大剂量~(60)Co照射后造血干细胞潜在的残留损伤

本文对受到临界全致死剂量——8.5Gy~(60)Co照射后的小鼠造血干细胞(HSC)的自我更新力进行了测试,并对照射后4个月,造血功能业已恢复的小鼠HSC的造血重建功能进行了研究。结果表明:应用骨髓连续移植实验所测得的照后3个月中骨髓CFU_s的自我更新潜能明显衰退了。用照射后造血恢复小鼠的CFU_s给全致死剂量照射的受体进行移植治疗,发现其移植效力比正常的显著减弱。在受体存活30天时,CFU_s的再生速率只有正常的1/17。通过对性染色体追踪观察的资料分析,此种小鼠的??造血细胞在受体中难以形成长期稳定的嵌合体。以上事实反映出,照射后小鼠的HSC的造血重建功能大大削弱了,揭示出残存干细胞质量上的缺陷。对于这种潜在的残留损伤的机制,从“干细胞增殖力耗竭学说”和“基因自我修整假说”的角度进行了讨论。     

Spatial and temporal localization of FGF receptors in Xenopus laevis

Summary Mesoderm formation is a result of cell-cell interactions between the vegetal and animal hemisphere and is thought to be mediated by inducing peptide growth factors including members of the FGF and TGF superfamilies. Our immunochemical study analyses the distribution of FGF receptors coded by the human flg gene during embryogenesis of Xenopus laevis. Immunostaining was detected in the dorsal and ventral ectoderm and also in the marginal zone of early cleavage, blastula and gastrula stages. Signals were very strong in the mid and late blastula (stage 8 and 9) and declined slightly in the early gastrula (stage 10). A dramatic decrease was observed up to the late gastrula (stage 11⁺). In stage 13 embryos, immunostaining was only found in cells around the blastopore. Isolated ectoderm cultured in vitro showed a similar temporal expression and decrease of the signal as the normal embryos. These results indicate that receptor expression is independent of the interaction of the animal cells with the vegetal part of the embryo. Of interest is the fact that the signal cannot only be found at or near the cell surface but also within the cell. This suggests the presence of an intracellular isoform of the receptor resulting from the endogenous expression of splice variants and the internalization of transmembrane receptor. Taken together our results suggest that the loss of competence (for bFGF around stage 10) is not directly correlated with the presence of receptors. The possible roles of heparan sulphate glucosaminoglycans (low affinity receptors) and control mechanisms in the intracellular signalling pathway downstream of the receptor level should be taken into consideration.     

Application of good laboratory practice (GLP) to culture collections of microbial and cell cultures

Although the principles and the necessity for good laboratory practice (GLP) guidelines to confirm the credibility, integrity, and quality of non-clinical laboratory studies have been known for more than a decade, culture collection activities are not subject to them. Because of recent advances in biotechnology, culture collections face increased demands not only for quality cultures but also current information. When applied in culture collections, GLP guidelines prove to be an excellent management tool as well as a cost-effective system of providing authentic and reliable microbial and cell cultures and associated data.     

外胚层细胞诱导后的间隙连接

用电镜观察了经受诱导作用之后胚胎细胞的冷冻蚀刻复型膜。和未经诱导作用的对照组比较,早期和中期神经胚的神经上皮细胞以及经过豚鼠骨髓粗提液(BME)——一种有效的异源中胚层诱导物——处理过的早期原肠胚外胚层,它们的间隙连接都处于活跃的动态状态。用图像分析仪测得的间隙连接连接子的排列密度,指出经受过诱导作用的三组分别和未经受诱导作用的对照组比较,计算求出P值,神经上皮两组和对照组的差别为非常显著,BME处理过的细胞和对照组的差别为显著。结合对照组与诱导后胚胎细胞间隙连接连接子的变化讨论了它们在信息传递上可能起的作用。     

Distribution and recovery of15N after fertilization of Douglas-fir saplings with different nitrogen sources

Summary Four-year-old Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) saplings planted in pots with a sand and peat mix (11) were fertilized at the rate of 200 kg N/ha of (¹⁵NH₂)₂CO (U-15),¹⁵NH₄NO₃ (A-15) and NH₄ ¹⁵NO₃(An-15). They were placed in a shadehouse and watered regularly to maintain soil moisture at field capacity over periods of one and two years. Quantity of¹⁵N in foliage generally increased from old to current growth, irrespective of the nitrogen source. Utilization of¹⁵N fertilizers by saplings after the first and second growing seasons following fertilization was greatest with nitrate labelled ammonium nitrate AN-15, and nearly equal for urea U-15 and ammonium labelled ammonium nitrate A-15. The soil immobilized more fertilizer nitrogen-15 from U-15 and A-15 than from AN-15. Data from the present study, in which leaching losses of fertilizer were minimized, demonstrated that in terms of nitrogen uptake by the saplings the nitrate fertilizer was superior to ammonium fertilizer.     

Distribution of N,P, K,Ca, Mg,S, Zn,Fe, Mn and Cu in groundnut

Summary Concentration of N, P, K, Ca, Mg and S in summer groundnut crop was higher than in kharif while Zn, Fe, Mn and Cu contents were higher in summer crop. Kernel's N, P and Zn; Leaflet's Ca and Mn; Stem's K and Fe; Root's S and Cu and Petiole's Mg contents were highest. Shell's N, P, K, Mg, S, Zn and Cu; Kernel's Ca, Fe and Mn contents were the least. N, P, K, S, Zn and Cu concentrations decreased linearly as the crop grew. Ca, Mg, Fe and Mn concentrations did not display any distinct pattern. Ca concentration was positively correlated with pod yield in both the seasons.     

