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951.
The in vitro inhibitory effect of SR 27417, an antagonist of the platelet-activating factor (PAF) receptor, on PAF-induced platelet aggregation was studied in blood collected from seven healthy Friesien calves. Inhibitory effects of SR 27417 were determined at thirteen different concentrations (0.1-400 nM) by using the dose-response curves of PAF on calf platelet aggregation. In the presence of SR 27417, the maximal slopes of aggregation (%/min) induced by low and high concentrations of PAF were significantly different from the control values obtained without an antagonist at p < or = 0.05 and p < or = 0.01 respectively. In vitro PAF-induced calf platelet aggregation was dose-dependently inhibited by SR 27417. The drug inhibited PAF-induced platelet aggregation in a competitive reversible manner (pA2 = 10.46 +/- 2.36 mol x L(-1)). In conclusion, the results of our study showed that addition of SR 27417 to bovine platelet in vitro inhibits PAF-induced platelet aggregation. 相似文献
952.
Nutrient concentrations and acidity in ferralitic soil under perennial cropping, fallow and primary forest in central Amazonia 总被引:2,自引:0,他引:2
G. Schroth R. Seixas L. F. da Silva W. G. Teixeira & W. Zech 《European Journal of Soil Science》2000,51(2):219-231
The long‐term productivity on the acidic, nutrient‐poor upland soils of central Amazonia depends to a large extent on the chemical soil fertility as influenced by vegetation type and management. We compared soil and soil solution data from permanent cropping, fallow and primary forest on a Xanthic Ferralsol in central Amazonia to evaluate changes of soil fertility following forest conversion, agricultural use at different intensities and setting aside agricultural land. The agricultural systems included a perennial polyculture at two fertilizer inputs and a monoculture plantation. Soil and soil solution were collected to 2 m depth, and the soil solution was monitored over 2 years. Both soil and soil solution data showed decreasing soil fertility in the sequence: monoculture and polyculture at large input, polyculture at small input, forest and fallow. The soil solution data were more sensitive to effects of systems and fertilizer inputs on subsoil fertility. Fractionation of the N in the soil solution showed a larger proportion of dissolved organic N in the N‐poor fallow soil than in the soil under forest and agriculture. The soil under fallow, forest and low‐input agriculture had larger exchangeable acidity than that under high‐input agriculture, but the Al concentrations in the soil solution were very small because there were few cations with which to exchange and less nitrification. In high‐input agriculture, pronounced acidification peaks in the topsoil solution followed fertilization. The comparison of soil and soil solution data explained why the spontaneous vegetation thrives at very large exchangeable acidity in these soils, whereas agricultural systems often depend on liming to reduce the concentration of toxic Al in the soil. 相似文献
953.
Differently managed oxisols from Central Brazil were studied using a sequential P fractionation procedure because the effects
of land use on the distribution of P forms in these soils are barely known. Therefore levels of labile and recalcitrant P
forms in the natural Cerrado savanna were compared with those of crop, pasture and reforestation sites on differently textured
oxisols. Under natural conditions of strong P deficiency, >60% of labile P was organic P (Po), reflecting the high contribution of Po to plant nutrition. Fertilisation after land-use change only increased levels of inorganic P (Pi) forms, the increase being most accentuated in the labile Pi fraction. At the crop and the pasture sites P tended to accumulate as recalcitrant P forms in the clayey soils, while in
the loamy soils there was only a minor enrichment, probably due to the lower amounts of Fe- and Al-(hydr)oxides. In the reforestation
sites, labile P was maintained at high levels, most likely through efficient recycling of the litter. The P fractionation
procedure was also applied to particle-size fractions which reflected P transformations along an organic and mineralogical
gradient. The clay fraction corresponded to 69–87% of total P and appeared to be both a sink for highly recalcitrant P and
a source for labile P, especially labile Po. The sequential P fractionation procedure was also an effective method with which to detect the presence of fertiliser-P
residues in the coarse-silt fraction.
Received: 18 June 1999 相似文献
954.
Maria Manuela da Gama Jos Paulo Sousa Cristina Seabra Ferreira Helena Maria Barrocas 《Pedobiologia》2000,44(3-4)
The study of several arthropod groups in high endemism areas (HEA) of Algarve, the Southernmost province of Portugal, has revealed endemic species and species not yet recorded for the Portuguese fauna. The list includes 3 species of Isopoda endemic to Algarve, to Portugal or to the Iberian Peninsula, 2 species new to Portugal and 2 species new to the Iberian Peninsula; 2 species of Pseudoscorpiones not yet cited to Portugal; 11 species of Pauropoda new to Portugal, including one new species probably endemic; 15 species of Collembola endemic to the Portuguese or to the Iberian Peninsula faunas (Gama et al. 1997) and 37 species and 5 subspecies of Staphylinidae endemic to Algarve.With the exception of Collembola, which have been studied by us, the remaining groups have been submitted for study to several specialists.These findings heighten the biological richness of these areas of high endemism in terms of conservation of biological diversity. The authors draw attention to the necessity to preserve or restore the biological value of these areas, encouraging the adoption of protective measures and the creation of research programmes that include the implementation of taxonomic studies and co-operation between taxonomists and ecologists in order to preserve the biodiversity of these areas. 相似文献
955.
