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Biomedical subjects

Y Imai

Publications and source records attributed to Y Imai.

At least 703 records · Page 39Linked to original sources
PubMed1993

Nucleotide sequence of the Serratia marcescens threonine operon and analysis of the threonine operon mutations which alter feedback inhibition of both aspartokinase I and homoserine dehydrogenase I.

The nucleotide sequence of the Serratia marcescens threonine operon (thrA1A2BC) was determined. Three long open reading frames were identified; these open reading frames code for aspartokinase I (AKI)-homoserine dehydrogenase I (HDI), homoserine kinase, and threonine synthase, in that order. The predicted amino acid sequences of these enzymes were similar to the amino acid sequences of the corresponding enzymes in Escherichia coli. The AKI-HDI protein is apparently a tetramer composed of monomer polypeptides that are 819 amino acids long. A deletion analysis revealed that the central and C-terminal region was responsible for threonine-resistant HDI activity, a monomeric fragment extending from the N terminus to residue 306 was responsible for threonine-resistant AKI activity, and an N-terminal portion containing 468 residues was responsible for threonine-sensitive AKI activity. The thrA(1)1A(2)1 and thrA(1)5A(2)5 mutations of threonine-excreting strains HNr21 and TLr156, which result in the loss of threonine-mediated feedback inhibition of both AKI activity and HDI activity, cause single amino acid substitutions (Gly to Asp at position 330 and Ser to Phe at position 352, respectively) in the central region of the AKI-HDI protein. The thrA1+A(2)2 mutation of strain HNr59, which results in a threonine-sensitive AKI and a threonine-resistant HDI, also causes a single amino acid substitution (Ala to Thr at position 479).

Allosteric Regulation↗
PubMed1993

Schizosaccharomyces pombe map3+ encodes the putative M-factor receptor.

A defect in the map3 gene of the fission yeast Schizosaccharomyces pombe causes h+ mating-type-specific sterility. This gene was cloned by complementation. Nucleotide sequence analysis showed that it has a coding capacity of 365 amino acids. The deduced map3 gene product is a putative seven-transmembrane protein and has 20.0% amino acid identity with the a-factor receptor of Saccharomyces cerevisiae, encoded by STE3. It is also homologous with the Ustilago maydis mating pheromone receptors. The map3 gene is expressed in h+ cells but not in h- cells, and the transcripts are induced in response to nitrogen starvation. h+ cells defective in map3 do not respond to purified M-factor. When map3 is expressed ectopically in h- cells, they apparently acquire the ability to respond to the M-factor produced by themselves. The gpa1 gene, which encodes the alpha-subunit of a G-protein presumed to couple with the mating pheromone receptors, is essential for this function of map3. These observations strongly suggest that map3 encodes the M-factor receptor. Furthermore, this study provides strong support for the notion that pheromone signaling is essential for initiation of meiosis in S. pombe and that either M-factor signaling or P-factor signaling alone is sufficient.

Amino Acid Sequence↗
PubMed1993

Schizosaccharomyces pombe Spk1 is a tyrosine-phosphorylated protein functionally related to Xenopus mitogen-activated protein kinase.

Mitogen-activated protein kinase (MAPK) and its direct activator, MAPK kinase (MAPKK), have been suggested to play a pivotal role in a variety of signal transduction pathways in higher eukaryotes. The fission yeast Schizosaccharomyces pombe carries a gene, named spk1, whose product is structurally related to vertebrate MAPK. Here we show that Spk1 is functionally related to Xenopus MAPK. (i) Xenopus MAPK partially complemented a defect in the spk1- mutant. An spk1- diploid strain could not sporulate, but one carrying Xenopus MAPK could. (ii) Both Spk1 and Xenopus MAPK interfered with sporulation if overexpressed in S. pombe cells. (iii) Spk1 underwent tyrosine phosphorylation as does Xenopus MAPK. Tyrosine phosphorylation of Spk1 appeared to be dependent upon mating signals because it occurred in homothallic cells but not in heterothallic cells. Furthermore, this phosphorylation was diminished in a byr1 disruptant strain, suggesting that spk1 lies downstream of byr1, which encodes a MAPKK homolog in S. pombe. Taken together, the MAPKK-MAPK cascade may be evolutionarily conserved in signaling pathways in yeasts and vertebrates.

