Biomedical subjects
Publications and source records attributed to N Noda.
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A novel resin glycoside, merremin (1), has been isolated from the root of Merremia hungaiensis (Convolvulaceae). The structure has been determined to be an ester-type dimer of tuguajalapin X (2) on the basis of chemical and spectral data.
We measured intracellular NA+ concentration ([Na+]i) of diabetic rat ventricular myocytes using sodium-binding benzofuran isophthalate (SBFI). We used diabetic rats at 8 weeks after the injection of streptozotocin (45 mg/kg i.v.). The level of [Na+]i during the control perfusion was significantly lower in diabetic myocytes than that in normal myocytes (9.2 +/- 0.4 mM v.s. 12.0 +/- 0.3 mM, p < 0.01). After the 40 min perfusion of 1 microM hexamethylene amiloride (HMA), [Na+]i decreased significantly in both groups. However, there was no difference in [Na+]i between the two groups after the perfusion of HMA. It was suggested that the lower [Na+]i in diabetic myocytes could be due to the decreased activity of Na+/H+ exchange system.
Seven ether-soluble resin glycosides, stoloniferins, I-VII, were isolated in the pure state from the whole plants of Ipomoea stolonifera. Their structures were determined on the basis of chemical and spectral data.
Seven glycosphingolipids were obtained in the pure state from the clam worm, Marphysa sanguinea, by preparative HPLC with a reversed-phase column in a recycling mode. Their structures were elucidated based on detailed analyses of 1H- and 13C-NMR spectra of the intact compounds. The position and the geometry of double bonds in the long-chain base (LCB) were determined by the two-dimensional NMR (COSY, NOESY, and HMBC) analyses. All compounds are phosphocholine-bonded monogalactosylceramides and two of them have tri-unsaturated long-chain bases.
Thirty-two newly isolated strains of Rickettsia tsutsugamushi, 14 from patients with tsutsugamushi disease, 12 from wild rodents, and 6 from trombiculid mites parasitizing rodents in Gifu Prefecture, Japan, were examined for reactivities to 12 monoclonal antibodies by an indirect fluorescent-antibody test to classify their antigenicities. All of the isolates could be classified into one of six groups (KN-1, KN-2, KN-3, GJ-1, R158, and R161) according to their reactivities to the monoclonal antibodies. The KN-1 and GJ-1 strains that are prevalent among patients from Gifu Prefecture had the same reactivities as the Kawasaki and Kuroki strains, respectively, which have been isolated and are prevalent in the Miyazaki and Kagoshima prefectures in southwest Japan. The isolates from patients were different in serotype from those from rodents and mites (Leptotrombidium pallidum). The KN-2 and KN-3 strains were most prevalent among patients and among rodents and mites, respectively. No close similarity between KN-2 and other strains tested was observed. KN-3 is only a minor contributor to diseases in patients in Gifu Prefecture; however, it was proven that the same strain was prevalent in Niigata Prefecture in northern Japan. Thus, Gifu Prefecture is an area where southern, northern, and local strains are found. We hypothesize that humans are prone to infection with KN-2, GJ-1 (very similar to Kuroki), and KN-1 (very similar to Kawasaki), probably by infestation with Leptotrombidium scutellare. While both L. scutellare and L. pallidum parasitize wild rodents and may carry any rickettsial strain, the most virulent strain, KN-3, is predominant among wild rodents. Antigenic analysis using monoclonal antibodies to R. tsutsugamushi should be useful for epidemiological studies of infection with this organism.
To study the relationship between intracellular Na+ concentration ([Na+]i) and intracellular Ca2+ concentration ([Ca2+]i), guinea pig ventricular myocytes were loaded with both the Na(+)-sensitive probe, sodium-binding benzofuran isophthalate (SBFI), and the Ca(2+)-sensitive probe, fluo 3. [Na+]i was measured from the ratio image at 510 nm when excited at 340/380 nm. [Ca2+]i, expressed as the percent change of corrected fluo 3 fluorescence, was measured at 540 nm when excited at 500 nm. The fluorescent spectra of these probes were sufficiently different to allow for simultaneous measurement. After 30 min perfusion of K(+)-free solution, [Na+]i of rod-shaped cells increased from 6.4 +/- 0.5 to 20.6 +/- 2.6 mM, and [Ca2+]i increased to 256 +/- 36% of the control. [Ca2+]i was higher in spontaneously contracting cells and shortened cells than in rod-shaped cells at similar levels of [Na+]i. When Ca(2+)-free solution or Ni2+ (5 mM) was applied, [Ca2+]i was lower than in cells perfused with K(+)-free solution alone. It was suggested that extracellular Ca2+ and the Na(+)-Ca2+ exchange were involved in the increase in [Ca2+]i. In conclusion, we have developed a new method for the simultaneous measurement of [Na+]i and [Ca2+]i in isolated myocytes, which should be useful to study the relation between [Na+]i and [Ca2+]i.
