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J Koller

Publications and source records attributed to J Koller.

At least 19 recordsLinked to original sources
PubMed2001

Role of hydrogen bonding in the oxidation of thianthrene 5-oxide with peroxy acids.

The oxidation of thianthrene 5-oxide, i.e., a mechanistic probe for the assessment of the electronic character of various oxidants, with peroxybenzoic acids in various oxygen bases as solvents was investigated. The nucleophilicity (X(SO)) of peroxy acids was increasing with increasing basicity of the oxygen base. A good linear correlation was observed by plotting X(SO) values vs either the Kamlet-Taft beta values or the OOH (1)H NMR chemical shifts of m-chloroperoxybenzoic acid (m-CPBA) in solvents of various basicity. These observations, together with the results of IR and (1)H NMR spectroscopic studies of peroxybenzoic acids, and DFT (B3LYP/6-311++G) studies of the intramolecular hydrogen bonding in peroxyformic, peroxyacetic, and m-CPBA, as well as the intermolecular hydrogen bonding in the complexes of the these peroxy acids with dimethyl ether as a model oxygen base, support the involvement of the peroxy acid-oxygen base complexes in the transition states of these reactions. The increased nucleophilicity (X(SO)) of peroxy acids in basic solvents is most likely due to the increased negative charge on the terminal "electrophilic" peroxycarboxylic oxygen atom (OH), and/or the increased LUMO and HOMO energies of the peroxy acid in the complexes, as compared to those parameters in the intramolecularly hydrogen-bonded form of peroxy acids, believed to be operative in inert solvents.

Journal Article↗
PubMed2001

Reproducibility of lymphoscintigraphy in cutaneous melanoma: can we accurately detect the sentinel lymph node by expanding the tracer injection distance from the tumor site?

UNLABELLED: The aim of the study was to determine whether the sentinel lymph node (SLN) can be accurately detected in cutaneous melanoma patients when the injection distance from the tumor site is expanded. METHODS: In 100 patients with cutaneous melanoma, lymphoscintigraphy was performed twice. First, we injected 37 MBq (99m)Tc nanocolloid intracutaneously at a 2- to 5-mm distance from either the melanoma or the biopsy scar. The injection was followed by dynamic imaging, which continued until the SLN became visible. On another day, we repeated the investigation, injecting the radiopharmaceutical intracutaneously exactly 10 mm from the previous injection site. The detected SLNs of both investigations were compared to determine the number and location of SLNs for each patient. RESULTS: The SLN identification rate was 94% with close injection and 100% with 10-mm-distant injection. All SLNs detected with close injection were visible with distant injection. In 84 of 100 patients, the images of both investigations showed the same number and location of SLNs. In the remaining 16 patients, an additional SLN was detected with the distant injection. CONCLUSION: The reproducibility of lymphoscintigraphy using different injection distances was 84%. The discordance in the remaining 16% was caused by detection of a lymph node in addition to the original SLN with distant injection. Diagnostic excision of the primary tumor before lymphoscintigraphy was possible without preventing detection of the original SLN. However, in 16% of our patients, excision of an additional lymph node had to be considered when lymphoscintigraphy was performed after diagnostic excision.

Adult↗
PubMed2000

17O NMR spectroscopic characterization and the mechanism of formation of alkyl hydrotrioxides (ROOOH) and hydrogen trioxide (HOOOH) in the low-temperature ozonation of isopropyl alcohol and isopropyl methyl ether: water-assisted decomposition

Low-temperature ozonation of isopropyl alcohol (1a) and isopropyl methyl ether (1b) in [D6]acetone, methyl acetate, and tert-butyl methyl ether at -78 degrees C produced the corresponding hydrotrioxides, Me2C(OH)(OOOH) (2a) and Me2C(OMe)(OOOH) (2b), along with hydrogen trioxide (HOOOH). All the polyoxides investigated were characterized for the first time by 17O NMR spectroscopy of highly 17O-enriched species. The assignment was confirmed by GIAO/MP2/6-31++G* calculations of 17O NMR chemical shifts, which were in excellent agreement with the experimental values. Ab initio density functional (DFT) calculations at the B3LYP/ 6-31G*+ZPE level have clarified the transition structure (TS1, deltaE = 7.4 and 10.6 kcalmol(-1), relative to isolated reactants and the complex 1a-ozone, respectively) for the ozonation of 1a: this, together with the formation of HOOOH and some other products, indicates the involvement of radical intermediates (R*, *OOOH) in the reaction. The activation parameters for the decomposition of the hydrotrioxides 2a and 2b (Ea, = 23.5+/-1.5 kcalmol(-1), logA = 16+/-1.8) were typical for a homolytic process in which cleavage of the ROOOH molecule occurs to yield a radical pair [RO* *OOH] and represents the lowest available energy pathway. Significantly the lower activation parameters for the decomposition of HOOOH (Ea = 16.5+/-2.2 kcalmol(-1), logA = 9.5+/-2.0) relative to those expected for the homolytic scission of the HO-OOH bond [bond dissociation energy (BDE) = 29.8 kcalmol(-1), CCSD(T)/6-311++G**] are in accord with the proposal that water behaves as a bifunctional catalyst and therefore participates in a "polar" (non-radical) decomposition process of this polyoxide. A relatively large acceleration of the decomposition of the hydrotrioxide 2a in [D6]acetone, accompanied by a significant lowering of the activation energies, was observed in the presence of a large excess of water. Thus intramolecular 1,3-proton transfer probably also involves the participation of water and is similar to the mechanism proposed for the decomposition of HOOOH. This hypothesis was further substantiated by the B3LYP/6-31++ G*+ZPE calculations for the participation of water in the decomposition of CH3OOOH, which revealed two stationary points on the potential energy surface corresponding to a CH3OOOH-HOH complex and a six-membered cyclic transition state TS2. The energy barriers were comparable with those calculated for HOOOH, that is, deltaE = 15.0 and 21.5 kcalmol(-1) relative to isolated reactants and the CH3OOOH-HOH complex, respectively.

