Neuronal responses mediated by activation of the non-NMDA receptors: Potentiation by nootropes

Experiments on superfused slices of rat hippocampus showed that the nootropic drugs pyracetam, ethymizol, ambocarb, and nooglutil increase the amplitude of populational EPSP (pEPSP) of neurons of the dentate gyrus evoked by electrical stimulation of the perforant pathway (PP). Nootropes exert no effect on the process of presynaptic glutamate liberation from the PP axons, but increase the chemosensitivity of the postsynaptic AMPA/kainate receptors mediating EPSP generation in the dentate gyrus neurons. Inhibitors of protein kinase (A-buthamide) and guanylatecyclase (methylene blue) do not modify the effects of nootropes. The nootrope-induced potentiation of pEPSP does not develop against the background of the application of calmodulin inhibitor W-7. In the presence of protein kinase inhibitor C, polymixin B, nootropes reversibly depress pEPSP in the dentate gyrus neurons. Blocking of the NMDA receptor ionic channels by ketamine and of the voltage-dependent T-type calcium channels by Ni²⁺ does not significantly modify the effects of nootropic drugs. A blocker of Ca²⁺-ATPase of the Ca²⁺ stores sodium orthovanadate, potentiates the effects of nootropes. Dantrolene, which disrupts Ca²⁺ liberation from the non-mitochondrical depots, blocks the effects of nootropes and diminishes pEPSP depression evoked by nootropes in the presence of polymixin B. On the basis of presented data, it is supposed that nootropic drugs assist Ca²⁺ liberation from the neuronal depots and activate calmodulin-dependent protein kinase and protein kinase C. Protein kinases phosphorylate the intracellular domains of the AMPA/kainate receptors, and this process results in an increase in their sensitivity to excitatory amino acids.Neirofiziologiya/Neurophysiology, Vol. 26, No. 5, pp. 365–372, September–October, 1994.     

The identification of tryptophan residues responsible for ATP-induced increase in intrinsic fluorescence of myosin subfragment 1

ATP binding to myosin subfragment 1 (S1) induces an increase in tryptophan fluorescence. Chymotryptic rabbit skeletal S1 has 5 tryptophan residues (Trp113, 131, 440, 510 and 595), and therefore the identification of tryptophan residues perturbed by ATP is quite complex. To solve this problem we resolved the complex fluorescence spectra into log-normal and decay-associated components, and carried out the structural analysis of the microenvironment of each tryptophan in S1. The decomposition of fluorescence spectra of S1 and S1-ATP complex revealed 3 components with maxima at ca. 318, 331 and 339-342 nm. The comparison of structural parameters of microenvironment of 5 tryptophan residues with the same parameters of single-tryptophan-containing proteins with well identified fluorescence properties applying statistical method of cluster analysis, enabled us to assign Trp595 to 318 nm, Trp440 to 331 nm, and Trp 13, 131 and 510 to 342 nm spectral components. ATP induced an almost equal increase in the intensities of the intermediate (331 nm) and long-wavelength (342 nm) components, and a small decrease in the short component (318 nm). The increase in the intermediate component fluorescence most likely results from an immobilization of some quenching groups (Met437, Met441 and/or Arg444) in the environment of Trp440. The increase in the intensity and a blue shift of the long component might be associated with conformational changes in the vicinity of Trp510. However, these conclusions can not be extended directly to the other types of myosins due to the diversity in the tryptophan content and their microenvironments.     

Displaying behaviour and mating system in the Siberian Spruce Grouse (Falcipennis falcipennis Hartlaub 1855)

Summary The Siberian Spruce Grouse (Falcipennis falcipennis) is a species endemic to far-eastern Russia and a close relative toF. canadensis andF. franklinii of North-America. Prior to this study, little was known about the display behaviour, social organisation and seasonal movements of this grouse. We investigated these topics in 1990–1997, in 2 areas, 100 km N and 200 km NW of Komsomolsk/Amur. We caught, measured and marked 80 individuals. We determined the age of cocks by the size of combs and the length of neck feathers. Spatial organisation of the local population was studied by equipping 60 birds with transmitters and following them all-year-round.During the reproductive period males and females were territorial. Winter flocks (2–6 birds) break up by late March or early April, and spring flocks break up 1 month later. Cocks were present at the display ground from April 1 to May 25. Females visited the display grounds from April 25 to May 10. Eggs were laid between May 7 and May 20. The main display performances of cocks (upright posture and tail flicks, walks with tail swish, flutter jumps, flutter flights, drumming flights), courtship and agonistic behaviour were analysed from photographs and video recordings. Three-year-old cocks carried out most of the copulations. During the high season of display, we recorded activity (morning and evening displays, moving versus roosting) during continuous observations and counted flutter jumps, flutter flights and drumming flights.Parts of the displays of the Siberian spruce grouse are more diversified than those of the North-American species. The communication system is perfectly adapted to the dense habitat of the mountain taiga. Different acoustic signals for communication at very short, medium and longer distances seem to have evolved under specific predation pressure. The territorial system is very flexible, ranging from individual display grounds to an arena-like structure. The mating system is polygyny.

