Stroke Amplitude Research Articles

Physiology and Energetics of Pre-Flight Warm-Up in the Eastern Tent Caterpillar Moth Malacosoma Americanum

ABSTRACT Thoracic temperature (Tth) during pre-flight warm-up increased linearly with time at all air temperatures (Ta). The rate of pre-flight warm-up increased from 3·3 to 12·7 °C/min between Ta’s of 14 and 28 °C. Head temperature remained within a few °C of Tth during warm-up, while ventral abdominal temperature remained within a few °C of Ta. Pulsation rate of the dorsal vessel in the thorax increased directly with thoracic temperature. Wing-stroke frequency (n) varied from 15 s−1 at Tth = 16 °C to 58 s−1 at Tth= 40 °C and was similar at any given Tth between Ta’s of 14 and 28 °C. While stroke amplitude varied significantly between warmup and tethered flight, stroke frequency was similar for the two activities in the same Tth range. Calculated rates of heat production were tightly coupled to Tth and did not vary with Ta. The change in heat production during warm-up was dependent entirely on changes in frequency of muscle contraction. Stroke work was constant at 0·68 mW between Tth of 15 and 40 °C.

Optomotor control of wing beat and body posture in drosophila

Continuous movement of striped patterns was presented on either side of a tethered fruitfly, Drosophila melanogaster, in order to simulate the displacement of stationary landmarks within the visual field of the freely moving fly. The horizontal components of the stimulus elicit, predominantly, yaw-torque responses during flight, or turning responses on the ground, which counteract involuntary deviations from a streight course in the corresponding mode of locomotion. The vertical components elicit, predominantly, covariant responses of lift and thrust which enable the fly to maintain a given level of flight. Monocular stimulation is sufficient to produce antagonistic responses, if the direction of the stimulus is reversed. The following constituents of the responses were derived mainly from properties of wing beat and body posture on photographs of fixed flight under visual stimulation. Wing stroke modulation (W. S. M.): The difference, and the sum, of the stroke amplitudes on either side are independently controlled by horizontal and vertical movement components, respectively. The maximum range of modulation per wing (12.3°) is equivalent to a 63% change in thrust on the corresponding side. Leg stroke modulation (L.S.M.): In the walking fly each pair of legs is under control of visual stimulation. The details of leg articulation are still unknown. Abdominal deflection (A.D.): An actively induced posture effect. Facilitates steering during free flight at increased air speed. Hind leg deflection (H.L.D.): Same as before. On most of the photographs the hind legs were deflected simultaneously and in the same direction as the abdomen. Hitch inhibition (H.I.): The term "hitch" denotes a transient reduction of stroke amplitude which seems to occur spontaneously and independently on either side of the fly. The hitch angle (12.2±3.8° S.D.) is most probably invariant to visual stimulation. Hitches are comparatively frequent in the absence of pattern movement. Their inhibition under visual stimulation is equivalent to an increase of the average thrust of the corresponding wing. The different constituents contribute to the optomotor responses according to the following tentative scheme (Fig. 7). The torque response is essentially due to the effects of W.S.M., A.D., H.L.D. and H.I., and the turning response to L.S.M. and possibly H.L.D., if the landmarks drift from anterior to posterior. So far, H.I. seems to be the only source of the torque response, and L.S.M. the only source of the turning response, if the landmarks drift in the opposite direction. The lift/thrust response results essentially from the effects of W.S.M. and H.I., no matter whether the landmarks drift from inferior to superior or in the opposite direction. The results obtained so far suggest that the optomotor control of course and altitude in Drosophila requires at least eight independent input channels or equivalent means for the separation of the descending signals from the visual centres. Further extension and refinement of the "wiring scheme" is required in order to improve the identification of the sensory inputs of the motor system and the classification of optomotor defective mutants.

The Construction of an Apparatus for the Evaluation of Abrasive Properties of Dentifrice Using Radioisotopes

Construction of an original apparatus (brushing machine) designed to test the abrasiveness of dentifrice is described. The principle of the procedure employed consists in neutron activation of a human tooth subsequently brushed with the dentifrice under study in standard conditions. The radioactivity level of the dentifrice indicates the relative degree of its abrasive properties. The design of the apparatus meets the radiation safety requirements. Its working parameters crucial to the wearing process (i.e. the pressure applied to the tooth specimen, the total number, frequency and amplitude of the brushing strokes) can be programmed precisely.

Denaturation of oxyhemoglobin S by mechanical shaking

The oxy form of sickle hemoglobin precipitates rapidly during mechanical shaking. The rate of precipitation depends on shaking conditions such as stroke amplitude, frequency, angle between the vial axis and the shaking motion, volume and viscosity of hemoglobin solution and temperature. The rate increases linearly with either stroke ( S) or frequency ( n) above a certain value ( S  5mm or n  10Hz). The rate constant was maximum when the angle θ between the vial axis and the shaking direction was 30°. The rate of precipitation of sickle oxyhemoglobin was faster at high temperatures and always about 10 times greater than that of normal hemoglobin. The activation energies of precipitation of hemoglobin S and A are 20.3 and 21.3 kcal/mol, respectively. The thermogram of hemoglobin was measured by a differential scanning calorimeter. The denaturation temperatures determined from the peak of denaturation curves were 83.5°C for oxyhemoglobin S and 85°C for oxyhemoglobin A. The precipitated hemoglobin after mechanical shaking did not show any denaturation peak indicating that the protein molecules are irreversibly denatured by shaking.

