Anthropogenic Mercury Deposition to Arctic Lake Sediments     

Mark H. Hermanson 《Water, air, and soil pollution》1998,101(1-4):309-321

The history of atmosheric mercury inputs to remote arctic regions can be measured in lake sediment cores using lead-210 chronology. In this investigation, total mercury deposition is measured in sediments from Imitavik and Annak Lakes on the Belcher Islands in southeastern Hudson Bay, an area in the southern Canadian Arctic with no history of local industrial or agricultural sources of contamination. Both lakes received background and atmospheric inputs of mercury while Annak also received mercury from raw domestic sewage from the Hamlet of Sanikiluaq, a growing Inuit community of about 550 established in the late 1960's. Results from Imitavik show that anthropogenic mercury inputs, apparently transported through the atmosphere, began to appear in the mid-eighteenth century, and continued to the 1990's. Annak had a similar mercury history until the late 1960's when disposal of domestic sewage led to increased sediment and contaminant accumulation. The high input of mercury to Annak confirms that Sanikiluaq residents are exposed to mercury through native food sources.  相似文献   

The sloughing of potatoes     

Mark A. Barmore 《American Journal of Potato Research》1938,15(6):170-171

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Diversification Problems in a Rentier State: The Case of Brunei     

Mark Cleary  Wong Shuang Yann 《Asia Pacific viewpoint》1993,34(1):69-76

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Landscape cover type and pattern dynamics in fragmented southern Great Plains grasslands,USA   总被引：7，自引：1，他引：6  

Coppedge  Bryan R.  Engle  David M.  Fuhlendorf  Samuel D.  Masters  Ronald E.  Gregory  Mark S. 《Landscape Ecology》2001,16(8):677-690

We documented land cover and landscape pattern changes in an area of northwestern Oklahoma, USA using aerial photography from 1965, 1981, and 1995. This region of the southern Great Plains is fragmented by agricultural activity, and in recent years many remnant native grasslands have experienced extensive invasion by woody juniper (Juniperus virginiana L.). Concurrently, many cropland areas are being planted into perennial forage grasses and converted to intensively managed introduced grasslands as part of the U.S. Conservation Reserve Program (CRP). Our objectives were to document land cover and landscape pattern changes in the region relative to the expansion of juniper and CRP activity. We then examined how local landscape dominance by either anthropogenic or woody vegetation patches affected landscape pattern indices. Land cover changes from 1965 to 1995 included substantial increases in juniper woodlands and mixed woodlands that resulted from juniper encroachment into deciduous woodlands. Introduced grasslands also increased in many areas as a result of CRP implementation. Changes in landscape pattern generally reflected the influx of juniper into many areas. Landscapes dominated by woody vegetation had significantly more patches, smaller patches and patch core areas, more total edge, and higher patch diversity than landscapes dominated by anthropogenic cover types. Results indicate that expanding juniper is exacerbating the fragmentation process initiated by previous human activity, and represents a serious threat to the continued integrity and conservation of remaining southern Great Plains grasslands.This revised version was published online in May 2005 with corrections to the Cover Date.  相似文献   

Characterization of wild Prunus yedoensis analyzed by inter-simple sequence repeat and chloroplast DNA     

Mark S. Roh  Eun Ju Cheong  Ik-Young Choi  Young Hee Joung 《Scientia Horticulturae》2007

