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B Pfleiderer

Publications and source records attributed to B Pfleiderer.

At least 19 recordsLinked to original sources
PubMed2005

Radiation-induced capsule tissue reactions around textured breast implants in a rat model.

Capsule fibrosis and other complications around various filled breast implants were evaluated in a rat radiation model after 12 months of implantation. Model implants, one per rat, were implanted subcutaneously. One month after subcutaneous implantation, high voltage radiation followed one half each group. A higher rate of capsule fibrosis occurred in radiated animals. Malignant tumors at the implantation site developed in 40% of radiated and 24% of non-radiated animals, with a much higher rate of mitosis in the radiated group (Mann-Whitney, P=0.008). The presence of an implant is a cofactor for tumor development in rats (chi2-test, chi2=6.927; P=0.008) as well as radiation, since none of the control animals developed tumors. Applied to humans, capsule contracture (fibrosis) is a common complication of radiation, while development of radiation-induced sarcoma is a rare complication after postoperative radiotherapy by all account. Still further long-term follow-up human studies are necessary.

Animals↗
PubMed2004

Metabolic disturbances during short exercises in dermatomyositis revealed by real-time functional 31P magnetic resonance spectroscopy.

OBJECTIVE: (31)P magnetic resonance spectroscopy (MRS) is useful for evaluating metabolic disturbances in dermatomyositis (DM). However, short-term alterations of metabolic parameters such as Pi/PCr (inorganic phosphate/phosphocreatine) have not been assessed in detail, although they may reveal insights into the origin of the known long-term changes. We therefore performed real-time functional (31)P MRS to find out if there are characteristic short-term alterations of metabolic dynamics during muscular exercise and if they are of diagnostic relevance. METHODS: MRS measurements were performed on lower calf muscles of 10 DM patients and 18 healthy subjects throughout five short (1 min) cycles of submaximal exercise (50% maximum voluntary contraction). RESULTS: Pi/PCr ratios during exercise increased in patients and controls. They rapidly returned to baseline values in the controls, but both Pi and PCr remained above baseline values in patients and resulted in irregular Pi/PCr ratios. This was true for each individual patient, but resulted in broad variation in individual Pi/PCr values. To compare groups with limited patient numbers, it was therefore more appropriate to use a recovery index, i.e. the quotient of the Pi/PCr ratio during and after exercise, which was independent of individual parameters, such as age and the work/energy cost ratio. CONCLUSION: Evaluation of short-term changes by real-time functional (31)P MRS provides insight into alterations of Pi/PCr ratios and could improve diagnostic parameters in DM.

Adenosine Triphosphate↗
PubMed2004

N-acetylaspartate levels of left frontal cortex are associated with verbal intelligence in women but not in men: a proton magnetic resonance spectroscopy study.

The left frontal cortex plays an important role in executive function and complex language processing inclusive of spoken language. The purpose of this work was to assess metabolite levels in the left and right prefrontal cortex and left anterior cingulum by proton magnetic resonance spectroscopy and relate results to verbal intelligence (Wechsler Adult Intelligence Scale revised) in a sample of college-educated healthy volunteers (dorsolateral prefrontal cortex [DLPFC]: n=52, 23 females, and left anterior cingulum: n=62, 22 females; age range: 20-75 years). In women only, N-acetylaspartate in the DLPFC and in the left anterior cingulate cortex was positively correlated with vocabulary scores. Our data support the hypothesis of existing gender differences regarding the involvement of the left frontal cortex in verbal processing as reflected in different correlations of specific metabolites with verbal scores.

Adult↗
PubMed2003

Magnetic resonance imaging protocols for examination of the neurocranium at 3 T.

The increasing availability of high-field (3 T) MR scanners requires adapting and optimizing clinical imaging protocols to exploit the theoretically higher signal-to-noise ratio (SNR) of the higher field strength. Our aim was to establish reliable and stable protocols meeting the clinical demands for imaging the neurocranium at 3 T. Two hundred patients with a broad range of indications received an examination of the neurocranium with an appropriate assortment of imaging techniques at 3 T. Several imaging parameters were optimized. Keeping scan times comparable to those at 1.5 T we increased spatial resolution. Contrast-enhanced and non-enhanced T1-weighted imaging was best applying gradient-echo and inversion recovery (rather than spin-echo) techniques, respectively. For fluid-attenuated inversion recovery (FLAIR) imaging a TE of 120 ms yielded optimum contrast-to-noise ratio (CNR). High-resolution isotropic 3D data sets were acquired within reasonable scan times. Some artifacts were pronounced, but generally imaging profited from the higher SNR. We present a set of optimized examination protocols for neuroimaging at 3 T, which proved to be reliable in a clinical routine setting.

