Increase In Respiratory Activity Research Articles

Hypoxic Inhibition of Respiratory Neural Regulation in Anesthetized Rats.

To determine the neural mechanism of hypoxic respiratory inhibition, discharge patterns of efferent phrenic (Phr), vagal superior laryngeal (Xsl), and vagal pharyngeal (Xphar) nerves were analyzed during systemic hypoxia in the urethane-anesthetized, vagotomized and artificially ventilated rat. In the carotid sinus nerve (CSN) intact rat, moderate hypoxia (end-tidal Po2, 40-50 mmHg) caused an initial increase in respiratory activity which was followed by inhibition due to reduction in respiratory frequency (f). The decrease in f was associated with prolongation of decremental Xphar expiratory (E) activity and retardation of the onset of inspiratory (I) activity. Integrated peak Phr or Xs1 I and Xphar E activities remained augmented during respiratory inhibition. After bilateral CSN section, moderate hypoxia produced an extreme reduction in f due to delayed onset of I activity and a strong reduction in the Xphar E activity. Phr and Xs1 I activities were little affected, and changes in inspiratory time were small. These results suggest that hypoxia centrally inhibits the process of initiating the onset of rhythmic I activity and the activity of decremental Xphar E motoneurons. Carotid chemoreceptor stimulation was inadequate to offset the central inhibitory effect of hypoxia on the onset of I activity.

Energy relations of solute loading in sieve elements of willow

Experiments are described which attempt to clarify the quantitative relationship between sieve-tube loading of sucrose, and ATP-turnover rates in the phloem of willow (Salix viminalis L.). Two experimental approaches have been made towards the solution of this problem. In the first of these the respiratory breakdown of (14)C-sugars was measured in segments of willow stem when no sieve-tube transport was taking place, and also under conditions where transport was occurring in response to the feeding of individuals of the aphid Tuberolachnus salignus (Gmelin). An increase in respiratory activity, measured by the output of (14)CO2, was found to occur as a consequence of transport. Since the rate of sieve-tube sugar loading could be measured by the production of honeydew from the aphids, and by making assumptions concerning the production of ATP in respiration, it was concluded that the stoichiometry of sucrose loading was 1.9 mol ATP · (mol sucrose)(-1). A somewhat higher value of 2.5 mol ATP · (mol sucrose)(-1) was found using the second approach. In this, attempts were made to measure ATP turnover rates using [(32)P]orthophosphate supplied to strips of willow bark which bore exuding aphid stylets.

Growth hormone and liver mitochondria: effects on phospholipid composition and fatty acyl distribution.

Effects of growth hormone on phospholipid composition and fatty acyl distribution were studied in liver mitochondria of hypophysectomized rats. After hypophysectomy, only cardiolipin showed a 25% decrease. Its fatty acyl distribution, which consisted mainly of linoleic acid (55-60%) and oleic acid (20%), was unchanged. In phosphatidylcholine and phosphatidylethanolamine fractions the contents of docosahexaenoic and arachidonic acids were decreased with a concomitant increase in linoleic acid content. These changes could be accounted for by small but significant decreases in the activities of delta 9-desaturase (sucrose-induced), delta 5-desaturase and mitochondrial elongation enzymes. The activities of delta 6-desaturase, NADH cytochrome b5 ferri-reductase, cytochrome b5, NADH cytochrome c reductase and microsomal elongation enzymes remained virtually unchanged. Injection of bovine growth hormone daily for seven days restored cardiolipin and fatty acyl distribution and the enzyme activities. From these and other results, we conclude that growth hormone-dependent increase of respiratory activity of liver mitochondria may be partly mediated by the hormonal effects on membrane lipid distribution.

Coordinate induction of multiple cytochrome c mRNAs in response to thyroid hormone.

Because of the well documented influence of thyroid hormones in the general control of oxidative metabolism and their putative role in the transcriptional activation of specific genes, changes in the levels of multiple cytochrome c mRNAs were monitored in thyroidectomized rats after administration of 3,5,3'-triiodo-L-thyronine. In contrast to normal animals where the concentration of cytochrome c mRNAs in the polyadenylated RNA fraction is approximately 4- to 5-fold higher in kidney than in liver, hypothyroid animals displayed an equivalent low level of all three mRNAs (1400, 1100, and 700 nucleotides) in both tissues. Following the establishment of chronic hyperthyroidism, the levels of the three mRNAs were coordinately elevated by about 4- to 5-fold resulting in their restoration to approximately normal amounts for kidney but to a level substantially above the normal for liver. Only modest induction of mRNA is detected in the first 12 h following a single intravenous injection of 3,5,3'-triiodo-L-thyronine. The major increase occurs between 12 and 24 h with the plateau level attained between 24 and 48 h. The magnitude of the response is in excess of the general increase in total cellular RNA mediated by the hormone. Induction of the cytochrome c mRNAs is coincident with an elevation in gene transcription of comparable magnitude detected using nascent RNA chains synthesized by isolated nuclei. The kinetics of these responses are similar to those observed for the increase in respiratory activity mediated by the hormone.

