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1.
Science ; 381(6655): 306-312, 2023 07 21.
Artigo em Inglês | MEDLINE | ID: mdl-37471542

RESUMO

Implantable neuroelectronic interfaces have enabled advances in both fundamental research and treatment of neurological diseases but traditional intracranial depth electrodes require invasive surgery to place and can disrupt neural networks during implantation. We developed an ultrasmall and flexible endovascular neural probe that can be implanted into sub-100-micrometer-scale blood vessels in the brains of rodents without damaging the brain or vasculature. In vivo electrophysiology recording of local field potentials and single-unit spikes have been selectively achieved in the cortex and olfactory bulb. Histology analysis of the tissue interface showed minimal immune response and long-term stability. This platform technology can be readily extended as both research tools and medical devices for the detection and intervention of neurological diseases.


Assuntos
Encéfalo , Eletrodos Implantados , Microeletrodos , Encéfalo/fisiologia , Córtex Cerebral/fisiologia , Animais , Procedimentos Endovasculares
2.
Aging Dis ; 14(3): 892-903, 2023 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-37191419

RESUMO

We previously demonstrated that inhibition of miR-200c was protective against stroke in young adult male mice by augmenting sirtuin-1 (Sirt1). In the present study we assessed the role of miR-200c on injury, Sirt1, and bioenergetic and neuroinflammatory markers in aged male and female mice after experimental stroke. Mice were subjected to 1hr of transient middle cerebral artery occlusion (MCAO) and assessed for post-injury expression of miR-200c, Sirt1 protein and mRNA, N6-methyladenosine (m6A) methylated Sirt1 mRNA, ATP, cytochrome C oxidase activity, tumor necrosis factor alpha (TNFα), interleukin-6 (IL-6), infarct volume and motor function. MCAO induced a decrease in Sirt1 expression at 1d post-injury only in males. No differences in SIRT1 mRNA were observed between the sexes. Females had greater baseline miR-200c expression and a greater increase in miR-200c in response to stroke, while pre-MCAO levels of m6A SIRT1 was greater in females. Males had lower post-MCAO ATP levels and cytochrome C oxidase activity, and higher TNFα and IL-6. Post-injury intravenous treatment with anti-miR-200c reduced miR-200c expression in both sexes. In males, anti-miR-200c increased Sirt1 protein expression, reduced infarct volume, and improved neurological score. Conversely in females anti-miR-200c had no effect on Sirt1 levels and provided no protection against injury from MCAO. These results provide the first evidence of sexual dimorphism in the role of a microRNA in aged mice after experimental stroke and suggest sex-differences in epigenetic modulation of the transcriptome and downstream effects on miR biological activity may play a role in sexually dimorphic outcomes after stroke in aged brains.

3.
bioRxiv ; 2023 Mar 23.
Artigo em Inglês | MEDLINE | ID: mdl-36993229

RESUMO

Implantable neuroelectronic interfaces have enabled significant advances in both fundamental research and treatment of neurological diseases, yet traditional intracranial depth electrodes require invasive surgery to place and can disrupt the neural networks during implantation. To address these limitations, we have developed an ultra-small and flexible endovascular neural probe that can be implanted into small 100-micron scale blood vessels in the brains of rodents without damaging the brain or vasculature. The structure and mechanical properties of the flexible probes were designed to meet the key constraints for implantation into tortuous blood vessels inaccessible with existing techniques. In vivo electrophysiology recording of local field potentials and single-unit spikes has been selectively achieved in the cortex and the olfactory bulb. Histology analysis of the tissue interface showed minimal immune response and long-term stability. This platform technology can be readily extended as both research tools and medical devices for the detection and intervention of neurological diseases.

4.
Br J Anaesth ; 130(3): 248-250, 2023 03.
Artigo em Inglês | MEDLINE | ID: mdl-36682935

RESUMO

Perioperative organ injury is a frequent and major complication for the ∼240 million people undergoing surgery worldwide annually. Ischaemic preconditioning is a powerful technique that reduces organ injury in experimental models of heart, lung, gut, brain, and kidney ischaemia-reperfusion injury. However, ischaemic preconditioning has been a challenge to translate into clinical practice. We describe how utilising isolated pre-conditioned exosomes (secreted vesicles containing many cell-survival mediators), some of the translational hurdles of ischaemic preconditioning can be overcome. Delivery of exosomes in the perioperative period could become a promising new therapeutic strategy to prevent perioperative organ injury.


