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Bischof L, Schweitzer F, Schmitz HP, Heinisch JJ. The small yeast GTPase Rho5 requires specific mitochondrial outer membrane proteins for translocation under oxidative stress and interacts with the VDAC Por1. Eur J Cell Biol 2024; 103:151405. [PMID: 38503132 DOI: 10.1016/j.ejcb.2024.151405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Revised: 02/29/2024] [Accepted: 03/14/2024] [Indexed: 03/21/2024] Open
Abstract
Yeast Rho5 is a small GTPase which mediates the response to nutrient and oxidative stress, and triggers mitophagy and apoptosis. We here studied the rapid translocation of a GFP-tagged Rho5 to mitochondria under such stress conditions by live-cell fluorescence microscopy in the background of strains lacking different mitochondrial outer membrane proteins (MOMP). Fun14, Msp1 and Alo1 were found to be required for efficient recruitment of the GTPase, whereas translocation of Dck1 and Lmo1, the subunits of its dimeric GDP/GTP exchange factor (GEF), remained unaffected. An influence of the voltage-dependent anion channel (VDAC) Por1 on the association of GFP-Rho5 with mitochondria under oxidative stress conditions appeared to be strain-dependent. However, epistasis analyses and bimolecular fluorescence complementation (BiFC) studies indicate a genetic and physical interaction. All four strains lacking a single MOMP were investigated for their effect on mitophagy.
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Affiliation(s)
- Linnet Bischof
- Universität Osnabrück, Fachbereich Biologie/Chemie, AG Genetik, Barbarastr. 11, Osnabrück D-49076, Germany
| | - Franziska Schweitzer
- Universität Osnabrück, Fachbereich Biologie/Chemie, AG Genetik, Barbarastr. 11, Osnabrück D-49076, Germany
| | - Hans-Peter Schmitz
- Universität Osnabrück, Fachbereich Biologie/Chemie, AG Genetik, Barbarastr. 11, Osnabrück D-49076, Germany
| | - Jürgen J Heinisch
- Universität Osnabrück, Fachbereich Biologie/Chemie, AG Genetik, Barbarastr. 11, Osnabrück D-49076, Germany.
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Bischof L, Schweitzer F, Heinisch JJ. Functional Conservation of the Small GTPase Rho5/Rac1-A Tale of Yeast and Men. Cells 2024; 13:472. [PMID: 38534316 DOI: 10.3390/cells13060472] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2024] [Revised: 03/02/2024] [Accepted: 03/06/2024] [Indexed: 03/28/2024] Open
Abstract
Small GTPases are molecular switches that participate in many essential cellular processes. Amongst them, human Rac1 was first described for its role in regulating actin cytoskeleton dynamics and cell migration, with a close relation to carcinogenesis. More recently, the role of Rac1 in regulating the production of reactive oxygen species (ROS), both as a subunit of NADPH oxidase complexes and through its association with mitochondrial functions, has drawn attention. Malfunctions in this context affect cellular plasticity and apoptosis, related to neurodegenerative diseases and diabetes. Some of these features of Rac1 are conserved in its yeast homologue Rho5. Here, we review the structural and functional similarities and differences between these two evolutionary distant proteins and propose yeast as a useful model and a device for high-throughput screens for specific drugs.
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Affiliation(s)
- Linnet Bischof
- AG Genetik, Fachbereich Biologie/Chemie, University of Osnabrück, Barbarastrasse 11, D-49076 Osnabrück, Germany
| | - Franziska Schweitzer
- AG Genetik, Fachbereich Biologie/Chemie, University of Osnabrück, Barbarastrasse 11, D-49076 Osnabrück, Germany
| | - Jürgen J Heinisch
- AG Genetik, Fachbereich Biologie/Chemie, University of Osnabrück, Barbarastrasse 11, D-49076 Osnabrück, Germany
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Schweitzer F, Laurent S, Fink GR, Barnett MH, Hartung HP, Warnke C. Effects of disease-modifying therapy on peripheral leukocytes in patients with multiple sclerosis. J Neurol 2021; 268:2379-2389. [PMID: 32036423 PMCID: PMC8217029 DOI: 10.1007/s00415-019-09690-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Accepted: 12/24/2019] [Indexed: 12/11/2022]
Abstract
Modern disease-modifying therapies (DMTs) in multiple sclerosis (MS) have variable modes of action and selectively suppress or modulate the immune system. In this review, we summarize the predicted and intended as well as unwanted adverse effects on leukocytes in peripheral blood as a result of treatment with DMTs for MS. We link changes in laboratory tests to the possible therapeutic risks that include secondary autoimmunity, infections, and impaired response to vaccinations. Profound knowledge of the intended effects on leukocyte counts, in particular lymphocytes, explained by the mode of action, and adverse effects which may require additional laboratory and clinical vigilance or even drug discontinuation, is needed when prescribing DMTs to treat patients with MS.
