Biomedical subjects

Michael Schwarz

Publications and source records attributed to Michael Schwarz.

At least 19 recordsLinked to original sources

PubMed2007

Regulation of P53 stability in p53 mutated human and mouse hepatoma cells.

The tumor suppressor p53 is frequently mutated in cancer. We have investigated the regulation of P53 in p53 wild type mouse hepatoma cells (line 55.1c), in p53 heterozygeously mutated cells (56.1b) and in p53 defective cells (lines 56.1d, 70.4 and HUH7) under various experimental settings. The basal levels of P53 were low in 55.1c cells, but nuclear accumulation occurred upon UV-irradiation. Similarly, UV-exposure induced stabilization of P53 in the heterozygeously p53 mutated 56.1b hepatoma cells. By contrast, the 3 hepatoma lines, which lack transcriptionally active P53, demonstrated high basal nuclear concentrations of P53 protein and, unexpectedly, showed loss of P53 upon UV-irradiation. Expression of p53 mRNA was also decreased in p53 defective cells after 24 hr post UV-irradiation, which may be linked to induction of apoptosis of the irradiated cells under these conditions. Other stressors like H2O2 also mediated a decrease in P53 concentration in p53 defective cells. This effect occurred at very low concentrations and was already detectable 1-2 hr after exposure of cells. There were no signs of apoptosis of H2O2-exposed cells at this time point and no significant changes in p53 mRNA or MDM2 level. These unexpected findings indicate a new aspect related to regulation of P53 stability in cells with a defect in the tumor suppressor protein.

Animals↗

PubMed2007

Zonal gene expression in mouse liver resembles expression patterns of Ha-ras and beta-catenin mutated hepatomas.

Hepatocytes of the periportal and perivenous zones of the liver lobule differ in their levels and activities of various enzymes and other proteins. We have recently suggested that beta-catenin- and Ras-dependent signaling pathways play an important role in the regulation of perivenous and periportal gene expression profiles. This hypothesis was primarily based on similarities in zonal differences in gene expression of hepatocytes from normal liver with gene expression patterns of liver tumors: several proteins and mRNAs preferentially expressed in periportal hepatocytes were often overexpressed in Ha-ras mutated mouse liver tumors, whereas perivenous markers were overexpressed in Ctnnb1 (encoding beta-catenin) mutated tumors. We have now extended this work by use of data from two previously conducted microarray analyses aimed to analyze 1) global gene expression patterns of Ha-ras and Ctnnb1 mutated mouse liver tumors and 2) transcriptome differences between periportal and perivenous mouse hepatocytes. By comparison of the datasets, 134 genes or expressed sequences were identified that were present in both datasets. Gene expression patterns in perivenous hepatocytes and Ctnnb1 mutated hepatoma cells were strongly correlated: 96.5% of the genes present in both datasets were regulated in the same direction. In analogy, expression of 74.1% of the genes deregulated in Ha-ras mutated tumors was correlated with the respective expression patterns in periportal hepatocytes. These findings favor the hypothesis that gene expression patterns in periportal and perivenous hepatocytes are regulated, at least in part, by Ras- and beta-catenin-dependent signaling pathways.

Animals↗

PubMed2006

Effect of cyanidin-3-glucoside and an anthocyanin mixture from bilberry on adenoma development in the ApcMin mouse model of intestinal carcinogenesis--relationship with tissue anthocyanin levels.

