Microdialysis of extracellular endogenous opioid peptides from rat brain in vivo

The combination of microdialysis and a highly sensitive radioimmunoassay was developed in order to monitor the in vivo extracellular levels of endogenous opioid peptides from discrete regions of the rat brain. The radioimmunoassay cross-reacts 100% with peptides with alpha N-acetyl Tyr.Gly.Gly.Phe-Met or -Leu at the N terminus and thus recognizes all known endogenous opioid peptide fragments following acetylation of the sample. The assay was conducted on solid phase with antibody bound via protein A to 96-well plates and provided a limit of detection of approximately 0.2 fmol. A variety of dialysis membranes were evaluated with respect to their efficiency in recovering opioid peptides in vitro. Custom-made probes (4 mm active length) manufactured from polyacrylonitrile membranes and commercially available polycarbonate membrane probes proved most suitable with relative recoveries for [Met]- and [Leu]enkephalin in the range 6-10% at a flow rate of 2.7 microliters/min. Probes implanted in the globus pallidus/ventral pallidum of halothane/N2O anaesthetized rats recovered approximately 1.5 fmol of immunoreactive opioid material per 30-min sample in the absence of peptidase inhibitors. The majority of this immunoreactivity co-eluted with [Met]- and [Leu]enkephalin on reverse-phase high-performance liquid chromatography. A 2-min pulse of 100 mM K(+)-containing artificial cerebrospinal fluid in the perfusion medium during a 30-min sampling period increased the recovered immunoreactive material to 43.9 fmol +/- 12.4 S.E.M. A second stimulation 3 h later also resulted in elevated levels with an S2:S1 ratio of 0.64 +/- 0.03. The second stimulation was completely blocked by perfusion of a 10 mM EGTA-containing medium, basal release on average remaining unaffected.(ABSTRACT TRUNCATED AT 250 WORDS)

BAM-18: analgesia, hyperalgesia and locomotor effects

BAM-18, a proenkephalin A-derived opioid peptide, is widely distributed throughout rat CNS and displays high affinity for both mu and kappa opioid receptors. In the present study, BAM-18 was tested in two analgesia paradigms, tail-flick and hot-plate. Injections were centrally administered through a chronically implanted unilateral cannula in the lateral ventricle. In the tail-flick, low doses of BAM-18 (5 micrograms) produced a hyperalgesia while high doses of BAM-18 (50 micrograms) produced an analgesic response. Naloxone (10 mg/kg, s.c.) reversed the BAM-18-induced analgesia and unmasked a persistent hyperalgesia. Morphine-induced (1 microgram) analgesia was completely reversed by 5 micrograms BAM-18. In the hot-plate test, high doses of BAM-18 produced analgesia, with no hyperalgesia observed at any dose. Naloxone reversed the BAM-18-induced analgesia. The locomotor effects of BAM-18 did not differ from those of morphine except in effective dose (50 micrograms vs. 5 micrograms, respectively). Opioid and non-opioid effects of BAM-18 are discussed and compared with other endogenous peptides.

A clinical instrument for multi-element in vivo analysis by prompt, delayed and cyclic neutron activation using 252Cf

The design and construction of a versatile clinical instrument for multi-element in vivo neutron activation analysis of major and minor body elements is described. A 200 micrograms (4 GBq) 252Cf neutron source is stored below ground level and pneumatically propelled to one of two irradiation ports. These deliver collimated beams of fast neutrons either to a localised volume such as the liver or kidney, or across the width of a patient for a head-to-toe scanning whole-body measurement. The source control system allows selection of either a continuous or cyclic mode of activation. The instrument is intended primarily for measurement, by the prompt-gamma technique, of total and partial body calcium, total body nitrogen and partial body cadmium. The potential of the instrument for determination of these three elements has been established. Phantom results suggest that total body calcium can be measured with a precision of +/- 2.6% (CV) for an average whole-body skin dose equivalent of 6.4 mSv; total body nitrogen with a precision of +/- 2.0% for an average whole-body skin dose equivalent of less than 0.4 mSv; and a detection limit (2 SD of the background) of 2.4 mg of cadmium in the kidney has been obtained for a radiation dose equivalent to the skin of 3 mSv (QF = 10). The suitability of this instrument for the measurement of other elements is also discussed.

