Differential behavioral syndrome evoked in the rats after multiple doses of SSRI fluoxetine with selective MAO inhibitors rasagiline or selegiline.

This study investigated whether rasagiline and selegiline (MAO-B inhibitors) induce serotonin syndrome in fluoxetine-treated rats. Rats received rasagiline (0.1, 0.5, 2.0 mg/kg), or selegiline (0.8, 4.0, 16.0 mg/kg) (doses reflecting the clinical ratio of 1:8 base) in drinking water for 28 days. During the last 21 days, they received injections of fluoxetine 10 mg/kg (controls received water only, then saline injections; a fluoxetine only group received water only then fluoxetine). Serotonin syndrome was assessed using neurological severity score (NSS), food intake and weight gain. Mean NSS significantly increased, and weight and food consumption significantly decreased in rats receiving fluoxetine alone compared with controls. Selegiline 16 mg/kg but not rasagiline (regardless of dose) exacerbated these effects. We concluded that selegiline's amphetamine-like metabolites may increase synaptic cathecholamines and possibly serotonin, aggravating fluoxetine's effect. Rasagiline is devoid of this effect and may therefore be safer for use with serotonergic drugs in parkinsonian patients.

Rasagiline is neuroprotective in an experimental model of brain ischemia in the rat.

The neuroprotective effects of intravenous rasagiline were investigated in a rat model of stroke. Middle cerebral artery (MCA) occlusion was performed in male rats and the short- (neurological severity score [NSS], infarct size), intermediate- (cognition) and long-term (necrotic area) effects were assessed. A bolus (3 mg/kg) of rasagiline followed by a 3-h infusion (3 mg/kg/h), initiated immediately after MCA occlusion, reduced infarct size by 48.6% and NSS by 32.7% relative to saline treatment. Cognitive function, tested in a water maze 2-3 weeks after occlusion, also significantly improved compared with saline-treated controls. Necrotic brain area was 35-50% smaller with rasagiline than with saline following a single bolus dose. The single bolus rasagiline dose was as effective as a rasagiline bolus followed by rasagiline infusion in short-term outcomes. The neuroprotective effect of rasagiline was fully reproducible when administered at 2 h following occlusion but not after 4 h.

Magnetic minerals. Keystone-like crystals in cells of hornet combs.

The hexagonal brood-rearing cells inside the nest combs of the hornet Vespa orientalis are uniform in both their architecture and orientation. We have discovered that each cell contains a minute crystal that projects down from the centre of its domed roof and has a composition typical of the magnetic mineral ilmenite. These tiny crystals form a network that may act like a surveyor's spirit-level, helping the hornets to assess the symmetry and balance of the cells and the direction of gravity while they are building the comb.

Navigation and thermophotovoltaic activity by hornets at different light conditions: the influence of UVB blockers.

The aim of the present investigation was two-fold: a) to observe the homing of the Oriental hornet, Vespa orientalis (Hymenoptera, Vespinae) from different distances; and b) to study the photothermoelectric activity of hornet cuticle obtained from the subjects of goal (a) and kept frozen for a number of days prior to its testing. In both the above mentioned phases of the investigation, an attempt was made to assess how the covering of the hornets' cuticle with Ultra Violet B (UVB) blockers affects their activity as compared to the control. Flying hornets were observed to return to the nest from distances of up to 7 km, once they had learned the way back. However, covering of the cuticle with UVB blockers increases the percentage of 'non-returners' to nearly 100%. Covering the cuticle completely or partly with a number of UVB blockers (except for Sisley) proves lethal for the hornets within 24 hours. A statistical model on homing is proposed of the effect of range, of covering with UVB blockers and covering ocelli with Tippex. In the wing of the hornet there is increase in the electric current with rise in the temperature and decrease in the current upon drop of the temperature, but light has no effect on this alar (wing) current. Contrariwise, the body cuticle of the hornet responds to both temperature and illumination in terms of its electric current. Coating of the cuticle with UVB blockers causes in the wing (under all conditions of illumination) and in the cuticle (only in the dark) a moderation in the amplitude of the photothermoelectric current.

Thermal properties of hornet colonies: thermography of individual hornets and their nests and the role of the pupal silk in thermoregulation.

The present study focused on temperature assessments within a hornet nest. The measurements encompassed adult hornets, brood combs and the various stages of brood, and involved a thermographic method. Body parts of adult hornets were found to vary in their temperature, with the thorax eliciting the highest temperature and the abdomen the lowest. Similarly, there were thermal variances between larvae at instars 4-5, light-colored pupae and dark pupae. The measurements were made at day and night (when the entire population was present in the nest) on nests containing thousands of individuals at various ages. Most of the pupae measured during October were hornet drones. The usual air temperature between the (subterranean) combs was 28.7 degrees C, while the outside (ground level) temperature was 23.5 degrees C. The paper discusses the creation of heat by hornets, the thermoregulation throughout night and day, both by the hornets proper as well as by their products (comb and silk). Also discussed is the intra-nest conversion of one form of energy to another, as heat to electric current or vice versa.

Hypothesis on radar sensing and communication by hornets: comments on their antennal organulles and electrical activity.

