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The substantia nigra pars reticulata (SNr) is the primary output nucleus for the basal ganglia (BG) in the rat. The SNr is reciprocally connected with the pedunculopontine tegmental nucleus (PPN) in the brainstem, which provides cholinergic innervation to most BG nuclei. The cholinergic input into the BG is considered to be important because PPN activity is altered in Parkinson's disease (PD), a neurological disorder involving the BG, and cholinergic pharmacotherapy is beneficial in alleviating some of its symptoms. In order to better understand the role of cholinergic input to the BG, we examined the effects of nicotinic acetylcholine receptor (nAChR) activation in the GABAergic neurons in slices through juvenile rat SNr. With the aide of subtype selective antagonists, we found that SNr neurons express the alpha7 subtype of nAChRs, the function of which we assessed using the whole cell patch-clamp recording technique. Besides alpha7 nAChRs, GABAergic SNr neurons also contained functional non-alpha7 nAChRs. Using local photolysis of caged carbachol, a broad-spectrum cholinergic agonist, we mapped alpha7 nAChR-mediated currents along the visible extent of filled SNr neurons and found that alpha7 nAChRs can be functionally detected as far as 60 microm away from the soma. Our data are paving the way to a better understanding of the physiological roles of nAChRs in the BG.

Study Design. Fifty-five human thoracolumbar vertebrae were randomly fatigue loaded and analyzed. Objectives. The purpose of this study was to explore the relationship between fatigue loading, trabecular microfracture, and energy absorption to fracture in human cadaveric thoracolumbar vertebrae. Background. Although trabecular microfractures are found in vivo and have been produced by fatigue loading in vitro, the effect of the level of physiologic fatigue loading on microfracture and energy absorption has not been investigated. Methods. Fifty-five human thoracolumbar vertebrae (T11-L4) were randomly divided into 5 groups: 1) control (no loading, n = 6); 2) axial compression to yield (n = 7); and 3-5) 20,000 cycles of fatigue loading at 2 Hz (each n = 14). The level of fatigue loading was determined as a proportion of the yield load of Group 2 as follows: 10% (Group 3), 20% (Group 4), and 30% (Group 5). Half of the specimens in groups 3 to 5 were used for radiographic and histomorphometric analysis to determine microfracture density and distribution, whereas the other half were tested to determine the energy absorption to yield failure. Results. No radiographic evidence of gross fracture was found in any of the groups following fatigue loading. A mean 7.5% increase in stiffness was found in specimens subject to cyclic loading at 10% of yield stress (Group 3). Fatigue at 20% (Group 4) and 30% of yield stress (Group 5) caused significantly higher (P < 0.05) increases in mean stiffness of 23.6% and 24.2%, respectively. Microfracture density increased from 0.46/mm 2 in Group 3 to 0.66/mm 2 in Group 4 and 0.94/mm 2 in Group 5 (P < 0.05). The energy absorbed to failure decreased from 21.9 J in Group 3 to 18.1 J and 19.6 J in Groups 4 and 5, respectively (P < 0.05). Conclusions. Fatigue loading at physiologic levels produced microfractures that are not detectable by radiography. Increased fatigue load results in an increase in microfracture density and decrease energy absorbed to fracture, indicating a reduced resistance to further fatigue loading.

To observe the preliminary clinical outcome of using a new instrumentation Diapason system and to introduce the characterization and surgical technique of this new system for treatment of unstable lumbar spinal stenosis.16 patients with unstable spinal stenosis who were treated by decompression, posterolateral intertransverse arthrodesis and transpedicle instrumentation of Diapason system, were analyzed retrospectively.Lower back pain (LBP) of 16 patients were significantly alleviated after surgery (scores of LBP before operation: 47.5 +/- 0.8; scores of LBP after operation: 31.9 +/- 2.3, P0.001). There was no implant failure, no early or later infection and no neurological complications in 16 patients at an average of 6.2-month follow-ups. No pseudoarthrosis was observed on roentgenography.Our short-term follow-up and limited cases study showed satisfactory preliminary result of treating unstable lumbar spinal stenosis with Diapason internal fixation.

The ultrastructure of synapses three hours after formation of long-term potentiation (LTP) was examined in the local microslices of visual cortical brain slices of 18-20 d rats. Slices without potentiating stimulation which were similarly incubated served as controls. The following structural changes were examined using a graph analyzer: (1) synaptic cleft width; (2) thickness of the postsynaptic densities(PSD); (3) length of the active zones; and (4) curvature of the synaptic interface. The number of synapses of different types in layer II/III of visual cortex was quantified by double-blind scoring procedures. The various counts were converted to the number of synapses per unit volume using stereological quantitation method. Analysis of variance was used for statistical evaluation. Our results suggest that field potentials reached their peak values at about one and a half hours after tetanus and could be maintained as long as three hours without decay. In comparison with the control groups, synaptic cleft width, thickness of PSD, surface density per unit volume(Sv) of the active zones, curvature of the synaptic interface, numeric density per unit volume (Nv) of all synapses, spine synapses and the Nv of perforated synapses were all increased significantly. These data suggest that the increase of Sv of active zones and the increase of the curvature of synaptic interface may be the morphological feature characterizing the maintenance of LTP, in addition to the formation of perforated synapses.

