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Biomedical subjects

A A Frolov

Publications and source records attributed to A A Frolov.

At least 19 recordsLinked to original sources
PubMed1997

Fatty acid uptake in diabetic rat adipocytes.

The effect of diabetic status and insulin on adipocyte plasma membrane properties and fatty acid uptake was examined. Studies with inhibitors and isolated adipocyte ghost plasma membranes indicated 9Z, 11E, 13E, 15Z-octatetraenoic acid (cis-parinaric acid) uptake was protein mediated. Cis-parinaric acid uptake was inhibited by trypsin treatment or incubation with phloretin, and competed with stearic acid. The initial rate, but not maximal uptake, of cis-parinaric acid uptake was enhanced two-fold in adipocytes from diabetic rats. Concomitantly, the structure and lipid composition of adipocyte ghost membranes was dramatically altered. However, the increased initial rate of cis-parinaric acid uptake in the diabetic adipocytes was not explained by membrane alterations or by a two-fold decrease in cytosolic adipocyte fatty acid binding protein (ALBP), unless ALBP stimulated fatty acid efflux. Thus, diabetic status dramatically altered adipocyte fatty acid uptake, plasma membrane structure, lipid composition, and cytosolic fatty acid binding protein.

Adipocytes↗
PubMed1996

Acyl-CoA binding proteins: multiplicity and function.

The physiological role of long-chain fatty acyl-CoA is thought to be primarily in intermediary metabolism of fatty acids. However, recent data show that nM to microM levels of these lipophilic molecules are potent regulators of cell functions in vitro. Although long-chain fatty acyl-CoA are present at several hundred microM concentration in the cell, very little long-chain fatty acyl-CoA actually exists as free or unbound molecules, but rather is bound with high affinity to membrane lipids and/or proteins. Recently, there is growing awareness that cytosol contains nonenzymatic proteins also capable of binding long-chain fatty acyl-CoA with high affinity. Although the identity of the cytosolic long-chain fatty acyl-CoA binding protein(s) has been the subject of some controversy, there is growing evidence that several diverse nonenzymatic cytosolic proteins will bind long-chain fatty acyl-CoA. Not only does acyl-CoA binding protein specifically bind medium and long-chain fatty acyl-CoA (LCFA-CoA), but ubiquitous proteins with multiple ligand specificities such as the fatty acid binding proteins and sterol carrier protein-2 also bind LCFA-CoA with high affinity. The potential of these acyl-CoA binding proteins to influence the level of free LCFA-CoA and thereby the amount of LCFA-CoA bound to regulatory sites in proteins and enzymes is only now being examined in detail. The purpose of this article is to explore the identity, nature, function, and pathobiology of these fascinating newly discovered long-chain fatty acyl-CoA binding proteins. The relative contributions of these three different protein families to LCFA-CoA utilization and/or regulation of cellular activities are the focus of new directions in this field.

Animals↗
PubMed1996

Recent advances in membrane cholesterol domain dynamics and intracellular cholesterol trafficking.

Cholesterol is distributed nonrandomly in and between biological membranes. Despite over two decades' investigation of these phenomena, the origin, regulation, and function of membrane cholesterol asymmetry are not known. Likewise, although pathways of cellular cholesterol absorption/utilization as well as de novo synthesis have been investigated in depth, parallel progress in elucidating pathways of intracellular cholesterol trafficking and final deposition of cholesterol within membranes remains undefined. Understanding the nature and regulation of these processes is essential to resolving molecular mechanisms of cholesterol uptake, reverse cholesterol transport, steroidogenesis, and modulation of membrane function. Based on the fundamental observation that cholesterol is not distributed uniformly in the cell, three key concepts have contributed to recent advances in this field: First, cholesterol is asymmetrically distributed across the cell surface plasma membrane, wherein it translocates rapidly. Second, cholesterol is distributed within the plane of biomembrane bilayers into dynamic and static domains, with the latter predominating. The exact nature and physiological functions of such cholesterol domains or pools remain an enigma. Third, regulation of the size and kinetics of biomembrane cholesterol domains may be determining factors in intracellular cholesterol trafficking, targeting, and efflux. Contributions of both cytosolic carrier proteins and vesicular processes are recognized.

