Biomedical subjects

R Schulte

Publications and source records attributed to R Schulte.

At least 19 recordsLinked to original sources

PubMed2006

First attempts at prediction of DNA strand-break yields using nanodosimetric data.

We present the first results of our attempts to correlate yields of ionisation clusters in a gas model of DNA and corresponding double-strand break (DSB) yields in irradiated plasmids, using a simple statistical model of DNA lesion formation. Based on the same statistical model, we also provide a comparison of simulated nanodosimetric data for electrons and published DSB yields obtained with the PARTRAC code.

Algorithms↗

PubMed2005

[Treatment results following breast-conserving therapy in primary breast cancer].

OBJECTIVE: To evaluate mono-institutional results concerning tumor free survival, overall survival, local tumor control and rate of distant metastasis following breast-conserving therapy. PATIENTS AND METHODS: Retrospectively, 274 breast cancer patients who were treated between 1990-1997 in our institution were analysed. The whole breast was homogeneously irradiated (2.0 Gy to 50 Gy), followed by a boost of 10-16 Gy to the tumor bed. Mean follow-up was 55 months. Overall survival, local tumor control and rate of distant metastasis were analysed. RESULTS: Cause-specific survival at 5 years after treatment was 93 %. Within 3 to 60 months following treatment, 18 (7 %) patients suffered from ipsilateral breast recurrence. 24 (9 %) patients developed contralateral carcinoma. Survival from local recurrence (single manifestation) was 78 % at 5 years after treatment, 20 % at 7 years. Occurrence of local failures was significantly correlated to receptor status, contralateral carcinoma, distant metastasis and surgical technique and not to tumor size, margins, grading, nodal status, age or lymphangiosis. 9 % of the patients developed distant metastases, predominantly bone metastases (71 %). Survival from distant metastasis was 64 % at 5 years, 10 % at 7 years. Occurrence of distant metastasis was significantly correlated to grading, tumor size, receptor status, lymphangiosis or local recurrence. CONCLUSION: Our institutional results show that tumor free survival, overall survival, local tumor control and distant failure rate achieved by breast conserving therapy are within the range of literature data.

Adult↗

PubMed2004

Two-dimensional and quasi-three-dimensional dosimetry of hadron and photon beams with the Magic Cube and the Pixel Ionization Chamber.

Two detectors for fast two-dimensional (2D) and quasi-three-dimensional (quasi-3D) verification of the dose delivered by radiotherapy beams have been developed at University and Istituto Nazionale di Fisica Nucleare (INFN) of Torino. The Magic Cube is a stack of strip-segmented ionization chambers interleaved with water-equivalent slabs. The parallel plate ionization chambers have a sensitive area of 24 x 24 cm2, and consist of 0.375 cm wide and 24 cm long strips. There are a total of 64 strips per chamber. The Magic Cube has been tested with the clinical proton beam at Loma Linda University Medical Centre (LLUMC), and was shown to be capable of fast and precise quasi-3D dose verification. The Pixel Ionization Chamber (PXC) is a detector with pixel anode segmentation. It is a 32 x 32 matrix of 1024 cylindrical ionization cells arranged in a square 24 x 24 cm2 area. Each cell has 0.4 cm diameter and 0.55 cm height, at a pitch of 0.75 cm separates the centre of adjacent cells. The sensitive volume of each single ionization cell is 0.07 cm3. The detectors are read out using custom designed front-end microelectronics and a personal computer-based data acquisition system. The PXC has been used to verify dynamic intensity-modulated radiotherapy for head-and-neck and breast cancers.

Calibration↗

PubMed2003

Ion-counting nanodosimetry: current status and future applications.

