Half-maximal Amplitude Research Articles

PROGRAM FOR DETERMINING THE INFORMATIVE PARAMETERS OF SURFACE ELECTROMYOGRAPHIC SIGNALS

The article analyzes and calculates informative parameters of surface electromyographic signals (sEMS), which can be used to control biotechnical systems, as well as to diagnose the state of the musculoskeletal system. The analysis parameters in the time and frequency-time domains of the signal are considered. A program has been developed for calculating the informative indicators of the signal in the indicated areas. The program is implemented in the LabVIEW environment. To analyze the sEMG signal in the time domain, using the developed program, such indicators as Integral EMG, Average amplitude change, Wavelength, Simple quadratic integral, Absolute value of the 3rd time moment, and others were calculated; and to describe the signal spectrum by methods of time-frequency analysis, the average frequency of the spectrum (mean power frequency-MPF), the median frequency of the spectrum (median Frequency-MF), root mean square (RMS), power density spectrum (PDS), half width - the width of the spectrum at half maximum amplitude (HW). To test the program, files of real sEMQ signals were used. The calculated parameters of the sEMG analysis in the time and frequency-time domains make it possible to non-invasively and objectively assess the state of the musculoskeletal system. Keywords: Surface electromyographic signals, biotechnical systems, time-frequency analysis, Labvıew software.

High-speed 2D light-sheet fluorescence microscopy enables quantification of spatially varying calcium dynamics in ventricular cardiomyocytes.

Introduction: Reduced synchrony of calcium release and t-tubule structure organization in individual cardiomyocytes has been linked to loss of contractile strength and arrhythmia. Compared to confocal scanning techniques widely used for imaging calcium dynamics in cardiac muscle cells, light-sheet fluorescence microscopy enables fast acquisition of a 2D plane in the sample with low phototoxicity. Methods: A custom light-sheet fluorescence microscope was used to achieve dual-channel 2D timelapse imaging of calcium and the sarcolemma, enabling calcium sparks and transients in left and right ventricle cardiomyocytes to be correlated with the cell microstructure. Imaging electrically stimulated dual-labelled cardiomyocytes immobilized with para-nitroblebbistatin, a non-phototoxic, low fluorescence contraction uncoupler, with sub-micron resolution at 395fps over a 38μm × 170µm FOV allowed characterization of calcium spark morphology and 2D mapping of the calcium transient time-to-half-maximum across the cell. Results: Blinded analysis of the data revealed sparks with greater amplitude in left ventricle myocytes. The time for the calcium transient to reach half-maximum amplitude in the central part of the cell was found to be, on average, 2ms shorter than at the cell ends. Sparks co-localized with t-tubules were found to have significantly longer duration, larger area and spark mass than those further away from t-tubules. Conclusion: The high spatiotemporal resolution of the microscope and automated image-analysis enabled detailed 2D mapping and quantification of calcium dynamics of n = 60 myocytes, with the findings demonstrating multi-level spatial variation of calcium dynamics across the cell, supporting the dependence of synchrony and characteristics of calcium release on the underlying t-tubule structure.

Abstract WMP51: Baseline Ct Perfusion Parameters Differ In Large Vessel Occlusion Stroke Patients With Reduced Left Ventricular Ejection Fraction

