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211.
Hege Gundersen Erling J. Solberg Petter Wabakken Torstein Storaas Barbara Zimmermann Harry P. Andreassen 《European Journal of Wildlife Research》2008,54(2):335-346
We employed three different methods to estimate predation rates on moose in a newly colonized wolf territory in Norway. In
the first two methods, we estimated predation rates based on the difference in calf/cow ratios outside and inside the wolf
pack territory from (1) hunter observations and (2) aerial surveys. In the last method, (3) we estimated loss of calves of
radio-collared cows inside and outside the wolf pack territory. The difference in mortality rates estimated between the area
subject to predation and the area outside the wolf pack territory essentially constitutes the additive component of predation.
We also tested the sensitivity of violating the assumptions of methods 1 and 2 related to equal fecundity and mortality because
of other factors than predation inside and outside the wolf pack territory. Predation rates varied considerably between years
and methods used, with hunter observations (method 1) giving the lowest and aerial surveys (method 2) giving the highest estimates.
Method 3 (radio telemetry) was the most direct assessment of predation and probably the best approach to estimate predation
rates in moose. However, all three methods show the same yearly changes and may therefore be appropriate to question trends
trough time or between areas. 相似文献
212.
An increasing number of imaging techniques are in use to study the localization of molecules involved in cell-to-cell signaling. Here we describe the use of immunogold procedures to detect and quantify molecules on electron micrographs. To measure the areas of the subcellular compartments under investigation, the protocol uses an overlay screen with an array of regularly spaced points. On the basis of this, the densities of the gold-labeled molecules can be calculated. Despite the limited lateral resolution of the immunogold method as used by many investigators ( approximately 30 nm), it is possible to measure the content of molecules associated with tiny tissue compartments, e.g., synaptic vesicles and different types of membrane, such as plasma membranes and vesicle membranes. The quantification protocol can be carried out without using computer programs. The entire protocol can be completed in approximately 15 d. 相似文献
213.
214.
PER ALSTRÖM PAMELA C. RASMUSSEN URBAN OLSSON PER SUNDBERG 《Zoological Journal of the Linnean Society》2008,154(2):291-307
We demonstrate the importance of using multiple criteria in species delimitations, whatever the conceptual base for species delimitation. We do this by studying plumage, biometrics, egg coloration, song, mitochondrial DNA and habitat/altitudinal distribution in the Spotted Bush Warbler Bradypterus thoracicus (Blyth) complex, and by conducting playback experiments. Taxa that we suggest are best treated as separate species [B. thoracicus (Blyth), B. davidi (La Touche) and B. kashmirensis (Sushkin)] differ in most or all of these aspects, particularly in song and mitochondrial DNA, while those that we treat as subspecies (suschkini) or synonyms (przevalskii) differ slightly and only in morphology. © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society, 2008, 154 , 291–307. 相似文献
215.
216.
Two new programs are designed to supply biotechnology professionals with industry-specific skills required for successful biomedical product development. 相似文献
217.
Calcium bursts induced by nanosecond electric pulses 总被引:14,自引:0,他引:14
Vernier PT Sun Y Marcu L Salemi S Craft CM Gundersen MA 《Biochemical and biophysical research communications》2003,310(2):286-295
We report here real-time imaging of calcium bursts in human lymphocytes exposed to nanosecond, megavolt-per-meter pulsed electric fields. Ultra-short (less than 30 ns), high-field (greater than 1 MV/m), electric pulses induce increases in cytosolic calcium concentration and translocation of phosphatidylserine (PS) to the outer layer of the plasma membrane in Jurkat T lymphoblasts. Pulse-induced calcium bursts occur within milliseconds and PS externalization within minutes. Caspase activation and other indicators of apoptosis follow these initial symptoms of nanosecond pulse exposure. Pulse-induced PS translocation is observed even in the presence of caspase inhibitors. Ultra-short, high-field, electroperturbative pulse effects differ substantially from those associated with electroporation, where pulses of a few tens of kilovolts-per-meter lasting a few tens of microseconds open pores in the cytoplasmic membrane. Nanosecond pulsed electric fields, because their duration is less than the plasma membrane charging time, develop voltages across intracellular structures without porating the cell. 相似文献
218.
Dujardin DL Barnhart LE Stehman SA Gomes ER Gundersen GG Vallee RB 《The Journal of cell biology》2003,163(6):1205-1211
Cytoplasmic dynein has been implicated in numerous aspects of intracellular movement. We recently found dynein inhibitors to interfere with the reorientation of the microtubule cytoskeleton during healing of wounded NIH3T3 cell monolayers. We now find that dynein and its regulators dynactin and LIS1 localize to the leading cell cortex during this process. In the presence of serum, bright diffuse staining was observed in regions of active ruffling. This pattern was abolished by cytochalasin D, and was not observed in cells treated with lysophosphatidic acid, conditions which allow microtubule reorientation but not forward cell movement. Under the same conditions, using total internal reflection fluorescence microscopy, clear punctate dynein/dynactin containing structures were observed along the sides and at the tips of microtubules at the leading edge. Overexpression of dominant negative dynactin and LIS1 cDNAs or injection of antidynein antibody interfered with the rate of cell migration. Together, these results implicate a leading edge cortical pool of dynein in both early and persistent steps in directed cell movement. 相似文献
219.
Identification of novel roles of the cytochrome p450 system in early embryogenesis: effects on vasculogenesis and retinoic Acid homeostasis 总被引:5,自引:0,他引:5 下载免费PDF全文
Otto DM Henderson CJ Carrie D Davey M Gundersen TE Blomhoff R Adams RH Tickle C Wolf CR 《Molecular and cellular biology》2003,23(17):6103-6116
The cytochrome P450-dependent monooxygenase system catalyzes the metabolism of xenobiotics and endogenous compounds, including hormones and retinoic acid. In order to establish the role of these enzymes in embryogenesis, we have inactivated the system through the deletion of the gene for the electron donor to all microsomal P450 proteins, cytochrome P450 reductase (Cpr). Mouse embryos homozygous for this deletion died in early to middle gestation (approximately 9.5 days postcoitum [dpc]) and exhibited a number of novel phenotypes, including the severe inhibition of vasculogenesis and hematopoiesis. In addition, defects in the brain, limbs, and cell types where CPR was shown to be expressed were observed. Some of the observed abnormalities have been associated with perturbations in retinoic acid homeostasis in later embryogenesis. Consistent with this possibility, embryos at 9.5 dpc had significantly elevated levels of retinoic acid and reduced levels of retinol. Further, some of the observed phenotypes could be either reversed or exacerbated by decreasing or increasing maternal retinoic acid exposure, respectively. Detailed analysis demonstrated a close relationship between the observed phenotype and the expression of genes controlling vasculogenesis. These data demonstrate that the cytochrome P450 system plays a key role in early embryonic development; this process appears to be, at least in part, controlled by regional concentrations of retinoic acid and has profound effects on blood vessel formation. 相似文献
220.
MARK J. JORDAN J. MARK HIGLEY SEAN M. MATTHEWS OLIN E. RHODES MICHAEL K. SCHWARTZ REGINALD H. BARRETT PER J. PALSB
LL 《Molecular ecology resources》2007,7(5):797-801
We developed 22 new microsatellite loci for the fisher (Martes pennanti), a North American mesocarnivore. The loci were developed with samples from the southern Sierra Nevada Mountains in California, and were screened with samples from this population and four other populations. We observed a range of six to 21 polymorphic loci per population, with the Sierra Nevada population exhibiting markedly lower levels of variation compared to the other four. 相似文献