Biomedical subjects

B Fricke

Publications and source records attributed to B Fricke.

At least 19 recordsLinked to original sources

PubMed2005

Relativistic effects on the electronic structure and volatility of group-8 tetroxides MO4, where M=Ru, Os, and element 108, Hs.

The influence of relativistic effects on properties and volatility of the group-8 tetroxides MO4, where M=Ru, Os, and element 108, Hs, was studied on the basis of results of the fully relativistic (four component) and nonrelativistic density functional theory calculations. Relativistic effects were shown to increase bond strengths and decrease bond lengths in these molecules. They are responsible for a decrease in molecular polarizabilities and an increase in ionization potentials. The effects are much stronger in HsO4 than in the lighter congeners. Relativistic effects were also shown to slightly decrease dispersion interaction energies of RuO4, OsO4, and HsO4 with an inert (quartz or silicon nitride) surface, i.e., they increase volatility of these compounds as studied in the "one-atom-at-a-time" gas-phase chromatography experiments. They do, however, not influence the trend in group 8: both relativistically and nonrelativistically, volatility should change as RuO4<OsO4<HsO4. The reason for that is identical trends in the relativistic and nonrelativistic space distributions of the valence d electrons.

Journal Article↗

PubMed2005

Application of a newly developed visual navigation system in humans. First results.

A visual navigation system (VN) was developed which uses intraoperatively stored endoscopic images together with their specific 3D-address. A special calibration enables one to recalculate the distortion of the endoscopic images. Several modules (e. g., landmark tracking, virtual back-movement) are offered to the neurosurgeon. The system was tested in 12 human subjects during neuroendoscopic interventions and worked without problems in nearly all cases. The possibilities of digital image navigation can be used especially for control of instrument movement in case of red-out situations or blurred vision. Many further developments of the VN system are possible in order to increase the safety of neuroendoscopic interventions.

Adolescent↗

PubMed2005

Consideration of ergonomic aspects in the development of a new endoscopic navigation system.

During the development of new navigation systems, the ergonomic aspects of the accompanying software are seldom taken into account. The VN system is a navigation system working with real and previously stored neuroendoscopic images. The latter enable the module to execute virtual back movement, e.g. in case of bleeding. Several other modules are offered. The aim of the study was the ergonomic analysis of different modules and their learning curves in cadaveric heads. The endoscope was navigated by the neurosurgeon while another person operated the computer. A total of 128 experiments were performed with two software versions. When the landmark tracking module was used, a real learning curve could be observed. By contrast, testing the measurement module did not produce a learning curve. A significant reduction of the time required by the three modules investigated could be observed with software version 2. The module for virtual back movement works best with a minimum time of 20 s for image storage. During machine-human interactions ergonomic software use is important, especially if operative procedures are performed.

Clinical Competence↗

PubMed2004

A family showing recessively inherited multisystem pathology with aberrant splicing of the erythrocyte Band 7.2b ('stomatin') gene.

The case of a French child, born of consanguineous parents of Tunisian origin, is described. He showed a severe multisystem disease with dyserythropoietic, sideroblastic anaemia, delayed neurological development with hypotonia and convulsions, salt-losing nephropathy, chronic watery diarrhoea, lactic acidosis with mitochondrial dysfunction, brittle hair, hypergammaglobulinaemia, fatty liver with intermittent transaminasaemia, and terminal pulmonary fibrosis. Two siblings, of both sexes, were stillborn; two more lived only a short time. One sister is alive and well. SDS gel analysis of the red cell membranes showed a deficiency within 'Band 7' at 32 kDa. Analysis of the gene encoding 'stomatin', or 'erythrocyte membrane protein 7.2b', the principal protein of 'Band 7', revealed a complex series of aberrant spliceforms centred around exon 3, for which no explanatory genomic lesion could be found. The true underlying molecular cause of this condition remains obscure, but it suggests that the stomatin gene should be studied in other cases.

Alternative Splicing↗

PubMed2004

Vibrography: first experimental results in swine brains.

OBJECT: The aim of this study was to determine whether vibrography, an ultrasound-based real-time strain imaging method for registering the elastic properties of tissue, is superior to conventional ultrasound imaging techniques for detecting low-contrast space-occupying lesions in brain tissue and for delineating the boundaries between such lesions and the surrounding tissue. METHODS: As our experimental model we used swine brains taken from freshly slaughtered pigs. After injecting agarose into these brains at different depths, we compared both the conventional ultrasonographic images and the elastographic images of the region of interest with the corresponding anatomical brain sections. RESULTS: In 83.6 % of the experiments, it was possible to detect the polymerized agarose in the brain tissue with vibrographic techniques. In 17 experiments agarose lesions which were not detectable by ultrasound were visualized via vibrography. Furthermore, statistical analysis revealed that elastography is a more precise tool than conventional ultrasound for determining lesion size. CONCLUSION: These findings indicate that vibrography is a promising real-time imaging method with numerous potential applications in the field of neurosurgery. Visualization of the elastic properties provides the neurosurgeon with additional data on the lesion and the boundary between the lesion and the surrounding tissue.

