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Biomedical subjects

H Kaiya

Publications and source records attributed to H Kaiya.

At least 19 recordsLinked to original sources
PubMed2006

Ghrelin stimulates phagocytosis and superoxide production in fish leukocytes.

To clarify the role of ghrelin in the fish immune system, the in vitro effect of ghrelin was examined in phagocytic leukocytes of rainbow trout (Oncorhynchus mykiss). Administration of trout ghrelin and des-VRQ-trout ghrelin, in which three amino acids are deleted from trout ghrelin, increased superoxide production in zymosan-stimulated phagocytic leukocytes from the head kidney. Gene expression of growth hormone (GH) secretagogue-receptor (GHS-R) was detected by RT-PCR in leukocytes. Pretreatment of phagocytic leukocytes with a GHS-R antagonist, [D-Lys3]-GHRP-6, abolished the stimulatory effects of trout ghrelin and des-VRQ-trout ghrelin on superoxide production. Ghrelin increased mRNA levels of superoxide dismutase and GH expressed in trout phagocytic leukocytes. Immunoneutralization of GH by addition of anti-salmon GH serum to the medium blocked the stimulatory effect of ghrelin on superoxide production. These results suggest that ghrelin stimulates phagocytosis in fish leukocytes through a GHS-R-dependent pathway, and also that the effect of ghrelin is mediated, at least in part, by GH secreted by leukocytes.

Animals↗
PubMed2005

Peripheral ghrelin reduces food intake and respiratory quotient in chicken.

Ghrelin injection, either centrally or peripherally strongly stimulates feeding in human and rodents. In contrast, centrally injected ghrelin inhibits food intake in neonatal chickens. No information is available about the mechanism and its relationship with energy homeostasis in chicken. Since ghrelin is predominantly produced in the stomach, we investigated the effect of peripherally injected ghrelin (1 nmol/100g body weight) on food intake and energy expenditure as measured in respiratory cells by indirect calorimetry for 24h in one-week-old chickens. Plasma glucose, triglycerides, free fatty acids, total protein and T(3) were measured in a separate experiment until 60 min after injection. Food intake decreased until at least 1h after intravenous ghrelin administration. The respiratory quotient (RQ) in ghrelin-injected chickens was reduced until 14 h after administration whereas plasma glucose and triglycerides concentrations were not altered. Free fatty acids and total protein levels also remained unchanged. Ghrelin did not influence heat production and this was supported by the absence of changes in plasma T(3) levels when compared to the control values. In conclusion, peripheral ghrelin reduces food intake as well as RQ and might influence the type of substrate (macronutrient) that is used as metabolic fuel.

Animals↗
PubMed2003

Amidated fish ghrelin: purification, cDNA cloning in the Japanese eel and its biological activity.

We purified ghrelin from stomach extracts of a teleost fish, the Japanese eel (Anguilla japonica) and found that it contained an amide structure at the C-terminal end. Two molecular forms of ghrelin with 21 amino acids were identified by cDNA and mass spectrometric analyses: eel ghrelin-21, GSS(O-n-octanoyl)FLSPSQRPQGKDKKPP RV-amide and eel ghrelin-21-C10, GSS(O-n-decanoyl) FLSPSQRPQGKDKKPPRV-amide. Northern blot and RT-PCR analyses revealed high gene expression in the stomach. Low levels of expression were found only in the brain, intestines, kidney and head kidney by RT-PCR analysis. Eel ghrelin-21 increased plasma growth hormone (GH) concentrations in rats after intravenous injection; the potency was similar to that of rat ghrelin. We also examined the effect of eel ghrelin on the secretion of GH and prolactin (PRL) from organ-cultured tilapia pituitary. Eel ghrelin-21 at a dose of 0.1 nM stimulated the release of GH and PRL, indicating that ghrelin acts directly on the pituitary. The present study revealed that ghrelin is present in fish stomach and has the ability to stimulate the secretion of GH from fish pituitary. A novel regulatory pathway of GH secretion by gastric ghrelin seems to be conserved from fish to human.

Amino Acid Sequence↗
PubMed2002

Cerebral endothelial cells are a major source of adrenomedullin.

