Structural asymmetry in the frog retinal ganglion cell layer

The density of distribution and topographical features of small and large ganglion cells were investigated in total silver-impregnated preparations of the retina from two species of frogs (Rana ridibunda andR. temporaria). A horizontal band of increased density of ganglion cells was located in both species above the nasotemporal axis passing through the blind spot. Outside this band the density of the small cell population was maximal in the central zone of the retina, decreasing toward the periphery. In the upper halves of the retina the density of small cells was on average 26% greater than in the lower halves. Large ganglion cells, on the other hand, were more densely distributed in the lower half of the retina than in the upper half; this difference was particularly marked inR. temporaria (by 116%). The large cells were asymmetrically distributed relative to the dorsoventral axis also: In the nasal quadrants their density was 40–55% greater than in the temporal. Large cells were more densely distributed in the middle zone of the retina. Signs of asymmetry in the organization of the retinal output raster may be of adaptive ecologic importance and may determine the characteristics of formation of visually controlled food and avoidance behavioral reflexes.Research Institute of Applied Mathematics and Cybernetics, N. I. Lobachevskii State University, Gorkii. Translated from Neirofiziologiya, Vol. 17, No. 2, pp. 198–204, March–April, 1985.     

A protein backbone psi and phi angle dependence of 2J(N(i),C alpha(i-1)): the new NMR experiment and quantum chemical calculations

A new pulse sequence exploiting double- and zero-quantum evolution of two-spin ¹⁵N–¹³C coherence is proposed for the accurate measurements of ²J _{N( i ),C( i - 1)} coupling constants. Application of the new experiment is presented for ¹³C,¹⁵N-labeled ubiquitin sample. The density functional theory calculations of ²J _{N( i ),C( i - 1)} coupling constants have been performed to study their dependence on both (i - 1) and (i - 1) angle in model peptides, and the results exhibit a good correlation with experimental data.Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1007/s10858-004-7563-7This revised version was published online in April 2005. In the previous version, the name of the last author, Joanna Sadlej, was missing.     

Apoptosis induced by membrane damage in human lymphocytes; effects of arachidonic acid and its photoproducts

The effect of arachidonic acid (AA) combined with UVA irradiation was studied in a model system mimicking phototherapy PUVA (psoralen+UVA) ex vivo in vitro. The contribution of damage to the plasma membrane by PUVA was tested on human lymphocytes derived from healthy donors. The effect of arachidonic acid (AA) combined with UVA irradiation was compared with that of a psoralen photoadduct to AA added to the culture. The adduct, obtained photochemically and purified, was characterized by NMR and MS spectrometry as a cycloadduct of psoralen to the vinylene bond of the acid (AA<>PSO). The reactions of cultured cells, manifested 20 h after treatment by changes in apoptosis and mitochondrial depolarization, were monitored by flow cytometry by tagging lymphocytes with appropriate fluorescent probes. Treatment of lymphocyte suspension within AA doses from 40 to 100 microM gradually induced a shift from Anx-V(+) (single positive cells) to late apoptotic, Anx-V(+)PI(+) (double positive cells) in a dose dependent manner. The adduct, AAPSO, induced apoptotic changes at a concentration 2-3 times higher than free AA. Combination of psoralen (1 microM ) or arachidonic acid (20-120 microM) with UVA irradiation (2-6 J/cm(2)) accelerated the plasma membrane changes in a synergic way. Preliminary studies indicated that changes in the transmembrane potential of mitochondria paralleled the apoptosis when cells were treated by AA alone. Our findings showed that UVA radiation of lymphocytes in the presence of arachidonic acid, as in the presence of psoralen, enhanced apoptosis of cells in a synergic manner. Thus, PUVA-induced apoptosis may proceed in part by a still undefined signaling pathway(s) triggered in lymphocyte membranes.     

Interaction of tyrosine phenol-lyase with phosphoroorganic analogues of substrate amino acids.

The phosphinic analogues of tyrosine and pyruvate were first demonstrated to be substrates in the reactions of elimination and synthesis catalyzed by tyrosine phenol-lyase. Kinetic parameters of the enzymatic process were determined, and the first enzymic synthesis of an aminophosphinic acid was carried out. Replacement of the planar HOOC-group by the tetrahedral (HO)(O)PH-group in the substrate slightly affected its affinity for the enzyme but substantially diminished the conversion rate. For phosphonic analogues, containing (HO)2(O)P group, the affinity to the enzyme was decreased considerably while the conversion was completely prevented. Thus, the structural parameters of the acid group are important not only for the affinity for the enzyme, but also for the formation of the catalytically competent conformation of the active site.     

