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Biomedical subjects

C Wilke

Publications and source records attributed to C Wilke.

At least 19 recordsLinked to original sources
PubMed2006

Spatiotemporal synchronization of coupled oscillators in a laboratory plasma.

The spatiotemporal synchronization between two plasma instabilities of autonomous glow discharge tubes is observed experimentally. For this purpose, two tubes are placed separately and two chaotic waves interact with each other through a coupler. When the coupling strength is changed, the coupled oscillators exhibit synchronization in time and space. This is the first experimental evidence of spatiotemporal synchronization by mutual chaotic wave interaction in plasma.

Journal Article↗
PubMed2005

Stress susceptibility predicts the severity of immune depression and the failure to combat bacterial infections in chronically stressed mice.

Chronic psychological stress has been suggested to play a role in disorders in which the immune system unexpectedly fails to respond in a protective manner. Chronic combined acoustic and restraint stress compromises the anti-bacterial defense mechanisms of female BALB/c mice. The immunodeficiency is characterized by an apoptotic loss of lymphocytes, reduced ex vivo-inducibility of TNF but increased inducibility of IL10, reduced T-cell proliferation, and impaired phagocyte functions. Stressed mice develop depression-like behavior that was monitored by a stress severity score (SSS). Besides a strain (BALB/c>CBA) and gender (male>female) dependent susceptibility to chronic stress, inbred mice have an individual coping ability. Importantly, the individual SSS strongly correlates with Escherichia coli dissemination after infection as well as with IL10-inducibility and circulating corticosterone levels of each animal.

Acoustic Stimulation↗
PubMed2005

Kinetic resonances and stratification of the positive column of a discharge.

Resonance formation of the electron velocity distribution function (EDF) in an inert gas dc discharge at low pressures and small currents is analyzed on the basis of an accurate numerical solution of the Boltzmann kinetic equation in spatially periodic sinusoidally modulated striation-like fields. Calculations are performed for neon at pressures around 1 Torr . The dependences of the EDF, electron density and mean energy, and excitation rate on the electric field spatial period length are investigated. In addition to resonances corresponding to S and P striations predicted by linear analytical theory, the kinetic model indicates the presence of a resonance that can be attributed to an R striation. This resonance is more pronounced at lower pressures when R striations are observed experimentally. The influence of inelastic collisions on the EDF formation in the resonance fields is analyzed.

Journal Article↗
PubMed2004

Registration of biplane angiography and intravascular ultrasound for 3D vessel reconstruction.

UNLABELLED: If planned and applied correctly, intra-vascular brachytherapy (IVB) can significantly reduce the risk of restenosis after interventional treatment of stenotic arteries. OBJECTIVES: In order to facilitate computer-based IVB planning, a three-dimensional reconstruction of the stenotic artery based on intravascular ultrasound (IVUS) sequences is desirable. METHODS: To attain a 3D reconstruction, the frames of the IVUS sequence are properly aligned in space and completed with additional intermediate frames generated by interpolation. The alignment procedure uses additional information that is obtained from biplane X-ray angiography performed simultaneously during the capturing of the IVUS sequence. After IVUS images and biplane angiography data are acquired from the patient, the vessel-wall borders and the IVUS catheter are detected by an active contour algorithm. Next, the twist between adjacent IVUS frames is determined by a sequential triangulation method combined with stochastic analysis. RESULTS: The above procedure results in a 3D volume-model of the vessel, which also contains information from the IVUS modality. This data is sufficient for computer-based intravascular brachytherapy planning. CONCLUSION: The proposed methodology can be used to improve the current state-of-the-art IVB treatment planning by enabling computerized dosage computations on a highly accurate 3D model.

Algorithms↗
PubMed2003

Resonance effects in the electron distribution function formation in spatially periodic fields in inert gases.

The calculations of the electron distribution function (EDF) in striationlike, sinusoidally modulated electric fields were performed to determine the dependence on spatial period length. The calculations were done for a discharge in neon at pR=2 Torr cm, i/R=5 mA/cm, and electric field E/p=1.9 V cm(-1) Torr(-1). The presence of the resonances in the EDF and macroscopic parameters has been demonstrated. These resonances correspond to S and P striations observed in experiments. An interpretation of the results is proposed based on an analytical approximation of the numerical solution. Decomposition of EDF into two factors-amplitude and body-is carried out. The amplitude of the EDF is shown to be resonantly dependent on the value of the spatial period. One maximum in the EDF is formed at the value of the spatial period corresponding to the S striation, and two maxima at the value which corresponds to the P striation. The experimental measurements of the EDF in S and P striations with high spatial resolution showed agreement between the theoretical and the experimental results. Resonance effects in the EDF formation are considered based on the linear theory in the weakly modulated electric fields.