Adult↗
PubMed2003

Influence of local complications on capsule formation around model implants in a rat model.

We studied the capsule formation around various filled breast implants and other related changes in distant organs (e.g., liver, spleen, lymph nodes) in a rat model 3 and 6 months after implantation. Model implants, one per rat, (filled with saline, n = 19; silicone, n = 14; cohesive silicone, n = 17; and hydrogel, n = 19) were implanted subcutaneous in the lower back of rats. The animals were sacrificed regularly after 3 and 6 months of implantation or when wound defects occurred. The capsules and organs were examined histologically, and immunohistology of the capsules was performed. A monoclonal antibody specific for AIF-1 (allograft inflammatory factor 1) was used to detect activated macrophages. Wound defects occurred most frequently after implantation of saline and hydrogel implants. Increased capsule thickness was associated with increased grade of inflammation, fibrosis, and the type of implant filling. There was a significant positive correlation between capsule thickness, presence of chronic inflammation, and AIF-1-positive macrophages (p < 0.0001), indicating that inflammation plays an important role in capsule formation. Remarkably, saline and silicone implants (in absence of local complications) cause only a blande slight fibrosis in capsules after 6 months of implantation, whereas capsules around cohesive silicone implants exhibited a more severe fibrosis with an increased capsule thickness. Most importantly, hydrogel seems to be most potent to induce an inflammatory infiltrate with AIF-1 expressing macrophages at the implantation site, independent of implantation time, and capsules also produced a significant increase in thickness after 6 months.

Animals↗
PubMed2003

Metabolic changes within the left dorsolateral prefrontal cortex occurring with electroconvulsive therapy in patients with treatment resistant unipolar depression.

BACKGROUND: The dorsolateral prefrontal cortex (DLPFC) is involved in the pathophysiology of major depression. In particular, metabolic (functional hypometabolism) and structural alterations have been described. In this study metabolic changes within the DLPFC of severely depressed patients before and after electroconvulsive therapy (ECT) were evaluated by proton STEAM spectroscopy (1H-MRS). METHOD: Twelve severely depressed patients with a diagnosis of major depressive episode, unipolar with melancholic features (DSM-IV), were enrolled, and the left dorsolateral prefrontal cortex (DLPFC) was investigated before and after unilateral ECT by 1H-MRS. Three of the four non-responding patients were remeasured a third time after a combined ECT/antidepressant pharmacotherapy. The results were compared with 12 age- and gender-matched controls. RESULTS: In depressed patients reduced glutamate/glutamine (Glx) levels were measured pre-ECT; Glx concentrations correlated negatively with severity of depression. After successful treatment, Glx increased significantly and levels no longer differed from those of age-matched controls. CONCLUSIONS: Our results indicate that major depressive disorder is accompanied by state-dependent metabolic alterations, especially in glutamate/glutamine metabolism, which can be reversed by successful ECT.

Aged↗
PubMed2002

Visualization of auditory habituation by fMRI.

The aim of this study was to measure and quantify habituation phenomena within the auditory cortex of 18 healthy subjects by means of fMRI. Auditory stimulation was done by digitally generated pulsed (nu = 5 Hz) 800-Hz sine tones with three alternating ON (duration 2 min) and OFF (1 min) periods. Binaural stimulation resulted in symmetrical bihemispheric activation of the auditory cortex. Our data revealed a characteristic signal decay to repeated acoustic stimulation: the response to the second was even more pronounced, and the third stimulation block significantly lower compared to the first. Thus, our data clearly demonstrate habituation phenomena, probably due to reduced neuronal activity with increased duration and/or frequency of stimuli.

Acoustic Stimulation↗
PubMed2002

Silicone breast implants: correlation between implant ruptures, magnetic resonance spectroscopically estimated silicone presence in the liver, antibody status and clinical symptoms.

