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Biomedical subjects

G Krauss

Publications and source records attributed to G Krauss.

At least 19 recordsLinked to original sources
PubMed2005

Improved tolerability and efficacy in epilepsy patients with extended-release carbamazepine.

The authors conducted a 3-month, prospective, open-label study assessing the effects of switching from immediate-release carbamazepine formulations to an equal total daily dose of carbamazepine extended-release capsules (CBZ-ERC) in adolescents and adults with epilepsy. Using validated, epilepsy-specific measures the authors found that switching to CBZ-ERC significantly improved patients' adverse events and quality-of-life measures. Switching to CBZ-ERC also improved seizure control.

Adolescent↗
PubMed2003

Aquatic hyphomycetes in polluted groundwater habitats of central Germany.

Polluted groundwater wells located in a former copper shale mining district (11 sites; Mansfelder Land, Central Germany) and in meadows of the Mulde and Elbe rivers (2 sites) were assessed for occurrence and species richness of aquatic hyphomycetes. Water temperatures at all sites were relatively low and fluctuated less than in surface waters. Oxygen concentrations were always below saturation, whereas sulfate, nitrate, and phosphate levels reached extremely high values in several of the wells. Relatively high levels of Pb, Mn, and Fe were found in some of the wells, but overall few concentrations of individual metals and metalloids exceeded European guidelines for drinking water. Pollen tube growth inhibition, used to assess cytotoxicity of the water, ranged between 4 and 50%. Between 1 and 10 distinct species of aquatic hyphomycetes colonized sterile Alnus glutinosa leaves exposed at the Mansfelder Land sites; for the meadow sites, 8-20 species were found. Heliscus lugdunensis and Anguillospora sp. were the two most widespread species. Fungal colonization occurred much more slowly than in surface water, as demonstrated by scanning electron microscopy and the release of conidia from recovered leaves. The conidial output from exposed alder leaves ranged from 0.2 to 95 conidia mg (-1) dry mass, corresponding to 10% of the values for contaminated surface waters in the same region. Overall, groundwater appears to be a marginal habitat for aquatic hyphomycetes, but may nevertheless play a vital role as long-term reservoir facilitating rapid recolonization following a collapse in fungal communities in surface waters.

Copper↗
PubMed2002

UV light-damaged DNA and its interaction with human replication protein A: an atomic force microscopy study.

We have imaged a non-damaged and UV-damaged DNA fragment and its complexes with human replication protein A (RPA) using tapping mode atomic force microscopy (AFM). For imaging, molecules were immobilized under nearly physiological conditions on mica surfaces. Quantitative sizing of the 538 bp DNA before and after UV light treatment shows a reduction in the contour and persistence lengths and mean square end-to-end distance as a consequence of UV irradiation. Complexes of the UV-damaged DNA with RPA, an essential component of the initial steps of nucleotide excision repair, can be detected at high resolution with AFM and reveal conformational changes of the DNA related to complex formation. By phase image analysis we are able to discriminate between protein and DNA in the complexes. The DNA molecules are found to 'wrap' around the RPA, which in turn results in a considerable reduction in its apparent contour length.

DNA↗
PubMed2001

The protein ORF80 from the acidophilic and thermophilic archaeon Sulfolobus islandicus binds highly site-specifically to double-stranded DNA and represents a novel type of basic leucine zipper protein.

The cryptic high copy number plasmid pRN1 from the thermophilic and acidophilic crenarchaeote Sulfolobus islandicus shares three conserved open reading frames with other S.islandicus plasmids. One of the open reading frames, namely orf80, encodes a 9.5 kDa protein that has no homology to any characterised protein. Recombinant ORF80 purified from Escherichia coli binds to double-stranded DNA in a sequence-specific manner as suggested by EMSA experiments and DNase I footprints. Two highly symmetrical binding sites separated by approximately 60 bp were found upstream of the orf80 gene. Both binding sites contain two TTAA motifs as well as other conserved bases. Fluorescence measurements show that short duplex DNAs derived from a single binding site sequence are bound with submicromolar affinity and moderate cooperativity by ORF80. On DNA fragments carrying both binding sites, a rather large protein-DNA complex is formed in a highly cooperative manner. ORF80 contains an N-terminal leucine zipper motif and a highly basic domain at its C-terminus. Compared to all known basic leucine zipper proteins the order of the domains is reversed in ORF80. ORF80 may therefore constitute a new subclass of basic leucine zipper DNA-binding proteins.

