Identification and stabilization of a highly selective gastrin-releasing peptide receptor agonist.

The gastrin-releasing peptide receptor (GRPR) is part of the bombesin receptor family and a well-known target in cancer diagnosis and therapy. In the last decade, promising results have been achieved by using peptide-drug conjugates, which allow selective targeting of GRPR expressing tumor cells. Most ligands, however, have been antagonists even though agonists can lead to higher tumor uptake owing to their internalization. So far, only a few studies focused on the identification of small GRPR-selective agonists that are metabolically stable. Here, we developed novel bombesin analogs with high selectivity for the GRPR and improved blood plasma stability. The most promising analog [d-Phe6 , ß-Ala11 , NMe-Ala13 , Nle14 ]Bn(6-14) displays an activity of 0.3nM at the GRPR, a more than 4000-fold selectivity over the other two bombesin receptors and more than 75% stability in human blood plasma after 24 hours. This analog is proposed as a promising drug shuttle for the intracellular delivery of different payloads in targeted tumor therapy approaches.

The differential diagnostic value of serum NT-proBNP in hospitalized patients of heart failure with pneumonia.

Serum N-terminal pro-B-type natriuretic peptide (NT-proBNP) is considered as an effective predictor for patients with heart failure (HF), while a strong body of evidence has found its utility in inflammatory diseases. It is difficult to differentiate HF and HF coexisting with other inflammations by measuring NT-proBNP. The aim of this study was to estimate the differential diagnostic performance of serum NT-proBNP in hospitalized HF patients with pneumonia. A prospective study was launched. Sixty nine HF patients, 51 HF patients complicated with pneumonia, and 38 patients with pneumonia were enrolled. Serum NT-proBNP levels were measured on Roche Elecsys. X-ray and the European Society of Cardiology (ESC) diagnostic principles were adopted to identify patients with pneumonia and HF, respectively. The diagnostic performance of NT-proBNP was assessed by ROC. Serum NT-proBNP [7,039(1,008-24,672) pg/ml] in patients of HF complicated with pneumonia was significantly higher than that in those of patients with single HF [3,147(616-24,062) pg/ml] or single pneumonia [911(98-3,812) pg/ml] (P < 0.0001). No correlation was found between the level of NT-proBNP and hospital stay. The area under ROC curve (AUC) of NT-proBNP for distinguishing patients of HF with pneumonia was 0.8082. At the level of 4,691 pg/ml, the optimal cutoff value, 74.5% sensitivity and 81.8% specificity of NT-proBNP were predicted. Evaluation of serum NT-proBNP is conducive for clinicians to identify patients of HF with pneumonia, but its poor efficacy in monitoring the curative therapy in this entire cohort is not recommended.

(18)F, (64)Cu, and (68)Ga labeled RGD-bombesin heterodimeric peptides for PET imaging of breast cancer.

