Showing papers by "University of Crete published in 1994"
01 Mar 1994
TL;DR: The algorithm is divided into two phases, a dynamical neural network identifier is employed to perform "black box" identification and then a dynamic state feedback is developed to appropriately control the unknown system.
Abstract: In this paper, we are dealing with the problem of controlling an unknown nonlinear dynamical system. The algorithm is divided into two phases. First a dynamical neural network identifier is employed to perform "black box" identification and then a dynamic state feedback is developed to appropriately control the unknown system. We apply the algorithm to control the speed of a nonlinearized DC motor, giving in this way an application insight. In the algorithm, not all the plant states are assumed to be available for measurement. >
435 citations
255 citations
TL;DR: In this paper, it was shown that no causal Green's function can give the correct linearized response to certain bilocalized distributions, even though these distributions obey the constraints of linearization stability.
Abstract: Classical gravitation on de Sitter space suffers from a linearization instability. One consequence is that the causal response to a spatially localized distribution of positive energy cannot be globally regular. We use this fact to show that no causal Green's function can give the correct linearized response to certain bilocalized distributions, even though these distributions obey the constraints of linearization stability. We avoid the problem by working on the open submanifold spanned by conformal coordinates. The retarded Green's function is first computed in a simple gauge, then the rest of the propagator is inferred by analyticity — up to the usual ambiguity about real, analytic and homogeneous terms. We show that the latter can be chosen so as to give a propagator which does not grow in any direction. The ghost propagator is also given and the interaction vertices are worked out.
176 citations
TL;DR: In this article, the products of the 254 nm photolysis of ppm levels of DMDS have been studied as a function of the O2 partial pressure at 760 Torr (N2 + O2) and 298±2 K. The major sulfur containing compounds detected were SO2 and CH3SO3H (methane sulfonic acid, MSA).
Abstract: The products of the 254 nm photolysis of ppm levels of DMDS have been studied as a function of the O2 partial pressure at 760 Torr (N2 + O2) and 298±2 K. The major sulfur containing compounds detected were SO2 and CH3SO3H (methane sulfonic acid, MSA) and the major carbon containing compounds were CO, HCHO, CH3OH and CH3OOH (methyl hydroperoxide). Within the experimental error limits the observed sulfur and carbon balances were approximately 100%. CH3OOH has been observed for the first time in such a photooxidation system. Its observation provides evidence for the formation of CH3 radicals by the further oxidation of the CH3S radicals formed in the primary photolysis step. From the behavior of the DMDS photolysis products as a function of the O2 partial pressure, O3 concentration and added OH radical source it is postulated that the further reactions of CH3SOH (methyl sulfenic acid), formed in the reaction OH + CH3SCCH3 → CH3SOH + CH3S, are the main source of MSA in the 254 nm photolysis of DMDS. Some of the possible implications of the results of this study for the degradation mechanisms of other atmospherically important organic sulfur compounds, in particular DMS, are briefly considered.
155 citations
TL;DR: In this article, an upper bound for this linear form can be obtained by employing the Neron-Tate height function and a lower bound is provided by a recent theorem of S. David.
Abstract: In order to compute all integer points on a Weierstras equation for an elliptic curve E/Q, one may translate the linear relation between rational points on E into a linear form of elliptic logarithms. An upper bound for this linear form can be obtained by employing the Neron-Tate height function and a lower bound is provided by a recent theorem of S. David. Combining these two bounds allows for the estimation of the integral coefficients in the group relation, once the group structure of E(Q) is fully known. Reducing the large bound for the coefficients so obtained to a manageable size is achieved by applying a reduction process due to de Weger. In the final section two examples of elliptic curves of rank 2 and 3 are worked out in detail.
149 citations
TL;DR: In this article, the radiative transfer including both scattering and absorption has been computed for a range of model galaxies in various orientations to find the best observable diagnostics for the amount of internal extinction within spiral galaxies.
Abstract: In order to find the best observable diagnostics for the amount of internal extinction within spiral galaxies, we have constructed realistic models for disk galaxies with immersed dust layers. The radiative transfer including both scattering and absorption has been computed for a range of model galaxies in various orientations. Standard galaxy surface photometry techniques were then applied to the numerical data to illustrate how different observables such as total magnitude, color and luminosity distribution behave under given conditions of dust distribution. This work reveals a set of superior diagnostics for the dust in the disk. These include not only the integrated parameters, but also the apparent disk structural parameters, the amplitude of the asymmetry between the near and far sides of the galaxy as divided by the apparent major axis and their dependence on the orientation of the galaxy with respect to the observer. Combining the above diagnostics with our impressions of real galaxies, we arrive at the qualitative conclusion that galaxy disks are generally optically thin. Quantitative conclusions will appear in subsequent work.
