Tree effects on the chemical topsoil features of oak, beech and pine forests     

Elena Marcos  Leonor Calvo  José Antonio Marcos  Ángela Taboada  Reyes Tárrega 《European Journal of Forest Research》2010,129(1):25-30

We aimed to study tree effects on the chemical properties of forest soils. We compared soil features of three types of forest ecosystems, each with four stands (replicates): beech forests (Fagus sylvatica), oak forests (dominated by Quercus pyrenaica) and pine plantations (Pinus sylvestris). Five samples from the top 10 cm of soil were taken per stand, from which pH, organic matter content (O.M.), total nitrogen (N) and available calcium (Ca²⁺), magnesium (Mg²⁺), potassium (K⁺) and sodium (Na⁺) were determined. Litter layer depth was measured at each soil sampling point. We also measured tree density and crown diameters at each stand. Our results indicated that soil samples from the four pine plantation stands were more similar while oak and beech stands were characterised by great variability in terms of soil properties and leaf litter depth. Although the identity of the dominant tree species significantly influenced several topsoil chemical properties (increase in pH and available cations in oak forests and higher organic matter and total nitrogen in beech and pine ecosystems), there were other important factors affecting soil features that may be taken under consideration. Differences between soil properties of the three types of forest ecosystems were mainly related to the characteristics of the litter layer and less related to the tree layer structure. Finally, the establishment of pine plantations in naturally deciduous tree areas made the topsoil features more homogeneous.  相似文献   

Evidence that active transmission of porcine cysticercosis occurs in Venezuela     

Cortez Alcobedes  Maria M.  Boggio  Gonzalo  Guerra  Ma. de Lourdes  de Gavidia  Magda Rodríguez  Rojas Reyes  Glenda C.  Ferrer  Elizabeth  Lares  Maria  Alviarez  Yenny  Harrison  Leslie J. S.  Parkhouse  R. Michael E. 《Tropical animal health and production》2010,42(3):531-537

There is a paucity of quantitative data on the status of porcine cysticercosis in Venezuela, information which is essential for understanding the level of disease transmission. This study was, therefore, conducted in a typical small rural community in Yaracuy State, Venezuela, where previous cases of human Taenia solium taeniasis/cysticercosis had been reported and where the free-ranging pig management practices and the lack of rudimentary sanitary facilities indicated an obvious risk for transmission of the disease. Serum samples from 52 village pigs were screened by enzyme-linked immunosorbent assays for anti-cysticercal antibodies (Ab-ELISA), using T. solium cyst fluid as the antigen and the HP10, monoclonal antibody-based, antigen trapping ELISA for parasite antigen (HP10 Ag-ELISA). Significantly, a high proportion of the animals (65.4% for the Ab-ELISA and 42.3% for the HP10 Ag-ELISA) were sero-positive. Five of the pigs, which were selected on that basis of positive tongue palpation, were killed for autopsy, and large numbers of viable cysticerci were found in the carcases. This unequivocal documentation of porcine cysticercosis in Venezuelan pigs presents clear evidence that T. solium is actively transmitted in Venezuela. Further detailed studies and implementation of appropriate control measures are therefore indicated.  相似文献   

Expression of vascular endothelial growth factor and endothelial nitric oxide synthase is increased in the placenta of sheep at high altitude in the Andes     

Parraguez VH  Atlagich MA  Urquieta B  Galleguillos M  De Los Reyes M  Kooyman DL  Araneda S  Raggi LA 《Canadian journal of veterinary research》2010,74(3):193-199

