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PubMed1991

Respirator physiology research: answers in search of the question.

Adverse effects of respirators have been the focus of considerable research over the past decade. Individual research projects have generally focused on one specific category of effects: ventilatory, respiratory control, work limitation, subjective discomfort, psychologic effects, thermal loading, and cardiovascular changes. Most were studied in experimental laboratory situations rather than in actual worksites. Very little attention has been given to compliance with use and actual effectiveness in preserving health. Inasmuch as many types of effects have been demonstrated, there is a need to carefully define which type(s) of effects is/are most important for respirator design selection and worker medical certification in particular situations. In general, respirators should be assessed for their effect on all relevant variables.

Adaptation, Physiological↗
PubMed2005

Arabidopsis peroxisomal citrate synthase is required for fatty acid respiration and seed germination.

We tested the hypothesis that peroxisomal citrate synthase (CSY) is required for carbon transfer from peroxisomes to mitochondria during respiration of triacylglycerol in Arabidopsis thaliana seedlings. Two genes encoding peroxisomal CSY are expressed in Arabidopsis seedlings, and seeds from plants with both CSY genes disrupted were dormant and did not metabolize triacylglycerol. Germination was achieved by removing the seed coat and supplying sucrose, but the seedlings still did not use triacylglycerol. The mutant seedlings were resistant to 2,4-dichlorophenoxybutyric acid, indicating a block in peroxisomal beta-oxidation, and were unable to develop further after transfer to soil. The mutant phenotype was complemented with a cDNA encoding CSY with either its native peroxisomal targeting sequence (PTS2) or a heterologous PTS1 sequence from pumpkin (Cucurbita pepo) malate synthase. These results suggest that peroxisomal CSY in Arabidopsis is not only a key enzyme of the glyoxylate cycle but also catalyzes an essential step in the respiration of fatty acids. We conclude that citrate is exported from the peroxisome during fatty acid respiration, whereas in yeast, acetylcarnitine is exported.

Acetylcarnitine↗
PubMed1978

The influence of nasal respiration on the function of the auditory tube.

The importance of treating disturbances of nasal ventilation before any surgical intervention on the ear is stressed in many papers. It is said that ventilation of the auditory tube is not normal when respiration through the nose is handicapped. Based on these considerations, we have investigated by tympanometry the influence of abnormalities of nasal respiration measured by rhinomanometry on the auditory tube function. There was no significant relation between osseous occlusion of nasal ventilation or a swelling of the nasal mucous membranes or conchas and a dysfunction of the tube. The middle ear pressure varied within the normal range. This indicates that treatment of impaired nasal respiration before an operation on the ear is only necessary when an ascending nasal infection is feared or if there is nasopharyngeal disease.

Airway Obstruction↗
PubMed2006

Stem CO2 release under illumination: corticular photosynthesis, photorespiration or inhibition of mitochondrial respiration?

In illuminated stems and branches, CO2 release is often reduced. Many light-triggered processes are thought to contribute to this reduction, namely photorespiration, corticular photosynthesis or even an inhibition of mitochondrial respiration. In this study, we investigated these processes with the objective to discriminate their influence to the overall reduction of branch CO2 release in the light. CO2 gas-exchange measurements of young birch (Betula pendula Roth.) branches (< 1.5 cm) performed under photorespiratory (20% O2) and non-photorespiratory (< 2%) conditions revealed that photorespiration does not play a pre-dominant role in carbon exchange. This suppression of photorespiration was attributed to the high CO2 concentrations (C(i)) within the bark tissues (1544 +/- 227 and 618 +/- 43 micromol CO2 mol(-1) in the dark and in the light, respectively). Changes in xylem CO2 were not likely to explain the observed decrease in stem CO2 release as gas-exchange measurements before and after cutting of the branches did not effect CO2 efflux to the atmosphere. Combined fluorescence and gas-exchange measurements provided evidence that the light-dependent reduction in CO2 release can pre-dominantly be attributed to corticular refixation, whereas an inhibition of mitochondrial respiration in the light is unlikely to occur. Corticular photosynthesis was able to refix up to 97% of the CO2 produced by branch respiration, although it rarely led to a positive net photosynthetic rate.

Betula↗
PubMed2006

Does the pancreas move with respiration?

