Microneurography in rats: a minimally invasive method to record single C-fiber action potentials from peripheral nerves in vivo

Microneurography is a method suitable for recording intraneural single or multiunit action potentials in conscious subjects. Microneurography has rarely been applied to animal experiments, where more invasive methods, like the teased fiber recording technique, are widely used. We have tested the feasibility of microneurographic recordings from the peripheral nerves of rats. Tungsten microelectrodes were inserted into the sciatic nerve at mid-thigh level. Single or multiunit action potentials evoked by regular electrical stimulation were recorded, digitized and displayed as a raster plot of latencies. The method allows unambiguous recording and recognition of single C-fiber action potentials from an in vivo preparation, with minimal disruption of the nerve being recorded. Multiple C-fibers can be recorded simultaneously for several hours, and if the animal is allowed to recover, repeated recording sessions can be obtained from the same nerve at the same level over a period of weeks or months. Also, single C units can be functionally identified by their changes in latency to natural stimuli, and insensitive units can be recognized as 'silent' nociceptors or sympathetic efferents by their distinctive profiles of activity-dependent slowing during repetitive electrical stimulation, or by the effect on spontaneous efferent activity of a proximal anesthetic block. Moreover, information about the biophysical properties of C axons can be obtained from their latency recovery cycles. Finally, we show that this preparation is potentially suitable for the study of C-fiber behavior in models of neuropathies and nerve lesions, both under resting conditions and in response to drug administration.

Evaluation of perpendicular reflection intensity for assessment of caries lesion activity/inactivity

The aim of this study was to evaluate, using visual assessment, an experimental optical sensor measuring perpendicular reflection intensity (PRI) as an indicator of enamel caries lesion activity/inactivity. Forty teeth with either an active or an inactive enamel lesion were selected from a pool of extracted teeth. Each tooth was cut into halves, with a clinically sound half and a half with a non-cavitated enamel lesion. After gentle plaque removal, the teeth were kept moistened. The lesions were then photographed and a defined measuring site per lesion was chosen and indicated with an arrow on a printout. Independently, the chosen site was visually assessed for lesion activity, and its glossiness was measured with PRI assessment. Surface roughness (SR) was assessed with optical profilometry using a confocal microscope. Visual assessment and PRI were repeated after several weeks and a reliability analysis was performed. For enamel lesions visually scored as active versus inactive, significantly different values were obtained with both PRI and SR. PRI values of the clinically sound control surfaces were significantly different only from active lesions. Generally, inactive lesions had the same glossiness and the same roughness as the sound control surfaces. The reliabilities for visual assessment (? = 0.89) and for PRI (ICC = 0.86) were high. It is concluded that, within the limits of this study, PRI can be regarded as a promising tool for quantitative enamel lesion activity assessment. There is scope and potential for the PRI device to be considerably improved for in vivo use.

Adverse effect of noise in the operating theatre on surgical-site infection

The aim of this pilot study was to evaluate the noise level in an operating theatre as a possible surrogate marker for intraoperative behaviour, and to detect any correlation between sound level and subsequent surgical-site infection (SSI).

[Verification of normative values for the Swiss version of the Freiburg speech intelligibility test.]

BACKGROUND AND OBJECTIVE: In the Swiss version of the Freiburg speech intelligibility test five test words from the original German recording which are rarely used in Switzerland have been exchanged. Furthermore, differences in the transfer functions between headphone and loudspeaker presentation are not taken into account during calibration. New settings for the levels of the individual test words in the recommended recording and small changes in calibration procedures led us to make a verification of the currently used normative values.PATIENTS AND METHODS: Speech intelligibility was measured in 20 subjects with normal hearing using monosyllabic words and numbers via headphones and loudspeakers.RESULTS: On average, 50% speech intelligibility was reached at levels which were 7.5 dB lower under free-field conditions than for headphone presentation. The average difference between numbers and monosyllabic words was found to be 9.6 dB, which is considerably lower than the 14 dB of the current normative curves.CONCLUSIONS: There is a good agreement between our measurements and the normative values for tests using monosyllabic words and headphones, but not for numbers or free-field measurements.

