The dominant motivation in the mechanisms of the conditioned reflex

It is substantiated that the mechanisms of dominant motivations play an essential role in conditioning. It is shown that motivations change convergent and chemical characteristics of single neurons of different brain structures and, especially, their sensitivity to corresponding reinforcing stimuli. As a result, motivation plays a role of an initial "canvas", against the background of which molecular "engrams of reinforcement" are built. The processes of interaction between the dominant motivation and reinforcement are mainly addressed to the apparatus of the action result acceptor. It is shown that dominant motivations participate not only in construction of molecular reinforcement engrams but also in their forestalling retrieval.     

The resonance of the arterial system

The arterial system is assumed to consist of two elastic chambers connected by a conducting channel. It is assumed that a current of fluid enters one chamber, whereas the other chamber is drained by a pipe with a certain peripheral resistance. The continuity of the fluid is described by a differential equation for each chamber. The inertia resistance of the conducting channel is taken into consideration. It is shown that the system may possess a resonance frequency. The latter, if it exists, as well as the damping coefficients are expressed in terms of the elastic moduli of the chambers, the conductivity of the channel, and the peripheral resistance. It is shown that with plausible values of the latter variables the resonance frequency as determined theoretically has the right order of magnitude as found experimentally.     

The Role of the Root in the Induction of Xylem Differentiation in Peas

It is known that growing parts of the shoot induce the differentiationof vascular tissues below them and that this induction is dueto the production of auxin. The problem dealt with here is whythe formation of xylem proceeds in the growing roots. The redifferentiationof parenchyma to tracheary elements in grafts of pea plantswas used in this study. It is proved that this is not due tostimuli coming from the root tip but rather to the movementof a stimulus coming from the shoot into the root. The polarityof movement is maintained even in thin sections, but it canbe reversed by a strong shoot influence.     

On the origin of the genetic code and the stability of the translation apparatus

An “error theory” is developed which can be applied to determine the stability of a macromolecular translation machinery which reproduces itself. It is shown that the overall effects of a multitude of possible error versions of macromolecules can be treated statistically, and that such a statistical approach is of considerable usefulness in the theoretical treatment of complex macromolecular systems. The theory is developed within the context of a detailed treatment of the “frozen accident” hypothesis for the origin of the genetic code. A model is described which permits some thermodynamic characterization of the components involved in the code nucleation. The model also proves useful in resolving a stability “paradox” described by Orgel, which relates to the translation stability in present-day organisms and mechanisms of ageing. It indicates that any experimentally found decrease in translation accuracy with age is probably not due to an inherent instability in the translation apparatus. Relevant experiments are suggested.     

Reproducibility of the mean power frequency of the surface electromyogram

There is evidence in the literature that the decrease of mean power frequency (MPF) during exercise is greater as a muscle become more fatigued. After strenuous exercise this phenomenon can last several days. It is usually assumed, however, that the MPF has a good reproducibility. In this study the reproducibility of the MPF of the surface electromyogram of the biceps brachii muscle was investigated for five subjects on 5 successive days. Force level, muscle length and skin temperature were kept constant. The results show that interindividual differences in MPF were large (SD 11.5 Hz). However, during these 5 days, the range in MPF for individual subjects was small. The SD of the trials within subjects and days was 2.0 Hz, while the SD trials excluded). It is hypothesized that this SD may be due to variations in the electrode replacement. It is concluded that the variability in MPF for a subject is small compared to the decrease of the MPF associated with muscle fatigue and which can therefore be determined reliably during longitudinal studies.     

Scanning electron microscopic observation on the distal part of the male urethra of the mouse

In the proximal end of the navicular fossa, the stratified columnar epithelium lining the spongy part of the urethra abruptly changes into the stratified squamous one, presenting a sharp demarcation. It is considered that the junction between these 2 epithelia corresponds to the former site of the junction of the entoderm and ectoderm. The width of the microridges in the distal part of the navicular fossa was about doubled compared to that in the proximal part. It is suggested that the epithelium in the distal part is keratinized, while that in the proximal part is nonkeratinized.     

Evaluation of the role of the adaptive result in the theory of the functional systems

The fundamental of the theory of the functional systems, i.e., the concept of the useful adaptive result as a universal system-forming factor is considered. It is suggested that the adaptive result is not system-forming in behaviors actualized exclusively due to activity of systems developed earlier. It is argued that positive mutations may serve as the system-forming factor for hereditary determined behavioral forms. In all other cases of goal-directed behavior (except conditioning) the aim of performance as a model of the future result plays the decisive role. Only in conditioning the classical concept of the system-forming role of the adaptive result seems to be undeniable. The refined ideas about the mechanisms of formation of the functional systems may be useful in analysis of a number of animal and human functions (learning, emotional stress, neuroses, etc.).     

