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121.
A. Falconi M. Borde A. Hernández-Cruz F. R. Morales 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1995,176(5):679-689
Stimulation of the spinal cord of the electric fish Gymnotus carapo, evoked an abrupt increase in the discharge rate of the electric organ. At the maximum of this response, the rate increased an average of 26 ± 11.8%. The duration of the response was 4.9 ± 2.12 s; its latency was 10.4 ± 1.1 ms. Activation of the Mauthner axon played a decisive role in this phenomenon as indicated by the following: (1) recordings from the axon cap of the Mauthner cell demonstrated that the response was evoked if the Mauthner axon was antidromically activated and (2) a response that was similar to that produced by spinal cord stimulation, was elicited by intracellular stimulation of either Mauthner cell. Stimulation of the eighth nerve could also increase the discharge rate of the electric organ. The effect was greater if a Mauthner cell action potential was elicited. The findings described in the present report, indicate the existence of a functional connection between the Mauthner cell and the electromotor system in Gymnotus carapo. This connection may function to enhance the electrolocative sampling of the environment during Mauthner-cell mediated behaviors. This is a novel function for the Mauthner cell.Abbreviations
EHP
extrinsic hyperpolarizing potential
-
EOD
electric organ discharge
-
M-AIR
Mauthner initiated abrupt increase in rate
-
M-cell
Mauthner cell
-
M-axon
Mauthner axon
-
PM
pacemaker nucleus
-
PM-cell
pacemaker cell
-
PPn
prepacemaker nucleus
-
SPPn
sublemniscal prepacemaker nucleus 相似文献
122.
A mutation assay in cultured mammalian cells based on the direct analysis of minisatellite DNA was developed. Band pattern variations reflect DNA alterations ranging from single base changes to complex rearrangements. By DNA fingerprinting a large number of autosomal loci throughout the human genome can be simultaneously checked, therefore minimizing the size of the samples of cell colonies to be scored in the absence of phenotypic selection. For the mutation assay chinese hamster cells (V79) were treated with Nitrosoguanidine and 14 independent colonies were isolated and expanded. DNA fingerprints were obtained after digestion of the DNA extracted from each clone with bothHinfI andHae III, and hybridisation with both 33.15 and 33.6 probes. Twelve colonies from untreated cells were also analysed. Several differences in the band pattern of treated colonies were observed when compared with untreated cells; digestion withHae III and hybridisation with 33.15 probe allowed the detection of the highest frequency of induced variants. The results suggest that minisatellite sequences are hypermutable sites that can be used to monitor the mutagenic potential of chemical agents directly at the DNA level, without phenotypic selection. Moreover, with the method herein decribed, it is possible to distinguish between true mutations and epimutations, such as those caused by changes in DNA methylation. 相似文献
123.
Two key issues in the application of plant-cell-culture technology to the production of valuable secondary metabolites are reviewed: the selection of cell lines with suitable genetic, biochemical and physiological characteristics; and the optimization of bioreactor environments. Although great progress has been made in recent years in the design, selection and optimization of bioreactor hardware, optimization of environmental factors such as medium components, light irradiation and O2 supply needs detailed investigations for each case. With a better understanding of plant cell metabolism and physiology, further developments in cultivation processes, such as process integration and on-line monitoring and control, can be expected in the near future.J.-J. Zhong and J.-T. Yu are with the Research Institute of Biochemical Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, China T. Yoshida is with the International Center of Cooperative Research in Biotechnology (ICBiotech), Faculty of Engineering, Osaka University, Suita, Osaka 565, Japan. 相似文献
124.
Ward R. Rice Jeffrey A. Whitsett 《Biochimica et Biophysica Acta (BBA)/Molecular Cell Research》1984,805(3):261-267
Release of [3H]phosphatidylcholine from pulmonary Type II epithelial cells was stimulated by terbutaline, forskolin and cytochalasin D. Compound inhibited both basal and agonist-stimulated release of [3H]PC. The IC50 for inhibition by compound was 1–2 μg/ml, and was similar for inhibition of both basal and stimulated release of [3H]phosphatidylcholine. Inhibitory effects of were noted following a 1 h exposure to compound and persisted up to 3 h. The inhibitory effect of compound was entirely reversed by removing compound from the external milieu. Compound had no effect on cytosolic cyclic AMP levels or lactate dehydrogenase release. Inhibition of surfactant release produced by compound was unaffected by changes in extracellular calcium concentrations. Compound is a non-toxic inhibitor of phosphatidylcholine release from Type II epithelial cells. 相似文献
125.
F. Conti T. Parasassi N. Rosato O. Sapora E. Gratton 《Biochimica et Biophysica Acta (BBA)/Molecular Cell Research》1984,805(1):117-122
Changes in membrane properties during the differentiation process in K562 cells have been investigated. A decrease of lectin-induced agglutination has been detected. The agglutination assay revealed to be an early and sensitive test to monitor the induced differentiation of the K562 cells. Naturally occurring fluorescent fatty acids (cis- and trans-parinaric acids) and the recently developed multifrequency phase and modulation technique were used to study cell membrane properties. Changes in fluorescence lifetime and polarization are clearly associated with cell differentiation, suggesting the involvement of the cellular plasma membrane in the differentiation process. 相似文献
126.
