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141.
A method involving short pulses of 5-bromodeoxyuridine (brUdRib) followed by irraidation with 313 nm light was used to locate the time of replication of certain genes during the cell cycle of two cell lines, AF8 and AL106. AF8, a temperature-sensitive mutant of BHK21/13 cells, grows at 33°C but not at 39.5°C. AL106, a hybrid clone of tsAF8 and SV-40 transformed Lesch-Nyhan fibroblasts (LNSV), which retains all hamster chromosomes and one human chromosome (No. 3), has the ability to grow at 39.5°C. AF8 and AL106 cells synchronized at the G1-S boundary were released from their block and pulsed with brUdRib for 2-hour periods during the S phase. The cells were subsequently irradiated with 313 nm light. Colony-forming efficiency and revertants frequency were studied. Incorporation of brUdRib during the early S phase (0–4 hours from the begining of S), decreased the colony-forming efficiency of AL106 cells both at 33°C and 39.5°C, and also of AF8 cells at 33°C. No AF8 colonies grew at the nonpermissive temperature regardless of the treatment. Thus the time of replication of genes responsible for colony-forming ability was the same in tsAF8 at the permissive temperature and in AL106 at both temperatures. The time of replication of the genes responsible for the ts function in AF8 cells was located by determining the revertants frequency in synchronized AF8 cells pulsed with brUdRib and irradiated during 1- to 2-hour periods of the S phase. Back-mutants were scored by counting the number of clones capable of growing at 39.5°C (nonpermissive for AF8 cells). The highest frequency of induced back-mutations occurred in synchronized AF8 cells pulsed with brUdRib (and irradiated) between two to four hours from the begining of the S phase. Exposure to brUdRib during other periods of the S phase or during G1 had no effect on the reversion rate. This method can be used to locate the time of replication (in S) of ts genes in other temperature-sensitive mutants or of other specific genes in other conditional mutants. 相似文献
142.
G W Santos 《The Yale journal of biology and medicine》1982,55(5-6):477-485
Bone marrow transplantation offers two potential therapeutic advantages over more conventional therapy of leukemia. It allows more intensive treatment to be given without regard to marrow toxicity and allows in the case of allogeneic marrow an additional immunotherapeutic effect through graft-versus-host disease (GVHD). Initially, allogeneic transplants in HLA matched sibling donors were only employed in end-stage patients. Although there were encouraging results in terms of long-term therapeutic effects, the overall mortality was prohibitive. Subsequently, patients were transplanted in remission with a marked improvement in overall survival in both acute lymphocytic leukemia and acute non-lymphocytic leukemia. The major obstacles to further improvement in the therapeutic effects of this procedure have been identified (i.e., GVHD, viral infection, and relapse in ALL) and are subject to intensive investigations that already show encouraging results. Syngeneic marrow transplantation is limited for obvious reasons, but early results have shown significant therapeutic effects, in particular, in chronic myelogenous leukemia. These results have encouraged others to use autologous bone marrow. Marrow contamination with unseen tumor cells is being approached by pharmacologic and immunologic techniques designed to "purge" marrow of tumor cells. Animal and initial clinical studies have been encouraging. 相似文献
143.
James L. Catalfamo Michael W. Frohlich William B. Martin Helena Birecka 《Phytochemistry》1982,21(11):2677-2682
The qualitative and quantitative compositions of necines in plants of 20 Heliotropium species collected in Mexico and the U.S.A. and one species from Spain are reported. Trachelanthamidine, supinidine and retronecine were found in all species after hydrolysis of their alkaloids; lindelofidine was detected in most species, whereas heliotridine only in four. Trachelanthamidine, lindelofidine, and supinidine were dominant in four, two and one species, respectively; retronecine was dominant in 15 species, whereas heliotridine only in one. The dominant necine in H. ternatum was either retronecine or lindelofidine depending on the collection locality. Qualitative as well as quantitative differences depending on the collection locality were found in H. curassavicum. Plants from Oaxaca, Mexico, contained lindelofidine and a pyrrolizidine-diol as major necines, trachelanthamidine as minor, and traces of retronecine. Plants originating from two other localities contained trachelanthamidine (dominant), retronecine, and supinidine. The necine patterns found in the examined species differ significantly from those previously reported for 21 species mainly collected in Asia, the Middle East and Australia. 相似文献
144.
