Increase In Ventilation Frequency Research Articles

Catecholamines modulate the hypoxic ventilatory response of larval zebrafish (Danio rerio).

The hypoxic ventilatory response (HVR) in fish is an important reflex that aids O2 uptake when low environmental O2 levels constrain diffusion. In developing zebrafish (Danio rerio), the acute HVR is multiphasic, consisting of a rapid increase in ventilation frequency (fV) during hypoxia onset, followed by a decline to a stable plateau phase above fV under normoxic conditions. In this study, we examined the potential role of catecholamines in contributing to each of these phases of the dynamic HVR in zebrafish larvae. We showed that adrenaline elicits a dose-dependent β-adrenoreceptor (AR)-mediated increase in fV that does not require expression of β1-ARs, as the hyperventilatory response to β-AR stimulation was unaltered in adrb1-/- mutants, generated by CRISPR/Cas9 knockout. In response to hypoxia and propranolol co-treatment, the magnitude of the rapidly occurring peak increase in fV during hypoxia onset was attenuated (112±14 breaths min-1 without propranolol to 68±17 breaths min-1 with propranolol), whereas the increased fV during the stable phase of the HVR was prevented in both wild type and adrb1-/- mutants. Thus, β1-AR is not required for the HVR and other β-ARs, although not required for initiation of the HVR, are involved in setting the maximal increase in fV and in maintaining hyperventilation during continued hypoxia. This adrenergic modulation of the HVR may arise from centrally released catecholamines because adrenaline exposure failed to activate (based on intracellular Ca2+ levels) cranial nerves IX and X, which transmit O2 signals from the pharyngeal arch to the central nervous system.

A refined method to monitor arousal from hibernation in the European hamster

BackgroundHibernation is a physiological and behavioural adaptation that permits survival during periods of reduced food availability and extreme environmental temperatures. This is achieved through cycles of metabolic depression and reduced body temperature (torpor) and rewarming (arousal). Rewarming from torpor is achieved through the activation of brown adipose tissue (BAT) associated with a rapid increase in ventilation frequency. Here, we studied the rate of rewarming in the European hamster (Cricetus cricetus) by measuring both BAT temperature, core body temperature and ventilation frequency.ResultsTemperature was monitored in parallel in the BAT (IPTT tags) and peritoneal cavity (iButtons) during hibernation torpor-arousal cycling. We found that increases in brown fat temperature preceded core body temperature rises by approximately 48 min, with a maximum re-warming rate of 20.9℃*h-1. Re-warming was accompanied by a significant increase in ventilation frequency. The rate of rewarming was slowed by the presence of a spontaneous thoracic mass in one of our animals. Core body temperature re-warming was reduced by 6.2℃*h-1 and BAT rewarming by 12℃*h-1. Ventilation frequency was increased by 77% during re-warming in the affected animal compared to a healthy animal. Inspection of the position and size of the mass indicated it was obstructing the lungs and heart.ConclusionsWe have used a minimally invasive method to monitor BAT temperature during arousal from hibernation illustrating BAT re-warming significantly precedes core body temperature re-warming, informing future study design on arousal from hibernation. We also showed compromised re-warming from hibernation in an animal with a mass obstructing the lungs and heart, likely leading to inefficient ventilation and circulation.

Does ammonia trigger hyperventilation in the elasmobranch, Squalus acanthias suckleyi?

