J. Cvacka - Academia.edu (original) (raw)

Papers by J. Cvacka

Micron, 2006

Ultrastructure of the fat body was studied in following castes and developmental stages of Prorhi... more Ultrastructure of the fat body was studied in following castes and developmental stages of Prorhinotermes simplex: larvae of the first and the second instar, pseudergates, presoldiers, soldiers, nymphs, imagoes and mature ergatoid neotenic reproductives of both sexes. Fat body always consists of two principal cell types: adipocytes and urocytes. Adipocytes are characterized by a presence of large amounts of storage substances, namely lipid droplets, glycogen rosettes and proteins in the form of either biocrystals or vacuoles. Proportion of these components strongly varies during ontogeny. Adipocytes are equipped by a large central vacuole in which lipid droplets may resolve. Cytoplasm of urocytes contain glycogen rosettes and spherical or irregular concretions, other organelles are rare. Only adipocytes change their inner structure in the course of ontogeny: amount of glycogen decreases during the postembryonic development, it is the major kind of inclusion in the larvae but lacks in nymphs and imagoes; opposite trend is performed by lipids. The changes in protein content are less obvious but are explained and discussed. The total amount of triacylglycerols (TAGs) was found to be roughly 100 mg in a pseudergate, 250 mg in a nymph, and 30 mg in a soldier. The most abundant fatty acids in TAGs are oleic (O), stearic (S), palmitic (P) and linoleic (L) acid. TAGs form a complex mixture with OOO, OPO, OLO and OOS being the most abundant isomers. Only negligible differences exist among the castes. #

Organic Geochemistry, 2009

... gibberellins. Their use for plants growth promotion has been patented (Singh et al., 2004). .... more ... gibberellins. Their use for plants growth promotion has been patented (Singh et al., 2004). ... missing. Consequently, erroneous interpretations cannot always be avoided ([Chatterjee et al., 1972] and [Singh and Agrawal, 1994]). ...

Journal of Hazardous Materials, 2002

The photodegradation of the 1-nitropyrene (NPy) has been studied using conventional (Xe and mediu... more The photodegradation of the 1-nitropyrene (NPy) has been studied using conventional (Xe and medium pressure Hg lamps) and laser sources (XeCl excimer and Nd-YAG UV). Low energy monochromatic light sources were used to study the early stages of degradation (up to 50% conversion). The medium pressure Hg lamp was used for longer periods of irradiation (up to 6 h) and for greater degradation of NPy. The results of our work confirm that degradation occurs by radical mechanism. Aromatic hydroxymethyl, methoxy, hydroxy and nitroso derivatives of pyrene (Py) are created by low energy UV irradiation. After a massive UV irradiation, the Py aromatic system is destroyed and more polar low-molecular compounds are generated. The photochemical method described in this paper, based on irradiation by UV lamp, is therefore, suitable for degradation of fused benzene ring(s) and thus should also be effective for degradation of other nitrated polycyclic aromatic compounds.

Journal of Biological Chemistry, 2013

Background: Mechanism of CD36 inhibition by sulfo-N-succinimidyl oleate (SSO) was explored using ... more Background: Mechanism of CD36 inhibition by sulfo-N-succinimidyl oleate (SSO) was explored using mass spectrometry and mutagenesis. Results: SSO binds lysine 164 and inhibits uptake of fatty acids and oxLDL. Conclusion: Lysine 164 is important for CD36-mediated fatty acid uptake and Ca 2ϩ signaling. Significance: Fatty acids and oxLDL bind to the same site within a hydrophobic pocket of CD36 shared by several lipid ligands.

The Journal of Lipid Research, 2012

This article is available online at http://www.jlr.org Dietary WEs are an important source of ver... more This article is available online at http://www.jlr.org Dietary WEs are an important source of very long chain fatty alcohols and acids that exert regulatory roles in the cholesterol metabolism ( 11 ). Naturally occurring WEs usually form complex mixtures composed of many molecular species. These mixtures contain straight-and branchedchain esters of various chain lengths and numbers of double bonds depending on the biochemical synthetic pathways in particular organisms. WEs are also produced industrially and used in large quantities in cosmetics, polishes, lubricants, surface coating, and other applications ( 12 ). Gas chromatography (GC) has frequently been used for analyzing WEs, often after their hydrolysis. The separation of intact WEs has been made possible by the introduction of high-temperature columns. GC coupled with electron ionization mass spectrometry (GC/EI-MS) offers high separation effi ciency, ease of use, and mass spectra allowing structure elucidation. Other analytical methods based on liquid chromatography/mass spectrometry or matrix-assisted laser desorption/ionization mass spectrometry ( 13-15 ) can also be utilized, especially in the case of thermally unstable or insuffi ciently volatile WEs.

