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K Aida

Publications and source records attributed to K Aida.

At least 109 records · Page 6Linked to original sources
PubMed1994

Characteristics, day-night changes, subcellular distribution and localization of melatonin binding sites in the goldfish brain.

Melatonin binding sites in the goldfish brain were characterized by radioreceptor assay using 2-[125I]iodomelatonin as the radioligand. Specific binding of 2-[125I]iodomelatonin was rapid, stable, saturable and reversible. Saturation experiments demonstrated that 2-[125I]iodomelatonin binds to a single class of receptor site with an affinity constant (Kd) of 29.8 +/- 0.7 pM and a total binding capacity (Bmax) of 11.47 +/- 0.33 fmol/mg protein at mid-light. At mid-dark, the Bmax value decreased significantly to 7.90 +/- 0.23 fmol/mg protein (P < 0.01) with no significant variation in the Kd value (33.8 +/- 1.5 pM). Competition experiments revealed the following order of pharmacological affinities: 2-iodomelatonin > melatonin > 6-hydroxymelatonin > N-acetyl-5-hydroxytryptamine > 5-methoxytryptamine > 5-methoxytryptophol > 5-methoxyindole-3-acetic acid. 5-Hydroxytryptamine, 5-hydroxytryptophol, 5-hydroxyindole-3-acetic acid, norepinephrine and acetylcholine exhibited no inhibition. Subcellular distribution of melatonin binding sites was demonstrated to be greatest in the P2 and P3 fractions as compared with the P1 fraction. Localization of melatonin binding sites in discrete brain areas was determined to be highest in the optic tectum-thalamus and hypothalamus, intermediate in the telencephalon, cerebellum and medulla oblongata, and lowest in the olfactory bulbs and pituitary gland. These results suggest that characteristics of melatonin receptors are highly conserved during evolution and that in this species melatonin plays neuromodulatory roles in the central nervous system through specific receptors.

Animals↗
PubMed1994

Ultrastructural demonstration of salmon-type gonadotropin-releasing hormone (sGnRH) in the olfactory system of masu salmon (Oncorhynchus masou).

Immunocytochemical and immunoelectron microscopic localization of salmon-type gonadotropin-releasing hormone (sGnRH) were observed in the olfactory system (olfactory epithelium, olfactory nerve and olfactory bulb) of masu salmon (Oncorhynchus masou) to investigate its possible involvement in the olfactory functions. sGnRH-immunoreactive (ir) bipolar neuron, which might be related to the terminal nerve, was located in dorsal portion of the olfactory nerve. sGnRH-ir gold particles were concentrated on electron-dense granule-like structures of 50 nm in diameter in fibers of the olfactory nerve close both to the olfactory epithelium and to the olfactory bulb. These findings suggest that sGnRH might participate in neurotransmission and/or neuromodulation in the olfactory system of masu salmon. sGnRH would become a useful molecular marker for studying the olfactory imprinting and homing mechanisms in salmonids.

Animals↗
PubMed1994

Effects of photoperiod and temperature on gonadal activity and plasma steroid levels in an autumn-spawning bitterling, Acheilognathus rhombea, during different phases of its annual reproductive cycle.

The kanehira bitterling, Acheilognathus rhombea, which breeds during autumn in the underyearlings and during summer and autumn in the yearlings, was exposed to various photoperiodic and temperature regimes during different phases of its annual reproductive cycle. In early autumn, gonadal development and increase in plasma levels of female estradiol-17 beta (E2) and male testosterone (T) of underyearling fish occurred under the short day length condition (12L12D). In early winter, gonadal regression (GSI reduction in both sexes, termination of vitellogenesis in females, and termination of spermatogonia proliferation in males) and decrease in plasma levels of E2 in females and T in males were induced by the low-temperature treatment (13 degrees), while gonadal maturity was maintained under the moderate temperature (20 degrees). The low temperature did not prevent oocyte maturation and ovulation in females and spermiogenesis and spermiation in males, indicating that temperature effect on gonadal activity is quite different among the maturational stages. The gonadal development of yearling fish did not progress during spring, even under the short day length condition combined with moderate temperature, which suggests that this species is in the refractory period during this season. In early summer, however, the autonomous gonadal maturation of yearling fish kept under moderate temperature progressed even under the long day length condition (15L9D). It is concluded that the causative factor in the initiation of the spawning period of the underyearling fish is the short day length in autumn, and that the causative factor in the termination of the spawning period is the low temperature in winter. An internal factor such as circannual rhythm in the yearlings is probably involved in the refractoriness to the photoperiod during spring and the subsequent earlier maturation during summer.

