Biomedical subjects

W Lehmann

Publications and source records attributed to W Lehmann.

At least 19 recordsLinked to original sources

PubMed2007

High bone mineral density in pycnodysostotic patients with a novel mutation in the propeptide of cathepsin K.

INTRODUCTION: Pycnodysostosis is typically associated with short stature, multiple fractures without adequate trauma and high bone density on x-ray. The increased bone density is due to a genetic defect of cathepsin K, leading to dysfunctional osteoclastic bone resorption and bone remodeling. We wanted to know how this defect influences the trabecular and cortical volumetric bone mineral density of long bones as measured quantitatively by pQCT. METHODS: Three siblings of a consanguineous family were admitted to our hospital because of multiple fractures. Pycnodysostosis was diagnosed based on the clinical presentation with the characteristic dense appearance of their bones on x-ray. The distal and proximal radius of the patients and of control subjects was scanned using a Stratec XCT-2000 pQCT scanner and data were processed using the software provided by the manufacturer. Genomic DNA was extracted from blood samples of all three patients and their parents. The coding exons of the cathepsin K gene (CTSK) were amplified and sequenced. RESULTS: The patients displayed the typical features of pycnodysostosis: Short stature, delay of closure of the fontanelles, hypoplasia of the maxilla, spondylolysis of the lumbar spine, stubby hands and feet and a history of multiple fractures. Volumetric bone density was much higher in pycnodysostotic bone than in the control bones 686 +/- 28 mg/cm(3) in patients vs. 290 +/- 6 mg/cm(3) in controls; p = 0.001), especially in the trabecular compartment (733 +/- 26 mg/cm(3) in patients vs. 195 +/- 8 mg/cm(3) in controls; p < 0.001), but also in the cortical bone (1108 +/- 22 in patients vs. 1020 +/- 17 in controls; p < 0.01). In contrast to this finding, the patients displayed an elevation of alkaline phosphatase in the serum and free deoxypyridinoline-crosslinks (DPD) in the urine, suggesting osteomalacia. Sequencing of the cathepsin K gene revealed homozygosity for a novel missense mutation in all three patients predicting the amino acid exchange from arginine to tryptophan at position 46 (R46W). CONCLUSION: We present here for the first time quantitative data on the mineral density of bones of pycnodysostotic patients with a novel mutation in the propeptide of cathepsin K. The elevated bone mineral density in the cortex and the changes in the serum markers suggest an effect of cathepsin K not only on bone volume, but also on bone mineralization. This might in part explain the increased susceptibility to fractures of patients with pycnodysostosis.

Absorptiometry, Photon↗

PubMed2006

Marker-assisted combination of major genes for pathogen resistance in potato.

Closely linked PCR-based markers facilitate the tracing and combining of resistance factors that have been introgressed previously into cultivated potato from different sources. Crosses were performed to combine the Ry ( adg ) gene for extreme resistance to Potato virus Y (PVY) with the Gro1 gene for resistance to the root cyst nematode Globodera rostochiensis and the Rx1 gene for extreme resistance to Potato virus X (PVX), or with resistance to potato wart (Synchytrium endobioticum). Marker-assisted selection (MAS) using four PCR-based diagnostic assays was applied to 110 F1 hybrids resulting from four 2x by 4x cross-combinations. Thirty tetraploid plants having the appropriate marker combinations were selected and tested for presence of the corresponding resistance traits. All plants tested showed the expected resistant phenotype. Unexpectedly, the plants segregated for additional resistance to pathotypes 1, 2 and 6 of S. endobioticum, which was subsequently shown to be inherited from the PVY resistant parents of the crosses. The selected plants can be used as sources of multiple resistance traits in pedigree breeding and are available from a potato germplasm bank.

Animals↗

PubMed2005

Computer-assisted screw insertion into the first sacral vertebra using a three-dimensional image intensifier: results of a controlled experimental investigation.

