Boosting species evenness, productivity and weed control in a mixed meadow by promoting arbuscular mycorrhizas

Lowland meadows represent aboveground and belowground biodiversity reservoirs in intensive agricultural areas, improving water retention and filtration, ensuring forage production, contrasting erosion and contributing to soil fertility and carbon sequestration. Besides such major ecosystem services, the presence of functionally different plant species improves forage quality, nutritional value and productivity, also limiting the establishment of weeds and alien species. Here, we tested the effectiveness of a commercial seed mixture in restoring a lowland mixed meadow in the presence or absence of inoculation with arbuscular mycorrhizal (AM) fungi and biostimulation of symbiosis development with the addition of short chain chito-oligosaccharides (CO). Plant community composition, phenology and productivity were regularly monitored alongside AM colonization in control, inoculated and CO-treated inoculated plots. Our analyses revealed that the CO treatment accelerated symbiosis development significantly increasing root colonization by AM fungi. Moreover, the combination of AM fungal inoculation and CO treatment improved plant species evenness and productivity with more balanced composition in forage species. Altogether, our study presented a successful and scalable strategy for the reintroduction of mixed meadows as valuable sources of forage biomass; demonstrated the positive impact of CO treatment on AM development in an agronomic context, extending previous observations developed under controlled laboratory conditions and leading the way to the application in sustainable agricultural practices.

An Extract from Ficus carica Cell Cultures Works as an Anti-Stress Ingredient for the Skin

Psychological stress activates catecholamine production, determines oxidation processes, and alters the lipid barrier functions in the skin. Scientific evidence associated with the detoxifying effect of fruits and vegetables, the growing awareness of the long-term issues related to the use of chemical-filled cosmetics, the aging of the population, and the increase in living standards are the factors responsible for the growth of food-derived ingredients in the cosmetics market. A Ficus carica cell suspension culture extract (FcHEx) was tested in vitro (on keratinocytes cells) and in vivo to evaluate its ability to manage the stress-hormone-induced damage in skin. The FcHEx reduced the epinephrine (-43% and -24% at the concentrations of 0.002% and 0.006%, respectively), interleukin 6 (-38% and -36% at the concentrations of 0.002% and 0.006%, respectively), lipid peroxide (-25%), and protein carbonylation (-50%) productions; FcHEx also induced ceramide synthesis (+150%) and ameliorated the lipid barrier performance. The in vivo experiments confirmed the in vitro test results. Transepidermal water loss (TEWL; -12.2%), sebum flow (-46.6% after two weeks and -73.8% after four weeks; on the forehead -56.4% after two weeks and -80.1% after four weeks), and skin lightness (+1.9% after two weeks and +2.7% after four weeks) defined the extract's effects on the skin barrier. The extract of the Ficus carica cell suspension cultures reduced the transepidermal water loss, the sebum production, the desquamation, and facial skin turning to a pale color from acute stress, suggesting its role as an ingredient to fight the signs of psychological stress in the skin.

Extraction of short chain chitooligosaccharides from fungal biomass and their use as promoters of arbuscular mycorrhizal symbiosis

Short chain chitooligosaccharides (COs) are chitin derivative molecules involved in plant-fungus signaling during arbuscular mycorrhizal (AM) interactions. In host plants, COs activate a symbiotic signalling pathway that regulates AM-related gene expression. Furthermore, exogenous CO application was shown to promote AM establishment, with a major interest for agricultural applications of AM fungi as biofertilizers. Currently, the main source of commercial COs is from the shrimp processing industry, but purification costs and environmental concerns limit the convenience of this approach. In an attempt to find a low cost and low impact alternative, this work aimed to isolate, characterize and test the bioactivity of COs from selected strains of phylogenetically distant filamentous fungi: Pleurotus ostreatus, Cunninghamella bertholletiae and Trichoderma viride. Our optimized protocol successfully isolated short chain COs from lyophilized fungal biomass. Fungal COs were more acetylated and displayed a higher biological activity compared to shrimp-derived COs, a feature that-alongside low production costs-opens promising perspectives for the large scale use of COs in agriculture.

Symmetric dimethylarginine concentrations in dogs with hypothyroidism before and after treatement with levothyroxine

OBJECTIVES

To evaluate the serum symmetric dimethylarginine (SDMA) and serum creatinine concentrations in a population of hypothyroid dogs at the time of diagnosis and after treatment.

