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排序方式: 共有196条查询结果,搜索用时 31 毫秒
101.
Raymond M. Wheeler Kenneth L. Steffen Theodore W. Tibbitts Jiwan P. Palta 《American Journal of Potato Research》1986,63(11):639-647
The growth and tuberization of Norland potatoes were studied under five different temperatures and two photoperiods. Treatment levels included 12, 16, 20, 24, and 28 C with either a 24-h (continuous light) or a 12-h photoperiod at 400 μmol m-2 s-1 PPF. Plants were grown in 6-liter containers and harvested at 56-days-age. Stem length increased with increasing temperature under both photoperiods. The highest tuber yield occurred at 16 C under the 24-h photoperiod (755 g/plant) and at 20 C under the 12-h photoperiod (460 g/plant). Little or no tuber formation occurred at 28 C under either photoperiod or at 24 C under continuous light. As with tuber yield, the highest total plant dry weights also occurred at 16 C under the 24-h photoperiod and at 20 C under the 12-h photoperiod. Harvest index (tuber dry weight to total dry weight ratio) decreased with increasing temperatures and with continuous light. Results indicate that good growth and tuberization can occur under continuous light, and that increasing the photoperiod from 12 to 24 h effectively decreased the optimal temperature for tuber formation from near 20 C to 16 C. Alternatively, the results imply that at cooler temperatures, the potato becomes less obligate for dark period stimulation of tuberization. 相似文献
102.
Within the framework of the EU project DROPSA (‘Strategies to develop effective, innovative and practical approaches to protect major European fruit crops from pests and pathogens’), a review on pests (including pathogens) that have fruit species as their host plants was conducted. The focus was on pests that have been introduced into Europe or were found in the fruit trade during the last 10–15 years. Among the 387 recorded pests, the following groups were identified: 1. fruit and vinegar flies, 2. scale insects, 3. fungi, 4. plant viruses, 5. bacteria, 6. pests of unknown risk, 7. tropical fruit pests, 8. pests that had an unexpected change of hosts, 9. fruit pests not likely to be transported on fruit and 10. ‘hitchhikers’ (non‐fruit pests intercepted on fruit/fruit plants, fruit pests intercepted on other commodities than fruit). The large number of pests identified, from different taxonomic groups and origins, shows that fruit are an important pathway for pests, threatening fruit production in Europe. 相似文献
103.
Shrinkage potential and pore shrinkage capacity of differently developed volcanic ash soils under pastures in southern Chile
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Steffen Beck‐Broichsitter Heiner Fleige Marc‐Oliver Goebel José Dörner Jörg Bachmann Rainer Horn 《植物养料与土壤学杂志》2016,179(6):799-808
The drying process of volcanic ash soils often results in the formation of shrinkage cracks with consequences for their physical properties (i.e., decrease of water retention capacity) and land use management. This study presents the soil water characteristics and shrinkage behaviour (shrinkage phases in terms of void and moisture ratio), the shrinkage potential (COLE index), and the pore shrinkage capacity (PSI) for 5 and 20 cm depth of a Haplic Arenosol (tephric) and two Silandic Andosols under pasture management along a soil gradient from the Andean mountains to the coastal range in southern Chile. The main focus of the presented study is on the effect of soil development in conjunction with the weathering of volcanic ash soils on the shrinkage properties. The water retention and shrinkage curves were continuously determined for undisturbed soil samples (100 cm3) during a drying process under laboratory conditions. In addition, the shrinkage curve data were modelled to distinguish different shrinkage zones. The results suggest that the investigated soil properties vary depending on soil development. The more developed Andosols had higher total porosities (up to 70 cm3 cm?3) than the less developed Arenosol. The shrinkage behaviour of the Haplic Arenosol showed a wide structural shrinkage phase, whereas the Silandic Andosols revealed a more pronounced proportional shrinkage phase, which is related to the pore size distribution. In addition, wide and narrow coarse pores of the Haplic Arenosol and medium and fine pores of the Silandic Andosols determine the shrinkage potential (COLE) and the pore shrinkage capacity, respectively. The finer‐grained and organic matter‐rich Andosols indicate a higher COLE index (> 0.03–0.09) compared to the Arenosol (≤ 0.03). The pore shrinkage index (PSI) of the total pores (TP) varied significantly (P < 0.05) with values of 0.042–0.149 in 5 cm depth and 0.04–0.091 in 20 cm depth of sites 1–3, respectively.In summary, the shrinkage potential and pore shrinkage capacity are positively correlated to the organic carbon content and decrease with increasing dry bulk density. The study points out a higher risk of soil degradation due to irreversible drying processes for the more clayey and allophane containing Andosols than the Arenosol. 相似文献
104.
