RESUMO
We report on the conditions necessary for the electrical injection of spin-polarized electrons into indium nitride nanowires synthesized from the bottom up by molecular beam epitaxy. The presented results mark the first unequivocal evidence of spin injection into III-V semiconductor nanowires. Utilizing a newly developed preparation scheme, we are able to surmount shadowing effects during the metal deposition. Thus, we avoid strong local anisotropies that arise if the ferromagnetic leads are wrapping around the nanowire. Using a combination of various complementary techniques, inter alia the local Hall effect, we carried out a comprehensive investigation of the coercive fields and switching behaviors of the cobalt micromagnetic spin probes. This enables the identification of a range of aspect ratios in which the mechanism of magnetization reversal is single domain switching. Lateral nanowire spin valves were prepared. The spin relaxation length is demonstrated to be about 200 nm, which provides an incentive to pursue the route toward nanowire spin logic devices.
Assuntos
Cristalização/métodos , Galvanoplastia/métodos , Índio/química , Nanoestruturas/química , Nanoestruturas/ultraestrutura , Semicondutores , Substâncias Macromoleculares/química , Teste de Materiais , Conformação Molecular , Tamanho da Partícula , Propriedades de SuperfícieRESUMO
This study characterized the current epidemiology of vibrio infections in Florida and examined cases reported from 1998 to 2007. Logistic regression was used to determine risk of death. There were 834 vibrio infections in 825 individuals (average annual incidence rate 4·8/1,000,000). Common Vibrio species reported were Vibrio vulnificus (33%), V. parahaemolyticus (29%), and V. alginolyticus (16%). Most exposures were attributed to wounds (42%), and the most common clinical syndromes were wound infections (45%) and gastroenteritis (42%). Almost half of individuals reported an underlying health condition. Risk of death was associated with any underlying condition and increased with the number of conditions (P<0·0001). In Florida, incidence of vibriosis associated with raw oyster consumption has decreased while incidence associated with wound infections has increased. Most prevention efforts to date have focused on oyster consumption. New educational messages focusing on the risk of vibriosis from wound infections should target high-risk populations.
Assuntos
Vibrioses/epidemiologia , Vibrioses/microbiologia , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Criança , Pré-Escolar , Comportamento Alimentar , Feminino , Florida/epidemiologia , Gastroenterite/epidemiologia , Gastroenterite/microbiologia , Gastroenterite/mortalidade , Humanos , Lactente , Recém-Nascido , Masculino , Pessoa de Meia-Idade , Análise de Sobrevida , Vibrioses/mortalidade , Vibrio alginolyticus/isolamento & purificação , Vibrio parahaemolyticus/isolamento & purificação , Vibrio vulnificus/isolamento & purificação , Infecção dos Ferimentos/epidemiologia , Infecção dos Ferimentos/microbiologia , Infecção dos Ferimentos/mortalidade , Adulto JovemRESUMO
This study explored the association between headache response and return to functioning, and identified migraine-associated symptoms related to functional status and acceptability of migraine treatment as reported by patients. Data from migraineurs enrolled in the active arms of a randomized, double-blind, parallel group, placebo-controlled, clinical trial were analysed. The relationships between headache response and functional response, and clinical factors and treatment acceptability were assessed using chi(2) tests of proportions and logistic regressions. A greater proportion of patients with headache response at 0.5 h were functioning at 0.5, 1 and 2 h compared with patients who did not attain a headache response at 0.5 h (P < 0.0001). These patients also were more likely to find their treatment acceptable (P < 0.05). The results suggest a direct temporal relationship among the key determinants of migraine resolution. Rapid headache response is associated with faster return to functioning; rapid headache and functional responses are significant attributes of treatment acceptability.
