Specific Force of the Rat Extraocular Muscles, Levator and Superior Rectus, Measured In Situ

2001 ◽  
Vol 85 (3) ◽  
pp. 1027-1032 ◽  
Author(s):  
Bartley R. Frueh ◽  
Paul Gregorevic ◽  
David A. Williams ◽  
Gordon S. Lynch
Keyword(s):  
Skeletal Muscles ◽  
Muscle Length ◽  
Extraocular Muscles ◽  
Specific Force ◽  
Sectional Area ◽  
Cross Sectional ◽  
Superior Rectus ◽  
Muscle Cross Sectional Area

Extraocular muscles are characterized by their faster rates of contraction and their higher resistance to fatigue relative to limb skeletal muscles. Another often reported characteristic of extraocular muscles is that they generate lower specific forces ( sP o, force per muscle cross-sectional area, kN/m2) than limb skeletal muscles. To investigate this perplexing issue, the isometric contractile properties of the levator palpebrae superioris (levator) and superior rectus muscles of the rat were examined in situ with nerve and blood supply intact. The extraocular muscles were attached to a force transducer, and the cranial nerves exposed for direct stimulation. After determination of optimal muscle length ( L o) and stimulation voltage, a full frequency-force relationship was established for each muscle. Maximum isometric tetanic force ( P o) for the levator and superior rectus muscles was 177 ± 13 and 280 ± 10 mN (mean ± SE), respectively. For the calculation of specific force, a number of rat levator and superior rectus muscles were stored in a 20% nitric acid-based solution to isolate individual muscle fibers. Muscle fiber lengths ( L f) were expressed as a percentage of overall muscle length, allowing a mean L f to L o ratio to be used in the estimation of muscle cross-sectional area. Mean L f: L owas determined to be 0.38 for the levator muscle and 0.45 for the superior rectus muscle. The sP o for the rat levator and superior rectus muscles measured in situ was 275 and 280 kN/m2, respectively. These values are within the range of sP o values commonly reported for rat skeletal muscles. Furthermore P o and sP o for the rat levator and superior rectus muscles measured in situ were significantly higher ( P < 0.001) than P oand sP o for these muscles measured in vitro. The results indicate that the force output of intact extraocular muscles differs greatly depending on the mode of testing. Although in vitro evaluation of extraocular muscle contractility will continue to reveal important information about this group of understudied muscles, the lower sP o values of these preparations should be recognized as being significantly less than their true potential. We conclude that extraocular muscles are not intrinsically weaker than skeletal muscles.

Influence of site of tracheal pressure measurement on in situ estimation of endotracheal tube resistance

1994 ◽  
Vol 77 (6) ◽  
pp. 2899-2906 ◽  
Author(s):  
P. Navalesi ◽  
P. Hernandez ◽  
D. Laporta ◽  
J. S. Landry ◽  
F. Maltais ◽  
...  
Keyword(s):  
Endotracheal Tube ◽  
Fluid Dynamic ◽  
Reference Value ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Tracheal Pressure

In situ measurement of distal tracheal pressure (Ptr) via an intraluminal side-hole catheter (IC) has been used to determine endotracheal tube (Rett) and intrinsic patient (Rpt) resistances in intubated subjects. Because of differences in cross-sectional area between the endotracheal tube (ETT) and trachea, fluid dynamic principles predict that IC position should critically influence these results. Accordingly, the aim of this study was to determine the effect of IC position on Rett. Ptr was recorded in vitro through an IC from 2 cm inside, at the tip of, or 2 cm outside an ETT (7, 8, and 9 mm ID) situated within an artificial trachea (13, 18, and 22 mm ID). A reference value of Rett was also obtained. Results were unaffected by IC position during inspiration, overestimating Rett by 7.9 +/- 0.7% (SE). In contrast, during expiration, Rett fell as IC position changed from outside to inside the ETT and was underestimated by 41.3 +/- 3.6% with Ptr recorded inside the ETT. Varying ETT or tracheal size had little effect on the relative error in Rett. The IC itself did increase Rett due to a reduction in effective cross-sectional area, the change varying directly with IC size and inversely with ETT caliber. In vivo values in 11 intubated patients were comparable to in vitro results. In summary, IC position and size can have important consequences on in situ measurements of Ptr and should be considered when clinically monitoring Rett or Rpt.

