A Biodegradable, Bio-Based Polymer for the Production of Tools for Aquaculture: Processing, Properties and Biodegradation in Sea Water.

Bio-based, biodegradable polymers can dramatically reduce the carbon dioxide released into the environment by substituting fossil-derived polymers in some applications. In this work, prototypes of trays for aquaculture applications were produced via injection molding by using a biodegradable polymer, Mater-Bi®. A characterization carried out via calorimetric, rheological and mechanical tests revealed that the polymer employed shows properties suitable for the production of tools to be used in aquaculture applications. Moreover, the samples were subjected to a biodegradation test in conditions that simulate the marine environment. The as-treated samples were characterized from gravimetrical, morphological and calorimetric point of views. The obtained data showed a relatively low biodegradation rate of the thick molded samples. This behavior is of crucial importance since it implies a long life in marine water for these manufacts before their disappearing.

Calcium Channel-Dependent Induction of Long-Term Synaptic Plasticity at Excitatory Golgi Cell Synapses of Cerebellum.

Golgi cells, together with granule cells and mossy fibers, form a neuronal microcircuit regulating information transfer at the cerebellum input stage. Despite theoretical predictions, little was known about long-term synaptic plasticity at Golgi cell synapses. Here, we have used whole-cell patch-clamp recordings and calcium imaging to investigate long-term synaptic plasticity at excitatory synapses impinging on Golgi cells. In acute mouse cerebellar slices, mossy fiber theta-burst stimulation (TBS) could induce either long-term potentiation (LTP) or long-term depression (LTD) at mossy fiber-Golgi cell and granule cell-Golgi cell synapses. This synaptic plasticity showed a peculiar voltage dependence, with LTD or LTP being favored when TBS induction occurred at depolarized or hyperpolarized potentials, respectively. LTP required, in addition to NMDA channels, activation of T-type Ca2+ channels, while LTD required uniquely activation of L-type Ca2+ channels. Notably, the voltage dependence of plasticity at the mossy fiber-Golgi cell synapses was inverted with respect to pure NMDA receptor-dependent plasticity at the neighboring mossy fiber-granule cell synapse, implying that the mossy fiber presynaptic terminal can activate different induction mechanisms depending on the target cell. In aggregate, this result shows that Golgi cells show cell-specific forms of long-term plasticity at their excitatory synapses, that could play a crucial role in sculpting the response patterns of the cerebellar granular layer.SIGNIFICANCE STATEMENT This article shows for the first time a novel form of Ca2+ channel-dependent synaptic plasticity at the excitatory synapses impinging on cerebellar Golgi cells. This plasticity is bidirectional and inverted with respect to NMDA receptor-dependent paradigms, with long-term depression (LTD) and long-term potentiation (LTP) being favored at depolarized and hyperpolarized potentials, respectively. Furthermore, LTP and LTD induction requires differential involvement of T-type and L-type voltage-gated Ca2+ channels rather than the NMDA receptors alone. These results, along with recent computational predictions, support the idea that Golgi cell plasticity could play a crucial role in controlling information flow through the granular layer along with cerebellar learning and memory.

The European study on centralisation of childhood cancer treatment.

BACKGROUND: It is generally agreed to centralise treatment of childhood cancers (CCs). We analysed (1) the degree of centralisation of CCs in European countries and 2) the relations between centralisation and survival. PATIENTS AND METHODS: The analysis comprised 4415 CCs, diagnosed between 2000 and 2007 and followed up to the end of 2013, from Belgium, Bulgaria, Finland, Ireland, the Netherlands and Slovenia. All these countries had national population-based cancer registries and were able to provide information on diagnosis, treatment, treatment hospitals, and survival. Each case was then classified according to whether the patient was treated in a high- or a low-volume hospital among those providing CC treatment. A Cox proportional hazard model was used to calculate the relation between volume category and five-year survival, adjusting by age, sex and diagnostic group. RESULTS: The number of hospitals providing treatment for CCs ranged from six (Slovenia) to slightly more than 40 (the Netherlands and Belgium). We identified a single higher volume hospital in Ireland and in Slovenia, treating 80% and 97% of cases, respectively, and three to five major hospitals in the other countries, treating between 65% and 93% of cases. Outcome was significantly better when primary treatment was given in high-volume hospitals compared to low-volume hospitals for central nervous system tumours (relative risk [RR] = 0.71), haematologic tumours (RR = 0.74) and for all CC combined (RR = 0.83). CONCLUSION: Treatment centralisation is associated with survival benefits and should be further strengthened in these countries. New plans for centralisation should include ongoing evaluation.