There is a growing interest in the study of interactions of ionizing radiation with condensed matter at the nanometer level. The motivation for this research is the hypothesis that the number of ionizations occurring within short segments of DNA-size subvolumes is a major factor determining the biological effectiveness of ionizing radiation. A novel dosimetry technique, called nanodosimetry, measures the spatial distribution of individual ionizations in an irradiated low-pressure gas model of DNA. The measurement of nanodosimetric event size spectra may enable improved characterization of radiation quality, with applications in proton and charged-particle therapy, radiation protection, and space research. We describe an ion-counting nanodosimeter developed for measuring radiation-induced ionization clusters in small, wall-less low-pressure gas volumes, simulating short DNA segments. It measures individual radiation-induced ions, deposited in 1 Torr propane within a tissue-equivalent cylindrical volume of 2-4 nm diameter and up to 100 nm length. We present first ionization cluster size distributions obtained with 13.6 MeV protons, 4.25 MeV alpha particles and 24.8 MeV carbon nuclei in propane; they correspond to a wide LET range of 4-500 keV/microm. We are currently developing plasmid-based assays to characterize the local clustering of DNA damage with biological methods. First results demonstrate that there is increasing complexity of DNA damage with increasing LET. Systematic comparison of biological and nanodosimetric data will help us to validate biophysical models predicting radiation quality based on nanodosimetric spectra. Possible applications for charged particle radiation therapy planning are discussed.

DNA↗

PubMed2003

Molecular systematics and phylogeography of Amazonian poison frogs of the genus Dendrobates.

The study of Amazonian biodiversity requires detailed knowledge of the phylogenetic relationships of closely related taxa distributed across Amazonia. The Amazonian poison frogs of the genus Dendrobates have undergone many taxonomic revisions, but the phylogenetic relationships within this group remain poorly understood. Most previous classifications were based on morphology and skin toxin analyses, with limited use of DNA sequence data. Using mtDNA sequence data from four gene regions (cytochrome b, cytochrome oxidase I, 16S rRNA, and 12S rRNA), we present a molecular phylogenetic analysis of the evolutionary relationships within a representative group of Amazonian Dendrobates. We use the resulting phylogenetic hypothesis to investigate different biogeographic hypotheses concerning genetic divergence and species diversity in Amazonia. The results of the analysis support the presence of ancient paleogeographic barriers to gene flow between eastern and western Amazonia, and indicate substantial genetic divergence between species found in the northern and southern regions of western Amazonia.

Animals↗

PubMed2002

Wall-less ion-counting nanodosimetry applied to protons.

A wall-less ion-counting nanodosemeter, conceived for precise ionisation-cluster measurements in an accelerator environment, is described. The technique provides an accurate means for counting single radiation-induced ions, in dilute gas models of condensed matter. The sensitive volume dimensions, a few tissue-equivalent nm in diameter by a few tens of nm, are tunable by a proper choice of the gas pressure and electric fields; nanometric sub-sections can be electronically selected. Detailed ion-cluster distributions are presented for protons of 7.15, 13.6 and 19.3 MeV, in biologically relevant DNA-like sensitive volumes of low-pressure propane. Experimental results are compared to model simulations.

Computer Simulation↗

PubMed2001

Molecular phylogenetic evidence for a mimetic radiation in Peruvian poison frogs supports a Müllerian mimicry hypothesis.

Examples of Müllerian mimicry, in which resemblance between unpalatable species confers mutual benefit, are rare in vertebrates. Strong comparative evidence for mimicry is found when the colour and pattern of a single species closely resemble several different model species simultaneously in different geographical regions. Todemonstrate this, it is necessary to provide compelling evidence that the putative mimics do, in fact, form a monophyletic group. We present molecular phylogenetic evidence that the poison frog Dendrobates imitator mimics three different poison frogs in different geographical regions in Peru. DNA sequences from four different mitochondrial gene regions in putative members of a single species are analysed using parsimony, maximum-likelihood and neighbour-joining methods. The resulting hypotheses of phylogenetic relationships demonstrate that the different populations of D.imitator form a monophyletic group. To our knowledge, these results provide the first evidence for a Müllerian mimetic radiation in amphibians in which a single species mimics different sympatric species in different geographical regions.

Animals↗

PubMed2001

Modeling of radiation action based on nanodosimetric event spectra.

