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51.
The ascidian egg contains muscle and endoderm determinants that play critical roles in the specification of muscle and endoderm cells, respectively. Endoderm cells of the ascidian embryo express alkaline phosphatase (AP) as a tissue-specific enzyme. We obtained egg fragments from the unfertilized eggs of Ciona savignyi by means of centrifugal force. The largest fragment (red fragments) contained the egg nucleus while other small fragments (black, clear and brown fragments) were anucleate. When inseminated, only red fragments developed into partial embryos, which showed only epidermis cell differentiation and, very rarely, AP activity. When red fragments were fused with other fragments, only black fragments promoted AP expression, suggesting that endoderm determinants were concentrated in the black fragments. A lower dose (1500 J/m2 ) of ultraviolet (UV) light did not eliminate the AP-promoting ability of black fragments, while this dose significantly repressed the ability to promote the expression of the muscle-marker. A higher dose (4500 J/m2 ) of UV light markedly reduced the AP-promoting activity of black fragments. These results suggest that factors for endodermal AP development are inactivated by UV irradiation, but are more resistant than muscle determinants. 相似文献
52.
Fully developed thalli of Chondrus crispus, Gracilaria chilensis, Gymnogongrus furcellatus and Mazzaella laminarioides were used to assess tissue compatibility. The effect of thallus polarity on grafting and regeneration was also evaluated. Fusion did occur between fragments of the same life history phase in C. crispus, G. chilensis, G. furcellatus and M. laminarioides. Fusion between sporophytic and gametophytic tissue occurred in C. crispus, G. chilensis and M. laminarioides. Intergeneric fusion was observed between C. crispus and M. laminarioides, but not between G. chilensis and G. furcellatus.Outer cell wall, cortex and medulla were continuous at the contact face in compatible combinations. Medullary cells in the attached fragments were thinner and longer than normal cells, forming an interwoven scar plate. Thallus polarity did not modify fusion and regeneration. 相似文献
53.
James D. Pancook Jürgen C. Becker Stephen D. Gillies R. A. Reisfeld 《Cancer immunology, immunotherapy : CII》1996,42(2):88-92
A major problem in the treatment of solid tumors is the eradication of established, disseminated metastases. Here we describe
an effective treatment for established experimental hepatic metastases of human neuroblastoma in C. B.-17 scid/scid mice. This was accomplished with an antibody-cytokine fusion protein, combining the unique targeting ability of antibodies
with the multifunctional activity of cytokines. An anti-(ganglioside GD2) antibody (ch14.18) fusion protein with interleukin-2
(ch14.18-IL2), constructed by fusion of a synthetic sequence coding for human interleukin-2 (IL-2) to the carboxyl end of
the Cγ1 gene of ch14.18, was tested for its therapeutic efficacy against xenografted human neuroblastoma in vivo. The ch14.18-IL2
fusion protein markedly inhibited growth of established hepatic metastases in SCID (severe combined immunodeficiency) mice
previously reconstituted with human lymphokine-activated killer cells. Animals treated with ch14.18-IL2 showed an absence
of macroscopic liver metastasis. In contrast, treatment with combinations of ch14.18 and recombinant IL2 at dose levels equivalent
to the fusion protein only reduced the tumor load. Survival times of SCID mice treated with the fusion protein were more than
double that of control animals. These results demonstrate that an immunotherapeutic approach using a cytokine targeted by
an antibody to tumor sites is highly effective in eradicating the growth of established tumor metastases.
Received: 7 November 1995 / Accepted: 15 December 1995 相似文献
54.
55.
Intergeneric transfer of a partial genome and direct production of monosomic addition plants by microprotoplast fusion 总被引:7,自引:0,他引:7
K. S. Ramulu P. Dijkhuis E. Rutgers J. Blaas F. A. Krens W. H. J. Verbeek C. M. Colijn-Hooymans H. A. Verhoeven 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1996,92(3-4):316-325
Results are reported on the transfer of single, specific chromosomes carrying kanamycin resistance (KanR) and -glucuronidase (GUS) traits from a transformed donor line of potato (Solanum tuberosum) to a recipient line of the tomato species Lycopersicon peruvianum through microprotoplast fusion. Polyethylene glycol-induced mass fusion between donor potato microprotoplasts containing one or a few chromosomes and normal recipient diploid L. peruvianum protoplasts gave several KanR calli. A high frequency of plants regenerated from KanR calli expressed both KanR and GUS, and contained one or two copies of npt-II and a single copy of gus. Genomic in situ hybridization showed that several microprotoplast hybrid plants had one single potato donor chromosome carrying npt-II and gus genes and the complete chromosome complement of the recipient L. peruvianum (monosomic additions). Several monosomic-addition hybrid plants could be regenerated within the short time of 3 months and they were phenotypically normal, resembling the recipient line. These results suggest that the transfer of single chromosomes is tolerated better than is the transfer of the whole donor genome. The unique advantages of microprotoplast fusion are discussed: these include the direct production of monosomic addition lines for the transfer and introgression of economically important traits in sexually-incongruent species, the construction of chromosome-specific DNA libaries, high-resolution physical mapping and the identification of alien chromosome domains related to gene expression. 相似文献
56.