Introduction: Reduced left ventricular ejection fraction (EF) is associated with worse outcomes after stroke. CT perfusion (CTP) is widely used in acute stroke evaluation; its reliability in patients with reduced EF is unknown. We hypothesized that patients with reduced EF would have abnormal dose-time curves that may impair standard perfusion maps and reduce their quality. Methods: A retrospective database of all patients presenting to Stanford University for large vessel occlusion (LVO) stroke between 2010-2019 was used. CTPs were post-processed using RAPID software. Concentration-time curve metrics—width of the venous output function (VOF) at half maximum amplitude and VOF peak amplitude—were assessed automatically for each case. A reader blinded to EF visually evaluated the VOF curve for evidence of truncation (yes/no) and graded the quality of the time to maximum (Tmax) map on a scale from 0 (excellent) to 3 (poor), based on the degree of “speckling” present on the map. Continuous parameters were compared using the t-test or Mann-Whitney test and dichotomous parameters with the Fisher’s exact or Chi-square test, where appropriate. Results: 160 patients with sufficient quality baseline CTP and in-hospital echocardiogram were evaluated; 34 had EF <50%. Mean age, scan time, and cumulative contrast dose did not differ; men were more prevalent in the reduced EF group (68% vs 44%; p=0.016). Compared to patients with normal EF, patients with low EF more often had truncation of the VOF (11.8% vs 0.8%; p=0.007), had a lower VOF peak amplitude (mean 245.04 HU vs 299.07; p=0.013, 95% CI for difference 11.61 to 96.45), had wider VOF at half maximum amplitude (mean 17.84 seconds vs 14.56; p<0.0001, 1.9 to 4.65), and had worse Tmax quality (median 2 (IQR 1-3) vs 1 (0-2); p=0.002). Conclusion: Patients with reduced EF have dispersion of the contrast bolus as evidenced by a VOF curve that is wider and has a lower peak. Consequently, the quality of the Tmax map in patients with low EF is reduced, which may render automated CTP results unreliable. Additional studies are needed to determine to what extent poor CTP image quality in patients with low EF affects treatment decisions.

Susceptible Plasmonic Photonic Crystal Fiber Sensor with Elliptical Air Holes and External-Flat Gold-Coated Surface

This paper proposes and analyzes a simple surface plasmon resonance (SPR)-based elliptical air hole photonic crystal fiber (PCF) sensor. The fiber structure comprises an analyte channel of the fiber surface coated with a gold layer on the flat surface and the fiber’s external surface. Numerical simulations are conducted using the finite element method (FEM) with an external sensing approach. We found that the thickness of plasmonic material (Au) is the most crucial factor that affects the full width at half maximum (FWHM) and confinement loss amplitude. We also demonstrated that the proposed elliptical air hole SPR-PCF is superior to circular air hole SPR-PCF in terms of confinement loss and FWHM. According to the wavelength interrogation technique, the simulation results show that the designed SPR-PCF sensor can attain a maximum sensitivity of 116,500 nm/RIU and a resolution of 8.58 × 10−7 RIU (RIU: refractive index unit) for the analyte RI of 1.395. We believe the proposed SPR-PCF sensor can be a potential candidate for biomolecular and biological analyte detection.

The Parameter Estimation of Double Exponential Pulse Based on a Least Infinity Norm Fitting Method

This paper presents an estimation method of double exponential pulse (DEP) between the physical parameters rise time (t r), full width at half maximum amplitude (t FWHM) and the mathematical parameters α, β. A newly fitting method based on the least infinity norm criterion is proposed to deal with the estimation problem of DEP. The calculation process and equation of parameters of this method is proposed based on an m-th-order polynomial fitting model. This estimation method is compared with the least square method by the same data and fitting function. The results show that the maximum estimation error of parameters of double exponential pulse obtained by the least infinity norm method is 1.5 %.