Amino Acid Sequence↗
PubMed1993

Ambulatory blood pressure of adults in Ohasama, Japan.

We performed a cross-sectional study in a small town in northern Japan to evaluate the distribution, reference values, and daily variation in ambulatory blood pressure. A total of 705 subjects (229 men aged 61.3 +/- 13.4 years [mean +/- SD] and 476 women aged 57.5 +/- 13.3 years; 41.1% of the regional adult population, n = 1716), including those treated with antihypertensive drugs (n = 231, 66.5 +/- 9.5 years) as well as untreated subjects (n = 474, 55.0 +/- 13.5 years), participated in the study. Both ambulatory and screening blood pressures were measured in 659 subjects. Ambulatory blood pressure was measured with an automatic device (Colin ABPM-630). The 24-hour ambulatory blood pressure in the total population was 121.7 +/- 13.0/71.1 +/- 7.6 mm Hg (95th percentile value [95%] = 146/85 mm Hg). The corresponding value in the untreated subjects was 119.4 +/- 12.5/70.1 +/- 7.4 mm Hg (95% = 144/83 mm Hg). The 24-hour average ambulatory blood pressure was 118.0 +/- 11.1/69.4 +/- 6.8 mm Hg (95% = 139/81 mm Hg) in subjects identified as normotensive by their screening blood pressure (n = 448, 57.2 +/- 13.1 years) and 133.6 +/- 14.2/78.9 +/- 8.8 mm Hg in those identified as hypertensive by their screening blood pressure (n = 73, 63.1 +/- 10.6 years). Based on the mean+SD of the 24-hour ambulatory blood pressure in the normotensive subjects by their screening blood pressure (129/76 mm Hg), the 24-hour ambulatory blood pressures in 25 (34.2%) of these 73 hypertensive subjects by screening blood pressure were below this level. Nine (2%) of 448 normotensive subjects by screening blood pressure were above the mean+2 SDs (140/83 mm Hg) of the 24-hour ambulatory blood pressure in the normotensive group by screening blood pressure. Ambulatory and screening blood pressures increased with age. The age-dependent increase in ambulatory blood pressure was less apparent in men. The 24-hour average pulse rate decreased with age. The daily variation in ambulatory blood pressure (standard deviation) increased with age, whereas that of pulse rate decreased with age. Increases in blood pressure variation were observed in nighttime and daytime blood pressure values. The differences between day versus night ambulatory blood pressures decreased with age in men but not in women.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1993

Modulation of noradrenaline release via activation of presynaptic beta-adrenoceptors in rabbits with adriamycin-induced cardiomyopathy.

We investigated the role of beta-adrenoceptors at postganglionic sympathetic nerve endings in noradrenaline release in rabbits with cardiomyopathic congestive heart failure produced by adriamycin (1 mg/kg, I.V., twice a week for 8 weeks). Plasma noradrenaline levels were measured before, 30 min after, and 60 min after the start of continuous intravenous administration of adrenaline (0.06 micrograms/kg/min) in adriamycin-treated and vehicle-treated rabbits in anesthetized condition and pithed condition with electrically stimulated sympathetic outflow (3 Hz, 1 ms square wave pulse, 90 V). In both the anesthetized and pithed conditions, adrenaline increased plasma noradrenaline levels in vehicle-treated rabbits. However, in the adriamycin-treated rabbits, adrenaline had no effect on the plasma noradrenaline level. Pretreatment with propranolol (0.2 mg/kg, bolus I.V. + 0.1 mg/kg/hr, continuous infusion) almost completely abolished the rise in plasma noradrenaline associated with adrenaline infusion in vehicle-treated rabbits. These results suggest that in rabbits with adriamycin-induced cardiomyopathy, the noradrenaline release from the sympathetic nerve endings via the activation of presynaptic beta-adrenoceptors is reduced. This might be due to down-regulation of presynaptic beta-adrenoceptors caused by the elevated plasma noradrenaline due to cardiac failure. However, other possibilities such as reduced affinity or impaired signal transduction cannot be excluded.

