Biomedical subjects

A Naito

Publications and source records attributed to A Naito.

At least 55 records · Page 3Linked to original sources

PubMed2000

The therapeutic efficacy of VP-343, a selective vasopressin V2 receptor antagonist, in the experimental SIADH rat model.

The aim of this work is to investigate the therapeutic efficacy of VP-343 ((N-[4-[[(2S,3aR)-2-hydroxy-2,3,3a,4-tetrahydropyrrolo[1,2-a]qunoxalin-5(1H)-yl]phenyl]-4'-methyl[1,1'-biphenyl]-2-carboxamide), a selective vasopressin V2 receptor antagonist, using the experimental SIADH (syndrome of inappropriate secretion of antidiuretic hormone) rat model. In the model, which was accomplished by administering continuously 1-desamino-8-D-arginine vasopressin (DDAVP), serum sodium levels (S(Na)) and serum osmolarity levels (S(Osm)) significantly and remarkably decreased, which was accompanied with hyper-osmolarity of urine and oliguria. VP-343 increased rapidly and dose-dependently S(Na) and S(Osm). VP-343 exhibited marked diuretic action and decreased urine osmolarity dose-dependently. In the SIADH rat model, all serum levels of chloride, calcium, creatinine, total cholesterol, and uric acid decreased when compared with normal levels. VP-343 increased all serum levels of chloride, calcium, and total cholesterol. These results indicate that VP-343 has efficacy to normalize the abnormalities in DDAVP-induced SIADH.

Animals↗

PubMed2000

Pharmacological profile of VP-343, a novel selective vasopressin V2 receptor antagonist, in rats.

The pharmacological profile of a novel selective vasopressin V2 receptor antagonist, VP-343(N-[4-[[(2S,3aR)-2-hydroxy-2,3,3a,4-tetrahydropyrrolo[ 1,2-a]quinoxalin-5(1H)-yl]carbonyl]phenyl]-4'-methyl[1,1'-biphenyl ]-2-carboxamide) was characterized in several in vitro and in vivo rat models. The IC50 values of VP-343 for vasopressin V1A and V2 receptors were 110 and 0.77 nM, respectively. VP-343 inhibited dose-dependently the pressor response to exogenous arginine vasopressin (AVP; 30 mU/kg, i.v.) in pithed rats, with an ID50 value of 0.57 mg/kg (i.v.). VP-343 induced strong aquaresis in normal saline-loaded conscious rats. Antidiuretic activities of VP-343 have not been detected in AVP deficient Brattleboro rats, showing its lack AVP V2 agonistic activity. During repeated administration for 21 d (3 mg/kg, p.o.) and after recovery, the aquaretic action of VP-343 still remained. In the aged (17 month) saline-loaded conscious rats study, VP-343 (3 mg/kg, p.o.) exhibited remarkable diuretic action. In a single dose oral toxicity study in mice, VP-343 did not produce any clinical signs and mortality at any of the tested doses. The results indicate that VP-343 is a potent, orally active, selective V2 receptor antagonist, suggesting that it can be expected to be useful as an aquaretic drug.

Animals↗

PubMed2000

[Tracing the past half century of my microbial transformation studies].

In the middle of 1950's, microbial transformation technology was introduced into the field of synthetic chemistry as a new methodology. There was a sudden interest in research on the problems of producing steroid hormones by microbial transformation. At that time, the first project entitled "The Study for Microbial Transformation of Steroids", the "Tsuda Project", was established in the Institute of Applied Microbiology (IAM), University of Tokyo, in the spring 1956, in which I took part. This paper summarizes a number of results of our microbial transformation reactions not only in the synthesis of steroidal compounds, but also more broadly for other organic compounds, such as pravastatin, etc. The results are divided into five categories: 1) Microbial transformation of steroids, 2) Correlation between isolation sources of Pseudomonas spp. and their transformation activities, 3) Fermentation Production of prednisolone by Bacillus pulvifaciens SANK 71760, 4) Microbial transformation of siccanin, and 5) Development and fermentation production of pravastatin. About 30 years later, almost at the end of my microbial transformation studies, I had the opportunity to find some microbial strains having superior hydroxylation ability of ML-236BNa to pravastatin. Fortunately, Streptomyces carbophilus SANK 62585 was finally selected as a potent microbial converter with the formation of a lesser amount of by-products. With the view of industrial production of pravastatin, many studies and improvements were made to the culturing conditions to obtain productivity available commercially.

