The effect of water deprivation on the expression of atrial natriuretic pepide and its receptors in the spinifex hopping mouse, Notomys alexis

This study investigated the mRNA expression of the atrial natriuretic peptide (ANP) system (peptide and receptors) during water deprivation in the spinifex hopping mouse, Notomys alexis, a native of central and western Australia that is well adapted to survive in arid environments. Initially, ANP, NPR-A and NPR-C cDNAs (partial for receptors) were cloned and sequenced, and were shown to have high homology with those of rat and mouse. Using a semi-quantitative multiplex PCR technique, the expression of cardiac ANP mRNA and renal ANP, NPR-A, and NPR-C mRNA was determined in 7- and 14-day water-deprived hopping mice, in parallel with control mice (access to water). The levels of ANP mRNA expression in the heart remained unchanged, but in the kidney ANP mRNA levels were increased in the 7-day water-deprived mice, and were significantly decreased in the 14-day water-deprived mice. NPR-A mRNA levels were significantly higher in 7-day water-deprived mice while no change for NPR-A mRNA expression was observed in 14-day water-deprived mice. No variation in NPR-C mRNA levels was observed. This study shows that water deprivation differentially affects the expression of the ANP system, and that renal ANP expression is more important than cardiac ANP in the physiological adjustment to water deprivation.

Functional analysis of natriuretic peptide receptors in the bladder of the toad, bufo marinus

This study aimed to localize and characterize natriuretic peptide binding sites in the urinary bladder of Bufo marinus and to then examine the effect of natriuretic peptides on the bladder vascular tone and water reabsorption in isolated perfused bladder preparations. Specific ¹²⁵I-rat atrial natriuretic peptide (¹²⁵I-rANP) binding sites were present on blood vessels, muscle, and epithelium. In tissue sections and/or isolated membranes, the binding was completely displaced by frog ANP, rat ANP, and porcine C-type natriuretic peptide (CNP; membranes only). However, a reduction in binding was observed after incubation with ¹²⁵I-rANP and 1 μM of the natriuretic peptide receptor-C (NPR-C) ligand C-ANF, but residual binding remained suggesting the presence of two distinct binding sites. Electrophoresis of bladder membranes cross-linked to ¹²⁵I-rANP identified two bands at approximately 70 and 140 kDa that correspond to the monomeric mass of NPR-C and the guanylate cyclase receptors, respectively. Furthermore, the presence of natriuretic peptide receptor-A and NPR-C mRNA in the bladder was demonstrated with reverse transcription–polymerase chain reaction. In addition, rat ANP, frog ANP, and porcine CNP stimulated a significant increase in cGMP generation in bladder membrane preparations, which indicated the presence of guanylate cyclase-linked receptors. In perfused bladder preparations, arginine vasotocin increased perfusion pressure and water permeability. The infusion of frog ANP or porcine CNP failed to alter perfusion pressure or water reabsorption in the presence or absence of arginine vasotocin. This study identified a well-developed natriuretic peptide receptor system in the urinary bladder of B. marinus but the function of the receptors remains unclear.

Toad atrial natriuretic peptide : cDNA cloning and functional analysis in isolated perfused kidneys

Complementary DNA (cDNA) encoding Bufo marinus (toad) preproatrial natriuretic peptide (preproANP) was isolated by reverse-transcription polymerase chain reaction. Sequence analysis of toad preproANP cDNA revealed an open reading frame of 150 amino acid residues, which shared 72% and 66% identity with Rana catesbeiana and Xenopus laevis preproANP, respectively. The deduced amino acid sequence of toad ANP that corresponded to ANP 1–24 of R. catesbeiana and Rana ridibunda was identical, but it differed by four residues from that of X. laevis. ANP mRNA transcripts were also shown to be expressed in the toad kidney. Subsequently, the effect of frog ANP (1–24) on renal function in toad was examined using a perfused kidney preparation. The arterial infusion of frog ANP caused a dose-dependent decrease in the arterial perfusion pressure that was associated with an increase in the glomerular filtration rate (GFR) and a renal natriuresis and diuresis. The renal natriuresis and diuresis resulted predominantly from an increased GFR rather than from direct tubular effects. This study demonstrates that ANP can regulate renal function, which suggests it may be involved in overall fluid volume regulation.

