Biomedical subjects

K Aida

Publications and source records attributed to K Aida.

At least 19 recordsLinked to original sources

PubMed2004

Effect of betamethasone administration to the pregnant baboon at 0.75 gestation on placental eNOS distribution and activity.

Betamethasone is frequently administered to pregnant women at risk of premature labor to accelerate fetal lung maturation. Maternally administered betamethasone produces pronounced changes in the fetal peripheral vasculature, raises fetal blood pressure and produces fetal growth restriction. Endothelial nitric oxide synthase (eNOS) plays an important role in regulating vascular tone. We hypothesized that effects of betamethasone on the fetal vasculature include decreased eNOS activity. We determined a significant depression of total placental eNOS protein measured by ELISA (betamethasone treated vs control, 0.48 +/- 0.28 vs 1.57 +/- 0.45, p < 0.05) and immunohistochemistry in both syncytiotrophoblast and vascular endothelium. Following betamethasone exposure, eNOS mRNA and enzyme activity showed decreasing trends which were not statistically significant. eNOS protein was higher in the placentas of both control and betamethasone treated baboons in the presence of a female fetus compared with a male fetus. The same effect of the sex of the fetus was observed in the betamethasone group for eNOS mRNA. In conclusion, maternally administered betamethasone produces a consistent decrease in several indices of placental eNOS function that may play a role in the altered cardiovascular dynamics and fetal growth retardation produced by betamethasone administration in late pregnancy.

Animals↗

PubMed2004

Circadian rhythm of melatonin release from the photoreceptive pineal organ of a teleost, ayu (Plecoglossus altivelis) in flow-thorough culture.

In the present study, we tested whether the pineal organ of ayu (Plecoglossus altivelis), an osmerid teleost close relative of salmonids, harbours a circadian oscillator regulating rhythmic melatonin release using flow-through culture. The pineal organ maintained under light/dark cycles released melatonin in a rhythmic fashion with high levels during the dark phase. A circadian rhythm of melatonin release persisted in constant darkness for at least four cycles. Characteristics of the circadian rhythm (free-running period, phase and amplitude) exhibited small variations among cultures when the data was normalized, indicating that this system is sufficient for the analysis of the circadian rhythm both at qualitative and quantitative levels. Six-hour extension of the light phase from the normal onset time of the dark phase or exposure to constant light for 36 or 48 h before transfer to constant darkness significantly inhibited melatonin release. Phase shifts in the circadian rhythm of melatonin release were also observed. Thus, the ayu pineal organ contains all the three essential components of the circadian system (a circadian clock, the photoreceptor responsible for photic entrainment of the clock, and melatonin generating system as an output pathway). This system should provide a useful model for analysing the physiological and molecular basis of the vertebrate circadian system. In addition, further comparative studies using salmonids and related species including ayu will provide some insight into the evolution of the roles of the pineal organ in the vertebrate circadian system.

Animals↗

PubMed2004

Identification of the growth hormone receptor in an advanced teleost, the tilapia (Oreochromis mossambicus) with special reference to its distinct expression pattern in the ovary.

There is considerable evidence that the GH/IGF-I axis plays an important role in female reproduction. We report the isolation and characterization of the GH receptor (GH-R) and its gene expression profile during oogenesis in the tilapia, Oreochromis mossambicus. cDNA encoding GH-R was cloned and sequenced from the tilapia liver. The predicted GH-R preprotein consisted of 635 amino acids and contained a putative signal peptide, an extracellular region with a characteristic motif, a single transmembrane region, and a cytoplasmic region with conserved box 1 and 2 domains. The tilapia GH-R shared 34-74% identities with known GH-Rs in vertebrates. A binding assay using COS-7 cells showed that the cloned GH-R bound specifically to tilapia GH. Northern blot analysis showed a single mRNA transcript in the liver and ovary. In situ hybridization revealed intense signals of GH-R in the cytoplasm and nucleus of immature oocytes. The granulosa and theca cells surrounding vitellogenic oocytes also contained the GH-R mRNA signals. About a tenfold greater level of GH-R mRNA was found in the immature oocytes versus the mature oocytes, along with high levels of IGF-I mRNA. There were no significant changes in mRNA levels of GH-R and IGF-I in the liver or in plasma IGF-I levels during oocyte development. No correlation was found between hepatic GH-R mRNA and ovarian GH-R mRNA. These results suggest that the GH/IGF-I axis in the ovary may be involved in the early phases of oogenesis, under a different regulatory mechanism of GH-R gene expression from that of the liver.

