Biomedical subjects

J M Conlon

Publications and source records attributed to J M Conlon.

At least 127 records · Page 7Linked to original sources

PubMed1996

Isolation and cardiovascular activity of a second bradykinin-related peptide ([Arg0, Trp5, Leu8]bradykinin) from trout.

Previous work has shown that incubation of heat-denatured plasma from the rainbow trout Oncorhynchus mykiss with porcine pancreatic kallikrein generates [Lys0, Trp5, Leu8]bradykinin (trout [Lys0]BK). We have now isolated a second BK-related peptide from kallikrein-treated trout plasma with the primary structure: Arg-Arg-Pro-Gly-Trp-Ser-Pro-Leu-Arg (trout [Arg0]BK). Bolus injections of both trout [Arg0]BK and [Lys0]BK (> 100 pmol/kg) into the dorsal aorta of conscious trout produced multiphasic effects on arterial blood pressure. An initial pressor response of short duration (1-2 min) was followed by a fall in pressure (to below basal values in 11 out of 15 animals) and then by a sustained rise in pressure lasting up to 60 min. The maximum rise in pressure produced by trout [Arg0]BK (10 nmol/kg) was approximately one-fourth of the maximum rise produced by angiotensin II in the same animals. Intracerebroventricular injections of trout [Arg0]BK (500 pmol) into conscious trout had no effect on arterial blood pressure or heart rate. Trout [Arg0]BK did not affect the tension of vascular rings from trout efferent branchial and caeliacomesenteric arteries and anterior cardinal vein. Trout des [Arg9]BK had no effect on cardiovascular parameters, either in vivo or in vitro, indicating that the C-terminal arginine residue of the peptide is important in interaction with the trout kinin receptor(s).

Amino Acid Sequence↗

PubMed1996

Isolation of a peptide structurally related to mammalian corticostatins from the lamprey Petromyzon marinus.

Peptides in an extract of skin from the agnathan Petromyzon marinus (sea lamprey) were purified by reversed-phase high-performance liquid chromatography and characterized by Edman degradation. The primary structure of a cysteine- and arginine-rich peptide (termed lamprey corticostatin-related peptide [LCRP]) was established as Cys-Pro-Cys-Gly-Arg-Arg-Arg-Cys-Cys-Val-Arg-Gly-Leu-Asn-Val-Tyr-Cys-Cys- Phe. Mass spectrometry indicated that all cysteine residues are intramolecularly linked. This amino acid sequence shows structural similarity to rat corticostatin R4 and rabbit corticostatin R1. In particular, LCRP contains the polyarginine sequence at the N-terminus of the peptide that is believed to mediate both the inhibition of ACTH stimulated steroidogenesis and the antimicrobial (defensin-like) actions of the corricostatins.

Amino Acid Sequence↗

PubMed1996

Pharmacological profile of the tachykinin receptor involved in the stimulation of corticosteroid secretion in the frog Rana ridibunda.

It has recently been shown that the adrenal gland of the frog Rana ridibunda is densely innervated by a network of fibers containing two novel tachykinins, i.e. ranakinin (the counterpart of substance P) and [Leu3, Ile7]neurokinin A. Both ranakinin and [Leu3, Ile7]neurokinin A stimulate corticosteroid secretion from frog adrenal glands in vitro. In the present study, we have investigated the pharmacological profile of the receptors involved in the stimulatory action of ranakinin on perifused frog adrenal slices. The selective NK-1 receptor antagonists [D-Pro4, D-Trp7,9]substance P 4-11 and CP-96,345, did not affect the stimulatory action of ranakinin. The selective NK-1 agonist substance P 6-11 had no effect on corticosteroid secretion. The non-peptidic NK-1 receptor antagonist RP 67580 significantly reduced the stimulatory effect of ranakinin on corticosterone and aldosterone secretion by 57 and 55%, respectively. In addition, the dual NK-1/NK-2 receptor antagonist FK-224 significantly inhibited the effect of ranakinin on corticosterone (- 80%) and aldosterone secretion (- 95%). Finally, the amphiphilic analogue of substance P, [D-Pro2, D-Phe7, D-Trp9]substance P, had no effect on corticosteroid secretion. These data suggest that in the frog adrenal gland the stimulatory action of ranakinin on steroid secretion is mediated by a novel type of receptor which differs substantially from the mammalian NK-1 receptor subtype.