BACKGROUND AND AIM: The pancreas is a retroperitoneal organ and has been classically considered to be immobile on respiration. Recent radiological studies assessing the mobility of the pancreas have challenged this traditional concept. The present study was conducted to assess the movement of pancreas with respiration using fluoroscopy, a simple and inexpensive method. METHODS: Patients with chronic pancreatitis who had either pancreatic calcification evident on fluoroscopy or an indwelling pancreatic duct stent were studied. The movement of the pancreas was assessed under fluoroscopy by measuring the displacement of the stent or calcification in relationship to the spine in maximum inspiration followed by maximum expiration. RESULTS: Twenty-two patients (mean age 35.45 + or - 11.29 years, 17 men) with chronic pancreatitis were included in the study. Ten patients had pancreatic calcification and 12 had an indwelling pancreatic duct stent (two in the dorsal duct, 10 in the ventral duct). In all patients, the pancreas moved downward in the craniocaudal direction on deep inspiration. Pancreatic excursion from maximum inspiration to maximum expiration ranged from 0.1 to 3.4 cm. In addition, a medial movement of the head of pancreas was also noted in most of the patients. On univariate analysis, no association was found between the range of movement and the age or sex of the patient, duration or etiology of disease, presence or absence of calcification, severity of ductal changes of chronic pancreatitis and the length or diameter of the pancreatic stent placed. CONCLUSION: The pancreas moves craniocaudally with respiration and the head moves medially on inspiration.

Adult↗
PubMed1997

Respiration patterns during feeding in Rett syndrome.

Feeding problems are common in Rett syndrome in which there are characteristic oropharyngeal abnormalities. This study investigated the ways in which individuals regulated their respiration accordingly, and how this affected their overall feeding ability. Respiration during feeding was studied in 28 individuals, recording nasal airflow, chest and abdominal movements, and swallow sounds. Time to first swallow was defined as that between introduction of liquid/solid on a spoon and the first swallow. Six individuals also had videofluoroscopy with simultaneous respiration monitoring. Results indicated different respiratory patterns according to the time to first swallow and neurological status; the amount of time spent in apnoea was particularly important. Videofluoroscopy showed that apnoeas occurred most often when liquid was delayed in the pharynx, but this could be overcome in subjects with a lower level of disability. The carer's estimate of the time for feeding was significantly related to the time spent in apnoea with liquids.

Adolescent↗
PubMed1997

Heritability of respiratory sinus arrhythmia: dependency on task and respiration rate.

In this study, we investigated the genetic and environmental origin of individual differences in respiratory sinus arrhythmia (RSA) during rest and during four stress tasks. We used a multivariate model including age, RSA, and respiration rate. Participants were 208 male and female pairs of middle-aged twins. A model without sex differences, specifying additive genetic and unique environmental factors, showed the best fit across all conditions. Heritability of RSA ranged from 28% to 43%. Correction for respiration rate yielded RSA heritabilities of similar size. The covariance between respiration rate and RSA was best explained by a combination of correlated unique environmental and correlated additive genetic factors. Combined with data from an earlier project, RSA from 317 adolescent and 712 middle-aged individuals of both sexes was available. This large data set showed that (a) sex differences in mean RSA are absent and (b) RSA decreases considerably from adolescence (111.5 ms) to middle age (60.0 ms).

Adolescent↗
PubMed2004

Brain-derived respiring mitochondria exhibit homogeneous, complete and cyclosporin-sensitive permeability transition.

The mitochondrial permeability transition (mPT) is increasingly implicated in neuronal cell death. In the present study, isolated respiring brain mitochondria were examined for their ability to undergo calcium-induced mPT and their sensitivity to mPT inhibition by cyclosporin A (CsA). Previous studies have suggested a heterogeneous response to calcium, a limitation of CsA inhibition, and a relative resistance in the ability of respiring brain mitochondria to undergo mPT. Using fluorometric and electron microscopic analyses, we found that virtually the whole population of respiring brain mitochondria readily undergo mPT and swell upon calcium exposure. Further, brain mitochondria were highly sensitive to CsA which potentiated morphological recovery after transient swelling as well as completely blocked mPT induction in the presence of a low concentration of ADP. Using flow cytometry, which allows analysis of individual mitochondria, we demonstrate that both brain and liver mitochondria display homogeneous responses to calcium-induced mPT. We conclude that the mPT is one likely target for the broad in vivo neuroprotective effects displayed by CsA when allowed to penetrate the blood-brain barrier, and that development of compounds inhibiting mPT may prove beneficial for the treatment of severe brain disease.

