http://espace.library.uq.edu.au/ The University of Queensland en Fez http://blogs.law.harvard.edu/tech/rss http://espace.library.uq.edu.au/view/UQ:64157 Neuronal and glial high-affinity transporters regulate extracellular glutamate concentration, thereby terminating synaptic transmission and preventing neuronal excitotoxicity. Glutamate transporter activity has been shown to be modulated by protein kinase C (PKC) in cell culture. This is the first study to demonstrate such modulation in situ, by following the fate of the non-metabolisable glutamate transporter substrate, D-aspartate. In the rat retina, pan-isoform PKC inhibition with chelerythrine suppressed glutamate uptake by GLAST (glutamate/aspartate transporter), the dominant excitatory amino acid transporter localized to the glial Muller cells. This effect was mimicked by rottlerin but not by Go6976, suggesting the involvement of the PKCdelta isoform, but not PKCalpha, beta or gamma. Western blotting and immunohistochemical labeling revealed that the suppression of glutamate transport was not due to a change in transporter expression. Inhibition of PKCdelta selectively suppressed GLAST but not neuronal glutamate transporter activity. These data suggest that the targeting of specific glutamate transporters with isoform-specific modulators of PKC activity may have significant implications for the understanding of neurodegenerative conditions arising from compromised glutamate homeostasis, e.g. glaucoma and amyotrophic lateral sclerosis. 2007-08-14T00:00:00Z Bull, N. D. og Barnett, N. L. http://espace.library.uq.edu.au/view/UQ:287811 2012-12-23T00:55:36Z Jain, Umang og Woodruff, Trent og Stadnyk, Andrew http://espace.library.uq.edu.au/view/UQ:275706 Insights into the anatomical organization of complex neural circuits provide important information about function, and thus tools that facilitate neuroanatomical studies have proved invaluable in neuroscience. Advances in molecular cloning have allowed the production of novel recombinant neuroinvasive viruses for use in transynaptic neural tracing studies. However, the vast majority of these viruses have motility in the retrograde direction only, therefore limiting their use to studies of synaptic input circuitry. Here we describe the construction of an EGFP reporting herpes simplex virus, strain H129, which preferentially moves along synaptically connected neurons in the anterograde direction. In vitro and in vivo characterization studies confirm that the HSV-1 H129–EGFP retains comparable replication and neuroinvasiveness as the wildtype H129 virus. As a proof of principle we confirm anterograde movement of the H129–EGFP along polysynaptic pathways by inoculating the upper airways and tracking time-dependent EGFP expression in previously described ascending sensory pathways. These data confirm a genomic locus for recombining HSV-1 H129 such that normal viral function and replication is maintained. Novel viral recombinants such as HSV-1 H129–EGFP will be useful tools for delineating the central organization of peripheral sensory pathways as well as the synaptic outputs from central neuronal populations. 2012-06-14T10:38:08Z McGovern, Alice E. og Davis-Poynter, Nicholas og Rakoczy, Joanna og Phipps, Simon og Simmons, David G. og Mazzone, Stuart B. http://espace.library.uq.edu.au/view/UQ:161143 2009-01-19T00:00:00Z Stephan, Carl N. http://espace.library.uq.edu.au/view/UQ:193798 Multiple organ failure (MOF) and compromised immune function, which results in increased susceptibility to sepsis, remain major causes of burn morbidity and mortality. The major frustration for the burns team is for the patient to survive the critical care period, only to succumb to infection, which is known to cause over 75% of burn deaths. 2010-01-25T00:00:00Z Ranasinghe, K. og Cross, S. E. og Venkatesh, B. http://espace.library.uq.edu.au/view/UQ:220407 2010-11-15T00:00:00Z Willis, Sarah og Stoll, James og Sweetman, Lawrence og Borges, Karin http://espace.library.uq.edu.au/view/UQ:191463 Anticonvulsant effects of the ketogenic diet (KD) have been reported in the mouse, although previous studies did not control for intake of vitamins, minerals and antioxidants. The aim of this study was to examine the effects of balanced ketogenic and control diets in acute mouse seizure models. The behavior in four mouse seizure models, plasma d-β-hydroxybutyrate (d-BHB) and glucose levels were determined after feeding control diet, 4:1 and 6:1 KDs with matched vitamins, minerals and antioxidants. Feeding 4:1 and 6:1 KDs ad lib to 3-week-old (adolescent) mice resulted in 1.2–2.2 mM d-BHB in plasma, but did not consistently change glucose levels. The 6:1 KD reproducibly elevated the CC50 (current that initiates seizures in 50% mice tested) in the 6-Hz model after 14 days of feeding to adolescent CD1 mice. Higher plasma d-BHB levels correlated with anticonvulsant effects. Despite ketosis, no consistent anticonvulsant effects of KDs were found in the fluorothyl or pentylenetetrazole CD1 mouse models. The 4:1 KD was neither anticonvulsant nor neuroprotective in hippocampus in the C3H mouse kainate model. Taken together, the KD's anticonvulsant effect was limited to the 6-Hz model, required chronic feeding with 6:1 fat content, and was independent from lowering plasma glucose. 