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PubMedDate not supplied

Basic scientific considerations in total disc arthroplasty.

BACKGROUND CONTEXT: Total disc arthroplasty serves as the next frontier in the surgical management of intervertebral discogenic pathology. PURPOSE: As we move from an era of interbody spinal arthrodesis to one in which segmental motion is preserved, this promising new technology offers increasing clinical and research challenges in the areas of spinal kinematics, histologic osseointegration at the prosthetic-bone interface and the effects of particulate wear debris. STUDY DESIGN: The primary focus of this paper is to provide a methodologic basis to investigate the spinal kinematics, histologic osseointegration and particulate wear debris after total disc arthroplasty by using in vitro and in vivo models. METHODS: Part I: Using an in vitro cadaveric model, multidirectional flexibility testing evaluated the functional unit kinematics under the following L4-L5 reconstruction conditions: 1) intact spine, 2) Charite disc prosthesis, 3) BAK cages, 4) BAK cages+ISOLA pedicle screw or rod fixation (anteroposterior). Part II: A total of 27 mature baboons (n=27, Papio cynocephalus) underwent L5-L6 total disk replacement procedures to investigate the biomechanical, histochemical and biologic ingrowth characteristics of two different lumbar disc prostheses (AcroFlex and Charite) for total disc arthroplasty. Functional spinal unit fusion status was assessed by using radiographic analysis, biomechanical testing, undecalcified histopathologic and histomorphometric analyses. Part III: Using a total of 50 New Zealand white rabbits, this investigation served to quantify the neural and systemic tissue histopathologic response, after epidural application of four different types of spinal instrumentation particulate wear debris: 1) sham (control) (n=10), 2) stainless steel 316LVM (n=10), 3) titanium alloy Ti-6AL-4V (n=10), 4) cobalt chrome alloy (n=10) and 5) ultrahigh molecular weight polyethylene (UHMWPE) (n=10). RESULTS: In vitro multidirectional flexibility testing demonstrates the operative and adjacent level motion-preserving properties of total disc arthroplasty versus interbody arthrodesis cages and pedicle screw spinal instrumentation. To this end, disc replacement preserves the normal centrode or locus of intervertebral rotation at the operative and adjacent intervertebral spinal levels compared with conventional stabilization implants. On the basis of nonhuman primate modeling in the current studies, porous titanium interface surfaces afforded the greatest percentage of trabecular ingrowth at the prosthesis-end plate interface. In vivo segmental motion under multidirectional testing was preserved with the Charite device and slightly diminished with the AcroFlex implants. The porous ingrowth coverage at the bone-metal interface was more favorable for total disk replacement (range, 40% to 50%) compared with that reported for cementless total joint components in the appendicular skeleton (range, 10% to 30%). Direct epidural application of spinal instrumentation particulate wear debris elicits a chronic histiocytic reaction localized primarily within the epidural fibrous layers. Moreover, particles have the capacity to diffuse intrathecally, eliciting a macrophage and cytokine response within the epidural tissues, cerebrospinal fluid and spinal cord itself. Overall, on the basis of the postoperative time periods evaluated, no evidence was observed of an acute neural or systemic histopathologic response to the materials included in the current project. CONCLUSION: The implementation of dynamic spinal stabilization systems for fusionless correction of spinal deformity, dynamic posterior stabilization and total disc arthroplasty necessitates improved understanding with regard to spinal kinematics, patterns and mechanisms of histologic osseointegration and the neurohistopathologic response to particulate wear debris. Collectively, the current studies provide a methodologic basis to comprehensively evaluate these three areas.

Animals↗

PubMed2005

Synthesis of a poly(L-lysine)-calcium phosphate hybrid on titanium surfaces for enhanced bioactivity.