MATERIALS AND METHODS

Serum SDMA and serum creatinine were measured in serum samples of 24 healthy dogs and 24 hypothyroid dogs, at the time of diagnosis (T0) and after supplementation with levothyroxine (T1).

RESULTS

The mean SDMA concentrations (reference intervals [RI] <18 μg/dL and <14 μg/dL depending on the source) were 11.7 ± 3.5 μg/dL, 13.8 ± 3.1 μg/dL and 11.83 ± 2.87 μg/dL in healthy dogs, and in the hypothyroid dogs at T0 and T1, respectively. The SDMA concentrations were higher in the hypothyroid dogs at T0 in comparison with the healthy dogs. Of the hypothyroid dogs, 1 out of 24 had an SDMA concentration above 18 μg/dL and 12 out of 24 above 14 μg/dL at T0. At T1, none of the hypothyroid dogs had SDMA concentrations above 18 μg/dL and two of them had SDMA concentrations above 14 μg/dL. The serum creatinine concentration was higher in the hypothyroid dogs at T0 as compared to the healthy dogs. At T0, 8 out of 24 hypothyroid dogs had serum creatinine concentrations above the RI (>1.4 mg/dL). In all but one dog, serum creatinine normalised after treatment.

CLINICAL SIGNIFICANCE

The SDMA and serum creatinine concentrations were higher in hypothyroid dogs at diagnosis as compared to healthy dogs. Serum creatinine concentrations were increased in one-third of the hypothyroid dogs and in the majority of cases normalised after levothyroxine supplementation. SDMA concentrations were rarely above the upper limit of the RI when the higest (<18 μg/dL) cut-off was employed. The diagnostic accuracy of SDMA in dogs with thyroid dysfunction requires additional evaluation.

TPLATE Recruitment Reveals Endocytic Dynamics at Sites of Symbiotic Interface Assembly in Arbuscular Mycorrhizal Interactions

Introduction: Arbuscular mycorrhizal (AM) symbiosis between soil fungi and the majority of plants is based on a mutualistic exchange of organic and inorganic nutrients. This takes place inside root cortical cells that harbor an arbuscule: a highly branched intracellular fungal hypha enveloped by an extension of the host cell membrane-the perifungal membrane-which outlines a specialized symbiotic interface compartment. The perifungal membrane develops around each intracellular hypha as the symbiotic fungus proceeds across the root tissues; its biogenesis is the result of an extensive exocytic process and shows a few similarities with cell plate insertion which occurs at the end of somatic cytokinesis. Materials and Methods: We here analyzed the subcellular localization of a GFP fusion with TPLATE, a subunit of the endocytic TPLATE complex (TPC), a central actor in plant clathrin-mediated endocytosis with a role in cell plate anchoring with the parental plasma membrane. Results: Our observations demonstrate that Daucus carota and Medicago truncatula root organ cultures expressing a 35S::AtTPLATE-GFP construct accumulate strong fluorescent green signal at sites of symbiotic interface construction, along recently formed perifungal membranes and at sites of cell-to-cell hyphal passage between adjacent cortical cells, where the perifungal membrane fuses with the plasmalemma. Discussion: Our results strongly suggest that TPC-mediated endocytic processes are active during perifungal membrane interface biogenesis-alongside exocytic transport. This novel conclusion, which might be correlated to the accumulation of late endosomes in the vicinity of the developing interface, hints at the involvement of TPC-dependent membrane remodeling during the intracellular accommodation of AM fungi.

Local endoreduplication as a feature of intracellular fungal accommodation in arbuscular mycorrhizas

The intracellular accommodation of arbuscular mycorrhizal (AM) fungi is a paradigmatic feature of this plant symbiosis that depends on the activation of a dedicated signaling pathway and the extensive reprogramming of host cells, including striking changes in nuclear size and transcriptional activity. By combining targeted sampling of early root colonization sites, detailed confocal imaging, flow cytometry and gene expression analyses, we demonstrate that local, recursive events of endoreduplication are triggered in the Medicago truncatula root cortex during AM colonization. AM colonization induces an increase in ploidy levels and the activation of endocycle specific markers. This response anticipates the progression of fungal colonization and is limited to arbusculated and neighboring cells in the cortical tissue. Furthermore, endoreduplication is not induced in M. truncatula mutants for symbiotic signaling pathway genes. On this basis, we propose endoreduplication as part of the host cell prepenetration responses that anticipate AM fungal accommodation in the root cortex.