The Role of TRPV4 Cation Channels in Smooth Muscle Contractile Activity in Rats

Although it was shown that transient receptor potential channels are expressed in the intestinal and myometrial smooth muscle cells and can control gastrointestinal motility and regulate uterine contractility the specific role of transient receptor potential vanilloid-type 4 channel in smooth muscle cells contraction remain largely unknown. The purpose of the study was to test the action of transient receptor potential vanilloid-type 4 selective agonist GSK1016790A on smooth muscle cells contraction in rat’s colon with experimental Parkinson`s disease and in the pregnant rat uterus (18-22 days of gestation). Material and methods. The Parkinson’s disease was induced by single unilateral stereotaxic injection of 12 μg 6-OHDA. The percentage of destroyed dopaminergic neurons was evaluated in apomorphine test (0.5 mg/kg, i.p.) at 1 and 2 weeks after surgery. The water content in faeces was evaluated on the 1st day, then at the 3rd week and 7th month of the experiment. The daily volume of water consumption and gastrointestinal transit time were evaluated at the 3rd week and 7th month after surgery. The action of transient receptor potential vanilloid-type 4 agonist GSK1016790A (0.3 mmol) on smooth muscle cells of colon and myometrium strips contraction was estimated by isometric tension recording. Results and discussion. The apomorphine test showed a progressive increase in the number of turns between the 1st and 2nd week after inducing 6-OHDA-PD. The water content in faeces was increased at the 3rd week (P<0.05) vs. 1st day of the experiment. The rats with 6-OHDA-PD drank less water vs. placebo and intact groups. We observed a 17% delayed GI transit time in 6-OHDA-PD rats (P<0.01) vs. intact and 21% vs. sham-lesioned group of rats 3 weeks after the 6-OHDA treatment. 7 months after the surgery GI transit time was increased more than twice in all studied groups. Transient receptor potential vanilloid-type 4 agonist action on smooth muscle cells of 6-OHDA-PD rats was reduced by 21% compared to intact group and by 46% in sham-lesioned group (P<0.05). After the application of GSK1016790A the rat myometrium strips a 28.4% (P<0.05) decrease of the contractile force was recorded. It was accompanied by a 30.7% (P<0.05) decline of the muscle work estimated as the area under the contractile curve. Suppression of the amplitude of uterine contraction was also followed by a 39.7% (P<0.05) decline of the rise time constant of peaks but unchanged peak duration at the half maximal amplitude. Conclusion. We conclude that pharmacological activation of transient receptor potential vanilloid-type 4 ion channels by their selective agonist GSK1016790A decreased the contractile activity of both colon smooth muscle cells in Parkinson’s disease rats’ model and the myometrium in pregnant rats

Progress curve analysis of microtitre plate plasma clotting assays. Assessment of tissue factor levels

MTP plasma clotting assays monitor the time course of fibrin formation in re-calcified plasma by absorbance measurements and are increasingly used as alternatives to traditional one-point clot time assays employed in clinical laboratories to detect thrombotic disorders. The parameters derived from these analyses are analogous to thromboelastography viz. time, rate and maximum extent of clot formation. The derived parameters, based on the whole course of the clotting reaction are more robust, informative and quantitative than single-point clot time assays. However, the parameters themselves are usually obtained arbitrarily by crude graphical analysis of subjectively selected points of progress curves. The current work aimed to investigate the sensitivity and reproducibility of an MTP clotting assay and examine its suitability for measuring tissue factor (TF) levels in cell culture medium and patient urine. The results demonstrate that progress curves can be analysed by fitting a logistic equation, derived from a simplified autocatalytic clot formation model. The parameters, maximum amplitude (Fm), rate constant (k), time to half-maximum amplitude (tm) and maximum rate of clot formation (vm), fit a power curve showing limiting effects with increasing TF concentration. Log/log plots of tm and k against TF concentration provide standard curves for assessment of unknowns.

Fitting viscoelastic mechanical models to seismic attenuation and velocity dispersion observations and applications to full waveform modelling