Assuntos
Exossomos , Precondicionamento Isquêmico Miocárdico , Precondicionamento Isquêmico , Traumatismo por Reperfusão , Humanos , Traumatismo por Reperfusão/prevenção & controle , Precondicionamento Isquêmico/métodos , Rim , Precondicionamento Isquêmico Miocárdico/métodos
5.
Front Ophthalmol (Lausanne) ; 3: 1168650, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-38983004

RESUMO

Epiretinal membranes (ERMs) are the result of fibro-cellular proliferation that cause distortion and impairment of central vision. We hypothesized that select microRNAs (miRs) regulate retinal fibro-proliferation and ERM formation. Following IRB approval, a pilot study was performed in patients presenting for retina surgery with and without clinical ERMs. Total RNA was isolated from ERM tissue and controls from non-ERM vitreous and subjected to miR profiling via microarray analysis. MiR-494 was identified as the only miR selectively expressed at significantly greater levels, and in silico analysis identified p27 as a putative fibroproliferative gene target of miR-494. In vitro testing of miR-494 and p27 in fibrotic transformation was assessed in spontaneously immortalized human retinal pigment epithelial (RPE) and human Müller cell lines, stimulated to transform into a fibroproliferative state via transforming growth factor beta (TGFß). Fibroproliferative transformation was characterized by de novo cellular expression of alpha smooth muscle actin (αSMA). In both RPE and Müller cells, both TGFß and miR-494 mimic decreased p27 expression. In parallel experiments, transfection with p27 siRNA augmented TGFß-induced αSMA expression, while only in RPE cells did co-transfection with miR-494 inhibitor decrease αSMA levels. These results demonstrate that miR-494 augments fibrotic transformation in both Müller cells and RPEs, however only in RPEs does miR-494 mediate fibrotic transformation via p27. As p27 is known to regulate cellular proliferation and differentiation, future studies should extend clinical testing of miR-494 and/or p27 as a potential novel non-surgical therapy for ERMs, as well as identify relevant miR-494 targets in Müller cells.

6.
ACS Chem Neurosci ; 13(7): 1014-1029, 2022 04 06.
Artigo em Inglês | MEDLINE | ID: mdl-35302736

RESUMO

Intracerebral hemorrhage (ICH) is devastating among stroke types with high mortality. To date, not a single therapeutic intervention has been successful. Cofilin plays a critical role in inflammation and cell death. In the current study, we embarked on designing and synthesizing a first-in-class small-molecule inhibitor of cofilin to target secondary complications of ICH, mainly neuroinflammation. A series of compounds were synthesized, and two lead compounds SZ-3 and SK-1-32 were selected for further studies. Neuronal and microglial viabilities were assessed by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay using neuroblastoma (SHSY-5Y) and human microglial (HMC-3) cell lines, respectively. Lipopolysaccharide (LPS)-induced inflammation in HMC-3 cells was used for neurotoxicity assay. Other assays include nitric oxide (NO) by Griess reagent, cofilin inhibition by F-actin depolymerization, migration by scratch wound assay, tumor necrosis factor (TNF-α) by enzyme-linked immunosorbent assay (ELISA), protease-activated receptor-1 (PAR-1) by immunocytochemistry and Western blotting (WB), and protein expression levels of several proteins by WB. SK-1-32 increased neuronal/microglial survival, reduced NO, and prevented neurotoxicity. However, SZ-3 showed no effect on neuronal/microglial survival but prevented microglia from LPS-induced inflammation by decreasing NO and preventing neurotoxicity. Therefore, we selected SZ-3 for further molecular studies, as it showed potent anti-inflammatory activities. SZ-3 decreased cofilin severing activity, and its treatment of LPS-activated HMC-3 cells attenuated microglial activation and suppressed migration and proliferation. HMC-3 cells subjected to thrombin, as an in vitro model for hemorrhagic stroke, and treated with SZ-3 after 3 h showed significantly decreased NO and TNF-α, significantly increased protein expression of phosphocofilin, and decreased PAR-1. In addition, SZ-3-treated SHSY-5Y showed a significant increase in cell viability by significantly reducing nuclear factor-κ B (NF-κB), caspase-3, and high-temperature requirement (HtrA2). Together, our results support the novel idea of targeting cofilin to counter neuroinflammation during secondary injury following ICH.


