Various characteristics of the activity of skeletal muscles in humans and dogs during postnatal ontogenesis

At normal ambient temperatures, in absence of stress, in babies during first months of life (in contrast to less maturely born mammals), the respiratory activity of skeletal muscles is not realized, being observed only under stress conditions. In 1-1 1/2 months old puppies, after deafferentation of the hindlimb, the frequency of movements of a jerk type increases approximating the level observed in newborn animals. At normal ambient temperatures, these puppies exhibit respiratory activity of skeletal muscles which is not observed at this age in control animals.     

The coupled evolution of breathing and locomotion as a game of leapfrog

Because the increase in metabolic rate related to locomotor activity places demands on the cardiorespiratory apparatus, it is not surprising that the evolution of breathing and of locomotion are coupled. As the respiratory faculty becomes more refined, increasingly aerobic life strategies can be explored, and this activity is in turn expedited by a higher-performance respiratory apparatus. This apparent leapfrogging of respiratory and locomotor faculties begins in noncraniate chordates and continues in water-breathing and air-breathing vertebrates. Because both locomotor and cardiorespiratory activities are coordinated in the brain, neurological as well as biochemical coupling is evident. In spite of very different breathing mechanisms in various vertebrate groups, the basic respiratory control mechanisms appear to have been conserved, and respiratory-locomotor coupling is evident in all classes of vertebrates. Hypaxial body wall muscles that were strictly locomotor in fish have respiratory function in amniotes, but some locomotor function remains in all groups.     

Action of dioxidine on the membrane apparatus of the bacterial cell

A study of dioxydine effect on the membrane apparatus of Staphylococcus aureus 209 P and Micrococcus lysodeikticus revealed a decrease in the dehydrogenase activity of membrane preparations and in the specific concentration of cytochromes, if cells had been cultivated in a medium with subbacteriostatic concentrations of dioxydine. The total activity of the respiratory chain was slightly decreased. Conservatism of the membrane apparatus of the bacteria studied was demonstrated.     

Contribution to the structure of respiration control]

A structure is reported which describes the relatively free availability of the motor respiratory apparatus to non-respiratory functions due to the presence of a respiratory control both on homeostatic and motor levels. It is assumed that, at the motor level, a competition develops of two or more regulators for the same parameter (e.g. the activity of neurons that can be claimed both by respiratory and by a second skeletal motor process). The compromise being reached is dependent on the amplification in the competing circuits. The correlation between the metabolic value and that of the respiration-time volume may be accomplished by the fact that amplification in the respiratory-motor circuit is rendered variable as a result of its interconnection with the chemical respiratory control. The high time constant of the latter allows for the instantaneous free availability of the motor respiratory apparatus to non-respiratory functions. The postulated structure offers better interpretations for the actual respiration behaviour than those considering the respiratory function alone.     

Protein oxidation in G0 cells of Saccharomyces cerevisiae depends on the state rather than rate of respiration and is enhanced in pos9 but not yap1 mutants.

Immunodetection of protein carbonyl groups demonstrates that growth arrest elicited by carbon or nitrogen starvation causes an increased oxidation of proteins in Saccharomyces cerevisiae. Mutant analysis suggests that the response regulator Pos9p is involved in mitigating self-inflicted oxidative damages in G(0) cells, whereas Yap1p is primarily required in growing cells. The data also suggest that oxidation of target proteins is not a priori an effect of arrest of cell division or nutrient depletion and cannot be explained by the respiratory activity alone nor a high ratio of catabolic/anabolic activity in G(0) cells. Instead, we observed that starvation elicits a transition in the respiratory state (from phosphorylating to nonphosphorylating respiration) and that this transition is associated with a stepwise increase in protein oxidation. During carbon starvation, this transition and increase in oxidation occurs immediately as the carbon source is depleted, growth is arrested, and the respiratory rate falls drastically. In contrast, during nitrogen starvation and excess carbon the respiratory state transition and stepwise increase in protein oxidation are markedly delayed and occur long after the nitrogen source has been depleted and division and growth-arrested. Oxidation in G(0) cells could be enhanced by treating cells with low concentrations of antimycin A and attenuated with myxothiazol, indicating that protein oxidation is intimately linked to reactive oxygen species generated by semiquinones of the Q-cycle. Thus, the work presented suggests that the degree of coupling in the mitochondrial respiratory apparatus rather then the overall rate of respiration affects the degree of protein oxidation in nondividing yeast cells.     

