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1.
The phylogeny of the hominoid primates: a statistical analysis of the DNA-DNA hybridization data 总被引:1,自引:0,他引:1
Sibley and Ahlquist compared the single-copy nuclear DNA sequences of the
hominoid primates using DNA-DNA hybridization. From this data set they
estimated a phylogeny that clusters man and chimpanzees using a distance
Wagner procedure. However, no assessment of statistical confidence in this
estimated phylogeny was made, despite the fact that their data set contains
internal inconsistencies concerning the correct branching order. This paper
presents a modification of Pielou's Q- statistic that allows one to make
nonparametric tests of phylogenetic relationship from distance data. The
results of this analysis indicate that the estimated phylogeny of Sibley
and Ahlquist is without statistical significance owing to the internal
inconsistencies of the data set. A survey and additional analyses of other
types of molecular data indicate that the phylogeny that clusters
chimpanzees and gorillas and has the human lineage splitting off earlier is
statistically consistent with all the molecular data (including the DNA-DNA
hybridization data), whereas the phylogeny estimated by Sibley and Ahlquist
can be rejected at the 5% level using the data on restriction- endonuclease
sites in the mitochondrial genome.
相似文献
2.
Molecular analysis of a beta-lactam resistance gene encoded within the cephamycin gene cluster of Streptomyces clavuligerus.
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A Streptomyces clavuligerus gene (designated pcbR) which is located immediately downstream from the gene encoding isopenicillin N synthase in the cephamycin gene cluster was characterized. Nucleotide sequence analysis and database searching of PcbR identified a significant similarity between PcbR and proteins belonging to the family of high-molecular-weight group B penicillin-binding proteins (PBPs). Eight of nine boxes (motifs) conserved within this family of proteins are present in the PcbR protein sequence in the same order and with approximately the same spacing between them. When a mutant disrupted in pcbR was constructed by gene replacement, the resulting pcbR mutant exhibited a significant decrease in its resistance to benzylpenicillin and cephalosporins, indicating that pcbR is involved in beta-lactam resistance in this organism. Western blot (immunoblot) analysis of S. clavuligerus cell membranes using PcbR-specific antibodies suggested that PcbR is a membrane protein. PcbR was also present in cell membranes when expressed in Escherichia coli and was able to bind radioactive penicillin in a PBP assay, suggesting that PcbR is a PBP. When genomic DNAs from several actinomycetes were probed with pcbR, hybridization was observed to some but not all beta-lactam-producing actinomycetes. 相似文献
3.
Dr AR Holmes RD Cannon HF Jenkinson 《Journal of industrial microbiology & biotechnology》1995,15(3):208-213
The yeastCandida albicans coaggregates with a variety of streptococcal species, an interaction that may promote oral colonization by yeast cells.C. albicans andCandida tropicalis are the yeasts most frequently isolated from the human oral cavity and our data demonstrate that both these species bind toStreptococcus gordonii NCTC 7869 while two otherCandida species (Candida krusei andCandida kefyr) do not. Adherence ofC. albicans was greatest when the yeast had been grown at 30° C to mid-exponential growth phase. For 21 strains ofC. albicans there was a positive correlation between the ability to adhere toS. gordonii and adherence to experimental salivary pellicle. Whole saliva either stimulated or slightly inhibited adherence ofC. albicans toS. gordonii depending on the streptococcal growth conditions. The results suggest that the major salivary adhesins and coaggregation adhesins ofC. albicans are co-expressed. 相似文献
4.
Cytochrome P-448 (mol wt 55,000 Daltons) from rabbit liver was purified to a specific content of 16.6 nmol/mg. Mice were immunised with this preparation, their spleens removed and dissociated lymphocytes hybridised with myeloma cells. Four monoclonal antibodies against cytochrome P-448 were raised and partially characterised. All four antibodies interacted with cytochrome P-448 in intact microsomal fractions and selectively immunoadsorbed cytochrome P-448 from solubilised microsomal preparations. One of the antibodies inhibited benzo[a] pyrene hydroxylase activity in a reconstituted system, one had no effect on activity and two increased activity. The possible applications of such antibodies are discussed. 相似文献
5.
