scholarly journals Force per cross-sectional area from molecules to muscles: a general property of biological motors

2016 ◽  
Vol 3 (7) ◽  
pp. 160313 ◽  
Author(s):  
Jean-Pierre Rospars ◽  
Nicole Meyer-Vernet
Keyword(s):  
Molecular Motors ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Specific Tension ◽  
Order Of Magnitude ◽  
Taxonomic Groups ◽  
Large Animals ◽  
Basic Order ◽  
Biological Motors

We propose to formally extend the notion of specific tension, i.e. force per cross-sectional area—classically used for muscles, to quantify forces in molecular motors exerting various biological functions. In doing so, we review and compare the maximum tensions exerted by about 265 biological motors operated by about 150 species of different taxonomic groups. The motors considered range from single molecules and motile appendages of microorganisms to whole muscles of large animals. We show that specific tensions exerted by molecular and non-molecular motors follow similar statistical distributions, with in particular, similar medians and (logarithmic) means. Over the 10 19 mass ( M ) range of the cell or body from which the motors are extracted, their specific tensions vary as M α with α not significantly different from zero. The typical specific tension found in most motors is about 200 kPa, which generalizes to individual molecular motors and microorganisms a classical property of macroscopic muscles. We propose a basic order-of-magnitude interpretation of this result.

Aging, muscle fiber type, and contractile function in sprint-trained athletes

2006 ◽  
Vol 101 (3) ◽  
pp. 906-917 ◽  
Author(s):  
Marko T. Korhonen ◽  
Alexander Cristea ◽  
Markku Alén ◽  
Keijo Häkkinen ◽  
Sarianna Sipilä ◽  
...  
Keyword(s):  
Fiber Type ◽  
Cross Sectional Area ◽  
Rate Of Force Development ◽  
Knee Extensors ◽  
Type I ◽  
Sectional Area ◽  
Cross Sectional ◽  
Specific Tension ◽  
Force Development ◽  
Aging Muscle

Biopsy samples were taken from the vastus lateralis of 18- to 84-yr-old male sprinters ( n = 91). Fiber-type distribution, cross-sectional area, and myosin heavy chain (MHC) isoform content were identified using ATPase histochemistry and SDS-PAGE. Specific tension and maximum shortening velocity ( Vo) were determined in 144 single skinned fibers from younger (18–33 yr, n = 8) and older (53–77 yr, n = 9) runners. Force-time characteristics of the knee extensors were determined by using isometric contraction. The cross-sectional area of type I fibers was unchanged with age, whereas that of type II fibers was reduced ( P < 0.001). With age there was an increased MHC I ( P < 0.01) and reduced MHC IIx isoform content ( P < 0.05) but no differences in MHC IIa. Specific tension of type I and IIa MHC fibers did not differ between younger and older subjects. Vo of fibers expressing type I MHC was lower ( P < 0.05) in older than in younger subjects, but there was no difference in Vo of type IIa MHC fibers. An aging-related decline of maximal isometric force ( P < 0.001) and normalized rate of force development ( P < 0.05) of knee extensors was observed. Normalized rate of force development was positively associated with MHC II ( P < 0.05). The sprint-trained athletes experienced the typical aging-related reduction in the size of fast fibers, a shift toward a slower MHC isoform profile, and a lower Vo of type I MHC fibers, which played a role in the decline in explosive force production. However, the muscle characteristics were preserved at a high level in the oldest runners, underlining the favorable impact of sprint exercise on aging muscle.

scholarly journals Age-related changes in contractile properties of single skeletal fibers from the soleus muscle

1999 ◽  
Vol 86 (3) ◽  
pp. 881-886 ◽  
Author(s):  
LaDora V. Thompson ◽  
Marybeth Brown
Keyword(s):  
Soleus Muscle ◽  
Cross Sectional Area ◽  
Contractile Properties ◽  
Brown Norway ◽  
Type I ◽  
Sectional Area ◽  
Cross Sectional ◽  
Specific Tension ◽  
Age Related ◽  
Age Related Changes

