Low frequency electromagnetic fields and the Belousov-Zhabotinsky reaction

Low frequency magnetic fields can influence biochemical reactions and consequently physiological rhythms and oscillations. To test this for a model reaction we used the chemical Belousov-Zhabotinsky (BZ) reaction, which is one of the simplest chemical oscillators. The oscillation frequency of the reaction was tracked optically by the absorption of blue light. Field treatment was carried out at room temperature in the middle of two Helmholtz coils. After starting the reaction, for 5 min the oscillations were monitored as control measurement, then during the next 10 min monitoring was with a magnetic field switched on, followed by a period of 5 min with the field switched off. A variety of exposure conditions have been tested: the frequency was varied between 5 and 1000 Hz, the field strength was varied up to 2.7 mT, different pulse shapes were used, the influence of the exposure temperature was tested, and the influence of the optimum exposure conditions (static magnetic field and the frequency of the dynamic field) as predicted by the ion parametric resonance (IPR) model has been measured. In conclusion, in no case any statistical significant influence of the magnetic treatment on the oscillation frequency of the BZ reaction could be detected (P > .05, t-test).     

The Influence of a gradient static magnetic field on an unstirred Belousov-Zhabotinsky reaction

It is believed that static magnetic fields (SMF) cannot affect the pattern formation of the Belousov-Zhabotinsky (BZ) reaction, which has been frequently studied as a simplified experimental model of a nonequilibrium open system, because SMF produces no induced current and the magnetic force of SMF far below 1 T is too low to expect the effects on electrons in the BZ reaction. In the present study, we examined whether the velocity of chemical waves in the unstirred BZ reaction can be affected by a moderate-intensity SMF exposure depending on the spatial magnetic gradient. The SMF was generated by a parallel pair of attracting rectangular NdFeB magnets positioned opposite each other. The respective maximum values of magnetic flux density (B(max)), magnetic flux gradient (G(max)), and the magnetic force product of the magnetic flux density its gradient (a magnetic force parameter) were 206 mT, 37 mT/mm, and 3,000 mT(2)/mm. The ferroin-catalyzed BZ medium was exposed to the SMF for up to 16 min at 25 degrees C. The experiments demonstrated that the wave velocity was significantly accelerated primarily by the magnetic gradient. The propagation of the fastest wave front indicated a sigmoid increase along the peak magnetic gradient line, but not along the peak magnetic force product line. The underlying mechanisms of the SMF effects on the anomalous wave propagation could be attributed primarily to the increased concentration gradient of the paramagnetic iron ion complexes at the chemical wave fronts induced by the magnetic gradient.     

Simplified method for isolation of white cells from whole blood suitable for direct polymerase chain reaction

A simple method for isolating mononuclear cells from whole blood is described. The procedure utilizes phytohemagglutinin to agglutinate the erythrocytes, separating white cells from whole blood in a very brief handling time. The isolated cells are readily subjected to DNA isolation simply by boiling, and the released DNA can be directly employed for the polymerase chain reaction analysis. The efficiency of this method is similar to other conventional methods, but less costly and less time-consuming. This method is particularly useful in analyzing DNA samples from the peripheral blood cells when the simplicity and low cost of the assay are preferable.     

Simplified dynamics model of planar two-joint arm movements

A theoretical framework is presented that describes a way in which the inverse dynamics equations of motion of planar two-joint arm movements (EX-model) are reformulated in a simple form. A single point was assumed to define both the wrist and elbow joint centers, and thus the motion of two points in extrinsic space was represented by second-order differential equations to provide the variables in the reformulation (RE-) model. Through an analytical processes, it was shown that the RE-model for reproducing the shoulder joint torque consists of the linearly scaled moment per unit mass responsible for accelerating the wrist and elbow points about the shoulder joint, while that for reproducing the elbow joint torque consists of the linearly scaled moment per unit mass responsible for accelerating the wrist point about the elbow. The scaling factors for variables in the RE-model were based solely on the values for segment lengths, while in the EX-model the inertial parameter data for the segments are involved in its representation. The inertial parameter data of six-arm specimens from the cadaver experiment of Chandler et al. (1975, AMRL Technical Report, Wright-Patterson Air Force Base, OH) were used to develop and verify the numeric solutions of the RE-model. The adequacy of the model varied somewhat among subjects, but minor changes of the physical parameters of the arm segments enabled perfect reformulation, regardless of the specimens. The potential abilities of the RE-model to deal with the complexities in motor control with more simple control schemes are discussed.     

