The p16/Cdkn2a/Ink4a gene is frequently deleted in nitrosourea-induced rat glial tumors

The present study investigates nitrosourea-induced rat (Rattus norvegicus) glioma cell lines for the functional status of the p16/Cdkn2a/Ink4a gene, which encodes the p16 cdk4 inhibitor and the alternative reading frame protein, p19ARF. We detected homozygous deletions of the p16/Cdkn2a/Ink4a gene locus in 4 of 5 glioma cell lines (C6, F98, RG2, and RGL.3), but not in the 9L gliosarcoma cell line or in a rat primary fibroblast cell line. RT-PCR demonstrated expression of the p16 and p19ARF mRNAs only in 9L cells and in rat fibroblasts. Comparative genomic in situ hybridization showed that the copy number of rat chromosome RNO5 was not altered in any of the glioma cell lines investigated, indicating that the deletions result from a discrete loss in the region of the p16/Cdkn2a/Ink4a locus. This is the first report of p16/Cdkn2a/Ink4a deletions present in nitrosourea-induced rat glioma cell lines. Since this genetic alteration is also commonly observed in human malignant glial tumors, our results validate the use of chemically induced rat glioma cell lines as an experimental model in the development of gene therapy strategies.

Induction and characterization of human glioma clones with different radiosensitivities

To facilitate investigation of the molecular mechanisms of tumor cell radiosensitivities, we have generated a set of clones with different radiosensitivities from a human glioma cell line U-251 MG-Ho. Forty-four colonies were isolated by subjecting parent cells to the mutagen N-methylnitrosourea and then irradiating these cells with increasing doses of x-rays. About half of the clones displayed different radiosensitivities than the parent cells. We selected one of the most sensitive clones (X3i) and one of the most resistant clones (Y6) for further study. Isoeffective doses for these two clones differed by about a factor of 1.7; the relative radiosensitivities of both clones were stable for at least 30 cell culture passages. These two clones do not differ significantly in either the induction or repair of radiation-induced DNA double-strand breaks as measured by pulsed field gel electrophoresis. Radiation-induced apoptosis measured by terminal deoxynucleotide transferase-mediated dUTP nick end labeling assay and micronucleus formation were similar in both clones. However, potentially lethal damage repair was greater in the radioresistant Y6 clone than in the radiosensitive X3i clone as determined by colony-forming efficiency assay.

Distribution and activity of transglutaminase in rat brain carcinogenesis and in gliomas

Tissue transglutaminase is a calcium-dependent enzyme which may influence cell morphology, cytoskeletal processes and membrane functions. During rat brain carcinogenesis induced by transplacental administration of N-ethyl-N-nitrosourea to BD IX rats, cytosolic tissue transglutaminase activity was increased by about 140% at 30 days of extrauterine life and returned towards the control values at 3-5 months. In the particulate fraction, enzyme activity progressively increased, reaching values similar to those present in the developed gliomas. Tissue transglutaminase activity in gliomas had a behavior inverse to that observed in controls, with a decrease (about 50%) in the cytosol and a marked increase (380%) in the particulate fraction, indicating a redistribution of enzyme activity.

Laminin receptor alpha6beta4 integrin is highly expressed in ENU-induced glioma in rat

Laminins and their receptors influence neoplastic growth and invasiveness. We recently reported the abnormal expression of a laminin receptor, alpha6beta4 integrin, in human astrocytomas. To further investigate the role of alpha6beta4 in gliomas, we produced an experimental model of glioma in rat by transplacental ethylnitrosourea (ENU) administration. This animal model allowed us to study the timing of alpha6beta4 expression during tumor development and the topography of expression in the tumor and the surrounding tissue. Immunohistochemistry, in situ hybridization, and immunoprecipitation studies demonstrated that alpha6beta4 heterodimer forms in experimental gliomas, and confirmed that alpha6beta4 is expressed diffusely in neoplastic cells and reactive astrocytes, but not in normal glia surrounding the tumors. Interestingly, alpha6beta4 was expressed from the early phases of tumor development, and more highly expressed by cells in the proliferative centers of the tumors. Both neoplastic cells and reactive astrocytes also expressed the glial growth factor (neuregulin) receptors, Erb-B2 and Erb-B3. Finally, alpha6beta4 expression was reduced in a subset of tumor blood vessels. Thus, this study suggests a potential role for alpha6beta4 in the pathogenesis of gliomas. Furthermore, this is the first description of altered integrin expression in experimental gliomas; transplacental ENU-induced gliomas in rat will provide a useful model to study the role of altered adhesion in the pathogenesis of human gliomas.

