Movement of zoospores of Phytophthora citricola in saturated porous media

The genus Phytophthora comprises numerous plant pathogens in both natural and managed ecosystems. For Phytophthora spp. that infect roots, dispersal occurs in soil water through a combination of advection and swimming of specialized motile propagules (zoospores). Specific biological and physico-chemical processes, however, remain poorly understood, due to difficulties in studying phenomena in opaque media and lack of a theoretical framework for analyzing transport of motile microorganisms. The goal of this research was to elucidate the impacts of advection and swimming on zoospore movement in a saturated, ideal soil. The work was accomplished in two stages, (i) conceptualization of 3-dimensional topography and flow field heterogeneity at the subpore-scale, and (ii) observation of behavior of zoospore suspensions infiltrated into saturated media. Chapter 2 introduces a 3-dimensional particle tracking method and presents two studies investigating particle transport in simplified 'ideal pores'. The first study describes 'avoidance' by latex microspheres of a volume surrounding orthogonal grain contacts and the second describes 'capture', translation, and retention of microspheres under conditions unfavorable to deposition. Chapter 3 expands on the first study and demonstrates, with the aid of computational fluid dynamics, that low flow zones associated with orthogonal grain contacts are minimally connected to the main flow. Thus, probability of entry into these regions for large, non-Brownian particles by advection alone is low. In zoospore infiltration experiments, zoospore plumes 'converged' rather than dispersing as expected. To assess the possibility of zoospore auto-aggregation driving this 'convergence', Chapter 4 delves into the 'pattern swimming' observed in free-swimming zoospore suspensions, concluding that the concentrating is an example of bioconvection. Chapter 5 introduces a conceptual model to explain the anomalous zoospore plume behavior. Random walk simulations replicated plume convergence but were less successful at modeling anisotropic dispersion. At low infiltration rates (<100 μm s⁻¹), simulations predict that zoospores will remain at or near the soil surface, resulting in greater opportunity to find host tissues or to be transported with surface water. Further investigation is necessary to develop a robust theoretical framework with appropriate conceptualization of the subpore hydrodynamic environment for predicting transport of zoospores and other motile microorganisms in porous media

Effects of green manures on verticillium wilt of potatoes and on soil properties related to disease suppression

Increasing regulation and costs of soil fumigation to manage diseases such as Verticillium wilt caused by soil-borne pathogens have prompted a search for management alternatives. Single-year microplot experiments were conducted in 2002 and 2003 in central Oregon to evaluate the effects of Austrian winter pea, broccoli, and Sudan grass green manures applied at three rates (6, 12, or 24 Mg h⁻¹) on soil and potato root populations of Verticillium dahliae, severity of Verticillium wilt of potato, and tuber yield. Amendment rate had no effect on inoculum density (ID) or root infection (RI), but affected relative area under the senescence progress curve (RAUSPC). Green manures of broccoli applied at all three rates, Sudan grass applied at 6 or 12 Mg ha⁻¹, and Austrian winter pea applied at 24 Mg ha⁻¹ reduced soil populations of V. dahliae compared to the unamended control. For green manures of broccoli or Sudan grass, reduction in ID could partially account for reduction of RAUSPC (r = 0.44 and 0.46, respectively). Green manures of Austrian winter pea applied at 12 or 24 Mg ha⁻¹ and broccoli or Sudan grass applied at 24 Mg ha⁻¹ reduced RAUSPC by 74, 70, 70, and 52%, respectively, compared to the unamended control. None of the green manure treatments in either experiment was able to significantly increase yield relative to the unamended control. However, in 2002, Sudan grass applied at 12 and 24 Mg ha⁻¹, and broccoli applied at 24 Mg ha⁻¹ resulted in a mean different from that of the uninfested plots and yield was negatively correlated with disease severity (r = -0.61, P ≤ 0.0001). In 2003, due to an earlier harvest, there were no differences in yield between amended and unamdended plots and no relationship between yield and disease severity. To explore possible mechanisms of suppression, soil chemical and microbial properties related to severity of Verticillium wilt were identified using regression analyses. We then assessed how these soil properties were affected by the green. manure treatments. Soil population of V dahliae predicted 48 and 52% of the variability in disease severity in 2002 and 2003, respectively. In 2002, after accounting for different levels of ID, inclusion of a tenn for pH improved goodnessof- fit of the regression model to 60%. Severity of Verticillium wilt was overwhelmingly influenced by a wide soil pH gradient (pH 5.2 to 7.5) across the 2002 field. Soil pH was positively related to disease severity and was not affected by green manure treatments. In 2003, after accounting for different levels of ID, inclusion of a term for NO₃-N, microbial biomass (MBC), or microbial respiration (MR), improved fit of the model to 64, 66 or 62%, respectively. All soil properties identified in 2003 were negatively related to disease severity and were positively associated with green manure amendment rate. Finally, stepwise regression using data pooled from both studies resulted in a model which included terms for ID, soil pH, and FDA and accounted for 63% of the variability in RAUSPC

