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Biomedical subjects

K Wagner

Publications and source records attributed to K Wagner.

At least 19 recordsLinked to original sources
PubMed2006

Dephasing in (Ga,Mn)As nanowires and rings.

To understand quantum mechanical transport in a ferromagnetic semiconductor, the knowledge of basic material properties such as the phase coherence length and corresponding dephasing mechanism are indispensable ingredients. The lack of observable quantum phenomena has prevented experimental access to these quantities so far. Here we report the observations of universal conductance fluctuations in ferromagnetic (Ga,Mn)As. The analysis of the length and temperature dependence of the fluctuations reveals a T(-1) dependence of the dephasing time.

Journal Article↗
PubMed2006

Levetiracetam reduces frequency and duration of epileptic activity in patients with refractory primary generalized epilepsy.

PURPOSE: Levetiracetam (LEV) is a new antiepileptic drug highly effective as add-on treatment in refractory partial epilepsies. In animal models, LEV is effective against absence seizures. A limited number of case reports and series indicate that LEV reduces seizure frequency in patients with generalized epilepsies. METHOD: We evaluated with continuous EEG eight adult patients with idiopathic generalized epilepsy (IGE). All patients were refractory to the conventional therapy for IGE. Four patients received LEV as add-on therapy, and in four, a conversion to LEV monotherapy was undergone. Epileptic activity was analyzed in order to determine spike-wave density as well as median and maximal duration of spike-wave discharges. Each patient underwent a 24h EEG baseline monitoring before starting LEV therapy. A second 24h EEG examination was performed after a mean follow-up period of 136 days. RESULTS: Spike-wave density (spikes/h) was reduced by 78% after LEV administration. Median spike-wave duration decreased by 72% (p < 0.05). Maximal spike-wave duration was 6s before, and 1.5s after LEV with a percentage change of 81% (p < 0.05). The four patients on LEV monotherapy evidenced also a considerably improvement after conversion. CONCLUSIONS: This study showed that LEV produces a consistent long-term reduction of interictal epileptic activity in patients with refractory IGE. The reduction in the spike-wave activity additionally correlated with a clinically relevant antiepileptic effect. Our results support the concept that LEV could be an alternative therapy in primary generalized epilepsies.

Adolescent↗
PubMed2006

[Specific aspects of hypertension control in the geriatric patient].

Hypertensive patients older than 65 obtain greater benefit from antihypertensive therapy than do younger patients. The universally accepted values for the adjustment of blood pressure--140/90 mmHg--also apply in the case of the elderly. Hypertension control in this age group necessitates the taking into account of a number of peculiarities, including a tendency for these patients to develop postprandial hypotension, and to exhibit a diminishment in thirst, impairment of renal function and cognitive performance on the one hand, and an increase in salt sensitivity, comorbidity and a need for further medications. With regard to medicinal treatment, the basic rule is "start low, go slow", that is, a combination approach should be initiated at the lowest possible dose, which can then be gradually increased. Medical treatment is supplemented by age-group-related recommendations for general measures.

Age Factors↗
PubMed2006

Increase in serum resistin during weight loss in overweight subjects is related to lipid metabolism.

OBJECTIVE: Human resistin has been stated to influence preadipocyte cell numbers and to stimulate adipocyte triglyceride lipolysis in vivo and in vitro. However, its role in human obesity remains unclear. DESIGN: Cross-sectional study for comparisons of lean and obese subjects, and subsequent longitudinal 4-month weight loss intervention study in obese subjects. SUBJECTS: Healthy subjects, lean (n=20, BMI<25) and overweight (n=43, BMI>or=25). MEASUREMENTS: Serum resistin, body weight, body fat, waist-to-hip ratio, as well as markers of insulin resistance and lipid metabolism at baseline and after 4 months of intervention. RESULTS: Serum resistin was positively correlated to HOMA-IR (partial r=0.288; P=0.055), serum fructosamines (partial r=0.280; P=0.062), serum NEFA (partial r=0.276; P=0.066) and negatively to age (partial r=-0.349; P=0.019) and serum apolipoprotein A-1 (partial r=-0.363; P=0.014). During the intervention, serum resistin increased significantly (P<0.001). The increase was inversely related to changes in waist-to-hip ratio (P=0.025) and positively to serum apolipoprotein B (P=0.011). In males only, the increase in resistin during weight loss was predicted by total serum cholesterol at baseline (r=0.703, P=0.007). No relation was observed between changes in resistin and changes in HOMA-IR. CONCLUSION: The present study indicates an association between serum resistin and markers of abdominal fat distribution as well as the regulation of lipid metabolism. However, human resistin is unlikely to play an independent role in the regulation of glucose metabolism.