Adrenomedullin is a peptide hormone with multifunctional biological properties. Its most characteristic effects are the regulation of circulation and the control of fluid and electrolyte homeostasis through peripheral and central nervous system actions. Although adrenomedullin is a vasodilator of cerebral vasculature, and it may be implicated in the pathomechanism of cerebrovascular diseases, the source of adrenomedullin in the cerebral circulation has not been investigated thus far. We measured the secretion of adrenomedullin by radioimmunoassay and detected adrenomedullin mRNA expression by Northern blot analysis in primary cultures of rat cerebral endothelial cells (RCECs), pericytes and astrocytes. We also investigated the expression of specific adrenomedullin receptor components by reverse transcriptase-polymerase chain reaction and intracellular cAMP concentrations in RCECs and pericytes. RCECs had approximately one magnitude higher adrenomedullin production (135 +/- 13 fmol/10(5) cells per 12 h; mean +/- SD, n = 10) compared to that previously reported for other cell types. RCECs secreted adrenomedullin mostly at their luminal cell membrane. Adrenomedullin production was not increased by thrombin, lipopolysaccharide or cytokines, which are known inducers of adrenomedullin release in peripheral endothelial cells, although it was stimulated by astrocyte-derived factors. Pericytes had moderate, while astrocytes had very low basal adrenomedullin secretion. In vivo experiments showed that adrenomedullin plasma concentration in the jugular vein of rats was approximately 50% higher than that in the carotid artery or in the vena cava. Both RCECs and pericytes, which are potential targets of adrenomedullin in cerebral microcirculation, expressed adrenomedullin receptor components, and exhibited a dose-dependent increase in intracellular cAMP concentrations after exogenous adrenomedullin administration. Antisense oligonucleotide treatment significantly reduced adrenomedullin production by RCECs and tended to decrease intraendothelial cAMP concentrations. These findings may suggest an important autocrine and paracrine role for adrenomedullin in the regulation of cerebral circulation and blood-brain barrier functions. Cerebral endothelial cells are a potential source of adrenomedullin in the central nervous system, where adrenomedullin can also be involved in the regulation of neuroendocrine functions.

Adrenomedullin↗
PubMed2001

Adrenomedullin regulates blood-brain barrier functions in vitro.

Adrenomedullin (AM) is an important vasodilator in cerebral circulation, and cerebral endothelial cells are a major source of AM. This in vitro study aimed to determine the AM-induced changes in blood-brain barrier (BBB) functions. AM administration increased, whereas AM antisense oligonucleotide treatment decreased transendothelial electrical resistance. AM incubation decreased BBB permeability for sodium fluorescein (mol. wt 376 Da) but not for Evan's blue albumin (mol. wt 67 kDa), and it also attenuated fluid-phase endocytosis. AM treatment resulted in functional activation of P-glycoprotein efflux pump in vitro. Our results indicate that AM as an autocrine mediator plays an important role in the regulation of BBB properties of the cerebral endothelial cells.

Adrenomedullin↗
PubMed2001

Bullfrog ghrelin is modified by n-octanoic acid at its third threonine residue.

We have identified the amphibian ghrelin from the stomach of the bullfrog. We also examined growth hormone (GH)-releasing activity of this novel peptide in both the rat and bullfrog. The three forms of ghrelin identified, each comprised of 27 or 28 amino acids, possessed 29% sequence identity to the mammalian ghrelins. A unique threonine at amino acid position 3 (Thr(3)) in bullfrog ghrelin differs from the serine present in the mammalian ghrelins; this Thr(3) is acylated by either n-octanoic or n-decanoic acid. The frog ghrelin-28 has a complete structure of GLT (O-n-octanoyl)FLSPADMQKIAERQSQNKLRHGNM; the structure of frog ghrelin-27 was determined to be GLT(O-n-octanoyl)FLSPADMQKIAERQSQNKLRHGN; frog ghelin-27-C10 possessed a structure of GLT(O-n-decanoyl)FLSPADMQKIAERQSQNKLRHGN. Northern blot analysis demonstrated that ghrelin mRNA is predominantly expressed in the stomach. Low levels of gene expression were observed in the heart, lung, small intestine, gall bladder, pancreas, and testes, as revealed by reverse transcription polymerase chain reaction analysis. Bullfrog ghrelin stimulated the secretion of both GH and prolactin in dispersed bullfrog pituitary cells with potency 2-3 orders of magnitude greater than that of rat ghrelin. Bullfrog ghrelin, however, was only minimally effective in elevating plasma GH levels following intravenous injection into rats. These results indicate that although the regulatory mechanism of ghrelin to induce GH secretion is evolutionary conserved, the structural changes in the different ghrelins result in species-specific receptor binding.

