RESUMEN
We report the first observation of room temperature spontaneous electric polarization in an electronic ferroelectric material, a YbFe2O4 single crystal. The observation was based on second harmonic generation (SHG), a nonlinear optical process. Tensor analysis of the SHG signal revealed that this material has a polar charge superstructure with Cm symmetry. This result settles the long-term discussion on the uncertainty about electronic ferroelectric properties, including the charge order structure. We present a complete picture of the polar charge ordering of this material via consistent results from two different characterization methods. The SHG signal shows the same temperature dependence as the superlattice signal observed in neutron diffraction experiments. These results prove ferroelectric coupling to electron ordering in YbFe2O4, which results in electronic ferroelectricity which is enabled by the real space ordering of iron cations with different valences. The existence of electronic ferroelectricity holds promise for future electronics technologies where devices run a thousand times faster than frequency of the present CPU (a few gigahertz) embedded in smartphones, etc.
RESUMEN
In strongly correlated electron systems, enhanced fluctuations in the proximity of the ordered states of electronic degrees of freedom often induce anomalous electronic properties such as unconventional superconductivity. While spin fluctuations in the energy-momentum space have been studied widely using inelastic neutron scattering, other degrees of freedom, i.e., charge and orbital, have hardly been explored thus far. Here, we use resonant inelastic x-ray scattering to observe charge fluctuations proximate to the charge-order phase in transition metal oxides. In the two-leg ladder of Sr(14-x)Ca(x)Cu24O41, charge fluctuations are enhanced at the propagation vector of the charge order (qCO) when the order is melted by raising temperature or by doping holes. In contrast, charge fluctuations are observed not only at qCO but also at other momenta in a geometrically frustrated triangular bilayer lattice of LuFe2O4. The observed charge fluctuations have a high energy (~1 eV), suggesting that the Coulomb repulsion between electrons plays an important role in the formation of the charge order.
RESUMEN
To investigate the roles of G-protein receptor kinases (GRKs) in the light responses of vertebrate photoreceptors, we generated transgenic zebrafish lines, the rods of which express either cone GRK (GRK7) or rod GRK (GRK1) in addition to the endogenous GRK1, and we then measured the electrophysiological characteristics of single-cell responses and the behavioural responses of intact animals. Our study establishes the zebrafish expression system as a convenient platform for the investigation of specific components of the phototransduction cascade. The addition of GRK1 led to minor changes in rod responses. However, exogenous GRK7 in GRK7-tg animals led to lowered rod sensitivity, as occurs in cones, but surprisingly to slower response kinetics. Examination of responses to long series of very dim flashes suggested the possibility that the GRK7-tg rods generated two classes of single-photon response, perhaps corresponding to the interaction of activated rhodopsin with GRK1 (giving a standard response) or with GRK7(giving a very small response). Behavioural measurement of optokinetic responses (OKR) in intact GRK7-tg zebrafish larvae showed that the overall rod visual pathway was less sensitive, in accord with the lowered sensitivity of the rods. These results help provide an understanding for the molecular basis of the electrophysiological differences between cones and rods.
Asunto(s)
Quinasas de Receptores Acoplados a Proteína-G/metabolismo , Fototransducción , Células Fotorreceptoras Retinianas Bastones/enzimología , Animales , Animales Modificados Genéticamente , Quinasa 1 del Receptor Acoplado a Proteína-G/genética , Quinasa 1 del Receptor Acoplado a Proteína-G/metabolismo , Quinasas de Receptores Acoplados a Proteína-G/genética , Cinética , Larva/enzimología , Potenciales de la Membrana , Modelos Biológicos , Fosforilación , Estimulación Luminosa , Rodopsina/metabolismo , Umbral Sensorial , Visión Ocular , Pez Cebra , Proteínas de Pez CebraRESUMEN
A 31-year-old male presented with increase of aortic valve regurgitation 5 years after implantation of Prima Plus Stentless bioprosthesis in a bicuspid aortic valve. He underwent redo aortic valve replacement with a mechanical valve concomitant with replacement of the ascending aorta. Pathological examination of the explanted stentless valve presented no inflammatory cell infiltration. The prosthetic valve regurgitation was considered to be due to small injury at the 1st operation.
