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1.
Pax genes are expressed in specific patterns in the nervous system during development and in the adult. Recent findings suggest a link between the expression of Pax-2 and axonal guidance. Mice with a targeted deletion of Pax-2 are an excellent tool for studying axonal pathfinding at the molecular level, especially with respect to the optic chiasm. The date reviewed here suggest that Pax-2 regulates the expression of surface molecules involved in contact attraction and that the mutual regulation of the expression of Pax-2 and the Sonic hedgehog gene is of importance in the formation of the chiasm region. 相似文献
2.
LL McCabe 《Canadian Metallurgical Quarterly》1998,152(9):839-842
Agrobacterium tumefaciens transfers part of its Ti plasmid, the T-DNA, to plant cells during tumorigenesis. It is routinely used for the genetic modification of a wide range of plant species. We report that A. tumefaciens can also transfer its T-DNA efficiently to the filamentous fungus Aspergillus awamori, demonstrating DNA transfer between a prokaryote and a filamentous fungus. We transformed both protoplasts and conidia with frequencies that were improved up to 600-fold as compared with conventional techniques for transformation of A. awamori protoplasts. The majority of the A. awamori transformants contained a single T-DNA copy randomly integrated at a chromosomal locus. The T-DNA integrated into the A. awamori genome in a manner similar to that described for plants. We also transformed a variety of other filamentous fungi, including Aspergillus niger, Fusarium venenatum, Trichoderma reesei, Colletotrichum gloeosporioides, Neurospora crassa, and the mushroom Agaricus bisporus, demonstrating that transformation using A. tumefaciens is generally applicable to filamentous fungi. 相似文献
3.
We have shown that normal and human papillomavirus (HPV) type 16 immortalized human foreskin keratinocytes are growth inhibited by tumor necrosis factor alpha (TNF-alpha), whereas HPV-18- and SV40-immortalized keratinocytes are resistant to this cytokine (1). In this report, we investigated the expression of mitotic regulatory proteins, such as cyclin A, cyclin B, and p34cdc2. After exposure to TNF-alpha, normal and HPV-16-immortalized cells exhibited a dramatic decrease in the expression of these proteins. In contrast, no alteration in the levels of these proteins was observed after treatment of the resistant cell lines, as well as two HPV-positive cervical carcinoma cell lines. Expression of cyclin E does not seem to be modulated by TNF-alpha in any of the cells tested. On the other hand, cyclin D1, expression is slightly increased in normal keratinocytes and in the HPV-16-immortalized cells, whereas no alteration was observed in the HPV-18-transfected cells. The phosphorylation state of pRb correlated with cell growth; sensitive cells, which accumulate in G0-G1, after exposure to TNF-alpha, exhibited an accumulation of hypophosphorylated pRb, whereas no effect on pRb phosphorylation was observed for HPV-18-immortalized cells. These results clearly correlate with TNF-alpha-induced growth arrest in G0-G1. 相似文献
4.
The objectives of this work were to apply several profile comparison approaches to dissolution data of four different but bioequivalent metoprolol tartrate tablet formulations to (1) identify the advantages and disadvantages of each approach, (2) quantify the metric for comparing dissolution profiles of each method, (3) determine metric limits that are consistent with the observed bioequivalence, and (4) rationalize the observed metric limits with respect to the role of dissolution in overall metoprolol absorption. Dissolution was performed by the USP monograph method on four formulations of metoprolol tartrate tablets (Lopressor plus fast, medium, and slow dissolving test formulations). Three general approaches to compare dissolution profiles were examined; they were ANOVA-based, model-independent, and model-dependent approaches. It is concluded that model-independent approaches and several model-dependent approaches yielded numerical results that can serve as objective and quantitative metrics for comparing entire dissolution profiles of the four metoprolol tartrate formulations. However, these methods presented complications. Some metrics were dependent on the length of the dissolution profile and the sampling scheme. Results from the pairwise procedures also depended on the pairing assignment of individual profiles. In spite of complications, these methods suggested wide dissolution specification limits. Wide dissolution specifications were rationalized through an analysis of in vitro-in vivo relationships, which indicated metoprolol dissolution from these formulations was not the rate-limiting step; hence, a range of dissolution profiles can be expected to yield equivalent plasma profiles. 相似文献
5.
