Rapid method for total carotenoid detection in canary yellow-fleshed watermelon.

Yellow-fleshed watermelons (Citrullus lanatus[Thunb.] Matsum. and Nakai) contain many different carotenoids, all in low to trace amounts. Since there is not 1 predominant carotenoid in yellow-fleshed watermelon, testing the total carotenoid content among watermelon lines is important in determining the antioxidant potential and thus potential health benefits of different varieties. Unfortunately, current methods to assay total carotenoid content are time consuming and require organic solvents. This report describes a rapid and reliable light absorption method to assay total carotenoid content for yellow-fleshed watermelon that does not require organic solvents. Light absorption of 78 watermelon flesh purees was measured with a diode array xenon flash spectrophotometer that can measure actual light absorption from opaque samples; results were compared with a hexane extraction method. The puree absorbance method gave a linear relationship (R(2)= 0.88) to total carotenoid content and was independent of watermelon variety within the total carotenoid concentration range measured (0 to 7 mug/g fresh weight).

Deterministic recurrences of sequential F-wave latencies.

PURPOSE: Historically, F-waves have been classified by various linear descriptors like persistence, latency, duration, amplitude, chrono-dispersion and number of repeater waves. But because physiological signals are notoriously nonlinear in nature, the objective of this study was to apply modern nonlinear methodology to F-waves sequences to assess the presence of underlying deterministic structures. Subtle changes in these sensitive markers could give early warnings for neurological problems. METHODS: F-waves were elicited in the left abductor pollicis breivs muscle by supra-maximally stimulating the median nerve percutaneously at the wrist. Approximately 200 stimuli were applied (0.5 Hz) to three subjects for at least four trials each. F-wave latencies were measured and assembled into sequences in proper order. Recurrence quantification analysis (RQA) was applied to these F-wave sequences from different dimensional perspectives. Controls were constructed by randomly shuffling the ordered sequences. RQA has a theoretical mathematical foundation and practical performance record on numerous other physiological systems. RESULTS: Recurrence analysis showed that sequential F-waves form recurrent patterns with parallel trajectories with deterministic and laminated structures. These features could be destroyed by randomizing the sequential orders of F-waves, upholding the hypothesis that sequences of F-waves are deterministically formed from underlying physiological rules. CONCLUSIONS: F-wave time series are fully amenable to recurrence analysis which provides a higher-dimensional perspective on the physiological dynamic. The recurrent patterns are complex, but not random, meaning that physiological rules dominate the sequence of F-waves. Disease processes within the central or peripheral nervous system may alter F-wave patterns. If so, RQA potentially may be a diagnostic tool to help discern subtleties between altered deterministic rules operating in disease.

Phytotoxic and fungitoxic activities of the essential oil of kenaf (Hibiscus cannabinus L.) leaves and its composition.

The chemical composition of the essential oil of kenaf (Hibiscus cannabinus) was examined by GC-MS. Fifty-eight components were characterized from H. cannabinus with (E)-phytol (28.16%), (Z)-phytol (8.02%), n-nonanal (5.70%), benzene acetaldehyde (4.39%), (E)-2-hexenal (3.10%), and 5-methylfurfural (3.00%) as the major constituents. The oil was phytotoxic to lettuce and bentgrass and had antifungal activity against Colletotrichum fragariae, Colletotrichum gloeosporioides, and Colletotrichum accutatum but exhibited little or no algicidal activity.

Elucidating protein secondary structures using alpha-carbon recurrence quantifications.

Secondary structures of proteins were studied by recurrence quantification analysis (RQA). High-resolution, 3-dimensional coordinates of alpha-carbon atoms comprising a set of 68 proteins were downloaded from the Protein Data Bank. By fine-tuning four recurrence parameters (radius, line, residue, separation), it was possible to establish excellent agreement between percent contribution of alpha-helix and beta-sheet structures determined independently by RQA and that of the DSSP algorithm (Define Secondary Structure of Proteins). These results indicate that there is an equivalency between these two techniques, which are based upon totally different pattern recognition strategies. RQA enhances qualitative contact maps by quantifying the arrangements of recurrent points of alpha carbons close in 3-dimensional space. For example, the radius was systematically increased, moving the analysis beyond local alpha-carbon neighborhoods in order to capture super-secondary and tertiary structures. However, differences between proteins could only be detected within distances up to about 6-11 A, but not higher. This result underscores the complexity of alpha-carbon spacing when super-secondary structures appear at larger distances. Finally, RQA-defined secondary structures were found to be robust against random displacement of alpha carbons upwards of 1 A. This finding has potential import for the dynamic functions of proteins in motion.