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Balzverhalten und Paarungssystem des Sichelhuhns (Falcipennis falcipennis Hartlaub 1855)

Zusammenfassung Das Sichelhuhn (Falcipennis falcipennis) als endemisches Raufußhuhn des Fernen Ostens Russlands ist eng verwandt mit den nordamerikanischen FichtenhühnernF. canadensis undF. franklinii. Von 1990–1997 wurden Ökologie und Verhalten dieser Art in zwei Gebieten (100 km N und 200 km NW von Komsomolsk am Amur) studiert. 80 Vögel wurden gefangen, vermessen und markiert. Zwei Maße (Größe der Überaugenwülste und Halsfederlänge) gestatten eine Altersbestimmung der Hähne. 60 besenderte Vögel lieferten rund um das Jahr Daten zu Raum- und Habitatnutzung, Reproduktion und Mortalität. Individuelle Markierung und Ortung zu beliebigen Zeiten erleichterten auch die Verhaltensstudien. In der Reproduktionsperiode besaßen sowohl Hähne als auch Hennen Reviere. Winterflüge aus 2–6 Vögeln lösten sich Ende März/Anfang April auf; die Frühjahresgruppen einen Monat später. Die Hähne waren im Mittel zwischen 1. April und 25. Mai an den Balzplätzen anzutreffen, die Hennen erschienen dort zwischen 25. April und 10. Mai. Zwischen 7. und 20. Mai erfolgte die Eiablage. Die wichtigsten Elemente des Territorialverhaltens (Aufrechthaltung mit Schwanzspreizen, Imponierläufe mit Schwanzfederzischen, Flattersprünge, Flatterflüge und Trommelflüge), Revierverteidigung und Werbung werden nach Foto- und Videoaufzeichnungen beschrieben. Dreijährige Hähne vollzogen die meisten Paarungen. Zwischen 1. und 9. Mai, wenn Werbe- und Paarungsverhalten kulminieren, wurden durch Ganztagsbeobachtungen Morgen- und Abendaktivität, Ortsveränderungen und Ruhephasen quantitativ erfasst, ebenso der tägliche Anteil von Flattersprüngen, Flatter-und Trommelflügen. Im Vergleich zu den nordamerikanischen Geschwisterarten sind Teile des Verhaltensrepertoires des Sichelhuhns zur Balzzeit stärker differenziert. Das Kommunikationssystem ist an dichte Habitate der borealen Bergtaiga angepasst: Verschiedene akustische Signale, die auf sehr kurze, mittlere and längere Distanzen wirken, sind offenbar in Anpassung an den spezifischen Feinddruck entstanden. Das Reviersystem erscheint flexibel: Die Spanne reicht von solitär agierenden Hähnen bis zu Arena — ähnlichen Balzplätzen. Das Paarungssystem ist Polygynie.

     

Src and Pyk2 mediate G-protein-coupled receptor activation of epidermal growth factor receptor (EGFR) but are not required for coupling to the mitogen-activated protein (MAP) kinase signaling cascade

