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- Lexell, Jan, et al.
(författare)
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Distribution of different fibre types in human skeletal muscles : A statistical and computational study of the fibre type arrangement in m. vastus lateralis of young, healthy males
- 1984
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Ingår i: Journal of the Neurological Sciences. - 0022-510X .- 1878-5883. ; 65:3, s. 353-365
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Tidskriftsartikel (refereegranskat)abstract
- To test whether the arrangement of fibre types in the human muscle (m. vastus lateralis) from clinically healthy and young males can be regarded as random, fascicles at different parts of the muscle and with different fibre type proportions were studied. The randomness of the arrangement of fibre types was assessed by the number of enclosed fibres in a fascicle and, on the basis of a model, tested by simulating muscle cross-sections using a microcomputer. The fibre type proportion was found to vary within a fascicle, so the original model for the test of randomness was modified to allow for different fibre type proportions on the border of the fascicle and internally. The effect of different sizes of the fibre types was also considered. The various aspects considered had only a marginal effect on the original model. For this muscle (m. vastus lateralis) the arrangement of fibre types was therefore considered random. Thus, a sample from this muscle, taken from individuals of the same sex and age group, can be tested for non-randomness, as an indication of a successive denervation and reinnervation process
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| 2. |
- Lexell, Jan, et al.
(författare)
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Distribution of different fibre types in human skeletal muscles : fibre type arrangement in m. vastus lateralis from three groups of healthy men between 15 and 83 years
- 1986
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Ingår i: Journal of the Neurological Sciences. - 0022-510X .- 1878-5883. ; 72:2-3, s. 211-222
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Tidskriftsartikel (refereegranskat)abstract
- The effects of age on the fibre type arrangement in the human muscle m. vastus lateralis were studied. There were 10, 6 and 8 healthy men in the three age-groups with means 24, 52 and 77 years, respectively. For each fascicle considered, the numbers of type 1 (ST) and type 2 (FT) fibres on the boundary and internally, and the numbers of enclosed fibres of either type, were counted. The randomness of the fibre type arrangement was considered in terms of the numbers of enclosed fibres and assessed by a Monte Carlo significance test. Fibre type grouping was shown to increase with increasing age. The proportion of type 2 fibres on the boundary of a fascicle was consistently greater than internally, but the difference was less pronounced in the old group. It is argued that the process of denervation and reinnervation of individual fibres has started before the age of 50, is a major factor in a progressive reduction of fibres with increasing age and is probably caused by a continuous loss of motor neurons in the spinal cord.
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| 3. |
- Lexell, Jan, et al.
(författare)
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Distribution of different fibre types in human skeletal muscles. A statistical and computational model for the study of fibre type grouping and early diagnosis of skeletal muscle fibre denervation and reinnervation
- 1983
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Ingår i: Journal of the Neurological Sciences. - 1878-5883 .- 0022-510X. ; 61:3, s. 301-314
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Tidskriftsartikel (refereegranskat)abstract
- To define fibre type grouping in terms of random and non-random arrangements of the two fibre types, type 1 (ST) and type 2 (FT), we adopted the measure of counting the number of "enclosed fibres". The statistical properties of the number of enclosed fibres, and the number and size of groups of enclosed fibres were studied in computer-simulated muscle cross-sections, using a model based upon hexagonal-shaped fibres. The effects on the results of differences in the sizes of the muscle fibres were considered. The applicability of the model, and the derived results and methods of analysis were tested on 10 samples from a cross-section of a whole human muscle. The results show that the model can be applied to various shapes and sizes of muscle samples and various sizes of muscle fibres. The number of enclosed fibres within a muscle sample is the best of the three measures of non-randomness considered. A test is also described for assessing whether or not the observed number of enclosed fibres is random at a given significance level.
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| 4. |
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| 5. |
- Lexell, Jan, et al.
(författare)
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What is the cause of the ageing atrophy? : number, size and proportion of different fiber types studied in whole vastus lateralis muscle from 15- to 83-year-old men
- 1988
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Ingår i: Journal of the Neurological Sciences. - 0022-510X .- 1878-5883. ; 84:2-3, s. 275-294
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Tidskriftsartikel (refereegranskat)abstract
- In order to study the effects of increasing age on the human skeletal muscle, cross-sections (15 micron) of autopsied whole vastus lateralis muscle from 43 previously physically healthy men between 15 and 83 years of age were prepared and examined. The data obtained on muscle area, total number, size, proportion and distribution of type 1 (slow-twitch) and type 2 (fast-twitch) fibers were analysed using multivariate regression. The results show that the ageing atrophy of this muscle begins around 25 years of age and thereafter accelerates. This is caused mainly by a loss of fibers, with no predominant effect on any fiber type, and to a lesser extent by a reduction in fiber size, mostly of type 2 fibers. The results also suggest the occurrence of several other age-related adaptive mechanisms which could influence fiber sizes and fiber number, as well as enzyme histochemical fiber characteristics
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