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321.
C M Tipton L A Sebastian J M Overton C R Woodman S B Williams 《Journal of applied physiology》1991,71(6):2206-2210
Studies with male spontaneously hypertensive rats (SHR) were initiated to determine the hemodynamic relationships associated with the lower resting caudal artery systolic blood pressure (SBP) of endurance-trained SHR populations. After assignment into nontrained (NT, n = 38) and trained (T, n = 38) groups, the T animals were exercised 5 times/wk on a motor-driven treadmill for 12-16 wk at a moderate intensity that ranged from 40 to 70% of their maximum O2 consumption capacity (VO2max). SBP, VO2max, and treadmill run time were determined before the experimental period began and before the animals were instrumented for hemodynamic measurements. At the end of the study, the T rats exhibited significantly lower SBP (NT = 210 +/- 3, T = 200 +/- 3 mmHg) and significantly higher VO2max (NT = 75 +/- 2, T = 83 +/- 2 ml.min-1.kg-1) and run durations (NT = 11.4 +/- 0.4, T = 14.5 +/- 0.3 min). When the animals were anesthetized for insertion of catheters and microprobes for blood pressure and cardiac output (thermodilution) measurements, the T rats had lower values for body mass, heart rate, mean blood pressure, cardiac output, and cardiac index than the NT rats; however, only the body mass and heart rate differences were statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
322.
1. Antlions are opportunistic trap building predators that cannot control prey encounter. Their trap should ideally retain a great diversity of prey. However, building a single trap that captures many prey with varying characteristics can be challenging. 2. A series of five different ant species ranging from thin to large, of sizes ranging from 2.75 to 6.5 mm, and a mean weight ranging from 0.54 to 6.00 mg were offered in a random succession to antlions. The state of satiation of the antlions was controlled, and their mass and the depth of their pit were recorded. The reaction of antlion to the prey, the probability of capture as well as the time to escape were recorded. 3. The probability of an antlion reaction is an increasing function of the pit depth and a decreasing function of antlion mass. The probability of capture is highest for intermediate prey mass and is an increasing function of pit depth. The time to escape is a declining function of prey mass and an increasing function of pit depth. 4. There is an upper limit to prey mass given that large prey escape out of the pit. There is a lower limit to prey mass given the difficulty to apprehend the smallest, thin species. Consequently, there is a range of prey mass, corresponding to a medium‐sized ant of 2 mg, for which the pit functions best. The physics of insect locomotion on sandy slopes was identified as the key to understanding the functioning of antlion pits. 相似文献
323.
Drummond FA Collins JA Choate B Woodman D Jennings DT Forsythe HY Cokendolpher JC 《Environmental entomology》2010,39(5):1428-1440
Over a period of 19 yr, the harvestman (Opiliones) community associated with the lowbush blueberry agro-ecosystem in Maine was studied. Eight species representing five genera, four subfamilies, and two families of harvestmen belonging to the suborder Eupnoi were collected. The harvestman community was dominated by two introduced, synanthropic species: Phalangium opilio in all but 1 yr (that year dominated by Rilaena triangularis). Rilaena was recorded for the first time from eastern North America. Relative abundance of harvestman adults increases throughout the season and the temporal pattern of trap capture does not refute speculated life cycles of the harvestmen being univoltine with overwintering eggs. Some blueberry management practices were found to affect trap capture. We did find that on average (with opposite results 1 yr) trap captures are greater in pruned fields than in fruit-bearing fields. Organic fields were found to have higher relative abundance of harvestmen than conventionally managed fields. Conventionally managed fields with reduced-risk insecticides showed no difference in harvestmen relative abundance compared with those conventionally managed fields using the older more persistent organophosphate insecticides. Insecticide trials with common insecticides used in blueberry insect pest management showed that the organophosphate insecticide, phosmet, and the pyrethroid insecticide, esfenvalerate, were detrimental to P. opilio adults when exposed to leaf residues, whereas the reduced-risk insecticide, spinosad, showed no negative effects compared with nonsprayed foliage. 相似文献
324.
325.
Boris Musset Susan ME Smith Sindhu Rajan Vladimir V Cherny Deri Morgan Thomas E DeCoursey 《Channels (Austin, Tex.)》2010,4(4):260-265
The voltage-gated proton channel exists as a dimer, although each protomer has a separate conduction pathway, and when forced to exist as a monomer, most major functions are retained. However, the proton channel protomers appear to interact during gating. Proton channel dimerization is thought to result mainly from coiled-coil interaction of the intracellular C-termini. Several types of evidence are discussed that suggest that the dimer conformation may not be static, but is dynamic and can sample different orientations. Zn2+ appears to link the protomers in an orientation from which the channel(s) cannot open. A tandem WT-WT dimer exhibits signs of cooperative gating, indicating that despite the abnormal linkage, the correct orientation for opening can occur. We propose that C-terminal interaction functions mainly to tether the protomers together. Comparison of the properties of monomeric and dimeric proton channels speaks against the hypothesis that enhanced gating reflects monomer-dimer interconversion.Key words: voltage-gated proton channels, voltage gating, voltage-sensing domains, phagocytes, coiled-coil, oligomerization, proton currents, pH, dimerization, C-terminus 相似文献
326.