We verify the validity of the optical characterization of the 2D electron gas confined in modulation doped (GaAl)/As/GaAs heterojunctions designed for both high electron mobility devices. The properties of the 2D electron gas are evaluated from the magneto photoluminescence and the microwave influenced photoluminescence detected on the GaAs excitons in the flat band region. We evaluate the electron density and mobility from the oscillation of the photoluminescence intensity in a magnetic field, and the effective mass from the resonant change of the PL intensity under additional microwave radiation. We attribute these non-linear optical properties to the vertical transport and the bimolecular exciton formation of photoexcited carriers. We proved these specific transport and exciton formation processes by time-resolved photoluminescence experiments, where an extremely long exciton formation time and a strong signal of anti-stokes emissions under resonant excitations are observed. Furthermore, we realized a significant amplification of the photoluminescence intensity by exciting the heterojunction with two temporarily delayed laser pulses. The amplification of the luminescence intensity reflects unambiguously the recycling through the bimolecular exciton formation of the photo-excited carriers accumulated in the flat band region after vertical transport.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The Herbst corpuscle, found only in birds, is one of the morphologically distinct types of lamellated sensory nerve endings. Its response properties were studied electrophysiologically in anesthetized pigeons by recording from: (A) afferents emerging from single Herbst corpuscles located in the interosseous region of the shank, (B) from vibration-sensitive cells found in the dorsal root ganglia near the lumbosacral enlargement of the spinal cord, and (C) from nerve fibers dissected out of the sciatic nerve. Vibration-sensitive cells in the dorsal root ganglia and in sciatic nerve fibers exhibited properties that were very similar to those found at the Herbst corpuscle itself. All three recording approaches indicated that Herbst corpuscles are vibration-sensitive mechano-receptors with broad bandpass tuning curves. With all approaches, the lowest threshold always fell in the frequency range between 400 and 800 Hz. The value of the threshold, however, varied with the method, being as low as 0.08 μm with method C and as high as 1 μm with method A. Regardless of method, these neurons exhibited no spontaneous activity, and their firing displayed a special sensory coding pattern at high stimulus amplitude: the nerve impulses were phase locked to the stimulus cycle, exhibiting a 1:1 relationship with it up to a frequency of 500 Hz. Comparison of these data with prior behavioral data suggests that the Herbst corpuscle peripheral mechanoreceptors are part of a vibratory sensory system which acts as a warning device, given attentive behavior.

Seven types of auditory interneurons were characterized from the prothoracic ganglion of the bushcricket. They are sensitive in the range of 7-18 kHz and fire with distinct discharge patterns. They encode sound intensity and temporal parameters in various way. They show significant directional sensitivity, dependent on sound frequency. The acoustic tracheal system can partly account for the directional hearing of the bushcricket.

Observing the basophil releasability of 17 patients with allergic rhinitis and 14 nonatopic subjects stimulated with house dust mite and concanavalin A (ConA), we found that the histamine release was much higher in patients with allergic rhinitis than in normal controls and that no positive correlation was found between the histamine release rate and the serum total IgE. This result suggests that the enhanced basophil releasability might be an important factor in allergic disorders, and might contribute to a means for the differentiation between allergic and non-allergic disorders.

NiO/NiFe bilayer thin films were prepared by rf reactive and dc magnetron sputtering, respectively. The exchange coupling strength between NiO and NiFe as a function of NiO texture and interface roughness was investigated by using different sputtering pressures, Au, and Cu buffer layers. The experimental results show that the exchange coupling field strongly depends on the NiO/NiFe interface roughness. In addition, we found the exchange coupling is largest for the (200) texture compared to the (111)‐texture films. This is surprising since the bulk spin structure of NiO predicts the (200) plane to be compensated while the (111) plane is to be uncompensated.

The C2 deoxy and C6 electron isosteric analogs of a new antiglaucoma agent, erycibe alkaloid II, were designed and synthesized. The main pharmacological results were as follows: 1. The C2-OH in erycibe alkaloid II was one of the key groups for its myotic activity; 2. It was worth noting that compounds 2 and 4 showed cholinergic and anticholinergic activities, respectively. This phenomenon in tropane alkaloids was not reported before; 3. The C6 electron isosteric compounds 16 and 17 showed neither anticholinergic nor cholinergic activities.

Recently, 2-halogenated deoxyadenosine analogs (F, Cl, and Br) have been shown to have antitumor activity. These analogs are phosphorylated by cells and are believed to exert their cytotoxic action at the nucleoside triphosphate level. In this work the interaction of these nucleoside triphosphate analogs with potential targets, such as DNA polymerase alpha, beta, and gamma, DNA primase, and ribonucleotide reductase was examined in detail. All of these compounds competitively inhibited the incorporation of dAMP into DNA by DNA polymerase alpha, beta, or gamma. F-dATP was able to completely substitute for dATP using DNA polymerase alpha and gamma, but not with DNA polymerase beta. Cl-dATP and Br-dATP substituted poorly for dATP using DNA polymerase alpha and beta. Extension of a 32P-labeled primer by DNA polymerase alpha, beta, or gamma on a single-stranded M13 template showed that these compounds were incorporated into the 3' end of the growing DNA chain and that elongation beyond the incorporated analogs was significantly retarded for Cl-dATP and Br-dATP using either DNA polymerase alpha or beta. DNA primase using poly(dC) as template was inhibited by these compounds at a concentration 4 to 5 times greater than that required for 2-F-araATP. The 2-halogenated dATP analogs were potent inhibitors of ADP reduction by ribonucleotide reductase. In conclusion, the cytotoxic action of 2-Cl-deoxyadenosine and 2-Br-deoxyadenosine may partially be mediated through the mechanism of "self-potentiation," by depression of the deoxynucleoside triphosphate pools due to inhibition of ribonucleotide reductase, which would facilitate their incorporation into DNA and result in the inhibition of DNA synthesis.