Development of a new critical size defect model in the paranasal sinus and first approach for defect reconstruction-An in vivo maxillary bone defect study in sheep.

Fractures of the paranasal sinuses often require surgical intervention. Persisting bone defects lead to permanent visible deformities of the facial contours. Bone substitutes for reconstruction of defects with simultaneous induction of new bone formation are not commercially available for the paranasal sinus. New materials are urgently needed and have to be tested in their future area of application. For this purpose critical size defect models for the paranasal sinus have to be developed. A ≥2.4 cm large bilateral circular defect was created in the anterior wall of the maxillary sinus in six sheep via an extraoral approach. The defect was filled with two types of an osteoconductive titanium scaffold (empty scaffold vs. scaffold filled with a calcium phosphate bone cement paste) or covered with a titanium mesh either. Sheep were euthanized after four months. All animals performed well, no postoperative complications occured. Meshes and scaffolds were safely covered with soft tissue at the end of the study. The initial defect size of ≥2.4 cm only shrunk minimally during the investigation period confirming a critical size defect. No ingrowth of bone into any of the scaffolds was observed. The anterior wall of the maxillary sinus is a region with low complication rate for performing critical size defect experiments in sheep. We recommend this region for experiments with future scaffold materials whose intended use is not only limited to the paranasal sinus, as the defect is challenging even for bone graft substitutes with proven osteoconductivity. Graphical abstract.

Audiological profile of adult Long COVID patients.

INTRODUCTION: Hearing loss is one of the self-reported symptoms of Long COVID patients, however data from objective and subjective audiological tests demonstrating diminished hearing in Long COVID patients has not been published. MATERIALS AND METHODS: Respondents of a large Long COVID online survey were invited to the ENT-department for an otologic exam. The participants were split into three groups based on their history of SARS-CoV-2 infection and persistence of symptoms. Respondents with a history of a SARS-CoV-2 infection were allocated to the Long COVID group, if they reported persistent symptoms and to the Ex COVID group, if they had regained their previous level of health. Participants without a history of SARS-CoV-2 infection made up the No COVID control group. In total, 295 ears were examined with otoscopy, tympanograms, pure tone audiometry and otoacoustic emissions. Ears with known preexisting hearing loss or status post ear surgery, as well as those with abnormal otoscopic findings, non-type A tympanograms or negative Rinne test were excluded. RESULTS: Compared to the No COVID and Ex COVID groups, we did not find a clinically significant difference in either hearing thresholds or frequency specific TEOAEs. However, at 500 Hz the data from the left ear, but not the right ear showed a significantly better threshold in the Ex COVID group, compared to Long COVID and No COVID groups. Any of the other tested frequencies between 500 Hz and 8 kHz were not significantly different between the different groups. There was a significantly lower frequency-specific signal-to-noise-ratio of the TEOAEs in the Long COVID compared to the No COVID group at 2.8 kHz. At all other frequencies, there were no significant differences between the three groups in the TEOAE signal-to-noise-ratio. CONCLUSION: This study detected no evidence of persistent cochlear damage months after SARS-CoV-2 infection in a large cohort of Long COVID patients, as well as those fully recovered.

The benefits of co-location in primary care practices: the perspectives of general practitioners and patients in 34 countries.

