Showing papers by "Martin Luther University of Halle-Wittenberg published in 1995"

LEDA: A Platform for Combinatorial and Geometric Computing

Abstract: Combinatorial and geometric computing is a core area of computer science (CS). In fact, most CS curricula contain a course in data structures and algorithms. The area deals with objects such as graphs, sequences, dictionaries, trees, shortest paths, flows, matchings, points, segments, lines, convex hulls, and Voronoi diagrams and forms the basis for application areas such as discrete optimization, scheduling, traffic control, CAD, and graphics. There is no standard library of the data structures and algorithms of combinatorial and geometric computing. This is in sharp contrast to many other areas of computing. There are, for example, packages in statistics (SPSS), numerical analysis (LINPACK, EISPACK), symbolic computation (MAPLE, MATHEMATICA), and linear programming (CPLEX).

Ion efflux systems involved in bacterial metal resistances

Abstract: Studying metal ion resistance gives us important insights into environmental processes and provides an understanding of basic living processes. This review concentrates on bacterial efflux systems for inorganic metal cations and anions, which have generally been found as resistance systems from bacteria isolated from metal-polluted environments. The protein products of the genes involved are sometimes prototypes of new families of proteins or of important new branches of known families. Sometimes, a group of related proteins (and presumedly the underlying physiological function) has still to be defined. For example, the efflux of the inorganic metal anion arsenite is mediated by a membrane protein which functions alone in Gram-positive bacteria, but which requires an additional ATPase subunit in some Gram-negative bacteria. Resistance to Cd2+ and Zn2+ in Gram-positive bacteria is the result of a P-type efflux ATPase which is related to the copper transport P-type ATPases of bacteria and humans (defective in the human hereditary diseases Menkes' syndrome and Wilson's disease). In contrast, resistance to Zn2+, Ni2+, Co2+ and Cd2+ in Gram-negative bacteria is based on the action of proton-cation antiporters, members of a newly-recognized protein family that has been implicated in diverse functions such as metal resistance/nodulation of legumes/cell division (therefore, the family is called RND). Another new protein family, named CDF for 'cation diffusion facilitator' has as prototype the protein CzcD, which is a regulatory component of a cobalt-zinc-cadmium resistance determinant in the Gram-negative bacterium Alcaligenes eutrophus. A family for the ChrA chromate resistance system in Gram-negative bacteria has still to be defined.

Superresolution three-dimensional images of fluorescence in cells with minimal light exposure.

Abstract: Fluorescent probes offer insight into the highly localized and rapid molecular events that underlie cell function. However, methods are required that can efficiently transform the limited signals from such probes into high-resolution images. An algorithm has now been developed that produces highly accurate images of fluorescent probe distribution inside cells with minimal light exposure and a conventional light microscope. This method provides resolution nearly four times greater than that currently available from any fluorescence microscope and was used to study several biological problems.

Radiation therapy in ewing's sarcoma: an update of the cess 86 trial

Abstract: Purpose : We present an update analysis of the multiinstitutional Ewing's sarcoma study CESS 86. Methods and Materials : From January 1986 through June 1991, 177 patients with localized Ewing's sarcoma of bone, aged 25 years or less, were recruited. Chemotherapy consisted of four 9-week courses of vincristine, actinomycin D, cyclophosphamide, and adriamycin (VACA) in low-risk tumors (extremity tumors < 100 cm 3 ), or vincristine, actinomycin D, ifosfamide, and adriamycin (VAIA) in high-risk tumors (central tumors and extremity tumors ≥ 100 cm 3 ). Local therapy was an individual decision in each patient and was either radical surgery (amputation, wide resection) or resection plus postoperative irradiation with 45 Gy or definitive radiotherapy with 60 Gy (45 Gy plus boost). Irradiated patients were randomized concerning the type of fractionation in either conventional fractionation (once daily 1.8-2.0 Gy, break of chemotherapy) or hyperfractionated split-course irradiation simultaneously with the VACA/VAIA chemotherapy (twice daily 1.6 Gy, break of 12 days after 22.4 Gy and 44.8 Gy, total dose and treatment time as for conventional fractionation). For quality assurance in radiotherapy, a central treatment planning program was part of the protocol. Results : Forty-four patients (25%) received definitive radiotherapy ; 39 (22%) had surgery, and 93 (53%) had resection plus postoperative irradiation. The overall 5-year survival was 69%. Thirty-one percent of the patients relapsed, 30% after radiotherapy, 26% after radical surgery, and 34% after combined local treatment. The better local control after radical surgery (100%) and resection plus radiotherapy (95%) as compared to definitive radiotherapy (86%) was not associated with an improvement in relapse-free or overall survival because of a higher frequency of distant metastases after surgery (26 % vs. 29% vs. 16%). In irradiated patients, hyperfractionated split-course irradiation and conventional fractionation yielded the same results (5-year overall survival of definitively irradiated patients 63% after conventional fractionation and 65% after hyperfractionation ; relapse-free survival 53% vs. 58% ; local control 76% vs. 86%, not significant). The six local failures after radiotherapy did not correlate with tumor size or response to chemotherapy. Radiation treatment quality (target volume, technique, dosage) was evaluated retrospectively and was scored as unacceptable in only 1 out of 44 patients (2%) with definitive radiotherapy. Grade 3-4 complications developed in 4 out of 44 (9%) patients after definitive radiotherapy. Conclusions : Under the given selection criteria for local therapy, radiation therapy yielded relapse-free and overall survival figures comparable to radical surgery. Hyperfractionated split-course irradiation simultaneously with multidrug chemotherapy did not significantly improve local control or survival.

