Static and moving minimum audible angle: Independent contributions of reverberation and position

Two measures of auditory spatial resolution, the minimum audible angle and the minimum audible movement angle, have been obtained in a simulated acoustic environment using Ambisonics sound field reproduction. Trajectories were designed to provide no reliable cues for the spatial discrimination task. Larger threshold angles were found in reverberant compared to anechoic conditions, for stimuli on the side compared to the front, and for moving compared to static stimuli. The effect of reverberation appeared to be independent of the position of the sound source (same relative threshold increase) and was independently present for static and moving sound sources.

Corrigendum: Effects of acute ischemic stroke on binaural perception

[This corrects the article DOI: 10.3389/fnins.2022.1022354.].

On the Effect of High Stimulation Rates on Temporal Loudness Integration in Cochlear Implant Users

Long stimuli have lower detection thresholds or are perceived louder than short stimuli with the same intensity, an effect known as temporal loudness integration (TLI). In electric hearing, TLI for pulse trains with a fixed rate but varying number of pulses, i.e. stimulus duration, has mainly been investigated at clinically used stimulation rates. To study the effect of an overall effective stimulation rate at 100% channel crosstalk, we investigated TLI with (a) a clinically used single-channel stimulation rate of 1,500 pps and (b) a high stimulation rate of 18,000 pps, both for an apical and a basal electrode. Thresholds (THR), a line of equal loudness (BAL), and maximum acceptable levels (MALs) were measured in 10 MED-EL cochlear implant users. Stimulus durations varied from a single pulse to 300 ms long pulse trains. At 18,000 pps, the dynamic range (DR) increased by 7.36 ± 3.16  dB for the 300 ms pulse train. Amplitudes at THR, BAL, and MAL decreased monotonically with increasing stimulus duration. The decline was fitted with high accuracy with a power law function (R 2 = 0.94 ± 0.06 ). Threshold slopes were - 1.05 ± 0.36 and - 1.66 ± 0.30  dB per doubling of duration for the low and high rate, respectively, and were shallower than for acoustic hearing. The electrode location did not affect the amplitudes or slopes of the TLI curves. THR, BAL, and MAL were always lower for the higher rate and the DR was larger at the higher rate at all measured durations.

Effects of acute ischemic stroke on binaural perception

Stroke-induced lesions at different locations in the brain can affect various aspects of binaural hearing, including spatial perception. Previous studies found impairments in binaural hearing, especially in patients with temporal lobe tumors or lesions, but also resulting from lesions all along the auditory pathway from brainstem nuclei up to the auditory cortex. Currently, structural magnetic resonance imaging (MRI) is used in the clinical treatment routine of stroke patients. In combination with structural imaging, an analysis of binaural hearing enables a better understanding of hearing-related signaling pathways and of clinical disorders of binaural processing after a stroke. However, little data are currently available on binaural hearing in stroke patients, particularly for the acute phase of stroke. Here, we sought to address this gap in an exploratory study of patients in the acute phase of ischemic stroke. We conducted psychoacoustic measurements using two tasks of binaural hearing: binaural tone-in-noise detection, and lateralization of stimuli with interaural time- or level differences. The location of the stroke lesion was established by previously acquired MRI data. An additional general assessment included three-frequency audiometry, cognitive assessments, and depression screening. Fifty-five patients participated in the experiments, on average 5 days after their stroke onset. Patients whose lesions were in different locations were tested, including lesions in brainstem areas, basal ganglia, thalamus, temporal lobe, and other cortical and subcortical areas. Lateralization impairments were found in most patients with lesions within the auditory pathway. Lesioned areas at brainstem levels led to distortions of lateralization in both hemifields, thalamus lesions were correlated with a shift of the whole auditory space, whereas some cortical lesions predominantly affected the lateralization of stimuli contralateral to the lesion and resulted in more variable responses. Lateralization performance was also found to be affected by lesions of the right, but not the left, basal ganglia, as well as by lesions in non-auditory cortical areas. In general, altered lateralization was common in the stroke group. In contrast, deficits in tone-in-noise detection were relatively scarce in our sample of lesion patients, although a significant number of patients with multiple lesion sites were not able to complete the task.

