The gaussian curvature elastic modulus of N-monomethylated dioleoylphosphatidylethanolamine: relevance to membrane fusion and lipid phase behavior

The energy of intermediates in fusion of phospholipid bilayers is sensitive to kappa(m), the saddle splay (Gaussian curvature) elastic modulus of the lipid monolayers. The value kappa(m) is also important in understanding the stability of inverted cubic (Q(II)) and rhombohedral (R) phases relative to the lamellar (L(alpha)) and inverted hexagonal (H(II)) phases in phospholipids. However, kappa(m) cannot be measured directly. It was previously measured by observing changes in Q(II) phase lattice dimensions as a function of water content. Here we use observations of the phase behavior of N-mono-methylated dioleoylphosphatidylethanolamine (DOPE-Me) to determine kappa(m). At the temperature of the L(alpha)/Q(II) phase transition, T(Q), the partial energies of the two phases are equal, and we can express kappa(m) in terms of known lipid monolayer parameters: the spontaneous curvature of DOPE-Me, the monolayer bending modulus kappa(m), and the distance of the monolayer neutral surface from the bilayer midplane, delta. The calculated ratio kappa(m)/kappa(m) is -0.83 +/- 0.08 at T(Q) approximately 55 degrees C. The uncertainty is due primarily to uncertainty in the value of delta for the L(alpha) phase. This value of kappa(m)/kappa(m) is in accord with theoretical expectations, including recent estimates of the value required to rationalize observations of rhombohedral (R) phase stability in phospholipids. The value kappa(m) substantially affects the free energy of formation of fusion intermediates: more energy (tens of k(B)T) is required to form stalks and fusion pores (ILAs) than estimated solely on the basis of the bending elastic energy. In particular, ILAs are much higher in energy than previously estimated. This rationalizes the action of fusion-catalyzing proteins in stabilizing nascent fusion pores in biomembranes; a function inferred from recent experiments in viral systems. These results change predictions of earlier work on ILA and Q(II) phase stability and L(alpha)/Q(II) phase transition mechanisms. To our knowledge, this is the first determination of the saddle splay (Gaussian) modulus in a lipid system consisting only of phospholipids.     

Experimental evidence suggesting that nitric oxide diffuses from tissue into blood but not from blood into tissue

The aim of this study was to evaluate in vivo whether nitric oxide (NO) is able to diffuse from blood into tissues and vice versa from tissues into blood. We used an in vivo model of intestinal ischemia (superior mesenteric artery occlusion) selectively increasing NO levels in intestinal tissue and an infusion of L-arginine selectively increasing NO levels in blood. In this model we followed formation of nitrosyl complexes of hemoglobin (Hb-NO) in blood and nitrosyl-diethyldithiocarbamate-iron complexes (DETC--Fe--NO) in ischemic intestine and normoxic tissues by means of electron paramagnetic resonance spectroscopy. NO trapping by DETC--Fe in the tissues resulted in a reduction of Hb--NO levels in blood accompanied by the formation of water-insoluble DETC--Fe-NO complexes in ischemic intestine and normoxic tissues both during ischemia and during reperfusion. Administration of L-arginine increased NO levels in blood but neither in ischemic intestine nor in normoxic tissue. Our data suggest that NO released in blood from endothelial cells does not diffuse into tissue. In contrast, NO formed in tissue diffuses into blood. The latter indicates that NO formed in tissues may exert its biological activities systematically.     

The analytical characteristics of the dynamics of interneuronal functional connections during conditioned-reflex activity]

The dynamics of functional relations between neurons was studied in the frontal cortex of dogs performing reversal conditioning task. To reveal the functionally relevant relationships between the temporal patterns of correlated firing and behavioral events, we developed an original processing technique. The technique included the following procedures: a) isolation of the "coupled spikes" (CS) from simultaneously recorded impulse trains: b) search for the temporal patterns of correlated firings and their classification by clustering single trials with similar temporal distribution of CS; c) assessment of behavioral significance of the identified patterns by evaluation of the probabilities of coincidence of behavioral events and different CS patterns. Significant correlations between impulse trains were revealed in 38 neuronal pairs of 456 analyzed. The effects of change in behavioral context on the CS dynamics during the task performance were found in 87% of neuronal pairs with correlated activity. In 17 pairs the behavioral conditions were identified, under which potentially connected neurons fired independently during all the periods of the behavioral task. The potentialities of the advanced processing technique are discussed. We suggest that this analysis can provide useful information about the temporal distribution of correlated firings under conditions of nonstereotyped behavior, when an animal reacts in the dynamically organized experimental context.     