BACKGROUND: There is no clear evidence as to whether the co-location of primary care professionals in the same facility positively influences their way of working and the quality of healthcare as perceived by patients. The aim of this study was to identify the relationships between general practitioner (GP) co-location with other GPs and/or other professionals and the GP outcomes and patients' experiences. METHODS: We wanted to test whether GP co-location is related to a broader range of services provided, the use of clinical governance tools and inter-professional collaboration, and whether the patients of co-located GPs perceive a better quality of care in terms of accessibility, comprehensiveness and continuity of care with their GPs. The source of data was the QUALICOPC study (Quality and Costs of Primary Care in Europe), which involved surveys of GPs and their patients in 34 countries, mostly in Europe. In order to study the relationships between GP co-location and both GPs' outcomes and patients' experience, multilevel linear regression analysis was carried out. RESULTS: The GP questionnaire was filled in by 7183 GPs and the patient experience questionnaire by 61,931 patients. Being co-located with at least one other professional is the most common situation of the GPs involved in the study. Compared with single-handed GP practices, GP co-location are positively associated with the GP outcomes. Considering the patients' perspective, comprehensiveness of care has the strongest negative relationship of GP co-location of all the dimensions of patient experiences analysed. CONCLUSIONS: The paper highlights that GP mono- and multi-disciplinary co-location is related to positive outcomes at a GP level, such as a broader provision of technical procedures, increased collaboration among different providers and wider coordination with secondary care. However, GP co-location, particularly in a multidisciplinary setting, is related to less positive patient experiences, especially in countries with health systems characterised by a weak primary care structure.

Cholinergic nerve fibers in bone defects of a rat osteoporosis model and their regulation by implantation of bone substitution materials.

OBJECTIVES: Bone is innervated by autonomic nervous system that consists of sympathetic and parasympathetic nerves that were recently identified in bone. Thus we asked whether parasympathetic nerves occur in bone defects and at the interface of substitution materials that were implanted for stabilization and improvement of healing in an osteoporosis animal model. METHODS: Osteoporosis was induced in rats by ovariectomy and deficiency diet. A wedge-shaped osteotomy was performed in the metaphyseal area of femur. Eight different implants were inserted that were based on calcium phosphate cement, iron, silica-mineralized collagen, and modifications with strontium. Nerves were identified by immunohistochemistry with antibodies against vesicular acetylcholine transporter (VAChT), tyrosine hydroxylase (TH) and protein gene product 9.5 (PGP 9.5) as neuronal marker. RESULTS: Cholinergic nerves identified with VAChT immunostaining were detected in defects filled with granulation tissue and in surrounding mast cells. No immunolabeling of cholinergic nerves was found after implantation. The general presence of nerves was reduced after implantation as shown by PGP 9.5. Sympathetic nerves identified by TH immunolabeling were increased in strontium functionalized materials. CONCLUSION: Since cholinergic innervation was diminished after implantation a further increase in the compatibility of substitution materials to nerves could improve defect healing especially in osteoporotic bone.

Cluster analysis of long COVID symptoms for deciphering a syndrome and its long-term consequence.

The long-term symptoms of COVID-19 are the subject of public and scientific discussions. Understanding how those long COVID symptoms co-occur in clusters of syndromes may indicate the pathogenic mechanisms of long COVID. Our study objective was to cluster the different long COVID symptoms. We included persons who had a COVID-19 and assessed long-term symptoms (at least 4 weeks after first symptoms). Hierarchical clustering was applied to the symptoms as well as to the participants based on the Euclidean distance h of the log-values of the answers on symptom severity. The distribution of clusters within our cohort is shown in a heat map.From September 2021 to November 2023, 2371 persons with persisting long COVID symptoms participated in the study. Self-assessed long COVID symptoms were assigned to three symptom clusters. Cluster A unites rheumatological and neurological symptoms, cluster B includes neuro-psychological symptoms together with cardiorespiratory symptoms, and a third cluster C shows an association of general infection signs, dermatological and otology symptoms. A high proportion of the participants (n = 1424) showed symptoms of all three clusters. Clustering of long COVID symptoms reveals similarities to the symptomatology of already described syndromes such as the Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) or rheumatological autoinflammatory diseases. Further research may identify serological parameters or clinical risk factors associated with the shown clusters and might improve our understanding of long COVID as a systemic disease. Furthermore, multimodal treatments can be developed and scaled for symptom clusters and associated impairments.

Altered activity-rest patterns in mice with a human autosomal-dominant nocturnal frontal lobe epilepsy mutation in the ß2 nicotinic receptor.

