Presynaptic actions of 4-Aminopyridine and γ-aminobutyric acid on rat sympathetic ganglia in vitro

Responses to bath-applications of 4-aminopyridine (4-AP) and -aminobutyric acid (GABA) were recorded intracellularly from neurones in the rat isolated superior cervical ganglion. 4-aminopyridine (0.1–1.0 mmol/l) usually induced spontaneous action potentials and excitatory postsynaptic potentials (EPSPs), which were blocked by hexamethonium. Membrane potential was unchanged; spike duration was slightly increased. Vagus nerve B-and C-fibre potentials were prolonged. In 4-AP solution (0.1–0.3 mmol/l), GABA (0.1 mmol/l), 3-aminopropanesulphonic acid or muscimol evoked bursts of spikes and EPSPs in addition to a neuronal depolarization. These bursts, which were not elicited by glycine, glutamate, taurine or (±)-baclofen, were completely antagonised by hexamethonium, tetrodotoxin or bicuculline methochloride. It is concluded that: (a) 4-AP has a potent presynaptic action on sympathetic ganglia; (b) presynaptic actions of GABA can be recorded postsynaptically in the presence of 4-AP; and (c) the presynaptic GABA-receptors revealed in this condition are similar to those on the postsynaptic membrane

Near-infrared (NIR) spectroscopy. A new method for arthroscopic evaluation of low grade degenerated cartilage lesions. Results of a pilot study

<p>Abstract</p> <p>Background</p> <p>Arthroscopy is a highly sensitive method of evaluating high-grade cartilage lesions but the detection of low-grade lesions is often is unreliable. Objective measurements are required. A novel NIRS (near-infrared-spectroscopy) device for detection of low-grade cartilage defects was evaluated in a preliminary clinical study.</p> <p>Methods</p> <p>In 12 patients who had undergone arthroscopy, the cartilage lesions within the medial knee compartment were classified according to the ICRS protocol.</p> <p>With a NIR spectrometer system and an optical probe, similar in design to a hook used for routine arthroscopy, the optical properties of cartilage were measured during arthroscopy.</p> <p>Results</p> <p>The mean ratio of 2 NIR absorption bands of intact cartilage 3.8 (range 2.3 to 8.7).was significantly lower than that of cartilage with grade 1 lesions (12.8, range 4.8 to 19.6) and grade 2 lesions (13.4, range 10.4 to 15.4).</p> <p>No differences were observed between grade 1 and grade 2 lesions.</p> <p>Conclusion</p> <p>NIRS can be used to distinguish between ICRS grade 1 lesions and healthy cartilage during arthroscopic surgeries. The results of this clinical study demonstrate the potential of NIRS to objectify classical arthroscopic grading systems.</p

Ion Channel Density Regulates Switches between Regular and Fast Spiking in Soma but Not in Axons

The threshold firing frequency of a neuron is a characterizing feature of its dynamical behaviour, in turn determining its role in the oscillatory activity of the brain. Two main types of dynamics have been identified in brain neurons. Type 1 dynamics (regular spiking) shows a continuous relationship between frequency and stimulation current (f-Istim) and, thus, an arbitrarily low frequency at threshold current; Type 2 (fast spiking) shows a discontinuous f-Istim relationship and a minimum threshold frequency. In a previous study of a hippocampal neuron model, we demonstrated that its dynamics could be of both Type 1 and Type 2, depending on ion channel density. In the present study we analyse the effect of varying channel density on threshold firing frequency on two well-studied axon membranes, namely the frog myelinated axon and the squid giant axon. Moreover, we analyse the hippocampal neuron model in more detail. The models are all based on voltage-clamp studies, thus comprising experimentally measurable parameters. The choice of analysing effects of channel density modifications is due to their physiological and pharmacological relevance. We show, using bifurcation analysis, that both axon models display exclusively Type 2 dynamics, independently of ion channel density. Nevertheless, both models have a region in the channel-density plane characterized by an N-shaped steady-state current-voltage relationship (a prerequisite for Type 1 dynamics and associated with this type of dynamics in the hippocampal model). In summary, our results suggest that the hippocampal soma and the two axon membranes represent two distinct kinds of membranes; membranes with a channel-density dependent switching between Type 1 and 2 dynamics, and membranes with a channel-density independent dynamics. The difference between the two membrane types suggests functional differences, compatible with a more flexible role of the soma membrane than that of the axon membrane

Radial volumetric imaging breath-hold examination (VIBE) with k-space weighted image contrast (KWIC) for dynamic gadoxetic acid (Gd-EOB-DTPA)-enhanced MRI of the liver: advantages over Cartesian VIBE in the arterial phase