Asunto(s)
Insuficiencia de la Válvula Aórtica/cirugía , Bioprótesis/efectos adversos , Prótesis Valvulares Cardíacas/efectos adversos , Adulto , Humanos , Masculino , Diseño de Prótesis , ReoperaciónRESUMEN
BACKGROUND: Surgical treatment for ischemic heart disease (IHD) has changed after the administration of off-pump coronary artery bypass grafting (CABG) [OPCAB] and left ventricular restoration (LVR). We studied the development of the treatment and the surgical results. PATIENTS AND METHODS: Since May 2000 when the indication for OPCAB and LVR was defined, surgical treatment for IHD has been performed in 1,251 patients. The age ranged from 32 to 91 (mean 66 +/- 10) years and there were 977 men and 274 women. The elective operation was 1,130 and emergency 121. Definite indication for OPCAB was calcified ascending aorta, significant cerebrovascular disease, hemorrhagic tendency, and single vessel lesion. Conventional CABG (C-CAB) was the first choice and morbidity and surgical results were examined. RESULTS: OPCAB was performed in 297 (29.9%) and combined operation with CABG was required in 258 patients (20.6%). In elective operation, hospital mortality was one in OPCAB and one in C-CAB. In OPCAB and C-CAB, stroke was none and one, and mediastinitis was 0 and 0, respectively. CONCLUSION: The technique for OPCAB is necessary for CABG; however, it is not appropriate to persist with only OPCAB for CABG. Combined operation is often required with CABG and it is essential to perform precise C-CAB.
Asunto(s)
Isquemia Miocárdica/cirugía , Adulto , Anciano , Anciano de 80 o más Años , Puente de Arteria Coronaria , Puente de Arteria Coronaria Off-Pump , Femenino , Humanos , Masculino , Persona de Mediana EdadRESUMEN
We have previously reported overlapping cardiac volume reduction operation (OLCVR) for dilated cardiomyopathy. Because of the acceptable clinical outcome and especially the excellent ellipsoidal shape of the left ventricle (LV) after surgery, we extended this indication for ischemic cardiomyopathy (ICM) with dilated LV. In such cases we combined OLCVR with mitral annuloplasty and papillary muscles approximation (PMA), called integrated overlapping ventriculoplasty (IOLVP). From March 2003 to July 2004, we performed IOLVP with coronary artery bypass grafting (CABG) for 8 patients who were diagnosed ICM. There is no operative mortality. Pre- and postoperative hemodynamics data are follows: LV ejection fraction (LVEF) improved from 22.4 +/- 11.9 to 33.4 +/- 10.5%, LV end-diastolic volume index (LVEDVI) decreased from 155.5 +/- 26.5 to 93.7 +/- 13.5 ml/m2 and LV end-diastolic diameter (LVDd) diminished from 66.0 +/- 8.9 to 60.5 +/- 8.4mm. Mitral regurgitation changed from 2.6 +/- 0.8 to 0.1 +/- 0.2 degree. New York Heart Association (NYHA) functional class improved from 3.3 +/- 0.5 to 1.3 +/- 0.5. LV shape became ellipsoidal without akinesis lesion. IOLVP is considered as a good option for ICM with dilated left ventricle.
Asunto(s)
Cardiomiopatía Dilatada/cirugía , Ventrículos Cardíacos/cirugía , Isquemia Miocárdica/cirugía , Anciano , Procedimientos Quirúrgicos Cardíacos/métodos , Cardiomiopatía Dilatada/diagnóstico por imagen , Puente de Arteria Coronaria , Ecocardiografía , Femenino , Humanos , Masculino , Persona de Mediana Edad , Insuficiencia de la Válvula Mitral/complicaciones , Isquemia Miocárdica/diagnóstico por imagen , Músculos Papilares/diagnóstico por imagen , Función Ventricular IzquierdaRESUMEN
The patient was 75-year-old woman. The patient was referred to our hospital for operation due to a developing right coronary artery aneurysm. The coronary artery angiography showed that the aneurysm was 3 cm in diameter which had not existed two years previously, and with a 75% distal stenosis. The operation was made during cardiac arrest. A sapheous vein graft was used to bypass to the distal artery first. Then the aneurysm was resected, and both proximal and distal arteries were ligated. The pacemaker was implanted on the third postoperative day for sick sinus syndrome, the patient got a better recovery. Surgical treatment should be recommended to coronary artery aneurysm, and sapheous vein was a good selection for bypass graft when the diameter of native artery was relatively large.
