Automatic selection of uncontaminated electromyogram as applied to respiratory muscle fatigue

An automatic procedure for detecting artifacts in the electromyogram (EMG) has been developed and applied to a study of respiratory muscle fatigue. Signal segments are characterized by a set of features, the normal variations of which have been estimated in a training session. From the features are calculated a classification variable, which expresses the degree of deviation from normal conditions. A deviation larger than a certain threshold value designates a segment as disturbed. The study deals with the choice of features, the selection of a suitable segment length, and the determination of an optimal classification threshold. The four features chosen include measures of amplitude symmetry, extreme excursions in the signal tracing, the signal-to-noise ratio, and the shape of the EMG power spectrum. Recordings from three subjects were used for the evaluation of the method. The results indicate that a segment length of 250 ms is appropriate. Accepting a 10% rate of false detections, the average rate of missed detections was 2.2%.     

Non-random-coil behavior as a consequence of extensive PPII structure in the denatured state

Unfolded proteins may contain a native or nonnative residual structure, which has important implications for the thermodynamics and kinetics of folding, as well as for misfolding and aggregation diseases. However, it has been universally accepted that residual structure should not affect the global size scaling of the denatured chain, which obeys the statistics of random coil polymers. Here we use a single-molecule optical technique—fluorescence correlation spectroscopy—to probe the denatured state of a set of repeat proteins containing an increasing number of identical domains, from 2 to 20. The availability of this set allows us to obtain the scaling law for the unfolded state of these proteins, which turns out to be unusually compact, strongly deviating from random coil statistics. The origin of this unexpected behavior is traced to the presence of an extensive nonnative polyproline II helical structure, which we localize to specific segments of the polypeptide chain. We show that the experimentally observed effects of polyproline II on the size scaling of the denatured state can be well-described by simple polymer models. Our findings suggest a hitherto unforeseen potential of nonnative structure to induce significant compaction of denatured proteins, significantly affecting folding pathways and kinetics.     

Adaptation to the action of several teratogens as a consequence of preliminary administration of pesticides to females]

The effect of DDT and lindane pesticides on the intensity of the teratogenic action of sodium acetylxalicylate (SA) and of the cabomate benlate group of pesticides was studied on Wistar rats given the mentioned pesticides from the onset of pregnancy. The teratogens were administered on the 10th and the 12th days of gestation, respectively. Preliminary administration of these pesticides was found to weaken the teratogenic and the embryotoxic action of benlate given in a dose of 250 mg/kg, and of SA administered in a dose of 400 mg/kg. When SA was given in a dose of 600 mg/kg preliminary administration of the pesticides decreased the postimplantation mortality of the embryos, but the number of fetuses with developmental anomalies was the same as in the isolated action of the preparation given in this dose.     

The spectrum analysis of the electromyogram: the adaptation of autoregressive models to the interference electromyogram]

Power-density spectra of interference electromyograms of M. biceps brach. and triceps brach. from two subjects were estimated by the Tukey spectral window and by autoregressive series. By fitting autoregressive models parametric represeentations of spectra are obtained. The models for the electromyograms obtained from biceps (agonist) and triceps (antagonist) differed in the length of the autoregressive series. The intra-individual variation of the spectra from three time intervals of the same contraction was relatively small.     

Morphological diversification of fish as a consequence of the divergence of ontogenetic trajectories]

The possibilities of the investigation of ontogenetic changes in the morphological features of fish using multidimensional "ontogenetic channels," within which individual ontogenetic trajectories run, are demonstrated using African barbs. (Barbus intermedius complex) as an example. The position of ontogenetic channels allows one to judge how the differences of adult individuals in morphological characters arise during development and how their morphological diversity is formed.     

The evolutionary consequence of the individualistic response to climate change

The Quaternary fossil record has abundant evidence for ecologically nonanalogue communities made up of combinations of modern taxa not seen in sympatry today. A brief review of the literature detailing these nonanalogue communities is given with a discussion of their various proposed causes. The individualistic, Gleasonian, response of species to climate and environmental change is favoured by many. The degree to which communities are nonanalogue appears to increase with greater time depth, and this progressive process is a necessary outcome of the individualistic response of species to climate change through time. In addition, it is noted that populations within species, as well as the species as a whole, respond individualistically. This paper proposes that many elements of nonanalogue communities are extinct populations, which may explain their environmentally anomalous combinations. These extinct populations are, by definition, lineages without descendents. It is further proposed that the differential extinction of populations, as a result of continuous ecological reassembly, could amount to a significant evolutionary phenomenon.     

Assessment of the functional state of the cerebral cortex in rabbits according to electroencephalographic findings using a computer diagnostic system]

Computer estimation of the current functional state of the cerebral cortex in rabbits by the EEG data permitted to distinguish its peculiarities in dark and light adaptation of different duration under the action of nembutal; individual peculiarities of the cerebral cortex activity were revealed in various rabbits. The automatic converter system and that of recording and analysis of multiprocess information (apromin system) and computer diagnostic system (mds) were used in complex for the multistage processing of the multiprocess information. Final results are presented on the plane as points reflecting multidimentional images of the current functional states of the cerebral cortex in animals.     

