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排序方式: 共有298条查询结果,搜索用时 31 毫秒
61.
Heinrich Wilhelm Weber 《Forstwissenschaftliches Centralblatt》1931,53(5):165-171
Ohne ZusammenfassungDiese Abhadlung hat uns der am 15. I. 30 freiwillig aus dem Leben geschiedene Gie\ener Universitätsprofessor wenige Tage vor feinem Tod übersandt. In einem Begleitbrief sagt er, da\ fie gleichfam das Programm einer Geschichte der Forstwirschtslehre darstelle, mit deren Absassung er zur Zeit beschäftigt fet.Das Klingt viel mehr nach Lebens- und Schaffenslust als nach überdru\ oder Verzweiflung. Heute muten uns aber seine hier folgenden mahnenden Worte und Fingerzeige zum rechten Weg wie ein bewu\tes Vermächtnis an seine Fachgenossen auf den Lehrstühlen an. Sie zeigen zugleich, wie ernst H. W. Weber es mit seiner Wissenschaft genommen hat, lassen aber auch seinen schwarzseherischen Geist erkennen, der seinem eigenen Sein zum Verhängnis geworden ift. Er, unberfrtedigt jeden Augenbild von sich und seiner Umwelt arbeitete bis zu seinem le\ten Tag an der Förderung seines Faches, leider ohne durch diese Arbeit die faustische Erlösung zu finden.Wir danken ihm für manche wertvolle Arbelt, indemwir sein Andenken ehren und weden seiner demnächst nach in einem Nachruf aus Feder eines Freundes gedenken. 相似文献
62.
The micromorphological changes occurring in the bark tissues of beech and spruce trees during natural degradation in the forest have been investigated and compared with those obtained previously using wood-decaying fungi. The relevance of the bark degradation process for the environment is also briefly discussed. 相似文献
63.
Nunn AJ Weiser G Reiter IM Häberle KH Grote R Havranek WM Matyssek R 《Tree physiology》2006,26(11):1391-1403
The broad range in plant responses to chronic O(3) exposure compels a search for integrative, underlying principles. One such approach is the unifying theory proposed by Reich (1987), which combines the O(3) response of contrasting physiognomic classes of plants on the basis of their intrinsic leaf diffusive conductance and, hence, capacity for O(3) uptake. Physiognomic classes differ in the proportional decline in photosynthesis and growth when compared on the basis of cumulative O(3) exposure per unit time, but converge when compared on the basis of O(3) uptake per unit time or cumulative O(3) uptake over the entire lifetime of the leaf. The theory is based on observations on a large number of contrasting plant species, relying primarily on studies of juvenile trees subjected to short-term O(3) exposure. To test the applicability of the unifying theory to mature trees, broadleaf deciduous European beech (Fagus sylvatica L.) and the evergreen conifer Norway spruce (Picea abies (L.) Karst.) in a mature mixed stand were exposed to either ambient air (control) or air with twice the ambient O(3) concentration delivered into the canopy by means of a free-air fumigation system. We accounted for differences in growing season length, leaf longevity and O(3)-related effects on leaf diffusive conductance in determining total O(3) uptake over the lifetime of the leaf. On this basis, Norway spruce needles required 5 years to take up as much O(3) as did beech leaves in one growing season. The core of the unifying theory on O(3) sensitivity was substantiated in relation to O(3) exposure and uptake. However, contrary to the unifying theory, which was formulated on the basis of results with juvenile trees, the O(3) response of mature trees in a natural stand was more complex. The increased complexity was attributed to additional environmental stressors, stress compensation at the whole-tree level, and differential O(3) sensitivities of leaves according to age class and position within the canopy. Contrary to the theory, photosynthesis was no less sensitive to O(3) in Norway spruce than that of beech, and was reduced in the twice-ambient O(3) regime in the first year of exposure. 相似文献
64.
Siegfried Salomon Attila Gácser Sebastian Frerichmann Cathrin Kr?ger Wilhelm Sch?fer Christian A. Voigt 《European journal of plant pathology / European Foundation for Plant Pathology》2012,134(1):23-37
Mitogen activated protein (MAP) kinases are key components in signalling networks. In Fusarium graminearum, one of the most devastating fungal plant pathogens, two MAP kinases are known to be involved in pathogenicity, Mgv1 and the Gibberella pathogenicity MAP kinase Gpmk1. ??gpmk1 mutants with a disrupted GPMK1 gene are unable to infect wheat spikelets. They exhibit altered secretion of several extracellular enzymes. Among those, the lipase FGL1 is known to be a major virulence factor of F. graminearum. FGL1 gene expression was decreased in ??gpmk1 strains during wheat head infection. To uncouple FGL1 expression from Gpmk1 activity, we generated ??gpmk1 strains that constitutively express FGL1 under control of the Cochliobolus heterostrophus glyceraldehyde 3-phosphate dehydrogenase (GPD) promoter. The level of extracellular lipolytic activity of these strains in culture was comparable to the wild-type. These mutants showed fully restored conidiation and partial complementation of defects in development that were reported from the ??gpmk1 mutant. They also partially complemented the apathogenic disease phenotype of the ??gpmk1 mutants causing lesions in directly inoculated wheat spikelets. But in contrast to wild-type, their growth was restricted to directly inoculated spikelets. A barrier-like formation was observed at the rachis node. Based on these results, we could show that the lipase FGL1 is necessary but not sufficient to restore complete pathogenicity to the apathogenic ??gpmk1 mutant. Hence, we hypothesize that the MAP kinase Gpmk1 is involved in the regulation of additional factors required for complete virulence of F. graminearum. 相似文献
65.
