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111.
In order to regulate cell volume during hyperosmotic stress, the intertidal copepod Tigriopus californicus, like other aquatic crustaceans, rapidly accumulates high levels of intracellular alanine, proline, and glycine. Glutamate-pyruvate transaminase (GPT; EC 2.6.1.2), which catalyzes the final step of alanine synthesis, is genetically polymorphic in T. californicus populations at Santa Cruz, California. Spectrophotometric studies of homogenates derived from a homozygous isofemale line of each of the two common GPT alleles indicated that the GPTF allozyme has a significantly higher specific activity than the GPTS allozyme. Under conditions of hyperosmotic stress, individual adult copepods of GPTF and GPTF/S genotypes accumulated alanine, but not glycine or proline, more rapidly than GPTS homozygotes. When young larvae were subjected to the same hyperosmotic conditions, GPTS larvae suffered a significantly higher mortality than GPTF or GPTF/S larvae. These results suggest that the biochemical differences among GPT allozymes result in specific physiological variation among GPT genotypes and that this physiological variation is manifested in differential genotypic survivorships under some naturally occurring environmental conditions.This work was supported in part by a grant from the Lerner Fund for Marine Research of the American Museum of Natural History, an NIH Training Grant in Integrative Biology, and NIH Grants GM 28016 and GM 10452. 相似文献
112.
113.
Deoxyribonucleic Acid Synthesis in Ultraviolet-Light-Irradiated Chinese Hamster Cells 总被引:2,自引:0,他引:2
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Two mammalian cell lines, Chinese hamster ovary (CHO) which can recover colony-forming ability between fractionated doses of ultraviolet light (UV), and Chinese hamster B-14FAF28 which cannot recover, were tested for the ability to bypass UV-induced photoproducts in DNA during postirradiation DNA synthesis. The molecular weight distributions of newly synthesized DNA in UV-irradiated populations of both cell lines showed evidence for photoproduct bypass. Hence, the bypass mechanism does not correlate with recovery after UV. 相似文献
114.
Properties of Hamster Embryo Fibroblasts Transformed In Vitro After Exposure to Ultraviolet-Irradiated Herpes Simplex Virus Type 2 总被引:53,自引:30,他引:23
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An in vitro method which led to the transformation of hamster embryo fibroblasts after exposure to herpes simplex virus type 2 (HSV-2) inactivated with ultraviolet irradiation is described. The transformed cells (333-8-9) produced tumors when inoculated into newborn Syrian hamsters but not when injected into weanling Syrian hamsters of the same LSH inbred strain. However, after one in vivo passage, the 333-8-9 cells became highly oncogenic in weanling hamsters. No infectious virus was recovered from these cells. Herpes simplex virus antigens were detected in the transformed cells by the indirect immunofluorescence technique. Sera from tumor-bearing hamsters contained antibody with highly specific neutralizing activity against HSV-2. These studies indicate the continued involvement of the HSV-2 genome in an oncogenic cell line. 相似文献
115.
NUCLEAR-CYTOPLASMIC RELATIONS IN THE MITOSIS OF SEA URCHIN EGGS : III. γ-Ray-Induced Damage to Whole Eggs and Nucleate and Anucleate Half-Eggs
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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)
Sea urchin eggs were cut into halves. The nucleate and anucleate halves and whole eggs were irradiated with γ-rays and then fertilized with normal sperm. The first mitosis of the diploid half-egg was more delayed than the division of the whole egg. There was a small, but highly significant, delay of the mitosis of the haploid half-egg, thus demonstrating cytoplasmic sensitivity to ionizing radiation. Since the sensitivity of nucleate cells is influenced by cytoplasmic volume, the problem of the role of cytoplasm in repair is considered in relation to these data and other reports in the literature. 相似文献
116.
117.
Howard L. Clark J.F.M. Ronald L. Stuckey J.W.T. R.E.S. B. Lowy Thomas C. Rambo 《Economic botany》1974,28(2):237-244
118.