Titanium has been a successful implant material owing to its excellent strength to weight ratio, toughness, and bioinert oxide surface. Significant progress has been made on the improvement of titanium's bioactivity by coating its oxide surface with calcium phosphates and bioactive molecules. Here, we report on the coating of titanium with a poly(L-lysine)-calcium phosphate hybrid material with a nanoscale texture. This hybrid coating was grown by first nucleating seed crystals of calcium phosphate, directly on the Ti surface and then exposing this surface to solutions containing Ca(2+), PO(4)(3-), and poly(L-lysine). The resultant hybrid coating was characterized by electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, and elemental analysis. This material contained 14% by weight poly(L-lysine), and this organic component decreased greatly the dimensions of the surface features, thus enhancing surface area relative to the inorganic control. The highly textured hybrid material was more susceptible than the control to acidic and enzymatic degradation. The amino acid cysteine was covalently linked to the hybrid material, demonstrating the potential of this coating for further functionalization. These hybrid coatings may prove useful in enhancing the bioactivity of titanium.

Calcium Chloride↗

PubMed2006

Physicochemical degradation studies of calcium phosphate glass ceramic in the CaO-P2O5-MgO-TiO2 system.

The aim of this work was to evaluate the in vitro degradation behaviour of a 45CaO-37P(2)O(5)-5MgO-13TiO(2) (mol.%) glass ceramic, under two different simulated physiological conditions: normal physiological pH 7.4, and pH 3.0, which was designed to simulate the acidic conditions produced by osteoclast cells. The in vitro testing was carried out at 37 degrees C for up to 42 days for the pH 7.4 solution and for up to 1 day for the pH 3.0 solution. The incorporation of TiO(2) into the glass structure leads to the precipitation of specific crystalline phases in the glass matrix, namely alpha- and beta-Ca(2)P(2)O(7), TiP(2)O(7) and CaTi(4)(PO(4))(6). The degradation testing at pH 3.0 showed a higher weight loss compared with degradation testing at pH 7.4; the weight loss under the acidic condition after 1 day (24 h) was about 10 times higher than the weight loss after 42 days of immersion at pH 7.4. The ionic release profile of Ca(2+), PO(4)(3-), Mg(2+) and Ti(4+) showed a continuous increase in concentration over all immersion times for both testing solutions. After 1 day of immersion at pH 3.0, the concentration levels of Mg(2+), Ca(2+), PO(4)(3-) were about six times higher than the levels achieved after 42 days of immersion at pH 7.4. The glass ceramic showed similar degradation to hydroxyapatite, and therefore has potential to be used in certain clinical applications where relatively slow resorption of the implant and replacement by bone is required, e.g. cranioplasty.

Biocompatible Materials↗

PubMed2004

The use of skeletal anchorage in open bite treatment: a cephalometric evaluation.

The aims of the present study were to assess the effectiveness of skeletal anchorage for intrusion of maxillary posterior teeth, to correct open bite malocclusion, and to evaluate the usage of titanium miniplates for orthodontic anchorage. Anterior open bite is one of the most difficult malocclusions to treat orthodontically. Currently, surgical impaction of the maxillary posterior segment is considered to be the most effective treatment option in adult patients. Various studies have reported the use of implants as anchorage units at different sites of midfacial bones for orthodontic tooth movement. The zygomatic buttress area could be a valuable anchorage site to achieve intrusion of maxillary posterior teeth. Ten patients, 17 to 23 years old and characterized with an anterior open bite and excessive maxillary posterior growth, were included in this preliminary study. Titanium miniplates were fixed bilaterally to the zygomatic buttress area, and a force was applied bilaterally with nine mm Ni-Ti coil springs between the vertical extension of the miniplate and the first molar buccal tube. The results showed that, with the help of skeletal anchorage, maxillary posterior teeth were intruded effectively. As compared with an osteotomy, this minimally invasive surgical procedure eased treatment and reduced treatment time and did not require headgear wear or anterior box elastics for anterior open bite correction. In conclusion, the zygomatic area was found to be a useful anchorage site for intrusion of the molars in a short period of time.

