Antinuclear antibodies positivity is not rare during multiple sclerosis and is associated with relapsing status and IgG oligoclonal bands positivity.

INTRODUCTION: As an immune-mediated disease of the central nervous system, multifaceted aspects of a humoral immune response are widely described during multiple sclerosis (MS). However, the prevalence of different auto-antibodies, such as antinuclear antibodies (ANA), during MS is very variable and their clinical relevance remains controversial. Our aim was to evaluate the prevalence and clinical correlations of ANA positivity in South Tunisian MS patients. MATERIAL AND METHODS: We performed ANA screening using indirect immunofluorescence (IIF) on HEp-2 cells (Biosystems®) in 82 MS patients. For ANA positive samples (titer ≥1/160), anti-ds-DNA detection (IIF on Crithidia luciliae (Biosystems®)) and extractable nuclear antigen typing (immunodot (Euroimmun®)) were performed. RESULTS: ANA were positive in 35/82 MS patients (42.7%). The titer was ≥1/320 in 16/35 patients. The antigenic specificity of ANA was identified in 7/35 patients. None of the patients had extra-neurological manifestations. No correlation was found between ANA and age, gender, MS course, disease duration, disability, annual relapse rate nor IgG index. ANA positivity was more frequent in patients with IgG oligoclonal bands (OCB) (47.1%) than in patients without IgG OCB (16,6%) (p=0.049). Regarding disease activity, ANA positivity was significantly more frequent in patients with relapse (52.6%) than in patients in remission (25.9%) (p=0.031). CONCLUSION: Our results showed that ANA positivity in MS disease is not rare. This positivity was not associated with clinical expression of any connective tissue disease. ANA occurrence in MS was associated with IgG OCB+ profile and relapsing status, probably reflecting an ongoing immune dysregulation.

Neuromyelitis optica spectrum disorders in South of Tunisia: A rare entity with low seroprevalence of anti-aquaporin 4 autoantibodies.

INTRODUCTION: Screening for anti-aquaporin 4 (anti-AQP4) antibodies, a specific marker of neuromyelitis optica spectrum disorders (NMOSD), is part of the immunological investigation performed in a context of central nervous system (CNS) inflammation with optic neuritis and/or myelitis. The aim of our study was to evaluate the prevalence and the diagnostic value of anti-AQP4 antibodies in Tunisian patients with such inflammatory neurological conditions. METHODS: During 3years, 170 consecutive serum samples of Tunisian patients with CNS inflammatory disorders and optico-spinal involvement were tested in our laboratory for anti-AQP4 antibodies using indirect immunofluorescence on transfected cells. RESULTS: The global seroprevalence of anti-AQP4 in our study was 4.1% (7 cases/170). The diagnosis of NMOSD was made for the 7 seropositive patients and for 2 seronegative patients, which leads to a seroprevalence of 77.7% in our NMOSD subgroup. The detection of anti-AQP4 allowed the diagnosis of NMOSD in 4 patients with incomplete clinical presentation and 5 patients with positive antinuclear antibodies. In one case, seropositivity was detected in a second sample, one year after an initial seronegativity. CONCLUSION: NMOSD seem to represent a rare etiology of optic neuritis and/or myelitis in Tunisian patients. Despite its low global seroprevalence in our study population, anti-AQP4 appears to be a very clinically relevant marker for NMOSD diagnosis. Repeating the screening in case of initial negativity could be interesting in clinical practice.

[Impact of physical disability and concomitant emotional disturbances on post-stroke quality of life]. / Impact du handicap physique et des troubles émotionnels concomitants sur la qualité de vie en post-AVC.

INTRODUCTION: The physical and/or psycho-cognitive changes after stroke may lead to a decline in the quality of life (QOL) of patients. The aims of our study were to evaluate the QOL of stroke survivors and to investigate its relationships with the physical disability degree and the emotional disorders (anxiety and depression). METHODS: We conducted a cross-sectional study, which included 147 patients, followed for stroke that had occurred over the past year, in the outpatient neurology department at the university hospital Habib Bourguiba of Sfax (Tunisia). For each patient, we collected socio-demographic characteristics and clinical and therapeutic data. The quality of life of our patients was assessed using the SF-36 scale. The HAD scale was used to screen for anxiety and depression, whereas the modified Rankin scale was used to measure the degree of disability. RESULTS: The average age of our patients was 60.58 years. The overall mean score of the SF-36 ranged from 20.81 to 89.81 with an average of 55.27. Impaired QOL was found in 68% of patients. The study of the dimensional average scores revealed that only two dimensions of the SF-36 were not altered: physical pain and life and relationship with others. The physical component was slightly more altered than the mental component (41.4 and 42.9 respectively). A minimal disability was found in 32% of patients, while a moderate and severe disability was found in 19% and 21.1% of patients. Anxiety was detected in 55.1% of patients and depression in 67.3% of them. Impaired mental component QOL was significantly correlated with the presence of anxiety (P=0.008) and depression (P<<0.05). The severe degree of disability had a significant negative impact on all areas of QOL except that of life and relationships with others. CONCLUSION: It appears from our study that among the important effects of stroke is the constant deterioration of QOL in its various dimensions. The occurrence of emotional disturbances such as anxiety and depression and the degree of physical disability seem to be predictors of QOL impairment. Therefore, special attention should be given to such patients at higher risk of decline in their QOL.

