A quantitative comparative analysis of the size of the frontoparietal sinuses and brain in vombatiform marsupials

Cranial sinuses result from the resorption and deposition of bone in response to biomechanical stress during a process known as pneumatisation. The morphology of a pneumatic bone represents an optimisation between strength and being light weight. The presence of very large sinuses has been described in a number of extinct marsupial megafauna, the size of which no longer exist in extant marsupials. With advances in digital visualisation, and the discovery of a number of exceptionally preserved fossil crania, a unique opportunity exists to investigate hypotheses regarding the structure and evolution of the atypically voluminous sinuses. Sinus function is difficult to test without first obtaining data on sinus variation within and between species. Therefore, the crania of seven species of extinct and extant vombatiform marsupials were studied using CT scans to provide a volumetric assessment of the endocast and cranial sinuses. Sinus volume strongly correlates with skull size and brain size. In the extinct, large bodied palorchestids and diprotodontids the sinuses expand around the dorsal and lateral parts of the braincase. Brain size scales negatively with skull size in vombatiform marsupials. In large species the brain typically fills less than one quarter of the total volume of the endocranial space, and in very large species, it can be less than 10%. Sinus expansion may have developed in order to increase the surface area for attachment of the temporalis muscle and to lighten the skull. The braincase itself would have provided insufficient surface area for the predicted muscle masses

Three dimensional digital reconstruction of the jaw adductor musculature of the extinct marsupial giant Diprotodon optatum

The morphology and arrangement of the jaw adductor muscles in vertebrates reflects masticatory style and feeding processes, diet and ecology. However, gross muscle anatomy is rarely preserved in fossils and is, therefore, heavily dependent on reconstructions. An undeformed skull of the extinct marsupial, Diprotodon optatum, recovered from Pleistocene sediments at Bacchus Marsh in Victoria, represents the most complete and best preserved specimen of the species offering a unique opportunity to investigate functional anatomy. Computed tomography (CT) scans and digital reconstructions make it possible to visualise internal cranial anatomy and predict location and morphology of soft tissues, including muscles. This study resulted in a 3D digital reconstruction of the jaw adductor musculature of Diprotodon, revealing that the arrangement of muscles is similar to that of kangaroos and that the muscle actions were predominantly vertical. 3D digital muscle reconstructions provide considerable advantages over 2D reconstructions for the visualisation of the spatial arrangement of the individual muscles and the measurement of muscle properties (length, force vectors and volume). Such digital models can further be used to estimate muscle loads and attachment sites for biomechanical analyses

The biomechanical role of the chondrocranium and sutures in a lizard cranium

The role of soft tissues in skull biomechanics remains poorly understood. Not least, the chondrocranium, the portion of the braincase which persists as cartilage with varying degrees of mineralization. It also remains commonplace to overlook the biomechanical role of sutures despite evidence that they alter strain distribution. Here, we examine the role of both the sutures and the chondrocranium in the South American tegu lizard Salvator merianae. We use multi-body dynamics analysis (MDA) to provide realistic loading conditions for anterior and posterior unilateral biting and a detailed finite element model to examine strain magnitude and distribution. We find that strains within the chondrocraniumare greatest during anterior biting and are primarily tensile; also that strain within the cranium is not greatly reduced by the presence of the chondrocraniumunless it is given the same material properties as bone. This result contradicts previous suggestions that the anterior portion (the nasal septum) acts as a supporting structure. Inclusion of sutures to the cranium model not only increases overall strain magnitudes but also leads to a more complex distribution of tension and compression rather than that of a beam under sagittal bending

Morphology of the Jaw-Closing Musculature in the Common Wombat (Vombatus ursinus) Using Digital Dissection and Magnetic Resonance Imaging