Adolescent↗

PubMed2000

Structural response and relative strength of a laminated composite hip prosthesis: effects of functional activity.

To obtain a better appreciation for the structural performance of a laminated composite hip prosthesis (CP), we examined in situ prosthesis structural response and relative strengths as a function of walking and stair climbing using our previously developed analysis guidelines. Accordingly, we examined overall prosthesis structural response utilizing a global continuum level modeling approach and prosthesis relative strengths using a local microstructural (or ply-level) modeling approach. As a reference and control, we examined the structural performance of the intact natural femur (NAT) and a titanium alloy (Ti) based hip prosthesis. In terms of the overall structural response, i.e., the femur/prosthesis deformational response, stem/bone interfacial stress transfer, and calcar strain energy density restored, the performance of the CP prosthesis was moderately improved over that of the control Ti prosthesis and better approximates the NAT response. In terms of relative strength, we found that the neck of the CP prosthesis failed for all activities with the exception of the mid-stance phase of level walking. However, the prosthesis appears to have sufficient relative strength for function at positions distal to the neck of the prosthesis. While these results dampen enthusiasm for consideration of laminated composite hip prostheses designed with a shape based on a metal alloy implant, they indirectly support consideration of alternate hip prosthesis structural designs such as using a better supported prosthesis neck or utilizing metal/composite hybrid constructions. Importantly, our simulation and analysis approach could be utilized in the design of other laminated composite biomedical structural components.

Alloys↗

PubMed2004

Mesenchymal stem cell adhesion and spreading on nanostructured biomaterials.

Bone marrow-derived human mesenchymal stem cells were seeded in serum-free media onto ion beam-deposited nanostructured metalloceramic (Ti-Cr-N) films and plasma-nitrided titanium disks, which were left uncoated as well as precoated with fetal bovine serum. Precoating the disks with serum appears to stimulate cell spreading on both the titanium nitride and metalloceramic materials for as little as 1 hour incubation time. The implication is that both of these materials can adsorb serum proteins in amounts sufficient to influence cell adhesion and spreading for potentially improved in vivo response of orthopedic and dental implants. The materials in this study may prove to exhibit enhanced biological and mechanical properties when compared to conventional micron-scale implant materials such as titanium or cobalt-chrome alloys.

Bone Substitutes↗

PubMed1985

Hormonal modulation of responses to thymus-independent and thymus-dependent antigens in autoimmune NZB/W mice.

Previous work suggested that gonadal steroids influence immunity through the thymus, but the mechanisms were unclear. To investigate the effects of these hormones on immune responses to T1 and TD antigens in autoimmune mice, we studied hybrid NZB/W mice and the nonautoimmune DBA/2 strain. Mice castrated at 14 days of age were implanted with Silastic capsules releasing, in adults, physiologic levels of E2 in males or Te in females. Sham-operated controls received empty capsules. Splenic PFC were quantified 4 to 5 days after challenge with the TI2 antigen TNP-Ficoll, the TI1 antigen TNP-LPS, or the TD antigen SRBC. Young castrated NZB/W males implanted with E2 had striking enhancement of IgM responses to TNP-Ficoll when compared to castrated Te-treated females and comparable sham-operated controls of both sexes. E2 also stimulated responses to TNP-LPS. In response to challenge with SRBC, young E2-treated NZB/W males had a consistent trend to increased IgM PFC, and the stimulatory effect of E2 on IgG plaques was variable. Physiologic doses of Te had no consistent effect on responses in young mice. In old female NZB/W mice, Te caused PFC response after immunization with TNP-Ficoll to resemble age-matched NZB/W males. As sham-operated NZB/W females grew older, PFC responses to SRBC fell. This age-related phenomenon was delayed, however, in female castrates implanted with Te. In contrast, Te clearly suppressed responses to TNP-LPS. Implantation of E2 did not alter responses to TNP-Ficoll, TNP-LPS, or SRBC in nonautoimmune DBA/2 males. This finding suggested that exogenous E2 given in physiologic doses did not influence immunologic responsiveness in a normal strain to the degree seen in hormone-sensitive NZB/W mice. It was concluded that E2 enhanced responses to a variety of exogenous antigens in autoimmune NZB/W mice. The most consistent E2-induced increase in PFC response was observed with TI antigens, suggesting that E2 exerted its effects on B cells or Ts.