We examined the ventilatory response of the spiny dogfish, to elevated internal or environmental ammonia. Sharks were injected via arterial catheters with ammonia solutions or their Na salt equivalents sufficient to increase plasma total ammonia concentration [TAmm]a by 3–5 fold from 145±21μM to 447±150μM using NH4HCO3 and a maximum of 766±100μM using (NH4)2SO4. (NH4)2SO4 caused a small increase in ventilation frequency (+14%) and a large increase in amplitude (+69%), while Na2SO4 did not. However, CO2 partial pressure (PaCO2) also increased and arterial pHa and plasma bicarbonate concentration ([HCO3−]a) decreased. NH4HCO3 caused a smaller increase in plasma ammonia resulting in a smaller but significant, short lived increases in ventilation frequency (+6%) and amplitude (36%), together with a rise in PaCO2 and [HCO3−]a. Injection with NaHCO3 which increased pHa and [HCO3−]a did not change ventilation. Plasma ammonia concentration correlated significantly with ventilation amplitude, while ventilation frequency showed a (negative) correlation with pHa. Exposure to high environmental ammonia (1500μM NH4HCO3) did not induce changes in ventilation until plasma [TAmm]a increased and ventilation amplitude (but not frequency) increased in parallel. We conclude that internal ammonia stimulates ventilation in spiny dogfish, especially amplitude or stroke volume, while environmental ammonia only stimulates ventilation after ammonia diffuses into the bloodstream.

Effects of different rhizosphere ventilation treatment on water and nutrients absorption of maize

The objective of this study was to explore the effects of different rhizosphere ventilation treatment on water and nutrients absorption of maize. The pot experiment was conducted using three methods: no ventilation, two day ventilation and four day ventilation, under conditions of the different levels of irrigation methods. As such, the influence of rhizosphere ventilation treatment on the physiological, water and nutrient absorption of maize was studied. Results showed that, with the increase in ventilation frequency, plant height, leaf area and the content of chlorophyll in maize increased to a certain degree. Root activity of once in every four days ventilation was the biggest (8.237 mg/(g.h)), followed by that of once in every two days ventilation (6.171 mg/(g.h)), and that of no ventilation was the least (4.940 mg/(g.h)). Consequently, it increased by 66.7 and 29.9%, respectively. The chlorophyll content experimental results showed that, rhizosphere ventilation treatment does not affect transpiration of potted maize and has no significant difference on the irrigation water utilization rate.

The effect of progressive hypoxia on spontaneous activity in single and shoaling golden grey mulletLiza aurata

The hypothesis of a differential effect of hypoxia on activity in shoaling v. solitary fish was tested in golden grey mullet Liza aurata. In both solitary and shoaling fish, (1) swimming activity increased significantly at <or=60% air saturation compared with normoxia, (2) aquatic surface respiration increased significantly below 15% air saturation and (3) a significant increase in ventilation frequency was observed between 40 and 10% air saturation. Swimming activity was higher in shoaling than in solitary fish, possibly due to social interactions in shoaling fish. Despite showing a higher swimming activity, shoaling individuals showed similar ventilation frequency to the less active solitary fish. This suggests that shoaling exerts a calming effect on L. aurata, probably related to increased safety while in numbers. In addition, shoaling fish spent a higher proportion of time performing aquatic surface respiration at 15% air saturation (i.e. the highest oxygen level at which aquatic surface respiration was observed) than solitary fish, possibly because of (1) synchronization of aquatic surface respiration in shoaling fish and (2) lower risk of predation perceived by shoaling fish.

Extrabranchial chemoreceptors involved in respiratory reflexes in the neotropical fish Colossoma macropomum (the tambaqui).

In a previous study, complete denervation of the gills in the tambaqui Colossoma macropomum did not eliminate the increase in breathing amplitude seen during exposure of this species to hypoxia. The present study was designed to examine other sites of putative O(2)-sensitive receptors that could be involved in this reflex action. Superfusion of the exposed brain of decerebrate, spinalectomized fish did not reveal the presence of central chemoreceptors responsive to hyperoxic, hypoxic, hypercarbic, acidic or alkaline solutions. Subsequent central transection of cranial nerve IX and X, removing not only all innervation of the gills but also sensory input from the lateral-line, cardiac and visceral branches of the vagus nerve, did not eliminate the increase in breathing amplitude that remained following peripheral gill denervation alone. Administration of exogenous catecholamines (10 and 100 nmol kg(-1) adrenaline) to fish with intact brains and minimal surgical preparation reduced both respiratory frequency and amplitude, suggesting that humoral release of adrenaline also could not be responsible for the increase in breathing amplitude that remained following gill denervation. Denervation of the mandibular branches of cranial nerve V and the opercular and palatine branches of cranial nerve VII in gill-denervated fish (either peripheral gill denervation or central section of cranial nerves IX and X), however, did eliminate the response. Thus, our data suggest that hypoxic and hyperoxic ventilatory responses as well as ventilatory responses to internal and external injections of NaCN in the tambaqui arise from O(2)-sensitive receptors in the orobranchial cavity innervated by cranial nerves V and VII and O(2)-sensitive receptors on the gills innervated by cranial nerves IX and X. Our results also revealed the presence of receptors in the gills that account for all of the increase in ventilation amplitude and part of the increase in ventilation frequency during hyperoxic hypercarbia, a group or groups of receptors, which may be external to the orobranchial cavity (but not in the central nervous system), that contribute to the increase in ventilation frequency seen in response to hyperoxic hypercarbia and the possible presence of CO(2)-sensitive receptors that inhibit ventilation frequency, possibly in the olfactory epithelium.

