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R Ludwig

Publications and source records attributed to R Ludwig.

At least 19 recordsLinked to original sources
PubMed2004

A dual RF resonator system for high-field functional magnetic resonance imaging of small animals.

A new apparatus has been developed that integrates an animal restrainer arrangement for small animals with an actively tunable/detunable dual radio-frequency (RF) coil system for in vivo anatomical and functional magnetic resonance imaging of small animals at 4.7 T. The radio-frequency coil features an eight-element microstrip line configuration that, in conjunction with a segmented outer copper shield, forms a transversal electromagnetic (TEM) resonator structure. Matching and active tuning/detuning is achieved through fixed/variable capacitors and a PIN diode for each resonator element. These components along with radio-frequency chokes (RFCs) and blocking capacitors are placed on two printed circuit boards (PCBs) whose copper coated ground planes form the front and back of the volume coil and are therefore an integral part of the resonator structure. The magnetic resonance signal response is received with a dome-shaped single-loop surface coil that can be height-adjustable with respect to the animal's head. The conscious animal is immobilized through a mechanical arrangement that consists of a Plexiglas body tube and a head restrainer. This restrainer has a cylindrical holder with a mouthpiece and position screws to receive and restrain the head of the animal. The apparatus is intended to perform anatomical and functional magnetic resonance imaging in conscious animals such as mice, rats, hamsters, and marmosets. Cranial images acquired from fully conscious rats in a 4.7 T Bruker 40 cm bore animal scanner underscore the feasibility of this approach and bode well to extend this system to the imaging of other animals.

Animals↗
PubMed2003

Characterisation of cellobiose dehydrogenases from the white-rot fungi Trametes pubescens and Trametes villosa.

Cellobiose dehydrogenase (CDH) is an extracellular haemoflavoenzyme that is produced by a number of wood-degrading and phytopathogenic fungi and it has a proposed role in the early events of lignocellulose degradation and wood colonisation. In the presence of a suitable electron acceptor, e.g. 2,6-dichloro-indophenol, cytochrome c, or metal ions, CDH oxidises cellobiose to cellobionolactone. When screening 11 different Trametes spp. for the formation of CDH activity, all the strains investigated were found to secrete significant amounts of CDH when cultivated on a cellulose-containing medium. Amongst others, Trametes pubescens and Trametes villosa were identified as excellent, not-yet-described, producer strains of this enzyme activity that has various potential applications in biotechnology. CDH from both strains was purified to apparent homogeneity and subsequently characterised. Both monomeric enzymes have a molecular mass of approximately 90 kDa (gel filtration) and a pI value of 4.2-4.4. The best substrates are cellobiose and cellooligosaccharides; additionally, lactose, thiocellobiose, and xylobiose are efficiently oxidised. Glucose and maltose are poor substrates. The preferred substrate is cellobiose with a Km value of 0.21 mM and a kcat value of 22 s(-1) for CDH from T. pubescens; the corresponding values for the T. villosa enzyme are 0.21 mM and 24 s(-1), respectively. Both enzymes showed very high activity with one-electron acceptors such as ferricenium, ferricyanide, or the azino-bis-(3-ethyl-benzthiazolin-6-sulfonic acid) cation radical.

2,6-Dichloroindophenol↗
PubMed2003

Optimisation of cellobiose dehydrogenase production by the fungus Sclerotium (Athelia) rolfsii.

The phytopathogenic fungus Sclerotium (Athelia) rolfsii CBS 191.62 is a very efficient producer of the hemoflavoprotein, cellobiose dehydrogenase (CDH), forming up to 225 mg l(-1) (15,000 units cytochrome c activity l(-1)) of this protein, which is of biotechnological interest for sensors, biocatalysis and bioremediation. Both cellulose as inducing substrate and the use of a rich medium containing increased concentrations of peptone from meat or suitable amino acids are important for attaining high CDH yields. CDH, containing a protease-sensitive linker region, can be cleaved by endogenous proteases into a catalytically active flavin fragment and an inactive heme domain. By using increased concentrations of peptone, or certain amino acids such as valine or leucine, or by adding exogenous protease inhibitors, this cleavage can be almost completely inhibited, so that more than 95% intact CDH is obtained under optimised culture conditions. When using non-inhibitory amino acids, e.g. glutamine or lysine, in the medium, more than 80% of the total cellobiose-oxidising activity can be attributed to the flavin fragment.