OBJECTIVE: To determine the impact of implant integrity on clinical symptoms and antibody status in women with silicone breast implants (SBIs). METHODS: Ninety consecutive women were examined by means of magnetic resonance imaging (MRI) to assess the integrity of their silicone breast implants. The presence of silicone in the liver was estimated by (1)H localized stimulated echo acquisition mode (STEAM) magnetic resonance spectroscopy (MRS). Results were correlated with patients' complaints, as evaluated by a standardized questionnaire, physical examination by a rheumatologist and antibody screening. RESULTS: Breast MRI revealed defects in 24 patients (26.6%); in 13 (54.2%) of these women, silicone was detected in the liver by MRS. Of the 66 patients with MRI-estimated intact implants, 15 (22.7%) had apparent silicone in their liver, arguing for gel bleeding. Clinically, two patients had had rheumatoid arthritis before SBIs, whereas the other patients revealed no typical symptoms of arthritis or connective tissue disease (CTD). The patients with MRS evidence of silicone in the liver had no statistically significant differences in their complaints with the exception of the most frequent symptom, tingling/numbness of the fingers (82.1 vs 51.6%, P=0.006). A positive pattern of antinuclear antibodies (ANA) was obtained in 13 of the 28 MRS-positive patients (46.4%) and in 15 of the 62 MRS-negative patients (24.2%, P=0.033). However, in only one of these 28 ANA-positive patients was a specific weak antibody titre against SS-A detected by ELISA. CONCLUSION: Implant integrity has no major impact on rheumatic symptoms of women with SBIs. This finding supports the standpoint that silicone does not cause either a specific CTD or any other distinct disease entity. However, the moderately increased incidences of ANA-positivity and neuropathy-associated symptoms require explanation.

Adult↗
PubMed2001

Determination of low molecular weight silicones in plasma and blood of women after exposure to silicone breast implants by GC/MS.

A sensitive, one-step sample preparation method for detection of volatile, low molecular weight (LMW) cyclic silicones hexamethylcyclotrisiloxane (D3), octamethyl-cyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) in plasma and blood using gas chromatography coupled with mass spectrometry (GC/MS, SIM mode) is presented. In spiked experiments, extraction efficiencies for these siloxanes (100-20 000 ng/mL) were approximately 90% for plasma and approximately 80% for blood; only in the case of D3 was the recovery very low. Plasma and blood of women who are or were exposed to silicone gel-filled implants and of control subjects were analyzed for low molecular weight silicones. D3-D6 were not detectable in control plasma or blood. Although the investigated numbers of patients samples are very limited, and thus, no statistical analysis is possible, our data clearly show a general increase in the amount of LMW cyclic siloxanes in the bodies of women with silicone implants. In particular, several years after ruptured silicone implants were removed, siloxanes could still be found in blood samples from several women. Siloxane compound D3 varied between 6 and 12 ng/mL (plasma) and between 20 and 28 ng/mL (blood), whereas the concentration range of D4 was 14-50 ng/mL (plasma) and 79-92 ng/mL (blood). D5 and D6, with one exception, could not be detected.

Adult↗
PubMed2001

[MRI and MR spectroscopy after silicone breast implants in the female breast].

This paper reviews the evaluation of the breast of women by MR-techniques after implantation with silicon gel protheses. The main topics are the diagnosis of implant defects such as extensive "gel bleed" and intra- and extracapsular ruptures. Moreover, the MR-detection of siliconomas (encapsulated silicone) and differentiation from malignomas as well as MR-features of chronic foreign body reactions are presented. "Gel bleed" is difficult to diagnose unambiguously by MRI alone. The "linguini" sign is the only reliable mans to diagnose intracapsular ruptures. The presence of silicone outside the implant capsule indicates extracapsular rupture. The MR-spectroscopic detection of silicone in the liver suggests after short implantation times and a normal MR scan the diagnosis "gel bleed", and after longer implantation times of more than 10 years and missing "linguini" sign the diagnosis of ruptures due to a dissolved shell of the implant. MRI, in comparison to other imaging modalities, has the highest specificity and sensitivity in the diagnosis of implant defects. Due to its high costs, however, MR is not suitable as a screening tool and should only be used in cases of sonographic suspected rupture or after radical mastectomy. In these cases MRI is the method of choice.

