The antimalarials quinacrine and chloroquine potentiate the transplacental carcinogenic effect of ethylnitrosourea on ependymal cells

Quinacrine and chloroquine, two widely used antimalarials, bind strongly to deoxyribonucleic acid, thus preventing mutagenesis. We studied a possible chemoprotective effect of these substances on carcinogenesis of the nervous system induced in Wistar rats by transplacental administration of ethylnitrosourea. One experimental group consisted of rats born from mothers treated with quinacrine prior to prenatal exposure to ethylnitrosourea; a second group consisted of rats chronically treated with chloroquine after prenatal exposure to ethylnitrosourea. When compared with controls, no significant differences were observed in tumor incidence. However, early tumor growth was observed in both rats treated with quinacrine (P < 0.0004) and rats treated with chloroquine (P < 0.02). These differences were due mostly to rapid development of ependymomas of the spinal cord. Our results suggest that quinacrine and chloroquine do not prevent the structural alterations induced in DNA by ethylnitrosourea, which lead, in the long term, to a high incidence of neoplasms in the nervous system. Moreover, the antimalarials studied seem to promote the carcinogenic effects of ethylnitrosourea on ependymal cells.

A rare case of lumbosacral meningioma: nondural attachment and possible enlargement by orally administered sex steroid

STUDY DESIGN

A case report is presented.

OBJECTIVES

To present a very rare case of orally ingested sex hormone pills inducing nondurally attached meningioma in the lumbosacral region.

SUMMARY OF BACKGROUND DATA

Meningiomas are known to enlarge in response to female sex hormones. At this writing, few cases of nondurally based intradural meningioma have been reported. Moreover, meningiomas in the lumbosacral region are very rare. Spinal meningiomas predominantly arise in the fourth to sixth decades of life and are more common in women.

METHODS

The patient was a 20-year-old woman. She had undergone oral sex steroid therapy for long-term oligomenorrhea. The patient complained of intolerable lumbago and numbness in her buttocks. Nonopioid analgesics did not relieve her pain, and she was unable to walk without the aid of a walker. Radiography disclosed a lumbosacral intradural tumor.

RESULTS

Complete removal of the tumor was performed. The tumor was not adherent to the dura, and its appearance was that of a typical neurilemmoma. However, the pathologic diagnosis was meningioma.

CONCLUSIONS

The tumor in the reported case may have enlarged in response to orally ingested sex steroid pills. Nondural attachment intradural meningiomas are quite uncommon. The gross appearance of the tumor during surgery was typical of neurilemmoma. All the cases reported so far, including the current case, have involved tumor located in the lumbosacral region. Care must be taken in the management of lumbosacral intradural tumors because tumors resembling neurilemmoma may in fact represent meningioma, some subtypes of which possess a high rate of recurrence.

The effects of 860 MHz radiofrequency radiation on the induction or promotion of brain tumors and other neoplasms in rats

Sprague-Dawley rats were irradiated with a continuous- wave (CW) or a pulsed-wave (P) radiofrequency (RF) for 6 h/day, 5 days/week from 2 up to 24 months of age. The RFs emanated from dipole antennas (1 W average output) 2.0 +/- 0.5 cm from the tip of each rat's nose. The RFs had an 860 MHz frequency, and the specific absorption rate was 1.0 W/ kg averaged over the brain. Fifteen groups of 60 rats (900 total) were formed from offspring of females injected i.v. with 0 (groups 1, 2, 9, 10, 13), 2.5 (groups 5, 6, 7, 8, 11, 12, 14) or 10 mg/kg (groups 3, 4, 15) ethylnitrosourea (ENU) to induce brain tumors. Groups 1, 3, 5 and 7 received the PRF, and groups 9 and 11 the CWRF; groups 2, 4, 6, 8, 10 and 12 were sham-irradiated, and groups 13-15 were cage controls. All rats but 2, totaling 898, were necropsied, and major tissues were studied histopathologically. There was no statistically significant evidence that the PRF or CWRF induced neoplasia in any tissues. Additionally, there was no significant evidence of promotion of cranial or spinal nerve or spinal cord tumors. The PRF or CWRF had no statistically significant effect on the number, volume, location, multiplicity, histological type, malignancy or fatality of brain tumors. There was a trend for the group that received a high dose of ENU and was exposed to the PRF to develop fatal brain tumors at a higher rate than its sham group; however, the result was not significant using the log-rank test (P = 0.14, 2-tailed). No statistically significant differences were related to the PRF or CWRF compared to controls in the low- or zero-dose groups regarding tumors of any kind.

Spontaneous and nitrosourea-induced primary tumors of the central nervous system in Fischer 344 rats exposed to frequency-modulated microwave fields

