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PubMed1988

[Processing of the results of experiments on molecular DNA-DNA hybridization by using the Elektronika BZ-34 programmable microcomputer].

The programs for microcomputer "Electronika" BZ-34 permitting to compute the molecular DNA-DNA hybridization data with thermal stability duplex analysis have been developed. The proper different programs are offered for analysis of results obtained in different conditions of DNA hybridization. These programs are especially useful for accelerated calculation of large series of experimental data.

DNA↗
PubMed1988

Probing the mechanism of ATP hydrolysis on F-actin using vanadate and the structural analogs of phosphate BeF-3 and A1F-4.

The binding of phosphate analogs to F-ADP-actin filaments and their effect on the dynamics of the polymer have been investigated. Orthovanadate binds to F-actin with the same affinity as phosphate and, at low saturation levels, stabilizes the filament structure in a Pi-like fashion; at higher concentration, it promotes destabilization of the filament. BeF-3 and A1F-4 bind to F-ADP-actin in competition with Pi, with a stoichiometry of 1 mol/mol of F-actin subunit and an affinity 3 orders of magnitude higher than Pi (KD = 2 and 25 microM for BeF-3 and A1F-4, respectively). BeF-3 and A1F-4 mimic Pi in stabilizing F-actin and slow down the rate of actin dissociation from filaments 150-fold. Only 1% of F-ADP-BeF3 subunits provide extensive stabilization of the filament. A quantitative analysis of the stabilization by BeF-3 is proposed. While Pi appears in rapid equilibrium with F-ADP-actin, BeF-3 binds to and dissociates from F-ADP-actin at very slow rates (k+ = 4 M-1 S-1; k = 8.10(-6) S-1). In addition, although functionally similar to the reconstituted F-ADP-Pi species, F-ADP-BeF3 has a different conformation as indicated by the 17% quenching of pyrenyl fluorescence linked to BeF-3 binding. We suggest that BeF-3 may be a good analog of the transition state F-ADP-P* and that Pi release following cleavage of ATP on F-actin might be rate-limited by the isomerization of F-ADP-P*.

Actins↗
PubMed1985

Stability of the ankle joint. Analysis of the function and traumatology of the ankle ligaments.

The purpose of this study was to elucidate the function of the ligamentous structures of the ankle joint, the traumas in which they may rupture, and the types of instability caused by such ruptures. Most previous experimental investigations on the function of ankle ligaments have been performed on osteoligamentous preparations either by forcing a movement in the joint into more or less well-defined directions and observing the resulting injuries or else by cutting ligaments in various combinations and describing the resulting instability. As a rule, this has been done without inducing the increased mobility by a defined torque and without being able to demonstrate the instability continuously in all degrees of dorsi- or plantar flexion. On the basis of these previous studies, the anterior talofibular ligament appears to limit internal rotation, while its role in adduction of the talus has not been clarified. The calcaneofibular ligament per se does not seem to be a factor in adduction. True, there is not complete agreement in this respect, and a few authors have been able to rupture this ligament in isolation by forced adduction. The posterior talofibular ligament seems to restrict dorsiflexion, and perhaps it plays a role, in conjunction with the calcaneofibular ligament, in adduction when the ankle joint is in dorsiflexion. The anterior tibiofibular ligament, and the distal tibiofibular structures on the whole, are assumed to limit external rotation, but it has not been clarified whether they influence adduction and abduction in the ankle joint. Little has been reported about the individual structures which make up the deltoid ligament, as most authors have not distinguished them from each other. However, in combination with the anterior talofibular ligament, the tibiotalar ligament seems to limit the translatory forward gliding of the talus - the so-called anterior drawer sign - and together they presumably inhibit plantar flexion. It has not been possible to find any description of the function of the intermediate tibiotalar ligament, while the posterior tibiotalar ligament has been reported by one author to inhibit internal rotation. Judging by the literature, the function of the tibiocalcaneal ligament seems comprehensive, since it is reported to limit external rotation, dorsiflexion, as well as plantar flexion. The present investigations were divided into three phases: Phase 1 was concerned with elucidating the correlation of injuries to the lateral collateral ligaments to internal rotatory instability, talar tilt, and the anterior drawer sign.(ABSTRACT TRUNCATED AT 400 WORDS)

Ankle Joint↗
PubMed1986

[Nutrition and dyslipoproteinemias in schoolchildren aged 13 to 16].

