Relating structure and function of inner hair cell ribbon synapses

In the mammalian cochlea, sound is encoded at synapses between inner hair cells (IHCs) and type I spiral ganglion neurons (SGNs). Each SGN receives input from a single IHC ribbon-type active zone (AZ) and yet SGNs indefatigably spike up to hundreds of Hz to encode acoustic stimuli with submillisecond precision. Accumulating evidence indicates a highly specialized molecular composition and structure of the presynapse, adapted to suit these high functional demands. However, we are only beginning to understand key features such as stimulus-secretion coupling, exocytosis mechanisms, exo-endocytosis coupling, modes of endocytosis and vesicle reformation, as well as replenishment of the readily releasable pool. Relating structure and function has become an important avenue in addressing these points and has been applied to normal and genetically manipulated hair cell synapses. Here, we review some of the exciting new insights gained from recent studies of the molecular anatomy and physiology of IHC ribbon synapses.

The transcription factor VvWRKY33 is involved in the regulation of grapevine (Vitis vinifera) defense against the oomycete pathogen Plasmopara viticola

Grapevine (Vitis vinifera ssp. vinifera) is one of the most important fruit species; however, it is highly susceptible to various pathogens, which can cause severe crop losses in viticulture. It has been shown that several WRKY class transcription factors (TFs) are part of the signal transduction cascade, which leads to the activation of plant defense reactions against various pathogens. In the present investigation, a full-length cDNA was isolated from V. vinifera leaf tissue encoding a predicted protein, designated VvWRKY33, which shows the characteristics of group I WRKY protein family. VvWRKY33 induction correlates with the expression of VvPR10.1 (pathogenesis-related 10.1) gene in the leaves of the resistant cultivar 'Regent' after infection with Plasmopara viticola, whereas in the susceptible cultivar 'Lemberger' VvWRKY33 and VvPR10.1 are not induced. Corresponding expression of the TF and VvPR10.1 was even obtained in uninfected ripening berries. In planta, analysis of VvWRKY33 has been performed by ectopic expression of VvWRKY33 in grapevine leaves of greenhouse plants mediated via Agrobacterium tumefaciens transformation. In consequence, VvWRKY33 strongly increases resistance to P. viticola in the susceptible cultivar 'Shiraz' and reduces pathogen sporulation of about 50-70%, indicating a functional role for resistance in grapevine. Complementation of the resistance-deficient Arabidopsis thaliana Columbia-0 (Col-0) mutant line wrky33-1 by constitutive expression of VvWRKY33 restores resistance against Botrytis cinerea to wild-type level and in some complemented mutant lines even exceeds the resistance level of the parental line Col-0. Our results support the involvement of VvWRKY33 in the defense reaction of grapevine against different pathogens.

Transforaminal versus intra-articular facet corticosteroid injections for the treatment of cervical radiculopathy: a randomized, double-blind, controlled study

BACKGROUND AND PURPOSE

Transforaminal corticosteroid injections can be performed in the management of cervical radiculopathy but carry the risk of catastrophic complications. This study compares the efficacy of transforaminal and facet corticosteroid injections at 4 weeks' follow-up.

MATERIALS AND METHODS

We randomly assigned 56 subjects to receive CT-guided transforaminal (15 men, 13 women; mean age, 52 years; range, 28-72 years) or facet (8 men, 20 women; mean, 44 years; range, 26-60 years) injections. The primary outcome was pain severity rated on a Visual Analog Scale (0-100). Secondary outcomes were the Neck Disability Index and the Medication Quantitative Scale.

RESULTS

In the intention-to-treat and as-treated analyses, for a mean baseline score, facet injections demonstrated a significant pain score reduction of 45.3% (95% CI, 21.4-69.2) and 37.0% (95% CI, 9.2-64.7), while transforaminal injections showed a nonsignificant pain score reduction of 9.8% (95% CI, +11.5-31.2) and 17.8% (95% CI, +6.6-42.2). While facet injections demonstrated an improvement in the Neck Disability Index score of 24.3% (95% CI, +2.9-51.5) and 20.7% (95% CI, +6.2-47.6) as opposed to transforaminal injections of 9.6% (95% CI, +15.2-34.4) and 12.8% (95% CI, +11.2-36.7), the results were not statistically significant. Noninferiority of facet to transforaminal injections was demonstrated for baseline pain scores of ≤60, while noninferiority analysis was inconclusive for baseline pain scores of ≥80 and for the Neck Disability Index. Neither intervention showed a significant medication-intake score reduction with time.

