PubMed Health⌕ Search

Biomedical subjects

M Becker

Publications and source records attributed to M Becker.

At least 19 recordsLinked to original sources
PubMed2007

The SERS and TERS effects obtained by gold droplets on top of Si nanowires.

We show that hemispherical gold droplets on top of silicon nanowires when grown by the vapor-liquid-solid (VLS) mechanism, can produce a significant enhancement of Raman scattered signals. Signal enhancement for a few or even just single gold droplets is demonstrated by analyzing the enhanced Raman signature of malachite green molecules. For this experiment, trenches (approximately 800 nm wide) were etched in a silicon-on-insulator (SOI) wafer along <110> crystallographic directions that constitute sidewalls ({110} surfaces) suitable for the growth of silicon nanowires in <111> directions with the intention that the gold droplets on the silicon nanowires can meet somewhere in the trench when growth time is carefully selected. Another way to realize gold nanostructures in close vicinity is to attach a silicon nanowire with a gold droplet onto an atomic force microscopy (AFM) tip and to bring this tip toward another gold-coated AFM tip where malachite green molecules were deposited prior to the measurements. In both experiments, signal enhancement of characteristic Raman bands of malachite green molecules was observed. This indicates that silicon nanowires with gold droplets atop can act as efficient probes for tip-enhanced Raman spectroscopy (TERS). In our article, we show that a nanowire TERS probe can be fabricated by welding nanowires with gold droplets to AFM tips in a scanning electron microscope (SEM). TERS tips made from nanowires could improve the spatial resolution of Raman spectroscopy so that measurements on the nanometer scale are possible.

Gold↗
PubMed2006

[A symptom oriented diagnostic approach to the workup of secondary forms of uveitis -- an internet based program for better and easier orientation in differential diagnosis].

BACKGROUND: The long list of ophthalmologic findings and symptoms at a baseline examination of a patient with uveitis can have an impact on further laboratory workup and differential diagnosis. METHODS: Based on publications and previous work, a decision tree was transformed into the expert system shell D3. A web-based Java Servlet was then programmed and published on our website (http://www.uveitiscenter.de at DiagnoseFinder). Ophthalmologic findings and symptoms of the patient can be checked with this online questionnaire, and recommendations for further laboratory tests and further care of the patient received. RESULTS: Retrospective analysis of 62 patients with characteristic features of secondary uveitis showed a good correlation between the actual diagnosis of the patient and the diagnosis found by the program. In 74% of cases, the correct diagnosis was found among other options. In 37%, only the correct diagnosis was found, while in 37% the correct diagnosis was found among other probable diagnoses. Not all forms of secondary uveitis were found easily by the software. CONCLUSION: This program is meant to be an easily accessible and simply employable help for the care of patients with a secondary form of uveitis. It is intended to be a support not only for residents in particular, but also for ophthalmologists in private practice who rarely treat patients with uveitis.

Decision Making, Computer-Assisted↗
PubMed2006

[Chondroblastic osteosarcoma of the mandible: a case report with 14 years follow-up].

INTRODUCTION: Osteosarcoma, the second most frequent primary malignant bone tumor, is usually found in long bones: femur, tibia or humerus with only 6 to 7% of cases occurring in the jaws. Patients with osteosarcoma of the mandible usually complain of a swelling, which can be painful or not, accompanied by paresthesia of one of the trigeminal nerve branches in about 20% of cases. OBSERVATION: We report a case of chondroblastic osteosarcoma of the mandible affecting a 33-year-old woman with 14 years follow-up illustrating the difficulties of a rapid diagnosis. DISCUSSION: The prognosis of osteosarcoma of the mandible relies on its histological grade and the amount of time elapsing from diagnosis to treatment onset. The treatment of choice is radical surgery providing a 5-year survival rate up to 80%. The definitive surgical treatment is usually performed only after several interventions because operative-room pathology cannot be obtained due to the necessity of decalcification. In order to avoid multiple resections, an interim bridging with a reconstructive plate with a condylar head can be proposed before definitive graft reconstruction. The prognosis of osteosarcoma of the mandible is better than that of long bones. Chemotherapy or radiotherapy, which are very efficient for osteosarcoma in general, do not change the prognosis of osteosarcoma of the mandible.