SUMMARY The Cole–Cole mechanical model can match a simple seismic attenuation curve over a broad frequency range, but it is not a suitable model for replicating complicated seismic attenuation dispersion curves which exhibit multiple peaks or display pronounced asymmetry. In this case, we use the General Fractional Zener (GFZ) Model, which comprises multiple Cole–Cole elements, to approximate the attenuation observations. The observations here represent the arbitrary (frequency-dependent) dispersion behaviour from actual measurements (phase velocities and/or dissipation factors) or from some physical dissipation mechanism(s) such as local induced fluid flow in effective Biot theory. The key parameters of these viscoelastic models, which include the stress and strain relaxation times and the fractional derivative orders, are determined with a simulated annealing method. Instead of searching for the relaxation times directly, we search for the Zener peak attenuation points and corresponding frequencies, each of which corresponds to a pair of relaxation times. We show that just two fractional Zener elements can sometimes provide a satisfactory approximation to the observations over the entire frequency range. A simple deterministic method is developed to extract the parameters of the single element Zener model using phase velocity observations. As a special case of the GFZ model, we found and proved the constancy of the width of the attenuation curves at the half maximum amplitude point (FWHM) for all Zener models which is critical to the design of reasonable observation frequencies. We stress and demonstrate that ignoring the frequency-dependence of Q may result in significant discrepancies of calculated waveforms with observed or predicted values.

Performance Evaluation of a Novel Preclinical Micro-CT System In Vitro and In Vivo

With the advent of innovation in the preclinical studies, micro-CT provides optimized resolution by high-power X-ray output tube and flat-panel detector with ultra-short scanning time. The aim of this study was to evaluate the performance of a novel preclinical micro-CT with different parameters and protocols. Imaging quality was evaluated by micro-CT HA and wire phantom. The high power output X-ray tube provides tube voltage from 40 to 90 kV with tube current, 10 to 800 μA. The detector with 1536 × 1944 pixels was implemented by three different binning modes (1 × 1, 2 × 2 and 4 × 4). The GPU-based reconstruction was applied with Feldkamp’s algorithm. The maximum reconstruction volume was 1944 × 1944 × 4536 per scan. The phantom images were acquired by four modes with pixel sizes of 44.9, 22.5,15 and 9 μm. In the animal study, ovariectomy mice were imaged followed by analysis of bone mineral density (BMD) and BV/TV ratio (bone volume/total bone volume). Linearity (R2) measured in all imaging settings were > 0.9 and was 0.99962 at setting of 0.2 mm Cu filter, 90 kV tube voltage and 556 μA tube current. The spatial resolution as measured by full width half-maximum amplitude (FWHM) was 24 µm in the mode ultra-high resolution. The bone analysis results show the operated cohort has high significant (p < 0.05), whereas the control cohort revealed insignificant either in the BMD. In summary, this novel micro-CT system demonstrated the flexible capability and high spatial resolution with ultra-short acquisition time, and a feasible quantitative BMD software.

Automatic Detection and Classification of Ca2+ Release Events in Line- and Frame-Scan Images

Analysis of Ca2+ signals obtained in various cell types (i.e., cardiomyocytes) is always a tradeoff between acquisition speed and signal/noise ratio of the fluorescence signal. This becomes especially apparent during fast two- or three-dimensional confocal imaging when local intracellular fluorescence signals originating from Ca2+ release from intracellular Ca2+ stores (e.g., sarcoplasmic reticulum) need to be examined. Mathematical methods have been developed to remedy a high noise level by fitting each pixel with a transient function to “denoise” the image. So far, current available analytical approaches have been impaired by a number of constraints (e.g., inability to fit local, concurrent, and consecutive events) and the limited ability to customize implementation. Here, we suggest a, to our knowledge, novel approach for detailed analysis of subcellular micro-Ca2+ events based on pixel-by-pixel denoising of confocal frame- and line-scan images. The algorithm enables spatiotemporally overlapping events (e.g., a Ca2+ spark occurring during the decaying phase of a Ca2+ wave) to be extracted so that various types of Ca2+ events can be detected at a pixel time level of precision. The method allows a nonconstant baseline to be estimated for each pixel, foregoing the need to subtract fluorescence background or apply self-ratio methods before image analysis. Furthermore, by using a clustering algorithm, identified single-pixel events are grouped into “physiologically relevant” Ca2+ signaling events spanning multiple pixels (sparks, waves, puffs, transients, etc.), from which spatiotemporal event parameters (e.g., full duration at half maximal amplitude, full width at half maximal amplitude, amplitude, wave speed, rise, and decay times) can be easily extracted. The method was implemented with cross-platform open source software, providing a comprehensive and easy-to-use graphical user interface enabling rapid line-scan images and rapid frame-scan image sequences (up to 150 frames/s) to be analyzed and repetitive Ca2+ events (Ca2+ sparks and Ca2+ puffs) originating from clusters of Ca2+ release channels located in the sarcoplasmic reticulum membrane (ryanodine receptors and inositol 1,4,5-trisphosphate receptors) of isolated cardiomyocytes to be examined with a high level of precision.