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Affiliation(s)
- F Schweitzer
- Department of Neurology, University of Cologne, Faculty of Medicine and University Hospital Cologne, Kerpener Straße 62, 50937, Cologne, Germany
| | - S Laurent
- Department of Neurology, University of Cologne, Faculty of Medicine and University Hospital Cologne, Kerpener Straße 62, 50937, Cologne, Germany
| | - G R Fink
- Department of Neurology, University of Cologne, Faculty of Medicine and University Hospital Cologne, Kerpener Straße 62, 50937, Cologne, Germany
- Cognitive Neuroscience, Institute of Neuroscience and Medicine (INM-3), Research Center Jülich, Jülich, Germany
| | - Michael H Barnett
- Department of Neurology, Royal Prince Alfred Hospital, and Brain and Mind Centre, University of Sydney, Sydney, Australia
| | - H P Hartung
- Department of Neurology, Medical Faculty, and Center for Neurology and Neuropsychiatry, LVR Klinikum, Heinrich-Heine-University Düsseldorf, Moorenstr. 5, 40225, Düsseldorf, Germany.
| | - C Warnke
- Department of Neurology, University of Cologne, Faculty of Medicine and University Hospital Cologne, Kerpener Straße 62, 50937, Cologne, Germany.
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Goereci Y, Schweitzer F, Wellstein A, Silling S, Borchmann S, Tresckow B, Adams O, Martin R, Schlamann M, Schroeter M, Fink GR, Wattjes MP, Warnke C. Clearance of JC polyomavirus from cerebrospinal fluid following treatment with interleukin‐2 and pembrolizumab in an individual with progressive multifocal leukoencephalopathy and no underlying immune deficiency syndrome. Eur J Neurol 2020; 27:2375-2377. [DOI: 10.1111/ene.14435] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Accepted: 06/26/2020] [Indexed: 01/13/2023]
Affiliation(s)
- Y. Goereci
- Department of Neurology Medical Faculty University Hospital of Köln Köln Germany
| | - F. Schweitzer
- Department of Neurology Medical Faculty University Hospital of Köln Köln Germany
| | - A. Wellstein
- Georgetown University Medical School Washington DC USA
| | - S. Silling
- Institute for Virology Medical Faculty University Hospital of Köln KölnGermany
| | - S. Borchmann
- Department of Haematology Medical Faculty University Hospital of Köln KölnGermany
| | - B. Tresckow
- Department of Haematology University Hospital Essen EssenGermany
| | - O. Adams
- Institute for Virology Medical Faculty University Hospital of Düsseldorf Düsseldorf Germany
| | - R. Martin
- Department of Neurology University Medical Center Zürich Zürich Switzerland
| | - M. Schlamann
- Department of Radiology Medical Faculty University Hospital of Köln KölnGermany
| | - M. Schroeter
- Department of Neurology Medical Faculty University Hospital of Köln Köln Germany
| | - G. R. Fink
- Department of Neurology Medical Faculty University Hospital of Köln Köln Germany
- Cognitive Neuroscience Institute of Neuroscience and Medicine (INM‐3) Research Centre Jülich JülichGermany
| | - M. P. Wattjes
- Department of Diagnostic and Interventional Neuroradiology Hannover Medical School Hannover Germany
| | - C. Warnke
- Department of Neurology Medical Faculty University Hospital of Köln Köln Germany
