Biomedical subjects

U Zimmermann

Publications and source records attributed to U Zimmermann.

At least 37 records · Page 2Linked to original sources

PubMed2003

Impact of hypoosmotic challenges on spongy architecture of the cytoplasm of the giant marine alga Valonia utricularis.

The ultrastructure of the several micrometers thick cytoplasmic layer of the giant marine alga Valonia utricularis displays characteristics which are apparently linked with the capability of this alga to regulate turgor pressure. Transmission and scanning electron microscopy of cells prefixed in different ways, including a protocol that allows prefixation of the alga in a turgescent state, revealed a highly dendritic network of cytoplasmic strands connecting and enveloping the chloroplasts and the nuclei. Innumerable vacuolar entities are embedded in the network, giving the cytoplasm a spongy appearance. Vacuolar perfusion of turgor-pressure-clamped cells with prefixation solution containing tannic acid presented evidence that these vacuolar entities together with the huge central vacuole form a large unstirred continuum. In contrast to the tonoplast, the plasmalemma followed smoothly the lining of the cell wall, even at the numerous cell wall ingrowths. Sucrose, but not polyethylene glycol 6000, induced chloroplast clustering. Acute hypoosmotic treatment (established by reduction of external NaCl or by replacement of part of the external NaCl by equivalent osmotic concentrations of sucrose or polyethylene glycol 6000) resulted in a local relocation of the chloroplasts and cytoplasm towards the central vacuole. This effect did not occur when the relatively low reflection coefficients of these two osmolytes were taken into account. The increase in spacing between the spongy cytoplasm and the plasmalemma by chloroplast relocation (viewed by confocal laser scanning microscopy) was associated with a speckled appearance of the affected surface area under the light microscope. As indicated by electron microscopy, hypoosmotically induced chloroplast relocation resulted from disproportionate swelling of the vacuolar entities located close to the plasmalemma. The cytoskeleton in the cytoplasm and the mucopolysaccharide network in the central vacuole apparently resisted swelling of these compartments. This finding has the important consequence that relevant hydrostatic pressure gradients can be built up throughout the entire multifolded vacuolar space. This gradient could represent the trigger for turgor pressure regulation which is manifested electrically first in the tonoplast.

Chlorophyta↗

PubMed2003

Cross-linking properties of alginate gels determined by using advanced NMR imaging and Cu(2+) as contrast agent.

The entrapment of enzymes, drugs, cells or tissue fragments in alginates cross-linked with Ca(2+) or Ba(2+) has great potential in basic research, biotechnology and medicine. The swelling properties and, in turn, the mechanical stability are key factors in designing an optimally cross-linked hydrogel matrix. These parameters depend critically on the cross-linking process and seemingly minor modifications in manufacture have a large impact. Thus, sensitive and non-invasive tools are required to determine the spatial homogeneity and efficacy of the cross-linking process. Here, we show for alginate microcapsules (between 400 microm and 600 microm in diameter) that advanced (1)H NMR imaging, along with paramagnetic Cu(2+) as contrast agent, can be used to validate the cross-linking process. Two- and three-dimensional images and maps of the spin-lattice relaxation time T(1) of Ba(2+) cross-linked microcapsules exposed to external Cu(2+) yielded qualitative as well as quantitative information about the accumulation of Cu(2+) within and removal from microcapsules upon washing with Cu(2+) free saline solution. The use of Cu(2+) (having a slightly higher affinity constant to alginate than Ba(2+)) for gelling gave a complementary insight into the spatial homogeneity of the cross-linking process together with information about the mechanical stability of the microcapsules. The potential of this technique was demonstrated for alginates extracted from two different algal sources and cross-linked either externally by the conventional air-jet dropping method or internally by the "crystal gun" method.

Alginates↗

PubMed2003

[The effects of auditory research on clinical practice].

Recent research has shown that only the inner hair cells pass information on to the brain while the outer hair cells serve as an active amplifier and thus stimulate the inner cells. The electromotility of the outer hair cells is very vulnerable. If it is lacking, sensorineuronal hearing loss occurs. Substances, that compete for the chloride combining site of the motor protein prestin, such as salicylate, might have a blocking effect on the regulation of electromotility. On the other hand, the control of the intracellular Ca(2+) level and the intracellular combination of ions in the outer hair cells might protect their electromotile properties against damage caused by harmful substances (ototoxic drugs) or mechanisms (exposition to noise), which would otherwise lead to irreversible sensorineuronal hearing loss. This is because an increase in the intracellular Ca(2+) level activates phosphorylating enzymes. Thus the stiffness of the outer hair cells is reduced, causing an increase in electromotility.