Fetal weight and the placenta of sheep at high altitude (HA) are affected by hypoxia. Placental changes (an increase in placental size and vascularization) are greater in ewes from populations that have lived for several generations at HA than in those exposed during just 1 gestation. This study investigated placental expression of vascular endothelial growth factor (VEGF) and endothelial nitric oxide synthase (eNOS), 2 molecules involved in placental angiogenesis that could be upregulated by hypoxia. Two groups of ewes were maintained at HA (3589 m) during pregnancy: HA-native ewes (group HH) and ewes native to lowlands but moved to HA immediately after the diagnosis of pregnancy (group LH). A control group (LL) was kept at sea level. Near term, placentomes were removed, weighed, and processed for immunohistochemical detection of VEGF and eNOS, as well as for vascular area measurement. Placental weight was significantly higher in the HH group than in the LH and LL groups; between the latter 2 groups there was no significant difference. The placental area occupied by vasculature was significantly greater in both the HA groups than in the LH group; the number of placentomes was greatest in the LL group. The density of VEGF and eNOS in the placentome tissue was significantly greater in both HA groups than in the LL group. Although the density of VEGF was significantly lower in the HH group than in the LH group, no differences were observed in eNOS density between the HH and LH animals. These results demonstrate that chronic hypoxia upregulates the expression of placental VEGF and eNOS, suggesting an important role of these molecules in the placental response to HA hypoxia. In addition, an attenuated response to hypoxia in VEGF synthesis may be part of the long-term process of adaptation to HA.  相似文献   

d24-hour changes in circulating prolactin, follicle-stimulating hormone, luteinizing hormone and testosterone in male rats subjected to social isolation     

Esquifino AI  Chacón F  Jimenez V  Reyes Toso CF  Cardinali DP 《Journal of circadian rhythms》2004,2(1):1

BACKGROUND: This work analyzes the effect of social isolation (a mild stressor) on the 24-h variation of pituitary-testicular function in young Wistar rats, assessed by measuring circulating levels of prolactin, FSH, LH and testosterone. METHODS: Animals were either individually caged or kept in groups (4-5 animals per cage) under a 12:12 h light-dark cycle (lights on at 0800 h) for 30 days starting on day 35 of life. Rats were killed at 4-h intervals during a 24-h cycle, beginning at 0900 h. RESULTS: Isolation brought about a decrease in prolactin, LH and testosterone secretion and an increase of FSH secretion. In isolated rats the 24-h secretory pattern of prolactin and testosterone became modified, i.e., the maximum in prolactin seen in control animals at the beginning of the activity span was no longer detected, whereas the maximum in circulating testosterone taking place at 1700 h in controls was phase-delayed to 2100 h in isolated rats. CONCLUSION: Social isolation affects the 24-h variation of pituitary-testicular function in young rats. Secretion of prolactin, LH and testosterone decreases, and secretion of FSH increases, in isolated rats. The maximum in prolactin seen in group-caged rats at the beginning of the activity span is not observed in isolated rats. The maximum in circulating testosterone taking place at the second part of the rest span in controls is phase-delayed to the light-dark transition in isolated rats.  相似文献   

Red-bellied black snake (Pseudechis porphyriacus) envenomation in 17 dogs: clinical signs,coagulation changes,haematological abnormalities,venom antigen levels and outcomes following treatment with a tiger-brown snake antivenom     

ER Finney  AM Padula  EM Leister 《Australian veterinary journal》2020,98(7):319-325

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亚硒酸钠浸种对春小麦种子萌发特性的研究     

冯魁  马艳明  田新年  贾永红  张金汕  迪里夏提·尔肯  刘俊  石书兵 《种子》2017,(9):39-43

为研究硒浸种对春小麦种子活力和幼苗生长特性的影响,分别设置0,0.5,1.0,2.5,3.5,5.0,10.0,50.0 mg/L共8个亚硒酸钠溶液浓度,通过发芽试验,比较研究了不同浓度的亚硒酸钠浸种对春小麦种子萌发和幼苗生长的影响.结果表明:随着亚硒酸钠溶液浓度升高,春小麦种子的发芽率、发芽势、发芽指数、活力指数、幼苗和根长以及干鲜重等指标均呈先升高后下降的趋势;1.0 mg/L的亚硒酸钠溶液对小麦种子萌发和幼苗生长有促进作用;随着亚硒酸钠浓度的升高(≥2.5 mg/L),其各项指标显著下降,并对根和苗的生长表现出抑制作用;因此在实际生产中,掌握合适的硒浸种浓度非常关键.  相似文献   

