Contribution of the arbuscular mycorrhizal symbiosis to heavy metal phytoremediation

High concentrations of heavy metals (HM) in the soil have detrimental effects on ecosystems and are a risk to human health as they can enter the food chain via agricultural products or contaminated drinking water. Phytoremediation, a sustainable and inexpensive technology based on the removal of pollutants from the environment by plants, is becoming an increasingly important objective in plant research. However, as phytoremediation is a slow process, improvement of efficiency and thus increased stabilization or removal of HMs from soils is an important goal. Arbuscular mycorrhizal (AM) fungi provide an attractive system to advance plant-based environmental clean-up. During symbiotic interaction the hyphal network functionally extends the root system of their hosts. Thus, plants in symbiosis with AM fungi have the potential to take up HM from an enlarged soil volume. In this review, we summarize current knowledge about the contribution of the AM symbiosis to phytoremediation of heavy metal

Posterior Cerebral Artery Aneurysms

Objective: Aneurysms of the posterior cerebral artery are rare vascular lesions. The overall incidence is less than 1%, representing around 7% of posterior circulation aneurysms. Due to this low incidence, most of the institutional series on PCA aneurysms are small and contain less than 25 patients. Only one other series comparable in scope to ours has been previously published. The presented study analyzes and describes the characteristic features of PCA aneurysms as well as investigates the relevant treatment strategies and their outcomes. A particular focus is in the description and analysis of PCA aneurysms treated from a subtemporal approach and the pres - entation of an associated aneurysm treatment from a lateral supraorbital approach. Patients and Methods: We reviewed 121 patients diagnosed with 135 PCA aneurysms, all of whom were treated between 1980 and 2012 at two Finnish neurosurgical units (Department of Neurosurgery at the University of Eastern Finland, Kuopio and Department of Neurosurgery at the University of Helsinki). Additionally, twelve historical (pre-1980) cases were presented. Detailed analyses of cerebral angiographies were conducted for 93 PCA aneurysms in 81 patients. A further subgroup analysis of 34 patients diagnosed with 37 PCA aneurysms treated via subtemporal approach was also performed. Results: Of the 121 patients with 135 PCA aneurysms, 52 (39%) aneurysms were ruptured and 83 (61%) unruptured . The following distribution along the PCA segments was observed: P1 segment (n=53), P1/2 junction (n=39), P2 segment (n=28), and P3 segment (n=15); no P4 segment aneurysms were found. Saccular aneurysms were more common than fusiform PCA aneurysms (76% vs. 24%). The detailed angiographic analysis showed that the median aneurysm size was 7 mm for ruptured PCA aneurysms and 4 mm for unruptured aneurysms. Saccular aneurysms (n=69, 74%) had a characteristic dome projection for each location: P1 segment, upward (67%); P1/P2 junction, anterior/upward (80%); P2 segment, lateral (67%); and P3 segment, posterior (50%). The following treatment results at 1-year follow-up were achieved for patients with: unruptured PCA aneurysms (n=19; 12 good outcomes, 63%; 6 moderate, 31%; 1 poor, 5%), ruptured PCA aneurysms (n=27; 10 good, 37%; 9 moderate, 33%; 8 poor, 30%), and patients with complex neurovascular pathologies and PCA aneurysms (n=96; 42 good, 43%; 40 moderate, 42%; 14 poor, 15%). Analyzing the subtemporal approach we found that most complications were not related to the subtemporal approach itself but to the specific nature of the PCA aneurysms treated and the chosen strategy. The most common (12 out of 34; 35%) serious complication in this series was an ipsilateral PCA infarction after parent vessel occlusion. Conclusion: PCA