Mechanical deficit persists during long-term muscle hypertrophy

1990 ◽  
Vol 69 (3) ◽  
pp. 861-867 ◽  
Author(s):  
S. C. Kandarian ◽  
T. P. White
Keyword(s):  
Isometric Force ◽  
Force Production ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Plantaris Muscle ◽  
Cross Sectional ◽  
Control Value ◽  
Muscle Cross Sectional Area ◽  
Synergistic Muscle

Hypotheses were tested that the deficit in maximum isometric force normalized to muscle cross-sectional area (i.e., specific Po, N/cm2) of hypertrophied muscle would return to control value with time and that the rate and magnitude of adaptation of specific force would not differ between soleus and plantaris muscles. Ablation operations of the gastrocnemius and plantaris muscles or the gastrocnemius and soleus muscles were done to induce hypertrophy of synergistic muscle left intact in female Wistar rats (n = 47) at 5 wk of age. The hypertrophied soleus and plantaris muscles and control muscles from other age-matched rats (n = 22) were studied from days 30 to 240 thereafter. Po was measured in vitro at 25 degrees C in oxygenated Krebs-Ringer bicarbonate. Compared with control values, soleus muscle cross-sectional area increased 41-15% from days 30 to 240 after ablation, whereas Po increased 11 and 15% only at days 60 and 90. Compared with control values, plantaris muscle cross-sectional area increased 52% at day 30, 40% from days 60 through 120, and 15% at day 240. Plantaris muscle Po increased 25% from days 30 to 120 but at day 240 was not different from control value. Changes in muscle architecture were negligible after ablation in both muscles. Specific Po was depressed from 11 to 28% for both muscles at all times. At no time after the ablation of synergistic muscle did the increased muscle cross-sectional area contribute fully to isometric force production.

Effect of passive myocardium on the compliance of porcine coronary arteries

2003 ◽  
Vol 285 (2) ◽  
pp. H653-H660 ◽  
Author(s):  
Leila H. Hamza ◽  
Quang Dang ◽  
Xiao Lu ◽  
Ayesha Mian ◽  
Sabee Molloi ◽  
...  
Keyword(s):  
Coronary Arteries ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Arterial Tree ◽  
Cross Sectional ◽  
Video Densitometry ◽  
Relationship Of ◽  
Intravascular Pressure

The objective of this study was to determine the effect of passive myocardium on the coronary arteries under distension and compression. To simulate distension and compression, we placed a diastolic-arrested heart in a Lucite box, where both the intravascular pressure and external (box) pressure were varied independently and expressed as a pressure difference (ΔP = intravascular pressure – box pressure). The ΔP-cross-sectional area relationship of the first several generations of porcine coronary arteries and the ΔP-volume relationship of the coronary arterial tree (vessels >0.5 mm in diameter) were determined using a video densitometric technique in the range of +150 to –150 mmHg. The vasodilated left anterior descending (LAD) coronary artery of six KCl-arrested hearts were perfused with iodine and 3% Cab-O-Sil. The intravascular pressure was varied in a triangular pattern, whereas the absolute cross-sectional area of each vessel and the total arterial volume were calculated using video densitometry under different box pressures (0, 50, 100, and 150 mmHg). In the range of positive ΔP, we found that the compliance of the proximal LAD artery in situ (4.85 ± 3.8 × 10–3 mm2/mmHg) is smaller than that of the same artery in vitro (16.5 ± 6 × 10–3 mm2/mmHg; P = 0.009). Hence, the myocardium restricts the compliance of the epicardial artery under distension. In the negative ΔP range, the LAD artery does not collapse, whereas the same vessel readily collapses when tested in vitro. Hence, we conclude that myocardial tethering prevents collapse of large blood vessel under compression.

Decline in isokinetic force with age: muscle cross-sectional area and specific force

1997 ◽  
Vol 434 (3) ◽  
pp. 246-253 ◽  
Author(s):  
S. A. Jubrias ◽  
I. R. Odderson ◽  
Peter C. Esselman ◽  
Kevin E. Conley
Keyword(s):  
Cross Sectional Area ◽  
Specific Force ◽  
Sectional Area ◽  
Cross Sectional ◽  
Muscle Cross Sectional Area

Functional characteristics of canine costal and crural diaphragm

1988 ◽  
Vol 65 (5) ◽  
pp. 2253-2260 ◽  
Author(s):  
G. A. Farkas ◽  
D. F. Rochester
Keyword(s):  
Contractile Properties ◽  
Force Frequency ◽  
Cross Sectional ◽  
Volume Functional ◽  
Generating Capacity ◽  
Residual Capacity ◽  
Crural Diaphragm ◽  
Muscle Cross Sectional Area