Peak absolute force, specific tension (peak absolute force per cross-sectional area), cross-sectional area, maximal unloaded shortening velocity ( V o; determined by the slack test), and myosin heavy chain (MHC) isoform compositions were determined in 124 single skeletal fibers from the soleus muscle of 12-, 24-, 30-, 36-, and 37-mo-old Fischer 344 Brown Norway F1 Hybrid rats. All fibers expressed the type I MHC isoform. The mean V o remained unchanged from 12 to 24 mo but did decrease significantly from the 24- to 30-mo time period (from 1.71 ± 0.13 to 0.85 ± 0.09 fiber lengths/s). Fiber cross-sectional area remained constant until 36 mo of age, at which time there was a 20% decrease from the values at 12 mo of age (from 5,558 ± 232 to 4,339 ± 280 μm2). A significant decrease in peak absolute force of single fibers occurred between 12 and 24 mo of age (from 51 ± 2 × 10−5 to 35 ± 2 × 10−5 N) and then remained constant until 36 mo, when another 43% decrease occurred. Like peak absolute force, the specific tension decreased significantly between 12 and 24 mo by 20%, and another 32% decline was observed at 37 mo. Thus, by 24 mo, there was a dissociation between the loss of fiber cross-sectional area and force. The results suggest time-specific changes of the contractile properties with aging that are independent of each other. Underlying mechanisms responsible for the time-dependent and contractile property-specific changes are unknown. Age-related changes in the molecular dynamics of myosin may be the underlying mechanism for altered force production. The presence of more than one β/slow MHC isoform may be the mechanism for the altered V o with age.

Dimensional and hygroexpansive behaviors of cellulose microfibrils (MFs) from kraft pulp-based fibers as a function of relative humidity

Holzforschung ◽  
2012 ◽  
Vol 66 (8) ◽  
pp. 1001-1008 ◽  
Author(s):  
Jung Myoung Lee ◽  
Joel J. Pawlak ◽  
John A. Heitmann
Keyword(s):  
Kraft Pulp ◽  
Mean Value ◽  
Model Material ◽  
Cross Sectional Area ◽  
Cellulose Microfibrils ◽  
Sectional Area ◽  
Cross Sectional ◽  
Dimensional Changes ◽  
Bleached Kraft Pulp ◽  
Order Of Magnitude

Abstract Cellulose aggregate fibrils (CAFs) with dimensions of 100,000×3000×300 nm from unbleached kraft pulp (KP), oxygen delignified KP (KPox.del), and fully bleached kraft pulp (BKP) were liberated by a series of high shear and fractionation operations. The CAFs served as microfibril model material to evaluate their dimensional and hygroexpansive behaviors when submitted to variable relative humidities (RHs). The atomic force microscopy images of CAFs from different sources of kraft fibers were obtained during a RH cycle from 50% RH to 78% RH and then to 21% RH while being kept at 23°C. The resulting images were analyzed to determine dimensional changes in length, its concurrent cross-sectional area, width, and height. The mean value of changes in length and width was in the range of 2.3–3.2% and 1.9–3.3%, respectively. The changes in area and height were in the range of 14.5–18.2% and 12.4–17.3%, respectively. The length of CAFs showed a negative correlation with RH, whereas cross-sectional area, width, and height changes correlated positively with RHs. In the out-of-plane direction, such as area and height, the hygroexpansivity was one order of magnitude larger than the in-plane hygroexpansivity, i.e., in terms of length and width.

