Functional evolution of the feeding system in rodents

The masticatory musculature of rodents has evolved to enable both gnawing at the incisors and chewing at the molars. In particular, the masseter muscle is highly specialised, having extended anteriorly to originate from the rostrum. All living rodents have achieved this masseteric expansion in one of three ways, known as the sciuromorph, hystricomorph and myomorph conditions. Here, we used finite element analysis (FEA) to investigate the biomechanical implications of these three morphologies, in a squirrel, guinea pig and rat. In particular, we wished to determine whether each of the three morphologies is better adapted for either gnawing or chewing. Results show that squirrels are more efficient at muscle-bite force transmission during incisor gnawing than guinea pigs, and that guinea pigs are more efficient at molar chewing than squirrels. This matches the known diet of nuts and seeds that squirrels gnaw, and of grasses that guinea pigs grind down with their molars. Surprisingly, results also indicate that rats are more efficient as well as more versatile feeders than both the squirrel and guinea pig. There seems to be no compromise in biting efficiency to accommodate the wider range of foodstuffs and the more general feeding behaviour adopted by rats. Our results show that the morphology of the skull and masticatory muscles have allowed squirrels to specialise as gnawers and guinea pigs as chewers, but that rats are high-performance generalists, which helps explain their overwhelming success as a group

Reframing Childhood Disability: Pushing Boundaries in the Rehabilitation Sciences

The purpose of this study was to critically examine the ways that dominant discourses surrounding childhood disability, as constructed in the neoliberal context, shape knowledge and practice in children’s rehabilitation. I carried out a critical discourse analysis of text within the rehabilitation sciences, including peer-reviewed research, websites, and qualitative interview transcripts. Drawing on disability studies scholarship as well as my Foucauldian conceptual framework, I called attention to complex interactions between discourse, power, and knowledge that shape thought and action in the rehabilitation sciences. My findings suggest that despite a growing recognition of the harms associated with deficit-based understandings of disability, reformulation will require a considerable disruption of the durable neoliberal assumptions which ground contemporary Western society. This work adds to a growing body of literature which advocates for alternative, affirmative understandings of childhood disability through interdisciplinary collaboration, particularly between disability studies and the rehabilitation sciences

Spinal motor neuron loss occurs through a p53-and-p21-independent mechanism in the Smn

Spinal muscular atrophy (SMA) is a pediatric neuromuscular disease caused by genetic deficiency of the survival motor neuron (SMN) protein. Pathological hallmarks of SMA are spinal motor neuron loss and skeletal muscle atrophy. The molecular mechanisms that elicit and drive preferential motor neuron degeneration and death in SMA remain unclear. Transcriptomic studies consistently report p53 pathway activation in motor neurons and spinal cord tissue of SMA mice. Recent work has identified p53 as an inducer of spinal motor neuron loss in severe Δ7 SMA mice. Additionally, the cyclin-dependent kinase inhibitor P21 (Cdkn1a), an inducer of cell cycle arrest and mediator of skeletal muscle atrophy, is consistently increased in motor neurons, spinal cords, and other tissues of various SMA models. p21 is a p53 transcriptional target but can be independently induced by cellular stressors. To ascertain whether p53 and p21 signaling pathways mediate spinal motor neuron death in milder SMA mice, and how they affect the overall SMA phenotype, we introduced Trp53 and P21 null alleles onto the Sm

Biological intratumoral therapy for the high-grade glioma part I: intratumoral delivery and immunotoxins.

Management of high-grade gliomas remains a complex challenge. Standard of care consists of microsurgical resection, chemotherapy and radiation, but despite these aggressive multimodality therapies the overall prognosis remains poor. A major focus of ongoing translational research studies is to develop novel therapeutic strategies that can maximize tumor cell eradication while minimizing collateral side effects. Particularly, biological intratumoral therapies have been the focus of new translational research efforts due to their inherent potential to be both dynamically adaptive and target specific. This two-part review will provide an overview of biological intratumoral therapies and summarize key advances and remaining challenges in intratumoral biological therapies for high-grade glioma. Part I focuses on discussion of the concepts of intratumoral delivery and immunotoxin therapies

Biological intratumoral therapy for the high-grade glioma part II: vector- and cell-based therapies and radioimmunotherapy.

Management of high-grade gliomas (HGGs) remains a complex challenge with an overall poor prognosis despite aggressive multimodal treatment. New translational research has focused on maximizing tumor cell eradication through improved tumor cell targeting while minimizing collateral systemic side effects. In particular, biological intratumoral therapies have been the focus of novel translational research efforts due to their inherent potential to be both dynamically adaptive and target specific. This two part review will provide an overview of biological intratumoral therapies that have been evaluated in human clinical trials in HGGs, and summarize key advances and remaining challenges in the development of these therapies as a potential new paradigm in the management of HGGs. Part II discusses vector-based therapies, cell-based therapies and radioimmunotherapy

Functional tests of the competitive exclusion hypothesis for multituberculate extinction

