Functional morphology of the Andean climbing catfishes (Astroblepidae,Siluriformes): Alternative ways of respiration,adhesion, and locomotion using the mouth

Astroblepidae or “climbing catfishes” encompass a single genus of species living in high altitude rivers in the Andes of South America. They are characterized by a specialized head morphology closely resembling their better known, widely radiated sister family Loricariidae, or armored suckermouth catfishes. Existent data show that even though both families share important traits, there are some striking differences as well. Albeit poorly known, Astroblepus species possess a duplicated gill opening, and have the ability to climb vertical rocks or waterfalls. In this study, morphological and kinematic data are combined to yield insights into the functions of the mobile elements of the astroblepid head, and to compare head morphology and biomechanics with those of Loricariidae. We found that, even though there is substantial similarity in head structure of both families, there are major differences in functionally important structures. These include a different lower lip muscle configuration, an alternative oral valve system, and an incurrent gill opening only found in astroblepids. Kinematic analyses confirm that the astroblepid suckermouth, freed from its inhalatory function, offers advantages for climbing in the high‐altitude environment, and is used alternately with the extremely mobile pelvic girdle, in a crawling, nonundulatory motion. J. Morphol. 274:1164–1179, 2013. © 2013 Wiley Periodicals, Inc.     

Kinematic motion of the anterior cruciate ligament deficient knee during functionally high and low demanding tasks

The purpose of this study was to determine whether mechanical adaptations were present in patients with anterior cruciate ligament (ACL)-deficient knees during high-demand activities. Twenty-two subjects with unilateral ACL deficiency (11 males and 11 females, 19.6 months after injury) performed five different activities at a comfortable speed (level walking, ascending and descending steps, jogging, jogging to a 90-degree side cutting toward the opposite direction of the tested side). Three-dimensional knee kinematics for the ACL-deficient knees and uninjured contralateral knees were evaluated using the Point Cluster Technique. There was no significant difference in knee flexion angle, but an offset toward the knee in less valgus and more external tibial rotation was observed in the ACL-deficient knee. The tendency was more obvious in high demand motions, and a significant difference was clearly observed in the side cutting motions. These motion patterns, with the knee in less valgus and more external tibial rotation, are proposed to be an adaptive movement to avoid pivot shift dynamically, and reveal evidence in support of a dynamic adaptive motion occurring in ACL-deficient knees.     

Modeling and dynamic simulation of astronaut’s upper limb motions considering counter torques generated by the space suit

Extravehicular activity (EVA) is an inevitable task for astronauts to maintain proper functions of both the spacecraft and the space station. Both experimental research in a microgravity simulator (e.g. neutral buoyancy tank, zero-g aircraft or a drop tower/tube) and mathematical modeling were used to study EVA to provide guidance for the training on Earth and task design in space. Modeling has become more and more promising because of its efficiency. Based on the task analysis, almost 90% of EVA activity is accomplished through upper limb motions. Therefore, focusing on upper limb models of the body and space suit is valuable to this effort. In previous modeling studies, some multi-rigid-body systems were developed to simplify the human musculoskeletal system, and the space suit was mostly considered as a part of the astronaut body. With the aim to improve the reality of the models, we developed an astronauts’ upper limb model, including a torque model and a muscle-force model, with the counter torques from the space suit being considered as a boundary condition. Inverse kinematics and the Maggi-Kane’s method was applied to calculate the joint angles, joint torques and muscle force given that the terminal trajectory of upper limb motion was known. Also, we validated the muscle-force model using electromyogram (EMG) data collected in a validation experiment. Muscle force calculated from our model presented a similar trend with the EMG data, supporting the effectiveness and feasibility of the muscle-force model we established, and also, partially validating the joint model in kinematics aspect.     

Effect of caudal fin height on swimming kinematics in the mackerel Scomber scombrus L.

Geometry of the caudal fin of the mackerel Scomber scombrus was modified to examine the effect of the height of the fin on swimming kinematics. Mackerel with reduced caudal fin height had significantly shorter stride length and higher tail beat amplitude compared with the control having an intact caudal fin ( P  < 0·005).     

Pendular motion in the brachiation of captive Lagothrix and Ateles

Pendular motion during brachiation of captive Lagothrix lagothricha lugens and Ateles fusciceps robustus was analyzed to demonstrate similarities, and differences, between these two closely related large bodied atelines. This is the first captive study of the kinematics of brachiation in Lagothrix. Videorecordings of one adult male of each species were made in a specially designed cage constructed at the DuMond Conservancy/Monkey Jungle, Miami, FL. Java software (Jandel Scientific Inc., San Rafael, CA) was used for frame‐by‐frame kinematic analysis of individual strides/steps. Results demonstrate that the sequence of hand and tail contacts differ significantly between the two species with Lagothrix using a new tail hold with every hand hold, while Ateles generally utilizes a new tail hold with only every other hand hold. Stride length and stride frequency, even after adjusting for limb length, also differ significantly between the two species. Lagothrix brachiation utilizes short, choppy strides with quick hand holds, while Ateles uses long, fluid strides with longer hand holds. During brachiation not only is Lagothrix's body significantly less horizontal than that of Ateles but also, within Ateles, there are significant differences between steps depending on tail use. Because of the unique nature of tail use in Ateles, many aspects of body positioning in Lagothrix more closely resemble Ateles steps without a simultaneous tail hold rather than those with one. Overall pendulum length in Lagothrix is shorter than in Ateles. Tail use in Ateles has a significant effect on maximum pendulum length during a step. Although neither species achieves the extreme pendulum effect and long period of free‐flight of hylobatids in fast ricochetal brachiation, in captivity both consistently demonstrate effective brachiation with brief periods of free‐flight and pendular motion. Morphological similarities between ateline brachiators and hylobatids are fewer and less pronounced in Lagothrix than in Ateles. This study demonstrates that Lagothrix brachiation is also less hylobatid‐like than that of Ateles. Am. J. Primatol. 48:263–281, 1999. © 1999 Wiley‐Liss, Inc.     