2010-01-06T00:00:00Z Samala, Ramakrishna og Willis, Sarah og Borges, Karin http://espace.library.uq.edu.au/view/UQ:191919 2010-01-10T00:00:00Z Borges, K. og Willis, S. og Sweetman, L. og Stoll, J. http://espace.library.uq.edu.au/view/UQ:220340 2010-11-15T00:00:00Z Borges, K. og Thomas, N. K. og Stoll, J. og Seth, S. http://espace.library.uq.edu.au/view/UQ:202379 2010-04-11T00:00:00Z Iyer, Abishek og Fenning, Andrew og Lim, Junxian og Le, Giang T og Reid, Robert C og Halili, Maria A og Fairlie, David P og Brown, Lindsay http://espace.library.uq.edu.au/view/UQ:245655 2011-08-17T00:00:00Z Lousberg, Erin L. og Diener, Kerrilyn R. og Fraser, Cara K. og Phipps, Simon og Foster, Paul S. og Chen, Weisan og Uematsu, Satoshi og Akira, Shizuo og Robertson, Sarah A. og Brown, Michael P. og Hayball, John D. http://espace.library.uq.edu.au/view/UQ:233985 2011-03-09T00:00:00Z Flood-Page, P. og Menzies-Gow, A. og Phipps, S. og Ying, S. og Wangoo, A. og Ludwig, M. S. og Barnes, N. og Robinson, D. og Kay, A. B. http://espace.library.uq.edu.au/view/UQ:220168 2010-11-11T00:00:00Z Ghazanfari, N. og Gervasio, O. L. og Ngo, S. T. og Reddel, S. R. og Phillips, W. D. http://espace.library.uq.edu.au/view/UQ:79563 The aim of this study was to determine the effects of dietary antioxidant supplementation with a-tocopherol and a-lipoic acid on cyclosporine-induced alterations to erythrocyte and plasma redox balance, and cyclosporine-induced endothelial and smooth muscle dysfunction. Rats were randomly assigned to either control, antioxidant, cyclosporine or cyclosporine + antioxidant treatments. Cyclosporine A was administered for 10 days after an 8-week feeding period. Plasma was analyzed for alpha-tocopherol, total antioxidant capacity, malondialdehyde and creatinine. Erythrocytes were analyzed for glutathione, methemoglobin, superoxide dismutase, catalase, glutathione peroxidase, glucose-6-phosphate dehydrogenase, alpha-tocopherol and malondialdehye. Vascular endothelial and smooth muscle function was determined in vitro. Antioxidant supplementation resulted in significant increases in erythrocyte a-tocopherol concentration and glutathione peroxidase activity in both of the antioxidant-supplemented groups. Cyclosporine administration caused significant decreases in glutathione concentration, methemoglobin concentration and superoxide dismutase activity. Antioxidant supplementation attenuated the cyclosporine-induced decrease in superoxide dismutase activity. Cyclosporine therapy impaired both endothelium-independent and -dependent relaxation of the thoracic aorta, and this was attenuated by antioxidant supplementation. In summary, dietary supplementation with alpha-tocopherol and alpha-lipoic acid attenuated the cyclosporine-induced decrease in erythrocyte superoxide dismutase activity and attenuated cyclosporine-induced vascular dysfunction. 2007-08-15T00:00:00Z Lexis, L. A. og Fenning, A. og Brown, L. og Fassett, R. G. og Coombes, J. S. http://espace.library.uq.edu.au/view/UQ:110249 We used replication-deficient adenoviruses overexpressing antisense against G(q) class alpha-subunits to determine the roles of G(q) and G(11) in mediating M-3-receptor-coupled Ca2+ mobilization in intact HT29 human colonic carcinoma epithelial cells. Western blot analysis and confocal microscopy showed that the viruses expressing antisense directed against the alpha-subunits of G(q) or G(11) produced isoform-specific reductions in the levels of these alpha-subunits. Fura-2 was used to measure changes in the Ca2+ response following activation of the M-3 receptors by carbachol. The G(alphaq) antisense virus suppressed the peak Ca2+ response by 70%, whereas the G(alpha11) antisense virus reduced it by 34%. We then used co-infection with both viruses to determine the effect of concomitant suppression of both G(alphaq) and G(alpha11). Overexpression of antisense to both alpha-subunits reduced by approximately 50% the levels of both G(alphaq) and G(alpha11). It also almost completely inhibited the Ca2+ response to carbachol. These data show that both G(q) and G(11) are involved in mediating the action of the M-3 receptor on cytosolic Ca2+ in HT29 cells. Furthermore, they suggest that the coupling of the M-3 receptor to these G proteins is specific, in that G(alphaq) cannot substitute for G(alpha11), and vice versa. 2007-09-19T00:00:00Z Cummins, M. M. og O'Mullane, L. M. og Barden, J. A. og Cook, D. I. og Poronnik, P. http://espace.library.uq.edu.au/view/UQ:228042 2011-02-03T00:00:00Z Keren, Daniel og Osdachy, Rita og Gal, Yaniv http://espace.library.uq.edu.au/view/UQ:256602 Sea turtles undertake long migrations in the open ocean, during which they rely at least partly on magnetic cues for navigation. In principle, sensitivity to polarized light might be an additional sensory capability that aids navigation. Furthermore, polarization sensitivity has been linked to ultraviolet (UV) light perception which is present in sea turtles. Here, we tested the ability of hatchling loggerheads (Caretta caretta) to maintain a swimming direction in the presence of broad-spectrum polarized light. At the start of each trial, hatchling turtles, with their magnetic sense temporarily impaired by magnets, successfully established a steady course towards a lightemitting diode (LED) light source while the polarized light field was present. When the LED was removed, however, hatchlings failed to maintain a steady swimming direction, even though the polarized light field remained. Our results have failed to provide evidence for polarized light perception in young sea turtles and suggest that alternative cues guide the initial migration offshore. 