An apparatus for altering the mechanical load of the respiratory system

We describe an apparatus for altering the mechanical load against which the respiratory muscles operate in humans. A closed system incorporates a rolling seal spirometer. The spirometer piston shaft is coupled to a fast-responding linear actuator that develops force in proportion to desired command signals. The command signal may be flow (resistive loading or unloading), volume (elastic loading or unloading), constant voltage (continuous positive or negative pressure), or any external function. Combinations of loads can be applied. Logic circuits permit application of the load at specific times during the respiratory cycle, and the magnitude of the loads is continuously adjustable. Maximum pressure output is +/- 20 cmH2O. The apparatus permits loading or unloading over a range of ventilation extending from resting levels to those observed during high levels of exercise (over 100 l/min). In response to a square-wave input, pressure rises exponentially with a time constant of 20 ms.     

Mathematical Modeling of Respiratory System Mechanics in the Newborn Lamb

In this paper, a mathematical model of the respiratory mechanics is used to reproduce experimental signal waveforms acquired from three newborn lambs. As the main challenge is to determine specific lamb parameters, a sensitivity analysis has been realized to find the most influent parameters, which are identified using an evolutionary algorithm. Results show a close match between experimental and simulated pressure and flow waveforms obtained during spontaneous ventilation and pleural pressure variations acquired during the application of positive pressure, since root mean square errors equal to 0.0119, 0.0052 and 0.0094. The identified parameters were discussed in light of previous knowledge of respiratory mechanics in the newborn.     

Bacterial defense against aging: role of the Escherichia coli ArcA regulator in gene expression,readjusted energy flux and survival during stasis.

Using two-dimensional gel electrophoresis and N-terminal amino acid sequencing analysis, we demonstrate that a mutant of the global regulatory protein ArcA fails to decrease the synthesis of the TCA cycle enzymes malate dehydrogenase, isocitrate dehydrogenase, lipoamide dehydrogenase E3 and succinate dehydrogenase in response to stasis, while the increased production of the glycolysis enzymes phosphoglycerate mutase and pyruvate kinase is unaffected. Microcalorimetric and respiratory measurements show that the continued production of TCA cycle enzymes in the (delta)arcA mutant is manifested as an elevated rate of respiration and total metabolic activity during starvation. The (delta)arcA mutant is severely impaired in surviving prolonged periods of exogenous carbon starvation, a phenotype that can be alleviated by overproducing the superoxide dismutase SodA. In addition, flow cytometry demonstrates that starving (delta)arcA mutant cells, in contrast to wild-type cells, fail to perform reductive division, remain large and contain multiple chromosomal copies. We suggest that the ArcA-dependent reduced production of electron donors and the decreased level and activity of the aerobic respiratory apparatus during growth arrest is an integral part of a defense system aimed at avoiding the damaging effects of oxygen radicals and controlling the rate of utilization of endogenous reserves.     

Functional variability of the indices of ventilation and gas exchange in healthy young men in Western Siberia

The variability of standardized values of indices of the external respiration function (ERF) of healthy young men living in Western Siberia has been estimated. Three different states of ERF have been found: (i) normal respiration (normal ventilation efficiency at different levels); (ii) compensatory hyperventilation, during which the ventilation apparatus is strained, which indicates that there are some changes in the morphological structure of the respiratory regions of the lungs (this state can be considered a borderline between the normal state and pathology); and (iii) deep, highly effective respiration; it has no signs of the tension of the function or the apparatus of external respiration, and it can be considered a normal genotypic/phenotypic variant.     

Inactivation of mitochondrial complex I stimulates chloroplast ATPase in Physcomitrium patens

Light is the ultimate source of energy for photosynthetic organisms, but respiration is fundamental for supporting metabolism during the night or in heterotrophic tissues. In this work, we isolated Physcomitrella (Physcomitrium patens) plants with altered respiration by inactivating Complex I (CI) of the mitochondrial electron transport chain by independently targeting on two essential subunits. Inactivation of CI caused a strong growth impairment even in fully autotrophic conditions in tissues where all cells are photosynthetically active, demonstrating that respiration is essential for photosynthesis. CI mutants showed alterations in the stoichiometry of respiratory complexes while the composition of photosynthetic apparatus was substantially unaffected. CI mutants showed altered photosynthesis with high activity of both Photosystems I and II, likely the result of high chloroplast ATPase activity that led to smaller ΔpH formation across thylakoid membranes, decreasing photosynthetic control on cytochrome b6f in CI mutants. These results demonstrate that alteration of respiratory activity directly impacts photosynthesis in P. patens and that metabolic interaction between organelles is essential in their ability to use light energy for growth.