Radiolabeled RGD (Arg-Gly-Asp) and bombesin (BBN) radiotracers that specifically target integrin alpha(v)beta(3) and gastrin releasing peptide receptor (GRPR) are both promising radiopharmaceuticals for tumor imaging. We recently designed and synthesized a RGD-BBN heterodimeric peptide with both RGD and BBN motifs in one single molecule. The (18)F-labeled RGD-BBN heterodimer exhibited dual integrin alpha(v)beta(3) and GRPR targeting in a PC-3 prostate cancer model. In this study we investigated whether radiolabeled RGD-BBN tracers can be used to detect breast cancer by using microPET. Cell binding assay demonstrated that the high GRPR expressing breast cancer cells typically express low to moderate level of integrin alpha(v)beta(3), while high integrin alpha(v)beta(3) expressing breast cancer cells have negligible level of GRPR. We labeled RGD-BBN heterodimer with three positron emitting radionuclides (18)F, (64)Cu, and (68)Ga and investigated the corresponding PET radiotracers in both orthotopic T47D (GRPR(+)/low integrin alpha(v)beta(3)) and MDA-MB-435 (GRPR(-)/integrin alpha(v)beta(3)(+)) breast cancer models. The three radiotracers all possessed in vitro dual integrin alpha(v)beta(3) and GRPR binding affinity. The advantages of the RGD-BBN radiotracers over the corresponding BBN analogues are obvious for imaging MDA-MB-435 (GRPR(-)/integrin alpha(v)beta(3)(+)) tumor. (18)F-FB-PEG(3)-RGD-BBN showed lower tumor uptake than (64)Cu-NOTA-RGD-BBN and (68)Ga-NOTA-RGD-BBN but was able to visualize breast cancer tumors with high contrast. Synthesis of (64)Cu-NOTA-RGD-BBN and (68)Ga-NOTA-RGD-BBN is much faster and easier than (18)F-FB-PEG(3)-RGD-BBN. (64)Cu-NOTA-RGD-BBN showed prolonged tumor uptake but also higher liver retention and kidney uptake than (68)Ga-NOTA-RGD-BBN and (18)F-FB-PEG(3)-RGD-BBN. (68)Ga-NOTA-RGD-BBN possessed high tumor signals but also relatively high background uptake compared with the other two radiotracers. In summary, the prosthetic labeling groups, chelators, and isotopes all have a profound effect on the tumor targeting efficacy and in vivo kinetics of the RGD-BBN tracers for dual integrin and GRPR recognition. Further development of suitably labeled RGD-BBN tracers for PET imaging of cancer is warranted.

68Ga-radiolabeled bombesin-conjugated to trimethyl chitosan-coated superparamagnetic nanoparticles for molecular imaging: preparation, characterization and biological evaluation.

INTRODUCTION: Nowadays, nanoparticles (NPs) have attracted much attention in biomedical imaging due to their unique magnetic and optical characteristics. Superparamagnetic iron oxide nanoparticles (SPIONs) are the prosperous group of NPs with the capability to apply as magnetic resonance imaging (MRI) contrast agents. Radiolabeling of targeted SPIONs with positron emitters can develop dual positron emission tomography (PET)/MRI agents to achieve better diagnosis of clinical conditions. METHODS: In this work, N,N,N-trimethyl chitosan (TMC)-coated magnetic nanoparticles (MNPs) conjugated to S-2-(4-isothiocyanatobenzyl)-1,4,7,10-tetraazacyclododecane tetraacetic acid (DOTA) as a radioisotope chelator and bombesin (BN) as a targeting peptide (DOTA-BN-TMC-MNPs) were prepared and validated using fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), and powder X-ray diffraction (PXRD) tests. Final NPs were radiolabeled with gallium-68 (68Ga) and evaluated in vitro and in vivo as a potential PET/MRI probe for breast cancer (BC) detection. RESULTS: The DOTA-BN-TMC-MNPs with a particle size between 20 and 30 nm were efficiently labeled with 68Ga (radiochemical purity higher than 98% using thin layer chromatography (TLC)). The radiolabeled NPs showed insignificant toxicity (>74% cell viability) and high affinity (IC50=8.79 µg/mL) for the gastrin-releasing peptide (GRP)-avid BC T-47D cells using competitive binding assay against 99mTc-hydrazinonicotinamide (HYNIC)-gamma-aminobutyric acid (GABA)-BN (7-14). PET and MRI showed visible uptake of NPs by T-47D tumors in xenograft mouse models. CONCLUSION: 68Ga-DOTA-BN-TMC-MNPs could be a potential diagnostic probe to detect BC using PET/MRI technique.

Comparison of [(11)C]Choline ([(11)C]CHO) and [(18)F]Bombesin (BAY 86-4367) as Imaging Probes for Prostate Cancer in a PC-3 Prostate Cancer Xenograft Model.

