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The aim of the study was to evaluate the oral environment and the taste function of Japanese HIV-infected patients treated with antiretroviral therapy. Their median age of 73 patients taking anti-HIV drugs was 46 years. The median period of taking anti-HIV drugs was 30 months. The oral condition was evaluated by measurement of oral moisture, amount of saliva secretion, the number of oral bacteria, presence of oral candida, a taste test, and the number of missing teeth. The levels of oral moisture and secreted saliva were significantly lower in the HIV-infected group than in the healthy volunteer (control) group. The HIV-infected group showed a more robust decrease in taste sensation than the control group. The number of missing teeth was significantly higher in the HIV-infected group than in the control group. Furthermore, all of the evaluated oral conditions were worse in the HIV-infected patients whose CD4+ T lymphocyte counts were less than 500/mm3 than in the control group. It became clear that the patients taking anti-HIV drugs, especially the CD4+ count < 500/mm3 group, had a deteriorated oral environment and dysgeusia, suggesting that the management of oral hygiene is necessary to maintain oral health, which leads to systemic health.
Assuntos
Infecções por HIV , Paladar , Terapia Antirretroviral de Alta Atividade , Contagem de Linfócito CD4 , Infecções por HIV/tratamento farmacológico , Humanos , Japão/epidemiologia , Pessoa de Meia-IdadeRESUMO
The low-lying isomeric state of ^{229}Th provides unique opportunities for high-resolution laser spectroscopy of the atomic nucleus. We determine the energy of this isomeric state by taking the absolute energy difference between the excitation energy required to populate the 29.2-keV state from the ground state and the energy emitted in its decay to the isomeric excited state. A transition-edge sensor microcalorimeter was used to measure the absolute energy of the 29.2-keV γ ray. Together with the cross-band transition energy (29.2 keVâground) and the branching ratio of the 29.2-keV state measured in a recent study, the isomer energy was determined to be 8.30±0.92 eV. Our result is in agreement with the latest measurements based on different experimental techniques, which further confirms that the isomeric state of ^{229}Th is in the laser-accessible vacuum ultraviolet range.
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STUDY DESIGN: Retrospective study at a rehabilitation center. OBJECTIVES: Patients with spinal cord injury, even if they are wheelchair users, sometimes suffer from fractures of the lower limb bones. As their bones are too weak to have surgery, and because a precise reduction is not required for restoration, such patients are often indicated for conservative treatment. This case series study investigated the use of a hinged, soft-plastic brace as a conservative approach to treating fractures of the lower extremities of patients with spinal cord injury. SETTING: National Rehabilitation Center, Japan. METHODS: Fifteen patients (male, n=10; female, n=5; average age, 52.7 years) with 19 fractures of the femur or the tibia who were treated with a newly-developed hinged, soft-plastic brace were studied. All of them used wheelchairs. We analyzed the time taken for fracture union and for wearing orthotics, degree of malalignment, femorotibial angle and side effects. RESULTS: The fractures in this series were caused by relatively low-energy impact. The average time taken for fracture union was 80.1 (37-189) days, and the average amount of time spent wearing orthotics was 77.9 (42-197) days. On final X-ray imaging, the average femorotibial angle was 176.9° (s.d. ±8.90), and 15° of misalignment in the sagittal plane occurred in one patient. CONCLUSION: A hinged, soft-plastic brace is a useful option as a conservative approach for treating fractures of the lower extremities in patients with spinal cord injury.
Assuntos
Braquetes , Fraturas Ósseas/etiologia , Fraturas Ósseas/terapia , Extremidade Inferior/fisiopatologia , Plásticos/uso terapêutico , Traumatismos da Medula Espinal/complicações , Adulto , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos RetrospectivosRESUMO
BACKGROUND: Dental professionals have so many opportunities to use injection needles and sharp instruments during dental treatment that they face an increased risk of needlestick injuries. This retrospective study reports the utilization and clinical outcomes of occupational post-exposure prophylaxis (PEP) with anti-retroviral agents after being potentially exposed to HIV at the dental departments of Hiroshima University Hospital. OBJECTIVE: This study reports the utilization and clinical outcomes of occupational post-exposure prophylaxis (PEP) with antiretroviral agents after being potentially exposed to HIV at dental departments of Hiroshima University Hospital. METHODS: Data on the clinical status of HIV-infected source patients and information on HIV-exposed dental professionals from 2007 to 2018 were collected. RESULTS: Five dentists with an average experience of 5.6 years (1-15 years) were exposed. The averaged CD4-positive cell number and HIV-RNA load were 1176 (768-1898) /µl and less than 20 copies/ml, respectively, in all the patients. Two of the five HIV exposed dentists received PEP. Three months after the exposures, all of their results were negative in HIV antibody/antigen tests. CONCLUSION: ; These data might support the concept of "undetectable equals untransmittable", although HIV exposure in this study was not through sexual transmission.
