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P Komárek

Publications and source records attributed to P Komárek.

At least 19 recordsLinked to original sources
PubMed2002

[Biodistribution of low-molecular-weight proteins and technetium (99mTc) labeled peptides in an animal model of inflammation].

The aim of this study was to evaluate accumulation of the low molecular peptides and proteins labelled with 99mTc in rat inflammatory/infection foci. Peptides (human leukocyte dialysate--HLD, thymosin fraction 5--TF5, aprotinin--APT), proteins (human IgG-HIG) were labelled with 99mTc using a redox polymer. The labelling efficiency was evaluated using paper, TLC and/or column chromatography and electrophoresis. The biodistribution of the labelled substances was evaluated in Wistar rats with Staphylococcus aureus infection or with sterile kaolin suspension-induced inflammation in the left inguinal region 24 h after abscess induction. Accumulation of 99mTc activity was determined both by external gamma camera imaging and by counting dissected tissues 1-4 hours after administration. The evaluated peptides and proteins show a high labelling efficiency (99mTc-HLD > 98%, 99mTc-TF5 > 95%, 99mTc-APT > 98%, 99mTc-HIG > 95%). Use of redox polymer for labelling raises the stability of 99mTc-labelled substances so that the labelling efficiency remains to be virtually the same (95-98%) after 8 hours at least. In experimentally induced inflammation, the amount of 99mTc-peptides and 99mTc-HIG activity accumulated is 2.5-6.5 and 5.3-10.6 times, respectively, that in control tissue. A comparison of two types of model inflammations(inflammation induced by kaolin and Staphylococcus-induced inflammation) revealed the values measured with 99mTc-peptides are more than a double that induced by kaolin suspension. The studied low molecular peptides labelled with 99mTc allow rapid localisation of infection foci in the animal model. 99mTc labelled HIG seems to be useful for the detection of both infections and inflammatory lesions.

Abscess↗
PubMed2000

[Labeling products of photochemical degradation of insulin with technetium (99mTc)].

Irradiation with UV light at a wavelength of 250 nm allows to convert disulphidic groups in the structure of insulin to free SH groups with high affinity to direct labelling with 99mTc. The amount of terminal SH groups depends on irradiation time. HPLC analysis revealed that while 34% of the original amount of insulin was present after 15 minutes of irradiation (approx. intensity of 500 microW.cm2), the amounts were 25%, 10%, and 2% after 30; 60, and 120 minutes, respectively. These results correlate with the amount of SH groups released by photoactivation measured using Ellman's reagent. The product of the degraded porcine insulin was labelled with 99mTc using the redox polymer RP G25 IDA under the following conditions: pH 6.8-7.9, labelling time 15 minutes, room temperature. Radiochemical purify of the labelled product was higher than 96%. Insulin and products of its degradation were evaluated by means of size exclusion chromatography (SEC). The biodistribution of the labelled substances in laboratory animals showed activity mostly in the kidneys and liver. No specific biodistribution of the labelled products was observed in rats with experimentally induced diabetes.

Animals↗
PubMed2000

The use of redox polymers in labelling procedures of proteins and peptides with 99mTc. I. Properties of redox polymers and technique of labelling.

BACKGROUND: Using a polymer-analogue reaction, redox polymers with a dextran matrix to anchor the end alpha(beta)-alanine-N,N'-diacetate group converted into the Sn(2+) cycle have been developed for the labelling of proteins, peptides, and labile compounds with (99m)Tc. The reaction kinetics and the labelling efficiency of (99m)Tc depend primarily on the degree of dextran matrix cross-linking and the qualitative nature of the redox polymer end groups. METHODS: Preparation for labelling takes place directly in basic protein and peptide solutions without adjusting pH or adding other adjuvants. Prior to the final modification into kit form, the redox polymers are removed by ultrafiltration. RESULTS: The results of labelling of model compounds (aspartic acid, cysteine) with (99m)Tc at various solution pH values clearly show that, at pH values over 6.0, it will be primarily the free end SH groups that will serve as binding sites for the proteins and peptides. To label proteins and peptides, we selected a redox polymer with G-25 cross-linking, which allows the achievement of a radiochemical purity over 95% and high stability of the labelled compounds. CONCLUSION: The method of radiolabelling compounds with (99m)Tc based on redox polymers was developed mainly to overcome the problems faced when using other conventional methods in the labelling of sensitive compounds.

Journal Article↗
PubMed2000

The use of redox polymers in labelling procedures of proteins and peptides with 99mTc. II. Technique of preparation of kits for protein labelling by 99mTc and its effect on the stability and radiochemical purity.

