Postsurgical Outcomes of Mesial Temporal Lobe Epilepsy due to Hippocampal Sclerosis Associated with Calcified Neurocysticercosis

The aim of this study was to analyze postsurgical outcomes for individuals with mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS) who underwent anterior temporal lobectomy, based on the presence of calcified neurocysticercosis (cNCC). A retrospective cross-sectional study was conducted on 89 patients with MTLE-HS who underwent anterior temporal lobectomy between January 2012 and December 2020 at a basic epilepsy surgery center located in Lima, Peru. We collected sociodemographic, clinical, and diagnostic information. The postsurgical results were analyzed using bivariate analysis according to the Engel classification. We included 89 individuals with a median age of 28 years (interquartile range [IQR]: 24-37), and more than half (55.1%) were male. Seventeen (19.1%) were diagnosed with cNCC. A greater number of patients with cNCC had lived in rural areas of Peru during their early life compared with those without cNCC (12 [70.6%] versus 26 [36.1%]; P = 0.010). Patients with cNCC exhibited a greater median frequency of focal to bilateral tonic-clonic seizures per month (1 [IQR: 0-2] versus 0 [0-0.5]; P = 0.009). Conversely, a lower proportion of patients with cNCC reported a history of an initial precipitating injury in comparison to the group without cNCC (4 [23.5%] versus 42 [58.3%]; P = 0.014). At the 1-year follow-up, most patients (82.4%) with cNCC were categorized as Engel IA. Similarly, at the 2-year follow-up, nine (75.0%) were classified as Engel IA. Our findings suggest that most patients diagnosed with cNCC exhibit favorable postsurgical outcomes, comparable to those without cNCC. Additionally, it can be postulated that cNCC may play a role as an initial precipitating injury.

Establishing efficient toluene elimination over cobalt-manganese bimetallic oxides via constructing strong Co-Mn interaction

Doping proves to be an efficacious method of establishing intermetallic interactions for enhancing toluene oxidation performance of bimetallic oxides. However, conventional bimetallic oxide catalysts are yet to overcome their inadequacy in establishing intermetallic interactions. In this work, the dispersion of Mn-Co bimetallic sites was improved by hydrolytic co-precipitation, strengthening the intermetallic interactions which improved the structural and physicochemical properties of the catalysts, thus significantly enhancing its catalytic behavior. MnCo-H catalysts fabricated by the hydrolytic co-precipitation method showed promising catalytic performance (T50 = 223 °C, T90 = 229 °C), robust stability (at least 100 h) and impressive water resistance (under 10 vol.% of water) for toluene elimination. Hydrolytic co-precipitation has been found to improve dispersion of MnCo elements and to enhance interaction between Co and Mn ions (Mn4+ + Co2+ = Mn3+ + Co3+), resulting in a lower reduction temperature (215 °C) and a weaker Mn-O bond strength, creating more lattice defects and oxygen vacancies, which are responsible for superior catalytic properties of MnCo-H samples. Furthermore, in situ DRIFTs showed that gaseous toluene molecules adsorbed on the surface of MnCo-H were continuously oxidized to benzyl alcohol → benzaldehyde → benzoate, followed by a ring-opening reaction with surface-activated oxygen to convert to maleic anhydride as the final intermediate, which further generates water and carbon dioxide. It was also revealed that the ring-opening reaction for the conversion of benzoic acid to maleic anhydride is the rate-controlling step. This study reveals that optimizing active sites and improving reactive oxygen species by altering the dispersion of bimetals to enhance bimetallic interactions is an effective strategy for the improvement of catalytic behavior, while the hydrolytic co-precipitation method fits well with this corollary.

Nivolumab plus ipilimumab in melanoma patients with asymptomatic brain metastases: 7-year outcomes and quality of life from the multicenter phase III NIBIT-M2 trial

BACKGROUND

The primary analysis of the phase III NIBIT-M2 study showed a 41% 4-year overall survival (OS) of melanoma patients with asymptomatic brain metastases treated with ipilimumab plus nivolumab.

METHODS

Here, we report the 7-year efficacy outcomes and the Health-Related Quality of Life (HRQoL) analyses of the NIBIT-M2 study.

RESULTS

As of May 1, 2023, at a median follow-up of 67 months (mo), the median OS was 8.5 (95% CI: 6.6-10.3), 8.2 (95% CI: 2.1-14.3) and 29.2 (95% CI: 0-69.9) mo for the fotemustine (F) Arm A, ipilimumab plus fotemustine Arm B, and ipilimumab plus nivolumab Arm C, respectively. The 7-year OS rate was 10.0% (95% CI: 0-22.5) in Arm A, 10.3% (95% CI: 0-22.6) in Arm B, and 42.8% (95% CI: 23.4-62.2) in Arm C. HRQoL was preserved in all treatment arms. Most functional scales evaluated from baseline to W12 were preserved, with a lower mean score decrease for EORTC Quality of Life Questionnaire (QLQ)-C30 and an increase for EORTC QLQ-Brain neoplasm (BN20) in patients receiving ipilimumab plus nivolumab.

CONCLUSIONS

With the longest follow-up available to date in melanoma patients with asymptomatic brain metastases, the NIBIT-M2 study continues to show persistent therapeutic efficacy of I ipilimumab plus nivolumab while preserving HRQoL.

Bioelectrocatalytic reduction by integrating pyrite assisted manganese cobalt-doped carbon nanofiber anode and bacteria for sustainable antimony catalytic removal

A novel manganese cobalt metal-organic framework based carbon nanofiber electrode (MnCo/CNF) was prepared and used as microbial fuel cell (MFC) anode. Pyrite was introduced into the anode chamber (MnCoPy_MFC). Synergistic function between pyrite and MnCo/CNF facilitated the pollutants removal and energy generation in MnCoPy_MFC. MnCoPy_MFC showed the highest chemical oxygen demand removal efficiency (82 ± 1%) and the highest coulombic efficiency (35 ± 1%). MnCoPy_MFC achieved both efficient electricity generation (maximum voltage: 658 mV; maximum power density: 3.2 W/m3) and total antimony (Sb) removal efficiency (99%). The application of MnCo/CNF significantly enhanced the biocatalytic efficiency of MnCoPy_MFC, attributed to its large surface area and abundant porous structure that provided ample attachment sites for electroactive microorganisms. This study revealed the synergistic interaction between pyrite and MnCo/CNF anode, which provided a new strategy for the application of composite anode MFC in heavy metal removal and energy recovery.

Platelet Membrane Biomimetic Manganese Carbonate Nanoparticles Promote Breast Cancer Stem Cell Clearance for Sensitized Radiotherapy

Introduction

The presence of cancer stem cells (CSCs) significantly limits the therapeutic efficacy of radiotherapy (RT). Efficient elimination of potential CSCs is crucial for enhancing the effectiveness of RT.

