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101.
102.
The concept of the accumulated O2 deficit (AOD) assumes that the O2 deficit increases monotonically with increasing work rate (WR), to plateau at the maximum AOD, and is based on linear extrapolation of the relationship between measured steady-state oxygen uptake (O2) and WR for moderate exercise. However, for high WRs, the measured O2 increases above that expected from such linear extrapolation, reflecting the superimposition of a "slow component" on the fundamental O2 mono-exponential kinetics. We were therefore interested in determining the effect of the O2 slow component on the computed AOD. Ten subjects [31 (12) years] performed square-wave cycle ergometry of moderate (40%, 60%, 80% and 90%
), heavy (40%), very heavy (80%) and severe (110% O2 peak) intensities for 10–15 min, where
is the estimated lactate threshold and is the WR difference between
and O2 peak. O2 was determined breath-by-breath. Projected "steady-state" O2 values were determined from sub-
tests. The measured O2 exceeded the projected value after ~3 min for both heavy and very heavy intensity exercise. This led to the AOD actually becoming negative. Thus, for heavy exercise, while the AOD was positive [0.63 (0.41) l] at 5 min, it was negative by 10 min [–0.61 (1.05) l], and more so by 15 min [–1.70 (1.64) l]. For the very heavy WRs, the AOD was [0.42 (0.67) l] by 5 min and reached –2.68 (2.09) l at exhaustion. For severe exercise, however, the AOD at exhaustion was positive in each case: +1.69 (0.39) l. We therefore conclude that the assumptions underlying the computation of the AOD are invalid for heavy and very heavy cycle ergometry (at least). Physiological inferences, such as the "anaerobic work capacity", are therefore prone to misinterpretation. 相似文献
103.
A. Dörge F. X. Beck G. Rechkemmer 《Pflügers Archiv : European journal of physiology》1998,436(2):280-288
The mammalian distal colon, which is composed of different cell types, actively transports Na, K and Cl in absorptive and
K and Cl in secretory directions. To further characterize the K absorption process and to identify the cells involved in K
absorption, unidirectional Rb fluxes and luminal Rb uptake into different epithelial cell types were determined in isolated
guinea-pig distal colon. Net Rb absorption (1.5–2.5 μmol·h–1·cm–2) was not influenced by inhibition of Na transport with amiloride or by incubating both sides of the epithelium with Na-free
solutions, but was almost completely abolished by luminal ouabain, ethoxzolamide or by incubating both sides of the epithelium
with Cl-free solutions. Luminal Rb uptake, blockable by luminal ouabain, preferentially occurred in columnar surface and neck
cells, to a lesser extent in surface goblet cells and to an insignificant degree in lower crypt cells. Employing a luminal
Rb-Ringer (5.4 mM Rb) the Rb concentration increased within 10 min in columnar surface and neck, surface goblet and lower
crypt cells to 70, 32 and about 10 mmol·kg–1 wet weight, respectively. The presence of 5.4 mM K in the luminal incubation solution reduced Rb uptake almost completely
indicating a much higher acceptance of the luminal H-K-ATPase for K than for Rb. The increase in Na and decrease in K concentrations
in surface and neck cells induced by luminal ouabain might indicate inhibition of the basolateral Na-K-ATPase or drastic enhancement
of cellular Na uptake by the Na-H exchanger. Bilateral Na-free incubation did not alter Rb uptake, but bilateral Cl-free incubation
drastically reduced it. Inhibition of net Rb absorption by ethoxzolamide and inhibition of both Rb absorption and Rb uptake
by bilateral Cl-free incubation support the notion that cellular CO2 hydration is a necessary prerequisite for K absorption and that HCO3 leaves the cell via a Cl-HCO3 exchanger. Since ouabain-inhibitable transepithelial Rb flux and luminal Rb uptake rate by surface and neck cells were about
the same, Rb(K) absorption seems to be accomplished mainly by columnar surface cells.
Received: 4 August 1997 / Received after revision: 12 November 1997 / Accepted: 4 December 1997 相似文献
104.
