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Silva MP, Rodrigues CG, Machado DC, Nogueira RA. Long-term memory in Staphylococcus aureus α-hemolysin ion channel kinetics. Eur Biophys J 2023; 52:661-671. [PMID: 37542583 DOI: 10.1007/s00249-023-01675-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Revised: 07/03/2023] [Accepted: 07/20/2023] [Indexed: 08/07/2023]
Abstract
The kinetics of an ion channel are classically understood as a random process. However, studies have shown that in complex ion channels, formed by multiple subunits, this process can be deterministic, presenting long-term memory. Staphylococcus aureus α-hemolysin (α-HL) is a toxin that acts as the major factor in Staphylococcus aureus virulence. α-HL is a water-soluble protein capable of forming ion channels into lipid bilayers, by insertion of an amphipathic β-barrel. Here, the α-HL was used as an experimental model to study memory in ion channel kinetics. We applied the approximate entropy (ApEn) approach to analyze randomness and the Detrended Fluctuation Analysis (DFA) to investigate the existence of long memory in α-HL channel kinetics. Single-channel currents were measured through experiments with α-HL channels incorporated in planar lipid bilayers. All experiments were carried out under the following conditions: 1 M NaCl solution, pH 4.5; transmembrane potential of + 40 mV and temperature 25 ± 1 °C. Single-channel currents were recorded in real-time in the memory of a microcomputer coupled to an A/D converter and a patch-clamp amplifier. The conductance value of the α-HL channels was 0.82 ± 0.0025 nS (n = 128). The DFA analysis showed that the kinetics of α-HL channels presents long-term memory ([Formula: see text] = 0.63 ± 0.04). The ApEn outcomes showed low complexity to dwell times when open (ApEno = 0.5514 ± 0.28) and closed (ApEnc = 0.1145 ± 0.08), corroborating the results of the DFA method.
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Affiliation(s)
- M P Silva
- Department of Animal Morphology and Physiology, Federal Rural University of Pernambuco, Recife, Pernambuco, Brazil
| | - C G Rodrigues
- Department of Biophysics and Radiobiology, Federal University of Pernambuco, Recife, Pernambuco, Brazil
| | - D C Machado
- Department of Biophysics and Radiobiology, Federal University of Pernambuco, Recife, Pernambuco, Brazil
| | - R A Nogueira
- Department of Animal Morphology and Physiology, Federal Rural University of Pernambuco, Recife, Pernambuco, Brazil.
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2
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Licá ICL, Frazão GCCG, Nogueira RA, Lira MGS, dos Santos VAF, Rodrigues JGM, Miranda GS, Carvalho RC, Silva LA, Guerra RNM, Nascimento FRF. Immunological mechanisms involved in macrophage activation and polarization in schistosomiasis. Parasitology 2023; 150:401-415. [PMID: 36601859 PMCID: PMC10089811 DOI: 10.1017/s0031182023000021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Revised: 12/21/2022] [Accepted: 12/24/2022] [Indexed: 01/06/2023]
Abstract
Human schistosomiasis is caused by helminths of the genus Schistosoma. Macrophages play a crucial role in the immune regulation of this disease. These cells acquire different phenotypes depending on the type of stimulus they receive. M1 macrophages can be ‘classically activated’ and can display a proinflammatory phenotype. M2 or ‘alternatively activated’ macrophages are considered anti-inflammatory cells. Despite the relevance of macrophages in controlling infections, the role of the functional types of these cells in schistosomiasis is unclear. This review highlights different molecules and/or macrophage activation and polarization pathways during Schistosoma mansoni and Schistosoma japonicum infection. This review is based on original and review articles obtained through searches in major databases, including Scopus, Google Scholar, ACS, PubMed, Wiley, Scielo, Web of Science, LILACS and ScienceDirect. Our findings emphasize the importance of S. mansoni and S. japonicum antigens in macrophage polarization, as they exert immunomodulatory effects in different stages of the disease and are therefore important as therapeutic targets for schistosomiasis and in vaccine development. A combination of different antigens can provide greater protection, as it possibly stimulates an adequate immune response for an M1 or M2 profile and leads to host resistance; however, this warrants in vitro and in vivo studies.
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Affiliation(s)
- Irlla Correia Lima Licá
- Graduate Program in Health Sciences, Center for Biological and Health Sciences, Federal University of Maranhão, São Luís, MA, Brazil
- Laboratory of Immunophysiology, Center for Biological and Health Sciences, Federal University of Maranhão, São Luís, MA, Brazil
| | - Gleycka Cristine Carvalho Gomes Frazão
- Graduate Program in Health Sciences, Center for Biological and Health Sciences, Federal University of Maranhão, São Luís, MA, Brazil
- Laboratory of Immunophysiology, Center for Biological and Health Sciences, Federal University of Maranhão, São Luís, MA, Brazil
| | - Ranielly Araujo Nogueira
- Graduate Program in Health Sciences, Center for Biological and Health Sciences, Federal University of Maranhão, São Luís, MA, Brazil
- Laboratory of Immunophysiology, Center for Biological and Health Sciences, Federal University of Maranhão, São Luís, MA, Brazil
| | - Maria Gabriela Sampaio Lira
- Graduate Program in Health Sciences, Center for Biological and Health Sciences, Federal University of Maranhão, São Luís, MA, Brazil
- Laboratory of Immunophysiology, Center for Biological and Health Sciences, Federal University of Maranhão, São Luís, MA, Brazil
| | - Vitor Augusto Ferreira dos Santos
- Graduate Program in Health Sciences, Center for Biological and Health Sciences, Federal University of Maranhão, São Luís, MA, Brazil
- Laboratory of Immunophysiology, Center for Biological and Health Sciences, Federal University of Maranhão, São Luís, MA, Brazil
| | - João Gustavo Mendes Rodrigues
- Department of Parasitology, Institute of Biological Sciences, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Guilherme Silva Miranda
- Department of Biology, Federal Institute of Education, Science and Technology of Maranhão, São Raimundo das Mangabeiras, Brazil
