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Biomedical subjects

A Burger

Publications and source records attributed to A Burger.

At least 19 recordsLinked to original sources
PubMed2006

Growth of aligned ZnO nanorods.

Growth of high-density and aligned ZnO nanorods on ZnO film substrate has been demonstrated using vapor-transport of thermally evaporated Zn metal powders followed by condensation. Morphological studies show that the nanorods grow preferentially from a hexagonal ZnO base with a uniform hexagonal structure following three-dimensional island-like growth mechanism. Structural and spectroscopic properties clearly indicate that the nanorods are relatively good and defect-free in quality. These nanorods have potential for technological implications.

Crystallization↗
PubMed2005

Surface-enhanced Raman spectroscopy using silver-coated porous glass-ceramic substrates.

Surface-enhanced Raman scattering (SERS) has been studied using a silver-coated porous glass-ceramic material as a new type of substrate. The porous glass-ceramic is in the CaO-TiO2-P2O5 system prepared by controlled crystallization and subsequent chemical leaching of the dense glass-ceramic, leaving a solid skeleton with pores ranging in size from 50 nm to submicrometer. Silver was coated on the surface of the porous glass-ceramic by radio frequency (RF) sputtering or e-beam evaporation in vacuum. SERS spectra of excellent quality were obtained from several dyes and carboxylic acid molecules, including rhodamine 6G, crystal violet, isonicotinic acid, and benzoic acid, using this new substrate. This new substrate showed a good compatibility with these molecules. The porous glass ceramic with a nanometer-structured surface accommodated both test molecules and silver film. The absorbed molecules were therefore better interfaced with silver for surface-enhanced Raman scattering.

Benzoic Acid↗
PubMed2004

Bioinformatics integration and agent technology.

Vast amounts of life sciences data are scattered around the world in the form of a variety of heterogeneous data sources. The need to be able to co-relate relevant information is fundamental to increase the overall knowledge and understanding of a specific subject. Bioinformaticians aspire to find ways to integrate biological data sources for this purpose and system integration is a very important research topic. The purpose of this paper is to provide an overview of important integration issues that should be considered when designing a bioinformatics integration system. The currently prevailing approach for integration is presented with examples of bioinformatics information systems together with their main characteristics. Here, we introduce agent technology and we argue why it provides an appropriate solution for designing bioinformatics integration systems.

Algorithms↗
PubMed2003

In vivo deamination of cytosine-containing cyclobutane pyrimidine dimers in E. coli: a feasible part of UV-mutagenesis.

We have estimated in vivo deamination rates for cytosines in cyclobutane pyrimidine dimers (CPD or PyPy) in UV-irradiated E. coli deficient in uracil DNA glycosylase. The protocol consisted of UV-irradiation, holding in buffer to allow for deamination of cytosines in CPDs and photoreversal (PR) to establish uracils where cytosines in CPD deaminated. The deamination rate at TC photoproducts targeting glutamine tRNA suppressor mutations was estimated from the increase in the mutation frequency after PR (MF(PR)) that developed as UV-irradiated cells were held before PR. Evidence suggested that an earlier study with this protocol under-estimated the deamination rate at sites producing the same mutations in an E. coli B/r strain. With a K12 strain, where the targeting apparently is principally by CPD and not (6-4) photoproducts, a larger rate of k = 0.0091 min(-1) at 42 degrees C resulted. The dark assay for MF also increased significantly with time for deamination consistent with a model for efficient mutation by translesion synthesis at uracil-containing CPD. In addition, we used a strain constructed by Cupples and Miller in which beta-galactosidase was inactive because -GGG- was at codon 461 and would revert to Lac(+) only when replaced by -GAG- or -GAA- for glutamate. CC photoproducts at this target site in the opposite DNA strand could reveal effects of first and second deaminations in the same CPD. MF(PR) for Lac(+) mutations increased and then decreased as a function of deamination time (at six temperatures 36-48 degrees C). Fitting an approximate model equation that distinguished two different deamination rates to these data suggested a first deamination producing Lac(+) at a rate about eight-fold less than a second deamination restoring the Lac(-) phenotype. We conclude that deamination, changing a cytosine-containing CPD to a uracil-containing CPD, could be an integral part of UV-induced C-to-T mutations.

Cytosine↗
PubMed2003

Efficacy and safety of inhaled recombinant interleukin-2 in high-risk renal cell cancer patients compared with systemic interleukin-2: an outcome study.