Farias FM Passos CS Arbo MD Barros DM Gottfried C Steffen VM Henriques AT 《Fitoterapia》2012,83(6):1138-1143
Psychotria is a complex genus whose neotropical species are known by the presence of glucosidic monoterpene indole alkaloids. These compounds are able to display a large range of effects on the central nervous system, such as anxiolytic, antidepressant, analgesic, and impairment of learning and memory acquisition. The aims of this study were to investigate the effects displayed by strictosidinic acid, isolated from Psychotria myriantha Mull. Arg. (Rubiaceae) leaves, on monoamine levels in rat hippocampus and on monoamine oxidase activity. A significance (p<0.01) of 83.5% reduction in 5-HT levels was observed after intra-hippocampal injection (20 μg/μl). After treatment by intraperitoneal route (10 mg/kg), a 63.4% reduction in 5-HT levels and a 67.4% reduction in DOPAC values were observed. The results indicate that strictosidinic acid seems to act on 5-HT system in rat hippocampus, possibly inhibiting precursor enzymes of 5-HT biosynthesis. The decrease verified in DOPAC levels suggests a role of strictosidinic acid in the dopaminergic transmission, probably due to an inhibition of monoamine oxidase activity, confirmed by the enzymatic assay, which demonstrated an inhibitory effect on MAO A in rat brain mitochondria. 相似文献
105.
Seliger C Schaerer B Kohn M Pendl H Weigend S Kaspers B Härtle S 《Veterinary immunology and immunopathology》2012,145(1-2):86-99
The automated analysis of total white blood cell count and white blood cell differentials is routine in research and clinical diagnosis in mammalian species. In contrast, in avian haematology these parameters are still estimated by conventional microscopic procedures due to technical difficulties associated with the morphological peculiarities of avian erythrocytes and thrombocytes. Both cell types are nucleated and fairly resistant to cell lysis, a prerequisite for automated leukocyte quantification and differentiation by commercial instruments. By using an anti-CD45 monoclonal antibody in combination with selected subset specific markers we have established a simple (no-lyse no-wash single-step one-tube) flow cytometry based technique for high precision chicken blood cell quantification. EDTA-blood samples are diluted, spiked with fluorescence beads and incubated with a mixture of fluorochrome conjugated chicken leukocyte specific antibodies. We demonstrate that total leukocyte numbers as well as thrombocyte, monocyte, T-cell, B-cell and heterophilic granulocyte numbers can be determined by flow cytometry in a single step without prior cell lysis, cell separation or cell washing steps. Importantly, we also show that blood samples can be fixed prior to cell staining which enables shipping of samples making the technology widely available. Comparison of this technique with conventional microscopy revealed superior precision. By comparing leukocyte differentials of two chicken populations and during immune system development after hatch we demonstrate that large sample numbers can be analysed within hours. This technique will help to overcome previous restrictions in immune status analysis in chickens in experimental systems, during vaccine testing and health status monitoring in chicken flocks. Advances in avian genomics should facilitate the development of appropriate tools for other avian species in the future which will make this technique broadly applicable. 相似文献
106.
Steffen Keiter Thomas Braunbeck Susanne Heise Stefan Pudenz Werner Manz Henner Hollert 《Journal of Soils and Sediments》2009,9(3):168-179
Background, aim, and scope Ecotoxicological risk assessment of sediments is usually based on a multitude of data obtained from tests with different endpoints.
In the present study, a fuzzy logic-based model was developed in order to reduce the complexity of these data sets and to
classify sediments on the basis of results from a battery of in vitro biotests.
Materials and methods The membership functions were adapted to fit the specific sensitivity and variability of each biotest. For this end, data
sets were categorized into three toxicity levels using the box plot and empirical methods. The variability of each biotest
was determined to calculate the range of the gradual membership. In addition, the biotests selected were ranked according
to the biological organisation level in order to consider the ecological relevance of the endpoints measured by selected over-
or underestimation of the toxicity levels. In the next step of the fuzzy logic model, a rule-base was implemented using if...and...then decisions to arrive at a system of five quality classes.
Results The results of the classification of sediments from the Rhine and Danube Rivers showed the highest correlation between the
biotest results and the fuzzy logic alternative based on the empirical method (i.e. the classification of the data sets into
toxicity levels).