In a 2-year bioassay, we exposed Fischer 344 rats to a frequency-modulated (FM) signal (836.55 MHz +/- 12.5 KHz deviation) simulating radiofrequency exposures in the head of users of hand-held mobile phones. We tested for effects on spontaneous tumorigenicity of central nervous system (CNS) tumors in the offspring of pregnant rats and also for modified incidence of primary CNS tumors in rats treated with a single dose of the neurocarcinogen ethylnitrosourea (ENU) in utero. ENU dosage (4 mg/kg) was selected to give an expected brain tumor incidence of 10-15% over the mean life span of 26 months. Pregnant dams (n = 102) were randomly assigned to six groups. Their offspring were treated as cohorts in each of the six groups (n = 90 per group; total, n = 540): Sham ENU/Sham Field, Sham ENU/Field Exposed, ENU/Sham Field, ENU/Field Exposed, ENU/Cage Control, and Sham ENU/Cage Control. Intermittent field exposures began on gestation day 19 and continued until weaning at 21 days, resuming thereafter at 31 days and continuing until experiment termination at 731-734 days. Energy absorption rates (SARs) in the rats' brains were similar to localized peak brain exposures of a phone user (female, 236 g, 1.0 W/kg; male, 450 g, 1.2 W/kg). Of the original 540 rats, 168 died before the termination of the experiment. In these rats, ENU significantly reduced survival from a mean of 708 days in three groups without ENU treatment to 645 days in three groups treated with ENU (P < 0.0005). There were no effects on survival attributable to FM field exposure in either ENU-treated or in sham-treated groups. Spontaneous CNS tumor incidence in control groups was 1.1-4.4% but sharply higher in rats receiving ENU (14.4-22.2%; P < 0.0001). No FM field-mediated changes were observed in number, incidence, or histological type of either spontaneous or ENU-induced brain tumors, nor were gender differences detected in tumor numbers. These negative findings with FM fields contrast with our study using standard digital phone fields pulsed on and off at 50/se, where a trend was noted toward reduced incidence of both spontaneous and ENU-induced CNS tumors (W. R. Adey et al., Radiat. Res., 152: 293-302, 1999). Although consistent but not attaining significance in the experiment overall (spontaneous CNS tumors, P < 0.08 one-tailed; P < 0.16 two-tailed; ENU-induced CNS tumors, P < 0.08 one-tailed, P < 0.16 two-tailed), the trend was significant (P < 0.015 one-tailed, P < 0.03, two-tailed) in rats that received ENU and died prior to experiment termination, with a primary brain tumor as the cause of death. We discuss differences in the signaling structure of digital and FM fields. Certain bioeffects induced by either amplitude-modulated or pulsed radiofrequency fields at athermal levels have not been seen with fields of similar average power but unvarying in intensity (continuous wave or frequency-modulated fields).

Evaluation of the potential promoting effect of 60 Hz magnetic fields on N-ethyl-N-nitrosourea induced neurogenic tumors in female F344 rats

The present study investigated the possible effect of 60 Hz magnetic fields (MFs) as promoters of neurogenic tumors initiated transplacentally by a chemical carcinogen, N-ethyl-N-nitrosourea (ENU). In a preliminary study, 5 mg of ENU was shown to induce 30 to 40% neurogenic tumors in F344 rats offspring after 420 days of observation. In the present study, 400 female rats were divided into eight different groups (50 animals/group) and exposed in utero (on day 18 of gestation) to a single intravenous dose of either Saline (Group I), or ENU, 5 mg/kg (Group II to VIII). Dams in group II were given no further treatment while dams in Groups III to VII were exposed to 5 different intensities of MFs forty eight hours later. Animals in group III were sham exposed (<0.02 microT) while groups IV to VII were exposed to 2, 20, 200, and 2000 microT, respectively. Dams in Group VIII were injected intraperitoneally with 12-O-tetradecanoylphrobol-13-acetate (TPA; 10 micrograms/kg) from day 19 until delivery, and then their female offspring continued to be injected every 15 days, starting at day 14 after birth until sacrifice (positive controls). Accordingly, this study included three different types of controls: Internal controls (Groups II and III) and positive control (Group VIII). Body weight, mortality and clinical observations were evaluated in all groups of animals during in-life exposure. Necropsy was performed on all exposed and control animals that died, were found moribund or sacrificed at termination of the study. Histopathological evaluation was done for all brains, spinal cords, cranial nerves, major organs (lungs, liver, spleen, kidneys, pituitary, thyroid and adrenals) and all gross lesions observed during necropsy. All clinical observations and pathological evaluations were conducted under "blinded" conditions. The findings from this ENU/MFs promotion study clearly demonstrate that, under our defined experimental conditions, exposure to 60 Hz linear (single axis) sinusoidal, continuous wave MFs had no effect on the survival of female F344 rats or on the number of animals bearing neurogenic tumors. These results suggest that MFs have no promoting effect on neurogenic tumors in the female F344 rats exposed transplacentally to ENU.

Evaluation of ENU-induced gliomas in rats: nomenclature, immunochemistry, and malignancy

Rats developed mixed gliomas, oligodendrogliomas, and a few astrocytomas in response to transplacental ethylnitrosourea. The neoplastic cell composition of mixed gliomas must be defined; this study required a 20-80% admixture of neoplastic astrocytes and oligodendroglia for the diagnosis of mixed glioma. A battery of immunoantibodies, including Leu-7, S-100, and vimentin, were helpful in classifying rat gliomas, and the histologic features of each tumor type are described. Other brain tumor characteristics that may decide the outcome of carcinogenicity studies include incidence, multiplicity, latency, fatality, size, and malignancy. The size of tumors was determined by measuring their 3-dimensional volumes. Brain tumor volume was found to be highly correlated with malignancy and fatality. Systematic evaluation of the malignancy of brain tumors is an important but often overlooked adjunct method of measuring the effectiveness of a carcinogen. A system to estimate malignancy, one that grades 9 tumor characteristics and weights, each according to clinical outcome, was developed. It was found that mixed gliomas grew larger, had a shorter latency, and were significantly more malignant than were other gliomas.

