Publications by authors named "Motoharu Oishi"

17 Publications

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Assessing thoraco-pelvic covariation in Homo sapiens and Pan troglodytes: A 3D geometric morphometric approach.

Am J Phys Anthropol 2020 11 30;173(3):514-534. Epub 2020 Aug 30.

Departamento de Paleobiología, Museo Nacional de Ciencias Naturales (CSIC), Madrid, Spain.

Objectives: Understanding thoraco-pelvic integration in Homo sapiens and their closest living relatives (genus Pan) is of great importance within the context of human body shape evolution. However, studies assessing thoraco-pelvic covariation across Hominoidea species are scarce, although recent research would suggest shared covariation patterns in humans and chimpanzees but also species-specific features, with sexual dimorphism and allometry influencing thoraco-pelvic covariation in these taxa differently.

Material And Methods: N = 30 adult H. sapiens and N = 10 adult Pan troglodytes torso 3D models were analyzed using 3D geometric morphometrics and linear measurements. Effects of sexual dimorphism and allometry on thoraco-pelvic covariation were assessed via regression analyses, and patterns of thoraco-pelvic covariation in humans and chimpanzees were computed via Two-Block Partial Least Squares analyses.

Results: Results confirm the existence of common aspects of thoraco-pelvic covariation in humans and chimpanzees, and also species-specific covariation in H. sapiens that is strongly influenced by sexual dimorphism and allometry. Species-specific covariation patterns in chimpanzees could not be confirmed because of the small sample size, but metrics point to a correspondence between the most caudal ribs and iliac crest morphology that would be irrespective of sex.

Conclusions: This study suggests that humans and chimpanzees share common aspects of thoraco-pelvic covariation but might differ in others. In humans, torso integration is strongly influenced by sexual dimorphism and allometry, whilst in chimpanzees it may not be. This study also highlights the importance not only of torso widths but also of torso depths when describing patterns of thoraco-pelvic covariation in primates. Larger samples are necessary to support these interpretations.
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http://dx.doi.org/10.1002/ajpa.24103DOI Listing
November 2020

Three-dimensional geometric morphometrics of thorax-pelvis covariation and its potential for predicting the thorax morphology: A case study on Kebara 2 Neandertal.

J Hum Evol 2020 10 14;147:102854. Epub 2020 Aug 14.

Paleoanthropology Group, Museo Nacional de Ciencias Naturales (CSIC), J.G. Abascal 2, 28006, Madrid, Spain.

The skeletal torso is a complex structure of outstanding importance in understanding human body shape evolution, but reconstruction usually entails an element of subjectivity as researchers apply their own anatomical expertise to the process. Among different fossil reconstruction methods, 3D geometric morphometric techniques have been increasingly used in the last decades. Two-block partial least squares analysis has shown great potential for predicting missing elements by exploiting the covariation between two structures (blocks) in a reference sample: one block can be predicted from the other one based on the strength of covariation between blocks. The first aim of this study is to test whether this predictive approach can be used for predicting thorax morphologies from pelvis morphologies within adult Homo sapiens reference samples with known covariation between the thorax and the pelvis. The second aim is to apply this method to Kebara 2 Neandertal (Israel, ∼60 ka) to predict its thorax morphology using two different pelvis reconstructions as predictors. We measured 134 true landmarks, 720 curve semilandmarks, and 160 surface semilandmarks on 60 3D virtual torso models segmented from CT scans. We conducted three two-block partial least squares analyses between the thorax (block 1) and the pelvis (block 2) based on the H. sapiens reference samples after performing generalized Procrustes superimposition on each block separately. Comparisons of these predictions in full shape space by means of Procrustes distances show that the male-only predictive model yields the most reliable predictions within modern humans. In addition, Kebara 2 thorax predictions based on this model concur with the thorax morphology proposed for Neandertals. The method presented here does not aim to replace other techniques, but to rather complement them through quantitative prediction of a virtual 'scaffold' to articulate the thoracic fossil elements, thus extending the potential of missing data estimation beyond the methods proposed in previous works.
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http://dx.doi.org/10.1016/j.jhevol.2020.102854DOI Listing
October 2020

Changes in the skeletal dimensions of the digits of the thoracic limb of Holstein cows after maturation.