Trunk muscle activation pattern in parkinsonian camptocormia as revealed with surface electromyography

IntroductionCamptocormia is frequently seen in Parkinson's disease (PD) and multiple system atrophy. It is characterized by a pathological forward bending of the trunk during standing, often combined with a lateral trunk deviation. The etiology of camptocormia in PD is still unknown. Muscle MRI studies show abnormalities mainly of the erector spinae confirmed by muscle biopsies. Quantitative electromyographic examination of trunk muscle activity is missing. MethodsVentral (rectus and obliquus externus abdominis) and dorsal (iliocostalis lumborum, longissimus, multifidus) trunk muscles and the rectus femoris were recorded bilaterally with surface electromyography in standing PD patients with camptocormia (n = 10) and matched healthy controls (n = 10) who mimicked the patients' posture. EMG amplitudes were compared quantitatively. In controls, the relation between varying degrees of trunk flexion and EMG was established systematically. ResultsIncreasing forward trunk flexion was associated with increasing back muscle activity in controls, while abdominal muscle activity was negligible. During anterolateral trunk flexion, back muscle activity increased particularly on the contralateral side. The patients showed a similar pattern. However, normalized EMG activity of their trunk extensors was significantly higher than in controls, often reaching half-maximal amplitudes. Their rectus femoris and oblique abdominal muscles were overactive, but to a lesser extent. ConclusionsPD patients with camptocormia must use the functional reserve of their lumbar trunk muscles to counteract gravity. We interpret this as a weakness of the paravertebral muscles. Compared to the other examined muscles the paravertebral muscles are most affected. The increased EMG activity of the rectus femoris warrants further research.

Different output properties of perisomatic region-targeting interneurons in the basal amygdala.

The perisomatic region of principal neurons in cortical regions is innervated by three types of GABAergic interneuron, including parvalbumin-containing basket cells (PVBCs) and axo-axonic cells (AACs), as well as cholecystokinin and type 1 cannabinoid receptor-expressing basket cells (CCK/CB1BCs). These perisomatic inhibitory cell types can also be found in the basal nucleus of the amygdala, however, their output properties are largely unknown. Here, we performed whole-cell recordings in morphologically identified interneurons in slices prepared from transgenic mice, in which the GABAergic cells could be selectively targeted. Investigating the passive and active membrane properties of interneurons located within the basal amygdala revealed that the three interneuron types have distinct single-cell properties. For instance, the input resistance, spike rate, accommodation in discharge rate, or after-hyperpolarization width at the half maximal amplitude separated the three interneuron types. Furthermore, we performed paired recordings from interneurons and principal neurons to uncover the basic features of unitary inhibitory postsynaptic currents (uIPSCs). Although we found no difference in the magnitude of responses measured in the principal neurons, the uIPSCs originating from the distinct interneuron types differed in rise time, failure rate, latency, and short-term dynamics. Moreover, the asynchronous transmitter release induced by a train of action potentials was typical for the output synapses of CCK/CB1BCs. Our results suggest that, despite the similar uIPSC magnitudes originating from the three perisomatic inhibitory cell types, their distinct release properties together with the marked differences in their spiking characteristics may contribute to accomplish specific functions in amygdala network operation.