Asunto(s)
Aneurisma Coronario/cirugía , Puente de Arteria Coronaria , Anciano , Procedimientos Quirúrgicos Cardíacos/métodos , Aneurisma Coronario/complicaciones , Aneurisma Coronario/patología , Puente de Arteria Coronaria/métodos , Enfermedad de la Arteria Coronaria/complicaciones , Femenino , Humanos , Vena Safena/trasplanteRESUMEN
OBJECTIVES: This study was designed to correlate fetuses in a normal prenatal population who exhibited transient nuchal translucency (NT) with both prenatal course and pregnancy outcome. METHODS: The fetuses with abnormal NT were followed by ultrasonography at 1-2-week intervals during their prenatal course. Fetuses with NT who exhibited no detectable congenital malformations were defined as the NTO group; fetuses with abnormal NT and structural malformations but no chromosomal abnormalities were placed in the SM group; and fetuses with abnormal NT, structural malformations, and chromosomal abnormalities were categorized as the CA group. The groups were compared by: maternal age, weeks of gestation by ultrasound and the NT value at the initial exam, the maximum NT value, and the duration of abnormal NT. RESULTS: During the study period, 92 fetuses with abnormal NT were found, monochorionic twins excluded. Of the 92 fetuses, 80 were in the NTO group, 10 were in the SM group, and two were in the CA group. The maternal age and the gestational weeks at the initial diagnosis were not significantly different in the NTO and the SM groups. However, the NT value at the initial diagnosis, maximum NT value, and the duration of abnormal NT were significantly greater in the SM group than those values in the NTO group. CONCLUSIONS: Fetuses with transient nuchal translucency commonly had structural malformations, particularly fetuses with significant and large persistent NT.
Asunto(s)
Aberraciones Cromosómicas/embriología , Cuello/embriología , Resultado del Embarazo , Adulto , Femenino , Edad Gestacional , Humanos , Edad Materna , Cuello/diagnóstico por imagen , Embarazo , Ultrasonografía PrenatalRESUMEN
We evaluated the potential ischemia of the forearm after harvesting of radial artery (RA) for coronary artery bypass grafting (CABG) by near infrared spectroscopy (NIRS). The subjects consist of two groups; patients group (group P) including 18 patients who received CABG with RA and control group (group C) including 9 healthy volunteers. Group P was divided into two groups; early post operative group (group E, n = 11) and mid-term post operative group (group M, n = 7). NIRS was used to measure the recovery time (RT) in the muscles of the forearm during occlusion test. There was a significant prolongation of the RT in group P than group C. There was no significant difference of the RT between group E and group M. In conclusion, harvesting of RA may cause ischemia of the forearm and it may continue for a long time.
Asunto(s)
Puente de Arteria Coronaria , Antebrazo/irrigación sanguínea , Isquemia/diagnóstico , Arteria Radial , Espectroscopía Infrarroja Corta , Anciano , Femenino , Predicción , Humanos , Masculino , Persona de Mediana Edad , Flujo Sanguíneo Regional , Recolección de Tejidos y ÓrganosRESUMEN
Vertebrate cryptochrome homologs (CRYs) are negative regulators for the transcription/translation-based autoregulatory feedback loop of the circadian clock. In this study we identified two Cry genes in the chicken, cCry1 and cCry2, which are expressed in the pineal gland. Messenger RNA levels of both cCry1 and cCry2 displayed circadian oscillation in cultured pineal cells under light/dark and constant darkness conditions. Noticeably, their mRNA levels during the light period were significantly higher than those in the dark, indicating light-dependent up-regulation of the two Cry genes mediated by photoreceptor(s) intrinsic to the chick pineal cells. These cCRYs inhibited E-box element-dependent cBMAL1/2-cCLOCK-induced transcription, suggesting that the chick pineal circadian oscillator is composed of molecules that are functionally similar to those of mammals but are subject to light-regulation distinct from the mammalian clockwork.