Our study shows that the antenna of the hornet is densely covered from base to tip with six types of organulles, namely, a trichoid organulle, about 23 microm in length, a campaniform organulle which is 12 microm long, a heretofore undescribed structure measuring about 9 microm in length which we have now named the Agmon organulle, a rather flattened placoid organulle measuring about 25 microm in length and not projecting on the antennal surface, and finally rounded structures about 3 microm in diameter which are indented in the cuticle and resemble extraretinal photoreceptors. All the above-mentioned structures occur in the workers and drones, and the latter also possess an additional structure, namely, the tyloid which is about 254 microm long. Such organulles as protrude from the antennal surface are mostly orientated distally and their length is about half that of similar organulles on the hornets body. Yet their density on the antenna is greater than elsewhere on the body and in fact on all the antennal segments (12 in the workers and 13 in the drones) the entire surface area seems to be occupied by them. The most numerous are the trichoids, while the other organulles mentioned are fewer in number. In measuring the electric properties of the antennae, we obtained the following values: 10-80 nanoAmpers (nA), 60-100 milliVolt (mV) and several scores of Mega Ohms (Momega) in the dark, as compared to 10-20 nA, 150-200 mV and few Momega under illumination. We found that in many respects, the cuticle in the antenna behaves like an organic semiconductor possessing thermophotovoltaic (TPV) properties. Apart from contemplating that the role of the antennal organulles is as a mechanoreceptor, a chemoreceptor or a combination of the two, we also raise the conjecture that these organulles might serve as elements that pick up and broadcast at submillimetric wavelengths, and that the electric energy extant in the vespan antennae supplies the energy source for this kind of activity.

Thermophotovoltaic (TPV) properties of hornet cuticle as dependent on relative humidity.

This paper deals with the thermophotovoltaic (TPV) properties of the cuticle of the Oriental hornet as assessed over time under different regimens of relative humidity (RH). The tests were run at two levels of RH, namely, 30% vs. 90%. Each experiment entailed measuring the cuticular voltage and current in the dark as compared to under illumination (white light = 700 Lux), and at a temperature range of 20-30 degrees C. It was found that increase in the RH level boosts the current values by 2-3 orders of magnitude; contrariwise, the voltage values rise by about three times with drop in the RH. At high RH, the changes in current become rhythmical and each cycle of warming-cooling assumes a distinctly cyclic pattern. Under illumination, the current decreases, the polarity reverses and the resistance increases. The obtained results are describable by a model of electric conductance upon a surface, in this case the hornet cuticle; the findings are also discussed and compared with similar phenomena recorded from other substances possessing the properties of organic semiconductors.

The solar cell in hornet cuticle: nanometer to micrometer scale.

This paper focuses on structures observed by scanning and transmission electron microscopy and atomic force microscopy upon and within the abdominal cuticle of the Oriental hornet, Vespa orientalis. Taken together, these structures form an 'organ' whose function is the absorption ef sunlight and storage of the resultant electrical energy. In principle, this organ resembles a solar cell. The gaster of the hornet is cone-shaped and comprised of the following components: (i) structures protruding from the epicuticular surface, which are arranged lengthwise and generally parallel to one another like furrows; (ii) these furrows overlie straight, terrace-like flat surfaces, which are shaped like imperfect polygons, each about 100 microm2 in area; (iii) each terrace abuts an area that is positioned lower than it, the juncture between the two is comprised of a stripe, which is vertical to the topmost polygonal flat and perpendicular to the furrows; (iv) between the juncture stripes, at distances of 10-100 microm apart, there are smooth flat surfaces reminiscent of a parabolic mirror of about 20 microm2, each possessing a rounded, eccentric area recessed to a depth of about 7.5 microm (i.e. a heat sinking housing), underneath which can be seen the upper part of the peripheral photoreceptor (PP); (v) cuticular lamellae, about 30 in number, create a pore between them in the PP region, fold in vertical fashion and enwrap the entire PP down to its broad base which is immersed in a yellow bacterial layer and where the cuticular layers are very thin. Presumably the light energy impinges vertically upon the individual terraced flat surfaces while the hornet is in flight, creating such situations for a fraction of a second at a time. The insolation is absorbed more intensively in the furrows, owing to their shape. The picked up solar energy is now transmitted as electric charges from the furrows to the conduction stripes between abutting terraces, and thence to: (a) the rhodopsin pigment in the PP (the smaller moiety), or (b) the numerous cuticular layers, depending on the energy level of the picked up photons (the larger moiety), and (c) finally to the bacterial layer for storage in its walls. The latter region will be a p-type as compared to the energy stored in the layers of brown cuticle. The cuticle thus was found to contain many PPs but within the cuticle they are dispersed in contrast to the situation in the compound eye, where the many photoreceptors are concentrated.

Light curtails sleep in anesthetized hornets: extraretinal light perception.

In the present study effects of light on the sleep duration of anesthetized hornets (Vespa orientalis) were investigated. Following initial anesthesia by diethyl ether the sleeping time of workers and drones at 22 degrees C in the dark was 59 +/- 15 min. After repeated anesthesia the sleeping time was 30 +/- 15 min in the dark. When exposed to polychromatic light from a halogen lamp of 230 mW/cm2, focused on a spot of the cuticle of the hornet, the sleeping time was markedly shortened so that following initial as well as repeated anesthesia the hornets woke up after 4.5 +/- 2.9 min. Any decrease in light intensity resulted in an increase in the sleeping time but irradiances of less than 14 mW/cm2 had no measurable influence on the wake-up time. After illumination with polychromatic light from a mercury lamp the sleeping times were much shorter than after illumination with a halogen lamp at the same conditions and intensity. This difference is attributed to the relatively higher portion of U.V. light in the total emission of the Hg lamp. Effects of the spectral composition of the incident light beam on the wake-up of the sleeping hornets were also investigated. Near U.V. light in the 300-400 nm region was found to be most efficient. Shorter wavelengths as well as wavelengths between 400-470 nm had less influence and wavelengths above 470 nm had very little effect on the wake up. The sleeping times of hibernating queens were relatively longer than those of workers and drones under the same conditions. These effects are ascribed to the extraretinal light perception. The possible reasons underlying this phenomenon are discussed.