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Biomedical subjects

G Burkard

Publications and source records attributed to G Burkard.

At least 19 recordsLinked to original sources
PubMed2005

Dephasing of a superconducting qubit induced by photon noise.

We have studied the dephasing of a superconducting flux qubit coupled to a dc-SQUID based oscillator. By varying the bias conditions of both circuits we were able to tune their effective coupling strength. This allowed us to measure the effect of such a controllable and well-characterized environment on the qubit coherence. We can quantitatively account for our data with a simple model in which thermal fluctuations of the photon number in the oscillator are the limiting factor. In particular, we observe a strong reduction of the dephasing rate whenever the coupling is tuned to zero. At the optimal point we find a large spin-echo decay time of .

Journal Article↗
PubMed2000

Universal quantum computation with the exchange interaction.

Various physical implementations of quantum computers are being investigated, although the requirements that must be met to make such devices a reality in the laboratory at present involve capabilities well beyond the state of the art. Recent solid-state approaches have used quantum dots, donor-atom nuclear spins or electron spins; in these architectures, the basic two-qubit quantum gate is generated by a tunable exchange interaction between spins (a Heisenberg interaction), whereas the one-qubit gates require control over a local magnetic field. Compared to the Heisenberg operation, the one-qubit operations are significantly slower, requiring substantially greater materials and device complexity--potentially contributing to a detrimental increase in the decoherence rate. Here we introduced an explicit scheme in which the Heisenberg interaction alone suffices to implement exactly any quantum computer circuit. This capability comes at a price of a factor of three in additional qubits, and about a factor of ten in additional two-qubit operations. Even at this cost, the ability to eliminate the complexity of one-qubit operations should accelerate progress towards solid-state implementations of quantum computation.

Journal Article↗
PubMed2000

[Background and evaluation plan of a study on self-management of anticoagulation in patients with non-valvular atrial fibrillation (SMAAF Study)].

The objective of this open, randomized, multicenter study is to investigate the benefits and economic efficiency of self-management of oral anticoagulation in patients with atrial fibrillation (SMAAF study) in comparison with a group of patients given conventional care by a general practitioner or specialist. Two thousand patients suitable for self-management will be assigned at random to either the self-management group or the control group. The numbers of thromboembolic and hemorrhagic complications requiring treatment during the 2-year follow-up period will be recorded as the primary end point. The secondary endpoint variables will be maintenance of the INR value in the individual target range, INR variance, the course of complications over time, and the cost efficiency of self-management compared with the routine procedures. The last of these parameters will include the diagnostic and/or therapeutic measures carried out, the duration of inpatient hospital treatment, and the social consequences (subsequent rehabilitation treatment, inability to work, forced retirement). The estimate of the required number of patients was based on the assumption that during long-term anticoagulant therapy within the framework of primary and secondary prevention 4% of patients with chronic non-valvular atrial fibrillation would have severe thromboembolic of hemorrhagic complications each year. Since this rate can be halved by self-management, a one-tailed chi 2-test of 80% power and a 5% significance threshold would require n = 997 patients per group. The results of the SMAAF study will establish the socioeconomic benefits of self-management in patients with non-valvular atrial fibrillation.

Administration, Oral↗
PubMed1996

Heavy-metal-responsive genes in maize: identification and comparison of their expression upon various forms of abiotic stress.

To identify genes involved in defense against heavy-metal stresses, a cDNA library originating from mercuric chloride-treated maize (Zea mays L. cv. INRA 258) leaves was constructed and analysed by differential screening using cDNAs derived from treated and untreated plants. Transcriptionally activated cDNA clones, designated CHEM (chemically-activated), were isolated and characterized. They represent various known proteins, such as glycine-rich proteins, pathogenesis-related proteins, chaperones and membrane proteins. The expression of the genes encoding these proteins was studied in maize subjected to other forms of abiotic stress. Expression of glycine-rich proteins was greatly enhanced by heat stress, and also stimulated by NaCl, polluted rainwater, wounding and cold stress. Pathogenesis-related proteins were strongly induced by ultraviolet light and to a lesser extent by NaCl, polluted rainwater and wounding. Heat-shock protein was mainly induced by heat and cold, and ubiquitin by wounding. Expression of the membrane channel protein was stimulated by heat stress, NaCl, polluted rainwater and ultraviolet-light irradiation.

