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Biomedical subjects

A Yamaguchi

Publications and source records attributed to A Yamaguchi.

At least 163 records · Page 9Linked to original sources
PubMed1999

Developmental changes in urinary elimination of theophylline and its metabolites in pediatric patients.

We investigated the developmental changes in the pattern of urinary metabolites of theophylline, a substrate for CYP1A2, to study when CYP1A2, which is absent in the perinatal period, fully develops during childhood. The urinary ratios of three metabolites (1-methyluric acid, 3-methylxanthine, and 1,3-dimethyluric acid) to theophylline in patients over 3 y of age show a much larger interindividual variation compared with those under 3 y of age, and the mean values of the ratios in patients over 3 y of age were greater than those in patients under 1 y of age. The urinary ratio of 1,3-dimethyluric acid (a metabolite generated by several cytochrome P450s) to 3-methylxanthine or 1-methyluric acid (metabolites generated by CYP1A2 exclusively) seemed to be relatively constant over 3 y of age; in patients under 3 y of age, these ratios were much higher than those in patients over 3 y of age. The urinary ratio of 1-methyluric acid to 3-methylxanthine or 3-methylxanthine to 1-methyluric acid seemed to be relatively invariable in all patients except those less than 1 y of age. These findings suggest that CYP1A2 activity may be programmed to mature by around 3 y of age and that CYP1A2 probably plays a major role in theophylline 8-hydroxylation at a therapeutic concentration after the full development of CYP1A2 activity.

Aging↗
PubMed1999

[Methods of sleep induction for EEG recordings: comparison between three hypnotics and natural sleep].

We compared the effects of three oral hypnotics, monosodium trichloroethyl phosphate (MTP), chloral hydrate (CH), and pentobarbital calcium (PTB), to those of non-medication on wake-sleep states and sleep activation of epileptic seizure discharges. The subjects consisted of 410 epileptics and 171 non-epileptic outpatients (mean age: 12.5 years) of the Department of Pediatrics, Nagoya City University Hospital. Complete EEG records including awake and sleep states were obtained in 230/241 (95%) of patients with MTP, 20/22 (91%) of those with CH, 72/85 (85%) of those with PTB, and 225/233 (97%) of those without any hypnotics. There were no statistically significant differences in the effect of sleep induction among the four groups. Sleep activation effects were observed in 25% of patients with natural sleep and 35% of those with induced sleep. There was no statistical difference (p > 0.05). These results suggested MTP, CH, and PTB are useful hypnotics for sleep EEG recordings.

Adolescent↗
PubMed1999

[Ventricular fibrillation during mild hypothermic therapy in a patient undergoing neurosurgery].

A 35 year old male for mild hypothermic therapy for neurosurgery, developed ventricular fibrillation. Total resection of cerebral arteriovenous malformation was performed under mild hypothermic therapy, with the target core temperature of 33 degrees C. Intraoperatively cooling rate was low and a reduction of peripheral temperature associated with metabolic acidosis was noted. After the conclusion of the operation and during transferring the patient to an intensive care unit, multiple ventricular premature beats were noted. Thereafter, ventricular tachycardia developed proceeding ventricular fibrillation. We suggest that careful management of thermal and cardiovascular systems is required to prevent adverse events during mild hypothermic therapy.

Adult↗
PubMed1999

[The influence of ketamine on the bispectral index, the spectral edge frequency 90 and the frequency bands power during propofol anesthesia].

To investigate the influence of ketamine on the bispectral index (BIS), the spectral edge frequency 90 (SEF 90) and relative power in four frequency bands (beta, alpha, theta, sigma), we studied 13 patients (ASA I-II) undergoing elective surgery. In the first study (n = 7), we administered ketamine (1.0 mg.kg-1, bolus, i.v.) during propofol anesthesia. Thirty minutes after the administration, BIS, SEF 90 and relative beta power increased significantly. In the second study (n = 6), bolus administration of ketamine (0.5 mg.kg-1 i.v.) followed by continuous infusion was started during propofol anesthesia. The infusion rate of ketamine was 0.5 mg.kg-1.h-1 for 30 minutes and then increased to 1.0 mg.kg-1.h-1. BIS, SEF 90 and relative beta power increased significantly after ketamine administration, but the parameters did not change in dose-related manner. We conclude that further investigation is necessary to use electroencephalographic parameters as an indicator of the anesthesia depth during propofol/ketamine anesthesia.

