Interlaboratory reproducibility of gastrin measurements by radioimmunoassay

A collaborative study was conducted to determine interlaboratory variations in the measurement of gastrin by radioimmunoassay (RIA). A kit containing reagents for a communal RIA method, as well as test samples containing different amounts of human synthetic gastrin (SHG I) and test samples of serum from a fasting normal patient admixed with varying volumes of serum from a patient with the Zollinger-Ellison syndrome, was sent to each collaborating investigator. Each investigator was requested to measure the gastrin concentrations in test samples by means of the communal RIA method, as well as the RIA method utilized in his or her laboratory. Use of the communal RIA method resulted in no significant interlaboratory variation in the determination of gastrin concentration in SHG I test samples and a maximum two- to threefold variation in determination of gastrin serum test samples. In contrast, when individual RIA methods were used to measure gastrin concentrations, the amount of SHG I in test samples reported by one laboratory was significantly different than that reported by the other three. In addition, use of different RIA methods resulted in a 2- to 19-fold interlaboratory variation in serum gastrin measurements and the maximum variation was found when the gastrin in normal fasting serum was measured. Increased variations in results, when different RIA methods were used, may be due to differences in preparation and purification of labeled antigen, to differences in separation of bound from free hormone, and to differences in the antibodies themselves.

Plasma levels of secretin in man and dogs: validation of a secretin radioimmunoassay

We have developed and validated a secretin radioimmunoassay that is sufficiently sensitvie to measure circulating levels of secretin in the plasma of man and dogs. At a final dilution of 1:50,000, the antibody bound 30 percent to 40 percent of radioiodinated (125 I) 6-tyrosyl synthetic secretin. Pure natural porcine secretin was used as a reference standard and a linear dose-response curve was generated with 10 to 1,000 pg. of the polypeptide. Little or no cross-reactivity was found when graded doses of other gastrointestinal polypeptides were assayed in the radioimmunoassay and immunoreactive secretin (IRS) in volumes of serum up to 300 mul could be measured accurately.

Bile inhibits release of cholecystokinin and neurotensin

We have investigated the effect of bile on fat-stimulated release and basal plasma levels of cholecystokinin-33/39 (CCK) and neurotensin in six awake dogs prepared with chronic gastric and duodenal cannulas. Experimental bile diversion was achieved by catheterization of the common bile duct through the duodenal cannula; the gallbladder was undisturbed. Bile diversion significantly enhanced the release of both CCK and neurotensin that was stimulated by intraduodenal (ID) infusion of a triglyceride suspension (corn oil) (0.5 gm/kg-hr). The integrated release with ID triglyceride (ng [0 to 90 min]/ml) for CCK was control 5.58 +/- 0.83, bile diversion 14.47 +/- 2.81, bile excess 1.68 +/- 0.56, and for neurotensin was control 0.35 +/- 0.19, bile diversion 1.26 +/- 0.35, and bile excess 0.45 +/- 0.31. ID infusion of excessive bile (bile collected during bile diversion) significantly inhibited both the release and basal levels of CCK. Bile diversion alone did not modify plasma levels of CCK or neurotensin. We conclude that: endogenous bile exerts a negative feedback effect on release of CCK and neurotensin induced by triglyceride and on basal plasma levels of CCK; bile is unnecessary for the stimulation of endocrine cells in the intestinal mucosa by dietary fat; and measured basal levels of CCK and neurotensin represent a real amount of circulating peptide in the fasting state, that is, the basal levels are real and not artifactual.