Amino Acid Sequence↗
PubMed1996

[The effects of treatment with trapidil compared to nifedipine on physical, emotional and cognitive exercise tolerance in patients with coronary heart disease].

The present study was carried out to investigate exercise test results and the outcome of the quality of life after administration of trapidil (CAS 15421-84-8, Rocornal) or nifedipine (CAS 21829-25-4) to patients with coronary heart disease. The characteristics of the life quality in combination with the results of exercise test are considered of great importance for selecting medical treatment in patients with chronic stable angina pectoris. However, little information is available on how this first evaluation may be used to select the best pharmacological approach in individual patients. In this prospective multicentre study, 144 patients with stable angina were enrolled in 6 centres. Due to protocol violations and drop-outs 116 patients were evaluated for tolerability; 101 patients were evaluated for efficacy. After baseline evaluation, consisting of an exercise test and a questioning investigating patients' anginal symptoms and several psychometric testings, the patients were randomly allocated to double-blind treatment for 12 weeks with either trapidil, 200 mg t.i.d. or nifedipine, 10 mg t.i.d. according to a parallel group design. After 6 and 12 weeks exercise tests and psychometric testings were repeated. Both trapidil and nifedipine prolonged exercise tolerance (trapidil 39.2% vs. nifedipine 33.3%) or increased the total exercise over baseline levels (trapidil 57.8% vs. nifedipine 61.2%). Using Mann-Whitney U-test the SB-S-rating scale and the physician's assessment revealed a comparable improvement of life quality (trapidil 69.4% vs. nifedipine 80.0%) under both treatments. In addition patient questioning showed a significant reduction in angina attacks and in nitroglycerin consumption. None of the characteristics of anginal symptoms or exercise test gave evidence for a significant difference between nifedipine and trapidil. Both drugs demonstrated similar safety profiles (adverse events (AEs) 12.7% for trapidil and 11.1% for nifedipine); four patients of the trapidil group and one of the nifedipine group discontinued the clinical trial because of AEs. The results of a baseline exercise test and rating questionnaires may offer useful information for selecting medical treatment in stable angina pectoris.

Aged↗
PubMed1995

DNA sequence analysis of a cyclophilin gene from maize: developmental expression and regulation by salicylic acid.

In plants, such as maize, cyclophilin (Cyp) genes are expressed at a basal level in all tissues. Amounts of Cyp mRNA above the basic level are observed in germinating seedlings, in growing tissues/organs such as roots and leaf meristematic tissue of young maize plants, nodes and embryonic female inflorescences of adult plants and also in non-proliferating tissues such as the internodes of adult plants. Salicylic acid (SA) enhances the transcription of maize Cyp genes. The possible involvement of SA in the pathway leading to defense responses induced by abiotic stresses such as mercuric chloride treatment is discussed. A maize Cyp genomic clone isolated using a maize Cyp cDNA probe contains 737 bp of the 5' upstream and the entire coding region. This Cyp gene is not interrupted by intervening sequences. In the 5' upstream region, characteristic transcription signals as well as putative regulatory sequences were identified. Two TATA boxes are found at positions -56 bp and -66 bp with respect to the transcription start site. Two putative heat shock elements were identified in the promoter region; a metal regulatory element and a third heat shock element were localized in the 5' untranslated leader. Several putative polyadenylation signals and (G)T-rich sequence motifs were identified in the 3' untranslated region.

Amino Acid Isomerases↗
PubMed1995

Relationships between the degree of Helicobacter pylori colonisation and the degree and activity of gastritis, surface epithelial degeneration and mucus secretion.

