Bioprinting on sheet-based scaffolds applied to the creation of implantable tissue-engineered constructs with potentially diverse clinical applications: Tissue-Engineered Muscle Repair (TEMR) as a representative testbed.

Purpose: This report explores the overlooked potential of bioprinting to automate biomanufacturing of simple tissue structures, such as the uniform deposition of (mono)layers of progenitor cells on sheetlike decellularized extracellular matrices (dECM). In this scenario, dECM serves as a biodegradable celldelivery matrix to provide enhanced regenerative microenvironments for tissue repair. The Tissue-Engineered Muscle Repair (TEMR) technology-where muscle progenitor cells are seeded onto a porcine bladder acellular matrix (BAM), serves as a representative testbed for bioprinting applications. Previous work demonstrated that TEMR implantation improved functional outcomes following VML injury in biologically relevant rodent models.Materials and Methods: In the described bioprinting system, a cell-laden hydrogel bioink is used to deposit high cell densities (1.4 × 105-3.5 × 105 cells/cm2), onto both sides of the bladder acellular matrix as proof-of-concept.Results: These bioprinting methods achieve a reproducible and homogeneous distribution of cells, on both sides of the BAM scaffold, after just 24hrs, with cell viability as high as 98%. These preliminary results suggest bioprinting allows for improved dual-sided cell coverage compared to manual-seeding.Conclusions: Bioprinting can enable automated fabrication of TEMR constructs with high fidelity and scalability, while reducing biomanufacturing costs and timelines. Such bioprinting applications are underappreciated, yet critical, to expand the overall biomanufacturing paradigm for tissue engineered medical products. In addition, biofabrication of sheet-like implantable constructs, with cells deposited on both sides, is a process that is both scaffold and cell-type agnostic, and furthermore, is amenable to many geometries, and thus, additional tissue engineering applications beyond skeletal muscle.

Visualizing surface plasmons with photons, photoelectrons, and electrons.

Both photons and electrons may be used to excite surface plasmon polaritons, the collective charge density fluctuations at the surface of metal nanostructures. By virtue of their nanoscopic and dissipative nature, a detailed characterization of surface plasmon (SP) eigenmodes in real space-time ultimately requires joint nanometer spatial and femtosecond temporal resolution. The latter realization has driven significant developments in the past few years, aimed at interrogating both localized and propagating SP modes. In this mini-review, we briefly highlight different techniques employed by our own groups to visualize the enhanced electric fields associated with SPs. Specifically, we discuss recent hyperspectral optical microscopy, tip-enhanced Raman nano-spectroscopy, nonlinear photoemission electron microscopy, as well as correlated scanning transmission electron microscopy-electron energy loss spectroscopy measurements targeting prototypical plasmonic nanostructures and constructs. Through selected practical examples from our own laboratories, we examine the information content in multidimensional images recorded by taking advantage of each of the aforementioned techniques. In effect, we illustrate how SPs can be visualized at the ultimate limits of space and time.

A mechanism of Cu work function reduction in CsBr/Cu photocathodes.

Thin films of CsBr deposited on Cu(100) have been proposed as next-generation photocathode materials for applications in particle accelerators and free-electron lasers. However, the mechanisms underlying an improved photocathode performance as well as their long-term stability remain poorly understood. We present Density Functional Theory (DFT) calculations of the work function reduction following the application of CsBr thin film coatings to Cu photocathodes. The effects of both flat and rough interface and van der Waals forces are examined. Calculations suggest that CsBr films can reduce the Cu(100) work function by about 1.5 eV, which would explain the observed increase in quantum efficiency (QE) of coated vs. uncoated photocathodes. A model explaining the experimentally observed laser activation of photocathodes is provided whereby the photo-induced creation of Br vacancies and Cs-Br di-vacancies and their subsequent diffusion to the Cu/CsBr interface lead to a further increase in QE after a period of laser irradiation.

Structure and properties of electronic and hole centers in CsBr from theoretical calculations.

The electronic structure, geometry, diffusion barriers and optical properties of fundamental defects of CsBr are calculated using hybrid functional DFT and TD-DFT methods. The B3LYP functional with a modified exchange contribution has been used in an embedded cluster scheme to model the structure and spectroscopic properties of the self-trapped triplet exciton, interstitial Br atoms and ions, self-trapped holes and Br vacancies. The calculated migration barriers and positions of maxima of optical absorption bands are in good agreement with experiment, justifying the obtained defect geometries. The off-center triplet exciton luminescence energy is also accurately calculated.

