DNA polymerase κ suppresses inflammation and inflammation-induced mutagenesis and carcinogenic potential in the colon of mice

BACKGROUND

Chronic inflammation induces DNA damage and promotes cell proliferation, thereby increasing the risk of cancer. DNA polymerase κ (Pol κ), involved in translesion DNA synthesis, counteracts mutagenesis induced by inflammation in the colon of mice. In the present study, we examined whether Pol κ suppressed inflammation-induced colon tumorigenesis by treating inactivated Polk knock-in (Polk^-/-) mice with dextran sulfate sodium (DSS), an inducer of colon inflammation.

RESULTS

Male and female Polk^-/- and Polk^+/+ mice were administered 2% DSS in drinking water for six consecutive days, succeeded via a recovery period of 16 days, followed by 2% DSS for another two days. DSS treatment strongly induced colitis, and the severity of colitis was higher in Polk^-/- mice than in Polk^+/+ mice. The mice were sacrificed after 19 weeks from the initiation of the first DSS treatment and subjected to pathological examination and mutation analysis. DSS treatment induced colonic dysplasia, and the multiplicity of dysplasia was higher in Polk^-/- mice than in Polk^+/+mice. Some of the dysplasias in Polk^-/- mice exhibited β-catenin-stained nucleus and/or cytoplasm. Mutation frequencies in the gpt reporter gene were increased by DSS treatment in Polk^-/- mice, and were higher than those in Polk^+/+ mice.

CONCLUSIONS

Pol κ suppresses inflammation and inflammation-induced dysplasia as well as inflammation-induced mutagenesis. The possible mechanisms by which Pol κ suppresses colitis- and colitis-induced dysplasia are discussed.

o-Aminoazotoluene, 7,12-dimethylbenz[a]anthracene, and N-ethyl-N-nitrosourea, which are mutagenic but not carcinogenic in the colon, rapidly induce colonic tumors in mice with dextran sulfate sodium-induced colitis

BACKGROUND

Several rodent models with chemically induced colon cancer have been developed. Among these models, dextran sulfate sodium (DSS), a colitis inducer, combined with azoxymethane as a colon mutagenic carcinogen, is commonly used. We previously reported that although benzo [a] pyrene (BP) is mutagenic but not carcinogenic in the colon, it rapidly develops colon tumors at a high incidence/multiplicity after treatment with DSS. In the present study, we examined whether other colon-mutagenic non-carcinogens (CMNCs) induced colon tumors after treatment with DSS.

RESULTS

o-Aminoazotoluene, 7,12-dimethylbenz[a]anthracene, and N-ethyl-N-nitrosourea were selected as CMNCs. Male CD2F1 mice were orally administered CMNC for 5 consecutive days. After a 9-day dose-free period, mice were treated with 4% DSS in drinking water for 1 week. Three months after DSS treatment, colon samples were collected for histopathology and β-catenin immunohistochemistry analyses. All CMNCs in combination with DSS induced colonic adenocarcinomas at a high incidence/multiplicity in the distal and middle parts of the colon, coinciding with the location of colitis. Unlike in normal cells where β-catenin is exclusively located on the cell membrane, in adenocarcinoma cells, it was translocated to both the nucleus and cytoplasm or only to cytoplasm. The translocation of β-catenin is closely associated with colon carcinogenesis in rodents and humans. No colonic tumors or dysplastic lesions were found after exposure to either CMNC or DSS alone.

CONCLUSION

We provided further evidence clearly showing that CMNCs can rapidly induce colonic tumors in mice with DSS-induced colitis, even if they are not colonic carcinogens.

DNA polymerase kappa counteracts inflammation-induced mutagenesis in multiple organs of mice

In vitro studies indicate that DNA polymerase kappa (Polκ) is able to accurately and efficiently perform DNA synthesis using templates containing various types of DNA damage, including benzo[a]pyrene (BP)-induced N² -deoxyguanosine adducts. In this study, we examined sensitivity of inactivated Polk knock-in (Polk^-/- ) mice to BP carcinogenicity in the colon by administering an oral dose of BP plus dextran sulfate sodium (DSS), an inflammation causing promoter of carcinogenesis. Although colon cancer was successfully induced by BP plus DSS, there was no significant difference in tumor incidence or multiplicity between Polk^-/- and Polk^+/+ mice. Malignant lymphoma was induced in thymus by the treatment only in Polk^-/- mice, but it lacked statistical significance. Mutant frequencies (MFs) in the gpt reporter gene were strongly enhanced in colon; almost to the same extent in both types of mice. Micronucleus formation in bone marrow at the high dose of BP and DNA adducts in colon and lung was not significantly different between two types of mice. Surprisingly, however, Polk^-/- mice exhibited significantly higher MFs in colon and lung than did Polk^+/+ mice when they were treated with DSS alone. The most prominent mutation induced by DSS treatment was G:C to C:G transversion, whose specific MF in proximal colon was 30 times higher in Polk^-/- than in Polk^+/+ mice. DSS alone did not enhance MF at all in Polk^+/+ mice. The results indicate that Polκ does not suppress BP-induced mutagenesis and carcinogenesis in the colon, but counteracts inflammation-induced mutagenesis in multiple organs. Environ. Mol. Mutagen. 60:320-330, 2019. © 2019 Wiley Periodicals, Inc.

Wif1 and Ifitm3 gene expression preferentially altered in the colon mucosa of benzo[a]pyrene pre-treated mice following exposure to dextran sulfate sodium

Benzo[a]pyrene (BP) is highly mutagenic and yet does not lead to tumor development in the murine colon. We recently reported the generation of colonic tumors one week after treatment with BP followed by dextran sulfate sodium (DSS), a colitis-inducer. In this BP/DSS model, male CD2F1 mice were treated orally with BP at 125 mg/kg/day for 5 days, followed by 4% DSS in drinking water for one week. There has been no report so far on the molecular mechanisms involved in tumor development in this model. In the present study, we performed global gene expression analysis on the colonic mucosae obtained from BP-exposed mice one week after treatment with DSS and those treated with the vehicle, BP, or DSS alone. Global gene expression analysis revealed that there were 563 genes preferentially altered (≥2-fold vs vehicle group) in the colonic mucosae exposed to both BP and DSS. Furthermore, comparative gene expression analysis combined with Ingenuity Pathway Analysis™ identified 2 genes associated with Wnt/β-catenin signaling pathway that were preferentially up-regulated (≥2-fold vs vehicle group) when BP and DSS were treated in combination in the distal part (site of predilection for tumor induction) of the colonic mucosae, especially in colonic tumors: WNT inhibitory factor 1 (Wif1; 14.6-fold increase) and interferon induced membrane protein 3 (Ifitm3; 5.7-fold increase). In colonic tumors, expression of Wif1 and Ifitm3 proteins were both confirmed by western blot analysis. These findings suggest that these genes are associated with rapid induction of colonic tumors in mice after exposure to BP/DSS, providing insights into the mechanisms of the BP/DSS short-term colon carcinogenesis.

