PubMed Health⌕ Search

Biomedical subjects

S Ogawa

Publications and source records attributed to S Ogawa.

At least 19 recordsLinked to original sources
PubMed1992

Synthesis of (+)- and (-)-nojirimycin and their 1-deoxy derivatives from myo-inositol.

The conversion of the naturally abundant cyclitol, myo-inositol (4), into (+)-nojirimycin (1a), its enantiomer (1b), and their 1-deoxy analogues (2a and 2b) is described. Biological assay of 2a, 2b, and the bisulfite adducts of 1a and 1b (3a and 3b) showed that the compounds having the unnatural L-gluco configuration (2b and 3b) possess moderate-to-high inhibitory activity against almond beta-D-glucosidase and bovine liver beta-D-galactosidase.

1-Deoxynojirimycin↗
PubMed1992

Dynamic mapping of the human visual cortex by high-speed magnetic resonance imaging.

We report the use of high-speed magnetic resonance imaging to follow the changes in image intensity in the human visual cortex during stimulation by a flashing checkerboard stimulus. Measurements were made in a 2.1-T, 1-m-diameter magnet, part of a Bruker Biospec spectrometer that we had programmed to do echo-planar imaging. A 15-cm-diameter surface coil was used to transmit and receive signals. Images were acquired during periods of stimulation from 2 s to 180 s. Images were acquired in 65.5 ms in a 10-mm slice with in-plane voxel size of 6 x 3 mm. Repetition time (TR) was generally 2 s, although for the long flashing periods, TR = 8 s was used. Voxels were located onto an inversion recovery image taken with 2 x 2 mm in-plane resolution. Image intensity increased after onset of the stimulus. The mean change in signal relative to the prestimulation level (delta S/S) was 9.7% (SD = 2.8%, n = 20) with an echo time of 70 ms. Irrespective of the period of stimulation, the increase in magnetic resonance signal intensity was delayed relative to the stimulus. The mean delay measured from the start of stimulation for each protocol was as follows: 2-s stimulation, delay = 3.5 s (SD = 0.5 s, n = 10) (the delay exceeds stimulus duration); 20- to 24-s stimulation, delay = 5 s (SD = 2 s, n = 20).

Brain Mapping↗
PubMed1992

Intrinsic signal changes accompanying sensory stimulation: functional brain mapping with magnetic resonance imaging.

We report that visual stimulation produces an easily detectable (5-20%) transient increase in the intensity of water proton magnetic resonance signals in human primary visual cortex in gradient echo images at 4-T magnetic-field strength. The observed changes predominantly occur in areas containing gray matter and can be used to produce high-spatial-resolution functional brain maps in humans. Reducing the image-acquisition echo time from 40 msec to 8 msec reduces the amplitude of the fractional signal change, suggesting that it is produced by a change in apparent transverse relaxation time T*2. The amplitude, sign, and echo-time dependence of these intrinsic signal changes are consistent with the idea that neural activation increases regional cerebral blood flow and concomitantly increases venous-blood oxygenation.

Brain Chemistry↗
PubMed1992

Synthesis of 2-O-(2-acetamido-2-deoxy-beta-D-glucopyranosyl)-5a-carba-alpha-D- mannopyranose, and 5a-carba-2-O- and 3,6-di-O-(alpha-D-mannopyranosyl)-alpha-D-mannopyranoses.

Protected derivatives of the title carba-trisaccharide 1, and carba-disaccharides 4 and 6 have been synthesised by conventional glycosylation of the precursors 8, 9, or 22 of 5a-carba-alpha-D-mannopyranose with sugar halides. These are carba-sugar analogues of the oligosaccharide chains frequently occurring as structural units in biologically important glycoconjugates, and could be utilised as the building blocks for construction of higher carba-oligosaccharides of biological interest.

Carbohydrate Sequence↗
PubMed1992

Chemical modification of the sugar part of methyl acarviosin: synthesis and inhibitory activities of nine analogues.

Nine analogues of methyl acarviosin (1), the core structure of acarbose and its homologues, the 6-hydroxy-(2), 6-azido-(3), 6-amino- (4), 6-acetamido-(5), 6-methoxy-(6), 6-hydroxy-2-O-methyl-(8), and 6-hydroxy-3-O-methyl derivatives (9), including the 5-methoxycarbonyl analogue (7) and 3,6-anhydro derivative (10) of 2, were synthesized by chemical modification of the sugar part of 2 derived by condensation of methyl 3,4-anhydro-alpha-D-galactopyranoside (17) and 4,7:5,6-di-O-isopropylidenevalienamine (26) or by direct coupling between 26 and the 6-substituted methyl 3,4-anhydro-alpha-D-galactopyranoside derivatives. Compounds 2 and 8 show notable inhibitory activity against yeast alpha-D-glucosidase almost comparable to that of 1. Introduction of a polar substituent at C-6 of 1 decreases the inhibitory activity. Interestingly, inversion of the conformation of the sugar part of 1 by introduction of the 3,6-anhydro bridge elicits almost no effect on the inhibitory activity.

