Deletion of Sod1 in Motor Neurons Exacerbates Age-Related Changes in Axons and Neuromuscular Junctions in Mice.

Whole-body knock-out of Cu,Zn superoxide dismutase (Sod1KO) results in accelerated, age-related loss of muscle mass and function associated with neuromuscular junction (NMJ) breakdown similar to sarcopenia. In order to determine whether altered redox in motor neurons underlies this phenotype, an inducible neuron-specific deletion of Sod1 (i-mnSod1KO) was compared with wild-type (WT) mice of different ages (adult, mid-age, and old) and whole-body Sod1KO mice. Nerve oxidative damage, motor neuron numbers and structural changes to neurons and NMJ were examined. Tamoxifen-induced deletion of neuronal Sod1 from two months of age. No specific effect of a lack of neuronal Sod1 was seen on markers of nerve oxidation (electron paramagnetic resonance of an in vivo spin probe, protein carbonyl, or protein 3-nitrotyrosine contents). i-mnSod1KO mice showed increased denervated NMJ, reduced numbers of large axons and increased number of small axons compared with old WT mice. A large proportion of the innervated NMJs in old i-mnSod1KO mice displayed a simpler structure than that seen in adult or old WT mice. Thus, previous work showed that neuronal deletion of Sod1 induced exaggerated loss of muscle in old mice, and we report that this deletion leads to a specific nerve phenotype including reduced axonal area, increased proportion of denervated NMJ, and reduced acetyl choline receptor complexity. Other changes in nerve and NMJ structure seen in the old i-mnSod1KO mice reflect aging of the mice.

Skeletal muscle transcriptomics identifies common pathways in nerve crush injury and ageing.

Motor unit remodelling involving repeated denervation and re-innervation occurs throughout life. The efficiency of this process declines with age contributing to neuromuscular deficits. This study investigated differentially expressed genes (DEG) in muscle following peroneal nerve crush to model motor unit remodelling in C57BL/6 J mice. Muscle RNA was isolated at 3 days post-crush, RNA libraries were generated using poly-A selection, sequenced and analysed using gene ontology and pathway tools. Three hundred thirty-four DEG were found in quiescent muscle from (26mnth) old compared with (4-6mnth) adult mice and these same DEG were present in muscle from adult mice following nerve crush. Peroneal crush induced 7133 DEG in muscles of adult and 699 DEG in muscles from old mice, although only one DEG (ZCCHC17) was found when directly comparing nerve-crushed muscles from old and adult mice. This analysis revealed key differences in muscle responses which may underlie the diminished ability of old mice to repair following nerve injury.

Assessing cross-resistance within the pyrethroids in terms of their interactions with key cytochrome P450 enzymes and resistance in vector populations.

BACKGROUND: It is important to understand whether the potential impact of pyrethroid resistance on malaria control can be mitigated by switching between different pyrethroids or whether cross-resistance within this insecticide class precludes this approach. METHODS: Here we assess the relationships among pyrethroids in terms of their binding affinity to, and depletion by, key cytochrome P450 enzymes (hereafter P450s) that are known to confer metabolic pyrethroid resistance in Anopheles gambiae (s.l.) and An. funestus, in order to identify which pyrethroids may diverge from the others in their vulnerability to resistance. We then investigate whether these same pyrethroids also diverge from the others in terms of resistance in vector populations. RESULTS: We found that the type I and II pyrethroids permethrin and deltamethrin, respectively, are closely related in terms of binding affinity to key P450s, depletion by P450s and resistance within vector populations. Bifenthrin, which lacks the common structural moiety of most pyrethroids, diverged from the other pyrethroids tested in terms of both binding affinity to key P450s and depletion by P450s, but resistance to bifenthrin has rarely been tested in vector populations and was not analysed here. Etofenprox, which also lacks the common structural moiety of most pyrethroids, diverged from the more commonly deployed pyrethroids in terms of binding affinity to key P450s and resistance in vector populations, but did not diverge from these pyrethroids in terms of depletion by the P450s. The analysis of depletion by the P450s indicated that etofenprox may be more vulnerable to metabolic resistance mechanisms in vector populations. In addition, greater resistance to etofenprox was found across Aedes aegypti populations, but greater resistance to this compound was not found in any of the malaria vector species analysed. The results for pyrethroid depletion by anopheline P450s in the laboratory were largely not repeated in the findings for resistance in malaria vector populations. CONCLUSION: Importantly, the prevalence of resistance to the pyrethroids α-cypermethrin, cyfluthrin, deltamethrin, λ-cyhalothrin and permethrin was correlated across malaria vector populations, and switching between these compounds as a tool to mitigate against pyrethroid resistance is not advised without strong evidence supporting a true difference in resistance.