Time course of the incidence/multiplicity and histopathological features of murine colonic dysplasia, adenoma and adenocarcinoma induced by benzo[a]pyrene and dextran sulfate sodium

Benzo[a]pyrene (BP) is mutagenic but noncarcinogenic in the murine colon. Recently, we reported rapid induction of colonic tumors by treatment of CD2F₁ mice with BP (125 mg/kg for 5 days) followed by a colitis inducer, dextran sulfate sodium (DSS) (4% in drinking water for 1 or 2 weeks). However, there are no reports on detailed time course and histopathological features of colonic proliferative lesions in this model. Here, we show the detailed time course of colonic dysplasia, adenoma and adenocarcinoma induced by treatment with BP, DSS, and a combination of the two (BP/DSS). In the colon of mice exposed to BP/DSS, 14.6 dysplastic foci per mouse were present one week after DSS treatment (week 4). The number of dysplastic foci decreased with time to 3.1 at week 9 and thereafter remained almost constant. At week 4, 1.5 adenocarcinomas were also observed, with a marked increase in numbers with time, reaching 29.3 at week 14. In contrast, the number of dysplastic foci induced by DSS alone showed a time course similar to that following BP/DSS treatment; however, only a few tumors appeared. Neither dysplastic foci nor neoplastic lesions were induced by BP only. In mice exposed to BP/DSS, β-catenin was demonstrated immunohistochemically in the nucleus and/or cytoplasm of the tumor cells, and this translocation from the cell membrane was evident in subsets of dysplastic foci. In dysplastic foci induced by DSS alone, β-catenin was absent in the nucleus/cytoplasm. These finding suggest that aberrant β-catenin accumulation in dysplastic foci is associated with tumor progression in this BP/DSS model.

Brunner's gland lesions in rats induced by a vascular endothelial growth factor receptor inhibitor

Vascular endothelial growth factor (VEGF) receptor tyrosine kinase (RTK) inhibitors are reported to cause reversible mucosal hyperplasia (adenosis) in the duodenum of rats; however, the pathogenesis is not fully elucidated. Using lenvatinib, a VEGF RTK inhibitor, we characterized the histologic time course of this duodenal change in rats. At 4 weeks, there was degeneration and necrosis of Brunner's gland epithelium accompanied by neutrophil infiltration around the affected glands. At 13 weeks, the inflammation was more extensive, and Brunner's gland epithelium was attenuated and flattened and was accompanied by reactive hyperplasia of duodenal epithelium. At 26 weeks, the changes became more severe and chronic and characterized by marked cystic dilation, which extended to the external muscular layer. These dilated glands exhibited morphological characteristics of duodenal crypt epithelium, suggestive of replacement of disappeared Brunner's glands by regenerative duodenal crypt epithelial cells. Similar changes were not present in similar time course studies in dog and monkey studies, suggesting that this is a rodent- or species-specific change. Based on the temporal progression of Brunner's gland lesion, we identify degeneration and necrosis of the Brunner's glands as the primary change leading to inflammation, cystic dilatation, and regeneration with cells that are morphologically suggestive of duodenal crypt epithelium.

Granulomatous nephritis consistent with malakoplakia in a cynomolgus monkey

Malakoplakia is a rare form of chronic granulomatous inflammation in mammals, and usually affects the urinary tract in humans. In this report, we present a case of granulomatous nephritis consistent with malakoplakia in a 4-year-old male cynomolgus monkey. Gross examination showed that the kidney was markedly enlarged and adhered to the surrounding organs. Histology showed that there was diffuse interstitial infiltration of histiocytes with abundant foamy eosinophilic cytoplasm resembling von Hansemann cells, PAS-positive granular cytoplasm and occasional PAS- and iron-positive intracellular small inclusion bodies. Electron microscopy showed that these histiocytes contained abundant lysosomes and phagolysosomes but no obvious Michaelis-Gutmann bodies. Based on these findings, a diagnosis of granulomatous nephritis consistent with early malakoplakia was made. This is the first report in a monkey of a renal lesion consistent with malakoplakia.

Spontaneous gingivitis related to hair penetration in rats

Maxillary gingivae from male and female Crl:CD(SD) rats at 12, 16, 21, and 34 weeks of age were examined histologically. The incidence of gingivitis was approximately 40%, with no age or sex predilection, and was most frequent between the first and second molar. Lesions were characterized by acute focal neutrophilic infiltration into the gingival mucosa, occasionally with inflammatory exudate. In severe cases, inflammation extended to the periodontal ligament with abscess formation, and adjacent alveolar bone destruction/resorption. The most characteristic finding was the presence of hair shafts associated with the lesion, which was observed in approximately 80% of the rats with gingivitis. These findings suggest that molar gingivitis occurs in rats from an early age and persists thereafter, and that the main cause of gingivitis in rats is hair penetration into the gingiva. It would be prudent to keep these background lesions in mind as potential modifiers in toxicity studies.

Efficacy of oral E1210, a new broad-spectrum antifungal with a novel mechanism of action, in murine models of candidiasis, aspergillosis, and fusariosis

E1210 is a first-in-class, broad-spectrum antifungal with a novel mechanism of action-inhibition of fungal glycosylphosphatidylinositol biosynthesis. In this study, the efficacies of E1210 and reference antifungals were evaluated in murine models of oropharyngeal and disseminated candidiasis, pulmonary aspergillosis, and disseminated fusariosis. Oral E1210 demonstrated dose-dependent efficacy in infections caused by Candida species, Aspergillus spp., and Fusarium solani. In the treatment of oropharyngeal candidiasis, E1210 and fluconazole each caused a significantly greater reduction in the number of oral CFU than the control treatment (P < 0.05). In the disseminated candidiasis model, mice treated with E1210, fluconazole, caspofungin, or liposomal amphotericin B showed significantly higher survival rates than the control mice (P < 0.05). E1210 was also highly effective in treating disseminated candidiasis caused by azole-resistant Candida albicans or Candida tropicalis. A 24-h delay in treatment onset minimally affected the efficacy outcome of E1210 in the treatment of disseminated candidiasis. In the Aspergillus flavus pulmonary aspergillosis model, mice treated with E1210, voriconazole, or caspofungin showed significantly higher survival rates than the control mice (P < 0.05). E1210 was also effective in the treatment of Aspergillus fumigatus pulmonary aspergillosis. In contrast to many antifungals, E1210 was also effective against disseminated fusariosis caused by F. solani. In conclusion, E1210 demonstrated consistent efficacy in murine models of oropharyngeal and disseminated candidiasis, pulmonary aspergillosis, and disseminated fusariosis. These data suggest that further studies to determine E1210's potential for the treatment of disseminated fungal infections are indicated.

Rapid induction of colonic adenocarcinoma in mice exposed to benzo[a]pyrene and dextran sulfate sodium

Previously, we reported that the mutation frequency was markedly increased in the colon after the oral treatment of mice with an environmental mutagen/carcinogen, benzo[a]pyrene (BP); however this was not followed by tumor development. The reasons for this are as yet unresolved. The purpose of the present study is to explore the mechanisms why a high frequency of mutations induced by BP in the colon is not associated with subsequent tumor development. We show in this study that oral administration of BP to CD2F(1) mice at 125 mg/kg/day for 5 days can lead to adenocarcinomas in the mouse colon both at Weeks 4 (5/8 mice) and 11 (100% of mice), but only in the presence of inflammation induced by 4% dextran sulfate sodium (DSS) in the drinking water for up to 2 weeks. These data indicate that, in this DSS model, BP induced mutagenic events lead to tumors in the mouse colon, a tissue which is not a BP target organ. DSS-induced inflammation in a tissue primed with mutagenic risk is a key to the induction of tumors in this model. This study provides a novel, rapid and useful colon carcinogenesis model (BP/DSS model).