Amino Acids↗
PubMed2002

Multicentre analysis of anthracycline-induced cardiotoxicity in children following treatment according to the nephroblastoma studies SIOP No.9/GPOH and SIOP 93-01/GPOH.

BACKGROUND: To study cardiac function and the incidence of anthracycline-induced cardiotoxicity in children following treatment according to the nephroblastoma studies SIOP No.9/GPOH and SIOP 93-01/GPOH. PROCEDURE: Analysis of clinical status, echocardiography, and ECG findings prior to administration of anthracyclines (median cumulative doxorubicin dose: 250 mg/m(2) [range: 90-411 mg/m(2)] and after a median posttherapeutic interval of 2.9 years [range: 0-10.2 years]. Data on cardiac function before and/or after therapy could be obtained of 186 patients. RESULTS: Posttherapy left ventricular fractional shortening was reduced in 4/157 (2.5%) patients. Out of the 4 children, 2 had clinically reduced tolerance to exercise and received anticongestive therapy. Abnormal ECG findings that were not detectable prior to therapy were found in 7/124 (5.6%) children. CONCLUSIONS: The incidence of abnormal findings is low in our study group in comparison to data from the literature and might be due to the comparably short posttherapeutic interval.

Adolescent↗
PubMed2002

Coupled microstrip line transverse electromagnetic resonator model for high-field magnetic resonance imaging.

The performance modeling of RF resonators at high magnetic fields of 4.7 T and more requires a physical approach that goes beyond conventional lumped circuit concepts. The treatment of voltages and currents as variables in time and space leads to a coupled transmission line model, whereby the electric and magnetic fields are assumed static in planes orthogonal to the length of the resonator, but wave-like along its longitudinal axis. In this work a multiconductor transmission line (MTL) model is developed and successfully applied to analyze a 12-element unloaded and loaded microstrip line transverse electromagnetic (TEM) resonator coil for animal studies. The loading involves a homogeneous cylindrical dielectric insert of variable radius and length. This model formulation is capable of estimating the resonance spectrum, field distributions, and certain types of losses in the coil, while requiring only modest computational resources. The boundary element method is adopted to compute all relevant transmission line parameters needed to set up the transmission line matrices. Both the theoretical basis and its engineering implementation are discussed and the resulting model predictions are placed in context with measurements. A comparison between a conventional lumped circuit model and this distributed formulation is conducted, showing significant departures in the resonance response at higher frequencies. This MTL model is applied to simulate two small-bore animal systems: one of 7.5-cm inner diameter, tuned to 200 MHz (4.7 T for proton imaging), and one of 13.36-cm inner diameter, tuned to both 200 and 300 MHz (7 T).

Animals↗
PubMed2002

Cellobiose dehydrogenase production by Sclerotium species pathogenic to plants.

AIMS: Evaluation of various Sclerotium spp. as producers of the biotechnologically attractive enzyme cellobiose dehydrogenase. METHODS AND RESULTS: All isolates of S. coffeicola, S. delphinii and S. rolfsii grown in shaken flasks on a cellulose-based medium produced appreciable amounts of the extracellular enzyme cellobiose dehydrogenase. CONCLUSIONS: Cellobiose dehydrogenase seems to play an important role in phytopathogenic Sclerotium spp.; a possible function could be either in the degradation of rigid lignocellulose or as a protective mechanism against toxic quinones. SIGNIFICANCE AND IMPACT OF THE STUDY: S. coffeicola and S. delphinii were identified as potent, not-yet-described producers of cellobiose dehydrogenase (CDH). The high levels of intact CDH produced by the different Sclerotium species should make them attractive producers for further studies and applications.

Ascomycota↗
PubMed2001

Functional imaging of brain activity in conscious monkeys responding to sexually arousing cues.

Olfactory cues can elicit intense emotional responses. This study used fMRI in male common marmoset monkeys to identify brain areas associated with sexual arousal in response to odors of ovulating female monkeys. Under light anesthesia, monkeys were secured in a specially designed restrainer and positioned in a 9.4 T magnetic resonance spectrometer. When fully conscious, they were presented with the scents of both ovariectomized and ovulating monkeys. The sexually arousing odors of the ovulating monkeys enhanced signal intensity in the preoptic area and anterior hypothalamus compared to the odors of ovariectomized monkeys. These data corroborate previous findings in monkeys based on invasive electrical lesion and stimulation techniques and demonstrate the feasibility of using non-invasive functional imaging on fully conscious common marmosets to study cue-elicited emotional responses.

