Biomedical subjects

T E Adrian

Publications and source records attributed to T E Adrian.

At least 37 records · Page 2Linked to original sources

PubMed2000

The intracellular mechanism of insulin resistance in pancreatic cancer patients.

The diabetes that frequently occurs in pancreatic cancer patients is characterized by profound peripheral insulin resistance. The intracellular mechanism of this insulin resistance was investigated in skeletal muscle biopsies from pancreatic cancer patients with or without diabetes and control subjects. Insulin receptor (IR) binding, tyrosine kinase activity, IR messenger RNA (mRNA), IR substrate-1 content, GLUT-4, and GLUT-4 mRNA content were all normal in pancreatic cancer patients. In contrast, multiple defects in glycogen synthesis were found in pancreatic cancer patients, especially in those with diabetes. Glycogen synthase I activity, total activity, and mRNA levels were significantly decreased in pancreatic cancer patients compared with controls. The fractional velocity of glycogen synthase was decreased only in the diabetic pancreatic cancer group. Glycogen phosphorylase a and b activities were increased in diabetic pancreatic cancer patients, but glycogen phosphorylase mRNA levels were not significantly different. The insulin resistance associated with pancreatic cancer is associated with a post-IR defect, which impairs skeletal muscle glycogen synthesis and glycogen storage.

Blotting, Western↗

PubMed2000

Alteration of the Langerhans islets in pancreatic cancer patients.

An abnormal glucose metabolism occurs in up to 80% of pancreatic cancer patients shortly or a few months before the first clinical admission. Reasons for this abnormality are obscure. We investigated immunohistochemically the pattern of islets in 14 pancreatic cancer specimens and used 14 chronic pancreatitis samples and 10 normal pancreata as controls. To study the topographical relationship of these islets to the cancer, islets in four different arbitrary zones within and around the cancer were evaluated. Ten out of 14 cancer specimens showed a significant loss of beta cells (p < 0.005) and eight of them also showed a significant increase of alpha cells (p < 0.005), all of them from hyperglycemic patients. Most affected islets were found within zone 1 (intratumoral) and zone 2 (peritumoral), to a lesser extent in zone 3 (acini close to tumor) and none in zone 4 (acini remote from tumor). No comparable changes were found in chronic pancreatitis patients. The incidence of 72% with alteration of islets in our material correlates with the frequency of abnormal glucose levels in human pancreatic cancer patients. Our findings support the notion that islet cell abnormalities is likely caused by substances released from cancer cells.

Adult↗

PubMed2000

Gastrointestinal growth factors and pancreatic islet hormones during postoperative IGF-I supplementation in man.

Insulin-like growth factor-I (IGF-I) has been demonstrated to exert a nitrogen sparing effect, both experimentally and in patients after abdominal surgery. IGF-I is a major mediator for the anabolic effects of growth hormone (GH). Whether elevated circulating IGF-I levels are the sole mediator of the anabolic effects following GH has not been clarified. IGF-I influences glucose metabolism, both through its own specific receptor and by activating the insulin receptor, and has also been proposed to influence pancreatic islet secretion directly. In the present study, the postoperative effects of IGF-I on plasma levels of other gastrointestinal and pancreatic islet hormones and growth factors were measured in patients after abdominal surgery. Fifteen patients who were candidates for large bowel resection were randomly divided into two groups: IGF-I-treated (n=8) and placebo-treated (n=7). The IGF-I group received daily two s.c. injections of human recombinant IGF-I (80 microg/kg body weight) for five days, beginning on the morning of the first postoperative day. The other group received placebo injections. Fasting plasma levels of gastrointestinal growth factors (epidermal growth factor, transforming growth factor-alpha, IGF-II), gastrointestinal hormones (gastrin, enteroglucagon, peptide YY), and islet hormones (insulin, islet amyloid polypeptide (IAPP) and pancreatic glucagon) were determined by RIA preoperatively and after five days of treatment. No significant effects of IGF-I on other growth factors or gastrointestinal hormones were seen. A marked increase in plasma insulin postoperatively compared with the preoperative levels (42+/-3 vs 61+/-5 pM, P<0.05) was seen in the placebo group, whereas the postoperative levels in the IGF-I-treated patients remained unchanged (44+/-3 vs 45+/-4 pM). A similar pattern was observed for IAPP and cortisol concentrations. No differences in glucagon concentrations were seen. In conclusion, these results suggest that IGF-I does not influence production of other gastrointestinal hormones thought to be involved in alimentary growth or pancreatic glucagon. In contrast, IGF-I caused a marked reduction of insulin and IAPP secretion. The inhibition of beta-cell secretion could be direct or, alternatively, could involve an improvement in postoperative insulin resistance, perhaps by reducing serum cortisol.

