Protein disulfide isomerase A1 regulates fenestration dynamics in primary mouse liver sinusoidal endothelial cells (LSECs)

Protein disulfide isomerases (PDIs) are involved in many intracellular and extracellular processes, including cell adhesion and cytoskeletal reorganisation, but their contribution to the regulation of fenestrations in liver sinusoidal endothelial cells (LSECs) remains unknown. Given that fenestrations are supported on a cytoskeleton scaffold, this study aimed to investigate whether endothelial PDIs regulate fenestration dynamics in primary mouse LSECs. PDIA3 and PDIA1 were found to be the most abundant among PDI isoforms in LSECs. Taking advantage of atomic force microscopy, the effects of PDIA1 or PDIA3 inhibition on the fenestrations in LSECs were investigated using a classic PDIA1 inhibitor (bepristat) and novel aromatic N-sulfonamides of aziridine-2-carboxylic acid derivatives as PDIA1 (C-3389) or PDIA3 (C-3399) inhibitors. The effect of PDIA1 inhibition on liver perfusion was studied in vivo using dynamic contrast-enhanced magnetic resonance imaging. Additionally, PDIA1 inhibitors were examined in vitro in LSECs for effects on adhesion, cytoskeleton organisation, bioenergetics, and viability. Inhibition of PDIA1 with bepristat or C-3389 significantly reduced the number of fenestrations in LSECs, while inhibition of PDIA3 with C-3399 had no effect. Moreover, the blocking of free thiols by the cell-penetrating N-ethylmaleimide, but not by the non-cell-penetrating 4-chloromercuribenzenesulfonate, resulted in LSEC defenestration. Inhibition of PDIA1 did not affect LSEC adhesion, viability, and bioenergetics, nor did it induce a clear-cut rearrangement of the cytoskeleton. However, PDIA1-dependent defenestration was reversed by cytochalasin B, a known fenestration stimulator, pointing to the preserved ability of LSECs to form new pores. Importantly, systemic inhibition of PDIA1 in vivo affected intra-parenchymal uptake of contrast agent in mice consistent with LSEC defenestration. These results revealed the role of intracellular PDIA1 in the regulation of fenestration dynamics in LSECs, and in maintaining hepatic sinusoid homeostasis.

Changes in stiffness of the optic nerve and involvement of neurofilament light chains in the course of experimental autoimmune encephalomyelitis, an animal model of multiple sclerosis

Multiple sclerosis and its animal model, experimental autoimmune encephalomyelitis (EAE), are often accompanied by optic neuritis associated with neurofilament disruption. In this study, the stiffness of the optic nerve was investigated by atomic force microscopy (AFM) in mice with induced EAE in the successive phases of the disease: onset, peak, and chronic. AFM results were compared with the intensity of the main pathological processes in the optic nerve: inflammation, demyelination, and axonal loss, as well as with the density of astrocytes, assessed by quantitative histology and immunohistochemistry. Optic nerve tissue and serum levels of neurofilament light chain protein (NEFL) were also examined by immunostaining and ELISA, respectively. The stiffness of the optic nerve in EAE mice was lower than that in control and naïve animals. It increased in the onset and peak phases and sharply decreased in the chronic phase. Serum NEFL level showed similar dynamics, while tissue NEFL level decreased in the onset and peak phases, indicating a leak of NEFL from the optic nerve to body fluids. Inflammation and demyelination gradually increased to reach the maximum in the peak phase of EAE, and inflammation slightly declined in the chronic phase, while demyelination did not. The axonal loss also gradually increased and had the highest level in the chronic phase. Among these processes, demyelination and especially axonal loss most effectively decrease the stiffness of the optic nerve. NEFL level in serum can be regarded as an early indicator of EAE, as it rapidly grows in the onset phase of the disease.

WITHDRAWN: Foreword to the special issue on different approaches to force spectroscopy in the research of cell pathologies

The Publisher regrets that this article is an accidental duplication of an article that has already been published in Micron, Volume 161, October 2022, 103325, https://doi.org/10.1016/j.micron.2022.103325. The duplicate article has therefore been withdrawn. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.

Biomechanical changes in the liver tissue induced by a mouse model of multiple sclerosis (EAE) and the effect of anti-VLA-4 mAb treatment

Experimental autoimmune encephalomyelitis (EAE) is a mouse model of demyelinating diseases, such as multiple sclerosis (MS). MS can be accompanied by autoimmune hepatitis. In this study, nanomechanical, biorheological and histological examinations were carried out by atomic force microscopy (AFM), rheology, and immunofluorescence microscopy to investigate changes in the liver tissue of EAE mice and the effect of natalizumab, a monoclonal antibody against α4-integrin (VLA-4) cell adhesion molecule, used in MS therapy. Liver samples collected from EAE mice in three successive phases of the disease showed inflammatory changes manifested by leukocyte infiltrations and elevated levels of proinflammatory cytokine IL-1β. Liver stiffness and viscoelasticity increased in the onset phase of EAE, decreased in the peak phase and increased again in the chronic phase to reach the highest values. These changes were not associated with inflammation parameters which increased in the peak phase and decreased to the lowest values in the chronic phase. Moreover, anti-VLA treatment, which reduced the inflammation parameters, had an ambiguous effect on stiffness and viscoelasticity: it increased them in the peak phase but decreased in the chronic phase. The observed discrepancies can result from a complex network of interactions between inflammation and fibrosis, as well as between liver cells and the extracellular matrix influencing the biomechanical properties of the liver tissue.