Animals↗
PubMed1994

Gonadotropin-releasing hormones of terminal nerve origin are not essential to ovarian development and ovulation in goldfish.

The involvement of gonadotropin-releasing hormones (GnRHs) from the terminal nerve (TN) in ovarian development and ovulation was examined by olfactory tract section (OTX) in goldfish. After OTX, brain contents of salmon GnRH (sGnRH) and chicken GnRH-II (cGnRH-II) were measured by specific radioimmunoassays. Olfactory tracts of sexually maturing females were sectioned prior to the spawning season and were kept under natural conditions. Two months later, brain sGnRH contents markedly decreased in all brain areas (telencephalon, hypothalamus, optic tectum-thalamus, cerebellum, medulla oblongata) except in the olfactory bulbs, whereas cGnRH-II contents did not obviously change. Despite the large decreases in brain sGnRH contents, OTX and sham-operated female fish underwent vitellogenesis. Sexually mature OTX females could be stimulated to ovulate by increased water temperatures during spawning season. Brain sGnRH contents of these OTX fish also markedly decreased with no changes in cGnRH-II. It appears that sGnRH of TN origin, which comprises most of the brain sGnRH in the goldfish, is not a prerequisite for basal gonadotropin secretion and ovarian development, and is not likely to be related to the preovulatory gonadotropin surge which stimulates ovulation in goldfish.

Animals↗
PubMed1994

Insulin and insulin-like growth factors I and II induce final maturation of oocytes of red seabream, Pagrus major, in vitro.

The effects of various growth factors and peptides on in vitro germinal vesicle breakdown (GVBD) were examined in oocytes of the red seabream, Pagrus major, a daily spawning marine teleost. The oocytes used underwent GVBD in response to HCG but not to 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (DHP). Insulin (1 microM) and insulin-like growth factor-I (IGF-I, 10 nM) and IGF-II (13 nM) induced GVBD. Salmon gonadotropin-releasing hormone (GnRH), chicken GnRH (100 nM), angiotensin II and III (10 micrograms/ml), inhibin A, activin A (200 ng/ml), and epidermal growth factor (1 nM) were ineffective. IGF-I was the most potent inducer of GVBD. In the presence of DHP, oocytes underwent GVBD in response to low doses of IGF-I or -II or insulin which alone were ineffective. GVBD occurred in response to DHP after oocytes were preincubated with IGF-I or with HCG. Actinomycin D inhibit GVBD induced by HCG alone or in combination with DHP, but actinomycin D did not block GVBD induced by IGF-I alone or in combination with DHP. Cycloheximide totally inhibited induction of GVBD by HCG or IGF-I, alone or in combination with DHP. These results suggest, for the first time in teleost, that growth factors, such as IGF-I, are involved in the induction of GVBD of oocytes. IGF-I appears to act directly on oocytes, and not via maturation-inducing hormone production, to induce GVBD.

Animals↗
PubMed1994

Salmon gonadotropin-releasing hormone and gonadotropin are involved in precocious maturation induced by photoperiod manipulation in underyearling male masu salmon, Oncorhynchus masou.

The relationship between gonadal maturation, salmon gonadotropin-releasing hormone (sGnRH), and gonadotropin (GTH) subunit contents in the brain and pituitary was investigated in underyearling masu salmon, Oncorhynchus masou. Gonadal maturation was manipulated by changing photoperiod to examine the involvement of these hormones in this process. Fish were divided into short (8 hr L: 16 hr D) and long photoperiod (16 hr L:8 hr D) groups in mid-June and maintained for 4 months until October. Gonadal maturation occurred in most males (precocious males), while a few remaining males and all females did not mature throughout the experiment irrespective of photoperiodic group. In precocious males, pituitary contents of sGnRH, GTH I beta, and GTH II beta increased faster under short photoperiod than under long photoperiod, and spermiation was observed in August. Under long photoperiod, these hormones gradually increased until October when spermiation occurred. sGnRH concentrations in the telencephalon of precocious males were high when spermiation occurred; in August, they were higher in the short photoperiod than in the long photoperiod group; in October, they were higher in the long photoperiod group. The increases of sGnRH and GTH in the pituitary and sGnRH in the brain appear to be involved in precocious maturation inducible by manipulation of photoperiod.