Adenosine Diphosphate↗
PubMed2004

Inhibition of brain mitochondrial respiration by dopamine and its metabolites: implications for Parkinson's disease and catecholamine-associated diseases.

A structure-potency study examining the ability of dopamine (DA), its major metabolites and related amine and acetate congeners to inhibit NADH-linked mitochondrial O(2) consumption was carried out to elucidate mechanisms by which DA could induce mitochondrial dysfunction. In the amine studies, DA was the most potent inhibitor of respiration (IC(50) 7.0 mm) compared with 3-methoxytryramine (3-MT, IC(50) 19.6 mm), 3,4-dimethoxyphenylethylamine (IC(50) 28.6 mm), tyramine (IC(50) 40.3 mm) and phenylethylamine (IC(50) 58.7 mm). Addition of monoamine oxidase (MAO) inhibitors afforded nearly complete protection against inhibition by phenylethylamine, tyramine and 3,4-dimethoxyphenylethylamine, indicating that inhibition arose from MAO-mediated pathways. In contrast, the inhibitory effects of DA and 3-MT were only partially prevented by MAO blockade, suggesting that inhibition might also arise from two-electron catechol oxidation and quinone formation by DA and one-electron oxidation of the 4-hydroxyphenyl group of 3-MT. In the phenylacetate studies, 3,4-dihydroxyphenylacetic acid (DOPAC) was equipotent with DA in inhibiting respiration (IC(50) 7.4 mm), further implicating the catechol reaction as the cause of inhibition. All other carboxylate congeners; phenylacetic acid (IC(50) 13.0 mm), 4-hydroxyphenylacetic acid (IC(50) 12.1 mm), 4-hydroxy-3-methoxyphenylacetic acid (HVA, IC(50) 12.0 mm) and 3,4-dimethoxyphenylacetic acid (IC(50) 10.2 mm), were equipotent respiratory inhibitors and two- to fourfold more potent than their corresponding amine. These latter findings suggest that the phenylacetate ion can also contribute independently to mitochondrial inhibition. In summary, mitochondrial respiration can be inhibited by DA and its metabolites by four distinct MAO-dependent and independent mechanisms.

3,4-Dihydroxyphenylacetic Acid↗
PubMed2005

Increased mitochondrial respiration maintains the mitochondrial membrane potential and promotes survival of cerebellar neurons in an endogenous model of glutamate receptor activation.

It is thought that the combination of extracellular glutamate accumulation and mitochondrial damage is involved in neuronal death associated with brain ischemia and hypoglycemia, and some neurodegenerative diseases such as Huntington's disease. However, the mechanism whereby those two factors interact together to trigger neurodegeneration in this and other neurodegenerative disorders is still elusive. Here, we have addressed this issue using a model of mild and sustained accumulation of extracellular glutamate in cerebellar cultured neurons, which are mostly glutamatergic and commonly used to study glutamate neurotoxicity. The resulting stimulation of glutamate receptors triggered a approximately 50% persistent increase in mitochondrial respiration that was associated with free radicals formation, and which was found to be necessary to prevent the collapse of the mitochondrial membrane potential (Deltapsim) and apoptotic cell death. In fact, hampering the glutamate-mediated increase in mitochondrial respiration with an inhibitor of the mitochondrial respiratory chain stopped neurons from producing free radicals, but led them to undergo rapid and profound Deltapsim collapse and apoptotic cell death. Thus, we suggest that the formation of reactive oxygen species by glutamate receptor activation is the unavoidable consequence of an increase in the mitochondrial respiration aimed to prevent Deltapsim collapse and neurodegeneration. These results may be relevant to understand the pathophysiology of those neurodegenerative diseases associated with both mitochondrial respiratory chain and glutamate transporter defects.

Animals↗
PubMed1974

The effects of some prostaglandins on respiration in anaesthetized cats.

1 Some prostaglandins have been found to be capable of affecting respiration in anaesthetized cats.2 Prostaglandins E(1), E(2), F(2alpha), A(1) and A(2) all elicited increases in respiratory frequency when administered to cats anaesthetized with either pentobarbitone or alpha-chloralose. This effect was abolished by bilateral vagotomy.3 Prostaglandins of the E and A series, but not prostaglandin F(2alpha), elicited increases in tidal volume which were accompanied by falls in systemic blood pressure in cats anaesthetized with pentobarbitone. The changes in blood pressure were also obtained in cats anaesthetized with alpha-chloralose, but not the tidal volume changes.4 It is unlikely that the prostaglandins influenced respiration by direct actions on arterial chemoreceptors or baroreceptors.5 Mechanisms by which the prostaglandins may be acting to affect respiration are discussed.