Animals↗

PubMed2003

Effects of fasting on growth hormone/insulin-like growth factor I axis in the tilapia, Oreochromis mossambicus.

Effects of fasting on the growth hormone (GH)-insulin-like growth factor I (IGF-I) axis were examined in the tilapia (Oreochromis mossambicus) acclimated to fresh water. Fasting for 2 weeks resulted in significant reductions in body weight, specific growth rate and hepatosomatic index in both males and females. Significant reductions in specific growth rates were observed after 1 and 2 weeks in both sexes, although the decrease in body weight was not significant in the female. A significant reduction was also seen in the condition factor of females after 2 weeks. No change was seen in the gonadosomatic index in either sex. Two weeks of fasting also produced a significant reduction in plasma IGF-I but not in plasma GH, prolactin (PRL(188)) or cortisol. Significant reductions in the hepatic IGF-I mRNA were seen in both sexes. On the other hand, a significant increase was observed in cortisol receptor mRNA in the female liver. Plasma IGF-I levels were correlated significantly with specific growth rate, condition factor and hepatosomatic index, indicating that plasma IGF-I is a good indicator of growth in the tilapia. No change was seen in plasma glucose or osmolality after 2 weeks of fasting. During fasting, tilapia appears to convert metabolic energy from growth to basal metabolism including maintenance of ion and water balance.

Animals↗

PubMed2003

Dual mode of cortisol action on GH/IGF-I/IGF binding proteins in the tilapia, Oreochromis mossambicus.

Glucocorticoids are known to impede somatic growth in a wide range of vertebrates. In order to clarify the mechanisms through which they may act in an advanced teleost fish, we examined the effects of cortisol administration on the growth hormone (GH)/insulin-like growth factor-I (IGF-I)/IGF-binding protein (IGFBP) system in the tilapia (Oreochromis mossambicus). In a short-term experiment, fish were injected intraperitoneally with cortisol (2 or 10 microg/g), and killed at 2, 4, 8 and 24 h after the injection. In a longer-term experiment, fish were killed 24 and 48 h after cortisol injection (2, 10 and 50 microg/g). Cortisol at doses of 2 and 10 microg/g significantly increased IGFBPs of four different sizes (24, 28, 30, and 32 kDa) in the plasma within 2 h without altering plasma levels of IGF-I or GH. On the other hand, cortisol at doses of 10 and 50 microg/g significantly reduced plasma IGF-I levels after 24 and 48 h. IGF-I mRNA levels in the liver were also significantly reduced by cortisol at doses of 10 and 50 microg/g after 48 h, suggesting that a decrease in plasma IGF-I levels is mediated through the attenuation of IGF-I gene expression in the liver. In contrast, no significant change was observed in plasma or pituitary contents of GH at any time point examined, which would appear to indicate that cortisol reduces IGF sensitivity to GH (GH-resistance). These results clearly indicate that cortisol induces a rapid increase in plasma IGFBPs and a more delayed decrease in IGF-I production. The dual mode of cortisol action may contribute to the inhibitory influence of cortisol on somatic growth in teleosts.

Animals↗

PubMed2001

Inhibition of RNA synthesis differentially affects in vitro melatonin release from the pineal organs of ayu (Plecoglossus altivelis) and rainbow trout (Oncorhynchus mykiss).

The effects of actinomycin D (RNA synthesis inhibitor) and cycloheximide (protein synthesis inhibitor) on melatonin release from the cultured pineal organ of two teleosts with or without the circadian regulation of melatonin production (ayu Plecoglossus altivelis and rainbow trout Oncorynchus mykiss, respectively) were investigated. Actinomycin D decreased melatonin release from the pineal organ during the dark phase but there was a significant difference between the two species (22.2% for ayu and 59.1% for trout as compared with the respective control). This difference might be due to whether the circadian regulation via gene transcription of melatonin synthesis exists or not. On the other hand, cycloheximide decreased melatonin release to approximately 1% in both species, indicating that the fish pineal organ requires de novo protein synthesis to maintain rhythmic melatonin release.