Journal Article↗
PubMed2003

Two-dimensional nonlocal model of axially and radially inhomogeneous plasma of cylindrical magnetron discharge.

A cylindrical magnetron discharge (CMD) with two coaxial electrodes, a uniform axially directed magnetic field, and discharge ends closed by the shields biased at the cathode potential is considered. The presence of the shields creates axial inhomogeneity of plasma, which is taken into account in this study. At low pressures and small magnetic fields the pronounced nonlocal regime of the electron distribution function (EDF) formation is realized. The electron component is analyzed on the basis of radially and axially inhomogeneous Boltzmann kinetic equation. Unmagnetized electrons that move in axial direction are trapped in the axial potential well, their energy relaxation length exceeds the discharge vessel length, and the kinetic equation can be averaged over axial flights of electrons. Using a model two-dimensional potential profile, the EDFs at the different axial positions are obtained and two-dimensional distributions of the electron density, ionization rate, and current on cathode are calculated. The results of the modeling and experiments are compared for the dc CMD in Ar at a pressure of 3 Pa, magnetic field strength of 10 mT, and current of 150 mA.

Journal Article↗
PubMed2002

Nonlocal electron kinetics and excited state densities in a magnetron discharge in argon.

The densities of argon metastable (3)P(2), and resonance (1)P(1), (3)P(1) states were measured along a cylindrical magnetron discharge radius by absorption spectroscopy using a narrow bandwidth single mode diode laser. The theoretical treatment includes calculations of the rates of numerous excitation and decay processes based on nonlocal electron kinetics, and analysis of the transport equations for the resonance and metastable atoms. The solution technique of the Biberman-Holstein equation of radiation transport is developed in conformity with magnetron discharge geometry. The radial profile of the effective lifetime is obtained, taking into account radiation escape on the inner and outer electrodes. The distinction in formations of the radial profiles of the resonance and metastable atoms caused by specifics of radiation transport and diffusion is demonstrated. The results of experiments and calculations are compared.

Journal Article↗
PubMed2001

Experimental evidence for a torus breakdown in a glow discharge plasma.

A global bifurcation scenario for a two-frequency torus breakdown depicted by Baptista and Caldas [Physica D 132, 325 (1999)] is observed on a glow-discharge experiment. The torus is broken through a crisis with an unstable periodic orbit. The torus section before the bifurcation is a sided polygon that has a number of edges equal to the period of the unstable orbit. Since the discharge is an extended system the two-frequency torus breakdown is shown to be a possible way to space-time chaos.

Journal Article↗
PubMed2001

The effect of tibial lengthening using the Ilizarov method on the cartilage and the menisci of the knee joint.

In order to investigate possible acute damage to the knee joint cartilage and the menisci during tibial lengthening, sixteen young beagle dogs underwent 30% lengthening of the right tibia of 2.5 cm by callus distraction at a distraction rate of twice 0.5 mm per day. A further four dogs comprised the control group with fixator and osteotomy but without lengthening. After a distraction period of 25 days half the dogs were killed (group A) while the other half (eight dogs with limb lengthening and two dogs without) were killed after a further period of 25 days (group B). At the end of the study, the menisci were removed together with three cartilage-bone cylinders from both femoral condyles from the weight-bearing zones as well as from the corresponding tibial condyles. Serial sections from the menisci were stained with haematoxylin and eosin (H&E) and Elastica van Gieson. Sections of the cartilage-bone cylinders were stained with H&E and safranin-O. Cartilage thickness was measured and the glycosaminoglycan content of the joint cartilage was determined using microspectrophotometry. None of the histological preparations obtained from the untreated and distracted sides showed any signs of damage to the cartilage or to the menisci. There were no significant differences between cartilage thickness and proteoglycan content of the untreated side and the lengthened side. Thus, tibial lengthening using the llizarov method does not appear to cause acute damage to the cartilage of the knee joint or to the menisci.

