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1.
Zhonghua Nei Ke Za Zhi ; 61(6): 659-663, 2022 Jun 01.
Artigo em Zh | MEDLINE | ID: mdl-35673746

RESUMO

Objective: To determine whether insulin resistance is associated with all-cause mortality in subjects without diabetes. Methods: A total of 505 participants without diabetes, 198 with normal glucose tolerance (NGT) and 307 with impaired glucose tolerance (IGT), were recruited from the Daqing Diabetes Study. The participants were followed up for 30 years. They were stratified into three groups (tertiles) according to baseline homeostasis model assessment of insulin resistance(HOMA-IR) levels, as the HOMA-IR 0, the HOMA-IR 1 and the HOMA-IR 2 groups, to assess the predictive effect of insulin resistance on risk of all-cause mortality. Results: During the 30-year follow-up, 52, 56 and 78 participants died across the three HOMA-IR groups, respectively. The corresponding mortality per 1 000 person-years (95%CI) were 12.12 (9.56-15.01), 13.10 (10.46-16.03) and 19.91 (16.73-23.15), respectively. Participants in the HOMA-IR 2 group had a significantly higher risk of death than those in the HOMA-IR 0 group after adjustment of age, sex and smoking status (HR=1.97,95%CI 1.38-2.81, P<0.001). Cox analyses showed that a one standard deviation increase in HOMA-IR was associated with a 22% increase in the mortality after adjustment of potential confounders (HR=1.22, 95%CI 1.08-1.39, P=0.002). Conclusions: Insulin resistance is associated with increased risk of all-cause death in Chinese people without diabetes, suggesting that improving insulin resistance could be beneficial for people without diabetic in reducing risk of long-term all-cause mortality.


Assuntos
Diabetes Mellitus Tipo 2 , Resistência à Insulina , Glicemia , Seguimentos , Teste de Tolerância a Glucose , Humanos , Insulina
2.
Zhonghua Nei Ke Za Zhi ; 58(5): 372-376, 2019 May 01.
Artigo em Zh | MEDLINE | ID: mdl-31060146

RESUMO

Objective: To explore the influence of lifestyle intervention on long-term diabetes in subjects with impaired glucose tolerance (IGT) returned to normal glucose tolerance (NGT) within 6 years. Methods: A total of 577 subjects (aged 25-74 years old) with IGT in Daqing were enrolled and randomly assigned to control, and diet, exercise and diet plus exercise groups in a six-year intervention trial in 1986. Subjects who were non-diabetic at the end of the intervention were followed up for additional 14 years. Results: Among all the subjects, 41.38% of them who had returned to NGT from IGT within 6 years maintained NGT status after 20 years, and had a lower incidence of diabetes than subjects maintained IGT status (46.55% vs. 75.25%). Of note, in the intervention group, the percentage of participants developed diabetes in the NGT subjects was significantly lower than that in the IGT group (43.71% vs. 76.25%) after 20 years. There was high long-term risk for diabetes in the IGT subjects after the adjustment of age, sex and baseline glucose (HR=1.81, 95%CI 1.27-2.58, P=0.001), whereas in the non-intervention group, no significant difference could be viewed in long-term diabetic risk between subjects maintained IGT status and those returned to NGT (71.43% vs. 65.22%) after adjusting of the same confounders (HR=1.03, 95%CI 0.45-2.35, P=0.94). Conclusions: IGT subjects who had returned to NGT in early years had lower risk for future diabetes than those who remained IGT. However, this beneficial effect could only be viewed in the intervention group, but not in the non-intervention group.


Assuntos
Diabetes Mellitus Tipo 2/prevenção & controle , Intolerância à Glucose/prevenção & controle , Insulina/metabolismo , Adulto , Idoso , Glicemia/análise , Diabetes Mellitus Tipo 2/diagnóstico , Exercício Físico , Seguimentos , Intolerância à Glucose/complicações , Teste de Tolerância a Glucose , Hemoglobinas Glicadas/análise , Humanos , Hiperglicemia/complicações , Hiperglicemia/diagnóstico , Pessoa de Meia-Idade , Comportamento de Redução do Risco
3.
Opt Express ; 23(23): 30104-17, 2015 Nov 16.
Artigo em Inglês | MEDLINE | ID: mdl-26698491

RESUMO

Multipartite quantum entanglement is a key resource for ensuring security in quantum network. We show that by using a unified parameter in terms of reduced noise variances one can determine different types of tripartite entanglement of a given state generated in a hybrid optomechanical system, where an atomic ensemble is located inside a single-mode cavity with a movable mirror, with different thresholds for each type. In particular, the special quantum states which allow both entanglement and steering genuinely shared among atom-light-mirror modes can be observed, even though there is no direct interaction between the mirror and the atomic ensemble. We further show the robustness against mechanical thermal noise and damping, the relaxation time of atomic ensemble, as well as the effect of gain factors involved in the criteria. Our analysis provides an experimentally achievable method to determine the type of tripartite quantum correlation in a way.

