Acute effects of quinidine on K exchange and distribution in the dog ventricle

1960 ◽  
Vol 199 (1) ◽  
pp. 151-156 ◽  
Author(s):  
Hadley L. Conn ◽  
John C. Wood
Keyword(s):  
Oxygen Consumption ◽  
Gas Exchange ◽  
Action Potential ◽  
Respiratory Quotient ◽  
Resting Potential ◽  
Acute Effects ◽  
Dog Heart ◽  
Potassium Influx ◽  
Potassium Exchange ◽  
Potassium Metabolism

Some of the effects of quinidine on potassium metabolism and gas exchange were studied in the isolated perfused dog heart. The major changes found were an increase in cell K and transcellular K exchange, and a decrease in oxygen consumption and respiratory quotient. The increase in K exchange was apparently due to an increased resting potential potassium exchange with little or no alteration in exchange during the action potential. The accumulation of cell K seemed to be dependent mainly on an initial resting phase increase in potassium influx.

Acute Effects of Diuretics on Potassium Exchange, Mechanical Function and the Action Potential in Rabbit Myocardium

1978 ◽  
Vol 55 (6) ◽  
pp. 555-559
Author(s):  
P. A. Poole-Wilson ◽  
S. M. Cobbe ◽  
C. H. Fry
Keyword(s):  
Action Potential ◽  
Interventricular Septum ◽  
Papillary Muscles ◽  
Mechanical Function ◽  
Acute Effects ◽  
Rabbit Myocardium ◽  
Potassium Exchange

1. We have studied the acute effects of frusemide, triamterene and amiloride on potassium exchange, the action potential and mechanical function of isolated rabbit myocardium. 2. Potassium exchange in the myocardium was unaltered by these diuretics. 3. Frusemide and amiloride did not affect the action potential of rabbit papillary muscles. Triamterene caused a transient shortening of the action potential. 4. Frusemide and triamterene did not alter myocardial mechanical function in rabbit papillary muscles or the interventricular septum. Amiloride caused a reduction of about 5% in developed tension in two out of three papillary muscles.

Quantitative methanol-burning lung model for validating gas-exchange measurements over wide ranges of F I O 2

1998 ◽  
Vol 84 (6) ◽  
pp. 2177-2182 ◽  
Author(s):  
Saul Miodownik ◽  
Jose Melendez ◽  
Vittoria Arslan Carlon ◽  
Brian Burda
Keyword(s):  
Carbon Dioxide ◽  
Oxygen Consumption ◽  
Gas Exchange ◽  
Combustion Rate ◽  
Respiratory Quotient ◽  
Infusion Rate ◽  
Carbon Dioxide Production ◽  
Lung Model ◽  
Burner Device ◽  
Extended Range

The methanol-burning lung model has been used as a technique for generating a predictable ratio of carbon dioxide production (V˙co 2) to oxygen consumption (V˙o 2) or respiratory quotient (RQ). Although an accurate RQ can be generated, quantitatively predictable and adjustableV˙o 2 andV˙co 2 cannot be generated. We describe a new burner device in which the combustion rate of methanol is always equal to the infusion rate of fuel over an extended range of O2 concentrations. This permits the assembly of a methanol-burning lung model that is usable with O2 concentrations up to 100% and provides continuously adjustable and quantitativeV˙o 2 (69–1,525 ml/min) and V˙co 2 (46–1,016 ml/min) at a RQ of 0.667.

Mode of exercise and sex are not important for oxygen consumption during and in recovery from sprint interval training

2014 ◽  
Vol 39 (12) ◽  
pp. 1388-1394 ◽  
Author(s):  
Logan K. Townsend ◽  
Katie M. Couture ◽  
Tom J. Hazell
Keyword(s):  
Sex Differences ◽  
Oxygen Consumption ◽  
Gas Exchange ◽  
Interval Training ◽  
Whole Body ◽  
Exercise Session ◽  
Sprint Interval Training ◽  
Acute Effects ◽  
Males And Females ◽  
Excess Postexercise Oxygen Consumption