Assuntos
Fármacos Anti-HIV/uso terapêutico , Antirretrovirais/uso terapêutico , Infecções por HIV/tratamento farmacológico , Ferimentos Penetrantes Produzidos por Agulha/tratamento farmacológico , Exposição Ocupacional/prevenção & controle , Profilaxia Pós-Exposição/métodos , Adulto , Clínicas Odontológicas/estatística & dados numéricos , Odontólogos/estatística & dados numéricos , Feminino , Hospitais Universitários/estatística & dados numéricos , Humanos , Japão , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Fatores de RiscoRESUMO
Cage bedding for laboratory rodents can influence animal wellbeing and thus the experimental data. In addition, a large amount of used bedding containing excrement is discharged as medical waste from life science institutes and breeding companies. We developed a ground-breaking system to improve fresh bedding and recycle used bedding by applying a soft hydrothermal process with high-temperature and high-pressure dry steam. The system removes both harmful organic components and aromatic hydrocarbons that can affect animals' metabolism. The purpose of the present study was to evaluate the chemical and physical properties of the improved fresh bedding and the recycled used bedding treated by the system. The results showed that 68-99% of the predominant aromatic hydrocarbons were removed from fresh bedding treated at 0.35 MPa and 140 degrees C for 120 min ('improved bedding'). In addition, 59.4-99.0% of predominant harmful organic compounds derived from excrement were removed from used bedding treated at 0.45 MPa and 150 degrees C for 60 min ('recycled bedding'). The soft hydrothermal treatment increased the number of acidic functional groups on the bedding surface and gave it the high adsorptive efficiency of ammonia gas. Harmful substances such as microorganisms, heavy metals and pesticides decreased below the detection limit. The results clearly showed that the improved and recycled bedding is safer for laboratory rodents and has the potential to ameliorate conditions in primary and secondary enclosures (e.g. cages and animal rooms) used for maintaining laboratory animals. This process may be one of the most advanced techniques in providing an alternative to softwood and other bedding, economizing through the recycling of used bedding and reducing bedding waste from animal facilities.
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Criação de Animais Domésticos/métodos , Animais de Laboratório , Roupas de Cama, Mesa e Banho/veterinária , Conservação dos Recursos Naturais/métodos , Bem-Estar do Animal , Animais , Camundongos , Ratos , Organismos Livres de Patógenos EspecíficosRESUMO
After major noncardiac thoracic operations, various types of arrhythmia would occur. Particularly atrial fibrillation (Af), have remained one of the most frequent complications. In the literatures, risk factors for post operative Af have identified age, male, extent of pulmonary resection and mediastinal lymph node dissection. When we would meet the patients complicated with arrhythmia, the etiology of it must be identified and treated before operations. If accidental arrhythmia occurred during or after operations, the etiology of arrhythmia as hypoxia, hypercapnea, electrolyte disorder, overhydration and cardiac ischemia would be checked and cleared at first. Then appropriate drugs should be considered to use due to the type of arrhythmia. In supraventricular tachyarrhythmia, especially Af, landiolol and verapamil would be effective for the rate control and disopyramide and procaineamide for the defibrillation. Lidocaine and propranolol would be an appropriate choice for ventricular tachyarrhythmia during operations. For ventricular tachyarrhythmia related with acute myocardial infarction, lidocaine and mexiletine would be proper. In bradyarrhythmias a temporary pacing should be the first choice for urgent therapy. A prompt assessment and an adequate therapy must be mandatory for the arrhythmias after major noncardiac thoracic operations.
