Protection against ischemia: a physiological function of the renin-angiotensin system.

The renin-angiotensin system (RAS) is involved in a complex mechanism that serves to preserve the blood supply to organs so that they can maintain cellular function. Angiotensin II exerts this effect, independently of the blood pressure generated, through two time-related events: a fast opening of the reserve collateral circulation and a much slower response of new vessel formation or angiogenesis. This effect is observed in rats with ligation of the abdominal aorta and in gerbils with abrupt or progressive unilateral carotid artery ligation. Inhibition of the angiotensin-converting enzyme (ACE) or the angiotensin II receptor represses this effect, and it appears that it is mediated through a non-AT1 receptor site of angiotensin II. Many tumors, both benign and malignant, express renin and angiotensin. It seems that the stimulating action of angiotensin II on angiogenesis could also be involved in preserving the blood supply to tumor cells. Administration of converting enzyme inhibitors increases survival and decreases tumor size in tumor-bearing rats. These observations support the hypothesis that the RAS, directly or indirectly, is involved in situations in which the restoration of blood supply is critical for the viability of cells and that it is present not only in normal but also in pathological conditions such as tumors. In view of the ubiquitous presence of renins and angiotensins, it is also likely to be involved in other conditions, such as inflammation, arthritis, diabetic retinopathy, and retrolental fibroplasia, among others in which angiogenesis is prominent. In addition, angiotensin II could be involved, through the counterbalance of the AT1 and AT2 receptors, in the rarefaction of blood vessels as an etiologic component of essential hypertension.

Cost and survival analysis of metastatic cerebral tumors treated by resection and radiation.

The surgical treatment of metastatic brain tumors remains controversial, primarily because of the limited prognosis of patients with metastatic cancer. The cost effectiveness of even standard therapies is of increasing concern to third-party payers. We reviewed the records of patients who had a single metastatic brain tumor resected at the Medical Center Hospital of Vermont (a referral center in a rural state) since cost data recording began. The 32 patients ranged in age from 35 to 77 years, with a 2.2:1 female-to-male ratio. Thirty-four percent of tumors originated in the lung, 15.6% were renal, 12.5% were breast, 12.5% were gynecological, 9.4% were gastrointestinal, and 9.4% were ultimately of unknown origin. Thirty-one tumors were completely resected; 30 patients were irradiated, most after surgery (mean dose, 3,908 +/- 1,250 cGy). Karnofsky scores improved from 80 +/- 11 to 88 +/- 16 postoperatively (P = 0.0038, one-tailed paired t-test). Patients were hospitalized an average of 8.22 +/- 6.26 days postoperatively, with total operative and postoperative charges of $19,190 +/- 5,684, noninclusive of radiotherapy. The expected median survival of all patients was 26 months (Kaplan-Meier estimate). The presence of disseminated disease was not significantly correlated with survival (P = 0.237). The number of postoperative days was more for patients with disseminated disease (P = 0.0274), but not for patients with infratentorial tumors (P = 0.6991). Age higher than the median was not correlated with an increased number of postoperative days (P = 0.1366) nor was a preoperative Karnofsky score of 70 or less (P = 0.1382).(ABSTRACT TRUNCATED AT 250 WORDS)

Solitary eosinophilic granuloma of the frontal lobe.

Solitary intracranial eosinophilic granulomas are rare and most frequently involve the hypothalamus. We report an unusual case of solitary eosinophilic granuloma of the frontal lobe in a patient without evidence of systemic disease. Previously reported cases of solitary intracranial nonhypothalamic lesions are reviewed, and the clinical, radiographic, and histological features of this case are discussed.

Inhibition of epidermal growth factor receptor-associated tyrosine kinase blocks glioblastoma invasion of the brain.

