Sensitization inHelix snail: Morphofunctional correlates in command neurons of withdrawal behavior

Electrophysiological effects have been studied in command neurons of withdrawal behavior inHelix snail. In parallel, correlated changes in the content of bound calcium (Ca-b), as well as changes in DNA condensation, were investigated using a chlortetracycline fluorescent probe and the fluorescent dye bisbenzimide, respectively. Short-term electrophysiological changes (depolarization of the membrane and elevation of its excitability) in sensitized snails have been found to be accompanied by an increase in the Ca-b level in the cell nucleus and by partial DNA decondensation. Long-term effects were characterized by more pronounced synaptic components of the responses — slow EPSPs evoked by sensory stimuli, as well as by further DNA decondensation and considerable elevation of the Ca-b content in the nucleus and cytoplasm. The results obtained inin vitro conditions have shown that Ca-binding nonhistone proteins of chromatin are components of the cell nucleus whose content may be measured by chlortetracycline fluorescence.Translated from Neirofiziologiya, Vol. 25, No. 2, pp. 150–157, March–April, 1993.     

Human Discrimination of the Angular Velocity of the Vertical Movement of an Acoustic Image in Opposite Directions

The discrimination of the angular velocity of ventrodorsal and dorsoventral movement of an acoustic image was studied in nine test subjects. The experiments were performed using an apparent movement produced by consecutive activation of loudspeakers located along an arc in the vertical plane. The differential thresholds were measured by the minimum increment method. As the velocity of an acoustic image movement in opposite directions increased, the values of its mean absolute differential thresholds increased monotonically. Regression lines plotted by linear approximation of these values did not differ significantly.     

Natural variability of Actinomyces lavendulae, a producer of cholesterol oxidase

Five variants of Actinomyces lavendulae differing in the morphology of their colonies were found when natural variability of this organism was studied. A correlation was established between the colony morphology of the variants and their activity of cholesterol decomposition. The variants forming colonies of the basic and folded type had the highest activity. A variant with an elevated activity of cholesterol oxidase was selected. In order to maintain the high activity of the culture, it is necessary to examine its variability and to select variants corresponding to the basic type in their morphology.     

Olfactory experience modifies the effect of odour on feeding behaviour in a goal-related manner

Natural food odours elicit different behavioural responses in snails. The tentacle carries an olfactory organ, and it either protracts toward a stimulating carrot odour or retraces in a startle-like fashion away from a cucumber odour. The tentacle retraction to cucumber was still present after the snails were fed cucumber during inter-trial periods. Also, snails without any food experience displayed a longer latency to the first bite of cucumber than of carrot and rejected cucumber more often. After tasting these foods, the latency to carrot was not affected while the latency to and number of rejections of cucumber decreased. These results suggest that initial repulsive features of food odour can be only partially compensated by olfactory learning and feeding experience. In the present study, we demonstrated that an invertebrate can be repulsed or attracted by the same natural odour at the same time and that these behavioural responses are likely aimed at achieving different physiologically relevant goals.     

A novel glycosphingolipid from gram-negative aquatic bacteria.

The chloroform-methanol extractable lipids of the Gram-negative fresh-water bacteria Arcocella aquatica NO-502 and Flectobacillus major FM were found to contain an unusual ninhydrin-positive glycolipid. It was purified by two-stage silica gel-column chromatography. By the use of IR and (1)H-NMR spectroscopy, mass spectrometry and chemical-degradation experiment, the lipid was established to be 1-O-monoglycosyl ceramide, the carbohydrate moiety of which was the alpha-pyranose-ring form of 7-desoxy-7-amino-D-manno-heptulosonic acid, or 1-hydroxycarbonyl-6-deoxy-6-amino-alpha-D-mannopyranose. The ceramide portion consisted mainly (by 95% in the A. aquatica glycolipid and 80% in the F. major glycolipid) of 2-N-(2'-D-hydroxy-13'-methyltetradecanoyl)-15-methyl-4(E)-hexad ecasph ingenine. The minor molecular species differed from the major one only in fatty acid structure. The glycolipid accounted for 8 and 11% of the total lipids extracted from A. aquatica NO-502 and F. major FM cells, respectively.     

Giant Enhancement of Transmitted Light and Its Localization Due to Elastic Surface Plasmon–Polariton Scattering by a Thin Dielectric Diffraction Grating

The enhancement factor for surface plasmon–polaritons scattering by a thin dielectric grating was measured experimentally. Scattering of a p-polarized wave may be up to 30,000 times stronger than the non-resonant scattering of an s-polarized wave by the same grating. A detailed comparison between the theoretical calculations and experimental measurements was performed. Strong localization of the scattered field near the edges of diffraction grating grooves was found. Such localization is very promising for numerous applications, e.g., biological sensors, optical tweezers for catching particles, or viruses, etc.     

Study of the mechanism of postcoital contraception in the combination of streoids and the central m-cholinolytic, amizil]

Experiments on female rats showed the blocking of the M-cholinoreactive system with amizyl to significantly contribute to the estrogen/norsteroid contraceptive effect during the postcoital periods. This effect was accompanied by decrease in the gonadotropin level and by the change in the LH/FSH ratio, this creating an unfavourable background for implantation of the fertilized ovicell in the endometrium. There was a change in the transport rate in the tube and a delay in the decidual reaction. Changes in the rate of the ovicell transport were not accompanied by distrubances in the process of fertilization or with the cytotoxic action. Mestranol and ethynylestradiol in combination with norethynodrel (1:20) and with the central cholinolytic amizyl were agents with future prospects for short-term postcoital contraception.