Crystal structure, optical spectroscopy and energy transfer properties in NaZnPO4:Ce3+, Tb3+ phosphors for UV-based LEDs.

A new series of Ce3+, Tb3+ singly doped and Ce3+/Tb3+ co-doped NaZnPO4 (NZPO) phosphors have been synthesized via a high-temperature solid-state reaction method at 800 °C. The crystal cell structure, luminescence proprieties, energy transfer, and chromaticity coordinates of the as-prepared phosphors were investigated in detail. The photoluminescence spectra of NZPO:Ce3+ phosphors exhibited broad emission in the 300-380 nm range, while under UV excitation, the singly doped NZPO:Tb3+ phosphor showed emission peaks at ∼485-690 nm among which the green emission peak appears at ∼543 nm. The Tb3+ green emission was significantly enhanced almost 20 times via energy transfer from Ce3+ to Tb3+. The energy transfer (ET) mechanism from Ce3+ to Tb3+ in NZPO is identified to be a resonant type via the dipole-dipole interaction mechanism with an ET efficiency of 91%. Intense green emission is obtained at very low Tb3+ concentrations under 285 nm excitation, making NZPO:Ce3+/Tb3+ an efficient UV-excited green phosphor. The NaZnPO4:Ce3+/Tb3+ phosphors are promising UV convertible materials of green light for UV -LEDs applications.

How a pilot hole size affects osteosynthesis at the screw-bone interface under immediate loading.

An inappropriate pilot hole size (PHS) is one of several factors that affects the stiffness of the screw-bone fixation. The present study uses finite element models to investigate the effect of varying the PHS on the biomechanical environment of the screw-bone interface of the fractured bone, after the screw insertion and under the immediate body weight pressure (BWP). Four PHS from 71% up to 85% of the screw external diameter (SED) were considered for analysis. A non linear material behaviour of the bone with ductile damage properties was used in the study. To validate the numerical models, an experimental pull-out test was carried out using a synthetic bone. The results of the insertion process demonstrated that the relatively smaller holes (71% and 75.5% of SED) increased the insertion torque value within the recommended level, caused more bone radial extension deformation and maximized the contact area between the bone threads and the screw, in comparison to the PHS higher than 80% of SED. Under the immediate BWP after osteosynthesis, the stress level exceeds the elastic limit and becomes high enough to initiate the ductile damage of the bone. Also, enlarging PHS from 71% to 75.5% of SED increased the bone microdisplacement at the screw-bone interface from 75 up to 100 µm, and that reduced the stiffness of the fixation.

[Paradoxal growth hormone and cortisol response to hypoglycemia caused by endogenous hyperinsulinemia: a case report]. / Inhibition paradoxale de la réponse somatotrope et corticotrope à l'hypoglycémie par hyperinsulinisme endogène: à propos d'une observation.

Growth hormone (GH) together with cortisol are two important counter-regulatory hormones maintaining normal glycemia. Hyperinsulinemic hypoglycemia is a disorder of this counter-regulation described in neonates. We report here a rare case of reversible dissociated hypopituitarism secondary to an insulinoma in a 38-year-old man referred for investigation of hypoglycemic episodes. Hormonal investigations were in favour of dissociated anterior pituitary failure, with growth hormone and corticotroph deficiency. The hypothalamic-pituitary MRI was normal. The fasting test argued in favour of a hyperinsulinemic hypoglycemia. The abdominal scan and the endoscopic ultrasound showed a mass within the tail of the pancreas. Distal pancreatectomy was performed. Histology disclosed an insulinoma. On follow-up, no hypoglycemic episodes recurred and cortisol and GH response to induced hypoglycemia was normal. Our clinical case shows that hyperinsulinemia and hypoglycemia in patients with insulinoma can give rise to functional growth hormone and corticotrophin deficiency. The pathophysiological mechanism of this defective counter-regulation remains to be clarified; some studies suggest it could be related to hyperinsulinemia-induced decreased in CRF secretion and GHRH pulse.