Connexin 26 Expression in Mammalian Cardiomyocytes.

Connexins are a family of membrane-spanning proteins named according to their molecular weight. They are known to form membrane channels mediating cell-cell communication, which play an essential role in the propagation of electrical activity in the heart. Cx26 has been described in a number of tissues but not in the heart, and its mutations are frequently associated with deafness and skin diseases. The aim of this study was to assess the possible Cx26 expression in heart tissues of different mammalian species and to demonstrate its localization at level of cardiomyocytes. Samples of pig, human and rat heart and H9c2 cells were used for our research. Immunohistochemical and molecular biology techniques were employed to test the expression of Cx26. Interestingly, this connexin was found in cardiomyocytes, at level of clusters scattered over the cell cytoplasm but not at level of the intercalated discs where the other cardiac connexins are usually located. Furthermore, the expression of Cx26 in H9c2 myoblast cells increased when they were differentiated into cardiac-like phenotype. To our knowledge, the expression of Cx26 in pig, human and rat has been demonstrated for the first time in the present paper.

Geographical variability in survival of European children with central nervous system tumours.

Survival for childhood central nervous system (CNS) tumours varies across Europe, partly because of the difficulty of distinguishing malignant from non-malignant disease. This study examines bias in CNS tumours survival analysis to obtain the reliable and comparable survival figures. We analysed survival data for about 15,000 children (age <15) diagnosed with CNS between 2000 and 2007, from 71 population-based cancer registries in 27 countries. We selected high-quality data based on registry-specific data quality indicators and recorded observed 1-year and 5-year survival by countries and CNS entity. We provided age-adjusted survival and used a Cox model to calculate the hazard ratios (HRs) of death, adjusting by age, site and grading by country. Recording of non-malignant lesions, use of appropriate morphology codes and completeness of life status follow-up differed among registries. Five-year survival by countries varied less when non-malignant tumours were included, with rates between 79.5% and 42.8%. The HRs of dying, for registries with good data, adjusting by age and grading, were between 0.7 and 1.2; differences were similar when site (supra- and infra-tentorial) was included. Several sources of bias affect the correct definition of CNS tumours, the completeness of incidence series and the goodness of follow-up. The European Network of Cancer Registries needs to improve childhood cancer registration and stress the need to update the International Classification for Cancer. Since survival differences persisted even when restricting the analysis to registries with satisfactory data, and since diagnosis of CNS tumours is difficult and treatment complex, national plans must aim for the revision of the diagnosis and the coordination of care, with adequate national and international networks.

Preparation of three-layered porous PLA/PEG scaffold: relationship between morphology, mechanical behavior and cell permeability.

Interface tissue engineering (ITE) is used to repair or regenerate interface living tissue such as for instance bone and cartilage. This kind of tissues present natural different properties from a biological and mechanical point of view. With the aim to imitating the natural gradient occurring in the bone-cartilage tissue, several technologies and methods have been proposed over recent years in order to develop polymeric functionally graded scaffolds (FGS). In this study three-layered scaffolds with a pore size gradient were developed by melt mixing polylactic acid (PLA) and two water-soluble porogen agents: sodium chloride (NaCl) and polyethylene glycol (PEG). Pore dimensions were controlled by NaCl granulometry while PEG solvation created a micropores network within the devices. Scaffolds were characterized from a morphological and mechanical point of view in order to find a correlation between the preparation method, the pore architecture and compressive mechanical behavior. Biological tests were also performed in order to study the effect of pore size gradient on the permeation of different cell lines in co-culture. To imitate the physiological work condition, compressive tests were also performed in phosphate buffered saline (PBS) solution at 37°C. The presented preparation method permitted to prepare three-layered scaffolds with high control of porosity and pore size distribution. Furthermore mechanical behaviors were found to be strongly affected by pore architecture of tested devices as well as the permeation of osteoblast and fibroblast in-vitro.