Aged↗

PubMed2000

Biologic instability of pancreatic cancer xenografts in the nude mouse.

Tumor transplants into nude mice (NM) may reveal abnormal biological behavior compared with the original tumor. Despite this, human tumor xenografts in NM have been widely used to study the biology of tumors and to establish diagnostic and therapeutic modalities. Clearly, precise differences in the biology of a given tumor in human and in NM cannot be assessed. We compared the growth kinetics, differentiation pattern and karyotype of an anaplastic Syrian hamster pancreatic cancer cell line in NM and in allogenic hamsters. As with the original tumor, transplants in hamsters grew fast, were anaplastic and expressed markers related to tumor malignancy like galectin 3, TGF-alpha and its receptor EGFR at high levels. However, tumors in the NM were well-differentiated adenocarcinomas, grew slower, had increased apoptotic rate and had a high expression of differentiation markers such as blood group A antigen, DU-PAN-2, carbonic anhydrase II, TGF-beta(2) and mucin. Karyotypically, the tumors in the NM acquired additional chromosomal damage. Our results demonstrate significant differences in the morphology and biology of tumors grown in NM and the allogenic host, and call for caution in extrapolating data obtained from xenografts to primary cancer.

Animals↗

PubMed1999

Lipoxygenase inhibition induced apoptosis, morphological changes, and carbonic anhydrase expression in human pancreatic cancer cells.

Epidemiologic and animal studies have linked pancreatic cancer growth with fat intake, especially unsaturated fats. Arachidonic acid release from membrane phospholipids is essential for tumor cell proliferation. Lipoxygenases (LOX) constitute one pathway for arachidonate metabolism. We previously reported that 5-LOX and 12-LOX are upregulated in human pancreatic cancer cells and that blockade of these enzymes abolishes pancreatic cancer cell growth. The present study was aimed at evaluating the effect of LOX inhibition on differentiation and apoptosis in pancreatic cancer cells in parallel with growth inhibition. Four human pancreatic cancer cell lines, PANC-1, MiaPaca2, Capan2, and HPAF, were used. Apoptosis was evaluated by three separate methods, including DNA propidium iodide staining, DNA fragmentation, and the TUNEL assay. Morphological changes and carbonic anhydrase activity were used to determine the effect of LOX inhibitors on differentiation. The general LOX inhibitor NDGA, the 5-LOX inhibitor Rev5901, and the 12-LOX inhibitor baicalein all induced apoptosis in all four pancreatic cancer cell lines, as confirmed by all three methods, suggesting that both the 5-LOX and 12-LOX pathways are important for survival of these cells. Furthermore, NDGA, Rev5901, or baicalein resulted in marked cellular morphological changes in parallel with increased intracellular carbonic anhydrase activity, indicating that LOX blockade induced a more differentiated phenotype in human pancreatic cancer cells. Together with our previous findings, this study suggests that perturbations of LOX activity affect pancreatic cancer cell proliferation and survival. Blockade of LOX enzymes may be valuable for the treatment of human pancreatic cancer.

Apoptosis↗

PubMed1999

Lipoxygenase inhibitors abolish proliferation of human pancreatic cancer cells.

