Search PubMed⌕ Search

Biomedical subjects

J M Conlon

Publications and source records attributed to J M Conlon.

At least 109 records · Page 6Linked to original sources
PubMed1997

Primary structure of insulin from the african lungfish, Protopterus annectens.

Among the extant Sarcopterygii, the interrelationship between the Dipnoi (lungfishes), Actinistia (coelacanths), and Tetrapoda (tetrapods) is controversial. Insulin has been purified from an extract of the pancreas of the African lungfish Protopterus annectens and its primary structure established as A-chain, Gly-Ile-Val-Glu-Gln-Cys-Cys-His-Lys-Pro10-Cys-Ser-Leu- Tyr -Glu-Leu-Glu-Asn-Tyr-Cys20-Asn-Val-Pro; and B-chain, Ala-Val-Leu-Asn-Gln-His-Leu-Cys-Gly-Ser10-His-Leu-Val- Glu- Ala-Leu-Tyr-Leu-Val-Cys20-Ala-Asp-Asn-Gly-Phe- Phe-Tyr-Lys-Pro-Ser30-Gly. Lungfish insulin contains unusual structural features, such as the dipeptide extension to the C-terminus of the A-chain and the substitution Arg --> Asn at position B-23 in the putative receptor binding region of insulin, which may be expected to influence appreciably its biological potency relative to mammalian insulins. Lungfish insulin also contains amino acid substitutions such as Gly --> Ala at position B-21, Glu --> Asp at position B-22, and a Lys --> Ser residue at position B-30, previously found in insulins from amphibia. This observation is consistent with paleontological data suggesting that lungfish and amphibia share a close phylogenetic relationship.

Amino Acid Sequence↗
PubMed1997

Multiple bradykinin-related peptides from the skin of the frog, Rana temporaria.

The skin of the European common frog, Rana temporaria, contains a very high concentration of bradykinin (BK) but the mode of biosynthesis of the peptide is unknown. In addition to BK, we have isolated from an extract of R. temporaria skin the metabolites [des-Arg9]BK and [hydroxyprolyl3]BK. Peptides were also isolated that represent partially processed intermediates in the biosynthetic pathway to BK and comprise BK extended from its N-terminus by -Gly-Val-Ile-Pro-Leu-Leu and three peptides comprising BK extended from its C-terminus by -Ile-Ala, by -Ile-Ala-Pro-Ala-Ser-Thr-Leu, and by -Ile-Ala-Pro-Ala-Ser-Ile-Leu. The isolation of two C-terminally extended BK-containing peptides differing by a single amino substitution indicates that the biosynthetic precursor of frog skin BK may contain more than one copy of the BK sequence and/ or more than one gene encoding BK is expressed. The structures of the biosynthetic intermediates suggest that BK in frog skin is generated by the action of cellular endoproteinase(s) cleaving at the site of monobasic residues rather than by the action of the kallikrein-kinin system.

Amino Acid Sequence↗
PubMed1997

Tachykinins (substance P, neurokinin A and neuropeptide gamma) and neurotensin from the intestine of the Burmese python, Python molurus.

Peptides with substance P-like immunoreactivity, neurokinin A-like immunoreactivity and neurotensin-like immunoreactivity were isolated in pure form from an extract of the intestine of the Burmese python (Python molurus). The primary structure of python substance P (Arg-Pro-Arg-Pro-Gln-Gln-Phe-Tyr-Gly-Leu- Met-NH2) shows one amino acid substitution (Phe8-->Tyr) compared with chicken/alligator substance P and an additional substitution (Lys3-->Arg) as compared with mammalian substance P. The neurokinin A-like immunoreactivity was separated into two components. Python neuropeptide gamma (Asp-Ala-Gly-Tyr- Ser-Pro-Leu-Ser-His-Lys-Arg-His-Lys-Thr-Asp-Ser-Phe-Val-Gly-Leu-Met-NH2 shows three substitutions (Gly5-->Ser, Gln6-->Pro and Ile7-->Leu) compared with alligator neuropeptide gamma and an additional substitution (His4-->Tyr) compared with mammalian neuropeptide gamma. Python neurokinin A (His-Lys-Thr-Asp-Ser-Phe-Val-Gly- Leu-Met.NH2) is identical to human/chicken/alligator neurokinin A. Python neurotensin (pGlu-Leu-Val-His-Asn-Lys-Ala-Arg-Pro-Tyr-Ile-Leu) is identical to chicken/alligator neurotensin. The data are indicative of differential evolutionary pressure to conserve the amino acid sequences of reptilian gastrointestinal peptides.