Cardiovascular and respiratory reflexes in the tropical fish, traira ( Hoplias malabaricus): CO 2/pH chemoresponses

To examine the distribution and physiological role of CO 2/pH-sensitive chemoreceptors in the gills of the tropical fish, traira ( Hoplias malabaricus), fish were exposed to acute environmental hypercarbia (1.25, 2.5 and 5.0% CO 2 in air) and subjected to injections of HCl into the ventral aorta and buccal cavity. This was done before and after selective denervation of branchial branches of the IXth and Xth cranial nerves to various gills arches. Hypercarbia produced a significant decrease in heart rate, a mild hypotension as well as increases in both ventilation rate and ventilation amplitude. The data suggest that the hypercarbic bradycardia and increase in ventilation frequency arise from receptors exclusively within the gills but present on more than the first gill arch, while extra-branchial receptors may also be involved in controlling the increase in ventilation amplitude. With the exception of a decrease in heart rate in response to HCl injected into the ventral aorta, the acid injections (internal and external) did not mimic the cardiorespiratory responses observed during hypercarbia suggesting that changes in CO 2 are more important than changes in pH in producing cardiorespiratory responses. Finally, the data indicate that chemoreceptors sensitive to CO 2/pH and to O 2 in the gills of this species involved in producing ventilatory responses are distributed in a similar fashion, but that those involved in producing the bradycardia are not.

Cardiovascular regulation during anoxia in the turtle: an in vivo study.

This study describes the integrated cardiovascular response of instrumented turtles to acute anoxic exposure (approximately 2 h) and also determines the factors that regulate these responses. Trachemys scripta were chronically implanted with ultrasonic blood flow probes for the measurement of total pulmonary and systemic blood flows and heart rate. In addition, catheters were implanted into the right aortic arch for the measurement of systemic blood pressure, arterial blood gases, and pH. Animals were free to swim within an aquarium but could only breathe within a small chamber located at the surface. Cardiovascular variables were continuously monitored during normoxia, 2 h of anoxia, and during recovery at normoxia. In addition, some animals were treated with atropine or epinephrine during the anoxic exposure. During the onset of nitrogen breathing there was an increase in ventilation frequency, heart rate, pulmonary blood flow, and systemic blood flow and the development of a net left-to-right cardiac shunt. These changes lasted up to 1 h, followed by bradycardia (heart rate was reduced by 50% from control values) and the development of a large net right-to-left shunt (approximately 80% of the total cardiac output). These changes lasted the duration of the anoxic exposure and were rapidly reversed on return to a normoxic environment. Injections of epinephrine during anoxia had no effect on heart rate, pulmonary blood flow, or systemic blood flow. In contrast, injection of atropine during anoxia resulted in an increase in the heart rate and systemic blood flow, suggesting that the anoxic cardiac response is partially mediated through cholinergic mechanisms.