Methods

In this study, we developed a biomimetic hybrid nano-system (PMC) composed of MnCO3 as the inner core and platelet membrane (PM) as the outer shell. By exploiting the specific recognition properties of membrane surface proteins, PMC enables precise targeting of CSCs. Sonodynamic therapy (SDT) was employed using manganese carbonate nanoparticles (MnCO3 NPs), which generate abundant reactive oxygen species (ROS) upon ultrasound (US) irradiation, thereby impairing CSC self-renewal capacity and eradicating CSCs. Subsequent RT effectively eliminates common tumor cells.

Results

Both in vitro cell experiments and in vivo animal studies demonstrate that SDT mediated by PMC synergistically enhances RT to selectively combat CSCs while inhibiting tumor growth without noticeable side effects.

Discussion

Our findings offer novel insights for enhancing the efficacy and safety profiles of RT.

Adopting duplex sequencing technology for genetic toxicity testing: A proof-of-concept mutagenesis experiment with N-ethyl-N-nitrosourea (ENU)-exposed rats

Duplex sequencing (DS) is an error-corrected next-generation sequencing method in which molecular barcodes informatically link PCR-copies back to their source DNA strands, enabling computational removal of errors in consensus sequences. The resulting background of less than one artifactual mutation per 107 nucleotides allows for direct detection of somatic mutations. TwinStrand Biosciences, Inc. has developed a DS-based mutagenesis assay to sample the rat genome, which can be applied to genetic toxicity testing. To evaluate this assay for early detection of mutagenesis, a time-course study was conducted using male Hsd:Sprague Dawley SD rats (3 per group) administered a single dose of 40 mg/kg N-ethyl-N-nitrosourea (ENU) via gavage, with mutation frequency (MF) and spectrum analyzed in stomach, bone marrow, blood, and liver tissues at 3 h, 24 h, 7 d, and 28 d post-exposure. Significant increases in MF were observed in ENU-exposed rats as early as 24 h for stomach (site of contact) and bone marrow (a highly proliferative tissue) and at 7 d for liver and blood. The canonical, mutational signature of ENU was established by 7 d post-exposure in all four tissues. Interlaboratory analysis of a subset of samples from different tissues and time points demonstrated remarkable reproducibility for both MF and spectrum. These results demonstrate that MF and spectrum can be evaluated successfully by directly sequencing targeted regions of DNA obtained from various tissues⁠, a considerable advancement compared to currently used in vivo gene mutation assays.

Oriented Design of Transition-Metal-Oxide Hollow Multishelled Micropolyhedron Derived from Bimetal-Organic Frameworks for the Electrochemical Detection of Multipesticide Residues

Transition-metal oxides (TMOs) with a hollow multishelled structure have emerged as highly potential materials for high-performance electrochemical sensing, benefiting from their superior electronic conductivity, exceptionally large specific surface area, excellent stability, and electrochemistry properties. In particular, binary TMOs are expected to outperform unitary TMOs due to the synergistic effect of the different metals. Herein, MnCo₂O_4.5 hollow quadruple-shelled porous micropolyhedrons (MnCo₂O_4.5 HoQS-MPs) were prepared and employed to construct an ultrasensitive sensing platform for a multipesticide assay. Profiting from complex hollow interior structures and abundant active sites, the MnCo₂O_4.5 HoQS-MPs manifest outstanding electrochemical properties as electrode materials for the pesticide assay. The MnCo₂O_4.5 HoQS-MP-based biosensor demonstrated remarkable performance for monocrotophos, methamidophos, and carbaryl detection, with wide linear ranges, as well as low detection limits. This work unveils a new pathway for the ultrasensitive detection of pesticides and demonstrates tremendous potential for detecting other environmentally deleterious chemicals.

Role of intracellular energy metabolism in Mn(Ⅱ) removal by the novel bacterium Stenotrophomonas sp. MNB17

Microorganism-mediated Mn(Ⅱ) removal has gained increasing attention as a valuble bioremediation approach. In this study, a novel strain Stenotrophomonas sp. MNB17 - obtained from marine sediments - was found to show Mn(Ⅱ) removal efficiencies of 98.51-99.38% within 7 days and 92.24% within 20 days at Mn(Ⅱ) concentrations of 10-40 mM and 50 mM, respectively. On day 7, 80.44% of 50 mM Mn(Ⅱ) was oxidized to Mn(Ⅲ/Ⅳ), whereas only 2.11-2.86% of 10-40 mM Mn(Ⅱ) was oxidized. This difference in the proportion of Mn-oxides suggested that the strain MNB17 could remove soluble Mn(Ⅱ) via distinct mechanisms under different Mn(Ⅱ) concentrations. At 10 mM Mn(Ⅱ), indirect mechanisms were employed by strain MNB17 to remove Mn(Ⅱ). The sufficient energy generated by increased cellular respiration led to enhanced ammonification, and MnCO₃ was the main component of the Mn-precipitates (97.27%). Meanwhile, intracellular fatty acids were degraded and served as an important carbon source for respiration. At 50 mM Mn(Ⅱ), most of the soluble Mn(Ⅱ) was oxidized, and Mn-oxides dominated the Mn-precipitates (80.44%). Mn(Ⅱ) oxidation likely contributed to electrons for energy production, as the down-regulation of respiratory pathways resulted in a deficit of electron supply, which warrants futher study. The exogenous addition of tricarboxylic acid cycle substrates (malate, α-ketoglutarate, oxaloacetate, succinate, and fumarate) was found to accelerate Mn(Ⅱ) removal as MnCO₃ at a concentration of 50 mM. Overall, this study reports a novel strain MNB17 with the biotechnological potential of Mn(Ⅱ) removal and elucidates the function of cellular energy metabolism during the Mn(Ⅱ) removal process. In addition, it demonstrates the potential of aerobic respiration-related substrates in accelerating the removal of high concentrations of Mn(Ⅱ) for the first time.

Comparative transcriptomic analysis of Stenotrophomonas sp. MNB17 revealed mechanisms of manganese tolerance at different concentrations and the role of histidine biosynthesis in manganese removal

Bacteria possess protective mechanisms against excess Mn(Ⅱ) to reduce its toxicity. Stenotrophomonas sp. MNB17 showed high Mn(Ⅱ) removal capacity (92.24-99.16 %) by forming Mn-precipitates (MnCO₃ and Mn-oxides), whose Mn-oxides content increased with increasing Mn(Ⅱ) concentrations (10-50 mM). Compared with 0 mM Mn(Ⅱ)-stressed cells, transcriptomic analysis identified genes with the same transcriptional trends in 10 mM and 50 mM Mn(Ⅱ)-stressed cells, including genes involved in metal transport, cell envelope homeostasis, and histidine biosynthesis, as well as genes with different transcriptional trends, such as those involved in oxidative stress response, glyoxylate cycle, electron transport, and protein metabolism. The upregulation of histidine biosynthesis and oxidative stress responses were the most prominent features of these metabolisms under Mn(Ⅱ) stress. We confirmed that the increased level of reactive oxygen species was one of the reasons for the increased Mn-oxides formation at high Mn(Ⅱ) concentrations. Metabolite analysis indicated that the enhanced histidine biosynthesis rather than the tricarboxylic acid cycle resulted in an elevated level of α-ketoglutarate, which helped eliminate reactive oxygen species. Consistent with these results, the exogenous addition of histidine significantly reduced the production of reactive oxygen species and Mn-oxides and enhanced the removal of Mn(Ⅱ) as MnCO₃. This study is the first to correlate histidine biosynthesis, reactive oxygen species, and Mn-oxides formation at high Mn(Ⅱ) concentrations, providing novel insights into the molecular regulatory mechanisms associated with Mn(Ⅱ) removal in bacteria.