Nonlinear time-course of lumbar muscle fatigue using recurrence quantifications.

Isometric skeletal muscle fatigue is usually assumed to be a linear process based upon the monotonic decrease in spectral frequency of the EMG. Since spectral analysis by fast Fourier transform (FFT) constitutes a linear transformation of the data, the present study was designed to reevaluate the time-course of muscle fatigue with a nonlinear tool, recurrence quantification analysis (RQA). Surface EMG recordings were obtained from the multifidus muscle of 17 human subjects during isometric posture-holding of the upper torso. The process of muscle fatigue was found to be linear for 59% of the subjects by FFT criteria, but nonlinear for 76% by RQA criteria. As a demonstrative control, both slow and fast transients occurring within a nonlinear mathematical process could be accurately depicted by RQA, but not by FFT. It is concluded that assessment of EMG patterns by nonlinear techniques can give insight into the time-course of fatiguing muscles attributed to the summation of several nonlinear and competing processes.

The role of hydrophobicity patterns in prion folding as revealed by recurrence quantification analysis of primary structure.

It has been suggested that the number and strength of local contacts are the major factors governing conformation accessibility of model two ground-state polypeptide chains. This phenomenology has been posed as a possible factor influencing prion folding. To test this conjecture, recurrence quantification analysis was applied to two model 36mers, and the Syrian hamster prion protein. A unique divergence of the radius function for the recurrence quantification variable %DET of hydrophobicity patterns was observed for both 36mers, and in a critical region of the hamster prion protein. This divergence suggests a partition between strong short- and long-range hydrophobicity patterns, and may be an important factor in prion phenomenology, along with other global thermodynamic factors.

Recurrence quantification analysis in structure-function relationships of proteins: an overview of a general methodology applied to the case of TEM-1 beta-lactamase.

Protein structure-function relationships have been increasingly scrutinized by a variety of correlational and information theoretic measures. In an effort to extend this methodology, a technique originally developed in non-linear science, recurrence quantification analysis, was combined with traditional principal components analysis to study a large number (56) of TEM-1 beta-lactamase mutants. The hydrophobicity profiles corresponding to the primary structure of 13 naturally occurring mutations partially impairing function, together with 43 artificial non-tolerated mutations were subjected to discriminant analysis, derived from the results of recurrence quantification analysis, coupled to a principal exponents extraction. Eleven (85%) of the naturally occurring mutants and 36 (84%) of the artificial mutants were correctly classified (p < 0.0001). We conclude that this technique may be useful in protein engineering and, in general, in structure-function studies of biopolymers.

Lumbar paraspinal muscle fatigability in repetitive isoinertial loading: EMG spectral indices, Borg scale and endurance time.

The purpose of this study was to develop a submaximal repetitive isoinertial back muscle endurance test by defining the relationships between the power spectral indices of paraspinal muscle electromyographic (EMG) activities, endurance time and a subjective estimate of fatigue (Borg scale). Bilateral surface EMG recordings were obtained over the lumbar paraspinal muscles in ten individuals who were currently free from back pain. All subjects performed repetitive upper trunk extensions (25 degrees flexion and 5 degrees extension, 30 repetitions per min), while movement below the third lumbar vertebral body was mechanically restricted. The load level depended upon upper body mass, sex, and age. The tests continued for as long as the subjects were able to maintain the required repetition rate (endurance time). Median (MF) and mean power frequency (MPF) slopes were calculated by performing a fast Fourier transformation after confirmation of EMG stationarity by recurrence quantification analysis. MF and MPF correlations with endurance time/Borg scale were measured for the first 60 s (0.60-0.88/0.42-0.86), the first 90 s (0.62-0.89/0.52-0.90), the first 120 s (0.50-0.76/0.41-0.73), and the entire repetitive run (0.63-0.88/0.54-0.90). To test for the reproducibility of the spectral indices EMGs were recorded for 2 min during repetitive loading from the same subjects on two consecutive days. Corresponding spectral slopes of MF and MPF were correlated at 60 s (0.36-0.93), 90 s (0.58-0.92), and 120 s (0.70-0.94) at the L3-L4 and L5-S1 levels, indicating good reproducibility of results from alternate recording sessions at the L5-S1 level. It is concluded that paraspinal muscle spectral indices (MF and MPF) measured before the onset of total muscle fatigue are good predictors of endurance time and are closely related to the subjective perception of fatigue.

