Mechanosensing at the Nuclear Envelope by Nuclear Pore Complex Stretch Activation and Its Effect in Physiology and Pathology

Cell fate is correlated to mechanotransduction, in which forces transmitted by the cytoskeleton filaments alter the nuclear shape, affecting transcription factor import/export, cells transcription activity and chromatin distribution. There is in fact evidence that stem cells cultured in 3D environments mimicking the native niche are able to maintain their stemness or modulate their cellular function. However, the molecular and biophysical mechanisms underlying cellular mechanosensing are still largely unclear. The propagation of mechanical stimuli via a direct pathway from cell membrane integrins to SUN proteins residing in the nuclear envelop has been demonstrated, but we suggest that the cells’ fate is mainly affected by the force distribution at the nuclear envelope level, where the SUN protein transmits the stimuli via its mechanical connection to several cell structures such as chromatin, lamina and the nuclear pore complex (NPC). In this review, we analyze the NPC structure and organization, which have not as yet been fully investigated, and its plausible involvement in cell fate. NPC is a multiprotein complex that spans the nuclear envelope, and is involved in several key cellular processes such as bidirectional nucleocytoplasmic exchange, cell cycle regulation, kinetochore organization, and regulation of gene expression. As several connections between the NPC and the nuclear envelope, chromatin and other transmembrane proteins have been identified, it is reasonable to suppose that nuclear deformations can alter the NPC structure. We provide evidence that the transmission of mechanical forces may significantly affects the basket conformation via the Nup153-SUN1 connection, both altering the passage of molecules through it and influencing the state of chromatin packing. Finally, we review the known correlations between a pathological NPC structure and diseases such as cancer, autoimmune disease, aging and laminopathies.

Multi-Scale Analysis of the Toraymyxin Adsorption Cartridge Part II: Computational Fluid-Dynamic Study

Extracorporeal endotoxin removal by means of the Toraymyxin device is based on the ability of polymyxin B to bind endotoxins with a high specificity. The endotoxins/polymyxin molecular interactions were computationally analyzed in a parallel work (Part I). In this paper we investigate with a multi-scale approach the phenomena involving blood and plasma fluid dynamics inside the device. The macro- and mesoscale phenomena were studied by means of 3D models using computational fluid dynamics. The flow behavior in the sorbent material was focused, modeling the sorbent as a homogeneous porous medium at the macroscale level, or accounting for the realistic geometry of its knitted fibers at the mesoscale level. A microscale model was then developed to analyze the behavior of endotoxin molecules subjected to the competition of flow drag and molecular attraction by fibergrafted polymyxin B. The macroscale results showed that a very regular flow field develops in the sorbent, furthermore supplying the peak velocity to be input in the lower-scale model. The mesoscale analysis yielded the realistic range for wall shear stresses (WSSs) acting on fiber walls. With WSS values in the entire range, the results of the microscale analysis demonstrated that the capability of polymyxin B to capture endotoxin molecules from the flow extends at distances one order of magnitude greater than the characteristic distance of the stable intermolecular bond. We conclude that the use of an integrated, multi-scale analysis allows for a comprehensive understanding of the complex mechanisms involved in endotoxin sorption phenomena with immobilized polymyxin B.

Electrical conditioning of adipose-derived stem cells in a multi-chamber culture platform

In tissue engineering, several factors play key roles in providing adequate stimuli for cells differentiation, in particular biochemical and physical stimuli, which try to mimic the physiological microenvironments. Since electrical stimuli are important in the developing heart, we have developed an easy-to-use, cost-effective cell culture platform, able to provide controlled electrical stimulation aimed at investigating the influence of the electric field in the stem cell differentiation process. This bioreactor consists of an electrical stimulator and 12 independent, petri-like culture chambers and a 3-D computational model was used to characterize the distribution and the intensity of the electric field generated in the cell culture volume. We explored the effects of monophasic and biphasic square wave pulse stimulation on a mouse adipose-derived stem cell line (m17.ASC) comparing cell viability, proliferation, protein, and gene expression. Both monophasic (8 V, 2 ms, 1 Hz) and biphasic (+4 V, 1 ms and -4 V, 1 ms; 1 Hz) stimulation were compatible with cell survival and proliferation. Biphasic stimulation induced the expression of Connexin 43, which was found to localize also at the cell membrane, which is its recognized functional mediating intercellular electrical coupling. Electrically stimulated cells showed an induced transcriptional profile more closely related to that of neonatal cadiomyocytes, particularly for biphasic stimulation. The developed platform thus allowed to set-up precise conditions to drive adult stem cells toward a myocardial phenotype solely by physical stimuli, in the absence of exogenously added expensive bioactive molecules, and can thus represent a valuable tool for translational applications for heart tissue engineering and regeneration.