Animals↗

PubMed2006

Short-term microvascular response of striated muscle to cp-Ti, Ti-6Al-4V, and Ti-6Al-7Nb.

Due to excellent mechanical properties and good corrosion resistance, titanium-aluminium-vanadium (Ti-6Al-4V) and titanium-aluminium-niobium (Ti-6Al-7Nb) are extensively used for orthopedic surgery. Concern has been voiced concerning the implications of the constituent vanadium in Ti-6Al-4V on the surrounding environment. Particularly in osteosynthesis where the alloys stand in direct contact to skeletal muscle, undesirable biologic reactions may have severe consequences. In a comparative study, we assessed in vivo nutritive perfusion and leukocytic response of striated muscle to the metals Ti-6Al-4V, Ti-6Al-7Nb, and commercially pure titanium (cpTi), thereby drawing conclusions on their short-term inflammatory potential. In 28 hamsters, utilizing the dorsal skinfold chamber preparation and intravital microscopy, we quantified primary and secondary leukocyte-endothelial cell interaction, leukocyte extravasation, microvascular diameter change, and capillary perfusion in collecting and postcapillary venules of skeletal muscle. A manifest discrepancy between the metals concerning impact on local microvascular parameters was not found. All metals induced an only transient and moderate inflammatory response. Only a slight increase in leukocyte recruitment and a more sluggish recuperation of inflammatory parameters in animals treated with Ti-6Al-4V compared to the other two metals suggested a minor, overall not significant discrepancy in biocompatibility. Gross toxicity of bulk Ti-6Al-4V on surrounding tissue could not be found. Conclusively, the commonly used biomaterials Ti-6Al-4V, Ti-6Al-7Nb, and cpTi induce an only transient inflammatory answer of the skeletal muscle microvascular system. Our results indicate that on the microvascular level the tested bulk Ti-alloys and cpTi do not cause adverse biologic reactions in striated muscle.

Alloys↗

PubMed2001

Dynamic study about metal release from titanium miniplates in maxillofacial surgery.

It has been shown that titanium (Ti) has had dramatic success in many surgical procedures as a result of its excellent mechanical properties and resistance to corrosion. There is still concern, however, about the release of metal and controversy surrounding whether or not the plates should be removed after bone healing. This study has been conducted to investigate whether or not there is a relationship between duration of plating and metal release from Ti miniplates in maxillofacial surgery. A prospective cohort study design was used. The concentration of Ti, in the soft tissues covering the plates, was examined in all patients who underwent removal of Ti miniplates from January 1998 to April 1999 (51 cases). Inductively Coupled Plasma-Optical Emission Spectrometry was used to measure Ti. Total ti and soluble Ti levels were compared to duration of plating (ranged from 15 days to 3 years, mean = 8 months). Correlation coefficients and two-way ANOVA were data processed. The average amount of total Ti in the soft tissues surrounding the plates was 1306 micrograms/g dry tissue. The mean of soluble Ti was 0.53 microgram/g dry tissue. The results of this study do not support the existence of a relationship between duration of plating and total Ti (correlation coefficient = 0.093 (P > 0.1) nor soluble Ti (correlation coefficient = 0.009 (P > 0.1) in the soft tissue surrounding the plates. Moreover, the only independent factor of Ti release found was associated with mechanical constraints during surgery. Almost 100% of Ti is released during the osteosynthesis. Then Ti levels remain constant in the surrounding tissues. Most of the time, Ti seems to be clinically inert. Compared to the possible risks of a second operation, removal of Ti miniplates should not be a routine procedure except in the case of complaints from patients, particularly in the case of infection, hypersensitivity, dehiscence or screw loosening.