This study investigates the question as to whether, in Helicobacter pylori (H.p.) gastritis, any statistically significant relationships are to be found between the following histological parameters: degree of H.p. colonisation, the degree and activity of gastritis, degree of replacement of the foveolar epithelium by regenerating epithelium, and degree of mucus depletion. Forceps biopsy material obtained from 240 patients with NUD and H.p. gastritis (3 specimens from the antrum, 2 from the corpus) were investigated. The 5 histological parameters employed were graduated semiquantitatively as follows: 0 = normal findings, 1 = minimal, 2 = low-grade, 3 = medium-grade, 4 = high-grade. The evaluation showed that the degree and activity of gastritis, the degree of replacement of foveolar epithelium by regenerating epithelial cells, and the degree of mucus depletion are dependent upon the degree of H.p. colonisation (p < 0.0001). The gastritis parameters were more marked in the antrum than in the corpus. The intercorrelations were highly significant for all five parameters investigated, both in the antrum and corpus (p < 0.0001). On the basis of these results it is concluded that for the histological assessment of H.p. gastritis, in addition to H.p. colonisation, and the degree and activity of gastritis, but also the state of the foveolar epithelium and the mucus production of these epithelial cells should be considered.

Adult↗
PubMed1994

Bean cyclophilin gene expression during plant development and stress conditions.

Cyclophilins (Cyp) are ubiquitous proteins with peptidyl-prolyl cis-trans isomerase activity that catalyses rotation of X-Pro peptide bonds and facilitates the folding of proteins; these enzymes are believed to play a role in in vivo protein folding. During development of normal bean plants, Cyp transcripts are first detected three days after beginning of germination and are present in all plant tissues examined. In a general way, higher amounts of Cyp mRNAs are found in developing tissues. Cyp mRNA accumulates in alfalfa mosaic virus-infected bean leaves and after ethephon and salicylic acid treatments. In response to a localized chemical treatment Cyp mRNA accumulation is observed in the untreated parts of the plants; however these changes in mRNA levels are restricted to the aerial part of the plant. A comparative study of Cyp mRNA accumulation in bean and maize in response to various external stimuli shows striking differences in profiles between the two plants. For instance, in response to heat shock, maize Cyp mRNA significantly accumulates, whereas no remaining mRNA is observed a few hours after the beginning of the heat stress in bean. Differences in mRNA accumulation profiles are also observed upon salt stress which induces the response earlier in maize than in bean, whereas the opposite situation is observed when plants are cold-stressed. All these findings further suggest that cyclophilin might be a stress-related protein.

Alfalfa mosaic virus↗
PubMed1994

Benefits and risks of the hypericum extract LI 160: drug monitoring study with 3250 patients.

Effectiveness and acceptance of a 4-week treatment with hypericum extract LI 160 were investigated by 663 private practitioners. The results of the 3250 patients (76% women and 24% men), were recorded using data sheets. The age of the patients ranged from 20 to 90 years (mean 51 years). Of the patients, 49% were mildly depressed, 46% intermediate, and 3% severely depressed. In about 30% of the patients, the situation normalized or improved during the therapy. Undesired drug effects were reported in 79 (2.4%) patients and 48 (1.5%) discontinued the therapy. Most frequently noted side effects were gastrointestinal irritations (0.6%), allergic reactions (0.5%), tiredness (0.4%), and restlessness (0.3%).

Adult↗
PubMed1993

[Treatment of chronic diarrhea in Crohn disease. A pilot study of the clinical effect of tannin albuminate and ethacridine lactate].