Assuming that the number of ionizations events within short segments of DNA-size volumes is a major factor of the biological effectiveness of ionizing radiation, we have designed and manufactured a new nanodosimetric detector counting ionization events in small wall-less gas volumes, which simulate such DNA segments. The detector measures individual ionizations in low-pressure (~1 Torr) propane or any other gas corresponding to a tissue-equivalent cylindrical volume of 2-4 nm diameter and up to 30 nm length. While first nanodosimetric event spectra with protons and alpha particles are being obtained, it is important to develop and test a theory that relates these spectra to biological endpoints such as strand breakage, mutations, and lethal cellular events. This paper describes the two-compartment theory, which is based on the premise that energy deposition in nanometer sites can be broadly divided into two categories: a low-energy deposition compartment comprising events with a total number of 2-5 ionizations, and a high-energy deposition compartment comprising events containing 6-10 ionizations. Under standard biochemical conditions, these events will lead to different biological consequences. The fate of DNA lesions produced by low-energy deposition events will mostly depend on the repair capacity of the irradiated cells, whereas events produced by high-energy deposition events will be irreparable. These events are therefore the biologically most relevant lesions, since they inevitably lead to mutation and cell death.

Animals↗

PubMed2000

Translocation of Yersinia entrocolitica across reconstituted intestinal epithelial monolayers is triggered by Yersinia invasin binding to beta1 integrins apically expressed on M-like cells.

Yersinia enterocolitica cross the intestinal epithelium via translocation through M cells, which are located in the follicle-associated epithelium (FAE) of Peyer's patches (PP). To investigate the molecular basis of this process, studies were performed using a recently developed in vitro model, in which the enterocyte-like cell line Caco-2 and PP lymphocytes are co-cultured in order to establish FAE-like structures including M cells. Here, we demonstrate that Y. enterocolitica does not adhere significantly to the apical membrane of differentiated enterocyte-like Caco-2 cells that express binding sites for Ulex europaeus agglutinin (UEA)-1. In contrast, Y. enterocolitica adhered to, and was internalized by, cells that lacked UEA-1 binding sites and displayed a disorganized brush border. These cells were considered to be converted to M-like cells. Further analysis revealed that part of these cells expressed beta1 integrins at their apical surface and, as revealed by comparison of wild-type and mutant strains, interacted with invasin of Y. enterocolitica. Consistently, anti-beta1 integrin antibodies significantly inhibited internalization of inv-expressing yersiniae. Experiments with Yersinia mutant strains deficient in YadA or Yop secretion revealed that these virulence factors play a minor role in this process. After internalization, yersiniae were transported within LAMP-1-negative vacuoles to, and released at, the basal surface. Internalization and transport of yersiniae was inhibited by cytochalasin D, suggesting that F-actin assembly is required for this process. These results provide direct evidence that expression of beta1 integrins at the apical surface of M cells enables interaction with the invasin of Y. enterocolitica, and thereby initiates internalization and translocation of bacteria.

Adhesins, Bacterial↗

PubMed2000

Yersinia enterocolitica invasin protein triggers IL-8 production in epithelial cells via activation of Rel p65-p65 homodimers.

Enteropathogenic Yersinia bacteria trigger the production of the proinflammatory chemokine IL-8, an important chemokine for the recruitment of polymorphonuclear leukocytes (PMN). Yersinia is resistant to phagocytosis by PMN, and the recruitment of these cells is thought to be part of a pathogenic strategy of Yersinia to establish infection by allowing the pathogen to gain access to, and disseminate within, host tissue. We report here that Yersinia expressing the outer membrane protein invasin triggers IL-8 production in epithelial cells. The 195 carboxyl-terminal amino acids of invasin when linked to latex beads are sufficient to trigger IL-8 production. By means of IL-8 promoter reporter gene assays and electrophoretic mobility shift assay experiments, the minimal optimal region of the IL-8 promoter responsive to invasin was identified and invasin-responsive control elements were characterized. Invasin-induced activation of the IL-8 promoter was found to be mediated through a previously identified NF-kappaB element. This NF-kappaB binding site preferentially binds Rel p65-p65 homodimers as well as some p50-p65 heterodimers in response to stimulation by invasin. Invasin-induced NF-kappaB activation correlated with degradation of IkappaBalpha and the inhibition of NF-kappaB by specific inhibitors of IkappaB activation blocked invasin-induced IL-8 secretion. Invasin-triggered IL-8 production does not depend on invasin-triggered uptake of bacteria, and is independent of a functional PI3-kinase. This report is the first to demonstrate the molecular basis of IL-8 production triggered by enteropathogenic bacteria. Together, these data elucidate the possible early pathomechanisms operating in Yersinia infection and may have implications for the design of novel therapeutics directed against this enteropathogen.

