Effects of cytokines on multiplication of Toxoplasma gondii in microglial cells

Microglia may play a role in host defense against Toxoplasma gondii in the central nervous system. In our study, the antitoxoplasma activity of murine microglia was investigated. T. gondii multiplied readily in cultured microglial cells, and activation of these cells with IFN-gamma plus LPS suppressed (p < 0.01) intracellular growth of this parasite. This antitoxoplasma defense of activated microglia was significantly blocked by neutralizing antibodies against TNF-alpha and transforming growth factor-beta, suggesting that these cytokines play a role in the inhibitory process. Consistent with this hypothesis, activation of microglia with IFN-gamma plus TNF-alpha or transforming growth factor-beta inhibited, in a dose-dependent manner, T. gondii multiplication. Treatment with pentoxifylline or dexamethasone, drugs that suppress production of TNF-alpha, prevented (p < 0.01) the microglia from exerting an anti-T. gondii effect. These findings suggest that the host defense function of microglia against T. gondii is dependent primarily on the activating properties of IFN-gamma and TNF-alpha, and that agents that interfere with cytokine-mediated activation may promote the pathogenesis of this infection.

Effects of cytokines on multiplication of Toxoplasma gondii in microglial cells

Microglia may play a role in host defense against Toxoplasma gondii in the central nervous system. In our study, the antitoxoplasma activity of murine microglia was investigated. T. gondii multiplied readily in cultured microglial cells, and activation of these cells with IFN-gamma plus LPS suppressed (p &lt; 0.01) intracellular growth of this parasite. This antitoxoplasma defense of activated microglia was significantly blocked by neutralizing antibodies against TNF-alpha and transforming growth factor-beta, suggesting that these cytokines play a role in the inhibitory process. Consistent with this hypothesis, activation of microglia with IFN-gamma plus TNF-alpha or transforming growth factor-beta inhibited, in a dose-dependent manner, T. gondii multiplication. Treatment with pentoxifylline or dexamethasone, drugs that suppress production of TNF-alpha, prevented (p &lt; 0.01) the microglia from exerting an anti-T. gondii effect. These findings suggest that the host defense function of microglia against T. gondii is dependent primarily on the activating properties of IFN-gamma and TNF-alpha, and that agents that interfere with cytokine-mediated activation may promote the pathogenesis of this infection.

Identification of a chemotactic domain of the pro-inflammatory S100 protein CP-10

We previously reported the purification and partial amino acid sequence of a novel murine cytokine designated CP-10, which has chemotactic activity for murine polymorphonuclear cells (PMN) and macrophages. The complete cDNA encoding an 88-amino acid polypeptide has been isolated and the sequence is presented here. Transient transfection of CP-10 cDNA into CV-1 cells confirmed the chemotactic activity of rCP-10 for murine PMN. CP-10 has sequence homology with members of the S100 family of Ca(2+)-binding proteins with pronounced amino acid sequence similarities within the putative N- and C-terminal Ca(2+)-binding sites, but differences within their connecting hinge and C-terminal regions. We have confirmed the hypothesis of Kligman and Hilt that functional specificity of individual members of the S100 protein family may reside in the hinge region. A synthetic peptide corresponding to the hinge region of CP-10 (CP-10(42-55) was compared with native CP-10 in chemotaxis and skin test assays. Native CP-10 had potent activity for phagocytic cells, but not lymphocytes, in vitro (optimal activity, 10(-11) to 10(-13) M) and elicited a sustained recruitment of neutrophils and mononuclear cells over 24 h in vivo. The hinge-region peptide had strong chemotactic activity for murine phagocytic cells (optimal activity, 10(-10) - 10(-11) M) but elicited only a transient infiltration of neutrophils over 4 to 8 h after intradermal injection. Results indicate that although the hinge region contributes significantly to the functional specificity of the S100 protein CP-10, sustained cellular recruitment typical of a delayed type hypersensitivity response is apparently dependent on the structural integrity of the protein.