N. Freudenberg P. Rahner C. Darda U. N. Riede M. Schubert K. Frenzer-Welle A. Kiss G. Veres T. Nees R. Lamers C. Kortsik 《Virchows Archiv : an international journal of pathology》1996,428(3):187-194
We investigated the reaction of the cellular immune system of liver and blood in the C57BL/6 mouse to a metastasizing Lewis lung carcinoma. The cellular immune system of the liver consists of mature and immature macrophages, B-cells, T-cells including their subpopulations, and natural killer cells, and their percentage frequencies differ significantly from those in the corresponding mononuclear blood cell (MBC) compartment. This suggests that the hepatic immune cells represent a system with autonomous function showing a typical homing of its members. Imminent metastasis to the liver is signalled by impressive alterations in the percentage frequencies of nonparenchymal liver cells (NPLC). There are a dramatic loss of mature macrophages, an increase in immature macrophages, a reduction of T-helper cells leading to a low CD4/CD8 ratio, and an increase in natural killer cells. In the blood, the corresponding precursor cells show comparable changes with a delay of at least 2 days. Early metastasis is accompanied by a significant increase in mononuclear NPLC producing tumour necrosis factor . The alterations in percentage frequencies of the NPLC during tumour metastasis differ markedly from the changes in these cells in the liver during endotoxinaemia. 相似文献
105.
Differentiation of extracellular matrix in the cellular cartilage ("Zellknorpel") of the mouse pinna
Summary Differentiation of cellular cartilage was studied in the mouse pinna with particular reference to matrix material. Fixation of glycosaminoglycans was performed by the use of acridine orange and elastin was identified by staining thin sections with tannic acid and uranyl acetate.Condensation of mesenchymal cells (prechondroblasts) initiates the formation of a blastema of cartilaginous tissue at postnatal day 4. The synthesis of acidic glycosaminoglycans begins at postnatal day 8 when prechondroblasts transform to chondroblasts. Glycosaminoglycans can be detected within secretory vesicles of chondroblasts at postnatal day 8, in the extracellular space at postnatal day 13. Delicate collagen fibrils and elastic fiber microfibrils are seen between prechondroblasts and chondroblasts. Deposition of elastin begins at postnatal day 11. A network of elastic fibers and lamellae is formed, which replaces both collagen fibrils and elastic fiber microfibrils. In the interstice of mature cellular cartilage only elastin and proteoglycans are present (postnatal day 21).These findings indicate that cellular cartilage represents an independent kind of supporting tissue, which may serve as a progenitor of hyaline or elastic cartilage (transitional cellular cartilage) but does not differentiate from hyalin cartilage.With financial support from the Hochschuljubiläumsstiftung der Stadt Wien. Part of this work has been presented at the 3. Arbeitstagung der Anatomischen Gesellschaft, Würzburg, 6.-8. 10. 1982 相似文献
106.
107.
M. B. Bromberg G. Pamel B. S. Stephenson A. B. Young J. B. Penney 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1987,69(1):53-59
Summary High affinity glutamate uptake into corticofugal fiber terminals was measured in the ventrolateral thalamus and red nucleus at varying time intervals after lesions were made by kainic acid in the contralateral interpositus nucleus of the cerebellum in rats. Under similar conditions the density of cortical fiber terminals was estimated using the Fink-Heimer impregnation technique. 1. Glutamate uptake steadily increased in the ventrolateral thalamus up to 60 days after lesions in the contralateral cerebellum. 2. Similar changes were noted in the red nucleus. 3. The changes were dependent on the integrity of corticofugal fibers to the thalamus and red nucleus. 4. No changes in uptake of gammaaminobutyric acid were noted. 5. Saturation curves for glutamate uptake suggested a change in the maximal number of transport sites. 6. Fink-Heimer degeneration studies showed an increase in cortical terminals in the ipsilateral ventrolateral thalamus and in both rostral and caudal regions of the red nucleus following lesions in the contralateral interpositus nucleus. The data are consistent with an increase in the number of cortical fiber terminals in reaction to loss of cerebellar input to the ventrolateral thalamus and red nucleus. This study correlates anatomical and biochemical evidence for collateral sprouting in a model based on electrophysiologic data in the red nucleus and extends the model to include the thalamus. 相似文献
108.
Structural studies of murine I-E and human DR antigens. 总被引:8,自引:0,他引:8
The structures of murine I-E antigens from two strains of mice were compared to each other and to human DR antigens. Murine and human antigens were isolated by using allo- and xenoantiserum, respectively, and purified by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The murine I-E and human DR antigens consist of two polypeptide chains designated α and β. The Eα and DRα chains display a high degree of amino acid sequence homology as do the Eβ and DRβ chains, provided a gap is inserted at position 1 of the DRβ chain. Comparison of N-terminal sequences reveals several differences between the β chains of I-E antigens from the two strains of mice. In contrast no sequence differences between the two α chains are observed. In addition, comparison of tryptic peptides examined by isoelectrofocusing reveals several differences between the two Eβ chains, but not between the two Eα chains. Thus, the polymorphism of murine I-E antigens and by analogy human DR antigens, may result from structural differences in the smaller (β) chain. 相似文献
109.