Wombats are unique among marsupials in having one pair of upper incisors, and hypsodont molars for processing tough, abrasive vegetation. Of the three extant species, the most abundant, the common wombat (Vombatus ursinus), has had the least attention in terms of masticatory muscle morphology, and has never been thoroughly described. Using MRI and digital dissection to compliment traditional gross dissections, the major jaw adductor muscles, the masseter, temporalis and pterygoids, were described. The masseter and medial pterygoid muscles are greatly enlarged compared to other marsupials. This, in combination with the distinctive form and function of the dentition, most likely facilitates processing a tough, abrasive diet. The broad, flat skull and large masticatory muscles are well suited to generate a very high bite force. MRI scans allow more detail of the muscle morphology to be observed and the technique of digital dissections greatly enhances the knowledge obtained from gross dissections

Cranial biomechanics, bite force and function of the endocranial sinuses in Diprotodon optatum, the largest known marsupial

The giant extinct marsupial Diprotodon optatum has unusual skull morphology for an animal of its size, consisting of very thin bone and large cranial sinuses that occupy most of the internal cranial space. The function of these sinuses is unknown as there are no living marsupial analogues. The finite element method was applied to identify areas of high and low stress, and estimate the bite force of Diprotodon to test hypotheses on the function of the extensive cranial sinuses. Detailed three‐dimensional models of the cranium, mandible and jaw adductor muscles were produced. In addition, manipulations to the Diprotodon cranial model were performed to investigate changes in skull and sinus structure, including a model with no sinuses (sinuses ‘filled’ with bone) and a model with a midsagittal crest. Results indicate that the cranial sinuses in Diprotodon significantly lighten the skull while still providing structural support, a high bite force and low stress, indicating the cranium may have been able to withstand higher loads than those generated during feeding. Data from this study support the hypothesis that pneumatisation is driven by biomechanical loads and occurs in areas of low stress. The presence of sinuses is likely to be a byproduct of the separation of the outer surface of the skull from the braincase due to the demands of soft tissue including the brain and the large jaw adductor musculature, especially the temporalis. In very large species, such as Diprotodon, this separation is more pronounced, resulting in extensive cranial sinuses due to a relatively small brain compared with the size of the skull

Description of new cranial material of Propalorchestes (Marsupialia: Palorchestidae) from the Middle Miocene Camfield Beds, Northern Territory, Australia

Additional material referable to Propalorchestes novaculacephalus from the middle Miocene Camfield Beds is described. A cranium prepared in 1999-2000 from material collected on the T. H. Rich expedition of 1981 represents the most complete skull of the genus found to date. The detailed preservation of the previously unknown rostral anatomy supports the hypothesis that Propalorchestes possessed retracted nasal morphology. Cheek teeth from the skull and an additional isolated mandibular fragment from the same site, adds to the dental record for the genus. It further supports the intermediate condition of the molar morphology between the fully bilophodont Palorchestes and the subselenodont/semilophodont wynyardiid morphologies. The highly retracted nasal morphology and corresponding mandibular features demonstrate an advanced and highly derived condition in contrast to the plesiomorphic features previously described for the basicranium. In comparison to the generalized rostral anatomy of the sister group, the early to middle Miocene Diprotodontidae, this more complete record of Propalorchestes cranial morpholgy, suggests a significantly earlier origin for the highly derived facial anatomy in the Palorchestidae

Assessing healthcare quality using routine data: evaluating the performance of the national tuberculosis programme in South Africa