Minor gait impairment despite white matter damage in pure small vessel disease

OBJECTIVE

Gait impairment is common in patients with cerebral small vessel disease (SVD). However, gait studies in elderly SVD patients might be confounded by age-related comorbidities, such as polyneuropathy or sarcopenia. We therefore studied young patients with the genetically defined SVD CADASIL. Our aim was to examine the effects of pure SVD on single and dual task gait, and to investigate associations of gait performance with cognitive deficits and white matter alterations.

METHODS

We investigated single task walking and calculatory, semantic, or motoric dual task costs in 39 CADASIL patients (mean age 50 ± 8) using a computerized walkway. We obtained 3.0T MRI and neuropsychological data on processing speed, the main cognitive deficit in CADASIL. Spatiotemporal gait parameters were standardized based on data from 192 healthy controls. Associations between white matter integrity, assessed by diffusion tensor imaging, and gait were analyzed using both a global marker and voxel-wise analysis.

RESULTS

Compared to controls, CADASIL patients showed only mild single task gait impairment, and only in the rhythm domain. The semantic dual task additionally uncovered mild deficits in the pace domain. Processing speed was not associated with gait. White matter alterations were related to single task stride length but not to dual task performance.

INTERPRETATION

Despite severe disease burden, gait performance in patients with pure small vessel disease was relatively preserved in single and dual tasks. Results suggest that age-related pathologies other than small vessel disease might play a role for gait impairment in elderly SVD patients.

Right or Left Ventricular Pacing in Young Minipigs With Chronic Atrioventricular Block

Background—

Left ventricular (LV) dyssynchrony may occur as a result of right ventricular (RV) pacing and is a known risk factor for the development of heart failure. In children with complete atrioventricular block, pacing-induced dyssynchrony lasting for decades might be especially deleterious for LV function. To determine the hemodynamic and ultrastructural remodeling after either RV free wall or LV apical pacing, we used a chronic minipig model.

Methods and Results—

Fourteen piglets 8 weeks of age underwent atrioventricular node ablation and were paced from either the RV free wall or the LV apex at 120 bpm for 1 year (7 age-matched minipigs served as controls with spontaneous heart rates of 104±5 bpm). Echocardiographic examinations, pressure-volume loops, patch-clamp investigations, and examinations of connexin43, calcium-handling proteins, and histomorphology were carried out. RV free wall–paced minipigs exhibited significantly more LV dyssynchrony than LV apex–paced animals, which was accompanied by worsening of LV function (maximum LV mechanical delay/LV ejection fraction: RV free wall pacing, 154±36 ms/28±3%, LV apical pacing, 52±19 ms/45±2%, control 47±14 ms/62±1%; P =0.0001). At the cellular level, both pacemaker groups exhibited a significant reduction in L-type calcium and peak sodium current, shortening of action potential duration and amplitude, increased cell capacity, and alterations in the calcium-handling proteins that were similar for RV free wall– and LV apex–paced animals.

Conclusions—

The observed molecular remodeling seemed to be more dependent on heart rate than on dyssynchrony. LV apical pacing is associated with less dyssynchrony, a more physiological LV contraction pattern, and preserved LV function as opposed to RV free wall pacing.

Improving cardiac gap junction communication as a new antiarrhythmic mechanism: the action of antiarrhythmic peptides