Modeling of stochastic behavior of pacemaker potential in interstitial cells of Cajal

It is widely accepted that interstitial cells of Cajal (ICCs) generate pacemaker potentials to propagate slow waves along the whole gastrointestinal tract. Previously, we constructed a biophysically based model of ICCs in mouse small intestine to explain the pacemaker mechanism. Our previous model, however, could not explain non-uniformity of pacemaker potentials and random occurrence of unitary potentials, thus we updated our model. The inositol 1,4,5-trisphosphate (IP3)-mediated Ca2+ mobilization is a key event to drive the cycle of pacemaker activity and was updated to reproduce its stochastic behavior. The stochasticity was embodied by simulating random opening and closing of individual IP3-mediated Ca2+ channel. The updated model reproduces the stochastic features of pacemaker potentials in ICCs. Reproduced pacemaker potentials are not uniform in duration and interval. The resting and peak potentials are −75.5 ± 1.1 mV and −0.8 ± 0.5 mV, respectively (n = 55). Frequency of pacemaker potential is 14.3 ± 0.4 min−1 (n = 10). Width at half-maximal amplitude of pacemaker potential is 902 ± 6 ms (n = 55). There are random events of unitary potential-like depolarization. Finally, we compared our updated model with a recently published model to speculate which ion channel is the best candidate to drive pacemaker depolarization. In conclusion, our updated mathematical model could now reproduce stochastic features of pacemaker activity in ICCs.

Effect of exercise training on Ca2+ release units of left ventricular myocytes of spontaneously hypertensive rats

In cardiomyocytes, calcium (Ca2+) release units comprise clusters of intracellular Ca2+ release channels located on the sarcoplasmic reticulum, and hypertension is well established as a cause of defects in calcium release unit function. Our objective was to determine whether endurance exercise training could attenuate the deleterious effects of hypertension on calcium release unit components and Ca2+ sparks in left ventricular myocytes of spontaneously hypertensive rats. Male Wistar and spontaneously hypertensive rats (4 months of age) were divided into 4 groups: normotensive (NC) and hypertensive control (HC), and normotensive (NT) and hypertensive trained (HT) animals (7 rats per group). NC and HC rats were submitted to a low-intensity treadmill running protocol (5 days/week, 1 h/day, 0% grade, and 50-60% of maximal running speed) for 8 weeks. Gene expression of the ryanodine receptor type 2 (RyR2) and FK506 binding protein (FKBP12.6) increased (270%) and decreased (88%), respectively, in HC compared to NC rats. Endurance exercise training reversed these changes by reducing RyR2 (230%) and normalizing FKBP12.6 gene expression (112%). Hypertension also increased the frequency of Ca2+ sparks (HC=7.61±0.26 vs NC=4.79±0.19 per 100 µm/s) and decreased its amplitude (HC=0.260±0.08 vs NC=0.324±0.10 ΔF/F0), full width at half-maximum amplitude (HC=1.05±0.08 vs NC=1.26±0.01 µm), total duration (HC=11.51±0.12 vs NC=14.97±0.24 ms), time to peak (HC=4.84±0.06 vs NC=6.31±0.14 ms), and time constant of decay (HC=8.68±0.12 vs NC=10.21±0.22 ms). These changes were partially reversed in HT rats (frequency of Ca2+ sparks=6.26±0.19 µm/s, amplitude=0.282±0.10 ΔF/F0, full width at half-maximum amplitude=1.14±0.01 µm, total duration=13.34±0.17 ms, time to peak=5.43±0.08 ms, and time constant of decay=9.43±0.15 ms). Endurance exercise training attenuated the deleterious effects of hypertension on calcium release units of left ventricular myocytes.

Allosteric regulation of the P2X4 receptor channel pore dilation.