Adhesins, Bacterial↗

PubMed2000

Confining proton beams with longitudinal magnetic fields: Monte Carlo calculations.

The problem of the lateral containment of a 160 MeV proton beam interacting with a medium simulating biological material was studied. The confining action of a longitudinal magnetic field was calculated by means of Monte Carlo simulation, where scattering and motion in the magnetic field were treated simultaneously. Appreciable compression of the beam could only be achieved using fields of the order at least 50 T, much beyond the realm of practical feasibility.

Humans↗

PubMed2000

Yersinia enterocolitica invasin protein triggers differential production of interleukin-1, interleukin-8, monocyte chemoattractant protein 1, granulocyte-macrophage colony-stimulating factor, and tumor necrosis factor alpha in epithelial cells: implications for understanding the early cytokine network in Yersinia infections.

Yersinia enterocolitica infection of epithelial cells results in interleukin-8 (IL-8) mRNA expression. Herein we demonstrate that besides IL-8, increased mRNA levels of five other cytokines, IL-1alpha, IL-1beta, monocyte chemoattractant protein 1 (MCP-1), granulocyte-macrophage colony-stimulating factor (GM-CSF), and tumor necrosis factor alpha (TNF-alpha), can be detected upon infection of HeLa cells with Yersinia. Yersinia-triggered cytokine production was not affected by blocking phosphatidylinositol-3-phosphate kinase with wortmannin, which inhibited bacterial invasion. Comparable cytokine mRNA responses were triggered by Escherichia coli expressing Yersinia inv, while no response was triggered by an inv-deficient Yersinia mutant. Moreover, cytokine responses were independent from metabolic activity of the bacteria, as killed bacterial cells were sufficient for triggering cytokine responses in HeLa cells. Semiquantitative reverse transcription-PCR analysis was used to assess the kinetics of cytokine mRNA expression in infected HeLa cells. IL-8, IL-1alpha, IL-1beta, MCP-1, GM-CSF, and TNF-alpha mRNA expression increased within 1 h postinfection, reached a maximum after 3 to 4 h, and then declined to preinfection levels within 3 h. IL-8, MCP-1, and GM-CSF were secreted by HeLa cells, whereas IL-1alpha and IL-1beta were not secreted and thus were found exclusively intracellularly. TNF-alpha protein could not be detected in cell lysates or supernatants. Stimulation of HeLa cells with IL-1alpha was followed by increased IL-8 mRNA expression, whereas stimulation with IL-8 did not induce cytokine production. Likewise, MCP-1 and GM-CSF did not induce significant cytokine responses in HeLa cells. Our results implicate that the initial host response to Yersinia infection might be sustained by IL-8, MCP-1, and GM-CSF produced by epithelial cells.

Adhesins, Bacterial↗

PubMed2000

[Multifunctional testing of PTCA balloon catheters].

New in vitro measuring methods for balloon catheters used for percutaneous transluminal coronary angioplasty (PTCA) and their verification in a complex test device are presented. This system can mimic all relevant application situations. The central element of the test device is a coronary vessel model matching the physiological situation in terms of geometrical structure and frictional properties. Reactive force sensors are used to measure the application-relevant forces exerted by the catheter on the model vessel walls and accessories, such as guide wire and guiding catheter. To generate a kink-free advancement of the catheter and permit measurement of the active forces, an alternating drive unit has been specially developed. The testing and application of the newly developed methods revealed statistically significant differences between various types of catheter. The test device closes a gap between complex but subjective clinical tests, and individual objective, but application-removed in vitro test setups for PTCA catheters. While the initial prototype had shortcomings with regard to the reproducibility of measurements, successor systems developed for industrial use are now in production. The properties of these measuring systems developed for the benefit of manufacturer and reprocessor of PTCA catheters are discussed.