Small-molecule inhibitor - tyrphostin AG1296 regulates proliferation, survival and migration of rhabdomyosarcoma cells

Rhabdomyosarcoma (RMS) is the most commonly occurring malignant soft tissue tumor in children. Despite improving its treatment methods, the current outcome in the advanced stages of this tumor is not satisfactory. RMS cells are characterized by abnormal cellular signaling due to the changes in the activity of the tyrosine kinases. Thus, substances blocking the mitogenic signal transmitted by receptors with tyrosine kinase activity raise hopes for inhibition of the uncontrolled cell growth. In this study, we examined the anticancer activity of tyrphostin AG1296, a tyrosine kinase inhibitor that binds to the intracellular domain of the PDGF (platelet-derived growth factor) receptor in human RMS alveolar and embryonal cell lines. We have discovered that tyrphostin AG1296 completely inhibited cell proliferation and effectively inhibited cell viability. Tyrphostin AG1296 induced apoptosis of the RMS cells and significantly inhibited their migration. Additionally, investigated inhibitor slightly inhibited expression of AKT and phosphorylation of ERK in alveolar RMS cells. Importantly, the inhibitor exerted also potent effects on the nanomechanical properties and cytoskeleton organization of RMS cells. To conclude, tyrphostin AG1296 is a promising compound in the treatment of alveolar RMS. Undoubtedly, a better knowledge of receptor pathomechanism of tyrosine kinases may contribute to developing new, more effective ways of RMS treatment.

Biophysical nanocharacterization of liver sinusoidal endothelial cells through atomic force microscopy

The structural-functional hallmark of the liver sinusoidal endothelium is the presence of fenestrae grouped in sieve plates. Fenestrae are open membrane bound pores supported by a (sub)membranous cytoskeletal lattice. Changes in number and diameter of fenestrae alter bidirectional transport between the sinusoidal blood and the hepatocytes. Their physiological relevance has been shown in different liver disease models. Although the structural organization of fenestrae has been well documented using different electron microscopy approaches, the dynamic nature of those pores remained an enigma until the recent developments in the research field of four dimensional (4-D) AFM. In this contribution we highlight how AFM as a biophysical nanocharacterization tool enhanced our understanding in the dynamic behaviour of liver sinusoidal endothelial fenestrae. Different AFM probing approaches, including spectroscopy, enabled mapping of topography and nanomechanical properties at unprecedented resolution under live cell imaging conditions. This dynamic biophysical characterization approach provided us with novel information on the 'short' life-span, formation, disappearance and closure of hepatic fenestrae. These observations are briefly reviewed against the existing literature.

Changes in spinal cord stiffness in the course of experimental autoimmune encephalomyelitis, a mouse model of multiple sclerosis

Experimental autoimmune encephalomyelitis (EAE) is a commonly used mouse model of multiple sclerosis, a chronic inflammatory disease of the central nervous system (CNS) characterized by demyelination leading to brain and spinal cord malfunctions. We postulate that not only biological but also biomechanical properties play an important role in impairements of CNS function. Atomic force microscopy (AFM) was applied to investigate mechanical properties of spinal cords collected from EAE mice in preonset, onset, peak, and chronic disease phases. Biomechanical changes were compared with histopathological alterations observed in the successive phases. The deformability of gray matter did not change, while rigidity of white matter increased during the onset phase, remained at the same level in the peak phase and decreased in the chronic phase. Inflammatory infiltration and laminin content accompanied the tissue rigidity increase, whereas demyelination and axonal damage showed an opposite effect. The increase in white matter rigidity can be regarded as an early signature of EAE.

AFM assessing of nanomechanical fingerprints for cancer early diagnosis and classification: from single cell to tissue level

Cancer development and progression are closely associated with changes both in the mechano-cellular phenotype of cancer and stromal cells and in the extracellular matrix (ECM) structure, composition, and mechanics. In this paper, we review the use of atomic force microscopy (AFM) as a tool for assessing the nanomechanical fingerprints of solid tumors, so as to be potentially used as a diagnostic biomarker for more accurate identification and early cancer grading/classification. The development of such a methodology is expected to provide new insights and a novel approach for cancer diagnosis. We propose that AFM measurements could be employed to complement standard biopsy procedures, offering an objective, novel and quantitative diagnostic approach with the properties of a blind assay, allowing unbiased evaluation of the sample.

