PubMed Health⌕ Search

Biomedical subjects

Y Fukada

Publications and source records attributed to Y Fukada.

At least 37 records · Page 2Linked to original sources
PubMed2000

Circadian activation of bullfrog retinal mitogen-activated protein kinase associates with oscillator function.

The vertebrate retina retains a circadian oscillator, and its oscillation is self-sustained with a period close to 24 h under constant environmental conditions. Here we show that bullfrog retinal mitogen-activated protein kinase (MAPK) exhibits an in vivo circadian rhythm in phosphorylation with a peak at night in a light/dark cycle. The phosphorylation rhythm of MAPK persists in constant darkness with a peak at subjective night, and this self-sustained rhythm is also observed in cultured retinas, indicating its close interaction with the retinal oscillator. The rhythmically phosphorylated MAPK is detected only in a discrete subset of amacrine cells despite ubiquitous distribution of MAPK throughout the retinal layers. Treatment of the cultured retinas with MAPK kinase (MEK) inhibitor PD98059 suppresses MAPK phosphorylation during the subjective night, and this pulse perturbation of MEK activity induces a significant phase delay (4-8 h) of the retinal circadian rhythm in MAPK and MEK phosphorylation. These observations strongly suggest that the site-specific and time-of-day-specific activation of MAPK contributes to the circadian time-keeping mechanism of the retinal clock system.

Animals↗
PubMed2000

Vertebrate ancient-long opsin: a green-sensitive photoreceptive molecule present in zebrafish deep brain and retinal horizontal cells.

Nonretinal/nonpineal photosensitivity has been found in the brain of vertebrates, but the molecular basis for such a "deep brain" photoreception system remains unclear. We conducted an extensive search for brain opsin cDNAs of the zebrafish (Danio rerio), a useful animal model for genetic studies, and we have isolated a partial cDNA clone encoding an ortholog of vertebrate ancient (VA) opsin, the function of which is unknown. Subsequent characterization revealed the occurrence of two kinds of mRNAs encoding putative splicing variants, VA and VA-Long (VAL) opsin, the latter of which is a novel variant of the former. Both opsins shared a common core sequence in the membrane-spanning domains, but VAL-opsin had a C-terminal tail much longer than that of VA-opsin. Functional reconstitution experiments on the recombinant proteins showed that VAL-opsin with bound 11-cis-retinal is a green-sensitive pigment (lambdamax approximately 500 nm), whereas VA-opsin exhibited no photosensitivity even in the presence of 11-cis-retinal. Immunoreactivity specific to this functionally active VAL-opsin was localized at a limited number of cells surrounding the diencephalic ventricle of central thalamus, and these cells were distributed over approximately 200 micrometer along the rostrocaudal axis. Taken together with the previous study on the locus of the teleost brain photosensitivity (von Frisch K, 1911), it is strongly suggested that the VAL-positive cells in the zebrafish brain represent the deep brain photoreceptors. The VAL-specific immunoreactivity was also detected in a subset of non-GABAergic horizontal cells in the zebrafish retina. The existence of VAL-opsin, a new member of the rhodopsin superfamily, in these tissues may indicate its multiple roles in visual and nonvisual photosensory physiology.

Animals↗
PubMed2000

Diversity of opsin immunoreactivities in the extraretinal tissues of four anuran amphibians.

The pineal complex, deep brain, and skin have been known to function as extraretinal photoreceptors in non-mammalian vertebrates. To see the diversity of localization of extraretinal photoreceptors in lower vertebrates having different habitats, we analyzed the opsin-like immunoreactivities in anuran amphibians, Xenopus laevis, Rana catesbeiana, Rana nigromaculata, and Bufo japonicus. An antiserum (toad Rh-AS) was raised against rhodopsin purified from the retinas of Japanese toad, B. japonicus. In the retina of all the anurans examined, the outer segments of rods were immunopositive to toad Rh-AS. The outer segments of most pinealocytes were immunopositive in R. catesbeiana, R. nigromaculata, and B. japonicus. The outer segments of photoreceptor-like cells within the frontal organ of R. nigromaculata were immunostained. Interestingly, toad Rh-AS immunostained many secretory cells of mucous glands in the head skin of B. japonicus, implying the presence of a novel photoreceptive molecule. Within the hypothalamus, toad Rh-AS immunostained many cells in the magnocellular preoptic nucleus of R. catesbeiana and B. japonicus. Toad Rh-AS also labeled cerebrospinal fluid (CSF)-contacting cells in the anterior preoptic nucleus of R. nigromaculata and those adjacent to the lateral ventricle within the septum of R. catesbeiana. Thus the distribution patterns of the rhodopsin-like immunoreactivities among the anurans were highly diverged, and there was no relationship between the distribution patterns and their habitats. J. Exp. Zool. 286:136-142, 2000.