CONCLUSIONS

Facet injections are effective for the treatment of cervical radiculopathy and represent a valid and safer alternative to transforaminal injections.

The response of soil organism communities to the application of the insecticide lindane in terrestrial model ecosystems

The EU plant protection regulation 1107/2009/EC defines the requirements for active ingredients to be approved, specifically including the assessment of effects on biodiversity and ecosystems. According to that, semi-field methods are expected to be more important in the near future. Therefore, a higher-tier experiment suitable to assess the risk for soil organisms was conducted to further develop the TME (terrestrial model ecosystems) methodology in a dose-response design with the persistent insecticidal model compound lindane (gamma-HCH). The effects of lindane on soil communities such as collembolans, oribatid mites, nematodes, soil fungi and plant biomass were determined in 42 TME. Intact TME-soil cores (diameter 300 mm, height 400 mm) from undisturbed grassland were stored outdoor under natural climatic conditions. Lindane was applied in five concentrations between 0.032 mg active ingredients (ai)/kg dry soil and 3.2 mg ai/kg dry weight soil, six-fold replicated each. Twelve TME served as untreated controls. Abundance and community structures of oribatids, collembolans, enchytraeids, nematodes and fungi were recorded. Oribatid mites' community responded 3 months after treatment, although they were not significantly affected by the overall treatment regimen. Collembolans in total and species-specific abundance as well as the community endpoints (principal response curves, diversity measures) were adversely affected by moderate dosages of lindane. Effects were transient between 3 and 5 months after treatment with a recovery within 1 year. No significant effects could be detected for enchytraeids, nematodes and fungi. The study design and the obtained results allow for calculations of no observed effect concentrations below the highest treatment level for populations and for soil communities as defined entities, as well as effective concentrations. The paper discusses the limits of effect detection in the light of achievable coefficients of variation and by means of minimum detectable differences. Outdoor TME are useful to analyze and assess functional and structural endpoints in soil organisms' communities and their possible recovery after pesticide treatment within 1 year.

Neural circuit development in the mammalian cochlea

The organ of Corti, the sensory epithelium of the mammalian auditory system, uses afferent and efferent synapses for encoding auditory signals and top-down modulation of cochlear function. During development, the final precisely ordered sensorineural circuit is established following excessive formation of afferent and efferent synapses and subsequent refinement. Here, we review the development of innervation of the mouse organ of Corti and its regulation.

[Super-resolution optical microscopy of the organ of Corti. Investigations on the fine structure of the inner hair cell afferent synapse by the 4Pi and STED techniques]

BACKGROUND

Inner hair cells encode sound into action potentials in the auditory nerve. Spiral ganglion neurons form the afferent innervation of inner hair cells via the hair cell synapse. The structure and function of this ribbon-type synapse is considered to have a major impact on the sound encoding process itself. In this study we have used conventional confocal microscopy as well as super-resolution techniques to investigate the synaptic organization in the inner hair cells of mice.

MATERIAL AND METHODS

Functionally relevant proteins of the afferent inner hair cell synapse were selectively marked using immunohistochemical methods and investigated with conventional confocal and super-resolution 4Pi- and stimulated emission depletion (STED) techniques.

RESULTS

Synapse and innervation density was mapped over the entire tonotopic axis. We found inner hair cells in the region of best hearing to have about twice the number of afferent fibres compared to the apex or base of the cochlea. For the first time 4Pi and STED microscopic techniques were employed to resolve the fine structure of these synapses beyond the resolution of conventional light microscopy. With 4Pi a resolution of approximately 100 nm in the z-axis direction is feasible. In practice STED delivers an effective resolution between 150 and 30 nm, depending on the power of the lasers employed. Synapses at different tonotopic positions of the cochlea exhibit no relevant structural differences at this level of resolution. The 4Pi and STED microscopic techniques are capable of showing the structure of afferent synapses in the organ of Corti with unsurpassed resolution. These images contribute to our understanding of sound-encoding mechanisms in the inner ear.