Journal of Chromatography A, 2001

Validity of five models suggested for expressing the relationship between vapour pressures and GC... more Validity of five models suggested for expressing the relationship between vapour pressures and GC retention times measured on a non-polar capillary column were tested on a common set of compounds [five homologous series of the type H-(CH ) -Y, where Y denotes Cl, Br, CHO, OCOCH and COOCH , and n varies from 6 to 14]. Standard methods of 2 n 3 3 statistical analysis, as well as vapour pressure values obtained independently from direct vapour pressure measurements were used as validity criteria. For the 40-compound data set examined, the methods provided vapour pressures agreeing within 9.2-24.7% (average absolute percent error) with direct experimental data.

Fresenius' journal of analytical chemistry, 2001

The use of modern electroanalytical techniques, namely differential pulse polarography, different... more The use of modern electroanalytical techniques, namely differential pulse polarography, differential pulse voltammetry on hanging mercury drop electrode or carbon paste electrode, adsorptive stripping voltammetry and high performance liquid chromatography with electrochemical detection for the determination of trace amounts of carcinogenic N-nitroso compounds, azo compounds, heterocyclic compounds, nitrated polycyclic aromatic hydrocarbons and aromatic and heterocyclic amines is discussed. Scope and limitations of these methods are described and some practical applications based on their combination with liquid-liquid or solid phase extraction are given.

The Annals of occupational hygiene, 1998

As a part of a program devoted to the destruction of antineoplastic agents, three chemical method... more As a part of a program devoted to the destruction of antineoplastic agents, three chemical methods readily available in the hospital environment, viz. oxidation with sodium hypochlorite (NaClO, 5%), hydrogen peroxide (H2O2, 30%), and Fenton reagent (FeCl2.2H2O; 0.3 g in 10 ml H2O2, 30%), were tested for the degradation of four anticancer drugs: Amsacrine, Azathioprine, Asparaginase and Thiotepa. The efficiency of the degradation was monitored by high-performance liquid chromatography. The mutagenicity of the degradation residues were tested by Ames test using tester strains Salmonella typhimurium TA 97a, TA 98, TA 100 and TA 102 with and without an exogenous metabolic activation system. Using sodium hypochlorite, 98.5% of Amsacrine, 99.0% of Azathioprine, 99.5% of Asparaginase and 98.7% of Thiotepa were destroyed after 1 hr. The hydrogen peroxide treatment destroyed 99% of Asparaginase and 98.7% of Thiotepa in 1 hr. However, this procedure was not efficient for the treatment of Amsa...

Journal of Biological Chemistry, 2013

Background: Mechanism of CD36 inhibition by sulfo-N-succinimidyl oleate (SSO) was explored using ... more Background: Mechanism of CD36 inhibition by sulfo-N-succinimidyl oleate (SSO) was explored using mass spectrometry and mutagenesis. Results: SSO binds lysine 164 and inhibits uptake of fatty acids and oxLDL. Conclusion: Lysine 164 is important for CD36-mediated fatty acid uptake and Ca 2ϩ signaling. Significance: Fatty acids and oxLDL bind to the same site within a hydrophobic pocket of CD36 shared by several lipid ligands.

Chemical Senses, 2012

Within the multitude of chemical signals used by termites, the trail marking by means of pheromon... more Within the multitude of chemical signals used by termites, the trail marking by means of pheromones is ubiquitous. Chemistry and biology of the trail-following communication have been described in more than 60 species from all families except for the Neotropical Serritermitidae. The chemical ecology of Serritermitidae is of special interest not only as a missing piece of knowledge on the diversity and evolution of isopteran pheromones but also because it may contribute to the debate on the phylogenetic position of this family, which is still unresolved. Therefore, we aimed in this study to identify the trail-following pheromone of the serritermitid Glossotermes oculatus. Based on a combined approach of analytical chemistry, electrophysiology, and behavioral bioassays, we propose (10Z,13Z)-nonadeca-10,13-dien-2-one to be the trail-following pheromone of G. oculatus, secreted by the sternal gland of pseudergates. Thus, we report on a new termite trail-following pheromone of an unexpected chemical structure, a ketone with 19 carbons, contrasting with unsaturated alcohols containing 12 carbons as trail-following pheromones in other advanced termite families. In addition to this unique trail-following pheromone, we also describe the sternal gland in pseudergates as an organ of unusual shape, size, and structure when compared with other isopteran species. These results underline the peculiarity of the family Serritermitidae and prompt our interest in the chemistry of pheromones in the other genus of the family, Serritermes.

