Mutation rate at the hprt locus in human cancer cell lines with specific mismatch repair-gene defects

Spontaneous mutation rates at the hypoxanthine-guanine phosphoribosyl transferase (hprt) locus were measured in human cancer cell lines defective in the mismatch repair (MMR) genes hMLH1, hPMS2, or GTBP, as well as in a cell line carrying mutations in both hMLH1 and hPMS2. The mutation rate was determined by quantitating mutant frequency increases within a single culture as a function of cell division. These MMR- deficient cell lines exhibited a 50- to 750-fold increase in mutation rate relative to a MMR-proficient cancer cell line. From lowest to highest, the spontaneous mutation rates relative to the MMR-gene defects studied here are as follows: hMLH1- < GTBP- < hPMS2- < hMLH1- / hPMS2-. In addition, a cell line in which MMR was restored by chromosome transfer exhibited a mutation rate 12-fold below the MMR- deficient parental cell line. These data support the notion that MMR plays an important role in controlling the rate of spontaneous mutation and suggest that different MMR-gene defects may vary in their ability to repair different types of DNA mismatches, thus leading to measurable quantitative differences in spontaneous mutagenesis. Furthermore, a difference in mutation rates was observed between a hPMS2-defective cell line (3.1 x 10(-5) mutations/cell/generation) and two hMLH1- defective cell lines (4.0 x 10(-6) and 7.3 x 10(-6) mutations/cell/generation). Assuming the hPMS2- and hMLH1-gene products only function in the proposed hMutL alpha heterodimer, then defects in either gene should yield comparable mutation rates. These data suggest that hPMS2 plays a critical role in MMR, while additional hMLH1 homologues or hPMS2 alone may function to partially complement defects in hMLH1.      

Human chorionic gonadotrophin-beta gene sequences in women with disorders of HCG production

Women with recurrent abortion, primary unexplained infertility, and gestational trophoblastic neoplasia (GTN) manifest disordered human chorionic gonadotrophin (HCG) secretion. Mutations in the HCG beta/luteinizing hormone (LH) beta gene complex could cause aberrant HCG production in these disorders. The purpose of this study was to determine whether HCG beta gene deletions occur in women with recurrent abortion or primary unexplained infertility, and whether HCG beta gene duplications are present in women with GTN. DNA was extracted from 10 patients with unexplained recurrent abortion, 10 patients with unexplained primary infertility, 12 patients with GTN, three partners of women with GTN, and 30 controls. Southern blots were constructed and hybridized with DNA probes for HCG beta-5 and the LH beta gene. No gene deletions were identified in patients with recurrent abortion or primary unexplained infertility. Likewise, no gene duplications were identified in women with GTN. A previously described Mbol restriction fragment length polymorphism (RFLP) was identified in both patients and controls. A new Pstl RFLP was also characterized, but was present in patients and controls. Deletion/duplication mutations in the HCG beta/LH beta gene complex do not appear to be common causes of aberrant HCG production in humans with these disorders.      

The molecular mechanisms of oocyte maturation and early embryonic development are unveiling new insights into reproductive medicine

The purpose of the present review is to outline the current understanding on the molecular mechanisms governing various stages of oocyte maturation, transition from maternal to embryonic control and the initial steps of pre-embryo development. The cytoplasmic and nuclear maturation of the oocyte during pre-ovulatory development can be viewed as separate entities. Cytoplasmic maturation and the acquisition of stores of RNA and protein dominates oocyte development between the premordial and pre-ovulatory stages of development. Initiation of nuclear maturation is marked by the breakdown of the nuclear envelope, or germinal vesicle and is triggered by the midcycle luteinizing hormone peak. In vitro, this is associated with a decrease in the intracellular concentrations of cAMP. This and several subsequent steps of meiosis are controlled by the M-phase promoting factor (MPF). While the constituents of MPF, p34cdc2 kinase and B-type cyclin, are also present in mitotically dividing cells, in meiotically dividing oocytes the regulation of MPF activity differs. An oocyte- specific protein kinase, c-mos, plays an important role in up- regulating the activity of MPF at various stages of final oocyte maturation. Several lines of evidence suggest that the proper function of the c-mos-MPF system is associated with important features of the last stages of oocyte maturation such as the resumption of meiotic maturation, inhibition of DNA replication between meiosis I and II, and the maintenance of the oocyte at metaphase II arrest until it is fertilized. Eventually the destruction of c-mos and active MPF following fertilization allows the initiation of mitotic cell division in the pre-embryo. The very first cell divisions of the human pre- embryo are still under the control of maternally inherited mRNA and protein. Several lines of evidence suggest that in humans, zygotic gene expression is initiated between the 4- and 8-cell stages, after which the pre-embryo begins to utilize its own genes. Some of the first genes to be expressed in the human pre-embryo encode proteins that are associated with cell division, extracellular growth modulatory signals as well as factors associated with implantation. We acknowledge that most of the data presented comes from species other than human, therefore at present the full biological role of the proposed regulatory pathways and control mechanisms for human biology remains speculative.      

