Morphological Variations in Developing Ectomycorrhizae of Dryas integrifolia and Five Fungal Species

A comparative study of ectomycorrhiza formation between the host species Dryas integrifolia and four fungal species belonging to the Basidiomycotina ( Laccaria bicolor, L. laccata, Hebeloma cylindrosporum, Paxillus involutus) and one species in the Ascomycotina (Cenococcum geophilum) showed that patterns in ectomycorrhizal development were distinctive enough to characterize each fungal symbiont. Several aspects of hyphal growth on the plant root during colonization were studied in order to demonstrate the usefulness of SEM in observing the ontogeny of ectomycorrhizae. Each fungal species had a different rate of colonization, and varying root and root hair interactions. As a consequence mantle morphology and the overall appearance of mature ectomycorrhizal apices were also characteristic for each fungal species. Results indicate that the mycobiont plays a major role in determining the morphology of mature ectomycorrizae

Scanning Electron Microscopy of Ectomycorrhizae Potential and Limitations

Scanning electron microscopy (SEM) has added considerably to an understanding of the morphology of ectomycorrhizae. Features of the mantle of mature ectomycorrhizae have been studied most frequently. There is considerable variation in arrangement of hyphae and therefore in the appearance of the outer mantle. This variation is due primarily to the fungal symbiont although the host genome may also influence this feature. The Hartig net has been studied from fractured ectomycorrhizal roots and, in the present study, from fractured cryopreserved specimens; general features of the interaction between Hartig net hyphae and contiguous root cells have been described. There are few published accounts of using SEM techniques to study the ontogeny of ectomycorrhizae. This study demonstrates the usefulness of such techniques in studying the initial interaction of hyphae with root hairs and root surfaces, including the extramatrical phase which is normally very difficult to study using other techniques

Altered Fungal Morphogenesis During Early Stages of Ectomycorrhiza Formation in Eucalyptus Pilularis

Scanning electron microscopy (SEM) of Eucalyptus pilularis roots inoculated with Pisolithus tinctorius, under controlled conditions, revealed altered morphogenesis of fungal hyphae in contact with the root surface. These changes occurred prior to the formation of a full fungal mantle and resulted in the formation of a compact fungal layer as a consequence of fusion of proliferating, branching hyphae. Although similar growth patterns have been observed in the inner mantle of fully developed ectomycorrhizae using contrast interference microscopy, this is the first time this feature has been observed during early mantle formation using SEM. Changes in fungal morphology during early stages of colonization may be correlated with recognition between the symbionts, and the subsequent establishment of a symbiotic relationship between compatible partners

Protozoan communities around conifer roots colonized by ectomycorrhizal fungi

Abstract Protozoan communities around roots with different types of ectomycorrhizae were distinct. These protozoan communities differed both qualitatively and quantitatively with the host (Pinus ponderosa, Pseudotsuga menziesii, Picea sitchensis, Tsuga heterophylla and Abies grandis) and the ectomycorrhizal fungal species. Based on the species identified and the numbers of individuals of each species, six communities of protozoa were found associated with specific ectomycorrhizae. Previous researchers have shown that mycorrhizal colonization of roots alters the amounts and types of exudates produced by roots, which in turn alters the bacterial community present. Most likely, mycorrhizal colonization of roots influences the protozoan community around roots by controlling the bacterial community. However, the protozoan community may in turn influence the successional dynamics of ectomycorrhizal fungi on different host root systems by a variety of mechanisms. These mechanisms could include: (1) preying upon individuals and perhaps removing particular species of bacteria from the mycorrhizosphere; and (2) controlling nitrogen mineralization in the rhizosphere. Further work needs to be performed to determine the interaction between these quadrate (plantbacteria-fungi-protozoa) associations

COMBINING PHOTOGRAPHY AND A GEOGRAPHIC INFORMATION SYSTEM TO MEASURE WINTER BROWSE USE

Browse use surveys such as the twig-length method typically used to assess browsing by ungulates are time-consuming and costly. Here, we describe a modification of the twig-length method that utilizes digital photography and a Geographic Information System (GIS) technique to quantify browse shoot removal. Linear regression analysis indicated that the cumulative shoot length (cm) and biomass removal (g) estimated with our indirect method was similar to direct measurements on Scouler’s willows (Salix scouleriana). Our results suggest that this indirect browse assessment procedure could reduce field time, presumably increase sample size and efficiency, and create a photographic record of each plant for long-term assessment of moose (Alces alces) browsing

Incidence and Outcomes of Acute Implant Extrusion Following Anterior Cervical Spine Surgery.