Currently there are few data available regarding the application and efficacy of computer-assisted procedures in the sacral spine. In order to optimize and standardize this procedure, a controlled experimental investigation has been performed. The aim of the study is to systematically assess the efficacy of a novel three-dimensional image intensifier used for navigated transiliac screw insertion into the first sacral vertebra. Screws were inserted iliosacrally into the first sacral vertebra of preserved human cadaver specimens. The instrument navigated procedure was performed with the "Siremobil Iso-C(3D) " (Siemens Medical Solutions) and the "Navigation System" by Stryker. The accuracy and quality of the imaging procedure as well as the fluoroscopic exposure times were measured. These results were compared to three control groups (CT-based navigation, C-arm navigation, and fluoroscopic guidance). In each group a total amount of 20 screws was implanted. Screw position was postoperatively assessed by Iso-C(3D) or CT-scan. The navigated procedure using the Iso-C(3D) provided good feasibility characteristics without requiring a specific matching process. It revealed the shortest procedure time of all navigated procedures and significantly decreased fluoroscopic time compared to C-arm navigation and fluoroscopic guidance. Furthermore, Iso-C(3D) navigation showed no screw malposition and was in this regard superior to C-arm navigated and fluoroscopic guided procedures. The quality of imaging was sufficient for accurate placement, but did not share the high-resolution level of CT-based navigation. These findings indicate that application of the Iso-C(3D) for navigated transiliac screw insertion into S1 can be recommended as a feasible and safe technique, enabling the surgeon to reduce procedure and fluoroscopic time. Further progress in improving the quality of the Iso-C(3D) image should be attempted.

Bone Screws↗

PubMed2005

[Clinical relevance of "bone bruise" detected by MRI following spinal injuries in children].

BACKGROUND: MRI is a sensitive diagnostic tool, which is especially suited for the diagnosis of vertebral injuries in children since no radiation has to be applied to gonads or blood-producing organs. An indirect sign of vertebral injury is the presence of "bone bruise," an edema of the vertebral body without other bony lesions. The purpose of this study was to elucidate the clinical significance of "bone bruise" following vertebral trauma in children. PATIENTS AND METHODS: Between 1998 and 2003 a total of 66 children with vertebral injuries were treated at our institution; 34 of these patients initially underwent MRI. In this retrospective study 20 of these children who were diagnosed with a vertebral injury based on the presence of a "bone bruise" in an MRI on admission were examined clinically as well as by follow-up MRI. RESULTS: All 20 patients stated they felt no limitations in daily activities. On examination there were no significant pathologic findings. We did not note persistence of a "bone bruise" or a collapse of the affected bone in the follow-up MRI. CONCLUSION: If a "bone bruise" is detected in the MRI after vertebral trauma in children, it usually has a good prognosis. With adequate therapy, which in our regimen consists of bedrest and early mobilization, we did not note any secondary collapse of the affected vertebrae.

Child↗

PubMed2005

Response of primary fibroblasts and osteoblasts to plasma treated polyetheretherketone (PEEK) surfaces.

Polyetheretherketone (PEEK) is a synthetic polymer with suitable biomechanical and stable chemical properties, which make it attractive for use as an endoprothetic material and for ligamentous replacement. However, chemical surface inertness does not account for a good interfacial biocompatibility, and PEEK requires a surface modification prior to its application in vivo. In the course of this experimental study we analyzed the influence of plasma treatment of PEEK surfaces on the cell proliferation and differentiation of primary fibroblasts and osteoblasts. Further we examined the possibility of inducing microstructured cell growth on a surface with plasma-induced chemical micropatterning. We were able to demonstrate that the surface treatment of PEEK with a low-temperature plasma has significant effects on the proliferation of fibroblasts. Depending on the surface treatment, the proliferation rate can either be stimulated or suppressed. The behavior of the osteoblasts was examined by evaluating differentiation parameters. By detection of alkaline phosphatase, collagen I, and mineralized extracellular matrix as parameters for osteoblastic differentiation, the examined materials showed results comparable to commercially available polymer cell culture materials such as tissue culture polystyrene (TCPS). Further microstructured cell growth was produced successfully on micropatterned PEEK foils, which could be a future tool for bioartificial systems applying the methods of tissue engineering. These results show that chemically inert materials such as PEEK may be modified specifically through the methods of plasma technology in order to improve biocompatibility.