DC Chhieng AR Frost S Niwas H Weiss WE Grizzle S Beeken 《Biotechnic & histochemistry》2013,88(1):25-36
Small biopsy samples are used increasingly to assess the biomarker expression for prognostic information and for monitoring therapeutic responses prior to and during neoadjuvant therapy. The issue of intratumor heterogeneity of expression of biomarkers, however, has raised questions about the validity of the assessment of biomarker expression based on limited tissue samples. We examined immunohistochemically the expression of HER-2neu (p185erbB-2), epidermal growth factor receptor (EGFR), Bcl-2, p53, and proliferating cell nuclear antigen (PCNA) in 30 breast carcinomas using archived, paraffin embedded tissue and determined the extent of intratumor heterogeneity. Each section was divided into four randomly oriented discrete regions, each containing a portion of the infiltrating carcinoma. For each tumor, the entire lesion and four regions were analyzed for the expression of these markers. Scores of both membrane and cytoplasmic staining of HER-2neu and EGFR, scores of cytoplasmic staining of Bcl-2, and scores of nuclear staining of both p53 and PCNA were recorded. The intensity of staining and the proportion of immunostained cells were determined. A semiquantitative immunoscore was calculated by determining the sum of the products of the intensity and corresponding proportion of stained tumor cells. We analyzed both invasive (IDC) and in situ (DCIS) carcinomas. The Wilcoxon signed-rank test was used for paired comparisons between overall and regional immunoscores and between overall and regional percentages of stained cells. Spearman's correlation coefficients were used to assess the level of agreement of overall biomarker expression with each of the regions. Generalized linear models were used to assess overall and pair-wise differences in the absolute values of percent changes between overall and regional expression of biomarkers. For IDCs, there were no statistically significant differences in the expression of the biomarkers in terms of either the percentage of cells staining or the immunoscores when comparing the entire tumor with each region except for the lower EGFR expression of arbitrarily selected region 1 and lower p53 expression of region 1 compared to that of the entire tumor section. For DCIS, there were no statistically significant differences in the expression of the biomarkers between the entire tumor and each region except in PCNA of region 2 compared to that of entire tumor section. Positive correlation of immunoscores was observed between the entire tumor and each region as well as across all four regions for IDC. Similar observations were noted with DCIS except for HER-2neu and PCNA. No statistically significant differences were observed in the absolute values of percent changes of biomarker expression between overall and the four regions for both DCIS and IDC. Therefore, no significant intratumor heterogeneity in the expression of HER-2neu, Bcl-2, and PCNA was observed in IDC. Minor regional variations were observed for EGFR and p53 in IDC. Similarly, no significant regional variation in the expression of markers was observed in DCIS except for PCNA. 相似文献
6.
GÖRAN I. V. KLOBUČAR MARTINA PODNAR MIŠEL JELIĆ DAMJAN FRANJEVIĆ MATEJ FALLER ANAMARIA ŠTAMBUK SANJA GOTTSTEIN VLADICA SIMIĆ IVANA MAGUIRE 《Freshwater Biology》2013,58(6):1089-1105
1. This study examines phylogeography and phylogeny of the threatened stone crayfish, Austropotamobius torrentium, in order to elucidate the role of the Dinaric Karst geology in shaping the evolutionary history and genetic diversity of aquatic fauna in the western Balkans. Mitochondrial 16S rRNA and COI genes were partially sequenced from 188 and 159 crayfish, respectively, sampled from 70 localities. Phylogenetic relationships were reconstructed using four methods of phylogenetic inference. Divergence times between phylogroups were estimated in a Bayesian framework, and their demographic history was examined using neutrality tests and mismatch distribution analysis. 2. Seven geographically localised phylogroups separated by pronounced genetic gaps were found. Five of them have a distribution range within the northern‐central Dinaric (NCD) region, while the remaining two include populations from the southern Balkans (SB) and central and south‐eastern Europe (CSE). The oldest divergence event separated two NCD lineages from the rest of populations in the Late Miocene or Early Pliocene. Divergences amongst the five NCD phylogroups and SB + CSE occurred in the Pliocene. The most recent split separated SB and CSE phylogroups during the Late Pliocene. For both genes, uncorrected pairwise divergences between most of the phylogroups (4.1–8.7% for COI and 1.6–4.8% for 16S rRNA) were of the same range as, or higher than, some of the interspecific distances previously reported for the genus Austropotamobius. 3. Geographically isolated and deeply divergent cryptic monophyletic phylogroups within A. torrentium in the NCD region arose in the course of intensification of Neotectonic movements during the Pliocene and the beginning of the Pleistocene and the development of karstification that has heavily fragmented the palaeohydrography of the area. The results confirm a gradual north–south expansion of stone crayfish during the pre‐Pleistocene that preceded the rapid northward post‐glacial re/colonisation of central Europe (CSE phylogroup) through the Danube drainage. 4. Austropotamobius torrentium comprises morphologically cryptic but molecularly distinct taxa. Considering the relatively small geographical areas they inhabit, the NCD phylogroups of stone crayfish should be given the highest conservation priority. 相似文献
7.