A dynamic distention protocol for whole-organ bladder decellularization: histological and biomechanical characterization of the acellular matrix

A combined physical-chemical protocol for whole full-thickness bladder decellularization is proposed, based on organ cyclic distention through repeated infusion/withdrawal of the decellularization agents through the urethra. The dynamic decellularization was intended to enhance cell removal efficiency, facilitating the delivery of detergents within the inner layers of the tissue and the removal of cell debris. The use of mild chemical detergents (hypotonic solution and non-ionic detergent) was employed to limit adverse effects upon matrix 3D ultrastructure. Inspection of the presence of residual DNA and RNA was carried out on decellularized matrices to verify effective cell removal. Histological investigation was focused on assessing the retention of adequate structural and functional components that regulate the biomechanical behaviour of the acellular tissue. Biomechanical properties were evaluated through uniaxial tensile loading tests of tissue strips and through ex vivo filling cystometry to evaluate the whole-organ mechanical response to a physiological-like loading state. According to our results, a dynamic decellularization protocol of 17 h duration with a 5 ml/min detergent infusion flow rate revealed higher DNA removal efficiency than standard static decellularization, resulting in residual DNA content < 50 ng/mg dry tissue weight. Furthermore, the collagen network and elastic fibres distribution were preserved in the acellular ECM, which exhibited suitable biomechanical properties in the perspective of its future use as an implant for bladder augmentation.

Capsule endoscopy of the small bowel in the clinical practice: outpatient management is feasible and cheaper

AIM

Four Italian regions have cost coding for outpatient capsule-endoscopy. Elsewhere it is performed in ordinary hospital admission. To identify, in a cohort of patients of a Gastroenterology Unit, those feasible for outpatient versus inpatient treatment; to analyze costs distribution in both management areas.

METHODS

We retrospectively analysed 100 clinical records of admissions to A.O. San-Carlo-Borromeo, Milan between 2005-2008. Hospitalization criteria (at least 3): 1) occult/obscure gastrointestinal bleeding; 2) hemoglobin ≤ 8 gr/dL; 3) indication for blood transfusions; 4) urgent hospital admission.

RESULTS

A total of 62 patients had urgent admission, 60 blood transfusions, 81 underwent EGD and colonoscopy, 8 enteroscopy and 5 surgery. Mean haemoglobin value was 8.67 g/dL. Capsule-endoscopy was positive in 70, uncertain in 8, negative in 22. Positive cases: 33 angiodyplasia, 18 ulcers/erosions, 13 polyps/masses, 5 overt bleeding, 1 celiac disease. 47/100 were appropriate as outpatient, saving 432 days of hospital stays. Admission coding was grouped into 7 DRGs (overall expense: 98,366 Euros). Considering EGD/colonoscopy outpatient costs and 1.100 euros as estimated value for capsule-endoscopy, the total expense could be 53.919.

CONCLUSION

Outpatient capsule-endoscopy small bowel examination is feasible in half of the cases. It is cost saving, (about 45.000 Euros/100 patients), reducing inappropriate hospital stays.

Mechanisms of polymyxin B endotoxin removal from extracorporeal blood flow: molecular interactions

The outer leaflet of Gram-negative bacteria membrane contains a great amount of lipopolysaccharides, also known as endotoxins, which play a central role in the pathogenesis of septic shock. It has been demonstrated that the polymyxin B (PMB) molecule has both antibacterial and antiendotoxin capabilities; in fact, it is able to compromise the bacterial outer membrane and bind lipopolysaccharides, thereby neutralizing its toxic effects. Extracorporeal hemoperfusion treatments based on cartridges containing PMB-immobilized fibers (Toraymyxin PMX-F; Toray Industries, Tokyo, Japan) are used to remove endotoxins circulating in the blood flow. In this study, we focused on the characterization of the interactions occurring in the formation of the PMB-endotoxin complex at the molecular level. In particular, the molecular mechanics approach was used to evaluate the interaction energy and eventually the interaction force between the two molecules. PMB was faced with five molecular portions of lipopolysaccharides differing in their structure. The interaction energy occurring for each molecular complex was calculated at different intermolecular distances and the binding forces were estimated by fitting interaction energy data. Results show that the short-range interactions between PMB and endotoxins are mediated mainly by hydrophobic forces, while in the long term, the complex formation is driven by ionic forces only. Maximum binding forces calculated via molecular mechanics for the PMB-endotoxin complex are in the range of 1.39-3.79 nN. Understanding the interaction mechanism of the single molecular complex is useful both in order to figure out the molecular features of such interaction and to perform higher scale level analysis, where such nanoscale detail is impractical but could be used to account for molecular behavior at a coarse level of discretization.

Gastroenterology in Italian clinical practice. The RING Study: six years' data from gastroenterology departments

AIM

Computer systems in hospitals provide information on the work of each single operative unit and the complexity of its caselist. However, in Italy, there is no official data-base for Gastroenterology Departments, to summarize their work.

METHODS

The RING (Ricerca-INformatizzata-in-Gastroenterologia) study has collected, through a software made on purpose, 113 237 hospital discharge files (HDF) from 55 Italian hospital Gastroenterology Units, since 2001. This caselist provides a picture of the patients and is useful for clinical/management evaluation.

RESULTS

Between January 2001 and December 2006, 55 Gastroenterology Units gathered 88240 HDF referring to ''ordinary admissions''. The male:female rate was 1:1, mean age was 61.3+/-18.5 years. Mean hospital stay was around eight days. Over the years there was a significant drop in DRG183 (miscellaneous digestive disorders-without complications) from 11.5% to 7.4% (P<0.0001), with no similar increase in DRG182 (with complications) which rose from 3.1% to 4.0%. Principal discharge diagnoses are post-hepatic and alcohol-related cirrhosis, hepatocarcinoma, acute pancreatitis, duodenal/gastric ulcer.

