bluuebunny/crossref_metadata_2025_split huggingface dataset:
Apoptosis levels increase after castration in the CWR22 human prostate cancer xenograft
Authors: Smitherman Andrew B. , Gregory Christopher W. , Mohler James L. 
Published: July 2003

AbstractBackgroundThe role of apoptosis in the regression of human prostate cancer after androgen deprivation therapy remains controversial. Detection of caspase‐3, an ubiquitous effector of apoptosis, is a highly specific technique for in vivo evaluation of apoptosis.MethodsApoptotic rates were evaluated in the androgen‐dependent CWR22 human prostate cancer xenograft in tumors that represented time points throughout the progression from androgen‐stimulated to recurrent prostate cancer. Caspase‐3 levels in formalin‐fixed, paraffin‐embedded specimens were quantified using immunohistochemical detection and video image analysis. Western blot analysis was used to confirm the results of immunodetection.ResultsExpression of caspase‐3 reached a maximum on day 2 after castration, decreased on day 6, and remained low until tumor recurrence. The percentage of tumor area expressing caspase‐3 increased from 2.51 ± 0.44% in tumors from intact mice to 20.84 ± 1.75% on day 2 after castration. Among immunopositive cells, the intensity of caspase‐3 expression measured using the mean optical density (MOD) increased 45% (0.3762 ± 0.003 to 0.5461 ± 0.001) on day 2 after castration compared to levels detected in tumors from intact mice.ConclusionsApoptosis contributes to tumor regression after castration in the CWR22 human prostate cancer xenograft model. Prostate 57: 24–31, 2003. © 2003 Wiley‐Liss, Inc.
Extensive analysis of the 13q14 region in human prostate tumors: DNA analysis and quantitative expression of genes lying in the interval of deletion
Authors: Latil Alain , Chêne Laurent , Mangin Philippe , Fournier Georges , Berthon Philippe , Cussenot Olivier 
Published: July 2003

AbstractBACKGROUNDLoss of heterozygosity (LOH) on chromosome arm 13q14 is one of the most consistent genetic alterations in sporadic prostate cancer. This alteration may be involved in prostate oncogenesis through inactivation of one or more tumor suppressor genes (TSGs). Candidate gene expression is an approach to focus the search for TSGs in this region.METHODSWe tested 41 human sporadic prostate tumors for 13q14 LOH by using seven polymorphic markers overlapping the critical region and used a real‐time quantitative RT‐PCR assay to study the same tumors for expression of the 31 genes located in this genomic region (localized by the Human Genome Project Working Draft).RESULTSAllelic loss on at least one locus was found in 18 (41%) of the 41 tumor DNAs. Only four genes (ITM2B, CHC1L, KIAA0970, and LOC51131), located in the region most frequently deleted in prostate carcinoma, showed a significant difference in expression between normal and neoplastic prostate tissues.CONCLUSIONSGiven their location in the LOH hotspot, as indicated by our genomic analysis, ITM2B, CHC1L, KIAA0970, and LOC51131 are candidate tumor suppressor genes in this region. ITM2B that showed a significant association (P < 0.005) between expression and LOH at the corresponding locus could, furthermore, be the main target of the observed LOH at 13q in prostate tumors. Prostate 57: 39–50, 2003. © 2003 Wiley‐Liss, Inc.
C16 ceramide accumulates following androgen ablation in LNCaP prostate cancer cells
Authors: Eto Masatoshi , Bennouna Jaafar , Hunter Oriana C. , Hershberger Pamela A. , Kanto Tatsuya , Johnson Candace S. , Lotze Michael T. , Amoscato Andrew A. 
Published: July 2003

