Distribution of soluble and microsomal epoxide hydrolase in the mouse brain and its contribution to cerebral epoxyeicosatrienoic acid metabolism

Epoxide hydrolases comprise a family of enzymes important in detoxification and conversion of lipid signaling molecules, namely epoxyeicosatrienoic acids (EETs), to their supposedly less active form, dihydroxyeicosatrienoic acids (DHETs). EETs control cerebral blood flow, exert analgesic, anti-inflammatory and angiogenic effects and protect against ischemia. Although the role of soluble epoxide hydrolase (sEH) in EET metabolism is well established, knowledge on its detailed distribution in rodent brain is rather limited. Here, we analyzed the expression pattern of sEH and of another important member of the EH family, microsomal epoxide hydrolase (mEH), in mouse brain by immunohistochemistry. To investigate the functional relevance of these enzymes in brain, we explored their individual contribution to EET metabolism in acutely isolated brain cells from respective EH -/- mice and wild type littermates by mass spectrometry. We find sEH immunoreactivity almost exclusively in astrocytes throughout the brain, except in the central amygdala, where neurons are also positive for sEH. mEH immunoreactivity is abundant in brain vascular cells (endothelial and smooth muscle cells) and in choroid plexus epithelial cells. In addition, mEH immunoreactivity is present in specific neuronal populations of the hippocampus, striatum, amygdala, and cerebellum, as well as in a fraction of astrocytes. In freshly isolated cells from hippocampus, where both enzymes are expressed, sEH mediates the bulk of EET metabolism. Yet we observe a significant contribution of mEH, pointing to a novel role of this enzyme in the regulation of physiological processes. Furthermore, our findings indicate the presence of additional, hitherto unknown cerebral epoxide hydrolases. Taken together, cerebral EET metabolism is driven by several epoxide hydrolases, a fact important in view of the present targeting of sEH as a potential therapeutic target. Our findings suggest that these different enzymes have individual, possibly quite distinct roles in brain function and cerebral EET metabolism.

[Clinical accuracy of fluoroscopic navigation at the thoracic and lumbar spine]

The aim of the present study was the verification of the accuracy of 2-D fluoroscopy-based navigated pedicle screws at the thoracic and lumbar spine in a case series of traumatised patients. Within 36 months 111 pedicle screws in 29 patients were instrumented using C-arm based navigation, 60 at the thoracic and 51 at the lumbar spine. All screw positions were evaluated postoperatively by a routine thin slice CT scan using multiplanar reconstruction. The position of a screw in relation to its pedicle was classified in a) screw completely intraosseous, b) screw perforated less than thread level and c) screw perforated more than thread level. In 34 thoracic (56.7%) and 32 lumbar (62.7%) screws complete intraosseous placement was observed, 14 thoracic (23.3%) and 14 lumbar (27.5%) screws perforated less than thread level. Perforations more than thread level were found in 12 thoracic (20%) and 5 lumbar (9.8%) screws. Only medial and lateral perforations of the pedicle were documented (without neurological signs), cranial or caudal ones did not occur. Segmentation of the C-arm navigation into two comparable treatment periods showed a learning curve with a reduction of perforations in the second sequence (after 57 pedicle instrumentations) of about 15%, this was found to be not statistically significant. The fluoroscopic navigation of pedicle screws is a safe procedure at the lumbar spine with equal accuracy compared to the non-navigated conventional instrumentation. Application of C-arm navigation at the thoracic spine showed more inaccuracies, so that 3-D-based navigation seems to be advantageous in this region.

Biomechanical comparison of two side plate fixation techniques in an unstable intertrochanteric osteotomy model: Sliding Hip Screw and Percutaneous Compression Plate

BACKGROUND

Our objective was to determine the biomechanical primary stability of two different side plate fixation devices in an unstable intertrochanteric cadaver model: the Sliding Hip Screw with an additional derotation screw was compared with the Percutaneous Compression Plate.

METHODS

Eight pairs of human cadaver femurs were tested for comparison of the primary stability of the two implants in two modes: (a) cyclic loading up to 200 N, 400 N, 600 N, 800 N, and 1000 N, respectively. In vitro combined axial and bending loads were applied. Angular displacements of the proximal head fragment during loading were recorded in rotational, varus-valgus, and anterior-posterior directions. (b) The load to failure was determined.

FINDINGS

Specimens fixed with the Percutaneous Compression Plate showed higher displacements in the varus during loading up to 200 N (P=0.033), and 400 N (P=0.001), compared to the Sliding Hip Screw. A similar tendency was observed for higher loads. The Percutaneous Compression Plate allowed more external rotation of the proximal fragment only at loads up to 800 N (P=0.019). No statistical difference could be found for the slight migrations in the posterior direction. Load to failure also revealed no statistical difference between the two implants.

INTERPRETATION

The Percutaneous Compression Plate as a double-axis fixation device with a sliding capability allows higher displacements in the varus direction and also in external rotation at 800 N loading compared to the Sliding Hip Screw as a single-axis fixation device combined with an additional derotation screw. While both implants are successful used in clinical practice, this should be considered in treatment of unstable intertrochanteric fractures with inferior comminution in osteoporotic patients.

Therapieindikationen und -optionen bei ossären Metastasen

Pathological fractures are dreaded complications due to skeletal metastasis. Modern oncological therapies and more sophisticated new radiological techniques such as MRI and positron emission tomography have improved multimodal treatment concepts. Surgical intervention is determined by the primary disease, general condition and life expectancy of the patient. The goals of surgical treatment are improvement of life quality, pain relief and maintenance of mobility.

Hip arthroplasty with proximal transmission of force: first clinical results with a new partially cemented femoral stem

BACKGROUND

Proximal stem fixation by partial cementing is a new concept in hip arthroplasty. We conducted a prospective clinical and radiological analysis to evaluate the preliminary outcome of this new technique with the Option 3000 stem (Mathys Orthopaedics, Bettlach, Switzerland).

METHODS AND FOCUS

One hundred and thirty-three hip replacements in 123 patients have been performed between 1996 and 2003: All of them were followed up regularly both clinically and radiological and 53 were analysed with the EBRA-FCA method. Eighty-six patients with 95 hips could be seen in August 2004. At this point of time, the mean follow-up time was 61 months (5.08 years) with a maximum of 100 months (8.33 years)

RESULTS

The clinical data reported an average Harris Hip Score of 85.5. Nine stems had to be exchanged over the period of study. The EBRA-FCA analysis reported a mean subsidence less than 1.5 mm after 2 years, then an average stable subsidence of 2.4 mm. So the results are similar to the early results obtained with other fixation concepts and the long-term results appear promising.

Navigationsgestützte Arthrodese des Iliosakralgelenks

Arthrodesis of the sacroiliac joint (SI) usually requires a large surgical exposure using the lateral approach. Computer-assisted surgery based on intraoperative 3D fluoroscopy imaging can reduce the approach to stab incisions. The clinical example shows the insertion of two screws and a cylindrical bone graft to achieve an arthrodesis of the SI joint. The intraoperatively navigated placement of implants and bone graft was performed only by stab incisions.

Crystal structures of beta-galactosidase from Penicillium sp. and its complex with galactose

Beta-galactosidases catalyze the hydrolysis of beta(1-3) and beta(1-4) galactosyl bonds in oligosaccharides as well as the inverse reaction of enzymatic condensation and transglycosylation. Here we report the crystallographic structures of Penicillium sp. beta-galactosidase and its complex with galactose solved by the SIRAS quick cryo-soaking technique at 1.90 A and 2.10 A resolution, respectively. The amino acid sequence of this 120 kDa protein was first assigned putatively on the basis of inspection of the experimental electron density maps and then determined by nucleotide sequence analysis. Primary structure alignments reveal that Penicillium sp. beta-galactosidase belongs to family 35 of glycosyl hydrolases (GHF-35). This model is the first 3D structure for a member of GHF-35. Five distinct domains which comprise the structure are assembled in a way previously unobserved for beta-galactosidases. Superposition of this complex with other beta-galactosidase complexes from several hydrolase families allowed the identification of residue Glu200 as the proton donor and residue Glu299 as the nucleophile involved in catalysis. Penicillium sp. beta-galactosidase is a glycoprotein containing seven N-linked oligosaccharide chains and is the only structure of a glycosylated beta-galactosidase described to date.

