Differential expression of the neurotensin gene in the developing rat and human gastrointestinal tract

Neurotensin (NT) is an important hormone regulating gut motility, secretion, and growth. The purpose of this study was to determine the developmental expression of the NT/neuromedin N gene (NT/N) in the gut and pancreas of rats and humans. We found that NT/N expression, initially low in the fetal rat jejunum and ileum, is increased by postnatal day 3. This increase is independent of contact with luminal nutrients as demonstrated by elevated NT/N expression in rat jejunoileal grafts implanted in nude mice. NT/N expression reaches maximal levels in the small bowel by postnatal day 14. After postnatal day 28, NT/N mRNA levels remain constant in the ileum but decrease in the jejunum. Transient NT/N expression is found in the colon of fetal and postnatal rats. Similar to the rat, NT/N expression is low in the human fetal ileum but increases in the adult. In the human colon, NT/N is transiently expressed in the fetus at midgestation but disappears by birth and, similarly, is not apparent in the adult. We conclude the following. 1) The NT/N gene demonstrates a complex pattern of tissue-specific expression; the jejunum and ileum show a similar pattern of expression until the end of the fourth postnatal week, when NT/N levels decrease in the jejunum to assume the distinctive adult topographical distribution with NT/N increasing along the jejunoileal axis. 2) NT/N is transiently expressed in the colon of rats and humans during a developmental stage characterized by morphological and functional similarities to the small bowel; therefore, NT/N may provide a useful endocrine marker to further define the complex differentiation pathway leading to small bowel and colonic phenotypes.

Effect of 5-HT3 receptor antagonist (ondansetron) on functioning human pancreatic carcinoid cells

5-Hydroxytryptamine (5-HT) is a mitogen for selected cell types. We have reported that 5-HT is an autocrine growth factor for functioning human pancreatic carcinoid (BON) cells; autocrine growth effect is transmitted by 5-HT1A but not 5-HT1C/2 receptors, activation of which decreases cyclic AMP production through a pertussis toxin-sensitive inhibitory GTP-binding protein. In this study, the effect of 5-HT3 receptor antagonist, ondansetron, on BON was examined. Ondansetron did not affect growth of BON cells and also affected neither stimulation of phosphatidylinositol hydrolysis or inhibition of cyclic AMP production evoked by 5-HT in BON cells. Ondansetron, however, inhibited mobilization of intracellular calcium evoked by 5-HT. Present findings suggest that BON cells possess 5-HT3 receptors, but their roles in pancreatic carcinoid cells are still unknown.

Developmental expression of the neurotensin gene in the rat liver

OBJECTIVE

This study determined whether the neurotensin gene is expressed during early development of the liver.

SUMMARY BACKGROUND DATA

Neurotensin (NT), a gut tridecapeptide localized mainly to the distal small bowel and brain of adults, is an important hormone regulating gut motility, secretion and mucosal growth. Expression of NT peptide and the gene is found in fibrolamellar hepatocarcinomas, a variant of hepatocellular carcinoma, but not in the normal adult liver.

METHODS

Northern and in situ hybridization techniques were used to determine expression of the neurotensin gene (NT/N) in the normal developing liver.

RESULTS

NT/N is expressed in the fetal and early postnatal rat liver, but expression is repressed in the liver of the adult. In situ hybridization confirms the authors' Northern data and demonstrates a random distribution of NT/N expression in the fetal and 3-day postnatal liver.

CONCLUSIONS

The authors conclude from this study that NT/N is expressed during early development of the rat liver with subsequent repression in the adult. NT/N may be reexpressed with malignant transformation of the liver.

Glutamine is essential for epidermal growth factor-stimulated intestinal cell proliferation

BACKGROUND

Glutamine stimulates growth of intestinal mucosa in vivo, but the mechanisms involved are unknown. The purpose of this study was to determine whether glutamine is essential for proliferation of enterocytes stimulated by epidermal growth factor (EGF). In addition, we determined which specific mitogenic actions of EGF require glutamine.

METHODS

A nontransformed rat intestinal mucosal cell line (IEC-6) was stimulated with EGF (20 ng/ml) without and with glutamine (0.1 to 10 mmol/L). DNA, RNA, and protein synthesis were quantitated by determining incorporation of tritiated thymidine, tritiated uridine, and 14C-leucine, respectively. Cell numbers and messenger RNA levels of early growth response genes (zif268, jun-B, c-myc) were also determined.