Discussion Many different classification systems based on biological test systems are depending on respective data sets; therefore, they
are difficult to compare with other locations. Furthermore, they don‘t consider the inherent variability of biotests and the
ecological relevance of these test systems as well. In order to create a comprehensive risk assessment for sediments, mathematical
models should be used which take uncertainties of biotest systems into account, since they are of particular importance for
a reliable assessment. In the present investigation, the variability and ecological relevance of biotests were incorporated
into a classification system based on fuzzy logic. Furthermore, since data from different sites and investigations were used
to create membership functions of the fuzzy logic, this classification system has the potential to be independent of locations.
Conclusions In conclusion, the present fuzzy logic classification model provides an opportunity to integrate expert knowledge as well
as acute and mechanism-specific effects for the classification of sediments for an ecotoxicological risk assessment.
Recommendations and perspectives In order to achieve a more comprehensive classification, further investigation is needed to incorporate results of chemical
analyses and in situ parameters. Furthermore, more discussions are necessary with respect to the relative weight attributed
to different ecological and chemical parameters in order to obtain a more precise assessment of sediments. 相似文献
107.
Kelling CL Steffen DJ Cooper VL Higuchi DS Eskridge KM 《American journal of veterinary research》2002,63(8):1179-1186
OBJECTIVE: To compare experimentally induced concurrent infection with bovine viral diarrhea virus (BVDV) and bovine rotavirus (BRV) with infection of either virus alone in calves. ANIMALS: Seventeen 1-day-old gnotobiotic calves. PROCEDURE: Calves were allotted to 8 treatments as follows: group 1, mock-infected control calves (n = 2); group 2, inoculated with BVDV on day 1 (2); groups 3, 5, and 7, inoculated with BRV on days 1 (2), 4 (1), or 7 (2), respectively; and groups 4, 6, and 8, inoculated with BVDV on day 1 and with BRV on days 1 (2), 4 (2), or 7 (4), respectively. Concentrations of BVDV in serum and ileal tissues were measured, and BRV shedding in feces was determined. Histologic examination and immunohistochemical analysis were conducted to detect lesions and viral antigens. RESULTS: Neonatal calves inoculated with BVDV alone or with BVDV on day 1 and BRV on day 7 developed villus atrophy and submucosal inflammation of the intestines. Concurrent BVDV and BRV infections acted synergistically in the intestinal tract, causing more severe enteric disease than infection with either virus alone. Severe lymphoid depletion was associated with BVDV infection in calves regardlesss of concurrent BRV infection. CONCLUSIONS AND CLINICAL RELEVANCE: Infection with BVDV played direct and indirect roles in enteritis in neonatal calves, causing villus atrophy in the duodenum and submucosal inflammation of the intestines. Also, BVDV potentiated effects of BRV. Concurrent infection with BVDV and BRV resulted in more severe enteric disease in neonatal calves than infection with BRV or BVDV alone. 相似文献
108.
109.
ANIMAL STUDIED: A Royal Boa constrictor presented with retained spectacle of the right eye and a tumor-like appearance of the left eye. PROCEDURE: The snake was euthanized, the head fixed in buffered formaldehyde, and histologic examination of both spectacles and both eyes performed. RESULTS: The left orbital rim encircled a solid, scaly mass projecting 5-6 mm from the spectacular area. A cup-shaped tumor with a central keratin plug was observed microscopically. There was a thickening of the proliferating squamous epithelium, with squamous eddies and single cell keratinization. A few mitotic figures were seen in the basal layers but the tumor showed no infiltrative growth. The same morphology was observed in the right eye but to a lesser extent. The remaining parts of the eye were normal. CONCLUSIONS: The diagnosis was keratoacanthoma and this is the first reported keratoacanthoma of the spectacle in a reptile. Keratoacanthoma should be considered as a differential diagnosis when trying to remove retained spectacles from a reptile eye. 相似文献
110.
Geigy CA Heid S Steffen F Danielson K Jaggy A Gaillard C 《Veterinary journal (London, England : 1997)》2007,173(3):548-553
The prevalence of deafness is high in cat populations in which the dominant white gene is segregating. The objective of this study was to investigate whether there is a gene that is responsible for deafness as well as for blue eyes and to establish a plausible mode of inheritance. For this purpose, data from an experimental colony with deaf cats were analyzed. The hearing status was determined by acoustically evoked brain stem responses (BAER). Complex segregation analyses were conducted to find out the most probable mode of inheritance using maximum likelihood procedures. The prevalence of deafness and partial hearing in the experimental colony was 67% and 29%, respectively. The results of the bivariate segregation analysis support the hypothesis of a pleiotropic major gene segregating for deafness and blue iris colour. The high heritability coefficients for both traits, 0.55 and 0.75 respectively, indicate that beside the major gene there is an important influence of polygenic effects. 相似文献