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  • Leiter, J. C.  (9)
  • 1990-1994  (9)
  • 1
    Online Resource
    Online Resource
    Ventilatory and hematopoietic responses to chronic hypoxia in two rat strains
    American Physiological Society ; 1992
    In:  Journal of Applied Physiology Vol. 72, No. 6 ( 1992-06-01), p. 2354-2363
    Details
    In: Journal of Applied Physiology, American Physiological Society, Vol. 72, No. 6 ( 1992-06-01), p. 2354-2363
    Abstract: Hilltop (H) and Madison (M) strains of Sprague-Dawley rats exhibit strikingly different susceptibilities to the effects of chronic altitude exposure. The H rats develop greater polycythemia, hypoxemia, and pulmonary hypertension. We studied ventilation, pulmonary gas exchange, tissue oxygenation, and hematologic adaptations in the two rat strains during a 50-day exposure to a simulated altitude (HA) of 5,500 m (18,000 ft). There were no strain differences among the variables we studied under sea level (SL) conditions. Within the first 14 days of hypoxic exposure, the only significant strain differences were that erythropoietin (EPO) rose much higher and erythroid activity was greater in the H rats, even though arterial Po2 and PCo2 (Pao2 and PaCo2, respectively), renal venous PO2 (Prvo2), and ventilation (VE) were equivalent in the two strains during this time. By day 14 at HA, the H rats had significantly higher erythroid activity, hematocrit (Hct), and EPO levels, significantly lower PaO2 and PrvO2, but equivalent VE and PaCO2. These changes persisted for the remainder of the exposure, except that the Hct continued to rise and the increase was greater in H rats. Despite the greater O2-carrying capacity of H rats in the later stages of hypoxic exposure, PaO2 and PrvO2 were significantly lower in H rats. There were no strain differences at either SL or HA in ventilatory responses to hypercapnia or hypoxia, in blood O2 affinity or 2,3-diphosphoglycerate, in extrarenal production of EPO, or in EPO clearance. We conclude that early in the hypoxic exposure the H rats produce more EPO at apparently equivalent levels of hypoxia, and this is the first step in the pathogenesis of the maladaptation to HA manifest by H rats. We find no consistent evidence that differences in VE contribute to the variable susceptibility to hypoxia in the two rat strains.
    Type of Medium: Online Resource
    ISSN: 8750-7587 , 1522-1601
    URL: Article
    DOI: 10.1152/jappl.1992.72.6.2354
    RVK:
    WA 15000
    RVK:
    XA 52094
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1992
    detail.hit.zdb_id: 1404365-8
    SSG: 12
    SSG: 31
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  • 2
    Online Resource
    Online Resource
    Control of segmental upper airway resistance in patients with obstructive sleep apnea
    American Physiological Society ; 1993
    In:  Journal of Applied Physiology Vol. 74, No. 6 ( 1993-06-01), p. 2694-2703
    Details
    In: Journal of Applied Physiology, American Physiological Society, Vol. 74, No. 6 ( 1993-06-01), p. 2694-2703
    Abstract: We sought to determine if the upper airway response to an added inspiratory resistive load (IRL) during wakefulness could be used to predict the site of upper airway collapse in patients with obstructive sleep apnea (OSA). In 10 awake patients with OSA, we investigated the relationship between resistance in three segments of the upper airway (nasal, nasopharyngeal, and oropharyngeal) and three muscles known to influence these segments (alae nasi, tensor veli palatini, and genioglossus) while the patient breathed with or without a small IRL (2 cmH2O.l–1.s). During IRL, patients with OSA exhibited increased nasopharyngeal resistance and no significant increase in either the genioglossus or tensor veli palatini activities. Neither nasal resistance nor alae nasi EMG activity was affected by IRL. We contrasted this to the response of five normal subjects, in whom we found no change in the resistance of either segment of the airway and no change in the genioglossus EMG but a significant activation of the tensor palatini. In six patients with OSA, we used the waking data to predict the site of upper airway collapse during sleep and we had limited success. The most successful index (correct in 4 of 6 patients) incorporated the greatest relative change in segmental resistance during IRL at the lowest electromyographic activity. We conclude, in patients with OSA, IRL narrows the more collapsible segment of the upper airway, in part due to inadequate activation of upper airway muscles. However, it is difficult to predict the site of upper airway collapse based on the waking measurements where upper airway muscle activity masks the passive airway characteristics.
