Artificial nutrition and intestinal mucosal barrier functionality.

The gastrointestinal tract has a major role in digestion and absorption of nutrients while playing a leading role in defense of the body. It forms a shield against the invasion of various microorganisms or their products (e.g. antigens, toxins) and therefore it is important to establish its integrity and functionality. That depends on the route of administration and the composition of the artificial nutrition. This study concentrates on the influences of different kinds of artificial nutrition in the functionality of the intestinal mucosal barriers. It seems that full macromolecular solutions of enteral nutrition ensure an adequate mucous immune response, while a lack of nutritional stimulus in the lumen leads rapidly to a dysfunction of gastric-associated lymphatic tissue and mucosal immune system. This dysfunction renders the patients susceptible to infections in distant organs, hospital pneumonia, and multiorgan failure of non-infectious etiology. In patients with indication of total parenteral nutrition administration, addition of bombesin or glutamine preserves mucosal immune response and may limit the adverse effects.

The majority of dorsal spinal cord gastrin releasing peptide is synthesized locally whereas neuromedin B is highly expressed in pain- and itch-sensing somatosensory neurons.

BACKGROUND: Itch is one of the major somatosensory modalities. Some recent findings have proposed that gastrin releasing peptide (Grp) is expressed in a subset of dorsal root ganglion (DRG) neurons and functions as a selective neurotransmitter for transferring itch information to spinal cord interneurons. However, expression data from public databases and earlier literatures indicate that Grp mRNA is only detected in dorsal spinal cord (dSC) whereas its family member neuromedin B (Nmb) is highly expressed in DRG neurons. These contradictory results argue that a thorough characterization of the expression of Grp and Nmb is warranted. FINDINGS: Grp mRNA is highly expressed in dSC but is barely detectable in DRGs of juvenile and adult mice. Anti-bombesin serum specifically recognizes Grp but not Nmb. Grp is present in a small number of small-diameter DRG neurons and in abundance in layers I and II of the spinal cord. The reduction of dSC Grp after dorsal root rhizotomy is significantly different from those of DRG derived markers but similar to that of a spinal cord neuronal marker. Double fluorescent in situ of Nmb and other molecular markers indicate that Nmb is highly and selectively expressed in nociceptive and itch-sensitive DRG neurons. CONCLUSION: The majority of dSC Grp is synthesized locally in dorsal spinal cord neurons. On the other hand, Nmb is highly expressed in pain- and itch-sensing DRG neurons. Our findings provide direct anatomic evidence that Grp could function locally in the dorsal spinal cord in addition to its roles in DRG neurons and that Nmb has potential roles in nociceptive and itch-sensitive neurons. These results will improve our understanding about roles of Grp and Nmb in mediating itch sensation.

Imaging small human prostate cancer xenografts after pretargeting with bispecific bombesin-antibody complexes and targeting with high specific radioactivity labeled polymer-drug conjugates.