Asunto(s)
Ritmo Circadiano/fisiología , Proteínas de Drosophila , Proteínas del Ojo , Flavoproteínas/genética , Células Fotorreceptoras de Invertebrados , Glándula Pineal/fisiología , Transcripción Genética/fisiología , Secuencia de Aminoácidos , Animales , Pollos , Criptocromos , Oscuridad , Expresión Génica/fisiología , Iluminación , Datos de Secuencia Molecular , Receptores Acoplados a Proteínas GRESUMEN
BACKGROUND: To report clinical experiences with disseminated intravascular coagulation (DIC) associated with aortic aneurysms (AA) and discuss therapeutic strategy. DESIGN AND SETTINGS: uncontrolled, observational study in a university hospital. PATIENTS: among 547 patients with AA treated between 1991 and 1999, 10 patients (7 males, 3 females, mean age 68.5+/-2.5) presenting a preoperative DIC score (defined by the Ministry of Health and Welfare in Japan) of 6 or higher were analyzed. The etiology was dissection for 5 and non-dissection for 5 patients. Six of 10 patients had a bleeding tendency. Eight patients received preoperative anticoagulant therapy. Prosthetic replacement was undertaken for 8 patients except for 2 patients in poor condition. RESULTS: There were no operative deaths in 8 surgical cases. One non-surgical case died of deteriorated bleeding tendency. The mean DIC score was 8.0+/-0.6 at admission, which was reduced to 4.4+/-0.5 at discharge (p<0.05). Prothrombin time, platelet counts, and fibrinogen levels tended to be normalized by the 7th postoperative day. Serum FDP levels decreased with surgery, but tended to increase at the time of discharge and the later follow-up period. Hematologic disturbances and bleeding tendency recurred in 2 patients in the follow-up period. CONCLUSIONS: In the majority of patients presenting DIC with aortic aneurysm, surgical treatment can be performed safely if adequately managed by anticoagulant therapy. Consumptive coagulopathy usually resolved after surgical intervention, but some patients developed DIC in the later period. If DIC recurs, it is essential to search for contributory causes.
Asunto(s)
Aneurisma de la Aorta/complicaciones , Coagulación Intravascular Diseminada/complicaciones , Anciano , Anticoagulantes/administración & dosificación , Aneurisma de la Aorta/cirugía , Distribución de Chi-Cuadrado , Coagulación Intravascular Diseminada/diagnóstico , Femenino , Hemorragia/etiología , Humanos , Masculino , Persona de Mediana Edad , Estadísticas no Paramétricas , Tomografía Computarizada por Rayos X , Resultado del TratamientoRESUMEN
BACKGROUND: In a transcription/translation-based autoregulatory feedback loop of vertebrate circadian clock systems, a BMAL1-CLOCK heterodimer is a positive regulator for the transcription of the negative element gene Per. The chicken pineal gland represents a photosensitive clock tissue, but the pineal clock genes constituting the oscillator loop have been less well characterized. RESULTS: We identified expression of the Per2, Bmal1, Bmal2 and Clock genes in the chicken pineal gland. Messenger RNA levels of these genes exhibited overt circadian rhythms in the pineal cells, both in vivo and in culture. In vitro functional analyses revealed the formation of cBMAL1-cCLOCK and cBMAL2-cCLOCK heteromers. Both of the cBMAL-cCLOCK heteromers activated E-box element-dependent transcription, which was negatively regulated by cPER2 in luciferase assays. Co-expression of cCLOCK, cBMAL1 and cBMAL2 co-operatively activated E-box element-dependent transcription, and a greater level of expression of cBMAL2 inhibited the activation. In the cultured pineal cells, an over-expression of either cBMAL1 or cBMAL2 disrupted the circadian rhythm of melatonin production. CONCLUSION: The functional characterization of the chicken pineal clock molecules supports the key roles of BMAL1, BMAL2 and CLOCK which contribute to the E-box-dependent transcriptional regulation in the circadian clock system.