CONCLUSIONS

The RING data show that the gastroenterologist has been working increasingly with patients whose pathologies would have been ''inappropriately'' treated surgically (DRGs 204 and 174). Inappropriate gastroenterological treatment seems to have decreased as well as the DRG183 with no apparent ''opportunistic'' compensatory increase in DRGs with complications, such as 182.

Management and outcomes of hepatic cirrhosis: Findings from the RING study

BACKGROUND/AIM

Hepatic cirrhosis is a frequent reason for ordinary hospital admission (OA). The RING study collected hospital discharge files (HDF) from Italian hospital gastroenterology units (IGU). This caselist provides a broad picture of the patients admitted for this pathology.

MATERIAL/METHODS

More than 50,000 HDF for OA were collected between 2001 and 2004 from 26 IGU.

RESULTS

Eight thousand four hundred and eighty-seven HDF (16%) had a diagnosis of hepatic cirrhosis; Child-Pugh classes were 20.2% A, 34.8% B and 45.0% C. Patients' mean age was 63.7+/-12.1 years and 62.5% were male. A 61.1% of the cirrhosis cases had ascites, 29.9% portal-systemic encephalopathy, 29.2% hepatocellular carcinoma (HCC), 10% bleeding varices, 3.0% hepatorenal syndrome (HRS). Mortality for OA for cirrhosis was 5.7% versus 2.6% for other diagnoses. The proportion varied with the severity of the cirrhosis: 0% for Child A, 1.1% B, 10.5% C. Mortality was significantly associated with: Child-Pugh at admission (odds ratio: OR 9.2), HRS (OR 11.7), bleeding varices (OR 2.2), HCC (OR 1.8).

CONCLUSIONS

Hepatic cirrhosis was found in 16% of the OA to IGU and mortality was double the rate for all the other pathologies in the same wards. Child-Pugh is a useful prognostic tool, higher classes implying a greater risk of death. HRS and bleeding varices were the complications with most influence on in-hospital mortality.

Seasonal patterns of hospital treatment for inflammatory bowel disease in Italy

AIM

It is still debated whether clinical flare-ups of chronic inflammatory bowel disease follow a seasonal pattern, and the various reports are based on general practitioners' records or hospital discharge charts. There are, however, no specific figures for treatment in hospital gastroenterology units, which serve as a reference point for these disorders. This study was therefore designed to investigate whether there is a seasonal pattern in admissions for inflammatory intestinal disease in Italy, differing from what is generally known about gastrointestinal pathologies, since there are no nation-wide figures on the subject.

METHODS

The RING (Ricerca Informatizzata in Gastroenterologia) project is an observational study collecting hospital discharge forms from 22 centers in Italy.

RESULTS

From winter 2000 to autumn 2003, the 22 gastroenterology units participating in the RING project discharged 32,357 patients following ordinary hospital admissions. Of these, 2,856 (8.8%) had a main diagnosis of inflammatory bowel disease: 1,541 Crohn's disease, and 1,315 ulcerative colitis. No seasonal patterns were detected for either category, or when the analysis was done by age, sex and site of disease.

CONCLUSIONS

The most serious flare-ups of inflammatory bowel disease, i.e. those requiring routine hospital treatment, do not appear to follow any seasonal pattern, regardless of the site of the disease or the patient's age or sex.

Multi-scale analysis of the toraymyxin adsorption cartridge. Part I: molecular interaction of polymyxin B with endotoxins

Endotoxins or lipopolysaccharides are the main constituents of the outer leaflet of Gram-negative bacteria membrane and play a central role in the pathogenesis of the septic shock. Polymyxin B has both antibacterial and antiendotoxin capability; indeed it is able to destroy the bacterial outer membrane and bind endotoxin neutralizing its toxic effects. Cartridges containing polymyxin B-immobilized fibers (Toraymyxin PMX-F, Toray Industries, Japan) are used in extracorporeal hemoperfusion to remove circulating endotoxin. The aim of this study is the characterization of the polymyxin B-endotoxin system at the molecular level, thus providing quantitative evaluation of the binding forces exerted in the molecular complex. Polymyxin B was interfaced with five molecular models of lipopolysaccharides differing in their structure and molecular mechanics simulations were performed at different intermolecular distances aimed at calculating the interaction energies of the complex. Binding forces were calculated by fitting interaction energies data. Results show that in the short range the polymyxin B-endotoxin complex is mediated by hydrophobic forces and in the long range the complex is driven by ionic forces only. From a mechanical standpoint, polymyxin B-endotoxin complex is characterized by maximum binding forces ranging between 1.39 nN to 3.79 nN. The knowledge of the binding force behavior at different intermolecular distances allows further investigations at higher scale level (Part II).