RESULTS

Glutamine was required for EGF stimulation of DNA, RNA, and protein synthesis and cell replication; however, EGF-stimulated expression of zif268, jun-B, and c-myc occurred in the absence of glutamine.

CONCLUSIONS

This study showed that glutamine is essential for EGF-stimulated intestinal mucosal cell proliferation. The mitogenic effects of EGF can be divided into the glutamine-independent, such as the signal transduction pathway leading to the induction of early growth response genes, and the glutamine-dependent, including DNA, RNA, and protein synthesis.

Novel action of transforming growth factor beta 1 in functioning human pancreatic carcinoid cells

We have shown recently that 5-HT is an autocrine growth stimulatory factor for a cell line (BON) that is derived from a human pancreatic carcinoid tumor. This action is mediated by a 5-HT receptor-linked decrease of cyclic adenosine monophosphate (AMP) production, but not mediated by a 5-HT receptor-linked stimulation of phosphatidylinositol hydrolysis. The BON cells also express transforming growth factor betas (TGF beta s) (1, 2, and 3) and release TGF beta into their medium. In this study, we examined the effects of TGF beta on the secretion of 5-HT, on signal transduction pathways involved in 5-HT secretion, and on growth of BON cells. TGF beta 1 inhibited basal and acetylcholine-stimulated release of 5-HT, but did not inhibit isobutylmethylxanthine-stimulated release of 5-HT. TGF beta 1 inhibited both basal and acetylcholine-stimulated hydrolysis of phosphatidylinositol in a dose dependent manner, but did not affect cyclic AMP production. TGF-beta 1 inhibited growth of BON cells in culture; this effect was reversed by exogenously administered 5-HT. Three different specific and saturable TGF beta 1 binding sites were identified; binding assays performed after mild acid wash (0.1% acetic acid, pH 2.5) conditions uncovered TGF beta receptors that were apparently occupied by endogenously produced TGF beta species. Affinity cross-linking assay showed that BON cells had three different TGF beta binding proteins. These results suggest that TGF beta 1 can inhibit growth of BON cells by altering secretory responses of 5-HT by means of receptor-mediated inhibition of phosphatidylinositol hydrolysis. We conclude that growth of BON cells is regulated, at least in part, by the opposing receptor-mediated autocrine actions of 5-HT and TGF beta.

Accidental poisoning of a group of yearling cattle by the organophosphate insecticide trichloronat

Eight yearling cattle were accidentally poisoned with the agricultural organophosphate insecticide trichloronat. One animal showed signs of acute organophosphate poisoning and died. The others showed signs of chronic organophosphate poisoning (organophosphate-induced delayed neuropathy) after 2-3 weeks and one animal died from renal failure at 12 weeks. High levels of trichloronat were measured in fat samples at 6 1/2 weeks. The remaining animals still showed signs of ataxia, possibly due to distal axonopathy, 1 year later but no trichloronat was detected in fat samples at this time.

Pituitary adenylate cyclase activating polypeptide stimulates release of peptide YY

The purpose of these experiments was to examine the effects of the recently discovered gastrointestinal peptide, pituitary adenylate cyclase activating polypeptide (PACAP), and two structurally related peptides, vasoactive intestinal polypeptide and secretin, on release of peptide YY (PYY) in conscious dogs. Intravenous administration of PACAP-27 or -38 stimulated a dose-related release of PYY; PACAP-27 was more potent than PACAP-38. PACAP-stimulated release of PYY was inhibited significantly by atropine, whereas ganglionic or beta-adrenergic blockade with hexamethonium and propranolol treatment, respectively, did not affect PACAP-induced release of PYY significantly (P > 0.05). These results indicate that PACAP-induced release of PYY is cholinergic dependent and that beta-adrenergic tone and ganglionic transmission do not participate in PACAP-induced release of PYY. PACAP may play a role in the neural regulation of PYY release.

Insulinlike growth factor-binding protein modulates the growth response to insulinlike growth factor 1 by human gastric cancer cells

BACKGROUND

This study determined whether the resistance to the mitogenic effect of insulinlike growth factor 1 (IGF-1) in AGS (we found that IGF-1 had almost no effect on the growth of AGS) cells is caused by the absence of IGF-1 receptor on the cells or by the interference of endogenous IGFs and IGF-binding protein (IGFBP).