Analytical Chemistry, 2003

The fabrication and characterization of boron-doped diamond microelectrodes for use in electroche... more The fabrication and characterization of boron-doped diamond microelectrodes for use in electrochemical detection coupled with capillary electrophoresis (CE-EC) is discussed. The microelectrodes were prepared by coating thin films of polycrystalline diamond on electrochemically sharpened platinum wires (76-, 25-, and 10-µm diameter), using microwave-assisted chemical vapor deposition (CVD). The diamond-coated wires were attached to copper wires (current collectors), and several methods were explored to insulate the cylindrical portion of the electrode: nail polish, epoxy, polyimide, and polypropylene coatings. The microelectrodes were characterized by scanning electron microscopy, Raman spectroscopy, and cyclic voltammetry. They exhibited low and stable background currents and sigmoidally shaped voltammetric curves for Ru(NH 3 ) 6 3+/2+ and Fe(CN) 6 3-/4at low scan rates. The microelectrodes formed with the large diameter Pt and sealed in polypropylene pipet tips were employed for end-column detection in CE. Evaluation of the CE-EC system and the electrode performance were accomplished using a 10 mM phosphate buffer, pH 6.0, run buffer, and a 30-cm-long fused-silica capillary (75-µm i.d.) with dopamine, catechol, and ascorbic acid serving as test analytes. The background current (∼100 pA) and noise (∼3 pA) were measured at different detection potentials and found to be very stable with time. Reproducible separation (elution time) and detection (peak current or area) of dopamine, catecho,l and ascorbic acid were observed with response precisions of 4.1% or less. Calibration curves constructed from the peak area were linear over 4 orders of magnitude, up to a concentration between 0.1 and 1 mM. Mass limits of detection for dopamine and catechol were 1.7 and 2.6 fmol, respectively (S/N ) 3). The separation efficiency was ∼33 000, 56 000, and 98 000 plates/m for dopamine, catechol, and ascorbic acid, respectively. In addition, the separation and detection of 1-and 2-naphthol in 160 mM borate buffer, pH 9.2, was investigated. Separation of these two analytes was achieved with efficiencies of 118 000 and 126 000 plates/m, respectively.

Micron, 2006

Ultrastructure of the fat body was studied in following castes and developmental stages of Prorhi... more Ultrastructure of the fat body was studied in following castes and developmental stages of Prorhinotermes simplex: larvae of the first and the second instar, pseudergates, presoldiers, soldiers, nymphs, imagoes and mature ergatoid neotenic reproductives of both sexes. Fat body always consists of two principal cell types: adipocytes and urocytes. Adipocytes are characterized by a presence of large amounts of storage substances, namely lipid droplets, glycogen rosettes and proteins in the form of either biocrystals or vacuoles. Proportion of these components strongly varies during ontogeny. Adipocytes are equipped by a large central vacuole in which lipid droplets may resolve. Cytoplasm of urocytes contain glycogen rosettes and spherical or irregular concretions, other organelles are rare. Only adipocytes change their inner structure in the course of ontogeny: amount of glycogen decreases during the postembryonic development, it is the major kind of inclusion in the larvae but lacks in nymphs and imagoes; opposite trend is performed by lipids. The changes in protein content are less obvious but are explained and discussed. The total amount of triacylglycerols (TAGs) was found to be roughly 100 mg in a pseudergate, 250 mg in a nymph, and 30 mg in a soldier. The most abundant fatty acids in TAGs are oleic (O), stearic (S), palmitic (P) and linoleic (L) acid. TAGs form a complex mixture with OOO, OPO, OLO and OOS being the most abundant isomers. Only negligible differences exist among the castes. #

Organic Geochemistry, 2009

... gibberellins. Their use for plants growth promotion has been patented (Singh et al., 2004). .... more ... gibberellins. Their use for plants growth promotion has been patented (Singh et al., 2004). ... missing. Consequently, erroneous interpretations cannot always be avoided ([Chatterjee et al., 1972] and [Singh and Agrawal, 1994]). ...