New UK graduates' knowledge of training and service provision within restorative dentistry - a survey.

Objective To assess new UK graduates' knowledge of training and service provision within restorative dentistry.Design A national descriptive cross-sectional survey.Subjects and methods An online survey assessing clinicians' knowledge of restorative dentistry, who had graduated within the last four years in the UK, was distributed across the UK via postgraduate dental deaneries. One-hundred responses were accepted as a sample of a potential population of 4,000.Main outcome measure How well respondents understood the service provision and training aspects of the specialty of restorative dentistry.Results The responses were received from graduates from a variety of dental schools across the UK. Of those respondents, 41 reported receiving career guidance within restorative dentistry. 45 new graduates were confident in their understanding of the specialty, while 53 were confident in the differences between restorative dentistry and monospecialty training. The respondents appeared unaware regarding treatment priorities within restorative dentistry departments. Most respondents felt that receiving teaching on restorative dentistry as a specialty and career pathway would be beneficial.Conclusion The results suggest that new graduates may benefit from clarification regarding the specialty of restorative dentistry, however, caution must be taken due to the limitations of the study.

Information regarding restorative dentistry for new graduates.

A recent national survey has shown the need for clarification regarding the various disciplines encompassed by restorative dentistry and their respective training pathways. This document aims to address this by outlining the remit of restorative dentistry, in addition to the various job roles involved. This information is being disseminated by the British Society for Restorative Dentistry, and given the relevance to referrers and those looking for insight into the speciality, it has been reproduced here. Roles within the speciality range from dentists with special interests to specialists and consultants, whether primarily academic or clinical. The choice that a new graduate may make to choose a specific route will likely depend on a number of factors, often specific to each individual. Guidance on ways to gain experience and sources of further information are also provided.

Balancing the risks and benefits associated with cosmetic dentistry - a joint statement by UK specialist dental societies.

Cosmetic dentistry has become increasingly popular, largely as a result of social trends and increased media coverage. This understandable desire for the alleged 'perfect smile' needs to be tempered with an appropriate awareness of the significant risks associated with invasive cosmetic procedures such as veneers and crowns. Patients need to be properly informed that elective removal of healthy enamel and dentine can result in pulpal injury and poorer periodontal health in the longer term, particularly if they are young. The duty of candour means that they ought to be informed that aggressive reduction of sound tooth tissue is not biologically neutral and results in structural weakening of their teeth. Less invasive procedures such as bleaching on its own or for example, combined with direct resin composite bonding, can satisfy many patient's demands, while still being kinder to teeth and having much better fall-back positions for their future requirements. It is the opinion of the British Endodontic Society, British Society for Restorative Dentistry, Restorative Dentistry UK, Dental Trauma UK, British Society of Prosthodontics and the British Society of Paediatric Dentistry that elective invasive cosmetic dental treatments can result in great benefit to patients, but that some aggressive treatments used to achieve them can produce significant morbidities in teeth which were previously healthy. This is a worrying and growing problem with many ethical, legal and biologic aspects, but many adverse outcomes for patients who request cosmetic dental improvements are preventable by using biologically safer initial approaches to treatment planning and its provision.

Differential effects of short-term ß agonist and growth hormone treatments on expression of myosin heavy chain IIB and associated metabolic genes in sheep muscle.

