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Biomedical subjects

R Meyer

Publications and source records attributed to R Meyer.

At least 37 records · Page 2Linked to original sources
PubMed2004

Vascular endothelial growth factor (VEGF) levels as a tool to discriminate between malignant and nonmalignant ascites.

Ascites formation is commonly associated with cancer, although it is also present in other diseases. The aim of this study was to evaluate the usefulness of vascular endothelial growth factor as a malignancy marker in ascites of different etiologies. The levels of VEGF in 32 malignant and in 31 non-malignant ascites were determined by enzyme immunoassay (ELISA). VEGF levels were significantly higher in malignant than in non-malignant ascites (median=1265.9 pg/ml x 114.6 pg/ml; p<0.0001). We observed 72% sensitivity and 90% specificity, using 662 pg/ml as a cut-off value. Therefore, this approach can be used as a marker for a first screening to discriminate between malignant and nonmalignant ascites.

Ascites↗
PubMed2004

Epicardial and microvascular graft vessel disease in children.

AIM: Graft vessel disease (GVD) is one of the main limiting factors to long-term survival after adult heart transplantation (HTx). The incidence of epicardial and microvascular GVD in paediatric patients was studied. METHODS: A total of 137 coronary angiographies from 130 paediatric HTx and heart and lung transplant (HLTx) patients (70 male, 60 female, aged 0-18 y) were evaluated according to the Stanford classification and its supplements (minor vessel alterations). In H&E stainings from right ventricular endomyocardial biopsies (EMB = 397), light microscopic diagnosis of acute cellular rejection (ISHLT classification) and vascular reaction (morphology of endothelial cells and vessel walls) was performed. RESULTS: Moderate rejection was present in 32.8% and severe rejection in 13.3% of EMB. Microvascular EC swelling was found in 33.5% and vessel wall thickening in 53.8% of EMB. The results of the coronary angiographic investigations were: Stanford lesions = 61.2%, peripheral obliterations = 52.5%, diameter fluctuations = 86.3%, pathologic tapering = 64.0%, calcifications = 10.8%. Long-term survivors (> or =5 y) showed macrovascular alterations in 78% of cases and microvascular alterations in 67% of cases. CONCLUSION: The development of micro- and macrovascular GVD is one of the predominant complications in long-term survivors after paediatric HTx and HLTx.

Adolescent↗
PubMed2003

Experimental Corynebacterium pseudotuberculosis primary infection in goats: kinetics of IgG and interferon-gamma production, IgG avidity and antigen recognition by Western blotting.

Corynebacterium pseudotuberculosis is the cause of caseous lymphadenitis (CLA) in small ruminants, a chronic granulomatous disease that provokes significant zootechnics losses to ovine and goat breeders in northern Brazil. The present work was conducted to analyse aspects of humoral and cellular immune responses after experimental infection. Eight goats were infected intradermally with a single dose of virulent C. pseudotuberculosis strain and specific IgG, interferon-gamma (IFN-gamma) production as well as IgG avidity and antigens pattern recognition dynamics against an excreted-secreted antigen were recorded during 20 weeks. At the end of the follow-up, animals were slaughtered and necropsied. Although no animals showed apparent clinical signs of infection at the end of the trial, IFN-gamma response, even more so than the humoral response, differentiated animals into two groups of high or medium/low response. The time-course of IFN-gamma production presented a short-lived primary response on day 5 after infection of animals of both groups, and a strong and long lasting secondary response starting on day 16 after infection in the high response group. The indirect ELISA used was able to detect a positive antibody titre between 6 and 11 days after infection in the two groups. IgG avidity index oscillated initially between 15 and 45%, and showed approximately 5% units increment during the 20 follow-up weeks. With only one individual exception, the qualitative antigens pattern recognition showed on day 11 after infection remained constant through the experiment. IgG avidity is highly correlated with IgG production, but could not be related with specific immunodominant bands. Both humoral and cellular responses kinetics presented a similar pattern of activation/deactivation but necropsy results suggested that the IFN-gamma test would be a very specific marker of CLA status.

Animals↗
PubMed2003

Determination of atomic structure of the metal-oxide interface: Pd nanodeposits on an FeO(111) film.

Palladium was vapor deposited on a thin FeO(111) film grown on a Pt(111) substrate. Scanning tunneling microscopy study has revealed that Pd wets the FeO substrate and at elevated temperatures forms extended Pd(111) monolayer islands in contrast to other oxide supports previously studied. For the first time, we have imaged the metal-oxide interface structure with atomic resolution and explained the results on the basis of ab initio calculations.

Journal Article↗
PubMed2003

Inhibitors of DNA methylation and histone deacetylation activate cytomegalovirus promoter-controlled reporter gene expression in human glioblastoma cell line U87.