Histopathological Characteristics of Luteal Hypertrophy Induced by Ethylene Glycol Monomethyl Ether with a Comparison to Normal Luteal Morphology in Rats

Ethylene glycol monomethyl ether (EGME) is a known reproductive toxicant that induces luteal hypertrophy in rat ovaries. In this study, we characterized the histopathological features of corpora lutea (CL) from EGME–treated rats and compared them with normal CL formation and regression. Normally cycling female Sprague-Dawley rats were treated with 5-bromo-2′-deoxyuridine (BrdU) intraperitoneally on the morning of estrus and their ovaries were examined 1 (metestrus), 4 (estrus), 8 (estrus), or 12 (estrus) days later to observe the transition of BrdU-labeled cells within in the CL. CL at each time point of estrus stage were classified into 4 types: Type I (newly formed CL), Type II (mature CL), Type III (regressing CL), and Type IV (residual CL). CL almost fully regressed within 4 estrus cycles. In contrast, in female rats given EGME orally (30, 100, or 300 mg/kg for 2 or 4 weeks), luteal cells were hypertrophic with abundant cytoplasm. Although the size of CL varied, all CL in EGME–treated rats had histological features similar to Type II CL, but they were more hypertrophic with less apoptosis. These results suggest that EGME has a luteal hypertrophic effect on all CL phases, including regression.

Collaborative work on evaluation of ovarian toxicity. 11) Two- or four-week repeated-dose studies and fertility study of ethylene glycol monomethyl ether in female rats

The objective of this study was to determine the optimal period of administration for detection of ovarian toxicity in rat repeated-dose toxicity studies. A well-known ovarian toxicant, ethylene glycol monomethyl ether (EGME), was administered to female rats at dose levels of 0, 30, 100, or 300 mg/kg for 2 or 4 weeks (repeated-dose toxicity studies). The same doses were administered to female rats for 2 weeks prior to mating, during mating, and until Day 6 of pregnancy (fertility study). In the repeated-dose toxicity studies, continuous diestrus was observed at > or = 100 mg/kg regardless of period of administration. The alterations of ovarian morphology observed at > or = 100 mg/kg after 2 or 4 weeks of administration were characterized by hypertrophy of the corpora lutea with decreased cellular debris indicating apoptosis, and increased proliferating cell nuclear antigen (PCNA)-negative large atretic follicles. The finding that newly-formed basophilic corpora lutea were scarce in affected animals exhibiting continuous diestrus suggested suppression of ovulation due to hypertrophic corpora lutea. In the fertility study, irregular estrous cycles, prolonged mating periods, lower pregnancy rates and decreased corpora lutea of pregnancy were observed at > or = 100 mg/kg. The irregularities of estrous cycle observed in some animals at 30 mg/kg were minimal. The ovarian histopathological changes in repeated-dose toxicity studies correlated well with impairment of female fertility found in the fertility study. It is concluded that a repeated-dose toxicity study with a treatment period for 2 weeks or longer is sufficient for evaluation of ovarian toxicity induced by EGME.

Prothrombin activation during carbon tetrachloride-induced acute liver injury in mice

Serine protease thrombin is a central factor for blood coagulation and is an integral part of inflammatory reactions. Prothrombin activation of the liver homogenates during carbon tetrachloride-induced liver injury was investigated. At 72 h after administration of carbon tetrachloride, the prothrombin activation activity reached the maximal value, and then decreased to the basal level at 168 h. The alanine transaminase (ALT) activity, an index of tissue injury, was dramatically elevated at 36 h after treatment, and almost recovered to normal levels at 72 h. Histochemical analysis revealed that the proliferation of hepatocytes and remarkable phagocytosis by macrophages was observed at 72 h, in contrast to severe tissue damage at 36 h. Finally, we showed that prothrombinase activity, composed of factor Xa and factor Va, was involved in the injury-associated prothrombin activation. Taken together, these results strongly suggest that prothrombin activation by the prothrombinase complex occurred following tissue destruction in carbon tetrachloride-induced liver injury.

A nuclear receptor-mediated xenobiotic response and its implication in drug metabolism and host protection

Regulation of the Phase I CYP enzymes and Phase II conjugating enzymes is implicated in both drug metabolism and drug-drug interactions. Moreover, the elimination of numerous xenobiotic and endobiotic toxic chemicals also requires a concerted function of Phase I and II enzymes, as well as the membrane spanning drug transporters. The genes that encode these enzymes and transporters are inducible by numerous xenobiotics, yet the inducibility shows clear species specificity. In the last 3-4 years, orphan nuclear receptors (NRs) such as PXR, CAR, and FXR have been established as species-specific xeno-sensors that regulate the expression of Phase I and II enzymes, as well as selected drug transporters. This transcriptional regulation is achieved by binding of these xenobiotic receptors to the NR response elements found within the promoter regions of target genes. The identification of NRs as xenosensors represents a major step forward in understanding the genetic mechanisms controlling the expression of drug metabolizing enzymes. The establishment of NR-mediated and mechanism-guided xenobiotic screening systems by using cultured cells or genetically engineered mouse models has not only advanced our understanding of the molecular complexity of this drug-induced xenobiotic response, but has also provided in vitro and in vivo platforms to facilitate the development of safer drugs.

Biological function and mode of action of nuclear xenobiotic receptors

Two related nuclear receptors, the pregnane X receptor (PXR) and the constitutive androstane receptor (CAR), act as xenobiotic sensors that protect the body from a multitude of foreign chemicals (xenobiotics) and play a central role in the metabolism and clearance of steroids and toxic endogenous lipids (endobiotics). A structurally diverse array of chemicals including pharmaceutical drugs, steroids, herbal extracts, and pesticides activate PXR or CAR. This activation results in induction of overlapping, but yet distinct drug clearance pathways consisting of cytochrome P450 enzymes, conjugating enzymes, drug transporters, and other related proteins. Similar pathways are also utilized to protect the body from toxic compounds of endogenous origin. Thus, the xenobiotic regulatory circuit contributes both to drug-drug and food-drug interactions as well as endocrine disruption. Consistent with the notion that xenobiotic receptors regulate drug clearance, single nucleotide polymorphisms (SNPs) in either the receptors themselves or receptor-binding sites in the regulatory region of genes encoding metabolic enzymes appear to contribute to the polymorphic expression of components of drug clearance pathways. Together, the xenobiotic receptors PXR and CAR confer metabolic immunity via the ability to control an integrated array of target genes.

An oral introduction of intestinal bacteria prevents the development of a long-term Th2-skewed immunological memory induced by neonatal antibiotic treatment in mice

BACKGROUND

Recent epidemiological studies indicate that antibiotic use in infancy may be associated with an increased risk of developing atopy. Our previous work on animals demonstrated that kanamycin use during infancy promotes a shift in the Th1/Th2 balance towards a Th2-dominant immunity.

OBJECTIVE

The first purpose of this study is to clarify whether or not the supplementation of intestinal bacteria can reverse such a Th2-skewed response induced by neonatal antibiotic use. The second objective is to elucidate the contribution of genetic factors to antibiotic-induced immune-deviation.

METHODS

BALB/c or C57BL/6 mice at 3 weeks of age were orally administered 600 microg/day of kanamycin sulphate for seven consecutive days. Thereafter, the mice were inoculated with one type of intestinal bacterial species: Enterococcus faecalis, Lactobacillus acidophilus or Bacteroides vulgatus. Blood samples were collected 10 weeks after the cessation of kanamycin treatment, and the effect of the kanamycin treatment on Th1/Th2 balance was evaluated based on in vivo antibody levels.

RESULTS

A kanamycin-induced elevation of the serum IgE levels was reversed by the supplementation with Enterococcus faecalis, and to a lesser extent by that with Lactobacillus acidophilus. The IgE/IgG2a ratio in the mice supplemented with Enterococcus faecalis significantly decreased in comparison with that in the kanamycin-treated mice without any bacterial supplementation, while such a ratio was enhanced in the mice inoculated with Bacteroides vulgatus. No antibiotic-induced Th2-skewed response was seen in C57BL/6 mice that are genetically biased towards Th1-dominant immunity.

