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131.
A V79 Chinese hamster cell line XR-V15B exhibiting hypersensitivity to X-ray has been isolated and characterized. Additionally to increased X-ray-sensitivity (approximately 8-fold, as judged by D10 values), cross-sensitivity to bleomycin (3-fold increase), 4NQO (3-fold), H2O2, EMS, MMS (2-fold) were observed also. No increased sensitivity to UV and MMC was found. Genetic complementation analysis indicates that XR-V15B belongs to the same complementation group as the X-ray-sensitive (xrs) mutants of Chinese hamster ovary (CHO) cells described by Jeggo (1985). Biochemical analysis of XR-V15B confirms this finding: the mutant showed a decreased ability to rejoin double-strand breaks induced by X-ray as measured by neutral elution. After 4 h of repair more than 50% of the double-strand breaks remain in comparison to 3% in V79 cells. No difference was observed between wild-type and XR-V15B cells in the initial number of single-strand breaks induced, in the kinetics of their rejoining and in the final level of unrejoined single-strand breaks. Treatment with 5-azacytidine did not have an effect on the reversion frequency of XR-V15B, contrary to the results obtained with the xrs mutants. XR-V15B has been grown in continuous culture for more than 3 months without evidence of reversion. The mutation induction by X-ray irradiation at the HPRT locus is not significantly increased in the mutant, but at doses giving the same degree of cell killing, XR-V15B cells are hypomutable. 相似文献
132.
Wolfson M. R.; Tran N.; Bhutani V. K.; Shaffer T. H. 《Journal of applied physiology》1988,65(3):1436-1443
In this report, an experimental approach and newly designed apparatus for liquid ventilation of preterm animals are described. Findings of age-related changes in cardiopulmonary function of this animal preparation are presented. Thirty-one lambs, 102-137 days gestation (term 147 +/- 3 days), were studied. The carotid artery, jugular vein, and trachea of the exteriorized fetus were cannulated under local anesthesia. Immediately after cesarean section delivery, ventilation commenced; warmed (39 degrees C) and oxygenated (PIO2 greater than 500 Torr) liquid fluorocarbon (RIMAR 101) was delivered to the lung by a mechanically assisted liquid ventilation system. Skeletal muscle paralysis, low-dose exogenous buffering, and thermal support were maintained during the 3-h experiment. Pulmonary gas exchange, acid-base status, and cardiopulmonary and metabolic function were assessed. By utilizing these techniques, effective arterial oxygenation, CO2 elimination, acid-base status, and cardiovascular stability were supported independent of gestational age. The results demonstrate a developmental increase in specific lung compliance and mean arterial pressure and decrease in heart rate and systemic O2 consumption per kilogram with advancing gestational age. These findings demonstrate that liquid ventilation negates the dependency of effective pulmonary gas exchange on surfactant development, thereby extending the limits of viability of the immature extrauterine lamb. As such this new experimental approach is useful for the study of physiological development over an age range previously limited to fetal animal preparations and, therefore, may provide insight regarding adaptation of the premature to the extrauterine environment. 相似文献
133.
Michael L. Mavrovouniotis Patrick Bayol Tu-Kien Michael Lam George Stephanopoulos Gregory Stephanopoulos 《Biotechnology Techniques》1988,2(1):23-28
Using Gibbs Energies of compounds, as well as Gibbs Energy changes and equilibrium constants of biochemical reactions, the contributions of functional groups to the Gibbs Energy (in aqueous solution, temperature 25°C, and pH=7) have been estimated. These contributions allow the estimation of the Gibbs Free Energy and the equilibrium constant of a biochemical reaction, given the structure of the reactants and products. 相似文献
134.
Summary Protoplasts were isolated from leaf mesophyll of hybrid poplar (Populus nigra X P. maximowiczii) with a mean yield of 10.4 x 106 protoplasts per g fresh weight using 2.0% Cellulase Onozuka R-10, 0.8% Macerozyme R-10, 1.2% Hemicellulase, 2.0% Driselase, and 0.05% Pectolyase Y-23 with CPW salts solution containing 0.6 M mannitol, 0.002 M DTT, 3 mM MES at pH 5.6. A liquid plating method produced the highest frequency of dividing protoplasts (48.6%) using an MS medium without NH4NO3. The highest percent of colony formation was 22.8%, produced with fabric supported semi-solid (0.5% w/v) agar plating method using the same culture medium. Growing cell colonies and/or micro-calli were transferred to a fresh semisolid agar medium containing 0.44 M BAP and 9.0 M 2,4-D. Multiple shoots were produced from protoplast-derived callus after culture on MS medium containing 6.8 M zeatin. After root induction on half-strength MS medium that lacked growth regulators, shoots were transferred to pots containing artificial soil mix.Abbreviations CPW
Cell and Potoplast Wash solution
- LPM
Liquid Plating Method
- LDM
Liquid Drop Method
- HDM
Hanging Drop Method
- FSPM
Fabric supported Semi-solid agar Plating Method
- DTT
Dithiothreitol
- MES
2-(N-morpholino) ethane sulfonic acid
- BAP
6-benzylaminopurine
- 2,4-D
2,4-dichlorophenoxy acetic acid
- NAA
-naphthalene acetic acid
- MS
Murashige and Skoog (1962) 相似文献
135.
