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1.
The properties of acyl hydrolase enzymes purified from the leaves of Phaseolus multiflorus have been studied. Hydrolase I which deacylates phosphatidylcholine and oleoylglycerol had a pH optimum towards phosphatidylcholine of 5.3. Hydrolase II which deacylates glycosylglycerides and oleoylglycerol showed pH optima of 7.3 (monogalactosyldiglyceride, MGDG) and 4.3 (sulphoquinovosyldiglyceride, SQDG). Both enzymes showed activity peaks towards oleoylglycerol at pH 6.8 and 8.8. Unesterified fatty acids and Triton X-100 inhibited the rate of SQDG hydrolysis while bovine serum albumin increased activity. An apparent Km for SQDG of 0.15 mM was found. Hydrolase II catalysed transmethylation of liberated fatty acids during the hydrolysis of oleoylglycerol when methanol was included in the assay system. A number of salts inhibited SQDG hydrolysis but their effect on oleoylglycerol was less consistent. The position of ester cleavage of oleoylglycerol was determined by the use of H218O. Cell-free extracts from P. multiflorus leaves degraded SQDG as far as sulphoquinovose. 相似文献
2.
3.
Fluorescence polarization (FP) is an established technique for the study of biological interactions and is frequently used in the high-throughput screening (HTS) of potential new drug targets. This work describes the miniaturization of FP receptor assays to 1536-well formats for use in HTS. The FP assays were initially developed in 384-well microplates using CyDye-labeled nonpeptide and peptide ligands. Receptor expression levels varied from approximately 1 to 10 pmols receptor per mg protein, and ligand concentrations were in the 0.5- to 1.0-nM range. The FP assays were successfully miniaturized to 1536-well formats using Cy3B-labeled ligands, significantly reducing reagent consumption, particularly the receptor source, without compromising assay reliability. Z' factor values determined for the FP receptor assays in both 384- and 1536-well formats were found to be > 0.5, indicating the assays to be robust, reliable, and suitable for HTS purposes. 相似文献
4.
Stomatal numbers of soybean and response to water stress 总被引:2,自引:0,他引:2
B. R. Buttery C. S. Tan R. I. Buzzell J. D. Gaynor D. C. MacTavish 《Plant and Soil》1993,149(2):283-288
The relationship among stomatal density, photosynthetic rate, leaf conductance, plant growth, bean yield and kaempferol triglucoside (K9) in the leaves of soybean (Glycine max (L.) Merr.) was examined in two field tests. K9 in the leaves was associated with reduced stomatal density, reduced photosynthetic rate, reduced stomatal conductance, reduced plant weight and lower bean yield. Plants with high stomatal frequency (lacking K9) were better able to take advantage of increased water supply by increasing stomatal conductance (upper surface), transpiration and bean yield. Plants with low stomatal frequency (with K9) were unresponsive to irrigation and in this sense were more tolerant of water stress, but their overall yield was low. 相似文献
5.
Inducible and reversible perturbation of the activity of selected neurons in vivo is critical to understanding the dynamics of brain circuits. Several genetically encoded systems for rapid inducible neuronal silencing have been developed in the past few years offering an arsenal of tools for in vivo experiments. Some systems are based on ion-channels or pumps, others on G protein coupled receptors, and yet others on modified presynaptic proteins. Inducers range from light to small molecules to peptides. This diversity results in differences in the various parameters that may determine the applicability of each tool to a particular biological question. Although further development would be beneficial, the current silencing tool kit already provides the ability to make specific perturbations of circuit function in behaving animals. 相似文献
6.
