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1.
H.-J. Pachur M. Ahrens M. Ricking H.-P. Rper 《Land Degradation \u0026amp; Development》1993,4(4):351-360
Sediments from the Berlin area were analysed for heavy metals and chlorinated hydrocarbons. the sedimentological and hydrogeological aspects of the Holocene sediments are discussed and an adapted sampling device for muds with a high water content is described. the contamination of surface sediments and dated cores is shown back in the 19th century; the hydrological influences on the degree of contamination and potential threats to groundwater and, via remobilisation, to surface waters are considered. It is concluded that the sediments of the Berlin area are highly contaminated. 相似文献
2.
Detection of the German grapevine yellows (Vergilbungskrankheit) MLO in grapevine,alternative hosts and a vector by a specific PCR procedure 总被引:5,自引:0,他引:5
M. Maixner U. Ahrens E. Seemüller 《European journal of plant pathology / European Foundation for Plant Pathology》1995,101(3):241-250
A polymerase chain reaction procedure was developed which enables specific amplification of a ribosomal sequence from the mycoplasmalike organism (MLO) associated with German grapevine yellows (Vergilbungskrankheit, VK) and stolbur-related diseases of solanaceous plants. Successful amplification from all samples prepared from various cultivars collected in different viticultural areas indicates that the causal agent is a relatively homogeneous organism. Amplification was also achieved with template DNA prepared from naturally infected weeds in vineyards such asConvolvolus arvensis andSolanum nigrum, and from the planthopperHyalesthes obsoletus that was collected in the vineyards. Feeding of insects of this species on grapevine seedlings resulted in the development of typical yellows symptoms by the grapes.H. obsoletus could therefore be identified as a vector of Vergilbungskrankheit.Abbreviations FD
Flavescence dorée
- GY
Grapevine yellows
- MLO
Mycoplasmalike organism
- PCR
Polymerase chain reaction
- RFLP
restriction fragment length polymorphism
- VK
Vergilbungskrankheit (German grapevine yellows) 相似文献
3.
4.
Aarestrup FM AgersŁ Y Ahrens P JŁrgensen JC Madsen M Jensen LB 《Veterinary microbiology》2000,74(4):353-364
The species distribution, susceptibility to 19 antimicrobial agents and presence of selected genes encoding resistance to macrolides, streptogramins and tetracyclines were examined among 118 staphylococcal isolates from infections of poultry in Denmark. Isolates were identified using a combination of conventional biochemical testing and 16S rDNA sequencing. The most common species were Staphylococcus aureus (83), Staphylococcus hyicus (11), Staphylococcus xylosus (9) and Staphylococcus cohnii (6). The isolates were susceptible to most antimicrobials tested. A high frequency of S. aureus (30%) was resistant to ciprofloxacin. Only six (7%) S. aureus isolates and one Staphylococcus saprophyticus were penicillin resistant. Resistance to sulphamethoxazole was observed among 16 (19%) of S. aureus isolates and two coagulase negative staphylococci (CNS). Twenty (24%) of the S. aureus isolates were resistant to erythromycin and 19 of these isolates contained the ermA gene, whereas the remaining isolate contained the ermC gene. Eleven (48%) of the novobiocin resistant CNS were resistant to erythromycin and all these isolates contained the ermA gene. Two isolates identified as S. xylosus, were found to be resistant to streptogramins and both contained the vatB- and the vgaB-genes. Thirty-nine (47%) of the S. aureus isolates, three of nine S. hyicus and eight of the 23 novobiocin resistant CNS were tetracycline resistant and all contained the tet(K) gene. A single S. aureus isolate also contained the tet(M) gene. The present study showed a frequent occurrence of resistance to fluoroquinolones, tetracycline and macrolides among staphylococci isolated from broilers in Denmark, whereas the occurrence of resistance to other antimicrobial agents remains low. Similar genes, encoding resistance to erythromycin, tetracycline and streptogramins to those previously observed, were detected. 相似文献
5.