Animals↗
PubMed1993

Enhanced production of platelet-activating factor in stimulated rat leukocytes caused by the blockade of lysophospholipid acylation.

We have previously reported that triacsin C, an acyl-CoA synthetase inhibitor, enhanced the production of platelet-activating factor (PAF) in calcium ionophore-activated rat polymorphonuclear leukocytes (PMNs). In this report, we further demonstrated that the production of PAF by PMNs in response to opsonized zymosan was significantly enhanced by pretreatment with triacsin C and also by the pretreatment with merthiolate, which was reported to be an inhibitor of acyl-CoA/lysolecithin acyltransferase. Pretreatment with triacsin C or merthiolate also enhanced the lyso-PAF content in the stimulated PMNs. Addition of lyso-PAF in the incubation mixture of PMNs in the presence of opsonized zymosan augmented the production of PAF. The enhancement of PAF production by lyso-PAF has been reported by several authors, and the importance of lyso-PAF in the remodeling pathway of PAF synthesis has been generally recognized. Therefore, from the above findings, it is assumed that blockades of the reacylation of lyso-phospholipids, by inhibitors such as triacsin C and merthiolate, might lead to accumulation of lyso-PAF and might result in the enhancement of PAF production when the remodeling pathway is active.

1-Acylglycerophosphocholine O-Acyltransferase↗
PubMed1993

A case of secondary aldosteronism similar to Bartter's syndrome with no abnormality in renal chloride reabsorption.

We had a 20-year-old male patient of secondary aldosteronism similar to Bartter's syndrome, which had proved to be evident after the remission of nephrotic syndrome. In the patient, hypokalemic alkalosis and hyperreninemic hyperaldosteronemia were observed, although the blood pressure was normal. Hyperplasia of juxtaglomerular cells was observed and no abnormalities indicating either glomerulonephritis or renal artery stenosis were found; the pressor response to intravenously infused angiotensin (ang) II was markedly decreased; urinary prostaglandin (PG) E2, kallikrein and kinin excretion were elevated. The inhibition of PG synthesis with indomethacin decreased renal PG production and partially corrected both hypokalemia and pressor responsiveness to ang II. Thus, this case is considered to be a case of Bartter's syndrome. Contrary to the previously reported observations, the effective fractional chloride reabsorption rate in the renal distal tubules was normal (> 80%) and not changed by PG inhibition. Plasma atrial natriuretic peptide level was normal. An interaction between renin-angiotensin and PG systems appears to play a prior role in this case. To explain the pathophysiology, we have hypothesized an abnormal function of ang II receptor signal transduction which excessively stimulates PLA2, resulting in overproduction of PG synthesis in tissues.

Adult↗
PubMed1993

Benign, non-parasitic hepatic cyst causing obstructive jaundice.

A 71-year-old woman with an hepatic cyst that led to obstructive jaundice is reported. Percutaneous intracystic fluid aspiration was useful in transiently decreasing the jaundice. Thereafter, the cyst was extirpated, and was found to be large (nearly 10 cm), benign and non-parasitic. This patient and 15 similar cases reported in the literature, indicate that the risk of jaundice induced by a simple hepatic cyst is related to its size (larger than 10 cm) and location near the common hepatic duct.

Aged↗
PubMed1993

Exocytosis in the lingual mucus cells of Rana esculenta evoked by acetylcholine: observation of living cells by confocal laser scanning microscopy.