Pharmacological properties of a proenkephalin A-derived opioid peptide: BAM 18

BAM 18 is a derivative of the opioid precursor proenkephalin A. Although it exists in rat and guinea-pig brain in relatively high concentrations, its physiological function is presently unknown. In the present study we have determined the opioid receptor selectivity of this peptide using radioligand binding and peripheral tissue bioassay. When selective binding conditions were used, BAM 18 bound to the mu opioid receptor with an affinity three times that of the kappa opioid receptor and over 10 times that of the delta opioid receptors (Ki = 0.29, 0.75, and 3.2 nM respectively). BAM 18 also displayed mixed receptor selectivity in in vitro bioassay. Ke values for naloxone antagonism of BAM 18 agonist activity in the electrically stimulated guinea-pig ileum and the mouse vas deferens were 4.3 and 9.9 nM, respectively. These data indicate that BAM 18 binds to all three opioid receptor subtypes with a selectivity profile of mu greater than kappa greater than delta.

Isolation of enzyme cDNA clones by enzyme immunodetection assay: isolation of a peptide acetyltransferase

The biological activity of many proteins and peptides can be profoundly affected by enzyme-catalyzed covalent modifications such as acetylation, sulfation, glycosylation, or amidation. This article describes the cloning of such an enzyme, a peptide acetyltransferase from rat brain that catalyzes the amino-terminal acetylation of endorphins and perhaps other substrates in vivo. Blot-hybridization analysis suggests that the mRNA encoding the acetyltransferase is approximately 2.0 kilobases, is present in whole rat brain and rat hypothalamus, and is slightly larger in mouse AtT20 tumor cells. The acetyltransferase was cloned by using a strategy whereby a cDNA expression library was screened with a solid-phase enzyme-activity assay; this technique combines the use of the substrate coupled to a solid support and subsequent recognition of the product by using a specific antiserum. We have called this method the enzyme immunodetection assay (EIDA). The EIDA should prove useful in the isolation of other clones for proteins that possess enzymatic activity upon expression in bacterial hosts.

Cloning and sequence analysis of cDNA for bovine carboxypeptidase E

Carboxypeptidase E (enkephalin convertase) was first identified as the carboxypeptidase B-like enzyme involved in the biosynthesis of enkephalin in bovine adrenal chromaffin granules. A similar enzyme is present in many brain regions and in purified secretory granules from rat pituitary and rat insulinoma. Within the secretory granules, carboxypeptidase E (CPE) activity is found in both a soluble and a membrane-bound form, which differ slightly in relative molecular mass (Mr). Here, to investigate whether the CPE activities in the various tissues are produced from a single gene, purified CPE was partially sequenced and oligonucleotide probes were used to isolate a clone encoding CPE from a bovine pituitary complementary DNA library. This cDNA hybridizes to bovine pituitary poly(A)+ RNAs of approximately 3.3, 2.6 and 2.1 kilobases (kb), with the 3.3-kb messenger RNA the predominant species. The predicted amino-acid sequence of the cDNA clone contains the partially determined sequences of CPE, several pairs of basic amino acids and displays some homology with both carboxypeptidases A and B. Restriction analysis of bovine genomic DNA suggests only one gene for CPE. This is consistent with a broad role for CPE in the biosynthesis of many neuropeptides.

