X-ray induced translocations in spermatogonia. I. Dose and fractionation responses in mice

The frequency of recirprocal translocations, inducedm by X-irradiation of mouse spermatogonial cells and observed at diakinesis-metaphase I in primary spermatocytes, was measured over a dose range of 0–1200 R. The resulting dose-response curve gave a best fit to the model Y = bD+CD² over the range of 0–500 R. Above 600 R, howeverm, the yeild of translocations decreased with increasing dose, leadiong to a “humped” dose-response curve over the whole dose range studied, as has been observed by several worker previously.The significance of the nonlinear dose-response curve over the lower dose range is discussed in terms of the known fractionation and dose-rate effects for reciprocal translocations induced in spermatogonia.A dose of 800 R was split into two 400-R fractions separated by 8 weeks, or one of 1200 R into three equal parts, each separated by an 8-week interval. The resulting yield of translocations was the same as the sum of two, or three, separate 400-dose doses, but was much higher than a single dose of 800 R or 1200 R.It is suggested that these results, namely the shape of the dose-response curve and the “reverse” fractionation effect, can be explained in terms of resistant and sensitive stem-cell populations, but that any one cell can be in either population, depending upon the stage of the cell cycle in which it is at the time of irradiation.     

Reaction center and antenna processes in photosynthesis at low temperature

Around 1960 experiments of Arnold and Clayton, Chance and Nishimura and Calvin and coworkers demonstrated that the primary photosynthetic electron transfer processes are not abolished by cooling to cryogenic temperatures. After a brief historical introduction, this review discusses some aspects of electron transfer in bacterial reaction centers and of optical spectroscopy of photosynthetic systems with emphasis on low-temperature experiments.Abbreviations (B)Chl (bacterio)chlorophyll - (B)Phe (bacterio)pheophytin - FMO Fenna-Matthews-Olson - LH1, LH2 light harvesting complexes of purple bacteria - LHC II, CP47 light harvesting complexes of Photosystem II - P, P870 primary electron donor - RC reaction center     

microRNAs参与韧带成纤维细胞成骨分化相关分子表达的调节

韧带成纤维细胞成骨分化与强直性脊柱炎等多种异位骨化相关性疾病有关,但其机制尚不清楚.本研究目的在于观察韧带成纤维细胞在成骨分化过程中microRNA和mRNA的表达谱变化,以期为揭示成纤维细胞成骨分化机制提供研究基础.原代培养韧带成纤维细胞、地塞米松、抗坏血酸和β 磷酸甘油体外诱导其成骨分化, RT-PCR检测成骨标志物骨钙素和Runx2的表达.采用表达谱基因芯片分析诱导0、7、14 d后韧带成纤维细胞的microRNAs和mRNAs表达,并用实时定量PCR（RT-qPCR）和Western印迹方法验证生物信息学分析结果.结果显示,与未诱导前相比,成骨分化第7 d有66个microRNAs和640个mRNA表达上调,94个microRNAs和744个mRNA表达下调;成骨分化第14 d有58个microRNAs和781个mRNA表达上调,96个microRNAs和603个mRNA表达下调.实时定量PCR和Western印迹验证结果显示,miR-29b在成骨分化过程中表达上调,TGFβ3表达水平降低,与芯片结果一致,miR-29b通过抑制TGFβ3蛋白的翻译来促进Runx2的表达,从而促进韧带成纤维细胞向成骨细胞分化.韧带成纤维细胞成骨分化过程中,microRNA调控基因及mRNA差异表达基因除涉及BMPs、Wnt和Ihh等信号通路外,在成纤维细胞成骨分化过程中可能还存在其它的新机制.     

The regulation of human exposure to mutagens amidst scientific controversy

Human peripherial lymphocytes were irradiated with different doses of 15.0-MeV neutrons. The frequency of different aberration types was determined and the dose-response relation was calculated. The data were fitted by least-squared regression analysis to different models. The dicetric, dicentric+centric ring, and different acentric data gave the best fit to the linear quadratic model. The RBE of 15.0-MeV neutrons versus 220 kV X-rays decreased significantly with increasing dose.     

Mutagenic effectiveness of 14.1 MeV neutrons and 200 kV X-rays at the dumpy complex locus of Drosophila melanogaster.

The effectiveness of 14.1 MeV neutrons relative to 200 kV X-rays for the induction of the various kinds of dumpy mutation in mature sperm of Drosophila melanogaster was investigated. The estimated RBE values are: 0.52 for all complete mutations; 0.64 for the (olv, ov) types; 0.33 for the (ol, lv, o, v, c) types; 0.33 for all fractional mutations. These data lend support to the thesis that (1) complete dumpy mutations of the olv and ov types are more frequently associated with chromosomal aberrations than those of the ol, lv, o, v and c types, and (2) fractional mutations and complete mutations of the (ol, lv, o, v, c) types are most probably point mutational events.     