Animals↗
PubMed1997

Effects of trout bradykinin on the motility of the trout stomach and intestine: evidence for a receptor distinct from mammalian B1 and B2 subtypes.

1. Trout bradykinin ([Arg0, Trp5, Leu8]-bradykinin; trout BK), recently isolated from kallikrein-treated trout plasma, produced sustained and concentration-dependent contractions of isolated longitudinal muscle from rainbow trout stomach (pD2 = 7.01 +/- 0.03) and proximal small intestine (pD2 = 7.37 +/- 0.07). The maximum responses were 85 +/- 2% (stomach) and 101 +/- 35% (intestine) of the corresponding responses to 10(-5) M acetylcholine. Strips of circular smooth muscle from trout stomach and intestine did not contract in response to trout BK. 2. The potency of trout BK on gastric smooth muscle motility was significantly (5 fold; P < 0.01) reduced in the presence of the cyclo-oxygenase inhibitor, indomethacin (10(-5) M) and by 4 fold (P < 0.05) in the presence of the lipoxygenase inhibitor, MK-886 (10(-6) M), but there was no effect on the maximum response. Potency was also significantly reduced in the presence of 10(-6) M methysergide (3 fold; P < 0.02) and 10(-6) M tetrodotoxin (2 fold, P < 0.05) but atropine was without effect. 3. [Tyr0, Trp5, Leu8]-BK was a full agonist but was approximately 50 fold less potent (pD2 = 5.35 +/- 0.08) than trout BK, [Arg0, Trp5, Leu8]des-Arg9-BK was a partial) agonist (pD2 = 6.80 +/- 0.03; 56 +/- 7% of the maximum response to trout BK) but [Trp5, Leu8]-BK, [Trp5,Leu8]-des-Arg9-BK and mammalian BK produced no, or only very weak, contractions of the trout stomach. 4. The mammalian B1 receptor antagonist, [Leu8]des-Arg9-BK was without effect on the response of the trout stomach to trout BK. The potent mammalian B2 receptor antagonist Hoe 140 was a partial agonist (pD2 = 7.44 +/- 0.12; 57 +/- 15% of the maximum response to trout BK). 5. We conclude that the effects of trout BK on the motility of rainbow trout gastric smooth muscle are mediated through interaction with a receptor that has appreciably different ligand-binding properties than the mammalian B1 and B2 receptor subtypes. An involvement of arachidonic acid metabolites and 5-hydroxytryptaminergic nerves in the mechanism of action of the peptide is suggested.

Animals↗
PubMed1997

Purification, structural characterization, and cardiovascular activity of cod bradykinins.

Incubation of plasma from the Atlantic cod Gadus morhua with trypsin generated two peptides identified as [Trp5,Leu8]bradykinin (cod BK) and [Arg0,Trp5,Leu8]bradykinin (cod [Arg0]BK). Bolus intraarterial injections of synthetic cod [Arg0]BK (0.1-10 nmol/kg) into conscious cod produced an immediate increase in ventral aortic pressure that was of relatively short duration (<5 min) and an increase in heart rate. Cod [Arg0]BK was approximately 10 times more potent than cod BK, and the maximal pressor response produced by the peptide was significantly (P < 0.05) greater. Bolus intra-arterial injections of either mammalian BK or cod des-Arg9,[Arg0]BK, in doses up to 100 nmol/kg, had no effect on pressure or heart rate. The data indicate that the ligand binding properties of the BK receptors in cod are different from those of the mammalian B1- and B2-receptor subtypes. The pressor response to 1 nmol/kg cod [Arg0]BK was reduced (by 51 +/- 6%; P < 0.05) in prasozin-treated fish, whereas in enalapril-treated fish, the response to the peptide was enhanced (by 42 +/- 12%; P < 0.05). The data indicate an involvement of catecholamines but not an activation of the renin-angiotensin system in mediating the vasopressor action of BK in the cod.

