Electrical signals and their physiological significance in plants

Electrical excitability and signalling, frequently associated with rapid responses to environmental stimuli, are well known in some algae and higher plants. The presence of electrical signals, such as action potentials (AP), in both animal and plant cells suggested that plant cells, too, make use of ion channels to transmit information over long distances. In the light of rapid progress in plant biology during the past decade, the assumption that electrical signals do not only trigger rapid leaf movements in 'sensitive' plants such as Mimosa pudica or Dionaea muscipula, but also physiological processes in ordinary plants proved to be correct. Summarizing recent progress in the field of electrical signalling in plants, the present review will focus on the generation and propagation of various electrical signals, their ways of transmission within the plant body and various physiological effects.     

Autonomic neural signals in bone: physiological implications for mandible and dental growth

Signals derived from the autonomic nervous system exert potent effects on osteoclast and osteoblast function. A ubiquitous sympathetic and sensory innervation of all periosteal surfaces exists and its disruption affects bone remodeling. Several neuropeptides, neurohormones and neurotransmitters and their receptors are detectable in bone. Bone mineral content decreased in sympathetically denervated mandibular bone. When a mechanical stress was superimposed on mandibular bone by cutting out the lower incisors, an increase in bone density ensued providing the sympathetic innervation was intact. A lower eruption rate of sympathetically denervated incisors at the impeded eruption side, and a higher eruption rate of denervated incisors at the unimpeded side were also observed. A normal sympathetic neural activity appears to be a pre-requisite for maintaining a minimal normal unimpeded incisor eruption and for keeping the unimpeded eruption to attain abnormally high velocities under conditions of stimulated incisor growth. These and other results suggest that the sympathetic nervous system plays an important role in mandibular bone metabolism.     

Processing of physiological signals in automotive research.

The development of innovative driver assistance systems requires the evaluation of the predisposed hypotheses such as acceptance and driving safety. For this purpose, the conduction of experiments with end-users as subjects is necessary. Analysis and evaluation are based on the recording of numerous sensor values and system variables. Video, gaze and physiological data are recorded for the analysis of gaze distraction and emotional reactions of subjects to system behaviour. In this paper, a modular data streaming and processing architecture is suggested and a concept for this architecture is defined for consistent data evaluation, which integrates off-the-shelf products for data analysis and evaluation.     

Magnetic-stimulation-related physiological artifacts in hemodynamic near-infrared spectroscopy signals

Hemodynamic responses evoked by transcranial magnetic stimulation (TMS) can be measured with near-infrared spectroscopy (NIRS). This study demonstrates that cerebral neuronal activity is not their sole contributor. We compared bilateral NIRS responses following brain stimulation to those from the shoulders evoked by shoulder stimulation and contrasted them with changes in circulatory parameters. The left primary motor cortex of ten subjects was stimulated with 8-s repetitive TMS trains at 0.5, 1, and 2 Hz at an intensity of 75% of the resting motor threshold. Hemoglobin concentration changes were measured with NIRS on the stimulated and contralateral hemispheres. The photoplethysmograph (PPG) amplitude and heart rate were recorded as well. The left shoulder of ten other subjects was stimulated with the same protocol while the hemoglobin concentration changes in both shoulders were measured. In addition to PPG amplitude and heart rate, the pulse transit time was recorded. The brain stimulation reduced the total hemoglobin concentration (HbT) on the stimulated and contralateral hemispheres. The shoulder stimulation reduced HbT on the stimulated shoulder but increased it contralaterally. The waveforms of the HbT responses on the stimulated hemisphere and shoulder correlated strongly with each other (r = 0.65–0.87). All circulatory parameters were also affected. The results suggest that the TMS-evoked NIRS signal includes components that do not result directly from cerebral neuronal activity. These components arise from local effects of TMS on the vasculature. Also global circulatory effects due to arousal may affect the responses. Thus, studies involving TMS-evoked NIRS responses should be carefully controlled for physiological artifacts and effective artifact removal methods are needed to draw inferences about TMS-evoked brain activity.     

