Local blood flow changes in malignant brain tumours under induced hypertension

Changes in tumour blood flow under an induced hypertensive state were examined in malignant brain tumours to know if the precondition for the effectiveness of induced hypertensive chemotherapy--relative increase in tumour blood flow--are fulfilled. Tumour blood flow was measured under both a resting and an induced hypertensive state in 12 patients with various malignant brain tumours (6 gliomas, 6 metastatic brain tumours) using xenon-enhanced computed tomography. The blood pressure was elevated 40% above the systemic blood pressure of the resting state by the infusion of angiotensin II. Tumour blood flow increased 30% on average above the normal brain tissue blood flow after the induction of an induced hypertensive state (p < 0.05). The tumour blood flow increased in 11 cases of malignant tumours, but decreased in one case with massive brain oedema after induced hypertension. The increase in blood flow was higher in hypervascular tumours and less in hypovascular tumours. Therefore, induced hypertensive chemotherapy probably will be more effective in hypervascular malignant brain tumours with small mass effects.

Platelet-derived growth factor and its receptors in human glioma tissue: expression of messenger RNA and protein suggests the presence of autocrine and paracrine loops

The expression of platelet-derived growth factor (PDGF) and its receptors was analyzed in 14 gliomas of various degrees of malignancy and compared with three gliosis cases by in situ hybridization and immunohistochemistry techniques. Expression of both PDGF A- and B-chains was higher in glioblastomas than in astrocytomas. The PDGF A-chain mRNA was predominantly found in cell-rich areas in glioblastomas. The cognate PDGF-alpha receptor (PDGFR-alpha) mRNA was heterogeneously distributed in gliomas of all grades, and PDGFR-alpha expression was higher in gliomas than in gliosis. Within some glioblastomas probed with PDGFR-alpha complementary RNA, cells heavily loaded with grains were intermingled with others containing low or moderate signals. The heavily labeled cells were often found in the vicinity of proliferating capillaries. Immunostaining with an anti-PDGF antibody and an affinity-purified antiserum against the PDGFR-alpha showed strong staining of most tumor cells with both antibodies in glioblastoma. In addition, the PDGFR-alpha antibodies yielded a strong staining of scattered cells, and the anti-PDGF antibody yielded staining of a few cells within the astrocytoma. Furthermore, high levels of the PDGF-beta receptor (PDGFR-beta) and PDGF B-chain mRNA as well as the beta receptor protein were found in hyperplastic capillaries. These results suggest the presence of autocrine and paracrine loops in glioma, activating the PDGFR-alpha in glioma cells and the PDGFR-beta in endothelial cells.

[Ultrastructure of glioma vessel--morphometric study for proliferative potential of endothelial cell]

In this study we quantified the morphological abnormalities of human glioma vasculature in operated sample of low grade astrocytomas and malignant gliomas. Only those vessels with a diameter of less than 10 micron and containing one nucleus at least on axial section present in the marginal area of the tumors devoid of necrosis were subjected to the present study. A total of 58 vessels were analyzed with computer assisted morphometry for ultrastructural evidence of proliferative potentials of endothelial cells. 5 specific features of the endothelial cells and/or the capillaries which were not related to the vascular permeability were assessed: (1) Degree of vascular luminal narrowing (LN: Ratio of luminal area to abluminal area), (2) Thickness of basement membrane (BM), (3) Mean % ratio of the endothelial cells including Weibel-Palade bodies to whole endothelial cells (WPB-1) and the number of Weibel-Palade bodies in an endothelial cell section (WPB-2), (4) Irregularity of nuclear shape (NA: semiquantified grade 0 to 3). (5) Mitochondrial density (MIT). We found that: (1) LN was significantly stronger in malignant glioma capillaries (MGC, 28%) than low grade astrocytoma capillaries (LAC, 39%). (2) BM was significantly thicker in MGC (2.9 microns) than in LAC (1.2 microns), (3) WPB-1 and WPB-2 were significantly higher in MGC (34% and 0.92) than LAC (14% and 0.39). (4) NA was significantly higher in MGC (grade 2.1) than LAC (grade 1.3), (5) MIT was significantly higher in MGC (5.6%) than LAC (4.2%).(ABSTRACT TRUNCATED AT 250 WORDS)

