Several in vivo and in vitro studies with different loading regimens showed that mechanical stimuli have an influence on proliferation and differentiation of bone cells. Prerequisite for this ...influence is the transduction of mechanical signals into the cell, a phenomenon that is termed mechanotransduction, which is essential for the maintenance of skeletal homeostasis in adults. Mechanoreceptors, such as the integrins, cadherins, and stretch-activated Ca
2+ channels, together with various signal transduction pathways, are involved in the mechanotransduction process that ultimately regulates gene expression in the nucleus. Mechanotransduction itself is considered to be regulated by hormones, the extracellular matrix of the osteoblastic cells and the mode of the mechanical stimulus.
An interdisciplinary study based on animal experiments, cell culture studies, and finite element models is presented. In a sheep model, the influence of the osteotomy gap size and interfragmentary ...motion on the healing success was investigated. Increasing gap sizes delayed the healing process. Increasing movement stimulated callus formation but not tissue quality. Typical distributions of intramembranous bone, endochondral ossification, and connective tissue in the fracture gap are quantified. The comparison of the mechanical data determined by a finite element model with the histologic images allowed the attribution of certain mechanical conditions to the type of tissue differentiation. Intramembranous bone formation was found for strains smaller than approximately 5% and small hydrostatic pressure (< 0.15 MPa). Strains less than 15% and hydrostatic pressure more than 0.15 MPa stimulated endochondral ossification. Larger strains led to connective tissue. Cell culture studies on the influence of strain on osteoblasts supported these findings. Proliferation and transforming growth factor beta production was increased for strains up to 5% but decreased for larger strains. Osteoblasts under larger strains (> 4%) turned away from the principal strain axis and avoided larger deformations. It is hypothesized that gap size and the amount of strain and hydrostatic pressure along the calcified surface in the fracture gap are the fundamental mechanical factors involved in bone healing.
Nutritional constraints including not only caloric restriction or protein deficiency, but also energy-dense diets affect metabolic health and frequently lead to obesity and insulin resistance, as ...well as glucose intolerance and type 2 diabetes. The effects of these environmental factors are often mediated via epigenetic modifiers that target the expression of metabolic genes. More recently, it was discovered that such parentally acquired metabolic changes can alter the metabolic health of the filial and grand-filial generations. In mammals, this epigenetic inheritance can either follow an intergenerational or transgenerational mode of inheritance. In the case of intergenerational inheritance, epimutations established in gametes persist through the first round of epigenetic reprogramming occurring during preimplantation development. For transgenerational inheritance, epimutations persist additionally throughout the reprogramming that occurs during germ cell development later in embryogenesis. Differentially expressed transcripts, genomic cytosine methylations, and several chemical modifications of histones are prime candidates for tangible marks which may serve as epimutations in inter- and transgenerational inheritance and which are currently being investigated experimentally. We review, here, the current literature in support of epigenetic inheritance of metabolic traits caused by nutritional constraints and potential mechanisms in man and in rodent model systems.
Impaired cutaneous wound healing is a major complication in elderly people and patients suffering from diabetes, the rate of which is rising in industrialized countries. Heterogeneity of clinical ...manifestations hampers effective molecular diagnostics and decisions for appropriate therapeutic regimens. Using a customized positional quantitative proteomics workflow, we have established a time-resolved proteome and N-terminome resource from wound exudates in a clinically relevant pig wound model that we exploited as a robust template to interpret a heterogeneous dataset from patients undergoing the same wound treatment. With zyxin, IQGA1, and HtrA1, this analysis and validation by targeted proteomics identified differential abundances and proteolytic processing of proteins of epidermal and dermal origin as prospective biomarker candidates for assessment of critical turning points in wound progression. Thus, we show the possibility of using a fine-tuned animal wound model to bridge the translational gap as a prerequisite for future extended clinical studies with large cohorts of individuals affected by healing impairments. Data are available via ProteomeXchange with identifier PXD006674.