Animals↗
PubMed2001

Optimal duration of preoperative therapy in unilateral and nonmetastatic Wilms' tumor in children older than 6 months: results of the Ninth International Society of Pediatric Oncology Wilms' Tumor Trial and Study.

PURPOSE: To determine the optimal duration of preoperative chemotherapy to further increase the proportion of stage I tumors by comparison of two regimens in the treatment of patients older than 6 months who have unilateral Wilms' tumor. PATIENTS AND METHODS: Eligible patients (n = 382) initially received four weekly doses of vincristine (VCR) and two courses of actinomycin D (AMD) and were randomized either to be operated on (4-week group [n = 193]) or to receive 4 more weeks of the same chemotherapy regimen (8-week group [n = 189]). The assessment criterion was the observed percentage of stage I tumors. After surgery, patients were assigned according to tumor stage and histology to four different treatment groups: stage I and favorable histology (n = 5) were to have no further treatment (NFT); stage I and standard histology or anaplasia (n = 244), VCR and AMD for 17 weeks (AV); stages II and III and favorable or standard histology, VCR, AMD, and an anthracycline for 27 weeks (AVE) with no abdominal radiotherapy for stage II N0 disease (n = 75) or with a 15-Gy dose of abdominal irradiation (RTH) in case of stages IIN1 and III (n = 56). Anaplastic tumors staged higher than I or clear-cell sarcoma of the kidney (14), AMD, VCR, an anthracycline, and ifosfamide for 36 weeks (DEVI). RESULTS: No advantage was found in favor of prolonged preoperative treatment. The percentages obtained for the 4-week and the 8-week groups, respectively, were as follows: stage I, 64% versus 62%; intraoperative tumor rupture rate, 1% versus 3%; 2-year EFS, 84% versus 83%; and 5-year OS, 92% versus 87%. Two-year EFS and 5-year OS rates, respectively, of the different treatment groups were as follows: NFT, 100% for both EFS and OS; AV, 88% and 93%; AVE, 84% and 88%; AVE RTH, 71% and 85%; and DEVI, 71% and 71%. The rate of abdominal recurrences in stage II N0 nonirradiated patients was 6.6%. CONCLUSION: The 4-week schedule pre-nephrectomy chemotherapy regimen should be considered the standard treatment. Clinical trials should continue to improve the cure rate of high-risk patients and the quality of life of children with a more favorable prognosis.

Adolescent↗
PubMed2001

Preparation and crystal structure of tetraphenylphosphonium triiodotetrabromide [PPh4][I3Br4].

Tetraphenylphosphonium triiodotetrabromide [PPh4][I3Br4] is obtained by the reaction of tetraphenylphosphonium bromide with iodine monobromide. It is the first example of an iodine rich, seven-membered polybromide. [PPh4][I3Br4] crystallizes triclinic in the space group P1 with a = 10.947(1) A, b = 11.945(1) A, c = 12.896(1) A, alpha = 66.80(1) degrees, beta = 77.21(1) degrees, gamma = 85.73(1) degrees, and two formula units per unit cell. The final R indices [I > 4 sigma(I)] are R1 = 0.0362 and wR2 = 0.0944.

Journal Article↗
PubMed2001

Beta-tricalcium phosphate as a bone substitute for dorsal spinal fusion in adolescent idiopathic scoliosis: preliminary results of a prospective clinical study.

The aim of this study is to evaluate the ability of beta-tricalcium phosphate (TCP) in granular form to achieve dorsal spondylodesis in adolescent idiopathic scoliosis (AIS). Twenty-eight patients underwent surgical correction and were followed up for 13+/-8 (range 6-33) months. Posterolateral grafting was performed, using either autograft bone mixed with allograft bone (n=19; "bone group") or autograft bone mixed with 25 g TCP (n=9; "TCP group"). Patients were followed by clinical examination, X-rays and computed tomographic (CT) scans to measure bone mineral density. Fusion involved 12+/-1 (range 10-14) vertebrae. The segments were fused after 6+/-1 months in both groups according to the radiographs. No pseudarthrosis was observed. Bone mineral density was 430+/-111 (range 273-629) mg/cm3 in the TCP group versus 337+/-134 (range 130-669) mg/cm3 in the bone group. Resorption of TCP was complete on the radiographs after 8+/-2 (range 6-10) months. Based upon the results of this small preliminary study, the use of TCP appears to be a valuable alternative to allografts for application in the spine, even when large amounts of bone are needed.

