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A A Polezhaev

Publications and source records attributed to A A Polezhaev.

16 recordsLinked to original sources
PubMed1993

[The instrumental extirpation of the esophagus via an abdominocervical approach].

The authors operated on 6 patients with cancer of the lower thoracic esophagus and cardioesophageal carcinoma, Stage III. All the patients underwent esophageal extirpation from the abdominocervical access by using an extractor inserted into the esophageal lumen through a cut in its wall above the tumor. The esophagus was drawn out from the mediastinum into the abdomen, similar to subcutaneous vein removal by the Bebcock method. A single esophagoplasty was performed in 4 patients. In the postoperative period one patient died from pulmonary embolism. No complications due to the procedure of esophageal removal were observed. In the authors' opinion, during operations using the abdominocervical access, instrumental esophagectomy by means of an extractor is more traumatic and simple than manual esophageal mobilization.

Cardia↗
PubMed1992

A mathematical model of the mechanism of vertebrate somitic segmentation.

A mathematical model for the mechanism of periodic pattern formation in the process of somitogenesis is proposed. It is assumed that the metameric arrangement first appears before somite formation at the stage of transition of mesodermal cells into a polarized state. The model is based on the assumption that besides the mechanism of contact cell polarization there exists a mechanism of polarization suppression due to excretion of some chemical substance by polarized cells. Periodicity appears as a result of interaction of a kinematic wave of somitogenic cell determination with the cell cycles of mesodermal cells.

Animals↗
PubMed1988

Mathematical modelling of intercellular regulation causing the formation of spatial structures in bacterial colonies.

Bacterial colonies may grow forming stable spatial, particularly circular, structures. For instance, motile bacteria Proteus vulgaris or Escherichia coli grown on agar under certain conditions may form concentric rings with the centre in the inoculation point (Rüss-Münzer, 1935, Bact. Parasit Kde (Abt 1) 7, 214; Budriené, 1985, Dokl. Acad. Nauk SSR, 283, 470). A similar picture can be observed in a different situation, i.e. when a lawn of non-motile Salmonella typhimurium bacteria is cultivated on a solid agar with the locally introduced substrate (Hoppensteadt & Jäger, 1980, Lecture Notes in Biomath. 38, 68). This paper describes a mechanism of bacterial interactions through a hypothetical mediator released by the organisms. A mathematical model has been built. Its analysis has shown that the selected laws of secretion and reception of the mediator can adequately account for the formation of circular structures in the case of both motile and non-motile bacteria.

Animals↗
PubMed1988

[Prevention of bronchial fistula and empyema after resection and removal of the lung].

Pulmonectomies in 231 patients and resections of a lung in 320 patients were followed by the development of bronchial fistulas in 33 patients (5.9%): after pneumonectomy--in 17 patients (7.3%) and after lobe- and bilobectomy in 16 patients (5%). Empyema of the pleura was noted in 20 patients (3.6%): in 12 patients (5.2%) and 8 patients (2.5%) correspondingly. Seventeen of 53 patients with these complications died. The use of a manual method of suturing the bronchus without a stump with the local application of fibrinogen, complex bronchological sanitation and intraoperative bronchofibroscopy (drainage of the pleural cavity after pneumonectomy with the following filling of the cavity with an antiseptic solution and formation of the selective pneumoperitoneum) allowed to decrease the incidence of bronchial fistulas in 102 patients to 2.9%, and empyema of the pleura--to 1.9%.

Adolescent↗
PubMed1985

On the possibility of reduction of dissipative structure models to a simple form.

A multicomponent reaction-diffusion system containing two different space scales (contrasting system) is considered. It is shown that if the system answers several conditions enumerated, it can be reduced to a bicomponent system which describes a dissipative structure either of a peak or of a step type. While in the first case the original and the final systems are equivalent only in the neighbourhood of zero, in the second case the equivalence is more general as the solution of these systems does not leave the region for which the procedure of reduction was developed.

Biometry↗
PubMed1981

On the possible mechanism of cell cycle synchronization.

The influence of exchanges of lipids and antioxidants (AO) between the cells on the cell proliferation is studied in the frame of the membrane model of the cell cycle. It is shown theoretically that the easy-oxidative lipids exchange favours the synchronization of cell division, while the AO exchange leads to desynchronization. The analytical consideration and some numerical estimations are carried out. The qualitative consequences accessible to experimental verification are discussed.

Animals↗
PubMed1981

On kinetics of phase transitions in cell membranes.

Phase transitions in a bicomponent lipid membrane are considered. It is shown that in this case metastable states practically do not arise and phase transitions are smooth and hysteresisless. An elastic frame on the surface of the membrane changes the character of phase transitions: they become sharp and hysteretic. The role of membrane phase transitions for regulation of cell processes is considered.

Cell Membrane↗
PubMed1977

A mathematical model of periodic processes in membranes (with application to cell cycle regulation).

A mathematical model of the regulation of the cell cycle by the plasma membrane is suggested. The model is based on the hypothesis that structural transitions of the cell membrane play an important role in the regulation of cell division. Conditions of transition from the proliferating state to the resting state and back are investigated. Possible qualitative differences between models of the cell cycle of a normal and a tumour cell are pointed out.

Cell Cycle↗
PubMedDate not supplied

Cell surface and cell division.

A mathematical model of the regulation of cell division is suggested. The model is based on the hypothesis that the process giving rhythm to cell division is located in the cell membrane: i.e., the process of free-radical oxidation of membrane lipids. Much depends on the physical state of the membrane. In the membrane, phase transitions take place because of the changes in lipid composition. These transitions differ in normal and tumor cells: in normal cells they are sharp and hysteretic owing to the presence of a framework (membrane skeleton) on the surface of the membrane, while in tumor cells the integrity of the surface is violated so that the transitions are smooth. This model makes it possible to explain differences in the regulation of normal and cancer cell proliferation. Within the limits of the model, such phenomena as density dependent inhibition of growth, reverse transformation, influence of cyclic AMP and ions of Ca2+ on the cell cycle, the actions of serum and of proteases on the cycle, and so on, are explained. A rational scheme for the appearance of the selective damage found in tumor cells is proposed.

Animals↗
PubMedDate not supplied

[A mechanism of development of spatial-temporal orderliness in bacterial systems].

Peculiarities of the mechanism of intercellular regulation capable of initiating nonhomogeneous spatial structures in different experimental bacterial systems are analysed. A model of band formation of bacterial density in agar-stabilized bacterial system with opposite gradients of the substrate and oxygen is suggested. It is shown that for the appearance of spatial structures in the bacterial systems a time delay in the cell response to the external signal is of principal importance, as well as the hysteresis of transitions between differentiated bacterial states.

Bacteria↗
PubMedDate not supplied

[Emergence of a quasi-periodic spatial structure in the model of aggregation of moving, dividing cells, possessing chemotactic properties].

It has been analyzed the Keller-Segel model of aggregation of divided cells possessed hemotaxis. During the cell division homogeneous stationary distribution becomes unstable due to increasing of the common cells amount. It is shown that accidental variation of the primary stable homogeneous stationary distribution result to forming of a like periodical space structure with characteristic scale that basically is defined by the cell division rate. This approach allows to explain the arising of complex space structures in the movable bacterium colonies.

Animals↗