Biomedical subjects

D S Longnecker

Publications and source records attributed to D S Longnecker.

At least 73 records · Page 4Linked to original sources

PubMed1989

Inhibition of a transplantable pancreatic carcinoma by castration and estradiol administration in rats.

Influence of sex steroids on the growth of an azaserine-induced transplantable rat pancreatic carcinoma, DSL-2, was studied. This established transplantable tumor has been maintained in syngeneic rats. Inbred male Lewis rats were pretreated with castration and s.c. implantation of 1.0-mg 17 beta-estradiol (CAS: 50-28-2; estradiol) pellets at 7 weeks of age. Tumor cells were inoculated s.c. on the back of intact male, castrated male, or 17 beta-estradiol-treated castrated male rats. Additional male rats served as non-tumor-bearing controls. There was no difference in the body weight between tumor-bearing and non-tumor-bearing male rats. A distinct difference in the tumor growth was observed in variously conditioned recipients. In castrated male hosts, the serum testosterone levels and the epididymis weights were significantly decreased, and the tumor weights were significantly less as compared to intact control hosts. Additional pretreatment with 17 beta-estradiol caused a markedly slower growth of tumors and increases of the serum 17 beta-estradiol levels and the pituitary weights in castrated male recipients. The remarkable response of tumor growth to castration was also observed in a fast-growing tumor derived from DSL-2. Moreover, close positive relationships between tumor weights and the activities of both serum amylase and lipase were observed. Results showed that the pretreatment with castration alone or in combination with 17 beta-estradiol treatment was able to inhibit the growth of the transplantable tumor. In addition, tumor cells had an ability to produce amylase and lipase, and the amount of enzymic activity was related to the tumor volume. Thus, these data indicate that the transplantable rat pancreatic carcinoma retains physiological function. Our previous study has shown the modulation by sex steroids of azaserine-induced preneoplastic lesions of pancreas in rats. Therefore, androgens and estrogens may play key roles as promoters and inhibitors during the process of pancreatic carcinogenesis.

Amylases↗

PubMed1989

Inhibitory effects of estrogen and castration on the early stage of pancreatic carcinogenesis in Fischer rats treated with azaserine.

Effects of sex steroids on pancreatic carcinogenesis during the early stage were studied in azaserine-treated rats of both sexes. Fischer rats were given weekly i.p. injections of azaserine (30 mg/kg) [CAS:115-02; diazoacetate serine(ester)] at 2 and 3 weeks of age and were divided into six groups. Castration, ovariectomy, and s.c. implantations of either a 0.3-mg or a 1.0-mg 17 beta-estradiol (CAS:50-28.2; estradiol) pellet were performed at 7 weeks of age. The groups were as follows: group 1, intact male; group 2, castrated; group 3, castrated plus 0.3 mg estradiol; group 4, castrated plus 1.0 mg estradiol; group 5, ovariectomized; and group 6, intact female. Rats were killed 4 months after the last injection of azaserine. Azaserine treatment induced atypical acinar cell foci and nodules (AACN) in both sexes. The acidophilic AACN are considered preneoplastic lesions. An apparent sex difference was observed; the number of acidophilic AACN was greater in male rats than in female rats. Castration caused a significant decrease in both the serum testosterone levels and the number of acidophilic AACN, which were comparable to those in ovariectomized female rats. Furthermore, when estradiol treatment was administered to the castrated male rats, a linear decrease in the number of acidophilic AACN and an elevation in the serum estradiol levels were observed and were dose dependent. There were also positive relationships between estradiol treatments and the mean pituitary and pancreas weights. These results showed that estradiol treatment and the drop in testosterone levels caused by castration were highly effective in inhibiting the development and growth of preneoplastic lesions of the pancreas of the rats treated with azaserine. This estradiol effect was dose dependent. The present study, therefore, provides evidence that estrogen may act as an inhibitor and androgen as a promoter in the early stage of pancreatic carcinogenesis in rats.

Animals↗

PubMed1988

Stimulation of the growth of azaserine-induced nodules in the rat pancreas by dietary camostate (FOY-305).