Anat Histol Embryol 2020 May 22;49(3):333-344. Epub 2020 Jan 22.

Laboratory of Anatomy 1, School of Veterinary Medicine, Azabu University, Kanagawa, Japan.

The 12 left digits of the thoracic limb of Holstein female cows were obtained from a slaughterhouse, and 13 linear measurements of skeletal specimens of the digits of the thoracic limb were used in this study. Bivariate plots, regressions and correlation analyses were performed to assess the relationships between osteometric data and age, and between osteometric data and body size. The geometric mean (GM) of the metacarpal size was used as a proxy of body weight. The results of the regression analysis demonstrated that the length and the width of the distal phalanx were significantly correlated with age, whereas those of other bones were not. In addition, the correlations of the distal phalanx tended to be higher with age than with the GM of the metacarpal size, and their skeletal measurements tended to be longer in older animals than in younger animals. These findings suggest that the distal phalanx is slightly elongated and enlarged in its solear aspect with increasing age in skeletally mature cows. Moreover, although the side difference in the distal phalanx between the lateral and medial digits did not increase significantly with age, the solear aspect of the distal phalanx tended to be rougher, and deformation of the flexor tubercle tended to be more pronounced in the medial digit compared with the lateral digit. Therefore, in the distal phalanx of the front feet, the skeletal deformation with age and asymmetrical bone development might be related to the pathogenesis of claw horn lesions, as in the hind feet.
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http://dx.doi.org/10.1111/ahe.12532DOI Listing
May 2020

Arrangement of foot interosseous muscles in African great apes.

Am J Phys Anthropol 2018 12 10;167(4):924-929. Epub 2018 Oct 10.

Laboratory of Anatomy 1, Department of Veterinary Medicine, School of Veterinary Medicine, Azabu University, Sagamihara, Kanagawa, Japan.

Objectives: The dorsal interossei of the human foot are arranged so that they abduct the digits around the second digit, while those of non-hominoid anthropoid primates are mostly arranged around the third or fourth digit. This is thought to relate to the medial shift in the functional axis, an essential modification in the evolution of the human foot. However, studies of the arrangement of interosseous muscles are relatively limited and there is some debate about their arrangement in great apes. In particular, some researchers claim that the interossei of chimpanzees are arranged around the second digit, whereas others claim that their foot axis lies on the third digit.

Materials And Methods: We examined the arrangement of the foot interosseous muscles in ten chimpanzees, one bonobo, and three gorillas.

Results: The interossei were arranged around the second digit in two chimpanzees, one bonobo, and one gorilla, whereas the third digit was the axis in the other specimens.

Discussions: The variation observed suggests that the arrangement of the interosseous muscles of the great apes is in a transitional condition from monkey-type to human-type. Considering that osteological and foot pressure research supports the idea that the foot axis is on the second digit in great apes, modification in the interosseous muscles appears to lag behind modification in the metatarsals and foot motion.
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http://dx.doi.org/10.1002/ajpa.23685DOI Listing
December 2018

Multivariate analysis of variations in intrinsic foot musculature among hominoids.

J Anat 2018 05 12;232(5):812-823. Epub 2018 Jan 12.

Laboratory of Anatomy 1, School of Veterinary Medicine, Azabu University, Kanagawa, Japan.