Spike activity of mesencephalic neurons during nociceptive stimulation of the alert cat

Rate of reorganizations of neuronal impulse activity in the ventromedial parts of the midbrain of alert rats in conditions of nociceptive and non-nociceptive actions is determined by biological value of used stimuli and closely correlates with spontaneous and evoked changes of the motor activity and oscillations of vegetative parameters. The character of reorganizations of discharge activity (activation, inhibition) significantly differs in cells of various types, singled out on the basis of differences of electrophysiological properties and predominantly localized in different parts of the studied brain areas. The revealed characteristics of the functional properties of the neurones are discussed in connection with supposed differences of their neurotransmitter specificity and their role in providing for different chains of adaptive activity of the organism.     

Concerted transpositions of mobile genetic elements coupled with fitness changes in Drosophila melanogaster

In an inbred low-activity (LA) strain of Drosophila melanogaster with a low level of fitness and a complex of inadaptive characters, in situ hybridization reveals an invariant pattern of distribution of three copia-like elements (mdg-1, mdg-3, and copia). Rare, spontaneous, multiple transpositions of mobile elements in the LA strain were shown to be coupled with a drastic increase of fitness. A changed pattern of various types of mobile elements was also observed on selecting the LA strain for higher fitness. High-fitness strains show transpositions of mobile elements to definite chromosomal sites ("hot spots"). Concerted changes in the location of three different mobile elements were found to be coupled with an increase of fitness. The mdg-1 distribution patterns were also examined in two low-fitness strains independently selected from the high-fitness ones. Fitness decrease was accompanied by mdg-1 excision from the hot spots of their location usually detected in the high-fitness strains. The results suggest the existence of a system of adaptive transpositions of mobile elements that takes part in fitness control.      

Current sheets formed by Alfvén and magnetosonic pulses in the vicinity of the null line of the magnetic field

A study is made of the propagation of an Alfvén pulse and the superposition of an Alfvén and a magnetosonic pulse in the vicinity of the magnetic null line (the X point). It is shown that, on long time scales, the poloidal components of the velocity and magnetic field relax to steady-state distributions similar to those in the case of a magnetosonic pulse. In the essentially nonlinear problem under investigation, the steady-state distributions of the toroidal components of the velocity and magnetic field are found to be close to those in the corresponding linear problem. It is established that two-dimensional effects play an important role in the evolution of the forming current sheets.     

Effect of Helminthosporic Root Rot on the Lipid Content in Wheat Seedlings

The concentration of dry matter and the content of esterified fatty acids in total lipids of roots and etiolated shoots of 3- to 10-day-old seedlings of wheat (Triticum aestivum L.) infected with Bipolaris sorokiniana (Sacc.) Schoemaker, the agent of helminthosporic root rot, were determined in the course of germination. At the onset of germination, fungal infection caused a considerable increase in the dry matter concentration in both roots and shoots due to the enhanced mobilization of seed reserves. However, after the 7th day of germination, dry matter concentration fell below the level of noninfected control seedlings as a result of infection. The content of total lipids rose immediately after infection and always exceeded the control index up to the end of germination, in spite of a continuous decrease in this index in both control and infected seedling. It is concluded that an increase in the content of cellular lipids is a characteristic response of both shoots and roots to the root rot infection of wheat seedlings.     

On the issue of innervation of dorsal longitudinal musculature of <Emphasis Type="Italic">Lymnaea stagnalis</Emphasis> with inferior cervical nerve

Using the method of the anterograde dextran tetramethylrhodamin transport, there is obtained the topographic picture of branching of inferior cervical nerve axons on fibers of the dorsal longitudinal muscle in Lymnaea stagnalis (L.). Using the retrograde staining, the neuronal bodies sending their processes into this nerve are marked. Manifestations of asymmetry in distribution of neurons stained through the right and left nerves are described. The electron microscopic studies have shown that the main number of the inferior cervical nerve axons is represented by thin fibers presumably belonging to the sensory cells. A part of the nerve fibers and their endings show imunoreactivity to serotonin and acetylcholine. The serotoninergic fibers predominate quantitatively over the cholinergic ones and account for a half of the fibers stained with dextran. A possible functional role of the serotoninergic and cholinergic innervation of the dorsal longitudinal muscle in Lymnaea stagnalis is discussed.Translated from Zhurnal Evolyutsionnoi Biokhimii i Fiziologii, Vol. 40, No. 6, 2004, pp. 569–578.