Puente-Maestu L Sánz ML Sánz P Nuñez A González F Whipp BJ 《European journal of applied physiology》2001,85(5):434-441
To be clinically useful as indices reflective of altered physiological function consequent to interventions in patients with
chronic obstructive pulmonary disease (COPD), the time constant (τ) and steady-state amplitude of the kinetic responses for
oxygen uptake (
) carbon dioxide output (
) ventilation (
) and heart rate (HR) have to be appropriately differentiable and reproducible. We therefore assessed the reproducibility
of τ and steady state amplitude values in 41 patients with severe COPD [mean (SD)] [forced expiratory volume in 1 s=41 (7)%
predicted], aged 64 (5) years. Of the total, 6 of the patients (15%) did not produce breath-by-breath data of sufficient quality
to warrant kinetic analysis. The remaining 35 patients completed two moderate-intensity 10 min square-wave exercise tests
separated by 2 h, both before and after an endurance training programme. Tests were conducted on an electromagnetically-braked
cycle ergometer at an exercise intensity corresponding to 80% of the estimated lactate threshold (θLa) or 50% of peak oxygen uptake if θLa was insufficiently differentiable. Breath-by-breath measurements of
,
,
and HR were averaged into 10 s bins and the on-transient response kinetics were estimated using a mono-exponential model.
Analysing the pre-training and the post-training test 1 and test 2 comparisons together, the test 1 –test 2 differences were
not significantly different from 0 for either τ or A. The standard deviation of the test 1 –test 2 differences allowed us
to define the magnitude of change that would reach statistical significance. For τ, this averaged some 8, 10, 11 and 8 s,
for
,
,
and HR, respectively, for a one-tailed paired-comparisons test (i.e. appropriate for assessing hypothesised improvements resulting
from an intervention); for a two-tailed comparison, the differences were approximately 2 s greater. The corresponding one-tailed
values for A were 100 ml·min–1, 95 ml·min–1, 2.5 1·min–1 and 4 beats·min–1, respectively; the two-tailed values were 10%–15% greater. We therefore conclude that both τ and A for moderate-intensity
exercise can be reproducibly estimated in patients with COPD when the data set provides a sufficiently large amplitude of
response and sufficiently low sample variability to allow appropriate parameter estimation.
Electronic Publication 相似文献
110.
C. Strazielle R. Lalonde L. Riopel M.I. Botez T.A. Reader 《Journal of chemical neuroanatomy》1996,10(2):157-171
The neurological cerebellar mutant lurcher is characterized by a primary degeneration of Purkinje cells as well as a retrograde secondary partial degeneration of cerebellar granule cells and inferior olivary neurons. Since serotonin (5-HT) has been implicated in the modulation of excitatory amino acid systems of the cerebellum, the 5-HT innervation of the normal and lurcher mice was examined by quantifying uptake sites using [3H]citalopram autoradiography, and by biochemical assays of the indoles 5-HT, 5-hydroxy-
-tryptophan and 5-hydroxyindole-3-acetic acid using high-performance liquid chromatography. Comparable results were found between [3H]citalopram binding and 5-HT tissue concentrations in different brain regions. The highest [3H]citalopram labelling was observed in defined structures of the mesencephalic and upper pontine regions, in limbic structures, in hypothalamus and in discrete thalamic divisions, while the lowest labelling of uptake sites was documented in cerebellum and brainstem reticular formation. In lurcher mutants, the histology confirmed cell degeneration and the reduction in width, leading to 65%, 45% and 25% atrophies of total cerebellum, deep nuclei and inferior olivary nucleus, respectively. The [3H]citalopram labelling corrected for surface loss was 45% and 20% higher in cerebellar deep nuclei and red nucleus, respectively, but remained unchanged in the cerebellar cortex and inferior olivary nucleus. Moreover, higher labelling was found in nucleus raphe dorsalis, ventral tegmental area, inferior colliculus, locus coeruleus, pontine central grey and anterior thalamic nuclei, areas known to be part of cerebellar afferent and efferent systems. The present results indicate that in such pathological conditions as described for the lurcher mutant, the 5-HT system may modulate motor function not only at the level of the cerebellum, but also in other forebrain structures functionally related to the motor system. 相似文献