ObjectiveTo assess the performance of healthcare facilities by means of indicators based on guidelines for clinical care of TB, which is likely a good measure of overall facility quality.MethodsWe assessed quality of care in all public health facilities in South Africa using graphical, correlation and locally weighted kernel regression analysis of routine TB test data.ResultsFacility performance falls short of national standards of care. Only 74% of patients with TB provided a second specimen for testing, 18% received follow‐up testing and 14% received drug resistance testing. Only resistance testing rates improved over time, tripling between 2004 and 2011. National awareness campaigns and changes in clinical guidelines had only a transient impact on testing rates. The poorest performing facilities remained at the bottom of the rankings over the period of study.ConclusionThe optimal policy strategy requires both broad‐based policies and targeted resources to poor performers. This approach to assessing facility quality of care can be adapted to other contexts and also provides a low‐cost method for evaluating the effectiveness of proposed interventions. Devising targeted policies based on routine data is a cost‐effective way to improve the quality of public health care provided.ObjectifEvaluer la performance des établissements de santé au moyen d’indicateurs basés sur des directives pour les soins cliniques de la tuberculose (TB), qui sont probablement une bonne mesure de la qualité globale des établissements.MéthodesNous avons évalué la qualité des soins dans tous les établissements de santé publique en Afrique du Sud à l’aide d’une analyse de régression graphique, de corrélation et localement pondérée des données de dépistage de routine de la TB.RésultatsLa performance des établissements ne respecte pas les normes nationales de soins. Seuls 74% des patients TB ont fourni un deuxième échantillon pour les tests, 18% ont reçu des tests de suivi et 14% ont reçu des tests de résistance aux médicaments. Seuls les taux de dépistage de la résistance se sont améliorés au cours du temps, en triplant entre 2004 et 2011. Les campagnes de sensibilisation nationales et les changements apportés aux directives cliniques n’ont eu qu’un impact transitoire sur les taux de dépistage. Les établissements avec la plus mauvaise performance sont restés au bas du classement au cours de la période étudiée.ConclusionLa stratégie politique optimale requiert à la fois des politiques générales et des ressources ciblées pour la mauvaise performance. Cette méthode d’évaluation de la qualité des soins peut être adaptée à d’autres contextes et procure également une méthode peu coûteuse pour évaluer l’efficacité des interventions proposées. L’élaboration de politiques ciblées basées sur des données de routine est un moyen rentable pour améliorer la qualité des soins de santé publique fournis.Mots‐clésqualité des soins, mesure de la qualité, prestation des soins de santé, politique de santé, tuberculose, résistance aux antibiotiques, Afrique du SudObjetivoEvaluar el desempeño de los centros sanitarios por medio de indicadores basados en guías para la atención clínica de la TB, lo cual podría ser una buena medida de la calidad general de las instalaciones.MétodosHemos evaluado la calidad de la atención en centros sanitarios públicos de Sudáfrica mediante análisis gráficos, correlaciones y regresiones ponderadas de Kernel utilizando datos rutinarios de TB.ResultadosEl desempeño de los centros está por debajo de los estándares nacionales de cuidado. Solo un 74% de los pacientes con TB proveyeron un segundo espécimen para pruebas, un 18% recibió pruebas de seguimiento, y un 14% pruebas de resistencia a medicamentos. Solo mejoraron a lo largo del tiempo las tasas de las pruebas de resistencia, triplicándose entre el 2004‐2011. Las campañas de concienciación nacionales y los cambios en las guías clínicas solo tenían un impacto transitorio sobre las tasas de las pruebas. Los centros con los peores resultados continuaron en lo más bajo de la clasificación a lo largo del periodo de estudio.ConclusiónLa estrategia óptima requiere tanto el uso de políticas de base amplia como de recursos dirigidos a quienes tienen un peor desempeño. Esta aproximación para evaluar la calidad de la atención de los centros puede adaptarse a otros contextos, y también provee un método de bajo coste para evaluar la efectividad de las intervenciones propuestas. La elaboración de políticas orientadas, basadas en datos rutinarios, es una forma coste‐efectiva de mejorar la calidad de la atención sanitaria pública.Palabras clavecalidad de la atención, calidad de medidas, entrega de atención sanitaria, política sanitaria, tuberculosis, resistencia a antibióticos, SudáfricaPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135966/1/tmi12819.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/135966/2/tmi12819_am.pd

Does directly observed therapy improve tuberculosis treatment? More evidence is needed to guide tuberculosis policy

