Sample Size Required for the Accurate Determination of Fiber Area and Capillarity of Human Skeletal Muscle

1998 ◽  
Vol 23 (6) ◽  
pp. 594-599 ◽  
Author(s):  
Gary E. Mccall ◽  
William C. Byrnes ◽  
Arthur L. Dickinson ◽  
Steven J. Fleck
Keyword(s):  
Skeletal Muscle ◽  
Sample Size ◽  
Biceps Brachii ◽  
Accurate Determination ◽  
Sequential Estimation ◽  
Type I ◽  
College Age ◽  
Fiber Area ◽  
Key Words Muscle

This study aimed to determine the skeletal muscle fiber sample size required for a reliable, valid representation of an individual's average fiber area and capillary contacts (CC) per fiber. Biopsies were obtained from the biceps brachii of 11 college-age, recreational resistance-trained men in conjunction with a study investigating how muscle morphology changed after 12 weeks of resistance training. The effect of additional measurements on the rolling cumulative means for fiber area and CC per fiber was evaluated using sequential estimation analysis. Results showed that group cumulative mean and standard deviation had stabilized by 50 fiber measurements per individual for type I and II fibers and CC per fiber. Significant correlations (.96-.99; p < .05) existed between the 50th and 95th/100th cumulative individual means. These results indicate that a typical skeletal muscle needle biopsy would be sufficient to characterize type I and II fiber areas and CC per fiber of an individual in most subject populations, although the required sample size for characterizing fiber subtypes might be different. Key words: muscle biopsy; sequential estimation analysis

scholarly journals Losartan has no additive effect on the response to heavy-resistance exercise in human elderly skeletal muscle

2018 ◽  
Vol 125 (5) ◽  
pp. 1536-1554 ◽  
Author(s):  
Mette Flindt Heisterberg ◽  
Jesper L. Andersen ◽  
Peter Schjerling ◽  
Alberte Lund ◽  
Simone Dalskov ◽  
...  
Keyword(s):  
Gene Expression ◽  
Skeletal Muscle ◽  
Angiotensin Ii ◽  
Resistance Training ◽  
Resistance Exercise ◽  
Satellite Cells ◽  
Type I ◽  
Elderly Men ◽  
Fiber Area ◽  
Heavy Resistance Exercise

Our purpose here was to investigate the potential of blocking the angiotensin II type I receptor (AT1R) on the hypertrophy response of elderly human skeletal muscle to 4 mo of heavy-resistance exercise training. Fifty-eight healthy elderly men (+65 yr) were randomized into three groups, consuming either AT1R blocker (losartan, 100 mg/day) or placebo for 4 mo. Two groups performed resistance training (RT) and were treated with either losartan or placebo, and one group did not train but was treated with losartan. Quadriceps muscle biopsies, MR scans, and strength tests were performed at baseline and after 8 and 16 wk. Biopsies were sectioned for immunohistochemistry to determine the number of satellite cells, capillaries, fiber type distribution, and fiber area. Gene expression levels of myostatin, connective tissue, and myogenic signaling pathways were determined by real-time RT-PCR. Four months of heavy-resistance training led in both training groups to expected improvements in quadriceps (∼3–4%) and vastus lateralis (∼5–6%), cross-sectional area, and type II fiber area (∼10–18%), as well as dynamic (∼13%) and isometric (∼19%) quadriceps peak force, but with absolutely no effect of losartan on these outcomes. Furthermore, no changes were seen in satellite cell number with training, and most gene targets failed to show any changes induced by training or losartan treatment. We conclude that there does not appear to be any effect of AT1R blocking in elderly men during 4 mo of resistance training. Therefore, we do not find any support for using AT1R blockers for promoting muscle adaptation to training in humans. NEW & NOTEWORTHY Animal studies have suggested that blocking angiotensin II type I receptor (AT1R) enhances muscle regeneration and prevents disuse atrophy, but studies in humans are limited. Focusing on hypertrophy, satellite cells, and gene expression, we found that AT1R blocking did not result in any greater responses with 4 mo of resistance training. These results do not support previous findings and question the value of blocking AT1R in the context of preserving aging human muscle.

scholarly journals Satellite cell content is specifically reduced in type II skeletal muscle fibers in the elderly