Journal Article↗
PubMed2000

Accuracy of echocardiographic right ventricular parameters in patients with different end-stage lung diseases prior to lung transplantation.

BACKGROUND: Because there are few data available on the accuracy of 2D-echocardiography to assess right ventricular (RV) size and function in patients with far-advanced lung disease, in this prospective study, we compared various echocardiographic RV parameters with RV volumes derived from magnetic resonance imaging (MRI). METHODS: In 32 patients (18 male, 17 female) presenting for lung transplantation, we measured RV end-diastolic and end-systolic area as well as derived RV fractional area change, long-axis diameter, short-axis diameter, tricuspid valve anulus diameter (using 2D apical or sub-costal 4-chamber view), and RV end-diastolic diameter (using M-mode in the parasternal short-axis view). These values were compared with RV end-diastolic and end-systolic volumes derived by MRI, serving as the gold standard. RESULTS: Right ventricular end-diastolic area was the most accurate echocardiographic parameter of RV size (correlation to MRI: r = 0.88, p < 0.001), followed by RV end-diastolic short-axis diameter (r = 0.75, p < 0.001), long axis diameter (r = 0.66, p < 0.001), and tricuspid valve anulus diameter (r = 0.63, p < 0.001). In contrast, M-mode measurement of RV end-diastolic diameter was possible in only 24/35 (68%) patients and showed a weak correlation to MRI-derived RV end-diastolic volume (r = 0.56, p = 0.004). Right ventricular fractional area change correlated well with MRI-derived RV ejection fraction (r = 0.84, p < 0.0001). In a sub-group analysis, patients with vascular lung disease showed best agreement between both methods for RV end-diastolic area and RV fractional area change compared with patients with restrictive or obstructive lung disease. CONCLUSION: This study shows that in patients with far-advanced lung diseases, RV end-diastolic area demonstrated the best correlation with MRI-derived measurement of RV end-diastolic volume, and RV fractional area change compared favorably with MRI-derived ejection fraction. Despite reduced image quality, especially in patients with obstructive lung disease, these parameters can yield clinically valuable information.

Adult↗
PubMed2000

Whole-body scintigraphy in melanoma patients: comparison of 99Tcm-tetrofosmin and 201Tl.

The aim of this study was to determine the diagnostic value of 99Tcm-tetrofosmin whole-body imaging in comparison to 201Tl scintigraphy in patients with metastatic melanoma. In 27 patients with known or suspected melanoma metastases we performed 201Tl scintigraphy and 99Tcm-tetrofosmin scintigraphy using a 1-day protocol. In five patients with known locoregional metastasis the in vivo uptake kinetics of both radiotracers were compared. The final diagnosis was confirmed by surgical histology in 39 lesions (group I) and computed tomography (CT) and clinical course in 14 lesions (group II). In group I, containing mainly locoregional metastases, 201Tl scintigraphy correctly identified 36 of 39 metastases and 99Tcm-tetrofosmin 35 of 39 resulting in a sensitivity of 92% and 90% respectively. The T/B ratios of 201Tl (1.4-4.0, mean 2.15) were statistically significantly higher in comparison to tetrofosmin (1.3-3.0, mean 1.88). However, both radiotracers showed similar uptake and washout kinetics with a maximum of tracer uptake between 1 and 5 min p.i. In group II, containing mainly cerebral and pulmonary metastases, both methods correctly identified six of 14 metastases resulting in a sensitivity of only 43%. We conclude that the uptake of 99Tcm-tetrofosmin and 201Tl in melanoma metastases is very similar. The T/B ratios with 99Tcm-tetrofosmin are significantly lower than with 201Tl. In locoregional melanoma metastases the sensitivity of tetrofosmin scintigraphy is identical with 201Tl imaging and amounts to 90%. In cerebral and lung metastases the sensitivity of both methods is limited when using whole-body scintigraphy.

Adult↗
PubMed2000

[Detection of melanoma metastases with Tc-99m-tetrofosmin].