Analgesics↗
PubMed1999

[Clinical evaluation of weekly hepatic arterial infusion chemotherapy in patients with unresectable metastatic liver cancer].

Twenty-five cases with unresectable metastatic liver cancers were experienced in our hospital over the past five years who underwent weekly 24-hour continuous hepatic arterial infusion chemotherapy using 5-FU and CBDCA. The response rate was 20%, the median survival was 23 months, and the one/two year overall survival rates averaged 81.3/45.5%. In 77% of patients, this therapy prevented death from hepatic metastases. Moreover, since adverse effects were limited compared with bolus infusion, weekly 24-hour continuous hepatic arterial infusion chemotherapy was thought to be a favorable method.

Adult↗
PubMed1999

[Five cases of cerebral and/or cerebellar embolism after insertion of a heparin-coated catheter from the left thoracoacromial artery].

We reported five cases of cerebral and/or cerebellar embolism after insertion of a heparin-coated catheter from the left thoracoacromial artery for multiple liver metastases. They were one patient with multiple liver metastases from the angiosarcoma of the scalp, and 4 others with gastrointestinal cancer liver metastases. The first case suffered a cerebeller embolism just after removal of a catheter that had been obstructed. In this case, it is possible that the thrombus quickly migrated into a cranial vessel from around the catheter. In the others with patent catheters, the cerebral embolisms occurred more than a month after insertion of the catheters. In the latter cases, it is thought that embolisms did not occur because of catheter insertion maneuver. However, a thrombus that grew around the catheter migrated into the left common carotid artery or the left vertebral artery. The anti-coagulation therapy should be considered for prophylactic treatment.

Aged↗
PubMed1999

[Elderly dyserythropoietic anemia first diagnosed after presentation of hemorrhagic gastric ulcer].

A 71-year-old man presented with epigastralgia and tarry stool. Laboratory examination showed anemia (Hb 7.1 g/dl) due to hemorrhagic gastric ulcer and positive Coombs' test without features of hemolysis. Initial bone marrow smears disclosed normal granulocytes and megakaryocytes, but only erythroid hyperplasia with multinuclearity and megaloblastosis was identified. Cytogenetic studies revealed normal karyotype. Congenital dyserythropoietic anemia (CDA) type II was initially suspected. Serologically, however, acid hemolysis and anti-I * i tests were negative as were the results of another Coombs' test. The second bone marrow aspiration disclosed a marked decrease in multinucleated erythroblasts together with an increase in those that had internuclear chromatin bridges. Electron microscopy of bone marrow specimens demonstrated morphological features of CDA types I and II, thus yielding a final diagnosis of elderly dyserythropoietic anemia, which is similar to both CDA types. It was suggested that the reactive secretion of erythropoietin due to bleeding played a role in these pathologic changes.

Aged↗
PubMed1999

International cooperation in neonatal screening: technical training course for newborn and infant screening.

We report the outline and results of our experience with a group training course of neonatal screening for health care professionals in developing countries. Sapporo City Institute of Public Health (SCIPH) has been offered a training course on neonatal screening once a year since 1991 under the Technical Training Program of the Japan International Cooperation Agency (JICA). The aims of this training course are to enhance the participants' technical knowledge and skills, and also to deepen their understanding of the principle of neonatal screening as well as the relevant diseases. Lectures and laboratory practice on phenylketonuria (PKU), congenital hypothyroidism (CH), congenital adrenal hyperplasia (CAH) and neuroblastoma are included in the 3-month program. After the completion of the training, participants are expected to play a major role in establishing and expanding neonatal screening system in each of their countries. We have received a total of 67 participants from 25 countries until March 1998: 58 pediatricians; 2 gynecologists; 6 biochemists; 1 administrative officer. After they returned to their countries, 11 engaged in neonatal screening and started PKU and CH screening in their institute, city or province in Argentina, Brazil, Mexico, Peru and Thailand. We believe that these results fulfilled our objectives. Also, for follow-up, SCIPH has been giving information and consultation to the participants on requests. This international cooperation network could also benefit our present network of the International Society Screening in the future.