Enhancing BOLD response in the auditory system by neurophysiologically tuned fMRI sequence

Auditory neuroscience has not tapped fMRI's full potential because of acoustic scanner noise emitted by the gradient switches of conventional echoplanar fMRI sequences. The scanner noise is pulsed, and auditory cortex is particularly sensitive to pulsed sounds. Current fMRI approaches to avoid stimulus-noise interactions are temporally inefficient. Since the sustained BOLD response to pulsed sounds decreases with repetition rate and becomes minimal with unpulsed sounds, we developed an fMRI sequence emitting continuous rather than pulsed gradient sound by implementing a novel quasi-continuous gradient switch pattern. Compared to conventional fMRI, continuous-sound fMRI reduced auditory cortex BOLD baseline and increased BOLD amplitude with graded sound stimuli, short sound events, and sounds as complex as orchestra music with preserved temporal resolution. Response in subcortical auditory nuclei was enhanced, but not the response to light in visual cortex. Finally, tonotopic mapping using continuous-sound fMRI demonstrates that enhanced functional signal-to-noise in BOLD response translates into improved spatial separability of specific sound representations.

BOLD correlates of edge detection in human auditory cortex

Edges are important cues defining coherent auditory objects. As a model of auditory edges, sound on- and offset are particularly suitable to study their neural underpinnings because they contrast a specific physical input against no physical input. Change from silence to sound, that is onset, has extensively been studied and elicits transient neural responses bilaterally in auditory cortex. However, neural activity associated with sound onset is not only related to edge detection but also to novel afferent inputs. Edges at the change from sound to silence, that is offset, are not confounded by novel physical input and thus allow to examine neural activity associated with sound edges per se. In the first experiment, we used silent acquisition functional magnetic resonance imaging and found that the offset of pulsed sound activates planum temporale, superior temporal sulcus and planum polare of the right hemisphere. In the planum temporale and the superior temporal sulcus, offset response amplitudes were related to the pulse repetition rate of the preceding stimulation. In the second experiment, we found that these offset-responsive regions were also activated by single sound pulses, onset of sound pulse sequences and single sound pulse omissions within sound pulse sequences. However, they were not active during sustained sound presentation. Thus, our data show that circumscribed areas in right temporal cortex are specifically involved in identifying auditory edges. This operation is crucial for translating acoustic signal time series into coherent auditory objects.

Human temporal bones versus mechanical model to evaluate three middle ear transducers

A life-size mechanical middle ear model and human temporal bones were used to evaluate three different middle ear transducers for implantable hearing aids: the driving rod transducer (DRT), the floating mass transducer (FMT) or vibrant sound bridge, and the contactless transducer (CLT). Results of the experiments with the mechanical model were within the range of the results for human temporal bones. However, results with the mechanical model showed better reproducibility. The handling of the mechanical model was considerably simpler and less time-consuming. Systematic variations of mounting parameters showed that the angle of the rod has virtually no effect on the output of the DRT, the mass loading on the cable of the FMT has a larger impact on the output than does the tightness of crimping, and the output level of the CLT can be increased by 10 dB by optimizing the mounting parameters.

