Zusammenfassung In einer intensiv landwirtschaftlich genutzten Fläche des schweizerischen Mittellandes wurden 1983–1987 vier Feldlerchenaggregationen mit maximal 39 Brutpaaren untersucht. Die Tradition (Ortstreue) bestimmte in erster Linie die Revierwahl und das Verteilungsmuster. Die Reviere waren mit
ha sehr groß; ihre Größe korrelierte negativ mit der Anzahl Parzellen pro Fläche und der Kulturendiversität. Die Nutzung des Ressourcenangebots (Nistplatz, Nahrung, Schutz) war abhängig von den Fortbewegungsmöglichkeiten. In großparzellig strukturierten Flächen mit geringer Kulturendiversität kam es häufig zu Revierverschiebungen und Reviervergrößerungen. Die Feldlerche versucht, im Laufe der Brutperiode den Getreideanteil im Revier zu verkleinern und Kulturen wie Rüben, Kartoffeln und auch Mais zu aquirieren. Die Nistplatzwahl zeigte eine deutliche Präferenz für alle nicht zu dicht stehenden, grasartigen Kulturen (Weizen, Hafer, Fettwiese). Eine Vegetationshöhe von 15–25 cm und eine Bodenbedeckung von 20–50 % bieten optimale Bedingungen für den Nestbau. 51 % aller Nester wurden in der Fettwiese angelegt, 20 % im Winterweizen und 18 % im Mais. Je nach Bewirtschaftungsart brüteten die im Mittel 2,4–2,8mal pro Brutsaison. Die Schlüpfrate von 220 Gelegen betrug 0,58. 44 % der geschlüpften Jungvögel verließen das Nest. Der Bruterfolg (nestverlassende Junge/gelegte Eier) lag bei max. 25 %. Dem Fütterungsverhalten der Altvögel nach zu schließen, wurden maximal 50 % der nestverlassenden Jungen flügge. Durchschnittlich war mit 0,9 flüggen Jungen pro Brutpaar und Jahr zu rechnen. Brutverluste waren kulturspezifisch und daher in erster Linie vom Neststandort abhängig.
Territoriality and breeding biology of Skylark (Alauda arvensis) in an intensively farmed area in Switzerland
Summary In 1983–1987 four plots (total surface 307 ha) with up to 39 breeding pairs were studied in an area of intensive cultivation in the Swiss Lowlands (390 m asl). Distribution pattern and selection of territories are determined by a strong site tenacity of the birds. The size of territories averaged 3,3±0,9 hectares. It correlates negatively with the number of different crops per unit area and the diversity of cultures.The mobility within the vegetation determined which types of farmland ressources may be used for nesting, feeding and cover. Shifts of territories and attempts to enlarge them were frequent in areas of large plots with low crop diversity. During the season, Skylarks tried to reduce the proportion of cereal fields within their territory and to gain plots planted with sugar-beet, potatoes and corn.Their choice of nesting sites showed a strong preference for less dense grass crops such as wheat, oat or meadows. Optimal conditions for nest sites were in fields with a vegetation height of 15–25 cm and a ground coverage of 20–50 %. 51 % of 220 nests were constructed in heavily manured meadows, 20 % in winter wheat fields and 18 % in corn fields. Females bred on average 2,4–2,8 times per breeding season, depending on the type of cultivation (agriculture, husbandry). Hatching rate was 58 % out of 220 clutches, and 44 % of the hatched young left the nest. Maximum breeding success (i. e. young birds leaving the nest/number of eggs laid) was thus maximal 25 %. Observations of parental feeding behaviour suggest that a maximum of 50 % of the young larks which leave the nests survive to the age of fledging. It is estimated that 0,9 fledglings are raised per breeding pairs and year. Losses of broods vary according to farming practises in the different crops and therefore are largely depending on nesting sites.