A numerical and experimental study of compliance and collapsibility of preterm lamb tracheae

Knowledge of the mechanical behaviour of immature tracheae is crucial in order to understand the effects exerted on central airways by ventilatory treatments, particularly of Total Liquid Ventilation. In this study, a combined experimental and computational approach was adopted to investigate the compliance and particularly collapsibility of preterm lamb tracheae in the range of pressure likely applied during Total Liquid Ventilation (-30 to 30 cmH2O). Tracheal samples of preterm lambs (n = 5; gestational age 120-130 days) were tested by altering transmural pressure from -30 to 30 cmH2O. Inflation (Si) and collapsing (Sc) compliance values were calculated in the ranges 0 to 10 cmH2O and -10 to 0 cmH2O, respectively. During the tests, an asymmetric behaviour of the DeltaV/V0 vs. P curves at positive and negative pressure was observed, with mean Si = 0.013 cmH2O(-1) and Sc = 0.053 cmH2O(-1). A different deformed configuration of the sample regions was observed, depending on the posterior shape of cartilaginous ring. A three-dimensional finite-element structural model of a single tracheal ring, based on histology measurements of the tested samples was developed. The model was parameterised in order to represent rings belonging to three different tracheal regions (craniad, median, caudal) and numerical analyses replicating the collapse test conditions were performed to evaluate the ring collapsibility at pressures between 0 and -30 cmH2O. Simulation results were compared to experimental data to verify the model's reliability. The best model predictions occurred at pressures -30 to -10 cmH2O. In this range, a model composed of median rings best interpreted the experimental data, with a maximum error of 2.7%; a model composed of an equal combination of all rings yielded an error of 12.6%.

Pressure drop vs flow relationship in isolated preterm lamb tracheae

Knowledge of immature tracheae mechanical behavior is fundamental in understanding the effects exerted on the upper airways by tidal liquid ventilation (TLV). Particularly, negative pressure can take place along the airways during expiration, which can cause airway collapse and flow limitation; therefore, representing a critical issue in preterm infant patients, whose airways are less stiff than adult ones. In this study, we investigated the expiratory pressure drop vs flow relationship of isolated preterm lamb tracheal samples to determine their hydraulic resistance, collapse pressure and collapse flow rate; a liquid flow through the samples was obtained by applying negative pressure at the outlet (cephalad) extremity of the tra-cheal sample, while keeping the inlet (caudal) extremity at atmospheric pressure. Histological analyzes were performed on the tracheal samples after each test session, in order to examine the morphological structure of the tracheal wall. Flow resistance tests demonstrated progressive lumen narrowing at increasing pressure drop (&#8710;P=P in -P out ). The flow rate increased with &#8710;P un-til a plateau was reached, and then decreased, describing the onset of a collapse phenomenon; however, complete occlusion was not reached. The tracheal samples demonstrated a similar behavior to that of a Starling resistor during the collapse phase: when a critical &#8710;P was reached, collapse was observed starting at the outlet region, which was subjected to the greatest negative pressure, then propagating towards the caudal direction. (Journal of Applied Biomaterials & Biomechanics 2004; 2: 177-82).

Myosin head mechanical performance under different conformational change mechanisms

The present paper puts forward a mathematical approach to model the conformational changes of the myosin head due to ATP hydrolysis, which determine the head swinging and consequent sliding of the actin filament. Our aim is to provide a simple but effective model simulating myosin head performance to be integrated into the overall model of sarcomere mechanics under development at our Laboratory (J. Biomech. 34 (2001) 1607). We began by exploring myosin head mechanics in recent findings about myosin ultrastructure, morphology and energetics in order to calculate the working stroke distance (WS) and the force transmitted to the actin filament during muscle contraction. Two different working stroke mechanisms were investigated, assuming that the swinging of the myosin head occurs either as a consequence of purely conformational changes (Science 261 (1993a) 58) or by thermally driven motion (ratchet mechanism) followed by conformational changes (Cell 99 (1999) 421). Our results show that force and WS values vary markedly between the two models. The maximum force generated is about 10 pN for the first model and 31 pN for the second model, and the WSs are about 13 and 4 nm, respectively. These results are then discussed and compared with published data. The experimental data used for comparison are scarce and non-homogeneous; hence, the final remarks do not lead to definite conclusions. In any event, relatively speaking, the first model is more coherent with experimental findings.

Finite element analysis of a knee joint replacement during a gait cycle

A three-dimensional (3-D) computer model was developed to predict, simultaneously, the knee joint replacement motions and the stresses occurring within the tibial insert under complex loading conditions. Friction contacts, polyethylene elastic- plastic behavior and soft tissue restraints were considered. Finite element analysis of the entire gait cycle was performed applying the displacement and loading conditions reported in the draft ISO 14243-1. The 3-D model was used to predict contact stresses and areas occurring within the polyethylene insert, when static loads of single instants on the gait cycle were applied. Results at 13% and 46% of the gait cycle were calculated with both entire cycle sim-ulation and single instant simulations. The predicted peak contact stress and contact area values were greater for single in-stant analyzes (respectively, 21% and 9%) if compared with those of the entire cycle simulation. In addition, single instant simulations were unable to predict accurately the contact region location, which was displaced in the anterior direction. Two different configurations of soft tissue restraints were compared; the first adopted from the draft ISO 14243-1 and the second from literature data. There were no significant differences observed between the two configurations. In particular, peak contact stresses followed the same trend, although the restraints of the literature data provided lower values in the last phase of the gait cycle. A preliminary verification of model reliability was performed comparing the tibial insert motions with data reported in the literature, under simplified loading conditions applied to the femoral component. (Journal of Applied Biomaterials & Biomechanics 2004; 2: 45-54).

Inflammatory bowel disease and hospital treatment in Italy: the RING multi-centre study

AIM

To explore the management of chronic inflammatory bowel disease, specifically Crohn's disease and ulcerative colitis, in Italian gastroenterology units.

