| 1. |
- Downham, David, et al.
(författare)
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Distribution of different fibre types in human skeletal muscles: A method for the detection of neurogenic disorders
- 1987
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Ingår i: IMA journal of mathematics applied in medicine and biology. - : Oxford University Press (OUP). - 0265-0746 .- 1471-6879. ; 4:1, s. 81-91
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Tidskriftsartikel (refereegranskat)abstract
- Human skeletal muscles are composed of two distinguishable types of fibres, which in healthy muscles appear to be randomly arranged. Large groups of one fibre type are commonly regarded as evidence of a neuropathological process affecting the peripheral nerves or the nerve cells in the spinal cord. An objective method that detects non-random arrangements as a sign of a neurogenic disorder, particularly in its early stages, could improve diagnosis. The randomness, or otherwise, of the fibre type arrangement is here considered in terms of the numbers of fibres surrounded entirely by others of the same type (enclosed fibres). The distribution of the number of enclosed fibres is studied for a free-sampling model using Monte Carlo methods. The negative binomial distribution is shown to fit closely, where the parameters can be expressed in terms of the number of fibres and the fibre type proportion in a sample area. This result permits the calculation of significance levels for a sample area and the combination of information in several sample areas. Finally, the method is applied to whole cross-sections of 24 male human autopsied muscles.
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| 2. |
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| 3. |
- Edman, Anne-Christine, et al.
(författare)
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Structural diversity in muscle fibres of chicken breast
- 1988
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Ingår i: Cell and Tissue Research. - 0302-766X .- 1432-0878. ; 251:2, s. 281-289
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Tidskriftsartikel (refereegranskat)abstract
- hicken breast muscle is usually considered to be a relatively homogeneous white muscle and has therefore been widely used for studies of muscle proteins. In a previous study, however, we have found different M-region structures in different fibres from this muscle. Because of this result, we have now carried out a combined histochemical and ultrastructural survey of this muscle. In particular, we have made use of large transverse cryo-sections that include most of the muscle cross-section. Although the white region is fairly homogeneous in fibre content according to normal histochemical criteria (mATPase), we have found that there is a gradation of fibre structure across the muscle. The bulk of the muscle stains conventionally for Type-II fibres according to mATPase tests (the "white" part) but, in the small "red" part of the muscle, there are also Type-I fibres together with the Type-II fibres. Superimposed on this division into Type-I and Type-II fibres are variations in fibre size, oxidative and glycolytic staining properties, and variations of Z-band width and M-band structure; there is no strict correlation among any of these parameters. The apparently uniform staining across most of the muscle when tested for myofibrillar ATPase may be a misleading indicator of fibre properties.
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| 4. |
- Henriksson-Larsén, K., et al.
(författare)
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Distribution of different fibre types in human skeletal muscles : I. Method for the preparation and analysis of cross-sections of whole tibialis anterior
- 1983
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Ingår i: The Histochemical Journal. - 0018-2214 .- 1573-6865. ; 15:2, s. 167-178
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to examine whether small biopsy specimens are representative of the whole human skeletal muscle or whether the different fibre types are unevenly distributed at different depths of the muscle. Ten micrometre thick cross-sections of whole human tibialis anterior were prepared using LKB PMV Cryo-Microtomes with a stroke length of 160 to 480 mm and the sections were stained for myofibrillar ATPase according to a modified procedure. The total and relative number of different fibres (Types 1 and 2) was determined in every 9th mm2 of the section. The data obtained were analysed by means of a computer program, which allowed assessment of bivariate data in the form of contour plots. The total number of fibres varied greatly between individuals (from 96 000 to 162 000; five individuals). The relative number of different fibres varied systematically in all individuals as a function of depth in the muscle. There was a gradual, often dramatic, relative increase in Type 2 fibre occurrence from the surface of the muscle (about 10--25%) towards the deeper regions (30--50%), the maximum being approximately along a line slightly posterior to the middle of the muscle. Additionally, superficial peaks were seen in places. In conclusion, the fibre type distribution in the tibialis anterior is not random. These results point to the importance of defining biopsy depth
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| 5. |
- Lexell, Jan, et al.
