Molecular Sensing and Manipulation of Protein Oligomerization in Membrane Nanotubes with Bolaamphiphilic Foldamers

Adaptive and reversible self-assembly of supramolecular protein structures is a fundamental characteristic of dynamic living matter. However, the quantitative detection and assessment of the emergence of mesoscale protein complexes from small and dynamic oligomeric precursors remains highly challenging. Here, we present a novel approach utilizing a short membrane nanotube (sNT) pulled from a planar membrane reservoir as nanotemplates for molecular reconstruction, manipulation, and sensing of protein oligomerization and self-assembly at the mesoscale. The sNT reports changes in membrane shape and rigidity caused by membrane-bound proteins as variations of the ionic conductivity of the sNT lumen. To confine oligomerization to the sNT, we have designed and synthesized rigid oligoamide foldamer tapes (ROFTs). Charged ROFTs incorporate into the planar and sNT membranes, mediate protein binding to the membranes, and, driven by the luminal electric field, shuttle the bound proteins between the sNT and planar membranes. Using Annexin-V (AnV) as a prototype, we show that the sNT detects AnV oligomers shuttled into the nanotube by ROFTs. Accumulation of AnV on the sNT induces its self-assembly into a curved lattice, restricting the sNT geometry and inhibiting the material uptake from the reservoir during the sNT extension, leading to the sNT fission. By comparing the spontaneous and ROFT-mediated entry of AnV into the sNT, we reveal how intricate membrane curvature sensing by small AnV oligomers controls the lattice self-assembly. These results establish sNT-ROFT as a powerful tool for molecular reconstruction and functional analyses of protein oligomerization and self-assembly, with broad application to various membrane processes.

Molecular Shape Solution for Mesoscopic Remodeling of Cellular Membranes

Cellular membranes self-assemble from and interact with various molecular species. Each molecule locally shapes the lipid bilayer, the soft elastic core of cellular membranes. The dynamic architecture of intracellular membrane systems is based on elastic transformations and lateral redistribution of these elementary shapes, driven by chemical and curvature stress gradients. The minimization of the total elastic stress by such redistribution composes the most basic, primordial mechanism of membrane curvature-composition coupling (CCC). Although CCC is generally considered in the context of dynamic compositional heterogeneity of cellular membrane systems, in this article we discuss a broader involvement of CCC in controlling membrane deformations. We focus specifically on the mesoscale membrane transformations in open, reservoir-governed systems, such as membrane budding, tubulation, and the emergence of highly curved sites of membrane fusion and fission. We reveal that the reshuffling of molecular shapes constitutes an independent deformation mode with complex rheological properties.This mode controls effective elasticity of local deformations as well as stationary elastic stress, thus emerging as a major regulator of intracellular membrane remodeling.

Nonlinear material and ionic transport through membrane nanotubes

Membrane nanotubes (NTs) and their networks play an important role in intracellular membrane transport and intercellular communications. The transport characteristics of the NT lumen resemble those of conventional solid-state nanopores. However, unlike the rigid pores, the soft membrane wall of the NT can be deformed by forces driving the transport through the NT lumen. This intrinsic coupling between the NT geometry and transport properties remains poorly explored. Using synchronized fluorescence microscopy and conductance measurements, we revealed that the NT shape was changed by both electric and hydrostatic forces driving the ionic and solute fluxes through the NT lumen. Far from the shape instability, the strength of the force effect is determined by the lateral membrane tension and is scaled with membrane elasticity so that the NT can be operated as a linear elastic sensor. Near shape instabilities, the transport forces triggered large-scale shape transformations, both stochastic and periodic. The periodic oscillations were coupled to a vesicle passage along the NT axis, resembling peristaltic transport. The oscillations were parametrically controlled by the electric field, making NT a highly nonlinear nanofluidic circuitry element with biological and technological implications.

Reconstitution and real-time quantification of membrane remodeling by single proteins and protein complexes

Cellular membrane processes, from signal transduction to membrane fusion and fission, depend on acute membrane deformations produced by small and short-lived protein complexes working in conditions far from equilibrium. Real-time monitoring and quantitative assessment of such deformations are challenging; hence, mechanistic analyses of the protein action are commonly based on ensemble averaging, which masks important mechanistic details of the action. In this protocol, we describe how to reconstruct and quantify membrane remodeling by individual proteins and small protein complexes in vitro, using an ultra-short (80- to 400-nm) lipid nanotube (usNT) template. We use the luminal conductance of the usNT as the real-time reporter of the protein interaction(s) with the usNT. We explain how to make and calibrate the usNT template to achieve subnanometer precision in the geometrical assessment of the molecular footprints on the nanotube membrane. We next demonstrate how membrane deformations driven by purified proteins implicated in cellular membrane remodeling can be analyzed at a single-molecule level. The preparation of one usNT takes ~1 h, and the shortest procedure yielding the basic geometrical parameters of a small protein complex takes 10 h.

