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  • American Physiological Society  (13)
  • 1990-1994  (13)
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  • American Physiological Society  (13)
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  • 1990-1994  (13)
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Subjects(RVK)
  • 1
    Online Resource
    Online Resource
    Nature of pulmonary hypertension in canine oleic acid pulmonary edema
    American Physiological Society ; 1990
    In:  Journal of Applied Physiology Vol. 69, No. 1 ( 1990-07-01), p. 293-298
    Details
    In: Journal of Applied Physiology, American Physiological Society, Vol. 69, No. 1 ( 1990-07-01), p. 293-298
    Abstract: It has recently been suggested that pulmonary hypertension secondary to oleic acid lung injury mainly results from an increase in the critical closing pressure of the pulmonary vessels [Boiteau et al., Am. J. Physiol. 251 (Heart Circ. Physiol. 20): H1163-H1170, 1986]. To further test this hypothesis, we studied 1) the pulmonary arterial pressure- (Ppa) flow (Q) relationship with left atrial pressure (Pla) kept constant (n = 7) and 2) the Ppa-Pla relationship with Q kept constant (n = 9) in intact anesthetized an d ventilated dogs before and after lung injury induced by oleic acid (0.09 ml/kg iv). Q was manipulated by use of a femoral arteriovenous bypass and a balloon catheter inserted in the inferior vena cava. Pla was manipulated with a balloon catheter placed by thoracotomy in the left atrium. Ppa-Q plots were rectilinear before as well as after oleic acid. Before oleic acid, the extrapolated pressure intercept of the Ppa-Q plots approximated Pla. Oleic acid administration resulted in a parallel shift of the Ppa-Q plots to higher pressure; i.e., the pressure intercept increased, whereas the slope was not modified. Increasing Pla at constant Q before oleic acid led to a proportional augmentation of Ppa. After oleic acid, however, changes in Pla over the same range affected Ppa only at the highest levels of Pla. These results suggest that oleic acid lung injury increases the critical closing pressure that exceeds Pla, becomes the effective outflow pressure of the pulmonary circulation, and is responsible for the pulmonary hypertension.
    Type of Medium: Online Resource
    ISSN: 8750-7587 , 1522-1601
    URL: Article
    DOI: 10.1152/jappl.1990.69.1.293
    RVK:
    WA 15000
    RVK:
    XA 52094
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1990
    detail.hit.zdb_id: 1404365-8
    SSG: 12
    SSG: 31
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  • 2
    Online Resource
    Online Resource
    Nature of the mammalian ciliary metachronal wave
    American Physiological Society ; 1993
    In:  Journal of Applied Physiology Vol. 75, No. 1 ( 1993-07-01), p. 458-467
    Details
    In: Journal of Applied Physiology, American Physiological Society, Vol. 75, No. 1 ( 1993-07-01), p. 458-467
    Abstract: The temporal and spatial coordination of ciliary beat (metachronicity) is fundamental to effective mucociliary transport. Metachronal wave period (MWP) and ciliary beat frequency (CBF) of fresh excised sheep and canine tracheal epithelial tissues were measured with the use of a newly developed alternating focal spot laser light scattering system. MWP was determined from cross correlation of the heterodyne signals from the alternating focal spots. CBF was determined by autocorrelation of the heterodyne signals from each of the spots. MWP and CBF were measured in four sheep tracheal epithelial tissues with the use of longitudinal interfocal spot distances of 6 and 18 microns. In three canine tracheal epithelial tissues MWP and CBF were measured both longitudinally and circumferentially with interfocal spot distances of 5, 15, 65, 87, and 96 microns. For the sheep tracheal epithelial tissues the mean CBF was 5.9 +/- 0.4 Hz (mean of means; range 3.6 +/- 0.5 to 9.9 +/- 1.5 Hz), whereas the mean MWPs for 6- and 18-microns interfocal spot distances were 0.50 +/- 0.1 and 0.47 +/- 0.1 s, respectively. For the canine tracheal epithelial tissues the mean CBF was 4.0 +/- 0.2 Hz (2.0 +/- 0.8 to 7.2 +/- 3.2 Hz), whereas the mean longitudinal MWP was 1.5 s and the mean circumferential MWP was 2.1 s. Geometric combination of the MWP components leads to a derived MWP of 2.6 s with a propagation direction of 54 degrees with respect to the longitudinal axis of the trachea. MWP was found to be episode modulated with 12- to 20-min intervals in the longitudinal direction, but modulation was not as apparent in the circumferential direction. These data suggest that MWP and CBF are regulated by separate intracellular, intercellular, and intraciliary mechanisms.