The effects of dietary camostate (FOY-305), a synthetic trypsin inhibitor, on the early stages of pancreatic carcinogenesis in the rat were studied because of earlier reports that feeding soy bean trypsin inhibitor stimulated growth and promoted carcinogenesis in the pancreas of rats. These effects are attributed to excess secretion of cholecystokinin, a trophic hormone for pancreatic acinar cells. Camostate has been shown to induce pancreatic enlargement in rats by the same mechanism. In preliminary experiments, pancreatic growth was studied in adult Fischer 344 (F344) and Lewis rats fed camostate mixed in the diet to define a level that induced pancreatic hypertrophy and hyperplasia. As little as 0.02% fed 3 days per week was effective. In a second experiment, F344 rats were injected with azaserine and thereafter were given camostate by gavage 5 days a week until autopsy 18 weeks later. In a third experiment, azaserine-treated Lewis rats were fed camostate in the diet 3 days a week for 8 or 16 weeks until autopsy. In the latter two experiments the number and size of atypical acinar cell foci and nodules (AACN) were measured in pancreas sections. Growth of acidophilic AACN was stimulated in camostate-fed groups; both the number and the size were increased in comparison with the control groups. The data suggest a promoting effect of dietary camostate on the growth of azaserine-induced preneoplastic lesions in the pancreas of both rat strains. The number of basophilic AACN was decreased in camostate-fed Lewis rats suggesting that the camostate diet also affected the phenotype of the carcinogen-induced AACN.

Animals↗

PubMed1988

Inhibition of pancreatic and liver carcinogenesis in rats by retinoid- and selenium-supplemented diets.

Chemoprevention by a synthetic retinoid, selenium, and these agents in combination during the postinitiation stages of carcinogenesis induced in rats by azaserine was evaluated. Male Lewis rats were given three weekly injections of 30 mg/kg azaserine while being fed a purified diet. One week after completion of carcinogen treatment, groups of rats were switched to the purified diet supplemented with either a retinoid, N-(2-hydroxyethyl)retinamide, at a level of 0.5 or 1 mmol/kg diet, or with 5 ppm sodium selenite, or with a combination of retinoid and selenium. One year after the diet change, the incidence of pancreatic and other neoplasms was determined by autopsy and histologic study. The incidence of pancreatic carcinoma (including carcinoma-in-situ, CIS) among nonretinoid-treated controls was 68%. Since the dietary supplements were fed after completion of exposure to the carcinogen, the effects on both pancreatic and liver carcinogenesis were exerted during the postinitiation phase of carcinogenesis. As in previous studies, the retinoid inhibited the progression of pancreatic carcinogenesis in a dose-related fashion. Selenium alone had no effect. However, the combination of retinoid plus selenium was more effective than retinoid alone, although the increase in inhibition was not large. The retinoid was also found to inhibit liver carcinogenesis induced by azaserine. Selenium, either alone or in combination with retinoid, was ineffective. Finally, testicular atrophy, noted as a toxic effect of retinoids in other studies, was not observed in this work.

Animals↗

PubMed1987

Effect of bombesin and caerulein on early stages of carcinogenesis induced by azaserine in the rat pancreas.

This study was designed to analyze the effect of two pancreaticotrophic peptides on pancreatic carcinogenesis in the azaserine-rat model. The rats were treated with bombesin or caerulein for 16 weeks after initiation with azaserine. Two-week-old Lewis rats were given injections of a single dose of azaserine (30 mg/kg) and the control pups received an injection of saline. They were divided into ten groups for peptide treatment as follows: Group 1, azaserine-saline; Group 2, azaserine-bombesin, 10 micrograms/kg; Group 3, azaserine-bombesin, 30 micrograms/kg; Group 4, azaserine-caerulein, 5 micrograms/kg; Group 5, azaserine-caerulein, 15 micrograms/kg; Group 6, control-saline; Group 7, control-bombesin, 10 micrograms/kg; Group 8, control-bombesin, 30 micrograms/kg; Group 9, control-caerulein, 5 micrograms/kg; and Group 10, control-caerulein, 15 micrograms/kg. At 3 weeks of age, they were weaned. Peptides or saline were injected 3 consecutive days a week for 16 weeks. Rats were autopsied 4 months after the administration of azaserine. Pancreatic weight was increased by bombesin and decreased by caerulein treatment. Quantitative histological analysis of azaserine-induced atypical acinar cell nodules in the pancreas showed that the size and number of atypical acinar cell nodules were increased in both bombesin- and caerulein-treated groups. Thus, these peptides appear to stimulate the growth of preneoplastic acinar cell lesions.