Electrophysiological Methods for Detection of Membrane Leakage and Hemifission by Dynamin 1

Membrane fusion and fission are indispensable parts of intracellular membrane recycling and transport. Electrophysiological techniques have been instrumental in discovering and studying fusion and fission pores, the key intermediates shared by both processes. In cells, electrical admittance measurements are used to assess in real time the dynamics of the pore conductance, reflecting the nanoscale transformations of the pore, simultaneously with membrane leakage. Here, we described how this technique is adapted to in vitro mechanistic analyses of membrane fission by dynamin 1 (Dyn1), the protein orchestrating membrane fission in endocytosis. We reconstitute the fission reaction using purified Dyn1 and biomimetic lipid membrane nanotubes of defined geometry. We provide a comprehensive protocol describing simultaneous measurements of the ionic conductance through the nanotube lumen and across the nanotube wall, enabling spatiotemporal correlation between the nanotube constriction by Dyn1, leading to fission and membrane leakage. We present examples of "leaky" and "tight" fission reactions, specify the resolution limits of our method, and discuss how our results support the hemi-fission conjecture.

The 2018 biomembrane curvature and remodeling roadmap

The importance of curvature as a structural feature of biological membranes has been recognized for many years and has fascinated scientists from a wide range of different backgrounds. On the one hand, changes in membrane morphology are involved in a plethora of phenomena involving the plasma membrane of eukaryotic cells, including endo- and exocytosis, phagocytosis and filopodia formation. On the other hand, a multitude of intracellular processes at the level of organelles rely on generation, modulation, and maintenance of membrane curvature to maintain the organelle shape and functionality. The contribution of biophysicists and biologists is essential for shedding light on the mechanistic understanding and quantification of these processes. Given the vast complexity of phenomena and mechanisms involved in the coupling between membrane shape and function, it is not always clear in what direction to advance to eventually arrive at an exhaustive understanding of this important research area. The 2018 Biomembrane Curvature and Remodeling Roadmap of Journal of Physics D: Applied Physics addresses this need for clarity and is intended to provide guidance both for students who have just entered the field as well as established scientists who would like to improve their orientation within this fascinating area.

Membrane fission by dynamin: what we know and what we need to know

The large GTPase dynamin is the first protein shown to catalyze membrane fission. Dynamin and its related proteins are essential to many cell functions, from endocytosis to organelle division and fusion, and it plays a critical role in many physiological functions such as synaptic transmission and muscle contraction. Research of the past three decades has focused on understanding how dynamin works. In this review, we present the basis for an emerging consensus on how dynamin functions. Three properties of dynamin are strongly supported by experimental data: first, dynamin oligomerizes into a helical polymer; second, dynamin oligomer constricts in the presence of GTP; and third, dynamin catalyzes membrane fission upon GTP hydrolysis. We present the two current models for fission, essentially diverging in how GTP energy is spent. We further discuss how future research might solve the remaining open questions presently under discussion.

Expression of Bax Protein and Morphological Changes in the Myocardium in Experimental Acute Pressure Overload of the Left Ventricle

The expression of Bax protein, marker of intracellular pathway of apoptosis initiation, in viable left ventricular cardiomyocytes and morphological changes in the myocardium in acute pressure overload of the left ventricle were studied in experiment on male rabbits. The content of Bax protein in the cardiomyocyte cytoplasm decreased, this indicating that the mitochondrial pathway was not involved in the realization of the apoptotic program. This decrease was associated with manifest destructive changes in the left ventricular myocardium.

