P–574 Examination of inter centre variation in PGT-A “no result rate” and efficacy of rebiopsy - Analysis of 22,833 samples 2015–2019

Study question

Are there significant differences in PGT-A “no result” rates and clinical outcomes following rebiopsy between ART clinics, and do rebiopsied embryos perform better than transferring with no result?

Summary answer

There is significant differences between clinics in terms of “no result rate” in PGT-A and utilisation of rebiopsy. What is known already: With any testing platform used in PGT-A, there is always a chance that a sample will not yield a result and rebiopsy may be considered to ascertain an embryos cytogenetic status. Studies have demonstrated rebiopsy yields results and adds to embryos genetically suitable for transfer. Clinical outcome data, however, remains scarce, leading to difficulty for clinics in benchmarking their performance when rebiopsied embryos are transferred.

Study design, size, duration

A retrospective analysis was performed of trophectoderm samples submitted for PGT-A via NGS over a 5yr period, 2015–2019. The no result (NR) rate was calculated per year and per clinic. Clinics were contacted for follow up data on NR embryos in terms of usage and clinical outcomes. Clinical outcomes from rebiopsied embryos were compared with those transferred as NR without rebiopsy.

Participants/materials, setting, methods

Data was collected on 22833 trophectoderm samples, submitted by 30 IVF laboratories. NR rate was analysed by year and by clinic. Clinics were asked if NR embryos had undergone rebiopsy, and if so if they had survived warming and rebiopsy. Clinics were asked if embryos selected for transfer had survived (re)warming, and to provide clinical follow-up including hCG test, clinical pregnancies, miscarriage and livebirth. The two tailed Fishers exact test was used for statistical analysis.

Main results and the role of chance

There was a wide range in sample numbers submitted by clinics over the time period, ranging from 9 samples through to 2633. In tclinics submitting over 500 samples the NR rate ranged from 0.6% to 7.4%, and in the those submitting 100–499 samples it ranged from 1.1% to 5.8%. Both these differences proved to be statistically significant (p < 0.05) between the best and worst performing clinics, and shows that a gap in performance exists between clinics. Less than 50% of NR embryos underwent rebiopsy. While the majority of embryos undergoing rebiopsy yielded a result (92.3%) and 31.4% of these were euploid or mosaic, almost half still remain in storage. The rate of livebirth/ongoing implantation in the rebiopsy group is 35.5% and 17.1% in the non rebiopsy group, illustrating a non significant trend towards a higher chance of implantation and livebirth in the rebiopsy group. Of 58 patients undergoing rebiopsy without any euploids in their initial cycle, 18 had a euploid embryo identified for future use. The additional manipulations involved in rebiopsy do not impact on survival at warming for transfer, but clinical outcomes in rebiopsied embryos appear poorer than those where a result was generated at first biopsy.

Limitations, reasons for caution

Despite starting with 22833 samples, 1115 of which were classified as NR, there were only 31 rebiopsied and 42 NR embryos transferred. It was therefore not possible to analyse transfer data by clinic or by embryo quality.

Wider implications of the findings: Rebiopsy yields genetic results and embryos suitable for patient use, including for patients who produced no other euploid/mosaic embryos in their cycle. However, it is not offered/performed in many cases. Clinical outcome data must continue to be compiled and analysed to confirm performance exceeds transfer of NR embryos.

Trial registration number

Not applicable

AB0037 EXPRESSION OF NEGATIVE CHECKPOINT MOLECULES BTLA AND HVEM IS DYSREGULATED IN AUTOIMMUNE DISEASES

Background:

Immune checkpoint blockade with agents targeting CTLA4 and PD-1/PD-L1 alone or in combination has demonstrated exceptional efficacy in multiple cancer types by “unleashing” the cytotoxic action of quiescent, tumor-infiltrating T cells. However, the therapeutic action of these immunotherapies goes hand in hand with the loss of immune tolerance and appearance of immune-related adverse events such as colitis, arthralgia and inflammatory arthritis in responsive patients. Therefore, immune checkpoint molecules have been proposed as targets for the treatment of autoimmune diseases.

Objectives:

Herein, we interrogate the potential of BTLA/HVEM axis as a target for restoring immune homeostasis in rheumatoid arthritis (RA), Systemic Lupus Erythematosus (SLE) and Sjogren’s Syndrome (SjS) by examining their expression patterns in autoimmune disease tissues.

Methods:

Message and protein expression of BTLA and HVEM were examined in RA and SLE synovial tissues, SLE cutaneous lesions, SjS salivary glands and peripheral blood samples of autoimmune disease by RNA sequencing and flow cytometry.

Results:

Tissue dysregulation of the BTLA-HVEM axis was observed: Increased BTLA RNA level in RA synovium, SLE-affected skin, and SjS salivary gland samples, whereas HVEM level was affected only in the RA synovium when compared to unaffected tissues. Detailed immunophenotyping of B, T, and myeloid cell populations in RA, SLE, SjS and healthy control PBMCs revealed differential modulation of the BTLA+ or HVEM+ immune cell subsets in a disease-context dependent manner. SjS patients showed an overall decrease in memory B cells and most of the BTLA+ B cell subsets while a decrease in HVEM+ B cells was observed only in SLE PBMC samples and not RA and SLE samples. Immunophenotyping with a T cell panel exhibited decreased BTLA and HVEM expression on T cell subsets in SjS and SLE but not in RA patients. In addition, protein levels of HVEM were differentially decreased in SLE myeloid cell subsets. Finally, we demonstrate tissue-specific surface expression patterns of BTLA in RA and SLE samples: higher surface BTLA levels on RA and SLE PBMC B cells than matched tissue-derived B cells.

Conclusion:

Our results demonstrate a dysregulation of the BTLA/HVEM axis in either lesional tissue or peripheral blood in an autoimmune disease context-dependent manner. These results also indicate the potential of targeting BTLA-HVEM axis for the treatment of multiple autoimmune diseases.

Disclosure of Interests:

Sunil Nagpal Shareholder of: Janssen Pharmaceuticals, Employee of: Janssen Pharmaceuticals, Suzanne Cole Shareholder of: Janssen Research & Development employee, Employee of: Janssen Research & Development employee, Achilleas Floudas: None declared, Mihir Wechalekar Grant/research support from: Grant from Janssen Research & Development, Qingxuan Song Shareholder of: Employee of Janssen Research, Employee of: Employee of Janssen Research, Tom Gordon: None declared, Roberto Caricchio Grant/research support from: Financial grant from Janssen Research & Development, Douglas Veale: None declared, Ursula Fearon: None declared, Navin Rao Shareholder of: Janssen Pharmaceuticals, Employee of: Janssen Pharmaceuticals, Ling-Yang Hao Shareholder of: Employee of Janssen Research, Employee of: Employee of Janssen Research

In Vitro Models, Standards, and Experimental Methods for Tobacco Products

Traditional tobacco products have well-known systemic and local oral effects, including inflammation, vasoconstriction, delayed wound healing, and increased severity of periodontal disease. Specifically in the oral cavity and the lung, cigarette smoking produces cancer, increased infectivity, acute and chronic inflammation, changes in gene expression in epithelial lining cells, and microbiome changes. In recent years, cigarette smoking has greatly decreased in the United States, but the use of new tobacco products has gained tremendous popularity. Without significant knowledge of the oral sequelae of products such as electronic cigarettes, researchers must evaluate current in vitro and in vivo methods to study these agents, as well as develop new tools to adequately study their effects. Some in vitro testing has been performed for electronic cigarettes, including toxicologic models and assays, but these mostly study the effect on the respiratory tract. Recently, direct exposure of the aerosol to in vitro 3-dimensional tissue constructs has been performed, demonstrating changes in cell viability and inflammatory cytokines. For in vivo studies, a universal e-cigarette testing machine or standard vaping regime is needed. A standard research electronic cigarette has recently been developed by the National Institute of Drug Abuse, and other devices delivering aerosols with different nicotine concentrations are becoming available. One of the biggest challenges in this research is keeping up with the new products and the rapidly changing technologies in the industry.

