Sianette Kwee's research while affiliated with Aarhus University and other places

Publications (33)

Article
Full-text available
This paper describes the effect of weak microwave fields on the amounts of heat-shock proteins in cell cultures at various temperatures. The field was generated by signal simulation of the Global System for Mobile communications (GSM) of 960 Mhz, used in portable phones. Transformed human epithelial amnion (AMA) cells, growing on glass coverslips,...
Article
The number of reports on the effects induced by radiofrequency (RF) electromagnetic fields and microwave (MW) radiation in various cellular systems is still increasing. Until now no satisfactory mechanism has been proposed to explain the biological effects of these fields. One of the current theories is that heat generation by RF/MW is the cause, i...
Chapter
In spite of numerous studies of the biological effects from exposure to weak electromagnetic(EM) fields, the issue of whether continuous exposure to these fields involves health risks, is still a subject for considerable debate. On cellular level effects on cell proliferation, enzyme activities, calcium transport, transcription and chromosome abera...
Article
Due to the use of mobile telephones, there is an increased exposure of the environment to weak radiofrequency (RF) electromagnetic fields, emitted by these devices. This study was undertaken to investigate if the microwave radiation from these fields will have a similar effect on cell proliferation as weak electromagnetic (ELF) fields. The field wa...
Article
A significant increase in cell growth was registered in human epithelial amnion (AMA) cells, when exposed to a sinusoidal 50 Hz, 50 μT electromagnetic field (S. Kwee and P. Raskmark, Bioelectrochem. Bioenerg., 36 (1995) 109). To study the effects of incoherent magnetic fields on the biological changes caused by the electromagnetic fields, varying l...
Article
To study the effect of extremely low frequency (ELF) magnetic fields on cell growth, human cells (AMA cells) and K14 skin fibroblasts cells, growing in monolayer culture, were exposed to a sinusoidal 50 Hz, 80 μT field. Exposure times varied from 15 to 90 min. Changes in cell proliferation rates were then studied during subsequent field-free incuba...
Article
A comparative study of the electroporation of transformed human amnion (AMA) cells and their primary counterpart is presented. The differences in conditions for electroporation, membrane resealing and viability between these two cell types are reported, as well as the effects of the introduction of three different antibodies on cell proliferation a...
Chapter
A technique was developed to introduce monoclonal antibodies into cultured cells by electroporation, while retaining cell viability at the same time (Kwee et al., 1990). This enabled us to study cell growth and DNA synthesis in response to electroporation and the following uptake of specific antibodies.
Article
Cultured cells grown in monolayers were permeabilized by applying low-voltage electric pulses. The permeabilized cells were able to incorporate extracellular nucleotides into their DNA, as well as various monoclonal antibodies as determined by indirect immunofluorescence. Complete reversibility and long term viability were retained. Both applied vo...
Article
Cultured cells grown in monolayers were permeabilized by applying low-voltage electric pulses. The permeabilized cells were able to incorporate extracellular nucleotides into their DNA, as well as various monoclonal antibodies as determined by indirect immunofluorescence. Complete reversibility and long term viability were retained. Both applied vo...
Article
Full-text available
Comprehensive, computerized databases of cellular protein information derived from the analysis of two-dimensional gels, together with recently developed techniques to microsequence proteins offer a new dimension to the study of genome organization and function. In particular, human protein databases provide an ideal framework in which to focus the...
Article
Databases of protein information from human embryonal lung fibroblasts (MRC-5) have been established using computer analyzed two-dimensional gel electrophoresis. One thousand four hundred and eighty-two cellular proteins (1060 with isoelectric focusing and 422 with nonequilibrium pH gradient electrophoresis, in the first dimension) ranging in molec...
Article
Databases of protein information derived from the analysis of two-dimensional gels have been established from transformed human amnion cells (AMA) and peripheral blood mononuclear cells (PBMCs). A total of 1781 [35S]methionine-labeled AMA proteins (1274 IEF, 537 NEPHGE) and a total of 1311 proteins from PBMC (948 IEF, 363 NEPHGE) were resolved and...
Chapter
The process of the reduction of oxygen to water in the mitochondria has been widely studied in the course of time. It is generally accepted that oxygen is reduced by cytochrome oxidase, the terminal enzyme in the electron transport chain, in a single 4-electron 4-proton step. However, the discussion about the true mechanism of the process is still...
Article
The oxidation of 6,7-dimethyltetrahydropterin (2-amino-6,7-dimethyl-5,6,7,8-tetrahydro-4-pteridone) was studied by electroanalytical techniques and by its reaction with the one-electron acceptors oxygen and ferricytochrome c. The results indicated that the oxidation process consisted of two one-electron steps, involving the transient generation of...
Article
The application of quinoxaline as a mediator in the indirect electrolysis of various hemoproteins is presented.Quinoxaline is reduced primarily to the radical anion, which can transfer its electron. Metalloproteins can serve as electron acceptors, in which case the metal ion is reduced. Hemoglobin, myoglobin, cytochrome c and cytochrome oxidase are...