Pleomorphic xanthoastrocytoma with desmoplastic reaction: angiomatous variant. Report of two cases

Two cases of cerebral pleomorphic xanthoastrocytomas (PXA-s) with prominent vascularity and desmoplastic changes occurring in young subjects are presented. The tumors displayed the marked pleomorphism characteristic of PXA-s and had variable cellularity. The cytoplasm of many tumor cells contained an abundance of lipid droplets. Most tumor cells were positive for glial fibrillary acidic protein. The unusual feature about these tumors was the presence of very large numbers of tiny blood vessels with variable thickness of their walls. In many areas the small vessels and the neoplastic astrocytes were in close proximity to each other, with capillaries adjacent to or protruding into tumor cell cytoplasm, reminiscent of the pattern seen in highly vascularized or "angiomatous" meningiomas. In other areas extensive fibrosis was seen. We feel that the latter, as in the cases of comparably vascular meningiomas, had its origin in congelation and secondary organization of plasma proteins that have exuded through leaky walls of newly formed blood vessels. These are the first reported cases of PXA with an angiogliomatous pattern.

[The astrocyte-endothelial interface in cerebellar astrocytoma]

The astrocyte-endothelial interface is a component of the anatomical blood-brain barrier in the central nervous system and is of interest in neoplastic lesions. We, therefore, investigated the fine structure of this interface in five, well-differentiated cerebellar astrocytomas. The astrocyte-endothelial interface in cerebellar astrocytomas revealed various abnormalities. The perivascular space is usually wide and contains various amounts of collagen fibers, fibroblasts and pericytes. The basal lamina of the endothelial cell is mostly single-layered and continuous, but sometimes multilayered and discontinuous. The basal lamina of the neoplastic astrocytic cell is usually single-layered and continuous, but is occasionally absent in foci. The basal lamina of the endothelial cell is more prominent than that of the astrocyte. The neoplastic astrocyte has not so well developed cell junctions and poorly formed peripheral expansions of the processes. The relationship between the basal lamina of the endothelial cell and that of the astrocyte in cerebellar astrocytomas is compared to that in ependymomas.

[Morphologic findings and biologic behavior in the high grade glioma--a postmortem study of 22 cases]

Morphologic features of the autopsied specimen of 22 cases with supratentorial gliomas treated by surgery, radiation and/or chemotherapy were analysed, and the characteristics of recurrence of gliomas were searched for. The cases consisted of anaplastic 12 astrocytoma and 10 glioblastoma. The results were as follows: 1) Characteristic CT findings before death were regrowth of the tumor mass or the occurrence of a new enhanced lesion in 21 out of 22 cases. The enhanced lesion showing regrowth of the tumor located in the same site as the previous tumor mass in 21 cases. The new enhanced lesion resulting from a trans-or subependymal tumor spread, was seen in the ventricular wall, and these findings were a characteristic feature of the recurrence of gliomas. 2) Modes of extension of the tumor were subdivided into 3 types. One was the expansive or infiltrative type caused by regrowth of the residual tumor. In the second pattern, a spread of tumor cells occurred along the myelinated fiber tracts to the brain stem (60%), or to the contralateral cerebral hemisphere through the corpus callosum (50%). The third mode of tumor propagation was cerebrospinal fluid seeding with intraventricular or subarachnoid tumor regrowth (45%). 3) Characteristic histological findings shown in the original tumor bed were those of increased cellularity with endothelial proliferation, widespread necrosis with occlusion of the blood vessels, occurrence of the gemistocytic astrocytes and large bizarre cells. Thickening of wall of the blood vessels due to effect by radiation was followed by occlusion of the blood vessels. Large necrosis in the tumor tissue was caused by those process and others. Necrotic area was mainly circumscribed and corresponded to the territory of the vessels. One of the specific findings in the morphological changes of the tumor cells was giant cell formation which were monstrous cell, giant cell (12 cases out of 22), and gemistocytic cell (in all cases). These specific cells were supposed to the degenerative changes of the tumor cells exposed while withstanding such adverse conditions as hypoxia, radiation and chemotherapy. 4) Infiltration distant from the primary lesion which were defined only by microscopical examination was demonstrated as both through myelinated fiber tracts in 8 cases and through perivascular spaces in 2 cases. Reinvasion of the tumor cells from the subarachnoid spaces to the brain parenchyma was along the Virchow-Robins spaces of the penetrating blood vessels in the latter cases.(ABSTRACT TRUNCATED AT 400 WORDS)