Amino Acid Sequence↗
PubMed2000

Distribution of orexin/hypocretin in the rat median eminence and pituitary.

We determined the distribution of orexin-A and orexin-B (also known as hypocretin-1 and hypocretin-2) and their receptors in the rat median eminence and pituitary using sensitive radioimmunoassays coupled with high-performance liquid chromatography, immunohistochemistry, and in situ hybridization. Orexin-A and -B were present in the median eminence, adenohypophysis, and neurohypophysis. Orexin fibers were abundant in the median eminence, and a few fibers projected to the neurohypophysis. Both the orexin(1)- and orexin(2)-receptor mRNAs were expressed robustly in the pituitary intermediate lobe, whereas in the anterior lobe, the orexin(1) receptor was more markedly expressed than the orexin(2) receptor. These two receptor mRNAs were also found in the posterior lobe. These findings may implicate orexin's involvement in additional as yet undefined physiological functions in the hypothalamo-hypophyseal tract.

Animals↗
PubMed2000

Panic disorder and perceived parental rearing behavior investigated by the Japanese version of the EMBU scale.

Although recent studies have found dysfunctional parental rearing behaviour is associated with certain aspects of psychopathology of panic disorder (PD), the results are not in complete agreement. By using a translated Japanese version of the EMBU (Egna Minnen Beträffande Uppfostran), we investigated the parental rearing behavior perceived by 103 normal subjects, 71 PD patients with agoraphobia, and 32 PD patients without agoraphobia. The PD patients scored both parents as more rejecting and overprotective than did the controls. However, subgroup analysis showed that the patients with agoraphobia reported significantly more rejection from both parents and less emotional warmth from mothers, while the patients without agoraphobia, by contrast, reported more overprotection from both parents and more favouring subject from fathers than did the controls. Interestingly, these results were consistent with those documented in the Western literature, which reported "affectionless control" as a parenting style in PD, and, furthermore, indicated a cross-cultural similarity of parental rearing factor. In addition, it was suggested that a lack of care might be associated with the development of agoraphobia in Japan.

Adult↗
PubMed1999

Efficacy of media in motivating patients with panic disorder to visit specialists.

In 97 patients who visited Akasaka Clinic, their chief complaints, the form of media which motivated patients to visit the clinic, and their DSM-IV diagnoses were examined. The media which most frequently motivated the patients were books (35%), TV programs (23%), and the Internet (16%). While many of patients complained of panic attacks, 74.2% were diagnosed as having anxiety disorder, 12% had somatoform disorder and 8% did not have any mental illness. The rate of panic disorder tended to be higher in patients motivated by TV programs (70%) and significantly lower in those motivated by the reading of books (48%). These results suggest that enlightenment of panic disorder using the media, especially that by TV programs, effectively motivates patients with panic disorder.

Adult↗
PubMed1999

Mediation of humoral catecholamine secretion by the renin-angiotensin system in hypotensive rainbow trout (Oncorhynchus mykiss).

The individual contributions of, and potential interactions between, the renin-angiotensin system (RAS) and the humoral adrenergic stress response to blood pressure regulation were examined in rainbow trout. Intravenous injection of the smooth muscle relaxant, papaverine (10 mg/kg), elicited a transient decrease in dorsal aortic blood pressure (PDA) and systemic vascular resistance (RS), and significant increases in plasma angiotensin II (Ang II) and catecholamine concentrations. Blockade of alpha-adrenoceptors before papaverine treatment prevented PDA and RS recovery, had no effect on the increase in plasma catecholamines, and resulted in greater plasma Ang II concentrations. Administration of the angiotensin-converting enzyme inhibitor, lisinopril (10(-4) mol/kg), before papaverine treatment attenuated the increases in the plasma concentrations of Ang II, adrenaline, and noradrenaline by 90, 79, and 40%, respectively and also prevented PDA and RS recovery. By itself, lisinopril treatment caused a gradual and sustained decrease in PDA and RS, and reductions in basal plasma Ang II and adrenaline concentrations. Bolus injection of a catecholamine cocktail (4 nmol/kg noradrenaline plus 40 nmol/kg adrenaline) in the lisinopril+papaverine-treated trout, to supplement their circulating catecholamine concentrations and mimic those observed in fish treated only with papaverine, resulted in a temporary recovery in PDA and RS. These results indicate that the RAS and the acute humoral adrenergic response are both recruited during an acute hypotensive stress, and have important roles in the compensatory response to hypotension in rainbow trout. However, whereas the contribution of the RAS to PDA recovery is largely indirect and relies on an Ang II-mediated secretion of catecholamines, the contribution from the adrenergic system is direct and relies at least in part on plasma catecholamines.