A giant plexiform schwannoma of the brachial plexus: case report

We report the case of a patient who noticed muscle weakness in his left arm 5 years earlier. On examination, a biloculate mass was observed in the left supraclavicular area, and Tinel's sign caused paresthesia in his left arm. Magnetic resonance imaging showed a continuous, multinodular, plexiform tumor from the left C5 to C7 nerve root along the course of the brachial plexus to the left brachia. Tumor excision was attempted. The median and musculocutaneous nerves were extremely enlarged by the tumor, which was approximately 40 cm in length, and showed no response to electric stimulation. We resected a part of the musculocutaneous nerve for biopsy and performed latissimus dorsi muscle transposition in order to repair elbow flexion. Morphologically, the tumor consisted of typical Antoni A areas, and immunohistochemistry revealed a Schwann cell origin of the tumor cells moreover, there was no sign of axon differentiation in the tumor. Therefore, the final diagnosis of plexiform Schwannoma was confirmed

Methods for colloid transport visualization in pore networks

Prediction of colloid transport in the subsurface is relevant to researchers in a variety of fields such as contaminant transport, wastewater treatment, and bioremediation. Investigations have traditionally relied on column studies whereby mechanistic inferences must be drawn on the basis of colloid behavior at the outlet. Over the past decade, development of noninvasive visualization techniques based on visible light, magnetic resonance, and X rays have provided insight into a number of colloid transport mechanisms by enabling direct observation of individual colloids at the pore scale and colloid concentrations at longer length scales. As research focus shifts from transport of ideal colloids in ideal media such as glass beads to natural colloids in natural porous media, these noninvasive techniques will become increasingly useful for studying the collection of mechanisms at work in heterogeneous pore systems. It is useful at this juncture to review recent progress in colloid transport visualization as a starting point for further development of visualization tools to support investigation of colloids in natural systems. We briefly discuss characteristics of visualization systems currently used to study colloid transport in porous media and review representative microscale and mesoscale visualization studies conducted over the past decade, with additional attention given to two optical visualization systems being developed by the authors.Keywords: Review, Methods, Colloids, Visualization, Porous medi

Enhanced wound healing associated with Sharpey’s fiber-like tissue formation around FGF-2-apatite composite layers on percutaneous titanium screws in rabbits

BACKGROUND:Pin-tract infections are the most common complications of external fixation. To solve the problem, we developed a fibroblast growth factor-2 (FGF-2)-apatite composite layer for coating titanium screws. The purpose of this study was to elucidate the mechanism of the improvement in infection resistance associated with FGF-2-apatite composite layers.METHOD:We analyzed FGF-2 release from the FGF-2-apatite composite layer and the mitogenic activity of the FGF-2-apatite composite layer. We evaluated time-dependent development of macroscopic pin-tract infection around uncoated titanium control screws (n = 10). Screws coated with the apatite layer (n = 16) and FGF-2-apatite composite layer (n = 16) were percutaneously implanted for 4 weeks in the medial proximal tibia in rabbits.RESULTS:A FGF-2-apatite composite layer coated on the screws led to the retention of the mitogenic activity of FGF-2. FGF-2 was released from the FGF-2-apatite composite layer in vitro for at least 4 days, which corresponds to a period when 30% of pin-tract infections develop macroscopically in the percutaneous implantation of uncoated titanium control screws. The macroscopic infection rate increased with time, reaching a plateau of 80-90% within 12 days. This value remained unchanged until 4 weeks after implantation. The screws coated with an FGF-2-apatite composite layer showed a significantly higher wound healing rate than those coated with an apatite layer (31.25 vs. 6.25%, p < 0.05). The interfacial soft tissue that bonded to the FGF-2-apatite composite layer is a Sharpey\u27s fiber-like tissue, where collagen fibers are inclined at angles from 30 to 40° to the screw surface. The Sharpey\u27s Wber-like tissue is rich in blood vessels and directly bonds to the FGF-2-apatite composite layer via a thin cell monolayer (0.8-1.7 μm thick).CONCLUSION:It is suggested that the enhanced wound healing associated with the formation of Sharpey\u27s fiber-like tissue triggered by FGF-2 released from the FGF-2-apatite composite layer leads to the reduction in the pin-tract inflammation rate