In current studies of dyslipoproteinemia (DLP) development great emphasis is laid on the type of nutrition, its quantitative and qualitative characteristics, harmful habits, their formation in childhood and an attempt to influence them. However the problem of the start of stable DLP development and the role of dietary habits is yet to be solved. A random subsample of 169 school children aged 13 to 16 in the Krasnopresnensky District of Moscow was examined, among them 73 boys and 96 girls. High values of mean alimentary cholesterol, total and saturated fats and low mean amounts of consumed polyunsaturated fats were revealed. It could be inferred that the examined population was characterized by a high risk of the formation of atherogenic DLP stability. An analysis of the findings showed a considerable increase in the consumption of total and saturated fats as well as food rich in cholesterol in the group of children with stable DLP forms confirming the effect of the environmental factors including the alimentary ones, on processes of DLP formation in childhood. Further investigation of DLP in children should be conducted in the form of prospective studies otherwise design of activities in early prevention of atherogenic DLP seems impossible.

Adolescent↗
PubMed1974

Products of linoleic hydroperoxide-decomposing enzyme of alfalfa seed.

Alfalfa seeds and seedlings contain an enzyme that catalyzes a reaction with the 13- and 9-hydroperoxides of linoleic acid to form 13-hydroxy-10-oxo-trans-octadecenoic acid and 9-hydroxy-12-oxo-trans-10-octadecenoic acid, respectively. When commercial lipoxygenase is used to generate the hydroperoxides, the above acids appear in about 2:1 proportions, respectively. The products of the action of the enzyme on the hydroperoxides were stabilized for analysis by reduction with H(2) and LiAIH(4). Trimethylsilyl derivatives of reduced products were analyzed by combined gas-liquid chromatography-mass spectrometry. Specific deuterium labeling permitted definite location of the oxo functions. (18)O(2) labeling experiments showed that the oxygens of both the oxo and the hydroxyl functions were derived from the hydroperoxide. Retention of both oxygens suggests that the reaction proceeds through a cyclic epiperoxide followed by a ketohydroxy-forming rearrangement. No products of hydroperoxide isomerase were found in reactions catalyzed by the crude enzyme from alfalfa seeds.

Aluminum↗
PubMed1984

Promoter recognition and transcription initiation in E. coli.

Analysis of stability maps of sequences harbouring E. coli RNA polymerase promoters shows a characteristic splitting in homostable domains, despite the heterogeneity of the sequences. Correlation of stability maps with results from static approaches giving the contact points of the enzyme on promoters and functional studies employing abortive initiation assay allow us to propose a general mechanism for recognition of promoters and transcription start.

Base Composition↗
PubMed1984

5'-dephosphorylated 2',5'-adenylate trimer and its analogs. Inhibition of tobacco mosaic virus replication in tobacco mosaic virus-infected leaf discs, protoplasts, and intact tobacco plants.

