The initial period of no-flow anoxia can be divided in at least two parts. During the first period lasting approximately 1 min., the O2 available in tissue gives rise to CO2 which increases hydrogen ion activity and may lead to Na+ influx2 (presumably due to increased membrane permeability to Na+). In the second period, starting after the first minute, the increase in lactate content leads to further decrease in pH and is accompanied by extensive sodium influx and a distinct potassium efflux. However, it is striking that the isolated perfused rat liver is able to tolerate 1 hour of norm-flow anoxia without severe cellular damage, whereas two minutes of no-flow anoxia lead to a decrease in cellular ATP content by 28%.

Adenosine Triphosphate↗

PubMedDate not supplied

Oxygen supply to the cirrhotic liver following various portacaval shunt procedures.

Direct measurements of local oxygen pressure by means of a platinum multiwire electrode were performed to investigate the effect of five different portacaval shunt procedures on hepatic oxygen content in the cirrhotic rat liver. End-to-side shunt, side-to-side shunt, mesenterico caval shunt, splenocaval shunt, and portacaval transposition were performed and surface PO2 was determined immediately after operation, 24 hours following operation and after one week. Portacaval transposition and end-to-side shunt led to a striking oxygen deficit of the liver tissue with no incidence of compensation by the hepatic artery; Oxygen supply was improved considerably by a side-to-side shunt and tissue hypoxia could be prevented by a mesenterico-caval shunt and splenocaval shunt. This improving effect is thought to be due to the pancreatico-duodenal venous blood supply which should be carefully preserved for the liver circulation when a shunt needs to be performed.

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PubMedDate not supplied

PO2 histograms and extracellular activity of K+ of skeletal muscle in tourniquet shock.

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Animals↗

PubMedDate not supplied

Hypoxia-induced tumour cell migration in an in vivo chicken model.

To investigate the relationship between hypoxia, neovascularisation and tumour cell spread, experiments on the area vasculosa of the early chick embryo under different oxygen concentrations were performed in vivo. Human glioblastoma cells (U-138MG) were inoculated onto the area vasculosa and the fertilised eggs were incubated under conditions of normoxia or hypoxia. For evaluation, we performed in vivo video-microscopy of the area vasculosa and determination of microvessel density (MVD), as well as a histological examination of the fixed specimen. Under hypoxia, MVD was significantly increased compared to normoxic conditions. Only under hypoxic conditions was tumour cell spread found outside the main tumour mass and within the vessels, at times followed by the subsequent development of secondary tumour cell bulks on the area vasculosa. These data lead to the conclusion that hypoxia can stimulate tumour cell migration in this in vivo model.

Animals↗

PubMedDate not supplied

Micro-light guide spectrophotometric measurement of changes in local haemoglobin oxygenation and concentration in the rabbit lung induced by hypoxia and hyperoxia.

Due to the high flexibility of the micro-light guides used with the Erlangen micro-light guide spectrophotometer (EMPHO) the instrument can be coupled to the lung surface without interfering with the local lung mechanics. The local pressure exerted on the lung varies between 45 and 47 mg/cm2. This enables the continuous investigation of local haemoglobin oxygenation and relative local haemoglobin concentration. The effect of different inspired oxygen concentrations on local oxygen saturation of intravascular haemoglobin and relative local haemoglobin concentration was investigated in 6 rabbits. The animals were anaesthetized, intubated and artificially ventilated. After thoracotomy, a light guide was placed on the pleural lung surface and haemoglobin spectra were measured at a frequency of 5 Hz using the EMPHO. Two types of changes in the local haemoglobin concentration were observed; one was correlated with the respiratory cycle. During inspiration a decrease in relative local haemoglobin concentration was observed. Opposite changes occurred during expiration. These changes were observed with simultaneous changes in local haemoglobin oxygenation. The oxygenation increased during inspiration and decreased during expiration. The amplitude of the oxygenation changes depended on the fraction of inspired oxygen FiO2. A second type of reaction in local haemoglobin concentration was observed when the inspired oxygen concentration was decreased or increased by changing the FiO2. A decrease in the oxygen partial pressure in the inspired gas mixture (PiO2) was associated with an increase in relative local haemoglobin concentration, whereas an increase in PiO2 was accompanied by a decrease in relative local haemoglobin concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMedDate not supplied

Influence of environmental oxygen concentration on growth and vascular density of the area vasculosa in chick embryos.

The influence of different environmental oxygen concentrations on vascularization was studied in the yolk sac blood vessel system of chick embryos. The eggs were incubated at normoxic (20.9% oxygen, n = 29), hypoxic (10% oxygen, n = 36) or hyperoxic (100% oxygen, n = 26) conditions and evaluated on day 4 of incubation. In vivo photographs were taken of the vascularized part of the yolk sac membrane (area vasculosa). Prints of a given enlargement were evaluated by histometrical methods to measure the extension of the area vasculosa, the density and the total area of blood vessels. Hypoxia induced an increase in vascular density, in area occupied by blood vessels (44.4%, normoxia = 40.6%) and an enlargement of the area vasculosa (441 +/- 78.6 mm2, normoxia = 380 +/- 68.7 mm2). Hyperoxia also induced an increase in vascular density and in the area occupied by blood vessels (45.9%), but a decline in the extension of the vascularized area (287 +/- 48.8 mm2). Thus the total number of blood vesels as well as the total exchange surface decrease in hyperoxia. Our results indicate that in the area vasculosa of the early chick embryo hypoxia possibly causes an upregulation of vascular growth factors. From the present results it cannot be decided whether vasculogenesis or angiogenesis is stimulated.

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