Genetic and environmental influence on the asymmetry of dermatoglyphic traits

Fluctuating asymmetry (FA) is defined as random deviations from bilateral symmetry of the body. Thus, its magnitude is often used to evaluate developmental homeostasis. In this study we evaluate the following hypotheses: 1) FA of dermatoglyphic traits has a significant genetic component; 2) prenatal maternal environment (PME) has a significant effect on the FA of dermatoglyphic traits in developmentally healthy individuals; and 3) genetic or environmental factors affect FA on organismal or systemic levels. Therefore, their effect is better seen in composite scores of FA rather than in FA indices for single traits. We analyzed 15 dermatoglyphic traits from 140 pairs of monozygous twins, 120 pairs of dizygous twins, and 106 pairs of mothers and daughters. All individuals were developmentally healthy. The influence of genetic and environmental factors on FA was evaluated by analysis of variance and regression analysis. For a majority of the traits in our study, FA showed significant but weak heritabilities, with values falling within the 0.20-0.35 range. None of the traits taken separately demonstrated the effect of PME on FA to be significantly greater than zero. The composite score of FA tended to have greater heritability values than individual traits. One of them, obtained in principal components analysis, showed a significant PME effect, supporting the hypothesis that FA is a systemic property.     

Association between relative bone mass and vitamin D receptor gene polymorphism

The paper reports a search for association between the relative bone tissue mass (percent of total body mass, %BT) and FokI (rs10735810), BsmI (rs1544410), and TaqαI (rs731236) vitamin D receptor gene polymorphisms. The group of apparently healthy young adults born in the central and northern regions of European Russia included 61 men and 60 women aged 16–23 years. No statistical association was detected between the FokI polymorphism and %BT. The carriers of the BsmI *A allele exhibited a higher %BT (p = 0.0172) compared to the subjects bearing the BsmI *G*G allele. The subjects with the *C*C TaqαI genotype were characterized by increased %BT compared to the carriers of the *T allele (p = 0.0018). The data are in good correspondence with the results obtained in the studies involving apparently healthy representatives of Central European and Northern European populations of the corresponding age.     

Homozygous Defects in LMNA, Encoding Lamin A/C Nuclear-Envelope Proteins, Cause Autosomal Recessive Axonal Neuropathy in Human (Charcot-Marie-Tooth Disorder Type 2) and Mouse

The Charcot-Marie-Tooth (CMT) disorders comprise a group of clinically and genetically heterogeneous hereditary motor and sensory neuropathies, which are mainly characterized by muscle weakness and wasting, foot deformities, and electrophysiological, as well as histological, changes. A subtype, CMT2, is defined by a slight or absent reduction of nerve-conduction velocities together with the loss of large myelinated fibers and axonal degeneration. CMT2 phenotypes are also characterized by a large genetic heterogeneity, although only two genes---NF-L and KIF1Bbeta---have been identified to date. Homozygosity mapping in inbred Algerian families with autosomal recessive CMT2 (AR-CMT2) provided evidence of linkage to chromosome 1q21.2-q21.3 in two families (Zmax=4.14). All patients shared a common homozygous ancestral haplotype that was suggestive of a founder mutation as the cause of the phenotype. A unique homozygous mutation in LMNA (which encodes lamin A/C, a component of the nuclear envelope) was identified in all affected members and in additional patients with CMT2 from a third, unrelated family. Ultrastructural exploration of sciatic nerves of LMNA null (i.e., -/-) mice was performed and revealed a strong reduction of axon density, axonal enlargement, and the presence of nonmyelinated axons, all of which were highly similar to the phenotypes of human peripheral axonopathies. The finding of site-specific amino acid substitutions in limb-girdle muscular dystrophy type 1B, autosomal dominant Emery-Dreifuss muscular dystrophy, dilated cardiomyopathy type 1A, autosomal dominant partial lipodystrophy, and, now, AR-CMT2 suggests the existence of distinct functional domains in lamin A/C that are essential for the maintenance and integrity of different cell lineages. To our knowledge, this report constitutes the first evidence of the recessive inheritance of a mutation that causes CMT2; additionally, we suggest that mutations in LMNA may also be the cause of the genetically overlapping disorder CMT2B1.     

Influence of the activation of the immune system cells on the parameters of lipid metabolism in macrophages

The influence of tumor necrosis factor a (TNF-alpha) and media, conditioned by activated macrophages and lymphocytes and containing a complex of biologically active compounds (including cytokines), on the parameters of lipid metabolism in macrophages was studied. The addition of recombinant TNF-alpha and immunocompetent cell-conditioned media to mouse peritoneal macrophages culture stimulated labelled oleate incorporation into cholesterol esters and triglycerides, as well as labelled glycerine incorporation into cholesterol esters, but inhibited labelled cholesterol incorporation into cholesterol esters. One of the mechanisms of the influence of activated immunocompetent cells on cholesterol metabolism in macrophages was, supposedly, the stimulation of sphigmomyelinase activity by a complex of anti-inflammatory cytokines produced by these cells on their activation.