ENDOTHELIAL PROGENITOR CELL ADHESION, GROWTH AND CHARACTERIZATION ON TRABECULAR TITANIUM AND TRABECULAR TITANIUM COATED WITH COLLAGEN OR DECELLULARIZED ECM.

Adequate blood supply is essential for prosthesis osteointegration and bone healing as it supplies oxygen, nutrition and progenitor cells. The bone healing process and vascularization depend upon the endothelial cells, which speed up implant osteointegration. Endothelial Progenitor Cells (EPC) are a population of stem cells that can reproduce, migrate and acquire mature endothelial phenotype. Their recruitment occurs in the tissue lesion to enhance neovascularization. Trabecular TitaniumTM (TTTM) is a new biomaterial with very interesting biomechanical characteristics and fast osteointegration. This study has investigated adhesion, proliferation and characteristics of EPC on three types of biomaterial: unmodified trabecular titanium, trabecular titanium coated with the ECM deposited by human mesenchymal stem cells isolated from subcutaneous adipose tissue and decellularized and trabecular titanium coated with type I collagen (control scaffold). MTT assay showed similar percentages of EPCs seeded on the different kinds of scaffold: 67% on TT, 70% on decellularized scaffolds and 82% on collagen-coated scaffolds. There were no statistically significant differences between the three groups. We therefore conclude that TTTM allows EPC adhesion and proliferation and, consequently, by permitting vascularization, it favours prosthesis osteointegration.

Effect of temperature on the release of carvacrol and cinnamaldehyde incorporated into polymeric systems to control growth and biofilms of Escherichia coli and Staphylococcus aureus.

This study assessed the effect of temperature on the release of essential oil components incorporated by melt compounding into polymeric films. Specifically, polyethylene-co-vinylacetate (EVA) films containing carvacrol (CAR) and cinnamaldehyde (ALD), alone and in combination, were prepared and their surface and mechanical properties and antibacterial and anti-biofilm activity against Escherichia coli and Staphylococcus aureus were evaluated. The addition of ALD and CAR did not provoke variation in the surface morphology of EVA and allowed their delivery. At 37°C, films containing CAR, ALD or their combination (25+75%) were found to have the strongest bactericidal effect, whereas at lower temperatures a lower killing rate was observed. There was no clear evidence of the influence of temperature on the anti-biofilm activity of the essential oil component-based polymeric films. The biomass formed on EVA containing ALD, CAR or their combination (25+75) was significantly lower (60-80% reduction) than that formed on the EVA control at both 37° and 22°C.

Click chemistry, a potent tool in medicinal sciences.

This review focuses on the application of click chemistry in medicinal sciences, and particularly on its role in drug discovery. Because of its high modularity, click chemistry helps to accelerate the current drug discovery process, which relies on massive screening of chemical libraries. This article describes examples of click chemistry applications that are aimed at finding new lead candidates against pathologies such as cancer, AIDS and Alzheimer's disease, and explores the impact that the technique could have in therapy and prevention in the near future, through application in drug delivery systems, bioconjugation and diagnostic. An introduction, addressed to researchers who intend to use this methodology, examines the opportunities to perform click reactions according to the most common and best studied techniques, such as synthesis in water, on solid phase, and under microwave or ultrasound irradiation. Every topic is furnished with examples which have appeared in the literature in the last five years and is clarified by schemes and figures.

Hck inhibitors as potential therapeutic agents in cancer and HIV infection.