Autologous Cell Therapy Approach for Duchenne Muscular Dystrophy using PiggyBac Transposons and Mesoangioblasts

Duchenne muscular dystrophy (DMD) is a lethal muscle-wasting disease currently without cure. We investigated the use of the PiggyBac transposon for full-length dystrophin expression in murine mesoangioblast (MABs) progenitor cells. DMD murine MABs were transfected with transposable expression vectors for full-length dystrophin and transplanted intramuscularly or intra-arterially into mdx/SCID mice. Intra-arterial delivery indicated that the MABs could migrate to regenerating muscles to mediate dystrophin expression. Intramuscular transplantation yielded dystrophin expression in 11%-44% of myofibers in murine muscles, which remained stable for the assessed period of 5 months. The satellite cells isolated from transplanted muscles comprised a fraction of MAB-derived cells, indicating that the transfected MABs may colonize the satellite stem cell niche. Transposon integration site mapping by whole-genome sequencing indicated that 70% of the integrations were intergenic, while none was observed in an exon. Muscle resistance assessment by atomic force microscopy indicated that 80% of fibers showed elasticity properties restored to those of wild-type muscles. As measured in vivo, transplanted muscles became more resistant to fatigue. This study thus provides a proof-of-principle that PiggyBac transposon vectors may mediate full-length dystrophin expression as well as functional amelioration of the dystrophic muscles within a potential autologous cell-based therapeutic approach of DMD.

Protocol of single cells preparation for time of flight secondary ion mass spectrometry

There are several techniques like time of flight secondary ion mass spectrometry (ToF SIMS) that require a special protocol for preparation of biological samples, in particular, those containing single cells due to high vacuum conditions that must be kept during the experiment. Frequently, preparation methodology involves liquid nitrogen freezing what is not always convenient. In our studies, we propose and validate a protocol for preparation of single cells. It consists of four steps: (i) paraformaldehyde fixation, (ii) salt removal, (iii) dehydrating, and (iv) sample drying under ambient conditions. The protocol was applied to samples with single melanoma cells i.e. WM115 and WM266-4 characterized by similar morphology. The surface and internal structures of cells were monitored using atomic force, scanning electron and fluorescent microscopes, used to follow any potential protocol-induced alterations. To validate the proposed methodology for sample preparation, ToF SIMS experiments were carried out using C60(+) cluster ion beam. The applied principal component analysis (PCA) revealed that chemical changes on cell surface of melanoma cells were large enough to differentiate between primary and secondary tumor sites. Subject category: Mass spectrometry.

Comparing surface properties of melanoma cells using time of flight secondary ions mass spectrometry

Various techniques have been already reported to differentiate between normal (non-malignant) and cancerous cells based on their physico-chemical properties.

Differentiation between single bladder cancer cells using principal component analysis of time-of-flight secondary ion mass spectrometry

Time-of-flight-secondary ion mass spectrometry (TOF-SIMS) mass spectra measurements combined with an appropriate sample preparation protocol are the powerful tools to obtain unique information about the chemical composition of biological materials. In our studies, two questions were addressed, i.e., whether it is possible to develop a fixative-based sample preparation protocol and whether it allows one to distinguish between cells originating from various stages of cancer progression. Therefore, four human bladder cancer cell lines (with distinct malignancy degree) have been investigated. A chemical fixation protocol has been used for TOF-SIMS measurements, and mass spectra were obtained using a Bi3(+) primary ion beam. The principal component analysis (PCA) has been applied to analyze the whole range of mass spectra (without preselection of any particular masses) using two approaches of data preprocessing, namely, mean centering and autoscaling. The PC3 versus PC2 plot has showed significant differences between nonmalignant cancer cells and the cancerous ones for both of preprocessing approaches. The analysis of mass spectra of human bladder cells allows one to find a list of mass peaks with intensities significantly larger in cancerous bladder cells compared to nonmalignant cell cancer of the ureter (HCV29 cells). These findings show that TOF-SIMS in combination with PCA can be used to identify reference, human bladder cells from cancerous ones.

The softening of human bladder cancer cells happens at an early stage of the malignancy process

Various studies have demonstrated that alterations in the deformability of cancerous cells are strongly linked to the actin cytoskeleton. By using atomic force microscopy (AFM), it is possible to determine such changes in a quantitative way in order to distinguish cancerous from non-malignant cells. In the work presented here, the elastic properties of human bladder cells were determined by means of AFM. The measurements show that non-malignant bladder HCV29 cells are stiffer (higher Young's modulus) than cancerous cells (HTB-9, HT1376, and T24 cell lines). However, independently of the histological grade of the studied bladder cancer cells, all cancerous cells possess a similar level of the deformability of about a few kilopascals, significantly lower than non-malignant cells. This underlines the diagnostic character of stiffness that can be used as a biomarker of bladder cancer. Similar stiffness levels, observed for cancerous cells, cannot be fully explained by the organization of the actin cytoskeleton since it is different in all malignant cells. Our results underline that it is neither the spatial organization of the actin filaments nor the presence of stress fibers, but the overall density and their 3D-organization in a probing volume play the dominant role in controlling the elastic response of the cancerous cell to an external force.