Assuntos
Fatores de Despolimerização de Actina , Lesões Encefálicas , Fatores de Despolimerização de Actina/metabolismo , Fatores de Despolimerização de Actina/farmacologia , Lesões Encefálicas/metabolismo , Humanos , Inflamação/metabolismo , Lipopolissacarídeos/toxicidade , Microglia , NF-kappa B/metabolismo , Doenças Neuroinflamatórias
7.
eNeuro ; 6(4)2019.
Artigo em Inglês | MEDLINE | ID: mdl-31427401

RESUMO

The cellular and molecular mechanisms regulating postinjury neurogenesis in the adult hippocampus remain undefined. We have previously demonstrated that preinjury treatment with anti-microRNA (miR)-181a preserved neurons and prevented astrocyte dysfunction in the hippocampal cornu ammonis-1 (CA1) following transient forebrain ischemia. In the present study, we assessed postinjury treatment with anti-miR-181a on recovery of CA1 neurons following transient forebrain ischemia in rats. Stereotactic CA1 injection of miR-181a antagomir at either 2 h or 7 d postinjury resulted in improved restoration of CA1 measured at 28 d postinjury. Treatment with antagomir was associated with overexpression of the mir-181a target cell adhesion-associated, oncogene-related protein and enhanced expression of the neuroprogenitor cell marker doublecortin (DCX) in the CA1. Assessment of GFAP+ cell fate by Cre/Lox-mediated deletion demonstrated that some GFAP+ cells in CA1 exhibited de novo DCX expression in response to injury. In vitro experiments using primary neuronal stem cells confirmed that miR-181a inhibition augmented the expression of DCX and directed cellular differentiation toward a neuronal fate. These results suggest that miR-181a inhibition plays a central role in the restoration of CA1 neurons via augmentation of early latent neurogenic gene activation in neural progenitor cells, including some reactive astrocytes. Therapeutic interventions targeting this restorative process may represent a novel postinjury approach to improve clinical outcomes in survivors of forebrain ischemia.


Assuntos
Antagomirs/administração & dosagem , Isquemia Encefálica/metabolismo , Região CA1 Hipocampal/metabolismo , MicroRNAs/antagonistas & inibidores , Neurônios/metabolismo , Animais , Astrócitos/efeitos dos fármacos , Astrócitos/metabolismo , Região CA1 Hipocampal/efeitos dos fármacos , Proteína Duplacortina , Masculino , Células-Tronco Neurais/efeitos dos fármacos , Células-Tronco Neurais/metabolismo , Neurogênese/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Prosencéfalo/efeitos dos fármacos , Prosencéfalo/fisiopatologia , Ratos Sprague-Dawley
8.
Mol Cancer ; 17(1): 32, 2018 02 15.
Artigo em Inglês | MEDLINE | ID: mdl-29448937

RESUMO

Intratumor heterogeneity of tumor clones and an immunosuppressive microenvironment in cancer ecosystems contribute to inherent difficulties for tumor treatment. Recently, chimeric antigen receptor (CAR) T-cell therapy has been successfully applied in the treatment of B-cell malignancies, underscoring its great potential in antitumor therapy. However, functional challenges of CAR-T cell therapy, especially in solid tumors, remain. Here, we describe cancer-immunity phenotypes from a clonal-stromal-immune perspective and elucidate mechanisms of T-cell exhaustion that contribute to tumor immune evasion. Then we assess the functional challenges of CAR-T cell therapy, including cell trafficking and infiltration, targeted-recognition and killing of tumor cells, T-cell proliferation and persistence, immunosuppressive microenvironment and self-control regulation. Finally, we delineate tumor precision informatics and advancements in engineered CAR-T cells to counteract inherent challenges of the CAR-T cell therapy, either alone or in combination with traditional therapeutics, and highlight the therapeutic potential of this approach in future tumor precision treatment.


Assuntos
Engenharia Genética , Imunoterapia Adotiva , Neoplasias/imunologia , Neoplasias/terapia , Receptores de Antígenos Quiméricos/metabolismo , Linfócitos T/imunologia , Linfócitos T/metabolismo , Animais , Edição de Genes , Engenharia Genética/métodos , Humanos , Imunoterapia Adotiva/métodos , Neoplasias/genética , Neoplasias/metabolismo , Fenótipo , Medicina de Precisão , Receptores de Antígenos Quiméricos/genética , Subpopulações de Linfócitos T/imunologia , Subpopulações de Linfócitos T/metabolismo , Evasão Tumoral/genética , Evasão Tumoral/imunologia , Microambiente Tumoral
9.
A A Case Rep ; 9(12): 337-338, 2017 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-28767475

RESUMO

We report the first description of oculocardiac reflex elicited with injection of local anesthetic in an empty orbit, and highlight clinical indicators for patients that may be at risk for an exaggerated oculocardiac reflex. We describe a patient with prior head and eye trauma treated for anophthalmic socket reconstruction at an outpatient eye surgery center. Injection of local anesthetic into the empty orbit induced an extended sinus arrest. This exaggerated response was avoided in a subsequent surgery by pretreatment with high-dose anticholinergics.