4.
Phys Rev Lett ; 114(6): 060402, 2015 Feb 13.
Artigo em Inglês | MEDLINE | ID: mdl-25723192

RESUMO

Using Venn diagrams, we classify the different types of two-mode Gaussian continuous variable quantum correlation including directional entanglement and Einstein-Podolsky-Rosen (EPR) steering. We establish unified signatures for one- and two-way quantum steering, entanglement, and discord beyond entanglement in terms of an EPR-type variance. By focusing on Gaussian states, we link an optimized condition for entanglement based on an EPR variance to the Simon-Peres condition. This allows us to quantify the asymmetry of the Gaussian entanglement, and to relate the asymmetry to a directional quantum teleportation protocol where Alice and Bob possess asymmetrically noisy channels. Our analysis enables a determination of the type and direction of quantum correlation in a way that is easily measured in experiment. We also find that for symmetric states, when discord exceeds a certain threshold, the states are necessarily steerable.

5.
Nanotechnology ; 25(46): 465707, 2014 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-25360878

RESUMO

Well-ordered silicon nanowires (SiNWs) are applied as surface-enhanced Raman scattering (SERS) substrates. Laser interference lithography is used to fabricate large-area periodic nanostructures. By controlling the reaction time of metal assisted chemical etching, various aspect ratios of SiNWs are generated. Ag nanoparticles are decorated on the substrates via redox reaction to allow a good coverage of Ag over the SiNWs. As the height of the SiNWs increases, the light scattering inside the structures is enhanced. The number of the probing molecules within the detection volume is increased as well. These factors contribute to stronger light-matter interaction and thus lead to higher SERS signal intensity. However, the light trapping effect is more significant for higher SiNWs, which prevents the detection of the SERS signals. An optimized aspect ratio ∼5:1 (1 µm height and 200 nm width) for the SiNW array is found. The well-ordered SiNWs demonstrate better SERS signal intensity and uniformity than the randomly arranged SiNWs.

7.
Phys Rev Lett ; 109(4): 043001, 2012 Jul 27.
Artigo em Inglês | MEDLINE | ID: mdl-23006081

RESUMO

We report an experimental and theoretical study of very low-energy photoelectrons in tunneling ionization process from noble gas atoms interacting with ultrashort intense infrared laser pulses. A universal peak structure with electron energy well below 1 eV in the photoelectron spectrum, corresponding to the double-hump structure in the longitudinal momentum distribution, is identified experimentally for all atomic species. Our quantum and semiclassical analysis reveal the role of long-range Coulomb potential in the production of this very low-energy peak structure.

8.
Zhonghua Liu Xing Bing Xue Za Zhi ; 42(6): 1030-1036, 2021 Jun 10.
Artigo em Zh | MEDLINE | ID: mdl-34814502

RESUMO

Objective: To examine the effect of physical activity (PA) on the incident risk of stroke among adults aged 40 years and above. Methods: The baseline data including PA and demographic characteristics were obtained from the Adult Chronic Disease Surveillance with population representativeness in Ningbo in 2015. The follow-up data of interested health outcomes from 2015 to 2019 were retrieved from a population-based Integrated Noncommunicable Disease Collaborative Management System in Ningbo. The two databases were matched to form a queue. PA was divided into three levels of low-intensity, moderate-intensity, and vigorous-intensity according to the metabolic equivalents (METs) spent per week. Cox regression model was used to calculate the hazard ratio (HR) and 95% confidence interval. Results: A total of 3 353 subjects were included at baseline survey in 2015. Until Dec 31, 2019, there had been 31 stroke events had occurred since then, with accumulative incidence rate of 242/100 000, and an average follow-up time of (50.28±2.54) months. When adjusted for gender, age, education level, smoking status, alcohol consumption, BMI and hypertension, multivariate Cox regression analysis showed that greater PA was associated with a 37.9% reduction of incidence of stroke (HR=0.621,95%CI:0.393-0.983). Compared with those who had low-intensity PA, those who were with vigorous-intensity. PA appeared associated with a 63.1% decrease in the incidence of stroke (HR=0.369, 95%CI: 0.139-0.976). However, there was no statistical significance with moderate-intensity PA (HR=0.712,95%CI:0.323-1.569), noticed. Conclusions: Greater PA is likely to reduce the incidence of stroke. Our findings indicated that people should be encouraged to increase the PA level and developing a healthy supportive environment in the community.


