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81.
Roberto Bacilieri Alexis Ducousso Rmy J. Petit Antoine Kremer 《Evolution; international journal of organic evolution》1996,50(2):900-908
The sessile (Quercus petraea [Matt.] Liebl.) and pedunculate (Quercus robur L.) oaks are two closely related species having a wide sympatric distribution over Europe. Under natural conditions, they frequently form mixed forests, where hybridization is suspected to occur. In this paper, two different approaches have been applied to the study of the mating system and the interspecific gene flow in a mixed stand formed by the two species. The mating systems of both species have been studied separately by means of the mixed-mating model. The relative contribution of the parental species to the progenies have been estimated with two different methods. The first uses the admixture model. The second is an extension of the mixed-mating model and subdivides the outcrossing rate into intra- and interspecific components. The two species were almost completely outcrossing. This high level of outcrossing and interspecific gene flow could play an important role in the maintenance of the genetic diversity in these long-lived forest tree species. The contribution of the sessile oak to the pedunculate oak progenies varied from 17% to 48%. In contrast, ovules of sessile oak trees appear to be preferentially fertilized by other extreme sessile genotypes. We suggest that interspecific and directional gene flow was responsible for such patterns. Pedunculate oak is considered as a pioneer species and is progressively replaced by sessile oak. Our present findings add a further genetic component to this succession scheme, suggesting that unidirectional gene flow reinforces succession between the two species. 相似文献
82.
In the ecotone research region of the Danube in Austria (Man-and-the-Biosphere (MaB)- project 5/21, Austrian Academy of Science) the macrophytes are one of the most important groups of organisms investigated. The species composition and the plant mass in hydrologically dynamic, and in predominantly stagnant sections of a system of lateral branches and sloughs were studied. This study showed that areas protected from frequent disturbance by floods had a greater number of species and higher biomass of aquatic macrophytes. Some species were shown to be evenly distributed throughout the branch system, whereas other species tended to form rare, but large singular patches. A set of new data elaboration techniques enabled us to describe the distribution pattern of the aquatic vegetation in this large branch system of the River Danube. 相似文献
83.
Isozyme analysis of Galaxias species (Teleostei: Galaxiidae) from the Taieri River, South Island, New Zealand: a species complex revealed 总被引:2,自引:0,他引:2
Richard M. Allibone Todd A. Crowl Jean M. Holmes Tania M. King Robert M. McDowall Colin R. Townsend Graham P. Wallis 《Biological journal of the Linnean Society. Linnean Society of London》1996,57(2):107-127
We examined genetic differentiation among 23 samples of non-migratory river galaxias from 17 streams in the Taieri River system, South Island, New Zealand. Four major genetic types were found, two of which occur in narrow sympatry in one location. These were compared with topotypical material representing Galaxias anomalus from the Clutha system (Otago) and G. vulgaris from the Waimakariri system (Canterbury) in order to establish identity. Morphological examination of these four major genetic types revealed consistent concomitant differences. The results suggest that there are at least three species of river galaxias in the Taieri system: G. anomalus, G. vulgaris and at least one previously undescribed species. We propose that the genetic structuring and subsequent speciation of this group has been promoted by the absence of the marine juvenile phase that is found in five other members of the genus native to New Zealand. This structuring may be exacerbated by population fragmentation over the last century owing to the negative influence of introduced trout. The phylogenetic diversity within the river system mirrors the diverse flora and invertebrate fauna of the region, and has conservation implications that parallel those resulting from our improved knowledge of the New Zealand herpetofauna through the application of genetic analysis. 相似文献
84.
H. Schöne 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1996,179(4):587-592
Honeybees returning from foraging trips were video-filmed while they walked through a narrow transparent gangway to reach the hive entrance. On their way they were presented with black-and-white gratings viewed underneath as well as to both sides of the gangway. Bees could exit the gangway through one of two or three side exits installed at different distances from the gangway entrance. In one set of experiments, the substrate on which the bees walked was moved either in the bee's direction or against it. In another set of experiments, the substrate was stationary, but the pattern was moved in one or the other direction. The bee's walking speed (WS) was evaluated from the video tapes. When the substrate moved against, or the pattern in the bee's direction, in either case decreasing the speed of pattern flow (PFS), the bees increased WS, and, at the same time, they preferred the more distant exit. When the substrate moved in, or the pattern against the bee's direction, thus increasing PFS, WS decreased and the bees preferred the nearer exit. These results suggest that the speed of optic flow controls the speed of locomotion and might therefore also serve for assessing the distance travelled.Abbreviations
PFS
pattern-flow speed
-
WS
walking speed
Dedicated to Hans-Jochen Autrum, editor emeritus, for help in giving birth to this and many other papers over very many years, often with criticism but nevertheless with encouragement and sympathy. 相似文献
85.
- 1. o
- 2. 1. Isoproterenol increased interscapular brown adipose tissue (BAT) blood flow and temperature.
- 3. 2. Phenylephrine increased BAT temperature, but did not affect blood flow. The effect was completely suppressed by Nω-nitro- -arginine methyl ester ( -NAME), an inhibitor of endogenous NO synthesis.