Developing Countries↗
PubMed1999

VATS-stepwise resection of a giant bulla in an oxygen-dependent patient.

We report a case of a giant bulla in a 16-year-old boy who was oxygen and wheelchair dependent. He had been diagnosed with Marfan's syndrome and had severe kyphoscoliosis. The giant bulla occupying his entire left thoracic cavity compressed the contralateral lung. Until referral to our hospital, a bullectomy had been deferred during the preceding 5 years because of his poor pulmonary function and severe chest wall deformity. The patient was considered a candidate for thoracoscopic bullectomy. A stepwise resection technique was used. First, the bulla should be emptied by aspiration or wall perforation. Second, the redundant wall of the bulla should be resected by a looped ligation without opening the cavity. Third, a stapled resection of the downsized bulla should be performed. After a successful bullectomy, his subjective symptoms and pulmonary function improved. The reduction of the bulla makes bullectomy easily and decreases the number of staplers, and reduces operating time compared with opening the bulla and suturing it. Therefore, when treating a giant bulla, we recommend a stepwise resection technique.

Adolescent↗
PubMed1998

Site-directed chemical modification of cysteine-scanning mutants as to transmembrane segment II and its flanking regions of the Tn10-encoded metal-tetracycline/H+ antiporter reveals a transmembrane water-filled channel.

Cysteine-scanning mutants, E32C to G62C, of the metal-tetracycline/H+ antiporter were constructed in order to precisely determine the membrane topology around putative transmembrane segment II. None of the mutants lost the ability to confer tetracycline resistance, indicating that the cysteine mutation in each mutant did not alter the protein conformation. [14C]N-Ethylmaleimide (NEM) binding to these cysteine mutants in isolated membranes was then investigated. The peptide chain of this region passes through the membrane at least once because residues 36 and 65 are exposed on the outside and inside surfaces of the membrane, respectively (Kimura, T., Ohnuma, M., Sawai, T., and Yamaguchi, A. (1997) J. Biol. Chem. 272, 580-585). However, there was no continuous segment in which all of the introduced cysteine residues showed almost no reactivity with [14C]NEM. The proportion of the unbound positions in the second half downstream from position 45 was 55% (10/18), which was clearly higher than that in the first half (21%; 3/14), suggesting that the second half is a transmembrane segment. Positions reactive to NEM appear periodically in the second half. They are located on one side of the helical wheel, suggesting that this side of the transmembrane helix faces a water-filled channel. The cysteine mutants as to the reactive positions in the second half were severely inactivated by NEM except for the P59C mutant, whereas the A40C mutant was the only one inactivated by NEM in the first half. These results suggest that the water-filled channel along this helical region may be a substrate translocation pathway.

Amino Acid Sequence↗
PubMed1998

Membrane topology of the staphylococcal tetracycline efflux protein Tet(K) determined by antibacterial resistance gene fusion.

To determine the membrane topology of Tet(K), conventional antibiotic resistance genes were used as reporter molecules. A series of fusion genes comprising a resistance gene-beta-lactamase (amp) or chloramphenicol acetyl transferase (cat)-and one loop of the 14 putative transmembrane segments of Tet(K) was constructed. Escherichia coli TG1 with the tet(K)-amp fusion gene at the site of the putative periplasmic loop showed resistance to ampicillin, but the bacterium with the tet(K)-cat fusion gene at the site of the putative cytoplasmic loop showed resistance to chloramphenicol. These findings supported a topology of 14 membrane-spanning segments for Tet(K). Three exceptional cases were observed, which were apparently due to the presence of an acidic residue, Glu, in the preceding transmembrane segment. Mutants in which these acidic residues was substituted for alanine were also constructed, and the effect of glutamic acid in the transmembrane segment on the topology of the fusion proteins was examined.

Amino Acid Sequence↗
PubMed1998

Potential role of cbfa1, an essential transcriptional factor for osteoblast differentiation, in osteoclastogenesis: regulation of mRNA expression of osteoclast differentiation factor (ODF).