Quantitative tissue sodium concentration mapping of the growth of focal cerebral tumors with sodium magnetic resonance imaging

Tissue sodium concentration (TSC), as determined by in vivo 23Na magnetic resonance imaging (MRI) and the ex vivo classical 22Na radionuclide dilution assay (RDA), has been compared in a rat model of a focal glioma. The 23Na MRI method used a three-dimensional, twisted projection acquisition scheme at short echo time to minimize signal losses from relaxation of transverse magnetization. Calibration standards within the field of view allowed quantification of the sodium signal in terms of a TSC after correction for B1 nonuniformity and tissue water concentration. The 23Na MRI method measured focally increased TSC values in tumors that were equivalent statistically to the destructive 22Na RDA method. The noninvasive 23Na MRI method provided a quantitative means with which to monitor focal brain tumor growth.

Glial tumors in the MNU rat model: induction of pure and mixed gliomas that do not require typical missense mutations of p53

Gliomas were induced in adult male Sprague-Dawley rats by continuous exposure to 100 ppm of N-nitrosmethylurea (MNU) in drinking water. Latency periods for such tumors were 20 and 50 weeks following completion of exposure intervals of 20, 15, and 10 weeks, respectively. Based on histomorphology and the pattern of GFAP immunoreactivity, a large percentage of MNU-induced tumors (>40%) were anaplastic mixed gliomas, having both neoplastic astrocytic and oligodendroglial components. Typical oligodendrogliomas and astrocytomas also occurred less frequently. Unlike the majority of tumors induced by ethylnitrosourea (ENU), MNU yielded glial tumors that did not express synaptophysin. Anaplastic mixed gliomas and glioblastoma multiforme (GBMs) had no missense p53 mutations in the commonly mutated exons 4 through 8 and did not overexpress wild-type p53, suggesting that MNU-induced oncogenesis in rat brain tumors may not require inactivation/alteration of the p53 tumor suppressor gene. The K-ras gene was also analyzed and found to have no activating mutations in brain tumors. This model is suitable for studying genetic events leading to the majority of gliomas that apparently express functional p53.

Effect of dietary vitamin A or N-acetylcysteine on ethylnitrosourea-induced rat gliomas

It is our hypothesis that low grade gliomas are the glial counterparts of other precancerous lesions such as colon polyps and, therefore, suitable targets for chemoprevention. Steps in the molecular progression of gliomas have been described, indicating that an accumulation of abnormalities is required for progression to a high grade and interruption of this progression might be possible. An animal model of chemical glial carcinogenesis was used to test this hypothesis. Pregnant rats were injected intravenously with ENU (ethylnitrosourea) on the 18th day of gestation to induce gliomas in the offspring, which were randomized to receive control diet, diet supplemented with vitamin A palmitate, or diet supplemented with N-acetylcysteine. Animals exposed to ENU and receiving a control diet developed brain tumors and had a shortened life expectancy compared with rats unexposed to ENU. The animals treated with NAC showed no statistically significant delay in the time to tumor and no change in the histologic grade of the tumors when compared with animals receiving control diet, but the time to death from any cause of NAC treated animals differed significantly from untreated animals. Animals receiving high dose VA had statistically significantly prolonged time to tumor, survived significantly longer than untreated animals, but had no reduction in the total number of tumors or change in the histologic grade of their tumors. The theoretical basis of these results is likely due to the putative mechanism of action of these agents. These data indicate that glioma chemoprevention is possible and deserves further exploration.