Assuntos
Anestésicos Locais/efeitos adversos , Órbita/efeitos dos fármacos , Reflexo Oculocardíaco/efeitos dos fármacos , Adulto , Humanos , Masculino
10.
Mol Cell Neurosci ; 82: 118-125, 2017 07.
Artigo em Inglês | MEDLINE | ID: mdl-28522364

RESUMO

Whether the effect of miR-181a is sexually dimorphic in stroke is unknown. Prior work showed protection of male mice with miR-181a inhibition. Estrogen receptor-α (ERα) is an identified target of miR181 in endometrium. Therefore we investigated the separate and joint effects of miR-181a inhibition and 17ß-estradiol (E2) replacement after ovariectomy. Adult female mice were ovariectomized and implanted with an E2- or vehicle-containing capsule for 14d prior to 1h middle cerebral artery occlusion (MCAO). Each group received either miR-181a antagomir or mismatch control by intracerebroventricular injection 24h before MCAO. After MCAO neurologic deficit and infarct volume were assessed. Primary male and female astrocyte cultures were subjected to glucose deprivation with miR-181a inhibitor or transfection control, and E2 or vehicle control, with/without ESRα knockdown with small interfering RNA. Cell death was assessed by propidium iodide staining, and lactate dehydrogenase assay. A miR-181a/ERα target site blocker (TSB), with/without miR-181a mimic, was used to confirm targeting of ERα by miR-181a in astrocytes. Individually, miR-181a inhibition or E2 decreased infarct volume and improved neurologic score in female mice, and protected male and female astrocyte cultures. Combined miR-181a inhibition plus E2 afforded greater protection of female mice and female astrocyte cultures, but not in male astrocyte cultures. MiR-181a inhibition only increased ERα levels in vivo and in female cultures, while ERα knockdown with siRNA increased cell death in both sexes. Treatment with ERα TSB was strongly protective in both sexes. In conclusion, the results of the present study suggest miR-181a inhibition enhances E2-mediated stroke protection in females in part by augmenting ERα production, a mechanism detected in female mice and female astrocytes. Sex differences were observed with combined miR-181a inhibition/E2 treatment, and miR-181a targeting of ERα.


Assuntos
Astrócitos/metabolismo , Isquemia Encefálica/genética , Receptor alfa de Estrogênio/genética , Ataque Isquêmico Transitório/metabolismo , MicroRNAs/genética , Animais , Astrócitos/efeitos dos fármacos , Isquemia Encefálica/metabolismo , Modelos Animais de Doenças , Feminino , Ataque Isquêmico Transitório/genética , Masculino , Camundongos Endogâmicos C57BL , Neurônios/metabolismo , Fármacos Neuroprotetores/farmacologia , Traumatismo por Reperfusão/genética , Traumatismo por Reperfusão/metabolismo , Fatores Sexuais
11.
J Immunol Res ; 2017: 3597613, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28299344

RESUMO

Glioblastoma multiforme (GBM) is the most common primary malignant brain tumor in adults. Patients with GBM have poor outcomes, even with the current gold-standard first-line treatment: maximal safe resection combined with radiotherapy and temozolomide chemotherapy. Accumulating evidence suggests that advances in antigen-specific cancer vaccines and immune checkpoint blockade in other advanced tumors may provide an appealing promise for immunotherapy in glioma. The future of therapy for GBM will likely incorporate a combinatorial, personalized approach, including current conventional treatments, active immunotherapeutics, plus agents targeting immunosuppressive checkpoints.