Assuntos
Exercício Físico , Acidente Vascular Cerebral , Adulto , Humanos , Incidência , Estudos Prospectivos , Fatores de Risco , Acidente Vascular Cerebral/epidemiologia
9.
Mol Cell Biol ; 11(5): 2558-66, 1991 May.
Artigo em Inglês | MEDLINE | ID: mdl-2017165

RESUMO

The epsilon-globin gene is the first of the human beta-like globin genes to be expressed during development. We have analyzed protein-DNA interactions in the epsilon-globin promoter region by DNase I footprinting and electrophoretic mobility shift experiments using nuclear extracts from K562 human erythroid cells and from nonerythroid HeLa cells. A restricted set of ubiquitous proteins, including Sp1, bound to regions of the promoter including the CACCC and CCAAT sites. Three interactions, at positions -213, -165, and +3 relative to the transcription start site, were erythroid specific and corresponded to binding of GATA-1, a transcription factor highly restricted to the erythroid lineage. Interestingly, the GATA-1 site at -165 has been conserved in the promoters of 10 mammalian embryonic globin genes. Point mutations demonstrate that GATA-1 binding to this site is necessary for interaction with an erythroid-specific enhancer but that in the absence of an enhancer, GATA-1 does not increase transcription.


Assuntos
Proteínas de Ligação a DNA/metabolismo , Globinas/genética , Regiões Promotoras Genéticas , Fatores de Transcrição/metabolismo , Transcrição Gênica , Animais , Sequência de Bases , Sítios de Ligação , Linhagem Celular , Cloranfenicol O-Acetiltransferase/genética , Cloranfenicol O-Acetiltransferase/metabolismo , Desoxirribonuclease I , Fatores de Ligação de DNA Eritroide Específicos , Fator de Transcrição GATA1 , Regulação da Expressão Gênica , Células HeLa/metabolismo , Humanos , Dados de Sequência Molecular , Mapeamento de Nucleotídeos , Sondas de Oligonucleotídeos , Plasmídeos , Homologia de Sequência do Ácido Nucleico , Especificidade da Espécie , Transfecção
10.
Mol Cell Biol ; 16(11): 6055-64, 1996 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-8887635

RESUMO

Much of our understanding of the process by which enhancers activate transcription has been gained from transient-transfection studies in which the DNA is not assembled with histones and other chromatin proteins as it is in the cell nucleus. To study the activation of a mammalian gene in a natural chromatin context in vivo, we constructed a minichromosome containing the human epsilon-globin gene and portions of the beta-globin locus control region (LCR). The minichromosomes replicate and are maintained at stable copy number in human erythroid cells. Expression of the minichromosomal epsilon-globin gene requires the presence of beta-globin LCR elements in cis, as is the case for the chromosomal gene. We determined the chromatin structure of the epsilon-globin gene in both the active and inactive states. The transcriptionally inactive locus is covered by an array of positioned nucleosomes extending over 1,400 bp. In minichromosomes with a (mu)LCR or DNase I-hypersensitive site 2 (HS2) which actively transcribe the epsilon-globin gene, the nucleosome at the promoter is altered or disrupted while positioning of nucleosomes in the rest of the locus is retained. All or virtually all minichromosomes are simultaneously hypersensitive to DNase I both at the promoter and at HS2. Transcriptional activation and promoter remodeling, as well as formation of the HS2 structure itself, depended on the presence of the NF-E2 binding motif in HS2. The nucleosome at the promoter which is altered upon activation is positioned over the transcriptional elements of the epsilon-globin gene, i.e., the TATA, CCAAT, and CACCC elements, and the GATA-1 site at -165. The simple availability of erythroid transcription factors that recognize these motifs is insufficient to allow expression. As in the chromosomal globin locus, regulation also occurs at the level of chromatin structure. These observations are consistent with the idea that one role of the beta-globin LCR is to maintain promoters free of nucleosomes. The restricted structural change observed upon transcriptional activation may indicate that the LCR need only make a specific contact with the proximal gene promoter to activate transcription.