内吞作用与胚胎诱导

在两柄类胚胎初级诱导的研究中,诱导物质如何进入反应细胞是一个受到重视(Grunzand Staubach,1979;Toivonen,1979)、但是仍未能解决的问题。为了对这一问题有所阐明,进行了离体诱导实验和电镜的观察。东方蝾螈(Cynops orientalis)早期原肠胚的外胚层块用豚鼠骨髓粗提液(BME)——有效的中胚层诱导物(Toivonen,1953)——处     

Patterns of protein synthesis during the germination of pea axes,and the effects of an interrupting desiccation period

As germination of axes of Pisum sativum L. seeds progressed, profound quantitative and qualitative changes occurred in the patterns of protein synthesis. This was shown by fluorography of gels following two-dimensional polyacrylamide gel electrophoresis separation of [³⁵S]methioninelabelled proteins. The effects of desiccation during germination on these in-vivo protein-synthesis patterns were followed. Desiccation differentially affected the synthesis of proteins. Usually, however, upon rehydration following desiccation the types of proteins being synthesized were recognizable as those synthesized earlier during imbibition of control, once-imbibed axes: seeds imbibed for 8 h, and then dried, did not recommence synthesis of proteins typical of 8-h-imbibed control seeds, but rather of 4-h-imbibed control seeds. Seeds imbibed for 12 h, and then dried and rehydrated, synthesized proteins typical of 4-h-and 8-h-control seeds. Thus drying of germinating pea axes caused the proteinsynthesizing mechanism to revert to producing proteins typical of earlier stages of imbibition. Drying during germination never caused the seed to revert to the metabolic status of the initial mature dry state, however.Abbreviation DR dried and rehydrated     

Early ontogeny of Adinia xenica (Pisces,Cyprinodontiformes): 3. Comparison and evolutionary significance of some patterns in epigenesis of egg-scattering,hiding and bearing cyprinodontiforms

Synopsis Developmental patterns as seen in cyprinodontiforms fishes with different reproductive styles are compared, and discussed in relation to ecology and evolutionary significance. The discussion centres around Adinia xenica (its detailed ontogeny presented in two previous sequels to this paper), and, from the existing literature, Fundulus heteroclitus (closely related), Austrofundulus myersi (an annual) and Platypoecilus maculatus (a livebearer). The embryonic resting interval is present in various forms in the first three species, and differences in it and the overall patterns of development are shown to be consistent with ecological conditions. Termination of the resting interval leads immediately to hatching, a process in A. xenica, as in F. heteroclitus, apparently initiated by the appropriate summation of internal and external factors. These factors include any or all of: metabolic changes and increased oxygen requirements, response to light, reduced environmental oxygen, agitation, and increased hydrostatic pressure. They all can cause increased movement by the embryo which is credited with rupturing hatching gland cells and releasing the enzyme(s). Annual fishes experience 3 pronounced resting intervals, termed diapauses. These are discussed in the context of apparent steps and thresholds, and evolutionary ecology. A possible evolutionary sequence, from a simple fractional spawning pattern to diapause, is presented. Morphological differences in primary embryonic respiratory surfaces, as seen in the four species, are related to environmental conditions. The above illustrate ways in which the same basic structures and events are modified to cope with different habitats.     

Effect of soil temperature on stem sap flow,shoot gas exchange and water potential of Picea engelmannii (Parry) during snowmelt

Summary The effect of cold soils on stem sap flow, shoot gas exchange and water potential of Picea engelmannii (Parry) was investigated during the snowmelt period in the Medicine Bow Mountains, Wyoming, USA. Shoot net photosynthetic rates were higher in young trees (1.5–1.8 m in height) growing in cold soils (<3.5° C) associated with snowpack, than trees in warm soils until about 1500 h. Higher shoot photosynthetic rates of trees in cold soils continued after snow was removed and could not be completely explained by higher visible irradiance over highly reflective snow. Following soil warming higher photosynthetic rates were evident in these trees for five days. High nutrient availability associated with snowmelt may improve shoot nutrient status leading to higher gas-exchange rates during snowmelt. Shoot conductance to water vapor was higher in trees in cold soil until midday, when declining shoot conductance led to lower intercellular CO₂ concentrations. Midday through afternoon shoot water potentials of trees in cold soils were similar or higher than those of trees in warm soils and the lower afternoon shoot conductances in cold soils were not the result of lower bulk shoot water potentials. Decline in net photosynthesis of trees in cold soils at 1500 h paralleled increases in intercellular CO₂ concentrations, implying a nonstomatal limitation of photosynthesis. This scenario occurred consistently in mid-afternoon following higher morning and midday photosynthesis in cold soils, suggesting a carbohydrate feedback inhibition of photosynthesis. Diurnal patterns in stem sap flow of all trees (cold and warm soils) reflected patterns of shoot conductance, although changes in stem sap flow lagged 1–3 h behind shoot conductance apparently due to stem water storage. Total daily stem sap flow was similar in trees in cold and warm soils, although diel patterns differed. The morning surge and night-time drop in sap flow commenced 1–2 h earlier in trees in cold soils. Overnight stem sap flow was lower in trees in cold soils, possibly due to higher resistance to root water uptake in cold soils, which may explain lower predawn shoot water potentials. However, midday shoot water potentials of trees in cold soils equalled or exceeded those of trees in warm soils. Higher resistance to root water uptake in P. engelmannii in cold soils was apparently overshadowed by transpirational forces and significant shoot water deficits did not develop.