The effect of the 5'-dephosphorylated 2',5'-adenylate trimer and its 2',5'-trimer core analogs on the inhibition of tobacco mosaic virus (TMV) replication was determined in tobacco leaf discs, protoplasts, and whole tobacco plants, using infectivity tests and enzyme-linked immunosorbent assays. A structure-activity-metabolic stability-toxicity analysis of the 2',5'-adenylate trimer core molecule in TMV-infected Nicotiana glutinosa was determined. Modification at either the 6-amino position of the adenylate residues (i.e. inosinate trimer core) or at the 2' terminus (i.e. A-A-ara-A or A-A-Tu) inhibited replication of TMV. Modification of the 3'-hydroxyl group of the adenylate residues to 3-deoxyribose (i.e. the 2',5'-cordycepin trimer core) inhibited TMV replication better than the 2',5'-adenylate trimer core molecule. With enzyme-linked immunosorbent assays, there was complete inhibition of TMV replication by 200 nM 2',5'-adenylate trimer core for 60 h and by 200 nM 2',5'-cordycepin trimer core for 96 h. The amount of 2',5'-oligonucleotides associated with the leaves was determined using 2',5'-[3H]cordycepin trimer core; 1 X 10(-12) mol/cm2 of plant leaves inhibited TMV replication by 99%. No 2',5'-phosphodiesterase activity was detected in TMV-infected and noninfected leaf extracts. Therefore, the 2',5'-trimer cores were potent inhibitors of TMV replication at nanomolar concentrations, i.e. at 1000-fold lower concentration than that required in mammalian systems.

Adenosine↗
PubMed1995

[Estrogen replacement in postmenopause, blood coagulation and fibrinolysis: comparison of a new kind of transdermal estradiol treatment with oral therapy with conjugated estrogens].

Estrogen replacement therapy (ERT) appears to markedly reduce the risk of cardiovascular disease in postmenopausal women. There is evidence that estrogen effects on blood coagulation and fibrinolysis are important mediators of this beneficial effect. It is the acute phase reactants such as factor VII (F VII), von Willebrand factor (vWF) and fibrinogen (Fbg) as well as the main inhibitor of the fibrinolytic system, the plasminogen activator inhibitor (PAI 1), which have been shown to be associated with a particular predisposition or poor prognosis of cardiovascular disease. Additionally, the analysis of stabile reaction products of the coagulation cascade allows for an assessment of the loss of endothelial anticoagulant properties, i.e. endothelial injury. We compared the effects of oral versus transdermal ERT on these key parameters of the hemostatic system. 42 postmenopausal women were randomly assigned to receive either a novel transdermal system releasing 50 micrograms 17-beta-estradiol/24 hours or oral therapy with 0.6 mg conjugated estrogens combined with cyclic medrogestone 5 mg on day 11-21 for three treatment cycles. The study was performed according to the criteria of good clinical practise. We observed no adverse effects on the hemostatic system. Particularly, no increase of coagulatory reaction products, i.e. activity was found. Differences between groups were seen with regard to the extent of favourable effects: While the continuous transdermal ERT significantly reduced factor VII activity, oral ERT had no effect. However, oral ERT significantly reduced PAI 1 concentration by 40% suggesting an improved fibrinolytic capacity.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Cutaneous↗
PubMed1998

Stability of finite difference deconvolution II: simulation studies.

Theoretical analysis of the stability of finite difference deconvolution (FDD) indicates that if the cumulative amount function is used to characterize the drug input the method is stable for any sampling schedule for an intravenous unit impulse response function. The analysis also indicates that the method is stable for an oral unit impulse response only for well designed sampling schedules. This article confirms these results through numerical simulation experiments. It is shown that the assumption that the unit impulse response is error-free has an influence on the performance of FDD which is generally of no practical significance, except possibly for the first few points estimated. It is also shown that there is no significant interaction between the statistical error due to data noise and the deterministic algorithm error. The major source of error in practice is likely to be the data noise in the input response function. The simulations confirm that, with the estimated cumulative amount function as the quantity estimated and, with a well designed sampling schedule for the case of an oral unit impulse response, FDD is in practice an accurate and stable method with acceptable precision under a typical error disturbance.

Algorithms↗
PubMed2001

Lumbar lateral interbody cage with plate augmentation: in vitro biomechanical analysis.

