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201.
Regulation of gene expression in adult rat hepatocytes cultured on a basement membrane matrix 总被引:26,自引:0,他引:26
E G Schuetz D Li C J Omiecinski U Muller-Eberhard H K Kleinman B Elswick P S Guzelian 《Journal of cellular physiology》1988,134(3):309-323
Freshly isolated adult rat hepatocytes, when cultured on type I collagen (commercially available as Vitrogen), assume a polygonal shape, form a stable monolayer within 24 hours, but lose the capacity to express some liver-specific functions over time in culture. We incubated hepatocytes in a serum-free medium on a reconstituted basement membrane gel, "matrigel" (prepared from an extract of extracellular matrix of the murine Engelbreth-Holm-Swarm sarcoma), and observed that the cells adhered firmly, remained rounded as single cells or clusters, and maintained liver-specific gene expression for more than 1 week in vitro. Hepatocytes on matrigel secreted substantially higher amounts of albumin, transferrin, haptoglobin, and hemopexin, Northern blot analyses of extracted cellular RNA, expressed increased amounts of mRNA for the liver-specific protein albumin (as compared with cells on vitrogen). In cultures treated with phenobarbital, cytochrome P-450b, and cytochrome P-450e, mRNAs and proteins were barely detectable in cells on Vitrogen but were induced to levels similar to those in the liver in vivo in matrigel cultures. Likewise, the use of matrigel greatly enhanced the induction of mRNA and protein for P-450c by 3-methylcholanthrene and for P-450p by steroidal and nonsteroidal inducers. However, neither substratum permitted induction of P-450d by 3-methylcholanthrene, suggesting that the effects of matrigel are selective even for expression in liver of members of the superfamily of cytochrome P-450 genes. Within 5 days in cultures on Vitrogen, hepatocytes expressed detectable amounts of fetal liver aldolase activity and also mRNA for vimentin and type I collagen, each considered a phenotypic change reflecting hepatocyte "dedifferentiation." None of these was present in cells on matrigel. Responsiveness to mitogenic stimuli, as judged by incorporation of 3H-thymidine into DNA, was also decreased in hepatocytes cultured on matrigel. Finally, there was a remarkable increase in the levels of both matrices during the first 2 days in culture. However, the continuously cytoskeleton mRNA over time in culture than did the rounded cells on matrigel. We conclude that hepatocytes cultured on matrigel, as opposed to the standard collagen, exhibit remarkably enhanced expression of many liver-specific functions. 相似文献
202.
Molecular genotypes of the human T cell receptor gamma-chain 总被引:2,自引:0,他引:2
New RFLP of the human TCR gamma-chain defined by a single restriction enzyme (PvuII) are described. They define three alleles and allow haplotype assignments within families. They occur at a high frequency within the population studied and are useful for studies on disease associations with the gamma-chain genes. The PvuII sites flank the C gamma 2 gene. A polymorphic site maps to an area 0.5 kb downstream of C gamma 2-exon III. The second RFLP appears to be the result of a 3-kb insertion giving rise to differences in the number of copies of exon II in the C gamma 2 gene. 相似文献
203.
Structural features of pyrimidine.pyrimidine mismatches in the interior of oligonucleotide duplexes have been investigated by high resolution two-dimensional proton nuclear magnetic resonance (n.m.r.) spectroscopy. These studies were conducted on the self-complementary d(C-G-C-T-A-G-C-T-T-G-C-G) duplex (designated T.T 12-mer) and the self-complementary d(C-G-C-C-A-G-C-T-C-G-C-G) duplex (designated C.C 12-mer) containing T.T and C.C pairs located at identical positions four base-pairs from either end of the duplex. Proton n.m.r. studies on the T.T 12-mer duplex were undertaken in the neutral pH range, while studies on the C.C 12-mer duplex were recorded at acidic pH. The proton spectra narrowed considerably on lowering the pH below neutrality for the C.C 12-mer duplex. Two-dimensional nuclear Overhauser enhancement spectroscopy (NOESY) data sets have been recorded on the T.T 12-mer and C.C 12-mer duplexes in high salt H2O and D2O solution. The magnitude of the NOE crosspeaks and the directionality of the NOE connectivities demonstrate that both duplexes are right-handed with all bases, including those at the mismatch site, adopting an anti configuration about the glycosidic bond. The observed base and sugar proton chemical shifts suggest structural similarities for the trinucleotide segments centered about the T.T and C.C mismatches. A NOE is detected between the resolved imino protons of T4 and T9 at the mismatch site, consistent with formation of a stacked "wobble" T4(anti).T9(anti) pair in the T.T 12-mer duplex. A comparison of the imino proton chemical shift and NOE data suggests that the imino-carbonyl hydrogen bonds in the wobble T.T mismatch are weaker than the corresponding imino-carbonyl hydrogen bonds in the wobble G.T mismatch. The 4-amino protons of C4 and C9 at the mismatch site in the C.C 12-mer duplex do not exhibit the pattern of hydrogen-bonded and exposed protons separated by approximately 1.5 parts per million characteristic of cytidine amino protons involved in Watson-Crick G.C pairing. The experimental data are insufficient to differentiate between wobble C(anti).C+(anti) and other pairing possibilities for the mismatch in the C.C 12-mer duplex at acidic pH. 相似文献
204.
