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  • American Physiological Society  (7)
  • Englisch  (7)
Materialart
Verlag/Herausgeber
  • American Physiological Society  (7)
Sprache
  • Englisch  (7)
Erscheinungszeitraum
Fachgebiete(RVK)
  • 1
    Online-Ressource
    Online-Ressource
    American Physiological Society ; 1993
    In:  Journal of Applied Physiology Vol. 75, No. 2 ( 1993-08-01), p. 704-711
    In: Journal of Applied Physiology, American Physiological Society, Vol. 75, No. 2 ( 1993-08-01), p. 704-711
    Kurzfassung: The combination of high inflation and low vascular pressures in zone 1 lungs is assumed to collapse alveolar vessels, making them inaccessible to vascular liquid. To test this assumption, we perfused isolated rat lungs in zone 1 (n = 5) with fluorescent albumin solution (inflation pressure = 25 cmH2O, pulmonary arterial pressure = 10 cmH2O, left atrial pressure = 0 cmH2O; flow = 0.11 +/- 0.06 ml.100 g body wt-1 x min-1) and rapidly froze them. Histologically, 33 +/- 19% (SD) of alveolar septa fluoresced, demonstrating that the perfusate had not been excluded. However, we could not resolve whether the fluorescence originated in the septal microvascular lumen or in the adjacent perimicrovascular interstitial space. To address this issue, we perfused an additional lung with horseradish peroxidase (HRP) and examined it by transmission electron microscopy. HRP filled interstitial spaces around septal vessels and extraseptal alveolar corner vessels, but because the septal vascular lumina were too compressed, we were unable to determine whether they also contained HRP. Therefore we perfused two additional lungs with particles of colloidal gold (0.05 microns diam). Using transmission electron microscopy, we found gold particles in 15–25% of septal vascular lumina, demonstrating that septal vessels were at least partially accessible in zone 1. Our interpretations is that filtration in zone 1 may occur from septal vessels and extraseptal alveolar vessels. Furthermore, results of the HRP study suggest that the perimicrovascular interstitial space is less compressible than the septal vascular lumen.
    Materialart: Online-Ressource
    ISSN: 8750-7587 , 1522-1601
    RVK:
    RVK:
    Sprache: Englisch
    Verlag: American Physiological Society
    Publikationsdatum: 1993
    ZDB Id: 1404365-8
    SSG: 12
    SSG: 31
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 2
    Online-Ressource
    Online-Ressource
    American Physiological Society ; 1959
    In:  American Journal of Physiology-Legacy Content Vol. 197, No. 1 ( 1959-07-01), p. 99-101
    In: American Journal of Physiology-Legacy Content, American Physiological Society, Vol. 197, No. 1 ( 1959-07-01), p. 99-101
    Kurzfassung: Tracer doses of Mg 28 were used to study the metabolism of parenterally administered magnesium. Plasma clearance was rapid, and accumulation of radioactivity in bone started within 2 hours. Of the tissues studied, skin and muscle showed the lowest concentrations of Mg 28 . In most tissues the ratio of tissue to serum radioactivity became fairly constant after 18 hours. The values for the exchangeable body pool of magnesium, calculated from the specific activities of urine specimens obtained between 18 and 24 hours, approximated the carcass content of magnesium. During starvation the renal excretion of endogenous magnesium amounted to 61.7 mEq/kg of weight loss.
    Materialart: Online-Ressource
    ISSN: 0002-9513
    RVK:
    RVK:
    Sprache: Englisch
    Verlag: American Physiological Society
    Publikationsdatum: 1959
    ZDB Id: 1477334-X
    ZDB Id: 2065807-2
    ZDB Id: 1477287-5
    ZDB Id: 1477308-9
    ZDB Id: 1477297-8
    ZDB Id: 1477331-4
    ZDB Id: 1477300-4
    ZDB Id: 1477329-6
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 3
    Online-Ressource
    Online-Ressource
    American Physiological Society ; 2004
    In:  Journal of Applied Physiology Vol. 96, No. 1 ( 2004-01), p. 245-252
    In: Journal of Applied Physiology, American Physiological Society, Vol. 96, No. 1 ( 2004-01), p. 245-252
    Kurzfassung: Effects of vasoconstriction on the distribution of perfusion among alveoli are not well understood. To address this, we used a new method we developed to determine how microvascular perfusion distribution was affected by a potent vasoconstrictor, the thromboxane receptor analog U-46619. Our method was to infuse 4-μm-diameter fluorescent latex microspheres into the circulation of isolated rat lungs vasoconstricted with U-46619. We used a confocal microscope to image trapping patterns of the particles in dried sections of the lungs and then used dispersion index analysis to quantify the particle patterns in the images, which encompassed ∼2,000 alveoli. Dispersion indexes revealed significantly more particle clustering (inhomogeneous distribution) in vasoconstricted lungs than in normal flow controls or in controls in which flow was reduced by either lowering pulmonary arterial pressure or raising left atrial pressure. These results suggest that vasoconstriction occurred in the microvessels themselves, which are much smaller vessels than those previously thought to be capable of vasoconstriction.