Animals↗
PubMed2000

Role of circadian activation of mitogen-activated protein kinase in chick pineal clock oscillation.

A circadian pacemaker generates a rhythm with a period of approximately 24 hr even in the absence of environmental time cues. Several photosensitive neuronal tissues such as the retina and pineal gland contain the autonomous circadian pacemaker together with the photic-input pathway responsible for entrainment of the pacemaker to the daily light/dark cycle. We show here that, in constant darkness, chick pineal mitogen-activated protein kinase (MAPK) exhibited an in vivo circadian rhythm in tyrosine phosphorylation and in enzymatic activity with a peak during subjective night. Phosphorylated and hence activated MAPK was rapidly dephosphorylated after light illumination during the nighttime when light induces a phase-shift of the pacemaker. The circadian rhythmicity in MAPK phosphorylation was also observed in the cultured pineal gland, and importantly, MAPK kinase inhibitor treatment during subjective night not only shifted the time-of-peak of MAPK phosphorylation but also induced a remarkable phase-delay of the circadian pacemaker. These results indicate an important role of MAPK for time keeping in circadian clock systems.

Animals↗
PubMed2000

Colocalization of pinopsin with two types of G-protein alpha-subunits in the chicken pineal gland.

Pinopsin is a photoreceptive molecule present in the outer segments of chicken pinealocytes. In this paper, the localization of alpha-subunits of G-proteins, rod transducin (Gt1) and Gq/11, was examined by immunoelectron microscopy to investigate whether these G-proteins colocalize with pinopsin in the outer segments. Ultrathin sections of the chicken pineal gland were double-immunolabeled with antibodies to pinopsin and either Gt1alpha or Gq/11alpha. As shown previously, the outer segments around the follicular lumen exhibited divergent morphology with ciliary, bulbous, or lamellate shapes, and most of them displayed pinopsin immunoreactivity. The majority (>90%) of pinopsin-immunopositive outer segments were labeled by anti-Gt1alpha and/or anti-Gq/11alpha antibodies. Application of double-immunolabeling to serial sections demonstrated that a large number of the pinopsin-immunopositive outer segments contained both Gt1alpha and Gq/11alpha immunoreactivities. These results suggest that Gt1alpha and Gq/11alpha are functionally coupled with light-activated pinopsin within a single outer segment.

Animals↗
PubMed2000

Rod-type transducin alpha-subunit mediates a phototransduction pathway in the chicken pineal gland.

The chicken pineal gland is a photosensitive neuroendocrine organ producing melatonin in circadian clock-regulated and light-sensitive manners. To understand the relationship between the photoreceptive molecule pinopsin and the light-dependent melatonin suppression that is sensitive to pertussis toxin treatment, we have searched for pertussis toxin-sensitive G protein alpha-subunits expressed in the chicken pineal gland. Here we report the cDNA cloning of the pineal transducin alpha-subunit (Gtalpha), which is highly homologous to human retinal rod cell-specific Gt(1)alpha. Concurrent cDNA cloning of chicken retinal Gt(1)alpha and Gt(2)alpha (rod and cone cell-specific alpha-subunits of transducin, respectively) revealed that the chicken pineal Gtalpha is identical to the retinal Gt(1)alpha. Double-immunostaining analysis of the chicken pineal sections localized Gt(1)alpha-immunoreactivity in the rudimentary outer segments of both follicular and parafollicular pinealocytes that were immunopositive to anti-pinopsin antibody. To examine whether pineal Gt(1)alpha is involved in the pineal phototransduction pathway, trypsin protection assay was applied for detecting the conversion of GDP-bound Gt(1)alpha into the guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS)-bound form in the pineal membrane homogenate. It was clearly demonstrated that the pineal Gt(1)alpha is activated in a light-dependent manner in the presence of GTPgammaS. These data together suggest strongly that pineal Gt(1)alpha mediates the phototransduction pathway triggered by pinopsin in the chicken pinealocytes.

Amino Acid Sequence↗
PubMed2000

Dimeric inhibin A as a fourth marker for Down's syndrome maternal serum screening in native Japanese women.

