Biomedical subjects

Y Ueta

Publications and source records attributed to Y Ueta.

At least 91 records · Page 5Linked to original sources

PubMed1997

Different electrophysiological character of I-, ClO4-, and SCN- in the transport by Na+/I- symporter.

The electrophysiological characteristics of the Na+/I- symporter were examined using the Chinese hamster ovary (CHO) cell line, which was transfected with the rat Na+/I- symporter gene and stably expressed the Na+/I- symporter. In this cell line, iodide uptake was dependent on Na+, and kinetic studies revealed that the K(m) for iodide was 35 microM, similar to that of FRTL-5 cells. The maximal velocity at the cell protein level was 6- to 10-fold higher than in FRTL-5 cells. ClO-4 and SCN- dose-dependently inhibited iodide uptake in a competitive manner. Electrophysiological characteristics were examined using the whole-cell patch-clamp technique. The holding current at-40 mV rapidly shifted inwardly when the cells were perfused with 1 mEq I- or SCN-. The inward current induced by 1 mEq I- did not increase when bathing solution was replaced with a Tyrode solution with 10 mEq I-, indicating that 1 mEq I- was a saturating amount. The inward current induced by 1 mEq I- increased 1.5-fold by changing the bathing solution to a Tyrode solution containing 1 mEq I- and 1 mEq SCN-. The inward current induced by 0.5 mEq SCN- decreased when the bathing solution was changed to a Tyrode solution containing 0.5 mEq SCN- and 10 mEq I-. These findings indicated that the I- ion and the SCN- ion were carried by the NA+/ I- symporter with at least two Na+ ions. The current induced by the transport of SCN- was larger than that induced by the transport of I-, possibly because the number of Na+ ions that was carried with one SCN- ion was larger than the number of Na+ ions carried with one I- ion. Surprisingly, the perfusion of ClO-4 did not induce an inward current, indicating that ClO-4 bound to the Na+/I- symporter, but was not carried by it, or that one ClO-4 ion was carried with one Na+ ion.

Animals↗

PubMed1997

A novel mutation causing complete deficiency of thyroxine binding globulin.

OBJECTIVE: Thyroxine binding globulin (TBG) is a serum protein that transports thyroxine. Three naturally occurring mutations have been reported to produce complete deficiency of TBG (TBG-CD). The first to be reported was TBG-CD5 in caucasian families of French-Canadian origin and consists of substitutions in exons 2 and 3. TBG-CD of English ethnic origin (TBG-CD6) is characterized by a thymine deletion in codon 165 (exon 1). In Japanese families with TBG-CD (TBG-CDJ), a variant has been characterized with a deletion of the first base of the codon for amino acid 352 (exon 4) in the common type TBG. In this communication we report a new type of TBG-CD in a family of Japanese ethnic origin that is characterized by a single nucleotide substitution in place of two nucleotides in exon 1. This is an uncommon mutation which we have been unable to find in other genes. DESIGN: Exons of the TBG gene amplified by the polymerase chain reaction (PCR) were subcloned and sequenced. To examine for the presence of the same mutation in potentially affected individuals, we performed PCR using primer-directed mutagenesis or allele-specific amplification. PATIENTS: The index case was of Japanese ethnic origin, and was diagnosed as having TBG deficiency on the basis of undetectable serum TBG. The patient consented to this evaluation and the protocol was in accordance with IRB standards. MEASUREMENTS: Serum thyroid hormones, thyrotrophin binding inhibitory immunoglobulin and TBG concentrations were measured by conventional radio-immunoassay. Genomic DNA was extracted from white blood cells. RESULTS: In the index case exons 2, 3 and 4 were normal, but nucleotides 144 (cytosine) and 145 (thymine) in exon 1 were substituted with a single base (adenine) which induced a frame shift in the reading frame, resulting in an early stop codon at codon 51. The patient and his daughters were confirmed as having this mutation using primer-directed mutagenesis or allele-specific amplification. CONCLUSIONS: We have described a novel mutation in the TBG gene in a Japanese family. This results in a frame shift and premature stop codon, and was associated with undetectable serum TBG in the index case.

Exons↗

PubMed1997

Osmotic modulation in glutamatergic excitatory synaptic inputs to neurons in the supraoptic nucleus of rat hypothalamus in vitro.

