Detection of mycoplasmalike organisms in declining oaks by polymerase chain reaction     

U. Ahrens  E. Seemüller 《Forest Pathology》1994,24(1):55-63

By polymerase chain reaction, mycoplasmalike organisms (MLOs) were detected in several declining trees of Quercus robur sampled at two locations of Germany. The MLOs associated with declining oaks were, within the 16S rDNA studied, genetically uniform and closely related to the MLOs associated with European stone fruit yellows and apple proliferation.  相似文献   

PROPOSALS FOR THE PRESERVATION OF THE WISENT     

Ahrens TG 《Science (New York, N.Y.)》1923,58(1493):107

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表面活性剂、喷液量及杂草叶角对普杀特喷后附着量的影响   总被引：7，自引：1，他引：7  

由振国  李秉礼  吴罗罗  李孙荣  姜德峰  何雄魁  W. H. Ahrens 《植物保护学报》1994,21(3):283-287

表面活性剂、喷液量及杂草叶角对普杀特在非敏感杂草马唐叶片上的喷后附着量有明显的独立影响和交互影响,其中表面活性剂的影响最大。供试的6种非离子型表面活性剂均因显著降低了普杀特药液的表面张力从而显著提高了其在马唐叶片上的喷后附着量,其中ScOil和Silwet—L77对其提高幅度最大;普杀特在马唐叶片上的喷后附着量随着喷液量的减少逐步增加,但在0—90°范围内随着马唐叶角的减小而减少,其由于喷液量的增大或马唐叶角的减小而引起的下降量,可通过加入非离子型表面活性剂而得到补偿,加入非离子型表面活性剂配合下午微液量(90L/ha)喷施,可望最大限度地增加普杀特在其非敏感杂草叶片上的喷后附着量,进而提高其药效,降低其使用成本和减少其在土壤中的残留。  相似文献   

What is your diagnosis? Pneumoperitoneum     

Ahrens SA  Côté E 《Journal of the American Veterinary Medical Association》1999,215(10):1425-1426

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A scoring index for disease activity in canine inflammatory bowel disease     

Jergens AE  Schreiner CA  Frank DE  Niyo Y  Ahrens FE  Eckersall PD  Benson TJ  Evans R 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2003,17(3):291-297

The clinical course of inflammatory bowel disease (IBD) in dogs is characterized by spontaneous exacerbations and remissions, which makes assessment of disease burden difficult. The objectives of this study were to develop a scoring system for evaluation of canine IBD activity and to validate this scoring method by correlating it to objective laboratory and histologic indices of intestinal inflammation. Fifty-eight dogs with IBD were evaluated prospectively and compared to 9 disease-free control dogs. Clinical disease activity was quantified by a simple scoring system, the canine IBD activity index (CIBDAI), and compared to serum concentrations of C-reactive protein (CRP), haptoglobin (HAP), alpha-acid glycoprotein (AGP), and serum amyloid A (SAA), as well as histology scores derived from endoscopic biopsy specimens. Forty-six dogs were available for a reevaluation of the CIBDAI, CRP HAP, and AGP, and 34 dogs had repeat analysis of SAA performed after medical therapy. Serum concentrations of CRP were significantly (P < .02) increased in dogs with CIBDAI scores > or = 5 (mild disease activity or greater) compared to controls. Among IBD dogs, the CIBDAI showed good correlation (r = 0.82, P < .0001) to both histology and HAP scores, but CRP also was a strong co-correlate of disease activity. The IBD dogs showed significantly (P < .0001) decreased CIBDAI and CRP values but significantly (P < .0001) increased HAP concentrations after medical therapy compared to pretreatment values. We conclude that the CIBDAI is a reliable measure of inflammatory activity in canine IBD and that CRP is suitable for laboratory evaluation of the effect of therapy in these patients.  相似文献   

Evaluation of serum and milk ELISAs for paratuberculosis in Danish dairy cattle     

Klausen J  Huda A  Ekeroth L  Ahrens P 《Preventive veterinary medicine》2003,58(3-4):171-178

A milk and a serum ELISA for detection of antibodies against Mycobacterium avium ssp. paratuberculosis (MAP) were evaluated against the complement-fixation test (CFT) and culture of faecal samples from 580 cows collected between August 1996 and December 1996. Milk and serum were obtained concurrently from six dairy herds infected with MAP and from two dairy herds without history of infection with MAP.

A cut-off value of 7 OD% was used in the ELISAs. At this cut-off value, all six culture-positive herds were positive in the serum ELISA but one was negative in the milk ELISA. All six culture-positive herds were positive in the CFT. In the two culture-negative herds, the serum and the milk ELISA deemed all serum samples negative at this cut-off value, whereas four serum samples from one of these herds were positive in the CFT. The highest cut-off value enabling the milk ELISA to record all six culture-positive herds as positive was 4 OD%. The highest cut-off value enabling the serum ELISA to record all six culture-positive herds as positive was 17 OD%. Individual-sample relative sensitivities of the ELISAs ranged from 49 to 64% and relative specificities were 80–96% at the cut-off values of 4, 7 and 17 OD%.  相似文献   

Genomic diversity among Danish field strains of Mycoplasma hyosynoviae assessed by amplified fragment length polymorphism analysis     

Kokotovic B  Friis NF  Nielsen EO  Ahrens P 《Veterinary microbiology》2002,85(3):221-231

