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Biomedical subjects

G V Maksimov

Publications and source records attributed to G V Maksimov.

At least 19 recordsLinked to original sources
PubMed2006

Self-organized critical gating of ion channels: on the origin of long-term memory in dwell time series.

We present the model of an ion channel, operating in a regime of self-organized criticality. It is suggested that complex cooperative dynamics takes place in the protein and the overall tension of it facilitates an open or closed state of the rigid gates in the pore-making domain. For the first time multifractal spectra of ion channel dynamics are presented. Our model well reproduces the multifractal properties of ion channel dwell time series and provides an insight on the origin of the long-term correlations in these series.

Biophysics↗
PubMed2006

Study of changes in diacylglycerol content on nerve excitation.

Rhythmic excitation of a rabbit myelin nerve increased diacylglycerol (DAG) content from 1.53 to 2.17 microg/mg lipids. Inhibition of phosphoinositide-specific phospholipase C decreased DAG content. This suggests involvement of this enzyme in processes accompanying rhythmic excitation. The increase in membrane potential of the nerve fiber (K+-depolarization) was accompanied by increase in DAG and phosphatidylinositol monophosphate and decrease in phosphatidylinositol triphosphate and phosphatidylinositol diphosphate content. Treatment of the nerve with DAG or a protein kinase C activator increased (45)Ca influx by 40%, whereas treatment with an inhibitor of this enzyme, polymyxin, inhibited this parameter by 34%. The role of phosphoinositides and protein kinase C in the regulation of Ca2+ transport during rhythmic excitation of the myelin nerve is discussed.

Animals↗
PubMed2005

Interference microscopy under double-wavelet analysis: a new approach to studying cell dynamics.

This Letter combines a novel experimental approach to the study of intracellular processes with a newly developed technique for multimode time-series analysis. Experiments are performed on isolated pond snail (Lymnaea stagnalis) neurons. Local variations in the cellular refractive index as detected by laser interference microscopy are related to the processes in the cell. A wavelet analysis shows the presence of several identifiable modes in the membrane and intracellular dynamics, and a double-wavelet analysis reveals nonlinear interactions between the regulatory processes in the form of mutual frequency and amplitude modulations.

Animals↗
PubMed2005

Role of viscosity and permeability of the erythrocyte plasma membrane in changes in oxygen-binding properties of hemoglobin during diabetes mellitus.

Changes in viscosity and permeability of the plasma membrane and conformation of erythrocyte hemoglobin hematoporphyrin were found in patients with diabetes mellitus. The decrease in oxygen binding and increase in deoxyhemoglobin concentration during diabetes mellitus were accompanied by changes in viscosity and permeability of the membrane for Na+, H+, Ca2+, and K+. Our results suggest that oxygen-binding properties of hemoglobin depend on viscosity and permeability of the erythrocyte plasma membrane.

Calcium↗
PubMed2005

Erythrocyte membrane fluidity and haemoglobin haemoporphyrin conformation: features revealed in patients with heart failure.

This study examined the possible involvement of abnormal erythrocyte oxygen (O(2)) transport in the pathogenesis of heart failure. Haemoglobin (Hb) haemoporphyrin conformation was assessed by Raman spectroscopy (RS) of blood samples, whereas membrane fluidity was estimated at depths of 0.6-0.8 and 2.2nm by electron-paramagnetic resonance spectroscopy of erythrocytes loaded with spin-labeled 5-doxylstearic acid and 16-doxylstearic acid, respectively. The fluidity of erythrocyte membranes from patients with heart failure was decreased in the area near the membrane surface and remained unchanged in the deeper hydrophobic membrane regions. The same differences were also detected in healthy controls subjected to chronic high-altitude hypoxia. RS demonstrated that in heart failure the total content of Hb-ligand complexes and the relative content of Hb-nitric oxide (NO) complexes with cleaved Fe(2+)-globin bond was decreased, whereas content of Hb-NO complexes with preserved Fe(2+)-globin bond was increased. We propose that this phenomenon contributes to the reduced O(2) tissue supply seen in patients with heart failure.

Journal Article↗
PubMed2005

[The role of plasmatic erythrocytic membrane in formation of hypoxia in patients with chronic cardiac failure].

AIM: To study oxygen supply to erythrocytes in patients with chronic cardiac failure as a factor provoking hypoxia. MATERIAL AND METHODS: The trial enrolled 12 men with chronic cardiac failure (CCF) of functional NYHA class II aged 37 to 74 years (group A). Group B--healthy donors (n = 10) aged 20-40 years. Conformation changes of hemoporphirine were detected with degradation spectroscopy, viscosity of plasmatic membrane--with resonance spectroscopy. Degradation spectroscopy estimated content of Hb-ligant complexes as 0.34 +/- 0.013; complexes I Hb-NO 0.73 +/- 0.11, complexes II Hb-NO 0.28 +/- 0.08 (group A). RESULTS: Electronic-paramagnetic spectroscopy has estimated: S--0.716 +/- 0.005 (group A), 0.667 +/- 0.011 (group B). In group B- 0.5 +/- 0.08; 0.41 +/- 0.22; 0.55 +/- 0.12, respectively. CONCLUSION: Patients with CHF have high microviscosity of plasmatic erythrocytic membrane near location of polar lipid groups; subnormal content of oxyhemoglobin and elevation of the number of complexes of nitric hemoglobin-oxide; altered binding of nitric oxide with hemoglobin.

