Hyperelastic parameter identification of human articular cartilage and substitute materials.

Numerical simulations are a valuable tool in the field of tissue engineering for cartilage repair and can help to understand which mechanical properties affect the behavior of chondrocytes and contribute to the success or failure of surrogate materials as implants. However, special attention needs to be paid when identifying corresponding material parameters in order to provide reliable numerical predictions of the material's response. In this study, we identify hyperelastic material parameters for numerical simulations in COMSOL Multiphysics® v. 5.6 for human articular cartilage and two surrogate materials, commercially available ChondroFillerliquid, and oxidized alginate-gelatin (ADA-GEL) hydrogels. We consider several hyperelastic isotropic material models and provide separate parameter sets for the unconditioned and the conditioned material response, respectively, based on previously generated experimental data including both compression and tension experiments. We compare a direct parameter identification approach assuming homogeneous deformation throughout the specimen and an inverse approach, where the experiments are simulated using a finite element model with realistic boundary conditions in COMSOL Multiphysics® v. 5.6. We demonstrate that it is important to consider both compression and tension data simultaneously and to use the inverse approach to obtain reliable parameters. The one-term Ogden model best represents the unconditioned response of cartilage, while the conditioned response of cartilage and ADA-GEL is equally well represented by the two-term Ogden and five-term Mooney-Rivlin models. The five-term Mooney-Rivlin model is also most suitable to model the unconditioned response of ADA-GEL. For ChondroFillerliquid, we suggest using the five-term Mooney-Rivlin or two-term Ogden model for the unconditioned and the two-term Ogden model for the conditioned material response. These results will help to choose appropriate material models and parameters for simulations of whole joints or to advance mechanical-stimulation assisted cartilage tissue engineering in the future.

Complex mechanical behavior of human articular cartilage and hydrogels for cartilage repair.

The mechanical behavior of cartilage tissue plays a crucial role in physiological mechanotransduction processes of chondrocytes and pathological changes like osteoarthritis. Therefore, intensive research activities focus on the identification of implant substitute materials that mechanically mimic the cartilage extracellular matrix. This, however, requires a thorough understanding of the complex mechanical behavior of both native cartilage and potential substitute materials to treat cartilage lesions. Here, we perform complex multi-modal mechanical analyses of human articular cartilage and two surrogate materials, commercially available ChondroFillerliquid, and oxidized alginate-gelatin (ADA-GEL) hydrogels. We show that all materials exhibit nonlinearity and compression-tension asymmetry. However, while hyaline cartilage yields higher stresses in tension than in compression, ChondroFillerliquid and ADA-GEL exhibit the opposite trend. These characteristics can be attributed to the materials' underlying microstructure: Both cartilage and ChondroFillerliquid contain fibrillar components, but the latter constitutes a bi-phasic structure, where the 60% nonfibrillar hydrogel proportion dominates the mechanical response. Of all materials, ChondroFillerliquid shows the most pronounced viscous effects. The present study provides important insights into the microstructure-property relationship of cartilage substitute materials, with vital implications for mechanically-driven material design in cartilage engineering. In addition, we provide a data set to create mechanical simulation models in the future.

Plasma gelsolin promotes re-epithelialization.

Woundhealing disorders characterized by impaired or delayed re-epithelialization are a serious medical problem that is painful and difficult to treat. Gelsolin (GSN), a known actin modulator, supports epithelial cell regeneration and apoptosis. The aim of this study was to estimate the potential of recombinant gelsolin (rhu-pGSN) for ocular surface regeneration to establish a novel therapy for delayed or complicated wound healing. We analyzed the influence of gelsolin on cell proliferation and wound healing in vitro, in vivo/ex vivo and by gene knockdown. Gelsolin is expressed in all tested tissues of the ocular system as shown by molecular analysis. The concentration of GSN is significantly increased in tear fluid samples of patients with dry eye disease. rhu-pGSN induces cell proliferation and faster wound healing in vitro as well as in vivo/ex vivo. TGF-ß dependent transcription of SMA is significantly decreased after GSN gene knockdown. Gelsolin is an inherent protein of the ocular system and is secreted into the tear fluid. Our results show a positive effect on corneal cell proliferation and wound healing. Furthermore, GSN regulates the synthesis of SMA in myofibroblasts, which establishes GSN as a key protein of TGF-ß dependent cell differentiation.