Assuntos
Cromatina/fisiologia , Cromatina/ultraestrutura , Proteínas de Ligação a DNA/metabolismo , Globinas/biossíntese , Globinas/genética , Regiões Promotoras Genéticas , Fatores de Transcrição/metabolismo , Ativação Transcricional , Animais , Núcleo Celular/metabolismo , Replicação do DNA , Fatores de Ligação de DNA Eritroide Específicos , Fator de Transcrição GATA1 , Humanos , Mamíferos , Fator de Transcrição NF-E2 , Subunidade p45 do Fator de Transcrição NF-E2 , Proteínas Nucleares/metabolismo , Nucleossomos/metabolismo , Nucleossomos/ultraestrutura , Sequências Reguladoras de Ácido Nucleico , Mapeamento por Restrição , Transcrição Gênica , Transfecção , Células Tumorais Cultivadas
11.
Sci Rep ; 5: 12346, 2015 Jul 27.
Artigo em Inglês | MEDLINE | ID: mdl-26212901

RESUMO

A practical scheme for the demonstration of perfect one-sided device-independent quantum secret sharing is proposed. The scheme involves a three-mode optomechanical system in which a pair of independent cavity modes is driven by short laser pulses and interact with a movable mirror. We demonstrate that by tuning the laser frequency to the blue (anti-Stokes) sideband of the average frequency of the cavity modes, the modes become mutually coherent and then may collectively steer the mirror mode to a perfect Einstein-Podolsky-Rosen state. The scheme is shown to be experimentally feasible, it is robust against the frequency difference between the modes, mechanical thermal noise and damping, and coupling strengths of the cavity modes to the mirror.

12.
Neuroscience ; 304: 29-35, 2015 Sep 24.
Artigo em Inglês | MEDLINE | ID: mdl-26079110

RESUMO

Icariin is derived most commonly from the traditional Chinese herb Epimedium brevicornum Maxim. Our previous studies have shown that icariin protects neurons from neurotoxic and ischemic conditions. This study aims to investigate the effect of icariin on the expression of amyloid precursor protein (APP) and the level of amyloid-ß peptide (Aß), as well as neurogenesis in the brain of Tg2576 mice, an animal model of Alzheimer's disease (AD). Tg2576 mice and wild-type littermates (WT) were randomized into the following three groups: Tg2576, Tg2576+icariin, and WT groups. All 9-month-old mice were treated with icariin (60mg/kg/d) or distilled water for 3months. Following this, the spatial working memory of Tg2576+icariin mice, as examined in the Y-maze task, was found to improve. Furthermore, reduced levels of insoluble Aß1-40 (69%) and Aß1-42 (50%) after icariin treatment were determined in the brain by enzyme-linked immunosorbent assay (ELISA). Western blot analysis indicated the downregulation of APP expression after icariin treatment, and double staining showed an increased number of 5-bromo-2-deoxyuridine (BrdU)/Neuron-specific nuclear protein (NeuN) double-positive cells in the dentate gyrus region of the hippocampus in Tg2576+icariin mice compared with the Tg2576 mice. The current study demonstrated that icariin improved memory function, decreased the levels of Aß and APP in the brain, and enhanced neurogenesis in the hippocampus of Tg2576 mice. Collectively, these results suggest the potential therapeutic value of icariin in AD.


Assuntos
Doença de Alzheimer/tratamento farmacológico , Peptídeos beta-Amiloides/metabolismo , Encéfalo/efeitos dos fármacos , Flavonoides/farmacologia , Neurogênese/efeitos dos fármacos , Nootrópicos/farmacologia , Doença de Alzheimer/patologia , Doença de Alzheimer/fisiopatologia , Precursor de Proteína beta-Amiloide/genética , Precursor de Proteína beta-Amiloide/metabolismo , Animais , Encéfalo/patologia , Encéfalo/fisiopatologia , Modelos Animais de Doenças , Feminino , Humanos , Masculino , Aprendizagem em Labirinto/efeitos dos fármacos , Aprendizagem em Labirinto/fisiologia , Memória de Curto Prazo/efeitos dos fármacos , Memória de Curto Prazo/fisiologia , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Neurogênese/fisiologia , Neurônios/efeitos dos fármacos , Neurônios/patologia , Neurônios/fisiologia , Fármacos Neuroprotetores/farmacologia , Distribuição Aleatória , Memória Espacial/efeitos dos fármacos , Memória Espacial/fisiologia
13.
Pharmacogenetics ; 11(4): 357-68, 2001 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-11434514