Animals↗

PubMed2001

Effects of photoperiod on pituitary gonadotropin levels in masu salmon.

We examined the effects of photoperiod on pituitary levels of two types of gonadotropin (GTH), GTH I and GTH II, in masu salmon Oncorhynchus masou to study their mechanism of synthesis. In Experiment 1, the effects of long or short photoperiod combined with castration were examined using 8-month-old precocious males. Castration was carried out in early August and then the fish were reared under a short (8L16D) or long (16L8D) photoperiod for 60 days. In Experiment 2, the effects of photoperiod combined with testosterone treatment were examined using 12-month-old immature females. Silastic tubes containing testosterone (500 microg /fish) or vehicle were implanted intra-peritoneally in early October. Fish were reared under 16L8D for 60 days, and then half of the fish were transferred to 8L16D, while the remaining fish were kept under 16L8D until Day 90. In Experiment 1, GTH I contents were higher under 16L8D than under 8L16D in the castrated group on Day 30. Moreover, GTH I contents were higher in the castrated group than the control group under 16L8D on Day 30. GTH II contents increased with testicular maturation in the control groups, whereas they remained at low levels in the castrated groups regardless of photoperiodic treatment. In Experiment 2, GTH I contents did not change remarkably in all the groups, while GTH II contents were remarkably increased by testosterone treatment regardless of photoperiodic treatment. These results indicate that the synthesis of GTH I and GTH II are differently regulated by photoperiod and testosterone in masu salmon.

Animals↗

PubMed2001

The novel sequences of major plasma apolipoproteins in the eel Anguilla japonica.

cDNAs encoding major plasma apolipoproteins (apo) were cloned from the eel Anguilla japonica liver and their nucleotide sequences determined. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that eel lipoproteins contain apolipoproteins of 28 kDa and 14 kDa as major components. Each of the two apolipoproteins showed two isoforms having different isoelectric points as demonstrated by two-dimensional electrophoresis. The two 28 kDa components had different N-terminal amino acid sequences, whereas the two 14 kDa components had an identical one. Then cDNA clones encoding these apolipoproteins were isolated from a cDNA library constructed from the eel liver. An acidic 28 kDa component (28 kDa-1) consisted of 259 amino acids including a putative signal peptide of 27 residues, whereas a basic 28 kDa component (28 kDa-2) was composed of 260 amino acids containing a putative signal peptide of 23 residues. The tandem repeating units, which are characteristic of apolipoproteins, for 28 kDa-1 showed 27.8% identity to that of porcine apoA-IV, although mammalian apoA-IV is about 40 kDa and much larger than 28 kDa-1. However, the repeating units of 28 kDa-2 showed 52.5% identity to that of Atlantic salmon apoA-I. The 14 kDa apolipoprotein consisted of 142 amino acids containing a putative signal peptide of 20 residues. It has a novel sequence differing from apolipoproteins of other vertebrates. The transcriptional expressions of 28 kDa-1, 28 kDa-2, and 14 kDa components were all restricted to the liver, except for the transcripts of 28 kDa-2 which were also slightly expressed in the intestine.

Amino Acid Sequence↗

PubMed2001

cDNA cloning of two gonadotropin beta subunits (GTH-Ibeta and -IIbeta) and their expression profiles during gametogenesis in the Japanese flounder (Paralichthys olivaceus).

To clarify the profiles of two distinct gonadotropin (GTH-I and -II) mRNA levels during gametogenesis in a multiple spawner, the Japanese flounder (Paralichthys olivaceus), the cDNAs encoding GTH-Ibeta and -IIbeta from the pituitary gland have been cloned and sequenced. The nucleotide sequence of GTH-Ibeta was 542 bp long, encoding 120 amino acids, and that of GTH-IIbeta was 554 bp long, encoding 145 amino acids. In females, Northern blot analysis has revealed that relative mRNA levels of GTH-Ibeta and -IIbeta were low in immature fish, showed a gradual increase with ovarian development, and reached the highest level at the maturation stage. Both GTH-Ibeta and -IIbeta mRNA levels were highly correlated with gonadosomatic index (GSI) values and with circulating estradiol-17beta and testosterone (T) levels. In males, the mRNA levels of GTH-Ibeta increased with the increase in GSI values and in circulating 11-ketotestosterone and T levels, whereas the mRNA levels of GTH-IIbeta did not show any correlation with GSI values and with circulating steroid levels, suggesting a difference in regulatory mechanisms of GTH-I and -II synthesis in males. The similar changes in GTH-Ibeta and -IIbeta mRNA levels during oogenesis are considered to be characteristic of GTH synthesis in multiple spawners, differing from the differential changes reported in annual spawners such as salmonids.