327.
Julie Woodman Matthew Hoffman Monika Dzieciatkowska Kirk C. Hansen Paul C. Megee 《Molecular biology of the cell》2015,26(21):3754-3767
The cohesion of replicated sister chromatids promotes chromosome biorientation, gene regulation, DNA repair, and chromosome condensation. Cohesion is mediated by cohesin, which is deposited on chromosomes by a separate conserved loading complex composed of Scc2 and Scc4 in Saccharomyces cerevisiae. Although it is known to be required, the role of Scc2/Scc4 in cohesin deposition remains enigmatic. Scc2 is a phosphoprotein, although the functions of phosphorylation in deposition are unknown. We identified 11 phosphorylated residues in Scc2 by mass spectrometry. Mutants of SCC2 with substitutions that mimic constitutive phosphorylation retain normal Scc2–Scc4 interactions and chromatin association but exhibit decreased viability, sensitivity to genotoxic agents, and decreased stability of the Mcd1 cohesin subunit in mitotic cells. Cohesin association on chromosome arms, but not pericentromeric regions, is reduced in the phosphomimetic mutants but remains above a key threshold, as cohesion is only modestly perturbed. However, these scc2 phosphomimetic mutants exhibit dramatic chromosome condensation defects that are likely responsible for their high inviability. From these data, we conclude that normal Scc2 function requires modulation of its phosphorylation state and suggest that scc2 phosphomimetic mutants cause an increased incidence of abortive cohesin deposition events that result in compromised cohesin complex integrity and Mcd1 turnover. 相似文献
328.
Woodman JD Cooper PD Haritos VS 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》2007,147(2):514-520
Water loss and VCO(2) relative to temperature and oxygen tension was investigated in a log-dwelling onychophoran (Euperipatoides rowelli) and a sympatric, un-described millipede species using flow-through respirometry. Onychophorans possess a tracheal system featuring permanently open spiracles. Total body water loss was consistently very high in E. rowelli and there was a positive correlation with increasing temperature. CO(2) output was continuous, increasing with higher temperatures and decreasing under lower oxygen concentrations. The millipede which has occludible spiracles also showed continuous gas exchange; however water loss was up to an order of magnitude lower than E. rowelli. An ability to survive under hypoxia is apparent for both species and corresponds with reports of hypoxic conditions within rotting logs. The rotting log habitat common to both taxa is characterized by high relative humidity and typically cool temperatures that approach 0 degrees C at night in winter. Consequently, dispersal through the higher temperatures and lower humidity of the exposed and dry understorey between suitable habitat may be hazardous for E. rowelli due to high desiccation susceptibility. 相似文献
329.
Molecular phylogenetic evidence that the phylum Haplosporidia has an alveolate ancestry 总被引:1,自引:0,他引:1
The phylogenetic position of the phylum Haplosporidia among other protists
was investigated with the complete 16S-like rRNA gene sequences from two
species in the phylum: Haplosporidium nelsoni, a parasite of oysters, and
Minchinia teredinis, a parasite of shipworms. Because the lack of obvious
morphological homologies with other protists hampered decisions regarding
taxonomic composition for sequence alignment and phylogenetic analysis, the
complete sequences for these two haplosporidians were directed as search
queries to the blast/ncbi.nlm.nih.gov electronic mail server. The results
of this heuristic similarity search provided a basis for constructing a
preliminary higher-taxonomic-level analysis comparing the haplosporidians
with species from the slime molds, fungi, algae, amoebae, ciliates,
dinoflagellates, and apicomplexans. Maximum parsimony yielded equivocal
results, whereas transversionally weighted parsimony suggested an affinity
with the alveolates (i.e., the ciliates, dinoflagellates, and
apicomplexans). Multiple alignment of the two haplosporidian sequences
against 17 taxa in a secondary analysis focusing on the alveolates and
subsequent parsimony analysis placed the phylum Haplosporidia as a
monophyletic group within the Alveolata and as a taxon of equal rank with
the other three alveolate phyla. The precise placement within the Alveolata
was sensitive to weighting.
相似文献
330.