A hemi-fission intermediate links two mechanistically distinct stages of membrane fission

Fusion and fission drive all vesicular transport. Although topologically opposite, these reactions pass through the same hemi-fusion/fission intermediate^1,2, characterized by a ‘stalk’ in which only the inner monolayers of the two compartments have merged to form a localized non-bilayer connection^1-3. Formation of the hemi-fission intermediate requires energy input from proteins catalyzing membrane remodeling; however the relationship between protein conformational rearrangements and hemi-fusion/fission remains obscure. Here we analyzed how the GTPase cycle of dynamin, the prototypical membrane fission catalyst^4-6, is directly coupled to membrane remodeling. We used intra-molecular chemical cross-linking to stabilize dynamin in its GDP•AlF₄^--bound transition-state. In the absence of GTP this conformer produced stable hemi-fission, but failed to progress to complete fission, even in the presence of GTP. Further analysis revealed that the pleckstrin homology domain (PHD) locked in its membrane-inserted state facilitated hemi-fission. A second mode of dynamin activity, fueled by GTP hydrolysis, couples dynamin disassembly with cooperative diminishing of the PHD wedging, thus destabilizing the hemi-fission intermediate to complete fission. Molecular simulations corroborate the bimodal character of dynamin action and indicate radial and axial forces as dominant, although not independent drivers of hemi-fission and fission transformations, respectively. Mirrored in the fusion reaction^7-8, the force bimodality might constitute a general paradigm for leakage-free membrane remodeling.

Features of the Structure of the Circadian Rhythm of Blood Pressure and Heart Rate under Genetically Determined Hypertension in the Experiment

In SHR rats of different ages (22, 26, 30, 34, and 38 weeks), continuous 24-h telemetric monitoring of BP and HR was performed. The amplitude and power of oscillations of diastolic BP significantly decreased at the later stages of arterial hypertension (38 weeks), which was considered as a poor prognostic marker. We also observed a significant decrease in the mean daytime, nighttime, and maximum HR and mesor on weeks 30 and 34, but not on week 38, which can reflect triggering of the adaptive response followed by its exhaustion.

Effect of phosphocreatine and ethylmethylhydroxypyridine succinate on the expression of Bax and Bcl-2 proteins in left-ventricular cardiomyocytes of spontaneously hypertensive rats

We studied the effect of phosphocreatine and ethylmethylhydroxypyridine succinate on the expression of Bax and Bcl-2 proteins in left-ventricular cardiomyocytes of spontaneously hypertensive rats (SHR). Both drugs have no effect on the expression of Bcl-2, but significantly reduce the level of Bax protein (phosphocreatine produces more pronounced effect). These data attest to an important role of energy deficit and oxidative stress in the induction of cardiomyocyte apoptosis in genetically determined arterial hypertension.

[Analysis of the state of coronary arteries in patients with acute coronary syndrome in dependence on the integrin (1-3 gene polymorphism]

Aim of this study was to analyze the state of coronary arteries in patients with acute coronary syndrome according to polymorphism of integrin β-3 (ITGB3) gene. All patients were divided into 2 groups: carries and non-carries of PLA2 allele. Carriers of PLA2 allele compared with noncarriers had lesser grades of coronary artery stenoses but greater number of involved arteries. Carriers had more repetitive acute coronary events.

Geometric catalysis of membrane fission driven by flexible dynamin rings

Biological membrane fission requires protein-driven stress. The guanosine triphosphatase (GTPase) dynamin builds up membrane stress by polymerizing into a helical collar that constricts the neck of budding vesicles. How this curvature stress mediates nonleaky membrane remodeling is actively debated. Using lipid nanotubes as substrates to directly measure geometric intermediates of the fission pathway, we found that GTP hydrolysis limits dynamin polymerization into short, metastable collars that are optimal for fission. Collars as short as two rungs translated radial constriction to reversible hemifission via membrane wedging of the pleckstrin homology domains (PHDs) of dynamin. Modeling revealed that tilting of the PHDs to conform with membrane deformations creates the low-energy pathway for hemifission. This local coordination of dynamin and lipids suggests how membranes can be remodeled in cells.

[The influence of ITGB3 gene polymorphism on the frequency of arterial hypertension in patients with acute coronary syndrome]

PLA polymorphism of platelet integrin receptor, GpIIIa glycoprotein, (PLA polymorphism of the ITGB3 gene) is associated with the risk of myocardial infarction and CHD especially in young subjects. We analyzed ITGB3 gene polymorphism in patients with acute coronary insufficiency. It was shown that increased AP and altered blood lipid spectrum in the acute period of disease in carriers of the PLA allele (PLA1/PLA2 and PLA2/PLA2 genotypes) can be regarded as manifestations of stress reaction. The data obtained indicate that the PLA2 allele is a predictor of complications of acute coronary insufficiency. This observation is of importance for the choice of adequate therapy for the patients with this disorder.