    Materialart: Online-Ressource
    ISSN: 8750-7587 , 1522-1601
    RVK:
    RVK:
    Sprache: Englisch
    Verlag: American Physiological Society
    Publikationsdatum: 2004
    ZDB Id: 1404365-8
    SSG: 12
    SSG: 31
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 4
    Online-Ressource
    Online-Ressource
    American Physiological Society ; 2000
    In:  Journal of Applied Physiology Vol. 89, No. 3 ( 2000-09-01), p. 1198-1204
    In: Journal of Applied Physiology, American Physiological Society, Vol. 89, No. 3 ( 2000-09-01), p. 1198-1204
    Kurzfassung: High lung inflation pressures compress alveolar septal capillaries, impede red cell transit, and interfere with oxygenation. However, recently introduced acellular hemoglobin solutions may enter compressed lung capillaries more easily than red blood cells. To test this hypothesis, we perfused isolated rat lungs with fluorescently labeled diaspirin cross-linked hemoglobin (DCLHb; 10%) and/ or autologous red cells (hematocrit, 20). Septal capillaries were compressed by setting lung inflation pressure above vascular pressures (zone 1). Examination by confocal microscopy showed that DCLHb was distributed throughout alveolar septa. Furthermore, this distribution was not affected by adding red blood cells to the perfusate. We estimated the maximum acellular hemoglobin mass within septa to be equivalent to that of 15 red blood cells. By comparison, we found an average of 2.7 ± 4.6 red cells per septum in zone 1. These values increased to 30.4 ± 25.8 and 50.4 ± 22.1 cells per septum in zones 2 and 3, respectively. We conclude that perfusion in zone 1 with a 10% acellular hemoglobin solution may increase the hemoglobin concentration per septum up to fivefold compared with red cell perfusion.
    Materialart: Online-Ressource
    ISSN: 8750-7587 , 1522-1601
    RVK:
    RVK:
    Sprache: Englisch
    Verlag: American Physiological Society
    Publikationsdatum: 2000
    ZDB Id: 1404365-8
    SSG: 12
    SSG: 31
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 5
    Online-Ressource
    Online-Ressource
    American Physiological Society ; 2001
    In:  Journal of Applied Physiology Vol. 91, No. 4 ( 2001-10-01), p. 1730-1740
    In: Journal of Applied Physiology, American Physiological Society, Vol. 91, No. 4 ( 2001-10-01), p. 1730-1740
    Kurzfassung: To evaluate the transport properties of the alveolar epithelium, we instilled hetastarch (Het; 6%, 10 ml, 1 − 1 × 10 4 kDa) into the trachea of isolated rat lungs and then measured the molecular distribution of Het that entered the lung perfusate from the air space over 6 h. Het transport was driven by either diffusion or an oncotic gradient. Perfusate Het had a unique, bimodal molecular weight distribution, consisting of a narrow low-molecular-weight peak at 10–15 kDa (range, 5–46 kDa) and a broad high-molecular-weight band (range 46–2,000 kDa; highest at 288 kDa). We modeled the low-molecular-weight transport as (passive) restricted diffusion or osmotic flow through a small-pore system and the high-molecular-weight transport as passive transport through a large-pore system. The equivalent small-pore radius was 5.0 nm, with a distribution of 150 pores per alveolus. The equivalent large-pore radius was 17.0 nm, with a distribution of one pore per seven alveoli. The small-pore fluid conductivity (2 × 10 −5 ml · h −1 · cm −2 · mmHg −1 ) was 10-fold larger than that of the large-pore conductivity.