N-nitrosoethylenethiourea formation at environmentally-relevant concentrations of ethylenethiourea in a pooled groundwater sample

N-nitroso compounds form from the interaction between nitrosatable precursors and nitrite under acidic conditions. A majority of N-nitroso compounds tested show evidence of carcinogenicity in animal models. Formation of N-nitroso compounds may occur from exposure to precursors in drinking water, but the extent of formation depends on a number of factors, including concentration of substrates, presence of catalysts and inhibitors, and pH. The objective of this study was to examine these factors in pesticide-associated N-nitroso (PANN) compound formation in drinking water. In preliminary screening experiments, nine nitrosatable pesticides and degradation products were individually reacted at environmentally-relevant concentrations (≤ 20 μg L^--1) with sodium nitrite (NaNO₂) and hydrochloric acid (HCl) in ultra-pure water. Only ethylenethiourea (ETU) showed evidence of PANN compound formation in initial experiments and was further tested for N-nitrosoethylenethiourea (N-ETU) formation in a pooled groundwater sample (comprised of five tap water samples combined into one homogenous sample) collected from an agricultural region of Prince Edward Island in Canada, where nitrate contamination is a known concern. Evidence of N-ETU formation in the groundwater sample was observed within 30 min at concentrations 7.5, 10, and 20 μg L^-1. Analysis of target compounds and semi-target PANN compounds was performed using ultra-high pressure liquid chromatography coupled with high resolution orbital ion trap mass spectrometry. These preliminary experiments serve to inform about potential PANN compound formation in groundwater. The results of this study suggest that ETU is capable of forming potentially carcinogenic N-ETU in water containing nitrite/nitrate at trace concentrations under acidic conditions. Thus, these findings suggest that N-ETU formation may be a concern for individuals exposed to low concentrations of ETU in groundwater.

[A Case of Adult T-Cell Leukemia/Lymphoma with Severe Hand-Foot Syndrome during Administration of Modified LSG15 Regimen]

The patient was a 56-year-old woman. A modified LSG15(VCAP-AMP-VECP)regimen was initiated as the first-line treatment for acute adult T-cell leukemia/lymphoma. On day 13 from the initiation of the second course of chemotherapy, the onset of hand-foot syndrome(HFS)(hands: Grade 2; feet: Grade 1)occurred. Therefore, the administration of a heparin analog cream and betamethasone butyrate propionate ointment was initiated. On day 20 from the start of the second course of chemotherapy, the foot symptoms improved; however, hand symptoms deteriorated to Grade 3. Frequent use of alcohol-based hand hygiene products is associated with infection prevention during neutropenia, but was likely an exacerbating factor. The symptoms gradually improved after this was taken into consideration, and the usage was discontinued. At the start of the third course, the symptoms had improved to Grade 1, and chemotherapy was continued. On day 11, symptoms worsened(Grade 2). HFS management was performed similar to that in the second course, and symptoms improved again.

Electron Microscopic Study of Viral Particles in the Pancreas of Normal and Leukemic Mice

An electron microscopic study of viral particles was conducted on pancreas, thymus, and bone marrow of normal and leukemic (C57BL x C3Hf) F1 (BC3) and SWR mice. The leukemic mice had developed thymic lymphosarcoma after neonatal injection of N-nitrosomethylurea or urethan. An intense proliferation of type C particles morphologically identical to the murine leukemia virus was found in the acinar cells of the exocrine pancreas of BC3 mice. The particles were predominantly located in intracytoplasmic vacuoles but they were also numerous in dilated cisternae of the rough endoplasmic reticulum and in extracellular spaces. A substantial quantitative difference of type C particles between the pancreases of leukemic and healthy mice was not observed. No viral particles were found in the pancreas of SWR mice. In the thymus and bone marrow of BC3 and SWR mice a small number of type C particles and intracisternal type A particles was found in all the experimental and control groups. The observation of a high number of type C particles in the exocrine pancreas of BC3 mice is discussed in relation to a viral etiology of chemically-induced lymphomas.

Nitrosourea-Induced Brain Tumors in the Rat. Comments on the Pathogenesis of Mixed and Polymorphic Gliomas

Mixed gliomas are among the most frequent of brain tumors induced by nitrosourea derivatives. In a personal collection of 300 experimental tumors 142 were gliomas. The characteristics of the various oncotypes are described, with special reference to mixed and polymorphic gliomas. Generally, gliomas develop from microtumors and polymorphic gliomas from isomorphic gliomas. For this reason mixed gliomas probably represent an intermediate stage of the transformation. The principal cellular components of mixed gliomas in order of frequency are: oligodendroglial, astrocytic, ependymal and sarcomatous. Some pathogenetic hypotheses are advanced to explain the changes observed in gliomas during their development.

N-Nitrosomethylurea-Induced Rat Mammary Tumours as Models of Human Breast cancer

A histopathological study is reported of the autopsy findings in two strains of rats treated with N-methyl-N-nitrosourea (MNU). The induced mammary tumours were histologically indistinguishable from those produced by dimethylbenz(a)anthracene (DMBA). A number of other primary tumours were found and there was no evidence of metastases.

Sensitivity of DBLA-6 leukemia of rats to known antitumor agents in relation to their clinical effects

Of 4 lines of myelogenous rat leukemias induced by N-nitrosobutylurea (NBU), DBLA-6 was selected as a screening model for antileukemic agents because of the following characteristics: a) High transplantability either by intravenous (i.v.) or intraperitoneal (i.p.) inoculation; b) linear relationship between inoculum size and survival time; c) marked increase of leucocyte counts in the peripheral blood as the tumor progresses after intravenous inoculation. To investigate reliability in its predicting clinical efficacy, its sensitivity to known antileukemics was studied. To determine the effects, a change of leucocyte counts in the peripheral blood together with the prolongation of life span was checked in the following systems; i.v.-i.v. (i.v.-inoculation, i.v.-injection), i.v.-i.p., i.p.-i.p., i.p.-i.v. Fifty percent cure was obtained with Vincristine, Vinblastine, Daunorubicin, 6-Mercaptopurine, and alkylating agent 838D or 864T. The success of treatment was measured by decrease of leucocytes. Methotrexate, cytosine arabinoside (Ara-C), and cyclophosphamide showed only poor effects, and Mitomycin C, L-asparaginase, and Bleomycin were ineffective. In addition, the chemotherapeutic effects of Vincristine and 864 on this leukemia were quite dependend both on the route of drug injection and on the site of tumor inoculation. Subsequently, our studies are being extended to cover the correlation between drug distribution and tumor localization or dissemination.