Adolescent↗
PubMed2001

Clinical impact of histologic subtypes in localized non-anaplastic nephroblastoma treated according to the trial and study SIOP-9/GPOH.

BACKGROUND: Histologic subtypes of standard histology Wilms' tumor (WT) and the effect of preoperative therapy on their clinical and histologic features, deserve to be analysed in respect to outcome to find an adequate baseline for therapy. PATIENTS AND METHODS: The German Society of Paediatric Oncology & Haematology enrolled patients from January 1989 to March 1994 for therapy according the International Society of Paediatric Oncology trial & study 9. Standardised preoperative therapy with dactinomycin and vincristine for 4-8 weeks was generally applied in patients between 0.5 and 16 years with localized renal tumors and imaging typical for WT. In 99.5% of cases representative material was sent for review to the Kiel Paediatric Tumour Registry. For prospective subtyping of 329 WT (258 after preoperative therapy, 71 with immediate surgery) modified Beckwith & Palmer criteria were used. Reduction in volume measured by imaging prior to chemotherapy and surgery was used to assess response (poor response: reduction < 40%; good response: reduction > or = 40%). RESULTS: There were 39% of patients treated with immediate surgery and 12.4% of patients with preoperative therapy in the age group up to 12 months. The difference in age (P = 0.022) was linked with different amounts of epithelial WT (15.5% vs. 3.1%), median age: 0.58 and 0.93 years. Due to the effect of chemotherapy the amount of other WT changed: stromal 0% to 14%, mixed 45.1% to 29.4%, blastemal 39.4% to 9.3%). After preoperative therapy 37.6% of WT were predominantly regressive, 6.6% completely necrotic. Poor response was frequent in differentiated WT (86% of stromal, 75% of epithelial WT) but none relapsed. In the other WT with viable tumor left after preoperative therapy > 70% had good response, poor response was a risk factor (P = 0.0057). CONCLUSIONS: Subtyping according modified Beckwith & Palmer can be used in WT after preoperative therapy to stratify postoperative therapy in future. A milder therapy could be tested in differentiated WT at low stages and an intensified in the others with viable tumor left and poor response, i.e., mainly blastemal WT.

Adolescent↗
PubMed2001

Kinetics and dose-response of photosensitivity in cream psoralen plus ultraviolet A photochemotherapy: comparative in vivo studies after topical application of three standard preparations.

BACKGROUND: Topical photochemotherapy with bath psoralen plus ultraviolet (UV) A irradiation (PUVA) has been developed to reduce possible side-effects of oral PUVA therapy. Although the efficacy of bath PUVA therapy appears to be similar to oral PUVA therapy, provision of bathing facilities has obvious economic, logistic and sanitary implications. Cream PUVA therapy has recently been developed as a variation of topical PUVA. OBJECTIVES: To understand the photobiological effects and to increase the safety and effectiveness of this novel topical PUVA therapy, we assessed the kinetics and dose-response of phototoxicity of 8-methoxypsoralen (8-MOP) cream in order to develop a treatment schedule for this treatment option. METHODS: Ninety-eight patients (63 men and 35 women) undergoing cream PUVA therapy were studied. The phototoxic properties of topically applied 8-MOP in three different water-in-oil creams as vehicles were assessed. In a dose-response study, four concentrations of 8-MOP cream (0.0006-0.005%) were used for determination of the minimal phototoxic dose (MPD). The kinetics of photosensitization were tested by determination of MPDs after different application times of 8-MOP cream (10, 20, 30 and 60 min). The persistence of phototoxicity was assessed by UVA exposure at defined time intervals after application of 8-MOP cream (0, 30, 60 and 120 min). RESULTS: The concentration required to produce sufficient but not undue photosensitization of the skin was 0.001% 8-MOP. The duration of application leading to the lowest MPD was 30 min. Greatest photosensitization was achieved when UVA irradiation was performed between 0 and 30 min after 8-MOP removal. These findings showed no significant difference between the three vehicles used. CONCLUSIONS: Based on our data we recommend application of 0.001% 8-MOP in a water-in-oil cream for 30 min. Irradiation with UVA should be performed within 30 min after removal of 8-MOP cream, as there is a rapid decrease in photosensitivity thereafter.