[Navigation of tumors and metastases in the area of the thoraco-lumbar spine]

In this clinical feasibility study, CT-based verification of the efficacy of navigated decompression and pedicle screw placement in patients who had tumor-related posterior surgery was demonstrated. Eighty-six percent of the pedicle screws were positioned centrally in the bone without perforation; in all patients accurate decompression was seen. The accuracy of transpedicle screw implantation postoperatively was investigated with CT. In contrast to other published studies, no postoperative neurologic deterioration was seen in the patients as a result of using computer-aided surgical procedures. At the same time we were able to achieve complete decompression of the neural structures for radiologic and neurologic findings. Because of inaccurate registration, it was not possible to use computer-aided implantation surgery for 15% of the pedicles and, therefore, a conventional fluoroscopic approach was used. Our initial results indicate that computer-aided frameless navigation of tumor surgery of the spine is a safe technique which improves surgical performance during posterior decompression and transpedicle stabilization. In addition, CAS surgery improved the intraoperative information about the tumor and the current surgical intervention during decompression. Nevertheless the technique should be used only by experienced surgeons who can, if required, continue the operation using conventional techniques. Furthermore, the surgeon should have a complete theoretical understanding of the navigation system to minimize possible misinterpretation of computer guidance information.

[Precision of navigation-assisted surgery of the thoracic and lumbar spine]

The goal of these studies was to evaluate the accuracy of in vivo and in vitro application of CT- and C-arm-based navigation at the thoracic and lumbar spine. With CT based navigation, 82 pedicle screws were consecutively inserted, 53 into the thoracic and 29 into the lumbar spine. Seven (13%) perforations were detected at the thoracic spine and two (7%) at the lumbar spine. Additionally, minor perforations below the thread depth were seen in six (11%) thoracic and in two (7%) lumbar instrumentation. With C-arm-based navigation, 74 screws were consecutively placed into 38 thoracic and 36 lumbar pedicles. Perforations were noted in ten (26%) thoracic and four (11%) lumbar implants. Minor perforations were observed in another nine (24%) thoracic and ten (28%) lumbar pedicles. The observer-independent and standardized in vitro study based on a transpedicular 3.2-mm drill hole aiming a 4-mm steel ball in a plastic bone model showed pedicle perforations of the drill canal only in thoracic vertebrae, 1 of 15 in CT-based and 3 of 15 in C-arm navigation. The quantitative calculation of the smallest distance between the central line through the drill canal and the center of the steel ball resulted in 1.4 mm (0.5-4.8 mm) for the CT-based navigation at the thoracic spine and in 1.8 mm (0.5-3 mm) at the lumbar spine. For the C-arm based navigation the distance was 2.6 mm (0.9-4.8 mm) for the thoracic spine and 2 mm (1.2-3 mm) for the lumbar spine. In our opinion, the clinical results of the comparative accuracy of CT- and C-arm-based navigation in the present study showed moderate advantages of the CT-based technique in the thoracic spine, whereas CT- and C-arm based navigation had comparable perforation rates at the lumbar pedicle. The results of the experimental study correlated with the clinical data.

Difference in metallic wear distribution released from commercially pure titanium compared with stainless steel plates

INTRODUCTION

Stainless steel and commercially pure titanium are widely used materials in orthopedic implants. However, it is still being controversially discussed whether there are significant differences in tissue reaction and metallic release, which should result in a recommendation for preferred use in clinical practice.

MATERIALS AND METHODS

A comparative study was performed using 14 stainless steel and 8 commercially pure titanium plates retrieved after a 12-month implantation period. To avoid contamination of the tissue with the elements under investigation, surgical instruments made of zirconium dioxide were used. The tissue samples were analyzed histologically and by inductively coupled plasma atomic emission spectrometry (ICP-AES) for accumulation of the metals Fe, Cr, Mo, Ni, and Ti in the local tissues. Implant corrosion was determined by the use of scanning electron microscopy (SEM).

RESULTS

With grades 2 or higher in 9 implants, steel plates revealed a higher extent of corrosion in the SEM compared with titanium, where only one implant showed corrosion grade 2. Metal uptake of all measured ions (Fe, Cr, Mo, Ni) was significantly increased after stainless steel implantation, whereas titanium revealed only high concentrations for Ti. For the two implant materials, a different distribution of the accumulated metals was found by histological examination. Whereas specimens after steel implantation revealed a diffuse siderosis of connective tissue cells, those after titanium exhibited occasionally a focal siderosis due to implantation-associated bleeding. Neither titanium- nor stainless steel-loaded tissues revealed any signs of foreign-body reaction.

CONCLUSION

We conclude from the increased release of toxic, allergic, and potentially carcinogenic ions adjacent to stainless steel that commercially pure Ti should be treated as the preferred material for osteosyntheses if a removal of the implant is not intended. However, neither material provoked a foreign-body reaction in the local tissues, thus cpTi cannot be recommend as the 'golden standard' for osteosynthesis material in general.

Ergebnisse nach Osteosynthese intraartikulärer Kalkaneusfrakturen mit der „Low contact” Platte

Calcaneus fractures are a major cause of accident- related invalidity. Long-term results are unsatisfactory with various therapy concepts as reported in the literature. Objective of this study is the long-term clinical and radiological outcome of a patient group treated with a low contact plate. Subjective assessment of function by the patient was an important evaluation criterion. From 01/92 to 12/98 a total of 182 patients with 209 calcaneus fractures were treated. Out of them 95 patients with 109 calcaneus fractures had a follow-up over a period ranging from 6 to 88 months (average 37.9 months). Severe impairment of walking was reported by 34.7 % of the patients. Severe impairment for work was declared by 68.4 % of the patients. 74.7 % of the patients complained middle or severe burden-pain. 64.3 % of the patients felt their quality of life impaired. After the injury 75.8 % of the patients were still employed. Arthrosis of the inferior ankle joint was found in 91.5 % of the cases. Within this collective three patient groups were formed with different follow-up periods to evaluate the temporal course, showing no significant differences. Frequently good functional and subjective results cannot be expected even with standardized operative procedures.

Strahlendosis im OP ? ein Vergleich computerassistierter Verfahren

Since the 1990s, computer-assisted methods have been well-established in the field of orthopedics and traumatology. In addition to the proven improvement in the field of surgical precisioncompared with conventional techniques, the decrease in the amount of emitted ionizing radiation inside of the operating room was cited to constitute an additional major advantage of computer-based navigation. The goal of this study was to quantify X-ray dose values exposed during both conventional methods and computer-assisted procedures, the latter being performed using a C-arm device SIREMOBIL Iso-C3D (Siemens Medical Solutions). The clinical measurements were supplemented by laboratory experiments using a pinpoint ionization chamber placed inside a standard lucite phantom. The clinical part of the study investigated the application of new, i.e. computer assisted, techniques in comparison with conventional procedures on in total 42 patients experiencing surgery either on their lower extremities (n = 14) or on the spine (n = 28). The techniques applied were: (1) conventional surgical procedure, (2) CT-based navigation, (3) C-arm navigation, and (4) Iso-C3D-navigation. The main focus of the clinical evaluation was the determination of radiation dose values by means of thermoluminescence dose meters, accompanied by the registration of the operation times of the X-ray tube during a surgical intervention. The conclusions from the clinical studies are in agreement with the results from the laboratory measurements. Computer-assisted techniques led to a significant reduction in X-ray dose exposure and drastically shortened irradiation times. The most pronounced decrease in the emission of ionizing radiation was achieved in case of the Iso-C3D-navigation, which has only recently been introduced into clinical practice, i.e. during runtime of this study.

Sequestration of biological reactive intermediates by trapping as covalent enzyme-intermediate complex

One important class of biological reactive intermediates arising in the course of human xenobiotic metabolism are arene and alkene oxides. The major safeguard against the potential genotoxic effects of these compounds is the microsomal epoxide hydrolase (mEH). This enzyme has a broad substrate specificity but--on the first sight--seems to be inadequately suited for this protection task due to its low turnover number with most of its substrates. The recent progress in the understanding of the mechanism of enzymatic epoxide hydrolysis has shed new light on this apparent dilemma: Epoxide hydrolases convert their substrates via the intermediate formation of a covalent enzyme-substrate complex, and it has been shown that the formation of the intermediate proceeds by orders of magnitudes faster than the subsequent hydrolysis, i.e. the formation of the terminal product. Thus, the enzyme acts like a molecular sponge by binding and inactivating the dangerous metabolite very fast while the subsequent product release is considerably slower, and quantification of the latter heavily underestimates the speed of detoxification. Usually, the slow enzyme regeneration does not pose a problem, since the mEH is highly abundant in human liver, the organ with the highest capacity to metabolically generate epoxides. Computer simulation provides evidence that the high amount of mEH enzyme is crucial for the control of the steady-state level of a substrate epoxide and can keep it extremely low. Once the mEH is titrated out under conditions of extraordinarily high epoxide concentration, the epoxide steady-state level steeply rises, leading to a sudden burst of the genotoxic effect. This prediction of the computer simulation is in perfect agreement with our experimental work. V79 Chinese Hamster cells that we have genetically engineered to express human mEH at about the same level as that observed in human liver are well protected from any measurable genotoxic effect of the model compound styrene oxide (STO) up to an apparent threshold level of 100 microM in the cell culture medium. In V79 cells that do not express mEH, STO triggers the formation of DNA strand breaks in a dose-dependent manner with no apparent threshold. Above 100 microM, the genotoxic effect of STO in the mEH-expressing cell line parallels the one in the parental cell line.