History, 20th Century↗

PubMed2000

Compensatory renal hypertrophy and changes of renal function following nephrectomy.

We studied the changes in the serum creatinine level and the volume of the remaining kidney following nephrectomy using contrast-enhanced compounded tomogram (CT) scans. Twenty-five patients undergoing nephrectomy for renal cell carcinoma without obvious disease in the remaining kidney were carefully followed for a period of at least two years at our hospital. Twelve patients received follow-up CT scans each year after nephrectomy. The ellipsoid volume of the kidney was calculated by measuring the 3-dimensional size on CT scans. The mean relative volume (%) of the remaining kidney increased up to year 3 postoperatively, and the final mean relative volume at varying periods from years 2 to 7 was 120%. Kidneys that were smaller prior to nephrectomy showed a tendency to have a larger final relative volume after nephrectomy, although there was no significant correlation between the kidney volume prior to nephrectomy and at final measurement. The mean serum creatinine level was significantly increased at one year after nephrectomy, but it decreased significantly over time. Therefore, both compensatory renal hypertrophy and improved renal function seemed to be established within several years after nephrectomy. However, the improvement of serum creatinine was delayed compared with the increase of kidney volume. That is, renal plasma flow might be increased early by compensatory renal hypertrophy, followed within a few years by an increase in glomerular filtration and a decrease of serum creatinine.

Adult↗

PubMed1999

Association of protein-tyrosine phosphatase PTP-BAS with the transcription-factor-inhibitory protein IkappaBalpha through interaction between the PDZ1 domain and ankyrin repeats.

PTP-BAS is a membrane-associated protein tyrosine phosphatase containing a band-4.1 homology region and five PDZ (PSD-95 Dlg ZO-1) [discs-large homology region ('DHR')/Gly-Leu-Gly-Phe ('GLGF')] domains. The second and fourth PDZ domains were reported to associate with Fas/CD95. By using the first PDZ domain as a bait in yeast two-hybrid screening, we have identified IkappaBalpha as a binding protein. IkappaBalpha associated with PDZ1 through the stretch of the N-terminal three ankyrin repeats. The association was also confirmed in HeLa cells by co-immunoprecipitation experiments. Inhibition of PTP-BAS by expression of dominant-negative PTP-BAS mutant resulted in tyrosine-phosphorylation of IkappaBalpha. Tyrosine-phosphorylation of IkappaBalpha is a key event in activation of nuclear factor (NF)-kappaB during reoxygenation. PTP-BAS may thus play a regulatory role in activation of NF-kappaB under high oxidative stress.

Ankyrins↗

PubMed1999

Evaluation of asialoglycoprotein receptor imaging agent as a marker of hepatic ischemia-reperfusion injury and recovery.

Protection of hepatocytes from ischemia-reperfusion injury is a clinically important issue. The purpose of this study was to evaluate changes in acute liver damage and recovery after ischemia-reperfusion in rats with asialoglycoprotein receptor (ASGP-R) ligand. Ischemia was induced by clamping the hepatoduodenal ligament for 90 min. At 1, 3, 24, 48 hr, 1 and 2 wk after reperfusion, I-125-GSA was injected. Five min after injection, blood samples were obtained and the liver was removed. Several regions from each lobe were dissected, weighed and counted. Mean uptakes (% dose/g) in the liver and blood samples were calculated. Histologic sections stained with hematoxylin-eosin (H-E) stain showed ischemic damage at 1 and 3 hr, and focal hepatocyte necrosis at 24 hr. Predominant massive necrosis was not seen. The mitotic index with H-E stain and proliferating cell nuclear antigen (PCNA) labeling index were highest at 1 wk, indicating liver regeneration. At 1 and 3 hr, liver uptake was significantly decreased, and blood uptake was significantly increased, indicating decreased tissue blood flow and ischemic damage. Liver uptake showed significant increases at 48 hr and 1 wk, and was the highest at 1 wk, indicating liver regeneration during the convalescence stage. ASGP-R binding may provide valuable information on ischemia-reperfusion injury and recovery.