Animals↗
PubMed2000

Internally driven spatiotemporal irregularity in a dc glow discharge

Spatiotemporal dynamics of an undriven dc glow discharge at intermediate pressures (p(0)r(0)=6.2 Torr cm, i<50 mA) is investigated experimentally. Spatiotemporal irregularity and windows of regular nonlinear waves occur and are found to depend on the discharge current. Above a threshold current column head oscillations arise and inject high-frequency ionization waves into the positive column that decay towards the anode through nonlinear wave coupling with a discrete eigenmode of the positive column. Regularity was found to be a result of commensuration of both waves and obeys a devil's staircase. Since column head oscillations occur in the transition region from cathode fall to positive column as result of discharge formation, the irregularities were internally driven. Spatiotemporal analysis by means of biorthogonal decomposition gives insights into the mechanism of irregularity and can be employed for characterization of spatiotemporal complexity.

Journal Article↗
PubMed1999

Distinct CXC chemokines mediate tumorigenicity of prostate cancer cells.

Prostate cancer is the second leading cause of malignancy-related mortality in males in the United States. As a solid tumor, clinically significant tumor growth and metastasis are dependent on nutrients and oxygen supplied by tumor-associated neovasculature. As such, there is a selective tumorigenic advantage for those neoplasms that can produce angiogenic mediators. We show here that human prostate cancer cell lines can constitutively produce angiogenic CXC chemokines. Tumorigenesis of PC-3 prostate cancer cells was shown to be attributable, in part, to the production of the angiogenic CXC chemokine, interleukin (IL)-8. Neutralizing antisera to IL-8 inhibits PC-3 tumor growth in a human prostate cancer/SCID mouse model. Furthermore, angiogenic activity in PC-3 tumor homogenates was attributable to IL-8. In contrast, the Du145 prostate cancer cell line uses a different angiogenic CXC chemokine, GRO-alpha, to mediate tumorigenicity. Neutralizing antisera to GRO-alpha but not IL-8 reduced tumor growth in vivo and reduced the angiogenic activity in tumor homogenates. Thus, prostate cancer cell lines can use distinct CXC chemokines to mediate their tumorigenicity.

Animals↗
PubMed1996

Frequent breakpoints in the 3p14.2 fragile site, FRA3B, in pancreatic tumors.

FRA3B, at chromosomal band 3p14.2, is the most active common fragile site in the human genome. Homozygous deletions in the region of FRA3B have been observed in many types of solid tumors. Recently, the FHIT gene was reported to span FRA3B and was shown to be homozygously deleted in several gastric and colonic tumor cell lines. Several microsatellite markers that precisely define the 1.0-Mb region surrounding FRA3B and FHIT have been utilized, along with other 3p microsatellites, to analyze the loss of 3p sequences in 25 primary pancreatic adenocarcinomas. The high density of microsatellite markers in the 3pl4.2 region enabled us to both identify losses within and flanking FRA3B in pancreatic cancer and define the breakpoints. We observed loss of het erozygosity of 3pl4.2 markers in 16 of 25 pancreatic tumors and loss of heterozygosity of 3p markers outside of 3pl4.2 in only 2 of 25 tumors of this type. There appears to be a dramatic clustering of chromosomal breakpoints at 3pl4.2 in and immediately distal to FRA3B in pancreatic cancer. We detected no homozygous deletions in this region.

Adenocarcinoma↗
PubMed1995

Precise localization of aphidicolin-induced breakpoints on the short arm of human chromosome 3.

The common fragile site at 3p14.2 (FRA3B) has been described as the most active fragile site in the human genome. This locus may predispose chromosome 3 to specific losses due to deletions and translocations that have been associated with several malignancies, including hereditary renal cell carcinoma. We have previously described induction of breakage around FRA3B using aphidicolin in a somatic cell hybrid whose only human component was a single intact chromosome 3. That work led to the isolation of hybrids with breakpoints in the 3p13-p21.1 region with loss of all sequences distal to their respective breakpoints. In this report we describe the further characterization of the breakpoints in many of these cell lines using newly available molecular markers. We also report the identification of YAC clones that span the breakpoints present in many of these hybrids.

Aphidicolin↗
PubMed1995

A "balanced" Y;16 translocation associated with Turner-like neonatal lymphedema suggests the location of a potential anti-Turner gene on the Y chromosome.