异细胞质八倍体小黑麦的获得及其细胞遗传 总被引:5,自引:1,他引:4
改变小黑麦细胞质有可能增加减数分裂的稳定性,提高小黑麦的结实率与籽粒饱满度。作者以不同细胞质的“中国春”小麦与黑麦杂交,F_1幼苗用秋水仙素加倍获得双二倍体、或以八倍体小黑麦为父本与F_1杂交,获得异细胞质八倍体小黑麦(Triticale 8x)8个品系。实验结果表明:细胞质不同的“中国春”小麦与黑麦杂交结实率差异显著,出苗率亦不同,F_1株型多为两亲的中间型,花药不开裂,个别组合出现雄蕊雌化现象,有的组合表现生长弱性,减数分裂中期Ⅰ常出现1至数个末端交叉的棒状二价体,其数量在不同组合间差异显著,表明异细胞质对染色体配对有影响。D类细胞质对改进八倍体小黑麦的结实率可能有一定的作用。 相似文献
205.
206.
This paper is a revision of genus Crotalaria(Papilionaceae) in Yunnan. 30 species and 2 varieties of this genus have been described so far. Hence, there are 27 species, including 4 exotic species, and 4 varieties are distributed in this very province. Among them, 1 new variety, C. mairei var. pubescens, and 3 new combinations, C. yunnanensis var. heqingensis, C. peguana var. qiubeiensis, and C. albida var. gengmaensis, and 1 new record of China, C. humifusa, are included. In addition, 2 species are combined, they are C. jingpingensis to C. prostrata and C. yuanjiangensis to C. medicaginea. Besides, the pollen morphology in some taxa of this genus has been examined. 相似文献
207.
208.
209.
我国沙漠中部地区主要不同生态类型植物脯氨酸的累积、光合、呼吸和叶绿素含量 总被引:21,自引:0,他引:21
中生植物脯氨酸含量为0.42mg/g.dw, 低于少浆旱生植物(1.73mg/g.dw)。多浆旱生植物脯氨酸含量最高(7.22mg/g.dw),为前两者的17倍和4倍,两类旱生植物在干旱条件下(非灌溉)脯氨酸含量均高于灌水处理。少浆与多浆旱生植物的光合强度(16.74,14.04CO2mg/g.dw.h)差异不大,而中生植物(37.57mg/g.dW.h)略高于多浆旱生植物(4.73CO2Mg/g.dw.h),与中生植物(7.60Co2mg/g.dw.h)接近,光合/呼吸值,少浆,多浆与中生植物分别为2.50,3.09和4.59,说明中生植物的合成明显大于消耗,季节动态中,中生植物显著高于两类旱生植物,叶绿素总量三类植物差异甚微。 相似文献
210.
大叶杨组组间杂交花粉-柱头相互作用的超微结构研究 总被引:3,自引:1,他引:2
以大叶杨为母本,分别与小叶杨、欧洲黑杨、响叶杨进行人工杂交,并以大叶杨×大叶杨为对照,观察其花粉与柱头相互作用的超微结构变化。结果表明,大叶杨柱头细胞在授粉前表现生理活跃,含丰富的细胞器,壁外被含分支通道的角质层。接受大叶杨及欧洲黑杨花粉的柱头细胞内部仍有丰富的细胞器,膜结构保存完好。接受小叶杨及响叶杨花粉的柱头细胞衰亡较快,授粉部位沉积厚的胼胝质,细胞内部液泡化,膜结构逐渐消失,细胞质电子密度加大。欧洲黑杨花粉行为与大叶杨花粉行为相似,花粉能迅速萌发,并以短管形式穿入柱头,异常行为罕见。小叶杨及响叶杨花粉萌发后只有半数花粉管能以短管形式进入柱头,其中部分管内沉积胼胝质,另半数花粉管在柱头上表现各种异常行为——扭曲、爬行、肿胀、提前破裂释放内容物及先端沉积胼胝质。由各种花粉在大叶杨柱头上的行为和大叶杨柱头对各种授粉的反应判断,与大叶杨杂交亲和力在柱头阶段表现由强至弱依次是欧洲黑杨、小叶杨、响叶杨。 相似文献