To compare radial volumetric imaging breath-hold examination with k-space weighted image contrast reconstruction (r-VIBE-KWIC) to Cartesian VIBE (c-VIBE) in arterial phase dynamic gadoxetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (DCE-MRI) of the liver. We reviewed 53 consecutive DCE-MRI studies performed on a 3-T unit using c-VIBE and 53 consecutive cases performed using r-VIBE-KWIC with full-frame image subset (r-VIBEfull) and sub-frame image subsets (r-VIBEsub; temporal resolution, 2.5-3 s). All arterial phase images were scored by two readers on: (1) contrast-enhancement ratio (CER) in the abdominal aorta; (2) scan timing; (3) artefacts; (4) visualisation of the common, right, and left hepatic arteries. Mean abdominal aortic CERs for c-VIBE, r-VIBEfull, and r-VIBEsub were 3.2, 4.3 and 6.5, respectively. There were significant differences between each group (P < 0.0001). The mean score for c-VIBE was significantly lower than that for r-VIBEfull and r-VIBEsub in all factors except for visualisation of the common hepatic artery (P < 0.05). The mean score of all factors except for scan timing for r-VIBEsub was not significantly different from that for r-VIBEfull. Radial VIBE-KWIC provides higher image quality than c-VIBE, and r-VIBEsub features high temporal resolution without image degradation in arterial phase DCE-MRI. aEuro cent Radial VIBE-KWIC minimised artefact and produced high-quality and high-temporal-resolution images. aEuro cent Maximum abdominal aortic enhancement was observed on sub-frame images of r-VIBE-KWIC. aEuro cent Using r-VIBE-KWIC, optimal arterial phase images were obtained in over 90 %. aEuro cent Using r-VIBE-KWIC, visualisation of the hepatic arteries was improved. aEuro cent A two-reader study revealed r-VIBE-KWIC's advantages over Cartesian VIBE.ArticleEUROPEAN RADIOLOGY. 24(6):1290-1299 (2014)journal articl

Arthroscopy vs. MRI for a detailed assessment of cartilage disease in osteoarthritis: diagnostic value of MRI in clinical practice

<p>Abstract</p> <p>Background</p> <p>In patients with osteoarthritis, a detailed assessment of degenerative cartilage disease is important to recommend adequate treatment. Using a representative sample of patients, this study investigated whether MRI is reliable for a detailed cartilage assessment in patients with osteoarthritis of the knee.</p> <p>Methods</p> <p>In a cross sectional-study as a part of a retrospective case-control study, 36 patients (mean age 53.1 years) with clinically relevant osteoarthritis received standardized MRI (sag. T1-TSE, cor. STIR-TSE, trans. fat-suppressed PD-TSE, sag. fat-suppressed PD-TSE, Siemens Magnetom Avanto syngo MR B 15) on a 1.5 Tesla unit. Within a maximum of three months later, arthroscopic grading of the articular surfaces was performed. MRI grading by two blinded observers was compared to arthroscopic findings. Diagnostic values as well as intra- and inter-observer values were assessed.</p> <p>Results</p> <p>Inter-observer agreement between readers 1 and 2 was good (kappa = 0.65) within all compartments. Intra-observer agreement comparing MRI grading to arthroscopic grading showed moderate to good values for readers 1 and 2 (kappa = 0.50 and 0.62, respectively), the poorest being within the patellofemoral joint (kappa = 0.32 and 0.52). Sensitivities were relatively low at all grades, particularly for grade 3 cartilage lesions. A tendency to underestimate cartilage disorders on MR images was not noticed.</p> <p>Conclusions</p> <p>According to our results, the use of MRI for precise grading of the cartilage in osteoarthritis is limited. Even if the practical benefit of MRI in pretreatment diagnostics is unequivocal, a diagnostic arthroscopy is of outstanding value when a grading of the cartilage is crucial for a definitive decision regarding therapeutic options in patients with osteoarthritis.</p

FDG PET imaging of paragangliomas of the neck: comparison with MIBG SPET

Two patients with cervical paragangliomas underwent positron emission tomography (PET) with 2-[ 18 F]-fluoro-2-deoxy-D-glucose (FDG). There was marked tumor uptake and retention of FDG. Adjacent salivary gland accumulation of FDG was minimal, though quite prominent with meta -iodobenzylguanidine. FDG PET offers another potentially useful approach to functional imaging of these uncommon tumors, independent of the presence of specific amine uptake mechanisms or cell surface receptors required by other scintigraphic techniques.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46837/1/259_2004_Article_BF00801625.pd