Influence of propofol and volatile anaesthetics on the inflammatory response in the ventilated lung

BACKGROUND

The immunomodulatory effects of volatile anaesthetics in vitro and the protective effect of propofol in lung injury spurred us to study the effects of volatile anaesthetics and propofol on lung tissue in vivo.

METHODS

Twenty-seven pigs were randomized to 4-h general anaesthesia with propofol (8 mg/kg/h, group P, n=9), sevoflurane [minimum alveolar concentration (MAC)=1.0, group S, n=9) or desflurane (MAC=1.0, group D, n=9). Four healthy animals served as the no-ventilation group. Bronchoalveolar lavage fluid (BALF) was obtained to measure the cell counts, platelet-activating factor acetylhydrolase (PAF-AcH), phospholipase A(2) (PLA(2)) and superoxide dismutase (SOD) activity. Lung tissues were evaluated histologically and for caspase-3 expression.

RESULTS

Volatile anaesthetics reduced PAF-AcH levels without affecting PLA(2) activity and resulted in decreased alveolar macrophage and increased lymphocyte counts in BALF (sevoflurane: 29 ± 23%; desflurane: 26 ± 6%, both P<0.05 compared with 4 ± 2% in the no-ventilation group). These findings were accompanied by atelectasis and inflammatory cells' infiltration in the inhalational anaesthetics groups. Also, sevoflurane reduced SOD activity and both sevoflurane and desflurane induced significant caspase-3 expression. In contrast, propofol resulted in a minor degree of inflammation and preserved BALF cells' composition without triggering apoptosis.

CONCLUSION

Halogenated anaesthetics seem to trigger an immune lymphocytic response in the lung, inducing significant apoptosis and impairment of PAF-AcH. In contrast, propofol preserves anti-inflammatory and anti-oxidant defences during mechanical ventilation, thus preventing the emergence of apoptosis.

Intracellular nanomanipulation by a photonic-force microscope with real-time acquisition of a 3D stiffness matrix

A traditional photonic-force microscope (PFM) results in huge sets of data, which requires tedious numerical analysis. In this paper, we propose instead an analog signal processor to attain real-time capabilities while retaining the richness of the traditional PFM data. Our system is devoted to intracellular measurements and is fully interactive through the use of a haptic joystick. Using our specialized analog hardware along with a dedicated algorithm, we can extract the full 3D stiffness matrix of the optical trap in real time, including the off-diagonal cross-terms. Our system is also capable of simultaneously recording data for subsequent offline analysis. This allows us to check that a good correlation exists between the classical analysis of stiffness and our real-time measurements. We monitor the PFM beads using an optical microscope. The force-feedback mechanism of the haptic joystick helps us in interactively guiding the bead inside living cells and collecting information from its (possibly anisotropic) environment. The instantaneous stiffness measurements are also displayed in real time on a graphical user interface. The whole system has been built and is operational; here we present early results that confirm the consistency of the real-time measurements with offline computations.

Induced Delusional Disorder in Rural Areas: A Case of Folie a Quatre

Background and aim:

Induced delusional disorder or folie a deux is characterized by the presence of similar delusional ideas in two or more individuals. The delusional system develops as a result of a close relationship with a person with an established psychotic disorder. Most commonly the affected persons are members of a family.

Methods:

An unusual case of folie a famille involving four siblings, brother and three sisters, (folie a quatre) is presented. This case was detected in the context of a community-based psychiatric service in Greece, the Mobile Psychiatric Unit of the prefectures of Ioannina and Thesprotia.

Results:

A 46-year-old woman was referred from primary care physicians for the management of a psychotic exacerbation. On the examination it was revealed that she and her three older siblings were sharing the delusional idea of being affected by their neighbors with magic. These siblings had been living in social isolation for long and have been querulant and aggressive toward their neighbors, against whom they had undertaken a succession of lawsuits. None of the rest siblings accepted to be examined so it could not be determined who the inducer was or what the diagnoses were for each of the affected persons. The patient did not receive the prescribed medication and did not engage in follow-up.

Conclusions:

Cases of induced delusional disorder may be difficult to be detected and treated. Mobile psychiatric units in co-operation with primary care physicians may have an opportunity to provide appropriate treatment for such patients in rural areas.

The systemic inflammatory response in coronary artery bypass grafting: what is the role of the very low ejection fraction (EF < or = 30%)?