Activities of some caspase cascade enzymes and myocardial contractility in experimental left ventricular focal ischemia

Focal left ventricular ischemia was modeled in male Chinchilla rabbits. Activities of caspase-3 and caspase-8 in the left and right ventricular myocardium and myocardial contractility were studied after 1, 3, and 5 days. Caspase-3 activity increased significantly in the left ventricular peri-infarction zone and right ventricular myocardium, while caspase-8 activity did not differ from the control. Left ventricular contractility decreased significantly and the hemodynamic load of the right ventricle sharply increased. These results attest to induction of the internal (mitochondrial) pathway of apoptosis in myocardial cells most likely caused by left ventricular hypoxia and right ventricular overload.

Staging of hemodynamic parameters during development of experimental arterial hypertension in rabbits

The study analyzed changes in parameters of the central and intracardiac hemodynamics during the development of experimental arterial hypertension, which were assessed as the adaptive in nature. The development of hypertension demonstrated staging of the adaptive processes. The development of the adaptive responses was characterized by changes in the magnitude and probabilistic distribution of the hemodynamic parameters.

[The effect of ETA receptor blockade on cardiomyocyte apoptosis and myocardial hypertrophy development in genetically hypertensive rats]

Cardiomyocyte apoptosis and hypertrophy have been studied in the left and right ventricular myocardium of spontaneously hypertensive rats without treatment and after 10-day administration of the ETA-receptor antagonist BQ-123. It is established that BQ-123 prevents the activation of cardiomyocyte apoptosis and significantly decreases the extent of hypertrophy development in the left ventricular myocardium, but does not influence the same mechanisms in the right ventricular myocardium.

Lipid polymorphisms and membrane shape

Morphological plasticity of biological membrane is critical for cellular life, as cells need to quickly rearrange their membranes. Yet, these rearrangements are constrained in two ways. First, membrane transformations may not lead to undesirable mixing of, or leakage from, the participating cellular compartments. Second, membrane systems should be metastable at large length scales, ensuring the correct function of the particular organelle and its turnover during cellular division. Lipids, through their ability to exist with many shapes (polymorphism), provide an adequate construction material for cellular membranes. They can self-assemble into shells that are very flexible, albeit hardly stretchable, which allows for their far-reaching morphological and topological behaviors. In this article, we will discuss the importance of lipid polymorphisms in the shaping of membranes and its role in controlling cellular membrane morphology.

Dynamin: functional design of a membrane fission catalyst

Dynamin, best studied for its role in clathrin-mediated endocytosis, is the prototypical member of a family of multidomain GTPases involved in fission and remodeling of multiple organelles. Recent studies have shown that dynamin alone can catalyze fission of membrane tubules and vesicle formation from planar lipid templates. Thus, dynamin appears to be a self-sufficient fission machine. Here we review the biochemical activities and structural features of dynamin required for fission activity. As all changes in membrane topology require energetically unfavorable rearrangements of the lipid bilayer, we discuss the interplay between dynamin and its lipid substrates that are critical to defining a nonleaky pathway to membrane fission. We propose a two-stage model for dynamin-catalyzed fission. In stage one, dynamin's mechanochemical activities induce localized curvature stress and position its lipid-interacting pleckstrin homology domains to create a catalytic center that, in stage two, guides lipid remodeling through hemifission intermediates to drive membrane fission.

[Assessment of caspase-3 activity in rabbit myocardial tissue during experimental hemodynamic overload of the left ventricle of the heart]

It's well known that chronic overload of the cardiac left ventricle is accompanied by an increase in the cardiomyocyte apoptosis rate. However direction and extent of programmed cell death changes under an acute overload of the left ventricle still requires detailed investigation. Caspase-3 activity has been investigated in myocardium of rabbits on the 1, 3 and 5 days after modeling of left ventricle hemodynamic overload caused by surgical narrrowing of the ascending aorta. Control group included intact animals. It was found that caspase-3 activity significantly increased in both ventricles on day 1; it increased more than twofold above controls on day 3; it began to decrease by day 5. On the basis of the obtained data it was concluded that: an acute hemodynamic overload of the left ventricle is a cause of apoptosis acceleration in the myocardial tissue of both cardiac ventricles during first days of the investigated process.