Immunity against mouse thymus-leukemia antigen (TL) protects against development of lymphomas induced by a chemical carcinogen, N-butyl-N-nitrosourea

Mouse thymus-leukemia antigens (TL) are aberrantly expressed on T lymphomas in C57BL/6 (B6) and C3H/He (C3H) mice, while they are not expressed on normal T lymphocytes in these strains. When N-butyl-N-nitrosourea (NBU), a chemical carcinogen, was administered orally to B6 and C3H strains, lymphoma development was slower than in T3(b)-TL gene-transduced counterpart strains expressing TL ubiquitously as self-antigens, suggesting that anti-TL immunity may play a protective role. In addition, the development of lymphomas was slightly slower in C3H than in B6, which seems to be in accordance with the results of skin graft experiments indicating that both cellular and humoral immunities against TL were stronger in C3H than B6 mice. The interesting finding that B lymphomas derived from a T3(b)-TL transgenic strain (C3H background) expressing a very high level of TL were rejected in C3H, but not in H-2K(b) transgenic mice (C3H background), raises the possibility that TL-specific effector T cell populations are eliminated and/or energized to a certain extent by interacting with H-2K(b) molecules.

A chemically induced model for squamous cell carcinoma of the lung in mice: histopathology and strain susceptibility

Lung cancer, primarily associated with tobacco use, is the leading cause of cancer morbidity and mortality in the United States. Squamous cell carcinoma (SCC) is one of the four major histological types of lung cancer. Although there are several established models for lung adenoma and adenocarcinomas, there is no well-established mouse model for lung SCC. We treated eight different inbred strains of mice with N-nitroso-tris-chloroethylurea by skin painting and found that this regimen induced lung SCCs in five strains of mouse (SWR/J, NIH Swiss, A/J, BALB/cJ, and FVB/J) but not in the others (AKR/J, 129/svJ, and C57BL/6J). Mouse lung SCCs have similar histopathological features and keratin staining to human SCC. Moreover, a wide spectrum of abnormal lung squamous phenotypes including hyperplasia, metaplasia, carcinoma in situ, and invasive carcinoma, were observed. There are strain-specific differences in susceptibility to Lscc induction by N-nitroso-tris-chloroethylurea with NIH Swiss, A/J, and SWR/J mice developing scores of SCCs whereas the resistant strains AKR/J, 129/svJ, and C57BL/6J failed to develop any SCCs. FVB/J and BALB/cJ mice had an intermediate response. We conducted whole-genome linkage disequilibrium analysis in seven strains of mice, divided into three phenotype categories of susceptibility, using Fisher's exact test applied to 6,128 markers in publically available databases. Three markers were found significantly associated with susceptibility to SCC with the P < 0.05. They were D1Mit169, D3Mit178, and D18Mit91. Interestingly, none of these sites overlap with the major susceptibility loci associated with lung adenoma/adenocarcinoma development in mice. The mouse SCC described here is highly significant for preclinical studies of lung cancer chemopreventive agents because most human trials have been conducted against precancerous lesions for SCC. Furthermore, this model can be used in determining genetic modifiers that contribute to susceptibility or resistance to lung SCC development.

Rodent models of genetic disease

The genetic study of rats and mice using natural variants, natural mutations, chemical or radiation induced mutations, engineered mutations and conditional engineered mutations has provided the tools for investigating the genetics of disease. The completion of the mouse genomic sequence and progress towards sequencing the rat genome in the past year will enable the molecular identification of quantitative trait loci and induced mutations. Sequence-based single nucleotide polymorphism discovery and a greater understanding of the haplotype structure of inbred strains is revitalising quantitative trait locus mapping and there are now plans for an ambitious eight-way recombinant inbred cross and renewed interest in existing resources such as heterogeneous stocks. In the past year there have been refinements to ENU mutagenesis approaches including balancer chromosomes and a new gene-driven approach.

Superoxide activates constitutive nitric oxide synthase in a brain particulate fraction

Nitric oxide (*NO) can act as an antioxidant by directly scavenging reactive free radicals, inhibiting the oxidative chemistry of iron, and signaling the up-regulation of antioxidant enzymes. However, the cellular utility of *NO as an antioxidant requires that constitutive nitric oxide synthase (NOS) be activated rapidly by a signal(s) for oxidant formation. We report here that superoxide (O2*-), added directly as potassium superoxide (KO2), produced a superoxide dismutase-sensitive and hydrogen peroxide-independent stimulation of NOS activity, measured by the conversion of [3H]arginine to [3H]citrulline and nitrite formation, in a synaptic particulate fraction from rat brain cerebral cortex. O2*- produced maximal activation of NOS in the presence of the antioxidant urate and ATP. Stimulation of NOS activity by O2*- was abolished by N-monomethyl-L-arginine and by the Ca2+ chelator EGTA but not by 7-nitroindazole, which would be expected to inhibit neuronal NOS. We propose that limited activation of NOS by O2*- may be an important contributor to brain oxidant defenses and, more generally, a signal for cellular adaptation and survival, although excessive generation of nitrogen oxides would be expected to produce neurotoxicity.

Deviated overexpression of TCR-beta, TCR-gamma, CD4, and CD8 on thymic lymphomas induced by 1-propyl-1-nitrosourea: destruction of the allelic exclusion of TCR-beta and expression of functional TCR-betagamma heterodimer on a lymphoma, cFTL53

Thymic lymphomas (FTLs) induced by the chemical carcinogen 1-propyl-1-nitrosourea (PNU) in F344 rats showed deviated overexpression of TCR-beta, TCR-gamma, CD4, and CD8. Even though most FTLs were in the CD4+ CD8+ stage, all FTLs expressed TCR-beta mRNA with TCR-gamma mRNA, but without TCR-alpha mRNA or TCR-delta mRNA. One of the FTLs, cFTL53, expressed two kinds of TCR-beta mRNA and two kinds of TCR-gamma mRNA, but did not express any mRNA of TCR-alpha or TCR-delta. Both alleles of TCR-beta loci were rearranged on cFTL53. cDNA cloning and sequencing analysis showed that one TCR-gamma mRNA, Vgamma4-Jgamma1-Cgamma1, and both TCR-beta mRNA, Vbeta2-Dbeta2-Jbeta2.1 and Vbeta19-Dbeta2-Jbeta2.1-Cbeta2, on cFTL53 were in the productive form, while the other TCR-gamma mRNA, Vgamma1-Jgamma4-Cgamma4L, was not. Both TCR beta-chains and a TCR gamma-chain were expressed on cFTL53, making a novel set of TCR-betagamma heterodimer. Cross-linking of TCR-betagamma heterodimer on cFTL53 resulted in a calcium flux, indicating that TCR-betagamma works as a signal transduction receptor. Thus, there are four strange phenomena on FTLs; CD4 and CD8 are expressed without TCR-alphabeta or TCR-gammadelta, TCR-beta mRNA and TCR-gamma mRNA were expressed simultaneously without TCR-alpha and TCR-delta mRNA on FTLs, the allelic exclusion of TCR-beta was destroyed in cFTL53, and a novel set of functional TCR-betagamma heterodimer was expressed on cFTL53.

