Clinical application of reticulocyte counts in dogs and cats.

Reticulocytes are anucleate immature red blood cells that contain a network of RNA, organelles, and mitochondria, which stain with supravital dyes. Both aggregate and punctate reticulocytes are present in domestic cats, and aggregate reticulocytes are used to assess the degree of regeneration in anemic dogs and cats. Multiple factors influence the degree of regenerative response to anemia. These factors include time of reticulocyte measurement, concurrent diseases, species, and ongoing therapy. Although many automated systems for reticulocyte enumeration exist, manual counts remain the gold standard in veterinary medicine.     

毛皮动物野生习性调查与驯化技术

毛皮动物一般指那些能提供高档裘皮产品的动物,属于野生或经过人工驯化饲养的哺乳类动物。作者对毛皮动物的栖息环境、采食习性、行为等野生习性及驯化的关键问题和方法进行了综述。     

Live-cell imaging of enzyme-substrate interaction reveals spatial regulation of PTP1B

Endoplasmic reticulum-localized protein-tyrosine phosphatase PTP1B terminates growth factor signal transduction by dephosphorylation of receptor tyrosine kinases (RTKs). But how PTP1B allows for RTK signaling in the cytoplasm is unclear. In order to test whether PTP1B activity is spatially regulated, we developed a method based on F?rster resonant energy transfer for imaging enzyme-substrate (ES) intermediates in live cells. We observed the establishment of a steady-state ES gradient across the cell. This gradient exhibited robustness to cell-to-cell variability, growth factor activation, and RTK localization, which demonstrated spatial regulation of PTP1B activity. Such regulation may be important for generating distinct cellular environments that permit RTK signal transduction and that mediate its eventual termination.     

Reluctant to dive: coelomic effusion in a frog

An adult female, albino South African Clawed frog (Xenopus laevis) from a research colony at the Biological Resources Facility of the College of Agriculture and Life Sciences at North Carolina State University (NCSU) was presented with depression, lethargy, loss of diving reflex, and a distended abdomen. Cytologic examination of coelomic effusion fluid at the NCSU veterinary teaching hospital revealed a mixed population of inflammatory cells, including heterophils and a predominance of large mononuclear cells (macrophages) that often contained intracytoplasmic, negatively-stained, rod-shaped to filamentous organisms consistent with Mycobacterium sp. Ziehl-Neelsen stain revealed bright pink to red, acid-fast organisms with a beaded appearance. Histopathologic findings in tissues obtained at necropsy included marked, multifocal to coalescing, heterophilic, granulomatous and fibrinous coelomitis as well as severe multifocal heterophilic and granulomatous hepatitis, interstitial pneumonia and sinusitis/rhinitis. Slender gram-positive, acid-fast bacterial rods were identified in sections of coelomic pleura, kidneys, nasal cavities, spleen, liver, and pulmonary interstitium, indicative of systemic mycobacteriosis. Based on mycobacterial culture, the organism was identified as M marinum complex. Mycobacteria are variably gram-positive, often acid-fast, small rods that are ubiquitous in aquatic environments. The clinical and pathologic spectrum of disease in amphibians depends on host and pathogen status. Xenopus sp and several other frogs are good models for studying the pathogenesis of M tuberculosis infection. In addition to culture, polymerase chain reaction assays may be used for definitive identification of the organisms; accurate speciation may require further genetic investigation.     

Relationships between traits of cow-calf pairs and a measure of partial efficiency

Angus cow-calf pairs (N = 114) were individually fed grass silage diets under conditions chosen to approximate nutrient intake under a free grazing, noncreep situation. Postfactum comparison with a subsequently conducted study on pasture indicated that the procedures used produced animal responses similar to those provided by a tall fescue pasture averaging 58% dry matter digestibility. Cow-calf pair efficiency was expressed as the ratio of estimated total digestible nutrient (ETDN) intake of the pair to calf weight at weaning. Initial cow weight per se was unrelated to pair efficiency. When considered jointly with calf weight at weaning, initial cow weight was unfavorably and calf weight was favorably related to pair efficiency. Calf age at weaning and milk production were favorably related to pair efficiency through their relationship with calf weight at weaning. Initial cow fat thickness, estimated ultrasonically, was not related to this measure of efficiency, indicating compensations between the year just completed and the next year in the relationship between cow fat thickness at weaning and pair efficiency. Mating schemes resulting in selection of relatively smaller females and larger males, within the variation available in a straightbred population, would be expected to alter the cow weight-calf weight ratio in a direction favorable to the component of efficiency defined in this study.     

