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R Oyasu

Publications and source records attributed to R Oyasu.

At least 91 records · Page 5Linked to original sources
PubMed1990

In vitro malignant conversion of low-grade rat urinary bladder carcinoma cells by exposure to N-methyl-N-nitrosourea.

The cause of deeply invasive human bladder carcinoma is unknown. Animal studies suggest that a malignant (invasive) conversion is inducible in low-grade noninvasive tumors by further exposure to a chemical carcinogen. To elucidate what molecular mechanism(s) is involved in the conversion, an in vitro system has been established in which conversion from low- to high-grade carcinoma can be induced. A rat bladder carcinoma cell line D44, derived from an N-methyl-N-nitrosourea (MNU)-induced low-grade noninvasive rat bladder carcinoma was used in the present investigation. Cloned D44 cells (D44c) were exposed to MNU, 50 to 400 micrograms/ml, for 1 h at 37 degrees C once a week for up to 6 weeks. After exposure to MNU, cells with altered morphology were cloned. The yield of altered clones was highest after a total dose of 150 to 200 micrograms of MNU used in 1 to 3 doses. Of 21 clones with altered morphology, 4 clones were further treated with MNU at the initial dose once a week for up to 3 weeks and then subcloned. Thirty-three of these subclones were examined for tumorigenicity in athymic nude mice. Twenty-seven formed highly invasive carcinomas, mostly squamous type, whereas the parental D44c cells failed to develop tumors upon inoculation. Pulmonary metastases were observed in 17 of the 27 clones. Plasminogen activator activity was elevated 4- to 9-fold as compared to parent D44c cells. ras p21 mutations at codon 12 were detected in 5 of 30 clones. These results indicate that the in vitro system described here may provide a useful model to study the molecular mechanisms involved in the conversion of noninvasive bladder carcinomas to metastasizing ones.

Animals↗
PubMed1990

Effects of alpha-difluromethylornithine on the development of deeply invasive urinary bladder carcinomas in mice.

alpha-Difluoromethylornithine (DFMO), was examined for its ability to suppress the development of invasive urinary bladder carcinoma in C3H/He male mice. Continuous administration of 0.2% DFMO in water following carcinogen treatment (0.05% N-butyl-N-(4-hydroxybutyl)nitrosamine, BHBN, in drinking water for 8 weeks) was effective in suppressing urinary bladder carcinomas (P less than 0.05) as compared with the control group. However, when comparison was made based on tumors involving the entire urinary tract, protective effects could not be demonstrated. Coadministration of DFMO (0.2%) and BHBN (0.01%) did not alter tumor induction by the latter. These results were in sharp contrast to the protective effects in rats. Since bladder tumors in rats are of low grade and superficial whereas those in mice are of high grade and deeply invasive, our data indicate that DFMO has little to no effects against the development of aggressive forms of bladder carcinoma.

Animals↗
PubMed1990

Involvement of urine in epithelial-stromal interactions in urinary bladder carcinogenesis.

The role of urine in epithelial-stromal interactions in urinary bladder carcinogenesis was investigated using the 'Stroma' bladder model established in our laboratory. Rats treated with 0.05% N-butyl-N-(4-hydroxybutyl) nitrosamine (BHBN) in drinking water for 4 weeks or age-matched untreated rats served as donors of bladders with denuded epithelium ('stroma' bladders), which were resurfaced 4 days later with urothelial cells from rats treated with 0.05% BHBN for 4 weeks. Subsequently, the transplants received weekly injections of normal rat urine or saline. In the urine-free environment, cell implants developed hyperplastic changes but few tumor formations with no significant difference between the two types of 'stroma' bladder. In contrast, urine instillation stimulated neoplastic growth, and tumor-enhancing effect was significantly accelerated in the BHBN-treated 'stroma' bladder group as compared to the control group. These results suggest that epithelial-stromal interactions are altered in such a way that bladder carcinogenesis is enhanced by prior exposure of the bladder stroma to carcinogen and subsequent urine contact.

Animals↗
PubMed1990

Stimulation of urinary bladder tumorigenesis by carcinogen-exposed stroma.