Monitoring and healing analysis of 100 tibial shaft fractures

BACKGROUND

We assessed the value of measuring biomechanical stiffness by assessing the fixator's external deformation as an objective means for monitoring fracture healing and determining the postoperative treatment regime, as compared to clinical and radiographic means of evaluation.

PATIENTS AND METHODS

One hundred patients with tibial shaft fractures managed by unilateral external fixation had their fracture stiffness monitored. Stiffness was measured and clinical and radiological examinations were performed every 3-4 weeks.

RESULTS

The time required for healing as indicated by stiffness measurement was an average of 2.5 weeks earlier than by radiological assessment. Eighty-two patients healed within 19 weeks (12.1+/-3.3 weeks) and ten patients in the following 6 weeks (24+/-4.3 weeks). Eight patients did not show an increase in fracture stiffness and received intramedullary nailing at a second operation. The average healing time was 11.3+/-4 weeks for type A, 13.1+/-3.6 weeks for type B fractures, and 15.1+/-5.9 weeks for type C fractures. The healing time for closed fractures was 11.3+/-3.2 weeks and for open fractures 14+/-4.9 weeks.

CONCLUSIONS

The measurement of fracture stiffness allows the detection of patients at risk for nonunions. The healing time increased with increasing fracture gap size and was less in patients with younger age, less complex fractures, and lesser degrees of soft tissue damage.

[Combined posterior and anterior endoscopic supported instrumentation of the thoracic and lumbar spine. Arguments, concepts and first clinical results]

The operative therapeutic principles of thoracic and lumbar spine injuries are based on reposition, decompression and stabilization of the unstable area. Secondary loss of correction and consecutive deformation have negative impact on the long-term results after defect fractures of vertebral bodies and will be minimized only by the reconstruction of all involved spinal columns. With dissemination of thoracoscopic techniques at the thoracic spine and minimal invasive retroperitoneal approaches at the lumbar spine a decrease of the morbidity was achieved with equal effectivity for recalibration and fusion. Our experiences with the first consecutive 42 patients, treated minimal invasive are presented. Indications for anterior thoracoscopic and minimal invasive instrumentations after posterior transfixation are remaining osseous defects of the end plates of more than a quarter of the volume of the involved vertebra in case of migration of the vertebral disc, wedging of the vertebral body after posterior reposition of more than 10 degrees and persisting anterior encroachment of the spinal canal of more than 30 %. The decision is based on radiographs and CT-scans, performed after posterior stabilization.

[Sources of error and risks in CT based navigation]

Based on the experience of 4 cervical, 102 thoracic/lumbar pedicle screw and 14 transiliosacral screw implantations all problems and complications were collected. Problems noted within the data collection in the preoperative CT were an incomplete acquisition of the surgical target (n = 3), an exceeding of the processable scan slices (n = 1) and a non focused field of view. Transmission of the CT datas often were documented as incomplete (n = 16). Segmentation of the CT dataset turned out to be the significant problem with incorrect differentiation of the bone-soft tissue transition (n = 2), where as the choice of the matching points and the trajectories did not provoke any mistakes in the planning modus. The intraoperative matching of both corresponding datasets was insufficient (n = 7), while the assignment of the CT dataset to the correct vertebral was not a major problem (n = 1). Navigation was not possible (n = 2) due to an instability of the spinal process. All fiducial based matching procedures (pelvis) were carried out without any problems. During intraoperative navigation potential complications resulted from deformation of instruments (n = 1) and interaction of instruments and the data reference base (n = 2). Further, the CT-based navigation of fractured vertebrae or unstable iliosacral joints is not safe, because dislocations between acquisition of the dataset and operation will lead to misguidance.

Spinal navigation in cervical fractures--a preliminary clinical study on Judet-osteosynthesis of the axis

OBJECTIVE

To evaluate the accuracy of CT-based and computer-aided screw insertion into the pedicles of the axis using the method of Judet. Materials and Methods In two patients, four transpedicular implants of C2 were positioned using a computer-guided technique. One patient with iatrogenic destabilization of the posterior structures C3 and C4 and one patient with a hangman's fracture of the axis required pedicular fixation. In addition, intraoperative documentation of the additional time required for the navigation procedures was made. Finally, postoperative CTs of each patient provided further information about transpedicular implant localization.

RESULTS

Image-guided implantation of screws was possible in all scheduled pedicles of the axis. In the postoperative CT scans, none of the inserted screws perforated the medial or lateral pedicle. All screws were accurately positioned within the pedicles, and no anterior perforation of the screws into the vertebral foramen was observed.

CONCLUSIONS

Our initial results using computer-aided implantation of Judet screws showed that these screws were inserted correctly. However, it is important to realize that movements can occur in the vertebral arch and lateral mass during the time between preoperative CT and surgery. This possibility for movement should be taken into account when procedures such as CT-based insertion of image-guided screws into patients with fractures of the isthmus C2 are performed, because damage to neurovascular structures can result. Therefore, this navigation system should only be used by experienced surgeons who can, if necessary, continue the intervention with more conventional techniques. In addition, it is essential that the surgeon have a complete understanding of the principles of the tracking systems to prevent possible misinterpretation of computer-generated information.

[Influence of prosthesis design on intramedullary pressure formation in femur shaft implants of cemented hip endoprostheses]

The increase of intramedullary femoral pressure can lead to the intravasation of bone marrow and fat cells into the blood stream of the femoral vein and consequently into the pulmonary circulation. This effect is the same in intramedullary nailing and in the implantation of femoral stem prostheses. In a prospective study we evaluated the intraoperative, intramedullary pressure in the distal femur during the implantation of femoral stem prostheses with two different designs. In eight patients we implanted Müller straight stems and in another eight we implanted stem type Option 3000. Intramedullary pressure was recorded continuously by the implantation of a microtip pressure probe (piezoresistive principle, 50 Hz) in the distal femur. We found markedly higher pressure in Müller straight stem prostheses: range: 590-2,570 mmHg (median = 1,293, SD = 627 mmHg). Intramedullary pressure in stem prosthesis type Option 3000 was much lower: range: 59-574 mmHg (median = 289, SD = 219 mmHg). The differences were statistically significant (p = 0.0008). By changing the designs of femoral stem prostheses, the intramedullary pressure can be markedly reduced. In the case of elderly patients or those with pulmonary illness we recommend femoral stem prosthesis designs, which induce little increase in the intramedullary pressure, in order to reduce cardiopulmonary complications.

[Precision in standardized Iso-C-Arm based navigated boring of the proximal femur]

C-arm navigation is a new tool in computer assisted surgery. The aim of this study is to evaluate the accuracy of Iso-C-arm based drill holes in the proximal femur. In nine artificial proximal femura, two holes with an angle of 135 degrees and 100 degrees in relation to the shaft axis were drilled in the direction of the femoral head. The defined target of the 3.2 mm drillings was a 4 mm steel ball, which had previously been placed and fixed at the cranial center of the femoral head. All the drillings were standardized with a navigated drilling machine fixed to a frame which only allowed movement of the system in the direction of the drill. During navigation the positions of the drill before commencement and at the deepest point of the canal were recorded. After drilling all specimens were evaluated by CT, and the coordinates of the center of the start and the end of the drilled hole and the center of the ball were determined. Using vector calculation, the smallest distance between the straight line, defined by the center of the starting point and the end point of the drill hole, and the center of the ball was calculated. Additionally, the coordinates of the intersection between the perpendicular to the center of the ball and the straight line were determined (xv, yv, zv), to evaluate the direction of misplacement of the drilled canal in relation to the target. For the 135 degrees drill holes, a median of 2.5 mm for the smallest distance between the straight line, given by the center of the start and the end of the hole, and the center of the ball was investigated (range 1.6-3.7 mm). For the 100 degrees holes the median was 3.1 mm (range 1.8-4.2 mm). The main plane of deviation in all of the 135 degrees holes was posteriorly, whereas in the 100 degrees holes posterior deviation occurred in four cases, cranial in three cases, and in one case each caudal and anterior deviation occurred. In our opinion, the accuracy of fluoroscopy based navigation applied in the region of the proximal femur is sufficient and reproducible. This technique can be used for implant placement at the proximal femur in the future.