To determine the cost-effectiveness/utility of a superabsorbent wound dressing (Zetuvit Plus Silicone) versus the current standard of care (SoC) dressings, from the NHS perspective in England, in ...patients with moderate-to-high exudating leg ulcers.
A model-based economic evaluation was conducted to analyse the cost-effectiveness/utility of a new intervention. We used a microsimulation state-transition model with a time horizon of six months and a cycle length of one week. The model uses a combination of incidence base and risk prediction approach to inform transition probabilities. All clinical efficiency, health-related quality of life (HRQoL), cost and resource use inputs were informed by conducting a systematic review of UK specific literature.
Treatment with the superabsorbent dressing leads to a total expected cost per patient for a six month period of £2887, associated with 15.933 expected quality adjusted life weeks and 10.9% healing rate. When treated with SoC, the total expected cost per patient for a six month period is £3109, 15.852 expected quality adjusted life weeks and 8% healing rate. Therefore, the superabsorbent dressing leads to an increase in quality-adjusted life weeks, an increase in healing rate by 2.9% and a cost-saving of £222 per single average patient over six months. Results of several scenario analyses, one-way deterministic sensitivity analysis, and probabilistic sensitivity analysis confirmed the robustness of base-case results. The probabilistic analysis confirmed that, in any combination of variable values, the superabsorbent dressing leads to cost saving results.
According to the model prediction, the superabsorbent dressing leads to an increase in health benefits and a decrease in associated costs of treatment.
Protein allostery plays a pivotal role in many regulatory processes. Prominent examples are cell-surface receptors, which allosterically transmit ligand-generated signals to their cytoplasmic ...domains, or bacterial transcription factors, which alternate between a free conformation and a DNA-bound conformation in response to binding an effector molecule. The bacterial transcription factor Tet repressor (TetR) belongs to the latter category and is regarded as highly adapted to tetracyclines (tc's) as effectors. However, peptides isolated in this study were able to trigger distinct allosteric behavior including induction, anti-induction and corepression. Binding of the peptides' C-terminal residues consistently occurs within the tc-binding pocket of TetR. However, an extensive analysis of TetR mutants revealed that inducing and anti-inducing peptides utilize different parts of the binding pocket to elicit their respective regulatory responses. This study demonstrates that even for transcription factors evolved for high effector specificity, alternative molecular structures can exert similar and even novel effects, provided that sufficient chemical diversity and molecular flexibility, as found in peptide libraries, is accompanied by an efficient in vivo selection system. The high number of bioactive peptides and their extensive sequence diversity suggests that switching from small-molecule-controlled transcription regulation to a signal transduction network might be rather easily accomplished. These findings will strongly affect protein-mediated regulation of gene expression.
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► The bacterial transcription factor TetR is regarded as highly adapted to tc's. ► However, peptides were isolated capable of triggering diverse activities in TetR. ► Isolated molecules include inducing, anti-inducing and corepressing peptides ► Peptide activity correlates with distinct structural motifs. ► The study shows that even for highly effector adapted proteins, alternative allostery exists.
We tested the hypothesis whether the number of applied load cycles and the frequency of uniaxial strain have an effect on proliferation of human bone derived osteoblast-like cells. A new approach was ...developed in order to differentiate between the effects of frequency and the effects of cycle number and strain duration. Monolayers of subconfluently grown cells were stretched in rectangular silicone dishes with cyclic predominantly uniaxial movement along there longitudinal axes. Strain was applied over 2 days varying the number of applied load cycles (4–3600) at a constant frequency (1
Hz) or varying the frequency (0.1–30
Hz) at a constant number of applied cycles (1800) or at a constant strain duration (5
min). At a constant frequency, proliferative response increases (103%) with the number of applied cycles until a cycle number maximum (1800 cycles) was reached. 3600 cycles reduced cell number (43%) in contrast to the maximum. The variation of the frequency of applied strain tended to result in slight differences with regard to cell proliferation when cycle number was left constant. However, combined with an appropriate number of cycles there was an optimal frequency (1
Hz) as stimulus for bone cell proliferation (84%). A higher frequency (30
Hz) in combination with a high cycle number (9000) reduced cell number to control level (4%). This study demonstrates a frequency and cycle number dependent proliferative response of human osteoblast-like cells. It could be shown that effects of the frequency should not be considered separately from the effects of the cycle number.