Adolescent↗

PubMed2005

Comparative study of osteoconduction on micromachined and alkali-treated titanium alloy surfaces in vitro and in vivo.

This study sought to evaluate osteoconduction of Ti-6Al-4V surfaces under various conditions, including micro-patterned, alkali-treated, micro-patterned plus alkali-treated, and surfaces without any treatment as the control. The through-mask electrochemical micromachining (EMM) was used to fabricate micro-hole arrays on the titanium alloy surface. In vitro calcium phosphate formation on titanium surfaces was in static and dynamic simulated body fluid (SBF). In vivo comparison was conducted in the medullary cavity of dog femur using the implant cages which could provide the same physiological environment for specimens with different surface conditions. In vitro experiments indicate good conduction of calcium phosphate on the alkali-treated surfaces, and also better calcium phosphate deposition on the micro-hole surface than on the flat surfaces in dynamic SBF. In vivo experiments confirm the beneficial effect of alkaline treatment on osteoconduction. The results of in vivo experiments also indicate a synergistic effect of the alkaline treatment and the topographic pattern on osteoconduction.

Alkalies↗

PubMed1996

In vivo wear of Ti6A14V femoral heads: a retrieval study.

The surface characteristics of sixteen "monobloc" titanium-6% aluminum-4% vanadium (Ti6A14V) femoral components (two of the 6-Ti-28 type and 14 of the 6-Ti-32 type) retrieved after periods of 78-131 months following loosening of the femoral component, as well as two unimplanted controls, were studied. The femoral heads were examined by a combination of noncontact light profilometry, scanning electron microscopy, and energy-dispersive X-ray analysis. No consistent correlations were found between classical surface roughness parameters (average, root mean square, peak-to-valley roughness, and radius of curvature) and any clinical parameter studied (patient gender, weight, and height; primary diagnosis; implantation time; or calculated force applied on the hip joint). This extensive quantitative topographic analysis suggests that wear mechanisms in vivo are complex and that wear of titanium alloy femoral heads is partly attributed to a combination of an imperfect nature of the surface before implantation, removal of the oxide layer causing abrasion of the alloy, subsequent deformation of the bearing surface including polishing, and, to a very small degree, patient parameters.

Aged↗

PubMed1998

Long-term effect of VVI pacing on atrial and ventricular function in patients with sick sinus syndrome.

