Forelimb Muscles Research Articles

Cheap labor: myosin fiber type expression and enzyme activity in the forelimb musculature of sloths (Pilosa: Xenarthra).

Sloths are canopy-dwelling inhabitants of American neotropical rainforests that exhibit suspensory behaviors. These abilities require both strength and muscular endurance to hang for extended periods of time; however, the skeletal muscle mass of sloths is reduced, thus requiring modifications to muscle architecture and leverage for large joint torque. We hypothesize that intrinsic muscle properties are also modified for fatigue resistance and predict a heterogeneous expression of slow/fast myosin heavy chain (MHC) fibers that utilize oxidative metabolic pathways for economic force production. MHC fiber type distribution and energy metabolism in the forelimb muscles of three-toed ( Bradypus variegatus, n = 5) and two-toed ( Choloepus hoffmanni, n = 4) sloths were evaluated using SDS-PAGE, immunohistochemistry, and enzyme activity assays. The results partially support our hypothesis by a primary expression of the slow MHC-1 isoform as well as moderate expression of fast MHC-2A fibers, whereas few hybrid MHC-1/2A fibers were found in both species. MHC-1 fibers were larger in cross-sectional area (CSA) than MHC-2A fibers and comprised the greatest percentage of CSA in each muscle sampled. Enzyme assays showed elevated activity for the anaerobic enzymes creatine kinase and lactate dehydrogenase compared with low activity for aerobic markers citrate synthase and 3-hydroxyacetyl CoA dehydrogenase. These findings suggest that sloth forelimb muscles may rely heavily on rapid ATP resynthesis pathways, and lactate accumulation may be beneficial. The intrinsic properties observed match well with suspensory requirements, and these modifications may have further evolved in unison with low metabolism and slow movement patterns as means to systemically conserve energy. NEW & NOTEWORTHY Myosin heavy chain (MHC) fiber type and fiber metabolic properties were evaluated to understand the ability of sloths to remain suspended for extended periods without muscle fatigue. Broad distributions of large, slow MHC-1 fibers as well as small, fast MHC-2A fibers are expressed in sloth forelimbs, but muscle metabolism is generally not correlated with myosin fiber type or body size. Sloth muscles rely on rapid, anaerobic pathways to resist fatigue and sustain force production.

Optogenetic surface stimulation of the rat cervical spinal cord

Electrical intraspinal microstimulation (ISMS) at various sites along the cervical spinal cord permits forelimb muscle activation, elicits complex limb movements and may enhance functional recovery after spinal cord injury. Here, we explore optogenetic spinal stimulation (OSS) as a less invasive and cell type-specific alternative to ISMS. To map forelimb muscle activation by OSS in rats, adeno-associated viruses (AAV) carrying the blue-light sensitive ion channels channelrhodopsin-2 (ChR2) and Chronos were injected into the cervical spinal cord at different depths and volumes. Following an AAV incubation period of several weeks, OSS-induced forelimb muscle activation and movements were assessed at 16 sites along the dorsal surface of the cervical spinal cord. Three distinct movement types were observed. We find that AAV injection volume and depth can be titrated to achieve OSS-based activation of several movements. Optical stimulation of the spinal cord is thus a promising method for dissecting the function of spinal circuitry and targeting therapies following injury. NEW & NOTEWORTHY Optogenetics in the spinal cord can be used both for therapeutic treatments and to uncover basic mechanisms of spinal cord physiology. For the first time, we describe the methodology and outcomes of optogenetic surface stimulation of the rat spinal cord. Specifically, we describe the evoked responses of forelimbs and address the effects of different adeno-associated virus injection paradigms. Additionally, we are the first to report on the limitations of light penetration through the rat spinal cord.

Interspecific Differences in Behavioral Responses and Neuromotorics between Laboratory Rodents Receiving Rations with Easily Digested Carbohydrates.