Administration, Cutaneous↗
PubMed2001

Reconstruction of segmental defects during revision procedures of the acetabulum with the Burch-Schneider anti-protrusio cage.

Sixty-three Burch-Schneider rings in 62 patients with segmental or combined defects were followed up after a mean of 5.45 years. The mean Harris hip score was 74.9 points. Aseptic loosening occurred in 3 cases, and septic loosening occurred in 2 cases. All cases of aseptic loosening had Paprosky stage IIIb defects and defects of the posterior column. Radiologic migration analysis showed increased migration with increase in the Paprosky defect stage, defects of the posterior column, and cranial defects. The cage has the lowest migration and loosening rate in cases with medial defects or anterior column defects. Surgical treatment of defects of the posterior column is associated with an increased rate of aseptic loosening, whereas implantation with cranial defects shows a higher migration rate with no significant increase in loosening.

Acetabulum↗
PubMed2001

Primary nephrectomy for emergency: a rare event in the International Society of Paediatric Oncology Nephroblastoma Trial and Study no. 9.

Experience of the International Society of Paediatric Oncology (SIOP) Trials and Studies indicates that the preoperative chemotherapy in Wilms' tumour improves stage distribution, decreases complication rate and reduces postoperative treatment. However, some situations may lead to prompt primary surgery. The aim of the study is to assess reasons leading to primary emergency nephrectomy. Records of 720 patients with non-metastatic unilateral nephroblastoma who were registered in the SIOP Trial and Study 9 were reviewed. Twenty-four (3%) cases of primary emergency nephrectomy were identified. Reasons leading to emergency nephrectomy were massive bleedings from ruptured tumours in 13 patients, suspicion of an "acute abdomen" in 7, bowel occlusion in 2 and other in 2. Postoperative treatment included radiotherapy in 71% of cases and anthracyclines in 92%. Complications were frequent and happened in 25% of patients, the outcome however, was favourable and 22 of 24 patients are alive (from 9 to 79 months). The 7 patients with a suspicion of an "acute abdomen" probably constitute the group which could have been markedly reduced if adequately diagnosed and observed prior to surgery.

Child↗
PubMed2000

Crystal structure of (difluoro)methoxyoxo iodine(V) IF2(O)OCH3.

(Difluoro)methoxyoxo iodine(V) (IF2(O)OCH3), the methyl ester of the unknown difluoro iodic acid (IF2(O)OH), was obtained by the reaction of methoxytrimethyl silane with iodine pentafluoride. IF2(O)OCH3 crystallizes orthorhombic in the space group Pbca with a = 7.605(1) A, b = 7.360(1) A, c = 15.017(1) A, and eight formula units per unit cell. The final R indices [I > 2 sigma(I)] are R1 = 0.0264 and wR2 = 0.0516. Additionally, IF2(O)OCH3 was characterized by its vibrational spectra and quantum mechanical calculations were performed.

Journal Article↗
PubMed2000

Calixarenes in analytical and separation chemistry.

Discovered in the 1940's, [1n]metacyclophanes with the common name calix[n]arenes which is derived from for the molecule's shape enjoyed a remarkable interest in almost all fields of chemistry since the 1980's, which is highlighted by several books [1-8]. Over 50 reviews concerning their synthesis, properties and applicabilities were published, many of those with emphasis on organic synthesis and structural properties are cited in [P. 5-6 in 2]. Of interest for analytical chemists are reviews on calixarenes and the structurally related resorcin[n]arenes (or calix[n]resorcarenes) and calixpyrroles concerning potentiometric sensors [9-12], chromo- and fluorophores [13, 14], molecular switches [15], metal ion binding in solution [16-19], redox properties [20] and anion binding [21-24]. Other recent reviews deal with thermodynamic aspects [25], organometallic compounds [26], P-containing calixarenes [27-29], as well as molecular dynamics modeling [30-33]. It is a vital field with over 200 publications per year. Therefore, this article presents only selected results on complexation, solvent extraction and membrane transport with the emphasis on ion and molecular recognition which can be used for analytical purposes, without attempting to cover all available references.

Journal Article↗