Adult↗
PubMed2006

Differential interaction of magnetic nanoparticles with tumor cells and peripheral blood cells.

PURPOSE: The separation of tumor cells from healthy cells is a vital problem in oncology and hematology, especially from peripheral blood. Magnetic assisted cell sorting (MACS) is a possibility to fulfill these needs. METHODS: Tumor cell lines and leukocytes from peripheral blood were incubated with carboxymethyl dextran-coated magnetic nanoparticles under various conditions and separated by MACS. RESULTS: We studied the interaction of magnetic nanoparticles devoid of antibodies with healthy and tumor cells. The magnetic nanoparticles interact with tumor cells and leukocytes and are located predominantly within the cell cytoplasm. Incubation of cell culture cells with magnetic nanoparticles led to a labeling of these cells without reduced biological properties for at least 14 days. The interaction of the magnetic nanoparticles with cells depends on several factors. The ionic strength (osmolality) of the solvent plays an important role. We could show that an increase in osmolality led to a dramatic reduction of labeled leukocytes. Tumor cells, however, are mildly affected. This could be detected not only in pure cultures of tumor cells or leukocytes but also in mixed cell populations. CONCLUSION: This observation gives us the opportunity to selectively label and separate tumor cells but not leukocytes from the peripheral blood.

Blood Cells↗
PubMed2006

Oxygen status of lung granulomas in Mycobacterium tuberculosis-infected mice.

It is often assumed that Mycobacterium tuberculosis (Mtb)-induced granulomatous lesions, particularly those undergoing central caseation, are anoxic, and that the survival of Mtb in these lesions requires the integrity of its non-oxidative respiratory pathways. Using the hypoxia marker pimonidazole, we now provide immunohistochemical evidence that in the most frequently used animal model system of inbred mice Mtb-induced granulomas, even after more than one year of aerogenic infection, are not severely hypoxic. In contrast, chronic aerosol infection with M. avium strain TMC724 was associated with hypoxia surrounding necrotizing granuloma centres. Direct measurements of oxygen tension with a flexible microelectrode in mouse lungs chronically infected with Mtb disclosed a wide range of oxygen partial pressures in different parts of the lungs which, however, rarely approached the anoxic conditions consistently found in necrotizing tumours. We further show that an Mtb mutant, defective in nitrate reductase (narG) necessary for survival under anaerobic conditions in vitro, can persist in the lungs of chronically infected mice to a similar extent as wild-type Mtb. These findings have important implications for the use of the mouse model of Mtb infection in developing eradication chemotherapy and for evaluating putative mechanisms of chronic persistence and latency of Mtb.

Animals↗
PubMed2006

Serum resistin increases in a postprandial state during liquid meal challenge test in healthy human subjects.

The role of resistin in humans is controversial although resistin has been linked to atherosclerotic and inflammatory processes. In rodents, resistin expression is suppressed after food restriction while central administration of resistin promotes short-term satiety. However, the nature of postprandial responses in circulating resistin in humans is unknown. Therefore, we investigated postprandial resistin concentrations in a pilot study in 19 healthy subjects and 19 controls matched for age and body mass index (BMI). Serum resistin, insulin and non-esterified fatty acids (NEFA) concentrations as well as plasma glucose and triglycerides were repeatedly assessed before and after ingestion of an isocaloric standardized liquid meal during a 300 min period.After consumption of liquid meal, serum resistin levels increased compared to fasting control (p=0.037). Postprandial plasma glucose and serum insulin increased (p<0.001) with lower glucose responses in females (p=0.001) and lower insulin responses in males (p=0.012). Plasma triglycerides increased and serum NEFA decreased with similar gender responses (p=0.025 and p<0.001, respectively). Serum resistin was not correlated to glucose, insulin, triglyceride, and NEFA responses to liquid meal challenge tests. The present data suggest that serum resistin increases postprandially in healthy humans. Additional studies are needed to elucidate normal 24-h daytime profiles in humans and differential response of serum resistin to macronutrient composition of meals.

Adult↗
PubMed2006

Unprotected intercourse among people living with HIV/AIDS: The importance of partnership characteristics.