M.C. Peleteiro C. Pinto J.J. Correia J.F. Silva & S. Branco 《Veterinary dermatology》2000,11(4):299-304
This paper presents two cases of cutaneous neoplasia in Friesian cows, on the island of S. Miguel, Azores. The lesions consisted of raised pink plaques, with no pruritus or signs of associated pain, that were extensively distributed over both lateral and ventral body surfaces. The histological examination of the material obtained by skin biopsy or post-mortem suggested a T cell lymphoma with extensive epidermal infiltration. The lymph nodes showed extensive invasion by tumour cells. The results of immunocytochemistry, which were the same for the tumour cells in the skin and in the lymph node, were positive for CD3, confirming the T cell origin of the tumour cells. It was concluded that these were cases of T cell lymphoma, involving both skin and lymph nodes. Although there have been other reports of cutaneous lymphosarcoma in the literature, these are the first cases identified in the Azores. 相似文献
956.
本文记述寄生于红嘴相思鸟[Leiothrixlutea(scopoli)]肌胃的一线虫新种。新种特征:缺侧翼,具粗大环纹,雄虫尾部腹面复盖盾片和大小相等的尾翼,尾乳突排列对称且肛后乳突特大,引带铲形,有别于其他种。 相似文献
957.
958.
Evaluation of Quality Parameters in the Meat of Pintado Amazônico,Female Pseudoplatystoma fasciatum × Male Leiarius marmoratus,Subjected to Different Slaughter Methods
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Luzilene A. Cassol Marcelo A. Martins Elayna C. da Silva Maciel Daniella M. Pinto Janessa S. de Abreu Edivaldo S. de Almeida Filho 《Journal of the World Aquaculture Society》2015,46(5):475-489
The objective of this study was to check the effect of different stunning methods on the meat quality of Pintado Amazônico, female Pseudoplatystoma fasciatum × male Leiarius marmoratus, stored on ice for 18 d. A total of 90 specimens (2.5 ± 0.45 kg and 58.21 ± 6.20 cm) were divided into three groups and subjected to stunning by: water saturated with CO2, hypothermia on ice, or asphyxia in air. Subsequently, samples were removed to be analyzed after (times) 0, 2, 4, 6, 8, 10, 12, 14, 16, and 18 d. At the established times, aerobic mesophilic heterotrophic microorganisms and aerobic psychrotrophic heterotrophic microorganisms were quantified, and the pH, total volatile base nitrogen, color (L*a*b*), and sensory traits were analyzed. The stunning method significantly affected (P < 0.05) the meat quality. The group stunned on ice showed the best results compared with the other treatments. 相似文献
959.
Nicolás Vidal Franco Teixeira de Mello Iván González-Bergonzoni Anahí López-Rodríguez Giancarlo Tesitore Joaquín Pais Samanta Stebniki Ivana Silva Alejandro D’Anatro 《Ecology of Freshwater Fish》2020,29(2):334-345
Unravelling the effect of climate variability on species biology has been one of the main goals of ecological studies. Environmental factors such as river discharge and temperature have being proposed as triggers of reproductive cycle in fish. In temperate climates, fish reproduction is affected mainly by temperature, while is influenced by flood pulses in large tropical rivers. We evaluated the influence of temperature and river discharge as triggers of Iheringichthys labrosus’ reproduction. We studied the following reproductive variables: gonadosomatic index (GSI), hepatosomatic index (HSI) and condition factor (K). Females of I. labrosus were examined in a time series of ten years along three sites located in Lower Uruguay River at the beginning (last week of November-first week of December, spring) and by the end of the reproductive period (middle-end of April, autumn). Generalised linear models detected a positive effect of mean winter temperature and site on the spring mature female GSI. Site was significant in addition to the interaction between temperature and site. Moreover, the effect of winter temperature was stronger than water discharge in triggering reproductive timing of I. labrosus, contrary to the model proposed for other species in tropical systems. Additionally, a literature review suggested a latitudinal gradient on reproduction, occurring earlier and prolonged with decreasing latitude (and increasing temperature). In this study, we stated the effect of temperature on the life history in a Neotropical fish using a multifaceted approach, particularly important in the current context of global climate warming. 相似文献
960.