2007 ◽  
Vol 292 (1) ◽  
pp. E151-E157 ◽  
Author(s):  
Lex B. Verdijk ◽  
René Koopman ◽  
Gert Schaart ◽  
Kenneth Meijer ◽  
Hans H. C. M. Savelberg ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Muscle Fiber ◽  
Fiber Type ◽  
The Elderly ◽  
Type I ◽  
Type Ii ◽  
Fiber Area ◽  
Muscle Fiber Atrophy ◽  
Fiber Atrophy ◽  
Type Ii Fibers

Satellite cells (SC) are essential for skeletal muscle growth and repair. Because sarcopenia is associated with type II muscle fiber atrophy, we hypothesized that SC content is specifically reduced in the type II fibers in the elderly. A total of eight elderly (E; 76 ± 1 yr) and eight young (Y; 20 ± 1 yr) healthy males were selected. Muscle biopsies were collected from the vastus lateralis in both legs. ATPase staining and a pax7-antibody were used to determine fiber type-specific SC content (i.e., pax7-positive SC) on serial muscle cross sections. In contrast to the type I fibers, the proportion and mean cross-sectional area of the type II fibers were substantially reduced in E vs. Y. The number of SC per type I fiber was similar in E and Y. However, the number of SC per type II fiber was substantially lower in E vs. Y (0.044 ± 0.003 vs. 0.080 ± 0.007; P < 0.01). In addition, in the type II fibers, the number of SC relative to the total number of nuclei and the number of SC per fiber area were also significantly lower in E. This study is the first to show type II fiber atrophy in the elderly to be associated with a fiber type-specific decline in SC content. The latter is evident when SC content is expressed per fiber or per fiber area. The decline in SC content might be an important factor in the etiology of type II muscle fiber atrophy, which accompanies the loss of skeletal muscle with aging.

Functional and metabolic consequences of skeletal muscle remodeling in hypothyroidism

1991 ◽  
Vol 260 (2) ◽  
pp. E272-E279 ◽  
Author(s):  
R. M. McAllister ◽  
R. W. Ogilvie ◽  
R. L. Terjung
Keyword(s):  
Skeletal Muscle ◽  
Citrate Synthase ◽  
Control Group ◽  
Type I ◽  
Tetanic Contraction ◽  
Plantaris Muscle ◽  
Tension Development ◽  
Fiber Area ◽  
And Control ◽  
Muscle Remodeling

Functional and metabolic responses of hypothyroid skeletal muscle were evaluated during steady-state isometric contraction conditions, using an isolated perfused rat hindlimb preparation. Treating rats with propylthiouracil (PTU) for 4-5 mo resulted in a 55% decrease (P less than 0.001) in citrate synthase activity in plantaris muscle and phenotypic remodeling of the plantaris, evident by a threefold increase in type I fiber area and a 13% decrease in type II fiber area. Perfusion of PTU (n = 9) and control (n = 9) rat hindlimbs of similar size, with similar inflow (approximately 10 ml/min) and oxygen content (approximately 20 g/100 ml), resulted in similar oxygen deliveries to the contracting muscles (PTU 11.4 +/- 0.58, control 9.54 +/- 0.75 mumol.min-1.g-1; P greater than 0.05). Ten-minute tetanic contraction (100 ms at 100 Hz) periods at 4, 8, 15, 30, and 45 tetani/min were elicited in consecutive ascending order. Oxygen consumption (VO2) was lower in the PTU group at all contraction frequencies (P less than 0.005), with a decrease in peak VO2 of 44% (PTU 3.01 +/- 0.29, control 5.35 +/- 0.42 mumol.min-1.g-1; P less than 0.001). Oxygen extraction by the PTU muscle was only approximately 25% of that delivered. Developed tension was initially less (15%; P less than 0.05) in the PTU group but declined in a similar manner, as a percent of initial, to that of the control group. The slightly lower absolute tension development of the PTU muscle could not account for the large reduction in VO2.(ABSTRACT TRUNCATED AT 250 WORDS)

Contrasts in muscle and myofibers of elite male and female bodybuilders

1989 ◽  
Vol 67 (1) ◽  
pp. 24-31 ◽  
Author(s):  
S. E. Alway ◽  
W. H. Grumbt ◽  
W. J. Gonyea ◽  
J. Stray-Gundersen
Keyword(s):  
Lean Body Mass ◽  
Body Mass ◽  
Biceps Brachii ◽  
Body Height ◽  
Type I ◽  
Type Ii ◽  
Cross Sectional ◽  
Fiber Area ◽  
Fiber Number ◽  
Muscle Cross Sectional Area