Quantitative assessment of the expression of melanoma-associated antigens by non-competitive reverse transcription polymerase chain reaction

The assessment of tumor-associated antigens (TAA) recognized by T lymphocytes is a prerequisite for diagnosis and immunotherapy of melanoma. Different reverse transcription-polymerase chain reaction (RT-PCR) protocols allowing the quantification of the TAA mRNA expression in the solid tumor or the detection of circulating melanoma cells have been described. We have recently shown a positive correlation between the amount of specific product formed by RT-PCR and the staining intensity in immunohistochemical analysis of the corresponding sample. Here we describe a quantification procedure based on the direct digitization of the PCR products after separation on ethidium bromide-stained agarose gels, followed by computer-assisted densitometry. To standardize our method, we examined the linear range of the densitometric quantification procedure as reflected by the correlation of signal intensity to the amount of the corresponding DNA. As an internal measure for the so-termed cDNA in the different samples after RNA isolation and reverse transcription, a beta-actin PCR was introduced. Subsequently, we chose four sets of primers for the melanoma-associated antigens MAGE1, tyrosinase, Melan A/MART-1 and gp100/Pmel17 and performed PCR analysis over a range of cycle numbers. In each case, the amplification rate remained constant up to at least 26 cycles under the respective conditions. Plotting the logarithm of the amount of product against the cycle number yields a slope that equals the logarithm of the amplification rate. The amount of starting material can be determined from the intercept with the ordinate. In summary, the method introduced in the present work allows the quantification of TAA in melanoma which might be important for the monitoring of disease. Technically the method is sound and sensitive, avoids post-PCR manipulations and can be performed with the standard equipment of a molecular biology laboratory. It can be applied also to other solid tumors and leukemias.

[Precision analysis of navigation-assisted implanted thoracic and lumbar pedicled screws. A prospective clinical study]

A prospective clinical trial was performed to study the accuracy of pedicle screw placement of consecutive computer-aided and conventional techniques. Concerning the clinical performance of the navigation system, the average time of matching has been 8.4 minutes per vertebrae. For evaluation of the results, only complete intraosseous placement of the pedicle screw has been defined as correct position. Any medial or lateral perforation of the cortical structure of the pedicle was recorded as malplacement. In the CT-controlled patients complete intrapedicular placement of the screw was obtained in 36 of 45 thoracic (80%) and in 22 of 27 navigated lumbar (81%) pedicles. In the conventional cohort group 27 of 34 (79%) thoracal and 43 of 52 (83%) lumbar screws were completely in. No radicular neurologic damage, caused by a malplaced transpedicular screw has been observed in both groups. In the presented study is shown, that the application of the computer-assisted freehand navigation can improve results concerning the precision of spinal screw placement. Although, the spinal navigator has to consider a learning curve for the clinical inauguration of the system and the qualification of the implant system for computer-assisted application.

[Computer assisted surgery, 2001 development and prospects. Results of a congress at Reisensburg Castle, 23-24 November 2000]]

The progress in computer assisted surgery (CAS) is influenced by new technologies in imaging as well as by the input of the users. At present, CAS procedures are established in dorsal spine instrumentation, prosthetics and long bone surgery. Present status and future of CAS was a topic of an expert meeting at the Reisensburg castle. Imaging will speed up in the future using multi-detector techniques. C-arm navigation will gain more information using the 3D technology intraoperatively. CT based navigation procedures are standard in spine and will be established in pelvic surgery. CAS in robotics at the moment means the use of robot-assistance. A new concept is the modality-based navigated surgery, which can be used at various skeletal locations. Visualization of patient data will improve using 3D semi-transparencies with real time update. In the future it will be mandatory to find algorithms to fuse the different possibilities and techniques. A new concept of surgical training is necessary to teach CAS procedures. Therefore discussion must go on to improve these systems.

[Incidence of complications of the screw osteosynthesis of odontoid process fractures]

In this retrospective clinical study the incidence of complications in 58 consecutive, with anterior screw fixation stabilized patients after fractures of the odontoid process is evaluated. In 51 patients the fracture has been defined as type II according to Anderson, in 6 patients an oblique type II fracture was present and one patient showed a cephalad type III fracture. Preoperatively, in only 19 % of the patients (n = 11) no dislocation of the dens occurred. 32 patients were treated with single screw osteosynthesis, in 26 patients two screws were implanted. Significant complications with clinical relevance were registered in 14 patients (24 %), in 10 cases (17 %) an operative reintervention was required. Intraoperatively, in one patient a rupture of the carotid artery while winding around the motor drill occurred and in another case a complete malplacement of the screw posteriorly to the odontoid process was observed. A clearly excentric positioning of the implant was evaluated in 5 patients with a consecutive high rate of implant migration (n = 3). Two patients died perioperatively not related to the cervical injury. Postoperatively, one patient with a wound infection due to an iatrogenic perforation of the esophagus required reoperation as well as 4 patients with instability because of implant migration. Patients beyond the age of 65 years (n = 3) were significantly overrepresented in that group. In one case, the secondary intervention was caused by a pseudarthrosis of the dens axis. Complications without any relevance to the clinical and functional long term result were fusions in malposition of the odontoid process in 14 patients (24 %) and 10 (17 %) marginal screw perforations laterally. Differences in the use of one or two screws have not been observed in this study, although the investigations showed a tendency between marginal lateral screw perforations and double screw osteosynthesis and an increasing number of complications in the geriatric cohort.

[Computer-assisted surgery: developments and prospects in 2001. Results of a workshop at Schloss Reisenburg, 23-24 November 2000]

The progress in computer assisted surgery (CAS) is influenced by new technologies in imaging as well as by the input of the users. At present, CAS procedures are established in dorsal spine instrumentation, prosthetics and long bone surgery. Present status and future of CAS was a topic of an expert meeting at the Reisensburg castle. Imaging will speed up in the future using multi-detector techniques. C-arm navigation will gain more information using the 3D technology intraoperatively. CT based navigation procedures are standard in spine and will be established in pelvic surgery. CAS in robotics at the moment means the use of robot-assistance. A new concept is the modality-based navigated surgery, which can be used at various skeletal locations. Visualization of patient data will improve using 3D semi-transparencies with real time update. In the future it will be mandatory to find algorithms to fuse the different possibilities and techniques. A new concept of surgical training is necessary to teach CAS procedures. Therefore discussion must go on to improve these systems.

Early inflammatory mediator response following isolated traumatic brain injury and other major trauma in humans

The inflammatory response following isolated traumatic brain injury (TBI) is characterised by the release of pro- and anti-inflammatory mediators. In order to determine the important mediators regarding survival and outcome of patients with severe traumatic isolated head injuries, we performed this prospective preclinical and clinical study starting upon arrival at the site of the accident. After approval by the local ethics board committee, 94 multiple-injury patients were enrolled. Of these, 72 patients suffered from major injuries; the other 22 patients had a severe isolated brain injury and were allotted to subsets of survival or nonsurvival. Of the pro- and anti-inflammatory mediators (cytokines, arachidonic acid metabolites and soluble adhesion molecules), interleukin-6 (IL-6), IL-12 and malone dialdehyde (MDA) appeared to be of specific importance; maximum IL-6 plasma levels were eightfold higher in cases of nonsurvival than in those of survival. Patients that did not survive TBI were the only ones to express an IL-12 increase, whereas survivors and patients with other major trauma did not show any increase within the first 24 h. An early distinct decrease of MDA showed in patients who did not survive TBI, in contrast to survivor patients who exposed almost constant levels during the first 24 h.

[Surgical treatment of injuries of the thoracolumbar transition--3: Follow-up examination. Results of a prospective multi-center study by the "Spinal" Study Group of the German Society of Trauma Surgery]

OBJECTIVES

Prospective, multicenter study addressing late results after operative treatment of acute thoracolumbar spinal injuries.

METHODS

682 patients (T10-L2) were included and 372 (80%) were postoperatively followed for 2 1/4 years (4-61 months).