Animals↗
PubMed1994

Activation of salmon gonadotropin-releasing hormone synthesis by 17 alpha-methyltestosterone administration in yearling masu salmon, Oncorhynchus masou.

Juvenile salmonid pituitary gonadotropin (GTH) contents are elevated after steroid hormone treatment, but the involvement of gonadotropin-releasing hormone (GnRH) is unclear. Activation of salmon GnRH (sGnRH) synthesis by 17 alpha-methyltestosterone (MT) administration has been examined in the brain of yearling masu salmon (future precocious males and immature females) using an in situ hybridization technique combined with radioimmunoassay. Oral MT application markedly increased pituitary GTH II beta, but not GTH I beta, contents in both sexes. In future precocious males, MT treatment increased the number of cells expressing sGnRH mRNA in the preoptic area about threefold, whereas there were no significant differences in the olfactory bulbs and the ventral telencephalon. No significant changes were observed in cell sizes nor the numbers of silver grain per 100 microns2 cell in any of the brain regions. Thus, in future precocious males, preoptic sGnRH neurons may be activated by sex steroids. In contrast, no significant changes were observed in sGnRH mRNA levels of immature females after MT treatment. These differences in responses to sex steroids of sGnRH cells in the preoptic area between future precocious males and immature females suggest that MT has indirect actions via sGnRH and/or direct actions on the pituitary in the former, and that MT acts directly on the pituitary in the latter.

Animals↗
PubMed1994

Lack of the steroid 15 alpha-hydroxylase gene (Cyp2a-4) in wild mouse strain Mus spretus: rapid evolution of the P450 gene superfamily.

Steroid 15 alpha-hydroxylase P450(15 alpha) and coumarin 7-hydroxylase P450coh genes Cyp2a-4 and Cyp2a-5 are members of the mouse P450 2A subfamily. Whereas Mus musclus domesticus strains contain both genes, wild mouse strain Mus spretus contains only Cyp2a-5. Evolutionarily, therefore, Cyp2a-5 is ancestral to Cyp2a-4. Moreover, the line to Cyp2a-4 descended as recently as 3 million years ago in an ancestral mouse. This evidence implies a rapid evolution of the P450 gene superfamily.

Animals↗
PubMed1994

Melatonin signal transduction in the goldfish, Carassius auratus.

Generation and reception of melatonin signals in the goldfish, Carassius auratus, are reviewed. The photoreceptive pineal gland of the goldfish generates circulating melatonin rhythms according to a given photoperiod under light-dark cycles and in a circadian manner under continuous dark conditions. Melatonin is also produced in the retina in a similar fashion. Melatonin produced in the pineal gland and retina is considered to act as internal zeitgeber in the brain and retina, respectively, controlling various physiological events via specific melatonin binding sites that are coupled with G protein. The goldfish exhibit clear diurnal locomotor activity rhythms under light-dark cycles and free-running rhythms under constant conditions. However, the relationship between melatonin and locomotor activity rhythms in the goldfish remains unclear. Further studies should be required to demonstrate the roles of melatonin in the circadian system in this species.

Animals↗
PubMed1994

Purification and characterization of gonadotropin I and II from pituitary glands of tuna (Thunnus obesus)

The duality of teleost pituitary gonadotropins was established in an advanced marine fish, the tuna (Thunnus obesus). Two different molecular forms of gonadotropins, designated tGTH I and tGTH II, were isolated from an alcoholic extract of pituitary glands following ion-exchange chromatography and reversed-phase HPLC. Both tGTH I and tGTH II stimulated estradiol-17 beta and testosterone production in tuna ovarian follicles in vitro, although responses to tGTH II were significantly greater than those to tGTH I. Each gonadotropin consisted of alpha- and beta-subunits. tGTH I was stable in acidic conditions, whereas tGTH II dissociated into two subunits after acid treatment. Alpha subunits of tGTH I and tGTH II had identical amino acid sequences of 94 amino acid residues. The tGTH I beta and tGTH II beta consisted of 102 and 115 amino acid residues, respectively, and showed 35% sequence identity. tGTH I beta is structurally more similar to salmon GTH I beta than to salmon GTH II beta, whereas tGTH II beta is more similar to salmon GTH II beta. Thus it is evident that the tuna pituitary gland produces two chemically distinct gonadotropins.

Amino Acid Sequence↗
PubMed1993

Cloning and nucleotide sequence of a novel, male-predominant carboxylesterase in mouse liver.