2011-10-18T00:00:00Z Mathger, Lydia M. og Lohmann, Kenneth J. og Limpus, Colin J. og Fritsches, Kerstin A. http://espace.library.uq.edu.au/view/UQ:109259 Although mouse oocytes and cleavage-stage embryos prefer pyruvate and lactate for metabolic fuels, they do take up and metabolize glucose. Indeed, presentation of glucose during the cleavage stages is required for subsequent blastocyst formation, which normally relies on uptake and metabolism of large amounts of glucose. Expression of the facilitative glucose transporter GLUT1 was examined using immunohistochemistry and Western blotting, and in polyspermic oocytes, metabolism of glucose was measured and compared with that of pyruvate and glutamine. GLUT1 was observed in all oocytes and embryos, and membrane and vesicular staining was present. Additionally, however, in polyspermic oocytes, the most intense staining was in the pronuclei, and this nuclear staining persisted in cleaving normal embryos. Furthermore, GLUT1 expression appeared to be up-regulated both in nuclei and plasma membranes following culture of oocytes in the absence of glucose. in polyspermic oocytes, the metabolism of glucose, but not of pyruvate or glutamine, was directly proportional to the number of pronuclei formed. After compaction, nuclear staining diminished, and GLUT1 localized to basolateral membranes of the outer cells and trophectoderm In blastocysts, a weak but uniform staining of inner-cell-mass plasma membranes was apparent. The results are discussed in terms of potential roles for GLUT1 in pronuclei of oocytes and zygotes, nuclei of cleavage-stage embryos, and a transepithelial transport function for GLUT1, probably coupled with GLUT3, in compacted embryos and blastocysts. 2007-09-19T00:00:00Z Pantaleon, M. og Ryan, J. P. og Gil, M. og Kaye, P. L. http://espace.library.uq.edu.au/view/UQ:36833 Arylamine N-acetyltransferase (NAT) was first identified as the inactivator of the anti-tubercular drug isoniazid, The enzyme was shown to catalyse the transfer of an acetyl group from acetyl-CoA to the terminal nitrogen of the hydrazine drug. The rate of inactivation of isoniazid was polymorphically distributed in the population and was one of the first examples of pharmacogenetic variation, NAT was identified recently in Mycobacterium tuberculosis and is a candidate for; modulating the response to isoniazid, Genome sequences have revealed many homologous members of this unique family of enzymes. The first three-dimensional structure of a member of the NAT family identifies a catalytic triad consisting of aspartate, histidine and cysteine proposed to form the activation mechanism. So far, all procaryotic NATs resemble the human enzyme which acetylates isoniazid (NAT2), Human NAT2 is characteristic of drug-metabolizing enzymes: it is found in liver and intestine, In humans and other mammals, there are up to three different isoenzymes. If only one isoenzyme is present, it is like human NAT1. Human NAT1 and its murine equivalent specifically acetylate the folate catabolite p-amino-benzoylglutamate. NAT1 and its murine homologue each have a ubiquitous tissue distribution and are expressed early in development at the blastocyst stage, During murine embryonic development, NAT is expressed in the developing neural tube. The proposed endogenous role of NAT in folate metabolism, and its multi-allelic nature, indicate that its role in development should be assessed further. 2007-08-13T00:00:00Z Sim, E og Payton, M og Noble, M og Minchin, R http://espace.library.uq.edu.au/view/UQ:76051 The external loop linking the M2 and M3 transmembrane domains is crucial for coupling agonist binding to channel gating in the glycine receptor chloride channel (GlyR). A substituted cysteine accessibility scan previously showed that glycine activation increased the surface accessibility of 6 contiguous residues (Arg(271) Lys(276)) toward the N-terminal end of the homomeric alpha 1 GlyR M2 - M3 loop. In the present study we used a similar approach to determine whether the allosteric antagonist, picrotoxin, could impose conformational changes to this domain that cannot be induced by varying agonist concentrations alone. Picrotoxin slowed the reaction rate of a sulfhydryl-containing compound ( MTSET) with A272C, S273C, and L274C. Before interpreting this as a picrotoxin-specific conformational change, it was necessary to eliminate the possibility of steric competition between picrotoxin and MTSET. Accordingly, we showed that picrotoxin and the structurally unrelated blocker, bilobalide, were both trapped in the R271C GlyR in the closed state and that a point mutation to the pore-lining Thr(6') residue abolished inhibition by both compounds. We also demonstrated that the picrotoxin dissociation rate was linearly related to the channel open probability. These observations constitute a strong case for picrotoxin binding in the pore. We thus conclude that the picrotoxin-specific effects on the M2 - M3 loop are mediated allosterically. This suggests that the M2 - M3 loop responds differently to the occupation of different binding sites. 