The purpose of this study was to determine the relative importance and interactive effects of partnership characteristics in unprotected intercourse among people living with HIV/AIDS (PLWHA). An interview study was conducted among a convenience sample of PLWHA in care. Of all the demographic, health status, risk history and behaviors and partnership covariates explored, only the partnership covariates were significantly associated with unprotected intercourse. Significant covariates included having a steady partner (OR and 95%CI = 4.2; 1.3, 13.5), HIV-positive (OR and 95%CI = 2.7; 1.0, 6.9 versus HIV-negative partner) or unknown serostatus partner (OR and 95%CI = 4.6; 1.1, 18.3 versus HIV-negative partner) and men who have sex with men (MSM) partnerships (OR and 95%CI = 3.0; 1.2, 7.3). Partnership covariates explained 23% of the variance in unprotected intercourse; other groups of covariates did not significantly improve model fit. Significant interaction terms between reported partner HIV status, partnership type and sexual orientation revealed the greatest likelihood of unprotected intercourse in two groups of individuals: those in steady relationships with HIV-positive partners and MSM in relationships with partners of unknown serostatus. Prevention interventions for PLWHA should focus on partnership characteristics.

Cross-Sectional Studies↗
PubMed2006

Characterization of a de novo complex chromosome rearrangement (CCR) involving chromosomes 2 and 12, associated with mental retardation and impaired speech development.

We report on a currently six-year-old patient with a de novo complex chromosome rearrangement (CCR) involving chromosomes 2 and 12. A translocation 2;12 that appeared to be reciprocal after standard banding turned out to be a complex event with seven breaks after molecular cytogenetic analyses. Array CGH analysis showed no imbalances at the breakpoints but revealed an additional microdeletion of about 80 kb on chromosome 11. The same deletion was also present in the phenotypically normal father. The patient showed relatively mild mental retardation, defined mainly as impaired speech development (orofacial dyspraxia) and psychomotor retardation. In addition, mild dysmorphic facial features like hypertelorism, a prominent philtrum and down-turned corners of the mouth were observed. We narrowed down all breakpoint regions to about 100 kb, using a panel of mapped bacterial artificial chromosome (BAC) clones for fluorescence in situ hybridization (FISH). BACs spanning or flanking all seven breakpoints were identified and no chromosomal imbalances were found consistent with the array CGH results. Our investigations resulted in the following karyotype: 46,XY,t(2;12)(2pter-->2p25.3::2p23.3-->2p25.2::2p23.3-->2p14::2q14.3-->2p14::2q14.3-->2q14.3::12q 12-->12qter;12pter-->12q12::2p25.3-->2p25.2::2q14.3-->2qter).

Child↗
PubMed2005

Epigenetic alteration at the DLK1-GTL2 imprinted domain in human neoplasia: analysis of neuroblastoma, phaeochromocytoma and Wilms' tumour.

Epigenetic alterations in the 11p15.5 imprinted gene cluster are frequent in human cancers and are associated with disordered imprinting of insulin-like growth factor (IGF)2 and H19. Recently, an imprinted gene cluster at 14q32 has been defined and includes two closely linked but reciprocally imprinted genes, DLK1 and GTL2, that have similarities to IGF2 and H19, respectively. Both GTL2 and H19 are maternally expressed RNAs with no protein product and display paternal allele promoter region methylation, and DLK1 and IGF2 are both paternally expressed. To determine whether methylation alterations within the 14q32 imprinted domain occur in human tumorigenesis, we investigated the status of the GTL2 promoter differentially methylated region (DMR) in 20 neuroblastoma tumours, 20 phaeochromocytomas and, 40 Wilms' tumours. Hypermethylation of the GTL2 promoter DMR was detected in 25% of neuroblastomas, 10% of phaeochromocytoma and 2.5% of Wilms' tumours. Tumours with GTL2 promoter DMR hypermethylation also demonstrated hypermethylation at an upstream intergenic DMR thought to represent a germline imprinting control element. Analysis of neuroblastoma cell lines revealed that GTL2 DMR hypermethylation was associated with transcriptional repression of GTL2. These epigenetic findings are similar to those reported in Wilms' tumours in which H19 repression and DMR hypermethylation is associated with loss of imprinting (LOI, biallelic expression) of IGF2. However, a neuroblastoma cell line with hypermethylation of the GTL2 promoter and intergenic DMR did not show LOI of DLK1 and although treatment with a demethylating agent restored GTL2 expression and reduced DLK1 expression. As described for IGF2/H19, epigenetic changes at DLK1/GTL2 occur in human cancers. However, these changes are not associated with DLK1 LOI highlighting differences in the imprinting control mechanisms operating in the IGF2-H19 and DLK1-GTL2 domains. GTL2 promoter and intergenic DMR hypermethylation is associated with the loss of GTL2 expression and this may contribute to tumorigenesis in a subset of human cancers.

