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21.
This paper deals with the role of light in the germination of akinetes of Anabaena azollae. The two maxima action spectra are situated at 385 and 615 nm and the stimulation of the germination process by photosynthate was confirmed. The photoreceptor absorbing at 385 nm was identified as a flavin and that at 615 nm as a phytochrome. A model is suggested for the mode of action of light in the germination of akinetes of blue-green algae.C. Tsui 相似文献
22.
The experiments described emphasize the effects of several factors crucial to the maintenance of cell divisions leading to increased cell numbers in suspension and colony formation from cotyledon protoplasts of Pinus Pinaster Ait. Osmotic potential of the incubation and culture media are critical. Reducing the osmolality from 680 mOsm kg H2 O−1 during protoplast isolation to 610 mOsm kg H2 O−1 during washing and culture was essential to achieve a high frequency of cell division. Survival of the cells beyond 3 weeks of culture occurs only if the calcium concentration is decreased from 5.6 m M to 1.5 m M . Glutamine as sole source of nitrogen shortens the lag phase of response of the protoplasts and increases their plating efficiency. After 6 weeks of culture, a combination of low osmolality (225 mOsm kg H2 O−1 ) and high level of glutamine (40 m M ) is a prerequisite for obtaining actively growing cell suspensions. 相似文献
23.
Edith Doucet Jacques Bourbon Michel Rieutort Lea Marin Claude Tordet 《In vitro cellular & developmental biology. Plant》1987,23(3):189-198
Summary Lung organ culture has been a widely used system for studying differentiation and maturation of alveolar epithelium through
various culture conditions. The purpose of this work was to carefully characterize in vitro lung biochemical diffeentiation
through isolation of surfactant fraction from tissue and to search for optimal culture conditions. Fetal rat lung was explanted
on the 18th gestational day for studying glycogen storage, and on the 20th gestational day for studying surfactant accretion,
and cultivated for 48 h. Morphologic differentiation was studies byelectron microscopy tissue explanted on the 17th or 18th
gestational days and cultivated for various times. Glycogen storage was greater on fluid medium, although less than occurring
in vivo. Cellular integrity and surfactant accumulation were maximal on a semisolid medium containing 0.5% agar. Use of O2-CO2 instead of air-CO2 for gassing the explants slighlty decreased phospholipid accumulation. Among media used in previous lung culture studies,
Waymouth MB 752/1 was the only one to allow net glycogen accumulation in vitro. The most favorable media for surfactant phospholipid
accretion were Waymouth MB 752/1, Eagle’s minimum essential and its Dulbeccco’s modification, CMRL 1066, and NCTC 109. They
allowed a 12- to 14-fold increase of surfactant fraction phospholipids in vitro, which is similar to the increase occurring
in vivo during the same peiod. Ham’s F10 and F12 media allowed a six fold increase. RPMI 1640 and medium 199 (M199) allowed
only a three fold increase. Phospholipid concentration in nonsurfactant fraction only doubled during culture, and differences
between various media were much less marked. DNA concentration changed little during culture. Morphologic differentiation
of epithelial cells was advanced as compared with in vivo timing in a medium allowing maximal surfactant accretion (Waymouth
MB 752/1) but not in a medium allowing low surfactant increase (RPMI 1640). The possible role of compositional differences
between media is discussed. 相似文献
24.
25.
根癌农杆菌Ti质粒的T区DNA带有致瘤基因,其基因1和基因2编码生长素吲哚乙酸生物合成途径中的两个酶。以pGV 354(pBR322质粒中插有Ti质粒C 58 T区DNA的HindⅢ15—HindⅢ22大片段)重组质粒出发,我们分离了基因1和基因2,并构建了带有卡那霉素抗性基因的重组质粒pBZ 692,通过基因载体pGV 3850,我们将基因1和基因2引入了高等植物。结果证明基因1和基因2能促使烟草、向日葵、土豆等转化组织分化长根,转化的根在MS_0培养基上能脱分化形成愈伤组织并自主生长,在转化的组织中有转化标记胭脂碱的存在。 相似文献
26.
Suzanne Knauf Jean Kalwas B. Frederick Helmkamp Lee W. Harwell Jackson Beecham Edith M. Lord 《Cancer immunology, immunotherapy : CII》1986,21(3):217-225
Summary Murine monoclonal antibodies (MCAs) against human ovarian tumor associated antigen NB/70K have been prepared. One of these MCAs, NB12123, was chosen for the development of a radioimmunoassay for measuring serum NB/70K levels. In this assay, the average NB/70K level in 75 normal, healthy controls was 11.9 activity units (AU) with an SD of 14.9 AU. The normal cut off value for this assay was set at 45 AU (mean +2 SD). 24 of 46 (52%) ovarian cancer patients, 7 of 18 (39%) patients with benign ovarian cysts or tumors and 3 of 85 (4%) control samples had elevated serum NB/70K levels. Comparison of NB/70K levels measured in the NB12123 assay with levels measured in an assay using a polyclonal antiNB/70K previously developed in our laboratory [13] indicated that although both assays had approximately the same percentage of positive ovarian cancer patient samples, there appeared to be no correlation between the absolute NB/70K levels measured by the two assays. The rank of ovarian cancer patient samples was also different for the two assays. Also, almost 40% of patients with benign ovarian cysts and tumors had elevated serum NB/70K levels as measured by the NB12123 assay as compared to 0% for the polyclonal assay. Reciprocal cross-blocking experiments, absorption studies, and immune precipitate analysis indicated that both the monoclonal NB12123 assay and the polyclonal antiNB/70K assay measured the same population of NB/70K molecules. However, the polyclonal antibody recognizes epitopes in addition to that recognized by NB12123. Taken together, these results suggest that the epitope recognized by NB12123 is not as specific for malignant ovarian tumors as the epitope(s) recognized by polyclonal antiNB/70K and/or that more than the one epitope detected by the MCA is responsible for the specificity for ovarian cancer of the polyclonal NB/70K assay. In spite of this, the greater sensitivity and range of the monoclonal NB12123 assay make it possible to monitor serum NB/70K levels in ovarian cancer patients. In four patients examined, the fluctuating serum NB/70K levels appeared to correlate well with clinical statusSupported in part by ACS # PDT 231 and a grant from the Elsa U. Pardee Foundation 相似文献
27.
Jacques Defaye Hugues Driguez Bernard Henrissat Edith Bar-Guilloux 《Carbohydrate research》1983,124(2):265-273
(1,1′-13C)α,α-Trehalose was obtained in 37% yield from the Pavia condensation of 2,3,4,6-tetra-O-benzyl-d-(1-13C)glucopyranose, in dichloromethane in the presence of trifluoromethanesulfonic anhydride, followed by the usual deprotection techniques. The hydrolysis of this substrate by cockchafer trehalase was monitored at 37° by using 13C-n.m.r. spectroscopy with short recording times. Equimolecular amounts of α- and β-d-glucopyranose are released simultaneously by the action of the enzyme. This result is consistent with a bimolecular substitution mechanism, taking into account previous results involving C-2 asymmetric participation in the catalytic step of hydrolysis of α,α-trehalose. For comparative evaluation of its accuracy, the usual polarimetric technique was also used for the determination of the anomeric configuration of the d-glucose released by the action of the enzyme on α,α-trehalose. 相似文献
28.
Richard P. Bunge Mary Bartlett Bunge Edith R. Peterson 《The Journal of cell biology》1965,24(2):163-191
29.