Mechanisms of recognition of the outlines of “vanishing” optotypes

The aim of the present work was to study the interaction between the optical properties of images of “ disappearing” optotypes and their recognition thresholds. The “disappearing” optotypes were figures with complex outlines and had a unique property-they were close to the threshold of recognition and observation, which increases the accuracy of measurement of visual acuity and the subjects’ attention to them. The recognition distances of “disappearing” optotypes were measured. A relationship was found between the recognition distance of “disappearing” optotypes and different optical density profiles on the one hand and the spatial and spatial frequency characteristics of the stimuli on the other. The decisive factor determining the threshold of recognition of optotypes in spatial frequency terms is its spatial frequency spectrum; that in spatial terms is the width of the black/white pair or black-white triad in the complex outline. Regardless of the shape of the optotype, one of the most important limiting factors was the concordance of this test with the scattering function of the subject’s eye optics. __________ Translated from Rossiiskii Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 91, No. 9, pp. 1080–1090, September, 2005.     

Investigation of the “valency” of antibodies by means of azoproteins

Summary The valency of antibodies was studied by the method of exhaustion of antisera against mono-and diazoproteins, and subsequent cross reactions both with the antibodies left over in the supernatant fluid of the serum and with the precipitating and nonprecipitating antibodies isolated from the precipitate.It was proved that the antibodies interact with the antigens as multivalent compounds.The valency determined with regard to the azoproteins is dependent upon the number of groups introduced.Thus, bivalent antibodies correspond to monoazoproteins and trivalent ones to diazoproteins.The valency of antibodies is, evidently, determined by the structural similarity of the heterologous and the immunizing antigens as well as by the less complete specific conformity between the individual structural peculiarities of the antigen and its antibody.From the Tashkent Pharmaceutical Institute (Director-Docent M. A. Azizov)Presented by Active Member AMN SSSR N. N. Zhukov-Verezhnikov     

Initiation of the alternative pathway of complement and the history of “tickover”

The evolutionary history of complement suggests that the alternative pathway arose prior to the arrival of the classical and lectin pathways. In these pathways, target specificity is provided by antibodies and sugar specific lectins. While these efficient initiation systems dominate activation on most targets, the alternative pathway produces most of the C3b and 80%-90% of the C5b-9. While the tickover process, originally proposed by Peter Lachmann, provided ancient hosts with a crude self/non-self-discriminatory system that initiated complement attack on everything foreign, tickover clearly plays a more minor role in complement activation in modern organisms possessing classical and lectin pathways. Spontaneous activation of the alternative pathway via tickover may play a major role in human pathologies where tissue damage is complement-mediated. The molecular mechanism of tickover is still not convincingly proven. Prevailing hypotheses include (a) spontaneous hydrolysis of the thioester in C3 forming the C3b-like C3(H₂O) in solution and (b) “enhanced tickover” in which surfaces cause specific or non-specific contact activated conformational changes in C3. Theoretical considerations, including computer simulations, suggest that the latter mechanism is more likely and that more research needs to be devoted to understanding interactions between biological surfaces and C3.     

The “critical zones” of entrapment of the nerves of the lower limb

Summary The author has studied, in a group of 40 dissections on cadavers of individuals of different ages, the main critical zones of entrapment of some terminal branches of the lumbo-sacral plexus, which include canals (fibrous, osteo-fibrous, fibro-muscular), intervals (intermuscular, fibro-muscular, musculo-ligamentous), rings (fibrous or fibro-muscular) and foramina. They provide the topographical anatomical basis for possible compressive phenomena of the nerves of the lower limb.

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Les zones critiques d'étranglement des nerfs du membre inférieur

Résumé L'auteur a étudié sur 40 dissections cadavériques d'individus d'âges différents, les principales zones critiques d'étranglement de certaines branches terminales du plexus lombo-sacré, constituées de canaux (fibreux, ostéo-fibreux, fibro-musculaires) d'interstices (musculaires, fibro-musculaires, ligamento-musculaires), d'anneaux (fibreux, fibro-musculaires) et de trous. Elles représentent les bases anatomotopographiques d'èventuels phénomènes de compression des nerfs du membre inférieur.