Comparative analysis of the foot muscle architecture among extant great apes is important for understanding the evolution of the human foot and, hence, human habitual bipedal walking. However, to our knowledge, there is no previous report of a quantitative comparison of hominoid intrinsic foot muscle dimensions. In the present study, we quantitatively compared muscle dimensions of the hominoid foot by means of multivariate analysis. The foot muscle mass and physiological cross-sectional area (PCSA) of five chimpanzees, one bonobo, two gorillas, and six orangutans were obtained by our own dissections, and those of humans were taken from published accounts. The muscle mass and PCSA were respectively divided by the total mass and total PCSA of the intrinsic muscles of the entire foot for normalization. Variations in muscle architecture among human and extant great apes were quantified based on principal component analysis. Our results demonstrated that the muscle architecture of the orangutan was the most distinctive, having a larger first dorsal interosseous muscle and smaller abductor hallucis brevis muscle. On the other hand, the gorilla was found to be unique in having a larger abductor digiti minimi muscle. Humans were distinguished from extant great apes by a larger quadratus plantae muscle. The chimpanzee and the bonobo appeared to have very similar muscle architecture, with an intermediate position between the human and the orangutan. These differences (or similarities) in architecture of the intrinsic foot muscles among humans and great apes correspond well to the differences in phylogeny, positional behavior, and locomotion.
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http://dx.doi.org/10.1111/joa.12780DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5879964PMC
May 2018

Ultrasonographic assessment of the male koala (Phascolarctos cinereus) reproductive tract.

Res Vet Sci 2018 Apr 27;117:219-223. Epub 2017 Dec 27.

School of Agriculture and Food Sciences, The University of Queensland, Gatton campus, Queensland, Australia.

Studies documenting the application of ultrasonography to depict normal and pathological changes in koalas (Phascolarctos cinereus), especially in the male, are scarce. Sixty-two wild koalas were used in this study to define ultrasonographic protocols and features for the assessment of the male koala reproductive tract. Testis, epididymis and spermatic cord were examined using a hockey stick transducer. The normal koala testis showed a homogeneous echogenicity and an obvious hyper-echoic band corresponding to the tunica albuginea. The cauda epididymis was characterised by hypo- and hyper-echoic regions and was most effectively imaged in sagittal section. The koala prostate was assessed using a micro-curved transducer positioned midline, caudal to the bladder. On transverse section, it showed distinct margins and a well-defined internal structure, although the prostatic urethra was not apparent on most scans. To image the bulbourethral glands (BGs), the hockey stick transducer was placed lateral to the cloaca. BGIII was located just below the skin, while BGII was located deeper than BGIII. BGI was too small and not sufficiently echogenic to be detected. The ultrasonographic appearance of the BGs was similar to that of the testes but with more obvious hypo-echoic stippling. This comprehensive review of the ultrasonographic appearance of normal male koala reproductive tract can be used by veterinarians and others, in zoos or those working with wild koalas, during assessment of the reproductive tract of male koalas in relation to seasonal changes in accessory gland function or for the pathological investigation of reproductive lesions and infertility problems.
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http://dx.doi.org/10.1016/j.rvsc.2017.12.019DOI Listing
April 2018

3D geometric morphometrics of thorax variation and allometry in Hominoidea.

J Hum Evol 2017 12 1;113:10-23. Epub 2017 Sep 1.

Department of Mechanical Engineering, Faculty of Science and Technology, Keio University, Yokohama 223-8522, Japan.