Epidemiologic and animal studies have linked pancreatic cancer growth with fat intake, especially unsaturated fats. Arachidonic acid release from membrane phospholipids is essential for tumor cell proliferation. Lipoxygenases (LOX) constitute one pathway for arachidonate metabolism, but their role in pancreatic cancer growth is unknown. The expression of 5-LOX and 12-LOX as well as their effects on cell proliferation was investigated in four human pancreatic cancer cell lines (PANC-1, MiaPaca2, Capan2, and ASPC-1). Expression of 5-LOX and 12-LOX mRNA was measured by nested RT-PCR. Effects of LOX inhibitors and specific LOX antisense oligonucleotides on pancreatic cancer cell proliferation were measured by (3)H-thymidine incorporation. Our results showed that (1) 5-LOX and 12-LOX were expressed in all pancreatic cancer cell lines tested, while they were not detectable in normal human pancreatic ductal cells; (2) both LOX inhibitors and LOX antisense markedly inhibited cell proliferation in a concentration-dependent and time-dependent manner; (3) the 5-LOX and 12-LOX metabolites 5-HETE and 12-HETE as well as arachidonic and linoleic acids directly stimulated pancreatic cancer cell proliferation; (4) LOX inhibitor-induced growth inhibition was reversed by 5-HETE and 12-HETE. The current studies indicate that both 5-LOX and 12-LOX expression is upregulated in human pancreatic cancer cells and LOX plays a critical role in pancreatic cancer cell proliferation. LOX inhibitors may be valuable for the treatment of pancreatic cancer.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗

PubMed1999

A factor from pancreatic and colonic cancer cells stimulates glucose uptake and lactate production in myoblasts.

Patients with cancer cachexia exhibit increased glucose flux and lactate production in skeletal muscle. The aim of this study was to examine the direct effect of cancer cell-conditioned media on glucose metabolism in L6 myoblasts. Media from PANC-1 and Colo 320 cells caused a marked time-dependent and concentration-dependent increase of 2-deoxyglucose uptake in GLUT-4 transfected L6 myoblasts. This effect was greater than maximal acute stimulation by insulin and the effect of insulin was additive. Glucose utilization and lactate production increased in parallel to glucose uptake. The effect was inhibited by the protein synthesis inhibitor, cycloheximide and the glucose transport inhibitor, cytochalasin B. The bioactive factor had a molecular weight of approximately 5,000 and the biological activity was destroyed by proteinase K digestion. Radioimmunoassay and immunoneutralization studies indicated the major factor involved is not TNFalpha, IL-1beta, insulin, IGF-I or IGF-II. Further purification and characterization are needed to reveal the identity of this novel factor or factors which may have other metabolic effects that contribute to the cancer cachexia and insulin resistance.

Animals↗

PubMed1999

Optimization of treatment conditions for studying the anticancer effects of retinoids using pancreatic adenocarcinoma as a model.

Retinoids are natural differentiation-inducing compounds that are promising as anticancer agents. Cancer cell lines are valuable in the investigation of the potential of retinoids for the treatment of specific cancers. However, using different treatment conditions but the same cell lines, investigators have produced markedly contradictory results for the effectiveness of retinoids. The present study examined different factors in the treatment conditions that may have masked or interfered with the effects of retinoids and, thereby, resulted in this conflict. Our studies revealed that the effects of retinoids on cancer cell proliferation were influenced by serum, the choice of vehicle (DMSO vs ethanol) and its concentration, phenol red, the degree of cellular confluence, and the method of assessing proliferation (cell number or [3H]thymidine uptake vs the MTT assay). Optimized conditions were the use of serum-free, ethanol-free, and phenol red-free media, investigating cells in the log phase of growth, using </=0.01% DMSO as the vehicle, and monitoring proliferation by cell number or [3H]thymidine incorporation into DNA measured after TCA precipitation. Using these conditions, retinoids were found to exhibit potent antiproliferative effects in pancreatic cancer cells with a variety of degrees of differentiation, even in cell lines previously documented as being retinoid resistant. Retinoids also induced morphological changes and cellular death that may indicate terminal differentiation and apoptosis.