RESUMO

The original novel UGT1 complex locus previously shown to encode six different UDP-glucuronosyltransferase (transferase) genes has been extended and demonstrated to specify a total of 13 isoforms. The genes are designated UGT1A1 through UGT1A13p with four pseudo ones. UGT1A2p and UGT1A11p through UGT1A13p have either nucleotide deletions or flawed TATA boxes and are therefore pseudo. In the 5' region of the locus, the 13 unique exons 1 are arranged in a tandem array with each having its own proximal TATA box element and, in turn, are linked to four common exons to allow for the independent transcriptional initiation to generate overlapping primary transcripts. Only the lead exon in the nine viable primary transcripts is predicted to undergo splicing to the four common exons generating mRNAs with identical 3' ends and transferase isozymes with an identical carboxyl terminus. The unique amino terminus specifies acceptor-substrate selection, and the common carboxyl terminus apparently specifies the interaction with the common donor substrate, UDP-glucuronic acid. In the extended region, the viable TATA boxes are either A(A)TgA(AA)T or AT14AT; in the original locus the element for UGT1A1 is A(TA)7A and TAATT/CAA(A) for all of the other genes. UGT1A1 specifies the critically important bilirubin transferase isoform. The relationships of the exons 1 to each other are as follows: UGT1A2p through UGT1A5 comprises a cluster A that is 87-92% identical, and UGT1A7 through UGT1A13p comprises a cluster B that is 67-91% identical. For the two not included in a cluster, UGT1A1 is more identical to cluster A at 60-63%, whereas UGT1A6 is identical by between 48% and 56% to all other unique exons. The locus was expanded from 95 kb to 218 kb. Extensive probing of clones beyond 218 kb with coding nucleotides for a highly conserved amino acid sequence present in all transferases was unable to detect other exons 1. The mRNAs are differentially expressed in hepatic and extrahepatic tissues. This locus is indeed novel, indicating the least usage of exon sequences in specifying different transferase isozymes that have an expansive substrate range.


Assuntos
Glucuronosiltransferase/genética , Família Multigênica , Sequência de Bases , Cromossomos Artificiais Bacterianos , Clonagem Molecular , Cosmídeos , Primers do DNA/genética , Éxons , Biblioteca Gênica , Humanos , Isoenzimas/genética , Fígado/enzimologia , Dados de Sequência Molecular , Pseudogenes , Capuzes de RNA/genética , Splicing de RNA , RNA Mensageiro/genética , Deleção de Sequência , Homologia de Sequência do Ácido Nucleico , TATA Box
14.
Neuropharmacology ; 43(4): 701-14, 2002 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-12367616

RESUMO

Withdrawal from the neurosteroid 3alpha,5alpha-allopregnanolone after chronic administration of progesterone increases anxiety in female rats and up-regulates the alpha4 subunit of the GABA(A) receptor (GABA(A)-R) in the hippocampus. We investigated if these phenomena would also occur in male rats. Progesterone withdrawal (PWD) induced higher alpha4 subunit expression in the hippocampus of both male and female rats, in association with increased anxiety (assessed in the elevated plus maze) comparable to effects previously reported. Because alpha4-containing GABA(A)-R are insensitive to the benzodiazepine (BDZ) lorazepam (LZM), and are positively modulated by flumazenil (FLU, a BDZ antagonist), we therefore tested the effects of these compounds following PWD. Using whole-cell patch clamp techniques, LZM-potentiation of GABA ((EC20))-gated current was markedly reduced in CA1 pyramidal cells of male rats undergoing PWD compared to controls, whereas FLU had no effect on GABA-gated current in control animals but increased it in PWD animals. Behaviorally, both male and female rats were significantly less sensitive to the anxiolytic effects of LZM. In contrast, FLU demonstrated significant anxiolytic effects following PWD. These data suggest that neurosteroid regulation of the alpha4 GABA(A)-R subunit may be a relevant mechanism underlying anxiety disorders, and that this phenomenon is not sex-specific.


Assuntos
Ansiedade/psicologia , Progesterona/efeitos adversos , Receptores de GABA-A/efeitos dos fármacos , Síndrome de Abstinência a Substâncias/metabolismo , Animais , Western Blotting , Feminino , Flumazenil/farmacologia , Moduladores GABAérgicos , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Lorazepam/farmacologia , Masculino , Potenciais da Membrana/fisiologia , Atividade Motora/efeitos dos fármacos , Técnicas de Patch-Clamp , Células Piramidais/efeitos dos fármacos , Ratos , Caracteres Sexuais
15.
Neuroreport ; 14(1): 43-6, 2003 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-12544828

RESUMO

Hippocampal alpha4betadelta GABA(A) receptors (GABA(A)-R) are increased following progesterone withdrawal (PWD) in a rodent model of premenstrual anxiety. This alpha4betadelta receptor isoform uniquely responds to the GABA agonist gaboxadol (THIP) with a maximum current greater than that gated by GABA, and is potentiated more by pentobarbital than are other GABA(A)-R. We therefore investigated the anxiolytic effects of these drugs using the elevated plus maze. Gaboxadol (1.25 mg/kg) was markedly more anxiolytic in animals undergoing PWD than in controls. Pentobarbital (10 mg/kg) also produced a greater anxiolytic effect during PWD. These results suggest that the pharmacological properties of alpha4betadelta GABA(A)-R following PWD are evident behaviorally. Alterations in the alpha4betadelta GABA(A)-R population may have implications for the etiology and treatment of premenstrual syndrome.