Animals↗

PubMed2003

Structural peculiarities dominate the turgor pressure response of the marine alga Valonia utricularis upon osmotic challenges.

The pressure response of (plant) cells to osmotic challenges depends on the reflection coefficient, sigma, of osmotically active solutes; it is less than predicted by the van't Hoff equation if sigma < 1. In Valonia utricularis, sigma is significantly reduced by internal (and, to a lesser extent, by external) unstirred layers, protecting the cytoplasm against vacuolar osmotic fluctuations. As shown by scanning and transmission electron microscopy, diffusion-restricted spaces are formed by innumerable small vacuoles that are interconnected with each other and with the central vacuole. They are embedded in networks of cytoplasmic strands connecting and encircling the organelles. Unstirred layers are also created in the central vacuole by an extensive network of acid mucopolysaccharide filaments (visualized by alcian blue staining). Mucopolysaccharides apparently also affect steady-state turgor by reducing the water activity. When the effective vacuolar osmotic pressure was adjusted to that of the bath by perfusion with an artificial vacuolar sap (AVS), an "offset turgor pressure" of 17 +/- 5 kPa was recorded. Consistent with the ultrastructural data, sigma values less than unity were calculated from the pressure response upon vacuolar addition of KCl or sucrose by perfusion (sigma(iKCl) = 0.63 +/- 0.13; sigma(isuc) = 0.58 +/- 0.17). Dilution of AVS yielded slightly higher sigma(iKCl) values (0.73 +/- 0.35). External addition to the artificial sea water (ASW) indicated that sigma(e) > sigma(i) for these osmotica. However, even in this case, sigma(esuc) (0.86 +/- 0.09) and sigma(ePEG) (0.58 +/- 0.08) were significantly less than sigma(eNaCl) (0.94 +/- 0.05) and sigma(eKCl) (0.91 +/- 0.13), presumably due to unstirred layers within the 4 micro m thick cell wall. Consistent with the low sigma values, a partial replacement of NaCl by osmotically equivalent amounts of sucrose (ASW(suc)), PEG and dextran, respectively, as well as replacement of Cl(-) by the large anion MES(-) induced an 'anomalous' hyposmotic turgor pressure response followed by the usual backregulation of pressure. After a 2-day preincubation in ASW(suc), significantly lower sigma(e) values were obtained both hyperosmotically (sigma(eNaCl) = 0.78 +/- 0.14; sigma(esuc) = 0.72 +/- 0.15) and hyposmotically (sigma(eNaCl) = 0.70 +/- 0.17; sigma(esuc) = 0.63 +/- 0.09), probably due to long-term effects on membrane structure to be elucidated yet. The freshwater alga Chara corallina lacked these apparently closely related structural and biophysical features of Valonia.

Cell Membrane↗

PubMed2003

Gating of Cl- currents in protoplasts from the marine alga Valonia utricularis depends on the transmembrane Cl- gradient and is affected by enzymatic cell wall degradation.

The electrical properties of protoplasts of the turgor pressure-regulating giant marine alga Valonia utricularis were investigated by using the patch-clamp technique. In the whole-cell configuration, large inward currents were elicited by negative-going voltage pulses. The time-dependent component was predominantly carried by Cl-, as revealed by 'tail current' analysis. When experiments were performed on protoplasts directly after mechanical release from the 'mother cell', small outward currents were additionally observed at membrane voltages more positive than ECl-. These outward currents disappeared to a large extent after treatment of the protoplasts with a mixture of cell wall-degrading enzymes. Plots of the chord conductance versus the clamped membrane voltage revealed that enzymatic treatment affected the gating properties. By fitting Boltzmann distributions to the data, a midpoint potential of + 5 +/- 5 mV (n = 7) was obtained in symmetrical Cl- solutions for mechanically released protoplasts. In contrast, protoplasts treated additionally with enzymes exhibited a midpoint potential of -13 +/- 5 mV (n = 8). By varying the external and internal Cl- concentration, gating was also shown to depend on the Cl- gradient across the plasmalemma both in enzymatically treated and untreated protoplasts. Plotting of the midpoint potential against the Nernst potential of Cl- rendered a slope less than 1 (0.70 and 0.64, respectively) indicating that gating did not strictly depend on the electrochemical Cl- gradient. The voltage- and Cl--dependence as well as inhibition experiments with 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) suggested that the Cl- conductance of the membrane is dominated by the Valonia Anion Channel 1 (VAC1) described by Heidecker, M., Wegner, L.H., Zimmermann, U. 1999: A patch-clamp study of ion channels in proto-plasts prepared from the marine alga Valonia utricularis. J. Membrane Biol. 172:235-247. The relevance of the findings for membrane potential control and turgor regulation in V. utricularis as well as the general implications of the data for electrophysiological work on protoplasts (that are usually obtained by enzymatic digestion of plant tissue) are discussed.

