An unusual Z-system in the obliquely striated muscles of crinoids: three-dimensional structure and computer simulations
Articolo
Data di Pubblicazione:
1986
Citazione:
An unusual Z-system in the obliquely striated muscles of crinoids: three-dimensional structure and computer simulations / M.D. Candia Carnevali, A Saita, A. Fedrigo. - In: JOURNAL OF MUSCLE RESEARCH AND CELL MOTILITY. - ISSN 0142-4319. - 7:6(1986), pp. 568-578. [10.1007/BF01753572]
Abstract:
The peculiar functional structure of the Z-line in the obliquely striated muscles of some feather stars is described. It is known that cross-striated muscles are characterized by linear and continuous Z-bands, and obliquely striated muscles by disconnected, obliquely aligned Z-elements. Owing to this discontinuous organization, the sarcomere can perform wide active lengthenings, shortenings, and even 'super-elongations' in the helical fibres. In contrast, the obliquely striated fibres of crinoids show markedly continuous and homogeneous oblique Z-lines; such a structure is not compatible with 'super-performances' like sliding and shearing of the sarcomere elements, but instead could allow functions comparable to those characteristic of a cross-striated muscle (quick, short movements, mechanically amplifiable by bone levers). This odd situation, only interpretable in terms of evolutionary constraint, could be considered opposite and symmetrical to that of cross-striated 'super-contracting' muscles, where the Z-line is exceptionally fragmented to allow the sarcomere to super-contract. The possible architecture of a significant parameter such as the Z-line, which determines muscle fibre potential capacities, is analysed in detail: (1) through qualitative-quantitative evaluation of electron micrographs, supported by statistical analysis of the data; and (2) by computer simulations. The data obtained suggest that the most realistic conformation of the whole Z-complex in these muscles consists of a multiple system of continuous, ribbon-like helical planes running in parallel along the fibre from end to end and regularly cutting it with a constant thickness. The proposed model seems morphologically compatible with the experimentally verified situations and functionally compatible with the mechanical requirements for a normal contraction and for a balanced distribution of the involved strengths.
Tipologia IRIS:
01 - Articolo su periodico
Elenco autori:
M.D. Candia Carnevali, A. Saita, A. Fedrigo
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