PURPOSE: Carbon-11- and fluorine-18-labeled choline derivatives are commonly used in prostate cancer imaging in the clinical setting for staging and re-staging of prostate cancer. Due to a limited detection rate of established positron emission tomography (PET) tracers, there is a clinical need for innovative tumor-specific PET compounds addressing new imaging targets. The aim of this study was to compare the properties of [(18)F]Bombesin (BAY 86-4367) as an innovative biomarker for prostate cancer imaging targeting the gastrin-releasing peptide receptor and [(11)C]Choline ([(11)C]CHO) in a human prostate tumor mouse xenograft model by small animal PET/X-ray computed tomography (CT). PROCEDURES: We carried out a dual-tracer small animal PET/CT study comparing [(18)F]Bombesin and [(11)C]CHO. The androgen-independent human prostate tumor cell line PC-3 was implanted subcutaneously in the flanks of nu/nu NMRI mice (n = 10) (PET/CT measurements of two [(11)C]Choline mice could not be analyzed due to technical reasons). [(18)F]Bombesin and [(11)C]CHO PET/CT imaging was performed about 3-4 weeks after the implantation of PC-3 cells on two separate days. After the intravenous tail vein injection of 14 MBq [(18)F]Bombesin and 37 MBq [(11)C]CHO, respectively, a dynamic study over 60 min was acquired in list mode using an Inveon animal PET/CT scanner (Siemens Medical Solutions). The sequence of [(18)F]Bombesin and [(11)C]CHO was randomized. Image analysis was performed using summed images as well as dynamic data. To calculate static and dynamic tumor-to-muscle (T/M), tumor-to-blood (T/B), liver-to-blood (L/B), and kidney-to-blood (K/B) ratios, 4 × 4 × 4 mm(3) volumes of interest (VOIs) of tumor, muscle (thigh), liver, kidney, and blood derived from transversal slices were used. RESULTS: The mean T/M ratio of [(18)F]Bombesin and [(11)C]CHO was 6.54 ± 2.49 and 1.35 ± 0.30, respectively. The mean T/B ratio was 1.83 ± 0.79 for [(18)F]Bombesin and 0.55 ± 0.10 for [(11)C]CHO. The T/M ratio as well as the T/B ratio for [(18)F]Bombesin were significantly higher compared to those for [(11)C]CHO (p < 0.001, respectively). Kidney and liver uptake was statistically significantly lower for [(18)F]Bombesin (K/B 3.41 ± 0.81, L/B 1.99 ± 0.38) compared to [(11)C]CHO [K/B 7.91 ± 1.85 (p < 0.001), L/B 6.27 ± 1.99 (p < 0.001)]. The magnitudes of the time course of T/M and T/B ratios (T/M and T/Bdyn ratios) were statistically significantly different (showing a higher uptake of [(18)F]Bombesin compared to [(11)C]CHO); additionally, also the change of the T/M and T/B ratios over time was significantly different between both tracers in the dynamic analysis (p < 0.001, respectively). Furthermore, there was a statistically significantly different change of the K/B and L/B ratios over time between the two tracers in the dynamic analysis (p = 0.026 and p < 0.001, respectively). CONCLUSIONS: [(18)F]Bombesin (BAY 86-4367) visually and semi-quantitatively outperforms [(11)C]CHO in the PC-3 prostate cancer xenograft model. [(18)F]Bombesin tumor uptake was significantly higher compared to [(11)C]CHO. [(18)F]Bombesin showed better imaging properties compared to the clinically utilized [(11)C]CHO due to a higher tumor uptake as well as a lower liver and kidney uptake.

Quantification of the bombesin/gastrin releasing peptide antagonist RC-3095 by liquid chromatography-tandem mass spectrometry.