The applicability of two methods (pyrolysis gas chromatography and acidification-wet oxidation) for determining14CO2 incorporation into soil microorganisms was investigated. Both methods were able to distinguish biologically incorporated14C from abiotically adsorbed14C, but to varying degrees, there being a larger carryover of abiotic14C into the organic fraction and a higher percentage of assimilated14C in the organic fraction with the wet oxidation method. Using14C assimilation as a measure, it was possible to determine microbial activities in soils of diverse properties under a variety
of conditions, including polar soils under harsh environmental conditions. Both light and dark14CO2 fixation was measurable.14CO2 assimilation was not always proportional to the enumerable microorganisms. A new design for measurement of microbial activityin situ enabled measurement of total C influx (primary productivity) into soils with minimal perturbation to the natural soil ecosystem. 相似文献
119.
Since the introduction of “staging laparotomy” (to determine the disease''s stage) in assessing Hodgkin''s disease, some observers have argued that lymphangiography could be safely omitted in the initial diagnostic evaluation.To test these opinions a series of 75 patients with Hodgkin''s disease who had a staging laparotomy and histological correlation with lymphangiograms was reviewed. Of 16 examinations with positive results, one proved to be a false positive. Of the 14 examinations with equivocal results, one proved histologically positive. In the remaining 45 lymphangiograms, five were falsely negative. In all five of these patients abdominal lymph nodes were involved, but in areas that do not routinely opacify on lower extremity lymphangiography. The overall accuracy was 90 percent.Therapeutically, the lymphangiogram permits accurate planning for treatment by radiation therapy so that all known disease is treated and yet bone marrow is not excessively irradiated. Changes in lymph node architecture after therapy provide valuable information as to regression of the disease or signs of its early recurrence. 相似文献
120.
Preliminary characterization of Thy-1.1 and Ag-B antigens from rat tissues solubilized in detergents 总被引:12,自引:4,他引:8
Michelle Letarte-Muirhead Ronald T. Acton Alan F. Williams 《The Biochemical journal》1974,143(1):51-61
1. A radioactive binding assay for Thy-1.1 alloantigen which functions in the presence of detergents was established by using glutaraldehyde-fixed thymocytes as target cells. Thy-1.1 activity in detergent extracts was then assayed by measuring inhibition of the binding assay. 2. Solubilization of Thy-1.1 from whole thymocytes, and their membranes by a large number of non-ionic detergents and deoxycholate was studied. In the same extracts Ag-B(4) histocompatibility antigenic activities were measured. With the exception of Nonidet P-40, the detergents did not affect the antigenicity of Thy-1.1, but only Lubrol-PX and deoxycholate gave effective solubilization as measured by activity remaining in the supernatant after centrifugation at 200000g for 40min. With Ag-B(4) antigen, Triton X-100, Triton X-67 and Nonidet P-40 gave effective solubilization as well as Lubrol-PX and deoxycholate. Solubilization of Thy-1.1 activity from leukaemia cells and a brain homogenate was also studied, but none of the non-ionic detergents gave satisfactory results with these tissues. 3. Extracts from thymocyte membranes were further examined by gel filtration and sucrose gradient centrifugation. The Thy-1.1 activity behaved as a single component in deoxycholate with a density similar to that of a globular protein, but in Lubrol-PX the antigen was contained in a low-density complex. In Lubrol-PX extracts Ag-B(4) was also found in aggregates not observed in deoxycholate. 4. The s(20,w) values for Thy-1.1 and Ag-B(4) antigens in deoxycholate were 2.4 and 4.4, and v values were 0.70 and 0.75 respectively. The Stokes radius observed for Thy-1.1 was 3.1nm and for Ag-B(4) 5.3nm. By using these values the molecular weights for the antigen-detergent complexes were calculated to be 28000 for Thy-1.1 and 100000 for Ag-B(4). 相似文献