Amino Sugars↗
PubMed1992

Synthesis and enzyme-inhibitory activity of methyl acarviosin analogues having the alpha-manno configuration.

Two methyl acarviosin analogues 3a and 4a, having the alpha-manno configuration, and their dihydro derivatives 6a and 7a were synthesised by coupling the protected pseudo-sugar epoxides with methyl 4-amino-4-deoxy- and -4,6-dideoxy-alpha-D-mannopyranoside. Similarly, two analogous compounds 5a and 8a composed of the 1,6-anhydro-beta-D-mannopyranose residues were prepared. Compound 7a showed mild inhibitory activity against Jack bean alpha-D-mannosidase, and 3a was a moderate inhibitor of both alpha-D-mannosidase and yeast alpha-D-glucosidase.

Amino Sugars↗
PubMed1992

Left ventricular ejection performance in mitral stenosis, and effects of successful percutaneous transvenous mitral commissurotomy.

Impaired left ventricular ejection performance was reported in pure mitral stenosis. The speculative mechanisms included insufficient preload, increased wall stress, high right ventricular pressure and unknown myocardial factors, but no definitive mechanism has been established. Fifteen patients with tight mitral stenosis who underwent successful percutaneous transvenous mitral commissurotomy were studied to ascertain whether ejection performance would improve with sufficient blood filling. The indexes of preload (end-diastolic volume) and ejection performance (stroke volume, ejection fraction, and mean systolic and mean normalized ejection rates) were calculated angiographically before and immediately after mitral commissurotomy. Improved blood filling (the result of successful mitral commissurotomy) produced an increase in end-diastolic volume (mean +/- SD 99.0 +/- 30.2 to 112.1 +/- 30.1 ml/m2; p less than 0.05). All 4 indexes of ejection performance also improved. There was good correlation between end-diastolic and stroke volumes before intervention (stroke volume = 0.476 x end-diastolic volume + 16.77; r = 0.76), and the relation between them showed no change even after mitral commissurotomy. It is concluded that both left ventricular preload and ejection performance improved after successful percutaneous transvenous mitral commissurotomy. Insufficient preload could affect ejection performance in patients with tight mitral stenosis.

Adult↗
PubMed1992

Functional relationships between cyclodextrin glucanotransferase from an alkalophilic Bacillus and alpha-amylases. Site-directed mutagenesis of the conserved two Asp and one Glu residues.

Comparison of the amino acid sequences of cyclodextrin glucanotransferases (CGTases) with those of alpha-amylases revealed that two Asp and one Glu residues, which are considered to be the catalytic residues in alpha-amylases, were also conserved in CGTases. To analyze the function of the three conserved amino acid residues in CGTases, site-directed mutagenesis was carried out. The three mutant CGTases, in which Asp229, Glu257 and Asp328 were individually replaced by Asn or Gln, completely lost both their starch-degrading and beta-cyclodextrin-forming activities, whereas another mutant CGTase, in which Glu264 was replaced by Gln, retained these activities. The three inactive enzymes retained the ability to be bound to starch. These results suggest that Asp229, Glu257 and Asp328 play an important role in the enzymatic reaction catalyzed by CGTase and that a similar catalytic mechanism is present in both CGTases and alpha-amylases.

Aspartic Acid↗
PubMed1992

Subzonal insemination with a single spermatozoon using manipulation assisted sperm adhesion onto the ooplasmic membrane in mouse ova.

A simple and successful method of microinjection of a single spermatozoon under the zona pellucida of a mouse oocyte has been developed. A characteristic of this method is that the tip of the sperm injection needle pierces the zona pellucida without touching the ooplasmic membrane. All the ova (277) used for this series of experiments had normal morphology after the injection procedure. Spermatozoa preincubated in culture medium for capacitation and those treated with ionophore A23187 for induction of acrosome reaction were used. In combination with some of these injections, a manipulation assisting the adhesion of the sperm head onto the ooplasmic membrane was employed. The fertilization rate (67.3%) of the ova injected with the ionophore-treated sperm using the sperm-adhesion treatment was significantly higher (P less than 0.005) than that obtained by the injection of the preincubated sperm without applying the adhesion treatment (23.6%). All three of the recipients that received the 24 fertilized ova became pregnant and gave birth to 11 offspring (45.8%). The inseminations performed with the sperm-adhesion treatment using the immotile sperm from the preincubated population and/or those from the ionophore-treated population did not result in fertilization in any case. These results suggest that the fertilization rate of subzonal insemination with motile ionophore-treated sperm can be improved by applying the sperm-adhesion treatment and that sperm motility might be involved in the establishment of fertilization, even after the adhesion of the sperm head with the mouse ovum membrane.