Dynalets: A new method for modelling and compressing biological signals. Applications to physiological and molecular signals

The biological information coming from electrophysiologic sensors like ECG, pulse sensor or from molecular signal devices like NMR spectrometry has to be visualized and manipulated in a compressed way for an efficient medical use by clinicians, if stored in scientific data bases or in personalized patient records repositories. Here, we define a new transform called Dynalet based on Liénard ordinary differential equations susceptible to model the mechanism at the source of the studied signal, and we propose to apply this new technique first to the modelling and compression of real biological periodic signals like ECG and pulse rhythm. We consider that the cardiovascular activity results from the summation of cellular oscillators located in the cardiac sinus node and we show that, as a result, the van der Pol oscillator (a particular Liénard system) fits well the ECG signal and the pulse signal. The reconstruction of the original signal (pulse or ECG) using Dynalet transform is then compared with that of Fourier, counting the number of parameters to be set for obtaining an expected signal-to-noise ratio. Then, we apply the Dynalet transform to the modelling and compression of molecular spectra obtained by protein NMR spectroscopy. The reconstruction of the original signal (peak) using Dynalet transform is again compared with that of Fourier. After reconstructing visually the peak, we propose to periodize the signal and give it to hear, the whole process being called the protein “stethoscope”.     

Testing and mapping non-stationarity in animal behavioral processes: a case study on an individual female bean weevil

Statistical analysis based on two characteristics of a small-world network, and on Lempel-Ziv's measure of Kolmogorov-Chaitin's algorithmic complexity are first proposed to scan through an individual behavioral sequence for possible existence of non-stationarity. Due to fixed window width, these tests have drawbacks in mapping out regions of non-stationarity. A non-parametric approach based on sparse coding schemes is employed to segment the whole behavioral sequence into unequal length segments, thus resultant avoiding further efforts for grouping. Then attempts are made to entangle the resultant segmentation with other non-local behavioral patterns onto such sequence to ascertain that the non-stationarity corresponds to a sequence of different categories of underlying driving force. It is of potential importance that this segmentation, represented by a hierarchy of code sequences, provides a natural platform for detecting intrinsically coherent behavioral patterns based on continuously recorded data. Illustrations throughout the developments are made exclusively on data encoded from a nearly 4-h video-recording of a female bean weevil's behavior.     

Frequency as a property of physiological signals in plants

Abstract. The 'hormone' idea is based on a peculiarly chemical notion of substance and time. Although the chemical view of substance is advanced, its view of time is primitive compared to that of physics. This leads to considerable difficulties when applied to oscillatory systems, such as the nutating hypocotyl. There is evidence of involvement of a wide range of oscillatory systems in plants. In considering the properties of such systems, the possibility of physiological signals based on frequency becomes apparent. Some implications of this possibility for both theory and experimental programmes are discussed.     

Analysis of physiological signals for recognition of boredom,pain, and surprise emotions

Background

The aim of the study was to examine the differences of boredom, pain, and surprise. In addition to that, it was conducted to propose approaches for emotion recognition based on physiological signals.

Methods

Three emotions, boredom, pain, and surprise, are induced through the presentation of emotional stimuli and electrocardiography (ECG), electrodermal activity (EDA), skin temperature (SKT), and photoplethysmography (PPG) as physiological signals are measured to collect a dataset from 217 participants when experiencing the emotions. Twenty-seven physiological features are extracted from the signals to classify the three emotions. The discriminant function analysis (DFA) as a statistical method, and five machine learning algorithms (linear discriminant analysis (LDA), classification and regression trees (CART), self-organizing map (SOM), Naïve Bayes algorithm, and support vector machine (SVM)) are used for classifying the emotions.

Results

The result shows that the difference of physiological responses among emotions is significant in heart rate (HR), skin conductance level (SCL), skin conductance response (SCR), mean skin temperature (meanSKT), blood volume pulse (BVP), and pulse transit time (PTT), and the highest recognition accuracy of 84.7 % is obtained by using DFA.

Conclusions

This study demonstrates the differences of boredom, pain, and surprise and the best emotion recognizer for the classification of the three emotions by using physiological signals.     

Tryptophan phosphorescence signals characteristic changes in protein dynamics at physiological temperatures

The Arrhenius plot of the de-excitation rate of tryptophan triplet state deviates from linearity in the physiological temperature range for several proteins with buried tryptophans, similarly to the behaviour of enzyme activity. A model is presented featuring two de-excitation pathways whose effectiveness is regulated by protein dynamics.     

Chemical signals in insects and other arthropods: from molecular structure to physiological functions

Chemical communication is virtually universal among terrestrial and aquatic organisms. Chemical signals control the interactions of cells and organs (hormones) as well as the intra- (pheromones) and interspecific (allelochemicals) relationships between animals. The review considers three examples for chemical communication in insects and other arthropods on different hierarchic levels of biological organization, from the intraindividual level, where hormones control development and reproduction of the animals, to the interspecific level, where semiochemicals function as defense agents against predators or may be used for finding and recognizing food resources. Knowledge of the function of these systems and of the molecular structures of the chemical compounds involved may provide the basis for highly selective techniques of pest control.     