Early outcomes and complications of posterior vertebral column resection.

BACKGROUND CONTEXT: Hyperkyphosis confers a significant risk for neurologic deterioration as well as compromised cardiopulmonary function. Posterior vertebral column resection (PVCR) is a challenging but effective technique for spinal cord decompression and deformity correction that even under the setting of limited resources can be performed to reduce the technical difficulties, the operating time, and possibly the complications of the traditional two-staged vertebral column resection (VCR). PURPOSE: To report on the results of VCR performed through a single posterior approach (PVCR) in the treatment of severe rigid kyphosis in a series of patients treated and followed at a Scoliosis Research Society Global Outreach Program site in West Africa. STUDY DESIGN: Retrospective case series. PATIENT SAMPLE: Forty-five consecutive patients treated with PVCR for correction of severe rigid kyphosis. OUTCOME MEASURES: Clinical and radiographic outcomes and complications; Scoliosis Research Society outcome instrument (SRS-22). METHODS: From 2002 to 2009, 45 patients (20 male and 25 female) underwent PVCR for kyphosis from congenital deformity (nine) or secondary to tuberculosis of the spine (36). Preoperative demographics, preop and postop neurologic status, SRS-22 scores and complications were recorded; upright full spine X-rays were available in all patients. Mean age was 14 years (6-47 years); mean follow-up 27 months (2-79 months). Mean preoperative kyphosis measured 108°. The deformity apex was resected via a costotransverse (thoracic) or posterolateral (lumbar) approach; neurosurveillance with sensory (somatosensory-evoked potentials) and motor (motor-evoked potentials) potential was used in all cases. Posterior instrumentation was used in all patients, and anterior structural cage was used in 32 patients. RESULTS: Intraoperative monitoring changes occurred in 10 patients (22%), and one patient progressed to complete spinal cord injury. Average preoperative local kyphosis was 108° and corrected to 600 postoperatively. Postoperatively, no additional patient showed neurologic deterioration; of the 11 patients with preoperative gait disturbances, 4 improved to normal gait, 5 remained the same, and 2 showed deterioration of their walking ability to nonambulating level. Total SRS-22 scores improved from 3.18 to 3.54 (p=.01), primarily self-image domain. CONCLUSIONS: Posterior vertebral column resection was successfully undertaken for the management of thoracic and thoracolumbar hyperkyphosis, demonstrating improvements in overall kyphosis and clinical outcome. Neuromonitoring provided the required safety to perform these challenging complex spine deformity procedures.

Subsurface synthesis and characterization of Ag nanoparticles embedded in MgO.

Metal nanoparticles exhibit a localized surface plasmon resonance (LSPR) which is very sensitive to the size and shape of the nanoparticle and the surrounding dielectric medium. The coupling between the electromagnetic radiation and the localized surface plasmon in metallic nanoparticles results in a sizable enhancement of the incident fields, making them possible candidates for plasmonic applications. In particular, partially exposed metallic nanoparticles distributed in a dielectric matrix can provide prime locations for LSPR spectroscopy and sensing. We report the synthesis and characterization of a plasmonic substrate consisting of Ag nanoparticles partially buried in MgO. Ag nanoparticles of different shapes and size distributions were synthesized below the surface of MgO by implanting 200 keV Ag(+) ions followed by annealing at 1000 °C for 10 and 30 h. A detailed optical and structural characterization was carried out to understand the evolution of the Ag nanoparticle and size distribution inside the MgO matrix. Micro x-ray diffraction (Micro-XRD) was employed to investigate the structural properties and estimate the crystallite size. The nanoparticles evolved from a spherical to a faceted morphology with annealing time, assuming an octahedral shape truncated at the (001) planes, as visualized from aberration-corrected transmission electron microscopy (TEM) images. The nanoparticles embedded in MgO were shown to be pure metallic Ag using atom probe tomography (APT). The nanoparticles were partially exposed to the surface by employing plasma etch techniques to remove the overlaying MgO. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were employed to study the surface morphology and obtain a height distribution for the partially exposed nanoparticles.

Role of Photoexcitation and Field Ionization in the Measurement of Accurate Oxide Stoichiometry by Laser-Assisted Atom Probe Tomography.