Löhrke B Viergutz T Kanitz W Becker F Göllnitz K Hurtienne A Schweigert FJ 《Berliner und Münchener tier?rztliche Wochenschrift》2005,118(7-8):265-269
An imbalance between formation and detoxification of oxygen radicals leads to oxidant stress that may increase in more intense oxidative metabolism caused by a high intake of metabolizable energy to provide metabolic intermediates for the milk synthesis and secretion. This hypothesis was tested using dairy cows and the concentration of hydroperoxides in lipids (LHP) extracted from circulative lipoprotein particles of low and very low density (LDL and VLDL/chylomicrons) as oxidant stress indicator. The particles were prepared by ultracentrifugation of serum obtained by coccygeal bleeding (13 cows, 1. parity, n=8 and 2. parity, n=5, lactation stage, 53 +/- 1.4 days post partum) and purified by precipitation. Concentrations of LHP-LDL/mg Lipoprotein correlated significantly with daily milk yield (r = 0.73, P = 0.004) or daily milk energy output (r = 0.77, P = 0.003) in contrast to LHP of VLDL/chylomicron particles. Thus, some evidence was obtained for an almost linear, positive relationship between milk productivity and oxidant stress occurring in LDL. 相似文献
66.
Ritzmann M Wilhelm S Zimmermann P Etschmann B Bogner KH Selbitz HJ Heinritzi K Truyen U 《DTW. Deutsche tier?rztliche Wochenschrift》2005,112(9):348-351
Porcine circovirus type 2 (PCV2) seems to cause reproductive failure in sows not only in experimental studies. A retrospective study was made with a total of 252 aborted fetuses, mummified fetuses, stillborn and nonviable neonatal piglets to determine the presence of PCV2, porcine parvovirus (PPV) and porcine respiratory and reproductive syndrome virus (PRRSV) by PCR. PCV2 was found in all stages of gestation in 27.1 percent of samples examined. A statistically significant association could be shown between the detection of PCV2 and PRRSV. However, no significant association was seen between the detection of PCV2 and PPV and between PPV and PRRSV. 相似文献
67.
Favrot C Wilhelm S Grest P Meli ML Hofmann-Lehmann R Kipar A 《Veterinary dermatology》2005,16(6):407-412
Two cases of feline leukaemia virus (FeLV)-associated dermatosis are described. The first cat was affected by an ulcerative dermatitis identified as a giant-cell dermatosis. The second case was a cutaneous lymphoma. In both cases, FeLV antigens and FeLV genome were demonstrated in the affected skin immunologically and with polymerase chain reaction, respectively. The first case suggests that, like other retroviruses, at least some strains of FeLV can induce syncytium formation. As FeLV antigens and genome were demonstrated in a serologically negative cat, the second case suggests that focal skin FeLV replication may occur. FeLV-associated dermatoses are rare skin conditions that may be under-diagnosed. 相似文献
68.
果树病毒RNA的二氧化硅提取法 总被引:3,自引:1,他引:3
针对果树组织含有较高的多酚和多糖物质,研究建立了适合果树病毒日常进行大量RT-PCR检测时,病毒RNA的快速、经济、高效的提取方法。该方法是基于在适宜条件下,二氧化硅对RNA的吸附和洗脱作用,避免了常规方法使用的酚、氯仿等有机溶剂。在2 h内同时可以进行数十个样品的提取,由于提取的是总RNA,1次提取,1次反转录得到的cDNA样品可以用于各种待检病毒的PCR检测。得到的总RNA和cDNA在-20℃条件下可以长期保存备用,大大提高了核酸的提取效率。 相似文献
69.
The aim of this study was to report 20 cases of Lynxacarus radovskyi infestation in 20 cats . Lynxacarus radovskyi was diagnosed by physical examination and microscopic examination of plucked hair where countless adult mites and immature stages were identified. Microscopic examination was repeated every 7 days. The animals were observed daily for the first 7 days, and again on day 15 and day 30 for mites, pruritus and clinical signs. Clinical signs included salt-and-pepper appearance to a dull and opaque hair coat, alopecia of the dorsal and lateral areas of the hind limbs, and evidence of self-mutilation. One case had papules and crusts of the hind limbs. The pruritus was mild in animals with low infestation, but very intense in those with a heavy infestation. Most mites occurred in the lateral area of the hind limbs and sacral area. Twenty of 100 animals had confirmed L. radovskyi infestation. Therefore, we suggest that the transmission occurs through fomites. Treatment consisted of 0.5 mL application of Fipronil® (Frontline TopSpot) per cat, with resolution in 100% of cases by day 15.
Funding: Merial. 相似文献
Funding: Merial. 相似文献
70.
Schneider F Brüssow KP Kanitz W 《Berliner und Münchener tier?rztliche Wochenschrift》2008,121(3-4):110-120
The hypothalamic gonadotropin-releasing hormone (GnRH) is seen as the key hormone of neuroendocrine regulation of reproduction. The ability of GnRH and its analogues to stimulate the release of the gonadotropins FSH and LH is world-wide utilized for various veterinary purposes, including treatment of certain hormone-dependent disturbances and stimulation of ovulation in controlled breeding programmes. A large difference is striking, however, when comparing the efficiencies reported. This may underline the importance of accurate treatment and reflect the manifold influences by animals and their environment on reproductive performance. During the last years, novel analytical methods have been established enabling a significant progress in reproductive research. The discovery and characterization of natural GnRH variants and their receptors in several vertebrate species may become more important.The reason is, that these GnRHs affect the release of the gonadotropins FSH and LH, but they may transmit, moreover, seasonal and nutritive signals to reproductive organs. It might be expected that the further exploration of these functions may serve as basis for the development of new and effective biotechnical methods in farm animal treatment. 相似文献