IN VIVO ANTIVIRAL ACTIVITY OF 1,3-BIS(2-CHLOROETHYL)-1-NITROSOUREA

A prolongation in the lives of Swiss mice inoculated intracerebrally with lymphocytic choriomeningitis virus (LCM) was observed after treatment with 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU). A variety of treatment schedules, including therapy once or twice daily up to 17 days and single treatments at various times after virus inoculation, were employed. Virus titers ranging to greater than 10(4) were detected in the blood and brains of surviving drug-treated animals. In three comparative studies in which different treatment schedules were used, BCNU was shown to exert a protective effect approximately equal to that of methotrexate in LCM virus-infected mice. Tests were also carried out to investigate the activity of BCNU in mice experimentally infected with eastern equine encephalomyelitis (EEE) virus, western equine encephalomyelitis virus, Semliki Forest (SF) virus, herpes simplex virus, influenza virus strain PR8, vaccinia virus strain WR, Rous sarcoma virus, Friend leukemia virus (FLV), and poliovirus. Slight increases in life span were observed in the treated EEE, SF, and influenza PR8 virus-infected animals. Significant reduction in splenomegaly in FLV-infected animals treated with BCNU was demonstrated. The possible mechanisms of LCM virus inhibition by BCNU, on the basis of these and other studies, were postulated to be either specific antiviral activity or inhibition of "lethal" immune response to the LCM virus. Each of these postulates is discussed.

Reduced fidelity of DNA synthesis in cell extracts from chemically induced primary thymic lymphomas of mice

To examine whether the fidelity of DNA synthesis is reduced in tumor cells, M13 mp2-based fidelity assays were carried out using 15 samples of whole-cell extracts from primary mouse thymic lymphomas induced by alkylating agents. We found that DNA synthesis activities of thymic lymphomas, detected as incorporation of [3H]TTP into acid-insoluble materials, were 2- to 10-fold higher compared to those of normal thymus. Furthermore, mutant frequencies in the forward mutation assay of DNA synthesis were increased 2- to 7-fold in cell extracts from thymic lymphomas compared to those from normal thymus. As the DNA polymerase beta (pol beta) activity was extremely high in the thymic lymphomas, we screened mutations in the pol beta gene to examine the possibility of involvement of mutated pol beta in reduction of the fidelity of DNA synthesis. Of 20 lymphomas, one case of point mutation (T to A) was found by reverse transcription-PCR single-strand conformation polymorphism analysis. These results suggest that the mutagenic DNA synthesis is involved in murine thymic lymphoma genesis, although mutation of the pol beta gene is not a major causal event.

Genetic regulation of development of thymic lymphomas induced by N-propyl-N-nitrosourea in the rat

To clarify the linkage between Hbb and Tls-1 (thymic lymphoma susceptible-1) loci and to investigate other loci concerned in thymic lymphomagenesis, the BUF/Mna rat, which is highly sensitive to the lymphomagenic activity of N-propyl-N-nitrosourea (PNU), the WKY/NCrj rat, reported to be resistant, and their cross offspring were subjected to genetic analysis. F1 hybrid and backcross generations were raised from the 2 strains, and 6 genetic markers including Hbb were analyzed in individuals of the backcross generation. However, no linkage between Hbb and Tls-1 loci could be demonstrated since WKY rats also developed a high incidence of thymic lymphomas in response to PNU. Nevertheless, thymic lymphomas developed more rapidly and reached a larger size in the BUF rats. F1 rats expressed a rather rapid and large tumor growth phenotype, while the [(WKY X BUF) X WKY] backcross generation consisted of rats with either rapidly growing or slowly growing tumors. It was thus concluded that rapid development of thymic lymphomas is determined by a gene, provisionally designated Tls-3. Analysis of the relationship between 6 genetic markers and development of thymic lymphoma in the backcross generation demonstrated that the Tls-3 locus is loosely linked to the Gc locus, suggesting a possible location on rat chromosome 14. Tls-3 may not be identical with Tls-1 and other genes known to be relevant to thymic tumors, but its relationship with Tls-2 remains obscure.

In vitro carcinogenesis of hamster pancreatic duct cells: cellular and molecular alterations

Neoplastic transformation of Syrian golden hamster (SGH) pancreatic duct cells was induced by in vitro treatment with the direct-acting carcinogens N-methylnitrosourea (MNU) and N-(2-hydroxypropyl)nitrosourea (HPNU), with subsequent selection by sustained culture in serum- and epidermal growth factor (EGF)-deprived medium. The present study examines the efficacy of serum and EGF deprivation as a selection pressure and the effect of the carcinogen dose, frequency and interval of exposure on tumorigenesis and K-ras mutation. Selection of carcinogen-initiated duct cells by serum and EGF deprivation is highly reproducible and effective, increasing the incidence of tumors from 26 to 93% for MNU or from 0 to 100% for HPNU. SGH pancreatic duct cells exposed to 0.5 mM MNU for 13 weeks (long-treatment schedule) produced K-ras mutations at codon 12 in six of six tumors. However, when cells were exposed to 0.125, 0.25 or 0.5 mM MNU daily for 5 days (short-treatment schedule), mutations of K-ras at codon 13 were identified in four of 16 tumors, the remaining 12 showing no mutations. Duct cells exposed to 0.5 mM HPNU by the short-treatment schedule produced K-ras mutations in codon 13 in six of six tumors, as contrasted to 12 tumors that developed from cells exposed to 0.125 or 0.25 mM HPNU, which all contained K-ras codon 12 mutations. The current experiments demonstrate that K-ras mutation in pancreatic carcinogenesis in vitro by MNU or HPNU can be modified by the nature and dose of the carcinogen as well as the frequency and duration of exposure.

Erythroblasts as an index of initial stage of 2,7-FAA, ENU and BNU-induced rat leukemia

The appearance of orthochromatic erythroblasts in the peripheral blood was evaluated as an index of the initial stage of leukemia induced in rats by the oral administration of N,N'-2,7-fluorenylenebisacetamide, 1-ethyl-1-nitrosourea and 1-butyl-1-nitrosourea. Solitary leukemia lesions found mainly in the bone marrow and composed of one or a few nodular foci were found by using erythroblasts as an index. The time interval from the first appearance of erythroblasts to autopsy was short in solitary lesions, slightly longer in scattered lesions, and even longer in diffuse leukemia lesions. Although the appearance of orthochromatic erythroblasts in the peripheral blood was due to several causes other than leukemia, this appearance was useful as an index of the initial stage of chemically induced leukemia in rats.

Treatment of recurrent gliomas and metastatic brain tumors with a polydrug protocol designed to combat nitrosourea resistance

PURPOSE

The study was undertaken to evaluate a chemotherapy protocol against recurrent malignant gliomas that was designed to combat presumed chloroethyl-nitrosourea (NU) resistance.