Size matters: three methods for estimating nuclear size in mycorrhizal roots of Medicago truncatula by image analysis

BACKGROUND

The intracellular accommodation of arbuscular mycorrhizal (AM) fungi involves a profound molecular reprogramming of the host cell architecture and metabolism, based on the activation of a symbiotic signaling pathway. In analogy with other plant biotrophs, AM fungi are reported to trigger cell cycle reactivation in their host tissues, possibly in support of the enhanced metabolic demand required for the symbiosis.

RESULTS

We here compare the efficiency of three Fiji/ImageJ image analysis plugins in localizing and quantifying the increase in nuclear size - a hallmark of recursive events of endoreduplication - in M. truncatula roots colonized by the AM fungus Gigaspora margarita. All three approaches proved to be versatile and upgradeable, allowing the investigation of nuclear changes in a complex tissue; 3D Object Counter provided more detailed information than both TrackMate and Round Surface Detector plugins. On this base we challenged 3D Object Counter with two case studies: verifying the lack of endoreduplication-triggering responses in Medicago truncatula mutants with a known non-symbiotic phenotype; and analysing the correlation in space and time between the induction of cortical cell division and endoreduplication upon AM colonization. Both case studies revealed important biological aspects. Mutant phenotype analyses have demonstrated that the knock-out mutation of different key genes in the symbiotic signaling pathway block AM-associated endoreduplication. Furthermore, our data show that cell divisions occur during initial stages of root colonization and are followed by recursive activation of the endocycle in preparation for arbuscule accommodation.

CONCLUSIONS

In conclusion, our results indicate 3D Object Counter as the best performing Fiji/ImageJ image analysis script in plant root thick sections and its application highlighted endoreduplication as a major feature of the AM pre-penetration response in root cortical cells.

Size matters: three methods for estimating nuclear size in mycorrhizal roots of Medicago truncatula by image analysis

BACKGROUND

The intracellular accommodation of arbuscular mycorrhizal (AM) fungi involves a profound molecular reprogramming of the host cell architecture and metabolism, based on the activation of a symbiotic signaling pathway. In analogy with other plant biotrophs, AM fungi are reported to trigger cell cycle reactivation in their host tissues, possibly in support of the enhanced metabolic demand required for the symbiosis.

RESULTS

We here compare the efficiency of three Fiji/ImageJ image analysis plugins in localizing and quantifying the increase in nuclear size - a hallmark of recursive events of endoreduplication - in M. truncatula roots colonized by the AM fungus Gigaspora margarita. All three approaches proved to be versatile and upgradeable, allowing the investigation of nuclear changes in a complex tissue; 3D Object Counter provided more detailed information than both TrackMate and Round Surface Detector plugins. On this base we challenged 3D Object Counter with two case studies: verifying the lack of endoreduplication-triggering responses in Medicago truncatula mutants with a known non-symbiotic phenotype; and analysing the correlation in space and time between the induction of cortical cell division and endoreduplication upon AM colonization. Both case studies revealed important biological aspects. Mutant phenotype analyses have demonstrated that the knock-out mutation of different key genes in the symbiotic signaling pathway block AM-associated endoreduplication. Furthermore, our data show that cell divisions occur during initial stages of root colonization and are followed by recursive activation of the endocycle in preparation for arbuscule accommodation.

CONCLUSIONS

In conclusion, our results indicate 3D Object Counter as the best performing Fiji/ImageJ image analysis script in plant root thick sections and its application highlighted endoreduplication as a major feature of the AM pre-penetration response in root cortical cells.