C. Kaendler M. Fladung H. Uhrig 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1996,92(3-4):455-462
A successful hybridization of a diploid clone of Solanum tuberosum with a rolC-transgenic, diploid S. papita clone is reported. By using leaf expiants of this S. papita clone, which after transformation expressed kanamycin resistance, intact protoplasts were obtained, but these protoplasts did not develop to microcalli or regenerate to mature plants. However, protoplasts of the S. tuberosum clone showed a high capacity to regenerate plants from isolated protoplasts. On a medium containing Kanamycin only calli regenerated to plants, which revealed a rolC phenotype (reduced apical dominance with a large number of adventitious shoots and a pale green color of leaves) and later on turned out to be true hybrids. Self fusions of S. papita never developed to microcalli and those of S. tuberosum ceased to develop on the kanamycin-containing medium. Identification of somatic hybrids was done by RFLP and RAPD analysis. In the greenhouse, out of four selected hybrids only FK3.1 was successfully crossed with two standard S. tuberosum varieties (Datura, Desirée). Out of all the seeds germinated, only rolC-negative F1 seedlings were further characterized. Within the seedling population obvious differences were evident in respect of the S. papita and S. tuberosum characteristics. 相似文献
57.
Lindl T 《Cytotechnology》1996,21(3):183-193
This article describes the current status in the development of human monoclonal antibodies. Over the last ten years a lot of information about the human immune system has emerged. Combining these with the many new (bio-)technologies it is plausible that the long awaited breakthrough of this technology is close. This paper focuses on the classical cell-biological methods of achieving stable, antibody-producing human cell lines via cell fusion methods or virus derived transformations of human B-lymphocytes, as well as genetic engineering methods e.g. DNA libraries or phage display technology. The available in vitro immunization methods are critically reviewed and their impact on this topic is discussed. Therapeutic applications for cancer treatment or passive immunization against infectious diseases with antibodies derived by both ways are also reviewed. 相似文献
58.
一株种间融合的三倍体杂种酵母减数分裂产物的遗传学分析 总被引:1,自引:0,他引:1
通过原生质体融合技术将二倍体酿酒酵母(Saccharomycescerevisiaevar.ellopsiodeus)与单倍体糖化酵母(Saccharomycesdiastaticus)构建成遗传上稳定的种间三倍体融合杂种。实验结果表明,这种融合杂种象有性杂种一样能诱导产孢;对其完整和非完整四分子的遗传分析,证明了通过遗传标记互补选择法获得的种间三倍体融合杂种HU-KDF-240在产孢过程中,标记基因发生了分离和交换,出现了亲二型和重组类型;四分子对可溶性淀粉的发酵和不发酵分离比为1∶2,而原养型与营养缺陷型的分离比是1∶1。 相似文献
59.
系统地研究了细胞色素c在多种氨基酸和多肽修饰电极上的电化学反应。并对影响加速细胞色素c电化学反应的因素进行了讨论。 相似文献
60.
Corticotropin-releasing hormone (CRH) has been shown to be a central mediator for most, if not all, stress-induced responses. Since stressful stimuli may decrease hypothalamic tuberoinfundibular and tuberohypophysial dopaminergic neuronal activities, we aimed to determine whether CRH is involved. Using central administration of various doses of ovine CRH (oCRH; 1, 3 and 10 µg/rat) into the lateral cerebroventricle of either male or female rats, the neurochemical changes in various parts of the central nervous system, including the hypothalamus, were determined by high-performance liquid chromatography at various times after the injection (30, 60, 120 and 240 min). The concentrations of 3,4-dihydroxyphenylacetic acid (DOPAC) and 3-methoxy-4-hydroxy-phenylethyleneglycol (MHPG), two major metabolites of dopamine and norepinephrine, respectively, in discrete brain regions were used as indices for catecholaminergic neuron activity. Plasma corticosterone levels increased significantly after all doses of oCRH and at all time points studied. oCRH also exerted significant stimulatory effects on noradrenergic neuron terminals in the frontal cortex, and on dopaminergic neuron terminals in the nucleus accumbens, hypothalamic paraventricular and periventricular nuclei, and intermediate pituitary lobe. Dopaminergic neuron terminals in the median eminence and the neural lobe of the pituitary, however, were not affected. There was no major difference in the responses between male and female rats. We conclude that CRH has a differential effect on central catecholaminergic neurons. 相似文献