Co-ordinated electrical activation of the heart is maintained by intercellular coupling of cardiomyocytes via gap junctional channels located in the intercalated disks. These channels consist of two hexameric hemichannels, docked to each other, provided by either of the adjacent cells. Thus, a complete gap junction channel is made from 12 protein subunits, the connexins. While 21 isoforms of connexins are presently known, cardiomyocytes typically are coupled by Cx43 (most abundant), Cx40 or Cx45. Some years ago, antiarrhythmic peptides were discovered and synthesised, which were shown to increase macroscopic gap junction conductance (electrical coupling) and enhance dye transfer (metabolic coupling). The lead substance of these peptides is AAP10 (H-Gly-Ala-Gly-Hyp-Pro-Tyr-CONH(2)), a peptide with a horseshoe-like spatial structure as became evident from two-dimensional nuclear magnetic resonance studies. A stable D: -amino-acid derivative of AAP10, rotigaptide, as well as a non-peptide analogue, gap-134, has been developed in recent years. Antiarrhythmic peptides act on Cx43 and Cx45 gap junctions but not on Cx40 channels. AAP10 has been shown to enhance intercellular communication in rat, rabbit and human cardiomyocytes. Antiarrhythmic peptides are effective against ventricular tachyarrhythmias, such as late ischaemic (type IB) ventricular fibrillation, CaCl(2) or aconitine-induced arrhythmia. Interestingly, the effect of antiarrhythmic peptides is higher in partially uncoupled cells and was shown to be related to maintained Cx43 phosphorylation, while arrhythmogenic conditions like ischaemia result in Cx43 dephosphorylation and intercellular decoupling. It is still a matter of debate whether these drugs also act against atrial fibrillation. The present review outlines the development of this group of peptides and derivatives, their mode of action and molecular mechanisms, and discusses their possible therapeutic potential.

Is locking nailing of humeral head fractures superior to locking plate fixation?

The optimal surgical treatment of displaced proximal humeral fractures is controversial. New implants providing angular stability have been introduced to maintain the intraoperative reduction. In a multi-institutional study, we prospectively enrolled and followed 152 patients with unilateral displaced and unstable proximal humeral fractures treated either with an antegrade angular and sliding stable proximal interlocking nail or an angular stable plate. Fractures were classified according to the Neer four-segment classification. Clinical, functional, and radiographic followups were performed 3, 6, and 12 months after surgery. Absolute and relative (to the contralateral shoulder) Constant-Murley scores were used to assess postoperative shoulder function. Using age, gender, and fracture type, we identified 76 pairs (152 patients) for a matched-pairs analysis. Relative Constant-Murley scores 12 months after treatment with an angular and sliding stable nail and after plate fixation were 81% and 77%, respectively. We observed no differences between the two groups. Stabilization of displaced proximal humeral fractures with either an angular stable intramedullary or an extramedullary implant seems suitable with both surgical treatment options.

LEVEL OF EVIDENCE

Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Human cardiac gap-junction coupling: effects of antiarrhythmic peptide AAP10

AIMS

Ventricular arrhythmia is one of the most important causes of death in industrialized countries and often accompanies myocardial infarction and heart failure. In recent years modification of gap-junctional coupling has been proposed as a new antiarrhythmic principle. We wanted to examine whether the gap junction modulator (antiarrhythmic peptide) AAP10 exerts effects on human cardiac gap junctions, whether the effect might be enhanced in uncoupled cells, whether it affects electrical and metabolic coupling, and which of the cardiac connexin isoforms (Cx40, Cx43, Cx45) may be affected.

METHODS AND RESULTS

We determined the influence of 50 nM AAP10 (H(2)N-Gly-Ala-Gly-4Hyp-Pro-Tyr-CONH(2)) on macroscopic gap junction conductance by dual whole-cell voltage clamping in human and rat cardiomyocytes. Cells were partially uncoupled by CO(2)-mediated acidosis (pH 6.3) or kept at 'normal' conditions (pH 7.4, T 36 degrees C). Furthermore, we investigated effects of AAP10 in HeLa cells stably transfected with connexin 40, 43, or 45 and on metabolic coupling determined by dye transfer (Lucifer yellow). AAP10 (50 nM)-enhanced gap-junctional intercellular coupling in human and rat cardiomyocytes, completely prevented CO(2)-acidosis-induced uncoupling and improved metabolic coupling. The coupling effect of AAP10 was significantly enhanced in previously uncoupled cells. Regarding the connexin isoforms, AAP10-enhanced electrical and metabolic coupling in HeLa cells expressing Cx43 or Cx45, but not in HeLa cells expressing Cx40.

CONCLUSION

We conclude that the antiarrhythmic peptide AAP10, which improves gap-junctional intercellular coupling and prevents uncoupling by acidification in human cardiomyocytes, might be useful for antiarrhythmic strategies regarding arrhythmias caused by uncoupling of Cx43 and Cx45, but not Cx40.