Crush injury to motor nerves in the G93A transgenic mouse model of amyotrophic lateral sclerosis promotes muscle reinnervation and survival of functionally intact nerve-muscle contacts

Selective survival of small motor nerve fibers and their neuromuscular contacts in the SOD1^G93A transgenic mouse model of amyotrophic lateral sclerosis (ALS) suggests that smaller regenerated nerve fibers are more able to sustain reformed nerve-muscle connections as functionally intact motor units (MUs). The sciatic nerve was crushed unilaterally in SOD1^G93A transgenic mice at 40 days of age and contractile forces of reinnervated muscles and their MUs were recorded at 90 days in order to determine the capacities of the nerves to regenerate and to form and retain functional neuromuscular connections. Reduced MU numbers in fast-twitch tibialis anterior, extensor digitorum longus and medial gastrocnemius muscles and the lesser reductions in slow-twitch soleus muscle of SOD1^G93A transgenic mice were reversed in reinnervated muscles: there were more reinnervated MUs and their contractile forces and the muscle forces and weights increased. In line with the contrasting ability of only small not large nerve fibers to sprout to form enlarged MUs in the SOD1^G93A transgenic mouse, the smaller regenerating nerve fibers formed enlarged MUs that were better able to survive. Because nerve fibers with and without muscle contacts were severed by the sciatic nerve crush injury, the conditioning lesion is untenable as the explanation for improved maintenance of reinnervated neuromuscular junctions. Elevated neurotrophic factor expression in axotomized motoneurons and/or denervated Schwann cells and the synapse withdrawal from axotomized motoneurons are other factors that, in addition to reduced size of nerve fibers reinnervating muscles, may account for increased survival and size of reinnervated MUs in ALS.

The Role of Stimulation in the Delay of Onset of Crying in the Newborn Infant

Crying is said to result from stimulus need. An experiment was done in which infants were stimulated during quiet periods to see if this would postpone the onset of crying. The results were positive. An alternative explanation in terms of internal temperature control is considered.

Barley Stripe Rust Resistance QTL: Development and Validation of SNP Markers for Resistance to Puccinia striiformis f. sp. hordei

Quantitative trait loci (QTL) for barley stripe rust resistance were mapped in recombinant inbred lines (RIL) from a 'Lenetah' × 'Grannelose Zweizeilige' (GZ) cross. GZ is known for a major seedling resistance QTL on chromosome 4H but linked markers suitable for marker-assisted selection have not been developed. This study identified the 4H QTL (log of the likelihood [LOD] = 15.94 at 97.19 centimorgans [cM]), and additional QTL on chromosomes 4H and 6H (LOD = 5.39 at 72.7 cM and 4.24 at 34.46 cM, respectively). A QTL on chromosome 7H (LOD = 2.04 at 81.07 cM) was suggested. All resistance alleles were derived from GZ. Evaluations of adult plant response in Corvallis, OR in 2013 and 2015 provided evidence of QTL at the same positions. However, the minor QTL on 4H was not statistically significant in either location/year, while the 7H QTL was significant in both. The single-nucleotide polymorphism markers flanking the resistance QTL were validated in RIL from a '95SR316A' × GZ cross for their ability to predict seedling resistance. In 95SR316A × GZ, 91 to 92% of RIL with GZ alleles at the major 4H QTL and at least one other were resistant to moderate in reaction. In these populations, at least two QTL were required to transfer the barley stripe rust resistance from GZ.

The use of brief post-surgical low frequency electrical stimulation to enhance nerve regeneration in clinical practice

Despite efforts to enhance peripheral nerve regeneration, there has been little progress in improving clinical outcomes. Recently, a method of brief post-surgical low frequency electrical stimulation of surgically repaired nerves has been developed. It was shown to accelerate axon outgrowth across the repair site and it hastened target reinnervation. In this brief review, we describe the mechanistic insights and functional impacts of the post-surgical electrical stimulation that have been gained through animal studies. Brain-derived neurotrophic factor, cyclic AMP and regeneration-associated genes play a vital role in expediting the outgrowth of axons across the injury site. The method of stimulation has also been shown to be effective in patients with severe compressive neuropathy as well as those with digital nerve laceration. Its clinical feasibility and positive impact open the door of further clinical translation in other peripheral nerve injuries.

Instrumentation and Measurement Strategy for the NOAA SENEX Aircraft Campaign as Part of the Southeast Atmosphere Study 2013

Natural emissions of ozone-and-aerosol-precursor gases such as isoprene and monoterpenes are high in the southeast of the US. In addition, anthropogenic emissions are significant in the Southeast US and summertime photochemistry is rapid. The NOAA-led SENEX (Southeast Nexus) aircraft campaign was one of the major components of the Southeast Atmosphere Study (SAS) and was focused on studying the interactions between biogenic and anthropogenic emissions to form secondary pollutants. During SENEX, the NOAA WP-3D aircraft conducted 20 research flights between 27 May and 10 July 2013 based out of Smyrna, TN. Here we describe the experimental approach, the science goals and early results of the NOAA SENEX campaign. The aircraft, its capabilities and standard measurements are described. The instrument payload is summarized including detection limits, accuracy, precision and time resolutions for all gas-and-aerosol phase instruments. The inter-comparisons of compounds measured with multiple instruments on the NOAA WP-3D are presented and were all within the stated uncertainties, except two of the three NO₂ measurements. The SENEX flights included day- and nighttime flights in the Southeast as well as flights over areas with intense shale gas extraction (Marcellus, Fayetteville and Haynesville shale). We present one example flight on 16 June 2013, which was a daytime flight over the Atlanta region, where several crosswind transects of plumes from the city and nearby point sources, such as power plants, paper mills and landfills, were flown. The area around Atlanta has large biogenic isoprene emissions, which provided an excellent case for studying the interactions between biogenic and anthropogenic emissions. In this example flight, chemistry in and outside the Atlanta plumes was observed for several hours after emission. The analysis of this flight showcases the strategies implemented to answer some of the main SENEX science questions.

