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Biomedical subjects

B Westermann

Publications and source records attributed to B Westermann.

36 records · Page 2Linked to original sources
PubMed1997

Noninvasive tracking of patient's head movements during computer-assisted intranasal microscopic surgery.

A noninvasive system designed for patient tracking during image-guided intranasal sinus surgery is described. It is based on optical digitizing with a custom-made registration and reference system, locatable surgical instruments, and a self-localizing operating microscope. Experimental and clinical results reveal a high degree of accuracy for the system. A mean spatial error of 0.82 +/- 0.31 mm was determined for repositioning of the reference system in a plastic model of the skull. For the positioning of the microscope, a mean error of 2.3 +/- 0.83 mm was calculated. Measurements of repositioning accuracy in 24 patients who received surgery for various sinus diseases had a mean spatial error of 1.56 +/- 0.76 mm. The 95% error interval for locating intranasal structures using the surgical instrument was 2.05 mm, and it was 4.92 mm using the microscope. These results suggest that the use of our noninvasive registration and reference system may be effective, accurate, and useful for noninvasive tracking of patient movements in computer-assisted intranasal surgery.

Head Movements↗
PubMed1997

A non-invasive patient registration and reference system for interactive intraoperative localization in intranasal sinus surgery.

A basic problem common to all systems for computer assisted surgery (CAS) is patient referencing, or the transfer of preoperative image data to the intraoperative pathology. The authors describe a highly precise CAS system with non-invasive referencing that can be used in ear, nose and throat (ENT) surgery of the paranasal sinuses. It is based on optical digitizing with several custom-made self-localizing surgical instruments. The accuracy of the system was tested in an experimental model using a plastic head. Measurements of repositioning the reference bow had a mean error of 0.81 mm +/- 0.31 mm. The system was evaluated clinically with 11 patients who received surgery for different pathologies of the paranasal sinuses. These trials met with a high rate of success and specific results are reported.

Biopsy↗
PubMed1996

The nucleotide exchange factor MGE exerts a key function in the ATP-dependent cycle of mt-Hsp70-Tim44 interaction driving mitochondrial protein import.

Import of preproteins into the mitochondrial matrix is driven by the ATP-dependent interaction of mt-Hsp70 with the peripheral inner membrane import protein Tim44 and the preprotein in transit. We show that Mge1p, a co-chaperone of mt-Hsp70, plays a key role in the ATP-dependent import reaction cycle in yeast. Our data suggest a cycle in which the mt-Hsp70-Tim44 complex forms with ATP: Mge1p promotes assembly of the complex in the presence of ATP. Hydrolysis of ATP by mt-Hsp70 occurs in complex with Tim44. Mge1p is then required for the dissociation of the ADP form of mt-Hsp70 from Tim44 after release of inorganic phosphate but before release of ADP. ATP hydrolysis and complex dissociation are accompanied by tight binding of mt-Hsp70 to the preprotein in transit. Subsequently, the release of mt-Hsp70 from the polypeptide chain is triggered by Mge1p which promotes release of ADP from mt-Hsp70. Rebinding of ATP to mt-Hsp70 completes the reaction cycle.

Adenosine Triphosphate↗
PubMed1996

Computer assisted brain surgery for small lesions in the central sensorimotor region.

The capacity of a new optical navigation device is demonstrated by six microsurgical procedures for small subcortical lesions within the central sensorimotor strip. This small series is aimed at less invasive resection in this functionally critical region, independently of primary diagnosis and outcome. Guided by high resolution CT imaging data five brain tumours and one cavernous angioma was selectively located and most sparingly removed without additional sensorimotor deficit. In two cases improvement of a pre-operative paresis was observed immediately after surgery. Thanks to light-weight freehand pointing instruments and a ranging accuracy of +/- 1 mm, damage to functionally important brain areas and vessels was avoided by using uncommonly oblique, e.g., transsulcal ways of access which would hardly have been possible even with guidance by conventional stereotaxy. The demanding systematic cortical stimulation of the precentral gyrus applied in three cases was only sensitive in infiltrating tumours-e.g., low grade astrocytomas-where for want of adjuvant therapy it was essential to proceed to the extreme limits of resection. In general, precise anatomical localisation by computer aided surgery (CAS) is sufficient in small central lesions which guarantees minimally invasive surgery. The potential of this new, soon commercially available optical navigation system in (neuro) surgery, quality control and teaching is discussed.

Adult↗
PubMed1996

[Computer-assisted surgery of the paranasal sinuses with an opto-electronic stereotaxic system].