Animals↗

PubMed1999

Long-distance effects of site-directed mutations on backbone conformation in bacteriorhodopsin from solid state NMR of [1-13C]Val-labeled proteins.

We have recorded 13C cross-polarization-magic angle spinning and dipolar decoupled-magic angle spinning NMR spectra of [1-13C]Val-labeled wild-type bacteriorhodopsin (bR), and the V49A, V199A, T46V, T46V/V49A, D96N, and D85N mutants, in order to study conformational changes of the backbone caused by site-directed mutations along the extracellular surface and the cytoplasmic half channel. On the basis of spectral changes in the V49A and V199A mutants, and upon specific cleavage by chymotrypsin, we assigned the three well-resolved 13C signals observed at 172.93, 172.00, and 171. 11 ppm to [1-13C]Val 69, Val 49, and Val 199, respectively. The local conformations of the backbone at these residues are revealed by the conformation-dependent 13C chemical shifts. We find that at the ambient temperature of these measurements Val 69 is not in a beta-sheet, in spite of previous observations by electron microscopy and x-ray diffraction at cryogenic temperatures, but in a flexible turn structure that undergoes conformational fluctuation. Results with the T46V mutant suggest that there is a long-distance effect on backbone conformation between Thr 46 and Val 49. From the spectra of the D85N and E204Q mutants there also appears to be coupling between Val 49 and Asp 85 and between Asp 85 and Glu 204, respectively. In addition, the T2 measurement indicates conformational interaction between Asp 96 and extracellular surface. The protonation of Asp 85 in the photocycle therefore might induce changes in conformation or dynamics, or both, throughout the protein, from the extracellular surface to the side chain of Asp 96.

Bacteriorhodopsins↗

PubMed1999

Conformational changes of bacteriorhodopsin along the proton-conduction chain as studied with (13)C NMR of [3-(13)C]Ala-labeled protein: arg(82) may function as an information mediator.

We have recorded (13)C NMR spectra of [3-(13)C]Ala-labeled wild-type bacteriorhodopsin (bR) and its mutants at Arg(82), Asp(85), Glu(194), and Glu(204) along the extracellular proton transfer chain. The upfield and downfield displacements of the single carbon signals of Ala(196) (in the F-G loop) and Ala(126) (at the extracellular end of helix D), respectively, revealed conformational differences in E194D, E194Q, and E204Q from the wild type. The same kind of conformational change at Ala(126) was noted also in the Y83F mutant, which lacks the van der Waals contact between Tyr(83) and Ala(126) present in the wild type. The absence of a negative charge at Asp(85) in the site-directed mutant D85N induced global conformational changes, as manifested in displacements or suppression of peaks from the transmembrane helices, cytoplasmic loops, etc., as well as the local changes at Ala(126) and Ala(196) seen in the other mutants. Unexpectedly, no conformational change at Ala(126) was observed in R82Q (even though Asp(85) is protonated at pH 6) or in D85N/R82Q. The changes induced in the Ala(126) signal when Asp(85) is uncharged could be interpreted therefore in terms of displacement of the positive charge of Arg(82) toward Tyr(83), where Ala(126) is located. It is possible that disruption of the proton transfer chain after protonation of Asp(85) in the photocycle could cause the same kind of conformational change we detect at Ala(196) and Ala(126). If so, the latter change would be also the result of rearrangement of the side chain of Arg(82).

Alanine↗

PubMed1999

Location of a cation-binding site in the loop between helices F and G of bacteriorhodopsin as studied by 13C NMR.