Assuntos
Cefaleia/tratamento farmacológico , Cefaleia/epidemiologia , Transtornos de Enxaqueca/tratamento farmacológico , Transtornos de Enxaqueca/epidemiologia , Satisfação do Paciente/estatística & dados numéricos , Recuperação de Função Fisiológica , Agonistas do Receptor de Serotonina/uso terapêutico , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Comorbidade , Método Duplo-Cego , Feminino , Humanos , Incidência , Masculino , Maryland/epidemiologia , Pessoa de Meia-Idade , Avaliação de Resultados em Cuidados de Saúde/métodos , Pirrolidinas/uso terapêutico , Sumatriptana/uso terapêutico , Resultado do Tratamento , Triptaminas/uso terapêuticoRESUMO
Cytotoxic T lymphocytes (CTL) play a vital role in host defense against viral and intracellular bacterial infections. However, nonreplicating vaccines administered by intramuscular injection using a syringe and needle elicit predominantly humoral responses and not CTL responses. Here we report that epidermal powder immunization (EPI), a technology that delivers antigens on 1.5- to 2.5-microm gold particles to the epidermis using a needle-free powder delivery system, elicits CTL responses to nonreplicating antigens. Following EPI, a majority of the antigen-coated gold particles were found in the viable epidermis in the histological sections of the target skin. Further studies using transmission electron microscopy revealed the intracellular localization of the gold particles. Many Langerhans cells (LCs) at the vaccination site contained antigen-coated particles, as revealed by two-color immunofluorescence microscopy, and these cells were found in the draining lymph nodes 20 h later. Immune responses to several viral protein antigens after EPI were studied in mice. EPI with hepatitis B surface antigen (HBsAg) and a synthetic peptide of influenza virus nucleoprotein (NP peptide) elicited antigen-specific CTL responses as well as antibody responses. In an in vitro cell depletion experiment, we demonstrated that the CTL activity against HBsAg elicited by EPI was attributed to CD8(+), not CD4(+), T cells. As controls, needle injections of HBsAg or the NP peptide into deeper tissues elicited solely antibody, not CTL, responses. We further demonstrated that EPI with inactivated A/Aichi/68 (H3N2) or A/Sydney/97 (H3N2) influenza virus elicited complete protection against a mouse-adapted A/Aichi/68 virus. In summary, EPI directly delivers protein antigens to the cytosol of the LCs in the skin and elicits both cellular and antibody responses.
Assuntos
Anticorpos Antivirais/biossíntese , Antígenos Virais/imunologia , Epiderme/imunologia , Antígenos de Superfície da Hepatite B/administração & dosagem , Vírus da Hepatite B/imunologia , Vírus da Influenza A/imunologia , Vacinas contra Influenza/administração & dosagem , Linfócitos T Citotóxicos/imunologia , Animais , Ensaio de Imunoadsorção Enzimática , Epiderme/ultraestrutura , Feminino , Camundongos , Camundongos Endogâmicos BALB C , Microscopia Eletrônica , Pós , Proteínas Virais/imunologiaRESUMO
In order to use bovine dentin instead of human dentin for in vitro adhesion and cytotoxicity tests the permeability characteristics of human and bovine dentin should be similar. In the present study hydraulic conductance (Lp) and diffusional water flux (J5) of human and bovine dentin slices were compared. The permeability experiments were performed in a split chamber using tritiated water in physiological saline. Lp and Js of bovine dentin were 0.7- to 2.4-fold and 1.1- to 3.5-fold that of human dentin (not statistically significant). For human and bovine dentin Lp and Js increased with etching and showed an inverse linear relationship (r > or = 0.7) with dentin thickness. The variability of bovine data was low (perfusion = 30%, diffusion = 22%) and about half that of the human data. In conclusion bovine dentin near the cementoenamel junction seems to be a suitable alternative for coronal human dentin for in vitro tests with respect to transdentinal permeability characteristics.