Animals↗

PubMed2003

The curious genomic path from leaky red cell to nephrotic kidney.

The human red cell has proved to be an invaluable model cell for the study of many aspects of membrane structure and function. It has a series of transport pathways which mediate the movements of the univalent cations Na and K, which are either identical or similar to systems in other human tissues, including the human kidney. The balance between the energy-consuming NaK pump and a 'passive leak' component maintains a net deficit of cations within the cell, which defends the cell volume against osmotic swelling. There exist a series of dominantly inherited human red cell conditions, gathered under the generic title 'hereditary stomatocytoses', in which the so-called 'passive leak' to Na and K is pathologically increased. In the more severe variants this compromises the integrity of the cell and the patients suffer haemolytic anaemia. Some less severe variants present with pseudohyperkalaemia caused by loss of K from red cells on storage of blood at room temperature. The most severe variants show a deficiency in a widely distributed 'raft' protein known as stomatin. The stomatin protein is homologous to the 'podocin' protein, the gene for which is mutated in a recessively inherited form of nephrotic syndrome. Among other possible functions, both proteins could be involved in the trafficking of membrane proteins to and from the plasma membrane.

Anemia, Hemolytic, Congenital↗

PubMed2002

Relativistic density functional calculations for Pt2.

First full-relativistic density functional calculations with the extension of the spin-polarization functional for the relativistic density functional theory in their collinear and noncollinear form are presented here for the molecular system Pt2. The agreement with experiment is very good.

Journal Article↗

PubMed2001

The cell envelope-bound metalloprotease (camelysin) from Bacillus cereus is a possible pathogenic factor.

A novel membrane proteinase of the nosocomial important bacteria species Bacillus cereus (synonyms: camelysin, CCMP) was purified up to homogeneity as was shown by mass spectrometry in its amphiphilic form. Camelysin is a neutral metalloprotease with a molecular mass of 19 kDa. Its unique N-terminus Phe-Phe-Ser-Asp-Lys-Glu-Val-Ser-Asn-Asn-Thr-Phe-Ala-Ala-Gly-Thr-Leu-Asp-Leu-Thr-Leu-Asn-Pro-Lys-Thr-Leu-Val-Asp-(Ile-Lys-Asp)- was not detected in the protein data bases during BLAST searches, but in the partially sequenced genome of Bacillus anthracis, coding for an unknown protein. Cleavage sites of the membrane proteinase for the insulin A- and B-chains were determined by mass spectrometry and N-terminal sequencing. Camelysin prefers cleavage sites in front of aliphatic and hydrophilic amino acid residues (-OH, -SO3H, amido group), avoiding bulky aromatic residues. The internally quenched fluorogenic substrates of the matrix metalloproteases 2 and 7 were cleaved with the highest efficiency at the Leu-decrease-Gly or Leu-decrease-Ala bond with the smaller residue in the P1' position. The protein specificity is broad--all various kinds of casein were cleaved as well as acid-soluble collagen, globin and ovalbumin; intact insulin was destroyed only to a low extent. Actin, collagen type I, fibrinogen, fibrin, alpha2-antiplasmin and alpha1-antitrypsin were cleaved. The protease formed SDS-stable complexes with Glu-plasminogen and antithrombin III, visible after SDS electrophoresis by gold staining and Western blot. The CCMP-plasminogen complex caused a partial activation of plasminogen to plasmin. Camelysin interacts with proteins of the blood coagulation cascade and could facilitate the penetration of fibrin clots and of the extracellular matrix during bacterial invasion.

Amino Acid Sequence↗

PubMed2001

Nerve fibers innervating the cranial and spinal meninges: morphology of nerve fiber terminals and their structural integration.

Pachymeninx and leptomeninx of cranial cavity and spine are considerably different in their collagenous fiber texture, cellular composition, vascularization, and innervation. The majority of meningeal nerve fibers terminate as free nerve endings whereas encapsulated and lamellated nerve terminals additionally occur in higher vertebrates including man. With respect to nerve fiber classification, arborization pattern, topography, and organization of the microenvironment at the termination site afferent and efferent nerve terminals are differentiated. Only the dura mater and the pial subcompartment of the leptomeninx possess the morphological prerequisites for neurogenic inflammation. In the current review, the results of morphological studies regarding the meningeal innervation including the sites of CSF (cerebrospinal fluid) production and absorption are discussed with emphasis on their structure-function relationships.