136.
G. H. Canullo R. Rodríguez‐kábana J. W. Kloepper 《Biocontrol Science and Technology》1992,2(2):159-169
The efficacy of 2‐furfuraldehyde for control of Sclerotium rolfsii was studied in laboratory and greenhouse experiments. Mycelial growth of the fungus was reduced proportionally with concentrations of 0.1–0.5 ml furfuraldehyde l‐1 agar medium, and viability of sclerotia diminished on exposure to 2‐furfuraldehyde vapours. Detectable populations of bacteria and fungi, including Trichoderma spp., were reduced significantly (9=0.05) when furfuraldehyde was added to the agar used for soil dilution plates of untreated soil. Repeated treatments of natural soil with the fumigant significantly increased populations of Trichoderma spp. and bacteria, but diminished numbers of actinomycetes. Increasing dosages applied to soil artificially infested with S. rolfsii caused a reduction of disease on lentil, Lens culinaris. Results indicate that the compound, when applied to field soil, changes the composition of soil microflora and has potential for integrated control of S. rolfsii. 相似文献
137.
Tracey C. Bourner Enrique Vargas‐Osuna Trevor Williams Candido Santiago‐Alvarez Jenny S. Cory 《Biocontrol Science and Technology》1992,2(4):315-326
Agrotis segetum nuclear polyhedrosis virus (AsNPV) and granulosis virus (AsGV), propagated in laboratory cultures of A. segetum in England and A. ipsilon in Spain, respectively, were applied to plots of maize plants at the one‐ to four‐leaf stage of growth. Plots were arranged in a 6 x 6 Latin square design and infested with second‐instar A. segetum larvae (the common cutworm). Each virus was applied in separate treatments by two application methods; as an aqueous spray containing 0.1% Agral as a wetting agent, and as a bran bait. The NPV was applied at a rate of 4 X 1012 polyhedra/ha, and the GV at 4 X 1013 granules/ha. Soil and plants were sampled for larvae on three occasions following virus treatment: 24 h, 4 days and 11 days. The larvae were reared on diet in the laboratory, until death or pupation, to examine the rate and level of viral infection. Infection data showed 87.5% and 91% NPV infection and 12.5% and 55% GV infection in spray and bait treatments, respectively, in larvae sampled 24 h after treatment. In larvae sampled 4 days after treatment, the results were 78% and 100% NPV infection, and 13% and 6% GV infection. A total of only six larvae were retrieved on day 11. In both treatments larvae infected with AsNPV died significantly more rapidly and at an earlier instar than those infected with AsGV, indicating that AsNPV appears to have better potential as a control agent for A. segetum. 相似文献
138.
The presence of immunoreactive endothelin (IR-ET) in human saliva and rat parotid gland was investigated by radioimmunoassay. The IR-ET concentration (mean +/- SEM) in saliva taken from normal volunteers was 2.0 +/- 0.2 pmol/l (n = 15). The IR-ET concentration in rat parotid gland was 19.2 +/- 2.2 fmol/g wet weight (n = 10). Fast protein liquid chromatography (FPLC) of human saliva extract revealed 6 peaks; one peak eluting in the void volume, one in a position between ET-1 and -3, and the other four in the positions of synthetic ET-1, -2, -3 and big ET(1-38), respectively. A similar pattern of rat parotid gland extract was noted with FPLC, except that there was no peak after the void volume. Presence of endothelin, a potent growth factor, in saliva and salivary gland points to a role in maintaining the integrity of the oral and gastrointestinal tract mucosa. 相似文献
139.
140.
Autonomous DNA replication in human cells is affected by the size and the source of the DNA. 总被引:31,自引:13,他引:18
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We previously developed short-term and long-term assays for autonomous replication of DNA in human cells. This study addresses the requirements for replication in these assays. Sixty-two random human genomic fragments ranging in size from 1 to 21 kb were cloned in a prokaryotic vector and tested for their replication ability in the short-term assay. We found a positive correlation between replication strength and fragment length, indicating that large size is favored for efficient autonomous replication in human cells. All large fragments replicated efficiently, suggesting that signals which can direct the initiation of DNA replication in human cells are either very abundant or have a low degree of sequence specificity. Similar results were obtained in the long-term assay. We also used the same assays to test in human cells a random series of fragments derived from Escherichia coli chromosomal DNA. The bacterial fragments supported replication less efficiently than the human fragments in the short-term and long-term assays. This result suggests that while the sequence signals involved in replication in human cells are found frequently in human DNA, they are uncommon in bacterial DNA. 相似文献