Adult↗
PubMed2005

Analysis of myocardial deformation based on pixel tracking in two dimensional echocardiographic images enables quantitative assessment of regional left ventricular function.

OBJECTIVE: To evaluate whether myocardial strain and strain rate calculated from two dimensional echocardiography by automatic frame-by-frame tracking of natural acoustic markers enables objective description of regional left ventricular (LV) function. METHODS: In 64 patients parasternal two dimensional echocardiographic views at the apical, mid-ventricular and basal levels were obtained. An automatic frame-by-frame tracking system of natural acoustic echocardiographic markers was used to calculate radial strain, circumferential strain, radial strain rate and circumferential strain rate for each LV segment in a 16 segment model. Cardiac magnetic resonance imaging (cMRI) was performed to define segmental LV function as normokinetic, hypokinetic or akinetic. RESULTS: Image quality was sufficient for adequate strain and strain-rate analysis from two dimensional echocardiographic images obtained from parasternal views in 88% of segments. Obtained radial strain data were highly reproducible and analysis was affected by only small intraobserver (mean 4.4 (SD 1.6)%) and interobserver variabilities (7.3 (2.5)%). Each of the analysed strain and strain-rate parameters was significantly different between segments defined as normokinetic, hypokinetic or akinetic by cMRI (radial strain 36.8 (10.5)%, 24.1 (7.5)% and 13.4 (4.8)%, respectively, p < 0.001). Peak systolic radial strain enabled detection of hypokinesis or akinesis with a sensitivity of 83.5% and a specificity of 83.5% (cut off value 29.1%, receiver operating characteristic (ROC) curve area 0.905, 95% CI 0.883 to 0.923). Peak systolic radial strain analysis also enabled detection of akinesis versus hypokinesis with a sensitivity of 82.7% and a specificity of 94.5% (cut off value 21.0%, ROC curve area 0.946). Peak systolic radial strain-rate analysis was less accurate than peak systolic radial strain analysis to detect cMRI-defined segmental function abnormalities. The accuracy of peak systolic circumferential strain and strain rate was similar to that of corresponding radial parameters. CONCLUSIONS: Frame-by-frame tracking of acoustic markers in two dimensional echocardiographic images enables accurate analysis of regional systolic LV function.

Adult↗
PubMed2005

[Therapy for infertile couples].

Therapy for infertile couples comprises gender-specific as well as couple-specific aspects. Diagnostic and therapeutic procedures focus on the causes of the infertility such as refertilization or epididymovasostomy on the one hand and assisted fertilization with extracted spermatozoa on the other. Using an interdisciplinary approach including urology, gynecology, reproductive medicine and human genetics, the treating physicians are able to fulfil the desire of infertile couples for a healthy child in many cases.

Couples Therapy↗
PubMed2005

[A federal technical college for blacksmiths].

In 1890 the former Veterinary School of Zurich received the order to build a "Eidgenössische Lehrschmiede" (Federal School for Black Smiths) on its campus. It was the intention not only to get more space but simultaneously to build a representative edifice. To make the most of the site the building was to be placed immediately at the wall of the channel of the river Sihl. But this was against the urban regulations of the city of Zurich. During the negotiations with the Council of Zurich the Veterinary School was elevated to a faculty of the university in 1901. All the emphasis now was laid on the changeover to the university and additionally the matter "smithy" was delayed because of the need of a larger building of the institute for anatomy. Finally the huge changes in the private and public transport by trains and motor car reduced the importance of a school for black smiths. However the importance of other projects gained like the enlargement of the stables. The beginning of the First World War buried all plans of a school for black smiths.