Anthocyanins are dietary flavonoids, which can prevent carcinogen-induced colorectal cancer in rats. Here, the hypotheses were tested that Mirtoselect, an anthocyanin mixture from bilberry, or isolated cyanidin-3-glucoside (C3G), the most abundant anthocyanin in diet, interfere with intestinal adenoma formation in the Apc(Min) mouse, a genetic model of human familial adenomatous polyposis, and that consumption of C3G or Mirtoselect generates measurable levels of anthocyanins in the murine biophase. Apc(Min) mice ingested C3G or Mirtoselect at 0.03, 0.1 or 0.3% in the diet for 12 weeks, and intestinal adenomas were counted. Plasma, urine and intestinal mucosa were analyzed for presence of anthocyanins by high-pressure liquid chromatography with detection by UV spectrophotometry (520 nm) or tandem mass spectrometry (multiple reaction monitoring). Ingestion of either C3G or Mirtoselect reduced adenoma load dose-dependently. At the highest doses of C3G and Mirtoselect adenoma numbers were decreased by 45% (p < 0.001) or 30% (p < 0.05), respectively, compared to controls. Anthocyanins were found at the analytical detection limit in the plasma and at quantifiable levels in the intestinal mucosa and urine. Anthocyanin glucuronide and methyl metabolites were identified in intestine and urine. Total anthocyanin levels in mice on C3G or Mirtoselect were 43 ng and 8.1 microg/g tissue, respectively, in the intestinal mucosa, and 7.2 and 12.3 microg/ml in the urine. The efficacy of C3G and Mirtoselect in the Apc(Min) mouse renders the further development of anthocyanins as potential human colorectal cancer chemopreventive agents worthwhile.

Adenoma↗

PubMed2006

Differential gene expression in periportal and perivenous mouse hepatocytes.

Hepatocytes located in the periportal and perivenous zones of the liver lobule show remarkable differences in the levels and activities of various enzymes and other proteins. To analyze global gene expression patterns of periportal and perivenous hepatocytes, enriched populations of the two cell types were isolated by combined collagenase/digitonin perfusion from mouse liver and used for microarray analysis. In total, 198 genes and expressed sequences were identified that demonstrated a >/= 2-fold difference in expression between hepatocytes from the two different zones of the liver. A subset of 20 genes was additionally analyzed by real-time RT-PCR, validating the results obtained by the microarray analysis. Several of the differentially expressed genes encoded key enzymes of intermediary metabolism, including those involved in glycolysis and gluconeogenesis, fatty acid degradation, cholesterol and bile acid metabolism, amino acid degradation and ammonia utilization. In addition, several enzymes of phase I and phase II of xenobiotic metabolism were differentially expressed in periportal and perivenous hepatocytes. Our results confirm previous findings on metabolic zonation in liver, and extend our knowledge of the regulatory mechanisms at the transcriptional level.

Amino Acids↗

PubMed2006

Development of analyses by high-performance liquid chromatography and liquid chromatography/tandem mass spectrometry of bilberry (Vaccinium myrtilus) anthocyanins in human plasma and urine.

Anthocyanins are potent antioxidants that may possess chronic disease preventive properties. Here, rapid, reliable, and reproducible solid-phase extraction, high-performance liquid chromatography (HPLC), and mass spectrometry techniques are described for the isolation, separation, and identification of anthocyanins in human plasma and urine. Recoveries of cyanidin-3-glucoside (C3G) were 91% from water, 71% from plasma, and 81% from urine. Intra- and interday variations for C3G extraction were 9 and 9.1% in plasma and 7.1 and 9.1% in urine and were less than 15% for all anthocyanins from a standardized bilberry extract (mirtoselect). Analysis of mirtoselect by HPLC with UV detection produced spectra with 15 peaks compatible with anthocyanin components found in mirtoselect within a total run time of 15 min. Chromatographic analysis of human urine obtained after an oral dose of mirtoselect yielded 19 anthocyanin peaks. Mass spectrometric analysis employing multiple reaction monitoring suggests the presence of unchanged anthocyanins and anthocyanidin glucuronide metabolites.

Anthocyanins↗

PubMed2006

Rex3 (reduced in expression 3) as a new tumor marker in mouse hepatocarcinogenesis.