Analysis of cementless implants using interface nonlinear friction--experimental and finite element studies.

Measured interface nonlinear friction properties are used to develop models to study the short-term fixation response of smooth- and porous-surfaced posts, bone screws, and plates fixed with and without posts/screws. Experimental studies are carried out to validate the model predictions and identify the relative role of posts and screws in fixation of a plate on a polyurethane block under symmetric/eccentric axial compression loads. The idealized Coulomb's friction is also used for the sake of comparison. The incorporation of measured nonlinear, rather than the idealized Coulomb, friction is essential to compute realistic results. For plate fixation, the experimental and finite element results show that the screw fixation yields the stiffest response followed by the smooth- and then porous-coated post fixation. For example, under 1000 N eccentric axial compression, the edge of the plate opposite the loaded edge is measured to lift by 1147 +/- 72, 244 +/- 38, or 112 +/- 28 microns, respectively, for the cases with no fixation, with smooth-surfaced posts, or with screws. The corresponding models predict, respectively, values of 1538, 347, or 259 microns and also 556 microns for the plate fixed with porous coated posts. The satisfactory agreement between numerical and experimental results confirms the importance of proper interface modelling for the analysis of posts, screws, and complex fixation systems. This becomes further evident when considering cementless implants in which the bone-implant interface exhibits relatively large displacements as the maximum resistance force is reached. The developed models can be used to investigate the post-operative short-term stability of various cementless implant designs.

Fixation pull-out response measurement of bone screws and porous-surfaced posts.

Screws and posts are used in various implant designs to contribute to the short- and long-term fixation stability of artificial joints. This study was undertaken to measure the detailed pull-out load-displacement response of bone screws, beaded porous coated posts, and smooth-surfaced posts in both proximal tibial cancellous bone and polyurethane material under monotonic static and repetitive cyclic loadings. The effect of a number of parameters such as insertion site on the proximal tibia, rate of displacement, insertion depth, outside diameter, drill size, repetitive loading and boundary conditions were studied. Bone screws resisted significantly larger loads than posts of the same size. Smooth-surfaced posts demonstrated much larger (about twice) pull-out forces than beaded porous coated posts of the same size. The pull-out force in the proximal tibia was markedly larger at the medial region followed by the lateral region. The central region exhibited the least force. The resistance of screws and posts diminished with repetitive cyclic loads/displacements, especially when these were larger than 50% of their respective values at pull-out force evaluated under monotonic static loading conditions. The smooth-surfaced posts showed superior performance in maintaining their resistance in fatigue than did the porous coated posts and bone screws. The pull-out force was found to also depend on the pull-out material arrangement and boundary conditions. Pull-out results measured with a specific test design should not, therefore, be compared with those performed using different design configurations.

Modeling of biomedical interfaces with nonlinear friction properties.

Proper isotropic and anisotropic friction constitutive equations are developed based on previous friction measurements at cancellous bone-porous coated implant interfaces exhibiting nonlinear load-displacement curves. The simulated friction response is dependent on relative tangential displacements in both orthogonal directions. The interface constitutive matrix contains cross-stiffness terms identical in isotropic friction but different in anisotropic friction. These terms are due mainly to nonlinearity in response and vanish in unidirectional friction along a principal direction and in cases with Coulomb or linear friction. The interface ultimate resistance is evaluated by an elliptic criterion which becomes circular in isotropic cases. These constitutive relations are implemented in a finite element program which is employed to analyze a bone cube sliding on top of a porous-surfaced metallic plate, an experimental model used in our earlier measurements. The results for both isotropic and anisotropic frictions demonstrate the coupling between two orthogonal directions. The direction of resultant displacement under a variable load coincides with that of the load only when the friction is isotropic with coupling terms considered. In anisotropic friction, the resultant displacement occurs in a direction different from that of loading. Our previous bi-directional measurements corroborate well the findings of this study.

Fixation response of two cementless tibial implants under static and fatigue compression loading.