Animals↗

PubMed2005

Tumor necrosis factor alpha (TNF-alpha) coordinately regulates the expression of specific matrix metalloproteinases (MMPS) and angiogenic factors during fracture healing.

Recent studies from our laboratory demonstrate that TNF-alpha signaling contributes to the regulation of chondrocyte apoptosis and a lack of TNF-alpha signaling leads to a persistence of cartilaginous callus and delayed resorption of mineralized cartilage. This study examines how delays in the endochondral repair process affect the expression of specific mediators of proteolytic cartilage turnover and vascularization. Simple closed fractures were produced in wild type and TNF-alpha receptor (p55-/-/p75-/-)-deficient mice. Using ribonuclease protection assay (RPA) and microarray analysis, the expression of multiple mRNAs for various angiogenic factors and the metalloproteinase gene family were measured in fracture calluses. The direct actions of TNFalpha on the expression of specific angiogenic factors and metalloproteinases (MMPs) was examined in both cultured callus cells and articular chondrocytes to compare the effects of TNF-alpha in growth cartilage versus articular cartilage. MMPs 2, 9, 13, and 14 were quantitatively the most prevalent metalloproteases and all showed peaks in expression during the chondrogenic period. In the absence of TNF-alpha signaling, the expression of all of these mRNAs was reduced. The angiopoietin families of vascular regulators and their receptors were expressed at much higher levels than the VEGFs and their receptors and while the angiopoietins showed diminished or delayed expression in the absence of TNF-alpha signaling, VEGF and its receptors remained unaltered. The expression of vascular endothelial growth inhibitor (VEGI or TNFSF15) showed a near absence in its expression in the TNF-alpha receptor-deficient mice. In vitro assessment of cultured fracture callus cells in comparison to primary articular chondrocytes showed that TNF-alpha treatment specifically induced the expression of MMP9, MMP14, VEGI, and Angiopoietin 2. These results suggest that TNF-alpha signaling in chondrocytes controls vascularization of cartilage through the regulation of angiopoietin and VEGI factors which play counterbalancing roles in the induction of growth arrest, or apoptosis in endothelial cells. Furthermore, TNF-alpha appears to regulate, in part, the expression of two key proteolytic enzymes, MMP 9 and MMP14 that are known to be crucial to the progression of vascularization and turnover of mineralized cartilage. Thus, TNF-alpha signaling in healing fractures appears to coordinate the expression of specific regulators of endothelial cell survival and metalloproteolytic enzymes and is essential in the transition and progression of the endochondral phase of fracture repair.

Angiogenic Proteins↗

PubMed2004

Factors influencing the quality of life after burst fractures of the thoracolumbar transition.