Cells, Cultured↗

PubMed2003

Fabrication of homogeneously cross-linked, functional alginate microcapsules validated by NMR-, CLSM- and AFM-imaging.

Cross-linked alginate microcapsules of sufficient mechanical strength can immunoisolate cells for the long-term treatment of hormone and other deficiency diseases in human beings. However, gelation of alginate by external Ba(2+) (or other divalent cations) produces non-homogeneous cross-linking of the polymeric mannuronic (M) and guluronic (G) acid chains. The stability of such microcapsules is rather limited. Here, we show that homogeneous cross-linking can be achieved by injecting BaCl(2) crystals into alginate droplets before they come into contact with external BaCl(2). The high effectiveness of this crystal gun method is demonstrated by confocal laser scanning microscopy and by advanced nuclear magnetic resonance imaging. Both techniques gave clear-cut evidence that homogeneous cross-linkage throughout the microcapsule is only obtained with simultaneous internal and external gelation. Atomic force microscopy showed a very smooth surface topography for microcapsules made by the crystal gun method, provided that excess Ba(2+) ions were removed immediately after gelation. In vitro experiments showed greatly suppressed swelling for crystal gun microcapsules. Even alginate extracted from Lessonia nigrescens (highly biocompatible) yielded microcapsules with long-term mechanical stability not hitherto possible. Encapsulation of rat islets, human monoclonal antibodies secreting hybridoma cells and murine mesenchymal stem cells transfected with cDNA encoding for bone morphogenetic protein (BMP-4) revealed that injection of BaCl(2) crystals has no adverse side effects on cell viability and function. However, the release of low-molecular weight factors (such as insulin) may be delayed when using alginate concentrations in the usual range.

Alginates↗

PubMed2003

A highly sensitive cell assay for validation of purification regimes of alginates.

Among the hydrogels used for microencapsulation of cells and tissues, alginate has been and will continue to be one of the most important biomaterials. A mandatory requirement for clinical immunoisolated transplantations is the reproducible production of biocompatible alginate. As shown here for alginates extracted from freshly collected algal stipes, the current assays used for validation of the quality of the alginate are not sufficient to screen for impurities arising from spores of gram-positive bacteria (and related contaminants). To assess the quality of alginate, we have developed a cell assay based on the induction of apoptosis in Jurkat cells. This assay allows in combination with the "modified mixed lymphocyte" assay a rapid and sensitive screening for any fibrosis-inducing impurities in alginate samples (even during the purification regime) as demonstrated by transplantation experiments performed in parallel with BB rats (exhibiting an elevated macrophage activity). The results clearly demonstrate that the quality of the input algal material is of key relevance for the production of transplantation-grade alginate.

Alginates↗

PubMed2003

Root surface debridement and endotoxin removal.

OBJECTIVE: This study assessed associations between the number of standardized scaling strokes and the reduction of endotoxin on the root surface. BACKGROUND: Therapy of periodontally involved teeth attempts removal of accretions by scaling and root planing. The amount of mechanical therapy required to free the root surface from etiologic factors remains unknown. METHODS: Twenty-four extracted human caries-free single rooted teeth with at least 5 mm attachment loss were used. A region of interest (ROI) which contained subgingival calculus was defined on the root surface of each tooth. Standardized force instrumentation was applied using a force-measuring curet. Fifty working strokes were applied to every ROI. Forces applied were recorded. The force recordings were converted from Millivolts into Newtons (N). After every unit of 5 strokes, presence of calculus was evaluated and scaling debris was collected. Endotoxin concentration was determined in the debris samples. RESULTS: The endotoxin values for strokes 1-5 were statistically significantly greater than the values from all other stroke intervals. Complete calculus removal occurred after a mean of 9.3 strokes. The endotoxin concentration reached a minimal level with concentrations of 0.03-0.306 EU/ml after calculus removal was complete. CONCLUSION: These findings suggest that completion of calculus removal coincides with endotoxin levels associated with clinically healthy teeth.