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Massardo L, Schweitzer F, Pineda C, Pons-Estel B, Cardiel M, Soriano E, Galarza C, Levy R, Sacnum M, Caballero-Uribe C, Bianchi W, Gonzalez H, Montufar R, Pinto R, Ramirez L, Zerbini C, Laurindo I, Barra I. SAT0123 Radiographic Severity of Rheumatoid Arthritis in Latin American Patients: Results from The Gladar Cohort. Ann Rheum Dis 2016. [DOI: 10.1136/annrheumdis-2016-eular.5125] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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Teutsch K, Schweitzer F, Knops E, Kaiser R, Pfister H, Verheyen J, Göbel H, Cingöz T, Di Cristanziano V. Early identification of renal transplant recipients with high risk of polyomavirus-associated nephropathy. Med Microbiol Immunol 2015; 204:657-64. [DOI: 10.1007/s00430-015-0398-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Accepted: 02/21/2015] [Indexed: 02/07/2023]
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Schweitzer D, Schenke S, Hammer M, Schweitzer F, Jentsch S, Birckner E, Becker W, Bergmann A. Towards metabolic mapping of the human retina. Microsc Res Tech 2007; 70:410-9. [PMID: 17393496 DOI: 10.1002/jemt.20427] [Citation(s) in RCA: 133] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Functional alterations are first signs of a starting pathological process. A device that measures parameter for the characterization of the metabolism at the human eye-ground would be a helpful tool for early diagnostics in stages when alterations are yet reversible. Measurements of blood flow and of oxygen saturation are necessary but not sufficient. The new technique of auto-fluorescence lifetime measurement (FLIM) opens in combination with selected excitation and emission ranges the possibility for metabolic mapping. FLIM not only adds an additional discrimination parameter to distinguish different fluorophores but also resolves different quenching states of the same fluorophore. Because of its high sensitivity and high temporal resolution, its capability to resolve multi-exponential decay functions, and its easy combination with laser scanner ophthalmoscopy, multi-dimensional time-correlated single photon counting was used for fundus imaging. An optimized set up for in vivo lifetime measurements at the human eye-ground will be explained. In this, the fundus fluorescence is excited at 446 or 468 nm and the time-resolved autofluorescence is detected in two spectral ranges between 510 and 560 nm as well as between 560 and 700 nm simultaneously. Exciting the fundus at 446 nm, several fluorescence maxima of lifetime t1 were detected between 100 and 220 ps in lifetime histograms of 40 degrees fundus images. In contrast, excitation at 468 nm results in a single maximum of lifetime t1 = 190 +/- 16 ps. Several fundus layers contribute to the fluorescence intensity in the short-wave emission range 510-560 nm. In contrast, the fluorescence intensity in the long-wave emission range between 560 and 700 nm is dominated by the fluorescence of lipofuscin in the retinal pigment epithelium. Comparing the lateral distribution of parameters of a tri-exponential model function in lifetime images of the fundus with the layered anatomical fundus structure, the shortest component (t1 = 190 ps) originates from the retinal pigment epithelium and the second lifetime (t2 = 1,000 ps) from the neural retina. The lifetime t3 approximately 5.5 ns might be influenced by the long decay of the fluorescence in the crystalline lens. In vitro analysis of the spectral properties of expected fluorophores under the condition of the living eye lightens the interpretation of in vivo measurements. Taking into account the transmission of the ocular media, the excitation of NADH is unlikely at the fundus.
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Affiliation(s)
- D Schweitzer
- Department of Experimental Ophthalmology, University of Jena, Germany.