Acute Disease↗
PubMed1997

Local synthesis of natriuretic peptides in the eel intestine.

The intestine is a major osmoregulatory organ in euryhaline fishes which allows them to survive in the sea, and natriuretic peptides have been implicated in regulation of transmural transport. Atrial (ANP) and ventricular natriuretic peptide (VNP) were identified in eel intestine. Elution profiles of ANP and VNP from high-performance liquid chromatography (HPLC) were determined by radioimmunoassay using highly specific antisera. Elution times of immunoreactive ANP and VNP in HPLC were identical to those of authentic peptide standards and were consistent with the relative molecular masses of these peptides. Tissue localization of ANP and VNP was accomplished by fluorescence immunohistochemistry. Immunoreactive cells were observed in the epithelium of anterior, middle, and posterior regions of intestine. Reverse transcription of mRNA isolated from intestine and subsequent polymerase chain reaction amplification yielded appropriate-size products consistent with ANP and VNP expression. Together, these data show that natriuretic peptides are synthesized locally in eel intestine, rather than trapped from the circulation.

Anguilla↗
PubMed1997

Primary structure and bioactivity of bullfrog calcitonin.

Calcitonin was isolated from the bullfrog, Rana catesbeiana, and the first amino acid sequence of an amphibian calcitonin was determined to be Cys-Ser-Gly-Leu-Ser-Thr-Cys-Ala-Leu-Met-Lys-Leu-Ser-Gln-Asp-Leu-His- Arg-Phe-Asn-Ser-Tyr-Pro-Arg-Thr-Asn-Val-Gly-Ala-Gly-Thr-Pro-NH2. Some portions of this sequence are specific to bullfrog calcitonin, and other portions are similar both to teleost calcitonins and to mammalian calcitonins. Administration of 5 pmol of bullfrog calcitonin to rats revealed a hypocalcemic potency similar to that of salmon calcitonin, at least for the first 3 hr.

Amino Acid Sequence↗
PubMed1997

Interaction of osmotic and volemic mechanisms in secretion of atrial and ventricular natriuretic peptides in eels.

In eels, plasma osmolality rather than blood volume is a major regulator of atrial and ventricular natriuretic peptide (ANP and VNP) secretion. The present study examined the effects of changes in blood volume on ANP and VNP secretion stimulated by an increase in plasma osmolality in freshwater-adapted eels. Basal plasma ANP and VNP levels were decreased by 2 ml of blood withdrawal (28% of total blood volume), but not changed by blood volume expansion with 2 ml of 0.9% NaCl solution containing 2% dextran. The blood loss suppressed the increased plasma ANP level caused by an injection of 2.5 ml/kg of 1.7 M NaCl solution at 60 min (120.5 +/- 31.0 fmol/ml, n = 5) compared with controls without blood volume manipulation (586. 6 +/- 43.6 fmol/ml, n = 5), but the plasma ANP level transiently increased in bled fish immediately after osmotic stimulus, probably due to the release of ANP stored in the cardiac tissues after the blood loss. Changes in plasma VNP were not so evident as those of ANP. In contrast, blood volume expansion augmented the increase in plasma ANP and VNP levels within 60 min after osmotic stimulus compared with controls. The recovery of plasma VNP level was quicker than that of plasma ANP. Increases in plasma Na, Cl concentrations, and osmolality were not different among hypovolemic, normovolemic, and hypervolemic eels after osmotic stimulation. It is concluded that volume itself is a minor regulator for ANP and VNP secretion compared with osmotic stimulus, but it plays a modulatory role in osmotically induced ANP and VNP secretion in eels.

Adaptation, Physiological↗
PubMed1996

Atrial and ventricular natriuretic peptide concentrations in plasma of freshwater- and seawater-adapted eels.

