Hydrological Responses and Flow Pathways in an Acrisol on a Forested Hillslope with a Monsoonal Subtropical Climate

The nature of subsurface flow depends largely on hydraulic conductivity of the vadoze zone, permeability of the underlying bedrock, existence of soil layers differing in hydraulic properties and macropore content, soil depth, and slope angle.Quantification of flow pathways on forested hillslopes is essential to understand hydrological dynamics and solute transport patterns.Acrisols, with their argic Bt horizons, are challenging in this respect.To further elucidate flow pathways of water and short-term variability of soil moisture patterns in Acrisols, a field study was conducted on a forested hillslope in a sub-catchment of the Tie Shan Ping(TSP)watershed, 25 km northeast of Chongqing City, China.This catchment is covered by a mixed secondary forest dominated by Masson pine(Pinus massoniana).Soil saturated hydraulic conductivity(K sat) was significantly reduced at the interface between the AB and Bt horizons(2.6 × 10~(-5) vs.1.2 × 10~(-6) m s~(-1)), which led to that the flow volume generated in the Bt horizon was of little quantitative importance compared to that in the AB horizon.There was a marked decrease in porosity between the OA and AB horizons, with a further decrease deeper in the mineral subsoil.Especially, the content of soil pores 300 μm was higher in the AB horizon(14.3%)than in the Bt horizon(6.5%).This explained the difference in soil K sat values.This study showed that Bt horizon had limited water transport capability, forcing part of the infiltrated rainwater as interflow through the OA and AB horizons.Thus, the topsoil responded quickly to rainfall events, causing frequent cycles of saturation and aeration of soil pores.     

Repair of radial fractures in toy breed dogs with self-reinforced biodegradable bone plates, metal screws, and light-weight external coaptation

OBJECTIVE: To describe a surgical technique for, and outcome after, treatment of radial fractures with biodegradable self-reinforced polylactide plates and metal screws, and external coaptation. STUDY DESIGN: Prospective clinical study. SAMPLE POPULATION: Eleven Toy breed dogs. METHODS: Radial fractures were repaired by application of a single or 2 stacked biodegradable self-reinforced polylactide plates (poly-L/D, L-lactide, stereocopolymer [LL-and DL-lactide ratio 70/30]; SR-PLA (70/30) implants) secured with metal screws, and light-weight external coaptation. Healing was evaluated clinically and by radiography at 2, 4, 6, 8, 9, 12, 24-26 weeks, and at 1 and 2 years. Owners were interviewed 3 years after surgery. RESULTS: Radial fracture lines disappeared within 4-14 weeks in 10 dogs; an implant failed in 1 dog. Ambulation was excellent for healed fractures. Excessive skin tension led to removal of implants in 1 dog and suture repair in another dog. No foreign body reaction from implant degradation was observed and the plate was usually no longer palpable at 2 years. One dog had a fracture through a screw hole at 1 year. CONCLUSION: Healing and complication rates after repair of radial fractures with SR-PLA (70/30) plates were considered similar or better than reported after repair with metallic plates or external fixation in Toy breed dogs. No radiographic signs of osteopenia were identified under the plate during follow-up. CLINICAL RELEVANCE: Biodegradable polylactide plates could be considered as an alternative to metal plates for radial fracture repair in Toy breed dogs, however available plates are likely not strong enough when used as a single plate. Implant removal is usually not needed.     

Viral expression and leukocyte adhesion after in vitro infection of goat mammary gland cells with caprine arthritis-encephalitis virus

A characteristic lesion in goats infected by the lentivirus CAEV is mastitis with lymphoid hyperplasia. In order to investigate the mechanism of lesion formation, cultures highly enriched in microvascular endothelial cells, mature and immature luminal epithelial cells, fibroblasts and myoepithelial cells were established from goat mammary gland biopsies. Their susceptibility to in vitro infection with two distinct types of CAEV was investigated by PCR, antigen expression and cytopathy. The capacity of infected mammary gland cells to bind uninfected caprine leukocytes was determined by flow cytometry. All cell types tested were susceptible to CAEV infection in vitro, with different levels of sensitivity according to cell phenotype. Our results suggest that the limited extent of natural infection of mammary gland cells reflects a protective local immune response, and that the myoepithelial cell could act as a reservoir cell. After infection, the mature luminal cell acquires the capacity to bind leukocytes in vitro, which could indicate a facilitation of cellular interactions. The distinct reactions of the different cell types to CAEV infection may be correlated with events leading to progressive lesion development during the natural infection.     