2007-08-15T00:00:00Z Hawthorne, Rebecca L. og Lynch, Joseph W. http://espace.library.uq.edu.au/view/UQ:197519 Different types of senile plaques occur in brains of Alzheimer’s disease (AD) patients. Senile plaques seen in early preclinical stages of AD differ from those in clinical stages both in their composition of Aβ-peptides of different lengths and other proteins, e.g., apoE. ApoE is involved in Aβ-transport and -uptake. Therefore, it is tempting to speculate that apoE plays a role in senile plaque generation. To characterize the association between apoE and Aβ-peptides of different lengths and its impact on initial Aβ-deposition, we studied the medial temporal lobe of 60 autopsy cases encompassing the full spectrum of AD-related pathology as well as controls. Aβ-deposits in regions becoming newly involved in a given stage of β-amyloidosis exclusively consisted of new-formed plaques. In 36 cases, apoE was present in these new-formed plaques. Here, apoE was frequently co-localized with Aβ-deposits detectable with anti-Aβ42 but not with antibodies raised against N-terminal epitopes of Aβ. In contrast, immunoreactivity against apoE was completely absent in new-formed plaques of other cases where at the same time immunoreactivity against N-terminal epitopes of Aβ was present. The lacking co-localization of N-terminal epitopes of Aβ with apoE in new-formed plaques suggests that these deposits represent apoE-Aβ complexes in which the N-terminal epitopes of Aβ are often concealed after complexing with apoE, thus, preventing subsequent binding of antibodies. 2010-03-03T00:00:00Z Thal, D. R. og Capetillo-Zarate, E. og Schultz, C. og Rüb, U. og Saido, T. C. og Yamaguchi, H. og Haass, C. og Griffin, S. T. og Braak, H. og Ghebremedhin, E. http://espace.library.uq.edu.au/view/UQ:197340 2010-03-02T00:00:00Z Thal, D. R. og Capetillo-Zarate, E. og Schultz, C. og Rub, U. og Saido, T. C. og Yamaguchi, H. og Haass, C. og Griffin, W. S. T. og Del Tredici, K. og Braak, H. og Ghebremedhin, E. http://espace.library.uq.edu.au/view/UQ:189368 Different types of amyloid beta-protein (Abeta)-containing plaques occur in brains of Alzheimerrsquos disease (AD) patients. Diffuse plaques seen during early stages of AD differ from neuritic plaques in later stages both with respect to the length of the Abeta peptides and the presence of other proteins, e.g., apolipoprotein-E (apoE). Since apoE is involved in Abeta transport and clearance, and the epsi4-allele of the apolipoprotein-E gene (APOE) is a major risk factor for sporadic AD, it is plausible to speculate that apoE plays a pathophysiological role in the initiation of Abeta deposition. To address the issue of whether binding of apoE to Abeta is involved in initial Abeta deposition, we studied the human medial temporal lobe of 60 autopsy cases encompassing the full spectrum of AD-related pathology. In temporal lobe regions, which become involved for the first time at a given stage of beta-amyloidosis, all plaques represent newly formed plaques, and these were studied with immunohistochemical methods. ApoE was present in 36 cases, and was frequently co-localized with newly formed Abeta deposits detectable with anti-Abeta42 but not with antibodies raised against N-terminal epitopes of Abeta. In 10 additional cases, immunoreactivity against apoE was completely lacking in newly formed plaques, which, at the same time, displayed immunoreactivity against N-terminal epitopes of Abeta. The failure of N-terminal epitopes of Abeta to co-localize with apoE in newly formed plaques indicates that these deposits presumably contain apoE-Abeta complexes, in which the N-terminal epitopes of Abeta are often concealed after complexing with apoE, thus preventing subsequent binding of antibodies. Moreover, apoE-positive newly formed plaques were seen more frequently in APOE epsi4/4 cases than in non-APOE epsi4/4 individuals, thereby underlining the potentially crucial role of apoE for the development of Abeta deposits. 2009-12-08T00:00:00Z Thal, Dietmar R. og Capetillo-Zaratel, Estibaliz og Schultz, Christian og Rub, Udo og Saido. Takaomi, C. og Yamaguchi, Haruyasu og Haass, Christian og Griffin, Sue T. og Del Tredici, Kelly og Braak, Heiko og Ghebremedhin, Estifanos http://espace.library.uq.edu.au/view/UQ:250435 2011-09-10T00:00:00Z Cuttle, L. og Kempf, M. og Hayes, M. T. og Mill, J. og Fraser, J. F. og Kimble, R. M. http://espace.library.uq.edu.au/view/UQ:96845 Spermine is a potent, voltage-dependent blocker of the olfactory cyclic nucleotide-gated channel from both the intracellular and extracellular sides. However, its sites of action are unknown. This study investigated the external spermine binding site in the rat CNC alpha3 subunit. Neutralization of a glutamic acid residue (E342Q) in the P-loop region eliminated voltage-dependence of block by externally applied spermine. The charge-conservative E342D mutation had little effect on spermine block. Thus, E342 forms the binding site for externally applied spermine. However, spermine remained a potent voltage-independent blocker of the E342Q mutant channel, suggesting that the mutation either created a novel binding site outside the membrane electrical field or that it dramatically changed the properties of the existing pore site. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved. 2007-08-24T00:00:00Z Nevin, S. og Haddrill, J. L. og Lynch, J. W. http://espace.library.uq.edu.au/view/UQ:140509 Spermine is a potent, voltage-dependent blocker of the olfactory cyclic nucleotide-gated channel from both the intracellular and extracellular sides. However, its sites of action are unknown. This study investigated the external spermine binding site in the rat CNCgreek small letter alpha3 subunit. Neutralization of a glutamic acid residue (E342Q) in the P-loop region eliminated voltage-dependence of block by externally applied spermine. The charge-conservative E342D mutation had little effect on spermine block. Thus, E342 forms the binding site for externally applied spermine. However, spermine remained a potent voltage-independent blocker of the E342Q mutant channel, suggesting that the mutation either created a novel binding site outside the membrane electrical field or that it dramatically changed the properties of the existing pore site. 2008-06-10T00:00:00Z Nevin, Simon T. og Haddrill, Justine L. og Lynch, Joseph W. http://espace.library.uq.edu.au/view/UQ:76112 2007-08-15T00:00:00Z Woodruff, Trent M. og Arumugam, Thiruma V. og Shiels, Ian A. og Newman, Michelle L. og Ross, Paul A. og Reid, Robert C. og Fairlie, David P. og Taylor, Stephen M. http://espace.library.uq.edu.au/view/UQ:160284 Cholesterol is one of multiple factors, other than familial genetic mutations, that can influence amyloid-β peptide (Aβ) metabolism and accumulation in Alzheimer disease (AD). The effect of a high-cholesterol diet on amyloid precursor protein (APP) processing in brain has not been thoroughly studied. This study was designed to further investigate the role of cholesterol in the production of Aβ and APP intracellular domain (AICD) in 12-month-old Tg2576 transgenic mice. The mice were maintained on a high-cholesterol diet for 6 weeks. We found that diet-induced hypercholesterolemia increased the APP cytosolic fragment AICD and reduced sAPPα in the Tg2576 mice compared to the mice on a control basal diet. In addition, the levels of detergent-extracted Aβ40 were reduced, although no change in guanidine-extracted Aβ levels was observed. Full-length APP, α/βC-terminal fragment (α/βCTF), and β-secretase (BACE) were not different in the cholesterol-fed mice compared to the control diet-fed mice. This study suggests that a high dietary cholesterol in aged mice may not only influence Aβ metabolism, but also regulate the AICD levels. AICD has a proposed role in signal transduction and apoptosis, hence modulation of AICD production could be an alternative mechanism by which cholesterol contributes to AD pathogenesis. 2009-01-09T00:00:00Z George, Amee J og Holsinger, R. M. Damian og McLean, Catriona A. og Laughton, Katrina M. og Beyreuther, Konrad og Evin, Genevieve og Masters, Colin L. og Li, Qiao-Xin http://espace.library.uq.edu.au/view/UQ:140854 2008-06-10T00:00:00Z Fukui, Y. Y. og Bedi, K. S. http://espace.library.uq.edu.au/view/UQ:78674 2007-08-15T00:00:00Z Miki, og Satriotomo, I. og Li, H. og Matsumoto, og Gu, H. og Yokoyama, T. og Lee, K.Y. og Bedi, K. S. og Takeuchi, Y. http://espace.library.uq.edu.au/view/UQ:112844 To activate skeletal muscle contraction, action potentials must be sensed by dihydropyridine receptors (DHPRs) in the T tubule, which signal the Ca2+ release channels or ryanodine receptors (RyRs) in the sarcoplasmic reticulum (SR) to open. We demonstrate here an inhibitory effect of the T tubule on the production of sparks of Ca2+ release. Murine primary cultures were confocally imaged for Ca2+ detection and T tubule visualization. After 72 h of differentiation, T tubules extended from the periphery for less than one-third of the myotube radius. Spontaneous Ca2+ sparks were found away from the region of cells where tubules were found. Immunostaining showed RyR1 and RyR3 isoforms in all areas, implying inhibition of both isoforms by a T tubule component. To test for a role of DHPRs in this inhibition, we imaged myotubes from dysgenic mice (mdg) that lack DHPRs. These exhibited T tubule development similar to that of normal myotubes, but produced few sparks, even in regions where tubules were absent. To increase spark frequency, a high-Ca2+ saline with 1 mM caffeine was used. Wildtype cells in this saline plus 50 mu M nifedipine retained the topographic suppression pattern of sparks, but dysgenic cells in high-Ca2+ saline did not. Shifted excitation and emission ratios of indo-1 in the cytosol or mag-indo-1 in the SR were used to image [Ca2+] in these compartments. Under the conditions of interest, wild-type and mdg cells had similar levels of free [Ca2+] in cytosol and SR. These data suggest that DHPRs play a critical role in reducing the rate of spontaneous opening of Ca2+ release channels and/or their susceptibility to Ca2+-induced activation, thereby suppressing the production of Ca2+ sparks. 2007-09-19T00:00:00Z Zhou, Jingsong og Yi, Jianxun og Royer, Leandro og Launikonis, Bradley S. og Gonzalez, Adom og Garcia, Jesus og Rios, Eduardo http://espace.library.uq.edu.au/view/UQ:130431 Picrotoxin, an antagonist of structurally-rated GABAA receptors (GABA(A)Rs) and glycine receptors (GlyRs), is an equimolar mixture of picrotoxinin (PTXININ) and picrotin (PTN). These compounds share a common structure except that PTN contains a slightly larger climethylmethanol in place of the PTXININ isopropenyl group. Although the homomeric alpha 1 GlyR is equally sensitive to both compounds, we show here that homomeric alpha 2 and alpha 3 GlyRs, like most GABA(A)Rs, are selectively inhibited by PTXININ. As conservative mutations to pore-lining 6' threonines equally affect the sensitivity of the alpha 1 GlyR to both compounds, we conclude that PTXININ and PTN bind to 6' threonines by hydrogen bonding with exocyclic oxygens common to both molecules. In contrast, substitution of the 2' pore-lining glycine by serine selectively reduces PTN sensitivity, whereas the introduction of 2' alanines selectively increases PTXININ sensitivity. These results define the orientation of PTXININ and PTN binding in the all GlyR pore and allow us to conclude that the relatively reduced sensitivity of PTN at GABA(A)Rs and alpha 2 and alpha 3 GlyRs is due predominantly to its larger size and reduced ability to form hydrophobic interactions with 2' alanines. 