Assuntos
Arritmias Cardíacas/terapia , Procedimentos Cirúrgicos Torácicos , Arritmias Cardíacas/etiologia , Humanos , Complicações Intraoperatórias/terapia , Complicações Pós-Operatórias/terapiaRESUMO
The NK-2 homeobox genes have been shown to play critical roles in the development of specific organs and tissues. Nkx2.6 is a member of the NK-2 homeobox gene family and is most closely related to the Drosophila tinman gene. Nkx2.6 is expressed in the caudal pharyngeal pouches, the caudal heart progenitors, the sinus venosus, and the outflow tract of the heart and in a short segment of the gut at early stages of embryogenesis. To investigate the function of Nkx2.6 in vivo, we generated mice with null mutations of Nkx2.6 by the gene targeting technique. Homozygous Nkx2.6 mutant mice were viable and fertile. There were no obvious abnormalities in the caudal pharyngeal pouch derivatives (the thymus, parathyroid glands, and thyroid gland), heart, and gut. Expression of Nkx2.6 overlaps that of Nkx2.5 in the pharynx and heart and that of Nkx2.3 in the pharynx. Interestingly, in mutant embryos homozygous for Nkx2.6, Nkx2.5 expression extended to the lateral side of the pharynx, suggesting a compensatory function of Nkx2.5 in the mutant pharyngeal pouches.
Assuntos
Regulação da Expressão Gênica , Proteínas de Homeodomínio/genética , Animais , Marcação de Genes , Camundongos , MutaçãoRESUMO
Nkx2.5 and Nkx2.6 are murine homologs of Drosophila tinman. Their genes are expressed in the ventral region of the pharynx at early stages of embryogenesis. However, no abnormalities in the pharynges of embryos with mutations in either Nkx2.5 or Nkx2.6 have been reported. To examine the function of Nkx2.5 and Nkx2.6 in the formation of the pharynx, we generated and analyzed Nkx2.5 and Nkx2.6 double-mutant mice. Interestingly, in the double-mutant embryos, the pharynx did not form properly. Pharyngeal endodermal cells were largely missing, and the mutant pharynx was markedly dilated. Moreover, we observed enhanced apoptosis and reduced proliferation in pharyngeal endodermal cells of the double-mutant embryos. These results demonstrated a critical role of the NK-2 homeobox genes in the differentiation, proliferation, and survival of pharyngeal endodermal cells. Furthermore, the development of the atrium was less advanced in the double-mutant embryos, indicating that these two genes are essential for both pharyngeal and cardiac development.
Assuntos
Proteínas de Drosophila , Genes Homeobox , Proteínas de Homeodomínio/metabolismo , Faringe/embriologia , Fatores de Transcrição , Proteínas de Xenopus , Animais , Apoptose , Divisão Celular , Drosophila melanogaster/genética , Desenvolvimento Embrionário e Fetal , Endoderma/citologia , Expressão Gênica , Coração/embriologia , Proteína Homeobox Nkx-2.5 , Proteínas de Homeodomínio/química , Proteínas de Homeodomínio/genética , Hibridização In Situ , Marcação In Situ das Extremidades Cortadas , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Miocárdio/metabolismo , Faringe/química , Faringe/citologia , Fenótipo , Proteínas Repressoras/química , Proteínas Repressoras/genética , Transativadores/química , Transativadores/genéticaRESUMO
Cyclin-dependent kinase 2 (cdk2) plays a critical role in the G1- to S-phase checkpoint of the cell cycle. Adult cardiomyocytes are believed to withdraw from the cell cycle. To determine whether forced overexpression of cdk2 results in altered cell-cycle regulation in the adult heart, we generated transgenic mice specifically overexpressing cdk2 in hearts. Transgenic hearts expressed high levels of both cdk2 mRNA and catalytically active cdk2 proteins. Cdk2 overexpression significantly increased the levels of cdk4 and cyclins A, D3, and E. There was an increase in both DNA synthesis and proliferating cell nuclear antigen levels in the adult transgenic hearts. The ratio of heart weight to body weight in cdk2 transgenic mice was significantly increased in neonatal day 2 but not in adults compared with that of wild-type mice. Analysis of dispersed individual adult cardiomyocytes showed a 5.6-fold increase in the proportion of smaller mononuclear cardiomyocytes in the transgenic mice. Echocardiography revealed that transgenic heart was functionally normal. However, adult transgenic ventricles expressed beta-myosin heavy chain and atrial natriuretic factor. Surgically induced pressure overload caused an exaggerated maladaptive hypertrophic response in transgenic mice but did not change the proportion of mononuclear cardiomyocytes. The data suggest that overexpression of cdk2 promotes smaller, less-differentiated mononuclear cardiomyocytes in adult hearts that respond in an exaggerated manner to pressure overload.
