Effect of contractile duration on intracellular Po2 kinetics in Xenopus single skeletal myocytes

2005 ◽  
Vol 98 (5) ◽  
pp. 1639-1645 ◽  
Author(s):  
Casey A. Kindig ◽  
Richard A. Howlett ◽  
Michael C. Hogan
Keyword(s):  
Fiber Type ◽  
Rate Of Change ◽  
Whole Body ◽  
Transient Kinetics ◽  
Phosphorescence Quenching ◽  
First Order ◽  
Skeletal Myocytes ◽  
Mean Response Time ◽  
Contraction Duration ◽  
Initial Onset

It has been suggested that skeletal muscle O2 uptake (V̇o2) kinetics follow a first-order control model. Consistent with that, V̇o2 should show both 1) similar onset kinetics and 2) an on-off symmetry across submaximal work intensities regardless of the metabolic perturbation. To date, consensus on this issue has not been reached in whole body studies due to numerous confounding factors associated with O2 availability and fiber-type recruitment. To test whether single myocytes demonstrate similar intracellular Po2 (PiO2) on- and off-transient kinetics at varying work intensities, we studied Xenopus laevis single myocyte ( n = 8) PiO2 via phosphorescence quenching during two bouts of electrically induced isometric muscle contractions of 200 (low)- and 400 (high)-ms contraction duration (1 contraction every 4 s, 15 min between trials, order randomized). The fall in PiO2, which is inversely proportional to the net increase in V̇o2, was significantly greater ( P < 0.05) during the high (24.1 ± 3.2 Torr) vs. low (17.4 ± 1.6 Torr) contraction bout. However, the mean response time (MRT; time to 63% of the overall change) for the fall in PiO2 from resting baseline to end contractions was not different (high, 77.8 ± 11.5 vs. low, 76.1 ± 13.6 s; P > 0.05) between trials. The initial rate of change at contraction onset, defined as ΔPiO2/MRT, was significantly greater ( P < 0.05) in high compared with low. PiO2 off-transient MRT from the end of the contraction bout to initial baseline was unchanged (high, 83.3 ± 18.3 vs. low, 80.4 ± 21.6 s; P > 0.05) between high and low trials. These data revealed that PiO2 dynamics in frog isolated skeletal myocytes were invariant despite differing contraction durations and, by inference, metabolic demands. Thus these findings demonstrate that mitochondria can respond more rapidly at the initial onset of contractions when challenged with an augmented metabolic stimulus in accordance with an apparent first-order rate law.

Kinetics of muscle deoxygenation and microvascular Po2 during contractions in rat: comparison of optical spectroscopy and phosphorescence-quenching techniques

2012 ◽  
Vol 112 (1) ◽  
pp. 26-32 ◽  
Author(s):  
Shunsaku Koga ◽  
Yutaka Kano ◽  
Thomas J. Barstow ◽  
Leonardo F. Ferreira ◽  
Etsuko Ohmae ◽  
...  
Keyword(s):  
Infrared Spectroscopy ◽  
Visible Light ◽  
Near Infrared Spectroscopy ◽  
Near Infrared ◽  
Fiber Type ◽  
Type I ◽  
Phosphorescence Quenching ◽  
Mean Response Time ◽  
Muscle Deoxygenation ◽  
Visible Light Spectroscopy