INTRODUCTION: Dorsal stabilisation has represented the standard procedure for the treatment of burst fractures of the thoracolumbar spine for a long time, but in the last few years the combined dorsoventral stabilisation has gained in significance due to its higher mechanical stability. However, there are no data yet available indicating whether the patients benefit from the combined operation with regard to their postoperative quality of life and what the advantages are in comparison with the dorsal procedures. Therefore, the question was researched in the framework of a matched-pairs analysis of patients suffering from an unstable fracture of the thoracolumbar transition. MATERIALS AND METHODS: From a consecutive series of patients treated in our clinic between 1995 and 2000, 10 patients with combined and 10 patients with a purely dorsal stabilisation were selected and included in the study. Their quality of life was summed up in retrospect with the SF-36 questionnaire. The X-rays were analysed, and the Cobb angle as well as the sagittal index were calculated. Only patients with burst fractures of the thoracolumbar transition without accompanying co-morbidity and neurological deficits were included in the study. Both of the treated groups were matched with regard to sex, age and radiological patterns of injury. RESULTS: Patients who had undergone only a dorsal stabilisation showed a significant loss of correction according to the sagittal index at the time of the examination (0.88+/-0.02 postoperative vs 0.77+/-0.03 at 4 years postoperatively, p=0.01). In the group of patients treated with the combined therapy, there was no statistically relevant loss of correction with regard to the sagittal vertebral profile. The SF-36 questionnaire showed a reduced quality of life in both groups compared with an age-referenced norm population, especially concerning the parameters of bodily health. No statistically relevant difference was observed between the two groups. Further, there was no statistically relevant association between the parameters of the SF-36 and the clinical and radiological data. After performing several regression analyses it could be shown that the patient's mental health is a strong predictor of the postoperative vitality (r=0.803, p<0.01). However, none of the remaining parameters was able to predict the postoperative quality of life. CONCLUSION: The patients in this study showed a reduced quality of life, independent of the method of surgical treatment. Although better radiological results could be seen for the combined procedure, regarding the postoperative quality of life no advantage could be proved compared with the dorsally stabilized patients. Furthermore, there was no relation between the radiological results and the quality of life parameters. Therefore, it can be assumed that the injury itself seems to be the main cause of the decreased quality of life after a burst fracture of the thoracolumbar transition.

Adult↗

PubMed2004

[Bone grafts endoscopically applied to the spine Ergebnisse der anterioren Fusion und therapeutische Konsequenzen].

The application of autogenous bone grafts represents the golden standard for reconstruction of the load-bearing anterior column in the thoracolumbar spine. However, the osseous integration of the implanted grafts is demanding and delayed union or pseudarthrosis may occur. There are no standardized data available yet indicating the further course in such cases. The aim of this study was to evaluate the incorporation of endoscopically applied grafts and to develop therapeutic strategies for delayed or non-fusions. Twenty patients suffering from unstable injuries of the thoracolumbar spine were studied in a prospective clinical trial. After primary dorsal stabilization, the anterior column was thoracoscopically reconstructed with an autogenous iliac crest graft and a fixed-angle implant (MACS). The osseous integration of the bone grafts was detected by MSCT 1 year postoperatively. Complete integration of the transplanted bone grafts was observed in only 65% of the cases. In 25% partial integration was detected and in two cases a fracture of the transplanted iliac crest graft occurred. Despite the incomplete integration of the bone grafts, the further course without surgical intervention revealed no clinical or radiological evidence of a concomitant implant loosening or a relevant secondary loss of correction. Similar to the open technique, endoscopic reconstruction of the anterior column with autogenous bone grafts may lead to disadvantageous results concerning the integration and healing of the applied bone grafts. Decision making in such cases depends on the individual clinical and radiological findings (i.e., evidence of implant loosening and concomitant loss of correction).

Adult↗

PubMed2004

The role of angiogenesis in a murine tibial model of distraction osteogenesis.

Distraction osteogenesis (DO) is one of the most dramatic in vivo applications of mechanical stimulation as a means of inducing bone regeneration. A simple and reproducible murine model of tibia distraction osteogenesis was developed using a monolateral fixator. Bone formation was assessed histologically over a 35-day time course. The steady state expression of a broad family of angiogenesis-associated genes was assessed by microarray hybridization analyses over the same time course, while the immediate gene response that was induced during each cycle of distraction was assessed at 30 min and 8 h after the first and last rounds of activation of the fixator. Distraction osteogenesis promoted new bone formation primarily through an intramembranous process with maximal osteogenesis during the active distraction period. Histological analysis also showed that dense cortical bone continued to be formed, during the consolidation phase, for 2 weeks after distraction ended. The analysis of steady state mRNA expression levels over the time course of DO showed that VEGF-A and neuropilin, an alternate receptor for VEGF-A, both angiopoietin (Ang) 1 and 2 factors, and the Ang receptor Tie2 were the critical angiogenic factors during DO. A key transcriptional regulator of many of the angiogenic factors, hypoxia-induced factor1alpha (Hif-1a), the FGF binding protein pleiotropin/OSF1, and multiple MMP(s), were also induced during the active distraction period. Examination of the expression of angiogenic factors that were induced after each cycle of activation, demonstrated that Hif-1a, Nrp1, and VEGF-A were all cyclically induced after each increment of distraction. These results suggest that these factors are early mediators that are produced by distraction and contribute toward the processes that promote bone formation. These experiments represent the first step in defining the molecular mechanisms that regulate skeletal regeneration and the functional relationship between angiogenesis and osteogenesis during distraction osteogenesis.