Assuntos
Neoplasias Encefálicas/terapia , Vacinas Anticâncer/uso terapêutico , Glioblastoma/imunologia , Glioblastoma/terapia , Imunoterapia , Adulto , Antígeno B7-H1/imunologia , Neoplasias Encefálicas/imunologia , Neoplasias Encefálicas/fisiopatologia , Antígeno CTLA-4/imunologia , Ensaios Clínicos como Assunto , Glioblastoma/fisiopatologia , Humanos , Imunoterapia/métodos , Medicina de Precisão
12.
J Immunol Res ; 2017: 5210459, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28116322

RESUMO

A significant proportion of hematological malignancies remain limited in treatment options. Immune system modulation serves as a promising therapeutic approach to eliminate malignant cells. Cytotoxic T lymphocytes (CTLs) play a central role in antitumor immunity; unfortunately, nonspecific approaches for targeted recognition of tumor cells by CTLs to mediate tumor immune evasion in hematological malignancies imply multiple mechanisms, which may or may not be clinically relevant. Recently, genetically modified T-cell-based adoptive immunotherapy approaches, including chimeric antigen receptor (CAR) T-cell therapy and engineered T-cell receptor (TCR) T-cell therapy, promise to overcome immune evasion by redirecting the specificity of CTLs to tumor cells. In clinic trials, CAR-T-cell- and TCR-T-cell-based adoptive immunotherapy have produced encouraging clinical outcomes, thereby demonstrating their therapeutic potential in mitigating tumor development. The purpose of the present review is to (1) provide a detailed overview of the multiple mechanisms for immune evasion related with T-cell-based therapies; (2) provide a current summary of the applications of CAR-T-cell- as well as neoantigen-specific TCR-T-cell-based adoptive immunotherapy and routes taken to overcome immune evasion; and (3) evaluate alternative approaches targeting immune evasion via optimization of CAR-T and TCR-T-cell immunotherapies.


Assuntos
Neoplasias Hematológicas/terapia , Imunoterapia Adotiva/métodos , Receptores de Antígenos de Linfócitos T/genética , Linfócitos T Citotóxicos/transplante , Animais , Antígenos de Neoplasias/imunologia , Terapia Genética , Neoplasias Hematológicas/imunologia , Humanos , Proteínas Recombinantes de Fusão/genética , Linfócitos T Citotóxicos/imunologia , Evasão Tumoral
13.
Anal Cell Pathol (Amst) ; 2016: 9369240, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27313981

RESUMO

Cellular heterogeneity is a fundamental characteristic of many cancers. A lack of cellular homogeneity contributes to difficulty in designing targeted oncological therapies. Therefore, the development of novel methods to determine and characterize oncologic cellular heterogeneity is a critical next step in the development of novel cancer therapies. Single-cell sequencing (SCS) technology has been recently employed for analyzing the genetic polymorphisms of individual cells at the genome-wide level. SCS requires (1) precise isolation of the single cell of interest; (2) isolation and amplification of genetic material; and (3) descriptive analysis of genomic, transcriptomic, and epigenomic data. In addition to targeted analysis of single cells isolated from tumor biopsies, SCS technology may be applied to circulating tumor cells, which may aid in predicting tumor progression and metastasis. In this paper, we provide an overview of SCS technology and review the current literature on the potential application of SCS to clinical oncology and research.


Assuntos
Pesquisa Biomédica/métodos , Oncologia/métodos , Neoplasias/terapia , Análise de Sequência de DNA/métodos , Análise de Célula Única/métodos , DNA de Neoplasias/química , DNA de Neoplasias/genética , Progressão da Doença , Humanos , Metástase Neoplásica , Neoplasias/genética , Neoplasias/patologia , Reação em Cadeia da Polimerase
15.
Biomed Res Int ; 2015: 643409, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26221602

RESUMO

Anti-NMDAR encephalitis is a recently identified autoimmune disease, described by an immune-mediated loss of NMDA glutamate receptors, resulting in progressive mental deterioration. To date, literature on anti-NMDAR encephalitis has been largely clinically oriented, including descriptions of the clinical presentation and course, diagnostic methods, and potential clinical treatments. However, the underlying molecular mechanisms contributing to the complex immunological cellular transformation that is associated with the progression of anti-NMDAR encephalitis remain to be adequately explored. This review will provide a summary of the current literature on anti-NMDAR encephalitis, including the immunologic molecular mechanisms contributing to disease progression. In particular this review will focus on the effect of anti-NMDAR on GluN2-NMDAR expression and the molecular transformation of B and T leukocytes in the loss of self-tolerance. Further research on the immunologic mechanisms contributing to anti-NMDAR encephalitis may provide an avenue for future novel diagnostic approaches, such as immunologic surveillance, as well as new therapeutic strategies for this recently identified autoimmune disease.