The overarching presumption with near-infrared spectroscopy measurement of muscle deoxygenation is that the signal reflects predominantly the intramuscular microcirculatory compartment rather than intramyocyte myoglobin (Mb). To test this hypothesis, we compared the kinetics profile of muscle deoxygenation using visible light spectroscopy (suitable for the superficial fiber layers) with that for microvascular O2 partial pressure (i.e., PmvO2, phosphorescence quenching) within the same muscle region (0.5∼1 mm depth) during transitions from rest to electrically stimulated contractions in the gastrocnemius of male Wistar rats ( n = 14). Both responses could be modeled by a time delay (TD), followed by a close-to-exponential change to the new steady level. However, the TD for the muscle deoxygenation profile was significantly longer compared with that for the phosphorescence-quenching PmvO2 [8.6 ± 1.4 and 2.7 ± 0.6 s (means ± SE) for the deoxygenation and PmvO2, respectively; P < 0.05]. The time constants (τ) of the responses were not different (8.8 ± 4.7 and 11.2 ± 1.8 s for the deoxygenation and PmvO2, respectively). These disparate (TD) responses suggest that the deoxygenation characteristics of Mb extend the TD, thereby increasing the duration (number of contractions) before the onset of muscle deoxygenation. However, this effect was insufficient to increase the mean response time. Somewhat differently, the muscle deoxygenation response measured using near-infrared spectroscopy in the deeper regions (∼5 mm depth) (∼50% type I Mb-rich, highly oxidative fibers) was slower (τ = 42.3 ± 6.6 s; P < 0.05) than the corresponding value for superficial muscle measured using visible light spectroscopy or PmvO2 and can be explained on the basis of known fiber-type differences in PmvO2 kinetics. These data suggest that, within the superficial and also deeper muscle regions, the τ of the deoxygenation signal may represent a useful index of local O2 extraction kinetics during exercise transients.

Relationship between intracellular Po2 recovery kinetics and fatigability in isolated single frog myocytes

2005 ◽  
Vol 98 (6) ◽  
pp. 2316-2319 ◽  
Author(s):  
Casey A. Kindig ◽  
Brandon Walsh ◽  
Richard A. Howlett ◽  
Creed M. Stary ◽  
Michael C. Hogan
Keyword(s):  
Negative Relationship ◽  
Oxidative Capacity ◽  
Metabolic Demand ◽  
Constant Frequency ◽  
Phosphorescence Quenching ◽  
Skeletal Myocytes ◽  
Mean Response Time ◽  
Lumbrical Muscle ◽  
The Mean ◽  
The Relationship

In single frog skeletal myocytes, a linear relationship exists between “fatigability” and oxidative capacity. The purpose of this investigation was to study the relationship between the intracellular Po2 (PiO2) offset kinetics and fatigability in single Xenopus laevis myocytes to test the hypothesis that PiO2 offset kinetics would be related linearly with myocyte fatigability and, by inference, oxidative capacity. Individual myocytes ( n = 30) isolated from lumbrical muscle were subjected to a 2-min bout of isometric peak tetanic contractions at either 0.25- or 0.33-Hz frequency while PiO2 was measured continuously via phosphorescence quenching techniques. The mean response time (MRT; time to 63% of the overall response) for PiO2 recovery from contracting values to resting baseline was calculated. After the initial square-wave constant-frequency contraction trial, each cell performed an incremental contraction protocol [i.e., frequency increase every 2 min from 0.167, 0.25, 0.33, 0.5, 1.0, and 2.0 Hz until peak tension fell below 50% of initial values (TTF)]. TTF values ranged from 3.39 to 10.04 min for the myocytes. The PiO2 recovery MRT ranged from 26 to 146 s. A significant ( P < 0.05), negative relationship (MRT = −12.68TTF + 168.3, r2 = 0.605) between TTF and PiO2 recovery MRT existed. These data demonstrate a significant correlation between fatigability and oxidative phosphorylation recovery kinetics consistent with the notion that oxidative capacity determines, in part, the speed with which skeletal muscle can recover energetically to alterations in metabolic demand.