[Morphological changes in basement membrane associated with endothelial proliferation in astrocytic tumors--an immunohistochemical study of laminin]

Morphological changes of the basement membrane associated with endothelial proliferation in astrocytic tumors are studied in this report. Laminin is known to be a specific glycoprotein of basement membranes. We applied this characteristic of laminin to enable us to observe various characteristics of the basement membrane. The presence of laminin in 13 glioblastomas, 15 anaplastic astrocytomas, 7 astrocytomas, and 6 pilocytic astrocytomas was examined by peroxidase-antiperoxidase (PAP) staining of formalin-fixed and paraffin-embedded surgical specimens. White matter from five normal cerebral hemispheres obtained during autopsy and subsequently embedded using the same method, were used as a control. Laminin was observed at the glioma-mesenchymal junction in astrocytic tumors, and the deposits of laminin made the tumor vasculature come into intense relief. The destructive changes of the basement membrane, including disruption, thickening, disconnection, dissociation, winding, and conjunction, became greater with progressive endothelial proliferation in astrocytic tumors. Those changes were seen to be most remarkable in glioblastoma. In addition, there was a marked variety of morphological change in the basement membrane in different areas of glioblastomas, although the changes were almost constant in other astrocytic tumors. We present a schematic hypothesis of the stages of angiogenesis in glioblastoma based on the above morphological changes of the basement membrane and discuss it in this report.(ABSTRACT TRUNCATED AT 250 WORDS)

Vascular bundles and wickerworks in childhood brain tumors

We reviewed 114 childhood brain tumors and brain sections from 30 children with no nervous system lesions to determine the incidence of vascular bundles (VB) and vascular wickerworks (VW). VB consist of a group of small blood vessels running parallel to each other. VW denote spiralling or twisting of two or more small blood vessels around one another, resembling vines. By light microscopy, VB cannot be differentiated from VW; both appear as a group of small blood vessels oriented in the same direction. VB and VW have been described in normal and abnormal brains at all ages, in association with aging, in neovascularization following necrosis, and in brain tumors. They occur rarely in normal brains, but are a common histological feature of cerebellar pilocytic astrocytomas in contrast to diencephalic pilocytic astrocytomas, anaplastic astrocytomas of cerebrum and cerebellum, and meningiomas.