CONCLUSION

These results suggest that adequate probiotic intervention after antibiotic treatment may improve the intestinal ecosystem, and thereby prevent the Th2-shifted immunity induced by neonatal antibiotic use. In addition, the difference of genetic backgrounds also contributes to such an antibiotic-induced Th2-skewed response.

Podocyte injury promotes progressive nephropathy in zucker diabetic fatty rats

The zucker diabetic fatty (ZDF-fa/fa) rat is one of the attractive models for type II diabetes based on impaired glucose tolerance caused by the inherited insulin-resistance gene fa. Characterization of nephropathy in this model may provide useful insights into the mechanism of the progression of diabetic nephropathy. The present study analyzed the pathophysiology of diabetes and nephropathy, including the process of glomerulosclerosis in this model by biochemical and morphometric analyses. In addition, we conducted studies in podocytes in culture to examine the direct effects of high glucose on podocytes. ZDF-fa/fa rats showed overt diabetes despite hyperinsulinemia as early as 3 months of age. Blood glucose levels increased further with a considerable decrease of insulin levels at 5 months. Glomerular filtration rate (GFR) was significantly elevated until 3 months, but fell to the level seen in lean rats by 7 months. Proteinuria started to rise during the period of increased GFR, and increased further after GFR had fallen to within the normal range. Renal fibronectin, collagen iv, and vascular endothelial growth factor mRNA levels were increased at 7 months. Glomerulosclerosis commenced as early as 5 months of age, and was associated with glomerular hypertrophy and mild mesangial expansion with evidence of accentuated podocyte injury, as revealed by increased expression of desmin. Electron microscopy suggested that degeneration of podocytes and the development of tuft adhesions were responsible for the glomerular sclerosis in this model. In addition, glomeruli from the diabetic rats showed up-regulation of the cyclin kinase inhibitors, p21 and p27. Further studies suggested that the increase in p27 expression was predominantly caused by podocytes, because predominant immunolocalization of p27 in podocytes in diabetic rats and high glucose medium induced cell hypertrophy accompanied by p27 up-regulation in differentiated podocyte cell lines. In conclusion, progressive diabetic nephropathy in ZDF-fa/fa rats is associated with evidence of podocyte injury. High concentrations of ambient glucose induced podocyte hypertrophy and stress in vitro, suggesting that the podocyte is a likely target of the diabetic milieu.

Functional disorders of the sympathetic nervous system in mice lacking the alpha 1B subunit (Cav 2.2) of N-type calcium channels

N-type voltage-dependent Ca(2+) channels (VDCCs), predominantly localized in the nervous system, have been considered to play an essential role in a variety of neuronal functions, including neurotransmitter release at sympathetic nerve terminals. As a direct approach to elucidating the physiological significance of N-type VDCCs, we have generated mice genetically deficient in the alpha(1B) subunit (Ca(v) 2.2). The alpha(1B)-deficient null mice, surprisingly, have a normal life span and are free from apparent behavioral defects. A complete and selective elimination of N-type currents, sensitive to omega-conotoxin GVIA, was observed without significant changes in the activity of other VDCC types in neuronal preparations of mutant mice. The baroreflex response, mediated by the sympathetic nervous system, was markedly reduced after bilateral carotid occlusion. In isolated left atria prepared from N-type-deficient mice, the positive inotropic responses to electrical sympathetic neuronal stimulation were dramatically decreased compared with those of normal mice. In contrast, parasympathetic nervous activity in the mutant mice was nearly identical to that of wild-type mice. Interestingly, the mutant mice showed sustained elevation of heart rate and blood pressure. These results provide direct evidence that N-type VDCCs are indispensable for the function of the sympathetic nervous system in circulatory regulation and indicate that N-type VDCC-deficient mice will be a useful model for studying disorders attributable to sympathetic nerve dysfunction.

Drosophila Brain Tumor is a translational repressor

The Drosophila brain tumor (brat) gene encodes a member of the conserved NHL family of proteins, which appear to regulate differentiation and growth in a variety of organisms. One of the founding family members, Caenorhabditis elegans LIN-41, is thought to control posttranscriptional gene expression. However, the mechanism by which LIN-41, or any other NHL protein, acts has not been clear. Using a yeast "four-hybrid" interaction assay, we show that Brain Tumor is recruited to hunchback (hb) mRNA through interactions with Nanos and Pumilio, which bind to the RNA to repress its translation. Interaction with the Nanos/Pumilio/RNA complex is mediated by the Brat NHL domain; single amino acid substitutions in this domain compromise quaternary complex assembly in vitro and hb regulation in vivo. Thus, recruitment of Brat is necessary for translational repression and the normal development of posterior embryonic pattern. In addition to regulating abdominal segmentation, previous genetic analysis has shown that Brat, Nanos, and Pumilio govern a variety of developmental processes. We examined the role of Brat in two of these processes-regulation of maternal Cyclin B mRNA in the embryo and regulation of imaginal disc development. The results of these experiments suggest that NHL domain proteins are recruited to various mRNAs by combinatorial protein-protein interactions.

Effects of biopsy on lung metastasis

In order to clarify whether biopsy promotes lung metastasis, open or needle aspiration biopsy was performed 10 or 21 days after S-SLM osteosarcoma cells were transplanted subcutaneously in Fischer rats. The lungs were excised after six weeks and the lung weight and the number of metastatic nodules were measured. The mean weight was more in open than needle biopsy, and the number of nodules was significantly higher in open biopsy after 10 days, compared to the control. From these results we concluded that open is more likely to promote lung metastases compared to needle biopsy under the specific experimental conditions of this study.

New ferromagnetic bone cement for local hyperthermia

We have developed a ferromagnetic bone cement as a thermoseed to generate heat by hysteresis loss under an alternate magnetic field. This material resembles bioactive bone cement in composition, with a portion of the bioactive glass ceramic component replaced by magnetite (Fe3O4) powder. The temperature of this thermoseed rises in proportion to the weight ratio of magnetite powder, the volume of the thermoseed, and the intensity of the magnetic field. The heat-generating ability of this thermoseed implanted into rabbit and human cadaver tibiae was investigated by applying a magnetic field with a maximum of 300 Oe and 100 kHz. In this system, it is very easy to increase the temperature of the thermoseed in bone beyond 50 degrees C by adjusting the above-mentioned control factors. When the temperature of the thermoseed in rabbit tibiae was maintained at 50 to 60 degrees C, the temperature at the interface between the bone and muscle (cortical surface) surrounding the material rose to 43 to 45 degrees C; but at a 10-mm distance from the thermoseed in the medullary canal, the temperature did not exceed 40 degrees C. These results demonstrate that ferromagnetic bone cement may be applicable for the hyperthermic treatment of bone tumors.

Establishment of a quantitative mouse dorsal air sac model and its application to evaluate a new angiogenesis inhibitor

We have developed an improved mouse dorsal air sac model for quantifying in vivo tumor-induced angiogenesis. In our improved model, tumor angiogenesis is determined by measuring the blood volume in an area of skin held in contact with a tumor cell-containing chamber, using 51Cr-labeled red blood cells (RBC). The blood volume induced by murine B16-BL6 melanoma cells increased linearly with the cell number in the range from 2 x 10(5) to 5 x 10(6). Ten of 11 human tumor cell lines examined induced a significant increment in blood volume. For three representative human tumor cell lines (A549, WiDr. and HT1080 cells) that showed different angiogenic potencies, the levels of vascular endothelial growth factor (VEGF) produced by the tumor cells cultured under conditions of hypoxia and high cell density were correlated with the degree of in vivo angiogenesis. Using the improved model, it was confirmed that TNP-470, a well-known inhibitor, and borrelidin, an antibiotic from Streptomyces rochei, significantly inhibited the WiDr cell-induced angiogenesis. Borrelidin also inhibited spontaneous lung metastasis of B16-BL6 melanoma at the same dose that inhibited angiogenesis. Our results suggest that the improved mouse dorsal air sac model can be used for simple and quantitative measurement of tumor-induced angiogenesis and its inhibition.