To clarify influence of osmotic stimulation on the excitatory synaptic inputs to the neurosecretory cells of the supraoptic nucleus (SON), the blind patch technique was used in rat hypothalamic slice preparations. Stable whole-cell recordings were made from 22 neurons in the SON. To observe spontaneous excitatory postsynaptic currents (sEPSCs) in the SON neurons, membrane potentials were clamped between -50 and -90mV. The effects of hypertonic stimulation on the frequency of the sEPSCs were tested in 18 SON neurons. Bath application of mannitol 30 or 60 mM increased the frequency of the sEPSCs. During the application of mannitol (60 mM), the frequency of the sEPSCs increased in 12 of 15 neurons without a change in amplitude. Hypertonic stimulation with NaCl (30 mM) had similar effects to that of mannitol. The increased frequency of miniature EPSCs (mEPSCs) during mannitol application persisted in the presence of TTX in all 8 SON neurons tested with no change in amplitude. Both the non-NMDA antagonist CNQX at 10-30 microM (n = 6) and the non-selective glutamate antagonist kynurenic acid at 1 mM (n = 3) almost completely blocked the EPSCs while the NMDA antagonist AP-5 at 10 microM had no effect on the frequency of the EPSCs in the 4 neurons tested. During application of CNQX, mannitol (60 mM) was added to the perfusion medium in 3 SON neurons. Under these conditions, mannitol had no effect on the frequency of EPSCs. We conclude that hypertonic stimulation directly influences glutamatergic inputs to the neurosecretory cells of the SON by an action on the presynaptic terminals and enhances the excitatory synaptic events.

6-Cyano-7-nitroquinoxaline-2,3-dione↗

PubMed1997

Pertechnetate thyroid uptake is not always suppressed in patients with subacute thyroiditis.

The authors studied the clinical courses and immunologic aspects in 15 patients (age range, 32-69 years old; 14 women) with clinical features that were similar to subacute thyroiditis (SAT). In 2 patients (group A) whose thyrotropin-binding inhibitory immunoglobulins (TBII) and thyroid stimulating antibody (TSAb) showed strongly positive activity at the initial visit, Tc-99m pertechnetate thyroid uptake (Tc-99m uptake) was elevated (5.6% and 3.8%, respectively, normal; 0.7-3.0%). In 6 (group B) of 13 other patients, Tc-99m uptake was not completely suppressed (2 normal, 4 near normal) and imaging showed uptake in one lobe. In 7 (group C), however, there was no evidence of uptake in either lobe. Inflammatory process was localized in one lobe in all group B patients, and was in both lobes in all group C patients but one. Serum TSH levels were detectable in at least 4 patients (2 group B, 2 group C) low in all. There were no patients in both groups B and C in whom TBII and/or TSAb were detected at the initial visit. In SAT, marked suppression of Tc-99m uptake may be ascribed mainly to inflammatory follicular cell damage, but it is not always suppressed, owing to an association similar to Graves' disease and other unknown mechanism(s).

Adult↗

PubMed1997

Water deprivation increases the expression of pituitary adenylate cyclase-activating polypeptide gene in the rat subfornical organ.

The effect of water deprivation on the expression of pituitary adenylate cyclase-activating polypeptide (PACAP) was examined in the rat subfornical organ (SFO), using a combination of immunohistochemistry and in situ hybridization histochemistry. In the euhydrated condition, PACAP-immunoreactivity (PACAP-IR) and the expression of PACAP gene was observed in the SFO. Water deprivation for 24 h and 48 h caused a significant increase in PACAP gene transcripts in the SFO, compared with euhydrated animals. Additionally, water deprivation for 48 h caused an increase in PACAP-IR. This increase of PACAP-IR was demonstrated in both nerve fibers and cell bodies. High correlation was found between the localization of PACAP-IR cell bodies and PACAP messenger RNA synthesizing cell bodies in the peripheral part of the SFO. These results suggest that PACAP in the SFO may play a role in the humoral and neural changes associated with the regulation of body fluid balance after water deprivation.

Analysis of Variance↗

PubMed1997

Pituitary adenylate cyclase-activating polypeptide potentiation of Ca2+ entry via protein kinase C and A pathways in melanotrophs of the pituitary pars intermedia of rats.

