Novel inhibitors of the sodium-calcium exchanger: benzene ring analogues of N-guanidino substituted amiloride derivatives.

A series of N-guanidino substituted 2,4-diamino-5-carbonylguanidine molecules related to amiloride were synthesised and evaluated for their ability to inhibit the sodium-calcium exchanger in rat insulinoma cells (RINm5F) and human platelets. Specific chemical pathways were used to prepare the benzene derivatives designed as bioisosteric analogues of the pyrazine derivatives of amiloride. Several so-called 'simplified analogues', where some substituents of amiloride were omitted or replaced, were also prepared and included in the biological evaluation. The inhibitory potency of the sodium-calcium exchanger was screened on both cell types by measuring their effect on 45Ca(2+) uptake. Among the most active compounds, N-(2-amino-5-chloro-4-nitrobenzoyl)-N'-(1-naphtylmethyl)guanidine (IC(50)=3.4 microM) was found more active than amiloride (IC(50)=690 microM) and 3,4-dichlorobenzamil (IC(50)=15.2 microM), the reference inhibitor.

Localization of neuropeptides in the nervous system of the brittle star Ophiura ophiura.

Immunocytochemical investigations using antisera against the SALMFamide neuropeptide S1 and RFamide were carried out on whole mounts of the radial nerve cord and circumoral ring of the brittle star Ophiura ophiura. Both antisera show an abundant immunoreactivity in the ectoneural tissue and give similar patterns of distribution. They show that in the radial nerve cord there are discrete populations of neurons organized in an identical pattern in each segment. At the junction with the ring, however, the two proximal segments of the nerve cord are differentiated from the distal ones by increased numbers of immunoreactive neurons. This is probably due to the more complex integrative function in that area. In the ring, immunolabelling is simple and consists of fibre tracts and two local ganglia. In each segment both antisera label either one or two giant neurons the shape of which is similar to that of a class of fibres that have been described from intra-cellular dyefills. The S1- and RFamide-like distributions, although very similar, show some neurons which are only labelled by one antiserum. Since preabsorption controls indicate no cross-reactivity between antisera, there is evidence of two distinct neuropeptides in the nervous system of the brittle star.

In-target production of [13N]ammonia via proton irradiation of dilute aqueous ethanol and acetic acid mixtures.

A reliable, reproducible method has been developed for the in situ production of decicurie quantities of [13N]ammonia by proton irradiation of pressurized, dilute aqueous solutions of acetic acid and ethanol. Some of the parameters investigated for their effect on the 13N product distribution included dose, dose rate, solute concentration, target body material, beam strike volume and proton energy. For the conditions investigated, [13N]NH3 was produced directly in the target in yields greater than 75%.