The aim of the present study was to compare the potential of bacterial cultivation (BC), PCR, in situ hybridisation (ISH), and immunohistochemistry (IHC) in the diagnosis of Haemophilus somnus, when applied to pneumonic bovine tissue. Lungs from 65 field cases submitted for bacteriological examination were included in the study. The PCR-detection was performed on three different samples: plate-PCR (detection on plate washes after incubation of lung tissue on agar plates); swab-PCR (direct detection on a swab from the cut surface); and, whenever possible, a bronchus-PCR (direct detection on a swab from the main bronchus of the right cranial lung lobe). In order to examine the pathological significance of the findings, a histopathological examination of the cases was performed. H. somnus was detected by one or more techniques in 33 cases in total. By BC the bacterium was isolated from 10 cases, IHC and ISH were positive in 17 and 19 cases, and plate- and swab-PCR were positive in 21 and 29 cases, respectively. The bronchus-PCR was positive in 30 out of 61 cases examined. The PCR-technique was the most sensitive method, and as this technique is fast and relatively inexpensive, it should be considered as a supplementary tool in the diagnosis of H. somnus induced calf pneumonia. 相似文献
6.
Reconciling 14C and minirhizotron‐based estimates of fine‐root turnover with survival functions
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The turnover of fine‐roots is a crucial component for the input of C to the soil. The amount of root litter input is depending on estimates of turnover times from different techniques. Turnover times from fine‐root cameras (minirhizotrons) often yield 75% higher root litter input estimates than turnover times estimated with the bomb‐radiocarbon signature of fine roots. We introduce a generic framework for the analysis of fine‐root 14C with different survival functions. So far, mostly an exponential function has been used to estimate the turnover time and mean age of fine roots. In the context of the introduced survival function framework we clarify the terms turnover time, mean residence time, mean longevity, and mean age, which are commonly used in studies of root turnover. Using a unique time series of fine‐root 14C (Fröberg 2012), we test if survival functions other than the exponential function are better in accordance with turnover‐time estimates commonly found with other methods. A survival function that corresponds to a two‐pool model was best in agreement with minirhizotron‐based estimates (mean residence time of 1.9 y). We argue that using fine‐root 14C and minirhizotron time‐to‐death data together would give the best constraints on fine‐root turnover. At the same time this could allow quantifying systematic biases inherent to both techniques. 相似文献
7.
Jeanloz R Ahrens TJ Lally JS Nord GL Christie JM Heuer AH 《Science (New York, N.Y.)》1977,197(4302):457-459
Transmission electron microscope (TEM) observations of an experimentally shock-deformed single crystal of natural peridot, (Mg(0.88)Fe(0.12))(2)SiO(4), recovered from peak pressures of about 56 x 10(9) pascals revealed the presence of amorphous zones located within crystalline regions with a high density of tangled dislocations. This is the first reported observation of olivine glass. The shocked sample exhibits a wide variation in the degree of shock deformation on a small scale, and the glass appears to be intimately associated with the highest density of dislocations. This study suggests that olivine glass may be formed as a result of shock at pressures above about 50 to 55 x 10(9) pascals and that further TEM observations of naturally shocked olivines may demonstrate the presence of glass. 相似文献
8.
Rubber mats covering concrete slatted flooring are a developing market in dairy barns but remain rare in beef cattle facilities. The aim of this study was to investigate the effects of covering slatted concrete floor with perforated rubber mats on behaviour and occurrence of skin and claw lesions in fattening bulls. The groups of six bulls each with a total average age of 9.8 months were kept over 1 year on either slatted concrete (CONCRETE PEN) or on slatted concrete covered completely (RUBBER PEN) or partially (CHOICE PEN) with perforated rubber mats. Every quarter-year, behaviour (preference of flooring, lying, aggression, mounting) was recorded. In two-weekly intervals the incidence of skin lesions was examined. At 12 and 18 months of age the rising time of the bulls was measured. At the beginning of the study and after slaughter claw dimensions were recorded. Bulls in the CHOICE PEN preferred (P<0.01) the rubber coated area throughout the experiment. Animals in the RUBBER and the CHOICE PENS showed more lying periods (P<0.01) and had a lesser incidence of skin lesions (P<0.01) compared to bulls in the CONCRETE PEN. Bulls in the CHOICE PEN needed less time for rising (2.7+/-0.3s) than bulls in the CONCRETE PEN (4.4+/-0.5s, P<0.01). Net claw growth differed significantly between all pens (RUBBER>CHOICE>CONCRETE; P<0.05). In conclusion, the results of this study indicate that rubber coated slatted flooring has a positive influence on the housing conditions of beef cattle. 相似文献
9.
