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Compensatory substitutions and the evolution of the mitochondrial 12S rRNA gene in mammals 总被引:5,自引:2,他引:3
12S ribosomal RNA (rRNA) gene sequences from a suite of mammalian taxa (13
placentals, 4 marsupials, 1 monotreme), for which phylogenetic
relationships are well established based on independent criteria, were
employed to study the evolution of this gene. Phylogenetic analysis of 12S
sequences produces a phylogeny that agrees with expectations. Base
composition provides evidence for directional symmetrical substitution
pressure in loops; in stems, base composition is much more even. Rates of
nucleotide substitution are lower in stems than loops. Patterns of
nucleotide substitution show an overall preference for transitions over
transversions, with this difference more profound in stems than loops.
Among different transversion pathways, there is a wide range of
transformation frequencies. An analysis of compensatory substitutions shows
that there is strong evidence for their occurrence and that a weighting
factor of 0.61 should be applied in phylogenetic analyses to account for
the dependence of mutations at stem positions relative to positions where
changes are independent. Among stem variables (i.e., stem length,
interaction distance, substitution rates, G+C content, and the percentage
of bases that are paired), several significant correlations were
discovered, but stem length and interaction distance are uncorrelated with
other variables.
相似文献
2.
Statins produce large, clinically important beneficial effects on total low-density lipoprotein (LDL) cholesterol and triglycerides while raising high-density lipoprotein (HDL) cholesterol--each of which increases the risks for cardiovascular disease (CVD). In randomized trials of secondary and primary prevention, and their meta-analyses, statins confer statistically significant, clinically important reductions in myocardial infarction, stroke, and CVD death. In 2001, the National Cholesterol Education Program (NCEP) Adult Treatment Panel (ATP) III included LDL as the primary target, recommending optional goals of < 100 mg/dL for high-risk patients, < 130 mg/dL for moderate-risk patients, and < 160 mg/dL for low-risk patients. We conducted a search of randomized trials of statins whose results were published since May 15, 2001. We extracted overall trial results and data on adverse events, when available. We reviewed 7 published trials of statins, some of which contributed to the recent addendum to the NCEP ATP III guidelines that recommend reducing LDL goals to < 70 for very high-risk and < 100 for moderately high-risk patients via statins. Data from these trials demonstrate that greater LDL reductions produce larger CVD benefits in various categories of high- and moderate-risk patients, including a large number of primary prevention patients with metabolic syndrome who should be treated as aggressively as patients who have survived a myocardial infarction or stroke. Together, these recent statin trials and the NCEP ATP III revised guidelines, if implemented by primary healthcare providers, would result in many more patients receiving statins of proven benefit and reassuring adverse event profile. 相似文献
3.
Laura Hollar Julius Luke Dmitri A. Maslov 《The Journal of eukaryotic microbiology》1998,45(3):293-297
To obtain additional information on the phylogenetic relationships within the family Trypanosomatidae (order Kinetoplastida), we have sequenced the small subunit ribosomal RNA genes from the endosymbiont containing species Herpetomonas roitmani TCC080, Herpetomonas sp. TCC263, Crithidia oncopelti ATCC 12982 and a partial large subunit rRNA gene from H. roitmani. The small subunit sequences in the two isolates of Herpetomonas are very similar but not identical, and so are their restriction digest profiles of kinetoplast DNA. The size of minicircles in both isolates is 4.2 kilobases. The inferred ribosomal RNA phylogenetic trees shows the genera Herpetomonas and Crithidia as polyphyletic. Endosymbiont-bearing herpetomonads cluster with the endosymbiont-bearing crithidias and a blastocrithidia to form a monophyletic clade, whereas the endosymbiont-free members of these genera are found elsewhere in the tree. These data support the hypothesis of a monophyletic origin of endosymbiosis in trypanosomatid evolution and also suggest that a taxonomic revision is needed in order to better describe the natural affinities in this family. 相似文献
4.