High-affinity nicotinic receptors containing ß2 subunits (ß2*) are widely expressed in the brain, modulating many neuronal processes and contributing to neuropathologies such as Alzheimer's disease, Parkinson's disease and epilepsy. Mutations in both the α4 and ß2 subunits are associated with a rare partial epilepsy, autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE). In this study, we introduced one such human missense mutation into the mouse genome to generate a knock-in strain carrying a valine-to-leucine mutation ß2V287L. ß2(V287L) mice were viable and born at an expected Mendelian ratio. Surprisingly, mice did not show an overt seizure phenotype; however, homozygous mice did show significant alterations in their activity-rest patterns. This was manifest as an increase in activity during the light cycle suggestive of disturbances in the normal sleep patterns of mice; a parallel phenotype to that found in human ADNFLE patients. Consistent with the role of nicotinic receptors in reward pathways, we found that ß2(V287L) mice did not develop a normal proclivity to voluntary wheel running, a model for natural reward. Anxiety-related behaviors were also affected by the V287L mutation. Mutant mice spent more time in the open arms on the elevated plus maze suggesting that they had reduced levels of anxiety. Together, these findings emphasize several important roles of ß2* nicotinic receptors in complex biological processes including the activity-rest cycle, natural reward and anxiety.

A flexible microrobotic platform for handling microscale specimens of fibrous materials for microscopic studies.

One of the most challenging issues faced in handling specimens for microscopy, is avoiding artefacts and structural changes in the samples caused by human errors. In addition, specimen handling is a laborious and time-consuming task and requires skilful and experienced personnel. This paper introduces a flexible microrobotic platform for the handling of microscale specimens of fibrous materials for various microscopic studies such as scanning electron microscopy and nanotomography. The platform is capable of handling various fibres with diameters ranging from 10 to 1000 µm and lengths of 100 µm-15 mm, and mounting them on different types of specimen holders without damaging them. This tele-operated microrobotic platform minimizes human interaction with the samples, which is one of the main sources contributory to introducing artefacts into the specimens. The platform also grants a higher throughput and an improved success rate of specimen handling, when compared to the manual processes. The operator does not need extensive experience of microscale manipulation and only a short training period is sufficient to operate the platform. The requirement of easy configurability for various samples and sample holders is typical in the research and development of materials in this field. Therefore, one of the main criteria for the design of the microrobotic platform was the ability to adapt the platform to different specimen handling methods required for microscopic studies. To demonstrate this, three experiments are carried out using the microrobotic platform. In the first experiment, individual paper fibres are mounted successfully on scanning electron microscopy specimen holders for the in situ scanning electron microscopy diagonal compression test of paper fibres. The performance of the microrobotic platform is compared with a skilled laboratory worker performing the same experiment. In the second experiment, a strand of human hair and an individual paper fibre bond are mounted on a specimen holder for nanotomography studies. In the third experiment, individual paper fibre bonds with controlled crossing and vertical angles are made using the microrobotic platform. If an industrial application requires less flexibility but a higher speed when handling one type of sample to a specific holder, then the platform can be automated in the future.

COVID-19 vaccination strategy for hospital staff in Germany: a cross-sectional study in March-April 2021.

BACKGROUND: SARS-CoV-2 vaccination for healthcare workers (HCWs) started in Germany in December 2020. Hospitals had little time to prepare a vaccination strategy. AIM: To gather information on the initial vaccination strategy for HCWs from the infection control practitioners in Germany. METHODS: A cross-sectional, ethically approved questionnaire was developed, formatted as an online survey and pre-tested. Infection control practitioners responsible for hygiene/infection prevention in 987 randomly selected German hospitals were invited to participate in the survey in March and April 2021. For statistical analysis, the hospitals were categorized into two groups based on bed capacity (<500 beds: small; ≥500 beds: large). FINDINGS: One hundred out of 987 (10%) infection control practitioners completed the survey. In 80% of the participating hospitals, HCW vaccination prioritization was based on recommendations of the German standing committee on vaccination (STIKO). Even so, only 54% prioritized the vaccination of HCWs with contact to vulnerable patients, thus deviating from STIKO recommendations. HCWs with a high personal health risk were prioritized for vaccination in 24% of the hospitals. Transferring unvaccinated HCWs to an area with less infection risk was considered by 2% of large and 12% of small hospitals. CONCLUSION: Vaccination prioritization differed across hospitals and deviated from STIKO recommendations. A pandemic preparedness concept should address the potential impact of divergent strategies compared to a common approach. In addition, further studies analysing the reasons why HCWs remain unvaccinated are needed to adopt effective strategies. This is especially important against the background of facility-based compulsory vaccination.