Milk ejection disorders in Swiss dairy cows: a field study

A questionnaire was sent to 2099 dairy farms to investigate the occurrence of poor milkability. Based on that, the frequency of poor milkability in Swiss dairy cows was 4% and the percentage of cows treated with oxytocin (OT) was 2%. In addition, 270 dairy farms that had reported cases of animals with poor milkability were contacted for an interview to classify the disorders. Farmers suspected disturbed milk ejection in 52%, anatomical dysfunction of the teat and/or the udder in 16% and milk ejection disorder or impaired milkability caused by discernable environmental factors in 32% of the cases. Forty-eight animals from 18 farms with suspected milk ejection disorders were selected for an experimental field study which included milk flow recording and OT administration to induce milk ejection. After cessation of the spontaneous milk flow, a low dose of OT (0.2, 0.5 or 1 i.u.) was injected i.v. to test the responsiveness of the udder to OT at a physiological level. When milk flow ceased again, 10 i.u. OT was injected i.v. (supraphysiological) to ensure complete udder emptying and to determine the residual milk. Milk ejection disorder could be confirmed in 69% of the cases, i.e. if residual milk was >20% of the total milk. Because in 27% of the animals milk ejection disorder was not confirmed on the basis of elevated residual milk, an anatomical disorder of the teat and/or the udder was suspected. Milk ejection disorder could be confirmed in 69% of the cases whereas in 27% of the suspected cases an anatomical disorder of the teat and/or the udder was suspected. An increased cortisol production in cows with milk ejection disorder was not obvious because faecal concentrations of cortisol metabolites with a 5 beta-androstane-3 alpha,11 oxo-structure were not augmented in animals with disturbed milk ejection.

Multicenter study with a direct acoustic cochlear implant

OBJECTIVE To confirm the clinical efficacy and safety of a direct acoustic cochlear implant. STUDY DESIGN Prospective multicenter study. SETTING The study was performed at 3 university hospitals in Europe (Germany, The Netherlands, and Switzerland). PATIENTS Fifteen patients with severe-to-profound mixed hearing loss because of otosclerosis or previous failed stapes surgery. INTERVENTION Implantation with a Codacs direct acoustic cochlear implant investigational device (ID) combined with a stapedotomy with a conventional stapes prosthesis MAIN OUTCOME MEASURES Preoperative and postoperative (3 months after activation of the investigational direct acoustic cochlear implant) audiometric evaluation measuring conventional pure tone and speech audiometry, tympanometry, aided thresholds in sound field and hearing difficulty by the Abbreviated Profile of Hearing Aid Benefit questionnaire. RESULTS The preoperative and postoperative air and bone conduction thresholds did not change significantly by the implantation with the investigational Direct Acoustic Cochlear Implant. The mean sound field thresholds (0.25-8 kHz) improved significantly by 48 dB. The word recognition scores (WRS) at 50, 65, and 80 dB SPL improved significantly by 30.4%, 75%, and 78.2%, respectively, after implantation with the investigational direct acoustic cochlear implant compared with the preoperative unaided condition. The difficulty in hearing, measured by the Abbreviated Profile of Hearing Aid Benefit, decreased by 27% after implantation with the investigational direct acoustic cochlear implant. CONCLUSION Patients with moderate-to-severe mixed hearing loss because of otosclerosis can benefit substantially using the Codacs investigational device.

Influence of Loudness Compression on Hearing with Bone Anchored Hearing Implants

Bone Anchored Hearing Implants (BAHI) are routinely used in patients with conductive or mixed hearing loss, e.g. if conventional air conduction hearing aids cannot be used. New sound processors and new fitting software now allow the adjustment of parameters such as loudness compression ratios or maximum power output separately. Today it is unclear, how the choice of these parameters influences aided speech understanding in BAHI users. In this prospective experimental study, the effect of varying the compression ratio and lowering the maximum power output in a BAHI were investigated. Twelve experienced adult subjects with a mixed hearing loss participated in this study. Four different compression ratios (1.0; 1.3; 1.6; 2.0) were tested along with two different maximum power output settings, resulting in a total of eight different programs. Each participant tested each program during two weeks. A blinded Latin square design was used to minimize bias. For each of the eight programs, speech understanding in quiet and in noise was assessed. For speech in quiet, the Freiburg number test and the Freiburg monosyllabic word test at 50, 65, and 80 dB SPL were used. For speech in noise, the Oldenburg sentence test was administered. Speech understanding in quiet and in noise was improved significantly in the aided condition in any program, when compared to the unaided condition. However, no significant differences were found between any of the eight programs. In contrast, on a subjective level there was a significant preference for medium compression ratios of 1.3 to 1.6 and higher maximum power output.