Growth hormone (GH) and ß agonists increase muscle mass, but the mechanisms for this response are unclear and the magnitude of response is thought to vary with age of animal. To investigate the mechanisms driving the muscle response to these agents, we examined the effects of short-term (6 day) administration of GH or cimaterol (a ß2-adrenergic agonist, BA) on skeletal muscle phenotype in both young (day 60) and mature (day 120) lambs. Expression of myosin heavy chain (MyHC) isoforms were measured in Longissimus dorsi (LD), Semitendinosus (ST) and Supraspinatus (SS) muscles as markers of fibre type and metabolic enzyme activities were measured in LD. To investigate potential mechanisms regulating the changes in fibre type/metabolism, expression or activity of a number of signalling molecules were examined in LD. There were no effects of GH administration on MyHC isoform expression at either the mRNA or protein level in any of the muscles. However, BA treatment induced a proportional change in MyHC mRNA expression at both ages, with the %MyHCI and/or IIA mRNA being significantly decreased in all three muscles and %MyHCIIX/IIB mRNA significantly increased in the LD and ST. BA treatment induced de novo expression of MyHCIIB mRNA in LD, the fastest isoform not normally expressed in sheep LD, as well as increasing expression in the other two muscles. In the LD, the increased expression of the fastest MyHC isoforms (IIX and IIB) was associated with a decrease in isocitrate dehydrogenase activity, but no change in lactate dehydrogenase activity, indicating a reduced capacity for oxidative metabolism. In both young and mature lambs, changes in expression of metabolic regulatory factors were observed that might induce these changes in muscle metabolism/fibre type. In particular, BA treatment decreased PPAR-γ coactivator-1ß mRNA and increased receptor-interacting protein 140 mRNA. The results suggest that the two agents work via different mechanisms or over different timescales, with only BA inducing changes in muscle mass and transitions to a faster, less oxidative fibre type after a 6-day treatment.

Amino acid turnover by human oocytes is influenced by gamete developmental competence, patient characteristics and gonadotrophin treatment.

STUDY QUESTION: Can amino acid profiling differentiate between human oocytes with differing competence to mature to metaphase II (MII) in vitro? SUMMARY ANSWER: Oocytes which remained arrested at the germinal vesicle (GV) stage after 24 h of in vitro maturation (IVM) displayed differences in the depletion/appearance of amino acids compared with oocytes which progressed to MII and patient age, infertile diagnosis and ovarian stimulation regime significantly affected oocyte amino acid turnover during IVM. WHAT IS KNOWN ALREADY: Amino acid profiling has been proposed as a technique which can distinguish between human pronucleate zygotes and cleavage stage embryos with the potential to develop to the blastocyst stage and implant to produce a pregnancy and those that arrest. Most recently, the amino acid turnover by individual bovine oocytes has been shown to be predictive of oocyte developmental competence as indicated by the gamete's capacity to undergo fertilization and early cleavage divisions in vitro. STUDY DESIGN, SIZE, DURATION: The study was conducted between March 2005 and March 2010. A total of 216 oocytes which were at the GV or metaphase I (MI) stages at the time of ICSI were donated by 67 patients. PARTICIPANTS/MATERIALS, SETTINGS, METHODS: The research was conducted in university research laboratories affiliated to a hospital-based infertility clinic. Oocytes were cultured for 24 h and the depletion/appearance of amino acids was measured during the final 6 h of IVM. Amino acid turnover was analysed in relation to oocyte meiotic progression, patient age, disease aetiology and controlled ovarian stimulation regime. MAIN RESULTS AND THE ROLE OF CHANCE: The depletion/appearance of key amino acids was linked to the maturation potential of human oocytes in vitro. Oocytes which arrested at the GV stage (n = 9) depleted significantly more valine and isoleucine than those which progressed to MI (n = 32) or MII (n = 107) (P < 0.05). Glutamate, glutamine, arginine and valine depletion or appearance differed in MII versus degenerating oocytes (n = 20) (P < 0.05). Glutamine, arginine, methionine, phenylalanine, total depletion and total turnover all differed in oocytes from patients aged < 35 years versus patients ≥35 years (P < 0.05). MII oocytes obtained following ovarian stimulation with recombinant FSH depleted more isoleucine (P < 0.05) and more alanine and lysine (P < 0.05) appeared than oocytes from hMG-stimulated cycles. MII oocytes from patients with a polycystic ovary (PCO) morphology (n = 33) depleted more serine (P < 0.05) than oocytes from women with normal ovaries (n = 61). LIMITATIONS, REASONS FOR CAUTION: Immature oocytes collected at the time of ICSI were used as the model for human oocyte maturation. These oocytes have therefore failed to respond to the ovulatory hCG trigger in vivo (they are meiotically incompetent), and have limited capacity to support embryo development in vitro. The lack of cumulus cells and stress of the conditions in vitro may have influenced turnover of amino acids, and owing to the small sample sizes further studies are required to confirm these findings. WIDER IMPLICATIONS OF THE FINDINGS: The findings provide support for the hypothesis that oocyte metabolism reflects oocyte quality. Longitudinal studies are required to link these functional metabolic indices of human oocyte quality with embryo developmental competence. Oocyte amino acid profiling may be a useful tool to quantify the impact of new assisted reproduction technologies (ART) on oocyte quality. STUDY FUNDING/COMPETING INTERESTS: This project was funded by the UK Biology and Biotechnology Research Council (BB/C007395/1) and the Medical Research Council (G 0800250). K.E.H was in receipt of a British Fertility Society/Merck Serono studentship. H.J.L. is a shareholder in Novocellus Ltd, a company which seeks to devise a non-invasive biochemical test of embryo health.

