91,631 results

  • Investigation into the role of gap junction modulation of intracortical connectivity in mouse neocortical brain slices

    Voss, LJ; Gauffin, E; Ringqvist, A; Sleigh, James (2014-03-17)

    Journal article
    The University of Auckland Library

    General anesthetics are hypothesized to cause unconsciousness by interrupting communication pathways within the cerebral cortex. A correlate of this has been demonstrated in mouse neocortical slices, where anesthetics disrupt the spread of population field potential activity--resulting in a "decoupling" of activity recorded across spatial locations within the slice. In this study we investigated whether this decoupling can be explained by gap junction blockade, with a particular focus on the connexin36 (Cx36) subtype. Baseline, coupled seizure-like event (SLE) activity was recorded from two extracellular electrodes in slices perfused with no-magnesium artificial cerebrospinal fluid (aCSF). The connexin36 gap junction blocker mefloquine (25 ??M) failed to decouple SLE activity in wild-type mice (median(range) decoupling rate of 0.70(0.03-3.00)%, not significantly different from controls). Slices from Cx36 knock-out mice exhibited coupled SLE activity under baseline conditions and readily decoupled when exposed to the general anesthetic etomidate. The general gap junction blocker carbenoxolone (CBX, 100 ??M) strongly decoupled SLE activity compared to controls in wild-type mice (2.7(0.1-42.5) % compared to 0.03(0.0-0.5)%, p=0.0001). Taken together, the results show that Cx36 gap junction blockade does not cause decoupling of intracortical population activity, but the involvement of other gap junction subtypes cannot be ruled out.

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  • Intra-cranial mechanisms for preserving brain blood flow in health and disease

    McBryde, Fiona; Malpas, Simon; Paton, Julian (2017-01)

    Journal article
    The University of Auckland Library

    The brain is an exceptionally energetically demanding organ with little metabolic reserve, and multiple systems operate to protect and preserve the brain blood supply. But how does the brain sense its own perfusion? In this review, we discuss how the brain may harness the cardiovascular system to counter threats to cerebral perfusion sensed via intracranial pressure (ICP), cerebral oxygenation and ischemia. Since the work of Cushing over 100 years ago, the existence of brain baroreceptors capable of eliciting increases in sympathetic outflow and blood pressure has been hypothesized. In the clinic, this response has generally been thought to occur only in extremis, to perfuse the severely ischemic brain as cerebral autoregulation fails. We review evidence that pressor responses may also occur with smaller, physiologically-relevant increases in ICP. The incoming brain oxygen supply is closely monitored by the carotid chemoreceptors, however, hypoxia and other markers of ischemia are also sensed intrinsically by astrocytes or other support cells within brain tissue itself, and elicit reactive hyperaemia. Recent studies suggest that astrocytic oxygen signalling within the brainstem may directly affect sympathetic nerve activity and blood pressure. We speculate that local cerebral oxygen tension is a major determinant of the mean level of arterial pressure, and discuss recent evidence that this may be the case. We conclude that intrinsic intra- and extra-cranial mechanisms sense and integrate information about hypoxia/ischemia and intracranial pressure, and play a major role in determining the long-term level of sympathetic outflow and arterial pressure, in order to optimise cerebral perfusion. This article is protected by copyright. All rights reserved.

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  • A Feminist Quality Appraisal Tool: exposing gender bias and gender inequities in health research

    Morgan, Tessa; Williams, Lisa; Gott, Caryl (2017)

    Journal article
    The University of Auckland Library

    Quality appraisal tools used in systematic reviews to evaluate health literature do not adequately address issues related to gender. This oversight is significant because disparities between genders have been identified as a major health equity concern, and systematic reviews are regarded as a powerful means for informing policy that could redress gender inequities. In this paper, we present our Feminist Quality Appraisal Tool that offers researchers a template to undertake a comprehensive gendered analysis of studies they review. Informed by a feminist perspective, the tool addresses issues of power, gender and inequity, thereby giving researchers the means to interrogate the scientific rigour of systematic reviews that focus on gender. Specifically, our tool outlines ways gender can be critically examined in terms of study design, data collection, analysis, discussion and recommendations. We argue that this tool has the potential to improve the provision of public health by providing solid understandings and critical reflections on the reasons why women continue to face barriers in their access to optimal health care.