Morphine inhibits the release of tumor necrosis factor in human peripheral blood mononuclear cell cultures

Opiates modulate a variety of immune responses of peripheral blood mononuclear cells (PBMC). When PBMC were treated with morphine for 24 h, cells released less (P < 0.05) bioactive TNF, a cytokine important in host defense, in the following 24-h incubation period when stimulated with lipopolysaccharide and phytohemagglutinin. Morphine alone did not significantly alter the release of TNF from PBMC cultures. Pretreatment of PBMC cultures for 1 h with naloxone blocked (P < 0.05) the inhibitory effect of morphine on the release of TNF upon stimulation with phytohemagglutinin, but not with lipopolysaccharide, suggesting the involvement of an opioid receptor. The mechanism of morphine-induced suppression of TNF release appears to be counteracted by the effect of this opiate on the release of transforming growth factor (TGF)-beta, since antibodies to this immunoregulatory cytokine further enhanced morphine-related inhibition of TNF release. Taken together, these findings indicate that morphine suppresses the release of bioactive TNF from PBMC and that TGF-beta plays a modulatory role in this inhibitory process.

Recombinant human transforming growth factor-beta 1: expression by Chinese hamster ovary cells, isolation, and characterization

A partial cDNA clone encoding the gene for human transforming growth factor-beta 1 (TGF-beta 1) was isolated from a human bladder carcinoma cell line (5637) cDNA library. Following restriction enzyme processing and ligation of synthetic oligonucleotide linkers, the gene was inserted into a plasmid and transfected into Chinese hamster ovary cells. Clonal selection and growth conditions resulted in a method for production of recombinant human TGF-beta 1 at 7 mg/liter in conditioned cell medium. Through a combination of low pH treatment, cation-exchange chromatography, and salt precipitation, the recombinant human TGF-beta 1 was purified in milligram amounts to > 95% purity in a yield of about 36%. Purification to homogeneity was accomplished by chromatography on C18 silica gel. Amino acid analysis, N-terminal sequencing, and growth inhibition assays indicate identity with the molecule from human platelets.

Identification of a chemotactic domain of the pro-inflammatory S100 protein CP-10

We previously reported the purification and partial amino acid sequence of a novel murine cytokine designated CP-10, which has chemotactic activity for murine polymorphonuclear cells (PMN) and macrophages. The complete cDNA encoding an 88-amino acid polypeptide has been isolated and the sequence is presented here. Transient transfection of CP-10 cDNA into CV-1 cells confirmed the chemotactic activity of rCP-10 for murine PMN. CP-10 has sequence homology with members of the S100 family of Ca(2+)-binding proteins with pronounced amino acid sequence similarities within the putative N- and C-terminal Ca(2+)-binding sites, but differences within their connecting hinge and C-terminal regions. We have confirmed the hypothesis of Kligman and Hilt that functional specificity of individual members of the S100 protein family may reside in the hinge region. A synthetic peptide corresponding to the hinge region of CP-10 (CP-10(42-55) was compared with native CP-10 in chemotaxis and skin test assays. Native CP-10 had potent activity for phagocytic cells, but not lymphocytes, in vitro (optimal activity, 10(-11) to 10(-13) M) and elicited a sustained recruitment of neutrophils and mononuclear cells over 24 h in vivo. The hinge-region peptide had strong chemotactic activity for murine phagocytic cells (optimal activity, 10(-10) - 10(-11) M) but elicited only a transient infiltration of neutrophils over 4 to 8 h after intradermal injection. Results indicate that although the hinge region contributes significantly to the functional specificity of the S100 protein CP-10, sustained cellular recruitment typical of a delayed type hypersensitivity response is apparently dependent on the structural integrity of the protein.

