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PubMed1977

Temperature relations of aerial and aquatic respiration in six littoral snails in respiration in six littoral snails in relation to their vertical zonation.

Aerial and aquatic rates of oxygen consumption were determined over a range of 5 degrees to 45 degrees C at 5 degrees C intervals for six species of marine littoral snails: including the sublittoral species, Acmaea testudinalis, Mitrella lunata, and Lacuna vincta; and the truly intertidal species, Littorina obtusata, L. littorea, and L. saxatilis. Polarographic oxygen electrodes were used with normally active snails collected from populations on Nobska and Manomet Points, Massachusetts. Three subtidal species, A. testudinalis, Lacuna vincta, and M. lunata, do not display any metabolic adjustment to increasing temperature, with thermal limits reached at 30 degrees to 35 degrees C. Aerial respiration in A. testudinalis is similar to aquatic O2 uptake, but rates average only 36.4% of aquatic rates. The intertidal congeners, Littorina obtusata, L. littorea and L. saxatilis, have varying degrees of aerial and aquatic metabolic regulation with increasing temperature. L. obtusata, a low intertidal snail exposed to air for 15% to 45% of the tidal cycle, displays a respiratory pattern of "passive endurance" to high temperatures both in air and in water. L. littorea, the dominant snail of the midlittoral region, remains active when exposed to air (30% to 75% of the tidal cycle) and has a zone of metabolic regulation between 20 degrees C and 30 degrees C. Over this, the normal ambient temperature range, the Q10 closely approximates one, and nearly equivalent O2 uptake rates occur in air and in water. L. saxatilis from the upper littoral region is exposed to air for 70% to 95% of the tidal cycle and is characterized by reduced aerial and aquatic O2 uptake rates above 25 degrees C, representing a reversible torpor up to its thermal maximum at 44 degrees C. For these six snail species, respiratory responses to increasing temperature are thus directly related to the pattern of vertical distribution in the intertidal environment. Discussion of this relationship stresses that the evolution of other nearterrestrial structures and functions in littoral snails has proceeded in a discontinuous fashion. Despite this, the temperature responses in respiration parallel the functional morphology of the pallial structures and the physiological patterns of response to low oxygen stress, as well as adaptive features of reproduction, larval development, water-control, and nitrogenous excretion.

Acclimatization↗

PubMed1975

Effects of a welding helmet and dust respirators on respiration at rest and during exercise.

The influence of welders' protective devices on respiration at rest and during exercise was studied under laboratory conditions. During exercise the devices caused increased ventilation and increased arterial carbon dioxide tension. In the case of the welding helmet the increase was probably a consequence of increased dead space. It is concluded that the physiological affects on respiration are of minor importance in themselves, but they should be taken into account when the degree of exposure to welding fumes is evaluated.

Adult↗

PubMed1998

Replication-dependent and selection-induced mutations in respiration-competent and respiration-deficient strains of Saccharomyces cerevisiae.

Adaptive or selection-induced mutations are defined as mutations that occur in non-dividing cells as a response to prolonged non-lethal selective pressure such as starvation for an essential amino acid. In the absence of DNA replication, the processing of endogenous DNA lesions by repair enzymes probably acts as a source of mutations. We are studying selection-induced reversions of frameshift alleles in the eukaryote Saccharomyces cerevisiae. Here we show that respiration-deficient strains, totally devoid of mitochondrial DNA, yield selection-induced mutants at slightly elevated frequencies compared to isonucleic respiration-competent strains. Therefore factors of mitochondrial origin such as reactive oxygen species or hypothetical recombinogenic DNA fragments are unlikely to be mediators of selection-induced nuclear frameshift mutation in yeast. Furthermore we compared sequence spectra of reversions of the +1 hom3-10 frameshift allele and found a strong preference for -1 deletions in mononucleotide repeats in selection-induced and replication-dependent revertants, indicating slippage errors during DNA repair synthesis as well as during DNA replication. Remarkably, a higher degree of variation in the site of the reverting frameshift and accompanying base substitutions was found among selection-induced revertants.

Adaptation, Biological↗

PubMed2005

Soil respiration in a mixed temperate forest and its contribution to total ecosystem respiration.

Soil respiration (SR) was measured with an infrared gas analyzer in nine plots representative of the heterogeneous vegetation in a mixed coniferous-deciduous forest in the Belgian Campine region. Selected plots included the two most representative overstory species (Pinus sylvestris L. and Quercus robur L.) in combination with the most representative understory species of the forest. A model that includes temperature and water as the main controlling variables was fitted to the data. We found large spatial variability in SR among plots, with typically lower fluxes under the coniferous overstory than under the deciduous overstory (means of 4.8 +/- 0.4 and 8.8 +/- 0.5 Mg C ha(-1) year(-1), respectively). Total annual soil carbon (C) emissions were estimated by weighting fluxes from different types of vegetation according to their relative contribution to the footprint area of the eddy covariance flux measurement. The relative contribution of the two main tree species to the footprint-weighted total SR varied among seasons with the more abundant coniferous overstory contributing the most to total SR during most of the year. Nonetheless, during summer, the contribution of deciduous plots to total SR was disproportionally high because of the more pronounced seasonality of belowground metabolic activity. Net ecosystem carbon dioxide exchange was measured by eddy covariance, and we estimated total ecosystem respiration (TER) with footprint-constrained nighttime fluxes. Mean total annual SR and TER were 6.1 +/- 0.11 and 9.1 +/- 1.15 Mg C ha(-1) year(-1), respectively. The 95% confidence interval of the ratio of annual SR:TER ranged from 0.58 to 0.76, with a mean of 0.67. The contribution of SR to TER tended to vary seasonally, with minimum contributions during summer (less than 50% of TER) and maximum contributions during winter (about 94% of TER).

