0000000000002968
AUTHOR
Gerhard Thews
Energiehaushalt und Arbeitsphysiologie
Zur Aufrechterhaltung der Korperfunktionen und der Korperstruktur ist eine standige Energiezufuhr in Form von Nahrstoffen erforderlich. Die beim Abbau der Nahrstoffe anfallende Energie kann nur teilweise in Arbeit umgesetzt werden, ein anderer Teil wird zwangslaufig — dem 2. Hauptsatz der Thermodynamik entsprechend — als Warme frei. Daruber hinaus dient die Stoffwechselenergie zur Biosynthese von Enzymen, Hormonen und zellularen Strukturelementen sowie zur Anlage von Nahrstoffdepots.
Transport- und Regelprozesse
Die Funktionen der Zellen und Gewebe — Stoffwechsel, Reproduktion, Wachstum, Regeneration, Kontraktion, Sekretion und Erregbarkeit — erfordern einen standigen Transport von Stoffen und Flussigkeiten innerhalb des Organismus. Sauerstoff und Nahrstoffe mussen laufend den Zellen zugefuhrt, Kohlendioxid und andere Stoffwechselendprodukte an die Umgebung abgegeben werden. Voraussetzung fur den kontrollierten Ablauf der Stoffwechsel- und Erregungsprozesse sind ferner bestimmte Ionenkonzentrationen innerhalb der Zellen, die durch spezifische Transportsysteme der Zellmembran aufrechterhalten werden. In Abhangigkeit von der Flussigkeitsaufnahme und -ausscheidung vollzieht sich schlieslich der Flussi…
Time Courses of Erythrocytic Oxygenation in Capillaries of the Lung: Lower and Upper Bounds on Red Cell Transit Times
With the aid of a 2-dimensional computer simulation (Groebe and Thews, 1986), time courses of erythrocytic oxygen uptake in the lung were calculated.
The Interdependence of Respiratory Gas Values and pH as a Function of Base Excess in Human Blood at 37°C
The accurate estimation of the transport function of human blood for respiratory gases as well as the respiratory gas exchange in human body requires detailed knowledge of the respiratory gas partial pressures and the acid-base status in the blood. Because there is an interdependence between the different respiratory gas parameters described as Bohr and Haldane effect (3,4), it is possible to obtain a general picture of the whole transport system, if these interrelations are known.
Wasser-, Elektrolyt- und Säure-Basen-Haushalt
Von allen Bestandteilen des Korpers hat das Wasser den grosten Anteil. Beim Neugeborenen entfallen darauf etwa 75%, beim erwachsenen Mann (je nach Korpergewicht und Alter) 50–70% des Korpergewichts.
Impact of Localized Microwave Hyperthermia on the Oxygenation Status of Malignant Tumors
Considerable insight into the mechanisms of heat induced cell death in vitro has been gained during recent years (for reviews see 1–3). Besides the direct cell killing effect of heat, many microenvironmental or milieu factors seem to play an important role during heat treatment of solid tumors in vivo, such that a preferential effect of hyperthermia on tumors has been postulated for the in situ conditions. Environmental factors affecting the tumor milieu, such as tissue oxygen partial pressures, pH values, glucose (?) and lactate levels, nutrient supply and drainage of wastes, have thus become a subject of topical interest.
Basic Mechanisms of Diffusive and Diffusion-Related Oxygen Transport in Biological Systems: A Review
In mammals, energy metabolism of active tissues requires permanent availability of oxygen. Because cessation of O 2 supply results in loss of organ function within seconds or minutes, continual feed of adequate amounts of O 2 to tissue is the most vital task for living organisms. For many years, it therefore has been one of the greatest challenges to physiologists to understand the mechanisms provided by nature to satisfy this need for oxygen.
Nierenfunktion und Miktion
Gliederung des Nierenparenchyms. Die Niere gliedert sich in die Nierenrinde und das Nierenmark, in dem sich wiederum eine Ausenzone und eine Innenzone unterscheiden lassen (Abb. 10-1). Das Mark ist durch Saulen der Rindensubstanz in 8–16 Markpyramiden unterteilt, deren Spitzen zum Zentrum hin konvergieren. Diese Spitzen, die Nierenpapillen, sind von den schlauchformigen Nierenkelchen uberzogen. Sie fangen den fertigen Harn auf und leiten ihn uber den Sammelraum des Nierenbeckens in den Ureter.