Glial tumoral proliferation induces changes in the state and physical properties of water during ENU-induction of brain tumors in rats

Modifications of water state were analyzed during ethylnitrosourea-induction of brain tumor in rats. Four different steps were identified in the cancerization process according to NMR and histological findings. Two analogies were observed in the pattern of bound' water at decreasing temperatures: first the pattern was similar in tumor area and white matter, second the pattern was similar in the same area of normal brain tissue and cortical gray matter. This phenomenon, which corroborates previous reports on liver cancerization, points out that pathological proliferation of glial cells, and their progressive organization into multiple layers, is accompanied by a transformation of water properties at the cellular level.

Drug resistance and apoptosis in ENU-induced rat brain tumors treated with anti-cancer drugs

To cast light on the mechanisms of drug-resistance, experimental brain tumors were immunohistochemically evaluated for expression of glutathione S-transferase (GST)-alpha, mu, pi, p-glycoprotein and apoptosis-related factors, such as bcl-2 and p53, as well as by the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labelling (TUNEL) method. Rat brain tumors induced by means of prenatal exposure to ethylnitrosourea (ENU) were treated with 1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3-(2-chloroethyl)-3-nitrosourea hydrochloride (ACNU) and/or vincristine. Tumors more than 2 mm in size were considered to be drug resistant. The expression of GST-mu was strongly positive in ACNU-treated brain tumors, while p-glycoprotein was overexpressed in vincristine-treated brain tumors. Neither p53 nor bcl-2 expression directly correlated with apoptosis identified by TUNEL method, but tumors lacking apoptotic cells always demonstrated the expression of either GST-mu or p-glycoprotein. These results indicate that tumors resistant to chemotherapy might not be susceptible to induction of apoptosis, and therefore that mechanisms of drug resistance are related to programmed cell death in brain tumors.

Nutritional factors in the etiology of brain tumors: potential role of nitrosamines, fat, and cholesterol

Several possible risk factors for brain tumors have been suggested in the past, including N-nitroso compounds, but with the exception of ionizing radiation, none has been consistently confirmed. The present study was aimed at assessing the influence of nutritional factors, including N-nitroso compounds, in the etiology of brain tumors, specifically gliomas and meningiomas. One hundred and thirty-nine cases with confirmed brain tumors diagnosed between 1987 and 1991 in central Israel and 278 controls matched according to age, sex, and ethnic origin were interviewed. Nutritional data were obtained using a semiquantitative food frequency approach. A significant positive association for both types of brain tumors was found with high protein intake (odds ratio (OR) = 1.94, 95% confidence interval (CI) 1.03-3.63), while intake of sodium was inversely related to both types of brain tumors (OR = 0.52, 95% CI 0.31-0.87). Increased consumption of total fat and cholesterol was inversely related to gliomas (high intake of fat: OR = 0.45, 95% CI 0.20-1.07; high intake of cholesterol: OR = 0.38, 95% CI 0.14-1.01). However, neither fat intake nor cholesterol intake was significantly related to the risk of meningiomas. Although N-nitroso compounds were not found to be directly associated with brain tumors, the data suggested the presence of an interaction between the effects of N-nitroso compounds and protein intake and between N-nitroso compounds and cholesterol intake. The data suggest that dietary factors may play an important, though yet undefined, role in the development of brain tumors.

Retrospective assessment of occupational exposure to chemicals in community-based studies: validity and repeatability of industrial hygiene panel ratings

BACKGROUND

Occupational hygiene panels are increasingly being used to rate retrospective occupational exposures to chemicals in community-based studies. This study aimed to assess the validity, reliability and feasibility of using such an expert panel in a brain tumour case-control study.

METHODS

A panel of five experts was recruited to rate exposure to 21 chemicals for 298 job descriptions to investigate the level of agreement. Validity was assessed by comparing the ratings of the experts for 49 of the jobs with objective quantitative exposure data which existed for these jobs. Repeatability was assessed by comparing the results for 50 resubmissions.

RESULTS

Specificity was high for reporting that exposure occurred (all above 90%), but sensitivity was variable with values between 48% and 79%. Weaker validity was found for rating exposure level and exposure frequency. The raters showed the greatest inter-rater agreement for exposure to three of the 21 chemicals considered (kappa = 0.64 for cutting fluids, kappa = 0.57 for welding fumes and kappa = 0.42 for lubricating oils). Intra-rater reliability, based on the 50 resubmitted jobs, was fair to good (kappa = 0.46, 0.73).