This study was initiated to attempt clarify the identities of taxa referred to as Prunus yedoensis that grows under natural environments in Jeju, Korea and of Yoshino cherry hybrids of cultivated origin (also recorded as P. × yedoensis) in Japan, and to understand the difference between these two taxa. P. yedoensis and other species collected from natural habitats from Jeju, Korea and cultivated materials of Yoshino cherries from Tokyo and Washington, DC, were analyzed with inter-simple sequence repeat (ISSR) markers, and sequence analysis of two chloroplast DNA (cpDNA) genes, rpl16 and trnL-trnF spacer. Depending on the source of Yoshino cherry, accessions show variations with ISSR and cpDNA. Accessions belonging to each of P. serrulata var. spontanea, P. serrulata var. pubescens, and P. sargentii were grouped closely to P. yedoensis and Yoshino cherry accessions. However, two Yoshino cherry accessions that include ‘Akebono’ showed the same rpl16 haplotype of A and A at the position of 113 and 206, respectively, which were found in 4 out of 16 P. yedoensis accessions. Twelve accessions of P. yedoensis and 11 other Yoshino cherries showed rpl16 haplotype of T and A at these positions. P. yedoensis native to Korea can be considered different from Yoshino cherry of hybrid origin from Japan based on ISSR markers and rpl16 haplotypes. Therefore, it may be concluded that the Korean taxon currently referred to as P. yedoensis can be considered indigenous and sufficiently distinct to warrant recognition as a distinct entity.  相似文献   

Challenge with Bovine viral diarrhea virus by exposure to persistently infected calves: protection by vaccination and negative results of antigen testing in nonvaccinated acutely infected calves          下载免费PDF全文

Robert W. Fulton  Bill J. Johnson  Robert E. Briggs  Julia F. Ridpath  Jeremiah T. Saliki  Anthony W. Confer  Lurinda J. Burge  Douglas L. Step  Derek A. Walker    Mark E. Payton 《Canadian journal of veterinary research》2006,70(2):121-127

Calves persistently infected (PI) with Bovine viral diarrhea virus (BVDV) represent an important source of infection for susceptible cattle. We evaluated vaccine efficacy using calves PI with noncytopathic BVDV2a for the challenge and compared tests to detect BVDV in acutely or transiently infected calves versus PI calves. Vaccination with 2 doses of modified live virus vaccine containing BVDV1a and BVDV2a protected the calves exposed to the PI calves: neither viremia nor nasal shedding occurred. An immunohistochemistry test on formalin-fixed ear notches and an antigen-capture enzyme-linked immunosorbent assay on fresh notches in phosphate-buffered saline did not detect BVDV antigen in any of the acutely or transiently infected calves, whereas both tests had positive results in all the PI calves.  相似文献   

Evaluation of the evidence.     

Mark A Holmes 《Veterinary Clinics of North America: Small Animal Practice》2007,37(3):447-462

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Characterization and cooled storage of semen from corn snakes (Elaphe guttata).     

Brooke M Fahrig  Mark A Mitchell  Bruce E Eilts  Dale L Paccamonti 《Journal of zoo and wildlife medicine》2007,38(1):7-12

The phylogenetic order Squamata has many representatives that could benefit from the use of semen preservation as a tool for assisting conservation. To date, few studies have been made evaluating the potential for collecting and preserving semen from snakes. The objectives of this study were to characterize semen parameters of the corn snake (Elaphe guttata), including appearance, volume, concentration, sperm motility, and sperm morphology, and to determine the longevity of corn snake sperm motility stored at 4 degrees C. Single semen samples were collected from 22 adult corn snakes. The appearance of the corn snake semen was generally cloudy, and the color was white to tan. Corn snake spermatozoa initially exhibited a median motility of 92.5%. Corn snakes were found to produce small-volume ejaculates (median 0.01 ml). However, the overall concentration of the snake ejaculate was high (chi = 852 x 10(6) +/- 585 x 10(6) spermatozoa/ml). Morphologically, a mean of 75.7 +/- 9.3% of the sperm cells in an ejaculate were normal. Snake ejaculate with a white appearance had significantly higher sperm concentrations (chi = 1,859 x 10(6) +/- 1,008 x 106 sperm cells/ml; F = 15.74, P = 0.001) than tan ejaculates (chi = 601 x 10(6) +/- 439 x 106 sperm cells/ml). Sperm motility decreased significantly in samples that were stored at 4 degrees C for greater than 48 hr in a refrigerator or Equitainer I. This is the first study to characterize semen volume, appearance, and concentration; sperm motility; and sperm morphology in captive corn snakes. The information derived from this study can be used to develop a model for a collection, cooled storage, and shipping program for semen from endangered or threatened captive and wild snakes.  相似文献   

Pharmacokinetics of orally administered ibuprofen in African and Asian elephants (Loxodonta africana and Elephas maximus).     