There is evidence to suggest that control mechanisms, either growth-stimulatory, inhibitory or inductive, may play a role in carcinogenesis. To test the hypothesis that treatment of rat urinary bladder with carcinogen induces alterations in the stroma which result in modified epithelial-stromal interactions, experiments were conducted using a rat model specifically designed for the study. Following exposure of Fischer F344 rats in drinking water to the urinary bladder carcinogen, N-butyl-N-(4-hydroxybutyl)nitrosamine (BHBN) for four weeks, bladders were removed and subjected to a brief detergent treatment to completely remove epithelium. The bladders without epithelium ("stroma" bladder) were heterotopically transplanted to syngeneic recipients. Four days later, the denuded mucosa surface was resurfaced with intraluminal instillation of urothelial cells, either untreated or treated with BHBN for six weeks (6w-BHBN) or 10 weeks (10w-BHBN). Examination at 12 weeks posttransplant of the "stroma" bladders that had received 6w-BHBN urothelial cells showed a higher tumor incidence of carcinoma in the BHBN-exposed "stroma" bladders as compared with the incidence in the carcinogen-unexposed "stroma" bladders (p less than 0.05). Examination at 18 weeks posttransplant showed 100% incidence of tumors in all "stroma" bladders irrespective of the lengths of BHBN exposure of urothelial cells. However, among the bladders that had received 6w-BHBN urothelial cells, carcinogen-exposed "stroma" bladders proved to be better "soil" for neoplastic cells to proliferate; the mean tumor volume as well as the mean total tumor volume per bladder were significantly higher than in the control "stroma" bladders (p less than 0.01 for each comparison). Similarly, among the bladders that had been resurfaced with 10w-BHBN urothelial cells, the mean total tumor volume per bladder was greater in the carcinogen-treated "stroma" bladders than in the controls (p less than 0.05). No proliferative or neoplastic changes were observed in the BHBN exposed "stroma" bladders which had been resurfaced with normal urothelial cells. Our data indicate that neoplastic growth of carcinogen treated urothelium is enhanced when such cells interact with the stroma which has also been exposed to carcinogen.

Animals↗
PubMed1990

Stimulation of stromal cell growth by normal rat urothelial cell-derived epidermal growth factor.

Primary cultured adult rat urothelial (RU) cells caused increased thymidine incorporation in rat bladder stromal (RS) cells in a coculture system. The concentrated conditioned medium derived from RU cell culture (CM-RU) also stimulated the growth of RS cells, and induced anchorage independent growth of NRK-49F cells. Since these activities were heat and acid resistant, we investigated whether epidermal growth factor (EGF) and/or transforming growth factors were the humoral factor(s) responsible. The immunodiffusion analysis of CM-RU gave a positive precipitin line with rabbit anti-rat EGF IgG but not with rabbit anti-rat transforming growth factor-alpha antibodies. The anti-rat EGF IgG inhibited CM-RU-stimulated thymidine incorporation into RS cells, whereas normal rabbit IgG did not. By immunofluorescent technique using rabbit anti-rat EGF antibodies, immunoreactive EGF was demonstrated in RU cells and the urothelial of cryoinjury-induced reparative hyperplasia. Immunofluorescent technique also demonstrated the presence of EGF receptors on the cell membrane of RU and RS cells, basal cells of normal rat urothelium, and cells of whole epithelial layers of reparative hyperplasia. These data strongly suggest that EGF or an EGF-like substance produced by RU cells and released into medium stimulates the growth of RS cells possibly mediated by EGF receptors.

Animals↗
PubMed1989

Inhibitory action of alpha-difluoromethylornithine on N-butyl-N-(4-hydroxybutyl)nitrosamine-induced rat urinary bladder carcinogenesis.