AIM: The aim of this study was to evaluate Tc-99m-tetrofosmin whole-body imaging in the detection of metastases in patients with malignant melanoma. METHODS: In 30 patients with suspected melanoma metastases we performed whole body imaging. After administration of about 600 MBq Tc-99m-tetrofosmin dynamic images up to 10 min were performed in 7 patients (1 image per 10 sec) to evaluate the optimal tracer uptake in the metastases. In all patients whole-body images were performed 5-10 min p.i. using an acquisition time of 5 min per image. The final diagnosis was confirmed by surgical histology in 30 lesions, by computertomography and clinical course in the remaining lesions. RESULTS: Out of 64 melanoma metastases 49 were detected using Tc-99m-tetrofosmin scintigraphy (49 rp., 15 fn.). The overall sensitivity for the detection of malignant lesions was 77%. Referring only to the lymph node metastases, the sensitivity was 87% (26 rp.; 4 fn.). The maximal tracer uptake was reached 1 min after injection, with a slow decrease in the following 10 minutes. The size of the lesions ranged between 0.5 and 7.0 cm and the T/B ratios between 1.3 and 3.0 (mean 1.88). CONCLUSIONS: Tc-99m-tetrofosmin whole body imaging is a simple and side-effectless method for the detection of melanoma metastases especially of lymph node metastases. The results are comparable to Tc-99m-sestamibi and Tl-201 scintigraphy.

Adult↗
PubMed2000

Resorption and calcification of chemically modified collagen/hyaluronan hybrid membranes.

The objectives of this study were to characterize collagen/hyaluronan hybrid membrane before and after different chemical crosslinking, as well as to investigate the impact of the treatment method on resorption and calcification processes by in vivo tests. The kinetics study of resorption of collagen/hyaluronan membranes showed that after 28 days the membranes were completely resorbed. The modification of the membranes with glutaraldehyde comparing to the similar modification of pericardial tissue conducts higher calcification. Treatment with hexamethylene diisocyanate together with poly(oxyethylene) improved mechanical properties but the resorption process was similar. Additional treatments with diphenylphosphorylazide and 1-ethyl-3-(3-dimethylamino-propyl) carbodiimide (EDAC) resulted in prolongation of the resorption time. Calcification was suppressed in case of treatment with EDAC.

Administration, Cutaneous↗
PubMed1999

[Use of membranes based on collagen as tissue substitutes].

Collagen, as biocompatible and bioactive non-specific polymer, occupies prominent position in the field of tissue engineering. The advanced biomaterials prefer collagen as a matrix for biodegradable implants as are biosynthetic skin substitutes, tendon and ligament substitutes, but also cartilage. Many studies notice the application of chemically modified collagen membranes for hernia and anastomoses reparations, vascular prosthetic materials, or for collagen tubes used in regeneration of peripheral nerves. Besides of defining main problems of tissue engineering, the paper analyses the developmental tendency of these biomaterials in the world, and compares it with the situation in Slovak Republic.

Biocompatible Materials↗
PubMed1999

Changing pattern of infection in the Bratislava Burn Center.

Infection still remains one of the major problems in burn treatment. The authors investigated the occurrence of burn wound pathogens in burn wound biopsies and/or semiquantitative wound surface off-prints. As the results have shown, trends of a decreased contribution of "classical pathogens", like Staphylococcus aureus and Pseudomonas aeruginosa, to burn wound infections were observed. The role of "other pathogens", like Enterobacter, Acinetobacter, etc., which were quite rare in the past, is on the opposite, increasing. One of the explanations can be the increasing rate of early surgical treatment methods of deep burns. The results were in accordance with similar studies from other burn centres.

Acinetobacter Infections↗
PubMed1998

Detection of melanoma metastases with thallium-201 scintigraphy.

UNLABELLED: Thallium-201 accumulates well in various malignant tumors. The aim of this study was to evaluate the potential of 201Tl imaging in patients with metastatic melanoma. METHODS: Fifty patients with suspected melanoma metastases were studied after intravenous injection of a mean tracer activity of 100 MBq 201Tl-chloride. We took sequence images up to 5 min (15 sec/image) and immediate whole-body images with a double-headed camera and a high-resolution collimator. RESULTS: Of 36 patients with metastatic melanoma confirmed by histopathology, metastases were detected in 28 patients using 201Tl imaging. The tumor-to-background ratio ranged from 2.0 to 4.5 (mean 3.2). There were 8 patients with false-negative findings (sensitivity = 78%). Five false-negative findings were lymph nodes greater than 1.5 cm with tumor-to-background ratios lower than 1.5. Only a few cutaneous metastases smaller than 1 cm could be detected. There was one false-positive finding of an inflamed lymph node. The optimum time for imaging was 2-5 min postinjection. CONCLUSION: These data suggest that 201Tl imaging is an accurate method for the detection of melanoma metastases. The short waiting period after injection, the lack of side effects and the sensitivity of about 80% may qualify this method as a routine investigation in patients with high-risk melanoma.

Adult↗