Simplified neuron model as a principal component analyzer

A simple linear neuron model with constrained Hebbian-type synaptic modification is analyzed and a new class of unconstrained learning rules is derived. It is shown that the model neuron tends to extract the principal component from a stationary input vector sequence.     

On architectures of circuits implemented in simulated Belousov-Zhabotinsky droplets

When lipid vesicles filled with Belousov-Zhabotinsky (BZ) excitable chemical medium are packed in tight assembles, waves of excitation may travel between the vesicles. When several waves meet in a vesicle some fragments may deflect, others can annihilate or continue their travel undisturbed. By interpreting waves as Boolean values we can construct logical gates and assemble them in large circuits. In numerical modelling we show two architectures of one-bit half-adders implemented in BZ-vesicles.     

A reaction–diffusion model for long bones growth

Bone development is characterized by differentiation and growth of chondrocytes from the proliferation zone to the hypertrophying one. These two cellular processes are controlled by a complex signalling regulatory loop between different biochemical signals, whose production depends on the current cell density, constituting a coupled cell-chemical system. In this work, a mathematical model of the process of early bone growth is presented, extending and generalizing other earlier approaches on the same topic. A reaction–diffusion regulatory loop between two chemical factors: parathyroid hormone-related peptide (PTHrP) and Indian hedgehog (Ihh) is hypothesized, where PTHrP is activated by Ihh and inhibits Ihh production. Chondrocytes proliferation and hypertrophy are described by means of population equations being both regulated by the PTHrP and Ihh concentrations. In the initial stage of bone growth, these two cellular proceses are considered to be directionally dependent, modelling the well known column cell formation, characteristic of endochondral ossification. This coupled set of equations is solved within a finite element framework, getting an estimation of the chondrocytes spatial distribution, growth of the diaphysis and formation of the epiphysis of a long bone. The results obtained are qualitatively similar to the actual physiological ones and quantitatively close to some available experimental data. Finally, this extended approach allows finding important relations between the model parameters to get stability of the physiological process and getting additional insight on the spatial and directional distribution of cells and paracrine factors.     

Simplified Microassay for Pullulan Synthesis

A simple radiometric microassay for extracellular polysaccharide elaboration by yeast-like cells of Aureobasidium pullulans was developed, based upon a procedure originally described by Catley (FEBS Lett. 20:174-176, 1972). Incorporation of [¹⁴C]glucose into pullulan was linear with respect to time and cell dose. The pH and temperature optima for elaboration were 5.3 and 30°C, respectively. Polysaccharide elaboration declined linearly with culture age.     

Simplified Radioimmunoassay for Diagnostic Serology

A simplified, indirect radioimmunoassay is described for Escherichia coli, vaccinia virus, and herpesvirus. The antigens were affixed to glass cover slips; thus both the primary and secondary reactions take place on the cover slips, and the unbound antiserum is easily separated from the bound antiserum by rinsing. Rabbit or human immune sera were reacted with the antigens, and the primary immune complex was quantitated by a secondary reaction with (125)I-indicator globulin (anti-rabbit or anti-human). A direct relationship between the antiserum concentration and the (125)I absorption was established. Variations in titers were detectable, and the titers were comparable to complement fixation titers. Homologous and heterologous reactions were distinguishable. The method affords an objective, quantitative, and qualitative evaluation of antibody, and results are reproducible.     

Simplified nomenclature for compound flaps

The unique niche for compound flaps is their potential role for the repair of massive defects that demands the simultaneous restoration of multiple, missing tissue types. These complex flaps can be sorted into two major classes, and their subtypes on the basis of their means of vascularization are described. (1) Solitary vascularization, the composite flap: "multiple tissue components with a single vascular supply and dependent parts." (2) Combined flaps: (a) Siamese flaps: "multiple flap territories, dependent due to some common physical junction, yet each retaining their independent vascular supply"; (b) conjoint flaps: "multiple independent flaps, each with an independent vascular supply, but linked by a common indigenous source vessel"; and (c) sequential flaps: "multiple independent flaps, each with an independent vascular supply, and artificially linked by a microanastomosis." Many technical modifications that have improved or will improve the reliability of these flaps should not be confused as distinct flap types, but rather acknowledged as variations that can be more conveniently classified for the purposes of improved communication and research by using this basic schema as a guideline.     