Reconstitution of proapoptotic BAK function in liposomes reveals a dual role for mitochondrial lipids in the BAK-driven membrane permeabilization process

BAK is a key effector of mitochondrial outer membrane permeabilization (MOMP) whose molecular mechanism of action remains to be fully dissected in intact cells, mainly due to the inherent complexity of the intracellular apoptotic machinery. Here we show that the core features of the BAK-driven MOMP pathway can be reproduced in a highly simplified in vitro system consisting of recombinant human BAK lacking the carboxyl-terminal 21 residues (BAKΔC) and tBID in combination with liposomes bearing an appropriate lipid environment. Using this minimalist reconstituted system we established that tBID suffices to trigger BAKΔC membrane insertion, oligomerization, and pore formation. Furthermore, we demonstrate that tBID-activated BAKΔC permeabilizes the membrane by forming structurally dynamic pores rather than a large proteinaceous channel of fixed size. We also identified two distinct roles played by mitochondrial lipids along the molecular pathway of BAKΔC-induced membrane permeabilization. First, using several independent approaches, we showed that cardiolipin directly interacts with BAKΔC, leading to a localized structural rearrangement in the protein that "primes" BAKΔC for interaction with tBID. Second, we provide evidence that selected curvature-inducing lipids present in mitochondrial membranes specifically modulate the energetic expenditure required to create the BAKΔC pore. Collectively, our results support the notion that BAK functions as a direct effector of MOMP akin to BAX and also adds significantly to the growing evidence indicating that mitochondrial membrane lipids are actively implicated in BCL-2 protein family function.

[Myocardial structural changes in acute left ventricular overload in an experiment]

Acute left ventricular (LV) overload was simulated in rabbits, by applying a metal spiral to narrow the ascending aorta by one third of its baseline diameter. A control group comprised intact animals. Studies were conducted 1, 3, and 5 days after surgery for simulation of LV overload in parallel series. In the first series of the experiment, semifine LV sections were examined by light microscopy and morphometry. The rate of cardiomyocyte (CMC) apoptosis was estimated calculating the free lying nuclei--the morphologically unchanged nuclei that were present in the extracellular space. In the second series, CMC apoptosis underwent immunohistochemical assessment, by running the TUNEL test. During its acute hemodynamic overload, the LV myocardium showed significant tissue destruction and a substantially lower number of viable myofibrils, and an increase in the count of apoptotically altered CMCs.

Contractile function of the heart and the state of some stages of lipid metabolism during acute diphtheritic intoxication

Acute diphtheritic intoxication was modeled in rabbits by intravenous administration of native diphtherin (0.3 minimal lethal dose per 1 kg body weight). The contractile function of the left and right ventricles (peak systolic pressure under conditions of basal hemodynamics and during 5-sec occlusion of the aorta and pulmonary artery, respectively) was estimated 1, 3 and 5 days after the start of the pathological process, the intensity of lipid peroxidation was evaluated by measuring the content of TBA- reactive products in the myocardium. Impairment of the contractile function of both ventricles was observed in the course of intoxication. The level of TBA-reactive products in the left ventricle significantly decreased on day 1, but then returned to normal. Thus, impairment of the contractile function of the left ventricle at the early stages of diphtheritic intoxication is not mediated by activation of lipid peroxidation in cardiomyocytes.

System analysis of changes in cardiovascular circulatory dynamics in experimental diphtheria in rabbit

Trivariate correlation analysis of hemodynamic indices of the cardiovascular system in rabbits with diphtheria showed that adaptation of this system to direct action of diphtherin can be visualized by analysis of trivariate correlation tightness for indices of intraventricular pressure in the left and right ventricles and indices of systemic blood pressure. Using empirical production functions for systemic blood pressure indices we found that the contribution of intraventricular pressure in the left and right ventricles on blood pressure values is changed in diphtheria compared to the control. Basing on entropy analysis we established that the regimen of control over values of working intraventricular pressure in both left and right ventricles in diphtheria is changed from quasidetermined to stochastic.