Efficacy of aflibercept (EYLEA®) on inhibition of human VEGF in vitro.

INTRODUCTION: Pathological formation of blood vessels plays a key role in the growth and metastasis of tumors and also in several serious ophthalmological diseases such as wet age-related macular degeneration (AMD) or diabetic retinopathy. In AMD treatment, aflibercept (tradename EYLEA®) is used to deactivate the underlying pathological neovascularisation. Aflibercept is a recombinant fusion protein which binds to vascular endothelial growth factor (VEGF) receptors, thereby inhibiting VEGF pathway activation. VEGF is one of the most important angiogenesis factors. OBJECTIVE: This analysis investigates lasting efficacy of aflibercept in vitro for later application as therapeutic agent against macular degeneration (AMD). MATERIAL AND METHODS: VEGF-ELISA assays were performed to investigate binding affinities at different aflibercept concentrations. The impact of VEGF on the proliferation of human umbilical vein endothelial cells (HUVEC) was investigated using proliferation assays. Moreover, time-dependent kinetic studies were performed to analyze different aflibercept storage durations with regard to its inhibitory capabilities on human VEGF. RESULTS AND CONCLUSION: Our results reveal that aflibercept significantly lowers the amount of unbound VEGF as well as the proliferation rate of HUVEC. Moreover, in contrast to specifications given by the manufacturer, aflibercept retains its full inhibitory effect up to at least 120h after transference from the original vial into the injection syringe.

Expression of recombinant surfactant protein SFTA3 in the human kidney cell line HEK 293T.

Pulmonary surfactant is broadly known to keep the lung dry, clean and open by lowering the surface tension of the fluid-film that lines the alveoli. The surfactant's protein component, the so called surfactant proteins (SPs), make up a multifunctional protein family. In addition to the four "classical" surfactant proteins (SP-A, SP-B, SP-C and SP-D), which possess immunologic as well as surfactant regulatory properties, two novel putative surfactant proteins (SFTA2 and SFTA3) have recently been described. Neither of them shows sequential nor structural similarity with the already known surfactant proteins. However, bioinformatic analyses as well as first molecular-biological studies reveal properties that have already been described for known surfactant proteins. In our present work we introduce a technique to synthesize, purify and stabilize recombinant SFTA3 derived from the human embryonic kidney cell line HEK 293T. This will provide investigators with a valuable source of further examination and characterization of this fascinating novel member of the surfactant protein family.

[Anatomy and physiology of the nasolacrimal ducts]. / Anatomie und Physiologie der ableitenden Tränenwege.

Ophthalmologists and interventional radiologists are not the only professionals for whom diseases of the efferent tear duct system occupy centre stage; this applies also to ENT specialists involving endonasal conservative or surgical treatment. On the basis of current knowledge and taking account of results yielded by own research in recent years and of clinical aspects, we here give an overview of basic knowledge on the anatomy and physiology of the nasolacrimal system. In doing so functional aspects regarding tear transport as well as embryological and pathophysiological issues are integrated.

Surfactant proteins of the human larynx.

PURPOSE: Surfactant proteins (SPs) originally identified in lung tissue are important players in the innate immune system. Beyond this, they contribute to stability and rheology of gaseous or aqueous interphases. In the present study, we determined the expression and presence of SPs (A, B, C and D) in different areas of the human larynx. METHODS: mRNA expression of SP-A, -B, -C and -D was analyzed by means of RT-PCR in healthy samples of epiglottis, vocal and vestibular folds, subglottis and trachea. Distribution and localization of all four SPs were analyzed by Western blot and immunohistochemistry in healthy human tissue samples. RESULTS: All four SPs were detected at the mRNA- and protein level in the human larynx as well as by means of immunohistochemistry in the different tissue samples of the human larynx. CONCLUSION: The results reveal that all four SPs are produced with different expression patterns within the human larynx. Based on the known functions, our results suggest that SPs might be involved in maintaining mucus rheology and subsequently they could be essential components for proper phonation. Moreover, the proteins seem to play a role in immune defense of the larynx.

Recombinant expression of surfactant protein H (SFTA3) in Escherichia coli.