Effect of extracellular Po 2 on the fall in intracellular Po 2 in contracting single myocytes

2003 ◽  
Vol 94 (5) ◽  
pp. 1964-1970 ◽  
Author(s):  
Casey A. Kindig ◽  
Richard A. Howlett ◽  
Michael C. Hogan
Keyword(s):  
Skeletal Muscle ◽  
Time Delay ◽  
Time Constant ◽  
Initial Rate ◽  
Metabolic Response ◽  
Rate Of Change ◽  
Phosphorescence Quenching ◽  
Mean Response Time ◽  
The Mean ◽  
Lumbrical Muscles

The purpose of this investigation was to study the effects of altered extracellular Po 2 (Pe O2 ) on the intracellular Po 2(Pi O2 ) response to contractions in single skeletal muscle cells. Single myocytes ( n = 12) were dissected from lumbrical muscles of adult female Xenopus laevis and injected with 0.5 mM Pd- meso-tetra(4-carboxyphenyl)porphine for assessment of Pi O2 via phosphorescence quenching. At a Pe O2 of ∼20 (low), ∼40 (moderate), and ∼60 (high) Torr, tetanic contractions were induced at a frequency of 0.67 Hz for ∼2 min with a 5-min recovery between bouts (blocked order design). The Pi O2 response to contractions was characterized by a time delay followed by a monoexponential decline to steady-state (SS) values. The fall in Pi O2 to SS values was significantly greater at each progressively greater Pe O2 (all P < 0.05). The mean response time (time delay + time constant) was significantly faster in the low (35.2 ± 5.1 s; P < 0.05 vs. high) and moderate (43.3 ± 6.4 s; P < 0.05 vs. high) compared with high Pe O2 (61.8 ± 9.4 s) and was correlated positively ( r = 0.965) with the net fall in Pi O2 . However, the initial rate of change of Pi O2 (calculated as net fall in Pi O2 /time constant) was not different ( P > 0.05) among Pe O2 trials. These latter data suggest that, over the range of 20–60 Torr, Pe O2 does not play a deterministic role in setting the initial metabolic response to contractions in isolated frog myocytes. Additionally, these results suggest that oxidative phosphorylation in these myoglobin-free myocytes may be compromised by Pe O2 at values nearing 60 Torr.

scholarly journals Growth and zinc homeostasis in the severely Zn-deficient rat

1984 ◽  
Vol 52 (3) ◽  
pp. 545-560 ◽  
Author(s):  
R. Giugliano ◽  
D. J. Millward
Keyword(s):  
Body Weight ◽  
Growth Rates ◽  
Control Diet ◽  
Rate Of Change ◽  
Zinc Homeostasis ◽  
Whole Body ◽  
Zn Deficiency ◽  
Control Groups ◽  
Body Weights ◽  
Cyclic Changes

1. Male weanling rats were fed on diets either adequate (55 mg/kg), or severely deficient (0.4 mg/kg) in zinc, either ad lib. or in restricted amounts in four experiments. Measurements were made of growth rates and Zn contents of muscle and several individual tissues.2. Zn-deficient rats exhibited the expected symptoms of deficiency including growth retardation, cyclic changes in food intake and body-weight.3. Zn deficiency specifically reduced whole body and muscle growth rates as indicated by the fact that (a) growth rates were lower in ad lib.-fed Zn-deficient rats compared with rats pair-fed on the control diet in two experiments, (b) Zn supplementation increased body-weights of Zn-deficient rats given a restricted amount of diet at a level at which they maintained weight if unsupplemented, (c) Zn supplementation maintained body-weights of Zn-deficient rats fed a restricted amount of diet at a level at which they lost weight if unsupplemented (d) since the ratio, muscle mass:body-weight was lower in the Zn-deficient rats than in the pair-fed control groups, the reduction in muscle mass was greater than the reduction in body-weight.4. Zn concentrations were maintained in muscle, spleen and thymus, reduced in comparison to some but not all control groups in liver, kidney, testis and intestine, and markedly reduced in plasma and bone. In plasma, Zn concentrations varied inversely with the rate of change of body-weight during the cyclic changes in body-weight.5. Calculation of the total Zn in the tissues examined showed a marked increase in muscle Zn with a similar loss from bone, indicating that Zn can be redistributed from bone to allow the growth of other tissues.6. The magnitude of the increase in muscle Zn in the severely Zn-deficient rat, together with the magnitude of the total losses of muscle tissue during the catabolic phases of the cycling, indicate that in the Zn-deficient rat Zn may be highly conserved in catabolic states.