Hematopoietic cell kinase (Hck) is a member of the Src-family of non-receptor tyrosine kinases, which plays many roles in signalling pathways involved in the regulation of cell processes. Hck is expressed in cells of hematopoietic origin, specifically myelomonocytic cells and B lymphocytes. It participates in phagocytosis, adhesion, migration, regulation of protrusion formation on cell membrane, lysosome exocytosis, podosome formation and actin polymerization. More importantly from a medicinal chemistry point of view, high levels of Hck are involved in chronic myeloid leukemia and other hematologic tumors. Furthermore, Hck activity has been associated with virus infections including HIV-1. In particular, Hck is activated by the HIV-1 accessory protein Nef, a multifunctional HIV-1 protein that accelerates progression to AIDS and enhances the infectivity of progeny viruses. Nef binding to Hck leads to kinase activation which is important in AIDS pathogenesis. For these reasons, Hck represents a potentially good therapeutic target for the treatment of both specific cancers and HIV infection. This article summarizes Hck biological activities connected with malignancies and HIV infection, many of which have been only recently reported, and presents an overview of the compounds endowed with Hck inhibitory activity, especially focusing on the medicinal chemistry aspect.

Available evidence and new biological perspectives on medical treatment of advanced thymic epithelial tumors.

Thymic epithelial tumors (TETs) are rare primary mediastinal tumors arising from thymic epithelium. Their rarity and complexity hinder investigations of their causes and therapy development. Here, we summarize the existing knowledge regarding medical treatment of these tumors, and thoroughly review the known genetic aberrations associated with TETs and the present status of potential biological treatments. Epidermal growth factor receptor (EGFR), stem-cell factor receptor, insulin-like growth factor-1 receptor (IGF1R), and vascular endothelial growth factors (VEGF-A, VEGF-B, and VEGF-2) are overexpressed in TETs. EGFR overexpression in TETs is associated with higher stage, and IGF1R overexpression has poor prognostic value. Data indicate that anti-IGF1R monoclonal antibodies, and inhibitors of angiogenesis, somatostatin receptors, histone deacetylase, mammalian target of rapamycin, and cyclin-dependent kinases may be active against TETs. Continued investigations in this field could lead to advancement of targeted and biological therapies for TETs.

Development and characterization of essential oil component-based polymer films: a potential approach to reduce bacterial biofilm.

The development of new polymeric materials aimed to control the bacterial biofilm appears to be an important practical approach. The goal of the present study was to prepare and characterize poly(ethylene-co-vinyl acetate) copolymer (EVA) films containing citronellol, eugenol, and linalool and evaluate their efficiency on growth and biofilm formation of Listeria monocytogenes, Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, and Pseudomonas aeruginosa in monospecies and dual species. The results showed that the addition of oil components influenced the elastic modulus (15 % decrease), the tensile stress (30 % decrease), the elongation at break (10 % increase), and the contact angle values (10-20° decrease) while leaving the homogeneity of the surface unaltered. Among the polymeric films, EVA + citronellol and EVA + eugenol at 7 wt% had the best inhibitory effect. After 24-48 h of incubation, EVA + citronellol was more effective against the growth (30-60 % reduction) than EVA + eugenol (15-30 % inhibition). However, this inhibition decreased after 240 h of incubation. On the contrary, the biofilm evaluation revealed a strong inhibition trend also after prolonged incubation time: the amount of biomass per square centimeter formed on copolymer with oil components was significantly less (40-70 % decrease) than that on pure copolymer control for L. monocytogenes, S. aureus, and E. coli. When polymeric materials were simultaneously inoculated with combinations of S. aureus and E. coli, the biomass accumulated was higher for EVA + citronellol and lower for EVA + eugenol than that in monoculture biofilm. The findings were similar to the results obtained by 2,3-bis[2-methyloxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide assay that measures the metabolic activity of viable cells.

Late-onset bursts evoked by mossy fibre bundle stimulation in unipolar brush cells: evidence for the involvement of H- and TRP-currents.