| | - Rafael Cardoso Carvalho
- Graduate Program in Health Sciences, Center for Biological and Health Sciences, Federal University of Maranhão, São Luís, MA, Brazil
| | - Lucilene Amorim Silva
- Graduate Program in Health Sciences, Center for Biological and Health Sciences, Federal University of Maranhão, São Luís, MA, Brazil
- Laboratory of Immunophysiology, Center for Biological and Health Sciences, Federal University of Maranhão, São Luís, MA, Brazil
- Department of Pathology, Center for Biological and Health Sciences, Federal University of Maranhão, São Luís, MA, Brazil
| | - Rosane Nassar Meireles Guerra
- Graduate Program in Health Sciences, Center for Biological and Health Sciences, Federal University of Maranhão, São Luís, MA, Brazil
- Laboratory of Immunophysiology, Center for Biological and Health Sciences, Federal University of Maranhão, São Luís, MA, Brazil
- Department of Pathology, Center for Biological and Health Sciences, Federal University of Maranhão, São Luís, MA, Brazil
| | - Flávia Raquel Fernandes Nascimento
- Graduate Program in Health Sciences, Center for Biological and Health Sciences, Federal University of Maranhão, São Luís, MA, Brazil
- Laboratory of Immunophysiology, Center for Biological and Health Sciences, Federal University of Maranhão, São Luís, MA, Brazil
- Department of Pathology, Center for Biological and Health Sciences, Federal University of Maranhão, São Luís, MA, Brazil
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3
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Nogueira RA, Lira MGS, Licá ICL, Frazão GCCG, Dos Santos VAF, Filho ACCM, Rodrigues JGM, Miranda GS, Carvalho RC, Nascimento FRF. Praziquantel: An update on the mechanism of its action against schistosomiasis and new therapeutic perspectives. Mol Biochem Parasitol 2022; 252:111531. [PMID: 36375598 DOI: 10.1016/j.molbiopara.2022.111531] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 11/03/2022] [Accepted: 11/10/2022] [Indexed: 11/13/2022]
Abstract
Praziquantel (PZQ) is the drug of choice for the treatment of all forms of schistosomiasis, although its mechanisms of action are not completely understood. PZQ acts largely on adult worms. This narrative literature review describes what is known about the mechanisms of action of PZQ against schistosomes from in vitro and in vivo studies and highlights the molecular targets in parasites and immune responses induced in definitive hosts by this drug. Moreover, new therapeutic uses of PZQ are discussed. Studies have demonstrated that in addition to impacting voltage-operated Ca2 + channels, PZQ may interact with other schistosome molecules, such as myosin regulatory light chain, glutathione S-transferase, and transient receptor potential channels. Following PZQ administration, increased T regulatory type 1 (Tr1) cell differentiation and decreased inflammation were observed, indicating that PZQ promotes immunoregulatory pathways. Although PZQ is widely used in mass drug administration schemes, the existence of resistant parasites has not been proven; however, it is a concern that should be constantly investigated in human populations. In addition, we discuss studies that evaluate health applications of PZQ (other than helminth infection), such as its effect in cancer therapy and its adjuvant action in vaccines against viruses.
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Affiliation(s)
- Ranielly Araujo Nogueira
- Graduate Program in Health Sciences, Center for Biological and Health Sciences, Federal University of Maranhão, São Luís, MA, Brazil
| | - Maria Gabriela Sampaio Lira
- Graduate Program in Health Sciences, Center for Biological and Health Sciences, Federal University of Maranhão, São Luís, MA, Brazil; Department of Education, Federal Institute of Education, Science and Technology of Maranhão, Zé Doca, MA, Brazil
| | - Irlla Correia Lima Licá
- Graduate Program in Health Sciences, Center for Biological and Health Sciences, Federal University of Maranhão, São Luís, MA, Brazil
| | | | - Vitor Augusto Ferreira Dos Santos
- Graduate Program in Health Sciences, Center for Biological and Health Sciences, Federal University of Maranhão, São Luís, MA, Brazil
| | | | - João Gustavo Mendes Rodrigues
- Department of Parasitology, Institute of Biological Sciences, Federal University of Minas Gerais, Belo Horizonte, MG, Brazil
| | - Guilherme Silva Miranda
- Department of Education, Federal Institute of Education, Science and Technology of Maranhão, São Raimundo das Mangabeiras, MA, Brazil
| | - Rafael Cardoso Carvalho
- Graduate Program in Health Sciences, Center for Biological and Health Sciences, Federal University of Maranhão, São Luís, MA, Brazil
| | - Flávia Raquel Fernandes Nascimento
- Graduate Program in Health Sciences, Center for Biological and Health Sciences, Federal University of Maranhão, São Luís, MA, Brazil; Department of Pathology, Center for Biological and Health Sciences, Federal University of Maranhão, São Luís, MA, Brazil.
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Abstract
Ion channels are transport proteins present in the lipid bilayers of biological membranes. They are involved in many physiological processes, such as the generation of nerve impulses, hormonal secretion, and heartbeat. Conformational changes in the ion channel-forming protein allow the opening or closing of pores to control the ionic flux through the cell membranes. The opening and closing of the ion channel have been classically treated as a random kinetic process, known as a Markov process. Here the time the channel remains in a given state is assumed to be independent of the condition it had in the previous state. More recently, however, several studies have shown that this process is not random but a deterministic one, where both the open and closed dwell-times and the ionic current flowing through the channel are history-dependent. This property is called long memory or long-range correlation. However, there is still much controversy regarding how this memory originates, which region of the channel is responsible for this property, and which models could best reproduce the memory effect. In this article, we provide a review of what is, where it is, its possible origin, and the mathematical methods used to analyze the long-term memory present in the kinetic process of ion channels.