Pelvic Canal Narrowing Caused by Triple Pelvic Osteotomy in the Dog

1994 ◽  
Vol 07 (03) ◽  
pp. 110-113 ◽  
Author(s):  
D. L. Holmberg ◽  
M. B. Hurtig ◽  
H. R. Sukhiani
Keyword(s):  
Postoperative Complications ◽  
Pelvic Osteotomy ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Canal Width ◽  
Operative Complications ◽  
Post Operative Complications

SummaryDuring a triple pelvic osteotomy, rotation of the free acetabular segment causes the pubic remnant on the acetabulum to rotate into the pelvic canal. The resulting narrowing may cause complications by impingement on the organs within the pelvic canal. Triple pelvic osteotomies were performed on ten cadaver pelves with pubic remnants equal to 0, 25, and 50% of the hemi-pubic length and angles of acetabular rotation of 20, 30, and 40 degrees. All combinations of pubic remnant lengths and angles of acetabular rotation caused a significant reduction in pelvic canal-width and cross-sectional area, when compared to the inact pelvis. Zero, 25, and 50% pubic remnants result in 15, 35, and 50% reductions in pelvic canal width respectively. Overrotation of the acetabulum should be avoided and the pubic remnant on the acetabular segment should be minimized to reduce postoperative complications due to pelvic canal narrowing.When performing triple pelvic osteotomies, the length of the pubic remnant on the acetabular segment and the angle of acetabular rotation both significantly narrow the pelvic canal. To reduce post-operative complications, due to narrowing of the pelvic canal, overrotation of the acetabulum should be avoided and the length of the pubic remnant should be minimized.

DETERMINATION OF THE FUNCTION OF THE ROD’S CROSS-SECTIONAL AREA USING VIBRATION EIGENFREQUENCIES

2020 ◽  
Vol 0 (4) ◽  
pp. 19-24
Author(s):  
I.M. UTYASHEV ◽  
◽  
A.A. AITBAEVA ◽  
A.A. YULMUKHAMETOV ◽  
◽  
...  
Keyword(s):  
Cross Sectional Area ◽  
Variable Cross ◽  
Sectional Area ◽  
Longitudinal Vibrations ◽  
Cross Sectional ◽  
Method Error ◽  
Various Boundary Conditions ◽  
Elastic Fixation ◽  
Crosssectional Area

The paper presents solutions to the direct and inverse problems on longitudinal vibrations of a rod with a variable cross-sectional area. The law of variation of the cross-sectional area is modeled as an exponential function of a polynomial of degree n . The method for reconstructing this function is based on representing the fundamental system of solutions of the direct problem in the form of a Maclaurin series in the variables x and λ. Examples of solutions for various section functions and various boundary conditions are given. It is shown that to recover n unknown coefficients of a polynomial, n eigenvalues are required, and the solution is dual. An unambiguous solution was obtained only for the case of elastic fixation at one of the rod’s ends. The numerical estimation of the method error was made using input data noise. It is shown that the error in finding the variable crosssectional area is less than 1% with the error in the eigenvalues of longitudinal vibrations not exceeding 0.0001.

Changes in the parameters of nasal breathing and parameters of the upper respiratory tract during orthognathic operations in patients with II and III skeletal class of jaw anomalies

2020 ◽  
pp. 22-27
Author(s):  
S.Sh. Gammadaeva ◽  
M.I. Misirkhanova ◽  
A.Yu. Drobyshev
Keyword(s):  
Respiratory Tract ◽  
Nasal Cavity ◽  
Nasal Septum ◽  
Cross Sectional Area ◽  
Upper Respiratory Tract ◽  
Sectional Area ◽  
Nasal Breathing ◽  
Cross Sectional ◽  
Skeletal Class ◽  
Upper Respiratory

The study analyzed the functional parameters of nasal breathing, linear parameters of the nasal aperture, nasal cavity and nasopharynx, volumetric parameters of the upper airways in patients with II and III skeletal class of jaw anomalies before and after orthognathic surgery. The respiratory function of the nose was assessed using a rhinomanometric complex. According to rhinoresistometry data, nasal resistance and hydraulic diameter were assessed. According to the data of acoustic rhinometry, the minimum cross-sectional area along the internal valve, the minimum cross-sectional area on the head of the inferior turbinate and nasal septum and related parameters were estimated. According to the CBCT data, the state of the nasal septum, the inferior turbinates, the nasal aperture, the state of the nasal cavity, and the linear values of the upper respiratory tract (nasopharynx) were analyzed. The patients were divided into 4 groups according to the classification of the patency of the nasal passages by

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