Chromosomal rearrangements induced in mouse spermatogonia by 14.5-MeV neutrons

Inbred CBA male mice were irradiated with 14.5-MeV neutrons. Three acute doses, 75, 150 and 250 rad, and one chronic dose, 250 rad, were given. The percentages of affected spermatocytes as counted from reciprocal translocations which had been induced in spermatogonia were 0.7, 0.8 and 1.6 respectively for the acute series and 2.2 after chronic exposure. The data could be fitted to a linear or concave curvilinear regression line. There seemed to be a slight increase of damage with dose, even if the percentages were generally lower than those reported earlier for fast neutrons with energies around 1 MeV. The existence of dose-rate effects is discussed, and the conclusion drawn so far is that there seems to be no such effect either for 1-MeV fast neutrons or 14.5-MeV high energy neutrons. The term “reversed dose-rate effect”, as used earlier, relates to another phenomenon. The difference between the point estimates for the chronic and acute 250 rad series is not significant. The effectiveness of neutrons with energies around 14 MeV versus neutrons with energies around 1 MeV is discussed.     

Cryptomonad biliproteins: Bilin types and locations

Two crytophycean phycocyanins (Cr-PCs), Hemiselmis strain HP9001 Cr-PC 612 and Falcomonas daucoides Cr-PC 69 were purified and characterized with respect to bilin numbers, types and locations. Each biliprotein carried one bilin on the subunit and three on the subunit. Cr-PC 612 carried phycocyanobilin at -Cys-18, -Cys-82, and -Cys-158, and a doubly-linked 15,16-dihydrobiliverdin at -DiCys-50,61. Cr-PC 569 carried phycocyanobilin at -Cys-18 and -Cys-82, a singly-linked Bilin 584 at -Cys-158, and a doubly-linked Bilin 584 at -DiCys-50,61. This work, in conjunction with earlier studies on Cr-PE 545, Cr-PE 555, Cr-PE 566, and Cr-PC 645, shows that there is no conserved location for the bilin with longest wavelength visible absorption band among these proteins, and, consequently, that there is no conserved energy transfer pathway common to all native cryptophycean biliproteins. Only phycocyanobilin or phycoerythrobilin is found at -Cys-82; there is greater bilin variability at the other three attachment sites.Abbreviations Cr-PC cryptophycean phycocyanin - Cr-PE cryptophycean phycoerythrin - DBV 15,16-dihydrobiliverdin - MBV mesobiliverdin - PCB phycocyanobilin - PEB phycoerythrobilin - HPLC high performance liquid chromatography - TFA trifluoroacetic acid     

Radiation-induced human chromosome aberrations. II. Human in vitro irradiation compared to in vitro and in vivo irradiation of marmoset leukocytes

Whole blood cultures from humans and from the New World primate, Saguinus fuscicollis, were irradiated with various doses of 250 kV X-rays. The resulting centric ring plus dicentric aberration yields were fitted to the three models, Y = a+bD, Y = a+bD+cD², and Y = a+cD², by least squares regression. In both instances the best fit was to the model Y = a+bD+cD², with coefficients of the one- and two-track components for human and marmoset being: b = (0.78 ± 0.09)·10⁻³, c = (5.92 ± 0.31)·10⁻⁶, and b = (1.11 ± 0.36)·⁻³, c = (7.7 ± 1.7)·10⁻⁶, respectively.     

Comparative study of gamma-ray and high-energy carbon ion irradiation on negative gravitaxis inEuglena gracilisZ

The effects of ⁶⁰Co gamma-ray and 290 MeV/amu carbon ion irradiation on negative gravitaxis was studied in the photosynthetic flagellate Euglena gracilis strain Z in a dose-response dependent manner. Cells were exposed to the doses (0-200 Gy for water). The negative gravitaxis was quantified by the r-value observed in a recently developed biomonitoring system. The present results demonstrate the inhibitory effects of gamma-rays and 290 MeV/amu carbon ions on negative gravitaxis of the Euglena gracilis strain Z. The 290 MeV/amu carbon ions had a greater impact at a low dose (<40 Gy) than the ⁶⁰Co gamma-rays.     

辐射相关microRNA研究进展

microRNA(miRNA)是一类由内源基因编码的长度约22核苷酸的非编码单链RNA分子,主要以碱基互补方式与靶基因mRNA的3'非翻译区特异性结合,通过降解mRNA或抑制蛋白翻译合成而实现对靶基因的转录后调控。研究发现,miRNA在电离辐射诱导的生物学反应中发挥重要作用。我们从以下层面概述辐射相关miRNA的研究进展,即辐射调节miRNA表达、miRNA对辐射后DNA损伤的调节、miRNA参与的辐射生物学效应。     

低能铁离子束对原卟啉IX二钠盐的辐照效应研究

110ke V Fe^ 离子注入原卟啉IX二钠盐薄膜亲品后的一些谱学分析结果表明,低能铁离子束辐照可以导致生物分子的损伤和化学改性,并且初步证实注入铁离子在样品分子中慢化沉积后形成含铁的金属络合物,即注入铁离子的质量沉积。     

原卟啉IX二钠盐的低能铁离子束辐照产物对实验性小鼠再生障碍性贫血的疗效初步研究

利用110keV Fe^ 离子注入原卟啉IX二钠盐薄膜,动物实验和细胞学观察等表明辐照混合产物对于治疗^60Coγ射线所致实验性小鼠再生障碍性贫血具有一定的疗效,且无明显的毒副作用,有望从中筛选治疗再生障碍性贫血的新药或其先导化合物。