METHODS

IGF-1 receptors were examined by radioligand binding assay. The protein in conditioned medium and the molecular weight of IGF-1 receptors on AGS cells were determined by affinity cross-linking with 125I-IGF-1 followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Messenger RNAs for IGF-1, IGF-2, and IGFBP-4 were detected by Northern analysis.

RESULTS

AGS cells possessed a single class of high-affinity binding sites for IGF-1 (dissociation constant [Kd], 0.51), with a binding capacity approximately 4 x 10(4) sites per cell. The size of the alpha subunit of IGF-1 receptors on cell membranes was approximately 130 kilodaltons. des (1-3) IGF-1, a truncated IGF-1 with very low affinity to IGFBPs, stimulated AGS cell growth in dose-dependent fashion. The medium conditioned by AGS cells contained IGFBPs of 27-32 and 37-42 kilodaltons. AGS cells expressed messenger (mRNA) RNAs for IGF-2 and IGFBP-4 but not for IGF-1, whereas another gastric carcinoma cell line (SIIA), whose growth is stimulated by IGF-1, expressed mRNA IGF-2 but did not express mRNA for IGF-1 or IGFBP-4:

CONCLUSIONS

The relative absence of growth response of AGS cells to IGF-1 is due to the endogenously produced IGFBPs sequestering IGF-1 and preventing receptor interaction.

Radioimmunoimaging of xenograft pancreatic cancer with 131I-monoclonal antibody P2

Monoclonal antibodies (McAbs) to pancreatic cancer were developed by fusing SP2/0 cells and splenocytes from Balb/c mice immunized with CH-2 cells. The specific binding rates of McAb P1 and P2 were 40.1 and 43.8%, respectively, shown by binding radioreactivity assay in vitro, which were in sharp contrast with those of control groups (p < 0.05). The biodistribution of radioiodinated McAb P2 was studied by measuring parameters of tumor-specific radioreactivity in nude mice bearing CH-2 tumors. The ratios of tumors to nontumors were all > 2 at 48 h. The localization index of cancer and the ratio of tumor to pancreas were 4.05 and 4.16, respectively, at 72 h. Therefore, 131I-McAbs may be useful for radioimmunoimaging (RII) of pancreatic cancer. After intraperitoneal injection of 131I-McAb P2 into tumor-bearing nude mice, imaging of xenograft pancreatic cancer became increasingly distinct with the nonspecific background fading, especially in the period of 72-96 h. Examination of pancreatic cancer tissues by immunohistochemical methods revealed that McAb P2 was strongly positive (86%) in comparison with other tumors and normal tissues. The results demonstrated that clinical RII of pancreatic cancer was feasible with McAb P2.

Neurotensin regulates growth of human pancreatic cancer

OBJECTIVE

The effect of neurotensin (NT) on in vitro-growth of human pancreatic cancer cells (MIA PaCa-2) was examined. Furthermore, the intracellular signal-transduction pathways by which neurotensin regulates growth of MIA PaCa-2 cells were determined.

SUMMARY BACKGROUND DATA

NT is trophic for normal rat pancreas, but the effect of NT on growth of human pancreatic cancer is not known.

METHODS

Effects of NT (10(-12) to 10(-6) mol/l) on growth of MIA PaCa-2 cells were determined by both count of cell numbers and 3H-thymidine incorporation. Action of NT on phosphatidylinositol (PI) hydrolysis, cyclic AMP production, and intracellular calcium level were determined by conventional methods. The effects of 8-bromo-cyclic AMP and prostaglandin E2 on cell growth were determined.

RESULTS

Low concentrations of NT (10(-12) to 10(-9) mol/l) stimulated growth in a dose-dependent manner, but higher concentrations of NT (10(-8) to 10(-6) mol/l) did not stimulate growth of MIA PaCa-2 cells. NT (10(-12) to 10(-6) mol/l) stimulated PI hydrolysis and increased intracellular calcium levels in a dose-dependent manner. High concentrations of NT (10(-8) to 10(-6) mol/l) stimulated production of cyclic AMP in a dose-dependent manner. 8-bromo-cyclic AMP inhibited growth of MIA PaCa-2 cells; prostaglandin E2 did not affect growth of MIA PaCa-2 cells.

