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  • 1
    Electronic Resource
    Electronic Resource
    Morphological changes during fiber type transitions in low-frequency-stimulated rat fast-twitch muscle (1994)
    Springer
    Cell & tissue research 277 (1994), S. 363-371 
    Details
    ISSN: 1432-0878
    Keywords: Fiber-type transition ; Low-frequency stimulation ; Muscle fiber morphology ; Myosin heavy chain isoform ; Satellite cell ; Rat (Wistar)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract This study investigates morphological adaptations of rat extensor digitorum longus muscle to chronic low-frequency stimulation (10 Hz, 10 h/d, up to 61±7d). During the early stimulation period (2–4 d), increased basophilia and accumulation of RNA were seen predominantly in type-IIB fibers. Putative satellite cell activation, as indicated by 3H-thymidine incorporation, was also evident during this phase. By 12 d, fiber composition remained unaltered, but there was a decrease in the cross-sectional area of the type-IIB fibers. Following 28 d of low-frequency stimulation, the percentage of type-IIB fibers decreased from 43±3% to 0%, while type-IID fibers increased from 30±3% to 60±6%. The fraction of type-IIA fibers tended to increase (controls 19±3%; stimulated 29±4%), whereas that of the type-I fibers was unaltered (4±1%). At this time, the cross-sectional area of type-IID fibers was unaltered, but that of type-IIA and type-I fibers increased. Further stimulation resulted in a return of type-IID fibers to control levels (23±5%), and a marked increase in type-IIA fibers (45±8%). The percentage of type-I fibers increased from 4±1% to 8±1%. Throughout each stage of chronic stimulation, there was no histological evidence of fiber degeneration and regeneration. These results indicate that, in contrast to the rabbit, chronic low-frequency stimulation-induced fiber conversion in the rat extensor digitorum longus muscle is entirely due to fiber transformation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00327784
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Morphological changes during fiber type transitions in low-frequency-stimulated rat fast-twitch muscle (1994)
    Springer
    Cell & tissue research 277 (1994), S. 363-371 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Fiber-type transition ; Low-frequency stimulation ; Muscle fiber morphology ; Myosin heavy chain isoform ; Satellite cell ; Rat (Wistar)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. This study investigates morphological adaptations of rat extensor digitorum longus muscle to chronic low-frequency stimulation (10 Hz, 10 h/d, up to 61 ± 7d). During the early stimulation period (2–4 d), increased basophilia and accumulation of RNA were seen predominantly in type-IIB fibers. Putative satellite cell activation, as indicated by 3H-thymidine incorporation, was also evident during this phase. By 12 d, fiber composition remained unaltered, but there was a decrease in the cross-sectional area of the type-IIB fibers. Following 28 d of low-frequency stimulation, the percentage of type-IIB fibers decreased from 43 ± 3% to 0%, while type-IID fibers increased from 30 ± 3% to 60 ± 6%. The fraction of type-IIA fibers tended to increase (controls 19 ± 3%; stimulated 29 ± 4%), whereas that of the type-I fibers was unaltered (4 ± 1%). At this time, the cross-sectional area of type-IID fibers was unaltered, but that of type-IIA and type-I fibers increased. Further stimulation resulted in a return of type-IID fibers to control levels (23 ± 5%), and a marked increase in type-IIA fibers (45 ± 8%). The percentage of type-I fibers increased from 4 ± 1% to 8 ± 1%. Throughout each stage of chronic stimulation, there was no histological evidence of fiber degeneration and regeneration. These results indicate that, in contrast to the rabbit, chronic low-frequency stimulation-induced fiber conversion in the rat extensor digitorum longus muscle is entirely due to fiber transformation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410050163
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  • 3
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    Morphological changes during fiber type transitions in low-frequency-stimulated rat fast-twitch muscle (1994)
    Springer
    Details
    Publication Date: 1994-07-01
    Print ISSN: 0302-766X
    Electronic ISSN: 1432-0878
    Topics: Biology , Medicine
    Published by Springer
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  • 4
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    Morphological changes during fiber type transitions in low-frequency-stimulated rat fast-twitch muscle (1994)
    Springer
    Details
    Publication Date: 1994-08-01
    Print ISSN: 0302-766X
    Electronic ISSN: 1432-0878
    Topics: Biology , Medicine
    Published by Springer
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  • 5
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    Simulated Microgravity Induces Regionally Distinct Neurovascular and Structural Remodeling of Skeletal Muscle and Cutaneous Arteries in the Rat (2020)
    Frontiers Media
    Details
    Publication Date: 2020-06-30
    Electronic ISSN: 1664-042X
    Topics: Biology
    Published by Frontiers Media
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  • 6
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    Apollo Lunar Astronauts Show Higher Cardiovascular Disease Mortality: Possible Deep Space Radiation Effects on the Vascular Endothelium (2016)
    Springer Nature
    Details
    Publication Date: 2016-07-28
    Electronic ISSN: 2045-2322
    Topics: Natural Sciences in General
    Published by Springer Nature
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  • 7
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    Spaceflight influences gene expression, photoreceptor integrity, and oxidative stress-related damage in the murine retina (2019)
    Springer Nature
    Details
    Publication Date: 2019-09-16
    Description: Extended spaceflight has been shown to adversely affect astronaut visual acuity. The purpose of this study was to determine whether spaceflight alters gene expression profiles and induces oxidative damage in the retina. Ten week old adult C57BL/6 male mice were flown aboard the ISS for 35 days and returned to Earth alive. Ground control mice were maintained on Earth under identical environmental conditions. Within 38 (+/−4) hours after splashdown, mice ocular tissues were collected for analysis. RNA sequencing detected 600 differentially expressed genes (DEGs) in murine spaceflight retinas, which were enriched for genes related to visual perception, the phototransduction pathway, and numerous retina and photoreceptor phenotype categories. Twelve DEGs were associated with retinitis pigmentosa, characterized by dystrophy of the photoreceptor layer rods and cones. Differentially expressed transcription factors indicated changes in chromatin structure, offering clues to the observed phenotypic changes. Immunofluorescence assays showed degradation of cone photoreceptors and increased retinal oxidative stress. Total retinal, retinal pigment epithelium, and choroid layer thickness were significantly lower after spaceflight. These results indicate that retinal performance may decrease over extended periods of spaceflight and cause visual impairment.