OBJECTIVE: Glioblastoma multiforme is a malignant primary brain tumor associated with short patient survival despite aggressive treatment, in part because of its propensity to aggressively infiltrate into brain tissue. Glioblastoma multiforme is also unique because it is the only nonepithelial human tumor for which excessive activation of epidermal growth factor receptor (EGFR) has been consistently linked to tumor growth and patient survival, and EGFR activation promotes glioblastoma multiforme infiltration in vitro. METHODS: Cocultures of human glioblastoma spheroids (derived from three separate patients) and fetal rat brain aggregates were examined for infiltration using confocal microscopy, in the presence of 0 to 100 mumol/L genistein, a tyrosine kinase (TK) inhibitor, and 3 mumol/L tyrphostin A25, a specific EGFR-TK inhibitor. RESULTS: Infiltration (not attachment) was completely inhibited by genistein at 10 mumol/L, the IC20 for monolayer growth inhibition in two cell lines. Tyrphostin A25 at 3 mumol/L (the IC20 for monolayers) reduced invasion in a third cell line from 38.8 +/- 6.1% invasion-hour per hour (n = 5) to 2.9 +/- 1.2% invasion-hour per hour (n = 6) (P = 0.0002, two-tailed t test, 93% inhibition), and from 0.54 +/- 0.065% per hour (slope) to 0.028 +/- 0.018% per hour (P = 0.00001, 95% inhibition). Maximal percent invasion was reduced from 100 +/- 0 to 7.4 +/- 5.6% of the fetal rat brain aggregate. No change was detected in EGFR-associated tyrosine phosphorylation at those doses in monolayers by 32P immunolabeling, consistent with the known effects of low concentrations of TK inhibitors. An increase in expression of wild-type and truncated EGFR was demonstrated by Western blotting. Invasion was equally well inhibited by a monoclonal antibody to the high-affinity ligand binding domain of EGFR and not by antibody to an inactive domain. CONCLUSION: Our observations support the role of EGFR activation as a determinant by which glioblastoma invades normal brain tissue, and we show that invasion can be effectively inhibited at much lower concentrations of TK inhibitors than are necessary for growth suppression.

Inhibition of phospholipase C-gamma1 activation blocks glioma cell motility and invasion of fetal rat brain aggregates.

OBJECTIVE: Phospholipase C (PLC)-gamma is a cytosolic enzyme activated by several growth factor (GF) receptors (epidermal GF receptor [EGFR], platelet-derived GF receptor, and insulin-like GF 1 receptor), and its activation is associated with increased cell motility (but not cell proliferation) in nonglioma cell lines. Because up-regulated activation of EGFR has been consistently linked to poor patient survival in patients with glioblastoma multiforme (GBM) and because inhibition of EGFR activation by tyrosine kinase inhibitors prevents glioma infiltration in vitro, we hypothesized that inhibition of PLC-gamma activation would inhibit glioma cell invasiveness. METHODS: Our experimental model assesses tumor spheroid invasion of fetal rat brain spheroids by confocal microscopy. We treated U87 GBM spheroids, and those derived from a single patient, with the PLC inhibitor U73122. We also transfected rat C6 glioma cells with the PLCz complementary deoxyribonucleic acid coding for a dominant negative PLC-gamma1 src-homology-2/src-homology-3 peptide fragment, which blocks binding and activation of PLC-gamma1 by GF receptors. Two clones (C6F and C6E) were grown into spheroids and were tested for invasiveness in the spheroid model and for responsiveness to GFs in a standard in vitro motility assay. RESULTS: The infiltration rate of the patient GBM cell line overexpressing wild-type EGFR was reduced by 2 micromol/L U73122 from a slope (percent invasion/h) of 0.74+/-0.08 (with the inactive congener U73343) to 0.04+/-0.053 (P = 8 x 10(-7) by two-tailed t test, 92% reduction); the integral rate, another measure of invasion, was reduced from 49.7+/-13 percent-hours per hour to 13.6+/-12 (P = 0.002, 72% reduction). The U87 spheroid invasion rate was reduced by 0.5 micromol/L U73122 from 46.7+/-8.5 percent-hours per hour to 11.2+/-4.6 (P = 3 x 10(-5)); the slope decreased from 1.7+/-0.41 percent per hour to 0.35+/-0.14 (P = 0.0001). The C6F and C6E clones demonstrated attachment to and "surrounding" of the fetal rat brain aggregate but no true invasion by confocal or light microscopy. PLCz blocked the motility response to epidermal GF, platelet-derived GF, and insulin-like GF. There was a significant decrease in PLC-gamma1-associated tyrosine phosphorylation. CONCLUSION: These results support a key role for PLC-gamma activation as a common postreceptor pathway for GF-induced tumor infiltration and further identify PLC-gamma1 as a possible target for anti-invasive therapy for GBMs.

Intraventricular cryptococcal granuloma. Report of two cases.

Infection by Cryptococcus neoformans, a budding nonmycelial yeast, involves the central nervous system in 70% of patients at the time of diagnosis. Meningitis and meningoencephalitis are common manifestations of infection; solid granulomas occur but are unusual, and intraventricular granulomas are distinctly rare. Two cases of intraventricular cryptococcal granuloma are reported. The diagnosis and treatment of mass lesions due to cryptococcal infection are discussed, with special reference to intraventricular granulomas.