Children's memory of recurring events: is the first event always the best remembered?

Three experiments were conducted to examine the effect of age (4-5 and 6-8 years) and retention interval on children's ability to remember separate occurrences of a repeated event that varied in terms of content (items, dialog, etc.) Experiment 1 explored children's ability to recall the first versus last occurrence of a series of six events, at either one week or six weeks delay. Experiments 2 and 3 explored children's ability to identify the position of items in terms of their order of presentation within the series across two retention intervals. Overall, the results revealed clear age differences in children's performance. In general, the 6- to 8-year+old children performed better on all tasks than the 4- to 5-year-old children. Further, the older children showed relatively good memory of the first and last items compared to the middle items, although the last items were more likely to be forgotten or misplaced in the sequencing tasks over time that the first items. For the younger children, the patterns of results were sometimes but not always consistent with that of the older children The relevance and generalisability of these findings to the legal setting are discussed as well as directions for future research.

Renal C-type natriuretic peptide and natriuretic peptide receptor B mRNA expression are affected by water deprivation in the Spinifex Hopping mouse

This study investigated the effect of water deprivation on the expression of C-type natriuretic peptide (CNP) and natriuretic peptide receptor B (NPR-B) mRNA, and the ability of NPR-B to generate cGMP in the Spinifex Hopping mouse, Notomys alexis. This rodent is a native of central and western Australia that is well adapted to survive in arid environments. Initially, CNP and NPR-B cDNAs (partial for NPR-B) were cloned and sequenced, and were shown to have high homology with those of rat and mouse. RT-PCR analysis showed CNP mRNA expression in the kidney, proximal and distal colon and small intestine, whilst NPR-B mRNA expression was found in the kidney, proximal and distal colon and the atria. Using a semi-quantitative multiplex PCR technique, the expression of renal CNP and NPR-B mRNA was determined in 7- and 14-day water-deprived hopping mice, in parallel with control hopping mice (access to water). Water deprivation significantly decreased the relative levels of CNP and NPR-B mRNA expression in both the 7- and 14-day water-deprived hopping mice, when compared to control hopping mice. In contrast, the ability of CNP to stimulate cGMP production was significantly increased after 14 days of water deprivation. This study shows that alterations in the renal CNP/NPR-B system may be an important physiological adjustment when water is scarce.

Cloning and mRNA expression of guanylin, uroguanylin, and guanylyl cyclase C in the Spinifex hopping mouse, Notomys alexis

Guanylin and uroguanylin are peptides that activate guanylyl cyclase C (GC-C) receptors in the intestine and kidney, which causes an increase in the excretion of salt and water. The Spinifex hopping mouse, Notomys alexis, is a desert rodent that can survive for extended periods without free access to water and it was hypothesised that to conserve water, the expression of guanylin, uroguanylin, and GC-C would be down-regulated to reduce the excretion of water in urine and faeces. Accordingly, this study examined the expression of guanylin, uroguanylin, and GC-C mRNA in Notomys under normal (access to water) and water-deprived conditions. Initially, guanylin and uroguanylin cDNAs encoding the full open reading frame were cloned and sequenced. A PCR analysis showed guanylin and uroguanylin mRNA expression in the small intestine, caecum, proximal and distal colon, heart, and kidney. In addition, a partial GC-C cDNA was obtained and GC-C mRNA expression was demonstrated in the proximal and distal colon, but not the kidney. Subsequently, a semi-quantitative PCR method showed that water deprivation in Notomys caused a significant increase in guanylin and uroguanylin mRNA expression in the distal colon, and in guanylin and GC-C mRNA expression in the proximal colon. No significant difference in guanylin and uroguanylin mRNA expression was observed in the kidney. The results of this study indicate that there is, in fact, an up-regulation of the colonic guanylin system in Notomys after 7 days of water deprivation.

