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Article ; Online: The biomechanical significance of the elongated rodent incisor root in the mandible during incision.

Morris, Philip J R / Cox, Philip G / Cobb, Samuel N F

2022 Volume 12, Issue 1, Page(s) 3819

Abstract: Rodents are characterised by a distinctive masticatory apparatus which includes a single pair of enlarged and continually growing incisors. This morphology, termed diprotodonty, has also independently evolved in a number of other mammals, including the ... ...

Abstract	Rodents are characterised by a distinctive masticatory apparatus which includes a single pair of enlarged and continually growing incisors. This morphology, termed diprotodonty, has also independently evolved in a number of other mammals, including the aye-aye. This study examined the functional significance of the internal "root" of the elongated rodent-like incisor. The mandibles of four rodents and an aye-aye were modelled to exhibit incrementally shorter incisor roots. Finite element analysis was used to predict stress and strain patterns across the jaw to determine whether the length of the incisor root contributes to the resistance of mechanical forces encountered in the mandible during incision. It was found that von Mises stresses increase in the region of the mandible local to where the incisor is removed, but that the stress distribution across the wider mandible is only minimally affected. Thus, the long internal incisor appears to play a small role in resisting bending forces close to the incisor alveolus, and may act with the arch-like mandibular shape to strengthen the mandible in this region. However, the impact across the whole mandible is relatively limited, suggesting the highly elongate incisor in diprotodont mammals may be principally driven by other factors such as rapid incisor wear.
MeSH term(s)	Animals ; Finite Element Analysis ; Incisor/anatomy & histology ; Mandible/anatomy & histology ; Mandible/surgery ; Rodentia/anatomy & histology ; Tooth Root
Language	English
Publishing date	2022-03-09
Publishing country	England
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	2615211-3
ISSN	2045-2322 ; 2045-2322
ISSN (online)	2045-2322
ISSN	2045-2322
DOI	10.1038/s41598-022-07779-z
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: The biomechanical significance of the elongated rodent incisor root in the mandible during incision

Philip J. R. Morris / Philip G. Cox / Samuel N. F. Cobb

Scientific Reports, Vol 12, Iss 1, Pp 1-

2022 Volume 11

Abstract: Abstract Rodents are characterised by a distinctive masticatory apparatus which includes a single pair of enlarged and continually growing incisors. This morphology, termed diprotodonty, has also independently evolved in a number of other mammals, ... ...

Abstract	Abstract Rodents are characterised by a distinctive masticatory apparatus which includes a single pair of enlarged and continually growing incisors. This morphology, termed diprotodonty, has also independently evolved in a number of other mammals, including the aye-aye. This study examined the functional significance of the internal “root” of the elongated rodent-like incisor. The mandibles of four rodents and an aye-aye were modelled to exhibit incrementally shorter incisor roots. Finite element analysis was used to predict stress and strain patterns across the jaw to determine whether the length of the incisor root contributes to the resistance of mechanical forces encountered in the mandible during incision. It was found that von Mises stresses increase in the region of the mandible local to where the incisor is removed, but that the stress distribution across the wider mandible is only minimally affected. Thus, the long internal incisor appears to play a small role in resisting bending forces close to the incisor alveolus, and may act with the arch-like mandibular shape to strengthen the mandible in this region. However, the impact across the whole mandible is relatively limited, suggesting the highly elongate incisor in diprotodont mammals may be principally driven by other factors such as rapid incisor wear.
Keywords	Medicine ; R ; Science ; Q
Language	English
Publishing date	2022-03-01T00:00:00Z
Publisher	Nature Portfolio
Document type	Article ; Online
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Article: Mechanical significance of morphological variation in diprotodont incisors.

Morris, Philip J R / Cox, Philip G / Cobb, Samuel N

Royal Society open science

2019 Volume 6, Issue 3, Page(s) 181317

Abstract: All rodents possess a single pair of enlarged incisors that grow throughout life. This condition (diprotodonty) is characteristic of Rodentia, but is also found in other mammals such as lagomorphs, hyraxes, the aye-aye and common wombat. This study ... ...