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  • Acute effects of calcium supplements on blood pressure: randomised, crossover trial in postmenopausal women

    Billington, Emma; Bristow, Sarah; Gamble, Gregory; de Kwant, Jordyn; Stewart, A; Mihov, Borislav; Horne, Anne; Reid, Ian (2017-01)

    Journal article
    The University of Auckland Library

    Calcium supplements appear to increase cardiovascular risk, but the mechanism is unknown. We investigated the acute effects of calcium supplements on blood pressure in postmenopausal women. The reduction in systolic blood pressure was smaller after calcium compared with the placebo in the hours following dosing. INTRODUCTION: Calcium supplements appear to be associated with increased cardiovascular risk; however, the mechanism of this is uncertain. We previously reported that blood pressure declined over a day in older women, and that this reduction was smaller following a calcium supplement. To confirm this finding, we investigated the acute effects of calcium supplements on blood pressure. METHODS: This was a randomised controlled crossover trial in 40 healthy postmenopausal women (mean age 71 years and BMI 27.2 kg/m(2)). Women attended on two occasions, with visits separated by ???7 days. At each visit, they received either 1 g of calcium as citrate, or placebo. Blood pressure and serum calcium concentrations were measured immediately before, and 2, 4 and 6 h after each intervention. RESULTS: Ionised and total calcium concentrations increased after calcium (p?????0.0001 versus placebo). Systolic blood pressure decreased after both calcium and placebo, but significantly less so after calcium (p???=???0.02). The reduction in systolic blood pressure from baseline was smaller after calcium compared with placebo by 6 mmHg at 4 h (p???=???0.036) and by 9 mmHg at 6 h (p???=???0.002). The reduction in diastolic blood pressure was similar after calcium and placebo. CONCLUSIONS: These findings are consistent with those of our previous trial and indicate that the use of calcium supplements in postmenopausal women attenuates the post-breakfast reduction in systolic blood pressure by around 6-9 mmHg. Whether these changes in blood pressure influence cardiovascular risk requires further study.

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  • Acute effects of calcium supplements on blood pressure and blood coagulation: secondary analysis of a randomised controlled trial in post-menopausal women

    Bristow, Sarah; Gamble, Gregory; Stewart, A; Horne, Anne; Reid, Ian (2015-12)

    Journal article
    The University of Auckland Library

    Recent evidence suggests that Ca supplements increase the risk of cardiovascular events, but the mechanism(s) by which this occurs is uncertain. In a study primarily assessing the effects of various Ca supplements on blood Ca levels, we also investigated the effects of Ca supplements on blood pressure and their acute effects on blood coagulation. We randomised 100 post-menopausal women to 1 g/d of Ca or a placebo containing no Ca. Blood pressure was measured at baseline and every 2 h up to 8 h after their first dose and after 3 months of supplementation. Blood coagulation was measured by thromboelastography (TEG) in a subgroup of participants (n 40) up to 8 h only. Blood pressure declined over 8 h in both the groups, consistent with its normal diurnal rhythm. The reduction in systolic blood pressure was smaller in the Ca group compared with the control group by >5 mmHg between 2 and 6 h (P???0??02), and the reduction in diastolic blood pressure was smaller at 2 h (between-groups difference 4??5 mmHg, P=0??004). Blood coagulability, assessed by TEG, increased from baseline over 8 h in the calcium citrate and control groups. At 4 h, the increase in the coagulation index was greater in the calcium citrate group compared with the control group (P=0??03), which appeared to be due to a greater reduction in the time to clot initiation. These data suggest that Ca supplements may acutely influence blood pressure and blood coagulation. Further investigation of this possibility is required.

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  • Threshold tracking primary motor cortex inhibition: the influence of current direction

    Cirillo, John; Byblow, Winston (2016-10)