    Type of Medium: Online Resource
    ISSN: 8750-7587 , 1522-1601
    URL: Article
    DOI: 10.1152/jappl.1993.74.6.2694
    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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  • 3
    Online Resource
    Online Resource
    Role of sex hormones in development of chronic mountain sickness in rats
    American Physiological Society ; 1994
    In:  Journal of Applied Physiology Vol. 77, No. 1 ( 1994-07-01), p. 427-433
    Details
    In: Journal of Applied Physiology, American Physiological Society, Vol. 77, No. 1 ( 1994-07-01), p. 427-433
    Abstract: After chronic exposure to hypoxia, Hilltop Sprague-Dawley rats developed excessive polycythemia and severe pulmonary hypertension and right ventricular (RV) hypertrophy, signs consistent with human chronic mountain sickness; however, there were gender differences in the magnitude of the polycythemia and susceptibility to the fatal consequence of chronic mountain sickness. Orchiectomy and ovariectomy were performed to evaluate the role of sex hormones in the gender differences in these hypoxic responses. After 40 days of exposure to simulated high altitude (5,500 m; barometric pressure of 370 Torr and inspired Po2 of 73 Torr), both sham-gonadectomized male and female rats developed polycythemia and had increased RV peak systolic pressure and RV hypertrophy. The hematocrit was slightly but significantly higher in males than in females. Orchiectomy did not affect these hypoxic responses, although total ventricular weight was less in the castrated high-altitude rats. At high altitude, the mortality rates were 67% in the sham-operated male rats and 50% in the castrated animals. In contrast, ovariectomy aggravated the high-altitude-associated polycythemia and increased RV peak systolic pressure and RV weight compared with the sham-operated high-altitude female rats. Both sham-operated control and ovariectomized females suffered negligible mortality at high altitude. The present study demonstrated that 1) the male sex hormones play no role in the development of the excessive polycythemia, pulmonary hypertension, and RV hypertrophy during chronic hypoxic exposure or in the associated high mortality and 2) the female sex hormones suppressed both the polycythemic and cardiopulmonary responses in vivo during chronic hypoxic exposure.
    Type of Medium: Online Resource
    ISSN: 8750-7587 , 1522-1601
    URL: Article
    DOI: 10.1152/jappl.1994.77.1.427
    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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  • 4
    Online Resource
    Online Resource
    ALKALINE SUCRALFATE ASPIRATIONS : SUBACUTE AND CHRONIC HISTOLOGIC EFFECTS IN RATS
    Ovid Technologies (Wolters Kluwer Health) ; 1994
    In:  Anesthesiology Vol. 81, No. SUPPLEMENT ( 1994-09), p. A315-
    Details
    In: Anesthesiology, Ovid Technologies (Wolters Kluwer Health), Vol. 81, No. SUPPLEMENT ( 1994-09), p. A315-
    Type of Medium: Online Resource
    ISSN: 0003-3022
    URL: Article
    DOI: 10.1097/00000542-199409001-00314
    RVK:
    XA 22600
    Language: English
    Publisher: Ovid Technologies (Wolters Kluwer Health)
    Publication Date: 1994
    detail.hit.zdb_id: 2016092-6
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  • 5
    Online Resource
    Online Resource
    Response of genioglossus EMG activity to passive tilt in men
    American Physiological Society ; 1993
    In:  Journal of Applied Physiology Vol. 74, No. 1 ( 1993-01-01), p. 73-81
    Details
    In: Journal of Applied Physiology, American Physiological Society, Vol. 74, No. 1 ( 1993-01-01), p. 73-81
    Abstract: Increased blood pressure (BP) leads to inhibition of respiratory activity of hypoglossal nerve in anesthetized cats, implying that arterial baroreceptor activity may inhibit upper airway motor outputs. We examined the effect of passive tilt on upper airway muscle activity in men under the assumption that changes in degree of tilt would change local pressure at the carotid baroreceptors. We also examined the possibility that inhibition of upper airway muscle activity occurred secondary to a decrease in level of arousal. In seven normal awake adult males, we measured electromyogram activity of the genioglossus (EMGge), electroencephalogram (EEG), electrocardiogram, ventilation, end-tidal fractional concentration of CO2, and BP while the subject was on a tilt table wearing inflatable antishock pants. Three tilt table positions were used: 60 degrees head-up (60 degrees increases), supine (S), and 30 degrees head-down (30 degrees decreases), with pants either deflated (P-) or inflated (P+) to 40 mmHg. During P-, moving the subject from 60 degrees increases to S to 30 degrees decreases positions resulted in steady-state heart rates of 94.8 +/- 1.7, 66.9 +/- 0.7, and 68.9 +/- 0.8 beats/min and EMGge activities of 54.4 +/- 4.4, 37.7 +/- 2.0, and 31.5 +/- 2.4% of maximum, respectively. During P+, changes in heart rate were similar but significantly reduced from P-, and positional changes in EMGge were eliminated. The level of arousal was unchanged. The transient response of EMGge to tilt was biphasic: when moving from upright to supine position, there was a rapid increase in activity during the tilt maneuver followed by a progressive decline.(ABSTRACT TRUNCATED AT 250 WORDS)