Most sprint interval training (SIT) research involves cycling as the mode of exercise and whether running SIT elicits a similar excess postexercise oxygen consumption (EPOC) response to cycling SIT is unknown. As running is a more whole-body–natured exercise, the potential EPOC response could be greater when using a running session compared with a cycling session. The purpose of the current study was to determine the acute effects of a running versus cycling SIT session on EPOC and whether potential sex differences exist. Sixteen healthy recreationally active individuals (8 males and 8 females) had their gas exchange measured over ∼2.5 h under 3 experimental sessions: (i) a cycle SIT session, (ii) a run SIT session, and (iii) a control (CTRL; no exercise) session. Diet was controlled. During exercise, both SIT modes increased oxygen consumption (cycle: male, 1.967 ± 0.343; female, 1.739 ± 0.296 L·min−1; run: male, 2.169 ± 0.369; female, 1.791 ± 0.481 L·min−1) versus CTRL (male, 0.425 ± 0.065 L·min−1; female, 0.357 ± 0.067; P < 0.001), but not compared with each other (P = 0.234). In the first hour postexercise, oxygen consumption was still increased following both run (male, 0.590 ± 0.065; female, 0.449 ± 0.084) and cycle SIT (male, 0.556 ± 0.069; female, 0.481 ± 0.110 L·min−1) versus CTRL and oxygen consumption was maintained through the second hour postexercise (CTRL: male, 0.410 ± 0.048; female, 0.332 ± 0.062; cycle: male, 0.430 ± 0.047; female, 0.395 ± 0.087; run: male, 0.463 ± 0.051; female, 0.374 ± 0.087 L·min−1). The total EPOC was not significantly different between modes of exercise or males and females (P > 0.05). Our data demonstrate that the mode of exercise during SIT (cycling or running) is not important to O2 consumption and that males and females respond similarly.

GASEOUS METABOLISM IN PREMATURE INFANTS AT 32-34°C AMBIENT TEMPERATURE

PEDIATRICS ◽  
1964 ◽  
Vol 33 (1) ◽  
pp. 75-82
Author(s):  
Forrest H. Adams ◽  
Tetsuro Fujiwara ◽  
Robert Spears ◽  
Joan Hodgman
Keyword(s):  
Carbon Dioxide ◽  
Oxygen Consumption ◽  
Premature Infants ◽  
Rectal Temperature ◽  
Respiratory Quotient ◽  
Carbon Dioxide Production ◽  
Open Circuit ◽  
Co2 Production ◽  
O2 Consumption ◽  
Rate Of Increase

Thirty-four measurements of oxygen consumption, carbon dioxide production, respiratory quotient, and rectal temperature were made on 22 premature infants with ages ranging from 2½ hours to 18 days. The studies were conducted at 32-34°C utilizing an open circuit apparatus and a specially designed climatized chamber. Oxygen consumption and carbon dioxide production were lowest in the first 12 hours and increased thereafter. The rate of increase in O2 consumption was greater than that of CO2 production, with a consequent fall in respiratory quotient during the first 76 hours of life. A reverse relation of O2 consumption and CO2 production was found following the 4th day of life with a consequent rise in respiratory quotient. There was a close correlation between O2 consumption and rectal temperature regardless of age. A respiratory quotient below the value of 0.707 for fat metabolism was observed in 7 premature infants with ages ranging from 24 to 76 hours.

Electrophysiology of the Giant Nerve Cell Bodies of Limnaea Stagnalis (L.) (Gastropoda: Pulmonata)

1974 ◽  
Vol 60 (3) ◽  
pp. 653-671
Author(s):  
D. B. SATTELLE
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Cell Types ◽  
Resting Potential ◽  
Constant Field ◽  
Bathing Medium ◽  
Mean Values ◽  
Relative Contribution ◽  
External Potassium ◽  
Limnaea Stagnalis

1. A mean resting potential of -53.3 (S.D. ±2.7) mV has been obtained for 23 neurones of the parietal and visceral ganglia of Limnaea stagnalis (L.). Changes in the resting potential of between 28 and 43 mV accompany tenfold changes in [K+0]. A modified constant-field equation accounts for the behaviour of most cells over the range of external potassium concentrations from 0-5 to 10.o mM/1. Mean values have been estimated for [K+1, 56.2 (S.D.± 9-0) mM/1 and PNa/PK, 0-117 (S.D.±0-028). 2. Investigations on the ionic basis of action potential generation have revealed two cell types which can be distinguished according to the behaviour of their action potentials in sodium-free Ringer. Sodium-sensitive cells are unable to support action potentials for more than 8-10 min in the absence of sodium. Sodium slopes of between 29 and 37 mV per decade change in [Na+0] have been found for these cells. Tetrodotoxin (5 x 10-5 M) usually blocks action potentials in these neurones. Calcium-free inger produces a marked reduction in the overshoot potential and calcium slopes of about 18 mV per decade change in [Ca2+o] are found. Manganous chloride only partially reduces the action potential overshoot in these cells at concentrations of 10 mM/l. 3. Sodium-insensitive neurones maintain action potentials in the absence of external sodium. Stimulation only slightly reduces the amplitude of the action potential under these conditions and such cells are readily accessible to potassium ions in the bathing medium. A calcium-slope of 29 mV per decade change in [Ca2+o] has been observed in these cells in the absence of external sodium. 4. It is concluded that both sodium and calcium ions can be involved in the generation of the action potential in neurones of Limnaea stagnate, their relative contribution varying in different cells.