Angioplasty, Balloon, Coronary↗

PubMed1998

Wortmannin blocks Yersinia invasin-triggered internalization, but not interleukin-8 production by epithelial cells.

In response to bacterial infection epithelial cells up-regulate expression and secretion of proinflammatory cytokines. Previous work from our laboratory showed that basolateral infection of polarized T84 cells with Yersinia enterocolitica induces interleukin-8 (IL-8) secretion in the absence of significant invasion. Here we studied Y. enterocolitica-induced IL-8 secretion by epithelial HeLa cells as a function of Yersinia invasion or adhesion. For this purpose we tried to separated induction of IL-8 secretion from invasion by treating HeLa cells with signal transduction inhibitors prior to infection. While staurosporin and genistein inhibited both Yersinia invasion and Yersinia-triggered IL-8 secretion, wortmannin, an inhibitor of the phosphatidylinositol-3-phosphate kinase (PI3-K), blocked invasion of Y. enterocolitica into HeLa cells but did not show any effect on IL-8 secretion. These results suggest that Yersinia adhesion might be sufficient to induce IL-8 secretion by epithelial cells. Further analysis demonstrated the requirement of the Yersinia invasion locus inv for adhesion-mediated induction of IL-8 secretion. Thus, HeLa cells infected with an E. coli strain expressing the Y. enterocolitica inv locus induced IL-8 secretion in the presence and absence of wortmannin. Reverse transcription-polymerase chain reaction analysis revealed that adhesion of inv-expressing Y. enterocolitica or E. coli results in the transcriptional activation of the IL-8 gene. These results suggest that Y. enterocolitica adhesion to host cells via Inv activates de novo synthesis and secretion of IL-8.

Adhesins, Bacterial↗

PubMed1998

Yersinia enterocolitica-induced interleukin-8 secretion by human intestinal epithelial cells depends on cell differentiation.

In response to bacterial entry epithelial cells up-regulate expression and secretion of various proinflammatory cytokines, including interleukin-8 (IL-8). We studied Yersinia enterocolitica O:8-induced IL-8 secretion by intestinal epithelial cells as a function of cell differentiation. For this purpose, human T84 intestinal epithelial cells were grown on permeable supports, which led to the formation of tight monolayers of polarized intestinal epithelial cells. To analyze IL-8 secretion as a function of cell differentiation, T84 monolayers were infected from the apical or basolateral side at different stages of differentiation. Both virulent (plasmid-carrying) and nonvirulent (plasmid-cured) Y. enterocolitica strains invaded nondifferentiated T84 cells from the apical side. Yersinia invasion into T84 cells was followed by secretion of IL-8. After polarized differentiation of T84 cells Y. enterocolitica was no longer able to invade from the apical side or to induce IL-8 secretion by T84 cells. However, Y. enterocolitica invaded and induced IL-8 secretion by polarized T84 cells after infection from the basolateral side. Basolateral invasion required the presence of the Yersinia invasion locus, inv, suggesting beta1 integrin-mediated cell invasion. After basolateral infection, Yersinia-induced IL-8 secretion was not strictly dependent on cell invasion. Thus, although the plasmid-carrying Y. enterocolitica strain did not significantly invade T84 cells, it induced significant IL-8 secretion. Taken together, these data show that Yersinia-triggered IL-8 secretion by intestinal epithelial cells depends on cell differentiation and might be induced by invasion as well as by basolateral adhesion, suggesting that invasion is not essential for triggering IL-8 production. Whether IL-8 secretion is involved in the pathogenesis of Yersinia-induced abscess formation in Peyer's patch tissue remains to be shown.

Cell Differentiation↗

PubMed1998

Ambiguous role of interleukin-12 in Yersinia enterocolitica infection in susceptible and resistant mouse strains.