The effects of Escherichia coli heat-stable enterotoxin (ST) on chloride efflux rate were investigated in 3 fractions of enterocytes isolated in a villus-to-crypt gradient from porcine jejunum. There was no difference in chloride efflux rates between mature and immature cells from controls. Heat-stable enterotoxin significantly increased chloride efflux in all fractions. Morphine inhibited ST-augmented secretion in mature enterocytes. Atropine or clonidine had no effect. Calcium efflux rates and glucose or glutamic acid metabolism were not altered by ST. The results indicate that ST may stimulate chloride secretion in both villus and crypt cells and that opiates inhibit intestinal secretion by a direct action on villus epithelial cells. 相似文献
10.
Enemark HL Bille-Hansen V Lind P Heegaard PM Vigre H Ahrens P Thamsborg SM 《Veterinary parasitology》2003,113(1):35-57
With the intention of developing a standardised method for assessment of pathogenicity of Cryptosporidium parvum, the CPB-0 isolate was studied by propagation in 1-day-old calves followed by inoculation into specific pathogen free (SPF) piglets. The experiment was repeated. Diarrhoea and shedding of oocysts were seen in all animals infected with the CPB-0 isolate. Clinical signs included depression, inappetence, vomiting (exclusively in the piglets), and death. Histological examination at 17 and 19 days post-infection revealed parasitic stages and microscopic changes primarily restricted to colon and rectum.The unintended presence of rotavirus in some of the experimental animals revealed an additive or synergistic effect between rotavirus and C. parvum as indicated by prolonged diarrhoea, increased oocyst shedding, decreased weight gain and elevated levels of serum haptoglobin and serum amyloid A (SAA) in piglets infected simultaneously with both pathogens. The difference in daily weight gain between infected and control animals was significant only for piglets co-infected with rotavirus. The acute phase response of haptoglobin and SAA was characterised by a large individual variation. In piglets, co-infected with rotavirus, the levels of serum haptoglobin were 3.5 and 4.6 times higher in the infected versus the controls 6 and 9dpi, respectively (mean values: 2411microg/ml+/-S.D. 2023 and 1840 microg/ml+/-S.D. 1697). In the controls infected with rotavirus, peak haptoglobin concentration was seen 3dpi (mean: 1022 microg/ml+/-S.D. 425). Elevated levels of SAA were seen in 1 of 6 piglets infected with C. parvum, and in 5 of 6 piglets co-infected with rotavirus. Tumour necrosis factor alpha (TNFalpha) was undetectable in all serum samples from piglets.The obvious advantages of the SPF pig model are the naturally acquired intestinal microflora, the development of distinct clinical signs similar to cryptosporidiosis in humans and calves, the size of the animals, and the accessibility of individuals born within a short time span. This makes the model ideal for dose-response studies, evaluation of therapeutic agents as well as for assessment of differences in the clinical response to isolates of diverse genetic background. In conclusion, it was shown that the CPB-0 isolate was pathogenic to calves and piglets at a dose of 2.5 x 10(5) oocysts, and that the clinical signs could be replicated during separate experiments. Moreover, diarrhoea, oocyst shedding, body weight changes, histological alterations, and the acute phase response of haptoglobin and SAA were identified as useful parameters for discrimination of isolate-specific differences of pathogenicity. 相似文献