Asunto(s)
Pollos/fisiología , Ritmo Circadiano/fisiología , Glándula Pineal/metabolismo , Transactivadores/metabolismo , Factores de Transcripción/metabolismo , Factores de Transcripción ARNTL , Secuencia de Aminoácidos , Animales , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico , Northern Blotting , Proteínas CLOCK , Proteínas de Ciclo Celular , Células Cultivadas , Cartilla de ADN/química , Elementos E-Box/genética , Proteínas del Ojo/genética , Proteínas del Ojo/metabolismo , Glutatión Transferasa/metabolismo , Secuencias Hélice-Asa-Hélice/fisiología , Luz , Ratones , Datos de Secuencia Molecular , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Proteínas Circadianas Period , Reacción en Cadena de la Polimerasa , ARN Mensajero/metabolismo , Homología de Secuencia de Aminoácido , Transactivadores/genética , Factores de Transcripción/genéticaRESUMEN
The chicken pineal gland contains the autonomous circadian oscillator together with the photic-input pathway. We searched for chicken pineal genes that are induced by light in a time-of-day-dependent manner, and isolated chicken homolog of bZIP transcription factor E4bp4 (cE4bp4) showing high similarity to vrille, one of the Drosophila clock genes. cE4bp4 was expressed rhythmically in the pineal gland with a peak at very early (subjective) night under both 12-h light/12-h dark cycle and constant dark conditions, and the phase was nearly opposite to the expression rhythm of cPer2, a chicken pineal clock gene. Luciferase reporter gene assays showed that cE4BP4 represses cPer2 promoter through a E4BP4-recognition sequence present in the 5'-flanking region, indicating that cE4BP4 can down-regulate the chick pineal cPer2 expression. In vivo light-perturbation studies showed that the prolongation of the light period to early subjective night maintained the high level expression of the pineal cE4bp4, and presumably as a consequence delayed the onset of the induction of the pineal cPer2 expression in the next morning. These light-dependent changes in the mRNA levels of the pineal cE4bp4 and cPer2 were followed by a phase-delay of the subsequent cycles of cE4bp4/cPer2 expression, suggesting that cE4BP4 plays an important role in the phase-delaying process as a light-dependent suppressor of cPer2 gene.
Asunto(s)
Proteínas de Unión al ADN/fisiología , Proteínas del Ojo/fisiología , Glándula Pineal/fisiología , Factores de Transcripción/fisiología , Secuencia de Aminoácidos , Animales , Factores de Transcripción con Cremalleras de Leucina de Carácter Básico , Pollos , Ritmo Circadiano/fisiología , Factores de Unión a la G-Box , Luz , Datos de Secuencia Molecular , Alineación de Secuencia , Transcripción GenéticaRESUMEN
OBJECTIVE: The purpose of this study was to assess the accuracy, informative rate, detection rate, and clinical utility of prenatal interphase fluorescence in situ hybridization (FISH) analysis of amniotic fluid samples from Japanese women. METHODS: Amniotic fluid specimens from 2,639 Japanese women were received for prenatal interphase FISH and chromosome analysis. A questionnaire was designed to evaluate FISH clinical utility by collaboration sites. RESULTS: Based on 2,319 tested samples, the accuracy (100%), informative (94%), and detection (87.6%) rates were all high. The accuracy (100%), informative (90.2%), and detection (90.0%) rates were also remarkable in third-trimester pregnancies. We perceive significant advantages from this test regarding medical management and patient satisfaction. CONCLUSIONS: This novel report shows that in Japan prenatal interphase FISH testing is highly informative and accurate, not only in second-trimester pregnancies but also in third-trimester pregnancies. This test provides advantages to both physicians and patients, provided that its capabilities and limitations are understood.