Responses of Caladium Tubers to Low, Nonfreezing Temperatures

Abstract Storage of Caladium × hortulanum L. tubers at 5°C for 1 to 3 weeks resulted in an elevation in CO2 production when transferred to 22°. A decrease in storage temperature from 22° to 1° resulted in an increase in respiratory activity following transfer of tubers to 22°. The respiratory burst associated with low temperature storage was greatest following 24 hr at 22°, after which a decline in CO2 production was seen. Electrolyte leakage from ‘Carolyn Whorton’ tuber disks increased when tubers were held for either 3 weeks at 5° or 2 weeks at 1°, as compared to shorter durations of chilling or higher temperatures. Sprouting (days to emergence) of planted tubers was delayed following low temperature storage, as compared to tubers held at 22°. Although delayed, all tubers sprouted when held a maximum of 3 weeks at 5°, or 2 weeks at 1°.

Effects of centrally administered naloxone on phrenic nerve activity

The present study examined the effect on respiration of naloxone administered centrally. Experiments were performed on anesthetized, paralyzed cats whose vagi and carotid sinus nerves had been cut. The animals' end-tidal pCO 2 and body temperature were kept constant with servocontrollers. Naloxone administered into the third cerebral ventricle in doses of 40 μg/kg and 400 μg/kg resulted in significant (P < 0.05) increases in phrenic neural activity. The response to the 400 μg/kg dose was significantly greater (P < 0.05) than the response to the 40 μg/kg dose. A dose of 40 μg/kg naltrexone administered to each of two animals produced similar increases in respiratory activity. These data indicate that in the preparation studied endogenous opiates exert a tonic inhibitory effect on respiration through their action on central opiate receptors.

Influence of dimethylsulphoxide on the functional state of isolated rat hepatocytes

1. 1. The effect of dimethylsulphoxide upon respiration, glycolysis and gluconeogenesis in isolated rat hepatocytes was studied. 2. 2. The results show that the glycolysis pathway is strongly inhibited by the action of dimethylsulphoxide in the hepatocytes, with increased glucose uptake and reduced net flux. 3. 3. However, the alterations in respiration and the gluconeogenesis pathway are less pronounced, the only significant change being an increase in respiratory activity during the first 10 min of incubation with dimethylsulphoxide.

Simultaneous Measurement of Water Loss and Carbon Dioxide Production in the Cricket, Acheta Domesticus

ABSTRACT The relationship between respiration and its contribution to total water loss in arthropods is based almost entirely on correlations obtained from independent plots of gravimetrically-determined transpiration rates and manometrically-determined gas exchange (Ahearn, 1970; Hadley, 1970). Recently a new system, the ‘transpiration monitor’ has been developed to detect the amount of water released by an arthropod into a moving air stream (Hadley, Stuart &amp; Quinlan, 1982). The transpiration monitor not only permits the continuous recording of very small and sporadic losses of moisture, but can be interfaced with either an oxygen or carbon dioxide analyser to provide a simultaneous measure of the arthropod’s gas exchange. Thus, peaks that correspond to bursts of moisture can be correlated with concurrent increases in respiratory activity. We report here the application of this system to measure water loss and carbon dioxide production in the cricket, Acheta domesticas, under isothermal conditions and at increasing temperatures.

Respiratory and cardiovascular effects of intraventricular cholecystokinin

Cholecystokinin (1–300 ng) was administered into the lateral brain ventricle of chloralose-anesthetized cats while monitoring tracheal airflow, arterial blood pressure, and heart rate. Dose-related increases in respiratory activity occurred in each animal tested, and were due to an increase in tidal volume. When 300–1000 ng of cholecystokinin was administered intravenously, no respiratory stimulant effect was observed. These results indicate that cholecystokinin acts in the brain to stimulate respiration.

Effect of 5-hydroxytryptophan on electrocortical activity and breathing movements of fetal sheep

5-Hydroxytryptophan administered intravenously to sheep fetuses, in which chronic catheters had been placed in the carotid artery, jugular vein, and trachea and electroencephalogram electrodes in the brain, caused prolonged high-voltage electrocortical activity in all fetuses. In those more mature fetuses (>126 days) there was also a significant increase in respiratory activity. The respiratory activity involved both the diaphragmatic and intercostal muscle movement.

