- Email: [email protected]
Aberrant processing of the pancreatic polypeptide precursor in the African clawed frog, Xenopus laevis
270
ULTRASTRUCTURAL LOCALISATION OF NEUROPEPTIDE IMMUNOREACTIVITIES IN THE NEMATODE ROUNDWORM, ASCAR1S SUUM BY IMMUNOGOLD LABELLING. D. J. A. BROWNLEE, G. P. BRENNAN, I. FAIRWEATHER, C. F. JOHNSTON & D. W. HALTON. Comparative Neuroendocrinology Research Group, Queen's University, Belfast BT7 INN. Ascaris is an important helminth parasite of man infecting more than one billion people
worldwide. Although the gross anatomy of the nematode nervous system is well established, little is known about its ultrastructure. Transmission electron microscopy (TEM) has revealed that the anterior nerve ring (ANR) is composed of a neuropile of nerve axons and an outer rind of nerve cell bodies. From the nerve ring arise ventral, dorsal, and lateral nerve cords, comprising a series of parallel nerve axons and neuromuscular connections. Previous studies have indicated the presence of neurosecretory (peptidergic) cells in the NS of Ascaris. More recently, a number of neuropeptides have been demonstrated in Ascaris by immunocytochemical techniques. They include pancreatic polypeptide (PP), peptide YY (PYY), neuropeptide Y (NPY), substance P (SP), cholecystokinin (CCK) and FMRFamide; with the major distribution of immunoreactivity occurring with members of the NPY superfamily and the invertebrate peptide, FMRFamide. The ultrastructural distribution of PP- and FMRFamide-immunoreactivity have been examined using immunogold labelling techniques. Labelling was obtained with both PP and FMRFamide antisera within cell bodies, nerve axons, and nerve terminals of the main ganglia and nerve cords in the CNS. The labelling was specific; in all cases the gold probe was confined to dense-cored vesicles. The results indicate that peptide immunoreactivities localised by immunocytochemical techniques at the light level are present within neuronal vesicles. They also confirm the putative neurotransmitter/neuromodulatory roles for peptides suggested by previous studies and emphasize the importance of neuropeptides in the neurobiology of Ascaris.
ABERRANT PROCESSING OF THE PANCREATIC POLYPEPTIDE PRECURSOR IN THE AFRICAN CLAWED FROG, XENOPUS LAEVIS
C.Shaw I, B.McCorry I, D.W.Halton I, L.Thim 2 and R.Tinsley 3, Icomparative Neuroendocrinology Research Group, The Queen's Universit~ of Belfast, Northern Ireland, 2Novo Nordisk A/S, Bagsvaerd, Denmark and Queen Mary and Westfield College, University of London, U.K. The primary structures of two anuran amphibian pancreatic polypeptides (PP) have been established from the American bullfrog (Rana catesbe~ana) and the European common frog (Rana temporaria). Gel permeation chromatography (GPC) of pancreatic extracts of both frogs resolved a single major immunoreactive peptide, coeluting with bovine PP, which was homogenous during sequential reverse phase HPLC. In contrast, GPC of pancreatic extracts from X.laevis resolved two immunoreaetants, the larger of which was of apparently greater molecular weight than other amphibian PPs. This predominant immunoreactant was homogenous during HPLC purification and, although no sequence data were obtained, a molecular mass of 5913 Da was obtained by mass spectroscopy. This is significantly larger than all known PPs. Reverse phase HPLC analysis of the lower molecular weight immunoreactant found it to be highly-heterogenous. The PP antiserum employed is C-terminal amide-dependent implying that all immunoreactive peptides were C-terminally amidated. In conclusion, the pancreatic polypeptide precursor of X. laevis appears to be aberrantly processed resulting in the predominance of an N-terminally extended peptide. This finding may be relevant in the unravelling of the evolutionary pathway of the NPY/PP superfamily in vertebrates.
ULTRASTRUCTURAL LOCALISATION OF NEUROPEPTIDE IMMUNOREACTIVITIES IN THE NEMATODE ROUNDWORM, ASCAR1S SUUM BY IMMUNOGOLD LABELLING. D. J. A. BROWNLEE, G. P. BRENNAN, I. FAIRWEATHER, C. F. JOHNSTON & D. W. HALTON. Comparative Neuroendocrinology Research Group, Queen's University, Belfast BT7 INN. Ascaris is an important helminth parasite of man infecting more than one billion people
worldwide. Although the gross anatomy of the nematode nervous system is well established, little is known about its ultrastructure. Transmission electron microscopy (TEM) has revealed that the anterior nerve ring (ANR) is composed of a neuropile of nerve axons and an outer rind of nerve cell bodies. From the nerve ring arise ventral, dorsal, and lateral nerve cords, comprising a series of parallel nerve axons and neuromuscular connections. Previous studies have indicated the presence of neurosecretory (peptidergic) cells in the NS of Ascaris. More recently, a number of neuropeptides have been demonstrated in Ascaris by immunocytochemical techniques. They include pancreatic polypeptide (PP), peptide YY (PYY), neuropeptide Y (NPY), substance P (SP), cholecystokinin (CCK) and FMRFamide; with the major distribution of immunoreactivity occurring with members of the NPY superfamily and the invertebrate peptide, FMRFamide. The ultrastructural distribution of PP- and FMRFamide-immunoreactivity have been examined using immunogold labelling techniques. Labelling was obtained with both PP and FMRFamide antisera within cell bodies, nerve axons, and nerve terminals of the main ganglia and nerve cords in the CNS. The labelling was specific; in all cases the gold probe was confined to dense-cored vesicles. The results indicate that peptide immunoreactivities localised by immunocytochemical techniques at the light level are present within neuronal vesicles. They also confirm the putative neurotransmitter/neuromodulatory roles for peptides suggested by previous studies and emphasize the importance of neuropeptides in the neurobiology of Ascaris.
ABERRANT PROCESSING OF THE PANCREATIC POLYPEPTIDE PRECURSOR IN THE AFRICAN CLAWED FROG, XENOPUS LAEVIS
C.Shaw I, B.McCorry I, D.W.Halton I, L.Thim 2 and R.Tinsley 3, Icomparative Neuroendocrinology Research Group, The Queen's Universit~ of Belfast, Northern Ireland, 2Novo Nordisk A/S, Bagsvaerd, Denmark and Queen Mary and Westfield College, University of London, U.K. The primary structures of two anuran amphibian pancreatic polypeptides (PP) have been established from the American bullfrog (Rana catesbe~ana) and the European common frog (Rana temporaria). Gel permeation chromatography (GPC) of pancreatic extracts of both frogs resolved a single major immunoreactive peptide, coeluting with bovine PP, which was homogenous during sequential reverse phase HPLC. In contrast, GPC of pancreatic extracts from X.laevis resolved two immunoreaetants, the larger of which was of apparently greater molecular weight than other amphibian PPs. This predominant immunoreactant was homogenous during HPLC purification and, although no sequence data were obtained, a molecular mass of 5913 Da was obtained by mass spectroscopy. This is significantly larger than all known PPs. Reverse phase HPLC analysis of the lower molecular weight immunoreactant found it to be highly-heterogenous. The PP antiserum employed is C-terminal amide-dependent implying that all immunoreactive peptides were C-terminally amidated. In conclusion, the pancreatic polypeptide precursor of X. laevis appears to be aberrantly processed resulting in the predominance of an N-terminally extended peptide. This finding may be relevant in the unravelling of the evolutionary pathway of the NPY/PP superfamily in vertebrates.