Many studies have concluded that stand alone cages provide limited stabilization to the spine, and this primary stabilization decreases postoperatively due to various factors. A supplemental fixation may, therefore, be needed to improve the stability. Extensive biomechanical analysis was performed in the present study to further evaluate the stabilization achieved by a laterally inserted cage and the role of an anterior lateral supplemental fixation. Eight human cadaver functional spinal units were subjected sequentially to four different test conditions: (1) intact, (2) instrumented laterally with a long cylindrical threaded cage, (3) the same cage supplemented with a lateral fixation plate, the plate being firmly connected to the cage, and (4) removal of the connection between the plate and the cage. Pure moments were applied to each specimen in a quasi static manner, ranging from -7 Nm to 7 Nm in flexion/extension, lateral bending and axial rotation. Three-dimensional segmental motions were simultaneously recorded under each loading condition. Statistical analysis was carried out on the motion parameters, including the range of motion (ROM) and the neutral zone (NZ). Inter-group comparisons were made using the Friedman test and the Wilcoxon test. The results showed that the stand alone lateral cage provided stabilization by increasing segmental stiffness above that of the intact spine. The stiffness increase ratios were: 1.6 in flexion/extension ( P=0.07), 1.3 in lateral bending ( P=0.4) and 1.0 in axial rotation ( P=0.67). A supplemental plate provided significant reinforcement of the stabilization. The stiffness increase ratios relative to the intact spine were: 3.1 in flexion/extension ( P=0.012), 5.0 in lateral bending ( P=0.012) and 2.3 in axial rotation ( P=0.012). After removal of the connection between the cage and the plate, the stiffness ratios were: 2.7 in flexion/extension ( P=0.027), 4.6 in lateral bending ( P=0.027) and 2.1 in axial rotation ( P=0.027). Globally, the cage alone increased the segmental stiffness above that of the intact spine by a factor of 1.1 ( P=0.39), with the supplemental plate, segmental stiffness increased by a factor of 3.1 ( P<0.01), and the unconnected cage/plate increased stiffness by a factor of 3.0 ( P=0.02). Supplementation of the lateral cage with an anterolateral plate was thus shown to provide significant additional stabilization in all directions, which may potentially compensate for the postoperative decrease in segmental stability.

Adult↗
PubMed1999

Antibody analysis of the localisation, expression and stability of HlyD, the MFP component of the E. coli haemolysin translocator.

HlyD has a single transmembrane domain (residues 59-80) and a large periplasmic domain, and is essential for the secretion of haemolysin from Escherichia coli. Using an antibody raised against HlyD, the protein was localised to the cell envelope by immunofluorescence and to the cytoplasmic membrane by sucrose gradient analysis. We have examined the stability of this protein in the presence and absence of other putative components of the translocator, HlyB and TolC. HlyD is normally highly stable but in the absence of TolC, the steady-state level of HlyD is greatly reduced and the protein has a half-life at 37 degrees C of 36 min. In the absence of HlyB, HlyD is also unstable and specific degradation products are detected, which co-fractionate with the inner membrane, indicating in this case limited cleavage at specific sites. However, the effect of removing both HlyB and TolC is not additive. On the contrary, in the absence of both HlyB and TolC the half-life of HlyD is approximately 110 min. This result shows that in the presence of HlyB removal of TolC renders HlyD more unstable than it is in the absence of both HlyB and TolC. This suggests that the presence of HlyB induces a structural change in HlyD. In addition, HlyB itself appears to be less stable in the absence of HlyD. These results are consistent with an interaction between HlyD/TolC and HlyB/HlyD. A derivative of HlyD, HlyD22, lacking the 40 N-terminal residues of HlyD assembles into the inner membrane displaying the same stability with and without HlyB as wild type HlyD does. This N-terminal region therefore appears to play no role in stable localisation but is involved in secretion, since HlyD22 is completely secretion defective. Modification of the C-terminus on the other hand completely destabilised the molecule and HlyD was not detectable in the envelope. Secretion of active haemolysin is limited to a brief period during mid to late exponential phase. In contrast, HlyD is apparently synthesised constitutively throughout the growth phase, demonstrating that the production of this component of the translocator is not the limiting factor for growth phase-dependent secretion.