    Journal article
    The University of Auckland Library

    Paired-pulse transcranial magnetic stimulation (TMS) can be used to probe inhibitory activity in primary motor cortex (M1). Recruitment of descending volleys with TMS depends on the induced current direction in M1. Anterior-posterior (AP) stimulation preferentially activates late indirect- (I-) waves that are most susceptible to paired-pulse TMS. Threshold tracking TMS can assess intracortical inhibition; however, previous studies have only used a current direction that preferentially recruits early I-waves [posterior-anterior (PA)]. Our objective was to examine intracortical inhibition with threshold tracking TMS designed to preferentially recruit early vs. late I-waves with PA and AP stimulation respectively. Electromyographic recordings were obtained from the right first dorsal interosseous muscle of 15 participants (21???50 years). Motor evoked potentials elicited by TMS over left M1 were recorded for PA, AP and lateromedial (LM) induced currents, with I-wave recruitment calculated as the onset latency difference between PA-LM and AP-LM. Short- and long-interval intracortical inhibition (SICI and LICI) were examined across a range of conditioning stimulus intensities and interstimulus intervals (3 and 100???260 ms) with threshold tracking TMS for PA and AP stimulation. SICI and LICI were greater for AP compared with PA current direction using threshold tracking. In addition, the efficacy of late I-wave recruitment was associated with the extent of SICI for AP but not PA stimulation, and was not associated with LICI. These findings indicate that threshold tracking with an AP-induced current provides a more robust and sensitive measure of M1 intracortical inhibition than PA.

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  • Renal dosing of allopurinol results in suboptimal gout care

    Neogi, T; Dalbeth, Nicola; Stamp, L; Castelar, G; Fitzgerald, J; Gaffo, A; Mikuls, TR; Singh, J; V??zquez-Mellado, J; Edwards, NL (2017-01)

    Journal article
    The University of Auckland Library

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  • Testing neocortical slice viability in non-perfused no-magnesium artificial cerebrospinal fluid solutions

    Voss, LJ; George, SA; Sleigh, James (2012-03-15)

    Journal article
    The University of Auckland Library

    The acute in vitro brain slice model is a widely used neurophysiological research tool. When applying this method, most researchers continuously perfuse slices with carbogenated artificial cerebrospinal fluid (ACSF) to maintain pH balance and tissue oxygen delivery. Common wisdom suggests that static recordings are incompatible with submerged bath methodology because of deficiency in tissue oxygen supply. However, to our knowledge this has not been tested. In this study, we wanted to determine whether neocortical mouse slice viability could be maintained in the medium term (up to 2h) in a shallow, submerged recording bath under non-perfused, static conditions. Seizure-like events (SLEs) were generated in the slices utilizing no-magnesium ACSF and recorded for 2h under three conditions: (1) perfused ACSF condition (n=8), where slices were perfused continuously with carbogenated no-magnesium ACSF; (2) static ACSF condition (n=12), where slices were recorded in pre-carbogenated, but non-perfused (static) no-magnesium ACSF; and (3) static HEPES ACSF condition (n=12), where slices were recorded in non-perfused (static) no-magnesium ACSF with no pre-carbogenation but buffered with HEPES. SLE activity was stable for 2h across all three conditions. There was no statistically significant difference in SLE frequency, amplitude or length between static and perfused conditions. SLE frequency and amplitude were generally lower in the static HEPES buffer condition. The data indicate that robust and stable neocortical SLE activity can be generated for at least 2h in a submersion bath without ACSF perfusion if pH is adequately controlled.

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  • Variation in morphology and life-history strategy of an exploited sparid fish

    Parsons, Darren; Morrison, MA; Gillanders, BM; Clements, Kendall; Bury, SJ; Bian, R; Spong, KT (2016)

    Journal article
    The University of Auckland Library

    Defining appropriate management units to balance productivity and yield of exploited species is fundamental to effective resource management. Anecdotal and tag-recapture information related to morphology, movement behaviour and life-history strategy suggest that separate groups of snapper (Chrysophrys auratus) exist in the Hauraki Gulf, New Zealand. To address the existence of discrete groups, we examined morphology, meristics and otolith chemistry from snapper collected throughout the Hauraki Gulf. We also used tag-recapture information, stable isotope analysis and interpreted functional aspects of morphology and meristics data to understand potential life-history strategy differences. Snapper from rocky reef habitats did not display morphology and meristic features distinct from snapper from soft sediment habitats and differences in otolith chemistry and stable isotope ratios could respectively be explained by a locational influence and predominance of kelp in rocky reef food webs. Conversely, snapper collected from a known spawning area had distinct morphological and meristic features consistent with semi-pelagic sparids and stable isotope analysis also indicated a potentially more pelagic and higher trophic-level diet. Maintenance of population complexity such as this is generally beneficial to fish populations, and can be achieved by revisiting the spatial units used for fishery management.

