Peptides related to vasopressin in invertebrates

Identification of a vasopressin-like immunoreactive substance in hydra

Vasopressin (VP)-like immunoreactivity has long been known in the hydra nervous system, but has not yet been structurally identified. In this study, using HPLC fractionation and an immunological assay, we have purified two peptides, FPQSFLPRGamide and SFLPRGamide, from Hydra magnipapillata. Both the peptides shared the same C-terminal structure, -PRGamide, with Arg-VP. The nonapeptide proved to be Hym-355, a peptide that stimulates neuronal differentiation in hydra. Detailed evaluation by competitive enzyme-linked immunosorbent assay (ELISA) and double immunostaining using anti-VP and anti-Hym-355 antibodies enabled us to conclude that the two peptides account for a major part of the VP-like immunoreactivity in hydra nerve cells.

Isolation, structural characterization and biological function of a lysine-conopressin in the central nervous system of the pharyngobdellid leech Erpobdella octoculata

Several neuropeptides are suspected to act on the control of hydric balance in leeches. One of these peptides, a peptide immunoreactive to an antibody against oxytocin, was previously characterized from the central nervous system of the leech Erpobdella octoculata [Salzet, M., Wattez, C., Verger-Bocquet, M., Beauvillain, J.-C. & Malecha, J. (1993) Brain Res. 601, 173-184]. This paper reports the isolation from the central nervous system of E. octoculata of another peptide of the oxytocin/vasopressin family; a lysine-vasopressin-like molecule. Its purification was performed by reverse-phase high-performance liquid chromatography combined with both dot immunobinding assay and enzyme-linked immunosorbent assay for lysine-vasopressin. The amino acid sequence was established by Edman degradation and confirmed by electrospray-mass-spectrometry measurement. The nonapeptide obtained corresponded to the lysine-conopressin previously isolated from the venom of the mollusc Conus geographus [Cruz, L. L., de Santos, V., Zafaralla, G. C., Ramilo, C. A., Zeikus, R., Gray, W. R. & Olivera, B. M. (1987) J. Biol. Chem. 262, 15821-15824]. In leeches, synthetic lysine-conopressin exerts a diuretic effect which can be compared to that of the arginine-vasopressin-like peptide isolated in the Insect Locusta migratoria [Proux, J., Miller, C. A., Li, J. P., Carney, R. L., Girardie, A., Delaage, M. & Schooley, D. A. (1987) Biochem. Biophys. Res. Commun. 149, 180-186].

Epitope mapping with ELISA of an antibody against oxytocin used for the characterization of an oxytocin-like epitope in the sex segmental ganglia of the leech Erpobdella octoculata

1. Using direct, inhibiting and competitive enzyme-linked immunosorbent assay (ELISA), two steps were involved in the mapping of the recognition site of a polyclonal antibody against oxytocin (OT). 2. The percentage of cross-reactivity between OT and the N-terminal or the C-terminal fragment of OT demonstrated that the C-terminal fragment is the antigenic part of OT. 3. The percentage of cross-reactivity between OT and other molecules of the OT family indicated that the amino acid in the 8-position and the C-terminal amide of the OT molecule contribute to the recognition. 4. In the two sex segmental ganglia of the leech Erpobdella octoculata, where cells immunoreactive to the anti-OT are detected, the antibody has allowed to characterize an epitope close to the mammalian OT by its C-terminal part.

Vasopressin-immunoreactive neurons and neurohemal systems in cockroaches and mantids