Instrumentation and Measurement Strategy for the NOAA SENEX Aircraft Campaign as Part of the Southeast Atmosphere Study 2013

Natural emissions of ozone-and-aerosol-precursor gases such as isoprene and monoterpenes are high in the southeast of the US. In addition, anthropogenic emissions are significant in the Southeast US and summertime photochemistry is rapid. The NOAA-led SENEX (Southeast Nexus) aircraft campaign was one of the major components of the Southeast Atmosphere Study (SAS) and was focused on studying the interactions between biogenic and anthropogenic emissions to form secondary pollutants. During SENEX, the NOAA WP-3D aircraft conducted 20 research flights between 27 May and 10 July 2013 based out of Smyrna, TN. Here we describe the experimental approach, the science goals and early results of the NOAA SENEX campaign. The aircraft, its capabilities and standard measurements are described. The instrument payload is summarized including detection limits, accuracy, precision and time resolutions for all gas-and-aerosol phase instruments. The inter-comparisons of compounds measured with multiple instruments on the NOAA WP-3D are presented and were all within the stated uncertainties, except two of the three NO₂ measurements. The SENEX flights included day- and nighttime flights in the Southeast as well as flights over areas with intense shale gas extraction (Marcellus, Fayetteville and Haynesville shale). We present one example flight on 16 June 2013, which was a daytime flight over the Atlanta region, where several crosswind transects of plumes from the city and nearby point sources, such as power plants, paper mills and landfills, were flown. The area around Atlanta has large biogenic isoprene emissions, which provided an excellent case for studying the interactions between biogenic and anthropogenic emissions. In this example flight, chemistry in and outside the Atlanta plumes was observed for several hours after emission. The analysis of this flight showcases the strategies implemented to answer some of the main SENEX science questions.

Association mapping of North American spring wheat breeding germplasm reveals loci conferring resistance to Ug99 and other African stem rust races

BACKGROUND

The recently identified Puccinia graminis f. sp. tritici (Pgt) race TTKSK (Ug99) poses a severe threat to global wheat production because of its broad virulence on several widely deployed resistance genes. Additional virulences have been detected in the Ug99 group of races, and the spread of this race group has been documented across wheat growing regions in Africa, the Middle East (Yemen), and West Asia (Iran). Other broadly virulent Pgt races, such as TRTTF and TKTTF, present further difficulties in maintaining abundant genetic resistance for their effective use in wheat breeding against this destructive fungal disease of wheat. In an effort to identify loci conferring resistance to these races, a genome-wide association study was carried out on a panel of 250 spring wheat breeding lines from the International Maize and Wheat Improvement Center (CIMMYT), six wheat breeding programs in the United States and three wheat breeding programs in Canada.

RESULTS

The lines included in this study were grouped into two major clusters, based on the results of principal component analysis using 23,976 SNP markers. Upon screening for adult plant resistance (APR) to Ug99 during 2013 and 2014 in artificial stem rust screening nurseries at Njoro, Kenya and at Debre Zeit, Ethiopia, several wheat lines were found to exhibit APR. The lines were also screened for resistance at the seedling stage against races TTKSK, TRTTF, and TKTTF at USDA-ARS Cereal Disease Laboratory in St. Paul, Minnesota; and only 9 of the 250 lines displayed seedling resistance to all the races. Using a mixed linear model, 27 SNP markers associated with APR against Ug99 were detected, including markers linked with the known APR gene Sr2. Using the same model, 23, 86, and 111 SNP markers associated with seedling resistance against races TTKSK, TRTTF, and TKTTF were identified, respectively. These included markers linked to the genes Sr8a and Sr11 providing seedling resistance to races TRTTF and TKTTF, respectively. We also identified putatively novel Sr resistance genes on chromosomes 3B, 4D, 5A, 5B, 6A, 7A, and 7B.

CONCLUSION

Our results demonstrate that the North American wheat breeding lines have several resistance loci that provide APR and seedling resistance to highly virulent Pgt races. Using the resistant lines and the SNP markers identified in this study, marker-assisted resistance breeding can assist in development of varieties with elevated levels of resistance to virulent stem rust races including TTKSK.

Computational modeling of nanoscale and microscale particle deposition, retention and dosimetry in the mouse respiratory tract

Comparing effects of inhaled particles across rodent test systems and between rodent test systems and humans is a key obstacle to the interpretation of common toxicological test systems for human risk assessment. These comparisons, correlation with effects and prediction of effects, are best conducted using measures of tissue dose in the respiratory tract. Differences in lung geometry, physiology and the characteristics of ventilation can give rise to differences in the regional deposition of particles in the lung in these species. Differences in regional lung tissue doses cannot currently be measured experimentally. Regional lung tissue dosimetry can however be predicted using models developed for rats, monkeys, and humans. A computational model of particle respiratory tract deposition and clearance was developed for BALB/c and B6C3F1 mice, creating a cross-species suite of available models for particle dosimetry in the lung. Airflow and particle transport equations were solved throughout the respiratory tract of these mice strains to obtain temporal and spatial concentration of inhaled particles from which deposition fractions were determined. Particle inhalability (Inhalable fraction, IF) and upper respiratory tract (URT) deposition were directly related to particle diffusive and inertial properties. Measurements of the retained mass at several post-exposure times following exposure to iron oxide nanoparticles, micro- and nanoscale C60 fullerene, and nanoscale silver particles were used to calibrate and verify model predictions of total lung dose. Interstrain (mice) and interspecies (mouse, rat and human) differences in particle inhalability, fractional deposition and tissue dosimetry are described for ultrafine, fine and coarse particles.

Reduced expression of regeneration associated genes in chronically axotomized facial motoneurons

Chronically axotomized motoneurons progressively fail to regenerate their axons. Since axonal regeneration is associated with the increased expression of tubulin, actin and GAP-43, we examined whether the regenerative failure is due to failure of chronically axotomized motoneurons to express and sustain the expression of these regeneration associated genes (RAGs). Chronically axotomized facial motoneurons were subjected to a second axotomy to mimic the clinical surgical procedure of refreshing the proximal nerve stump prior to nerve repair. Expression of α1-tubulin, actin and GAP-43 was analyzed in axotomized motoneurons using in situ hybridization followed by autoradiography and silver grain quantification. The expression of these RAGs by acutely axotomized motoneurons declined over several months. The chronically injured motoneurons responded to a refreshment axotomy with a re-increase in RAG expression. However, this response to a refreshment axotomy of chronically injured facial motoneurons was less than that seen in acutely axotomized facial motoneurons. These data demonstrate that the neuronal RAG expression can be induced by injury-related signals and does not require acute deprivation of target derived factors. The transient expression is consistent with a transient inflammatory response to the injury. We conclude that transient RAG expression in chronically axotomized motoneurons and the weak response of the chronically axotomized motoneurons to a refreshment axotomy provides a plausible explanation for the progressive decline in regenerative capacity of chronically axotomized motoneurons.