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  • Interventions for preventing gestational diabetes mellitus: an overview of Cochrane Reviews (Protocol)

    Lawrence, RL; Brown, Julie; Middleton, P; Shepherd, E; Brown, S; Crowther, Caroline (2016-10-12)

    Journal article
    The University of Auckland Library

    This is the protocol for a review and there is no abstract. The objectives are as follows: To summarise the evidence from Cochrane systematic Reviews regarding the effects of interventions for preventing gestational diabetes mellitus.

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  • Inositol for subfertile women with polycystic ovary syndrome

    Showell, Marian; Mackenzie-Proctor, R; Jordan-Cole, Vanessa; Hodgson, R; Brown, Julie; Farquhar, Cynthia (2016-09-30)

    Journal article
    The University of Auckland Library

    This is the protocol for a review and there is no abstract. The objectives are as follows: To evaluate the effectiveness and safety of oral supplementation with inositol on reproductive outcomes for subfertile women with polycystic ovary syndrome (PCOS).

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  • Wireless Channel Characterization in Burning Buildings Over 100???1000 MHz

    Austin, Andrew (2016-07)

    Journal article
    The University of Auckland Library

    A 3-D implementation of the finite-difference time-domain (FDTD) method is used to model 100-1000-MHz radio wave propagation in a generalized office building. Fire within this building is modeled as a cold plasma medium. The presence of fire is found to decrease the sector-averaged received power by up to 10 dB. The FDTD results also showing propagation through fire can introduce rotation in linearly polarized signals, increasing the power of cross-polarized components. Uncertainties in the plasma properties are modeled using nonintrusive polynomial chaos, and can introduce up to ??8 dB variation in the sector-averaged power.

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  • Meeting of the Strategic Advisory Group of Experts on immunization, October 2016 - conclusions and recommendations

    Turner, Nicola; Strategic Advisory Group of Experts. (2016-12-02)

    Journal article
    The University of Auckland Library

    The Strategic Advisory Group of Experts (SAGE) on immunization met on 18???20 October 2016. This report summarizes the discussions, conclusions and recommendations.

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  • Meeting of the Strategic Advisory Group of Experts on immunization, October 2015 - conclusions and recommendations

    Turner, Nicola; Strategic Advisory Group of Experts (2015-12-11)

    Journal article
    The University of Auckland Library

    The Strategic Advisory Group of Experts on immunization (SAGE)1 met on 20???22 October 2015. This report summarizes the discussions, conclusions and recommendations.

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  • Induction and Mentoring in Early Childhood Educational Organizations: Embracing the complexity of teacher learning in contexts

    Langdon, Frances; Alexander, Patricia; Farquhar, Sandra; Tesar, Marek; Courtney, MGR; Palmer, M (2016-07)

    Journal article
    The University of Auckland Library

    This mixed-method study looked at perceptions of induction and mentoring among New Zealand early childhood educators. Specifically, 213 respondents drawn from five regions representing urban, rural and differing socioeconomic levels, school organizations, and professional roles completed a 19-item psychometrically sound survey. There were significant differences in responses for leaders/mentors in contrast to mentees or teaching staff. Based on quantitative outcomes, two focus groups of school leaders/mentors and mentees were convened. Qualitative analysis of the transcripts revealed several important themes that served to amplify or extended the survey results. Implications of the quantitative and qualitative results are overviewed.

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  • Gems of New Zealand Primary Health Care Research: COPD self-management in New Zealand: patient attitudes and behaviours

    Sheridan, Nicolette; Kenealy, Timothy; Salmon, E; Rea, Harold; Raphael, Deborah; Schmidt-Busby, J (2011)

    Journal article
    The University of Auckland Library

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  • Exhibitions and the Development of Modern Planning Culture, edited by Robert Freestone and Marco Amati [book review]

    Haarhoff, Errol (2015)

    Unclassified
    The University of Auckland Library

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  • We're catching fish but not value: why QMS needs reform

    Simmons, Glenn; Whittaker, D; Haworth, Nigel (2016-08-29)

    Unclassified
    The University of Auckland Library

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  • Re: Is there an alternative to centralization for pancreatic resection in New Zealand?

    Windsor, John; Pandanaboyana, Sanjay; Bartlett, Adam (2016-09)

    Journal article
    The University of Auckland Library

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  • Hongi Hika???s Self-Portrait

    Brown, Deidre (2016-06-01)

    Journal article
    The University of Auckland Library

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