    Type of Medium: Online Resource
    ISSN: 8750-7587 , 1522-1601
    URL: Article
    DOI: 10.1152/jappl.1993.75.1.458
    RVK:
    WA 15000
    RVK:
    XA 52094
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1993
    detail.hit.zdb_id: 1404365-8
    SSG: 12
    SSG: 31
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    Online Resource
  • 3
    Online Resource
    Online Resource
    The polyphasic nature of the respiratory process at the mitochondrial level
    American Physiological Society ; 1990
    In:  American Journal of Physiology-Cell Physiology Vol. 258, No. 3 ( 1990-03-01), p. C504-C511
    Details
    In: American Journal of Physiology-Cell Physiology, American Physiological Society, Vol. 258, No. 3 ( 1990-03-01), p. C504-C511
    Abstract: The kinetics of oxygen consumption by rat liver mitochondria, respiring under a variety of metabolic conditions, have been studied. Respiration was initiated by injecting oxygen into anaerobic suspensions of mitochondria. It was found that, irrespective of the metabolic state of the mitochondria and the nature of the respiratory substrate, the rates of electron flow and oxygen consumption follow the pattern of a polyphasic reaction. The rates of oxygen uptake during the first phase are extremely fast and depend on oxygen concentration. The second phase represents a transition in which net oxidation of cytochrome-c oxidase stops and the rates of oxygen consumption suddenly decrease. The third phase is characterized by its changeability. Depending on initial conditions the rates may increase, decrease, or remain constant, although the reaction is not one of zero order. During the last phase, the rates decrease and the oxidase becomes increasingly reduced. It is postulated that the mitochondrial respiratory process is basically a cyclic event in which the redox state of the membrane and the rates of oxygen consumption oscillate with amplitudes and frequencies conditioned by the energy demand and energy-yielding capacity of the cell.
    Type of Medium: Online Resource
    ISSN: 0363-6143 , 1522-1563
    URL: Article
    DOI: 10.1152/ajpcell.1990.258.3.C504
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1990
    detail.hit.zdb_id: 1477334-X
    SSG: 12
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  • 4
    Online Resource
    Online Resource
    Fractal nature of short-term systolic BP and HR variability during lower body negative pressure
    American Physiological Society ; 1994
    In:  American Journal of Physiology-Regulatory, Integrative and Comparative Physiology Vol. 267, No. 1 ( 1994-07-01), p. R26-R33
    Details
    In: American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, American Physiological Society, Vol. 267, No. 1 ( 1994-07-01), p. R26-R33
    Abstract: We have shown previously that the heart rate variability (HRV) signal is fractal in nature with a high degree of complexity, as given by the calculated fractal dimension (DF). We have also reported that loss of complexity, as indicated by a reduction in DF of HRV, is associated with orthostatic hypotension and impending syncope. To extend this investigation of cardiovascular responses, we have investigated the signal characteristics of short-term systolic blood pressure variability (BPV) coincident with measurements of HRV during orthostatic stress. Eight healthy men completed a test protocol of 20 min supine rest followed sequentially by 10 min at each of -5, -15, -25, -40, and -50 mmHg lower body negative pressure (LBNP) and 10 min supine recovery. We found that resting BPV and HRV were fractal with approximately 70% of both variables in the fractal component of the variability signal. The slope of the 1/f beta relationship was 1.16 +/- 0.12 for HRV and 2.31 +/- 0.17 for BPV. With increasing levels of orthostatic stress, the 1/f beta slope of HRV increased significantly to 1.68 +/- 0.08 at -50 mmHg LBNP, whereas the 1/f beta slope was unchanged for BPV. Indicators of parasympathetic and sympathetic nervous system activity derived from heart rate variability suggested reduced and increased values, respectively, as the LBNP increased. These data indicate important differences in heart rate and blood pressure control under orthostatic stress.