110 citations
TL;DR: In this article, the authors consider tree-order graviton scattering amplitudes on a -dimensional de Sitter background in conformally flat coordinates and show that the physical problem at tree order is late interaction times rather than small spatial coordinate momenta, despite a mathematical problem at small momenta in the naive mode expansion of the propagator.
Abstract: We consider tree-order graviton scattering amplitudes on a -dimensional de Sitter background in conformally flat coordinates. Infra-red divergences which cannot be absorbed using conventional techniques are shown to arise because conformal factors from the vertices are not compensated either by propagators or by external wavefunctions. The physical problem at tree order is therefore late interaction times rather than small spatial coordinate momenta, despite a mathematical problem at small momenta in the naive mode expansion of the propagator. Even in loops, concern over small spatial momenta is physically irrelevant because the chaotic conditions likely to prevail after the Big Bang could not have resulted in the simultaneous onset of inflation over a patch extending much beyond the Hubble radius. This motivates our proposal for a propagator which can be used to compute expectation values well inside the de Sitter patch of a plausible initial state.
109 citations
TL;DR: The crystal structure of the dimeric PvuII restriction endonuclease (R.PvuII) has been determined and potential catalytic residues can be deduced from the structural similarities to R.EcoRV; a possible classification of end onuclease structures on the basis of the positions of the scissile phosphates is discussed.
Abstract: The crystal structure of the dimeric PvuII restriction endonuclease (R.PvuII) has been determined at a resolution of 2.4A. The protein has a mixed alpha/beta architecture and consists of two subdomains. Despite a lack of sequence homology, extensive structural similarities exist between one R.PvuII subdomain and the DNA-binding subdomain of EcoRV endonuclease (R.EcoRV); the dimerization subdomains are unrelated. Within the similar domains, flexible segments of R.PvuII are topologically equivalent to the DNA-binding turns of R.EcoRV; potential catalytic residues can be deduced from the structural similarities to R.EcoRV. Conformational flexibility is important for the interaction with DNA. A possible classification of endonuclease structures on the basis of the positions of the scissile phosphates is discussed.
102 citations
TL;DR: In this article, the elastic constants of realistic amorphous carbon networks were analyzed and it was shown that there is always softening of elastic constants even in the case of nearly tetrahedral coordinations.
Abstract: We calculated and analyzed for the first time the local atomic stress distributions and the elastic constants of realistic amorphous carbon networks. We found that there is always softening of the elastic constants of these isotropic systems, even in the case of nearly tetrahedral coordinations. The local stresses play a very important role in determining the hybridization of a site during the formation of the amorphous phase.
101 citations
TL;DR: Protein sequence comparisons with the available RXR sequences indicate that although insect USP-like sequences are more related to each other than to vertebrates RXRs, their inter se similarities are lower than in the case of the vertebrate RXRs.
93 citations
TL;DR: It is proposed that singlet oxygen, which is generated during aerobic illumination of the PS II complex, is responsible for the photobleaching of photosynthetic pigments, D1 protein degradation and protein cross-linking.
TL;DR: Amoxicillin-clavulanate caused a higher and more persistent increase in gastrointestinal colonization by yeasts compared to ciprofloxacin, sulfamethoxazole-trimethoprim or ampicillin when the same antibiotics were used.
Abstract: The effects of four antibiotics on the yeast flora of the human gut were evaluated. Forty adult cancer patients who received therapy with amoxicillin-clavulanate, ciprofloxacin, sulfamethoxazole-trimethoprim or ampicillin were studied prospectively. Quantitative stool cultures for yeasts were performed immediately before, at the end of and one week after the end of the antibiotic treatment. Amoxicillin-clavulanate caused a higher and more persistent increase in gastrointestinal colonization by yeasts compared to ciprofloxacin, sulfamethoxazole-trimethoprim or ampicillin. The present results are similar to those obtained in a mouse model of gastrointestinal colonization by Candida albicans when the same antibiotics were used.