Chapter
Binding of dodecyl octaethyleneglycol monoether (C12E8), purified Triton X-100 and dodecyldimethylamino oxide (DDAO) to various integral membrane proteins was studied by chromatographic procedures. Binding capacity decreased in the following order: bacteriorhodopsin ~ mammalian rhodopsin > photochemical reaction center > sarcoplasmic reticulum Ca2+...
Article
An electrochemical synthesis of isomer-free 6-methylpterin from folic acid has been developed. Folic acid is reduced to 7,8-dihydrofolic acid via 5,8-dihydrofolic acid. Under acidic conditions the C(9)N(10) bond in 7,8-dihydrofolic acid is reduced electrochemically, resulting in 6-methyl-7,8-dihydropterin and p-aminobenzoylglutamic acid. 6-Methylp...
Article
Binding of dodecyloctaethyleneglycol monoether (C12E3) and purified Triton X-100 to various integral membrane proteins was studied by chromatographic procedures. Binding capacity decreased in the following order: bovine rhodopsin greater than photochemical reaction center greater than sarcoplasmic reticulum Ca2+-ATPase. The detergents were bound in...
Article
Tetrahydrofolic acid (H4PteGlu) functions as a cofactor for a large group of enzyme-catalyzed reactions. Due to the stereoselective nature of these reactions only one diastereomer can be utilized. In the reduction of L-folic acid to tetrahydrofolic acid a second asymmetric centre is created (at C-6) yielding 2 diastereomers. Tetrahydrofolic acid ca...
Article
An electrochemical synthesis of 5,6,7,8-tetrahydrofolic acid (H4PteGlu) from folic acid (PteGlu) has been developed. In the first step folic acid is reduced, via 5,8-dihydrofolic acid (5,8-H2PteGlu), to 7,8-H2PteGlu. Reduction of the protonated 7,8-H2PteGlu cleaves C(9)-N(10), but reduction of the unprotonated compound at a more negative potential...
Article
The electrochemical reduction of the disulfide bonds in α-chymotrypsin and trypsin is described. After reduction a separation of the respective chains is attempted by gel-filtration. It is shown that biological activity is dependent on the number of disulfide bonds cleaved.
Article
Direct electrolysis of proteins in neutral solutions has been met with limited success, but an electrochemical reduction of disulfide bonds in proteins may be obtained in the presence of a pteridone, which has been previously employed as a mediator in other systems. In certain cases the addition of guanidine hydrochloride made possible a more compl...
Article
Some Macromolecular compounds have been reduced or oxidized electrolytically by means of two mediator systems, both derived from 2-aminopteridone-4. As substrates NAD+ (reduction to NADH), NADH (oxidation to NAD+, cytochrome c (reduction), hemoglobin (reduction to ferrooxyhemoglobin or to ferrohemoglobin), and insulin (reduction of two or three dis...
Article
Some substituted 4(3H)-pteridones have been investigated by classical polarography, cyclic voltammetry, and controlled potential electrolysis; based on these results, the following reaction path for substituted 2-amino-4(3H)-pteridones seems likely. In neutral and slightly alkaline solution the first step is a reversible two-electron reduction to t...
Chapter
In acidic and neutral solution 4-dimethylamino, 4-amino, 4-mercapot, 4-methylrnercapto-derivatives of quinazolines are reduced in a 2 e step to their respective 3,4-dihydro derivatives. This is followed by elimination of the substituent group, resulting in a generation of the 3,4 double bond and formation of quinazoline itself. Quinazoline is then...
Article
Durch elektrolytische Reduktion der Nitroverbindungen (I) bei kontrolliertem Kathodenpotential zu den Benzamidrazonen (II), anschließenden Ringschluß und Ammoniakabspaltung unter Bildung der Dihydrotriazine (III) und Oxidation entstehen die Benzotriazine (IV) (85-96% Ausbeute).

Citations

... Permeability and electrical conductance of lipid bilayers are rapidly increased by many orders of magnitude, where membrane changes can be reversible or irreversible, depending mainly on pulse magnitude and duration. Electroporation is known to occur in metabolically inactive systems, such as black lipid membranes [ 12] and red blood cell ghosts [ 13], as well as in isolated living cells, cells in monolayers [ 14], and cells which are part of intact living tissues [15,16]. Electroporation occurs when the transmembrane voltage reaches approximately 0.5-1 V for electric field pulses typically of 10 p.s to 10 ms duration. ...
... Several lines of evidence supported the idea that CcO may exist as a dimer in the inner mitochondrial membrane. For example, (i) the hydrodynamic size of the isolated CcO, as measured by gel filtration, was often interpreted as representing a dimeric complex [27][28][29][30]; (ii) dimeric CcO was detected by velocity and equilibrium sedimentation studies at neutral pH with a low concentration of nonionic detergent Triton X-100 [31]; (iii) functional studies revealed the interaction of cytochrome c with the isolated enzyme [32]; (iv) in early studies, CcO was found to be certainly dimeric within both two-dimensional and three-dimensional crystalline arrays [33][34][35]. On the basis of these observations, it was suggested that the dimeric structure exists under physiological conditions. ...