Respiratory and acid‐base disturbances in rainbow trout blood during exposure to chloramine‐T under hypoxia and hyperoxia

Rainbow trout Oncorhynchus mykiss were exposed acutely to chloramine‐T at a therapeutic concentration (9mg l−1) under moderately hypoxic (water P o2: l00 mmHg) or hyperoxic (water P o2: 430mmHg) conditions and arterial blood gas tensions (P ao2 and P aco2) and pH were monitored using an extracorporeal circulation. Hypoxia, alone, resulted in an increased ventilation frequency, a decrease in both arterial P co2 and P o2 and an increase in arterial pH. There was no effect of chloramine‐T exposure on the measured variables as compared with pre‐exposure (hypoxia baseline) values. Hyperoxia, alone, resulted in a decrease in ventilation frequency, an increase in arterial P co2 and Po2, and a decrease in arterial pH. Chloramine‐T exposure under these conditions caused a significant increase in ventilation frequency, but no significant effect on arterial blood gases or pH as compared with the hyperoxia baseline values. Despite the increase in ventilation caused by chloramine‐T during hyperoxia, there was no reduction in Pco2 or increase in Po2. Although these results were of little pathological significance, this study suggests that chloramine‐T, although stimulating ventilation, was impairing the diffusion of co2 across the gill probably by the secretion of branchial mucus and enhancing the gill boundary layer.

Metabolic Responses to Sulfur in Lucinid Bivalves

SYNOPSIS. Lucinid bivalves occur widely in habitats ranging from subtidal to deep ocean basins. The evidence reported to date supports the contention that all lucinids contain intracellular, sulfur-oxidizing bacterial symbionts which contribute substantially to the nutrition of the intact association. These burrowing bivalves are found in both high and low sulfide habitats. Examinations of sulfur compounds in the hemolymph of lucinids reveal that thiosulfate may be a key intermediate in the metabolism of sulfide in all members of this family. The presence of free sulfide in the hemolymph of both freshly collected and experimental clams suggests that the total sulfide oxidation/detoxification capacity of the lucinids may be substantially lower than that found in other sulfur bacteria/invertebrate symbioses. Intracellular granules catalyze the oxidation of sulfide in L. floridana , one apparent line of sulfide toxicity defense in this species. These electron-dense granules occur in high densities in the bacteriocytes (bacteria-containing gill cells) of all lucinids. Thiosulfate produced during this detoxification may be available for further oxidation by the abundant symbionts housed in these same cells. Hemolymph thiol and elementalsulfur levels in clams from low sulfide habitats suggest that these animals have evolved mechanisms for sulfur acquisition. In sulfur-free seawater, sulfur-starved Lucina floridana are infrequent, periodic ventilators, but in the presence of sulfur show a significant increase in ventilation frequency. This periodic ventilation may be a trait of all lucinids that plays a substantial role in reducing metabolic costs during low nutrient availability.

Pulmonary Blood Flow at Rest and during Swimming in the Green Turtle, Chelonia mydas

Miniature pulsed Doppler flow probes were implanted on the left pulmonary artery and left aorta of juvenile green turtles (Chelonia mydas) to measure the cardiovascular changes associated with intermittent ventilation at rest and its conversion to a continuous pattern during swimming at 0.4 m·s⁻¹. In resting turtles, respiratory frequency, tidal volume, and oxygen uptake were also measured and convection requirements and the oxygen-content difference across the lungs calculated. Respiration-related increases in heart rate and blood flow were most pronounced in resting turtles in which bursts of breaths, rather than single breaths, occurred in ventilatoryperiods. Hypoxia (10% O₂) produced continuous ventilation in resting turtles, and pulmonary blood flow was maintained at a high, steady level Increases in heart rate and both left pulmonary and left aortic blood flow were associated with the sevenfold increase in ventilation frequency observed during swimming. Most of the increase in left pulmonary flow du...