RESULTS

Comparing the initially included patients (n = 682) with the study group (n = 372), no differences were observed and results were assumed to be representative. A C-type lesion or polytrauma significantly prolonged the hospital stay. The method of operative treatment did not affect the length of the rehabilitation period. Neurological improvement was observed in 3 out of 7 patients with complete, and in 44 out of 64 (69%) with incomplete lesion. The operative method did not affect the improvement rate. The physical capacity significantly decreased. After a mean of 1/2 year of disability only 71% returned to work. 48% returned to their preoperative physical level. The mean Hannover Spine Score was 68 points (preoperative 94, p < 0.001), indicating permanent impairment of function. The angle-stable internal fixator was superior in restoration of spinal alignment and best radiological results were noted after combined stabilization. Posterior stabilization lead to high re-kyphosing. No correlations between radiologic and clinical parameters were observed.

CONCLUSIONS

All treatment methods under study were appropriate for achieving comparable clinical and functional outcome. The internal fixator is superior in restoration of the spinal alignment. Best radiological outcome is achieved by combined stabilization. Merely by direct reconstruction of the anterior column the postoperative re-kyphosing is prevented and a gain in segmental angle is achieved.

Combined anteroposterior spinal fixation provides superior stabilisation to a single anterior or posterior procedure

Fusion is the main goal in the surgical management of the injured and unstable spine. A wide variety of implants is available to enhance this. Our study was performed to evaluate the stabilising characteristics of several anterior, posterior and combined systems of fixation. Six thoracolumbar (T11 to L2) spines from 13-week-old calves were first tested intact. Then the vertebral body of T13 was removed and the defect replaced and supported by a wooden block to simulate bone grafting. Dorsal implants consisting of a Universal Spine System (USS) fracture system and an AO Fixateur interne (AOFI), and ventral implants comprising of a Kaneda Classic, a Kaneda SR, a prototype of the VentroFix single clamp/single rod construct (SC/SR) and the VentroFix single clamp/double rod construct (SC/DR) were first implanted individually to stabilise the removal of the vertebral body. Simulating the combined anteroposterior stabilisations, all ventral implants were combined with the AOFI. The range of motion (ROM) was measured under loads of up to 7.5 Nm. The load was applied in a custom-made spine tester in the three primary directions while measuring the intervertebral movements using a goniometric linkage system. The dorsal systems limited ROM in flexion below 0.9 degrees and in extension between 3.3 degrees and 3.6 degrees (median values). The improved Kaneda System SR yielded a mean ROM of 1.8 degrees in flexion and in extension. The median rotation found with the VentroFix (SC/DR) was 3.2 degrees for flexion and 2.8 degrees for extension. Reinforcement of the ventral constructs with a dorsal system reduced the ROM in flexion and extension in all cases to 0.4 degrees and lower. In rotation, the median ROM of the anterior systems ranged from 2.7 degrees to 5.1 degrees and for the posterior systems from 3.9 degrees to 5.7 degrees, while the combinations provided a ROM of 1.2 degrees to 1.9 degrees. In lateral bending, the posterior implants restricted movement to 1.1 degrees, whereas the anterior implants allowed up to 5.2 degrees. The combined systems provided the highest stability at less than 0.6 degrees. Our study revealed distinct differences between posterior and anterior approaches in all primary directions. Also, different stabilisation characteristics were found within the anterior and posterior groups. Combinations of these two approaches provided the highest stability in all directions.

Combined anteroposterior spinal fixation provides superior stabilisation to a single anterior or posterior procedure

Fusion is the main goal in the surgical management of the injured and unstable spine. A wide variety of implants is available to enhance this. Our study was performed to evaluate the stabilising characteristics of several anterior, posterior and combined systems of fixation. Six thoracolumbar (T11 to L2) spines from 13-week-old calves were first tested intact. Then the vertebral body of T13 was removed and the defect replaced and supported by a wooden block to simulate bone grafting. Dorsal implants consisting of a Universal Spine System (USS) fracture system and an AO Fixateur interne (AOFI), and ventral implants comprising of a Kaneda Classic, a Kaneda SR, a prototype of the VentroFix single clamp/single rod construct (SC/SR) and the VentroFix single clamp/double rod construct (SC/DR) were first implanted individually to stabilise the removal of the vertebral body. Simulating the combined anteroposterior stabilisations, all ventral implants were combined with the AOFI. The range of motion (ROM) was measured under loads of up to 7.5 Nm. The load was applied in a custom-made spine tester in the three primary directions while measuring the intervertebral movements using a goniometric linkage system.

The dorsal systems limited ROM in flexion below 0.9° and in extension between 3.3° and 3.6° (median values). The improved Kaneda System SR yielded a mean ROM of 1.8° in flexion and in extension. The median rotation found with the VentroFix (SC/DR) was 3.2° for flexion and 2.8° for extension. Reinforcement of the ventral constructs with a dorsal system reduced the ROM in flexion and extension in all cases to 0.4° and lower.

In rotation, the median ROM of the anterior systems ranged from 2.7° to 5.1° and for the posterior systems from 3.9° to 5.7°, while the combinations provided a ROM of 1.2° to 1.9°. In lateral bending, the posterior implants restricted movement to 1.1°, whereas the anterior implants allowed up to 5.2°. The combined systems provided the highest stability at less than 0.6°.

Our study revealed distinct differences between posterior and anterior approaches in all primary directions. Also, different stabilisation characteristics were found within the anterior and posterior groups. Combinations of these two approaches provided the highest stability in all directions.

Internal fixation on the lower cervical spine--biomechanics and clinical practice of procedures and implants

The decision to opt for a particular internal fixation procedure of a traumatized unstable lower cervical spine should be based on analysis and implementation of scientific and clinical data on the biomechanics of the intact, the unstable and the implant-fixed spine. The following recommendations for surgical stabilization of the lower cervical spine seem, therefore, to be justified. Firstly, the surgical procedure should be to bring about decompression, realignment, and stability. Secondly, the anterior approach should be the primary and preferred one. With regard to surgical and positioning technique, this access clearly involves fewer problems than the posterior approach; if required, unrestricted additional cord decompression can take place; implant fixation is technically simple, and the fusion is under direct compression, thus allowing optimal fusion healing. The awareness of instability and type of implant permits functional therapy, above all for the paraplegic patient. Thirdly, for traumatic conditions, posterior methods should be reserved for exceptional indications. The restriction to this approach is that the anterior column must be intact and a multi-segmental fixation must be used. Posterior fixation seems, therefore, to be more appropriate for degenerative, rheumatoid or tumorous instabilities than for traumatic instabilities. The cerclage wire technique depends on intact osseous posterior elements, while after laminectomy only implants fixed with screws can create safe stability. The disadvantages of the posterior access for the proprioception of the cervical muscles and the subjective symptoms of the patient are known and must be taken into account. Fourthly, combined techniques are indicated for highly unstable or particularly complex injuries. On the cervicothoracic junction, or in cases of Bechterew's disease, the decision is justifiably made in favor of this technique, which can be performed as a one-stage or two-stage operation. Finally, whenever possible, selection of the implant should take into account the foreseeable developments in diagnostic procedures, and therefore, in view of the modern imaging techniques likely to be used in any follow-up examinations required later, the implant chosen should be made of titanium.

Differential effects of fluvoxamine and other antidepressants on the biotransformation of melatonin

Melatonin, the predominant product of the pineal gland, is involved in the maintenance of diurnal rhythms. Nocturnal blood concentrations of melatonin have been shown to be enhanced by fluvoxamine, but not by other serotonin reuptake inhibitors. Because fluvoxamine is an inhibitor of several cytochrome P450 (CYP) enzymes, the authors studied the biotransformation of melatonin and the effects of fluvoxamine on the metabolism of melatonin in vitro using human liver microsomes and recombinant human CYP isoenzymes. Melatonin was found to be almost exclusively metabolized by CYP1A2 to 6-hydroxymelatonin and N-acetylserotonin with a minimal contribution of CYP2C19. Both reactions were potently inhibited by fluvoxamine, with a Ki of 0.02 microM for the formation of 6-hydroxymelatonin and 0.05 microM for the formation of N-acetylserotonin. Other than fluvoxamine, fluoxetine, paroxetine, citalopram, imipramine, and desipramine were also tested at 2 and 20 microM. Among the other antidepressants, only paroxetine was able to affect the metabolism of melatonin at supratherapeutic concentrations of 20 microM, which did not reach by far the magnitude of the inhibitory potency of fluvoxamine. The authors concluded that fluvoxamine is a potent inhibitor of melatonin degradation. Because this inhibitory action is also found in vivo, fluvoxamine might be used as an enhancer of melatonin, which might offer new therapeutic possibilities of fluvoxamine.

