| 1. |
- Drake, Anna Maria, et al.
(författare)
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The structure and function of the ankle dorsiflexor muscles in young and moderately active men and women.
- 2003
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Ingår i: Journal of Applied Physiology. - : American Physiological Society. - 1522-1601 .- 8750-7587. ; 95:6, s. 2416-2424
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Tidskriftsartikel (refereegranskat)abstract
- The aim was to investigate determinants of ankle dorsiflexor muscle (DF) strength and size in moderately active young men and women ( n = 30; age 20–31 yr). Concentric (Con) and eccentric (Ecc) strength were measured isokinetically. Magnetic resonance imaging was used to determine the muscle cross-sectional area (CSA). Multiple biopsies were obtained from the tibialis anterior muscle to determine total numbers, areas (Area I and II) and proportions (Prop I and II) of type I and II fibers, respectively, and relative contents of myosin heavy chain (MHC) isoforms MHC1, MHC2a, and MHC2x. Women had lower Con and Ecc strength (24 and 27%; P < 0.01), smaller CSA (19%; P < 0.001), lower Ecc DF specific strength (strength/CSA) (10%; P < 0.01), and smaller Area I and Area II (21 and 31%; P < 0.01) than men. Prop I, MHC1, estimated total number of fibers, and Con DF specific strength were similar for both sexes. Con DF strength was up to 72% determined by CSA and Prop I, and Ecc DF strength was up to 81% determined by CSA, Prop I, and sex; variables other than CSA explained at most 9%. Body weight and fiber areas explained >50% of the variation in CSA. In conclusion, CSA was the predominant determinant of DF strength, CSA was to a great extent determined by the body weight and the sizes of muscle fibers, and sex differences in Ecc specific strength require further study.
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| 3. |
- Machold, Robert, et al.
(författare)
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Sonic hedgehog is required for progenitor cell maintenance in telencephalic stem cell niches
- 2003
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Ingår i: Neuron. ; 39:6, s. 937-950
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Tidskriftsartikel (refereegranskat)abstract
- To directly test the requirement for hedgehog signaling in the telencephalon from early neurogenesis, we examined conditional null alleles of both the Sonic hedgehog and Smoothened genes. While the removal of Shh signaling in these animals resulted in only minor patterning abnormalities, the number of neural progenitors in both the postnatal subventricular zone and hippocampus was dramatically reduced. In the subventricular zone, this was partially attributable to a marked increase in programmed cell death. Consistent with Hedgehog signaling being required for the maintenance of stem cell niches in the adult brain, progenitors from the subventricular zone of floxed Smo animals formed significantly fewer neurospheres. The loss of hedgehog signaling also resulted in abnormalities in the dentate gyrus and olfactory bulb. Furthermore, stimulation of the hedgehog pathway in the mature brain resulted in elevated proliferation in telencephalic progenitors. These results suggest that hedgehog signaling is required to maintain progenitor cells in the postnatal telencephalon.
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