Osmotic effects on the CA1 neuronal population in hippocampal slices with special reference to glucose

1991 ◽  
Vol 65 (5) ◽  
pp. 1055-1066 ◽  
Author(s):  
B. A. Ballyk ◽  
S. J. Quackenbush ◽  
R. D. Andrew
Keyword(s):  
Action Potential ◽  
Single Cell ◽  
Epileptiform Activity ◽  
Hippocampal Slices ◽  
Stratum Radiatum ◽  
Resting Potential ◽  
Excitatory Postsynaptic Potential ◽  
Stratum Pyramidale ◽  
Postsynaptic Potential ◽  
Axonal Excitability

1. Lowered osmolality promotes epileptiform activity both clinically and in the hippocampal slice preparation, but it is unclear how neurons are excited. We studied the effects of altered osmolality on the electrophysiological properties of CA1 pyramidal cells in hippocampal slices by the use of field and intracellular recordings. The excitability of these neurons under various osmotic conditions was gauged by population spike (PS) amplitude, single cell properties, and evoked synaptic input. 2. The orthodromic PS recorded in stratum pyramidale and the field excitatory postsynaptic potential (EPSP) in stratum radiatum were inversely proportional in amplitude to the artificial cerebrospinal fluid (ACSF) osmolality over a range of +/- 80 milliosmoles/kgH2O (mosM). The effect was osmotic because changes occurred within the time frame expected for cellular expansion or shrinkage and because permeable substances such as dimethyl sulfoxide or glycerol were without effect. Dilutional changes in ACSF constituents were experimentally ruled out as promoting excitability. 3. To test whether the field data resulted from a change in single-cell excitability, CA1 cells were intracellularly recorded during exposure to +/- 40 mosM ACSF over 15 min. There was no consistent effect upon CA1 resting potential, cell input resistance, or action potential threshold. 4. Osmotic alteration of orthodromic and antidromic field potentials might involve a change in axonal excitability. However, the evoked afferent volley recorded in CA1 stratum pyramidale or radiatum, which represents the compound action potential (CAP) generated in presynaptic axons, remained osmotically unresponsive with regard to amplitude, duration, or latency. This was also characteristic of CAPs evoked in isolated sciatic and vagus nerve preparations exposed to +/- 80 mosM. Therefore axonal excitability and associated extracellular current flow generated periaxonally are not significantly affected by osmotic shifts. 5. The osmotic effect on field potential amplitudes appeared to be independent of synaptic transmission because the inverse relationship with osmolality held for the antidromically evoked PS. Moreover, as recorded with respect to ground, the intracellular EPSP-inhibitory postsynaptic potential (IPSP) sequence (evoked from CA3 stratum radiatum) was not altered by osmolality. 6. The PS could occasionally be recorded intracellularly as a brief negativity interrupting the evoked EPSP. In hyposmotic ACSF, the amplitude increased and action potentials arose from the trough of the negativity as expected for a field effect. This is presumably the result of enhanced intracellular channeling of current caused by the increased extracellular resistance that accompanies cellular swelling.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Is action potential duration of the intact dog heart related to contractility or stimulus rate?

1982 ◽  
Vol 331 (1) ◽  
pp. 499-510 ◽  
Author(s):  
Angela J. Drake ◽  
Mark I. M. Noble ◽  
Vincent Schouten ◽  
Anthony Seed ◽  
Henk E. D. J. Ter Keurs ◽  
...  
Keyword(s):  
Action Potential ◽  
Action Potential Duration ◽  
Dog Heart ◽  
Stimulus Rate

scholarly journals The Acute Effects of Different Forms of Suspension Push‐Ups on Oxygen Consumption, Salivary Testosterone and Cortisol and Isometric Strength

2018 ◽  
Vol 64 (1) ◽  
pp. 77-85 ◽  
Author(s):  
David Bellar ◽  
Cory Etheredge ◽  
Lawrence W. Judge
Keyword(s):  
Oxygen Consumption ◽  
Repeated Measures ◽  
Bench Press ◽  
Body Height ◽  
Isometric Strength ◽  
Exercise Session ◽  
Acute Effects ◽  
Hands And Feet ◽  
The Impact ◽  
Push Up