Beef carcase characteristics that may be of value in selecting for genetic merit     

ER JOHNSON 《Australian veterinary journal》1996,73(6):233-240

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The Effect of Hypertensin on the Inactivation of Oxytocin by the Serum of Pregnant Women     

Croxatto H  Croxatto R  Reyes M 《Science (New York, N.Y.)》1948,108(2815):658-659

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Pharmacokinetic study of enrofloxacin in Nile tilapia (Oreochromis niloticus) after a single oral administration in medicated feed          下载免费PDF全文

J. A. Teles  L. C. Castello Branco  M. Del Bianchi  F. Pilarski  F. G. R. Reyes 《Journal of veterinary pharmacology and therapeutics》2016,39(2):205-208

The objective of this study was to evaluate the disposition kinetics of enrofloxacin (ENR) in the plasma and its distribution in the muscle tissue of Nile tilapia (Oreochromis niloticus) after a single oral dose of 10 mg/kg body weight via medicated feed. The fish were kept at a temperature between 28 and 30 °C. The collection period was between 30 min and 120 h after administration of the drug. The samples were analyzed by high‐performance liquid chromatography with a fluorescence detector (HPLC‐FLD). The ENR was slowly absorbed and eliminated from the plasma (C_max = 1.24 ± 0.37 μg/mL; T_max = 8 h; T_1/2Ke = 19.36 h). ENR was efficiently distributed in the muscle tissue and reached maximum values (2.17 ± 0.74 μg/g) after 8 h. Its metabolite, ciprofloxacin (CIP), was detected and quantified in the plasma (0.004 ± 0.005 μg/mL) and muscle (0.01 ± 0.011 μg/g) for up to 48 h. After oral administration, the mean concentration of ENR in the plasma was well above the minimum inhibitory concentrations (MIC₅₀) for most bacteria already isolated from fish except for Streptococcus spp. This way the dose used in this study allowed for concentrations in the blood to treat the diseases of tilapia.  相似文献   

The consequences of diet limitation in juvenile threespine stickleback: growth,lipid storage and the phenomenon of compensatory growth          下载免费PDF全文

Miguel L. Reyes  John A. Baker 《Ecology of Freshwater Fish》2017,26(2):301-312

Many organisms exhibit compensatory growth (CG), an accelerated growth rate during recovery from periods of low nutrient resources. Despite numerous studies, many aspects of CG, particularly fine‐scale temporal effects early in life, remain poorly understood. We manipulated early‐life feeding regimens in threespine stickleback (Gasterosteus aculeatus) to study compensatory responses in growth rate and lipid storage during the first growing season. Laboratory‐reared stickleback, including ancestral oceanic and derived freshwater populations, were divided into three age‐specific dietary treatment groups – DPR1, DPR2 and DPR3 – which were exposed to a half‐ration nutrient deprivation for 30 days at the onset of 2, 3 and 4 months of age, respectively. We hypothesised that these month‐long periods of nutrient deprivation would result in strong, yet variable CG responses across stickleback populations and dietary treatments following a return to optimal ration levels. The youngest two age classes of fish (DPR1 &and DPR2) exhibited strong CG responses, matching growth rates and lipid generation levels seen in control fish fed an ad libitum diet. The oldest nutrient‐deprived group (DPR3) showed a reduced CG response, with body growth recovering only partially, and lipid levels exhibiting even less recovery. Our results demonstrate that compensatory growth responses in juvenile stickleback depend on the timing of deprivation during the first growing season and further that responses to late‐season deprivation have favoured development of a larger body frame entering the overwintering season over lipid regeneration.  相似文献