    Type of Medium: Online Resource
    ISSN: 8750-7587 , 1522-1601
    URL: Article
    DOI: 10.1152/jappl.1993.74.1.73
    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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  • 6
    Online Resource
    Online Resource
    Hypoglossal and phrenic nerve responses to carotid baroreceptor stimulation
    American Physiological Society ; 1993
    In:  Journal of Applied Physiology Vol. 75, No. 3 ( 1993-09-01), p. 1395-1403
    Details
    In: Journal of Applied Physiology, American Physiological Society, Vol. 75, No. 3 ( 1993-09-01), p. 1395-1403
    Abstract: We examined the relationship between hypoglossal and phrenic nerve activities and carotid sinus pressure. In 12 adult cats that were decerebrate, vagotomized, paralyzed, and mechanically ventilated, we isolated the left carotid sinus for perfusion and denervated the right carotid sinus. Mean arterial blood pressure was maintained at 90–100 mmHg using a low resistance-reservoir containing saline and connected to the abdominal aorta. Constant pressure was applied to the carotid sinus region. We found that increased carotid sinus pressure immediately inhibited inspiratory-synchronous (phasic) hypoglossal nerve activity and that there was a direct inverse relationship between phasic hypoglossal activity and carotid sinus pressure up to a carotid pressure of 285 mmHg. Increased carotid sinus pressure had no effect on tonic hypoglossal nerve activity and only slightly inhibited phrenic nerve activity. Cutting the left carotid sinus nerve abolished this response. We also applied pressure pulses to the carotid sinus at discrete times during the phrenic cycle. We found that baroreceptor inhibition of phasic hypoglossal nerve activity was gated during the phrenic cycle: maximum inhibition occurred when the pulse was applied in late expiration. We conclude that carotid baroreceptor stimulation preferentially inhibits inspiratory synchronous hypoglossal nerve activity and that this afferent information traveling in the carotid sinus nerve is gated by the respiratory control center.
    Type of Medium: Online Resource
    ISSN: 8750-7587 , 1522-1601
    URL: Article
    DOI: 10.1152/jappl.1993.75.3.1395
    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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  • 7
    Online Resource
    Online Resource
    Selective reflex activation of the genioglossus in humans
    American Physiological Society ; 1990
    In:  Journal of Applied Physiology Vol. 68, No. 6 ( 1990-06-01), p. 2581-2587
    Details
    In: Journal of Applied Physiology, American Physiological Society, Vol. 68, No. 6 ( 1990-06-01), p. 2581-2587
    Abstract: In anesthetized or decerebrate animals, negative pressure applied to the upper airway selectively activates the hypoglossal nerve compared with the phrenic nerve. Conversely, positive pressure reduces hypoglossal nerve activity out of proportion to any change in the phrenic neurogram. We have tested the hypothesis that analogous pressure changes applied to awake humans would selectively inhibit or activate genioglossal electromyographic (EMGge) activity relative to diaphragmatic electromyographic activity (EMGdi). We studied seven normal subjects in a head-out body plethysmograph. Pressure at the mouth was either atmospheric, +10 cmH2O, or -10 cmH2O, and lung volume was held constant by applying an identical pressure to the body surface. Thus the transmural pressure distorting the respiratory system was applied only to the upper airway. Subjects breathed CO2-enriched (2-3%) room air to stimulate phasic respiratory EMGge activity. We found that -10 cmH2O pressure applied selectively to the upper airway resulted in a 49% enhancement of peak-integrated EMGge activity, but EMGdi activity remained at control levels. Positive pressure did not result in any changes in EMGge or EMGdi activity. Neither pressure resulted in significant changes in the magnitude or pattern of ventilation. We conclude that reflex mechanisms maintaining upper airway patency are demonstrable in awake humans and probably have an important role in moment-to-moment modulation of upper airway muscle activity in normal awake humans.