     

Reflex regulation of the “spontaneous” activity of the chemoreceptors of the tongue

Summary The spontaneous activity of the chemoreceptors of the frog's tongue was studied during stimulation of the interoceptors of the stomach and of the sympathetic chain. It was found to be under the control of the nervous system, adapting the receptors to give improved perception, and it indicates the preparedness of these apparatuses to receive stimuli. Spontaneous activity may be fundamentally a partial principle of the functioning of receptor elements. Further electrophysiological investigations of this problem are proceeding.(Presented by Active Member AMN SSSR P. K. Anokhin) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 55, No. 8, pp. 7–11, August, 1963     

Behavior of Rats of Two Strains Contrasting in Terms of “Audiogenic Epilepsy”

Neuroscience and Behavioral Physiology - Behavior in the open field test was compared in rats of two strains differing in terms of the manifestation of convulsions in response to sound (audiogenic...     

Studies of the Mechanism of Development of “Deprivation” Potentiation of Population Responses of Neurons in Field CA1 of Living Hippocampal Slices

Experiments on rat hippocampal slices were performed with testing of the synaptic connections of Schaffer collaterals and neurons in field CA1 to study the effects of interrupting low-frequency test stimulation (0.05 Hz) on the amplitude of population spikes. These studies demonstrated a correlation between the duration of pauses in stimulation (form 10 to 120 min) and increases in the amplitude of spikes (on average by 30–100% of baseline response magnitude). This deprivation potentiation was additive and could persist for long periods of time (testing was up to 1 h). Preliminary induction of long-term post-tetanic potentiation, which prevented the subsequent development of the late, but not the short-term phase, for 1–3 h, led to suppression of the development of deprivation potentiation after a 60-min pause in stimulation. Similar results were obtained in experiments using 20 M polymyxin B, which blocks protein kinase C and the PKC-dependent phase of long-term post-tetanic potentiation; this is evidence supporting the previously advanced hypothesis that the development of deprivation potentiation and the late, PKC-dependent phase of long-term post-tetanic potentiation share common mechanisms, associated with people phosphorylation.     

”Rodent-like” and ”primate-like” types of astroglial architecture in the adult cerebral cortex of mammals: a comparative study

Previous observations disclosed that astroglia with interlaminar processes were present in the cerebral cortex of adult New and Old World monkeys, but not in the rat, and scarcely in the prosimian Microcebus murinus. The present report is a more systematic and comprehensive comparative analysis of the occurrence of such processes in the cerebral cortex of several mammalian species. Brain samples were obtained from adult individuals from the following orders: Carnivora (canine), Rodentia (rat and mouse), Marsupialia (Macropus eugenii), Artiodactyl (bovine and ovine), Scandentia (Tupaia glis), Chiroptera (Cynopteris horsfieldii and C. brachyotis), and Primate: Prosimian (Eulemur fulvus), non-human primate species (Cebus apella, Saimiri boliviensis, Callithrix, Macaca mulatta, Papio hamadryas, Macaca fascicularis, Cercopithecus campbelli and C. ascanius) and from a human autopsy. Tissues were processed for immunocytochemistry using several antibodies directed against glial fibrillary acidic protein (GFAP), with or without additional procedures aimed at the retrieval of antigens and enhancement of their immunocytochemical expression. The cerebral cortex of non-primate species had an almost exclusive layout of stellate astrocytes, with only the occasional presence of long GFAP-IR processes in the dog that barely crossed the extent of lamina I, which in this species had comparatively increased thickness. Species of Insectivora and Chiroptera showed presence of astrocytes with long processes limited to the ventral basal cortex. Interlaminar GFAP-IR processes were absent in Eulemur fulvus, at variance with their limited presence and large within- and inter-individual variability as reported previously in Microcebus murinus. In New World monkeys such processes were absent in Callithrix samples, at variance with Cebus apella and Saimirí boliviensis. Overall, the expression of GFAP-IR interlaminar processes followed a progressive pattern: bulk of non-primate species (lack of interlaminar processes) –Chiroptera and Insectivora (processes restricted to allocortex) <strepsirhini <haplorhini (platirrhini<catarrhini). This trend is suggestive of the emergence of new evolutionary traits in the organization of the cerebral cortex, namely, the emergence of GFAP-IR long, interlaminar processes in the primate brain. Interlaminar processes may participate in a spatially restricted astroglial role, as compared to the one provided by the astroglial syncytium. It is proposed that the widely accepted concept of an exclusively astroglial syncytium is probably linked with a specific laboratory animal species (”rodent-type” or, rather, ”general mammalian-type” model) that misrepresents the astroglial architecture present in the cerebral cortex of most anthropoid adult primates (”primate-type” model), including man. Accepted: 28 June 1999     