We assessed the effect of intake of easily digested carbohydrates for 133 days on quantitative parameters of neuromotorics and cognitive function in Wistar rats and C57Bl/6J mice. Neuromotorics (muscle tone) was assessed in rats and mice by the forelimb muscle force (grip strength) over 4 months. Anxiety was assessed in the elevated plus-maze test and cognitive function (short-term and long-term memory) was evaluated by conditioned passive avoidance response (CPAR) test over 3 months. The mice, in contrast to rats, receiving the diet with easily digested sugars demonstrated suppression of neuromotorics. Anxiety increased with age in female mice, but not in rats, irrespective of the diet. Cognitive function in rats receiving experimental rations did not change significantly in comparison with the control. In mice, consumption of equimolar mixture of fructose and glucose impared short-term, but not long-term memory, in comparison with the group receiving glucose alone. We revealed a small (by 14-17%), but statistically significant increase in the brain weight in mice receiving fructose and sucrose. The study demonstrates sufficient interspecies differences in the influence of carbohydrate rations on neuromotorics and behavioral responses in the in vivo metabolic syndrome model.

Muscle Fiber‐type Composition of Primates in Relation to Brain Size

There are many metabolic hypotheses for how humans can afford such large brains. The Expensive Tissue Hypothesis (ETH) addresses the metabolic cost of the brain in accordance to the costs of other metabolically “expensive” organs in the body. Skeletal muscle is composed of two main fiber types; type I (slow‐twitch) and type II (fast‐twitch). Type I fibers convert glucose to ATP using oxygen, while type II fibers rely primarily on anaerobic metabolic processes. When active, skeletal muscle is in direct competition with the brain for glucose and is an expensive tissue to maintain. Skeletal muscle acting as expensive tissue however, has not been addressed in context to the ETH. Based on these observations, we hypothesize that primates will have a decrease in type I fibers in accordance to their brain mass to account for the expensive tissue. For this preliminary study, our goal was to measure type I and type II fiber frequencies in various primates using immunohistochemistry to provide us with a muscle fiber composition profile. Two forelimb muscles (deltoid, pectoralis major) and two hindlimb muscles (gastrocnemius, soleus) were biopsied from 10 species of primates (N=11) for histological analysis. Formalin‐fixed paraffin embedded muscle samples were sectioned (12um) and immunostained using type I and type II Myosin heavy‐chain antibodies. Histological analysis of muscle morphology was visualized and quantified using light microscopy. Through muscle fiber‐typing, we found that primates appear to have fewer type I fibers than type II fibers. Results from this study have been implemented as part of a larger study (Muchlinski et al., 2018) to clarify the relationship between muscle mass and brain mass to better illustrate how muscle fiber composition could be used to address evolutionary questions in relation to energetics.Support or Funding InformationNational Society for Histotechnology (NSH)This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

First detailed anatomical study of bonobos exposes bonobos as best model for human‐chimp ancestor and just‐so stories of human evolution, bipedalism and tool use

Just‐so stories are prominent in human evolution literature because of our tendency to create simple progressionist narratives about our ‘special’ place in nature, despite the fact that these stories are almost exclusively based on hard tissue data. How can we be so certain about the evolution of human facial communication, bipedalism, tool use, or speech without detailed knowledge of the internal anatomy of, for instance, one of the two extant species more closely related to us, the bonobos? Here I show how many of these stories now become obsolete, after such a comprehensive knowledge on the anatomy of bonobos and other primates is finally put together. Specifically, each and every muscle that has been long accepted to be ‘uniquely human’ and to provide ‘crucial singular functional adaptations' for our bipedalism, tool use and/or vocal/facial communication, is actually present as a variant or even as normal phenotype in bonobos and/or other apes. Importantly, chimps and in particular bonobos also provide a remarkable case of evolutionary stasis: within >120 head‐neck (HN) and forelimb (FL) muscles, since the chimp‐human split c.8Mya there were only four minor changes in the chimp clade, and all were reversions to the ancestral condition. Outstandingly, since the common chimp‐bonobo split c.2 Mya not even a single change occurred in bonobos, i.e. regarding the HN‐FL musculature bonobos are the best living model for the common chimp‐bonobo LCA and the chimp‐human LCA. The extremely static Pan evolution becomes even clearer when hindlimb data are added: only two muscle absence/presence differences occur between common chimps‐bonobos, and none of these species has muscles not found in other primates. Puzzlingly, there is an evolutionary mosaicism between each of these species and humans. I discuss these data in the context of available genomic information and debates on whether the common chimp‐bonobo divergence is linked to heterochrony, and put these data together with that available for humans and other other primates in order to provide a more comprehensive, and less biased, understanding of primate and human anatomical evolution.Support or Funding InformationThis project has received funding from NSF grants 1516557 and 1440624, as well as an American Association of Anatomists Innovation grant to RDThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Neurovasculature of the Upper Extremity in the Aye‐aye, Daubentonia madagascariensis