- 4. 3. Isoproterenol plus phenylephrine increased BAT blood flow and temperature earlier than isoproterenol alone.
- 5. 4. CL316,243 increased BAT blood flow and temperature. These effects were also inhibited by -NAME.
- 6. 5. These data suggest that BAT blood flow as well as thermogenesis is regulated mainly by β-adrenoreceptors and partly by α1-adrenoreceptors, and NO may be a common mediator for their regulations.
86.
R. S. SENOCK J. M. HAM T. M. LOUGHIN B. A. KIMBALL D. J. HUNSAKER P. J. PINTER G. W. WALL R. L. GARCIA R. L. LaMORTE 《Plant, cell & environment》1996,19(2):147-158
The effects of elevated carbon dioxide (CO2) concentration on plant water use are best evaluated on plants grown under field conditions and with measurement techniques that do not disturb the natural function of the plant. Heat balance sap flow gauges were used on individual main stems of wheat (Triticum aestivum L. cv Yecora rojo) grown under normal ambient conditions (control) and in a free-air CO2 enrichment (FACE) system in Arizona with either high (control + high H2O = CW; FACE + high H2O = FW) or low (control + low H2O = CD; FACE + low H2O = FD) irrigation regimens. Over a 30d period (stem elongation to anthesis), combinations of treatments were monitored with,10–40 gauges per treatment. The effects of increased CO2 on tiller water use were inconsistent in both the diurnal patterns of sap flow and the statistical analyses of daily sap flow (Ftot). Initial results suggested that the reductions in Ftot, from CO2 enrichment were small (,0–10%) in relation to the H2O treatment effect (,20–30%). For a 3d period, Ftot of FW was,19–26% less than that of CW (P = 0.10). Examination of the different sources of variation in the study revealed that the location of gauges within the experimental plots influenced the variance of the sap flow measurements. This variation was probably related to positional variation in subsurface drip lines used to irrigate plots. A sampling design was proposed for use of sap flow gauges in FACE systems with subsurface irrigation that takes into account the main treatment effects of CO2 enrichment and the other sources of variation identified in this study. Despite the small and often statistically non-significant differences in Ftot between the CW and FW treatments, cumulative water use of the FW treatment at the end of the first three test periods ranged from 7 to 23% lower than that of the CW treatment. Differences in sap flow between FW and CW compared well with treatment differences in evapotranspiration. The results of the study, based on the first reported sap flow measurements of wheat, suggest that irrigation requirements for wheat production, in the present climatic regimen of the south-western US, may be predicted to decrease slightly because of increasing atmospheric CO2. 相似文献
87.
Shun Hirota Margareta Svensson-Ek Pia Ädelroth Nobuhito Sone Thomas Nilsson Bo G. Malmström Peter Brzezinski 《Journal of bioenergetics and biomembranes》1996,28(6):495-501
The time course of absorbance changes following flash photolysis of the fully-reduced carboxycytochrome oxidase fromBacillus PS3 in the presence of O2 has been followed at 445, 550, 605, and 830 nm, and the results have been compared with the corresponding changes in bovine cytochrome oxidase. The PS3 enzyme has a covalently bound cytochromec subunit and the fully-reduced species therefore accommodates five electrons instead of four as in the bovine enzyme. In the bovine enzyme, following CO dissociation, four phases were observed with time constants of about 10 s, 30 s, 100 s, and 1 ms at 445 nm. The initial, 10-s absorbance change at 445 nm is similar in the two enzymes. The subsequent phases involving hemea and CuA are not seen in the PS3 enzyme at 445 nm, because these redox centers are re-reduced by the covalently bound cytochromec, as indicated by absorbance changes at 550 nm. A reaction scheme consistent with the experimental observations is presented. In addition, internal electron-transfer reactions in the absence of O2 were studied following flash-induced CO dissociation from the mixed-valence enzyme. Comparisons of the CO recombination rates in the mixed-valence and fully-reduced oxidases indicate that more electrons were transferred from hemea
3 toa in PS3 oxidase compared to the bovine enzyme. 相似文献
88.