Animals↗
PubMed1992

The laws of delayed photohaemolysis sensitized by chlorin e6.

The relationships between the rate of post-irradiated photohaemolysis sensitized by chlorin e6 and parameters such as the light fluence (time of irradiation) and sensitizer concentration were studied. On the basis of the single-parametric approach proposed by Valenzeno and Pooler, it was found that the haemolytic rate varies with the square of both the light fluence and the sensitizer concentration. Thus it can be concluded that, in a single erythrocyte lesion, two chlorin e6 molecules participate, each absorbing one photon. The possibility of suppression of post-irradiation haemolysis was also studied using the lipophilic antioxidant, butylated hydroxytoluene (BHT), and scavengers of 1O2, O2.- and HO. radicals. It was found that BHT inhibits, to a considerable extent, the post-irradiation lysis of cells, by about a factor of 2.5 at a BHT concentration of 9 microM. The addition to the medium of NaN3 (a scavenger of 1O2), superoxide dismutase (a scavenger of O2.- radicals), ethanol and D-mannitol (scavengers of HO. radicals), when irradiation was interrupted, did not produce a marked influence on the kinetics of subsequent haemolysis. On the basis of the results obtained, the nature of erythrocyte targets, which are crucial for the photodynamic effect of chlorin e6, is discussed.

Biological Transport↗
PubMed1991

[The physicochemical evaluation of the bile using infrared spectroscopy].

Native bile, inspissated bile, and cholesterol choleliths were examined by infrared spectroscopy. Model compounds spectra were compared with native bile spectra. The spectra were divided into 3 groups: with acid fragments or cholesterol groups predominating and intermediate group. The peak of 3620 cm-1, absent in normal human bile and liable to augment if acid fragment level reduced was detected. The authors suggest a technique of infrared spectroscopy permitting early detection of disordered physicochemical characteristics of the bile in the course of cholesterol cholelithiasis development.

Bile↗
PubMed1990

Chlorin e6-liposome interaction. Investigation by the methods of fluorescence spectroscopy and inductive resonance energy transfer.

On the basis of spectral fluorescence and polarization measurements and results obtained on the luminescence quenching of the membrane fluorescent probe 1,6-diphenyl-1,3,5-hexatriene (DPH) by incorporated chlorin e6 (chl e6) molecules, it is shown that the interaction of the water-soluble pigment with smaller unilamellar lipid vesicles occurs by a mechanism of partition between the aqueous and lipid phases (partition coefficient Kp = 6.7 x 10(3) and provides rigid fixing of chl e6 monomers at the boundary between the polar and non-polar parts of the lipid membrane. In terms of inductive resonance electronic excitation energy transfer between DPH and chl e6 (R0 = 36.2 A), we have analysed data on DPH fluorescence quenching under different conditions of chl e6 localization in the lipid bilayer and have concluded that the incorporation of the pigment molecules into the vesicles from the aqueous phase occurs mainly into the external monolayer.

Chlorophyllides↗
PubMed1990

[A spectral analysis and mathematical modelling of the brain electrical activity in normal rats and in genetically conditioned convulsibility].

Spectral signs of genetically conditioned convulsibility of rats of the Krushinskiĭ-Molodkina (KM) strain were determined when studying the background electrical brain activity. These signs were: an increase of the delta-activity power in motor and visual cortical zones; considerable increase of the hippocampal potential power; weakening of the caudate nucleus potential power. Spectra of biopotentials being approximated by theoretical spectral function, model parameters simulating physiological characteristics of neural networks were estimated (an inverse problem of modelling). Spectral signs of convulsibility were shown to reflect changes in properties of the neural network. On the basis of calculations it is supposed that genetically determined convulsibility of KM rats results from weakening of inhibitory functions of the caudate nucleus as well as from increased excitability (reactivity) of hippocampal and neocortical neurons.