The effect of infant formula samples on breastfeeding practice

To determine whether infant formula samples affect breastfeeding practice, 95 breastfeeding mothers were randomly assigned to receive or not receive formula samples on discharge from a postpartum unit. Unaware of the specific nature of the study, these mothers were interviewed by telephone six to seven weeks postpartum by an investigator blind to the randomization status. Although more women who had discontinued breastfeeding were among the group who had received samples than those who had not received samples, the difference was not statistically significant. Significant differences were not found in three subgroups hypothesized to be more vulnerable to the samples: less educated women, primiparas, and women who were ill postpartum.

Unexpected mobilisation of lead during cisplatin chemotherapy

During an investigation by X-ray fluorescence of platinum uptake in the kidney after chemotherapy with cisplatin, lead was found to have accumulated in the kidney in four subjects. The average kidney lead burden in one case exceeded 800 micrograms/g. Although two of the subjects had been occupationally exposed to lead, the other two had not. The tibia lead burden was also high in the two subjects in whom it was measured. The origins of this mobilised lead and the implications for cisplatin nephrotoxicity are discussed.

Effects of beta-endorphin on ornithine decarboxylase in tissues of developing rats: a potential role for this endogenous neuropeptide in the modulation of tissue growth

Ornithine decarboxlyase (ODC) catalyzes the initial step in the bio-synthesis of the polyamines spermidine and spermine, which are key regulators of cell growth, proliferation and differentiation. Intracisternal administration of beta-endorphin (1 microgram) to 6 day-old rats markedly decreased brain, liver, heart and kidney ODC activity. Conversely, subcutaneous administration of beta-endorphin increased ODC activity in the heart and liver. Thus, ODC inhibition in peripheral organs in rat pups given beta-endorphin intracisternally appears to reflect central effects of this neuropeptide. Experiments were also carried out to test whether opioid receptors are involved in these tissue ODC responses. Naloxone prevented the decreases in brain ODC indicating the participation of opioid receptors in that process. In contrast, naloxone did not alter ODC responses in peripheral organs in rat pups given beta-endorphin intracisternally, indicating that these effects are independent of its classical opioid character. These results support the view that endogenous beta-endorphin may play an important role in organogenesis by modulating the growth-related enzyme ODC. The data also suggest that the regulation of peripheral organ development by beta-endorphin may be mediated through the release of growth regulatory substances from the CNS.

Proteolytic processing of a peptide precursor in Aplysia neuron R14

The large neurons of the mollusc Aplysia are useful for studying the biogenesis of neuropeptides in single cells. Neuron R14 in the abdominal ganglion synthesizes large quantities of a 10-kDa neuropeptide precursor. The amino acid sequence of this precursor has been defined by analysis of the nucleotide sequence of a cDNA clone. We labeled proteins in vivo by microinjection of radioactive amino acids into individual R14 neurons. The labeled peptides were fractionated by high performance liquid chromatography and subjected to Edman degradation, thus enabling us to determine post-translational processing sites. Cleavage of the signal sequence was observed and at two internal sites. Cleavage at these internal sites occurs at basic amino acids and results in three products, a 2.9-, a 4.9-, and a 1.4-kDa peptide. These studies of protein processing serve as a basis for further investigations of the biogenesis and physiological activities of the neuropeptides.

Selection and performance of monoclonal and polyclonal antibodies in an IgM antibody capture enzyme immunoassay for rubella

Monoclonal anti-human IgM and anti-rubella antibodies were prepared and tested in an IgM capture enzyme immunoassay (MACEIA) for rubella-specific IgM and compared with polyclonal reagents. Assay sensitivity was increased with monoclonal antibodies resulting in the improved discrimination of adult sera with low levels of specific IgM. Despite high IgM binding, interference by IgM anti-Ig was not a major problem. The use of monoclonal antibodies allowed assay simplification by the simultaneous rather than sequential addition of antigen and conjugate. Although comparable results were obtained with 33 test samples in the sequential and simultaneous MACEIA, the specificity and sensitivity of this modification requires further evaluation.