We conducted a prospective, 6-month echocardiographic study on the effect of VVI pacing on left atrial and ventricular function and dimensions in patients with sick sinus syndrome. Thirty-nine patients (23 women and 16 men, aged 71 +/- 9.2 years; 30 in sinus rhythm and 9 in atrial fibrillation) who had a VVI pacemaker implanted because of sick sinus syndrome were recruited in the study. In 26 patients who presented with and remained in sinus rhythm, paced left ventricular ejection fraction and stroke volume were significantly decreased (71.4% +/- 11.8% to 67.0% +/- 13.6%, and 73.9 +/- 29.0 cm3 to 66.3 +/- 21.1 cm3, respectively, P < 0.001 for both), whereas the paced diastolic dimension of the left atrium was significantly increased (3.2 +/- 0.7 cm to 3.7 +/- 0.9 cm, P < 0.001) at 6 months as compared with preimplantation. In nine patients with atrial fibrillation at implantation paced left ventricular ejection fraction at follow-up was significantly decreased (67.7% +/- 10.1% to 64.2% +/- 10.6%, P =0.003), but paced stroke volume and left atrial diastolic dimension were not significantly changed (75.1 +/- 25.6 cm3 to 79.0 +/- 22.7 cm3, and 4.3 +/- 1.2 cm to 4.6 +/- 1.5 cm, P = NS for both) at follow-up. Cessation of pacing and restoration of sinus rhythm in 21 patients at follow-up did not result in any significant change of ejection fraction (67.5% +/- 10.2% ti 67.6% +/- 9.7%, P = NS) whereas stroke volume was increased (59.1 +/- 19.6 cm3 to 69.1 +/- 22.3 cm3, P < 0.0001) in comparison with paced values. However, compared with preimplantation values, ejection fraction was significantly decreased (70.4% +/- 10.0% to 67.6% +/- 9.7%, P = 0.001), whereas stroke volume was not significantly changed (68.4 +/- 22.3 cm3 to 69.1 +/- 22.3 cm3, P = NS) during sinus rhythm at follow-up. In 14 of those patients, discontinuation of pacing resulted in a significant increase of left atrial fractional shortening (8.1% +/- 1.7% to 20.1% +/- 4.3%, P < 0.001) and significant increase of left atrial diastolic dimension compared with paced and preimplantation levels (3.8 +/- 0.7 cm vs 3.6 +/- 0.7 cm and 3.0 +/- 0.5 cm, respectively, P < 0.001). Long-term VVI pacing in patients with sick sinus syndrome results in increase of the left ventricular end-systolic dimension and permanent reduction of the left ventricular ejection fraction. In the left atrium, VVI pacing causes an immediate reduction of the fractional shortening as well as long-term increase of the diastolic dimension.

Aged↗

PubMed2004

In vitro comparative analysis of the fit of gold alloy or commercially pure titanium implant-supported prostheses before and after electroerosion.

STATEMENT OF PROBLEM: For implant-supported prostheses, passive fit is critical for the success of rehabilitation, especially when alternative materials are used. PURPOSE: The purpose of this study was to compare interfacial fit of implant-supported prostheses cast in titanium to those cast in gold alloy. MATERIAL AND METHODS: Five 3-unit fixed partial dentures were fabricated in gold alloy (Degudent U) as 1-piece castings, and 5 others were similarly cast in commercially pure titanium (Grade 1). The interfacial gaps between the prostheses and the abutments were evaluated with an optical microscope, before and after electroerosion. Readings were made with both screws tightened (10 N.cm torque), and with only 1 side tightened, so as to also evaluate the passive fit of the prostheses. Data were compared statistically by 2-way analysis of variance and the post hoc Tukey multiple range test (alpha=.05). RESULTS: Before electroerosion, the interfacial gaps for the 1-piece prostheses were significantly smaller (P<.001) in the gold alloy group when the screws were tightened (Au=12.6 +/- 3.0 microm, compared to Ti=30.1 +/- 6.4 microm). When the side opposite the tightened side was analyzed, there was no significant difference between the gold alloy and titanium groups (Au=69.2 +/- 24.9 microm and Ti=94.2 +/- 39.6 microm). The electroerosion procedure significantly (P<.001) reduced the gaps at the interfaces for both groups under all conditions. Comparison between groups after electroerosion did not present significant differences when the side opposite the tightened side was analyzed, but the gold alloy group showed better fit when the tightened side was analyzed (12.8 +/- 1.4 microm for gold alloy; 29.6 +/- 4.4 microm for titanium) and when both screws were tightened (5.4 +/- 2.3 microm for gold alloy; 16.1 +/- 5.5 microm for titanium). CONCLUSIONS: Cast titanium prostheses, despite showing larger interfacial gaps between the prosthesis and abutment than those obtained with gold alloy, had improved fit after being subjected to electroerosion.

Analysis of Variance↗

PubMedDate not supplied

Patient experiences with atrial fibrillation and treatment with implantable atrial defibrillation therapy.