Prevention of metastasis by a polyamine synthesis inhibitor in an animal bone metastasis model

In order to better understand the development of skeletal metastases, we developed an appropriate animal model, as the natural progression of metastases in humans cannot be studied on the cellular level. In this study, we established a new animal model which developed bone metastasis in a bone grafted subcutaneously. C57BL/6 mice, which had received a bone (femur or tibia) transplanted in the dorsal subcutis, were injected with B16 melanoma cells into the left heart ventricle. Metastasis was found in approximately 70% of the extraskeletal bones. Using this model, the antimetastatic effect of a polyamine synthesis inhibitor was investigated. Inhibitors of the polyamine biosynthetic pathway have received considerable attention for their potential use in the treatment of cancer as they are responsible for the greatly increased production of the polyamines putrescine, spermidine, and spermine. A polyamine synthesis inhibitor, methylglyoxal-bis(cyclopentylamidinohydrazone) MGBCP, was investigated for its inhibitory effects on bone metastases. MGBCP (20 mg/kg) was administered intraperitoneally every day for 4 weeks and demonstrated strong inhibitory effects on bone metastases. MGBCP inhibited angiogenesis in the transplanted bone and the growth of B16 melanoma cells, thus suggesting a preventive mechanism in bone metastasis. No remarkable adverse effects of MGBCP were observed in any animal throughout the experimental period. Our results indicate that MGBCP has a strong potential for use as an anti-metastatic drug.

Comparison of the mutational spectra of the lacZ transgene in four organs of the MutaMouse treated with benzo[a]pyrene: target organ specificity

We recently demonstrated that not all organs with a high rate of induction of mutation in the lacZ transgene develop tumors in the lambdalacZ transgenic mice (MutaMouse) used for a long-term carcinogenicity study with benzo[a]pyrene (BP). To better understand the role of chemical-induced in vivo mutations in carcinogenesis, we compared the mutational spectra of the lacZ transgene in four organs of the MutaMouse obtained 2 weeks after five daily consecutive oral treatments with 125 mg/kg/day BP. lacZ transgenes were analyzed in two target organs (forestomach and spleen) and two non-target organs (colon and glandular stomach) for BP-induced carcinogenesis in MutaMouse, and all of these organs were highly mutated in the lacZ transgene. The sequence data showed similar mutational spectra of the lacZ transgene between the two target organs; the predominant mutations were G:C-->T:A transversions (55% and 50% for forestomach and spleen, respectively), followed by deletions (20% and 21% for forestomach and spleen, respectively) mainly at G:C site. The frequent G:C-->T:A transversions are consistent with reports of the mutational spectra produced in the p53 gene in tumors generated in rats and mice exposed to BP. In contrast, the mutational spectra of the lacZ transgene in the two non-target organs are different from those in the target organs, and are also suggested to differ from one another. These findings suggest an organ/tissue-specific mechanism of mutagenesis.

Green tea polyphenols induce apoptosis in vitro in peripheral blood T lymphocytes of adult T-cell leukemia patients

Green tea polyphenols (TEA) are known to exhibit antioxidative activity as well as tumor-suppressing activity. In order to examine the tumor-suppressing activity of TEA against adult T-cell leukemia (ATL), we cultivated peripheral blood T lymphocytes of ATL patients (ATL PBLs), an HTLV-I-infected T-cell line (KODV) and healthy controls (normal PBLs) for 3 days in the presence of TEA and its main constituent, epigallocatechin-3-gallate (EGCg), to measure cell proliferation and apoptosis, and to quantitate mRNAs of HTLV-I pX and beta-actin genes of the cultured cells. Growth of ATL PBLs was significantly inhibited by 9-27 microg/ml of TEA and EGCg, in contrast to minimal growth inhibition of T cells of normal PBLs. Inhibition of KODV was intermediate between ATL PBLs and normal PBLs. The ATL PBLs and KODV treated with 27 microg/ml of either TEA or EGCg induced apoptotic DNA fragmentation, producing terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL)-positive cells, while the normal PBLs treated with the same concentration of TEA or EGCg produced a negligibly small number of TUNEL-positive cells, in which apoptotic DNA fragmentation was not detectable. Expression of HTLV-I pX mRNA was suppressed more than 90% in ATL PBLs by treatment with 3-27 microg/ml of either TEA or EGCg, while expression of beta-actin mRNA was much less suppressed by treatment with the same concentration of TEA or EGCg. These results indicate that TEA and EGCg inhibit growth of ATL PBLs, as well as HTLV-I-infected T-cells, by suppressing HTLV-I pX gene expression and inducing apoptotic cell death.

Recruitment of Nanos to hunchback mRNA by Pumilio

Translational regulation of hunchback (hb) mRNA is essential for posterior patterning of the Drosophila embryo. This regulation is mediated by sequences in the 3'-untranslated region of hb mRNA (the Nanos response elements or NREs), as well as two trans-acting factors-Nanos and Pumilio. Pumilio recognizes the NREs via a conserved binding motif. The mechanism of Nanos action has not been clear. In this report we use protein-protein and protein-RNA interaction assays in yeast and in vitro to show that Nanos forms a ternary complex with the RNA-binding domain of Pumilio and the NRE. Mutant forms of the NRE, Nos, and Pum that do not regulate hb mRNA normally in embryos do not assemble normally into a ternary complex. In particular, recruitment of Nos is dependent on bases in the center of the NRE, on the carboxy-terminal Cys/His domain of Nos, and on residues in the eighth repeat of the Pum RNA-binding domain. These residues differ in a closely related human protein that also binds to the NRE but cannot recruit Drosophila Nos. Taken together, these findings suggest models for how Nos and Pum collaboratively target hb mRNA. More generally, they suggest that Pum-like proteins from other species may also act by recruiting cofactors to regulate translation.

Rapid development of hepatic metastasis with high incidence following orthotopic transplantation of murine colon 38 carcinoma as intact tissue in syngeneic C57BL/6 mice

BACKGROUND AND OBJECTIVES

Orthotopic transplantation of human colon tumors was a useful method for producing hepatic metastasis in mice. In many cases, however, it took about 3 months for evaluation. We examined an in vivo model of hepatic metastasis for only 4 weeks by conducting orthotopic transplantation of murine Colon 38 tumor using intact tissue in syngeneic mice and determined the efficacy of chemotherapeutic agents against hepatic metastasis.

METHODS

Twenty milligrams of tumor tissues were prepared from subcutaneously (s.c.) growing Colon 38 tumor and orthotopically transplanted on the cecum in C57BL/6 mice. Mice were autopsied about 4 weeks after transplantation. Metastases to various organs were detected macroscopically or histochemically and tumor invasion into the cecum was observed histochemically. In experimental chemotherapy, mice bearing orthotopically transplanted Colon 38 tumor were separated into three equal groups and were either treated with fluorouracil or cisplatin (CDDP), or untreated. Four weeks after transplantation, activities of both agents against local tumor growth and hepatic metastasis were evaluated.