Mauricio Goihman-Yahr Leo Pine Maria Cecilia Albornoz Luis Yarzabal Maria Helena De Gomez Blanca San Martin Ana Ocanto Tulio Molina Jacinto Convit 《Mycopathologia》1980,71(2):73-83
Mild sonication was used to obtain single cell suspensions of Paracoccidioides brasiliensis. These cells were intact by microscopic criteria. Direct cell counts in a given inoculum and colony formation on various media were used to determine plating efficiency. Sonicated and nonsonicated cell suspensions were used to study plating efficiency and to estimate viability by means of vital dyes. Methylene blue, Erythrosin B, and Janus green were unreliable when used with P. brasiliensis, but vital dyes were accurate when tested with Candida albicans.Acridine orange gave more meaningful results of viability. Estimates of viability, however, changed significantly as a result of relatively minor alterations in the composition of the suspending medium.In initial experiments, the plating efficiency of P. brasiliensis was dismally low. It descended abruptly with increasing dilution of inoculum. Efficiency was much improved if horse serum was added to brain heart infusion plates or if glucose glycine yeast extract (GGY) plates were incubated at room temperature and mycelial colonies were counted. With the technique we report, current plating efficiency of sonicated suspensions is of the order of 25 %. Our results and procedures have an important bearing upon those studies concerned with in vitro killing of P. brasiliensis in suspensions or with isolating this fungus from clinical or environmental specimens. 相似文献
145.
146.
Helena C. Kraemer Byron Alexander Cathy Clark Curt Busse David Riss 《Primates; journal of primatology》1977,18(4):825-833
A method is suggested to evaluate on an empirical basis sampling plans for the longitudinal study of primate behavior in those
very common situations in which the mathematical structure of behavior is unknown. The method is based on a randomization
procedure applied to a pilot sample of the behavior organized so that cost of implementation of a sampling plan can be evaluated
vis á vis the sampling error intrinsic to the plan. 相似文献
147.
Marden A. de Alvarenga Raimundo Braz Fo Otto R. Gottlieb João P. de P. Dias Aderbal F. Magalhães Eva G. Magalhães Gouvan C. de Magalhães Mauro T. Magalhães José G.S. Maia Raquel Marques Anita J. Marsaioli Antônio A.L. Mesquita Anselmo A. de Moraes Alaide B. de Oliveira Geovane G. de Oliveira Gentil Pedreira Sebastião K. Pereira Sonildes L.V. Pinho Celira C. Santos 《Phytochemistry》1978,17(3):511-516
Wood samples, infested by fungi during storage, were shown to contain, besides the known 5-methyl-mellein, additional (3R)-8-hydroxy-3-methyl-3,4-dihydroisocoumarins substituted by 7-methyl, 5-formyl, 5-carboxy, 5-hydroxy, 5-methoxy, 6-methoxy-5-methyl and 6,7-dimethoxy-5-methyl groups, as well as 6-formyl-7-hydroxy-5-methoxy-4-methylphthalide. Several 2-methylchromanones were synthesized in order to show that this class of compounds can be distinguished from 3-methyl-3,4-dihydroisocoumarins by MS. 相似文献
148.
Summary
Trifolium subterraneum, Trifolium glomeratum andOrnithopus compressus were grown in soil and solution culture at varying P concentrations. Efficiency of P utilization was determined using the
following criteria: (1) The ability to produce tops dry matter with a given amount of applied P, (2) Tops dry matter produced
per unit of P taken up, (3) Tops dry matter produced at a constant plant P level and (4) Phosphorus uptake per unit root weight.
The order of efficiency varied according to the crieteria used. Using the agronomic definition (1), Serradella was the most
efficient species at 70 days.
The need to clearly define what is meant by an efficient species is demonstrated. 相似文献
149.
Using the C-banding technique, the morphology and meiotic behaviour of four different types of B-chromosomes present in several populations of Eyprepocnemis plorans have been studied. The possible relationship between these four types is discussed. The analysis of chiasma frequency in A and B-chromosomes suggests the existence of interchromosomal interference and demonstrates that the chiasma frequency of B-s depends on the genetic background of the individual carrying them. 相似文献
150.
NMR redox studies of Desulfovibrio vulgaris Cytochrome c3. Electron transfer mechanisms 总被引:1,自引:0,他引:1
J J Moura H Santos I Moura J LeGall G R Moore R J Williams A V Xavier 《European journal of biochemistry》1982,127(1):151-155
The 300-MHz proton NMR spectra of the tetrahaem cytochrome c3 from Desulfovibrio vulgaris were examined while varying the pH and the redox potential. The analysis of the complete NMR reoxidation pattern was done taking into account all the 16 redox states that can be present in the redox titration of a tetra-redox-center molecule. A network of saturation transfer experiments performed at different oxidation stages, between the fully reduced and the fully oxidized states, allowed the observation of different resonances for some of the haem methyl groups. In the present experimental conditions, some of the haems show a fast intramolecular electron exchange rate, but the intermolecular electron exchange is always slow. In intermediate reoxidation stages, large shifts of the resonances of some haem methyl groups were observed upon changing the pH. These shifts are discussed in terms of a pH dependence of the haem midpoint redox potentials. The physiological relevance of this pH dependence is discussed. 相似文献