bluuebunny/crossref_metadata_2025_split huggingface dataset:
Glia Mediates the Neuroprotective Action of Estradiol on β-Amyloid-Induced Neuronal Death
Authors: Sortino M. A. , Chisari M. , Merlo S. , Vancheri C. , Caruso M. , Nicoletti F. , Canonico P. L. , Copani A. 
Published: August 2004

Abstract
17β-Estradiol (17β-E2) is known to exert neuroprotective activity against β-amyloid, but its exact target and mechanism of action in this effect have not been elucidated. The involvement of astroglia in neuroprotection of 17β-E2 against the β-amyloid fragment [βAP(25–35)] has been evaluated using an experimental paradigm in which medium conditioned from rat astroglia pretreated with 17β-E2 was transferred to pure rat cortical neurons challenged with 25 μm βAP(25–35) for 24 h. The toxicity of βAP(25–35) was assessed by flow cytometry, evaluating the ability of the peptide to induce an aberrant mitotic cell cycle in neurons. The results obtained indicate that conditioned medium from astrocytes preexposed to 17β-E2 for 4 h increased the viability of cortical neurons treated with βAP(25–35). This effect was not modified by treatment with the estrogen receptor antagonist ICI 182,780, added directly to neurons, nor was it mimicked by direct addition of 17β-E2 to neuronal cultures during exposure to βAP(25–35). A soluble factor stimulated by 17β-E2 seemed to be involved, and accordingly, the intracellular and released levels of TGF-β1 were increased by 17β-E2 treatment, as established by Western blot analysis. In addition, the intracellular content of TGF-β1 in immunopositive cells, as detected by flow cytometry, was reduced, suggesting that 17β-E2 stimulated mainly the release of the cytokine. In support of a role for TGF-β1 in astrocyte-mediated 17β-E2 neuroprotective activity, incubation with a neutralizing anti-TGF-β1 antibody significantly modified the reduction of neuronal death induced by 17β-E2-treated astrocyte-conditioned medium.
Mitogenic Activity of Estrogens in Human Breast Cancer Cells Does Not Rely on Direct Induction of Mitogen-Activated Protein Kinase/Extracellularly Regulated Kinase or Phosphatidylinositol 3-Kinase
Authors: Gaben Anne-Marie , Saucier Cécile , Bedin Monique , Redeuilh Gérard , Mester Jan 
Published: August 2004

Abstract
We have addressed the question of rapid, nongenomic mechanisms that may be involved in the mitogenic action of estrogens in hormone-dependent breast cancer cells. In quiescent, estrogen-deprived MCF-7 cells, estradiol did not induce a rapid activation of either the MAPK/ERK or phosphatidylinositol-3 kinase (PI-3K)/Akt pathway, whereas the entry into the cell cycle was documented by the successive inductions of cyclin D1 expression, hyperphosphorylation of the retinoblastoma protein (Rb), activity of the promoter of the cyclin A gene, and DNA synthesis. However, pharmacological inhibitors of the src family kinases, 4-amino-5-(4-methylphenyl)-7-(t-butyl) pyrazolo[3,4-d] pyrimidine (PP1) or of the PI-3K (LY294002) did prevent the entry of the cells into the cell cycle and inhibited the late G1 phase progression, whereas the inhibitor of MAPK/ERK activation (U0126) had only a partial inhibitory effect in the early G1 phase. In agreement with these results, small interfering RNA targeting Akt strongly inhibited the estradiolinduced cell cycle progression monitored by the activation of the promoter of the cyclin A gene. The expression of small interfering RNA targeting MAPK 1 and 2 also had a clear inhibitory effect on the estradiol-induced activation of the cyclin A promoter and also antagonized the estradiol-induced transcription directed by the estrogen response element. Finally, transfection of the estrogen receptor into NIH3T3 fibroblasts did not confer to the cells sensitivity to a mitogenic action of estradiol. We conclude that the induction of the cell cycle by estradiol does not require a direct activation of MAPK/ERK or PI-3K signaling protein kinase cascades, but that these kinases appear to have a permissive role in the cell cycle progression.
A Novel Estrogen Receptor α-Associated Protein Alters Receptor-Deoxyribonucleic Acid Interactions and Represses Receptor-Mediated Transcription
Authors: Loven Margaret A. , Davis Roger E. , Curtis Carol D. , Muster Nemone , Yates John R. , Nardulli Ann M. 
Published: August 2004