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Schweitzer D, Beuermann B, Hammer M, Schweitzer F, Richter S, Leistritz L, Scibor M, Thamm E, Kolb A, Anders R. Fundusspektrometrie bei altersbezogener Makulopathie. Klin Monbl Augenheilkd 2005; 222:396-408. [PMID: 15912457 DOI: 10.1055/s-2005-858088] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
BACKGROUND Spectroscopic methods permit the non-invasive detection of fundus pigments by the wavelength-dependent absorption of fluorescence as well as by the fluorescence lifetime. From the relative concentrations of haemoglobin and oxyhaemoglobin, the oxygen saturation can be calculated. The onset of age-related maculopathy might be delayed by a high optical density of xanthophyll. The detection of alterations in fundus autofluorescence points to age-related pathomechanisms (accumulation of lipofuscin, formation of connective tissue). The detection of autofluorescence of redox-pairs of coenzymes results in information about metabolic states at the cellular level, and might make possible an early detection of age-related changes when they are still reversible. METHOD The evaluation of reflectance spectra, detected by imaging ophthalmo-spectrometry, results in the calculation of oxygen saturation or in the optical density of xanthophyll or of melanin. Fluorescence spectra can be measured also by this technique. For the 2-dimensional determination of the distribution of xanthophyll, a very simple method was developed, requiring fundus illumination by one wavelength only. In the detection of time-resolved autofluorescence, the fluorescence lifetime is used for the determination of endogenous fluorophores. RESULTS As result of comparing studies between ARM patients and healthy subjects, the consumption of retinal oxygen was increased already in the children of ARM patients. An increasing optical density of xanthophyll was determined after lutein supplementation. Differences in fluorescence lifetime were determined between ARM patients and healthy subjects, but their interpretation requires investigations of cell or of organ model cultures. CONCLUSIONS The described methods permit in vivo basic investigations of ARM and can be considered as impulses for the development of diagnostic devices.
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Affiliation(s)
- D Schweitzer
- FSU Jena, Klinik für Augenheilkunde, Bereich Experimentelle Ophthalmologie, Jena.
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Hammer M, Nagel E, Schweitzer D, Richter S, Schweitzer F, Königsdörffer E, Strobel J. [Spectral separation in ocular fundus autofluorescence images in patients suffering from age-related macular degeneration]. Ophthalmologe 2005; 101:1189-93. [PMID: 15069574 DOI: 10.1007/s00347-004-1019-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
INTRODUCTION Alterations in the intrinsic ocular fundus fluorescence are under discussion particularly in connection with age-related macular degeneration. However, further knowledge of the chemical substrate of fluorescence is necessary. METHOD Ocular fundus autofluorescence was observed using a fundus camera. The fluorescence emission was recorded using a 3-chip CCD camera. For comparison, the fluorescence spectra of lipofuscin, A2-E, FAD, NADH(2) and AGE's were recorded by the Jena ophthalmo-spectrometer. RESULTS In contrast to the homogeneous intrinsic fluorescence of a normal fundus, the fluorescence images of patients suffering from AMD showed remarkable local differences. The detected fluorescence spectra showed remarkable overlaps. DISCUSSION We introduced a new technique enabling the detection of spectral differences in images of ocular fundus autofluorescence. Besides the fluorescence of lipofuscin, we found a green one in patients suffering from nonexudative AMD.
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Affiliation(s)
- M Hammer
- Augenklinik, Friedrich-Schiller-Universität, Jena.
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Schweitzer D, Hammer M, Schweitzer F. Grenzen der konfokalen Laser Scanning Technik bei Messungen der zeitaufgelösten Autofluoreszenz am Augenhintergrund / Limits of the confocal laser-scanning technique in measurements of time-resolved autofluorescence of the eye-ground. BIOMED ENG-BIOMED TE 2005; 50:263-7. [PMID: 16185033 DOI: 10.1515/bmt.2005.038] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
GOAL The 2-dimensional measurement of the time-dependent autofluorescence has in combination of confocal laser scanner technique and time correlated single photon counting the potential for the investigation of the metabolism state at the eye ground. It was to be examined, to what extent these measurements are influenced through the auto-fluorescence of the crystalline lens. MATERIAL AND METHOD The time-dependent auto-fluorescence was measured on eyes of 21 patients with age-related macular degeneration (AMD) and of 26 healthy subjects in 40 degrees fundus images. The experimental set-up used, was developed at the eye clinic of the University of Jena. In this scanning laser ophthalmoscope, the fundus was excited at 446 nm by pulses of 100 ps full width at half maximum and 40 MHz repetition rate. The auto-fluorescence was detected with a time resolution of 25 ps for wavelengths > 500 nm. The dynamic auto-fluorescence of each pixel was approximated by a tri-exponential model function. In order to determine the influence of the fluorescence of the crystalline lens, healthy eyes and eyes were compared with implanted artificial intra-ocular lenses. For comparison the frequency distributions were used, which the decay times t1, t2 and t3 in the fundus images had been calculated with. RESULTS Clear differences were shown in the frequency distributions of the fluorescence lifetimes between AMD-patients and healthy subjects, It resulted, however, from a crucial analysis that the fluorescence of the crystalline lens is not suppressed by the confocal laser scanning principle sufficiently. In particular the long lifetime t3 is overlapped by the fluorescence of the crystalline lens of about 4.6 ns. To the complete suppression of the influence of the lens fluorescence in measurements of the time-resolved fundus auto-fluorescence it is suggested to combine the confocal laser scanning technique with the principle of the aperture diaphragm division. CONCLUSION In order to be able to determine the capability of measurements of the time-dependent fundus auto-fluorescence as diagnostic tool exactly, the influence of the crystalline lens is to reduce through the combination of confocal laser scanning ophthalmoscopy with the principle of the aperture diaphragm division diversely.