超声血管造影在肝癌介入治疗前后的应用价值

目的探讨超声血管造影对原发性肝癌（ＨＣＣ）在经皮肤动脉栓塞术（ＴＡＥ）治疗前后的应用价值。方法采用超声造影剂Ｌｅｖｏｖｉｓｔ经肘静脉注入的方法,检查１２例ＨＣＣ患者在ＴＡＥ治疗前后血供的变化情况。要用彩色多普勒血流显像（ＣＤＦＩ）的半定量测量方法,判定栓塞前后肿瘤血供的丰富程度,并与Ｘ线数字减影血管造影（ＤＳＡ）进行对比分析。结果超声血管造影与ＤＳＡ在探查肝癌ＴＡＥ治疗前后肿瘤血供方面无差异（Ｐ〉     

Detection of monosomy 7 and trisomy 8 in myeloid neoplasia: a comparison of banding and fluorescence in situ hybridization

Fluorescence in situ hybridization (FISH) is a powerful tool for detection of numerical and structural chromosomal aberrations. We have compared conventional banding techniques and FISH for the detection of monosomy 7 (-7) and trisomy 8 (+8) in 89 patients with myeloid malignancies. Of these patients, 21 had -7, 30 had +8, four had both, and 34 had no aberrations or aberrations other than -7 or +8 as assessed by banding techniques. Sequential samples were available in 23 patients. Alphoid DNA probes specific for chromosomes no. 7 and 8 were used for FISH. As controls, 10 normal bone marrow (BM) samples were hybridized with the chromosomes no. 7 and 8 probes, and in addition all tumor samples were hybridized with a chromosome no. 1 specific probe. The cut-off value for -7 was 18% one-spot cells, and for +8 was 3% three-spot cells. FISH analysis of 44 samples with -7 or +8, and at least 10 metaphases evaluated, showed that the proportions of aberrant metaphase cells mirrored the interphase clone sizes. Most samples with nonclonal metaphase aberrations, including those with only a few metaphases, had increased numbers of aberrant interphase cells: 20% to 80% for -7, and 3% to 43% for +8. Interphase cytogenetics of the 34 samples without -7 or +8 did not show significant cell populations with -7 or +8. In four patients, -7 or +8 could not be confirmed by FISH due to additional structural aberrations, marker chromosomes, or wrongly interpreted banding results. As FISH will be used more and more in cytogenetic diagnosis, clinical follow-up, and therapy monitoring, it will be necessary to standardize FISH procedures and supplement the Standing Committee on Human Cytogenetic Nomenclature (ISCN) definitions of a clone with criteria specifically for in situ hybridization.     

The long-term results of fistulising trabeculotomy in chronic open-angle glaucoma

Background : Fistulising trabeculotomy has been used for nearly 20 years to combine the minimally invasive surgery of trabeculotomy with production of a subconjunctival fistula.
Methods : The canal of Schlemm was unroofed 2mm on one side of a 3mm half-thickness scleral flap. A trabeculotomy probe was passed about 30° along the canal on the opposite side and rotated into the anterior chamber.
Results : Of 99 eyes of 74 patients, 35 eyes of 25 patients were available for follow-up at 10 or more years. The mean IOP was 14 ± 4 mmHg (range 7 to 23 mmHg) from a preoperative IOP of 29 ± 8 mmHg (17 to 60 mmHg). Results in 44 similar patients undergoing trabeculectomy and 44 undergoing fistulising trabeculotomy were very similar at five-year follow-up.
Conclusion : Fistulising trabeculotomy was effective for lowering intraocular pressure with a low complication rate and a large area of subconjunctival fistulisation.