2008-02-18T00:00:00Z Yang, Zhe og Cromer, Brett A. og Harvey, Robert J. og Parker, Michael W. og Lynch, Joseph W. http://espace.library.uq.edu.au/view/UQ:64150 PRL and placental lactogen (PL) play key roles in maintaining the rodent corpus luteum through pregnancy. Suppressors of cytokine signaling (SOCS) have been shown to decrease cell sensitivity to cytokines, including PRL, and so here we have addressed the issue of whether luteolysis induced by prostaglandin F-2alpha (PGF(2alpha)) might up-regulate SOCS proteins to inhibit PRL signaling. In d 19 pregnant rats, cloprostenol, a PGF(2alpha) analog, rapidly induced transcripts for SOCS-3 and, to a lesser extent, SOCS-1. We also found increased SOCS-3 protein in the ovary by immunoblot and in the corpus luteum by immunohistochemistry. Increased SOCS-3 expression was preceded by an increase in STAT3 tyrosine phosphorylation 10 min after cloprostenol injection and was maintained for 4 h, as determined by gel shift and immunohistochemistry. Induction of SOCS-3 was accompanied by a sharp decrease in active STAT5, as determined by gel-shift assay and by loss of nuclear localized STAT5. Four hours after cloprostenol administration, the corpus luteum was refractory to stimulation of STAT5 by PRL administration, and this was not due to down-regulation of PRL receptor. Therefore, induction of SOCS-3 by PGF(2alpha) may be an important element in the initiation of luteolysis via rapid suppression of luteotropic support from PL. 2007-08-14T00:00:00Z Curlewis, J. D. og Sau-Ping, T. og Lau, W. F. P. og Kusters, D. H. L. og Barclay, J og Anderson, S. T. og Waters, M. J. http://espace.library.uq.edu.au/view/UQ:286111 The topographic projection from the eye to the tectum (amphibians and fish) / superior colliculus (birds and mammals) is a paradigm model system for studying mechanisms of neural wiring development. It has previously been proposed that retinal ganglion cell axons use distinct guidance strategies in fish versus mammals, with direct guidance to the tectal target zone in the former, and overshoot followed by biased branching towards the target zone in the latter. Here, we visualized individual retinal ganglion cell axons as they grew over the tectum in zebrafish for periods of 10-21 hours, and analyzed these results using an array of quantitative measures. We found that, while axons were generally guided directly towards their targets, this occurred without growth cone turning. Instead, axons branched dynamically and profusely throughout pathfinding, and successive branches oriented growth cone extension towards a target zone in a stepwise manner. These data suggest that the guidance strategies used between fish and mammals may be less distinct than previously thought. 2012-11-23T10:57:22Z Simpson, Hugh D. og Kita, Elizabeth M. og Scott, Ethan K. og Goodhill, Geoffrey J. http://espace.library.uq.edu.au/view/UQ:140508 2008-06-10T00:00:00Z Schreiber, R. W. og Pavenstadt, H. og Greger, R. og Kunzelmann, K. H. P. http://espace.library.uq.edu.au/view/UQ:127703 An increase in left ventricular collagen (cardiac fibrosis) is a detrimental process that adversely affects heart function. Strong evidence implicates the infiltration of inflammatory cells as a critical part of the process resulting in cardiac fibrosis. Inflammatory cells are capable of releasing arachidonic acid, which may be further metabolized by cyclooxygenase, lipoxygenase, and cytochrome P450 monooxygenase enzymes to biologically active products, including PGs, leukotrienes, epoxyeicosatrienoic acids, and hydroxyeicosatetraenoic acids. Some of these products have profibrotic properties and may represent a pathway by which inflammatory cells initiate and mediate the development of cardiac fibrosis. In this study, we critically review, the current literature on the potential link between this pathway and cardiac fibrosis. 2008-02-18T00:00:00Z Levick, SP og Loch, DC og Taylor, SM og Janicki, JS http://espace.library.uq.edu.au/view/UQ:128142 Neuronal communication relies on the fusion of neurotransmitter-containing vesicles with the neuronal plasma membrane. Recent genetic studies have highlighted the critical role played by polyunsaturated fatty acids in neurotransmission, however, there is little information available about which fatty acids act on exocytosis and, more importantly, by what mechanism. We have used permeabilized chromaffin cells to screen various fatty acids of the n-3 and n-6 series for their acute effects on exocytosis. We have demonstrated that an n-6 series polyunsaturated fatty acid, arachidonic acid, potentiates secretion from intact neurosecretory cells regardless of the secretagogue used. We have shown that arachidonic acid dose dependently increases soluble NSF attachment protein receptor complex formation in chromaffin cells and bovine cortical brain extracts and that a non-hydrolysable analogue of arachidonic acid causes a similar increase in SNARE complex formation. This prompted us to examine the effect of arachidonic acid on SNARE protein interactions with Munc18a, a protein known to prevent Syntaxin1a engagement into the SNARE complex in vitro. In the presence of arachidonic acid, we show that Munc18a can interact with