    Electronic ISSN: 2045-2322
    Topics: Natural Sciences in General
    Published by Springer Nature
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  • 8
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    Effects of hindlimb unweighting on the mechanical and structure properties of the rat abdominal aorta (2003)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Previous studies have shown that hindlimb unweighting of rats, a model of microgravity, reduces evoked contractile tension of peripheral conduit arteries. It has been hypothesized that this diminished contractile tension is the result of alterations in the mechanical properties of these arteries (e.g., active and passive mechanics). Therefore, the purpose of this study was to determine whether the reduced contractile force of the abdominal aorta from 2-wk hindlimb-unweighted (HU) rats results from a mechanical function deficit resulting from structural vascular alterations or material property changes. Aortas were isolated from control (C) and HU rats, and vasoconstrictor responses to norepinephrine (10(-9)-10(-4) M) and AVP (10(-9)-10(-5) M) were tested in vitro. In a second series of tests, the active and passive Cauchy stress-stretch relations were determined by incrementally increasing the uniaxial displacement of the aortic rings. Maximal Cauchy stress in response to norepinephrine and AVP were less in aortic rings from HU rats. The active Cauchy stress-stretch response indicated that, although maximum stress was lower in aortas from HU rats (C, 8.1 +/- 0.2 kPa; HU, 7.0 +/- 0.4 kPa), it was achieved at a similar hoop stretch. There were also no differences in the passive Cauchy stress-stretch response or the gross vascular morphology (e.g., medial cross-sectional area: C, 0.30 +/- 0.02 mm(2); HU, 0.32 +/- 0.01 mm(2)) between groups and no differences in resting or basal vascular tone at the displacement that elicits peak developed tension between groups (resting tension: C, 1.71 +/- 0.06 g; HU, 1.78 +/- 0.14 g). These results indicate that HU does not alter the functional mechanical properties of conduit arteries. However, the significantly lower active Cauchy stress of aortas from HU rats demonstrates a true contractile deficit in these arteries.
    Keywords: Aerospace Medicine
    Type: Journal of applied physiology (Bethesda, Md. : 1985) (ISSN 8750-7587); Volume 94; 2; 439-45
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  • 9
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    Acute and chronic head-down tail suspension diminishes cerebral perfusion in rats (2002)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The purpose of this study was to test the hypothesis that regional brain blood flow and vascular resistance are altered by acute and chronic head-down tail suspension (HDT). Regional cerebral blood flow, arterial pressure, heart rate, and vascular resistance were measured in a group of control rats during normal standing and following 10 min of HDT and in two other groups of rats after 7 and 28 days of HDT. Heart rate was not different among conditions, whereas mean arterial pressure was elevated at 10 min of HDT relative to the other conditions. Total brain blood flow was reduced from that during standing by 48, 24, and 27% following 10 min and 7 and 28 days of HDT, respectively. Regional blood flows to all cerebral tissues and the eyes were reduced with 10 min of HDT and remained lower in the eye, olfactory bulbs, left and right cerebrum, thalamic region, and the midbrain with 7 and 28 days of HDT. Total brain vascular resistance was 116, 44, and 38% greater following 10 min and 7 and 28 days of HDT, respectively, relative to that during control standing. Vascular resistance was elevated in all cerebral regions with 10 min of HDT and remained higher than control levels in most brain regions. These results demonstrate that HDT results in chronic elevations in total and regional cerebral vascular resistance, and this may be the underlying stimulus for the HDT-induced smooth muscle hypertrophy of cerebral resistance arteries.
    Keywords: Aerospace Medicine
    Type: American journal of physiology. Heart and circulatory physiology (ISSN 0363-6135); Volume 282; 1; H328-34
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  • 10
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    Decreases in bone blood flow and bone material properties in aging Fischer-344 rats (2002)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The purpose of this study was to quantify precisely aging-induced changes in skeletal perfusion and bone mechanical properties in a small rodent model. Blood flow was measured in conscious juvenile (2 months old), adult (6 months old), and aged (24 months old) male Fischer-344 rats using radiolabeled microspheres. There were no significant differences in bone perfusion rate or vascular resistance between juvenile and adult rats. However, blood flow was lower in aged versus adult rats in the forelimb bones, scapulas, and femurs. To test for functional effects of this decline in blood flow, bone mineral density and mechanical properties were measured in rats from these two age groups. Bone mineral density and cross-sectional moment of inertia in femoral and tibial shafts and the femoral neck were significantly larger in the aged versus adult rats, resulting in increased (+14%-53%) breaking strength and stiffness. However, intrinsic material properties at midshaft of the long bones were 12% to 25% lower in the aged rats. Although these data are consistent with a potential link between decreased perfusion and focal alterations in bone remodeling activity related to clinically relevant bone loss, additional studies are required to establish the mechanisms for this putative relationship.
    Keywords: Aerospace Medicine
    Type: Clinical orthopaedics and related research (ISSN 0009-921X); 396; 248-57
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