CONCLUSIONS

NT stimulates growth of MIA PaCa-2 cells through stimulation of PI hydrolysis and mobilization of calcium. Stimulation of the cyclic AMP pathway by high concentrations of NT abolishes the growth-stimulatory effect of NT that is mediated through PI hydrolysis or calcium mobilization.

Progressive loss of pancreatic function in chronic pancreatitis is delayed by main pancreatic duct decompression. A longitudinal prospective analysis of the modified puestow procedure

OBJECTIVE

This study evaluated the effect of operative drainage of the main pancreatic duct (MPD) on functional derangements associated with chronic pancreatitis (CP).

SUMMARY BACKGROUND DATA

The author previously reported delayed functional impairment in an evaluation of the impact of operative drainage in patients with CP. The author now reports on a prospective study of 143 patients with this diagnosis.

METHODS

Each patient underwent 1) ERCP, 2) the Bentiromide PABA, 3) 72-hour fecal fat test, 4) oral glucose tolerance test (OGTT) and 5) fat meal (LIPOMUL)--stimulated pancreatic polypeptide release (PP). All patients were stratified as mild/moderate (M/M) or severe CP on the basis of a 5-point system that was developed by the author. Patients were studied at 16-month intervals.

RESULTS

All 143 patients underwent initial and follow-up evaluations in a mean follow-up of 47.3 months; 83 of 143 patients had M/M grade at initial evaluation. Eighty-seven patients underwent (MPD) decompression to relieve abdominal pain. In a separate prospective 17 patients with a diagnosis of CP, a grade of M/M and non-disabling abdominal pain were randomized to operative or non-operative treatment; 9 of these randomized patients were operated upon and 8 were not. No patient improved their grade during follow-up; 47 of 83 M/M patients had operative drainage and 36 did not. This grade was preserved in 41 of 47 (87%) operated patients but in only 8 of the 36 non-operated patients (22%). In the randomized trial, seven of nine operated patients retained their functional status in follow-up, whereas only two of eight patients (25%) randomized to non-operation preserved their functional grade.

CONCLUSIONS

These data in this large study as well as among a previous randomized sample, support a policy of early operative drainage before the development of irreversible functional impairment in patients with chronic pancreatitis and associated dilation of the main pancreatic duct.

Age-related changes in gallbladder contractility and cytoplasmic Ca2+ concentration in the guinea pig

Gallbladder (GB) motility diminishes with aging. This study was performed to characterize mechanisms that are involved in changes in GB contractility that occur during aging. Cytoplasmic Ca2+ concentrations ([Ca2+]i) and the contractile force of guinea pig GB muscle strips were simultaneously measured using fura-2 and force-displacement transducers. The binding ability of the Ca2+ channel antagonist and GB muscle compliance were also examined. The COOH-terminal octapeptide of cholecystokinin (CCK-8) evoked a dose-dependent increase in force and [Ca2+]i. Changes of [Ca2+]i and contractile force of muscle strips in response to CCK-8 were significantly greater in young (2 mo old) compared with mature and aged (12 and 24 mo old) guinea pigs (changes in [Ca2+]i, ED50: 46.1 nM at 2 mo, 6.1 microM at 12 mo, and 2.8 mM at 24 mo; changes of contractile force, ED50: 24.8 microM at 2 mo, 2.1 mM at 12 mo, and 357 mM at 24 mo). However, the magnitude of the contraction at each percent change in [Ca2+]i was actually similar in young and aged guinea pigs. In a Ca(2+)-free buffer, the responses of [Ca2+]i and force to CCK-8 in both young and aged GB muscles decreased, but those were still dose and age dependent. Binding ability of the Ca2+ channel antagonist did not differ in the young and aged groups, but the compliance of the GB muscle strip decreased with aging. These results suggest that both a reduced mobilization of intracellular Ca2+ and a decreased muscle compliance are responsible, at least in part, for age-related reduced contraction of guinea pig GB in response to CCK.