Trends in Trabecular and Cortical Bone in the Radius Compared with Whole Body Calcium Balance in Osteoporosis

1984 ◽  
Vol 66 (1) ◽  
pp. 109-112 ◽  
Author(s):  
R. Hesp ◽  
A. C. Deacon ◽  
Patricia Hulme ◽  
J. Reeve
Keyword(s):  
Trabecular Bone ◽  
Cortical Bone ◽  
Distal Radius ◽  
Rate Of Change ◽  
Whole Body ◽  
Calcium Balance ◽  
Total Absorption ◽  
Balance Study ◽  
Attenuation Coefficients ◽  
Change Trend

1. Mean linear attenuation coefficients for trabecular bone (T) in the distal radius and total absorption coefficients (TA) in the radial mid-shafts of 22 patients with crush fracture osteoporosis were measured serially for a year by using computed tomography. After approximately 6 months, each patient was admitted to a metabolic ward for an 18-day calcium balance study. 2. The rate of change (trend) in trabecular bone (T) in the distal radius was a better predictor of calcium balance than the trend in mid-shaft cortical bone (TA). 3. The scatter in the regressions of the trends of T and TA on calcium balance could be accounted for by known methodological uncertainties.

Estimating oxygen consumption rates of arteriolar walls under physiological conditions in rat skeletal muscle

2005 ◽  
Vol 289 (1) ◽  
pp. H295-H300 ◽  
Author(s):  
Masahiro Shibata ◽  
Shigeru Ichioka ◽  
Akira Kamiya
Keyword(s):  
Vascular Tone ◽  
Consumption Rate ◽  
Vascular Wall ◽  
Surrounding Tissue ◽  
Phosphorescence Quenching ◽  
Physiological Conditions ◽  
First Order ◽  
Vascular Walls ◽  
Consumption Rates

To examine the effects of vascular tone reduction on O2 consumption of the vascular wall, we determined the O2 consumption rates of arteriolar walls under normal conditions and during vasodilation induced by topical application of papaverine. A phosphorescence quenching technique was used to quantify intra- and perivascular Po2 in rat cremaster arterioles with different branching orders. Then, the measured radial Po2 gradients and a theoretical model were used to estimate the O2 consumption rates of the arteriolar walls. The vascular O2 consumption rates of functional arterioles were >100 times greater than those observed in in vitro experiments. The vascular O2 consumption rate was highest in first-order (1A) arterioles, which are located upstream, and sequentially decreased downstream in 2A and 3A arterioles under normal conditions. During papaverine-induced vasodilation, on the other hand, the O2 consumption rates of the vascular walls decreased to similar levels, suggesting that the high O2 consumption rates of 1A arterioles under normal conditions depend in part on the workload of the vascular smooth muscle. These results strongly support the hypothesis that arteriolar walls consume a significant amount of O2 compared with the surrounding tissue. Furthermore, the reduction of vascular tone of arteriolar walls may facilitate an efficient supply of O2 to the surrounding tissue.

scholarly journals Development and evaluation of the focused assessment of sonographic pathologies in the intensive care unit (FASP-ICU) protocol

Critical Care ◽  
2021 ◽  
Vol 25 (1) ◽  
Author(s):  
Stefan Schmidt ◽  
Jana-Katharina Dieks ◽  
Michael Quintel ◽  
Onnen Moerer
Keyword(s):  
Intensive Care Unit ◽  
Intensive Care ◽  
Conclusive Evidence ◽  
Rate Of Change ◽  
University Hospital ◽  
High Rate ◽  
Whole Body ◽  
Routine Surveillance ◽  
Organ Systems ◽  
Training Schemes

