Activation of extrasynaptic GABA. receptors inhibits cyclothiazide- induced epileptiform activity in hippocampal CA1 neurons

Extrasynaptic GABAA receptors （GABAARs）-mediated tonic inhibition is reported to involve in the patho- genesis of epilepsy. In this study, we used cyclo- thiazide （CTZ）-induced in vitro brain slice seizure model to explore the effect of selective activation of extrasynaptic GABAARS by 4,5,6,7-tetra- hydroisoxazolo[5,4-c] pyridine-3-ol （THIP） on the CTZ-induced epileptiform activity in hippocampal neurons. Perfusion with CTZ dose-dependently induced multiple epileptiform peaks of evoked population spikes （PSs）in CA1 pyramidal neurons, and treatment with THIP （5 μmol/L） significantly reduced the multiple PS peaks induced by CTZ stimulation. Western blot showed that the 6-subunit of the GABAAR, an extrasynaptic specific GABAAR subunit, was also significantly down-regulated in the cell membrane 2 h after CTZ treatment. Our results suggest that the CTZ-induced epileptiform activity in hippocampal CA1 neurons is suppressed by the activation of extrasynaptic GABAARs, and further support the hypothesis that tonic inhibition mediated by extrasynaptic GABAARs plays a prominent role in seizure generation.     

Activation of extrasynaptic GABAA receptors inhibits cyclothiazide-induced epileptiform activity in hippocampal CA1 neurons

Extrasynaptic GABA_A receptors (GABA_ARs)-mediated tonic inhibition is reported to involve in the pathogenesis of epilepsy. In this study, we used cyclothiazide (CTZ)-induced in vitro brain slice seizure model to explore the effect of selective activation of extrasynaptic GABA_ARs by 4,5,6,7-tetrahydroisoxazolo[5,4-c] pyridine-3-ol (THIP) on the CTZ-induced epileptiform activity in hippocampal neurons. Perfusion with CTZ dose-dependently induced multiple epileptiform peaks of evoked population spikes (PSs) in CA1 pyramidal neurons, and treatment with THIP (5 μmol/L) significantly reduced the multiple PS peaks induced by CTZ stimulation. Western blot showed that the δ-subunit of the GABA_AR, an extrasynaptic specific GABA_AR subunit, was also significantly down-regulated in the cell membrane 2 h after CTZ treatment. Our results suggest that the CTZ-induced epileptiform activity in hippocampal CA1 neurons is suppressed by the activation of extrasynaptic GABA_ARs, and further support the hypothesis that tonic inhibition mediated by extrasynaptic GABA_ARs plays a prominent role in seizure generation.     

Digital droplet PCR (ddPCR) for the precise quantification of human T-lymphotropic virus 1 proviral loads in peripheral blood and cerebrospinal fluid of HAM/TSP patients and identification of viral mutations

An elevated human T cell lymphotropic virus 1 (HTLV)-1 proviral load (PVL) is the main risk factor for developing HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) in HTLV-1 infected subjects, and a high cerebrospinal fluid (CSF) to peripheral blood mononuclear cell (PBMC) PVL ratio may be diagnostic of the condition. However, the standard method for quantification of HTLV-1 PVL—real-time PCR—has multiple limitations, including increased inter-assay variability in compartments with low cell numbers, such as CSF. Therefore, in this study, we evaluated a novel technique for HTVL-1 PVL quantification, digital droplet PCR (ddPCR). In ddPCR, PCR samples are partitioned into thousands of nanoliter-sized droplets, amplified on a thermocycler, and queried for fluorescent signal. Due to the high number of independent events (droplets), Poisson algorithms are used to determine absolute copy numbers independently of a standard curve, which enables highly precise quantitation. This assay has low intra-assay variability allowing for reliable PVL measurement in PBMC and CSF compartments of both asymptomatic carriers (AC) and HAM/TSP patients. It is also useful for HTLV-1-related clinical applications, such as longitudinal monitoring of PVL and identification of viral mutations within the region targeted by the primers and probe.     

Liver Transplantation in Recipients With High Model for End-stage Liver Disease Score

Objectives

The score in the Model of End-stage Liver Disease, or MELD, is a good indicator of the survival in patients on the liver transplant waiting list. In this study, an analysis is performed on the benefits of liver transplant on those patients with a very high MELD score and who thus start from a very severe baseline state that could affect the surgical outcome.

Comparison of a 28-channel receive array coil and quadrature volume coil for morphologic imaging and T2 mapping of knee cartilage at 7T

Purpose:

To compare a new birdcage‐transmit, 28‐channel receive array (28‐Ch) coil and a quadrature volume coil for 7T morphologic MRI and T2 mapping of knee cartilage.

Materials and Methods:

The right knees of 10 healthy subjects were imaged on a 7T whole body magnetic resonance (MR) scanner using both coils. 3D fast low‐angle shot (3D‐FLASH) and multiecho spin‐echo (MESE) sequences were implemented. Cartilage signal‐to‐noise ratio (SNR), contrast‐to‐noise ratio (CNR), thickness, and T2 values were assessed.

Results:

SNR/CNR was 17%–400% greater for the 28‐Ch compared to the quadrature coil (P ≤ 0.005). Bland–Altman plots show mean differences between measurements of tibial/femoral cartilage thickness and T2 values obtained with each coil to be small (?0.002 ± 0.009 cm / 0.003 ± 0.011 cm) and large (?6.8 ± 6.7 msec/?8.2 ± 9.7 msec), respectively. For the 28‐Ch coil, when parallel imaging with acceleration factors (AF) 2, 3, and 4 was performed SNR retained was: 62%–69%, 51%–55%, and 39%–45%.

Conclusion:

A 28‐Ch knee coil provides increased SNR/CNR for 7T cartilage morphologic imaging and T2 mapping. Coils should be switched with caution during clinical studies because T2 values may differ. The greater SNR of the 28‐Ch coil could be used to perform parallel imaging with AF2 and obtain similar SNR as the quadrature coil. J. Magn. Reson. Imaging 2012;441‐448. © 2011 Wiley Periodicals, Inc.

     

Abnormal cardiac function in the streptozotocin-diabetic rat. Changes in active and passive properties of the left ventricle.

To provide an integrated assessment of changes in systolic and diastolic function in diabetic rats, we measured conscious hemodynamics and performed ex vivo analysis of left ventricular passive-elastic properties. Rats given streptozotocin (STZ) 65 mg/kg i.v. (n = 14) were compared with untreated age-matched controls (n = 15) and rats treated with insulin after administration of STZ (n = 11). After 7 d, diabetic rats exhibited decreases in heart rate and peak developed left ventricular (LV) pressure during aortic occlusion. After 26 d of diabetes there were significant decreases in resting LV systolic pressure, developed pressure, and maximal +dP/dt, whereas LV end-diastolic pressure increased and the time constant of LV relaxation was prolonged. The passive LV pressure-volume relationship was progressively shifted away from the pressure axis, and the overall chamber stiffness constant was decreased. However, "operating chamber stiffness" calculated at end-diastolic pressure was increased at 7 d, and unchanged at 26 d. LV cavity/wall volume and end-diastolic volume were increased after 26 d of diabetes. Myocardial stiffness was unchanged at both time intervals. All of the above abnormalities were reversed by the administration of insulin. We conclude that the hemodynamic and passive-elastic changes that occur in diabetic rats represent an early dilated cardiomyopathy which is reversible with insulin.