CONCLUSIONS

The potential effect of exposure misclassification from using expert panels was quantified and found to be a significant source of bias. The optimum situation occurred where three of the five raters concurred, where an odds ratio of 2.2 was observed for a true odds ratio of 4.0. Future studies which plan to use expert panels should screen the experts for their suitability by validating their performance against jobs with known exposure data.

Effects of basic fibroblast growth factor on in vivo cerebral tumorigenesis in rats

OBJECTIVE

In vitro evidence suggests that basic fibroblast growth factor (bFGF) promotes tumor cell proliferation and angiogenesis. In this study, we evaluated the early and delayed effects of recombinant human bFGF on the early and late phases of in vivo, in situ tumorigenesis in rats.

METHODS

Brain tumors were induced by transplacentally exposing fetal rats to N-nitrosoethylurea on Day 17 of pregnancy. On postnatal (PN) Day 60 or 90, N-nitrosoethylurea-exposed rats underwent stereotactic intraventricular implantation of Gelfoam saturated with bFGF (60 micrograms) or vehicle; the rats were killed 4 days (early group) or 30 days (delayed group) later. The early and delayed effects of bFGF on the early phase of tumorigenesis (PN Day 60) were evaluated in 14 and 10 rats, respectively; early and delayed effects on the late phase of tumorigenesis (PN Day 90) were evaluated in 12 rats each.

RESULTS

Histological examination 30 days after implantation showed a significantly higher tumor rate in rats that had been treated with bFGF on PN Day 90, compared with vehicle-treated control rats (P < 0.05); furthermore, in the bFGF-treated animals there was significantly greater intratumoral and periventricular glial fibrillary acidic protein expression, as determined immunohistochemically. Increased vascularity in the tumor ipsilateral to the implant was found in 2 of 14 rats that had been treated with bFGF on PN Day 60.

CONCLUSION

These findings support in vitro evidence that bFGF and its receptor complex are implicated in the genesis and progression of N-nitrosoethylurea-induced brain tumors in this animal model.

VEGF and bFGF mRNA are expressed in ethylnitrosourea-induced experimental rat gliomas

1. Which angiogenic growth factors actually mediate tumor growth in ethylnitrosourea (ENU)-induced gliomas in rats was examined. 2. In situ hybridization histochemistry with digoxigenin-labeled oligonucleotide probes was used to investigate the cellular expression and distribution of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) mRNAs in ENU-induced gliomas. 3. Both VEGF and bFGF mRNAs were not detected in normal gial cells but in ENU-induced glioma cells. 4. Our results suggest that the growth of ENU-induced glioma may be regulated by multiple angiogenic growth factors and that these gliomas may proliferate by synthesizing such growth factors.

Glioma and occupational exposure in Sweden, a case-control study

OBJECTIVES

The aim of the study was to analyse whether any job titles, industrial codes, and certain occupational exposures were associated with an increased risk of glioma.

METHODS

A population based case-control study of incident primary brain tumours in adults was carried out in Uppsala, Sweden in the period 1987-90. The study included 192 cases of glioma and 192 matched controls. It also included cases with other tumours of the central nervous system with matched controls. Information from all 343 controls was used in this study. Information was collected by means of a questionnaire that was sent to all subjects. An occupational hygienist reviewed the questionnaires for self reported exposures to substances and assessed whether these reported exposures were plausible or not in the corresponding occupation.

RESULTS

The kappa coefficient for those classified by the two methods ranged between 0.46 and 0.88, and they were almost the same for cases and controls. For men exposed to solvents a relative risk (RR) of 2.6 (95% CI 1.3 to 5.2) was found. For men exposed to pesticides the RR was 1.8 (95% CI 0.6 to 5.1), and for plastic materials the RR was 3.6 (95% CI 1.0 to 12.4). For men employed in forestry and logging the RR was 2.2 (95% CI 0.9 to 5.3) and in basic metal industries 2.0 (95% CI 1.0 to 4.0).

CONCLUSION

An increased risk of glioma was associated with use of solvents, pesticides, and plastic materials but this should be interpreted with some caution.

