Assessing Adipocyte Viability and Surgeons' Work Efficiency by Comparing Different Liposuction Methods.

Background: Autologous fat grafting is widely used in plastic and reconstructive surgery. Liposuction methods play a key role in surgeons' work efficiency, adipocyte viability, graft survival, and outcomes. We investigated the effect of four liposuction methods on adipocyte viability, debris, and surgeons' work efficiency by measuring the active energy expenditure and changes in heart rate. Methods: Human lipoaspirate was harvested from patients' removed abdominal flaps using four different liposuction methods, and we counted calories per aspirated volume and surgeons' heart rate. Adipocytes were separated from the lipoaspirate immediately by digestion with 0.1% type I collagenase. After digestion, parts of the cells and debris were measured. Adipocytes were plated in an adipocyte maintenance medium containing Alamar blue reagent. The adipocyte metabolic activity was measured using a spectrophotometer. Results: After evaluating the active energy expenditure and changes in surgeons' heart rate, the ultrasonic-assisted liposuction (UAL) method was determined to be the most ergonomic liposuction device for surgeons. In addition, adipocyte viability was higher in the UAL group than in the other groups, and debris was the lowest in the power-assisted liposuction 1 group (PAL1). Conclusions: Adipocyte viability is crucial for improving fat grafting outcomes. This study revealed that the viability of adipocytes is best preserved using the UAL and PAL1 liposuction methods. The UAL and PAL1 methods caused the least damage to the cells. The UAL method yielded the best results for surgeons' work efficiency.

Saturation of visual responses explains size tuning in rat collicular neurons.

The receptive field of many visual neurons is composed of a central responsive area, the classical receptive field, and a non-classical receptive field, also called the "suppressive surround." A visual stimulus placed in the suppressive surround does not induce any response but modulates visual responses to stimuli within the classical receptive field, usually by suppressing them. Therefore, visual responses become smaller when stimuli exceed the classical receptive field size. The stimulus size inducing the maximal response is called the preferred stimulus size. In cortex, there is good correspondence between the sizes of the classical receptive field and the preferred stimulus. In contrast, in the rodent superior colliculus, the preferred size is often several fold smaller than the classical receptive field size. Here, we show that in the rat superior colliculus, the preferred stimulus size changes as a square root of the contrast inverse and the classical receptive field size is independent of contrast. In addition, responses to annulus were largely independent of the inner hole size. To explain these data, three models were tested: the divisive modulation of the gain by the suppressive surround (the "normalization" model), the difference of the Gaussians, and a divisive model that incorporates saturation to light flux. Despite the same number of free parameters, the model incorporating saturation to light performed the best. Thus, our data indicate that in rats, the saturation to light can be a dominant phenomenon even at relatively low illumination levels defining visual responses in the collicular neurons.

An efficient rAAV vector for protein expression in cortical parvalbumin expressing interneurons.

Recombinant adeno-associated viruses (rAAV) are extensively used in both research and clinical applications. Despite significant advances, there is a lack of short promoters able to drive the expression of virus delivered genes in specific classes of neurons. We designed an efficient rAAV vector suitable for the rAAV-mediated gene expression in cortical interneurons, mainly in the parvalbumin expressing cells. The vector includes a short parvalbumin promoter and a specialized poly(A) sequence. The degree of conservation of the parvalbumin gene adjoining non-coding regions was used in both the promoter design and the selection of the poly(A) sequence. The specificity was established by co-localizing the fluorescence of the virus delivered eGFP and the antibody for a neuronal marker. rAAV particles were injected in the visual cortex area V1/V2 of adult rats (2-4 months old). Neurons expressing the virus delivered eGFP were mainly positive for interneuronal markers: 66.5 ± 2.8% for parvalbumin, 14.6 ± 2.4% for somatostatin, 7.1 ± 1.2% for vasoactive intestinal peptide, 2.8 ± 0.6% for cholecystokinin. Meanwhile, only 2.1 ± 0.5% were positive for CaMKII, a marker for principal cells in the cortex. The efficiency of the construct was verified by optogenetic experiments: the expression of the virus delivered ChR2 channels was sufficient to evoke by blue light laser high frequency bursts of action potentials in putative fast spiking neurons. We conclude that our promoter allows highly specific expression of the rAAV delivered cDNAs in cortical interneurons with a strong preference for the parvalbumin positive cells.

