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71.
72.
Altered functional connectivity and genetic diversity of a threatened salamander in an agroecosystem
John A. Crawford William E. Peterman Andrew R. Kuhns Lori S. Eggert 《Landscape Ecology》2016,31(10):2231-2244
Context
Amphibian metapopulations have become increasingly fragmented in the Midwestern United States, with wetland-breeding salamanders being especially dependent on intact, high-quality forested landscapes. However, the degree to which amphibian populations are isolated, the factors that influence dispersal and, ultimately, functional connectivity remain areas in need of investigation.Objectives and methods
We combined population demographic and genetic approaches to assess how a landscape fragmented by agriculture influences functional connectivity and metapopulation dynamics of a locally threatened salamander (Ambystoma jeffersonianum).Results
We found that the allelic richness and heterozygosity of this species was significantly related to the level of connectivity with other occupied breeding wetlands and that decreased connectivity resulted in increased genetic differentiation. We also found that effective population size appears to be declining and, while correlative, our focal landscape has experienced significant losses of forested upland habitats and potential wetland breeding habitats over the last 200 years.Conclusions
By combining population and landscape genetic analyses with an assessment of regional wetland occupancy, our study has uniquely synthesized genetic and metapopulation processes, while also incorporating the effects of the landscape matrix on dispersal, connectivity, and population differentiation. The significant relationship between connectivity with heterozygosity, allelic richness, and genetic divergence observed in this study reinforces empirical observations of long distance dispersal and movements in ambystomatid salamanders. However, our results show that protection of core habitat around isolated wetlands may not sufficiently minimize genetic differentiation among populations and preserve critical genetic diversity that may be essential for the long-term persistence of local populations.73.
74.
75.
Sensitive PCR analysis of animal tissue samples for fragments of endogenous and transgenic plant DNA
Nemeth A Wurz A Artim L Charlton S Dana G Glenn K Hunst P Jennings J Shilito R Song P 《Journal of agricultural and food chemistry》2004,52(20):6129-6135
An optimized DNA extraction protocol for animal tissues coupled with sensitive PCR methods was used to determine whether trace levels of feed-derived DNA fragments, plant and/or transgenic, are detectable in animal tissue samples including dairy milk and samples of muscle (meat) from chickens, swine, and beef steers. Assays were developed to detect DNA fragments of both the high copy number chloroplast-encoded maize rubisco gene (rbcL) and single copy nuclear-encoded transgenic elements (p35S and a MON 810-specific gene fragment). The specificities of the two rbcL PCR assays and two transgenic DNA PCR assays were established by testing against a range of conventional plant species and genetically modified maize crops. The sensitivities of the two rbcL PCR assays (resulting in 173 and 500 bp amplicons) were similar, detecting as little as 0.08 and 0.02 genomic equivalents, respectively. The sensitivities of the p35S and MON 810 PCR assays were approximately 5 and 10 genomic equivalents for 123 bp and 149 bp amplicons, respectively, which were considerably less than the sensitivity of the rbcL assays in terms of plant cell equivalents, but approximately similar when the higher numbers of copies of the chloroplast genome per cell are taken into account. The 173 bp rbcL assay detected the target plant chloroplast DNA fragment in 5%, 15%, and 53% of the muscle samples from beef steers, broiler chickens, and swine, respectively, and in 86% of the milk samples from dairy cows. Reanalysis of new aliquots of 31 of the pork samples that were positive in the 173 bp rbcL PCR showed that 58% of these samples were reproducibly positive in this same PCR assay. The 500 bp rbcL assay detected DNA fragments in 43% of the swine muscle samples and 79% of the milk samples. By comparison, no statistically significant detections of transgenic DNA fragments by the p35S PCR assay occurred with any of these animal tissue samples. 相似文献
76.
Willows (Salix spp.) are beneficial as a potential source of renewable energy, riparian barriers and riverbank control, yet are considered
invasive weeds when they clog watercourses and lead to erosion and flooding. Interactions between willow rustMelampsora epitea (Thüm.) (Uredinales: Melampsoraceae) and leaf beetlePhratora spp. (Coleoptera: Chrysomelidae) feeding damage have an impact on effective pest management and biological control. The present
study investigated the effects of(a) prior mechanical leaf damage on rust development, and(b) rust infection on beetle feeding under laboratory conditions for different time intervals and levels of damage. Willow rust
infection significantly reduced the amount of leaf area consumed by beetles. The result was similar when a compatible or an
incompatible rust pathotype was sprayed ontoSalix viminalis (L.) ‘Mullatin’ plants. There were no overall significant effects of mechanical damage on rust development, although the
lowest level of rust infection was found with the incremental damage treatment. There were, however, differences of significance
for leaf position and damage status, with damaged leaves at all positions having fewer pustules and a smaller pustule area
than the corresponding undamaged leaves. There was no detectable effect of possible volatile emissions from crushed willow
leaves on rust infection and development, although the volatile compoundcis-3-hexenyl acetate significantly reduced pustule diameter and overall pustule area. The results are discussed in terms of
the implications for pest management and biological control.