Summary Primary and passaged cultures of normal colon epithelial cells, derived from human fetuses (13 to 17 wk of conceptual age)
have been established. These cultures have been passaged 16 times thus far. The cultures have been initiated and maintained
in medium consisting of 50% Dulbecco's minimum essential medium and 50% Ham's F12 medium and supplemented with antibiotics
(penicillin, 100 U/ml; streptomycin, 100 μg/ml); ascorbic acid, 40 μg/ml;l-isoleucine, 50 μg/ml; epidermal growth factor, 20 ng/ml; insulin, 5 μg/ml; cholera toxin, 5 ng/ml; transferrin, 1 μg/ml;
fetal bovine serum (10%); and HEPES, 25 mM final concentration, and incubated at 37°C in humidified gas containing 5% CO2: 95% air.
The cellular and subcellular characteristics of primary and passaged cultures were defined using light microscopy and scanning
and transmission electron microscopy. The cells exhibited microvilli on cell surfaces and showed junctional complexes and
interdigitations between cells. Indented nuclei with dense chromatin and marginated heterochromatin, numerous mitochondria,
rough endoplasmic reticulum, polysomes, and extensive Golgi zones were conspicuous. Also, periodic acid Schiff's reagent-positive
staining of the cells suggests the active synthesis of complex mucopolysaccharides in the cytoplasm.
This study was supported by USPHS Grant CA-30185 from the National Large Bowel Cancer Project, National Cancer Institute. 相似文献
127.
R. Godbout B. L. Gallie R. A. Phillips 《In vitro cellular & developmental biology. Plant》1984,20(6):479-485
Summary A variant nontransformed clone, I21, was selected from the spontaneously transformed mouse fibroblast line, IT22. Selection
was done by plating IT22 in methylcellulose and picking single cells after 2 d. Cultures derived from these single cells were
selected again and one clone, I21, derived from the second round of selection was characterized extensively. I21 and IT22
have the same plating efficiency (PE) on plastic, but in agarose they differ by 1000-fold. In comparison to IT22, I21 has
a normal morphological appearance, a lower saturation density, a higher viability in stationary phase, an increased doubling
time, an increased chromosome content, and is unable to form tumors in nude mice. I21 has remained remarkably stable in culture
and has not reverted to the transformed phenotype for at least 300 generations in culture. Over 100 clones of I21, expanded
to 106 cells, failed to show an increased PE in agarose. Even expansion of the rare colonies of I21 that grow in agarose failed
to produce clones similar to IT22.
The research was supported by the Medical Research Council and the National Cancer Institute of Canada. R. Godbout was supported
by a 1967 Science Scholarship and by an MRC Studentship. B. L. Gallie is a Research Associate of the Ontario Cancer Treatment
and Research Foundation. 相似文献
128.
Coordinated synthesis of the nuclear protein cyclin and DNA in serum-stimulated quiescent 3T3 cells 总被引:7,自引:0,他引:7
R Bravo 《FEBS letters》1984,169(2):185-188
Quantitative two-dimensional gel electrophoretic analysis (IEF) of the nuclear polypeptide cyclin together with autoradiographic studies have revealed a coordinate synthesis of cyclin and DNA after serum stimulation of quiescent 3T3 cells. These results strengthen the notion that cyclin may be a central component of the pathway(s) that regulate cell proliferation. 相似文献
129.
Summary Cell suspensions of Petunia hybrida were subjected to a selection procedure in which the concentration of the selective agent, methotrexate (MTX), was gradually elevated. In mammalian cells, this procedure frequently results in MTX-resistant mutants due to amplification of the gene coding for dihydrofolate reductase (DHFR), the target protein of MTX.Five suspension lines were isolated, with degrees of resistance ranging from 10 to 500 M MTX (in wild type the LD99.9 is 0.2 M). MTXR phenotypes were unstable, as manifested by the loss of resistance upon prolonged growth in the absence of drug. All of the mutants also exhibited high values of MTX-binding protein (60- to 400-fold higher than that of the wild type), which declined to intermediate values upon MTX withdrawal. Finally, cellular extracts from all of the mutants also showed high specific staining of DHFR-activity in gels.The results suggest that the resistance of MTX in these plant cell-lines is mediated by the elevation of the amounts of DHFR, probably as a consequence of gene amplification. 相似文献
130.
Stephen C. Fry 《Phytochemistry》1984,23(1):59-64
[14C]Cinnamate was taken up very rapidly by cultured spinach cells and completely incorporated into low-MW conjugates within 20 min. The 14C-labelled products were similar whether the [14C]cinnamate was supplied continuously over a period of hours via a peristaltic pump or instantaneously. Radioactivity was slowly recruited from the low-MW pool into aromatic components of the cell-wall fraction. Saponification of the radioactive wall fraction yielded, in addition to radioactive ferulate and p-coumarate, large amounts of ethyl acetate-soluble radioactive material with the properties of oxidatively coupled phenols. The coupled material was associated with the most highly ‘Driselase’-resistant fractions of the cell wall. In contrast, ‘Driselase’ released most of the wall's ferulate and p-coumarate on disaccharide fragments. It is suggested that the oxidatively coupled phenols are formed from simpler phenols by peroxidase and that they cross-link the polysaccharides to which they are attached, making these polysaccharides relatively ‘Driselase’-resistant. 相似文献