Chromogenic Compounds↗

PubMed2002

Intracellular delivery of trehalose into mammalian cells by electropermeabilization.

The disaccharide trehalose is increasingly being used as a very efficient stabilizer of cells, membranes and macromolecules during cryo- and lyoconservation. Although extracellular trehalose can reduce cryo- and lyodamage to mammalian cells, the sugar is required on both sides of the plasma membrane for maximum protection efficiency. In the present study, mouse myeloma cells were loaded with the disaccharide by means of reversible electropermeabilization in isotonic trehalose-substituted medium, which contained 290 mM trehalose as the major solute. By using the membrane-impermeable fluorescent dye propidium iodide as the reporter molecule, optimum electropulsing conditions were found, at which most permeabilized cells survived and recovered (i.e., resealed) their original membrane integrity within a few minutes after electric treatment. Microscopic examination during the resealing phase revealed that electropulsed cells shrank gradually to about 60% of their original volume. The kinetics of the dye uptake and the volumetric response of cells to electropulsing were analyzed using a theoretical model that relates the observed cell volume changes to the solute transport across the transiently permeabilized cell membrane. From the best fit of the model to the experimental data, the intracellular trehalose concentration in electropulsed cells was estimated to be about 100 mM. This loading efficiency compares favorably to other methods currently used for intracellular trehalose delivery. The results presented here point toward application of the electropermeabilization technique for loading cells with membrane-impermeable bioprotectants, with far-reaching implications for cryo- and lyopreservation of rare and valuable mammalian cells and tissues.

Animals↗

PubMed2001

Dielectric spectroscopy of Schizosaccharomyces pombe using electrorotation and electroorientation.

Two complementary AC electrokinetic techniques electrorotation (ER) and electroorientation (EO) enabled the dielectric characterization of the rod-shaped fission yeast Schizosaccharomyces pombe. The use of microstructured electrodes allowed both ER and EO measurements to be performed over wide ranges of field frequency and medium conductivity. Due to their layered structure, living S. pombe cells exhibited up to three well resolved peaks in their ER spectra and also two distinct orientations, i.e., parallel or perpendicular to the imposed linear field. Heat treatment and enzymatic protoplast isolation led to dramatic changes in the electrokinetic behavior of fission yeast. Application of the theoretical models linking the ER and EO spectra yielded the dielectric parameters of the major structural units of S. pombe cells (cell wall, plasma membrane and cytosol). The dielectric characterization of yeasts has an enormous impact in biotechnology and biomedicine, because electric field pulse techniques (electrofusion and electropermeabilization) are widely used for production of transgenic yeast strains of economic importance. The present study also showed that combined ER and EO measurements can be employed as a powerful diagnostic tool for analyzing changes in yeast structure and physiology upon exposure to various stress conditions.

Electric Conductivity↗

PubMed2001

Reversible electropermeabilization of mammalian cells by high-intensity, ultra-short pulses of submicrosecond duration.

Mouse myeloma cells were electropermeabilized by single square-wave electric pulses with amplitudes of up to approximately 150 kV/cm and durations of 10-100 nsec. The effects of the field intensity, pulse duration and medium conductivity on cell viability and field-induced uptake of molecules were analyzed by quantitative flow cytometry using the membrane-impermeable fluorescent dye propidium iodide as indicator molecule. Despite the extremely large field strengths, the majority of cells survived the exposure to ultra-short field pulses. The electrically induced dye uptake increased markedly with decreasing conductivity of the suspending medium. We assigned this phenomenon to the transient electrodeformation (stretching) force that assumes its maximum value if cells are suspended in low-conductivity media, i.e., if the external conductivity sigmae is smaller than that of the cytosol sigmai. The stretching force vanishes when sigmae is equal to or larger than sigmai. Due to their capability of delivering extremely large electric fields, the pulse power systems used here appear to be a promising tool for the electropermeabilization of very small cells and vesicles (including intracellular organelles, liposomes, etc.).

Animals↗

PubMed2001

Trehalose improves survival of electrotransfected mammalian cells.