Effects of a vesicular-arbuscular mycorrhizal fungus and other soil microorganisms on growth, mineral nutrient acquisition and root exudation of soil-grown maize plants

Abstract: Maize (Zea mays L. cv. Alize) plants were grown in a calcareous soil in pots divided by 30-μm nylon nets into three compartments, the central one for root growth and the outer ones for hyphal growth. Sterle soil was inoculated with either (1) rhizosphere microorganisms other than vesicular-arbuscular mycorrhizal (VAM) fungi, (2) rhizosphere microorganisms together with a VAM fungus [Glomus mosseae (Nicol. and Gerd.) Gerdemann and Trappel], or (3) with a gamma-irradiated inoculum as control. Plants were grown under controlled-climate conditions and harvested after 3 or 6 weeks. VAM plants had higher shoot∶root ratios than non-VAM plants. After 6 weeks, the concentrations of P, Zn and Cu in roots and shoots had significantly increased with VAM colonization, whereas Mn concentrations had significantly decreased. Root exudates were collected on agar sheets placed on the interface between root and hyphal compartments. Six-week-old VAM and non-VAM plants had similar root exudate compositions of 72–73% reducing sugars, 17–18% phenolics, 7% organic acids and 3% amino acids. In another experiment in which root exudates were collected on agar sheets with or without antibiotics, the amounts of amino acids and carbohydrates recovered were similar in VAM and non-VAM plants. However, threeto sixfold higher amounts of carbohydrates, amino acids and phenolics were recovered when antibiotics were added to the agar sheets. Thus, the high microbial activity in the rhizosphere and on the rhizoplane limits the exudates recovered from roots.

Gene therapy for brain tumors

Abstract: Gene therapy has opened new doors for treatment of neoplastic diseases. This new approach seems very attractive, especially for glioblastomas, since treatment of these brain tumors has failed using conventional therapy regimens. Many different modes of gene therapy for brain tumors have been tested in culture and in vivo. Many of these approaches are based on previously established anti-neoplastic principles, like prodrug activating enzymes, inhibition of tumor neovascularization, and enhancement of the normally weak anti-tumor immune response. Delivery of genes to tumor cells has been mediated by a number of viral and synthetic vectors. The most widely used paradigm is based on the activation of ganciclovir to a cytotoxic compound by a viral enzyme, thymidine kinase, which is expressed by tumor cells, after the gene has been introduced by a retroviral vector. This paradigm has proven to be a potent therapy with minimal side effects in several rodent brain tumor models, and has proceeded to phase 1 clinical trials. In this review, current gene therapy strategies and vector systems for treatment of brain tumors will be described and discussed in light of further developments needed to make this new treatment modality clinically efficacious.

Jasmonate‐induced lipoxygenase forms are localized in chloroplasts of barley leaves (Hordeum vulgare cv. Salome)

Abstract: Barley leaves respond to application of (−)-jasmonic acid (JA), or its methylester (JM) with the synthesis of abundant proteins, so-called jasmonate induced proteins (JIPs). Here Western blot analysis is used to show a remarkable increase upon JM treatment of a 100 kDa lipoxygenase (LOX), and the appearance of two new LOX forms of 98 and 92 kDa. The temporal increase of LOX-100 protein upon JM treatment was clearly distinguishable from the additionally detectable LOX forms. JM-induced LOX forms in barley leaves were compared with those of Arabidopsis and soybean leaves. Both dicot species showed a similar increase of one LOX upon JM induction, whereas, leaves from soybean responded with additional synthesis of a newly formed LOX of 94 kDa. Using immunofluorescence analysis and isolation of intact chloroplasts, it is demonstrated that JM-induced LOX forms of barley leaves are exclusively located in the chloroplasts of all chloroplast-containing cells. Analogous experiments carried out with Arabidopsis and soybean revealed a similar plastidic location of JM-induced LOX forms in Arabidopsis but a different situation for soybean. In untreated soybean leaves the LOX protein was mainly restricted to vacuoles of paraveinal mesophyll cells. Additionally, LOX forms could be detected in cytoplasm and nuclei of bundle sheath cells. Upon JM treatment cytosolic LOX was detectable in spongy mesophyll cells, too. The intracellular location of JM-induced LOX is discussed in terms of stress-related phenomena mediated by JM.