Antibodies, Monoclonal↗
PubMed2002

Quantitative analysis of factors affecting intraoperative precision and stability of optoelectronic and electromagnetic tracking systems.

This study aims to provide a quantitative analysis of the factors affecting the actual precision and stability of optoelectronic and electromagnetic tracking systems in computer-aided surgery under real clinical/intraoperative conditions. A "phantom-skull" with five precisely determined reference distances between marker spheres is used for all measurements. Three optoelectronic and one electromagnetic tracking systems are included in this study. The experimental design is divided into three parts: (1) evaluation of serial- and multislice-CT (computed tomography) images of the phantom-skull for the precision of distance measurements by means of navigation software without a digitizer, (2) digitizer measurements under realistic intraoperative conditions with the factors OR-lamp (radiating into the field of view of the digitizer) or/and "handling with ferromagnetic surgical instruments" (in the field of view of the digitizer) and (3) "point-measurements" to analyze the influence of changes in the angle of inclination of the stylus axis. Deviations between reference distances and measured values are statistically investigated by means of analysis of variance. Computerized measurements of distances based on serial-CT data were more precise than based on multislice-CT data. All tracking systems included in this study proved to be considerably less precise under realistic OR conditions when compared to the technical specifications in the manuals of the systems. Changes in the angle of inclination of the stylus axis resulted in deviations of up to 3.40 mm (mean deviations for all systems ranging from 0.49 to 1.42 mm, variances ranging from 0.09 to 1.44 mm), indicating a strong need for improvements of stylus design. The electromagnetic tracking system investigated in this study was not significantly affected by small ferromagnetic surgical instruments.

Biophysical Phenomena↗
PubMed2002

The elusive atomic rationale for DNA base pair stability.

A systematic analysis of the electrostatic interaction between 27 natural DNA base pairs was carried out, based on ab initio correlated wave functions and the topology of the electron density. Using high rank multipole moments we show that the atomic partitioning of the interaction energy contains many substantial contributions between distant atoms. Profiles of cumulative energy versus internuclear distance show large fluctuations and provide an electrostatic fingerprint of the partitioning of interaction energy in a complex. A quantified comparison between each pair of energy profiles, one for each base pair, makes clear that there is no correlation between the total base pair interaction energy and the shape of the profile. In other words, base pairs with similar interaction energy are not stable for the same reasons in terms of atomic partitioning. In summary, simple rules to rationalize the pattern of energetic stability of naturally occurring base pairs in terms of subsets of atoms are elusive. Our work cautions against inappropriate use of Jorgensen's secondary interaction hypothesis.

Base Pairing↗
PubMed2000

Thermal stability of the plasma membrane calcium pump. Quantitative analysis of its dependence on lipid-protein interactions.

Thermal stability of plasma membrane Ca(2+) pump was systematically studied in three micellar systems of different composition, and related with the interactions amphiphile-protein measured by fluorescence resonance energy transfer. Thermal denaturation was characterized as an irreversible process that is well described by a first order kinetic with an activation energy of 222 +/- 12 kJ/mol in the range 33-45 degrees C. Upon increasing the mole fraction of phospholipid in the mixed micelles where the Ca(2+) pump was reconstituted, the kinetic coefficient for the inactivation process diminished until it reached a constant value, different for each phospholipid species. We propose a model in which thermal stability of the pump depends on the composition of the amphiphile monolayer directly in contact with the transmembrane protein surface. Application of this model shows that the maximal pump stability is attained when 80% of this surface is covered by phospholipids. This analysis provides an indirect measure of the relative affinity phospholipid/detergent for the hydrophobic transmembrane surface of the protein (K(LD)) showing that those phospholipids with higher affinity provide greater stability to the Ca(2+) pump. We developed a method for directly measure K(LD) by using fluorescence resonance energy transfer from the membrane protein tryptophan residues to a pyrene-labeled phospholipid. K(LD) values obtained by this procedure agree with those obtained from the model, providing a strong evidence to support its validity.