Characterization of endorphins from the pituitary of the spiny dogfish Squalus acanthias

Opioid-like immunoreactive material was extracted from the pituitary and brain of the Spiny Dogfish Shark Squalus acanthias. The immunoreactive material in the pituitary extracts was purified to apparent homogeneity by reverse phase high performance liquid chromatography and subsequently characterized by amino acid analysis, Edman degradation and fast atom bombardment mass spectrometry. The largest opioid-like peptide isolated contained 30 amino acids and showed 80 percent homology with salmon endorphin-II but less than 50 percent homology with human beta-endorphin. Three structural variants of this molecule were also characterized. These variants were shown to be shorter N-terminal fragments, two of which corresponded to cleavage products at the single basic residues arginine and lysine. Cleavage at a single lysine residue has not been reported for posttranslational processing of beta-endorphin in mammals and could represent a modification seen only in lower vertebrates. The remaining fragment corresponded to a loss of 3 residues from the C-terminus of the parent molecule. No alpha-N-acetylated peptides were detected. These results provide the first unequivocal confirmation of beta-endorphin in an elasmobranch and provide evidence of novel N-terminal variants of beta-endorphin.

Co-localization and characterization of immunoreactive peptides derived from two opioid precursors in guinea pig adrenal glands

Peptides derived from both proenkephalin and prodynorphin have been identified in guinea pig adrenal medulla. In extracts of whole adrenal glands radioimmunoassays directed to the prodynorphin-derived peptides alpha-neoendorphin, dynorphin A, and dynorphin B detected high concentrations of immunoreactive material ranging from 113 to 216 pmol/gm. The concentrations measured by radioimmunoassays directed to the proenkephalin products met-enkephalin-Arg-Gly-Leu and met-enkephalin-Arg-Phe were 878 and 484 pmol/gm, respectively. No metorphamide or dynorphin(1-8) could be detected in the adrenals. Leucine-enkephalin immunoreactivity which can be generated from either prodynorphin or proenkephalin could also be measured in the extracts. Gel filtration showed the immunoreactive material, with the exception of that measured by the alpha-neoendorphin radioimmunoassay, to be predominantly of high molecular weight ranging from Mr = 3,000 to 12,000. Immunocytochemistry, using well characterized antisera to alpha-neoendorphin and met-enkephalin-Arg-Gly-Leu, demonstrated that the prodynorphin and proenkephalin products were present in the same cells in the medulla region of the gland. The results show that two opioid peptide precursors can be localized in the same cells and exhibit some common features in their processing. As a relatively homogeneous, localized system, the guinea pig adrenal gland should prove a valuable, in vivo model for the study of co-localized opioid precursors.

A feasibility study for the in vivo measurement of beryllium by photonuclear activation

Diagnosis of the beryllium-induced disease, berylliosis, is often difficult and always requires that the presence of the metal in tissue be demonstrated. The feasibility of developing an in vivo method of measurement, which exploits the uniquely low photonuclear reaction threshold of 1.67 MeV in beryllium, has been investigated. Suitable photon sources and detector systems were assessed, both experimentally by phantom studies and theoretically by use of a Monte-Carlo neutron transport code. It is concluded that by using a filtered source of 124Sb for bilateral irradiation of the chest, and an array of twenty BF3 counters, beryllium could be measured to an accuracy of 0.33 mg per lung, which corresponds to a 2 SD detection limit of 0.67 mg, for a skin dose of 50 mGy delivered within a period of 90s. Such a facility would be capable of contributing to the aetiology of the disease in a large proportion of cases, but the wider use of the method for screening exposed workers would require further improvements in detection efficiency.

Effects of dehydration on pro-dynorphin derived peptides in the neuro-intermediate lobe of the rat pituitary

Dehydration significantly reduced the concentration of immunoreactive dynorphin A(1-17), dynorphin A(1-8), alpha-neo-endorphin, beta-neo-endorphin, and leu-enkephalin in the rat pituitary posterior-intermediate lobe. A statistically significant increase in immunoreactive dynorphin A(1-8), alpha-neo-endorphin and leu-enkephalin was observed in the hypothalamus. Comparison of the molar ratios of dynorphin A(1-17): dynorphin A(1-8) and alpha-neo-endorphin: beta-neo-endorphin showed an altered profile of stored pro-dynorphin cleavage products in the posterior-intermediate lobe of the pituitary of dehydrated rats.