TL;DR: The findings suggest that the enhancer effect is mediated by synergistic interactions between the trans-acting factors which recognize the apo C-III regulatory elements and HNF-4 which binds to the proximal apo A-IV promoter.
Abstract: Apolipoprotein A-IV expression is limited to intestinal and hepatic cells, suggesting a tissue specific transcriptional regulation of its gene. To investigate the mechanism controlling apo A-IV transcription we have analysed its promoter region by in vitro DNA binding and transient transfection experiments. DNase I footprinting analysis of the proximal promoter with rat liver nuclear extracts revealed four protected regions: AIVA (-32 to -22), AIVB (-84 to -42), AIVC (-148 to -92) and AIVD (-274 to -250). Element AIVC which is necessary for maximal promoter activity, binds HNF-4, Arp-1 and Ear-3 with similar affinity in a mutually exclusive manner. HNF-4 transactivated chimeric constructs containing intact AIVC site in the context of either the apo A-IV promoter or the heterologous thymidine kinase minimal promoter, while Arp-1 and Ear-3 repressed this activation. Increasing amounts of HNF-4 alleviated Arp-1 or Ear-3 mediated repression, suggesting that the observed opposing effects is a result of direct competition of these factors for the same recognition site. In transient transfection assays the apo A-IV promoter region (-700 to +10) had a very low activity in cells of hepatic (HepG2) and intestinal (CaCo2) origin. This activity was increased 13 to 18-fold when the upstream elements of the distantly linked apo C-III gene were fused to the proximal promoter. Results obtained with different 5' and 3' deletion constructs indicated that the cis-acting elements F to J between the nucleotides -500 and -890 of the apo C-III promoter were absolutely necessary to drive maximal enhancement in HepG2 and CaCo2 cells. The apo C-III upstream elements enhanced the activity of the minimal AdML promoter or the apo A-IV site C mutant less efficiently than the intact apo A-IV or AdML promoter constructs containing single HNF-4 sites. The findings suggest that the enhancer effect is mediated by synergistic interactions between the trans-acting factors which recognize the apo C-III regulatory elements and HNF-4 which binds to the proximal apo A-IV promoter.
TL;DR: Results show that the dnaA cognate comes from Wolbachia, and evidence is presented that presence of the bacterium can cause partial cytoplasmic incompatibility between infected and non‐infected D, melanogaster strains.
Abstract: Using oligonucleotide primers derived from the aligned polypeptide sequences of several prokaryotic dnaA genes, we amplified from Drosophila melanogaster DNA a 557 bp fragment containing a single open reading frame. The predicted peptide sequence shows a significant similarity to previously characterized protein sequences that are encoded by the dnaA genes of several prokaryotes. The dnaA sequences are also detectable by PCR in DNA from Drosophila simulans and Nasonia vitripennis flies which are infected by a symbiotic bacterium assigned to the type species Wolbachia pipientis. A tetracycline treatment that eradicates bacterial parasites from insects, abolishes the dnaA sequences from Drosophila and Nasonia DNA. In addition, dnaA-positive Drosophila melanogaster contain numerous rod-shaped bacteria in embryos, which are abolished in subsequent generations after treatment with tetracycline. Combined with phylogenetic analysis of DnaA and 16S rRNA sequences, these results show that the dnaA cognate comes from Wolbachia. A survey of Drosophila stocks using PCR amplification of dnaA and 16S rRNA sequences showed that Wolbachia is widely spread among D. melanogaster laboratory strains but absent from several established strains of the Mediterranean fruit fly Ceratitis capitata. Evidence is also presented that presence of the bacterium can cause partial cytoplasmic incompatibility between infected and non-infected D. melanogaster strains.
TL;DR: Ground- and drinking water volumes of 1-2.5 l at concentrations levels of 0.1-5 micrograms/l were used for application of the Trace enrichment and determination method, and both adsorbents provided recoveries of 75-95%.
TL;DR: An extension of the well-known coherent-potential approximation is developed for the study of various properties of random arrangements of spherical dielectric scatterers and suggests that the positions of the band gaps in periodic dielectic structures are closely related with the range of localized states in random dielectrics media.