Plasma levels of atrial and ventricular natriuretic peptide (ANP and VNP) were measured in freshwater (FW)- and seawater (SW)-adapted eels using homologous radioimmunoassays. Anesthesia with tricaine (MS222) and exposure of the pericardium for blood sampling from the ventral aorta affected plasma ANP and VNP levels. ANP and VNP levels in the ventral aorta were higher than those in the dorsal aorta when blood was collected simultaneously from both aortae of cannulated conscious FW eels, perhaps reflecting branchial extraction of the peptides. This phenomenon was not observed in SW eels. Based on these results, blood was sampled from conscious eels through a catheter implanted in the ventral aorta because it appears to reflect most accurately ANP secretion. Plasma ANP and VNP levels measured in more than 100 conscious FW and SW eels displayed large variations at each month despite acclimation to laboratory conditions at 180 for more than 1 week in FW eels or for more than 2 weeks in SW eels. However, concentrations of ANP and VNP averaged from all data were not different between FW and SW eels: 68.1 +/- 2.9 (FW: n = 155) vs 60.7 +/- 3.6 (SW: n = 104) for ANP, 51.6 +/- 3.0 (FW: n = 69) vs 55.0 +/- 3.7 (SW: n = 54) for VNP (fmol/ml in each case). Plasma Na concentration and osmolality were significantly higher in SW eels than in FW eels. Plasma ANP and VNP levels thus do not seem to be affected by chronic changes in plasma Na concentration and osmolality.

Adaptation, Physiological↗
PubMed1996

Changes in plasma atrial and ventricular natriuretic peptide concentrations after transfer of eels from freshwater to seawater or vice versa.

Changes in plasma atrial and ventricular natriuretic peptide (ANP and VNP) concentrations were examined in conscious eels, Anguilla japonica, after transfer from freshwater (FW) to seawater (SW) or vice versa. These changes were compared in ventral and dorsal aortic blood since clearance receptors are present in the gills. Plasma Na concentration and osmolality in the ventral aortic blood rose linearly after transfer of FW eels to SW. Six hours after transfer, plasma ANP levels increased from 28.1 +/- 2.9 to 44.8 +/- 5.4 fmol/ml (n = 6) (P < 0.05) and plasma VNP levels also increased from 63.6 +/- 3.8 to 91.2 +/- 6.2 fmol/ml (n = 6) (P < 0.05). However, the levels gradually returned to the FW levels despite plasma Na concentration and osmolality remaining elevated. Dorsal aotic plasma ANP and VNP levels were unchanged after transfer of FW eels to SW, possibly due to extraction of secreted peptides by the branchial clearance receptors. After transfer of SW-adapted eels to FW, plasma ANP and VNP levels were unchanged, while both plasma Na concentration and osmolality decreased. These results indicate that plasma ANP and VNP levels are increased by an increase in plasma Na concentration or osmolality after transfer of FW eels to SW. However, the sustained increase in plasma Na concentration or osmolality no longer stimulated ANP and VNP secretion, and plasma ANP and VNP levels gradually returned to the FW levels gradually on adaptation to SW.

Adaptation, Physiological↗
PubMed1996

Whole body autoradiography and microautoradiography in eels after intra-arterial administration of 125I-labeled eel ANP.

125I-labeled eel atrial natriuretic peptide (ANP) was administered into the ventral or dorsal aorta of freshwater (FW) and seawater (SW) eels, Anguilla japonica, and the major target organs were explored by whole body autoradiography. Localization of the ANP binding in the target organs was also examined at tissue and cell levels by microautoradiography using tissue sections. Whole body autoradiography revealed that the specific label was accumulated predominantly in the gill, with lesser amounts in the atrium, kidney, liver, and urinary bladder. Autoradiographic grains were most dense in the secondary lamellae of the gill, particularly on the side of the efferent filamental artery. Other binding sites in target tissues were the glomerulus of the kidney, epicardium and endocardium of the atrium, bile duct/blood vessels of the liver, and interrenal cells of the head kidney. There was no difference in the distribution and density of grains between injections into the ventral aorta and dorsal aorta, although, in the former, injected 125I-labeled eel ANP passes through the gill before reaching peripheral target tissues. There was a tendency for downregulation of ANP binding sites in SW eels, especially in the gill. These results show that specific ANP binding sites are present in organs that are implicated in osmoregulation and cardiovascular regulation in eels and further suggest that the number of ANP binding sites varies according to changes in the environmental salinity.

Anguilla↗