The addition of pulsed lasers to atom probe tomography (APT) extends its high spatial and mass resolution capability to nonconducting materials, such as oxides. For a prototypical metal oxide, MgO, the measured stoichiometry depends strongly on the laser pulse energy and applied voltage. Very low laser energies (0.02 pJ) and high electric fields yield optimal stoichiometric accuracy. Correlated APT and aberration-corrected transmission electron microscopy (TEM) are used to establish the high density of corner and terrace sites on MgO sample surfaces before and after APT. For MgO, long-lifetime photoexcited holes localized at oxygen corner sites can assist in the creation of oxygen neutrals that may spontaneously desorb either as atomic O or as molecular O2. The observed trends are best explained by the relative field-dependent ionization of photodesorbed O or O2 neutrals. These results emphasize the importance of considering electronic excitations in APT analysis of oxide materials.

Plasmon-enhanced photocathode for high brightness and high repetition rate x-ray sources.

In this Letter, we report on the efficient generation of electrons from metals using multiphoton photoemission by use of nanostructured plasmonic surfaces to trap, localize, and enhance optical fields. The plasmonic surface increases absorption over normal metals by more than an order of magnitude, and due to the localization of fields, this results in over 6 orders of magnitude increase in effective nonlinear quantum yield. We demonstrate that the achieved quantum yield is high enough for use in rf photoinjectors operating as electron sources for MHz repetition rate x-ray free electron lasers.

A long antisense RNA in plant chloroplasts.

Based on computational prediction of RNA secondary structures, a long antisense RNA (asRNA) was found in chloroplasts of Arabidopsis, Nicotiana tabacum and poplar, which occurs in two to three major transcripts. Mapping of primary 5' ends, northern hybridizations and quantitative real-time reverse transcription polymerase chain reaction (qPCR) experiments demonstrated that these transcripts originate from a promoter that is typical for the plastid-encoded RNA polymerase and are over their full length in antisense orientation to the gene ndhB and therefore were designated asRNA_ndhB. The asRNA_ndhB transcripts predominantly accumulate in young leaves and at physiological growth temperatures. Two nucleotide positions in the mRNA that are subject to C-to-U RNA editing and which were previously found to be sensitive to elevated temperatures are covered by asRNA_ndhB. Nevertheless, the correlation between the accumulation of asRNA_ndhB and RNA editing appeared weak in a temperature shift experiment. With asRNA_ndhB, we describe the first asRNA of plant chloroplasts that covers RNA editing sites, as well as a group II intron splice acceptor site, and that is under developmental control, raising the possibility that long asRNAs could be involved in RNA maturation or the control of RNA stability.

Ecological genomics of marine picocyanobacteria.

Marine picocyanobacteria of the genera Prochlorococcus and Synechococcus numerically dominate the picophytoplankton of the world ocean, making a key contribution to global primary production. Prochlorococcus was isolated around 20 years ago and is probably the most abundant photosynthetic organism on Earth. The genus comprises specific ecotypes which are phylogenetically distinct and differ markedly in their photophysiology, allowing growth over a broad range of light and nutrient conditions within the 45 degrees N to 40 degrees S latitudinal belt that they occupy. Synechococcus and Prochlorococcus are closely related, together forming a discrete picophytoplankton clade, but are distinguishable by their possession of dissimilar light-harvesting apparatuses and differences in cell size and elemental composition. Synechococcus strains have a ubiquitous oceanic distribution compared to that of Prochlorococcus strains and are characterized by phylogenetically discrete lineages with a wide range of pigmentation. In this review, we put our current knowledge of marine picocyanobacterial genomics into an environmental context and present previously unpublished genomic information arising from extensive genomic comparisons in order to provide insights into the adaptations of these marine microbes to their environment and how they are reflected at the genomic level.

Multiple bilateral spinal nerve root calcifications in Charcot-Marie-Tooth disease.

We present a patient with Charcot-Marie-Tooth disease with multiple bilateral symmetrical cervical nerve root calcifications. To our knowledge, such a finding has not been described in the literature in association with this disease. We propose that multiple bilateral symmetrical spinal nerve root calcifications may be an additional imaging feature, possibly diagnostic, in this hereditary motor and spinal neuropathy.

Multiple, novel biologically active endophytic actinomycetes isolated from upper Amazonian rainforests.