Survival analysis of composite Dahl restorations provided to manage localised anterior tooth wear (ten year follow-up).

OBJECTIVE: To evaluate ten-year survival and clinical performance of resin-based composite restorations placed at increased vertical dimension as a 'Dahl' type appliance to manage localised anterior tooth wear.Design A prospective survival analysis of restorations provided at a single centre.Setting UK NHS hospital and postgraduate institute. METHODS: The clinical performance of 283 composite resin restorations on 26 patients with localised anterior tooth wear was reviewed after a ten year follow-up period. The study used modified United States Public Health Service (USPHS) criteria for assessing the restorations. Survival of the restorations was analysed using Kaplan-Meier survival curves, the log-rank test, and the Cox proportional hazards regression analysis. RESULTS: The results indicated that the median survival time for composite resin restorations was 5.8 years and 4.75 years for replacement restorations when all types of failure were considered. The restorations commonly failed as a result of wear, fracture and marginal discoloration. The factors that significantly influenced the survival of these restorations were the incisal relationship, aetiology, material used, and the nature of opposing dentition. The biological complications associated with this treatment regime were rare. Patient satisfaction remained high despite the long term deterioration of the restorations. CONCLUSION: With some degree of maintenance, repeated use of composite resin restorations to treat localised anterior tooth wear at an increased occlusal vertical dimension is a viable treatment option over a ten-year period.

Examination of myosin heavy chain isoform expression in ovine skeletal muscles.

The contractile and associated metabolic characteristics of muscles are determined by their myosin heavy chain (MHC) isoform expression. In large mammals, the level of MHCIIB expression, which is associated with fast glycolytic-type muscle fibers, has not been fully characterized. In this study, quantitative reverse transcription-PCR and SDS-PAGE methodologies were developed for the analyses of adult ovine MHC isoform expression and used to characterize MHC expression in 3 skeletal muscles [LM, semitendinosus, and supraspinatus) from 66-d-old lambs. Three MHC isoforms (MHCI, MHCIIA, and MHCIIX) were detected at both the protein and messenger RNA levels in all 3 muscles, with greater proportions of type II than type I MHC. The expression of MHCIIB could not be detected at the protein level in any of the muscles and was detectable (in semitendinosus muscle) only at the messenger RNA level by using semiquantitative reverse transcription-PCR, indicating that MHCIIX is the predominant fast glycolytic fiber type in the sheep muscles studied. The methodologies developed are suitable for studying fiber type transformations at the molecular level, as well as allowing analyses of very small samples, including biopsies, when histochemical analysis may not be possible.

