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91.
92.
Elizabeth G. Cutter 《American journal of botany》1964,51(3):318-324
Regular sequences of leaf and bud formation occur in several members of the Hydrocharitaceae, including Hydrocharis, in which buds are normally formed in the axil of every second leaf of the phyllotactic spiral. Leaf inception begins by periclinal divisions of the inner cells of the 2-layered tunica. Bud formation, which occurs in the apical meristem itself, immediately following the inception of the subtending leaf primordium, begins by divisions in various planes in the corpus, the 2 tunica layers remaining continuous throughout. The young bud meristem soon gives rise to a lateral bud, before leaf formation begins upon it. Because of these and other features, this species is one of considerable morphogenetic interest. Morphogenesis of the whole plant, and in particular the factors controlling the regular sequence of leaf and bud formation, have been and are being investigated experimentally. 相似文献
93.
An Electron Microscope Study of Intranuclear Inclusions in Mouse Liver and Hepatoma 总被引:8,自引:0,他引:8
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![点击此处可从《The Journal of cell biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
An electron microscope study of intranuclear inclusions which occur in giant cells in a transplantable mouse hepatoma and in enlarged liver cells in mice fed a diet containing bentonite demonstrates that these inclusions are formed by invaginations of the nuclear envelope, and corroborates a previous histochemical study which revealed that the contents of the inclusions are of cytoplasmic origin. In the hepatoma cells the intranuclear inclusions are abundant, small, and situated close to the border of the nucleus, and there are wide openings from the cytoplasm into the invaginations whose contents include lipid droplets, ergastoplasm, and structurally normal mitochondria. In the enlarged liver cells the inclusions are fewer in number, generally much larger than those in the hepatoma, hence they extend deeper into the nucleus, and the interior is continuous with the cytoplasm through only a small opening. Some normal ergastoplasm is present within the inclusions but all other constituents are abnormal. Both normal and degenerating mitochondria occur in the cytoplasm but only degenerating ones are found within the inclusions. Both types of inclusions arise in greatly enlarged cells in which an attempt is made to maintain the normal nuclear surface/nuclear volume ratio by the development of the invaginations of the nuclear envelope. 相似文献
94.
95.
Vanillic, syringic, gallic, and protocatechuic acids, methyl-p-hydroxybenzoate, and propyl-p-hydroxybenzoate generally inhibited respiration in vitro of Escherichia coli, Proteus vulgaris, Pseudomonas aeruginosa, and Aerobacter aerogenes in human urine. In the absence of any other available carbon source, certain of the phenolic compounds were utilized. Reproduction was generally suppressed in urine buffered to pH 7, 5.6, 4.5, and 4.0. The phenolic compounds were used in the range of 0.11 to 0.99 μmole/ml. 相似文献
96.
Cultures of gram-negative bacteria with oxidative glucose metabolism were isolated from surface waters by a highly selective technique, and were classified into 11 types. The predominant type, making up about 50% of the isolated cultures, was cytochrome oxidase-positive, produced fluorescent pigment, and failed to grow at 37 C. A similar type, which differed in being cytochrome oxidase-negative, constituted about 10% of the isolates. Both types of bacteria probably were composed of more than one species. A third type, composed of purple-pigmented pseudomonads, made up approximately 30% of the isolated cultures, and probably represented the predominant species. Other bacterial types isolated constituted less than 10% of the cultures examined. 相似文献
97.
98.
The linkage between the polysaccharide and mucopeptide components of the cell wall of Lactobacillus casei 总被引:14,自引:8,他引:6
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![点击此处可从《The Biochemical journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)
1. The linkage between the polysaccharide and mucopeptide components of the cell wall of Lactobacillus casei is rapidly hydrolysed under mild acid-hydrolysis conditions. 2. The release of the polysaccharide is accompanied by the hydrolysis of an N-acetylhexosaminide linkage. The N-acetylhexosamine residue readily forms chromogen and it is concluded that it is substituted on C(3) by the adjacent sugar. 3. Continued heating of the polysaccharide in acid results in a slower release of reactive N-acetylhexosamine due to the hydrolysis of glycosidic linkages within the polysaccharide. 4. After the linkage between the polysaccharide and mucopeptide has been hydrolysed, acid phosphatase will release approx. 40% of the total phosphorus as inorganic phosphate. 5. It is concluded that the polysaccharide component of the cell wall is joined through its reducing end group to a phosphate grouping in the mucopeptide. 相似文献
99.
Elizabeth B. Gargus Douglas H. Robinson James K. Bubien Lawrence B. Bugaisky Dale J. Benos 《In vitro cellular & developmental biology. Plant》1989,25(5):435-441
Summary Six- and seven-day post-coitus (p.c.) rabbit embryos have been cultured in an attempt to establish a trophectodermal cell
line. Results indicate that cells with epithelial characteristics (i.e. positive staining for cytokeratin) will survive in
culture until Passage 3. At that time a fibroblastlike cell becomes predominant. In addition, we have found that the presence
of the inner cell mass is required for embryo explants often results in the development of cells that spontaneously contract.
These cells stain positively for myosin, which indicates that they may be precardiac cells. Maximum diastolic potential was
−59±1.2 mV and the threshold potential was −53±2.3 mV. Spontaneously contracting cells did not respond to atropine, acetylcholine,
epinephrine, isoproterenol, or propranolol. Action potential seems to be a result of an inward calcium current, because the
beating rate is decreased in a dose-related manner with the calcium channel blocker verapamil, whereas the voltage-sensitive
sodium channel blocker tetrodotoxin was without effect.
This work was supported by grants HD21302, HD07069, DK31091, and HL37320 from the National Institutes of Health, Bethesda,
MD, with additional support from a University of Alabama at Birmingham Cardviovascular Research and Training Center Award. 相似文献
100.