Enhanced photodynamic destruction of a transplantable fibrosarcoma using photochemical internalisation of gelonin

Photochemical internalisation (PCI) is a technique for releasing biologically active macromolecules from endocytic vesicles by light activation of a photosensitiser localised in the same vesicles of targeted cells. This study investigated the PCI of the toxin gelonin as a way of enhancing the effect of photodynamic therapy (PDT) on a human malignant fibrous histiocytoma transplanted into nude mice using the photosensitiser disulphonated aluminium phthalocyanine (AlPcS_2a). Pharmacokinetic studies after intraperitoneal administration showed that the serum level of AlPcS_2a fitted a biexponential model (half-lives of 1.8 and 26.7 h). The tumour concentration was roughly constant up to 48 h, although fluorescence microscopy showed that the drug location was initially mainly vascular, but became intracellular by 48 h. To compare PDT with PCI, 48 h after intraperitoneal injection of 10 mg kg⁻¹ AlPcS_2a, and 6 h after direct intratumour injection of 50 μg gelonin (PCI) or a similar volume of phosphate-buffered saline (PDT controls), tumour-bearing animals were exposed to red light (150 J cm⁻²). Complete response was observed for more than 100 days in 50% of the PCI tumours but only 10% of the PDT tumours (P<0.01). In tumours examined histologically 4 days after light delivery, the depth of necrosis was 3–4 mm after PDT, but 7 mm after PCI. The deeper effect after PCI demonstrates that the light fluence needed to kill tumour is less than with PDT. We conclude that PCI with gelonin can markedly enhance the effect of PDT on this type of tumour and may have a role clinically as an adjunct to surgery to control localised disease.

Porphyrin-related photosensitizers for cancer imaging and therapeutic applications

A photosensitizer is defined as a chemical entity, which upon absorption of light induces a chemical or physical alteration of another chemical entity. Some photosensitizers are utilized therapeutically such as in photodynamic therapy (PDT) and for diagnosis of cancer (fluorescence diagnosis, FD). PDT is approved for several cancer indications and FD has recently been approved for diagnosis of bladder cancer. The photosensitizers used are in most cases based on the porphyrin structure. These photosensitizers generally accumulate in cancer tissues to a higher extent than in the surrounding tissues and their fluorescing properties may be utilized for cancer detection. The photosensitizers may be chemically synthesized or induced endogenously by an intermediate in heme synthesis, 5-aminolevulinic acid (5-ALA) or 5-ALA esters. The therapeutic effect is based on the formation of reactive oxygen species (ROS) upon activation of the photosensitizer by light. Singlet oxygen is assumed to be the most important ROS for the therapeutic outcome. The fluorescing properties of the photosensitizers can be used to evaluate their intracellular localization and treatment effects. Some photosensitizers localize intracellularly in endocytic vesicles and upon light exposure induce a release of the contents of these vesicles, including externally added macromolecules, into the cytosol. This is the basis for a novel method for macromolecule activation, named photochemical internalization (PCI). PCI has been shown to potentiate the biological activity of a large variety of macromolecules and other molecules that do not readily penetrate the plasma membrane, including type I ribosome-inactivating proteins, immunotoxins, gene-encoding plasmids, adenovirus, peptide-nucleic acids and the chemotherapeutic drug bleomycin. The background and present status of PDT, FD and PCI are reviewed.

Photochemical Internalization Enhances the Cytotoxic Effect of the Protein Toxin Gelonin and Transgene Expression in Sarcoma Cells¶