Abstract
The ubiquitous pathogen Listeria monocytogenes lives either saprophytically in the environment or within cells in a vertebrate host, thus adapting its lifestyle to its ecological niche. ...Growth experiments at 24 and 37 °C (environmental and host temperature) with ammonium or glutamine as nitrogen sources revealed that ammonium is the preferred nitrogen source of L. monocytogenes. Reduced growth on glutamine is more obvious at 24 °C. Global transcriptional microarray analyses showed that the most striking difference in temperature-dependent transcription was observed for central nitrogen metabolism genes, glnR (glutamine synthetase repressor GlnR), glnA (glutamine synthetase GlnA), amtB (ammonium transporter AmtB), glnK (PII regulatory protein GlnK), and gdh (glutamate dehydrogenase) when cells were grown on glutamine. When grown on ammonium, both at 24 and 37 °C, the transcriptional level of these genes resembles that of cells grown with glutamine at 37 °C. Electrophoretic mobility shift assay studies and qPCR analyses in the wild-type L. monocytogenes and the deletion mutant L. monocytogenes ∆glnR revealed that the transcriptional regulator GlnR is directly involved in temperature- and nitrogen source-dependent regulation of the respective genes. Glutamine, a metabolite known to influence GlnR activity, seems unlikely to be the (sole) intracellular signal mediating this temperature-and nitrogen source-dependent metabolic adaptation.
In the present study, the impact of temperature on nitrogen metabolism in the pathogenic bacterium Listeria monocytogenes was investigated.
Zusammenfassung
Wir berichten über eine 56-jährige Frau mit bilateraler Abduzensparalyse nach einem schweren Motorradunfall. Die Patientin erhielt in den ersten 3 Monaten zweimal 10 Units ...Botulinumtoxin (Dysport
®
) in den M. rectus medialis an beiden Augen zur Kontraktionsvermeidung. Die Motilität zeigte sich nach der Injektion klinisch unverändert. Eine einzeitige Schieloperation nach Jensen an beiden Augen wurde 5 Monate nach dem Unfall durchgeführt. Die Rücklagerung des M. rectus medialis beidseits war bei passiv nahezu freier Motilität nicht erforderlich.
Postoperativ bestanden konsekutive Adduktionseinschränkungen mit Divergenzstellung, in erster Linie aufgrund des Botulinumtoxins, die sich innerhalb der darauffolgenden zwei Monate postoperativ deutlich besserte. Vier Monate später hatte die Patientin wieder Stereosehen, eine Kopfzwangshaltung musste nicht mehr eingenommen werden.
Schlussfolgerungen
Bilaterale posttraumatische Abduzensparalysen zeigen eine geringe Tendenz zur Spontanremission. Besonders bei Wunsch nach baldiger Rehabilitation stellt die einzeitige beidseitige Teiltransposition eine gute Therapieoption mit gleichzeitiger Gefäßschonung dar. Die präoperative Anwendung von Botulinumtoxin verhinderte eine Kontraktur des M. rectus medialis beidseits, wodurch sich die Anzahl der zu operierenden Muskeln reduzierte.
Protein kinase C (PKC), protein kinase A (PKA), prostaglandin synthesis, and various mitogen-activated protein kinases (MAPKs) have been reported to be activated in bone cells by mechanical loading. ...We studied the involvement of these signal transduction pathways in the downregulation of HB-GAM expression in osteoblastic cells after cyclic stretching. Specific antagonists and agonists of these signal transduction pathways were added to cells before loading and to non-loaded control cells. Quantitative RT-PCR was used to evaluate gene expression. The data demonstrated that the extracellular signal-regulated kinase (ERK) 1/2 pathway, PKC, PKA, p38, and c-Jun N-terminal kinase MAPK participated in the mechanical downregulation of HB-GAM expression, whereas prostaglandin synthesis did not seem to be involved.
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