Age-related changes in duodenal adaptation after distal small bowel resection in rat

Two groups of male Fisher 344 rats (young: 4 months old; aged: 25 months old) underwent either 70% distal small bowel resection or sham operation (small bowel transection). Rats from each treatment group of each age were sacrificed on the 10th (N = 15: young rats; N = 13: aged rats) or 20th (N = 15: young; N = 13: aged) postoperative day (POD), and the duodenal mucosa was weighed and assayed for DNA, RNA, and protein contents, as well as for specific activities of the disaccharidase, sucrase, maltase, and lactase. Compared to the sham operation, distal small bowel resection significantly increased DNA by 48%, RNA by 122%, and protein by 75% in young rats and DNA by 40%, RNA by 92%, and protein by 71% in aged rats on the 20th POD. Both young and aged rats showed similar adaptive hyperplasia on the 10th POD. On the 20th POD after distal small bowel resection, specific activities of all tested enzymes were significantly increased in young rats (sucrase +86%, maltase +110% and lactase +64%), but showed no significant changes in aged rats. These findings suggest that the duodenum of aged rats may have sufficient proliferative potential to respond to distal small bowel resection, but that the mechanisms governing return of function in response to distal small bowel resection are inhibited in aged rats, compared to those mechanisms in the young.

Effects of aging on gastrin and somatostatin secretion from isolated perfused rat stomach

We have examined the release of gastrin and somatostatin from the isolated perfused stomach of rats of three different age groups (4 months, 12 months, and 24 months old) in response to bombesin and carbachol. The basal release of gastrin was diminished in 24-month-old rats. Basal somatostatin release showed an age-related decrease. Bombesin (10(-10) and 10(-9) M) and carbachol (10(-8) and 10(-7) M) stimulated gastrin release in each age group. The integrated release of gastrin in response to bombesin (10(-10) and 10(-9) M) or carbachol (10(-8) M) did not differ among the three age groups, although integrated gastrin release in response to carbachol (10(-7) M) decreased in 24-month-old rats. Bombesin-stimulated release of somatostatin decreased in 12- and 24-month-old rats. Carbachol inhibited release of somatostatin in each age group. Compared with 4-month-old rats, the inhibition of somatostatin release by carbachol was less in 24-month-old rats at 10(-8) and 10(-7) M, and less in 12-month-old rats at 10(-7) M. The decreased basal gastrin secretion and well-preserved gastrin response were further confirmed in conscious aged rats tested by means of oral gavage with 10% peptone. Our findings indicate that gastrin response to the stimuli is well preserved with aging, whereas the response of somatostatin diminishes in an age-related manner. Aging has different effects on the release of gastrin and somatostatin from the rat stomach.

Successful intracerebroventricular allotransplantation of parathyroid tissue in rats without immunosuppression

The lateral ventricle of the brain may be an immunoprivileged site for viable allografts. Allotransplanted parathyroid tissue from histoincompatible ACI rats survived and remained functional for more than 3 months in the cerebroventricles of recipient F344 rats. Microscopic examination proved that the allotransplanted parathyroid tissues retained normal histological features. In sharp contrast, when the parathyroid was placed beneath the renal capsule the allografted parathyroid tissue uniformly lost its capacity to liberate parathyroid hormone within one month, and only residual scar tissue remained at the transplantation site. After allotransplantation of parathyroid tissue into the cerebroventricle, the serum concentrations of both Ca++ and parathyroid hormone were maintained at levels similar to those before parathyroidectomy, until the time of sacrifice. During the 3-month period of post-transplantation observation, no neurological symptoms were noted in any of the F344 rats.

Differential effect of submandibular gland resection on the growth of pancreatic cancer in cheek pouch and subcutaneous tissue

Exogenous administration of epidermal growth factor (EGF) enhances tumor growth of H2T, a hamster pancreatic cancer that is inoculated in the cheek pouch. The effect of endogenous EGF on tumor growth, however, is not known. The main source of EGF in the body is the submandibular glands. This study examined the influence of submandibular gland resection (SMx) on H2T tumor growth in the cheek pouch and compared it to the growth in SC tissue. Bilateral SMx or sham operation was performed on male Syrian golden hamsters. In 30 hamsters (n = 15 for each operation group), 5 x 10(4) and 5 x 10(5) H2T cells were inoculated in the bilateral cheek pouches and intrascapular SC tissue, respectively (Exp. 1). In another 30 hamsters (n = 15 for each operation group), 5 x 10(5) and 1 x 10(6) H2T cells were inoculated at the same sites (Exp. 2). Two longest perpendicular diameters of the tumor were measured once a week for 12 wk (Exp. 1) or 8 wk (Exp. 2), and the tumor area was calculated. The tumor area in the cheek pouch became significantly smaller in the SMx group than the sham-operated group after the 8th wk (Exp. 1) or the 7th wk (Exp. 2). On the other hand, the tumor area in the SC tissue did not show any difference between groups through the experiments.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of peptide-YY release in response to intracolonic infusion of amino acids