Assuntos
Quinases relacionadas a CDC2 e CDC28 , Quinases Ciclina-Dependentes/biossíntese , Miocárdio/citologia , Proteínas Serina-Treonina Quinases/biossíntese , Animais , Western Blotting , Bromodesoxiuridina/metabolismo , Ciclo Celular/genética , Divisão Celular , Núcleo Celular/química , Quinase 2 Dependente de Ciclina , DNA/análise , DNA/biossíntese , Expressão Gênica , Camundongos , Camundongos Transgênicos , Modelos Animais , Pressão , Antígeno Nuclear de Célula em Proliferação/metabolismoRESUMO
A lipolytic substance in the ascites fluid of mice with Sarcoma 180, called toxohormone-L, was purified and characterized. The lipolytic activity of toxohormone-L was measured in vitro using rat adipose tissue slices. Toxohormone-L, purified approximately 90-fold from the ammonium sulfate fraction, gave a single band on polyacrylamide gel electrophoresis. Its molecular weight was about 75,000, and its isoelectric point was 4.7. Toxohormone-L is heat labile and nondialyzable, but, on its digestion with trypsin, an active fragment that was heat stable and dialyzable was produced. Toxohormone-L is a protein and is also present in the ascites fluid of patients with hepatoma and Grawitz's tumor.
Assuntos
Endotoxinas/isolamento & purificação , Lipólise , Proteínas de Neoplasias/isolamento & purificação , Sarcoma Experimental/análise , Animais , Exsudatos e Transudatos/análise , Ponto Isoelétrico , Camundongos , Peso Molecular , Triglicerídeos/metabolismoRESUMO
OBJECTIVE: To find out the optimal surgical indication in stage IV lung cancer patients, we evaluated them retrospectively. METHODS & RESULTS: From 1975 to 2005, 62 patients without multiple metastases were operated at our hospital. The most common histological type was adenocarcinoma (67.7%). The metastatic lesions were lung (33.9%), brain (24.2%), liver, bone, adrenal gland and so on. The overall survival rate of stage IV lung cancer was 10.4% at 5-year. Five-year survival for patients with lung or brain metastasis who had no lymph node metastasis were significantly more superior than those with lymph node metastasis (p=0.0389, 0.0021). Four of 62 patients had 5-year survival. Two were lung and the others were brain and adrenal gland metastasis without lymph node metastasis. CONCLUSION: Stage IV lung cancer with lung or brain or adrenal gland metastasis without lymph node metastasis should be resected.