Abstract	All rodents possess a single pair of enlarged incisors that grow throughout life. This condition (diprotodonty) is characteristic of Rodentia, but is also found in other mammals such as lagomorphs, hyraxes, the aye-aye and common wombat. This study surveyed lower incisor morphology across extant diprotodonts to examine shape variation within and between rodents and other diprotodonts, and to determine if tooth shape varies in a manner predictable from mechanics. Six linear and area variables were recorded from microCT scans of the mandibles of 33 diprotodont mammals. The curvature of the rodent lower incisors, as measured by the proportion of a circle it occupies, was shown to vary between 20 and 45%, with non-Glires taxa falling outside this range. Relative lengths of the portions of the incisor within and external to the mandible were not significantly correlated when the overall size was taken into account. Cross-sectional geometry of the incisor was significantly correlated with the external length of the incisor. Overall, incisor morphology was shown to vary in a way predictable from ecology and mechanics, in order to resist bending. Among non-rodents, lagomorph incisors closely resemble those of rodents, and, relative to rodents, hyrax and wombat incisors are somewhat smaller but aye-aye incisors are much more extreme in morphology.
Language	English
Publishing date	2019-03-27
Publishing country	England
Document type	Journal Article
ZDB-ID	2787755-3
ISSN	2054-5703
ISSN	2054-5703
DOI	10.1098/rsos.181317
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Article ; Online: Craniofacial biomechanics: in vivo to in silico.

Cobb, Samuel N

Journal of anatomy

2010 Volume 218, Issue 1, Page(s) 1–2

MeSH term(s)	Animals ; Biomechanical Phenomena ; Computer Simulation ; Facial Bones/anatomy & histology ; Finite Element Analysis ; Humans ; Imaging, Three-Dimensional/methods ; Skull/anatomy & histology
Language	English
Publishing date	2010-12-31
Publishing country	England
Document type	Introductory Journal Article
ZDB-ID	2955-5
ISSN	1469-7580 ; 0021-8782
ISSN (online)	1469-7580
ISSN	0021-8782
DOI	10.1111/j.1469-7580.2010.01328.x
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Article ; Online: Convergent evolution in the Euarchontoglires.

Morris, Philip J R / Cobb, Samuel N F / Cox, Philip G

Biology letters

2018 Volume 14, Issue 8

Abstract: Convergence-the independent evolution of similar phenotypes in distantly related clades-is a widespread and much-studied phenomenon. An often-cited, but hitherto untested, case of morphological convergence is that between the aye-aye and squirrels. The ... ...

Abstract	Convergence-the independent evolution of similar phenotypes in distantly related clades-is a widespread and much-studied phenomenon. An often-cited, but hitherto untested, case of morphological convergence is that between the aye-aye and squirrels. The aye-aye (
MeSH term(s)	Animals ; Coleoptera ; Feeding Behavior/physiology ; Larva ; Mandible/anatomy & histology ; Phylogeny ; Sciuridae/anatomy & histology ; Sciuridae/classification ; Skull/anatomy & histology ; Strepsirhini/anatomy & histology ; Strepsirhini/classification
Language	English
Publishing date	2018-08-01
Publishing country	England
Document type	Journal Article ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, Non-P.H.S.
ZDB-ID	2135022-X
ISSN	1744-957X ; 1744-9561
ISSN (online)	1744-957X
ISSN	1744-9561
DOI	10.1098/rsbl.2018.0366
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Article ; Online: Mechanical significance of morphological variation in diprotodont incisors

Philip J. R. Morris / Philip G. Cox / Samuel N. Cobb

Royal Society Open Science, Vol 6, Iss

2019 Volume 3

Abstract	All rodents possess a single pair of enlarged incisors that grow throughout life. This condition (diprotodonty) is characteristic of Rodentia, but is also found in other mammals such as lagomorphs, hyraxes, the aye-aye and common wombat. This study surveyed lower incisor morphology across extant diprotodonts to examine shape variation within and between rodents and other diprotodonts, and to determine if tooth shape varies in a manner predictable from mechanics. Six linear and area variables were recorded from microCT scans of the mandibles of 33 diprotodont mammals. The curvature of the rodent lower incisors, as measured by the proportion of a circle it occupies, was shown to vary between 20 and 45%, with non-Glires taxa falling outside this range. Relative lengths of the portions of the incisor within and external to the mandible were not significantly correlated when the overall size was taken into account. Cross-sectional geometry of the incisor was significantly correlated with the external length of the incisor. Overall, incisor morphology was shown to vary in a way predictable from ecology and mechanics, in order to resist bending. Among non-rodents, lagomorph incisors closely resemble those of rodents, and, relative to rodents, hyrax and wombat incisors are somewhat smaller but aye-aye incisors are much more extreme in morphology.
Keywords	incisor ; mechanics ; morphology ; diprotodont ; rodents ; Science ; Q
Subject code	590
Language	English
Publishing date	2019-03-01T00:00:00Z
Publisher	The Royal Society
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: The facial skeleton of the chimpanzee-human last common ancestor.