BACKGROUND: Electropermeabilization is widely used for introduction of DNA and other foreign molecules into eukaryotic cells. However, conditions yielding the greatest molecule uptake and gene expression can result in low cell survival. In this study, we assessed the efficiency of trehalose for enhancing cell viability after excessive electropermeabilization. This disaccharide was chosen because of its capability of stabilizing cell membranes under various stressful conditions, such as dehydration and freezing. MATERIALS AND METHODS: Various mammalian cell lines were electropermeabilized by single exponentially decaying electric pulses of few kV/cm strength and of several-microsecond duration. Propidium iodide (PI) and a plasmid encoding green fluorescent protein (GFP), respectively, served as reporter molecules. The effects of trehalose on PI-uptake, GFP gene expression, transfection yield, and short- and long-term viability were analyzed by flow cytometry and electronic cell counting. RESULTS: The substitution of inositol by trehalose in pulse media protected cells against field-induced cell lysis. The protection effect saturated at about 40-50 mM trehalose. Transfection yield and gene expression were not significantly affected by trehalose. But the transfection efficiency was generally higher in the presence of trehalose, mainly because of the increased cell survival. CONCLUSIONS: We demonstrated that trehalose-substituted media are superior to standard trehalose-free pulse media for improving cell survival and achieving higher electrotransfection efficiency.

Animals↗

PubMed2001

CD19+ B lymphocytes are the major source of human antibody-secreting hybridomas generated by electrofusion.

Human monoclonal antibodies may be generated by electrofusion of human B lymphocytes with a human/mouse heteromyeloma line. In addition to a fusion protocol optimised for the fusion partners, the activation of B lymphocytes is crucial for fusion and hybrid efficiency. In this study, we initially treated peripheral blood mononuclear cells (PBMC) from normal blood donors with a large panel of known stimulants and determined the yield of human antibody-secreting hybridomas after electrofusion with the heteromyeloma cell line H73C11; 3- to 5-day incubation with phytohaemagglutinin L (PHA-L) resulted in the highest number of secreting hybrids. In a second set of experiments, PBMC were depleted from various cell populations, including CD14+ monocytes, CD8+ T lymphocytes, and CD2+ T cells, respectively. Undepleted PBMC stimulated with PHA-L were shown to give rise to the highest number of secreting hybridomas when subjected to electrofusion, whereas depletion of CD2+ T lymphocytes greatly reduced the yield. In a final set of experiments, CD19+ B lymphocytes were identified as the major source of secreting hybridomas. For optimal fusion efficiency, CD19+ B cells were shown to require direct physical contact with other cell populations, most probably T lymphocytes, during the stimulation process. Our data highlight the importance of an adequate stimulation prior to electrofusion and may be helpful to further facilitate the development of human monoclonal antibodies.

Animals↗

PubMed2001

No evidence of somatic FGFR3 mutation in various types of carcinoma.

Germline specific point mutations in the gene encoding fibroblast growth factor receptor 3 (FGFR3) are associated with autosomal dominant human skeletal dysplasia and craniosynostosis syndromes. Mutations identical to the germinal activating mutations found in severe skeletal dysplasias have been identified in certain types of cancer: at low frequency in multiple myeloma and cervix carcinoma and at high frequency in bladder carcinoma. We analysed, by SSCP and sequencing, the prevalence of FGFR3 mutations in 116 primary tumours of various types (upper aerodigestive tract, oesophagus, stomach, lung and skin). The regions analysed encompassed all FGFR3 point mutations previously described in severe skeletal dysplasia and cancers. No mutations were detected in the tumour types examined, suggesting that FGFR3 mutations are restricted to a few tumour types, the evidence to date suggesting that they are very specific to bladder carcinomas.

Bone Diseases, Developmental↗

PubMed2001

Thyroid hormone-deficient period prior to the onset of hearing is associated with reduced levels of beta-tectorin protein in the tectorial membrane: implication for hearing loss.

The genes for alpha- and beta-tectorin encode the major non-collagenous proteins of the tectorial membrane. Recently, a targeted deletion of the mouse alpha-tectorin gene was found to cause loss of cochlear sensitivity (). Here we describe that mRNA levels for beta-tectorin, but not alpha-tectorin, are significantly reduced in the cochlear epithelium under constant hypothyroid conditions and that levels of beta-tectorin protein in the tectorial membrane are lower. A delay in the onset of thyroid hormone supply prior to onset of hearing, recently described to result in permanent hearing defects and loss of active cochlear mechanics (), can also lead to permanently reduced beta-tectorin protein levels in the tectorial membrane. beta-Tectorin protein levels remain low in the tectorial membrane up to one year after the onset of thyroid hormone supply has been delayed until postnatal day 8 or later and are associated with an abnormally structured tectorial membrane and the loss of active cochlear function. These data indicate that a simple delay in thyroid hormone supply during a critical period of development can lead to low beta-tectorin levels in the tectorial membrane and suggest for the first time that beta-tectorin may be required for development of normal hearing.

