Microbial community changes in heathland soil communities along a geographical gradient: interaction with climate change manipulations     

Alwyn Sowerby  Bridget Emmett  Albert Tietema  Marc Estiarte  Steven Hughes 《Soil biology & biochemistry》2005,37(10):1805-1813

Climate change constitutes a serious threat for European heathlands as unlike other sources of damage, such as over-grazing, local remediation is not a possibility. Within the large pan-European projects, CLIMOOR and VULCAN, the effect of periodic drought and increased temperature were investigated in four heathland ecosystems along a geographical and climatic gradient across Europe. Fluorogenically labelled substrates for four enzymes (glucosidase, sulphatase, phosphatase, leucine amino peptidase) were used to measure extra-cellular enzyme activity in soil samples from each of the CLIMOOR sites. Microbial extra-cellular enzyme production is linked to microbial activity as well as soil physico-chemical properties, making soil enzymes one of the more reactive components of terrestrial ecosystems and potentially excellent indicators of soil microbial functional status and diversity.Across all sites and over all the substrates, organic matter content was exponentially, inversely related to enzyme activity. Although the increase in temperature produced by the CLIMOOR roofs was small (on average 0.9 °C), this was sufficient to increase enzyme activity in all sites (on average by 45%). The increase was within the range of seasonal variability at each of the sites. The effect of drought on enzyme activity was more pronounced in the Northern European sites than the southern European, and most moisture limited, site. This suggests that the effect of temperature increases may be observed across all regions; however, the soils of northern Europe may be more sensitive to changes in rainfall patterns than more moisture limited Southern European soils.  相似文献   

Seasonal patterns of root-surface phosphatase activities in a Mediterranean shrubland. Responses to experimental warming and drought   总被引：2，自引：0，他引：2  

Jordi Sardans  Josep Peñuelas  Marc Estiarte 《Biology and Fertility of Soils》2007,43(6):779-786

Mediterranean ecosystems are water limited and the current general circulation Models (GCM) and ecophysiological models forecast a warming and a further increase of drought in the next decades. A stronger water stress can decrease the capacity for nutrient absorption by plants. We conducted a field experiment to simulate forecasted drought and warming in a Mediterranean calcareous shrubland to assess the performance of root-surface phosphatase activities of the dominant shrub Globularia alypum. These enzyme activities were higher in autumn and spring, when the climate conditions were optimal for plant activity, than in summer or winter, when there was either lack of water or cold temperatures. A decrease in soil moisture in drought plots decreased root-surface phosphatase activity (29% in summer and 25% in autumn). The decrease in root-surface phosphatase activity in drought plots coincided with a decrease in P leaf concentrations and P accumulation in aboveground biomass and loss of photosynthetic capacity of some dominant shrub species of this ecosystem, and with a tendency to increase total soil-P. These results suggest that the expected drier conditions in this Mediterranean shrubland in the next decades will slow down the P uptake by plants, thereby, diminishing the P contents in biomass and increasing total P contents in soil in non-available forms and that this can be, in part, attributable to a result of the decrease in root-surface phosphatase activity.  相似文献   

Central Venous Pressure Measurements in the Caudal Vena Cava of Sedated Cats     

Roslyn G. Machon B.V.Sc.  M.V.Sc.  M.S.    Marc R. Raffe D.V.M. M.S.  Elaine P. Robinson B.Vet.Med.  M.V.Sc. 《Journal of Veterinary Emergency and Critical Care》1995,5(2):121-129

The caudla vena cava (CVA) was evaluated as an laternative site for the measurement of central venous pressure (CPV) in six healthy, sedated (ketamine 10 mg/km, midazolam 0.1 mg/kg, and atropine 0.04 mg/kg IM) cats. The CVC was cathererized via medial saphenous puncture, and estimates of CPV from this site compared to those obtained via a jugular catheter. Simulataneous CPV values were recorded electronically (mmgh), via calibrated pressure transducer positioned at the level of the manubrium in cats in lateral recumbency. Five readings, performed at 1 minute intervals, were collected from the jugular and CVC catheters at rest (baseline) and following a rapid fluid bolus. Twenty-four hours later, cats were resedated, baseline measurements repeated, and CVPs recorded following a rapid, 25% whole-blood volume bleed. CVP measurements from the jugular and CVC were statistically compared using repeated measures ANOVA (p<0.05). There were no significant differences between the two sites in the baseline and bleed trials. Significant defferences between jugular and CVC CVPs were noted at 1 and 2 minutes following the fluid bolus. It was concluded that CVC is an alternative site for measurement of CPV in sedated cats.  相似文献   

Fascicular nerve biopsy in the dog     

K G Braund  T L Walker  M Vandevelde 《American journal of veterinary research》1979,40(7):1025-1030

A nerve fascicular biopsy technique that preserves the functional integrity of the parent nerve is reported in the dog. Fascicular biopsies from ulnar and peroneal nerves did not produce clinical sensory or motor deficits. Electrodiagnostic testing for the modalities of latency, duration, amplitude, and conduction velocities were not markedly altered after fascicular biopsies. Morphometric analysis of muscle fiber types, delineated by histochemic techniques, revealed no statistical (P greater than 0.05) difference between muscles from biopsied or control limbs. Fascicular biopsies resulted in small neuromas in all dogs.  相似文献   

"Vomiting and wasting disease" in piglets in Switzerland]     