BACKGROUND: Our research into new methods of labelling biologically active substances with technetium ((99m)Tc) to be used in nuclear medicine is focused on proteins and peptides whose labelling is difficult and continues to pose a problem. Use of redox polymers is the most gentle of methods as there is no need to use other compounds to modify reaction conditions, as is the way with the currently employed methods. METHODS: Kits containing proteins, e.g., human immunoglobulin (IgG), human leukocytes dialysate (HLD), were labelled with (99m)Tc using a redox polymer (RP-IDA) and/or using reduction of pertechnetate ((99m)Tc) with stannous chloride. The radiochemical purity was evaluated using paper and/or electrophoresis of the labelled proteins. The results were confirmed by column chromatography of the labelled IgG. RESULTS: Use of a redox polymer for labelling raises the stability of (99m)Tc labelled proteins so that labelling efficiency remains virtually the same (96-98%) after 30 hours while it is about 45% with the routine method using stannous chloride. The stability of protein-containing kits prepared using redox polymers was improved; the labelling efficiency of HLD and IgG after 300 days of kit storage was over 97% and 87%, respectively. CONCLUSIONS: The labelling procedure using redox polymers can be used in formulating protein- and peptide-based radiopharmaceuticals to improve their stability and (99m)Tc labelling efficiency.

Journal Article↗
PubMed1999

[Use of redox polymers for insulin labeling with technetium (99mTc)].

The paper describes a method for porcine insulin labelling with technetium(99mTc). When preparing this peptide, an insoluble redox polymer on the basis of cross-linked dextran (RP G25-IDA) was used for labelling. The prepared kits were labelled with 99mTc with a high labelling efficiency (more than 95%) and stability, as assessed using methods of chromatography. 99mTc-insulin biodistribution in rats with experimentally induced diabetes--compared with a control group--did not demonstrate specific accumulation of the labelled substance in any organ. The method for kit preparation and its labelling are mild, HPLC and SEC did not reveal any products of insulin degradation and insulin content met the standards of Ph.B. 97. This is the first case of insulin labelling with technetium(99Tc) and, also, the first use of a redox polymer for this purpose.

Animals↗
PubMed1997

[Use of photoactivation in the preparation of radiopharmaceuticals. II. Dialysate of human leukocytes labelled with technetium (99mTc)].

The paper evaluates the effect of photoactivation on dialysate of human leukocytes, on their labelling with technetium(99mTc), and on biodistribution in rats. Dialysate of human leukocytes was irradiated with UV light at 254 nm and labelled with technetium(99mTc) by reduction of pertechnetate(99mTc) with stannous chloride. Radiochemical purity was evaluated using paper chromatography. The biodistribution of labelled dialysate of human leukocytes in rats with experimentally induced inflammation was determined by counting the activity of isolated organs or by planar gamma camera imaging 4 hours after administration. Photoactivation mildly raises the number of free SH groups in leukocyte dialysate. A high labelling efficacy (97%) and stability 8 hours after labelling (94%) was achieved. An effect of radiation on labelling efficacy and stability was not demonstrated. Photoactivation has a beneficial effect on the distribution of 99mTc dialysate of human leukocytes into experimental inflammation as measured in isolated organs of rats; however, deposition into inflammatory lesions is not quite sufficient for scintigraphic imaging.

Animals↗
PubMed1997

[Non-biodegradable labelled particles for studying biodistribution of orally administered drugs].

The present paper aims at the search for radioactively labelled non-biodegradable particles of a suitable size, whose release from dosage forms and the fate in the organism can be examined scintigraphically. Particles of resins of the Amberlit and Dowex type labelled with 99mTc and 113mIn show a high efficacy of labelling. These model radioactive particles can be used in the dry form or in the form of a suspension for further studies of drug distribution from peroral dosage forms.

Administration, Oral↗
PubMed1997

[Use of photoactivation in the preparation of radiopharmaceuticals. I. Human immunoglobulin labelled with technetium (99mTc)].

The aim of the study was to evaluate the photochemical effects of ultraviolet (UV) light on biologically active substances usable in radionuclide diagnosis. Human immunoglobulin (IgG) was irradiated with UV light at 254 nm and labelled with technetium(99mTc) by reducing pertechnetate(99mTc) with stannous chloride, or by use of redox polymer (RP SP-C25). Radiochemical purity was evaluated using paper chromatography. The biodistribution of labelled IgG in rats with experimentally induced inflammation was determined by counting the 99mTc activity of isolated organs or by planar gamma camera imaging 4 and 26 hours after administration. Irradiated IgG shows a higher efficacy of 99mTc labelling (98%) compared with non-irradiated IgG (95%) and photoactivation raises the number of free SH groups. UV light has a beneficial effect on 99mTc-IgG stability. The stability of a kit prepared using redox polymer is significantly higher (by 20%) compared with that of a kit prepared using stannous chloride (by 10%). Human IgG irradiation more than triples 99mTc deposition into inflammatory lesions. Photoactivation can be used in formulating protein-based radiopharmaceuticals in an effort to improve their biodistribution in nuclear medicine diagnostic imaging.