Allosteric modulators of ligand-gated receptor channels induce conformational changes of the entire protein that alter potencies and efficacies for orthosteric ligands, expressed as the half maximal effective concentration (EC50) and maximum current amplitude, respectively. Here, we studied the influence of allostery on channel pore dilation, an issue not previously addressed. Experiments were done using the rat P2X4 receptor expressed in human embryonic kidney 293T cells and gated by adenosine 5'-triphosphate (ATP) in the presence and absence of ivermectin (IVM), an established positive allosteric regulator of this channel. In the absence of IVM, this channel activates and deactivates rapidly, does not show transition from open to dilated states, desensitizes completely with a moderate rate, and recovers only fractionally during washout. IVM treatment increases the efficacy of ATP to activate the channel and slows receptor desensitization during sustained ATP application and receptor deactivation after ATP washout. The rescue of the receptor from desensitization temporally coincides with pore dilation, and the dilated channel can be reactivated after washout of ATP. Experiments with vestibular and transmembrane domain receptor mutants further established that IVM has distinct effects on opening and dilation of the channel pore, the first accounting for increased peak current amplitude and the latter correlating with changes in the EC50 and kinetics of receptor deactivation. The corresponding kinetic (Markov state) model indicates that the IVM-dependent transition from open to dilated state is coupled to receptor sensitization, which rescues the receptor from desensitization and subsequent internalization. Allosterically induced sensitization of P2X4R thus provides sustained signaling during prolonged and repetitive ATP stimulation.

椭圆弧型过渡段有界波模拟器

A bounded-wave simulator with ellipse-arc transitional section structure is proposed and designed. The electric field waveform in the simulator is simulated and compared with the tapered transitional section simulator by using the electromagnetic-field simulating software CST. The double exponential pulse with rise time 2 ns, full-width at half-maximum (FWHM) amplitude 25 ns and the step pulse with rise time 2 ns, duration about 80 ns are obtained in the experiment. And a comparison is carried out between the two simulators. The results of simulation and experiment both indicate that the bounded-wave simulator eliminates the interference effectively coming from the discontinuity at the junction of the transitional section and parallel-plate section.

Effects of Peripheral Blood Mononuclear Cells Morphology on Vascular Calcification in Uremic Patients on Maintenance Hemodialysis

We used high-resolution atomic force microscopy (AFM) to examine possible changes in the morphology of peripheral blood mononuclear cells (PBMCs), and to investigate their influence on vascular calcification in uremic patients on maintenance hemodialysis (MHD). 36 uremic patients had cardiovascular diseases after MHD (MHD group1) and 30 uremic patients did not (MHD group 2), and 20 healthy volunteers were the control group. The extent of coronary artery calcification was assessed with coronary artery calcification score (CACS). AFM was used to analyze PBMCs nuances. Concentrations of bone morphogenetic protein-2 (BMP-2) in PBMC supernatants were detected by ELISA. Protein expressions of BMP-2 were measured by Western blot. No significant differences in PBMC morphology were observed among groups by light microscopy. AFM images revealed that uremic patients exhibited significant differences of PBMC morphology and vascular calcification when compared with healthy volunteers. The PBMCs in uremic patients were larger in volume, mean height, half-maximum amplitude, average roughness and higher concentrations and expression of BMP-2 and CACS (P < 0.05), with granular processes or caveolae of uneven size distributed over cell surfaces. These differences were also significant between MHD group 1 and group 2 (P < 0.05). PBMC volume, mean height, half-maximum amplitude, and average roughness were positively correlated with BMP-2 and CACS. Moreover, the correlation PBMC with BMP-2 was higher than with CACS. PBMC morphology in MHD patients was related to the degree of vascular calcification. The larger mean height, half-maximum amplitude, average roughness and cell volume were, the higher degree of vascular calcification was.