(författare)
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Distribution of different fiber types in human skeletal muscles : effects of aging studied in whole muscle cross sections
- 1983
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Ingår i: Muscle and Nerve. - : Wiley. - 0148-639X .- 1097-4598. ; 6:8, s. 588-595
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Tidskriftsartikel (refereegranskat)abstract
- The effects of aging on the total number and size of fibers, and the proportion and distribution of type 1 (slow twitch) and type 2 (fast twitch) fibers were studied in cross sections (15 mu thick) of autopsied whole m. vastus lateralis from two age groups. Each group consisted of six, previously physically healthy males (mean age 72 +/- 1 years and 30 +/- 6 years, respectively). The size of the muscles of the older individuals was 18% smaller (P less than 0.01) and the total number of fibers was 25% lower (P less than 0.01) than those of the young individuals (mean number 364,000 +/- 50,000 vs 478,000 +/- 56,000). There was, however, no significant difference in the mean fiber size (indirectly determined) or the proportion of the two fiber types, though a preferential reduction in type 2 fiber number in the aged individuals was seen. The relative occurrence of the fiber types at various depths in the aged muscles was found to be more even than in muscles from the young individuals. The results suggest that the aging atrophy in m. vastus lateralis, at least up to the age of 70, is primarily the result of a loss of fibers.
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| 6. |
- 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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| 7. |
- Lexell, Jan, et al.
(författare)
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Distribution of different fibre types in human skeletal muscles : 2. A study of cross-sections of whole m. vastus lateralis
- 1983
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Ingår i: Acta Physiologica Scandinavica. - : Wiley. - 0001-6772 .- 1365-201X. ; 117:1, s. 115-122
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Tidskriftsartikel (refereegranskat)abstract
- In order to determine the total number of fibres and the extent to which the relative occurrence of different fibre types varies within m. vastus lateralis, 15 micrometers thick cross-sections of whole muscles were prepared. The total number of type 1 and type 2 fibres was determined in every 48th square millimetre of the section, and the results thus obtained were analysed using a computer program allowing an assessment of bivariate data in the form of contour plots. The total number of fibres varied both in proximal to distal direction in the same muscle and between individuals. No obvious correlation existed between the mean fibre area and the muscle cross-sectional area. The proportion of type 1 fibres in the whole muscle varied between individuals (from 44% to 57%) with a mean value for all five of 52%. The distribution of different fibre types varied within the muscle, mainly as a function of depth, with a predominance to type 2 fibres at the surface and type 1 fibres in deeper regions of the muscle. Thus, the fibre type distribution in m. vastus lateralis is not random. This must be taken into consideration when data on fibre type composition are compared with functional variables
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| 8. |
- 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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| 9. |
- Lexell, Jan, et al.
(författare)
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Morphological detection of neurogenic muscle disorders : how can statistical methods aid diagnosis?
- 1987
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Ingår i: Acta Neuropathologica. - 0001-6322 .- 1432-0533. ; 75:2, s. 109-115
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Tidskriftsartikel (refereegranskat)abstract
- The light microscopical observation of groups of histochemically similar muscle fibres, referred to as fibre-type grouping, is commonly considered to be evidence of a denervation and reinnervation process affecting the spinal motor neurons or the peripheral nerves. It can be difficult to assess whether such groups have occurred by chance or are due to a slowly progressive pathological process in an early stage of development. Consequently, there is a need for one or more objective methods for assessing the fibre-type arrangement in healthy and diseased human muscles. The purposes here are to review the methods for the detection of fibre-type grouping that have been published in the last two decades, to describe some unsolved problems, and to indicate some likely lines of development
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| 10. |
- 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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