We previously have shown that urine components capable of stimulating ornithine decarboxylase activity of urothelium can enhance rat urinary bladder carcinogenesis, and that alpha-difluoromethylornithine (DFMO), an irreversible inhibitor of ornithine decarboxylase, suppresses carcinogen-initiated rat urinary bladder carcinogenesis. The present investigation was conducted to determine whether DFMO's suppressive effect is stage specific during carcinogenesis and whether the suppressive effect lasts with its continued use. Following initiation with 0.05% N-butyl-N-(4-hydroxybutyl)-nitrosamine in drinking water for 6 wk, male Fischer 344 rats initially weighing 125 to 150 g were randomly divided into two groups, the first receiving 0.2% DFMO in drinking water ad libitum and the second receiving tap water only. Groups of animals were killed at regular intervals until the completion of the experiment at 75 wk. The effect of DFMO was evaluated by monitoring the incidence of tumors, the mean number of tumors per rat, the mean volume of individual tumors, and the mean total tumor volume per rat. The results showed that continuous treatment with DFMO significantly reduced tumor formation until 60 wk (P less than 0.017). The effect was only of borderline significance (0.017 less than P less than 0.035) at 75 wk. Discontinuation of DFMO treatment at 40 wk resulted in the loss of protective effect in all comparisons except for the borderline effect on the tumor number and total tumor volume per rat. DFMO had no significant effect on the incidence or development of preneoplastic early lesions. Mucosal polyamine (spermidine and spermine) levels were reduced and correlated well with the reduction in tumor growth, suggesting that the reduction in tumor growth rate by DFMO may be due to its ability to reduce polyamine levels in urothelium. There were no side effects attributable to DFMO treatment. DFMO may be a useful chemopreventive agent to retard the recurrence of human superficial bladder cancer.

Animals↗
PubMed1989

Identification of epidermal growth factor as a component of the rat urinary bladder tumor-enhancing urinary fractions.

Using the heterotopically transplanted rat urinary bladder, we have shown that normal rat urine has a potent tumor-enhancing effect on bladder carcinogenesis. In an attempt to isolate tumor-enhancing factor(s), urine was fractionated by Bio-Gel P-100 column chromatography and each eluate fraction was examined for inducibility of ornithine decarboxylase (ODC) in a target rat bladder carcinoma cell line, 804G. We have identified two ODC-inducible peaks, one located in a high molecular weight region designated as Fraction I (Fr. I) and the second in a low molecular weight region designated as Fraction II (Fr. II). Fr. I consisted of two principal elements, transferrin and a component which induced ODC. The present investigation was conducted to characterize the ODC-inducible activity in Fr. I and II. Chromatographic analysis of Fr. I by Sephacryl S-200 and Fr. II by Bio-Gel P-10 chromatography separated several ODC-inducible peaks. However, the major ODC inducibility was due to a high concentration (460 ng/mg Fr. I residue, approximate Mr 54,000, and 580 ng/mg Fr. II residue, approximate Mr 6,100) of epidermal growth factor (EGF) as determined by radioimmunoassay. Aliquots obtained from these peaks competed with mouse EGF for EGF receptors in A431 cells. Preincubation of Fr. I and II with rabbit anti-rat EGF IgG significantly reduced ODC inducibility. Transforming growth factor alpha activity as determined by radioimmunoassay was also demonstrated in both Fr. I (34 ng/mg) and Fr. II (9 ng/mg). The results of the present study together with our previous data indicate that the majority of the ODC-inducing activity in the tumor-enhancing urinary components Fr. I and Fr. II is due to EGF itself and EGF-related growth factors of high molecular weight and that Fr. I also contains transferrin.

Animals↗
PubMed1989

Effects of urinary transferrin and ornithine decarboxylase-inducing fraction on rat bladder carcinogenesis.

Using heterotopically transplanted rat urinary bladder (HTB) system, we previously have shown that contact with urine enhanced bladder carcinogenesis initiated by carcinogen. In order to screen urine for promoter substances, several short term in vitro assays were developed and their results were correlated with the in vivo assay results. Chromatographically separated urine fractions were examined for the inability to induce ornithine decarboxylase (ODC), to enhance incorporation of [3H]thymidine in a bladder carcinoma cell line (804G) and to form colonies in soft agar by NRK-49F. Data from the ODC assay and soft agar colony formation correlated well with the results derived from chronic animal studies. Thus then two assays appear useful in further screening urine for promoter substance. Data furthermore indicate that ODC-inducing urine component(s) may play a primary role in the steps following initiation whereas transferrin, a mitogenic urine component, may play a secondary role.

