scholarly journals NOTA SULLA NON LINEARITÀ DEL SISTEMA RESPIRATORIO: COME L’EMOGLOBINA LEGA GASTON TISSANDIER A REINHOLD MESSNER

2020 ◽  
Author(s):  
Guido Ferretti
Keyword(s):  
Respiratory System ◽  
Equilibrium Curve ◽  
Supplementary Oxygen ◽  
Mount Everest ◽  
Oxygen Equilibrium ◽  
Non Linear ◽  
Linear Behaviour ◽  
History Of ◽  
Functional Consequences ◽  
Oxygen Equilibrium Curve

This article starts from an aeronautical tragedy to track briefly the history of the oxygen equilibrium curve and the creation of Hill’s model of it. After having argued that the characteristics of such a curve determine the non-linear behaviour of the respiratory system, I discussed some functional consequences of this behaviour, which explain how it happened that Reinhold Messner succeeded in the extraordinary enterprise of climbing Mount Everest without supplementary oxygen.

scholarly journals Oxygen equilibrium curve of normal human blood and its evaluation by Adair's equation.

1977 ◽  
Vol 252 (7) ◽  
pp. 2331-2337 ◽  
Author(s):  
R M Winslow ◽  
M L Swenberg ◽  
R L Berger ◽  
R I Shrager ◽  
M Luzzana ◽  
...  
Keyword(s):  
Human Blood ◽  
Equilibrium Curve ◽  
Oxygen Equilibrium ◽  
Normal Human ◽  
Oxygen Equilibrium Curve ◽  
Normal Human Blood

Modeling and Simulation of Physical Parameters of Human Respiratory System

2014 ◽  
Vol 658 ◽  
pp. 447-452
Author(s):  
Catarina Meireles ◽  
José Machado ◽  
Celina P. Leão
Keyword(s):  
Respiratory System ◽  
Respiratory Cycle ◽  
Physical Parameters ◽  
System Control ◽  
Common Control ◽  
Non Linear ◽  
Linear Behaviour ◽  
Physiological Profiles ◽  
Mathematical Equations

The respiratory system, due to its non-linear behaviour, is of difficult representation through fixed physical components and common control systems. Therefore, mathematical equations, that represents the respiratory cycle; mechanical components, giving dimension and movement to the simulator; and the electronic components, allowing data acquisition and system control are some factors that must be known and synchronized. The presented work describes the implementation of a mathematical model (in MatLab) that reproduces the non-linear behaviour of the respiratory system, allowing the characterization of different pathophysiological situations. In parallel a graphical interface was developed enabling the user track the change in air flow and volume handled during the respiratory cycle and build physiological profiles of different patients.

Effect of haemoglobin concentration on the oxygen affinity of intact lamprey erythrocytes

1995 ◽  
Vol 198 (11) ◽  
pp. 2393-2396 ◽  
Author(s):  
S Airaksinen ◽  
M Nikinmaa
Keyword(s):  
Blood Cell ◽  
Red Blood Cell ◽  
Haemoglobin Concentration ◽  
Oxygen Affinity ◽  
Equilibrium Curve ◽  
Volume Changes ◽  
Oxygen Equilibrium ◽  
The Mean ◽  
The Right ◽  
Oxygen Equilibrium Curve

We investigated whether the oxygen affinity of lamprey haemoglobin decreases with increasing oxygen concentration at the high (10­25 mmol l-1 monomeric) haemoglobin concentrations prevailing within the erythrocytes. The intracellular concentration of haemoglobin was experimentally adjusted by shrinking the cells osmotically: the osmolality of the equilibration medium was increased from approximately 250 mosmol kg-1 by 90 mosmol kg-1 to 340 mosmol kg-1 or by 180 mosmol kg-1 to 430 mosmol kg-1 by adding sucrose in the medium. This increased the mean cellular haemoglobin concentration from 16.9±0.23 mmol l-1 (monomeric haemoglobin) to 20.0±0.20 mmol l-1 (monomeric haemoglobin) and to 23.0±0.36 mmol l-1 (monomeric haemoglobin), respectively (means ± s.e.m., N=35­40; all the samples from 7­8 different pools of blood at each osmolality combined). The oxygen equilibrium curves at each osmolality were determined by Tucker's method. An increase in haemoglobin concentration shifted the oxygen equilibrium curve to the right as indicated by the P50 values, which were 4.26±0.07 kPa at the lowest, 4.64±0.13 kPa at the intermediate and 5.64±0.40 kPa (means ± s.e.m., N=7­8) at the highest haemoglobin concentrations. The decrease in haemoglobin oxygen-affinity was attributed to the volume changes, since the intracellular pH did not decrease with increasing mean cellular haemoglobin concentration. Thus, the variations in red blood cell volume commonly observed during hypoxia may play a role in the regulation of haemoglobin function.

scholarly journals A study of the properties of hybrids of oxyhaemoglobin and deoxyhaemoglobin with two porphyringlobin species

1974 ◽  
Vol 137 (2) ◽  
pp. 339-348 ◽  
Author(s):  
Amyra Treffry ◽  
Stanley Ainsworth
Keyword(s):  
Fast Moving ◽  
Dissociation Constants ◽  
Initial Increase ◽  
Equilibrium Curve ◽  
Thiol Groups ◽  
Oxygen Equilibrium ◽  
Partial Pressures ◽  
Thiol Reagent ◽  
Slow Moving ◽  
Oxygen Equilibrium Curve

The fluorescence of porphyringlobin is quenched on adding haemoglobin to its solutions. It is suggested that this result indicates the formation of hybrids (comprising a dimer of porphyringlobin and a dimer of haemoglobin) in which quenching occurs by energy transfer from the porphyrin to the haem groups of the protein. From an analysis of fluorescence quenching, dissociation constants were calculated for the hybrids of oxy- and deoxyhaemoglobin with the fast- and slow-moving porphyringlobin species isolated by chromatography on CM-Sephadex (Treffry & Ainsworth, 1974). The values obtained are: deoxyhaemoglobin–fast-moving porphyringlobin, 0.8X10−9m; deoxyhaemoglobin–slow-moving porphyringlobin, 5X10−10m; oxyhaemoglobin–fast-moving porphyringlobin, 0.8X10−6m; oxyhaemoglobin–slow-moving porphyringlobin, 1.2X10−7m. The rates of reactions of solutions of haemoglobin and porphyringlobin, containing hybrids, with the thiol reagent 4,4′-dithiodipyridine showed that the thiol groups of the hybrids deoxyhaemoglobin–fast-moving porphyringlobin and oxyhaemoglobin–slow-moving porphyringlobin react more slowly than expected on the basis of composition alone: this result indicates that the deoxy and slow-moving conformations are the more stable, imposing themselves partially on to the fast-moving or oxy dimer of the hybrid. Also the rate of the reaction of CO with deoxyhaemoglobin is decreased when slow-moving porphyringlobin is added to its solutions: this is reflected in a movement of the oxygen equilibrium curve of such a mixture to higher oxygen partial pressures. Similar experiments with deoxyhaemoglobin solutions containing fast-moving porphyringlobin, showed an initial increase in the rate of CO uptake. Correspondingly, the oxygen equilibrium curve of the mixture showed an increased affinity for oxygen. Approximate calculations to determine the oxygen equilibria of the hybrids indicate that a functional dimer retains co-operative characteristics even when the dimer accompanying it within the tetramer has the reacted conformation.

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