An advantage of legged locomotion is the ability to climb over obstacles. We studied deathhead cockroaches as they climbed over plastic blocks in order to characterize the leg movements associated with climbing. Movements were recorded as animals surmounted 5.5-mm or 11-mm obstacles. The smaller obstacles were scaled with little change in running movements. The higher obstacles required altered gaits, leg positions and body posture. The most frequent sequence used was to first tilt the front of the body upward in a rearing stage, and then elevate the center of mass to the level of the top of the block. A horizontal running posture was re-assumed in a leveling-off stage. The action of the middle legs was redirected by rotations of the leg at the thoracal-coxal and the trochanteral-femoral joints. The subsequent extension movements of the coxal-trochanteral and femoral-tibial joints were within the range seen during horizontal running. The structure of proximal leg joints allows for flexibility in leg use by generating subtle, but effective changes in the direction of leg movement. This architecture, along with the resulting re-direction of movements, provides a range of strategies for both animals and walking machines.Keywords Climbing AE Center of mass AE Body-substrate angle AE Kinematics AE Joint angle Abbreviations CoM center of mass AE CTr coxatrochanter joint AE FTi femur-tibia joint AE T 1 first thoracic (prothoracic) segment or leg AE T 2 second thoracic (mesothoracic) segment or leg AE T 3 third thoracic (metathoracic) segment or leg AE ThC thorax-coxa joint AE TrF trochanter-femur joint
A biofuel cell incorporating a bienzymatic trehalase|glucose oxidase trehalose anode and a bilirubin oxidase dioxygen cathode using Os complexes grafted to a polymeric backbone as electron relays was designed and constructed. The specific power densities of the biofuel cell implanted in a female Blaberus discoidalis through incisions into its abdomen yielded maximum values of ca. 55 μW/cm(2) at 0.2 V that decreased by only ca. 5% after ca. 2.5 h of operation.
Animals negotiating complex natural terrain must consider cues around them and alter movement parameters accordingly. In the arthropod brain, the central complex (CC) receives bilateral sensory relays and sits immediately upstream of premotor areas, suggesting that it may be involved in the context-dependent control of behavior. In previous studies, CC neurons in various insects responded to visual, chemical, and mechanical stimuli, and genetic or physical lesions affected locomotor behaviors. Additionally, electrical stimulation of the CC led to malformed chirping movements by crickets, and pharmacological stimulation evoked stridulation in grasshoppers, but no more precise relationship has been documented between neural activity in the CC and movements in a behaving animal. We performed tetrode recordings from the CC of cockroaches walking in place on a slippery surface. Neural activity in the CC was strongly correlated with, and in some cases predictive of, stepping frequency. Electrical stimulation of these areas also evoked or modified walking. Many of the same neural units responded to tactile antennal stimulation while the animal was standing still but became unresponsive during walking. Therefore, these CC units are unlikely to be reporting only sensory signals, but their activity may be directing changes in locomotion based on sensory inputs.
This laboratory has developed a semiquantitative scale for grading the natural healing process of defects drilled into articular cartilage. The scale is composed of four parameters: percent filling of the defect, reconstitution of the osteochondral junction, matrix staining and cell morphology; it has a score range from 0 (best) to 14 (worst). The scale was used to evaluate the healing of defects drilled into rabbit knee articular cartilage at 2, 14, 30, 60 and 120 days after surgery. No statistically significant difference in the graded score was found between the two different defect sizes (2.7 and 1.5 mm). However, the differences in score observed between specimens from different sacrifice times were significant (p < 0.01). Currently many investigators are manipulating cartilaginous lesions in an attempt to improve healing, and this scale will provide a means for quantitatively comparing results from control and experimental groups.
The central complex (CC) is a group of midline neuropils in the protocerebrum of all insects (Williams, J Zool, 176:67-86, 1975; Strausfeld, Prog Brain Res, 123:273-284, 1999). Its columnar organization coupled with the anatomical tracts to and from this region suggests that the CC may supervise various forms of locomotion. In cockroach, lesions of the CC affect turning and controlled climbing over blocks (Ridgel et al., J Comp Physiol A, 193:385-402, 2007). Since these behaviors are largely directed by tactile cues detected by antennae, we predicted that some neurons in the CC respond to mechanical antennal stimulation. We used 16-channel probes to record from broad regions within the CC, while mechanically stimulating one or the other antenna. Using cluster cutting procedures, we examined 277 units in 31 preparations. Many of these units responded to mechanical stimulation of the antennae, and of these, most responded equally well to medial or lateral stimulation of either antenna. However, several units either responded to only one antenna or responded significantly more strongly to one of them. Most of the units responding to antennal stimulation were sensitive to changes in the velocity as well as changes in light. Our data reveal a large population of mult-sensory neurons in the CC that could contribute to locomotion control.
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