Heme active-site structural characterization of chloroperoxidase by resonance Raman spectroscopy

Resonance Raman spectra are reported for the nitric oxide adducts of ferric and ferrous chloroperoxidase and carbon monoxide adducts of ferrous chloroperoxidase. The stretching, v(Fe-NO), and bending, delta(FeNO), modes are detected at 538 and 558 cm-1, respectively, for the ferric nitrosylchloroperoxidase. These two bands shift to 534 and 546 cm-1, respectively, upon substitution by 15N16O. The v(Fe-NO) mode of the nitric oxide adduct of ferrous chloroperoxidase is located at 542 cm-1, which shifts to 528 (15N16O), 540 (14N18O), and 524 (15N18O) cm-1 as the mass of the bound nitric oxide increases by 1 atomic unit. Two distinct states of the carbon monoxide adduct of chloroperoxidase, the acidic and alkaline forms, are found to undergo a reversible pH-induced transition. The v(Fe-CO) mode shifts from 484 to 492 cm-1 and the delta(FeCO) mode at 562 cm-1 disappears as the pH is reduced from 6.0 to 3.3. In addition, two low frequency modes at 382 and 420 cm-1, assignable to the delta(CbC1C2) bending of propionate and vinyl groups, respectively, also show pH sensitivity. The results suggest a peroxidase-like heme active-site environment for chloroperoxidase and indicate a facile conformational change of heme groups accompanying the acid-base transition.

Activation of K+ channel in vascular smooth muscles by cytochrome P450 metabolites of arachidonic acid

Arachidonic acid can be oxidatively metabolized by cytochrome P450 epoxygenase to four regioisomeric epoxyeicosatrienoic acids (5,6-; 8,9-; 11,12-; 14,15-EET), which exhibit vasorelaxant effects in vivo and in vitro with unknown mechanisms. In this study, the patch-clamp method was used to examine the effects of EETs on the Ca(2+)-activated K+ channel in cells from rabbit portal vein, rat caudal artery, guinea pig aorta and porcine coronary artery. In all four cell types, EETs in the bath activated the K+ channel in cell-attached patches by increasing the single channel open-state probability. Potencies of the four EETs did not differ significantly for each cell type. The concentrations for doubling open-state probability were 0.1 microM in portal vein and coronary artery, 0.3-1 microM in aorta and 1-3 microM in caudal artery. In caudal artery cells, K+ channel activation by 3 microM 5,6- and 1 microM 11,12-EET was blocked and reversed by glyburide at 0.5 microM. In aorta, coronary artery, and caudal artery cells, micromolar EETs induced a dose-dependent and reversible augmentation of whole-cell K+ current by 50-120% and a 5-12 mV hyperpolarization. EETs on the cytosolic side of inside-out patches produced little or no potentiation of K+ channels, implying an interaction of receptor-mediated nature. Thus, EETs may promote vasodilation by functioning as endogenous K+ channel openers.

Coupling of endothelin receptors to ion channels in rat glomerular mesangial cells

Endothelin (ET) induces depolarization and contraction of glomerular mesangial cells (MCs), thereby influencing intraglomerular hemodynamics and filtration rate. In an attempt to clarify the ionic mechanism by which ET regulates MC function, we examined, using the whole-cell configuration of the patch-clamp technique, the effects of ET-1 and its related peptides, ET-3, sarafotoxin 6c (S6c), and IRL 1620, on ion currents and membrane potential in the primary culture of rat MCs. The resting potential of MCs was -48.4 +/- 1.9 mV (n = 23). It depolarized in response to ET-1, ET-3, and IRL 1620 by 14 (n = 7), 8 (n = 5), and 13 mV (n = 9), respectively. Whole-cell recording in combination with ion substitution ascertained the coexistence of potassium (IK) and chloride (ICl) currents. ET-1 (0.01-100 nM), ET-3 (1-100 nM), IRL 1620 (0.1-100 nM), and S6c (0.01-10 nM) augmented ICl in a concentration-dependent fashion, with ET-1 and S6c being the most potent. These actions were blocked by IRL 1038, a selective ETB receptor antagonist, but not by 1 microM BQ 123 (a selective ETA receptor antagonist) or 0.1 microM nifedipine (an L-type Ca(2+)-channel blocker). These results suggest a close coupling of the ETB receptor to ICl. ET-1, IRL 1620, and SRTX-6c in a similar concentration range also caused suppression of IK. This action was partially blocked by IRL 1038 and minimally affected by BQ 123, indicating a contributory role for ETB receptors in the regulation of IK.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of transforming growth factor-beta on murine astrocyte glutamine synthetase activity. Implications in neuronal injury