AbstractBackgroundAdenocarcinoma of the prostate is the most frequently diagnosed non‐cutaneous cancer and the second leading cause of cancer‐related deaths among men in the United States. The most successful therapies to date for this tumor have involved some form of androgen ablation. However, these therapies become ineffective as the tumor evolves to an androgen‐insensitive state. Ceramide is a lipid second messenger that has been shown to mediate growth arrest or cell death when added exogenously to prostate cancer cells. As a first step toward understanding the events that lead to the transition of prostate cancer cells to an androgen‐independent state, we considered investigating the effect of androgen ablation on endogenous ceramide levels in androgen‐sensitive and androgen‐insensitive prostate cancer cells.MethodsTo investigate the mechanisms of growth arrest/apoptosis in androgen‐sensitive (LNCaP) and insensitive (DU‐145, PC–3) cells, we used various methods including nonyl acridine orange (NAO) staining, propidium iodide (PI) staining/cell‐cycle analysis, lipid analysis, and Western blotting assays.ResultsIn this study, we demonstrate that androgen ablation drives G0/G1‐phase cell‐cycle arrest followed by progressive apoptosis in vitro, in LNCaP cells. Lipid analysis indicated an increase in C16 ceramide, which was generated via the de novo pathway as revealed by blockade of ceramide synthase by fumonisin B1. The addition of 5α‐dihydrotestosterone (DHT) or fumonisin B1 rescued LNCaP cells from apoptosis induced by androgen ablation, and decreased levels of intracellular C16 ceramide. Neither apoptosis nor an increase in C16 ceramide was observed in androgen‐independent cell lines following androgen ablation. Prostate 57: 66–79, 2003. © 2003 Wiley‐Liss, Inc.
Induction of cellular and humoral immune responses to tumor cells and peptides in HLA‐A24 positive hormone‐refractory prostate cancer patients by peptide vaccination
Authors: Noguchi Masanori , Kobayashi Kazuhiko , Suetsugu Norie , Tomiyasu Katsurou , Suekane Shigetaka , Yamada Akira , Itoh Kyogo , Noda Shinshi 
Published: July 2003

AbstractBackgroundTo assess the safety and immune response of a peptide‐based immunotherapy for patients with hormone‐refractory prostate cancer, a phase I clinical trial was conducted.MethodsThis study first investigated whether cytotoxic T‐lymphocyte (CTL) precursors reacting to peptide with vaccine candidates (14 peptides for HLA‐A24 positive patients) were detectable in the pre‐vaccination peripheral blood mononuclear cells (PBMCs) of ten patients with hormone‐refractory prostate cancer. Patients were then vaccinated subcutaneously with only those peptides to which pre‐vaccination PBMCs reacted (CTL precursor‐oriented peptide vaccine) for up to four kinds of peptides.ResultsOverall vaccinations were generally well tolerated, but most patients (nine of ten) developed grade 1 local redness and swelling at the injection site. Increased CTL response to both peptides and cancer cells were observed in four of ten patients. Anti‐peptide IgG antibodies were also detected in post‐vaccination sera of seven of ten patients. One patient achieved a partial response with an 89% decrease in PSA. Stable disease was demonstrated in five of ten patients (50%) for the median duration of 2 months (range, 2–5 months). There were no objective responses of measurable lesions.ConclusionsIncrease in cellular and humoral immune responses, and decrease in PSA level in some patients support further development of peptide‐based immunotherapy for hormone refractory prostate cancer. Prostate 57: 80–92, 2003. © 2003 Wiley‐Liss, Inc.
Increased growth factor production in a human prostatic stromal cell culture model caused by hypoxia
Authors: Berger Andreas P. , Kofler Kurt , Bektic Jasmin , Rogatsch Hermann , Steiner Hannes , Bartsch Georg , Klocker Helmut 
Published: July 2003

AbstractBACKGROUNDLocal hypoxia may be one of the triggers of embryonic reawakening of the stroma and subsequent hyperplastic growth in the prostate. Using a cell culture model of human prostatic stromal cells, we investigated the effects of hypoxia on activation of hypoxia‐inducible factor 1 (HIF 1) and on the production of growth factors.METHODSPrimary prostatic stromal cells were grown in normal and hypoxic (1% O2) atmosphere. Activation of HIF 1 was evaluated after different time intervals by Western blot. Induced secretion of growth factors VEGF, FGF‐7, TGF‐β, IL 8, and FGF‐2 were analyzed by ELISA. To confirm the in vitro findings we also performed immunohistochemistry of HIF 1α as well as pro‐collagen I, collagens I, III, and IV in the benign tissue of radical prostatectomy specimens.RESULTSHIF 1 is activated in a time‐dependent manner, already starting 1 hr after exposure of stromal cells to hypoxic conditions. Secretion of VEGF, FGF‐7, TGF‐β, FGF‐2, and IL 8 is increased under hypoxic in vitro conditions in comparison to normoxia. Levels of TGF‐β, VEGF, and IL 8 were rapidly and statistically significantly increased in the supernatant of hypoxic cells. Consistent with the in vitro findings, immunohistochemistry of HIF 1α in (benign prostatic hyperplasia) BPH tissue revealed strong HIF 1α nuclear staining in hyperplastic areas. No difference was observed in the collagen pattern between hyperplastic and normal prostate tissue.CONCLUSIONSProstatic stromal cells respond to hypoxia by upregulation of secretion of several growth factors suggesting that hypoxia can trigger prostatic growth. Therefore, hypoxia might be a key factor contributing to the pathogenesis of BPH. Prostate 57: 57–65, 2003. © 2003 Wiley‐Liss, Inc.
Condensation and pattern formation in cold exciton gases
Authors: Butov L. V. 
Published: July 2003