Pharmacologic rescue of motor and sensory function by the neuroprotective compound P7C3 following neonatal nerve injury

Nerve injuries cause pain, paralysis and numbness that can lead to major disability, and newborns often sustain nerve injuries during delivery that result in lifelong impairment. Without a pharmacologic agent to enhance functional recovery from these injuries, clinicians rely solely on surgery and rehabilitation to treat patients. Unfortunately, patient outcomes remain poor despite application of the most advanced microsurgical and rehabilitative techniques. We hypothesized that the detrimental effects of traumatic neonatal nerve injury could be mitigated with pharmacologic neuroprotection, and tested whether the novel neuroprotective agent P7C3 would block peripheral neuron cell death and enhance functional recovery in a rat neonatal nerve injury model. Administration of P7C3 after sciatic nerve crush injury doubled motor and sensory neuron survival, and also promoted axon regeneration in a dose-dependent manner. Treatment with P7C3 also enhanced behavioral and muscle functional recovery, and reversed pathological mobilization of spinal microglia after injury. Our findings suggest that the P7C3 family of neuroprotective compounds may provide a basis for the development of a new neuroprotective drug to enhance recovery following peripheral nerve injury.

Immunization with 60 kD Ro peptide produces different stages of preclinical autoimmunity in a Sjögren's syndrome model among multiple strains of inbred mice

Sjögren's syndrome is a chronic illness manifested characteristically by immune injury to the salivary and lacrimal glands, resulting in dry mouth/eyes. Anti-Ro [Sjögren's syndrome antigen A (SSA)] and anti-La [Sjögren's syndrome antigen B (SSB)] autoantibodies are found frequently in Sjögren's subjects as well as in individuals who will go on to develop the disease. Immunization of BALB/c mice with Ro60 peptides results in epitope spreading with anti-Ro and anti-La along with lymphocyte infiltration of salivary glands similar to human Sjögren's. In addition, these animals have poor salivary function/low saliva volume. In this study, we examined whether Ro-peptide immunization produces a Sjögren's-like illness in other strains of mice. BALB/c, DBA-2, PL/J, SJL/J and C57BL/6 mice were immunized with Ro60 peptide-274. Sera from these mice were studied by immunoblot and enzyme-linked immunosorbent assay for autoantibodies. Timed salivary flow was determined after pharmacological stimulation, and salivary glands were examined pathologically. We found that SJL/J mice had no immune response to the peptide from Ro60, while C57BL/6 mice produced antibodies that bound the peptide but had no epitope spreading. PL/J mice had epitope spreading to other structures of Ro60 as well as to La, but like C57BL/6 and SJL/J had no salivary gland lymphocytic infiltration and no decrement of salivary function. DBA-2 and BALB/c mice had infiltration but only BALB/c had decreased salivary function. The immunological processes leading to a Sjögren's-like illness after Ro-peptide immunization were interrupted in a stepwise fashion in these differing mice strains. These data suggest that this is a model of preclinical disease with genetic control for epitope spreading, lymphocytic infiltration and glandular dysfunction.

Sprouting capacity of lumbar motoneurons in normal and hemisected spinal cords of the rat

Nerve sprouting to reinnervate partially denervated muscles is important in several disease and injury states. To examine the effectiveness of sprouting of active and inactive motor units (MUs) and the basis for a limit to sprouting, one of three rat lumbar spinal roots was cut under normal conditions and when the spinal cord was hemisected at T12. Muscle and MU isometric contractile forces were recorded and muscle fibres in glycogen-depleted single muscle units enumerated 23 to 380 days after surgery. Enlargement of intact MUs by sprouting was effective in compensating for up to 80% loss of innervation. For injuries that removed >70-80% of the intact MUs, muscle contractile force and weight dropped sharply. For partial denervation of <70%, all MUs increased contractile force by the same factor in both normally active muscles and muscles whose activity was reduced by T12 hemisection. Direct measurements of MU size by counting glycogen-depleted muscle fibres in physiologically and histochemically defined muscle units, provided direct evidence for a limit in MU size, whether or not the activity of the muscles was reduced by spinal cord hemisection. Analysis of spatial distribution of muscle fibres within the outer boundaries of the muscle unit demonstrated a progressive increase in fibres within the territory to the limit of sprouting when most of the muscle unit fibres were adjacent to each other. We conclude that the upper limit of MU enlargement may be explained by the reinnervation of denervated muscle fibres by axon sprouts within the spatial territory of the muscle unit, formerly distributed in a mosaic pattern.

Rolipram-induced elevation of cAMP or chondroitinase ABC breakdown of inhibitory proteoglycans in the extracellular matrix promotes peripheral nerve regeneration

The inhibitory growth environment of myelin and extracellular matrix proteoglycans in the central nervous system may be overcome by elevating neuronal cAMP or degrading inhibitory proteoglycans with chondroitinase ABC (ChABC). In this study, we asked whether similar mechanisms operate in peripheral nerve regeneration where effective Wallerian degeneration removes myelin and extracellular proteoglycans slowly. We repaired transected common peroneal (CP) nerve in rats and either elevated cAMP in the axotomized neurons by subcutaneous rolipram, a specific inhibitor of phosphodiesterase IV, and/or promoted degradation of proteoglycans in the distal nerve stump by local ChABC administration. Rolipram treatment significantly increased the number of motoneurons that regenerated axons across the repair site at 1 and 2 weeks, and increased the number of sensory neurons that regenerated axons across the repair site at 2 weeks. Local application of ChABC had a similar effect to rolipram treatment in promoting motor axon regeneration, the effect being no greater when rolipram and ChABC were administered simultaneously. We conclude that blocking inhibitors of axon regeneration by elevating cAMP or degrading proteoglycans in the distal nerve stump promotes peripheral axon regeneration after surgical repair of a transected nerve. It is likely that elevated cAMP is sufficient to encourage axon outgrowth despite the inhibitory growth environment such that simultaneous enzymatic proteoglycan degradation does not promote more axon regeneration than either elevated cAMP or proteoglycan degradation alone.

Workshop Summary: Phosgene-Induced Pulmonary Toxicity Revisited: Appraisal of Early and Late Markers of Pulmonary Injury From Animal Models With Emphasis on Human Significance