Limited Spatial Spread Explains the Dependence of Visual Response Adaptation on Stimulus Size in Rat Superior Colliculus Neurons.

Although adaptation to light occurs in the eye and mainly preserves the full dynamic range of neuronal responses during changing background illumination, it affects the entire visual system and helps to optimize visual information processing. We have shown recently that in rat superior colliculus (SC) neurons adaptation to light acts as a local low-pass filter because, in contrast to the primate SC, in rat collicular neurons adaptation to small stimuli is largely limited to the vicinity of the adaptor stimulus. However, it was unclear whether large visual stimuli would induce the same spatially limited adaptation. We addressed this question by evaluating the effects of 1.8°, 6.2° and 20.8° wide adaptor stimuli on test stimuli of variable size. Single unit recordings in the adult rat SC were employed to estimate the response amplitude. Small, 1.8° and 6.2° adaptors habituated visual responses only to stimuli smaller than the adaptive stimuli. However, the 20.8° adaptor dramatically reduced responses even to test stimuli >3 times wider than the adaptor (up to 70° wide). The latter result may be explained by a nearly complete occlusion by a large adaptor of the neuron's receptive field (RF). All these results are consistent with the idea of a limited spatial spread of adaptation in rat SC neurons that is the consequence of high convergence of retinal inputs, in which small RFs limit the spatial spread of adaptation. It is concluded that, in this limited spatial spread of adaptation, rodent SC resembles higher visual system areas in primates and indicates potential differences in visual information processing between rodents and primates.

Subacute Arterial Bleeding After Simultaneous Mastopexy and Breast Augmentation with Implants.

Breast augmentation with implants is one of the most commonly performed plastic surgery procedures. The goal of the operation is to increase the size, shape or fullness of the breast. It is accomplished by placing silicone, saline or alternative composite breast implants under the chest muscles, fascia or the mammary gland. This type of operation is no exception concerning the occurrence of complications. The most common early complications include an infectious process, a seroma, and a hematoma, and the late ones are capsular contracture, reoperation, implant removal, breast asymmetry, and rupture or deflation of the implant. The authors present a case of subacute arterial bleeding after simultaneous mastopexy and breast augmentation with silicone implants in a 27-year-old woman. The patient complained of worsening swelling and soreness in the right breast. The patient denied having had any traumas. Ultrasonography indicated 2.5 cm heterogeneous fluid sections around the implant. Therefore, revision surgery was performed, and a hematoma of 650 mL was removed. Hemorrhaging from a branch of an internal mammary artery was found. After the revision, the implant was returned to the lodge. The postoperative period was uneventful. This case report presents a description of a subacute hematoma after simultaneous mastopexy and breast augmentation with silicone implants, which is an extremely rare complication in esthetic surgery.

Experimentally derived model shows that adaptation acts as a powerful spatiotemporal filter of visual responses in the rat collicular neurons.

Adaptation of visual responses enhances visual information processing mainly by preserving the full dynamic range of neuronal responses during changing light conditions and is found throughout the whole visual system. Although adaptation in the primate superior colliculus neurons has received much attention little is known about quantitative properties of such adaptation in rodents, an increasingly important model in vision research. By employing single unit recordings, we demonstrate that in the rat collicular neurons visual responses are shaped by at least two forms of adaptation. When visual stimuli were repeatedly presented in the same location, visual responses were reduced in the majority of single units. However, when the adaptor stimulus was outside a small diameter receptive field (RF), responses to stimulus onset but not offset were enhanced in the majority of units. Responses to stimulus offset were reduced less and recovered faster than responses to stimulus onset and the effect was limited to a fraction of RF area. Simulations showed that such adaptation acted as a powerful spatiotemporal filter and could explain several tuning properties of collicular neurons. These results demonstrate that in rodents the adaption of visual responses has a complex spatiotemporal structure and can profoundly shape visual information processing.

Comparison of non-surgical methods for the treatment of deep partial thickness skin burns of the hand.