The aye‐aye, Daubentonia madagascariensis, is an arboreal lemuroid primate and is the sole representative of its genus. The aye‐aye has unique anatomical characteristics including a thin, long, flexible third digit, unique dental anatomy, a single pair of inguinal mammary glands, greater brain size than those of other strepsirrhines, and large mobile ears that separate it from other lemuroids and make it an interesting organism to study from an anatomical, developmental, and evolutionary standpoint. The aye‐aye also has a distinctive method of obtaining its food from trees known as percussive foraging, which entails tapping on wood with its long middle finger, listening to the resulting sounds to determine the locations of cavities that may contain larvae, and then scooping out the larvae with its specialized third digit. The bony and muscular anatomy of the brachium, antebrachium, and manus of the aye‐aye has been previously studied and described in detail. However, there have been no studies that have described and depicted the complete neurovasculature of the forelimb of the aye‐aye, including the important brachial plexus. Given the unique anatomy and behavioral forelimb adaptations of this species, understanding the various nerves and blood vessels in relation to the musculature will provide a more complete picture of aye‐aye functional morphology and comparative anatomy.This study identifies and describes the neurovasculature of the forelimb of the aye‐aye with emphasis placed on the musculature and neurovasculature on the hand. The forelimbs from one female Daubentonia madagascariensis were dissected, photographed, and described in detail. In this specimen, we confirmed that the anatomy of the forelimb muscles was generally consistent with previous descriptions, although we observed a few minor variations. The brachial plexus was found to originate from the C5‐T2 roots, a feature that has also been observed in other lemurs and rhesus monkeys. The large deltoid and brachioradialis muscles observed in this specimen may serve to support the frequent use of head‐first descent, which requires a robust shoulder girdle and specific alterations in hand and body position that allow the forelimbs to undergo increased compressive forces. Future studies will analyze the development of the muscles of the arm and hand, along with the vasculature that migrated with them, and also compare them to the developmental patterns of related primates which can give insight into the aye‐aye's specialized adaptations.Support or Funding InformationThis research was supported by a Midwestern University Kenneth A. Suarez summer research fellowship to MA.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Intralimb and Interlimb Cutaneous Reflexes during Locomotion in the Intact Cat.

When the foot contacts an obstacle during locomotion, cutaneous inputs activate spinal circuits to ensure dynamic balance and forward progression. In quadrupeds, this requires coordinated reflex responses between the four limbs. Here, we investigated the patterns and phasic modulation of cutaneous reflexes in forelimb and hindlimb muscles evoked by inputs from all four limbs. Five female cats were implanted to record muscle activity and to stimulate the superficial peroneal and superficial radial nerves during locomotion. Stimulating these nerves evoked short-, mid-, and longer-latency excitatory and/or inhibitory responses in all four limbs that were phase-dependent. The largest responses were generally observed during the peak activity of the muscle. Cutaneous reflexes during mid-swing were consistent with flexion of the homonymous limb and accompanied by modification of the stance phases of the other three limbs, by coactivating flexors and extensors and/or by delaying push-off. Cutaneous reflexes during mid-stance were consistent with stabilizing the homonymous limb by delaying and then facilitating its push-off and modifying the support phases of the homolateral and diagonal limbs, characterized by coactivating flexors and extensors, reinforcing extensor activity and/or delaying push-off. The shortest latencies of homolateral and diagonal responses were consistent with fast-conducting disynaptic or trisynaptic pathways. Descending homolateral and diagonal pathways from the forelimbs to the hindlimbs had a higher probability of eliciting responses compared with ascending pathways from the hindlimbs to the forelimbs. Thus, in quadrupeds, intralimb and interlimb reflexes activated by cutaneous inputs ensure dynamic coordination of the four limbs, producing a whole-body response.SIGNIFICANCE STATEMENT The skin contains receptors that, when activated, send inputs to spinal circuits, signaling a perturbation. Rapid responses, or reflexes, in muscles of the contacted limb and opposite homologous limb help maintain balance and forward progression. Here, we investigated reflexes during quadrupedal locomotion in the cat by electrically stimulating cutaneous nerves in each of the four limbs. Functionally, responses appear to modify the trajectory or stabilize the movement of the stimulated limb while modifying the support phase of the other limbs. Reflexes between limbs are mediated by fast-conducting pathways that involve excitatory and inhibitory circuits controlling each limb. The comparatively stronger descending pathways from cervical to lumbar circuits controlling the forelimbs and hindlimbs, respectively, could serve a protective function.