Amino Acid Sequence↗

PubMed2001

The effects of testosterone on upstream migratory behavior in masu salmon, Oncorhynchus masou.

Effects of testosterone (T) on upstream migratory behavior in masu salmon, Oncorhynchus masou, were studied by use of artificial raceways. In Experiment 1, yearling precocious males castrated in August were implanted with a capsule of medical silicone tube containing 500 microg of T in September. Their upstream migration was recorded in an artificial raceway with castrated and sham-operated precocious males implanted with a capsule containing vehicle for 2 months. In Experiment 2, upstream migratory behavior of yearling immature parr implanted with a capsule containing T 500 microg or vehicle was observed from September through November. In Experiment 3, upstream migratory behavior of castrated, castrated + T 50 microg, castrated + T 500 microg, and sham-operated precocious males was observed from September through October. In Experiment 4, upstream migratory behavior of the control, T 50 microg-, T 500 microg-, and T 1000 microg-treated immature parr was observed from September through October. In each experiment, plasma and pituitary samples were taken from the fish that moved upstream and remained to measure levels of T, gonadotropin (GTH) II, thyroxine (T(4)), and triiodothyronine (T(3)) by radioimmunoassay. Administration of T caused increases in plasma T levels within the physiological range. In Experiment 1, the frequency of migration upstream was 0, 19.2, and 35.7% in the castrated, castrated + T 500 microg, and sham-operated groups, respectively. The frequency was higher in the castrated + T 500 microg and sham-operated groups than in the castrated group. In Experiment 2, the frequency was higher in T 500 microg-treated parr (22%) than in the control (2.6%). In Experiments 1 and 2, pituitary contents of GTH II in the T-treated groups and precocious males were higher than those in the castrated precocious males and immature parr. In Experiment 3, castrated + T 50 microg, castrated + T 500 microg, and sham-operated fish showed upstream migratory behavior, whereas castrated fish without T did not. In Experiment 4, the frequency was 5.7, 22.9, 17.1, and 28.6% in the control, T 50 microg-, T 500 microg-, and T 1000 microg-treated groups, respectively. In each experiment, plasma levels of T(4) in migrants were lower than those in nonmigrants, whereas plasma levels of T(3) did not show such changes. From these results, it is inferred that T is a factor influencing upstream migration in masu salmon.

Animals↗

PubMed2001

Gonadotropin-releasing hormones (GnRHs) in a primitive teleost, the arowana: phylogenetic evidence that three paralogous lineages of GnRH occurred prior to the emergence of teleosts.

Multiple molecular forms of gonadotropin-releasing hormone (GnRH) are present in a single vertebrate species. To extend the knowledge on GnRH evolution and the number of GnRH forms in one organism, GnRH cDNAs have been isolated and characterized from one of the most primitive teleosts, the arowana Scleropages jardini. This species had two molecular forms of GnRH: salmon-type GnRH (sGnRH) and chicken-II-type GnRH (cGnRH-II). Sequence comparison between the prepro-GnRHs of the arowana and those of other teleosts indicated that sGnRH represented a paralogue separate from any other forms of GnRH. Consistently, subsequent phylogenetic analysis showed that known forms of GnRH in teleosts fell into three paralogous lineages: sGnRH alone on one lineage, cGnRH-II on another, and many other forms on the other. These results suggest that an ancestral GnRH gene duplicated twice prior to the emergence of teleosts and, therefore, that teleosts, and probably also tetrapods, would possess three paralogous forms of GnRH in individual brains.

Amino Acid Sequence↗

PubMed2001

Regulation of gonadotropin beta subunit gene expression by testosterone and gonadotropin-releasing hormones in the goldfish, Carassius auratus.