Spontaneous and nitrosourea-induced primary tumors of the central nervous system in Fischer 344 rats chronically exposed to 836 MHz modulated microwaves

We have tested an 836.55 MHz field with North American Digital Cellular (NADC) modulation in a 2-year animal bioassay that included fetal exposure. In offspring of pregnant Fischer 344 rats, we tested both spontaneous tumorigenicity and the incidence of induced central nervous system (CNS) tumors after a single dose of the carcinogen ethylnitrosourea (ENU) in utero, followed by intermittent digital-phone field exposure for 24 months. Far-field exposures began on gestational day 19 and continued until weaning at age 21 days. Near-field exposures began at 35 days and continued for the next 22 months, 4 consecutive days weekly, 2 h/day. SAR levels simulated localized peak brain exposures of a cell phone user. Of the 236 original rats, 182 (77%) survived to the termination of the whole experiment and were sacrificed at age 709-712 days. The 54 rats (23%) that died during the study ("preterm rats") formed a separate group for some statistical analyses. There was no evidence of tumorigenic effects in the CNS from exposure to the TDMA field. However, some evidence of tumor-inhibiting effects of TDMA exposure was apparent. Overall, the TDMA field-exposed animals exhibited trends toward a reduced incidence of spontaneous CNS tumors (P < 0. 16, two-tailed) and ENU-induced CNS tumors (P < 0.16, two-tailed). In preterm rats, where primary neural tumors were determined to be the cause of death, fields decreased the incidence of ENU-induced tumors (P < 0.03, two-tailed). We discuss a possible approach to evaluating with greater certainty the possible inhibitory effects of TDMA-field exposure on tumorigenesis in the CNS.

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.

Pharmacodynamics of phenobarbital anesthesia and pentylenetetrazol-induced maximal seizures in a rat model of neoplastic spinal cord compression

The purpose of this investigation was to determine whether paraplegia induced by neoplastic cord compression affects the pharmacodynamics of phenobarbital general anesthesia or of pentylenetetrazol (PTZ)-induced convulsions. Paraplegic rats harboring a thoracolumbar epidural tumor, or an identical hindlimb tumor mass, received an i.v. infusion of phenobarbital until the onset of anesthesia. At that point, the phenobarbital concentrations in the CSF and serum were measured. Similarly, PTZ was infused until the onset of maximal seizures. It was found that changes related to systemic tumor growth and newly developed paraplegia due to neoplastic spinal cord compression did not attenuate the pharmacodynamics of phenobarbital. However, sustained paraplegia of 4 days' duration reduced CNS sensitivity to the hypnotic action of the barbiturate as evidenced by the higher cerebrospinal fluid phenobarbital concentration required to induce anesthesia (170 +/- 31 vs 125 +/- 20 mg/L; P < 0.05). On the other hand, sustained paraplegia did not affect brain threshold concentration for PTZ-induced seizures.

Expression of neuronal markers in the so-called ENU-induced schwannomas

The present data show that the so-called ENU-induced malignant schwannomas express neuronal markers. This finding supports the hypothesis that a population of tumor cells in these neoplasms are neuroblastic in nature, and suggests the classification of ENU-induced schwannomas as primitive neuroectodermal tumors.

High susceptibility of analbuminemic rats to neurogenic tumor induction by transplacental administration of N-ethyl-N-nitrosourea

The susceptibilities of Nagase analbuminemic rats (NAR) and control Sprague-Dawley rats (SDR) to N-ethyl-N-nitrosourea (ENU) were compared. In Experiment I, the rats were given daily subcutaneous injections of 10 mg/kg of ENU for a week from 4 weeks of age. In Experiment II, mother rats were given a single subcutaneous injection of 60 mg/kg of ENU on day 17 of pregnancy and tumor development in their offspring was examined. In Experiment I, the incidence of neurogenic tumors was slightly, but not significantly, higher in NAR than in control rats. In Experiment II, the incidence of total tumors including neurogenic tumors was significantly higher in NAR (40/43, 93.0%) than in SDR (13/61, 21.3%). NAR showed particularly high susceptibility to induction of neurogenic tumors (34/43, 79.1%) and renal tumors (15/43, 34.9%). In an attempt to elucidate the underlying mechanisms of the increased susceptibility of NAR to ENU, O6-ethylguanine, a major premutagenic ethylated DNA adduct, was quantitated in fetal brain DNA of NAR and SDR after a pulse exposure to 60 mg/kg ENU. No significant difference in the initial formation or subsequent repair of O6-ethylguanine was observed in the two strains, indicating that abnormality at some later stage(s) of chemical carcinogenesis may lead to the increased susceptibility of NAR to induction of neurogenic tumors.

Spinal cord tumors: gadolinium-DTPA-enhanced MR imaging

To assess the utility of gadolinium-DTPA (Gd) and of MR imaging in the evaluation of spinal cord tumors, ten consecutive patients were prospectively evaluated. T1-proton density-, and T2-weighted images were obtained in sagittal or axial planes. T1-weighted images were obtained before and after intravenous administration. Five tumors were within the cervical spinal cord; 3 neoplasms were within the thoracic cord; 1 neoplasm extended from the cervical to the thoracic cord and 1 neoplasm extended from the cervical cord to the conus medullaris. Four tumors were ependymomas; 3 were astrocytomas; 1 was an hemangioblastoma, and 1 was a metastatic malignant peripheral nerve sheath tumor. The remaining patient died prior to spinal surgery and no autopsy was obtained. Of the precontrast sequences, tumors were best evaluated using T1-weighted images. Abnormal findings included cord widening, presence of a tumor mass, intratumoral or other associated cyst(s), and hemorrhage. Nevertheless, T1-weighted images obtained following the administration of GD were superior relative to all other pre- and post-contrast sequences for defining tumor margins, characterizing cyst(s) and delineating tumor masses. Based primarily on their appearance on post-contrast T1-weighted images, tumor-associated cysts could be subcategorized into 3 types: intratumoral cysts (found within the contrast-enhancing soft tissue mass); nonenhancing extratumoral cysts (found eitherrostral or caudal to the enhancing tumor mass); and enhancing extratumoral cysts (having an enhancing wall or containing an enhancing nodule).(ABSTRACT TRUNCATED AT 250 WORDS)

