In Vivo and In Vitro Characterization of Primary Human Liver Macrophages and Their Inflammatory State

Liver macrophages (LMs) play a central role in acute and chronic liver pathologies. Investigation of these processes in humans as well as the development of diagnostic tools and new therapeutic strategies require in vitro models that closely resemble the in vivo situation. In our study, we sought to gain further insight into the role of LMs in different liver pathologies and into their characteristics after isolation from liver tissue. For this purpose, LMs were characterized in human liver tissue sections using immunohistochemistry and bioinformatic image analysis. Isolated cells were characterized in suspension using FACS analyses and in culture using immunofluorescence staining and laser scanning microscopy as well as functional assays. The majority of our investigated liver tissues were characterized by anti-inflammatory LMs which showed a homogeneous distribution and increased cell numbers in correlation with chronic liver injuries. In contrast, pro-inflammatory LMs appeared as temporary and locally restricted reactions. Detailed characterization of isolated macrophages revealed a complex disease dependent pattern of LMs consisting of pro- and anti-inflammatory macrophages of different origins, regulatory macrophages and monocytes. Our study showed that in most cases the macrophage pattern can be transferred in adherent cultures. The observed exceptions were restricted to LMs with pro-inflammatory characteristics

Effect of glucose and insulin supplementation on the isolation of primary human hepatocytes

Primary human hepatocytes (PHHs) remain the gold standard for in vitro investigations of xenobiotic metabolism and hepatotoxicity. However, scarcity of liver tissue and novel developments in liver surgery has limited the availability and quality of tissue samples. In particular, warm ischemia shifts the intracellular metabolism from aerobic to anaerobic conditions, which increases glycogenolysis, glucose depletion and energy deficiency. Therefore, the aim of the present study was to investigate whether supplementation with glucose and insulin during PHH isolation could reconstitute intracellular glycogen storage and beneficially affect viability and functionality. Furthermore, the study elucidated whether the susceptibility of the tissue’s energy status correlates with body mass index (BMI). PHHs from 12 donors were isolated from human liver tissue obtained from partial liver resections using a two-step EDTA/collagenase perfusion technique. For a direct comparison of the influence of glucose/insulin supplementation, we modified the setup, enabling the parallel isolation of two pieces of one tissue sample with varying perfusate. Independent of the BMI of the patient, the glycogen content in liver tissue was notably low in the majority of samples. Furthermore, supplementation with glucose and insulin had no beneficial effect on the glycogen concentration of isolated PHHs. However, an indirect improvement of the availability of energy was shown by increased viability, plating efficiency and partial cellular activity after supplementation. The plating efficiency showed a striking inverse correlation with increasing lipid content of PHHs. However, 60 h of cultivation time revealed no significant impact on the maintenance of albumin and urea synthesis or xenobiotic metabolism after supplementation. In conclusion, surgical procedures and tissue handling may decrease hepatic energy resources and lead to cell stress and death. Consequently, PHHs with low energy resources die during the isolation process without supplementation of glucose/insulin or early cell culture, while their survival rates are improved with glucose/insulin supplementation

Visual activation of auditory cortex reflects maladaptive plasticity in cochlear implant users

Cross-modal reorganization in the auditory cortex has been reported in deaf individuals. However, it is not well understood whether this compensatory reorganization induced by auditory deprivation recedes once the sensation of hearing is partially restored through a cochlear implant. The current study used electroencephalography source localization to examine cross-modal reorganization in the auditory cortex of post-lingually deafened cochlear implant users. We analysed visual-evoked potentials to parametrically modulated reversing chequerboard images between cochlear implant users (n = 11) and normal-hearing listeners (n = 11). The results revealed smaller P100 amplitudes and reduced visual cortex activation in cochlear implant users compared with normal-hearing listeners. At the P100 latency, cochlear implant users also showed activation in the right auditory cortex, which was inversely related to speech recognition ability with the cochlear implant. These results confirm a visual take-over in the auditory cortex of cochlear implant users. Incomplete reversal of this deafness-induced cortical reorganization might limit clinical benefit from a cochlear implant and help explain the high inter-subject variability in auditory speech comprehensio