Abstract Background Tuberculosis (TB) now ranks alongside HIV as the leading infectious disease cause of death worldwide and incurs a global economic burden of over $12 billion annually. Directly observed therapy (DOT) recommends that TB patients complete the course of treatment under direct observation of a treatment supporter who is trained and overseen by health services to ensure that patients take their drugs as scheduled. Though the current WHO End TB Strategy does not mention DOT, only “supportive treatment supervision by treatment partners”, many TB programs still use it despite the fact that the has not been demonstrated to be statistically significantly superior to self-administered treatment in ensuring treatment success or cure. Discussion DOT is designed to promote proper adherence to the full course of drug therapy in order to improve patient outcomes and prevent the development of drug resistance. Yet over 8 billion dollars is spent on TB treatment each year and thousands undergo DOT for all or part of their course of treatment, despite the absence of rigorous evidence supporting the superior effectiveness of DOT over self-administration for achieving drug susceptible TB (DS-TB) cure. Moreover, the DOT component burdens patients with financial and opportunity costs, and the potential for intensified stigma. To rigorously evaluate the effectiveness of DOT and identify the essential contributors to both successful treatment and minimized patient burden, we call for a pragmatic experimental trial conducted in real-world program settings, the gold standard for evidence-based health policy decisions. It is time to invest in the rigorous evaluation of DOT and reevaluate the DOT requirement for TB treatment worldwide. Summary Rigorously evaluating the choice of treatment supporter, the frequency of health care worker contact and the development of new educational materials in a real-world setting would build the evidence base to inform the optimal design of TB treatment protocol. Implementing a more patient-centered approach may be a wise reallocation of resources to raise TB cure rates, prevent relapse, and minimize the emergence of drug resistance. Maintaining the status quo in the absence of rigorous supportive evidence may diminish the effectiveness of TB control policies in the long run.http://deepblue.lib.umich.edu/bitstream/2027.42/134652/1/12879_2016_Article_1862.pd

Clarifying Relationships Between Cranial Form and Function in Tapirs, With Implications for the Dietary Ecology of Early Hominins

Paleontologists and paleoanthropologists have long debated relationships between cranial morphology and diet in a broad diversity of organisms. While the presence of larger temporalis muscle attachment area (via the presence of sagittal crests) in carnivorans is correlated with durophagy (i.e. hard-object feeding), many primates with similar morphologies consume an array of tough and hard foods—complicating dietary inferences of early hominins. We posit that tapirs, large herbivorous mammals showing variable sagittal crest development across species, are ideal models for examining correlations between textural properties of food and sagittal crest morphology. Here, we integrate dietary data, dental microwear texture analysis, and finite element analysis to clarify the functional significance of the sagittal crest in tapirs. Most notably, pronounced sagittal crests are negatively correlated with hard-object feeding in extant, and several extinct, tapirs and can actually increase stress and strain energy. Collectively, these data suggest that musculature associated with pronounced sagittal crests—and accompanied increases in muscle volume—assists with the processing of tough food items in tapirs and may yield similar benefits in other mammals including early hominins

An assessment of the role of the falx cerebri and tentorium cerebelli in the cranium of the cat (Felis silvestris catus)

© 2018 The Author(s). The falx cerebri and the tentorium cerebelli are two projections of the dura mater in the cranial cavity which ossify to varying degrees in some mammalian species. The idea that the ossification of these structures may be necessary to support the loads arising during feeding has been proposed and dismissed in the past, but never tested quantitatively. To address this, a biomechanical model of a domestic cat (Felis silvestris catus) skull was created and the material properties of the falx and tentorium were varied for a series of loading regimes incorporating the main masticatory and neck muscles during biting. Under these loading conditions, ossification of the falx cerebri does not have a significant impact on the stress in the cranial bones. In the case of the tentorium, however, a localized increase in stress was observed in the parietal and temporal bones, including the tympanic bulla, when a non-ossified tentorium was modelled. These effects were consistent across the different analyses, irrespective of loading regime. The results suggest that ossification of the tentorium cerebelli may play a minor role during feeding activities by decreasing the stress in the back of the skull