Santos Carlos Chandler Karen Zimmer Stephen Fisher Paul B. Gunthert Ursula Anderson Kimberly Ward 《Cell biochemistry and biophysics》1995,26(1):1-19
A parallel-plate flow chamber was used to quantify the detachment of normal cloned rat embryo fibroblasts (CREF) fibroblasts,ras-transformed CREF fibroblasts (CREF T24), and CREF T24 fibroblasts transfected with a Krev/RAP1A suppressor gene (HK B1) from
a confluent monolayer of normal CREF fibroblasts to determine if the expression patterns of CD44 variants (mol wt 110 and
140 kDa) corresponded with detachment properties and metastatic potential. In the detachment assay, known shear stresses ranging
from 20–24 dyn/cm2 were applied to the adherent cells and the number of cells detached from the monolayer after 180 s was determined. Results
showed that cellular expression of CD44 variants correlated with the metastatic potential of the cells and with the cells’
ability to detach from a monolayer of normal cells. Western blot analysis showed a low level of expression of the CD44 variants
in the normal cell line, CREF, and the lowly metastatic cell line, HK B1. Detachment studies showed a low percentage of detachment
of both of these cell lines from a normal cell monolayer. Tumor-derived (HK B1-T) and lung nodule-derived (HK B1-M) cell lines
were established and both formed tumors and metastasis with reduced latency periods as compared to HK B1, but still showed
a markedly delayed latency period compared to the highly metastatic cell line, CREF T24. Both of these cell lines showed a
higher expression of the CD44 variants as compared to CREF and HK B1, and detached easier than CREF and HK B1. CREF T24 showed
a much higher level of expression of the variants and had a higher percentage detachment than all other cell lines. To further
test the role of the CD44 variants in the ability of the cells to detach from the normal monolayer, CREF cells were transfected
with a DNA construct that constitutively expresses the CD44 variants and the detachment properties of three randomly selected
clones were studied. Clones 2 and 3 showed a low level of expression of the CD44 variants after transfection and detached
from the normal monolayer similar to CREF. Clone 1 showed a high level of expression of the CD44 variants and the detachment
of these cells was significantly higher than CREF. From these results, it is concluded that in the five cell lines studied,
expression of the CD44 variants play a significant role in the ability of the cells to detach from a monolayer of normal cells.
It is hypothesized that this detachment may be an important component of a cell’s ability to metastasize. 相似文献
89.
The effect of the antiarrhythmic drugs lidocaine, quinidine and procainamide on macrophage function was investigated in RAW 264.7 mouse monocytic macrophage cell. Cells stimulated by either zymosan or phorbol ester were found to generate both superoxide (O
2
–
) and H2O2. The production of O2 was detected as superoxide dismutase inhibitable ferricytochrome c reduction. H2O2 production was monitored in both chemical and flow cytometric fluorescent assays. Although all three drugs inhibited both O2 and H2O2 release in a dose dependent manner, only quinidine was found to have significant inhibitory effects. The amounts of quinidine required to cause a 50% inhibition in O2 production in zymosan and phorbol ester stimulated cells were found to be 250 M and 300 M, respectively and the amounts required to cause one-half optimum levels of H2O2 production in these cells were found to be 50 M and 100 M, respectively. The effect of these drugs on O2 producing NADPH oxidase was investigated and only procainamide was found to have a significant effect (p<0.001) in inhibiting the oxidase activity. Lidocaine and quinidine had no significant effect on the activation of the respiratory burst oxidase. A sensitive and convenient differential phagocytosis assay was devised on the basis of number of particles engulfed by individual phagocytes using flow cytometric techniques. It appears to be remarkably free of interference and was applied to investigate the role of antiarrhythmic drugs on the phagocytosis of fluorescent latex beads. All three antiarrhythmic drugs inhibited phagocytosis of latex beads in a dose dependent manner irrespective of the number of particles phagocitized by the cells. The results of these studies do not conclusively establish a mechanism of action of these drugs on the generation of O2 and H2O2 by stimulated macrophages; nevertheless, it is interesting that all three drugs inhibited the phagocytic activity. 相似文献
90.
C. S. Degoute C. Dubreuil M. J. Ray J. Guitton M. Manchon V. Banssillon J. L. Saumet 《European journal of applied physiology and occupational physiology》1994,69(5):414-420
Studies by laser-Doppler flowmetry of middle ear microcirculation changes induced by physical and chemical stimuli in the animal have only recently been made. This prospective study, performed in humans, was designed to compare the effects of a postural manoeuvre (headup tilt 30°), hypotension and locally applied vasoconstriction on middle ear blood flow during anaesthesia. Circulatory changes provoked by a headup tilt of 30°, and successive intravenous boluses of potent vasodilators, were compared with circulatory changes provoked by locally applied adrenaline, in ten healthy patients in good physical states undergoing middle ear surgical repair. Heart rate and direct arterial pressure were continuously recorded via a radial artery cannula. Middle ear blood flow was continuously recorded via a laser-Doppler probe placed on the promontorium cavi tympani. Metabolic parameters (partial pressure of O2 and CO2 in arterial blood, pH, arterial lactate concentrations) and arterial concentrations of propofol were measured just before and just after the experiment. Headup tilt did not modify heart rate, mean arterial pressure or middle ear blood flow. Vasodilators (nicardipine, nitroprusside, nitroglycerin) provoked a fall in arterial pressure (P<0.0001,P<0.0001,P<0.019, respectively), but did not induce any significant variations in heart rate; variations occurred in middle ear blood flow (P>0.05, not significant) which were different according to patients and agents. Locally applied adrenaline provoked a fall in the middle ear blood flow (P<0.0012), with no effect on heart rate and arterial pressure. There were no significant changes in metabolic values, or propofol serum concentrations. The behaviour of the middle ear blood flow submitted to hypotension, posture, or to vasoconstriction could be related to counteracting regulatory responses and/or to direct vascular effects. 相似文献