Peptide-YY-(1-36) [PYY-(1-36)] is an endocrine peptide that is found primarily in the mucosal layer of the colon. We reported previously that a direct intracolonic (IC) infusion of amino acids in dogs resulted in a robust release of PYY compared to other nutrients (fat, glucose, and protein). The objective of this study was to investigate the possible mechanisms underlying the release of PYY in response to IC infusion of amino acids. Intracolonic infusion of a mixture of tryptophan and phenylalanine (Trp+Phe; 100 mM; 200 ml/h) resulted in a significant release of PYY [integrated PYY release, 74.5 +/- 14.0 ng (0-120 min)/ml], which was not affected by iv atropine, hexamethonium, or propranolol treatment. Intravenous infusion of Trp+Phe failed to release PYY [integrated PYY release, -0.6 +/- 0.9 ng (0-120 min)/ml]. Intracolonic infusion of aromatic amino acids (Trp+Phe) was more potent in releasing PYY than aliphatic (leucine and glycine) and charged (arginine) amino acids. PYY release in response to IC infusion of the deamino and decarboxylated forms of Phe was significantly (P < 0.05) decreased [integrated PYY release, 17.5 +/- 2.6 and 12.1 +/- 2.8 ng (0-120 min)/ml, respectively] compared to that in response to intact Phe [integrated PYY release, 39.4 +/- 4.3 ng (0-120 min)/ml]. These results suggest that 1) PYY release in response to IC administered amino acids is independent of ganglionic, cholinergic, and beta-adrenergic transmission; 2) PYY release in response to IC amino acids is due to a direct contact of amino acids with the luminal pole of PYY cells in the colon and is not the result of a stimulatory action of amino acids via the general circulation; and 3) the amino and carboxylic groups of an amino acid as well as the ring structures of aromatic amino acids are structural requirements for PYY release.

Studies of growth regulation in a neuroendocrine cell line

Studies of growth-regulation of neuroendocrine cells have been hampered by a lack of suitable in vitro models. We established and have maintained a functioning human pancreatic carcinoid cell (BON) line. BON cells synthesize and secrete several growth factors. Among those, we have found that serotonin stimulates growth of BON cells through specific receptors linked to cyclic AMP pathway. In this study, effects of other growth factors on growth and serotonin release, and the effects of serotonin and TGF-beta 1 on the polyamine biosynthetic pathway, were examined. TGF-beta 1 inhibited both growth and serotonin release in a dose-dependent fashion. Basic FGF stimulated growth, but failed to affect serotonin release. Other peptide growth factors had no effect on either growth or serotonin release. Serotonin stimulated ODC enzyme activity, but TGF-beta 1 failed to affect ODC enzyme activity. These findings suggest that growth of neuroendocrine cells can be delicately regulated by their own products in an autocrine fashion.

The extracellular matrix components laminin, fibronectin, and collagen IV are present among the epithelial cells forming Rathke's pouch

Cell-matrix interactions probably play a cooperative role with cell-hormone interactions to ensure normal differentiation of the adenohypophysis. The extracellular matrix (ECM) surrounding adult adenohypophysial cells contains laminin but its embryonic development has not been described. This study was carried out to test the hypothesis that adenohypophysial cells are associated with components in the ECM prior to cellular differentiation in the adenohypophysis. Fetuses were removed from Golden Syrian hamsters every 12 h from embryonic days 8.5-14. Coronal and sagittal 5-microns-thick sections of paraplast-embedded embryos were stained for fibronectin, laminin, or collagen IV using avidin-biotin immunoperoxidase staining. The adenohypophysial anlage was observed initially as a group of epithelial cells (Rathke's pouch) in the roof of the stomatodeum in contact with a basement membrane. The basement membrane stained positively for laminin, collagen IV and fibronectin. Lighter staining for laminin, fibronectin and collagen IV was observed between the developing adenohypophysial cells in Rathke's pouch. Proliferative activity was apparent in the antero-inferior region of Rathke's pouch and resulted in the formation of the bulk of the adenohypophysis. Mesenchyme infiltrates the region between the base of Rathke's pouch and the oral epithelium, thus separating the two. The basement membrane surrounding the pouch appears to become discontinuous in the regions of high proliferative activity. These results show that ECM components appear early during the development of adenohypophysial cells prior to their cellular differentiation into hormone-containing cells. This association between ECM components and developing adenohypophysial cells provides the anatomical basis for cell-ECM interactions to influence adenohypophysial development and differentiation.