Bombesin (BN) and its mammalian equivalent, gastrin-releasing peptide (GRP), stimulate cell proliferation and are involved in the pathogenesis of several types of human cancer. BN/GRP and their receptors were shown to be critical for the growth of various human malignancies, such as small-cell lung, prostate, ovary, stomach and breast cancers in the human tumor xenograft model. In the present study, a fast, sensitive, robust method was developed for the determination and quantification of a BN/GRP receptor antagonist RC-3095 (D-Tpi-Gln-Trp-Ala-Val-Gly-His-Leupsi(CH2NH)Leu-NH2), in human plasma by liquid chromatography coupled with tandem mass spectrometry. RC-3095 was extracted from 0.2 ml human plasma by protein precipitation using cold acetonitrile (0.4 ml). The method has a chromatographic run of 10 min using a C(8) analytical column (150 mm x 4.6 mm i.d.) and the linear calibration curve over the range was linear from 20 to 10000 ng ml(-1) (r(2)>0.994). The between-run precision, based on the relative standard deviation replicate quality controls, was 5.7% (60 ng ml(-1)), 7.1% (600 ng ml(-1)) and 6.8% (8000 ng ml(-1)). The between-run accuracy was +/-0.0, 2.1 and 3.1% for the above-mentioned concentrations, respectively. The developed procedure allows the quantitative determination of peptide RC-3095 for pharmacokinetics studies in human plasma.

Involvement of bombesin in spermine-induced corticosterone secretion and intestinal maturation in suckling rats.

In this study we investigated whether brain-gut peptides are implicated in the activation of the hypophysial-adrenal axis (HAA) in suckling rats treated orally with spermine. The first group of rats received i.p. injections of bombesin, vasoactive intestinal polypeptide (VIP), somatostatin or neurotensin, starting on day 11 of life, and killed on day 14. The small intestine was removed and analysed for its content of proteins, DNA, polyamines and for its specific activity (SA) of disaccharidases. The second group of rats received one of the hormones cited above and was killed 45 min after the treatment for determination of corticosterone plasma concentration. Rats of the third group were adrenalectomised then treated with bombesin as the first group. The fourth group of rats was orally treated with spermine and sacrificed 2, 3, 4, 6 and 8 h thereafter for analysis of plasma and intestinal concentrations of bombesin. The i.p. injection of bombesin increased the sucrase and maltase SA in the whole small intestine, while it decreased the lactase SA in the distal part. Intestinal weight and length, contents of DNA, protein, spermidine and spermine, and corticosterone plasma levels were enhanced by bombesin treatment. Somatostatin, neurotensin and VIP were ineffective on all the parameters studied. Adrenalectomy, in bombesin-treated rats, decreased the sucrase and maltase SA in the whole intestine, and decreased the lactase SA in the proximal intestine. It has no effect on intestinal weight and length, and protein content. Oral administration of spermine had no effect on plasma concentration of bombesin, whereas it decreased the content of this peptide in the whole small intestine. It is possible that bombesin may control intestinal development in suckling rats and be a link between the ingestion of spermine and the liberation of corticosterone by the adrenal glands.

Tumor markers in patients with lung cancer.

The most examined tumor markers in lung cancer patients are CEA, hormonal peptides, and some neurogenic enzymes in small cell carcinoma. Calcitonin, ACTH, ADH, CEA, neurophysin, oxytocin, beta-endorphin, neuron-specific enolase, and CK BB are elevated in serum specimens in 25-75% of cases of small cell carcinoma. The level of these markers is related to the stage of the disease in groups of patients; elevated pretreatment levels decrease with tumor regression. Marker levels are not valid in defining the tumor load and the presence of disease in the individual patient. It has not yet been documented that the markers can be used for clinical decisions on antineoplastic therapy. A recent development is the finding that measurement of CSF and plasma concentrations of ADH, calcitonin, CK BB, bombesin, and neuron-specific enolase may contribute in the diagnosis of CNS metastases including meningeal carcinomatosis.

Concomitant production of immunoreactive gastrin-releasing peptide and calcitonin in medullary carcinoma of the thyroid.