Angiotensin I↗
PubMed1997

Cardiovascular effects of homologous bradykinin in rainbow trout.

Bradykinins have only recently been identified in fish, and a detailed analysis of their cardiovascular actions is lacking. The present study examines the cardiovascular effects of trout bradykinin ([Arg0,Trp5,Leu8]bradykinin; tBK) in conscious trout, Oncorhynchus mykiss. tBK (1-10 nmol/kg body wt bolus) produced triphasic pressor-depressor-pressor responses. In phase 1, cardiac output (CO), ventral aortic (P(VA)), dorsal aortic (P(DA)), and central venous pressure increased, whereas systemic (R(S)) and gill resistance (R(G)) were unchanged. In phase 2, R(G) increased, whereas R(S), CO, and heart rate decreased, reducing P(VA) and P(DA). Plasma prostaglandin E2 and the prostacyclin metabolite, 6-ketoprostaglandin F1alpha, were significantly elevated during phase 2, whereas leukotrienes C4 and B4 and thromboxane B2 were unaffected. Phase 3 was produced by an increased CO and R(S) and the return of R(G) to control. Phase 1 pressor response was not blocked by inhibitors of cyclooxygenase, angiotensin-converting enzyme (ACE) or alpha-adrenoceptors (alpha-AD), whereas phase 2 depressor and plasma prostaglandin responses were prevented by cyclooxygenase inhibition. Phase 3 was partially blocked by ACE and alpha-AD inhibitors and is a response to the preceding hypotension. In vitro, tBK only decreased vascular resistance in the perfused splanchnic or skeletal muscle-kidney preparations. These results show that although tBK has multiple effects on the trout cardiovascular system, none of the effects are due to direct tBK stimulation of vascular smooth muscle. Phase 2 vasodilation has features consistent with release of vasodilator prostaglandins while the mechanism of phase 1 constriction is unknown.

6-Ketoprostaglandin F1 alpha↗
PubMed1996

Mechanisms of smokeless tobacco-induced oral mucosa inflammation: role of bradykinin.

The purpose of this study was to determine whether an aqueous extract of smokeless tobacco (moist snuff) increases clearance of macromolecules from postcapillary venules in the in situ oral mucosa and, if so, whether bradykinin mediated this response. Using intravital microscopy, we found that 20-min suffusion of the extract elicited significant concentration-dependent leaky site formation and increase in clearance of FITC-dextran (molecular mass, 70 kDa) from the hamster cheek pouch (p < 0.05). These responses were associated with a significant increase in bradykinin-like immunoreactivity in the suffusate. Smokeless tobacco extract-induced leaky site formation and increase in clearance of FITC-dextran were significantly attenuated by NPC 17647 and Hoe 140 (p < 0.05), two bradykinin B2 receptor antagonists, but not by desArg9,[Leu8]bradykinin, a bradykinin B1 receptor antagonist. Both bradykinin B2 receptor antagonists had no significant effects on adenosine-induced responses. Indomethacin had no significant effects on smokeless tobacco extract-induced responses. Exposure to smokeless tobacco extract was associated with a significant decrease in angiotensin I-converting enzyme activity and a small, but significant, increase in neutral endopeptidase 24.11 activity in the cheek pouch, two peptidases widely distributed in the microcirculation that cleave and inactivate bradykinin (p < 0.05). Overall, these data suggest that smokeless tobacco elicits plasma exudation in the oral mucosa in vivo in a specific fashion, and that this response is mediated by bradykinin.

