Biomedical subjects

H Watari

Publications and source records attributed to H Watari.

At least 37 records · Page 2Linked to original sources

PubMed1991

High-resolution magnetic resonance imaging of the human temporal bone.

A magnetic resonance imaging (MRI) system (Hitachi, Naka, Japan) with a superconductive magnet running at 2.11 T was used to obtain 2-mm-thick slices of fixed, decalcified and celloidin-embedded human temporal bone. The temporal bone was then sectioned and stained for routine histological evaluation. Both the MR images and the histological sections were in the mid-modiolar slice plane, and comparable images and sections were analyzed to confirm the identity of the inner-ear structures visualized on the MR images. The cochlear duct, scala tympani, scala vestibuli and basement membrane of all three cochlear turns were clearly imaged on MRI. In addition, the vestibule and three semicircular ducts were also clearly seen. This study raises the possibility of some day using MRI for the diagnosis of inner-ear diseases.

Basement Membrane↗

PubMed1991

Dose effects of cholecystokinin and acetylcholine on phosphorus compounds and secretory responses in isolated perfused pancreas of rat.

Phosphorus nuclear magnetic resonance (31P NMR) spectroscopy was used to study energy supply for protein secretion in the isolated perfused rat pancreas. Stimulation with cholecystokinin (CCK-8) increased fluid secretion and protein output. With 10pM of CCK-8, the tissue contents of ATP, inorganic phosphate (Pi), and creatine phosphate (PCr) remained unchanged. With 100pM of CCK-8, which induced the maximum response in fluid secretion and protein output, Pi increased slightly, ATP and PCr remained almost unchanged. A high dose of CCK-8 (1 nM) suppressed the fluid and protein secretory rates, decreased ATP, and increased Pi significantly, but PCr showed a tendency of increase. Significant changes in ATP and Pi occurred on withdrawal of CCK-8 (1 nM), suggesting activation of ATP hydrolysis for recovery from secretory suppression. During stimulation with 0.1, 0.3, and 3.0 microM of acetylcholine, the similar dose-dependent response was observed in the secretion and the phosphorus metabolism. The present study demonstrated that cytosolic energy metabolism for secretory responses in the pancreas is low and the Lohmann reaction showed less contribution than in the salivary gland. The findings suggest that the energy supply for protein secretion may be cytosolic diffusion of ATP and that the Lohmann reaction system may contribute to synthesis and storing of secretory protein at resting state.

Acetylcholine↗

PubMed1990

Measurement of intracellular Na in the rat salivary gland: a 23Na-NMR study using double quantum filtering.

23Na in the prefused rat mandibular salivary gland was measured by spin-echo double quantum filter 23Na-NMR spectroscopy at 8.45 T. Resonances due to the intracellular 23Na and the interstitial 23Na were observed in the perfused gland at 25 degrees C. The resonance due to intracellular 23Na consisted of two Lorentzian signals stemming from the [1/2 mean value of -1/2[ coherence (sharp resonance) and the [-1/2 mean value of -3/2[ and [3/2 mean value of 1/2[ coherences (broad resonance). The transverse relaxation rate constant corresponding to the [1/2 mean value of -1/2[ coherence was 95 +/- 4 s-1 and that corresponding to the [-1/2 mean value of -3/2[ and [3/2 mean value of 1/2[ coherences was 1360 +/- 75 s-1 (mean +/- S.E., n = 5). The resonance due to the interstitial 32Na had longer relaxation rate constants, and disappeared upon administration of dysprosium triethylenetetramine-N,N',N",N",N"'-hexaacetic acid.

Acetylcholine↗

PubMed1990

Role of phosphocreatine in energy transport in skeletal muscle of bullfrog studied by 31P-NMR.