A workshop was held February 14, 2007, in Arlington, VA, under the auspices of the Phosgene Panel of the American Chemistry Council. The objective of this workshop was to convene inhalation toxicologists and medical experts from academia, industry and regulatory authorities to critically discuss past and recent inhalation studies of phosgene in controlled animal models. This included presentations addressing the benefits and limitations of rodent (mice, rats) and nonrodent (dogs) species to study concentration x time (C x t) relationships of acute and chronic types of pulmonary changes. Toxicological endpoints focused on the primary pulmonary effects associated with the acute inhalation exposure to phosgene gas and responses secondary to injury. A consensus was reached that the phosgene-induced increased pulmonary extravasation of fluid and protein can suitably be probed by bronchoalveolar lavage (BAL) techniques. BAL fluid analyses rank among the most sensitive methods to detect phosgene-induced noncardiogenic, pulmonary high-permeability edema following acute inhalation exposure. Maximum protein concentrations in BAL fluid occurred within 1 day after exposure, typically followed by a latency period up to about 15 h, which is reciprocal to the C x t exposure relationship. The C x t relationship was constant over a wide range of concentrations and single exposure durations. Following intermittent, repeated exposures of fixed duration, increased tolerance to recurrent exposures occurred. For such exposure regimens, chronic effects appear to be clearly dependent on the concentration rather than the cumulative concentration x time relationship. The threshold C x t product based on an increased BAL fluid protein following single exposure was essentially identical to the respective C x t product following subchronic exposure of rats based on increased pulmonary collagen and influx of inflammatory cells. Thus, the chronic outcome appears to be contingent upon the acute pulmonary threshold dose. Exposure concentrations high enough to elicit an increased acute extravasation of plasma constituents into the alveolus may also be associated with surfactant dysfunction, intra-alveolar accumulation of fibrin and collagen, and increased recruitment and activation of inflammatory cells. Although the exact mechanisms of toxicity have not yet been completely elucidated, consensus was reached that the acute pulmonary toxicity of phosgene gas is consistent with a simple, irritant mode of action at the site of its initial deposition/retention. The acute concentration x time mortality relationship of phosgene gas in rats is extremely steep, which is typical for a local, directly acting pulmonary irritant gas. Due to the high lipophilicity of phosgene gas, it efficiently penetrates the lower respiratory tract. Indeed, more recent published evidence from animals or humans has not revealed appreciable irritant responses in central and upper airways, unless exposure was to almost lethal concentrations. The comparison of acute inhalation studies in rats and dogs with focus on changes in BAL fluid constituents demonstrates that dogs are approximately three to four times less susceptible to phosgene than rats under methodologically similar conditions. There are data to suggest that the dog may be useful particularly for the study of mechanisms associated with the acute extravasation of plasma constituents because of its size and general morphology and physiology of the lung as well as its oronasal breathing patterns. However, the study of the long-term sequelae of acute effects is experimentally markedly more demanding in dogs as compared to rats, precluding the dog model to be applied on a routine base. The striking similarity of threshold concentrations from single exposure (increased protein in BAL fluid) and repeated-exposure 3-mo inhalation studies (increased pulmonary collagen deposition) in rats supports the notion that chronic changes depend on acute threshold mechanisms.

Early detection of denervated muscle fibers in hindlimb muscles after sciatic nerve transection in wild type mice and in the G93A mouse model of amyotrophic lateral sclerosis

The cell adhesion molecule N-CAM is localized to the adult neuromuscular junction but is also expressed in the extrajunctional membrane of denervated muscles concurrent with extrajunctional acetylcholine receptors. Here we used N-CAM immunohistochemistry to determine whether we could detect early denervation in hindlimb muscles of the G93A transgenic mouse model of amyotrophic lateral sclerosis (ALS). In denervated wild type mouse muscles, N-CAM immunoreactivity on the sarcolemma of all fiber types and within the sarcoplasm of only type IIA fibers was detected at day 2: approximately 30% of the muscle fibers in cross-section were fully circumscribed by N-CAM immunoreactivity and approximately 25% of fibers were incompletely circumscribed. The proportion of the latter fibers remained constant over the next 8 days as the proportions of the former fibers increased exponentially. Thereafter, fully circumscribed muscle fibers increased to a maximum by 30 days with a concomitant fall in the incompletely circumscribed fibers. Hence, early muscle denervation was detected by the incomplete circumscription of fiber membranes by N-CAM immunoreactivity with full circumscription and intracellular localization indicating more long-term denervation. In the G93A transgenic mouse, rapid denervation of fast-twitch muscles was readily detected by a corresponding proportion of muscle fibers in cross-section with positive N-CAM immunoreactivity. The proportions of incompletely and completely circumscribed muscle fibers corresponded well with the rate of decline in intact motor units and reduced muscle contractile forces. Progressively more fully circumscribed muscle fibers became evident with age. We conclude that the N-CAM immunoreactivity on muscle fiber membranes in muscle cross-sections provides a sensitive means of detecting early muscle fiber denervation.

Preferential motor unit loss in the SOD1 G93A transgenic mouse model of amyotrophic lateral sclerosis

The present study investigated motor unit (MU) loss in a murine model of familial amyotrophic lateral sclerosis (ALS). The fast-twitch tibialis anterior (TA) and medial gastrocnemius (MG) muscles of transgenic SOD1(G93A) and SOD1(WT) mice were studied during the presymptomatic phase of disease progression at 60 days of age. Whole muscle maximum isometric twitch and tetanic forces were 80% lower (P < 0.01) in the TA muscles of SOD1(G93A) compared to SOD1(WT) mice. Enumeration of total MU numbers within TA muscles showed a 60% reduction (P < 0.01) within SOD1(G93A) mice (38 +/- 7) compared with SOD1(WT) controls (95 +/- 12); this was attributed to a lower proportion of the most forceful fast-fatigable (FF) MU in SOD1(G93A) mice, as seen by a significant (P < 0.01) leftward shift in the cumulative frequency histogram of single MU forces. Similar patterns of MU loss and corresponding decreases in isometric twitch force were observed in the MG. Immunocytochemical analyses of the entire cross-sectional area (CSA) of serial sections of TA muscles stained with anti-neural cell adhesion molecule (NCAM) and various monoclonal antibodies for myosin heavy chain (MHC) isoforms showed respective 65% (P < 0.01) and 28% (P < 0.05) decreases in the number of innervated IIB and IID/X muscle fibres in SOD1(G93A), which paralleled the 60% decrease (P < 0.01) in the force generating capacity of individual fibres. The loss of fast MUs was partially compensated by activity-dependent fast-to-slower fibre type transitions, as determined by increases (P < 0.04) in the CSA and proportion of IIA fibres (from 4% to 14%) and IID/X fibres (from 31% to 39%), and decreases (P < 0.001) in the CSA and proportion of type IIB fibres (from 65% to 44%). We conclude that preferential loss of IIB fibres is incomplete at 60 days of age, and is consistent with a selective albeit gradual loss of FF MUs that is not fully compensated by sprouting of the remaining motoneurons that innervate type IIA or IID/X muscle fibres. Our findings indicate that disease progression in fast-twitch muscles of SOD1(G93A) mice involves parallel processes: (1) gradual selective motor axon die-back of the FF motor units that contain large type IIB muscle fibres, and of fatigue-intermediate motor units that innervate type IID/X muscle fibres, and (2) activity-dependent conversion of motor units to those innervated by smaller motor axons innervating type IIA fatigue-resistant muscle fibres.

cAMP promotes neurite outgrowth and extension through protein kinase A but independently of Erk activation in cultured rat motoneurons

It is well established that cAMP counteracts myelin inhibition to permit axon regeneration in the central nervous system. On the other hand, the role of cAMP in axonal growth on permissive substrates remains controversial because the evidence available is contradictory. In view that elevation of cAMP represents an attractive therapeutic target to promote nerve regeneration in vivo, we investigated the effect of cAMP on neurite outgrowth and extension in motoneurons. We manipulated cAMP levels pharmacologically in cultured motoneurons and investigated targets downstream of cAMP of neurite outgrowth and extension on a permissive substrate. Reduction of cAMP by the adenylyl cyclase inhibitor SQ22536 inhibited, and elevation of cAMP by forskolin, dibutyryl cAMP, IBMX and rolipram increased outgrowth and extension of neurites. The cAMP-mediated effects occur via activation of protein kinase A (PKA) and were reduced by the inhibitors, H89 and Rp-cAMP. However, cAMP elevation did not lead to Erk activation that is an essential downstream component of neurotrophin signaling. These findings provide evidence for a key role of cAMP in promoting peripheral nerve regeneration after nerve injuries and indicate that this effect is unusual in not being mediated via Erk phosphorylation.