[Myocardial architectonic changes and cardiomyocytic apoptosis in the course of experimental diphtheria intoxication]

Diphtheria intoxication was simulated in rabbits, by intravenously injecting native diphtheria toxin in a dose of 0.3 MLD (minimal lethal dose) per kg body weight. Intact rabbits were used as a control. Following 1, 3, and 5 days of the onset on intoxication, the chests were opened under 2% rometar anesthesia and the hearts were extirpated, semithin left and right ventricular myocardial sections were prepared and light microscopic morphometry (at a magnification of x 1000) was carried out with video-assisted imaging. The rate of cardiomyocytic (CMC) apoptosis was determined, by calculating the free lying nuclei - the morphologically changed nuclei that were present in the extracellular space. Both ventricular CMC destruction characteristic of necrotic death was ascertained to significantly increase just on day 1 of the experiment and to further enhance during its course. By day 5, the rate of CMC apoptosis increased in both the left and right ventricles. Furthermore, there was an increasing reduction in myocardial collagen levels.

Domain-driven morphogenesis of cellular membranes

Cellular membrane systems delimit and organize the intracellular space. Most of the morphological rearrangements in cells involve the coordinated remodeling of the lipid bilayer, the core of the membranes. This process is generally thought to be initiated and coordinated by specialized protein machineries. Nevertheless, it has become increasingly evident that the most essential part of the geometric information and energy required for membrane remodeling is supplied via the cooperative and synergistic action of proteins and lipids, as cellular shapes are constructed using the intrinsic dynamics, plasticity and self-organizing capabilities provided by the lipid bilayer. Here, we analyze the essential role of proteo-lipid membrane domains in conducting and coordinating morphological remodeling in cells.

Cooperative elastic stresses, the hydrophobic effect, and lipid tilt in membrane remodeling

One of the fundamental properties of biological membranes is the high lateral integrity provided by the lipid bilayer, the structural core and the foundation of their barrier function. This tensile strength is due to the intrinsic properties of amphiphilic lipid molecules, which spontaneously self-assemble into a stable bilayer structure due to the hydrophobic effect. In the highly dynamic life of cellular membranes systems, however, this integrity has to be regularly compromised. One of the emerging puzzles is the mechanism of localized rupture of lipid monolayer, the formation of tiny hydrophobic patches and flipping of lipid tails between closely apposed monolayers. The energy cost of such processes is prohibitively high, unless cooperative deformations in a small membrane patch are carefully organized. Here we review the latest experimental and theoretical data on how such deformations can be conducted, specifically describing how elastic stresses yield tilting of lipids leading to cooperative restructuring of lipid monolayers. Proteins specializing in membrane remodeling assemble into closely packed circular complexes to arrange these deformations in time and space.

[The influence of GPIIIA gene polymorphism on the variability of standard electrocardiogram in patients with acute coronary syndrome]

The authors analyse effect of GPIIIA gene (PI a allele) polymorphism on the frequency of complicated coronary heart disease in patients with dyslipidemia and hypertensive disease. Specific features of ventricular repolarization (T-wave variability) in patients with acute coronary syndrome are described.

Analysis of central blood pressure during diphtheria intoxication in rabbits

Diphtheria intoxication was induced in rabbits by a single intravenous injection of native diphtheria toxin in dose of 0.3 MLD/kg, preliminary titrated on guinea pigs. Significant decrease in diastolic and systolic blood pressure and in intraventricular pressure in the left ventricle was established to take place during intoxication. Pulse wave propagation time was prolonged, likely due to prolongation of pressure wave, while the reflection wave appeared at the same time. Reduction of central blood pressure was concluded to result from changes in biomechanical characteristics of the left ventricle, and not to be associated with changes in elastic properties of the arterial wall.

Seasonal adaptation of the cardiovascular system in rabbits

Analysis of the effects of seasonal changes in the myocardium on variability of arterial and intraventricular pressure in both ventricles showed that the objects of homeostatic regulation were the values of these parameters and their probability distribution. The adaptation mechanisms are mainly visualized by the analysis of the characteristics of probability distribution of the parameters (asymmetry and excess coefficients).

On some pathogenetic and adaptation mechanisms of acute coronary disease

Acute coronary failure was modeled in rabbits by ligation of the descending left coronary artery at the interface of its middle and lower thirds. The function and morphology of left-ventricular and right-ventricular myocardium were studied on days 1, 3, and 5 of the pathological process. It was found that left-ventricular contractility decreased, while right-ventricular contractility increased. Deep morphological changes were observed in both ventricles: pronounced extracellular edema, increased content of collagen, decreased percentage of myofibrils. Hence, acute coronary failure involves both compartments of the heart, but the adaptive mechanisms more actively develop in the right ventricle.