Calcium-Transporting ATPases↗
PubMed2004

Differential transition-state stabilization in enzyme catalysis: quantum chemical analysis of interactions in the chorismate mutase reaction and prediction of the optimal catalytic field.

Chorismate mutase is a key model system in the development of theories of enzyme catalysis. To analyze the physical nature of catalytic interactions within the enzyme active site and to estimate the stabilization of the transition state (TS) relative to the substrate (differential transition state stabilization, DTSS), we have carried out nonempirical variation-perturbation analysis of the electrostatic, exchange, delocalization, and correlation interactions of the enzyme-bound substrate and transition-state structures derived from ab initio QM/MM modeling of Bacillus subtilis chorismate mutase. Significant TS stabilization by approximately -23 kcal/mol [MP2/6-31G(d)] relative to the bound substrate is in agreement with that of previous QM/MM modeling and contrasts with suggestions that catalysis by this enzyme arises purely from conformational selection effects. The most important contributions to DTSS come from the residues, Arg90, Arg7, Glu78, a crystallographic water molecule, Arg116, and Arg63, and are dominated by electrostatic effects. Analysis of the differential electrostatic potential of the TS and substrate allows calculation of the catalytic field, predicting the optimal location of charged groups to achieve maximal DTSS. Comparison with the active site of the enzyme from those of several species shows that the positions of charged active site residues correspond closely to the optimal catalytic field, showing that the enzyme has evolved specifically to stabilize the TS relative to the substrate.

Catalysis↗
PubMed1991

Sex differences in the course of personality development: a meta-analysis.

Size and stability of sex differences in personality growth throughout adolescence and adulthood are examined. Studies using the Washington University Sentence Completion Test of ego development served as the primary source data. Sixty-five studies (encompassing more than 9,000 Ss) generated 113 independent effect sizes. Sex differences in ego development were moderately large among junior and senior high-school students (female advantage), declined significantly among college-age adults, and disappeared entirely among older men and women. Sex differences were relatively stable during early and middle adolescence. The greater maturity displayed by adolescent girls is not an artifact of superior verbal abilities. Sex differences in ego development were more than twice the magnitude of differences in vocabulary skills (Hyde & Linn, 1988). The present findings, together with findings from reviews of sex differences in moral judgment, aggression, and empathy, suggest that adolescent girls achieve developmental milestones earlier than boys, a difference that declines with age.

Adolescent↗
PubMed1990

Orthotic stabilization of thoracolumbar injuries. A biomechanical analysis of the Jewett hyperextension orthosis.

Spinal orthoses have been traditionally used in the management of thoracolumbar injuries treated with or without surgical stabilization. However, the orthotic treatment modality in the management of spinal fractures remains subjective since few objective data are available on the effectiveness of orthoses in stabilizing injured segments. This study used a finite element model of the spine to evaluate the effectiveness of a hyperextension orthosis in controlling the progression of deformities at the injury site under gravitational and flexion loads. Two types of injuries were simulated: a single-level injury at T12-L1 and a two-level injury at T11-T12-L1 segments. An injury of increasing severity was simulated by progressively reducing the bending stiffness of the affected segments relative to the normal values in flexion-extension mode. The interaction of a three-point hyperextension orthosis with the spine was simulated using experimentally measured stiffness properties of the orthosis. The authors' results suggest that in single-level injuries that cause up to 50% loss of segmental stiffness, the orthosis can restore normal resistance to deformity at the injured segments, under gravitational as well as large flexion loads. In loss of stiffness between 50% and 85% of normal, such as severe two-column disruptions, the orthosis can restore resistance to deformity under restricted patient activity level in the brace (low-flexion moment). Beyond 85% loss of segmental stiffness, such as three-column injuries, the orthosis alone appears to be ineffective in preventing progression of deformity.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomechanical Phenomena↗