Exposure to barbiturates in utero and during childhood risk of intracranial and spinal cord tumors

Barbiturate exposure during childhood was assessed from medical records of 237 children with intracranial and spinal cord tumors and 474 matched controls in a prepaid health plan. In utero exposure was also examined in a subset of 86 "cases" and 172 controls whose mothers were health plan members during pregnancy. No association of in utero exposure to barbiturates was found [odds ratio (O.R.) = 0.96, 95% confidence interval (C.I.) = 0.47, 1.94]. An association was noted for barbiturate use during childhood (O.R. = 1.80, 95% C.I. = 1.18, 2.74) but was reduced (O.R. = 1.41, 95% C.I. = 0.89, 2.21) when history of epilepsy was taken into account and was no longer significant. An apparent dose-response effect disappeared after adjustment for a history of epilepsy. Although barbiturate use for epilepsy due to preexisting brain tumors clearly explains some of the observed association, the small, residual risk prevents us from ruling out a possible carcinogenic effect of barbiturates. Further study of cohorts of adult as well as childhood users of barbiturates and other anticonvulsants is recommended.

Immunohistochemical investigations in experimentally induced tumors of the nervous system

35 tumors of brain, spinal cord and cranial and peripheral nerves were induced with ENU (ethyl-nitrosourea) in the offspring of treated BD-IX pregnant rats. 36 tumors--35 of the nervous system, one nephroblastoma--were observed in 14 rats. With these results, the number of experimental nervous system tumors of the own collection induced in BD-IX rats and classified next to the rules of human neurooncology, amounts to 2,216. All 35 tumors of the nervous system were treated by a panel of immunohistochemical reactions comprising antibodies against cytoskeleton intermediary filaments such as GFAP (glial fibrillary acid protein), neurofilament proteins, vimentin and cytokeratins and some nervous system antigens such as NSE (neuron specific enolase), MBP (myelin basic protein) and S-100 protein. In central tumors, considered to be malignant gliomas, focal reactivity against vimentin and GFAP was found. Expression of other tested markers was weak or absent. In neurinoma of trigeminal and peripheral nerves, reactivity to S-100 antigen was lacking, whilst there was strong reaction to the vimentin antigen.

Non-Hodgkin's lymphoma of the central nervous system after treatment of Hodgkin's disease

A case of a 34-year-old man with stage IIIB nodular sclerosis Hodgkin's disease complicated by the development of a central nervous system non-Hodgkin's lymphoma is described. The second tumor became symptomatic eight months after the initial diagnosis of Hodgkin's disease, but a tissue diagnosis was not made until autopsy two months later. The Hodgkin's disease was, at that time, in remission, and the autopsy revealed no persistent or recurrent Hodgkin's disease. Despite radiotherapy, the brain lymphoma had progressed to involve the spinal leptomeninges extensively, but there was no lymphoma outside the central nervous system (CNS) at autopsy. The significance of this unique case is discussed in light of the known risk for non-Hodgkin's lymphoma as a second malignancy after Hodgkin's disease and in view of recent information concerning CNS lymphoma.

Steroid-induced spinal epidural lipomatosis: CT survey

A new case of spinal cord compression secondary to steroid-induced epidural lipomatosis is reported in a patient treated for dermatomyositis. Computed tomography was performed before the institution of steroid therapy, during spinal cord compression, and after effective surgical treatment. The development of epidural lipomatosis does not require a preexisting lipoma and may occur in a previously normal spine.

Symptomatic spinal epidural lipomatosis as a complication of steroid immunosuppression in cardiac transplant patients. Report of two cases

Patients with Cushing's syndrome may develop spinal epidural lipomatosis, an abnormal accumulation of fat in the spinal epidural space. This accumulation of fat may cause compression of the spinal cord or cauda equina with resulting neurological deficit. Two cases of symptomatic spinal lipomatosis are reported in cardiac transplant patients receiving chronic corticosteroid treatment. The literature is reviewed, and diagnostic and therapeutic considerations are discussed.

Periphery of ethylnitrosourea-induced spinal gliomas in rats with special reference to the vascular structure

The histology and ultrastructure of ten spinal cord gliomas, mainly oligodendrogliomas, induced transplacentally in rat with ethylnitrosourea were studied. The characteristic feature of seven spinal tumours was distinct delineation of neoplastic tissue from the edematous surrounding zone by a ring of irregular, proliferating capillaries, among which immature capillary buds prevailed. The alterations were proliferation of endothelium with endothelial overlapping, elongation of interendothelial junctions and enhancement of pinocytotic vesicles on luminal and abluminal surfaces. The basal membranes, besides other changes, were often replaced by some floccular condensations. In the edematous zone the capillary walls were deprived of contact with glial processes. The lack of contact between astrocytic processes and vascular wall may contribute to the persistent immature state of peripheral capillaries.

Chemotherapy in intracerebrally transplanted tumors induced with transplacental administration of ethylnitrosourea in rats

Four tumors of the spinal cord were induced with ethylnitrosourea in rats by transplacental administration and transplanted into the brains of animals of the same strain. One of these intracerebrally grafted tumor lines (G-XIII) was followed up over the first 10 passages and treated with CCNU and other alkylating drugs. The results were compared with findings in an earlier established line (G-XII) in passage 12 and 59, which in the first instance was sensitive to CCNU. The CCNU application prolonged survival in treated animals in various treatment schedules in the first 10 intracerebrally grafted generations of the tumor up to 59%. Induction times of tumors became increasingly shorter. The susceptibility of early passages was similar in both lines. Its loss in late passages went together with diffuse growth of the tumor and reticulin fiber production. In addition, glial fibrillary acid protein expression and formation of intermediate filaments in perivascular tumor cells was lost.