Grading of astrocytomas. A simple and reproducible method

This study determines the effectiveness and reproducibility of a previously published method of grading gliomas. The method under study is for use on "ordinary astrocytoma" cell types, i.e., fibrillary, protoplasmic, gemistocytic, anaplastic astrocytomas and glioblastomas, and is based upon the recognition of the presence or absence of four morphologic criteria: nuclear atypia, mitoses, endothelial proliferation, and necrosis. The method results in a summary score which is translated into a grade as follows: 0 criteria = grade 1, 1 criterion = grade 2, 2 criteria = grade 3, 3 or 4 criteria = grade 4. The histologic material and clinical data were derived from a previously reported series of patients with astrocytomas, radiotherapeutically treated at Mayo Clinic between the years 1960 and 1969. From this series, initially graded 1 to 4, according to the Kernohan system, 287 "ordinary astrocytomas" were entered into the study; 51 pilocytic astrocytomas and microcystic cerebellar-type astrocytomas also were included for comparison. Among ordinary astrocytomas, the grading method under study distinguished 0.7% of grade 1, 17% of grade 2, 18% of grade 3, and 65.3% of grade 4. A 15-year period of follow-up was available on all surviving patients. Statistical analysis showed that in ordinary astrocytomas, each of the four histologic criteria, as well as the resultant grade, were strongly correlated to survival (P less than 0.0001). Median survival was 4 years in grade 2, 1.6 years in grade 3, and 0.7 years in grade 4 tumors. Of the two patients with grade 1 ordinary astrocytomas, 1 had 11 years of survival, and the other was alive at 15 years. Furthermore, based upon the Cox Model, grade was found to be the major prognostic factor, superceding the effects of age, sex, and location. Among ordinary astrocytomas, the grading system under consideration clearly distinguished four distinct grades of malignancy, whereas, the Kernohan grading system accurately distinguished only two major groups of patients. Survival curve of patients with our grade 2 tumors coincided with the grade 1 and 2 Kernohan survival curves. Similarly, our grade 4 survival curve coincided with the Kernohan grade 3 and 4 survival curves. As a result, our proposed grading method generated an individualized curve corresponding to grade 3 tumors. Double-blind grading between two independent observers was concordant in 94% of ordinary astrocytomas; reproducibility was 81% in low-grade (grades 1 and 2) and 96% in high-grade (grades 3 and 4) astrocytomas of ordinary type.(ABSTRACT TRUNCATED AT 400 WORDS)

The great radicular artery of Adamkiewicz in man. Demonstration of a possibility to predict its functional territory

A women in her early sixties suffered from a malignant intramedullary astrocytoma. It had caused a nearly complete neurological deficit extending from the 12th thoracic segment downward. Since progressive tumour growth caused excruciating pain it was decided to remove the tumorous non-functional part of the spinal cord. As the great radicular artery was located in the region of the tumour it was feared that it might have to be sacrificed during surgery. In order to be informed as to its vascularization and the clinical consequence of interrupting it, an anaesthetic agent (Etomidate) was injected through this vessel. This resulted in a temporary increase in the neurological deficit by two dermatomes. Fortunately during surgery the Adamkiewicz artery was preserved. This intervention completely abolished the patient's complaints.

A quantitative assessment of microvessel ultrastructure in C6 astrocytoma spheroids transplanted to brain and to muscle

Normal blood vessels invading a growing neoplasm undergo dramatic changes in morphology. Whether vessel characteristics are dictated entirely by the tumor, or from developmental restrictions in normal vessels from which tumor vessels originate is not known. To address this question we challenged two morphologically different types of capillaries (brain and muscle) with the same tumor environment (C6 astrocytoma), and quantified the invading vessel morphology. A vascular spheroids of C6 astrocytoma cells were implanted singly into rat cerebral cortex or iliacus muscle. Microvessels from the tumor, peritumoral tissue and control tissue were examined ultrastructurally and quantified. Tumor vessels differed significantly from host vessels but not from each other, regardless of implantation site. Neoplastic vessels were thick-walled relative to normal host vessels, had low densities of mitochondria and vesicular structures, and had both fenestrations and enlarged junctional clefts characteristic of highly permeable vessels. Control brain vessels were typically thin-walled, had a high density of mitochondria, a low density of endothelial vesicles and continuous tight junctions. Control muscle vessels were thin-walled with a low density of mitochondria, high density of vesicles and junctional zones with occasional enlarged clefts. Peritumoral vessel morphology was intermediate between that of tumor and the corresponding control tissue. We propose that C6 astrocytoma cells influence invading endothelial cells to develop a permeable phenotype radically different from host tissue endothelium, and host vessel phenotype does not influence tumor vessel morphology.