Assuntos
Permeabilidade da Dentina/fisiologia , Condicionamento Ácido do Dente , Algoritmos , Análise de Variância , Animais , Materiais Biocompatíveis/toxicidade , Bovinos , Colagem Dentária , Dentina/efeitos dos fármacos , Dentina/metabolismo , Dentina/ultraestrutura , Difusão , Cultura em Câmaras de Difusão , Humanos , Modelos Lineares , Microscopia Eletrônica de Varredura , Modelos Animais , Compostos Radiofarmacêuticos , Cloreto de Sódio , Estatística como Assunto , Colo do Dente/efeitos dos fármacos , Colo do Dente/metabolismo , Colo do Dente/ultraestrutura , Trítio , ÁguaRESUMO
OBJECTIVE: To identify epidemiological trends and measure outcomes in elderly patients hospitalized for cardiac conduction disorders or arrhythmias. DESIGN: Review of the standard 5% samples of the Medicare Provider Analysis and Review Files to characterize 144,512 discharges from 1991 through 1998 in which the principal diagnosis was a conduction disorder or arrhythmia, using the corresponding Enrollment Databases for denominator data. SETTING: Short-stay hospitals in the United States. PARTICIPANTS: Medicare beneficiaries age 65 and older in the standard 5% sample. MEASUREMENTS: Diagnosis-specific trends and rates; discharges by year; cumulative age-, race-, and sex-specific discharge rates; mean length of stay in hospital and in intensive care; mean Medicare reimbursement to the hospital; case-fatality rate in hospital; discharge destinations of patients discharged alive. RESULTS: Annual hospitalizations for sinoatrial node dysfunction, atrial flutter, atrial fibrillation, or ventricular fibrillation increased more rapidly than did the elderly Medicare beneficiary population. Hospitalizations with a principal diagnosis of ventricular extrasystoles or asystole showed steep secular declines. Discharge rates for sinoatrial node dysfunction, a group of rhythms with a nonsinus pacemaker, atrial fibrillation, Mobitz I, or complete atrioventricular block all increased steeply and continuously with patient age. In contrast, discharge rates for atrial flutter or ventricular tachycardia or fibrillation peaked among 75- to 84-year-old patients. White men were at uniquely high risk of hospitalization for atrial flutter or ventricular tachycardia or fibrillation, and, among the white majority, men had higher discharge rates than women for nine of the 11 commonest rubrics. Whites, particularly white women, had the highest discharge rates for atrial fibrillation. Blacks, especially black women, were at disproportionate risk for hospitalization for the group of nonsinus pacemaker rhythms. Diagnosis-specific mean resource costs were strongly correlated with each other and with mean Medicare reimbursement but not with case-fatality rate. CONCLUSION: Medicare claims data demonstrated striking differences among and within diagnoses of heart blocks or arrhythmias in terms of the populations at greatest risk for hospitalization. This variation should be explored further to generate and test hypotheses about differential causation or delivery of care.
Assuntos
Arritmias Cardíacas/epidemiologia , Hospitalização/estatística & dados numéricos , Resultado do Tratamento , Negro ou Afro-Americano/estatística & dados numéricos , Distribuição por Idade , Idoso , Idoso de 80 Anos ou mais , Arritmias Cardíacas/diagnóstico , Arritmias Cardíacas/etiologia , Centers for Medicare and Medicaid Services, U.S. , Feminino , Pesquisa sobre Serviços de Saúde , Mortalidade Hospitalar , Hospitalização/tendências , Humanos , Incidência , Formulário de Reclamação de Seguro/estatística & dados numéricos , Formulário de Reclamação de Seguro/tendências , Tempo de Internação/estatística & dados numéricos , Tempo de Internação/tendências , Masculino , Medicare Part A/estatística & dados numéricos , Medicare Part A/tendências , Vigilância da População , Prognóstico , Mecanismo de Reembolso/estatística & dados numéricos , Mecanismo de Reembolso/tendências , Fatores de Risco , Distribuição por Sexo , Análise de Sobrevida , Estados Unidos/epidemiologia , População Branca/estatística & dados numéricosRESUMO
SUMMARY: In recent years, our understanding of macromolecular transport processes across the nuclear envelope has grown dramatically, and a large number of soluble transport receptors mediating either nuclear import or nuclear export have been identified. Most of these receptors belong to one large family of proteins, all of which share homology with the protein import receptor importin beta (also named karyopherin beta). Members of this family have been classified as importins or exportins on the basis of the direction they carry their cargo. To date, the family includes 14 members in the yeast Saccharomyces cerevisiae and at least 22 members in humans. Importins and exportins are regulated by the small GTPase Ran, which is thought to be highly enriched in the nucleus in its GTP-bound form. Importins recognize their substrates in the cytoplasm and transport them through nuclear pores into the nucleus. In the nucleoplasm, RanGTP binds to importins, inducing the release of import cargoes. In contrast, exportins interact with their substrates only in the nucleus in the presence of RanGTP and release them after GTP hydrolysis in the cytoplasm, causing disassembly of the export complex. Thus, common features of all importin-beta-like transport factors are their ability to shuttle between the nucleus and the cytoplasm, their interaction with RanGTP as well as their ability to recognize specific transport substrates.