Respiratory Gas Transport in Heart
The purpose of this paper is to describe an attempt to obtain a better understanding of the dynamics of the oxygen supply of the myocardium under physiological and pathophysiological conditions by examining the oxygen diffusion in the heart muscle tissue during systole and diastole. In comparison to other organs the oxygen supply of the myocardium is characterized by a number of specific features. The most important one is that the gas exchange in the myocardium is a nonsteady-state diffusion process.
Respiratory GAS Exchange and pO2- Distribution in Splenic Tissue
Little attention has been paid to physiological aspects of O2 supply to splenic tissue. Studies are performed to examine the factors determining the supply conditions for the rabbit’s spleen, which has little reservoir function and, therefore, it is very similar to the human spleen. Previous studies on respiratory gas exchange, applying the arterial and spleno-venous blood gas values, have shown a mean arterio-venous O2-difference of 0.5 Vol.% (2). Taking into account a mean splenic blood flow of 110 ml/100g/min (12), the O2 consumption of splenic tissue amounts to 0.6 ml/100g/min.
Theoretical Analysis of Factors Influencing Recovery of Ventilation Distributions from Inert Gas Washout Data
For the quantitative analysis of intraregional ventilation inhomogeneities, one classically applies the inert gas washout method [7,24] in which an inert gas of negligible solubility in blood and tissue is washed into the lungs. After washin is complete, the inspiratory inert gas fraction is set to a smaller value and the time course of the mixed endexpiratory inert gas fraction during the subsequent inert gas washout is recorded. The determinants of this time course are: The endexpiratory alveolar volume at the instant of change in inspiratory inert gas fraction, the anatomical dead space, the gas exchange ratio, the respiratory frequency, the in- and expiratory tidal volumes, and the inho…
Stoff- und Flüssigkeitstransport
Die Funktionen der Zellen und Gewebe — Stoffwechsel, Reproduktion, Wachstum, Regeneration, Sekretion, Resorption, Kontraktion und Erregbarkeit — erfordern einen standigen Transport von Stoffen und Flussigkeiten innerhalb des Organismus. Sauerstoff und Nahrstoffe mussen laufend den Zellen zugefuhrt, Kohlendioxid und andere Stoffwechselendprodukte an die Umgebung abgegeben werden. Voraussetzung fur den kontrollierten Ablauf der Stoffwechsel- und Erregungsprozesse sind ferner Konzentrationsgradienten bestimmter Ionen zwischen Intra- und Extrazellularraum. In Abhangigkeit von der Flussigkeitsaufnahme und -ausscheidung vollzieht sich schlieslich der Flussigkeitstransport im Organismus in enger K…
O2 Supply Conditions in Tumor Tissue in Vivo
During the last few years O2 supply of tumor tissue has very carefully been investigated using GULLINO’ s model of a “tissue isolated” implantation tumor (GULLINO and GRANTHAM, 1961; GUNTHER et al., 1972; VAUPEL et al., 1971; VAUPEL, 1974). We analysed the O2 supply for a DS-Carcinosarcoma in the rat kidney by two methods: 1. direct measurement of O2 pressures in the tissue by means of gold micro-electrodes, 2. PO2 calculation according to diffusion laws considerring the experimentally determined parameters in the arterial and venous blood.
Heterogeneous Oxygenation of Rectal Carcinomas in Humans: A Critical Parameter for Preoperative Irradiation?
The surgical treatment of rectal carcinoma in humans is often combined with irradiation. However, the efficacy of this latter treatment modality is crucially influenced by the oxygenation status of the tumor tissue to be treated. Therefore, the knowledge of the O2 supply to the tumor tissue is a decisive prerequisite for the assessment of the efficiency of radiotherapy.