BACKGROUND: Patient perspectives about their illness experiences, symptoms, and treatment are essential aspects of quality of life and provide direction for patient and provider decision making regarding innovative therapies such as implantable devices for arrhythmia. PURPOSE: The purpose of this qualitative study was to describe: 1) the experience of patients living with symptomatic, drug-refractory atrial fibrillation (AF) and 2) patient experiences and acceptance of treatment with the implantable cardioverter defibrillator (ICD) with atrial therapies (ICD-AT) including ventricular and atrial defibrillation therapy. PARTICIPANTS: Subjects were 3 women and 8 men, 35 to 80 years of age, who received the Medtronic Jewel AF 7250 ICD-AT as therapy for recurrent, drug-refractory AF, had a history of AF for 3 to 20 years and had experienced multiple treatment modalities including frequent external cardioversion in an effort to control their AF. METHODS: A semi-structured interview addressed experiences of symptoms and prior treatment for AF and experiences, concerns, and perceived benefits of the ICD-AT. Interviews were recorded and transcribed verbatim. Narratives were coded and categorized using Atlas Ti(R) software. Qualitative interpretive analysis methods were used to identify key themes. RESULTS: Before ICD-AT, patient themes focused on AF that was: 1) misdiagnosed, minimized, and poorly treated; 2) distressful because of frequent and intense AF symptoms (fatigue, dizziness, shortness of breath, and anxiety) before ICD-AT; 3) limiting of activities of daily living; 4) associated with distress from enduring previous treatment; and 5) associated with the continuous pursuit of successful treatment and maintenance of normalcy. Decision making regarding ICD-AT therapy included weighing symptom or treatment distress versus anticipated risks or benefits, hope for better outcomes, and lack of options. After ICD-AT, themes included positive perceptions of the device because of AF symptom relief, ability to resume normalcy, and medication tolerance; incorporation of shock experiences into life routines; and patient suggestions regarding preparation and social support. IMPLICATIONS: Symptoms of AF have a major negative impact on overall quality of life. Treatment with the ICD-AT confers a sense of security and reduced symptom distress. Greater provider attention to patient preparation and facilitating social support are important for future ICD-AT patient care.

Adult↗

PubMedDate not supplied

Cytokines in the oviparity/viviparity transition: evidence of the interleukin-1 system in a species with reproductive bimodality, the lizard Lacerta vivipara.

Placental viviparity is a reproductive strategy usually attributed to mammals. However, it is also present in other vertebrate species, e.g. in Squamate reptiles. Although the immunological mechanisms that allow the survival of the semi-allogenic embryo in maternal tissues are still largely unknown, cytokines seem to play an important role in mammalian reproduction. Previous studies in our laboratory showed that interleukin-1 (IL-1), a cytokine associated with implantation in mice, is also expressed at the materno-fetal interface of placental viviparous Squamates. In this study, we used the model of Lacerta vivipara, which exhibits reproductive bimodality, that is, the coexistence of oviparous and viviparous populations. By means of immunohistochemistry and anti-human antibodies, we showed that uterine tissues of L. vivipara (seven oviparous and six viviparous animals) expressed the two IL-1 isoforms, IL-1alpha and IL-1beta, and the type I IL-1 receptor (IL-1R tI) both at the pre-ovulatory stage and during gestation, with no significant difference between oviparous and viviparous females. In L. vivipara, as in most oviparous Squamates, an important phase of embryonic development takes place in the mother's oviduct, before egg-laying. Moreover, although thinner than in oviparous females, an eggshell membrane persists throughout gestation in viviparous females also, which develop a very simple type of placenta. The data suggest that immunological mechanisms that allow the survival of the semi-allogenic embryo in maternal tissues are independent of the timing or intimacy of contact between maternal and fetal tissues.

Animals↗

PubMed2003

Serum cobalt levels after metal-on-metal total hip arthroplasty.