Abstract Suspension exercise systems are being used in strength and conditioning facilities, fitness centers, rehabilitation centers and home gyms. Though some evidence exists regarding the impact of training with these systems, more work is needed for a better understanding. The purpose of the present investigation was to examine the acute effects of an exercise session with 2 (hands only) and 4 straps (hands and feet) in the push-up exercise compared to a work-matched bench press exercise session. The participants for this repeated measures, cross-over investigation were 18 healthy college-aged males (age: 24.8 ± 3.5 yrs, body mass: 81.8 ± 7.8 kg, body height: 178.9 ± 4.5 cm). The conditions were 6 sets of 10 repetitions of suspension push-ups using two straps (DUAL) for the hands, fours straps (QUAD) for hands and feet and a traditional bench press exercise matched to the average resistance during the suspension push-up. The participants performed all repetitions at a controlled cadence. Expired gases, and heart rate were monitored continuously during the exercise session. Pre and post exercise saliva samples were collected to quantify changes in testosterone and cortisol. Upper body isometric strength tests ( UBIST) were performed (Post, 1 hr, 24 hr, 48 hr) to evaluate changes in force production during recovery. Data analysis via repeated measures ANOVA revealed a significant trend for increased oxygen consumption in the QUAD condition compared to the bench press (p = 0.019). Additionally, both suspension conditions resulted in a reduced respiratory exchange ratio as compared to the bench press (p < 0.05). A significant main effect was noted for time in all conditions regarding isometric strength (p < 0.001), but no differences between conditions were revealed. Testosterone and cortisol responses did not differ between conditions. Based upon these data, it appears that when matched for work, suspension exercise results in equivalent reductions in muscle force, but greater oxygen consumption compared to isotonic exercise.

Dichotomy of Action-Potential Backpropagation in CA1 Pyramidal Neuron Dendrites

2001 ◽  
Vol 86 (6) ◽  
pp. 2998-3010 ◽  
Author(s):  
Nace L. Golding ◽  
William L. Kath ◽  
Nelson Spruston
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Pyramidal Neurons ◽  
Synaptic Activity ◽  
Resting Potential ◽  
Model Parameters ◽  
Voltage Sensitivity ◽  
Whole Cell ◽  
Ca1 Pyramidal Neurons ◽  
Whole Cell Recordings

In hippocampal CA1 pyramidal neurons, action potentials are typically initiated in the axon and backpropagate into the dendrites, shaping the integration of synaptic activity and influencing the induction of synaptic plasticity. Despite previous reports describing action-potential propagation in the proximal apical dendrites, the extent to which action potentials invade the distal dendrites of CA1 pyramidal neurons remains controversial. Using paired somatic and dendritic whole cell recordings, we find that in the dendrites proximal to 280 μm from the soma, single backpropagating action potentials exhibit <50% attenuation from their amplitude in the soma. However, in dendritic recordings distal to 300 μm from the soma, action potentials in most cells backpropagated either strongly (26–42% attenuation; n = 9/20) or weakly (71–87% attenuation; n = 10/20) with only one cell exhibiting an intermediate value (45% attenuation). In experiments combining dual somatic and dendritic whole cell recordings with calcium imaging, the amount of calcium influx triggered by backpropagating action potentials was correlated with the extent of action-potential invasion of the distal dendrites. Quantitative morphometric analyses revealed that the dichotomy in action-potential backpropagation occurred in the presence of only subtle differences in either the diameter of the primary apical dendrite or branching pattern. In addition, action-potential backpropagation was not dependent on a number of electrophysiological parameters (input resistance, resting potential, voltage sensitivity of dendritic spike amplitude). There was, however, a striking correlation of the shape of the action potential at the soma with its amplitude in the dendrite; larger, faster-rising, and narrower somatic action potentials exhibited more attenuation in the distal dendrites (300–410 μm from the soma). Simple compartmental models of CA1 pyramidal neurons revealed that a dichotomy in action-potential backpropagation could be generated in response to subtle manipulations of the distribution of either sodium or potassium channels in the dendrites. Backpropagation efficacy could also be influenced by local alterations in dendritic side branches, but these effects were highly sensitive to model parameters. Based on these findings, we hypothesize that the observed dichotomy in dendritic action-potential amplitude is conferred primarily by differences in the distribution, density, or modulatory state of voltage-gated channels along the somatodendritic axis.

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