Regional blood-to-tissue transport in an irradiated rat glioma model

To assess vascular permeability in intracerebral grafts of the 36B-10, F-344 rat glioma following 20 Gy 137Cs whole brain irradiation, the blood-to-tissue transport constant, K, of [14C]-alpha-aminoisobutyric acid (AIB) was measured with quantitative autoradiography. Mean, 90th percentile, and 95th percentile values of K were determined in individual tumors and in treatment groups. In 15-day-old unirradiated control tumors, mean, 90th percentile, and 95th percentile values of K were, respectively, 11.3, 18.4, and 20.8 ml kg-1 min-1. In 15-day-old tumors irradiated on Day 14 (Day 1 postirradiation tumors) the K values were 5.9, 9.4, and 10.4, all of which were significantly less than the respective control values (P less than 0.01). In 16-day-old tumors irradiated on Day 14 (Day 2 postirradiation tumors), the K values were 10.8, 15.0, and 16.0, respectively, none of which was significantly different from control tumors. Mean K values for Day 2 vs Day 1 postirradiation tumors (10.8 vs 5.9) yielded P less than 0.05, but the 90th percentile and 95th percentile values for Day 2 vs Day 1 yielded 0.05 less than P less than 0.10. Separate experiments measured AIB and 86RbCl uptake in 36B-10 cells in vitro 1 and 2 days following 20 Gy irradiation to assess whether this radiation dose reduced the capacity of tumor cells to trap AIB or Rb+. Irradiation did not reduce the accumulation of either tracer, but rather was associated with an increased accumulation of AIB. Therefore, the AIB transport data suggest that vascular permeability and/or surface area decreases significantly in the day following 20 Gy irradiation and that this decrease reverses by the second day following irradiation.

The relationship between the capillary structure and hemorrhage in gliomas

A 48-year-old man was admitted with the sudden onset of symptoms of stroke caused by hemorrhage in an oligodendroglioma. Despite surgery and antiedema treatment, the patient died. Histological evaluation revealed an oligodendroglioma with calcified capillaries of the retiform type. To further investigate this phenomenon, a total of 160 gliomas were reviewed: 90 glioblastomas multiforme, 30 oligodendrogliomas, and 40 astrocytomas. Sufficient data were available for clinical evaluation in 100 cases. Of these, 5% (two oligodendrogliomas and three glioblastomas multiforme) were related to clinically significant hemorrhages. Of the remaining cases, microhemorrhages were found in 53.0% of the glioblastomas, in 56.7% of the oligodendrogliomas, and in 10.0% of the astrocytomas. In each case reviewed, the capillaries were assigned to one of three groups: axial, retiform, or glomeruloid. Statistical analysis revealed a significant association between hemorrhages and retiform capillaries in all three types of tumors, except that in oligodendrogliomas the statistical significance held true when calcification of the capillaries was also present. Glomeruloid-type capillaries were only weakly associated with hemorrhages, and no association was found for axial capillaries. A large-scale prospective study is necessary to more precisely assess the role of each of the three types of capillaries in hemorrhages of gliomas. Based on data available so far, patients with glial tumors with retiform capillaries, confirmed on biopsy, should be carefully monitored to exclude possible intratumoral hemorrhage.

rCBF in brain tumours as measured by xenon enhanced CT

Heretofore, the rCBF of brain tumours has been measured by the 133Xe clearance method, but the resolving power of this method is limited and flow values measured by this method correlate poorly with the anatomical structure. On the other hand, our xenon-enhanced method has several advantages over the conventional isotope method and enables us to evaluate rCBF with a resolving power of 4 mm. With this method, we evaluated rCBF in 15 brain tumour cases and obtained the following results: Mean rCBF value of the tumour is a little lower than that of grey matter and higher than that of white matter with oedematous change. The xenon-enhanced method enables us to distinguish the demarcation between the tumour area and the surrounding oedematous area and offers useful information for determining the extent of resection in surgery. Mean lambda value of the tumour which is not obtainable in vivo by radionuclide scanning, was 1.02 +/- 0.06 for gliomas and 0.72 +/- 0.09 for metastatic tumours.