Center/surround organization of retinal bipolar cells: High correlation of fundamental responses of center and surround to sinusoidal contrasts

Receptive field organization of cone-driven bipolar cells was investigated by intracellular recording in the intact light-adapted retina of the tiger salamander (Ambystoma tigrinum). Centered spots and concentric annuli of optimum dimensions were used to selectively stimulate the receptive field center and surround with sinusoidal modulations of contrast at 3 Hz. At low contrasts, responses of both the center and surround of both ON and OFF bipolar cells were linear, showing high gain and thus contrast enhancement relative to cones. The contrast/response curves for the fundamental response, measured by a Fast Fourier Transform, reached half maximum amplitude quickly at 13% contrast followed by saturation at high contrasts. The variation of the normalized amplitude of the center and surround responses was remarkably similar, showing linear regression over the entire response range with very high correlations, r2 = 0.97 for both ON and OFF cells. The contrast/response curves of both center and surround for both ON and OFF cells were well fit (r2 = 0.98) by an equation for single-site binding. In about half the cells studied, the nonlinear waveforms of center and surround could be brought into coincidence by scaling and shifting the surround response in time. This implies that a nonlinearity, common to both center and surround, occurs after polarity inversion at the cone feedback synapse. Evidence from paired whole-cell recordings between single cones and OFF bipolar cells suggests that substantial nonlinearity is not due to transmission at the cone synapse but instead arises from intrinsic bipolar cell and network mechanisms. When sinusoidal contrast modulations were applied to the center and surround simultaneously, clear additivity was observed for small responses in both ON and OFF cells, whereas the interaction was strikingly nonadditive for large responses. The contribution of the surround was then greatly reduced, suggesting attenuation at the cone feedback synapse.

Habenula “Cholinergic” Neurons Corelease Glutamate and Acetylcholine and Activate Postsynaptic Neurons via Distinct Transmission Modes

Acetylcholine is an important neurotransmitter, and the habenulo-interpeduncular projection is a major cholinergic pathway in the brain. To study the physiological properties of cholinergic transmission in the interpeduncular nucleus (IPN), we used a transgenic mouse line in which the light-gated cation channel ChannelRhodopsin-2 is selectively expressed in cholinergic neurons. Cholinergic axonal terminals were activated by light pulses, and postsynaptic responses were recorded from IPN neurons. Surprisingly, brief photostimulation produces fast excitatory postsynaptic currents that are mediated by ionotropic glutamate receptors, suggesting wired transmission of glutamate. By contrast, tetanic photostimulation generates slow inward currents that are largely mediated by nicotinic acetylcholine receptors, suggesting volume transmission of acetylcholine. Finally, vesicular transporters for glutamate and acetylcholine are coexpressed on the same axonal terminals in the IPN. These results strongly suggest that adult brain "cholinergic" neurons can corelease glutamate and acetylcholine, but these two neurotransmitters activate postsynaptic neurons via different transmission modes.

Theory and applications of geometric scaling of localized calcium release events

Geometric measures of localized calcium release (LCR) events have been used to understand their biophysical basis. We found power law scaling between three such metrics-maximum amplitude (MA), mass above half-maximum amplitude (MHM), and area at half-maximum amplitude (AHM). In an effort to understand this scaling a minimal analytic model was employed to simulate LCR events recorded by confocal line scan. The distribution of logMHM as a function of logAHM, pMHM(pAHM), was dependent on model parameters such as channel open time, current size, line scan offset, and apparent diffusion coefficient. The distribution of log[MHM/AHM] as a function of logMA, p[MHM/AHM](pMA), was invariant, reflecting the gross geometry of the LCR event. The findings of the model were applied to real LCR line scan data from rabbit portal vein myocytes, rat cerebral artery myocytes, and guinea pig fundus knurled cells. pMHM(pAHM) could be used to distinguish two populations of LCR events in portal vein, even at the scale of "calcium noise," and to calculate the relative current of the two. The relative current was 2. pMHM(pAHM) could also be used to study pharmacological effects. The pMHM(pAHM) distribution of knurled cell LCR events was markedly contracted by ryanodine, suggesting a reduction in channel open time. The p[MHM/AHM](pMA) distributions were invariant across all cell types and were consistent with the model, underlying the common physical basis of their geometry. The geometric scaling of LCR events demonstrated here may help with their mechanistic characterization.