We measured the oxygen (O2) consumption of isolated blowfly eyes using a magnetic diver balance, a device for high-resolution volumetric O2 consumption measurements. The light-induced O2 consumption ...is at most three times the value of the dark consumption, which is 0.6 nl O2 s-1 eye-1, and is in good agreement with the estimates based on electrophysiological data. With longer stimuli the increase follows a double exponential time course. The respective time constants are approximately 2 and 20 s and show no dependence on light intensity, whereas the dependence of amplitudes can be fitted by a Hill equation. Decreasing the stimulus duration reveals that the peak in O2 consumption overshoots the time course induced by long stimuli. We suggest this may be a general feature of mitochondrial activation. The dependence of the O2 consumption peak on stimulus duration at high light intensity has a hump with stimulus durations of 10-20 ms, coinciding with the stimulus durations that start to induce the adaptation of the receptor potential.
Regulation of light flux by pupil mechanisms in the UV-sensitive superposition eye of owl-fly Ascalaphus macaronius (Neuroptera) was studied with a fast reflection microspectrophotometric technique. ...The spectral sensitivity of pupil reaction, which was calculated on the basis of changes of transient amplitude reflection, was almost identical with the one of Deilephila eye. This indicates that in spite of different life styles and spectral sensitivities of photoreceptors, pupil closing is triggered by the same photosensitive structure in both eyes. By measuring the spectra of reflected light from the Ascalaphus eye between 400 and 700 nm after different dark periods following light stimulation, it was established that the restoration of reflection was much faster in the red than in the blue spectral range. Based on this, we propose that two different pupil mechanisms with different spectral absorption characteristics are involved in light-flux regulation. Fast-reacting pupil is probably represented by screening pigment migration in the secondary pigment cells and a slow blue-absorbing system by the activity in primary pigment cells. The importance of two different pupils for the photoregeneration of visual pigment is discussed.
A possible method for detection of wood-boring insects in wood is the measurement of oxygen consumption. In order to develop such a method, several parameters have to be determined first. The most ...important one is to determine the respiration rate of possible pest species. To obtain the data for establishing the method mentioned above, the respiration rates of the following species were determined: the old house borer,
Hylotrupes bajulus, common furniture beetle,
Anobium punctatum and subterranean termite,
Reticulitermes lucifugus. We compared the O
2 consumption between different species as well as between adults and larvae of one species in different environmental conditions (temperature, day/night and light/dark regime). The most intensive respiration rates were found for the larvae of
Hylotrupes bajulus (4.0 ml/g h O
2) and
Anobium punctatum (3.9 ml/g h O
2). Less intensive breathing was measured by
Reticulitermes lucifugus (workers 2.9 ml/g h, nymphs 2.6 ml/g.h and soldiers 2.0 ml/g h O
2). These results indicate that it is possible to detect the presence of wood-boring insects respirometrically. To detect the presence of an individual insect in the wood by means of respirometry, the sensitivity of the instrument for oxygen measurement at the optimal conditions must be around 0.2 ml/h.
Com pound Eye, Pigment Migration, Adrenaline, Octopamine, Noradrenaline The light-induced expansion of the screening pigment in the com pound eyes of the sphingid moth Deilephila and the owlfly ...Ascalaphus is counteracted by local application of noradrenaline or octopamine. Ata critical concentration, similar for both drugs, the expanding effect caused by a light stimulus is completely neutralized, and at higher drug concentrations light stimulation induces a contraction of the screening pigment. The contracting effect of noradrenaline and octopamine is counteracted by adrenaline. None of the other putative neuroactive substances tested (acetylcholine, GABA , histamine, melatonin, serotonin and taurine) has a com parable effect on light-induced pigment movement. It is hypothesized that pigment migration is controlled by a system of antagonistically acting catecholamines, similar to the noradrenaline/adrenaline system present in vertebrates.
Geometric model of muscle contraction Hafner, I.; Simunic, B.; Valencic, V. ...
The IEEE Region 8 EUROCON 2003. Computer as a Tool,
2003, Letnik:
2
Conference Proceeding
We use a function transformation that leaves volume unchanged as the basis for geometric model of muscle contraction. The model is built after making an experiment on a frog leg muscle under single ...electrical stimulus.