aneurysms are infrequent vascular lesions that are often associated with other vascular pathologies. Most ruptured PCA aneurysms are smaller than 10 mm and distally located. The saccular PCA aneurysms have a typical dome orientation at each PCA segment. Microsurgery and endovascular treatment are effective options for the occlusion of PCA aneurysms. As a result, individual treatment strategies are required. Despite commonly adequate vessel collateralization of the distal PCA territory, preservation or reconstruction of the parent vessel is crucial for favorable treatment outcomes. The subtemporal approach is favorable for the treatment of PCA aneurysms in proximity to the tentorium. Frontolateral approaches allow the treatment of proximal PCA aneurysms and ipsilateral anterior circulation aneurysms inside the Circle of Willis.Tausta: Takimmaisen aivovaltimon (posterior cerebral artery, PCA) aneurysmat ovat harvinaisia. Niiden insidenssi on alle 1 % kaikista aneurysmista ja noin 7 % takakierron aneurysmista. Matalan insidenssin vuoksi valtaosa potilassarjoista on pieniä, korkeintaan 25 potilaasta. Aiemmin on julkaistu vain yksi sarja, joka on nyt julkaistun sarjan kokoinen. Nyt tehty tutkimus analysoi ja kuvaa PCA-aneurysmien erityisominaisuuksia, hoitostrategioita ja hoidon tuloksia. Erityinen painoarvo on subtemporaalireittiä hoidettujen PCA-aneurysmien analyysillä, sekä lateraalista supraorbitaalista reittiä PCA-aneurysman ohessa hoidettujen aneurysmien kuvauksella. Analysoimme 121 potilasta, joilla oli yhteensä 135 PCA-aneurysmaa. Potilaat oli hoidettu kahdessa suomalaisessa neurokirurgian yksikössä (KYS Neurokirurgia ja HYKS Neurokirurgia) vuosina 1980 2012. Lisäksi kuvaamme 12 ennen vuotta 1980 hoidettua potilasta. Aivovaltimoangiografioiden yksityiskohtainen analyysi tehtiin 81 potilaalle, joilla oli yhteensä 93 PCA aneurysmaa. Edelleen analysoimme 34 potilasta, joilla oli hoidettu 37 PCA-aneurysmaa subtemporaalireitin kautta. Tulokset: 121 potilaalla oli yhteensä 135 PCA-aneurysmaa: näistä vuotaneita oli 52 (39 %) ja vuotamattomia 83 (61 %). Aneurysmista sijaitsi P1-segmentissä 52, P1/2 haarautumiskohdassa 39, P2-segmentissä 28 ja P3-segmentissä 15. Yksikään aneurysma ei sijainnut P4-segmentissä. Sakkulaariset aneurysmat olivat yleisempiä kuin fusiformiset (76 % vs. 24 %). Vuotaneiden aneurysmien mediaanikoko oli 7 mm ja vuotamattomien 4 mm. Sakkulaaristen aneurysmien (n=69, 74 %) suuntautuminen riippui aneurysman sijainnista: P1-aneurysmat suuntautuivat ylös (67 %), P1/P2 eteen/ylös (80 %), P2 sivulle (67 %) ja P3-aneurysmat taakse (50 %). Vuotamattoman aneurysman hoidon jälkeen potilaista oli vuoden seurannassa toipunut hyvin 12 (63 %), kohtalaisesti 6 (31 %) ja huonosti 1 (1 %). Vuotaneen aneurysman hoidon jälkeen hyvin oli toipunut 10 (37 %), kohtalaisesti 9 (33 %) ja huonosti 14 (15 %). Subtemporaalireittiä käytettäessä valtaosa komplikaatioista ei liittynyt leikkausreittiin vaan PCA-aneurysmien erityisominaisuuksiin ja aneurysman sulkutekniikkaan. Yleisin vakava komplikaatio oli saman puolen PCA:n sulusta aiheutunut aivoinfarkti. Yhteenveto: PCA-aneurysmat ovat harvinaisia vaskulaarisia muutoksia, jotka usein liittyvät muihin verisuonien patologioihin. Suurin osa vuotaneista PCA-aneurysmista on pienempiä kuin 10 mm ja ne sijaitsevat suonessa distaalisesti. Sakkulaariset aneurysmat suuntautuvat tiettyyn suuntaan eri PCA:n osissa. Mikrokirurgia ja endovaskulaarinen hoito ovat molemmat tehokkaita PCA-aneurysmien sulussa, mutta yksilöllinen hoitostrategian suunnittelu on tarpeen. Hyvän hoitotuloksen saavuttamiseksi PCA:n säilyttäminen avoimena on välttämätöntä huolimatta kollateraalikierrosta. Subtemporaalireitti soveltuu hyvin pikkuaivoteltan proksimaalipuolella sijaitsevien PCA-aneurysmien hoitoon. Frontolateraalisen reitin kautta voidaan hoitaa sekä proksimaalinen PCA-aneurysma että samalla puolella circulus Willisissä olevat aneurysmat

