New complexity measures reveal that topographic loops of human alpha phase potentials are more complex in drowsy than in wake

A number of measures, stemming from nonlinear dynamics, exist to estimate complexity of biomedical objects. In most cases they are appropriate, but sometimes unconventional measures, more suited for specific objects, are needed to perform the task. In our present work, we propose three new complexity measures to quantify complexity of topographic closed loops of alpha carrier frequency phase potentials (CFPP) of healthy humans in wake and drowsy states. EEG of ten adult individuals was recorded in both states, using a 14-channel montage. For each subject and each state, a topographic loop (circular directed graph) was constructed according to CFPP values. Circular complexity measure was obtained by summing angles which directed graph edges (arrows) form with the topographic center. Longitudinal complexity was defined as the sum of all arrow lengths, while intersecting complexity was introduced by counting the number of intersections of graph edges. Wilcoxon’s signed-ranks test was used on the sets of these three measures, as well as on fractal dimension values of some loop properties, to test differences between loops obtained in wake vs. drowsy. While fractal dimension values were not significantly different, longitudinal and intersecting complexities, as well as anticlockwise circularity, were significantly increased in drowsy

Kinetic parameters for thermal inactivation of soluble peroxidase from needles of Serbian spruce Picea omorika (Pancic) Purkyne

Thermal inactivation of peroxidase (POD) in an extract of Picea omorika (Pancic) Purkyne needles initiated by heat treatment was studied. This is the first study of this kind on a conifer species. Non-linear regression analysis was applied on the inactivation rate data, combining Mitscherlich and Arrhenius equations, treating time and temperature simultaneously as explaining variables. We determined the inactivation rate constant k, the Arrhenius energy of inactivation E and the remaining activity C-min for the crude extract and for separated acidic and basic enzyme fractions, as well as for individual isoenzymes separated electrophoretically. A comparison of inactivation parameters for acidic and basic fractions shows that the thermal inactivation rate of the basic fraction is higher. The obtained value of inactivation energy for crude extract was between the values for acidic and basic isoenzyme fractions. One of the three analysed individual isoenzymes was characterised by a lower inactivation rate constant and higher inactivation energy. Another isoenzyme showed considerably higher level of remaining activity compared to the others, which identified it as the most resistant to high temperatures. The acquired values of Arrhenius energy of inactivation for POD in crude extract were intermediate, considering a range of POD values for various other plant species

Generalized Poincaré plots analysis of heart period dynamics in different physiological conditions: Trained vs. untrained men

Background Recently we proposed a new method called generalized Poincare´ plot (gPp) analysis which gave a new insight into the pattern of neurocaridac control. In this study we examined potential of gPp method to reveal changes in cardiac neural control in young athletes during three conditions: supine rest, running and relaxation, with respect to untrained subjects. Methods This method is based on the quantification of Pearson's correlation coefficients r(j, k), between symmetrical (j = k) and asymmetrical summed j previous and k following RR intervals up to the 100th order (j,k.100). Results Differences between groups were obtained at all levels of this analysis. The main result is the significant difference of NAI, normalized index of asymmetry, between groups in running, which was originated in different positions of local maxima of r(j, k). Compared with untrained subjects, these findings indicate modified neural control and altered intrinsic heart rate behavior in athletes which are related to some kind of memory mechanism between RR intervals. Conclusion Obtained results provide great potential of gPp method analysis in the recognition of changes in neurocardiac control in healthy subjects. Further studies are needed for identification of altered cardiac regulatory mechanisms whose background may be useful in the evaluation of genesis of athletes neurocardiovascular pathology. © 2019 Platiša et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Extracting complexity waveforms from one-dimensional signals

Background: Nonlinear methods provide a direct way of estimating complexity of one-dimensional sampled signals through calculation of Higuchi's fractal dimension (1<FD<2). In most cases the signal is treated as being characterized by one value of FD and consequently analyzed as one epoch or, if divided into more epochs, often only mean and standard deviation of epoch FD are calculated. If its complexity variation (or running fractal dimension), FD(t), is to be extracted, a moving window (epoch) approach is needed. However, due to low-pass filtering properties of moving windows, short epochs are preferred. Since Higuchi's method is based on consecutive reduction of signal sampling frequency, it is not suitable for estimating FD of very short epochs (N < 100 samples).Results: In this work we propose a new and simple way to estimate FD for N < 100 by introducing 'normalized length density' of a signal epoch,.where yn(i) represents the ith signal sample after amplitude normalization. The actual calculation of signal FD is based on construction of a monotonic calibration curve, FD = f(NLD), on a set of Weierstrass functions, for which FD values are given theoretically. The two existing methods, Higuchi's and consecutive differences, applied simultaneously on signals with constant FD (white noise and Brownian motion), showed that standard deviation of calculated window FD (FDw) increased sharply as the epoch became shorter. However, in case of the new NLD method a considerably lower scattering was obtained, especially for N < 30, at the expense of some lower accuracy in calculating average FDw. Consequently, more accurate reconstruction of FD waveforms was obtained when synthetic signals were analyzed, containig short alternating epochs of two or three different FD values. Additionally, scatter plots of FDwof an occipital human EEG signal for 10 sample epochs demontrated that Higuchi's estimations for some epochs exceeded the theoretical FD limits, while NLD-derived values did not.Conclusion: The presented approach was more accurate than the existing two methods in FD(t) extraction for very short epochs and could be used in physiological signals when FD is expected to change abruptly, such as short phasic phenomena or transient artefacts, as well as in other fields of science. © 2009 Kalauzi et al; licensee BioMed Central Ltd