Animals↗

PubMed1987

gamma-Glutamyltransferase activity in atypical acinar cell nodules of rat pancreas.

The biochemical and histochemical measurement of the enzyme gamma-glutamyltransferase (GGT) was undertaken in normal rat pancreas and in rat pancreas containing azaserine-induced preneoplastic nodules. A steady decrease in pancreatic GGT activity was observed in the normal animals as they aged from 5 to 34 weeks. The azaserine-induced nodules contained a lower average GGT activity than the control pancreas although a 10-fold variation was noted in the GGT activity of individual nodules. A significant increase in concentrations of both reduced glutathione and oxidized glutathione was noted in pancreatic nodules from azaserine-treated rats compared to concentrations found in both control pancreas from untreated rats and internodular pancreas from azaserine-treated rats. A pancreatic acinar cell carcinoma contained low GGT activity--similar to that found in large nodules and about 10% of the level found in control pancreas. Pancreatic GGT levels were higher in 5- and 7-week-old rats fed chow than in rats fed a purified diet, but this effect of chow was not observed at 34 weeks of age. Feeding a purified diet supplemented with a retinoid, N-2-hydroxyethylretinamide (2-HER), for a period of 2 weeks did not influence the GGT activity level in either normal pancreas or in the azaserine-induced nodules. While decreased GGT activity does not serve as a marker for all atypical acinar cell nodules, deficient activity with concomitant increased glutathione levels appears to correlate generally with increased growth potential.

Animals↗

PubMed1987

Pancreatic carcinogenesis in azaserine-treated rats: inhibition by a solvent mixture in the diet.

The growth of azaserine-induced foci and nodules in a 4-month experiment and the incidence of carcinomas in a 15-month experiment were greater in LEW/CrlBR inbred rats fed a purified diet (AIN-76A) than in rats fed a natural-ingredient diet (chow). Addition of a mixture of several solvents to either diet reduced the incidence of adenocarcinomas in the pancreas in the long-term study but failed to reduce the number or size of pancreatic atypical acinar cell foci in the experiments of 4 months and 6 months (chow only) duration. Apparently, some component of the solvent mixture inhibits a late stage in the development of pancreatic carcinoma. Glyceryl monooleate and propylene glycol are implicated as the components of the mixture most likely to be responsible for the inhibitory effect, but neither the identity of the critical component nor the mechanism of the inhibition is known. The solvent mixture also contained ethanol and trioctanoin.

Animals↗

PubMed1987

Growth of pancreatic foci and development of pancreatic cancer with a single dose of azaserine in the rat.

Studies were undertaken to characterize the growth of the azaserine-induced putative preneoplastic lesions in rats and to determine if a single dose of azaserine would be carcinogenic. Male Lewis rats were given a single i.p. injection of 30 mg L-azaserine/kg body weight at 7 weeks of age. A purified diet was fed throughout the study. Rats (10-12 per group) were autopsied at 6, 9, 12, 15 and 18 months post-initiation, and pancreases were quantitatively evaluated to characterize the growth of acidophilic and basophilic foci and nodules (henceforth called foci), and the incidence of neoplasms. All azaserine-treated rats had foci, and at all times approximately equal numbers of acidophilic and basophilic foci were present in the pancreas. The number of basophilic foci increased with time, and while their size also increased, the change was small compared with the increase in size of the acidophilic foci. Conversely, all acidophilic foci appeared to be present by 6-9 months, and their size greatly increased with time. The data suggest that virtually all foci persist rather than regress or remodel. At 9 months the incidence of carcinoma in situ was 30% and by 18 months there was a 100% incidence of pancreatic cancers (58% carcinoma in situ and 42% carcinoma).

Animals↗

PubMed1987

Effect of castration and hormone replacement on azaserine-induced pancreatic carcinogenesis in male and female Fischer rats.