PURPOSE: Pretargeting with bispecific monoclonal antibodies (bsMAb) for tumor imaging was developed to enhance target to background activity ratios. Visualization of tumors was achieved by the delivery of mono- and divalent radiolabeled haptens. To improve the ability to image tumors with bsMAb, we have combined the pretargeting approach with targeting of high specific activity radiotracer labeled negatively charged polymers. The tumor antigen-specific antibody was replaced with bombesin (Bom), a ligand that binds specifically to the growth receptors that are overexpressed by many tumors including prostate cancer. Bomanti- diethylenetriaminepentaacetic acid (DTPA) bispecific antibody complexes were used to demonstrate pretargeting and imaging of very small human prostate cancer xenografts targeted with high specific activity ¹¹¹In- or 99mTc-labeled negatively charged polymers. METHODS: Bispecific antibody complexes consisting of intact anti-DTPA antibody or Fab' linked to Bom via thioether bonds (Bom-bsCx or Bom-bsFCx, respectively) were used to pretarget PC-3 human prostate cancer xenografts in SCID mice. Negative control mice were pretargeted with Bom or anti-DTPA Ab. 111In-Labeled DTPA-succinyl polylysine (DSPL) was injected intravenously at 24 h (7.03 ± 1.74 or 6.88 ± 1.89 MBq ¹¹¹In-DSPL) after Bom-bsCx or 50 ± 5.34 MBq of 99mTc-DSPL after Bom-bsFCx pretargeting, respectively. Planar or single photon emission computed tomography (SPECT)/CT gamma images were obtained for up to 3 h and only planar images at 24 h. After imaging, all mice were killed and biodistribution of 111In or 99mTc activities were determined by scintillation counting. RESULTS: Both planar and SPECT/CT imaging enabled detection of PC-3 prostate cancer lesions less than 1-2 mm in diameter in 1-3 h post 111In-DSPL injection. No lesions were visualized in Bom or anti-DTPA Ab pretargeted controls. 111In-DSPL activity in Bom-bsCx pretargeted tumors (1.21 ± 0.36 %ID/g) was 5.4 times that in tumors pretargeted with Bom or anti-DTPA alone (0.22 ± 0.08, p = 0.001). PC-3 xenografts pretargeted with Bom-bsFCx and targeted with 99mTc-DSPL were visualizable by 1-3 h. Exquisite tumor uptake at 24 h (6.54 ± 1.58 %ID/g) was about 15 times greater than that of Bom pretargeted controls (0.44 ± 0.17, p = 0.002). CONCLUSION: Pretargeting prostate cancer with Bom-bsCx or Bom-bsFCx enabled fast delivery of high specific radioactivity ¹¹¹In- or 99mTc-labeled polymer-drug conjugates resulting in visualization of lesions smaller than 1- 2 mm in diameter within 3 h.

A novel vaccine targeting gastrin-releasing peptide: efficient inhibition of breast cancer growth in vivo.

Gastrin-releasing peptide (GRP), a bombesin-like peptide, is an autocrine growth factor that can stimulate the growth of various cancer cells. We developed a novel protein vaccine HSP65-(GRP-10)(6) (HG6) that consists of six copies of a 10-amino acid residue epitope of GRP C-terminal fragment carried by mycobacterial 65 kDa HSP65 and then immunized mice via subcutaneous injection. Strong humoral and cell-mediated immune responses were induced. High titer of anti-GRP antibodies was detected in immunized mice sera by ELISA and verified by Western blot analysis. Activity of CD4+T lymphocytes, especially high levels of interferon (INF)-gamma, were developed in mice immunized with HG6 when compared with HSP65 or PBS. We found that immunogene tumor therapy with a vaccine based on GRP was effective at both protective and therapeutic antitumor immunity in breast tumor models in mice. The purified GRP monoclonal antibody (McAb) was proved to be potential in inhibiting EMT-6 tumor cell proliferation in vitro. The attenuation induced by active immune responses on tumor-induced angiogenesis was observed with an intradermal tumor model in mice. Taken together, we demonstrate for the first time that immune responses that are elicited by a novel chimeric protein vaccine targeting GRP can suppress the proliferation of breast tumor cell EMT-6 in mice, and it may be of importance in the further exploration of the applications of other autocrine growth factor identified in human and other animal in cancer therapy.

Immunomodulatory functions of the diffuse neuroendocrine system: implications for bronchopulmonary dysplasia.