METHOD: The present prospective controlled study investigated the effect of a combination of 500 mg of tannin albuminate and 50 mg ethacridine lactate (Tannacomp) on chronic diarrhea in stable-phase Crohn's disease. Of the 30 patients admitted to the study, Crohn's disease was confined to the small intestine in 5, involved both small and large bowel in 11 patients, and only the large intestine in 14 cases. TREATMENT: Basic treatment was continued throughout the study; in addition, three times 2 tablets of Tannacomp were administered for 5 days, followed by a 5-day period of no such treatment, and then a further 5 days with the same regimen. RESULTS: At the end of the treatment phases, there was a significant reduction in stool frequency from 5.5 +/- 0.6 (mean +/- SEM) to 4.0 +/- 0.8, and the summed score of the symptoms decreased from 6.3 +/- 0.6 to 5.3 +/- 0.6; in comparison with the initial situation or at the end of the five-day period of no additional treatment, the consistency of the stools also increased. The effect of Tannacomp showed a tendency to be more marked among patients with Crohn's disease limited to the large intestine, as compared with patients with small intestinal involvement. However, before Tannacomp can be recommended as treatment of chronic diarrhea in stable-phase Crohn's disease, further studies are needed.

Adult↗
PubMed1993

Differential expression of bean chitinase genes by virus infection, chemical treatment and UV irradiation.

Three chitinases have been shown previously to be induced upon various stresses of bean leaves. Time course studies of mRNA accumulation of two of them (P3- and P4-chitinases) have been studied upon virus infection, mercuric chloride treatment and UV irradiation. In alfalfa mosaic virus (AlMV)-infected plants both mRNAs, absent in uninfected bean leaves, become detectable 36 h after inoculation. A maximum level of mRNAs is reached 84 h after inoculation and, whereas the amount of P3-ch mRNA decreases soon after having reached the maximum, the amount of P4-ch mRNA remains at high levels for several days. In mercuric chloride-treated leaves P4-ch mRNA becomes detectable 1-1.5 h after onset of treatment and a maximum level is observed between 6 h and 24 h after treatment; P3-ch mRNA becomes detectable later than P4-ch mRNA in treated leaves and reaches a maximum as late as 18 h after treatment has been applied. UV light also induces the synthesis of both mRNAs but, here again, important differences are observed in the accumulation rate of the two transcripts. The relative amounts of each mRNA induced by the different stresses have been compared. The most effective inducer of P3-ch mRNA is AlMV. In contrast, mercuric chloride induces P4-ch mRNA more efficiently than AlMV or UV light. We have also determined the complete nucleotide sequence of the cDNA encoding P3-chitinase that has been isolated from a cDNA library by using the cucumber lysozyme-chitinase cDNA as a probe. The 1072 bp P3-ch cDNA encodes a mature protein of 268 amino acid residues and the 25 residue NH2-terminal signal peptide of the precursor. Because of its high structural homology to the cucumber and Arabidopsis acidic chitinases as well as to the N-terminal amino acid sequence of the bifunctional lysozyme-chitinase from P. quinquifolia, bean P3-chitinase can be considered to belong to the class III chitinases. Southern blot analysis of bean genomic DNA revealed that P3-chitinase is encoded by a single gene.

Amino Acid Sequence↗
PubMed1992

[Long-term study "Neurodermatitis therapy using urea-containing Externa"].

A long-term study on the therapy of atopic dermatitis with topical urea agents was conducted by over 400 practising dermatologists and pediatricians in Western Germany from March 1989 to March 1991. 1905 patients of all ages who had a baseline diagnosis of acute exacerbation of their neurodermatic skin condition were entered into this open, uncontrolled, multicenter study. Acute attacks were treated with a combination of hydrocortisone and urea. Once the acute symptoms had subsided, therapy was continued with a 10% urea ointment. Over the 12-month observational period, a total of 84% of the patients were exclusively treated with the two trial preparations and only 16% additionally required other corticosteroids.

Administration, Topical↗
PubMed1991

The complete amino acid sequence of the pathogenesis-related (PR2) protein induced in chemically stressed bean leaves.