Adult↗
PubMed2004

Investigation of erythrocyte shape, plasma membrane fluidity and conformation of haemoglobin haemoporphyrin under the influence of long-term space flight.

The investigation of long-term space flight (SF) effect on the blood cells function is of great importance for modern space biology and medicine. We established that the number of discocytes decreased in the period of early rehabilitation after long-term SF. After SF plasma membrane fluidity and phospholipid content decreased and cholesterol content increased. After SF the amount of haemoglobin decreased and the parameters characterizing haemoglobin haemoporyphyrin (HH) conformation changed. We suppose that erythrocyte shape, membrane fluidity and HH conformation are among factors affecting oxygen transfer during and after space flight.

Cholesterol↗
PubMed2002

Role of ionic transport in regulation of hemoglobin affinity for oxygen in diabetes mellitus.

The rate of Na(+)/H(+) exchange is increased by 24%, activities of Ca-dependent K+ channels is increased by 13%, and activity of erythrocyte Ca(2+)-ATPase decreased by 17% in patients with diabetes mellitus concomitant with essential hypertension in comparison with patients with essential hypertension without disorders of carbohydrate metabolism. Changes in activity of Na(+)/H(+) exchange, Ca-dependent K(+) channels, and erythrocyte Ca(2+)-ATPase and increased oxygen affinity of hemoglobin are due to increased glucose concentration in the plasma and are leveled by olifen.

Calcium-Transporting ATPases↗
PubMed2001

Study on conformational changes in hemoglobin protoporphyrin in essential hypertension.

Changes in protoporphyrin conformation, partial pressures of O2 and CO2, and the mechanisms responsible for regulation of pCa and pH in erythrocytes were studied in essential hypertension (EH). Changes in protoporphyrin conformation in EH were accompanied by a decrease in the partial pressure of O2 and an increase in the partial pressure of CO2. This was associated with increased activities of Na+/H+-exchange and Ca2+-dependent K+-channels and with a decreased activity of Ca2+-ATPase. The changes in protoporphyrin conformation in EH are suggested to decrease the efficiency of O2 metabolism in hemoglobin and increase the values of intracellular pCa and pH of erythrocytes.

Calcium-Transporting ATPases↗
PubMed2001

A study of demyelination of nerve fibers using dynamic phase contrast microscopy.

Dynamic phase microscopy was used for evaluation of changes in myelinated axon segment in the paranodal region of nerve fibers during demyelination. Normally paranodal myelin sheath is characterized by regular oscillations of the optical path difference with frequences of 4.2 and 6.7 Hz. Demyelination decreased the amplitude and conduction velocity in nerve fibers and shifted the characteristic frequencies of optical path difference oscillations to 2.8, 3.2, and 11 Hz. These shifts of optical path difference frequencies probably resulted from disturbances in the state of charged phospholipids and a decrease in the level of bound Ca(2+)during demyelination of nerve fiber.

Animals↗
PubMed1992

[The mechanisms of the porphyrin conformation of normal blood hemoglobin and in pathology].

The spectra of resonance Raman scattering of blood in norm and under pathology (myocardial infarction and sepsis), as well after artificial hemotransfusion or UV photomodification have been studied. It has been shown that under heart pathology the structure of hemoglobin porphyrin macrocycle of erythrocytes changes, the size of porphyrin "nucleus" increases. The opposite conditions are observed at blood sepsis. It has been found that the traditional methods in tissue restoration, hemotransfusion and UV photomodification of blood don't result in complete restoration of hemoporphyrin molecule.

Blood↗
PubMed1989

[Molecular mechanisms of the action of local anesthetics].

Raman spectroscopy revealed a suppression of the polyene chain of C40-carotenoids in membrane of the frog nerve during local action of an anesthetic agent in resting and excitation. The phosphatidylcholine binding decreased during rhythmic excitation and local anesthetic action. A mechanism of potential-dependent changes of the carotenoid conformation during local anesthetic action, was discussed.

Action Potentials↗
PubMed1986

[Binding of 3H-bungarotoxin by nerve trunks of the frog during excitatory conduction].

In the frog nerve, 3H-bungarotoxin and 3H-acetylcholine binding increased whereas the acetylcholinesterase activity decreased in rhythmic stimulation. The enhancement of 3H-bungarotoxin binding to nerve during the rhythmic stimulation seems to stem from transformation of "inactive" forms of acetylcholine receptor of glial membrane to "active" ones.

Acetylcholine↗
PubMed1984

[Calcium ion binding in somatic nerves during conduction of rhythmic excitation].

Increase of Ca entry upon excitation depended on stimulation frequency and the types of nerves in crab, frog and squid. The amount of absorbed Ca was high in myelinated nerves whereas the velocity of absorption was higher in nonmyelinated nerves. The maximal level of Ca entry during rhythmic excitation was observed in the frog nerve. The data obtained suggest a mechanism of Ca entry in somatic nerves during rhythmic excitation.

Animals↗