Characterization of rat NCA/CD9 cell surface antigen and its expression by normal and malignant neural cells

As part of investigations on ethylnitrosourea (EtNU)-induced neuro-oncogenesis in the rat, we have produced monoclonal antibodies (Mabs) specific for neural cell surface antigens (NCAs) by immunization with cells of the clonal tumorigenic neural rat cell line BT4Ca. Mabs designated as anti-NCA (alpha NCA1, alpha NCA2, alpha NCA3, alpha NCA4, and alpha NCA5) recognize proteins of 25 kDa and 23 kDa, as shown by immunoprecipitation and Western blot. The predominant 25-kDa protein was purified from BT4Ca cells by immunoaffinity chromatography with immobilized Mab alpha NCA1 and identified by N-terminal sequencing as the rat homologue of the CD9 antigen. Identification of proline as N-terminal amino acid of the purified protein suggests post-translational modification of CD9 in the rat central nervous system. The NCA/CD9 protein was localized in distinct regions of fetal and adult rat brain by immunofluorescence staining of frozen sections. Flow cytometric analyses of isolated fetal rat brain cells (FBC) showed that the proportion and number of NCA/CD9-expressing cells increased during prenatal development. Immunoreactivity of approximately 40% of brain cells isolated 13 days post conception (p.c.) indicated that NCA/CD9 is expressed by neuronal precursors at this stage of development. In primary cultures of rat FBC isolated 18 days p.c., the NCA/CD9 antigen was expressed by all premature and mature astrocytes, oligodendrocytes, ependymal cells, and microglial cells, but not by E-N-CAM-expressing neuronal progenitor cells and neurons. Furthermore, eight out of ten EtNU-induced malignant neural rat cell lines as well as EtNU-induced tumors of the central and peripheral nervous system exhibited intermediate or strong immunoreactivity with Mab alpha NCA1. Expression of the NCA/CD9 protein is, therefore, characteristic of both normal glial precursor cells and their malignant counterparts in the rat.

Risk of nervous system cancer among workers exposed to lead

Experimental animal studies suggest that lead compounds may increase the risk of gliomas. To study whether occupational exposure to lead increases the risk, we followed nervous system cancer incidence among 20,741 employees biologically monitored for their blood lead (B-Pb) concentrations. We also performed a nested case-referent study, comprising 26 male cases of nervous system cancer (16 of which had gliomas). Those cases a B-Pb > or = 1.4 mumol/L had a twofold increase in the odds ratio of nervous system cancer as compared with those employees whose B-Pb had not exceeded 0.7 mumol/L. The excess was confined to gliomas (odds ratio 11, 95% confidence interval 1.0 to 630 for B-Pb > or = 1.4 mumol/L; overall P value for trend, 0.037). We obtained lifetime information on exposure and potential confounders for 58% of the cases. The odds ratio of glioma was associated with indices of lifetime exposure to lead, and potential confounders seemed not to explain the effects. The results suggest that there may be an association between occupational lead exposure and the risk of gliomas. No firm conclusions can be drawn because of the small number of cases and loss of material.

[New transplantable brain gliomas in rats]

The paper provides the characteristics of 11 original transplanted rat brain gliomas that are part of the collection of experimental tumors of the nervous system, which has been developed at the Institute of Human Morphology, Russian Academy of Medical Sciences. The biological features of brain tumour strains, methods of their transplantation and cryoconservation are outlined in the paper.

Effects of barbital on neuro-oncogenesis in a transplacental carcinogenicity model using F344 rats

Effects of barbital (BB) on neuro-oncogenesis were examined in a rat transplacental carcinogenesis model. Pregnant F344 rats were divided into 7 groups. Dams in group I received subcutaneous injections of 10 mg/rat 1-butyl-1-nitrosourea (BNU) on the days 15, 18 and 21 of pregnancy and dams in groups II-IV, 1mg/rat BNU on the same time schedule. In addition to the treatment with BNU, dams in group IV were given 0.125% BB solution as their drinking water from the day 12 of pregnancy to parturition. Offspring in groups III and IV received 0.125% BB solution as drinking water from 4 weeks of age until the termination of the study. Animals in groups V and VI were given 0.25% and 0.125% BB solutions, respectively, in the peri- and postnatal period without BNU treatment. Dams in group VII received 250 mg/kg BB subcutaneously on the days 15, 18 and 21 of pregnancy. Offspring in all groups were observed until 105-116 weeks of age. High yields of neurogenic tumors, such as gliomas and neurinomas, were observed in group I. In groups II, III and IV, single cases of a chordoma, a granular cell tumor, and a neurinoma and a malignant reticulosis, which are known to occur spontaneously, were noted, although no gliomas were found. No neurogenic tumors were observed in groups V-VII. With regard to lesions other than those in neurogenic organs, a significant increase in liver tumors was observed in group III compared to group II. In contrast, lung tumors were not found in group III, while they were observed in groups II and IV. These results suggest that BB has no neuro-carcinogenic activity in the rat transplacental carcinogenesis model.