    Type of Medium: Online Resource
    ISSN: 8750-7587 , 1522-1601
    URL: Article
    DOI: 10.1152/jappl.1990.68.6.2581
    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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  • 8
    Online Resource
    Online Resource
    Analysis of pharyngeal resistance and genioglossal EMG activity using a model of orifice flow
    American Physiological Society ; 1992
    In:  Journal of Applied Physiology Vol. 73, No. 2 ( 1992-08-01), p. 576-583
    Details
    In: Journal of Applied Physiology, American Physiological Society, Vol. 73, No. 2 ( 1992-08-01), p. 576-583
    Abstract: A model of orifice flow has been used to analyze the relationships among pressure, flow, and genioglossal electromyographic activity in the human pharynx during inspiration. The orifice flow model permits one to assess the character of airflow (laminar or turbulent) and to estimate the cross-sectional area of the orifice from pressure and flow measurements. On the basis of other data (J. Appl. Physiol. 73: 584–590, 1992), this analysis suggests that pharyngeal airflow is turbulent. Furthermore the area of the pharynx appears to increase as flow increases, but the actual change in pharyngeal diameter necessary to fit the pressure-flow data is quite small (0.11–0.87 cm, depending on the assumptions in the model). The flow-related increase in orifice area can be attributed, in part, to the activation of the genioglossus muscle. However, other flow-related factors may also contribute to pharyngeal dilation as airflow increases. Different airway shapes (circular and elliptical) and orientations (major axis anteroposterior and lateral) were incorporated into the model calculations; these factors modify considerably the apparent efficiency of genioglossal electromyographic activity. Genioglossal muscle shortening increases pharyngeal area and reduces pharyngeal resistance more effectively when the pharynx is elliptical, with the long axis of the ellipse oriented laterally. Hence the genioglossus may operate at a significant mechanical disadvantage in those patients with obstructive sleep apnea with a small sagittally oriented pharyngeal lumen.
    Type of Medium: Online Resource
    ISSN: 8750-7587 , 1522-1601
    URL: Article
    DOI: 10.1152/jappl.1992.73.2.576
    RVK:
    WA 15000
    RVK:
    XA 52094
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1992
    detail.hit.zdb_id: 1404365-8
    SSG: 12
    SSG: 31
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  • 9
    Online Resource
    Online Resource
    Dependence of pharyngeal resistance on genioglossal EMG activity, nasal resistance, and airflow
    American Physiological Society ; 1992
    In:  Journal of Applied Physiology Vol. 73, No. 2 ( 1992-08-01), p. 584-590
    Details
    In: Journal of Applied Physiology, American Physiological Society, Vol. 73, No. 2 ( 1992-08-01), p. 584-590
    Abstract: We investigated the quantitative relationships among pharyngeal resistance (Rph), genioglossal electromyographic (EMGge) activity, nasal resistance (Rna), and airflow in 11 normal men aged 19–50 while they were awake. We made measurements with subjects seated with the head erect, seated with the head flexed forward approximately 40 degrees, and supine. Each subject wore a face mask connected to a pneumotachograph to measure airflow. After topical anesthesia of the nose, two catheters for measuring nasal and pharyngeal airway pressures were passed through one nostril: the nasal pressure catheter was positioned at the nasal choanae, and the pharyngeal pressure catheter was positioned just above the epiglottis. We measured EMGge activity with an intraoral surface electrode. The subjects breathed exclusively through the nose while inhaling room air or rebreathing CO2. We measured Rph, Rna, airflow, and EMGge activity at approximately 90-ms intervals throughout each inspiration. Rph was invariant as head position was changed. At any given head position, EMGge activity rose as airflow increased, and Rph remained constant. In contrast, Rna increased as airflow increased. Because Rph was constant, EMGge activity was not correlated with Rph, but EMGge was positively correlated with Rna and airflow. On the basis of the stability of Rph in the face of marked changes in collapsing forces, we conclude that the dynamic interplay of posture, head and jaw position, and upper airway muscle activity quite effectively maintains pharyngeal patency, and interactions among these factors are subtle and complex.
    Type of Medium: Online Resource
    ISSN: 8750-7587 , 1522-1601
    URL: Article
    DOI: 10.1152/jappl.1992.73.2.584
    RVK:
    WA 15000
    RVK:
    XA 52094
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1992
    detail.hit.zdb_id: 1404365-8
    SSG: 12
    SSG: 31
    Location Call Number Limitation Availability
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