Sex steroids differentially regulate gonadotropin (GTH) beta subunits (FSHbeta and LHbeta) gene expression in the pituitary of goldfish: a strong in vivo inhibitory effect on FSHbeta mRNA production, but a weak stimulatory effect on LHbeta in sexually immature and recrudescent fish. In the present study, to examine a direct effect of testosterone (T) and gonadotropin-releasing hormone (GnRH) on the mRNA levels of FSHbeta and LHbeta subunits in the pituitary, in vitro experiments were performed using dispersed pituitary cells of sexually immature, recrudescent, mature and regressed goldfish. T treatment in vitro did not significantly decrease FSHbeta mRNA levels, but increased that of LHbeta only in the cells of immature fish. Salmon-type GnRH increased FSHbeta mRNA levels in cells of mature fish, but decreased the levels in cells of sexually regressed fish. From these results, it was suggested that: (1) in vivo effect of sex steroids on gene expression of GTH beta subunits is not always exerted on the pituitary; and (2) the different responses of GTH beta subunits by sex steroids between in vivo and in vitro are partly due to a complex pathway through hypothalamic factors, such as GnRH, in the case of in vivo.

Animals↗

PubMed2001

The involvement of sex steroid hormones in downstream and upstream migratory behavior of masu salmon.

From May through July when masu salmon, Oncorhynchus masou, commence downstream migration under natural conditions, yearling precocious male masu salmon (resident form) showed higher GSI and plasma levels of testosterone (T) and 11-ketotestosterone (11-KT) in contrast to immature smolts (migratory form). From March through September coinciding with the upstream migration period, 2-year-old male and female adults also showed higher GSI and plasma levels of T, estradiol-17beta (E(2)) 11-KT, 17alpha-hydroxyprogesterone and 17alpha,20beta-dihydroxy-4-pregnene-3-one (DHP). In order to test the effects of steroid hormones on migratory behaviors, silascone tube capsules containing 500 microg of T, E(2), 11-KT, DHP, or a vehicle was implanted into smolts, castrated precocious males, or immature parr, and downstream and upstream behavior were observed in artificial raceways in spring and autumn. Downstream behavior of smolts was inhibited significantly by T, E(2) and 11-KT. Upstream behavior was stimulated by T and 11-KT in castrated precocious males and stimulated by T, E(2) and 11-KT in immature parr. These results indicate that T, E(2) and 11-KT are the factors regulating downstream and upstream migratory behavior. In particular, because of its changing patterns in plasma and significant effects, T, the common precursor hormone of E(2) (female) and 11-KT (male), is considered to play central roles in both types of behavior.

Animals↗

PubMed2001

Identification and characterization of two distinct GnRH receptor subtypes in a teleost, the medaka Oryzias latipes.

We report the identification and characterization of two distinct GnRH receptor (GnRH-R) subtypes, designated GnRH-R1 and GnRH-R2, in a model teleost, the medaka Oryzias latipes. These seven-transmembrane receptors of the medaka contain a cytoplasmic C-terminal tail, which has been found in all other nonmammalian GnRH-Rs cloned to date. The GnRH-R1 gene is composed of three exons separated by two introns, whereas the GnRH-R2 gene has an additional intron and therefore consists of four exons and three introns. The GnRH-R1 and GnRH-R2 genes, both of which exist as single-copy genes in the medaka genome, were mapped to linkage groups 3 and 16, respectively. Inositol phosphate assays using COS-7 cells transfected with GnRH-R1 and GnRH-R2 demonstrated that they had remarkably different ligand sensitivities, although both receptors showed highest preference for chicken-II-type GnRH. Phylogenetic analysis showed the presence of three paralogous lineages for vertebrate GnRH-Rs and indicated that neither GnRH-R1 nor GnRH-R2 is the medaka ortholog to mammalian GnRH-Rs that lack a cytoplasmic tail. This, together with an observation that medaka-type GnRH had low affinity for GnRH-R1 and GnRH-R2, suggests that a third GnRH-R may exist in the medaka.

Amino Acid Sequence↗

PubMed2001

Production and characterization of recombinant Phanerochaete chrysosporium cellobiose dehydrogenase in the methylotrophic yeast Pichia pastoris.