Microbial biodiversity provides an increasingly important source of medically and industrially useful compounds. We have isolated 14 actinomycete species from a collection of approximately 300 plant stem samples from the upper Amazonian rainforest in Peru. All of the cultured isolates produce substances with inhibitory activity directed at a range of potential fungal and bacterial pathogens. For some organisms, this activity is very broad in spectrum while other organisms show specific activity against a limited number of organisms. Two of these organisms preferentially inhibit bacterial test organisms over eukaryotic organisms. rDNA sequence analysis indicates that these organisms are not equivalent to any other cultured deposits in GenBank. Our results provide evidence of the untapped biodiversity in the form of biologically active microbes present within the tissues of higher plants.

Synergism among volatile organic compounds resulting in increased antibiosis in Oidium sp.

Oidium sp. has been recovered as an endophyte in Terminalia catappa (tropical chestnut) in Costa Rica. The volatile organic compounds (VOCs) of this organism uniquely and primarily consist of esters of propanoic acid, 2-methyl-, butanoic acid, 2-methyl-, and butanoic acid, 3-methyl-. The VOCs of Oidium sp. are slightly inhibitory to many plant pathogenic fungi. Previous work on the VOCs of Muscodor albus demonstrated that besides esters of small organic acids, a small organic acid and a naphthalene derivative were needed to obtain maximum antibiotic activity. Thus, the addition of exogenous volatile compounds such as isobutyric acid and naphthalene, 1,1'-oxybis caused a dramatic synergistic increase in the antibiotic activity of the VOCs of Oidium sp. against Pythium ultimum. In fact, at elevated concentrations, there was not only 100% inhibition of P. ultimum but killing as well. In addition, a coculture of Muscodor vitigenus (making only naphthalene) and Oidium sp. plus isobutyric acid produced an additive antibiosis effect against P. ultimum. The biological implications of multiple volatile compounds acting to bring about antibiosis in nature are discussed.

Bioactive endophytic streptomycetes from the Malay Peninsula.

Three novel endophytic streptomycetes have been isolated and characterized from plants with ethnobotanical uses on the Malay Peninsula including: Thottea grandiflora (family -Aristolochiaceae), Polyalthia spp. (family -Annonaceae), and Mapania sp. (family -Cyperaceae). Each isolate, as studied by scanning electron microscopy, has small hyphae, and produces typical barrel-shaped spores arising by hyphal fragmentation. Interestingly, although none has any detectable antibacterial killing properties, each has demonstrable killing activity against one or more pathogenic fungi including organisms such as Phytophthora erythroseptica, Pythium ultimum, Sclerotinia sclerotiorum, Mycosphaerella fijiensis and Rhizoctonia solani. Molecular biological studies on the rRNA gene sequence of each isolate revealed that it is distinct from all other genetic accessions of streptomyectes in GenBank, and each bears some genetic similarity to other streptomycetes. The bioactivity of each microbe was extractable in various organic solvents.

Biologically active endophytic streptomycetes from Nothofagus spp. and other plants in Patagonia.

Endophytic streptomycetes have been isolated and characterized from several species of Nothofagus and other plants growing in the southern reaches of Patagonia. No endophytic streptomycete was obtained from any plant species studied in Northern Patagonia. However, from Southern Patagonia, biologically active Streptomyces spp. from several plant species were isolated. Each isolate, as studied by scanning electron microscopy (SEM), has small hyphae, some produce typical barrel-shaped spores in culture and each has some unique hyphal surface structures. Interestingly, although none has any detectable antibacterial killing properties, each has demonstrable killing activity against one or more pathogenic fungi including representative plant pathogenic organisms such as Phytophthora erythroseptica, Pythium ultimum, Sclerotinia sclerotiorum, Mycosphaerella fijiensis, and Rhizoctonia solani. The 16S rDNA sequences of the isolates were distinct from all other genetic accessions of Streptomyces in GenBank. However, isolate C-2 from Chiliotrichum diffusum (Compositae) is identical, in all respects, to isolate C-4 obtained from Misodendrum punctulatum (Loranthaceae). These results confirm that endophytic streptomycetes represent a novel source of biologically active microorganisms.

[Experiments on prosody perception with cochlear implants]. / Experimente zur Perzeption prosodischer Merkmale mit Kochleaimplantaten.