Pituitary adenylate cyclase-activating polypeptide (PACAP) has been reported to stimulate melanotroph secretion, and PACAP-like immunoreactivity and expression of PACAP type I receptor messenger RNA have been identified in the pituitary pars intermedia (PI). The present study showed that PACAP messenger RNA is also expressed in the PI. To examine the mechanism of PACAP action in the PI, cytosolic Ca2+ concentrations ([Ca2+]i) and ionic currents were measured in acutely dissociated rat melanotrophs. In about 40% of the melanotrophs studied, PACAP induced an increase in [Ca2+]i, which was suppressed by extracellular Ca2+ removal; extracellular Na+ replacement; the blocker of L-type Ca2+ channels, nicardipine; or the secreto-inhibitory neurotransmitter, dopamine. The PACAP-induced [Ca2+]i increase was mimicked by activators of protein kinase A (PKA) and protein kinase C (PKC), Sp-diastereomer of cAMP and 1-oleoyl-2-acetyl-sn-glycerol, and was reduced by inhibitors of PKA and PKC, Rp-diastereomer of cAMP and staurosporine. Patch-clamp analysis revealed that PACAP caused inward currents with a reversal potential of -0.8 mV and facilitated voltage-dependent Ba2+ currents. It further revealed that PACAP-induced inward currents were mimicked by 1-oleoyl-2-acetyl-sn-glycerol and inhibited by staurosporine, and that Sp-diastereomer of cAMP facilitated Ba2+ currents. These results suggest that PACAP potentiates Ca2+ entry mechanisms of rat melanotrophs by activation of nonselective cation channels via PKC and facilitation of voltage-dependent Ca2+ channels via PKA.

Animals↗

PubMed1996

PACAP type I receptor gene expression in the paraventricular and supraoptic nuclei of rats.

We have examined the distribution of pituitary adenylate cyclase-activating polypeptide (PACAP) type I receptor gene expression in the rat paraventricular (PVN) and supraoptic nuclei (SON) using in situ hybridization histochemistry. PACAP type I receptor gene was expressed moderately in the whole area of the PVN and the SON. In particular, PACAP type I gene transcripts were found in both the magnocellular and the parvocellular parts of the PVN. The results are consistent with the hypothesis that neurosecretory cells in the PVN and the SON might be modulated by PACAP through PACAP type I receptor.

Animals↗

PubMed1996

Adrenomedullin-sensitive receptors are preferentially expressed in cultured rat mesangial cells.

By using cultured rat mesangial cells, we compared the effects on cyclic nucleotide levels of adrenomedullin with those of the structurally related peptides, calcitonin gene-related peptide (CGRP) and amylin. Adrenomedullin potently increased cAMP levels 7-fold in a time- and concentration-dependent manner. Its EC50 was 3 x 10(-9) M. CGRP was less potent (2-fold) with an EC50 of 10(-7) M, and amylin had no effect on cAMP levels. All three peptides failed to increase cGMP levels. Treatment of cells with near maximal concentrations of adrenomedullin (10(-7) M) and CGRP (10(-6) M) had no additive effect on cAMP levels. Human adrenomedullin-(22-52)-NH2, a putative adrenomedullin receptor antagonist, inhibited the production of cAMP elicited by adrenomedullin (IC50: 7 x 10(-8) M) and CGRP (IC50: 5 x 10(-8) M). Human CGRP-(8-37), a CGRP receptor antagonist, conversely, reduced the cAMP elevation caused by these peptides with a lower potency (IC50: 10(-6) M for both peptides). This demonstrated that human adrenomedullin-(22-52)-NH2 was a more effective antagonist for adrenomedullin- and CGRP-specific receptors than human CGRP-(8-37). Results suggest that receptors sensitive to adrenomedullin are preferentially expressed in cultured rat mesangial cells. Immunohistochemical study showed almost no immunoreactive adrenomedullin and CGRP, if any, in the cells. Adrenomedullin may regulate mesangial function as either a paracrine or circulating hormone via a cAMP- but not a cGMP-dependent mechanism.

Adrenomedullin↗

PubMed1996

Amitriptyline inhibits the G protein and K+ channel in the cloned thyroid cell line.