    Materialart: Online-Ressource
    ISSN: 8750-7587 , 1522-1601
    RVK:
    RVK:
    Sprache: Englisch
    Verlag: American Physiological Society
    Publikationsdatum: 2001
    ZDB Id: 1404365-8
    SSG: 12
    SSG: 31
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 6
    Online-Ressource
    Online-Ressource
    American Physiological Society ; 2003
    In:  Journal of Applied Physiology Vol. 94, No. 2 ( 2003-02-01), p. 420-428
    In: Journal of Applied Physiology, American Physiological Society, Vol. 94, No. 2 ( 2003-02-01), p. 420-428
    Kurzfassung: Pulmonary vascular perfusion has been shown to follow a fractal distribution down to a resolution of 0.5 cm 3 (5E11 μm 3 ). We wanted to know whether this distribution continued down to tissue volumes equivalent to that of an alveolus (2E5 μm 3 ). To investigate this, we used confocal microscopy to analyze the spatial distribution of 4-μm-diameter fluorescent latex particles trapped within rat lung microvessels. Particle distributions were analyzed in tissue volumes that ranged from 1.7E2 to 2.8E8 μm 3 . The analysis resulted in fractal plots that consisted of two slopes. The left slope, encompassing tissue volumes less than 7E5 μm 3 , had a fractal dimension of 1.50 ± 0.03 (random distribution). The right slope, encompassing tissue volumes greater than 7E5 μm 3 , had a fractal dimension of 1.29 ± 0.04 (nonrandom distribution). The break point at 7E5 μm 3 corresponds closely to a tissue volume equivalent to that of one alveolus. We conclude that perfusion distribution is random at tissue volumes less than that of an alveolus and nonrandom at tissue volumes greater than that of an alveolus.
    Materialart: Online-Ressource
    ISSN: 8750-7587 , 1522-1601
    RVK:
    RVK:
    Sprache: Englisch
    Verlag: American Physiological Society
    Publikationsdatum: 2003
    ZDB Id: 1404365-8
    SSG: 12
    SSG: 31
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 7
    Online-Ressource
    Online-Ressource
    American Physiological Society ; 1993
    In:  American Journal of Physiology-Heart and Circulatory Physiology Vol. 265, No. 5 ( 1993-11-01), p. H1536-H1543
    In: American Journal of Physiology-Heart and Circulatory Physiology, American Physiological Society, Vol. 265, No. 5 ( 1993-11-01), p. H1536-H1543
    Kurzfassung: Effects of infusing pentafraction (Pen), a synthetic hydroxyethyl starch plasma volume expander, on lung and soft tissue lymph flux were compared in nonanesthetized sheep that were protein depleted by batch plasmapheresis. Pen (5%) was infused to raise pulmonary arterial wedge pressure by 5 mmHg for 2 h (1.8 +/- 0.3 l). Pen raised plasma osmotic pressure from plasmapheresis baseline (10.7 +/- 2.2 mmHg; preplasmapheresis baseline, 19.6 +/- 0.6 mmHg) to 16.6 +/- 2.4 mmHg. After Pen, lung lymph flows peaked at 3.9 +/- 2.0 times a preplasmapheresis baseline value of 1.0 (plasmapheresis baseline, 2.7 +/- 0.7), but soft tissue lymph flows rose insignificantly. Plasma Pen concentrations were 2.3 +/- 1.0% postinfusion and 1.6 +/- 0.3% at 12 h. Pen mean molecular masses at these times, measured by high-performance liquid chromatography, were 160 +/- 44 and 129 +/- 23 kDa, respectively. In lung lymph, Pen concentrations were 0.8 +/- 0.6% postinfusion and 0.7 +/- 0.2% at 12 h, with mean molecular masses of 125 +/- 44 and 112 +/- 18 kDa, respectively. In soft tissue lymph Pen was nearly undetectable postinfusion, but at 12 h concentrations averaged 0.3 +/- 0.2% with a mean molecular mass of 80 +/- 10 kDa. The osmotic effectiveness of Pen may be related to its molecular mass, which was large enough to restrict filtration so that the plasma-to-lung lymph osmotic pressure gradient widened. Pen remained effective in the circulation for at least 24 h.
    Materialart: Online-Ressource
    ISSN: 0363-6135 , 1522-1539
    RVK:
    Sprache: Englisch
    Verlag: American Physiological Society
    Publikationsdatum: 1993
    ZDB Id: 1477308-9
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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