A Markovian formalization of heart rate dynamics evinces a quantum-like hypothesis.

Most investigations into heart rate dynamics have emphasized continuous functions, whereas the heart beat itself is a discrete event. We present experimental evidence that by considering this quality, the dynamics may be appreciated as a result of singular dynamics arising out of non-Lipschitz formalisms. Markov process analysis demonstrates that heart beats may then be considered in terms of quantum-like constraints.

Influence of isometric loading on biceps EMG dynamics as assessed by linear and nonlinear tools.

The summed electrical discharges generated by a contracting skeletal muscle constitute a dynamic system conveying electromyographic (EMG) information indicative of muscle physiological status. "Steady states" of activity can be achieved with light loads, but with heavy loads the dynamic system experiences continuous status transitions that culminate in task failure. The present study was designed to assess the applicability of two mathematical tools, one linear and the other nonlinear, in addressing the time course of EMG alterations under different loading challenges. Surface EMGs of the biceps brachii muscle were recorded from 14 healthy human volunteers during light and heavy loadings, and task failure occurred at varying times among the subjects. Digitized EMG signals were analyzed by linear spectral analysis (fast Fourier transform) and nonlinear recurrence-plot analysis. With light loading, computed variables from both analyses gave "quasi-steady-state" values over time, with recurrence-plot analysis having the higher variance. With heavy loading, the nonlinear variable (%determinism) increased sooner and exhibited larger changes from control values than decreases in the linear variable (spectral center frequency). Experimental results support the conclusion that both analyses can be combined to give a fuller assessment of the biceps EMG during light or heavy loading. Implications for the detection of muscular fatigue are discussed.

Developing gossypol derivatives with enhanced antitumor activity.

Preclinical and clinical studies have pointed to the antitumor potential of the naturally occurring polyphenolic binaphthyl dialdehyde, gossypol, as well as its purified (-,+) enantiomers. To explore further the antitumor properties of this multifunctional agent, we synthesized several reactive derivatives including the (-,+) enantiomers of gossypolone and four different gossypol Schiff's bases (AR1, AR2, AR3, AR4). The biological activities of these new agents were screened by measuring their in vitro antiproliferative activity against malignant (MCF-7, MCF-7/adr) or immortalized (HBL-100) human breast epithelial cell lines. Racemic gossypolone showed relatively uniform antiproliferative activity against all of the breast epithelial cell lines with 3- to 5-fold less activity than (--)-gossypol against MCF-7 and MCF-7/adr cells. Of interest, the relative antitumor potency of purified gossypolone enantiomers was reverse that of gossypol enantiomers, since (+)-gossypolone showed up to 3-fold greater inhibition of MCF-7 culture growth than (--)-gossypolone. Of the Schiff's base derivatives only AR3 with its isopropyl amine substituent demonstrated cytotoxic activity comparable to that of (--)-gossypol; derivatives with ethyl, propyl, or butyl amine substituents (AR1, AR2, AR4) had little growth inhibitory activity at culture concentrations up to 25 microM. AR3 activity was greatest against HBL-100 and MCF-7 cells [MCF-7 IC50 values: AR3 = 0.9 microM, (--)-gossypol = 2.3 microM]; unlike (--)-gossypol, however, AR3 showed substantially reduced activity against the multidrug-resistant subline, MCF-7/adr. These structure-activity comparisons suggest that isolation of (-,+)-enantiomers of AR3 and additional chemical modifications including the synthesis of an isopropyl amine Schiff's base of gossypolone will likely yield a newer generation of gossypol analogues with enhanced anticancer potential.

Dynamical assessment of physiological systems and states using recurrence plot strategies.

