Biomedical subjects

Lev V Beloussov

Publications and source records attributed to Lev V Beloussov.

6 recordsLinked to original sources

PubMed2006

Information about a form (on the dynamic laws of morphogenesis).

How a developing embryo becomes "informed" about its form?" This problem remains obscure and controversial. We argue that the "information about a form" is distributed throughout three main components: the dynamic laws, the parameters and the initial/boundary conditions. In the absence of a dynamic law two other components are "blind", that is, do not contain any unambiguous information. We present a version of a dynamic law of morphogenesis, based upon the presumption of a feedback between passive and active mechanical stresses. We explore several models of shape formation based upon this law and show that, as depending upon the parameters values, they generate a large set of realistic shapes. Genetic and epigenetic basis of the models parameters is discussed.

Animals↗

PubMed2006

Morphomechanics: goals, basic experiments and models.

Morphomechanics is a branch of developmental biology, studying the generation, space-time patterns and morphogenetic role of mechanical stresses (MS) which reside in embryonic tissues. All the morphogenetically active embryonic tissues studied in this respect have been shown to bear substantial mechanical stresses of tension or pressure. MS are indispensable for organized cell movements, expression of a number of developmentally important genes and the very viability of cells. Even a temporary relaxation of MS leads to an increase in the morphological variability and asymmetry of embryonic rudiments. Moreover, MS may be among the decisive links of morphogenetic feedback required for driving forth embryonic development and providing its regular space-time patterns. We hypothesize that one such feedback is based upon the tendency of cells and tissues to hyperrestore (restore with an overshoot) their MS values after any deviations, either artificial or produced by neighboring morphogenetically active tissues. This idea is supported by a number of observations and experiments performed on the tissue and individual cell levels. We describe also the models demonstrating that a number of biologically realistic stationary shapes and propagating waves can be generated by varying the parameters of the hyperrestoration feedback loop. Morphomechanics is an important and rapidly developing branch of developmental and cell biology, being complementary to other approaches.

Animals↗

PubMed2006

Gastrulation in amphibian embryos, regarded as a succession of biomechanical feedback events.

Gastrulation in amphibian embryos is a composition of several differently located morphogenetic movements which are perfectly coordinated with each other both in space and time. We hypothesize that this coordination is mediated by biomechanical interactions between different parts of a gastrulating embryo based upon the tendency of each part to hyper-restore the value of its mechanical stress. The entire process of gastrulation in amphibian embryos is considered as a chain of these mutually coupled reactions, which are largely dependent upon the geometry of a given embryo part. We divide gastrulation into several partly overlapped steps, give a theoretical interpretation for each of them, formulate the experiments for testing our interpretation and describe the experimental results which confirm our point of view. Among the predicted experimental results are: inhibition of radial cell intercalation by relaxation of tensile stresses at the blastula stage; inversion of convergent intercalation movements by relaxation of circumferential stresses at the early gastrula stage; stress-promoted reorientation of axial rudiments, and others. We also show that gastrulation is going on under a more or less constant average value of tensile stresses which may play a role as rate-limiting factors. A macro-morphological biomechanical approach developed in this paper is regarded as complementary to exploring the molecular machinery of gastrulation.

Animals↗

PubMed2003

Integrating self-organization theory into an advanced course on morphogenesis at Moscow State University.

A lecture course on morphogenesis for fourth-year Moscow State University Specialist Diploma students specializing in embryology is described. The main goal of the course is to give the students an extensive theoretical background based on the tenets of the modern theory of Self-Organization and to show them how important this theory is for the proper understanding of developmental events. The corresponding mathematics are bound as tightly as possible to the actual morphogenetic processes. All of the lectures take the format of an active dialogue between the students and a tutor.

Developmental Biology↗

PubMedDate not supplied

Exploring the dynamic background of the developmental processes and cell reactions with the use of an ultraweak photon emission.

Any reactions of the living systems are to a great extent context-dependent. Meanwhile, the biological essence of a "context" remains to be obscure. We suggest that it may be based upon an ensemble of molecular-supramolecular oscillators, which have different characteristic times. For testing this hypothesis, we applied the Fourier statistics to the time series of the records of an ultraweak photon emission (UWPE) registered from fish eggs and embryos and from cell cultures. We detected the regular changes of the UWPE Fourier spectra (FS) during embryonic development and physiological reactions of cell cultures. In many cases, such changes were going on in a holistic manner, i.e. involving broad spectral areas rather than single frequency maxims. FS of the earlier developmental stages showed greater instability and the presence of a short-range order only. On the contrary, at the advanced developmental stages a long-range order has emerged within the spectra. Another distinction of the highly organized biological samples (developing embryos, confluent fibroblasts cultures) from non-biological controls and "poorly organized" samples (non-fertilized eggs, non-confluent, poorly spread cell cultures) was the UWPE correlation dynamics which was more cooperative in highly organized samples. A non-invasive technique of UWPE registration may be useful for exploring a fluctuated oscillatory background of the developmental and physiological states of biological samples.

Animals↗

PubMedDate not supplied

Formative capacities of mechanically stressed networks: developmental and evolutionary implications.

We present a biomechanical model of morphogenesis highlighting the extensive formative capacities of stressed networks with a very simple initial geometry. They consist of a restricted number of kinematically independent elements exerting a pressure to each other and increasing thus the local curvatures. The pressure is applied as a series of periodic impulses and is opposed by a constant quasi-elastic resistance force. Single elements can be also regarded as the half wave-lengths of the undulations determined by the mechanical properties of a given body. All of the model parameters are assumed to be evenly spread throughout a body (no prepatterns are implied). On the other hand, the model parameters can be associated with genetic factors. Thus, our model relates to as yet unsolved problem of genetic regulation of shape formation. We classify the modeled shapes according to their symmetry orders and compare them with the ancient Echinodermata and with Arthropods. Possible evolutionary and developmental implications are discussed.

Biological Evolution↗