Glial cells modulate the synaptic transmission of NTS neurons sending projections to ventral medulla of Wistar rats

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Chronic Intermittent Hypoxia Depresses Afferent Neurotransmission in NTS Neurons by a Reduction in the Number of Active Synapses

Long-term synaptic plasticity has been recently described in brainstem areas associated to visceral afferent sensory integration. Chronic intermittent hypoxia (CIH), an animal model for studying obstructive sleep apnea in humans, depresses the afferent neurotransmission in nucleus tractus solitarii (NTS) neurons, which affect respiratory and autonomic regulation. Here we identified the synaptic mechanisms of CIH-induced depression of the afferent neurotransmission in NTS neurons in juvenile rats. We verified that CIH reduced the amplitude of both NMDA and non-NMDA glutamatergic excitatory currents (eEPSCs) evoked by tractus solitarii stimulation (TS-eEPSC) of second-order neurons in the NTS. No changes were observed in release probability, evidenced by absence of any CIH-elicited effects on short-term depression and failures in EPSCs evoked in low calcium. CIH also produced no changes in TS-eEPSC quantal size, since the amplitudes of both low calcium-evoked EPSCs and asynchronous TS-eEPSCs (evoked in the presence of Sr2+) were unchanged. Using single TS afferent fiber stimulation in slices from control and CIH rats we clearly show that CIH reduced the quantal content of the TS-eEPSCs without affecting the quantal size or release probability, suggesting a reduction in the number of active synapses as the mechanism of CIH induced TS-eEPSC depression. In accordance with this concept, the input-output relationship of stimulus intensity and TS-eEPSC amplitude shows an early saturation in CIH animals. These findings open new perspectives for a better understanding of the mechanisms underlying the synaptic plasticity in the brainstem sensory neurons under challenges such as those produced by CIH in experimental and pathological conditions.

Chronic intermittent hypoxia alters glutamatergic control of sympathetic and respiratory activities in the commissural NTS of rats

Costa-Silva JH, Zoccal DB, Machado BH. Chronic intermittent hypoxia alters glutamatergic control of sympathetic and respiratory activities in the commissural NTS of rats. Am J Physiol Regul Integr Comp Physiol 302: R785-R793, 2012. First published December 28, 2011; doi:10.1152/ajpregu.00363.2011.-Sympathetic overactivity and altered respiratory control are commonly observed after chronic intermittent hypoxia (CIH) exposure. However, the central mechanisms underlying such neurovegetative dysfunctions remain unclear. Herein, we hypothesized that CIH (6% O-2 every 9 min, 8 h/day, 10 days) in juvenile rats alters glutamatergic transmission in the commissural nucleus tractus solitarius (cNTS), a pivotal site for integration of peripheral chemoreceptor inputs. Using an in situ working heart-brain stem preparation, we found that L-glutamate microinjections (1, 3, and 10 mM) into the cNTS of control rats (n = 8) evoked increases in thoracic sympathetic nerve (tSN) and central vagus nerve (cVN) activities combined with inhibition of phrenic nerve (PN) activity. Besides, the ionotropic glutamatergic receptor antagonism with kynurenic acid (KYN; 250 mM) in the cNTS of control group (n = 7) increased PN burst duration and frequency. In the CIH group (n = 10), the magnitude of L-glutamate-induced cVN excitation was smaller, and the PN inhibitory response was blunted (P < 0.05). In addition, KYN microinjections into the cNTS of CIH rats (n = 9) did not alter PN burst duration and produced smaller increases in its frequency compared with controls. Moreover, KYN microinjections into the cNTS attenuated the sympathoexcitatory response to peripheral chemoreflex activation in control but not in CIH rats (P < 0.05). These functional CIH-induced alterations were accompanied by a significant 10% increase of N-methyl-D-aspartate receptor 1 (NMDAR1) and glutamate receptor 2/3 (GluR2/3) receptor subunit density in the cNTS (n = 3-8, P < 0.05), evaluated by Western blot analysis. These data indicate that glutamatergic transmission is altered in the cNTS of CIH rats and may contribute to the sympathetic and respiratory changes observed in this experimental model.

