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1.
  总被引:1,自引:0,他引:1  
In genetic transformation, long deletions dramatically increase the frequency of wild-type recombinants in 2-point crosses. In 3-point crosses in which the deletion was localized between 2 point mutations we demonstrated that this hyper-recombination was the result of genetic conversion extending over several scores of bases outside the deletion. As this conversion did not require an active DNA polymerase A gene, it was proposed that the mechanism of conversion involves breakage and ligation between DNA molecules. A similar hyper-recombination was observed when donor DNA carried an insertion. These results suggest that long heterologies participated in recombination so that surrounding homologous regions are almost completely paired and that these long heterologies are converted. It appears that it is a process that evolved to correct errors of replication which lead to long deletions and which are not eliminated by other systems.  相似文献   
2.

Study design

A prospective treatment study with a new brace was conducted Objective. To evaluate radiological and subjective clinical results after one year conservative brace treatment with pressure onto lordosis at the thoracolumbar joint in children with scoliosis and kyphosis.

Summary of background data

Conservative brace treatment of adolescent scoliosis is not proven to be effective in terms of lasting correction. Conservative treatment in kyphotic deformities may lead to satisfactory correction. None of the brace or casting techniques is based on sagittal forces only applied at the thoracolumbar spine (TLI= thoracolumbar lordotic intervention). Previously we showed in patients with scoliosis after forced lordosis at the thoracolumbar spine a radiological instantaneous reduction in both coronal curves of double major scoliosis.

Methods

A consecutive series of 91 children with adolescent scoliosis and kyphosis were treated with a modified symmetric 30 degrees Boston brace to ensure only forced lordosis at the thoracolumbar spine. Scoliosis was defined with a Cobb angle of at least one of the curves [greater than or equal to] 25 degrees and kyphosis with or without a curve <25 degrees in the coronal plane. Standing radiographs were made i) at start, ii) in brace at beginning and iii) after one year treatment without brace.

Results

Before treatment start ??in brace?? radiographs showed a strong reduction of the Cobb angles in different curves in kyphosis and scoliosis groups (sagittal n = 5 all p < 0.001, pelvic obliquity p < 0.001). After one year of brace treatment in scoliosis and kyphosis group the measurements on radiographs made without brace revealed an improvement in 3 Cobb angles each.

Conclusion

Conservative treatment using thoracolumbar lordotic intervention in scoliotic and kyphotic deformities in adolescence demonstrates a marked improvement after one year also in clinical and postural criteria. An effect not obtained with current brace techniques.  相似文献   
3.
The ITS sequences of Acropora spp. are the shortest so far identified in any metazoan and are among the shortest seen in eukaryotes; ITS1 was 70-80 bases, and ITS2 was 100-112 bases. The ITS sequences were also highly variable, but base composition and secondary structure prediction indicate that divergent sequence variants are unlikely to be pseudogenes. The pattern of variation was unusual in several other respects: (1) two distinct ITS2 types were detected in both A. hyacinthus and A. cytherea, species known to hybridize in vitro with high success rates, and a putative intermediate ITS2 form was also detected in A. cytherea; (2) A. valida was found to contain highly (29%) diverged ITS1 variants; and (3) A. longicyathus contained two distinct 5.8S rDNA types. These data are consistent with a reticulate evolutionary history for the genus Acropora.   相似文献   
4.
    
The intrinsic characteristics of islands make them a unique study system for the investigation of ecological and evolutionary dynamics. The Mediterranean Basin, an island-rich biodiversity hotspot, still lacks a comprehensive spatial database for these geographic features. This study presents the first comprehensive spatial database of all Mediterranean islands larger than 0.01 km2, aiding ecological investigations and interdisciplinary research.  相似文献   
5.
The unusual behavior of the mutation ami36, which generates hyperrecombination in two point crosses, was previously attributed to a localized conversion process changing A/G mispairs into CG pairs. Although the mechanism was found to be dependent on the DNA polymerase I, the specific function responsible for this correction was still unknown. Analysis of the pneumococcal genome sequence has revealed the presence of an open reading frame homologous to the gene mutY of Escherichia coli. The gene mutY encodes an adenine glycosylase active on A/G and A/7,8-dihydro-8-oxoguanine (8-OxoG) mismatches, inducing their repair to CG and C/8-OxoG, respectively. Here we report that disrupting the pneumococcal mutY homologue abolishes the hyperrecombination induced by ami36 and leads to a mutator phenotype specifically enhancing AT-to-CG transversions. The deduced amino acid sequence of the pneumococcal MutY protein reveals the absence of four cysteines, highly conserved in the endonuclease III/MutY glycosylase family, which ligate a [4Fe-4S](2+) cluster. The actual function of this cluster is still intriguing, inasmuch as we show that the pneumococcal gene complements a mutY strain of E. coli.  相似文献   
6.
Vegetation History and Archaeobotany - Knowledge about the vegetation history of Sardinia, the second largest island of the Mediterranean, is scanty. Here, we present a new sedimentary record...  相似文献   
7.
The chloroperoxidase catalyzed oxidation of methyl phenyl sulfide to (R)-methyl phenyl sulfoxide was investigated, both in batch and membrane reactors, using as oxidant H2O2, or O2 in the presence of either dihydroxyfumaric acid or ascorbic acid. The effects of pH and nature and concentration of the oxidants on the selectivity, stability, and productivity of the enzyme were evaluated. The highest selectivity was displayed by ascorbic acid/O2, even though the activity of chloroperoxidase with this system was lower than that obtained with the others. When the reaction was carried out in a membrane reactor, it was possible to reuse the enzyme for several conversion cycles. The results obtained with ascorbic acid/O2 and dihydroxyfumaric acid/O2 as oxidants do not seem to be compatible with either a mechanism involving hydroxyl radicals as the active species or with the hypothesis that oxidation occurs through the initial formation of H2O2. Copyright 1999 John Wiley & Sons, Inc.  相似文献   
8.
    