PATIENTS AND METHODS

All patients had malignant gliomas and had failed prior therapy. Patients were stratified as having either glioblastoma multiforme (GM) or anaplastic gliomas (AG) and as having failed radiotherapy (RT) only or both RT and chemotherapy. Chemotherapy consisted of six drugs: before lomustine (CCNU), thioguanine (TG), dibromodulcitol (mitolactol; DBD), and procarbazine (PCB) were given to enhance CCNU-induced tumor-cell kill and to reduce alkyltransferase repair of ethylated DNA. A fluorouracil-hydroxyurea (FUHU) combination was given 2 weeks later to kill cells that began to cycle after the challenge of the first four drugs (TPDC-FUHU chemotherapy).

RESULTS

Of the 88 assessable patients, 37 had GM, 38 had AG, and 13 had other primary and metastatic brain tumors. For GM patients, 61% had a partial response (PR) or stable disease (SD) for a median of 9.3 months if RT only failed, and 58% had a PR or SD for a median of 5.1 months if they had previously been treated with an NU. For AG patients, 92% had a PR or SD for a median of 15 months if RT only had failed, but only 38% had a PR or SD for a median of 10.6 months if they had been previously treated with a NU. Activity was also seen against other recurrent or progressive primary and metastatic brain tumors.

CONCLUSIONS

TDPC-FUHU chemotherapy is a highly effective form of chemotherapy for both recurrent GM and AG patients. This study suggests but does not prove that this combination may be superior to other NU-based treatments for recurrent malignant glioma patients who fail RT. Because of the activity of this chemotherapy, we intend to evaluate more fully this approach in a randomized study.

Initial changes of rat leukemia induced by 1-ethyl-1-nitrosourea and 1-butyl-1-nitrosourea

The initial histological changes of leukemia were investigated in rats to which 1-ethyl-1-nitrosourea and 1-butyl-1-nitrosourea were orally administered. The appearance of orthochromatic erythroblasts in the peripheral blood was used as the index of the initial stage of leukemia. The rat leukemia progressed from solitary lesions to scattered and further diffuse lesions. These leukemias are thought to begin as one, or only a few nodular foci, mainly in the bone marrow and partly in the spleen.

Mouse bronchiolar cell carcinogenesis. Histologic characterization and expression of Clara cell antigen in lesions induced by N-nitrosobis-(2-chloroethyl) ureas

Female Swiss mice (Cr:NIH(S)) developed bronchiolar cell hyperplasia, dysplasia, metaplasia, and various morphologic types of bronchiolar cell tumors after topical (skin) application of N-nitroso-methyl-bis-chloroethylurea (NMBCU) or N-nitroso-tris-chloroethylurea (NTCU). These compounds are the first found to induce systemically bronchiolar cell tumors in mice in high incidence. Twice a week, with a 3-day interval, a 25-microliter drop of 0.04 mol/l (molar) NMBCU or NTCU in acetone was applied to the shaved interscapular integument for a maximum of 35 to 40 weeks. The earliest lung neoplasms were seen in mice that died after 23 weeks of treatment and affected 11 of 19 with NMBCU and 14 of 19 with NTCU treatment. Tumor growth pattern was nodular or the neoplastic tissue was frequently disseminated throughout the parenchyma, starting from multicentric peribronchiolar foci. The most common tumor types were squamous cell carcinomas and adenosquamous carcinomas, followed by adenocarcinomas with or without secretory cells, and a single ciliated-cell tumor. Histochemical and immunohistochemical studies were carried out on paraffin-embedded lungs using the avidin-biotin immunoperoxidase complex procedure and antisera against keratin, Clara cell antigen, surfactant apoprotein, neuron-specific enolase, bombesin, and chromogranin A. In several mice from both groups, hyperplasias and tumors were composed of cells expressing Clara cell antigen. No tumor cells were found expressing alveolar type II or neuroendocrine cell markers. It appeared that bronchiolar cells, in particular Clara cells, had migrated from terminal bronchioles or invaded bronchiolar walls to extend into the alveolar parenchyma. Squamous cell metaplasia with keratin expression was seen within airways or associated with glandular tumors, especially at the periphery. A unique cell type, with large eosinophilic globules and associated eosinophilic crystals, was seen lining airways or forming hyperplastic and neoplastic lesions. N-nitroso-methyl-bis-chloroethylurea- and NTCU-induced mouse bronchiolar cell alterations could be an interesting new model to study mechanisms of bronchiolar cell differentiation and tumor formation.

Sequential study on spontaneous colony formation by bone marrow cells during butylnitrosourea-induced leukemogenesis in the rat

The spontaneous colony (SC)-forming activity of bone marrow cells of rats during butylnitrosourea (BNU) treatment was studied sequentially in an attempt to analyze stages of leukemogenesis. Aspirated bone marrow cells from female Sprague-Dawley (SD) rats that had been given continuous access to drinking water containing 400 ppm BNU were examined at intervals of 3-5 weeks for colony formation of granulomonocytic cells with or without supplemental colony-stimulating factor (CSF). Granulocytic leukemia was first observed at week 12, and the cumulative incidence reached 80% by week 30. SCs were obtained in 56% of rats in the early stage (3 weeks) and in up to 59% of rats in the late stages (20-25 weeks). However, in the middle stages colony formation was rare, even with the addition of CSF. When adherent cells were removed from the bone marrow cells, the SC-forming activity in the early stage was almost entirely lost, whereas much of that in the late stage remained. It is possible that in the former case, overproduction of endogenous CSF by adherent cells under the influence of BNU treatment could be involved. In contrast, late stage SC formation may be associated with the generation of altered cells, including leukemic or preleukemic elements, which have increased capacity for autonomous growth. The loss of SC-forming activity in the middle stage appeared to be attributable to an extreme reduction in endogenous CSF due to marked devastation of the bone marrow. Technical improvement in adjusting more precisely the level of CSF in the culture medium is required to enable further analysis of leukemogenesis, focused on the colony-forming activity of target cells.

Similar carcinogenic actions of nitrosoalkylureas of varying structure given to rats by gavage

To relate the tumorigenic effects of directly acting alkylating nitrosoalkylureas to their chemical structure, a series of these compounds was given to F344 rats by gavage at approximately equimolar doses. In some cases, more than one dose rate was used. Potency, as measured by time to death with tumors, was similar for nitrosomethylurea and nitrosoethylurea, although the tumor pattern was different between the two. Nitrosoallylurea was of similar potency, and induced a spectrum of tumors similar to nitroethylurea. Nitroso-n-butyl-, n-amyl- and n-hexyl-ureas were less potent than nitrosoethylurea, but induced a similar pattern of tumors. All of the nitrosoureas induced tumors of the forestomach, usually in high incidence, except nitroso-2-hydroxypropylurea, which caused death of the rats with thymic lymphoma within 6 months. Nitroso-3-hydroxypropylurea was much less potent than its 2-isomer, but induced no tumors of the thymus and was the only one of this group to induce tumors of the glandular stomach. Only nitrosomethylurea induced a high incidence of tumors of the nervous system, but no mammary carcinomas, which most of the other nitrosoureas induced in high incidence in females. Tumors of the lung, duodenum, colon and intestines were induced by several of the compounds, more commonly in males than in females, but a high incidence of liver tumors was found only in rats of both sexes given nitroso-2-phenylethylurea.