Adrenal Cortex Hormones↗

PubMed1996

A proenkephalin A-derived peptide analogous to bovine adrenal peptide E from frog brain: purification, synthesis, and behavioral effects.

A peptide derived from the posttranslational processing of proenkephalin A was isolated from an extract of the brain of the European green frog Rana ridibunda and its primary structure established as: Tyr-Gly-Gly-Phe-Met-Arg-Arg-Val-Gly-Arg10- Pro-Glu-Trp-Trp-Gln-Asp-Tyr-Gln-Lys-Arg20-Tyr-Gly-Gly-Phe-Met. The structure was confirmed by chemical synthesis. The peptide represents an amphibian equivalent of bovine adrenal peptide E [preproenkephalin A (206-230)-peptide] but the sequence contains two amino acid substitutions (Met15-->Gln and Leu25-->Met) compared with the mammalian peptide. The data support previous hypotheses that the Leu-enkephalin sequence is not present in preproenkephalin A of amphibians. Intracerebroventricular injections of frog peptide E (10 and 100 ng) in mice had no significant effect on horizontal locomotor activity. The peptide, in doses up to 1 microgram, had no effect on latency of escape jumping in the hot plate test and the peptide (100 ng) did not modify responses (paw licking, rearing, and escape jumping) in morphine-treated mice.

Adrenal Glands↗

PubMed1996

Cardiovascular actions of trout urotensin II in the conscious trout, Oncorhynchus mykiss.

The central and peripheral cardiovascular effects of synthetic trout urotensin II (UII) were investigated in the conscious rainbow trout. Intracerebroventricular injection of 50 pmol UII produced a slight (3%) but significant (P < 0.05) increase in heart rate but had no effect on mean arterial blood pressure. Injection of 500 pmol UII icv produced a significant (P < 0.05) rise (8%) in blood pressure with no change in heart rate. In contrast to the weak pressor effect of centrally administered UII, intra-arterial injection of UII produced a dose-dependent increase in arterial blood pressure and decrease in heart rate with significant (P < 0.05) effects on both parameters observed at a dose of 25 pmol. Higher doses of the peptide produced a sustained decrease in cardiac output that accompanied the bradycardia and rise in arterial blood pressure. The UII-induced bradycardia, but not the increase in pressure, was abolished by pretreatment with phentolamine. Trout UII produced a sustained and dose-dependent contraction of isolated vascular rings prepared from trout efferent branchial [-log 50% of the concentration producing maximal contraction (pD2) = 8.30] and celiacomesenteric (pD2 = 8.22) arteries but was without effects on vascular rings from the anterior cardinal vein. The data indicate that the pressor effect of UII in trout is mediated predominantly, if not exclusively, by an increase in systemic vascular resistance. The UII-induced hypertensive response does not seem to involve release of catecholamines, but the bradycardia may arise from adrenergic-mediated activation of cardioinhibitory baroreflexes.

Angiotensin II↗

PubMed1996

Loop diuretics attenuate bradykinin-induced increase in clearance of macromolecules in the oral mucosa.

