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1.
Background
Invasive ecosystem engineers can facilitate their invasions by modifying the physical environment to improve their own performance, but this positive feedback process has rarely been tested empirically except in sessile organisms. The invasive crayfish Procambarus clarkii is an ecosystem engineer that destroys aquatic macrophytes, which provide a physical refuge for animal prey, and this destruction is likely to enhance vulnerability to predators. Using two series of mesocosm experiments, we tested the hypothesis that the invasive crayfish increases its feeding efficiency on animal prey by reducing submerged macrophytes, thus increasing its individual growth rate in a positive density-dependent manner.Results
In the first experiment, increasing crayfish density reduced both macrophytes and animal prey (dragonfly and chironomid larvae) and, importantly, increased the growth rate of individual crayfish, in accordance with our expectation. In the second experiment, we used artificial macrophytes to clarify whether the physical architecture of macrophytes itself protects animal prey and limits crayfish growth rate. Increasing the artificial macrophyte quantity not only increased the survival of animal prey, but also retarded the crayfish growth rate.Conclusions
We conclude that macrophytes strengthen bottom-up control of crayfish, but this effect can be relaxed by increasing the density of crayfish via reduction in macrophytes. This positive feedback process may explain the crayfish outbreaks and regime shifts occasionally observed in invaded freshwater ecosystems.2.
We induced various flower morphologies in torenia (Torenia fournieri Lind.) by the application of forchlorfenuron (CPPU). Those morphologies were the combination of four basic morphological changes, the development of serrate petals, incised petals, a paracorolla, and an increased number of floral organs. These morphological changes occurred systematically depending on the floral stage at the time of CPPU application. Serrate petals were induced when CPPU was applied during the stages of corolla development, whereas application at younger stages induced petal incision. The serrate petal margin resulted from preferential proliferation of cells around the vascular bundles, whereas petal incision likely resulted from the lateral outgrowths of petal. A paracorolla was induced at the adaxial petal face when CPPU was applied between the sepal development stage and early corolla development. The paracorolla appears to have arisen from the lateral outgrowths of the stamen. The numbers of stamens, petals, and sepals increased when CPPU was applied at and before the differentiation of sex organs and the corolla. Enlargement of the floral meristem probably caused this increase. Application of N6-benzylaminopurine and zeatin did not induce these morphological changes. 相似文献
3.
Chicón R López-Fandiño R Quirós A Belloque J 《Journal of agricultural and food chemistry》2006,54(6):2333-2341
Beta-lactoglobulin (beta-Lg) was subjected to high pressures up to 400 MPa and proteolysis with chymotrypsin. The hydrolysates were analyzed by SDS-PAGE and RP-HPLC, and the fragments obtained were identified by ESI-MS/MS. The results obtained showed that beta-Lg was hydrolyzed by chymotrypsin in a "progressive proteolysis" manner at either atmospheric or high pressure. Proteolysis during or after high-pressure treatment showed longer and more hydrophobic peptides than proteolysis at atmospheric pressure. Chymotrypsin showed a behavior similar to that of trypsin, with some differences, probably related to the orientation of the target residues specific for each enzyme. The similarities between proteolytic fragments produced by the two enzymes support that proteolysis enhancement under high pressure depends on the substrate changes rather than the enzyme. High pressure seemed to accelerate the first steps of proteolysis, probably through dimer dissociation, while leaving portions of the molecule more resistant to the enzyme. 相似文献
4.
Effects of β‐carotene‐enriched dry carrots on β‐carotene status and colostral immunoglobulin in β‐carotene‐deficient Japanese Black cows 
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下载免费PDF全文 Yoshitaka Nishijima Saya Taniguchi Shuntaro Ikeda Kenichi Yoshitani Takashi Hamano Hiroshi Tani Masahiko Fujita Kenji Murakami Keisuke Kogusa Kenji Sato Miki Sugimoto Shinichi Kume 《Animal Science Journal》2017,88(4):653-658
Data from 18 β‐carotene‐deficient Japanese Black cows were collected to clarify the effects of feeding β‐carotene‐enriched dry carrots on β‐carotene status and colostral immunoglobulin (Ig) in cows. Cows were assigned to control or carrot groups from 3 weeks before the expected calving date to parturition, and supplemental β‐carotene from dry carrots was 138 mg/day in the carrot group. Plasma β‐carotene concentrations in the control and carrot groups at parturition were 95 and 120 μg/dL, and feeding dry carrots slightly improved plasma β‐carotene at parturition. Feeding dry carrots increased colostral IgA concentrations in cows and tended to increase colostral IgG1, but colostral IgM, IgG2, β‐carotene and vitamin A were not affected by the treatment. Feeding dry carrots had no effects on plasma IgG1, IgA and IgM concentrations in cows, but plasma IgG1 concentrations decreased rapidly from 3 weeks before the expected calving date to parturition. These results indicate that feeding β‐carotene‐enriched dry carrots is effective to enhance colostral IgA and IgG1 concentrations in β‐carotene‐deficient cows. 相似文献
5.
