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Biomedical subjects

S Imai

Publications and source records attributed to S Imai.

At least 523 records · Page 29Linked to original sources
PubMed1988

[Nuclear magnetic resonance (NMR) spectroscopy and its application to biomedical research].

The principles of nuclear magnetic resonance (NMR) spectroscopy were explained and its application to biomedical research discussed. With 31P-NMR, it is feasible to conduct a continuous, non-invasive measurement of the contents of myocardial high-energy phosphate compounds and the intracellular pH (determined by monitoring the pH dependent shift of the inorganic phosphate peak relative to that of creatine phosphate), and to correlate them with the mechanical function. The determination of the free magnesium concentration is also possible on a similar principle to that for pH determination (the shift of MgATP peaks relative to ATP is utilized in this case). It is estimated to be 0.3 mM and was found not to be changed during ischemia. Several examples of studies including our own conducted to delineate the ischemic derangements of the myocardial energy metabolism and the effects of various interventions thereupon were illustrated. Finally a brief mention was made of the saturation transfer technique. This is the only method with which one can study the kinetics of the enzyme reactions under in vivo conditions. The application of the method for analysis of the creatine kinase reaction and the ATP synthesis was demonstrated.

Animals↗
PubMed1988

Adrenergic receptor effects and antihypertensive actions of beta-adrenoceptor-blocking agents with ancillary properties.

The acute antihypertensive effects and possible underlying mechanisms of 3 beta-adrenergic-blocking drugs with alpha-blocking activity, i.e. labetalol, drugs with alpha-blocking activity, i.e. labetalol, nipradilol and arotinolol, were studied in conscious spontaneously hypertensive rats (SHR) and compared with the effects of prazosin, propranolol and hydralazine. Prazosin produced a dose-dependent antihypertensive effect which paralleled inhibition of the pressor response to phenylephrine. Labetalol (30 mg/kg), nipradilol (30 and 100 mg/kg) and arotinolol (30 and 100 mg/kg) also produced a fall in blood pressure. However, inhibition of the pressor response to phenylephrine was not seen in association with the antihypertensive effect after the lower dose of nipradilol and arotinolol. Propranolol (100 mg/kg) did not lower blood pressure. These results suggest that a mechanism(s) other than an alpha-adrenergic-blocking effect plays a role in the acute antihypertensive effects produced by the lower dose of nipradilol and arotinolol.

Adrenergic alpha-Antagonists↗
PubMed1988

[Paradoxical fall in repetitive learning of a random series of digits].

In this study, on each trial subjects were presented visually a different random series of nine digits, and required to memorize and recall them immediately. Among a sequence of trials there were three repetitive learning trials, a few trials apart one from another. On these trials an identical series of nine digits was presented repeatedly. Recall rates of the series of digits on repetitive learning trials rose from the first trial to the second, and, by contraries, fell on the third. We call this fall "paradoxical fall," since it is contrary to the expectation of standard theories of learning. It was pointed out that we should investigate the detailed cognitive process, i.e., the microcognitive process, in learning.memory of simple series of digits, because it involves the important basic cognitive process of learning.memory.

Adult↗
PubMed1988

Studies on the biosynthesis of bialaphos (SF-1293). 8. Purification and characterization of 2-phosphinomethylmalic acid synthase from Streptomyces hygroscopicus SF-1293.

2-Phosphinomethylmalic acid (PMM) synthase catalyzes the condensation of phosphinopyruvic acid (PPA), an analog of oxalacetic acid, and acetyl-CoA to form PMM. The enzyme was purified approximately 700-fold from a cell-free extract of Streptomyces hygroscopicus SF-1293, a bialaphos producing organism, to an electrophoretically homogeneous state. The purified PMM synthase has a subunit molecular weight of 48,000 by SDS-polyacrylamide gel electrophoresis and a native molecular weight of 90,000 approximately 98,000 by gel filtration. PMM synthase was relatively unstable, showed maximum activity at pH 8.0 and 30 degrees C, and was inhibited strongly by p-chloromercuribenzoate, iodoacetamide and EDTA. Enzyme activity suppressed by EDTA was completely restored by adding Co++ or Mn++ and partially restored by addition of Ca++, Fe++ or Mg++. The specific substrates of this enzyme are PPA or oxalacetic acid in addition to acetyl-CoA. The enzyme does not catalyze the liberation of CoA from acetyl-CoA in the presence of alpha-keto acids, such as pyruvate, alpha-ketoglutarate, deamino-alpha-ketodemethylphosphinothricin or phosphonopyruvate. The condensation reaction did not take place when propionyl-CoA or butyryl-CoA was used as a substrate in place of acetyl-CoA. The Km values of the enzyme were 0.05 mM for acetyl-CoA, 0.39 mM for PPA and 0.13 mM for oxalacetate. PMM synthase is very similar to (R)-citrate synthase of Clostridium in the inhibition pattern by sulfhydryl compounds, its metal ion requirement and stereospecificity; unlike (R)-citrate synthase PMM synthase was not inhibited by oxygen.