Epidermal growth factor-induced epithelio-mesenchymal transition in human breast carcinoma cells

PMC42-LA cells display an epithelial phenotype: the cells congregate into pavement epithelial sheets in which E-cadherin and beta-catenin are localized at cell-cell borders. They abundantly express cytokeratins, although 5% to 10% of the cells also express the mesenchymal marker vimentin. Stimulation of PMC42-LA cells with epidermal growth factor (EGF) leads to epithelio-mesenchymal transition-like changes including up-regulation of vimentin and down-regulation of E-cadherin. Vimentin expression is seen in virtually all cells, and this increase is abrogated by treatment of cells with an EGF receptor antagonist. The expression of the mesenchyme-associated extracellular matrix molecules fibronectin and chondroitin sulfate proteoglycan also increase in the presence of EGF. PMC42-LA cells adhere rapidly to collagen I, collagen IV, and laminin-1 substrates and markedly more slowly to fibronectin and vitronectin. EGF increases the speed of cell adhesion to most of these extracellular matrix molecules without altering the order of adhesive preference. EGF also caused a time-dependent increase in the motility of PMC42-LA cells, commensurate with the degree of vimentin staining. The increase in motility was at least partly chemokinetic, because it was evident both with and without chemoattractive stimuli. Although E-cadherin staining at cell-cell junctions disappeared in response to EGF, beta-catenin persisted at the cell periphery. Further analysis revealed that N-cadherin was present at the cell-cell junctions of untreated cells and that expression was increased after EGF treatment. N- and E-cadherin are not usually coexpressed in human carcinoma cell lines but can be coexpressed in embryonic tissues, and this may signify an epithelial cell population prone to epithelio-mesenchymal-like responses.

Improving children's recall of an occurrence of a repeated event: is it a matter of helping them to generate options?

Three experiments were conducted to explore whether children's recall of an occurrence of a repeated event could be improved by encouraging them to consider various details that occurred across a series of events prior to making a judgement about which details were included in the target (to-be-recalled) occurrence. Experiment 1 explored whether children's recall of the target occurrence was better after the interviewer presented all the items from the series prior to the child identifying the final item. Experiment 2 explored whether having the children generate all the items facilitated their subsequent recall of the target occurrence. Finally, Experiment 3 directly compared the effectiveness of the above 2 procedures. Regardless of the children's age, the retention interval, or the type of item, children's capacity to identify which details were included in a target occurrence was enhanced when they were initially provided with all the possible details from the series of events. However, without relying on the interviewer to generate the options, the benefit of the technique was directly contingent on the children's ability to generate content details; this was a distinct source of difficulty for the children. Indeed, having children generate options had no beneficial effect on decisions about the temporal position of items unless performance was made conditional on the children's ability to remember the relevant details in the first place. The implications of the findings for the legal setting and for future research are discussed.

The effect of contextual cues on children`s ability to remember an occurence of a repeated event

Purpose. This study examined the usefulness of contextual cues in enhancing the accuracy of children's narrative accounts of an occurrence of a repeated event.

Method. Children aged 6 to 7 years took part in the same staged event four times whereby 16 target details varied in each occurrence (e.g. the colour of a cloak varied each time). Three days later, the children's free recall of the final occurrence was elicited. This occurrence was identified in one of two ways. Either it was identified via the temporal term 'last', or else the term 'last' was combined with a feature related to the environmental context or setting that was unique to the occurrence (i.e., the interviewer referred to a new object that was worn throughout the occurrence or a new person who carried out the event). For each condition, performance was compared to that of children who experienced the event only once.