Infection control strategies for patients and accompanying persons during the COVID-19 pandemic in German hospitals: a cross-sectional study in March-April 2021.

BACKGROUND: Patients are at risk of nosocomial COVID-19 infection. The role of accompanying persons/visitors as potential infection donors is not yet well researched, but the risk will be influenced by prevention measures recommended by infection control practitioners. AIM: To collect information about COVID-19 infection control strategies for patients and accompanying persons from infection control practitioners in German hospitals. METHODS: A cross-sectional questionnaire was developed, ethically approved, pre-tested and formatted as an online tool. Infection control practitioners in 987 randomly selected German hospitals were invited to participate in March and April 2021. For statistical analysis, the hospitals were categorized as small (0-499 beds) or large (≥500 beds). FINDINGS: One hundred surveys were completed (response rate: 10%). A higher proportion of large (71%) than small (49%) hospitals let patients decide freely whether to wear medical or FFP2 masks. Most hospitals reported spatial separation for COVID-19 patients and non-COVID-19 cases (38%) or additionally for suspected COVID-19 cases (53%). A separation of healthcare teams for these areas existed in 54% of the hospitals. Accompaniment bans were more prevalent in large (52%) than in small hospitals (29%), but large hospitals granted more exemptions. CONCLUSION: The decision as to whether to separate areas and teams seemed to depend on the hospital's structural conditions, therefore impairing the implementation of recommendations. Accompaniment regulations differ between hospital sizes and may depend on patient numbers, case type/severity and patients' requirements. In the dynamic situation of a pandemic, it can be difficult to stay up to date with findings and recommendations on infection control.

Diffractive optical elements utilized for efficiency enhancement of photovoltaic modules.

Common solar cells used in photovoltaic modules feature metallic contacts which partially block the sunlight from reaching the semiconductor layer and reduce the overall efficiency of the modules. Diffractive optical elements were generated in the bulk glass of a photovoltaic module by ultrafast laser irradiation to direct light away from the contacts. Calculations of the planar electromagnetic wave diffraction and propagation were performed using the rigorous coupled wave analysis technique providing quantitative estimations for the potential efficiency enhancement of photovoltaic modules.

Determinants of the calcium permeation of ligand-gated cation channels.

Fast synaptic transmission in the vertebrate brain is mediated by ligand-gated channel receptors. As some of these receptors have been implicated in learning and memory, it is important to understand their mechanism of action at a molecular level. Excitatory receptors are members of large gene families of related channels that are gated by acetylcholine, serotonin, and the most abundant neurotransmitter, glutamate. Within the last year, a number of important studies have focused on the ability of these channels to flux calcium ions. Calcium entry into neurons through some of these channels triggers biochemical cascades, which can lead to changes in synaptic efficacy, presumed to be a requisite for memory formation, or if it occurs in excess, to cell death. Recent studies that attempt to determine the channel structures responsible for this calcium conductance will be discussed.

Development of an osteoblast/osteoclast co-culture derived by human bone marrow stromal cells and human monocytes for biomaterials testing.