Ever since the seminal papers of Keith and Schultz, hominoid primate ribcages have been described as either "funnel-" or "barrel-shaped." Following this dichotomic typology, it is currently held that Homo sapiens and hylobatids (gibbons and siamangs) share a barrel-shaped ribcage and that they are more similar to each other than to the funnel-shaped thoraces of great apes (Gorilla, Pan, and Pongo). Other researchers hypothesized that thoracic width and the invagination of the thoracic spine into the thorax are related to allometry. However, analyses that take into account the complex three-dimensional (3D) shape of the ribcage are lacking. Here, we address hypotheses about thorax shape and evolution using 3D morphometrics of thoraces in anatomical connection obtained by computed tomography scans of 23 hominoid cadavers and 10 humans and examining thorax compartments composed of seven ribs (1-7 thorax) and of 11 ribs (1-11 thorax). In the 1-7 thorax analyses, the human thorax is uniquely flat because of torsion of the upper and central ribs, differing from all non-human hominoids including hylobatids. In the 1-11 thorax analyses, humans are markedly different from African great apes, with hylobatids and orangutans intermediate. In full shape space analyses, affinities between orangutans and humans on the one hand and between hylobatids and African great apes on the other are evident. Therefore, we reject the hypothesis that humans and hylobatids bear any special affinities in overall 3D thorax shape to each other. We find that larger thoraces are wider and flatter, with a more invaginated spine, supporting the allometric hypothesis. Hominoid thorax variation shows complex interactions between allometry, rib curves, torsion, and declination, and the morphology of the costo-vertebral joint and the thoracic vertebral column. When considering functional specializations alongside phylogenetic relationships, an overly simplistic dichotomy between funnel-shaped and barrel-shaped thoraces is not supported.
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http://dx.doi.org/10.1016/j.jhevol.2017.08.002DOI Listing
December 2017

Muscle architectural properties in the common marmoset (Callithrix jacchus).

Primates 2017 Jul 8;58(3):461-472. Epub 2017 May 8.

Department of Biosciences and Informatics, Faculty of Science and Technology, Keio University, Yokohama, 223-8522, Japan.

The common marmoset, Callithrix jacchus, is a small New World monkey that has recently gained attention as an important experimental animal model in the field of neuroscience as well in rehabilitative and regenerative medicine. This attention reflects the closer phylogenetic relationship between humans and common marmosets compared to that between humans and other experimental animals. When studying the neuronal mechanism behind various types of neurological motor disorders using the common marmoset, possible differences in muscle parameters (e.g., the force-generating capacity of each of the muscles) between the common marmoset and other animals must be taken into account to permit accurate interpretation of observed motor behavior. Differences in the muscle architectural properties are expected to affect biomechanics, and hence to affect neuronal control of body movements. Therefore, we dissected the forelimbs and hind limbs of two common marmosets, including systematic analysis of the muscle mass, fascicle length, and physiological cross-sectional area (PCSA). Comparisons of the mass fractions and PCSA fractions of the forelimb and hind limb musculature among the common marmoset, human, Japanese macaque, and domestic cat demonstrated that the overall muscle architectural properties of the forelimbs and hind limbs in the common marmoset are very similar to those of the Japanese macaque, a typical quadrupedal primate. However, muscle architectural properties of the common marmoset differ from those of the domestic cat, which has relatively larger hamstrings and pedal digital flexor muscles. Compared to humans, the common marmoset exhibits relatively smaller shoulder protractor, retractor, and abductor muscles and larger elbow extensor and rotator-cuff muscles in the forelimb, and smaller plantarflexor muscles in the hind limb. These differences in the muscle architectural properties must be taken into account when interpreting motor behaviors such as locomotion and arm-reaching movements in the common marmoset.
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http://dx.doi.org/10.1007/s10329-017-0608-9DOI Listing
July 2017

Mobility of the forearm in the raccoon (Procyon lotor), raccoon dog (Nyctereutes procyonoides) and red panda (Ailurus fulgens).

J Vet Med Sci 2017 Jan 11;79(1):224-229. Epub 2016 Nov 11.

Laboratory of Veterinary Anatomy, Department of Basic Veterinary Medicine, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan.