AbstractEstrogen receptor α (ERα) serves as a ligand-activated transcription factor, turning on transcription of estrogen-responsive genes in target cells. Numerous regulatory proteins interact with the receptor to influence ERα-mediated transactivation. In this study, we have identified pp32, which interacts with the DNA binding domain of ERα when the receptor is free, but not when it is bound to an estrogen response element. Coimmunoprecipitation experiments demonstrate that endogenously expressed pp32 and ERα from MCF-7 breast cancer cells interact. Although pp32 substantially enhances the association of the receptor with estrogen response element-containing DNA, overexpression of pp32 in MCF-7 cells decreases transcription of an estrogen-responsive reporter plasmid. pp32 Represses p300-mediated acetylation of ERα and histones in vitro and inhibits acetylation of ERα in vivo. pp32 Also binds to other nuclear receptors and inhibits thyroid hormone receptor β-mediated transcription. Taken together, our studies provide evidence that pp32 plays a role in regulating transcription of estrogen-responsive genes by modulating acetylation of histones and ERα and also influences transcription of other hormone-responsive genes as well.
Structural and functional adaptation to hypoxia in the rat brain
Authors: LaManna Joseph C. , Chavez Juan Carlos , Pichiule Paola 
Published: August 2004

SUMMARY
Chronic exposure to a hypoxic environment leads to structural and functional adaptations in the rat brain. One significant adaptation is a decrease in intercapillary distances through a near doubling of the capillary density, which begins after about 1 week of hypoxic exposure and is completed by 3 weeks. Hypoxic angiogenesis is controlled by activation of downstream genes by Hypoxia Inducible Factor-1 and Angiopoietin-2. The processes that increase capillary density are reversible upon restoration of the ambient oxygen concentration. Capillary regression, which also occurs over a 3-week period, is accomplished through activation of apoptosis. The implication from these observations is that the brain naturally functions in a low, but controlled, oxygen environment. Acute imbalances in oxygen delivery and metabolic demand are addressed through changes in blood flow; persistent imbalances activate mechanisms that adjust capillary density. The mechanisms that control these processes decline with age.
Clinical perspectives: neuroprotection lessons from hypoxia-tolerant organisms
Authors: Bickler Philip E. 
Published: August 2004

SUMMARYAn effective treatment for brain ischemia is a pressing medical need. Research on brain ischemia has largely focused on understanding the mechanisms of neuron death as a way of identifying targets for therapy. An attractive alternative approach is to identify the survival strategies of hypoxia-tolerant neurons. The adaptation of vertebrate neurons to hypoxia occurs in at least three major ways: (1) as a constitutive property of neurons in anoxia-tolerant turtles and fish, (2) as a property of intra-uterine and early post-natal mammalian development, and (3) as part of a slower, chronic process, as in acclimitization to high altitude. Research on hypoxia-tolerant neurons has already revised several earlier concepts, including the role of calcium in cell death and survival, and the value of N-methyl-d-aspartate (NMDA) receptor antagonism. A broad and fundamental understanding of how neurons adapt to hypoxia is likely to help guide efforts to find new treatments for brain hypoxia and ischemia.
Erythropoietin and the hypoxic brain
Authors: Marti Hugo H. 
Published: August 2004

SUMMARYNormal tissue function in mammals depends on adequate supply of oxygen through blood vessels. A discrepancy between oxygen supply and consumption(hypoxia) induces a variety of specific adaptation mechanisms at the cellular,local and systemic level. These mechanisms are in part governed by the activation of hypoxia-inducible transcription factors (HIF-1, HIF-2), which in turn modulate expression of hypoxically regulated genes such as those encoding vascular endothelial growth factor (VEGF) and erythropoietin(EPO).EPO is a glycoprotein that is produced mainly by interstitial fibroblasts in the kidneys of the adult and in hepatocytes in the foetus. Released into the circulation, EPO makes its way to the bone marrow, where it regulates red cell production by preventing apoptosis of erythroid progenitor cells. Recently, EPO has emerged as a multifunctional growth factor that plays a significant role in the nervous system. Both EPO and its receptor are expressed throughout the brain in glial cells, neurones and endothelial cells. Hypoxia and ischaemia have been recognised as important driving forces of EPO expression in the brain. EPO has potent neuroprotective properties in vivo and in vitro and appears to act in a dual way by directly protecting neurones from ischaemic damage and by stimulating endothelial cells and thus supporting the angiogenic effect of VEGF in the nervous system. Thus,hypoxia-induced gene products such as VEGF and EPO might be part of a self-regulated physiological protection mechanism to prevent neuronal injury,especially under conditions of chronically reduced blood flow (chronic ischaemia).In this review, I will briefly summarize the recent findings on the molecular mechanisms of hypoxia-regulated EPO expression in general and give an overview of its expression in the central nervous system, its action as a growth factor with non-haematopoietic functions and its potential clinical relevance in various brain pathologies.
Cellular oxygen sensing need in CNS function: physiological and pathological implications
Authors: Acker Till , Acker Helmut 
Published: August 2004