The epidermal growth factor receptor (EGFR) and the non-receptor protein tyrosine kinases Src and Pyk2 have been implicated in linking a variety of G-protein-coupled receptors (GPCR) to the mitogen-activated protein (MAP) kinase signaling cascade. In this report we apply a genetic strategy using cells isolated from Src-, Pyk2-, or EGFR-deficient mice to explore the roles played by these protein tyrosine kinases in GPCR-induced activation of EGFR, Pyk2, and MAP kinase. We show that Src kinases are critical for activation of Pyk2 in response to GPCR-stimulation and that Pyk2 and Src are essential for GPCR-induced tyrosine phosphorylation of EGFR. By contrast, Pyk2, Src, and EGFR are dispensable for GPCR-induced activation of MAP kinase. Moreover, GPCR-induced MAP kinase activation is normal in fibroblasts deficient in both Src and Pyk2 (Src-/-Pyk2-/- cells) as well as in fibroblasts deficient in all three Src kinases expressed in these cells (Src-/-Yes-/-Fyn-/- cells). Finally, experiments are presented demonstrating that, upon stimulation of GPCR, activated Pyk2 forms a complex with Src, which in turn phosphorylates EGFR directly. These experiments reveal a role for Src kinases in Pyk2 activation and a role for Pyk2 and Src in tyrosine phosphorylation of EGFR following GPCR stimulation. In addition, EGFR, Src family kinases, and Pyk2 are not required for linking GPCRs with the MAP kinase signaling cascade.     

Apoptosis of peripheral lymphocytes of healthy donors and patients with laryngeal neoplasms after gamma-irradiation in vitro

Apoptosis in peripheral blood lymphocytes of healthy donors and cancer patients after gamma-irradiation with different doses was studied by the flow cytometry method. Wide intra- and interindividual variabilities of the lymphocyte radiosensitivity were observed. The radiosensitivity did not depend on the subpopulation composition of the lymphocyte pool. The persons with very low and high lymphocyte radiosensitivities were found significantly more often among the cancer patients than among the healthy donors. One can suggest that this method is useful as a biomarker of future cancer risk and prognosis of radiotherapy efficiency.     

Generation of a wakefield during gas ionization

One-dimensional equations are derived that describe the hydrodynamic and electrodynamic properties of a plasma created through gas ionization by a short intense laser pulse. Different approaches (in particular, the particle-in-cell method) are used to show that, with ionization processes included, the excitation of a wakefield by an intense laser pulse can be described by the method of slowly varying amplitudes. It is shown that ionization processes enhance the wakefield excited by a moderate-intensity laser by about 10% in the case of a linearly polarized laser and by about 50% in the case of a circularly polarized laser. Ionization processes in light gases irradiated with high-intensity laser pulses have essentially no effect on the wakefield during the resonant excitation of a plasma wave by the ponderomotive force and play a governing role far from the resonance.     

Epithelial structural changes in the urinary tubules of the kidney of the white rat in the early period of corrosive sublimate nephrosis

Examination of serial semithin (0.5 micron) methacrylate and paraffin (8 micron) sections of the rat kidney 6, 12, 24 and 48 hours after subcutaneous injection of sublimate in a dose of 0.6 mg/100 g bw has demonstrated that the damage to the different parts of the tubular component of nephron is heterogeneous in nature. Both complete and partial necrosis of nephrocyte cytoplasm can be seen in the proximal part of nephron. The distal parts of nephron and collective tubules are characterized by partial necrosis of the apical areas of the cytoplasm. During the period between 12 and 24 hours after sublimate injection, one can observe the onset of destructive processes together with intracellular recovery processes in partially damaged but still viable nephrocytes, which is confirmed by the enlargement of the nucleolar size. The regeneration of the tubular epithelium at the expense of cellular renewal was unmarked 24 hours after sublimate injection.     

Electron microscopic-radioautographic study of RNA synthesis in the epithelial cells of the kidney urinary tubules of white rats in corrosive sublimate poisoning

Radioautographic study of ultrathin selections of proximal white rat renal canals labeled with 3H-uridine revealed diffuse transition of peripheral and paranuclear heterochromatin to be observed in nuclei of undamaged epithelia cells and those affected by partial necrosis in case of sublimate nephrosis. Nucleus degranulation as well as decrease in its size accompanied by inhibition of RNA synthesis is also observed. Nucleus reparation being observed 48 hours after subcutaneous injection of 0.4/0.1 kg corrosive sublimate in some cells and characterized by the appearance of granular component as well as the increase of nucleolar vacuole count is usually revealed in case of decondensation form of peripheral and paranuclear chromatin in the enlarged nuclei.     

Electron and proton acceleration in superstrong laser field: Simulations and models

Results of particle-in-cell simulations of the interaction of an intense femtosecond laser pulse with a thin aluminum foil the front surface of which is covered with a hydrogen preplasma layer are compared with predictions of simple analytical models. It is shown that light pressure may be the most efficient mechanism for proton acceleration in the initial stage of laser-plasma interaction.