Breast↗
PubMed2000

[Spectroscopic imaging (1H-2D-CSI) of the prostate: sequence optimization and correlation with histopathological results].

PURPOSE: Methodological optimization of a 1H MR spectroscopic imaging sequence (1H-2D-CSI) and evaluation of its potential to diagnose prostate cancer as validated by histopathological maps. METHODS: The prostates of 18 patients were evaluated by 1H-MR-CSI (voxel dimension: 1 cm3) at 1.5 Tesla. This sequence was additionally combined with a frequency selective fat suppression. RESULTS: It was possible to distinguish prostate carcinoma from prostate hyperplasia spectroscopically by the ratio of citrate/(choline + creatine). Differentiation of high-grade prostatic intraepithelial neoplasia (PIN, high-grade) from prostate carcinoma was not unambiguously possible. Prediction of tumor differentiation was not possible by the ratio of citrate/(choline + creatine) by our maximum spatial resolution of 1 cm3. CONCLUSION: 1H-2D-CSI is suitable for tumor detection. Tumor differentiation was not possible with the spatial resolution used.

Aged↗
PubMed1999

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Journal Article↗
PubMed1999

Biodegradation of polysiloxanes in lymph nodes of rats measured with 29Si NMR.

Linear and cyclic polysiloxanes and extracts (free polymer) from a silicone gel-filled implant are used to investigate the reactivity of silicones in vivo. Aqueous emulsions of polysiloxanes and controls (without polysiloxanes) are injected once (day 0, approximately 10% w/v) or six times (starting at day 0, every 14 days, approximately 3% w/v) in the right thigh of rats and the popliteal and lumbar lymph nodes are harvested (3 rats per time point and compound investigated) at 2, 16, 30, 44, 58 and 72 days after the injection. 29Si NMR spectroscopy is used to detect and evaluate the presence of polysiloxanes and their metabolites in the lymph nodes. In addition to the resonance associated with the polysiloxane injected (approximately -20 ppm), the NMR spectra of lymph nodes show new resonances that are attributed to partially hydrolyzed polysiloxanes (-5 to -15 ppm) and silica (-90 to - 120 ppm). These resonances are not present in polysiloxanes emulsions before injection or in the lymph nodes of controls. Our results demonstrate that all polysiloxanes and extracts from silicone gel-filled implants are biotransformed in the lymph nodes, but high molecular weight polymer degrades at a slower rate than oligomers.

Animals↗
PubMed1996

Silicone gel-filled breast implants in women: findings at H-1 MR spectroscopy.

PURPOSE: To evaluate, at hydrogen-1 magnetic resonance (MR) spectroscopy, the effect of implantation time, implant status, and implant removal on the amount of silicone in the liver in women with silicone gel-filled breast prostheses. MATERIALS AND METHODS: The study population included 55 women (39 patients with silicone gel-filled prostheses and seven from whom implants had been removed, and nine control subjects [eight with no implant and one with saline-filled implants]). Stimulated-echo acquisition mode, or STEAM, H-1 MR spectroscopy was performed to determine the concentration of silicone in the liver. Implant status at the time of spectroscopy was diagnosed at MR imaging. RESULTS: Twenty of 39 (51%) women with implants had ruptured prostheses. Resonances associated with the presence of silicone and partially hydrolyzed silicone (0.3 to -0.8 ppm with respect to water at 4.7 ppm) and other resonances that are not yet assigned (-2 to -5 ppm) were detected in 27 (69%) of the 39 women (17 with ruptured implants). Relative signal intensities of the silicone species detected in the liver in these women were found to vary substantially and were not correlated with the status of the implants (P > .70). Silicone resonances were not detected in the livers in the nine control subjects. After implant removal, no resonances between 0.3 and -0.8 ppm were observed in six of seven women, but silicone-related peaks were still detectable in the region of -2 to -5 ppm. CONCLUSION: Proton MR spectra obtained in the liver of women with silicone gel-filled breast implants helped measure silicone exposure.

Adult↗
PubMed1995

Study of aging of silicone rubber biomaterials with NMR.