the neuronal SNARE complex in a dose-dependent manner. We further demonstrate that arachidonic acid directly interacts with Syntaxin1a. 2008-02-18T00:00:00Z Latham, C. F. og Osborne, S. L. og Cryle, M. J. og Meunier, F. A. http://espace.library.uq.edu.au/view/UQ:184442 Diversity in the colour and appearance of avian eggshells has been proposed to serve a variety of visual functions, including crypsis from predation, mimicry and discrimination in facultative and obligate brood parasitism, and sexually selected intraspecific signalling of the extent of maternal investment in the egg. Here, we apply a photoreceptor noise-limited colour opponent model of avian perception to assess a necessary corollary of any intraspecific signalling hypothesis, namely that individual birds are able to discriminate between colours of eggs in different conspecific clutches. Clutches from 46 species in the superfamily Muscicapoidea were measured at the Natural History Museum collection in Tring, UK. The results demonstrate that, for these particular species, most eggs are predicted not to be easily discriminable from those in other conspecific clutches in terms of the shells' background coloration. These findings are of fundamental concern to any signalling hypothesis that looks to explain the evolution of avian-visible egg colour polymorphism through selection at the intraspecific level. Importantly, future studies should combine both the proximate mechanisms and the ultimate functions of trait variability when testing hypotheses of the variability in eggshell appearance. 2009-10-02T00:00:00Z Cassey, P. og Ewen, J. G. og Marshall, N. J. og Vorobyev, M. og Blackburn, T. M. og Hauber, M. E. http://espace.library.uq.edu.au/view/UQ:80973 Using in situ spectrometry data and visual system modeling, we investigate whether the colors conferred to the reef-building corals by GFP-like proteins would look colorful not only to humans, but also to fish occupying different ecological niches on the reef. Some GFP-like proteins, most notably fluorescent greens and nonfluorescent chromoproteins, indeed generate intense color signals. An unexpected finding was that fluorescent proteins might also make corals appear less colorful to fish, counterbalancing the effect of absorption by the photosynthetic pigments of the endosymbiotic algae, which might be a form of protection against herbivores. We conclude that GFP-determined coloration of corals may be an important factor in visual ecology of the reef fishes. 2007-08-15T00:00:00Z Matz, Mikhail V. og Marshall, N. Justin og Vorobyev, Misha http://espace.library.uq.edu.au/view/UQ:127744 Reproduction in plants often requires animal vectors. Fruit and flower colors are traditionally viewed as an adaptation to facilitate detection for pollinators and seed dispersers. This long-standing hypothesis predicts that fruits are easier to detect against their own leaves compared with those of different species. We tested this hypothesis by analyzing the chromatic contrasts between 130 bird-dispersed fruits and their respective backgrounds according to avian vision. From a bird's view, fruits are not more contrasting to their own background than to those of other plant species. Fruit colors are therefore not adapted toward maximized conspicuousness for avian seed dispersers. However, secondary structures associated with fruit displays increase their contrasts. We used fruit colors to assess whether the ultraviolet and violet types of avian visual systems are equally efficient in detecting color signals. In bright light, the chromatic contrasts between fruit and background are stronger for ultraviolet vision. This advantage is due to the lesser overlap in spectral sensitivities of the blue and ultraviolet cones, which disappears in dim light conditions. We suggest that passerines with ultraviolet cones might primarily use epigamic signals that are less conspicuous to their avian predators (presumably with violet vision). Possible examples for such signals are carotenoid-based signals. 2008-02-18T00:00:00Z Schaefer, H. Martin og Schaefer, Veronika og Vorobyev, Misha http://espace.library.uq.edu.au/view/UQ:244997 Type 2 diabetes is a major cause of cardiovascular disease.We have determined whether the metabolic and cardiovascular changes induced by a diet high in fructose in young adult male Wistar rats could be prevented or reversed by chronic intervention with natural antioxidants. We administered a regenerative antioxidant protocol using two natural compounds: α-lipoic acid together with vitamin E (α-tocopherol alone or a tocotrienol-rich fraction), given as either a prevention or reversal protocol in the food. These rats developed glucose intolerance, hypertension, and increased collagen deposition in the heart together with an increased ventricular stiffness. Treatment with a fixed combination of vitamin E (either α-tocopherol or tocotrienol-rich fraction, 0.84 g/kg food) and α-lipoic acid (1.6 g/kg food) normalized glucose tolerance, blood pressure, cardiac collagen deposition, and ventricular stiffness in both prevention and reversal protocols in these fructose-fed rats. These results suggest that adequate antioxidant therapy can both prevent and reverse the metabolic and cardiovascular damage in type 2 diabetes. 