Systemic IL-2 is an effective treatment for low to intermediate risk mRCC patients, its efficacy is marginal in high-risk cases. Therefore, other treatment approaches are required for this population. Ninety-four high-risk patients with RCC and pulmonary metastases were treated with inhaled plus concomitant low-dose subcutaneous rhIL-2. Clinical response, survival and safety were compared with those from IL-2 given systemically at the registered dose and schedule in 103 comparable historical controls. In the rhIL-2 INH group, treatment consisted of 6.5 MIU rhIL-2 nebulized 5x/day and 3.3 MIU rhIL-2 SC once daily. The rhIL-2 SYS group received treatment which consisted of intravenous infusion of 18.0 MIU/m2/day rhIL-2 or SC injection of 3.6-18.0 MIU rhIL-2. Some patients in both groups also received IFNalpha. Mean treatment durations were 43 weeks rhIL-2 INH and 15 weeks rhIL-2 SYS. Significantly longer overall survival and progression-free survival durations were observed in the rhIL-2 INH group. The probability of survival at 5 years was 21% for the rhIL-2 INH group. No patients survived 5 years in the rhIL-2 SYS group. A multivariate analysis of overall survival adjusting for differences in baseline characteristics between the two treatment groups resulted in a risk ratio of 0.43 (95% CI 0.30-0.63; P < 0.0001). The data suggested an association between the response (SD or better) and survival, especially in the rhIL-2 INH group. The inhalation regimen was well tolerated. This outcome study suggests that administration of rhIL-2 by inhalation is efficacious and safe in high-risk mRCC patients with pulmonary metastases, who have no other treatment option available.

Administration, Inhalation↗
PubMed2002

Widespread distribution of a single drug rifampicin formulation of inferior bioavailability in South Africa.

A pharmacokinetic study of rifampicin, isoniazid, pyrazinamide and ethambutol in 118 tuberculosis patients revealed low and variable concentrations of rifampicin after 2 months of treatment on standard daily doses. A group of 53 patients exposed to specific batches of formulations containing rifampicin alone showed particularly low and variable levels of the drug. The national drug regulatory authority subsequently withdrew the batches in question, as sufficient bioavailability data had not been submitted after what the manufacturer had considered to be a minor formulation change. The evidence supports initiatives to implement bioavailability testing of new formulations (and of established formulations subsequent to changes in the manufacturing process) prior to distribution. Concerns about the bioavailability of rifampicin-containing products, including those with adequate dissolution profiles, should not be confined to fixed-dose combination anti-tuberculosis drugs, but should also be applied to single drug formulations.

Adult↗
PubMed2001

Di-tert-butyl diethylphosphoramidite as the phosphitylating reagent in the preparation of 3-deoxy-3-C-methylene-D-ribo-hexose-6-phosphate and 3-deoxy-3-C-methylene-D-erythro-pentose-5-phosphate.

3-Deoxy-3-C-methylene-D-ribo-hexose-6-phosphate and 3-deoxy-3-C-methylene-D-erythro-pentose-5-phosphate were prepared from a common intermediate 3-deoxy-3-C-methylene-1,2-O-isopropylidene-alpha-D-ribo-hexofuranose. The preparation of the phosphorylated unsaturated sugars employed di-tert-butyl diethylphosphoramidite as the phosphitylating reagent. The removal of all the protecting groups was done under acidic conditions in the ultimate step. The unsaturated sugar phosphates were competitive inhibitors but neither substrates nor inactivators of glucose-6-phosphate and ribose-5-phosphate isomerases.

Aldose-Ketose Isomerases↗
PubMed2001

Polymorphism of racemic felodipine and the unusual series of solid solutions in the binary system of its enantiomers.