The communication of bone-forming osteoblasts and bone-resorbing osteoclasts is a fundamental requirement for balanced bone remodelling. For biomaterial research, development of in vitro models is necessary to investigate this communication. In the present study human bone marrow stromal cells and human monocytes were cultivated in order to differentiate into osteoblasts and osteoclasts, respectively. Finally, a cultivation regime was identified which firstly induces the differentiation of the human bone marrow stromal cells followed by the induction of osteoclastogenesis through the osteoblasts formed--without the external addition of the factors RANKL and M-CSF. As a feedback on osteoblasts enhanced gene expression of BSP II was detected for modifications which facilitated the formation of large multinuclear osteoclasts. Phenotype characterization was performed by biochemical methods (DNA, LDH, ALP, TRAP 5b), gene expression analysis (ALP, BSP II, RANKL, IL-6, VTNR, CTSK, TRAP, OSCAR, CALCR) as well as light microscopy, confocal laser scanning microscopy, and scanning electron microscopy. After establishing this model on polystyrene, similar positive results were obtained for cultivation on a relevant bone substitution material--a composite xerogel of silica, collagen, and calcium phosphate.

[Resorbable bone substitution materials: An overview of commercially available materials and new approaches in the field of composites]. / Resorbierbare Knochenersatzmaterialien: Eine Übersicht kommerziell verfügbarer Werkstoffe und neuer Forschungsansätze auf dem Gebiet der Komposite.

When acquired or inborn bony defects cannot heal by the natural regeneration process due to being above the critical size or to particular diseases, e.g. osteoporosis, it becomes necessary to use bone substitute materials. These are materials which replace the missing bone tissue in host tissue and stimulate the bone healing process by mechanical and structural support either alone or in combination with other substances. This supporting effect can be attended by natural as well as artificial bone substitute materials and in a variety of ways. The biological efficiency of a bone substitute material is often classified with respect to the terms osteogenic, osteoconductive and osteoinductive stimulation. In reality however there is an overlap of several effective principles. Due to the limited availability of autologous bone and the disadvantages for the patient associated with the removal, intensive research is being carried out into artificial alternatives. The present article aims to offer some orientation in this confusing field by a systematic description of the various bone substitute materials.

In vitro osteoclastogenesis on textile chitosan scaffold.

Textile chitosan fibre scaffolds were evaluated in terms of interaction with osteoclast-like cells, derived from human primary monocytes. Part of the scaffolds was further modified by coating with fibrillar collagen type I in order to make the surface biocompatible. Monocytes were cultured directly on the scaffolds in the presence of macrophage colony stimulating factor (M-CSF) and receptor activator of nuclear factor kappaB ligand (RANKL) for up to 18 days. Confocal laser scanning microscopy (CLSM) as well as scanning electron microscopy (SEM) revealed the formation of multinuclear osteoclast-like cells on both the raw chitosan fibres and the collagen-coated scaffolds. The modified surface supported the osteoclastogenesis. Differentiation towards the osteoclastic lineage was confirmed by the microscopic detection of cathepsin K, tartrate resistant acid phosphatase (TRAP), acidic compartments using 3-(2,4-dinitroanillino)-3'-amino-N-methyldipropylamine (DAMP), immunological detection of TRAP isoform 5b, and analysis of gene expression of the osteoclastic markers TRAP, cathepsin K, vitronectin receptor, and calcitonin receptor using reverse transcription-polymerase chain reaction (RT-PCR). The feature of the collagen-coated but also of the raw chitosan fibre scaffolds to support attachment and differentiation of human monocytes facilitates cell-induced material resorption--one main requirement for successful bone tissue engineering.

Characterization of a unique muscle cell line.

A clonal cell line derived from a mouse neoplasm is described which shares many properties with smooth muscle. The cells have electrically excitable membranes capable of generating overshooting action potentials, and they contract both spontaneously and with electrical stimulation. They respond to the iontophoretic application of acetylcholine with a depolarizing response, and to norepinephrine with a hyperpolarizing response. Electron microscopy reveals that the cells have a morphology similar in many, but not all, respects to that of smooth muscle cells in vivo. The cells secrete soluble collagen-like molecules in addition to several proteins of undefined function. Finally, there is an increase in the specific activities of creatine phosphokinase and myokinase associated with increased cell density and the cessation of cell division.

Control of proton sensitivity of the NMDA receptor by RNA splicing and polyamines.