Cytokines have been implicated in the pathogenesis of a number of brain diseases in which neurological dysfunction has been attributed to a change in amino acid neurotransmitter metabolism. In the present in vitro study, we investigated the effects of cytokines on astrocyte glutamine synthetase (GS) activity and subsequently on N-methyl-D-aspartate (NMDA) receptor-mediated neurotoxicity. Proinflammatory cytokines IL-1 alpha, IL-1 beta, and IL-6 at a concentration of 20 ng/ml did not affect GS activity; however, tumor necrosis factor-alpha inhibited this activity by 20% in mixed neuronal/astrocyte cultures. Treatment for 24 h with transforming growth factor (TGF)-beta 1 or -beta 2 inhibited up to 60% GS activity. TGF-beta 2 also inhibited GS in enriched astrocyte cultures with an ED50 of 10 pg/ml. Antibodies specific to TGF-beta 2 blocked this effect. Treatment of astrocytes with TGF-beta 2 (250 pg/ml) resulted in markedly dilated rough endoplasmic reticulum. Since astrocyte GS may play a protective role in NMDA receptor-mediated neurotoxicity, we treated mixed neuronal/astrocyte cultures with TGF-beta 2 (250 pg/ml) and found a threefold potentiation of NMDA receptor-mediated neurotoxicity. These data suggest that TGF-beta impairs astrocyte GS function and enhances neurotoxicity, thus providing insight into understanding one mechanism of cytokine-mediated central nervous system disease.

Resonance Raman studies of the carbonmonoxy form of catalase. Evidence for and effects of phenolate ligation

Resonance Raman spectra are reported for the carbon monoxide (CO) adduct of catalase formed from the reaction of peracetic acid or hydrogen peroxide with the azide adduct of catalase in the presence of CO. The expected three normal vibrations of the FE-CO fragment are detected at 1,908,593 and 543 cm-1 for the nu(C-O), delta(Fe-C-O) and nu(Fe-CO), respectively. The expected coordination of the phenolate group in this adduct is confirmed by the enhancement of an internal vibration of phenolate, nu 19a at 1,515 cm-1, and an extraordinary intensity enhancement of the nu(Fe-CO) mode.

Positive thinking reduces heart rate and fear responses to speech-phobic imagery

30 speech-anxious subjects imagined a phobic speech scene 10 times. The experimental conditions varied according to whether the subjects engaged in positive, neutral, or negative thinking prior to each scene presentation. Heart rate and self-reports of fear were measured during the imagery periods. Positive thinking just before visualization of the phobic images reduced both subjective anxiety about speech and cardiovascular responses.

Microglial cell upregulation of HIV-1 expression in the chronically infected promonocytic cell line U1: the role of tumor necrosis factor-alpha

Culture supernatants from lipopolysaccharide (LPS)-treated murine microglial cells were found to markedly induce the expression of human immunodeficiency virus (HIV)-1 in the chronically infected human promonocytic cell line U1 as detected by measurements of HIV-1 p24 antigen release into U1 culture supernatants. Antibody to tumor necrosis factor (TNF)-alpha had an inhibitory effect on the induction of virus by microglial cell supernatants. Also, treatment of microglia with pentoxifylline, an inhibitor of TNF-alpha production, resulted in suppressed amounts of TNF in the supernatants of LPS-treated microglia and in a reduced stimulatory capacity of these supernatants on HIV-1 expression in U1 cells. These findings support the concept that TNF-alpha production by glial cells plays a pathogenetic role in HIV-1-associated brain disease by promoting the expression of the virus in infected cells.