Immunoreactive gastrin-releasing peptide (IR-GRP) was found to be present in medullary carcinoma of the thyroid (MCT) by use of a radioimmunoassay (RIA) specific for the carboxyl-terminal portion of GRP. Immunohistochemical studies revealed IR-GRP in the MCT tumor cells, indicating that the tumor cells produce IR-GRP. Immunoreactive GRP was also detected in macroscopically normal thyroid tissue of patients with multiple endocrine neoplasia type II (MEN II, or Sipple's syndrome) and in areas of C cell hyperplasia and micronodules in the thyroids of patients with MCT. When these tissue extracts were examined with a bombesin RIA that recognizes bombesin but not GRP, no IR-bombesin was detected, suggesting that the IR-GRP detected in these tissues is more similar to GRP than to bombesin. IR-GRP was also undetectable in normal thyroid tissues. Plasma IR-GRP was also undetectable in normal thyroid tissues. Plasma IR-GRP was elevated to 130 to 780 pg/mL (normal: undetectable, less than 62.5 pg/mL) in three patients with metastatic MCT, and both calcium and tetragastrin increased the plasma levels of IR-GRP. Sephadex G-50 gel filtration of the MCT extracts revealed two peaks, one coeluted with porcine GRP (1-27) and the other eluted just after its carboxyl-terminal (14-27) fragment. There was a significant correlation (P less than 0.01) between the concentration of IR-GRP and that of IR-calcitonin in MCT tumor tissue and in macroscopically normal portions of thyroid tissue from two patients with MEN II, although the concentration of IR-GRP was only about 0.1% of that of IR-calcitonin.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of bombesin on gastric emptying of solids in man.

Intravenous infusion of bombesin (5 ng.kg(-1). min(-1) significantly delayed gastric emptying of solids in man. The gastrin response to meal increased following administration of the peptide; however no correlation was found between the difference in gastrin response (to meal alone and to meal plus bombesin) and the degree of delay in emptying. In addition the behavior of intragastric pH after eating was not modified by bombesin infusion. All of these data suggest a direct effect of the peptide on gastric emptying, which was probably connected with the strong contraction of the antrum and pylorus observed in this and in previous investigations.

Tobacco smoke exposure and bombesin-like peptides in guinea pigs.

Bombesin-like peptides (BLPs) are associated with tobacco smoke (TS)-induced diseases. We sought to determine if acute TS exposure releases BLPs into the pulmonary circulation. Sensitized and non-sensitized guinea pigs were chronically exposed to TS or compressed air. Thereafter, the lungs were acutely challenged with TS while perfused. Perfusates were analyzed for BLPs. TS increased BLPs in non-sensitized guinea pigs. A separate study determined daily bombesin exposure increased lung cell counts but not airway hyperresponsivensess. TS exposure releases BLPs into the pulmonary circulation but can be modified by host factors and bombesin itself does not induce airway hyperresponsiveness.

Effect of atropine and somatostatin on bombesin-stimulated plasma gastrin, cholecystokinin and pancreatic polypeptide in man.

Infusion of the neuropeptide bombesin stimulates the secretion of several gastrointestinal hormones by an unknown mechanism. We have investigated the effects of atropine (15 ng/kg as bolus followed by 2.5 ng/kg X 30 min) and somatostatin (125 micrograms as i.v. bolus followed by 62.5 micrograms/30 min) on the stimulation of 3 hormones (gastrin, cholecystokinin and pancreatic polypeptide) by 60 pmol/kg X 20 min bombesin in 6 healthy volunteers. Plasma samples for measurement of hormones by sensitive and specific radioimmunoassays were obtained at -5, 0, 2.5, 5, 7.5, 10, 15, 20, 25 and 30 min. Bombesin induced significant increases in plasma gastrin (12 +/- 2 to 34 +/- 3 pM; P less than 0.0005), cholecystokinin (1.2 +/- 0.2 to 8.9 +/- 0.7 pM; P less than 0.0001) and pancreatic polypeptide (22 +/- 4 to 72 +/- 19 pM; P less than 0.05). There were great differences between the effects of atropine and somatostatin on the hormonal responses to bombesin. Atropine slightly increased the response of gastrin by 19% and that of cholecystokinin by 15%, but strongly inhibited the bombesin-stimulated pancreatic polypeptide secretion by 97%. On the other hand, somatostatin inhibited the bombesin-induced secretion of gastrin by 48%, cholecystokinin by 82% and pancreatic polypeptide by 107%. These results point to considerable qualitative and quantitative differences in the stimulatory mechanisms of bombesin on the hormones studied.