Animals↗
PubMed1992

Subzonal insemination of a single mouse spermatozoon with a personal computer-controlled micromanipulation system.

A personal computer-controlled micromanipulation system was developed for automatic injection of spermatozoa into the perivitelline space of mouse ova. A pair of three-dimensional hydraulic micromanipulators driven by pulse motors was used for this automatic system. The pulse signals that regulate the motors are initiated by the computer program, and these signals cause the micromanipulator to move the microtool precisely. The computer program was designed to perform the most effective movements of the sperm injection needle used during manual micromanipulation. Prior to the manipulation, the computer locates the tip of the injection needle and the end of the egg-holding pipette in the microscope field using image processing. The trajectory of the injection needle is determined according to these initial positions. Using this robotic system, subzonal insemination with a single mouse spermatozoon was attempted in a total of 143 ova. The sperm insertion was successfully completed in all cases without damaging any of the ova. Spermatozoa treated with ionophore A23187 and those without the treatment were used. The fertilization rate (68.8%) of the ova inseminated with treated sperm was significantly higher than that (37.5%) obtained with the nontreated sperm (P less than 0.05). These findings suggest the feasibility and potential for further applications of a robotic microinsemination system and, in addition, that a higher fertility rate in the subzonal insemination of mouse ova can be achieved with the ionophore treatment of spermatozoa.

Animals↗
PubMed1992

Fading responses in the evoked EMG after rocuronium in cats.

This study was performed to evaluate the inhibitory effect on motor nerve terminals by rocuronium using recovery curves of muscle compound action potentials (CAPs) and train-of-four ratios (TOFRs) in anaesthetized cats, and to compare the results with other relaxants reported previously. Recovery curves were derived from the amplitude of the CAP induced in the gastrocnemius muscle by the second of a paired stimulus (test response) to the sciatic nerve and compared with results evoked by the first component (conditioning response). The interval between the paired stimuli was increased stepwise from 7 to 1,000 msec, and the differences in amplitude of the test and conditioning responses were plotted on a graph by relating the changes in paired intervals. The recovery curve after rocuronium was less inhibited than after pancuronium, (100.4 +/- 5.9%, 82.3 +/- 6.7% and 68.5 +/- 6.7% at 60, 100 and 500 msec intervals, compared with 70.3 +/- 3.3%, 59.0 +/- 4.7% and 46.7 +/- 4.3% after pancuronium (P < 0.05). The recovery curves with d-tubocurarine were more depressed than with pancuronium; however, the RC with vecuronium was similar to that of rocuronium. The degree of fade in TOF by rocuronium was also less than those seen with d-tubocurarine and pancuronium. The results obtained suggest that rocuronium has less inhibitory effect on motor nerve terminals than do d-tubocurarine and pancuronium, and has a similar effect to that of vecuronium.

Androstanols↗
PubMed1992

Recombinant human superoxide dismutase can attenuate ischemic neuronal damage in gerbils.

The effects of recombinant human superoxide dismutase (r-hSOD) on ischemic neuronal injury were examined. Cerebral ischemia was produced in Mongolian gerbils by occluding bilateral common carotid arteries for 5 min. Preischemic treatment with r-hSOD clearly reduced hippocampal neuronal damages while postischemic treatment did not. This result suggests that oxygen free radicals play an important role in selective vulnerability to ischemia and r-hSOD has a potential clinical usefulness against cerebral ischemia.

Analysis of Variance↗
PubMed1992

Determinants of left ventricular filling dynamics: alteration in the Doppler-derived transmitral filling profile with progressive impairment of cardiac function in a dog preparation.

To clarify the factors determining transmitral filling, left ventricular and atrial pressures (LVP and LAP) and Doppler-derived diastolic indices were analysed in six anaesthetized dogs at various right atrial pacing rates during dextran infusion. The relationship of the late to early diastolic peak velocity ratio (A/E ratio) to end-diastolic LVP (LVEDP) showed a quadratic curve concave to the LVEDP axis in five animals (r2 = 0.320-0.588). An elevation in LVEDP up to 25 mmHg accompanied an increase in A/E ratio (ascending limb), and further LVEDP elevation caused its inverse decline (descending limb). Multiple regression analysis indicated that A/E ratio correlated positively with maximal LVP, a-wave LAP and heart rate, and negatively with v-wave LAP in both limbs. The time constant of isovolumic LVP decline, which was prolonged as LVEDP was elevated, was a positive correlate of A/E ratio in the ascending limb, but lost its influence on A/E ratio in the descending limb. An elevation in v-wave LAP must have masked the expected effect of left ventricular relaxation abnormality on A/E ratio in this limb. Thus, the transmitral filling profile did not alter unidirectionally, but returned to that seen before volume loading, with a simultaneous progressive impairment of cardiac function.

Animals↗