Browsing by Author "Kohn, Tertius Abraham"

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    The effect of glycine supplementation on the skeletal muscle properties of captive cheetahs (Acinonyx jubatus)
    (University of the Western Cape, 2022) Adamson, Luqmaan; Kohn, Tertius Abraham
    The fastest known land mammal – the cheetah, possesses many anatomical adaptations that enables high-speed running. Current literature regarding the physiological aspects that facilitate their incredible sprinting ability, however, remains limited. Although ensuring the survival of the species, captive cheetahs experience several complications including reduced fecundity and an increased incidence of degenerative disorders rarely observed in freeranging cheetahs. A key difference in captive and free-ranging cheetahs is that their diets differ substantially with regards to nutrient composition and availability, and previous studies have highlighted the potential link between the diet of cheetahs and their overall poor performance in captivity.
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    An exploratory study of contractile force production in muscle fibers from patients with inflammatory myopathies
    (Wiley-Blackwell, 2020) Kohn, Tertius Abraham; Henning, F.
    Introduction: The mechanism by which weakness develops in idiopathic inflammatory myopathies (IIMs) is still unclear. In this study we investigated the maximum force of single muscle fibers from patients with IIMs. Methods: Permeabilized single muscle fibers from patients with IIMs and healthy controls were subjected to contractility measurements. Maximum force and specific force production (maximum force normalized to fiber size) and fiber type were determined for each isolated fiber. Results: A total of 178 fibers were studied from five patients with IIMs and 95 fibers from four controls. Specific force production was significantly lower in the IIM group for all fiber types. Discussion: The findings from this exploratory study suggest that weakness in IIMs may, in part, be caused by dysfunction of the contractile apparatus. These findings provide a basis for further studies into the mechanisms underlying weakness in IIMs.
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    Preservation of shortening velocity and power output in single muscle fibres from patients with idiopathic inflammatory myopathies
    (Springer, 2022) Henning, Franclo; Kohn, Tertius Abraham
    Idiopathic inflammatory myopathies (IIMs) are autoimmune disorders of skeletal muscle causing weakness and disability. Utilizing single fibre contractility studies, we have previously shown that contractility is affected in muscle fibres from individuals with IIMs. For the current study, we hypothesized that a compensatory increase in shortening velocity occurs in muscle fibres from individuals with IIMs in an effort to maintain power output. We performed in vitro single fibre contractility studies to assess force–velocity relationships and maximum shortening velocity ( Vmax) of muscle fibres from individuals with IIMs (25 type I and 58 type IIA) and healthy controls (66 type I and 27 type IIA) and calculated maximum power output ( Wmax) for each fibre. We found significantly higher Vmax (mean ± SEM) of fibres from individuals with IIMs, for both type I (1.40 ± 0.31 fibre lengths/s, n = vs. 0.63 ± 0.13 fibre lengths/s; p = 0.0019) and type IIA fibres (2.00 ± 0.17 fibre lengths/s vs 0.77 ± 0.10 fibre lengths/s; p < 0.0001). Furthermore, Wmax (mean ± SEM) was maintained compared to fibres from healthy controls, again for both type I and type IIA fibres (4.10 ± 1.00 kN/m2·fibre lengths/s vs. 2.00 ± 0.16 kN/m2·fibre lengths/s; p = ns and 9.00 ± 0.64 kN/m2·fibre lengths/s vs. 6.00 ± 0.67 kN/m2·fibre lengths/s; p = ns respectively). In addition, type I muscle fibres from individuals with IIMs was able to develop maximum power output at lower relative force. The findings of this study suggest that compensatory responses to maintain power output, including increased maximum shortening velocity and improved efficiency, may occur in muscle of individuals with IIMs. The mechanism underlying this response is unclear, and different hypotheses are discussed.