Electrical characteristics of female and male human skin

Bioimpedance spectroscopy (BIS) is a popular method for characterizing the electrical properties of biological tissues. In this study, BIS measurement data of female and male human skin were analyzed and compared. The electrical characteristics of tissue were followed according to four-parameters of the Cole-Cole model: low frequency resistance R0; high frequency resistance R∞; relaxation time t and parameter a. Individual electrical characteristics of human skin were determined for 30 women and 30 men. The distribution and one-way analysis of variance (one-way ANOVA) of the Cole-Cole parameters R0, R∞, t, a within the human population indicated their different dependence on gender. Parameter a, which is higher in the female subjects (a =0.83±0.03) than in the male subjects (a=0.7±0.05), is strongly dependent on gender (p=0). Parameter R∞ also significantly depends on gender (p=0.002), while t and R0 seem to be slightly related to gender (p>0.05)

Međuzavisnost oscilacija i tranzijenata indukcionih procesa zakasnele fluorescencije hlorofila u tilakoidnoj membrani intaktnog lista kukuruza - reakcije na delovanje viših temperatura i suše

Standard induction processes of delayed fluorescence (DF) of chlorophyll (induction signals) occur when an intact leaf segment of maize inbreds and hybrids is kept in the phosphoroscope darkroom for more than 15 minutes (t > 15 min), and at the same time the leaf is illuminated with the intermittent white light. Resolved induction processes of DF chlorophyll into transients: A, B, C, D and E occur when the intact leaf segment of maize inbreds and hybrids is kept in the phosphoroscope darkroom for a significantly shorter period (500 s > t > 30 s), with the time rate t of 30 s, prior to its illumination with the intermittent white light. Induction transients: A, B, C, D and E are characterized with the time of their generation: tA = 31±6 ms (A), tB = 5 ± 0,5 s (B), tC = 15±5 s (C), tD = 360±20 s (D) and tE = 670±35 s (E), dynamics of changes in transients intensities (IA, IB, IC, ID and IE) and mechanisms of their generation. The induction processes of chlorophyll DF of the intact leaf of maize inbreds and hybrids resolved into transients: A, B, C, D and E are accompanied by the occurrence and different levels of activation energy (Ea, kJ mol-1) that correspond to critical temperatures ranging from 28 to 33°C. The generation mechanisms of induction transients A, B, C, D and E classify them into two groups. Transients A and B are of a physical character, while the transients: C, D, and E are of a chemical character. It is shown that the generation of the induction transients: B, C, D and E simultaneously follows establishing of the oscillations of induction processes of the DF chlorophyll. Oscillating of induction processes of DF chlorophyll is explained by the ion (K+, Na+, H+, Cl-) transport mechanism across the thylakoid membrane of the intact leaf of maize inbreds and hybrids grown under conditions of air drought, increased temperatures and water deficiency in the medium.U ovom radu ostvaruje se primena poboljšanog fotosintetično-fluorescentnog metoda u proučavanju složenih indukcionih procesa zakasnele fluorescencije (ZF) hlorofila, koji su razloženi na tranzijente: A, B, C, D i E i kod kojih mogu da nastanu oscilacije. Međuzavisnost oscilacija i indukcionih tranzijenata: A, B, C, D i E javlja se kod intaktnih listova linija (ZPR 70ž i Oh 43) i hibrida (ZPDC 360, ZPSC 46A, ZPSC 704 i ZPSC 71) kukuruza koji su gajeni u staklari u uslovima različite vazdušne suše, delovanja viših temperatura i deficita vode u podlozi. Posebno se ukazuje na uslove pri kojima dolazi do uspostavljanja standardnih indukcionih procesa ZF hlorofila. Daje se kraći opis standardne indukcione krive ZF hlorofila. Znatno detaljnije daju se eksperimentalni rezultati o razlaganju indukcionih procesa ZF hlorofila na tranzijente: A, B, C, D i E. Pokazani su vremenski i fizičko-hemijski parametri za proučavane indukcione tranzijente. Objašnjeni su njihova priroda i mehanizmi nastajanja. Utvrđene su karakteristike i mehanizam nastajanja oscilacija indukcionih procesa ZF hlorofila. Dati su uslovi pri kojima dolazi do pojave pobuđenog stanja, nastajanja fluktuacija i uspostavljanja oscilacija indukcionih procesa ZF hlorofila u tilakoidnoj membrani intaktnog lista linija i hibrida kukuruza. Izneta je hipoteza o mehanizmu nastajanja oscilacija. Objašnjena je međuzavisnost uspostavljanja oscilacija i tranzijenata indukcionih procesa ZF hlorofila

