A proton nuclear Overhauser effect investigation of the subunit interfaces in human normal adult hemoglobin

High-resolution proton nuclear magnetic resonance spectroscopy and nuclear Overhauser effects for the low-field exchangeable proton resonances of human normal adult hemoglobin in aqueous solvents are being used to confirm and extend the assignments of these resonances to specific protons at the intersubunit interfaces of the molecule. Most of these exchangeable proton resonances of human normal adult hemoglobin have been found to be absent in the spectra of isolated alpha or beta subunits. This finding indicates that they are specific spectral markers for the quaternary structure of the hemoglobin tetramer. Based on the nuclear Overhauser effect results, we have assigned the exchangeable proton resonance at +7.4 ppm downfield from H2O to the hydrogen-bonded proton between alpha 103(G10)His and beta 108(G10)Asn at the alpha 1 beta 1 interface. The nuclear Overhauser effect results have also confirmed the assignments of the exchangeable proton resonances at +9.4 and +8.2 ppm downfield from H2O previously proposed by workers in this laboratory based on a comparison of human normal adult hemoglobin and appropriate mutant hemoglobins. This independent confirmation of previously proposed assignments is necessary in view of the possible long-range conformational effects of single amino-acid substitutions in mutant hemoglobin molecules.     

季节、环境温度与黄鼠冬眠的关系

观察了达乌尔黄鼠在实验室内冬眠的一般情况。常温黄鼠的体温有着规律性的年周期,与环境温度的年周期变动不完全呈依从关系。出眠初期(4月下旬),动物体温高而稳定。4月至6月常温黄鼠的平均体温(皮温)为35.6℃,波动菹围32—37.5℃。随着体重达到顶峰,体温逐渐降低。8月份部分黄鼠出现低于32℃的低常体温,表明部分黄鼠自8月盛夏开始冬眠。但就整个种群而言,北京地区实验室内黄鼠冬眠季自9月下半月开始。3月底止,共6.5个月。秋季室温下降,动物入眠趋势增长。浅低体温(31.9—15℃)的比数逐渐升高。9月至12月,低体温(低于31.9℃)的百分比从47％增至84.8％,反映了动物从浅冬眠向深冬眠过渡。1月至2月份,低体温占85％以上,深低体温(低于15℃)占绝对优势。标志着动物种群的深眠月份。秋季动物从常温期向冬眠期转化的界线是不清的,而春季从冬眠期向常温相转化的界限却比较明显。     

记辽宁东部新鳞齿鱼属一新种

本文记述了产自辽宁东部红庙子盆地下桦皮甸子组的新鳞齿鱼属—新种——Neolepidotes liaodongensis sp. nov..根据新材料,将 Neolepidotes 与 Lepidotes 等属作了补充比较,增订了新鳞齿鱼属的特征.     

初期采脂对马尾松木材构造的影响

广东省韶关林场采用标准的采脂工艺,在其马尾松人工林进行了两年的初期采脂试验。 在这些马尾松的采脂树的采脂盘上,主要呈现泌脂和木材增生,而在其下方距离0.5m的影响盘上。仅有一些创伤轴向树脂道和树脂囊。创伤树脂道使其邻近的轴向管胞的形状不规则,又与树轴倾斜近45°。 从山中试验区不同的松树林分,在其对照盘(对照树的)、影响盘上,自髓向外每隔一个生长轮的离析材料;另在采脂盘上密切邻近采脂面两侧,自圆盘周围向内各选4轮材料;分别测定轴向管胞的长度,得知这些30(20)年生的马尾松树仍在幼态期间,其管胞长度一般是增加的;至于采脂面两侧的管胞却显出不同程度的减短,其中一些管胞呈现种种不规则形状。     

Stages of B-lymphocyte differentiation in acute lymphoblastic leukemia

Blasts phenotype was determined in 61 children with the acute lymphoblastic leukemia. Non-T-cell acute lymphoblastic leukemia was diagnosed in 51 children. Stages of blasts differentiation were determined with the aid of monoclonal antibodies set using alkaline phosphatase-anti-alkaline phosphatase technique. Blasts in 50 patients belonged to B subpopulation confirmed by the presence of panB CD19 and CD22 antigens. Common antigen was seen in 76.5% of the examined patients with non-T-cell acute lymphoblastic leukemia. Cases of non-T-cell acute lymphoblastic leukemia were divided into 8 subgroups depending on the antigens of B-cells differentiation. An identification of pre-B subgroups of the acute lymphoblastic leukemia indicates heterogenicity of the acute lymphoblastic leukemias in childhood and enables their classification into groups corresponding to the early stages of lymphoblasts maturation.     

E.p.r.-spectroscopic studies on the molybdenum-iron site of nitrogenase from Clostridium pasteurianum.

The e.p.r. spectroscopy of the nitrogenase molybdenum-iron protein from Clostridium pasteurianum was re-investigated. The sharpness of the delta Ms = +/- 3 g'z peak from the +/- 3/2 Kramer's doublet enables the observation and quantification of incompletely resolved hyperfine splittings from the stable magnetic nuclei 95Mo and 57Fe in samples enriched in these isotopes. No couplings to 1H or 17O could be discerned by examination of spectra from samples exchanged into 2H2O and H2(17)O respectively. Simulation of the spectrum from 95Mo-enriched samples yields a hyperfine coupling of 2.9 MHz, and indicates that the earlier electron-nuclear-double-resonance-derived estimate of 8.1 +/- 0.2 MHz is substantially in error.     

Genetic convergence during serial in vitro passage of a polyclonal squamous cell carcinoma

A cell line was established from an in situ squamous cell carcinoma of the skin (Bowen's disease), and its in vitro karyotypic evolution was cytogenetically analyzed. Initially, considerable genetic heterogeneity was evident. Nine cytogenetically abnormal clones, eight of which were apparently unrelated, were found among the 83 metaphases analyzed from the primary culture and the first passage. With increasing time in culture this complexity was reduced, so that a single clone dominated passages 7-11. The clone that emerged from this genetic convergence had a t(12;17)(p13;q21) as the sole abnormality. Our findings indicate that the cytogenetic multiclonality that has been repeatedly detected in short-term cultures of squamous cell carcinomas is not caused by the in vitro conditions. Instead, the principles of Darwinian selection apply: the altered, but stable, selection pressure facing a newly established and initially multiclonal cell line will lead to a reduction of genetic heterogeneity until the one clone that now has the proliferative advantage outgrows the other subpopulations.