Cortivazol increases glucocorticoid receptor expression and inhibits growth of hamster pancreatic cancer (H2T) in vivo

Glucocorticoids are effective in the treatment of certain leukemias and lymphomas, but their effects on the growth of several solid tumors have not been determined. We report here that cortivazol (CVZ), a potent synthetic glucocorticoid, inhibits the growth of a hamster pancreatic adenocarcinoma, H2T, in vivo. CVZ regulation of glucocorticoid receptor (GR) expression was followed as a specific molecular correlate. H2T cells were injected into cheek pouches of male Syrian golden hamsters, where they formed readily measurable tumors. Two studies were performed. In the first, hamsters were randomized to three groups immediately after injection of tumor cells: control, CVZ (0.1 micrograms/g body wt), or CVZ (0.3 micrograms/g body wt). Injections of either CVZ or its vehicle were administered on a 14-day cycle of 5 treatment days, followed by 9 days off treatment. Tumors were measured and areas calculated weekly. On day 48, the hamsters were killed and the tumors excised, weighed, and analyzed for DNA, RNA, and protein content. In the second study, randomization and treatment schedule were as before, except that on day 33 the hamsters were killed, tumors were excised and weighed, and total RNA from the tumors was isolated. GR mRNA content was determined by filter hybridization with a 32P-labeled GR cDNA probe, and the signal normalized by reprobing for alpha-tubulin as an invariant, independent signal. At either dose, CVZ significantly inhibited H2T tumor area and weight and DNA, RNA, and protein content. Body weights of animals treated with CVZ were not significantly decreased as compared with controls. In addition, GR mRNA in H2T cells was increased approximately twofold by CVZ.(ABSTRACT TRUNCATED AT 250 WORDS)

Bombesin stimulates intracellular Ca2+ mobilization but not proliferation on human colon cancer cells

Increases in intracellular Ca2+ ([Ca2+]i) levels mediated by bombesin (BBS) are believed to be important signals leading to stimulation of DNA synthesis and an increase in cellular proliferative rate. Since the role of BBS on growth of normal or malignant cells in the GI tract is still unclear, we examined whether BBS affects in vitro growth of human colon cancer cells (COLO 320, HCT116 and LoVo). We also examined the effect of BBS on intracellular Ca2+ levels to determine if the growth-regulatory effect of BBS is mediated through increases in [Ca2+]i. Levels of [Ca2+]i in response to BBS were measured by single cell fluorescence after loading with fura-2. BBS stimulated the mobilization of [Ca2+]i in COLO 320, LoVo, and HCT116 cells in a dose-dependent fashion, but did not affect in vitro growth. These findings suggest that the BBS-mediated increase in [Ca2+]i does not always correlate with the growth-regulatory effect of BBS.

Bombesin stimulates growth of colon cancer in mice and decreases their survival

Bombesin (BBS) stimulates cellular proliferation of both normal and transformed cells. The mouse colon cancer cells (MC-26) possess specific binding sites for BBS. The purpose of this study, therefore, was to examine the effect of chronic administration of BBS on in vivo growth of MC-26 tumours in Balb/c mice and on survival of tumour-bearing mice. Three groups of mice (n = 10 each) inoculated with MC-26 cells received either saline containing 0.1% bovine serum albumin (BSA), or BBS (5 micrograms kg-1 or 20 micrograms kg-1) dissolved with 0.1% BSA saline by intraperitoneal route three times a day for 15 days. BBS increased weight, DNA and RNA contents of MC-26 tumours. To examine the effect of BBS on survival rates of mice with MC-26 tumours, three groups of mice (n = 20 each) were treated for 31 days, as above. One group of mice inoculated with MC-26 cells received 0.1% BSA saline; the other group of MC-26-inoculated mice and the control group without tumour received BBS (5 micrograms kg-1) dissolved with 0.1% BSA saline. BBS significantly decreased the survival rate of mice bearing MC-26 tumours (median survival; saline group: 42.5 days, BBS group: 32.0 days, P = 0.037). None of the mice in the control group died during the experiment. BBS may stimulate in vivo growth of MC-26 cells through specific receptors.