Animals↗
PubMed1996

Occurrence of two somatostatin variants in the frog brain: characterization of the cDNAs, distribution of the mRNAs, and receptor-binding affinities of the peptides.

In tetrapods, only one gene encoding a somatostatin precursor has been identified so far. The present study reports the characterization of the cDNA clones that encode two distinct somatostatin precursors in the brain of the frog Rana ridibunda. The cDNAs were isolated by using degenerate oligonucleotides based on the sequence of the central region of somatostatin to screen a frog brain cDNA library. One of the cDNAs encodes a 115-amino acid protein (prepro-somatostatin-14; PSS1) that exhibits a high degree of structural similarity with the mammalian somatostatin precursor. The other cDNA encodes a 103-amino acid protein (prepro-[Pro2, Met13]somatostatin-14; PSS2) that contains the sequence of the somatostatin analog (peptide SS2) at its C terminus, but does not exhibit appreciable sequence similarity with PSS1 in the remaining region. In situ hybridization studies indicate differential expression of the PSS1 and PSS2 genes in the septum, the lateral part of the pallium, the amygdaloid complex, the posterior nuclei of the thalamus, the ventral hypothalamic nucleus, the torus semicircularis and the optic tectum. The somatostatin variant SS2 was significantly more potent (4-6 fold) than somatostatin itself in displacing [125I-Tyr0, D-Trp8] somatostatin-14 from its specific binding sites. The present study indicates that the two somatostatin variants could exert different functions in the frog brain and pituitary. These data also suggest that distinct genes encoding somatostatin variants may be expressed in the brain of other tetrapods.

Amino Acid Sequence↗
PubMed1996

Molecular cloning of frog secretogranin II reveals the occurrence of several highly conserved potential regulatory peptides.

Secretogranin II (SgII) is an acidic secretory protein present in large dense core vesicles of neuronal and endocrine cells. Based on the sequence of a peptide derived from the processing of SgII in the brain of the frog Rana ridibunda, degenerate oligonucleotides were used to clone the cDNA encoding frog SgII from a pituitary cDNA library. This cDNA encodes a 574 amino acid protein which exhibits 46-48% sequence identity with mammalian SgII and contains 11 pairs of basic amino acids. Four potential processing products delimited by pairs of basic residues exhibited a much higher degree of identity (68-82%) with the corresponding mammalian SgII sequences. The frog SgII mRNA is approximately 4 kb in length and is differentially expressed in the brain and endocrine tissues. The present data reveal that several SgII-derived peptides have been highly conserved during evolution, suggesting that these peptides may play important neuroendocrine regulatory functions.

Amino Acid Sequence↗
PubMed1996

Urotensin II in the central nervous system of the frog Rana ridibunda: immunohistochemical localization and biochemical characterization.

Urotensin II (UII) is traditionally regarded as a product of the neurosecretory cells in the caudal portion of the spinal cord of jawed fishes. A peptide related to UII has been recently isolated from the frog brain, thereby providing the first evidence that UII is also present in the central nervous system of a tetrapod. In the present study, we have investigated the distribution of UII-immunoreactive elements in the brain and spinal cord of the frog Rana ridibunda by immunofluorescence using an antiserum directed against the conserved cyclic region of the peptide. Two distinct populations of UII-immunoreactive perikarya were visualized. The first group of positive neurons was found in the nucleus hypoglossus of the medulla oblongata, which controls two striated muscles of the tongue. The second population of immunoreactive cell bodies was represented by a subset of motoneurons that were particularly abundant in the caudal region of the cord (34% of the motoneuron population). The telencephalon, diencephalon, mesencephalon, and metencephalon were totally devoid of UII-containing cell bodies but displayed dense networks of UII-immunoreactive fibers, notably in the thalamus, the tectum, the tegmentum, and the granular layer of the cerebellum. In addition, a dense bundle of long varicose processes projecting rostrocaudally was observed coursing along the ventral surface of the brain from the midtelencephalon to the medulla oblongata. Reversed-phase high-performance liquid chromatography analysis of frog brain, medulla oblongata, and spinal cord extracts revealed that, in all three regions, UII-immunoreactive material eluted as a single peak which exhibited the same retention time as synthetic frog UII. Taken together, these data indicate that UII, in addition to its neuroendocrine functions in fish, is a potential regulatory peptide in the central nervous system of amphibians.