A male patient with Turner-like hydrops in the newborn period (Bonnevie-Ullrich syndrome) was studied. The karyotype was 46,X,t(Y;16)(q11.2;q24) in 100 cells. Chromosome painting with the heterochromatic Y chromosome-specific long arm repeat DYZ2 disclosed that all the hybridization was on the derivative 16. This was confirmed by chromosome painting with DYZ1, the other major Y long arm heterochromatic repeat, and DYZ3, the Y alphoid, centromeric repeat which showed chromosomal separation of the 2 stained regions. To further localize the breakpoint, FISH was performed using individual YACs from a Y-YAC contig (Foote et al., 1992). This disclosed two YACs (yOX111 and yOX123) which hybridized to both the Y and der16 chromosomes. The YACS spanning the translocation breakpoint region were located just proximal to the Y heterochromatin boundary. The recent discovery of a candidate gene for the azoospermia factor (AZF) in this region (Ma et al., 1993) suggests the possibility that there are several Y-expressed genes adjacent to the heterochromatin boundary (as there are near the pseudoautosomal boundary) which may include a gene involved with lymphedema which is disrupted by the translocation in this patient.

Chromosome Mapping↗
PubMed1994

Production of monocyte chemoattractant protein-1 and macrophage inflammatory protein-1 alpha by inflammatory granuloma fibroblasts.

The formation of hepatic granulomas around persistently deposited Schistosoma mansoni eggs leads to parenchymal damage, ongoing fibrosis, and ultimate loss of liver function. In this study, the production of macrophage inflammatory protein-1 alpha (MIP-1) and monocyte chemoattractant protein-1 (MCP-1) by granuloma fibroblasts was examined to establish the potential contribution of intragranuloma fibroblasts to the maintenance of the chronic inflammation. Isolated fibroblasts from dispersed acute infection hepatic granulomas were grown in tissue culture for 3 to 4 weeks and used on the third or fourth passage. We initially surveyed fibroblasts for production of MIP-1 and MCP-1 by reverse transcription-polymerase chain reaction (RT-PCR) after stimulation with interleukin (IL)-1, tumor necrosis factor, interferon (IFN)-gamma, IL-4, or IL-10: cytokines found within the granuloma. These studies demonstrated constitutive expression of MCP-1 and differential up-regulation of MIP-1 on cytokine stimulation. Protein expression was then verified by immunohistochemical localization of MIP-1 and MCP-1 in paraformaldehyde-fixed fibroblasts and by direct quantitation of MIP-1 and MCP-1 in culture supernatants by specific ELISAs. These studies demonstrated constitutive expression of MCP-1 in unstimulated and cytokine-stimulated granuloma fibroblasts. In contrast, IL-1 (0.1 to 2.5 ng/ml), IFN-gamma (10 micrograms/ml), and IL-10 (2.5 to 10 ng/ml) were able to induce the significant production of MIP-1 by the granuloma fibroblasts. Interestingly, normal noninflammatory fibroblasts from uninfected mice showed no significant production of MIP-1 or MCP-1 in response to these cytokines. These results suggest that granuloma fibroblasts may be phenotypically altered compared with normal fibroblasts and have a significant role in leukocyte recruitment, granuloma growth, and maintenance of the egg-induced lesion.

Animals↗
PubMed1988

[Stewart-Treves syndrome of the edematous arm following breast cancer operation].

In 1948, Stewart and Treves (158) described a lymphangiosarcoma on the edematous arm for the first time with reference to six cases involving arm edema after breast cancer operation. Since their publication, a further 313 cases have become known. In 1982, with communication of one case we published a statistical compilation comprising of 248 cases (Zeitschrift für Lymphologie VI, 1982, 51-66). A statistical compilation totalling 290 observations is now presented on the basis of further studies of the older literature supplemented by observations of the last six years including two of our own cases. So far, a total of 319 single observations has become known: 21 cases of Yap et al. (182), eight cases of Oshmianskaia et al. (123) and 290 cases in the statistical compilation we have drawn up and which is the basis of this publication. By histological investigation of the tissue material taken from a female patient within six weeks (exploratory excision, radical excision), detailed information could be obtained on the histological development of the Stewart-Treves-Syndrome (STS) from a preneoplasia to a mature lymphangiosarcoma. The second female patient is a relatively rare observation of an STS of fulminant course which remained restricted to the extremity, chest wall and neighboring parts of the back during the entire course.

Aged↗