Folk Music in the Baltics at the Age of Digital Globalization

Shaped by factors like global outreach and immediacy, particularly the internet represents the multi-layered nature of contemporary globalization (cf Held et al. 2002). How have digital newspapers, social media and other internet platforms altered the situation of smaller music microcultues, especially in regions that have been on the fringes of global networks? This paper analyses the situation of the Latvian postfolklore band Ilgi between 2001 and 2008. Focusing on the group’s label UPE, the paper highlights how the internet became a significant means of existence during this specific period. Having established a local niche with a sound studio and CD shops, UPE combined this physical basis with outreach strategies, such as marketing and direct internet sales, which guaranteed the survival of the independent label. This strategy was also taken up by the band itself who started to develop a strong presence on social media like MySpace. At the same time, Ilgi has been using the internet as a central means of communicating with diasporic communities in the U.S. and Canada – hereby creating structures that were described as « intercultures » by Slobin (1993). This indicates that the local-global dichotomy can no longer be sufficiently addressed by a horizontal or vertical two-dimensional perception. Falling also back on the fieldwork experiences gained in Latvia, the paper finally addresses the question of how internet representation relates to the actual local situation – and how this has been altering the fieldwork perception. With regard to this situation – how useful are the approaches that have been developed within the context of « Media Anthropology » that investigates mass media items as multi-layered, densified symbolic objects?

Malnutrition in the era of DRG

Malnutrition in hospital patients is of important medical and economic significance. The adverse consequences of malnutrition on quality of life and many more factors such as morbidity, mortality, tolerance of treatments and length of hospital stay are well documented in the medical literature. Nevertheless, the effects of malnutrition are still often underestimated and hence malnutrition is not recognised as a distinct diagnosis. Moreover, malnutrition is rarely documented in medical reports and often not adequately treated with adverse effects. The reason for this neglectfulness are diverse, e. g. inadequate training of doctors and nurses in clinical nutrition and lack of sensibilisation of the hospital staff for the problem of malnutrition. Therefore, a systematic screening for malnutrition is rarely undertaken in Swiss hospitals. The introduction of the Swiss-DRG system (DRG, diagnosis related groups) in January 2012 gave the chance to boost recording and to document malnutrition in a standardised way in the patient history, and to code precisely malnutrition as a distinct diagnosis. Moreover, this approach allowed to document the specific nutritional therapy. Here, we describe the way of documenting and coding malnutrition in the Swiss-DRG system and the medical and economic consequences of this procedure.

Long-term man–environment interactions in the Bolivian Amazon: 8000 years of vegetation dynamics

Only few studies documenting the vegetation history of the Llanos de Moxos, one of the largest seasonally flooded wetland areas in South America, are available and little is known about the environmental impact of pre-Columbian settlements. We use radiocarbon-dated terrestrial plant macrofossils to establish a sound chronology and palynological analyses to reconstruct the vegetation and fire history of the Lago Rogaguado area. The sedimentary pollen and spore record suggests that wetland and wooded savannah (Cerrado) environments occurred around the lake between 8100 and 5800 cal BP. Fire activity was high during this period and was probably connected to the dry Cerrado environments. The pollen evidence suggests early plant cultivation (Zea mays, Annonaceae and Cucurbitaceae) from 6500 cal BP onwards, which is significantly earlier than hitherto assumed for Amazonia. Gallery forests expanded after 5800 cal BP, when fire activity strongly declined. Forest expansion intensified around 2800 cal BP and continued until 2000 cal BP, when forest cover reached its maximum and fire activity its minimum. The late-Holocene forest expansion to the south and the decrease of fire activity may have resulted from a climatic shift to moister conditions (possibly a shorter dry season). New crops (e.g. Avena-type) or adventive plants (e.g. Rumex acetosella-type) document the impact of European economies after ca. 500 cal BP. Land use intensity remained rather stable over the most recent centuries, arguing against a collapse of settlements in response to the arrival of Europeans, as reconstructed from other Amazonian pollen records.