OBJECTIVE: This study was conducted to assess the usefulness of dimeric inhibin A as a fourth marker for Down's syndrome screening in addition to AFP, hCG and uE3 markers for native Japanese women. METHODS: Serum specimens from 367 native Japanese women in the second trimester were assayed for dimeric inhibin A levels. Day specific dimeric inhibin A medians were established for gestational ages 15.0-21.9. Weekly median values for the native Japanese were compared with those of a U.S. population. Selected Japanese specimens from 15 diagnosed Down's syndrome and 3 trisomy 18 cases were also assayed for dimeric inhibin A. RESULTS: Dimeric inhibin A levels did not vary greatly over the gestational age range as expected. Median value comparison showed that native Japanese dimeric inhibin A medians are higher than the U.S. population medians by an average of 7.95%. Native Japanese dimeric inhibin A median values in this study are 1.77 times higher in Down's syndrome cases than in unaffected pregnancies. Trisomy 18 dimeric inhibin A levels show no significant difference from the unaffected pregnancies. CONCLUSIONS: This report shows for the first time that dimeric inhibin A can be informative as a fourth marker for Down's syndrome screening in native Japanese women. We expect the addition of dimeric inhibin A to a triple marker protocol will increase the accuracy of predicted risk for all pregnancies screened and increase the detection rate of Down's syndrome affected pregnancies.

Biomarkers↗
PubMed2000

Triple marker screening for trisomy 21, trisomy 18 and open neural tube defects in singleton pregnancies of native Japanese pregnant women.

OBJECTIVE: To report the results of prenatal triple marker screening on a population of Japanese pregnant women. METHODS: From April 1994 through March 1999, a total of 32,925 native Japanese women with singleton pregnancies requested a triple marker-screening test. Multiples of the median values for 3 markers and individual risks for each patient were calculated following adjustment for the Japanese weight correction factor. The risk cut-off values used for Down syndrome (T21), open spina bifida (OSB) and trisomy 18 (T18) were 1: 295, 1: 290, and 1: 100, respectively. Follow-up information was collected postpartum and statistically analyzed. RESULTS: Detection rates (DR) of T21 for women less than 35 years, over 35 years and overall were 58, 94, and 83%, respectively. DR of T18 for women less than 35 years, over 35 years and overall were 75, 79, and 79%, respectively. DR of open neural tube defects (ONTD) was 100%. CONCLUSIONS: The first cumulative data of an intervention program and prospective follow-up studies in Japan have proven to be similar to other published reports. Individual risk values were calculated for each pregnancy for T21, T18 and ONTD. This screening program is more effective than age-dependent screening for detecting T21, T18 and ONTD pregnancies.

Adult↗
PubMed2000

Age-related changes in bone mineral density and serum bone-related proteins in premenopausal and postmenopausal Japanese women.

The purpose of this cross-sectional study was to characterize the age-related change in bone metabolism during the pre- and postmenopausal periods, and to define the standard levels of three serum markers of bone metabolism, pyridinoline cross-linked carboxyterminal telopeptide of type I collagen (ICTP), carboxyterminal propeptide of type I procollagen (PICP), and bone gla protein (BGP), in Japanese adult women. The bone mineral density (BMD) of the lumbar spine (L2-L4) and the serum levels of ICTP, PICP and BGP were determined in a total of 207 healthy Japanese women (108 premenopausal and 99 postmenopausal). The lumbar BMD decreased significantly with increasing age not only in postmenopausal women (P<0.001) but also in premenopausal women (P=0.014). There was a clear gap in the serum levels of ICTP, PICP and BGP between the premenopausal and postmenopausal group (P<0.001), but those were absolutely the same within each group except for ICTP in the postmenopausal women. These findings and the values of serum ICTP, PICP and BGP in pre- and postmenopausal women obtained in this study are expected to be very useful for treatment of postmenopausal osteoporosis.

Adult↗
PubMed2000

A pregnancy complicated with Fechtner syndrome: a case report.

A 21-year-old woman was diagnosed with Fechtner syndrome at 15 weeks gestation. She had a familial history of this disorder; her mother, two siblings and maternal grandmother were also affected. She presented with neither bleeding from the genital tract nor symptoms suggestive of placental abruption. Labor progressed uneventfully and resulted in the birth of a healthy female infant weighing 3436 g at 41 weeks of gestation. The puerperium was uneventful for both mother and infant.

Adult↗
PubMed1999

Exo-rhodopsin: a novel rhodopsin expressed in the zebrafish pineal gland.