Reduction of barotrauma in ventilated neonates by increase in ventilation frequency — first results of a prospective collaborative and randomised trial of two different ventilatory techniques : F. Pohlandt, U. Bernsau, K-D. Feilen, H. Hörnchen; A. Leonhardt, H-C. Oppermann, W. Pringsheim, H. Saule, H. Schröder and C. Wolff, Section Neonatology, University of Ulm, Ulm, Federal Republic of Germany

Reduction of barotrauma in ventilated neonates by increase in ventilation frequency — first results of a prospective collaborative and randomised trial of two different ventilatory techniques : F. Pohlandt, U. Bernsau, K-D. Feilen, H. Hörnchen; A. Leonhardt, H-C. Oppermann, W. Pringsheim, H. Saule, H. Schröder and C. Wolff, Section Neonatology, University of Ulm, Ulm, Federal Republic of Germany

Ecophysiological adaptations in Blennius pholis (L.) blood to intertidal rockpool environments

Field measurements of environmental variables in intertidal rockpools inhabited by Blennius pholis L. revealed changes in water P O 2 from 16–460 Torr, in temperature from 11–18°C, pH from 7.6 to 9.6 and in P CO 2 from 1 to 10 −2 Torr during daily tidal emersion cycles. Rapid changes in all variables were observed during the flood. In vitro measurements of blood respiratory properties of B. pholis haemoglobin revealed a low haematocrit (18%) together with a low haemoglobin concentration ( Hb 4 = 0.6 mmol · 1 blood −1). No measurable Root effect was observed in whole blood although a large, organic phosphate concentration dependent Bohr effect was seen ( Δlog P 50 ΔpH = −1.1 , ATP Hb = 3.0 , GTP Hb = 0.6 ). The temperature sensitivity of the haemoglobin was low, ΔH = −2.7 to −5.9 kcal · mol −1, and was dependent upon ATP GTP concentration as was oxygen affinity. The ATP Hb ratio averaged 2.2 and GTP Hb was 0.4. CO 2 binding curves revealed a large Haldane effect which was temperature dependent. The buffer value of true plasma was low and also temperature dependent. In vivo measurements of ventilation in B. pholis showed an increase in ventilation frequency during environmental hypoxia followed by a decrease during hyperoxia. The problems faced by fish living in intertidal rockpools are discussed in relation to blood respiratory variables and possible ecophysiological solutions.

Hypoxic Acclimation in the Lamprey, Lampetra Fluviatilis: Organismic and Erythrocytic Responses

ABSTRACT Acute exposure of Lampetra fluviatilis to hypoxia ( = 40–50 mmHg) resulted in a large increase in ventilation frequency and a significant increase in O2 consumption (from 40 to 60 mg kg−1h−1 at 8 °C). After 1 week’s hypoxia, the O2 consumption decreased (from 60 to 50 mg kg−1 h−1), indicating the existence of slow, acclimatory changes that remove some of the strain from the ventilatory response. The hypoxic animals had a higher blood O2 affinity than the normoxic controls. This acclimatory response is not the result of a decreased allosteric interaction between the haemoglobin and erythrocytic organic phosphates, as in teleost fish, but is attributable partly to dilution of haemoglobin within the red cells and partly to an increase in the intracellular pH. The intraerythrocytic pH of hypoxic animals, measured with a freeze-thaw method, was higher than the plasma pH, suggesting that protons are not passively distributed.

The Effect of Respiratory Frequency on Pulmonary Function During Artificial Ventilation

This is a review of previous studies on the effects of variations between 12 and 24 breaths per minute in ventilation frequency during artificial ventilation, minute ventilation being constant. The total material consisted of 66 healthy subjects investigated under anaesthesia with artificial ventilation and 43 patients investigated during prolonged respiratory treatment. An increase in ventilation frequency resulted in an increased ratio of dead space to tidal volume (VD/VT) and in diminished alveolar ventilation with a subsequent elevation of Paco2. The pressures in airways and alveoli were lowered. The dynamic compliance both of the lungs and of the chest wall was diminished and inspiratory resistance was slightly reduced. Intrapulmonary gas distribution was unaffected. Cardiac output was increased, as was venous admixture. Pao2 was slightly reduced. The more efficient gas exchange occurring at a low ventilation frequency makes this setting preferable in the treatment of patients with chronic obstructive lung disease, whereas a high ventilation frequency, by improving cardiac output, may be advantageous in patients with circulatory failure.