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Affiliation(s)
- D Schweitzer
- Experimentelle Ophthalmologie, Augenklinik der Friedrich Schiller Universität Jena.
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Schweitzer D, Hammer M, Schweitzer F, Richter S, Königsdörffer E. Zum Einfluss der Linsenfluoreszenz auf Messungen der Fluoreszenzlebensdauer am Augenhintergrund. Klin Monbl Augenheilkd 2004. [DOI: 10.1055/s-2004-836211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Schweitzer F, Ebeling W, Tilch B. Statistical mechanics of canonical-dissipative systems and applications to swarm dynamics. Phys Rev E Stat Nonlin Soft Matter Phys 2001; 64:021110. [PMID: 11497565 DOI: 10.1103/physreve.64.021110] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2001] [Indexed: 11/07/2022]
Abstract
We develop the theory of canonical-dissipative systems, based on the assumption that both the conservative and the dissipative elements of the dynamics are determined by invariants of motion. In this case, known solutions for conservative systems can be used for an extension of the dynamics, which also includes elements such as the takeup/dissipation of energy. This way, a rather complex dynamics can be mapped to an analytically tractable model, while still covering important features of nonequilibrium systems. In our paper, this approach is used to derive a rather general swarm model that considers (a) the energetic conditions of swarming, i.e., for active motion, and (b) interactions between the particles based on global couplings. We derive analytical expressions for the nonequilibrium velocity distribution and the mean squared displacement of the swarm. Further, we investigate the influence of different global couplings on the overall behavior of the swarm by means of particle-based computer simulations and compare them with the analytical estimations.
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Affiliation(s)
- F Schweitzer
- Real World Computing Partnership--Theoretical Foundation, GMD Laboratory, Schloss Birlinghoven, 53754 Sankt Augustin, Germany.
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Lane SD, Cibula DA, Milano LP, Shaw M, Bourgeois B, Schweitzer F, Steiner C, Dygert K, DeMott K, Wilson K, Gregg R, Webster N, Milton D, Aubry R, Novick LF. Racial and ethnic disparities in infant mortality: risk in social context. J Public Health Manag Pract 2001; 7:30-46. [PMID: 11338084 DOI: 10.1097/00124784-200107030-00007] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
This article presents the multifaceted efforts of Syracuse Healthy Start, a federally funded initiative of the Onondaga County Health Department and over 20 partnering agencies to reduce racial and ethnic disparities in infant mortality. The analyses presented in this article demonstrate that many women--Caucasian, African American, and Hispanic--have serious risks for low birth weight and infant death. In many cases, multiple, simultaneous risks complicate a pregnant woman's situation and in other cases the longitudinal cumulative risks impact health across generations. Infant mortality decreased overall, and for both Caucasian and African American infants during the first 3 years of the project.
