Ventilatory Mechanisms of the Amphibian, Xenopus Laevis; The Role of the Buccal Force Pump

1979 ◽  
Vol 80 (1) ◽  
pp. 251-269 ◽  
Author(s):  
S. S. BRETT ◽  
G. SHELTON
Keyword(s):  
Xenopus Laevis ◽  
Buccal Cavity ◽  
Respiratory Muscles ◽  
Lung Ventilation ◽  
Cavity Volume ◽  
Lung Volumes ◽  
Expired Air

1. Lung pressures, buccal pressures, lung volumes, and EMGs from respiratory muscles were measured in unrestrained Xenopus laevis to analyse their roles in the lung ventilation cycle. 2. Lung pressure was always maintained above atmospheric levels and a buccal pumping mechanism was used to fill the lungs in Xenopus, as in other Amphibia. 3. Xenopus, unlike other amphibians, does not ventilate the buccal cavity between lung ventilations. 4. Expiration of gases from the buccal cavity is aided by muscles which decrease buccal cavity volume. Other anurans increase buccal cavity volume during expiration. 5. The buccal phase of inspiration occurs after expired air has passed from the lung and buccal cavity, in comparison to the ranids and bufonids which inspire fresh air into the buccal cavity before expiration.

Breathing movements in the frog Rana pipiens. II. The power output and efficiency of breathing

1975 ◽  
Vol 53 (3) ◽  
pp. 345-353 ◽  
Author(s):  
N. H. West ◽  
D. R. Jones
Keyword(s):  
Body Weight ◽  
Power Output ◽  
Rana Pipiens ◽  
Buccal Cavity ◽  
Respiratory Muscles ◽  
Lung Ventilation ◽  
Pressure Change ◽  
Mechanical Efficiency ◽  
Lung Inflation ◽  
Anticlockwise Direction

The work done by the buccal cavity during buccal and lung ventilation cycles has been estimated from measurement of the area enclosed by pressure–volume loops for each cycle. The loops cycled in an anticlockwise direction with respect to time during buccal cycles. On the other hand, pressure–volume loops from the lungs cycled clockwise, showing that work was being done on the lungs by the buccal pump. Inflation and deflation of the buccal cavity from a syringe, in curarized frogs, gave a clockwise loop enclosing about 5.5–6.5% of the area enclosed by a naturally generated loop of the same pressure and volume. However, inflation and deflation of the lungs gave a loop which enclosed an area virtually identical with that obtained from a normally generated sequence of lung inflation and deflation. The power output of the buccal pump was directly proportional to body weight, the major determinant of the former being the larger buccal volume rather than pressure change as body weight increased. The mechanical efficiency of the buccal pump varied from 0.4% to 16.2%, efficiency increasing with increased power output over most of the physiological range. Mean efficiency of all buccal movements was calculated to be 8% and, at this value of efficiency, oxygen consumption of the respiratory muscles was 0.89 ml O2 100 g−1 min−1. In Rana pipiens at rest the oxygen cost of breathing appears to be about 5% of the total resting metabolism.

Respiratory response to partial paralysis in anesthetized dogs

1984 ◽  
Vol 56 (6) ◽  
pp. 1583-1588 ◽  
Author(s):  
A. Oliven ◽  
E. C. Deal ◽  
S. G. Kelsen ◽  
N. S. Cherniack
Keyword(s):  
Motor Activity ◽  
Respiratory Muscle ◽  
Respiratory Muscles ◽  
Peak Activity ◽  
Inspiratory Time ◽  
Muscle Paralysis ◽  
Anesthetized Dogs ◽  
Spontaneously Breathing ◽  
Partial Paralysis

The ability to maintain alveolar ventilation is compromised by respiratory muscle weakness. To examine the independent role of reflexly mediated neural mechanisms to decreases in the strength of contraction of respiratory muscles, we studied the effects of partial paralysis on the level and pattern of phrenic motor activity in 22 anesthetized spontaneously breathing dogs. Graded weakness induced with succinylcholine decreased tidal volume and prolonged both inspiratory and expiratory time causing hypoventilation and hypercapnia. Phrenic peak activity as well as the rate of rise of the integrated phrenic neurogram increased. However, when studied under isocapnic conditions, increases in the severity of paralysis, as assessed from the ratio of peak diaphragm electromyogram to peak phrenic activity, produced progressive increases in inspiratory time and phrenic peak activity but did not affect its rate of rise. After vagotomy, partial paralysis induced in 11 dogs with succinylcholine also prolonged the inspiratory burst of phrenic activity, indicating that vagal reflexes were not solely responsible for the alterations in respiratory timing. Muscle paresis was also induced with gallamine or dantrolene, causing similar responses of phrenic activity and respiratory timing. Thus, at constant levels of arterial CO2 in anesthetized dogs, respiratory muscle partial paralysis results in a decrease in breathing rate without changing the rate of rise of respiratory motor activity. This is not dependent solely on vagally mediated reflexes and occurs regardless of the pharmacological agent used. These observations in the anesthetized state are qualitatively different from the response to respiratory muscle paralysis or weakness observed in awake subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Assessment of the influence of lung inflation state on the quantitative parameters derived from hyperpolarized gas lung ventilation MRI in healthy volunteers