Interaction of neurotensin, secretin and cholecystokinin on pancreatic exocrine secretion in conscious dogs

The results of previous studies from our laboratory have shown that neurotensin can stimulate pancreatic secretion of bicarbonate and protein. This study was done to compare the stimulatory action of neurotensin on pancreatic exocrine secretion in conscious dogs to those of secretin and cholecystokinin (CCK). Six dogs with chronic pancreatic and gastric fistulas were given hydrochloric acid intraduodenally or CCK-8 intravenously to produce maximal bicarbonate or protein secretion. Neurotensin was then given intravenously in combination with intraduodenal hydrochloric acid or intravenous CCK-8. Incremental bicarbonate outputs in response to intraduodenal hydrochloric acid alone were measured and compared with intraduodenal hydrochloric acid plus intravenous neurotensin. Intravenous administration of neurotensin augmented pancreatic bicarbonate and protein secretory responses to a maximal dose of intraduodenal hydrochloric acid. Incremental protein responses to intravenous CCK-8 alone were measured and compared to intravenous CCK-8 plus intravenous neurotensin. Incremental bicarbonate responses to intravenous CCK-8 alone were compared with intravenous CCK-8 plus intravenous neurotensin. Similarly, intravenous neurotensin augmented pancreatic protein and bicarbonate secretory responses to a maximal dose of intravenous CCK-8. The results of this study indicate that neurotensin may stimulate pancreatic secretion of protein and bicarbonate by mechanisms which are different from those of CCK and secretin. Neurotensin apparently exerts its action through specific neurotensin receptors.

Pancreatic protein secretion and gastrointestinal hormone release in response to parenteral amino acids and lipid in dogs

Parenteral nutrition has been advocated for and used in clinical situations in which provision of calories without stimulation of pancreatic secretion is desired. A recent report, however, provided evidence for substantial stimulation of pancreatic secretion after parenteral administration of amino acids and fat. We have studied the effect of intravenous administration of crystalline amino acids and lipid on pancreatic protein secretion and release of gastrointestinal hormones in five dogs with chronic pancreatic fistulas. The amino acids were given as a 4.25% solution in 5% glucose at 2 gm/hr. Parenteral fat was administered as Intralipid 10% at 3.5 ml/kg/hr. Plasma concentrations of cholecystokinin (CCK) and pancreatic polypeptide (PP) and serum concentrations of gastrin, measured by radioimmunoassay, were determined before, and at intervals during, infusion of amino acids and fat. Pancreatic juice was collected simultaneously with blood sampling, and volume and protein output were measured. Basal concentrations of CCK, PP, and gastrin were not affected by intravenous infusion of amino acids. Pancreatic protein secretion and volume were also unaffected by parenteral amino acids. Parenteral infusion of fat resulted in a significant inhibition of integrated gastrin release but had no effect on plasma concentrations or integrated release of CCK or PP. Neither the volume nor protein output of pancreatic secretion was affected by intravenous fat administration. In summary, no stimulation of pancreatic secretion or release of CCK, PP, or gastrin occurred as a result of parenteral amino acid or fat administration. There is, therefore, no contraindication to the use of parenteral nutrition in situations in which it is desirable to keep the pancreas at rest.

Kinetics and proposed mechanism of the reaction of an immunoinhibition, particle-enhanced immunoassay

We report kinetic studies on the reaction of a latex agglutination immunoassay used to quantify phenytoin in serum. In this assay, polystyrene particles with a covalently attached analog of phenytoin react with an antiphenytoin monoclonal antibody to form light-scattering aggregates, with the rate of this reaction being decreased by addition of phenytoin from sample. In the absence of free (sample) phenytoin, this reaction did not exhibit a maximum rate of agglutination in the presence of excess antibody, i.e., an equivalence point. Furthermore, agglutination was inhibitable by free phenytoin even when the latter was added after agglutination of particles with antibody had begun. Most significantly, the immunoagglutination proceeded in an identical fashion with monovalent F(ab) fragment. These data are consistent with low-affinity immunospecific particle-antibody complexation, which then induces colloidal aggregation, without requiring immunospecific bridging by antibody molecules. The described mechanism is not generalizable to all latex agglutination immunoassays, although disturbance of colloidal stability may be a component in most assays.