The aim of this study was to investigate the binary phase diagram and the polymorphism and pseudopolymorphism of racemic and enantiomeric felodipine, including their spectroscopic and thermodynamic properties. Different crystal forms were obtained by crystallization from solvents or from the annealed melt and investigated by thermal analysis (hot stage microscopy, differential scanning calorimetry, thermogravimetric analysis), spectroscopic methods (Fourier transform infrared-and Fourier transform-Raman spectroscopy), and X-ray powder diffractometry. The binary melting phase diagram was constructed based on thermoanalytical investigations of quantitative mixtures of (+)- and (+/-)-felodipine. Two polymorphic forms of racemic felodipine, mod. I (mp, approximately 145 degrees C) and mod. II (mp, approximately 135 degrees C), as well as an acetone solvate (S(Ac )) were characterized. Melting equilibria of felodipine crystal forms decrease due to thermal decomposition. Enantiomeric felodipine was found to be dimorphic (En-mod. I: mp, approximately 144 degrees C; En-mod. II: mp, approximately 133 degrees C). Evaluation of the binary system of (+)- and (-)-felodipine results in the formation of a continuous series of mixed crystals between the thermodynamically stable and higher melting modifications, mod. I and En-mod. I. Their unusual curve course, termed as Roozeboom Type 2 b, passes through a maximum in the racemic mixture and is flanked by a minimum at 20% and at 80% (+)-felodipine. From the thermodynamic parameters, racemic mod. I and II are monotropically related. In contrast to S(Ac), the thermodynamically unstable mod. II shows a considerable kinetic stability. Because its crystallization is badly reproducible, the use of mod. II is not advisable for processing. However, desolvation of S(Ac) leads to a profitable crystal shape of mod. I, representing a pseudoracemate by definition.

Calcium Channel Blockers↗
PubMed2001

[Thyroid cancers: the Geneva experience].

AIM OF THE STUDY: To study the survival of patients with thyroid cancer operated in the same centre from 1978 to 1999. PATIENTS AND METHOD: This retrospective study included 218 patients operated on for thyroid carcinoma from january 1978 to december 1999. Modified neck dissection was performed only in the presence of one or more suspected lymph nodes. The stage of the cancer was defined according to the last TNM classification (1997). Survival data were taken from the Geneva Tumour Registry (168 patients = 77% of the series, 109 papillary carcinomas, 37 follicular, 14 undifferentiated and 8 medullary carcinomas). RESULTS: The overall 5, 10 and 15-year survival rates were respectively 88%, 84% and 80%. Papillary carcinoma was associated with the best survival at 5, 10 and 15 years (99%, 97% and 93%), despite a recurrence rate of 20% treated mainly by surgery often associated with radioiodine therapy. Follicular carcinoma had a survival rate of 83% at 5 years and 75% at 10 years. Undifferentiated carcinoma had a median survival rate of 56 days. None of the 8 patients with medullary carcinoma had died from that cancer in this series. CONCLUSION: Thyroid carcinoma carries such a good prognosis (except for undifferentiated carcinoma) that invasive surgery at first operation, like radical neck dissection, is not justified, despite a high rate of recurrence.

Adenocarcinoma, Follicular↗
PubMed2001

Short- and long-term results of total vs subtotal thyroidectomies in the surgical treatment of Graves' disease.

OBJECTIVE: Approximately one out of five patients with Graves' disease (GD) undergoes a thyroidectomy after a mean period of 18 months of medical treatment. This retrospective and non-randomized study from a teaching hospital compares short- and long-term results of total (TT) and subtotal thyroidectomies (ST) for this disease. METHODS: From 1987 to 1997, 94 patients were operated for GD. Thirty-three patients underwent a TT (mostly since 1993) and 61 a ST (keeping 4 to 8 grams of thyroid tissue--mean 6 g). All patients had received propylthiouracil and/or neo-mercazole and were in a euthyroid state at the time of surgery; they also took potassium iodide (lugol) for ten days before surgery. RESULTS: There were no deaths. Transient hypocalcemia (< 3 months) occurred in 32 patients (15 TT and 17 ST) and persistent hypocalcemia in 8 having had TT. Two patients developed transient recurrent laryngeal nerve palsy after ST (< 3 months). After a median follow-up period of seven years (1-15) with five patients lost to follow-up, 41 patients having had a ST are in a hypothyroid state (73%), thirteen are euthyroid (23%), and two suffered recurrent hyperthyroidism, requiring completion of thyroidectomy. All 33 patients having had TT--with follow-ups averaging two years (0.5-8)--are receiving thyroxin substitution. CONCLUSIONS: There were no instances of persistent recurrent laryngeal nerve palsy in either group, but persistent hypoparathyroidism occurred more frequently after TT. Long after ST, hypothyroidism developed in nearly three of four cases, whereas euthyroidy was maintained in only one-fourth; recurrent hyperthyroidy was rare.