[Minimal invasive implant removal after retrograde intramedullary nailing of the distal femur]

Recently, the retrograde femoral nailing has become a procedure with increasing acceptance. Indications for the retrograde femur nail are distal femoral fractures including dia- and transcondylar fractures, supracondylar osteotomies and distal periprosthetic femur fractures after total knee joint replacement. Controversial discussion is carried on about the implant removal, which is potentially afflicted with further damage to the knee joint. To minimize the operative damage due to the implant removal, an arthroscopic assisted procedure has been selected. The arthroscopic assisted implant removal was possible in all of our patients. Intraoperatively, 2/3 of the patients showed normal age-related findings of the chondral and meniscal structures. The arthroscopic assisted implant removal is a gentle procedure, which allows minimal invasive extraction of retrograde femur nails and prevents secondary damage to the knee joint due to the otherwise difficult localisation of the implant. The advantages of this procedure concerning gentleness and diagnostic capabilities are as convincing, that we indicate implant removal of retrograde femur nails in all younger patients (< 60 years), except in periprosthetic fractures.

[Temporary instrumentation in dixlocations, subluxations and fractures of the lower cervical spine]

The anterior interbody fusion with instrumentation seems to be the standard procedure in unstable traumatic lesions of the lower cervical spine. The goal of this study was to objective the outcome of patients, treated by only temporary stabilisation of the injured motion segment (without bone-graft fusion). Between 1990 and 1998 155 patients with traumatic lesions of the cervical spine were treated operatively, in 22 cases transfixation of the injured level without bone-graft application was performed, an implant-removal was carried out in 12 patients so long. Only patients were included into the study, who were less then 45 years old at trauma and who had no trauma related osseous or disc encrouchment of the spinal canal. Not included were patients with degenerative formations of the cervical spine at time of trauma. Until follow up all patients with implantat removal returned back to work in their former profession, 11 of 12 patients classified their result as excellent or good. No secondary instabilities or postraumatic disc prolapse were observed. Restmobility in flexion/extension of the injured level was demonstrated in 8 patients. The preservation of traumatized motion segments may reduce the incidence of degenerative alterations and hypermobilities in adjacent levels. The transfixation technique in anterior procedures leads to a reduced time of spinal exposure, complications as a result of spinal graft manipulation, pseudarthrosis or donor graft site problems are no more relevant.

Comparative stability of the "Internal Fixator" and the "Universal Spine System" and the effect of crosslinking transfixating systems. A biomechanical in vitro study

In this study, the three-dimensional stabilizing capabilities of the AO-Internal Fixator (IF) and the new Universal Spine System (USS) were investigated. Both devices were tested without and with the cross-link system (IF, IFC, USS, USSC). To determine biomechanical characteristics, a human thoracolumbar spine instability model with resection of the vertebral body Th12 was created. The vertebral body was replaced by a spacer and transpedicular posterior stabilization was performed from Th11 to L1. All devices reduced the range of motion (ROM) significantly compared to the values of the intact specimen. In flexion the IFC showed the highest reduction of ROM (85% of intact), followed by the USSC, USS and IF (79% of intact). In extension the ROM was restored again most by the IFC (52% of intact), followed by the USSC, IF and USS (44% of intact). In lateral bending stability was provided by the USSC (right 78% and left 81% of intact), followed in right lateral bending by the IF, IFC and USS and in left lateral bending by the USS, IF and IFC. In axial rotation the ROM was reduced primary by the IFC (right 51% and left 46% of intact), followed in right axial rotation by the USS, USSC and IF, in left axial rotation by the USSC, USS and IF. Additional stability by crosslinking has been provided in the IF and the USS in flexion and extension, in the USS in lateral bending and in the IF in axial rotation nonsignificantly. The neutral zone (NZ) was reduced by posterior instrumentation in flexion/extension and right/left lateral bending significantly. In axial rotation only the USSC decreased the NZ below intact levels. The study showed no statistical significant differences in the stabilizing capabilities of the USS compared to the IF. For both implants the cross-link system increased stability in the chosen instability model insignificantly only.

Induction of primary NY-ESO-1 immunity: CD8+ T lymphocyte and antibody responses in peptide-vaccinated patients with NY-ESO-1+ cancers

Cancer-testis antigen NY-ESO-1 is one of the most immunogenic tumor antigens defined to date. Spontaneous humoral and CD8+ T-cell responses to NY-ESO-1 are detected in 40-50% of patients with advanced NY-ESO-1-expressing tumors. A clinical trial was initiated to study the immunological effects of intradermal vaccination with 3 HLA-A2-binding NY-ESO-1 peptides in 12 patients with metastatic NY-ESO-1-expressing cancers. Seven patients were NY-ESO-1 serum antibody negative, and five patients were NY-ESO-1 serum antibody positive at the outset of the study. Primary peptide-specific CD8+ T-cell reactions and delayed-type hypersensitivity responses were generated in four of seven NY-ESO-1 antibody-negative patients. Induction of a specific CD8+ T-cell response to NY-ESO-1 in immunized antibody-negative patients was associated with disease stabilization and objective regression of single metastases. NY-ESO-1 antibody-positive patients did not develop significant changes in baseline NY-ESO-1-specific T-cell reactivity. However, stabilization of disease and regression of individual metastases were observed in three of five immunized patients. These results demonstrate that primary NY-ESO-1-specific CD8+ T-cell responses can be induced by intradermal immunization with NY-ESO-1 peptides, and that immunization with NY-ESO-1 may have the potential to alter the natural course of NY-ESO-1-expressing tumors.

[Computer-assisted surgery]

The term "computer-assisted surgery" (CAS) contains a variety of different applications. Priorities in trauma surgery have navigation systems. In fact, two basically different developments can be distinguished: on one hand, the possibility of navigation, based on preoperative CT data sets; and on the other hand navigation in intraoperative C-arm images. With the present available navigation technology, it can be assumed that intraoperative CT-based tracking in the field of spinal surgery can be performed accurately, regardless of whether active or passive markers are used. Another navigation option is C-arm-based osteosynthesis of the proximal femur. An application of navigation assistance in the field of pelvic surgery is osteotomy and placement of iliosacral screws. Future developments will have to concentrate on the technical characteristics of each navigation system. Advantageous concepts of visualization may generate required information to the surgeon in a way that unconstrained interaction at the operation table is combined with simultaneous integration of virtual and computer-aided visual information. New tracking systems will allow the reconstruction of data sets after reposition of segmented bone fragments, so that also in complex pelvic fractures the implantation of screws after reposition will be possible. Computer-aided surgery is able to improve the precision of operations in trauma surgery. In future, further developments of navigation systems can be expected. This fact is supported by the establishment of faster and cheaper hardware, as well as more intelligent and user-friendly software.

[Limits of CT-based computer navigation in spinal surgery]

Computer-assisted and navigation-based therapeutic tools have found their first application in the field of spinal surgery. Meanwhile, the basic principles have been extended to other procedures, such as screw osteosynthesis of the pelvis and navigation of long bones. Commonly, all procedures except C-arm navigation are based on three-dimensional data sets. Data acquisition and processing as well as planning require specific steps, which should guarantee adequate accuracy and successful navigation. All steps up to intraoperative navigation and potential pitfalls in every part of the interaction are demonstrated, with reasons of undesired results presented.

A new radiolucent system for vertebral body replacement: its stability in comparison to other systems

Anterior intervention of metastatic lesions of the spine can accomplish relief of pain, spinal decompression, and restoration of spinal stability. Ventral vertebral body replacements have been developed to provide these conditions but there have been problems with loosening at the implant-bone interface, mechanical failure, and X-ray artifacts from the metal. Intraoperative stability of the vertebral body replacement is especially critical to avoid loosening of the implant and to achieve long-term bony incorporation. This study compared the biomechanical performance in vitro of a new radiolucent system for vertebral body replacement to three currently marketed systems. The new system features a composite bioglass-polyurethane body and a new configuration of polymeric fastening hardware. Range of motion, neutral zone, and several interfacial motion parameters were measured under pure moments of 3.75 Nm in the three anatomical directions. The new system provided the significantly highest restraint of motion for all parameters. Mechanically, the new system is preferable at least initially to a sampling of systems representative of those currently used.