We have reported that thyroid K+ channel is activated by extracellular application of the thyroid-stimulating hormone (TSH) using single channel recording method performed on cloned normal rat thyroid cell (FRTL-5) membrane. Treatment of dibutyryladenosine cyclic monophosphate (Bt2 cAMP) also activated the TSH-dependent K+ channel. These findings indicate that the thyroid K+ channel is activated through the TSH-adenosine cyclic monophosphate (cAMP)-protein kinase A system. We examined the effects of amitriptyline on TSH-guanosine triphosphate binding protein (G protein)-adenylate cyclase-cAMP-K+ channel system in the cloned normal rat thyroid cell line FRTL-5. Amitriptyline inhibited the cAMP production induced by TSH. Amitriptyline also inhibited the cAMP production induced by cholera toxin, indicating that amitriptyline inhibited the thyroid G protein. Amitriptyline had no effect on TSH-receptor binding and cAMP production by forskolin (adenylate cyclase stimulator). Amitriptyline inhibited the K+ channel activation by cAMP, indicating that the suppressing mechanism is not the inhibition of TSH receptor or G protein but the direct suppression of K+ channel. It was concluded that amitriptyline inhibited the thyroid G protein and K+ channel.

Amitriptyline↗

PubMed1996

Enhanced glomerular profilin gene and protein expression in experimental mesangial proliferative glomerulonephritis.

Profilin is a cytoplasmic protein that binds to actin monomer and regulates actin polymerization. In a number of experimental and human glomerular diseases, the mesangial cell expresses alpha-smooth muscle actin and undergoes a phenotypic change to myofibroblast. We used a rat model of mesangial proliferative nephritis induced with antibody to the Thy 1 antigen present on mesangial cells to investigate whether profilin is upregulated. We amplified and sequenced rat profilin cDNA by the reverse-transcribed-polymerase chain reaction (RT-PCR). The nucleotide and amino acid sequences were highly conserved across the mammalian profilins. We raised affinity purified antibody to rat profilin in rabbits immunized with a synthetic profilin peptide (EFTMDLRTKS). At 7 days after disease induction, enhanced expression in both profilin mRNA and protein was demonstrated in the isolated glomeruli by RT-PCR and Western blot analysis. These results suggest that profilin may be involved in the pathogenesis of glomerulonephritis by reorganizing actin cytoskeleton.

Amino Acid Sequence↗

PubMed1996

Biphasic changes in behavioral, endocrine, and sympathetic systems in adjuvant arthritis in Lewis rats.

Adjuvant arthritis (AA) is an experimental model for rheumatoid arthritis, and is induced most easily in inbred Lewis rats by an intradermal injection of heat-killed Mycobacterium tuberculosis (MT) in incomplete Freund's adjuvant. Susceptivity to the arthritis in Lewis rats is thought to be related to a defect in their responses of the hypothalamo-pituitary-adrenal (HPA) axis to the disease. Because the use of an inbred strain is necessary for our immunological studies, we examined in Lewis rats changes in behavior, the HPA axis, and sympathetic nerve activities during development of the adjuvant arthritis. Following intradermal injections of heat-killed MT in adjuvant, the arthritis began to develop on day 12, reaching its maximum severity on day 21, and remained at the level for over a month. The body temperature rose from day 0 to 5 (the primary phase--before the onset of the arthritis). It then fell to normal temperature, and again rose from day 10 to 21 (the secondary phase--with fully developed arthritis). The behavioral (physical activity, food, and water intake) and hormonal parameters [plasma adrenocorticotropic hormone (ACTH) and corticosterone levels] also changed in two phases, similar to those observed in the temperature responses. No change in plasma vasopressin level was observed. Sympathetic nerve activities, assessed by changes in plasma noradrenalin levels, increased more in the primary than in the secondary phase. The possible causes for the biphasic changes associated with development of arthritis are discussed.

Animals↗

PubMed1996

Proadrenomedullin N-terminal 20 peptide (PAMP) reduces inward currents and Ca2+ rises induced by nicotine in bovine adrenal medullary cells.

