Functional testing of hepatocytes following their recovery from cryopreservation

Various tests of function have been suggested for assessing hepatocytes recovered from cryopreservation. In this study we have investigated hepatocyte attachment during tissue culture and cellular density in order to assess function and compared them with two classical dye exposure tests. The ability of hepatocytes to exclude trypan blue dye (TB) and metabolize fluorescein diacetate (FDA) was demonstrated. In populations of freshly prepared hepatocytes 88.07% were able to exclude TB and 87.31% were able to metabolize FDA. However in populations of hepatocytes recovered after cryopreservation using 1.5 M dimethyl sulfoxide as cryoprotectant only 33.44% were able to exclude TB and 31.59% able to metabolize FDA. Both of these tests gave the same estimate of functional ability. Density gradient centrifugation of hepatocytes on Percoll 400 (Pharmacia, Uppsala, Sweden) separated two populations of hepatocytes; one (density ca.1.07 g/ml Percoll) in which most of the cells were able to exclude TB and the second (density ca. 1.02 g/ml Percoll) in which they were stained blue. The dense population was highly enriched in dye-excluding hepatocytes: freshly prepared hepatocytes, 92.4%, and cryopreserved hepatocytes, 88.66%. When samples of these cells (2 x 10(6) dye-excluding cells per dish) were tested for their ability to attach to tissue culture dishes only 17.28% of the cryopreserved hepatocytes were able to attach compared to 55.28% of the freshly prepared cells. We conclude that cryopreservation of hepatocytes produces a population of cells which are not metabolically identical to a population of freshly prepared hepatocytes even though they appear to have the same buoyant density and dye-excluding capabilities.(ABSTRACT TRUNCATED AT 250 WORDS)     

噬菌体φHAU3的cos位点及其与寄主相互作用的功能位点attP和attB的定位

ＨＡＵ３是寄主范围很广的放线菌噬菌体。Ｓｏｕｔｈｅｒｎ杂交实验表明,ＨＡＵ３可以整合到吸水链霉菌应城变种１０－２２和变铅青链霉菌６６的突变体ＺＸ１的染色体中,形成溶原,其溶原菌自发释放ＨＡＵ３,不受热激和紫外线照射的诱导。通过比较ＨＡＵ３衍生噬粒ｐＩＪ８３００的ＤＮＡ酶切片段在加热前、后电泳带谱的区别,将ＨＡＵ３的ｃｏｓ位点在ｐＩＪ８３００的图谱上得到了定位。还利用Ｓｏｕｔｈｅｒｎ杂交的方法定位了ＨＡＵ３与宿主形成溶原时附着位点（ａｔｔＰ）,并利用脉冲电泳技术定位了在变铅青链霉菌ＺＸ７和吸水链霉菌应城变种１０－２２中形成溶原的附着位点（ａｔｔＢ）。这些信息均有利于以ＨＡＵ３为基础的载体的发展和优化。     

羊草与其主要伴生种竞争与共存的格局分析

在羊草种群与其它植物种群的交错区,应用频度、格避形式,格局强度指数对羊草及其主要伴生种之间的共存格局进行了分析。结果表明,羊草及其主要伴生种的格局呈多样化,集聚格局形式是羊草抵御外来物种入侵,或者是自身扩散的一种对策,羊草与其主要伴生种之间存在竞争与共存作用,羊草与芦苇之间通过拮抗作用实现竞争与共存,羊草与鸡儿肠通过竞争而实现共存,光稃茅香,碱茅以营养繁殖策略实现与羊草竞争,指子茅的生长受羊草竞争的抑制。     

ATM requirement in gene expression responses to ionizing radiation in human lymphoblasts and fibroblasts

The heritable disorder ataxia telangiectasia (AT) is caused by mutations in the AT-mutated (ATM) gene with manifestations that include predisposition to lymphoproliferative cancers and hypersensitivity to ionizing radiation (IR). We investigated gene expression changes in response to IR in human lymphoblasts and fibroblasts from seven normal and seven AT-affected individuals. Both cell types displayed ATM-dependent gene expression changes after IR, with some responses shared and some responses varying with cell type and dose. Interestingly, after 5 Gy IR, lymphoblasts displayed ATM-independent responses not seen in the fibroblasts at this dose, which likely reflect signaling through ATM-related kinases, e.g., ATR, in the absence of ATM function.     