Role of polyamine biosynthesis during gut mucosal adaptation after burn injury

The induction of ornithine decarboxylase (ODC) mRNA and of ODC enzyme activity are important events in gut repair after cutaneous burn injury. ODC catalyzes the rate-limiting step in the biosynthesis of polyamines that are necessary for normal cell growth; alpha-difluoromethylornithine (DFMO) specifically inhibits ODC activity. The purpose of this study was to examine the role of polyamines in the adaptive response of gut mucosa after burn injury. In experiment 1, male Sprague-Dawley rats (250 to 300 g; n = 6/group) were randomized into sham, 60% burn, or 60% burn plus DFMO. In experiment 2, rats with either a 60% burn or 60% burn plus DFMO treatment received spermidine by gavage. We measured ODC activity, polyamine levels, and DNA content at 0, 12, 24, and 48 hours postburn in the mucosa of both the proximal and distal small intestine. Burn injury produced early atrophy (by 12 hours postburn) of the gut mucosa characterized by decreased mucosal weight and DNA content. Increased ODC activity and polyamine content in both the proximal and distal gut mucosa of burned rats preceded restoration of mucosal weight and DNA content that occurred at 48 hours postburn; these responses were prevented by DFMO treatment. Spermidine administration failed to accelerate gut mucosal recovery after burn injury alone, but oral administration of spermidine reversed the inhibitory action of DFMO on gut mucosal repair. These data suggest that the early increases of gut ODC activity and polyamine levels after burn injury are crucial cellular events for the repair of subsequent gut mucosa.

Persistence of the circadian variation and altered response to hepatectomy of hepatic ornithine decarboxylase activity with malignant tumor burden

We measured the effect of MC-26 mouse colon cancers (of different sizes) on the circadian rhythm of hepatic ornithine decarboxylase (ODC) activity and hepatic ODC activity during the 24 hr after 60% hepatectomy. Tumor-free control mice showed a normal circadian rhythm of ODC activity with the highest levels at 1100 hr and the lowest levels at 2300 hr. The amplitude of the rhythm was diminished significantly in mice with a large tumor burden (3% of their body weight), and hepatic ODC activity was significantly less than in the tumor-free mice at every point during the 24 hr of the study. In mice with "early" tumors (0.3% of body weight), basal activity of ODC was normal and there was no reactive increase in activity following hepatectomy. In contrast, mice with "late" (3% of body weight) tumors had significantly lower basal ODC activities and the increase in ODC activity following hepatectomy was prolonged and exaggerated. We concluded that tumor burden is associated with abnormal ODC activity and that these differences are exaggerated after hepatectomy. Furthermore, although average ODC concentrations in tumor-bearing mice fell precipitously, the circadian rhythm in hepatic ODC persisted. This finding indicates early recognition by the host of tumor presence, which has a profound negative regulatory effect on hepatic ODC. Apparently, this effect does not impinge on circadian control mechanisms, indicating that these signals act independently.

Bombesin stimulates growth of human gastrinoma

BACKGROUND

We have previously reported the first establishment and characterization of a functioning human gastrinoma (PT) xenograft. Bombesin, the equivalent of the mammalian gastrin-releasing peptide, has trophic effects on normal and neoplastic tissues of the gastrointestinal tract; the effects of gut hormones on the growth of gastrinoma are not known. The purpose of this study was twofold: (1) to determine the presence of various gut peptides in PT and (2) to determine the effect of bombesin on the growth of PT xenografts.

METHODS

PT tumors were examined for expression (mRNA and protein) of various gut peptides by Northern hybridization and immunohistochemistry. In addition, PT xenografts were implanted as 3 mm2 pieces bilaterally subcutaneously in athymic nude mice. Mice were divided into two groups to receive either bombesin (5 micrograms/kg) or saline administered as intraperitoneal injections every 8 hours. Tumor area was measured twice weekly until mice were sacrificed (day 28), when tumor and normal pancreas were removed, weighed, and assayed for DNA and protein content.

RESULTS

Both mRNAs and peptides of gastrin and chromogranin A were present in PT tumors. Bombesin significantly stimulated growth of PT tumors from day 18 until mice were sacrificed (day 28). As expected, bombesin stimulated pancreatic growth.

CONCLUSIONS

We have demonstrated for the first time that bombesin is a trophic hormone for gastrinoma. The unique cell line PT contains gastrin and chromogranin A and will be a useful model to define the biologic mechanisms controlling the growth of human gastrinomas.