We estimated the in situ force-generating capacity of the costal and crural portions of the canine diaphragm by relating in vitro contractile properties and diaphragmatic dimensions to in situ lengths. Piezoelectric crystals were implanted on right costal and left crural diaphragms of anesthetized dogs, via midline laparatomy. With the abdomen reclosed, diaphragm lengths were recorded at five lung volumes. Contractile properties of excised muscle bundles were then measured. In vitro force-frequency and length-tension characteristics of the costal and crural diaphragms were virtually identical; their optimal force values were 2.15 and 2.22 kg/cm2, respectively. In situ, at residual volume, functional residual capacity (FRC), and total lung capacity the costal diaphragm lay at 102, 95, and 60% of optimal length (Lo), whereas the crural diaphragm lay at 88, 84, and 66% of Lo. Muscle cross-sectional area was 40% greater in costal than in crural diaphragms. Considering in situ lengths, cross-sectional areas, and in vitro length-tension characteristics at FRC, the costal diaphragm could exert 60% more force than the crural diaphragm.

scholarly journals Is there a correlation between upper lumbar disc herniation and multifidus muscle degeneration? A retrospective study of MRI morphology

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Chong Liu ◽  
Jiang Xue ◽  
Jingjing Liu ◽  
Gang Ma ◽  
Abu Moro ◽  
...  
Keyword(s):  
Lumbar Disc Herniation ◽  
Lumbar Disc ◽  
Fatty Infiltration ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Muscle Degeneration ◽  
Multifidus Muscle ◽  
Cross Sectional ◽  
Upper Lumbar Disc Herniation ◽  
Muscle Cross Sectional Area

Abstract Background The purpose of the study is to investigate the correlation between upper lumbar disc herniation (ULDH) and multifidus muscle degeneration via the comparison of width, the cross-sectional area and degree of fatty infiltration of the lumbar multifidus muscle. Methods Using the axial T2-weighted images of magnetic resonance imaging as an assessment tool, we retrospectively investigated 132 patients with ULDH and 132 healthy individuals. The total muscle cross-sectional area (TMCSA) and the pure muscle cross-sectional area (PMCSA) of the multifidus muscle at the L1/2, L2/3, and L3/4 intervertebral disc levels were measured respectively, and in the meantime, the average multifidus muscle width (AMMW) and degree of fatty infiltration of bilateral multifidus muscle were evaluated. The resulting data were analyzed to determine the presence/absence of statistical significance between the study and control groups. Multivariate logistical regression analyses were used to evaluate the correlation between ULDH and multifidus degeneration. Results The results of the analysis of the two groups showed that there were statistically significant differences (p < 0.05) between TMCSA, PMCSA, AMMW and degree of fatty infiltration. The multivariate logistic regression analysis indicated that the TMCSA, PMCSA, AMMW and the degree of fatty infiltration of multifidus muscle were correlated with ULDH, and the differences were statistically significant (P < 0.05). Conclusions A correlation could exist between multifidus muscles degeneration and ULDH, that may be a process of mutual influence and interaction. Lumbar muscle strengthening training could prevent and improve muscle atrophy and degeneration.

scholarly journals Rectus Femoris Mimicking Ultrasound Phantom for Muscle Mass Assessment: Design, Research, and Training Application

2021 ◽  
Vol 10 (12) ◽  
pp. 2721
Author(s):  
Nobuto Nakanishi ◽  
Shigeaki Inoue ◽  
Rie Tsutsumi ◽  
Yusuke Akimoto ◽  
Yuko Ono ◽  
...  
Keyword(s):  
Measurement Accuracy ◽  
Rectus Femoris ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Phantom Model ◽  
Ultrasound Measurements ◽  
Ultrasound Phantom

Ultrasound has become widely used as a means to measure the rectus femoris muscle in the acute and chronic phases of critical illness. Despite its noninvasiveness and accessibility, its accuracy highly depends on the skills of the technician. However, few ultrasound phantoms for the confirmation of its accuracy or to improve technical skills exist. In this study, the authors created a novel phantom model and used it for investigating the accuracy of measurements and for training. Study 1 investigated how various conditions affect ultrasound measurements such as thickness, cross-sectional area, and echogenicity. Study 2 investigated if the phantom can be used for the training of various health care providers in vitro and in vivo. Study 1 showed that thickness, cross-sectional area, and echogenicity were affected by probe compression strength, probe angle, phantom compression, and varying equipment. Study 2 in vitro showed that using the phantom for training improved the accuracy of the measurements taken within the phantom, and Study 2 in vivo showed the phantom training had a short-term effect on improving the measurement accuracy in a human volunteer. The new ultrasound phantom model revealed that various conditions affected ultrasound measurements, and phantom training improved the measurement accuracy.

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