METHODS

The RING (Ricerca Informatizzata in Gastroenterologia) project is an observational study collecting hospital discharge forms from 56 centres. Factors associated with the length of hospital stay were studied using multivariate logistic regression.

RESULTS

In 24 months starting from August 2000, out of 29,376 hospital discharge forms, 2131 (7.3%) were collected for inflammatory bowel disease (1163 for Crohn's disease and 968 for ulcerative colitis). The Crohn's disease and ulcerative colitis groups were compared according to demographic characteristics, diagnoses, procedures and hospital stay. In Crohn's disease, computed tomography/magnetic resonance imaging, x-rays/barium enema, number of procedures and number of diagnoses were significantly associated with a hospital stay longer than 10 days. In ulcerative colitis, this association was found for parenteral nutrition, malnutrition, computed tomography/magnetic resonance imaging and number of procedures.

CONCLUSIONS

Crohn's disease was confirmed as a disabling disorder requiring more frequent hospital treatment than ulcerative colitis. For the latter, parenteral nutrition and malnutrition were related to a longer hospital stay. The number of procedures, especially abdominal computed tomography/magnetic resonance imaging, was a major item for both pathologies.

Possible role of decorin glycosaminoglycans in fibril to fibril force transfer in relative mature tendons—a computational study from molecular to microstructural level

Experimental studies on immature tendons have shown that the collagen fibril net is discontinuous. Manifold evidences, despite not being conclusive, indicate that mature tissue is discontinuous as well. According to composite theory, there is no requirement that the fibrils should extend from one end of the tissue to the other; indeed, an interfibrillar matrix with a low elastic modulus would be sufficient to guarantee the mechanical properties of the tendon. Possible mechanisms for the stress-transfer involve the interfibrillar proteoglycans and can be related to the matrix shear stress and to electrostatic non-covalent forces. Recent studies have shown that the glycosaminoglycans (GAGs) bound to decorin act like bridges between contiguous fibrils connecting adjacent fibril every 64-68 nm; this architecture would suggest their possible role in providing the mechanical integrity of the tendon structure. The present paper investigates the ability of decorin GAGs to transfer forces between adjacent fibrils. In order to test this hypothesis the stiffness of chondroitin-6-sulphate, a typical GAG associated to decorin, has been evaluated through the molecular mechanics approach. The obtained GAG stiffness is piecewise linear with an initial plateau at low strains (<800%) and a high stiffness region (3.1 x 10(-11)N/nm) afterwards. By introducing the calculated GAG stiffness in a multi-fibril model, miming the relative mature tendon architecture, the stress-strain behaviour of the collagen fibre was determined. The fibre incremental elastic modulus obtained ranges between 100 and 475 MPa for strains between 2% and 6%. The elastic modulus value depends directly on the fibril length, diameter and inversely on the interfibrillar distance. In particular, according to the obtained results, the length of the fibril is likely to play the major role in determining stiffness in mature tendons.

Molecular detection of cell line cross-contaminations using amplified fragment length polymorphism DNA fingerprinting technology

We have tested amplified fragment length polymorphism (AFLP) technology, in comparison with isoenzyme analysis, for the simultaneous detection of inter- and intraspecific cell line cross-contaminations (CCCs) in the cell line collection held at the Istituto Zooprofilattico della Lombardia e dell'Emilia Romagna. Isoenzyme analysis identified four cases of interspecific CCCs. In a single experiment, AFLP was able to identify the species of origin of all cell lines for which a reference genomic deoxyribonucleic acid was available and to detect five interspecific contaminations. Four CCCs confirmed data on isoenzymes, whereas the fifth CCC was detected in a species for which isoenzyme analysis was noninformative. In addition, AFLP was able to identify the putative source of the contaminations detected. The utility of the technology in the detection of intraspecific cell line contaminations depends on the number of cell lines that have to be distinguished in a specific species and on the availability of highly informative fingerprinting systems. In mice, a single AFLP primer pair produced 16 polymorphisms and distinguished all the 15 strains of mouse cell lines analyzed. In humans, 18 AFLPs identified 83 different profiles in the 159 cell lines analyzed. Amplified fragment length polymorphism can conveniently be applied for cell line fingerprinting in species for which hypervariable markers are not available. In species for which a highly informative multiplex of microsatellite markers is available, AFLP can still provide a useful and cheap tool for simultaneously testing inter- and intraspecific contaminations.

Establishment and characterization of two new pig cell lines for use in virological diagnostic laboratories

Two pig cell lines derived from kidney and trachea tissues and referred to as newborn swine kidney (NSK) and newborn pig trachea (NPTr) were established following serial culture of primary cells. They were characterized by an epithelial-like morphology, high capacity to replicate and stability of the cell monolayer for several days after seeding. Their modal chromosome number was modified in comparison to that of primary swine cells and they both displayed a transforming potential in vitro and displayed oncogenicity in nude mice. Infection with pig endogenous retroviruses was detected. Almost all the swine viruses tested, i.e., pseudorabies virus, pig parvovirus, hog cholera virus, transmissible gastroenteritis virus of swine, encephalomyocarditis virus, swine vesicular disease virus and the enteroviruses, except pig reproductive respiratory syndrome virus, were capable of replicating in the new cell lines with titres similar to the ones detected in the reference culture systems. Furthermore, all the selected influenza virus sub-types isolated from human, swine and avian species replicated with cytopathic effect in NSK and NPTr cells, whereas, of all the equine influenza viruses tested only the Miami and Suffolk sub-types replicated.

