BIOCHEMICAL AND MORPHOLOGIC STUDIES OF CEREBRAL EDEMA ASSOCIATED WITH IXTRACEREBRAL TUMORS IN RABBITS

Experimental brain tumors and edema in rats. II. Tumor edema

Experimentally induced brain tumors in rats with the morphological characteristics of low differentiated gliomas were investigated with special consideration of the distribution of extravasated serum proteins within the tumor itself. Protein extravasation across tumor vessels occurs by pinocytotic vesicles which enclose serum proteins at the luminal surface of the endothelial cells. These vesicles move to the abluminal cell surface where proteins are released after fusion between vesicles and the cell membrane. Serum proteins then spread through the extracellular space from where they are taken up in tumor cells by pinocytosis. They are then transmitted to and digested by lysosomes in which acid phosphatase activity could be demonstrated. Tracer studies (human serum albumin, horseradish peroxidase) revealed that proteins reach the lysosomes 15 min after systemic application. The cellular content of tracers is variable even when systemic circulation has lasted 120 min.

Immunofluoroscopic investigation of extravasation of serum proteins in human brain tumours and adjacent structures

Forty-seven neurosurgical human specimens taken from malignant gliomas and peritumoural brain structures were investigated for extravasation of serum proteins. Serum proteins were visualized microscopically in paraffin-embedded material using a double layer immunofluorescence technique. Proteins accumulated in the tumour and in the adjacent peritumoural white matter, and were mainly located extracellularly. Intracellular uptake was observed in some but not all tumour cells, in reactive astrocytes and, occasionally, in oligodendrocytes and neurons. Diffuse infiltration of products was present in necrotic, cystic and haemorrhagic regions. The distribution of extravasated proteins corresponded precisely to that previously observed in transplanted tumours in cats (Hossmann et al. 1979), suggesting that the pathophysiology of human tumour oedema is similar to that of the experimental material. Since all patients were operated without corticosteroid therapy, the present results can be used as a reference for forthcoming studies on the effect of corticosteroids on peritumorous oedema.

The kallikrein-kinin system as mediator in vasogenic brain edema

✓ Plasma and bradykinin were perfused into the ventricular system of mongrel dogs to investigate whether either or both induce brain edema. Formation of cerebral edema was determined by measurement of cerebral water and electrolytes in periventricular white matter, cerebral cortex, and caudate nucleus. The response of cerebral tissue to exposure to bradykinin or to plasma, as a carrier of kininogens, was analyzed by assessment of the perfusate composition after ventricle passage. The authors report that cerebral administration of bradykinin induces cerebral edema. Ventricular perfusion with plasma also led to an increase of cerebral water content which was restricted to the white matter, but involved all brain tissue areas, if bradykinin was used. Ventricular perfusion with plasma was associated with consumption of the kinin precursor (kininogens) indicative of formation of kinins. Significant consumption of the precursor was found in five out of nine animals subjected to plasma perfusion of the ventricular system. In these animals a close correlation between the increase of white matter water content and kininogen-consumption as a measure of kinin-formation was obtained. Marked kinin-degrading activity was observed during ventricular perfusion with bradykinin as concluded from a considerable decrease of bradykinin concentration in the cisternal effluent compared to the inflowing perfusate concentration. Ventricular perfusion with plasma was associated with a decrease of K+ clearance capacity with continued duration, and in two animals with a release of glutamate into the plasma perfusate, suggesting an involvement of cytotoxic mechanisms.

These findings provide support for the hypothesis of a mediator function of the kallikrein-kinin (KK) system in vasogenic brain edema. The next question that needs to be answered to complete the picture — does spontaneous activation of the KK system occur in conditions leading to vasogenic edema? — is studied in a subsequent report.

Experimental brain tumors and edema in rats

In rats experimental brain tumors were produced by intracerebral implantation of a glioma cell clone. Peritumorous edema was investigated by light and electron microscopy, using exogenous tracers [human serum albumin (HSA), horseradish peroxidase] and immuno-histochemical methods for localization of endogenous serum proteins. An infiltration by serum proteins was observed in peritumoral grey and white matter. Peroxidase was found in pinocytotic vesicles of vascular endothelial cells, in pericytes and diffusely in the extracellular space. High concentrations of endogenous rat serum proteins and exogenous human serum albumin were also found in neurons of the grey matter and in oligodendrocytes of the white matter. A cellular uptake of extravasated proteins, therefore, may contribute to edema resolution.

Blood flow and regulation of blood flow in experimental peritumoral edema

In 27 pentobarbital-anesthetized cats cerebral blood flow and regulation of cerebral blood flow was measured one to 3 weeks following stereotactical xenotransplantation of a rat glioma clone into the internal capsula. Tumor growth was accompanied by severe vasogenic peritumoral edema in the white matter of the tumor-bearing hemisphere. White matter water content in the vicinity of the tumor increased from 69.1 +/- 0.9 to 0.5 +/- 0.7 ml/100 g wet weight (means +/- SE) which corresponds to an increase in tissue volume of about 60%. Intracranial pressure after 3 weeks was 12 +/- 2.6 mm Hg. Blood flow in the peritumoral white matter decreased from 32.2 +/- 5.6 to 18.6 +/- 1.9 ml/100/g/min but it did not change in the peritumoral grey matter or the opposite hemisphere. The decrease in blood flow was due to the volume expansion of the swollen edematous tissue and not to a compression of the microcirculation because neither flow nor vascular resistance changed when referred to dry rather than to wet weight of the edematous tissue. Flow regulation in the peritumoral edematous white matter was disturbed. CO2 reactivity of blood flow was 5.4% mm Hg change in aPCO2 (non-edematous contralateral white matter 6.4%/mm Hg), and the autoregulatory capacity between 40 and 170 mm Hg was 0.7%/mm Hg (non-edematous white matter 1.0% mm Hg). It is concluded that in the absence of significant intracranial hypertension, even severe degrees of vasogenic peritumoral edema do not interfere with blood flow and flow regulation. This is in contrast to the cytotoxic type of edema, and indicates that microcirculatory compression by edema, when present, is the consequence of pericapillary glial hydrops and not of an accumulation of extravasated edema fluid.

Spongy degeneration in the central nervous system of domestic animals. Part II: Chemical analysis and vascular permeability studies

Two experiments were completed in which brains and spinal cords from lambs affected with spongy degeneration of the central nervous system (CNS) were analysed for water, sodium and potassium, as measures of cerebral oedema. In a third experiment, lambs with CNS spongy degeneration were tested for permeability of cerebral blood vessels by intravenous injections of Evans blue. The CNS spongy degeneration was produced by poisoning with the hepatotoxic pyrrolizidine alkaloid lasiocarpine. In the first experiment, 2 male lambs were poisoned by lasiocarpine and a third injected with saline alone. One lamb injected with lasiocarpine showed widespread spongy changes in the CNS and the other 2 showed normal brains. In the second experiment, 5 males lambs were poisoned by lasiocarpine and 5 were injected with saline. Three of the 5 poisoned lambs showed widespread spongy changes, a fourth showed minor vascuolation and the remaining 6 had normal brains...