The relationship between the transition probability and oscillator concepts of the cell cycle and the nature of the commitment to replication

The oscillator concept of the cell cycle predicts the existence of threshold conditions within the cell which must be exceeded before replication is initiated. It is shown (a) that if the conditions are subthreshold, random disturbances can trigger a cycle of the oscillation (round of replication) and (b) that the probability of this occurring increases as the state of the system approaches the threshold. It is concluded that the oscillator concept explains the data on which the transition probability model is based. It also accounts for the ability of cells to replicate even when the mitogen is present for a limited period only.     

Computational modeling of the mechanical behavior of the cerebrospinal fluid system

A computational fluid dynamics (CFD) model of the cerebrospinal fluid system was constructed based on a simplified geometry of the brain ventricles and their connecting pathways. The flow is driven by a prescribed sinusoidal motion of the third ventricle lateral walls, with all other boundaries being rigid. The pressure propagation between the third and lateral ventricles was examined and compared to data obtained from a similar geometry with a stenosed aqueduct. It could be shown that the pressure amplitude in the lateral ventricles increases in the presence of aqueduct stenosis. No difference in phase shift between the motion of the third ventricle walls and the pressure in the lateral ventricles because of the aqueduct stenosis could be observed. It is deduced that CFD can be used to analyze the pressure propagation and its phase shift relative to the ventricle wall motion. It is further deduced that only models that take into account the coupling between ventricles, which feature a representation of the original geometry that is as accurate as possible and which represent the ventricle boundary motion realistically, should be used to make quantitative statements on flow and pressure in the ventricular space.     

Use of the leukomobilizing capacity of dextran sulfate for assessing the severity of an ionizing radiation lesion

It was shown that the number of lymphocytes migrating to the blood 3 h after the administration of dextran sulphate (DS) is a function of the radiation dose absorbed (up to 1.5 Gy). It is supposed that 3 populations of lymphocytes varying in radiosensitivity are present in the blood. The authors suggest that it is possible to estimate the degree of the radiation damage according to the number of lymphocytes circulating in the blood under the effect of DS. It was also shown that the number of CFUc in the blood after the injection of DS is a function of the radiation dose absorbed.     

The unsuitability of the uridine incorporation assay for the measurement of phagocytosis of Escherichia coli

The uridine incorporation technique for assaying phagocytosis is based on the fact that polymorphonuclear leucocytes are impermeable to labelled uridine, and therefore ingested bacteria inside phagocytic vacuoles will be unable to take it up. Extracellular bacteria, including those adherent to the phagocytic cell surface, can do so however. Differences in uptake between bacteria alone and in the presence of phagocytic cells can be used to measure ingestion. The present paper describes the application of this technique to Escherichia coli O-86 as the test organism. It appears that with this test species, the method is unsuccessful, because exposure of the non-ingested bacteria to some soluble product of the triggered polymorphonuclear leucocytes causes a large increase in their uridine uptake rates, over that of the control bacteria. The nature of the product responsible is unknown. It is unconnected with change in the pH of the medium, is heat stable, and is only produced by polymorphonuclear leucocytes which are actively phagocytosing. It may be that a release of phagolysosome contents is responsible.     

Variability of the lysozyme content in bream from the Rybinsk Reservoir in different seasons of the annual cycle

The seasonal variability of the lysozyme content has been detected in the liver, kidney, and spleen of bream. It is manifested in a higher lysozyme content in cold winter months and lower values in other seasons. It is shown that the enzyme activity is absent in blood serum of the studied fish regardless of its amount in immunocompetent organs. A high content of lysozyme in organs in the cold season of the year is not the result of the immunomodulatory effect of water temperature on this parameter but can be determined by physiological factors that do not depend on seasonal variations of the environmental temperature. It has been established that the blood serum in fish does not indicate the entire dynamics of the enzyme in the organism.     

The determination of the sequences present in the shadow bands of a dinucleotide repeat PCR.

A Polymerase Chain Reaction (PCR) of a DNA sequence containing a CA repeat produces a main band but also several shadow bands that differ by 2 base pairs below the main band. In the experiments described in this paper, these shadow bands were excised from a DNA sequencing gel and directly sequenced. It was found that the sequence in the CA repeat was ambiguous. However, the sequence 5' and 3' to the CA repeat was clear and unambiguous. It is proposed that the shadow bands are generated by 2 base pair random deletions in the CA repeat region. During this process the sequence becomes 'scrambled' only in the CA repeat region. The shadow bands were shown to occur during the PCR since the genomic DNA template did not contain the shadow bands. It is probable that the shadow bands arise by slippage during the PCR. It is predicted that a thermostable DNA polymerase with a high processivity would greatly reduce the occurrence of shadow bands.     