Abstract: An extension of the well-known coherent-potential approximation is developed for the study of various properties of random arrangements of spherical dielectric scatterers. Some of the short-range order is taken into account by considering a coated sphere as the basic scattering unit. A generalization of the energy-transport velocity is obtained. The validity of our approach is checked by comparison with experimental results, as well as with numerical calculations. Results for the long-wavelength effective dielectric constant, phase velocity, energy-transport velocity, mean free path, and diffusion coefficient are presented and compared with experiments on scattering from dielectric spheres. In addition, our findings suggest that the positions of the band gaps in periodic dielectric structures are closely related with the range of localized states in random dielectric media.
22 Aug 1994
TL;DR: A theory of equivalences for timed systems is developed, which concludes that two systems are equivalent iff external observers cannot observe differences in their behavior.
Abstract: We develop a theory of equivalences for timed systems. Two systems are equivalent iff external observers cannot observe differences in their behavior. The notion of equivalence depends, therefore, on the distinguishing power of the observers. The power of an observer to measure time results in untimed, clock, and timed equivalences: an untimed observer cannot measure the time difference between events; a clock observer uses a clock to measure time differences with finite precision; a timed observer is able to measure time differences with arbitrary precision.
TL;DR: PCR amplification using random primers was applied to distinguish between incipient species of the malaria vector Anopheles gambiae, providing a tool for rapid and efficient diagnosis, which previously relied on cytological examination of polytene chromosomes.
Abstract: We have applied PCR amplification using random primers to distinguish between incipient species of the malaria vector Anopheles gambiae. Individuals belonging to three chromosomally characterized West African forms of this mosquito, which are important epidemiologically as they differ in vectorial capacity, were sampled both from laboratory stocks and from wild populations collected in three localities. The techniques used allowed for the unambiguous classification of the mosquitoes, providing a tool for rapid and efficient diagnosis, which previously relied on cytological examination of polytene chromosomes.
TL;DR: In this article, the geometrical string has been formulated on the euclidean lattice, and it has been extended to random walks and random hypersurfaces (membrane and p-branes).
TL;DR: In this paper, a series of distannyl derivatives, 1-9, were studied for their application as phosphate-selective carriers in polymer-based liquid membranes, and a drastically different potentiometric behavior was observed depending on the distance between the tin(IV) coordinating centers and the ligands attached to them.
Abstract: A series of distannyl derivatives, 1–9, were studied for their application as phosphate-selective carriers in polymer-based liquid membranes. A drastically different potentiometric behavior was observed depending on the distance between the tin(IV) coordinating centers and the ligands attached to them. Some of the compounds examined, i.e. (PhSnBr2)2CH2(1) and (Me3SiCH2SnCl2CH2)2 (3) showed very high potentiometric selectivity towards phosphate over other lipophilic anions such as perchlorate and thiocyanate. Results indicate that (1) the optimal number of CH2 groups between the Sn-centers are either one or three, (2) the electron-withdrawing power of the organic ligands attached to Sn-centers strongly influences the overall response towards phosphate, and (3) the steric effect of the organic substituents is important in the potentiometric selectivity observed.
TL;DR: It is found that the addition of CB to glutathionyl-F-actin results in extensive fragmentation of the filaments, as demonstrated by electron microscopy and by a significant reduction of the relative viscosity of actin solutions, consistent with the idea that CB shortens glutathioneyl-Actin filaments by a mechanism distinct from barbed end capping.
TL;DR: The different responses of catalase expression in dividing and nondividing tobacco and grapevine mesophyll protoplasts may indicate a specificity ofCatalase related to induction of totipotency.
Abstract: Based on our previous results that peroxidase is induced in dividing tobacco protoplasts but it is not expressed in the nondividing grapevine (Vitis vinifera L.) protoplasts during culture (C.I. Siminis, A.K. Kanellis, K.A. Roubelakis-Angelakis [1993] Physiol Plant 87: 263-270), we further tested the hypothesis that oxidative stress may be implicated in the recalcitrance of plant protoplasts. The expression of catalase, a major defense enzyme against cell oxidation, was studied during isolation and culture of mesophyll protoplasts from the recalcitrant grapevine and regenerating tobacco (Nicotiana tabacum L.). Incubation of tobacco leaf strips with cell wall-degrading enzymes resulted in a burst of catalase activity and an increase in its immunoreactive protein; in contrast, no such increases were found in grapevine. The cathodic and anodic catalase isoforms consisted exclusively of subunits [alpha] and [beta], respectively, in tobacco, and of subunits [beta] and [alpha], respectively, in grapevine. The catalase specific activity increased only in grapevine protoplasts during culture. The ratio of the enzymatic activities to the catalase immunoreactive protein declined in dividing tobacco protoplasts and remained fairly constant in nondividing tobacco and grapevine protoplasts during culture. Also, in dividing tobacco protoplasts the de novo accumulation of the catalase [beta] subunit gave rise to the acidic isoenzymes, whereas in nondividing tobacco and grapevine protoplasts, after 8 d in culture, only the basic isoenzymes remained due to de novo accumulation of the [alpha] subunit. The pattern of catalase expression in proliferating tobacco leaf cells during callogenesis was similar to that in dividing protoplasts. The different responses of catalase expression in dividing and nondividing tobacco and grapevine mesophyll protoplasts may indicate a specificity of catalase related to induction of totipotency.