The expression of many cellular genes is modulated by DNA methylation and histone acetylation. These processes can influence malignant cell transformation and are also responsible for the silencing of DNA constructs introduced into mammalian cells for therapeutic or research purposes. As a better understanding of these biological processes may contribute to the development of novel cancer treatments and to study the complex mechanisms regulating gene silencing, we established a cellular system suitable to dissect the mechanisms regulating DNA methylation and histone acetylation. For this purpose, we stably transfected the neuroblastoma cell line U87 with a cytomegalovirus promoter-driven reporter gene construct whose expression was analyzed following treatment with the DNA methylation inhibitor 5'-aza-2'-deoxycytidine or histone deacetylation inhibitor trichostatin A. Both substances reactivated the silenced cytomegalovirus promoter, but with different reaction kinetics. Furthermore, whereas the kinetics of reactivation by trichostatin A did not substantially change over the time range considered (5 days), reactivation induced by 5'-aza-2'-deoxycytidine showed profound differences between day 1 and longer time points. We showed that this effect is related to the down-regulation of DNA replication by 5'-aza-2'-deoxycytidine. Finally, we have shown that the simultaneous administration of trichostatin A and 5'-aza-2'-deoxycytidine results in reactivation of the CMV promoter according to a cooperative, not synergistic or additive, mechanism. In conclusion, our cellular system should represent a powerful tool to investigate the complex mechanisms regulating gene silencing and to identify new anticancer drugs.

Animals↗
PubMed2003

[Atypical Leriche syndrome].

A 73-year old woman presented with mild paraparesis and hypesthesia of the legs. Furthermore, she complained dizziness, fainting and dyspnea. There was a history of peripheral artery disease, diabetes mellitus, arterial hypertension and chronic atrial fibrillation. Five years ago she had breast cancer with removal of the left mamma and additional radiation therapy. Cardiac catheterization at that time demonstrated no significant coronary stenoses. A contrast-enhanced CT-scan excluded lumbal spinal metastases. Instead, a subtotal occlusion of the abdominal aorta was noticed, but was initially interpreted as a chronic thrombosis because there were no typical symptoms and only moderate pain. About 24 hours later the patient developed an acute ischemic syndrome of the legs with progressive paraparesis, cold and pale legs in combination with acidosis and hyperventilation. Color-coded duplex ultrasound showed only a small turbulent flow in the ilial arteries, highly suspicious of a complete occlusion of the distal aorta. Angiography revealed an acute total occlusion of the infrarenal aorta without collaterals. During surgical intervention, complete obstruction of the abdominal aorta above the bifurcation was confirmed. Subsequent embolectomy was performed and an embolus consisting of several layers of different age was extracted. After successful surgical intervention with subsequent clinical improvement, the patient's clinical condition deteriorated a few day later. She died on day 9 after surgery from a complete ischemia of the small intestine and the colon ascendens.

Aged↗
PubMed2003

Gemcitabine, dexamethasone and cisplatin is an active and non-toxic chemotherapy regimen in relapsed or refractory Hodgkin's disease: a phase II study by the National Cancer Institute of Canada Clinical Trials Group.

BACKGROUND: Gemcitabine (difluorodeoxycytidine) is active as a single agent in Hodgkin's disease and has been used successfully in combination with cisplatin to treat a variety of solid tumors. PATIENTS AND METHODS: We evaluated the combination of gemcitabine/dexamethasone/cisplatin (GDP) as salvage chemotherapy in 23 patients with relapsed or refractory Hodgkin's disease (median age 36 years, range 19-57). Treatment consisted of gemcitabine 1000 mg/m(2) intravenously on days 1 and 8, dexamethasone 40 mg orally days 1-4 and cisplatin 75 mg/m(2) on day 1, every 21 days as an outpatient. Response was assessed following two cycles of treatment. RESULTS: There were four complete responses and 12 partial responses for a response rate of 69.5% (95% confidence interval 52% to 87%); the remaining seven patients had stable disease and no patient progressed on treatment. All patients had successful stem cell mobilization and underwent transplantation with a median 10.6 x 10(6) CD34+ cells/kg. Hematological toxicity from GDP was mild (grade 3 neutropenia 8.6%, grade 3 thrombocytopenia 13%). CONCLUSIONS: In summary, GDP is an active regimen for patients with relapsed or refractory Hodgkin's disease. The response rate is similar to the rates of other current salvage regimens, it can be given to outpatients with tolerable toxicity and it does not inhibit the mobilization of autologous stem cells.

Administration, Oral↗
PubMed2002

[Coronary artery bypass grafting in patients with highly impaired ventricular function. Long-term outcome].