Creutzfeldt-Jakob disease probably acquired from a cadaveric dura mater graft. Case report.

A case of Creutzfeldt-Jakob disease (CJD) is reported in a 28-year-old woman who had received a cadaveric dural graft 19 months earlier after resection of a cholesteatoma. The circumstances of the case point to the graft as the most likely source of the disease. Cadaveric dura should be added to the list of materials that may transmit CJD, and it must be very carefully screened if it is used at all for grafting. Autologous tissue should be considered whenever possible.

The effect of AGM-1470 in an improved intracranial 9L gliosarcoma rat model.

Angiogenesis is a process fundamental to the growth of many solid tumours. Agents that inhibit angiogenesis may have a role in preventing tumour growth. AGM-1470, a synthetic analogue of fumagillin, has been shown to inhibit tumour growth in several extracranial solid tumour models. Its use has been reported to have minimal side effects. No studies have been reported using AGM-1470 in the treatment of an intracranial tumour. To determine the effect of AGM-1470 on an intracranial glial tumour, we used an improved implantation technique to place 80,000 9L tumour cells into the right caudate nucleus of 25 male Fischer 344 rats. Starting on the first post-implantation day, 12 animals received 30 mg kg-1 AGM-1470 via intraperitoneal injection every other day until death. Thirteen control animals received vehicle only. Evidence of intracranial tumour was apparent in 22/23 animals (96%). All animals treated with AGM-1470 experienced a progressive and significant weight loss when compared to controls. At day 17, treated animals retained 80.0 +/- 2.2% of their initial weight, (mean +/- SD) compared to 100.9 +/- 3.6% for controls (p = 2.25 x 10(-12); student's t-test). AGM-1470 had no effect on survival. Median survival in the treatment group was 24.5 days compared to 25 days in the controls (p = 0.95; Mann-Whitney). AGM-1470, although promising in extracranial tumour models, may not be as effective in controlling the growth of intracranial tumours, and its use is not without significant systemic effects. More studies are needed before this drug is used in human brain tumour trials.(ABSTRACT TRUNCATED AT 250 WORDS)

Normal pressure hydrocephalus: an analysis of aetiology and response to shunting based on mathematical modeling.

The dynamics which maintain the state of enlarged cerebral ventricles and normal intracranial pressures (normal pressure hydrocephalus) are not completely understood, making the response to cerebrospinal fluid diversion difficult to predict. Using our previously described mathematical model of intracranial physiology which allows nonlinear relationships of pressure, volume, and flow in 7 distinct compartments, we desired to determine factors which could be responsible for the development and maintenance of the steady state of normal pressure hydrocephalus. Using typical starting values for CSF volume, pressure, and flow, the model indicates that this condition cannot be sustained, in spite of high CSF outflow resistance, unless capillary flow resistance is elevated. This condition can be the result of arterial hypertension. The additional modeling of a CSF diversion device demonstrates predicted time courses for ventricular size reduction which are consistent with clinical observations. We conclude that certain vascular conditions may allow for the maintenance of an enlarged ventricular size, and that mathematical modeling can assist in identifying factors for clinical study that may maintain normal pressure hydrocephalus even after treatment by CSF diversion.

A mathematical model of the intracranial system including autoregulation.

Cerebral autoregulation plays an important role in the dynamic processes of intracranial physiology. This work develops a four-compartment, lumped-parameter model for the interactions of intracranial pressures, volumes, and flows as a test bed for examining the consistent inclusion of explicit autoregulation in mathematical models of the intracranial system. It is hypothesized that autoregulation of the blood supply from the arterioles to the capillary bed can be modeled by allowing the flow resistance at the interface of the artery and capillary compartments in the model to be a function of pressure rather than a constant. The functional dependence on pressure of this resistance parameter is not specified in advance, but emerges naturally from the assumed relationship between pressure differences and flows. Results show that a constant flow from the artery to the capillary compartment can be maintained by a flow resistance which is resistance which is directly proportional to the pressure difference between these two compartments. Oscillatory flow is reestablished in the model at the capillary-cerebrospinal fluid and capillary-venous interfaces.

Cost and outcome analysis.

The analysis of cost issues has become increasingly important in all fields of medicine. Understanding these economic analyses can make providers more cognizant of the ultimate health, economic, and social outcomes of their treatment decisions. The methodology of cost studies and the surgical costs of treatment of intracranial metastatic tumors warrant review. Costs of surgical and radiosurgical treatment are in the range of that for the care of other serious illnesses, but comparison of the available options is still sensitive to assumptions, and open to varied interpretations.

