Cloning and nucleotide sequence analysis of genes coding for the major chlorophyll-binding protein of the moss Physcomitrella patens and the halotolerant alga Dunaliella salina

Two clones have been isolated from a genomic library of the moss Physcomitrella patens and a cDNA library of the halotolerant green alga Dunaliella salina. The isolates contain genes coding for the major light-harvesting chlorophyll-a/b-binding protein (CAB) in the photosystem II (PSII) light-harvesting complex (LHCII). The 2544-bp insert of the moss genomic clone contains the complete CAB-coding region and 5' and 3' flanking sequences. The coding region contains an intron of 359 bp which is spanned by a pair of 9-bp perfect direct repeats. There are two CCAAT boxes and five enhancer-like elements related to (G)TGGTTTAAA(G) (Weiher et al., 1983) residing in the intron. Comparisons of the moss cab gene with sequences of light-inducible genes of higher plants reveal homologous and repeated sequences similar to the enhancer element in the 5' region upstream from the TATA and CCAAT boxes thought to be responsive to light inducibility. The 1256-bp algal cDNA contains the complete CAB-coding sequence, a 170-bp 5'-nontranslated region, and a 264-bp 3'-nontranslated region. While the overall homology in the nontranslated regions is low between the cab gene of the moss and that of the alga, the 3'-nontranslated regions of the two contain some sequences that are conserved among the cab genes in higher plants. The deduced amino acid sequences of these two clones are highly conserved except for the N-terminal region. Their hydropathic plots are very similar and both possess three hydrophobic segments that are likely alpha-helical transmembrane segments. The proposed CAB transit peptide sequence of the alga is divergent from that of the moss or higher plants, suggesting that they may have evolved from different origins. Southern blot analysis shows that the cab genes in the moss and the alga, as in higher plants, are encoded by a number of homologous genes constituting a multigene family.     

Prostaglandin E2 induced changes in renal blood flow, renal interstitial hydrostatic pressure and sodium excretion in the rat

Prostaglandin E2, when infused into the renal artery of the dog, is a vasodilator and increases both renal interstitial hydrostatic pressure and sodium excretion. Similar studies in the rat, however, have been inconclusive. The present study examined the effect of prostaglandin E2 infusion into the renal interstitium, by means of a chronically implanted matrix, on renal blood flow, renal interstitial hydrostatic pressure and sodium excretion in the rat. Prostaglandin E2 was continuously infused directly into the kidney interstitium to mimic endogenous prostaglandin E2 production by renal cells. The maximum change in each of these parameters occurred when 10(-5) M PGE2 was infused. Renal blood flow increased from 4.70 +/- 0.91 to 5.45 +/- 0.35 ml/min (p less than 0.05) while renal interstitial hydrostatic pressure decreased from 3.9 +/- 0.4 to 2.6 +/- 0.5 mmHg (p less than 0.05) and fractional excretion of sodium decreased from 1.02 +/- 0.20 to 0.61 +/- 0.12% (p less than 0.05). Thus, the present study demonstrates that renal interstitial infusion of prostaglandin E2 increases total renal blood flow but decreases both renal interstitial hydrostatic pressure and urinary sodium excretion in the rat.     

What is the relationship between the endothelium derived relaxant factor and nitric oxide?

Nitric oxide gas in solution (NO) relaxes blood vessels with similar actions and pharmacodynamics as the endothelium derived relaxant factor (EDRF) and has been proposed to be a component of the materials released from stimulated endothelial cells. Certain data however suggest that EDRF and NO may not be identical. In some non-vascular smooth muscles, NO and EDRF exhibit markedly different pharmacologic profiles. Furthermore the interaction of EDRF and NO with anion exchange resins differ. The hypothesis that EDRF is identical to nitric oxide gas in solution or a nitrogen oxide containing compound is discussed.     

Overexpression of amyloid precursor protein alters its normal processing and is associated with neurotoxicity.

The recent discovery that point mutations in the beta/A4 amyloid precursor protein may be the cause of certain forms of familial Alzheimer's disease provides strong support for the view that a thorough understanding of the metabolism of this protein may elucidate the pathogenesis of most forms of the disease and thus serve as a basis for rational prevention and therapy. Here we show that overexpression of a portion of the amyloid precursor protein molecule produces at least four distinct fragments of the COOH-terminus of amyloid precursor protein, suggesting altered proteolysis of amyloid precursor protein, and that such overexpression is associated with cytotoxicity. The degree of toxicity in the P19 cell culture model (differentiating mouse embryonal carcinoma cells) is shown to be related to the two larger novel COOH-terminal protein fragments (16 and 14 kilodalton), as well as to levels of expression of these two fragments. The toxicity is manifested in several differentiated cell lineages, including neuronal cells.     