The role of Cbfa1 (core binding factor alpha1), an essential transcriptional factor for osteoblast differentiation, in osteoclastogenesis was investigated in vitro and in vivo using Cbfa1-deficient calvarial cells and mice. Co-cultures of calvarial cells isolated from embryos with three different Cbfa1 genotypes (Cbfa1+/+, Cbfa1+/- and Cbfa1-/-) and normal spleen cells generated TRAP-positive multinucleated osteoclast-like cells (OCLs) in response to 1alpha,25-dihydroxyvitamin D3 [1alpha,25(OH)2D3] and dexamethasone, but the number and bone-resorbing activity of OCLs formed in co-culture with Cbfa1-/- calvarial cells were significantly decreased in comparison with those formed in co-cultures with Cbfa1+/+ or Cbfa1+/- calvarial cells. The expression of osteoclast differentiation factor/osteoprotegerin ligand (ODF/OPGL) mRNA was increased by the treatment with 1alpha, 25(OH)2D3 and dexamethasone in calvarial cells from Cbfa1+/+ and Cbfa1+/- mouse embryos, but not from Cbfa1-/- embryos. In contrast, the expression of osteoprotegerin/osteoclastogenesis inhibitory factor (OPG/OCIF) mRNA was inhibited by 1alpha,25(OH)2D3 and dexamethasone similarly in all three types of calvarial cells. ODF/OPGL and OPG/OCIF mRNAs were highly expressed in the tibia and femur of Cbfa1+/+ and Cbfa1+/- embryos. In the tibia and femur of Cbfa1-/- embryos, however, ODF/OPGL mRNA was undetectable and the expression of OPG/OCIF mRNA was also decreased compared with those in Cbfa1+/+ and Cbfa1+/- embryos. These results suggested that Cbfa1 is somehow involved in osteoclastogenesis through regulation of ODF/OPGL.

Animals↗
PubMed1998

Acetylcholine triggers L-glutamate exocytosis via nicotinic receptors and inhibits melatonin synthesis in rat pinealocytes.

Rat pinealocytes, melatonin-secreting endocrine cells, contain peripheral glutaminergic systems. L-Glutamate is a negative regulator of melatonin synthesis through a metabotropic receptor-mediated inhibitory cAMP cascade. Previously, we reported that depolarization of pinealocytes by externally added KCl and activation of L-type Ca2+ channels resulted in secretion of L-glutamate by microvesicle exocytosis. What is unknown is how and what kinds of stimuli trigger glutamate exocytosis under physiological conditions. Here, we report that the nicotinic acetylcholine receptor can trigger glutamate exocytosis from cultured rat pinealocytes. Moreover, acetylcholine or nicotine inhibited norepinephrine-dependent serotonin N-acetyltransferase activity, which results in decreased melatonin synthesis. These activities were blocked by (2S,3S, 4S)-2-methyl-2-(carboxycyclopropyl)glycine, an antagonist of the metabotropic glutamate receptor. These results suggest that cholinergic stimulation initiates the glutaminergic signaling cascade in pineal glands and that parasympathetic neurons innervating the gland exert negative control over melatonin synthesis by way of the glutaminergic systems.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1998

D-aspartate modulates melatonin synthesis in rat pinealocytes.

It has been known that pinealocytes contain the highest level of D-aspartate among various neuroendocrine cells in the rat. Here, we report that exogenous D-aspartate strongly inhibited norepinephrine-dependent melatonin synthesis in the rat pineal gland, the concentration required for 50% inhibition being 75 microM. This inhibition was due at least partly to decreased norepinephrine-dependent serotonin N-acetyltransferase activity. Upon incubation, D-aspartate was gradually released from pinealocytes and accumulated in the incubation medium as determined by high-performance liquid chromatography on a Pirkle-type chiral column. These results suggest that D-aspartate acts as a negative regulator for melatonin synthesis in the pineal gland.

Animals↗
PubMed1998

Effects of nitric oxide from exogenous nitric oxide donors on osteoblastic metabolism.