Adenocarcinoma↗

PubMed1999

Gastric acid blockade with omeprazole promotes gastric carcinogenesis induced by duodenogastric reflux.

Duodenogastric reflux (DGR) in rats causes growth stimulation of the foregut mucosa that is potentiated by gastric acid blockade. It was the aim of this study to investigate if DGR with gastric acid blockade has a higher incidence of carcinomas of the foregut than DGR alone. DGR was induced in 40 Sprague-Dawley rats using a split gastroenterostomy. A cardiomyotomy was performed across the gastroesophageal junction, inducing reflux into the esophagus. Twenty of these rats received omeprazole postoperatively. After one year 18 rats (90%) with DGR + omeprazole treatment and 7 rats (35%) with DGR alone developed adenocarcinoma of the stomach (P < 0.05). None of the rats developed esophageal cancer, but esophageal mucosal hyperplasia was more pronounced in rats receiving omeprazole. Control rats, treated with omeprazole, did not develop carcinomas of the foregut. In conclusion, gastric acid blockade enhanced DGR-induced carcinogenesis of the stomach and promotes growth stimulation of the esophageal mucosa.

Adenocarcinoma↗

PubMed1999

Factors affecting outcome following proximal and distal intestinal resection in the dog: an examination of the relative roles of mucosal adaptation, motility, luminal factors, and enteric peptides.

In the clinical setting, resection of the ileum results in an inferior functional outcome compared to jejunal resection. This may be related to a greater adaptive capacity of the ileum, intrinsic structural and functional differences, or regional differences in motor and hormonal function. Our aim was to evaluate the relative contributions of these factors to functional outcome after resection of the proximal or distal intestine. Twenty-four dogs underwent either intestinal transection or 50% resection of the proximal or distal intestine. Studies (nutritional status, absorption, adaptation, motility, peptide levels) were performed every four weeks until the animals were killed at 12 weeks. Caloric intake was similar in all four groups. Weight loss was greater and more sustained after distal resection (DR). Serum cholesterol levels decreased significantly only in the DR group. While stool weight and moisture were similar, the DR animals had persistent, significant steatorrhea. Intraluminal anaerobic bacteria and SCFA concentrations were significantly greater in the ileum but were not influenced by resection. Intestinal remnant length increased to a greater extent after proximal resection (PR), but circumference increased to a similar extent after both resections. Villus height and crypt depth increased significantly only after PR. MMC frequency was similar in all four groups. In the DR animals 26% of migrating motor complexes (MMCs) originated within the remnant. The jejunal remnant of these animals had a dominance of cluster activity similar to the intact distal ileum. Following PR, the postprandial motilin response was decreased. After DR, there were transient increases in neurotensin and PYY. Of the various factors evaluated, mucosal adaptation and the intestinal motor response appear most likely to explain the inferior nutritional and absorptive outcome associated with resection of the distal small intestine.

Adaptation, Physiological↗

PubMed1999

Dissociated insulin and islet amyloid polypeptide secretion from isolated rat pancreatic islets cocultured with human pancreatic adenocarcinoma cells.

Abnormal insulin and islet amyloid polypeptide (IAPP) secretion are usually seen in patients with exocrine pancreatic cancer. The beta-cell dysfunction is a characteristic of the glucose intolerance found in pancreatic cancer patients. The effects of pancreatic cancer cells on insulin and IAPP secretion from beta cells are unclear. In this study, isolated rat pancreatic islets were cocultured with two human pancreatic adenocarcinoma cell lines (Panc-1 and HPAF) and a human colonic adenocarcinoma cell line (HT-29). As a control, islets were incubated in the absence of malignant cells. The accumulation of insulin and IAPP in culture media was measured by radioimmunoassay. Output of insulin and IAPP was decreased in islets cocultured with each malignant cell line. Molar ratio of secreted IAPP and insulin (IAPP/insulin) was increased in the islets cocultured with Panc-1 or HPAF cells, but not HT-29 cells. The decreased insulin and IAPP secretion were partly recovered after Panc-1, HPAF, or HT-29 cells were removed. The IAPP/insulin ratio was normalized after the removal of Panc-1 or HPAF cells. This study indicates that insulin and IAPP secretion are altered by the human adenocarcinoma cells investigated. The impairment induced by pancreatic adenocarcinoma cells is associated with a hypersecretion of IAPP relative to insulin on a molar basis.