Modularity and Intersection of “What”, “Where” and “How” Processing of Visual Stimuli: A New Method of fMRI Localization

Summary: Research on the modularity of perceptual and cognitive processes has often pointed to a ventral-dorsal distinction in cortical pathways that depend upon the nature of the stimuli and the task. However, it is not clear whether the dorsal, occipital-parietal stream specializes in locating visual objects (i.e., a “where” stream), or taking action toward objects (i.e., a “how” stream), although there is some consensus for a ventral, occipital-temporal “what” stream that specializes in the identification of visual objects. It is also not clear to what extent word and picture processing are modular along these streams, as functional imaging maps to date have not addressed the modularity question directly. Here we present two types of functional imaging maps that directly show modularity and intersection of processing function for word and picture stimuli in tasks that require decisions about “what is”, “where is”, or “how do you interact with” a stimulus (N=6 participants). Our results reveal a middle dorsal “how” stream with some modular regions of activation that are distinct from activation during “where” processing, and that words and pictures involve several modular regions of activation along these streams. This research was supported by the Natural Sciences and Engineering Research Council (NSERC) of Canada in the form of grants to R.B. and G.E.S., and a post-doctoral fellowship to C.K.F, and by the Canadian Institutes for Health Research (CIHR) and the Saskatchewan Health Services Utilization and Research Commission (HSURC) in the form of grants to G.E.S. We thank Jennifer Hadley and Francis Shih for technical assistance.     

“The Reality of Repressed Memories” Revisited and Principles of Science

Abstract

An article in the 1993 issue of the American Psychologist entitled “The reality of repressed memories” (Loftus, 1993) forms the foundation for how many contemporary professionals understand the recovered memory/false memory controversy. The message conveyed to the readership was that recovered memories are by-products of therapy. Paradoxically, the message enjoys wide-ranging influence on the basis of “facts” that lack the rigor of science. Status was established on the basis of speculative theory, artifacts of interpretation, and the power of selectively filtered information. The message illustrates the dilemma posed for readers without personal familiarity with the subject matter, when messages are advanced on the basis of imperfect disclosure of prevailing knowledge. This article revisits the “evidence” and acquaints readers with the many errors of omission and fact that plague the false memory message (Loftus, 1993), and that cloud the science concerning memory and learning.     

“Imprints of Reality” in the Systems Mechanisms of Brain Activity

Pavlov's concepts of the dynamic stereotype – imprints of reality – are developed on the basis of the theory of functional systems. Parameters of reality and especially the results of activity satisfying the leading needs of living organisms are dynamically impressed in the form of molecular engrams in structures of the results-of-actions acceptors involved in the dominant motivation. The dominant motivation plays the leading role in retrieval of previously formed engrams of the results-of-action acceptors in different functional systems. A general theoretical concept of the emotional and verbal forms of consciousness and their close interaction in humans is developed.     