This paper describes a randomized, controlled, parallel-group, single-center clinical trial designed to compare non surgical treatment methods of deep partial thickness skin burns of the hand. All patients were scanned with the Laser Doppler Imaging device to determine the depth of the burn wound. Viable keratinocytes sites were determined according to the established Perfusion Units (PU) measurement system. The trial enrolled 87 patients with hand burn wounds in the section of 260-600PU. Hand burn patients were divided into the following four groups: treated with hydrocolloid dressings; treated with mechanical debridement of monofilament polyester fibers pad and then applying silver sulfadiazine; treated with gauze dressings containing enzymatic collagenase preparation. The fourth group of patients was treated with silver sulfadiazine and gauze dressings. This group was considered as the control group. The wound healing status was assessed after 3, 7, 14 and 21 days. Burn scars and injured extremity function were assessed after six months according to the Vancouver Scar Scale and Disabilities of the Arm, Shoulder and Hand Outcome Measure. The fastest epithelialization of hand burn wounds was observed in the patients group treated with hydrocolloid dressings (15, 7 days, p<0,05). The patients of this group also had less scars and a better hand function.

Optogenetic control of mitochondrial metabolism and Ca2+ signaling by mitochondria-targeted opsins.

Key mitochondrial functions such as ATP production, Ca2+ uptake and release, and substrate accumulation depend on the proton electrochemical gradient (ΔµH+) across the inner membrane. Although several drugs can modulate ΔµH+, their effects are hardly reversible, and lack cellular specificity and spatial resolution. Although channelrhodopsins are widely used to modulate the plasma membrane potential of excitable cells, mitochondria have thus far eluded optogenetic control. Here we describe a toolkit of optometabolic constructs based on selective targeting of channelrhodopsins with distinct functional properties to the inner mitochondrial membrane of intact cells. We show that our strategy enables a light-dependent control of the mitochondrial membrane potential (Δψm) and coupled mitochondrial functions such as ATP synthesis by oxidative phosphorylation, Ca2+ dynamics, and respiratory metabolism. By directly modulating Δψm, the mitochondria-targeted opsins were used to control complex physiological processes such as spontaneous beats in cardiac myocytes and glucose-dependent ATP increase in pancreatic ß-cells. Furthermore, our optometabolic tools allow modulation of mitochondrial functions in single cells and defined cell regions.

Rat superior colliculus neurons respond to large visual stimuli flashed outside the classical receptive field.

Spatial integration of visual stimuli is a crucial step in visual information processing yet it is often unclear where this integration takes place in the visual system. In the superficial layers of the superior colliculus that form an early stage in visual information processing, neurons are known to have relatively small visual receptive fields, suggesting limited spatial integration. Here it is shown that at least for rats this conclusion may be wrong. Extracellular recordings in urethane-anaesthetized young adult rats (1.5-2 months old) showed that large stimuli of over 10° could evoke detectable responses well outside the borders of 'classical' receptive fields determined by employing 2° - 3.5° stimuli. The presence of responses to large stimuli well outside these 'classical' receptive fields could not be explained neither by partial overlap between the visual stimulus and the receptive field, nor by reflections or light dispersion from the stimulation site. However, very low frequency (<0.1 Hz) residual responses to small stimuli presented outside the receptive field may explain the obtained results if we assume that the frequency of action potentials during a response to a stimulus outside RF is proportional to the stimulus area. Thus, responses to large stimuli outside RF may be predicted by scaling according to the stimulus area of the responses to small stimuli. These data demonstrate that neurons in the superficial layers of the superior colliculus are capable of integrating visual stimuli over much larger area than it can be deduced from the classical receptive field.

Spatial synchronization of visual stimulus-evoked gamma frequency oscillations in the rat superior colliculus.

In the superior colliculus, visual stimuli can induce gamma frequency oscillations of neuronal activity. It has been shown that in cats, these oscillations are synchronized over distances of greater than 300 µm that may contribute toward visual information processing. We investigated the spatial properties of such oscillations in a rodent because the availability of molecular tools could enable future studies on the role of these oscillations in visual information processing. Using extracellular electrode array recordings in anesthetized rats, we found that visual stimuli-induced gamma and eta frequency (30-115 Hz) oscillations of the local field potential that were synchronized over distances of ∼ 600 µm. Multiple-unit events were phase locked to the local field potential signal and showed prominent oscillations during OFF responses. The rate of lower than 5 ms cross-electrode coincidences was in line with the response-corrected predictions for each electrode. These data suggest that the synchronized superior colliculus neuronal activity is largely network driven, whereas common synaptic inputs play a minor role.