Ectopic activation of cortical cell division during the accommodation of arbuscular mycorrhizal fungi

Arbuscular mycorrhizas (AMs) between plants and soil fungi are widespread symbioses with a major role in soil nutrient uptake. In this study we investigated the induction of root cortical cell division during AM colonization by combining morphometric and gene expression analyses with promoter activation and protein localization studies of the cell-plate-associated exocytic marker TPLATE. Our results show that TPLATE promoter is activated in colonized cells of the root cortex where we also observed the appearance of cells that are half the size of the surrounding cells. Furthermore, TPLATE-green fluorescent protein recruitment to developing cell plates highlighted ectopic cell division events in the inner root cortex during early AM colonization. Lastly, transcripts of TPLATE, KNOLLE and Cyclinlike 1 (CYC1) are all upregulated in the same context, alongside endocytic markers Adaptor-Related Protein complex 2 alpha 1 subunit (AP2A1) and Clathrin Heavy Chain 2 (CHC2), known to be active during cell plate formation. This pattern of gene expression was recorded in wild-type Medicago truncatula roots, but not in a common symbiotic signalling pathway mutant where fungal colonization is blocked at the epidermal level. Altogether, these results suggest the activation of cell-division-related mechanisms by AM hosts during the accommodation of the symbiotic fungus.

Catalytic Effect of Pd Clusters in the Poly(N-vinyl-2-pyrrolidone) Combustion

Pd(0) is able to catalyze oxygen-involving reactions because of its capability to convert molecular oxygen to the very reactive atomic form. Consequently, the embedding of a little amount of Pd(0) clusters in polymeric phases can be technologically exploited to enhance the incineration kinetic of these polymers. The effect of nanostructuration on the Pd(0) catalytic activity in the polymer incineration reaction has been studied using poly(N-vinyl-2-pyrrolidone) ([Formula: see text] = 10,000 gmol^-1) as polymeric model system. A change in the PVP incineration kinetic mechanism with significant increase in the reaction rate was experimentally found. The kinetic of the Pd(0)-catalyzed combustion has been studied by isothermal thermogravimetric analysis. After a short induction time, the combustion in presence of Pd(0) clusters shifted to a zero-order kinetic from a second-order kinetic control, which is operative in pure PVP combustion reaction. In addition, the activation energy resulted much lowered compared to the pure PVP incineration case (from 300 to 260 kJ/mol).

Graphene oxide prepared by graphene nanoplatelets and reduced by laser treatment

The Hummers' method for graphite oxide (GO) preparation has been applied to graphite nanoplatelets, in order to achieve higher reaction yield and faster kinetics. Aqueous GO solutions have been used to produce uniform GO films on a polyethylene terephthalate substrate, generating graphene patterns in a controlled way (widths of a few tens of microns). The reduction of GO deposited on the polymeric substrate has been performed by using a Nd:YVO₄ continuous-wave frequency-duplicated laser. Spectroscopic and diffractometric characterizations (FT-IR, visible-NIR, Raman, XPS, and XRD) have shown that the reduction process induced by the laser annealing technique is mainly due to dehydration of the GO layers. It has been obtained by means of a suitable laser optical apparatus, a controlled reduction of GO without damaging the substrate, and precise writing of micro-tracks that can be used as electrically and thermally conductive patterns.

The rice LysM receptor-like kinase OsCERK1 is required for the perception of short-chain chitin oligomers in arbuscular mycorrhizal signaling

The rice lysin-motif (LysM) receptor-like kinase OsCERK1 is now known to have a dual role in both pathogenic and symbiotic interactions. Following the recent discovery that the Oscerk1 mutant is unable to host arbuscular mycorrhizal (AM) fungi, we have examined whether OsCERK1 is directly involved in the perception of the short-chain chitin oligomers (Myc-COs) identified in AM fungal exudates and shown to activate nuclear calcium (Ca²⁺ ) spiking in the rice root epidermis. An Oscerk1 knockout mutant expressing the cameleon NLS-YC2.60 was used to monitor nuclear Ca²⁺ signaling following root treatment with either crude fungal exudates or purified Myc-COs. Compared with wild-type rice, Ca²⁺ spiking responses to AM fungal elicitation were absent in root atrichoblasts of the Oscerk1 mutant. By contrast, rice lines mutated in OsCEBiP, encoding the LysM receptor-like protein which associates with OsCERK1 to perceive chitin elicitors of the host immune defense pathway, responded positively to Myc-COs. These findings provide direct evidence that the bi-functional OsCERK1 plays a central role in perceiving short-chain Myc-CO signals and activating the downstream conserved symbiotic signal transduction pathway.

