Kazimir Drašlar

Substrate-borne sound communication in cydnidae (Heteroptera)

Summary1.Propagation and reception of communicative sound signals were studied ethologically in two species of Cydnidae (Tritomegas bicolor L.,Canthophorus dubius Scop.). The rivalry alternation or rival song evocation was chosen as criterion for successful communication.2.Sexually mature males in the presence of a female begin rivalry alternation within 2 min after a short courtship. Amputation of abdominal trichobothria does not essentially change the acoustical communication ability.3.Two males in separate cages do not emit coordinated sounds (heterophonic rival song) unless the frames of the cages are in direct contact (T. b.)(Fig. 3) or signal transmission is secured through plant stems or similar material (C. d.).4.Single males, stimulated with tape-recorded courtship (M-2) and rivalry (M-E) signals through a piezoelectric transducer, answered with M-R sounds only if the crystal was in contact with the frame of a cage. An air gap of a few millimeters between transducer and cage suffices to prevent the normal acoustical reaction (Figs. 4, 5).5.Animals (T. b.) without trichobothria or tarsi do not show any difference to the control animals in this experiment (Fig. 4a-c). Only animals without legs did not answer (Fig. 4d).6.From these experiments the following conclusions are drawn:a)The bugs of the fam. Cydnidae communicate acoustically primarily or exclusively by substrate-borne signals.b)The abdominal trichobothria are not the main mechanoreceptors in their acoustical communication system.c)The critical receptors are probably located in the legs at a site other than the tarsi.

Functional properties of trichobothria in the bugPyrrhocoris apterus (L.)

Summary1.The trichobothria on the abdomen of the bugPyrrhocoris apterus differ in the length of their sensory hairs and in their functional properties. Three types may be distinguished. On segment four they have the following properties:2.The sensory hair of type 1 is about 380 μm long. The receptor cell is spontaneously active. The spike frequency increases by deflection in caudal direction and decreases by deflection in the cranial direction. The adaptation is of the phasictonic type, and there is no significant change in sensitivity with prolonged stimulation. This receptor can follow sine stimuli synchronously up to about 160 Hz.3.Type 2 (sensory hair about 180 μm) has no spontaneous activity. The spike frequency is increased by deflections in cranial and caudal direction. The response is of the phasic-tonic type and phase-locked to the sine wave up to 80 Hz.4.The response of type 3 (sensory hair about 80 μm) is of the phasic type, and the adaptation is prompt. Like type 2 receptor is excited by deflections in either direction, and it follows sine waves synchronously up to 80 Hz. The significance of these findings for the possible function of trichobothria as near field sound receptors is discussed.

The Calliphora rpa mutant lacks the PDZ domain-assembled INAD signalling complex

The visual transduction cascade of fly photoreceptors is a G protein‐coupled phospholipase C‐signalling pathway which is assembled into a supramolecular signalling complex by the PDZ (postsynaptic density protein‐95, discs large, Z0–1) domain protein INAD (inactivation no afterpotential D). The norpA‐encoded phospholipase Cβ, the light‐activated transient receptor potential (TRP) Ca2+ channel and an eye‐specific protein kinase C are bound to INAD and together form the core of the signalling complex. In the present study we show that the Calliphora rpa mutant, which has previously been hypothesized to represent an equivalent of Drosophila norpA mutants, has normal amounts of norpA mRNA but fails to express inaD mRNA. Electrophysiological recordings from the eyes of the rpa mutant reveal that the electroretinogram is reduced (about 12% of wild type) but not completely absent, and that it exhibits markedly prolonged deactivation kinetics. Furthermore, rpa mutants display a slow, light‐dependent degeneration of the photoreceptor cells. With respect to the INAD signalling complex, the rpa mutant is similar to the Drosophila inaD null mutant: not only INAD itself, but also the other core components of the INAD signalling complex, are reduced or absent in photoreceptor membranes of rpa flies. Residual TRP is localized throughout the plasma membrane of the photoreceptor cell, rather than being restricted to the microvillar photoreceptor membrane. [35S]methionine‐labelling of newly synthesized retinal proteins reveals that TRP is synthesized in the rpa mutant at wild‐type level, but is transported to or incorporated into the microvillar photoreceptor membrane at a much lower rate. We thus suggest, that the formation of the INAD signalling complex is required for specifically targeting its components to the photoreceptor membrane.