[3H]2-phenylaminoadenosine ([3H]CV 1808) labels a novel adenosine receptor in rat brain

Earlier studies have demonstrated that the vasoactive compound CV 1808 displays 10-fold selectivity for the adenosine A2 receptor, and as such, was the first reported A2-selective agonist. After the radiolabeling of CV 1808, its binding characteristics were evaluated in rat striatal, cortical and hippocampal membranes. Using 5 nM [3H]CV 1808, unlabeled CV 1808 produced shallow inhibition curves in all three brain areas, with 61 to 75% of the binding displaying IC50 values of 16 to 24 nM, whereas the remaining 28 to 37% of binding had lower affinity (IC50 595-1130 nM). The A2-selective agonist CGS 21680 and the nonselective adenosine agonist 5'-N-ethylcarboxamidoadenosine displayed very low affinity (IC50 > 10 microM). The A1-selective compound N6-cyclopentyladenosine inhibited only 28 to 44% of specific binding, with IC50 of 272-1750 nM. In contrast, the nonselective adenosine antagonist CGS 15943A inhibited specific binding by 48 to 64% (at 1 microM) with IC50 ranging from 106 to 295 nM. Additionally, several novel adenosine analogs fully inhibited specific binding, producing multicomponent inhibition curves. Electrophysiological studies in porcine coronary artery cells demonstrated that CV 1808, but not CGS 21680, 5'-N-ethylcarboxamidoadenosine and N6-cyclopentyladenosine, activated potassium channels. Further, the CV 1808-induced activation was blocked by CGS 15943A. These results indicate that [3H]CV 1808 binding consists of two components in rat brain: a low-affinity site with A1-like characteristics, and a novel high-affinity site, designated as the A4 receptor, where potassium channel activation appears to be a functional correlate.

Activated microglia mediate neuronal cell injury via a nitric oxide mechanism

Activated microglial have been proposed to play a pathogenetic role in immune-mediated neurodegenerative diseases. To test this hypothesis, purified murine neonatal microglial were cocultured with neuronal cells derived from fetal brain. Activation with IFN-gamma and LPS of these cocultures brought about a sharp decrease in uptake of gamma-amino butyric acid and a marked reduction in neuronal cell survival. These effects varied with the density of microglia, the concentrations of the activation signals (IFN-gamma and LPS), and the duration of coculture. Inasmuch as addition of NG-monomethyl-L-arginine blocked these effects, a L-arginine-dependent neurocytotoxic mechanism was implicated. Abundant nitrite, a metabolite of the free radical nitric oxide (NO) derived from L-arginine, was detected in activated microglial/neuronal cell cocultures and in purified microglial cell cultures but not in purified astrocyte or neuronal cell cultures, suggesting that microglial were the principal source of the NO. These findings support the hypothesis that microglia are the source of a neurocytotoxic-free radical, and shed light on an additional mechanism of immune-mediated brain injury.

Activated microglia mediate neuronal cell injury via a nitric oxide mechanism

Activated microglial have been proposed to play a pathogenetic role in immune-mediated neurodegenerative diseases. To test this hypothesis, purified murine neonatal microglial were cocultured with neuronal cells derived from fetal brain. Activation with IFN-gamma and LPS of these cocultures brought about a sharp decrease in uptake of gamma-amino butyric acid and a marked reduction in neuronal cell survival. These effects varied with the density of microglia, the concentrations of the activation signals (IFN-gamma and LPS), and the duration of coculture. Inasmuch as addition of NG-monomethyl-L-arginine blocked these effects, a L-arginine-dependent neurocytotoxic mechanism was implicated. Abundant nitrite, a metabolite of the free radical nitric oxide (NO) derived from L-arginine, was detected in activated microglial/neuronal cell cocultures and in purified microglial cell cultures but not in purified astrocyte or neuronal cell cultures, suggesting that microglial were the principal source of the NO. These findings support the hypothesis that microglia are the source of a neurocytotoxic-free radical, and shed light on an additional mechanism of immune-mediated brain injury.