The high-affinity cation-binding sites of bacteriorhodopsin (bR) were examined by solid-state 13C NMR of samples labeled with [3-13C]Ala and [1-13C]Val. We found that the 13C NMR spectra of two kinds of blue membranes, deionized (pH 4) and acid blue at pH 1.2, were very similar and different from that of the native purple membrane. This suggested that when the surface pH is lowered, either by removal of cations or by lowering the bulk pH, substantial change is induced in the secondary structure of the protein. Partial replacement of the bound cations with Na+, Ca2+, or Mn2+ produced additional spectral changes in the 13C NMR spectra. The following conclusions were made. First, there are high-affinity cation-binding sites in both the extracellular and the cytoplasmic regions, presumably near the surface, and one of the preferred cation-binding sites is located at the loop between the helix F and G (F-G loop) near Ala196, consistent with the 3D structure of bR from x-ray diffraction and cryoelectron microscopy. Second, the bound cations undergo rather rapid exchange (with a lifetime shorter than 3 ms) among various types of cation-binding sites. As expected from the location of one of the binding sites, cation binding induced conformational alteration of the F-G interhelical loop.

Bacteriorhodopsins↗

PubMed1999

Novel vasopressin V2 receptor-selective antagonists, pyrrolo[2,1-a]quinoxaline and pyrrolo[2,1-c][1,4]benzodiazepine derivatives.

The intent of the work was to study the structure-activity relationships of AVP receptor antagonists bearing a chiral ring as a partial structure since such studies had been reported for only achiral compounds. In the present paper, we deal with compounds consisting of the chiral tricyclic hetero ring (1,2,3,3a,4,5-hexahydropyrrolo[1,2-a]quinoxaline and 1,2,3,10,11,11a-hexahydro-1H-pyrrolo[2,1-c][1,4]benzodiazepine) and 2-phenylbenzanilide analogues. These compounds exhibited a highly selective affinity for V2 receptor, and their stereochemical configuration had a great influence on V2 receptor binding. VP-343 (N-[4-[[(2S,3aR)-2-hydroxy-2,3,3a,4-tetrahydropyrrolo[1,2-a] quinoxalin-5(1H)-yl]carbonyl]phenyl]-4'-methyl[1,1'-biphenyl]-2-ca rboxamide), VP-365 (N-[4-[[(11aS)-2,3,11,11a-tetrahydro-1H-pyrrolo[2,1-c][1,4]benz odiazepin-10(5H)-yl]carbonyl]phenyl][1,1'-biphenyl-2-carboxamide) and VP-339 (N-[4-[[(11aS)-5-oxo-2,3,11,11a-tetrahydro-1H-pyrrolo[2,1-c][1,4]+ ++benzodiazepin-10(5H)-yl]carbonyl]phenyl][1,1'-biphenyl]-2-carboxami de) were the most potent compounds in vitro and in vivo. The IC50 values of VP-343, VP-365 and VP-339 against V2 receptor were 0.772, 1.18 and 0.216 nM, respectively. The ED300 values (dose required to increase three times the urine volume of the control rats; oral administration) of VP-343, VP-365 and VP-339 were 0.22, 0.31 and 0.78 mg/kg, respectively.

Animals↗

PubMed1999

Severe osteopetrosis, defective interleukin-1 signalling and lymph node organogenesis in TRAF6-deficient mice.

BACKGROUND: TRAF6, a member of the tumour necrosis factor receptor-associated factor family, was first identified as a transducer of CD40 and interleukin-1 receptor (IL-1R) signals based on the interaction of TRAF6 with the cytoplasmic tail of CD40 and with the IL-1R associated kinase in vitro. However, the functions of TRAF6 in vivo remain unidentified. RESULTS: We show that TRAF6-/- mice exhibit severe osteopetrosis and are defective in osteoclast formation. In vitro culture experiments revealed that osteoclast precursor cells derived from TRAF6-/- mice are unable to differentiate to functional osteoclasts in response to osteoclast differentiation factor (ODF). In bone marrow of TRAF6-/- mice, the number of sIgM+B220+ immature B cells is markedly reduced while the ratio of proB to preB cells is not affected. In contrast, development of thymocytes is not affected. Furthermore, TRAF6-/- mice are defective in lymph node organogenesis and IL-1 signalling in thymocytes. CONCLUSIONS: The results identify TRAF6 as an essential component of ODF signalling pathway, and also show that TRAF6 plays pivotal roles in immune and inflammatory systems in vivo.