Surfactant proteins are broadly understood to be an important structural and functional part of the lung surfactant system. These proteins influence the intra-alveolar surface tension and contribute to innate immunity of the lung. Beside the four already known surfactant proteins SP-A, SP-B, SP-C and SP-D, two novel SPs (SP-G/SFTA2 and SP-H/SFTA3) have recently been described. These show no sequential or structural similarity with the already known SPs. However, bioinformatic prediction tools suggest physicochemical properties, which have already been described for other surfactant proteins. Although it is known that SFTA2 and SFTA3 are expressed in different human tissues, their distinct functional properties remain unclear. Here, we describe the establishment of a stable expression system for recombinant SFTA3 protein synthesis in Escherichia coli. This gives rise to future experiments with the overall aim to further examine and characterize this novel protein in more detail.

[Updated incidence of dry eye syndrome in Germany]. / Aktuelle Inzidenz des Trockenen Auges in Deutschland.

BACKGROUND: Dry eye is one of the most common eye surface disorders. Patients suffer in particular from annoying subjective symptoms that compromise quality of life. The aim of the study was to find out when patients consult ophthalmologists in Germany and what symptoms they present. PATIENTS/MATERIAL AND METHODS: 170 patients treated at ophthalmological practices in Bavaria, Saxony and Saxony-Anhalt with dry eye were surveyed regarding their symptoms. RESULTS: The majority of those questioned were 40 years of age or older (88 %) (average: 60), female (59 %) and described a variety of subjective symptoms (65 %). More than five different concurrent symptoms were named. There is a recognisable increase in cases - by more than 3.5 times - at the age of forty (in women) and fifty (in men). CONCLUSIONS: We hope to contribute with the data obtained to a more complete understanding of this highly complex pathological process. A further aim is to facilitate recognition of this mostly chronic condition in its early stages when the symptoms are still poorly defined. The data on the German population obtained here should become part of a comparative analysis within the international context. Despite considerable scientific effort, dry eye remains a difficult challenge for both patients and attending physicians.

[The ocular surfactant system and its relevance in the dry eye]. / Das okuläre Surfactant-System und dessen Rolle bei entzündlichen Erkrankungen der Augenoberfläche.

The amphiphilic surfactant proteins B (SP-B) and C (SP-C) are tightly bound to phospholipids. These proteins play important roles in maintaining the surface tension-lowering properties of pulmonary surfactant. Surfactant protein A (SP-A) and D (SP-D) are hydrophilic and are thought to have a role in recycling surfactant and, especially, in improving host defense in the lung. Moreover, SP-A supports the hydrophobic surfactant proteins B and during surfactant subtype assembly and inhibits the secretion of lamellar bodies into the alveolar space. During recent years surfactant proteins have also been detected at locations outside the lung such as the lacrimal apparatus. In this review, the latest information regarding SP function and regulation in the human lacrimal system, the tear film and the ocular surface is summarised with regard to dry eye, rheological and antimicrobial properties of the tear film, tear outflow, certain disease states and possible therapeutic perspectives.

Individual differences in smoking reward from de-nicotinized cigarettes.

Most studies of cigarette smoking and smoking cessation have focused on the psychopharmacological effects of nicotine; relatively few have explored the role of sensory aspects of cigarette smoke. Sensory aspects of cigarette smoke play a role in the maintenance of smoking behavior, and may be particularly important for certain smokers. This paper presents the results of a pooled analysis of nine studies conducted in our laboratory, in order to explore the influence of demographic and smoking-related variables on ratings of de-nicotinized as compared to nicotine-containing cigarettes. A major finding of this analysis is that ratings of smoking derived from de-nicotinized, but not nicotine-containing, cigarettes appear to vary with level of tobacco dependence, suggesting that sensory factors may be more important to highly dependent, as compared to less-dependent, smokers. The implications of these findings for smoking cessation treatment and for future research are discussed.

Haloperidol reduces smoking of both nicotine-containing and denicotinized cigarettes.