RESULTS

Macroscopic metastases to various organs including the liver, the lung, and the peritoneum were developed during days 28 to 32 after inoculation. The frequency of hepatic metastasis was 96% (N = 23). Histological examination indicated that the local tumor invaded various layers of the cecum and metastasized to the liver and lung hematogenously. In experimental chemotherapy with fluorouracil and CDDP, only fluorouracil decreased the incidence of mice with hepatic metastasis (2/8 cases), compared with vehicle treatment (7/8 cases) and the number of metastatic nodules in the liver (P = 0.016), although the inhibition against local growth of CDDP in T/C [45%; mean tumor weight of the test group (T) compared with that of the control group (C)] was similar to that of fluorouracil (53%).

CONCLUSIONS

This model, with its rapid development of hepatic metastasis in high frequency, should be useful as a screening assay to find anti-metastatic agents for colorectal carcinoma.

Effect of amino acid substitution in amphiphilic alpha-helical peptides on peptide-phospholipid membrane interaction

It was previously found that a cationic amphiphilic peptide, Ac-(Leu-Ala-Arg-Leu)3-NHCH3 (4(3)), caused the destabilization of a phospholipid membrane and showed strong antibacterial activity [Lee et al. Biochim. Biophys. Acta 1986; 862: 211-219]. In order to investigate the effect of changing alpha-helix propensity, hydrophobicity and basicity in 4(3) on the peptide conformation and activity, the 4(3) analogs, [Gly (or Val)6]4(3), [Gly (or Val)2,6]4(3), [Gly (or Val)2,6,10]4(3), [Gln3]4(3), [Gln3,7]4(3) and [Gln3,7,11]4(3) were synthesized. Except for [Val2,6]4(3) and [Val2,6,10]4(3), which mainly formed a beta-structure, other peptides formed an alpha-helix and showed moderate membrane-perturbing activity toward neutral and acidic lipid vesicles. All the peptides other than [Val2,6,10]4(3) and [Gln3,7,10]4(3) had the antibacterial activity comparable with that of 4(3). The relationship between the membrane-perturbing activity and the antibacterial activity was not always parallel. Conclusively, the Ala-->Val substitution in 4(3) causes the change of peptide conformation and the presence of a cationic amino acid residue is necessary for the antibacterial activity.

Gene therapy of chondrosarcoma using retrovirus vectors encoding the herpes simplex virus thymidine kinase gene

Human chondrosarcoma cells (HCS-TG) were transduced with the gene for a herpes simplex virus thymidine kinase (HSV-tk) or Escherichia coli beta-galactosidase (lacZ). We investigated the cytotoxicity of human chondrosarcoma bearing an HSV-tk gene after treatment with ganciclovir. Chondrosarcoma cells bearing an HSV-tk gene were more sensitive than non-transduced cells. Coculturing with chondrosarcoma cells bearing both an HSV-tk gene (HCS-TG-tk) and lacZ gene (HCS-TG-Z) in various ratios showed a bystander effect. Chondrosarcoma implanted in nude mice were injected with HCS-TG-tk cells. After 4 weeks, the growth of tumors was significantly prevented.

Rapid development of hepatic metastasis with high incidence following orthotopic transplantation of murine colon 38 carcinoma as intact tissue in syngeneic C57BL/6 mice

BACKGROUND AND OBJECTIVES

Orthotopic transplantation of human colon tumors was a useful method for producing hepatic metastasis in mice. In many cases, however, it took about 3 months for evaluation. We examined an in vivo model of hepatic metastasis for only 4 weeks by conducting orthotopic transplantation of murine Colon 38 tumor using intact tissue in syngeneic mice and determined the efficacy of chemotherapeutic agents against hepatic metastasis.

METHODS

Twenty milligrams of tumor tissues were prepared from subcutaneously (s.c.) growing Colon 38 tumor and orthotopically transplanted on the cecum in C57BL/6 mice. Mice were autopsied about 4 weeks after transplantation. Metastases to various organs were detected macroscopically or histochemically and tumor invasion into the cecum was observed histochemically. In experimental chemotherapy, mice bearing orthotopically transplanted Colon 38 tumor were separated into three equal groups and were either treated with fluorouracil or cisplatin (CDDP), or untreated. Four weeks after transplantation, activities of both agents against local tumor growth and hepatic metastasis were evaluated.

RESULTS

Macroscopic metastases to various organs including the liver, the lung, and the peritoneum were developed during days 28 to 32 after inoculation. The frequency of hepatic metastasis was 96% (N = 23). Histological examination indicated that the local tumor invaded various layers of the cecum and metastasized to the liver and lung hematogenously. In experimental chemotherapy with fluorouracil and CDDP, only fluorouracil decreased the incidence of mice with hepatic metastasis (2/8 cases), compared with vehicle treatment (7/8 cases) and the number of metastatic nodules in the liver (P = 0.016), although the inhibition against local growth of CDDP in T/C [45%; mean tumor weight of the test group (T) compared with that of the control group (C)] was similar to that of fluorouracil (53%).

CONCLUSIONS

This model, with its rapid development of hepatic metastasis in high frequency, should be useful as a screening assay to find anti-metastatic agents for colorectal carcinoma.

Multiple organ mutation in the lacZ transgenic mouse (Muta mouse) 6 months after oral treatment (5 days) with benzo[a]pyrene

We have recently demonstrated that not all organs with high rates of mutation in the lacZ transgene develop tumors using the Muta Mouse. To better understand the role of in vivo mutation in carcinogenesis, we examined the mutant frequencies (MF) of the lacZ transgene in tumor-bearing and non tumor-bearing organs. MF, recovered after 2 weeks (the data taken from our previous study) and after 26 weeks following oral doses of 125 mg kg-1 day-1 benzo[a]pyrene (BP) for five days were compared. The organs examined included the target organs (forestomach, spleen, and lung) and non-target organs (colon, glandular stomach, and liver) for BP carcinogenesis. The data indicated that lacZ MF were markedly increased over spontaneous frequencies in the organs examined and that the organ which showed the highest MF was the colon, followed by the forestomach>spleen>glandular stomach, liver, and lung in that order. These findings indicate that the MF of the lacZ transgene in each organ, even 26 weeks after the start of the treatment does not fully correlate with the known target organs of BP. Furthermore, the lacZ MF in a non-papilloma region of a forestomach with a papilloma was equivalent to the two highest MF observed in the healthy colon (non-target organ) of mice at 26 weeks. These observations also indicate that the generation of tumors requires the induction of mutations as well as other factor(s) specific to the target organs. These results clearly suggest that highly mutated organs do not always progress to tumors in the transgenic mouse.

Growth inhibition of human osteosarcoma HuO9 cells by methylglyoxal bis(cyclopentylamidinohydrazone) in vitro and in vivo

Polyamines are considered to be important intracellular molecules for the proliferation of cancer cells. In this study, effects of methyl-glyoxal bis(cyclopentylamidinohydrazone) (MGBCP), a potent inhibitor of the polyamine biosynthetic pathway, on the growth of human osteosarcoma HuO9 cells have been investigated. MGBCP dose-dependently inhibited the growth of HuO9 cells, in which the contents of spermine, spermidine and putrescine decreased concomitantly. The MGBCP-treated cells clearly exhibited morphological changes, indicating the blebbing and chromatin condensation which are characteristic of apoptosis. Characteristic oligonucleosomal-sized DNA fragments were observed in the MGBCP-treated cells. In in vivo experiments MGBCP (20 or 50 mg/kg) inhibited the growth of transplanted HuO9 tumors in mice. These findings suggest that the inhibition of polyamine synthesis results in the suppression of growth of osteosarcoma HuO9 cells, eventually inducing apoptosis in these human osteosarcoma cells in vitro and in vivo.