Synaptic transmission at central synapses has usually short latency and graded amplitude, thereby regulating threshold crossing and the probability of action potential generation. In the granular layer of the vestibulo-cerebellum, unipolar brush cells (UBCs) receive a giant synapse generating a stereotyped excitatory postsynaptic potential (EPSP)-burst complex with early-onset (∼2 ms) and high reliability. By using patch-clamp recordings in cerebellar slices of the rat vestibulo-cerebellum, we found that mossy fibre bundle stimulation also evoked (in ∼80% of cases) a late-onset burst (after tens to hundreds of milliseconds) independent of EPSP generation. Different from the early-onset, the late-onset burst delay decreased and its duration increased by raising stimulation intensity or the number of impulses. Although depending on synaptic activity, the late-onset response was insensitive to perfusion of APV ((2R)-5-amino-phosphonopentanoate), NBQX (2,3-dioxo-6-nitro-tetrahydrobenzo(f)quinoxaline-7-sulfonamide) and MCPG ((RS)-α-methyl-4-carboxyphenylglycine) and did not therefore depend on conventional glutamatergic transmission mechanisms. The late-onset response was initiated by a slow depolarizing ramp driven by activation of an H-current (sensitive to ZD7288 and Cs(+)) and of a TRP- (transient receptor potential) current (sensitive to SKF96365), while the high voltage-activated and high voltage-activated Ca(2+) currents (sensitive to nimodipine and mibefradil, respectively) played a negligible role. The late-onset burst was occluded by intracellular cAMP. These results indicate that afferent activity can regulate H- and TRP-current gating in UBCs generating synaptically driven EPSP-independent responses, in which the delay rather than amplitude is graded with the intensity of the input pattern. This modality of synaptic transmission may play an important role in regulating UBC activation and granular layer functions in the vestibulo-cerebellum.

Combining in the melt physical and biological properties of poly(caprolactone) and chlorhexidine to obtain antimicrobial surgical monofilaments.

Bacterial infections on a sutured wound represent a critical problem, and the preparation of suture threads possessing antimicrobial properties is valuable. In this work, poly(caprolactone) (PCL) monofilaments were compounded at the concentration of 1, 2 and 4 % (w/w), respectively, to the antiseptic chlorhexidine diacetate (CHX). The incorporation was carried out in the melt by a single-step methodology, i.e. "online" approach. Mechanical tests revealed that the incorporation of CHX does not significantly change tensile properties of PCL fibres as the thermal profile adopted to prepare the compounded fibres does not compromise the antibacterial activity of CHX. In fact, CHX confers to compounded PCL fibres' antimicrobial property even at the lowest CHX concentration as revealed by microbiological assays performed on Escherichia coli, Micrococcus luteus and Bacillus subtilis strains. The scanning electron microscope micrographs and energy-dispersive X-ray analysis of compounded threads revealed that CHX is uniformly distributed on fibre surface and that the overall amount of superficial CHX increases by increasing compounded CHX concentration. This distribution determines a biphasic CHX release kinetics characterized by an initial rapid solubilisation of superficial CHX micro-crystals, followed by a slow and gradual release of CHX incorporated in the bulk. Interestingly, the compounded threads did not show any toxic effect compromising cell viability of human fibroblasts in vitro, differently from that observed using an equal amount of pure CHX. Thus, this study originally demonstrated the effectiveness of an "online" approach to confer antimicrobial properties to an organic thermoplastic polymeric material commonly used for medical devices.

Study on carvacrol and cinnamaldehyde polymeric films: mechanical properties, release kinetics and antibacterial and antibiofilm activities.