Mosses lacking mitochondrial Complex I show induced activation of chloroplast ATPase, demonstrating the impact of respiration on the metabolism of plant photosynthetic cells.     

Rapid Development of Mitochondria in Pea Cotyledons during the Early Stage of Germination

Rapid increases in activities and components of mitochondrial particles isolated from cotyledons of Pisum sativum var. Alaska during the early stage of germination are described. Respiratory rate of the cotyledons increased rapidly as hydration proceeded. A similar but slightly delayed increase in respiratory activity of the isolated mitochondrial fraction was observed. The respiratory control ratio and adenosine 5′-pyrophosphate/oxygen ratio rose during imbibition. Cytochrome oxidase and malate dehydrogenase activities in the mitochondrial fraction increased during the initial phase of imbibition. The increase seemed to precede that in respiratory activity. A significant activity of cytochrome oxidase and most of the malate dehydrogenase activity in the cotyledons were present in the postmitochondrial fraction in the case of the dry seeds. Mitochondrial protein and phospholipid also increased during imbibition, and the rise in the components seemed to concur with that in respiratory activity. The mechanism of mitochondrial development during imbibition is discussed.     

Online monitoring of the respiratory quotient reveals metabolic phases during microaerobic 2,3‐butanediol production with Bacillus licheniformis

Microaerobic cultivation conditions are often beneficial for the biotechnological production of reduced metabolites like 2,3‐butanediol. However, due to oxygen limitation, process monitoring based on oxygen transfer rate, or dissolved oxygen measurement provides only limited information. In this study, online monitoring of the respiratory quotient is used to investigate the metabolic activity of Bacillus licheniformis DSM 8785 during mixed acid‐2,3‐butanediol production under microaerobic conditions. Thereby, the respiratory quotient provides valuable information about different metabolic phases. Based on partial reaction stoichiometries, the metabolic activity in each phase of the cultivation was revealed, explaining the course of the respiratory quotient. This provides profound information on the formation or consumption of glucose, 2,3‐butanediol, ethanol and lactate, both, in shake flasks and stirred tank reactor cultivations. Furthermore, the average respiratory quotient correlates with the oxygen availability during the cultivation. Carbon mass balancing revealed that this reflects the increased formation of reduced metabolites with increasing oxygen limitation. The results clearly demonstrate that the respiratory quotient is a valuable online signal to reveal and understand the metabolic activity during microaerobic cultivations. The approach of combining respiratory quotient monitoring with stoichiometric considerations can be applied to other organisms and processes to define suitable cultivation conditions to produce the desired product spectrum.     

Synaptic and intrinsic activation of GABAergic neurons in the cardiorespiratory brainstem network

GABAergic pathways in the brainstem play an essential role in respiratory rhythmogenesis and interactions between the respiratory and cardiovascular neuronal control networks. However, little is known about the identity and function of these GABAergic inhibitory neurons and what determines their activity. In this study we have identified a population of GABAergic neurons in the ventrolateral medulla that receive increased excitatory post-synaptic potentials during inspiration, but also have spontaneous firing in the absence of synaptic input. Using transgenic mice that express GFP under the control of the Gad1 (GAD67) gene promoter, we determined that this population of GABAergic neurons is in close apposition to cardioinhibitory parasympathetic cardiac neurons in the nucleus ambiguus (NA). These neurons fire in synchronization with inspiratory activity. Although they receive excitatory glutamatergic synaptic inputs during inspiration, this excitatory neurotransmission was not altered by blocking nicotinic receptors, and many of these GABAergic neurons continue to fire after synaptic blockade. The spontaneous firing in these GABAergic neurons was not altered by the voltage-gated calcium channel blocker cadmium chloride that blocks both neurotransmission to these neurons and voltage-gated Ca(2+) currents, but spontaneous firing was diminished by riluzole, demonstrating a role of persistent sodium channels in the spontaneous firing in these cardiorespiratory GABAergic neurons that possess a pacemaker phenotype. The spontaneously firing GABAergic neurons identified in this study that increase their activity during inspiration would support respiratory rhythm generation if they acted primarily to inhibit post-inspiratory neurons and thereby release inspiration neurons to increase their activity. This population of inspiratory-modulated GABAergic neurons could also play a role in inhibiting neurons that are most active during expiration and provide a framework for respiratory sinus arrhythmia as there is an increase in heart rate during inspiration that occurs via inhibition of premotor parasympathetic cardioinhibitory neurons in the NA during inspiration.     