l-Ascorbate is taken up into brush border vesicles from kidney cortex of rat, rabbit and guinea pig by an efficient, Na+-dependent and potential-sensitive transport process. This uptake shows saturation () and is strongly stimulated by low concentrations of N3?. Erythorbate (d-isoascorbate) seems to be another, but poorer, substrate of the same transporter. 相似文献
Kinetic data obtained for deamination of pterin by the extracellular fraction from Dictyostelium discoideum yielded apparently linear Lineweaver-Burk plots for pterin. The Michaelis constant for pterin was 30 microM. The data for folic acid deamination yielded convex Lineweaver-Burk plots. Convex Lineweaver-Burk plots could result from the presence of two types of enzymes with different affinities. The data for folic acid deamination were analyzed mathematically for two types of enzymes. This analysis produced Michaelis constants for folic acid of 1.8 and 23 microM competition studies suggested that an enzyme with low affinity nonspecifically catalyzed the deamination of folic acid and pterin, whereas an enzyme with high affinity was a specific folic acid deaminase. A specific folic acid deaminase with high affinity appeared to be present on the surface of D. discoideum cells. The Michaelis constant for this enzyme was 2.6 microM. Cells growing in nutrient broth and cells starved in phosphate buffer released folic acid and pterin deaminases. The quantity of deaminase activities released by the cells appeared to be controlled by chemoattractants. Starving cells that were supplied with folic acid, pterin, or adenosine 3',5'-phosphate increased their extracellular folic acid and pterin deaminase activities to a larger extent than did cell suspensions to which no chemoattractants were added. Administration of folic acid or pterin to starving cells caused increases of the activity of extracellular adenosine 3',5'-phosphate phosphodiesterase and repressed increases of the activity of phosphodiesterase inhibitor. 相似文献
Pseudomonas sp. strain CBS3 was able to utilize 4-chlorophenylacetic acid as the sole source of carbon and energy. When this strain was grown with 4-chlorophenylacetic acid, homoprotocatechuic acid was found to be an intermediate which was further metabolized by the meta-cleavage pathway. Furthermore, three isomers of chlorohydroxyphenylacetic acid, two of them identified as 3-chloro-4-hydroxyphenylacetic acid and 4-chloro-3-hydroxyphenylacetic acid, were isolated from the culture medium. 4-Hydroxyphenylacetic acid was catabolized in a different manner by the glutathione-dependent homogentisate pathway. Degradation enzymes of both of these pathways were inducible. 相似文献
Gap junctions (GJ) are important determinants of cardiac conduction and the evidence has recently emerged that altered distribution of these junctions and changes in the expression of their constituent connexins (Cx) may lead to abnormal coupling between cardiomyocytes and likely contribute to arrhythmogenesis. However, it is largely unknown whether changes in the expression and distribution of the major cardiac GJ protein, Cx43, is a general feature of diverse chronic myocardial diseases or is confined to some particular pathophysiological settings. In the present study, we therefore set out to investigate qualitatively and quantitatively the distribution and expression of Cx43 in normal human myocardium and in patients with dilated (DCM), ischemic (ICM), and inflammatory cardiomyopathies (MYO). Left ventricular tissue samples were obtained at the time of cardiac transplantation and investigated with immunoconfocal and electron microscopy. As compared with the control group, Cx43 labeling in myocytes bordering regions of healed myocardial infarction (ICM), small areas of replacement fibrosis (DCM) and myocardial inflammation (MYO) was found to be highly disrupted instead of being confined to the intercalated discs. In all groups, myocardium distant from these regions showed an apparently normal Cx43 distribution at the intercalated discs. Quantitative immunoconfocal analyis of Cx43 in the latter myocytes revealed that the Cx43 area per myocyte area or per myocyte volume is significantly decreased by respectively 30 and 55% in DCM, 23 and 48% in ICM, and by 21 and 40% in MYO as compared with normal human myocardium. In conclusion, focal disorganization of GJ distribution and down-regulation of Cx43 are typical features of myocardial remodeling that may play an important role in the development of an arrhythmogenic substrate in human cardiomyopathies. 相似文献