Cell death and cell proliferation in cartilage layers in human anterior cruciate ligament tibial insertions after rupture

The purpose of this study is to investigate cellular responses and histological changes of cartilaginous layers in human anterior cruciate ligament (ACL) tibial insertions after rupture compared with those in normal insertions. Fully 16 tibial insertions of ruptured ACLs were obtained during primary ACL reconstructions. We also obtained 16 normal ACL tibial insertions from cadavers. Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labeling (TUNEL) to detect apoptosis, proliferating cell nuclear antigen (PCNA) staining, and histological examination were performed. The percentage of TUNEL-positive chondrocytes in ruptured ACL insertions (30.2 ± 15.6%) was higher than that in normal insertions (9.6 ± 5.8%). The percentage of PCNA-positive chondrocytes was significantly different between ruptured ACL insertions (19.9 ± 15.0%) and normal insertions (12.3 ± 7.3%). The average thickness of the cartilage layer, the glycosaminoglycan-stained area, and the number of chondrocytes per millimeter in ruptured ACL insertions was smaller than those in normal insertions. The decrease in the number of chondrocytes owing to an imbalance between cell death and cell proliferation in the ACL insertions after rupture, as compared with normal insertions, may lead to histological changes of the cartilage layer in the insertions. An in-depth understanding of injured ACL insertion may help elucidate the etiology of histological changes and the function and significance of the existence of the cartilage layer of insertion. This understanding may help in developing optimal treatment protocols for ACL injuries if apoptosis and cell proliferation are controlled

Correlation of histopathology with magnetic resonance imaging in Kienböck disease.

PURPOSE:Diagnosis and treatment remain controversial for Kienböck disease. A few reports have correlated magnetic resonance imaging (MRI), which is essential for early diagnosis, and histopathology of Kienböck biopsy specimens, but histopathological correlations of whole lunate bones or histological slices compared with MRI images are lacking. The purpose of this study was to compare presurgical MRI scans with corresponding histological slices of Kienböck-diseased lunates.METHODS:We excised whole lunates at the time of surgery from 6 patients with Kienböck disease (stage IIIB) undergoing tendon-ball replacement or a Graner procedure. We stained paraffin-embedded, coronally sectioned specimens with hematoxylin-eosin and compared them with presurgical coronal scans using MRI with a 47-mm microscopy surface coil.RESULTS:Toward the center of the lunates, the signal intensity in the proton density-weighted images was reduced, whereas the dorsal and palmar sides of the lunates exhibited no changes in intensity. In correlation, histopathological findings revealed strongly disrupted trabeculae toward the center of the lunates and intact trabeculae in the dorsal side of the lunates. Likewise, the necrotic and vitalized bone exhibited low and high signal intensities, respectively, in the proton density-weighted images; however, in the fast-field echo images, there were no correlations with histopathological observations.CONCLUSIONS:Proton density-weighted MRIs but not fast-field echo images using a 47-mm microscopy coil reflected the extent and localization of the necrotic area in Kienböck-diseased lunates, as evidenced by comparison with histological analyses of the lunate specimens.CLINICAL RELEVANCE:Proton density-weighted MRIs accurately reflect the vascular status of the lunate and may help plan treatment on a case-by-case basis