Animals↗

PubMed1999

Overexpression and genetic abnormality of p53 in parathyroid adenomas.

To study the significance of p53 abnormality in parathyroid tumors, 32 parathyroid adenomas and 22 hyperplastic glands from 14 cases of secondary hyperparathyroidism were analysed using immunohistochemistry, polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), single-strand conformation polymorphism (SSCP) and DNA sequencing. Immunohistochemical study revealed p53 overexpression in four parathyroid adenomas, of which two showed diffuse and one showed focal nuclear pleomorphism. Genetic analysis disclosed allelic loss in one, and a point mutation (R290H) and a polymorphism (L257 L) in another of the two other adenomas with diffuse nuclear pleomorphism. No abnormalities were discovered in the other two adenomas, although one had a R72P polymorphism in exon 4. There was no evidence of malignancy of the four tumors in either clinical or pathological terms. None of the 22 hyperplastic glands showed p53 overexpression. These results demonstrate that p53 abnormality can occur in benign parathyroid adenomas and is more prevalent in those with nuclear pleomorphism than in those without.

Adenoma↗

PubMed1999

Doc2alpha is an activity-dependent modulator of excitatory synaptic transmission.

Doc2alpha is a synaptic vesicle-associated Ca2 + -binding protein. To study the role of Doc2alpha in synaptic transmission and modulation, we generated homozygous null Doc2alpha mutant mice. In the CA1 region of hippocampal slices in the mutant mice, excitatory synaptic responses evoked with prolonged 5 Hz stimulation showed a significantly larger frequency facilitation followed by a steeper depression than those in wild-type mice, whereas there was no difference in synaptic transmission at lower frequencies or in paired-pulse facilitation. These results suggest that Doc2alpha regulates synaptic transmission when high Ca2 + concentrations in the presynaptic terminal are sustained. Furthermore, the mutant mice showed impairment in long-term potentiation and passive avoidance task. Thus, Doc2alpha may regulate transmitter release during repetitive synaptic activation, thereby contributing to memory formation.

6-Cyano-7-nitroquinoxaline-2,3-dione↗

PubMed1999

Clonal emergence in uremic parathyroid hyperplasia is not related to MEN1 gene abnormality.

It is difficult to differentiate between parathyroid neoplasia and hyperplasia. In an attempt to elucidate the clonality of uremic parathyroid hyperplasia and the molecular genetic abnormalities accounting for clonal emergence, we analyzed 20 cases of uremic parathyroid hyperplasia. Clonalities were determined using the X-chromosome-linked human androgen receptor (HUMARA) gene and the phosphoglycerate kinase (PGK) gene, and multiple endocrine neoplasia type 1 (MEN1) gene abnormality was analyzed by studying loss of heterozygosity (LOH) in 11q13 and somatic mutations in the MEN1 gene. As a positive control, a case of MEN1 with Zollinger-Ellison syndrome was analyzed simultaneously. Our analysis revealed that a majority (75%) of the uremic parathyroid hyperplasia tissues, including an autograft with recurrent hyperparathyroidism, was of monoclonal origin. Clonality did not correlate with serum carboxyl-terminal parathyroid hormone (C-PTH) level, calcium level, hemodialytic duration, gland weight or pathological features. Neither LOH in 11q13 nor somatic mutation in the MEN1 gene was detected. For the MEN1 case, a germline mutation (W198X) was detected in exon 3. We concluded that a majority of the uremic parathyroid hyperplasia cases was in fact monoclonal neoplasia. MEN1 gene abnormality played a minor role, if any, in the clonal emergence in uremic parathyroid hyperplasia.

Clone Cells↗

PubMed1999

[Cochlear implantation in children with inner ear malformation and postoperative performance].