To evaluate the energy-shuttle hypothesis of the phosphocreatine/creatine kinase system, diffusion rates for ATP, phosphocreatine and flux through the creatine kinase reaction were determined by 31P-NMR in resting bullfrog biceps muscle. The diffusion coefficient of phosphocreatine measured by 31P-pulsed gradient NMR was 1.4-times larger than ATP in the muscle, indicating the advantage of phosphocreatine molecules for the intracellular energy transport. The flux of the creatine kinase reaction measured by 31P-saturation transfer NMR was 3.6 mmol/kg wet wt. per s in the resting muscle. The flux is equal to the turnover rate of ATP, ADP, phosphocreatine and creatine molecules, therefore, the life-times of these substrates and the average distance traversed after the life-times by the diffusing molecules were calculated using the diffusion coefficients obtained by 31P-NMR. The mean square length of one-dimensional diffusion was 22 microns in ATP molecules and the minimum diffusion length was 1.8 microns in ADP molecules. The latter was calculated using free ADP concentration, 30 mumol/kg wet wt., obtained from the equilibrium constant of the creatine kinase reaction and the diffusion coefficient assumed to be the same of ATP in muscle. Similar diffusion lengths of ADP were calculated using the reported values for the flux of the creatine kinase reaction in heart and smooth-muscle. The diffusion lengths of all substrates involved in the creatine kinase reaction were larger than the radii of myofibrils. Therefore, in the muscles with an alternating arrangement of mitochondria and myofibrils, such as heart and certain skeletal muscles, ATP and ADP molecules can move freely between myofibrils and mitochondria without the aid of the creatine kinase reaction; thus, we conclude that the energy-shuttle hypothesis is not obligatory for energy transport between the mitochondria and the myofibrils.

Adenosine Triphosphate↗

PubMed1990

NMR characteristics of intracellular K in the rat salivary gland: a 39K NMR study using double-quantum filtering.

Intracellular K of the perfused rat mandibular salivary gland was measured by 39K NMR spectroscopy at 8.45 T. Multiple-quantum NMR arising from multiple-exponential decay was used to eliminate the resonance due to extracellular K in the perfused gland at 25 degrees C. The resonance due to intracellular K consisted of two Lorentzian signals stemming from the [spin 1/2 to -1/2] coherence (sharp resonance) and the [spin -1/2 to -3/2], [spin 3/2 to 1/2] coherences (broad resonance). The transverse relaxation time (T2) corresponding to the [spin 1/2 to -1/2] coherence was ca. 2.5 ms, and that corresponding to the [spin -1/2 to -3/2], [spin 3/2 to 1/2] coherences was ca. 0.4 ms. The relaxation time of the double-quantum coherence of rank 3 (originating from product operators like Ix2Iz) was determined to be ca. 0.2 ms. These results suggest the possibility of the presence of a single homogeneous population of intracellular K with a correlation time of ca. 2.5 x 10(-8) s and a quadrupolar coupling constant of ca. 1.4 MHz.

Animals↗

PubMed1990

Sodium-23 MR imaging of the kidney in guinea pig at 2.1 T, following arterial, venous, and ureteral ligation.

In vivo 23Na magnetic resonance images of guinea pig kidney were obtained at 2.1 T using a spin-echo sequence with an echo time of 19 ms. The intact kidney showed a very strong signal intensity in the sodium image. The signal intensity of the kidney decreased to 55% after ligation of the renal artery together with the vein and the ureter. The total sodium content in the excised kidney after arterial occlusion, measured by flame photometry, was 24% higher than that in the intact kidney. The transverse relaxation time (T2) of the extracellular sodium in the isolated kidney decreased to one-third of that in the intact kidney. This shortening of T2 may be partly responsible for the decrease in the 23Na signal intensity from the kidney after arterial occlusion.

Animals↗

PubMed1990

1H-NMR studies on water structures in the rat brain tissues with cerebral tumour or ischaemia.

Spin-lattice relaxation times (T1) of water protons and cross-relaxation times (T(IS)) between irradiated protein protons and observed water protons were measured to study water structure in various rat brain tissue. A tumour-bearing rat model and an incomplete forebrain ischaemia model of stroke prone spontaneously hypertensive rats (SHRSP) were used for the experiments. T(IS) and T1 were measured by the inversion recovery FT method with and without f2-irradiation at 7.13 p.p.m. and gamma H2/2 pi approximately 69 Hz, respectively, using a 360 MHz FT-NMR spectrometer. All of experiments on T1 and T(IS) yielded a single kind of component. In spite of small changes in T1 and water content, T(IS) values in peritumoural oedematous and ischaemic brain tissue were significantly shorter than those of normal brain and far shorter than those of brain tumour, indicating a large amount of hydration of marco-molecules in the oedematous and/or ischaemic rat brain tissue. T(IS) might be sensitive parameter for studying the water structure in various brain tissue.

