical and molecular toxicology》1994,9(5):261-268
A light addressable potentiometric sensor was used to measure acetylcholinesterase (AChE) activity in order to evaluate the protective effects of quaternary compounds and NaF against enzyme phosphorylation and aging by two organophosphates. The use of the immobilized AChE made possible the quick removal of reagents (i.e., organophosphate, 2-pralidoxime, and protectant), thereby permitting accurate determination of AChE activity before and after phosphorylation and aging. Paraoxon was 15-fold more potent in inhibiting AChE than DFP, while the percent aging following phosphorylation by diiso-propylfluorophosphate (DFP) was much higher. Sodium fluoride (NaF), the most effective protectant against phosphorylation and aging, and the quaternary ammonium compounds reduced significantly AChE inhibition by DFP and paraoxon, to similar degrees. Even though the percent AChE activity that was lost to aging was reduced by these agents, aging as a percent of phosphorylated AChE was not reduced. Thus, their major effect was in reducing the percent AChE phosphorylation, which consequently resulted in reduction of total aged AChE. The finding that quaternary ammonium compounds protect against phosphorylation is consonant with the proposed presence of the active site of AChE in an aromatic gorge. 相似文献