2019 ◽  
Vol 126 (1) ◽  
pp. 183-192 ◽  
Author(s):  
Paul J. C. Hughes ◽  
Laurie Smith ◽  
Ho-Fung Chan ◽  
Bilal A. Tahir ◽  
Graham Norquay ◽  
...  
Keyword(s):  
Healthy Volunteers ◽  
Lung Volume ◽  
Lung Ventilation ◽  
Lung Volumes ◽  
Lung Inflation ◽  
Longitudinal Measurements ◽  
Anatomical Images ◽  
Lower Lung ◽  
Ventilation Heterogeneity ◽  
Residual Capacity

In this study, the effect of lung volume on quantitative measures of lung ventilation was investigated using MRI with hyperpolarized 3He and 129Xe. Six volunteers were imaged with hyperpolarized 3He at five different lung volumes [residual volume (RV), RV + 1 liter (1L), functional residual capacity (FRC), FRC + 1L, and total lung capacity (TLC)], and three were also imaged with hyperpolarized 129Xe. Imaging at each of the lung volumes was repeated twice on the same day with corresponding 1H lung anatomical images. Percent lung ventilated volume (%VV) and variation of signal intensity [heterogeneity score (Hscore)] were evaluated. Increased ventilation heterogeneity, quantified by reduced %VV and increased Hscore, was observed at lower lung volumes with the least ventilation heterogeneity observed at TLC. For 3He MRI data, the coefficient of variation of %VV was <1.5% and <5.5% for Hscore at all lung volumes, while for 129Xe data the values were 4 and 10%, respectively. Generally, %VV generated from 129Xe images was lower than that seen from 3He images. The good repeatability of 3He %VV found here supports prior publications showing that percent lung-ventilated volume is a robust method for assessing global lung ventilation. The greater ventilation heterogeneity observed at lower lung volumes indicates that there may be partial airway closure in healthy lungs and that lung volume should be carefully considered for reliable longitudinal measurements of %VV and Hscore. The results suggest that imaging patients at different lung volumes may help to elucidate obstructive disease pathophysiology and progression. NEW & NOTEWORTHY We present repeatability data of quantitative metrics of lung function derived from hyperpolarized helium-3, xenon-129, and proton anatomical images acquired at five lung volumes in volunteers. Increased regional ventilation heterogeneity at lower lung inflation levels was observed in the lungs of healthy volunteers.

2,4-D Butoxyethyl Ester Kinetics in Embryos of Xenopus laevis: The Role of the Embryonic Jelly Coat in Reducing Chemical Absorption

2006 ◽  
Vol 52 (1) ◽  
pp. 113-120 ◽  
Author(s):  
Andrea N. Edginton ◽  
Claude Rouleau ◽  
Gerald R. Stephenson ◽  
Herman J. Boermans
Keyword(s):  
Xenopus Laevis ◽  
Chemical Absorption ◽  
Jelly Coat

scholarly journals Imaging patterns of calcium transients during neural induction in Xenopus laevis embryos

2000 ◽  
Vol 113 (19) ◽  
pp. 3519-3529 ◽  
Author(s):  
C. Leclerc ◽  
S.E. Webb ◽  
C. Daguzan ◽  
M. Moreau ◽  
A.L. Miller
Keyword(s):  
Xenopus Laevis ◽  
Calcium Signalling ◽  
Neural Induction ◽  
Calcium Transients ◽  
Free Calcium ◽  
Treated Animal ◽  
Cell Stage ◽  
Subsequent Formation ◽  
Xenopus Laevis Embryos