Animals↗
PubMed2005

[Indications and results of operative treatment in birth-related brachial plexus injuries].

INTRODUCTION: A review of the literature reveals that under conventional treatment alone or in combination with secondary muscle/tendon transfer about 4 to 43 % of cases show incomplete recovery with severe functional and/or aesthetic impairment. When these patients undergo early microsurgical brachial plexus revision, a regeneration without any significant functional and/or aesthetic impairment can be achieved in 80 to 90 % of the cases. Moreover, microsurgical reconstruction of the brachial plexus does increase the possibilities of secondary muscle/tendon transfers. MATERIALS AND METHODS: Our concept is based on our experience with more than 1700 patients presenting with brachial plexus lesions between 1981 and 2000 who were treated in our institution. Patient selection is done according a standardized algorithm which is presented. There were 418 obstetrical brachial plexus lesions. 189 could be treated conservatively. In 225 cases operative treatment was necessary. 104 cases underwent early revision of the brachial plexus and secondary tendon transfer was done in 121 patients. RESULTS: Personal results and an analysis of the literature reveal that in C5/C6 lesions good shoulder function can be achieved in 60 to 80 %, especially if the accessory nerve is routinely used. Good elbow function can be expected in over 90 %. In C5/C6/C7 lesions, there are only slightly inferior results. In both groups there is a significant functional improvement by secondary tendon transfer at the age of two to three years. In the rare C5 - Th1 lesions, the functional results depend on the number and quality of the remaining roots. CONCLUSIONS: Provided there is good patient selection, severe obstetrical brachial plexus injuries should be scheduled for early microsurgical revision. There is no need to wait for a frustrating spontaneous recovery.

Adolescent↗
PubMed2005

Polymorphisms of UDP-glucuronosyltransferase 1A7 are not involved in pancreatic diseases.

BACKGROUND: Xenobiotic mediated cellular injury is thought to play a major role in the pathogenesis of pancreatic diseases. Genetic variations that reduce the expression or activity of detoxifying phase II biotransformation enzymes such as the UDP-glucuronosyltransferases might be important in this respect. Recently, a UGT1A7 low detoxification activity allele, UGT1A7*3, has been linked to pancreatic cancer and alcoholic chronic pancreatitis. OBJECTIVE: To investigate whether UGT1A7 polymorphisms contribute to the risk of pancreatitis and pancreatic cancer. METHODS: Genetic polymorphisms in the UGT1A7 gene were assessed in a large cohort of patients with different types of pancreatitis and pancreatic cancer originating from the Czech Republic (n = 93), Germany (n = 638), Netherlands (n = 136), and Switzerland (n = 106), and in healthy (n = 1409) and alcoholic (n = 123) controls from the same populations. Polymorphisms were determined by melting curve analysis using fluorescence resonance energy transfer probes. In addition, 229 Dutch subjects were analysed by restriction fragment length polymorphism. RESULTS: The frequencies of UGT1A7 genotypes did not differ between patients with acute or chronic pancreatitis or pancreatic adenocarcinoma and alcoholic and healthy controls. CONCLUSIONS: The data suggest that, in contrast to earlier studies, UGT1A7 polymorphisms do not predispose patients to the development of pancreatic cancer and pancreatitis.

Adenocarcinoma↗
PubMed2004

Anticancer drug response and expression of molecular markers in early-passage xenotransplanted colon carcinomas.

