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61.
Solvent effects on cytoskeletal organization and in-vivo survival after freezing of rabbit oocytes 总被引:4,自引:0,他引:4
NBD-phallacidin revealed a polymerized actin distribution in the cortical region of the rabbit egg and along junctional feet. Staining with anti-alpha-tubulin antibody showed that the microtubule distribution was restricted to the barrel-shaped spindle. After cryoprotective treatment in the presence of propanediol, cortical polymerized actin was no longer visible within the egg and along junctional feet but filamentous actin was still present after treatment with dimethylsulphoxide. However, exposure to dimethylsulphoxide or propanediol led to the appearance of microtubules in the cytoplasm and to a disassembly of the spindle often associated with anomalies in chromosome position. Cytoplasmic microtubules formed by the action of propanediol were still present after freezing, thawing, and removal of the cryoprotectant, but after recovery of eggs in culture, they disappeared and barrel-shaped spindles were able to reform. When the effect of propanediol addition on in-vivo fertilization and development of frozen oocytes was examined, 39% (79/200) of frozen oocytes were fertilized and 9% (9/105) developed to normal fetuses, compared to 81% (38/47) and 32% (12/38) respectively for unfrozen control oocytes. 相似文献
62.
The EPR spectra of the high-salt form of reduced bovine spleen purple acid phosphatase (BSPAPr) and its complexes with inhibitory tetrahedral oxyanions, AMP, and fluorine have been examined in the 4-30 K temperature range. The EPR spectrum of the high-salt form of BAPAPr is identical to that previously reported for the low-salt form (Averill et al. (1987) J. Am. Chem. Soc. 109, 3760-3767), indicating that the substantial differences in conformation of the two forms result in undetectable alterations in the electronic structure of the binuclear iron center. Phosphate, AMP, and arsenate all result in broadened, highly anisotropic EPR spectra with decreased values of the antiferromagnetic coupling constant, -2J, while molybdate and tungstate produce a sharp axial or slightly rhombic spectrum, respectively, and fluoride produces an anomalous spectrum with an inverted g-tensor. These results are consistent with binding of the two classes of oxyanions (and AMP) to distinct sites at or near the binuclear iron center, while fluoride binds in yet a third mode. EPR spectra of the BSPAPr complex with molybdate show altered relaxation behavior in the presence of phosphate, consistent with a 50% decrease in the magnitude of -2J, suggesting that phosphate binds to the molybdate complex to produce a ternary complex analogous to that proposed for molybdate inhibition on the basis of kinetics studies. 相似文献
63.
Mitochondrial protein import 总被引:1,自引:0,他引:1
Most polypeptides of mitochondria are imported from the cytosol. Precursor proteins contain targeting and sorting information, often in the form of amino-terminal presequences. Precursors first bind to receptors in the outer membrane. Two putative import receptors have been identified: a 19-kilodalton protein (MOM19) inNeurospora mitochondria, and a 70-kilodalton protein (MAS70) in yeast. Some precursors integrate directly into the outer membrane, but the majority are translocated through one or both membranes. This process requires an electrochemical potential across the inner membrane. Import appears to occur through a hydrophilic pore, although the inner and outer membranes may contain functionally separate translocation machineries. In yeast, a 42-kilodalton protein (ISP42) probably forms part of the outer membrane channel. After import, precursors interact with chaperonin ATPases in the matrix. Presequences then are removed by the matrix protease. Finally, some proteins are retranslocated across the inner membrane to the intermembrane space. 相似文献
64.
The major developments in the field of nuclear activation analysis, from 1936 to 1989, are discussed. The developments are
grouped into five consecutive time periods. The impact of various scientists on the development of the field in the first
35 years is also discussed. 相似文献
65.
66.
67.
A. Petronis A. S. Bassett W. G. Honer J. B. Vincent Y. Tatuch T. Sasaki D. J. Ying T. A. Klempan J. L. Kennedy 《American journal of human genetics》1996,59(4):905-911
Evidence for genetic anticipation has recently become an important subject of research in clinical psychiatric genetics. Renewed interest in anticipation was evoked by molecular genetic findings of a novel type of mutation termed "unstable DNA." The unstable DNA model can be construed as the "best fit" for schizophrenia twin and family epidemiological data. We have performed a large-scale Southern blot hybridization, asymmetrical PCR-based, and repeat expansion-detection screening for (CAG)n/(CTG)n and (CCG)n/(CGG)n expansions in eastern Canadian schizophrenia multiplex families demonstrating genetic anticipation. There were no differences in (CAG)n/(CTG)n and (CCG)n/(CGG)n pattern distribution either between affected and unaffected individuals or across generations. Our findings do not support the hypothesis that large (CAG)n/(CTG)n or (CCG)n/(CGG)n expansions are the major etiologic factor in schizophrenia. A separate set of experiments directed to the analysis of small (30-130 trinucleotides), Huntington disease-type expansions in individual genes is required in order to fully exclude the presence of (CAG)n/(CTG)n- or (CCG)n/(CGG)n-type unstable mutation. 相似文献
68.
Judith D. DePue Matthew M. Clark Laurie Ruggiero Meredith L Medeiros Vincent Pera 《Obesity (Silver Spring, Md.)》1995,3(3):241-248
This study identified facilitators and obstacles to maintenance of weight loss following a very-low-calorie-diet and behavior modification program. A survey was mailed to a random sample of 178 program completers and received a 61% response rate; the most frequent follow-up period was more than 2 years. Twenty-nine percent reported weighing the same (within 10 lbs) or less than the end of their participation in the treatment program (maintainers), while 71% reported their present weight was a mean of 65% higher than their initial weight loss (regainers). Maintainers were significantly more likely to report engaging in regular aerobic exercise, attending a maintenance support group, and confidence in their ability to manage their weight in the future, while regainers were more likely to report stress and motivation as frequent weight management obstacles. Respondents consistently identified the need for low/no cost ongoing support. Maintainers and relapsers reported similar challenges in managing their weight, yet with different results, suggesting the need to identify subgroups for which different post-treatment support options could be applied. 相似文献
69.
Control of flower development and phyllotaxy by meristem identity genes in antirrhinum. 总被引:9,自引:0,他引:9 下载免费PDF全文
The flower meristem identity genes floricaula (flo) and squamosa (squa) promote a change in phyllotaxy from spiral to whorled in Antirrhinum. To determine how this might be achieved, we have performed a combination of morphological, genetic, and expression analyses. Comparison of the phenotypes and RNA expression patterns of single and double mutants with the wild type showed that flo and squa act together to promote flower development but that flo is epistatic to squa with respect to early effects on phyllotaxy. We propose that a common process underlies the phyllotaxy of wildtype, flo, and squa meristem development but that the relative timing of primordium initiation or growth is altered. This process depends on two separable events: setting aside zones for potential primordium initiation and partitioning these zones into discrete primordia. Failure of the second event can lead to the formation of continuous double spirals, which are occasionally seen in flo mutants. 相似文献
70.