SUMMARYStructural and functional integrity of brain function profoundly depends on a regular oxygen and glucose supply. Any disturbance of this supply becomes life threatening and may result in severe loss of brain function. In particular, reductions in oxygen availability (hypoxia) caused by systemic or local blood circulation irregularities cannot be tolerated for longer periods due to an insufficient energy supply to the brain by anaerobic glycolysis. Hypoxia has been implicated in central nervous system pathology in a number of disorders including stroke, head trauma, neoplasia and neurodegenerative disease. Complex cellular oxygen sensing systems have evolved for tight regulation of oxygen homeostasis in the brain. In response to variations in oxygen partial pressure (PO2) these induce adaptive mechanisms to avoid or at least minimize brain damage.A significant advance in our understanding of the hypoxia response stems from the discovery of the hypoxia inducible factors (HIF), which act as key regulators of hypoxia-induced gene expression. Depending on the duration and severity of the oxygen deprivation, cellular oxygen-sensor responses activate a variety of short- and long-term energy saving and cellular protection mechanisms. Hypoxic adaptation encompasses an immediate depolarization block by changing potassium, sodium and chloride ion fluxes across the cellular membrane, a general inhibition of protein synthesis, and HIF-mediated upregulation of gene expression of enzymes or growth factors inducing angiogenesis, anaerobic glycolysis, cell survival or neural stem cell growth. However, sustained and prolonged activation of the HIF pathway may lead to a transition from neuroprotective to cell death responses. This is reflected by the dual features of the HIF system that include both anti- and proapoptotic components.These various responses might be based on a range of oxygen-sensing signal cascades, including an isoform of the neutrophil NADPH oxidase, different electron carrier units of the mitochondrial chain such as a specialized mitochondrial, low PO2 affinity cytochrome c oxidase (aa3) and a subfamily of 2-oxoglutarate dependent dioxygenases termed HIF prolyl-hydroxylase (PHD) and HIF asparaginyl hydroxylase, known as factor-inhibiting HIF (FIH-1). Thus specific oxygen-sensing cascades, by means of their different oxygen sensitivities,cell-specific and subcellular localization, may help to tailor various adaptive responses according to differences in tissue oxygen availability.
Hypoxia tolerance in mammalian heterotherms
Authors: Drew K. L. , Harris M. B. , LaManna J. C. , Smith M. A. , Zhu X. W. , Ma Y. L. 
Published: August 2004

SUMMARYHeterothermic mammals tolerate severe hypoxia, as well as a variety of central nervous system insults, better than homeothermic mammals. Tolerance to hypoxia may stem from adaptations associated with the ability to survive hibernation and periodic arousal thermogenesis. Here, we review evidence and mechanisms of hypoxia tolerance during hibernation, euthermy and arousal in heterothermic mammals and consider potential mechanisms for regenerative-like processes, such as synaptogenesis, observed within hours of hypoxic stress associated with arousal thermogenesis.
Preparation, Characterization, and Reactivities of Highly Functional Titanium Oxide-Based Photocatalysts Able to Operate under UV–Visible Light Irradiation: Approaches in Realizing High Efficiency in the Use of Visible Light
Authors: Anpo Masakazu 
Published: August 2004