Substitute methadone prescribing is one of the main modes of treatment for opiate dependence. This study examined the relationship between methadone dose (measured by daily dose and methadone's active (R)‐enantiomer blood levels) and opiate receptor function. Nine subjects on substitute methadone (30‐90 mg daily) received three subcutaneous injections 1.5 hours apart (saline, 5 mg and 10 mg hydromorphone, a short‐acting opiate agonist) followed by measures of functional response in particular saccadic eye movements (SEMs), as well as self‐report measures. Ten mg of hydromorphone significantly slowed SEM parameters (peak velocity by 15%, p <0.005; peak acceleration by 20%, p <0.025; peak deceleration by 26%, p <0.025) and the SEM velocity changes correlated significantly with (R)‐methadone levels (r =0.844, p <0.005) and with the oral dose of methadone being taken (r =0.829, p <0.005). Although a similar trend was observed for 5 mg, this was not significant. These finding suggest that, at higher methadone doses (resulting in higher plasma concentrations), there is significant tolerance to the action of agonists. Such studies may help in refining our understanding of the actions of methadone and the SEM measure could help in defining the degree of tolerance in individuals using street heroin.  相似文献   
9.
One of the diseases of veterinary and public health importance affecting the Kafue lechwe (Kobus leche kafuensis) on the Kafue flats is brucellosis, for which only scant information is available. During the 2003 (October), 2004 (December), and 2008 (July-December) hunting seasons in the Kafue flats, we conducted a study to determine the seroprevalence of Brucella spp. in the Kafue lechwe and to evaluate serologic tests for detection of Brucella spp. antibodies in lechwe. The Rose Bengal Test (RBT), competitive enzyme-linked immunosorbent assay (cELISA), and fluorescence polarization assay (FPA) were used. A total of 121 Kafue lechwe were hunted for disease investigations in 2003, 2004, and 2008 in the Kafue Flat Game Management Area. Of these, 21.6%, (95% confidence interval [CI]: 14.2-29.1%) had detectable antibodies to Brucella spp. The Kafue lechwe in Lochnivar National Park had higher antibody results than those in Blue Lagoon National Park (odds ratio=3.0; 95% CI: 0.94-9.4). Infection levels were similar in females (21.6%) and males (21.7%). Results were similar among RBT, FPA, cELISA tests, suggesting that these could effectively be used in diagnosing brucellosis in the Kafue lechwe. Our study demonstrates the presence of Brucella infections in the Kafue lechwe in two national parks located in the Kafue flats and further highlights the suitability of serologic assays for testing the Kafue lechwe. Because the Kafue lechwe is the most hunted wildlife species in Zambia, hunters need to be informed of the public health risk of Brucella spp. infection.  相似文献   
10.
We investigated the denaturation of tetrameric 20 beta-hydroxysteroid dehydrogenase (20R)-17 beta,20 beta,21-trihydroxysteroid:NAD+ oxidoreductase, EC 1.1.1.53) to find out whether intermediate states are formed during the process. The denaturation process was studied in the presence and absence of stabilizers, both specific, such as NADH, and non-specific, such as the salting-out anion phosphate. Changes in enzymatic activity, intrinsic protein fluorescence and far-ultraviolet circular dichroism were monitored. When NADH was present, denaturation of the enzyme by urea was a one-step transition between the native and the completely denatured state. In dilute phosphate, and even more so in concentrated phosphate, the existence of intermediate states with different stability is evidenced by the noncoincidence of the transition curves that probe for different functional and conformational aspects of the enzyme. Therefore, for 20 beta-hydroxysteroid dehydrogenase the formation of intermediates can be prevented by adding NADH, or enhanced by adding concentrated phosphate.  相似文献   
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