STUDY DESIGN: Multi-institutional retrospective case series of 8887 patients who underwent anterior cervical spine surgery. OBJECTIVE: Anterior decompression from discectomy or corpectomy is not without risk. Surgical morbidity ranges from 9% to 20% and is likely underreported. Little is known of the incidence and effects of rare complications on functional outcomes following anterior spinal surgery. In this retrospective review, we examined implant extrusions (IEs) following anterior cervical fusion. METHODS: A retrospective multicenter case series study involving 21 high-volume surgical centers from the AOSpine North America Clinical Research Network. Medical records for 17 625 patients who received cervical spine surgery (levels from C2 to C7) between January 1, 2005, and December 31, 2011, were reviewed to identify occurrence of 21 predefined treatment complications. RESULTS: Following anterior cervical fusion, the incidence of IE ranged from 0.0% to 0.8% across 21 institutions with 11 cases reported. All surgeries involved multiple levels, and 7/11 (64%) involved either multilevel corpectomies or hybrid constructs with at least one adjacent discectomy to a corpectomy. In 7/11 (64%) patients, constructs ended with reconstruction or stabilization at C7. Nine patients required surgery for repair and stabilization following IE. Average length of hospital stay after IE was 5.2 days. Only 2 (18%) had residual deficits after reoperation. CONCLUSIONS: IE is a very rare complication after anterior cervical spine surgery often requiring revision. Constructs requiring multilevel reconstruction, especially at the cervicothoracic junction, have a higher risk for failure, and surgeons should proceed with caution in using an anterior-only approach in these demanding cases. Surgeons can expect most patients to regain function after reoperation

Pattern recognition based on HD-sEMG spatial features extraction for an efficient proportional control of a robotic arm.

To enable an efficient alternative control of an assistive robotic arm using electromyographic (EMG) signals, the control method must simultaneously provide both the direction and the velocity. However, the contraction variations of the forearm muscles, used to proportionally control the device’s velocity using a regression method, can disturb the accuracy of the classification used to estimate its direction at the same time. In this paper, the original set of spatial features takes advantage of the 2D structure of an 8 × 8 high-density surface EMG (HD-sEMG) sensor to perform a high accuracy classification while improving the robustness to the contraction variations. Based on the HD-sEMG sensor, different muscular activity images are extracted by applying different spatial filters. In order to characterize their distribution specific to each movement, instead of the EMG signals’ amplitudes, these muscular images are divided in sub-images upon which the proposed spatial features, such as the centers of the gravity coordinates and the percentages of influence, are computed. These features permits to achieve average accuracies of 97% and 96.7% to detect respectively 16 forearm movements performed by a healthy subject with prior experience with the control approach and 10 movements by ten inexperienced healthy subjects. Compared with the time-domain features, the proposed method exhibits significant higher accuracies in presence of muscular contraction variations, requires less training data and is more robust against the time of use. Furthermore, two fine real-time tasks illustrate the potential of the proposed approach to efficiently control a robotic arm

Dissociation of two-dimensional excitons in monolayer WSe₂

In two-dimensional semiconductors excitons are strongly bound, suppressing the creation of free carriers. Here, the authors investigate the main exciton dissociation pathway in p-n junctions of monolayer WSe2 by means of time and spectrally resolved photocurrent measurements

Characteristics of Patients Who Survived < 3 Months or > 2 Years After Surgery for Spinal Metastases: Can We Avoid Inappropriate Patient Selection?

PURPOSE: Survival after metastatic cancer has improved at the cost of increased presentation with metastatic spinal disease. For patients with pathologic spinal fractures and/or spinal cord compression, surgical intervention may relieve pain and improve quality of life. Surgery is generally considered to be inappropriate if anticipated survival is < 3 months. The aim of this international multicenter study was to analyze data from patients who died within 3 months or 2 years after surgery, to identify preoperative factors associated with poor or good survival, and to avoid inappropriate selection of patients for surgery in the future. PATIENTS AND METHODS: A total of 1,266 patients underwent surgery for impending pathologic fractures and/or neurologic deficits and were prospectively observed. Data collected included tumor characteristics, preoperative fitness (American Society of Anesthesiologists advisory [ASA]), neurologic status (Frankel scale), performance (Karnofsky performance score [KPS]), and quality of life (EuroQol five-dimensions questionnaire [EQ-5D]). Outcomes were survival at 3 months and 2 years postsurgery. Univariable and multivariable logistic regression analyses were used to find preoperative factors associated with short-term and long-term survival. RESULTS: In univariable analysis, age, emergency surgery, KPS, EQ-5D, ASA, Frankel, and Tokuhashi/Tomita scores were significantly associated with short survival. In multivariable analysis, KPS and age were significantly associated with short survival (odds ratio [OR], 1.36; 95% CI, 1.15 to 1.62; and OR, 1.14; 95% CI, 1.02 to 1.27, respectively). Associated with longer survival in univariable analysis were age, number of levels included in surgery, KPS, EQ-5D, Frankel, and Tokuhashi/Tomita scores. In multivariable analysis, the number of levels included in surgery (OR, 1.21; 95% CI, 1.06 to 1.38) and primary tumor type were significantly associated with longer survival. CONCLUSION: Poor performance status at presentation is the strongest indicator of poor short-term survival, whereas low disease load and favorable tumor histology are associated with longer-term survival