Funktion des Gastrointestinaltrakts
Die Hauptaufgabe des Gastrointestinaltrakts besteht in der Uberfuhrung der Nahrung in resorbierbare Bestandteile und in deren Aufnahme in den Korperkreislauf. Der erstgenannte Teilprozes, die Verdauung, wird durch mechanische Vorgange, durch Zerkleinerung, Transport und Durchmischung eingeleitet. In engem Zusammenhang damit erfolgt die Sekretion von Verdauungssaften. Die Einwirkung der Enzyme, die in den Verdauungssaften enthalten bzw. auf der inneren Darmwand lokalisiert sind, fuhrt dann zur hydrolytischen Spaltung der Eiweise, Kohlenhydrate und Fette. Im zweiten Teilprozes, der Resorption, werden die Endprodukte der Verdauung ebenso wie Wasser, Mineralstoffe und Vitamine aus dem Darmlumen…
Relationship Between Size and Oxygenation Status of Malignant Tumors
During advanced phases of malignant growth, there are typical changes in the microvasculature pattern within the tissue of many solid tumors. Partly due to these peculiarities of tumor vascularization, a series of characteristic variations of tumor microcirculation occurs (for a review see 1). These alterations lead not only to marked restrictions and inhomogeneities of both convective and diffusive transport but also to an impairment of the efficiency of antitumor therapies.
Determination Of Pulmonary Parameters (V̇A, $$ {D_{{L_{{O^2}}}}} $$ ) From Arterial O2 and CO2 Partial Pressures During Exercise
The arterial O2 and CO2 partial pressures mainly depend on the ventilation-perfusion ratio VA/Q and on the O2 diffusing capacity-perfusion ratio DLO2/Q. According to RAHN’s VA/Q concept, the dependence of the alveolar O2 and CO2 partial pressures on the ventilation-perfusion ratio can be determined graphically, and displayed in the form of a diagram (2,3). However, the application of the RAHN diagram is limited by the fact that during the passage of the blood through the lung capillaries, a complete adjustment of the capillary O2 partial pressure to the alveolar value frequently does not occur. This is particularly valid for gas exchange during exercise. For this case, the alveolar-endcapil…
Effects of Red Cell Spacing and Red Cell Movement Upon Oxygen Release Under Conditions of Maximally Working Skeletal Muscle
The impacts of the particulate nature of blood upon capillary O 2 release have been studied extensively by Federspiel and Sarelius [8] and by Federspiel and Popel [9]. The latter authors found that the O 2 flux out of a capillary decreases rapidly as intracapillary red blood cell spacing increases. The O 2 flux out of a single RBC, however, is enhanced as long as the inter-erythrocytic plasma gap does not exceed the “zone-of-influence” of a single RBC, which they determined to be about 1 capillary diameter. In their model, they considered spherical red cells contained in a cylindrical tube filled with plasma, on the lateral surface of which a boundary Po 2 was specified. Based on earlier st…
Blut und Abwehrfunktionen
Blut stellt aus funktioneller Sicht ein „flussiges Korpergewebe“ dar. Es besteht aus Zellen, die in einer elektrolyt- und eiweishaltigen Losung, dem Plasma, suspendiert sind. Das Blut, dessen Zusammensetzung und Volumen normalerweise nur geringen Schwankungen unterliegen, dient vor allem als Transportmittel innerhalb des Organismus. Daneben ist es an der Aufrechterhaltung eines konstanten inneren Milieus (Homoostase) und an der Abwehr eingedrungener Fremdstoffe und Krankheitserreger beteiligt.
Pathophysiological Aspects of Glucose Uptake by the Tumor Tissue under Various Conditions of Oxygen and Glucose Supply
Earlier examinations of the glucose uptake in neoplastic tissue by isolated DS- Carcinosarcoma implanted into the rat kidney had the results as follows (VAUPEL, 1974): 1. An increase of the tumor mass from 3 to 13 g wet weight caused an exponential decrease of the glucose consumption by the tumor tissue from 44.4 to 6.7/umoles per 100 g/min; very young tumors of 3 – 4 g bad uptake rates from 27.8 to 44.4/umoles/100 g/min. 2. Simultaneous measurements of the mean actual glucose concentrations in the tumor tissue showed that in the very young tumors the concentration still ranged from 1.75 to 2.25/umoles/g wet weight, whereas those in old tumors drop as low as 0 to 0.17/umoles/g.