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Affiliation(s)
- S D Lane
- Onondaga County Health Department, Syracuse, New York, USA
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Fleck C, Janz A, Schweitzer F, Karge E, Schwertfeger M, Stein G. Serum concentrations of asymmetric (ADMA) and symmetric (SDMA) dimethylarginine in renal failure patients. Kidney Int Suppl 2001; 78:S14-8. [PMID: 11168976 DOI: 10.1046/j.1523-1755.2001.59780014.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
BACKGROUND Nitric oxide (NO) synthesis is inhibited by the ADMA that accumulates in the plasma of patients with renal failure; however, the concentration of SDMA also is enhanced. Therefore, it has been hypothesized that ADMA and SDMA may contribute to hypertension in these patients. METHODS We measured the concentrations of ADMA, SDMA and 21 endogenous amino acids in 257 persons by high pressure liquid chromatography (HPLC). RESULTS The plasma concentrations of both ADMA and SDMA were significantly elevated in patients with chronic renal failure (CRF). The increase was more pronounced for SDMA (2.05 +/- 0.1 micromol/L vs. 0.5 +/- 0.04 micromol/L), whereas it was only moderate for ADMA (0.85 +/- 0.03 micromol/L vs. 0.73 +/- 0.06 micromol/L). In dialysis patients, the concentrations were further increased (ADMA, 1.05 +/- 0.04 micromol/L; SDMA, 2.68 +/- 0.13 micromol/L). After kidney transplantation, the concentration of SDMA returned to the baseline value (1.15 +/- 0.11 micromol/L), but that of ADMA remained enhanced (0.99 +/- 0.06 micromol/L). CONCLUSIONS In CRF, especially the concentration of SDMA is significantly increased. Not only ADMA, but also SDMA are likely to be responsible for hypertension. Competition for reabsorption between SDMA and arginine within the kidney has to be considered for the interpretation of changes in the ratio between dimethylarginines and arginine in renal failure. Hemodialysis is not suitable for a long-lasting removal of methylarginines. Whether the administration of arginine could have promising effects on hypertension and complications of CRF needs to be studied in prospective trials.
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Affiliation(s)
- C Fleck
- Department of Internal Medicine IV, and Institute of Pharmacology and Toxicology, University of Jena, Jena, Germany.
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Abstract
In the model of active motion studied here, Brownian particles have the ability to take up energy from the environment to store it in an internal depot and to convert internal energy into kinetic energy. Considering also internal dissipation, we derive a simplified model of active biological motion. For the take-up of energy two different examples are discussed: (i) a spatially homogeneous supply of energy, and (ii) the supply of energy at spatially localized sources (food centers). The motion of the particles is described by a Langevin equation which includes an acceleration term resulting from the conversion of energy. Dependent on the energy sources, we found different forms of periodic motion (limit cycles), i.e. periodic motion between 'nest' and 'food'. An analytic approximation allows the description of the stationary motion and the calculation of critical parameters for the take-up of energy. Finally, we derive an analytic expression for the efficiency ratio of energy conversion, which considers the take-up of energy, compared to (internal and external) dissipation.
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Affiliation(s)
- W Ebeling
- Institute of Physics, Humboldt University, Berlin, Germany.
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Abstract
"The growth of large urban aggregates (megacities) is analogous to the development of self-organized structures known in physics. Using empirical data about changes in the built-up areas of different cities as input, the self-organizing model employed here suggests that megacities evolve towards a hierarchical form of spatial organization, and provides estimates of the size of subclusters that compose the urban aggregate.... The model has been validated by reproducing the evolution of the Berlin area over a period of 35 years (1910-45). Using the same assumptions, the evolution of the built-up area of Daegu (Korea) is simulated up to the year 2010."
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Schweitzer F. Managing chronic retention of urine in obstructive uropathy. Trop Doct 1997; 27:67-8. [PMID: 9133782 DOI: 10.1177/004947559702700203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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Abstract
A simple model for interactive structure formation is studied to simulate the trail formation by ants based on local chemical communication. In our model, active random walkers, which do not have the ability of visual navigation or storage of information, first have to discover different distributions of food sources and then have to link these sources to a central place by forming a trail, using no other guidance than the chemical markings produced by themselves. The simulations show the spontaneous emergence of a collective trail system due to self-organization, which is both stable and flexible, to include newly discovered sources. The typical dendritic foraging patterns of desert ants, reported by Hölldobler and Möglich (Insectes Sociaux. 1980. 27(3). pp. 237 264) are reproduced by the simulations.
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Affiliation(s)
- F Schweitzer
- Emory University, Department of Physics, Atlanta, GA 30322, USA.