Acoustic Stimulation↗
PubMed1989

Role of the sensorimotor cortex in postural adjustments accompanying a conditioned paw lift in the standing cat.

The role of the sensorimotor cortex in the postural adjustments associated with conditioned paw lifting movements was investigated in the cat. Cats were trained to stand quietly on four strain gauge equipped platforms and to perform a lift-off movement with one forelimb when a conditioned tone was presented. The parameters recorded were the vertical forces exerted by the paws on each platform, the lateral and antero-posterior displacements of rods implanted on the T2, T12, L5 vertebrae as well as their rotation, and the EMG of triceps and biceps of both forelimbs. Before lesion, the postural adjustment consisted of a "non-diagonal" pattern where the CG was displaced laterally inside the triangle formed by the three remaining supporting limbs. Here a lateral bending of the thoracic column toward the supporting forelimb could be observed. The associated EMG pattern consisted of an early activation of the triceps lateral head in the moving limb which was probably responsible for the body displacement toward the opposite side, and a late biceps activation associated with the lift. In the supporting forelimb, a coactivation of the biceps and triceps was usually present. After contralateral sensorimotor lesion, the conditioned lifting movements were lost for 4-15 days after the lesion, before being subsequently recovered. The same lateral CG displacement and bending of the back was seen after lesion as before, which indicates that the goal of postural adjustment was preserved. However, the means of reaching it were modified.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

The learned rearrangement of an inborn postural pattern.

The postural displacement accompanying a learned movement was studied in the dog. Dogs were trained to change the diagonal postural pattern into an ipsilateral one. Such a rearrangement of inborn postural pattern is very difficult and requires several hundred trials. A biomechanical model connecting the changes of pressure of different limbs with kinematics of different part of the body is proposed.

Animals↗
PubMed1982

Biomechanical study of the mechanisms of postural adjustment accompanying learned and induced limb movements in cats and dogs.

Trajectories of the center of pressure and center of gravity projections were studied in dynamic conditions during learned movement and movement evoked by the motor cortex stimulation (induced movement) in dogs and cats. The learned movement began with initial displacement of the center of pressure towards the limb performing movement. It corresponded often with initial increasing of the performing limb pressure on support and it was a reason of initial acceleration of the center of gravity in the opposite direction. Induced movement began with decrease of the performing limb pressure on support. It could result in the initial displacement of the center of pressure in the wrong direction but usually it was corrected quickly and the general trajectories of the center of pressure and the center of gravity were similar to ones observed during learned movement. Results suggest different programs for movement and appropriate postural adjustment.

Animals↗
PubMed1979

[Analysis of geometric factors determining the parameters of an extracellularly recorded pyramidal neuron action potential].

Calculation of general extracellular field characteristics of a pyramidal neuron during generation of action potential included solution of the Laplas equation for extracellular field and Hodgkin--Huxley equations for electrotonic conduction along dendrites and for excitation of soma. The results were compared with available experimental data. The general factor for action potential amplitude near the soma seems to involve the distance from the soma rather than its size.

Action Potentials↗
PubMedDate not supplied

Certain methods of biomechanical description of various postural adjustment patterns during motoric learning in dogs.

Methods for the biomechanical description of spatial displacements of the center of mass of quadruped animal (dog), developed by the authors on the basis of an assessment of the vertical constituents of support pressures, as well as methods for the assessment of the postural adjustment pattern (coefficient of diagonality), are presented in this paper. The results are presented of an investigation of the role of the motor cortex in the accomplishment of the postural adjustment pattern of dogs, reorganized during learning, in the performance of an instrumental movement.

Animals↗