Chromatography, Gel↗
PubMed1988

The bialaphos resistance gene (bar) plays a role in both self-defense and bialaphos biosynthesis in Streptomyces hygroscopicus.

We inactivated the bialaphos (BA) resistance gene (bar) of a BA producer, Streptomyces hygroscopicus, by the gene replacement technique. The resulting BA-sensitive mutant (Bar-) was able to produce little BA but considerable amount of an intermediate demethylphosphinothricin (DMPT). The Bar- mutant was still able to convert the N-acetyl derivative (AcDMPT) of DMPT to BA. Introduction of normal bar containing plasmid restored both BA resistance and BA biosynthesis to levels as high as the parental BA producer. By contrast, introducing a multi copy glutamine synthetase gene (glnA) into the Bar- mutant restored BA resistance but not BA production. Thus, the bar gene plays a crucial role in both self-defense and a step of BA biosynthesis in the BA-producing S. hygroscopicus.

Anti-Bacterial Agents↗
PubMed1988

Replacement of Streptomyces hygroscopicus genomic segments with in vitro altered DNA sequences.

We have developed a method for gene replacement in Streptomyces hygroscopicus which permits introduction of an in vitro derived mutation carried on a plasmid into the chromosome. We constructed the plasmid pMSB212 which can replicate in S. hygroscopicus and contains the step5 gene of the bialaphos biosynthetic pathway which was inactivated by a frame-shift mutation caused by filling in the cohesive ends of the EcoR I site in the structural gene. pMSB212 was introduced into a bialaphos producer strain and by protoplast regeneration of the primary thiostrepton-resistant transformants, non-producing mutants, were obtained. Biochemical and genetical analyses indicated that these mutants were specifically blocked by introduction of the frame-shift mutation in the step5 gene on the chromosome. This method will enable us to obtain isogenic mutants of known genes and to identify new genes encoded on a cloned fragment.

Chromosomes, Bacterial↗
PubMed1988

The bialaphos biosynthetic genes of Streptomyces hygroscopicus: cloning and analysis of the genes involved in the alanylation step.

We have isolated and studied the genes involved in the alanylation step in the biosynthesis of a herbicide, bialaphos which is produced by Streptomyces hygroscopicus. Three bialaphos-nonproducing mutants, NP60, NP61 and NP62, isolated from S. hygroscopicus by treatment with N-methyl-N'-nitro-N-nitrosoguanidine were defective for the alanylation step and were not restored to productivity by any locus of the gene cluster previously cloned. Three plasmids were isolated using NP60, NP61 and NP62 as recipients. The genes which restored productivity to NP61 and NP62 hybridized to the contiguous region of the bialaphos biosynthetic gene cluster. The gene cluster involved in the bialaphos production was about 35 kb long. The gene which restored productivity to NP60 did not hybridize to the bialaphos biosynthetic gene cluster. VM3 and VM4, putative alanylation blocked mutants, were derived from a bialaphos producer by gene replacement of an unidentified region of the biosynthetic gene cluster with an in vitro altered DNA sequence. The genes which restored productivity to VM3 and VM4 were located between the genes which code for phosphinomethylmalic acid synthase and demethylphosphinothricin acetyltransferase in the cluster. These results suggest that multiple genes are involved in the alanylation step.

Alanine↗
PubMed1988

Effects of nitrogen dioxide on Mycoplasma pulmonis infection and humoral immune responses in mice.

The effects of continuous exposure to nitrogen dioxide (NO2) on the pathologic and immunologic responses of ddY mice to the infection with Mycoplasma pulmonis were investigated. The organisms grew well in the trachea as early as 7 days after infection but barely grew in the lung even after 28 days, causing slight pneumonic lesions in only a few of the infected mice exposed to 1 and 5 ppm NO2. When mice were exposed to 10 ppm NO2 at or after the infection, however, mycoplasmal growth in the lung, but not in the trachea, was greatly enhanced, and pneumonic lesions were evident in the lung of almost all the mice examined. The serum antibody titers to M. pulmonis increased with time after infection regardless of the concentration of NO2 exposed or the mycoplasmal number in the respiratory tract in the infected mice. The in vitro immune responses of the spleen cells of the infected mice were significantly depressed by exposure to 10 ppm NO2 in not only mitogenic response to LPS and ConA but also antibody production to SRBC, whereas uninfected healthy mice were apparently not modulated except for a slight decrease in Con A response.

Animals↗
PubMed1988

[A case of triple cancer--gastric, esophageal and hepatocellular carcinoma].