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Affiliation(s)
- M P Silva
- Department of Animal Morphology and Physiology, Federal Rural University of Pernambuco, Recife, Pernambuco, Brazil
| | - C G Rodrigues
- Department of Biophysics and Radiobiology, Federal University of Pernambuco, Recife, Pernambuco, Brazil
| | - W A Varanda
- Department of Physiology-Faculty of Medicine of Ribeirão Preto, University of São Paulo (Retired), Ribeirão Preto, São Paulo, Brazil
| | - R A Nogueira
- Department of Animal Morphology and Physiology, Federal Rural University of Pernambuco, Recife, Pernambuco, Brazil.
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5
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Lima HGIF, Lopes IMSS, Oliveira APB, Costa EVL, Aguiar LAA, Lindoso BPA, Silva MCO, Silva JES, Nogueira RA. Omega-3 effects on electrocorticographic patterns of adult Wistar rats exposed to ionizing radiation. Biochem Biophys Rep 2021; 26:100992. [PMID: 33898765 PMCID: PMC8056338 DOI: 10.1016/j.bbrep.2021.100992] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Revised: 03/15/2021] [Accepted: 03/25/2021] [Indexed: 11/27/2022] Open
Abstract
This study aimed to assess the effect of supplementation with omega-3 in Wistar rats exposed to ionizing radiation in a dose of 18 Gy on the cortical electrical activity, using mathematical methods such as the power spectrum (PS) and the detrended fluctuation analysis (DFA) in the evaluation of the electrocorticogram (ECoG) record. The PS analysis showed that in non-irradiated animals but supplemented with omega-3 there was a decrease in the power of the beta rhythm, while the DFA applied to different frequency ranges of the ECoG showed a significant increase in the long-range correlation only for the theta wave when compared with non-supplemented animals. In the evaluation of the radiation effect through the PS, an increase in the power of the theta rhythm was observed in both groups (non-supplemented and supplemented animals) only when they were evaluated one week after irradiation. The DFA method also showed difference in this wave. The PS and DFA methods applied to the ECoG record allowed a quantitative analysis of the cortical electrical activity in rats in response to the omega-3 effects, ionizing radiation, or both. PUFA omega-3 can act as a modulator of the cortical activity in rats. Ionizing radiation exposure promoted later effect in theta and beta waves. 3. The power spectrum and the DFA allowed a quantitative analysis of the ECoG in rats.
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Affiliation(s)
- H G I F Lima
- Laboratório de Biofísica Teórico-Experimental e Computacional, Departamento de Morfologia e Fisiologia Animal, Universidade Federal Rural de Pernambuco, Recife, PE, Brazil
| | - I M S S Lopes
- Laboratório de Biofísica Celular e Molecular - Universidade Federal de Pernambuco, Recife, PE, Brazil
| | - A P B Oliveira
- Instituto de Radioterapia Waldemir Miranda, IRWAN, Recife, PE, Brazil
| | - E V L Costa
- Laboratório de Biofísica Teórico-Experimental e Computacional, Departamento de Morfologia e Fisiologia Animal, Universidade Federal Rural de Pernambuco, Recife, PE, Brazil
| | - L A A Aguiar
- Laboratório de Biofísica Teórico-Experimental e Computacional, Departamento de Morfologia e Fisiologia Animal, Universidade Federal Rural de Pernambuco, Recife, PE, Brazil
| | - B P A Lindoso
- Laboratório de Biofísica Teórico-Experimental e Computacional, Departamento de Morfologia e Fisiologia Animal, Universidade Federal Rural de Pernambuco, Recife, PE, Brazil
| | - M C O Silva
- Laboratório de Biofísica Teórico-Experimental e Computacional, Departamento de Morfologia e Fisiologia Animal, Universidade Federal Rural de Pernambuco, Recife, PE, Brazil
| | - J E S Silva
- Laboratório de Biofísica Teórico-Experimental e Computacional, Departamento de Morfologia e Fisiologia Animal, Universidade Federal Rural de Pernambuco, Recife, PE, Brazil
| | - R A Nogueira
- Laboratório de Biofísica Teórico-Experimental e Computacional, Departamento de Morfologia e Fisiologia Animal, Universidade Federal Rural de Pernambuco, Recife, PE, Brazil
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Nogueira RA, Lira MGS, Santos SIP, Mondêgo-Oliveira R, Andrade FHED, Sousa EMD, Barbosa DS, Abreu-Silva AL, Carvalho RC. Intense transmission of visceral leishmaniasis in a region of northeastern Brazil: a situation analysis after the discontinuance of a zoonosis control program. ACTA ACUST UNITED AC 2021; 30:e020320. [PMID: 33909834 DOI: 10.1590/s1984-29612021015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Accepted: 02/04/2021] [Indexed: 11/22/2022]
Abstract
In São Luís, Maranhão, northeastern Brazil, the notification of visceral leishmaniasis (VL) cases intensified in 1982, showing endemic and epidemic patterns. In this city, the Center for Zoonoses Control (CZC) was an organization in charge of the control and prevention of the disease. However, technical and political reasons have led to a significant decline in the periodicity of its activities. Therefore, in this study we evaluated the epidemiological scenario of human visceral leishmaniasis (HVL) and the prevalence of the disease in dogs after the cessation of the CZC activities, covering the period of 2007 to 2016. The seroprevalence of canine leishmaniasis was determined based on clinical and serological profiles. HVL cases were notified using data provided by the Municipal Health Department of São Luís. A seropositivity rate of 45.8% (p = 0.0001) was found among dogs, 54% (p = 0.374) of which were asymptomatic. As for human cases, there were 415 notifications, with an increase in the incidence of the zoonosis observed during the aforementioned period. Thus, it can be inferred that after the control and surveillance activities were curtailed, there was an increase in the number of seropositive animals in circulation, acting as reservoirs of infection for dogs and humans.
