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B Pfleiderer

Publications and source records attributed to B Pfleiderer.

18 recordsLinked to original sources
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↗
PubMed1993

In vivo 1H chemical shift imaging of silicone implants.

In order to study the aging process (i.e., silicone migration, fat infiltration) of silicone (polydimethylsiloxane, PDMS) based biomaterials in living subjects by NMR imaging, a hybrid 1H selective excitation and saturation chemical shift imaging technique (IR/CHESS-CSSE) has been developed. This sequence allows selective mapping of the distribution of silicone protons in vivo, while suppressing the contributions of fat and water. Our results indicate that a combined inversion recovery and CHESS pulse, followed by a spoiler gradient, must be applied to suppress all contributions of fat protons to the NMR signal. The sensitivity of our experiments allows the detection of a chemically unchanged silicone concentration of 5% in a voxel of 0.9 mm3 at a signal/noise ratio of 2.

Adipose Tissue↗
PubMed1993

In vivo degradation of silicones.

29Si nuclear magnetic resonance (NMR) spectroscopy is applied to study the degradation of polysiloxanes (silicones) in vivo. Our results with animal models show that silicone migrates from the implant to the liver (29Si resonance at -20 ppm) and new silicon containing compounds form after the silicones are introduced into the rats. The new 29Si resonances in the chemical shift range of -40 to -85 ppm are related to hydrolyzed silicone, those at -90 to -115 ppm are indicative of the presence of silica (SiO2), and the peaks observed at -120 to -150 are related to high coordinated silicon complexes. These resonances are not present in the 29Si spectra of the silicones before implantation. Our findings demonstrate that silicones are not metabolically inert.

Animals↗
PubMed1993

In vivo localized proton NMR spectroscopy of silicone.

1H NMR localized spectroscopy (STEAM) can assess unambiguously the presence of free chemically unchanged silicone in animal tissue after injection of silicone oil. Although the signal-to-noise ratio obtained in 1H imaging is sufficient to detect the distribution of relatively large amounts of silicone in vivo, the specificity of silicone detection can be improved by using 1H localized spectroscopy techniques. The sensitivity of the STEAM experiments is sufficient to detect silicone at a concentration of 0.5% in a voxel of 27 mm3. Preliminary results from rats with silicone gel-filled implants show no detectable amounts of silicone in sites such as lymph nodes, the liver or the spleen, 3 or 6 months after implantation.

Animals↗
PubMed1993

Migration and biodegradation of free silicone from silicone gel-filled implants after long-term implantation.

In vivo 1H NMR chemical shift imaging (CSI), 1H NMR localized spectroscopy (STEAM) and multinuclear NMR spectroscopy (29Si, 13C, 1H) were used to characterize the aging process of silicone gel-filled implants in a rat model after long-term implantation. Although no significant changes could be observed in the implants or surrounding tissue by in vivo 1H chemical shift imaging, in vivo 1H localized spectroscopy of the livers from the longer term population revealed the presence of silicone. Ex vivo 29Si spectroscopy of the liver, spleen, and the capsule formed around the 9 and 12 month implants clearly demonstrated and confirmed for the first time that a significant amount of free silicone migrates from silicone gel-filled implants. Also, these results show that silicones are not metabolically inert, and their biodegradation in tissue and within the implant can be monitored after 9 and 12 months by changes in the 29Si chemical shifts seen in corresponding ex vivo spectra. The NMR findings are supported by those obtained by atomic absorption spectroscopy. Silicone aging changes not only the chemical composition of the gel, but also its proton T2 relaxation times, which increase with long implantation times. The three dimensional structure of the gel disintegrates (i.e., polymer chain rupture), increasing the molecular mobility of the polymer and, consequently, its protons T2 values. The relaxation data we obtained reflect this in vivo degradation, especially in the case of implant rupture. Additionally, small concentrations of fat in the silicone gel were found within the implants. The presence of these lipophilic substances also might increase the T2 values (plasticizer effect). These findings may assist in evaluating the implant integrity and disease symptoms related to their presence in humans.

Animals↗
PubMed1993

Echo-planar chemical shift imaging of silicone gel prostheses.

We have developed an echo-planar (EP) proton chemical shift imaging (CSI) MR technique that allow us to discriminate the polydimethylsiloxane (PDMS, silicone) proton MR signal from that of the fat and water protons found in tissues, in order to map the distribution of PDMA in humans who have silicone gel prostheses. Silicone gel-filled prosthetic implants induce histologic changes in the surrounding tissue which are attributed to the leakage of free PDMS from the prosthesis. The T2 relaxation measurements of three silicone gels show that there are two components in them, each with a different degree of molecular mobility. The presence of free silicone is confirmed by chloroform extraction, which removed 14-28% of the material. This free polymer present in the gel can pass through the intact or ruptured membrane of the implant into the surrounding tissue. Our preliminary imaging results indicate that EP-CSI MR might be useful as a diagnostic technique for implant malfunction.

Breast↗
PubMed1988

The semiotics of ritual healing in a North Indian Muslim shrine.

This paper reports phenomenological and semiotic research on therapeutic rituals in a Muslim shrine, concentrating on three cases studies. Women describe their experiences while being possessed by evil spirits and while undergoing ritual healing in the shrine. The semiotic structuring of their experiences and perceptions are analyzed as a culturally coded system of exorcism.

Adolescent↗