Relationship between functional characteristics of cat visual cortex neurons,their response to novelty,and short-term memory

In the visual cortex of unanesthetized cats, the number and frequency of discharges in response to a new stimulus differed from the subsequent responses: the first response was more intensive in 34% of the neurons, but in 30% it was inhibited. The phenomenon of short-term memory was detected in 19% of the cells: it was expressed in regeneration of the configuration of response discharges after the cessation of rhythmic stimulation. These peculiarities can be linked with functional organization of the neurons. We divided them into two groups according to their response to photic stimuli. The first group includes short-latent neurons that respond with discharges of the phasic type and that virtually or totally lack spontaneous activity. The second group consists of long-latent neurons with the tonic type of discharges and distinct spontaneous activity. In the overwhelming majority of cases, response to novelty and short-term memory were discovered in neurons of the second group. It is hypothesized that the population of neurons of the first group — having narrower afferent connections — takes part mainly in analysis of properties of a photic stimulus; the population of neurons of the second group participates in information processing at the final and highest level, on which mechanisms of memory and attention are implicated.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 2, No. 6, pp. 611–617, November–December, 1970.     

Canalization of Gene Expression and Domain Shifts in the Drosophila Blastoderm by Dynamical Attractors

The variation in the expression patterns of the gap genes in the blastoderm of the fruit fly Drosophila melanogaster reduces over time as a result of cross regulation between these genes, a fact that we have demonstrated in an accompanying article in PLoS Biology (see Manu et al., doi:10.1371/journal.pbio.1000049). This biologically essential process is an example of the phenomenon known as canalization. It has been suggested that the developmental trajectory of a wild-type organism is inherently stable, and that canalization is a manifestation of this property. Although the role of gap genes in the canalization process was established by correctly predicting the response of the system to particular perturbations, the stability of the developmental trajectory remains to be investigated. For many years, it has been speculated that stability against perturbations during development can be described by dynamical systems having attracting sets that drive reductions of volume in phase space. In this paper, we show that both the reduction in variability of gap gene expression as well as shifts in the position of posterior gap gene domains are the result of the actions of attractors in the gap gene dynamical system. Two biologically distinct dynamical regions exist in the early embryo, separated by a bifurcation at 53% egg length. In the anterior region, reduction in variation occurs because of stability induced by point attractors, while in the posterior, the stability of the developmental trajectory arises from a one-dimensional attracting manifold. This manifold also controls a previously characterized anterior shift of posterior region gap domains. Our analysis shows that the complex phenomena of canalization and pattern formation in the Drosophila blastoderm can be understood in terms of the qualitative features of the dynamical system. The result confirms the idea that attractors are important for developmental stability and shows a richer variety of dynamical attractors in developmental systems than has been previously recognized.     

A novel L-isoleucine metabolism in Bacillus thuringiensis generating (2S,3R,4S)-4-hydroxyisoleucine, a potential insulinotropic and anti-obesity amino acid

4-Hydroxyisoleucine (HIL) found in fenugreek seeds has insulinotropic and anti-obesity effects and is expected to be a novel orally active drug for insulin-independent diabetes. Here, we show that the newly isolated strain Bacillus thuringiensis 2e2 and the closely related strain B. thuringiensis ATCC 35646 operate a novel metabolic pathway for L-isoleucine (L-Ile) via HIL and 2-amino-3-methyl-4-ketopentanoic acid (AMKP). The HIL synthesis was catalyzed stereoselectively by an α-ketoglutaric acid-dependent dioxygenase and to be useful for efficient production of a naturally occurring HIL isomer, (2S,3R,4S)-HIL. The (2S,3R,4S)-HIL was oxidized to (2S,3R)-AMKP by a NAD(+)-dependent dehydrogenase. The metabolic pathway functions as an effective bypass pathway that compensates for the incomplete tricarboxylic acid (TCA) cycle in Bacillus species and also explains how AMKP, a vitamin B(12) antimetabolite with antibiotic activity, is synthesized. These novel findings pave a new way for the commercial production of HIL and also for AMKP.     

Disulfide-stabilized helical hairpin structure and activity of a novel antifungal peptide EcAMP1 from seeds of barnyard grass (Echinochloa crus-galli)

This study presents purification, activity characterization, and (1)H NMR study of the novel antifungal peptide EcAMP1 from kernels of barnyard grass Echinochloa crus-galli. The peptide adopts a disulfide-stabilized α-helical hairpin structure in aqueous solution and thus represents a novel fold among naturally occurring antimicrobial peptides. Micromolar concentrations of EcAMP1 were shown to inhibit growth of several fungal phytopathogens. Confocal microscopy revealed intensive EcAMP1 binding to the surface of fungal conidia followed by internalization and accumulation in the cytoplasm without disturbance of membrane integrity. Close spatial structure similarity between EcAMP1, the trypsin inhibitor VhTI from seeds of Veronica hederifolia, and some scorpion and cone snail toxins suggests natural elaboration of different functions on a common fold.     