Effect of antibodies to the neuropeptide GRP on distention-induced gastric acid secretion in the rat.

The present study examined and compared the effects of muscarinic blockade, beta-adrenergic blockade and immunoneutralization of the neuropeptide gastrin-releasing peptide (GRP) on distention-induced gastric acid secretion and gastrin release. In response to distention of rat stomachs with 0.9% NaCl, acid output rose from 3.5 +/- 0.5 mumol H+/30 min to 15.4 +/- 2.5 mumol H+/30 min (P less than 0.01). Intravenous administration of 4 mg/kg propranolol did not affect the acid secretory response to distention, however both 2 mg/kg atropine and 6 mg/kg pirenzepine significantly decreased gastric acid secretion by 44.8 +/- 7.8% and 40.9 +/- 5.7% (P less than 0.05), respectively. When specific antibodies to GRP were infused intravenously, the acid secretory response to distention was nearly abolished, decreasing to 5.1 +/- 0.8 mumol H+/30 min (P less than 0.01). In contrast to the effects on acid secretion, GRP antiserum did not significantly alter the gastrin release observed following distention. Results of these studies indicate that, under the conditions of these experiments, the acid secretory response to gastric distention may be independent of its effect on gastrin release. Although distention-induced gastric acid secretion may be partially governed by muscarinic pathways, the acid secretory response to distention in the rat appears to involve GRP-containing neurons.

Neuropeptide levels in premenstrual syndrome.

To determine whether changes in circulating levels of neuropeptides are associated with symptoms of premenstrual syndrome (PMS), 20 women with the diagnosis of PMS and 20 asymptomatic subjects were studied. The premenstrual beta-endorphin levels were significantly lower in PMS patients (P = 0.0001). The decrease in beta-endorphin levels during the luteal phase, compared with the follicular phase, in PMS patients was also significant (P = 0.0002). Neurotensin, human pancreatic peptide, vasoactive intestinal polypeptide, gastrin, and bombesin-like immunoreactivity levels did not reveal significant changes between days 7 and 25 in patients with PMS.

Radiochemical investigations of 177Lu-DOTA-8-Aoc-BBN[7-14]NH2: an in vitro/in vivo assessment of the targeting ability of this new radiopharmaceutical for PC-3 human prostate cancer cells.

Bombesin (BBN), a 14 amino acid peptide, is an analogue of human gastrin releasing peptide (GRP) that binds to GRP receptors (GRPr) with high affinity and specificity. The GRPr is over expressed on a variety of human cancer cells including prostate, breast, lung, and pancreatic cancers. The specific aim of this study was to identify a BBN analogue that can be radiolabeled with (177)Lu and maintains high specificity for GRPr positive prostate cancer tumors in vivo. A preselected synthetic sequence via solid phase peptide synthesis (SPPS) was designed to produce a DOTA-BBN (DOTA = 1,4,7,10-tetraazacyclododecane-N,N',N",N"'-tetraacetic acid) conjugate with the following general structure: DOTA-X-Q-W-A-V-G-H-L-M-(NH(2)), where the spacer group, X = omega-NH(2)(CH(2))(7)COOH (8-Aoc). The BBN-construct was purified by reversed phase-HPLC (RP-HPLC). Electrospray Mass Spectrometry (ES-MS) was used to characterize both metallated and non-metallated BBN-conjugates. The new DOTA-conjugate was metallated with (177)Lu(III)Cl(3) or non-radioactive Lu(III)Cl(3). The (177)Lu(III)- and non-radiolabeled Lu(III)-conjugates exhibit the same retention times under identical RP-HPLC conditions. The (177)Lu-DOTA-8-Aoc-BBN[7-14]NH(2) conjugate was found to exhibit optimal pharmacokinetic properties in CF-1 normal mice. In vitro and in vivo models demonstrated the ability of the (177)Lu-DOTA-8-Aoc-BBN[7-14]NH(2) conjugate to specifically target GRP receptors expressed on PC-3 human prostate cancer cells.