Asunto(s)
Aberraciones Cromosómicas/diagnóstico , Hibridación Fluorescente in Situ , Diagnóstico Prenatal , Adulto , Líquido Amniótico , Trastornos de los Cromosomas , Femenino , Humanos , Satisfacción del Paciente , Valor Predictivo de las Pruebas , Embarazo , Segundo Trimestre del Embarazo , Tercer Trimestre del Embarazo , Encuestas y CuestionariosRESUMEN
Chicken pinealocytes contain three major components of the circadian clock system: 1) a self-sustained oscillator, 2) a photic-input pathway to the oscillator, and 3) an overt output represented by the rhythmic production of melatonin. Even under cultured conditions of isolated pineal gland or dissociated pinealocytes, the input-oscillator-output functions are well maintained. Because of these experimental advantages, chicken pineal gland has been one of the best models for the study of the circadian clock system. Since the finding of a pineal-specific photoreceptive molecule, pinopsin, we have characterized the endogenous phototransduction pathway in the pinealocytes. On the other hand, despite the long history of chick pineal research, the molecular mechanism underlying the pineal clock oscillation has been largely unknown. Our recent characterization of the chick pineal clock genes strongly suggests that they constitute a transcription/translation-based autoregulatory feedback loop, which is very similar to that generating circadian rhythmicity in mammalian SCN.
Asunto(s)
Pollos/fisiología , Ritmo Circadiano/fisiología , Células Fotorreceptoras de Vertebrados/fisiología , Glándula Pineal/fisiología , Animales , Proteínas Aviares , Relojes Biológicos/fisiología , Luz , Fototransducción , Modelos Biológicos , Proteínas del Tejido Nervioso/metabolismo , Glándula Pineal/citología , Opsinas de Bastones/metabolismoRESUMEN
We performed electrophysiological study and catheter ablation on a 62-year-old patient with supraventricular tachycardia(SVT). This SVT was reproducibly initiated and terminated by atrial stimulation during the electrophysiological testing. The P-wave morphology and atrial activation sequence of intracardiac electrograms were identical to those in normal sinus rhythm. SVT was terminated with carotid sinus massage that increased vagal tone, and for this reason, the reentry circuit of SVT could be localized in sinus node. On the basis of these findings, the SVT was diagnosed as sinus node re-entrant tachycardia and was successfully eliminated by radiofrequency catheter ablation. Radiofrequency catheter ablation would be effective in patients with sinus node reentrant tachycardia refractory to anti-arrhythmic drugs. It should, however, be performed with careful consideration to the influence of the sinus node.
Asunto(s)
Ablación por Catéter/métodos , Taquicardia por Reentrada en el Nodo Sinoatrial/cirugía , Humanos , Masculino , Persona de Mediana EdadRESUMEN
We described disorders of a patient which were uniquely restricted to speech perception of syllable sequences after brain damage. The results of series of experiments using syllable sequences showed "negative recency effect," in which the subject's repetition performance at the latter syllable position was remarkably poor. Experimental analyses suggested that the "negative recency effect" could be due to dual factors: the lower rate of processing of speech sounds and the memory load of holding processes of preceding syllables imposed on the succeeding phonological processing. The results also suggested that the holding processes which imposed the memory load on the succeeding auditory phonological coding processing were modality nonspecific.
Asunto(s)
Afasia de Wernicke/diagnóstico , Trastornos de la Percepción Auditiva/diagnóstico , Putamen/patología , Percepción del Habla , Vocabulario , Adulto , Afasia de Wernicke/etiología , Ventrículos Cerebrales/patología , Lateralidad Funcional/fisiología , Humanos , Imagen por Resonancia Magnética , Masculino , Pruebas Neuropsicológicas , Fonética , Pruebas de Discriminación del Habla , Hemorragia Subaracnoidea/complicaciones , Hemorragia Subaracnoidea/diagnósticoRESUMEN
Chick pineal mitogen-activated protein kinase (MAPK) exhibits circadian activation and light-dependent deactivation at nighttime. Here we report that, in the chick pineal gland, levels of active forms of MAPK, MEK, Raf-1 and Ras exhibited synchronous circadian rhythms with peaks during the subjective night, suggesting a sequential activation of components in the classical Ras-MAPK pathway in a circadian manner. In contrast, the light-dependent deactivation of MAPK was not accompanied by any change of MEK activity, but it was attributed to the light-dependent activation of protein phosphatase dephosphorylating MAPK. These results indicate that the photic and clock signals regulate MAPK activity via independent pathways, and suggest a pivotal role of MAPK in photic entrainment and maintenance of the circadian oscillation.