BACKGROUND AND OBJECTIVE: Left ventricular function is the most important predictor of survival in patients with coronary artery disease. It is also an important indicator for hospital mortality after operation for end-stage coronary artery disease. In our study we investigated, how preoperative ventricular dysfunction influences long term survival after coronary bypass surgery. PATIENTS AND METHODS: Between 4/1986 and 12/2000, 1751 patients (1440 men/311 women) with left ventricular ejection fraction (LVEF) 10-30% underwent coronary bypass grafting (CABG) at the Deutsches Herzzentrum Berlin. The age of the patients was calculated to an average of 59,2 years. The prime criterion for CABG was ischemia ("hibernating myocardium") diagnosed by myocardial scintigraphy, echocardiography and in some cases with magnetic resonance imaging and positron emission tomography. RESULTS: Operative mortality for the group was 7,1%. The actuarial survival rate was 87,6% after 2 years, 76,0% after 5, and 53,3% after 9. 455 had LVEF 10-20%, in these actuarial survival was 79,8% after 2 years, 63,0% after 5 and 45,7% after 9 years. CONCLUSION: We conclude that CABG can be used successfully to improve life expectancy of patients with end-stage coronary artery disease. CABG leads to acceptable prognosis for these high-risk patients when the myocardium is preoperatively identified as being viable.

Adult↗
PubMed2002

[Relation of aortic wall alterations and ascending aorta diameter in patients with bicuspid aortic valve].

Patients with a bicuspid aortic valve tend to develop local enlargement in the convexity of the ascending aorta. There is controversial discussion as to whether this is a dilatation caused by abnormal hemodynamic stress or an aneurysm due to a common developmental defect of the aortic valve and the aortic media. Systematic studies of aortic wall specimens from patients with different diameters of the ascending aorta have not been available until now. We investigated histologically (HE, E.v.G., alpha-Actin, Alcian blue/van Gieson) aortic wall tissue obtained from 107 patients (31 female, 76 male, mean age 60.9+/-12.8 years) with a bicuspid aortic valve. According to the preoperative measurement of the ascending aorta diameter, which was done by CT scan, angiography or echocardiography, the patients were divided into three groups [Group 1: ascending aorta diameter <3.8 cm; Group 2: diameter >/=3.8-4.9 cm and Group 3: diameter >/=5.0 cm]. We looked for histological signs of dilatation or more severe structural changes. All patients of group 1 showed normal findings in histological examination. In 23 of 43 patients in group 2 (65.1%), we found histological signs of dilatation. Histological signs of dilatation were present in all patients in group 3. We conclude that in patients with a bicuspid aortic valve histological signs of dilatation were more frequently found with increasing diameter of the ascending aorta. More severe histological changes, such as cystic media necrosis, were not present.

Age Factors↗
PubMed2002

Phenotype/genotype associations for yield and salt tolerance in a barley mapping population segregating for two dwarfing genes.

Barley traits related to salt tolerance are mapped in a population segregating for a dwarfing gene associated with salt tolerance. Twelve quantitative trait loci (QTLs) were detected for seven seedling traits in doubled haploids from the spring barley cross Derkado x B83-12/21/5 when given saline treatment in hydroponics. The location of QTLs for seedling growth stage (leaf appearance rate), stem weight prior to elongation, and tiller number are reported for the first time. In addition, four QTLs were found for the mature plant traits grain nitrogen and plot yield. In total, seven QTLs are co-located with the dwarfing genes sdw1, on chromosome 3H, and ari-e.GP, on chromosome 5H, including seedling leaf response (SGa) to gibberellic acid (GA(3)). QTLs controlling the growth of leaves (GS2) on chromosomes 2H and 3H and emergence of tillers (TN2) and grain yield were independent of the dwarfing genes. Field trials were grown in eastern Scotland and England to estimate yield and grain composition. A genetic map was used to compare the positions of QTLs for seedling traits with the location of QTLs for the mature plant traits. The results are discussed in relation to the study of barley physiology and the location of genes for dwarf habit and responses to GA.

Adaptation, Physiological↗
PubMed2001

Isolation of Neospora caninum from the brain of a naturally infected dog, and production of encysted bradyzoites in gerbils.

Neospora caninum was isolated from the brain of an adult dog in Brazil. Cerebral tissue from the dog was inoculated into Mongolian gerbils. Gerbils were euthanized 3-4 months later and bradyzoite-containing tissue cysts were observed in their brains. N. caninum (designated NC-Bahia) was isolated in cell culture after inoculation with tissue cysts from the gerbils. The identity of the parasite was confirmed by immunohistochemical examination and polymerase chain reaction (PCR). Gerbils may be a useful alternative to immunosuppressed mice for isolation of N. caninum and for production of encysted bradyzoites.