Developmental abnormality contributes to cortex-dependent motor impairments and higher intracortical current requirement in the reeler homozygous mutants.

The motor deficit of the reeler mutants has largely been considered cerebellum related, and the developmental consequences of the cortex on reeler motor behavior have not been examined. We herein showed that there is a behavioral consequence to reeler mutation in models examined at cortex-dependent bimanual tasks that require forepaw dexterity. Using intracortical microstimulation, we found the forelimb representation in the motor cortex was significantly reduced in the reeler. The reeler cortex required a significantly higher current to evoke skeletal muscle movements, suggesting the cortical trans-synaptic propagation is disrupted. When the higher current was applied, the reeler motor representation was found preserved. To elucidate the influence of cerebellum atrophy and ataxia on the obtained results, the behavioral and neurophysiological findings in reeler mice were reproduced using the Disabled-1 (Dab1) cKO mice, in which the Reelin-Dab1 signal deficiency is confined to the cerebral cortex. The Dab1 cKO mice were further assessed at the single-pellet reach and retrieval task, displaying a lower number of successfully retrieved pellets. It suggests the abnormality confined to the cortex still reduced the dexterous motor performance. Although possible muscular dysfunction was reported in REELIN-deficient humans, the function of the reeler forelimb muscle examined by electromyography, morphology of neuromuscular junction and the expression level of choline acetyltransferase were normal. Our results suggest that the mammalian laminar structure is necessary for the forepaw skill performance and for trans-synaptic efficacy in the cortical output.

Anatomical Basis of Differences in Locomotor Behavior in Martens: A Comparison of the Forelimb Musculature Between Two Sympatric Species of Martes.

Arboreal locomotion imposes selective pressures that may affect the evolution of the locomotor apparatus. The limbs have to be mobile to reach across discontinuities, yet at the same time need to be forceful to move against gravity during climbing. However, as intermediaries between the arboreal and terrestrial environment, semi-arboreal mammals appear not extremely specialized and, thus, anatomical adaptations may be less evident than expected for arboreal climbers. Here, we present quantitative data on the muscle anatomy of the forelimbs (N = 14) of two closely related species of Mustelidae and relate the findings to their locomotor habits. The arboreal pine marten (Martes martes) and the more terrestrial stone marten (Martes foina) are the most similar sympatric carnivores in Europe, but distinctly differ in habitat selection and locomotor mode. Via dissections muscle architectural variables including muscle mass, pennation angle, and fiber length were measured and the physiological cross-sectional area and maximum isometric force were estimated for each muscle. The results reveal that the force-generating capacity of the limb flexor and retractor muscles and the excursion capability of the adductor muscles are greater in the pine marten compared to the stone marten. Since the two sympatric martens are very similar in terms of overall appearance, body size, intra-limb proportions, phylogenetic relationships and predation behavior, the differences in forelimb musculature are interpreted to reflect the greater climbing ability of the pine marten. The functional properties appear to facilitate locomotion in a three-dimensionally complex arboreal environment. Anat Rec, 301:449-472, 2018. © 2018 Wiley Periodicals, Inc.

Functional Morphology and Behavioral Correlates to Postcranial Musculature.