Assuntos
Neoplasias Pulmonares/patologia , Neoplasias Pulmonares/cirurgia , Adenocarcinoma/mortalidade , Adenocarcinoma/cirurgia , Adulto , Idoso , Idoso de 80 Anos ou mais , Neoplasias Encefálicas/mortalidade , Neoplasias Encefálicas/secundário , Feminino , Humanos , Neoplasias Pulmonares/mortalidade , Masculino , Pessoa de Meia-Idade , Estadiamento de Neoplasias/mortalidade , Estudos Retrospectivos , Análise de SobrevidaRESUMO
Overexpression of MYCN is a hallmark of neuroblastoma (NB). ALK(R1275Q), an activating mutation of ALK (anaplastic lymphoma kinase), has been found in sporadic and familial NB patients. In this report, we demonstrated that ALK(R1275Q) knock-in, MYCN transgenic compound mice developed NB with complete penetrance. Transcriptome analysis revealed that ALK(R1275Q) globally downregulated the expression of extracellular matrix (ECM)- and basement membrane (BM)-associated genes in both primary neuronal cells and NB tumors. Accordingly, ALK(R1275Q)/MYCN tumors exhibited reduced expression of ECM/BM-related proteins as compared with MYCN tumors. In addition, on MYCN transduction, ALK(R1275Q)-expressing neuronal cells exhibited increased migratory and invasive activities. Consistently, enhanced invasion and metastasis were demonstrated in ALK(R1275Q)/MYCN mice. These results collectively indicate that ALK(R1275Q) confers a malignant potential on neuronal cells that overexpress MYCN by impairing normal ECM/BM integrity and enhancing tumor growth and dissemination. Moreover, we found that crizotinib, an ALK inhibitor, almost completely inhibited the growth of ALK(R1275Q)/MYCN tumors in an allograft model. Our findings provided insights into the cooperative mechanism of the mutated ALK and overexpressed MYCN in the pathogenesis of NB and demonstrated the effectiveness of crizotinib on ALK(R1275Q)-positive tumors.
Assuntos
Matriz Extracelular/metabolismo , Mutação , Proteína Proto-Oncogênica N-Myc/genética , Neuroblastoma/etiologia , Receptores Proteína Tirosina Quinases/genética , Quinase do Linfoma Anaplásico , Animais , Crizotinibe , Camundongos , Camundongos Endogâmicos C57BL , Invasividade Neoplásica , Neuroblastoma/tratamento farmacológico , Neuroblastoma/genética , Neuroblastoma/patologia , Pirazóis/uso terapêutico , Piridinas/uso terapêutico , Receptores Proteína Tirosina Quinases/antagonistas & inibidores , Receptores Proteína Tirosina Quinases/fisiologiaRESUMO
The Hitomi Soft X-ray Spectrometer (SXS) was a pioneering non-dispersive imaging x-ray spectrometer with 5 eV FWHM energy resolution, consisting of an array of 36 silicon-thermistor microcalorimeters at the focus of a high-throughput soft x-ray telescope. The instrument enabled astrophysical plasma diagnostics in the 0.3-12 keV band. We introduce the SXS calibration strategy and corresponding ground calibration measurements that took place from 2012-2015, including both the characterization of the microcalorimeter array and measurements of the x-ray transmission of optical blocking filters.
RESUMO
The nature of the binding of saccharides to Ricinus communis agglutinin was studied by ultraviolet difference spectroscopy. Upon binding of galactose and galactose-containing saccharides, R. communis agglutinin displayed difference spectra with an extreme maximum at 291-293 nm and a smaller maximum at 284-285 nm. Such difference spectra suggest that the environment of a tryptophan residue located at or near the saccharide-binding site of R. communis agglutinin is being changed by an interaction between a tryptophan residue and the bound saccharides. The value of the difference spectra (delta epsilon) increased upon progressive addition of saccharide until the saccharide binding site was saturated with ligand. From the increase in delta epsilon at 291-293 nm, the association constants were obtained for the R. communis agglutinin-saccharide interaction over the temperature range 5-35 degrees C and various pH values. The results clearly demonstrate that the association constants are nearly equal in the range of pH 5-8, but decrease beyond the above pH range and with elevation of temperature. From the thermodynamic parameters for the binding of various saccharides to R. communis agglutinin, we suggest that there exists a subsite structure in the saccharide-binding site of the R. communis agglutinin molecule.
Assuntos
Metabolismo dos Carboidratos , Lectinas , Lectinas de Plantas , Sítios de Ligação , Galactose/metabolismo , Concentração de Íons de Hidrogênio , Lactose/metabolismo , Metilgalactosídeos/metabolismo , Rafinose/metabolismo , Espectrofotometria Ultravioleta , Temperatura , TriptofanoRESUMO
Carboxyl ester hydrolase was obtained from rat epididymal adipose tissue in an electrophoretically homogeneous form. Purification was achieved by acetone precipitation, followed by successive chromatographies on DEAE-cellulose and hydroxyapatite and then isoelectric focusing. The monomeric molecular weight of the enzyme was 65,000 and the enzyme associated to form trimers. The enzyme had an isoelectric point at pH 5.9 and contained 2.1% carbohydrate moiety per protein with a molecular weight of 65,000. The amino terminal residue of the enzyme was glycine. The enzyme catalyzed the hydrolysis of short chain triacylglycerols such as tributyrin and medium chain monoacylglycerols such as monocaprin, but not the hydrolysis of cholesterol ester. The optimum pH for the enzymatic function of this enzyme for methyl butylate was 8.0. An antibody against the highly purified enzyme preparation induced in rabbits strongly inhibited the esterase of rat adipose tissue, but did not inhibit the esterase of rat liver, intestinal mucosa and serum.