Amino Acid Sequence↗
PubMed2001

Binding of XPA and RPA to damaged DNA investigated by fluorescence anisotropy.

The proteins XPA and RPA are assumed to be involved in primary damage recognition of global genome nucleotide excision repair. XPA as well as RPA have been each reported to specifically bind DNA lesions, and ternary complex formation with damaged DNA has also been shown. We employed fluorescence anisotropy measurements to study the DNA-binding properties of XPA and RPA under true equilibrium conditions using damaged DNA probes carrying a terminal fluorescein modification as a reporter. XPA binds with low affinity and in a strongly salt-dependent manner to DNA containing a 1,3-d(GTG) intrastrand adduct of the anticancer drug cisplatin or a 6-nt mismatch (K(D) = 400 nM) with 3-fold preference for damaged vs undamaged DNA. At near physiological salt conditions binding is very weak (K(D) > 2 microM). RPA binds to damaged DNA probes with dissociation constants in the range of 20 nM and a nearly 15-fold preference over undamaged DNA. The presence of a cisplatin modification weakens the affinity of RPA for single-stranded DNA by more than 1 order of magnitude indicating that binding to the lesion itself is not a driving force in damage recognition. Our fluorescence anisotropy assays also show that the presence of XPA does not enhance the affinity of RPA for damaged DNA although both proteins interact. In contrast, cooperative binding of XPA and RPA is observed in EMSA. Our results point to a damage-sensing function of the XPA-RPA complex with RPA mediating the important DNA contacts.

Base Pair Mismatch↗
PubMed2001

Thermostable and site-specific DNA binding of the gene product ORF56 from the Sulfolobus islandicus plasmid pRN1, a putative archael plasmid copy control protein.

There is still a lack of information on the specific characteristics of DNA-binding proteins from hyperthermophiles. Here we report on the product of the gene orf56 from plasmid pRN1 of the acidophilic and thermophilic archaeon Sulfolobus islandicus. orf56 has not been characterised yet but low sequence similarily to several eubacterial plasmid-encoded genes suggests that this 6.5 kDa protein is a sequence-specific DNA-binding protein. The DNA-binding properties of ORF56, expressed in Escherichia coli, have been investigated by EMSA experiments and by fluorescence anisotropy measurements. Recombinant ORF56 binds to double-stranded DNA, specifically to an inverted repeat located within the promoter of orf56. Binding to this site could down-regulate transcription of the orf56 gene and also of the overlapping orf904 gene, encoding the putative initiator protein of plasmid replication. By gel filtration and chemical crosslinking we have shown that ORF56 is a dimeric protein. Stoichiometric fluorescence anisotropy titrations further indicate that ORF56 binds as a tetramer to the inverted repeat of its target binding site. CD spectroscopy points to a significant increase in ordered secondary structure of ORF56 upon binding DNA. ORF56 binds without apparent cooperativity to its target DNA with a dissociation constant in the nanomolar range. Quantitative analysis of binding isotherms performed at various salt concentrations and at different temperatures indicates that approximately seven ions are released upon complex formation and that complex formation is accompanied by a change in heat capacity of -6.2 kJ/mol. Furthermore, recombinant ORF56 proved to be highly thermostable and is able to bind DNA up to 85 degrees C.

Amino Acid Sequence↗
PubMed2001

Phase II trial of two-weekly gemcitabine in patients with advanced biliary tract cancer.

BACKGROUND: Patients with advanced biliary tract carcinoma face a dismal prognosis as no effective palliative therapy has been defined. The aim of the present phase II investigation was to evaluate the therapeutic efficacy and tolerance of a two-weekly high-dose gemcitabine regimen in this patient population. PATIENTS AND METHODS: Thirty-two consecutive patients with locally unresectable or metastatic biliary tract cancer were enrolled in this multicenter phase II trial. Treatment consisted of gemcitabine 2200 mg/m2 given as a 30-min intravenous infusion every two weeks for a duration of six months unless there was prior evidence of progressive disease. RESULTS: After a median number of 12 treatment courses, 7 of 32 (22%) patients had a partial response that lasted for a median duration of 6.0 months (range 3.5-10.0). Fourteen additional patients (44%) had stable disease, whereas eleven patients (34%) progressed despite therapy. The median time to progression was 5.6 months (range 1.8-13.0); median survival time was 11.5 months (range 3.0-24.0), and the probability of surviving beyond 12 months was 44%. The tolerance of treatment was remarkable with only two patients each experiencing grade 3 leukocytopenia, granulocytopenia and/or thrombocytopenia, and one patient had grade 3 anaemia. Similarly, nonhaematologic side effects were infrequent, and generally mild to moderate. CONCLUSIONS: Two-weekly high-dose gemcitabine seems to represent a potentially effective, safe and well-tolerated regimen for the palliative treatment of patients with advanced biliary tract cancer.