The purpose of this study was to determine whether loop diuretics attenuate bradykinin-induced increase in clearance of macromolecules in the oral mucosa in situ and, if so, to start to determine the mechanisms that mediated these responses. By using intravital microscopy, we found that bradykinin induced a significant concentration-dependent increase in fluorescein isothiocyanate-labeled dextran (mol mass 70 kDa) leaky site formation in the hamster cheek pouch. These responses were significantly attenuated by topical application of two structurally distinct loop diuretics, furosemide and ethacrynic acid, onto the cheek pouch (P < 0.05). Hydrochlorothiazide, a nonloop diuretic, had no significant effects on bradykinin-induced responses. Furosemide had no significant effects on adenosine-induced leaky site formation. Application of bradykinin after furosemide, but not after hydrochlorothiazide, was associated with a significant concentration-dependent decrease in bradykinin-like immunoreactivity in the cheek pouch suffusate (P < 0.05). Prostaglandins and changes in vasomotor tone did not modulate the effects of furosemide on bradykinin-induced responses. These data indicate that loop diuretics attenuate bradykinin-induced increase in clearance of macromolecules in the oral mucosa in a specific fashion, probably by amplifying local bradykinin catabolism. We suggest that topical loop diuretics could be useful in the treatment of oral mucosa inflammation elicited by bradykinin.

Adenosine↗

PubMed1996

Localization, identification, and action of galanin in the frog adrenal gland.

The distribution of galanin-like immunoreactivity was studied in the adrenal gland of the frog Rana ridibunda using the indirect immunofluorescence technique. A dense network of varicose fibers immunoreactive to galanin was found in the adrenal tissue. A combination of HPLC analysis and RIA detection was used to characterize galanin-like immunoreactivity in frog adrenal gland extracts. The elution profile revealed the existence of a single form of galanin exhibiting the same retention time as synthetic frog galanin. The possible involvement of galanin in the regulation of corticosteroid secretion was investigated in vitro using a perifusion system for frog adrenal slices. For concentrations ranging from 10(-9) to 3 x 10(-6) M, synthetic frog galanin induced a dose-dependent inhibition of corticosterone and aldosterone release. Repeated pulses of galanin (10(-6) M), given at 90-min intervals, resulted in a reproducible inhibition of corticosteroid secretion without any apparent tachyphylaxis. During prolonged administration of galanin (10(-6) M), the steroidogenic effect of ACTH (10(-9) M) was significantly reduced. In contrast, galanin did not attenuate the stimulation of corticosteroid secretion induced by the angiotensin II analog [Sar1,Val5]angiotensin II. These results show the occurrence of galanin in fibers innervating the frog adrenal gland. The data also demonstrate that synthetic galanin inhibits spontaneous and ACTH-induced corticosteroid release. Taken together, these findings suggest that galanin, released by nerve fibers in the adrenal tissue, can act locally as a modulator of steroid secretion.

Adrenal Glands↗

PubMed1996

Assessment of arthropod vectors of infectious diseases in areas of U.S. troop deployment in the Persian Gulf.

Beginning in August 1990, approximately 800,000 coalition troops were deployed to the Persian Gulf during Operations Desert Shield and Desert Storm. There was substantial concern about arthropod-borne diseases, particularly sand fly fever and cutaneous leishmaniasis, because of high morbidity rates in the Persian Gulf during World War II (WWII). In sharp contrast to WWII, there was no report of sand fly fever among coalition forces and only 31 cases of leishmaniasis among 697,000 U.S. troops. To further evaluate the risk of arthropod-borne diseases, an entomologic survey was conducted in 12 areas of Kuwait and Saudi Arabia. A total of 1,556 arthropods was collected during four survey periods in 1992. The suspected vectors of cutaneous Leishmania major infection, sand fly fever, West Nile fever, Rift Valley fever, and Crimean-Congo hemorrhagic fever were identified; however, there was no evidence of arboviruses or Leishmania among collected specimens nor from 51 trapped rodents. There are several possible reasons for the low risk of arthropod-borne infectious diseases among Desert Shield/Storm troops in an area where suspected vectors frequently were found: the use of insecticides and repellents, and the deployment of most ground troops to the open desert during the cooler, winter period--conditions least favorable for the transmission of arthropod-borne diseases.

Animals↗

PubMed1995

Distribution of two molecular forms of gonadotropin-releasing hormone (GnRH) in the central nervous system of the frog Rana ridibunda.