AIM

Patients with depressed left ventricular function are more susceptible to develop postoperative complications after cardiac surgery. The aim of the present study was to examine the effect of severe left ventricular dysfunction on the activation of systemic inflammatory reaction during and after coronary artery bypass grafting (CABG).

METHODS

Clinical prospective study; 32 selected patients underwent CABG; 16 patients had depressed left ventricular function before the operation (low ejection fraction [EF] <30%)--Low EF group (study group). Sixteen patients had normal left ventricular function (normal EF, >50%)--Normal EF group (control group). The levels of inflammatory mediators TNF-alpha, IL-6, IL-8 and IL-10 were measured preoperatively, during and after cardiopulmonary bypass (CPB) and 24 hours postoperatively.

RESULTS

Higher levels of almost all of inflammatory mediators were detected in patients with depressed left ventricular function compared with patients of normal EF group. IL-6 levels were found statistically significant higher in Low EF group before the induction of anesthesia (P=0.039) and after the administration of protamine (P=0.02). IL-8 levels were found statistically significant higher in Low EF group before the induction of anesthesia (P=0.05), 30 min after the start of CPB (P=0.02), after the administration of protamine (P=0.015) and 24 hours after the end of the operation (P=0.05). No statistically significant differences were demonstrated between the 2 groups of study relative to TNF-alpha and IL-10.

CONCLUSION

A greater activation of systemic inflammatory reaction occurred in patients with depressed left ventricular function than in patients with normal cardiac function when they underwent CABG with extracorporeal circulation.

Statins impair antitumor effects of rituximab by inducing conformational changes of CD20

BACKGROUND

Rituximab is used in the treatment of CD20+ B cell lymphomas and other B cell lymphoproliferative disorders. Its clinical efficacy might be further improved by combinations with other drugs such as statins that inhibit cholesterol synthesis and show promising antilymphoma effects. The objective of this study was to evaluate the influence of statins on rituximab-induced killing of B cell lymphomas.

METHODS AND FINDINGS

Complement-dependent cytotoxicity (CDC) was assessed by MTT and Alamar blue assays as well as trypan blue staining, and antibody-dependent cellular cytotoxicity (ADCC) was assessed by a 51Cr release assay. Statins were found to significantly decrease rituximab-mediated CDC and ADCC of B cell lymphoma cells. Incubation of B cell lymphoma cells with statins decreased CD20 immunostaining in flow cytometry studies but did not affect total cellular levels of CD20 as measured with RT-PCR and Western blotting. Similar effects are exerted by other cholesterol-depleting agents (methyl-beta-cyclodextrin and berberine), but not filipin III, indicating that the presence of plasma membrane cholesterol and not lipid rafts is required for rituximab-mediated CDC. Immunofluorescence microscopy using double staining with monoclonal antibodies (mAbs) directed against a conformational epitope and a linear cytoplasmic epitope revealed that CD20 is present in the plasma membrane in comparable amounts in control and statin-treated cells. Atomic force microscopy and limited proteolysis indicated that statins, through cholesterol depletion, induce conformational changes in CD20 that result in impaired binding of anti-CD20 mAb. An in vivo reduction of cholesterol induced by short-term treatment of five patients with hypercholesterolemia with atorvastatin resulted in reduced anti-CD20 binding to freshly isolated B cells.

CONCLUSIONS

Statins were shown to interfere with both detection of CD20 and antilymphoma activity of rituximab. These studies have significant clinical implications, as impaired binding of mAbs to conformational epitopes of CD20 elicited by statins could delay diagnosis, postpone effective treatment, or impair anti-lymphoma activity of rituximab.

Rheological properties of erythrocytes in patients with high risk of cardiovascular disease

Rheological properties of erythrocytes from patients with high risk of cardiovascular disease (CVD) were analyzed in relation to individual patient risk factors as well as to the medication. Additionally, comparative statistical analysis was performed considering plasma concentration of the selected mediators of vascular endothelium: 6-keto-prostaglandin F(1alpha) (PGF(1alpha)), sVCAM-1 and E-selectin adhesion molecules and interleukin-6 (IL-6). It was found that antihypertensive therapy with angiotensin-converting enzyme inhibitor (ACEI) is accompanied by improvement of RBC rheology: the increase of deformability and the decrease of aggregability. This improvement is probably mediated by endothelial prostacyclin and nitric oxide which are generated by ACEI. A correlation was observed between RBC deformability/aggregability and the patient's hematocrit level, what implicates that the hematocrit level should be explicitly taken into consideration when investigating rheological properties of erythrocytes. A strong relationship was also found between the plasma concentration of sVCAM-1 and patient's age.