Animals↗

PubMed1990

Leakage of cytoplasmic enzymes from rat heart by the stress of cardiac beating after increase in cell membrane fragility by anoxia.

The effects of spontaneous beating after anoxia and the pumping stress induced by a left ventricular balloon on the leakage of myocardial enzymes from the isolated perfused rat heart were investigated. Beating of the heart was arrested by perfusion with high-K+ medium. When the beating was arrested during reoxygenation after anoxia, the leakage of lactate dehydrogenase (LDH) was significantly lower than during reoxygenation with spontaneous cardiac beating. After changing from K+ arrest to spontaneous beating by perfusion with low-K+ medium during reoxygenation, the leakage of LDH increased markedly. Imposition of left ventricular wall stress on the K(+)-arrested heart by repetitive passive distension during aerobic perfusion and after 20 min and 60 min of anoxia caused LDH leakages of 1.0, 4.6 and 21.0 units/g in 30 min, respectively. Under this mechanical stress, the release of LDH as a percentage of its total myocardial activity coincided well with that of cytoplasmic aspartate aminotransferase (AST), while the percentage release of mitochondrial AST was much less. These results appeared to indicate that the leakage of cytoplasmic enzymes during reoxygenation is accelerated by cardiac beating because of fragility of the cell membranes developing during the preceding anoxia.

Adenosine Triphosphate↗

PubMed1990

Energetic recovery from hypothermic preservation in the rat liver.

Changes in energy metabolism induced by norepinephrine were observed in liver perfused immediately after dissection and in liver stored in Euro-Collins solution at 0 degrees C for 24 hr. Oxygen consumption, glucose output, ATP content, and tissue pH were measured in isolated perfused rat liver at 37 degrees C. In fresh liver, a two-fold increase in glucose output and oxygen consumption was induced by norepinephrine (1 microM), while changes in ATP content and tissue pH were minimal. In stored liver, the cumulative increments in glucose output and oxygen consumption induced by norepinephrine were 30 and 27% those of fresh liver, respectively. ATP content of the unstimulated liver was 76% that of the fresh liver, then decreased to 50% during stimulation. A transient decrease in tissue pH (0.14 pH unit) was significant compared with that of fresh liver. These results suggest that norepinephrine stimulation is useful for assessing energetic and functional recovery of reperfused liver following hypothermic storage.

Adenosine Triphosphate↗

PubMed1990

Adenosine triphosphate compartmentation in the rat heart: a 31P spin-lattice relaxation study.

Longitudinal relaxation times (T1) of phosphorus compounds in the perfused rat heart and erythrocytes were measured using the 31P Driven-Equilibrium Single-Pulse Observation of T1 relaxation (DESPOT) method at 33 degrees C. Both creatine phosphate in the heart and the three phosphate groups of adenosine triphosphate (ATP) in erythrocytes showed single-exponential relaxation. The three phosphate groups of ATP in the heart, however, had two T1 components. The T1 values of the short and the long T1 components of the beta-phosphate of ATP were ca. 0.4 and 14 s, respectively. The fraction with the long T1 represented ca. 30% of the total ATP content. These results suggested that there were two major pools of intracellular ATP in the rat heart which could be determined by 31P NMR spectroscopy.

Adenosine Triphosphate↗

PubMed1990

Structural transition of bovine plasma albumin in the alkaline region--the N-B transition.

Bovine plasma albumin (BPA) has approximately one SH group (Cys-34) which catalyzes the intramolecular SH, S-S exchange reaction in the alkaline region at low ionic strength, resulting in the formation of the aged form. So, the N-B transition at ionic strength above 0.20 and below 0.10 was studied using BPA and iodoacetamide-blocked BPA (IA-BPA), respectively. (1) pH profiles of [theta]262 and [theta]268 of BPA in 0.20 M KCl showed the characteristic changes in the pH region 7.0-9.0, corresponding to the N-B transition. On going from pH 7.0 to 9.0 in 0.10 M KCl or NaCl, IA-BPA did not show significant changes in rotational relaxation times of tryptophyl fluorophors, CD-resolved secondary structures, spin-echo 1H-n.m.r. spectra and cross-relaxation times (TIS) between irradiated and observed protein protons, which might reflect the rigidity of the domains and/or subdomains. On the other hand, rotational relaxation times of 1-anilino-8-naphthalenesulfonate-IA-BPA complex (IA-BPA-ANS0.9, molar ratio of ANS to IA-BPA = 0.9/1) showed significant decreases from 131 to 114 ns on going from the N- to the B-forms in 0.10 M KCl. The above results and reported experimental evidence might indicate that on going from the N- to the B-forms in 0.10 M KCl or NaCl, the mutual movement of subdomains, connected with a flexible hinge region (Brown & Shockley (1982)) might increase without loss in the helicity and the rigidity of subdomains. (2) The N-B transition of IA-BPA in the absence of salt was quite different from those in 0.10 M KCl or NaCl. Decreases in the helicity and the intramolecular rigidity, as monitored by TIS-measurements, were observed on going from the N- to the B-forms.