Exocytosis of a secretory cell is believed to occur when a part of the limiting membrane of the secretory granules fuses with the luminal plasma membrane to release their contents. Using a confocal laser scanning microscope, we have studied these events in living frog lingual gland cells. In a differential interference contrast (DIC) mode, secretory granules were found to be stable in general, but after stimulation with acetylcholine chloride (ACh) of more than 1 microM concentration, there were abrupt changes in the light intensity of granules as described in other cells. We found that with the same stimulation, two different types of secretion occurred. In the first type, a small vacuole was formed and granule contents were released from various regions of the cell. In the second type, a large vacuole was formed and granule contents were released all at once. Using two fluorescent dyes BCECF and Lucifer Yellow, we were able to perform positive and negative staining of the cell as well as its granules. Confocal images of the fluorescence mode clearly demonstrated the release process which corresponded to the DIC image observed simultaneously. The electron microscopic image also showed two different types of secretion.

Acetylcholine↗
PubMed1993

Revaluation of endoscopic laser therapy for treatment of early cancer in the stomach.

The efficacy and safety of the endoscopic laser therapy for eradication of early cancer in the stomach was revaluated in fourty-eight patients. In 37 of the 42 patients (88%) treated with the laser therapy alone, the procedure was effective and the complete eradication was confirmed at the end of the follow-up period. In seven of fourteen patients with the incomplete treatment, residual cancer cells were successfully removed by repeated laser therapy. The endoscopic mucosal resection was effective in 21 of the 30 patients (70%) with the early gastric cancer. Interestingly, six of the eleven cases with incomplete treatment with the endoscopic mucosal resection underwent the laser therapy and the complete eradication was achieved in all patients. Although the endoscopic mucosal resection is now the main method for the endoscopic treatment of the early gastric cancer, these data favor offering the endoscopic laser therapy as the combined method with the mucosal resection therapy.

Adult↗
PubMed1993

Presence of the entire coding region of GP IV mRNA in Nak(a)-negative platelets.

It has been reported that Nak(a)-negative platelets lack GP IV. To examine the GP IV genetic defects in Nak(a)-negative platelets, we studied four unrelated Nak(a)-negative subjects by amplifying their GP IV cDNA, which were synthesized from platelet mRNA using the reverse transcriptase/polymerase chain reaction (RT/PCR). We detected the entire coding region of GP IV mRNA in the platelets of all four subjects. Restriction enzyme analysis of the amplified GP IV cDNA showed fully predictable cutting sites. These results suggest that no gross deletion or insertion had occurred in the GP IV mRNA of Nak(a)-negative platelets.

Antigens, CD↗
PubMed1993

[Pre and postoperative left ventricular volume and function in infants and children with total anomalous pulmonary venous return].

From January, 1989, to December, 1991, 36 consecutive patients with total anomalous pulmonary venous return (TAPVR) underwent intracardiac repair (ICR) in our institute. We studied the relationship between the size of atrial septal defect (ASD), age and preoperative left ventricular end-diastolic diameter (LVEDD) in 28 patients with regression analysis. There was no statistical relationship between the size of ASD, age and LVEDD. We measured LVEDD, RV to LV pressure ratio (RVP/LVP) and LV fractional shortening (LVFS) using two dimensional echocardiography in 15 patients, prior to and following ICR. LVEDD increased from 1.16 +/- 0.40 cm to 1.62 +/- 0.28 cm immediately following ICR, and then increased to 1.79 +/- 0.34 cm one month following ICR again. LVFS decreased from 38% to 35% immediately following ICR but still remained within normal range (normal range 28-45%). RVP/LVP decreased from 1.0 to 0.69 immediately following ICR, and to 0.39 one month following ICR. We concluded that the decrease of preoperative LV end-diastolic volume in TAPVR was not due to the decrease of LV preload but to anterior deviation of the ventricular septum caused by high RV pressure. There was significant increase of LV volume immediately following ICR, but LVFS maintained in normal range. This study suggested that small LV volume in patients with TAPVR did not influence the surgical results.