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Abstract
A road network usually has to fulfill two requirements: (i) it should as far as possible provide direct connections between nodes to avoid large detours; and (ii) the costs for road construction and maintenance, which are assumed proportional to the total length of the roads, should be low. The optimal solution is a compromise between these contradictory demands, which in our model can be weighted by a parameter. The road optimization problem belongs to the class of frustrated optimization problems. In this paper, a special class of evolutionary strategies, such as the Boltzmann and Darwin and mixed strategies, are applied to find differently optimized solutions (graphs of varying density) for the road network, depending on the degree of frustration. We show that the optimization process occurs on two different time scales. In the asymptotic limit, a fixed relation between the mean connection distance (detour) and the total length (costs) of the network exists that defines a range of possible compromises. Furthermore, we investigate the density of states, which describes the number of solutions with a certain fitness value in the stationary regime. We find that the network problem belongs to a class of optimization problems in which more effort in optimization certainly yields better solutions. An analytical approximation for the relation between effort and improvement is derived.
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Affiliation(s)
- F Schweitzer
- Institute of Physics, Humboldt University, Berlin, Germany.
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Nipkow KE, Schweitzer F. Adolescents' justifications for faith or doubt in God: a study of fulfilled and unfulfilled expectations. New Dir Child Dev 1991:91-100. [PMID: 1956549 DOI: 10.1002/cd.23219915208] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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24
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25
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26
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Ebeling W, Schweitzer F, Schimansky-Geier L, Ulbricht H. Stochastic Approach to Cluster Formation in Adiabatically Expanding Molecular Beams. Z PHYS CHEM 1990. [DOI: 10.1515/zpch-1990-01138] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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27
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28
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Tridon P, Schweitzer F, Six V. [Rett syndrome]. Ann Med Psychol (Paris) 1989; 147:245-50. [PMID: 2802444] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- P Tridon
- Institut J.-B. Thiery, Maxeville
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Gilgenkrantz S, Mujica P, Gruet P, Tridon P, Schweitzer F, Nivelon-Chevallier A, Nivelon JL, Couillault G, David A, Verloes A. Coffin-Lowry syndrome: a multicenter study. Clin Genet 1988; 34:230-45. [PMID: 3069251 DOI: 10.1111/j.1399-0004.1988.tb02870.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The Coffin-Lowry syndrome is an inherited syndrome of mental retardation, characteristic facies and skeletal anomalies. The occurrence of severe manifestations in males, with no instance of male-to-male transmission, suggests an X-linked inheritance. The paper describes seven families from five European Centers.
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Schweitzer F. [The 65th birthday of Prof. Walter Pilgerstorfer]. Wien Med Wochenschr 1977; 127:359-60. [PMID: 333778] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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32
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Schweitzer F. [Circulatory disorders]. Wien Med Wochenschr 1972; 122:398-400. [PMID: 5045408] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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33
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Koblinger J, Schweitzer F, Weithaler A. [Carcinoid tumor. Special reference to a case of an endocrine active bronchial carcinoid with carcinoid syndrome]. Wien Med Wochenschr 1971; 121:530-1. [PMID: 5129950] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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34
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Hohenwallner W, Schweitzer F, Vinazzer G. [The preventive value of supplementary diabetes screening by the detection of cases of latent diabetes mellitus]. Wien Med Wochenschr 1971; 121:525-7. [PMID: 5129949] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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35
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Kuenkel H, Schweitzer F, Sternberg M, Sternberg P. Power spectrum analysis of higher central nervous rhythms in the human EEG. Electroencephalogr Clin Neurophysiol 1969; 27:677. [PMID: 4187327 DOI: 10.1016/0013-4694(69)91277-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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36
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Schweitzer F. [Electrotherapy of the heart and its after care]. Wien Med Wochenschr 1968; 118:592-5. [PMID: 4302671] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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37
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Michelmayr G, Schweitzer F. [The atypical heart infarct]. Wien Med Wochenschr 1967; 117:662-4. [PMID: 5585446] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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38
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Schweitzer F. [The Pickwick syndrome]. Wien Med Wochenschr 1965; 115:558-60. [PMID: 5829954] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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39
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Fellinger K, Schweitzer F. Gefäßerkrankungen nach Quecksilbervergiftungen. Int Arch Occup Environ Health 1938. [DOI: 10.1007/bf02123308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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