Abstract
A review of the research advances made in the design and development of highly reactive and functional titanium oxide photocatalysts, which can utilize not only UV but also visible or solar light, and a clarification of the active sites as well as the detection of the reaction intermediates at the molecular level have been presented here. The potential for the effective utilization and conversion of solar energy into useful and safe chemical energy by the modification of the electronic properties of such TiO2 photocatalysts is great when one considers their myriad applications as well as their non-polluting qualities. Such a modification process by methods such as ion-implantation can be applied not only for semiconducting bulk TiO2 photocatalysts but also for TiO2 thin film photocatalysts and titanium oxide photocatalysts highly dispersed within zeolite frameworks. Moreover, the photocatalytic reactivity of semiconducting TiO2 nano-powders was found to be dramatically enhanced by the loading of small amounts of Pt. This worked to enhance the reduction reaction, resulting in the charge separation of the electrons and holes generated by light irradiation. In addition, highly dispersed titanium oxide species prepared within zeolite frameworks as well as SiO2 or Al2O3 matrices showed much higher and unique photocatalytic performances as compared to semiconducting bulk TiO2 photocatalysts. Significantly, a new alternative method to directly prepare such visible light-responsive TiO2 thin film photocatalysts on various substrates has been successfully developed by applying a RF magnetron sputtering deposition method.
Thermodynamics and Kinetics of Formation of Intramolecular Naphthalene Dimer Radical Cation Studied by Near-IR Transient Absorption Spectroscopy
Authors: Fushimi Toshiki , Fujita Yusuke , Ohkita Hideo , Ito Shinzaburo 
Published: August 2004

Abstract
Thermodynamics and kinetics for formation of an intramolecular dimer radical cation of a series of α,ω-di(2-naphthyl)alkanes in solutions were quantitatively investigated by near-IR transient absorption spectroscopy, which allows one to observe dimer radical cations directly. The standard enthalpy (−ΔH°) for the formation of the intramolecular dimer radical cation increased as the chain length between the two naphthyl moieties increased, and was smaller than that of the intermolecular dimer radical cation of 2-ethylnaphthalene. This shows that −ΔH° depends on the strain required for the chain to form the ring-closure configuration. Destabilization due to repulsion between the two naphthyl moieties in the intramolecular dimer radical cation was evaluated to be ca. 20 kJ mol−1. This value is smaller than that of the naphthalene excimer, indicating that the separation distance and/or the overlap between the two naphthyl moieties are not as restricted as those of the excimer. The activation energy for the formation of the intramolecular dimer radical cation was comparable to the energy for local motions of a few methylene units linking the two naphthalene moieties.
An Investigation of Weak Ion Association Equilibria between Inorganic Anions and Tetraalkylammonium Ions in Ethanol–Aqueous Media Using Capillary Zone Electrophoresis
Authors: Mbuna Julius , Takayanagi Toshio , Oshima Mitsuko , Motomizu Shoji 
Published: August 2004

Abstract
Weak ion association equilibria between inorganic anions, ranging in charge from −1 to −4, and symmetrical tetraalkylammonium ions, R4N+ (R = Me, Et, Pr, Bu, n-Am), were investigated in formate buffer solutions containing a variable composition of ethanol (0–62.9% (m/m)). The individual effective mobilities of the inorganic anions in a series of tetraalkylammonium chloride solutions were measured using an ordinary silica capillary maintained at 25.0 ± 0.1 °C under a negative potential (−10 kV) and direct UV detection (λ = 220 nm). Under the stated experimental conditions, the association constants, Kass, showed a modest increase as the amount of ethanol in the buffer was increased. The concepts of medium effect and Gibbs free energy of transfer were applied to weak ion equilibria in order to investigate changes in association constant as the ethanol content in the buffer solutions was increased. The above treatment on selected associations revealed that the increased instability of the inorganic anion in mixed ethanolic solutions is responsible for the observed increase in Kass.
The Magnetic Susceptibilities and Electron Paramagnetic Resonance Spectra of 6H-Perovskites Ba3PrM2O9 (M = Ir, Ru)
Authors: Hinatsu Yukio , Oyama Shigeaki , Doi Yoshihiro 
Published: August 2004

Abstract
The magnetic properties of quaternary oxides Ba3PrM2O9 and Ba3CeM2O9 (M = Ir, Ru) have been investigated. They crystallize in the 6H-perovskite structure with the space group P63/mmc, in which the cation sites with the face-sharing octahedra are occupied by Ir (or Ru) ions, and those within the corner-sharing octahedra are occupied by Pr (or Ce) ions. Magnetic susceptibility measurements for Ba3PrIr2O9 show that an antiferromagnetic interaction between two Ir ions in the Ir2O9 dimer results in a large temperature-independent paramagnetic susceptibility over a wide temperature range. Another interesting result is in the small effective magnetic moments for Ba3PrIr2O9 (0.31(1) μB) and for Ba3PrRu2O9 (0.75(1) μB). The electron paramagnetic resonance (EPR) spectrum of Pr4+ in these compounds was measured by diluting them in the corresponding isomorphous compounds Ba3CeIr2O9 and Ba3CeRu2O9 and lowering the temperature to 4.2 K. A very large hyperfine interaction with the 141Pr nucleus was observed. The results were analyzed based on the weak field approximation. The measured g values are much smaller than |−10/7|, showing that the crystal field effect on the behavior of a 4f electron is large. The low g values correspond to the small effective magnetic moments of the Pr compounds.
Di(9-anthryl)carbene Revisited. Product Analysis and Spectroscopic Studies
Authors: Yoshida Ken-ichi , Iiba Eiji , Nozaki Yoshinori , Hirai Katsuyuki , Takahashi Yasutake , Tomioka Hideo , Lin Cheng-Tung , Gaspar Peter P 
Published: August 2004