Echocardiography↗
PubMed1993

Pathological findings in dicephalus dipus dibrachius: implications for mechanisms in two pairs of lateral conjoined twins.

The anatomical and pathological features of two pairs of dicephalic conjoined twins (case 1 and 2) are described. Both twins showed duplicitas lateralis representing diprosopus dipus dibrachius. There were two complete heads on two necks, one thorax, one abdomen and externally normal two arms and two legs. Case 1 showed dicephalus with anencephaly, two vertebral columns and two spinal cords, which converged from the thoracic region distally. The esophagus, stomachs and partial small intestines were duplicated, which fused at yolk sac (with Meckel's diverticulum). The heart was incompletely fused. The lungs and trachea were doubled. Two spinal cords were fused from the thoracic region caudally and showed myelomeningocele and Arnold-Chiari malformation in case 2. Two larynxes and two thracheas connected with the incompletely fused three lobes of lungs. The conjoined lungs were hypoplastic. The heart was single, showing ventral septal defect, transposition of great arteries, two cuspid aortic valves and preductal aortic coarctation. The duplicated esophagi were conjoined in Y-shape and single stomach, duodenum, intestine and colon were found. There were pairs of kidneys, adrenal glands and ureters and single female genitalia in both cases. These findings indicate that the craniocaudal paleoaxes were separated in the cranial region and converted or fused under the thoracic region like a Y-shape. Further development defects and deformations might be important factors to form malformations in these case.

Adult↗
PubMed1993

Infantile neuroaxonal dystrophy--immunohistochemical and ultrastructural studies on the central and peripheral nervous systems in infantile neuroaxonal dystrophy.

We performed pathological studies on the central and peripheral nervous systems of cases with infantile neuroaxonal dystrophy (INAD). Numerous spheroid bodies in the central and peripheral nervous systems, were seen and divided into large spheroid bodies (LSB) and small spheroid bodies (SSB) photo-microscopically. LSB had a relation to some specific neurons with weak expression of neuron specific enolase, neurofilament and chromogranin using PAP method. SSB showed a relation to the axon without immunohistochemical expression of neuron specific enolase, neurofilament, glial fibrillary acidic protein, myelin basic protein, chromogranin, S 100 protein or antitrypsin. LSB were prominent in the posterior column, gracile nucleus, cuneate nucleus, and the tegmentum of the midbrain and the pons associated with neuronal loss and gliosis. SSB were observed in the thalamus, basal ganglia and the cerebral cortex. The cerebellum was sclerotic with few microtubule-like structures disposed in a dense network in association with degenerated mitochondria. Similar changes were observed in the sural nerves, autonomic nerve endings in the skin, and the nerve plexus of the digestive tract. Although INAD is a generalized neurodegenerative disease, it is suggested that the primary disorder might occur in the neurons and axons of the sensory tracts.

Axons↗
PubMed1993

[The effects of intrarenal infusion of recombinant human erythropoietin on renal hemodynamics and renal function in anesthesized rabbits].

To determine whether recombinant human erythropoietin (rHuEPO) has direct effect on mean arterial pressure or renal function, rHuEPO was infused intrarenally at a rate of 100 U min-1 for 30 min in anesthetized rabbits without renal failure. Intrarenal infusion of rHuEPO resulted in no change in mean arterial pressure, renal blood flow, or renal vascular resistance as compared with vehicle control. rHuEPO also produced no significant change in glomerular filtration rate, filtration fraction, or arterial hematocrit. However, urine volume, urinary excretion of sodium and potassium, and fractional sodium excretion were significantly reduced by intrarenal infusion of rHuEPO. These observations demonstrate that rHuEPO has no direct effects on mean arterial pressure or renal hemodynamics, whereas rHuEPO stimulates net tubular sodium reabsorption possibly by direct tubular action, and reduces urine volume and urinary excretion of sodium and potassium in anesthetized rabbits without renal failure.

Anesthesia, Intravenous↗