Polyethylene-co-vinylacetate (EVA) films with different concentrations (3.5 wt% and 7 wt%) of essential oil constituents, carvacrol or cinnamaldehyde, were prepared and characterized by mechanical, antibacterial and antibiofilm properties. The incorporation of the compounds into copolymer films affected their elastic modulus, tensile stress and elongation at break. Carvacrol and cinnamaldehyde act as plasticizers which reduce the intermolecular forces of polymer chains, thus improving the flexibility and extensibility of the film. The analysis of the surface characteristics demonstrated that essential oil constituents lowered the contact angle values without causing any remarkable variation of the surface roughness. The films allowed progressive diffusion of the bioactive molecules and the kinetic of release was correlated with the damaging effect on bacterial growth. The kill curves proved that the film with essential oil constituents (7 wt%) had a significant bactericidal effect (reduction of 4 and 2 log CFU) against Staphylococcus aureus and Escherichia coli and a bacteriostatic effect against Staphylococcus epidermidis and Listeria monocytogenes (reduction of about 1 log CFU). With regard to biofilm formation the biomass formed on polymeric films surface was significantly reduced if compared with the pure copolymer control. The results were confirmed by fluorescence microscopy images by Live/dead staining. The reduction in the surface tension coupled to an inherent bactericidal property of carvacrol and cinnamaldehyde could in turn affect the initial attachment phase of bacteria and compromise the normal biofilm development.

NR2A subunit of the N-methyl D-aspartate receptors are required for potentiation at the mossy fiber to granule cell synapse and vestibulo-cerebellar motor learning.

Traditionally studies aimed at elucidating the molecular mechanisms underlying cerebellar motor learning have been focused on plasticity at the parallel fiber to Purkinje cell synapse. In recent years, however, the concept is emerging that formation and storage of memories are both distributed over multiple types of synapses at different sites. Here, we examined the potential role of potentiation at the mossy fiber to granule cell synapse, which occurs upstream to plasticity in Purkinje cells. We show that null-mutants of N-methyl d-aspartate-NR2A receptors (NMDA-NR2A(-/-) mice) have impaired induction of postsynaptic long-term potentiation (LTP) at the mossy fiber terminals and a reduced ability to raise the granule cell synaptic excitation, while the basic excitatory output of the mossy fibers is unaffected. In addition, we demonstrate that these NR2A(-/-) mutants as well as mutants in which the C terminal in the NR2A subunit is selectively truncated (NR2A(ΔC/ΔC) mice) have deficits in phase reversal adaptation of their vestibulo-ocular reflex (VOR), while their basic eye movement performance is similar to that of wild type littermates. These results indicate that NMDA-NR2A mediated potentiation at the mossy fiber to granule cell synapse is not required for basic motor performance, and they raise the possibility that it may contribute to some forms of vestibulo-cerebellar memory formation.

Combined heart and kidney transplantation: long-term analysis of renal function and major adverse events at 20 years.

BACKGROUND: Combined heart-kidney transplantation (HKTx) is an accepted therapeutic option for patients with end-stage heart disease associated with severely impaired renal function. We report our long-term follow-up with this combined procedure. PATIENTS AND METHODS: Between April 1989 to November 2009, nine patients underwent combined simultaneous (HKTx) at our center. Seven patients were males (mean age 45.2 +/- 10.12 years); seven patients were on dialysis at the time of transplantation. RESULTS: Surgical procedures were uneventful in all patients. One patient died in the intensive care unit 41 days after transplantation. During long-term follow-up, three patients died: one due to infection and multiorgan failure 148 months after HKTx, one due to a lung neoplasm after 6 years, and one, a cerebral stroke at 34 months after transplantation. Only one patient experience renal allograft failure secondary to hypertension and cyclosporine nephrotoxicity at 10 years after HKTx with the need for renal replacement therapy. Last estimated glomerular filtration rates of all other patients was 61.3 +/- 17.4 mL/min. CONCLUSIONS: In selected patients, with coexisting end-stage cardiac and renal failure, combined HKTx with an allograft from the same donor proved to give satisfactory short- and long-term results, with a low incidence of both cardiac and renal allograft complications.

Percutaneous coronary interventions in cardiac allograft vasculopathy: a single-center experience.