BACKGROUND: A basic problem common to all systems for computer-assisted surgery (CAS) is the exact registration and referencing, that is, the transfer of preoperative image data to the intraoperative pathology. A system for computer-assisted ENT surgery should provide high precision as well as noninvasive registration and referencing. We present a system designed for such use in paranasal sinus surgery that is based on optical digitizing with several custom-made self-localizing surgical instruments. METHODS AND RESULTS: The system tracks the correct alignment of the head during CT data acquisition and continuously throughout surgery. A transformation matrix and a plane equation of the CT scan are used to match points of the object space to the image space detecting fiducial markers on the CT scans by an automatic algorithm. For position measurements a special reference frame and surgical instruments were developed and equipped with infrared light-emitting diodes that could be detected in real time. Measurements for repositioning of the reference system in a model and during real operations demonstrated a mean error ranging from 0.69 to 1.01 mm and from 0.76 to 1.67 mm respectively. Clinical experience with the application of the system for 15 patients who underwent surgery for different paranasal sinus pathologies is reported. CONCLUSIONS: Results suggest that the non-invasive reference system and the locatable surgical tools may be effective, accurate and useful for computer-assisted identification of intranasal structures. Such systems may contribute to further improvement of minimal invasive intranasal sinus surgery.

Equipment Design↗
PubMed1996

Role of the mitochondrial DnaJ homolog Mdj1p as a chaperone for mitochondrially synthesized and imported proteins.

Mdj1p, a DnaJ homolog in the mitochondria of Saccharomyces cerevisiae, is involved in the folding of proteins in the mitochondrial matrix. In this capacity, Mdj1p cooperates with mitochondrial Hsp70 (mt-Hsp70). Here, we analyzed the role of Mdj1p as a chaperone for newly synthesized proteins encoded by mitochondrial DNA and for nucleus-encoded proteins as they enter the mitochondrial matrix. A series of conditional mutants of mdj1 was constructed. Mutations in the various functional domains led to a partial loss of Mdj1p function. The mutant Mdj1 proteins were defective in protecting the tester protein firefly luciferase against heat-induced aggregation in isolated mitochondria. The mitochondrially encoded var1 protein showed enhanced aggregation after synthesis in mdj1 mutant mitochondria. Mdj1p and mt-Hsp70 were found in a complex with nascent polypeptide chains on mitochondrial ribosomes. Mdj1p was not found to interact with translocation intermediates of imported proteins spanning the two membranes and exposing short segments into the matrix, in accordance with the lack of requirement of Mdj1p in the mt-Hsp70-mediated protein import into mitochondria. On the other hand, precursor proteins in transit which had further entered the matrix were found in a complex with Mdj1p. Our results suggest that Mdj1p together with mt-Hsp70 plays an important role as a chaperone for mitochondrially synthesized polypeptide chains emerging from the ribosome and for translocating proteins at a late import step.

DNA, Fungal↗
PubMed1995

The role of the GrpE homologue, Mge1p, in mediating protein import and protein folding in mitochondria.

Mge1p, a mitochondrial GrpE homologue, has recently been identified in the yeast Saccharomyces cerevisiae and a role for this protein in precursor import has been reported. To dissect the molecular mechanism of Mge1p function, conditional mge1 mutants were constructed. Cells harbouring mutant mge1 accumulated precursor proteins at restrictive temperature. Both kinetics and efficiency of import were reduced in mitochondria isolated from strains possessing mutant mge1. Binding of mitochondrial-Hsp70 (mt-Hsp70) to incoming precursor proteins was abolished at restrictive temperature. Nucleotide-dependent dissociation of mt-Hsp70 from the import component MIM44 was reduced in mitochondria from mutant mge1 strains. Furthermore, at restrictive temperature an increase of incompletely folded, newly imported protein and enhanced protein aggregation was observed in mitochondria isolated from the mutant strains. We conclude that Mge1p exerts an essential function in import and folding of proteins by controlling the nucleotide-dependent binding of mt-Hsp70 to substrate proteins and the association of mt-Hsp70 with MIM44.

Bacterial Proteins↗
PubMed1995

Optically-navigable operating microscope for image-guided surgery.

In computer-assisted surgery (CAS), optical digitizing is state-of-the-art. Unfortunately standard navigation instruments, e.g. small, LED-equipped pointers are frequently shadowed by the operating microscope when the camera-array is ceiling- or rack-mounted. Thus, for microsurgery, a navigation module consisting of a reference panel mounted onto the housing of the microscope and an object distance measuring unit attached in front of the objective lens was developed. By means of this navigation module the microscope can be located in space with an accuracy of +/- 1-2 mm. Focusing errors due to the high depth of view of modern microscopes and individual refraction anomalies are eliminated by laser distance measurement. This device has been clinically tested since September 1994 and a typical case is reported.

