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411.
Partial 18S rRNA sequences of five chelicerate arthropods plus a
crustacean, myriapod, insect, chordate, echinoderm, annelid, and
platyhelminth were compared. The sequence data were used to infer phylogeny
by using a maximum-parsimony method, an evolutionary-distance method, and
the evolutionary-parsimony method. The phylogenetic inferences generated by
maximum-parsimony and distance methods support both monophyly of the
Arthropoda and monophyly of the Chelicerata within the Arthropoda. These
results are congruent with phylogenies based on rigorous cladistic analyses
of morphological characters. Results support the inclusion of the
Arthropoda within a spiralian or protostome coelomate clade that is the
sister group of a deuterostome clade, refuting the hypothesis that the
arthropods represent the "primitive" sister group of a protostome coelomate
clade. Bootstrap analyses and consideration of all trees within 1% of the
length of the most parsimonious tree suggest that relationships between the
nonchelicerate arthropods and relationships within the chelicerate clade
cannot be reliably inferred with the partial 18S rRNA sequence data. With
the evolutionary-parsimony method, support for monophyly of the Arthropoda
is found in the majority of the combinations analyzed if the coelomates are
used as "outgroups." Monophyly of the Chelicerata is supported in most
combinations assessed. Our analyses also indicate that the
evolutionary-parsimony method, like distance and parsimony, may be biased
by taxa with long branches. We suggest that a previous study's inference of
the Arthropoda as paraphyletic may be the result of (a) having two few
arthropod taxa available for analysis and (b) including long-branched taxa.
相似文献
412.
Changes in Extracellular Amino Acids and Spontaneous Neuronal Activity During Ischemia and Extended Reflow in the CA1 of the Rat Hippocampus 总被引:7,自引:2,他引:5
Peter Andiné Owe Orwar Ingemar Jacobson Mats Sandberg Henrik Hagberg 《Journal of neurochemistry》1991,57(1):222-229
This study addresses the possible involvement of an agonist-induced postischemic hyperactivity in the delayed neuronal death of the CA1 hippocampus in the rat. In two sets of experiments, dialytrodes were implanted into the CA1 either acutely or chronically (24 h of recovery). During 20 min of cerebral ischemia (four-vessel occlusion model) and 8 h of reflow, we followed extracellular amino acids and multiple-unit activity. Multiple-unit activity ceased within 20 sec of ischemia and remained zero during the ischemic insult and for the following 1 h of reflow. During ischemia, extracellular aspartate, glutamate, taurine, and gamma-aminobutyric acid increased in both acute and chronic experiments (seven- to 26-fold). Multiple-unit activity recovered to preischemic levels following 4-6 h of reflow. In the group with dialytrodes implanted acutely, the continuous increase in multiple-unit activity reached 110% of basal at 8 h of reflow. In the group with dialytrodes implanted chronically, multiple-unit activity recovered faster and reached 140% of control at 8 h, paralleled by an increase in extracellular aspartate (5.5-fold) and glutamate (twofold). In conclusion, the postischemic increase of excitatory amino acids and the recovery of the neuronal activity may stress the CA1 pyramidal cells, which could be detrimental in combination with, e.g., postsynaptic impairments. 相似文献
413.
414.
Effects of context on judgements of odor intensities in humans 总被引:2,自引:2,他引:0
This study evaluated whether the intensity of previously smelled odors
could unintentionally influence the subsequent judgement of odor intensity.
The predicted context effect was based on the adaptation- level theory.
Before and 25 min after either WEAK or STRONG biasing odor concentrations,
51 subjects were required to rate the intensity of 10 different odor
concentrations of California Orange Oil. After the WEAK bias, subjects
judged the odor intensity as being stronger than they did after the STRONG
bias. Thus the intensity of odors smelled 25 min earlier can
unintentionally influence subsequent odor intensity judgement. The findings
are discussed in the light of two alternative explanations, namely, a
central implicit memory process and a stimulus- level-based change at the
peripheral level.
相似文献
415.
VO2 max is associated with ACE genotype in postmenopausal women 总被引:6,自引:0,他引:6
Hagberg James M.; Ferrell Robert E.; McCole Steve D.; Wilund Kenneth R.; Moore Geoffrey E. 《Journal of applied physiology》1998,85(5):1842-1846
Relationships have frequently been found betweenangiotensin-converting enzyme (ACE) genotype and various pathologicaland physiological cardiovascular outcomes and functions. Thuswe sought to determine whether ACE genotype affected maximalO2 consumption (O2 max) and maximalexercise hemodynamics in postmenopausal women with different habitualphysical activity levels. Age, body composition, and habitual physicalactivity levels did not differ among ACE genotype groups. However, ACEinsertion/insertion (II) genotype carriers had a 6.3 ml · kg1 · min1higher O2 max(P < 0.05) than the ACEdeletion/deletion (DD) genotype group after accounting for the effectof physical activity levels. The ACE II genotype group also had a 3.3 ml · kg1 · min1higher O2 max(P < 0.05) than the ACEinsertion/deletion (ID) genotype group. The ACE ID group tended to havea higher O2 max thanthe DD genotype group, but the difference was not significant. ACEgenotype accounted for 12% of the variation inO2 max among womenafter accounting for the effect of habitual physical activity levels.The entire difference inO2 max among ACEgenotype groups was the result of differences in maximal arteriovenousO2 difference (a-vDO2).ACE genotype accounted for 17% of the variation in maximal a-vDO2 inthese women. Maximal cardiac output index did not differ whatsoeveramong ACE genotype groups. Thus it appears that ACE genotype accountsfor a significant portion of the interindividual differences inO2 max among thesewomen. However, this difference is the result of genotype-dependentdifferences in maximala-vDO2 andnot of maximal stroke volume and maximal cardiac output. 相似文献
416.
417.
Strength training increases regional bone mineral density and bone remodeling in middle-aged and older men 总被引:7,自引:0,他引:7
418.
419.
420.
Nucleotide sequence of the D-loop region of the sperm whale (Physeter macrocephalus) mitochondrial genome 总被引:4,自引:0,他引:4
We have amplified, by the polymerase chain reaction, and have sequenced the
D-loop region of the mitochondrial DNA from the sperm whale (Physeter
macrocephalus). The sperm whale D-loop was aligned with D- loop sequences
from four other cetaceans (Commerson's dolphin, orca, fin whale, and minke
whale) and an out-group (cow). This alignment showed the sperm whale
sequence to be larger than that of other cetaceans. In addition, some
sequence blocks were highly conserved among all six species, suggesting
roles in the functioning of mitochondrial DNA. Other blocks that were
previously reported to be well conserved among cetaceans showed little
sequence conservation with the sperm whale D-loop, which argues against the
functional importance of these sequence blocks in cetaceans.
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