Assuntos
Ansiolíticos/farmacologia , Agonistas GABAérgicos/farmacologia , Hipocampo/metabolismo , Isoxazóis/farmacologia , Síndrome Pré-Menstrual/fisiopatologia , Progesterona/efeitos adversos , Isoformas de Proteínas/fisiologia , Receptores de GABA-A/fisiologia , Síndrome de Abstinência a Substâncias/metabolismo , Animais , Ansiolíticos/uso terapêutico , Implantes de Medicamento , Feminino , Agonistas GABAérgicos/uso terapêutico , Canais Iônicos/efeitos dos fármacos , Isoxazóis/uso terapêutico , Aprendizagem em Labirinto/efeitos dos fármacos , Pentobarbital/farmacologia , Pentobarbital/uso terapêutico , Síndrome Pré-Menstrual/tratamento farmacológico , Progesterona/administração & dosagem , Progesterona/farmacologia , Isoformas de Proteínas/efeitos dos fármacos , Subunidades Proteicas , Ratos , Receptores de GABA-A/efeitos dos fármacos
16.
Brain Res ; 910(1-2): 55-66, 2001 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-11489254

RESUMO

Previous work from this laboratory has demonstrated that withdrawal from the neuroactive steroid 3alpha,5alpha-THP (3alpha-hydroxy-5alpha-pregnan-20-one) after 3-week exposure to its parent compound, progesterone (P), increases anxiety and produces benzodiazepine (BDZ) insensitivity in female rats. These events were linked to upregulation of the alpha4 subunit of the GABA(A) receptor (GABAR) in the hippocampus [Brain Res. 507 (1998) 91; Nature 392 (1998) 926; J. Neurosci. 18 (1998) 5275]. The present study investigates the role of shorter term hormone treatment on alpha4 subunit levels as well as relevant behavioral and pharmacological end-points related to GABAR function. After 2-3 days of P exposure, two- to threefold increases in alpha4 protein levels were observed, which declined to control values after 5-6 days of hormone exposure. This effect was due to the GABA-modulatory metabolite of P, 3alpha,5alpha-THP. alpha4 upregulation was inversely correlated with BDZ potentiation of GABA-gated current, assessed using whole cell patch clamp techniques on acutely isolated hippocampal pyramidal cells. A near total BDZ insensitivity was observed by 2-3 days of hormone exposure in association with the maximal increase in alpha4 levels. Up-regulation of the alpha4 GABAR subunit was also reflected by an increase in anxiety in the elevated plus maze. A significant decrease in open arm entries was observed after 72-h exposure to P, an effect which recovered by 6 days of P treatment. As demonstrated in vitro, alpha4 upregulation also resulted in a relative insensitivity to the anxiolytic actions of BDZ. These results suggest that short-term exposure to 3alpha,5alpha-THP produces changes in GABAR subunit composition similar to those that occur after chronic exposure and withdrawal from the steroid.


Assuntos
Ansiedade/metabolismo , Hipocampo/efeitos dos fármacos , Células Piramidais/efeitos dos fármacos , Receptores de GABA-A/efeitos dos fármacos , Esteroides/farmacologia , Síndrome de Abstinência a Substâncias/metabolismo , Animais , Ansiedade/induzido quimicamente , Ansiedade/fisiopatologia , Comportamento Animal/efeitos dos fármacos , Comportamento Animal/fisiologia , Membrana Celular/efeitos dos fármacos , Membrana Celular/metabolismo , Modelos Animais de Doenças , Esquema de Medicação , Feminino , Hipocampo/metabolismo , Imuno-Histoquímica , Aprendizagem em Labirinto/efeitos dos fármacos , Aprendizagem em Labirinto/fisiologia , Técnicas de Patch-Clamp , Pregnanodionas/metabolismo , Síndrome Pré-Menstrual/metabolismo , Síndrome Pré-Menstrual/fisiopatologia , Progesterona/metabolismo , Progesterona/farmacologia , Células Piramidais/metabolismo , RNA Mensageiro/efeitos dos fármacos , RNA Mensageiro/metabolismo , Ratos , Ratos Long-Evans , Receptores de GABA-A/genética , Receptores de GABA-A/metabolismo , Esteroides/metabolismo , Frações Subcelulares/efeitos dos fármacos , Frações Subcelulares/metabolismo , Síndrome de Abstinência a Substâncias/etiologia , Síndrome de Abstinência a Substâncias/fisiopatologia , Fatores de Tempo
17.
Toxicon ; 29(12): 1489-500, 1991.
Artigo em Inglês | MEDLINE | ID: mdl-1666202