Animals↗
PubMed1997

The effect of respiration on the performance of the total artificial heart.

An electromechanical driven pusher plate type total artificial heart (TAH) has been developed in the Department of Surgery at Baylor College of Medicine. The control of this TAH is based upon Frank-Starling's law, and the output is likely to be affected by the respiration cycle. The necessity of an averaging system for the pumping to avoid this drifting of the output has been discussed in several papers. In this study, the effect of respiration on the performance of the TAH was evaluated in both in vitro and in vivo conditions. This TAH was driven without an averaging system in its control system. The results indicated that the mean output pressure was stable with minute changes in both the heart rate and outflow. This verifies that the electromechanical driven pusher plate type TAH, which is under development in our laboratory, compensated for the effect of respiration without an averaging system.

Animals↗
PubMed1980

Phase relationship between normal human respiration and baroreflex responsiveness.

1. We studied the influences of phase of respiration and breathing frequency upon human sinus node responses to arterial baroreceptor stimulation. 2. Carotid baroreceptors were stimulated with brief (0.6 sec), moderate (30 mmHg) neck suction during early, mid, and late inspiration or expiratin at usual breathing rates, or, during early inspiration and expiration at breathing rates of 3, 6, 12, and 24 breaths/min. 3. Baroreceptor stimuli applied during early and mid inspiration and late expiration provoked only minor sinus node inhibition; stimuli begun during late inspiration and early expiration provoked maximum sinus node inhibition. 4. At breathing rates of 3, 6 and 12 breaths/min, expiratory baroreflex responses were significantly greater than inspiratory responses; at 24 breaths/min, however, inspiratory and expiratory baroreceptor stimuli produced comparable degrees of sinus node inhibition. 5. Our results delineate an important central biological rhythm in normal man: human baroreflex responsiveness oscillates continuously during normal, quiet respiration. The phase shift of baroreflex responsiveness on respiration suggests that this interaction cannot be ascribed simply to gating synchronous with central inspiratory neurone activity. Regularization of heart rate during rapid breathing is associated with loss of the differential inspiratory-expiratory baroreflex responsiveness which is present at usual breathing rates.

Adult↗
PubMed2003

Nonlinear coupling among heart rate, blood pressure, and respiration in patients susceptible to neuromediated syncope.

The aim of this study is to evaluate the degree of coupling between the cardiovascular variability series and the respiration in subjects susceptible to neurally mediated syncope. Twenty-one informed patients susceptible to syncope and ten sex- and age-matched control subjects were enrolled in the study. ECG, respiration activity, and arterial blood pressure were simultaneously recorded at rest (controlled and free breathing) and during the 70 degrees head-up TILT test (free breathing). The degree of nonlinear coupling among heart rate variability (HRV), blood pressure variability (BPV), and respiration was quantified by means of two indices according to a multivariate embedding-based approach. Eleven patients developed syncope during the TILT test. We found that during the late TILT phase, the TILT-positive group experienced a significant increase in nonlinear coupling respect to the mid TILT phase (p < 0.01, Wilcoxon nonparametric test for pair data) while the TILT-negative group did not (p < 0.01, Mann-Whitney U-test). If the proposed nonlinear coupling indexes can be considered expression of the coupling mechanisms involved in the vagal regulation of the cardiovascular system, an increase in vagal tone accompanied by a decrease in sympathetic activity seem to occur before a vasovagal event.

Adolescent↗
PubMed2001

Influence of respiration-induced organ motion on dose distributions in treatments using enhanced dynamic wedges.

The mean velocity of respiration-induced organ motion in cranio-caudal direction is of the same magnitude as the velocity of the moving jaw during a treatment with an enhanced dynamic wedge. Therefore, if organ motion is present during collimator movement, the resulting dose distribution in wedge direction may differ from that obtained for the static case, i.e., without organ motion. The position as a function of time of the moving jaw has been derived from a log-file generated during each treatment. Parameters for the respiratory cycle and information about respiration-induced motion for organs in the upper abdomen were taken from the literature. Both movements were superimposed and the resulting monitor unit distribution has been calculated in the intrinsic coordinate system of the organ. The deviations from the static case have been studied as a function of wedge angle, amplitude of organ motion, respiratory rate, asymmetry of the respiratory cycle, beam energy, and the dose rate. If an amplitude of 30 mm and a respiratory rate of 10 min(-1) are assumed, the maximum deviation in monitor units is 2.5% for a 10 degees wedge, 7% for a 30 degrees wedge, and 16% for a 60 degrees wedge. Furthermore, a dose distribution for an organ undergoing respiration-induced motion has been generated and we found dose deviations of the same magnitude as calculated with the monitor unit distribution.