Aging dynamics of heterogeneous spin models

We investigate numerically the dynamics of three different spin models in the aging regime. Each of these models is meant to be representative of a distinct class of aging behavior: coarsening systems, discontinuous spin glasses, and continuous spin glasses. In order to study dynamic heterogeneities induced by quenched disorder, we consider single-spin observables for a given disorder realization. In some simple cases we are able to provide analytical predictions for single-spin response and correlation functions. The results strongly depend upon the model considered. It turns out that, by comparing the slow evolution of a few different degrees of freedom, one can distinguish between different dynamic classes. As a conclusion we present the general properties which can be induced from our results, and discuss their relation with thermometric arguments.Comment: 39 pages, 36 figure

CtIP and MRN promote non-homologous end-joining of etoposide-induced DNA double-strand breaks in G1

Topoisomerases class II (topoII) cleave and re-ligate the DNA double helix to allow the passage of an intact DNA strand through it. Chemotherapeutic drugs such as etoposide target topoII, interfere with the normal enzymatic cleavage/re-ligation reaction and create a DNA double-strand break (DSB) with the enzyme covalently bound to the 5′-end of the DNA. Such DSBs are repaired by one of the two major DSB repair pathways, non-homologous end-joining (NHEJ) or homologous recombination. However, prior to repair, the covalently bound topoII needs to be removed from the DNA end, a process requiring the MRX complex and ctp1 in fission yeast. CtIP, the mammalian ortholog of ctp1, is known to promote homologous recombination by resecting DSB ends. Here, we show that human cells arrested in G0/G1 repair etoposide-induced DSBs by NHEJ and, surprisingly, require the MRN complex (the ortholog of MRX) and CtIP. CtIP's function for repairing etoposide-induced DSBs by NHEJ in G0/G1 requires the Thr-847 but not the Ser-327 phosphorylation site, both of which are needed for resection during HR. This finding establishes that CtIP promotes NHEJ of etoposide-induced DSBs during G0/G1 phase with an end-processing function that is distinct to its resection function

ADHEAR device in bone conduction audiometry

ADHEAR is a bone conduction hearing aid that uses an adhesive skin adapter. In the current study, the use of ADHEAR as an audiometric bone stimulator was investigated in normal-hearing subjects by comparing it to the standard Radio-Ear B71. Bone conduction thresholds of 15 normal-hearing subjects (aged 21–36 years) were measured four times in a randomized order, twice with the B71 and twice with the ADHEAR. There were no significant differences in test-retest reliability between the two devices. Subjectively rated comfort was better for the ADHEAR. The development of a specific audiometric adhesive bone stimulator may be warranted

Differences in Supra-Threshold Auditory Function in young and elderly normal hearing Adults

Prior studies investigated why older adults, even in the absence of hearing impairment, typically experience increased difficulties understanding speech in noise. ("Speech understanding and aging. Working Group on Speech Understanding and Aging. Committee on Hearing, Bioacoustics, and Biomechanics, Commission on Behavioral and Social Sciences and Education, National Research Council" 1988); (Dubno et al. 2002); Helfer et al. (2008) According to CHABA age has been found to be a determining factor in the ability to understand speech. This age effect can be related to age-dependent alterations in one or several of three processing domains: peripheral, central, and cognitive. The peripheral domain, in particular the performance of the inner ear is motivation in the present work. Our study covered a selection of measures of hearing acuity, temporal processing, frequency selectivity and a speech recognition task in noise to get a broad profile of performances between young and elderly listeners. For a realistic and external valid impression of hearing performance of young and elderly participants in the present study both groups were not matched. We knew about the supposed weakness in the design, as we dipped into the discussion of peripheral age-related factors. Our study focused on supra-threshold auditory functions in young and elderly listeners without self-reported hearing loss referring to worse speech identification performance in elderly and less ganglion cells in aging inner ears

Investigating the use of a Gammatone filterbank for a cochlear implant coding strategy