Arachnoid↗

PubMed2000

Quantitative determination of zwitterionic detergents using salt-induced phase separation of Triton X-100.

Zwitterionic detergents interfere with the salt-induced phase separation for nonionic detergents in a concentration-dependent manner by shifting the normal cloud point of nonionic detergents to a higher ionic strength at room temperature. This phenomenon was used to determine the concentration of the zwitterionic detergents CHAPS, CHAPSO, and sulfobetaine SB-12 in solution by titration with ammonium sulfate in the presence of Triton X-100. Among the ionic detergents tested, the method was only applicable to sodium cholate. The assay can be used to control the removal of zwitterionic detergents during the reconstitution of membrane proteins in liposomes. However, it cannot be used to determine the specific binding of zwitterionic detergents to highly diluted, pure membrane proteins because of the limited sensitivity. Neither proteins nor phospholipids interfered with this method at concentrations up to 20 mg/ml of test solution (human serum albumin) or 10 mg/ml (phospholipids), respectively. Since the assay is based on the competition between salts and nonionic detergents for water molecules, it is important to equalize the ionic strength of samples and calibration standards.

Cholic Acids↗

PubMed2000

Epithelial Na+ channels and stomatin are expressed in rat trigeminal mechanosensory neurons.

Caenorhabditis elegans MEC-4 and MEC-10 are subunits of the degenerin/epithelial Na+ channel (DEG/ENaC) ion channel superfamily thought to be associated with MEC-2 (a stomatin-like protein) in a mechanotransducing molecular complex in specialized touch sensory neurons. A key question is whether analogous molecular complexes in higher organisms transduce mechanical signals. To address this question, we selected mechanoreceptors of the rat vibrissal follicle-sinus complex in the mystacial pad and the trigeminal ganglia for an immunocytochemical and molecular biological study. RT-PCR of poly(A+) mRNA of rat trigeminal ganglia indicated that alpha-, beta-, and gamma-ENaC and stomatin mRNA are expressed in rat trigeminal ganglia. Using immunocytochemistry, we found that alpha-, beta-, and gamma-ENaC subunits and stomatin are localized in the perikarya of the trigeminal neurons and in a minor fraction of their termination site in the vibrissal follicle-sinus complex, where longitudinal lanceolate endings are immunopositive. We conclude that alpha-, beta-, and gamma-ENaC subunits as well as the candidate interacting protein stomatin are coexpressed in a mammalian mechanoreceptor, a location consistent with a possible role in mechanotransduction.

Animals↗

PubMed2000

Virtual image navigation: a new method to control intraoperative bleeding in neuroendoscopic surgery. Technical note.

In this neuroendoscopic study the authors tested the newly developed "red-out module" of their visual navigation system that enables the neurosurgeon to achieve hemostasis if total visualization is lost due to hemorrhage ("red out") within the visual field. An optical position measurement system connected to the endoscope guarantees that digitized endoscopic images are coupled with the accurate endoscopic position. Computerized images are simultaneously stored with their respective position data, and this creates a virtual anatomical landscape. The system was tested in in vivo bleeding conditions in a rat model. Artificial endoscopic cavities were created in the inguinal, pelvic, and jugular regions in rats to imitate the conditions of the human ventricular system. Two experimental settings were tested: Technique I, in which a computer landmark has been previously determined at the point where the vessel will be lesioned; and Technique II, in which a landmark has been previously set in the surrounding area of the vessel. Immediately after hemorrhage obscures the visual field (red out), the computer automatically displays the virtual images on a separate monitor. The previously set landmarks and the graphic overlay of the coagulation fiber enable the surgeon to navigate within the operative field based on the virtual images and to perform coagulation at the site of the lesion. A total of 175 vessels were coagulated: 43 arteries and 132 veins. In using Technique I, 130 (90.9%) of 143 vessels and in using Technique II, 26 (81.2%) of 32 arteries were successfully coagulated. The authors' data revealed that virtual image guidance has the potential to be a helpful tool in neuroendoscopy.

Animals↗

PubMed1999

Characterization and purification of an outer membrane metalloproteinase from Pseudomonas aeruginosa with fibrinogenolytic activity.