Fine control of drug delivery for cochlear implant applications

Cochlear implants are neuroprostheses that are inserted into the inner ear to directly electrically stimulate the auditory nerve, thus replacing lost cochlear receptors, the hair cells. The reduction of the gap between electrodes and nerve cells will contribute to technological solutions simultaneously increasing the frequency resolution, the sound quality and the amplification of the signal. Recent findings indicate that neurotrophins (NTs) such as brain derived neurotrophic factor (BDNF) stimulate the neurite outgrowth of auditory nerve cells by activating Trk receptors on the cellular surface (1–3). Furthermore, small-size TrkB receptor agonists such as di-hydroxyflavone (DHF) are now available, which activate the TrkB receptor with similar efficiency as BDNF, but are much more stable (4). Experimentally, such molecules are currently used to attract nerve cells towards, for example, the electrodes of cochlear implants. This paper analyses the scenarios of low dose aspects of controlled release of small-size Trk receptor agonists from the coated CI electrode array into the inner ear. The control must first ensure a sufficient dose for the onset of neurite growth. Secondly, a gradient in concentration needs to be maintained to allow directive growth of neurites through the perilymph-filled gap towards the electrodes of the implant. We used fluorescein as a test molecule for its molecular size similarity to DHF and investigated two different transport mechanisms of drug dispensing, which both have the potential to fulfil controlled low-throughput drug-deliverable requirements. The first is based on the release of aqueous fluorescein into water through well-defined 60-μm size holes arrays in a membrane by pure osmosis. The release was both simulated using the software COMSOL and observed experimentally. In the second approach, solid fluorescein crystals were encapsulated in a thin layer of parylene (PPX), hence creating random nanometer-sized pinholes. In this approach, the release occurred due to subsequent water diffusion through the pinholes, dissolution of the fluorescein and then release by out-diffusion. Surprisingly, the release rate of solid fluorescein through the nanoscopic scale holes was found to be in the same order of magnitude as for liquid fluorescein release through microscopic holes.

Influence of contact points on the performance of caries detection methods in approximal surfaces of primary molars: an in vivo study

This in vivo study aimed to evaluate the influence of contact points on the approximal caries detection in primary molars, by comparing the performance of the DIAGNOdent pen and visual-tactile examination after tooth separation to bitewing radiography (BW). A total of 112 children were examined and 33 children were selected. In three periods (a, b, and c), 209 approximal surfaces were examined: (a) examiner 1 performed visual-tactile examination using the Nyvad criteria (EX1); examiner 2 used DIAGNOdent pen (LF1) and took BW; (b) 1 week later, after tooth separation, examiner 1 performed the second visual-tactile examination (EX2) and examiner 2 used DIAGNOdent again (LF2); (c) after tooth exfoliation, surfaces were directly examined using DIAGNOdent (LF3). Teeth were examined by computed microtomography as a reference standard. Analyses were based on diagnostic thresholds: D1: D 0 = health, D 1 –D 4 = disease; D2: D 0 , D 1 = health, D 2 –D 4 = disease; D3: D 0 –D 2 = health, D 3 , D 4 = disease. At D1, the highest sensitivity/specificity were observed for EX1 (1.00)/LF3 (0.68), respectively. At D2, the highest sensitivity/ specificity were observed for LF3 (0.69)/BW (1.00), respectively. At D3, the highest sensitivity/specificity were observed for LF3 (0.78)/EX1, EX2 and BW (1.00). EX1 showed higher accuracy values than LF1, and EX2 showed similar values to LF2. We concluded that the visual-tactile examination showed better results in detecting sound surfaces and approximal caries lesions without tooth separation. However, the effectiveness of approximal caries lesion detection of both methods was increased by the absence of contact points. Therefore, regardless of the method of detection, orthodontic separating elastics should be used as a complementary tool for the diagnosis of approximal noncavitated lesions in primary molars.