Previous reports have shown that pancreatic cancer was induced preferentially in male versus female azaserine-treated rats. This study was designed to determine the importance of estrogen and testosterone in this phenomenon. Fischer (F344) rats received a single injection of azaserine (30 mg/kg) at 21 days of age. At 28 days of age, they were weaned and divided into 12 groups of 9-10 rats as shown below. Surgery (castration or sham operation) was performed at 4 weeks of age. All drugs (estradiol, the antiestrogen tamoxifen, testosterone propionate and/or the antiandrogen flutamide) were administered, starting at weaning, in 3-week timed-release pellets until autopsy. Rats were killed 4 months after the administration of azaserine. The pancreas was weighed and prepared for quantitative histologic analysis of atypical acinar cell nodules (AACNs) which are putative preneoplastic lesions. Both number and size of AACNs were analyzed. In intact female rats, AACN burden was smaller than in intact males (P less than 0.05). Ovariectomy increased the AACN burden (P less than 0.05), while estradiol or tamoxifen treatments to ovariectomized females resorted the burden to control levels (P less than 0.05). Testosterone with tamoxifen treatment to ovariectomized females led to a significant increase in AACN burden over control values. In intact male rats, orchiectomy decreased the AACN burden (P less than 0.05). In orchiectomized rats, testosterone treatment slightly increased the AACN burden, flutamide treatment alone increased this parameter (P less than 0.05) but flutamide with estradiol decreased the AACN burden (P less than 0.01). These data strongly support the hypothesis that sex steroids play a major role in the higher incidence of pancreatic cancer in male versus female rats.

Animals↗

PubMed1987

Characterization of a 4-month protocol for the quantitation of BOP-induced lesions in hamster pancreas and its application in studying the effect of dietary fat.

The early putative pre-neoplastic lesions which arise in the Syrian golden hamster pancreas prior to the appearance of carcinomas following treatment with N-nitrosobis(2-oxopropyl)amine (BOP), have been characterized and quantitated in order to refine a protocol which permits post-initiation modulation to be evaluated within a relatively short period of time. The proposed 4-month protocol was used to investigate the modulating effects of dietary saturated fat on pancreatic carcinogenesis in hamsters. Hamsters were injected s.c. with 20 mg BOP/kg body wt at 5, 6 and 7 weeks of age. The animals were fed a low fat (LF) control diet (5% lard) or a high fat (HF) diet (20% lard) subsequent to the initiation protocol. At 4 months post-initiation, the pancreata were quantitatively examined for the number and size of putative pre-neoplastic lesions. The major attention was directed to intraductal epithelial hyperplasia of inter/intralobular or main ducts, cystic ductal complexes, tubular ductal complexes and ductal complexes that seemed to be intermediate between the latter two. The number of large ductal complexes of the intermediate and tubular category was significantly greater in hamsters fed a diet with 20% saturated fat as compared to animals maintained on 5% saturated fat. Furthermore, the number of ducts with intraductal hyperplasia was greater in the high fat group, and the proportion of such lesions judged to show atypia was also higher in this group. Dietary fat did not have a significant effect on either the cystic ductal complexes or the incidence of hyperplasia in the main pancreatic duct. These results suggest that a diet high in saturated fat enhances pancreatic carcinogenesis in the BOP-hamster model and, moreover, they suggest that a short-term (4-month) protocol may be useful for evaluation of the effects of potential modulating factors on pancreatic carcinogenesis in Syrian golden hamsters. The utility of the approach should be further evaluated and correlated with the results of long-term studies.

Adenocarcinoma↗

PubMed1987

In vivo and in vitro genotoxicity of selected compounds toward rodent pancreas.

Using the technique of alkaline elution analysis, the ability of 11 known or suspected pancreatic carcinogens to damage the DNA of pancreatic acinar cells when administered to rats and hamsters was examined. The two species respond differently to several agents. In selected instances, DNA damage was also assessed in cultured pancreatic acinar cells exposed in vitro to the agents. Comparisons of DNA damage produced in vivo with that produced in vitro gave useful information on the role of pancreatic metabolism in activating pancreatic carcinogens. Finally, information germane to the question of the cell of origin for pancreatic cancer was obtained.

Animals↗

PubMed1987

Effect of orchiectomy and testosterone on the early stages of azaserine-induced pancreatic carcinogenesis in the rat.