Further advantages in the treatment of soft-tissue sarcomas will only be achieved by tailoring the adjuvant therapy after surgery. The photochemically directed release of macro-molecules from endosomes and lysosomes into the cytosol is a novel technology, named photochemical internalization (PCI), that has been evaluated for treatment of sarcoma cells in vitro. Two human synovial sarcoma cell lines (SW 982 and CME-1) were treated with the photosensitizer meso-tetraphenylporphine with two sulfonate groups on adjacent phenyl rings (TPPS2a) and a plasmid encoding enhanced green fluorescent protein (EGFP) complexed to poly-L-lysine to investigate the influence of PCI on gene transfer and with 5 micrograms/mL gelonin to investigate PCI of a Type-I ribosome-inactivating protein toxin. In addition, both cell lines were transduced with an Adenovirus serotype 5 encoding the Escherichia coli lacZ gene (AdHCMV-lacZ, expressing beta-galactosidase) and treated with TPPS2a and light to evaluate the effect of PCI on the transduction rate. Photochemically induced transfection with the reporter gene EGFP in CME-1 cells increased from 0% of cells at no light to 40% of the cells after 60 s of light exposure. In contrast, the SW 982 cells showed no enhanced expression of the gene. The fraction of virally transduced cells was about doubled in both cell lines by means of PCI, although the transduction was more efficient in the CME-1 cells. Both cell lines became up to four-fold more sensitive to light when combining photochemical treatment with gelonin incubation. Our experiments showed that PCI induced the endocytic escape of therapeutic substances in cells derived from human soft-tissue sarcomas.

Phosphorus removal with membrane filtration for surface water treatment

Surface waters are often burdened with inflows of low quality water, so that drinking-water production, swimming or ground water charging must be restricted. To ensure the long-term use of such surface water it is necessary to treat the influents or the water used for ground water charging. The current treatment process for phosphorus and turbidity removal is a process combination called floc filtration. By using this conventional method it is possible to reduce the dissolved ortho-phosphate and the turbidity (particulate phosphorus) as well as the amounts of algae and pathogenic organisms to very low concentrations. The high degree of reduction is only achieved by a relatively high dosage of chemicals. A comparison will be made between this process, which represents the state-of-the-art, and the combination of precipitation/coagulation with micro-/ultrafiltration in dead-end filtration mode.

Replacement arthroplasty for hallux rigidus. 21 patients with a 2-year follow-up

21 patients underwent replacement arthroplasty of the metatarsophalangeal joint of the great toe. The indication for surgery was hallux rigidus in 16 patients and failed resection arthroplasty in 5 patients. The minimum follow-up period was 24 months. Clinical review showed an increased range of passive dorsiflexion from 10 degrees to 50 degrees postoperatively. 17 patients reported less pain or no pain and activity levels that were increased or maintained. Functional complications such as lack of toe purchase (n=5) or metatarsalgia (n=4) were successfully treated with orthotics.

Effects of photodynamic therapy on glioma spheroids

The present study describes the sensitivity of glioma cells to a haematoporphyrin derivative (Photosan-3) under laser activation (argon-pumped dye laser). The effects of photodynamic therapy (PDT) on cell growth, directional migration and cell invasion were investigated on two human glioma cell lines (GaMg and U-251 Mg). The directional cell migration and spheroid growth was determined for both cell lines exposed to increasing laser energy output (15-35J/cm2) with concentrations of 5 and 7 micrograms/ml of Photosan-3. Both cell lines showed a dose-dependent migratory response to increasing laser irradiation, that was more prominent in the 7 micrograms/ml treatment group. This effect occurred during the first 4 days after drug exposure. Also, spheroids from both cell lines showed a drug and laser output energy dose-dependent inhibition of growth which became apparent after a lag period of 6 days. The lag period was characterized by a decreased growth rate as compared with the control group. During this period the outer cell layers of the spheroids fell apart. The remaining spheroid tissue was not able to migrate and to regrow when exposed to the highest laser energy outputs (30-35J/cm2, 5 and 7 micrograms/ml Photosan-3). These spheroids showed, however, the ability for invasion when confronted with normal brain cell aggregated in vivo. Light microscopic observations of co-cultures between tumour tissue and brain cell aggregates revealed a normal tumour morphology. This indicates that the remaining tumour cells were not dead and could be stimulated to invade the normal tissue when exposed to a normal brain microenvironment.

Fistulous withers in horses: 14 cases (1978-1987)

Over an 8-year period, 14 horses were admitted to the New York State College of Veterinary Medicine for evaluation of fistulous withers. Of the 14 horses, 11 were treated surgically and 3 were not treated. Surgical techniques involved radical excision of the affected soft tissue and spinous processes of affected vertebrae. Recurrence rate was 30%, and these horses required additional surgery to resolve the problem.