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Affiliation(s)
- Ranielly Araujo Nogueira
- Programa de Pós-graduação em Ciências da Saúde, Centro de Ciências Biológicas e da Saúde, Universidade Federal do Maranhão - UFMA, São Luís, MA, Brasil
| | - Maria Gabriela Sampaio Lira
- Programa de Pós-graduação em Ciências da Saúde, Centro de Ciências Biológicas e da Saúde, Universidade Federal do Maranhão - UFMA, São Luís, MA, Brasil
| | - Sarah Ingrid Pinto Santos
- Programa de Pós-graduação em Ciência Animal, Centro de Ciências Agrárias, Universidade Estadual do Maranhão - UEMA, São Luís, MA, Brasil
| | - Renata Mondêgo-Oliveira
- Programa de Pós-graduação em Biotecnologia (Rede Nordeste de Biotecnologia), Centro de Ciências Biológicas e da Saúde, Universidade Federal do Maranhão - UFMA, São Luís, MA, Brasil
| | - Fábio Henrique Evangelista de Andrade
- Laboratório de Anatomopatologia, Curso de Medicina Veterinária, Centro de Ciências Agrárias, Universidade Estadual do Maranhão - UEMA, São Luís, MA, Brasil
| | | | - David Soeiro Barbosa
- Programa de Pós-graduação em Parasitologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais - UFMG, Belo Horizonte, MG, Brasil
| | - Ana Lucia Abreu-Silva
- Programa de Pós-graduação em Ciências da Saúde, Centro de Ciências Biológicas e da Saúde, Universidade Federal do Maranhão - UFMA, São Luís, MA, Brasil.,Programa de Pós-graduação em Ciência Animal, Centro de Ciências Agrárias, Universidade Estadual do Maranhão - UEMA, São Luís, MA, Brasil
| | - Rafael Cardoso Carvalho
- Programa de Pós-graduação em Ciências da Saúde, Centro de Ciências Biológicas e da Saúde, Universidade Federal do Maranhão - UFMA, São Luís, MA, Brasil
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Silva JAX, Albertini AVP, Fonseca CSM, Silva DCN, Carvalho VCO, Lima VLM, Fontes A, Costa EVL, Nogueira RA. Biomechanical and biochemical investigation of erythrocytes in late stage human leptospirosis. ACTA ACUST UNITED AC 2020; 53:e9268. [PMID: 32578717 PMCID: PMC7307891 DOI: 10.1590/1414-431x20209268] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Accepted: 04/01/2020] [Indexed: 12/22/2022]
Abstract
Leptospirosis is a zoonotic disease caused by bacteria of the genus
Leptospira, which can cause lipid changes in the
erythrocyte membrane. Optical tweezers were used to characterize rheological
changes in erythrocytes from patients with leptospirosis in the late stage.
Biochemical methods were also used for quantification of plasma lipid,
erythrocyte membrane lipid, and evaluation of liver function. Our data showed
that the mean elastic constant of erythrocytes from patients with leptospirosis
was around 67% higher than the control (healthy individuals), indicating that
patient’s erythrocytes were less elastic. In individuals with leptospirosis,
several alterations in relation to control were observed in the plasma lipids,
however, in the erythrocyte membrane, only phosphatidylcholine showed a
significant difference compared to control, increasing around 41%. With respect
to the evaluation of liver function of individuals with leptospirosis, there was
a significant increase in levels of alanine transaminase (154%) and aspartate
transaminase (150%), whereas albumin was 43.8% lower than control (P<0.01).
The lecithin-cholesterol acyltransferase fractional activity was 3.6 times lower
in individuals with leptospirosis than in the healthy individuals (P<0.01).
The decrease of the erythrocyte elasticity may be related to the changes of
erythrocyte membrane phospholipids composition caused by disturbances that occur
during human leptospirosis, with phosphatidylcholine being a strong candidate in
the erythrocyte rheological changes.
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Affiliation(s)
- J A X Silva
- Laboratório de Biofísica Teórico-Experimental e Computacional, Departamento de Morfologia e Fisiologia Animal, Universidade Federal Rural de Pernambuco, Dois Irmãos, Recife, PE, Brasil.,Centro de Apoio è Pesquisa, Universidade Federal Rural de Pernambuco, Dois Irmãos, Recife, PE, Brasil
| | - A V P Albertini
- Laboratório de Biofísica Teórico-Experimental e Computacional, Departamento de Morfologia e Fisiologia Animal, Universidade Federal Rural de Pernambuco, Dois Irmãos, Recife, PE, Brasil.,Centro de Apoio è Pesquisa, Universidade Federal Rural de Pernambuco, Dois Irmãos, Recife, PE, Brasil
| | - C S M Fonseca
- Laboratório de Química e Metabolismo de Lipídios e Lipoproteínas, Departamento de Bioquímica, Centro de Biociências, Universidade Federal de Pernambuco, Recife, PE, Brasil
| | - D C N Silva
- Colegiado de Ciências Biológicas, Universidade Federal do Vale do São Francisco, Petrolina, PE, Brasil
| | - V C O Carvalho
- Laboratório de Química e Metabolismo de Lipídios e Lipoproteínas, Departamento de Bioquímica, Centro de Biociências, Universidade Federal de Pernambuco, Recife, PE, Brasil
| | - V L M Lima
- Laboratório de Química e Metabolismo de Lipídios e Lipoproteínas, Departamento de Bioquímica, Centro de Biociências, Universidade Federal de Pernambuco, Recife, PE, Brasil
| | - A Fontes
- Departamento de Biofísica e Radiobiologia, Universidade Federal de Pernambuco, Recife, PE, Brasil
| | - E V L Costa
- Laboratório de Biofísica Teórico-Experimental e Computacional, Departamento de Morfologia e Fisiologia Animal, Universidade Federal Rural de Pernambuco, Dois Irmãos, Recife, PE, Brasil.,Centro de Apoio è Pesquisa, Universidade Federal Rural de Pernambuco, Dois Irmãos, Recife, PE, Brasil
| | - R A Nogueira
- Laboratório de Biofísica Teórico-Experimental e Computacional, Departamento de Morfologia e Fisiologia Animal, Universidade Federal Rural de Pernambuco, Dois Irmãos, Recife, PE, Brasil.,Centro de Apoio è Pesquisa, Universidade Federal Rural de Pernambuco, Dois Irmãos, Recife, PE, Brasil
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8
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Aguiar LAA, Silva IMS, Fernandes TS, Nogueira RA. Long-term correlation of the electrocorticogram as a bioindicator of brain exposure to ionizing radiation. ACTA ACUST UNITED AC 2015; 48:915-22. [PMID: 26445335 PMCID: PMC4617118 DOI: 10.1590/1414-431x20154473] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Accepted: 02/06/2015] [Indexed: 11/25/2022]
Abstract
Understanding the effects of radiation and its possible influence on the nervous
system are of great clinical interest. However, there have been few
electrophysiological studies on brain activity after exposure to ionizing radiation
(IR). A new methodological approach regarding the assessment of the possible effects
of IR on brain activity is the use of linear and nonlinear mathematical methods in
the analysis of complex time series, such as brain oscillations measured using the
electrocorticogram (ECoG). The objective of this study was to use linear and
nonlinear mathematical methods as biomarkers of gamma radiation regarding cortical
electrical activity. Adult Wistar rats were divided into 3 groups: 1 control and 2
irradiated groups, evaluated at 24 h (IR24) and 90 days (IR90) after exposure to 18
Gy of gamma radiation from a cobalt-60 radiotherapy source. The ECoG was analyzed
using power spectrum methods for the calculation of the power of delta, theta, alpha
and beta rhythms and by means of the α-exponent of the detrended fluctuation analysis
(DFA). Using both mathematical methods it was possible to identify changes in the
ECoG, and to identify significant changes in the pattern of the recording at 24 h
after irradiation. Some of these changes were persistent at 90 days after exposure to
IR. In particular, the theta wave using the two methods showed higher sensitivity
than other waves, suggesting that it is a possible biomarker of exposure to IR.