Cytokine release from microglia: differential inhibition by pentoxifylline and dexamethasone

Cytokines have been implicated in the pathogenesis of gram-negative bacterial meningitis. The effects of pentoxifylline and dexamethasone on the release of tumor necrosis factor (TNF), interleukin (IL)-1, and IL-6 from primary murine microglial cell cultures were explored using bioassays. When added concomitantly with lipopolysaccharide, pentoxifylline blocked the release of TNF and IL-1 but not IL-6, while dexamethasone inhibited the release of TNF and IL-6. After a 2-h exposure of microglia to lipopolysaccharide, pentoxifylline but not dexamethasone still inhibited the release of TNF. Release of TNF was enhanced 20-fold by priming of the microglia with interferon-gamma; only pentoxifylline blocked the priming effect of interferon-gamma on TNF release. These results demonstrate that pentoxifylline and dexamethasone differentially regulate the release of cytokines in microglial cell cultures and provide potential insight into their role in the treatment of gram-negative bacterial meningitis.

Influence of medicinal herbs on phagocytosis by bovine neutrophils

Twenty-six herbal preparations made from 24 medicinal herbs, categorized as antipyretics in Chinese materia medica, were tested in vitro to determine their effects upon phagocytosis of 32P-labelled Staphylococcus aureus by neutrophils isolated from bovine blood and milk. The percentage of phagocytosis was determined after incubating (1 hour at 37 degrees C) 1.25 x 10(7) neutrophils, 1 x 10(8) 32P-labelled S. aureus and 10% skimmed milk with herbal solutions. Concentrations of herbal preparations tested were 100%, 10% and 1% (v/v). When compared with PBSS (0.01 M phosphate buffered saline solution) controls, most of the herbs at high concentrations inhibited phagocytosis while at lower concentrations phagocytosis was increased. All 26 herbal preparations significantly increased blood neutrophil activity at their proper concentrations. The most active herbs in promoting blood neutrophil phagocytosis were observed for Herba verbenae, Flos chrysanthemi, Flos lonicerae, Radix sophorae flavescentis, Herba houttuyniae, Radix isatidis, Herba patriniae, Berberini sulfatis at the lowest concentration and for Folium hibisci at the high concentration with the increased percentage of more than 40.0% in comparison with PBSS control. Of the 19 herbal preparations tested with milk neutrophils, 18 herbs greatly increased phagocytosis at suitable concentrations. The most active preparations in stimulating milk neutrophil functions included Folium hibisci, Flos chrysanthemi, Radix bupleuri, Radix stellariae, Herba houttuyniae, Herba senecionis scandentis, Caulis lonicerae and Flos lonicerae which increased phagocytosis by over 35.0%.

[Establishment and preliminary application of competitive ELISA using monoclonal antibody against Trichinella spiralis]

Monoclonal antibody competitive ELISA was devised with a highly specific McAb (2G8) against T. spiralis. Among 20 rabbits infected with T. spiralis experimentally. 35% (7/20) were positive on the 17th day post infection (PI); 100% positive on the 31st day PI. No cross reaction was found with 29 sera of rabbits infected with other kinds of helminth. The dynamic antibody titer of five infected rabbits sera were studied with this method. The change may be helpful to judge the state of infection. In short, anti-T. spiralis McAb competitive ELISA can be regarded as a sensitive and specific immunological diagnostic method for T. spiralis infection.