In this the second issue of a two-volume set of the Anatomical Record on the relationship between muscle functional morphology and behavior, the focus is on the postcranial musculature. Traditionally, when talking of the postcranium we think of the skeletal parts that primarily provide the lever system necessary for body movements. However, without the force produced by muscle, the postcranial skeleton could not perform these or most other tasks. In this special issue, our colleagues present ten papers that focus on postcranial muscle morphology and function from different perspectives. They include papers on forelimb and hindlimb muscle functional morphology of vertebrates, including lizards, bats, primates, a carnivoran and a rodent, and involved in different substrate use (arboreal, terrestrial, and flying) and locomotion behavior (quadrupedal, leaper, and suspensory) along with a historical overview to help bookend the contextualization of the issues. The picture that these papers provide is one of great liveliness in the field of muscle functional morphology where both young students and affirmed professors continue to contribute with both traditional approaches and new techniques to further our knowledge of muscle morphology and its relationship with animal behavior. Anat Rec, 301:419-423, 2018. © 2018 Wiley Periodicals, Inc.

Is there evidence for a trade-off between sperm competition traits and forelimb musculature in the western grey kangaroo?

Males may use tactics before, during and after mating to increase their reproductive success. With finite energy resources available, theory predicts that there should be a trade-off between investment in pre-copulatory traits (e.g. body size, armaments) and post-copulatory traits (e.g. testes size, spermatogenic efficiency). Western grey kangaroos (Macropus fuliginosus) are found in large, labile mixed-sex groups, in which the males show a dominance hierarchy. Males show indeterminate growth, and will reach up to six times the body mass of females. While the largest males use their size as a reproductive advantage, forelimb musculature further aids male–male contest, female attraction and/or female coercion. Under a trade-off scenario, we therefore predicted that larger, more muscular males would show less investment in sperm competitive traits. Consistent with this prediction, more muscular males showed decreased spermatozoa velocity. However, muscularity was also positively correlated with mass of two pairs of bulbourethral accessory glands, as well as mass of the penis and its muscles of erection. Seasonal changes in muscularity and accessory gland masses were also evident. Male kangaroos therefore invest in multiple reproductive traits on which selection can work.

Neuromuscular control of locomotion is altered by tail autotomy in geckos.

Animal locomotion is driven by underlying axial and appendicular musculature. In order for locomotion to be effective, these muscles must be able to rapidly respond to changes in environmental and physiological demands. Although virtually unstudied, muscles must also respond to morphological changes, such as those that occur with tail autotomy in lizards. Tail autotomy in leopard geckos (Eublepharis macularius) results in a 25% loss of caudal mass and significant kinematic alterations to maintain stability. To elucidate how motor control of the locomotor muscles is modulated with these shifts, we used electromyography (EMG) to quantify patterns of in vivo muscle activity in forelimb and hindlimb muscles before and after autotomy. Forelimb muscles (biceps brachii and triceps brachii) exhibited no changes in motor recruitment, consistent with unaltered kinematics after autotomy. The amplitude of activity of propulsive muscles of the hindlimbs (caudofemoralis and gastrocnemius) was significantly reduced and coincided with decreases in the propulsive phases of femur retraction and ankle extension, respectively. The puboischiotibialis did not exhibit these changes, despite significant reductions in femur depression and knee angle, suggesting that the reduction in mass and vertical ground-reaction force by autotomy allows for the maintenance of a more sprawled and stable posture without increasing motor recruitment of the support muscles. These results highlight the significant neuromuscular shifts that occur to accommodate dramatic changes in body size and mass distribution, and illuminate the utility of tail autotomy as a system for studying the neuromuscular control of locomotion.