Erythrocyte stiffness probed using atomic force microscope

The stiffness of erythrocytes in patients (N=45) suffering from certain disorders, such as coronary disease, hypertension, and diabetes mellitus has been assessed using the Atomic Force Microscopy (AFM) and compared with that in a group of healthy individuals (N=13). For each blood sample, around 20 erythrocytes were selected at random and the stiffness of each one was probed in 20-30 arbitrarily chosen points. From these results, distributions of the cell Young's modulus (YM) were determined. Average values and widths of YM distributions significantly increased in samples taken from diabetes mellitus patients and cigarette smokers, as compared to those taken from healthy donors. At the same time, the average values of YM were found to increase as a function of the patient's age. We demonstrated that the atomic force microscope is a very sensitive tool for determination of cell stiffness with every prospect of a routine application as a diagnostic tool in quantitative analysis of the physiological and pathological states of red blood cells.

Hydrogel microspheres: influence of chemical composition on surface morphology, local elastic properties, and bulk mechanical characteristics

Hydrogel microspheres, beads, and capsules of uniform size, differing in their chemical composition, have been prepared by electrostatic complex formation of sodium alginate with divalent cations and polycations. These have served as model spheres to study the influence of the chemical composition on both surface characteristics and bulk mechanical properties. Resistance to compression experiments yielding the compression work clearly identified differences as a function of the composition, with forces at maximal compression in the range of 34-455 mN. The suitability and informative value of atomic force microscopy have been confirmed for the case where surface characterization is performed in a liquid environment equivalent to physiological conditions. Surface imaging and mechanical response to indentation revealed different average surface roughness and Young's moduli for all hydrogel types ranging from 0.9 to 14.4 nm and from 0.4 to 440 kPa, respectively. The hydrogels exhibited pure elastic behavior. Despite a relatively high standard deviation, resulting from both surface and batch heterogeneity, nonoverlapping ranges of Young's moduli were reproducibly identified for the selected model spheres. The findings indicate the reliability of contact mode atomic force microscopy to quantify local surface properties, which may have an impact on the biocompatibility of alginate-based hydrogel materials of different composition and conditions of preparation. Moreover, it seems that local elastic properties and bulk mechanical characteristics are subject to analogous composition influences.

Probing molecular interaction between concanavalin A and mannose ligands by means of SFM

Recently, the scanning force microscope (SFM) has been widely used for direct monitoring of specific interactions between biologically active molecules. Such studies have employed the SFM liquid-cell setup, which allows measurements to be made in the native environment with force resolution down to a tenth of a picoNewton. In this study, the ligand-receptor strength of monoclonal anti-human prostatic acid phosphatase and prostatic acid phosphatase, representing an antigen-antibody system with a single type of interaction, was determined. Then, the interaction force occurring between concanavalin A and the carbohydrate component of the glycoproteins arylsulfatase A and carboxypeptidase Y was measured. High mannose-type glycans were sought on the human prostate carcinoma cell surface. Application of an analysis based on the Poisson distribution of the number of bonds formed in all these measured systems allowed the strength of the molecular interaction to be calculated. The values of the force acting between two single molecules were 530+/-25, 790+/-32, and 940+/-39 pN between prostatic acid phosphatase and monoclonal anti-human prostatic acid phosphatase, between concanavalin A and arylsulfatase A, and between concanavalin A and carboxypeptidase Y, respectively. The value calculated from data collected for the force between concanavalin A and mannose-containing ligands present on the surface of human prostate carcinoma cells was smaller, 116+/-17 pN. The different values of the binding force between concanavalin A and mannose-containing ligands were attributed to the structural changes of the carbohydrate components.

Autoantibodies to lipids in bronchoalveolar lavage fluid of patients with acute respiratory distress syndrome

OBJECTIVE

To investigate the presence of autoantibodies to lipids in the bronchoalveolar lavage (BAL) fluid from adult patients with acute respiratory distress syndrome (ARDS).

DESIGN

Analysis of immunoglobulin G (IgG) in BAL fluid by electrophoresis followed by immunoblotting and characterization of immunoglobulins as antilipid autoantibodies.

SETTING

Intensive care unit of a university hospital and two research university laboratories.

SUBJECTS

Twenty-seven mechanically ventilated patients in total, including nine patients with ARDS and two control groups.

INTERVENTIONS

Patients were ventilated with a mechanical ventilation mode. Six aliquots of 20-mL sterile normal saline at 37 degrees C were infused through the working channel of the bronchoscope.

MEASUREMENTS

Total protein, detection of IgG by electrophoresis followed by immunoblotting, and characterization of IgG by enzyme-linked immunosorbent assay using different lipids as target antigens.

MAIN RESULTS

Antiphospholipid autoantibodies are present in BAL fluid of ARDS patients. Among the phospholipids tested, phosphatidic acid and phosphatidylserine gave the most significant activity. The IgG fraction, purified from BAL fluids by affinity chromatography, gave the same pattern of binding as that of the BAL fluid.