A new micromechanical approach for the preparation of graphene nanoplatelets deposited on polyethylene

An advantageous micromechanical technique to deposit large area graphene nanoplatelet (GNP) thin films on a low-density polyethylene substrate is proposed. This method is based on the application of shear-stress and friction forces to a graphite platelets/ethanol paste on the surface of a polymeric substrate; it allows us to obtain a continuous film of superimposed nanoplatelets mainly made of 13-30 graphene layers. X-ray diffraction (XRD), atomic force and transmission electron microscopy (TEM) measurements support the occurrence of a partial exfoliation of the graphite platelets due to shear-stress and friction forces applied during film formation. Scanning electron microscopy (SEM) observations point out that the surface of the polymer is uniformly coated by the overlap of GNPs, and TEM analysis reveals the tendency of the nanoplatelets to align parallel to the interface plane. It has been found that the deposited samples, under white light illumination, exhibit a negative photoconductivity and a linear photoresponse as a function of the applied voltage and the optical power density in the -120 ÷ 120 mV and 20.9 ÷ 286.2 mW cm^-2 ranges, respectively.

Comparative facile methods for preparing graphene oxide-hydroxyapatite for bone tissue engineering

Motivated by the success of using graphene oxide (GO) as a nanofiller of composites, there is a drive to search for this new kind of carbon material as a bioactive component in ceramic materials. In the present study, biomineralized GO was prepared by two different approaches, represented by in situ sol-gel synthesis and biomimetic treatment. It was found that in the biocomposites obtained by the sol-gel approach, the spindle-like hydroxyapatite nanoparticles, with a diameter of ca. 5 ± 0.37 nm and a length of ca. 70 ± 2.5 nm, were presented randomly and strongly on the surface. The oxygen-containing functional groups, such as hydroxyl and carbonyl, present on the basal plane and edges of the GO sheets, play an important role in anchoring calcium ions, as demonstrated by FT-IR and TEM investigations. A different result was obtained for biocomposites after biomimetic treatment: an amorphous calcium phosphate on GO sheet was observed after 5 days of treatment. These different approaches resulted in a diverse effect on the proliferation and differentiation of osteogenic mesenchymal stem cells. In fact, in biocomposites prepared by the sol-gel approach the expression of an early marker of osteogenic differentiation, ALP, increases with the amount of GO in the first days of cell culture. Meanwhile, biomimetic materials sustain cell viability and proliferation, even if the expression of alkaline phosphatase activity in a basal medium is delayed. These findings may provide new prospects for utilizing GO-based hydroxyapatite biocomposites in bone repair, bone augmentation and coating of biomedical implants and broaden the application of GO sheets in biological areas. Copyright © 2016 John Wiley & Sons, Ltd.

Niobia supported on silica as a catalyst for Biodiesel production from waste oil

The activity and stability of niobia supported on silica catalyst have been tested in continuous micro-pilot reactors, for biodiesel production starting from acid vegetable oils. A catalyst was prepared by the impregnation of silica pellets with a loading of 12% of Nb and was extensively characterized. The activity of this catalyst in both esterification and transesterification was tested in a continuous micro-pilot laboratory plant in which acid oil was fed (FFA 10% w/w) at a temperature of 220°C and at a pressure of 60 bar. The niobia based catalyst resulted in a very active catalyst in both esterification (FFA conversion = 95-90%) and transesterification reactions (FAME yield = 80-90%), and the activity remained quite constant for more than 100 h on stream. Notwithstanding this stability, a non-negligible leaching phenomena has been detected, in the case of long-time continuous runs, as the Nb concentration on the spent catalyst resulted lower than that on the fresh one. The obtained result confirms that the leaching of the active specie is one of the most strong problem in heterogeneous catalysis for biodiesel production.

Holographic patterning of graphene-oxide films by light-driven reduction

We report on the patterning and reduction of graphene-oxide films by holographic lithography. Light reduction can be used to engineer low-cost graphene-based devices by performing a local conversion of insulating oxide into the conductive graphene. In this work, computer-generated holograms have been exploited to realize complex graphene patterns in a single shot, different from serial laser writing or mask-based photolithographic processes. The technique has been further improved by achieving speckle noise reduction: submicron and diffraction-limited features have been obtained. In addition we have also demonstrated that the gray-scale lithography capability can be used to obtain different reduction levels in a single exposure.