Effects of vinblastine on cell membrane fluidity and the growth of SA-1 tumor in mice

Cell membranes can be targets of some anti-cancer drugs. Therefore, the purpose of this study was to determine whether vinblastine (VLB) can also affect the tumor cell membrane. On the in vivo SA-1 tumor model, alteration of cell membrane fluidity (measured by electron paramagnetic resonance, EPR), cytotoxicity and morphological changes of the SA-1 tumor cells after VLB treatment were studied. The cytotoxic effect of VLB was biphasic, with an initial fast increase in cytotoxicity followed by a plateau. The surviving cells had increased membrane fluidity and were morphologically changed. The dose-response curve of VLB on membrane fluidity was also biphasic with an initial fast increase in membrane fluidity followed by a plateau. Since dose-response curves of VLB cytotoxicity and its effect on membrane fluidity were similar, there was a high correlation between both effects. The effect of VLB on membrane fluidity was the most pronounced at 24 h and 48 h after treatment. The results of this study indicate that VLB affects cell membrane by increasing the membrane fluidity of SA-1 tumor cells in vivo in a dose-and time-dependent manner. Therefore, this finding may be beneficially implemented also in priming cells for other cytotoxic drugs and for appropriate timing of drug sequence in combined schedules.

Anterior lens epithelial cells attachment to the basal lamina.

To study the structure of the anterior lens epithelial cells (aLECs) and the contacts of the aLECs with the basal lamina (BL) in order to understand their role in the lens epitheliums function.

UV‐light‐dependent binding of a visual arrestin 1 isoform to photoreceptor membranes in a neuropteran (Ascalaphus) compound eye

Arrestins are regulators of the active state of G‐protein‐coupled receptors. Towards elucidating the function of different arrestin subfamilies in sensory cells, we have isolated a novel arrestin 1, Am Arr1, from the UV photoreceptors of the neuropteran Ascalaphus macaronius. Am Arr1 forms a phylogenetic clade with antennal and visual Arr1 isoforms of invertebrates. Am Arr1 undergoes a light‐dependent binding cycle to photoreceptor membranes, as reported earlier only for members of the arrestin 2 subfamily. This suggests a common control mechanism for the active state of invertebrate rhodopsins and G‐protein‐coupled receptors of antennal sensory cells. Furthermore, it implies that a strict correlation of distinct arrestin isoforms to distinct functions is not a general principle for invertebrate sensory cells.

Anterior lens epithelium in cataract patients with retinitis pigmentosa - scanning and transmission electron microscopy study.

In retinitis pigmentosa (RP) patients, relatively minor lens opacity in central part of posterior pole of the lens may cause disproportionate functional symptoms requiring cataract operation. To investigate the possible structural reasons for this opacity development, we studied the structure of the lens epithelium of patients with RP.

Anterior lens epithelium in intumescent white cataracts - scanning and transmission electron microscopy study

PurposeOur purpose was to study the structure of the lens epithelial cells (LECs) of intumescent white cataracts (IC) in comparison with nuclear cataracts (NC) in order to investigate possible structural reasons for development of IC.MethodsThe anterior lens capsule (aLC: basement membrane and associated LECs) were obtained from cataract surgery and prepared for scanning electron microscopy (SEM) and transmission electron microscopy (TEM).ResultsWe observed by SEM that in IC, LEC swelling was pronounced with the clefts surrounding the groups of LECs. Another structural feature was spherical formations, that were observed on the apical side of LEC’s, towards the fibre cell layer, both by SEM and TEM. Development of these structures, bulging out from the apical cell membrane of the LEC’s and disrupting it, could be followed in steps towards the sphere formation. The degeneration of the lens epithelium and the structures of the aLC in IC similar to Morgagnian globules were also observed. None of these structural changes were observed in NC.ConclusionsWe show by SEM and TEM that, in IC, LECs have pronounced structural features not observed in NC. This supports the hypothesis that the disturbed structure of LECs plays a role in water accumulation in the IC lens. We also suggest that, in IC, LECs produce bulging spheres that represent unique structures of degenerated material, extruded from the LEC.

Morphological and proliferative studies on ex vivo cultured human anterior lens epithelial cells - Relevance to capsular opacification

To determine the structural characteristics of lens epithelial cells (LECs) found on the anterior portion of the lens capsule and their pluripotency, proliferating and migrating potential when grown ex vivo with relevance to posterior capsular opacification (PCO) after cataract surgery.

Classical lepidopteran wing scale colouration in the giant butterfly-moth Paysandisia archon

The palm borer moth Paysandisia archon (Castniidae; giant butterfly-moths) has brown dorsal forewings and strikingly orange-coloured dorsal hindwings with white spots surrounded by black margins. Here, we have studied the structure and pigments of the wing scales in the various coloured wing areas, applying light and electron microscopy and (micro)spectrophotometry, and we analysed the spatial reflection properties with imaging scatterometry. The scales in the white spots are unpigmented, those in the black and brown wing areas contain various amounts of melanin, and the orange wing scales contain a blue-absorbing ommochrome pigment. In all scale types, the upper lamina acts as a diffuser and the lower lamina as a thin film interference reflector, with thickness of about 200 nm. Scale stacking plays an important role in creating the strong visual signals: the colour of the white eyespots is created by stacks of unpigmented blue scales, while the orange wing colour is strongly intensified by stacking the orange scales.