RATIONALE: Studies with laboratory animals and humans suggest that dopamine may play a role in maintaining cigarette smoking behavior via its interactions with nicotine. OBJECTIVES: This study was designed to replicate and extend previous findings showing that the dopamine D2 antagonist, haloperidol, produces blockade of smoking reward and compensatory increases in smoking. METHODS: We studied 20 subjects in a 2x3 within-subjects design, with nicotine-containing or denicotinized cigarettes crossed with oral placebo, haloperidol 1 mg, or haloperidol 2 mg. Subjects attended six sessions during which they received one of the cigarette/drug combinations, and smoked under both controlled and ad libitum conditions. Cigarette and mood ratings and smoking behavior were assessed. RESULTS: Haloperidol reduced the number of cigarettes smoked and the carbon monoxide boost associated with both types of cigarettes, at doses that did not appear to produce clinically significant behavioral effects. CONCLUSIONS: Dopamine appears to play a role in mediating smoking behavior, but this may occur through a non-nicotine mechanism.

The effect of the analyst's gender and other factors on post-termination patient-analyst contact: confirmation by a questionnaire study.

This questionnaire study was designed to confirm and further explore an earlier finding of a gender difference in post-termination patient-analyst contact, as well as to assess whether practices regarding post-termination contact have changed in the five-year interval since the first study. The hypothesis that women analysts are more likely to have post-termination contact with their analysands than men analysts was confirmed by the present study. Analysts who report thinking frequently about their most significant analyst are contacted by a much larger proportion of prior patients than those who rarely think about their analyst. Further, women analysts are more likely to feel they benefited from the analysis they consider their most significant analysis, and to feel positively about that analyst. In 1994, analysts were much more accepting of and more likely to propose post-termination contact than in 1989. What the analyst reports he/she says to the patient is associated with the likelihood of such contact.

Naltrexone blockade of nicotine effects in cigarette smokers.

RATIONALE: The role of endogenous opiate systems in cigarette smoking remains unclear. In laboratory animals, opiate antagonists block many of the effects of nicotine, but in humans they do not consistently alter smoking behavior. OBJECTIVE: This study explored the effects of naltrexone, alone and in combination with nicotine, on smoking behavior. METHODS: In a double-blind, double-dummy, within-subjects design, 19 regular smokers received four treatments of 1 week duration: naltrexone tablet (50 mg) plus placebo skin patch, placebo tablet plus nicotine skin patch (21 mg/24 h), naltrexone tablet plus nicotine skin patch, and placebo tablet plus placebo skin patch. During each treatment, subjects rated their responses to nicotine-containing and denicotinized cigarettes in the laboratory, and to their own brand of cigarette smoked ad libitum outside the laboratory. RESULTS: Pretreatment with the nicotine patch attenuated smoking-induced decreases in craving, negative affect, and rates of ad lib smoking, and potentiated the aversiveness of a cigarette. Naltrexone reversed these effects of the nicotine patch, and produced negative effects on mood. CONCLUSIONS: The blockade of nicotine's effects by naltrexone supports a role for opioid mechanisms in cigarette smoking.

Whole-body hyperthermia combined with ifosfamide and carboplatin causes hypotension and nephrotoxicity.

It was previously postulated on the basis of clinical data that the cardiovascular sequelae of extracorporeal whole-body hyperthermia (e-WBH), i.e., hypotension (which requires catecholamine support) results in unique nephrotoxicity in combination with select chemotherapeutic agents. In an attempt to explain this phenomenon, we mimicked e-WBH physiological conditions in a rat model. Animals were treated with and without ifosfamide (IFO) and/or carboplatin (CBDCA) at 37 degrees C or 41.5-41.8 degrees C, with blood pressure monitoring and catecholamine support comparable to the clinical setting. Ex vivo post-treatment data (24 h) from artificially perfused kidneys (i.e., histology, urine volume, perfusion rate, glomerular filtration rate, and the reabsorption of sodium, glucose, and water) demonstrated unique toxicity including proximal tubular necrosis for the combination of WBH and IFO, for WBH and CBDCA and for WBH and IFO plus CBDCA, but not for IFO and CBDCA without WBH. These data, considered together with results derived from a subsequent clinical trial and the laboratory work of others were consistent with the hypothesis.

Effects of d-amphetamine in grouped versus isolated humans.