Detection of Ca antigen in sera from normal individuals and patients with benign and malignant breast disease

Two assay procedures, an inhibition radioimmunoassay (Inhibition-RIA) and an immunoradiometric assay (IRMA), were established for the detection of circulating tumour-associated Ca antigen. There was a good correlation between results (r = 0.987) but the Inhibition-RIA was selected for extended tests on human sera from patients with breast disease because of its greater ease and economy in use. Circulating Ca antigen was not exclusive to malignancy and the level failed to discriminate between patients with primary carcinoma and those with benign disease. Ca antigen was present in sera of 100 healthy individuals (median 7.1 micrograms ml-1, range 1.8-24.4 micrograms ml)-1, 39 patients with benign disease (median 9.9 micrograms ml-1, range 2.5- greater than 100 micrograms ml-1) and in 67 patients with primary carcinoma (median 11.0 micrograms ml-1, range 3.8- greater than 100 micrograms ml-1). Elevated Ca antigen levels were found in 50% of patients with metastatic spread (median 30.7 micrograms ml-1, range 8.2- greater than 100 micrograms ml-1) and in some patients with primary disease but further studies are needed to determine the prognostic significance. Immunochemical studies confirmed that Ca antigen is a normal serum product but its function is unclear.

Isolation and characterization of an endogenous C-terminal fragment of the alpha-neo-endorphin/dynorphin precursor from bovine caudate nucleus

Antibodies have been raised to a synthetic peptide corresponding to the C-terminal 15-amino acid residues of prodynorphin, the common precursor to the neo-endorphins and dynorphins. The amino acid sequence of the antigen was based on the sequence deduced from mRNA isolated and cloned from porcine hypothalamus (Kakidani, H., Y. Furutani, H. Takahashi, M. Noda, Y. Morimoto, T. Hirose, M. Asai, S. Inayama, S. Nakanishi, and S. Numa (1982) Nature 298: 245-248). Using a radioimmunoassay developed from these antibodies we have isolated an endogenous prodynorphin C-fragment from bovine caudate nucleus. The isolated peptide displayed characteristics on gel filtration similar to those of synthetic prodynorphin C-fragment predicted from the porcine mRNA sequence but had low cross-reactivity in the radioimmunoassay. Sequencing and amino acid analysis showed a substitution of serine for asparagine at position 6 in the porcine sequence. Dynorphin B (rimorphin), which is adjacent to prodynorphin C-fragment in the precursor, was isolated from the same extract. Amino acid analysis and elution position on a gel filtration column confirmed its structure as that previously characterized from bovine pituitary extracts. The release of prodynorphin C-fragment and the C-terminus of dynorphin B from the porcine precursor would require cleavage at a single arginine residue. However, a terminal arginine was not present on either of these prodynorphin peptides isolated from bovine caudate. The data would suggest that processing at a single arginine residue results in elimination of the arginine, a feature in common with processing at paired basic residues.

Isolation and structure of a novel C-terminally amidated opioid peptide, amidorphin, from bovine adrenal medulla

Biologically active peptide hormones and neurotransmitters have been shown to be enzymatically liberated from larger, inactive precursor molecules by tissue-specific post-translational processing, particularly at the typical cleavage signals of paired basic residues. Subsequent N-terminal or C-terminal modifications may be of importance in regulating the biological activities of these peptides. C-terminal alpha-amidation is considered to be essential for the biological function of several non-opioid peptides. Here we present the isolation and structure of a novel C-terminally amidated opioid peptide, amidorphin, from bovine adrenal medulla. Amidorphin and the recently isolated octapeptide metorphamide (adrenorphin) are the only endogenous opioid peptides in mammals known to possess a C-terminal amide group. The amino acid sequence of amidorphin corresponds to the sequence 104-129 of bovine proenkephalin A. Very high concentrations of amidorphin were detected in bovine adrenal medulla and in a further endocrinological system, the hypothalamic-neurohypophyseal axis. Amidorphin may therefore be considered to be a major gene product of the opioid peptide precursor proenkephalin A in these endocrine tissues.