Physiological systems are best characterized as complex dynamical processes that are continuously subjected to and updated by nonlinear feedforward and feedback inputs. System outputs usually exhibit wide varieties of behaviors due to dynamical interactions between system components, external noise perturbations, and physiological state changes. Complicated interactions occur at a variety of hierarchial levels and involve a number of interacting variables, many of which are unavailable for experimental measurement. In this paper we illustrate how recurrence plots can take single physiological measurements, project them into multidimensional space by embedding procedures, and identify time correlations (recurrences) that are not apparent in the one-dimensional time series. We extend the original description of recurrence plots by computing an array of specific recurrence variables that quantify the deterministic structure and complexity of the plot. We then demonstrate how physiological states can be assessed by making repeated recurrence plot calculations within a window sliding down any physiological dynamic. Unlike other predominant time series techniques, recurrence plot analyses are not limited by data stationarity and size constraints. Pertinent physiological examples from respiratory and skeletal motor systems illustrate the utility of recurrence plots in the diagnosis of nonlinear systems. The methodology is fully applicable to any rhythmical system, whether it be mechanical, electrical, neural, hormonal, chemical, or even spacial.

Phase-dependent properties of the cardiac sarcoplasmic reticulum oscillator in cat right atrium: a mechanism contributing to dysrhythmias induced by Ca2+ overload.

These experiments analyse the phase-dependent properties of spontaneous oscillations of the sarcoplasmic reticulum (SR) induced by Ca2+ overload. Right atrial tissue was loaded with intracellular Ca2+ by exposure to a modified Tyrode solution containing 50% of normal Na+ and 0.5 mM K+. Verapamil (2 microM) was added to block regenerative activity. Intracellular Ca2+ overload elicited spontaneous, rhythmic voltage and tension oscillations that were phase locked 1:1. Voltage and tension oscillations were abolished by exposure to low (0.9 mM) external Ca2+, 1 microM ryanodine, or 10 mM caffeine, indicating that both voltage and tension oscillations resulted from spontaneous oscillations in SR Ca2+ release. Single pulses of nerve-stimulated ACh release elicited phase shifts in both voltage and tension oscillations. Sinusoidal current was used as a periodic stimulus to drive membrane voltage and elicit periodic voltage oscillations. Stimulated voltage oscillations entrained spontaneous tension oscillations 1:1 in a range of frequencies close to the basic spontaneous SR oscillatory cycle length, or 2:1 at frequencies close to one-half the spontaneous SR oscillatory cycle length. Stimulation frequencies between these two regions entrained tension oscillations in predictable fixed coupled ratios (4:3, 3:2) and resulted in Wenckeback-like voltage patterns. Stimulation frequencies between phase-locked regions resulted in complex coupling relationships and irregular voltage patterns. Exposure to 1 microM ryanodine, 0.9 mM external Ca2+, or 10 mM caffeine abolished irregular voltage patterns and tension. We conclude that the SR oscillator exhibits phase-dependent sensitivity to perturbations at the surface membrane. As a result, external perturbations can elicit phase differences between spontaneous SR oscillations and membrane voltage that cause either phase-locked or irregular voltage patterns. These findings identify an intracellular mechanism that may contribute to the development of cardiac dysrhythmias resulting from intracellular Ca2+ overload.

Structural change of the thorax in chronic obstructive pulmonary disease.

This study examines structural changes of the thorax in hyperinflated subjects with chronic obstructive pulmonary disease (COPD). Age-matched normal subjects were used for comparison. Thoracic dimensions were determined using anteroposterior and lateral chest radiographs performed at total lung capacity, functional residual capacity, and residual volume. Rib cage dimensions (lateral diameter, rib angle, anteroposterior diameter) and diaphragm position were determined at each lung volume. There were no significant differences in rib cage dimension between the COPD and normal subjects for all lung volumes. In contrast, the diaphragm was significantly lower in the COPD subjects. The change of rib cage dimensions in the COPD subjects (for a similar volume change) was not different from that in normal subjects, whereas the change of diaphragm position in the COPD subjects (for a similar volume change) was reduced. In conclusion, the primary structural change of the thorax in COPD with chronic hyperinflation is confined to the diaphragm, with no appreciable structural change in the rib cage.

High-frequency oscillations within early and late phases of the phrenic neurogram.