Involvement of somatostatin, bombesin and serotonin in the origin of the migrating myoelectric complex in sheep.

Antroduodenal myoelectric activity was recorded in conscious sheep by electrodes chronically implanted in the muscular wall. Furthermore, plasma immunoreactive (i.r.) motilin, somatostatin and bombesin concentrations were determined by RIA. The intravenous infusion of somatostatin (20 ng/kg/min), bombesin (10 ng/kg/min) or serotonin (5-HT, 4 micrograms/kg/min) for 5 min, induced a duodenal myoelectric activity front followed by a period of quiescence. These duodenal events were concomitant with an antral inhibition. This pattern resembled that observed in a spontaneous migrating myoelectric complex (MMC) in sheep. Bombesin and 5-HT evoked an additional and transient increase in antral activity simultaneously with the duodenal activity front. On the other hand, plasma i.r. motilin levels did not show any fluctuations during spontaneous MMC cycles or after somatostatin, bombesin or 5-HT infusions. Likewise, plasma i.r. bombesin levels remained unchanged during spontaneous MMC or after administration of somatostatin. However, 5-HT -induced duodenal activity fronts were closely associated with a sharp peak in plasma i.r. bombesin. Finally, plasma i.r. somatostatin concentrations rose at the end of spontaneous phase III and peaked in phase I. A similar pattern of somatostatin release in plasma was found while the duodenal activity front and quiescence period developed after either 5-HT or bombesin infusions. These results do not indicate a role for motilin in the control of MMCs in sheep, although a definitive conclusion cannot be drawn until synthetic sheep motilin is available. However, our data suggest that somatostatin and bombesin-like peptides as well as 5-HT, acting in a coordinated manner, could be involved in the regulation of cyclical antroduodenal motor events in sheep.

Obese women are less sensitive for the satiety effects of bombesin than lean women.

OBJECTIVE: The aim of this study was to investigate whether infusion of bombesin, when combined with a gastric preload, influence satiety and foot intake in obese and lean healthy women. DESIGN: Double blind, placebo controlled study. SETTING: Department of Gastroenterology, Leiden University Medical Center, The Netherlands. SUBJECTS: Obese (n = 7) and lean (n = 7) healthy women. INTERVENTIONS: Intravenous infusion of bombesin (0.09 nmol/kg ideal weight/h) or placebo for 165 min. Gastric preload of banana slices was administered at time 60 min. Meal ingestion started at time 75 min (banana slices). Food intake was calculated and satiety was measured by visual analog scales. RESULTS: During infusion of bombesin the amount of food eaten by the lean individuals (193+/-37 g) was significantly reduced compared to saline infusion (365+/-42 g, P < 0.05). However, bombesin induced no significant feeding suppression in obese women when compared to saline (241+/-46 vs 301+/-45 g, respectively). The decrease in food intake during bombesin infusion compared to saline was significantly greater in lean subjects (173+/-30 g) than in obese subjects (59+/-35 g; P < 0.05). Only in lean subjects subjective preprandial hunger feelings were significantly affected by bombesin infusion. CONCLUSIONS: Infusion of bombesin, when combined with a gastric preload, inhibits food intake and increases satiety in lean women. Obese women are less sensitive for these bombesin induced satiety effects.

Gastrointestinal hormones and short-term nutritional schedules in critically ill patients.