Beta-receptor-stimulated and cyclic adenosine 3',5'-monophosphate-mediated taurine release from LRM55 glial cells

Adrenergic stimulation of LRM55 glial cells results in the release of the neuroactive amino acid taurine. The present study characterizes the receptors involved in taurine release and shows that taurine release is mediated by cyclic adenosine 3',5'-monophosphate (cAMP). beta-Receptors in LRM55 cells were first characterized by [125I]iodohydroxybenzylpindolol binding. Binding was stereospecific and saturable with time and ligand concentration. Kinetic analysis of equilibrium binding at 37 degrees C revealed a single component of high affinity (Km = 113 pm; Bmax = 52.1 +/- 5.0 fmol/mg of protein). The pharmacologies of the stimulation of cAMP accumulation and taurine release were similar. The agonists isoproterenol (IPR), epinephrine (E) and norepinephrine (NE) showed a rank order of potency characteristic of a beta-adrenergic system (IPR greater than E greater than or equal to NE). The beta-antagonists alprenolol and propranolol inhibited the IPR stimulation of both processes; the alpha-antagonist phentolamine did not. The dependence of taurine release on cAMP was further suggested by the similarity of the two time courses and was demonstrated by the stimulation of taurine release by the cAMP analogue dibutyryl cAMP. Thus, one physiological response of glial cells to beta-adrenergic stimulation is the release of taurine. Receptor-activated release of taurine from glia represents a previously undescribed neuronal-glial interaction by which glia may actively regulate neuronal excitability.

Induction of gliomas in Mongolian gerbils (Meriones unguiculatus) following neonatal administration of N-ethyl-N-nitrosourea

Mongolian gerbils (Meriones unguiculatus) were given an sc injection (40 mg/kg body wt) of N-ethyl-N-nitrosourea [(ENU) CAS: 759-73-9] on postnatal day 1 (group I) or day 29 (group II). Untreated gerbils served as controls (group III). Of 32 gerbils in group I, 10 (31%) developed a total of 14 gliomas after an observation period of 12 months, whereas no gliomas were observed in groups II and III. Seven gliomas were located in the spinal cord, 6 were in the cerebrum, and 1 was in the cerebellum. Histologically, all were oligodendrogliomas. In group II, 1 meningeal tumor (4%) was observed among 27 gerbils. ENU also induced cutaneous melanomas (22% in group I, 15% in group II, and 0% in group III), kidney hemangiomas (6% in group I, 26% in group II, and 0% in group III), and ameloblastomas of the lower jaw (6% in group I and 0% in groups II and III).

Organ-specific carcinogenicity of N-methyl-N-nitrosourea in F344 and ACI/N rats

Male and female F344 rats were continuously administered N-methyl-N-nitrosourea (MNU) in their drinking water at concentrations of 200 or 100 ppm, and both sexes of ACI/N rats were given MNU at a concentration of 200 ppm. By the 42nd week of the experiment, high incidences of brain/spinal cord tumors were observed in both strains of rats. Histologically, many of them were astrocytomas or anaplastic astrocytomas. In addition, malignant neurinomas were also detected in the spinal nerve roots and trigeminal nerves, although their incidences were rather low. There was no difference in the type and incidence of these neurogenic tumors between the two strains of rats. Tumors of the tongue and esophagus were mainly observed in the high-dose group of F344 rats and those of the glandular stomach were observed in the low-dose group of F344 rats. In ACI/N rats, tumors of the heart and renal pelvis were detected. The organ-specific carcinogenicity of MNU in these two strains of rats was compared with that of MNU in Donryu rats. It was demonstrated that organ specificity of MNU given orally was influenced not only by the strain of rats but also by the dose level.

[Effect of PS-K on experimental neurogenic tumors in rats induced by ethylnitrosourea]

The effect of PS-K as immunomodulator was studied in Fischer rats bearing neurogenic tumors induced transplacentally by ENU. 114 rats were divided into control and PS-K treated groups. all rats were subjected to an autopsy at death and all of central nervous system were examined macroscopically. Final neurogenic tumor incidence in PS-K treated groups was significantly lower than that in the control group, but distribution of these neurogenic tumors and number of neurogenic tumors in a rat remained unchanged between the control and the each PS-K treated groups. Survival time of PS-K treated groups did not increase than the control group. From these experiments, it might be that induction of neurogenic tumors may be suppressed by administration of PS-K.

Spinal cord tumors induced by N-ethyl-N-nitrosourea in rats: presence of spinal subpial target cells

The correlation between induction of spinal cord tumor by N-ethyl-N-nitrosourea (ENU) (CAS: 759-73-9; 1-ethyl-1-nitrosourea) and postnatal cellular differentiation of the spinal cord was examined in 6 different strains of rats [noninbred Wistar and inbred F344, WF, LE, WF (female) X LE (male), and LE (female) X WF (male)]. By perinatal injection of 40 mg ENU/kg, 258 spinal cord tumors were induced in 175 of 372 ENU-treated rats. The spinal cords of rats at ages ranging from day 1 to day 8 after birth were particularly susceptible to the oncogenic effect of ENU. All spinal cord tumors developed in the white matter without any segmental predilection site. Moreover, most (93%) were found in the subpial region of the spinal cord and were classified as oligodendrogliomas. Morphologic and autoradiographic examinations revealed accumulation of spinal subpial immature glial cells from day 1 to day 8 after birth when the spinal cord had a high susceptibility and most of the cells were destined to differentiate into oligodendrocytes. These data show the existence of target cells in the spinal cords of rats after ENU carcinogenesis.