The function of the N-methyl-D-aspartate (NMDA)-preferring glutamate receptor can be regulated by extracellular pH, a process that may be important during ischemia in the brain or during seizures. Protons inhibit NMDA receptor function by 50 percent at pH 7.3 through interactions with the NR1 subunit, and both polyamines and NR1 exon 5 potentiate receptor function through relief of the tonic proton inhibition present at physiological pH. A single amino acid (lysine 211) was identified that mediates the effects of exon 5 in the rat brain. Electroneutral substitutions at this position restored pH sensitivity and, consequently, polyamine relief of tonic inhibition. This effect, together with the structural similarities between polyamines and the surface loop encoded by exon 5, suggest that exon 5 may act as a tethered pH-sensitive constitutive modulator of NMDA receptor function.

Ca2+ permeability of KA-AMPA--gated glutamate receptor channels depends on subunit composition.

NMDA (N-methyl-D-aspartate) receptors and non-NMDA receptors represent the two major classes of ion channel-linked glutamate receptors. Unlike the NMDA receptor channels, non-NMDA receptor channels have usually been thought to conduct monovalent cations only. Non-NMDA receptor ion channels that can be gated by kainic acid (KA) and alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) are formed by the glutamate receptor subunits GluR1, GluR2, and GluR3. These subunits were expressed in various combinations in Xenopus oocytes so that their permeability to divalent cations could be studied. At physiological resting potentials, KA and AMPA elicited inward calcium currents in oocytes expressing GluR1, GluR3, and GluR1 plus GluR3. In contrast, oocytes expressing GluR1 plus GluR2 or GluR3 plus GluR2 showed no such permeability. Thus, in neurons expressing certain KA-AMPA receptor subunits, glutamate may trigger calcium-dependent intracellular events by activating non-NMDA receptors.

Identification of a site in glutamate receptor subunits that controls calcium permeability.

The neurotransmitter glutamate mediates excitatory synaptic transmission throughout the brain. A family of genes encoding subunits of the non-N-methyl-D-aspartate (non-NMDA) type of glutamate receptor has been cloned. Some combinations of these subunits assemble into receptors with a substantial permeability to calcium, whereas others do not. To investigate the structural features that control ion permeation through these ligand-gated channels, mutant receptor subunits with single-amino acid changes were constructed. Mutation of a certain amino acid that results in a net charge change (from glutamine to arginine or vice versa) alters both the current-voltage relation and the calcium permeability of non-NMDA receptors. A site has thus been identified that regulates the permeation properties of these glutamate receptors.

Transmembrane channels based on tartaric acid-gramicidin A hybrids.

The gramicidin A transmembrane channel is believed to consist of two head-to-head beta helices. Computer-generated models were used to formulate the structure of new single-chain channel molecules based on the gramicidin motif. The chemical synthesis of two tartaric acid-gramicidin A hybrids and single-channel analyses of their conducting properties are reported. These studies illustrate the rational design and synthesis of long-lived channels with tunable conductance properties and provide support for current molecular models of the natural (dimeric) gramicidin channel.

Functional expression of a new pharmacological subtype of brain nicotinic acetylcholine receptor.

A new type of agonist-binding subunit of rat neuronal nicotinic acetylcholine receptors (nAChRs) was identified. Rat genomic DNA and complementary DNA encoding this subunit (alpha 2) were cloned and analyzed. Complementary DNA expression studies in Xenopus oocytes revealed that the injection of messenger RNAs (mRNAs) for alpha 2 and beta 2 (a neuronal nAChR subunit) led to the generation of a functional nAChR. In contrast to the other known neuronal nAChRs, the receptor produced by the injection of alpha 2 and beta 2 mRNAs was resistant to the alpha-neurotoxin Bgt3.1. In situ hybridization histochemistry showed that alpha 2 mRNA was expressed in a small number of regions, in contrast to the wide distribution of the other known agonist-binding subunits (alpha 3 and alpha 4) mRNAs. These results demonstrate that the alpha 2 subunit differs from other known agonist-binding alpha-subunits of nAChRs in its distribution in the brain and in its pharmacology.