Metabolic detoxification: implications for thresholds

The fact that chemical carcinogenesis involves single, isolated, essentially irreversible molecular events as discrete steps, several of which must occur in a row to finally culminate in the development of a malignancy, rather suggests that an absolute threshold for chemical carcinogens may not exist. However, practical thresholds may exist due to saturable pathways involved in the metabolic processing, especially in the metabolic inactivation, of such compounds. An important example for such a pathway is the enzymatic hydrolysis of epoxides via epoxide hydrolases, a group of enzymes for which the catalytic mechanism has recently been established. These enzymes convert their substrates via the intermediate formation of a covalent enzyme-substrate complex. Interestingly, the formation of the intermediate proceeds faster by orders of magnitude than the subsequent hydrolysis, ie, the formation of the terminal product. Under normal circumstances, this does not pose a problem, since the microsomal epoxide hydrolase (mEH), the epoxide hydrolases with the best documented importance in the metabolism of carcinogens, is highly abundant in the liver, the organ with the highest capacity to metabolically generate epoxides. Computer simulation provides evidence that the high amount of mEH enzyme is favorable for the control of the steady-state level of a substrate epoxide and can keep it extremely low. However, once the mEH is titrated out under conditions of extraordinarily high epoxide concentration, the epoxide steady-state level steeply rises, leading to a sudden burst of the genotoxic effect of the noxious agent. This prediction of the computer simulation is nicely supported by experimental work. V79 Chinese hamster cells that we have genetically engineered to express human mEH at about the same level as that observed in human liver are completely protected from any measurable genotoxic effect of the model compound styrene oxide (STO) up to a dose of 100 microM in the cell culture medium (toxicokinetic threshold). In V79 cells that do not express mEH, STO leads to the formation of DNA strand breaks in a dose-dependent manner with no toxicokinetic threshold observable. Above 100 microM, the genotoxic effect of STO in the mEH-expressing cell line parallels the one in the parental cell line. Thus, the saturable protection from STO-induced strand breaks by mEH represents a typical example of a practical threshold. However, it must be pointed out that even in the presence of protective amounts of mEH, a minute but definite level of STO is present that does not contribute sufficiently to the strand break formation to overcome the background noise of the detection procedure. As pointed out above, absolute thresholds probably do not exist in chemical carcinogenesis.

Monitoring CD8 T cell responses to NY-ESO-1: correlation of humoral and cellular immune responses

NY-ESO-1, a member of the cancer-testis family of antigens, is expressed in a subset of a broad range of different human tumor types. Patients with advanced NY-ESO-1-expressing tumors frequently develop humoral immunity to NY-ESO-1, and three HLA A2-restricted peptides were defined previously as targets for cytotoxic CD8(+) T cells in a melanoma patient with NY-ESO-1 antibody. The objectives of the present study were (i) to develop enzyme-linked immunospot (ELISPOT) and tetramer assays to measure CD8(+) T cell responses to NY-ESO-1, (ii) to determine the frequency of CD8(+) T cell responses to NY-ESO-1 in a series of HLA-A2 patients with NY-ESO-1 expressing tumors, (iii) to determine the relation between CD8(+) T cell and humoral immune responses to NY-ESO-1, and (iv) to compare results of NY-ESO-1 ELISPOT assays performed independently in two laboratories with T cells from the same patients. NY-ESO-1 ELISPOT and tetramer assays with excellent sensitivity, specificity, and reproducibility have been developed and found to correlate with cytotoxicity assays. CD8(+) T cell responses to HLA-A2-restricted NY-ESO-1 peptides were detected in 10 of 11 patients with NY-ESO-1 antibody, but not in patients lacking antibody or in patients with NY-ESO-1-negative tumors. The results of ELISPOT assays were concordant in the two laboratories, providing the basis for standardized monitoring of T cell responses in patients receiving NY-ESO-1 vaccines.

Identification of the putative brain tumor antigen BF7/GE2 as the (de)toxifying enzyme microsomal epoxide hydrolase

Malignant gliomas are the main cause of death from primary brain tumors. Despite surgery, radiation, and chemotherapy, patients have a median survival of less than a few years; therefore, it is clearly imperative to investigate new ways of treatment. The development of new therapeutic strategies for brain tumors is dependent on a better understanding of the differences between normal and tumoral brain cells. Our group had described previously a Mr 48,000 antigen defined by reactivity with two monoclonal antibodies (GE2 and BF7) obtained by immunization of mice with human glioblastoma cells. Here, we describe the identification of the GE2/BF7 antigen as microsomal epoxide hydrolase (mEH), a drug-metabolizing enzyme that is involved both in toxification and detoxification of carcinogens. We initially used immunoaffinity purification using GE2 and BF7 and analyzed the purified proteins by microsequencing. Edman degradation identified 15 amino acids of the NH2-terminal sequence that were 100% identical to mEH. To further confirm the identity of the BF7/GE2 antigen as mEH, we showed that the protein immunopurified with GE2 and BF7 was recognized by an anti-mEH antibody and that in vitro and in vivo synthesized human mEH is recognized by BF7 and GE2 antibodies. Furthermore, anti-mEH antibody recognizes an antigen expressed both in gliomas and reactive astrocytes, as do BF7 and GE2. Finally, we demonstrate that in contrast to what has been reported in rat embryo fibroblasts, p53 does not regulate mEH mRNA expression in glioma cells.

Identification of NY-ESO-1 epitopes presented by human histocompatibility antigen (HLA)-DRB4*0101-0103 and recognized by CD4(+) T lymphocytes of patients with NY-ESO-1-expressing melanoma

NY-ESO-1 is a member of the cancer-testis family of tumor antigens that elicits strong humoral and cellular immune responses in patients with NY-ESO-1-expressing cancers. Since CD4(+) T lymphocytes play a critical role in generating antigen-specific cytotoxic T lymphocyte and antibody responses, we searched for NY-ESO-1 epitopes presented by histocompatibility leukocyte antigen (HLA) class II molecules. Autologous monocyte-derived dendritic cells of cancer patients were incubated with recombinant NY-ESO-1 protein and used in enzyme-linked immunospot (ELISPOT) assays to detect NY-ESO-1-specific CD4(+) T lymphocyte responses. To identify possible epitopes presented by distinct HLA class II alleles, overlapping 18-mer peptides derived from NY-ESO-1 were synthetized and tested for recognition by CD4(+) T lymphocytes in autologous settings. We identified three NY-ESO-1-derived peptides presented by DRB4*0101-0103 and recognized by CD4(+) T lymphocytes of two melanoma patients sharing these HLA class II alleles. Specificity of recognition was confirmed by proliferation assays. The characterization of HLA class II-restricted epitopes will be useful for the assessment of spontaneous and vaccine-induced immune responses of cancer patients against defined tumor antigens. Further, the therapeutic efficacy of active immunization using antigenic HLA class I-restricted peptides may be improved by adding HLA class II-presented epitopes.

Structure of Aspergillus niger epoxide hydrolase at 1.8 A resolution: implications for the structure and function of the mammalian microsomal class of epoxide hydrolases

BACKGROUND

Epoxide hydrolases have important roles in the defense of cells against potentially harmful epoxides. Conversion of epoxides into less toxic and more easily excreted diols is a universally successful strategy. A number of microorganisms employ the same chemistry to process epoxides for use as carbon sources.

RESULTS

The X-ray structure of the epoxide hydrolase from Aspergillus niger was determined at 3.5 A resolution using the multiwavelength anomalous dispersion (MAD) method, and then refined at 1.8 A resolution. There is a dimer consisting of two 44 kDa subunits in the asymmetric unit. Each subunit consists of an alpha/beta hydrolase fold, and a primarily helical lid over the active site. The dimer interface includes lid-lid interactions as well as contributions from an N-terminal meander. The active site contains a classical catalytic triad, and two tyrosines and a glutamic acid residue that are likely to assist in catalysis.

CONCLUSIONS

The Aspergillus enzyme provides the first structure of an epoxide hydrolase with strong relationships to the most important enzyme of human epoxide metabolism, the microsomal epoxide hydrolase. Differences in active-site residues, especially in components that assist in epoxide ring opening and hydrolysis of the enzyme-substrate intermediate, might explain why the fungal enzyme attains the greater speeds necessary for an effective metabolic enzyme. The N-terminal domain that is characteristic of microsomal epoxide hydrolases corresponds to a meander that is critical for dimer formation in the Aspergillus enzyme.

Acute hepatotoxicity of the polycyclic musk 7-acetyl-1,1,3,4,4,6-hexamethyl-1,2,3,4-tetrahydronaphtaline (AHTN)

Synthetic musks are present in fine fragrances, cosmetics, soaps and laundry detergents. One of the most important synthetic musks is 7-acetyl-1,1,3,4,4,6-hexamethyl-1,2,3,4-tetrahydro-naphthaline+ ++ (AHTN; annual production: about 1500 metric tons). An increasing number of studies show that AHTN accumulates in surface water and fish and can be detected in human adipose tissue, as well in human milk. In the present report it is shown that a single high dose of AHTN leads to acute hepatic damage in rats, characterized by single cell necrosis, inflammation, swelling of liver parenchymal cells, and the presence of cytoplasmic condensations in the hepatocytes, while at the ultrastructural level disorganization of the rough endoplasmic reticulum and mitochondria as well as focal cytolysis is evident. Furthermore, evidence is presented that AHTN is not genotoxic, does not induce peroxisome proliferation, and does not lead to the induction of drug-metabolizing enzymes as phenobarbital and 3-methylcholanthrene do.