As a family of serine-dependent enzymes, the carboxylesterases (EC 3.1.1.1) demonstrate a broad substrate specificity. Mouse carboxylesterases comprise at least 20 genetically distinct loci. We cloned a full-length cDNA for a novel mouse carboxylesterase, Es-male which was expressed predominantly in male livers. This carboxylesterase consisted of 554 amino acid residues, and exhibited 43% and 42% similarities to the known mouse esterases Es-22 and pEs-N, respectively. Es-male contained a C-terminal ER-retention signal PEEL, indicating that it may be a microsomal carboxylesterase.

Amino Acid Sequence↗
PubMed1993

A case of congenital nephrotic syndrome associated with positive C1q immunofluorescence.

We present a 1-month-old girl with a congenital nephrotic syndrome and unusual histological findings. Immunofluorescence microscopy demonstrated granular mesangial deposition of C1q and electron microscopy revealed electron-dense mesangial deposits. Her heavy proteinuria gradually decreased and the steroid therapy did not have a significant effect. Her renal function was normal throughout the entire period of observation. The clinical evidence and histopathological features of this patient were compatible with C1q nephropathy.

Complement C1q↗
PubMed1993

A trans-acting locus regulates transcriptional repression of the female-specific steroid 15 alpha-hydroxylase gene in male mice.

Steroid 15 alpha-hydroxylase (P450(15 alpha)) is a female-specific enzyme in the livers of many inbred mice including DBA/2J. Run-on assays using liver nuclei from GH-deficient Little mice indicated that the P450(15 alpha) gene is transcriptionally repressed by GH in male mice. BALB/cJ is a variant strain in which the gene is expressed in the males as well as in the females. Genetic crosses between DBA/2J and BALB/cJ indicated that expression of the P450(15 alpha) gene in BALB/cJ males is inherited as a recessive trait and is regulated by a single locus. The parental origin of the P450(15 alpha) genes, determined using restriction site polymorphism in the exons of the P450(15 alpha) genes, divided the F2 males expressing the P450(15 alpha) gene into three phenotypes at a ratio of 1:1:2, the individuals expressing the gene from only BALB/cJ or DBA/2J and the individuals expressing the genes from both parents respectively. The results indicate that the repression of the P450(15 alpha) gene in male mice is regulated by a trans-acting regulatory locus between the DBA/2J and BALB/cJ pairs. Because hypophysectomy derepressed the P450(15 alpha) gene in F1 males and GH repressed the gene in hypophysectomized F1 males, the hormone appears to regulate gene repression through a trans-acting locus, named GH-dependent repression, GDR.

Animals↗
PubMed1992

Anti-platelet action of isoliquiritigenin, an aldose reductase inhibitor in licorice.

The mechanism was studied by which isoliquiritigenin, a new aldose reductase inhibitor purified from licorice (Glycyrrhizae radix), inhibits platelet aggregation. This new agent significantly inhibited the phosphorylation of 40,000- and 20,000-dalton proteins, and inhibited the formation of 12 (S)-hydroxy-5,8,10-heptadecatrienoic acid, 12-hydroxyeicosatetraenoic acid and thromboxane B2. The inhibitory effect of isoliquiritigenin on platelet aggregation in vitro was comparable to that of aspirin. Our findings may indicate that isoliquiritigenin elicits an anti-platelet action by inhibiting not only cyclooxygenase but also lipoxygenase or peroxidase activity in platelets. Isoliquiritigenin also showed an anti-platelet action in vivo. Isoliquiritigenin appears to be the only aldose reductase inhibitor with a significant anti-platelet action. Since the hyperaggregability of platelets has been implicated in the pathogenesis of diabetic complications, isoliquiritigenin may offer a unique benefit as an aldose reductase inhibitor.

Aldehyde Reductase↗
PubMed1992

Three N-terminal domains of beta-1,3-glucanase A1 are involved in binding to insoluble beta-1,3-glucan.