Assuntos
Tecido Adiposo/enzimologia , Hidrolases de Éster Carboxílico/isolamento & purificação , Aminoácidos/análise , Animais , Hidrolases de Éster Carboxílico/antagonistas & inibidores , Masculino , Peso Molecular , Compostos Organofosforados/farmacologia , Ratos , Ratos Endogâmicos , Especificidade por SubstratoRESUMO
Changes in the activity of membrane bound ATPase of Sarcoma 180 cells caused by immunoglobulin G (IgG) of anti-Sarcoma 180 was investigated in relation to the incorporation of amino acid by the cells. Enzymatic activity of ATPase was increased up to 160% of the original activity upon incubation of the cell with IgG. Kinetic studies showed that IgG did not change the affinity of this enzyme for the substrate, but exerted influence upon catalytic efficiency of the enzyme. The rate of incorporation of leucine into Sarcoma 180 cells was also affected by IgG, as observed in the effect of IgG on the enzymatic reaction of the cells.
Assuntos
Imunoglobulina G/metabolismo , Sarcoma 180/imunologia , ATPase Trocadora de Sódio-Potássio/metabolismo , Animais , Anticorpos Antineoplásicos , Adesão Celular , Membrana Celular/enzimologia , Leucina/metabolismo , Sarcoma 180/enzimologia , Sarcoma 180/metabolismo , ATPase Trocadora de Sódio-Potássio/imunologiaRESUMO
The ribosomal protein L2 (BstL2) from Bacillus stearothermophilus is a primary 23S rRNA binding protein. We made use of site-directed mutagenesis to identify essential basic and aromatic amino acid residues for 23S rRNA binding. Four mutants, R68Q, K70Q, R86Q, and R155Q, in which Arg-68, Lys-70, Arg-86, and Arg-155, respectively, are replaced by the Gln residue. showed reduced binding affinities as compared with that of the wild type BstL2 (a binding constant K=8.93 microM(-1)): K values of these mutants range between 0.24 and 1.86 microM(-1). As for aromatic amino acids, replacements of Phe-66, Tyr-95 or Tyr-102 by alanine significantly abolished the binding affinities. CD analysis of the mutant proteins indicated that the mutations of four basic residues (Arg-68, Lys-70, Arg-86 and Arg-155) did not affect protein structure, whereas those of aromatic residues (Phe-66, Tyr-95, and Tyr-102) appeared to cause slight structural perturbations. These results, together with sequence comparison of L2 family proteins, suggest that Arg-86 and Arg-155 in BstL2 may act as positively charged recognition groups for negatively charged phosphate backbone of the 23S rRNA, and that Phe-66, Tyr-95, and Tyr-102 may be candidate residues which stabilize the BstL2-23S rRNA interaction through intramolecular interactions.