Plasma concentrations of cholecystokinin in patients with duodenal ulcer disease

Cholecystokinin (CCK) is structurally similar to gastrin and is known to competitively inhibit the action of gastrin on the parietal cell, but little information has been accumulated about circulating levels of CCK in patients with duodenal ulcer (DU). In a group of 18 healthy volunteers (controls) and 22 DU patients (13 with active DU, nine with inactive DU), we stimulated endogenous release of CCK with oral administration of Lipomul corn oil. Plasma concentrations of CCK were measured by radioimmunoassay; ultrasonographic measurements of gallbladder volume were used as a biologic correlate for CCK in control patients and in patients with active DU. No significant difference was found in fasting plasma concentrations of CCK between controls (107 +/- 8 pg/ml) and DU patients (123 +/- 15 pg/ml), or in their total integrated release of CCK during the first hour after Lipomul ingestion (3.7 +/- 0.7 ng-min/ml in controls, 2.8 +/- 0.4 ng-min/ml in DU patients). Furthermore, no significant difference was found in integrated release of CCK between patients with active DU (2.9 +/- 0.6 ng-min/ml) and those with inactive DU (2.8 +/- 0.6 ng-min/ml). Gallbladder volume was highly correlated with plasma concentrations of CCK in controls (r = -0.91) and in active DU patients (r = -0.98). Patients with active DU had significantly smaller volumes of their resting gallbladders, they emptied less of their resting gallbladder contents in response to fat, and they showed diminished sensitivity to endogenously released CCK compared to controls. In six patients with active DU who underwent truncal vagotomy and drainage, integrated release of CCK increased significantly, from 1.9 +/- 0.6 ng-min/ml before vagotomy to 9.3 +/- 3.0 ng-min/ml after vagotomy. We found no evidence to suggest that abnormalities in release of CCK contributes to the development of duodenal ulcers. We speculate, however, that the increased release of endogenous CCK after truncal vagotomy may possibly play an etiologic role in the syndrome of postvagotomy diarrhea.

Gastrinoma

Although there are multiple etiologies of clinical hypergastrinemia, the most important cause is gastrinoma [Zollinger-Ellison (ZE) syndrome]. The most significant advance in the management of patients with the ZE syndrome has been the development of the ability to establish firmly the correct preoperative diagnosis by radioimmunoassay. We believe that all patients who have the ZE syndrome should undergo operation for two reasons: to identify and resect all tumor and because in patients in whom no tumor is found or in whom all tumor cannot be resected, the most reliable relief of hypersecretory symptoms for the life of the patient can be achieved by total gastrectomy.

Transmembrane signalling of cholinergic-stimulated contraction in isolated rat glomeruli

Exposure of isolated rat glomeruli to carbachol (Carb) 1 mM induces glomerular (mesangial cell) contraction which is inhibited by pirenzepine. To identify the cellular signalling mechanism, we analyzed Carb-activated phosphoinositide hydrolysis in myo-[2-3H] inositol preloaded cells of isolated rat glomeruli. Carb evoked a rapid (5 s, 30.4 +/- 8.3% of basal) and sustained (60 s, 157.2 +/- 1.2% of basal) inositol trisphosphate (IP3) response. Acetylcholine 100 microM (Ach) in the presence of eserine also evoked IP3 formation. Mobilization of Ca2+ was monitored by preloading glomerular cells with 45Ca2+ (200 microCi/ml) and analyzing the cellular efflux using a constant perifusion system. Both Carb and Ach induced transient 45Ca2+ efflux, with peak values above baseline of 69.0 +/- 19.9 and 71.5 +/- 7.9%, respectively. Incubation with pirenzepine or prior release of Ca2+ from an IP3-sensitive intracellular pool by Thapsigargin (2 microM) prevented Carb-evoked Ca2+ release (100 and 60%, respectively). Therefore, glomerular cells possess functional cholinergic receptors which stimulate contraction via IP3-mediated intracellular Ca2+ release.

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.