Results. Children's memory of details specific to the target occurrence was better after the single than the repeated event. However for both event types, children who were given the contextual and temporal cue performed better than those who were given the temporal cue only. The benefit of using a contextual cue did not result in an increase in errors.

Conclusion. Contextual cues (generated by an interviewer) can facilitate children's recall of an occurrence of an event. However, further research needs to determine whether this finding would generalize to a more practical situation where the child (rather than the interviewer) generates the cues.

Do simple "groundrules" reduce preschoolers' suggestibility about experienced and nonexperienced events?

This study examined whether providing preschool children with simple groundrules (the importance of being complete, saying „I don‟t know‟, correcting the interviewer and not guessing) would reduce false details in their recall of a staged event. Forty-nine preschool children participated in an event that consisted of two activities. One or two days later they were given a biasing interview that included false suggestions about one of the experienced activities as well as a non-experienced activity. For the other activity, no suggestions were made. Eight, 15, and 22 days after the event, the children were required to recall all three activities in their own words. Immediately prior to their recall, half of the children were provided with the groundrules while the remaining children were not. The children in the control group also participated in a fifth interview in which they received the groundrule instructions. The results revealed that the provision of the groundrules had negligible impact on the accuracy of information provided irrespective of the context or order of the interview or the activity being recalled. The implications of these results are discussed and suggestions for future research are offered.

Nitric oxide control of the dorsal aorta and the intestinal vein of the Australian short-finned eel Anguilla australis

This study investigated the mechanisms by which nitric oxide (NO) regulates the dorsal aorta and the intestinal vein of the Australian short-finned eel Anguilla australis. NADPH diaphorase histochemistry and immunohistochemistry using a mammalian endothelial nitric oxide synthase (NOS) antibody could not demonstrate NOS in the endothelium of either blood vessel; however, NOS could be readily demonstrated in the endothelium of the rat aorta that was used as a control. Both blood vessels contained NADPH diaphorase positive nerve fibres and nerve bundles, and immunohistochemistry using a neural NOS antibody showed a similar distribution of neural NOS immunoreactivity in the perivascular nerves. In vitro organ bath physiology showed that a NO/soluble guanylyl cyclase (GC) system is present in the dorsal aorta and the intestinal vein, since the soluble GC inhibitor oxadiazole quinoxalin^-1 (ODQ; 10^–5 mol l^–1) completely abolished the vasodilatory effect of the NO donor, sodium nitroprusside (SNP; 10^–4 mol l^–1). In addition, nicotine (3x10^–4 mol l^–1) mediated a vasodilation that was not affected by removal of the endothelium. The nicotine-mediated dilation was blocked by the NOS inhibitor, Nω-nitro-arginine (L-NNA; 10^–4 mol l^–1), and ODQ (10^–5 mol l^–1). More specifically, the neural NOS inhibitor, Nω-propyl-L-arginine (10^–5 mol l^–1), significantly decreased the dilation induced by nicotine (3x10^–4 mol l^–1). Furthermore, indomethacin (10^–5 mol l^–1) did not affect the nicotine-mediated dilation, suggesting that prostaglandins are not involved in the response. Finally, the calcium ionophore A23187 (3x10^–6 mol l^–1) caused an endothelium-dependent dilation that was abolished in the presence of indomethacin. We propose the absence of an endothelial NO system in eel vasculature and suggest that neurally derived NO contributes to the maintenance of vascular tone in this species. In addition, we suggest that prostaglandins may act as endothelially derived relaxing factors in A. australis.