In a previous microarray expression analysis, Rex3, a gene formerly not linked to tumor formation, was found to be highly overexpressed in both Ctnnb1-(beta-Catenin) and Ha-ras-mutated mouse liver tumors. Subsequent analyses by in situ hybridization and real-time PCR confirmed a general liver tumor-specific overexpression of the gene (up to 400-fold). To investigate the role of Rex3 in liver tumors, hepatoma cells were transfected with FLAG- and Myc-tagged Rex3 expression vectors. Rex3 was shown to be exclusively localized to the cytoplasm, as determined by fluorescence microscopy and Western blotting. However, forced overexpression of Rex3 did not significantly affect proliferation or stress-induced apoptosis of transfected mouse hepatoma cells. Rex3 mRNA was determined in primary hepatocytes in culture by real-time PCR. In primary mouse hepatocytes, expression of Rex3 increased while cells dedifferentiated in culture. This effect was abolished when hepatocytes were maintained in a differentiated state. Furthermore, expression of Rex3 decreased in mouse liver with age of mice and the expression profile was highly correlated to that of the tumor markers alpha-fetoprotein and H19. The findings suggest a role of Rex3 as a marker for hepatocyte differentiation/dedifferentiation processes and tumor formation.

Animals↗

PubMed2006

PCB 153, a non-dioxin-like tumor promoter, selects for beta-catenin (Catnb)-mutated mouse liver tumors.

Polychlorinated biphenyls (PCBs) are ubiquitous environmental toxicants which act as liver tumor promoters in rodents and can be classified as either dioxin-like or non-dioxin (phenobarbital [PB])-like inducers of cytochrome P-450. Since we have previously shown that tumor promotion by PB leads to clonal outgrowth of beta-catenin (Catnb)-mutated but not Ha-ras-mutated mouse liver tumors, we were interested to know whether the non-dioxin-like tumor promoter 2,2',4,4',5,5'-hexachlorobiphenyl (PCB 153) shows the same selective pressure during tumor promotion. Male B6129SF2/J mice were given a single injection of N-nitrosodiethylamine (90 mg/kg body weight) at 9 weeks of age, followed by 39 weeks of treatment with PCB 153 (20 biweekly ip injections of 300 mumol/kg body weight) or corn oil as a control. Animals were killed 15 weeks after the last PCB 153 injection and liver tumors were identified by immunohistochemical staining of glutamine synthetase (GS) and analyzed for Catnb, Ha-ras, and B-raf mutations. Quantitative analyses revealed that GS-positive tumors were much larger and more frequent in livers from PCB 153-treated mice than in control animals, whereas GS-negative tumors were similar in both groups. Almost 90% (34/38) of all tumors from PCB 153-treated animals contained Catnb mutations, which compares to approximately 45% (17/37) of tumors in the control group. Ha-ras- and B-raf-mutated liver tumors were rare and not significantly different between treatment groups. These results clearly indicate that PCB 153 strongly selects for Catnb-mutated, GS-positive liver tumors, which is similar to the known action of PB, a prototypical tumor promoter in rodent liver.

Animals↗

PubMed2006

Ablation of gap junctional communication in hepatocytes of transgenic mice does not lead to disrupted cellular homeostasis or increased spontaneous tumourigenesis.

Gap junctions between murine hepatocytes are composed of two subunit proteins, connexin26 (Cx26) and connexin32 (Cx32). Previously, we found increased formation of chemically induced liver tumours but no increase in spontaneous development of preneoplastic hepatic foci in mice that lacked Cx32 and expressed decreased amounts of Cx26. In order to clarify this tumour-suppressive effect and to overcome embryonic lethality of constitutive Cx26-deficient mice, cell type-specific targeting of the Cx26 gene was performed. Mice with loxP-flanked Cx26 coding DNA were crossed with mice expressing the Cre recombinase exclusively in hepatocytes. Progeny mice lacking Cx26 in the liver were viable and fertile with no obvious signs of phenotypic alterations. To generate mice that totally lack gap junctional intercellular coupling, these mice were crossed with constitutive Cx32-deficient mice. We found no increase in spontaneously induced liver tumour formation in Cx26 and double deficient Cx26/Cx32 mice. Occasionally, double deficient livers exhibited morphological alterations, like amyloidosis, and a slightly increased basal proliferation rate of hepatocytes. Although the absence of gap junction channels led to altered expression of adhesion-related proteins like E-cadherin and actin, microarray analyses of total liver transcripts yielded only few differences between Cx26-deficient and double deficient livers compared to control samples. Our results suggest that total lack of gap junctional communication due to hepatocytic ablation of Cx26 and Cx32 does not drastically alter basal hepatocytic function and does not lead to increased spontaneous liver tumour formation.