Animals↗
PubMed1989

Stimulation of epithelial hyperplasia in rat urinary bladder by Escherichia coli cystitis.

Using heterotopically transplanted rat urinary bladder, experiments were conducted to develop a reproducible animal model of bacterial cystitis-associated urothelial hyperplasia without calculus formation, and to elucidate which bacterial component(s) might induce urothelial hyperplasia. Bladder instillation of live Escherichia coli (E. coli) resulted in persistent infection and inflammation and also diffuse urothelial hyperplasia. Instillation of killed E. coli also induced diffuse hyperplasia. Hyperplastic changes regressed following withdrawal of the killed E. coli treatment. Urothelial hyperplasia was also induced by repeated instillation of protein-rich lipopolysaccharide (LPS), the endotoxin derived from gram-negative bacterial wall component, but not by protein-free LPS. A finding common to bladders showing hyperplasia was the infiltration of neutrophils into intercellular spaces of the urothelium. We conclude that urothelial hyperplasia is induced by E. coli cystitis, that LPS plays a significant role in the hyperplastic response, and that neutrophils may mediate the response.

Animals↗
PubMed1989

Suppression of rat urinary bladder carcinogenesis by alpha-difluoromethylornithine.

The inhibitory effect of oral administration of alpha-difluoromethylornithine (DFMO) on urinary bladder carcinogenesis induced by N-butyl-N-(4-hydroxybutyl)-nitrosamine (BHBN) was explored. Since DFMO in the drinking water at 0.5% and 0.2% had been demonstrated to inhibit tumorigenesis, lower doses (0.2%, 0.1%, 0.03% and 0.01%) of DFMO were examined in the present study. After six-week treatment with the drinking water containing 0.05% BHBN, water containing DFMO at 0.2%, 0.1%, 0.03%, 0.01% or 0% was administered during the subsequent 34 weeks. Incidence of bladder carcinoma was 15/35 (43%), 14/35 (40%), 21/35 (60%), 20/35 (57%) and 27/35 (77%) in the 0.2%, 0.1%, 0.03%, 0.01% and 0% DFMO groups, respectively. Stastistical analysis indicated significant tumor suppression in the 0.2% and 0.1% DFMO groups. Tumor multiplicity and size were not affected by DFMO treatment. No untoward effects were demonstrated in body weight gain or examination of pertinent organs. Our data indicate that bladder carcinogenesis induced by six-week exposure to 0.05% BHBN is significantly inhibited by daily administration of DFMO at the level of 0.1% or higher in drinking water.

Administration, Oral↗
PubMed1989

Invasive carcinomas of the urinary bladder. Evaluation of tunica muscularis mucosae involvement.

Awareness of the existence of a tunica muscularis mucosae in the urinary bladder complicates the assessment of muscle invasive carcinomas on bladder biopsy. Sixty cystectomy specimens and select bladder biopsies were reviewed to analyze this problem. The patterns of development of the tunica muscularis mucosae were categorized as continuous, interrupted, scattered, or absent. Most bladders demonstrated several patterns of development rather than a uniform appearance. The most frequently observed pattern was that of scattered smooth muscle fibers seen in 33 of 40 (82.5%) cases. The rarity of carcinomatous invasion limited to the tunica muscularis mucosae is emphasized. The authors conclude that the potential for overstaging bladder carcinomas because of misinterpretation of this structure is small.

Biopsy↗
PubMed1988

Conversion from low grade to high grade of rat urinary bladder carcinomas.