Two molecular forms of gonadotropin-releasing hormone (GnRH) have been recently characterized in the brain of the frog Rana ridibunda i.e. mammalian GnRH (mGnRH) and chicken GnRH-II (cGnRH-II). Using highly specific antisera against each form of GnRH, we have investigated the distribution of these two neuropeptides in the frog brain by the indirect immunofluorescence and the peroxidase-antiperoxidase techniques. mGnRH-immunoreactive cell bodies were restricted to a well defined region corresponding to the septal-anterior preoptic area. mGnRH-containing fibers projected through the ventral diencephalon and ended in the median eminence. In contrast, cGnRH-II-immunoreactive structures were widely distributed in the frog brain. In the telencephalon cGnRH-II-positive elements formed a ventromedial column extending from the olfactory bulb to the septal area, a pathway which corresponds to the terminal nerve. A dense accumulation of cGnRH-II-immunoreactive cell bodies was also found in the septal-anterior preoptic area; these neurons sent processes towards the median eminence via the hypothalamus. Double immunostaining revealed that, in this area, mGnRH- and cGnRH-II-like immunoreactivity co-existed in the same neurons. In the mid-diencephalon, numerous cGnRH-II-immunoreactive perikarya were found, surrounding the third ventricle, in the posterior preoptic and infundibular areas. Many of these neurons sent processes towards the ventricular cavity. More caudally, a dense population of cGnRH-II-immunoreactive perikarya was also observed in the nucleus of the paraventricular organ and the posterior tubercle. Dorsally, the thalamus, the tegmentum, the tectum and the granular layer of the cerebellum were richly innervated by cGnRH-II-positive fibers. In the medulla oblongata, numerous cGnRH-II-immunoreactive perikarya were seen in several cranial nerve nuclei. Ventrally, a dense plexus of immunoreactive fibers projected rostrocaudally into the spinal cord. The occurrence of mGnRH- and cGnRH-II-like immunoreactivity in the septal-anterior preoptic area and the hypothalamo-pituitary pathway supports the view that both peptides act as hypophysiotropic neurohormones. The widespread distribution of cGnRH-II-immunoreactive elements in the central nervous system of the frog strongly suggests that this peptide may also exert neuromodulator and/or neurotransmitter activities.

Animals↗

PubMed1995

Neuropeptide tyrosine in the brain of the African lungfish, Protopterus annectens: immunohistochemical localization and biochemical characterization.

Lungfishes, which share similarities with both fishes and amphibians, represent an interesting group in which to investigate the evolutionary transition from fishes to tetrapods. In the present study, we have investigated the localization and biochemical characteristics of neuropeptide Y (NPY)-immunoreactive material in the central nervous system of the African lungfish, Protopterus annectens. NPY-immunoreactive cell bodies were found in various regions of the brain, most notably in the telencephalon (septal area, ventral striatum, and nucleus accumbens), in the diencephalon (preoptic nucleus, periventricular region of the hypothalamus, and ventral thalamus), and in the tegmentum of the mesencephalon. A strong immunoreaction was also detected in cell bodies of the nervus terminalis. Immunoreactive nerve fibers were particularly abundant in the ventral striatum, the nucleus accumbens, the diagonal band of Broca, the hypothalamus, and the mesencephalic tegmentum. Positive fibers were also seen in the median eminence and in the neural lobe of the pituitary. The NPY-immunoreactive material localized in the brain and pituitary was characterized by combining high-performance liquid chromatography (HPLC) analysis and radioimmunological quantitation. The displacement curves obtained with synthetic porcine and frog NPY and serial dilutions of brain and pituitary extracts were parallel. Reversed-phase HPLC analysis of telencephalon, diencephalon, and pituitary extracts resolved a major NPY-immunoreactive peak that coeluted with frog NPY. The similarity between the distribution of NPY-containing neurons and the biochemical characteristics of the immunoreactive peptide in the brain of lungfish and frog strongly favors a close phylogenetic relationship between dipnoans and amphibians.

Animals↗

PubMed1995

Cardiovascular actions of frog urotensin II in the frog, Rana catesbeiana.