Carbon Dioxide↗

PubMed1996

Interactions between Photosynthesis and Respiration in the Green Alga Chlamydomonas reinhardtii (Characterization of Light-Enhanced Dark Respiration).

The rate of respiratory O2 consumption by Chlamydomonas reinhardtii cell suspensions was greater after a period of photosynthesis than in the preceding dark period. This "light-enhanced dark respiration" (LEDR) was a function of both the duration of illumination and the photon fluence rate. Mass spectrometric measurements of gas exchange indicated that the rate of gross respiratory O2 consumption increased during photosynthesis, whereas gross respiratory CO2 production decreased in a photon fluence rate-dependent manner. The rate of postillumination O2 consumption provided a good measure of the O2 consumption rate in the light. LEDR was substantially decreased by the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea or glycolaldehyde, suggesting that LEDR was photosynthesis-dependent. The onset of photosynthesis resulted in an increase in the cellular levels of phosphoglycerate, malate, and phosphoenolpyruvate, and a decrease in whole-cell ATP and citrate levels; all of these changes were rapidly reversed upon darkening. These results are consistent with a decrease in the rate of respiratory carbon flow during photosynthesis, whereas the increase in respiratory O2 consumption during photosynthesis may be mediated by the export of photogenerated reductant from the chloroplast. We suggest that photosynthesis interacts with respiration at more than one level, simultaneously decreasing the rate of respiratory carbon flow while increasing the rate of respiratory O2 consumption.

Journal Article↗

PubMed1985

Regulation of Respiration in the Leaves and Roots of Two Lolium perenne Populations with Contrasting Mature Leaf Respiration Rates and Crop Yields.

Measurements of O(2) uptake were made on leaves and roots of two populations of Lolium perenne L. cv S23 (GL66 and GL72), previously shown to have contrasting rates of CO(2) evolution and yields of dry matter. O(2) uptake was faster in the mature leaves of GL66 than those of GL72, but no difference was observed in the respiratory rates of meristematic leaf bases or mature roots. The growth rate of GL72 was faster than that of GL66. Cyanide resistance was substantial in mature leaves but the alternative path did not contribute to O(2) uptake in the dark. In both populations, adding malate and glycine stimulated O(2) uptake, but exogenous sucrose only stimulated when uncoupler was also present. The difference between the respiratory rates of the two populations was maintained under all investigated conditions. We conclude that the rate of mature leaf respiration in the dark in L. perenne is limited by adenylate control of glycolysis. The difference between the fast (GL66) and slow (GL72) respiring populations reflected a greater respiratory capacity and higher turnover of ATP in GL66. Alternative path capacity was also high in the roots of both and contributed substantially to O(2) uptake, as indicated by inhibition by salicylhydroxamic acid in the absence of KCN. The alternative path capacity of meristematic leaf bases was considerably less than that in mature leaves.Transverse and cross-sections were made of mature leaves of both populations to study anatomical features which might explain the differences in ATP turnover, suggested by the biochemical experiments. Leaves of GL72 were thicker but did not show a different anatomy when compared with GL66. The increased thickness was not due to more or larger cells but entirely to a larger intercellular volume.

Journal Article↗

PubMed1977

The inhibitory effect of papaverine on respiration-dependent contracture of guinea pig taenia coli in high-K medium. I. The relationship between contracture and respiration.

Papaverine (Pap) inhibited a tonic tension development in guinea pig taenia coli induced by an elevation of the potassium concentration of the medium to 40 mM (40-K). The ID50 of Pap was 4.5 x 10(-6) M. Inhibition of the 40-K induced tonic tension by Pap was dependent on the calculated concentration of non-ionized form, but not the ionized form. Inhibition of the tonic tension by Pap and various metabolic inhibitors was not antagonized by raising the Ca++ concentration in the medium. Results obtained from simultaneous measurement of the 40-K induced O2 consumption and tension illustrated that the inhibition of O2 consumption rapidly induced the inhibition of the tension. Furthermore, glucose removal, amytal or Pap resulted in a progressive relationship between the inhibition of O2 consumption and the inhibition of tension. The inhibition of Pap as determined by O2 consumption was not reversed by application of 10(-4) M 2,4-dinitrophenol (DNP). These results plus graphical analysis of the mechanical response suggest that Pap may penetrate the cell membrane and inhibit mitochondrial respiration, thereby inhibiting this very respiration-dependent contracture.