Abstract
Irradiation (λ &gt; 300 nm) of di(9-anthryl)diazomethane (1) in degassed benzene gave the trimer (3) of dianthrylcarbene (2) as the main product along with a small amount of a tetramer (4). The structures of those oligomers were characterized as caged compounds produced as a result of three- and four-fold coupling at the 10 and 10′ positions of 2. Photolysis of 1 in the presence of oxygen with short wavelength UV light resulted in the formation of di(9-anthryl) ketone (5) and anthraquinone (6), while similar irradiation with a longer wavelength light gave 5 and 9-anthryl 9-anthracenecarboxylate (9), which was found to give 6 upon irradiation with a short wavelength light in the presence of oxygen. On the other hand, the photolysis of 4 gave 3 as the main product, while 3 was almost completely photostable under similar conditions. However, irradiation of both 3 and 4 in the presence of oxygen gave 6. In order to elucidate the reactions observed, we carried out spectroscopic studies (matrix EPR and UV/vis spectroscopies as well as laser flash photolysis) with 1, 3, and 4. These studies revealed that 3 generated a trimer diradical (10) formed as a result of C–C bond cleavage upon irradiation and that 10 reformed 3 almost exclusively, while similar photolysis of 1 and 4 generated the same two transient species, 10 and a dimer diradical. It is proposed that triplet carbene 2 equilibrates with the dimer diradical 2-2 and that the main decay pathway of this mixture is to generate the trimer diradical 10 while dimer diradical 2-2 undergoes coupling to produce the tetramer 4. The structure of the triplet carbene in equilibrium with diradicals is also discussed.
Precise Structure Control of Enzymatically Synthesized Polyphenols
Authors: Mita Naruyoshi , Tawaki Shin-ichiro , Uyama Hiroshi , Kobayashi Shiro 
Published: August 2004

Abstract
The structural control and biodegradability of enzymatically synthesized polyphenols have been investigated. The peroxidase-catalyzed oxidative polymerization of various 4-substituted phenols was performed in aqueous organic solvents, in which the ratio of phenylene and oxyphenylene units of the polymer product could be precisely controlled by the nature of the solvents and the monomers. The unit ratio strongly depended on their hydrophobic parameters. The control of the structure was also examined by changing the feed ratio of the enzymatic copolymerization of the phenol derivatives. The biodegradability was evaluated by the BOD method. Poly(4-t-butylphenol) showed relatively good biodegradability, whereas little degradation of the polyphenol from unsubstituted phenol was observed.
Photochromism of Phenylazopyridines and Its Application to the Fluorescence Modulation of Zinc–Porphyrins
Authors: Otsuki Joe , Narutaki Koichi 
Published: August 2004

Abstract
Several 2- and 3-(phenylazo)pyridine derivatives were prepared. Most of their trans isomers have a large absorption band (∼2 × 104 M−1 cm−1 (1 M = 1 mol dm−3)) around 320 nm and a small absorption band (∼400 M−1 cm−1) around 450 nm. All of these compounds photoisomerize upon irradiation of the shorter (trans-to-cis) and longer (cis-to-trans) wavelength absorption bands. trans Isomers of 3-(phenylazo)pyridines axially coordinate more strongly to Zn–porphyrins than cis isomers, while the opposite is the case for 2-(phenylazo)pyridines, due to steric reasons. These phenylazopyridines quench the fluorescence of Zn–porphyrin upon coordination. These properties were exploited for the light-triggered fluorescence modulation of Zn–porphyrins. Light was irradiated to a mixed solution of phenylazopyridine and Zn–porphyrin to induce photoisomerization of the phenylazopyridine, which underwent association with, or dissociation from, the Zn–porphyrin, resulting in a decrease or increase of Zn–porphyrin fluorescence. For example, the fluorescence intensity of Zn–tetraphenylporphyrin reversibly changed by up to 50%, when 4-methoxy-2-(phenylazo)pyridine was employed.