cDNA structure and regulatory properties of a family of starvation-induced ribonucleases from tomato

Abstract: In previous work we have determined the primary structure of two of the five ribonucleases which are induced by phosphate starvation in cultured tomato cells. Here, we present the isolation and characterization of the cDNAs for the extracellular ribonuclease LE and the intracellular, but extravacuolar ribonuclease LX. Structural analysis of these cDNAs together with partial protein-sequencing of vacuolar ribonucleases LV1, LV2 and LV3 revealed a family of very similar ribonucleases. From these data we assume identity between ribonucleases LE and LV3 for which the targeting mechanism has to be shown. Furthermore, RNase LV1 and RNase LV2 might be posttranslational processing products of RNase LX which travel to the vacuoles after splitting off the putative ER retention signal present at RNase LX. Additionally, we show by northern blot analysis that phosphate starvation in plant cells leads to an increase in the steady-state level of this type of enzymes revealing close similarities of the plant response to a limited supply of inorganic phosphate with the PHO regulation in bacteria and fungi.

The catalysis of the stereospecific butadiene polymerization by Allyl Nickel and Allyl Lanthanide complexes — A mechanistic comparison

Abstract: A short overview on the general mechanistic principles of the allyl metal complex catalyzed stereo-specific butadiene polymerization is given. The present state of knowledge on the mechanism of stereoregulation and in the understanding of the catalytic structure reactivity relationships is discussed comparatively for allyl nickel and allyl lanthanide catalysts.

Nonselective cationic currents elicited by extracellular ATP in human B-lymphocytes

Abstract: Adenosine 5′-triphosphate-(ATP)-induced whole-cell currents were studied in human B-lymphocytes, transformed by the Epstein-Barr virus, by means of the tight-seal voltage-clamp technique. During bath application of ATP, the membrane conductance was increased. The change of membrane conductance occurred within milliseconds. The dose response relationship for the ATP4−-elicited membrane current (I p) was fitted by the Hill function with a Hill coefficient of 1 and a K D value of 0.2 mmol/l. Adenosine, as well as the Mg2+-bound form of ATP, did not effect the membrane conductance. I p did not desensitize within 1 min and could be evoked repeatedly up to 100 times in 1 cell in the presence of the G-protein blocker Guanosine 5′-o-(2-thiodiphosphate) (GDP [βS]). Therefore, it seems that ion channels in form of P 2Z purinoceptors are involved in the observed effects. The permeability (P) sequence for cations carrying I p was P Ca:P K:P Cs:P Na:P TRIS= 35∶2∶1.2∶1∶0.1. The reversal potential of I p was not changed by substitution of intracellular Cl− for aspartate, indicating that anions are not involved in the purinoceptor-dependent conductance. A single-channel conductance of P 2Z-receptor-dependent ion channels of about 3 pS was determined by noise analysis of I p.

HPLC on Calixarene Bonded Silica Gels. I. Characterization and Applications of the p-tert-Butyl-Calix[4]arene Bonded Material

Abstract: Molecules containing cavities of well-defined dimensions are able to include guest molecules stereoselectively. This work is concerned with the introduction and evaluation of a newly developed high-performance liquid chromatographic packing material based on calix[4]arene chemically bonded to silica gel. It is well documented that calixarenes representing cyclic condensates of para substituted phenols and formaldehyde have the ability to form intracavity inclusion complexes with ions and organic molecules in aqueous solutions. The silica bonded macrocyclic ligands form truncated cones similar to cyclodextrins. Data are presented illustrating the resolution characteristics for disubstituted aromatics, peptides, nucleosides, and nucleobases. The results indicate that the calix[4]arene silica gel behaves predominantly as a reversed-phase material. Some effects support the assumption that the cavity acting as an electron donator can influence the elution order

On the interaction of the morphological structure and the LC behaviour of LC side chain block copolymers

Abstract: The interaction between morphological structure and phase behaviour of a LC side group block copolymer has been investigated using DSC, TEM and small angle X-ray diffraction. All samples of Polystyrene-block-2-(3-cholesteryloxycarbonyloxy)ethyl methacrylate (PS-b-PChEMA) show a phase separation between the two blocks. It was found that in the case of those samples where the liquid crystalline sub-phase is not continuous (spheres), only a nematic phase is seen, whereas in all samples in which there is a continuous liquid crystalline sub-phase, the smectic A phase of the homopolymer is formed. On the other hand, the block copolymer seems to stabilize the LC phase; no dependency of the clearing temperatures on the molecular weight of the LC blocks has been observed.