Animals↗

PubMed1982

Cyanide-resistant respiration in a respiration-deficient mutant of Saccharomyces cerevisae.

A respiration-deficient mutant of Saccharomyces cerevisiae, grown aerobically with glucose as the sole source of energy and carbon, showed residual respiration resistant to cyanide. The differential sensitivity of cell fractions to inhibition by hydroxamic acids and carbon monoxide suggested that more than one type of organelle, probably mitochondria and microsomes, was involved in the consumption of oxygen.

Carbon Monoxide↗

PubMed1977

Effects of pulmonary gas embolism on circulation and respiration in the dog. II. Effects on respiration.

In mongrel dogs weighing 15--25 kg and anesthetized with thiopental-gamma-hydroxybutyric acid the effects of venous gas infusion and injection on several respiratory variables were investigated. During spontaneous respiration pulmonary gas embolism caused an increase of the ventilatory minute volume depending on the degree of embolization. The contribution of breathing frequency and tidal volume to the increase of ventilatory minute volume varied from one animal to the other. During constant artificial ventilation pulmonary gas embolism impaired the pulmonary gas exchange depending on the degree of embolization. How far a steady-state phase in gas exchange can be reached during continuous venous gas infusion depended on the adaptation of the circulation. At severe degrees of embolization circulation as well as gas exchange became deficient. Increasing artificial ventilation during pulmonary gas embolism improved the wash-out of carbon dioxide, but hardly affected the uptake of oxygen. The most important origin of the disturbed gas exchange in pulmonary gas embolism seemed to be an increased inequality of the ventilation-perfusion ratio distribution.

Animals↗

PubMed2002

Nonlinear measures of respiration: respiratory irregularity and increased chaos of respiration in patients with panic disorder.

BACKGROUND: Respiratory irregularity has been previously reported in patients with panic disorder using time domain measures. However, the respiratory signal is not entirely linear and a few previous studies used approximate entropy (APEN), a measure of regularity of time series. We have been studying APEN and other nonlinear measures including a measure of chaos, the largest Lyapunov exponent (LLE) of heart rate time series, in some detail. In this study, we used these measures of respiration to compare normal controls (n = 18) and patients with panic disorder (n = 22) in addition to the traditional time domain measures of respiratory rate and tidal volume. METHODS: Respiratory signal was obtained by the Respitrace system using a thoracic and an abdominal belt, which was digitized at 500 Hz. Later, the time series were constructed at 4 Hz, as the highest frequency in this signal is limited to 0.5 Hz. We used 256 s of data (1024 points) during supine and standing postures under normal breathing and controlled breathing at 12 breaths/min. RESULTS: APEN was significantly higher in patients in standing posture during normal as well as controlled breathing (p = 0.002 and 0.02, respectively). LLE was also significantly higher in standing posture during normal breathing (p = 0.009). Similarly, the time domain measures of standard deviations and the coefficient of variation (COV) of tidal volume (TV) were significantly higher in the patient group (p = 0.02 and 0.004, respectively). The frequency of sighs was also higher in the patient group in standing posture (p = 0.02). In standing posture, LLE (p < 0.05) as well as APEN (p < 0.01) contributed significantly toward the separation of the two groups over and beyond the linear measure, i.e. the COV of TV. CONCLUSION: These findings support the previously described respiratory irregularity in patients with panic disorder and also illustrate the utility of nonlinear measures such as APEN and LLE as additional measures toward a better understanding of the abnormalities of respiratory physiology in similar patient populations as the correlation between LLE, APEN and some of the time domain measures only explained up to 50-60% of the variation.

Adult↗

PubMed1986

[The behavior of intracranial pressure under spontaneous respiration or artificial respiration in hemorrhagic shock during volume substitution].

Haemorrhagic shock and cranial injury frequently present together in the polytraumatised patient. The effect of different forms of ventilation--spontaneous respiration, controlled normoventilation, and intubation followed by hyperventilation--on the raised intracranial pressure of young pigs given volume replacement subsequent to haemorrhagic shock, was therefore investigated. During volume substitution, the intracranial pressure (initially 30 mmHg) both of those animals breathing spontaneously and of those being ventilated rose significantly (44.6 and 49.2 mmHg respectively). In contrast, intubation and hyperventilation resulted in an initial fall in intracranial pressure to 18.6 mmHg, and a rise to just below initial values (27.4 mmHg) after volume replacement. A similar blood pressure rise was noted in all three groups but arterial PCO2 changes were analogous to those of intracranial pressure. In the presence of both haemorrhagic shock and cranial injury, volume replacement alone is not sufficient treatment, and can in some circumstances be dangerous. Early intubation and controlled hyperventilation course a fall in intracranial pressure secondary to decreasing the PCO2.

Animals↗

PubMed1965