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Affiliation(s)
- L A A Aguiar
- Departamento de Morfologia e Fisiologia Animal, Laboratório de Biofísica Teórico-Experimental e Computacional, Universidade Federal Rural de Pernambuco, PE, Recife, BR
| | - I M S Silva
- Departamento de Biofísica e Radiobiologia, Universidade Federal de Pernambuco, PE, Recife, BR
| | - T S Fernandes
- Departamento de Biofísica e Radiobiologia, Universidade Federal de Pernambuco, PE, Recife, BR
| | - R A Nogueira
- Departamento de Morfologia e Fisiologia Animal, Laboratório de Biofísica Teórico-Experimental e Computacional, Universidade Federal Rural de Pernambuco, PE, Recife, BR
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Miloski B, Moreira A, Andrade FC, Freitas VH, Peçanha T, Nogueira RA, Bara-Filho M. Do physical fitness measures influence internal training load responses in high-level futsal players? J Sports Med Phys Fitness 2014; 54:588-594. [PMID: 25270779] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
BACKGROUND The aim of the present study was to verify whether aerobic fitness and ability to perform repeated high-intensity efforts influence the internal training load (ITL), which consists of the actual stress imposed in the athletes' organisms, in professional futsal players. METHODS Twelve high-level futsal players (age: 26.3±4.9 years, body mass: 73.5±7.5 kg) participated in the study. The investigated athletes took part in a 5-week pre-season period. The ITL was quantified by means of the session-Rating of Perceived Exertion method. The athletes performed the Yo-yo Intermittent Recovery Test level 2 (YYIR2) in order to assess the ability to perform repeated high-intensity actions, and the multistage shuttle-run test (MSRT) in order to evaluate aerobic fitness, before (T0) and after (T1) the pre-season period. Maximal oxygen uptake (VO2max.), oxygen uptake at Respiratory compensation point (VO2-RCP) and maximal aerobic speed (MAS) obtained in MSRT were retained for analyses. RESULTS The results from Pearson's correlation test showed significant and a very large correlation between ITL and YYIR2 performance (r=-0.75). Moreover, a significant and large correlation between ITL and VO2max. (r=-0.62), ITL and MAS (r=-0.67), and ITL and VO2-RCP (r=-0.58) were also observed. CONCLUSION It can be concluded that aerobic fitness and ability to perform repeated high-intensity actions may influence ITL responses in professional futsal players.
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Affiliation(s)
- B Miloski
- Grupo de estudos e pesquisa em planejamento e monitoramento do treinamento físico e esportivo Escola de Educação Física e Esporte Departamento de Esporte Universidade de São Paulo, SP, Brasil -
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Nakagawa NK, Nogueira RA, Obuti CA, Correia CJ, Cruz JWMC, de Figueiredo LFP, e Silva MR, Sannomiya P. Effects of hypertonic saline solution and pentoxifylline on rat mesenteric microcirculation after hemorrhagic shock/reperfusion followed by cecal ligation/puncture: an intravital microscopic study. Crit Care 2007. [PMCID: PMC3301134 DOI: 10.1186/cc5794] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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11
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Abstract
Electronic calculations were carried out for the dilute ordered alloys Ga(0.94) (TM)(0.06)N (TM = Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, and Ag) in the zinc-blende structure. The theoretical framework used was the density functional theory, using the local spin density approximation, as implemented in the full-potential linearized augmented plane wave method. We examine energy band structures, densities of states, charge distributions, and local magnetic moments and anticipate the properties of these promising systems for applications in spin electronic devices.