粉纹夜蛾核型多角体病毒诱导的胸苷激酶特性研究

粉纹夜蛾(Trichoplusia ni)核型多角体病毒(TnNPV)感染草地贪夜蛾(Spodop-tera frugiperda)细胞后能诱导提高胸苷激酶的活性。不论是正常或感染细胞中的胸苷激酶都可将脱氧胞苷磷酸化,酶活最适pH及Mg~( )离子浓度值基本相同,DEAE-纤维素和Cibacron blue-sepharose柱层析所得酶活性图谱亦相似。TnNPV在胸苷激酶缺陷型的草地贪夜蛾细胞中能正常复制,但被感染细胞不具有胸苷激酶活性。由此可以确定,经TnNPV感染诱导后,活性有所提高的胸苷激酶不是病毒基因编码的。     

高温厌氧条件下纤维素的直接乙醇发酵

本文介绍了出分解纤维素的嗜热厌氧菌Clostridium celluloflavus sp.nov.直接发酵纤维素产乙醇的初步研究、发酵于60℃下进仃,其主要产物为乙醇、乙酸、氢气和二氧化碳。文中介绍了间歇发酵的若干特征与影响发酵的因素,1％纤维素发酵至120小时,大约有70％纤维素被分解;乙醇的转化率约为0.36g/g降解纤维素;发酵液中乙醇浓度达到56至61mM。发酵中乙醇与乙酸浓度的比值因发酵时间与其它发酵条件的不同而不同。     

Use of green fluorescent protein to visualize the early events of symbiosis between Rhizobium meliloti and alfalfa (Medicago sativa).

A gene encoding a variant of green fluorescent protein (GFP) of Aequorea victoria was put under the control of a promoter which is constitutive in Rhizobium meliloti. The heterologous GFP gene was expressed at high levels during all stages of symbiosis, allowing R. meliloti cells to be visualized as they grew in the rhizosphere, on the root surface, and inside infection threads. In addition, nodules that were infected with bacteria which were synthesizing GFP fluoresced when illuminated with blue light. GFP-tagged bacteria could be seen inside infection threads, providing the opportunity to measure the growth rate and determine the patterns of growth of R. meliloti residing inside its host plant.     

Overexpressions of cDNAs for β-Amyloid Precursor Proteins 695, 751, and 770 Enhance the Secretion of β-Amyloid Precursor Protein Derivatives and the Survival of P19-Derived Neurons

Abstract: P19 is a C3H mouse-derived line of multipotent embryonic carcinoma cells that differentiate into neural cells. P19 cell clones overexpressing the three major forms of β-amyloid precursor protein from their cDNA constructs were established. Unlike a previous study in which P19-derived neurons had a limited α-secretase activity, all of these clones produced significant amounts of secreted β-amyloid precursor protein. When treated with retinoic acid, these transformed lines differentiated into neurons and survived better than did nontransformed parental P19 cells. Furthermore, P19-derived neurons survived better in medium conditioned by the transformed P19 line, and survival was reduced by immunoabsorption with an antibody to β-amyloid precursor protein. These results suggest neurotrophic effects of secreted β-amyloid precursor protein and contrast with a previous report in which overexpression of a full-length cDNA for β-amyloid precursor protein led to degeneration of P19-derived neurons. Western blot analysis suggested that this difference might result from different levels of expression of putative neurotoxic C-terminal fragments of β-amyloid precursor protein; moreover, P19-derived neurons differ from P19 stem cells in the processing of these C-terminal fragments.     

Identification and characterization of three genes and two pseudogenes on chromosome 13

A study was conducted on the feasibility of isolating genes and pseudogenes that map to chromosome 13 by a hybridization-based approach using a 13-specific library and pools of repeat-free cDNA clones. Five pairs of cDNA and chromosome 13 genomic clones were identified and characterized. Partial or full-length sequence was derived from all cDNAs, and database searches were performed for putative gene identification. Partial sequence was also obtained from the chromosome 13 genomic clones for comparison with those of the hybridizing cDNAs. As a result of these analyses we identified three genes, a putative homologue of a porcine mRNA encoding an unidentified hepatic protein, a putative homologue of a yeast integral membrane protein, and a gene for a translationally controlled tumor protein, and two processed pseudogenes, ribosomal proteins L23a and S3a. The latter was formerly identified as the v-fos transformation effector gene, Fte-1, and recently cited as a possible candidate for the BRCA2 gene on chromosome 13. All genes and pseudogenes were localized to cytogenetic bands by in situ hybridization of metaphase chromosomes with probes derived from the chromosome 13 genomic clones.     

大肠癌中p53基因突变的研究

应用聚合酶链反应(PCR)──单链构型多态性(SSCP)结合银染法对14例大肠癌p53基因的第4、第5─6和第7外显子进行了点突变的研究,结果共检测出6例点突变,而且发现各外显子的突变频率存在差异。另外,利用购自ATCC的两个探针 (p53cDNA探针和pYNZ22探针)对大肠癌中p53基因的杂合性失去进行了研究,在14例大肠癌中共检出6例杂合性丢失。将点突变检测结果同杂合性丢失结果进行比较分析, 并着重探讨了大肠癌中p53基因失活导致肿瘤的作用方式。 Abstract:The exons 4-7 of p53 gene were examined in 14 colorectal Cancer patients by using PCR-SSCP-silver staining method.The results showed 6 cases of point mutation and the mutation frequencies of exons were different from each other.p53 cDNA and pYNZ22 VNTR were used as probes to examine LOH(Loss of heterozygosity)of 14 colorectal cancers.6 cases with LOH were found.The results of present research suggest that mutation and LOH of p53 gene are critical events in the progress and development of Cancer.There were different kinds of inactivation model of p53 gene in the process of development of cancer and transformation of cells.