Support of human hematopoiesis in long-term bone marrow cultures by murine stromal cells selectively expressing the membrane-bound and secreted forms of the human homolog of the steel gene product, stem cell factor

The maintenance and differentiation of hematopoietic stem cells is influenced by cells making up the hematopoietic microenvironment (HM), including bone marrow-derived stromal cells. We and several other investigators have recently demonstrated the molecular basis of abnormal HM observed in the steel mutant mouse and cloned the normal cDNA products of this gene (termed SCF, KL, or MCF). In this report, we focus on the human counterpart of the mouse Steel (Sl) gene. Alternative splicing of the human SCF pre-mRNA transcript results in secreted and membrane-bound forms of the protein. To investigate the role of these two forms of human SCF, we targeted an immortalized stromal cell line derived from fetal murine homozygous (Sl/Sl) SCF-deficient embryos for gene transfer of various human cDNAs encoding SCF. We report that stable stromal cell transfectants can differentially process the two forms of human SCF protein product. We also demonstrate that both soluble SCF and membrane-bound SCF are active in increasing the number of human progenitor cells in the context of stromal cell cultures, although in a qualitatively different manner. Hence, the membrane-bound form of SCF may play an important role in the cell-cell interactions observed between stromal and hematopoietic cells both in vitro and in vivo.

Immunologically mediated fatigue: a murine model

Chronic fatigue syndrome (CFS) is an idiopathic disorder in which the chief symptoms is profound fatigue. To explore the relationship between immune stimulation and fatigue, we developed a murine model for quantifying fatigue: reduction in voluntary running and delayed initiation of grooming after swimming. Inoculation of female BALB/c mice with Corynebacterium parvum antigen or the relatively avirulent Me49 strain of Toxoplasma gondii induced fatigue: baseline running reduced to less than 50 and 30% for 8 and 14 days, respectively, and delayed initiation of grooming after swimming in both immunologically stimulated groups. A threefold evaluation of serum transforming growth factor-beta levels, a cytokine increased in CFS patients, was found in fatigued C. parvum- and T. gondii-inoculated mice. This murine model appears promising for investigation of the pathogenesis of immunologically mediated fatigue.

[The use of 6-flavor Rehmannia decoction with additives in the prevention of ototoxic deafness induced by gentamicin in guinea pigs]

The purpose of this study is to discuss the effects of the Chinese medicine six-flavor Rehmannia Decoction with additives on preventing deafness induced by gentamicin (GM) in guinea pig by means of testing the thresholds of Preyer's reflex (PR) cochlear microphonic potential (CM), action potential of the auditory nerve (N1) and scanning electron microscope of inner ear (SEM). The results showed that the medicine is effective in reducing the ototoxic effect of GM on inner ear.

Characterization of the copper- and silver-thiolate clusters in N-terminal fragments of the yeast ACE1 transcription factor capable of binding to its specific DNA recognition sequence

N-terminal fragments of ACE1 protein spanning residues 1-122 or 1-110, termed ACE1(122*) and ACE1(110*), respectively, were investigated in regard to their metal- and double-stranded DNA-binding properties. Band mobility shift assays showed that binding to a specific oligonucleotide (termed UASc), containing two ACE1(122*) binding sites, requires the presence of Cu(I) or Ag(I) but does not occur in the presence of divalent metal ions. Both the Ag(I) and the Cu(I) forms of ACE1(122*) were characterized spectroscopically. The Tyr and metal cluster luminescence emission of Cu-ACE1(122*) was specifically quenched by the oligonucleotide UAScL, but not by an oligonucleotide of the same length and base composition but scrambled sequence. The room-temperature luminescence of Cu(I)-ACE1(122*) was assigned to a phosphorescence emission, on the basis of its long-lived luminescence of approximately 3.5 microseconds. We report the first observation of a Ag(I) metal cluster in solution for Ag(I)-ACE1(122*), which was found to exhibit a quantum yield and average luminescence lifetime that are ca. 6% of that of Cu(I)-ACE1(122*). The three-dimensional structure brought about by the binding of either metal ion appears to be very similar, since dynamic tyrosine fluorescence lifetime measurements, as well as circular dichroism spectra, were nearly identical for Cu- and Ag-ACE1(122*). Based on these results, we present a hypothetical model for the structure of the metal cluster in this class of proteins.