The present study was conducted to test if low-grade carcinomas induced by a single dose of N-methyl-Nitrosourea (MNU) can be converted to high-grade carcinomas by a second identical dose of the carcinogen. The heterotopically transplanted rat urinary bladder system was used. Four wk after heterotopic bladder transplantation, the recipient male Fischer 344 rats were divided into 2 groups. The first group received 0.25 mg of MNU into heterotopically transplanted rat urinary bladder; the second group (controls) received 0.9% NaCl solution. At week 29 of the experiment, 1/3 of the animals from each group were killed for histological examination of the heterotopically transplanted rat urinary bladders. The remaining animals from each group were divided into 2 subgroups, the first receiving 0.25 mg MNU and the second, 0.9% NaCl solution. All animals were killed at 50 wk of the experiment. MNU-induced carcinomas at week 29 were all of low histological grade and were noninvasive. Longer follow-up without a second carcinogen administration resulted in both an increase in tumor incidence (P less than 0.005) and more tumors per bladder (P less than 0.001), but high-grade invasive carcinomas were rare. The second dose of MNU administered at the stage when low-grade carcinomas were prevalent (week 29) resulted in a significant increase in invasive high-grade carcinomas (P less than 0.01). Our data are consistent with the view that the second carcinogen administration induces a new mutation(s) within low-grade carcinomas which leads to invasive carcinomas.

Animals↗
PubMed1988

Effects of alpha-difluoromethylornithine on initiation and promotion of urinary bladder carcinogenesis in a heterotopically transplanted rat urinary bladder.

We previously demonstrated that repeated intravesical instillation of DFMO, an irreversible inhibitor of ornithine decarboxylase, inhibits (or retards) urinary bladder carcinogenesis in rats. The present investigation was conducted to determine if high intraluminal concentration of DFMO alters initiation by MNU and to determine if DFMO inhibition is due to arrest of tumor progression or simply retardation of the tumor development. Results showed that the inhibitory effects demonstrated by DFMO treatment during the early phase of study disappeared as the observation period was extended. Failure to suppress tumor development might be due to failure to control intracellular polyamine levels below the critical level and this failure in turn might be due to the rapid fall of intravesical DFMO concentration following instillation.

Animals↗
PubMed1988

Renal functional changes in experimental cystic disease are tubular in origin.

Chronic (30 weeks) structural and functional changes were correlated in diphenylthiazole (DPT)-induced polycystic kidney disease (PKD) in rats. DPT induced two different types of progressive tubular changes: cystic transformation and hyperplastic/atrophic tubular changes. Cystic changes diffusely involved collecting tubules in the outer medulla and cortex, and they were progressive over 30 weeks. Hyperplastic/atrophic changes occurred as clusters of tubules in the cortex and involved between 25% and 50% of tubular profiles after 12 and 30 weeks of drug treatment. Thus, the two types of tubular change were independent of each other and represent different cellular responses to the drug. DPT treatment induced no detectable light- and electron-microscopic or histochemical alterations in glomeruli or renal blood vessels. Renal functional changes consisted of: (1) early (4 weeks) and persistent impairment of concentrating ability; (2) a progressive drop in creatinine clearance and elevation in BUN; and (3) the late onset (30 weeks) of moderate proteinuria. These findings suggest that cystic as well as hyperplastic-atrophic tubular changes contribute to the loss of tubular and renal function in DPT-induced PKD. Both types of tubular lesions may have a role in the development of impaired renal function in other forms of experimental and clinical PKD.

Animals↗
PubMed1988

Prostate specific antigen and acid phosphatase-reactive cells in cystitis cystica and glandularis.

Cystitis cystica (CC) and cystitis glandularis (CG) are common in the urothelium lining the bladder neck and trigone. Because some cases of CG show histologic features strikingly similar to prostatic acini, we hypothesized that some such foci may represent prostatelike metaplasia in the urinary bladder. Forty surgical and autopsy bladder specimens (23 males, 17 females) showing CC or CG were studied using anti-prostate specific antigen and anti-prostate specific acid phosphatase antibodies. Fourteen (35%) of these 40 cases showed positive staining for prostate specific antigen or prostate specific acid phosphatase or both in CC or CG foci. Among these were five female patients. The findings indicate that bladder epithelium is capable of undergoing prostatelike metaplasia and lend support to the hypothesis that the adult bladder stroma closest to the prostate may exert inductive influences on the overlying epithelium to show prostatelike metaplasia.

Acid Phosphatase↗
PubMed1987

Inhibition of N-butyl-N-(4-hydroxybutyl)nitrosamine-induced rat urinary bladder carcinogenesis by alpha-difluoromethylornithine.