Kinematics of prey capture in the tailed frog Ascaphus truei (Anura: Ascaphidae)

The kinematics of prey capture by Ascaphus truei was investigated. High-speed films (100 fps) of 13 successful and one unsuccessful prey capture sequences from six adult frogs were analysed. Ascaphus , the sister group of all living frogs, shares several aspects of feeding kinematics, including rotation of the tongue pad about the mandibular symphysis and mandibular bending during mouth opening and closing, with more derived frogs such as Bufo marinus. The times required for tongue retraction, mouth opening and closing are similar in Ascaphus and Bufo. However, because Bufo is much larger and protracts its tongue much farther than Ascaphus , the velocities of tongue retraction, mouth opening and mouth closing are relatively lower in Ascaphus than in Bufo. Differences in prey capture between Ascaphus and Bufo marinus are (1) the distance of tongue protraction is less in Ascaphus (±0.5 cm) than in Bufo (c. 2 cm); and (2) lunging of the whole body is more pronounced in Ascaphus. Prey capture is highly variable in Ascaphus. An intraoral transport sequence is sometimes (7 of 14 observations) inserted into the prey capture cycle before the completion of mouth closing. The gape cycles range from 80–150 ms for sequences with no oral transport and from 130–280 ms for sequences with oral transport. Also, the time required for tongue retraction is significantly longer in the unsuccessful capture attempt. This variability is generally greater than that observed during prey capture in salamanders, and suggests that frogs and salamanders may differ in the importance of sensory feedback in coordinating prey capture.     

In-vivo analysis of sliding distance and cross-shear in Bi-cruciate retaining total knee arthroplasty

Polyethylene remains the most popular bearing material for total knee arthroplasty (TKA). Despite its widespread use, wear continue to be one of major factors implicated in revision surgery. Sliding distance, cross-shear, and contact stress are the major factors influencing polyethylene wear. As previous studies have either relied on wear simulations, computational modeling, or in vitro measurements to quantify sliding distance and cross-shear, in vivo subject-specific sliding distance and cross-shear after bi-cruciate retaining (BCR) TKA has not been previously reported. The objective of this study was to quantify the 6°-of-freedom (6DOF) in vivo kinematics, sliding distance, and cross-shear in BCR TKA patients during gait. Twenty-nine unilateral BCR TKA patients performed level walking on a treadmill under dual fluoroscopic imaging system (DFIS) surveillance. Cumulative normalized sliding distances between the lateral and medial compartments did not change significantly (p > 0.05) during the gait cycle. Although the total normalized sliding distance was similar between the lateral and medial compartments, the cross-shear at the lateral compartment differed significantly from that at the medial compartment (p < 0.001). Significant differences in the relative length positions of the peak sliding distance and cross-shear were found between the lateral and medial bearing components. The flexion-extension motion of the reconstructed knee was more associated with the linear displacements (anterior-posterior, R² = 0.6; lateral-medial, R² = 0.8, proximal-distal, R² = 0.7) than the angular displacement (varus-valgus, R² = 0.18; internal-external rotation, R² = 0.28). Despite some differences in peak sliding distance and cross-shear positons, our results suggest similar articular contact patterns between the lateral and medial compartments in BCR TKA patients during gait. The data could provide insights into understanding the potential wear patterns in BCR TKAs.     

Indirect evidence for elastic energy playing a role in limb recovery during toad hopping

Elastic energy is critical for amplifying muscle power during the propulsive phase of anuran jumping. In this study, we use toads (Bufo marinus) to address whether elastic recoil is also involved after take-off to help flex the limbs before landing. The potential for such spring-like behaviour stems from the unusually flexed configuration of a toad''s hindlimbs in a relaxed state. Manual extension of the knee beyond approximately 90° leads to the rapid development of passive tension in the limb as underlying elastic tissues become stretched. We hypothesized that during take-off, the knee regularly extends beyond this, allowing passive recoil to help drive limb flexion in mid-air. To test this, we used high-speed video and electromyography to record hindlimb kinematics and electrical activity in a hindlimb extensor (semimembranosus) and flexor (iliofibularis). We predicted that hops in which the knees extended further during take-off would require less knee flexor recruitment during recovery. Knees extended beyond 90° in over 80% of hops, and longer hops involved greater degrees of knee extension during take-off and more intense semimembranosus activity. However, knee flexion velocities during recovery were maintained despite a significant decrease in iliofibularis intensity in longer hops, results consistent with elastic recoil playing a role.