Change in endocrine pancreatic function in short-term diet restriction

Long-term diet restriction can retard the aging process. Lower sustained plasma glucose levels may be one of the key factors for prolongation of life. The purpose of this study was to determine the effects of short-term diet restriction on the endocrine pancreas in rats. One hundred 5-wk-old male Sprague-Dawley rats were fed ad libitum for 1 wk, and then 10 rats (5 fed, 5 fasted for 24 h) were killed. The remaining 90 rats were divided into two groups, either fed ad libitum or maintained on a restricted food intake (60% of control/day). At regular intervals after the start of food restriction, rats from each group were killed, and plasma and the pancreas were collected for measurements of glucose, insulin, and glucagon concentration and content. At the end of the study, isolated pancreatic perfusions were performed to examine dynamic insulin response to glucose. Throughout the study, plasma glucose and insulin levels were lower in fed rats from the diet-restricted group than in fed rats from the normally fed group. Furthermore, there were no differences in plasma glucose or insulin levels between fed and fasted rats in the diet-restricted group. Pancreatic perfusion showed that the second phase of insulin release was significantly lower in rats from the diet-restricted group than in rats from the normally fed group. Decreased content of spermine in the pancreas of the diet-restricted rats may correlate with a decreased second phase of insulin release. These findings may partly explain why lowered plasma insulin levels are observed in diet-restricted rats.

Concentrations of gastrin and secretin in the alimentary tract of the cat

The distribution of gastrin and secretin in the alimentary tract of the cat was determined from the esophagogastric junction to the ileocecum. The total content and concentration of each of these hormones in mucosal extracts taken from the gastric fundus, gastric antrum, proximal and distal duodenum, proximal and distal jejunum, and ileum were measured with specific radioimmunoassays. The gastric antrum contained the highest concentration of gastrin, but appreciable amounts also were found in the duodenum. The highest concentrations of secretin were found in the duodenum, but impressive quantities were measured in the jejunum. The role of extra-antral gastrin and of those stores of secretin beyond the proximal duodenum (where the pH probably never falls to levels associated with release of secretin) currently are unknown.

Correlation of in vitro measurements of contractility of the gallbladder with in vivo ultrasonographic findings in patients with gallstones

The objective of this study was to examine the in vitro responsiveness to cholecystokinin-8 of gallbladder muscle strips from patients with gallstones and to correlate the findings with preoperative ultrasonographic studies of gallbladder contractility. The response of gallbladder muscle strips to cholecystokinin-8 of patients with noncontracting gallbladders was significantly reduced in comparison to that of patients with gallstones whose gallbladders contracted in response to fat.

Autoimmune hemolytic anemia with both cold and warm autoantibodies

Of 144 patients with a positive direct antiglobulin test and having autoimmune hemolytic anemia (AIHA), 12 (8.3%) satisfied diagnostic criteria for both warm antibody AIHA and cold agglutinin syndrome. All 12 patients had IgG and C3d sensitizing their erythrocytes, and samples of their serum contained IgM cold autohemagglutinins optimally reactive at 4 degrees C, but with a high thermal amplitude to 37 degrees C, and IgG warm autoantibodies. All red blood cell eluates contained IgG warm autoantibodies. The 12 patients had severe hemolytic anemia that responded dramatically to corticosteroid therapy, with the mean hemoglobin level increasing from 6.3 to 12.9 g/dL. Five patients (42%) had systemic lupus erythematosus, one patient (8%) had a non-Hodgkin's lymphoma, and six patients (50%) had idiopathic AIHA; four patients (33%) had concomitant thrombocytopenia (Evans' syndrome). Nine patients (75%) were female. Four patients had unexpected alloantibodies potentially capable of in vivo hemolysis of transfused blood. Because of the severe hemolysis, the serologic findings, and the dramatic initial clinical response to corticosteroid therapy, these patients represent a distinct catagory of AIHA and should be given corticosteroid therapy quickly.