Visual Stimuli Evoked Action Potentials Trigger Rapidly Propagating Dendritic Calcium Transients in the Frog Optic Tectum Layer 6 Neurons.

The superior colliculus in mammals or the optic tectum in amphibians is a major visual information processing center responsible for generation of orientating responses such as saccades in monkeys or prey catching avoidance behavior in frogs. The conserved structure function of the superior colliculus the optic tectum across distant species such as frogs, birds monkeys permits to draw rather general conclusions after studying a single species. We chose the frog optic tectum because we are able to perform whole-cell voltage-clamp recordings fluorescence imaging of tectal neurons while they respond to a visual stimulus. In the optic tectum of amphibians most visual information is processed by pear-shaped neurons possessing long dendritic branches, which receive the majority of synapses originating from the retinal ganglion cells. Since the first step of the retinal input integration is performed on these dendrites, it is important to know whether this integration is enhanced by active dendritic properties. We demonstrate that rapid calcium transients coinciding with the visual stimulus evoked action potentials in the somatic recordings can be readily detected up to the fine branches of these dendrites. These transients were blocked by calcium channel blockers nifedipine CdCl2 indicating that calcium entered dendrites via voltage-activated L-type calcium channels. The high speed of calcium transient propagation, >300 µm in <10 ms, is consistent with the notion that action potentials, actively propagating along dendrites, open voltage-gated L-type calcium channels causing rapid calcium concentration transients in the dendrites. We conclude that such activation by somatic action potentials of the dendritic voltage gated calcium channels in the close vicinity to the synapses formed by axons of the retinal ganglion cells may facilitate visual information processing in the principal neurons of the frog optic tectum.

Differential TGF-ß Signaling in Glial Subsets Underlies IL-6-Mediated Epileptogenesis in Mice.

TGF-ß1 is a master cytokine in immune regulation, orchestrating both pro- and anti-inflammatory reactions. Recent studies show that whereas TGF-ß1 induces a quiescent microglia phenotype, it plays a pathogenic role in the neurovascular unit and triggers neuronal hyperexcitability and epileptogenesis. In this study, we show that, in primary glial cultures, TGF-ß signaling induces rapid upregulation of the cytokine IL-6 in astrocytes, but not in microglia, via enhanced expression, phosphorylation, and nuclear translocation of SMAD2/3. Electrophysiological recordings show that administration of IL-6 increases cortical excitability, culminating in epileptiform discharges in vitro and spontaneous seizures in C57BL/6 mice. Intracellular recordings from layer V pyramidal cells in neocortical slices obtained from IL-6 -: treated mice show that during epileptogenesis, the cells respond to repetitive orthodromic activation with prolonged after-depolarization with no apparent changes in intrinsic membrane properties. Notably, TGF-ß1 -: induced IL-6 upregulation occurs in brains of FVB/N but not in brains of C57BL/6 mice. Overall, our data suggest that TGF-ß signaling in the brain can cause astrocyte activation whereby IL-6 upregulation results in dysregulation of astrocyte -: neuronal interactions and neuronal hyperexcitability. Whereas IL-6 is epileptogenic in C57BL/6 mice, its upregulation by TGF-ß1 is more profound in FVB/N mice characterized as a relatively more susceptible strain to seizure-induced cell death.

Can Optogenetic Tools Determine the Importance of Temporal Codes to Sensory Information Processing in the Brain?

There is no doubt that optogenetic tools caused a paradigm shift in many fields of neuroscience. These tools enable rapid and reversible intervention with a specific neuronal circuit and then the impact on the remaining circuit and/or behavior can be studied. However, so far the ability of these optogenetic tools to interfere with neuronal signal transmission in the time scale of milliseconds has been used much less frequently although they may help to answer a fundamental question of neuroscience: how important temporal codes are to information processing in the brain. This perspective paper examines why optogenetic tools were used so little to perturb or imitate temporal codes. Although some technical limitations do exist, there is a clear need for a systems approach. More research about action potential pattern formation by interactions between several brain areas is necessary in order to exploit the full potential of optogenetic methods in probing temporal codes.

A compact and autoclavable system for acute extracellular neural recording and brain pressure monitoring for humans.