The purpose of this study was to formulate a gelled self-emulsifying drug delivery system (SEDDS) containing ketoprofen as
an intermediate in the development of sustained release solid dosage form. Captex 200 (an oil), Tween 80 (a surfactant), and
Capmul MCM (a cosurfactant) were used to formulate SEDDS. Silicon dioxide was used as a gelling agent, which may aid in solidification
and retardation of drug release. Effect of concentrations of cosurfactant and gelling agent on emulsification process and
in vitro drug diffusion was studied using 32 factorial design. Multiple regression analysis data and response surfaces obtained showed that liquid crystal phase viscosity
increased significantly with increasing amount of silicon dioxide, which in turn caused an increase in average droplet size
of resultant emulsion and slower drug diffusion. Drug release from the formulation increased with increasing amount of cosurfactant. 相似文献
8.
The purpose of this research was to obtain directly compressible agglomerates of ibuprofen-paracetamol containing a desired
ratio of drugs using a crystallo-co-agglomeration technique. Crystallo-co-agglomeration is an extension of the spherical crystallization
technique, which enables simultaneous crystallization and agglomeration of 2 or more drugs or crystallization of a drug and
its simultaneous agglomeration with another drug or excipient. Dichloromethane (DCM)-water system containing polyethylene
glycol (PEG) 6000, polyvinyl pyrollidone, and ethylcellulose was used as the crystallization system. DCM acted as a good solvent
for ibuprofen and bridging liquid for agglomeration. The process was performed at pH 5, considering the low solubility of
ibuprofen and the stability of paracetamol. Loss of paracetamol was reduced by maintaining a low process temperature and by
the addition of dextrose as a solubility suppressant. The agglomerates were characterized by differential scanning calorimetry,
powder x-ray diffraction (PXRD), and scanning electron microscopy and were evaluated for tableting properties. The spherical
agglomerates contained an ibuprofen-paracetamol ratio in the range of 1.23 to 1.36. Micromeritic, mechanical, and compressional
properties of the agglomerates were affected by incorporated polymer. The PXRD data showed reduction in intensities owing
to dilution and reduced crystallinity. Thermal data showed interaction between components at higher temperature. Ethylcellulose
imparted mechanical strength to the agglomerates as well as compacts. The agglomerates containing PEG have better comparessibility
but drug release in the initial stages was affected owing to asperity melting, yielding harder compacts. The agglomeration
and properties of agglomerates were influenced by the nature of polymer. 相似文献
9.
Conclusion Hydrolyzed gelatins (Byco-A, Byco-O and Byco-C), when used as binders, yielded soft, uniform granules with good flow properties.
As the molecular weight and viscosity of hydrolyzed gelatins increased, the compressibility of granules decreased and their
compactability increased. The balance between compressibility and compactability of granules may be achieved by careful monitoring
of the molecular weight of hydrolyzed gelatins that can serve as potential binders. 相似文献
10.