Modification of cyclical activity in the spinal cord of the 16- to 20-day-old chick embryo due to changes in Ca2+ and Mg2+ concentrations

In isolated segments of the 16- to 20-day old chick embryo, increasing the Mg²⁺ concentration from 1.3 to 5.0 mmoles/liter in the superfusate caused complete suppression of spontaneous rhythmic activity that appeared as synchronous cyclical oscillations of electrotonic potentials in the dorsal and ventral roots. A similar change was recorded when the Ca²⁺ concentration was decreased from 2.6 to 1.0 mmole/liter, but in this case tonic discharges of impulses (spikes) could occur. Further, during the disappearance of the spontaneous activity due to changing the concentration of Ca²⁺ or Mg²⁺, in six out of eight experiments another type of rhythmic activity was seen, appearing as oscillations of electrotonic potentials in the ventral roots that were independent of oscillations in the dorsal roots. The amplitude of these oscillations of potential in the ventral roots was up to 200 µV, and their duration was up to 400 msec. The highest frequency of this activity was 0.4 sec^–1. The possible functional significance of the observed patterns of activity is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 23, No. 3, pp. 333–338, May–June, 1991.     

Mapping the amino acid properties of constituent nucleoporins onto the yeast nuclear pore complex

Visualization of molecular structures aids in the understanding of structural and functional roles of biological macromolecules. Macromolecular transport between the cell nucleus and cytoplasm is facilitated by the nuclear pore complex (NPC). The ring structure of the NPC is large and contains several distinct proteins (nucleoporins) which function as a selective gate for the passage of certain molecules into and out of the nucleus. In this note we demonstrate the utility of a python code that allows direct mapping of the physiochemical properties of the constituent nucleoporins on the scaffold of the yeast NPC׳s cytoplasmic view. We expect this tool to be useful for researchers to visualize the NPC based on their physiochemical properties and how it alters when specific mutations are introduced in one or more of the nucleoporins. The code developed using Python is available freely from the authors.     

Prediction of the three-dimensional structure of aflatoxin of Aspergillus flavus by homology modelling

Aflatoxins are polyketide-derived secondary metabolites produced by Aspergillus spp. The toxic effects of aflatoxins have adverse consequences for human health and agricultural economics. The aflR gene, a regulatory gene for aflatoxin biosynthesis, encodes a protein containing a zinc-finger DNA-binding motif. AFLR-Protein three-dimensional model was generated using Robetta server. The modeled AFLR-Protein was further optimization and validation using Rampage. In the simulations, we monitored the backbone atoms and the C-α-helix of the modeled protein. The low RMSD and the simulation time indicate that, as expected, the 3D structural model of AFLR-protein represents a stable folding conformation. This study paves the way for generating computer molecular models for proteins whose crystal structures are not available and which would aid in detailed molecular mechanism of inhibition of aflatoxin.     

Single nucleotide polymorphism rs1800872 in the promoter region of the IL10 gene is associated with predisposition to chronic hepatitis C in Russian population

Previously, we studied an association of two IL28B gene single nucleotide polymorphisms (SNPs) and three IL10 gene SNPs with predisposition to tick-borne encephalitis in a Russian population. In this study, a possible involvement of these SNPs in the development of predisposition to chronic hepatitis C (caused by structurally similar, related virus from the Flaviviridae family) was investigated in the same population. Only the IL10 promoter rs1800872 SNP was associated with predisposition to chronic hepatitis C. This SNP seems to be a common genetic marker of predisposition to two diseases caused by hepatitis C and tick-borne encephalitis viruses in Russian population.     

Basic principles of terminal flower formation

Studies of efflorescences of the mutants bractea and terminal flower1 and double mutant bra tfl1 of Arabidoipsis thaliana (L.) Heynh. have shown that the presence of a developed leaf in the node preceding the terminal flower is a necessary condition for the formation of the terminal flower perianth. This means that perianth cannot develop in an abracteose efflorescence of terminal flower. The second necessary condition for the terminal flower formation is a sufficient level of expression of the genes responsible for floral morphogenesis. Combination of these two conditions suffices for the development of a terminal flower with perianth. Since the general principles of organization are close for most flower plants, it can be stated that if the abracteose efflorescence is terminated by a flower with perianth, this is a consequence of forcing the lateral flower into the terminal position.     

The Principles of Data Formalization for Building Biological Model of Shoot Development in Flowering Plants

Shoot system of a plant can be divided into elementary molecules composed of phyllome, internode, and meristem of the lateral bud. The capacity of plants for open growth is manifested as multiple reproductions of the modules. These main principles of plant structural organization can be used to formalize and integrate the data from various disciplines studying shoot development—genetics of development, morphology, etc. At the example of a model species Arabidopsis thaliana we show that the data on genetic control of shoot development can be considered in terms of rearrangement of individual modules. Several variants of the module structural reorganization are allowed: reduction or transformation of phyllome, change in the internode length, and triggering active/inactive status of the lateral shoot meristem. Each variant of module structure corresponds to specific pattern of genes activity. Such integration of the data on genetic and structural aspects of morphogenesis can form a basis for mathematical modeling of plant development.     

Structure of flower in Arabidopsis thaliana: spatial pattern formation

Morphological analysis of flowers was carried out in Arabidopsis thaliana wild type plants and agamous and apetala2 mutants. No direct substitution of organs takes place in the mutants, since the number and position of organs in them do not correspond to the structure of wild type flower. In order to explain these data, a notion of spatial pattern formation in the meristem was introduced, which preceded the processes of appearance of organ primordia and formation of organs. Zones of acropetal and basipetal spatial pattern formation in the flower of wild type plants were postulated. It was shown that the acropetal spatial pattern formation alone took place in agamous mutants and basipetal spatial pattern formation alone, in apetala2 mutants. Different variants of flower structure are interpreted as a result of changes in the volume of meristem (space) and order of spatial pattern formation (time).     

N-methyl-D-aspartate effect on spontaneous activity of 16–20-day-old chick embryo spinal cord

The effects of N-methyl-D-aspartate (NMDA) and the NMDA receptor antagonist, 2-amino-5-phosphonovaleric acid (2-APV), on spontaneous activity of dorsal and ventral roots (DR and VR, respectively) generated by isolated spinal cord from 16–20-day-old chick embryo were studied. This activity was synchronous oscillations of electrotonic potentials in DR and VR. There was no impulse activity in the VR. When NMDA was applied at 2–25 µM, the amplitudes of the oscillations increased, the impulse activities in VR and DR developed, and the tonic component of electrotonic potentials appeared. At 20 µM, 2-APV decreased both, the spontaneous and NMDA induced activity. After sectioning of the spinal cord, the neuronal network of the isolated dorsal arm conserved the capacity to generate spontaneous activity in the DR which increased after NMDA application. There was no rhythm in the ventral part of the spinal cord. The localization of the NMDA-sensitive neuronal network, generator of the rhythmic (motor) activity, in the spinal cord is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 23, No. 2, pp. 205–213, March–April, 1991.