2011-08-05T00:00:00Z Patel, Jatin og Matnor, Nur Azim og Iyer, Abishek og Brown, Lindsay http://espace.library.uq.edu.au/view/UQ:59763 Although the principles of axon growth are well understood in vitro the mechanisms guiding axons in vivo are less clear. It has been postulated that growing axons in the vertebrate brain follow borders of neuroepithelial cells expressing specific regulatory genes. In the present study we reexamined this hypothesis by analysing the earliest growing axons in the forebrain of embryonic zebrafish. Confocal laser scanning microscopy was used to determine the spatiotemporal relationship between growing axons and the expression pattern of eight regulatory genes in zebrafish brain. Pioneer axons project either longitudinally or dorsoventrally to establish a scaffold of axon tracts during this developmental period. Each of the regulatory genes was expressed in stereotypical domains and the borders of some were oriented along dorsoventral and longitudinal planes. However, none of these borders clearly defined the trajectories of pioneer axons. In two cases axons coursed in proximity to the borders of shh and pax6, but only for a relatively short portion of their pathway. Only later growing axons were closely apposed to the borders of some gene expression domains. These results suggest that pioneer axons in the embryonic forebrain do not follow continuous pathways defined by the borders of regulatory gene expression domains, (C) 2000 Academic Press. 2007-08-14T00:00:00Z Hjorth, J. T. og Key, B. http://espace.library.uq.edu.au/view/UQ:184150 Hypoxanthine-guanine phosphoribosyltransferase (HPRT, EC 2.4.2.8) is a purine salvage enzyme that catalyses the conversion of hypoxanthine and guanine to their respective mononucleotides. Partial deficiency of this enzyme can result in the overproduction of uric acid leading to a severe form of gout, whilst a virtual absence of HPRT activity causes the Lesch-Nyhan syndrome which is characterised by hyperuricaemia, mental retardation, choreoathetosis and compulsive self-mutilation. The HPRT-encoding gene is located on the X chromosome in the region q26–q27 and consists of nine exons and eight introns totalling 57 kb. This gene is transcribed to produce an mRNA of 1.6 kb, which contains a protein encoding region of 654 nucleotides. With the advent of increasingly refined techniques of molecular biology, it has been possible to study the HPRT gene of individuals with a deficiency in HPRT activity to determine the genetic basis of the enzyme deficiency. Many different mutations throughout the coding region have been described, but in the absence of precise information on the three-dimensional structure of the HPRT protein, it remains difficult to determine any consistent correlation between the structure and function of the enzyme. 2009-09-24T10:30:10Z Sculley, Donna G. og Dawson, Paul A. og Emmerson, Bryan T. og Gordon, Ross B. http://espace.library.uq.edu.au/view/UQ:207199 2010-07-08T00:00:00Z Bellingham, Mark C. http://espace.library.uq.edu.au/view/UQ:146828 2008-06-06T00:00:00Z Douglas, R. H. og Marshall, J. http://espace.library.uq.edu.au/view/UQ:77937 2007-08-15T00:00:00Z Schwab, I.R. og Collin, S. P. http://espace.library.uq.edu.au/view/UQ:189284 2009-12-07T00:00:00Z Tolnay, M. og Ghebremedhin, Estifanos og Probst, Braak H. http://espace.library.uq.edu.au/view/UQ:268262 2012-02-24T12:10:21Z Probyn, Megan E. og Zanini, Simone og Ward, Leigh C. og Bertram, John F. og Moritz, Karen M. http://espace.library.uq.edu.au/view/UQ:109310 In many vertebrate and invertebrate systems, pioneering axons play a crucial role in establishing large axon tracts. Previous studies have addressed whether the first axons to cross the midline to from the corpus callosum arise from neurons in either the cingulate cortex (Koester and O'Leary [1994] J. Neurosci. 11:6608-6620) or the rostrolateral neocortex (Ozaki and Wahlsten [1998] J. Comp. Neurol. 400:197-206). However, these studies have not provided a consensus on which populations pioneer the corpus callosum. We have found that neurons within the cingulate cortex project axons that cross the midline and enter the contralateral hemisphere at E15.5. By using different carbocyanine dyes injected into either the cingulate cortex or the neocortex of the same brain, we found that cingulate axons crossed the midline before neocortical axons and projected into the contralateral cortex. Furthermore, the first neocortical axons to reach the midline crossed within the tract formed by these cingulate callosal axons, and appeared to fasciculate with them as they crossed the midline. These data indicate that axons from the cingulate cortex might pioneer a pathway for later arriving neocortical axons that form the corpus callosum. We also found that a small number of cingulate axons project to the septum as well as to the ipsilateral hippocampus via the fornix. In addition, we found that neurons in the cingulate cortex projected laterally to the rostrolateral neocortex at least 1 day before the neocortical axons reach the midline. Because the rostrolateral neocortex is the first neocortical region to develop, it sends the first neocortical axons to the midline to form the corpus callosum. We postulate that, together, both laterally and medially projecting cingulate axons may pioneer a path for the medially directed neocortical axons, thus helping to guide these axons toward and across the midline during the formation of the corpus callosum. (C) 2001 Wiley-Liss, Inc. 2007-09-19T00:00:00Z Rash, B. G. og Richards, L. J. http://espace.library.uq.edu.au/view/UQ:233995 2011-03-09T00:00:00Z Kay, A. B. og Phipps, S. og Robinson, D. S.