We examined the effects of nitric oxide (NO) on the differentiation and mineralization of newborn rat calvarial osteoblastic cells (ROB cells) using exogenous NO donors, sodium nitroprusside, 3-(2-hydroxy-1-methyl-2-nitrosohydrazino)-N-methyl-1-propanamin e (NOC-7) and 2,2'-(hydroxynitrosoydrazino)bis-ethanamine (NOC-18). Sodium nitroprusside and NOC-7 dose-dependently enhanced the rate of production of intracellular cGMP in ROB cells and the rat clonal osteogenic cell line ROB-C26. We used NOC (NOC is the trade name for NO complex manufactured by Dojindo, Kumamoto, Japan) as an NO donor in our experiments because sodium nitroprusside exhibited a marked cytotoxicity. Northern blot analysis revealed that the level of mRNA for osteocalcin, one of the osteoblastic differentiation markers, was enhanced in the ROB cells, which was continuously treated by NOC-18. NOC-18, however, did not affect the level of mRNA for alkaline phosphatase and the activity of alkaline phosphatase. Both the number and the total area of mineralized nodules that are a model of in vitro bone formation were shown to be increased by 10(-5) M NOC-18. Our data suggest that NO might act as a local regulator of the metabolism of osteoblastic cells.

Animals↗
PubMed1998

Identification of D-aspartate in rat pheochromocytoma PC12 cells.

D-Aspartate is now known to be present in mammalian neuronal and endocrine cells in vivo, and may play some role(s) in neurocrine and endocrine functions. However, origin of D-aspartate is unknown. Here, we report that free D-aspartate (108 pmoles/3 x 10(7) cells) is present in the cultured PC12 cells, a rat pheochromocytoma cell line, as determined with immunohistochemical techniques as well as high performance liquid chromatography (HPLC) on a Pirkle-type chiral column. The amount of D-aspartate does not change with the passage. The culture medium does not contain D-aspartate. These results strongly suggest the presence of a de novo biosynthetic pathway for D-aspartate in the endocrine cells.

Animals↗
PubMed1998

Roles of conserved arginine residues in the metal-tetracycline/H+ antiporter of Escherichia coli.

Seven arginine residues are conserved in all the tetracycline/H+ antiporters of Gram-negative bacteria. Four (Arg67, -70, -71, and -127) of them are located in the putative cytoplasmic loop regions and three (Arg31, -101, and -238) in the putative periplasmic loop regions [Eckert, B., and Beck, C. F. (1989) J. Biol. Chem. 264, 11663-11670]. These arginine residues were replaced by alanine, lysine, or cysteine one by one through site-directed mutagenesis. None of the mutants showed significant alteration of the protein expression level. The mutants resulting in the replacement of Arg31, Arg67, Arg71, and Arg238 with either Ala, Cys, or Lys retained tetracycline resistance levels comparable to that of the wild type. Among them, only the Arg238 --> Ala mutant showed very low transport activity in everted membrane vesicles, probably due to the instability of the mutant protein. The replacement of Arg70 and Arg127 with Ala or Cys resulted in a drastic decrease in the drug resistance and almost complete loss of the transport activity, while the Lys replacement mutants retained significant resistance and transport activity, indicating that the positively charged side chains at these positions conferred the transport function. On the other hand, neither the Ala, Cys, nor Lys replacement mutant of Arg101 exhibited any drug resistance or transport activity. As for the reactivity of the Cys replacement mutants, only two (Arg71 --> Cys and Arg101 --> Cys) were not reactive with NEM, the other five mutants being highly or moderately reactive. The reactivity of the cysteine-scanning mutants around Arg101 with NEM revealed that Arg101 is located in transmembrane helix IV. It is not likely that Arg101 confers the protein folding through a salt bridge with a transmembrane acidic residue because no double mutants involving Arg101 --> Ala and the replacement of one of three transmembrane acidic residues (Asp15, Asp84, and Asp285) showed the recovery of any tetracycline resistance or transport activity. The effect of tetracycline on the [14C]NEM binding to the combined mutants S65C/R101A and L97C/R101A suggests that Arg101 may cause a substrate-induced conformational change of the putative exit gate of TetA(B).

Amino Acid Sequence↗