Numerical integration of a stochastic model for the Volterra-Lotka reaction

Time-integration of the master equation governing the birth-and-death model of the Volterra-Lotka reaction is carried out for three different initial conditions, with the results:

1. Fluctuations destroy the deterministic steady state in a manner quantitatively predicted from a cumulant expansion;
2. The sustained oscillatory behavior predicted by the deterministic model degenerated after 1/4 cycle in the stochastic model;
3. It is possible to select initial distributions such that the asymptotic distribution is a spike at the origin of the plane of reactants.

     

Mathematical model for the luminol chemiluminescence reaction catalyzed by peroxidase

A kinetic model that accurately describes intensity vs. time reaction profiles for the chemiluminescence reaction between luminol and hydrogen peroxide, as catalyzed by horseradish perioxdase, is derived and evaluated. A set of three differential equations is derived and solved to provide intensity time information for the first 200 seconds of the reaction. The model accurately predicts intensity-time profiles when literature values are used for all but one of the reaction rate constants. Furthermore, the model predicts a nonlinear curve for plots of light intensity versus the initial hydrogen peroxide concentration. Experimental data confirm that such plots are nonlinear. Finally, a linear double-reciprocal plot is predicted by the model and the experimental data verify this relationship. (c) 1993 Wiley & Sons, Inc.     

On a general model structure for macroscopic biological reaction rates

Macroscopic modelling of bioprocesses requires the determination of a biological reaction scheme and a kinetic model. The a priori selection of an appropriate kinetic model structure is usually made difficult by the lack of detailed bioprocess knowledge and the profusion of apparently similar biological kinetic laws. Moreover, parameter identification is made arduous and time-consuming by the strong non-linearities involved in kinetic laws. In most cases, these kinetic structures are non-linearizable and no first parameter estimation can be deduced easily. In order to avoid such identification problems, Bogaerts et al. [Bogaerts, Ph., Castillo, J., Hanus, R., 1999. A general mathematical modelling technique for bioprocesses in engineering applications. Syst. Anal. Model. Simul. 35, 87-113] have developed a general linearizable kinetic structure which allows the representation of activation and/or inhibition effects of each component in the culture. This paper further generalizes this structure in order to improve the way saturation effects are taken into account, and in turn, improve the biological interpretation of the model parameters. The main advantage of the proposed structure lies in an associated systematic estimation procedure. The usefulness of the proposed model is tested with simulated as well as with experimental data.     

Coenzyme model reaction in lipid bilayers

Coenzyme model reactions, such as the H⁻ (H⁺ + 2e⁻) transfer from NADH models to triphenyl methane dyes, were investigated in the presence of lipid bilayers, for example, -α-dimyristoyl phosphatidyl choline and egg yolk lecithin. In the temperature dependence of the acceleration effect by the lipid bilayer, discontinuous points were observed, corresponding to the phase transition point such as gel-liquid crystal (T_c) or the segregation point (T_s). The T_c and T_s values of the bilayers varied with the reactant as a result of the difference of perturbing effect on the structure of the bilayers. The pressure effect on the transition point was also studied. Transition points such as T_c or T_s became higher with increasing pressure, and dT_c/dP or dT_s/dP was different for various bilayers. In the gel phase of the membrane, stereospecific reduction of malachite green was observed by chiral nicotinamide: the difference in the catalytic effect on the reduction rate between (R)- and (S)-dihydronicotinamides was larger in the gel phase than that in the liquid crystal phase or in the phase separated state, which suggests that the gel-state molecule can recognize the molecular structure better than the liquid-crystal state molecule.     

Simplified fluorometric assay for sphingosine bases

A simplified procedure for fluorometric determination of sphingosine bases is presented. Nitrogenous bases are reacted with fluorescamine and then extracted into a lower phase solvent, obviating the need to transfer the reaction products prior to quantitation. Consequently, the entire procedure may be carried out in a single set of screw-capped reaction tubes. Chloroform was found to be the best solvent of those tested for the maximal extraction of derivatized sphingosine bases with negligible extraction of nitrogenous contaminants derived from phospholipids and amino sugars. The simplified method retains excellent sensitivity and selectivity and allows for simultaneous processing of large numbers of samples. Furthermore, quantitation of glycolipid-derived hexosamine can be obtained by measuring the fluorescence of the aqueous phase after partitioning.