Comparative Myology of the Forelimb in Capuchin and Night Monkeys

Background: The capuchin monkey (Sapajus apella) and the night monkey (Aotus azarae infulatus) are primates with broad distribution in South America. Sapajus apella is best-studied species in the genus Cebus, and is commonly found in captivity in parks, zoos, and sorting centers in Brazil. Species in the genus Aotus have a primitive appearance with large eye sockets, and their nocturnal habits are unique among the apes today. Because these two species belong to the same order, they have similar morphological characteristics. In this work, we conduct a comparative study of the forelimb musculature between these two species to produce data for use in veterinary procedures.Materials, Methods & Results: Three capuchin monkey and three night monkey specimens were used, two females and one male for each species. Specimens were acquired from the National Center for Primates under approval from the Animal Research (CEPAN/IEC/SVS/MS) No. 008/2010. Specimens were frozen and donated after death by natural causes to the LaPMA (Animal Morphology Research Laboratory) at the Federal Rural University of Amazonia (UFRA). After being thawed in running water, the animals were fixed by intramuscular injection with 10% formaldehyde in aqueous solution and dissected to display thoracic limb muscle groups. Dissections were performed using basic instrumentation by creating a medial incision from the carpal region to the axillary region. After incision, the skin was folded and muscles were separated in order to identify muscle groups. The nomenclature adopted was based on the veterinary anatomy, and books about human anatomy for comparison of forearm muscles. The muscles that compound the shoulder was the supraspinal and infra-spinal. The arm was composed by the teres major and minor, the triceps brachii (long head, lateral head, and medial head), brachialis, biceps brachii, tensor muscle of the antebrachial fascia, coracobrachialis, and anconeous. The forearm included the extensor carpi radialis longus, extensor carpi radialis brevis, extensor digitorus, extensor digiti minimum, extensor carpi ulnaris, abductor pollicis longus, extensor pollicis brevis, flexor carpi ulnaris, flexor digitorum profundus, flexor digitorum superficialis, flexor carpi radialis, flexor pollicis longus, extensor carpi radialis brevis, and brachioradialis muscles. In general, the two species have the same muscle groups, except for the absence of the teres minor and brachioradialis in Capuchin monkey, and the absence of the long head of the triceps brachii and extensor carpi radialis brevis at night monkey.Discussion: The forelimb musculature in the capuchin and night monkey is similar that described in the literature for both domestic and wild species such as coati, paca, and bush dogs, with little variation among the studied species. Regarding the muscles of the forearm, the capuchin monkey and the night monkey have muscular anatomy similar to that of humans, with some variations. The anatomical variations in common traits do not impede function. Interspecific variation is a common occurrence in nature, and can be explained by species divergence which occurs over many years, for various reasons. Knowledge of the comparative miology of the capuchin monkey and the night monkey is still nascent, thus future research is needed to better understand the structure of these animals, which can then serve as a basis for studies of other ethological aspects of the species biology.

Myostatin inhibition using mRK35 produces skeletal muscle growth and tubular aggregate formation in wild type and TgACTA1D286G nemaline myopathy mice.

Nemaline myopathy (NM) is a heterogeneous congenital skeletal muscle disease with cytoplasmic rod-like structures (nemaline bodies) in muscle tissue. While weakness in NM is related to contractile abnormalities, myofiber smallness is an additional abnormality in NM that may be treatable. We evaluated the effects of mRK35 (a myostatin inhibitor developed by Pfizer) treatment in the TgACTA1D286G mouse model of NM. mRK35 induced skeletal muscle growth that led to significant increases in animal bodyweight, forelimb grip strength and muscle fiber force, although it should be noted that animal weight and forelimb grip strength in untreated TgACTA1D286G mice was not different from controls. Treatment was also associated with an increase in the number of tubular aggregates found in skeletal muscle. These findings suggest that myostatin inhibition may be useful in promoting muscle growth and strength in Acta1-mutant muscle, while also further establishing the relationship between low levels of myostatin and tubular aggregate formation.

Musculoskeletal networks reveal topological disparity in mammalian neck evolution

BackgroundThe increase in locomotor and metabolic performance during mammalian evolution was accompanied by the limitation of the number of cervical vertebrae to only seven. In turn, nuchal muscles underwent a reorganization while forelimb muscles expanded into the neck region. As variation in the cervical spine is low, the variation in the arrangement of the neck muscles and their attachment sites (i.e., the variability of the neck’s musculoskeletal organization) is thus proposed to be an important source of neck disparity across mammals. Anatomical network analysis provides a novel framework to study the organization of the anatomical arrangement, or connectivity pattern, of the bones and muscles that constitute the mammalian neck in an evolutionary context.ResultsNeck organization in mammals is characterized by a combination of conserved and highly variable network properties. We uncovered a conserved regionalization of the musculoskeletal organization of the neck into upper, mid and lower cervical modules. In contrast, there is a varying degree of complexity or specialization and of the integration of the pectoral elements. The musculoskeletal organization of the monotreme neck is distinctively different from that of therian mammals.ConclusionsOur findings reveal that the limited number of vertebrae in the mammalian neck does not result in a low musculoskeletal disparity when examined in an evolutionary context. However, this disparity evolved late in mammalian history in parallel with the radiation of certain lineages (e.g., cetartiodactyls, xenarthrans). Disparity is further facilitated by the enhanced incorporation of forelimb muscles into the neck and their variability in attachment sites.