Multinuclear nuclear magnetic resonance (NMR) spectroscopy (29Si, 13C, 1H) is used to characterize the aging process of silicone rubber-based biomaterials in a rat model. 1H NMR relaxation measurements (spin-lattice, T1, and spin-spin, T2, relaxation times) were performed to better understand the molecular dynamics of polysiloxane chains in implants. After 1 year of implantation in animals, changes in the 1H T2 relaxation times and the NMR spectra were observed in polydimethylsiloxane, Silastic sheets and chin implants, while these measurements remain unchanged in finger joints. Very small amounts of fat were detected in all types of silicone rubber implants at the end of the implantation period. This work shows that free silicone migrates from the implants to adjacent tissues and distant sites, such as spleen or liver, and is chemically modified.

Animals↗
PubMed1995

Migration and accumulation of silicone in the liver of women with silicone gel-filled breast implants.

1H NMR localized spectroscopy (STEAM), combined with echocardiography (ECG), respiratory gating, and water and fat suppression, was used to quantify silicone concentrations in the liver of women with silicone gel-filled breast implants. Localized spectroscopy was performed on 15 patients with silicone gel-filled breast prostheses and on eight volunteers with no implants. The 1H spectra in the liver of patients showed silicone resonances from 0.3 to -0.8 ppm, attributable to protons in the methyl groups of silicone. The presence of silicone in the liver could first be detected 3-4 years after breast prostheses implantation. No correlation between silicone concentrations and implantation times was observed. However, our results indicated that silicone concentrations may reflect implant integrity: detectable silicone concentrations in the liver appeared to be higher when the implants were ruptured than when the implants appeared intact. Moreover, new resonances in the range of -2.6 to -4 ppm were observed in most patients after long-term implantation. As these species increase with implantation time, the new resonances may reflect chemically changed silicone (paramagnetically shifted silicon complexes bound to iron) accumulated over time. The sensitivity of 1H NMR localized spectroscopy is sufficient to detect silicon concentrations as low as 0.20 mM. Results from one patient whose implants had been removed 14 months prior to the NMR examination showed no detectable silicone in the liver, indicating that it may have been excreted via bile or degraded to silica and high coordinated silicon complexes. Quantitative 1H localized spectroscopy of the liver in women with silicone gel-filled breast implants may provide valuable information concerning silicone accumulation and degradation in vivo, as well as about the kinetics of its elimination from the body after implant removal.

Breast Implants↗
PubMed1995

Manipulating rat lens glucose metabolism with exogenous substrates.

Diabetic lens glucose metabolism in vivo can be altered by a number of exogenous substrates. We have chosen two, one a glucose epimer (mannose) and the other a glycolytic intermediate (pyruvate), to demonstrate the possibility of this approach. D(+)-Mannose is a D(+)-glucose epimer but in lenses incubated in 35.5 mM mannose, no mannitol (the sorbitol equivalent) was detected, while both lactate production and 31P profile appeared normal. Mannose therefore is a good glucose substitute causing no polyol formation. Mannose metabolism in the rat lens in vivo was then examined. Diabetic rats fed mannose-enriched diet over a period of 14 days showed retardation of changes in 31P metabolites, specifically the levels of phosphorylcholine and glycerophosphorylcholine, suggesting a protective effect. Rat lenses incubated in 35.5 mM glucose in the presence of 5 mM pyruvate (pyr) showed 50% lower sorbitol than without pyr. With 5 mM pyr in the drinking water, i.e. pretreatment in vivo during a 3-day diabetes induction period, the diabetic rat lens accumulated acetate and alanine when incubated in the presence of pyr. The decrease in sorbitol was most likely due to a lower glucose flux rather than an increased polyol dehydrogenase activity. Increasing glucose concentration from 5.5 to 35.5 mM or provision of exogenous pyr both caused an intermediate increase in O2 consumption in the normal lens; a maximal activity was reached with both 35.5 mM glucose and 5 mM pyruvate in the incubating medium. In the diabetic lens, O2 consumption could reach the intermediate but not the maximal level. Dietary pyr pre-treatment also prevented normal and diabetic lenses from maximal pyr-stimulated O2 consumption. The NMR and O2 consumption data together indicated activation of alanine dehydrogenase and saturation of Krebs cycle. It appears that dietary supplement of mannose can preserve 31P membrane metabolites in the diabetic lens. Mannose can be used in conjunction with hypoglycemic therapy for the management of diabetic cataract. In addition, pyruvate may be effective in enhancing lens energy metabolism and lower sorbitol production.

Animals↗