RESUMO

Snake venom cardiotoxin (CTX) fractions induce contractures of skeletal muscle and hemolysis of red blood cells. The fractions also contain trace amounts of venom-derived phospholipase A2 (PLA2) contamination and activate tissue phospholipase C (PLC) activity. The present study examines the mechanisms of action of a CTX fraction from Naja naja kaouthia venom in skeletal muscle. Sphingosine competitively antagonized CTX-induced red blood cell hemolysis, but not skeletal muscle contractures. CTX rapidly lowered the threshold for Ca(2+)-induced Ca2+ release in heavy sarcoplasmic reticulum fractions, as monitored with arsenazo III. There was also a slower time-dependent reduction of Na+ currents, as assessed by whole cell patch-clamp techniques. The CTX fractions elevated levels of free fatty acids and diacylglycerol for 2 hr in primary cultures of human skeletal muscle by a combined action of venom-derived PLA2 contamination in the fraction and activation of endogenous PLC activity. The activation of tissue PLC activity could be readily distinguished from the contribution of the venom PLA2 by p-bromophenacyl bromide treatment of CTX fractions. The mechanism of action involved in contractures of skeletal muscle appears to be related to the immediate and specific effect of CTX (Ca2+ release by the sarcoplasmic reticulum), while the mechanisms involved in hemolysis of red blood cells and decreased Na+ currents in skeletal muscle most likely relate to long-term effects on lipid metabolism.


Assuntos
Cálcio/metabolismo , Proteínas Cardiotóxicas de Elapídeos/farmacologia , Músculos/efeitos dos fármacos , Fosfolipases A/toxicidade , Canais de Sódio/efeitos dos fármacos , Fosfolipases Tipo C/toxicidade , Animais , Cálcio/farmacologia , Células Cultivadas , Proteínas Cardiotóxicas de Elapídeos/análise , Eritrócitos/efeitos dos fármacos , Hemólise/efeitos dos fármacos , Humanos , Técnicas In Vitro , Metabolismo dos Lipídeos , Camundongos , Contração Muscular/efeitos dos fármacos , Fosfolipases A/análise , Fosfolipases A2 , Polimixina B/farmacologia , Retículo Sarcoplasmático/efeitos dos fármacos , Retículo Sarcoplasmático/metabolismo , Esfingosina/farmacologia , Fosfolipases Tipo C/análise
18.
Toxicon ; 27(12): 1339-49, 1989.
Artigo em Inglês | MEDLINE | ID: mdl-2629176

RESUMO

The action of a 16,300 mol. wt phospholipase A2 with cardiotoxin-like properties from Bungarus fasciatus venom on membrane electrical properties of two human cell types was examined in vitro by using tight-seal whole-cell recording methods. Epithelial cells exhibited a voltage- and Ca2(+)-activated K+ current; the sensitivity for voltage activation of the K+ current was enhanced by increasing free Ca2+ in the recording pipette from 10(-8) M to 2 x 10(-6) M. In contrast, peripheral blood lymphocytes possessed voltage-activated K+ currents that were inhibited by increasing intracellular Ca2+. Exposure of either preparation to B. fasciatus toxin (0.2-5 x 10(-6) M) for up to 30 min in the bath did not alter membrane leakage current, as judged by the maintenance of low pre-treatment values over the range of -140 mV to -40 mV. However, the sensitivity for voltage activation of the K+ current was enhanced in the epithelial cells even at the lowest concentrations tested. In contrast to the results with epithelial cells, toxin exposure inhibited the activation of voltage-activated K- currents in human lymphocytes, suggesting a specific increase in intracellular Ca2- levels in both cell types. The fluorescent probe indo-1/AM was used to monitor cytoplasmic Ca2+ levels. Exposure of either lymphocytes or epithelial cells to toxin (10(-6) M) resulted in a transient increase in Ca2+. However, while the Ca2+ response to toxin was transient, K-channel modulation by the toxin appeared to be irreversible over the experimental time course. The longer-lasting modulation of Ca2(+)-regulated K+ channels may reflect an irreversible action of the B. fasciatus phospholipase A2 on a Ca2+-dependent regulatory process.