GTPase cycle of dynamin is coupled to membrane squeeze and release, leading to spontaneous fission

The GTPase dynamin is critically involved in membrane fission during endocytosis. How does dynamin use the energy of GTP hydrolysis for membrane remodeling? By monitoring the ionic permeability through lipid nanotubes (NT), we found that dynamin was capable of squeezing NT to extremely small radii, depending on the NT lipid composition. However, long dynamin scaffolds did not produce fission: instead, fission followed GTPase-dependent cycles of assembly and disassembly of short dynamin scaffolds and involved a stochastic process dependent on the curvature stress imposed by dynamin. Fission happened spontaneously upon NT release from the scaffold, without leakage. Our calculations revealed that local narrowing of NT could induce cooperative lipid tilting, leading to self-merger of the inner monolayer of NT (hemifission), consistent with the absence of leakage. We propose that dynamin transmits GTP's energy to periodic assembling of a limited curvature scaffold that brings lipids to an unstable intermediate.

ER biogenesis: self-assembly of tubular topology by protein hairpins

The structure of the endoplasmic reticulum (ER) depends on members of the reticulon and DP1/Yop1p families. Two of these proteins are sufficient to form tubular membrane networks from pure phospholipid vesicles, thus revealing a new paradigm of ER morphogenesis.

Flexible scaffolding made of rigid BARs

Crescent-shaped BAR domains are generic actors in the creation of membrane curvature. In this issue, Frost et al. (2008) reveal how collective twisting of rigid F-BAR domains on a soft membrane surface may lead to different membrane curvatures.

Possible mechanisms for the regulation of neutrophil apoptosis during allergic inflammation

The neutrophil-mediated inflammatory response is regulated via activation of the apoptosis program, which decreases the degree of tissue alteration. In rabbits with allergic inflammation a significant negative correlation was revealed between the intensity of neutrophil apoptosis and blood interferon-gamma concentration.

Vesicle formation by self-assembly of membrane-bound matrix proteins into a fluidlike budding domain

The shape of enveloped viruses depends critically on an internal protein matrix, yet it remains unclear how the matrix proteins control the geometry of the envelope membrane. We found that matrix proteins purified from Newcastle disease virus adsorb on a phospholipid bilayer and condense into fluidlike domains that cause membrane deformation and budding of spherical vesicles, as seen by fluorescent and electron microscopy. Measurements of the electrical admittance of the membrane resolved the gradual growth and rapid closure of a bud followed by its separation to form a free vesicle. The vesicle size distribution, confined by intrinsic curvature of budding domains, but broadened by their merger, matched the virus size distribution. Thus, matrix proteins implement domain-driven mechanism of budding, which suffices to control the shape of these proteolipid vesicles.

Pathophysiological aspects of functional modulation of human peripheral blood neutrophils with propranolol

We studied the effect of beta-adrenoceptor antagonist propranolol on the regulation of spontaneous apoptosis in neutrophils, priming of lipopolysaccharide-treated neutrophils, and expression of neutrophil adhesion factors. The influence of propranolol on apoptosis, adhesion, and generation of oxygen radicals by neutrophils was shown to be an additional mechanism of the action of beta-adrenoceptor antagonists. This pathophysiological mechanism probably mediates the effect of neuroendocrine transmitters and explains the role of adrenergic antagonists in the pathogenesis and therapy of inflammation, cardiovascular diseases, and bronchial asthma.

[Ecological pathophysiology]

Ecological pathophysiology is characterized. Some mechanisms of development of diseases resultant from impaired natural relations between humans and environment are analysed.

Laser diffraction for standardization of heterogeneous pharmaceutical preparations

A new quantitative method for standardization of heterogeneous pharmaceutical preparations and their quality control during storage based on laser diffraction is proposed. A series of pharmaceutical dosage forms--suspensions, emulsions, tinctures, decoctions, cell preparations and others, are heterogeneous medicines. In some cases disperse phase can be formed during storage as a result of layering (L1/L2) or precipitation (S/L). Laser diffraction method proposed in this study can be used for standardization and quality control of medicines.

Blood Pressure and Contractile Function of Heart Ventricles at the Early Stages of Hypertonic Process

In rabbits, arterial hypertension was characterized by progressive elevation of systolic and diastolic blood pressure. The contractile function of the left ventricle augmented, but its potential working capacity decreased. Opposite changes were observed in the right ventricle. It was hypothesized that the compensatory mechanisms in the right ventricle during arterial hypertension are triggered at the very onset of the pathology, while in the left ventricle they develop later.