Cerebral and cerebellar uptake of 99mTc-(d,1)-hexamethyl-propyleneamine oxime (HM-PAO) in patients with brain tumor studied by single photon emission computerized tomography

The cerebral and cerebellar distribution of 99mTc-(d,1)-hexamethylpropyleneamine oxime (HM-PAO) was investigated by means of a rotating gamma camera in 12 patients with cerebral glioma. Using the corresponding contralateral region as control, reduced uptake of HM-PAO in the tumor region was demonstrated in 10 of the 12 patients. Reduced blood flow in a brain area remote from a circumscribed lesion reflects reduced activation following the interruption of afferent nervous pathways. Reduced HM-PAO uptake indicative of such diaschisis was demonstrated in the visual cortex contralateral to homonymous hemianopia in the two patients with this deficit. In the three patients with the most marked hemiparesis, the cerebellar hemisphere contralateral to the tumor showed significantly reduced HM-PAO uptake indicative of crossed cerebellar diaschisis. SPECT using commonly available gamma cameras and 99mTc-HM-PAO seems capable of depicting reduced flow in functionally inactivated brain areas, and may be clinically interesting as an alternative to more specialized techniques for the investigation of local cerebral blood flow.

A glial fibrillary acidic protein-expressing and tumorigenic cell line derived from an avian sarcoma virus-induced rat astrocytoma

A permanent cell line, S635c15, was derived from an anaplastic astrocytoma induced by the Schmidt-Ruppin strain of avian sarcoma virus (ASV) in a female F-344 rat. Persistent expression of the astrocytic differentiation protein, glial fibrillary acidic protein (GFAP), was detected both in cultured cells after 100 passages in vitro and in transplanted tumors. Subcutaneous and intracerebral transplantation of S635c15 cells in syngeneic rats resulted in a 100% tumor incidence and a reproducible mortality distribution. S635c15 cells formed discrete masses after subcutaneous injection but grew intracranially as infiltrative lesions. Tumor blood flow and blood-to-tissue transport studies yield comparable values to other rat glioma models; S635c15 intracranial tumors proved to be a homogeneous model with little variation within and between tumors with respect to morphology, GFAP expression, blood flow, and permeability. This cell line provides a GFAP-expressing brain tumor model that extends the use of autochthonous ASV-induced astrocytomas by allowing in vitro and in vivo studies. It may be useful for further studies in neurobiology and brain tumor biology, diagnosis, and therapy.

Blood flow and oxygen utilisation in the contralateral cerebral cortex of patients with untreated intracranial tumours as studied by positron emission tomography, with observations on the effect of decompressive surgery

Using positron emission tomography, regional cerebral blood flow and oxygen utilisation were measured in the contralateral cortex of 14 patients with a variety of intracranial tumours. A comparison was made with cortical values derived from 14 normal controls. Compared with normal subjects, patients with brain tumours had a significant reduction in oxygen utilisation and blood flow in their contralateral cortex. Decompression resulting from craniotomy and biopsy, led to a partial reversal of this cerebral hypofunction.

Concurrent measurements of blood flow and transcapillary transport in avian sarcoma virus-induced experimental brain tumors: implications for chemotherapy

A blood-to-tissue transfer constant, K, and tissue blood flow, F, were measured concurrently in seven rats with a total of 19 separate brain tumors induced by intracerebral inoculation of avian sarcoma virus. Regional and local measurements of K and F were obtained using double-label quantitative autoradiography with alpha-[14C]aminoisobutyric acid and [131I]iodoantipyrine, computerized microdensitometry and image analysis. Apparent tissue extraction fractions and capillary permeability-surface area products were calculated for different tumor regions, brain adjacent to tumor and tumor-free brain. The following observations were made: five histological categories of the tumors were found; significant local and regional variations of both K and F were typical in each group, resulting in marked regional variability of permeability-surface area products but more uniform values of apparent extraction fraction; the values of F, K, permeability-surface area products and apparent extraction fraction correlated poorly with morphological features of the tumors (necrosis, cellularity, cytology, location and size); the extraction fraction of alpha-aminoisobutyric acid was usually highest in tumor centers and then decreased in a gradient from tumor periphery through adjacent brain; and regardless of classification or histological features, capillary permeability and surface area, and not tissue perfusion or blood flow, seem to determine the blood-to-tissue transport processes (delivery of bloodborne materials) in most regions of these experimental brain tumors. An operational pharmacokinetic model of drug concentration in tumor tissue is developed and the results of our analysis indicate that increases in capillary permeability such as measured in these studies would not be sufficient to deliver adequate amounts of water-soluble drugs with short plasma half-lives to tumor tissue.