Veterinary medicine in New York State: overview of distribution patterns

An understanding of the distributional patterns of Veterinary practitioners in New York State can assist in optimizing veterinary services and opportunities. Veterinarians have been arrayed by type of practice and location within counties and major land form regions. Relationships between the number of practitioners and human and animal populations have been examined in these areas and show the inadequacy of basing veterinary needs on human population data. In contrast, large animal numbers show a much closer correspondence to veterinary practitioners, with ranges of 3341 to 6561 animals being serviced per veterinarian in the large and mixed service fields (98% of these totals are food animals). Data on age composition and degree institution (in-state versus out-of-state) provide indications of the length of service, turnover rate and retention rate for practitioners trained in New York State. At present 60 percent of New York State practitioners received their education at Cornell and more than three quarters of the active total completed their education since 1950.

Inhibition of human gastric adenocarcinoma xenograft growth in nude mice by alpha-difluoromethylornithine

We studied the effect of inhibition of polyamine biosynthesis by alpha-difluoromethylornithine on the growth of a human gastric adenocarcinoma (CLEES) xenotransplanted in nude mice. CLEES is a well-differentiated gastric adenocarcinoma of the intestinal type. The doubling time has ranged from 7 to 10 days through 11 passages. Electron microscopic and immunohistochemical studies comparing the original tumor and xenotransplants showed similar structure and similar amounts of carcinoembryonic antigen. Polyamine biosynthesis is required for cell division. alpha-Difluoromethylornithine inhibits ornithine decarboxylase, the rate-limiting enzyme in polyamine biosynthesis. In this study, 48 athymic mice were used in two experiments. In the first experiment, two groups of 12 mice each were inoculated with CLEES tumor cells and received either tap water or a 3% alpha-difluoromethylornithine solution as drinking water. Tumor size was measured twice weekly. Tumor size was significantly decreased from controls by the fourth week of treatment and at all points of analysis thereafter for 7 wk. In the second experiment, alpha-difluoromethylornithine significantly reduced tumor concentrations of the polyamines putrescine and spermidine. In addition, the tumor content of DNA was significantly reduced in treated mice (0.64 +/- 0.16 mg) compared to controls (4.76 +/- 0.92 mg). Our data suggest that inhibition of polyamine biosynthesis may be a useful component of multidrug chemotherapy for human gastric adenocarcinoma. Establishment of tumor lines such as this gastric adenocarcinoma will facilitate further studies on the biological behavior of human gastric cancer and its response to chemotherapeutic manipulation in vivo.

Effect of total jejunoileal denervation on fat-stimulated release of peptide YY and cholecystokinin

We have investigated the effect of total denervation of the jejunoileum (JDNv) on stimulated release of peptide YY (PYY) and cholecystokinin-33/39 in five dogs prepared with chronic gastric and duodenal cannulas. JDNv was performed by stripping the adventitia from the superior mesenteric artery and vein, transecting the small bowel mesentery, and division (with reanastomosis) of the small bowel at the ligament of Treitz and ileocecal junctio. Introduodenal corn oil (3 ml/kg/hr) was given before JDNv and 1 and 2 months after JDNv. Intravenous bombesin (400 pmol/kg/hr) was given (on nonconsecutive days) before JDNv and 1 month after JDNv. Plasma PYY and cholecystokinin levels were measured by specific radioimmunoassay. Release of PYY was enhanced after JDNv. The integrated release of PYY (ng.[0 to 60 min]/ml) after intraduodenal corn oil was as follows: before JDNv, 4.1 +/- 1.2; 1 month after JDNv, 16.0 +/- 2.7; and 2 months after JDNv, 10.3 +/- 2.2. Similar results were noted with intravenous bombesin (3.7 +/- 0.9 [before JDNv] vs 12.0 +/- 0.7 [1 month after JDNv]). Corn oil-stimulated release of cholecystokinin was abolished after JDNv (before JDNv 2.2 +/- 1.1; 1 month after JDNv, 0.6 +/- 0.3; and 2 months after JDNv, 0.4 +/- 0.6). Basal plasma levels of PYY and cholecystokinin were not affected by JDNv. We conclude that JDNv enhances PYY and abolished cholecystokinin release, which provides evidence for different mechanisms of neural control.