Adult↗
PubMed2000

A phase II trial of biweekly high dose gemcitabine for patients with metastatic pancreatic adenocarcinoma.

BACKGROUND: Although the novel cytidine analog gemcitabine has shown superior antitumor activity compared with weekly bolus 5-fluorouracil in patients with advanced pancreatic carcinoma, further improvements of therapeutic results are warranted. The current Phase II study was initiated to investigate whether this might be achieved by dose intensification. METHODS: Between August 1997 and September 1998, 43 consecutive patients with metastatic pancreatic adenocarcinoma were enrolled in this multicenter Phase II trial. Patients received 4 weekly courses of gemcitabine 2200 mg/m((2)) given as intravenous infusion during 30 minutes on Days 1 and 15 for a duration of 6 months unless there was prior evidence of progressive disease. The efficacy of treatment was assessed according to standard criteria, i.e., objective response, progression free survival, and overall survival, as well as by analysis of clinical benefit response (defined as >/= 50% reduction in pain intensity, >/= 50% reduction in daily analgesic consumption, and/or >/= 20 point improvement in Karnofsky performance status that was sustained for >/= 4 consecutive weeks). RESULTS: Of 43 patients evaluable for objective response, 1 achieved complete and 8 partial remissions, for an overall response rate of 21% (95% confidence interval, 10-36%); 18 additional patients (42%) had stable and 16 (37%) progressive disease. The median time to progression was 5.3 months. Median survival was 8.8 months, and the probability of surviving beyond 12 months was 26.3%. Of 36 patients with tumor-related symptoms who were considered evaluable for clinical benefit response, 16 (44%) experienced significant palliation. The median time to achieve a clinical benefit response was 6 weeks, and its median duration was 27 weeks. Chemotherapy was well tolerated, with leukopenia/granulocytopenia representing the most common side effect. Gastrointestinal and other subjective toxicities were infrequent and generally mild. CONCLUSIONS: Biweekly high dose gemcitabine seems to represent a safe, tolerable, and effective regimen for the palliative treatment of patients with advanced pancreatic carcinoma.

Adenocarcinoma↗
PubMed2000

Different generators in human temporal-parasylvian cortex account for subdural laser-evoked potentials, auditory-evoked potentials, and event-related potentials.

In order to localize cortical areas mediating pain we now report subdural cortical potentials evoked by auditory stimulation (auditory-evoked potentials - AEPs) and by cutaneous stimulation with a laser (laser-evoked potentials - LEPs). Stimulation with the laser evokes a pure pain sensation by selective activation of nociceptors. LEPs were maximal over the inferior aspect of the central sulcus and had the same polarity on either side of the sylvian fissure. AEPs were maximal posterior to the LEP maximum and had opposite polarity on opposite sides of the sylvian fissure, consistent with the location of a known generator in the temporal operculum. Auditory P3 (event-related) potentials were maximal over the temporal base. These findings demonstrate that the LEP generator is not in secondary somatosensory cortex on the parietal operculum and is different from the P3 generator.

Adult↗
PubMed2000

Treatment of unresectable, locally advanced pancreatic adenocarcinoma with combined radiochemotherapy with 5-fluorouracil, leucovorin and cisplatin.

The aim of the study was to evaluate the effectiveness and safety of a combined treatment modality including systemic chemotherapy with 5-fluorouracil (FU), leucovorin, cisplatin and external beam radiotherapy in patients with locally advanced pancreatic cancer. Systemic chemotherapy consisted of FU 400 mg m(-2) and leucovorin 20 mg m(-2) both given as intravenous bolus injection on days 1-4, plus cisplatin 20 mg m(-2) administered as 90-min infusion on days 1-4. Treatment courses were repeated every 4 weeks x 6 unless prior evidence of progressive disease. Radiation therapy using megavolt irradiation of > or = 6 MV photons with a 3- or 4-field technique was delivered during the second and third chemotherapy course, that was reduced in dose by 25%. Between October 1994 and July 1996, a total of 38 patients were entered onto this trial, all of whom were assessable for toxicity and survival. Eighteen of these (47%) had objective remissions to combined radiochemotherapy, including four CR (11%), 13 (34%) had stable disease and seven patients (18%) showed tumour progression during treatment. The median progression-free interval of the entire study population was 10 months (range 3-32), and median overall survival was 14.0 months (range 3-45+ months); 53% of all patients were alive at 12 months, and 18% of patients were alive at 24 months respectively. Severe haematological side-effects comprised neutropenia in 18%, thrombocytopenia in 8% and anaemia in 11%. The most frequent non-haematological side-effects were nausea/vomiting (WHO grade 3: 18%), and diarrhoea (grade 3: 13%). This combined radiochemotherapy regimen was tolerable and effective in patients with locally advanced pancreatic cancer. Since therapeutic results, in fact, compare favourably with other series, including surgical treatment of potentially resectable tumours, further evaluation of combined treatment modalities in the neoadjuvant setting seems warranted.