Muscle cross-sectional area (CSA), fiber area, and fiber number were determined from the biceps brachii of eight elite male bodybuilders (MB) and five elite female bodybuilders (FB) who had similar training characteristics. Biceps CSA was obtained from computer tomographic scanning and corrected for noncontractile tissue. Biceps CSA was twofold greater in MB relative to FB and strongly correlated to lean body mass (R = 0.93). Biceps CSA expressed per kilogram lean body mass (LBM) or per centimeter body height (BH) was 35% greater in MB compared with FB. Most of the gender difference in muscle CSA was because of greater absolute mean fiber areas in MB (9,607 microns2) relative to FB (5,386 microns2); however, MB also had a significantly greater population of small type II fibers (less than 2,000 microns2) compared with FB. Type II fiber area/LBM averaged 1.6-fold greater in MB compared with FB; however, type I fiber area/LBM was similar between groups. Biceps CSA was positively correlated to fiber CSA (R = 0.75) and fiber number (R = 0.55). This suggests that adaptations to resistance training may be complex and involve fiber hypertrophy and fiber number (e.g., proliferation). Alternatively, since the muscle characteristics before training are not known, these apparent adaptations might be genetically determined attributes.

Muscle fiber regeneration in nerve-intact and free skeletal muscle autografts in cats

1984 ◽  
Vol 246 (1) ◽  
pp. C96-C105 ◽  
Author(s):  
L. C. Maxwell
Keyword(s):  
Skeletal Muscle ◽  
Muscle Mass ◽  
Extensor Digitorum Longus ◽  
Contractile Properties ◽  
Type I ◽  
Tension Development ◽  
Fiber Area ◽  
Adult Cats ◽  
Type I Fibers ◽  
Muscle Fiber Regeneration

Extensor digitorum longus (EDL) muscles of adult cats were transplanted as free autografts (FRA) with the nerve severed or as nerve-intact autografts (NIA) with the nerve retained. Histochemical and contractile properties of NIA and FRA were analyzed at selected times from 1 to 14 wk after surgery. Regeneration was qualitatively similar in NIA and FRA. Regenerating fibers were observed in both NIA and FRA within 2 wk. After 14 wk there were fewer type I fibers in both NIA and FRA than in control EDL muscles. Capillarity was greater in NIA than FRA, but both types of autografts had significantly reduced capillarity relative to control muscles. Mean fiber area, muscle mass, and absolute tension development were greater in NIA than FRA but did not reach control muscle values. Muscle mass, mean fiber area, and contractile properties, but not the proportion of type I fibers, develop toward control values more quickly in autografts with the nerve left intact.

Strength conditioning in older men: skeletal muscle hypertrophy and improved function

1988 ◽  
Vol 64 (3) ◽  
pp. 1038-1044 ◽  
Author(s):  
W. R. Frontera ◽  
C. N. Meredith ◽  
K. P. O'Reilly ◽  
H. G. Knuttgen ◽  
W. J. Evans
Keyword(s):  
Skeletal Muscle ◽  
Muscle Hypertrophy ◽  
Vastus Lateralis ◽  
Peak Torque ◽  
Older Men ◽  
Vastus Lateralis Muscle ◽  
Type I ◽  
Skeletal Muscle Function ◽  
Muscle Area ◽  
Fiber Area

The effects of strength conditioning on skeletal muscle function and mass were determined in older men. Twelve healthy untrained volunteers (age range 60-72 yr) participated in a 12-wk strength training program (8 repetitions/set; 3 sets/day; 3 days/wk) at 80% of the one repetition maximum (1 RM) for extensors and flexors of both knee joints. They were evaluated before the program and after 6 and 12 wk of training. Weekly measurements of 1 RM showed a progressive increase in strength in extensors and flexors. By 12 wk extensor and flexor strength had increased 107.4 (P less than 0.0001) and 226.7% (P less than 0.0001), respectively. Isokinetic peak torque of extensors and flexors measured on a Cybex II dynamometer increased 10.0 and 18.5% (P less than 0.05) at 60 degrees/s and 16.7 and 14.7% (P less than 0.05) at 240 degrees/s. The torque-velocity relationship showed an upward displacement of the curve at the end of training, mainly in the slow-velocity high-torque region. Midthigh composition from computerized tomographic scans showed an increase (P less than 0.01) in total thigh area (4.8%), total muscle area (11.4%), and quadriceps area (9.3%). Biopsies of the vastus lateralis muscle revealed similar increases (P less than 0.001) in type I fiber area (33.5%) and type II fiber area (27.6%). Daily excretion of urinary 3-methyl-L-histidine increased with training (P less than 0.05) by an average 40.8%. Strength gains in older men were associated with significant muscle hypertrophy and an increase in myofibrillar protein turnover.