[Effect of polypeptide factors of the thymus, pineal gland, bone marrow and anterior hypothalamus on the realization of transplacental carcinogenesis]

The postnatal action of low-molecular polypeptide factors of thymus (FT), pineal gland (FP), bone marrow (FRM) and anterior hypothalamus (FAH) on transplacental carcinogenic effect of N-nitroso-N-ethylurea in rats was studied. Both FT and FP administrations decreased incidence and multiplicity of tumours and prolonged their mean latent periods. These drugs inhibited mainly the development of tumours of the spinal cord, kidneys and peripheral nervous system but not those of the brain. Both FBM and FAH had no significant influence on transplacental carcinogenesis. FT and FP anticarcinogenic effect is supposed to be due to their normalizing action on hormonal metabolic and immunological shifts arising in the body after transplacental administration of the carcinogen.

Reduction of N-nitroso-N-ethylurea-induced neurogenic tumors by X-radiation: a life-span study in rats

Whole-body X-irradiation after neonatal injection with N-nitroso-N-ethylurea (ENU) significantly reduced the incidence of induced neurogenic tumors in inbred HMT rats kept for their complete life-span. After administration of 10 mg ENU/kg and 1.25 Gy X-radiation, the incidence of schwannomas but not of gliomas was reduced as compared to the incidence in rats given 10 mg ENU/kg only. In contrast, after administration of 4 mg ENU/kg, 1.25 Gy reduced the incidence of gliomas but not of schwannomas. Administration of 1.25 Gy alone induced a remarkably high incidence of rats with neurogenic tumors (20%). Latency of tumor detection was not significantly affected by radiation. Among the most frequently occurring nonneurogenic tumors, squamous cell carcinomas were reduced in incidence by treatment with ENU, 1.25 Gy X-radiation, or both combined. No treatment affected the incidence of pituitary or mammary tumors. There was a preponderance of ovarian tumors in rats given 4 mg ENU/kg + 1.25 Gy. An incidental finding was the occurrence of granular cell tumors in 7 rats from different treatment groups.

Strain differences of tumorigenic effect of neonatally administered N-ethyl-N-nitrosourea in rats

The tumorigenicity of neonatally administered N-ethyl-N-nitrosourea (ENU) was studied in four different inbred strain rats, that is Wistar/Furth (WF), Long-Evans (LE), F1 of Wistar/Furth and Long-Evans (F1) and Fischer 344 (F344) rats. All strains developed tumors of the nervous system with high incidence (97-100%) during 6 months of observation. The incidence of tumor of the central nervous system, including the brain (82-88%) and the spinal cord (53-76%), was high in all strains, but that of the peripheral nervous system, including the cranial nerve (21-89%) and the spinal root (13-93%), differed by strain. The peripheral nervous system of WF and F344 rats had a low susceptibility to the tumorigenic effect of ENU, but that of LE rats had a high susceptibility. Many brain tumors were induced in the temporal and frontal cortex and subcortex in all strains of rats. Spinal cord tumors were observed at all levels of the white matter of the spinal cord without any predilection site. Spinal root tumors were located in lumbosacral plexuses in WF and F344 rats, but in LE and F1 rats cervical and thoracic root tumors were also observed. Histological examination revealed that most of the brain and spinal cord tumors were oligodendroglioma, but in F344 rats about half of the brain tumors were mixed glioma. Epidermoid cysts of the lumbar spinal cord were observed only in F344 rats. Tumors of the peripheral nervous system were so-called anaplastic schwannoma.

Effect of age at treatment on the incidence and location of neurogenic tumors induced in Wistar rats by a single dose of N-ethyl-N-nitrosourea

The effect of age at treatment on the incidence and location of neurogenic tumors induced by N-ethyl-N-nitrosourea (ENU) was investigated in 232 Wistar rats of both sexes. Rats were given 40 ng/kg of ENU on the 16th day of gestation (group I), on the day of birth (group II), and on the 1st week (group III), 2nd week (group IV), 3rd week (group V) and 4th week (group VI) after birth. Up to 6 months of observation, the brain consistently showed the highest susceptibility ranging from group I (93%) to group VI (36%), followed by the spinal cord (group I, 34%; group II, 64%; group III, 43%). However, the trigeminal nerve was only susceptible in group I (27%) and group II (36%) and the spinal root was susceptible exclusively in group II (46%). Most of the tumors obtained were oligodendrogliomas or mixed gliomas. Glioependymomas of the spinal cord were predominant only in group II. The temporal and paraventricular regions and hippocampus were the preferred sites of brain tumors in group I and II, but in groups III and IV frontal tumors were predominant. Mesenchymal tumors of the kidney were also induced, mainly in groups III (16%) and IV (16%).

Spinal tumors induced by neonatal administration of N-ethyl-N-nitrosourea in Wistar rats

The carcinogenic effect of N-ethyl-N-nitrosourea (ENU) administered by single neonatal injection (40 mg/kg) was examined in wistar rats. By 2 months after ENU administration, 30% of the examined animals had spinal cord tumors. After months all rats had neurogenic tumors, and the incidence of spinal tumor was as high as 86%. Spinal cord tumors were observed at all levels of the white matter of the spinal cord without any predilection site, though spinal root tumors were located exclusively on lumbosacral plexuses. Most of the spinal cord tumors were oligodedrogliomas or glioependymomas, whereas all the spinal root tumors were anaplastic schwannomas.