First Report of Necrotic Leaf Spot Caused by Plectosphaerella cucumerina on Lamb's Lettuce in Southern Italy

During spring 2013, lamb's lettuce plants (Valerianella locusta) cv. Calarasi (Rijk Zwaan) in a commercial greenhouse in Sele Valley (Salerno Province, southern Italy) exhibited small, black-brown, irregular spots (1 mm²) that became necrotic, enlarged, and coalesced. The spots were mostly on the tips of leaves, and were surrounded by a yellow halo. The disease was severe under greenhouse conditions of 60 to 90% RH and maximum air temperature of 26°C, and affected up to 70% of the plants. The greenhouses covered an area of ~3,000 ha where many salad species are grown. Tissue fragments were excised from symptomatic leaves, sterilized by sequential dipping in 70% ethanol for 30 s and in 1% NaOCl for 30 s, rinsed in sterilized distilled water, and placed in 9-cm-diameter petri dishes containing potato dextrose agar (PDA) medium amended with streptomycin sulfate (0.1 g/liter). The plates were incubated at 24°C in the dark. A fungus was isolated consistently from infected leaf tissue after 4 days. Each colony was whitish to orange. Mycelium was hyaline, branched, septate, 3 to 4 μm wide, with numerous anastomosis-forming hyphal coils. Conidiophores were solitary, hyaline, smooth, thin-walled, unbranched or rarely irregularly branched. Conidiogenous cells were phialidic, determinate, discrete, smooth, solitary, and formed on hyphal coils. Phialides were aseptate or occasionally 1-septate near the base. Conidia (n = 100) were ellipsoidal, hyaline, smooth, septate or aseptate, and 6.6 ± 0.9 × 2.8 ± 0.4 μm. On the basis of morphological criteria (3), the fungus was ascribed to Plectosphaerella cucumerina (L.) Laterr. (anamorph Plectosporium tabacinum). An aliquot (50 ng) of genomic DNA extracted from mycelium of five cultures obtained by monosporic isolation on PDA was used as template for a PCR reaction with primers ITS5/ITS4, specific for the ITS 5.8S rDNA region of fungi (3). The 500-bp sequences amplified from the five isolates were identical, and the sequence of isolate Val-2 was submitted to GenBank (KF753234). Sequence analysis with BLASTn showed 100% identity of this sequence to the ITS-5.8S rDNA sequences of 11 isolates of P. cucumerina in GenBank. Three isolates were selected for pathogenicity tests on the lamb's lettuce cv. Calarasi. Before planting, seeds were surface-disinfected in 1% NaOCl and rinsed with sterilized distilled water. Plants (35 days old, 30 plants tested/isolate) were grown in 0.7-liter pots filled with a sterilized (autoclaved at 112°C for 1 h on each of two consecutive days) mixture of soil:sand:perlite (2:1:1), and inoculated by spraying the leaves with a spore suspension (10⁶ CFU/ml, ~3 ml applied/plant) of each isolate prepared from 7-day-old cultures on PDA. As a control, five plants were sprayed with sterilized water. All plants were incubated in a growth chamber at 90% RH with a 12-h photoperiod at 24°C. Leaf spots typical of those on the original symptomatic plants appeared 7 to 10 days after inoculation on all inoculated plants. No symptoms were observed on control plants. P. cucumerina was re-isolated only from symptomatic leaves, as described for the original isolations. P. cucumerina has been associated with root and collar roots of some horticultural crops (1), and a leaf spot on Diplotaxis tenuifolia (2), often grown in rotation with lamb's lettuce in southern Italy. To our knowledge, this is the first report of P. cucumerina as a pathogen of V. locusta in Italy or elsewhere. The disease caused economic loss to lamb's lettuce, primarily used in Italy in fresh-cut, mixed salads. References: (1) A. Carlucci et al. Persoonia 28:34, 2012. (2) A. Garibaldi et al. Plant Dis. 96:1825, 2012. (3) T. J. White et al. PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, CA, 1990.

Mechanical properties of low-density polyethylene filled by graphite nanoplatelets

The mechanical properties of GNP/LDPE nanocomposites (graphite nanoplatelets/low density polyethylene) have been investigated, in order to establish the effect of nanoscale reinforcement within the polymer matrix. Results show that the presence of the filler does not involve a change in the microscopic structure of the polymer. However, on a macroscopic scale, GNPs limit the mobility of the polymer chains, resulting in an increase in stiffness for the final composite. Orientation of GNPs within the LDPE matrix is also an important issue that affects mechanical properties and it has been evaluated by testing nanocomposites made by different manufacturing techniques (compression moulding and blown extrusion). The comparison between the experimental data and the Halpin-Tsai model shows that the orientation of GNPs due to the extrusion process leads to values of tensile modulus higher than that obtained with the randomly oriented disposition resulting from the compression moulding technique.