Animals↗
PubMed1997

[Use of photoactivation in the preparation of radiopharmaceuticals. III. Human serum albumin labelled with technetium (99mTc)].

Human serum albumin was photoactivated by UV light at 254 nm and labelled with technetium(99mTc) by reducing pertechnetate(99mTc) with stannous chloride. Radiochemical purity was evaluated using paper chromatography, columns and electrophoresis. The biodistribution of labelled albumin in rats was determined by counting the activity in isolated organs 15 and 60 minutes after administration. Photoactivation raises the number of free SH groups, a fact exerting a beneficial effect on labelling efficacy. Irradiated albumin shows a higher labelling efficacy (99%) compared with non-irradiated albumin (96%). Structural changes depend on the dose of UV radiation, on the concentration of irradiated substance and on metal ion content (Sn2+). The results obtained suggest that the elimination, from blood, of albumin whose structure has been altered by photoactivation can be accelerated thereby creating the preconditions for its application in the diagnosis of inflammatory conditions.

Animals↗
PubMed1991

Myocardial scintigraphy using 99m-Tc-methoxyisobutylisonitrile (Tc-MIBI): Is it equivalent to 201-Tl?.

The results of selective coronary angiography, myocardial 201-Tl scintigraphy (stress and redistribution) and after 99m-Tc-methoxyisobutylisonitrile stress and rest injections (Tc-MIBI, Cardiolite, DuPont de Nemours, USA) were compared in 19 patients with manifest ischemic heart disease in identical three projections and after same ergometric load. All three investigations were carried out within three consecutive days. 16 patients had significant stenoses of 1-3 main coronary arteries inclusive of left coronary artery main stem, insignificant stenoses (less than 50%) were present in remaining 3 patients. Scintigraphic localizations of accumulation defects in both Tc-MIBI and 201-Tl stress scintigraphy were in accordance in 70.6% of evaluated left ventricular wall segments. A positive 201-Tl redistribution and rest-stress Tc-MIBI scintigraphic difference agreed in 52.6% images of all three projections with verified accumulation defects. The sensitivity of the detection of ischemic area in reference to the coronary angiography was nearly identical in 201-Tl (75%) and Tc-MIBI scintigraphy (81.2%). False positive accumulation defects in the apical area were revealed in three patients with insignificant coronaro-angographic findings equally after both radiopharmaceuticals. Better physical properties of 99m-Tc from the point of view of a gamma camera detection, a possibility to get markedly higher counting rate and sufficient accumulation of the radiopharmaceutical in the perfused myocardium enable to reach scintigraphic pictures with a high contrast after labelled Tc-MIBI injection, even in case of sequential impulse summation during heart cycle (gating). Thus MIBI labelled by 99m-Tc is equivalent to 201-Tl as used for myocardial scintigraphy in patients with ischemic heart disease.

Adult↗
PubMed1991

A contribution to our understanding of post-implantation cross-section reduction in the vascular prostheses.

Using theory of linear elasticity, a theoretical model describing the decrease in the flow section of artificial vascular prostheses in response to blood pressure changes in proposed. The model is based on the presumably different deformation behaviours of the vessel and the prosthesis. An increase in the vascular intima thickness in small-calibre prostheses allows greater deformations of their inner surface, closely resembling those observed in the inner surface of the intimal layer of the normal vessel. Results of an analysis presented in the article show that depending on the material properties of the vascular prosthesis there exists such a critical radius of the prosthesis that smaller calibre prostheses, when used, become occluded.

Blood Vessel Prosthesis↗
PubMed1990

[Mercaptoacetyltriglycine (MAG 3) 99mTc--a new radiopharmaceutic for uropoietic diagnoses].

The present authors show mercaptoacetyltrigylcine (MAG 3), labelled with 99mTc technetium, as a novel prospective diagnostic agent of the uropoietic system, replacing the injections of sodium iodohippurate labelled with 131I. The paper reports the procedure of labelling of this novel radiopharmaceutical with technetium 99mTc, evaluation of its quality by chromatographic methods, and biological distribution of MAG 3 in laboratory animals in comparison with the biodistribution of injections of sodium iodohippurate labelled with 131I.

Animals↗
PubMed1989

[Technetium 99m Tc labeled lipoproteins. I. Preparation and evaluation of quality].

Technetium 99m Tc labelled lipoproteins are novel diagnostic agents suitable for the study of the lipoprotein metabolism and prospectively for picturing the specific receptors. The paper reports the first results of the preparation and quality evaluation of very low density lipoproteins (VLDL) labelled with technetium 99m Tc. This radionuclide is, due to its advantageous properties, preferentially employed in nuclear medicine. The present paper resulted in a successful attempt to bind technetium 99m Tc to a lipoprotein carrier with selective transport and targeted organ-specific biodistribution.

Animals↗