Preservation of the knee joint in limb salvage of osteosarcoma in the proximal tibia. A case report

A 12-year-old boy with osteosarcoma in the proximal tibia underwent a successful limb-saving operation with preservation of the epiphyseal and articular cartilage of the proximal tibia as a result of his remarkable response to chemotherapy. There was no evidence of tumour invasion to the adjacent physis, as demonstrated by image findings. The bone defect was reconstructed using autoclaved autogeneous bone with a vascularized fibula. The patient exhibits excellent function of the affected limb, and the knee joint remains disease-free 55 months postoperatively.

Toxicity profile of benzo[a]pyrene in the male LacZ transgenic mouse (MutaMouse) following oral administration for 5 consecutive days

The toxicity profile of benzo[a]pyrene (BP) was examined in the MutaMouse. The transgenic mouse integrated with lambda gt10 lacZ vectors is used worldwide as an experimental animal in in vivo mutagenesis testing systems. There are few toxicity studies including carcinogenicity in the MutaMouse, and so far only a few carcinogenicity studies of BP accompanied with hematological and plasma biochemical examinations have been conducted even in generic mice. Accordingly, male mice were orally administered BP at doses of 75 and 125 mg/kg/day for 5 consecutive days, and complete autopsy was conducted together with pathological, hematological, and plasma biochemical examinations and measurement of organ weights 41 weeks after the last treatment. Squamous cell papilloma and hyperplasia in the forestomach were induced at incidences of 25 and 50%, respectively and were induced 26 weeks after the final treatment without any significant alterations in t he hematological and plasma biochemical parameters in mice of the 125 mg/kg/day BP-treated satellite group. Fourty-one weeks after the final treatments, 75 and 125 mg/kg/day BP induced squamous cell carcinoma, papilloma, and hyperplasia in the forestomach at incidences of 18 and 18%, 36 and 45%, and 91 and 91%, respectively, and anemia possibly due to continuous hemorrhage from tumors in the forestomach. BP (125 mg/kg/day) also produced malignant lymphoma with an incidence of 18%, accompanied by a marked increase in leukocyte count and decrease in erythrocyte count and by a remarkable decrease in body weights 26 and 39 weeks after the last treatment. Moreover, administration of 75 and 125 mg/kg/day BP induced bronchiolar-alveolar hyperplasia in the lung at incidences of 18 and 9%, respectively. Slight increases were also observed in the weight of the liver and in the levels of urea nitrogen, creatinine, and potassium ion in the plasma biochemical examinations, although no significant pathological alterations were found in the liver and kidney. This study provides new information about BP toxicity including carcinogenicity in the MutaMouse developed for in vivo mutational analysis.

The Pumilio RNA-binding domain is also a translational regulator

Posterior patterning in the Drosophila embryo requires the action of Nanos (Nos) and Pumilio (Pum), which collaborate to regulate the translation of maternal hunchback (hb) mRNA. Previous work demonstrated that Pum recognizes sites in the 3' UTR of hb mRNA. In this report, we first define the RNA-binding domain of Pum and then show that residues essential for translational repression are embedded within this domain. We also show that Nos and Pum can repress cap-independent translation from an internal ribosome entry site (IRES) in vivo, suggesting that they act downstream of the initial steps of normal, cap-dependent translation.

Comparison between in vivo mutagenicity and carcinogenicity in multiple organs by benzo[a]pyrene in the lacZ transgenic mouse (Muta Mouse)

To evaluate whether the in vivo mutagenicity test system using the lacZ transgenic mice (Muta Mouse) may be applied to carcinogenesis studies, both the in vivo mutagenicity and carcinogenicity of benzo[a]pyrene (BP) was tested in mice under the same administration conditions. The eleven organs of the mice on the 14th day after the final oral administration of BP at a dose of 125 mg kg(-1) day(-1) or corn oil for 5 consecutive days were tested for in vivo mutation by the positive-selection method. The data show that the colon had the highest lacZ mutant frequency (37-fold increase over the spontaneous frequency), followed by the ileum > forestomach > bone marrow, spleen > glandular stomach > liver, lung > kidney and heart. No significant mutations were found in the brain. These results may suggest that, in general, the organs with rapidly proliferative tissues have a marked increase in vivo mutant frequencies under the conditions of this experimental design. The forestomach and lymphatic organs including the spleen (malignant lymphoma) were the main target organs for BP carcinogenesis by 5 daily oral doses of 75 and 125 mg kg(-1) day(-1). These results suggest that the mutation results from the transgenic assay with BP reflect the carcinogenicity of BP in the mouse. They also indicate, however, that the magnitude of the in vivo lacZ mutant frequencies induced by BP in different organs did not fully correlate with the target organs for carcinogenicity.

Mutational analysis of the potato virus Y 5' untranslated region for alteration in translational enhancement in tobacco protoplasts

The 185 nucleotide 5' untranslated region (5'UTR) of potato virus Y ordinary strain (PVY-O) showed translation-enhancing activity on the beta-glucuronidase (GUS) gene in tobacco protoplasts. Mutational analysis of the 5'UTR was done to find sequence motifs necessary for the enhancement. Deletions within the 1-130 nucleotide region of 5'UTR stimulated the GUS expression in some cases, while the GUS activity declined with deletions in the 131-185 nucleotide region. The results indicated that the last 55 nucleotides of PVY-O 5'UTR might play the much important role in the translational enhancement in plant cells.

Beneficial effects of long-term enalapril treatment and low-salt intake on survival rate of dahl salt-sensitive rats with established hypertension

We investigated the effects of long-term treatment with the angiotensin-converting enzyme inhibitor enalapril and low-salt intake on the survival rate of Dahl salt-sensitive rats fed a high-salt (6.0% NaCl) diet. The systolic blood pressure of the rats increased gradually from 5 weeks of age and reached >240 mm Hg at 12 weeks of age. At this point, a low-salt diet group received a placebo (group 1, n = 10), and the high-salt diet group was divided into three groups: those given a placebo with the high-salt diet (group 2, n = 15), those given a chow change from a high- to a low-salt diet with a placebo (group 3, n = 14) and those given enalapril (30 mg/kg/day p.o., group 4, n = 14). At 19 weeks of age, all rats in group 1 were alive, and the survival rate of group 2 was only 40% (P < .001 vs. group 1). The survival rates of both groups 3 and 4 were significantly better: 86% (P < .01 vs. group 2) and 93% (P < .01), respectively. This beneficial effect on mortality was accompanied by an amelioration of the elevated plasma creatinine and urea nitrogen levels and a decrease in the glomerular sclerosis lesion scores in both groups. These results suggested that a high-salt content diet and the renin-angiotensin system are deterioration factors in lethal renal damage and the limitation of the diet salt content and inhibition of the renin-angiotensin system are important to improve the survival rate in high-salt-loaded hypertensive Dahl salt-sensitive rats.

Induction of apoptotic cell death in three human osteosarcoma cell lines by a polyamine synthesis inhibitor, methylglyoxal bis(cyclopentylamidinohydrazone) (MGBCP)

Our previous experiments have shown that methylglyoxal bis(cyclopentylamidinohydrazone) (MGBCP), a polyamine synthesis inhibitor, suppresses the growth of osteosarcoma cells repressing their intracellular polyamine levels, and that this inhibition of cell growth is only partially reversed by the addition of polyamines. In the present study, we found evidence indicating that the incomplete recovery of cell growth by the addition of polyamines to the polyamine-depleted cells was due to programmed cell death (apoptosis) induced by MGBCP. Morphological changes showing blebbing and chromatin condensation were observed in MGBCP-treated cells, and hypodiploid subpopulations containing apoptotic cells were clearly visible in the profile of flow cytometric analysis. Characteristic oligonucleosomal-sized fragments were increased as the concentration of MGBCP was increased. The results presented here suggest that in addition to reducing the growth rates, MGBCP can induce apoptotic cell death in three human osteosarcoma cell lines.