AbstractExcitons are Bose particles with small mass. Exciton Bose–Einstein condensation is expected to occur at a few degrees Kelvin. Experimentally, an exciton temperature well below 1 Kelvin is achieved in coupled quantum wells (CQWs). In this contribution, we review briefly experiments that show a strong enhancement of the exciton scattering rate with increasing exciton concentration revealing bosonic stimulation of exciton scattering, which is a signature of a degenerate Bose‐gas of excitons. Novel experiments with exciton condensation in potential traps, pattern formation in exciton system and macroscopically ordered exciton state are also reviewed briefly.
Optical tracking of high‐density cooled excitons in potential traps in Cu2O
Authors: Naka N. , Nagasawa N. 
Published: July 2003

AbstractThe density distribution of cold exciton clouds generated into a strain‐induced potential well by two‐photon excitation in Cu2O is studied at 2 K. The potential shapes of the double well are examined by two‐photon diagnostics. The motion of the exciton clouds is tracked by time‐resolved luminescence imaging and spectral imaging. We find that an anomalous spike appears on the center of the well in a specific excitation condition, i.e. ΔE = −5.0 meV, where ΔE is the detuning of the two‐photon excitation energy from the orthoexciton level under zero stress. The origin of the spike has been discussed in view of bosonic stimulation of the excitons into the ground state.
Exciton ionization in semiconductors
Authors: Koch Stephan W. , Hoyer Walter , Kira Mackillo , Filinov Vladimir S. 
Published: July 2003

AbstractTwo theoretical approaches, a dynamic density‐matrix approach and an equilibrium Monte‐Carlo technique, are combined to give new insight into the ionization behaviour of incoherent excitons in direct‐gap semiconductor heterostructures. In contrast to the widely spread picture of the excitonic Mott transition as an unbinding transition where the correlation length of a bound electron‐hole pair gradually increases until an ionized plasma is formed, the number of incoherent excitons is found to decrease continuously while the mean separation between electrons and holes within the remaining bound pairs is hardly changed, i.e., the pairs remain well correlated. In fact, the remaining excitons have a mean electron‐hole separation even below that of an isolated single pair.
Implementation of an all‐optical spin‐based quantum computer
Authors: Pazy E. , Calarco T. , D'Amico I. , Zanardi P. , Rossi F. , Zoller P. 
Published: July 2003

AbstractAn all‐optical implementation scheme of a spin‐based quantum computer is presented. Our quantum memory consists of the spin of electrons confined to quantum dots. Utilizing the Pauli blocking effect we are able to have ultra‐fast control and read out of the electronic spin degrees of freedom by conditionally coupling them with charged excitations of the quantum dot. Imperfections effecting gate operations are discussed and we show that final readout can still be performed by a quantum‐jump technique even in the presence of hole mixing, when the Pauli‐blocking selection rule is violated.
Phonon‐induced damping of Rabi oscillations in semiconductor quantum dots
Authors: Förstner Jens , Weber Carsten , Danckwerts Juliane , Knorr Andreas 
Published: July 2003

AbstractThe phonon‐induced dephasing dynamics of semiconductor quantum dots during nonlinear optical excitation is studied using quantum kinetic equations. We find that despite the decoherence process Rabi oscillations occur even for relatively long pulse durations and that their signatures in pump‐probe experiments only get suppressed for high input pulse areas.
The influence of four‐particle correlations on the parametric polariton amplification
Authors: Savasta Salvatore , Di Stefano Omar , Girlanda Raffaello 
Published: July 2003