Journal of Hazardous Materials, 2002

The photodegradation of the 1-nitropyrene (NPy) has been studied using conventional (Xe and mediu... more The photodegradation of the 1-nitropyrene (NPy) has been studied using conventional (Xe and medium pressure Hg lamps) and laser sources (XeCl excimer and Nd-YAG UV). Low energy monochromatic light sources were used to study the early stages of degradation (up to 50% conversion). The medium pressure Hg lamp was used for longer periods of irradiation (up to 6 h) and for greater degradation of NPy. The results of our work confirm that degradation occurs by radical mechanism. Aromatic hydroxymethyl, methoxy, hydroxy and nitroso derivatives of pyrene (Py) are created by low energy UV irradiation. After a massive UV irradiation, the Py aromatic system is destroyed and more polar low-molecular compounds are generated. The photochemical method described in this paper, based on irradiation by UV lamp, is therefore, suitable for degradation of fused benzene ring(s) and thus should also be effective for degradation of other nitrated polycyclic aromatic compounds.

Journal of Biological Chemistry, 2013

Background: Mechanism of CD36 inhibition by sulfo-N-succinimidyl oleate (SSO) was explored using ... more Background: Mechanism of CD36 inhibition by sulfo-N-succinimidyl oleate (SSO) was explored using mass spectrometry and mutagenesis. Results: SSO binds lysine 164 and inhibits uptake of fatty acids and oxLDL. Conclusion: Lysine 164 is important for CD36-mediated fatty acid uptake and Ca 2ϩ signaling. Significance: Fatty acids and oxLDL bind to the same site within a hydrophobic pocket of CD36 shared by several lipid ligands.

The Journal of Lipid Research, 2012

This article is available online at http://www.jlr.org Dietary WEs are an important source of ver... more This article is available online at http://www.jlr.org Dietary WEs are an important source of very long chain fatty alcohols and acids that exert regulatory roles in the cholesterol metabolism ( 11 ). Naturally occurring WEs usually form complex mixtures composed of many molecular species. These mixtures contain straight-and branchedchain esters of various chain lengths and numbers of double bonds depending on the biochemical synthetic pathways in particular organisms. WEs are also produced industrially and used in large quantities in cosmetics, polishes, lubricants, surface coating, and other applications ( 12 ). Gas chromatography (GC) has frequently been used for analyzing WEs, often after their hydrolysis. The separation of intact WEs has been made possible by the introduction of high-temperature columns. GC coupled with electron ionization mass spectrometry (GC/EI-MS) offers high separation effi ciency, ease of use, and mass spectra allowing structure elucidation. Other analytical methods based on liquid chromatography/mass spectrometry or matrix-assisted laser desorption/ionization mass spectrometry ( 13-15 ) can also be utilized, especially in the case of thermally unstable or insuffi ciently volatile WEs.

Journal of Chromatography A, 2001

Validity of five models suggested for expressing the relationship between vapour pressures and GC... more Validity of five models suggested for expressing the relationship between vapour pressures and GC retention times measured on a non-polar capillary column were tested on a common set of compounds [five homologous series of the type H-(CH ) -Y, where Y denotes Cl, Br, CHO, OCOCH and COOCH , and n varies from 6 to 14]. Standard methods of 2 n 3 3 statistical analysis, as well as vapour pressure values obtained independently from direct vapour pressure measurements were used as validity criteria. For the 40-compound data set examined, the methods provided vapour pressures agreeing within 9.2-24.7% (average absolute percent error) with direct experimental data.

Fresenius' journal of analytical chemistry, 2001

The use of modern electroanalytical techniques, namely differential pulse polarography, different... more The use of modern electroanalytical techniques, namely differential pulse polarography, differential pulse voltammetry on hanging mercury drop electrode or carbon paste electrode, adsorptive stripping voltammetry and high performance liquid chromatography with electrochemical detection for the determination of trace amounts of carcinogenic N-nitroso compounds, azo compounds, heterocyclic compounds, nitrated polycyclic aromatic hydrocarbons and aromatic and heterocyclic amines is discussed. Scope and limitations of these methods are described and some practical applications based on their combination with liquid-liquid or solid phase extraction are given.

The Annals of occupational hygiene, 1998

As a part of a program devoted to the destruction of antineoplastic agents, three chemical method... more As a part of a program devoted to the destruction of antineoplastic agents, three chemical methods readily available in the hospital environment, viz. oxidation with sodium hypochlorite (NaClO, 5%), hydrogen peroxide (H2O2, 30%), and Fenton reagent (FeCl2.2H2O; 0.3 g in 10 ml H2O2, 30%), were tested for the degradation of four anticancer drugs: Amsacrine, Azathioprine, Asparaginase and Thiotepa. The efficiency of the degradation was monitored by high-performance liquid chromatography. The mutagenicity of the degradation residues were tested by Ames test using tester strains Salmonella typhimurium TA 97a, TA 98, TA 100 and TA 102 with and without an exogenous metabolic activation system. Using sodium hypochlorite, 98.5% of Amsacrine, 99.0% of Azathioprine, 99.5% of Asparaginase and 98.7% of Thiotepa were destroyed after 1 hr. The hydrogen peroxide treatment destroyed 99% of Asparaginase and 98.7% of Thiotepa in 1 hr. However, this procedure was not efficient for the treatment of Amsa...

