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921.
J C Lambert G Vallette G E Seralini R Vranckx E Nunez C Stora 《Comptes rendus de l'Académie des sciences. Série III, Sciences de la vie》1986,302(9):353-358
Data are presented which indicate a possible action of alpha-fetoprotein (AFP) on female germinal cells. The in vitro maturation of mature mice oocytes was significantly inhibited when mouse AFP replaced albumin in the culture medium. In addition, the degenerative aspect of oocytes cultured with AFP seemed to indicate that this me?otic inhibition was caused by a premature degeneration of oocytes rather than by a blockage at a specific stage of maturation. Thus AFP, perhaps through its ligands, may play a role in the reduction of germinal cells during fetal and immediate post-natal life rather than in the arrest of me?osis at the diplotene stage. 相似文献
922.
Reactive line-shape narrowing in low-temperature inhomogeneous geminate recombination of CO to myoglobin 总被引:4,自引:0,他引:4
N Agmon 《Biochemistry》1988,27(9):3507-3511
The temporal shift in the near-IR absorption peak of myoglobin (Mb) following flash photolysis of MbCO at cryogenic temperatures appears to be due largely to an inhomogeneous reactive process rather than to relaxation. This conclusion, which follows from a new analysis of the experimental data, is based on the following three points: First, at very low temperatures (60 K) a transient line-narrowing effect can be detected. Second, there is a universal, temperature-independent, correlation between spectral shift and survival probability in the rebinding kinetics, and third, the same quantitative model which accounts for rebinding accounts semiquantitatively for the temporal shift in the peak. A fit to the model indicates that the inhomogeneous broadening of the near-IR peak in myoglobin is 15-20% of the total width. The same rebinding process which governs the loss of intensity of this peak is therefore most likely responsible for the shift in its center wavelength. 相似文献
923.
924.
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926.
927.
O G Ianovski? L A Zakharova A M Vasilenko 《Biulleten' eksperimental'no? biologii i meditsiny》1990,109(1):55-57
In addition to the immunostimulating activity, bone marrow mediators, myelopeptides (MP) show the dose-dependent effect on the development of pain sensitivity in mice. When injected in nanogram amounts, MP induce hyperalgesia and 3-9 fold higher production of antibodies against SREC. When injected in milligram amounts, they exhibit hypoalgesic effect and no influence on antibody production. Immunostimulating effect in MP (mol, mass less than 1 KD, fraction 3) is accompanied with hypoalgesia. Bone marrow factors of mol. masses 40-150 KD (fraction 1) eluted at Sephadex G-25 gel-filtration before MP enhance the pain sensitivity tHreshold and show a potent immunodepressive effect. Thus the bone marrow factors are capable of exhibiting the opposite effects on the immune system in the pain control system that evidences the tight interrelation between these systems. 相似文献
928.
R. Shainkin-Kestenbaum C. Caruso G. M. Berlyne 《Biological trace element research》1991,28(3):213-221
The effect of nickel on superoxide dismutase activity (SOD), as well as on rate of hydroxydopamine oxidation, was studied in vitro since lipid peroxidation has been implicated in cell damage by nickel, whose toxicity and carcinogenicity are well established. Nickel strongly inhibits SOD activity. The degree of inhibition is directly proportion to the nickel concentration (tested range 0.066 to 0.33 microgram/mL in the reaction mixture); to the substrate concentration (tested range 0.4 x 10 4M to 1.1 x 10 4M 6-hydroxydopamine); and to reaction mixture. Autoxidation of 6-hydroxydopamine was increased by nickel concentrations higher than 15 micrograms/mL. The combination of excessive oxygen free radical production and inhibition of their elimination by inhibition of SOD activity may contribute to the nickel toxicity that has been reported in industrial accidents, as well as to the high incidence of cancer occurring in nickel workers. It may also contribute to many complications in uremic patients, in whom increased serum nickel levels were reported to be in a similar range to those inhibiting SOD. 相似文献
929.
E. R. R. Rochedo L. F. C. Conti H. G. Paretzke 《Radiation and environmental biophysics》1996,35(4):243-261
The structure and mathematical model of PARATI, a detailed computer programme developed for the assessment of the radiological
consequences of an accidental contamination of urban areas, is described with respect to the scenarios used for the estimation
of exposure fields in a village or town, the models for the initial and secondary contamination with the radionuclide 137Cs, the concepts for calculating the resulting radiation exposures and the changes with time of the contamination and radiation
fields. Kerma rates at various locations in tropical urban areas are given, and the contribution of different contaminated
surfaces to these rates after dry or wet deposition are discussed.
Received: 12 April 1996 / Accepted in revised form: 30 August 1996 相似文献
930.
High levels of expression of full length human pro-alpha 2(V) collagen cDNA in pro-alpha 2(V)-deficient hamster cells 总被引:2,自引:0,他引:2
A full length cDNA encoding human pro-alpha 2(V) collagen was constructed. Partial sequencing of the cDNA and primer extension analysis of mRNA from fibroblasts found that pro-alpha 2(V) mRNA differs from the mRNAs of other fibrillar collagens in the increased length of its 5'-untranslated region. The pro-alpha 2(V) cDNA was placed downstream of the human cytomegalovirus immediate early promoter/regulatory sequences for expression studies in cultured Chinese hamster lung cells. These cells have been shown previously to synthesize large quantities of pro-alpha 1(V) homotrimers as their only collagenous product. Transfection resulted in a number of clonal cell lines that express human alpha 2(V) RNA at levels comparable to, and in some cases greater than, levels found in normal human skin fibroblasts. Pro-alpha 2(V) chains produced in the majority of clonal lines were of sufficient quantity to complex all available endogenous pro-alpha 1(V) chains. Chimeric heterotrimers, composed of hamster alpha 1(V) and human alpha 2(V) chains in a 2:1 ratio, were stable to pepsin digestion and were found predominantly associated with the cell layer. Surprisingly, pro-alpha 2(V) chains, in excess to pro-alpha 1(V) chains, were found in the extracellular matrix and, in much greater abundance, in media. These chains were pepsin sensitive, indicating that pro-alpha 2(V) chains can be secreted as nonstable homotrimers or as free chains. 相似文献