Asunto(s)
Ritmo Circadiano , Regulación Enzimológica de la Expresión Génica , Genes ras , Proteínas Quinasas Activadas por Mitógenos/metabolismo , Glándula Pineal/fisiología , Proteínas Serina-Treonina Quinasas/metabolismo , Proteínas Proto-Oncogénicas c-raf/metabolismo , Animales , Pollos , Activación Enzimática , Immunoblotting , Masculino , Proteínas Quinasas Activadas por Mitógenos/genética , Fotoperiodo , Glándula Pineal/enzimología , Proteínas Serina-Treonina Quinasas/genética , Proteínas Proto-Oncogénicas c-raf/genéticaRESUMEN
Pinopsin is a chicken pineal photoreceptive molecule with a possible role in photoentrainment of the circadian clock. Sequence comparison among members of the rhodopsin family has suggested that pinopsin might have properties more similar to cone visual pigments than to rhodopsin, but the lifetime of the physiologically active intermediate (meta II) of pinopsin is rather similar to that of metarhodopsin II, which is far more stable than meta II intermediates of cone visual pigments [Nakamura, A. et al., (1999) Biochemistry 38, 14738-14745]. In the present study, we investigated the amino acid residue(s) contributing to this unique property of pinopsin by using site-directed mutagenesis to pinopsin-specific structural features, (i) Ser171, (ii) Asn184, and (iii) the second extracellular loop two-amino acids shorter than that of cone visual pigments. The meta II stability of the 171/184 double mutant of pinopsin (S171R/N184D) is almost the same as that of wild-type pinopsin. In contrast, the meta II lifetime is markedly shortened (one third) by introduction of the third mutation (replacement of a six-amino acid stretch, 188-193, by the corresponding eight residues of chicken green-sensitive cone pigment) to the 171/184 double mutant of pinopsin. Consistently, meta II of the green-sensitive pigment mutant, in which the eight-amino acid stretch is inversely replaced by the corresponding six residues of pinopsin, is more stable than meta II of the wild-type pigment. These results strongly suggest that the specific sequence and/or the number of residues at amino acids 188-193 in pinopsin play an important role in the stabilization of the meta II intermediate.
Asunto(s)
Ritmo Circadiano/fisiología , Proteínas del Tejido Nervioso/química , Pigmentos Retinianos/química , Rodopsina/análogos & derivados , Opsinas de Bastones/química , Sustitución de Aminoácidos , Animales , Proteínas Aviares , Pollos , Mutagénesis Sitio-Dirigida/genética , Proteínas del Tejido Nervioso/genética , Células Fotorreceptoras/química , Células Fotorreceptoras/fisiología , Glándula Pineal/citología , Pliegue de Proteína , Pigmentos Retinianos/fisiología , Rodopsina/fisiología , Opsinas de Bastones/genéticaRESUMEN
Brain-Muscle-Arnt-Like-protein 2 (BMAL2; Arnt4) (aryl hydrocarbon receptor nuclear translocator) is a recently identified basic Helix-Loop-Helix-Per-Arnt-Sim (bHLH-PAS) transcription factor, which contributes to a positive regulation of autoregulatory feedback loop in vertebrate circadian clock systems. In this study, we cloned cDNAs encoding mouse and rat BMAL2 (mBMAL2 and rBMAL2) from mouse midbrain and rat-1 fibroblast cells, respectively. A phylogenetic analysis strongly suggested that vertebrate Bmal1 and Bmal2 genes were generated by a single gene duplication of an ancestral Bmal gene, a vertebrate ortholog of dCyc gene, and that 'BMAL2's putatively termed so far are orthologous. Interestingly, BMAL2 proteins have diverged about 20-fold more rapidly than BMAL1 proteins after the duplication, suggesting an as-yet-unidentified function conserved in BMAL1 but not in BMAL2. mBmal2 mRNA was constitutively expressed throughout the day under light-dark cycle in the mouse hypothalamus containing suprachiasmatic nucleus, the site of the central circadian oscillator in mammals.