Effects of methylglyoxal bis (cyclopentylamidinohydrazone) (MGBCP) on cell cycle progression in three human osteosarcoma cell lines

Our previous experiments have indicated that the antitumor effects of a polyamine biosynthetic inhibitor, methylglyoxal bis(cyclopentylamidinohydrazone) (MGBCP), on human osteosarcoma cell lines such as MG-63, G-292 and HOS cells are obtained by its action depleting the cellular polyamine contents. In the present study, the effects of polyamine depletion by MGBCP on the cell cycle progression in these osteosarcoma cell lines were investigated by flow cytofluormetric analysis. MGBCP arrested the tumor cells at the G1 phase by preventing the G/S phase transition. Mitotic indexes (MIs) in these MGBCP-inhibited tumor cells were also decreased. These findings suggest that MGBCP suppresses the cell cycle progression in osteosarcoma MG-63, G-292 and HOS cells by inhibiting intracellular polyamine biosynthesis.

Methylglyoxal bis (cyclopentylamidinohydrazone) (MGBCP): antitumor effect against human osteosarcoma cells and combined effect with methotrexate, adriamycin and 4-hydroperoxyifosfamide

The antitumor effect of a polyamine biosynthetic pathway inhibitor methylglyoxal bis(cyclopentylamidinohydrazone) (MGBCP) on human osteosarcoma cell lines such as KHOS-240S, MG-63 and G-292 cells, and its effect in combination with anticancer drugs such as methotrexate (MTX), adriamycin (ADM) and 4-hydroperoxyfosfamide (HIFO) have been investigated. The growth of these cultured osteosarcoma cells was inhibited by MGBCP in a dose-dependent manner. Spermidine and spermine levels were dose-dependently depressed in these MGBCP-treated osteosarcoma cells. The antitumor effect of MGBCP was additively potentiated by combined treatment with MTX, ADM and HIFO, respectively.

Characterization of new inbred strains of Dahl-Iwai salt-sensitive and salt-resistant rats

Dahl-Iwai salt-sensitive (S) and salt-resistant (R) rat strains were newly established as inbred strains. To characterize the strains, the Dahl-Iwai S and R rats were fed low-salt (0.3% NaCl) and high-salt (8.0% NaCl) diets from 5 weeks after birth, and systolic blood pressure and pathologic findings were examined at intervals. The distributions of alleles at 19 biochemical and immunologic loci also were examined in the aforementioned strains, together with those for the inbred SS/Sea and SR/Sea strains, which were derived from inbred SS/Jr and SR/Jr strains, respectively. The Dahl-Iwai S rats were hypertensive after 3 weeks of consuming the 8.0% NaCl diet and died from 6 to 10 weeks after the diet was initiated. Renal lesions developed after 4 weeks' consumption of the high-salt diet. The Dahl-Iwai S rats were not hypertensive until at least the age of 21 weeks while they consumed the 0.3% NaCl diet, whereas it was reported that the SS/Jr rats became hypertensive at about 20 weeks of age when they consumed the low-salt diet. The Dahl-Iwai R rats were normotensive whether fed the 0.3 or 8.0% NaCl diet. Hydronephrosis was not observed in the Dahl-Iwai R rats, though it develops in SR/Jr rats with high frequency. Different distributions were detected for kidney alkaline phosphatase-1 (Akp-1) and amylase-1 (Amy-1) alleles between the Dahl-Iwai S and SS/Sea strains, and for esterase-14 (Es-14) and seminal vesicle protein-1 (Svp-1) alleles between the Dahl-Iwai R and SR/Sea strains. The phenotypic differences between the substrains of inbred Dahl rats could be ascribed to different genetic backgrounds.

Pituitary carcinoma of pars distalis as a common neoplasm in Fischer-344 rats

The incidence of invasive spontaneous pituitary carcinomas in Fischer-344 rats were studied. The pituitaries were examined histopathologically together with surrounding tissues including sphenoid bone. The incidence of carcinoma was higher than that previously reported in Fischer-344 rats. All the carcinomas observed in this study showed evidence of local invasion either ventrally into bone and bone marrow or laterally into peripheral nerves and blood vessels. No dorsal infiltration into the brain was recognized. Pituitary carcinoma with local invasion is a relatively common neoplasm when examined histopathologically together with the surrounding tissues.

Protective effect of E3330, a novel quinone derivative, in galactosamine-induced hepatitis in rats

The effect of E3330 ((2E)-3-[5-(2,3-dimethoxy-6-methyl-1,4-benzoquinoyl)]-2-nonyl-2-++ +propenoic acid), a novel quinone derivative, was studied in the galactosamine-induced hepatitis model in F344 rats, in which endogenous endotoxin is believed to play a critical pathogenetic role. Subcutaneous injection of 300 mg/kg of galactosamine into rats resulted in liver injury. Oral treatment with E3330 (10-100 mg/kg) 1 hr after galactosamine challenge attenuated the liver injury. E3330 was also effective when administered p.o. 6 or 12 hr after galactosamine challenge. Subcutaneous injection of 1000 mg/kg of galactosamine into rats resulted in more severe liver injury with endotoxemia. The plasma endotoxin was detected 24 to 48 hr after the galactosamine challenge. The time course of increase in plasma endotoxin level was in good agreement with that in plasma aminotransferase activity. E3330 (100 mg/kg) significantly attenuated the liver injury, but did not affect the endotoxin level. Exogenous administration of endotoxin enhanced the hepatotoxicity of galactosamine. Pretreatment with E3330 also protected rats from severe liver injury induced with endotoxin plus galactosamine. These results suggest that E3330 may exert its hepatoprotective effects through inhibition of an effect of endotoxin in galactosamine-induced hepatitis in rats.

The unique feature of dog liver cytosolic glutathione S-transferases. An isozyme not retained on the affinity column has the highest activity toward 1,2-dichloro-4-nitrobenzene

In the adult dog liver cytosol we identified four glutathione S-transferase (GST) subunits, Yd1 (Mr 26,000), Yd2 (Mr 27,000), Yd3 (Mr 28,000), and Ydf (Mr 27,400), and purified GST forms comprising Yd1, Yd2, and Yd3, to apparent homogeneity. Unlike rat transferases the enzyme activity toward 1,2-dichloro-4-nitrobenzene (DCNB) was not retained on the affinity column. Thus the DCNB-active enzyme, GST YdfYdf, from the flow-through fraction of the affinity column was also purified to homogeneity by gel filtration, DE52 chromatography, chromatofocusing, and hydroxylapatite column chromatography. Immunoblot analysis of dog GSTs revealed that the subunits Yd1, Yd2, and Yd3 belong to the pi, alpha, and mu class, respectively. On the contrary, Ydf had no reactivity with antibodies raised against any of the three classes of GST. Each subunit, Yd1, Yd2, Yd3, and Ydf, was distinguishable by its own retention time on reverse-phase high performance liquid chromatography. N-terminal amino acid sequences of the dog GSTS Yd1Yd1 and Yd3Yd3 revealed a high degree of homology to the pi and mu class transferases from rat, human, and mouse, respectively, while the N terminus of Yd2Yd2 is blocked. N-terminal amino acid sequences of GST YdfYdf showed no homology to any of the three classes of GST. The most significant property noted of GST YdfYdf is the high specific activity toward DCNB, exceeding by 1 order of magnitude the corresponding values for the known mu class GSTs. The present results strongly suggest that dog GST YdfYdf is a unique enzyme distinct from the hitherto characterized GST isozymes.