AbstractWe present a microscopic theory of parametric polariton amplification in semiconductor microcavities including the influence of exciton–exciton correlations beyond mean‐field. The complexity induced by the Coulomb interaction between electrons determines the noninstantaneous character of exciton–exciton collisions. We find that the observed great enhancement of gain when increasing the polariton splitting origins from the unique interplay of the noninstantaneous nature of exciton–exciton interactions with the strong coupling regime giving rise to polaritons.
Resonant second‐harmonic generation and mode dispersion in photonic crystal waveguides
Authors: Andreani L. C. , Guizzetti G. , Patrini M. , Vecchi G. , Malvezzi A. M. , Businaro L. , Romanato F. , Di Fabrizio E. , Passaseo A. 
Published: July 2003

AbstractLinear and nonlinear optical measurements on GaAs/AlGaAs photonic crystal waveguides with square lattice are reported. Second‐harmonic generation in reflection shows a resonant enhancement when the pump beam is frequency‐ and momentum‐matched to a photonic mode in the slab. A full three‐dimensional theory of waveguide‐embedded photonic crystals allows to determine the dispersion of photonic modes and the intrinsic radiative losses of quasi‐guided modes lying above the light line.
Polariton amplification in semiconductor microcavities
Authors: Saba M. , Kundermann S. , Ciuti C. , Guillet T. , Staehli J. L. , Deveaud B. 
Published: July 2003

AbstractMicrocavity exciton polaritons, the fundamental optical excitations of semiconductor microcavities with quantum wells inside, have been proposed as promising candidates for observing stimulated scattering, condensation and other phenomena related to the bosonic nature of excitons. Having a light mass, quantum degeneracy of polaritons can be reached at low densities and high temperatures. But the radiative time of polaritons is very short (in the picosecond range) and usually prevents an efficient thermalization and cooling of the excited cloud of polaritons. A 'coherently‐driven condensate', not corresponding to a thermal equilibrium, but featuring multiple occupation of single‐particle states, can however be created by an external laser source resonantly exciting polaritons. Under this condition, stimulated parametric scattering of polaritons can provide huge optical gain on a weak probe pulse shined on the sample. In this work we demonstrate that this phenomenon can survive at temperatures close to room temperature and could be achieved in the next future even above this limit. Clever sample designs favour the thermal robustness of polariton parametric amplification, but from the experimental data it turns out that the parameter that ultimately limits the highest temperature for polariton parametric scattering is the exciton binding energy.
Semiconductor excitons in photonic crystals
Authors: Eichmann R. , Pasenow B. , Meier T. , Stroucken T. , Thomas P. , Koch S. W. 
Published: July 2003

AbstractOptical properties of a semiconductor quantum well in the vicinity of a two‐dimensional photonic crystal are investigated. Due to the periodic spatial modulation of the dielectric environment the effective Coulomb interaction potential exhibits the periodicity of the photonic crystal. As a consequence, the excitonic binding energy varies periodically by up to 50% depending on the spatial position of the exciton relative to the structured dielectric. The self image charge effects result in a position dependent shift of the single‐particle bandgap such that the spectral position of the absorption spectrum also develops the periodicity of the photonic surrounding.
Microscopic theory of the semiconductor terahertz response
Authors: Kira Mackillo , Hoyer Walter , Koch Stephan W. 
Published: July 2003

AbstractA microscopic theory for the terahertz response of excited semiconductor systems is presented. It is verified that the theory yields the correct effective‐mass Drude limit. For a fully interacting incoherent system, the terahertz response is shown to be determined by the electron–hole correlations. The theory is evaluated for the example of excitonic populations in a quantum‐well structure.
Exciton dynamics studied via internal THz transitions
Authors: Kaindl R. A. , Hägele D. , Carnahan M. A. , Lövenich R. , Chemla D. S. 
Published: July 2003

AbstractWe employ a novel, ultrafast terahertz probe to investigate the dynamical interplay of optically‐induced excitons and unbound electron–hole pairs in GaAs quantum wells. Resonant creation of heavy‐hole excitons induces a new low‐energy oscillator linked to transitions between the internal exciton degrees of freedom. The time‐resolved terahertz optical conductivity is found to be a probe well suited for studies of fundamental processes such as formation, relaxation and ionization of excitons.
How fast do charged particles get dressed?
Authors: Leitenstorfer A. , Huber R. , Tauser F. , Brodschelm A. 
Published: July 2003