Microvascular permeability in induced astrocytomas and peritumor neuropil of rat brain. A high-voltage electron microscope-protein tracer study

Brain tumors, benign and malignant, are characteristically more permeable to various types of tracer molecules than the neuropil in which they are embedded. Impermeability of brain neuropil capillaries is imparted by the blood-brain barrier, the anatomic basis of which is the network of interendothelial zonulae occludentes that seal capillary endothelial cells. To explore both the vascular elements of brain neoplasms and the route of tracer extravasation from them, as well as the possible effects of brain tumors on the permeability of peritumoral neuropil capillaries, brain tumors were induced in newborn Wistar rats by intracerebral (i.c.) injection of C-6 astrocytoma cells. The protein tracer horseradish peroxidase (HRP) was injected systemically into both normal and tumor-bearing rats to mark the pathway along which it flowed into the tumor parenchyma tissue spaces, and to signal any concomitant tracer loss from the tumor extracellular compartment or peritumoral brain capillaries, into the neuropil extracellular milieu. Electron-microscopic examination of thin plastic sections of tumor and peritumoral neuropil revealed massive extravasation of tracer into the tumor tissue spaces, but none was seen outside of the capillaries in the surrounding brain neuropil. Zonulae occludentes of both tumor capillary endothelium and brain capillary endothelium were devoid of tracer and judged tight (sealed). Tracer was seen in pinocytotic vesicles in the highly attenuated endothelium of tumor capillaries and also in cytoplasmic vesicles within the tumor cells. The peritumoral and contralateral neuropil capillary endothelium exhibited reaction product-filled pinocytotic vesicles and vesiculo-tubular conduits. Often, one end of a HRP-filled vesiculo-tubular channel appeared continuous with either the luminal or abluminal plasmalemma. High-voltage electron microscopy of these conduits often showed them to be continuous with both luminal and abluminal surfaces of the endothelium, thus forming a continuum across the capillary wall. In addition, these transendothelial channels, clearly constituted as chains of fused vesicles, were often seen in close proximity to, or fused with, dense bodies in the endothelial cytoplasm. In spite of the presence of HRP-filled structures in the peritumoral neuropil capillary endothelium of tumor-bearing rats, no evidence of tracer extravasation from these vessels was apparent. These results suggest that although peritumoral and contralateral neuropil capillaries possess the machinery for extravasation of tracer, likely as a response to the presence of the neoplasm, tracer is not lost but, instead, is degraded by endothelial enzymes.(ABSTRACT TRUNCATED AT 400 WORDS)

The vasculature of experimental brain tumours. Part 4. The quantification of vascular permeability

In order to quantify changes in vessel permeability seen previously in experimental astrocytomas produced in rats by an intracerebral injection of cultured neoplastic glial cells, the flux of mannitol across the vascular endothelium from the blood into the normal brain or tumour tissue was measured using a specially devised technique by which a steady level of radioactively labelled mannitol can be achieved rapidly and maintained in the bloodstream. This is done by a continuous injection given at a rate which is adjusted by a predetermined programme so as to replace the tracer at the rate at which it has been found to leave the circulation in previous experiments. In separate experiments on both tumour-bearing and control rats steady levels of the tracer were maintained in the circulation for progressively longer times of up to 30 min. The kinetic parameters of the process gave estimates for the apparent transfer constant of mannitol across the vascular endothelium and of the size of the extravascular extracellular mannitol space in the tumours. The apparent transfer constant for the movement of mannitol across the blood-brain barrier was increased more than a hundred-fold in the region of the tumour compared to the values for the brain of control rats or that of tumour-bearing rats remote from the tumour site. The extracellular extravascular space within the tumour was estimated to be 22%, somewhat larger than accepted normal values.