Exercise training normalizes an increased neuronal excitability of NTS-projecting neurons of the hypothalamic paraventricular nucleus in hypertensive rats

Stern JE, Sonner PM, Son SJ, Silva FC, Jackson K, Michelini LC. Exercise training normalizes an increased neuronal excitability of NTS-projecting neurons of the hypothalamic paraventricular nucleus in hypertensive rats. J Neurophysiol 107: 2912-2921, 2012. First published February 22, 2012; doi:10.1152/jn.00884.2011.-Elevated sympathetic outflow and altered autonomic reflexes, including impaired baroreflex function, are common findings observed in hypertensive disorders. Although a growing body of evidence supports a contribution of preautonomic neurons in the hypothalamic paraventricular nucleus (PVN) to altered autonomic control during hypertension, the precise underlying mechanisms remain unknown. Here, we aimed to determine whether the intrinsic excitability and repetitive firing properties of preautonomic PVN neurons that innervate the nucleus tractus solitarii (PVN-NTS neurons) were altered in spontaneously hypertensive rats (SHR). Moreover, given that exercise training is known to improve and/or correct autonomic deficits in hypertensive conditions, we evaluated whether exercise is an efficient behavioral approach to correct altered neuronal excitability in hypertensive rats. Patch-clamp recordings were obtained from retrogradely labeled PVN-NTS neurons in hypothalamic slices obtained from sedentary (S) and trained (T) Wistar-Kyoto (WKY) and SHR rats. Our results indicate an increased excitability of PVN-NTS neurons in SHR-S rats, reflected by an enhanced input-output function in response to depolarizing stimuli, a hyperpolarizing shift in Na+ spike threshold, and smaller hyperpolarizing afterpotentials. Importantly, we found exercise training in SHR rats to restore all these parameters back to those levels observed in WKY-S rats. In several cases, exercise evoked opposing effects in WKY-S rats compared with SHR-S rats, suggesting that exercise effects on PVN-NTS neurons are state dependent. Taken together, our results suggest that elevated preautonomic PVN-NTS neuronal excitability may contribute to altered autonomic control in SHR rats and that exercise training efficiently corrects these abnormalities.

Close-in air blast form a nuclear event in NTS desert alluvium.

"Issued: October 2, 1964."

Éleménts de botanique ...

Tome II "remaniée et augmentée par J. Constantin."

School children’s personal exposure to ultrafine particles in urban environments

This work was motivated by the limited knowledge on personal exposure to ultrafine (UF) particles, and it quantifies school children’s personal exposure to UF particles, in terms of number, using Philips Aerasense Nano Tracers (NTs). This study is being conducted in conjunction with the “Ultrafine Particles from Traffic Emissions and Children’s Health (UPTECH)” project, which aims to determine the relationship between exposure to traffic related UF particles and children’s health (http://www.ilaqh.qut.edu.au/Misc/UPTECH%20 Home.htm). To achieve this, air quality and some health data are being collected at 25 schools within the Brisbane Metropolitan Area in Australia over two years. The school children’s personal exposure to UF particles in the first 17 schools are presented here. These schools were tested between Oct 2010 and Dec 2011. Data collection is expected to be complete by mid 2012.

C-BN Single-Walled Nanotubes from Hybrid Connection of BN/C Nanoribbons: Prediction by ab initio Density Functional Calculations

We demonstrated for the first time by ab initio density functional calculation and molecular dynamics simulation that C0.5(BN)0.5 armchair single-walled nanotubes (NT) are gapless semiconductors and can be spontaneously formed via the hybrid connection of graphene/BN Nanoribbons (GNR/BNNR) at room temperature. The direct synthesis of armchair C0.5(BN)0.5 via the hybrid connection of GNR/BNNR is predicted to be both thermodynamically and dynamically stable. Such novel armchair C0.5(BN)0.5 NTs possess enhanced conductance as that observed in GNRs. Additionally, the zigzag C0.5(BN)0.5 SWNTs are narrow band gap semiconductors, which may have potential application for light emission. In light of recent experimental progress and the enhanced degree of control in the synthesis of GNRs and BNNR, our results highlight an interesting avenue for synthesizing a novel specific type of C0.5(BN)0.5 nanotube (gapless or narrow direct gap semiconductor), with potentially important applications in BNC-based nanodevices.