The incidence of carcinoma of the pancreas is higher among men than women. It is also higher among male than female carcinogen-treated rats. The role of testosterone in this preferential induction of pancreatic cancer was evaluated in a rat model of pancreatic carcinogenesis. Two-week-old Lewis rats were treated with a single injection of azaserine. At weaning (3 weeks), rats were divided into five groups as follows: females; intact males; sham-operated males; orchiectomized males; and orchiectomized males plus testosterone. Four months after administration of azaserine, quantitative histologic analysis of atypical acinar cell foci and nodules of the pancreas showed that in female and orchiectomized male rats, foci and nodules were smaller and less numerous than in intact males. Testosterone treatment partly reversed the effect of orchiectomy. This suggests that the susceptibility of male rats to induction of pancreatic carcinomas by azaserine is at least partially mediated by testosterone. Estrogen and testosterone receptors were assayed, but high-affinity receptors characteristic of gonadal tissues were not detected in normal pancreas or in a transplantable azaserine-induced acinar cell carcinoma. Thus, the effect of testosterone in the pancreas may depend on steroid-binding proteins of another type, or may be indirectly mediated.

Animals↗

PubMed1987

Mutagenicity of L-azaserine for V79 cells in a pancreatic acinar cell-mediated mutagenesis assay.

The mutagenicity of azaserine was determined in a pancreatic acinar cell-mediated mutagenesis assay using V79 cells as the responder cell line. The mutation frequency of V79 cells was increased in direct culture with azaserine as well as in coculture with rat and hamster pancreatic acinar cells. Although slightly higher mutation frequencies were seen with coculture, the mutation frequency induced by azaserine in coculture was not significantly enhanced over that observed in direct culture. Thus, azaserine cannot be used as a positive control to monitor the level of acinar cell metabolism in such cell-mediated mutagenesis assays. Statistical analysis suggested that hamster acinar cell cocultures were more effective at increasing the mutation frequency of azaserine as compared to rat acinar cell cocultures. Hamster acinar cell cocultures, but not rat acinar cell cocultures, increased the mutagenicity of azaserine in a dose-response fashion. These results suggest that azaserine may be a pancreatic carcinogen for the hamster as well as the rat.

Animals↗

PubMed1987

Interface between adaptive and neoplastic growth in the pancreas.

The adaptive changes of hypertrophy and hyperplasia are diffuse and reversible responses of the pancreas to growth promoting stimuli. Early stages of neoplastic growth in the pancreas have been studied in carcinogen treated animals and preneoplastic lesions including atypical acinar cell foci and nodules, tubular ductal complexes and intraductal hyperplasia were identified. Neoplastic growth is clonal rather than diffuse and involves multiple steps through preneoplastic stages to produce a tumour. The individual steps are commonly regarded as reflecting a series of changes in the genome of the cells. Although the changes are likely to be irreversible, completion of the sequence usually requires a major portion of the lifespan of the host. The rate of progression of preneoplastic lesions to cancer may be modulated by the same factors that control adaptive growth. It follows that such factors will influence the probability that a carcinoma will develop. Cholecystokinin (CCK) seems to provide one example of a hormone/growth factor that can stimulate normal, adaptive, and neoplastic growth, and it is to be expected that other such hormones will be identified.

Adaptation, Physiological↗

PubMed1986

Size and number of nuclei differ in normal and neoplastic acinar cells from rat pancreas.

Acinar cells were isolated by enzymatic digestion from normal pancreas and from azaserine-induced atypical acinar cell nodules and a transplantable acinar cell carcinoma. Normal acinar cells were predominately binuclear, with abundant cytoplasm. They were 10-24 micron in diameter, with a size distribution skewed toward smaller sizes but with a peak at 18 micron. Cells were isolated from 41 enucleated nodules varying in weight from 1.1 to 200 mg. These cells were predominantly mononuclear, with a more uniform size than normal cells and a peak at 9 micron diameter. Cells from all nodules studied were grossly similar, and there was no relation between nodule size and the degree of mononucleation. Cells from the transplantable tumor were small, with little cytoplasm, and were almost exclusively mononuclear. The extent of binucleation in normal and microscopic atypical acinar cell nodules was also studied in sections from the pancreas of rats injected with azaserine 4 months before killing. Nuclear and cell counts in these sections confirmed that binucleation is more frequent in normal than in nodule tissue. These studies emphasize the high degree of binucleation found in normal pancreatic acinar cells. They demonstrate the feasibility of using cell separation techniques to obtain preparations of acinar cells from normal and neoplastic pancreatic tissue for studies of functional and morphological differences in these cells.