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Affiliation(s)
- R de Paiva
- Departamento de Física, Universidade Federal de Minas Gerais, CP 702, 30123-970, Belo Horizonte, MG, Brazil
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Nakagawa N, Nogueira R, Sinosaki S, Shiwa S, Poli de Figueiredo L, Sannomiya P, Rocha e Silva M. Crit Care 2005; 9:P41. [DOI: 10.1186/cc3585] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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13
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Varanda WA, Liebovitch LS, Figueiroa JN, Nogueira RA. Hurst analysis applied to the study of single calcium-activated potassium channel kinetics. J Theor Biol 2000; 206:343-53. [PMID: 10988020 DOI: 10.1006/jtbi.2000.2131] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The gating of ion channels has been modeled by assuming that the transitions between open and closed states is a memoryless process. Nevertheless, analysis of records of unitary current events suggests that the kinetic process presents short-term memory, i.e. the open- and closed-dwell times are short-term correlated. Here the rescaled range analysis (R/S Hurst analysis) is used as a method to test long-term correlation, in single calcium-activated potassium channels present in Leydig cells. The Hurst coefficients, calculated for four different voltages (V) are: 0.634+/-0.022 (n=3) for V=+20 mV; 0.635+/-0.012 (n=4) for V=+40 mV; 0.606+/-0.020 (n=4) for V=+60 mV and 0.608+/-0.026 (n=4) for V=+80 mV. This indicates that open- and closed-dwell times are long-term correlated and do not change with the voltage applied to the patch at a 5% significance level (F=2.2402;p=0.140715). Randomly shuffling the experimental data removes the correlation in all voltages. When the Hurst method was applied to the results from a simulated three-state Markovian model, it could not account for the long-term correlation found in the experimental data. In this case, H has the following values: 0. 5498+/-0.018 (n=100) for V=+20 mV; 0.5557+/-0.0202 (n=100) for V=+40 mV; 0.5565+/-0.0246 (n=100) for V=60 mV and 0.5595+/-0.0247 (n=100) for V=+80 mV. Even a four-state Markovian model was not adequate to correctly simulate the long-term memory found experimentally, with H values significantly different from those found for the experimental data, in the same voltage range (F=15.0355;p=0.00001). In conclusion, this paper shows that: (1) the open- and closed-dwell times of the single calcium-activated potassium channel of Leydig cells are long-term correlated; (2) three- and four-state Markovian models, which describe very well the dwell time distributions, are not adequate to describe the long-term correlation found between the open and closed states of this ion channel.
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Affiliation(s)
- W A Varanda
- Department of Physiology-Faculty of Medicine of Ribeirão Preto, 14049-900, Brazil
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Krasilnikov OV, Merzlyak PG, Yuldasheva LN, Rodrigues CG, Nogueira RA. Heparin influence on alpha-staphylotoxin formed channel. Biochim Biophys Acta 1999; 1417:167-82. [PMID: 10076045 DOI: 10.1016/s0005-2736(98)00244-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The effects of heparin on ion channels formed by Staphylococcus aureus alpha-toxin (ST channel) in lipid bilayers were studied under voltage clamp conditions. Heparin concentrations as small as 100 pM induced a sharp dose-dependent increase in channel voltage sensitivity. This was only observed when heparin was added to the negative-potential side of lipid bilayers in the presence of divalent cations. Divalent cations differ in their efficiency: Zn2+>Ca2+>Mg2+. The apparent positive gating charge increased 2-3-fold with heparin addition as well as with acidification of the bathing solution. 'Free' carboxyl groups and carboxyl groups in ion pairs of the protein moiety are hypothesized to interact with sulfated groups of heparin through divalent cation bridges. The cis mouth of the channel (that protrudes beyond the membrane plane on the side of ST addition and to which voltage was applied) is less sensitive to heparin than the trans-mouth. It is suggested that charged residues which interact with heparin at the cis mouth of ST channels and which contribute to the effective gating charge at negative voltage may be physically different from those at the trans mouth and at positive voltage.
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Affiliation(s)
- O V Krasilnikov
- Laboratory of Molecular Physiology, Institute of Physiology and Biophysics, 700095, Tashkent, Uzbekistan.
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Krasilnikov OV, Merzlyak PG, Yuldasheva LN, Nogueira RA. Channel-sizing experiments in multichannel bilayers. Gen Physiol Biophys 1998; 17:349-63. [PMID: 10191420] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Abstract
The possibility of obtaining information about the radius of high and low conductance states of channels in multichannel membranes was tested experimentally. In spite of the interference of non-electrolytes on the numbers of channels that appeared in the membrane, the non-electrolyte-exclusion method was successfully adapted to multichannel bilayers to estimate the radius of the larger opening of the low conductance state of the channel induced by Staphylococcus aureus alpha-toxin. At the pH used, the channel transition to a low conductance state was accompanied by a decrease of the opening radius from 1.3 +/- 0.2 nm to 0.9 +/- 0.1 nm. The determination criteria for maximum size of a channel opening when using the non-electrolyte exclusion method is discussed.
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Affiliation(s)
- O V Krasilnikov
- Laboratory of Molecular Physiology, Institute of Physiology and Biophysics, Tashkent, Uzbekistan.
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Krasil'nikov OV, Da Cruz JB, Nogueira RA. [How can we measure a diameter of each entrance of a ion channel recording only channel conductance?]. Biofizika 1998; 43:299-303. [PMID: 9591104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The channel formed by colicin Ia in planar lipid bilayer was used to develop a method determining a diameter of each channel entrance. The method is based on measuring of a channel filling with nonelectrolytes through cis- and trans-entrance separately. To do this, one need to establish the two things only: the conductance of an ion channel and the conductivity of used solutions. Using the method to predict the internal geometry of a channel lumen is discussed.
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Krasilnikov OV, Da Cruz JB, Yuldasheva LN, Varanda WA, Nogueira RA. A novel approach to study the geometry of the water lumen of ion channels: colicin Ia channels in planar lipid bilayers. J Membr Biol 1998; 161:83-92. [PMID: 9430623 DOI: 10.1007/s002329900316] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
This paper describes a new approach to evaluate the inner structure (including a main constriction and its localization) of the water lumen of an ion channel. The method is based on the determination of channel filling by different nonelectrolyte molecules through each side of an ion channel. The method has two characteristic features that make its use attractive: (i) the possibility to ascertain the existence, localization and size of a narrow part inside an ion channel water lumen and (ii) the chances to determine the maximal size of both entrances of an ion channel and to obtain additional information about the geometry of its water lumen at the same time. Determinations were made on colicin Ia ion channels inserted into planar lipid bilayers. This channel was chosen because there is an apparent contradiction between its low single channel conductance and the large diameter of its water lumen. Our results show that the water lumen of the colicin Ia channel has a funnel-like structure with a small trans-entrance, with a diameter of about 1.0 nm, and a large cis-entrance, with a diameter of approximately 1.8 nm. A constriction with a diameter of approximately 0.7 nm is shown to be located close to the trans-entrance of the channel. The method can also be applied to patch clamp studies of single ion channels.