Myosin cross-bridge mechanics: geometrical determinants for continuous sliding

Advances in experimental techniques have provided new details on the molecular mechanisms governing the cross-bridge kinetics. Nevertheless, the issue of micromechanics of sliding is still debated. In particular, uncertainty exists regarding the myosin filament arrangement and structure and the mechanics of the myosin head with respect to the working stroke distance (WS) and the duty ratio (r), i.e. the fraction of the ATPase cycle time the myosin head is attached to the actin filament. The object of the present work is to provide a theoretical framework to correlate different features of cross-bridge mechanics; the main hypothesis is that the attachment between the actin filament and the surrounding myosin filaments has to be continuous through the sliding (continuous sliding hypothesis) in order to maximise the effect of the myosin head performance. A 3-D model of the sliding mechanism based on a geometrical approach is presented, which is able to identify the architectures that accomplish the continuous sliding under unloaded conditions. About 200 different configurations have been simulated by changing the myosin head binding range, i.e. its ability to reach an actin binding site from its rest position, WS, the myosin head orientation and the actin filament orientation. Only few configurations were consistent with the continuous sliding hypothesis. Depending on the parameter set adopted, the percentage of attached heads (%AH) calculated ranges between 4% and 28%, r between 0.08 and 0.02s(-1), and the sliding velocity between 0.7 and 10.6 microm/s. In all the cases, results were not affected by the WS value.

Experimental and computational approach for the evaluation of the biomechanical effects of dental bridge misfit

Dental bridges supported by osseointegrated implants are commonly used to treat the partially or completely edentulous jaw. The bridges are manufactured in metal alloy using a sequence of technological steps which well match the requirement to get custom overstructures but does not guarantee geometrical and dimensional tolerances. Dentists often experience that a perfect fit of the bridge with the abutments is almost impossible to achieve. When a misfitting bridge is forced on the abutments, deformations may occur inducing a permanent preload at the fixture-bone interface and the greater the misfit the greater is the preload and the risk of implant failure. This work gives an evaluation of the biomechanical effects induced by a misfitting bridge when forced on two supporting dental implants. The strains induced in the bridge have been measured using two purposely designed and fabricated experimental devices allowing different types of misfit. FEM 3D models of the bridge and of the bridge anchored to the bone by implants have been developed. The former has been validated by simulating the same loading conditions as in the experimental tests and comparing the bridge strains. Both models have been used for the evaluation of the stress induced in the bridge and at the fixture-bone interface by bridge length errors. The results show that the method may help to estimate the stress distribution in the bridge and bone as a consequence of different dental bridge misfits.

Prognostic significance of markers of thrombin generation in the acute and chronic phases of non cardioembolic ischemic stroke

BACKGROUND

Previous studies have shown there is activation of the hemostatic system, with thrombin generation, in the acute phase of stroke. Such an activation has unfavourable effects. It is still not known whether there is also a persistent hypercoagulability state in these patients as well as in subjects affected by acute coronary syndromes.

METHODS

To know more about the issue, we measured plasma levels of the prothrombin fragment 1 + 2 (F1 + 2) and the thrombin-antithrombin III complex (TAT) in 40 consecutive patients with first ischemic non-cardioembolic stroke; 16 matched involutive cardiomyopathy patients served as the control group. TATs and F1 + 2 were also assessed six months after the onset of stroke symptoms.

RESULTS

At baseline stroke patients had higher values than controls of both F1 + 2 and TAT (F1 + 2: 2.38 +/- 2.30 nmol/l vs 1.20 +/- 0.50; p < 0.03; TAT 16.11 +/- 19.60 ng/ml vs 5.51 +/- 4.29; p < 0.05) and these measurements were not related to the typical acute phase reactants. After 6 months F1 + 2 levels in stroke patients were still higher than controls (F1 + 2: 1.68 +/- 0.80 nmol/l vs 1.20 +/- 0.50; p < 0.05), but there were no differences from the baseline levels of F1 + 2 and TAT. According to survival curves mortality was significantly higher in patients with hypercoagulability (defined as F:1 + 2 and TAT levels more than two standard deviations above the mean).

CONCLUSIONS

These data confirm that for stroke patients there is sustained activation of the blood coagulation system like in unstable angina and myocardial infarction these abnormalites may have unfavourable prognostic significance.

Hypercoagulability and chronic atrial fibrillation: the role of markers of thrombin generation

BACKGROUND

We have studied 64 patients with congestive heart failure, half of them also with chronic nonvalvular atrial fibrillation (AF). Patients were also stratified according to a history of prior stroke.

METHODS

The generation of thrombin was investigated by means of the molecular markers prothrombin fragment 1 + 2 (F1 + 2) and thrombin-antithrombin III complex (TAT), because AF patients may have a hypercoagulable state. There was only a trend toward higher values of TAT and F1 + 2 for AF patients, while subjects with previous stroke (irrespective of AF) had increased levels of the markers of thrombin generation (TAT stroke+ 18.95 +/- 5.15 vs TAT stroke- 8.34 +/- 2.41; F1 + 2 stroke+ 2.22 +/- 0.29 vs F1 + 2 stroke- 1.32 +/- 0.12). The presence of spontaneous echo contrast (SEC) within left atrium was also investigated in 32 AF patients by transesophageal echocardiography.