... 14 J.C. Trivino Pardo et al. cell proliferation (Velizarov et al., 1999;Kwee and Raskmark, 1999) as well as genotoxic potential effects (Garaj-Vrhovac and Horvat, 1990;Singh, 1995, 1996;Adey, 1997;Phillips et al., 1998) in cell culture and animals. cDNA microarray analysis reveals that some of genes, which act as principal sensors of DNA damage and activate DNA repair signaling cascade, are early activated and their expressions were maintained high since to 48 h. ...
... The introduction of DNA during the application of high intensity short electric field pulses was first described by Neumann and coworkers in the early 1980s (Neumann et al. 1982), and in recent decades gene electrotransfer has become a standard method in the transfection of a wide variety of eukaryotic cell lines (Cegovnik and Novakovic 2004). Functional gene therapy by electroporation has been applied not only using naked plasmid DNA but also siRNAs, mRNAs and other active compounds (Kwee et al. 1990;Van Tendeloo et al. 2001;Huang et al. 2011). There have been reports suggesting that other gene transferring strategies using viral vectors, chemicals or liposome-based methods may contribute to alterations in gene expression and other phenotypic changes (Fedorov et al. 2005). ...
... The first attempts to induce stereoselective electron transfer by chiral electrodes date back to the 1970s [21][22][23] when enantiomers, e.g., phenylalanine methyl ester, were either adsorbed or chemically reacted with activated electrodes. This was followed by flourishing of the "chemically modified electrodes" era [5,[24][25][26] through which solid electrodes were modified by a variety of organic and organometallic species including electroactive polymers, conducting polymer, sol-gel-based polymers and enzymes as a means of inducing chirality. ...
... The amount of activated switches as estimated by the charge passed during electrochemical reduction was 2.6% of the amount required to account for the observed enzyme activity. However, the efficiency of electrochemical reduction of protein disulfide bond is difficult to quantify by electrochemical means as previously described (Kwee, 1976). ...
... Regardless, electroanalytical studies on this topic are very scarce. In 1968, Lund et al. [27] explored the polarographic reduction of BZT, and 20 years later Pedersen et al. [28] analyzed the polarographic reduction of some BZTs in protic and aprotic media. Later on, in 2010, the electrochemical behavior of BZT in a glassy carbon electrode was investigated by Lokesh et al. [29] by cyclic voltammetry (CV) at quite high concentrations (> 60 mg L -1 ). ...
... The conclusion of Nishikimi (9) was apparently supported by Heikkila and Cohen (10), who reported that reduction of ferricytochrome c, a common assay for superoxide, took place during autoxidation of H4B. However, it should be noted that tetrahydrobiopterin directly reduces cytochrome c 3ϩ , with a rather high rate constant (k ϭ 3.4 ϫ 10 6 M Ϫ1 s Ϫ1 ) (11,12). Hence, H4B-dependent reduction of cytochrome c 3ϩ cannot be used as evidence for the occurrence of reaction 2. Likewise, nitro blue tetrazolium reduction as applied by Nikishimi (9) can only be regarded as a weak indication for the intermediacy of superoxide, because Liochev and Fridovich (13) noted that "nitro blue tetrazolium can mediate O 2 . ...
... The adverse effects of RF-EMR related to oxidative stress have been supported by several human studies (Moustafa et al. 2001;Agarwal et al. 2009;Naziroglu et al. 2012;Zothansiama et al. 2017;Bektas et al. 2020), animal studies (Akbari et al. 2014;Avci et al. 2012;Chauhan et al. 2017;Djordjevic et al. 2015;Ghazizadeh and Nazıroğlu 2014;Ghoneim and Arafat 2016;Guler et al. 2010;Kesari et al. 2011;Kumari et al. 2012;Odaci and Oziylmaz 2015;Oyewopo et al. 2017) and cell culture studies (De-Iuliis et al. 2009;Kang et al. 2014;Kim et al. 2017;Kwee et al. 2001;Lu et al. 2012). However, several studies reported no significant effect of RF-EMR on oxidative stress in different study systems (Aydogan et al. 2015;Brescia et al. 2009;Cao et al. 2009;Dogan et al. 2012;Gannes et al. 2011;Hong et al. 2012;Khalil et al. 2011). ...
... The half-life of folic acid degradation at pH 5 or higher at ambient temperature was >700 h, but the half-life dramatically fell to 24-64 h at pH values below 4 [75]. Acid hydrolysis of the C9-N10 bond of folic acid took place and 6-methylpterin or 6-methyldihydropterin were obtained under aerobic condition [76]. Folic acid was stable in the absence of oxygen. ...