It has been argued that the limited genetic diversity and reduced allelic heterogeneity observed in isolated founder populations facilitates discovery of loci contributing to both Mendelian and complex disease. A strong founder effect, severe isolation, and substantial inbreeding have dramatically reduced genetic diversity in natives from the island of Kosrae, Federated States of Micronesia, who exhibit a high prevalence of obesity and other metabolic disorders. We hypothesized that genetic drift and possibly natural selection on Kosrae might have increased the frequency of previously rare genetic variants with relatively large effects, making these alleles readily detectable in genome-wide association analysis. However, mapping in large, inbred cohorts introduces analytic challenges, as extensive relatedness between subjects violates the assumptions of independence upon which traditional association test statistics are based. We performed genome-wide association analysis for 15 quantitative traits in 2,906 members of the Kosrae population, using novel approaches to manage the extreme relatedness in the sample. As positive controls, we observe association to known loci for plasma cholesterol, triglycerides, and C-reactive protein and to a compelling candidate loci for thyroid stimulating hormone and fasting plasma glucose. We show that our study is well powered to detect common alleles explaining ≥5% phenotypic variance. However, no such large effects were observed with genome-wide significance, arguing that even in such a severely inbred population, common alleles typically have modest effects. Finally, we show that a majority of common variants discovered in Caucasians have indistinguishable effect sizes on Kosrae, despite the major differences in population genetics and environment. 相似文献
In order to study the effects of temperature enhancement on alpine calcareous grassland species, a warming experiment was carried out in the Berchtesgaden National Park (Southeast Germany, Northern Calcareous Alps) between 2002 and 2004. The study was conducted in stands of the Carex sempervirens and the Carex firma communities; the two most widespread grassland types in the alpine zone of the Northern Calcareous Alps. The temperature of the vegetation stand and the upper soil was passively enhanced using open top chambers (OTCs). The construction of the OTCs was appropriate since temperature was clearly increased while water conditions (humidity, soil water content) were not changed.
By comparing manipulated (temperature enhancement) with non-manipulated plots, the effects of warming on growth and reproduction of selected key species were studied. To test if vegetation response to temperature enhancement is at least partly due to increases in nutrient availability, soil solution concentrations of nitrate and ammonium were analysed.
We found that most of the studied plant species are sensitive to temperature enhancement. Growth and/or reproduction of 12 of the 14 studied species were significantly stimulated by warming. Only two species showed no response; none of the species experienced decreases in growth or reproduction. Dwarf shrubs and graminoids showed a stronger response than herbaceous perennials. A significant effect of warming on nutrient availability could not be detected. The observed response of vegetation is therefore mainly caused by direct and not by indirect temperature effects. 相似文献
Wheat production will be impacted by increasing concentration of atmospheric CO2 [CO2], which is expected to rise from about 400 μmol mol?1 in 2015 to 550 μmol mol?1 by 2050. Changes to plant physiology and crop responses from elevated [CO2] (e[CO2]) are well documented for some environments, but field‐level responses in dryland Mediterranean environments with terminal drought and heat waves are scarce. The Australian Grains Free Air CO2 Enrichment facility was established to compare wheat (Triticum aestivum) growth and yield under ambient (~370 μmol?1 in 2007) and e[CO2] (550 μmol?1) in semi‐arid environments. Experiments were undertaken at two dryland sites (Horsham and Walpeup) across three years with two cultivars, two sowing times and two irrigation treatments. Mean yield stimulation due to e[CO2] was 24% at Horsham and 53% at Walpeup, with some treatment responses greater than 70%, depending on environment. Under supplemental irrigation, e[CO2] stimulated yields at Horsham by 37% compared to 13% under rainfed conditions, showing that water limited growth and yield response to e[CO2]. Heat wave effects were ameliorated under e[CO2] as shown by reductions of 31% and 54% in screenings and 10% and 12% larger kernels (Horsham and Walpeup). Greatest yield stimulations occurred in the e[CO2] late sowing and heat stressed treatments, when supplied with more water. There were no clear differences in cultivar response due to e[CO2]. Multiple regression showed that yield response to e[CO2] depended on temperatures and water availability before and after anthesis. Thus, timing of temperature and water and the crop's ability to translocate carbohydrates to the grain postanthesis were all important in determining the e[CO2] response. The large responses to e[CO2] under dryland conditions have not been previously reported and underscore the need for field level research to provide mechanistic understanding for adapting crops to a changing climate. 相似文献