Assuntos
Proteínas Nucleares/fisiologia , Transporte Ativo do Núcleo Celular , Evolução Molecular , Proteínas Fúngicas/fisiologia , Humanos , Carioferinas , Modelos Biológicos , Proteínas Nucleares/química , Proteínas Nucleares/genética , Estrutura Secundária de Proteína , Sequências Repetitivas de Aminoácidos , Proteína ran de Ligação ao GTP/fisiologiaRESUMO
Xpo1p (Crm1p) is the nuclear export receptor for proteins containing a leucine-rich nuclear export signal (NES). Xpo1p, the NES-containing protein, and GTP-bound Ran form a complex in the nucleus that translocates across the nuclear pore. We have identified Yrb1p as the major Xpo1p-binding protein in Saccharomyces cerevisiae extracts in the presence of GTP-bound Gsp1p (yeast Ran). Yrb1p is cytoplasmic at steady-state but shuttles continuously between the cytoplasm and the nucleus. Nuclear import of Yrb1p is mediated by two separate nuclear targeting signals. Export from the nucleus requires Xpo1p, but Yrb1p does not contain a leucine-rich NES. Instead, the interaction of Yrb1p with Xpo1p is mediated by Gsp1p-GTP. This novel type of export complex requires the acidic C-terminus of Gsp1p, which is dispensable for the binding to importin beta-like transport receptors. A similar complex with Xpo1p and Gsp1p-GTP can be formed by Yrb2p, a relative of Yrb1p predominantly located in the nucleus. Yrb1p also functions as a disassembly factor for NES/Xpo1p/Gsp1p-GTP complexes by displacing the NES protein from Xpo1p/Gsp1p. This Yrb1p/Xpo1p/Gsp1p complex is then completely dissociated after GTP hydrolysis catalyzed by the cytoplasmic GTPase activating protein Rna1p.
Assuntos
Proteínas de Transporte/metabolismo , Carioferinas , Receptores Citoplasmáticos e Nucleares , Proteínas de Saccharomyces cerevisiae , Transporte Ativo do Núcleo Celular , Sequência de Aminoácidos , Proteínas de Transporte/química , Proteínas de Transporte/genética , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Guanosina Trifosfato/metabolismo , Substâncias Macromoleculares , Dados de Sequência Molecular , Proteínas Monoméricas de Ligação ao GTP/genética , Proteínas Monoméricas de Ligação ao GTP/metabolismo , Sinais de Localização Nuclear/química , Sinais de Localização Nuclear/genética , Sinais de Localização Nuclear/metabolismo , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Proteína Exportina 1RESUMO
The GTPase Ran has recently been shown to stimulate microtubule polymerization in mitotic extracts, but its mode of action is not understood. Here we show that the mitotic role of Ran is largely mediated by the nuclear transport factor importin beta. Importin beta inhibits spindle formation in vitro and in vivo and sequesters an aster promoting activity (APA) that consists of multiple, independent factors. One component of APA is the microtubule-associated protein NuMA. NuMA and other APA components are discharged from importin beta by RanGTP and induce spindle-like structures in the absence of centrosomes, chromatin, or Ran. We propose that RanGTP functions in mitosis as in interphase by locally releasing cargoes from transport factors. In mitosis, this promotes spindle assembly by organizing microtubules in the vicinity of chromosomes.
Assuntos
Mitose/fisiologia , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Fuso Acromático/metabolismo , Proteínas de Xenopus , Proteína ran de Ligação ao GTP/metabolismo , Animais , Linhagem Celular , Clonagem Molecular , Feminino , GTP Fosfo-Hidrolases/genética , GTP Fosfo-Hidrolases/metabolismo , Expressão Gênica/fisiologia , Carioferinas , Mamíferos , Microtúbulos/metabolismo , Oócitos/citologia , Oócitos/metabolismo , Xenopus , Proteína ran de Ligação ao GTP/genéticaRESUMO
Molecular biological investigations of HIV have made fundamental contributions to our understanding of eukaryotic biology. These studies elucidated new paradigms in transcription, RNA and protein export from the nucleus to the cytoplasm, cellular activation, morphology and vesicular trafficking.