The short- and long-term success of tibial cementless implants depend on the initial fixation stability often provided by posts and screws. Excessive relative interface motions are known to inhibit bone ingrowth and, hence, biologic fixation. In the present study, the stability of two cementless tibial implants under static and cyclic loading was studied. An apparatus was developed to perform compression tests on tibial components fixed by screws or posts onto resurfaced tibiae. Motion transducers were placed to record liftoff and subsidence displacements. A load of 1000 N was eccentrically applied on the medial plateau via the femoral component. The response was measured under static and repetitive loading up to 4000 cycles at 1 Hz. Experimental results showed that the screw fixation yielded the stiffer response and, hence, provided greater initial stability. The tibial component fixed with posts demonstrated larger lift off displacements. Comparison of measured results of static tests before and after fatigue indicated that the load-displacement behavior was not significantly affected by the cyclic fatigue loading under 1000 N up to 4000 cycles at 1 Hz. Nevertheless, much larger permanent displacements were recorded for the post fixation systems. In contrast to screw fixation, posts fixation systems demonstrated marked deterioration under larger compression loads of approximately 2000 N.

[Diastematomyelia: antenatal diagnosis with successful outcome, two cases]. / Diastématomyélie: à propos de deux observations anténatales et revue de la littérature.

To discuss, through a review of the literature, clinical signification and antenatal and postnatal management of diastematomyelia. We present two cases highlighting the clinical presentation and discuss management options. The first case was diagnosed in a 32-year-old primagravida female physician. The conssanguinous couple had a history of primary hypofertility. Antenatal magnetic resonance imaging revealed the presence of a sagittal spinal spur separating two asymmetrical hemi cords. Pregnancy was not interrupted due to the lack of factors of poor prognosis. The infant was delivered at term and outcome has been favorable at 18 months follow-up. Ultrasonography performed at 22 weeks gestation provided the diagnosis in the second case. The mother was a 30-year-old primagravida anesthesist who had been addressed for suspected spina bifida. The consanguinous couple had a history of male hypoferility. The ultrasound scan revealed an echogenic spinal spur and integrity of the skin. Pregnancy was not interrupted due to the lack of factors of poor prognosis. The infant was delivered at term and outcome has been favorable at 18 months follow-up. Diastematomyelia is a rare malformation which can be diagnosed antenatally. Careful ultrasonography can distinguish diastematomyelia from myelomeningocele. Antenatal assessment is essential to identify forms with good prognosis because the neonatal outcome of isolated diastematomyelia is generally good, even if surgical repair is required.

Spectroscopic properties of Eu3+ doped RbLaP4O12 powders.

Monophasic RbLaP4O12 possessing monoclinic symmetry with varied Eu(3+) concentrations was synthesized by flux method. The obtained cyclotetraphosphate exhibits very small crystals and the dopant Eu(3+) ions were successfully incorporated into the sites of La(3+) ions of the host lattice. These compounds were characterized by infrared and Raman spectroscopy, X-ray diffraction (XRD) and luminescence spectroscopy. The spectroscopy properties confirm the potentiality of present RbLaP4O12 doped with Eu(3+) ions as luminophore host materials to produce an intense red luminescence at 616 nm corresponding to (5)D0→(7)F2 emission level and have significant importance in the development of emission optical systems.

Experimental determination of friction characteristics at the trabecular bone/porous-coated metal interface in cementless implants.

An apparatus was developed to measure load-displacement friction properties at the cancellous bone/porous-coated metal plate interface. Bone cubes were obtained from different proximal regions of four resurfaced cadaveric tibiae. Three different porous-surfaced metal plates (one fiber mesh and two bead) and a smooth-surface metal plate were used. In the presence of a constant normal contact pressure (0.10, 0.15, or 0.25 MPa), a variable tangential load up to the maximum resistance of the interface was applied and both relative normal and tangential displacements were recorded. Repetitive and fatigue loadings were also considered. Measured results show that the interface friction curve is highly nonlinear, exhibiting large relative tangential displacements in the range of 50-400 microns before the maximum load is reached. Relative displacements in the normal direction remain below 10 microns. The maximum resistance in friction is independent of the bone excision site, type of porous-surfaced metal plate, magnitude of normal load, placement of bone cubes on metal plates or vice versa, repetition of applied load, and conservation period of bone cubes in saline solution. The smooth-surfaced metal plate has significantly smaller friction resistance than porous-coated ones. The fatigue loading of up to 4000 cycles at 1 Hz, in the presence of 0.25 MPa contact pressure, slightly decreases the interface friction coefficient. Finally, the initial secant stiffness of the interface at 75% of the maximum resistance load is found to be larger for the bone cubes from the lateral and medial regions and for the metal plate with smooth surface.

Bidirectional friction study of cancellous bone-porous coated metal interface.