Adenocarcinoma↗
PubMed2000

Language lateralisation and early right ear deafness: was Wernicke right?

The effects of early right ear deafness on lateralisation of auditory language functions are not fully known. A 36 year old right handed man, with a history of perinatal right ear deafness and undergoing evaluation for surgical treatment of seizures that began at age 10 years was studied. Language lateralisation testing by intracarotid sodium amobarbital injection showed receptive and expressive language functions to be strongly lateralised to the left hemisphere. Results with intracarotid sodium amobarbital injection further suggested that transmission of auditory input to the patient's left hemisphere was partially dependent on ipsilateral left ear pathways. Cortical language mapping through implanted subdural electrodes localised auditory language functions to traditional left posterior perisylvian language areas. These results suggest that early right ear deafness does not impede left hemisphere lateralisation and localisation of auditory language functions. Moreover, transmission of auditory information to the patient's left hemisphere seems to be accomplished, in part, by recruitment of ipsilateral left ear pathways.

Adult↗
PubMed1999

Brief bursts of pulse stimulation terminate afterdischarges caused by cortical stimulation.

OBJECTIVE: To determine whether cortical electrical stimulation can terminate bursts of epileptiform activity in humans, we used afterdischarges (ADs) as a model of epileptiform activity. METHODS: Cortical stimulation was performed for clinical localization purposes using subdural electrodes implanted in patients undergoing preresection evaluations for treatment of medically intractable seizures. We used 0.3-millisecond pulses of alternating polarity, repeated at 50 pulses/second. When stimulation produced AD, we often applied short additional brief bursts of pulse stimulation (BPS). We examined the effectiveness of BPS in aborting ADs in 17 patients using survival analysis. RESULTS: With BPS, ADs stopped within 2 seconds in 115 cases, 2 to 5 seconds in 22 cases, and in more than 5 seconds in 89 cases. Without BPS, ADs stopped within 2 seconds in 21 cases, 2 to 5 seconds in 114 cases, and in more than 5 seconds in 340 cases. BPS was an effective method to abort ADs (Cox proportional hazards model: p<0.0001). At any time during the course of ADs, the instantaneous rate of stopping ADs within 2 seconds after BPS was applied was 4.6 times greater than when BPS was not applied (95% CI = 3.7, 5.7). In eight cases, ADs progressed to the occurrence of clinical seizures, always when BPS was not applied. CONCLUSIONS: Afterdischarges significantly decreased in duration after we applied brief bursts of pulse stimulation. Although afterdischarges are not identical to spontaneous epileptiform activity, these results support the idea that electrical stimulation, applied in an appropriate manner at seizure onset, could abort seizures in humans.

Adolescent↗
PubMed1999

Photocrosslinking locates a binding site for the large subunit of human replication protein A to the damaged strand of cisplatin-modified DNA.

The repair proteins XPA, XPC and replication protein A (RPA) have been implicated in the primary recognition of damaged DNA sites during nucleotide excision repair. Detailed structural information on the binding of these proteins to DNA lesions is however lacking. We have studied the binding of human RPA (hRPA) and hRPA-XPA-complexes to model oligonucleo-tides containing a single 1, 3-d(GTG)-cisplatin-modification by photocrosslinking and electrophoretic mobility shift experiments. The 70 kDa subunit of hRPA can be crosslinked with high efficiency to cisplatin-modified DNA probes carrying 5-iodo-2"-deoxyuridin (5-IdU) as crosslinking chromophore. High efficiency crosslinking is dependent on the presence of the DNA lesion and occurs preferentially at its 5"-side. Examination of the crosslinking efficiency in dependence on the position of the 5-IdU chromophore indicates a specific positioning of hRPA with respect to the platination site. When hRPA and XPA are both present mainly hRPA is crosslinked to the DNA. Our mobility shift experiments directly show the formation of a stable ternary complex of hRPA, XPA and the damaged DNA. The affinity of the XPA-hRPA complex to the damaged DNA is increased by more than one order of magnitude as compared to hRPA alone.