Growth inhibition of rat glioma cells in vitro and in vivo by aspirin

The effect of non-steroidal anti-inflammatory drugs (NSAIDs), acetylsalicylic acid (commonly known as aspirin), salicylic acid, piroxicam and indomethacin on the growth of rat glioma cells (RG 2) in vitro and aspirin in vivo was studied. The in vitro studies reveal that aspirin and salicylic acid strongly inhibit growth of rat glioma (RG 2) cells in concentrations used in medicine for treatment of rheumatic diseases. On the other hand, indomethacin and piroxicam had no effect, indicating that the inhibitory effect on tumor growth is not due to the inhibition of prostaglandin synthesis. The synthesis of ATP was markedly reduced (34% of control) in the presence of drugs, whereas protein synthesis measured as 3H-leucine incorporation was slightly more inhibited (73% of control) than cell growth. Aspirin administered to Fischer 344 rats inhibited growth of RG 2 cells inoculated into the caudate nucleus in vivo, both when administered the day before inoculation of tumor cells and when tumors had formed, i.e. 5 days post inoculation.

The RG2 rat glioma model

The ethylnitrosourea-induced cell line RG2 grows very well in infinite cell culture in vitro, and provides a simple, reproducible glioma model when inoculated into the brains of syngeneic Fischer 344 rats. We have used this tumor model in a series of therapy studies. We here report our experiences of the untreated (= tumor bearing control) animals, e.g. in terms of the techniques employed and also the growth, histology and effects upon the blood-brain barrier of the tumors. Weight loss as a measure of systemic effects during tumor development is also described. The RG2 model has considerable potential as a suitable tool for experimental neuro-oncology.

Lactate metabolism conducted by rat C6-glioma in the cells culture

In order to investigate the lactate metabolism conducted by rat C6-glioma, the author incubated the C6-glioma cells in culture medium with oxygen and glucose, and measured the daily glucose and lactate concentrations in the cell culture fluid by using an electrode-based analyzer. The cells proliferated by the fourth culture day, saturated at the fifth or sixth days, and then the cell counts started to decrease. They died by the twelfth day. A large amount of the glucose was consumed within the first six culture days, while the lactate was produced during the same time periods in the medium solution having abundant oxygen. The lactate, however, started to be consumed from the seventh day. The author demonstrated in vitro that C6-glioma cells conducted anaerobic glycolysis in the glucose-rich aerobic culture condition, and consumed lactate in a hyperproliferative and low-glucose state, probably by using the glutamine oxidation.

Measurement of amino acid metabolism derived from [1-13C]glucose in the rat brain using 13C magnetic resonance spectroscopy