Humans↗
PubMed1995

Microstereometrically guided cortical stimulation for the intraoperative identification of the central motor strip.

A rangable stimulation tool based on the sonar microstereometric system has been developed for the intraoperative identification of the central motor strip. The elicited motor evoked potentials (MEPs) were recorded with surface electrodes and displayed together with the corresponding stereometric coordinates of the stimulation site. MEP data were overlaid in 'real time' on preoperatively scanned CT images on a computer screen. The system has been used during open microsurgical procedures in 6 patients with small tumors near the central motor strip or related 'eloquent' areas. Three operations have been performed under local anesthesia, 3 under general anesthesia. It was possible to operate on tumors located closely to functionalal relevant areas of the brain not only stereotactically, but also with function guidance.

Adult↗
PubMed1994

XDJ1, a gene encoding a novel non-essential DnaJ homologue from Saccharomyces cerevisiae.

The gene encoding a novel DnaJ-like protein, termed Xdj1, has been identified by amplification of Saccharomyces cerevisiae genomic DNA. An open reading frame of 1380 bp was detected. Disruption of XDJ1 did not yield any detectable new phenotype. A double-deletion strain containing a disruption of both XDJ1 and YDJ1, another gene coding for a DnaJ-like protein, was still viable. Under a variety of growth conditions, no XDJ1 transcripts could be detected by Northern blot analysis and no translation product was found by immunoblotting with antibody against Xdj1 produced in Escherichia coli. Thus, XDJ1 is either expressed only under very specific conditions or represents a silent gene.

Amino Acid Sequence↗
PubMed1994

Mdj1p, a novel chaperone of the DnaJ family, is involved in mitochondrial biogenesis and protein folding.

Mdj1p, a novel member of the DnaJ family, is a heat shock protein that is associated with the inner membrane of mitochondria of Saccharomyces cerevisiae. Disruption of the MDJ1 gene resulted in a petite phenotype, loss of mitochondrial DNA, and inviability at 37 degrees C. Import of precursor proteins was not affected by a lack of Mdj1p, but folding of newly imported proteins was markedly impaired. The efficiency of refolding of a tester protein, dihydrofolate reductase, was significantly reduced in mitochondria lacking Mdj1p after incubation at elevated temperature. We conclude that Mdj1p is an important mitochondrial chaperone that participates in the folding of newly imported proteins and in the protection of proteins against heat denaturation and aggregation.

Amino Acid Sequence↗
PubMed1994

The N-terminal signal peptide of the murine cyclophilin mCyP-S1 is required in vivo for ER localization.

Cyclophilins are a class of enzymes that are thought to be involved in protein folding by accelerating the isomerization of Xaa-Pro peptide bonds and that mediate the immunosuppressive effect of cyclosporin A. We described previously a murine cyclophilin, mCyP-S1, whose cDNA encoded a putative NH2-terminal signal sequence which was not present in the mature protein. Here we investigate the intracellular localization of mCyP-S1. We show by overexpression of the wild-type and an NH2-terminally truncated derivative that its signal sequence is necessary and functional in vivo for the translocation into the endoplasmic reticulum (ER). Immunocytochemistry and cell fractionations demonstrate the preferential localization of endogenous mCyP-S1 in the ER, or subcompartments thereof. In addition, the results indicate the presence of this cyclophilin in the nucleus.

3T3 Cells↗
PubMed1990

[Results of physiologic occupational studies of intensive care unit nurses].

Continuous measures of the pulse by wireless telemeter to value the degree of work were performed by 6 nurses in intensive care unit during work in shifts about 476 hours. Work activity and time were registed simultaneously. In the outcome is ascertained that the work of these nurses is middle heavy on an average with heavy or very heavy short portions. To reduce or to avoid the latter proposals are recommended.

Adult↗
PubMedDate not supplied

Computer aided surgery with special focus on neuronavigation.

The term computer aided surgery (CAS) is now mainly used for an intraoperative navigation within the body combining a 3D-digitizer with preoperative CT/MR-imaging. This method has become indispensable in neurosurgery for the removal of deep-seated and/or critically located intracranial tumors and vascular malformations. Also ENT surgery within the paranasal sinuses and setting of pedicle screws in orthopedic surgery profit greatly from the high targeting precision of CAS. And still a growing number of surgical disciplines are employing this method. Today infrared-optical 3D-digitizers are state of the art, but electromagnetic spatial digitizing using novel, miniature localizers is promising, too. The results of our CAS study 1994-mid-1997 with 50 patients suffering from small intracranial lesions are presented.

Adolescent↗