Inhibition of glioma invasion of fetal brain aggregates.

Glioblastoma multiforme is a malignant primary brain tumor associated with short patient survival in part because of the ability of individual cells to migrate significant distances into brain tissue. Invasion is a difficult process to model, because many such human tumors do not invade immunologically competent animal tissue, tumors grown in animals do not invade human tissue, and relevant human tissue substrates are not easily reproduced. We discuss models for examining invasion in vitro, and in particular review work using the tumor spheroid--fetal rat brain aggregate co-culture model, assessed with confocal microscopy and four-dimensional imaging. Quantitation of invasion in this model is discussed, as well as the invasion-inhibitory properties of tyrosine kinase (TK) inhibitors. The effects of receptor-specific tyrphostins strongly support a dominant role for Epidermal Growth Factor Receptor activation in this process and show that invasion can be effectively inhibited at much lower concentrations of TK inhibitors than is necessary for growth suppression. Inhibition of activation of the purported growth factor receptor second messenger phospholipase C- gamma 1, by pharmacological means and gene transfection, also profoundly inhibits the invasive properties of human glioblastoma and rat C6 glioma cells. We have assessed invasiveness in several human tumor specimens, which may provide information relative to prognosis and recurrence risk. Our data supports the concept of differential control of invasion and proliferation, and points to possible strategies for anti-invasive therapy for glioblastoma multiforme.

Spontaneous spinal epidural hematoma.

Two cases of the spontaneous occurrence of spinal epidural hematomas of the high thoracic area are reported. Both acute and subacute presentations of paraplegia are represented. Neither patient had experienced any significant antecedent trauma. No predisposing medical conditions were present. Both patients recovered to independent ambulation following timely operative intervention. The pertinent literature on spinal epidural hematomas is reviewed, and the differential diagnosis of this entity is discussed. The need for prompt diagnosis and surgical treatment to achieve the best neurological outcome is emphasized.

A model of embolic cerebral ischemia in the rat.

Experimental studies of embolic cerebral ischemia using the rat are limited by variability in the location, size, and frequency of lesions produced. A technique is described herein which improves the reliability of an established model. Eight male Sprague-Dawley rats underwent injection of the cervical internal carotid artery with 0.1 ml of 1-h-old fragmented autologous blood clot through an external carotid artery cannula. The pterygopalatine artery was ligated prior to embolization. At killing 2 h after embolization, clot was observed in the proximal middle cerebral and posterior cerebral arteries in all animals. Areas of reduced blood flow at 2 h postembolization were assessed by digital image processing of iodo-[14C]antipyrine autoradiographic images. No-flow and low-flow areas were measured for each of approximately 25 serial brain sections with a computerized bit-pad. Volumes were calculated and lesions localized by anatomical reconstructions. No animal sustained a hemorrhagic lesion. One animal sustained only a very small area of ischemia in the internal capsule. Of the remaining seven, all had large regions of ischemia in the middle cerebral distribution involving cortex and basal ganglia. Posterior cerebral involvement was observed in six of the seven animals as well. The contralateral hemisphere was unaffected. Volume values could be calculated for primary vascular distributions. Most variability occurred in the pattern of posterior cerebral involvement. The technique described produces a relatively consistent region of ischemia in the middle and posterior cerebral artery distributions in the rat and is a useful model for the study of cerebral ischemia.

The effect of intravenous tissue-type plasminogen activator in a rat model of embolic cerebral ischemia.

Thrombolytic agents may be useful in the treatment of cerebral ischemia caused by arterial thrombosis or embolic occlusion. A trial of intravenous human tissue-type plasminogen activator (rt-PA) was carried out in seven male Sprague-Dawley rats subjected to embolic cerebral ischemia, with eight control animals. One-hour-old autogenous blood clot was injected into the internal carotid artery. A 30-minute infusion of 10 micrograms/kg/minute of rt-PA or saline followed. Areas of ischemia at two hours post-embolization were assessed by digital image processing of serial iodo-14C-antipyrine autoradiographic images. The volumes of "no-flow" (NF) and "low-flow" (LF) regions were calculated. One animal in each group suffered no detectable ischemia; the remainder had well-defined regions of middle and posterior cerebral artery ischemia. No animal sustained a hemorrhagic lesion. Treatment produced no noticeable effect on the patency of cervical vessels. Total NF and LF volumes were less for the treated group but did not reach statistical significance by t-test. In middle cerebral distribution sections, however, LF volume was significantly less (p less than 0.05) for treated animals (150 vs. 191 mm3), primarily due to a more significant decrease in LF volume in the anterior-middle cerebral overlap zone (47 vs. 90 mm3; p less than 0.025). Fibrinogen levels were not altered by drug treatment (p greater than 0.30).