Cochlear implantation in children with cochlear malformation is on the rise. However, only one case has been reported in Japan. The objective of this paper is to report the authors' experiences with cochlear implants in children with cochlear malformations and, to investigate the morphological classification of cochlear malformation, surgical procedure, complications, and speech perceptions after implantation. Five children (6 ears, including 1 Usher's syndrome and 1 CHARGE association) with congenital inner ear malformations were implanted with multichannel cochlear implants (Nucleus Mini 22 device) between 1994 and 1998. Malformations included common cavity deformity 2, and incomplete partition 4. On the other hand, 4 cases with incomplete partition deformity underwent cochlear implantation by the transmastoid facial recess approach, 2 patients with common cavity deformity received implantation by the transmastoid labyrinthotomy approach. Complications such as facial twitching, cerebrospinal fluid (CSF) gusger, and flap-related problems were encountered. Facial twitching occurred in 1 of 2 patients with common cavity where the electrode array extended into the internal auditory canal. CSF gusher was encountered in 1 of 4 patients with incomplete partition, and revision surgery was performed one week later. One patient had delayed cochlear implant infection and a split pericranial flap was used to cover the defect in the skin flap. Within 6 months, however, the revised pedestal site broke down because of recurrent flap infection. Finally, the cochlear implant was explanted, and the patient underwent a new cochlear implantation in the contralateral ear. All the patients had satisfactory speech reception and word acquisition, but still poor phonetic expression.

Cerebrospinal Fluid Otorrhea↗

PubMed1999

[A case of solitary metastatic lung tumor from follicular carcinoma of the thyroid in hemodialysis patient].

A 61-year-old female was admitted for abnormal shadow of chest X-ray film. The patient has been treated with hemodialysis for chronic renal failure since February 16, 1982, and was performed total thyroidectomy for follicular carcinoma of thyroid on October 24, 1989. Chest X-ray on September 8, 1994 showed the abnormal shadow of right lower lung, chest CT revealed tumor shadow which is suspected to malignancy. We performed partial resection of right lung including tumor on October 19, 1994. Histological examination certified the lung metastasis of follicular carcinoma of thyroid. Postoperative course has been uneventful and there has been no episode of recurrence for 3 years and half after the surgery. We reported this very few case with solitary metastatic lung tumor from follicular carcinoma of thyroid with a review of the literature.

Adenocarcinoma, Follicular↗

PubMed1999

[Roles of outpatient nurses in the care of cancer patients receiving MS Contin tablets].

Pain relief is very important to improve the QOL of cancer patients. Accurate pain assessment and offering suitable drug information on MS Contin tablets (MSC) are important roles of outpatient nurses for the effective use of MSC. We examined the present status of symptom relief among cancer outpatients and from this discuss the practice of outpatient nursing. Forty-eight outpatients receiving MSC were interviewed by mail with regard to pain relief, the side effects of MSC, and the drug information they had been provided. Cancer pain was well controlled in 68% of outpatients by MSC, but MSC was not effective in 13%. Some side effects were observed in 68% of patients, 10% of which were poorly controlled. Sixty-five percent of patients were informed about MSC, but only 47% were informed about measures against these side effects. The following conclusions were reached: 1) MSC should be explained individually and repeatedly, 2) exact informations on a patient's status should be collected using scales and charts, 3) nurse charts should record when MSC is initially administered and when the dosage is changed, and 4) the cases of poorly controlled patients should be studied and specialists consulted if necessary.

Ambulatory Care↗

PubMed1999

How to manage patients with hard-to-recognize postnasal drip?

Postnasal drip (PND), commonly regarded as a phenomenon wherein nasal fluid drips into the pharynx, is one of the main symptoms of chronic sinusitis and other nasal lesions. This definition is controversial, however, because some patients have PND with no evidence of fluid either in the oropharynx or around the choanae. Among 220 patients in whom PND was diagnosed at the University of Tokyo Hospital between January 1996 and December 1997, 19 (8.6%) had hard-to-recognize PND on routine examination. Through careful observation, responsible lesions could be identified in all patients with hard-to-recognize PND. Seven patients had latent chronic sinusitis, 5 had nasopharyngeal lesions, such as Tornwaldt's cyst and inflammation, 3 had "old man's PND", 2 had "reflux PND", and 2 had polyps around the sphenoid ostium. Five patients received no treatment. In the other patients, medical therapy, mainly long-term treatment with low doses of macrolides, now regarded as a standard regimen for intractable chronic sinusitis in Japan, was effective in alleviating symptoms regardless of the cause.

Body Fluids↗