Julius Lukeš Milan Jirků David Doležel Ivica Kral'ová Laura Hollar Dmitri A. Maslov 《Journal of molecular evolution》1997,44(5):521-527
To further investigate the phylogeny of protozoa from the order Kinetoplastida we have sequenced the small subunit (SSU)
and a portion of the large subunit (LSU) nuclear rRNA genes. The SSU and LSU sequences were determined from a lizard trypanosome,
Trypanosoma scelopori and a bodonid, Rhynchobodo sp., and the LSU sequences were determined from an insect trypanosomatid, Crithidia oncopelti, and a bodonid, Dimastigella trypaniformis. Contrary to previous results, in which trypanosomes were found to be paraphyletic, with Trypanosoma brucei representing the earliest-diverging lineage, we have now found evidence for the monophyly of trypanosomes. Addition of new
taxa which subdivide long branches (such as that of T. brucei) have helped to identify homoplasies responsible for the paraphyletic trees in previous studies. Although the monophyly of
the trypanosome clade is supported in the bootstrap analyses for maximum likelihood at 97% and maximum parsimony at 92%, there
is only a small difference in ln-likelihood value or tree length between the most optimal monophyletic tree and the best suboptimal
paraphyletic tree. Within the trypanosomatid subtree, the clade of trypanosomes is a sister group to the monophyletic clade
of the nontrypanosome genera. Different groups of trypanosomes group on the tree according to their mode of transmission.
This suggests that the adaptation to invertebrate vectors plays a more important role in the trypanosome evolution than the
adaptation to vertebrate hosts.
Received: 5 July 1996 / Accepted: 26 September 1996 相似文献
5.
Bu W Myers N McCarty JD O'Neill T Hollar S Stetson PL Sved DW 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2003,783(2):411-423
A liquid chromatographic-tandem mass spectrometric (LC-MS-MS) method without sample pretreatment was developed and validated for determination of porphyrins in samples of canine urine. Acidified urine samples were directly injected into the LC-MS system and a gradient elution program was applied. The mass spectrometer was operated in the multi-reaction monitoring (MRM) mode and six porphyrins were detected with excellent sensitivity and selectivity. The lower limits of quantification were 0.014 nmol/mL for mesoporphyrin IX, coproporphyrin I, 5-carboxylporphyrin, 6-carboxylporphyrin and 7-carboxylporphyrin, and 0.029 nmol/mL for uroporphyrin I. Good ln-quadratic responses of calibration standards over the range 0.01 to 1.0 nmol/mL for mesoporphyrin IX, coproporphyrin I, 5-carboxylporphyrin, 6-carboxylporphyrin and 7-carboxylporphyrin, and 0.02 to 1.0 nmol/mL for uroporphyrin I were demonstrated. This method should be easily adapted through cross-validation for use in determining the effects of chemicals and pharmaceuticals on the urinary excretion profile of porphyrins in preclinical studies with other species, and in assisting the diagnosis of porphyria in clinical studies. 相似文献
6.
Jewell Dennis E. Tavener Selena K. Hollar Regina L. Panickar Kiran S. 《Metabolomics : Official journal of the Metabolomic Society》2022,18(8):1-5
Metabolomics - The global population is aging. Preserving function and independence of our aging population is paramount. A key component to maintaining independence is the preservation of... 相似文献
7.
David W. Hollar 《Genetica》2009,137(3):253-264
This study investigates the different Human Leukocyte Antigen (HLA) genotypes and their possible associations with both disease
and behavior, specifically by describing significant associations between particular HLA genotypes and occurrence of intentional
violent death. A de-identified dataset of n = 216,426 deceased American organ donors was analyzed for all possible genotypes by comparing the Independent Variable (Each
specific HLA genotype vs. remainder of sample, non-genotype) on the Dependent Variable (Intentional Violent vs. Non-violent
death). For HLA-A, 17 heterozygotes were significantly associated with increased occurrence of intentional violent death,
with heightened prevalence for HLA-A2, HLA-A23, HLA-A30, HLA-A68, and HLA-A74 alleles. For HLA-B, 32 heterozygotes were significant,
25 of which (e.g., HLA-B7, HLA-B8, HLA-B35, HLA-B44, and HLA-B53) exhibited heightened prevalence of violent death. For HLA-BW,
homozygotes had significantly increased odds ratios for intentional violent death. For HLA-DRB1, 19 heterozygotes were significant,
with heightened prevalence only for the HLA-DRB1-4 allele. There were no racial differences in risk for the significant HLA-A
and HLA-B genotypes. These exploratory, not necessarily causal, results provide the first indications of possible HLA-aggression
associations in humans, supporting animal models. 相似文献
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