Biomedical subjects
Michael Dickinson
Publications and source records attributed to Michael Dickinson.
Sub-clinical dissemination of follicular lymphoma in normal sized lymph nodes may not be detected by radiologic staging: a case of disseminated follicular lymphoma detected in nodal clearance as part of therapy for cutaneous melanoma.
Patients with localized follicular lymphoma are potentially curable; however, the failure rate for local treatment suggests that a proportion of apparently localized disease is being under-staged. We report a case of incidentally diagnosed follicular lymphoma found in association with a stage II malignant melanoma, with immunohistochemical evidence of disseminated lymphoma in radiologically and clinically benign regional lymph nodes. This case provides some evidence to the cause of treatment failure in patients with clinically localized follicular lymphoma, and is a histologically proven example of the association between melanoma and lymphoma.
Molecular dynamics of cyclically contracting insect flight muscle in vivo.
Flight in insects--which constitute the largest group of species in the animal kingdom--is powered by specialized muscles located within the thorax. In most insects each contraction is triggered not by a motor neuron spike but by mechanical stretch imposed by antagonistic muscles. Whereas 'stretch activation' and its reciprocal phenomenon 'shortening deactivation' are observed to varying extents in all striated muscles, both are particularly prominent in the indirect flight muscles of insects. Here we show changes in thick-filament structure and actin-myosin interactions in living, flying Drosophila with the use of synchrotron small-angle X-ray diffraction. To elicit stable flight behaviour and permit the capture of images at specific phases within the 5-ms wingbeat cycle, we tethered flies within a visual flight simulator. We recorded images of 340 micros duration every 625 micros to create an eight-frame diffraction movie, with each frame reflecting the instantaneous structure of the contractile apparatus. These time-resolved measurements of molecular-level structure provide new insight into the unique ability of insect flight muscle to generate elevated power at high frequency.
The aerodynamic effects of wing-wing interaction in flapping insect wings.
We employed a dynamically scaled mechanical model of the small fruit fly Drosophila melanogaster (Reynolds number 100-200) to investigate force enhancement due to contralateral wing interactions during stroke reversal (the ;clap-and-fling'). The results suggest that lift enhancement during clap-and-fling requires an angular separation between the two wings of no more than 10-12 degrees . Within the limitations of the robotic apparatus, the clap-and-fling augmented total lift production by up to 17%, but depended strongly on stroke kinematics. The time course of the interaction between the wings was quite complex. For example, wing interaction attenuated total force during the initial part of the wing clap, but slightly enhanced force at the end of the clap phase. We measured two temporally transient peaks of both lift and drag enhancement during the fling phase: a prominent peak during the initial phase of the fling motion, which accounts for most of the benefit in lift production, and a smaller peak of force enhancement at the end fling when the wings started to move apart. A detailed digital particle image velocimetry (DPIV) analysis during clap-and-fling showed that the most obvious effect of the bilateral ;image' wing on flow occurs during the early phase of the fling, due to a strong fluid influx between the wings as they separate. The DPIV analysis revealed, moreover, that circulation induced by a leading edge vortex (LEV) during the early fling phase was smaller than predicted by inviscid two-dimensional analytical models, whereas circulation of LEV nearly matched the predictions of Weis-Fogh's inviscid model at late fling phase. In addition, the presence of the image wing presumably causes subtle modifications in both the wake capture and viscous forces. Collectively, these effects explain some of the changes in total force and lift production during the fling. Quite surprisingly, the effect of clap-and-fling is not restricted to the dorsal part of the stroke cycle but extends to the beginning of upstroke, suggesting that the presence of the image wing distorts the gross wake structure throughout the stroke cycle.
Animal locomotion: how to walk on water.
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