Rescue of American chestnut with extraspecific genes following its destruction by a naturalized pathogen     

Kim C. Steiner  Jared W. Westbrook  Frederick V. Hebard  Laura L. Georgi  William A. Powell  Sara F. Fitzsimmons 《New Forests》2017,48(2):317-336

Following the near-obliteration of American chestnut (Castanea dentata [Marsh.] Borkh.) by the chestnut blight early in the last century, interest in its restoration has been revived by efforts to develop a blight-resistant form of the species. We summarize progress and outline future steps in two approaches: (1) a system of hybridizing with a blight-resistant chestnut species and then backcrossing repeatedly to recover the American type and (2) transformation of American chestnut with a resistance-conferring transgene followed by propagation and conventional breeding. Several decades of effort have been invested in each approach. More work remains, but results indicate that success is within practical reach. The restoration of C. dentata to its native habitat now appears to be less a matter of time and conjecture than ever before in 90 years of work by public and private entities. The difficult and protracted task of incorporating extraspecific genes for resistance into a tree species with lethal susceptibility to a naturalized pathogen represents perhaps the most extreme of restoration challenges. Its pursuit by a small non-governmental organization supported primarily by philanthropy and volunteers may serve as a model for other species threatened by exotic pathogens or insects.  相似文献   

New aspects on the etiopathogenesis and treatment of cecal dilatation/-dislocation in cows--a review]     

A Steiner  M Meylan  R Eicher 《Schweizer Archiv für Tierheilkunde》1999,141(9):419-422

This paper describes the latest results of research in the areas of etiopathogenesis and treatment of cecal dilatation/-dislocation (CDD) in cows. Similar etiopathogenic mechanisms of CDD and displacement of the abomasum, as has been hypothesized in the literature, were not confirmed. Spontaneous CDD is most likely the consequence of a dysfunction of the spiral colon. Bethanechol is an appropriate motility-modulating drug for medical and postsurgical treatment of spontaneous CDD.  相似文献   

Visualization of three-dimensional chaos     

GO Fountain  DV Khakhar  JM Ottino 《Science (New York, N.Y.)》1998,281(5377):683-686

Most chaotic mixing experiments have been restricted to two-dimensional, time-periodic flows, and this has shaped advances in theory as well. A prototypical, bounded, three-dimensional flow with a moderate Reynolds number is presented; this system lends itself to detailed experimental observation and allows for high-precision computational inspection. The flow structure, captured by means of cuts with a laser sheet (experimental Poincare section), was visualized with the use of continuously injected fluorescent dye streams and revealed detailed chaotic structures with high-period islands.  相似文献   

Epidemiological Study of Pestiviruses in South American Camelids in Switzerland     

M. Mudry  M. Meylan  G. Regula  A. Steiner  R. Zanoni  P. Zanolari 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2010,24(5):1218-1223

Background: In the context of the ongoing eradication campaign for bovine viral diarrhea virus (BVDV) in cattle in Switzerland, the role of South American camelids (SAC) as a possible virus reservoir needed to be evaluated. Objective: To assess and characterize the prevalence of pestivirus infections in SAC in Switzerland. Animals: Serum samples collected from 348 animals (40 herds) in 2008 and from 248 animals (39 herds) in 2000 were examined for antibodies against pestiviruses and for the presence of BVDV viral RNA. Methods: Cross‐sectional study using stratified, representative herd sampling. An indirect BVDV‐ELISA was used to analyze serum samples for pestivirus antibodies, and positive samples underwent a serum neutralization test (SNT). Real‐time RT‐PCR to detect pestiviral RNA was carried out in all animals from herds with at least 1 seropositive animal. Results: In 2008, the overall prevalence of animals positive for antibodies (ELISA) and pestiviral RNA or was 5.75 and 0%, respectively. In 2000, the corresponding prevalences were 3.63 and 0%, respectively. The seroprevalences (SNT) for BVDV, border disease virus or undetermined pestiviruses were estimated to be 0, 1.73, and 4.02% in 2008, and 0.40, 1.21, and 2.02% in 2000, respectively. Conclusions and Clinical Importance: At the present time, SAC appear to represent a negligible risk of re‐infection for the BVDV eradication program in cattle in Switzerland.  相似文献