Animals↗

PubMed2006

Functional activation studies of word processing in the recovery from aphasia.

Some reviews on theories of recovery in aphasia put an emphasis on neural network models based on empirical data from evoked-potentials in aphasia as an approach to mapping recovery of cognitive function to neural structure. We will focus here on what we call an "anatomical" approach to look at recovery in aphasia. "Anatomical" theories of recovery stated by classical aphasiologists have contributed to the understanding of language representations in the human brain. But many aspects of these theories can only be investigated by using modern techniques of lesion analysis, psychometric assessment and functional imaging. Whereas structure-function relations have been primarily established by looking for the association of deficit symptoms with certain lesions, functional activation methods offer a means to study more directly the functional anatomy of recovered or retained functions in neuropsychological patients. To falsify or build up anatomical theories of recovery we will propose a stepwise approach of inference. The methodological pitfalls of this approach will be discussed by focussing on anatomical hypotheses of semantic word comprehension and its impairment and recovery in aphasia.

Aphasia↗

PubMed2006

Regulation of CYP1A1 gene expression by the antioxidant tert-butylhydroquinone.

CYP1A1, a major phase I enzyme, plays an important role in the metabolism of polycyclic aromatic hydrocarbons and in the chemical activation of xenobiotics to carcinogenic derivatives. The phenolic antioxidant tert-butylhydroquinone (tBHQ), often used as a food preservative, is generally considered to act only as a mono-functional inducer of phase II enzymes, thereby exerting chemo-protection. However, we recently observed that tBHQ elevated the activity of an aryl hydrocarbon receptor (AhR) response element (DRE)-driven luciferase reporter in human colon carcinoma cells (Caco-2). Therefore, we studied the effects of tBHQ on the activity of a DRE-driven reporter, CYP1A1 mRNA expression, and CYP1A enzyme activity in Caco-2 cells and human HepG2 hepatoma cells. We found tBHQ caused induction of reporter activity and CYP1A1 expression and activity in Caco-2 and HepG2 cells. Moreover, tBHQ combined with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) increased reporter activity and mRNA expression in Caco-2 cells in an additive manner. By contrast, tBHQ decreased TCDD-mediated induction of reporter activity and CYP1A1 mRNA expression in HepG2 cells. Resveratrol, an AhR antagonist, repressed the induction of CYP1A1 by tBHQ. Cotransfection of HepG2 cells with a dominant negative AhR nuclear translocator mutant abolished the tBHQ-induced CYP1A1 reporter activity. These findings indicate that CYP1A1 may be induced by the antioxidant tBHQ via an AhR-dependent mechanism.

Antioxidants↗

PubMed2006

Intraspecific molecular phylogeny, genetic variation and phylogeography of Reticulitermes speratus (Isoptera: Rhinotermitidae).

Population structure was investigated in Reticulitermes speratus populations in the Korean Peninsula and the Japanese Archipelago. All trees derived from analyses of the combined sequence dataset of two mitochondrial genes, COII and COIII, showed that R. speratus populations cluster into two major clades comprising the Korean/southern Japanese populations and the north-ern Japanese populations. Analysis of population ge-netic structure showed strong genetic partitioning between populations of the two clades. To understand historical migration routes and current distributions, the phylogeographic history of R. speratus was inferred from intra-/interspecific phylogeny and diver-gence times estimated between the clades of the phylogenetic tree. The estimated migration route and divergence time of ancestral R. speratus are congruent with recent paleogeographic hypotheses involving land-bridge connections between the Asian continent and the Japanese Archipelago. We suggest that ancestral R. speratus separated into northern and southern Japanese populations after its migration into the Japanese main islands from East China during the early Pleistocene via the East China Sea basin, which may have been exposed during that period. The Korean populations seem to have diverged recently from southern Japanese populations; this may explain the current distribution of R. speratus in the Japanese Arachipelago, and account for why it is restricted to northern areas of the Tokara Strait.