One of the most difficult tasks for the surgeon during the removal of low-grade gliomas is to identify as precisely as possible the borders between functional and non-functional brain tissue with the aim of obtaining the maximal possible resection which allows to the patient the longer survival. For this purpose, systems for acute extracellular recordings of single neuron and multi-unit activity are considered promising. Here we describe a system to be used with 16 microelectrodes arrays that consists of an autoclavable headstage, a built-in inserter for precise electrode positioning and a system that measures and controls the pressure exerted by the headstage on the brain with a twofold purpose: to increase recording stability and to avoid disturbance of local perfusion which would cause a degradation of the quality of the recording and, eventually, local ischemia. With respect to devices where only electrodes are autoclavable, our design permits the reduction of noise arising from long cable connections preserving at the same time the flexibility and avoiding long-lasting gas sterilization procedures. Finally, size is much smaller and set up time much shorter compared to commercial systems currently in use in surgery rooms, making it easy to consider our system very useful for intra-operatory mapping operations.

What limits the performance of current invasive brain machine interfaces?

The concept of a brain-machine interface (BMI) or a computer-brain interface is simple: BMI creates a communication pathway for a direct control by brain of an external device. In reality BMIs are very complex devices and only recently the increase in computing power of microprocessors enabled a boom in BMI research that continues almost unabated to this date, the high point being the insertion of electrode arrays into the brains of 5 human patients in a clinical trial run by Cyberkinetics with few other clinical tests still in progress. Meanwhile several EEG-based BMI devices (non-invasive BMIs) were launched commercially. Modern electronics and dry electrode technology made possible to drive the cost of some of these devices below few hundred dollars. However, the initial excitement of the direct control by brain waves of a computer or other equipment is dampened by large efforts required for learning, high error rates and slow response speed. All these problems are directly related to low information transfer rates typical for such EEG-based BMIs. In invasive BMIs employing multiple electrodes inserted into the brain one may expect much higher information transfer rates than in EEG-based BMIs because, in theory, each electrode provides an independent information channel. However, although invasive BMIs require more expensive equipment and have ethical problems related to the need to insert electrodes in the live brain, such financial and ethical costs are often not offset by a dramatic improvement in the information transfer rate. Thus the main topic of this review is why in invasive BMIs an apparently much larger information content obtained with multiple extracellular electrodes does not translate into much higher rates of information transfer? This paper explores possible answers to this question by concluding that more research on what movement parameters are encoded by neurons in motor cortex is needed before we can enjoy the next generation BMIs.

Spatial mismatch between the Na+ flux and spike initiation in axon initial segment.

It is widely believed that, in cortical pyramidal cells, action potentials (APs) initiate in the distal portion of axon initial segment (AIS) because that is where Na(+) channel density is highest. To investigate the relationship between the density of Na(+) channels and the spatiotemporal pattern of AP initiation, we simultaneously recorded Na(+) flux and action currents along the proximal axonal length. We found that functional Na(+) channel density is approximately four times lower in the AP trigger zone than in the middle of the AIS, where it is highest. Computational analysis of AP initiation revealed a paradoxical mismatch between the AP threshold and Na(+) channel density, which could be explained by the lopsided capacitive load imposed on the proximal end of the AIS by the somatodendritic compartment. Favorable conditions for AP initiation are therefore achieved in the distal AIS portion, close to the edge of myelin, where the current source-load ratio is highest. Our findings suggest that cable properties play a central role in determining where the AP starts, such that small plastic changes in the local AIS Na(+) channel density could have a large influence on neuronal excitability as a whole.

20Hz membrane potential oscillations are driven by synaptic inputs in collision-detecting neurons in the frog optic tectum.