To investigate the mechanisms regulating intracellular Na+ and Ca2+ concentrations ([Na+]i and [Ca2+]i, respectively), we monitored both ion concentrations simultaneously using fluorescent probes, Na(+)-binding benzofuran isophthalate (SBFI) and fluo 3, in unstimulated guinea pig ventricular myocytes. After the addition of 500 microM strophanthidin, [Na+]i increased gradually from 6.6 +/- 0.6 to 20.1 +/- 1.6 mM (mean +/- SE) at 50 min. [Ca2+]i, expressed as the percentage change of corrected fluo 3 fluorescence, was kept at the low level during the first 20 min and then began to increase to 447 +/- 81% of the control at 50 min. The addition of 1 microM hexamethylene amiloride prevented the increases in both [Na+]i and [Ca2+]i. The perfusion of Ca(2+)-free solution or 5 mM Ni(2+)-containing solution suppressed the increase in [Ca2+]i. In cells that exhibited spontaneous contractile activities, [Ca2+]i increased further than that in quiescent cells, whereas [Na+]i levels were similar. In the presence of 1 microM ryanodine, both the spontaneous contractile activities and the further increase in [Ca2+]i were eliminated. These findings indicated that 1) the pathway of Na+ entry was mainly through Na(+)-H+ exchange and that the elevated [Na+]i induced Ca2+ entry mediated by the reverse mode of Na(+)-Ca2+ exchange, and 2) the entered Ca2+ triggered the ryanodine-sensitive Ca2+ release from the sarcoplasmic reticulum, causing the dissociation in the relationship between [Na+]i and [Ca2+]i.
Ten resin glycosides (jalapins) named tuguajalapins I-X were isolated from the root of Merremia hungaiensis. Their structures have been determined on the bases of chemical and spectral data. Unlike the jalapins so far reported, all of their acyl groups consist of two or three long-chain fatty acids, that is, palmitic, stearic and/or arachidic acids.
Rat pancreatic islets were allografted in the liver and were studied morphologically in order to evaluate possible reinnervation. Islets isolated from rat pancreas were allotransplanted in the liver of streptozocin-induced diabetic rats via the portal vein. Electron microscopy revealed nerve endings with synaptic vesicles in the transplanted islets 100 days after transplantation, whereas axons in the islets appeared to degenerate several hours after isolation and prior to transplantation. These findings suggest that the nerve endings observed in the transplanted islets regenerate from nerves that innervate the recipient's liver. The tissue specimens were also investigated immunohistochemically using antityrosine hydroxylase antibody, and histochemically by the modified Karnovsky and Roots' method for visualizing acetylcholinesterase. Some nerve endings in the transplanted islets reacted positively to antityrosine hydroxylase antibody. Acetylcholinesterase was visualized in other nerves. These results indicate that norepinephrine- and acetylcholinesterase-containing nerves may reinnervate the transplanted islets.
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Five glycosphingolipids were obtained in the pure state from the marine annelid, Neanthes diversicolor. Final isolation of the individual compound was achieved by means of preparative HPLC with a reversed phase column in a recycling mode. They were assigned the structures, 1-O-beta-D-(6-O-[2'-(trimethylammonio)- ethylphosphoryl])galactopyranosyl, -N-hexadecanoyl-(4E,8E)-sphingadiene (1), -N-hexadecanoyl-(4E)-sphingenine (2), -N-heptadecanoyl-(4E)-sphingenine (3), -N-octadecanoyl-(4E)-sphingenine (4) and -N-hexadecanoyl-sphinganine (5). It is noted that they are the monogalactosyl ceramides carrying the phosphocholine group in the galactose moiety, and that one of them contains an odd numbered fatty acid residue.
Nine lyso glycerophospholipids were isolated in the pure state from the crude drug "Suitetsu", which is the dried body of the leech, Hirudo nipponica (Hirudidae). They were identified as 1-O-hexadecyl-(1), 1-O-octadecyl-(2), 1-O-tetradecyl-(3), 1-O-9-cis-hexadecenyl-(4), 1-O-hexadecanoyl-(5), 1-O-pentadecyl-(6), 1-O-15-methylhexadecyl-(7), 1-O-octadecanoyl-(8) and 1-O-heptadecyl-sn-glycero-3-phosphocholine (9). Two of them (5 and 8) are lysophosphatidylcholines and the other seven are lyso platelet-activating factors. One of them has an alkenyl carbon chain.