Compartmentation of metabolic systems in the regulation of dormancy in fungus spores

Dormancy in fungus spores can be due to a variety of causes relating to structural, physiological, or biochemical functions. Based on data reported here and earlier, compartmentation of endogenous reserves or of enzymes is proposed as the mechanism controlling dormancy in spores of Myrothecium verrucaria and Trichoderma reesei. Spores of both organisms contain a pool(s) of reserves composed of trehalose, amino acids, as well as unidentified compounds. Addition of hot water extracts of these reserves to spores results in rapid increases in respiratory activity and germination. This observation coupled with other data showing the stimulation of endogenous respiration by heat, freezing, or azide demonstrates that dormancy is due primarily, if not entirely, to sequestering or compartmentation of the endogenous reserves and not of the enzymatic systems involved in utilization of metabolites for germination. Presumably these reserves are contained within the vacuoles. Data on the interactions of treatments that stimulate endogenous respiration and on the effects of metabolism of exogenous substrates indicate that the transport pathways within the cell, from the pools or from the plasma membrane, to the loci of initial metabolism are not identical and that the total regulatory system is composed of a number of separable processes. It appears probable that examination of the spores of other fungi will show that compartmentation of reserves is not of uncommon occurrence and is not an unusual cause of dormancy.

Intercostal Muscle Activity in Chronic Obstructive Pulmonary Disease

Previous studies have shown that the normal compensatory increase in respiratory activity during ventilatory resistive loading is blunted in patients with chronic obstructive pulmonary disease.1 This impairment does not appear to be explained by respiratory muscle weakness per se, but may be related to a decrease in the mechanical advantage of the inspiratory muscles or to disordered thoracoabdominal movement as a result of hyperinflation of the lungs and changes in thoracic configuration.2

Intercostal Muscle Activity in Chronic Obstructive Pulmonary Disease

Previous studies have shown that the normal compensatory increase in respiratory activity during ventilatory resistive loading is blunted in patients with chronic obstructive pulmonary disease.1 This impairment does not appear to be explained by respiratory muscle weakness per se, but may be related to a decrease in the mechanical advantage of the inspiratory muscles or to disordered thoracoabdominal movement as a result of hyperinflation of the lungs and changes in thoracic configuration.2

Proposed respiratory 'gating' mechanism for cardiac slowing.

THREE of the essential variables concerned in the regulation of systemic cardiovascular performance are cardiac output, blood pressure and the resistance encountered by the blood in flowing through the systemic vascular bed. Cardiac output may be further considered as the product of cardiac stroke volume and heart rate. The latter is under the control of the vagi and sympathetic nerves but the reflex bradycardia produced by vagal activation as a result of increased blood pressure, increased carotid chemoreceptor activity or direct electrical stimulation of the carotid sinus nerve occurs only if the stimulus is delivered during expiration. A sustained stimulus which is able reflexly to activate the cardiac vagal efferents will, therefore, produce the pattern of heart rate known as sinus arrhythmia (that is, a slow heart rate regularly interrupted by periods of cardiac acceleration coinciding with inspiration). This association of inspiratory activity with the inhibition of bradycardia is also seen when stimulating certain areas of the brain: areas which produce an inhibition of bradycardia2,3 also produce an increase in respiratory activity, while other areas produce bradycardia and apnoea4. A vagal bradycardia unrelated to respiration can in fact only be induced by stimulating the cells of origin in the nucleus ambiguus5,6 or the vagus nerve itself. This nucleus lies in the medullary reticular formation ventro-lateral to the nucleus of the tractus solitarius. Since all known afferent stimuli which cause reflex bradycardia converge on the area of the nucleus tractus solitarius where “inspiratory” type neurones abound before passing on to the nucleus ambiguus, it is tempting to postulate that these inspiratory neurones may actually be part of a ‘gate’ which controls the passage of impulses through this reflex pathway. The rhythmical opening and closing of this gate with respiratory activity would result in sinus arrhythmia provided the gate remains open for a sufficient length of time and that there is an adequate background of vagal tone, which is in itself reflexly engendered. We have experimentally analysed some of the properties of this proposed respiratory gating mechanism and conclude that it is in fact influenced by both neural inspiratory activity and by lung inflation.

Effect of 5-fluorouracil and cycloheximide on the early development of Phycomyces blakesleeanus spores and the activity of N-acetylglucosamine synthesizing enzymes.