Animals↗

PubMed1990

Potassium-39 nuclear magnetic resonance observation of intracellular potassium without chemical shift reagents during metabolic inhibition in the isolated perfused rat heart.

The intracellular potassium content of perfused rat heart was measured by potassium-39 nuclear magnetic resonance (NMR) spectroscopy at 33 degrees C with an inversion recovery technique based on the fact that the spin-lattice relaxation time (T1) of the intracellular potassium (8.3 msec at 8.45 T) is much faster than that of the extracellular potassium (68 msec). Intracellular potassium decreased to 60.2 +/- 4.3% of the control level (mean +/- SEM, n = 6) at 40 minutes from the start of metabolic inhibition (2 mM cyanide, 0 mM glucose). Removal of cyanide restored intracellular potassium to 94.2 +/- 3.9% at 30 minutes from the restart of oxidative metabolism. The cumulative potassium loss was determined from the flow rate and potassium concentration of the coronary effluent, which reached 139 +/- 12 mumol/g dry wt during 40 minutes of metabolic inhibition. This value was calculated as 41.8% of intracellular potassium in the control heart and agreed with the decrement of intracellular potassium measured by NMR. During the metabolic inhibition and recovery period, a linear correlation was observed between the changes in 39K NMR-observed intracellular potassium and the cumulative potassium loss. The present results evaluate the inversion recovery technique as a method to successfully monitor the myocardial intracellular potassium.

Animals↗

PubMed1989

[Partial volume effect in MRI--a phantom study].

According to the direction and the thickness of the imaging slice in tomography, the border between the tissues becomes unclear (partial volume effect). In the present MRI experiment, we examined border area between fat and water components using phantom in order to investigate the partial volume effect in MRI. In spin echo sequences, the intensity of the border area showed a linear relationship with composition of fat and water. Whereas, in inversion recovery and field echo sequences, we found the parameters to produce an extremely low intensity area at the border region between fat and water. This low intensity area was explained by cancellation of NMR signals from fat and water due to the difference in the direction of magnetic vectors. Clinically, partial volume effect can cause of mis-evaluation of walls, small nodules, tumor capsules and the tumor invasion in the use of inversion recovery and field echo sequences.

Magnetic Resonance Imaging↗

PubMed1989

Vector electron paramagnetic resonance spectroscopy with first and second harmonic displays of ferrihemoglobin.

Superimposed plots of electron paramagnetic resonance spectra with the first and second harmonic displays of ferrihemoglobin at pH 9.1 and 90 K were measured at 20 degree intervals of phase angle using a phase-sensitive detector. The high spin signal in the g = 6 region was observed in both displays, and a small splitting of the signal was found in the calculated amplitude spectrum of the second harmonic display, with g values of 5.95 and 6.05. Low spin signals were observed at g = 2.55, 2.25 and 1.82 in both harmonic displays. A signal in the g = 2.05 region was observed only in the second harmonic display. The signal is probably associated with the low spin spectrum; however, its origin is obscure.

Electron Spin Resonance Spectroscopy↗

PubMed1989

[Significance of brain renin for pathogenesis of hypertension: effect of antihypertensive drugs on active and inactive renins in the brain of spontaneously hypertensive rat].