Thymic lymphomas induced by N-propyl-N-nitrosourea (PNU) in the BUF/Mna rat, an inbred strain with a high incidence of spontaneous thymoma

N-Propyl-N-nitrosourea (PNU) is known to be a strong leukemogen, inducing myelogenous leukemia or thymic lymphoma in some strains of rat. The thymic lymphomagenic effect of PNU has been demonstrated in F344 rats. On the other hand, the BUF/Mna rat has been established as an inbred strain that develops spontaneous thymomas after one year of age. In the present experiment, PNU was continuously administered in drinking water to male and female BUF/Mna rats starting at 5 weeks of age. Thymic lymphomas were induced in all PNU-treated rats with an average latent period as short as 14 experimental weeks. These results show the high susceptibility of the BUF/Mna rat to the lymphomagenic activity of PNU. The BUF/Mna rat is an ideal strain for studies on epithelial cell-lymphocyte interaction, not only in the development of thymic lymphomas but also in that of spontaneous thymoma. Karyotypes of twelve primary thymic lymphomas induced by PNU were analyzed for chromosomal abnormalities. Chromosomal abnormalities were often found in chromosomes 11 and 2. In some types of abnormality, dup (11q) and del(2q) were most frequently observed. In addition, trisomy of chromosome 7, on which the c-myc gene is mapped, was observed in five lymphomas, and monosomy of chromosomes 20 and X in six and five cases, respectively, though these changes were generally observed in a minor cell population in each case.

[Modifying effects of beraprost sodium (TRK-100) on N-methyl-N-nitrosourea (MNU) carcinogenesis in F344 rats]

The potential tumor-promoting effects of beraprost sodium (TRK-100), stable analogue of prostacyclin (PGI2), were investigated in rats pretreated with N-methyl-N-nitrosourea (MNU) which is a potent initiator of tumor development in a variety of organ or tissues. Male F344 rats were initially given injections of MNU (20 mg/kg b.w. i.p.) twice a week for 3 weeks, and then administered drinking water containing 6, 2, 0.7 or 0.2 ppm of beraprost sodium for the next 29 weeks. For comparison, positive control groups received N-propyl-N-nitrosourea (PNU), which is a carcinogen in hematopoietic system and small intestine on F344 rat, at the dose of 200, 50 and 12.5 ppm in their drinking water. Appropriate non-treated controls were also included. Numerous tumors were observed in many organs including the hematopoietic system, digestive tract, nervous system, Zymbal's gland (auditory sebaceous glands) and peritoneal mesothelium. However, no tumor-enhancing effects of beraprost sodium were observed. In contrast, the groups treated with PNU demonstrated increased development of tumors in the tongue, forestomach, large intestine and Zymbal's gland. These results thus indicate that beraprost sodium is not capable of modulating the development of MNU-induced tumors.

Induction of lung tumors and peritoneal mesotheliomas in F344 rats given intragastric N-propyl-N-nitrosourea and histochemical, immunohistochemical, and ultrastructural characteristics of induced mesotheliomas

N-Propyl-N-nitrosourea is a strong leukemogen that induces myelogenic leukemia in Donryu rats and thymic lymphoma in F344 rats when administered in drinking water. In the present study, a single or multiple doses of PNU (total 500 mg/kg body weight) was given to young male and female F344 rats via a stomach tube. The results demonstrated that the percentage of tumor-bearing rats was 100% in all PNU-treated male groups, while that of the control group was 46%. Predominant tumors induced by PNU in male rats were lung adenoma/adenocarcinoma followed by peritoneal mesothelioma, and forestomach papilloma. In females, the tumor incidence of PNU-treated groups varied between 58% and 92% while that of the control group was 42%. Although pituitary tumor was the most frequent tumor in PNU-treated female rats, it was thought to be spontaneous since its incidence in each experimental group was not statistically different from that of the control group. Lung tumors and forestomach papillomas were also induced by PNU in female rats. No thymic lymphoma, however, was found in any of the PNU-treated groups of either sex. Lung tumors developed in almost all PNU-treated male rats and in about one-third of PNU-treated female rats. Mesothelioma was induced only in male rats, and its incidence depended on the treatment schedule. Induced mesotheliomas were extensively examined histologically, histochemically, immunohistochemically, and electron microscopically.

Decontamination and disposal of nitrosoureas and related N-nitroso compounds

An improved procedure for chemically decontaminating residues of nitrosoureas and related N-nitroso compounds ("nitrosamides") commonly used in the cancer research laboratory is proposed. Treatment of accumulated wastes with aluminum:nickel alloy powder while progressively increasing the basicity of the medium consistently led to at least 99.98% destruction of each nitrosamide tested. Hazardous diazoalkanes were never detected in yields of greater than 0.1%. The mutagenicity of the completed reaction mixtures was never more than 3 times background except when the N-nitroso compound contained a 2-chloroethyl group. In most cases, the completeness of reaction could be determined chromatographically, not only to demonstrate the disappearance of the starting N-nitroso compound, but also to follow production of identifiable products in sufficient abundance to account for the starting material destroyed; none of the organic products observed was mutagenic in any of the four tester strains used. The procedure described herein proved reliable in two checker laboratories besides our own when applied to mixtures of seven N-nitroso compounds: N-methyl-N-nitroso-p-toluene-sulfonamide; N-methyl-N-nitrosourethane; N-methyl-N-nitrosourea; N-methyl-N'-nitro-N-nitrosoguanidine; N-ethyl-N-nitrosourea; N-ethyl-N'-nitro-N-nitrosoguanidine; and N-ethyl-N-nitrosourethane. All of the other procedures investigated for destruction of nitrosamides, including the widely used approach of dissolving the nitrosamides in alkali, were associated with important disadvantages.

Cytogenetic studies on rat thymic lymphomas induced by N-propyl-N-nitrosourea

N-Propyl-N-nitrosourea (PNU) was proved to be a strong leukemogen, which induces myelogenous leukemia or thymic lymphoma in rats. BUF/Mna rats and F344 rats were the strain most susceptible to thymic lymphomagenic activity of PNU. In addition, F1 rats between BUF/Mna and WKY rats were also susceptible to PNU-lymphomagenic activity. In the present experiment, karyotypes of 31 thymic lymphomas induced by PNU in BUF/Mna rats and in F1 rats between BUF/Mna and WKY rats were analysed for chromosomal abnormalities. Although no specific chromosomal abnormalities were observed throughout all lymphomas, del(11q) and dup(2q) were observed frequently in BUF/Mna rat lymphomas. Breakpoints and/or fusion-points were frequently observed in chromosome 11, followed by chromosomes 2, 5 and 6. Trisomy of chromosome 7, on which c-myc oncogene is mapped, was observed in seven cases, and monosomy of chromosomes 12, 18, 19, 20 and X was seen in seven or eight cases each, though these changes were generally observed in minor cell population in each case.