BACKGROUND: Contemporary speech processing strategies in cochlear implants (CIs) such as the Advanced Combination Encoder (ACE) use a standard Fast Fourier Transform (FFT) filterbank to extract envelopes. The assignment of the FFT bins to approximate the frequency resolution of the basilar membrane is only partly based on physiology, especially since the bins are distributed linearly below 1000Hz and logarithmically above 1000Hz. NEW METHOD: A Gammatone filterbank which provides a closer approximation to the bandwidths of filters in the human auditory system could replace the standard FFT filterbank in the ACE strategy. An infinite impulse response (IIR) all-pole design of the Gammatone filterbank was compared to the FFT filterbank with 128, 256 and 512 points resolutions and the effect of the frequency boundaries of the filters was also investigated. RESULTS: Melodic contour identification (MCI) and just noticeable difference (JND) experiments, both involving synthetic clarinet notes in octaves 3 and 4, were conducted with 6 normal hearing (NH) participants using noise vocoded stimuli; and 10 CI recipients just performed the MCI experiment. The MCI results for both NH and CI subjects, showed a significant effect of the filterbank on the percentage correct responses of the participants. COMPARISON WITH EXISTING METHODS: The Gammatone filterbank can better resolve the harmonics of tested synthetic clarinet notes which led to better performances in the MCI experiment. CONCLUSIONS: The total delay of the Gammatone filterbank can be made smaller than the delay of the FFT filterbank with the same frequency resolution at low frequencies

A neural-based vocoder implementation for evaluating cochlear implant coding strategies

Most simulations of cochlear implant (CI) coding strategies rely on standard vocoders that are based on purely signal processing techniques. However, these models neither account for various biophysical phenomena, such as neural stochasticity and refractoriness, nor for effects of electrical stimulation, such as spectral smearing as a function of stimulus intensity. In this paper, a neural model that accounts for stochastic firing, parasitic spread of excitation across neuron populations, and neuronal refractoriness, was developed and augmented as a preprocessing stage for a standard 22-channel noise-band vocoder. This model was used to subjectively and objectively assess consonant discrimination in commercial and experimental coding strategies. Stimuli consisting of consonant-vowel (CV) and vowel-consonant-vowel (VCV) tokens were processed by either the Advanced Combination Encoder (ACE) or the Excitability Controlled Coding (ECC) strategies, and later resynthesized to audio using the aforementioned vocoder model. Baseline performance was measured using unprocessed versions of the speech tokens. Behavioural responses were collected from seven normal hearing (NH) volunteers, while EEG data were recorded from five NH participants. Psychophysical results indicate that while there may be a difference in consonant perception between the two tested coding strategies, mismatch negativity (MMN) waveforms do not show any marked trends in CV or VCV contrast discrimination

A bio-inspired coding (BIC) strategy for cochlear implants

A bio-inspired coding (BIC) strategy was implemented in this study with the goal of better representation of spectral and temporal information. The auditory nerve fibers' (ANFs) characteristics such as refractory recovery, facilitation and spatial spread were obtained from ECAP data recorded in 11 CI recipients. These characteristics, together with a non-individualized model-derived adaptation effect, were integrated into the BIC strategy for a better selection of channels. Two variations of the BIC strategy were compared to the conventional advanced combination encoder (ACE) coding strategy: the BIC-I strategy based on the individual CI recipients' ECAP parameters, and the BIC-G strategy based on the median values of ECAP parameters from all CI recipients who participated in the study. The melodic contour identification (MCI) and Oldenburg sentence recognition in noise (OLSA) tests were used to assess and compare the three coding strategies. A significantly better performance in the transformed MCI test results with the rationalized arcsine transformation, was observed for both BIC strategy variations compared to the ACE strategy. There was no significant difference between the two variations of the BIC strategy and the ACE strategy in the OLSA test. No correlation was found between recovery time constants, absolute refractory periods, left and right width of SOE functions from three test electrodes and CI recipients' performances in the two experiments. However, significant correlations were found between facilitation time constant and amplitude and the results of the MCI and OLSA tests for the two variations of the BIC strategy