Journal of Biological Chemistry, 2013

Background: Mechanism of CD36 inhibition by sulfo-N-succinimidyl oleate (SSO) was explored using ... more Background: Mechanism of CD36 inhibition by sulfo-N-succinimidyl oleate (SSO) was explored using mass spectrometry and mutagenesis. Results: SSO binds lysine 164 and inhibits uptake of fatty acids and oxLDL. Conclusion: Lysine 164 is important for CD36-mediated fatty acid uptake and Ca 2ϩ signaling. Significance: Fatty acids and oxLDL bind to the same site within a hydrophobic pocket of CD36 shared by several lipid ligands.

Chemical Senses, 2012

Within the multitude of chemical signals used by termites, the trail marking by means of pheromon... more Within the multitude of chemical signals used by termites, the trail marking by means of pheromones is ubiquitous. Chemistry and biology of the trail-following communication have been described in more than 60 species from all families except for the Neotropical Serritermitidae. The chemical ecology of Serritermitidae is of special interest not only as a missing piece of knowledge on the diversity and evolution of isopteran pheromones but also because it may contribute to the debate on the phylogenetic position of this family, which is still unresolved. Therefore, we aimed in this study to identify the trail-following pheromone of the serritermitid Glossotermes oculatus. Based on a combined approach of analytical chemistry, electrophysiology, and behavioral bioassays, we propose (10Z,13Z)-nonadeca-10,13-dien-2-one to be the trail-following pheromone of G. oculatus, secreted by the sternal gland of pseudergates. Thus, we report on a new termite trail-following pheromone of an unexpected chemical structure, a ketone with 19 carbons, contrasting with unsaturated alcohols containing 12 carbons as trail-following pheromones in other advanced termite families. In addition to this unique trail-following pheromone, we also describe the sternal gland in pseudergates as an organ of unusual shape, size, and structure when compared with other isopteran species. These results underline the peculiarity of the family Serritermitidae and prompt our interest in the chemistry of pheromones in the other genus of the family, Serritermes.

Analytical Chemistry, 2003

The fabrication and characterization of boron-doped diamond microelectrodes for use in electroche... more The fabrication and characterization of boron-doped diamond microelectrodes for use in electrochemical detection coupled with capillary electrophoresis (CE-EC) is discussed. The microelectrodes were prepared by coating thin films of polycrystalline diamond on electrochemically sharpened platinum wires (76-, 25-, and 10-µm diameter), using microwave-assisted chemical vapor deposition (CVD). The diamond-coated wires were attached to copper wires (current collectors), and several methods were explored to insulate the cylindrical portion of the electrode: nail polish, epoxy, polyimide, and polypropylene coatings. The microelectrodes were characterized by scanning electron microscopy, Raman spectroscopy, and cyclic voltammetry. They exhibited low and stable background currents and sigmoidally shaped voltammetric curves for Ru(NH 3 ) 6 3+/2+ and Fe(CN) 6 3-/4at low scan rates. The microelectrodes formed with the large diameter Pt and sealed in polypropylene pipet tips were employed for end-column detection in CE. Evaluation of the CE-EC system and the electrode performance were accomplished using a 10 mM phosphate buffer, pH 6.0, run buffer, and a 30-cm-long fused-silica capillary (75-µm i.d.) with dopamine, catechol, and ascorbic acid serving as test analytes. The background current (∼100 pA) and noise (∼3 pA) were measured at different detection potentials and found to be very stable with time. Reproducible separation (elution time) and detection (peak current or area) of dopamine, catecho,l and ascorbic acid were observed with response precisions of 4.1% or less. Calibration curves constructed from the peak area were linear over 4 orders of magnitude, up to a concentration between 0.1 and 1 mM. Mass limits of detection for dopamine and catechol were 1.7 and 2.6 fmol, respectively (S/N ) 3). The separation efficiency was ∼33 000, 56 000, and 98 000 plates/m for dopamine, catechol, and ascorbic acid, respectively. In addition, the separation and detection of 1-and 2-naphthol in 160 mM borate buffer, pH 9.2, was investigated. Separation of these two analytes was achieved with efficiencies of 118 000 and 126 000 plates/m, respectively.