The hemoflavoenzyme cellobiose dehydrogenase (CDH) from the white-rot fungus Phanerochaete chrysosporium has been heterologously expressed in the methylotrophic yeast Pichia pastoris. After 4 days of cultivation in the induction medium, the expression level reached 1800 U/L (79 mg/L) of CDH activity, which is considerably higher than that obtained previously for wild-type CDH (wtCDH) and recombinant CDH (rCDH) produced by P. chrysosporium. Analysis with SDS-PAGE and Coomassie Brilliant Blue (CBB) staining revealed a major protein band with an approximate molecular mass of 100 kDa, which was identified as rCDH by Western blotting. The absorption spectrum of rCDH shows that the protein contains one flavin and one heme cofactor per protein molecule, as does wtCDH. The kinetic parameters for rCDH using cellobiose, ubiquinone, and cytochrome c, as well as the cellulose-binding properties of rCDH were nearly identical to those of wtCDH. From these results, we conclude that the rCDH produced by Pichia pastoris retains the catalytic and cellulose-binding properties of the wild-type enzyme, and that the Pichia expression system is well suited for high-level production of rCDH.

Carbohydrate Dehydrogenases↗

PubMed2001

[A case of AFP-producing gastric cancer responding to low-dose CPT-11 and low-dose cisplatin combination chemotherapy].

UNLABELLED: Gastric cancers that produce alpha feto protein (AFP) usually have a poor prognosis. We report an AFP-producing gastric cancer that showed a partial response to low-dose CPT-11 and low-dose cisplatin combination chemotherapy. AFP-producing gastric cancers successfully treated with chemotherapy have been reported, but to our knowledge this is the first report of successful treatment with low-dose CPT-11 and low-dose cisplatin combination chemotherapy. CASE: A 49 year-old woman who had gastric cardiac cancer with esophageal invasion was admitted to our institution. Since AFP-positive cells were demonstrated immunohistochemically in biopsy specimens and levels of AFP in serum were high, AFP-producing cancer was diagnosed. Because of metastasis to Virchow's node and the paraaortic lymph nodes, the tumor was considered unresectable. The patient's poor general condition necessitated chemotherapy with low toxicity and high efficacy. She was treated with low-dose CPT-11 and low-dose cisplatin combination chemotherapy. After two cycles of this treatment, the tumor volume and the serum levels of AFP had decreased markedly. The only side effect of the treatment was leukopenia.

Antineoplastic Agents↗

PubMed2000

A patient with type 2 diabetes mellitus associated with mutations in calcium sensing receptor gene and mitochondrial DNA.

A 44-year-old female with familial hypocalciuric hypercalcemia (FHH) due to a homozygous missense mutation (Pro40Ala) in calcium sensing receptor (CaSR) gene has type 2 diabetes mellitus. The identical heterozygous mutation of CaSR gene was observed in consanguineous parents and all other family members examined except her two sisters. Many subjects with abnormal glucose tolerance were observed in this family, which is compatible with maternal inheritance. Mitochondrial function of complex I (NADH-coenzyme Q reductase) activity in cybrid cells between mitochondrial DNA (mtDNA)-deleted (rho(0)) HeLa cells and mtDNA from the proband was decreased by 35%. The proband has eight substitutions and among these 4833 A/G is a missense substitution in NADH dehydrogenase 2 gene and may probably be a major pathogenic mutation of impaired complex I activity. These results suggest that coexistence of nuclear gene and mtDNA mutations may have caused or modified the development of abnormal glucose tolerance in this family.

Adult↗

PubMed2000

Photic regulation of arylalkylamine N-acetyltransferase 1 mRNA in trout retina.

Melatonin production in the pineal organ and retina is controlled by both light-dark cycles and a circadian clock via the oscillating activity of arylalkylamine N-acetyltransferase (AANAT) in most vertebrates. However, this clock regulation is absent in the rainbow trout (Oncorhynchus mykiss) pineal organ: the trout has two different AANAT genes (AANAT1 and AANAT2), and AANAT2 mRNA levels in the pineal organ did not exhibit circadian oscillation In this study, we confirmed by RT-PCR analysis that AANAT1 is expressed only in the retina, while AANAT2 is expressed in the pineal organ and brain. Real-time quantitative PCR analysis demonstrated that AANAT1 mRNA levels in the retina exhibited daily variations with high levels during the dark phase under light-dark cycles, but kept high and low titers under constant darkness and constant light, respectively. Thus, AANAT1 gene expression in the trout retina is regulated not by a circadian clock but by lighting conditions.

Animals↗