Ursula Bechert  J Mark Christensen 《Journal of zoo and wildlife medicine》2007,38(2):258-268

The pharmacokinetic parameters of S(+) and R(-) ibuprofen were determined in 20 elephants after oral administration of preliminary 4-, 5-, and 6-mg/kg doses of racemic ibuprofen. Following administration of 4 mg/kg ibuprofen, serum concentrations of ibuprofen peaked at 5 hr at 3.9 +/- 2.07 microg/ml R(-) and 10.65 +/- 5.64 microg/ml S(+) (mean +/- SD) in African elephants (Loxodonta africana) and at 3 hr at 5.14 +/- 1.39 microg/ml R(-) and 13.77 +/- 3.75 microg/ml S(+) in Asian elephants (Elephas maximus), respectively. Six-milligram/kilogram dosages resulted in peak serum concentrations of 5.91 +/- 2.17 microg/ml R(-) and 14.82 +/- 9.71 microg/ml S(+) in African elephants, and 5.72 +/- 1.60 microg/ml R(-) and 18.32 +/- 10.35 microg/ml S(+) in Asian elephants. Ibuprofen was eliminated with first-order kinetics characteristic of a single-compartment model with a half-life of 2.2-2.4 hr R(-) and 4.5-5.1 hr S(+) in African elephants and 2.4-2.9 hr R(-) and 5.9-7.7 hr S(+) in Asian elephants. Serum concentrations of R(-) ibuprofen were undetectable at 24 hr, whereas S(+) ibuprofen decreased to below 5 microg/ml 24 hr postadministration in all elephants. The volume of distribution was estimated to be between 322 and 356 ml/kg R(-) and 133 and 173 ml/kg S(+) in Asian elephants and 360-431 ml/kg R(-) and 179-207 ml/kg S(+) in African elephants. Steady-state serum concentrations of ibuprofen ranged from 2.2 to 10.5 microg/ml R(-) and 5.5 to 32.0 microg/ml S(+) (mean: 5.17 +/- 0.7 R(-) and 13.95 +/- 0.9 S(+) microg/ml in African elephants and 5.0 +/- 1.09 microg/ml R(-) and 14.1 +/- 2.8 microg/ml S(+) in Asian elephants). Racemic ibuprofen administered at 6 mg/kg/12 hr for Asian elephants and at 7 mg/kg/12 hr for African elephants results in therapeutic serum concentrations of this antiinflammatory agent.  相似文献   

Molecular assays for detection of falcon adenovirus.   总被引：1，自引：0，他引：1  

Mark Schrenzel  Eric Snook  Pascal Gagneux 《Journal of veterinary diagnostic investigation》2007,19(5):479-485

Falcon adenovirus is a newly recognized member of the family Aviadenoviridae and includes 2 closely related strains that are pathogenic to several species of falcons. Peregrine falcons appear to be one of the primary reservoirs, but recent outbreaks suggest that other carrier species probably exist. To allow screening of captive birds for virus shedding and investigations of disease outbreaks, conventional and real-time, quantitative polymerase chain reaction (PCR) assays and an in situ hybridization technique were developed. The diagnostic protocols were used on tissue and fecal samples from 7 species or subspecies of falcons infected with adenovirus as well as adenoviruses from other birds and mammals. The assays were specific for falcon adenovirus and detected both strains of virus in fecal samples from living animals or frozen and formalin-fixed, paraffinized tissues. Together with established serologic tests for falcon adenovirus, these molecular assays are valuable tools for management and conservation of falcons in captivity and the wild.  相似文献