OBJECTIVE: Cardiac allograft vasculopathy represents an accelerated form of obstructive coronary disease. It is the main cause of late death following heart transplantation. Percutaneous coronary intervention is considered a palliative procedure due to high restenosis rates. The aim of this study was to review our experience with percutaneous coronary interventions using stents in cardiac transplant recipients. METHODS: The present analysis included all primary adult heart transplanted patients who had been discharged from the hospital after transplantation, had a clinical follow-up of 12 months and underwent percutaneous coronary intervention (PCI). RESULTS: Seventy heart transplanted patients underwent percutaneous revascularization. Our analysis comprised 85 first-vessel procedures resulting in treatment of 135 lesions. The mean time from heart transplantation to first intervention was 9.3 +/- 4.8 years. Primary success was obtained in 96% lesions; at least 1 recurrent stenosis event occurred in 16 patients with primarily successful PCI. Lesions treated with drug-eluting stents experienced recurrent stenosis in 16% of cases. During a mean follow-up after PCI of 45.2 +/- 41.7 months, 27 deaths (19 cardiac) and 1 late re-transplantation occurred after PCI. CONCLUSION: In cardiac transplant recipients, percutaneous coronary intervention with stents can be performed safely with high rates of primary success. Restenosis rates were higher compared with coronary interventions in native coronary arteries. Drug-eluting stents seemed to favorably impact restenosis compared with bare-metal stents. The clinical benefit from percutaneous coronary intervention may be reduced due to disease progression in untreated coronary segments.

Subclavian embolization associated to carotid-subclavian bypass and stent-graft repair of acute type-B dissection.

Intentional closure of the left subclavian artery (LSA) during an endovascular procedure can be complicated by retrograde filling of the excluded aorta, increasing the risk of aneurysm expansion and sudden rupture. Retrograde coil embolization of the LSA, as alternative to open subclavian ligature, is a safe and effective method of rapid false lumen sealing in patients requiring coverage of the LSA and carotid-subclavian bypass, even in the setting of acute aortic syndromes.

Analysis of pre- and postsynaptic activity in the frog semicircular canal following ototoxic insult: differential recovery of background and evoked afferent activity.

Frogs were treated with a single dose of gentamicin administered intraotically to produce severe degeneration of posterior semicircular canal hair cells and to evaluate the time course of functional damage and recovery both at pre- and postsynaptic level. In isolated canal preparations the endoampullar potential, which reflects the summed receptor potentials of crista hair cells, was progressively reduced in amplitude and completely abolished 6 days after gentamicin treatment. At this time the crista epithelium was devoid of hair cells. The recovery of the endoampullar potential began around 9 days after the ototoxic insult and its amplitude progressively increased to reach, after 20 days, values close to those observed in control experiments. The endoampullar potential amplitude was related to the degree of hair cell regeneration in the crista epithelium. Consistent with the presynaptic damage, the slow generator potential (representing the summed miniature excitatory postsynaptic potential [mEPSP] activity of all posterior nerve fibres) and the resting and evoked spike discharge recorded from the whole ampullar nerve were abolished 6 days after gentamicin treatment. The recovery of the background and evoked afferent activity showed different behaviours. Background spike activity became detectable around 8 days after the ototoxic insult, but was not modulated by canal stimulation at this time, and no generator potential was detected. Moreover, the resting spike frequency fully recovered and reached control values around 15 days after gentamicin treatment, whereas the evoked activity attained normal values only 20 days after the ototoxic insult. These results were confirmed by intracellular recordings from single afferent fibres of the ampullar nerve in intact labyrinth preparations. Absence of any resting and evoked discharge was the most common pattern observed in the early period from 7 to 8 days after gentamicin treatment. Fifty-five percent of impaled afferents were silent while the others showed low resting frequencies of mEPSPs and spikes, and were unresponsive to canal rotation. In the intermediate period from 14 to 15 days after gentamicin treatment, background mEPSP and spike frequencies approached those evaluated in control experiments, but the frequencies of the evoked mEPSPs and spikes were clearly lower than in controls. In the late period, from 18 to 20 days after the ototoxic insult, the impaled afferents showed normal evoked mEPSP and spike frequencies. The present data indicate that the frog semicircular canal completely recovers its pre- and postsynaptic activity following severe ototoxic insult. During the regeneration process, the cytoneural junction regains function and the resting discharge reappears before recovery of mechanoelectrical transduction.