Gastrin-releasing peptide, a mammalian analog of bombesin, is present in human neuroendocrine lung tumors

Several reports have indicated that the amphibian peptide bombesin is present in oat-cell carcinoma of the human lung. The recent observation that gastrin-releasing peptide (GRP), a 27-amino acid peptide isolated from porcine intestine, may be the mammalian analog of bombesin led the authors to look for this peptide in human pulmonary tumors. Examination of 36 human lung tumors (8 carcinoids, 8 oat-cell carcinomas, and 20 non-oat-cell carcinomas) by immunohistochemistry and radioimmunoassay demonstrated the presence of high, although variable, levels of GRP in neuroendocrine tumors, and not in other histologic types. These findings indicate that bombesin immunoreactivity in human lung tumors should be attributed to GRP or GRP-like molecules and that GRP may be a useful marker of neuroendocrine differentiation.

A putative processing enzyme from Aplysia that cleaves dynorphin A at the single arginine residue

A peptidase activity cleaving at single arginine residues has been detected in extracts of the atrial gland of Aplysia Californica. The enzyme assay consisted of incubation of enzyme with the mammalian opioid peptide dynorphin A and detection by specific radioimmunoassay of dynorphin (1-8), a single arginine cleavage product. The peptidase activity was characterized following chromatography on DEAE-cellulose. Activity was abolished by a thiol-directed inhibitor and chelators and activated by dithiothreitol and cobalt chloride. The pH optimum was 6.2 in phosphate buffer. Analysis of the products of two substrates suggested that cleavage was occurring on the amino side of the arginine residue.

Human chorionic gonadotropin secreted by preimplantation embryos cultured in vitro

Human oocytes were collected by laparoscopy and fertilized and cultured in vitro. Human chorionic gonadotropin was detected in the medium surrounding two embryos cultured for more than 7 days after fertilization.

Metorphamide: isolation, structure, and biologic activity of an amidated opioid octapeptide from bovine brain

Acid acetone extracts of caudate nucleus from bovine brain were found to contain an amidated opioid octapeptide with the following structure: Tyr-Gly-Gly-Phe-Met-Arg-Arg-Val-NH2. The peptide has been named metorphamide. Bovine metorphamide appears to be derived by proteolytic cleavage from proenkephalin, the common precursor to [Met5]enkephalin and [Leu5]enkephalin. The cleavage within the precursor giving rise to the carboxyl terminus of metorphamide occurs at a single arginine residue and is followed by transformation of a carboxyl-terminal glycine into an amide group. Metorphamide was detected in bovine caudate nucleus extracts by radioimmunoassay, and it was purified to homogeneity by gel filtration and reversed-phase high performance liquid chromatography. Amino acid composition analysis and automated Edman degradation in the gas-phase sequencer confirmed the postulated amino acid sequence. Carboxyl-terminal amidation of bovine metorphamide was shown by stability to carboxypeptidase A digestion and full crossreactivity in a radioimmunoassay that required the carboxyl-terminal amide as part of the recognition site. A synthetic replicate of metorphamide as well as several synthetic analogs were tested for opioid activity in several bioassays and binding assays, and metorphamide was found to have a high mu-binding activity. Metorphamide is the only known naturally occurring opioid peptide that has a high mu-binding activity. The kappa-binding activity is approximately equal to 50% that of the mu-binding activity, but delta-binding activity is negligible.