Bidirectional friction tests between cancellous bone cubes and a porous-coated metal plate were performed to determine the mechanical properties of the interface required in 3-dimensional (3-D) finite element model studies of cementless implants. Bone specimens were obtained from different proximal regions of four resurfaced cadaveric tibiae. A beaded porous-surfaced plate similar to those used in implants was used. Tangential loads in perpendicular directions with different magnitudes were applied at the interface in the presence of constant normal pressure, and the displacements were monitored in the same directions. Measured results showed that the interface load-displacement curve is highly nonlinear with significant coupling between two perpendicular directions. The interface friction coefficient (defined as the ratio of the maximum resultant tangential force divided by the normal load) was found to remain nearly unchanged with the relative magnitude of tangential stresses and the bone location. Moreover, bidirectional tests suggested that the load-displacement relation when evaluated for resultant values is similar to that obtained in a unidirectional testing condition. Constitutive equations that account for the cross-stiffness coupling terms between perpendicular directions were also developed. These relations were used in a 3-D finite element model study of preceding bidirectional friction tests. The influence of the coupling terms on results was investigated by comparison of predictions with measurement results. A satisfactory agreement was found between the results of the experiments with those of finite element studies confirming the constitutive relations as well as the importance of coupling terms.

Experimental and finite element comparison of various fixation designs in combined loads.

The short- and long-term successes of tibial cementless implants depend on the initial fixation stability often provided by posts and screws. In this work, a metallic plate was fixed to a polyurethane block with either two bone screws, two smooth-surfaced posts, or two novel smooth-surfaced posts with adjustable inclinations. For this last case, inclinations of 0, 1.5, and 3 deg were considered following insertion. A load of 1031 N was eccentrically applied on the plate at an angle of approximately 14 deg, which resulted in a 1000 N axial compressive force and a 250 N shear force. The response was measured under static and repetitive loading up to 4000 cycles at 1 Hz. The measured results demonstrate subsidence under load, lift-off on the unloaded side, and horizontal translation of the plate specially at the loaded side. Fatigue loading increased the displacements, primarily during the first 100 cycles. Comparison of various fixation systems indicated that the plate with screw fixation was the stiffest with the least subsidence and liftoff. The increase in post inclination from 0 to 3 deg stiffened the plate by diminishing the liftoff. All fixation systems demonstrated deterioration under repetitive loads. In general, the finite element predictions of the experimental fixation systems were in agreement with measurements. The finite element analyses showed that porous coated posts (modeled with nonlinear interface friction with and without coupling) generated slightly less resistance to liftoff than smooth-surfaced posts. In the presence of porous coated posts, Coulomb friction greatly overestimated the rigidity by reducing the liftoff and subsidence to levels even smaller than those predicted for the design with screw fixation. The sequence of combined load application also influenced the predicted response. Finally, the finite element model incorporating measured interface friction and pull-out responses can be used for the analysis of cementless total joint replacement systems during the post-operation period.

Friction properties at the bone-metal interface: comparison of four different porous metal surfaces.

Detailed friction load-displacement response of four distinct metallic surfaces [one beaded porous metal (CTR) and three cast Co-Cr alloy ingrowth mesh surfaces, nonplanar mesh (INX), cast mesh 1 (CM1), and cast mesh 2 (CM2)] on poly-urethane and cancellous bone specimens of six tibiae were measured under different normal stresses (0.1, 0.15, or 0.025 MPa). Bone cubes were obtained from different proximal regions of resurfaced cadaveric tibiae. Both monotonic and cyclic fatigue loadings of up to 4000 cycles at 1 Hz were considered. Comparison of measured results indicated that the friction coefficient was not affected by the magnitude of normal stress and the bone excision site (medial, lateral, anterior, posterior, and central). The CM2 surface showed significantly greater resistance with friction coefficients of more than 0.9 for the bone and 0.8 for the polyurethane. The INX surface yielded the second largest resistance followed by CM1 and CTR surfaces. NO significant difference was found between these latter two surfaces. Fatigue tests of up to 4000 loading-unloading cycles showed about 10% reduction in friction coefficient for CTR and INX surfaces, while negligible reduction was found for CM1 and CM2 surfaces.

Relative cardiac cost and physical, mental and psychological work load among a group of post-operative care personnel.

Continuous registration of heart rate and careful minute-by-minute observation of all physical, mental and psychological job-related events was carried out in a group of nine post-operative care personnel. The relative cardiac cost (RCC) correlated significantly with the observed work events. The magnitude of participation of physical, mental and psychological work elements in the changes in RCC varied in the investigated subjects according to the type and magnitude of the different work events. However, collective data on the group indicated that changes in RCC were related mainly to physical effort and to a lesser, albeit significant, extent to psychological reaction. The results indicate the possibility of using the heart rate in monitoring working conditions and, probably, in guiding their improvement.