Animals↗

PubMed2006

Tumor promoting potency of PCBs 28 and 101 in rat liver.

Only few data are available on the carcinogenic potency of individual PCB congeners. In this study, we tested the 'non-dioxinlike' congeners PCB 28 and 101 for their potency as liver tumor promoters in female rats which received diethyl-N-nitrosamine as an initiator. After 8 or 16 weeks of PCB treatment (50 and 150 micromol/kg body weight per week), each congener was recovered in the liver according to the dose levels applied, with PCB 28, at the same dose level, showing nine- to 16-fold higher hepatic levels than PCB 101 (approximately, 44 micromol/kg versus 5 micromol/kg liver at low dose, 145 micromol/kg versus 9 micromol/kg liver at high dose). PCB 28 was found to mildly induce hepatic EROD activity, while both congeners induced PROD activity. With each congener, no significant increase in the number of ATPase-deficient or GSTP-positive preneoplastic foci was obtained, while a significant increase in the relative hepatic volume of ATPase-deficient foci was found in the livers of DEN pre-treated animals having received 50 micromol/kg body weight of PCB 101 per week over 16 weeks. Our results revealed that neither the accumulative PCB 28 nor the more readily metabolisable PCB 101 was an efficacious tumor promoter in the livers of female rats.

Alkylating Agents↗

PubMed2006

Zonal gene expression in murine liver: lessons from tumors.

Gene expression in hepatocytes within the liver lobule is differentially regulated along the portal to central axis; however, the mechanisms governing the processes of zonation within the lobule are unknown. A model for zonal heterogeneity in normal liver is proposed, based on observations of differential expression of genes in liver tumors from mice that harbor activating mutations in either Catnb (which codes for beta-catenin) or Ha-ras. According to the model, the regulatory control consists of two opposing signals, one delivered by endothelial cells of the central veins activating a beta-catenin-dependent pathway (retrograde signal), the other by blood-borne molecules activating Ras-dependent downstream cascades (anterograde signal). In conclusion, gradients of opposing signaling molecules along the portocentral axis determine the pattern of enzymes and other proteins expressed in hepatocytes of the periportal and pericentral domains of the liver lobule.

Animals↗

PubMed2006

Diagnostic aspects of early Parkinson's disease.

Insidious onset of mild, unspecific, sensitive, vegetative, psychopathological, cognitive and perceptive disturbances, i. e., visual and olfactory dysfunction, with a resulting change of personal behavior, i. e., reduced stress tolerance, precede the initially intermittently occurring motor symptoms in patients with Parkinson's disease (PD). Novel neuropathological findings suggest an expansion pattern of the neurodegenerative process beyond the nigral dopaminergic neurons with the initial event located outside the brain. This underlines the clinical concept of an initial premotor phase, which starts in nondopaminergic areas in PD. Moreover a more global general understanding of chronic neurodegeneration enables the performance of clinical trials on neuroprotection, since there is increasing evidence that diagnosis of PD at the threshold of onset of motor symptoms or cognitive symptoms in Alzheimer's disease is too late. Such an earlier diagnosis of chronic neurodegeneration will allow a more convincing demonstration of the efficacy of a neuroprotective or disease modifying compound. It will also support the concept of a clinically effective pharmacological intervention on a disease process, which is also more and more demanded by the health authorities for drug approval.

Antiparkinson Agents↗

PubMed2006

Duplex sonographic findings in children with torsion of the testicular appendages: overlap with epididymitis and epididymoorchitis.