TL;DR: C60 and C70 sensitize the photooxygenation of 2-methyl-2-butene as well as (E)-2-methyl -2-pentene-1, 1, 1-d3 by the intermediacy of singlet oxygen as mentioned in this paper.
TL;DR: The results suggest that the process of malignant transformation may be characterized by changes in the state of the polymerization of actin and in the stability of the microfilament network indicating that both features could potentially serve as markers determine the transformed state of keratinocytes.
Abstract: The state of polymerization of actin and the organization of actin filaments is widely believed to be related to cellular transformation. Since the intracellular monomer (G) and filamentous (F) actin content reflects the state of microfilament polymerization, we measured the G/total actin ratio in primary cultures of normal and malignant human keratinocytes. In normal keratinocytes the mean value of this ratio was 0.30 +/- 0.03 (mean +/- SE, n = 15), while in basal cell carcinoma (BCC) keratinocytes it was 0.49 +/- 0.03 (n = 8) and in squamous cell carcinoma keratinocytes (SCC) 0.5 +/- 0.07 (n = 4), indicating a 1.7-fold increase of the G/total actin ratio in malignant cells. These results imply that the proportion of polymerized actin is decreased markedly in malignant keratinocytes, suggesting alterations of microfilament structures which probably occur during the transformation process. This was supported by the morphological changes of microfilament structures as assessed by fluorescence microscopy. A different distribution of actin filaments in normal and malignant cells became evident; stress-fibres were converging in patches at several points in SCC cells, when compared to normal keratinocytes. Furthermore, incubation of normal and malignant keratinocytes with cytochalasin B indicated differences in the resistance of their microfilament networks. After 1 h exposure to 10(-6) and 10(-5) M cytochalasin B, microfilaments in normal cells appeared to be less affected than their counterparts in neoplastic cells. Even in a high excess of cytochalasin B (10(-4) M), normal keratinocytes preserved their shape, while both basal cell and SCC were totally disrupted.(ABSTRACT TRUNCATED AT 250 WORDS)
TL;DR: In this article, a formal theory and detailed calculations for phase-dependent laser-atom interactions involving autoionizing states are presented, which can be applied to a much more complex situation in Xe, involving many channels, not amenable to simple analytical expressions, but exhibiting equally profound effects, including a modification of the branching ratio of two different products.
Abstract: We present a formal theory and detailed calculations for phase-dependent laser-atom interactions involving autoionizing states. First, through simple models, we demonstrate that the simultaneous one- and three-photon excitation of one or two neighboring autoionizing states can exhibit profound changes of the line shape, as the relative phase of the two fields is varied from 0 to \ensuremath{\pi}. Through a proper choice of the field intensities and the phase, we obtain analytical results showing that one can cancel the transition to the discrete or the continuum part of the wave function, thereby leading to a flat or a completely symmetric line shape, respectively. At higher intensities, additional effects come into play, providing additional coupling between the discrete and continuum parts, which also exhibits a phase dependence. Finally, our theory is applied to a much more complex situation in Xe, involving many channels, not amenable to simple analytical expressions, but exhibiting nevertheless equally profound effects, including a modification of the branching ratio of two different products. The theory, which is here developed for atomic autoionization, is in fact fairly general and should pertain to related problems in any system involving discrete states embedded in continua.
TL;DR: It is suggested that endometriosis is a condition which induces a rise in interleukin levels and Danazol also appears significantly to reduce endometRIosis — associated autoimmune abnormalities.