We have established the complete sequence of the 155 amino acid residues of the pathogenesis-related protein PR2 accumulating in bean leaves treated with a mercuric chloride solution. Bean PR2 whose biological function remains to be elucidated, represents a structurally unfamiliar protein in which sequence arginine, cysteine, methionine and tryptophan residues are missing. This sequence is identical to that of bean PvPR1.

Amino Acid Sequence↗
PubMed1991

Isolation of a complementary DNA encoding the bean PR4 chitinase: an acidic enzyme with an amino-terminus cysteine-rich domain.

The amino acid sequences of peptides generated by trypsin and chymotrypsin digestions of the acidic PR4 chitinase from bean were determined. Oligonucleotide primers derived from this sequence were used to synthesize a PR4 chitinase-specific probe by PCR-amplification. This probe allowed the isolation of cDNA clones encoding PR4 chitinase that have been sequenced. This acidic and extracellular chitinase shows some homology to the basic isoform from the same plant, and differs from other known acidic chitinases by the presence of an amino-terminal cysteine-rich domain. Southern blot analysis of bean genomic DNA revealed that PR4 chitinase is encoded by a single gene.

Amino Acid Sequence↗
PubMed1990

[The psychosocial status of patients with endogenous eczema. A study using cluster analysis for the correlation of psychological factors with somatic findings].

The present study was performed to investigate whether patients with atopic dermatitis differ as a group from controls on psychological measures of mood and personality or whether psychologically deviant and normal patient subgroups can be distinguished. Furthermore, we were interested in what clinical characteristics might co-vary with psychological disability in patients with atopic dermatitis. In all, 93 patients filled in a standardized mood scale (Hamburg-Erlanger-Stimmungsbarometer) and a personality scale (Kurztest zur Erfassung der Persönlichkeitsstruktur). Compared with matched controls, patients described themselves as being more anxious, more aroused, more depressed and less energetic, and they reached higher neuroticism scores. A cluster analysis identified four patient subgroups. Only one of the subgroups (n = 17) was psychologically disabled according to the questionnaire scores. In contrast to a psychologically stabile patient group, the psychologically disabled patients showed an earlier age of onset of dermatitis, but less intense itching and scratching. They reported more somatic complaints and a higher level of familial stress, were more dissatisfied with their life situation and work, had fewer friends and experienced more losses of significant others. Furthermore, they more frequently rated their disorder as being determined by psychological factors and were more intelligent. Thus, the questionnaires identified a subgroup of patients who may need psychotherapeutic interventions.

Adolescent↗
PubMed1988

[Procedures for the quantitative follow-up control of computerized perimetric findings in glaucoma].

A statistical model for long-term follow-up of glaucomatous visual fields is described. Using an analysis of individual testpoints, a statistical evaluation of visual field change is done by the Bowker symmetry test. Eccentricity of test points in the visual field, density of scotomas and number of defective test points were used as parameters. The authors demonstrate that evaluation with this method is superior to methods using total sensitivity loss or mean sensitivity of the visual field. This model is currently being used in a retrospective and a prospective glaucoma study.

Follow-Up Studies↗
PubMed1987

In vitro synthesis and processing of a bean pathogenesis-related (PR4) protein.

When bean plants (Phaseolus vulgaris var. Saxa) are treated with mercuric chloride or infected with alfalfa mosaic virus, they produce pathogenesis-related (PR) proteins. We report here that functional mRNA encoding bean PR4 protein is only present when synthesis of this protein has been induced. Treatment with mercuric chloride results in a rapid induction of functional bean PR4 mRNA (within 2-3 h), whereas in virus-infected plants this mRNA can only be detected the second day following the infection. Bean PR4 protein is synthesized in vitro, using this mRNA in a rabbit reticulocyte lysate system, as a precursor of 35 kDa. This precursor can be processed into a polypeptide having the same molecular mass (33.5 kDa) as the in vivo PR4 protein by the addition to the cell-free translation system of canine pancreatic microsomal membranes.

Electrophoresis, Polyacrylamide Gel↗