Belloque J Chicón R López-Fandiño R 《Journal of agricultural and food chemistry》2007,55(13):5282-5288
The unfolding of beta-lactoglobulin during high-pressure treatment and its refolding after decompression were studied by 1H NMR and 2H/1H exchange at pH 6.8 and 2.5 and at 37 and 25 degrees C. The extent of unfolding increased with the pressure level. The structure of beta-lactoglobulin required higher pressures to unfold at pH 2.5 than at pH 6.8. More flexibility was achieved at 37 degrees C than at 25 degrees C. Results indicated that the structural region formed by strands F, G, and H was more resistant to unfold under acidic and neutral conditions. The exposure of Trp19 at an earlier time, as compared to other protein regions, supports the formation of a swollen structural state at pH 2.5. Refolding was achieved faster when beta-lactoglobulin was subjected to 200 MPa than to 400 MPa, to 37 degrees C than to 25 degrees C, and to acidic than to neutral pH. After treatment at 400 MPa for 20 min at neutral pH, the protein native structure was not recovered. All samples at acidic pH showed that the protein quickly regained its structure. Hydrolysis of beta-lactoglobulin by pepsin and chymotrypsin could be related to pressure-induced changes in the structure of the protein. Compared to the behavior of the protein at atmospheric pressure, no increased proteolysis was found in samples with no increased flexibility (100 MPa, 37 degrees C, pH 2.5). Slightly flexible structures were associated with significantly increased proteolysis (100 MPa, 37 degrees C, pH 6.8; 200 MPa, 37 degrees C, pH 2.5). Highly flexible structures were associated with very fast proteolysis (>or=200 MPa, 37 degrees C, pH 6.8; >or=300 MPa, 37 degrees C, pH 2.5). Proteolysis of prepressurized samples improved only when the protein was significantly changed after the pressure treatment (400 MPa, 25 degrees C, 20 min, pH 6.8). 相似文献
6.
Katayama M Nishijima N Okamura Y Katayama R Yamashita T Kamishina H Uzuka Y 《Journal of Feline Medicine and Surgery》2012,14(4):257-261
Clarithromycin (CLM) has been known to increase the cyclosporine (CsA) trough levels in human transplant patients. However, the interaction of CLM with CsA has not been reported in cats. In this study, the effects of oral dosing of CLM on the pharmacokinetics and dosing of CsA in cats were investigated. Co-administration of CLM with CsA resulted in significant increases of oral bioavailability of CsA. In addition, CLM reduced the CsA dosage required to maintain the therapeutic CsA trough levels to almost 35% of the initial CsA therapy and the dose frequency was successfully replaced from a twice a day schedule to once a day in a feline kidney transplant patient. The addition of CLM to the regular CsA-based immunosuppression could be used as an effective alternative to classical ketoconazole treatment in feline kidney transplant patients and may result in substantial cost saving and convenience for the cat owners. 相似文献
7.
Simple, rapid cleanup method for analysis of aflatoxins and comparison with various methods 总被引：1，自引：0，他引：1
H Kamimura M Nishijima K Yasuda H Ushiyama S Tabata S Matsumoto T Nishima 《Journal of the Association of Official Analytical Chemists》1985,68(3):458-461
A method is described for simple and rapid determination of aflatoxins in corn, buckwheat, peanuts, and cheese. Aflatoxins were extracted with chloroform-water and were purified by a Florisil column chromatographic procedure. Column eluates were concentrated and spotted on a high performance thin layer chromatographic (HPTLC) plate, which was then developed in chloroform-acetone (9 + 1) and/or ether-methanol-water (94 + 4.5 + 1.5) or chloroform-isopropanol-acetone (85 + 5 + 10). Each aflatoxin was quantitated by densitometry. The minimum detectable aflatoxin concentrations (micrograms/kg) in various test materials were 0.2, B1; 0.1, B2; 0.2, G1; 0.1, G2; and 0.1, M1. Recoveries of the aflatoxins added to corn, peanut, and cheese samples at 10-30 micrograms/kg were greater than 69% (aflatoxin G2) and averaged 91%, B1; 89%, B2; 91%, G1; 78%, G2; and 92%, M1. The simple method described was compared with the AOAC CB method, AOAC BF method, and AOAC milk and cheese method. These methods were applied to corn, peanut, and cheese composites spiked with known amounts of aflatoxins, and to naturally contaminated buckwheat and cheese. Recoveries were much lower for the BF method compared with our simple method and the CB method. 相似文献
8.
