Relationship between the gas composition of the middle ear and the venous blood at steady state

Luntz, Michał; Levi, Dafna; Sadé, Jacob; Herman, Michal

doi:10.1288/00005537-199505000-00012

Cited by 26 publications

(13 citation statements)

References 12 publications

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“…The present observation agrees with that of previous studies based mainly on pressure measurements, showing that changes in ME pressure are driven by the difference in N 2 partial pressure between the ME and blood (1,11,13,14,33,41,42).…”

Section: Phase IIsupporting

confidence: 93%

“…The rate of exchange of these gases between the ME and blood determines the net volume of transmucosal gas exchange. For N 2 , a difference in ME to blood partial pressure of up to ϳ50 Torr has been reported, whereas that of O 2 and CO 2 is nearly zero (16,26,33). Therefore, the net volume gas loss that we have observed in the steady state (30) should result mainly from transmucosal N 2 exchange.…”

mentioning

confidence: 63%

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Role of nitrogen in transmucosal gas exchange rate in the rat middle ear

Kania¹,

Herman²,

Huy³

et al. 2006

Journal of Applied Physiology

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. Role of nitrogen in transmucosal gas exchange rate in the rat middle ear. J Appl Physiol 101: [1281][1282][1283][1284][1285][1286][1287] 2006. First published July 13, 2006; doi:10.1152/japplphysiol.00113.2006.-This study investigates the role of nitrogen (N 2) in transmucosal gas exchange of the middle ear (ME). We used an experimental rat model to measure gas volume variations in the ME cavity at constant pressure. We disturbed the steady-state gas composition with either air or N 2 to measure resulting changes in volume at ambient pressure. Changes in gas volume over time could be characterized by three phases: a primary transient increase with time (phase I), followed by a linear decrease (phase II), and then a gradual decrease (phase III). The mean slope of phase II was Ϫ0.128 l/min (SD 0.023) in the air group (n ϭ 10) and Ϫ0.105 l/min (SD 0.032) in the N 2 group (n ϭ 10), but the difference was not significant (P ϭ 0.13), which suggests that the rate of gas loss can be attributed mainly to the same steady-state partial pressure gradient of N 2 reached in this phase. Furthermore, a mathematical model was developed analyzing the transmucosal N2 exchange in phase II. The model takes gas diffusion into account, predicting that, in the absence of change in mucosal blood flow rate, gas volume in the ME should show a linear decrease with time after steady-state conditions and gas composition are established. In accordance with the experimental results, the mathematical model also suggested that transmucosal gas absorption of the rat ME during steady-state conditions is governed mainly by diffusive N2 exchange between the ME gas and its mucosal blood circulation. rat model

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Section: Phase IIsupporting

confidence: 93%

mentioning

confidence: 63%

Role of nitrogen in transmucosal gas exchange rate in the rat middle ear

Kania¹,

Herman²,

Huy³

et al. 2006

Journal of Applied Physiology

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“…These niches vary in carbon metabolite and oxygen availability and also in ambient pH. For example, while the lung is a mostly aerobic environment (Worlitzsch et al, 2002) the middle ear is almost completely anaerobic (Luntz et al, 1995; Sade et al, 1995). It follows that H. influenzae , like other bacterial pathogens, should possess a repertoire of metabolic pathways that enables it to survive in the variety of the environments that it encounters in the human host.…”

Section: Introductionmentioning

confidence: 99%

Metabolic versatility in Haemophilus influenzae: a metabolomic and genomic analysis

et al. 2014

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Haemophilus influenzae is a host adapted human pathogen known to contribute to a variety of acute and chronic diseases of the upper and lower respiratory tract as well as the middle ear. At the sites of infection as well as during growth as a commensal the environmental conditions encountered by H. influenzae will vary significantly, especially in terms of oxygen availability, however, the mechanisms by which the bacteria can adapt their metabolism to cope with such changes have not been studied in detail. Using targeted metabolomics the spectrum of metabolites produced during growth of H. influenzae on glucose in RPMI-based medium was found to change from acetate as the main product during aerobic growth to formate as the major product during anaerobic growth. This change in end-product is likely caused by a switch in the major route of pyruvate degradation. Neither lactate nor succinate or fumarate were major products of H. influenzae growth under any condition studied. Gene expression studies and enzyme activity data revealed that despite an identical genetic makeup and very similar metabolite production profiles, H. influenzae strain Rd appeared to favor glucose degradation via the pentose phosphate pathway, while strain 2019, a clinical isolate, showed higher expression of enzymes involved in glycolysis. Components of the respiratory chain were most highly expressed during microaerophilic and anaerobic growth in both strains, but again clear differences existed in the expression of genes associated e.g., with NADH oxidation, nitrate and nitrite reduction in the two strains studied. Together our results indicate that H. influenzae uses a specialized type of metabolism that could be termed “respiration assisted fermentation” where the respiratory chain likely serves to alleviate redox imbalances caused by incomplete glucose oxidation, and at the same time provides a means of converting a variety of compounds including nitrite and nitrate that arise as part of the host defence mechanisms.

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“…The main histopathologic lesion in OME is chronically inflamed middle ear mucosa and this requires improvement as a priority. In the middle ear cavity, transmucosal gas exchange occurs passively due to the partial pressure gradient between the middle ear cavity and mucosal capillaries [2,3], and the change in the middle ear total pressure (METP) is caused by transmucosal gas exchange. Therefore, mucosal inflammation in the middle ear may alter transmucosal gas exchange and affect the METP.…”

Section: Introductionmentioning

confidence: 99%