An attempt to correlate the mitral valve echogram with the hemodynamics of patients with pure mitral insufficiency.

Echocardiographic, hemodynamic and angiocardiographic studies in 11 patients with pure mitral insufficiency were carried out with special reference to the correlation of the amplitude of motion of the anterior mitral valve with total stroke volume, regurgitant volume, regurgitant percent and ejection fraction respectively, and of the descent rate of the anterior mitral valve with total stroke volume, mean mitral valvular flow during diastole and Ry/v respectively. The characteristic findings of mitral valve echogram in mitral insufficiency were the increase in amplitude father than the increase in the descent rate of the anterior mitral valve. On the basis of echocardiographic findings patients with mitral insufficiency were classified into three groups. The increase in amplitude may be assumed due to the increase in total stroke volume, but no correlation was found between total stroke volume and amplitude, while positive correlation between amplitude and ejection fraction was found. Positive correlation between the descent rate of the mitral valve echogram and Ry/v was found. From these results it is suggested that one of the factors affecting the descent rate is elasticity of left atrium and that one of the factors affecting amplitude is total stroke volume corrected for left ventricular end-diastolic volume (ejection fraction).

Swimming behavior of the sand crab, Emerita analoga (Crustacea, Anomura)

1. A description of the swimming behavior of Emerita analoga was obtained by analysing the components of the uropod stroke and their temporal sequence cinematographically. There are three components of uropod movement: (1) return stroke/power stroke of the protopodite, (2) spreading/folding of the rami, (3) rotation of the whole appendage. 2. Total stroke duration and latencies and durations of the component movements are positively correlated with interval with the exception of the duration of the power stroke which is constant. Stroke amplitude is negatively correlated with stroke duration and interval. 3. The muscles responsible for the component movements were determined by recording electromyographs via electrodes implanted in the muscles of swimming crabs. The motor pattern consists of return-stroke muscle activity immediately followed by a very brief burst in the power-stroke muscle, followed by a pause before the next returnstroke begins. 4. Over the entire, threefold range of intervals, the powerstroke latency does not change in proportion to the interval change, but neither is it truly constant. During high frequency uropod beating, the phase of the power stroke is entrained at a constant position midway through the returnstroke cycle. 5. In addition to the movement of the uropods, an extension/flexion cycle of the abdomen occurs with each stroke. It is suggested that the unique mode of swimming of this crab may be derived from the “typical” crustacean tail-flip.

Muscle activity during flight in some large Lepidoptera.

ABSTRACT The names and functions of the main mesothoracic flight muscles in Lepidoptera are reviewed. The wingbeat period in satumiid moths and monarch butterflies is long and variable. The three parameters, wingbeat period, burst length (number of times a motor unit is activated per wingstroke) and stroke amplitude are interdependent and positively correlated. Partial amputation of the wings in satumiids decreases wingbeat period. Cutting the sensory nerves from the wings increases the period. These results indicate that the influence of wing movement on wingbeat period is mediated by receptors near the base of the wing. The central nervous mechanisms which generate motor patterns during flight in Lepidoptera are discussed and compared with those in locusts. It is proposed that both mechanisms can be described by a single model, with minor differences in the mechanism of burst production.

THE EFFECTS OF ATMOSPHERIC PRESSURE AND COMPOSITION ON THE FLIGHT OF DROSOPHILA

Wingbeat frequency of Drosophila repleta Wollaston was measured stroboscopically at 25 degrees C. as a function of atmospheric pressure, over the range from 100 mm. Hg to 3860 mm. Hg in air, in nitrogen-oxygen mixtures containing either more or less oxygen than air, and in two helium-oxygen mixtures. Similar measurements were made with D. virilis Sturtevant at 19.3 degrees C. and 25.9 degrees C. in air over the pressure range from 100 mm. Hg to 1520 mm. Hg; and at 760 mm. Hg, 25.9 degrees C., in a mixture of 6.1 per cent oxygen in nitrogen.The flight response was inhibited when total pressure was less than 80 to 100 mm. Hg, or when the oxygen tension was less than 15-20 mm Hg. Increasing the partial pressure of oxygen above the value for air did not increase the rate of wingbeat.Within the limits of experimental error, the rate was found equal at equal densities, irrespective of the medium in which it was measured. Wingbeat frequency is therefore independent of total pressure as such, and varies inversely in a logarithmic relationship with the density. The exponents measured for this relationship varied with different individuals between – 0.03 and – 0.15, approximately.The helium-oxygen mixtures had a detrimental effect on the response of the insects, which was less evident at higher pressures and reversed when the specimens were returned to air.Amputation of the halteres did not disturb the relationship between wingbeat frequency and density.Clipping portions from the wingtips increased the frequency of wingbeat. When only one wing was clipped, the increase was less than when both were shortened by equal amounts.Oxygen consumption of D. virilis was measured during flight in an oxygen atmosphere at 19.3 degrees C., at 760 mm. Hg, 400 mm. Hg and 200 mm. Hg, and was found to be relatively unaffected by variation in density.Since wingbeat frequency varied less rapidly with changes in density than would be expected if both power output and stroke volume were to remain constant, it is reasoned that partial compensation is effected through adjustments in stroke volume. A decrease in stroke amplitude was observed at higher densities, but it appears unlikely that amplitude can increase enough at lower densities to account for the stroke volume required. Arguments are given to show that the remaining compensation needed may be furnished by alteration within reasonable limits of the angle of attack.It is concluded that insect flight exhibits homeostatic characteristics, in that the strain which results from density change is distributed over several elements in the wing motion.