The control of death and lysis in staphylococcal biofilms: a coordination of physiological signals

The processes involved in the development of complex multicellular communities, including the programmed elimination of individual cells during the formation of specialized structures, exhibit fundamental similarities between prokaryotic and eukaryotic organisms. Mechanistic similarities may also exist at the molecular level, as bacterial proteins hypothesized to be related to the apoptosis regulator Bax/Bcl-2 family have been identified, fueling speculation about the existence of bacterial PCD. Here we review the regulatory networks controlling cell death and lysis in Staphylococcus aureus and examine the environmental parameters that might influence them during the development of a biofilm. We hypothesize that the heterogeneous environmental conditions found within a developing biofilm generate distinct physiological signals that coordinate the differential expression of cell death and lysis effectors.     

Power of shell-rapping signals influences physiological costs and subsequent decisions during hermit crab fights

Understanding the costs of signals used in fights is the key to understanding decisions made by contestants. Hermit crabs use shell rapping. This is a clearly defined agonistic signal, which can be quantified in temporal terms and in the power of the key shell-rapping signal component. We examine the relationship between the power expended by attacking hermit crabs and their consequent lactate levels. High power expenditure over the whole fight leads to high lactate, and attackers give up when lactate is high. Some defenders give up early in fights, particularly if the power of raps in early bouts they receive is high. These defenders and those not allowed to fight have low glucose, but those that successfully resist eviction have high glucose. Glucose is mobilized in an attempt to resist; nevertheless, some defenders that attempt resistance are still evicted by persistent attackers. Thus, early power of the signal is a major determinant of success for attackers, albeit at a cost. These data show the link between power, repetition of a signal, metabolic consequences and decisions of contestants in fights. The different activities, decisions and costs of the two roles are not adequately described by existing models of contests.     

Testing the threat-sensitive predator avoidance hypothesis: physiological responses and predator pressure in wild rabbits

Predation is a strong selective force with both direct and indirect effects on an animal’s fitness. In order to increase the chances of survival, animals have developed different antipredator strategies. However, these strategies have associated costs, so animals should assess their actual risk of predation and shape their antipredator effort accordingly. Under a stressful situation, such as the presence of predators, animals display a physiological stress response that might be proportional to the risk perceived. We tested this hypothesis in wild European rabbits (Oryctolagus cuniculus), subjected to different predator pressures, in Doñana National Park (Spain). We measured the concentrations of fecal corticosterone metabolites (FCM) in 20 rabbit populations. By means of track censuses we obtained indexes of mammalian predator presence for each rabbit population. Other factors that could modify the physiological stress response, such as breeding status, food availability and rabbit density, were also considered. Model selection based on information theory showed that predator pressure was the main factor triggering the glucocorticoid release and that the physiological stress response was positively correlated with the indexes of the presence of mammalian carnivore predators. Other factors, such as food availability and density of rabbits, were considerably less important. We conclude that rabbits are able to assess their actual risk of predation and show a threat-sensitive physiological response.     

Nuclear architecture supports integration of physiological regulatory signals for transcription of cell growth and tissue-specific genes during osteoblast differentiation

Metastatic model of human tumor xenografts have been developed using orthotopic transplantation of histologically intact tissue (onplantation) of lung, stomach, colon, pancreatic, prostate and bladder carcinomas. These models represent the entire process of the metastasis, consisting of local tumor growth, vascular and lymphatic invasion at the local site, flow in the vessels and lymphatic, extravasation at the metastatic organs, and seeding and growth at relevant metastatic sites. Orthotopically transplanted human small-cell lung carcinoma displayed a different chemosensitivity pattern compared with the subcutaneous transplanted model, suggesting different pharmacodynamics between the orthotopic lung and the ectopic subcutaneous sites. The intact-tissue orthotopic-onplantation model seems to be useful to study the mechanism of metastasis for discovery of antimetastatic agents and for the patient tumors and for this treatment design.     

A comparative evaluation of neural network classifiers for stress level analysis of automotive drivers using physiological signals