The effects of synthetic frog urotensin II on cardiac output and arterial blood pressure and on the motility of isolated vascular smooth muscle were investigated in the bullfrog, Rana catesbeiana. Bolus injections of frog urotensin II (100 nmol/kg) into the left systemic arch produced a rapid and sustained fall in blood flow through the right branch of the truncus arteriosus (to 62 +/- 5% of preinjection values; n = 8). The response exhibited strong tachyphylaxis. There were no significant effects on heart rate and central arterial blood pressure but the fact that a fall in cardiac output was not accompanied by a fall in pressure suggests that the peptide produced an increase in peripheral vascular resistance. Rings of vascular smooth muscle from the proximal and distal regions of the left and right systemic arches responded to urotensin II with sustained and concentration-dependent contractions. The tissues from the different regions did not significantly differ in their maximum response and sensitivity to the peptide (EC50 values from 4.6 x 10(-9) to 6.5 x 10(-9) M; n = 6). Acetylcholine (3 x 10(-8) to 3 x 10(-6) M) significantly (P < 0.05) relaxed the rings in an endothelium-dependent manner but urotensin II did not produce relaxation at any concentration tested. The contractile effect of urotensin II (10(-7) M) was not affected by preincubation of the rings with atropine, tetrodotoxin, and somatostatin-14 but indomethacin produced a significant (P < 0.05) decrease in the amplitude of the contractions of the systemic arch (to 18 +/- 2% of control values; n = 6). Arachidonic acid (10(-5) M) also produced a sustained contraction of the rings. The data suggest an involvement of prostaglandin synthesis in the contractile action of urotensin II on isolated frog vascular smooth muscle but, unlike in mammals, urotensin II does not stimulate nitric oxide synthesis in this tissue.

Acetylcholine↗

PubMed1995

Purification and structural characterization of vasoactive intestinal polypeptide from the trout and bowfin.

Vasoactive intestinal polypeptide (VIP) was purified from extracts of the stomachs of the rainbow trout, Oncorhynchus mykiss, and the bowfin, Amia calva. The primary structure of VIP from both species was the same: His-Ser-Asp-Ala-Ile-Phe-Thr-Asp-Asn-Tyr10- Ser-Arg-Phe-Arg-Lys-Gln-Met-Ala-Val-Lys20-Lys-Tyr-Leu-Asn-Ser-Val- Leu-Thr. This amino acid sequence shows only one amino acid substitution (Val5-->Ile) compared with the common sequence of VIP from the chicken, alligator, and European green frog. The structural identity of VIP from the trout and bowfin is consistent with the close phylogenetic relationship between the Salmoniformes and the Amiiformes and the data indicate that pressure to conserve the complete primary structure of VIP during vertebrate evolution has been very strong.

Amino Acid Sequence↗

PubMed1995

Urotensin II from the river lamprey (Lampetra fluviatilis), the sea lamprey (Petromyzon marinus), and the paddlefish (Polyodon spathula).

Urotensin II was isolated from extracts of the whole brain of the river lamprey (Lampetra fluviatilis) and the sea lamprey (Petromyzon marinus). The primary structure of the peptide from both species is the same (Asn-Asn-Phe-Ser-Asp-Cys-Phe-Trp-Lys-Tyr-Cys-Val) and this amino acid sequence is identical to that of urotensin II from the dogfish and skate. Consistent with previous morphological studies indicating that the Agnatha lack a caudal neurosecretory system, urotensin II was not detected in an extract of P. marinus spinal cord. The data suggest that the urotensin II may have functioned in the earliest vertebrates as a neurotransmitter/neuromodulator in the central nervous system rather than as a neurohormone of the caudal neurosecretory system. Urotensin II was also isolated from an extract of the spinal cord of a chondrostean fish, the paddlefish (Polyodon spathula). The primary structure of the paddlefish urotensin II (Gly-Ser-Thr-Ser-Glu-Cys-Phe-Trp-Lys-Tyr-Cys-Val) is the same as that of another chondrostean, the sturgeon (Acipenser ruthenus). The study provides further evidence for a widespread distribution of urotensin II in vertebrate species and suggests that the primary structure of the peptide is better conserved in these phylogenetically ancient fish than in teleosts.