The ranges of pronation/supination of forearms in raccoons, raccoon dogs and red pandas were nondestructively examined. Three carcasses of each species were used for CT analysis, and the left forearms were scanned with a CT scanner in two positions: maximal supination and maximal pronation. Scanning data were reconstructed into three-dimensional images, cross-sectional images were extracted at the position that shows the largest area in the distal part of ulna, and then, the centroids of each cross section of the radius and ulna were detected. CT images of two positions were superimposed, by overlapping the outlines of each ulna, and then, the centroids were connected by lines to measure the angle of rotation, as an index of range of mobility. The measurements in each animal were analyzed, using the Tukey-Kramer method. The average angle of rotation was largest in raccoons and smallest in raccoon dogs, and the difference was significant. In the maximally pronated forearm of all species, the posture was almost equal to the usual grounding position with palms touching the ground. Therefore, the present results demonstrate that the forearms of raccoons can supinate to a greater degree from the grounding position with palms on the ground, as compared with those of raccoon dogs and red pandas.
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http://dx.doi.org/10.1292/jvms.16-0241DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5289265PMC
January 2017

The seminiferous epithelial cycle and microanatomy of the koala (Phascolarctos cinereus) and southern hairy-nosed wombat (Lasiorhinus latifrons) testis.

J Anat 2013 Mar 1;222(3):380-9. Epub 2013 Jan 1.

Department of Veterinary Anatomy, School of Veterinary Medicine, Nippon Veterinary and Life Science University, Tokyo, Japan.

The koala (Phascolarctos cinereus) and southern hairy-nosed wombat (Lasiorhinus latifrons) are iconic Australian fauna that share a close phylogenetic relationship but there are currently no comparative studies of the seminiferous epithelial cell or testicular microanatomy of either species. Koala and wombat spermatozoa are unusual for marsupials as they possess a curved stream-lined head and lateral neck insertion that superficially is similar to murid spermatozoa; the koala also contains Sertoli cells with crystalloid inclusions that closely resemble the Charcot-Bottcher crystalloids described in human Sertoli cells. Eighteen sexually mature koalas and four sexually mature southern hairy-nosed (SHN) wombats were examined to establish base-line data on quantitative testicular histology. Dynamics of the seminiferous epithelial cycle in the both species consisted of eight stages of cellular association similar to that described in other marsupials. Both species possessed a high proportion of the pre-meiotic (stages VIII, I - III; koala - 62.2 ± 1.7% and SHN wombat - 66.6 ± 2.4%) when compared with post-meiotic stages of the seminiferous cycle. The mean diameters of the seminiferous tubules found in the koalas and the SHN wombats were 227.8 ± 6.1 and 243.5 ± 3.9 μm, respectively. There were differences in testicular histology between the species including the koala possessing (i) a greater proportion of Leydig cells, (ii) larger Sertoli cell nuclei, (iii) crystalloids in the Sertoli cell cytoplasm, (iv) a distinctive acrosomal granule during spermiogenesis and (v) a highly eosinophilic acrosome. An understanding of the seminiferous epithelial cycle and microanatomy of testis is fundamental for documenting normal spermatogenesis and testicular architecture; recent evidence of orchitis and epididymitis associated with natural chlamydial infection in the koala suggest that this species might be useful as an experimental model for understanding Chlamydia induced testicular pathology in humans. Comparative spermatogenic data of closely related species can also potentially reflect evolutionary divergence and differences in reproductive strategies.
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http://dx.doi.org/10.1111/joa.12020DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3582257PMC
March 2013

Muscle dimensions of the foot in the orangutan and the chimpanzee.

J Anat 2012 Oct 16;221(4):311-7. Epub 2012 Jul 16.

Department of Veterinary Anatomy, School of Veterinary Medicine, Nippon Veterinary and Life Science University, Tokyo, Japan.