Animals↗

PubMed2001

Differential expression of the subunits of the glucose-6-phosphatase system in the clear cell type of human renal cell carcinoma - no evidence for an overexpression of protein kinase B.

The expression of two components of the glucose-6-phosphatase system, the catalytic subunit (G6PaseC) and the glucose-6-phosphate transporter, was analyzed in the clear cell type of human renal cell carcinoma. The expression of G6PaseC was decreased in tumours compared with non-tumourous tissue of the same patient. The expression of G6PaseT varied with no general trend between tumours and control tissue. The expression of protein kinase B (PKB) was unchanged in the tumours, suggesting that the down-regulation of G6PaseC in clear cells and the maintenance of the transformed phenotype are not predominantly caused by an overexpression of PKB.

Aged↗

PubMed2001

[Life threatening hypercalcemia in a young man with ALL].

HISTORY AND ADMISSION FINDINGS: A 16-year-old man experienced fatigue, vomiting and diffuse abdominal pain. Since 4 days he had myalgia in both arms and legs. On examination only a tachycardia of 110/min was noticed. INVESTIGATIONS: Laboratory tests revealed hemoglobin 12.7 g/dl, leucocytes 10,300/microliter, platelets 89,000/microliter, LDH 191 U/l, sodium 134 mmol/l, potassium 2.76 mmol/l, calcium 4.52 mmol/l (I), creatinine 1.13 mg/dl, urea 72 mg/dl, uric acid 11.2 mg/dl. The levels of PTH (0 pg/ml), PTH-related peptide, vitamin D, vitamin A, IGF-1, STH, 5-HIES and interleukin 6 were within normal limits. TNF-alpha 25.9 pg/ml (< 8.1). The electrocardiography revealed a sinus rythm with a QT-time of 0.28 s (= 100%). Multiple osteolytic bone leasions were seen in thoracic CT-scan. Abdominal sonography showed normal liver structure, multiple subhepatic lymph nodes without splenomegaly. The cytologic examination of the bone marrow demonstrated a diffuse infiltration by a common acute leukemia. TREATMENT AND COURSE: The rehydration with physiologic saline (3500 ml/d) was initiated in the ICU. Furosemide was added for further renal excretion. Additionally prednisone (100 mg/d) and calcitonin (300 I.E./d) were given. The calcium level fell within two days. No cardiac arrhythmia nor acute renal failure were seen. After definitive diagnosing the patient was treated corresponding to a specific protocol. One year later the relapsing ALL was diagnosed also by hypercalcemia (5.9 mmol/l). The level of TNF-alpha before and after correction of hypercalcemia was 20 pg/ml. CONCLUSION: The acute treatment of hypercalcemia is independent of the underlying cause (rehydration with physiologic saline, renal excretion with furosemide, inhibition of osteoclastic activity). The main causes are hyperparathyreoidism or malignancys (90%). We describe TNF-alpha as a possible marker of tumoral load of a common ALL but we are not able to reveal a correlation between TNF-alpha and the calcium level.

Adolescent↗

PubMed2001

[Leiomyoma of the kidney. Differential diagnostic aspects of renal cell carcinoma with increasing clinical relevance].

Renal leiomyoma is a rare benign tumor which has its origin in smooth muscle cells of different structures of the kidney. The clinical incidence of renal leiomyoma is much lower than the frequency described in large autopsy studies. Renal leiomyomas are mainly located in the renal capsula and pelvis or next to those structures. Clinical symptoms are nonspecific (e.g., flank pain or flank tumor) or completely absent, making most of the leiomyomas an incidental finding during routine diagnostics. A differential diagnosis between renal leiomyoma and renal cell carcinoma on the basis of medical imaging is extremely difficult. Therefore, laparotomy and nephrectomy are performed in most cases of suspected renal cell carcinoma. The definitive diagnosis of a leiomyoma is only possible after histological examination of the tumor. Due to the rising number of diagnoses resulting from improved medical imaging, renal leiomyomas are gaining more importance in the differential diagnosis of renal cell carcinoma, especially with respect to kidney-sparing surgery.

Biomarkers, Tumor↗