Automotive driving under unacceptable levels of accumulated stress deteriorates their vehicle control and risk-assessment capabilities often inviting road accidents. Design of a safety-critical wearable driver assist system for continuous stress level monitoring requires development of an intelligent algorithm capable of recognizing the drivers’ affective state and cumulatively account for increasing stress level. Task induced modifications in rhythms of physiological signals acquired during a real-time driving are clinically proven hallmarks for quantitative analysis of stress and mental fatigue. The present work proposes a neural network driven based solution to learning driving-induced stress patterns and correlating it with statistical, structural and time-frequency changes observed in the recorded biosignals. Physiological signals like Galvanic Skin Response (GSR) and Photoplethysmography (PPG) were selected for the present work. A comprehensive performance analysis on the selected neural network configurations (both Feed forward and Recurrent) concluded that Layer Recurrent Neural Networks are most optimal for stress level detection. This evaluation achieved an average precision of 89.23%, sensitivity of 88.83% and specificity of 94.92% when tested over 19 automotive drivers. The biofeedback inferred about the driver's ongoing physiological state using this neural network based inference engine would provide crucial information to on-board safety embedded systems to activate accordingly. It is envisaged that such a driver-centric safety system will help save precious lives by way of providing fast and credible real-time alerts to drivers and their coupled cars.     

Long-term effects of different handling procedures on behavioural, physiological, and production-related parameters in silver foxes

Fifty-one silver fox vixens, subjected to three different handling treatments as cubs (no-handling, gentle or forced handling), were studied for long-term effects on behavioural, physiological and production-related parameters in a one and a half year period following the last handling session. As juveniles, the animals were exposed to three different behavioural tests at 18, 22, 28, and 32 weeks of age. Both forcibly and gently handled animals showed reduced fear responses compared with nonhandled controls in test situations involving close contact with humans (P < 0.05). The foxes were tested again as adults at 10, 13, 15, and 18 months of age with the same behavioural tests. It was revealed that forcibly handled animals persistently showed reduced fear responses compared with control animals, both in close contact with humans and when exposed to a novel object, whereas gently handled animals only differed from control animals in one of the tests involving some human contact and when exposed to a novel object (P < 0.05). Significant differences between adult gently handled and forcibly handled animals were found in the “confront’ test involving close human contact. In this test more flight responses were observed in the gently handled group than in the forcibly handled group (P < 0.01). Control animals had significantly larger adrenal weights compared with both forcibly handled animals and gently handled animals at 22 months of age (total mean adrenal weight: controls, 0.62 g; gentle, 0.54 g; forced, 0.54 g, P < 0.05, general linear models). Other physiological measures and production-related parameters such as body weight, body size, gastric ulceration and pelt qualities did not differ between treatments (P > 0.05). Early post-weaning handling made foxes less fearful towards humans. Forced handling seemed somewhat superior to gentle handling as a means to produce animals which, in the long term, adapted better to the farm environment both behaviourally and physiologically. Non-handled control animals suffered from long-term stress as reflected by high levels of fear responses and enlarged adrenals. Thus post-weaning handling may be beneficial in the long term for the wellbeing of farmed foxes. When applied as a management routine, handling had no significant influence on later production-related parameters and was not considered an economic risk.     

Graph-theoretic description of the interplay between non-linearity and connectivity in biological systems

The purpose of this article is to stress the implications that the consideration of nonlinearity has upon the extension and strength of connectivity, if this is understood as a characterization of the degree of interrelation between parts of the system. This objective is reached within the QP formalism for non-linear ODEs. The formalism is developed in a graph-theoretic setting, with the help of which the connectionist aspect of non-linearity becomes apparent. Topology-preserving transformations involve an exchange between the degree of non-linearity and the strengths of interactions, thus assembling systems of apparently different nature into classes of equivalence. We argue that, if we have in mind a classification of systems according to behavior, these classes of equivalence should be given their proper singularity. We characterize globally the connectivity of a class with an index, although we point out during the discussion that the mathematical conception of the complex idea of connectivity is still incomplete.     

Testing the 'free radical theory of aging' hypothesis: physiological differences in long-lived and short-lived colubrid snakes

We test the 'free radical theory of aging' using six species of colubrid snakes (numerous, widely distributed, non-venomous snakes of the family Colubridae) that exhibit long (> 15 years) or short (< 10 years) lifespans. Because the 'rate of living theory' predicts metabolic rates to be correlated with rates of aging and oxidative damage results from normal metabolic processes we sought to answer whether physiological parameters and locomotor performance (which is a good predictor of survival in juvenile snakes) mirrored the evolution of lifespans in these colubrid snakes. We measured whole animal metabolic rate (oxygen consumption Vo2), locomotor performance, cellular metabolic rate (mitochondrial oxygen consumption), and oxidative stress potential (hydrogen peroxide production by mitochondria). Longer-lived colubrid snakes have greater locomotor performance and reduced hydrogen peroxide production than short-lived species, while whole animal metabolic rates and mitochondrial efficiency did not differ with lifespan. We present the first measures testing the 'free radical theory of aging' using reptilian species as model organisms. Using reptiles with different lifespans as model organisms should provide greater insight into mechanisms of aging.