Relationship between blood pressure and brain renin was studied in four groups of spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY); as controls (n = 5), administered captopril (n = 5), trichlormethiazide (n = 5) and atenolol (n = 5). 1) Inactive renin in the hypothalamus of captopril-administered SHR was significantly lower than that of control SHR and captopril-administered WKY. On the other hand, active renin in the hypothalamus, thalamus and striatum of captopril-administered SHR was significantly lower than that of control SHR and captopril-administered WKY. 2) Inactive renin in the hypothalamus of trichlormethiazide administered SHR was significantly lower than that of control SHR and trichlormethiazide-administered WKY. On the other hand, active renin in the hypothalamus, thalamus and midbrain of trichlormethiazide-administered SHR was significantly lower than that of control SHR and trichlormethiazide-administered WKY. 3) Inactive renin in the hypothalamus of atenolol-administered SHR was significantly lower than that of control SHR and atenolol-administered WKY. On the other hand, active renin in the hypothalamus, thalamus and midbrain of atenolol-administered SHR was significantly lower than that of control SHR and atenolol-administered WKY. These results suggest that the production and/or activation of renin in the hypothalamus, thalamus, midbrain and striatum play an important role in the initiation and/or development of hypertension of SHR by the local generation of angiotensin II.

Animals↗

PubMed1989

Direct measurement of K movement by 39K NMR in perfused rat mandibular salivary gland stimulated with acetylcholine.

The intracellular K content (Kin) of the isolated perfused rat mandibular gland was measured by 39K NMR spectroscopy at 25 degrees C, using an inversion recovery technique based on the fact that the spin-lattice (T1) relaxation of Kin is much faster than that of the extracellular K. Kin decreased by 30-34% of the resting level and reached a plateau level during secretion evoked by a sustained infusion of 1 mumol/l acetylcholine. Addition of 1 mmol/l ouabain decreased Kin by an additional 41% of the resting level. The K net flux to the blood and saliva was calculated from the K concentrations and flow rates of the effluent and the saliva. At an initial stage of secretion the gland lost K to the vascular side at a rate of 12.6 +/- 1.8 mumol/g-min (mean +/- SEM, n = 7). During sustained secretion, the gland took K up from the vascular side at a rate of 3.3 +/- 0.7 mumol/g-min (n = 7), and the same amount of K was secreted into the saliva (4.7 +/- 1.1 at 5-10 min, 2.8 +/- 0.8 mumol/g-min at 20-30 min), resulting in no net K movement from the gland. Addition of 1 mmol/l ouabain stopped salivary secretion and caused a transient K release to the vascular side at a maximum rate of 12.8 +/- 1.1 mumol/g-min. Withdrawal of acetylcholine and ouabain induced K uptake from the vascular side (6.5 +/- 0.7 mumol/g-min) and the amount of K released was completely restored when Kin recovered completely.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗

PubMed1988

An experimental approach to 31P spin-lattice relaxation time measurement in biological systems.

The accuracy of measurement of the spin-lattice relaxation time (T1) in biological systems using the variable nutation angle method is discussed using computer simulations. This method could reduce the time required for measurement to 10% of that using the inversion recovery method. In the perfused salivary gland of the rat (310 K), the T1 values of sugar phosphates, creatine phosphate, gamma-phosphate, and beta-phosphate of nucleotide triphosphates determined by this method were 5.2, 4.8, 0.9, and 0.8 s, respectively. During secretion of saliva, the T1 value of sugar phosphates decreased to 3.7 s, which could be due to an increased chemical exchange of phosphate in glycolysis.

Animals↗

PubMed1988

Internal motion of a tryptophan residue in Streptomyces subtilisin inhibitor: deuterium nuclear magnetic resonance in solution.

Deuterium NMR spectroscopy was used to study internal motions of a deuterium-labeled single tryptophan (Trp) residue (per subunit) of Streptomyces subtilisin inhibitor (SSI) in solution. The free inhibitor with the five ring protons of the Trp replaced with deuterons showed a narrow resonance component (56 Hz) of about one-quarter of the total intensity, in addition to the broad resonance component (about 600 Hz) at 25 degrees C, showing that it exits in an equilibrium mixture of two conformers, in one of which the tryptophan side chain is highly mobile. In analogy to the two structures of SSI found in the crystal, these two conformers were attributed to the one in which the contact between the alpha-lobe and the beta-lobe of the subunit is tight and the other in which the same contact is loose. When SSI forms a complex with subtilisin BPN', the broad component becomes invisibly broad, but the narrow component increases with even further narrowing, suggesting that the binding to the enzyme favors the "loose" conformer over the "tight" conformer.

Bacterial Proteins↗