Time course of preferential motor unit loss in the SOD1G93A mouse model of amyotrophic lateral sclerosis

Electromyographical analyses of pre-symptomatic motor unit loss in the SOD1 G93A transgenic mouse model of amyotrophic lateral sclerosis (ALS) have yielded contradictory findings as to the onset and time course. We recorded hindlimb muscle and motor unit isometric forces to determine motor unit number and size throughout the life span of the mice. Motor unit numbers in fast-twitch tibialis anterior, extensor digitorum longus and medial gastrocnemius muscles declined from 40 days of age, 50 days before reported overt symptoms and motoneuron loss. Motor unit numbers fell after overt symptoms in the slow-twitch soleus muscle. Muscle forces declined in parallel with motor unit numbers, indicating little or no functional compensation by sprouting. Early muscle-specific decline was due to selective preferential vulnerability of large, fast motor units, innervated by large motoneurons. Large motoneurons are hence the most vulnerable in ALS with die-back occurring prior to overt symptoms. We conclude that size of motoneurons, their axons, and their motor unit size are important determinants of motoneuron susceptibility in ALS.

Comparison of injury and development in the neuromuscular system

Comparisons of development and regeneration have suggested that axotomized motoneurons and denervated muscles undergo dedifferentiation to an embryonic state with recovery of adult properties after reinnervation. Using electrophysiological and radioligand-binding techniques to monitor axonal size and numbers of extrajunctional acetylcholine receptors in axotomized motoneurons and denervated muscles respectively, we have demonstrated that this dedifferentiation is limited. We suggest that this limited dedifferentiation may be adaptive for survival, regeneration and reinnervation. Correlative physiological and histochemical studies of reinnervated motor units in cat and rat hindlimb muscles show that the processes of regeneration and reinnervation differ in a number of fundamental ways from developmental processes of axonal growth and muscle innervation. Enlargement of motor units after partial nerve injuries does not appear to be limited to the size of the neonatal motor unit as originally suggested but may be influenced by factors operating at the level of axonal branching. Regeneration after complete and partial nerve injuries is a random process in contrast to the specific nature of the innervation of targets during development. Regenerating axons frequently fail to make connections with their original muscles and newly reinnervated motor units contain muscle fibres which formerly belonged to several different motor units. Despite this misdirection of regenerating nerve fibres, neuromuscular plasticity restores neuromuscular properties to the extent that these are appropriate at the single motor unit level for the gradation of force by the orderly recruitment of units during movement.

Clinical optimization and multicenter validation of antigen-specific cut-off values on the INNO-LIA ANA update for the detection of autoantibodies in connective tissue disorders

OBJECTIVES

The INNO-LIA ANA Update is a qualitative multiparameter line immunoassay for detection of autoantibodies to several different antigens associated with connective tissue disorders. We sought to optimize and validate the cut-off values for its antigen-specific components: SmB, SmD, RNP-70k, RNP-A, RNP-C, SSA/Ro52, SSA/Ro60, SSB/La, Cenp-B, Topo-I, Jo-1, ribosomal P, and histones. Our aim was to achieve 98% specificity for each of the markers, with respect to differential disease controls, while maintaining sensitivity.

METHODS

For optimization, the cut-off value of the different antigen lines was fixed to achieve this specificity using an in-house set of 955 patient samples. Specificity was validated at multiple sites using a different set of 330 samples obtained from 158 apparently healthy blood donors, 100 patients with a variety of infections, 20 each with Wegener's granulomatosis, inflammatory bowel disease, and primary antiphospholipid syndrome, and 12 with psoriatic arthritis. Sensitivity was evaluated, using this optimized cut-off control, in 147 patients with scleroderma, 93 with Sjögren's disease, 40 with systemic lupus erythematosus, 40 with rheumatoid arthritis, 39 with mixed connective tissue disease, and 19 with polymyositis. Sensitivity and specificity of the INNO-LIA ANA Update were determined using the clinical diagnosis as reference.

RESULTS

The optimized cut-off values resulted in a specificity 98% or more for all LIA markers except one (histones 97.8%) in the validation set of 330 samples. The sensitivity for each marker tested in 378 samples from the target patient groups was comparable to that reported in the literature.

CONCLUSION

The INNO-LIA ANA Update shows uniformly high specificities combined with sensitivities very similar to those of reference assays, in a single test format.

Glial cell line-derived neurotrophic factor and brain-derived neurotrophic factor sustain the axonal regeneration of chronically axotomized motoneurons in vivo

In contrast to injuries in the central nervous system, injured peripheral neurons will regenerate their axons. However, axotomized motoneurons progressively lose their ability to regenerate their axons, following peripheral nerve injury often resulting in very poor recovery of motor function. A decline in neurotrophic support may be partially responsible for this effect. The initial upregulation of glial cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF) by Schwann cells of the distal nerve stump after nerve injury has led to the speculation that they are important for motor axonal regeneration. However, few experiments directly measure the effects of exogenous BDNF or GDNF on motor axonal regeneration. This study provided the first direct and quantitative evidence that long-term continuous treatment with exogenous GDNF significantly increased the number of motoneurons which regenerate their axons, completely reversing the negative effects of chronic axotomy. The beneficial effect of GDNF was not dose-dependent. A combination of exogenous GDNF and BDNF on motor axonal regeneration was significantly greater than either factor alone, and this effect was most pronounced following long-term continuous treatment. The ability of GDNF, either alone or in combination with BDNF, to increase the number of motoneurons that regenerated their axons correlated well with an increase in axon sprouting within the distal nerve stump. Thus long-term continuous treatment with neurotrophic factors, such as GDNF and BDNF, can be used as a viable treatment to sustain motor axon regeneration.

Neuromuscular activity impairs axonal sprouting in partially denervated muscles by inhibiting bridge formation of perisynaptic Schwann cells

Following partial denervation of rat hindlimb muscle, terminal Schwann cells extend processes from denervated endplates to induce and guide sprouting from the remaining intact axons. Increased neuromuscular activity significantly reduces motor unit enlargement and sprouting during the acute phase of sprouting. These findings led to the hypothesis that increased neuromuscular activity perturbs formation of Schwann cell bridges and thereby reduces sprouting. Adult rat tibialis anterior (TA) muscles were extensively denervated by avulsion of L4 spinal root and were immediately subjected to normal caged activity or running exercise (8 h daily) for 3, 7, 14, 21, and 28 days. Combined silver/cholinesterase histochemical staining revealed that the progressive reinnervation of denervated endplates by sprouts over a 1 month period in the extensively partially denervated TA muscles was completely abolished by increased neuromuscular activity. Immunohistochemical staining and triple immunofluorescence revealed that the increased neuromuscular activity did not perturb the production of Schwann cell processes, but prevented bridging between Schwann cell processes at innervated and denervated endplates. Our findings suggest that failure of Schwann cell processes to bridge between endplates accounts, at least in part, for the inhibitory effect of increased neuromuscular activity on sprouting.