Animals↗

PubMed2003

[Investigation of the health-related quality of life after a dorso ventral stabilization of the thoracolumbar junction].

OBJECTIVE: Combined dorsoventral stabilization provides superior mechanical stability in the operative treatment of thoracolumbar spine fractures. Currently, there are no data available reflecting the quality of life in trauma patients following the combined procedure. The aim of this investigation was to study the health-related quality of life after dorsoventral stabilization of the thoracolumbar junction using the SF-36 Health Survey. METHODS: In order to assess the quality of life, 30 patients from a consecutive series with unstable fractures of the thoracolumbar junction were investigated in a clinical study. After posterior stabilization with an internal fixator (USS, Synthes),anterior arthrodesis was performed subsequently by autogenous iliac bone grafting in combination with osteosynthesis (MACS, Aesculap; VentroFix, Synthes). The quality of life was investigated 2 years after surgery. Additionally, plain X-rays were obtained and the degree of kyphotic deformation was measured. RESULTS: The evaluation of the data obtained from the SF-36 revealed a reduced quality of life, especially regarding the "physical functioning index", the "bodily pain index", and the "emotional functioning index". Of the patients, 42% still suffered from moderate to severe pain. Measurement of the Cobb angle showed a slight loss of correction without occurrence of a relevant kyphotic deformity. Our statistical analyses did not show any correlation between the data obtained from the SF-36 and the clinical results. Especially there was no correlation between the "bodily pain index" and the Cobb angle ( r=0.112, Spearman's rank order correlation). CONCLUSION: The patients studied here showed a reduced quality of life 2 years after dorsoventral stabilization of the thoracolumbar junction predominantly resulting in long-term pain symptoms. As these findings could not be related to the radiological results (i.e., the occurrence of a kyphotic deformation), other factors such as injury of the motion segment of the spine and the major surgical procedure have to be considered as the main reasons for the reduced quality of life. In summary, it can be concluded that the SF-36 is a suitable tool for the investigation of the postoperative outcome following dorsoventral stabilization of the thoracolumbar junction in trauma patients.

Adolescent↗

PubMed2003

[Treatment of metaphyseal bone defects after fractures of the distal radius. Medium-term results using a calcium-phosphate cement (BIOBON)].

PROBLEM: Since 1998 the calcium-phosphate cement BIOBON has been an established tool for the operative treatment of metaphyseal bone defects. No data are currently available in the literature on the clinical results of employing BIOBON: METHODS: For the evaluation of the mediumterm outcome in the therapy of metaphyseal bone defects after distal radial fractures, we examined 29 patients in a retrospective study. These patients with unstable radial fractures were treated between 1998 and 2001 with BIOBON and additional osteosynthesis. RESULTS: We performed a clinical and radiological examination of 20 patients (69.0%) after an average period of 18.35 months (9-40 months). In all patients parts of the bone replacement material were still visible radiologically. The average outcome using the Gartland and Werley score was 7.5 points (2-21) and therefore a good result. CONCLUSION: Calcium-phosphate cements represent a good alternative to autogenous bone transplantation, especially in elderly patients.

Aged↗

PubMed2003

Expression of angiogenic factors during distraction osteogenesis.