Base Sequence↗
PubMed2005

Physicochemical and release properties of pellets coated with Kollicoat SR 30 D, a new aqueous polyvinyl acetate dispersion for extended release.

Kollicoat SR 30 D is a new aqueous colloidal polyvinyl acetate dispersion used for extended release coatings. Kollicoat SR 30 D is stable against sedimentation, has a low viscosity (54 mPas) and a negative zeta potential of -23.2 mV because of the presence of the anionic surfactant, sodium dodecyl sulfate. Because of its low minimum film formation temperature (MFT = 18 degrees C), plasticizer addition and a thermal after-treatment (curing) of coated pellets was not required. Coated pellets showed no aging or curing effect. The rate of release could be easily adjusted by varying the coating level. A subcoating layer of the hydrophilic polymer, polyvinyl alcohol, between an ibuprofen-containing core and the Kollicoat SR coating prevented the diffusion of the lipophilic, low melting ibuprofen into the polymer coating during storage. The drug release from Kollicoat SR 30 D coated pellets was almost independent of the pH and ionic strength of release medium.

Chemical Phenomena↗
PubMed2005

[Chronic radiculopathy. Use of minimally invasive percutaneous epidural neurolysis according to Racz].

Treatment of chronic low back pain exhibiting radicular symptoms poses a clinical problem that has not yet been solved. The technique of percutaneous minimally invasive neurolysis described by Racz is being performed increasingly to treat chronic radiculopathy. A total of 61 patients with corresponding symptomatology after screening for inclusion and exclusion criteria in the region of the lumbar spinal nerve were treated with the Racz catheter technique. Distinct clinical improvement was observed at the 3- and 6-month follow-ups after percutaneous minimally invasive epidural neurolysis. Subjective pain perception, quantified by the McNab score, clearly improved after 3 as well as 6 months. With the exception of partial catheter shearing in two cases and one occurrence of infection, no relevant side effects were noted. The Racz catheter technique for treatment of chronic radiculopathy following disk surgery is suitable with minimal side effects.

Analgesics↗
PubMed2005

An easy-to-use semiquantitative food record validated for energy intake by using doubly labelled water technique.

BACKGROUND: Estimating dietary intake is important for both epidemiological and clinical studies, but often lacks accuracy. OBJECTIVE: To investigate the accuracy and validity of energy intake estimated by an easy-to-use semiquantitative food record (EI(SQFR)) compared to total energy expenditure (TEE) estimated by doubly labelled water technique (EE(DLW)). DESIGN: TEE was measured in 29 nonobese subjects using the doubly labelled water method over a period of 14 days. Within this period, subjects reported their food consumption by a newly developed semiquantitative food record for 4 consecutive days. Energy intake was calculated using the German Food Code and Nutrition Data Base BLS II.3. RESULTS: A good correlation was observed between EI(SQFR) and EE(DLW) (r = 0.685, P < 0.001). The mean difference between EI(SQFR) and EE(DLW) was -1.7+/-2.6 MJ/day (-14+/-21%, P = 0.002). An underestimation of EI(SQFR) <10% was observed in nine subjects (31%), of 10-20% in six subjects (21%), and of >20% in nine subjects (31%). In five subjects (17%), an overestimation of EI(SQFR) was observed. CONCLUSIONS: The easy-to-use semiquantitative food record provided good estimates of EI in free-living and nonobese adults without prior detailed verbal instructions. The presented food record has limitations regarding accuracy at the individual level.

Adult↗
PubMed2005

Validation of a simplified physical activity record by doubly labeled water technique.

INTRODUCTION: For obtaining reliable information about physical activity in epidemiological studies, validated and easy-to-use instruments are required. Therefore, a new simplified physical activity record based on 15-min recording intervals was developed and validated. SUBJECTS: Nonobese volunteers (n = 31). MEASUREMENTS: Physical activity was recorded over a 7-day period without detailed instructions. Energy expenditure was calculated (EE(sPAR)) and compared to energy expenditure measured by doubly labelled water technique (EE(DLW)). RESULTS: A good agreement between EE(sPAR) (12.1+/-3.0) and EE(DLW) (11.7+/-3.3) with a mean difference of 0.33+/-1.55 MJ (r = 0.880, P < 0.001) was observed. The absolute difference between EE(sPAR) and EE(DLW) was < 10% in 65% of the subjects. The difference between EE(sPAR) and EE(DLW) was independent of gender, age, body weight, and body mass index. A weak positive association between the difference and total body fat was observed (r = 0.618, P < 0.001), suggesting a slight tendency to overestimate EE(sPAR) with increasing total body fat. CONCLUSION: The new simplified physical activity protocol needs no detailed instructions, provides valid estimates of physical activity in nonobese free-living adults and can be used in epidemiological studies to assess total daily energy expenditure and physical activity level.