Antibodies, Monoclonal↗
PubMed1999

Adenylosuccinate synthase from Saccharomyces cerevisiae: homologous overexpression, purification and characterization of the recombinant protein.

Adenylosuccinate synthase (EC 6.3.4.4) catalyses the first committed step in the synthesis of adenosine. We have overexpressed the cloned gene of Saccharomyces cerevisiae (ADE12) in S. cerevisiae. The recombinant enzyme exhibits similar kinetic behaviour to that of the native enzyme purified from S. cerevisiae. This ter-reactant dimeric enzyme shows Michaelis-Menten kinetics only with IMP. l-Aspartate and GTP display a weak negative co-operativity (Hill coefficient 0. 8-0.9). This negative co-operativity has not yet been reported for adenylosuccinate synthases from other organisms. Another unusual feature of the enzyme from S. cerevisiae is its negligible inhibition by adenine nucleotides and its pronounced inhibition by Cl(-) ions.

Adenine Nucleotides↗
PubMed1999

Identification of the binding site for the extrahelical target base in N6-adenine DNA methyltransferases by photo-cross-linking with duplex oligodeoxyribonucleotides containing 5-iodouracil at the target position.

DNA methyltransferases flip their target bases out of the DNA double helix for catalysis. Base flipping of C5-cytosine DNA methyltransferases was directly observed in the protein-DNA cocrystal structures of M.HhaI and M.HaeIII. Indirect structural evidence for base flipping of N6-adenine and N4-cytosine DNA methyltransferases was obtained by modeling DNA into the three-dimensional structures of M.TaqI and M.PvuII in complex with the cofactor. In addition, biochemical evidence of base flipping was reported for different N6-adenine DNA methyltransferases. As no protein-DNA cocrystal structure for the related N6-adenine and N4-cytosine DNA methyltransferases is available, we used light-induced photochemical cross-linking to identify the binding site of the extrahelical target bases. The N6-adenine DNA methyltransferases M.TaqI and M.CviBIII, which both methylate adenine within the double-stranded 5'-TCGA-3' DNA sequence, were photo-cross-linked to duplex oligodeoxyribonucleotides containing 5-iodouracil at the target position in 50-60% and almost quantitative yield, respectively. Proteolytic fragmentation of the M. CviBIII-DNA complex followed by Edman degradation and electrospray ionization mass spectrometry indicates photo-cross-linking to tyrosine 122. In addition, the mutant methyltransferases M. TaqI/Y108A and M.TaqI/F196A were photo-cross-linked with 6-fold and 2-fold reduced efficiency, respectively, which suggests that tyrosine 108 is the primary site of modification in M.TaqI. Our results indicate a close proximity between the extrahelical target base and tyrosine 122 in M.CviBIII or tyrosine 108 in M.TaqI. As both residues belong to the conserved motif IV ((N/D/S)(P/I)P(Y/F/W)) found in all N6-adenine and N4-cytosine DNA as well as in N6-adenine RNA methyltransferases, a similar spatial relationship between the target bases and the aromatic amino acid residue within motif IV is expected for all these methyltransferases.

Amino Acid Sequence↗
PubMed1999

Rapid assay for one-run determination of purine and pyrimidine nucleotide contents in neocortical slices and cell cultures.

The present study describes the measurement of endogenous nucleoside di- and triphosphate contents (ATP, GTP, UTP, CTP, ADP, GDP and UDP) in rat neocortical brain slices and mixed neuronal/astrocytic corticoencephalic cultures. Determination was by means of anion-exchange HPLC using a binary gradient of 0.3 M ammonium carbonate and water. In addition, a new method is described for the identification of nucleoside triphosphates, using digestion of the nucleotides by phosphoglycerate kinase and partial splitting of nucleoside diphosphates to shift the equilibrium of the phosphoglycerate kinase reaction in direction of breakdown of nucleoside triphosphates. Finally, the determination of the sum of creatine and creatine phosphate is suggested as an alternative reference value instead of protein under conditions when cells are cultured in protein-containing medium.

Animals↗