Goat endothelial cells may be infected in vitro by transmigration of caprine arthritis-encephalitis virus-infected leucocytes

The caprine arthritis-encephalitis lentivirus (CAEV) causes a lifelong persistent infection in goats, and induces infiltrations of leucocytes and tissue reorganization in target organs, with a cyclical pattern of viral expression. The mammary gland is an important site of infection, associated with mother-to-kid transmission by infected cells in colostrum and milk. The monocyte/macrophage is the principal target cell, but other cell types, including epithelial and endothelial cells and fibroblasts, are susceptible to in vitro infection with varying levels of viral replication. Such cells, perhaps at specific differentiation states, might play a role in the regulation and transfer of in vivo infection in target organs. In this paper we describe the in vitro infection of endothelial cell monolayers by the transmigration of monocytes carrying the CAEV provirus. The infected endothelial cells progress to expression of the viral p30 capsid antigen, suggesting viral proliferation. Such a process occurring in vivo during angiogenesis and leucocyte homing to the mammary gland in the final third of mammogenesis, might contribute to viral spread in this crucial target organ.     

Comparison of fluorescent antibody tests for tuberculosis and paratuberculosis with antigens coupled to insoluble spheres or taken up by macrophages

Sera of 106 cattle from farms with histories of Mycobacterium johnei infection and sera from 15 human tuberculous patients as well as a number of control sera were examined by means of two different fluorescent antibody tests (FAT) for the occurrence of antibodies against M. johnei and M. tuberculosis respectively. The antigens used were PPD johnin and PPD tuberculin. In the macrophage uptake FAT (MU/FAT) mouse macrophages after phagocytosis of the tuberculins served as the matrix; in the tests performed using the defined antigen substrate spheres (DASS) system, Sepharose beads activated by CNBr were used for the matrix. A good correlation was found between the results of the DASS/FAT and those of the MU/FAT, which is known to be a sensitive and specific test in the diagnosis of Johne's disease in cattle. It is suggested that the FAT, with utilization of the DASS system, might have good prospects for routine examination for antibodies against species of Mycobacterium.     

The Low-Temperature-Induced Viable-But-Nonculturable State Affects the Virulence of Ralstonia solanacearum Biovar 2

ABSTRACT The physiology and virulence of Ralstonia solanacearum biovar 2 strain 1609, kept in water at 4 and 20 degrees C, were studied. At 20 degrees C, total cell and plate count (colony forming units; CFU) numbers were similar, between log 5.03 and log 5.55 CFU, and log 5.03 and log 5.51 cells per ml, at days 0 and 132, respectively. However, CFU in the cultures kept at 4 degrees C dropped from log 6.78 CFU/ml at day 0 to below detection after 84 days. The presence of catalase in the agar resulted in higher CFU, and at day 84, log 1.95 CFU/ml still was detectable. No colonies were observed at day 125. The presence of viable-but-nonculturable (VBNC) cells in the 4 degrees C cultures was confirmed using SYTO9 viability staining. Viable cell numbers were log 1.77 higher than CFU on plates with catalase. At day 84 and after 125 days, log 3.70 viable cells per ml still were present. Shifts in subpopulations differing in viability were found by flow cytometric sorting of 4 degrees C-treated cells stained with SYTO9 (healthy) and propidium iodide (PI; compromised). The SYTO9-stained cell fractions dropped from 99 to 39%, and the PI-stained fractions increased from 0.7 to 33.3% between days 0 and 125. At 20 degrees C, the SYTO9-stained fraction remained stable at 99% until day 132. SYTO9-stained cells sorted from 4 degrees C cultures at day 100 were injected into tomato plants. Upon incubation for 30 days, these plants did not show wilting. However, more than log 4.19 CFU and log 8.17 cells were recovered from these plants. Cells from colonies isolated from the nonwilted plants did not regain their virulence as demonstrated by subsequent injection into several new sets of tomato plants. Cells from 4 degrees C cultures injected at day 125 were not able to cause wilting of, or proliferate in, tomato plants. The threat posed by VBNC R. solanacearum cells upon incubation at 4 degrees C was thus ephemeral because cells lost their capacity to cause disease after 125 days.     

Associations between management, climate, and Escherichia coli O157 in the faeces of feedlot cattle in the Midwestern USA

Our objective was to generate hypotheses for potential on-farm control strategies for Escherichia coli O157 by identifying associations between management practices and climate, and the presence of E. coli O157 in feedlot cattle. Faeces were obtained from 10,622 cattle in 711 pens on 73 feedlots between May and August 2001. Management and climate information was obtained by questionnaire and observation at the time of sampling. The prevalence of E. coli O157 was 10.2% at the sample level, 52.0% at the pen-level, and 95.9% at the feedlot-level. The factors associated with the presence of E. coli O157 in cattle faeces were the frequency of observing cats in the pens or alleys (most common when observed daily), the presence of E. coli O157 in the water tanks (positive association), the historical use of injectable mass medication (positive association), the use of antibiotics in the ration or water (negative association), the wetness of the pen, number of cattle in the pen (negative association), wind velocity (positive association), and height of the feed bunk (positive association).