Vasopressin-like neuropeptides of insects are of special interest because of their possible function as hormones and neuromodulators. Therefore, this study was undertaken by using whole-mount immunofluorescent staining by two antisera that recognize different types of vasopressin-like immunoreactive groups of neurons in the cockroaches Periplaneta americana, Leucophaea maderae, Nauphoeta cinerea, Diploptera punctata, and Blaberus discoidalis and in the mantids Litaneuria minor and Tenodera aridifolia sinensis. Using an antiserum to Arg/vasopressin, only two cells, the paired ventral paramedian (PVP) neurons, were immunostained in the central nervous system (CNS) of the cockroaches. These cells are located in the subesophageal ganglion, project throughout the CNS, and appear to be neurosecretory. Their varicose collaterals extend into the dorsal (motor) neuropil of the segmental ganglia, and this neuropil may be the principal site of the release of their neurosecretion. The PVP neurons were also stained by an antiserum to Lys/vasopressin; in addition, this antiserum stained several other groups of neurons, most of which appeared to be neurosecretory. Two pairs of Lys/vasopressin-immunoreactive cells are similar to the PVP neurons in that they are located in the subesophageal ganglion, extend through the ventral nerve cord, have collaterals in the dorsal neuropil of the segmental ganglia, and appear to be neurosecretory within the CNS. In addition, midventral and anteroventral clusters of Lys/vasopressin-immunoreactive neurosecretory neurons in the subesophageal ganglion project neurohemal release sites on the corpora allata. Other types of Lys/vasopressin-immunoreactive neurons include median and lateral neurosecretory cells of the protocerebrum and neurosecretory cells in the tritocerebrum, all of which project to the corpora cardiaca. In the abdominal ganglia there are posterolateral clusters of Lys/vasopressin neurosecretory neurons, and these cells extend to neurohemal release sites on the transverse and lateral cardiac nerves. In mantids the anti-Arg/vasopressin and anti-Lys/vasopressin antisera stained most of the same groups of neurons that these antisera recognized in cockroaches. The results of this study suggest that there are two or more vasopressin-like peptides in cockroaches and mantids and that these peptides may be released either as hormones in the blood or as neurosecretions within the CNS. Their function(s) in these insects remains to be determined.

Evidence for angiotensin-like molecules in the central nervous system of the leech Theromyzon tessulatum (O.F.M.). A possible diuretic effect

1. Cells in the central nervous system of the leech Theromyzon tessulatum were revealed with an antiserum against angiotensin II. Among these cells, a group of 4-5 pairs of neurons, called beta giant cells, and located in the posterior compartments of the supraesophageal ganglion was particularly investigated. 2. The amount of angiotensin II-like substance(s) in the brain increased notably in the days immediately following the third meal. 3. Injections of angiotensin II, fragments 1-4 or 5-8 or angiotensin II and of angiotensin III into stage 3 leeches showed that fragment 5-8 of angiotensin II was the most effective: it provokes a loss of mass of the leeches, which could express a diuretic effect.

The effects of vasopressin and related peptides on osmoregulation in Amoeba proteus

We describe the effects of arginine-vasopressin (AVP) and five related peptides on the contractile vacuole, the osmoregulatory organelle of the fresh water Amoeba proteus. Arginine-vasopressin, lysine-vasopressin, and SKF 101926, a synthetic antagonist of vasopressin, cause a significant increase in the rate of output of the contractile vacuole. Deamino-vasopressin (dAVP), oxytocin, and arginine-vasotocin have no such activity, although dAVP interferes with the action of AVP when present in equimolar concentration. Relatively high concentrations are required and the effect of active peptides is readily reversible. When the normal, hypotonic medium (a synthetic pond water) is replaced by isotonic sucrose, the action of AVP on the vacuole is abolished. Thus vasopressin is believed to act by increasing permeability of the Amoeba plasma membrane to water.

[Evidence of apparent vasopressin and oxytocin peptides in the brain of the leech Rhynchobdelle Theromyzon tessulatum (O.F.M.)]

Vasopressin- and oxytocin-immunoreactive cells have been demonstrated in the brain of the leech Theromyzon tessulatum. A mapping of their localization in the different compartments of the brain has been undertaken. The cells immunohistochemically identified have been compared to previously described cell types defined by classical staining methods for neurosecretory material. Preliminary results obtained with high performance liquid chromatography confirm the presence in brain homogenates of substances with chromatographic properties similar to that of vertebrate nonapeptides. The possible role of these vasopressin- and oxytocin-like substances in osmoregulation is discussed.