scholarly journals A Step-by-Step Process on Sample Size Determination for Medical Research

2021 ◽  
Vol 28 (2) ◽  
pp. 15-27
Author(s):  
Mohamad Adam Bujang
Keyword(s):  
Sample Size ◽  
Type I Error ◽  
Early Stage ◽  
Sample Size Determination ◽  
Type I ◽  
Minimum Sample Size ◽  
Size Determination ◽  
Prerequisite Knowledge ◽  
Minimum Sample

Determination of a minimum sample size required for a study is a major consideration which all researchers are confronted with at the early stage of developing a research protocol. This is because the researcher will need to have a sound prerequisite knowledge of inferential statistics in order to enable him/her to acquire a thorough understanding of the overall concept of a minimum sample size requirement and its estimation. Besides type I error and power of the study, some estimates for effect sizes will also need to be determined in the process to calculate or estimate the sample size. The appropriateness in calculating or estimating the sample size will enable the researchers to better plan their study especially pertaining to recruitment of subjects. To facilitate a researcher in estimating the appropriate sample size for their study, this article provides some recommendations for researchers on how to determine the appropriate sample size for their studies. In addition, several issues related to sample size determination were also discussed.

A quantitative approach to inner shell losses

1978 ◽  
Vol 36 (1) ◽  
pp. 526-527 ◽  
Author(s):  
R.D. Leapman ◽  
P. Rez ◽  
D.F. Mayers
Keyword(s):  
Energy Transfer ◽  
Cross Section ◽  
Cross Sections ◽  
Accurate Determination ◽  
Background Intensity ◽  
Core Excitation ◽  
Quantitative Basis ◽  
Cross Section Differential ◽  
Bound Electrons

Microanalysis by EELS has been developing rapidly and though the general form of the spectrum is now understood there is a need to put the technique on a more quantitative basis (1,2). Certain aspects important for microanalysis include: (i) accurate determination of the partial cross sections, σx(α,ΔE) for core excitation when scattering lies inside collection angle a and energy range ΔE above the edge, (ii) behavior of the background intensity due to excitation of less strongly bound electrons, necessary for extrapolation beneath the signal of interest, (iii) departures from the simple hydrogenic K-edge seen in L and M losses, effecting σx and complicating microanalysis. Such problems might be approached empirically but here we describe how computation can elucidate the spectrum shape.The inelastic cross section differential with respect to energy transfer E and momentum transfer q for electrons of energy E0 and velocity v can be written as

Fast calibration of CBED patterns for quantitative analysis

1993 ◽  
Vol 51 ◽  
pp. 674-675
Author(s):  
M.A. Gribelyuk ◽  
M. Rühle
Keyword(s):  
Reciprocal Lattice ◽  
Accurate Determination ◽  
Incident Beam ◽  
Crystal Thickness ◽  
Structure Model ◽  
Beam Direction ◽  
Transmitted Beam ◽  
Reciprocal Vector ◽  
On Line

A new method is suggested for the accurate determination of the incident beam direction K, crystal thickness t and the coordinates of the basic reciprocal lattice vectors V1 and V2 (Fig. 1) of the ZOLZ plans in pixels of the digitized 2-D CBED pattern. For a given structure model and some estimated values Vest and Kest of some point O in the CBED pattern a set of line scans AkBk is chosen so that all the scans are located within CBED disks.The points on line scans AkBk are conjugate to those on A0B0 since they are shifted by the reciprocal vector gk with respect to each other. As many conjugate scans are considered as CBED disks fall into the energy filtered region of the experimental pattern. Electron intensities of the transmitted beam I0 and diffracted beams Igk for all points on conjugate scans are found as a function of crystal thickness t on the basis of the full dynamical calculation.

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