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  • 1
    Online Resource
    Online Resource
    Skeletal muscle contractile and noncontractile components in young and older women and men
    American Physiological Society ; 2000
    In:  Journal of Applied Physiology Vol. 88, No. 2 ( 2000-02-01), p. 662-668
    Details
    In: Journal of Applied Physiology, American Physiological Society, Vol. 88, No. 2 ( 2000-02-01), p. 662-668
    Abstract: To examine the influences of age, gender, and habitual physical activity level on human skeletal muscle composition, we developed a relatively simple magnetic resonance imaging method for the quantitation of leg anterior compartment contractile and noncontractile content. We studied 23 young (11 women and 12 men, 26–44 yr old) and 21 older (10 women and 11 men, 65–83 yr old) healthy adults. Analysis was by two-factor (age, gender) ANOVA. Physical activity, quantitated by three-dimensional accelerometer worn about the waist for 1 wk, was not different between groups. Men had larger contractile and noncontractile cross-sectional areas (cm 2 ) than women, with no gender effect on percent noncontractile area. Young subjects had larger contractile areas and smaller absolute (cm 2 ) and relative (percent total) noncontractile areas than older subjects. There was a significant linear relationship between physical activity and percent noncontractile area in older ( r = −0.68, P = 0.002) but not young subjects. These data demonstrate a more than twofold increase in the noncontractile content of locomotor muscles in older adults and provide novel support for physical activity as a modulator of this age-related change in muscle composition.
    Type of Medium: Online Resource
    ISSN: 8750-7587 , 1522-1601
    URL: Article
    DOI: 10.1152/jappl.2000.88.2.662
    RVK:
    WA 15000
    RVK:
    XA 52094
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2000
    detail.hit.zdb_id: 1404365-8
    SSG: 12
    SSG: 31
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  • 2
    Online Resource
    Online Resource
    Chromatic Contrast Sensitivity During Optokinetic Nystagmus, Visually Enhanced Vestibulo-ocular Reflex, and Smooth Pursuit Eye Movements
    American Physiological Society ; 2009
    In:  Journal of Neurophysiology Vol. 101, No. 5 ( 2009-05), p. 2317-2327
    Details
    In: Journal of Neurophysiology, American Physiological Society, Vol. 101, No. 5 ( 2009-05), p. 2317-2327
    Abstract: Recently we showed that sensitivity for chromatic- and high-spatial frequency luminance stimuli is enhanced during smooth-pursuit eye movements (SPEMs). Here we investigated whether this enhancement is a general property of slow eye movements. Besides SPEM there are two other classes of eye movements that operate in a similar range of eye velocities: the optokinetic nystagmus (OKN) is a reflexive pattern of alternating fast and slow eye movements elicited by wide-field visual motion and the vestibulo-ocular reflex (VOR) stabilizes the gaze during head movements. In a natural environment all three classes of eye movements act synergistically to allow clear central vision during self- and object motion. To test whether the same improvement of chromatic sensitivity occurs during all of these eye movements, we measured human detection performance of chromatic and luminance line stimuli during OKN and contrast sensitivity during VOR and SPEM at comparable velocities. For comparison, performance in the same tasks was tested during fixation. During the slow phase of OKN we found a similar enhancement of chromatic detection rate like that during SPEM, whereas no enhancement was observable during VOR. This result indicates similarities between slow-phase OKN and SPEM, which are distinct from VOR.
    Type of Medium: Online Resource
    ISSN: 0022-3077 , 1522-1598
    URL: Article
    DOI: 10.1152/jn.91248.2008
    RVK:
    XA 10000 ; XA 552555
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2009
    detail.hit.zdb_id: 80161-6
    detail.hit.zdb_id: 1467889-5
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  • 3
    Online Resource
    Online Resource
    CO 2 -controlled sampling of alveolar gas in mechanically ventilated patients
    American Physiological Society ; 2001
    In:  Journal of Applied Physiology Vol. 90, No. 2 ( 2001-02-01), p. 486-492
    Details
    In: Journal of Applied Physiology, American Physiological Society, Vol. 90, No. 2 ( 2001-02-01), p. 486-492
    Abstract: A newly designed gas-sampling device using end-tidal CO 2 to separate dead space gas from alveolar gas was evaluated in 12 mechanically ventilated patients. For that purpose, CO 2 -controlled sampling was compared with mixed expiratory sampling. Alveolar sampling valves were easily controlled via CO 2 concentration. Concentrations of four volatile substances were determined in the expired and inspired gas. Isoflurane and isoprene, which did not occur in the inspired air, had ratios of end-tidal to mixed expired concentrations of 1.75 and 1.81, respectively. Acetone and pentane, found in both the inspired and expired air, showed ratios of 0.96 and 1.0, respectively. Precision of concentration measurements was between 2.4% (isoprene) and 11.2% (isoflurane); reproducibility (as coefficient of variation) was 5%. Because the only possible source of isoflurane and isoprene in this setting was patients' blood, selective enrichment of alveolar gas was demonstrated. By using the new sampling technique, sensitivity of breath analysis was nearly doubled.