The hindlimbs of two orangutans and four chimpanzees were dissected, and muscle parameters (mass, fascicle length, and physiological cross-sectional area: PCSA) were determined to explore possible interspecies variation in muscle dimensions. Muscle mass and PCSA were divided by the total mass and total PCSA of the entire foot muscles for normalization. The results indicate that the pedal interosseous and the intrinsic pedal digital extensor muscles in the orangutans probably have higher capacity for force production due to their relatively larger PCSAs than in chimpanzees. Moreover, the medial components of the intrinsic muscles exhibited relatively larger mass and PCSA ratios in orangutans. The mass and PCSA ratios of the hallucal muscles were larger in chimpanzees. These differences in foot muscle dimensions of the two species suggest that the orangutan is more specialized for hook-like digital gripping without involvement of the rudimentary hallux, while the chimpanzee is adapted to hallux-assisted power gripping in arboreal locomotion.
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http://dx.doi.org/10.1111/j.1469-7580.2012.01545.xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3458250PMC
October 2012

Muscle dimensions in the Japanese macaque hand.

Primates 2012 Oct 21;53(4):391-6. Epub 2012 Apr 21.

Department of Mechanical Engineering, Faculty of Science and Technology, Keio University, Kohoku-ku, Yokohama, Japan.

Macaques have been used as an important paradigm for understanding the neural control mechanisms of human precision grip capabilities. Therefore, we dissected the forearms and hands of two male Japanese macaques to systematically record the muscle mass, fascicle length and physiological cross-sectional area (PCSA). Comparisons of the mass fractions and PCSA fractions of the hand musculature among the Japanese macaque, chimpanzee, and human demonstrated that the sizes of the thenar and hypothenar eminence muscle groups are more balanced in the macaque and chimpanzee, but those of the thenar eminence group are much larger in the human, indicating that the capacity to generate force at the tip of the thumb is more restricted in macaques, despite their high manual dexterity. In the macaque, however, the extrinsic flexor muscles are much larger, possibly to facilitate weight bearing by the forelimbs in pronograde quadrupedal locomotion and forceful grasping of arboreal supports in gap-crossing movements such as leaping. Taking such anatomical differences imposed on the hand musculoskeletal system into consideration seems to be an important method of clarifying the mechanisms of precision grip in macaques.
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http://dx.doi.org/10.1007/s10329-012-0309-3DOI Listing
October 2012

Preliminary immunohistochemical study of natriuretic peptide receptor localization in canine and feline heart.

J Vet Med Sci 2011 Mar 19;73(3):375-8. Epub 2010 Oct 19.

Laboratory of Veterinary Anatomy, Nippon Veterinary and Life Science University, Tokyo.

We examined the immunohistochemical distributions of natriuretic peptide receptor (NPR)-A, -B and -C that bind with natriuretic peptide hormones A, B and C in four healthy crossbreed young canine and feline cardiac tissues using specific antibodies against human antigens. Cross-immunoreactivities between antigens and antibodies were confirmed using western blot analysis. NPR-A and -C were expressed more strongly in dogs than cats. In both species, these expressions were stronger in the atria than the ventricles, with stronger expression in the left ventricles than the right. NPR-B was largely very weekly or undetected. In canine and feline cardiac tissues, the expressional distribution of NPR-A, -B, and -C closely matched with that of atrial natriuretic peptide, brain natriuretic peptide, and C-type natriuretic peptide as the ligands for corresponding receptors.
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http://dx.doi.org/10.1292/jvms.10-0114DOI Listing
March 2011

Immunohistochemical localization and gene expression of carbonic anhydrase isoenzymes CA-II and CA-VI in canine lower airways and lung.

J Vet Med Sci 2009 Nov;71(11):1525-8

Department of Anatomy, School of Veterinary Medicine, Azabu University, Sagamihara, Kanagawa, Japan.

The immunohistolocalization and gene expression of carbonic anhydrase (CA) isoenzymes CA-II and CA-VI in the canine lower airways and lung were examined using specific canine CA-II and CA-VI antisera and the RT-PCR method. Laryngeal, tracheal and bronchial epithelia, serous acinar and bronchiolar secretory cells and pulmonary great alveolar cells showed immunopositive reactions to anti-CA-II and anti-CA-VI antisera. However, all mucous cells showed immunonegative reactions. The physiological roles of CA-II and CA-VI in the lower airways and lung may involve the maintenance of pH balance and the protection of mucosal surfaces against the acidic milieu.
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http://dx.doi.org/10.1292/jvms.001525DOI Listing
November 2009

Dimensions of forelimb muscles in orangutans and chimpanzees.