Corresponding author
http://www.phytoparasitica.org posting April 6, 2003. 相似文献
77.
Magdesian KG Dujowich M Madigan JE Hansen LM Hirsh DC Jang SS 《Journal of the American Veterinary Medical Association》2006,228(5):751-755
OBJECTIVE: To determine molecular characteristics, antimicrobial susceptibility, and toxigenicity of Clostridium difficile isolates from horses in an intensive care unit and evaluate associations among severity of clinical disease with specific strains of C difficile. DESIGN: Prospective study. ANIMALS: 130 horses. PROCEDURES: Feces were collected from horses admitted for acute gastrointestinal tract disease with loose feces and submitted for microbial culture and immunoassay for toxin production. Polymerase chain reaction assays were performed on isolates for toxins A and B genes and strain identification. RESULTS: Isolates were grouped into 3 strains (A, B, and C) on the basis of molecular banding patterns. Toxins A and B gene sequences were detected in 93%, 95%, and 73% of isolates of strains A, B, and C, respectively. Results of fecal immunoassays for toxin A were positive in 40%, 63%, and 16% of horses with strains A, B, and C, respectively. Isolates in strain B were resistant to metronidazole. Horses infected with strain B were 10 times as likely to have been treated with metronidazole prior to the onset of diarrhea as horses infected with other strains. Duration from onset of diarrhea to discharge (among survivors) was longer, systemic inflammatory response syndromes were more pronounced, and mortality rate was higher in horses infected with strain B than those infected with strains A and C combined. CONCLUSIONS AND CLINICAL RELEVANCE: Horses may be infected with a number of heterogeneous isolates of C difficile. Results indicated that toxigenicity and antimicrobial susceptibility of isolates vary and that metronidazole-resistant strains may be associated with severe disease. 相似文献
78.
Marla Lichtenberger DVM DACVECC ; Connie Orcutt DVM DABVP ; Carolyn Cray PhD ; Douglas H. Thamm VMD DACVIM ; Daniel DeBehnke MD FACEP ; Cheryl Page BSC CVT ; Lori Mull BSc CVT Rebecca Kirby DVM DACVIM DACVECC 《Journal of Veterinary Emergency and Critical Care》2009,19(5):467-472
Objective – The purpose of this study was to determine the LD50 for acute blood loss in mallard ducks ( Anas platyrhynchos ), compare the mortality rate among 3 fluid resuscitation groups, and determine the time required for a regenerative RBC response.
Design – Prospective study.
Setting – Medical College of Wisconsin Research facility.
Animals – Eighteen mallard ducks were included for the LD50 study and 28 for the fluid resuscitation study.
Interventions – Phlebotomy was performed during both the LD50 and fluid resuscitation studies. Ducks in the fluid resuscitation study received a 5 mL/kg intravenous bolus of crystalloids, hetastarch (HES), or a hemoglobin-based oxygen-carrying solution (HBOCS).
Measurements and Main Results – The LD50 for acute blood loss was 60% of total blood volume. This blood volume was removed in the fluid resuscitation study to create a model of acute blood loss. Following fluid administration, 6 birds in the crystalloid group (66%), 4 birds in the HES group (40%), and 2 birds in the HBOCS group (20%) died. No statistical difference in mortality rate was seen among the 3 fluid resuscitation groups. Relative polychromasia evaluated post-phlebotomy demonstrated regeneration starting at 24 hours and continuing through 48 hours.
Conclusions – The LD50 for acute blood loss in mallard ducks was 60% of their total blood volume. Although no statistical difference in mortality rate was appreciated among the 3 fluid resuscitation groups, a trend of decreased mortality rate was observed in the HBOCS group. An early regenerative response was apparent following acute blood loss. 相似文献
Design – Prospective study.
Setting – Medical College of Wisconsin Research facility.
Animals – Eighteen mallard ducks were included for the LD
Interventions – Phlebotomy was performed during both the LD
Measurements and Main Results – The LD
Conclusions – The LD
79.
80.
Christopher R. Lamb MA VetMB Lori E. Hartzband DVM Amy S. Tidwell DVM Susan H. Pearson CVT 《Veterinary radiology & ultrasound》1991,32(3):117-120
In a survey of patients with histologically-confirmed hepatic lymphosarcoma at Tufts University, abnormal ultrasound findings were detected in 3 of 14; two had diffuse hepatic hypoechogenicity, one had a focal hypoechoic lesion. In contrast, 5 of 6 patients with spleic lymphosarcoma had an abnormality on ultrasongraphy; two had diffuse hypoechogenicity, one had multiple hypoechoic foci, one had a large, cavitated-appearing mass, and one had an irregular border. In our experience, ultrasonography is an insensitive means of detecting hepatic lymphosarcoma but appears more sensitive for detection of splenic lymphosarcoma. 相似文献