Spectral analyses were performed on phrenic neurogram recordings from 18 cats to identify high-frequency oscillations (HFOs) inherent in the signals at different phases of inspiratory activity. Gating the analysis for the entire inspiratory phase resulted in dual spectral HFOs (27 and 83 Hz), both of which persisted when the analysis was repeated on the later phase of phrenic inspiratory activity alone (29 and 82 Hz). A third pass at the same data, gating for just the early phase of phrenic discharge, however, resulted in single spectral HFOs at the higher frequency only (86 Hz). Because both early and late recruited phrenic motoneurons carry both higher and lower spectral frequencies, these results demonstrate that the lower frequency HFO is distinctly delayed in onset compared with the higher frequency HFO, the latter of which is believed to have a brain stem origin. This delayed onset may be important in identifying the source of the lower frequency HFO, which appears to be specific to various respiratory efferent systems.

A C-language program for the computation of power spectra on a laboratory microcomputer.

A computer program is described which performs power-spectral analyses on time-domain data. The program is written in the C language and incorporates an algorithm for the fast Fourier transform translated from BASIC into C. Sequential segments of time-domain data are accessed by the program, transformed to the frequency domain, and ensemble-averaged to generate smoothed spectra. Specific application of the program to the detection of high-frequency oscillations in the phrenic neurogram of the cat is addressed. Thus, 100 successive 512-point fast Fourier transforms were found to accurately reveal the relative strength (power) and frequency position (spectrum) of multiple peaks in this respiratory motor pathway. Because C language programs are very transportable, this program should run on machines other than our LSI 11/23, provided a C-compiler is available.

Effect of hypoxic, hyperoxic or hypercapnic ventilation on inspiratory termination in the cat.

Intercostal nerve stimulation was used to examine the effects of altered concentrations of inspired oxygen or carbon dioxide on the termination of inspiration. Experiments were performed in decerebrate cats which were paralyzed, artificially ventilated and bilaterally vagotomized. The threshold current at which electrical stimulation of the T6 intercostal nerve terminated phrenic neural activity was determined at 10 different delays from the onset of phrenic nerve discharge. Ventilation with either hypercapnic normoxic gas (4% CO2) or hypoxic gas (17% O2) increased the threshold current required for inspiratory termination. Hyperoxic ventilation (45% O2), however, decreased the threshold for inspiratory termination. Bilateral section of the carotid sinus nerve abolished the response to hyperoxic ventilation, but did not alter the response to normoxic hypercapnia. These results demonstrate that an oxygen-related stimulus transduced by the peripheral chemoreceptors can influence the mechanism(s) responsible for inspiratory termination.

Respiratory effects of high cervical cord cold blockade on efferent vagal and phrenic discharges in the rabbit.

A technique of reversible cold blockade was applied in decerebrate and vagotomized rabbits that were immobilized and artificially ventilated to study the modulation of spontaneous respiratory rhythms. Respiratory discharges were recorded from vagal and phrenic efferents before and during cold blockade at the second cervical segment (C2) with a coolant-circulated thermode (-15 degrees C). Measurement of the cooling profile demonstrated that there was significant hypothermia in the regions of the phrenic nucleus (+25 degrees C) and obex of the medulla (+26 degrees C). Arterial pressure was maintained by continual norepinephrine infusion, end-tidal carbon dioxide tension was held at hypercapnic levels, and rectal temperature was regulated near 38 degrees C. The cold blockade of descending respiratory drives to the cervical phrenic nucleus inhibited the spontaneous activity in the phrenic nerve for more than 90 min. Phrenic activity could be induced by the intravenous injection of strychnine, but not doxapram, although this was not of respiratory quality. These results show that in the absence of descending and pharmacologic drives, but in the presence of phrenic hypothermia, spinalized rabbits are incapable of generating rhythmic patterns of discharge. C2 cold blockade also significantly slowed the spontaneous central respiratory rhythm with no change in integrated vagal amplitude, presumably due to a direct cooling effect on brainstem oscillators for breathing.

Estimation of frontal-plane cardiac vectors in heart disease.

Frontal-plane vector angle and magnitude values were clinically estimated in 100 patients with cardiac disease. Maximal deviations from isopotential in standard limb leads I and II were summed and mathematically transformed into estimated vector magnitudes (mV) and estimated angles (degrees). These values were then compared against reference vectors (previously shown to be excellent standards) defined from the same QRS complexes. The estimated magnitude values reached a degree of accuracy of +/- .25 mV in 78% of the cases, and the estimated angle values reached a degree of accuracy of +/- 15 degrees in 80% of the cases. The lowest estimate errors occurred in the infarct group, whereas the largest errors occurred in the chamber-enlargement and axis-deviation groups.