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Affiliation(s)
- O V Krasilnikov
- Laboratory of Molecular Physiology, Institute of Physiology and Biophysics, 700095 Tashkent, Uzbekistan
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Carneiro CM, Krasilnikov OV, Yuldasheva LN, Campos de Carvalho AC, Nogueira RA. Is the mammalian porin channel, VDAC, a perfect cylinder in the high conductance state? FEBS Lett 1997; 416:187-9. [PMID: 9369211 DOI: 10.1016/s0014-5793(97)01198-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The mammalian porin channel (VDAC, porin-31BM) was reconstituted in planar lipid bilayers under voltage clamp conditions. The radii of both entrances of the channel were examined using a method that consisted in filling the channel with different non-electrolytes through its cis or trans entrances while recording single channel conductances. As a result it was found that the geometry of channels formed by porin-31BM could not be approximated by a perfectly cylindrical pore. In fact there is an asymmetry in the geometry of the channel: the diameters of the cis and trans entrances were estimated to be approximately 2 nm and approximately 4 nm respectively.
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Affiliation(s)
- C M Carneiro
- Center of Biological Sciences, Department of Biophysics and Radiobiology, Federal University of Pernambuco, Recife, PE, Brazil
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Krasilnikov OV, Yuldasheva LN, Merzlyak PG, Capistrano MF, Nogueira RA. The hinge portion of the S. aureus alpha-toxin crosses the lipid bilayer and is part of the trans-mouth of the channel. Biochim Biophys Acta 1997; 1329:51-60. [PMID: 9370244 DOI: 10.1016/s0005-2736(97)00087-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
This paper compares the functional properties of ion channels formed in planar lipid membranes by the wild and mutant Staphylococcus aureus alpha-toxin. It was shown that replacement of the amino acid Gly at position 130 by Cys in the primary structure of the toxin decreases the single-channel conductance with a concomitant decrease in the pH at which the channel becomes unable to discriminate between Cl- and K+ ions. The mutation also induced an increase in the asymmetry in the current-voltage relationship of the channel. The results of our experiments suggest that the trans-mouth of the channel is responsible for all the observed changes in channel properties. It was assumed that this entrance is built by the glycine-rich hinge portion of the toxin and is situated close to the surface of monolayer facing the trans-compartment.
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Affiliation(s)
- O V Krasilnikov
- Laboratory of Molecular Physiology, Institute of Physiology and Biophysics, Tashkent, Uzbekistan.
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20
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Krasilnikov OV, Merzlyak PG, Yuldasheva LN, Azimova RK, Nogueira RA. Pore-forming properties of proteolytically nicked staphylococcal alpha-toxin: the ion channel in planar lipid bilayer membranes. Med Microbiol Immunol 1997; 186:53-61. [PMID: 9255767 DOI: 10.1007/s004300050046] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Staphylococcal alpha-toxin is a single-chain protein with a molecular mass of 33.2 kDa, which can form large water-filled pores both in lipid bilayers and in erythrocyte membranes. Limited proteolysis of the purified toxin with proteinase K led to time-dependent changes of all the functional features of the channels formed by the toxin. Single-channel conductance in planar bilayers was decreased about threefold. The anion selectivity of the channel was replaced with cation selectivity and the asymmetry in the current-voltage relationship of the channel became more pronounced. At the same time the nicked toxin kept its full ability to form ion channels in lipid bilayers, although it lost a considerable part of its hemolytic activity. In planar bilayers and in erythrocyte membranes, the proteolytically nicked toxin actually formed channels with a slightly smaller diameter (approximately 1.2 times) than that formed by the native toxin. This decrease was not marked enough to explain changes in the biological effects of the nicked toxin. The change in channel selectivity induced by the cleavage is considered to be the major determinant of the changes in the biological effects of the nicked toxin.
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Affiliation(s)
- O V Krasilnikov
- Laboratory of Molecular Physiology, Institute of Physiology and Biophysics, Tashkent, Uzbekistan.
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Krasilnikov OV, Capistrano MP, Yuldasheva LN, Nogueira RA. Influence of Cys-130 S. aureus alpha-toxin on planar lipid bilayer and erythrocyte membranes. J Membr Biol 1997; 156:157-72. [PMID: 9075647 DOI: 10.1007/s002329900198] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Replacement of an amino acid residue at position 130 -Gly by Cys- in the primary structure of Staphylococcus aureus alpha-toxin decreases the single-channel conductance induced by the toxin in planar lipid bilayers. Concomitantly, the pH value at which the channel becomes unable to discriminate between Cl- and K+ ions is also decreased. By contrast, the pH dependence of the efficiency of the mutant toxin to form ion channels in lipid bilayers was unchanged (maximum efficiency at pH 5.5-6.0). The asymmetry and nonlinearity of the current-voltage characteristics of the channel were increased by the point mutation but the diameter of the water pore induced by the mutant toxin, evaluated in lipid bilayers and in erythrocyte membranes, was found to be indistinguishable from that formed by wild-type toxin and equal to 2.4-2.6 nm. Alterations at the "trans mouth" were found to be responsible for all observed changes of the channel properties. This mouth is situated close to the surface of the second leaflet of a bilayer lipid membrane. The data obtained allows us to propose that the region around residue 130 in fact determines the main features of the ST-channel and takes part in the formation of the trans entrance of the channel.
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Affiliation(s)
- O V Krasilnikov
- Laboratory of Molecular Physiology, Institute of Physiology and Biophysics, 700095 Tashkent, Uzbekistan
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Krasilnikov OV, Carneiro CM, Yuldasheva LN, Campos-de-Carvalho AC, Nogueira RA. Diameter of the mammalian porin channel in open and "closed" states: direct measurement at the single channel level in planar lipid bilayer. Braz J Med Biol Res 1996; 29:1691-7. [PMID: 9222434] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Porin isolated from bovine skeletal muscle was reconstitute in planar lipid bilayers under voltage clamp conditions. A set of non-electrolytes were used as molecular probes for determining the pore diameter. The maximal diameter of the open channel was estimated to be 3.02 +/- 0.26 nm. As observed for other porin channels, a large transmembrane potential drove the channel into a "closed" state. The channel transition to the low conductance (closed) state was followed by a decrease in the maximal diameter of the channel to 2.4 +/- 0.08 nm.