Multituberculate mammals thrived during the Mesozoic, but their diversity declined from the mid-late Paleocene onwards, becoming extinct in the late Eocene. The radiation of superficially similar, eutherian rodents has been linked to multituberculate extinction through competitive exclusion. However, characteristics providing rodents with a supposed competitive advantage are currently unknown and comparative functional tests between the two groups are lacking. Here, a multifaceted approach to craniomandibular biomechanics was taken to test the hypothesis that superior skull function made rodents more effective competitors. Digital models of the skulls of four extant rodents and the Upper Cretaceous multituberculate Kryptobaatar were constructed and used (i) in finite-element analysis to study feeding-induced stresses, (ii) to calculate metrics of bite force production and (iii) to determine mechanical resistances to bending and torsional forces. Rodents exhibit higher craniomandibular stresses and lower resistances to bending and torsion than the multituberculate, apparently refuting the competitive exclusion hypothesis. However, rodents optimize bite force production at the expense of higher skull stress and we argue that this is likely to have been more functionally and selectively important. Our results therefore provide the first functional lines of evidence for potential reasons behind the decline of multituberculates in the changing environments of the Paleogene.Peer reviewe

Post-Concussion and Post-Traumatic Stress Symptoms after Pediatric Traumatic Brain Injury: Shared Vulnerability Factors?

Following pediatric traumatic brain injury (TBI), post-concussion symptoms (PCS) and post-traumatic stress symptoms (PTSS) occur commonly; however, it is unknown to what degree they overlap. The study examined PCS and PTSS persisting 7 weeks after injury in children and adolescents ages 8-15 years with TBI (n = 89) or extracranial injury (EI; n = 40) after vehicle collisions. TBI was divided into mild, complicated-mild/moderate, and severe groups. Parents retrospectively rated children\u27s pre-injury symptoms and behavior problems, and children completed self-report measures after injury. PCS and PTSS total scores were significantly correlated in TBI and EI groups, respectively, for child (rs = 0.75; rs = 0.44), and adolescent (rs = 0.61; rs = 0.67) cohorts. Generalized linear models examined whether injury type and severity, age, sex, and pre-injury symptom ratings predicted PCS and PTSS total scores and factor scores. Specific PCS and PTSS factor scores were elevated in different TBI severity groups, with most frequent problems following mild or severe TBI. PCS did not differ by age; however, girls had more emotional symptoms than boys. Only PTSS were predicted by pre-injury externalizing behavior. Significant age by sex interactions indicated that adolescent girls had more total, avoidance, and hyperarousal PTSS symptoms than younger girls or all boys. PCS and PTSS significantly overlapped in both TBI and EI groups, highlighting shared persistent symptoms after injury. Shared vulnerability factors included female sex, milder TBI, and poorer pre-injury adjustment. Older age was a unique vulnerability factor for PTSS. Psychological health interventions after injury should be customized to address comorbid symptoms

Mutations in CHMP2B in lower motor neuron predominant amyotrophic lateral sclerosis (ALS)

Background: Amyotrophic lateral sclerosis (ALS), a common late-onset neurodegenerative disease, is associated with fronto-temporal dementia (FTD) in 3-10% of patients. A mutation in CHMP2B was recently identified in a Danish pedigree with autosomal dominant FTD. Subsequently, two unrelated patients with familial ALS, one of whom also showed features of FTD, were shown to carry missense mutations in CHMP2B. The initial aim of this study was to determine whether mutations in CHMP2B contribute more broadly to ALS pathogenesis. Methodology/Principal Findings: Sequencing of CHMP2B in 433 ALS cases from the North of England identified 4 cases carrying 3 missense mutations, including one novel mutation, p. Thr104Asn, none of which were present in 500 neurologically normal controls. Analysis of clinical and neuropathological data of these 4 cases showed a phenotype consistent with the lower motor neuron predominant (progressive muscular atrophy (PMA)) variant of ALS. Only one had a recognised family history of ALS and none had clinically apparent dementia. Microarray analysis of motor neurons from CHMP2B cases, compared to controls, showed a distinct gene expression signature with significant differential expression predicting disassembly of cell structure; increased calcium concentration in the ER lumen; decrease in the availability of ATP; down-regulation of the classical and p38 MAPK signalling pathways, reduction in autophagy initiation and a global repression of translation. Transfection of mutant CHMP2B into HEK-293 and COS-7 cells resulted in the formation of large cytoplasmic vacuoles, aberrant lysosomal localisation demonstrated by CD63 staining and impairment of autophagy indicated by increased levels of LC3-II protein. These changes were absent in control cells transfected with wild-type CHMP2B. Conclusions/Significance: We conclude that in a population drawn from North of England pathogenic CHMP2B mutations are found in approximately 1% of cases of ALS and 10% of those with lower motor neuron predominant ALS. We provide a body of evidence indicating the likely pathogenicity of the reported gene alterations. However, absolute confirmation of pathogenicity requires further evidence, including documentation of familial transmission in ALS pedigrees which might be most fruitfully explored in cases with a LMN predominant phenotype