Assuntos
Encefalite Antirreceptor de N-Metil-D-Aspartato/genética , Animais , Encefalite Antirreceptor de N-Metil-D-Aspartato/imunologia , Encefalite Antirreceptor de N-Metil-D-Aspartato/terapia , Autoimunidade , Humanos , Tolerância Imunológica , Imunoterapia , Receptores de N-Metil-D-Aspartato/química , Resultado do Tratamento
16.
Hawaii Med J ; 70(5): 99-101, 2011 May.
Artigo em Inglês | MEDLINE | ID: mdl-21857740

RESUMO

Idiopathic granulomatous mastitis (IGM) is a rare inflammatory condition of the breast. The etiology and treatments options of IGM remain controversial. Previous case reports have suggested that Corynebacterium sp., a gram-positive bacillus endogenous to the skin, may be associated with IGM. In the present report, we describe the first case of IGM with a positive culture for Corynebacterium sp. reported in the United States.


Assuntos
Infecções por Corynebacterium/diagnóstico , Corynebacterium/isolamento & purificação , Mastite Granulomatosa/patologia , Mastite Granulomatosa/terapia , Adulto , Antibacterianos/uso terapêutico , Biópsia por Agulha , Infecções por Corynebacterium/terapia , Drenagem/métodos , Feminino , Seguimentos , Mastite Granulomatosa/microbiologia , Humanos , Imuno-Histoquímica , Infusões Intravenosas , Índice de Gravidade de Doença , Resultado do Tratamento
17.
J Physiol ; 562(Pt 2): 527-34, 2005 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-15550463

RESUMO

The purpose of this investigation was to utilize 2,3-butanedione monoxime (BDM; an inhibitor of contractile activation) to dissociate cytosolic [Ca(2+)] ([Ca(2+)](c)) from the putative respiratory regulators that arise from muscle contraction-induced ATP utilization in order to determine the relative contribution of [Ca(2+)](c) on intracellular P(O(2)) (P(iO(2))) kinetics during the transition from rest to contractions in single skeletal myocytes isolated from Xenopus laevis lumbrical muscle. Myocytes were subjected to electrically induced isometric tetanic contractions (0.25 Hz; 2-min bouts) while peak tension and either [Ca(2+)](c) (n= 7; ratiometric fluorescence microscopy) or P(iO(2)) (n= 7; phosphorescence microscopy) was measured continuously. Cells were studied under both control and 3 mm BDM conditions in randomized order. Initial (control, 100 +/- 0%; BDM, 72.6 +/- 4.6%), midpoint (control, 86.7 +/- 1.8%; BDM, 61.6 +/- 4.1%) and end (control, 85.0 +/- 2.8%; BDM, 57.5 +/- 5.0%) peak tensions (normalized to initial control values) were significantly reduced (P < 0.05) with BDM compared with control (n= 14). Despite the reduced peak tension, peak [Ca(2+)](c) was not altered (P > 0.05) between control and BDM trials. Thus, the peak tension-to-peak [Ca(2+)](c) ratio was reduced with BDM compared with control. The absolute fall in P(iO(2)) with contractions, which is proportional to the rise in , was significantly reduced with BDM (13.2 +/- 1.3 mmHg) compared with control (22.0 +/- 2.0 mmHg). However, P(iO(2)) onset kinetics (i.e. mean response time (MRT)) was not altered between BDM (66.8 +/- 8.0 s) and control (64.9 +/- 6.3 s) trials. Therefore, the initial rate of change (defined as the fall in P(iO(2))/MRT) was significantly slower in BDM fibres compared with control. These data demonstrate in these isolated single skeletal muscle fibres that unchanged peak [Ca(2+)](c) in the face of reduced metabolic feedback from the contractile sites evoked with BDM did not alter P(iO(2)) onset kinetics in isolated single frog myocytes, suggesting that metabolic signals arising from the contractile sites play a more substantial role than [Ca(2+)](c) in the signalling pathway to oxidative phosphorylation during the transition from rest to repeated tetanic contractions.


Assuntos
Cálcio/metabolismo , Citosol/fisiologia , Diacetil/análogos & derivados , Metabolismo/fisiologia , Fibras Musculares Esqueléticas/metabolismo , Consumo de Oxigênio/fisiologia , Difosfato de Adenosina/metabolismo , Difosfato de Adenosina/fisiologia , Trifosfato de Adenosina/metabolismo , Trifosfato de Adenosina/fisiologia , Animais , Diacetil/farmacologia , Estimulação Elétrica , Feminino , Técnicas In Vitro , Cinética , Fibras Musculares Esqueléticas/fisiologia , Fosforilação Oxidativa/efeitos dos fármacos , Fosfatos/metabolismo , Transdução de Sinais/fisiologia , Xenopus laevis
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