CONCLUSION

The presence of antiphospholipid autoantibodies in BAL fluid suggests involvement of autoimmune mechanisms in the pathogenesis of ARDS.

The characteristics of bronchoalveolar lavage from a patient with antiphospholipid syndrome who developed acute respiratory distress syndrome

The purpose of this study was to investigate the biochemical characteristics as well as the occurrence and specificity of antiphospholipid antibodies in the bronchoalveolar lavage (BAL) fluid from a patient with both antiphospholipid antibodies syndrome (APS) and acute respiratory distress syndrome (ARDS). Proteins, lipids, cells and autoantibodies were determined. Immunoglobulins were purified with affinity chromatography. Autoantibody identification was assessed with enzyme-linked immunosorbent assay (ELISA) and with electrophoresis, followed by immunoblotting and revelation with antihuman IgG-peroxidase conjugate. Antiphospholipid antibodies were found to be present in the BAL fluid as well as in the serum from a patient with APS. Specifically, antiphosphatidylserine and antiphosphatidic acid IgG antibodies in the BAL fluid and antiphosphatidylcholine and anticardiolipin IgG antibodies in the serum were detected at high levels. BAL fluid protein and the percentage of neutrophils were found to be increased. A quantitative as well as qualitative deficiency of surfactant phospholipids was also observed. Antibodies directed against surfactant phospholipids could cause surfactant abnormalities and an inflammatory reaction. These disorders may be one of the causes of the ARDS or a factor in the perpetuation of the inflammation.

The effect of chitosan on stiffness and glycolytic activity of human bladder cells

The cell's cytoskeleton together with the cell membrane and numerous accessory proteins determines the mechanical properties of cell. Any factors influencing cell organization and structure can cause alterations in mechanical properties of cell (its ability for deformation and adhesion). The determination of the local elastic properties of cells in their culture conditions has opened the possibility for the measurement of the influence of different factors on the mechanical properties of the living cells. The effect of the chitosan on the stiffness of the non-malignant transitional epithelial cells of ureter (HCV 29) and the transitional cell cancer of urine bladder (T24) was determined using scanning force microscopy. The investigations were performed in the culture medium (RPMI 1640) containing 10% fetal calf serum in the presence of the microcrystalline chitosan of the three different deacetylation degrees. In parallel, the effect of chitosan on production of lactate and ATP level was determined. The results showed the strong correlation between the decrease of the energy production and the increase in Young's modulus values obtained for the cancer cells treated with chitosan.

Elasticity of normal and cancerous human bladder cells studied by scanning force microscopy

Scanning force microscopy was used for the determination of the elastic properties of living cells in their culture conditions. The studies were carried out on human epithelial cells. Two similar lines of normal cells (Hu609 and HCV29) and three cancerous ones (Hu456, T24, BC3726) were measured using the scanning force microscope in order to collect the force versus indentation curves. The BC3726 line originates from the HCV29 cell line which was transformed by the v-ras oncogene. To evaluate their elastic properties, Young's modulus values were determined. The present study has shown that normal cells have a Young's modulus of about one order of magnitude higher than cancerous ones. Such a change might be attributed to a difference in the organisation of cell cytoskeletons and requires further studies.

Proteins and phospholipids in BAL from patients with hydrostatic pulmonary edema

The purpose of the present study is twofold: to evaluate alterations in total phospholipid content and individual phospholipid classes of the surfactant, and to detect markers of inflammatory reaction in bronchoalveolar lavage (BAL) from patients with hydrostatic pulmonary edema (HPE). Mechanically ventilated patients with HPE (Group 1) were compared with mechanically ventilated patients without cardiopulmonary disease (Group 2), considered as the control group. Group 3, including patients with high-permeability pulmonary edema, was used for further comparison. BAL was obtained and immediately cooled at 4 degrees C. Total proteins, albumin, and platelet-activating factor--acetylhydrolase (PAF-AcH) were measured. Total lipids were extracted and analyzed after thin-layer chromatographic separation. PAF was determined with bioassay. Total BAL proteins and albumin were found significantly higher in patients with HPE compared with control, but were lower compared with adult respiratory distress syndrome (ARDS). PAF was elevated in patients with HPE and ARDS, whereas in the control group it was actually in nondetectable levels. PAF was significantly higher in ARDS than in HPE patients. BAL neutrophils concentration was higher in HPE compared with control, but lower compared with ARDS. There was an inverse correlation between PAF-AcH and PAF. Quantitative reduction of total BAL phospholipids (PL) and qualititative deficiency was observed in both patients with HPE and ARDS. The findings of this study suggest that there is evidence of inflammation in the airspaces of patients with HPE.

Rapid tracheal infusion of surfactant versus bolus instillation in rabbits: effects on oxygenation, blood pressure and surfactant distribution

Surfactant bolus instillation may be associated with a drop in blood pressure. Platelet-activating factor (PAF) has been found in surfactant preparations. The aim of this study was to evaluate rapid tracheal infusion of surfactant during 5 min as an alternative to bolus instillation and to examine whether a PAF receptor antagonist is able to prevent the decrease in blood pressure.