Assuntos
Transporte Ativo do Núcleo Celular/fisiologia , HIV/metabolismo , Proteínas dos Retroviridae/metabolismo , Endocitose/fisiologia , Produtos do Gene rev/metabolismo , Produtos do Gene tat/metabolismo , HIV/genética , Humanos , Modelos Biológicos , Proteínas dos Retroviridae/genética , Transcrição Gênica/fisiologia , Produtos do Gene rev do Vírus da Imunodeficiência Humana , Produtos do Gene tat do Vírus da Imunodeficiência HumanaAssuntos
Sistemas de Liberação de Medicamentos/instrumentação , Sistemas de Liberação de Medicamentos/métodos , Vacinas contra Parainfluenza/administração & dosagem , Animais , Ensaio de Imunoadsorção Enzimática , Feminino , Humanos , Imunização/métodos , Influenza Humana/imunologia , Influenza Humana/prevenção & controle , Injeções Subcutâneas , Camundongos , Camundongos Endogâmicos BALB C , AgulhasRESUMO
The action of nuclear hormone receptors is tripartite, involving the receptor, its ligands, and its co-regulator proteins. The estrogen receptor (ER), a member of this superfamily, is a hormone-regulated transcription factor that mediates the effects of estrogens and anti-estrogens (e.g., tamoxifen) in breast cancer and other estrogen target cells. This chapter presents our recent work on several aspects of estrogen action and the function of the ER: 1) elucidation of ER structure-function relationships and development of ligands that are selective for one of the two ER subtypes, ERalpha or ERbeta; 2) identification of ER-selective co-regulators that potentiate the inhibitory effectiveness of anti-estrogens and dominant-negative ERs and modulate the activity of estrogens; 3) characterization of genes that are regulated by the anti-estrogen-ER versus the estrogen-ER complex; and 4) elucidation of the intriguing pharmacology of these ER complexes at different gene regulatory sites. These findings indicate that different residues of the ER hormone-binding domain are involved in the recognition of structurally distinct estrogens and anti-estrogens and highlight the exquisite precision of the regulation of ER activities by ligands, with small changes in ligand structure resulting in major changes in receptor character. Studies also explore the biology and distinct pharmacology mediated by ERalpha and ERbeta complexed with different ligands through different target genes. The upregulation of the anti-oxidant detoxifying phase II enzyme, quinone reductase, by the anti-estrogen-occupied ER, mediated via the electrophile response element in the QR gene, may contribute to the beneficial antioxidant effects of anti-estrogens in breast cancer and illustrates the activation of some genes by ER via non-estrogen response element sequences. The intriguing biology of estrogen in its diverse target cells is thus determined by the structure of the ligand, the ER subtype involved, the nature of the hormone-responsive gene promoter, and the character and balance of co-activators and co-repressors that modulate the cellular response to the ER-ligand complex. The continuing development of novel ligands and the study of how they function as selective agonists or antagonists through ERalpha or ERbeta should allow optimized tissue selectivity of these agents for hormone replacement therapy and treatment and prevention of breast cancer.
Assuntos
Receptores de Estrogênio/metabolismo , Sequência de Aminoácidos , Animais , Neoplasias da Mama/genética , Neoplasias da Mama/metabolismo , Estrogênios/química , Estrogênios/metabolismo , Estrogênios/farmacologia , Feminino , Humanos , Ligantes , Modelos Biológicos , Modelos Moleculares , Dados de Sequência Molecular , Proibitinas , Receptores de Estrogênio/química , Receptores de Estrogênio/genética , Proteínas Repressoras/genética , Proteínas Repressoras/metabolismoRESUMO
The bacterial extract OM-89 used for the prevention and treatment of recurrent urinary tract infections constitutes an effective immunostimulant in vitro and in vivo. Here we demonstrate that OM-89 shows mitogenic properties towards murine spleen cell cultures from LPS responder and non-responder mice. In macrophages the extract induces the translocation of NF-kappaB into the cell nucleus and RNI (radical nitrogen intermediates) release, which could be attributed to single fractions of the extract. Our findings on the in vitro immunostimulatory effect of OM-89, as well as its immunogenic and adjuvant properties, are of importance for understanding its therapeutic efficacy as demonstrated in clinical studies.
