Nitrergic Proprioceptive Afferents Originating from Quadriceps Femoris Muscle are Related to Monosynaptic Ia-Motoneuron Stretch Reflex Circuit in the Dog

1. The aim of the present study was to examine the occurrence of the neuronal nitric oxide synthase immunoreactivity in the stretch reflex circuit pertaining to the quadriceps femoris muscle in the dog.2. Immunohistochemical processing for neuronal nitric oxide synthase and histochemical staining for nicotinamide adenine dinucleotide phosphate diaphorase were used to demonstrate the presence of neuronal nitric oxide synthase in the proprioceptive afferents issuing in the quadriceps femoris muscle. The retrograde tracer Fluorogold injected into the quadriceps femoris muscle was used to detect the proprioceptive afferents and their entry into the L5 and L6 dorsal root ganglia.3. A noticeable number of medium-sized intensely nitric oxide synthase immunolabelled somata (1000–2000 μm² square area) was found in control animals in the dorsolateral part of L5 and L6 dorsal root ganglia along with large-caliber intraganglionic nitric oxide synthase immunolabelled fibers, presumed to be Ia axons. Before entering the dorsal funiculus the large-caliber nitric oxide synthase immunolabelled fibers of the L5 and L6 dorsal roots formed a massive medial bundle, which upon entering the dorsal root entry zone reached the dorsolateral part of the dorsal funiculus and were distributed here in a funnel-shaped fashion. The largest nitric oxide synthase immunolabelled fibers, 8.0–9.2 μm in diameter, remained close to the dorsal horn, while medium-sized fibers were seen dispersed across the medial portion of the dorsal funiculus. Single, considerably tapered nitric oxide synthase immunolabelled fibers, 2.2–4.6 μm in diameter, were seen to proceed in ventrolateral direction until they reached the mediobasal portion of the dorsal horn and the medial part of lamina VII. In lamina IX, only short fragments of nitric oxide synthase immunoreactive fibers and their terminal ramifications could be seen. Nitric oxide synthase immunolabelled terminals varying greatly in size were identified in control material at the base of the dorsal horn, in the vicinity of motoneurons ventrally and ventrolaterally in L5 and L6 segments and in Clarke’s column of L3 and L4 segments. Injections of the retrograde tracer Fluorogold into the quadriceps femoris muscle and cut femoral nerve, combined with nitric oxide synthase immunohistochemistry of the L5 and L6 dorsal root ganglia, confirmed the existence of a number of medium-sized nitric oxide synthase immunoreactive and Fluorogold-fluorescent somata presumed to be proprioceptive Ia neurons (1000–2000 μm² square area) in the dorsolateral part of both dorsal root ganglia. L5 and L6 dorsal rhizotomy caused a marked depletion of nitric oxide synthase immunoreactivity in the medial bundle of the L5 and L6 dorsal roots and in the dorsal funiculus of L5 and L6 segments.4. The analysis of control material and the degeneration of the large- and medium-caliber nitric oxide synthase immunoreactive Ia fibers in the dorsal funiculus of L5 and L6 segments confirmed the presence of nitric oxide synthase in the afferent limb of the monosynaptic Ia-motoneuron stretch reflex circuit related to the quadriceps femoris muscle. Abbreviations ABC, avidin–biotin complex; bNOS, neuronal nitric oxide synthase; bNOS-IR, neuronal nitric oxide synthase immunoreactive; bNOS-IRB_s, neuronal nitric oxide synthase immunoreactive boutons; cNOS, catalytic nitric oxide synthase; DAB, diaminobenzidine; DF, dorsal funiculus; DH, dorsal horn; DREZ-one, dorsal root entry zone; DRG_s, dorsal root ganglia; eNOS, endothelial nitric oxide synthase; FG, Fluorogold; FN, femoral nerve; mNOS, macrophage nitric oxide synthase; NADPHd, nicotinamide adenine dinucleotide phosphate diaphorase; NBT, nitroblue tetrazolium; NO, nitric oxide; NOS, nitric oxide synthase; NOS-IR, nitric oxide synthase immunoreactive; PBS, phosphate-buffered saline; VGLUT1 and VGLUT2, vesicular glutamate transporters     

Dopamine Release at Individual Presynaptic Terminals Visualized with FFNs

The nervous system transmits signals between neurons via neurotransmitter release during synaptic vesicle fusion. To observe neurotransmitter uptake and release from individual presynaptic terminals directly, we designed fluorescent false neurotransmitters as substrates for the synaptic vesicle monoamine transporter. Using these probes to image dopamine release in the striatum, we made several observations pertinent to synaptic plasticity. We found that the fraction of synaptic vesicles releasing neurotransmitter per stimulus was dependent on the stimulus frequency. A kinetically distinct "reserve" synaptic vesicle population was not observed under these experimental conditions. A frequency-dependent heterogeneity of presynaptic terminals was revealed that was dependent in part on D2 dopamine receptors, indicating a mechanism for frequency-dependent coding of presynaptic selection.Hui Zhang and Niko G. Gubernator contributed equally to this work.Download video file.^{(112M, mp4)}     

Adaptive Neuro-Fuzzy Appraisal of Plasmonic Studies on Morphology of Deposited Silver Thin Films Having Different Thicknesses