Pulse respiration quotient as a measure sensitive to changes in dynamic behavior of cardiorespiratory coupling such as body posture and breathing regime

In this research we explored the (homeo)dynamic character of cardiorespiratory coupling (CRC) under the influence of different body posture and breathing regimes. Our tool for it was the pulse respiration quotient (PRQ), representing the number of heartbeat intervals per breathing cycle. We obtained non-integer PRQ values using our advanced Matlab® algorithm and applied it on the signals of 20 healthy subjects in four conditions: supine position with spontaneous breathing (Supin), standing with spontaneous breathing (Stand), supine position with slow (0.1 Hz) breathing (Supin01) and standing with slow (0.1 Hz) breathing (Stand01).Main results: Linear features of CRC (in PRQ signals) were dynamically very sensitive to posture and breathing rhythm perturbations. There are obvious increases in PRQ mean level and variability under the separated and joined influence of orthostasis and slow (0.1 Hz) breathing. This increase was most pronounced in Stand01 as the state of joint influences. Importantly, PRQ dynamic modification showed greater sensitivity to body posture and breathing regime changes than mean value and standard deviation of heart rhythm and breathing rhythm. In addition, as a consequence of prolonged supine position, we noticed the tendency to integer quantization of PRQ (especially after 14 min), in which the most common quantization number was 4:1 (demonstrated in other research reports as well). In orthostasis and slow breathing, quantization can also be observed, but shifted to other values. We postulate that these results manifest resonance effects induced by coupling patterns from sympathetic and parasympathetic adjustments (with the second as dominant factor).Significance: Our research confirms that cardiorespiratory coupling adaptability could be profoundly explored by precisely calculated PRQ parameter since cardiorespiratory regulation in healthy subjects is characterized by a high level of autonomic adaptability (responsiveness) to posture and breathing regime, although comparisons with pathological states has yet to be performed. We found Stand01 to be the most provoking state for the dynamic modification of PRQ (cardiorespiratory inducement). As such, Stand01 has the potential of using for PRQ tuning by conditioning the cardiorespiratory autonomic neural networks, e.g., in the cases where PRQ is disturbed by environmental (i.e., microgravity) or pathologic conditions

Some details on the method for measuring activity changes of neuronal populations

Simple, complex action potentials (AP) and interspike recorded background activity (RBA) were detected and extracted from 12 rat cerebellar cortical recordings. For each recording, an averaged simple action potential (SAP) was formed. Fourier amplitude spectra of SAP and RBA were similar in all recordings. For one of the recordings, a series of RBA simulations (SBA) was generated, superimposing random SAPs, varying the superposition frequency (fsup). Average Fourier amplitude, Amp(SBA), was calculated, in order to use Amp(SBA)=f(fsup) as a calibration line for reading fsup of RBA, which is a measure of the population activity. A probability distribution for SAP intensities was derived and a family of calibration lines constructed. As all lines were linear and parallel (slope S) in log-log plots, a population activity change could be calculated as fsup2/fsup1=[Amp2(RBA)/Amp(RBA)]1/S.Jednostavni, složeni akcioni potencijali (AR) i međuspajkovna osnovna aktivnost (MOA) detektovani su i izdvojeni iz 12 registrovanih signala kore malog mozga pacova. Za svaku registraciju, formiran je usrednjeni jednostavni AR (JAR). Spektri Furijeovih amplituda JAR i MOA signala bili su slični kod svih registracija. Za jednu od registracija, superponiranjem slučajnih usrednjenih jednostavnih akcionih potencijala formiran je niz simulacija međuspajkovne osnovne aktivnosti (SOA), pri čemu je varirana frekvencija superpozicije (fsup). Izračunavana je srednja Furijeova amplituda, Amp(SBA), u cilju korišćenja Amp(SBA)=f(fsup) kao kalibracione linije za očitavanje fsup od MOA, što je mera za aktivnost populacije. Izvedena je raspodela verovatnoća za intenzitete JAR, pomoću koje je konstruisana familija kalibracionih linija. Kako su sve linije linearne i paralelne u log-log dijagramu, sa nagibom S, promena aktivnosti populacije može se izračunati kao fsup2/fsup1 =[Amp2(RBA)/Amp(RBA)]1/S.nul

The mechanism of the NH4 ion oscillatory transport across the excitable cell membrane

This paper presents results on typical oscillations of the membrane potential induced by the excitation of the cell membrane by different concentrations of the NH4Cl solution. The existence of four classes of oscillations of the membrane potential and several different single and local impulses rhythmically occurring were determined. It is known that the oscillatory processes of the membrane potential are in direct dependence on oscillatory transport processes of NH4 and Cl ions across the excitable cell membrane. A hypothesis on a possible mechanism of oscillatory transport processes of NH4 and Cl ions across the excitable cell membrane is also presented