Genomic diversity among strains of Mycoplasma hyosynoviae isolated in Denmark was assessed by using amplified fragment length polymorphism (AFLP) analysis. Ninety-six strains, obtained from different specimens and geographical locations during 30 years and the type strain of M. hyosynoviae S16(T) were concurrently examined for variance in BglII-MfeI and EcoRI-Csp6I-A AFLP markers. A total of 56 different genomic fingerprints having an overall similarity between 77 and 96% were detected. No correlation between AFLP variability and period of isolation or anatomical site of isolation could be demonstrated. An examination of the clonal appearance of M. hyosynoviae isolates recovered from seven herds affected with arthritis revealed presence of several genotypically distinct variants of the organism in a single herd, indicating that different strains may simultaneously be involved in an outbreak of the disease.  相似文献   

Cryptosporidium andersoni from a Danish cattle herd: identification and preliminary characterisation   总被引：4，自引：0，他引：4  

Enemark HL  Ahrens P  Lowery CJ  Thamsborg SM  Enemark JM  Bille-Hansen V  Lind P 《Veterinary parasitology》2002,107(1-2):37-49

In November 1997, Cryptosporidium andersoni, for the first time, was isolated from a Danish heifer. The isolate was characterised morphologically, molecularly, and furthermore inoculated into mice and one calf. Data on the distribution of cryptosporidia in the herd of origin were obtained at two separate visits in December 1997 and April 1998. C. andersoni was detected in 27 (19.0%) of 142 cattle examined at the first visit, whereas C. parvum was found in six (4.2%). At the following visit 42 (28.0%) of 150 cattle excreted C. andersoni, while 25 (16.7%) were positive for C. parvum. Oocysts of the Danish C. andersoni isolate were ovoid, 7.3(6.5-8.0) x 5.7(5.0-7.0) microm(2) (n=25), with smooth, colourless, single layer oocyst wall and distinct oocyst residuum. The length to width ratio was 1.27 (1.14-1.40, n=25). The identification was verified by sequencing of a 246bp fragment of the rDNA, which was identical to Cryptosporidium muris, the calf genotype (AF093496). The Danish C. andersoni isolate was not transmissible to mice, whereas oocysts were detected in the faeces of one experimentally infected calf from 25 days post-infection (DPI) and shed intermittently at low numbers until 165 DPI, the day of euthanasia. No macroscopic or microscopic changes that could be attributed to infection with C. andersoni were seen in the gastro-intestinal tract of the experimentally infected calf following necropsy and histological examination. This is to our knowledge the first report of C. andersoni in Scandinavia.  相似文献   

Characterization of Mycoplasma hyosynoviae strains by amplified fragment length polymorphism analysis,pulsed-field gel electrophoresis and 16S ribosomal DNA sequencing     

Kokotovic B  Friis NF  Ahrens P 《Journal of veterinary medicine. B, Infectious diseases and veterinary public health》2002,49(5):245-252

Mycoplasma hyospnoviae strains from Denmark, Germany, Japan, Sweden, the Netherlands and the UK were examined for variations in the genomic DNA and within the 16S ribosomal RNA (rRNA) gene. Variations in the chromosomal DNA among 57 isolates recovered from the respiratory tract and joints of pigs, were investigated by analysis of amplified fragment length polymorphisms of the Bg/II and MfeI restriction sites and by pulsed-field gel electrophoresis of a BssHII digest of chromosomal DNA. Both methods allowed unambiguous differentiation of the analysed strains and showed similar discriminatory potential for the differentiation of M. hyosynoviae isolates. Concordant results obtained with the two whole-genome fingerprinting techniques evidence the considerable intraspecies genetic heterogeneity of M. hyosynoviae. Sixteen field strains of M. hyosynoviae and the type strain S16(T) were further examined for variation within the 16S rRNA gene. Ten field strains possessed the 16S rDNA sequences identical to the type strain, while the remaining six strains had sequences that differed by one to two nucleotides from that obtained from the type strain.  相似文献   

Saving large fish through harvest slots outperforms the classical minimum‐length limit when the aim is to achieve multiple harvest and catch‐related fisheries objectives     

Robert N. M. Ahrens  Micheal S. Allen  Carl Walters  Robert Arlinghaus 《Fish and Fisheries》2020,21(3):483-510

We address the problem of optimal size‐selective exploitation in an age‐structured fish population model by systematically examining how density and size dependency in growth, mortality and fecundity affect optimal harvesting patterns when judged against a set of fisheries objectives. The study offers five key insights. First, while minimum‐length limits often maximize the biomass yield, exploitation using harvest slots (i.e. regulations that protect both immature and very large individuals) can generate within 95% of maximum yield; harvest slots also generally maximize the number of fish that are harvested. Second, density dependence in growth and size‐dependent mortality predict more liberal optimal size limits than those derived under assumptions of no density and size dependence. Third, strong density dependence in growth maximizes the catch of trophy fish only when modest harvest is introduced; the same holds for numbers harvested, when the stock–recruitment function follows the Ricker type. Fourth, the inclusion of size‐dependent maternal effects on fecundity or egg viability has only limited effects on optimal size limits, unless the increase in fecundity with mass (“hyperallometry”) is very large. However, large hyperallometry in fecundity shifts the optimal size limit for biomass yield from the traditional minimum‐length limit to a harvest slot. Fifth, harvest slots generally provide the best compromises among multiple objectives. We conclude that harvest slots, or more generally dome‐shaped selectivity to harvest, can outperform the standard minimum‐length selectivity. The exact configuration of optimal size limits crucially depends on objectives, local fishing pressure, the stock–recruitment function, and the density and size dependency of growth, mortality and fecundity.  相似文献