Abstract: The aim of this study was to verify to what extent danazol alters cell-mediated immunity. To this end, cell-mediated immunity was studied in 10 infertile patients with endometriosis and in 10 normal controls. Nonspecific parameters studied included serum SIL-2R, IL-6 and IL-1a levels. We also investigated the effect of treatment with Danazol on the levels of SIL-2R, IL-6 and IL-1a in women with endometriosis. Blood SIL-2R, IL-6 and IL-1a levels were measured in endometriotic women before treatment, during the last fifteen days of a 6-months course of Danazol and three months after treatment. Only one blood sample was taken from 10 women without endometriosis. SIL-2R, IL-6 and IL-1a levels were higher in women with endometriosis before treatment compared with controls. Administration of the drug significantly reduced the levels of SIL-2R (P<0.001), IL-6 (P<0.05) and IL-1a (P<0.01). Our findings suggest that endometriosis is a condition which induces a rise in interleukin levels. Danazol also appears significantly to reduce endometriosis — associated autoimmune abnormalities.
TL;DR: Selective extraction of the 22, 10 kDa, CP 26 and CP 29 proteins demonstrated that these species are not involved in the binding of the extrinsic proteins or the DCMU sensitivity of the Photosystem II complex.
Abstract: A highly purified oxygen evolving Photosystem II core complex was isolated from PS II membranes solubilized with the non-ionic detergent n-octyl-β-D-thioglucoside. The three extrinsic proteins (33, 23 and 17 kDa) were functionally bound to the PS II core complex. Selective extraction of the 22, 10 kDa, CP 26 and CP 29 proteins demonstrated that these species are not involved in the binding of the extrinsic proteins (33, 23 and 17 kDa) or the DCMU sensitivity of the Photosystem II complex.
TL;DR: In this article, the authors studied the deformation spaces of quasi-Fuchsian groups and showed that these spaces contain subspaces isomorphic to Teichmuller spaces, and are often useful for the study of properties of the punctured torus.
Abstract: Deformation spaces of quasi-Fuchsian groups provide the simplest nontrivial examples of deformation spaces of Kleinian groups. Their understanding is of interest with respect to the study of more general Kleinian groups. On the other hand, these spaces contain subspaces isomorphic to Teichmuller spaces, and are often useful for the study of properties of Teichmuller space. A recent example of this is the study of the Teichmuller space of the punctured torus by Keen and Series [KS].
TL;DR: BTC, loaded as its tetraacetoxymethyl ester (AM ester) into mouse myeloma P3X cells, responded only when cytoplasmic Ca2+ exceeded typical intracellular calcium concentrations, and appears to be useful in excitatory cells or extracellular spaces with intrace cellular calcium concentrations high enough to saturate typical excitation ratio Ca2- indicators such as Fura-2.
TL;DR: The results suggest a relationship between levels of C-myc p62, p53 and PCNA proteins and aggressiveness of the cutaneous T-cell lymphomas and neither LMP-1 expression nor EBV EBER l/2 transcripts were detected in the series suggesting that EBV is not involved in the pathogenesis of cutaneous lymphomas.
Abstract: The expression of C-myc p62, bcl-2, p53, PCNA and EBV-encoded LMP-1 proteins was studied by immunohistochemistry on paraffin-embedded skin specimens from 14 patients with early stage (premycotic erythema and second stage plaques) mycosis fungoides (MF), 21 patients with advanced stage MF (third stage plaques and tumors), 3 patients with Sezary's syndrome (SS) and 3 patients with pleomorphic medium and large cell cutaneous T-cell lymphomas (PML-CTCL). All 41 cases were also screened for the presence of EBV by using RNA in situ hybridization with EBER 1/2 oligonucleotides. Increased expression of C-myc p62, p53 and PCNA proteins was found in PML-CTCL and advanced stages of MF as compared to early stages of MF. These results suggest a relationship between levels of C-myc p62, p53 and PCNA proteins and aggressiveness of the cutaneous T-cell lymphomas. Furthermore, C-myc p62 and bcl-2 proteins were found to be frequently coexpressed in the present series. In view of the background information from in vitro findings and animal models that cooperation of C-myc and bcl-2 is important for lymphomagenesis, our results suggest that coexpression of these oncogenes may be implicated in the pathogenesis and/or the progression of cutaneous T-cell lymphomas. Neither LMP-1 expression nor EBV EBER l/2 transcripts were detected in our series suggesting that EBV is not involved in the pathogenesis of cutaneous T-cell lymphomas.