Endogenous interleukin-12 (IL-12) mediates protection against Yersinia enterocolitica in C57BL/6 mice by triggering gamma interferon (IFN-gamma) production in NK and CD4+ T cells. Administration of exogenous IL-12 confers protection against yersiniae in Yersinia-susceptible BALB/c mice but exacerbates yersiniosis in resistant C57BL/6 mice. Therefore, we wanted to dissect the different mechanisms exerted by IL-12 during Yersinia infections by using different models of Yersinia-resistant and -susceptible mice, including resistant C57BL/6 mice, susceptible BALB/c mice, intermediate-susceptible wild-type 129/Sv mice, 129/Sv IFN-gamma-receptor-deficient (IFN-gamma R-/-) mice and C57BL/6 tumor necrosis factor (TNF) receptor p55 chain-deficient (TNFR p55-/-) mice. IFN-gamma R-/- mice turned out to be highly susceptible to infection by Y. enterocolitica compared with IFN-gamma R+/+ mice. Administration of IL-12 was protective in IFN-gamma R+/+ mice but not in IFN-gamma R-/- mice, suggesting that IFN-gamma R-induced mechanisms are essential for IL-12-induced resistance against yersiniae. BALB/c mice could be rendered Yersinia resistant by administration of anti-CD4 antibodies or by administration of IL-12. In contrast, C57BL/6 mice could be rendered more resistant by administration of transforming growth factor beta (TGF-beta). Furthermore, IL-12-triggered toxic effects in C57BL/6 mice were abrogated by coadministration of TGF-beta. While administration of IL-12 alone increased TNF-alpha levels, administration of TGF-beta or TGF-beta plus IL-12 decreased both TNF-alpha and IFN-gamma levels in Yersinia-infected C57BL/6 mice. Moreover, IL-12 did not induce toxicity in Yersinia-infected TNFR p55-/- mice, suggesting that TNF-alpha accounts for IL-12-induced toxicity. Taken together, IL-12 may induce different effector mechanisms in BALB/c and C57BL/6 mice resulting either in protection or exacerbation. These results are important for understanding the critical balance of proinflammatory and regulatory cytokines in bacterial infections which is decisive for beneficial effects of cytokine therapy.

Animals↗

PubMed1998

[Quality criteria and quality standards--social medicine expert assessment and its effectiveness in the social insurance system].

Basing on formulated criteria of expertises opinions in social medicine, the results of four investigations are presented aiming at the utilisation of expert opinions from external surveyors for social insurance. Leaving aside deficits that may be compensated, the results and assessments justify the view that consideration of only a few quality standards may increase the sociomedical competence and relevance of expert opinions.

Disability Evaluation↗

PubMed1997

Proton therapy for pediatric cranial tumors: preliminary report on treatment and disease-related morbidities.

PURPOSE: Accelerated protons were used in an attempt to limit treatment-related morbidity in children with tumors in or near the developing brain, by reducing the integral dose to adjacent normal tissues. METHODS AND MATERIALS: Children treated with protons at Loma Linda University Medical Center between August 1991 and December 1994 were analyzed retrospectively. Twenty-eight children, aged 1 to 18 years, were identified as at risk for brain injury from treatment. Medical records, physical examinations, and correspondence with patients, their parents, and referring physicians were analyzed. The investigators tabulated post-treatment changes in pre-treatment signs and symptoms and made judgments as to whether improvement, no change, or worsening related to disease or treatment had supervened. Magnetic resonance images were correlated with clinical findings and radiographic impressions were tabulated. RESULTS: Follow-up ranged from 7 to 49 months (median 25 months). Four instances of treatment-related morbidity were identified. Forty-one instances of site-specific, disease-related morbidity were identified: 15 improved or resolved and 26 remained unchanged after treatment. Four patients had radiographic evidence of local failure. Three of these patients, including two with high-grade glioma, have died. CONCLUSION: Early treatment-related morbidity associated with proton therapy is low. Tumor progression remains a problem when treating certain histologies such as high-grade glioma. Escalating the dose delivered to target volumes may benefit children with tumors associated with poor rates of local control. Long-term follow-up, including neurocognitive testing, is in progress to assess integral-dose effects on cognitive, behavioral and developmental outcomes in children with cranial tumors.

Adolescent↗