To clarify the role of phospholipase C (PLC) in arrythmias and cell injury during myocardial ischemia/reperfusion, we studied its effects on electrophysiology and [Ca2+]i in guinea pig hearts. After exposure to PLC (1 and 2 U/ml), the action potential durations of right ventricular papillary muscles were decreased. Delayed afterdepolarizations were observed in all of the preparations, and some developed into triggered activities. Developed tension decreased after an initial increase for the first 5 min, while resting tension increased consistently. The effects of PLC (0.02, 0.1, and 0.2 U/ml) on [Ca2+]i of ventricular myocytes were measured using fura-2 fluorescence. The ratio of rod-shaped cells to all cells decreased in a time- and a concentration-dependent manner. Perfusion with 0.1 U/ml PLC elevated [Ca2+]i from 56 +/- 5 nM to 245 +/- 47 nM before cell rounding, and to 1167 +/- 172 nM after cell rounding, suggesting that PLC causes Ca2+ overload. In conclusion, activation of PLC may play a role in arrhythmias and cell injury during ischemia/reperfusion. The increase in [Ca2+]i during ischemia/reperfusion may activate phospholipase, which would further increase [Ca2+]i to form a vicious cycle.
To investigate the role of abnormal Ca2+ metabolism in the diminished contractile function of diabetic myocardium, we measured the Ca2+ transients and cell contraction of diabetic rat myocytes. Isolated diabetic (8 weeks after 40 mg/kg streptozotocin, i.v.) and normal myocytes were loaded with acetoxymethyl ester of indo-1 (indo-1/AM). Ca2+ transients and cell circumferential shortening were measured simultaneously, using high temporal resolution video image analysis. The diastolic base and systolic peak of Ca2+ transients were significantly lower in diabetic myocytes than in normal myocytes (peak ratios: 0.49 +/- 0.02 vs 0.56 +/- 0.01, p < 0.05; base ratios: 0.43 +/- 0.01 vs 0.48 +/- 0.01, p < 0.01, Mean +/- SE). The cell circumferential shortening of diabetic myocytes was also significantly lower than that of normal myocytes (2.9 +/- 0.3% vs 5.2 +/- 0.9%, p < 0.05). Although isoproterenol (10(-8) and 10(-7) M) increased the peak of Ca2+ transients in both diabetic and normal myocytes, the peak value of Ca2+ transients in the diabetic group was significantly lower than that in the normal group. The decreased Ca2+ transients may be responsible for the decreased contractile function in diabetic myocardium.
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To investigate the role of Ca2+ metabolism and pH in diabetic cardiomyopathy, intracellular Ca2+ concentration ([Ca2+]i) and intracellular pH (pHi) of isolated myocytes were measured simultaneously using fura-2 and BCECF. We used diabetic (D.M.) rats at 8 weeks after the injection of streptozotocin (45 mg/kg, i.v.). (1) [Ca2+]i of D.M. myocytes was lower than that of controls (53 +/- 3 and 75 +/- 5 nM, mean +/- S.E., P less than 0.01). There was no difference in pHi (7.06 +/- 0.02 in D. M., 7.07 +/- 0.02 in control). There was no difference in the percentage of non-rounded cells at 30 min after the perfusion of glucose-free solution which contained 2 mM sodium cyanide (NaCN) between D.M. and controls (53% and 52%). When cells were rounded, the value of [Ca2+]i was significantly lower in D.M. myocytes than that in controls (172 +/- 21 and 421 +/- 106 nM, P less than 0.05). (2) When the cells were shortened or rounded in the high [Ca2+]o solution (24.5 mM), [Ca2+]i of D.M. rats was significantly lower than that of control rats. (3) The percentage of non-rounded cells at 30 min after the perfusion of NaCN increased in controls by 50 mM glucose (95%, P less than 0.01), but not in D.M. (47%). Insulin (25 mU/ml) and glucose (15 mM) increased the percentage of non-rounded cells in D.M. after 30 min perfusion with NaCN (88%, P less than 0.01 v.s. 53% without glucose nor insulin). It is suggested that there are disturbances of Ca2+ metabolism in D.M. myocytes, and that there is a close relation between cell injury and glucose utilization during metabolic inhibition.
Two minor ether-soluble resin glycosides, scammonins VII and VIII, were isolated from Radix Scammoniae, the roots of Convolvulus scammonia. In addition to (2S)-2-methylbutyric acid and tiglic acid, they are composed, respectively, of orizabic acid A and a new glycosidic acid named scammonic acid B, with similar macrocyclic ester structures to those of the scammonic acid A-based scammonins I-VI. Isolation of genuine scammonins III-V, which were previously obtained as peracetates, is also described.