    Type of Medium: Online Resource
    ISSN: 8750-7587 , 1522-1601
    URL: Article
    DOI: 10.1152/jappl.2001.90.2.486
    RVK:
    WA 15000
    RVK:
    XA 52094
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2001
    detail.hit.zdb_id: 1404365-8
    SSG: 12
    SSG: 31
    Location Call Number Limitation Availability
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  • 4
    Online Resource
    Online Resource
    Discrimination of curvature from motion during smooth pursuit eye movements and fixation
    American Physiological Society ; 2017
    In:  Journal of Neurophysiology Vol. 118, No. 3 ( 2017-09-01), p. 1762-1774
    Details
    In: Journal of Neurophysiology, American Physiological Society, Vol. 118, No. 3 ( 2017-09-01), p. 1762-1774
    Abstract: Smooth pursuit and motion perception have mainly been investigated with stimuli moving along linear trajectories. Here we studied the quality of pursuit movements to curved motion trajectories in human observers and examined whether the pursuit responses would be sensitive enough to discriminate various degrees of curvature. In a two-interval forced-choice task subjects pursued a Gaussian blob moving along a curved trajectory and then indicated in which interval the curve was flatter. We also measured discrimination thresholds for the same curvatures during fixation. Motion curvature had some specific effects on smooth pursuit properties: trajectories with larger amounts of curvature elicited lower open-loop acceleration, lower pursuit gain, and larger catch-up saccades compared with less curved trajectories. Initially, target motion curvatures were underestimated; however, ∼300 ms after pursuit onset pursuit responses closely matched the actual curved trajectory. We calculated perceptual thresholds for curvature discrimination, which were on the order of 1.5 degrees of visual angle (°) for a 7.9° curvature standard. Oculometric sensitivity to curvature discrimination based on the whole pursuit trajectory was quite similar to perceptual performance. Oculometric thresholds based on smaller time windows were higher. Thus smooth pursuit can quite accurately follow moving targets with curved trajectories, but temporal integration over longer periods is necessary to reach perceptual thresholds for curvature discrimination. NEW & NOTEWORTHY Even though motion trajectories in the real world are frequently curved, most studies of smooth pursuit and motion perception have investigated linear motion. We show that pursuit initially underestimates the curvature of target motion and is able to reproduce the target curvature ∼300 ms after pursuit onset. Temporal integration of target motion over longer periods is necessary for pursuit to reach the level of precision found in perceptual discrimination of curvature.
    Type of Medium: Online Resource
    ISSN: 0022-3077 , 1522-1598
    URL: Article
    DOI: 10.1152/jn.00324.2017
    RVK:
    XA 10000 ; XA 552555
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2017
    detail.hit.zdb_id: 80161-6
    detail.hit.zdb_id: 1467889-5
    Location Call Number Limitation Availability
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  • 5
    Online Resource
    Online Resource
    Induction of angiotensin-converting enzyme after miR-143/145 deletion is critical for impaired smooth muscle contractility
    American Physiological Society ; 2014
    In:  American Journal of Physiology-Cell Physiology Vol. 307, No. 12 ( 2014-12-15), p. C1093-C1101
    Details
    In: American Journal of Physiology-Cell Physiology, American Physiological Society, Vol. 307, No. 12 ( 2014-12-15), p. C1093-C1101
    Abstract: MicroRNAs have emerged as regulators of smooth muscle cell phenotype with a role in smooth muscle-related disease. Studies have shown that miR-143 and miR-145 are the most highly expressed microRNAs in smooth muscle cells, controlling differentiation and function. The effect of miR-143/145 knockout has been established in the vasculature but not in smooth muscle from other organs. Using knockout mice we found that maximal contraction induced by either depolarization or phosphatase inhibition was reduced in vascular and airway smooth muscle but maintained in the urinary bladder. Furthermore, a reduction of media thickness and reduced expression of differentiation markers was seen in the aorta but not in the bladder. Supporting the view that phenotype switching depends on a tissue-specific target of miR-143/145, we found induction of angiotensin-converting enzyme in the aorta but not in the bladder where angiotensin-converting enzyme was expressed at a low level. Chronic treatment with angiotensin type-1 receptor antagonist restored contractility in miR-143/145-deficient aorta while leaving bladder contractility unaffected. This shows that tissue-specific targets are critical for the effects of miR-143/145 on smooth muscle differentiation and that angiotensin converting enzyme is one such target.
    Type of Medium: Online Resource
    ISSN: 0363-6143 , 1522-1563
    URL: Article
    DOI: 10.1152/ajpcell.00250.2014
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2014
    detail.hit.zdb_id: 1477334-X
    SSG: 12
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  • 6
    Online Resource
    Online Resource
    Keep your eyes on the ball: smooth pursuit eye movements enhance prediction of visual motion
    American Physiological Society ; 2011
    In:  Journal of Neurophysiology Vol. 105, No. 4 ( 2011-04), p. 1756-1767
    Details
    In: Journal of Neurophysiology, American Physiological Society, Vol. 105, No. 4 ( 2011-04), p. 1756-1767
    Abstract: Success of motor behavior often depends on the ability to predict the path of moving objects. Here we asked whether tracking a visual object with smooth pursuit eye movements helps to predict its motion direction. We developed a paradigm, “eye soccer,” in which observers had to either track or fixate a visual target (ball) and judge whether it would have hit or missed a stationary vertical line segment (goal). Ball and goal were presented briefly for 100–500 ms and disappeared from the screen together before the perceptual judgment was prompted. In pursuit conditions, the ball moved towards the goal; in fixation conditions, the goal moved towards the stationary ball, resulting in similar retinal stimulation during pursuit and fixation. We also tested the condition in which the goal was fixated and the ball moved. Motion direction prediction was significantly better in pursuit than in fixation trials, regardless of whether ball or goal served as fixation target. In both fixation and pursuit trials, prediction performance was better when eye movements were accurate. Performance also increased with shorter ball-goal distance and longer presentation duration. A longer trajectory did not affect performance. During pursuit, an efference copy signal might provide additional motion information, leading to the advantage in motion prediction.
    Type of Medium: Online Resource
    ISSN: 0022-3077 , 1522-1598
    URL: Article
    DOI: 10.1152/jn.00344.2010
    RVK:
    XA 10000 ; XA 552555
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2011
    detail.hit.zdb_id: 80161-6
    detail.hit.zdb_id: 1467889-5
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