Adolescent↗
PubMed2001

[Comparison of Hannover Functional Ability Questionnaire (FFbH) and the SF-36 subscale "Physical Functioning"].

Pretesting of a questionnaire for evaluating day-patient rehabilitation, which included comparison of the "Hannover Functional Ability Questionnaire" (FFbH) and the SF-36 subscale "physical functioning" (SF-36 PF), gave rise to more extensive validity testing of the two instruments. In the framework of an expanded pretest, a questionnaire including FFbH and SF-36 PF was sent out to 520 adult former patients who had undergone inpatient orthopaedic rehabilitation following total hip or knee replacement an average 16 months ago. Return rate was 76%. Checks on plausibility showed no complaints about the Hannover Functional Ability Questionnaire while, on the SF-36 subscale, it was found that 16 of 374 patients (4.3%) had confused positive and negative ratings. Moreover, problems were found concerning the wording of several items (understanding, multidimensionality). In contrast to the FFbH, the SF-36 subscale shows weaknesses in the formulation of its items and particularly its ratings.

Adult↗
PubMed2001

A highly efficient transposon mutagenesis system for the tomato pathogen Clavibacter michiganensis subsp. michiganensis.

A transposon mutagenesis system for Clavibacter michiganensis subsp. michiganensis was developed based on antibiotic resistance transposons that were derived from the insertion element IS1409 from Arthrobacter sp. strain TM1 NCIB12013. As a prerequisite, the electroporation efficiency was optimized by using unmethylated DNA and treatment of the cells with glycine such that about 5 x 10(6) transformants per microg of DNA were generally obtained. Electroporation of C. michiganensis subsp. michiganensis with a suicide vector carrying transposon Tn1409C resulted in approximately 1 x 10(3) transposon mutants per pg of DNA and thus is suitable for saturation mutagenesis. Analysis of Tn1409C insertion sites suggests a random mode of transposition. Transposition of Tn1409C was also demonstrated for other subspecies of C. michiganensis.

Actinomycetales↗
PubMed2001

Differences between the effects of thyroxine and tetraiodothyroacetic acid on TSH suppression and cardiac hypertrophy.

OBJECTIVE: We earlier reported marked qualitative differences between the effect of 3,5,3'-tri-iodothyroacetic acid (Triac) and tri-iodothyronine (T3) on cardiac hypertrophy at equivalent thyroid-stimulating hormone (TSH)-suppressive doses. We have now extended these studies to specific cardiac parameters. Due to its rapid metabolic clearance rate, Triac is not suitable for TSH suppression and therefore the slowly metabolized 3,5,3',5'-tetraiodothyroacetic acid (Tetrac), the precursor of Triac, was studied. METHODS: Hypothyroid rats were infused over 13 days with 1.5-40.5 nmol Tetrac/day per 100 g body weight (BW) or with 0.5-13.5 nmol thyroxine ((4)T4)/day per 100 g BW. RESULTS: The responses of serum TSH and of hepatic monodeiodinase type 1 were parallel for both hormones, their potency ratios could therefore be compared. Tetrac was revealed as being only half as active on hepatic monoiodinase type 1 despite a similar serum TSH levels. Tetrac can therefore be considered to have a preferential action on serum TSH suppression. The cardiac effects on Ca2+-ATPase (SERCA 2a) and monodeiodinase type 1 activity were qualitatively different and therefore one cannot give an overall quantitative estimate of these differences. The results showed clearly, however, that Tetrac is less efficient for all parameters studied, namely induction of cardiac hypertrophy, alpha-myosin heavy chain mRNA, monodeiodinase type 1 activity and mRNA levels of the sarcoplasmic SERCA 2a. CONCLUSION: We postulate therefore that, in the rat and possibly in man, Tetrac could represent a favorable alternative for suppression of serum TSH levels.

Animals↗
PubMed2000

Synthesis of 8-(omega-Hydroxyalkyl)-, 8-(omega-hydroxyalk-1-enyl)-, and 8-(omega-hydroxyalk-1-ynyl)adenines using the tert-butyldimethylsilyloxymethyl group, a new and versatile protecting group of adenine.