It has been recently reported that proadrenomedullin N-terminal 20 peptide (PAMP), which is secreted with adrenomedullin and catecholamines from the adrenal medulla, inhibits catecholamine release stimulated with nicotine. In the present study, to elucidate anticholinergic mechanisms of PAMP we employed the whole-cell patch-clamp and the intracellular Ca2+ imaging techniques in cultured bovine adrenal medullary cells. PAMP inhibited nicotinic currents and [Ca2+]i rises induced by nicotine in a dose-dependent manner (10(-9)-10(6) M). These inhibitions were selective, since PAMP alone did not induce any ionic currents, moreover it did not affect voltage-dependent Ba2+ currents or high K+ (50 mM)-induced [Ca2+]i rises. The onset of the inhibitory effect of PAMP (10(-6) M) was very rapid and reached a steady-state level within 10 sec. The effect of PAMP (10(-6) M) lasted for about 10-15 min. Desensitization process of the nicotinic current fitted to a single exponential function with a time constant of 6.4 +/- 0.3 sec. When PAMP (10(-6) M) simultaneously added with nicotine (10(-5) M), the desensitization process was facilitated and fitted to two exponentials with time constants of 0.46 +/- 0.08 and 2.5 +/- 0.8 sec. From the present results, the inhibition by PAMP of nicotinic currents which was well associated with that of nicotine induced [Ca2+]i rises leads to the attenuation of catecholamine release probably, at least in part, due to the facilitation of the desensitization process of the nicotinic currents.

Adrenal Medulla↗

PubMed1996

Activation of sympathetic outflow by recombinant human interleukin-1 beta in conscious rats.

The present study was undertaken to determine the effects of interleukin-1 beta (IL-1 beta) on renal sympathetic nerve activity (RSNA), arterial blood pressure (AP), heart rate (HR), and body temperature in conscious rats. Either intravenous or intracerebroventricular administration of IL-1 beta elicited increases in AP, HR, and RSNA accompanied by a rise in body temperature. The maximum changes in AP, HR, and RSNA occurred 10-15 min after intravenous injection of IL-1 beta (100 ng) and 20-25 min after intracerebroventricular injection (5 ng). The responses induced by the intravenous and intracerebroventricular injections lasted for approximately 15-30 min and did not appear when the animals were pretreated with the cyclooxygenase inhibitor indomethacin (10 mg/kg iv). Moreover, intracerebroventricular injection of prostaglandin E2 (1 microgram) produced responses similar to those induced by IL-1 but with shorter latency. Plasma norepinephrine and adrenocorticotropic hormone concentrations were increased after IL-1 beta injection. The results suggested that IL-1 beta augments cardiovascular and sympathetic outflow through the central action of prostaglandin E2 in conscious rats.

Adrenocorticotropic Hormone↗

PubMed1996

A new type of familial central diabetes insipidus caused by a single base substitution in the neurophysin II coding region of the vasopressin gene.

We studied the genetic basis of familial neurohypophyseal diabetes insipidus in a Japanese family. The members had polyuria and a deficiency of plasma vasopressin (AVP). Polymerase chain reaction (PCR) amplified exons of the AVP-neurophysin-II gene were subcloned and sequenced. Exons 1 and 3 were normal, but nucleotide 1884 Guanine (G) in exon 2 was substituted with Thymine (T), which induced a substitution of glycine (Gly) for valine (Val). To examine the presence of this mutation in the affected subjects, we designed two mutated primers. One of them induced a new endonuclease restriction site in the PCR fragments from normal, and the other induced a new endonuclease restriction site from patients with the mutation. DNA fragments from two affected members of this family were amplified with this primer, and the PCR products were digested by endonuclease and resolved by electrophoresis. The results indicated that these subjects had both normal and mutant alleles, indicating that the mutation was heterozygous. We concluded that this mutation caused neurohypophyseal diabetes insipidus in this family.

Arginine Vasopressin↗

PubMed1995

Adrenomedullin-immunoreactive neurons in the paraventricular and supraoptic nuclei of the rat.

The existence of adrenomedullin (AM) in the rat hypothalamus was examined by immunohistochemistry. AM-immunoreactive neurons were found in the supraoptic nucleus (SON) and in the magnocellular parts of the paraventricular nucleus (PVN). The co-existence of AM-, oxytocin- and/or vasopressin-immunoreactivity was identified in the same neurons in the hypothalamus. The results suggest that the AM may play a role in neurotransmission or in cardiovascular control with neurohypophyseal hormones.