Gene amplification in a p53-deficient cell line requires cell cycle progression under conditions that generate DNA breakage 总被引:1,自引:0,他引:1
Amplification of genes involved in signal transduction and cell cycle control occurs in a significant fraction of human cancers. Loss of p53 function has been proposed to enable cells with gene amplification to arise spontaneously during growth in vitro. However, this conclusion derives from studies employing the UMP synthesis inhibitor N-phosphonacetyl-L-aspartate (PALA), which, in addition to selecting for cells containing extra copies of the CAD locus, enables p53-deficient cells to enter S phase and acquire the DNA breaks that initiate the amplification process. Thus, it has not been possible to determine if gene amplification occurs spontaneously or results from the inductive effects of the selective agent. The studies reported here assess whether p53 deficiency leads to spontaneous genetic instability by comparing cell cycle responses and amplification frequencies of the human fibrosarcoma cell line HT1080 when treated with PALA or with methotrexate, an antifolate that, under the conditions used, should not generate DNA breaks. p53-deficient HT1080 cells generated PALA-resistant variants containing amplified CAD genes at a frequency of >10(-5). By contrast, methotrexate selection did not result in resistant cells at a detectable frequency (<10(-9)). However, growth of HT1080 cells under conditions that induced DNA breakage prior to selection generated methotrexate-resistant clones containing amplified dihydrofolate reductase sequences at a high frequency. These data demonstrate that, under standard growth conditions, p53 loss is not sufficient to enable cells to produce the DNA breaks that initiate amplification. We propose that p53-deficient cells must proceed through S phase under conditions that induce DNA breakage for genetic instability to occur. 相似文献
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8.
LL Gugushvili 《Canadian Metallurgical Quarterly》1993,33(7):35-8, 5
The author performed experiments on 350 dogs and X-ray postmortem studies of 1520 corpses of subjects who had died of various diseases and injuries. It was found that in occlusive great vessels in the ischemic organs and tissues, retrograde circulation developed, which completely maintained their viability under definite conditions. Retrograde venous blood flow to diseased organs and tissues drastically increased in insufficient retrograde arterial blood circulation. Under certain conditions, surplus venous blood influx caused edema and their dysfunctions. The mechanisms of retrograde circulation account for asymptomatic occlusion of the great vessels. 相似文献
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10.
PURPOSE: The phenoxyacetic acid, ethacrynic acid (ECA), has potential use in glaucoma therapy because it acts to increase aqueous outflow in vivo and in vitro. In human trabecular meshwork (HTM) cell culture, ECA acts to change cell shape and attachment, effects that have been correlated with microtubule (MT) alterations and chemical sulfhydryl (SH) reactivity. To further explore these actions, we evaluated two non-SH reactive phenoxyacetic acids, inadcrinone and ticrynafen, and the MT-disrupting drug vinblastine. METHODS: Excised bovine and porcine eyes were perfused and outflow facility measured. Calf pulmonary artery endothelial and HTM cells were grown in culture and cytoskeletal effects evaluated after drug treatment. RESULTS: Indacrinone, ticrynafen, and vinblastine all caused an increase in outflow facility. In contrast with ECA, the outflow effects of indacrinone and ticrynafen were not blocked by excess cysteine. Although indacrinone and ticrynafen produced changes in cell shape in vitro, the beta-tubulin staining pattern of treated cells was not altered. Vinblastine caused cell shape change and the expected MT disruption. CONCLUSIONS: Phenoxyacetic acids can increase aqueous outflow facility and alter HTM cell shape and attachment in vitro by a non-SH, non-MT mechanism (which is probably shared also by ECA). These findings suggest the possibility of a broader class of glaucoma drugs that may be directed at the HTM. An understanding of the cellular target for these drugs has implications both for potential glaucoma therapy and for the cytoskeletal mechanisms involved in normal outflow function. 相似文献