Assuntos
Adjuvantes Imunológicos/farmacologia , Antígenos de Bactérias/farmacologia , Linfócitos/imunologia , Macrófagos/imunologia , Animais , Células da Medula Óssea/citologia , Linhagem Celular , Células Cultivadas , Escherichia coli , Feminino , Interferon gama/farmacologia , Lipopolissacarídeos/farmacologia , Ativação Linfocitária , Linfócitos/efeitos dos fármacos , Macrófagos/efeitos dos fármacos , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , NF-kappa B/metabolismo , Óxido Nítrico/fisiologia , Proteínas Recombinantes , Salmonella , Baço/imunologiaRESUMO
Estrogens exert profound effects on the physiology of diverse target cells and these effects appear to be mediated by two estrogen receptor (ER) subtypes, ERalpha and ERbeta. We have investigated how ER ligands, ranging from pure agonists to antagonists, interact with ERalpha and ERbeta, and regulate their transcriptional activity on different genes. Mutational mapping-structure activity studies indicate that different residues of the ER ligand binding domain are involved in the recognition of structurally distinct estrogens and antiestrogens. We have identified from ligands of diverse structure, several particularly interesting ones that are high potency selective agonists via ERalpha and others that are full agonists through ERalpha while being full antagonists through ERbeta. Antiestrogens such as hydroxytamoxifen, which are mixed agonist/antagonists through ERalpha, are pure antagonists through ERbeta at estrogen response element-containing gene sites. Studies with ERalpha/beta chimeric proteins reveal that tamoxifen agonism requires the activation function 1 region of ERalpha. Through two-hybrid assays, we have isolated an ER-specific coregulator that potentiates antiestrogen antagonist effectiveness and represses ER transcriptional activity. We have also focused on understanding the distinct pharmacologies of antiestrogen- and estrogen-regulated genes. Although antiestrogens are thought to largely act by antagonizing the actions of estrogens, we have found among several new ER-regulated genes, quinone reductase (QR), a detoxifying phase II antioxidant enzyme, that has its activity up-regulated by antiestrogens in an ER-dependent manner in breast cancer cells. This response is antagonized by estrogens, thus showing 'reversed pharmacology'. Increased QR activity by antiestrogens requires a functional ER (ERalpha or ERbeta) and is, interestingly, mediated via the electrophile response element in the QR gene 5' regulatory region. The up-regulation of QR may contribute to the beneficial effects of tamoxifen, raloxifene, and other antiestrogens in breast cancer prevention and treatment. Estrogens rapidly up-regulate expression of several genes associated with cell cytoarchitectural changes including NHE-RF, the sodium hydrogen exchanger regulatory factor, also known as EBP50. NHE-RF/EBP50 is enriched in microvilli, and may serve as a scaffold adaptor protein in regulating early changes in cell architecture and signal transduction events induced by estrogen. Analyses of the regulatory regions of these primary response genes, and the antioxidant and other signaling pathways involved, are providing considerable insight into the mechanisms by which ligands, that function as selective estrogen receptor modulators or SERMs, exert their marked effects on the activities and properties of target cells. The intriguing biology of estrogens in its diverse target cells is thus determined by the structure of the ligand, the ER subtype involved, the nature of the hormone-responsive gene promoter, and the character and balance of coactivators and corepressors that modulate the cellular response to the ER-ligand complex. The continuing development of ligands that function as selective estrogens or antiestrogens for ERalpha or ERbeta should allow optimized tissue selectivity of these agents for menopausal hormone replacement therapy and the treatment and prevention of breast cancer.