Adenocarcinoma↗

PubMed1999

Differential inhibition of insulin and islet amyloid polypeptide secretion by intraislet somatostatin in the isolated perfused human pancreas.

Islet amyloid polypeptide (IAPP) and insulin are co-stored and generally secreted in parallel; however, studies have demonstrated that the IAPP/insulin molar secretory ratio may be altered in response to certain stimuli. Because we previously demonstrated that intraislet somatostatin is an inhibitory regulator of basal insulin secretion in the isolated perfused human pancreas, this study was designed to determine the relative influence on the regulation of IAPP versus insulin secretion. Single-pass perfusion was performed in pancreata obtained from cadaveric organ donors with continuous perfusion of a modified Krebs media with the glucose level maintained at constant 3.9 mM. Intraislet somatostatin was immunoneutralized by the infusion of either a highly sensitive monoclonal somatostatin antibody (SAb) or its FAb fragment (SFAb). Sequential test periods separated by basal periods were performed by infusion of either of the following: glucose, SAb, SFAb, or appropriate controls. IAPP/insulin molar secretory ratio decreased by 33% in response to infusion of either SAb or the SFAb, respectively (p < 0.01), and decreased by 67% in response to glucose infusion (p < 0.01). An alteration of the IAPP/insulin secretory ratio is seen in response to infusion of exogenous glucose or in response to the neutralization of intraislet somatostatin.

Adolescent↗

PubMed1999

Islet amyloid polypeptide tonally inhibits beta-, alpha-, and delta-cell secretion in isolated rat pancreatic islets.

Islet amyloid polypeptide (IAPP, or amylin) is produced in pancreatic beta-cells. The intraislet significance of IAPP is still uncertain. In the present study, paracrine effects of endogenous IAPP and somatostatin were investigated in isolated rat pancreatic islets. The intraislet IAPP activity was inhibited with an IAPP antiserum or a specific antagonist [IAPP-(8-37)]. Somatostatin activity was inhibited by immunoneutralization. Basal insulin and glucagon secretion were not affected by the somatostatin and/or IAPP blockade. Arginine-stimulated insulin and glucagon secretion were dose dependently increased by IAPP antiserum, IAPP-(8-37), and somatostatin antiserum, respectively. Arginine-stimulated somatostatin secretion was dose dependently potentiated by IAPP antiserum. Insulin secretion induced by 16.7 mM glucose was enhanced by IAPP antiserum and IAPP-(8-37), respectively. A combination of somatostatin antiserum with IAPP antiserum or IAPP-(8-37) further enhanced the arginine-stimulated insulin and glucagon secretion compared with effects when the blocking reagents were used individually. These results indicate that endogenously produced IAPP tonally inhibits stimulated insulin, glucagon, and somatostatin secretion. Furthermore, the paracrine effects of IAPP and somatostatin are additive.

Amyloid↗

PubMed1999

Bronchial vasodilator pathways in the vagus nerve of dogs.