Charge-controlled switchable CO2 capture on boron nitride nanomaterials

Increasing concerns about the atmospheric CO2 concentration and its impact on the environment are motivating researchers to discover new materials and technologies for efficient CO2 capture and conversion. Here, we report a study of the adsorption of CO2, CH4, and H2 on boron nitride (BN) nanosheets and nanotubes (NTs) with different charge states. The results show that the process of CO2 capture/release can be simply controlled by switching on/off the charges carried by BN nanomaterials. CO2 molecules form weak interactions with uncharged BN nanomaterials and are weakly adsorbed. When extra electrons are introduced to these nanomaterials (i.e., when they are negatively charged), CO2 molecules become tightly bound and strongly adsorbed. Once the electrons are removed, CO2 molecules spontaneously desorb from BN absorbents. In addition, these negatively charged BN nanosorbents show high selectivity for separating CO2 from its mixtures with CH4 and/or H2. Our study demonstrates that BN nanomaterials are excellent absorbents for controllable, highly selective, and reversible capture and release of CO2. In addition, the charge density applied in this study is of the order of 1013 cm–2 of BN nanomaterials and can be easily realized experimentally.

Association of a RFLP for the insulin receptor gene, but not insulin, with essential hypertension

Insulin has cardiovascular actions and patients with essential hypertension display insulin resistance. A cross-sectional study of the R1 RFLP of the insulin receptor gene (INSR) was carried out in 67 hypertensive (HT) and 75 normotensive (NT) subjects whose parents had a similar blood pressure status at age ≥50. The frequency of the minor (+) allele was 0.31 in HTs and 0.44 in NTs, and the difference between observed alleles in all subjects in each group was significant (χ2 = 4.8, P<0.05). Allele frequencies of a BglI RFLP of the insulin gene, however, did not differ between the HT and NT groups. The data thus provide evidence in favour of an association of HT with a polymorphism at the INSR locus (19p 13.3-13.2), so implicating this locus, and possibly a genetic variant of the insulin receptor itself, in HT.

Molecular genetic analyses of RFLPs for PCR-amplified growth hormone gene, renal kallikrein gene and atrial natriuretic factor gene in essential hypertension

The present study examined polymorphisms of genes that might be involved in the onset of essential hypertension (HT). These included the (i) growth hormone gene (GH1), whose locus has recently been linked to elevated blood pressure (BP) in the stroke-prone SHR, although recent sib-pair analysis of a polymorphism near the human chorionic somatomammotropin gene (a member of the GH cluster) was unable to show linkage with HT; (ii) renal kallikrein gene (KLK1); and (iii) atrial natriuretic factor gene (ANF), where a primary defect in production or activity of kallikrein or ANF could cause NaCl retention and vasoconstriction. Association analyses were conducted to compare restriction fragment length polymorphisms (RFLPs) of each gene in 85 HT and 95 normotensive (NT) Caucasian subjects whose parents had a similar BP status at age ≥50 years. The frequency of the minor allele of (i) a RsaI RFLP in the promoter of GH1, amplified from leukocyte DNA by the polymerase chain reaction, was 0.15 in the HT group and 0.14 in the NT group (χ1=0.34, P=0.55); (ii) a TaqI RFLP for KLK1 was 0.035 in the HT group and 0.015 in the NT group (χ2=1.5, P=0.21); and (iii) a XhoI RFLP for ANF was 0.50 in HTs and 0.46 in NTs (χ2=0.20, P=0.65). Studies of HT pedigrees found one family in which the ANF locus and HT were not linked, owing to an obligate recombinant. The present data thus provide no evidence for involvement of the growth hormone, renal kallikrein, nor ANF gene in the causation of essential hypertension.

Changing travel patterns and journeys to health services in Great Britain 1985-2012: An examination health service utilisation using the National Travel Survey

Background This paper examines changing patterns in the utilisation and geographic access to health services in Great Britain using National Travel Survey data (1985-2012). The National Travel Survey (NTS) is a series of household surveys designed to provide data on personal travel and monitor changes in travel behaviour over time. The utilisation rate was derived using the proportion of journeys made to access health services. Geographic access was analysed by separating the concept into its accessibility and mobility dimensions. Methods Variables from the PSU, households, and individuals datasets were used as explanatory variables. Whereas, variables extracted from the journeys dataset were used as dependent variables to identify patterns of utilisation i.e. the proportion of journeys made by different groups to access health facilities in a particular journey distance or time band or by mode of transport; and geographic access to health services. A binary logistic regression analysis was conducted to identify the utilisation rate over the different time periods between different groups. This analysis shows the Odds Ratios (ORs) for different groups making a trip to utilise health services compared to their respective counterparts. Linear multiple regression analyses were conducted to then identify patterns of change in the accessibility and mobility level. Results Analysis of the data has shown that that journey distances to health facilities were signi fi cantly shorter and also gradually reduced over the period in question for Londoners, females, those without a car or on low incomes, and older people. Although rates of utilisation of health services we re Oral Abstracts / Journal of Transport & Health 2 (2015) S5 – S63 S43 signi fi cantly lower because of longer journey times. These fi ndings indicate that the rate of utilisation of health services largely depends on mobility level although previous research studies have traditionally overlooked the mobility dimension. Conclusions This fi nding, therefore, suggests the need to improve geographic access to services together with an enhanced mobility option for disadvantaged groups in order for them to have improved levels of access to health facilities. This research has also found that the volume of car trips to health services also increased steadily over the period 1985-2012 while all other modes accounted for a smaller number of trips. However, it is dif fi cult to conclude from this research whether this increase in the volume of car trips was due to a lack of alternative transport or due to an increase in the level of car-ownership.