J Anat 2009 Oct 9;215(4):373-82. Epub 2009 Jul 9.

Department of Veterinary Anatomy, School of Veterinary Medicine, Nippon Veterinary and Life Science University, Musashino, 180-8602, Japan.

Eight forelimbs of three orangutans and four chimpanzees were dissected and the muscle mass, fascicle length and physiological cross-sectional area (PCSA) of all forelimb muscles were systematically recorded to explore possible interspecies variation in muscle dimensions. Muscle mass and PCSA were divided by the total mass and total PCSA of the entire forelimb muscles for normalization. The results indicate that the mass and PCSA ratios of the monoarticular elbow flexors (M. brachialis and M. brachioradialis) are significantly larger in orangutans. In contrast, the mass ratios of the biarticular muscles in the upper arm (the short head of M. biceps brachii and the long head of M. triceps brachii) are significantly larger in chimpanzees. For the rotator cuff muscles, the force-generating capacity of M. subscapularis is significantly larger in orangutans, whereas the opposite rotator cuff muscle, M. infraspinatus, is larger in chimpanzees. These differences in forelimb muscle dimensions of the two species may reflect functional specialization for their different positional and locomotor behaviors.
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http://dx.doi.org/10.1111/j.1469-7580.2009.01125.xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2766055PMC
October 2009

Dimensions of the foot muscles in the lowland gorilla.

J Vet Med Sci 2009 Jun;71(6):821-4

First Department of Anatomy, School of Veterinary Medicine, Azabu University, 1-17-71, Fuchinobe, Sagamihara, Kanagawa 229-8501, Japan.

We dissected the hindlimb of a female western lowland gorilla and determined the muscle dimensions (mass, fascicle length, and physiological cross-sectional area: PCSA). Comparisons of the muscle parameters of the measured gorilla with corresponding reported human data demonstrated that the triceps surae muscles were larger and had more capacity to generate force than the other muscle groups in both species, but this tendency was more prominent in the human, probably as an adaptation to strong toe-off during bipedal walking. On the other hand, PCSAs of the extrinsic pedal digital flexors and digiti minimi muscles were larger in the western lowland gorilla, suggesting that the foot, particularly the fifth toe, has a relatively high grasping capability in the lowland gorilla.
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http://dx.doi.org/10.1292/jvms.71.821DOI Listing
June 2009

Muscle architecture of the upper limb in the orangutan.

Primates 2008 Jul 1;49(3):204-9. Epub 2008 Mar 1.

Department of Anatomy 1st, School of Veterinary Medicine, Azabu University, Kanagawa, 229-8501, Japan.

We dissected the left upper limb of a female orangutan and systematically recorded muscle mass, fascicle length, and physiological cross-sectional area (PCSA), in order to quantitatively clarify the unique muscle architecture of the upper limb of the orangutan. Comparisons of the musculature of the dissected orangutan with corresponding published chimpanzee data demonstrated that in the orangutan, the elbow flexors, notably M. brachioradialis, tend to exhibit greater PCSAs. Moreover, the digital II-V flexors in the forearm, such as M. flexor digitorum superficialis and M. flexor digitorum profundus, tend to have smaller PCSA as a result of their relatively longer fascicles. Thus, in the orangutan, the elbow flexors demonstrate a higher potential for force production, whereas the forearm muscles allow a greater range of wrist joint mobility. The differences in the force-generating capacity in the upper limb muscles of the two species might reflect functional specialization of muscle architecture in the upper limb of the orangutan for living in arboreal environments.
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http://dx.doi.org/10.1007/s10329-008-0082-5DOI Listing
July 2008