Bronchial vasodilation in dogs is mediated largely by vagal pathways. To examine the relative contribution of cholinergic and noncholinergic parasympathetic pathways and of sensory axon reflexes to vagal bronchial vasodilation, we electrically stimulated the peripheral vagus nerve in 10 chloralose-anesthetized dogs and measured bronchial artery flow. Moderate-intensity electrical stimulation (which did not activate C-fiber axons) caused a rapid voltage- and frequency-dependent vasodilation. After atropine, vasodilation was slower in onset and reduced at all voltages and frequencies: bronchial vascular conductance increased by 9.0 +/- 1.5 (SE) ml. min-1. 100 mmHg-1 during stimulation before atropine and 5. 5 +/- 1.4 ml. min-1. 100 mmHg-1 after (P < 0.02). High-intensity stimulation (sufficient to recruit C fibers) was not studied before atropine because of the resulting cardiac arrest. After atropine, high-intensity stimulation increased conductance by 12.0 +/- 2.5 ml. min-1. 100 mmHg-1. Subsequent blockade of ganglionic transmission, with arterial blood pressure maintained by a pressure reservoir, abolished the response to moderate-intensity stimulation and reduced the increase to high-intensity stimulation by 82 +/- 5% (P < 0.01). In 13 other dogs, we measured vasoactive intestinal peptide-like immunoreactivity in venous blood draining from the bronchial veins. High-intensity vagal stimulation increased vasoactive intestinal peptide concentration from 5.7 +/- 1.8 to 18.4 +/- 4.1 fmol/ml (P = 0.001). The results suggest that in dogs cholinergic and noncholinergic parasympathetic pathways play the major role in vagal bronchial vasodilation.

Animals↗

PubMed1999

Early gastrointestinal regulatory peptide response to intestinal resection in the rat is stimulated by enteral glutamine supplementation.

BACKGROUND: Intestinal resection stimulates the synthesis and release of gastrointestinal peptides that regulate the growth and adaptation of the mucosa. Luminal nutrients are necessary for optimal proliferation and glutamine is the preferential nutrient to the small bowel. The interplay between glutamine and regulatory peptides could be important in treating short bowel syndrome. METHODS: 63 Sprague-Dawley rats were divided into 3 groups: resection; transection, or controls. After intestinal resection animals were orally fed either a diet without glutamine or a glutamine-supplemented diet for 2 days. Transected animals and controls without prior surgery were fed the same two diets. Epidermal growth factor (EGF), transforming growth factor-alpha, insulin-like growth factors I and II (IGF-I and IGF-II), peptide YY (PYY), and enteroglucagon were analyzed in mucosa from the proximal jejunum, distal ileum as well as in portal plasma when the animals were euthanized 72 h after surgery. RESULTS: Intestinal resection resulted in an early increase in portal plasma concentrations of PYY, EGF, enteroglucagon, and mucosal IGF-II and EGF content that were significant in glutamine-treated animals. Glutamine significantly increased PYY in portal blood after resection (p < 0.05). CONCLUSION: Glutamine could be of importance for the functional adaptation of residual small bowel mucosa by increasing PYY release.

Animals↗

PubMed1998

Establishment of tumor cell culture (ILA) derived from hamster pancreatic islets treated with BOP.

ILA cells were established from tumors induced by the pancreatic carcinogen N-nitrosobis(2-oxopropyl)amine (BOP) in hamster islets. The proliferation, morphology, karyotype, immunoreactivity with certain antibodies and growth factor secretion of these tumor cells were compared with the same parameters in tumor cells induced by BOP in hamster ductal cells (TAKA-1-BOP) established in a previous study. Minor differences were found in the morphology and ultrastructure of the 2 cell lines. Contrary to TAKA-1-BOP cells, ILA cells did not express cytokeratins 8.13, 13 or 18 but did express DU-PAN-2 and TAG-72, 2 known human pancreatic cancer-associated antigens. No endocrine cell markers were expressed. A significant difference also was found in the chromosomal pattern in that there were more abnormalities and marker chromosomes in ILA cells than in TAKA-1-BOP cells and the Y or X chromosomes were missing in ILA cells. ILA cells produced TGF-alpha, IGF-I, bombesin and gastrin and expressed specific binding sites for hEGF. TGF-alpha secretion from ILA cells was much greater than that from TAKA-1-BOP cells. Our results indicate that pancreatic cancer cells grown in vitro are not a single clone. We conclude that there are some genetic and biological differences between tumors arising from pancreatic duct and islets and that pancreatic ductal adenocarcinomas originating from islets have a profound malignant potential.