BACKGROUND: Systemic cobalt dissemination from the Metasul Co-28Cr-6Mo-0.2C metal-on-metal total hip prosthesis has been demonstrated in the first year after implantation. The aim of this prospective study was to monitor the serum cobalt concentrations in patients during the first five years after total hip arthroplasty with a metal-on-metal articulation. METHODS: A total hip arthroplasty was performed without cement in 100 consecutive patients who had either unilateral osteoarthritis or unilateral osteonecrosis. Fifty patients were randomized to be treated with a metal-on-metal articulation, and fifty patients, with a ceramic-on-polyethylene bearing. The femoral stem was made of a Ti-6Al-7Nb alloy, and the threaded acetabular cup was made of commercially pure titanium. Blood samples were taken before the operation and at multiple time-points for five years after the operation. Serum cobalt concentrations were measured with use of atomic absorption spectrometry. RESULTS: In the metal-on-metal group, the median serum cobalt concentration was 1 micro g/L at one year after surgery and 0.7 micro g/L at five years. The median of the serum cobalt concentrations measured from three to twelve months did not differ from the median of subsequent measurements, with the numbers available. The median serum cobalt level in the control group of patients treated with the ceramic-on-polyethylene articulation was below the detection limit at all time-points. CONCLUSIONS: Systemic cobalt release from Metasul metal-on-metal articulations was demonstrated throughout the five-year study period. The median serum cobalt concentrations were found to be slightly above the detection limit and remained in a constant range. The serum cobalt concentrations did not reflect a so-called run-in wear period of the metal-on-metal articulations.

Adolescent↗

PubMed1999

Silicon nitride coating on titanium to enable titanium-ceramic bonding.

Failures that occur in titanium-ceramic restorations are of concern to clinicians. The formation of poorly adhering oxide on titanium at dental porcelain sintering temperatures causes adherence problems between titanium and porcelain, which is the main limiting factor in the fabrication of titanium-ceramic restorations. To overcome this problem a 1-microm thick Si3N4 coating was applied to a titanium surface using a plasma-immersion implantation and deposition method. Such a coating serves as an oxygen diffusion barrier on titanium during the porcelain firings. The protective coating was characterized in the as-deposited condition and after thermal cycling. Cross sections of Ti/Si3N4-porcelain interface regions were examined by various electron microscopy methods and by energy dispersive analysis of X-rays to study the Si3N4 film's effectiveness in preventing titanium oxidation and in forming a bond with porcelain. The experiments have shown that this Si3N4 coating enables significant improvement in Ti-ceramic bonding.

Dental Porcelain↗

PubMed2003

Leptin regulation of the interleukin-1 system in human endometrial cells.

We have previously shown that (i). leptin and leptin receptor (Ob-R) are expressed in the human endometrium, and (ii). leptin secretion is regulated in blastocyst and endometrial epithelial cell (EEC) co-cultures. Interleukin-1beta (IL-1beta) up-regulates leptin and Ob-R, and both cytokines up-regulate beta3 integrin expression in EEC. In the present investigation we examined the effect of leptin on the expression of the IL-1 system in EEC and endometrial stromal cells (ESC) cultured in a medium containing insulin, leptin or IL-1beta (0-3 nmol/l). Leptin stimulated IL-1 antagonist (IL-1Ra), IL-1beta secretion and expression of IL-1 receptor type I (IL-1R tI) in both cell types. IL-1beta and IL-1Ra secretion were down-regulated by IL-1R tI blockade using specific antibodies. Interestingly, leptin partially neutralized this effect. The blockade of Ob-R neutralized the effects of both leptin and IL-1beta on expression of the IL-1beta system and beta3 integrin and on phosphorylation of signal transducer and activator of transcription 3 (Stat3). These results suggest that leptin regulates the IL-1 system and that the blockade of functional Ob-R impairs leptin and IL-1beta functions at the endometrial level. Leptin could be an important molecule for implantation and a molecular mediator for actions of the IL-1 system. The fact that leptin, in the absence of IL-1, can trigger the expression of markers of endometrial receptivity and of the invasive trophoblast phenotype (as does IL-1), suggest that leptin could substitute for these IL-1 functions during the implantation process.

Antibodies↗