Cloning and molecular characterization of a soluble epoxide hydrolase from Aspergillus niger that is related to mammalian microsomal epoxide hydrolase

Aspergillus niger strain LCP521 harbours a highly processive epoxide hydrolase (EH) that is of particular interest for the enantioselective bio-organic synthesis of fine chemicals. In the present work, we report the isolation of the gene and cDNA for this EH by use of inverse PCR. The gene is composed of nine exons, the first of which is apparently non-coding. The deduced protein of the A. niger EH shares significant sequence similarity with the mammalian microsomal EHs (mEH). In contrast to these, however, the protein from A. niger lacks the common N-terminal membrane anchor, in line with the fact that this enzyme is, indeed, soluble in its native environment. Recombinant expression of the isolated cDNA in Escherichia coli yielded a fully active EH with similar characteristics to the fungal enzyme. Sequence comparison with mammalian EHs suggested that Asp(192), Asp(348) and His(374) constituted the catalytic triad of the fungal EH. This was subsequently substantiated by the analysis of respective mutants constructed by site-directed mutagenesis. The presence of an aspartic acid residue in the charge-relay system of the A. niger enzyme, in contrast to a glutamic acid residue in the respective position of all mEHs analysed to date, may be one important contributor to the exceptionally high turnover number of the fungal enzyme when compared with its mammalian relatives. Recombinant expression of the enzyme in E. coli offers a versatile tool for the bio-organic chemist for the chiral synthesis of a variety of fine chemicals.

Humoral immune responses of cancer patients against "Cancer-Testis" antigen NY-ESO-1: correlation with clinical events

Humoral immune responses against the "Cancer-Testis" (CT) antigen NY-ESO-1 are frequently observed in patients with NY-ESO-1 expressing tumors. This is in contrast to other known tumor antigens (TA) defined by antibody or cytotoxic T cell (CTL) reactivity, i.e., MAGE-1, MAGE-3, SSX2, Melan A, and tyrosinase. No NY-ESO-1 antibody has been detected in healthy controls and patients with NY-ESO-1 negative tumors. In this study, we have assessed the NY-ESO-1 serum antibody response in patients with NY-ESO-1 positive tumors of different histological types and stages using Western blotting and an ELISA. Of the 12 patients analyzed, 10 had demonstrable NY-ESO-1 antibodies at the start of the study. All patients were followed for changes in NY-ESO-1 antibody titers during the course of tumor treatment and clinical evolution. In 4 patients, an increase of NY-ESO-1 antibody titer was observed with progression of disease or extensive tumor necrosis under treatment. One patient showed a stable NY-ESO-1 antibody titer over 3 years along with gradual regression of a large tumor mass. In 5 patients, a decrease of NY-ESO-1 antibody was detected: in 1 patient after curative tumor resection, in 3 patients with partial regression of metastatic disease under chemo- and immunotherapy, and in another patient with a NY-ESO-1 negative tumor relapse. Our results indicate that the induction and maintenance of NY-ESO-1 antibody is dependent on the presence of NY-ESO-1 expressing tumors. Furthermore, changes in NY-ESO-1 antibody titers correlate with the evolution of NY-ESO-1 positive disease.

Humoral immune responses of cancer patients against "Cancer-Testis" antigen NY-ESO-1: correlation with clinical events

Humoral immune responses against the "Cancer-Testis" (CT) antigen NY-ESO-1 are frequently observed in patients with NY-ESO-1 expressing tumors. This is in contrast to other known tumor antigens (TA) defined by antibody or cytotoxic T cell (CTL) reactivity, i.e., MAGE-1, MAGE-3, SSX2, Melan A, and tyrosinase. No NY-ESO-1 antibody has been detected in healthy controls and patients with NY-ESO-1 negative tumors. In this study, we have assessed the NY-ESO-1 serum antibody response in patients with NY-ESO-1 positive tumors of different histological types and stages using Western blotting and an ELISA. Of the 12 patients analyzed, 10 had demonstrable NY-ESO-1 antibodies at the start of the study. All patients were followed for changes in NY-ESO-1 antibody titers during the course of tumor treatment and clinical evolution. In 4 patients, an increase of NY-ESO-1 antibody titer was observed with progression of disease or extensive tumor necrosis under treatment. One patient showed a stable NY-ESO-1 antibody titer over 3 years along with gradual regression of a large tumor mass. In 5 patients, a decrease of NY-ESO-1 antibody was detected: in 1 patient after curative tumor resection, in 3 patients with partial regression of metastatic disease under chemo- and immunotherapy, and in another patient with a NY-ESO-1 negative tumor relapse. Our results indicate that the induction and maintenance of NY-ESO-1 antibody is dependent on the presence of NY-ESO-1 expressing tumors. Furthermore, changes in NY-ESO-1 antibody titers correlate with the evolution of NY-ESO-1 positive disease.

Contribution of c-erbB-2 and topoisomerase IIalpha to chemoresistance in ovarian cancer

Overexpression of the c-erbB-2 (HER-2/neu) oncogene, which encodes a transmembrane receptor tyrosine kinase, has been shown to be associated with poor prognosis in ovarian and breast cancer. Recent studies indicate that c-erbB-2 may also be involved in determining the chemosensitivity of human cancers. In the present study, we examined the role of c-erbB-2 for chemoresistance in ovarian cancer. Overexpression of c-erbB-2 mRNA in tumor tissue was associated with a shorter survival of patients with primary ovarian cancer (P = 0.0001; n = 77) and was an independent prognostic factor in the proportional-hazard model adjusted for International Federation of Gynecologists and Obstetricians stage, residual disease, chemotherapy, and age (P = 0.035). A significant association between expression of c-erbB-2 mRNA and survival was obtained for the subgroup of patients who received a standard chemotherapy with carboplatin or cisplatin and cyclophosphamide (P = 0.0003), whereas only a nonsignificant trend was observed for patients who did not receive a standard chemotherapy (P = 0.124). In addition, the application of a standard chemotherapy improved the survival of patients with relatively low c-erbB-2 expression (P = 0.013) but not of patients with overexpression of c-erbB-2 (P = 0.359). Expression of c-erbB-2 mRNA correlated with expression of topoisomerase IIalpha mRNA determined by a reverse semiquantitative PCR technique (P = 0.009), whereas expression of c-erbB-2 and topoisomerase IIbeta mRNA did not correlate (P = 0.221). To examine the hypothesis that coamplified and/or coregulated topoisomerase IIalpha contributes to the resistance of c-erbB-2-overexpressing carcinomas, we established a chemosensitivity assay using primary cells from an ovarian carcinoma that overexpressed both c-erbB-2 and topoisomerase IIalpha. The combination of carboplatin with nontoxic concentrations of the topoisomerase II inhibitors etoposide or novobiocin enhanced the toxicity of carboplatin. In contrast, the tyrosine kinase inhibitor emodin exhibited no chemosensitizing effect in cells of this individual carcinoma. In conclusion, overexpression of c-erbB-2 was associated with poor prognosis and poor response to chemotherapy. The data suggest that topoisomerase IIlalpha, which correlates with c-erbB-2 expression, contributes to the resistance of c-erbB-2-overexpressing carcinomas.

Use of PCR to screen for promoter elements in genomic DNA library clones

We report a modified PCR strategy to screen for promoter elements of genes of interest that is based upon consecutive rounds of PCR and appropriate subcloning. Following preliminary identification and sequencing of intron 1 by standardized PCR, the application of a suited cDNA/intron primer combination renders a succeeding PCR-mediated screening of cosmid or P1-derived artificial chromosome (PAC) libraries possible, thus identifying genomic clones comprising the searched promoter elements. We tested our approach in comparison with a commercially available promoter finder kit by searching the promoter elements of the CENP-C gene from the human and mouse genomes. Applying the kit system, we amplified the anticipated promoter from mouse, but failed in isolating human promoter elements. Our approach made use of a 5'-UTR/intron 1 primer combination in the second round of PCR, enabling the identification of positive clones from genomic DNA within a human PAC library possible. Subcloning and final PCR amplification revealed the successful isolation of the human promoter. Therefore, we conclude that our approach might represent a helpful alternative to identify promoter elements, especially when prior art genome walking, STS-based strategies or anchored PCR failed.