Passive stiffness

As expected, passive stiffness is low if expression of fetal titin isoforms dominates (discussed further below). 

Previous work on N2B titin-expressing myocardium has revealed that the N2B PEVK region and F-actin interact (Kulke et al, 2001 Yamasaki et al, 2001), enhancing passive stiffness. Evidence suggests that this interaction can be inhibited by SI 00, provided that calcium is present (Yamasaki et al., 2002). Whether the PEVK segment of N2BA titin also interacts with actin has not been studied. Considering the different composition of N2B... 

Fukuda, N., Wu, Y., and Granzier, H. (2004). Phosphorylation of titin modulates passive stiffness of cardiac muscle in a titin isoform-dependent manner./ Gen. Physiol. 125(3), 257-271. 

Lahmers, S., Wu, Y., and Call, D. R. (2004). Developmental control of titin isoform expression and passive stiffness in fetal and neonatal myocardium. Circ. Res. 94, 505-513. 

Trombitas, K., Redkar, A., and Centner, T. (2000). Extensibility of isoforms of cardiac titin Variation in contour length of molecular subsegments provides a basis for cellular passive stiffness diversity. Biophys. J. 79, 3226-3234. 

Condition Collagen morphology Types and crosslinking Passive stiffness... 

Neagoe, C., Opitz, C.A., Makarenko, I., and Linke, W.A. (2003) Gigantic variety expression patterns of titin isoforms in striated muscles and consequences for myofibrillar passive stiffness. 

Figure 10. Undeformed shape of the free wall of a normal rat left ventricle. The network superimposed on the wall geometry illustrates the finite-element substructure in the mathematical model. (Reproduced from Janz and Waldron Predicted effect of chronic apical aneurysms on the passive stiffness of the human left ventricle, Circ Res 42 255,1978 with permission from the American Heart Association.)...

Figure 5. Three critical cross-sectional shapes required for estimation of the average passive stiffness and active contraction of the myocardial fiber during a cardiac cycle, by application of plane-strain finite element analysis.

Uses. The use of titanium alloys for cast partial dentures offers light weight, low cost, good ductihty, adequate stiffness, chemical passivity toward foods and oral fluids, and biocompatibiHty with the oral tissues. 

Rigidity is muscular stiffness throughout the range of passive movement in a limb segment. Cogwheel rigidity, which is typical for parkinsonism, means that tremor is superimposed on muscle stiffness. 

As for other materials, the soil stiffnesses, Kv, Kh, and K0 are limited by ultimate soil capacities. Furthermore, reversals of movement and uplift can generate zero resistance and must be appropriately included in the analysis. The lateral stiffness, Kh, is determined from friction, adhesion, and passive pressure as applicable with an appropriate moment arm, h. 

Patient 1. This 24-year-old male university student was brought to the emergency department at 1600 h by his roommate. He was delirious and had a depressed level of consciousness. Although he had been well the previous day, that morning he had complained of a fever, severe headache, severe neck and back stiffness, nausea, and vomiting. He had become progressively unwell over 7-8 hours. On physical examination he was acutely ill with a temperature of 40°C. He was delirious and had neck rigidity with severe resistance to any attempt to passively flex his neck. A CT scan of his brain was normal. A spinal tap was performed and cerebrospinal fluid (CSF) was removed it was cloudy. 

Fig. 5. Schematic illustration of adjustments in titin expression that decrease titin-based passive myocardial stiffness during DCM heart failure (A) and increase titin-based passive myocardial stiffness during normal neonatal development (B). Titin gels are shown in the inset. They reveal that normal adult myocardium (control in A) expresses more N2B titin than N2BA titin and that N2BA titin in upregulated in myocardium of heart failure (HF) patients. In fetal myocardium (inset of B), N2BA titin also dominates. (Figure based on Nagueh et al, 2004 and Lahmers et at, 2004.)...

Wu, Y., Bell, S. P., and Trombitas, K. (2002). Changes in titin isoform expression in pacing-induced cardiac failure give rise to increased passive muscle stiffness. Circulation 106, 1384-1389. 

Passive transfer of the IgG fraction from a patient with breast cancer, Stiff-Person syndrome and amphiphysin antibodies resulted in stiffness and... 

Sommer C, Weishaupt A, Brinkhoff J, Biko L, Wessig C, Gold R, et al. Paraneoplastic stiff-person syndrome Passive transfer to rats by means of IgG antibodies to amphiphysin. Lancet 2005 365(9468) 1406-1411. 

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