Studies of stability mechanisms of early embryonal development of fruit fly Drosophila

Living organisms well adapt themselves to changes in the environment and are robust to potential damage such as mutations. The epigenetic mechanism whereby the suppression of phenotypic variation is achieved has been dubbed canalization. This paper summarizes results of research that employed experimental and theoretical approaches to uncover the mechanisms of canalization of variation in expression of segmentation genes.     

SEM: Structural Equation Modeling in Molecular Biology

Structural equation modeling (SEM) is a second-generation multivariate method to estimate the causal interactions in a set of variables and includes, as special cases, several statistical methods (regression analysis, path analysis, and confirmatory factor analysis). This review focuses on all of the main SEM models and various methods used to optimize the model parameters. Representative examples are discussed to illustrate SEM application in molecular biology, including modeling of biochemical processes, relationships between genetic markers and diseases, and interactions within gene networks.     

Morphogenetic networks which determine the spatial expression of zygotic genes in early <Emphasis Type="Italic">Drosophila</Emphasis> embryo

This review deals with the recent studies expanding the idea of positional information in the early embryogenesis of Drosophila melanogaster. Previous studies showed that, in the course of segment determination in Drosophila, information created by gradients of products of maternal coordinate genes is not “read” statically, being interpreted by their zygotic target genes via regulatory interactions. This leads to spatial shifts in the expression of target genes relative to the original positions as well as to dynamic reduction in the zygotic expression variability. However, according to recent data, interpretation of positional information includes the interaction between not only zygotic target genes but also the maternal coordinate genes themselves. Different systems of maternal coordinate genes (maternal systems)—the posterior-anterior, terminal, and dorsoventral—can interact with each other. This is usually expressed in the regulation of zygotic target genes of one maternal system by other maternal systems. The concept of a “morphogenetic network” was introduced to define the interaction of maternal systems during determination of spatial gene expression in the early Drosophila embryo.     

Effect of diazepam on cyclic change of excitability in a cortical epileptic focus

On application of penicillin solution to the motor cortex of rats and electrical stimulation of the ventroposterolateral thalamic nucleus (VPL) with a frequency of 1/sec and with a strength three times greater than the threshold for the primary evoked potential, alternation of "active" and "passive" neurons was observed in the zone of the epileptic focus. "Active" neurons were characterized by the regular appearance of epileptiform discharges in response to each stimulation of VPL. In the course of the "passive" periods stimulation of VPL led only to the appearance of primary evoked potentials. Diazepam in a dose of 2 mg/kg completely disturbed spike generation in the epleptic focus, but in a dose of 0.1 mg/kg it caused disturbance of the established cyclic change of excitability in the focus, which was restored after stimulation with a frequency of 2/sec.Institute of General Pathology and Pathological Physiology, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 12, No. 6, pp. 563–570, November–December, 1980.     

Correlation of biochemical blocks and genetic lesions in leucine auxotrophic strains of the imperfect yeast Candida maltosa

Summary The four enzymatic steps in the conversion of -ketoisovaleriate to leucine were examined in the wild type and in 13 leucine auxotrophic strains of Candida maltosa. The genetic lesions in the auxotrophs, involve at least five different loci and are correlated with three enzymatic steps. This was confirmed by gene cloning, protoplast fusion, and enzyme assays. The pathway for leucine biosynthesis in C. maltosa shows general similarity to that of other lower eukaryotes but there are individual differences in the numbers of genes responsible for single enzymatic steps. A disomic state of the chromosomes carrying genes coding for -isopropylmalate synthase and -isopropyl-malate dehydrogenase was elucidated.     

Structure comparison and evolutionary relations between elongation factors EF-Tu (EF-1α) and SUP 2 proteins

On the basis of high homology and structural similarity, three genes, SUP2 Saccharomyces cerevisiae, SUP2 Pichia pinus and GST1 Homo sapiens, might be considered as members of one family named SUP2. Comparison of the primary structure of SUP2 proteins and elongation factors EF-Tu(EF-1) from 19 different species was performed. It was found that SUP2 proteins bear more homology to eukaryotic elongation factor than to procaryotic EF-Tu, though the degree of sequence conservation in SUP2 proteins is smaller than in EF-1 factors. The extensive phylogenetic analysis of SUP2 and EF-Tu(EF-1) genes was performed by means of 3 methods, 2 phenetic and one cladystic (maximal parsimony). The data support the close relation of SUP2 genes to other elongation factor genes.