METHODS

Surfactant deficiency was induced in 16 adult rabbits by lung lavages with saline. Six animals received a bolus of a porcine surfactant preparation (Curosurf (CS); 200 mg/kg), labeled with red microspheres to assess pulmonary distribution. In another 5 rabbits, the same amount of labelled CS was instilled by tracheal infusion within 5 min. A third group of 5 animals received 3 mg/kg body weight of the PAF antagonist WEB 2170 before CS bolus instillation.

RESULTS

After CS bolus administration, mean PaO2 increased by 44.7 +/- 8.3 kPa (mean +/- SD) within 2 min and remained at this level. Mean arterial blood pressure dropped transiently by 2.3 +/- 2 kPa within 5 min. Pulmonary distribution of surfactant was even. After infusion, mean PaO2 rose by 22.4 +/- 16.3 kPa within 15 min. Blood pressure dropped by 1.8 +/- 1.1 kPa within 15 min. The distribution was extremely uneven. Blood pressure decreases also occurred after pretreatment with PAF receptor antagonist.

CONCLUSION

Rapid tracheal infusion of surfactant results in poorer oxygenation, an inhomogeneous distribution and a similar decrease in blood pressure compared to the bolus instillation method. Blood pressure changes could not be prevented by a PAF receptor-specific antagonist.

Surface characterization of ceramic brackets: a multitechnique approach

The purpose of this study was to investigate the microstructure and bonding mechanisms for four types of ceramic brackets by using information from several methods. Two of the bracket types provided exclusively micromechanical retention as a bonding mechanism, with the use of microspheres or microcrystals to achieve a rough structure for the bracket base. A silane layer that provided chemical adhesion was found to cover the bases of the two other types of brackets; one type also used central regions of increased roughness to provide additional micromechanical retention. Polarized-light optical microscopy showed that the silane layer was not continuous. Small area x-ray photoelectron spectroscopy analysis (SAXPS) of the silane layer was consistent with the presence of gamma-methacryloxypropyl trimethoxysilane. The study of the ceramic bracket bases revealed a wide variety in composition, structure, morphologic condition, and coating treatment that implies different bonding mechanisms to orthodontic adhesives.

Failure mode analysis of ceramic brackets bonded to enamel

The purpose of this study was to evaluate in vitro the failure pattern of ceramic brackets bonded to enamel with a light-cured orthodontic adhesive. Five types of ceramic brackets and 125 incisors were used in the study. The brackets were bonded onto enamel with a light-cured orthodontic adhesive. After 1 week storage and thermal cycling, the samples were debonded by one operator according to the individual technique for each bracket group proposed by each manufacturer. The fracture surfaces were examined under a stereomicroscope to reveal the type of failures. The effect of the debonding procedure on enamel structure was significantly affected by the various bonding mechanisms of the bracket bases. Cohesive enamel fractures were detected from brackets that provided a bonding mechanism of micromechanical retention and chemical adhesion. The brackets that combined mechanical retention and chemical adhesion, presented both cohesive resin fractures and fractures located at the bracket resin or the resin enamel interface. The higher frequency of cohesive bracket fractures was obtained from a monocrystalline bracket.

Isolation of a phospholipid inhibitor of platelet activating factor-induced activity from perfused rat liver: identification as phosphatidylglycerol

An endogenous inhibitor of platelet activating factor action was isolated from perfused rat liver. It was purified by thin-layer chromatography and high-performance liquid chromatography and subjected to chemical modifications in order to identify its structure. On the basis of its fast atom bombardment-mass spectrum it was characterized as phosphatidylglycerol composed mainly of 16:0/18:1 and 16:0/20:2 fatty acyl chains ([M+H]+ at m/z 749 and 775, respectively) and very minor levels of 18:0/18:1 and 18:0/20:2. The purified compound exhibited inhibition on rabbit platelet aggregation induced by 5 x 10(-10) M platelet activating factor (PAF) at an EC50 value near 2.5 x 10(-6) M and on the serotonin secretion at an EC50 7 x 10(-6) M. Other phospholipids isolated from the liver preparations, such as phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, sphingomyelin, cardiolipin (diphosphatidylglycerol), and phosphatidic acid, exhibited no inhibitory activity in the concentration range from 1 x 10(-4) to 1 x 10(-7) M nor did they induce any aggregation, or lysis, of the platelets. Of importance, phosphatidylglycerol could inhibit thrombin- and ADP-induced aggregation of rabbit platelets. These results suggested a possible site of inhibition common to the signal transduction pathway of these agonists. Preliminary binding experiments showed a noncompetitive type of inhibition on PAF binding to intact rabbit platelets.