[Relation between the protein composition of glial tumors and various clinico-morphologic indices]

The work was concerned with the study of 57 gliomas, among which were 30 glioblastomas, 20 astrocytomas, and 7 oligodendrogliomas. Specimens collected from 26 patients who underwent operation for severe craniocerebral trauma, meningioma, and carcinoma metastasis were examined as controls. The proteins of the tumor tissues and those of the brain matter surrounding the tumor and of normal brain matter were fractionated in polyacrylamide gel. It was found that the amount of water soluble protein, both in the total protein content and in all its fractions, was much greater in the glial tumors than in normal brain matter. The effect of 11 factors on the tissue protein composition was studied by factor analysis. The histological structure and extent of vascularization of the tumor as well as the presence of intracranial hypertension were found to produce the highest effect on the fractional distribution of the proteins.

The vasculature of experimental brain tumours. Part 3. Permeability studies

The aim of this work was to elucidate the direction and time-course of transport processes which may affect the accumulation of oedema associated with experimental brain tumours. Astrocytomas were produced in BD-IX rats by intracerebral injection of cultured neoplastic glial cells. The cell line used was cloned from a culture of a primary mixed glioma induced by transplacental administration of N-ethyl-N-nitrosourea (ENU). At various times after cell injection the protein tracer horseradish peroxidase (HRP) was given to tumour-bearing rats, either intravenously or into the lateral ventricles of the brain. The movement of the HRP into tumours and surrounding brain either from blood or from ventricular cerebrospinal fluid (CSF) was studied by light and electron microscopy at various intervals after the injection of the tracer. The time-course of subsequent clearance of the HRP from the tumours and surrounding brain was also investigated. After intravenous injection, HRP rapidly penetrated all vascularized tumours and became evenly distributed within 10-20 min. The HRP remained present in sufficient quantity within the tumours to maintain this intensity for several hours, after which it gradually disappeared, showing no reaction product after 12 h. After intraventricular injection, HRP penetrated periventricular brain tissue up to a maximal distance 1-2 mm within 2 min, and the reaction product remained visible in this region for at least 20 min. In all tumour-bearing animals, HRP penetrated further into periventricular tumour tissue than into adjacent brain tissue. In large tumours HRP reaction product was seen up to 7 mm from the ventricular ependymal lining, although permeation to this distance took up to 10 min.

Regional blood flow in ethylnitrosourea-induced brain tumors

Regional blood flow was measured in experimental brain tumors using iodoantipyrine labeled with carbon 14 and quantitative autoradiography. A total of fifteen oligodendrogliomas, sixteen mixed gliomas, one astrocytoma, one ependymoma, and three malignant schwannomas were studied in 9 rats. The mean tumor blood flows for all glioma classifications were similar, averaging 45 +/- 3 (standard error of the mean) ml . hg-1 . min-1. Flow was fairly uniform within individual oligodendrogliomas and there was no apparent correlation between blood flow and tumor size or location. The mixed gliomas were larger than the oligodendrogliomas and had a wider range of blood flow. Small focal areas of necrosis were observed in 7 mixed gliomas, and low flows were usually measured in these regions; these flows were not always the lowest regional values measured within the mixed gliomas or total group of tumors, however. Small tumor regions with increased vascularity, frequently with endothelial cell proliferation, were observed in oligodendrogliomas and to a greater extent in mixed gliomas; these regions were correlated with small elevations in blood flow (10 to 15 ml . hg-1 . min-1) in comparison with surrounding tumor tissue. Brain adjacent to tumor usually had higher blood flows than that in tumor periphery. Hemispheric differences in blood flow related to the site of primary tumor growth were not observed.