Adenoma, Islet Cell↗

PubMed1998

Radioimmunoassay of regulatory peptides in the presence of acetonitrile: marked improvement of cholecystokinin assays.

Radioimmunoassay has made it possible to measure the levels of many hormones. However, samples for some hormones, such as cholecystokinin (CCK), need to be purified by reverse phase chromatography before assay. Usually, samples are eluted from cartridges or HPLC columns in about 50% acetonitrile, dried on a vacuum centrifuge, and then reconstituted in buffer. Drying and reconstituting samples is time consuming and introduces additional sources of error and peptide loss. The present study investigated the effect of acetonitrile on radioimmunoassays for CCK to see if samples containing acetonitrile could be assayed directly. The non-specific binding of a radiolabeled peptide, the zero binding (B0), and the fall in the presence of 2.5 fmol unlabeled CCK were determined in the presence of various proportions of acetonitrile with 0.1% TFA. Additionally, standard curves were compared in the presence and absence of 200microl of 50% acetonitrile, (n = 5). For assays using two separate CCK antisera, increasing amounts of acetonitrile gave progressively higher zero binding and fall, thereby increasing sensitivity and antibody titer. The use of 200microl 50% acetonitrile, chosen to represent typical sample conditions, increased antiserum titers by three to four-fold, as well as increasing sensitivity considerably. For one antiserum (CCK2), the IC20 was 0.36+/-0.02 fmol CCK/tube in the presence of acetonitrile and 1.45+/-0.08 fmol/tube in its absence (P< 0.001). For the other antiserum (Dino 7), the IC20 was 0.40+/-0.02 fmol CCK/tube in the presence of acetonitrile and 0.63+/-0.01 fmol/tube in its absence (P<0.001). A similar increase in sensitivity was seen with a gastrin assay. However, no significant change in the gastrin antibody titer was evident. Assays for several other hormones were unaffected by 200 microl of 50% acetonitrile. At volumes encountered in samples following chromatography, acetonitrile did not adversely affect radioimmunoassays for a number of hormones, and the sensitivity and antibody titer of the CCK assays were improved. Measurement of CCK samples without drying and reconstitution increases assay efficiency and sensitivity.

Acetonitriles↗

PubMed1998

Peptides bind to eosinophils in the rat stomach.

BACKGROUND: An immunological role for eosinophils has been well established. However, roles for eosinophils in the physiological functions of the organs they populate are little explored. METHODS: Fixed, frozen, then vibratomed sections of rat stomach were exposed to biotinylated 1-17 gastrin (bG17), biotinylated gastrin-releasing peptide (bGRP), biotinylated neuromedin C (bNC), biotinylated vasoactive intestinal peptide (bVIP), and biotinylated substance P (bSP). Binding sites were identified using an avidin-biotin-glucose oxidase complex and tetranitroblue tetrazolium staining. RESULTS: bG17, bGRP, and bNC all bound to cells in the lamina propria and to a lesser extent in the submucosa. Neither bVIP nor bSP bound to cells in these sections. Stained cells were identified as eosinophils in the light microscope on the basis of their distribution and staining properties using the Luna stain for eosinophils and in the transmission electron microscope (TEM) on the basis of a light/TEM matching process. Plastic sections viewed in the light microscope showed that stain was localized to a granular component in the cytoplasm of the eosinophils. No other cell type, specifically neither mast cells nor plasma cells, stained. G17 competed for the bG17 binding site better than did NC. A competition study in which polyglutamic acid failed to compete with bG17 for the binding site, and the observation that bG17, bGRP, and bNC did not bind to other positively charged sites (e.g., collagen, red blood corpuscles), demonstrated that binding was not due to nonspecific electrostatic interactions alone. Binding of bG17 to a CCK(B)/gastrin-type receptor was ruled out when specific receptor antagonists failed to block binding. CONCLUSIONS: The particulate nature of the binding site suggests a secretory substance. If so, eosinophils might use that substance to destroy, neutralize, or control the activity of peptide hormones bound to it in the extracellular space.

Animals↗