Distraction osteogenesis is a unique and effective way to treat limb length inequality resulting from congenital and posttraumatic skeletal defects. However, despite its widespread clinical use, the cellular and molecular mechanisms by which this surgical treatment promotes new bone formation are not well understood. Previous studies in distraction osteogenesis have noted increased blood flow and vessel formation within the zone of distraction. These observations suggest that distraction osteogenesis may be driven in part by an angiogenic process. Using immunohistological analysis, the expression of two different angiogenic factors (VEGF and bFGF) was shown to localize at the leading edge of the distraction gap, where nascent osteogenesis was occurring. These cells were spatially adjacent to new vessels that were identified by staining for factor VIII. Microarray analysis detected maximal mRNA expression for a wide variety of angiogenic factors including angiopoietin 1 and 2, both Tie receptors, VEGF-A and -D, VEGFR2, and neuropilin 1. Expression of these factors was found to be maximal during the phase of active distraction. Expression of mRNA for extracellular matrix proteins and BMPs was also maximal during this period. A comparison between the patterns of gene expression in fracture healing and distraction osteogenesis revealed similarities; however, the expression of a number of genes showed selective expression in these two types of bone healing. These data suggest that bone formation during distraction osteogenesis is accompanied by the robust induction of factors associated with angiogenesis and support further investigations to elucidate the mechanisms by which angiogenic events promote bone repair and regeneration.

Angiogenesis Inducing Agents↗

PubMed2002

[Long-term outcomes after using porous hydroxyapatite ceramics (Endobon) for surgical management of fractures of the head of the tibia].

Endobon is a porous hydroxyapatite ceramic which has been used as a bone replacement substitute since 1989. Currently there are no data available reflecting long-term effects of Endobon in human bone grafting. In order to assess such effects 35 patients with fractures of the proximal tibia were studied retrospectively over a period up to 91 months. The metaphyseal defects were filled by Endobon and fractures were stabilized by internal plate fixation subsequently. A secondary loss of reduction due to mechanical failure of the bone replacement material did not occur even after removal of metal implants. No histological signs of resorption or degradation could be found 18 months after application. Our data show that Endobon provides good mechanical properties during a long term follow-up and can be recommended as a suitable therapeutic option versus cancellous bone graft.

Bone Substitutes↗

PubMed2001

Nasal and paranasal sinus carcinoma: are we making progress? A series of 220 patients and a systematic review.

BACKGROUND: The authors reviewed treatment results in patients with nasal and paranasal sinus carcinoma from a large retrospective cohort and conducted a systematic literature review. METHODS: Two hundred twenty patients who were treated between 1975 and 1994 with a minimum follow-up of 4 years were reviewed retrospectively. A systematic review of published articles on patients with malignancies of the nasal and paranasal sinuses during the preceding 40 years was performed. RESULTS: The 5-year survival rate was 40%, and the local control rate was 59%. The 5-year actuarial survival rate was 63%, and the local control rate was 57%. Factors that were associated statistically with a worse prognosis, with results expressed as 5-year actuarial specific survival rates, included the following: 1) histology, with rates of 79% for patients with glandular carcinoma, 78% for patients with adenocarcinoma, 60% for patients with squamous cell carcinoma, and 40% for patients with undifferentiated carcinoma; 2) T classification, with rates of 91%, 64%, 72%, and 49% for patients with T1, T2, T3, and T4 tumors, respectively; 3) localization, with rates of 77% for patients with tumors of the nasal cavity, 62% for patients with tumors of the maxillary sinus, and 48% for patients with tumors of the ethmoid sinus; 4) treatment, with rates of 79% for patients who underwent surgery alone, 66% for patients who were treated with a combination of surgery and radiation, and 57% for patients who were treated exclusively with radiotherapy. Local extension factors that were associated with a worse prognosis included extension to the pterygomaxillary fossa, extension to the frontal and sphenoid sinuses, the erosion of the cribriform plate, and invasion of the dura. In the presence of an intraorbital invasion, enucleation was associated with better survival. In multivariate analysis, tumor histology, extension to the pterygomaxillary fossa, and invasion of the dura remained significant. Systematic review data demonstrated a progressive improvement of results for patients with squamous cell and glandular carcinoma, maxillary and ethmoid sinus primary tumors, and most treatment modalities. CONCLUSIONS: Progress in outcome for patients with nasal and paranasal carcinoma has been made during the last 40 years. These data may be used to make baseline comparisons for evaluating newer treatment strategies.

