Interview with Donald Gumbis

Donald Gumbis is a Papua New Guinean who studied at the University of New South Wales (UNSW) in 2011-2012. He studied on a Colombo Plan Scholarship and completed a Masters in International Relations. The interview was conducted in English by Dr. Jonathan Ritchie of Deakin University and Dr. Musawe Sinebare of the Pacific Adventist University on 10 July 2014. This set comprises: a recording of the interview in two parts, a photograph, and a timed summary.

Natriuretic peptide receptors in the central vasculature of the toad, Bufo marinus

Natriuretic peptide receptors in the central vasculature of the toad, Bufo marinus, were characterized using autoradiographical, molecular, and physiological techniques. Specific ¹²⁵I-rat ANP binding sites were present in the carotid and pulmonary arteries, the lateral aorta, the pre- and post-cava, and the jugular vein, and generally occurred in each layer of the blood vessel. The ¹²5I-rat ANP binding was partially displaced by the specific natriuretic peptide receptor C ligand, C-ANF, which indicates the presence of two types of natriuretic peptide receptors in the blood vessels. This was confirmed by a RT-PCR study, which demonstrated that guanylyl cyclase receptor (NPR-GC) and NPR-C mRNAs are expressed in arteries and veins. An in vitro guanylyl cyclase assay showed that frog ANP stimulated the production of cGMP in arterial membrane fractions. Physiological recordings from isolated segments of the carotid and pulmonary arteries and the lateral aorta, which had been pre-constricted with arginine vasotocin, showed that rat ANP, frog ANP and porcine CNP relaxed the vascular smooth muscle with relatively similar potency. Together, the data show that the central vasculature contains two types of natriuretic peptide receptors (NPR-C and NPR-GC) and that the vasculature is a target for ANP and CNP.

Eliciting children's recall of events: how do computers compare with humans?

This study investigated the usefulness of an interactive computer program in eliciting children's reports about an event. Fifty-four 5–6- and fifty-nine  7–8-year old children participated in an event with their regular class teacher which involved several activities and a mildly negative secret. Four days and again 14 days later, the children were interviewed individually by computer (alone) or by a human interviewer. The computer program incorporated animation and audio whereby an animated figure asked the questions and the children were required to provide a verbal response. The accuracy and detail of the children’s reports was similar across the interview conditions. The children were more willing to review their answers with the computer than the adult interviewer. However, responses to the computer were less consistent across the interviews, and the children were less willing to disclose the secret in the second interview to the computer compared with the human interviewer. Overall, the computer revealed little benefit in eliciting children’s recall of the event over the standard face-to-face interview.

Immunolocalisation of sodium/proton exchanger-like proteins in the gills of elasmobranchs

Na⁺/H⁺ exchangers are integral membrane proteins that exchange Na⁺ and H⁺ across cell membranes. The Na⁺/H⁺ exchangers 2 and 3 are epithelial isoforms in mammals and contribute to acid–base homeostasis. The gills of fishes, including elasmobranchs, are also associated with acid/base balance, and are probably the primary acid/base regulatory organ. This study examines the presence of Na⁺/H⁺ exchangers 2 and 3 using immunohistochemistry and immunoblotting in the gills of four species of elasmobranchs, the banjo ray (Trygonorrhina fasciata), southern eagle ray (Myliobatis australis), the gummy shark (Mustelus antarcticus) and the Australian angel shark (Squatina australis) using heterologous antibodies. Na⁺/H⁺ exchanger 2-like immunoreactivity was observed in the gills of the banjo ray, eagle ray and angel shark. In the banjo and eagle rays, this Na⁺/H⁺ exchanger-like immunoreactivity co-localised with immunoreactivity to Na⁺/K⁺-ATPase, a marker for the mitochondrial-rich cells of fishes. Na⁺/H⁺ exchanger 3-like immunoreactivity was only observed in the gills of the angel and gummy sharks, some Na⁺/H⁺ exchanger 3-like cells also showed Na⁺/K⁺-ATPase immunoreactivity. However, immunoblotting of banjo and eagle ray gill membranes demonstrated Na⁺/H⁺ exchanger 3-like immunoreactivity, which was not consistent with the immunohistochemical results. These data demonstrate the presence of epithelial Na⁺/H⁺ exchangers 2 and 3 in the gills of elasmobranchs and a link with acid/base regulation is suggested.

Nitric oxide regulation of the central aortae of the toad Bufo marinus occurs independently of the endothelium

Nitric oxide (NO) signalling pathways were examined in the lateral aortae and dorsal aorta of the cane toad Bufo marinus. NADPH diaphorase histochemistry and nitric oxide synthase (NOS) immunohistochemistry found no evidence for endothelial NOS in the endothelium of toad aortae, but it could be readily demonstrated in rat aorta that was used as a control. Immunohistochemistry using a specific neural NOS antibody showed the presence of neural NOS immunoreactivity in the perivascular nerves of the aortae. The anatomical data was supported by in vitro organ bath physiology, which demonstrated that the vasodilation mediated by applied acetylcholine (10^-5 mol l^-1) was not dependent on the presence of the vascular endothelium; however, it was significantly reduced in the presence of a neural NOS inhibitor, vinyl-L-NIO (10-4 mol l^-1). In addition, atropine (10^-6 mol l^-1) (a muscarinic receptor inhibitor), L-NNA (10^-4 mol l^-1) (a NOS inhibitor) and ODQ (10^-5 mol l^-1) (an inhibitor of soluble guanylyl cyclase) abolished the vasodilatory effect of applied acetylcholine. In conclusion, we propose that an endothelial NO system is absent in toad aortae and that NO generated by neural NOS in perivascular nerves mediates vasodilation.