Editorial : Pathophysiology and treatment of fusiform intracranial aneurysms

Non peer reviewe

Percutaneous posterolateral approach for the simulation of a far-lateral disc herniation in an ovine model

This work describes a minimally invasive damage model for ovine lumbar discs via partial nucleotomy using a posterolateral approach. Two cadavers were dissected to analyze the percutaneous corridor. Subsequently, 28 ovine had their annulus fibrosus punctured via awl penetration under fluoroscopic control and nucleus pulposus tissue removed via rongeur. Efficacy was assessed by animal morbidity, ease of access to T12-S1 disc spaces, and production of a mechanical injury as verified by discography, radiography, and histology. T12-S1 were accessible with minimal nerve damage morbidity. Scar tissue sealed the disc puncture site in all animals within 6 weeks, withstanding 1 MP of intradiscal pressure. Partial nucleotomy led to a significant reduction in intervertebral disk height and an increased histological degeneration score. Inducing a reproducible injury pattern of disc degeneration required minimal time, effort, and equipment. The posterolateral approach allows operation on several discs within a single surgery and multiple animal surgeries within a single day.Peer reviewe

Micro-computed tomography, scanning electron microscopy and energy X-ray spectroscopy studies of facet joint degeneration : A comparison to clinical imaging

Segmental degeneration in the human lumbar spine affects both the intervertebral discs and facet joints. Facet joint degeneration not only affects the cartilage surface, but also alters the cellular properties of the cartilage tissue and the structure of the subchondral bone. The primary focus of this study is the investigation of these microstructural changes that are caused by facet joint degeneration. Microstructural analyses of degenerated facet joint samples, obtained from patients following operative lumbar interbody fusion, have not previously been extensively investigated. This study analyzes human facet joint samples from the inferior articular process using scanning electron microscopy, micro-computed tomography, and energy dispersive X-ray spectroscopy to evaluate parameters of interest in facet joint degeneration such as elemental composition, cartilage layer thickness and cell density, calcification zone thickness, subchondral bone portion, and trabecular bone porosity. These microstructural analyses demonstrate fragmentation, cracking, and destruction of the cartilage layer, a thickened calcification zone, localized calcification areas, and cell cluster formation as pathological manifestations of facet joint degeneration. The detailed description of these microstructural changes is critical for a comprehensive understanding of the pathology of facet joint degeneration, as well as the subsequent development and efficacy analysis of regenerative treatment strategies.Peer reviewe