Transplacental teratogenic and carcinogenic effects in rabbits chronically treated with N-ethyl-N-nitrosourea

Pregnant rabbits of two partially inbred strains, WH/J and IIIVO/J, were given ten consecutive daily ip injections of 10 mg N-ethyl-N-nitrosourea (ENU)/kg dissolved in trioctanoin starting on either day 10, 15, or 18 of gestation. Of 7 WH/J progeny weaned, 3 developed primary renal tumors at 6.8 +/- 0.6 months of age (mean +/- SE). Similarly, of 12 IIIVO/J progeny weaned, 10 developed primary renal tumors at 6.3 +/- 0.6 months of age (mean +/- SE); in addition, 1 fibroblastic osteosarcoma and 5 neurofibromas, some associated with neurilemma cysts, were observed. Renal tumors were nephroblastomas , which appeared to develop within small renal cortical cysts. The frequency of tumor induction for each strain was similar to that in our previous experiments with acute administration of ENU and ethyl-urea plus NaNO2, but the latency period (6.4 +/- 0.5 mo) was almost doubled. In addition, chronic treatment of ENU induced teratogenic effects. In a number of these progeny, a disproportionate stunting or miniaturization was evident, the frequency of which increased with the age of the treated fetuses. In contrast, holes were found in the parietal bones at birth, but with a frequency that decreased with increasing fetal age at time of treatment. No teratogenic effects were observed in the controls.

Carcinogenicity of nitrosotrialkylureas in Fischer 344 rats

Three nitrosotrialkylureas were administered to female F344 rats as approximately 1-mM solutions in drinking water. Nitrosotrimethylurea, given for 47 weeks, gave rise to astrocytomas of the brain and tumors of the forestomach; nitrosotriethylurea induced a high incidence of adenocarcinomas of the breast and uterus and tumors of the forestomach. Nitrosomethyldiethylurea induced almost exclusively a high incidence of both astrocytomas of the brain and tumors of the spinal cord.

N-ethyl-N-nitrosourea-induced spinal tumors in an inbred strain of W albino rats

Exposure to N-ethyl-N-nitrosourea (ENU) either transplacentally via the maternal bloodstream or postnatally by direct injection into the cerebellum or the cisterna magna resulted in a high incidence of spinal tumors in an inbred strain of W albino rats. After prenatal exposure to 60 mg ENU/kg maternal body weight, as many as 92% of the offspring developed 1 or more tumors in the spinal cord, whereas after postnatal exposure to 0.2 mg ENU/animal, 50% of the animals eventually developed spinal tumors. These tumors included relatively pure oligodendrogllomas, astrocytomas, and the usual mixed gllomas. Obvious clinical symptoms of paralysis of the limbs and weight loss accompanying the high incidence of tumors in the spinal cord make this system pertinent to the study of carcinogenesis in the central nervous system as well as to the study of related problems to the incidence of these tumors are discussed.

Teratogenic and carcinogenic effects of some chemicals during perinatal life in rats, Syrian golden hamsters, and minipigs

Teratogenic effects of ENU have been observed in the rat, Syrian golden hamster, and minipig. In BD and Wistar rats, as well as in hamsters, ENU is a potent carcinogen when administered prenatally. Other members of the homologous series of alkylnitrosoureas, except n-propylnitrosourea, have been shown to be less active or totally inactive as carcinogens in experiments on prenatal animals. Simultaneous oral administration of L-citrulline and sodium nitrite induced adenosarcomas of the kidney (Wilm's tumors) in 6 of 22 offspring. The importance of prophylactic measures in man during prenatal development is emphasized.

Induction of tumors of peripheral nervous system in female Donryu rats by continuous oral administration of 1-methyl-1-nitrosourea

Groups 1, 2, and 3 of female Donryu rats were given continuously 400, 200, or 100 ppm solution of 1-methyl-1-nitrosourea (MNU) as their drinking water. The incidence of neurogenic tumors was 12/27 (44%), 39/33 (91%), and 33/36 (92%) in Groups 1, 2, and 3, respectively. Among the neurogenic tumors, neurinomas developing from the spinal nerve roots were the most frequent. In addition, tumors of the digestive tract were found in 12, 1, and 2 rats in Groups 1, 2, and 3, respectively, and tumors in hematopoietic tissues developed in 6 rats. Tumors in other organs were infrequent.

Short and long term effects of methyl- and ethylnitrosourea (MNU & ENU) on the developing nervous system of the rat. I. Long term effects: the induction of (multiple) gliomas

Single injections on ENU to WAG-rats were given in the perinatal period and repeated injections of MNU to adult WAG-rats. In the tables illustrating the various experiments, the occurrence of tumors is given for each animal; the tumors are classified according to their sites. For the brain tumors a subdivision is made between those macroscopically visible and those discovered only under microscopy. It is noteworthy that the ratio between neural and extraneural tumors in the perinatally exposed animals is rather constant (about 90 and 10 per cent, respectively). In the experiments on young adult rats neural tumors still predominate, but estraneural ones rise to about 40 per cent. The incidence of neural tumors is impressively high in perinatal induction experiments (greater than 95 per cent). Almost all CNS tumors showed the characteristics of oligodendrogliomas; highly differentiated in the smaller tumors and more anaplastic with regressive changes in the larger ones.

Induction of tumors in the stomach and nervous system of the ACI/N rat by continuous oral administration of 1-methyl-3-acetyl-1-nitrosourea

Three groups of ACI/N rats of both sexes received continuous administration of 66 (Group I), 30 Group II), or 13(Group III) ppm solution of 1-methyl-3-acetyl-1-nitrosourea (Ac-MNU) in their drinking water. Tumors were found most frequently in the stomach and nervous system. The former was more frequently found in the male than in the female. The incidence was highest in males of Group II, 28/30 (93%), and lowest in females of Group I, 4/30 (13%). Histologically, all epithelial tumors of the stomach were benign adenomas except 5 adenocarcinomas. Neurogenous tumors were more frequently seen in the female than in the male. The incidence was highest in females of Group I, 29/30 (97%), and lowest in males of Group III, 6/28 (21%). The tumors were predominant in the central nervous system, especially in the hemispheres. Transplantation studies were done in some of these tumors. Although gastric tumors failed to get positive transplantation, all the neurogenous tumors transplanted were positive.