BACKGROUND AND OBJECTIVE: Prosody has a myriad of linguistic functions and involves specific aspects of speech, such as stress, intonation and pauses. The underlying acoustic quantities (amplitude envelope, pitch frequency, and temporal structure) can be processed and transmitted by cochlear implants (CI) only to a limited extent. At present, no adequate tests are available in the German-speaking world for evaluation of the perception of prosodic elements. Different experiments have been conducted to address several prosodic cues, and the results are to be used as a basis for appropriate tests. METHODS: Various prosodic materials were used for the experiments. Discrimination was measured for minimal pairs differing in frequency and/or duration, accents in words and phrases, questions versus statements and phrasing. Measurements were performed in ten normal-hearing subjects and five with cochlear implants. RESULTS AND CONCLUSIONS: In all test modules, the subjects with normal hearing proved to have high discrimination rates of 96-100%. The test of word stresses was problematic because the results were influenced by different confounders. The other measurements did prove to be basically suitable for use in the subjects with implants. Early results revealed that the subjects with CI had few problems with prosodic cues based on the temporal structure, the outcome being similar to that of the subjects with normal hearing in these tests. In contrast, the performance of subjects with CI in perceiving prosodic cues based on amplitude variations and, especially, on alterations in pitch frequency was worse, even though some of them achieved very good results in these tests too. These preliminary tests can form the basis for development of a German-language prosody test battery with a limited number of subtests addressing different prosodic cues.

Scanning electron microscopy of some endophytic streptomycetes in snakevine--Kennedia nigricans.

Soils of all types and locations have generally served as the major sources of streptomycetous bacteria. These organisms are the source of nearly 80% of the world's antibiotics. Now, it is realized that Streptomyces spp. (within the group of prokaryotic filamentous bacteria known as actinomycetes) can exist as endophytes within the interstices of some higher plants. While it is sometimes possible to isolate one or two different streptomycetes from certain plants, most plants are free of these organisms. However, the snakevine (Kennedia nigricans) of the Northern Territory of Australia has yielded at least 39 different endophytic actinomycetes (95% of them being Streptomyces spp.) Most of these isolates possessed no detectable antibiotic properties, while at least seven had antibacterial and antifungal activities. Examination of eight selected cultures by scanning electron microscopy (SEM) as well as environmental scanning electron microcopy (FEI ESEM FEG) (FEI Company, Hillsobro, Ore., USA) revealed unusual patterns, structures, and features of the spores and hyphae of these microorganisms. For instance, as revealed by ESEM FEG for the first time, it has become obvious that extremely fine hair-like structures (average 25-49 nm with gold-coated specimens) exist on the spores and hyphae of some endophytic streptomycetes. The biological purpose of these hair-like protrusions is unknown. Both SEM and ESEM FEG can be effectively used as tools in identification and elucidation of the biology of these organisms. In addition, unusual colony morphology, observed with the unaided eye can very easily be used to distinguish some of these isolates since characteristic donut and pseudo-horn shaped colonies appeared in culture.

New endophytic isolates of Muscodor albus, a volatile-antibiotic-producing fungus.

Muscodor albus, an endophytic fungus originally isolated from Cinnamomum zeylanicum, produces a mixture of volatile organic compounds (VOCs) in culture and its spectrum of antimicrobial activity is broad. Using the original isolate of M. albus as a selection tool, it has been possible to find other culturally and biochemically unique wild-type isolates of this organism existing as endophytes in a variety of other plant species, including Grevillea pterifolia (fern-leafed grevillea), Kennedia nigriscans (snake vine) and Terminalia prostrata (nanka bakarra) growing in the northern reaches of the Northern Territory of Australia. Interestingly, none of the new isolates had a culture morphology that was identical to the original isolate, nevertheless each possessed hyphal characteristics that resembled that isolate. Furthermore, their ITS-5.8S rDNA sequences were 96-99 % identical to that of M. albus and the isolates were considered M. albus on the basis of the DNA sequence data. However, the VOCs produced by these new isolates greatly differed in quality from the original strain by virtue of the production of naphthalene, naphthalene, 1,1'-oxybis-, and one or more other compounds. In bioassays with a range of test micro-organisms, including fungi and bacteria, each isolate possessed biological activity but the range of activity was great. Artificial mixtures of some of the VOCs mimicked the effects of the VOCs of the fungus. The value of these observations to the biology and practical uses of M. albus in agriculture and other applications is discussed.