Animal models of exocrine pancreatic carcinogenesis

In order to understand the evolution, histogenesis, and biological behaviour of exocrine pancreatic carcinoma, some reproducible experimental models have been developed in certain rodent species. To date, more than 16 chemicals, many of them structurally unrelated, have been shown to induce pancreatic tumors. Although some of these chemicals appear species specific in their effect on the pancreas, others have been shown to be capable of inducing pancreatic tumors in more than one species. In hamsters, the administration of diisopropylnitrosamine or its oxidized metabolites leads to the development of ductal adenocarcinomas that histologically resemble human pancreatic carcinomas. The histogenesis of the ductal type of adenocarcinoma in hamsters is complex, and appears to involve both the duct cells and dedifferentiated acinar cells. All pancreatic tumors in rats develop from acinar cells showing variable degrees of differentiation, regardless of the type of carcinogen used. The type of pancreatic lesions that develop in mice are also of acinar cell origin. In guinea pigs the tumors are adenocarcinomas of the ductal type and are shown to be derived from dedifferentiated acinar cells that have undergone duct-like transformation. Irrespective of the type of tumor that develops in these experimental animals, all of these models can be successfully used to evaluate the various modifying (risk) factors and biological behaviour of these neoplasms.

Long-term studies on carcinogenicity and promoting effect of phenylbutazone in DONRYU rats

The carcinogenicity and promoting effect of phenylbutazone were investigated in inbred DONRYU rats. In the carcinogenicity study, both sexes were administered the chemical at dietary levels of 0 (control), 0.125, or 0.25% for 2 years. Toxic lesions were associated with phenylbutazone treatment in the kidney and digestive tract, appearing to have an adverse effect on life expectancy. Various tumors were detected in all groups including the controls. With the exception of pheochromocytoma in the female high-dose group, no statistically significant increase in yield of any tumors, including leukemia, was apparent in the treated groups of either sex when the data were analyzed by Fisher's exact probability and/or chi-square tests. Application of an age-adjusted statistical analysis revealed a slight positive effect regarding the occurrence of pheochromocytomas, neoplastic liver nodules, and leukemias in females. However, these tumors are commonly observed to develop spontaneously in this rat strain, and no such effect was apparent in the male groups. In addition, no differences in incidences of relevant preneoplastic lesions were evident between control and treated groups. Thus phenylbutazone showed no carcinogenic activity in DONRYU rats when given continuously in the diet for 2 years. For the investigation of promoting effect, phenylbutazone was given as a dietary supplement for 2 years subsequent to initiation with N-ethyl-N-nitrosourea or N-propyl-N-nitrosourea. No enhancement of nitrosourea-induced leukemogenesis was apparent, although a slight promoting effect was demonstrated for renal and thyroid tumorigenesis.

Effects of radiation and other influences on chemical lymphomagenesis

Methylnitrosourea (MNU) or butylnitrosourea (BNU) was used to induce T cell lymphomas (thymomas) in BDF1 mice. In addition to the chemical, X-rays in various dose schedules were applied. An effect of the irradiation (shortening of the latency period) was seen with 12 X 0.25 Gy in protocols with a prolonged median induction time in the controls as a result of a dose reduction of the chemical (median induction time 27-36 weeks instead of 16-18 weeks under 'optimal' conditions using 50 mg kg-1 of MNU). Preirradiation 2-5 weeks before 40 mg kg-1 of MNU resulted in enhanced leukaemogenesis. Also, mice with regenerating lympho-haemopoiesis after lethal irradiation and bone marrow transplantation were more sensitive to the effect of both chemicals than were the controls. Treatment with anti-thy 1.2 and with corynebacterium parvum during the latency period had no influence.

N-methyl antitumour agents. A distinct class of anticancer drugs?

This article reviews the structure-activity characteristics, mode of action, pharmacokinetics and clinical utility of a group of chemically dissimilar antitumour agents which have as a common structural feature the N-methyl moiety. The importance of this feature is shown by the fact that molecules without a substituent on the nitrogen or compounds with N-alkyl groups other than methyl are usually inactive in experimental systems. This observation is supported by structure-activity studies with N-alkyl derivatives of s-triazines, triazenes, formamides, hydrazines and nitrosoureas. Representatives of these structural types which have found clinical application are, respectively, hexamethylmelamine, dacarbazine, N-methylformamide, procarbazine and streptozotocin. Mode of action studies have shown that dacarbazine, procarbazine and streptozotocin can give rise to species capable of methylating nucleic acid. This may be the lesion which produces antitumour activity. The mechanism of action of N-methylmelamines and N-methylformamide remains unclear. There is good evidence that, with the exception of N-methylnitrosoureas, host metabolism is prerequisite for activity with these agents. Although not pronounced, the clinical activity of N-methyl antitumour agents is useful, particularly as activity is not associated with severe haematological toxicity. Furthermore, responses may be observed in patients resistant to bifunctional alkylating agents. It is concluded that the drugs reviewed herein show a degree of coincidence in terms of their biological properties which may warrant a common classification. The term N-methyl antitumour agent is proposed.

Ab initio studies of the decomposition of nitrosourea in the presence of cations

Self-consistent (Hartree-Fock) calculations of the process of decomposition of protonated and lithiated syn-N-nitrosourea show that the presence of cations perturbs the electron distribution significantly. The decomposition of nitrosourea is facilitated when a proton or lithium ion is positioned at the oxygen of the nitroso group. These results may suggest clinical experimentation with nitrosoureas used in conjunction with lithium salts.

Carcinogenesis in F-344 rats induced by nitrosohydroxyalkyl-chloroethylureas

The two isomeric N-nitroso derivatives of 1-chloroethyl-3-(2-hydroxyethyl)-urea and of 1-chloroethyl-3-(2-hydroxypropyl)-urea were prepared and isolated. They were given by gavage in ethyl acetate/corn oil to groups of 20 male and female F-344 rats. The two nitroso-1-chloroethyl compounds were nephrotoxic and most animals died within 20 weeks; no neoplasms were seen in any of these animals. Nitroso-1-hydroxyethyl-3-chloroethylurea was given at 2 concentrations, 21 and 10.5 mg/ml; in both groups almost all animals died with neoplasms related to the treatment. These included hepatocellular and cholangiocellular neoplasms of the liver; many of the former metastasized. Many rats also had tubular cell neoplasms in the kidney. Nitroso-1-(2-hydroxypropyl)-3-chloroethylurea was a less potent carcinogen at equimolar doses, inducing fewer liver neoplasms than the nitrosohydroxyethyl analog and only few kidney neoplasms. Both of these carcinogens were less effective in female rats than in males, although the females, which were smaller, received a higher dose per unit body weight. The spectrum of neoplasms induced by the nitrosohydroxyalkyl-chloroethylureas was quite different from that induced by equimolar doses of each corresponding nitrosohydroxyalkylurea, neither of which induced neoplasms of the liver, although they were potent inducers of neoplasms in other organs.