Pulmonary neuroendocrine (NE) cells are believed to be the precursor of NE lung carcinomas, including well-differentiated (carcinoids) and moderately/poorly differentiated (atypical carcinoids and small-cell carcinomas, SCLCs) subtypes. In early studies, we determined mechanisms by which NE cell-derived peptides such as bombesin-like peptide (BLP) promote normal fetal lung development. Postnatally, BLP may normally regulate perinatal adaptation of the pulmonary circulation. However, elevated BLP levels in premature infants shortly after birth predict which infants are at high risk for developing bronchopulmonary dysplasia (BPD, chronic lung disease of newborns). An anti-BLP blocking antibody abrogates clinical and pathological evidence of lung injury in two baboon models of BPD. These observations indicate that BLP mediates lung injury in BPD, supporting a role for BLP as pro-inflammatory cytokines. We have directly tested the effects of BLP on eliciting inflammatory cell infiltrates in vivo. Surprisingly, mast cells are the major responding cell population. These data suggest that the diffuse NE system may be a newly recognized component of innate immunity in multiple organ systems. We speculate that overproduction of NE cell-derived peptides such as BLP may be responsible for a variety of chronic inflammatory disorders.

Effect of allotransplantation of embryonic brain tissues and administration of potentiated antibodies to bombesin on hemodynamics in rats with emotional hypertension.

Transcutaneous allotransplantation of embryonic tissues from the anterior hypothalamus and amygdaloid complex and administration of potentiated antibodies to bombesin normalized blood pressure and parameters of ECG in rats with emotional hypertension.

Colocalization of numerous immunoreactivities in endocrine cells of the chicken proventriculus at hatching.

The colocalization of regulatory peptide immunoreactivities in endocrine cells of the chicken proventriculus at hatching has been investigated using the avidin-biotin technique in serial sections and double immunofluorescence in the same section for light microscopy, and double immunogold staining for electron microscopy. In addition to the eight immunoreactivities previously described in this organ, cells immunoreactive for peptide histidine isoleucine (PHI), peptide gene product 9.5 (PGP), and the amidating enzyme, peptidylglycine alpha-amidating monooxygenase (PAM) were observed. All the cells immunoreactive to glucagon were also immunostained by the PHI antiserum. In addition, all the glucagon-like peptide 1, avian pancreatic polypeptide, and some of the neurotensin-like cells costored also glucagon- and PHI-immunoreactive substances. PGP- and PAM-immunoreactivities were also found in the glucagon-positive cells. A small proportion of the somatostatin-containing cells were positive for PHI but not for other regulatory peptides. These results could suggest either the existence of a very complex regulatory system or that the endocrine system of the newborn chickens is not yet fully developed.

An immunohistochemical study of endocrine cells in the alimentary tract of the red-bellied frog, Bombina orientalis.

The regional distribution and relative frequency of endocrine cells was studied immunohistochemically (PAP method) in the alimentary tract of the red-bellied frog, Bombina orientalis, using antisera against serotonin, somatostatin, chromogranin (CG), cholecystokinin (CCK)-8, bombesin, secretin, glucagon and pancreatic polypeptide (PP). Eight kinds of endocrine cells were identified in this study. These immunoreactive cells were located in the gastric glands of the stomach regions and in the intestinal or esophageal epithelium with variable frequencies. They were spherical or spindle-shaped. Serotonin- and somatostatin-immunoreactive cells were demonstrated in the whole alimentary tract including esophagus. CG-immunoreactive cells were restricted to the stomach. CCK-8-immunoreactive cells were observed from the antrum to the ileum. Bombesin-immunoreactive cells were restricted to the stomach. Secretin-immunoreactive cells were demonstrated in the pylorus, duodenum and ileum. Glucagon-immunoreactive cells were found in the antrum and duodenum. PP-immunoreactive cells were detected from the antrum to the rectum. In conclusion, throughout the alimentary tract of the red-bellied frog, the different regional distribution and relative frequency of endocrine cells were demonstrated. The regional distributions and relative frequencies of the endocrine cells in the alimentary tract of the red-bellied frog were resembled to those of the other anuran species except for esophagus.

Immunohistochemical distribution of bombesin-positive pulmonary neuroendocrine cells in a congenital diaphragmatic hernia.