The effect of oral administration of alpha-difluoromethylornithine (DFMO), an irreversible ornithine decarboxylase inhibitor, on N-butyl-N-(4-hydroxybutyl)nitrosamine (BHBN)-induced rat urinary bladder carcinogenesis was investigated. Four-wk-old male Fischer 344 rats, 30-38 per group, were divided into 3 groups; each group was divided into 3 subgroups. In Group A, 6-wk treatment with 0.05% BHBN in drinking water was followed by either 0.5% (A1), 0.2% (A2), or 0% (A3) DFMO in drinking water for 34 wk. In Group B, coadministration in drinking water of 0.01% BHBN and either 0.5% (B1), 0.2% (B2), or 0% (B3) DFMO was continued for 30 wk. Group C consisted of animals receiving 0.5%, 0.2%, or 0% DFMO in drinking water for 34 wk without prior or cocarcinogen treatment. Bladder tumorigenesis was clearly inhibited by DFMO; tumor incidence was 14 of 37 (38%) in A1, 16 of 38 (42%) in A2, and 31 of 35 (89%) in A3, and 7 of 35 (20%) in B1, 14 of 35 (40%) in B2, and 28 of 35 (80%) in B3 (P less than 0.01, DFMO groups as compared to the respective control A3 or B3). The average tumor volume was strikingly reduced in Group A rats given DFMO (3.0 mm3 in A1, 5.0 in A2, and 38.6 in A3). Significant suppression of tumor multiplicity (number of tumors/tumor-bearing bladder) was observed in DFMO-treated subgroups in Group B (1.1 in B1, 1.3 in B2, and 1.8 in B3). In both Groups A and B, however, DFMO failed to suppress hyperplastic changes (simple hyperplasia) or preneoplastic lesions (nodulopapillary hyperplasia). Systematic examination of all pertinent organs excluding the brain showed no adverse effects attributable to DFMO treatment except for decrease in body weight (less than 7%), which was consistently observed in the groups receiving 0.5% DFMO, and reduction in the combined weight of the prostate and seminal vesicles (less than 20%), which was noted in Group B in which exposure to DFMO was started at a younger age. These results indicate that oral administration of DFMO is quite effective in suppressing (or retarding) BHBN-induced carcinogenesis with minimal untoward effects and confirm the similar inhibitory effects demonstrated earlier with the heterotopically transplanted rat urinary bladder system.

Administration, Oral↗
PubMed1987

Transferrin as a growth factor for rat bladder carcinoma cells in culture.

Using the heterotopically transplanted rat urinary bladder system, we previously showed that normal urine has a tumor-enhancing effect on carcinogen-initiated urothelium. In an attempt to isolate a urinary growth-stimulating (tumor-enhancing) factor(s), urine was first fractionated by Bio-Gel P-100 column chromatography, and each fraction was tested for inducibility of ornithine decarboxylase (ODC) and growth-stimulatory activity in a target rat bladder carcinoma cell line, 804G. ODC inducibility was chosen as a marker for tumor-enhancing effect because it is a key characteristic of tumor promoters. There was a single peak demonstrating a strong growth-stimulatory activity as measured by [3H]thymidine incorporation. There were two ODC-inducible peaks, one located at a high molecular weight region and partly overlapped with the growth-stimulatory peak. The other was located at a lower molecular weight region. CM-Sephadex chromatography and subsequent high performance liquid chromatography successfully separated the high molecular weight-ODC activity from the growth-stimulatory activity. The latter component was found to contain transferrin (TF) by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunodiffusion with anti-rat TF antibody and was designated as urinary transferrin fraction. The urinary TF fraction and authentic rat TF stimulated growth of several rat bladder carcinoma cells maintained in a serum-free as well as a serum-deficient medium. The response was proportional to the concentration of TF ranging from 0.2 to 5 microgram/ml. Preincubation of the urinary TF fraction or TF with an anti-rat TF significantly reduced their growth-stimulatory effects in 804G cells. The high molecular weight-ODC also stimulated cell growth but to a lesser extent. These results when combined with our previous observations suggest that TF and possibly also ODC-inducible substances may be important urinary components participating in the tumor promotion by urine.

Animals↗