Animals↗
PubMed2001

Low-frequency vibrational properties of nanocrystalline materials.

The vibrational density of states (VDOS) of bulk nanocrystalline Ni and Cu (model) samples with grain diameters between 5 and 12 nm are derived from molecular-dynamics simulations. The results show an enhancement of the density of states at low and high energies. Because of large system sizes and a decomposition of the VDOS into grain and grain-boundary components, the low-frequency region can be investigated for the first time. It is found that the anomalous increase of the VDOS is mainly caused by the high number of grain-boundary atoms and that a power-law behavior of the low-frequency grain-boundary VDOS exists, which suggests a reduced dimensionality effect.

Journal Article↗
PubMed2001

Reliability of tissue Doppler wall motion monitoring after heart transplantation for replacement of invasive routine screenings by optimally timed cardiac biopsies and catheterizations.

BACKGROUND: Invasive screenings at predefined time intervals for acute rejection and transplant coronary artery disease (TxCAD) are standard procedures. However, cardiac biopsies and catheterizations are distressing and risky for the patients and are also costly. We assessed the reliability of pulsed-wave tissue Doppler imaging (PW-TDI) for the timing of invasive examinations in heart recipients in an attempt to avoid unnecessary endomyocardial biopsies (EMBs) and catheterizations. METHODS AND RESULTS: PW-TDI obtained at the basal left ventricular posterior wall before 408 EMBs and 293 catheterizations was tested for its diagnostic value regarding rejection and TxCAD with the use of International Society of Heart and Lung Transplantation biopsy grading, coronary angiography, and intravascular ultrasound as standards. Early diastolic peak wall motion velocity and relaxation time showed high sensitivities for clinically relevant rejection diagnosis (90.0% and 93.3%, respectively). The negative and positive predictive values for rejection of diastolic parameter changes appeared high enough (up to 96% and 92%, respectively) to allow a reliable noninvasive PW-TDI monitoring with efficiently timed, instead of routinely scheduled, EMBs. At definite cutoff values for systolic parameters, the probability for TxCAD reached 92% to 97%. The Fisher classification functions allowed TxCAD exclusion with 80% probability. CONCLUSIONS: Without diastolic parameter changes, acute rejection can be practically excluded, and serial PW-TDI can save patients from routine EMBs. The high specificity and negative predictive value for TxCAD of reduced systolic peak velocities and extended systolic time allow optimized timed catheterizations. Peak systolic velocity and systolic time allow diagnostic classifications that enable patients without known TxCAD but with high risk for catheterization to be spared routine angiographies.

Adult↗
PubMed2001

Acute neuronal apoptosis in a rat model of multiple sclerosis.

Demyelination caused by inflammation of the CNS has been considered to be a major hallmark of multiple sclerosis (MS). Using experimental autoimmune encephalomyelitis, a model of MS, we demonstrate that an immune-mediated attack of the optic nerve is accompanied by an early degeneration of retinal ganglion cells (RGCs). The decrease of neuronal cell density was correlated with functional disabilities as assessed by visual evoked cortical potentials and electroretinogram. Visual acuity was significantly reduced. DNA degradation and activation of caspase-3 in RGCs indicate that cell death of RGCs is apoptotic. These findings show for the first time that an inflammatory attack against myelin components can lead to acute neuronal cell loss by apoptosis.

Acute Disease↗
PubMed2001

Activation of estrogen receptor beta is a prerequisite for estrogen-dependent upregulation of nitric oxide synthases in neonatal rat cardiac myocytes.

Physiological effects of estrogen on myocardium are mediated by two intracellular estrogen receptors, ERalpha and ERbeta, that regulate transcription of target genes through binding to specific DNA target sequences. To define the role of ERbeta in the transcriptional activation of both endothelial (eNOS) and inducible nitric oxide synthase (iNOS) in cardiac myocytes, we used the complete ER-specific antagonist R,R-tetrahydrochrysene (R,R-THC). R,R-THC inhibited activation of iNOS/eNOS promoter-luciferase reporter constructs (iNOS/eNOS-Luc) in a dose-dependent fashion in COS7 cells selectively transfected with ERbeta, but failed to influence ERalpha-mediated increase of iNOS/ eNOS-Luc. In neonatal rat cardiomyocytes transfected with eNOS-Luc or iNOS-Luc, incubation with 17betaestradiol (E2, 10(-8) M) for 24 h stimulated expression of eNOS and iNOS. R,R-THC (10(-5) M) completely inhibited this effect. Furthermore, eNOS and iNOS protein expression in cardiac myocytes induced by E2 was completely blocked by R,R-THC as shown by immunoblot analysis. Taken together, these results show that ERbeta mediates transcriptional activation of eNOS and iNOS by E2.

Animals↗