Adrenomedullin↗

PubMed1995

GABAergic inhibitory inputs to subfornical organ neurons in rat slice preparations.

To investigate GABAergic inhibitory inputs to neurons of the subfornical organ (SFO), intracellular recordings were made in rat brain slice preparations. Inhibitory postsynaptic potentials, which occurred spontaneously or were evoked by focal electric stimulation, had reversal potentials of approximately -60 mV, and were almost totally abolished by the GABAA antagonists bicuculline at 3-100 microM or picrotoxin at 50 microM. Following the application of bicuculline or picrotoxin, the resting membrane potentials were decreased by 4-8 mV. GABA at 10-100 microM and the GABAA agonist muscimol at 1-100 microM decreased the membrane resistance and the firing rate in all neurons tested. The reversal potential of the response to muscimol was similar to that for inhibitory postsynaptic potentials. The actions of muscimol persisted in the presence of 1 microM tetrodotoxin, implying that muscimol must act directly on the recorded neurons. These results suggest that there is a tonic inhibitory GABAergic input to SFO neurons which are mainly mediated through GABAA receptors.

Animals↗

PubMed1995

Water deprivation induces regional expression of c-fos protein in the brain of inbred polydipsic mice.

We studied the effects of water deprivation on the expression of c-fos protein (Fos) in the brain of inbred polydipsic mice, STR/N strain, that show extreme polydipsia without a lack of vasopressin in the body. Non-polydipsic mice, ICR strain, were used as controls. All male animals were deprived of water for 24 and 48 h. Fos-like immunoreactivity (Fos-LI) in the brain was studied by immunohistochemical techniques. In both groups of mice water deprivation induced a remarkable increase in Fos-LI in the hypothalamic paraventricular (PVN) and supraoptic (SON) nuclei, the median preoptic nucleus (MnPO), the organum vasculosum laminae terminalis (OVLT) and the subfornical organ (SFO). A far more increase, however, was seen in the MnPO, the SFO and the area postrema (AP) of the polydipsic mice compared to those of the non-polydipsic control mice. In the nucleus of the tractus solitarius (NTS) and in the anteroventral part of the PVN (avPVN), water deprivation caused a clear increase in Fos-LI in the polydipsic mice, while in the non-polydipsic mice the same treatment induced no Fos-LI in the NTS and no change in the avPVN. These results indicate that neurons in the circumventricular organs and the NTS are strongly activated by water deprivation in the polydipsic mice, suggesting that these brain structures play an important role in the polydipsia.

Animals↗

PubMed1995

Presynaptic actions of morphine: blockade of cholecystokinin-induced noradrenaline release in the rat supraoptic nucleus.

1. This study aimed to establish the site at which morphine acts to inhibit oxytocin release in response to peripheral administration of cholecystokinin (CCK). 2. Conscious rats were given morphine or vehicle followed by CCK or vehicle (I.V.). Fos immunoreactivity was apparent 90 min after CCK injection in the supraoptic nucleus of vehicle- but not morphine-pretreated animals. 3. In the dorsomedial (C2/A2) and the ventrolateral (C1/A1) regions of the brainstem, about half of the cells immunoreactive for tyrosine hydroxylase (TH) expressed Fos-like protein after CCK injection. In the C2/A2 region, 20% of the Fos-positive cells also showed TH immunoreactivity, whereas in the C1/A1 region 68% did so. Morphine treatment did not significantly change the number of cells expressing Fos immunoreactivity, or the percentage of TH-positive cells expressing Fos-like protein. 4. Amine release was measured in the supraoptic nucleus of urethane-anaesthetized rats using a microdialysis probe. An I.V. injection of CCK increased the concentrations in the dialysate of noradrenaline and serotonin, but not of either adrenaline or dopamine. Pretreatment with morphine (I.V.) blocked the effects of CCK in a naloxone-reversible manner. 5. Inclusion of morphine in the dialysate also blocked the increase in noradrenaline and serotonin in response to CCK in a naloxone-reversible manner. 6. These observations indicate that morphine acts near or within the supraoptic nucleus to block CCK-evoked noradrenaline release presynaptically. This presynaptic action of morphine may be a cause of the blockade of oxytocin release after CCK.

Animals↗