Ulnar subluxation of the median nerve following carpal tunnel release: a case report

Complications of carpal tunnel release, while infrequent, include incomplete release resulting in persistent symptoms or recurrence due to postoperative scarring, as well as iatrogenic damage to nerves and vessels. We present the case of a patient who underwent carpal tunnel release with resolution of symptoms in the immediate postoperative period. At one and a half years post release he started to experience numbness and tingling in a median nerve distribution triggered by repetitive ulnar to radial deviation of the wrist, with no symptoms at rest. Dynamic ultrasound showed a subluxation of the median nerve from one side of the palmaris longus tendon to the other. The patient's symptoms were triggered as the median nerve squeezed in between the palmaris longus and flexor digitorum superficialis tendons.

Early prediction of femoral head avascular necrosis following neck fracture

Femoral neck fracture puts at risk functional prognosis in young patients and can be life-threatening in the elderly. The present study reviews methods of femoral head vascularity assessment following neck fracture, to address the following issues: what is the risk of osteonecrosis? And what, in the light of this risk, is the best-adapted treatment to avoid iterative surgery? Femoral head vascularity depends on retinacular vessels and especially the lateral epiphyseal artery, which contributes from 70 to 80% of the femoral head vascular supply. Fracture causes vascular lesions, which are in turn the prime cause of necrosis. Other factors combine with this: hematoma tamponade effect, reduced joint space and increased pressure due to lower extremity positioning in extension/internal rotation/abduction during surgery. Head deformity is not due to direct cell death but to the repair process originating from the surrounding living bone. In post-traumatic necrosis, proliferation rapidly invades the head, with significant osteogenesis. Pathologic fractures occur at the boundary between the new and dead bone. Many techniques have been reported to help assess residual hemodynamics and risk of necrosis. Some are invasive: superselective angiography, intra-osseous oxygen pressure measurement, or Doppler-laser hemodynamic measurement; others involve imaging: scintigraphy, conventionnal or dynamic MRI. The future seems to lie with dynamic MRI, which allows a new classification of femoral neck fractures, based on a non-invasive assessment of femoral head vascularity.

[Imaging of acute spinal injury]

The mechanism location and type of injury varies according to patient age and severity of trauma. The imaging work-up with radiographs, CT and MRI must be adapted to each individual case. In the setting of minor trauma, standard radiographs are obtained when clinically indicated. In all other cases of high energy trauma, spinal trauma with neurological deficit or incomplete or difficult standard radiographic evaluation, CT will be indicated for osseous injuries while MRI will provide optimal evaluation of soft tissues. Dislocations require immediate treatment. The imaging work-up should by no means delay management. Significant sprains are rare. Several diagnostic pitfalls occur at both extremities of life.

[Imaging of non-traumatic and non-tumoral cord lesions]

There is a wide range of spinal cord pathologies (vascular, inflammatory, infectious, metabolic, degenerative). They present clinically as acute partial or complete cord syndromes, or chronic myelopathies (more than 4 weeks in duration). MRI examination should be undertaken with a very strict protocol. Spinal cord lesions should be evaluated with regards to their T1W and T2W signal characteristics, involvement of grey and/or white matter, axial and sagittal extension, cord volume changes, contrast uptake and associated lesions (perimedullary, radicular or brain). The correlation of MR imaging features with clinical and biological data (blood and CSF) should suggest a differential diagnosis.

Effects of the veterinary pharmaceutical ivermectin on soil invertebrates in laboratory tests

As part of the risk assessment of veterinary pharmaceuticals, the potential impact of these chemicals on soil ecosystems has to be determined according to European law. However, almost no data from standardized laboratory tests are available. Therefore, in the EU FP6 ERAPharm, the effects of the widely used veterinary pharmaceutical ivermectin, an anthelminthic, were studied in chronic laboratory tests performed according to OECD (Organisation for Economic Co-operation and Development) and ISO (International Organization for Standardization) guidelines. In detail, three soil invertebrate species--the earthworm Eisenia fetida, the springtail Folsomia candida, and the predatory mite Hypoaspis aculeifer--were tested. The nominal concentrations of ivermectin mixed into the test substrate artificial soil was verified using residue analysis, which indicated that the test substance is persistent for at least up to 28 days. As expected when considering the mode of action of this substance, survival and reproduction of collembolans were clearly affected [LC(50) = 8.4 mg/kg soil dry weight (dw); NOEC(repro) = 0.3 mg/kg soil (dw)]. Predatory mites reacted less sensitively [LC(50) > or = 31.6 mg/kg soil (dw); NOEC(repro) = 3.2 mg/kg soil (dw)]. Earthworm survival and reproduction were affected in the same order of magnitude as the predatory mites [LC(50) > or = 10 mg/kg soil (dw); NOEC(repro) = 2.5 mg/kg soil (dw)]. These results are in good agreement with the few data known from nonstandardized tests for the same or related soil invertebrate species. The results of these tests indicate that the effects of ivermectin on soil invertebrates--in particular, collembolans--cannot be excluded at field-relevant concentrations, as determined in a risk assessment according to VICH guidelines. More sophisticated higher-tier tests (e.g., in multispecies or semifield test systems) are recommended in order to assess the potential risk more accurately.