This work presents an experimental analysis on the tunable localized surface plasmon resonance (LSPR), obtained from deposited silver (Ag) thin films of various thicknesses. Silver thin films are prepared using electron beam deposition and undergo an annealing process at different temperatures to produce distinctive sizes of Ag metal nanoparticles (MNPs). The variability of structure sizes and shapes provides an effective means of tuning the position of the LSPR within a wide wavelength range. This paper provides an estimation of LSPR over a broad wavelength range by a process in which the resonance spectra of silver nanoparticles differing in thickness are simulated using an adaptive neuro-fuzzy inference system (ANFIS) method. The ANFIS methodology allows for estimation of sizes of granular structures formed on top of a wafer at certain temperatures, whereupon these intelligent estimators are implemented using MATLAB and their subsequent performances are investigated. The results presented in this paper show the effectiveness of the method of simulation.     

A conference report from "Down Under": Talking autophagy at OzBio2010

OzBio2010 was held at the Melbourne Convention and Exhibition Centre, September 26 to October 1, 2010. This international conference catered to researchers in several fields having complementary interests including biochemistry, molecular biology, cell biology, plant physiology and health-related research. It was held under the auspices of two major international scientific societies, IUBMB and FAOBMB, and the ComBio2010 collective (representing nine professional societies and groupings from Australia). A number of pre-eminent speakers presented at plenary sessions and in a wide array of specialist symposia. One of the plenary sessions and a specialist symposium highlighted autophagy-related topics.     

Kinetics of Tissue Iron in Experimental Autoimmune Encephalomyelitis in Rats

To elucidate the role of iron in the pathomechanisms of autoimmune CNS disorders, we estimated the tissue concentrations of Fe²⁺ in the brain, spinal cord, and liver in the chronic relapsing form of experimental autoimmune encephalomyelitis (EAE). The disease was induced in Dark Agouti (DA) strain of rats, by subcutaneous injection of bovine brain homogenate in complete Freund's adjuvant (CFA). Control rats consisted of unsensitized rats and of rats treated with CFA or saline. The data obtained by clinical assessment and by inductively coupled plasma spectrometry have shown that the attacks of disease (on the 12th and 22nd post-immunization day) were followed by high accumulation of iron in the liver. Additionally, during the second attack of disease, the decreased concentration of Fe²⁺ was found in cervical spinal cord. The data point to regulatory effects of iron and hepatic trace elements regulating mechanisms in the pathogenesis of EAE.     

Spectral composition of photosynthetically active radiation penetrating into a Norway spruce canopy: the opposite dynamics of the blue/red spectral ratio during clear and overcast days

The spectral composition of photosynthetically active radiation (PAR) during clear and overcast days was studied above the canopy (U) and at two layers of a dense Norway spruce stand [Picea abies (L.) Karst.] characterized with an average LAI = 7.3 ± 0.8 (middle layer: M) and 12.3 ± 0.7 (lower layer: L). Whereas the spectral composition of PAR incoming on the canopy surface during cloudy days (characterized by diffuse index DI > 0.7) was almost independent of the solar elevation angle, the proportion of the blue-green spectral region of PAR was significantly reduced at low elevation angles during days with prevailing direct radiation (DI < 0.3). The PAR spectrum at both M and L levels was only slightly enriched in the green spectral region (more pronounced for DI < 0.3). The penetration of diffuse radiation into the canopy resulted in a slight (approx. 5%) reduction of the blue region proportion that remained stable during the day. On the contrary, under clear sky conditions the penetration of blue and red radiation was dependent on the solar elevation in an opposite manner in comparison with the spectral composition of PAR incident on canopy, giving almost twofold proportion of the blue part of the spectrum at a low elevation angle at M layer. We suggest that the blue enhancement of the spectrum within the Norway spruce canopy during clear days is due to a specific spatial arrangement of the assimilatory apparatus of a coniferous stand. Further, the possible consequences of the observed dynamics of the PAR spectrum inside the canopy during clear days on the efficiency of PAR absorption of the needles located within the canopy are discussed.     

Paradoxical Abatement of Striatal Dopaminergic Transmission by Cocaine and Methylphenidate

We combined in vitro amperometric, optical analysis of fluorescent false neurotransmitters and microdialysis techniques to unveil that cocaine and methylphenidate induced a marked depression of the synaptic release of dopamine (DA) in mouse striatum. In contrast to the classical dopamine transporter (DAT)-dependent enhancement of the dopaminergic signal observed at concentrations of cocaine lower than 3 μm, the inhibitory effect of cocaine was found at concentrations higher than 3 μm. The paradoxical inhibitory effect of cocaine and methylphenidate was associated with a decrease in synapsin phosphorylation. Interestingly, a cocaine-induced depression of DA release was only present in cocaine-insensitive animals (DAT-CI). Similar effects of cocaine were produced by methylphenidate in both wild-type and DAT-CI mice. On the other hand, nomifensine only enhanced the dopaminergic signal either in wild-type or in DAT-CI mice. Overall, these results indicate that cocaine and methylphenidate can increase or decrease DA neurotransmission by blocking reuptake and reducing the exocytotic release, respectively. The biphasic reshaping of DA neurotransmission could contribute to different behavioral effects of psychostimulants, including the calming ones, in attention deficit hyperactivity disorder.