A case of triple cancer involving a tubular adenocarcinoma of the stomach, a squamous cell carcinoma of the esophagus, and hepatocellular carcinoma of the live is reported. These three cancers had been diagnosed while the patient was alive and later were confirmed by autopsy. The esophageal cancer and hepatocellular carcinoma were found almost simultaneously, 6 years after surgery for the gastric cancer. Although many cases of triple cancer have been reported, a triple cancer of this combination is very rare (0.3% of all cases of triple cancer), our case being the fifth such case in Japan.

Adenocarcinoma↗
PubMed1988

Clearer demonstration of calcium/calmodulin-dependent events in synaptosomes by use of the differential effects of two calmodulin antagonists, N-(aminohexyl)-5-chloro-1-naphthalenesulfonamide and N-(6-aminohexyl)-1-naphthalenesulfonamide.

1. In order to demonstrate more clearly calcium/calmodulin-dependent events, the differential effects of two calmodulin antagonists, W-7 and W-5, on synapsin I phosphorylation and norepinephrine release associated with calcium influx, were investigated using 32Pi in synaptosomes derived from rat cerebral cortex. 2. The calcium ionophore (A23187)-stimulatory effect on synapsin I phosphorylation and norepinephrine release was markedly reduced by W-7 and slightly reduced by W-5; whereas neither the strong nor the weak calmodulin antagonist had an effect on A23187-stimulated synaptosomal uptake of calcium. 3. Preincubation with H-8 reduced both W-5- and W-7-inhibited A23187-stimulated synapsin I phosphorylation by the same amount but did not affect their inhibitory effect nor the ionophore-stimulated norepinephrine release, thereby suggesting that W-5 may serve as an appropriate control for non-calmodulin-mediated effect of both calmodulin antagonists.

Animals↗
PubMed1988

[Progression of coronary artery stenosis and compensatory development of collaterals: analysis of data of 25 patients who developed complete occlusion].

The correlation between progression of atherosclerotic lesions and the compensatory development of collaterals which prevent ischemic events, particularly myocardial infarction, were examined in patients who underwent repeated coronary angiography (CAG) after medical therapy. Twenty-five patients with lesions in their coronary arteries perfusing the viable myocardium during the first study, which progressed to total occlusion in the second study, were evaluated. The subjects' mean age was 55.1 years, and the mean time interval between the two studies was 44.1 months. CAG was performed in the chronic stage of myocardial infarction or the stable phase of angina pectoris, but three patients underwent repeated CAG studies during the acute phase of myocardial infarction. The percent diameter of the narrowing in the lesion was assessed according to the AHA system. Concerning the sites of lesions with progression to complete occlusion, 14 (56%) were located in the proximal segment of the left anterior descending artery (segment 6 or 7), and six lesions were in the main trunk of the right coronary artery (segment 1, 2 or 3). In 11 patients with stable angina, associated lesions showed progression from 90 or 99% stenosis to complete occlusion. Seven patients with lesions exhibiting 99% stenosis had collaterals, and four patients with lesions exhibiting 90% stenosis had no collaterals during the first study. However, good collaterals were demonstrated in all patients in the second study. Seven patients had episodes of newly developed unstable angina. The lesions in five of the seven patients progressed from 75% or 90% stenosis to complete occlusion, and in one patient with triple vessel disease the lesion progressed from 99% stenosis to complete occlusion in the second study. The former five patients did not have collaterals in the first study, but development of collaterals was demonstrated in all seven patients in the second study. Seven patients had episodes of myocardial infarction, and in six of these, the lesions progressed from 75% or less stenosis to complete occlusion.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1988

Echocardiographic findings in nine patients with cardiac amyloidosis: their correlation with necropsy findings.

The echocardiographic abnormalities of nine patients with cardiac amyloidosis were correlated with their postmortem findings. All had congestive heart failure and autopsy-proven amyloidosis. M-mode echocardiographic features included (1) small or normal left ventricular (LV) dimensions; (2) thickened interventricular septa and posterior LV walls (89%); (3) left atrial enlargement (89%); and (4) reduced LV distensibility (78%, 100%) and contractility (22%, 44%). Serial M-mode echocardiography revealed that cardiac amyloidosis was initially manifested as diastolic LV dysfunction rather than systolic dysfunction. The final stage of this disease was characterized by severe impairment of both systolic and diastolic LV functions. Two-dimensional echocardiography provided additional features: (1) a more accurate diagnosis of pericardial effusion (67%) and (2) a characteristic "granular sparkling" appearance of the ventricular wall (55%). In four of five cases, these hyperrefractile myocardial echoes corresponded to scattered amyloid deposits histopathologically. There was no correlation between the types of amyloid deposits and the hyperrefractile myocardial echoes. Thus, cardiac involvement in systemic amyloidosis could be non-invasively assessed by M-mode and two-dimensional echocardiography.

Adult↗