Morphometrical analyses of the immunohistochemical expression of bombesin, which is one of the peptides produced by pulmonary neuroendocrine (PNE) cells, were carried out on the bronchioles of human congenital diaphragmatic hernia (CDH) neonates, and the findings were then compared with those in a gestational and postnatal age-matched control group. As a result, no difference was found in the number of bombesin-positive cells between the lungs of the control group and the unaffected side lungs in the CDH group except for the ratio of the bombesin-positive cells per unit of the bronchiolar surface area (P < 0.05). However, compared with the lungs in the control group, the affected side of the lungs in the CDH group showed a significant increase in the expression of bombesin, namely, the ratio of the bombesin-positive cells per bronchiole (P < 0.05), the ratio of the bombesin-positive cells per unit perimeter of the bronchioles (P < 0.05), and the ratio of the bombesin-positive cells per unit of the bronchiolar surface area (P < 0.01). These results thus suggest that hyperplasia of the PNE-cell system in the lungs of the CDH cases, especially on the affected side, exists in human fetuses. We also further speculate that PNE cells may thus play a role in the problems associated with CDH during intrauterine life in human beings.

Correlation of expression of bombesin-like peptides and receptors with growth inhibition by an anti-bombesin antibody in small-cell lung cancer cell lines.

The murine anti-bombesin monoclonal antibody, 2A11, has been demonstrated to inhibit growth of some small-cell lung cancer (SCLC) cells in nude mice xenografts and in a clinical trial. To determine if the expression of bombesin-like peptides (BLP) and their receptors (GRP-R and NMB-R) correlate with an in vitro response to 2A11, we measured these parameters in seven SCLC cell lines. Gastrin releasing peptide (GRP) mRNA was detected in three of seven cell lines (NCI-H69, NCI-H345, NCI-H510) and neuromedin B (NMB) mRNA was detected in all seven lines using an RNase protection assay (RPA). Immunoreactive BLP was detected in the cell pellets of all lines (range 0.11-59.90 pmol/mg protein) by a solid phase GRP radioimmunoassay (RIA) using 125I-labeled 2A11. RPA detected GRP-receptor mRNA in two cell lines (NCI-H69 and NCI-H345) and NMB-receptor in three lines (NCI-H345, NCI-H510, and NCI-H660). Reverse transcriptase-PCR confirmed the presence of receptor mRNA in these lines and detected NMB-receptor in an additional three lines (NCI-H69, NCI-H82, and NCI-H187). Calcium mobilization in response to BLP stimulation was detected in the six cell lines expressing either GRP-R or NMB-R mRNA but not in NCI-N417, which had no detectable BLP-receptor. 2A11 (5 microg/ml) inhibited colony formation by 26-61% after 2 weeks in all cell lines except NCI-N417. Thus, growth inhibition by 2A11 requires the presence of at least one BLP-receptor. These findings may be useful in selecting patients with SCLC for treatment with 2A11.

Antitumor activity of a monoclonal antibody directed against gastrin-releasing peptide in patients with small cell lung cancer.

BACKGROUND: Small cell lung cancer (SCLC) cells express and secrete gastrin-releasing peptide (GRP) which binds to receptors and stimulates growth of these cells. A murine monoclonal antibody, 2A11, which binds GRP with high affinity, decreased growth of SCLC cells in vitro and in athymic nude mice. A phase 1 trial and pharmacokinetic modeling in patients with lung cancer has defined the phase 2 dose of 2A11 but the antitumor activity in patients is unknown. METHODS: Thirteen patients with previously treated SCLC received 2A11 at 250 mg/m2 over 1 h three times per week for 4 weeks. Serum GRP, urine GRP, serum levels of 2A11, and human antimouse antibodies (HAMA) were determined. RESULTS: One of 12 (8%; 95% confidence interval, 0 to 38%) evaluable patients had complete resolution of radiographically detectable tumor lasting 4 months. Four patients (33%) had stable disease. No toxic reactions were observed. The pretreatment serum GRP level of the responding patient was 3.1 fmol/mL and the median of nine nonresponding patients was 7.3 fmol/mL (range, <1.0 to 29.0). The mean trough serum 2A11 level was 49+/-18 microg/mL in the responding patient and 32 to 487 mg/mL (median, 117) in 10 nonresponding patients. HAMA did not increase during 2A11 administration in any patient. CONCLUSIONS: Interruption of the GRP autocrine growth factor loop with 2A11 results in clinical antitumor activity in a minority of patients with previously treated SCLC. Further evaluation of the antitumor effects of 2A11 is warranted to define characteristics associated with response to 2A11.