The effect of gonadal ablation on transplacentally induced neurogenic tumors in hamsters

The effects of gonadectomy on tumors induced transplancentally by the ethylnitrosourea precursors, ethylurea and sodium nitrite, were investigated in hamsters. The pregnant hamsters were exposed to four daily doses of ethylurea (100 mg/kg) and sodium nitrite (50 mg/kg) administered from Day 12 to 15 of pregnancy. Weaned offspring were gonadectomized when they reached the age of 5 weeks. Orchiectomized male progeny showed a multiplicity and greater frequency of peripheral nervous system tumors and of any other tumor types than did intact males or their ovariectomized and intact female siblings. The possible inhibitory effects of endogenous androgens on the development and growth of neurogenic tumors in the peripheral nervous system and the influence of an induced endocrinal imbalance on prenatally induced neoplasms are discussed.

Transplacental induction of neurogenic tumors in BD IX rats by intragastric administration of ethylnitrosourea precursors

The concurrent daily intragastric administration of ethylurea at two dose levels (50 mg/kg and 100 mg/kg bodyweight) together with one dose level of sodium nitrite (50 mg/kg bodyweight) by a stomach tube to pregnant BD IX rats from day 15 to day 22 of gestation resulted in the induction of neurogenic tumors in all offspring. Since both ENU-precursors alone do not produce neurogenic tumors, these results are evidence of ENU formation from its precursors under the influence of gastric juice. Differences in the survival time and the incidence of tumors at both dose levels were not significant. The amount of ethylnitrosourea synthesized in the animals was very close at both dose levels, and was dependent on the amount of sodium nitrite applied. The experimental results are consistent with the conclusion, that the rat fetuses had been exposed to a total amount of about 60 mg/kg ethylnitrosourea. Neurogenic tumors dominated with 98% incidence over the non-neurogenic. The incidence of neurogenic tumors per rat was high (6.0 for Group I and 6.7 for Group II). Neurogenic tumors were equally distributed among the central and peripheral nervous systems. The neurogenic tumors induced with the precursors of ethylnitrosourea were morphologically similar in all aspects to those induced with the carcinogen itself and could be classified as oligodendroglioma, astrocytoma, mixed glioma, anaplastic glioma, glioependymoma, ependymoma, and neurinoma. Three unusual tumors were found: one early anaplastic "septum ependymoma" in the dorsal column of the spinal cord, and two special mixed tumors of the cranial nerves, i.e. a neurinoma with portions of an oligodendroglioma and a neurinoma with parts of an invasive ependymoma.

Histopathological studies of the nervous system tumors in rats induced by N-nitroso-methyl-urea

Histopathological examinations were made on tumors of the nervous system induced in rats of Donryu strain by weekly intravenous injections with N-nitroso-methyl-urea (NMU) or by a single administration of NMU through the mothers. A total of 176 neural and nonneural neoplasms were produced in this study. It was suggested that the fetal nervous system of Donryu rats was also highly susceptible to the oncogenic effects of NMU. Of these tumors produced, those of the peripheral nervous system amounted to 121, comprising 68.7% of the total number of the neoplasm. Microscopically, most of the nerve tumors showed the histology corresponding to that of human neurinomas. Many tumors, however, disclosed more or less anaplastic cytological appearance. Fifteen gliomas were produced in the brain and spinal cord. Microscopically, they were classified into mixed glioma, oligondendroglioma and anaplastic astrocytoma. The commonest brain tumors produced in rats from intravenously treated group were periventricular mixed gliomas, while gliomas in rats from transplacentably treated group showed an isomorphic histology with a close resemblance to that of oligodendroglioma.

Induction of tumors of the nervous system in the ACI/N rat with 1-butyl-1-nitrosourea administered transplacentally, neonatally, or via maternal milk

1-Butyl-1-nitrosourea (BNU), a strong leukemogen for rats and mice, was administered prenatally, neonatally, and to sucklings via maternal milk in the ACI/N rats. A high incidence of neurogeneous tumor was obtained in the offspring of the mother rats that received 3 subcutaneous injections of 10 mg/rat of BNU at the late stage of pregnancy and also in the animals that received one subcutaneous injection of 100 mg/kg of BNU within 24 hr after birth. Though in low incidence, the tumors also developed in the offspring of the mothers that received the BNU treatment at the middle stage of their pregnancy or in the rats that were nursed by the mother rats which received 3 subcutaneous injections of 300 mg/kg of BNU during lactation. Contrary to expectations, leukemia developed in only one rat of all the offspring of the mother animals that received the BNU treatment during their pregnancy.

Differential oncogenic effects of methylnitrosourea

We investigated differences in the oncogenic effects of methylnitrosourea (MNU) which were induced by varying dose schedules and changing administration routes. The nervous system represented the target organ when MNU was given intravenously to rats. Carcinogen by other routes resulted in decreased numbers of neurogenic tumors and the appearance of neoplasms at the injection site. Increased oral doses of MNU caused shorter survival times, a decreased incidence of neuroglial tumors, and increased numbers of thymic lymphomas and mesenchymal tumors of the nervous system. The results suggest that many tissues are susceptible to the oncogenic effects of MNU, but the degree of exposure necessary for neoplastic transformation varies.