Amino Acid Sequence↗

PubMed1995

A peptide from the caudal neurosecretory system of the dogfish Scyliorhinus canicula that is structurally related to urotensin I.

Using reversed-phase HPLC in combination with a radioimmunoassay for ovine corticotropin-releasing hormone (CRH), a peptide with CRH-like immunoreactivity was isolated in pure form from an extract of the caudal spinal cord region of the spotted dogfish, Scyliorhinus canicula. The primary structure of the peptide was established as Pro-Ala-Glu-Thr-Pro-Asn-Ser-Leu10-Asp-Leu-Thr-Phe-His-Leu-Leu-Arg- Glu-Met-Ile- Glu20-Ile-Ala-Lys-His-Glu-Asn-Gln-Gln-Met-Gln30-Ala-Asp-Ser- Asn-Arg-Arg-Ile-Met - Asp-Thr40-Ile.NH2. This amino acid sequence shows moderate structural similarity to Catostomus urotensin I (51%) and to human CRH (56%). The data provide, therefore, chemical evidence to support the conclusions of earlier immunohistochemical studies that the diffuse caudal neurosecretory system of elasmobranchs produces a peptide that is immunochemically related to teleost urotensin I peptides. However, the primary structure of urotensin I has been poorly conserved during evolution.

Amino Acid Sequence↗

PubMed1995

Characterization of insulin, glucagon, and somatostatin from the river lamprey, Lampetra fluviatilis.

Insulin has been isolated from an extract of the pancreas of an Agnathan, the river lamprey Lampetra fluviatilis. The primary structure of the peptide (A-chain: GIVEQ CCHRK CSIYD MENYC N; B-chain: SALTG AGGTH LCGSH LVEAL YVVCG DRGFF YTPSK T) is the same as that of insulin from the sea lamprey Petromyzon marinus. In contrast, Lampetra glucagon (HAQGS FTSDY SKYLD SKQAK DFVIW LMNT), isolated from an extract of intestine, is structurally more similar to human glucagon (five amino acid substitutions) than to Petromyzon glucagon (six substitutions). Similarly, the primary structure of somatostatin (AAAAP GAAGG AQLPL GNRER KAGCK NFFWK TFSSC), isolated from Lampetra pancreas, contains eight amino acid substitutions and an additional residue compared with Petromyzon somatostatin. Somatostatin, isolated from Lampetra brain, has an identical structure to mammalian somatostatin-14 (AGCKN FFWKT FTSC), indicative of the same tissue-specific expression of different somatostatin genes that was previously observed in Petromyzon. In contrast to the reduced binding affinity of other fish insulins, lamprey insulin was equipotent with porcine insulin in inhibiting the binding of [3-[125I]iodotyrosine-A14] human insulin to the human insulin receptor.

Amino Acid Sequence↗

PubMed1995

Proinsulin and somatostatin from the islet organ of the southern-hemisphere lamprey Geotria australis.

An extract of the islet organ of the southern-hemisphere lamprey Geotria australis contained a high concentration of somatostatin-like immunoreactivity (34 nmol/g) but only trace amounts of insulin-like immunoreactivity. The primary structure of Geotria somatostatin-33 (AVQEAGGAAM10PPPGQRDRKA20GCKNFFWKTF30SSC) shows almost no similarity to somatostatins from the holarctic lampreys Petromyzon marinus and Lampetra fluviatilis in the N-terminal region but the functionally important C-terminal region, including the substitution Thr31 --> Ser, is the same. Insulin was not identified in the extract but proinsulin and an incompletely processed form with an intact A-chain/C-peptide junction were purified and partially characterized. The primary structure of the insulin region of Geotria proinsulin was established as A-chain; GIVEKCCHNR10CSIYQ MESYC20N; B-chain: SALTGSGGNY10LCGSYLVDAL20YLACGPRGFF30YTSTPV. This sequence contains 17 amino acid substitutions compared with the identical insulins from P. marinus and L. fluviatilis but the unusual extension to the N-terminus of the B-chain (SALTG) is present. Compared with mammalian insulins, Geotria insulin contains several substitutions of strongly conserved residues such as Gln(A5) --> Lys in the putative receptor-binding region, Glu(B26) --> Pro important in dimerization, and Leu(A13) --> Ile, His(B10) --> Tyr, and His(B21) --> Tyr important in hexamerization. Geotria proinsulin contains an Arg-Arg processing site at the B-chain/C-peptide junction but we speculate either that the Lys-Arg processing site at the C-peptide/A-chain junction is absent or that the Geotria pancreas is unable to synthesize a SPC2-type prohormone convertase. Our results are consistent with the view that G. australis and holarctic lampreys arose from a common stock but have been separated for a considerable period.

