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Fulltext Mandibular sawing in a snail-eating snake

Kojima Y, Fukuyama I, Kurita T, Hossman MYB, Nishikawa K

Sci Rep, 2020 07 29;10(1):12670.
PMID: 32728121 DOI: 10.1038/s41598-020-69436-7

The jaws of vertebrates display a striking diversity in form and function, but they typically open and close like a trapdoor rather than sliding like a saw. Here, we report unique feeding behaviour in the blunt-headed snail-eating snake, Aplopeltura boa (family Pareidae), where the snake cuts off and circumvents the indigestible part (the operculum) of its prey in the mouth using long sliding excursions of one side of the mandible, while the upper jaws and the mandible on the other side maintain a stable grasp on the prey. This behaviour, which we call 'mandibular sawing', is made possible by extraordinarily independent movements of the jaw elements and is a surprising departure from usual feeding behaviour in vertebrates.

Matched MeSH terms: Mandible/physiology
Fulltext In vivo bone strain and finite element modeling of a rhesus macaque mandible during mastication

Panagiotopoulou O, Iriarte-Diaz J, Wilshin S, Dechow PC, Taylor AB, Mehari Abraha H, et al.

Zoology (Jena), 2017 10;124:13-29.
PMID: 29037463 DOI: 10.1016/j.zool.2017.08.010

Finite element analysis (FEA) is a commonly used tool in musculoskeletal biomechanics and vertebrate paleontology. The accuracy and precision of finite element models (FEMs) are reliant on accurate data on bone geometry, muscle forces, boundary conditions and tissue material properties. Simplified modeling assumptions, due to lack of in vivo experimental data on material properties and muscle activation patterns, may introduce analytical errors in analyses where quantitative accuracy is critical for obtaining rigorous results. A subject-specific FEM of a rhesus macaque mandible was constructed, loaded and validated using in vivo data from the same animal. In developing the model, we assessed the impact on model behavior of variation in (i) material properties of the mandibular trabecular bone tissue and teeth; (ii) constraints at the temporomandibular joint and bite point; and (iii) the timing of the muscle activity used to estimate the external forces acting on the model. The best match between the FEA simulation and the in vivo experimental data resulted from modeling the trabecular tissue with an isotropic and homogeneous Young's modulus and Poisson's value of 10GPa and 0.3, respectively; constraining translations along X,Y, Z axes in the chewing (left) side temporomandibular joint, the premolars and the m1; constraining the balancing (right) side temporomandibular joint in the anterior-posterior and superior-inferior axes, and using the muscle force estimated at time of maximum strain magnitude in the lower lateral gauge. The relative strain magnitudes in this model were similar to those recorded in vivo for all strain locations. More detailed analyses of mandibular strain patterns during the power stroke at different times in the chewing cycle are needed.

Matched MeSH terms: Mandible/physiology*
Polymorphism in emergence of deciduous dentition: A cross-sectional study of Indian children

Kariya P, Tandon S, Singh S, Tewari N

J Investig Clin Dent, 2018 Feb;9(1).
PMID: 28349669 DOI: 10.1111/jicd.12266

AIM: The aim of the present study was to evaluate the timing and sequence of the eruption of deciduous teeth in Indian children.
METHOD: This cross-sectional study focused on children aged 5-36 months. One hospital was randomly selected from four geographic zones of the city. A total of 400 children from each hospital, fulfilling the inclusion criteria, constituted the sample. The examination was carried out by a single, trained examiner. The tooth was recorded as "present" or "absent" on the day of examination. The mean age of emergence was calculated using a probit model. Independent sample t-test was used to assess the statistical significance of differences in the mean age of tooth emergence.
RESULTS: The deciduous mandibular central incisor was the first tooth to erupt in the oral cavity (8.15±1.69 months). Girls showed delayed eruption compared to boys; however, no interarch variation was observed in the mean age of tooth eruption. There was also no difference in the sequence of eruption of deciduous teeth, as reported in other studies.
CONCLUSIONS: The present study establishes a chronological table for the eruption of deciduous teeth in Indian children. There was delayed eruption of deciduous teeth when compared to the reference ranges of Western populations.

Matched MeSH terms: Mandible/physiology*
Inter- and intraspecific aggression in the invasive longlegged ant (Hymenoptera: Formicidae)

Chong KF, Lee CY

J Econ Entomol, 2010 Oct;103(5):1775-83.
PMID: 21061979

The longlegged ant, Anoplolepis gracilipes (Fr. Smith) (Hymenoptera: Formicidae), is a highly invasive species that can aggressively displace other ant species. We conducted laboratory assays to examine interspecies aggression of A. gracilipes versus 15 sympatric ant species found in the urban environment and disturbed habitat in Malaysia: Monomorium pharaonis (L.), Monomorium floricola (Jerdon), Monomorium orientale Mayr, Monomorium destructor (Jerdon), Pheidole parva Mayr, Crematogaster sp., Solenopsis geminata (F.), Tapinoma indicum (Forel), Tapinoma melanocephalum (F.), Technomyrmnex butteli Forel, Dolichoderus thoracicus (Smith), Paratrechina longicornis (Latrielle), Oecophylla smaragdina (F), Camponotus sp., and Tetraponera rufonigra (Jerdon). A. gracilipes showed aggressive behavior toward all opponent species, except the smallest M. orientale. Opponent species size (body size, head width, and mandible width) was significantly correlated with A. gracilipes aggression level and mortality rate. We also found a significant positive relationship between A. gracilipes aggression level and the mortality of the opponent species. The results suggest that invasive populations of A. gracilipes would have the greatest impact on larger ant species. In addition, we examined the intraspecific aggression of A. gracilipes. We found that A. gracilipes from different localities in Malaysia showed intraspecific aggression toward one another. This finding differs from the results of studies conducted in Christmas Island earlier. Differences in the genetic variability among populations may explain these differing results.

Matched MeSH terms: Mandible/physiology
Intubation without muscle relaxant: an alternative technique for rapid tracheal intubation

Wong AK, Teoh GS

Anaesth Intensive Care, 1996 Apr;24(2):224-30.
PMID: 9133197

The quality of laryngoscopy and tracheal intubation with propofol augmented by alfentanil was investigated as an alternative technique for rapid tracheal intubation. 119 patients aged between 18 and 60 years (ASA 1 and 2) undergoing elective surgery were prospectively studied in a randomized double-blind controlled fashion. Tracheal intubation facilitated by suxamethonium 1.0 mg/kg alfentanil 15 mu g/kg alfentanil 30 mu g/kg or saline control was compared after propofol induction. The quality of laryngoscopy and intubation were graded according to jaw relaxation, ease of insertion of the endotracheal tube and coughing on intubation. Failure to intubate occurred in 4% and 17% with alfentanil 15 mu g/kg and saline control respectively Tracheal intubation was successful in all patients with alfentanil 30 mu g/kg and suxamethonium 1.0 mg/kg. Alfentanil 15 mu g/kg was not statistically significantly different from saline (P = 0.112). Alfentanil 30 mu g/kg provided similar overall intubating conditions (P = 0.5) to suxamethonium 1.0 mg/kg. Alfentanil in both dosages effectively attenuated the haemodynamic responses to laryngoscopy and tracheal intubation.

Matched MeSH terms: Mandible/physiology