Percutaneous access to the anterior spinal canal through a cervical disk.

We describe a CT-guided percutaneous technique for aspiration of an anterior intraspinal fluid collection through a cervical disk. The approach is identical to that of cervical diskography or percutaneous cervical diskectomy, with intentional placement of the needle tip in the spinal canal. This procedure had no adverse effects and avoided an open operation to exclude spinal cord compression.

Sublethal percussion trauma in vitro causes a persisting derangement in the nonthrombogenic properties of brain endothelial cells.

The delivery of a blow to the head represents a transfer of energy, part of which manifests itself as a short-lived pressure change within the skull. An in vitro model was developed to test whether cerebral endothelial cell hemostatic function is altered with exposure to this type of pressure event. Human cerebral microvascular endothelium (HCME) cells were subjected to rapid (2-5 msec) changes in pressure (delta atmosphere = 1.2-10), the sublethal range defined (delta atmosphere < or = 6.5), and the nonthrombogenic status of sublethally percussed HCME cells assessed using the adherence of alpha-thrombin activated platelets as an indicator. The HCME cells had lost their normal capacity to suppress adherence of activated platelets when evaluated 1 hour or 24 hours after percussion. Adherence of activated platelets to percussed HCME cells was blocked by the addition of PGI2, an inhibitor of platelet adherence, when evaluated at 1 hour but not 24 hours after percussion, indicating that percussed HCME cells were undergoing further derangement of their nonthrombogenic mechanisms. Percussed HCME cells cultured for 24 hours in medium containing scavengers of oxygen free radicals recovered their capacity to block platelet adherence. We conclude that sublethal percussion immediately compromises the nonthrombogenic character of HCME cells and initiates the development of a persisting prothrombotic state in HCME cells. This derangement appears linked to increased production of reactive oxygen species by percussed HCME cells.

Brain tumor invasion rate measured in vitro does not correlate with Ki-67 expression.

The need for more accurate prediction of the biological behavior of brain tumors has lead to the use of immunohistochemical methods for assessment of proliferating cell nuclear antigens such as Ki-67. There is a variable association of glioma Ki-67 labeling index with patient survival. Brain invasion by individual tumor cells also defines biological aggressiveness, and can be assessed in vitro. Further, proliferation and migration seem to be mutually exclusive behaviors for a given cell at a point in time. We studied the relationship between Ki-67 labeling index and invasion rate in a group of 10 gliomas, and 2 meningiomas. Human tumor spheroids obtained from operative specimen were co-cultured with fetal rat brain aggregates, and invasion rate was measured by confocal microscopic observation. There was no correlation between two measures of invasion and Ki-67 labeling. This finding supports the dichotomous nature of glioma proliferation and invasion, and may in part explain the limited usefulness of proliferation marker labeling.

Four-dimensional analysis of human brain tumor spheroid invasion into fetal rat brain aggregates using confocal scanning laser microscopy.

The advent of confocal microscopy and fluorescence probes has made possible the routine visualization of the complex three-dimensional structures of thick fixed or live specimens. Four-dimensional (4-D) imaging of biological specimens (three-dimensional image reconstruction of the same living sample at different time points), remains a seldom-used application of confocal microscopy. In the present study we used 4-D imaging techniques to quantitate the invasion of human brain tumor spheroids into fetal rat brain aggregates (FRBAs), using the vital fluorescence membrane dyes, 3, 3'-Dioctadecyloxacarbocyanine perchlorate (DiO) and 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI) as visualization probes. We found invasion patterns similar to the in vivo behavior of these tumors in the brain. Glioblastoma spheroids showed diffuse and circumscribed infiltration accompanied by cystic degeneration or necrosis of FRBAs. Spheroids from cerebral metastasis, however, showed a sharp delimitation of the invasive margin, and did not penetrate the FRBA beyond a depth of 55 microns. Measured rates of glioblastoma invasion varied with the tumor specimens examined. The slopes of the mid-portions of plots of % infiltration vs. time (hours) for four glioblastoma cell lines were 1.7 +/- 0.21 (SD), 0.67 +/- 0.11, 1.4 +/- 0.22 and 1.3 +/- 0.18. We conclude that confocal microscopy with vital fluorescence probes is a practical method that allows for close monitoring and quantitation of the process of invasion in live tissue preparations, and may be used for assessing the in vitro effects of various tumor treatments.