Assuntos
Cálcio/fisiologia , Venenos Elapídicos/farmacologia , Fosfolipases A/farmacologia , Fosfolipases/farmacologia , Potássio/fisiologia , Células Cultivadas , Proteínas Cardiotóxicas de Elapídeos/farmacologia , Células Epiteliais , Epitélio/efeitos dos fármacos , Humanos , Linfócitos/efeitos dos fármacos , Potenciais da Membrana/efeitos dos fármacos , Fosfolipases A2
19.
Toxicon ; 34(11-12): 1301-11, 1996.
Artigo em Inglês | MEDLINE | ID: mdl-9027986

RESUMO

Myonecrosis induced in vivo by cardiotoxin, melittin, and Asp49 and Lys49 phospholipase A2 (PLA2) myotoxins involves rapid lysis of the sarcolemma, myofibril clumping, and hypercontraction of sarcomeres. In contrast, skeletal muscle necrosis induced by crotamine and myotoxin a is much slower, consisting of mitochondrial and sarcoplasmic reticulum swelling, myofibril degeneration, and lack of sarcolemma or transverse tubule damage. The mechanisms contributing to the myonecrosis induced by these peptides were evaluated. Two cardiotoxins and two Lys49 PLA2 myotoxins lysed primary cultures of human skeletal muscle within 24 hr at a concentration of 0.25 microM, while melittin, crotamine, and myotoxin a, and an Asp49 PLA2 myotoxin were non-cytolytic at concentrations up to 5.0 microM, suggesting that cytolysis is not a good measure of myotoxicity. Crotamine and the Lys49 PLA2 myotoxin altered Ca2+ ion flux in human heavy sarcoplasmic reticulum by opening the ryanocine receptor. Whole-cell patch-clamp studies demonstrated that administrating crotamine intracellularly increased Na+ currents. Free fatty acids, liberated by activation of tissue phospholipase C or by the PLA2 activity of the myotoxins, were monitored for crotamine, myotoxin a and a Lys49 PLA2 myotoxin in cell cultures in which the lipids had been radiolabeled. Only the Lys49 myotoxin produced significant amounts of fatty acid in cell cultures, supporting a potential role for fatty acid production only in the mechanism of sarcolemma-destroying myotoxins. These findings, coupled with those in the literature, support a hypothesis in which the myotoxins and/or products of lipase activity (e.g. fatty acids) are acting at a site existing on both the Na+ channel and a protein involved in Ca2+ release and probably serving a modulatory function for ion regulation. Based on the similarities in mechanisms between the toxins and fatty acids, the most likely site would be a fatty acid binding site on the protein (either similar to that on fatty acid binding proteins, or an acylated cysteine residue) or in the membrane.


Assuntos
Proteínas Cardiotóxicas de Elapídeos/toxicidade , Meliteno/toxicidade , Neurotoxinas/toxicidade , Venenos de Abelha/toxicidade , Morte Celular/efeitos dos fármacos , Fracionamento Celular , Células Cultivadas , Venenos Elapídicos/toxicidade , Ativação Enzimática , Humanos , Lipase/metabolismo , Fosfolipases A/metabolismo , Fosfolipases A2 , Retículo Sarcoplasmático/efeitos dos fármacos , Canais de Sódio/efeitos dos fármacos , Relação Estrutura-Atividade
20.
Toxicol Lett ; 52(3): 339-45, 1990 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-2389262

RESUMO

The effects of cisplatin on electrical and mechanotransducer properties of the crayfish stretch receptor neuron was studied using a microelectrode voltage clamp technique. In the stretch receptor neuron, negligible changes in membrane capacitance, leak conductance, resting membrane potential, potential-dependent currents or mechanoreceptor current were seen either on acute cisplatin treatment or after long-lasting treatment for up to 2 weeks. The inhibitory GABA-sensitive synapse on the neuron was not affected by cisplatin. The cisplatin cytotoxicity on sensory neurons such as outer hair cells of the organ of Corti cannot be explained by direct effects on ionic channels of these cells including stretch-activated channels.


Assuntos
Cisplatino/toxicidade , Mecanorreceptores/efeitos dos fármacos , Neurônios Aferentes/efeitos dos fármacos , Animais , Astacoidea , Estimulação Elétrica , Eletrofisiologia , Antagonistas GABAérgicos , Potenciais da Membrana/efeitos dos fármacos , Microeletrodos , Movimento/efeitos dos fármacos
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