Limited proteolysis of beta-1,3-glucanase A1 by three different proteases, trypsin, chymotrypsin, and papain, gave three major active fragments. The sizes of the three major fragments generated by each protease treatment were identical to those of beta-1,3-glucanase A2, A3, and A4 detected in both the culture supernatant of Bacillus circulans WL-12 and the periplasmic space of Escherichia coli carrying a cloned glcA gene. These results indicate a four-domain structure for the enzyme. At the N terminus of the glucanase, duplicated segments of approximately 100 amino acids were observed. N-terminal amino acid sequence analysis revealed that the active fragments with sizes corresponding to those of A2 and A3 lack the first segment (domain) and both duplicated segments (domains), respectively. The fragment corresponding to A4 lacks both duplicated segments and the following ca. 120-amino-acid region. By losing the first, second, and third (corresponding to the segment of 120 amino acids) domains, beta-1,3-glucanase progressively lost the ability to bind to pachyman, beta-1,3-glucan. An active fragment which did not have the three N-terminal domains did not show significant binding to pachyman. Thus, all three N-terminal domains contribute to binding to beta-1,3-glucan, and the presence of three domains confers the highest binding activity on the glucanase. The loss of these binding domains remarkably decreased pachyman-hydrolyzing activity, indicating that the binding activity is essential for the efficient hydrolysis of insoluble beta-1,3-glucan.

Amino Acid Sequence↗
PubMed1992

The role of cyclic adenosine 3',5'-monophosphate and polyol metabolism in diabetic neuropathy.

The effects of a stable prostacyclin analog, Iloprost, and aldose reductase inhibitors (ONO-2235 and isoliquiritigenin) were studied to elucidate the role of cAMP in diabetic neuropathy in relation to polyol metabolism. In in vivo experiments, the cAMP and myoinositol contents in sciatic nerves and motor nerve conduction velocity were significantly reduced in diabetic rats. Iloprost significantly restored the reduced cAMP content in sciatic nerves and improved motor nerve conduction velocity in diabetic rats. However, the contents of sorbitol or myoinositol in sciatic nerves were not affected by Iloprost in diabetic rats. On the other hand, aldose reductase inhibitors significantly reduced the sorbitol content and increased the cAMP and myoinositol contents in the sciatic nerves of diabetic rats. The motor nerve conduction velocity was also slightly but significantly improved by treatment with aldose reductase inhibitors. There was a negative correlation between cAMP and sorbitol in the sciatic nerves of diabetic rats treated with aldose reductase inhibitors and a positive correlation between cAMP and motor nerve conduction velocity. In in vitro experiments, Iloprost significantly increased cAMP, but did not affect the sorbitol content in sciatic nerves. Aldose reductase inhibitors inhibited sorbitol accumulation and increased cAMP in sciatic nerves. Our data suggest that polyol pathway activation somehow results in cAMP reduction in sciatic nerves and that the reduction of cAMP in peripheral nerves may be closely related to the pathogenesis of diabetic neuropathy.

Aldehyde Reductase↗
PubMed1992

Characterization and localization of mRNA encoding the salmon-type gonadotrophin-releasing hormone precursor of the masu salmon.

Gonadotrophin-releasing hormone (GnRH) is considered to have an important role in the control of reproduction in salmonid fish, although we do not have any direct evidence. To clarify this problem by molecular techniques, we first determined the nucleotide sequence of the mRNA encoding the precursor of salmon-type GnRH (sGnRH) from the masu salmon, Oncorhynchus masou. The masu salmon sGnRH precursor was composed of a signal peptide, sGnRH and a GnRH-associated peptide (GAP) which was connected to sGnRH by a Gly-Lys-Arg sequence. The amino acid sequence of sGnRH and Gly-Lys-Arg were highly conserved when compared with the corresponding regions of African cichlid sGnRH and mammalian GnRH precursors. However, the GAP region was markedly divergent, with a 66% amino acid similarity to African cichlid GAP and an 8.3-15% similarity to mammalian GAPs. Northern blot analysis indicated the presence of a single mRNA species of about 600 bases in the olfactory bulb and telencephalon and in the diencephalon. The signal was more intense in the former regions. An in-situ hybridization study further revealed that sGnRH neurones were distributed in the olfactory nerve, the ventral part of the olfactory bulb, the ventral part of the telencephalon, the lateral preoptic area and the preoptic nucleus. The sGnRH neurones were thus longitudinally scattered between the olfactory nerve and the lateral preoptic area in the rostroventral part of brain. The intensity of the hybridization signals and the size of hybridization-positive somata were much greater in the olfactory nerve and the rostral olfactory bulb than in the other regions. Preoptic sGnRH neurones were scarcely detected in immature masu salmon, whereas they were more frequently observed in maturing animals. It is possible that the olfactory and the preoptic sGnRH neurones have different physiological roles in salmonid fish.

Amino Acid Sequence↗