Assuntos
Estrogênios/farmacologia , Receptores de Estrogênio/metabolismo , Antagonistas de Estrogênios/farmacologia , Moduladores de Receptor Estrogênico/farmacologia , Feminino , Regulação da Expressão Gênica/efeitos dos fármacos , Humanos , Ligantes , Receptores de Estrogênio/agonistas , Receptores de Estrogênio/antagonistas & inibidores , Receptores de Estrogênio/química , Moduladores Seletivos de Receptor Estrogênico/farmacologia , Relação Estrutura-Atividade , Especificidade por SubstratoRESUMO
Zinc oxide-eugenol (ZOE) is cytotoxic in vitro but does not cause pulp damage. Various dentin proteins may play a protective role in vivo. We investigated the influence of bovine serum albumin (BSA) and collagen on ZOE cytotoxicity in the Millipore filter test and a dentin barrier test. Agar or agarose with 1% or 5% BSA or calf collagen (1% and 2%) were introduced between L-929 fibroblasts and test specimens. ZOE was severely toxic in the absence of BSA. However BSA (1% and 3%) reduced cell damage to 50% and 35%. In contrast, collagen did not provide protection from ZOE cytotoxicity. When dentin was loaded with 3% BSA and the "pulpal" side of a dentin barrier test chamber was perfused with cell culture medium containing 3% BSA, cytotoxicity of ZOE was completely inhibited. Therefore we conclude that albumin may be one factor responsible for the absence of ZOE toxicity in pulp studies.
Assuntos
Colágeno/farmacologia , Substâncias Protetoras/farmacologia , Soroalbumina Bovina/farmacologia , Cimento de Óxido de Zinco e Eugenol/toxicidade , Ágar , Animais , Bovinos , Morte Celular/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Meios de Cultura , Citoproteção , Dentina/fisiologia , Cultura em Câmaras de Difusão , Fibroblastos/efeitos dos fármacos , Camundongos , Filtros Microporos , SefaroseRESUMO
Despite its fundamental role in cell division, the mitotic spindle remains an enigmatic figure in cell biology. This is due to the complex dynamic behaviour of microtubules, which form the spindle fibres responsible for segregating chromosomes to opposite ends of the cell during mitosis. Recent reports indicate that the small GTPase Ran, which plays a key role in nuclear transport, also has a role in mitosis by regulating microtubule nucleation and/or growth. The race is now on to determine how Ran exerts its effects on spindle assembly.
Assuntos
Mitose , Fuso Acromático , Proteína ran de Ligação ao GTP , Animais , Humanos , MicrotúbulosRESUMO
Transport of macromolecules across the nuclear envelope is an active process that depends on soluble factors including the GTPase Ran. Ran-GTP is predominantly located in the nucleus and has been shown to regulate cargo binding and release of import and export receptors in their respective target compartments. Recently, it was shown that transport of receptor-cargo complexes across the nuclear pore complex (NPC) does not depend on GTP-hydrolysis by Ran; however, the mechanism of translocation is still poorly understood. Here, we show that the direction of transport through the NPC can be inverted in the presence of high concentrations of cytoplasmic Ran-GTP. Under these conditions, two different classes of export cargoes are transported into the nucleus in the absence of GTP hydrolysis. The inverted transport is very rapid and can be blocked by known inhibitors of nuclear protein export. These results suggest that the NPC functions as a facilitated transport channel, allowing the selective translocation of receptor-cargo complexes. We conclude that the directionality of nucleocytoplasmic transport is determined mainly by the compartmentalized distribution of Ran-GTP.
Assuntos
Carioferinas , Membrana Nuclear/ultraestrutura , Proteínas Nucleares/metabolismo , Receptores Citoplasmáticos e Nucleares , Transporte Biológico , Proteínas de Transporte/metabolismo , Células Cultivadas , GTP Fosfo-Hidrolases/metabolismo , Proteínas de Ligação ao GTP/metabolismo , Guanosina Trifosfato/metabolismo , Humanos , Hidrólise , Modelos Biológicos , alfa Carioferinas , Proteína ran de Ligação ao GTP , Proteína Exportina 1RESUMO
Mitosis is triggered in vertebrate cells by the cyclin B1-Cdc2 complex. The activation of this complex at the end of G2 phase is accompanied by its translocation from the cytoplasm to the nucleus. We used digitonin-permeabilized human cells to analyze the mechanism by which cyclin B1-Cdc2 is imported into the nucleus. Cyclin B1-Cdc2 import was not blocked by inhibitors of the importin alpha-dependent import pathway or by dominant negative versions of the GTPase Ran or importin beta. However, the rate of cyclin B1 import was decreased by immunodepletion of importin beta from cytosol. Purified importin beta promoted cyclin B1 import in the absence of cytosol or Ran and in the presence of the dominant negative Ran mutant. We conclude that cyclin B1 import is mediated by an unusual importin beta-dependent mechanism that does not require Ran.