Despite some success in the treatment of colorectal carcinomas, novel rational therapies targeting specific cancer-related molecules are under development and urgently needed. These approaches need careful preclinical evaluation in models that closely mirror the clinical situation. Therefore, we established a panel of 15 xenotransplantable tumours directly from fresh surgical material. We showed that both the histology and expression of tumour-associated markers (Epithelial Cell Adhesion molecule (EpCAM), E-cadherin, carcinoembryonic antigen (CEA)) could be maintained during passaging in nude mice. Xenotransplanted tumours were characterised for chemosensitivity and revealed a response rate of 5/15 (33%) for 5-fluorouracil (5-FU), 15/15 (100%) for irinotecan and 8/14 (57%) for oxaliplatin. 5 patients out of 15 were treated with cytostatics because of synchronous metastases. The response to chemotherapy in these patients coincided very closely with the response of the individual xenografts. All of the xenografts expressed the proliferation marker Ki67 and the nuclear enzyme, Topoisomerase IIalpha (Topo IIalpha) at the protein level. Most of the xenografts also expressed the tumour suppressor, p53 (9/14) and the nuclear enzyme Topoisomerase Ialpha (Topo Ialpha) (13/14) at the protein level. Interestingly, the presence of a K-ras mutation in codon 12 (5/15 xenografts) coincided with a low response rate towards oxaliplatin. This observation needs further confirmation using a larger number of tumours. In conclusion, we were able to establish transplantable xenografts suitable to mimic the clinical situation. These well characterised models are useful tools for the preclinical development of novel therapeutic approaches and for investigating translational research aspects.

Animals↗
PubMed2004

In vivo models for endocrine-dependent breast carcinomas: special considerations of clinical relevance.

Tumours in hormone-regulated organs such as the breast, prostate or ovaries are among the most frequent malignancies. Because of their endocrine-dependent development and growth, they offer a unique opportunity for antihormonal treatment either single or long-term or in combination with radio- or chemotherapy. A prominent example is breast carcinoma, for which the anti-oestrogen tamoxifen has been used successfully for several years. Unfortunately, a substantial number of tumours are intrinsically tamoxifen-resistant, despite oestrogen-receptor positivity, and, eventually, almost all breast carcinomas acquire resistance towards tamoxifen. The recently developed pure anti-oestrogen Faslodex and the third-generation aromatase inhibitors (Letrozol, anastrozole (Arimidex) offer the possibility of alternative therapies. Preclinical models are needed, as most of the mechanisms of hormonal tumour dependence and the causes of the appearance of antihormone resistance are not yet fully understood. This review focuses on the development and characterisation of breast cancer xenografts derived directly from surgical resections. With their help, a deeper insight into the mechanisms of hormone regulation and anti-oestrogen resistance can be gained. The xenograft models have already been used in differential gene-expression analysis on DNA microarrays and for the evaluation of approaches to overcoming tamoxifen resistance.

Antineoplastic Agents, Hormonal↗
PubMed2004

Microspheres accurately predict regional bone blood flow.

Even though the microsphere method frequently is used to determinate bone blood flow, validation of this technique for bone blood flow measurement is incomplete. The method is based on the principle that injected microspheres are distributed with the arterial blood and trapped in the capillaries because of their diameter (15 microm). The number of spheres lodged in an organ is proportional to its blood flow. The number of radioactive or fluorescent microspheres in a specific organ is determined indirectly by measuring radioactivity or fluorescence intensity in the organ. In this study the reliability and precision of the microsphere method for determining bone blood flow was established using radioactive and fluorescent microspheres. Six female, anesthetized New Zealand rabbits received left ventricular injections of pairs of fluorescent and/or radioactive microspheres. The humerus, femur, and tibia were dissected in a standardized manner and blood flow was determined in each sample. Comparison of relative blood flow values showed an excellent correlation between radioactive and fluorescent microspheres. The percentage difference and variation between two simultaneously injected sets of microspheres was minimal for radioactive microspheres (0.8% +/- 9.6%) and for fluorescent microspheres (0.2% +/- 11.4%). Regional bone blood flow in different regions of the femur, tibia, or humerus ranged from 2.2-28.1 mL/minute/100 g, but there was no significant difference between right and left bone samples of the same region after repeated measurement. Radioactive and fluorescent microspheres allow precise determination of regional bone blood flow.