Comparative aspects of natriuretic peptide physiology in non-mammalian vertebrates: a review

The natriuretic peptide system is a complex family of peptides and receptors that is primarily linked to the maintenance of osmotic and cardiovascular homeostasis. A natriuretic peptide system is present in each vertebrate class but there are varying degrees of complexity in the system. In agnathans and chondrichthyians, only one natriuretic peptide has been identified, while new data has revealed that multiple types of natriuretic peptides are present in bony fish. However, it seems in tetrapods that there has been a reduction in the number of natriuretic peptide genes, such that only three natriuretic peptides are present in mammals. The peptides act via a family of guanylyl cyclase receptors to generate the second messenger cGMP, which  mediates a range of physiological effects at key targets such as the gills, kidney and the cardiovascular system. This review summarises the current knowledge of the natriuretic peptide system in non-mammalian vertebrates and discusses the physiological actions of the peptides.

The effect of water deprivation on signalling molecules that utilise cGMP in the Spinifex Hopping Mouse Notomys alexis

In mammals the natriuretic and guanylin peptides influence renal and intestinal fluid content and electrolyte transport by binding to and activating guanylyl cyclase (GC) receptors that in turn stimulate production of the intracellular second messenger guanosine 3':5'-cyclic monophospate
(cGMP). However, the role of natriuretic and guanylin peptides in desert mammals is not understood. The spinifex hopping-mouse (Notomys alexis), has a suite of behavioural and physiological mechanisms that permits survival for extended periods without access to free water. Because signalling molecules that generate cGMP are known to promote water excretion, it was predicted that natriuretic and guanylin peptide synthesis would be down regulated in water-deprived N. alexis, and thus reduce the amount of water lost in the urine and faeces. However, in the kidney ANP and GC-A mRNA levels were increased in water-deprived mice, but CNP and GC-B mRNA levels were decreased. Water deprivation increased guanylin and uroguanylin mRNA expression in the distal colon, but it remained unchanged in the kidney and proximal colon. The expression of GC-C mRNA increased in the proximal colon but not in the distal colon. This study shows that water deprivation differentially affects the expression of regulatory molecules that stimulate cGMP producti

The degree of usability from selected DVD menus and their navigational systems

The purpose of this research is to investigate the usability of DVD interfaces via their menus and navigation, inspired by Donald Norman who has had a pivotal role in user-centred design and usability. The paper encompasses theoretical aspects of interactivity, usability and DVD technology. A usability test was administered with the DVDs chosen. The results from the usability test were the main focus in this research. Such results were supportive of Normanrsquos claims, as participants experienced varying degrees of usability issues. Furthermore, the findings were used to develop a set of guidelines and recommendations designers could follow. If these were adhered to, it would have significantly alleviated the difficulty the participants had in interacting with the DVDs.

Nitric oxide control of large veins in the toad Bufo marinus

This study examined the nitric oxide (NO) control of the vascular smooth muscle of the ventral abdominal vein and vena cava of the toad, Bufo marinus, by using anatomical and physiological approaches. Nicotinamide adenine di-nucleotide phosphate-diaphorase histochemistry and immunohistochemistry using endothelial nitric oxide synthase (NOS) and neural NOS antibodies produced no evidence for endothelial NOS in the veins, but, neural NOS-immunoreactive perivascular nerves were present. Acetylcholine (10^–5 M) caused a vasodilation in both veins that was endothelium-independent, and which was blocked by the soluble guanylyl cyclase inhibitor, ODQ (10^–5 M). The NOS inhibitors, L-NNA (10^–4 M) and L-NAME (10^–4 M), did not significantly reduce the vasodilatory effect of acetylcholine in the veins; this suggested that the vasodilation was not due to NO. However, in the presence of phenoxybenzamine (10^–7–10^–8 M), L-NNA significantly reduced the vasodilatory effect of acetylcholine in the veins. This unusual response is due to phenoxybenzamine partially inactivating the muscarinic receptor pool in the veins. In addition, the neural NOS inhibitor, vinyl-L-NIO (10^–5 M), significantly reduced the acetylcholine-mediated vasodilation in the presence of phenoxybenzamine. The results show that in toad veins, nitrergic nerves rather than an endothelial NO system are involved in NO-mediated vasodilation.