Animals↗
PubMed1996

Characterization of an insulin from the three-toed amphiuma (Amphibia: Urodela) with an N-terminally extended A-chain and high receptor-binding affinity.

Insulin was isolated from an extract of the pancreas of a urodele, the three-toed amphiuma (Amphiuma tridactylum), and its primary structure established as Ala-Arg-Gly-Ile-Val-Glu-Gln-Cys-Cys-His10-Asn-Thr-Cys- Ser-Leu-Asn-Gln-Leu-Glu-Asn20-Tyr-Cys-Asn for the A-chain and Ile-Thr-Asn-Gln-Tyr-Leu-Cys-Gly-Ser-His10-Leu-Val-Glu-Ala- Leu-Tyr-Leu-Val-Cys-Gly20-Asp-Arg-Gly-Phe-Phe-Tyr-Ser-Pro-Lys for the B-chain. The N-terminus of the A-chain is extended by two amino acids (Ala-Arg) relative to all other known insulins suggesting an anomalous pathway of post-translational processing in the region of the C-peptide/A-chain junction of proinsulin. In common with chicken and Xenopus insulins, which contain a HisA8, amphiuma insulin was more potent (approx. 5-fold) than porcine insulin in inhibiting the binding of [125I-TyrA14]insulin to the soluble human insulin receptor from transfected 293EBNA cells (an adenovirus-transformed human kidney cell line). This result is consistent with previous data showing that insulin analogues extended at GlyA1 by uncharged groups have reduced binding affinity whereas high affinity is preserved in analogues extended by basic amino acid residues.

Amino Acid Sequence↗
PubMed1996

Isolation and structural characterization of proglucagon-derived peptides, pancreatic polypeptide, and somatostatin from the urodele Amphiuma tridactylum.

The expression of the preproglucagon gene in vertebrates is markedly species- and tissue-dependent. Three peptides derived from the posttranslational processing of preproglucagon were isolated from an extract of the pancreas of the urodele Amphiuma tridactylum (threetoed amphiuma). The primary structures of the peptides indicated identity with glucagon (HSQGTFTSDY10 SKYLDNRRAQ20 DFIQWLMST), glucagon-like peptide-1 (GLP-1) (HADGTLTSDI10 SSFLEKQATK20 EFIAWLVSGR30 GRRQ), and glucagon-like peptide-2 (GLP-2) (HADGSFTSDI10 NKVLDTIAAK20 EFLNWLISTK30 VTE). Thus, in a urodele, as in the bullfrog but in contrast to the chicken and all nontetrapod species yet studied, pancreatic preproglucagon mRNA encodes a GLP-2 sequence. The amino acid sequence of glucagon has been better conserved during evolution of tetrapods (3 substitutions between amphiuma and human) than the sequences of either GLP-1 (7 substitutions) or GLP-2 (15 substitutions). Pancreatic polypeptide was also isolated from the extract and its primary structure (APKEPEHPGD10 DASPEQLEKY20 YQDLFQYIIF30 ITRPRY.NH2) indicates that the amino acid sequence of this peptide has been very poorly conserved, even among the amphibia. Amphiuma pancreatic somatostatin is identical to mammalian somatostatin-14.

Amino Acid Sequence↗
PubMed1996

Synthesis and release of acetylcholine by the isolated perifused trout caudal neurosecretory system.