Animals↗
PubMed2003

Direct assessment and distribution of regional portal blood flow in the pig by means of fluorescent microspheres.

Measurement of regional organ blood flow by means of fluorescent microspheres (FM) is an accepted method. However, determination of regional portal blood flow (RPBF) cannot be performed by microspheres owing to the entrapment of the spheres in the upstream capillary bed of the splanchnic organs. We hypothesized that an adequate experimental setting would enable us to measure RPBF by means of FM and to analyze its distribution within the pig liver. A mixing chamber for the injection of FM was developed, and its capability to distribute FM homogeneously in the blood was evaluated in vitro. The chamber was implanted into the portal vein of six anesthetized pigs (23.5 +/- 2.9 kg body wt). Three consecutive, simultaneous injections of FM of two different colors into the chamber were performed. Reference portal blood samples were collected by means of a Harvard pump. At the end of the experiment, the liver was explanted and fixed in formalin before dissection. FM were isolated from the tissue samples by an automated process, and fluorescence intensity was determined. Comparison of 5,458 single RPBF values, determined by simultaneously injected FM, revealed good agreement (bias 2.5%, precision 12.7%) and high correlation (r = 0.97, r2 = 0,95, slope = 1.04, intercept = 0.05). Median RPBF was 1.07 +/- 0.78 ml x min(-1) x g(-1). Allocation of the blood flow values to the anatomic regions of the liver revealed a significantly higher RPBF (P = 0.01) in the liver tissue located close to the diaphragm compared with the rest of the organ and a significantly lower RPBF (P = 0.01) in the left liver lobe compared with the median and right lobes. The results show that the model presented makes it possible to measure RPBF by means of FM reliably and that RPBF is distributed heterogeneously in the porcine liver.

Animals↗
PubMed2003

Validity of fluorescent microspheres method for bone blood flow measurement during intentional arterial hypotension.

In this study, we compared bone blood flow values obtained by simultaneously injected fluorescent (FM) and radiolabeled microspheres (RM) at stepwise reduced arterial blood pressure. Ten anesthetized female New Zealand White rabbits received simultaneous left ventricular injections of FM and RM at 90, 70, and 50 mmHg mean arterial blood pressure (MAP). After the experiments, both kidneys and long bones of all four limbs were removed and dissected in a standardized manner. Radioactivity (corrected for decay, background, and spillover) and fluorescence were determined, and blood flow values were calculated. Relative blood flow values estimated for each bone sample by RM and FM were significantly correlated (r = 0.98, slope = 0.99, and intercept = 0.04 for 90 mmHg; r = 0.98, slope = 0.94, and intercept = 0.09 for 70 mmHg; r = 0.98, slope = 0.96, and intercept = 0.07 for 50 mmHg). Blood flow values (ml x min-1 x 100 g-1) of right and left bone samples determined at the different arterial blood pressures were identical. During moderate hypotension (70 mmHg MAP), blood flow in all bone samples remained unchanged compared with 90 mmHg MAP, whereas a significant decrease of bone blood flow was observed at severe hypotension (50 mmHg MAP). Our results demonstrate that the FM technique is valid for measuring bone blood flow. Differences in bone blood flow during altered hemodynamic conditions can be detected reliably. In addition, changes in bone blood flow during hypotension indicate that vasomotor control mechanisms, as well as cardiac output, play a role in setting bone blood flow.

Algorithms↗
PubMed2003

Antileukaemic activity of treosulfan in xenografted human acute lymphoblastic leukaemias (ALL).