AbstractOn a femtosecond timescale, we observe how Coulomb screening and collective scattering build up in an extreme nonequilibrium electron–hole plasma photoinjected in GaAs. To this end, we generate a plasma within 10 fs and probe the subsequent polarization response of the system with uncertainty‐limited temporal resolution via ultrabroadband THz spectroscopy. We show that the intrinsic material becomes conductive instantaneously upon carrier injection, whereas collective effects such as Coulomb screening and plasmon scattering exhibit a delayed onset. Thus, the ultrafast formation of dressed quasiparticles is directly monitored for the first time. The timescale for these phenomena is of the order of the inverse plasma frequency. Our findings support recent quantum kinetic simulations.
Microscopic modelling of semiconductor‐based quantum devices: a predictive simulation strategy
Authors: Iotti R. C. , Rossi F. 
Published: July 2003

AbstractWe review and discuss the first fully three‐dimensional study of non‐equilibrium carrier dynamics governing semiconductor‐based intersubband optoelectronic devices like, e.g., quantum‐cascade lasers. First, a multisubband Monte Carlo simulation scheme in a kinetic Boltzmann‐like approach is presented. Then, its generalisation into a density‐matrix quantum‐transport formalism is discussed. This allows us to directly access microscopic key‐features of the electron relaxation dynamics (without resorting to phenomenological parameters) as well as to investigate the nature, coherent vs incoherent, of charge injection/transport processes. Besides providing a quantitative investigation into the operation of these devices, our kinetic analysis can indeed serve as a predictive tool for the evaluation of new designs and strategies. Applications are presented concerning quantum‐cascade devices, both state‐of‐the‐art mid‐infrared lasers as well as novel Thz emitters.
Infrared absorption by excitons in Cu2O
Authors: Jörger M. , Tsitsishvili E. , Fleck T. , Klingshirn C. 
Published: July 2003

AbstractIn a differential absorption experiment the induced infrared transitions from the excitonic 1s to the 2p levels in Cu2O have been investigated. Intermediate densities of 1s excitons were created by cw‐laser excitation while the interexcitonic 1s to 2p transitions were probed simultaneously, using Fourier spectroscopy. Our data give evidence for a surprisingly large splitting of the 2p level (≈3.7 meV) the origin of which is a matter of speculation. An analysis of lineshape and width of the transitions results in a ratio of the effective masses m1s/m2p which deviates from the literature value.
Theory of the lineshape of quantum well intersubband transitions: optical dephasing and light propagation effects
Authors: Waldmüller Inès , Woerner Michael , Förstner Jens , Knorr Andreas 
Published: July 2003

AbstractWe outline a theoretical description of the absorption linewidth of quantum well intersubband transitions by solving Maxwell's equations for a non‐local susceptibility including many particle effects. We show that the intersubband absorption results from a complex interplay between mean‐field effects, dephasing contributions and light propagation effects, all being very sensitive to subband dispersion.
Level repulsion of exciton states in disordered semiconductor nanostructures
Authors: Zimmermann R. , Runge E. , Savona V. 
Published: July 2003

AbstractExciton states in semiconductor nanostructures with disorder exhibit level repulsion, a concept known from random matrix theory. Its manifestations in time‐resolved Rayleigh spectra and in the autocorrelation of optical nearfield spectra are explained, and available experimental results are critically discussed. It is proposed to investigate the intrasubband absorption in quantum wells with emphasis on the aspects of level repulsion.
Level‐statistics in the resonant Rayleigh scattering dynamics of monolayer‐split excitons
Authors: Kocherscheidt G. , Langbein W. , Savona V. 
Published: July 2003

AbstractThe dynamics of resonant Rayleigh scattering (RRS) from excitons localized in a disorder potential with large monolayer islands is investigated theoretically and experimentally. Experimentally, the coherent RRS dynamics from GaAs single quantum wells (SQWs) is deduced by means of passively stabilized spectral interferometry. The new technique is discussed in detail. The results retrieved by spectral interferometry are complemented by data obtained by time‐resolved and spectral speckle analysis. A strong dependence of the monolayer thickness of the SQW on the RRS spectra and the RRS dynamics is found. Changes in the well width corresponding to a fraction of one monolayer lead to drastic changes in the spectral and time‐resolved RRS intensity. A comparison between spectra and dynamics contradicts the assumption of uncorrelated exciton levels. The RRS intensity is derived theoretically by solving the Schrödinger equation for the center‐of‐mass motion of the 1s‐exciton in a disorder potential taking into account both interfaces with monolayer islands, the short range correlated disorder by segregation, and a correlation between the interfaces. The simulations reproduce qualitatively all observed features, determining in this way the characteristic disorder parameters like island sizes and interface roughness.