Type C periprosthetic fractures treated with locking plate fixation with a mean follow up of 2.5 years

BACKGROUND

Type C periprosthetic femoral fractures present fixation problems related to the extent of the fracture and the quality of the bone stock.

OBJECTIVES

The authors report a continuous and prospective series of type C periprosthetic femoral fractures to assess the mechanical stability of the femoral implant and the clinical outcome at the medium term.

MATERIAL AND METHODS

Between April 2004 and November 2006, we treated 17 patients (15 females, two males) presenting a prosthetic hip fracture (12 cases), between the hip prosthesis and the knee (one case), and with a knee prosthesis (four cases). All the implants had no sign of loosening at the time of fracture. The patients' mean age was 76.7 years (range, 39-93 years). Internal fixation was obtained with a locking compression plate (LCP) Synthes bridging the implant in place to prevent a weak zone. The rehabilitation protocol consisted in full weight bearing as much as possible.

RESULTS

The mean follow-up of the series was 31.5 months (range, 4-51 months). Four deaths were recorded during the follow-up. Minimally invasive surgery was performed in 15 patients.Total loading was possible immediately in 10 patients, partial loading at 20 kg in three patients,and no loading was possible until 6 weeks in four patients. Two infections and a bending-type mechanical complication of the plate secondary to a fall were observed. Consolidation was obtained in all cases with the appearance of callus formation beginning in the 6th week.

DISCUSSION

The technique used allies the principle of closed internal fixation (with preservation of the fracture hematoma) with mechanical stability. The screws locking to the plate warrant an internal fixator with increased stability that is sufficient for early loading with no risk of losing the secondary axis. Despite this increased rigidity, we did not observe any particular stress on the femoral implants. We recommend bridging the implant and spaced locking for better distribution of the stresses during loading. This hardware, with, if possible, insertion using a reduced approach, seems adapted to periprosthetic femoral fractures, particularly in the elderly.

LEVEL OF EVIDENCE

Level IV, prospective therapeutic study.

Assessing the toxicity of contaminated soils using the nematode Caenorhabditis elegans as test organism

In this study, nine uncontaminated reference soils and 22 contaminated soils with different physico-chemical properties and contamination patterns were tested with a standardized toxicity test, using the nematode, Caenorhabditis elegans, as test organism. Fertility, growth and reproduction of C. elegans in the soils were compared with the exposure in standard soil Lufa St.2.2. C. elegans showed 100% fertility and a very low variability of growth in the reference soils. Although, reproduction varied considerably between the various reference soils, validity criteria (>30 offspring per test organism) were met in all reference soils. Moreover, Lufa St. 2.2 turned out to be a suitable and representative control soil. In order to clearly classify the effects of the polluted soils on C. elegans, toxicity thresholds were derived for nematode fertility (20% inhibition), growth (10% inhibition) and reproduction (40% inhibition) on the basis of the test inherent variability (MDD=minimal detectable difference), as well as their variability between the uncontaminated reference soils (MTI=maximal tolerable inhibition). The contaminated soils showed clear toxic effects on the nematodes, whereas the toxicity was better correlated to organic than to heavy metal contamination in bulk soil. Interestingly, the results of the nematode toxicity test were not well correlated with those of tests with oligochaetes, collembolans and plants, performed with the same soils, showing that the results are not redundant. The toxicity test using C. elegans turned out to be suitable for testing the toxicity of field collected soils and might by a valuable addition to soil test batteries.