Ultrastructure of bombesin-like immunoreactive nerve terminals in the nucleus of the solitary tract and the dorsal motor nucleus.

Bombesin (gastrin-releasing peptide 14-27) inhibits gastric function and feeding when microinjected into the nucleus of the solitary tract (NTS)/dorsal motor nucleus of the vagus (DMV) complex. We performed a preembedding immunoelectron microscopic study in rats to describe the bombesin containing nerve terminals and to characterize their postsynaptic structures. 228 bombesin-L1 nerve terminals which made synaptic contacts in the NTS/DMV complex were studied. Labeling was heaviest over dense core vesicles and lighter over small clear vesicles. The dense core vesicles were typically located along the plasmalemma away from the synaptic face, a finding that is typical of neuropeptide containing nerve terminals. The postsynaptic structures were most often medium sized dendrites (56%) and small sized dendrites (27%), with similar percentages in the NTS and DMV. In the DMV, synapses on cell bodies (8%) were more frequent than in the NTS (1%). In the NTS, synapses on dendritic spines (10%) were more frequent than in the DMV (4%). Only a single axo-axonal contact was identified. These findings add to the increasing body of evidence that bombesin is a neurotransmitter/neuromodulator in the NTS/DMV complex. Bombesin rarely makes presynaptic (axo-axonal) contacts that might inhibit the release of excitatory neurotransmitters, but rather makes postsynaptic contacts potentially effecting vagal motoneurons.

Peptidergic innervation of the mesencephalic trigeminal nucleus in the cat.

BACKGROUND: The trigeminal processing of proprioceptive information is unique and very little is known about the neurochemical organization of trigeminal primary afferent neurons which mediate the sensory aspects of proprioception. In studies using immunocytochemicalretrograde tracing techniques, some classical neurotramsitters mediating the afferent modulation of the mesencephalic trigeminal nucleus (MTN) have been investigated. This paper summarizes our current understanding of the peptidergic innervation of the cat MTN. METHODS: The distribution of immunoreactive substances was studied using specific antisera against 11 major neuropeptides. Light and electron microscopic peroxidase-antiperoxidase immunocytochemical staining techniques in colchicine-treated animals were used to clarify the distribution of peptide-identified fibers related to the MTN. RESULTS: Immunoreactivity to any of the tested neuropeptides could not be detected in the MTN cell bodies. Numerous fibers containing various peptides such as substance P, bombesin, enkephalins, cholecystokinin, vasoactive intestinal polypeptide, vasopressin, and neuropeptide Y were present in the nucleus, however. These thin positive fibers covered the neuronal surface of the MTN cell bodies and some of the immunoreactive varicosities appeared to be in close proximity to profiles of MTN neurons. Electron microscopic observations revealed that perisomatic fibers were in direct apposition to perikarya of unstained large cells and some of them made synaptic contacts with their cell bodies and dendrites. CONCLUSIONS: The present results demonstrate that the MTN neurons receive dense basket-like innervation from peptidergic neurons on somata and processes and have supported earlier evidence that the MTN of the cat is under influence of peptidergic input. Results of this study provide further evidence that the neuropeptides examined may play an important role in the integration and transmission of trigeminal proprioceptive information. Most likely they may co-exist with a classical but hitherto unknown neurotransmitter(s), that is unique for this region and whose release can be modulated by peptides.