Forelimb muscle and joint actions in Archosauria: insights from Crocodylus johnstoni (Pseudosuchia) and Mussaurus patagonicus (Sauropodomorpha).

Many of the major locomotor transitions during the evolution of Archosauria, the lineage including crocodiles and birds as well as extinct Dinosauria, were shifts from quadrupedalism to bipedalism (and vice versa). Those occurred within a continuum between more sprawling and erect modes of locomotion and involved drastic changes of limb anatomy and function in several lineages, including sauropodomorph dinosaurs. We present biomechanical computer models of two locomotor extremes within Archosauria in an analysis of joint ranges of motion and the moment arms of the major forelimb muscles in order to quantify biomechanical differences between more sprawling, pseudosuchian (represented the crocodile Crocodylus johnstoni) and more erect, dinosaurian (represented by the sauropodomorph Mussaurus patagonicus) modes of forelimb function. We compare these two locomotor extremes in terms of the reconstructed musculoskeletal anatomy, ranges of motion of the forelimb joints and the moment arm patterns of muscles across those ranges of joint motion. We reconstructed the three-dimensional paths of 30 muscles acting around the shoulder, elbow and wrist joints. We explicitly evaluate how forelimb joint mobility and muscle actions may have changed with postural and anatomical alterations from basal archosaurs to early sauropodomorphs. We thus evaluate in which ways forelimb posture was correlated with muscle leverage, and how such differences fit into a broader evolutionary context (i.e. transition from sprawling quadrupedalism to erect bipedalism and then shifting to graviportal quadrupedalism). Our analysis reveals major differences of muscle actions between the more sprawling and erect models at the shoulder joint. These differences are related not only to the articular surfaces but also to the orientation of the scapula, in which extension/flexion movements in Crocodylus (e.g. protraction of the humerus) correspond to elevation/depression in Mussaurus. Muscle action is highly influenced by limb posture, more so than morphology. Habitual quadrupedalism in Mussaurus is not supported by our analysis of joint range of motion, which indicates that glenohumeral protraction was severely restricted. Additionally, some active pronation of the manus may have been possible in Mussaurus, allowing semi-pronation by a rearranging of the whole antebrachium (not the radius against the ulna, as previously thought) via long-axis rotation at the elbow joint. However, the muscles acting around this joint to actively pronate it may have been too weak to drive or maintain such orientations as opposed to a neutral position in between pronation and supination. Regardless, the origin of quadrupedalism in Sauropoda is not only linked to manus pronation but also to multiple shifts of forelimb morphology, allowing greater flexion movements of the glenohumeral joint and a more columnar forelimb posture.

The evolution of androgen receptor expression and behavior in Anolis lizard forelimb muscles.

The motor systems that produce behavioral movements are among the primary targets for the action of steroid hormones, including androgens. Androgens such as testosterone bind to androgen receptors (AR) to induce physiological changes in the size, strength, and energetic capacity of skeletal muscles, which can directly influence the performance of behaviors in which those muscles are used. Because tissues differentially express AR, resulting in tissue-specific sensitivity to androgens, AR expression may be a major target of selection for the evolution of behavior. Anolis lizards (i.e., anoles) provide a robust system for the study of androgen-regulated traits, including the behavioral traits that facilitate social display and locomotion. In this study, we examined six anole species that demonstrate significant variation in the behavioral use of the forelimbs to measure the proportion of myonuclei in the bicep muscles that express AR. Using phylogenetic comparative analyses, we found that species with a greater proportion of nuclei positive for AR expression in the biceps exhibited greater frequencies of locomotor movements and pushup displays. These results suggest that AR expression in skeletal muscles may influence the evolution of androgen-regulated behaviors in this group.