A membrane proteinase from Pseudomonas aeruginosa, called insulin-cleaving membrane proteinase (ICMP), was located in the outer membrane leaflet of the cell envelope. The enzyme is expressed early in the logarithmic phase parallel to the bacterial growth during growth on peptide rich media. It is located with its active center facing to the outermost side of the cell, because its whole activity could be measured in intact cells. The very labile membrane proteinase was solubilized by non-ionic detergents (Nonidet P-40, Triton X-100) and purified in its amphiphilic form to apparent homogeneity in SDS-PAGE by copper chelate chromatography and two subsequent chromatographic steps on Red-Sepharose CL-4B (yield 58.3%, purification factor 776.3). It consisted of a single polypeptide chain with a molecular mass of 44.6 kDa, determined by mass spectrometry. ICMP was characterized to be a metalloprotease with pH-optimum in the neutral range. The ICMP readily hydrolyzed Glu(13)-Ala(14) and Tyr(16)-Leu(17) bonds in the insulin B-chain. Phe(25)-Tyr(26) and His(10)-Leu(11) were secondary cleavage sites suggesting a primary specificity of the enzyme for hydrophobic or aromatic residues at P'(1)-position. The ICMP differed from elastase, alkaline protease and LasA in its cleavage specificity, inhibition behavior and was immunologically diverse from elastase. The amino acid sequence of internal peptides showed no homologies with the known proteinases. This outer membrane proteinase was capable of specific cleavage of alpha and beta fibrinogen chains. Among the p-nitroanilide substrates tested, substrates of plasminogen activator, complement convertase and kallikrein with arginine residues in the P(1)-subsite were the substrates best accepted, but they were only cleaved at a very low rate.

Amino Acid Sequence↗

PubMed1998

Development of an endoscopic navigation system based on digital image processing.

We developed a new system to couple the endoscope to an optical position measurement system (OPMS) so that the image frames from the endoscope camera can be labeled with the accurate endoscopic position. This OPMS is part of the EasyGuide Neuro navigation system, which is used for microsurgery and neuroendoscopy. Using standard camera calibration techniques and a newly developed system calibration, any 3-dimensional (3-D) world point can be mapped onto the view from the endoscope. In particular, we can display the coordinates of any anatomical landmark of the patient as it is viewed from the current position of the camera. This and other image-processing techniques are applied to the labeled frame sequence in order to offer the neurosurgeon a variety of control modules that increase the safety and flexibility of neuroendoscopic operations. Several modules, including a new motion alarm system and the "tracking" and "virtual map" modules, were tested in a human cadaveric model using the frontal and occipital approaches. A failure rate of 8.6% was experienced during testing of the first version of the software, but the second version was 100% successful. Thus, an endoscopic navigation system based on digital image processing has been developed that could be a revolutionary advance in image-guided surgery.

Cadaver↗

PubMed1997

Inhibition, reactivation, and determination of metal ions in membrane metalloproteases of bacterial origin using high-performance liquid chromatography coupled on-line with inductively coupled plasma mass spectrometry.

High-performance liquid chromatography coupled on-line with inductively coupled plasma mass spectrometry (HPLC-ICP-MS) was used for the characterization of metal ions in several metalloproteases of bacterial origin. The different components of the bacterial extracts were separated on a size-exclusion column. The eluent of the HPLC system was continuously transported to the ICP-MS system for rapid, reproducible, and sensitive analyses of trace elements in the metalloproteases. Two different membrane proteases from Bacillus cereus and Pseudomonas aeruginosa were characterized to be zinc metalloproteases using enzymological methods and HPLC-ICP-MS. The zinc content was determined to be three molecules of zinc per protein molecule for the B. cereus protease and one molecule of zinc per protein molecule for the P. aeruginosa protease. For another purified protease, a periplasmic alanyl aminopeptidase of P. aeruginosa, the lack of protein-bound metal ions could be clearly determined-a confirmation that this main aminopeptidase of P. aeruginosa belongs to the cysteine protease family. The presence of nonionic detergents can influence the distribution of trace elements during the HPLC separation. Therefore, the use of these substances should be avoided during enzyme purification for metal analyses or they should be exchanged later for zwitterionic and ionic detergents with more strongly dissociating properties.

Bacillus cereus↗

PubMed1997

Y-chromosome specific alleles and haplotypes in European and Asian populations: linkage disequilibrium and geographic diversity.