Restoration of periodontally compromised dentitions using cross-arch bridges. Principles of perio-prosthetic patient management.

Severe periodontal disease often leads to tooth loss, necessitating prosthetic rehabilitation to restore function and aesthetics. The concept of perio-prosthetic treatment using extensive bridges of cross-arch design was introduced approximately 30 years ago. Long term follow-up studies have shown that teeth with reduced periodontal support can be used as abutments for extensive fixed prostheses, provided periodontal disease has been treated successfully, and an effective recall programme has been instituted to prevent periodontal disease recurrence. Low complication rates have been reported with these extensive constructions.

The survival and clinical performance of resin-based composite restorations used to treat localised anterior tooth wear.

OBJECTIVE: To examine the clinical performance of resin-based composite restorations placed at an increased vertical dimension when used to manage localised anterior tooth wear. DESIGN: A retrospective analysis of cases treated at a single centre. SETTING: UK Hospital setting in the year 2000. SUBJECTS AND METHODS: Two hundred and twenty five restorations placed in 31 subjects were included. Assessment was made following examination of study casts and projected slides. Modified United States Public Health Services criteria were used and data analysed using the software Statistical Programme for Social Sciences (SPSS). Survival analysis was carried out at two levels, major failure only and all types of failure. Kaplan-Meier survival plots were produced against different variables and modes of failure were also noted. RESULTS: Major failure requiring replacement of the restoration was uncommon within the first five years. Minor failure requiring repair or refinishing presented mainly as wear, marginal discolouration or marginal fracture. Median survival was 4 years 9 months when all types of failure were considered. The restorations have good appearance and are well tolerated. CONCLUSION: Placement of resin-based composite restorations at an increased vertical dimension to treat localised anterior tooth wear, has good short to medium term survival. The technique is conservative and relatively easy to maintain.

Root resorption in retained deciduous canine and molar teeth without permanent successors in patients with severe hypodontia.

AIMS: The ability to predict the morbidity of retained deciduous teeth with no permanent successors, a characteristic of hypodontia, would be of considerable value in treatment planning, but is hampered by lack of data. METHODS: This problem was studied using 356 orthopantomogram radiographs (OPGs) from the records of 249 patients who had attended a specialist hypodontia clinic, and had retained deciduous teeth with no permanent successors. Due to their clinical importance, canine and molar teeth were chosen for examination. Resorption was assessed subjectively by three experienced clinicians. RESULTS: Un-weighted Kappa values for reproducibility were > 0.8, and for interobserver error 0.60-0.83. Gender related differences were minimal. Regardless of gender or radiographic age, the lower canines appear to show the least amount of resorption and the upper first molars the most. The upper and lower second molars have particularly unpredictable life spans. Whilst the lower first molars have a predictable life span that is poor, the life span for the upper first molars is slightly worse. CONCLUSIONS: Lower canines have a predictable life span that appears to be good, as do upper canines, but of lesser duration than lower canines. Molars have poorer and less predictable life spans.

Tooth wear treated with direct composite restorations at an increased vertical dimension: results at 30 months.