Cobb, Samuel N

Journal of anatomy

2008 Volume 212, Issue 4, Page(s) 469–485

Abstract: This review uses the current morphological evidence to evaluate the facial morphology of the hypothetical last common ancestor (LCA) of the chimpanzee/bonobo (panin) and human (hominin) lineages. Some of the problems involved in reconstructing ancestral ... ...

Abstract	This review uses the current morphological evidence to evaluate the facial morphology of the hypothetical last common ancestor (LCA) of the chimpanzee/bonobo (panin) and human (hominin) lineages. Some of the problems involved in reconstructing ancestral morphologies so close to the formation of a lineage are discussed. These include the prevalence of homoplasy and poor phylogenetic resolution due to a lack of defining derived features. Consequently the list of hypothetical features expected in the face of the LCA is very limited beyond its hypothesized similarity to extant Pan. It is not possible to determine with any confidence whether the facial morphology of any of the current candidate LCA taxa (Ardipithecus kadabba, Ardipithecus ramidus, Orrorin tugenensis and Sahelanthropus tchadensis) is representative of the LCA, or a stem hominin, or a stem panin or, in some cases, a hominid predating the emergence of the hominin lineage. The major evolutionary trends in the hominin lineage subsequent to the LCA are discussed in relation to the dental arcade and dentition, subnasal morphology and the size, position and prognathism of the facial skeleton.
MeSH term(s)	Animals ; Anthropology, Physical ; Biological Evolution ; Dentition ; Facial Bones/anatomy & histology ; Hominidae/anatomy & histology ; Humans ; Pan troglodytes ; Physiology, Comparative
Language	English
Publishing date	2008-04-02
Publishing country	England
Document type	Journal Article ; Review
ZDB-ID	2955-5
ISSN	1469-7580 ; 0021-8782
ISSN (online)	1469-7580
ISSN	0021-8782
DOI	10.1111/j.1469-7580.2008.00866.x
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Article: Functional tests of the competitive exclusion hypothesis for multituberculate extinction.

Adams, Neil F / Rayfield, Emily J / Cox, Philip G / Cobb, Samuel N / Corfe, Ian J

Royal Society open science

2019 Volume 6, Issue 3, Page(s) 181536

Abstract: 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 ... ...

Abstract	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
Language	English
Publishing date	2019-03-27
Publishing country	England
Document type	Journal Article
ZDB-ID	2787755-3
ISSN	2054-5703
ISSN	2054-5703
DOI	10.1098/rsos.181536
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Article ; Online: The multifactorial nature of beak and skull shape evolution in parrots and cockatoos (Psittaciformes).

Bright, Jen A / Marugán-Lobón, Jesús / Rayfield, Emily J / Cobb, Samuel N

BMC evolutionary biology

2019 Volume 19, Issue 1, Page(s) 104

Abstract: Background: The Psittaciformes (parrots and cockatoos) are characterised by their large beaks, and are renowned for their ability to produce high bite forces. These birds also possess a suite of modifications to their cranial architecture interpreted to ...

Abstract	Background: The Psittaciformes (parrots and cockatoos) are characterised by their large beaks, and are renowned for their ability to produce high bite forces. These birds also possess a suite of modifications to their cranial architecture interpreted to be adaptations for feeding on mechanically resistant foods, yet the relationship between cranial morphology and diet has never been explicitly tested. Here, we provide a three-dimensional geometric morphometric analysis of the developmental and biomechanical factors that may be influencing the evolution of psittaciformes' distinctive cranial morphologies. Results: Contrary to our own predictions, we find that dietary preferences for more- or less- mechanically resistant foods have very little influence on beak and skull shape, and that diet predicts only 2.4% of the shape variation in psittaciform beaks and skulls. Conversely, evolutionary allometry and integration together predict almost half the observed shape variation, with phylogeny remaining an important factor in shape identity throughout our analyses, particularly in separating cockatoos (Cacatuoidea) from the true parrots (Psittacoidea). Conclusions: Our results are similar to recent findings about the evolutionary trajectories of skull and beak shape in other avian families. We therefore propose that allometry and integration are important factors causing canalization of the avian head, and while diet clearly has an influence on beak shape between families, this may not be as important at driving evolvability within families as is commonly assumed.
MeSH term(s)	Animals ; Beak/anatomy & histology ; Biological Evolution ; Cockatoos/anatomy & histology ; Least-Squares Analysis ; Parrots/anatomy & histology ; Phylogeny ; Principal Component Analysis ; Skull/anatomy & histology
Language	English
Publishing date	2019-05-17
Publishing country	England
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ISSN	1471-2148
ISSN (online)	1471-2148
DOI	10.1186/s12862-019-1432-1
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Article ; Online: Transformation of tenofovir into stable ProTide nanocrystals with long-acting pharmacokinetic profiles.