Assuntos
Aminoácidos/química , RNA Ribossômico 23S/metabolismo , Proteínas Ribossômicas/metabolismo , Alanina/química , Sequência de Aminoácidos , Aminoácidos/genética , Arginina/química , Clonagem Molecular , Geobacillus stearothermophilus/genética , Glicina/química , Lisina/química , Dados de Sequência Molecular , Mutagênese Sítio-Dirigida , Plasmídeos , Reação em Cadeia da Polimerase , Proteínas Ribossômicas/biossíntese , Proteínas Ribossômicas/química , Alinhamento de SequênciaRESUMO
Basic amphipathic beta-structural peptides, Ac-(Ser-Val-Lys-Val)n-NHCH3 (1n, n = 1-3) and Ac-(Lys-Val)n-NHCH3 (2n, n = 2-4), were synthesized and their interaction with DPPC and DPPC-DPPG (3:1) bilayers was studied by CD, dye-leakage and fluorescence experiments. The CD data indicated that oligopeptides consisting of more than eight residues with alternating hydrophobic (Val) and hydrophilic amino acids (Ser and Lys) were able to form an amphipathic beta-structure in acidic phospholipid bilayers, but not or weakly in aqueous solution and in neutral phospholipid bilayers. The dye-leakage experiment showed that the basic amphipathic beta-structural peptides interact with acidic phospholipid bilayers to perturb them, but less effectively compared with basic amphipathic alpha-helical peptides. Fluorescent spectroscopic data suggest that hydrophobic side of the amphipathic peptides may immerse into membrane without deep penetration. Based on these results, we postulate that the formation of the basic amphipathic beta-structure on acidic lipid bilayers may be due to the combined effect of electrostatic and hydrophobic interactions between basic peptides and acidic lipid bilayers.
Assuntos
Bicamadas Lipídicas/metabolismo , Lipossomos/metabolismo , Peptídeos/síntese química , Fosfolipídeos/metabolismo , 1,2-Dipalmitoilfosfatidilcolina/metabolismo , Sequência de Aminoácidos , Dicroísmo Circular , Corantes Fluorescentes , Concentração de Íons de Hidrogênio , Dados de Sequência Molecular , Peptídeos/metabolismo , Fosfatidilgliceróis/metabolismo , Conformação Proteica , Cloreto de Sódio/farmacologia , Espectrometria de FluorescênciaRESUMO
The peptide-induced fusion of neutral and acidic liposomes was studied in relation to the amphiphilicities evaluated by alpha-helical contents of peptides by means of a carboxyfluorescein leakage assay, light scattering, a membrane intermixing assay and electron microscopy. An amphipathic mother peptide, Ac-(Leu-Ala-Arg-Leu)3-NHCH3 (4(3], and its derivatives, [Pro6]4(3) (1), [Pro2,6]4(3) (2), and [Pro2,6,10]4(3) (3), which have very similar hydrophobic moments, caused a leakage of contents from small unilamellar vesicles composed of egg yolk phosphatidylcholine and egg yolk phosphatidic acid (3:1). The abilities of the peptides to induce the fusion of the acidic liposomes increased with increasing alpha-helical content: in acidic liposomes the helical contents were in the order of 4(3) greater than 1 greater than 2 greater than 3 (Lee et al. (1989) Chem. Lett., 599-602). Electron microscopic data showed that 1 caused a transformation of the small unilamellar vesicles (20-50 nm in diameter) to large ones (100-300 nm). Based on the fact that these peptides have very similar hydrophobic moments despite of decreasing in the mean residue hydrophobicities to some extent, it was concluded that the abilities of the peptides to induce the fusion of liposomes depend on the extent of amphiphilic conformation evaluated by alpha-helical contents of the peptides in the presence of liposomes. For neutral liposomes of egg yolk phosphatidylcholine, all the proline-containing peptides showed no fusogenic ability but weak leakage abilities, suggesting that the charge interaction between the basic peptides and acidic phospholipid is an important factor to induce the perturbation and fusion of the bilayer.
Assuntos
Lipossomos , Peptídeos/química , Sequência de Aminoácidos , Fluoresceínas/química , Luz , Microscopia Eletrônica , Dados de Sequência Molecular , Ácidos Fosfatídicos/fisiologia , Fosfatidilcolinas/químicaRESUMO
Several cationic model peptides of the prepiece moieties of mitochondrial protein precursors were found to be active against Gram-positive bacteria, but inactive against Gram-negative bacteria. The CD spectra of the model peptides in the presence of phospholipid liposomes demonstrated that antimicrobial activity was generally in parallel with the content of the alpha-helical amphiphilicity. The results indicate that appropriate positioning of cationic and hydrophobic groups in the stable alpha-helical structure of the peptides is important to exhibit antimicrobial activity. These peptides also have an ability to leak carboxyfluorescein from acidic and neutral phospholipid vesicles, suggesting that the peptides interact with the bacterial membrane to perturb it.