Activities of Daily Living↗
PubMed2005

FDG-PET and MRI in potassium channel antibody-associated non-paraneoplastic limbic encephalitis: correlation with clinical course and neuropsychology.

OBJECTIVES: We report a patient with potassium channel antibody-associated non-paraneoplastic limbic encephalitis (NPLE) in whom repeated fluorodeoxyglucose-positron emission tomography (FDG-PET) and magnetic resonance imaging (MRI) are correlated with epileptic activity and memory performance during the course of disease. CASE SUMMARY: A 32-year-old woman suffered from prolonged global amnesia after two generalized tonic-clonic seizures due to NPLE. Initially, MRI showed swelling of the left hippocampus. In FDG-PET, however, bitemporomesial hypermetabolism was seen corresponding to frequent bitemporal independent seizure patterns. Also neuropsychological impairments pointed to a bitemporal involvement at this early stage. In parallel with improved control of electrographic seizure patterns, improvement was seen in FDG-PET and in memory performance. During the whole course, MRI showed only left-sided abnormalities, which correlated with a permanent verbal memory impairment. CONCLUSION: FDG-PET was more sensitive in showing the initial bitemporal involvement and correlated well with EEG findings and neuropsychological impairment in the acute phase of disease. In contrast, structural MRI better reflected persistent neuropsychological deficits.

Adult↗
PubMed2005

Association of polymorphisms and haplotypes in the human growth hormone 1 (GH1) gene with breast cancer.

The growth hormone 1 (GH1)/insulin-like growth factor I (IGF-I) axis plays an important role in the development of breast cancer. By binding to its receptor, GH1 stimulates the production of IGF-I and its binding protein IGFBP3, resulting in the regulation of cell proliferation, differentiation and apoptosis. The GH1 gene expression is regulated by a highly polymorphic proximal promoter and a distal locus control region (LCR) 14.5 kb upstream of the gene. We investigated the effect of single nucleotide polymorphisms (SNPs) in the LCR and in the promoter region and an intron 4 SNP (IVS4+90 T/A) on breast cancer risk in a large cohort of Polish and German familial breast cancer cases and controls. SNPs in the LCR did not show an influence on breast cancer risk, either alone or in haplotypes. Three SNPs in the promoter region (G-340T, A-68G/C and A-63T/C) showed an increased and four SNPs (A-137G, G-119T, G-93delG and T-4G) a decreased allele frequency in the cases compared with the controls. Two of the SNPs (A-137G and G-93delG) lead to a decreased breast cancer risk among the minor allele carriers in the joint analysis of the two populations (odds ratio (OR) 0.62, 95% confidence interval (95% CI) 0.44-0.89, P = 0.01 and OR 0.65, 95% CI 0.47-0.90, P = 0.01, respectively). Haplotype analysis with these seven promoter SNPs revealed a protective association (OR 0.61, 95% CI 0.37-1.00, P = 0.04) for the haplotype GAGdAAT, containing the G-93delG variant allele, which in the single analysis already showed a protective effect. The effect was marginally stronger in combination with the LCR GC haplotype (OR 0.49, 95% CI 0.23-1.01, P = 0.04).

Adult↗
PubMed2004

Effect of interstitial stereotactic radiosurgery on behavior and subjective handicap of epilepsy in patients with gelastic epilepsy.

Patients with symptomatic epilepsy due to hypothalamic hamartomas often are compromised not only by pharmacoresistant epileptic seizures but also by behavioral disturbances and cognitive dysfunction. We report the effect of successful treatment with stereotactic interstitial radiosurgery by intrahypothalamic implantation of 125I seeds on behavior and subjective handicap. In all patients rendered seizure-free or suffering only from auras, improvement of behavior was reported by parents and colleagues or schoolteachers. Parents' ratings according to the Child Behavior Checklist showed improvements with respect to social problems and attention. Self-ratings of quality of life by adult patients showed improvements in activities, working situation, and self-perception. These improvements were not observed in patients in whom clinically manifest seizures and interictal EEG discharges persisted after radiosurgery.

Activities of Daily Living↗