Animals↗

PubMed1986

Effects of retinoids in N-nitrosobis(2-oxopropyl)amine-treated hamsters.

The effect of feeding four synthetic retinoids was evaluated in carcinogen-treated hamsters. Syrian golden hamsters were injected with 20 mg/kg of N-nitrosobis(2-oxopropyl)amine (BOP) and then fed retinoid-supplemented diets for 39 weeks. All retinoid-treated groups grew more slowly than controls, and average survival was shorter in female retinoid-treated groups. A significant incidence of testicular atrophy was noted in male hamsters fed 2-hydroxyethylretinamide or 4-carboxyphenylretinamide. The incidence of pancreatic carcinomas was lower in 12 of 14 retinoid-fed groups than in the corresponding control groups, although the differences approached significance only in groups fed two of the retinoids--male hamsters fed N-4-propionyloxyphenylretinamide and those fed retinylidene dimedone. A low incidence of carcinoma in the control groups limits the conclusions that can be drawn from this study, but it is of note that there was no evidence of promotion.

Adenocarcinoma↗

PubMed1986

Effects of corn oil and benzyl acetate on number and size of azaserine-induced foci in the pancreas of LEW and F344 rats.

The response of LEW and F344 strain rats to the pancreatic carcinogen azaserine was compared using the size and number of azaserine-induced acidophilic acinar cell foci and nodules as parameters in a 4-month experiment. A second experiment compared the effect of corn oil intake by gavage and dietary routes on the growth of azaserine-induced pancreatic lesions in LEW rats. A third experiment tested the activity of benzyl acetate in regard to its ability to induce acinar cell foci or to promote the growth of such foci in azaserine-treated rats. The results showed that equivalent doses of azaserine induce two to seven times more foci in LEW than in F344 rats, and that LEW rats have a higher incidence of "spontaneous" foci than F344 rats. Azaserine-treated LEW rats that were given 5 mL corn oil/kg body weight 5 days per week by gavage developed more acinar cell foci than rats fed a basal diet (chow). Addition of an equivalent amount of corn oil to chow had a similar effect of enhancing the development of foci. Rats of neither strain developed acinar cell foci when benzyl acetate was given by gavage or in the diet nor was there evidence that benzyl acetate has a significant effect on the development of foci in azaserine-treated rats. These studies also demonstrate that the azaserine/rat model of pancreatic carcinogenesis which was developed in LEW rats can be adapted for use with F344 rats.

Animals↗

PubMed1986

Duct-like morphogenesis of Longnecker pancreatic acinar carcinoma cells maintained in vitro on seminiferous tubular basement membranes.

We have investigated the behavior of dissociated cells of a moderately differentiated Longnecker transplantable pancreatic acinar carcinoma (Longnecker et al., Cancer Lett., 7: 197-202, 1979) maintained in vitro on acellular seminiferous tubular basement membranes of rat testis. The tumor cells, which grow as solid masses in vivo with little organization, undergo organogenesis in vitro into distinct duct-like structures with lumina in the presence of basement membrane scaffoldings. These duct-like structures were formed by flattened epithelial cells, which exhibited poorly differentiated acinar cell characteristics with few or no zymogen (secretory) granules. The cells lining the duct-like structures retained the pancreatic acinar cell specific antigen as determined by indirect immunofluorescence. DNA synthesis did not accompany duct-like organization; however, all of the cells lining these structures continued to incorporate [3H]leucine for up to 4-5 days of culture. They continued to synthesize and secrete amylase, a marker protein of pancreatic acinar cells, into the medium. These results demonstrate that neoplastic epithelial cells of Longnecker pancreatic tumor differentiate into duct-like structures when they come into contact with a basement membrane scaffolding and do not accumulate well-formed secretory granules. This is in marked contrast to the previously reported in vitro differentiation of cells derived from another transplantable rat pancreatic acinar cell carcinoma where the neoplastic cells were fully cytodifferentiated on seminiferous tubular basement membrane without forming duct-like structures but accumulated abundant well-developed zymogen granules (Watanabe et al., Cancer Res., 44: 5361-5366, 1984). Although the basal lamina promotes differentiation of cells of two different pancreatic carcinomas in vitro, we conclude that the in vitro expression of morphogenetic and cytodifferentiation patterns is dependent upon the intrinsic properties of cells of these two transplantable pancreatic tumors.

Animals↗