Miyamoto M Nishijima Y Nakayama T Hamlin RL 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2000,14(4):445-451
Atrial fibrillation (AF) was induced in anesthetized Beagle hounds to determine the dose of diltiazem (D) that resulted in hemodynamic function similar to that observed during sinus rhythm (SR). Dogs were instrumented to record hemodynamic and electrophysiological parameters. Six dogs were given D, IV at cumulative doses of 0.063, 0.188, 0.438, 0.938, and 1.938 mg/kg, whereas 6 other dogs received vehicle in equivalent volumes. Plasma concentrations (PC) of D were measured. A cumulative dose of D between 0.438 and 0.938 mg/kg produced PC of 67.8 to 117.4 ng/mL and resulted in a heart rate (HR) closest to that observed during SR. At doses up to 0.938 mg/kg, no parameter of systolic function fell below that obtained during SR. At a dose of 0.938 mg/kg, the left ventricular end-diastolic and right atrial pressures exceeded those during SR. The rate-pressure product did not differ from that during SR at a dose of 0.938 mg/kg and fell below that during SR at the dose of 1.938 mg/kg. Left ventricular efficiency decreased from SR to AF, returned to values not different from those during SR at a dose of 0.938 mg/kg, and increased to values above those observed during SR at a dose of 1.938 mg/kg. In AF, slowing the HR with 0.438-0.938 mg/kg of D with resultant PC of 67.8-117.4 ng/mL results in cardiovascular function not different from that observed during SR. 相似文献
9.
Analysis of fine-scale spatial pattern of a grassland from remotely-sensed imagery and field collected data 总被引：6，自引：0，他引：6
An important practical problem in the analysis of spatial pattern in ecological systems is that requires spatially-intensive data, with both fine resolution and large extent. Such information is often difficult to obtain from field-measured variables. Digital imagery can offer a valuable, alternative source of information in the analysis of ecological pattern. In the present paper, we use remotely-sensed imagery to provide a link between field-based information and spatially-explicit modeling of ecological processes. We analyzed one digitized color infrared aerial photograph of a serpentine grassland to develop a detailed digital map of land cover categories (31.24 m × 50.04 m of extent and 135 mm of resolution), and an image of vegetation index (proportional to the amount of green biomass cover in the field). We conducted a variogram analysis of the spatial pattern of both field-measured (microtopography, soil depth) and image-derived (land cover map, vegetation index, gopher disturbance) landscape variables, and used a statistical simulation method to produce random realizations of the image of vegetation index based upon our characterization of its spatial structure. The analysis revealed strong relationships in the spatial distribution of the ecological variables (e.g., gopher mounds and perennial grasses are found primarily on deeper soils) and a non-fractal nested spatial pattern in the distribution of green biomass as measured by the vegetation index. The spatial pattern of the vegetation index was composed of three basic components: an exponential trend from 0 m to 4 m, which is related to local ecological processes, a linear trend at broader scales, which is related to a general change in topography across the study site, and a superimposed periodic structure, which is related to the regular spacing of deeper soils within the study site. Simulations of the image of vegetation index confirmed our interpretation of the variograms. The simulations also illustrated the limits of statistical analysis and interpolations based solely on the semivariogram, because they cannot adequately characterize spatial discontinuities. 相似文献
10.
Nakayama T Nishijima Y Miyamoto M Hamlin RL 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2007,21(3):445-450
BACKGROUND: There have been few trials in which dogs with mitral regurgitation (MR) have been treated with various cardioactive drugs to determine effects on left ventricular (LV) function. HYPOTHESIS: Four classes of cardiovascular drugs may improve LV function in dogs with MR without increasing MR. ANIMALS: Nine mature dogs were included in the study. METHODS: MR was produced in 9 dogs. Five months later under butorphanol narcosis, parameters of LV function and left atrial dimension (LAD) were monitored by LV micromanometry and echocardiography/Doppler. Dogs were given (in random order) enalaprilat, nitroglycerine, ouabain, milrinone, and placebo. RESULTS: Nitroglycerin produced no significant change; milrinone and ouabain increased contractility; ouabain decreased heart rate; and there was evidence that enalaprilat and milrinone decreased LAD. Milrinone and ouabain decreased isovolumetric contraction time and therefore the time available for MR. There was no evidence that a positive inotrope increased MR despite increasing LV contractility and stroke volume. CONCLUSION AND CLINICAL IMPORTANCE: This study contradicts the hypotheses that (1) strengthening the left ventricle may increase MR and (2) treatment of MR (even before symptoms of heart failure develop) may decrease LAD. It is reasonable that strengthening the force of LV contraction should increase the driving pressure for MR; however, this effect did not appear to increase MR. Although some investigators believe that treating dogs with MR with afterload reducers and decreasing hindrance to ejection of blood from the LV to aorta may lengthen life by decreasing MR, there did not appear to be a reduction in MR, at least in response to the angiotensin-converting enzyme (ACE) inhibitor. 相似文献