Amino Acid Sequence↗

PubMed1995

Isolation and biological activity of [Trp5]bradykinin from the plasma of the phylogenetically ancient fish, the bowfin and the longnosed gar.

The holostean fish occupy an important position in vertebrate phylogeny as extant representatives of a ancient group of ray-finned fish with evolutionary connections to present-day teleosts. Incubation of heat-denatured plasma from the bowfin Amia calva with trypsin generated bradykinin-like immunoreactivity. The primary structure of bowfin bradykinin was established as Ala-Pro-Pro-Gly-Trp-Ser-Pro-Phe-Arg. This amino acid sequence contains one amino acid substitution (Phe5 --> Trp) compared with mammalian bradykinin. The same peptide was generated in heat-denatured plasma from the longnosed gar Lepisosteus osseus. Treatment of plasma from either the bowfin or gar with glass beads under conditions previously shown to activate Factor XII in the plasma of mammals and reptiles did not generate bradykinin. Bolus injections of synthetic bowfin bradykinin (0.1, 0.3, and 1.0 nmol/kg) into the bulbus arteriosus of unanesthetized bowfin resulted in an immediate fall in arterial blood pressure of 5-10 min duration that was followed by a dose-dependent rise in pressure that was sustained for 30-60 min. There was no change in heart rate following bradykinin administration. The data suggest that the kallikrein-kinin system may predate the appearance of teleosts and may play a role in cardiovascular regulation in holosteans.

Amino Acid Sequence↗

PubMed1995

Tachykinins with unusual structural features from a urodele, the amphiuma, an elasmobranch, the hammerhead shark, and an agnathan, the river lamprey.

Tachykinins were purified from extracts of gastrointestinal tissues of the urodele, Amphiuma tridactylum (three-toed amphiuma), and the elasmobranch Sphyrna lewini (hammerhead shark), and from the brain of the agnathan Lampetra fluviatilis (river lamprey). The amphiuma substance P (SP) (DNPSVGQFYGLM-NH2) contains 12 amino residues compared with 11 for mammalian SP and lacks the Arg/Lys-Pro-Xaa-Pro motif that is characteristic of NK1 receptor-selective agonists. Lampetra SP (RKPHPKEFVGLM-NH2) is identical to SP from the sea lamprey and the shark SP-related peptide (AKFDKFYGLM-NH2) is identical to dogfish scyliorhinin I. Amphiuma neurokinin A (NKA) (HKDAFIGLM-NH2) and lamprey NKA (HFDEFVGLM-NH2) contain 9 amino acid residues compared with 10 for mammalian NKA. The shark NKA-related peptide (ASGPTQAGIV10GRKRQKGEMF20VGLM-NH2) shows limited structural similarity to mammalian neuropeptide gamma and the teleost tachykinin, carassin but contains 24 rather than 21 amino acid residues. The data show that the primary structures of the tachykinins have been very poorly conserved during vertebrate evolution and that pressure has acted only to maintain the functionally important sequence -Phe-Xaa-Gly Leu-Met-NH2 at the COOH-termini of the peptides.

Amino Acid Sequence↗