Studies of the Behavior of “Impulsive” and “Self-Controlled” Animals in an “Emotional Resonance” Test

Rats divided on the basis of a test in which they were presented with the “right” to choose a more valuable but delayed or a less valuable but immediate reinforcement into “impulsive” and “self-controlled” groups were studied using the “emotional resonance” method. These experiments showed that none of the rats of the “self-controlled” group, selecting the more valuable but delayed reinforcement, avoided defensive arousal signals from another individual of the same species, preferring to spend a large proportion of time in the dark “house.” Most (80%) of the animals of the “impulsive” group spent more than half the experimental period in the light sector, thus saving the partner from electrical stimulation. It is suggested that there are several common mechanisms underlying these two types of behavior.     

Evolutionary analysis of “hagfish amelogenin”

Hagfishes lack mineralized tissues and teeth. Part of a cDNA strand, allegedly from amelogenin, the major gene involved in enamel formation in mammals, has recently been cloned in a hagfish (Slavkin and Diekwish, Anat. Rec., 1996;245:131–150). This cloning is of great interest because it could change the current view about the evolution of mineralized tissues, but no phylogenetic analysis of this piece of DNA has been made by the authors. Phylogenetic analysis of this part of cDNA has been conducted using both phenetic and cladistic methods. The cDNA amplified in hagfish does not fit with a nonmammalian origin but fits well with a degraded rodent sequence. The gene cloned in hagfish is probably of mammalian origin due to contamination during PCR. Anat. Rec. 252:608–611, 1998. © 1998 Wiley-Liss, Inc.     

Genetic classification of “Sapporo-like viruses”

"Sapporo-like viruses" (SLVs) and "Norwalk-like viruses" (NLVs) are an important cause of acute gastroenteritis in humans. While NLVs have been genetically classified into three major genetic groups consisting of 17 genetic subgroups, a classification of SLVs into comparable genetic groups remains to be determined. In an attempt to classify both SLVs and NLVs uniformly, the sequences of 2 SLV strains newly detected from French infants were analysed together with the published sequences of 9 SLV and 19 NLV strains. Distance and phylogenetic analyses were conducted on the sequences of the capsid gene, RNA polymerase gene, 3' open reading frame (3'ORF), ORF overlapping the capsid gene, and 3' untranslated region (3'UTR). The histogram showing frequency distribution of pairwise distances and the topology of the phylogenetic tree demonstrated that SLVs and NLVs could be classified uniformly on the basis of the entire capsid sequences and that the 11 SLV strains could be genetically classified into 3 major genetic groups, genogroups I, II and III, comprised of 5 genetic subgroups. The differentiation of the 11 SLV strains into these genetic groups was also maintained in the 4 remaining genome regions, while the sequences at the junction between the RNA polymerase and capsid genes were shown to be genogroup-specific.     

The reflex nature of the phenomenon of “lagging” of respiratory movements in unilateral lung lesions

Summary In the presence of a unilateral focal pulmonary lesion the electric activity of the diaphragm is decreased on the homolateral side and increased on the contralateral side. This reflex lies at the basis of the physical sign known as lagging of respiratory movements on the side of the pulmonary lesion. The absence of compensatory increase of respiratory movements on the side of the lesion is evidently connected with active suppression of diaphragmatic activity taking place in the phrenic nerve center.Presented by Active Member AMN SSSR V. N. Chernigovskii     

The origin of the “spontaneous” electrical activity of the frog brain

Summary Preparations with chronically implanted electrodes showed that there are periods during which no electrical activity is present in the brain of intact, non-anesthetized frogs sitting unconstrained in water in a jar. The activity appeared immediately upon stimulation.The results obtained confirm the suggestion of I. M. Sechenov that the electrical activity of the brain occurs either reflexly, or is due to direct effects on the brain. Without such effects, there is no electrical activity.(Presented by Active Member AMN SSSR V. V. Parin) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 52, No. 12, pp. 17–22, December, 1961