Behavior of class-level landscape metrics across gradients of class aggregation and area

Habitat loss and fragmentation processes strongly affect biodiversity conservation in landscapes undergoing anthropogenic land use changes. Many attempts have been made to use landscape structure metrics to quantify the independent and joint effects of these processes. Unfortunately, ecological interpretation of those metrics has been plagued by lack of thorough understanding of their theoretical behavior. We explored behavior of 50 metrics in neutral landscapes across a 21-step gradient in aggregation and a 19-step gradient in area using a full factorial design with 100 replicates of each of the 399 combinations of the two factors to assess how well metrics reflected changes in landscape structure. Metric values from real landscapes were used to determine the extent of neutral landscape space that is represented in real landscapes. We grouped metrics into three major behavioral classes: strongly related to focal class area (n=15), strongly related to aggregation (n=7), and jointly responding to area and aggregation (n=28). Metrics strongly related to class area exhibited a variety of distinct behaviors, and many of these metrics have unique interpretations that make each of them particularly useful in certain applications. Metrics strongly related to aggregation, independent of class area, are particularly useful in assessing effects of fragmentation. Moreover, metrics in this group exhibited a range of specific behaviors, highlighting subtle but different aspects of landscape aggregation even though we controlled only one aspect of aggregation. The non-linear behavior exhibited by many metrics renders interpretation difficult and use of linear analytical techniques inappropriate under many circumstances. Ultimately, comprehensive characterization of landscapes undergoing habitat loss and fragmentation will require using several metrics distributed across behavioral groups.This revised version was published online in May 2005 with corrections to the Cover Date.     

Conversion of deciduous forest to silvopasture produces soil properties indicative of rapid transition to improved pasture

Differences in soil properties between forests and pastures have been well documented in the literature, especially under coniferous forests. However, since nearly all of these reports have been time-point comparisons, utilizing long-term paired-sites, properties of transitional states and time of their appearance can only be inferred at present. In this study, a deciduous forest ecosystem was converted to a silvopasture ecosystem by tree thinning, fertilization, and sheep incorporation of seed and forest litter. After 2 years, topsoil (0–15 cm) physico-chemical properties, particularly P fractions, and phosphatases were monitored over the growing season in these ecosystems, and a nearby pasture ecosystem. Initially, before spring vegetative growth, differences were found for pH, exchangeable cations and soil moisture, most of which could be explained by management history. Compared to forest, organic-C (C_o) and organic-N (N_o) concentrations were reduced in silvopasture by 17 and 9%, respectively, indicative of substantial litter decomposition. Most values for all these physico-chemical properties for silvopasture were intermediate between forest and pasture, and generally remained so throughout the growing season. Initial total P (TP_t), organic-P (TP_o) and inorganic-P (TP_i) concentrations were generally as anticipated for the forest and pasture. Silvopasture, however, had 36 and 23% greater TP_o than forest and pasture, respectively, presumably due to fertilizer-P immobilization induced by incorporation of forest litter. Total P components remained essentially constant over the growing season in all ecosystems, with the exception of pasture, likely due to high forage TP_i uptake. Bray I-extractable-organic-P (BrP_o) and bicarbonate-extractable-organic-P (BiP_o) concentrations, although consistently highest in the forest and silvopasture soils, were not reflective of the increase in TP_o under silvopasture. Acid phosphatase (PMEac) activities were highest in spring in all the ecosystems, then gradually declined to typically 25–50% initial activities. Alkaline phosphatase (PMEal) activities showed a broadly-similar pattern, with exception of forest and silvopasture soils, which exhibited low activities throughout the season. For the entire data set, PMEac and PMEal activities were poorly correlated with TP_i, BrP_i, and BiP_i. These results demonstrate that conversion of forest to silvopasture results in soil changes indicative of its rapid transition to pasture and that an increased P_o reservoir results that should be taken into account in fertilizer-P recommendations for temperate silvopastures.     

Localization and morphological effects of technetium-99 on higher plant cells

Autoradiographic studies by transmission electron microscopy (TEM) using technetium-95m (^95mTc) as the radioactive label indicated extensive membrane incorporation of technetium: seventy-seven percent of the incorporated grains were associated with membranous structures. Uptake studies following pretreatment with⁹⁹Tc involving Cs⁺, Cd⁺⁺, SeO₃ ^??, and thymidine revealed significant increases in active uptake relative to controls. To account for such uptake increases, the possible increase in cellular ATP levels due to technetium exposure is proposed. Excised soybean (Glycine max cv. Williams) seedling leaves directly exposed to 59.6μM⁹⁹Tc for four hours resulted in plasmolysis and abnormally shaped nuclei and chloroplasts. Mature tissue studies indicated similar results. Consequently, leaf plasmolysis and other cell responses to⁹⁹Tc previously observed by others following greater than 24 hours' exposure of intact seedlings to⁹⁹Tc were produced within a few hours at appropriate⁹⁹Tc concentrations and with direct exposures of leaves to⁹⁹Tc solutions.