The neurons of the caudal neurosecretory system of teleosts contain, in addition to urotensin I and urotensin II, a high concentration of acetylcholine (T. Ichikawa, 1978, Gen. Comp. Endocrinol. 35, 226-233). The isolated urophysis (and attached terminal spinal cord region) of the rainbow trout Oncorhynchus mykiss was incubated with [3H]choline (0.2 MBq/ml) for 45 min at 22 degrees in the presence of the cholinesterase inhibitor, physostigmine. Unreacted choline was removed by perifusion with fish Ringer solution. Incorporation of radioactivity into newly synthesized [3H]acetylcholine was 4.9 +/- 2.1 x 10(5) Bq/g wet tissue wt. When incubations were carried out in the presence of hemicholinium-3, an inhibitor of high-affinity choline uptake, or when physostigmine was omitted from the incubation buffer and/or when [3H]inulin was substituted for [3H]choline, the incorporation of radioactivity was greatly reduced (< 0.5 x 10(5) Bq/g). The release of [3H]acetylcholine from the preparation increased to 338 +/- 59% of basal (P < 0.05) when the concentration of K+ in the perifusion buffer was raised to 41 mM, but neither urotensin I (10(-7) M) nor urotensin II (10(-6) M) had a significant effect on release. The data indicate that the trout caudal neurosecretory system possesses a high-affinity uptake system for choline and that newly synthesized acetylcholine is released in response to a depolarizing stimulus.

Acetylcholine↗
PubMed1996

Vasoconstrictive effects of native tachykinins in the rainbow trout, Oncorhynchus mykiss.

The role of trout substance P (tSP) and neurokinin A (tNKA) in cardiovascular regulation was investigated in the rainbow trout, Oncorhynchus mykiss, in vivo and in vitro. In vivo, the coeliac arterial and ventral aortic relative blood flows were measured with Doppler flow probes, and blood pressure was measured via a cannula inserted into the dorsal aorta. tSP (0.1 and 1 nmol kg-1) and tNKA (1 nmol kg-1) increased both systemic and coeliac vascular resistances, leading to hypertension and bradycardia. In addition, cardiac output was decreased. The mammalian NK1 tachykinin receptor antagonist CP-96,345 did not affect the responses to tSP or tNKA. In vitro perfusions of the dorsal aortic and coeliacomesenteric vascular beds were performed using peristaltic pumps. The dorsal aortic vascular resistance was dose-dependently increased following infusion of the two peptides (pD2 values 7.6 +/- 0.1 and 7.3 +/- 0.1 for tSP and tNKA, respectively). Tetrodotoxin did not affect the tSP-induced hypertension. Increases in coeliac vascular resistance caused by tSP was correlated with stomach contractions when measurement of intragastric pressure was made using an inserted balloon. In conclusion, native SP and NKA are potent vasoconstrictors of rainbow trout vasculature, a property quite unusual to tachykinins compared with the vasodilation normally seen in mammals.

Amino Acid Sequence↗
PubMed1996

Production of [Asn1, Val5] angiotensin II and [Asp1, Val5] angiotensin II in kallikrein-treated trout plasma (T60K).

Incubation of heat-denatured plasma from the rainbow trout Oncorhynchus mykiss with porcine pancreatic kallikrein generates, in addition to bradykinin-related peptides, previously uncharacterized peptides that contract mammalian and amphibian vascular smooth muscle. Using rings of vascular smooth muscle from the bullfrog systemic arch as bioassay, we have isolated two myotropic peptides whose primary structures were established as: Asn-Arg-Val-Tyr-Val-His-Pro-Phe ([Asn1, Val5]angiotensin II) and Asp-Arg-Val-Tyr-Val-His-Pro-Phe ([Asp1, Val5]angiotensin II). These peptides are the same as those generated in salmon plasma by an extract of kidney. The data raise the possibility that activation of the kallikrein-kinin system in trout generates both bradykinin-related and angiotensin II-related peptides that may act synergistically in the regulation of blood pressure.

Amino Acid Sequence↗