    Type of Medium: Online Resource
    ISSN: 0363-6119 , 1522-1490
    URL: Article
    DOI: 10.1152/ajpregu.1994.267.1.R26
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1994
    detail.hit.zdb_id: 1477297-8
    SSG: 12
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  • 5
    Online Resource
    Online Resource
    Avian basal metabolic rates: their association with body composition and energy expenditure in nature
    American Physiological Society ; 1990
    In:  American Journal of Physiology-Regulatory, Integrative and Comparative Physiology Vol. 259, No. 2 ( 1990-08-01), p. R333-R340
    Details
    In: American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, American Physiological Society, Vol. 259, No. 2 ( 1990-08-01), p. R333-R340
    Abstract: Measurements of basal metabolic rate (BMR), body water, fat, and lean dry mass of different organs were obtained in 22 bird species, ranging from 10.8 to 1,253 g body mass. Residuals of BMR (after subtracting BMR allometrically predicted from body mass) were positively correlated with residuals of lean dry heart and kidney mass. Measurements of both BMR and the daily energy expenditure of parent birds (DEEpar) during the period of nestling care as assessed by labeled-water turnover were collected from the literature for 26 altricial bird species. The allometric relationships with body mass in this data set were: log BMR (W) = -1.385 + 0.684 log mass (g) [fraction of variance (r2) = 0.973] and log DEEpar (W) = -0.797 + 0.659 log mass (g) (r2 = 0.967). Residuals of log BMR and log DEEpar were positively correlated with each other. The parallel regressions and correlation of residuals lead to reduced variance in the ratio of BMR/DEEpar (mean 0.301; SD 0.086). We suggest that natural selection has led to an adjustment of the size of organs (such as heart and kidney) involved in sustaining energy metabolism at the DEE maximized during parental care and that size-independent variation in BMR reflects the relative size of this highly metabolically active machinery. These relationships of BMR lead to new interpretations of the decline in mass-specific BMR with increasing body size and decreasing latitude and of the difference in mass-specific BMR between birds and mammals.
    Type of Medium: Online Resource
    ISSN: 0363-6119 , 1522-1490
    URL: Article
    DOI: 10.1152/ajpregu.1990.259.2.R333
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1990
    detail.hit.zdb_id: 1477297-8
    SSG: 12
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  • 6
    Online Resource
    Online Resource
    Nature of [Ca2+]i transients during ventricular fibrillation and quinidine treatment in perfused rat hearts
    American Physiological Society ; 1994
    In:  American Journal of Physiology-Heart and Circulatory Physiology Vol. 266, No. 4 ( 1994-04-01), p. H1473-H1484
    Details
    In: American Journal of Physiology-Heart and Circulatory Physiology, American Physiological Society, Vol. 266, No. 4 ( 1994-04-01), p. H1473-H1484
    Abstract: We studied intracellular Ca2+ concentration ([Ca2+]i) and the electrocardiographic signals during pacing-induced ventricular fibrillation (VF) and quinidine treatment (0.4 mg/min) using surface fluorometry in indo 1-acetoxymethyl ester (AM)-loaded perfused rat hearts. [Ca2+] i was evaluated as the indo 1 fluorescence ratio (F400/F510) and expressed as a percentage of the control amplitude of F400/F510 transients. F400/F510 increased to approximately 250% during 2- (n = 14) or 20-min (n = 9) VF. Quinidine significantly decreased F400/F510 by 60% after 2-min VF; however, this effect was blunted after 20-min VF. After 2-min VF, F400/F510 and left ventricular pressure recovered almost to the control level. However, recovery of F400/F510 and ventricular function was poor after 20-min VF. The relationship between [Ca2+]i and the electrocardiogram (ECG) during VF was evaluated by power spectrum analysis of F400/F510 and ECG signals. During VF (25 +/- 3 Hz) with high irregularity, there were no clear [Ca2+] i transients (n = 110). When the cardiac rhythm (22 +/- 3 Hz) was regular, including ventricular tachycardia, there were recognizable [Ca2+]i signals with dominant frequencies that were the same (n = 2), one-half (n = 12), or one-third (n = 1) of the ECG frequencies. The highest frequency of the [Ca2+] i transients was 19 Hz. During quinidine treatment, the VF rate decreased significantly, and clear [Ca2+]i transients were noted in all records responding to every one or two ECG signals. The conclusions were the following: 1) [Ca2+] i responds to electrical signals rapidly (up to 19 Hz) during VF. This fast [Ca2+]i response is a probable cause of high [Ca2+] i during VF. 2) Quinidine decreased [Ca2+]i after 2-min VF possibly in part by slowing the VF and [Ca2+] i transients rates. 3) 20-min VF caused [Ca2+]i overload and poor functional recovery after d efibrillation.