F Steck  B Sch?ren  R Fatzer  M Vandevelde  E Scholl  H H?ni 《Schweizer Archiv für Tierheilkunde》1975,117(11):617-622

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Detection of Escherichia coli strains producing cytotoxic necrotizing factor type two (CNF2) by enzyme-linked immunosorbent assay     

Eric Oswald  Marc Tabouret  Roger Boivin  Jean De Rycke 《Veterinary microbiology》1994,40(3-4):209-218

Sheep and rabbit antisera were produced against lysates of E. coli strain 711 (pVir). This K-12 strain carries the Vir plasmid which codes for Cytotoxic Necrotizing Factor type 2 (CNF2). Immunoglobulin G (IgG) fractions of both immune sera were subsequently purified by a two-step precipitation method. To increase the specificity for CNF2, the sheep IgG preparation was extensively adsorbed against both a sonicated extract of isogenic K-12 strain 711 and intact phenol-treated cells of vaccine strain 711 (pVir). An enzyme-linked immunosorbent assay (ELISA) was developed to detect clinical isolates of E. coli producing CNF2, using the final preparations of rabbit and sheep IgG in a double sandwich technique. The results obtained with this CNF2-ELISA were compared to those obtained with the conventional HeLa cell cytotoxicity assay. The testing of 133 E. coli strains (49 CNF2 positive strains and 84 negative strains) resulted in no false-negative and no false-positive. Therefore, the CNF2-ELISA offers a good alternative to the HeLa cell culture assay for the detection of CNF2-producing strains where facilities for and experience with cell cultures is lacking.  相似文献   

Cerebrospinal fluid studies in neurologically sick dogs and cats     

M Vandevelde  A Richard  R Fankhauser 《Schweizer Archiv für Tierheilkunde》1987,129(9):443-456

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Evaluation of repetitive nerve stimulation in young dogs     

T. Gödde  A. Jaggy  M. Vandevelde  C. Gaillard 《The Journal of small animal practice》1993,34(8):393-397

Evaluation of neuromuscular transmission requires a complete electrodiagnostic evaluation including repetitive nerve stimulation. Supra-maximal stimulation of the peroneal nerve and recording of the compound muscle action potentials from the cranial tibial muscle were under-taken in 25 young dogs of two to 18 months of age. Proximal stimulation in the trochanteric fossa and distal stimulation in the popliteal fossa were chosen for small and large breeds, respectively. Highly consistent results were obtained when the examined muscle was kept at a constant temperature and the limb was firmly fixed. Neither sex- (14 females, 11 males) nor age- related (mean = 4·4 months] differences in neuromuscular transmission were found, but frequency-dependent phenomena were observed. These became more distinct with high frequency stimulation. Pseudofacilitation (n = 16/15 Hz; n = 7/50 Hz), was found to range within certain limits (6 to 26 per cent/15 Hz; 13 to 31 per cent/50 Hz). Its mean values at 50 Hz stimulation were apparently higher (26·88 per cent) than those at 15 Hz stimulation (11·3 per cent). Decremental responses occurred mainly with application of tetanic stimulation frequency (n = 1/15 Hz; n = 12/50 Hz) and may represent blocking of neuromuscular transmission. Each of these reaction patterns usually started to occur at the fourth potential of a series (81 per cent/15 Hz; 94 per cent/50 Hz) and remained constant during the second half of the stimulation train in most cases. The occurrence of post-tetanic phenomena in healthy dogs is poorly understood. Post-tetanic potentiation observed in the present material (24 per cent) may represent pseudofacilitation following high stimulation frequency (50 Hz/100 pulses).  相似文献   

Polioencephalomyelitis in cats.     

M Vandevelde  K G Braund 《Veterinary pathology》1979,16(4):420-427

Six cats with chronic progressive neurologic signs of ataxia, paresis, tremors, pupillary abnormalities and seizures had polioencephalomyelitis of probable viral origin. Lesions were most severe in the spinal cord. The uniformity in distribution and nature of the lesions in all six cats strongly suggested a common cause. The condition was compared with other viral infections of known and unknown cause.  相似文献   

Analysis of the in vitro activation and proliferation process in lymphocytes deriving from canine thymus and mesenteric lymphnode     

F. Kristensen  B. Kristensen  M. Vandevelde  R.J. Higgins  A.L. De Weck 《Veterinary immunology and immunopathology》1981,2(6):579-590

Lymphocytes from dog thymus and mesenteric lymphnodes have been stimulated in vitro with 3 different mitogens. Culture medium was enriched with either autologous plasma, fetal calf serum or a newly described defined serum substitute. In such cultures the number of surviving and activated cells was quantified by cytofluorometry and the proliferation was assessed by thymidine incorporation. Results obtained with the 3 media were very similar. A significant number of lymphocytes died during the first 42 hours of incubation. There was a tendency toward more surviving cells with fetal calf serum and the serum substitute, whereas more activated (G₁) cells and higher thymidine incorporation could be observed with autologous plasma. Furthermore, when results obtained with various mitogen concentrations and from individual dogs were analyzed, a high correlation between “highly activated (G_1b) cells and thymidine incorporation was found, i.e. r=0.84 for thymocytes and 0.68 for lymphnode cells. The correlation between all G₁ (G_1a+b) cells and thymidine incorporation was lower or absent (r=0.02 and 0.55, respectively). It is concluded from these results that the population of G_1b cells have received all required signals necessary for proliferation whereas the total G₁ cell population also include activated cells, which are not obligatorily undergoing subsequent proliferation  相似文献