The development of germinating Phycomyces spores was not inhibited by 5-fluorouracil (1mM) until the emergence of the germination tube. Fluorouracil was incorporated into RNA as efficiently as uracil; it did not inhibit the synthesis of proteins and the increase in respiratory activity during early development. Cycloheximide inhibited development as well as the increase in respiration and protein synthesis. This suggested that protein synthesis or some other cycloheximide dependent process, but no mRNA synthesis, was needed for the first developmental stages. The activity of two enzymes involved in the synthesis of N-acetylglucosamine increased markedly during germination. THis increase was inhibited by both 5-fluorouracil and cycloheximide; this suggested that those enzymes were synthesized on mRNA formed during germination.

Effect of Glucose and Cyclic Adenosine 3', 5'-Monophosphate on the Synthesis of Succinate Dehydrogenase and Isocitrate Lyase in Escherichia coli

Repressed respiration of Escherichia coli cells grown in the presence of 2% glucose was derepressed when the cells were incubated in a buffer containing casamino acids. The glucose-repressed cells were deficient in succinate dehydrogenase [EC 1.3.99.1] and isocitrate lyase [EC 4.1.3.1] activities, which increased during the incubation. The increases in respiratory activity and enzyme activity on incubation were repressed by glucose, but except for isocitrate lyase these repressions could be restored by the addition of cyclic adenosine 3',5'-monophosphate. Inhibitors of protein synthesis blocked the increase of enzyme activity on incubation without glucose, or with glucose and the cyclic nucleotide.

The Control Properties of Phosphofructokinase in Relation to the Respiratory Climacteric in Banana Fruit

Glucose 6-phosphate, fructose 6-phosphate, fructose 1, 6-diphosphate, and triose phosphates, and the enzymes phosphofructokinase, aldolase, and glucose 6-phosphate dehydrogenase were extracted from banana fruit (Musa cavendishii, Lambert var. Valery) at the (a) preclimacteric, (b) climacteric rise, (c) climacteric peak, and (d) postclimacteric stages of ripening. The level of fructose 1, 6-diphosphate increased 20-fold whereas the concentration of other intermediates changed no more than 2.5-fold between stages a and c. For these same extracts, phosphofructokinase activity increased 2.5-fold whereas the activity of glucose 6-phosphate dehydrogenase and aldolase changed only fractionally. Substrate saturation studies (fructose 6-phosphate) of phosphofructokinase activity showed a decrease in the [S](0.5) from 5.6 to 1.7 mM betwen stages a and c. The enzyme from both sources seems to be regulated by a negative cooperative effect with the control being more stringent in the enzyme from stage a. The difference in enzyme activity is consistent with the increase in respiratory activity between the two stages.

Biochemical maturation of flight muscle mitochondria in the colorado beetle, leptinotarsa decemlineata say

1. 1. The post-emergence maturation of Colorado beetle flight muscle mitochondria was studied under conditions leading to both diapause and non-diapause. 2. 2. The mitichondria showed an increase in respiratory activity with pyruvate/ malate and α-glycerophosphate as substrate during the first 6 days of flight muscle development. The respiration with succinate decreased during development. 3. 3. Both succinate and α-glycerophosphate dehydrogenase activities increased during the first 6 days. 4. 4. No significant changes in oxidative phosphorylation could be observed during development. 5. 5. Mitochondria from pre-diapause animals have the same characteristics as mitochondria from non-diapause animals. However, much less mitochondria could be isolated from pre-diapuase animals. 6. 6. The results suggest a long-term hormonal effect on mitochondriogenesis in the Colorado beetle.

Biochemical and Structural Changes in Mitochondria and Other Cellular Components of Pea Cotyledons During Germination

Integrated studies comprising biochemical and electron microscopic analysis suggested that the increase in respiratory activity of pea cotyledon mitochondria during germination results from further development of the original mitochondria present in dormant seeds. Electron microscopy of isolated mitochondria as well as mitochondria in situ has revealed that membranes are scarce in the mitochondria present in dormant seeds. Mitochondrial cristae become well developed during the initial stages of germination. Crude mitochondrial preparations from pea cotyledons were fractionated by sucrose density gradient centrifugation and analyzed through electron microscopy. These studies showed that, at all stages of germination, "peroxisome"-like structures were present in the fractions of higher sucrose densities than that containing mitochondria. Biochemical studies revealed that the activities of catalase (H2O2:H2O2 oxidoreductase, EC 1.11.1.6) and peroxidase (guaicol:H2O2 oxidoreductase, EC 1.11.1.7) were associated mainly with these fractions and their activities increased during germination.

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.