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Affiliation(s)
- O V Krasilnikov
- Laboratory of Molecular Physiology, Institute of Physiology and Biophysics, Tashkent, Uzbekistan.
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Krasilnikov OV, Yuldasheva LN, Nogueira RA, Rodrigues CG. The diameter of water pores formed by colicin Ia in planar lipid bilayers. Braz J Med Biol Res 1995; 28:693-8. [PMID: 8547854] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The effective size of colicin Ia channel was tested by a recently described method (FEMS, Microbiology and Immunology (1992). 105: 93-100) in which the nonelectrolyte molecules with different hydrodynamic diameters (0.52 to 5.0 nm) were used as molecular tools. We have shown that despite low conductance (55-105 pS at 1.5 M KCl, pH 7.0) the ion channels formed by colicin Ia have a fairly large water pore diameter equal to 1.66-1.88 nm. The results are discussed in terms of an energetic barrier for ions passing into the channel lumen.
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Affiliation(s)
- O V Krasilnikov
- Laboratory of Molecular Physiology, Institute of Physiology and Biophysics, Tashkent, Uzbekistan
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Nogueira RA, Varanda WA, Liebovitch LS. Hurst analysis in the study of ion channel kinetics. Braz J Med Biol Res 1995; 28:491-6. [PMID: 8520548] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Ion channels are protein molecules which can assume distinct open and closed conformational states. The transitions between these states can be controlled by the electrical field, ions and/or drugs. Records of unitary current events show that short open-time intervals are frequently adjacent to much longer closed-time intervals, and vice-versa, suggesting that the kinetic process has memory, i.e., the intervals are correlated in time. Here the rescaled range analysis (R/S Hurst analysis) is proposed as a method to test for correlation. Simulations were performed with a two-state Markovian model, which has no memory. The calculated Hurst coefficients (H) presented a mean +/- SD value of 0.493 +/- 0.025 (N = 100). For the Ca(2+)-activated K+ channels of Leydig cells, H was equal to 0.75, statistically different (1% level) from that calculated for the memoryless process. Randomly shuffling the experimental data resulted in an H = 0.55, not significantly different (1% level) from that found for the two-state Markovian model. For a linear three-state Markovian model, H was equal to 0.548 +/- 0.017 (N = 15), again not significantly different (1% level) from that of the memoryless process. Although the three-state Markovian model adequately describes the open- and closed-time distributions, it does not account for the correlation found in this Ca(2+)-activated K+ channel. Our results illustrate the efficacy of the R/S analysis in determining whether successive opening and closing events are correlated in time and can be of help in deciding which model should be used to describe the kinetics of ion channels.
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Affiliation(s)
- R A Nogueira
- Departamento de Biofísica e Radiobiologia, Universidade Federal de Pernambuco, Recife, PE, Brasil
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Krasilnikov OV, Merzliak PG, Yuldasheva LN, Nogueira RA, Rodrigues CG. Non stochastic distribution of single channels in planar lipid bilayers. Biochim Biophys Acta 1995; 1233:105-10. [PMID: 7532434 DOI: 10.1016/0005-2736(94)00231-d] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The selectivity of the planar lipid bilayers modified by two channel-forming proteins (alpha-toxin S. aureus and colicin Ia) was examined. It was established that in all cases the value of zero current potential depended on the amount of open ion channels and increased with the number of channels (from one to about 5-7). These facts point out both the interactions among ion channels and their non stochastic distribution on the membrane surface.
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Affiliation(s)
- O V Krasilnikov
- Laboratory of Molecular Physiology, Institute of Physiology and Biophysics, Tashkent, Uzbekistan
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Abstract
Colicin Ia forms voltage-dependent channels when incorporated into planar lipid bilayers. A membrane containing many Colicin Ia channels shows a conductance which is turned on when high positive voltages (greater than +10 mV) are applied to the cis side (side to which the protein is added). The ionic current flowing through the membrane in response to a voltage step shows at first an exponential and then a linear rise with time. The relationship between the steady-state conductance, achieved immediately after the exponential portion, and voltage is S-shaped and is adequately fit by a Boltzmann distribution. The time constant (tau) of the exponential is also dependent on voltage, and the relation between these two parameters is asymmetric around Vo (voltage at which half of the channels are open). In both cases the steepness of the voltage dependence, a consequence of the number of effective gating particles (n) present in the channel, is greatly influenced by the pH of the bathing solutions. Thus, increasing the pH leads to a reduction in n, while acidic pH's have the opposite effects. This result is obtained either by changing the pH on both sides of the membrane or on only one side, be it cis or trans. On the other hand, changing pH on only one side by addition of an impermeant buffer fails to induce any change in n. At the single-channel level, pH had an effect both on the unitary conductance, doubling it in going from pH 4.5 to 8.2, as well as on the fraction of time the channels stay open, F(v). For a given voltage, F(v) is clearly diminished by increasing the pH. This titration of the voltage sensitivity leads to the conclusion that gating in the Colicin Ia molecule is accomplished by charged amino- acid residues present in the protein molecule. Our results also support the notion that these charged groups are inside the aqueous portion of the channel.
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Affiliation(s)
- R A Nogueira
- Department of Physiology, Faculty of Medicine of Ribeirão Preto, University of São Paulo, Brazil
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Nogueira RA, de Jesús SP, Leitão JM. [Initial results with the use of Ro 6-4793-1 in the treatment of malaria]. Hospital (Rio J) 1968; 74:979-85. [PMID: 5310134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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Nogueira RA, de Jesús SP, Leitão JM. [Initial results with Ro 6-4793-1 in malaria]. Hospital (Rio J) 1968; 74:979-85. [PMID: 5303781] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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