BACKGROUND AND PURPOSE: Torsion of the testicular appendages (TTA) is the most common cause of acute scrotum in children, and yet there are only few dedicated studies of the imaging findings. OBJECTIVE: To review our experience with the use of duplex sonography in children with TTA and to evaluate if sonography can successfully distinguish TTA from epididymoorchitis. METHODS: We reviewed the medical files and imaging findings of 29 children aged 0.7 to 13.9 years (mean, 6.5 years) with a diagnosis of TTA based on testicular exploration who were evaluated preoperatively with duplex sonography. RESULTS: A tender upper pole nodule, the typical sign of TTA, was palpated in only 2 (6.9%) children. Duplex sonography demonstrated an extratesticular upper pole nodule in 9 (31%) children. Secondary inflammatory changes included hydrocele in 22 (75.9%), enlarged epididymis in 22 (75.9%), scrotal wall edema in 16 (55.2%), and swollen testis in 9 (31%) children. Fourteen (48%) children had inflammatory changes with no evidence of an extratesticular nodule. CONCLUSION: Duplex sonography findings of secondary inflammatory changes in the absence of evidence of an extratesticular nodule may suggest an erroneous diagnosis of epididymitis or epididymoorchitis in children with TTA.

Acute Disease↗

PubMed2006

Subtrochanteric femoral fractures due to simple bone cysts in children.

Seven children were treated surgically as a result of a pathologic fracture through a simple bone cyst in the subtrochanteric region of the proximal femur. Average age at surgery was 10.6 years. Six children were treated primarily. One child was operated for a refracture through a persistent cyst and malunion of a previous fracture that had been treated nonoperatively. Surgery included curettage of cysts in all patients. The cysts were filled with autologous bone graft in five patients and Osteoset bone substitute in two patients. The fracture was stabilized using a blade plate in three patients, a screw and side plate in three patients and an external fixator in one. At average follow-up of 4.7 years, all fractures had healed uneventfully. The cyst was fully obliterated in five patients and partially obliterated in two patients. One patient had a relative lengthening of 2 cm on the affected side. All patients were asymptomatic, fully active and had full range of motion.

Adolescent↗

PubMed2006

Altered processing of corollary discharge in thalamic lesion patients.

Accumulating evidence suggests that thalamic nuclei relay corollary discharge information of saccadic eye movements, enabling the visual system to update the representation of visual space. The present study aimed to explore the effect of thalamic lesions in humans on updating-related cortical processing. Event-related potentials were recorded while four patients with impairments in using corollary discharge information and 12 healthy control subjects performed a saccadic double-step task. In the experimental condition, which required the use of corollary discharge information, control subjects showed a pronounced positivity over the parietal cortex starting about 150 ms after first saccade onset, reflecting the updating process. In the patients, parietal processing related to updating was altered. Three patients showed evidence of reduced updating event-related potential effects, consistent with a unilateral deficit in using corollary discharge information. In two patients, the event-related potential topography differed significantly from the topography pattern observed in controls. Thalamic damage affects updating-related processing, presumably due to insufficient transfer of saccade-related information to parietal areas. This study thus provides further evidence for thalamic involvement in relaying corollary discharge information related to saccadic eye movements. Our data suggest that integration of corollary discharge and motor information occurs directly before the second saccade in a double-step task.

Adult↗

PubMed2005

Fabrication of alignment structures for a fiber resonator by use of deep-ultraviolet lithography.

We present a novel method to mount and align an optical-fiber-based resonator on the flat surface of an atom chip with ultrahigh precision. The structures for mounting a pair of fibers, which constitute the fiber resonator, are produced by a spin-coated SU-8 photoresist technique by use of deep-UV lithography. The design and production of the SU-8 structures are discussed. From the measured finesses we calculate the coupling loss of the SU-8 structures acting as a kind of fiber splice to be smaller than 0.013 dB.

Journal Article↗