    Type of Medium: Online Resource
    ISSN: 0363-6135 , 1522-1539
    URL: Article
    DOI: 10.1152/ajpheart.1994.266.4.H1473
    RVK:
    WA 15000
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1994
    detail.hit.zdb_id: 1477308-9
    SSG: 12
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  • 7
    Online Resource
    Online Resource
    On the fractal nature of heart rate variability in humans: effects of data length and beta-adrenergic blockade
    American Physiological Society ; 1994
    In:  American Journal of Physiology-Regulatory, Integrative and Comparative Physiology Vol. 266, No. 1 ( 1994-01-01), p. R40-R49
    Details
    In: American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, American Physiological Society, Vol. 266, No. 1 ( 1994-01-01), p. R40-R49
    Abstract: In the present study, we reinvestigated the question of whether human heart rate variability (HRV) is fractal in nature. Ten healthy volunteers participated in either of two studies conducted while beat-by-beat long-term HRV (8,500 heartbeats) was recorded for 2-3 h in the quiet, awake state in the supine position. In the first study, five subjects were tested four times each to evaluate the basic fractal nature of human HRV. The other five subjects were examined for the effects of oral propranolol (2 x 80 mg/day) on the fractal property of HRV in the second study. HRV data were analyzed by coarse-graining spectral analysis to break down their total power into harmonic and nonharmonic (fractal) components. The harmonic component was further divided into low (0.0-0.15 Hz; LF)- and high ( 〉 0.15 Hz; HF)-frequency components. From these spectral components, %Fractal, %LF, and %HF as functions of total power were calculated. The fractal component was used to calculate the spectral exponent, beta. The %Fractal of human resting HRV was 85.5 +/- 4.4% (mean +/- SD, n = 20). The beta for the fractal HRV was 1.08 +/- 0.18 (n = 20). With propranolol, these basic properties of fractal HRV dynamics remained unchanged despite an increase in the mean RR interval (placebo, 912 +/- 111 ms; propranolol, 1,134 +/- 133 ms, P 〈 0.05) and a change in the harmonic spectral shape evaluated by LF/HF (placebo, 2.76 +/- 1.57; propranolol, 1.82 +/- 0.81, P 〈 0.05). For short-term data, less power was extracted as fractal because of the absence of the very low frequency component, yet the beta and LF/HF were unchanged from long-term data. These findings indicate that 1) the observed inversely proportional frequency (1/f) spectrum in human resting HRV is due to underlying random fractal dynamics and 2) the sympathetic nervous system seemed to play a minor role in modulating the fractal HRV dynamics.
    Type of Medium: Online Resource
    ISSN: 0363-6119 , 1522-1490
    URL: Article
    DOI: 10.1152/ajpregu.1994.266.1.R40
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1994
    detail.hit.zdb_id: 1477297-8
    SSG: 12
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  • 8
    Online Resource
    Online Resource
    Effects of pulmonary blood flow on the fractal nature of flow heterogeneity in sheep lungs
    American Physiological Society ; 1994
    In:  Journal of Applied Physiology Vol. 77, No. 3 ( 1994-09-01), p. 1474-1479
    Details
    In: Journal of Applied Physiology, American Physiological Society, Vol. 77, No. 3 ( 1994-09-01), p. 1474-1479
    Abstract: The spatial heterogeneity of pulmonary blood flow can be described by the relative dispersion (RD) of weight-flow histograms (RD = SD/mean). Glenny and Robertson (J. Appl. Physiol. 69: 532–545, 1990) showed that RD of flow in the lung is fractal in nature, characterized by the fractal dimension (D) and RD for the smallest realizable volume element (RDref). We studied the effects of increasing total pulmonary blood flow on D and RDref. In eight in situ perfused sheep lung preparations, 15-microns radio-labeled microspheres were injected into the pulmonary artery at five different blood flows ranging, in random order, from 1.5 to 5.0 l/m. The lungs were in zone 2 at the lower flows and in zone 3 at the higher flows. The lungs were removed, dried, cut into 2 x 2 x 2-cm3 pieces, weighed, and then counted for microsphere radioactivity. Fractal plots of log(weight) vs. log(RD) were constructed by iteratively combining neighboring pieces and then calculating RD with the increasingly larger portion size. D, which is one minus the slope of the fit through this plot, was 1.14 +/- 0.09 and did not change as blood flow increased. However, RDref decreased significantly (P 〈 0.01) as total flow increased. We conclude that the fractal nature of pulmonary blood flow distribution is not altered by changes in overall flow.