RESULTS

TAT were significantly higher in subjects (n = 11) with SEC (TAT sec+ 37.5 +/- 13.41 vs TAT sec- 8.7 +/- 2.51, p = 0.008).

CONCLUSIONS

Finally, when we grouped into 1) those with both AF and stroke, 2) AF alone, 3) stroke alone and 4) sinus rhythm without stroke, levels of F1 + 2 were higher (and marginally higher TAT) in patients with AF and stroke than in those without stroke, revealing that there is a true clotting activation state in these subjects.

Fibrinolytic response in subjects with hypertriglyceridemia and low HDL cholesterol

The combination of hypertriglyceridemia and low high-density lipoprotein cholesterol (HDL-C) appears to be an excessively high risk factor for coronary artery disease (CAD). In the Helsinki study, both coronary events and mortality were decreased by gemfibrozil, especially in subjects with low HDL-C and high triglycerides (TG). On the other hand, it is known that high levels of TG can be associated with high levels of circulating plasminogen activator inhibitor (PAI), which is also a possible risk factor for CAD. The aim of the present study was to see: 1) whether the combination of low HDL-C and high TG is associated with a more impaired fibrinolytic response than in either isolated condition, and 2) whether gemfibrozil administration can improve fibrinolysis in patients with both high TG and low HDL-C. Twelve non-obese, non-diabetic subjects (eight men, four women; mean age 55 +/- 13 yrs) with low HDL-C (< 35 mg/dL men; < 45 mg/dL women) and high TG (mean 253.6 +/- 42.6 mg/dL) entered the study (Group A). Additionally fourteen comparable subjects with normal HDL-C were also investigated (Group B), plus 12 comparable subjects with isolated low HDL-C (Group C). Ten healthy people served as the control group. The following plasma fibrinolytic parameters were measured: tissue plasminogen activator antigen, PAI antigen and activity, euglobulin fibrinolytic activity (EFA) on fibrin plates, plasminogen and alpha-2-antiplasmin activities. All except the latter two values were also measured after venous occlusion (vo). In baseline conditions, patients in Groups A and B had higher EFA values before vo and higher PAI-1 antigen and alpha-2-antiplasmin levels after vo than those of controls or the subjects in Group C. The relationship between PAI antigen and PAI activity and TG was not confirmed in our population (n = 48). We also saw no interference due to HDL-C, while there was a significant relationship between EFA before vo and both TG and cholesterol. After gemfibrozil treatment (600 mg bid for 12 weeks), the lipid profiles of subjects with high TG and low HDL-C were significantly improved. There was also a slight reduction of PAI activity after vo, while the PAI-1 antigen had decreased significantly from baseline after vo (56.3 +/- 13 ng/mL before vo; 48.4 +/- 21 ng/mL after vo; P = 0.04). The higher risk of CAD in patients with low HDL-C and high TG might be in part related to impairment of fibrinolysis, which occurs in patients with isolated high TG. The close relationship existing between both TG and cholesterol levels and fibrinolytic activity confirm the key role of this latter process in the development of CAD.

Effects of two different HMG-CoA reductase inhibitors on thromboxane production in type IIA hypercholesterolemia

Many studies have found that familial hypercholesterolemia, a hyperlipoproteinemia associated with premature atherosclerosis, is characterized by enhanced platelet aggregation. This study was undertaken to measure the urinary excretion of the two main urinary thromboxane B2 (TXB2) metabolites (2, 3-dinor-TXB2 and 11-dehydro-TXB2) in 20 patients affected by familial hypercholesterolemia treated for one month with 40 mg/day of pravastatin (10 patients) in comparison to 10 normocholesterolemic subjects. After a run-in period, the type II A patients showed total cholesterol levels (296 +/- 32 mg/dL) significantly higher (P < 0.001) than those of control subjects (155 +/- 46 mg/dL). The urinary concentrations of 11-dehydro-TXB2 and 2,3-dinor-TXB2 also significantly differed (P < 0.001) between control group (1,463 +/- 1,440 and 386 +/- 447 pg/mg urinary creatinine) and treated patients (3,536 +/- 2,112 and 914 +/- 572 pg/mg urinary creatinine). At baseline there was a positive correlation between total cholesterol (TC) levels and urinary TXB2 metabolite concentrations (2,3-dinor-TXB2 r = 0.61, P < 0.02; 11-dehydro-TXB2, r = 48, P < 0.05), but not between low-density-lipoprotein cholesterol (LDL-C) and the urinary compounds. At the end of a four-week treatment. TC and LDL-C had decreased significantly from the baseline levels, by 27% and 30% in the fluvastatin group (P < 0.01) and by 23% and 31% in the pravastatin group (P < 0.01), with no significant difference between the two groups. After the two treatments with HMG-CoA reductase inhibitors, there was no statistically significant reduction of the urinary metabolite levels. In addition, the positive correlation seen at baseline between TC and TXB2 metabolites was no longer present. In accord with previous studies, we found a significant correlation between TC levels and TXB2 metabolites concentrations in type II A hypercholesterolemic patients. Although, short-term treatment with two statins reduced TC levels, it did not change the thromboxane metabolite excretion.