Cobb, Denise A / Smith, Nathan / Deodhar, Suyash / Bade, Aditya N / Gautam, Nagsen / Shetty, Bhagya Laxmi Dyavar / McMillan, JoEllyn / Alnouti, Yazen / Cohen, Samuel M / Gendelman, Howard E / Edagwa, Benson

Nature communications

2021 Volume 12, Issue 1, Page(s) 5458

Abstract: Treatment and prevention of human immunodeficiency virus type one (HIV-1) infection was transformed through widespread use of antiretroviral therapy (ART). However, ART has limitations in requiring life-long daily adherence. Such limitations have led to ... ...

Abstract	Treatment and prevention of human immunodeficiency virus type one (HIV-1) infection was transformed through widespread use of antiretroviral therapy (ART). However, ART has limitations in requiring life-long daily adherence. Such limitations have led to the creation of long-acting (LA) ART. While nucleoside reverse transcriptase inhibitors (NRTI) remain the ART backbone, to the best of our knowledge, none have been converted into LA agents. To these ends, we transformed tenofovir (TFV) into LA surfactant stabilized aqueous prodrug nanocrystals (referred to as NM1TFV and NM2TFV), enhancing intracellular drug uptake and retention. A single intramuscular injection of NM1TFV, NM2TFV, or a nanoformulated tenofovir alafenamide (NTAF) at 75 mg/kg TFV equivalents to Sprague Dawley rats sustains active TFV-diphosphate (TFV-DP) levels ≥ four times the 90% effective dose for two months. NM1TFV, NM2TFV and NTAF elicit TFV-DP levels of 11,276, 1,651, and 397 fmol/g in rectal tissue, respectively. These results are a significant step towards a LA TFV ProTide.
MeSH term(s)	Adenine/analogs & derivatives ; Adenine/chemistry ; Adenine/pharmacokinetics ; Adenine/pharmacology ; Alanine/chemistry ; Alanine/pharmacokinetics ; Alanine/pharmacology ; Animals ; Anti-HIV Agents/chemistry ; Anti-HIV Agents/pharmacokinetics ; Anti-HIV Agents/pharmacology ; Drug Stability ; Female ; HIV Infections/drug therapy ; HIV Infections/metabolism ; HIV Infections/virology ; HIV-1/drug effects ; HIV-1/physiology ; Humans ; Male ; Nanoparticles/chemistry ; Organophosphates/chemistry ; Organophosphates/pharmacokinetics ; Organophosphates/pharmacology ; Prodrugs/chemistry ; Prodrugs/pharmacokinetics ; Prodrugs/pharmacology ; Rats, Sprague-Dawley ; Tenofovir/analogs & derivatives ; Tenofovir/chemistry ; Tenofovir/pharmacokinetics ; Tenofovir/pharmacology ; Therapeutic Equivalency ; Rats
Chemical Substances	Anti-HIV Agents ; Organophosphates ; Prodrugs ; tenofovir diphosphate ; Tenofovir (99YXE507IL) ; tenofovir alafenamide (EL9943AG5J) ; Adenine (JAC85A2161) ; Alanine (OF5P57N2ZX)
Language	English
Publishing date	2021-09-16
Publishing country	England
Document type	Journal Article ; Research Support, N.I.H., Extramural ; Research Support, Non-U.S. Gov't
ZDB-ID	2553671-0
ISSN	2041-1723 ; 2041-1723
ISSN (online)	2041-1723
ISSN	2041-1723
DOI	10.1038/s41467-021-25690-5
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