Alternative News Sources as 'Collaboratory' Journalism. A case study of Helsingin Sanomat and its relation with the Youth Voice Editorial Board

The new paradigm of connectedness and empowerment brought by the interactivity feature of the Web 2.0 has been challenging the traditional centralized performance of mainstream media. The corporation has been able to survive the strong winds by transforming itself into a global multimedia business network embedded in the network society. By establishing networks, e.g. networks of production and distribution, the global multimedia business network has been able to sight potential solutions by opening the doors to innovation in a decentralized and flexible manner. Under this emerging context of re-organization, traditional practices like sourcing need to be re- explained and that is precisely what this thesis attempts to tackle. Based on ICT and on the network society, the study seeks to explain within the Finnish context the particular case of Helsingin Sanomat (HS) and its relations with the youth news agency, Youth Voice Editorial Board (NÄT). In that sense, the study can be regarded as an explanatory embedded single case study, where HS is the principal unit of analysis and NÄT its embedded unit of analysis. The thesis was able to reach explanations through interrelated steps. First, it determined the role of ICT in HS’s sourcing practices. Then it mapped an overview of the HS’s sourcing relations and provided a context in which NÄT was located. And finally, it established conceptualized institutional relational data between HS and NÄT for their posterior measurement through social network analysis. The data set was collected via qualitative interviews addressed to online and offline editors of HS as well as interviews addressed to NÄT’s personnel. The study concluded that ICT’s interactivity and User Generated Content (UGC) are not sourcing tools as such but mechanism used by HS for getting ideas that could turn into potential news stories. However, when it comes to visual communication, some exemptions were found. The lack of official sources amidst the immediacy leads HS to rely on ICT’s interaction and UGC. More than meets the eye, ICT’s input into the sourcing practice may be more noticeable if the interaction and UGC is well organized and coordinated into proper and innovative networks of alternative content collaboration. Currently, HS performs this sourcing practice via two projects that differ, precisely, by the mode they are coordinated. The first project found, Omakaupunki, is coordinated internally by Sanoma Group’s owned media houses HS, Vartti and Metro. The second project found is coordinated externally. The external alternative sourcing network, as it was labeled, consists of three actors, namely HS, NÄT (professionals in charge) and the youth. This network is a balanced and complete triad in which the actors connect themselves in relations of feedback, recognition, creativity and filtering. However, as innovation is approached very reluctantly, this content collaboration is a laboratory of experiments; a ‘COLLABORATORY’.

Effect of TiO2 electrode thickness on photovoltaic properties of dye sensitized solar cell based on randomly oriented Titania nanotubes

Anatase titania nanotubes (TNTs) have been synthesized from P25 TiO2 powder by alkali hydrothermal method followed by post annealing. The microstructure analysis by X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) revealed the formation of anatase nanotubes with a diameter of 9-10 nm. These NTs are used to make photo anode in dye-sensitized solar cells (DSSCs). Layer by layer deposition with curing of each layer at 350 C is employed to realize films of desired thickness. The performance of these cells is studied using photovoltaic measurements. Electrochemical impedance spectroscopy (EIS) is used to quantitatively analyze the effect of thickness on the performance of these cells. These studies revealed that the thickness of TiO2 has a pronounced impact on the cell performance and the optimum thickness lies in the range of 10-14 mu m. In comparison to dye solar cells made of P25, TNTs based cells exhibit an improved open circuit voltage and fill factor (FF) due to an increased electron lifetime, as revealed by EIS analysis. (C) 2011 Elsevier B.V. All rights reserved.