Ageing Changes in the Tensile Properties of Tendons: Influence of Collagen Fibril Volume Fraction

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
K. L. Goh ◽  
D. F. Holmes ◽  
H.-Y. Lu ◽  
S. Richardson ◽  
K. E. Kadler ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Collagen Fibril ◽  
Volume Fraction ◽  
Area Fraction ◽  
Sectional Area ◽  
Cross Sectional ◽  
P Values ◽  
Age Related ◽  
Fibril Diameter ◽  
Age Related Changes

Connective tissues are biological composites comprising of collagen fibrils embedded in (and reinforcing) the hydrated proteoglycan-rich (PG) gel within the extracellular matrices (ECMs). Age-related changes to the mechanical properties of tissues are often associated with changes to the structure of the ECM, namely, fibril diameter. However, quantitative attempts to correlate fibril diameter to mechanical properties have yielded inconclusive evidence. Here, we described a novel approach that was based on the rule of mixtures for fiber composites to evaluate the dependence of age-related changes in tendon tensile strength (σ) and stiffness (E) on the collagen fibril cross-sectional area fraction (ρ), which is related to the fibril volume fraction. Tail tendons from C57BL6 mice from age groups 1.6–35.3months old were stretched to failure to determine σ and E. Parallel measurements of ρ as a function of age were made using transmission electron microscopy. Mathematical models (rule of mixtures) of fibrils reinforcing a PG gel in tendons were used to investigate the influence of ρ on ageing changes in σ and E. The magnitudes of σ, E, and ρ increased rapidly from 1.6monthsto4.0months (P-values <0.05) before reaching a constant (age independent) from 4.0monthsto29.0months (P-values >0.05); this trend continued for E and ρ (P-values >0.05) from 29.0monthsto35.3months, but not for σ, which decreased gradually (P-values <0.05). Linear regression analysis revealed that age-related changes in σ and E correlated positively to ρ (P-values <0.05). Collagen fibril cross-sectional area fraction ρ is a significant predictor of ageing changes in σ and E in the tail tendons of C57BL6 mice.

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.

scholarly journals A Pilot Study on Developing Quantitative Indices for Age-Related Changes in Maxillary Primary Molar Root Canal Morphology

2021 ◽  
Author(s):  
Guili Dou ◽  
Bin Xia ◽  
Yijiao Zhao ◽  
Zhipeng Sun
Keyword(s):  
Correlation Coefficient ◽  
Root Canal ◽  
Primary Molars ◽  
Sectional Area ◽  
Cross Sectional ◽  
Root Canals ◽  
Age Related ◽  
Root Canal Morphology ◽  
Canal Morphology ◽  
Age Related Changes

Abstract Objectives To elucidate age-related changes in the root canal morphology of primary molars and determine new indices to detail the root canal anatomy by cone-beam computed tomography (CBCT).Materials and Methods CBCT data of primary molars from 57 children aged 3–8 years without systemic diseases that affect tooth development were collected. The following indices were defined and calculated using Mimics 17.0, 3-Matic 9.0, and ImageJ software: (i) the cross-sectional area of the root canal; (ii) R.15: the proportion of the lateral canal wall with an inner diameter less than 0.15 mm; (iii) LC/LR: the ratio between the canal length and root length; and (iv) Ndis: the discontinuous canal count. Correlation analysis and binary logistic regression were performed to assess the variants and age-related changes in canal morphology.Results On CBCT analysis, the cross-sectional area of the root canals for mesiobuccal (MB) roots, palatal (P) roots and distobuccal (DB) roots was negatively correlated with age (P<0.05), with a correlation coefficient of -0.41, -0.42, and -0.26, respectively. The R.15 of MB roots was positively correlated with age (P<0.05, rs=0.39). The value of LC/LR for MB, DB, and P roots decreased with age, with a correlation coefficient of -0.39, -0.42, and -0.29, respectively (P<0.05). The risk of discontinuous canals (Ndis) for MB, DB, and P roots increased with age (P<0.05), with an odds ratio of 1.61, 1.48, and 1.60 respectively.Conclusions The new indices developed in the study based on CBCT successfully demonstrate age-related changes in the root canals of primary molars.

AGE-RELATED CHANGES IN THE CROSS-SECTIONAL AREA OF THE I AND II PHALANGES, THEIR BONE MARROW CAVITIES AND COMPACTS IN THE POSTNATAL ONTOGENESIS OF ROMANOV SHEEP

2019 ◽  
Keyword(s):  
Bone Marrow ◽  
Cross Section ◽  
Cross Sectional Area ◽  
Postnatal Ontogenesis ◽  
Sectional Area ◽  
Cross Sectional ◽  
Morphological Studies ◽  
Age Related ◽  
The Cross ◽  
Age Related Changes

The article presents the results of morphological studies of cross-sectional area growth in the first and second phalanges, their bone-marrow cavities and compacted tissue in the postnatal ontogenesis of Ro-manov sheep. As the material for this work we used the I and II phalanges, taken from the left thoracic limb of opposite gender twins at birth, as well as at 3,6,9,12 months of age and in adults 3–4 years of age. To identify phalanges development patterns we used classical morphological methods of research: we determined the growth rate (“K”), age-related changes in the cross-sectional area of the first and second fingers, their bone-marrow cavities and compacts in the studied age periods (M ± m) and in relation to the same indicator in adult sheep in %.. The received digital material was subjected to static processing. It was established that, due to the periosteal growth of bone tissue, cross-sectional area of the I and II phalanges increases all the time, reaching the definitive value by 12 months at the I phalanx, and in the II phalanx it occurs somewhat later. More accelerated periosteal growth is observed in both phalanges in the first three months of lambs’ life. Due to the processes of bone resorption on the side of endosteum, the same thing happens with the cross section of bone marrow cavities, they only reach the definitive state a little earlier, that was noted in the cross section of the bones. In general, the intensity of periosteal growth and resorption processes occur more quickly in I phalanges compared with II.

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