The zebrafish, a useful animal model for genetic studies, has a photosensitive pineal gland, which has an endogenous circadian pacemaker entrained to environmental light-dark cycles [G.M. Cahill, Brain Res. 708 (1996) 177-181]. Although pinopsin has been found in the pineal glands of birds and reptiles, the molecular identity responsible for fish pineal photosensitivity remains unclear. This study reports identification of a novel opsin gene expressed in the zebrafish pineal gland. The deduced amino acid sequence is similar to, but not identical (74% identity) with that of canonical rhodopsin in the zebrafish retina. This novel rhodopsin is expressed in the majority of pineal cells but not in retinal cells, and hence named exo-rhodopsin after extra-ocular rhodopsin. This study first shows that two different rhodopsin genes are expressed in an individual animal each within a unique location. A phylogenetic analysis indicated that the exo-rhodopsin gene was produced by a duplication of the rhodopsin gene at an early stage in the ray-finned fish lineage. As expected, the exo-rhodopsin gene was found in the medakafish and European eel genomes, suggesting strongly that exo-rhodopsin is a pineal opsin common to teleosts. Identification of exo-rhodopsin in the zebrafish provides an opportunity for studying the role of pineal photoreceptive molecules by using genetic approaches.

Amino Acid Sequence↗
PubMed1999

Chimeric nature of pinopsin between rod and cone visual pigments.

Chicken pineal pinopsin is the first example of extra-retinal opsins, but little is known about its molecular properties as compared with retinal rod and cone opsins. For characterization of extra-retinal photon signaling, we have developed an overexpression system providing a sufficient amount of purified pinopsin. The recombinant pinopsin, together with similarly prepared chicken rhodopsin and green-sensitive cone pigment, was subjected to photochemical and biochemical analyses by using low-temperature spectroscopy and the transducin activation assay. At liquid nitrogen temperature (-196 degrees C), we detected two kinds of photoproducts, bathopinopsin and isopinopsin, having their absorption maxima (lambda(max)) at 527 and approximately 440 nm, respectively, and we observed complete photoreversibility among pinopsin, bathopinopsin, and isopinopsin. A close parallel of the photoreversibility to the rhodopsin system strongly suggests that light absorbed by pinopsin triggers the initial event of cis-trans isomerization of the 11-cis-retinylidene chromophore. Upon warming, bathopinopsin decayed through a series of photobleaching intermediates: lumipinopsin (lambda(max) 461 nm), metapinopsin I (460 nm), metapinopsin II (385 nm), and metapinopsin III (460 nm). Biochemical and kinetic analyses showed that metapinopsin II is a physiologically important photoproduct activating transducin. Detailed kinetic analyses revealed that the formation of metapinopsin II is as fast as that of a chicken cone pigment, green, but that the decay process of metapinopsin II is as slow as that of the rod pigment, rhodopsin. These results indicate that pinopsin is a new type of pigment with a chimeric nature between rod and cone visual pigments in terms of the thermal behaviors of the meta II intermediate. Such a long-lived active state of pinopsin may play a role in the pineal-specific phototransduction process.

Amino Acid Sequence↗
PubMed1999

Characterization of N-acylation of Go alpha purified from bovine retinas.

Heterogeneous N-terminal acylation has been identified in several retinal proteins localized predominantly in the outer segments of the photoreceptor cells, but it is still unclear whether such a unique heteroacylation is determined by a photoreceptor cell-specific factor or not. Here, we characterized the N-terminal modification of bovine retinal Go alpha, which seems to be involved in the neural activities and is not detected in the photoreceptor outer segments. In the proteolytic fragments of immunoaffinity-purified retinal Go alpha, we found a single N-terminal peptide modified with myristate, and concluded that retinal Go alpha is purely myristoylated, just like brain Go alpha. This result indicates that the heteroacylation has a more restricted origin in the retina, and supports the idea that it is a photoreceptor cell-specific modification.

Acylation↗
PubMed1999

Amniotic fluid alpha-fetoprotein testing in native Japanese women.

Owing to differences in maternal serum alpha-fetoprotein, human chorionic gonadotrophin and oestriol levels between native Japanese and Caucasian women screened in this laboratory, a study was conducted to measure amniotic fluid alpha-fetoprotein (AFAFP) levels in native Japanese pregnancies. When the native Japanese AFAFP levels were compared with a United States (non-Black) population, the Japanese medians did not decrease as rapidly over the 14 to 22 weeks of gestation period investigated. At 14 weeks, the difference was negligible, graduating to a difference of 20 per cent by 22 weeks' gestation. Native Japanese pregnancy AFAFP levels should be interpreted based upon population data from that group alone. From these findings, prenatal screening laboratories should be encouraged to collect preliminary data for comparison before screening is initiated for a defined ethnic group.

Amniocentesis↗