Adolescent↗

PubMed2001

Giant lateral electrostriction in ferroelectric liquid-crystalline elastomers.

Mechanisms for converting electrical energy into mechanical energy are essential for the design of nanoscale transducers, sensors, actuators, motors, pumps, artificial muscles, and medical microrobots. Nanometre-scale actuation has to date been mainly achieved by using the (linear) piezoelectric effect in certain classes of crystals (for example, quartz), and 'smart' ceramics such as lead zirconate titanate. But the strains achievable in these materials are small--less than 0.1 per cent--so several alternative materials and approaches have been considered. These include grafted polyglutamates (which have a performance comparable to quartz), silicone elastomers (passive material--the constriction results from the Coulomb attraction of the capacitor electrodes between which the material is sandwiched) and carbon nanotubes (which are slow). High and fast strains of up to 4 per cent within an electric field of 150 MV x m(-1) have been achieved by electrostriction (this means that the strain is proportional to the square of the applied electric field) in an electron-irradiated poly(vinylidene fluoride-trifluoroethylene) copolymer. Here we report a material that shows a further increase in electrostriction by two orders of magnitude: ultrathin (less than 100 nanometres) ferroelectric liquid-crystalline elastomer films that exhibit 4 per cent strain at only 1.5 MV x m(-1). This giant electrostriction was obtained by combining the properties of ferroelectric liquid crystals with those of a polymer network. We expect that these results, which can be completely understood on a molecular level, will open new perspectives for applications.

Journal Article↗

PubMed2001

Retrograde theory in sialolithiasis formation.

Sialolithiasis is a relatively frequent occurrence; however, cases of sialolithiasis originating around a "foreign body" nidus are rare. We describe a patient with submandibular sialolithiasis organized around a vegetal nidus and discuss the etiology of the case.

Female↗

PubMed2001

Biologically and chemically optimized composites of carbonated apatite and polyglycolide as bone substitution materials.

We report on the development and characterization of a new composite material consisting of amorphous carbonated apatite, Ca(5)(PO(4), CO(3))(3)(OH), and microstructured poly(hydroxyacetic acid), polyglycolide (PGA). This material is able to keep the pH of a surrounding solution within the physiological range (7.2-7.6). This was achieved by chemical fine-tuning of the counterplay between the acidic degradation of the polyester and the basic dissolution of calcium phosphate. Microporous samples with pore sizes of <1 microm and compact samples were prepared. The biological behavior was assayed in vitro by long-term osteoblast culture. Morphological and biochemical analyses of cell differentiation revealed excellent biocompatibility, leading to cell attachment, collagen and osteocalcin expression, and mineral deposition. This material could be of use as a biodegradable bone substitution material and as a scaffold for tissue engineering.

Animals↗

PubMed2001

Multiple forms of glycoproteins in the secretory product of the bovine subcommissural organ--an ancient glial structure.

The glial subcommissural organ (SCO) is a conserved structure of the vertebrate brain that secretes a glycoprotein-rich product into both the extracellular matrix and the cerebrospinal fluid of the third ventricle that forms Reissner's fibre (RF). In order to identify specific secretory proteins of the subcommissural organ, a panel of antigen- and epitope-specific monoclonal antibodies was raised against bovine RF to study the distribution of epitopes in Western blots of bovine RF. Six groups of epitopes that were specific for SCO secretion were distinguished on the basis of their phylogenetic conservation and their different grades of resistance against chemical denaturation. The monoclonal antibody aRFME 4 recognised a carbohydrate-containing epitope that was strongly conserved in vertebrates and unique for SCO secretion. All epitopes showed essentially the same distribution pattern over 15 bovine RF glycoprotein fractions of different molecular masses in immunoblots indicating that the different RF fractions are closely related. They may represent multiple forms of SCO spondin.

Animals↗