Distribution of some neuropeptides in the porcine inferior mesenteric ganglion.

The occurrence and distribution of vasoactive intestinal polypeptide, substance P, and bombesin/gastrin-releasing peptide in neuronal cell bodies and nerve fibers of the porcine inferior mesenteric ganglion were studied with the indirect immunohistochemical technique. Of all substances studied only vasoactive intestinal polypeptide was found in principal ganglionic neurons. The presence of nerve fibers immunoreactive to vasoactive intestinal polypeptide, bombesin/gastrin-releasing peptide, and substance P was also found in the ganglion. There were differences in the pattern of distribution and density of the nerve fibers immunoreactive to the particular peptides. Fibers containing vasoactive intestinal polypeptide and bombesin/gastrin-releasing peptide were numerous, while fibers containing substance P were comparatively scarce. The present results revealed both similarities and specific differences in the occurrence and localisation of various neuropeptides in the porcine inferior mesenteric ganglion in comparison with that of other mammalian species.

Epitope mapping of the gastrin-releasing peptide/anti-bombesin monoclonal antibody complex by proteolysis followed by matrix-assisted laser desorption ionization mass spectrometry.

We have developed a method to rapidly identify the antigenic determinant for an antibody using in situ proteolysis of an immobilized antigen-antibody complex followed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI/TOF). A mouse anti-bombesin monoclonal antibody was immobilized to agarose beads and then the antigen, gastrin-releasing peptide (GRP), was allowed to bind. Direct analysis of the immobilized antigen-antibody complex by MALDI/TOF is demonstrated and allows identification of ca. 1 pmol of the bound GRP. To identify the epitope, the immobilized antigen-antibody complex was subjected to proteolysis with trypsin, chymotrypsin, thermolysin, and aminopeptidase M. Following proteolysis, the part of the antigen in contact with the antibody and protected from proteolysis was identified directly by MALDI/TOF. Subsequently, the epitope was eluted from the immobilized antibody with 0.1 M glycine buffer (pH 2.3), separated by reversed-phase HPLC, and its identity confirmed by MALDI/TOF. Using this approach, the epitope for the anti-bombesin monoclonal antibody was shown to comprise the last 7-8 residues (HWAVGHLM-NH2) of GRP.

Phylogenetic aspects of the occurrence and distribution of secretogranin II immunoreactivity in lower vertebrate gut.

A novel monoclonal antibody raised against bovine secretogranin II (Sg II) was used in immunohistochemical studies on amphibian (Rana esculenta), reptilian (Podarcis sicula) and avian (Gallus gallus) gut. Sg II immunoreactivity was detected in epithelial and nervous elements. Cells immunoreactive for Sg II were examined by double immunostainings to determine whether they might also co-store certain previously known bioactive amine/peptide substances. Almost all the endocrine cells immunoreactive for bombesin, substance P, neurotensin, gastrin/cholecystokinin, neuropeptide tyrosine (NPY) and calcitonin gene-related peptide as well as some of those immunostained for serotonin, histamine, and polypeptide tyrosine tyrosine (PYY) also contained Sg II. Sg II-immunoreactive cells varied in number and distribution according to regions of the gut and animal species. The number of Sg II immunoreactive granules notably varied not only according to cell type, but also within the same cell population. Many histamine-, calcitonin gene-related peptide (CGRP)-, substance P-, PYY-, and neurotensin-immunoreactive neurons also contained Sg II. These were mostly situated in the myenteric plexus; their distribution pattern varied among the three species. These findings show that, despite being well conserved during phylogeny, Sg II has a heterogeneous distribution.

Distribution of gastrin-releasing peptide/bombesin-like immunoreactivity in the rainbow trout brain.