Although the firing patterns of collision-detecting neurons have been described in detail in several species, the mechanisms generating responses in these neurons to visual objects on a collision course remain largely unknown. This is partly due to the limited number of intracellular recordings from such neurons, particularly in vertebrate species. By employing patch recordings in a novel integrated frog eye-tectum preparation we tested the hypothesis that OFF retinal ganglion cells were driving the responses to visual objects on a collision course in the frog optic tectum neurons. We found that the majority (22/26) of neurons in layer 6 responding to visual stimuli fitted the definition of η class collision-detectors: they readily responded to a looming stimulus imitating collision but not a receding stimulus (spike count difference ∼10 times) and the spike firing rate peaked after the stimulus visual angle reached a threshold value of ∼20-45°. In the majority of these neurons (15/22) a slow frequency oscillation (f=∼20Hz) of the neuronal membrane potential could be detected in the responses to a simulated collision stimulus, as well as to turning off the lights. Since OFF retinal ganglion cells could produce such oscillations, our observations are in agreement with the hypothesis that 'collision' responses in the frog optic tectum neurons are driven by synaptic inputs from OFF retinal ganglion cells.

Origins of 1/f2 scaling in the power spectrum of intracortical local field potential.

It has been noted that the power spectrum of intracortical local field potential (LFP) often scales as 1/f(-2). It is thought that LFP mostly represents the spiking-related neuronal activity such as synaptic currents and spikes in the vicinity of the recording electrode, but no 1/f(2) scaling is detected in the spike power. Although tissue filtering or modulation of spiking activity by UP and DOWN states could account for the observed LFP scaling, there is no consensus as to how it arises. We addressed this question by recording simultaneously LFP and single neurons ("single units") from multiple sites in somatosensory cortex of anesthetized rats. Single-unit data revealed the presence of periods of high activity, presumably corresponding to the "UP" states when the neuronal membrane potential is depolarized, and periods of no activity, the putative "DOWN" states when the membrane potential is close to resting. As expected, the LFP power scaled as 1/f(2) but no such scaling was found in the power spectrum of spiking activity. Our analysis showed that 1/f(2) scaling in the LFP power spectrum was largely generated by the steplike transitions between UP and DOWN states. The shape of the LFP signal during these transitions, but not the transition timing, was crucial to obtain the observed scaling. These transitions were probably induced by synchronous changes in the membrane potential across neurons. We conclude that a 1/f(2) scaling in the LFP power indicates the presence of steplike transitions in the LFP trace and says little about the statistical properties of the associated neuronal firing.

Carbon nanotube composite coating of neural microelectrodes preferentially improves the multiunit signal-to-noise ratio.

Extracellular metal microelectrodes are widely used to record single neuron activity in vivo. However, their signal-to-noise ratio (SNR) is often far from optimal due to their high impedance value. It has been recently reported that carbon nanotube (CNT) coatings may decrease microelectrode impedance, thus improving their performance. To tease out the different contributions to SNR of CNT-coated microelectrodes we carried out impedance and noise spectroscopy measurements of platinum/tungsten microelectrodes coated with a polypyrrole-CNT composite. Neuronal signals were recorded in vivo from rat cortex by employing tetrodes with two recording sites coated with polypyrrole-CNT and the remaining two left untreated. We found that polypyrrole-CNT coating significantly reduced the microelectrode impedance at all neuronal signal frequencies (from 1 to 10 000 Hz) and induced a significant improvement of the SNR, up to fourfold on average, in the 150-1500 Hz frequency range, largely corresponding to the multiunit frequency band. An equivalent circuit, previously proposed for porous conducting polymer coatings, reproduced the impedance spectra of our coated electrodes but could not explain the frequency dependence of SNR improvement following polypyrrole-CNT coating. This implies that neither the neural signal amplitude, as recorded by a CNT-coated metal microelectrode, nor noise can be fully described by the equivalent circuit model we used here and suggests that a more detailed approach may be needed to better understand the signal propagation at the electrode-solution interface. Finally, the presence of significant noise components that are neither thermal nor electronic makes it difficult to establish a direct relationship between the actual electrode noise and the impedance spectra.

Na/K ATPase activity is coordinated with the persistent sodium current amplitude.

It is known that the Na+/K+ ATPase may control the frequency of slow action potential bursts that can be found in motor patterns generating neurons. Thus, Na+/K+ ATPase can participate in the formation of firing patterns in neurons and it is likely that the ATPase activity is coordinated with the expression of ionic channels. However, so far, there is no such evidence. Here it is shown that, in pyramidal neurons of the rat prefrontal cortex, the density of electrogenic sodium-potassium ATPase current was correlated with the density of the persistent sodium current (R2=0.62, P<0.002). It is speculated that such coordination may improve the control of the firing patterns in prefrontal cortex pyramidal neurons.