Humans↗
PubMed2006

Evaluation of an automated deformable image matching method for quantifying lung motion in respiration-correlated CT images.

We have evaluated an automated registration procedure for predicting tumor and lung deformation based on CT images of the thorax obtained at different respiration phases. The method uses a viscous fluid model of tissue deformation to map voxels from one CT dataset to another. To validate the deformable matching algorithm we used a respiration-correlated CT protocol to acquire images at different phases of the respiratory cycle for six patients with nonsmall cell lung carcinoma. The position and shape of the deformable gross tumor volumes (GTV) at the end-inhale (EI) phase predicted by the algorithm was compared to those drawn by four observers. To minimize interobserver differences, all observers used the contours drawn by a single observer at end-exhale (EE) phase as a guideline to outline GTV contours at EI. The differences between model-predicted and observer-drawn GTV surfaces at EI, as well as differences between structures delineated by observers at EI (interobserver variations) were evaluated using a contour comparison algorithm written for this purpose, which determined the distance between the two surfaces along different directions. The mean and 90% confidence interval for model-predicted versus observer-drawn GTV surface differences over all patients and all directions were 2.6 and 5.1 mm, respectively, whereas the mean and 90% confidence interval for interobserver differences were 2.1 and 3.7 mm. We have also evaluated the algorithm's ability to predict normal tissue deformations by examining the three-dimensional (3-D) vector displacement of 41 landmarks placed by each observer at bronchial and vascular branch points in the lung between the EE and EI image sets (mean and 90% confidence interval displacements of 11.7 and 25.1 mm, respectively). The mean and 90% confidence interval discrepancy between model-predicted and observer-determined landmark displacements over all patients were 2.9 and 7.3 mm, whereas interobserver discrepancies were 2.8 and 6.0 mm. Paired t tests indicate no significant statistical differences between model predicted and observer drawn structures. We conclude that the accuracy of the algorithm to map lung anatomy in CT images at different respiratory phases is comparable to the variability in manual delineation. This method has therefore the potential for predicting and quantifying respiration-induced tumor motion in the lung.

Algorithms↗
PubMed1961

Endogenous respiration of Bacillus cereus.

Clifton, C. E. (Stanford University, Stanford, Calif.), and J. M. Sobek. Endogenous respiration of Bacillus cereus. J. Bacteriol. 82:252-256. 1961.-The endogenous respiration of washed cells of Bacillus cereus varies with the nature of the growth medium and with time. The respiratory quotient of cells harvested from nutrient agar remained quite constant around 1.00 over a 2-hr period of respiration, whereas that of cells grown on glucose-nutrient agar decreased from 0.97 for the first hour to 0.87 for the second hour. Considerable amounts of ammonia were formed, the number of moles per mole of oxygen consumed decreasing with time for agar-grown cells and increasing for glucose-grown ones.C(14)-labeled, agar-grown cells utilized materials insoluble in cold or hot 5% trichloroacetic acid, ethanol, or chloroform as their endogenous substrate, the same behavior being noted with glucose-grown cells except that they utilized both hot trichloroacetic-soluble and -insoluble materials. These results indicate that the bulk of the endogenous substrates are chemically complex and, at least in part, are nitrogenous in character.

Agar↗
PubMed1964

INFLUENCE OF THE PHYSICAL STATE OF THE BACTERIAL CELL MEMBRANE UPON THE RATE OF RESPIRATION.

Henneman, Dorothy H. (Rutgers, The State University, New Brunswick, N.J.), and W. W. Umbreit. Influence of the physical state of the bacterial cell membrane upon the rate of respiration. J. Bacteriol. 87:1274-1280. 1964.-NaCl and KCl in concentrations of the order of 0.2 to 0.5 m inhibit the respiration of Escherichia coli B and other gram-negative organisms. Cell-free enzymes concerned in respiration and prepared from the same organisms are not inhibited by these salts, whereas these same enzymes tested in intact cells are. The physical state of the cell membrane appears to be a factor controlling its respiratory activity.

Bacteria↗