Abstract Background The use of ultrasonography in the intensive care unit (ICU) is steadily increasing but is usually restricted to examinations of single organs or organ systems. In this study, we combine the ultrasound approaches the most relevant to ICU to design a whole-body ultrasound (WBU) protocol. Recommendations and training schemes for WBU are sparse and lack conclusive evidence. Our aim was therefore to define the range and prevalence of abnormalities detectable by WBU to develop a simple and fast bedside examination protocol, and to evaluate the value of routine surveillance WBU in ICU patients. Methods A protocol for focused assessments of sonographic abnormalities of the ocular, vascular, pulmonary, cardiac and abdominal systems was developed to evaluate 99 predefined sonographic entities on the day of admission and on days 3, 6, 10 and 15 of the ICU admission. The study was a clinical prospective single-center trial in 111 consecutive patients admitted to the surgical ICUs of a tertiary university hospital. Results A total of 3003 abnormalities demonstrable by sonography were detected in 1275 individual scans of organ systems and 4395 individual single-organ examinations. The rate of previously undetected abnormalities ranged from 6.4 ± 4.2 on the day of admission to 2.9 ± 1.8 on day 15. Based on the sonographic findings, intensive care therapy was altered following 45.1% of examinations. Mean examination time was 18.7 ± 3.2 min, or 1.6 invested minutes per detected abnormality. Conclusions Performing the WBU protocol led to therapy changes in 45.1% of the time. Detected sonographic abnormalities showed a high rate of change in the course of the serial assessments, underlining the value of routine ultrasound examinations in the ICU. Trial registration The study was registered in the German Clinical Trials Register (DRKS, 7 April 2017; retrospectively registered) under the identifier DRKS00010428.

Daily Single-Dose and Daily Reduced-Dose Prednisone Therapy for Children With the Nephrotic Syndrome

PEDIATRICS ◽  
1989 ◽  
Vol 83 (5) ◽  
pp. 694-699
Author(s):  
Barry L. Warshaw ◽  
Leonard C. Hymes
Keyword(s):  
Nephrotic Syndrome ◽  
Single Dose ◽  
Divided Dose ◽  
Initial Therapy ◽  
Mean Response Time ◽  
Reduced Dose ◽  
Frequent Relapses ◽  
Initial Onset ◽  
Nephrotic Children ◽  
Minimal Lesion Nephrotic Syndrome

Most current reference sources recommend that initial therapy for minimal lesion nephrotic syndrome consist of prednisone, 60 mg/m2 per 24 hours or 2 mg/kg per 24 hours, given in divided doses, and that this regimen be repeated for each relapse. The need for divided-dose daily-administered prednisone is predicated on anecdotal observations that single-dose daily administration is not effective. Because single-dose daily-administered and reduced-dose daily-administered prednisone has been used to treat this condition for several years, experience with these regimens in nephrotic children was analyzed. Forty-one patients were studied, including 22 treated from the onset of their disease. Of these 22, 17 (77%) responded to single-dose daily-administered prednisone (2 mg/kg); after subsequent biospy, each of the nonresponders proved to have lesions other than minimal change disease. The mean response time with single-dose daily-administered prednisone (9.6 days for treatment of the initial onset of nephrotic syndrome and 11.1 days for treatment of relapses) was comparable to that previously reported with divided-dose regimens. In 14 patients with frequent relapses, a single reduced-dose daily-administered dose of prednisone (0.2 to 1.5 mg/kg/d) successfully induced remissions in 55 of 63 relapse episodes. It is concluded that a single morning dose of prednisone effectively induces remission in children with minimal lesion nephrotic syndrome. Among selected patients with frequent relapses, additional steroid sparing may be achieved by the use of this regimen with reduced doses during treatment of relapses.

