Adequate stimulus of the insect tympanic organ

Résumé Les réponses du nerf tympanique des Tettigonides sont conformes à la structure actuelle des transmetteurs du chant naturel mais non pas si le chant est reproduit par enregistrement magnétique ordinaire. On a montré que les constituants ultrasoniques sont essentiels et que les réponses parfaites ne sont obtenues que lorsqu'on a pu produire des fréquences très hautes.     

A visual stimulus in the courtship ofDrosophila suzukii

Summary The males ofDrosophila suzukii have a specific black spot on their wings and this was surgically removed. In this situation, the males were almost normally accepted by the females when they were stored under a diurnal light-dark cycle, but they were somewhat discriminated against by the females previously exposed to continuous light.     

Cancellation of cellular responses to nanoelectroporation by reversing the stimulus polarity

Nanoelectroporation of biomembranes is an effect of high-voltage, nanosecond-duration electric pulses (nsEP). It occurs both in the plasma membrane and inside the cell, and nanoporated membranes are distinguished by ion-selective and potential-sensitive permeability. Here we report a novel phenomenon of bioeffects cancellation that puts nsEP cardinally apart from the conventional electroporation and electrostimulation by milli- and microsecond pulses. We compared the effects of 60- and 300-ns monopolar, nearly rectangular nsEP on intracellular Ca²⁺ mobilization and cell survival with those of bipolar 60 + 60 and 300 + 300 ns pulses. For diverse endpoints, exposure conditions, pulse numbers (1–60), and amplitudes (15–60 kV/cm), the addition of the second phase cancelled the effects of the first phase. The overall effect of bipolar pulses was profoundly reduced, despite delivering twofold more energy. Cancellation also took place when two phases were separated into two independent nsEP of opposite polarities; it gradually tapered out as the interval between two nsEP increased, but was still present even at a 10-µs interval. The phenomenon of cancellation is unique for nsEP and has not been predicted by the equivalent circuit, transport lattice, and molecular dynamics models of electroporation. The existing paradigms of membrane permeabilization by nsEP will need to be modified. Here we discuss the possible involvement of the assisted membrane discharge, two-step oxidation of membrane phospholipids, and reverse transmembrane ion transport mechanisms. Cancellation impacts nsEP applications in cancer therapy, electrostimulation, and biotechnology, and provides new insights into effects of more complex waveforms, including pulsed electromagnetic emissions.     

Hypoxia as a negative reinforcing stimulus in the squirrel monkey

Summary Squirrel monkeys learned to avoid hypoxia by pressing a bar. Each bar-press replaced the noxious gas mixture with normal air for 3 sec. The data further indicated that O₂ itself has no positive reinforcing effect.     

Differentiation of haustoria in the germinating embryos of mistletoe without host stimulus

Zusammenfassung Die Samen vonScurrula pulverulenta, einem Baumparasiten, keimen auf einfachen Nährböden. Aus den embryonalen und endospermalen Geweben entwickeln sich in den In-vitro-Kulturen, auch bei Abwesenheit von Wirtsgewebe, Haustorien.     

Visual stimulus localization as a function of brightness

Résumé Dans une tâche consistant à localiser un point sur une barre horizontale ou verticale, on mesure l'information transmise en fonction de l'éclairement et de l'information du stimulus. On trouve une relation linéaire directe entre l'information transmise et le logarithme de l'éclairement. Cette relation reste valable pour diverses quantités d'information émise.

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Partly supported by the Fonds National belge de la Recherche Scientifique.     

Enhancement of the sensitivity of hamster cheek pouch arterioles to beta-adrenergic stimulus during pregnancy

Summary The adrenergic beta stimulant fenoterol induced a dose-dependent vasodilation of hamster cheek pouch arterioles. The response to fenoterol was significantly larger on day 14 of pregnancy than in metoestrous animals. Since the serum progesterone and 17 beta-oestradiol level were also elevated on day 14, a relationship was suggested between the enhancement of vascular sensitivity and sex-steroid hormone levels.     

Relation between stimulus intensity and neutrophil chemotactic response

Summary The effect of chemotactic peptides which lack chemokinetic activity has been investigated. The neutrophil response is proportional to the logarithm of the stimulus intensity, or alternatively a power function with an exponent of 0.3. Equal responses are obtained for equal ratios between the peptide concentration in the lower compartment and the threshold concentration. The significance of Weber-Fechner's law in leucocyte chemotaxis is discussed.We thank Miss B. Zanolari, Mrs M. Marti, Mrs Hauck and Mr Dietz for excellent technical assistance. This work was supported by the Swiss National Foundation for Scientific Research.     

The responses of units in the superior colliculus of the cat to a moving visual stimulus

Riassunto Alcune unità del collicolo superiore nel gatto pretrigeminale vengono attivate da un oggetto in movimento lungo un arco di 6–12° oppure di 30–45°. La velocità, direzione, verso e piano di spostamento sono differenti per ogni unità. La decorticazione completa non modifica le risposte unitarie, mentre la distruzione dei due nuclei genicolati laterali abolisce le risposte ai movimenti di massima ampiezza.

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This investigation was supported by USPHS grant NB-0299004.P.L.