BACKGROUND/AIMS: The purpose of the study is to evaluate the gastrointestinal hormone response in critically ill patients under different nutritional schedule (enteral vs. total parenteral) of short duration. METHODOLOGY: Twenty-one sedated and mechanically ventilated patients were nourished with continuous nasogastric schedule (Group A, 11 patients), or with total parenteral nutrition (Group B, 10 patients). Serum concentrations of gastrin, cholecystokinin, vasoactive intestinal peptide, neurotensin, and bombesin, were measured on the 2nd, 3rd and the 5th day of patients' admission, with radioimmunoassay methods. RESULTS: Changes of hormones concentrations were not significant either between the three measurements in each group or between the two groups at the same hospitalization day. CONCLUSIONS: The short-term parenteral nutrition in critically ill patients does not exert a different influence on the serum concentrations of gastrin, cholecystokinin, vasoactive intestinal peptide, neurotensin, and bombesin, compared to enteral nutrition. This conclusion is of clinical interest since the short-term administration of total parenteral nutrition is very often necessary during hospitalization in the intensive care unit.

Gastrointestinal disturbances with obesity.

Steatosis and steatohepatitis are associated with obesity. Despite florid histological changes, patients with non-alcoholic steatohepatitis generally remain asymptomatic, and it usually runs a relatively benign course. An elevated insulin level may be important in the pathogenesis. There is a marked regression of fatty changes after weight reduction. In obese subjects the risk of developing gallstones is increased due to an increased saturation of gallbladder bile with cholesterol and possible gallbladder stasis. During weight reduction with very low calorie diets the incidence in gallstones increases probably because of an increased saturation of bile during the loss of weight. Ursodeoxycholic acid appears to be a promising prophylactic agent. Chenodeoxycholic acid is not useful for these subjects. There is controversy over whether obesity contributes to gastroesophageal reflux and gastric emptying disturbances. There are changes in gastrointestinal peptide plasma levels in obesity but it is not clear if this contributes to its development. The risk for high-risk colorectal adenomas and carcinomas is reported to be increased in obese males. Vertical banded gastroplasty and gastric bypass procedures are nowadays the surgical options for the treatment of obesity. Nutritional deficiencies, particularly of vitamin B12, folate and iron are common after gastric bypass and must be sought and treated. Dumping is another potential complication of this operation. If stenosis and gastric outlet obstruction develop endoscopic dilatation is a good therapeutic option.

Influence of different chelators on the radiochemical properties of a 68-Gallium labelled bombesin analogue.

UNLABELLED: The radiolabelled bombesin analogue AMBA shows high potential for diagnosis and treatment of prostate and breast cancer, but the influence of different chelators, which differ in terms of radiochemical reactivity and stability, have not been explored so far. In order to find the best suitable chelator for labelling of AMBA, we synthesized AMBA analogues linked to the most commonly used chelators DOTA, NOTA and NODAGA and compared their reactivity and stability after labelling with 68-Gallium. METHODS: For the synthesis of DO3A-, NO2A- and NODAGA-AMBA, a solid-phase synthesis approach was used. The influence of concentration, pH and temperature on the radiolabelling was analysed. The in vitro stability of all complexes in saline, human serum, human whole blood and against transchelation and transmetallation was analysed. RESULTS: The peptides were synthesised in high yield and purity. Purity and identity of products and impurities were confirmed using UHPLC coupled to ESI-MS. Radiolabelling of these peptides was optimal at elevated temperature, although room temperature labelling was reported previously for NOTA and NODAGA chelators. The highest reactivity was observed for NODAGA-AMBA. On preparation of NO2A-AMBA, the formation of a by-product was detected with HPLC. More detailed analysis revealed the formation of an isomer with the same mass to charge ratio which led to the conclusion that a coordination isomer was formed. All complexes showed high stability in saline, human serum or when challenged with DTPA, transferrin and varying metals (Fe(3+), Cu(2+), Zn(2+)). Conversely, the stability in human blood was low, and varying metabolites were detected and identified by ESI-MS. CONCLUSION: All three precursors are available in high yields suitable for routine production. NODAGA-AMBA showed the most favoured features when labelled with 68-gallium, but a further comparison in vivo should be performed in order to confirm the superior features found in vitro.