Macroporous hydroxyapatite as alloplastic material for dental applications

In the dentistry field, synthetic hydroxyapatite can be conveniently used as semiabsorbable alloplastic material to solve a number of clinical problems. The hydroxyapatite structure influences bone ingrowth as well as its resorption. In particular, pore size must exceed 100 microm to allow new bone ingrowth. Because of its brittleness, highly porous hydroxyapatite is difficult to handle without causing damage, and, therefore, its mechanical performance has to be improved placing the material on a dense hydroxyapatite substrate. Dense/porous hydroxyapatite laminates can be obtained by slip casting technology. The method starts with the preparation of a ceramic powder-binder-solvent system. This slurry produces, after solvent evaporation, a soft green tape, that is successively baked at 300 degrees C to remove all organic component, and finally sintered at high temperature (1200 degrees C). The material porosity cannot be significantly modified by changes in the slurry composition and sintering temperature; therefore, the macroporous hydroxyapatite layer must be obtained using a porous hydroxyapatite powder. The powder is prepared by grinding of green tape pieces and the resulting coarse material is successively baked at 300 degrees C. Such material is mixed with a polymer solution and cast on a green tape substrate. Layer fractures are not observed in both film bulks and interface, because during sintering the consolidation of two layers happens simultaneously. In the resulting material, the first layer consisted of macroporous hydroxyapatite with high osteoconductive properties, and the second layer was a dense hydroxyapatite substrate able to improve the laminate mechanical properties.

Characterization of the interface between prefabricated gold copings and cast dental alloy in implant restorations

The objective of this study was to analyse the characteristics of the metal interface between the casting of a dental noble alloy and prefabricated gold copings (OCTA-ITI Implant System) after the fabrication procedures of a prosthetic implant-retained superstructure. The microscopical investigation, performed by optical microscopy (OM) and scanning electron microscopy (SEM), of the region around the cylinder after the casting process and the subsequent porcelain firing procedures showed the presence of an ideal interface, including: i) maintenance of coping and casting alloy microstructures up to the interface, and ii) absence of interfacial reaction products. A low content of porosity (less than 3% by volume in average) was observed in the casting alloy bulk as well as at interface. The investigation by energy-dispersive spectroscopy (EDS) of the alloy composition close to the interface showed the presence of a minimal elemental interdiffusion, suggesting that an adequate compatibility between alloy and coping characterized the materials used. A small decrease of the prefabricated coping hardness was also observed after the casting and porcelain firing procedures.

Preparation and characterization of new electrocardiogram electrodes

A new generation of electrocardiogram (ECG) electrodes have been fabricated and superficially modified by a special controlled precorrosion process. The electrodes have been characterized by scanning electron microscopy (SEM), resistance-capacitance measurements (RCM) and simulated defibrillation recovery (SDR). The resulting surface of the Sn alloys was rough, and, consequently, a large active surface area was available. As a result, a higher electrocardiogram electrode performance, including low alternating current (a.c.) impedance, excellent time stability and improved SDR, was achieved. Such new design can surely find important future applications in clinical diagnosis.

Comparison between in vitro and in vivo UHMW-PE degradation

There is an increasing interest in orthopedics for clinical problems associated with wear and failure of ultra-high-molecular-weight (UHMW) polyethylene devices. Wear not only affects the implant performance but, more importantly, produces the release of particulate debris in the surrounding tissues and fluids. The debris in turn cause a deleterious biological response that can include an inflammatory reaction with subsequent loosening of the implant components. Surface wear is certainly promoted from the oxidation process that can occur during the prosthesis life. However, the oxidation mechanism involved during the implantation period has not been described yet for the UHMW-polyethylene devices. Here, the comparison of FT-IR spectra of a retrieved acetabular cup (9 years in a human body) and thin UHMW-PE films treated respectively with: H2O2, KO2/THF, and Fe[II]/H2O2 solutions indicates the effect of the high reactive hydroxyl radicals as the most important cause of in vivo polymer degradation.