TETANUS IN A SURGICALLY CASTRATED BEETAL BUCK: A CASE REPORT

Tetanus is a fetal disease of human and animals caused by spore forming, Gram-positive, anaerobic bacterium Clostridium tetani. In present report, a 16-month old, Beetal buck, weighing about 40 kg was presented to outdoor clinics of Department of Clinical Medicine and Surgery, University of Agriculture, Faisalabad, Pakistan with complaint of anorexia, abnormal gait and gradual loss of body condition. History, indicated that animal was castrated 12 days before by a local quack using an ordinary shaving blade. Visual examination revealed that wound had not properly healed on the day of examination. Physical examination revealed stiffness of fore and hind limb muscles, prolapse of nictitating membrane and hyperesthesia. Owing to the presence of contaminated wound and clinical signs, Beetal Buck was diagnosed as tetanus. Animal was treated with procaine penicillin @ 44,000 IU IM/Kg, diazepam @ 0.1mg/kg IM. The treatment was prescribed for five days. Wound was debrided and washed with hydrogen peroxide. On the 3rd day of this treatment, trismus was reduced and the gait of the animal was im proved. All in all, tetanus was present in goats and treatment afforded an improvement in health parameters.

Architectural Properties of Sloth Forelimb Muscles (Pilosa: Bradypodidae)

Tree sloths have reduced skeletal muscle mass, and yet they are able to perform suspensory behaviors that require both strength and fatigue resistance to suspend their body mass for extended periods of time. The muscle architecture of sloths is hypothesized to be modified in ways that will enhance force production to compensate for this reduction in limb muscle mass. Our objective is to test this hypothesis by quantifying architecture properties in the forelimb musculature of the brown-throated three-toed sloth (Bradypus variegatus: N = 4). We evaluated architecture from 52 forelimb muscles by measuring muscle moment arm (r m), muscle mass (MM), belly length (ML), fascicle length (LF), pennation angle (θ), and physiological cross-sectional area (PCSA), and these metrics were used to estimate isometric force, joint torque, and power. Overall, the musculature becomes progressively more pennate from the extrinsic to intrinsic regions of the forelimb, and the flexors are more well developed than the extensors as predicted. However, most muscles are indicative of a mechanical design for fast joint rotational velocity instead of large joint torque (i.e., strength), although certain large, parallel-fibered shoulder (e.g., m. latissimus dorsi) and elbow (e.g., m. brachioradialis) flexors are capable of producing appreciable torques by having elongated moment arms. This type of functional tradeoff between joint rotational velocity and mechanical advantage is further exemplified by muscle gearing in Bradypus that pairs synergistic muscles with opposing LF/r m ratios in each functional group. These properties are suggested to facilitate the slow, controlled movements in sloths. In addition, the carpal/digital flexors have variable architectural properties, but their collective PCSA and joint torque indicates the capability for maintaining grip force and carpal stability while distributing load from the manus to the shoulder. The observed specializations provide a basis for understanding sustained suspension in sloths.

Myology of the forelimb of Majungasaurus crenatissimus (Theropoda, Abelisauridae) and the morphological consequences of extreme limb reduction.

Forelimb reduction occurred independently in multiple lineages of theropod dinosaurs. Although tyrannosaurs are renowned for their tiny, two-fingered forelimbs, the degree of their reduction in length is surpassed by abelisaurids, which possess an unusual morphology distinct from that of other theropods. The forelimbs of abelisaurids are short but robust and exhibit numerous crests, tubercles, and scars that allow for inferences of muscle attachment sites. Phylogenetically based reconstructions of the musculature were used in combination with close examination of the osteology in the Malagasy abelisaurid Majungasaurus to create detailed muscle maps of the forelimbs, and patterns of the muscular and bony morphology were compared with those of extant tetrapods with reduced or vestigial limbs. The lever arms of muscles crossing the glenohumeral joint are shortened relative to the basal condition, reducing the torque of these muscles but increasing the excursion of the humerus. Fusion of the antebrachial muscles into a set of flexors and extensors is common in other tetrapods and occurred to some extent in Majungasaurus. However, the presence of tubercles on the antebrachial and manual elements of abelisaurids indicates that many of the individual distal muscles acting on the wrist and digits were retained. Majungasaurus shows some signs of the advanced stages of forelimb reduction preceding limb loss, while also exhibiting features suggesting that the forelimb was not completely functionless. The conformation of abelisaurid forelimb musculature was unique among theropods and further emphasizes the unusual morphology of the forelimbs in this clade.