Hormonal and nutritional control of the fatty acid synthase promoter in transgenic mice

To study the molecular basis of tissue-specific and hormonally regulated expression of the fatty acid synthase (FAS) gene in vivo, we generated lines of transgenic mice carrying 2.1 kilobases of the 5'-flanking region (-2100 to +67) of the rat FAS gene fused to a chloramphenicol acetyltransferase (CAT) reporter gene. This reporter gene construct was strongly expressed in tissues that normally express high levels of FAS mRNA, which include liver and white adipose tissues. In contrast, CAT reporter activity was not detected in appreciable levels in lung, heart, kidney, and muscle tissues, which do not normally show significant levels of FAS activity. The relative levels of the CAT mRNA driven by the rat FAS promoter in various tissues of the transgenic animals approximated those of the endogenous mouse FAS mRNA. We also examined the hormonal and nutritional regulation of the FAS(2.1)-CAT reporter gene in transgenic mice. CAT activity was increased in both liver and white adipose tissue when fasted animals were refed a high carbohydrate, fat-free diet. These changes in CAT activity and CAT mRNA levels occurred in parallel to the changes in endogenous mouse FAS mRNA levels. On the other hand, fasting/refeeding did not change CAT activity appreciably in other tissues, such as muscle and brown adipose tissue. Administration of dibutyryl cAMP at the start of refeeding prevented an increase in CAT activity in liver. However, the cAMP effect was tissue-specific as cAMP treatment did not bring about change in CAT activity in adipose tissue. Next, to examine the effect of insulin, we made the transgenic mice insulin-deficient by streptozotocin treatment. Insulin treatment of the streptozotocin-diabetic mice increased both the CAT activity and CAT mRNA levels driven by the rat FAS promoter in liver and white adipose tissue. These changes in CAT expression by insulin paralleled those in endogenous FAS mRNA levels. Administration of glucocorticoids increased CAT activity in all tissues examined: liver, white and brown adipose tissues, lung, heart, and spleen. Overall, the first 2.1 kilobases of the 5'-flanking region of the rat FAS gene appear to contain sequence elements necessary to confer tissue-specific and hormonally regulated expression characteristic of the endogenous FAS gene.

[The new frontier of antithrombotic therapy: ASA + warfarin, the ideal solution?]

In the medical literature reports are accumulating a number of case reports suggesting the potential efficacy and safety of the combination of low-dose aspirin and warfarin to improve the efficacy of antithrombotic therapy in several clinical conditions, ranging from unstable angina to myocardial infarction. The advantages deriving from such a combination have to be considered together with its hemorrhagic risk. Thus the efficacy of such a treatment has to be proved by large clinical trials before the use of this potentially dangerous therapy can be transferred into common clinical practice.

Lipoprotein (a) and fibrinolytic system in liver cirrhosis. Coagulation Abnormalities in Liver Cirrhosis (CALC) Study Group

Several observations have suggested that lipoprotein (a) (Lp(a)) is a risk factor for coronary artery disease because of potential interference with fibrinolysis secondary to its activation of plasminogen. However, there are few data on the possible role of Lp(a) in liver cirrhosis. The present study was carried out, to better elucidate its relationship to the fibrinolytic system in liver cirrhosis. We studied the plasma levels of Lp(a) and the fibrinolytic parameters of 95 patients with liver cirrhosis (57 men, 38 women, aged 26-81). Patients in Child-Pugh class C (n = 32) had significantly lower levels of Lp(a) than those in class B (n = 45), and the class B had lower Lp(a) values than class A (n = 18) (1.4 (0.0-3.7) vs 2.9 (0.0-6.1) vs 3.4 (1.8-5.5); the data are log-transformed). Alpha-2-antiplasmin and plasminogen, had patterns similar to those of Lp(a), tissue plasminogen activator (t-PA) was significantly increased only in class C (class A: 7.5 +/- 5.8 ng/ml; class B: 10.8 +/- 7.7 ng/ml; class C: 19.1 +/- 11.3 ng/ml). Patients with systemic hyperfibrinolysis (cross-linked fibrin degradation products, XDP > 200 ng/ml) also had lower levels of Lp(a) than those without 1.6 (0.0-4.4) vs (0.0-6.1); p = 0.0002. There was a significant correlation between Lp(a) and plasminogen (r = 0.43; p = 0.001). Lipoprotein (a) progressively decreases as liver cirrhosis worsens but it appears unlikely to be involved in causing the hyperfibrinolytic state often observed in advanced liver cirrhosis, in which there are marked abnormalities of several other fibrinolytic parameters, also including increased t-PA and decreased inhibitors.

[Electro-clinical semiology of subintrant temporal lobe seizures]

The authors recorded 10 to 67 TLS (mean 29) in 10 patients (5 M, 5 F; 9 to 41 years, mean 23) during 'acute' (4-6 hours) stereo-EEG exploration. At the onset of seizures, we observed: subjective manifestations (often epigastric), autonomic symptoms, and oro-alimentary 'automatisms'. Affective, unpleasant, manifestations occurred in only 2 patients. The discharges may only affect the Ammon's horn, but they never involve only the amygdala. There is a strong relationship between the duration of the discharge, the number of cerebral structures (temporal and, later, extratemporal) involved in the discharge, and the clinical symptomatology. Somatomotor lateralized manifestations, and gestural 'automatisms' only occur when the discharges spread to extratemporal cerebral structures. The secondary generalizations are very rare and are also linked to a large extratemporal spread of the discharge.