Meiofauna and the origins of the Metazoa*

Possible alternative habitats and life-styles of the original metazoan are considered. It is argued from the dominance of the benthic habitat in present-day groups that the original metazoan habitat was benthic rather than planktonic. Similarly, plesiomorphic metazoan taxa tend to be holobenthic rather than pelago-benthic. It is therefore probable that the early Metazoa were holobenthic. The concept of plesiohabitats and apohabitats in the evolution of taxa is presented. This leads to the proposition that the early metazoans were interstitial bionts of fine sand. Finally, the controversy concerning the aerobic or anaerobic origin of the Metazoa is considered. It is shown that competition theory predicts that plesiomorphic taxa are likely to remain in plesiohabitats. Diagrams showing the possible evolution of major taxa in relation to available habitats are presented. It is concluded that the earliest Metazoa could have evolved in anaerobic marine sand and that the early Plathelminthomorpha and Aschelminthes did so.     

Modeling of the feedback stabilization of the resistive wall modes in a tokamak

The problem of feedback stabilization of the resistive wall modes (RWMs) in a tokamak is discussed. An equilibrium configuration with the parameters accepted for the stationary ITER scenario 4A is considered as the main scenario. The effect of the vacuum chamber's shape on the plasma stability is studied. Ideal MHD stability is analyzed numerically by using the KINX code. It is shown that, in a tokamak with the parameters of the designed T-15M tokamak, RWMs can be stabilized by a conventional stabilizing system made of framelike coils. However, the maximum possible gain in β in such a tokamak is found to be smaller than that in ITER. It is shown that, in this case, a reduction in the plasma—wall gap width by 10 cm allows one to substantially increase the β limit, provided that RWMs are stabilized by active feedback.     

Shape of the myosin head in the rigor complex. Three-dimensional image reconstruction of the actin-tropomyosin-heavy meromyosin complex

The structure of the actin-tropomyosin-heavy meromyosin rigor complex was studied by image analysis of electron micrographs. The arrowhead of the rigor complex has a whisker-like structure with a dense turning point at the "barb" of the arrowhead. The neck region of the myosin head in the reconstructed three-dimensional image is present in the area corresponding to the dense point. It is concluded that at least one extra-thin area contributes to the neck region, and that the two heads in the heavy meromyosin molecule join a double helical rope beyond the end of the large head (G in this study). (This is different from previous interpretations). It is also concluded that the heavy meromyosin has a short bent part near the head/rod junction in the rigor complex.     

Mechanical structure and function of the craniofacial skeleton of the domestic dog.

Masticatory habit is a major factor determining the morphology of the craniofacial skeleton. The craniofacial skeleton essentially comprises a series of bony stress-bearing bridges forming a structural framework. The structural framework of the skull of dog has been described as a rigid trestle-like structure; it can be illustrated by mechanically removing nonresistant areas of bone. It is then found that a framework is produced which is partially rigid (cranium) and partly flexible (rostrum). It is postulated that the flexibility of the rostrum acts to absorb shock and it is suggested that the primate postorbital bar is developed in response to craniofacial morphology which increases compressive bite forces.     

Bioassay systems for the pyrethrins; the mode of action of pyrethrum synergists

The components of 'synergistic action' are reviewed in the light of recent work. It has been shown that for sesamin and isobutylundecylenamide at least, synergistic action remains after physical effects are eliminated. The toxicity of the pyrethrins is increased by a factor of three when up to equimolecular proportions of the above synergists are added, further additions having no effect. It is suggested that a surface complex between synergist and insecticide is formed at the peripheral nerve sheath interfaces, resulting in the reorientation of the pyrethrins molecules to give a more efficient discharge of the resting potential at the interface.     

Theoretical structure of the polar regions of the tropocollagen molecule

The theoretical conformations of poly (Gly-Ala-Glu) have been studied. This peptide was chosen as a model for the glycine led triads of the polar regions in collagen. The most favorable conformations are found to be based on the extended and folded forms of the 2₇ helix (2_7a and 2_7b). It is suggested that triple-strand structures of folded 2₇ helices exist in the polar collagen regions, and a structural model is presented which is in accord with recent ultrastructural deformation studies. It is a necessary condition for this structure that glycine occur in the lead of the peptide triads. In regions of the collagen molecule where the primary sequence does not contain triads (e.g., in the telopeptide region), random structures based on energy minimization of peptide neighbors are considered briefly. It seems likely that such regions contain an admixture of left-hand α, polyproline II, and 2₇ helix structures.     

The role of the leukocytes in the blood-vasal regulation of the blood circulation

The ability of N-formyl-methionyl-leucyl-phenylalanine-activated leukocytes to influence platelets and vessels was studied. It is shown, that of activation of leukocytes causes a vasoconstriction. The de-endothelialization of the vessels increased this effect. In addition, activated leukocytes increased the platelet aggregation. It was concluded, that activation of leukocytes can trigger thrombogenesis, angiospasm, microembolic syndrome and other disturbances of blood circulation.