Household chagasic endemia detected as a consequence of a case of congenital infection]

During a study on prevalence of parasitic and viral serological markers in pregnant adolescents, a 17-year-old primipara from Polpaico, village near Santiago, gave birth to a normal male newborn in a Santiago hospital. As both of them presented positive an indirect hemagglutination test (IHAT) for Chagas' disease and the corresponding xenodiagnosis (XD), the infection in the infant was considered to be acquired through the placental route. According to recent epidemiological surveys Polpaico is an endemo-enzootic chagasic rural settlement, where 14.7% of dwellings were infested with Triatoma infestans, while triatominae, persons and domestic mammals were found infected with Trypanosoma cruzi. One month later the adolescent mother, her son and other 11 consanguineous members of the family were visited in their homes in order to submit each of them to a physical examination and to IHAT for Chagas' disease, and XD to those whose IHAT resulted positive. Thus, in 7 (53.8%) the IHAT was positive and in 4 (57.1%) out of these 7 presented positive the XD, results that as a whole yielded a household chagasic endemics.     

The morphofunctional transformation of skeletal muscle as a consequence of electroneurostimulation training]

By means of histological and histochemical methods slices of biopsies of the canine musculus latissimus dorsi have been investigated after electroneurostimulation for three months through the thoracodorsal nerve in situ and after cutting its initial part. Frequency of contractions increases gradually from 30 up to 80 per 1 min every 2 weeks. The preparations are stained with hematoxylin--eosin. Histochemical reactions for adenosinetriphosphatase (ATPase) (incubational medium pH 4.3 and 10.3) and for acetylcholinesterase (AChE) are performed. The muscle, stimulated in situ, preserves its normal structure. Transformation of muscle contractions from fast to slow, as well as increasing AChE activity in myoneural synapses are revealed. The muscle, stimulated after its cutting at its beginning, is subjected to adipose dystrophy. Activity of ATPase and AChE do not differ from that in the control.     

Mechanism of the fast neurogenic component of the respiratory response to muscular work]

Dynamics of pulmonary ventilation, electric activity of the intercostal muscles and of the alveolar gas composition was studied in 12 healthy men during dosaged muscular work; these men were given different gas mixtures to breathe. The respiratory response at the initial period of work in inhalation of the hypoxic-hypercapnic gas mixture was greater than that in persons who breathed room air. This response practically disappeared after oxygen hyperventilation. Apparently the rapid component of the ventilation response to the muscular work was largely due to increased sensitivity of the respiratory centre to the chemoreceptive drive.     

Antipredator responses of aphids to parasitoids change as a function of aphid physiological state

Under predation risk, prey may prioritize antipredator behaviours and sacrifice feeding. However, energetically constrained animals may choose to sacrifice or change antipredator responses and accept relatively greater risk in order to secure food. In this last case, the antipredator tactics chosen must balance safety and feeding in such a way that costs are minimized and benefits maximized. We studied the antipredator behaviour of pea aphid, Acyrthosiphon pisum (Harris) (Hemiptera: Aphididae) subjected to different periods of food deprivation, against the parasitoid Aphidius ervi (Hymenoptera: Braconidae). As the energetic internal stress of aphids increased, the predominant antipredator response changed from walking away and dropping to kicking behaviour, and parasitization avoidance decreased. Parasitoids did not show preference between food-deprived and nonfood-deprived aphids. Dropping and walking away reduced parasitization from 50 to 33%. These results support the hypothesis that the antipredator behaviour of an aphid changes as a function of internal stress. By performing less costly behaviour such as kicking under energetically constrained conditions, aphids seem to minimize their probability of energy shortfall. Given that aphid antipredator behaviour is a function of nutritional state, its occurrence under natural conditions may match host quality spatial distribution. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Juvenile migration in brown trout: a consequence of energetic state

1. We explored the mechanisms determining age and size at juvenile migration in brown trout Salmo trutta L. A ¹³³Cs tracer methodology was used to estimate food consumption of juvenile brown trout in a Norwegian stream, and the energy budgets of early migrants and stream residents were compared.
2. Fast-growing brown trout migrated to the lake earlier and at a smaller body size than slower-growing individuals. The 2+ migrants were significantly larger than those that remained 1 or more years longer in the stream. The 3+ migrants were significantly larger than the 2+ migrants. Some fast-growing males matured in the stream, whereas all females left the stream before maturing sexually.
3. The food consumption and the energy budgets for 2+ migrants were more than four times higher than those of the resident 2+ fish. Total energy allocated to growth was also higher among migrants, and the total metabolic costs were five times higher among migrants than among resident fish.
4. The proportional energy allocation to growth among the 2+ migrants was much lower (about half) than that of those remaining longer in the stream. The reduction in the proportion of energy available for growth from age 1+ to 2+ was larger among migrants (88%) than among resident fish (68%). Reduction in the proportion of energy available for growth is a probable explanation for why migrations are initiated at age 2.
5. Our study supports the hypothesis that fast-growing individuals shift their niche earlier and at a smaller body size than slower-growing individuals because they maintain higher metabolic rates and are energetically constrained at a younger age by limited food resources than slow growers.     

Non-propagated potentials in the electromyogram of mammalian ocular muscles]

Electromyograms of mammalian extraocular muscles were recorded by means of a coaxial electrode. Besides normal extracellular spike potentials (1-2 msec duration), monophasic waves (with a decline lasting up to 7 msec) were recorded. As to the interpretation of these potential changes in terms of a potential drop that is produced by local currents flowing from the resting region of a fibre towards the active region consideration is given to two cases. First, a propagated active region (spike potentials, at least diphasic) and second, a stationary active region (with resulting monophasic waves). In the EMGs spontaneous monophasic potentials recruit at a lower threshold than spike potentials; frequency changes were observed when head position was altered. The latter are interpreted as local depolarizations occurring at neuromuscular junctions of multiple innervated muscle fibres among those fibre types that compose extraocular muscles.