Limits of using signatures for permutation independent Boolean comparison

Abstract: This paper addresses problems that arise while checking the equivalence of two Boolean functions under arbitrary input permutations The permutation problem has several applications in the synthesis and verification of combinational logic: it arises in the technology mapping stage of logic synthesis and in logic verification A popular method to solve it is to compute a signature for each variable that helps to establish a correspondence between the variables Several researchers have suggested a wide range of signatures that have been used for this purpose However, for each choice of signature, there remain variables that cannot be uniquely identified Our research has shown that, for a given example, this set of problematic variables tends to be the same-regardless of the choice of signatures The paper investigates this problem

Urokinase infusion for severe intraventricular haemorrhage

Abstract: The purpose of this study was to explore in patients with intraventricular haematomas the effectiveness and complication rate of a treatment protocol including standard ventriculostomy and application of urokinase via the catheter. Our series includes 16 patients with severe CT-diagnosed intraparenchymal and predominantly intraventricular haemorrhages. In all cases, ventricular drainage was performed. Urokinase treatment was started immediately with intraventricular infusions of 10,000 U urokinase in 5 ml sterile physiological saline every 12 hours. Twelve patients had an excellent outcome, three good and one poor. There were no complications related to urokinase therapy. Side efects of the infusion volume were profuse sweating and headache which were present at 10 ml total infusion volume, but disappeared after reduction to 5 ml. A group of five patients with comparable lesions treated only with ventriculostomy served as controls. Two of them had a good outcome, two a poor one and one died. The late results in the urokinase-treated group were also favourable. Only one of the patients developed hydrocephalus and was shunted. In the control group, two patients required shunting for delayed hydrocephalus. We conclude that this protocol for urokinase treatment is safe and effective and can be used in almost all patients with intracerebroventricular haemorrhage.

The growth and properties of Pd and Pt on Al2O3/NiAl(110)

Abstract: Small metal particles have strongly size-dependent properties, which - in the case of supported particles - are also influenced by the particle substrate interaction. We have investigated such effects for Pd deposited on a thin alumina film grown on NiAl(i10) by probing the adsorption behaviour of CO. Structure and size of the metal islands were varied by employing different substrate temperatures during evaporation. We found that at 90 K small, disordered aggregates are formed, whereas deposition at 300 K results in larger crystallites with (111) facets. The CO thermal desorption spectra show a size-dependent behaviour which can be attributed to a higher degree of CO coordination with decreasing particle size. The results are compared with the corresponding behaviour of Pt. In contrast to Pd, Pt leads to a strong interaction with the substrate at 300 K. This gives rise to a desorption feature of CO in a temperature range which is typical for transition metal oxides.

Molecular and immunohistochemical p53 status in liposarcoma and malignant fibrous histiocytoma. Identification of seven new mutations for soft tissue sarcomas

Abstract: Background. p53 mutations are the most frequently observed tumor-related genetic changes. Mutational analysis concerns mostly carcinomas and is not comprehensive for soft tissue sarcomas. Among soft tissue sarcomas, malignant fibrous histiocytoma (MFH) and liposarcoma represent the most frequent tumor types. Most of the few identified mutations for soft tissue sarcomas are localized in the core domain of p53. A correlation between p53 positive immunoreactivity, missense mutations, and a poor prognosis is generally assumed. However, the character of p53 mutations and their functional importance for the clinical process is still unknown. Methods. Sixty-two soft tissue sarcoma samples were investigated for the presence of p53 mutations and for p53 immunoreactivity. Exons 4–9 of the p53 gene were amplified from genomic DNA with the polymerase chain reaction. A prescreen for mutations was performed by nonradioactive single strand conformation polymorphism analysis; striking cases were sequenced directly. For an evaluation of the immunohistochemical status, five p53 antibodies were used. Results. In 10 tumor samples 7 new p53 mutations and one polymorphism were identified. Mutations were detected for five liposarcomas (four patients) and four MFHs (three patients). Of the seven mutations, three were missense point mutations, three were deletions, and one was a complex conversion. All mutations but one were localized in the core domain of p53. Of 62 tumor samples, 56% (14 of 32 liposarcomas and 21 of 30 MFHs) were positive for p53 immunostaining. Conclusions. The mutations identified in the core domain affect codons that are structurally or functionally involved in DNA binding. A relation between p53 positive immunoreactivity and a poor prognosis, but not with an exclusively high tumor grade, is evident. p53 mutations in soft tissue sarcomas have a similar spectrum to those in carcinomas.