    Type of Medium: Online Resource
    ISSN: 8750-7587 , 1522-1601
    URL: Article
    DOI: 10.1152/jappl.1994.77.3.1474
    RVK:
    WA 15000
    RVK:
    XA 52094
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1994
    detail.hit.zdb_id: 1404365-8
    SSG: 12
    SSG: 31
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  • 9
    Online Resource
    Online Resource
    On the nature of enduring modifications induced in cells and organisms
    American Physiological Society ; 1990
    In:  American Journal of Physiology-Lung Cellular and Molecular Physiology Vol. 258, No. 2 ( 1990-02-01), p. L19-L24
    Details
    In: American Journal of Physiology-Lung Cellular and Molecular Physiology, American Physiological Society, Vol. 258, No. 2 ( 1990-02-01), p. L19-L24
    Abstract: The clarity of Mendelian genetics and the elegance of the molecular mechanisms of replication and readout of DNA have tended to obscure a solid body of evidence demonstrating that nongenetic, enduring modifications can be induced in the behavior of cells, modifications that continue to be expressed for many divisions after withdrawal of the inducing stimulus. The most prosaic case is the differentiated state of metazoan cells, which persists throughout the lifetime of the organism. Much less widely known but well-characterized examples are also cited for bacteria, protozoa, and cultured cells of higher plants and animals. The spontaneous neoplastic transformation of cultured mouse NIH 3T3 cells is introduced as an enduring adaptive response to moderate growth constraints. Evidence in support of the thesis that physiological adaptation is the driving force for chemically induced carcinogenesis in the intact animal is also presented. The cases described here involve integrated responses of many if not all of the regulatory components of the cell, rather than singular molecular mechanisms. The continuous generation of phenotypic heterogeneity, a process observed readily in cell culture, provides the basis for a model that accounts for enduring modifications. This model, designated progressive state selection, makes no attempt at a detailed biochemical explanation of heterogeneity, but uses it as a fundamental postulate to represent the adaptive behavior of the cells.
    Type of Medium: Online Resource
    ISSN: 1040-0605 , 1522-1504
    URL: Article
    DOI: 10.1152/ajplung.1990.258.2.L19
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1990
    detail.hit.zdb_id: 1477300-4
    SSG: 12
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  • 10
    Online Resource
    Online Resource
    On the nature of the circadian clock in mammals
    American Physiological Society ; 1993
    In:  American Journal of Physiology-Regulatory, Integrative and Comparative Physiology Vol. 264, No. 5 ( 1993-05-01), p. R821-R832
    Details
    In: American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, American Physiological Society, Vol. 264, No. 5 ( 1993-05-01), p. R821-R832
    Abstract: The evidence for the essential role of the suprachiasmatic nucleus (SCN) for the generation and maintenance of circadian rhythms in mammals is briefly reviewed. The pharmacology of the phase-response curve is considered and a new circadian measure, the phase-dose-response surface (PDRS), is introduced. The role of neurotransmission, ion fluxes, and non-neuronal cellular elements in the generation and maintenance of circadian rhythmicity is considered. Cell culture of the SCN is proposed as a tool for the functional analysis of clock mechanism. The critical contribution of coupling and synchronization of clock elements is reviewed in the context of the explicit predictions generated by a strong coupling model of the circadian clock. Finally, the nature of the circadian output signal is analyzed from a phylogenetic viewpoint.
    Type of Medium: Online Resource
    ISSN: 0363-6119 , 1522-1490
    URL: Article
    DOI: 10.1152/ajpregu.1993.264.5.R821
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1993
    detail.hit.zdb_id: 1477297-8
    SSG: 12
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