Variation on the Y chromosome may permit our understanding the evolution of the human paternal lineage and male gene flow. This study reports upon the distribution and non random association of alleles at four Y-chromosome specific loci in four populations, three Caucasoid (Italian, Greek and Slav) and one Asian. The markers include insertion/deletion (p12f), point mutation (92R7 and pY alpha I), and repeat sequence (p21A1) polymorphisms. Our data confirm that the p12f/TaqI 8 kb allele is a Caucasoid marker and that Asians are monomorphic at three of the loci (p12f, 92R7, and pY alpha I). The alleles at 92R7 and pY alpha I were found to be in complete disequilibrium in Europeans. Y-haplotype diversity was highly significant between Asians and all three European groups (P < 0.001), but the Greeks and Italians were also significantly different with respect to some alleles and haplotypes (P < 0.02). We find strong evidence that the p12f/TaqI 8 kb allele may have arisen only once, as a deletion event, and, additionally, that the present-day frequency distribution of Y chromosomes carrying the p12f/8 kb allele suggests that it may have been spread by colonising sea-faring peoples from the Near East, possibly the Phoenicians, rather than by expansion of Neolithic farmers into continental Europe. The p12f deletion is the key marker of a unique Y chromosome, found only in Caucasians to date, labelled 'Mediterranean' and this further increases the level of Y-chromosome diversity seen among Caucasoids when compared to the other major population groups.

Alleles↗

PubMed1997

Localization of alanyl aminopeptidase and leucyl aminopeptidase in cells of Pseudomonas aeruginosa by application of different methods for periplasm release.

Various methods for the isolation of periplasm were examined and compared with regard to the complete release of known periplasmic marker enzymes and the contamination of the periplasm by cytosol for Pseudomonas aeruginosa PAO1 as a significant Gram-negative test strain. The aim of the investigations was to clarify the exact localization of alanyl aminopeptidase (AAP) and leucyl aminopeptidase (LAP) of this microorganism and to evaluate these methods. The osmotic shock of NOSSAL and HEPPEL (1996) was the most effective method with the lowest contamination by the cytosolic marker enzyme malic enzyme, but some proteins, which are located near the inner side of the cytoplasmic membrane, can be released additionally into the periplasm. All other procedures like chloroform or polymyxin treatment, the magnesium chloride washing of intact bacteria and spheroblasting by lysozyme in the presence of EDTA or magnesium chloride resulted only in a partial, sometimes only very low release of periplasm. The periplasmic enzymes are bound either more by hydrophobic or more by ionic interactions to the cell envelope and show a different behaviour with the different releasing agents. These methods are useful for a further differentiation between really periplasmic protein, and those proteins, which were false positive found in periplasm as a result of the osmotic shock. Our results show that AAP from Pseudomonas aeruginosa is a periplasmic enzyme with hydrophobic interactions to the cytoplasmic membrane, corresponding to the early results of LAZDUNSKI and MURGIER for Escherichia coli (LAZDUNSKI et al. 1975a and b, MURGIER et al. 1977), and LAP is cytosolic, but located near the cytoplasmic membrane. The AAP is not a real amphipatic membrane protein, as could be demonstrated by phase separation experiments with Triton X-114.

Acid Phosphatase↗

PubMed1997

Topography and immunocytochemical characterization of nerve fibers in the leptomeningeal compartments of the rat. A light- and electron-microscopical study.

The localization of peptidergic, catecholaminergic, and nitroxidergic nerve fibers in the ventral leptomeningeal connective tissue compartment was studied in whole-mount preparations and serial semithin and ultrathin sections. For immunocytochemistry, whole-mount preparations of the leptomeninges and ventral brain slices with the meninges were incubated as free-floating specimens with primary antibodies against protein gene product 9.5 (PGP 9.5), substance P (SP), calcitonin gene-related peptide (CGRP), dopamine beta-hydroxylase (DbetaH), vasoactive intestinal polypeptide (VIP), neuropeptide Y (NPY), and nitric oxide synthase (NOS) using the avidin-biotin-peroxidase method. Based on the regional differences of the connective tissue organization, the leptomeninx is subdivided into the pial, trabecular, and adventitial leptomeninx. The antibody PGP 9.5 stains all unmyelinated nerve fibers in the leptomeninx. Although the highest density of nerve fibers occurs in the adventitial leptomeninx, nerve fibers, and terminals are additionally present in the trabecular and pial leptomeninx. DbetaH-, NPY-, VIP- and NOS-immunoreactive (IR) nerve fibers occur exclusively in the adventitial leptomeninx forming neuromuscular junctions. CGRP- and SP-IR nerve fibers are localized in all three leptomeningeal compartments where they terminate close to the subarachnoid space (type 1) or within the connective tissue (type 2). Due to their morphological and immunocytochemical characterization a possible chemo-, mechano- or nociceptive function is discussed in the context of pathophysiological aspects.

Animals↗