Richard W. Yarnell William Louis Phipps Steve Dell Lynne M. MacTavish Dawn M. Scott 《African Journal of Ecology》2015,53(3):287-294
Vulture restaurants are used worldwide as a conservation tool to provide threatened vultures with a source of supplementary carrion free from anthropogenic contaminants such as poisons and veterinary drugs. While the impacts of supplementary feeding sites on ecosystem and scavenging community dynamics have been investigated in Europe, no information is currently available for southern Africa. This study presents evidence that providing supplementary carrion for vultures stimulated an increase in local abundance of two species of mammalian carnivores, the brown hyaena (Hyaena brunnea) and the black‐backed jackal (Canis mesomelas). These findings require that the wider impacts of providing supplementary carrion for conserving threatened species are fully investigated. 相似文献
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Atmospheric Deposition to the Turkey Lakes Watershed: Temporal Variations and Characteristics 总被引:3,自引:0,他引:3
We investigated the atmospheric concentrations and deposition fluxes of major ions to the Turkey Lakes Watershed (TLW) between
1980 and 1996. During that time, daily SO4
2− concentrations in precipitation decreased markedly, while NO3
−, NH4
+, and H+ concentrations remained roughly constant. It appears that precipitation acidity did not decrease in spite of declining SO4
2− concentrations due to a concurrent and counterbalancing decrease in the concentrations of Ca2+, Mg2+, and K+ in precipitation. The reasons for the decline in base cations are unknown, but this decline is probably related to decreasing
emissions of soil-derived particles from agricultural, industrial, and road sources. A similar situation was seen during the
same period in other parts of Canada, the eastern United States, and Europe. Wet, dry, and total (wet + dry) deposition fluxes
of sulphur (S) and nitrogen (N) were estimated annually for the years 1980–96. The 17-year mean annual total (wet + dry) deposition
of S to the watershed was estimated at 38.5 mmol m−2 y−1 (range 24.3–50.3). Total S deposition decreased by 35% from the early 1980s (1982–84) to the mid-1990s (1994–96), a decline
consistent with the 23% decline in annual SO2 emissions in eastern North America during the same period. In contrast, the annual total (wet + dry) deposition of oxidized
N ranged from 39.8 to 60.4 mmol m−2 y−1, with a 15-year mean of 50.1 mmol m−2 y−1 and a net increase of 10% between the early 1980s (1983–85) and the mid-1990s (1994–96). This is in keeping with a 10% increase
in NOx emissions in eastern North America during the same period. For both S and N (oxidized), wet deposition dominated over dry
deposition as the major mechanism for atmospheric input to the watershed. Annually, wet deposition accounted for approximately
two-thirds of the total atmospheric deposition of both S and N. Dry S deposition was due more to gaseous SO2 deposition (two-thirds of dry S deposition) than to particulate SO4
2− deposition (one-third of dry S deposition). Dry deposition of oxidized N, however, was dominated (95%) by gaseous HNO3 deposition, with minimal input from particulate NO3
− deposition. Compared to several selected watershed/forest sites in Canada, the United States, and Europe, the estimated total
deposition of S and N at the TLW was relatively high during the measurement period.
Received 5 October 1999; accepted 1 March 2001. 相似文献
9.
W. Louis Phipps Kerri Wolter Michael D. Michael Lynne M. MacTavish Richard W. Yarnell 《PloS one》2013,8(10)
Cape vulture Gyps coprotheres populations have declined across their range due to multiple anthropogenic threats. Their susceptibility to fatal collisions with the expanding power line network and the prevalence of carcasses contaminated with illegal poisons and other threats outside protected areas are thought to be the primary drivers of declines in southern Africa. We used GPS-GSM units to track the movements and delineate the home ranges of five adult (mean ±SD minimum convex polygon area = 121,655±90,845 km2) and four immature (mean ±SD minimum convex polygon area = 492,300±259,427 km2) Cape vultures to investigate the influence of power lines and their use of protected areas. The vultures travelled more than 1,000 km from the capture site and collectively entered five different countries in southern Africa. Their movement patterns and core foraging ranges were closely associated with the spatial distribution of transmission power lines and we present evidence that the construction of power lines has allowed the species to extend its range to areas previously devoid of suitable perches. The distribution of locations of known Cape vulture mortalities caused by interactions with power lines corresponded to the core ranges of the tracked vultures. Although some of the vultures regularly roosted at breeding colonies located inside protected areas the majority of foraging activity took place on unprotected farmland. Their ability to travel vast distances very quickly and the high proportion of time they spend in the vicinity of power lines and outside protected areas make Cape vultures especially vulnerable to negative interactions with the expanding power line network and the full range of threats across the region. Co-ordinated cross-border conservation strategies beyond the protected area network will therefore be necessary to ensure the future survival of threatened vultures in Africa. 相似文献
10.
Empirically testing the effectiveness of thermal imaging as a tool for identification of large mammals in the African bushveldt
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Anne E. Goodenough William S. Carpenter Lynne MacTavish Dougal MacTavish Charles Theron Adam G. Hart 《African Journal of Ecology》2018,56(1):51-62
Monitoring animal populations often relies on direct visual observations. This is problematic at night when spotlighting can cause misidentification and inaccurate counting. Using infrared thermography (IRT) could potentially solve these difficulties, but reliability is uncertain. Here, we test the accuracy of 24 observers, differing in experience and skill levels, in identifying antelope species from IRT photographs taken in the African bush. Overall, 38% of identifications were correct to species level, and 50% were correct to genus/subfamily level. Identification accuracy depended on the confidence and skill of the observer (positive relationship), the number of animals present (positive relationship), and the distance at which it was taken (negative relationship). Species with characteristic features, horn morphology, or posture were identified with ~80% accuracy (e.g. wildebeest, kudu and impala) while others were considerably lower (e.g. blesbok and waterbuck). Experience significantly improved identification accuracy but the effect was not consistent between species and even experienced observers struggled to identify red hartebeest, reedbuck and eland. Counting inaccuracies were commonplace, particularly when group size was large. We conclude that thermal characteristics of species and experience of observers can pose challenges for African field ecologists, but IRT can be used to identify and count some species accurately, especially <100 m. 相似文献