To clarify the unique characteristics of amino acid metabolism derived from glucose in the central nervous system (CNS), we injected [1-13C]glucose intraperitoneally to the rat, and extracted the free amino acids from several kinds of tissues and measured the amount of incorporation of 13C derived from [1-13C]glucose into each amino acid using 13C-magnetic resonance spectroscopy (NMR). In the adult rat brain, the intensities of resonances from 13C-amino acids were observed in the following order: glutamate, glutamine, aspartate, gamma-aminobutyrate (GABA) and alanine. There seemed no regional difference on this labeling pattern in the brain. However, only in the striatum and thalamus, the intensities of resonances from [2-13C]GABA were larger than that from [2,3-13C]aspartate. In the other tissues, such as heart, kidney, liver, spleen, muscle, lung and small intestine, the resonances from GABA were not detected and every intensity of resonances from 13C-amino acids, except 13C-alanine, was much smaller than those in the brain and spinal cord. In the serum, 13C-amino acid was not detected at all. When the rats were decapitated, in the brain, the resonances from [1-13C]glucose greatly reduced and the intensities of resonances from [3-13C]lactate, [3-13C]alanine, [2, 3, 4-13C]GABA and [2-13C]glutamine became larger as compared with those in the case that the rats were sacrificed with microwave. In other tissues, the resonances from [1-13C]glucose were clearly detected even after the decapitation. In the glioma induced by nitrosoethylurea in the spinal cord, the large resonances from glutamine and alanine were observed; however, the intensities of resonances from glutamate were considerably reduced and the resonances from GABA and aspartate were not detected. These results show that the pattern of 13C label incorporation into amino acids is unique in the central nervous tissues and also suggest that the metabolic compartmentalization could exist in the CNS through the metabolic trafficking between neurons and astroglia.

Spermidine acetylation in N1 and N8 position in rat brain and in N-ethyl-N-nitrosourea-induced gliomas

N-ethyl-N-nitrosourea-induced rat gliomas showed a stimulation of cytosolic spermidine N-acetyltransferase activity compared with normal brain, with an increased formation of N1 and N8-acetylspermidine, suggesting the activation of two enzymes acetylating the polyamine in N1 and N8 position, respectively. The enhancement in cytosolic spermidine N1-acetyltransferase was probably responsible for an activation of the polyamine interconversion pathway in gliomas, as indicated by an accumulation of N1-acetylspermidine and a marked increase in putrescine. Spermidine N8-acetyltransferase, although acetylating histones at a high rate, seemed distinct from the nuclear enzyme, as, unlike from the latter, it showed very low affinity for putrescine and was not inhibited by methylglyoxal bis(guanylhydrazone).

Immunohistochemical localization of glycosaminoglycans in experimental rat glioma models

Changes of glycosaminoglycan distribution in and around C6 glioma and ethylnitrosourea(ENU)-induced glioma in rats were investigated using monoclonal antibodies that specifically recognize epitopes on chondroitin-0-sulfate proteoglycan (C-0-S), chondroitin-4-sulfate proteoglycan (C-4-S), dermatan sulfate proteoglycan (DS), chondroitin-6-sulfate proteoglycan (C-6-S) and keratan sulfate proteoglycan (KS) after chondroitinase ABC digestion. In the normal brain tissues, C-0-S was located on the surface of the neurons. In addition, extracellular staining in the cerebral cortex and axoplasmic staining in the brain stem and the reticular thalamic nucleus were seen. C-0-S was negative, however, both in the C6 and ENU-induced gliomas. C-4-S or DS was detected only in some of the neurons in the normal brain tissues. They were detected in the peripheral part of the ENU-induced gliomas, but not in the C6 gliomas. C-6-S was located on the surface of some neurons and in the white matter of the normal brain, but it was not detected in C6 gliomas. In all ENU-induced gliomas, C-6-S was identified in the adventitia of the vascular structures within the tumor. In some of them, C-6-S appeared in the peripheral part of the tumor. KS was immunostained in the glial cells in the hippocampus, corpus callosum, brain stem, and the floor of the third ventricle. It was also detected in the peritumoral brain tissues both in the C6 and ENU-induced rat gliomas. The significance of glycosaminoglycans in these glioma models was discussed.

Diamine oxidase activity in rat brain carcinogenesis and in gliomas

In the early stages of brain carcinogenesis induced by transplacental administration of N-ethyl-N-nitrosourea to BD IX rats, a constant increase in the activity of cerebral diamine oxidase, the rate-limiting enzyme in terminal catabolism of polyamines, was observed. Gliomas, which developed between the fifth and eight month of extrauterine life, showed an 8-fold increase in enzyme activity compared with normal brain from rats of the same age. Concomitantly, an 11-fold enhancement in putrescine, a physiological substrate of diamine oxidase, was also found. Such findings indicate that an increase in oxidative putrescine catabolism via diamine oxidase takes place in transformed cells and in gliomas and is probably linked to an activation of polyamine synthesis and turnover.