Treosulfan (L-threitol-1,4-bis-methanesulphonate; Ovastat(R)) is a bifunctional alkylating drug indicated for the treatment of advanced ovarian carcinoma. Recent data revealed immunosuppressive characteristics and substantial haematopoietic stem cell toxicity after repeated dosing of mice. Therefore, treosulfan is considered to be an alternative conditioning agent to busulfan (for example) administered prior to allogeneic/autologous stem cell transplantation of patients with haematological malignancies. An antineoplastic activity for treosulfan has been previously shown in preclinical models of melanoma, breast, lung and renal-cell carcinomas. Here, in vivo antileukaemic activity of treosulfan is compared with the activity of equitoxic doses of cyclophosphamide or busulfan for the first time using human acute lymphoblastic leukaemia (ALL)-models of paediatric origin xenotransplanted into non-obese diabetic (NOD)/severe combined immunodeficient (SCID) mice. Treosulfan treatment achieved an optimum treated to control (T/C) value of 159% (survival time) against B-ALL-SCID 7 and a T/C value of 0% (tumour growth) against T-ALL-SCID 4 and proB-ALL-SCID 19, respectively. Complete regression of established subcutaneously (s.c.) growing nodules of ALL-SCID 4 and 19 was obvious and long-term survivors without tumour re-growth were observed. Equitoxic doses of busulfan (ALL-SCID 4, 7, 19) or cyclophosphamide (ALL-SCID 19) were less effective with regard to the numbers of complete regressions and the number of cured animals. Side-effects included myelotoxicity and a small reduction in body weight, but these were tolerable. Treosulfan can be considered a highly active antileukaemic drug whose corresponding clinical value is to be tested in appropriate protocols with leukaemic patients.

Animals↗
PubMed2003

Time to progression is dependent on the expression of the tumour suppressor PTEN in ovarian cancer patients.

BACKGROUND: Quantitative analyses of PTEN expression of ovarian cancer tissues were performed in this study. PTEN expression was investigated in terms of each patient's progression-free interval to indicate the role of PTEN in the generation of platinum refractory tumours. MATERIALS AND METHODS: The study group comprised 20 ovarian cancer patients from whom fresh frozen tissues of both the primary tumour and specimens of progressive disease were available. The PTEN protein and phosphorylation of the downstream effector protein kinase B (PKB) were quantified by Western blot analyses and subsequent densitometry. Data were analyzed for individual PTEN variation with respect to the clinical course as defined by the progression-free interval. RESULTS: Applying the usual clinical criteria for platinum-sensitivity after progression, seven patients were considered platinum-sensitive whereas 13 patients had suffered a progression within 12 months after the chemotherapy. In 5/7 (71%) cases with prolonged time to progression, an increase in PTEN was observed. Decline of PTEN expression occurred in 9/13 (69%) patients with poor outcome. PTEN expression corresponds inversely to PKB phosphorylation in 14/20 (70%) tissues investigated. CONCLUSIONS: The data suggest that decreased PTEN expression accompanies the progression of ovarian cancer. Declining PTEN expression results in a shortened relapse-free interval, whereas an increase of PTEN prolongs the time to progression. However, as far as recurrence occurs, PTEN is not the only mechanism to suppress tumour progression in ovarian cancer.

Adult↗
PubMed2003

Effects of kinins on mammalian spermatozoa and the impact of peptidolytic enzymes.

Effects of kinins, mainly bradykinin (Bk), and other components of the kallikrein-kinin system on sperm motility and further fertility-related functions have been described repeatedly. However, reported data are in part controversial and the mechanism of kinin effects on sperm motility is not yet understood. In the present report we describe a significant promoting effect of Bk on sperm motility at subnanomolar concentrations. This effect was stabilized and even increased by suppression of Bk hydrolysis in semen samples. As sperm membrane-bound angiotensin-converting enzyme and neutral metalloendopeptidase are mainly involved in Bk hydrolysis, an effective cocktail of enzyme inhibitors promoting the sperm motility consists of phosphoramidon and lisinopril (both at 10-7 m). The effects of Bk on sperm cells are not mediated by the B2 Bk receptor. Using several biochemical, molecular and genetic methods we could not detect any Bk receptor on spermatozoa.

Angiotensin-Converting Enzyme Inhibitors↗