MR弥散加权成像对鉴别诊断良恶性椎体压缩性骨折的临床价值研究

目的：探讨MR弥散加权成像（DWI）鉴别诊断良恶性椎体压缩性骨折的临床价值。方法：对57例经临床或病理证实的椎体良恶性压缩性骨折患者行矢状位T1M、T2WI、T2WI／FS及DWI扫描,研究其在常规序列和DWI序列上的表现,将常规MR序列和DWI序列检出率进行比较,测量正常椎体及病变椎体的表观弥散系数（ADC）值,并进行统计学分析。结果：（1）MR常规序列和DWI序列（b=500s／mm2）表现：良性椎体压缩性骨折呈长T1长或等T2改变,T2WI／FS呈高信号,DWI可以呈高信号、等信号及低信号;恶性椎体压缩性骨折呈长T1长T2信号,大部分病灶T2WUFS及DWI呈高信号,少数变现为低信号;（2）MR常规序列和DWI序列（b=500s／mm2）病灶检出率的比较：T1WI、T2WI／FS及DWI序列病灶检出率均高于T2WI序列,其间的差别有显著性意义（P〈0．01）,T1WI、T2WI／FS及DWI序列病灶检出率之间无显著性差异（P〉0．01）;（3）ADC值比较：在DWI（b=500s／mm2）上,良性组ADC值为（2．03±0．83）×10^3mm^2/s,恶性组ADC值为（1．37±0．75）×10^-3mm^2/s,正常组ADC值为（0．36±0．21）×10^-3mm^2／s,成像条件相同时,良性组高于恶性组,两组间有明显的统计学意义（P〈0．05）。结论：DWI可较好的反映椎体的弥散特征,ADC值作为量化指标可对良恶性椎体压缩性骨折进行可靠鉴别。     

The role of hybridization in the origin and spread of asexuality in Daphnia

The molecular mechanisms leading to asexuality remain little understood despite their substantial bearing on why sexual reproduction is dominant in nature. Here, we examine the role of hybridization in the origin and spread of obligate asexuality in Daphnia pulex, arguably the best‐documented case of contagious asexuality. Obligately parthenogenetic (OP) clones of D. pulex have traditionally been separated into ‘hybrid’ (Ldh SF) and ‘nonhybrid’ (Ldh SS) forms because the lactase dehydrogenase (Ldh) locus distinguishes the cyclically parthenogenetic (CP) lake dwelling Daphnia pulicaria (Ldh FF) from its ephemeral pond dwelling sister species D. pulex (Ldh SS). The results of our population genetic analyses based on microsatellite loci suggest that both Ldh SS and SF OP individuals can originate from the crossing of CP female F₁ (D. pulex × D. pulicaria) and backcross with males from OP lineages carrying genes that suppress meiosis specifically in female offspring. In previous studies, a suite of diagnostic markers was found to be associated with OP in Ldh SS D. pulex lineages. Our association mapping supports a similar genetic mechanism for the spread of obligate parthenogenesis in Ldh SF OP individuals. Interestingly, our study shows that CP D. pulicaria carry many of the diagnostic microsatellite alleles associated with obligate parthenogenesis. We argue that the assemblage of mutations that suppress meiosis and underlie obligate parthenogenesis in D. pulex originated due to a unique historical hybridization and introgression event between D. pulex and D. pulicaria.     

Warm springs reduce parasitism of the cereal leaf beetle through phenological mismatch

Variation in weather among years may affect biological control of insect pests by influencing how well matched in phenology specialist parasitoids are with their pest hosts. A 10‐year study in western North America (Utah) revealed greater change with warm versus cool springs in the life cycle timing of the cereal leaf beetle (CLB), Oulema melanopus (L.), than of its principal enemy, the parasitoid wasp Tetrastichus julis (Walker). The beetle laid eggs, and larval populations developed in crop fields earlier on a calendar‐day basis, but nonetheless after more degree‐days had accumulated, in warmer than in cooler springs. The phenology of parasitism by wasps, in contrast, varied little among springs in relation to accumulated degree‐days. Consequently, in warmer springs, larval phenology of the CLB was delayed relative to adult parasitoid activity, and parasitism was reduced. Presently, a significant degree of biological control of the CLB results from parasitism by T. julis. By promoting phenological mismatch between host and parasitoid, however, a warming climate could weaken this biological control of the insect pest.