Estimate of mean tissue O2 consumption at onset of exercise in males

1987 ◽  
Vol 63 (4) ◽  
pp. 1578-1585 ◽  
Author(s):  
M. D. Inman ◽  
R. L. Hughson ◽  
K. H. Weisiger ◽  
G. D. Swanson
Keyword(s):  
Mathematical Model ◽  
Cardiac Output ◽  
Time Delay ◽  
Impedance Cardiography ◽  
Work Rate ◽  
Rate Of Change ◽  
O2 Consumption ◽  
Weighted Mean ◽  
Mean Response Time ◽  
The Mean

A mathematical model has been developed that permitted the calculation of the flow-weighted mean tissue O2 consumption (VO2T) at the onset of a step increase in work rate. From breath-by-breath measurements of alveolar O2 consumption (VO2A) and cardiac output (Q) by impedance cardiography and assumptions about the site of depletion of O2 stores, the rate of change in O2 stores (VO2s) was determined. The sum of VO2A + VO2s = VO2T. Six very fit males performed six repetitions of each of two step increases in work rate. STlo was a transition from rest to 100-W cycling; SThi was a transition from 100- to 200-W cycling. For each work rate transition, the responses of VO2A and Q were averaged over the six repetitions of each subject and the model was solved to yield VO2T. The responses of VO2A, VO2T, and Q after the increase in work rate were fit with a monoexponential function. This function included a time constant and time delay, the sum of which gave the mean response time (MRT). In the STlo test, the MRT of VO2A (24.9 +/- 1.1 s, mean +/- SE) was longer than that of VO2T (15.3 +/- 1.3 s) and of Q (16.5 +/- 6.5 s) (P less than 0.05). The MRT of VO2T and Q did not differ significantly. Also for SThi, the MRT of VO2A (34.4 +/- 3.3 s) was significantly longer than that of VO2T (30.0 +/- 3.4 s) (P less than 0.05). The MRT of VO2T and Q (30.3 +/- 5.5 s) were not significantly different at this work rate either.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Recovery of microvascular Po2 during the exercise off-transient in muscles of different fiber type

2004 ◽  
Vol 96 (3) ◽  
pp. 1039-1044 ◽  
Author(s):  
Paul McDonough ◽  
Brad J. Behnke ◽  
Timothy I. Musch ◽  
David C. Poole
Keyword(s):  
Fiber Type ◽  
Oxidative Capacity ◽  
Type I ◽  
Sprague Dawley ◽  
Vascular Control ◽  
Mean Response Time ◽  
Slow Twitch Muscle ◽  
Slow Twitch ◽  
Muscle Energetic ◽  
Slow Twitch Fibers

The speed with which muscle energetic status recovers after exercise is dependent on oxidative capacity and vascular O2 pressures. Because vascular control differs between muscles composed of fast- vs. slow-twitch fibers, we explored the possibility that microvascular O2 pressure (PmvO2; proportional to the O2 delivery-to-O2 uptake ratio) would differ during recovery in fast-twitch peroneal (Per: 86% type II) compared with slow-twitch soleus (Sol: 84% type I). Specifically, we hypothesized that, in Per, PmvO2 would be reduced immediately after contractions and would recover more slowly during the off-transient from contractions compared with Sol. The Per and Sol muscles of six female Sprague-Dawley rats (weight = ∼220 g) were studied after the cessation of electrical stimulation (120 s; 1 Hz) to compare the recovery profiles of PmvO2. As hypothesized, PmvO2 was lower throughout recovery in Per compared with Sol (end contraction: 13.4 ± 2.2 vs. 20.2 ± 0.9 Torr; end recovery: 24.0 ± 2.4 vs. 27.4 ± 1.2 Torr, Per vs. Sol; P ≤ 0.05). In addition, the mean response time for recovery was significantly faster for Sol compared with Per (45.1 ± 5.3 vs. 66.3 ± 8.1 s, Sol vs. Per; P < 0.05). Despite these findings, PmvO2 rose progressively in both muscles and at no time fell below end-exercise values. These data indicate that, during the recovery from contractions (which is prolonged in Per), capillary O2 driving pressure (i.e., PmvO2) is reduced in fast-compared with slow-twitch muscle. In conclusion, the results of the present investigation may partially explain the slowed recovery kinetics (phosphocreatine and O2 uptake) found previously in 1) fast- vs. slow-twitch muscle and 2) various patient populations, such as those with congestive heart failure and diabetes mellitus.

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