The synthesis of 12 analogues of adenine substituted at C-8 by an omega-hydroxyalkyl, omega-hydroxyalk-1-enyl, or omega-hydroxyalk-1-ynyl chain of various length has been carried out in five or six steps starting from adenine. The analogues were obtained using a new protecting group of adenine, the tert-butyldimethylsilyloxymethyl group. 9-tert-Butyldimethylsilyloxymethyl-adenine is more soluble than adenine in organic solvents. It was prepared regiospecificaly in two steps from adenine and was amenable to C-8 iodination under basic conditions and to subsequent introduction of the various carbon chains at C-8 by palladium-catalyzed cross-coupling reactions (Stille or Sonogashira). The protecting group was removed under acidic conditions, thus demonstrating its versatility.

Adenine↗
PubMed2000

(E)-1-alkyl-4-

(E)-1-Alkyl-4-[2-(alkylsulfonyl)-1-ethenyl]pyridinium salts were synthesized in two steps. These sulfones were stable at pH 7.3 and underwent a nucleophilic vinylic substitution (S(N)V) with mercaptans, including thiouracile, to give the corresponding 4-(thiovinyl)-pyridinium salts. The X-ray diffraction structure of (E)-1-methyl-4-[2-(ethylsulfanyl)-1-ethenyl]pyridinium iodide indicated conjugation of the sulfur with the pyridinium ring. (Z)-1-Methyl-4-[2-(methylsulfanyl)-1-ethenyl]pyridinium iodide, prepared from the corresponding thioether by reaction with methyl iodide in diethyl ether, underwent isomerization to the E isomer in a first-order reaction in deuterated [D6]DMSO with an activation energy of 14 kcalmol(-1). At pH 7, the (E)-1-methyl-4-[2-(methylsulfonyl)-1-ethenyl]pyridinium iodide (19) reacted specifically with thiols. The reaction of this sulfone with glutathione in a TES buffer at pH 7 was a second-order reaction (k = 4,100 M(-1)s(-1) at 30 degrees C) and gave the corresponding substitution product with an intense long wavelength absorption band (lambdamax=360 nm, epsilon = 27,500 M(-1)cm(-1)). The modification of different enzymes of known structure with 19 showed the high selectivity of this reagent towards thiol groups and its usefulness in the quantitative determination of free thiol groups in proteins.

Journal Article↗
PubMed2000

3'-Beta-ethynyl and 2'-deoxy-3'-beta-ethynyl adenosines: first 3'-beta-branched-adenosines substrates of adenosine deaminase.

The 3'-C-branched-adenosine and 2'-deoxyadenosine analogues 1-7 were tested as substrate of adenosine deaminase. The 9-(3'-C-ethynyl-beta-D-ribo-pentofuranosyl)adenine 1 and its 2'-deoxy analogue 7 were deaminated by the enzyme while the vinyl and ethyl derivatives 2 and 3 were not. The 9-(3'-C-branched-beta-D-xylo-pentofuranosyl)adenines 4-6 were deaminated by the deaminase.

Adenosine↗
PubMed2000

Energy/temperature diagram and compression behavior of the polymorphs of D-mannitol.

Three modifications of D-mannitol were produced and investigated: mod. I (mp 166.5 degrees C, heat of fusion 53.5 kJ mol(-1)), mod. II (mp 166 degrees C, heat of fusion 52.1 kJ mol(-1)), and mod. III (mp incongruent 150-158 degrees C, heat of transition, III to I 0.2 kJ mol(-1)). The measured densities are 1.490 +/- 0.000 g cm(-3) [95% confidence interval (CI)] for mod. I, 1.468 +/- 0.002 g cm(-3) (95% CI) for mod. II, and 1.499 +/- 0.004 g cm(-3) (95% CI) for mod. III. It was possible to relate the different modifications given in the literature to one of the three pure crystal forms or to mixtures of two or all three modifications. The thermodynamic relationship among the crystal forms is represented in a semi-schematic energy/temperature diagram. From these data we can conclude that mod. III is thermodynamically stable at absolute zero. It is enantiotropically related to mod. I and mod. II. FTIR and Raman spectra, differential scanning calorimetry curves, and X-ray powder patterns of these crystal forms are depicted for doubtless assignment in the future. The water uptake of the three modifications at 92% relative humidity and 25 degrees C is less than 1%. The differences of the heat capacities and the heats of solution between mod. II and III are not significant, whereas mod. I shows small significant differences compared with the other modifications. In addition, compaction studies of these crystal forms were performed by means of an instrumented hydraulic press. The results show that mod. III should have the best tableting behavior under these conditions.

Calorimetry, Differential Scanning↗