This study was designed to determine whether the subjective, behavioral or physiological effects of a stimulant drug in humans depend on whether subjects are tested under isolated or social conditions. Forty-two subjects were randomly assigned to either the Social (SOC) or Isolated (ISO) condition. SOC subjects participated in 4 h laboratory sessions in groups of 3 or 4, whereas ISO subjects participated in the sessions alone. All subjects participated in three sessions, during which they received capsules containing d-amphetamine (10 or 20 mg) or placebo, in mixed order under double blind conditions. Subjective, physiological and behavioral measures were obtained at regular intervals, d-amphetamine produced dose-related, prototypic stimulant effects on many measures, including self-reported mood states, behavioral indices and physiological measures. Most of these effects were unaffected by the setting in which subjects were tested (SOC vs ISO). However, body temperature was overall higher in the SOC group, and there was a trend for d-amphetamine to produce greater hyperthermic effects in the SOC group. In addition, 10 mg d-amphetamine increased heart rate in the SOC group but not in the ISO group. The results suggest that, like in laboratory animals, some of the effects of stimulants in humans are greater under aggregated conditions. However, unlike in the animal studies, this observed enhancement of the drug's effects under aggregated conditions was limited to physiological measures and did not apply to other subjective or behavioral measures.

Dopamine ligands and the stimulus effects of amphetamine: animal models versus human laboratory data.

Studies with laboratory animals have consistently demonstrated a role for dopamine in mediating the discriminative stimulus (i.e., interoceptive) effects of amphetamine. For example, D2 dopamine agonists mimic the discriminative stimulus effects of amphetamine and D1 and D2 dopamine antagonists generally block them. The discriminative stimulus effects of drugs in animals are believed to parallel their subjective effects in humans. Therefore, it is often assumed that dopamine plays a role in amphetamine-induced subjective effects in humans and it would be reasonable to expect that dopamine antagonists would block the subjective effects of amphetamine. Few studies have tested this hypothesis directly, and those that have have yielded inconsistent results. This paper will review data regarding the effects of dopamine agonists and antagonists on the discriminative stimulus effects of amphetamine in animals and its subjective effects in humans. Possible explanations for the discrepancies between animal and human data will be discussed, and classical assumptions underlying the use of animal models of drug effects will be examined.

High dose pimozide does not block amphetamine-induced euphoria in normal volunteers.

Studies with laboratory animals have shown that dopamine antagonists block the rewarding and interoceptive effects of amphetamine. However, studies using dopamine antagonists with humans have not consistently shown blockade of amphetamine-induced euphoria. The unexpected results in humans may relate to the low doses of dopamine antagonists tested. The purpose of this study was to evaluate the effects of a relatively high acute dose (8 mg) of the dopamine receptor antagonist, pimozide, on responses to d-amphetamine (10 and 20 mg) in normal volunteers. Male and female volunteers (N = 12) attended six sessions on which they received pimozide or placebo (7:30 am) followed by d-amphetamine or placebo (9:30 am). Subjective, physiological and behavioral measures were obtained at baseline (7:15 am) and hourly over a 5 h period. d-Amphetamine and pimozide, when administered alone, produced significant and opposite effects on ratings of Elation and Vigor, as well as on psychomotor performance and physiological measures. However, there were few significant interactions between pimozide and d-amphetamine. Thus, pimozide failed to consistently antagonize the effects of d-amphetamine, even at doses of pimozide that had behavioral and physiological effects when administered alone. Possible reasons for lack of robust dopamine antagonism of amphetamine-induced euphoria in humans are discussed.

Evaluation of phentermine and fenfluramine, alone and in combination, in normal, healthy volunteers.

Recent clinical reports indicate that combined administration of phentermine and fenfluramine may have useful effects in the treatment of drug abuse. The present study was designed to evaluate the subjective and mood-altering effects of these drugs, alone and in combination, in normal healthy volunteers. Seven male and five female volunteers participated in an eight-session, double-blind study in which each subject received each of the following drug conditions: d-amphetamine (10 and 20 mg), phentermine (30 mg), fenfluramine (40 and 80 mg), phentermine (30 mg) with fenfluramine (40 mg), phentermine (30 mg) with fenfluramine (80 mg), and placebo. Sessions were conducted in a laboratory setting two or three days a week. Subjects completed standardized self-report questionnaires and psychomotor tests before and at regular intervals after each drug administration. Phentermine produced effects that were similar to those of d-amphetamine, whereas fenfluramine produced different and apparently aversive effects (e.g., it increased measures of anxiety and confusion). Phentermine reduced the apparently aversive effects of fenfluramine when the two drugs were given together. These results suggest that the combination of phentermine and fenfluramine would have a low potential for abuse.