The distribution of gastrin-releasing peptide (14-27)/bombesin-like immunoreactivity was studied in the brain of the teleost Oncorhynchus mykiss using an indirect immunoperoxidase technique. Cell bodies were only found in the hypothalamic nuclei posterioris periventricularis, the anterior part of the recessus lateralis, and in the recessus posterioris. Immunoreactive fibers were widely distributed in the diencephalon, midbrain, and hindbrain. The highest density of immunoreactive fibers was found in the hypothalamus, whereas a moderate to low density of fibers was visualized in the periventricular thalamus. In the midbrain, a moderate density of fibers was observed at the level of the nuclei lateralis and centralis of the torus semicircularis, the stratum album centrale of the optic tectum, the nucleus of the rostral mesencephalic tegmentum, the nuclei lateralis valvulae, the lemnisci lateralis, istmi and locus coeruleus, as well as in the hindbrain at the level of the nuclei gustatorius secundarius, cerebelli, descendens nervi trigemini, and funiculi lateralis. These data suggest that the peptide could be involved in neuroendocrine (LT, nRL, nRP), visual (OT, nRTM, TS, Is), auditory (TS), and nociceptive (Vd, nufl) mechanisms.

Anti-bombesin monoclonal antibodies modulate fetal mouse lung growth and maturation in utero and in organ cultures.

Fetal pulmonary neuroendocrine cells (PNECs) contain abundant gastrin-releasing peptide (GRP, mammalian bombesin-like peptide [BLP]). Previously, addition of bombesin resulted in increased fetal lung growth and maturation in utero and in organ cultures. A monoclonal antibody (mAb) to bombesin (2A11) blocked baseline automaturation of lung organ cultures in serum-free medium. In the present study, we analyze lung development following daily in utero administration of 2A11 from gestational days 15-18. Fetal lung treated with 2A11 and then harvested on day 18 demonstrated a dose-dependent decrease in surfactant phospholipid synthesis compared to controls treated with MOPC, an unreactive mAb. However, 2A11-treated fetal lung harvested on day 17 showed paradoxical increases in 3H-choline incorporation into saturated phosphatidylcholine, 3H-thymidine incorporation into DNA, and relative numbers of differentiated type II pneumocytes. In serum-containing day 17 lung organ cultures, 2A11 stimulated choline and thymidine incorporation. Since epidermal growth factor (EGF) is the only agent besides bombesin known to stimulate both fetal lung growth and maturation, we added EGF to serum-free cultures and reconstituted the stimulatory effects. A murine EGF receptor mAb (ERA) blocked 2A11-induced lung growth and maturation in serum-containing cultures, and this effect was overcome by adding EGF. In vivo, ERA also blocked stimulatory effects of 2A11 in fetal lung on day 17. These observations suggest that EGF receptor up-regulation may maintain lung growth and maturation if BLP levels are diminished on day 17. Nonetheless, BLPs appear to be involved in lung maturation on day 18, supporting a role for PNECs in normal lung development.

Synthesis and immunological properties of bombesin analogs.

Bombesin (Bn, pGlu-Gln-Arg-Leu-Gly-Asn-Gln-Trp-Ala-Val-Gly-His-Leu-Met-NH2) is one of the most potent peptides, possessing a variety of physiological and pharmacological functions. We find from CD spectroscopy that the eight C-terminal residues of bombesin [Bn(7-14)NH2] have an ordered structure, and replacement of His-12 with Pro of Bn(7-14)NH2 changes the conformation from ordered to a more unordered form. Antibodies to Bn(7-14)NH2 cross-react to Bn and gastrin releasing peptide (GRP) in a dose-dependent manner. Antibodies to the Pro-analog do not recognize Bn or GRP. Substitution of the C-terminal amide by isopropylamide [Bn(7-14)NHC3H7(i)] makes its antibodies more specific to Bn than to GRP. It appears that this region of the peptide is an important antigenic determinant, which makes these antibodies differentiate between BN and GRP.