Immunoglobulin kappa light chain gene alleles are not associated with primary Sjögren's syndrome

The immunoglobulin kappa (Km) light chain gene is polymorphic and is believed to play a role in the pathology of infectious and autoimmune diseases. Polymorphisms within the constant region of the Km gene encode three alleles designated Km1, Km1,2 and Km3. Previous studies using serological detection of Km allotypes reported associations between specific Km allotypes, systemic lupus erythematosus and the presence of anti-La antibodies, yet these findings were not confirmed in other studies. In order to more precisely define any associations between Km alleles and anti-Ro/La antibodies we used the polymerase chain reaction and restriction fragment length polymorphisms for Km genotyping in a large cohort of patients with primary Sjögren's syndrome (SS). No associations were observed between specific Km alleles and primary SS when compared with a control population, nor within serologically defined subsets of SS patients. We conclude that Km alleles are not associated with primary SS or the Ro/La autoantibody response.

Tetrodotoxin prevents motor unit enlargement after partial denervation in rat hindlimb muscles

Findings that increased neuromuscular activity significantly reduced sprouting in partially denervated muscles prompted this present study to determine if the converse is true, namely that reduced activity promotes sprouting and motor unit (MU) enlargement. Partial denervation of rat hindlimb muscles by either the L4 or L5 spinal root avulsion resulted in extensive denervation (> 80 %) in tibialis anterior (TA) and medial gastrocnemius (MG) muscles, and moderate denervation (~50 %) in soleus (SOL) and plantaris (PL) muscles. The partially denervated muscles were then subjected to a 4 week programme of normal caged activity or TTX-induced neuromuscular inactivity. At 1 month, measurement of MU enlargement and quantification of sprouting were evaluated, respectively, by electrophysiological and histochemical means. Analysis of electrophysiological data showed that MU forces were significantly increased in both extensively and moderately denervated muscles 1 month after partial denervation and normal cage activity and that neuromuscular activity blockade by TTX completely abolished the MU enlargement in these partially denervated muscles. Histochemical analysis of sprouting revealed that the number of sprouts was significantly increased after partial denervation and normal cage activity, particularly after extensive denervation. TTX-induced neuromuscular inactivity dramatically reduced the number of sprouts and increased the number of free endplates in the extensively but not the moderately denervated muscles. These data demonstrate that a reduction in neuromuscular activity mediated by presynaptic blockade of neural action potentials reduces MU enlargement in partially denervated muscles by reducing axonal sprouting.

Effect of exercise on stability of chronically enlarged motor units

Chronic denervation syndromes such as the post-polio syndrome are associated with progressive muscle weakness and fatigue after motoneuron death. Neither the etiology nor the management of these syndromes is clear. To address this issue, we partially denervated rat hindlimb muscles for 1 or 12 months and examined whether chronically enlarged motor units (MUs) become destabilized with time and further destabilized by daily running on exercise wheels. MU enlargement, measured electrophysiologically and morphologically was significantly reduced at 12 months in extensively denervated muscles, and to a lesser extent in moderately denervated muscles, as compared to the findings at 1 month. A 1-month period of running exercise further reduced the size of the chronically enlarged MUs in the extensively denervated muscles. We have therefore (1) successfully established a rat model of time-related MU size reduction, in which destabilization of chronically enlarged MUs results in loss of axonal terminals, and (2) demonstrated that nonphysiological activity has small but significant effects of further destabilizing the chronically enlarged MUs.

A dose-dependent facilitation and inhibition of peripheral nerve regeneration by brain-derived neurotrophic factor

The time-dependent decline in the ability of motoneurons to regenerate their axons after axotomy is one of the principle contributing factors to poor functional recovery after peripheral nerve injury. A decline in neurotrophic support may be partially responsible for this effect. The up-regulation of BDNF after injury, both in denervated Schwann cells and in axotomized motoneurons, suggests its importance in motor axonal regeneration. In adult female Sprague-Dawley rats, we counted the number of freshly injured or chronically axotomized tibial motoneurons that had regenerated their axons 1 month after surgical suture to a freshly denervated common peroneal distal nerve stump. Motor axonal regeneration was evaluated by applying fluorescent retrograde neurotracers to the common peroneal nerve 20 mm distal to the injury site and counting the number of fluorescently labelled motoneurons in the T11-L1 region of the spinal cord. We report that low doses of BDNF (0.5-2 microg/day for 28 days) had no detectable effect on axonal regeneration after immediate nerve repair, but promoted axonal regeneration of motoneurons whose regenerative capacity was reduced by chronic axotomy 2 months prior to nerve resuture, completely reversing the negative effects of delayed nerve repair. In contrast, high doses of BDNF (12-20 microg/day for 28 days) significantly inhibited motor axonal regeneration, after both immediate nerve repair and nerve repair after chronic axotomy. The inhibitory actions of high dose BDNF could be reversed by functional blockade of p75 receptors, thus implicating these receptors as mediators of the inhibitory effects of high dose exogenous BDNF.

A decline in glial cell-line-derived neurotrophic factor expression is associated with impaired regeneration after long-term Schwann cell denervation

In the peripheral nervous system, regeneration of motor and sensory axons into chronically denervated distal nerve segments is impaired compared to regeneration into acutely denervated nerves. In order to find possible causes for this phenomenon we examined the changes in the expression pattern of the glial cell-line-derived neurotrophic factor (GDNF) family of growth factors and their receptors in chronically denervated rat sciatic nerves as a function of time with or without regeneration. Among the GDNF family of growth factors, only GDNF mRNA expression was rapidly upregulated in Schwann cells as early as 48 h after denervation. This upregulation peaked at 1 week and then declined to minimal levels by 6 months of denervation. The changes in the protein expression paralleled the changes in the expression of the GDNF mRNA. The mRNAs for receptors GFRalpha-1 and GFRalpha-2 were upregulated only after maximal GDNF upregulation and remained elevated as late as 6 months. There were no significant changes in the expression of GFRalpha-3 or the tyrosine kinase coreceptor, RET. When we examined the expression of GDNF in a delayed regeneration paradigm, there was no upregulation in the distal chronically denervated tibial nerve even when the freshly axotomized peroneal branch of the sciatic nerve was sutured to the distal tibial nerve. This study suggests that one of the reasons for impaired regeneration into chronically denervated peripheral nerves may be the inability of Schwann cells to maintain important trophic support for both motor and sensory neurons.