STATEMENT OF PROBLEM: Severe tooth wear localized to the anterior maxillary or mandibular teeth with loss of interocclusal space is difficult to manage. PURPOSE: This study evaluated the outcome of composite restorations placed at an increased vertical dimension of occlusion in such patients. METHODS AND MATERIAL: Sixteen patients were restored with 104 restorations in 2 groups. In group A, Durafill composite and Scotchbond Multipurpose dentine adhesive system were used to place direct anterior restorations (N = 52). In group B, Herculite XRV composite and Optibond dentine bonding agent was used (N = 52). The restorations were placed at an increased vertical dimension of occlusion creating a posterior disclusion of 1 to 4 mm. RESULTS: Clinical follow-up showed that the posterior occlusion remained satisfactorily restored after a mean duration of 4.6 months (range 1 to 11 months). Mean follow-up of 30 months has shown a combined success rate of 89.4% for both groups with 93 of the restorations remaining in service. Maintenance in group A was high with 33 failures, but low in group B with 6 failures. Patient satisfaction was reported as good. CONCLUSION: Direct composite restorations may be a treatment option for localized anterior tooth wear.

Periodontal splinting in general dental practice.

Splinting periodontally involved teeth is a technique that has been in use for centuries. This article gives a brief history and review of the literature concerning periodontal splinting and outlines the rationale and indications for the correct application of periodontal splinting in modern dental practice. The common types of splint and clinical techniques involved are described, addressing some of the clinical problems.

The provision of occlusal splints in primary dental care.

UNLABELLED: Occlusal splints (Michigan splints, night/bite guards or bite-raising appliances) can be an effective, inexpensive and reversible treatment for a wide range of dental problems. OBJECTIVE: The aim of this study was to analyse retrospectively the provision of occlusal splint ('Michigan' type) in general dental practice, following a prescription by a restorative dental consultant. METHOD: One hundred patients were recruited from consultant clinics in a department of conservative dentistry during 1995 and 1996. All patients were prescribed a maxillary, full-coverage, heat-cured, acrylic-resin splint (Michigan splint) as part of a treatment plan. An explanatory letter and questionnaire were sent to all patients and to their referring general dental practitioner in 1997 and 1998. RESULTS: A response rate of 79% was achieved in obtaining completed questionnaires from both patients and general dental practitioners. Of respondents 43% (34/79) received an occlusal splint of some form. A small proportion of the respondents (16.5% [13/79]) received a Michigan splint as prescribed. Irrespective of the type of appliance provided, most patients (82% [28/34]) found them helpful. Of those who did not receive an occlusal splint, 38% (17/45) of patients felt financial implications deterred them from obtaining an appliance. Other common reasons for non-provision included: patients felt that symptoms had improved (18% [8/45]) and patients did not agree with treatment (18% [8/45]). The general dental practitioners had similar opinions to their patients. DISCUSSION: These findings raise some serious doubts on the efficacy of consultant clinic advice in the prescription of occlusal splints in general dental practice. The financial and educational issues raised by this study will need to be addressed to improve service provision. CONCLUSION: The results of this study indicate that 16.5% of patient respondents prescribed a Michigan splint at a consultant clinic received such an appliance in general dental practice.

Variations in planning fixed bridgework--a group of dentists at a case-based postgraduate course.

Variations in treatment planning and prescription have been described in relation to routine restorative dentistry. This study examined dentists' decisions regarding treatment planning for fixed bridgework. Fifty five dentists who attended a Continuing Education course on fixed bridgework were given standard information about a patient in the form of study casts, photographs of radiographs and a clinical history. They were asked to design a bridge where a previous one had failed and to complete a proforma which was returned to the course organisers in advance of the event. The response rate was 65%. The data showed wide variation in identification of features of diagnostic importance. Seventy percent of respondents chose to use again as abutments teeth which were extensively damaged and had failed to retain the previous bridge: while only 30% noted features of the occlusion which if left unchanged would have precluded a successful bridge from being made. A further feature was that nearly 70% chose to use multiple abutments to support the bridge. The implications of these results were discussed with respect to current concepts of bridge design.

Case report: tooth wear associated with an unusual habit.

Pathological tooth wear is an increasing problem affecting a significant proportion of the population. Although different wear mechanisms have been described, most reports in the literature concentrate on cases in which the predominant mechanisms were erosion and attrition. This article presents an unusual case of abrasive tooth wear caused by a sand eating habit which the patient had adopted as a child. Different causes of "abrasive" wear are discussed and the difficulties in management of this case are also presented.