Through the injection of f-aequorin (a calcium-sensitive bioluminescent reporter) into the dorsal micromeres of 8-cell stage Xenopus laevis embryos, and the use of a Photon Imaging Microscope, distinct patterns of calcium signalling were visualised during the gastrulation period. We present results to show that localised domains of elevated calcium were observed exclusively in the anterior dorsal part of the ectoderm, and that these transients increased in number and amplitude between stages 9 to 11, just prior to the onset of neural induction. During this time, however, no increase in cytosolic free calcium was observed in the ventral ectoderm, mesoderm or endoderm. The origin and role of these dorsal calcium-signalling patterns were also investigated. Calcium transients require the presence of functional L-type voltage-sensitive calcium channels. Inhibition of channel activation from stages 8 to 14 with the specific antagonist R(+)BayK 8644 led to a complete inhibition of the calcium transients during gastrulation and resulted in severe defects in the subsequent formation of the anterior nervous system. BayK treatment also led to a reduction in the expression of Zic3 and geminin in whole embryos, and of NCAM in noggin-treated animal caps. The possible role of calcium transients in regulating developmental gene expression is discussed.

scholarly journals Role of zinc in the control of oocyte maturation in Xenopus laevis

2000 ◽  
Vol 21 (3) ◽  
pp. 165-168 ◽  
Author(s):  
KEN-ICHI WATANABE ◽  
TOSHINOBU TOKUMOTO ◽  
KATSUTOSHI ISHIKAWA
Keyword(s):  
Xenopus Laevis ◽  
Oocyte Maturation

scholarly journals Role of midbrain in the control of breathing in anuran amphibians

2007 ◽  
Vol 293 (1) ◽  
pp. R447-R457 ◽  
Author(s):  
Luciane H. Gargaglioni ◽  
Janice T. Meier ◽  
Luiz G. S. Branco ◽  
William K. Milsom
Keyword(s):  
Lung Ventilation ◽  
Control Of Breathing ◽  
Breathing Frequency ◽  
Attentional State ◽  
Anuran Amphibians ◽  
Auditory Integration ◽  
Stimulation Experiments ◽  
Mandibular Branch ◽  
Central Rhythm Generator

The present study was designed to explore systematically the midbrain of unanesthetized, decerebrate anuran amphibians (bullfrogs), using chemical and electrical stimulation and midbrain transections to identify sites capable of exciting and inhibiting breathing. Ventilation was measured as fictive motor output from the mandibular branch of the trigeminal nerve and the laryngeal branch of the vagus nerve. The results of our transection studies suggest that, under resting conditions, the net effect of inputs from sites within the rostral half of the midbrain is to increase fictive breathing frequency, whereas inputs from sites within the caudal half of the midbrain have no net effect on fictive breathing frequency but appear to act on the medullary central rhythm generator to produce episodic breathing. The results of our stimulation experiments indicate that the principal sites in the midbrain that are capable of exciting or inhibiting the fictive frequency of lung ventilation, and potentially clustering breaths into episodes, appear to be those primarily involved in visual and auditory integration, motor functions, and attentional state.

Breathing movements in the frog Rana pipiens. I. The mechanical events associated with lung and buccal ventilation

1975 ◽  
Vol 53 (3) ◽  
pp. 332-344 ◽  
Author(s):  
N. H. West ◽  
D. R. Jones
Keyword(s):  
Rana Pipiens ◽  
Buccal Cavity ◽  
Lung Ventilation ◽  
Cavity Pressure ◽  
Normal Pattern ◽  
Large Pressure ◽  
Dilator Muscle ◽  
Recovery Stroke ◽  
Two Phases ◽  
Low Pressures

The normal pattern of breathing movements in Rana pipiens has been studied by recording pressure and volume changes in the buccal cavity and lungs, and electromyograms from the muscles involved in this activity. Two types of breathing movement were obtained, one concerned with ventilation of the buccal cavity (buccal cycles) and the other with lung ventilation (lung cycles). Only in the latter type of movement were the nares and glottis actively involved. During buccal cycles the nares remained open and the glottis closed, so although excursions of the buccal floor were some two-thirds of the magnitude of those occurring during lung cycles, only low pressures were generated. The onset of a lung cycle was signalled by activity in the laryngeal dilator muscle. When the glottis opened, lung pressure and volume decreased, and buccal cavity pressure and volume increased. After closure of the nares, the buccal floor was rapidly elevated by the activity of the breathing muscles and air was forced into the lungs from the buccal cavity. At peak pressure in the lungs and buccal cavity the glottis closed and nares opened. The recovery stroke of the buccal pump was passive. No evidence was found for large pressure differentials between the buccal cavity and lungs when the glottis was open, and air-flow recordings at the external nares showed two phases of flow during each buccal cycle and four phases with each lung ventilation cycle.

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