The neurotrophin receptors, trkB and p75, differentially regulate motor axonal regeneration

Neurotrophic factors that support neuronal survival are implicated in axonal regeneration after injury. Specifically, a strong role for BDNF in motor axonal regeneration has been suggested based on its pattern of expression after injury, as well as the expression of its receptors, trkB and p75. Despite considerable in vitro evidence, which demonstrate specific and distinct physiological responses elicited following trkB and p75 activation, relatively little is known about the function of these receptors in vivo. To investigate the roles of the trkB and p75 receptors in motor axonal regeneration, we have used a tibial (TIB)- common peroneal (CP) cross suture paradigm in p75 homozygous (-/-) knockout mice, trkB heterozygous (+/-) knockout mice, as well as in their wild-type controls. Contralateral intact TIB motoneurons, and axotomized TIB motoneurons that regenerated their axons 10 mm into the CP distal nerve stump were identified by fluorescent retrograde tracers and counted in the T11-L1 spinal segments. Regeneration was evaluated 2, 3, 4, 6, and 8 weeks after nerve repair. Compared to wild-type animals, there are significantly fewer intact TIB motoneurons in p75 (-/-), but not trkB (+/-) mice. The number of motoneurons that regenerated their axons was significantly increased in the p75 (-/-) knockout mice, but significantly attenuated in the trkB (+/-) mice compared to wild-type controls. These results suggest that p75 is important for motoneuronal survival during development, but p75 expression after injury serves to inhibit motor axonal regeneration. In addition, full expression of trkB is critical for complete axonal regeneration to proceed.

Action of deferoxamine against Pneumocystis carinii

We found earlier that deferoxamine (DFO), a drug used for treatment of iron overload, is active against a rat model of Pneumocystis carinii pneumonia (PCP). We had assumed a mode of action by deprivation of nutritional iron; however, data here show that DFO penetrates P. carinii, causing irreversible damage, thus indicating a different mode of action. Penetration was demonstrated by showing DFO uptake by high-pressure liquid chromatography analysis. By using calcein-AM as an indicator, exposure to DFO was shown to cause a reduction in P. carinii cytoplasmic free iron. Exposure to >or=100 microM DFO for >or=8 h in vitro caused growth to cease and cell numbers to decline over several days. This direct and irreversible damage to P. carinii led to the prediction that infrequent delivery of DFO to the lungs via an aerosol would be an effective treatment in the animal model of PCP. This prediction was confirmed by demonstrating that a once-a-week aerosol treatment of rats was 100% effective both as a prophylactic and as a curative treatment in a rat model of PCP.

Do denervated peripheral nerve trunks become ischemic? The impact of chronic denervation on vasa nervorum

The long-term relationship between the peripheral nerve trunk and its vascular supply, the vasa nervorum, has not been considered in the context of denervation and regeneration. While the microvessels of peripheral nerve are not thought to influence Wallerian degeneration itself, in this work we explored how vasa nervorum respond to denervation of the nerve trunk. Our hypotheses were that the presence of axons had a significant impact on the vasa nervorum and that the absence of reinnervation might eventually lead to an unfavorable ischemic regenerative microenvironment. We studied rat sciatic nerve trunks for up to 6 months following transection and either prevented regeneration or allowed it to proceed. Vasa nervorum were studied in several ways: (i) measurements of local endoneurial blood flow using microelectrode hydrogen clearance polarography; (ii) measurements of erythrocyte flux (flow) in the extrinsic nerve plexus using laser Doppler flowmetry; (iii) India ink perfusion of microvessels in unfixed nerve; (iv) mRNA expression of vascular endothelial growth factor (VEGF) using reverse transcription polymerase chain reaction. Early after injury, there were rises in endoneurial and extrinsic flow, microvessel numbers, and VEGF mRNA expression. Angiogenesis was apparently confined to the epineurial and perineurial compartments. Later, however, there were substantial declines in flow observed in long-term (6-month) denervated sciatic nerve trunks associated with declines in the caliber of new microvessels. Reinnervated sciatic nerves had restored endoneurial blood flow. The findings confirm important relationships between axon presence and local blood flow. Angiogenesis is a feature of the injured peripheral nerve, but long term denervated nerve trunks have declines of flow despite retaining new microvessels.

Genetic variability in the development of pulmonary tolerance to inhaled pollutants in inbred mice

After repeated exposures, many individuals develop tolerance to the adverse health effects of inhaled pollutants. Pulmonary tolerance can be characterized as the ability of the lung to withstand the adverse actions of a toxic compound after repeated exposures. To determine whether genetic background is important to the development of pulmonary tolerance to inhaled pollutants, 11 inbred strains of mice were exposed once (1x) or for 5 consecutive days (5x) to 1.0 mg/m(3) of zinc oxide (ZnO). Development of pulmonary tolerance was assessed by measuring polymorphonuclear leukocyte and protein levels in bronchoalveolar lavage fluid and comparing the responses of the 1x and 5x groups. Significant interstrain variation in polymorphonuclear leukocyte and protein responses was observed between the groups with 1x and 5x exposures, which indicates that genetic background has an important role in the development of pulmonary tolerance. The BALB/cByJ strain and the DBA/2J strain were the most tolerant and nontolerant, respectively. The CByD2F1/J offspring were uniformly nontolerant. The development of tolerance was also investigated in BALB/cByJ and DBA/2J mice after 1x and 5x exposure to ozone and aerosolized endotoxin. Discordance in the phenotypic pattern of pulmonary tolerance among strains after exposure to ZnO, ozone, and endotoxin suggested that different mechanisms may be responsible for the development of pulmonary tolerance to these agents.

Detection of the PAX3-FKHR fusion gene in paediatric rhabdomyosarcoma: a reproducible predictor of outcome?

Rhabdomyosarcoma has 2 major histological subtypes, embryonal and alveolar. Alveolar histology is associated with the fusion genes PAX3-FKHR and PAX7-FKHR. Definition of alveolar has been complicated by changes in terminology and subjectivity. It is currently unclear whether adverse clinical behaviour is better predicted by the presence of these fusion genes or by alveolar histology. We have determined the presence of the PAX3/7-FKHR fusion genes in 91 primary rhabdomyosarcoma tumours using a combination of classical cytogenetics, FISH and RT-PCR, with a view to determining the clinical characteristics of tumours with and without the characteristic translocations. There were 37 patients with t(2;13)/PAX3-FKHR, 8 with t(1;13) PAX7-FKHR and 46 with neither translocation. One or other of the characteristic translocations was found in 31/38 (82%) of alveolar cases. Univariate survival analysis revealed the presence of the translocation t(2;13)/PAX3-FKHR to be an adverse prognostic factor. With the difficulties in morphological diagnosis of alveolar rhabdomyosarcoma on increasingly used small needle biopsy specimens, these data suggest that molecular analysis for PAX3-FKHR will be a clinically useful tool in treatment stratification in the future. This hypothesis requires testing in a prospective study. Variant t(1;13)/PAX7-FKHR appears biologically different, occurring in younger patients with more localised disease.

Neuroblastoma in monozygotic twins--a case of probable twin-to-twin metastasis

Concordance for neuroblastoma in monozygotic twins has been reported only rarely, and the cause of the shared pathology has not been established. We describe a case of infant monozygotic twins developing tumours that were morphologically, clinically and molecularly indistinguishable, but with a delay of 6 months between times of presentation. Both tumours were metastatic and had amplification of MYCN and deletion at 1p36. Twin 1, who developed neuroblastoma first, had constitutional karyotype abnormalities in at least 5% of peripheral blood mononuclear cells involving 1p and 3p, and a deletion of 1q44 in 21% of cells. Twin 2 had a normal constitutional karyotype and lacked rearrangement or deletion of these regions. We propose an acquired neuroblastoma predisposition specific for twin 1, and in utero metastatic spread of tumour cells to twin 2 via the shared placental circulation.