Spatio-temporal characterization of intercostal activity during breathing in the cat

It is envisaged that the motor control of the intercostal musculature--an assembly of mobile structures--can be characterized in terms of a conceptual spatially continuous control function, that underlies the discretely distributed muscular activity and reflects an inferred global dynamic control of the thoracic cage during breathing. The global control function is estimated by the spatio-temporal pattern obtained by averaging in time and space and interpolation of multichannel simultaneous intercostal EMG recording in the anaesthetized cat. Different examples of the experimental preparation in the presence of stimuli of different kinds are analysed. The resultant signal patterns are found to be self-consistent and capable of exhibiting systematically differing features in systematically differing experimental conditions, thus supporting the validity of the analysis and the choice of the estimator. It is concluded that a more detailed analysis of the requirements of this approach is then warranted. Such requirements are discussed, and, specifically, results that bear on the adequacy of spatial sampling rate are presented. It is suggested that such methods offer a promising approach in the study of motor control strategies of the respiratory apparatus.     

Circadian and circatidal rhythms of oxygen consumption in the sandy-beach isopod Tylos granulatus Krauss

The sandy-beach isopod Tylos granulatus Krauss burrows at the high tide mark, and has rhythms of nocturnal emergence coincident with the low tide period. Measurements of the respiration rate show that a low rate of oxygen consumption is maintained throughout the day but there is a circatidal rhythmic increase of between 300 and 700% during the nocturnal low tide. The height of this peak and the percentage of animals displaying a peak both increase from spring tide to neap tide suggesting a semi-lunar rhythm. The respiratory peaks have a 24.8 h periodicity, being later each night until low tide falls in the dawn, when there is a ‘switch-back’ so that peaks are then during the subsequent evening low tide. These respiratory rhythms are persistent under constant light and coincide with previously described activity rhythms. The respiratory rhythms considerably reduce metabolic energy losses, particularly as the activity rhythms ensure avoidance of high diurnal temperatures and activity during the cooler nocturnal period.     

Studies on stimulus-response coupling in human neutrophils. II. Relationships between the effects of changes of external ionic composition on the properties of N-formylmethionylleucylphenylalanine receptors and on the respiratory and secretory responses

Studies were carried out on the mechanism responsible for the enhancement of the respiratory and secretory responses to N-formylmethionylleucylphenylalanine (fMet-Leu-Phe) exhibited by human neutrophils suspended in Na+-free, high-K+ buffered solution. The results demonstrate that: (a) the variation of Na+ concentration in the suspending solution induces in human neutrophils a marked modification of the recognition apparatus for the chemotactic peptide fMet-Leu-Phe, the lack of or low concentration of this ion increasing the number of the receptors and their specific affinity for the ligand; (b) the greater respiratory burst and secretion induced by fMet-Leu-Phe in human neutrophils suspended in Na+-free, high-K+ medium are due to the increased formation of receptor-ligand complexes at the cell membrane; (c) the greater respiratory response is partially due also to a higher efficiency of these receptor-ligand complexes. The molecular mechanism by which Na+ exerts a regulative role on the properties of the recognition apparatus for the chemotactic peptide and its possible significance are discussed.     

Time-dependent variations of transcutaneous PCO2 level in normal subjects

Transcutaneous PCO2 (PtcCO2), which is linearly related to arterial PCO2, was continuously recorded in healthy, adult, normal volunteers for 8-h periods. Recording this variable with the apparatus employed permits measurement of changes in the level of ventilation while subjects are freely ambulant and unencumbered by invasive and flow-resistive respiratory apparatus. The time series obtained exhibited marked periodicities. The frequencies and amplitudes varied between subjects. Peak-to-peak variation was 10-20% of mean values. There was no apparent association between fluctuations in PCO2 and activity other than formal exercise. Visual inspection of the time series and preliminary statistical analysis of digitally converted data suggested that the time-dependent changes of PtcCO2 were normally distributed. However, more rigorous statistical examination revealed that in no case was PtcCO2 actually normally distributed.