Agronomic Management of Indigenous Mycorrhizas

Many of the advantages conferred to plants by arbuscular mycorrhiza (AM) are associated to the ability of AM plants to explore a greater volume of soil through the extraradical mycelium. Sieverding (1991) estimates that for each centimetre of colonized root there is an increase of 15 cm3 on the volume of soil explored, this value can increase to 200 cm3 depending on the circumstances. Due to the enhancement of the volume of soil explored and the ability of the extraradical mycelium to absorb and translocate nutrients to the plant, one of the most obvious and important advantages resulting from mycorrhization is the uptake of nutrients. Among of which the ones that have immobilized forms in soil, such as P, assume particular significance. Besides this, many other benefits are recognized for AM plants (Gupta et al, 2000): water stress alleviation (Augé, 2004; Cho et al, 2006), protection from root pathogens (Graham, 2001), tolerance to toxic heavy metals and phytoremediation (Audet and Charest, 2006; Göhre and Paszkowski, 2006), tolerance to adverse conditions such as very high or low temperature, high salinity (Sannazzaro et al, 2006), high or low pH (Yano and Takaki, 2005) or better performance during transplantation shock (Subhan et al, 1998). The extraradical hyphae also stabilize soil aggregates by both enmeshing soil particles (Miller e Jastrow, 1992) and producing a glycoprotein, golmalin, which may act as a glue-like substance to adhere soil particles together (Wright and Upadhyaya, 1998). Despite the ubiquous distribution of mycorrhizal fungi (Smith and Read, 2000) and only a relative specificity between host plants and fungal isolates (McGonigle and Fitter, 1990), the obligate nature of the symbiosis implies the establishment of a plant propagation system, either under greenhouse conditions or in vitro laboratory propagation. These techniques result in high inoculum production costs, which still remains a serious problem since they are not competitive with production costs of phosphorus fertilizer. Even if farmers understand the significance of sustainable agricultural systems, the reduction of phosphorus inputs by using AM fungal inocula alone cannot be justified except, perhaps, in the case of high value crops (Saioto and Marumoto, 2002). Nurseries, high income horticulture farmers and no-agricultural application such as rehabilitation of degraded or devegetated landscapes are examples of areas where the use of commercial inoculum is current. Another serious problem is quality of commercial available products concerning guarantee of phatogene free content, storage conditions, most effective application methods and what types to use. Besides the information provided by suppliers about its inoculum can be deceiving, as from the usually referred total counts, only a fraction may be effective for a particular plant or in specific soil conditions. Gianinazzi and Vosátka (2004) assume that progress should be made towards registration procedures that stimulate the development of the mycorrhizal industry. Some on-farm inoculum production and application methods have been studied, allowing farmers to produce locally adapted isolates and generate a taxonomically diverse inoculum (Mohandas et al, 2004; Douds et al, 2005). However the inocula produced this way are not readily processed for mechanical application to the fields, being an obstacle to the utilization in large scale agriculture, especially row crops, moreover it would represent an additional mechanical operation with the corresponding economic and soil compaction costs. It is well recognized that inoculation of AM fungi has a potential significance in not only sustainable crop production, but also environmental conservation. However, the status quo of inoculation is far from practical technology that can be widely used in the field. Together a further basic understanding of the biology and diversity of AM fungi is needed (Abbott at al, 1995; Saito and Marumoto, 2002). Advances in ecology during the past decade have led to a much more detailed understanding of the potential negative consequences of species introductions and the potential for negative ecological consequences of invasions by mycorrhizal fungi is poorly understood. Schwartz et al, (2006) recommend that a careful assessment documenting the need for inoculation, and the likelihood of success, should be conducted prior to inoculation because inoculations are not universally beneficial. Agricultural practices such as crop rotation, tillage, weed control and fertilizer apllication all produce changes in the chemical, physical and biological soil variables and affect the ecological niches available for occupancy by the soil biota, influencing in different ways the symbiosis performance and consequently the inoculum development, shaping changes and upset balance of native populations. The molecular biology tools developed in the latest years have been very important for our perception of these changes, ensuing awareness of management choice implications in AM development. In this context, for extensive farming systems and regarding environmental and economic costs, the identification of agronomic management practices that allow controlled manipulation of the fungal community and capitalization of AM mutualistic effect making use of local inoculum, seem to be a wise option for mycorrhiza promotion and development of sustainable crop production

Assessing the Effect of Disturbances on Ectomycorrhiza Diversity

Ectomycorrhiza (ECM) communities can be described on a species level or on a larger scale at an ecosystem level. Here we show that the species level approach of successional processes in ECM communities is not appropriate for understanding the diversity patterns of ECM communities at contaminated sites. An ecosystem based approach improves predictability since different biotic and abiotic factors are included. However, it still does not take into account the hierarchical structure of the ecosystem. We suggest that diversity patterns of ECMs communities in forests can best be investigated at three levels. This hypothetical approach for investigation can be tested at sites of secondary succession in areas contaminated with metals. Once the diversity patterns are appropriately described by a hierarchical ecosystem approach, to the species level is used to explain these patterns by populational and ecotoxicological mechanisms