Showing papers by "Tohoku University published in 1989"

Secret sharing scheme realizing general access structure

Abstract: As a method of sharing a secret, e.g., a secret key, Shamir's (k, n) threshold method is well known. However, Shamir's method has a problem in that general access structures cannot be realized. This paper shows that by providing the trustees with several information data concerning the distributed information of the (k, n) threshold method, any access structure can be realized. the update with the change of the secret trustees and the relation to the threshold graph are also discussed.

Correlation between cerebral blood flow and histologic changes in a new rat model of middle cerebral artery occlusion.

Abstract: We describe a new focal ischemia model consisting of unilateral middle cerebral artery occlusion with a silicone rubber cylinder attached to a nylon surgical thread inserted through the internal carotid artery in rats. Recirculation was accomplished by pulling the thread out of the artery. We evaluated the reliability of this model and studied the influence of reperfusion of the brain by measuring regional cerebral blood flow in 30 rats and by using conventional neuropathologic methods after different periods of occlusion in 48 rats. The anterior neocortex and the lateral part of the caudate putamen, which were supplied by the occluded middle cerebral artery, were the regions most frequently damaged. After 1 hour of occlusion in five rats, in the cortex supplied by the occluded artery mean +/- SD blood flow was 0.19 +/- 0.08 ml/g/min (approximately 15% of that in the corresponding region of five sham-operated control rats), and mild scattered ischemic cell change was observed. Three (n = 5) or six (n = 5) hours of occlusion reduced blood flow more severely and caused severe ischemic cell changes in the cortex supplied by the occluded artery in proportion to the duration of ischemia. Characteristically, in five rats subjected to 3 hours of occlusion followed by 3 hours of recirculation, blood flow was restored and spongy edematous change was observed in the cortex supplied by the recirculated artery. This change resulted in hypoperfusion of the neighboring cortical region surrounding the recirculated area. Our model should be useful in various investigations of the influence of reperfusion on focal ischemic brain injury.

Determination of diarrhetic shellfish toxins in various dinoflagellate species

Abstract: Sixteen species of unialgal samples of dinoflagellate, either wild or cultured, were tested for production of diarrhetic shellfish toxins such as okadaic acid (OA), dinophysistoxin-1 (DTX1), and pectenotoxins (PTXs). Determination of micro-quantities of the toxins was facilitated by fluorometry and UV HPLC. Seven Dinophysis species were confirmed to produce either OA or DTX1, or both. Toxin content and composition varied regionally and seasonally. Intraspecies variation was also observed among cultured strains of Prorocentrum lima. PTX2 was the only toxin detected among PTX family, and D. fortii was the only species to contain this toxin.

Dihydropyridine-sensitive low-threshold calcium channels in isolated rat hypothalamic neurones.

Abstract: 1. Low-voltage-activated Ca2+ channels which produce a transient inward current were studied in neurones freshly isolated from the ventromedial hypothalamic region of the rat. Membrane currents were recorded using a suction-pipette technique which allows for internal perfusion under a single-electrode voltage clamp. A concentration-jump technique was also used for rapid drug application. 2. In most cells superfused with 10 mM-Ca2+, a transient inward Ca2+ current was evoked by a step depolarization to potentials more positive than -65 mV from a holding potential of -100 mV. Such a low-threshold Ca2+ current could easily be separated from a high-threshold, steady type of Ca2+ current by selecting the holding and test potential levels, as well as by resistance to the wash-out during cell dialysis. 3. Activation and inactivation processes of the low-threshold Ca2+ current were highly potential dependent at 20-22 degrees C. For a test potential change from -60 to +20 mV, the time to peak of the current decreased from 45 to 9 ms, and the time constant of the current decay decreased from 90 to 40 ms. The steady-state inactivation occurred at very negative potentials, reaching a 50% level at -93 mV. Recovery from inactivation showed a time constant between 2.63 and 0.94 s for a potential change from -80 to -120 mV. 4. The amplitude of the low-threshold Ca2+ current depended on the external Ca2+ concentration [( Ca2+]o), approaching saturation at 100 mM [Ca2+]o. Ba2+ substituted for Ca2+ reduced the current amplitude by 30-50% while Sr2+ produced no definite changes in the current amplitude. 5. The low-threshold Ca2+ current was blocked by various di- or trivalent cations in the sequence of La3+ greater than Zn2+ greater than Cd2+ greater than Ni2+ greater than Co2+. The corresponding apparent dissociation constants (KD) were 7 x 10(-7), 1 x 10(-4), 3 x 10(-4), 6 x 10(-4) and 3 x 10(-3) M. 6. Various organic Ca2+ antagonists were effective in blocking the low-threshold Ca2+ current in the following sequence: flunarizine greater than nicardipine greater than nifedipine greater than nimodipine greater than D600 (methoxyverapamil) greater than diltiazem. The corresponding KDs were 7 x 10(-7), 3.5 x 10(-6), 5 x 10(-6), 7 x 10(-6), 5 x 10(-5) and 7 x 10(-5) M. These Ca2+ antagonists induced a use-dependent decrease in the current amplitude.(ABSTRACT TRUNCATED AT 400 WORDS)

On a construction of coordinates at infinity on manifolds with fast curvature decay and maximal volume growth

Abstract: On etudie le comportement asymptotique de varietes de Riemann. On construit des coordonnees a l'infini sous certaines conditions intrinseques

Nicorandil as a hybrid between nitrates and potassium channel activators.

Abstract: Nicorandil, although structurally a nitrate, differs from classic nitrates in several respects. It preferentially dilates resistive vessels. Its effect on venous return in dogs is not unanimously a decrease but rather an increase. In high doses or concentrations it suppresses myocardial contraction and ventricular automaticity, nearly sparing sinoatrial nodal automaticity and atrioventricular nodal conduction. It shortens the effective refractory period of myocardium. These cardiac effects of nicorandil have been explained by its mechanism of action as a potassium (K) channel activator. However, what part of the vascular effects of nicorandil this mechanism is responsible for has not been determined. BRL 34915 and pinacidil, nonnitrate vasodilators with a K-channel activator action, have essentially the same cardiovascular profile as nicorandil in isolated, blood-perfused canine heart preparations. In anesthetized, open-chest dogs the 2 K-channel activators decreased systemic blood pressure and increased venous return and cardiac output without elevating heart rate, unless the cardiodepressant effect emerged. The increase in venous return or cardiac output survived elimination of baroceptor functions. These results taken together with previous results on nicorandil suggest the following: (1) The property of nicorandil as a resistive vessel dilator highly selective for vasculature originates in its mechanism of action as a K-channel activator. The nonunanimous effect of nicorandil on venous return is a result of the opposing actions as a capacitive (action as a nitrate) and a resistive vessel dilator. Nicorandil, with its hybrid nature, is advantageous over specific K-channel activators and classic nitrates in therapeutic implications.

Tryptophan Raman bands sensitive to hydrogen bonding and side-chain conformation

Abstract: Raman Spectra of seven tryptophan derivatives in the crystalline state were examined to find Raman bands whose frequencies reflect the strength of hydrogen bonding at the N1H site of the indole ring or the conformation of the indole ring relative to the amino acid backbone. Two indole ring vibrations, W4 around 1490 cm−1 and W6 around 1430 cm−1, showed a correlation between their Raman frequencies and the infrared frequency of the N-1-H stretching mode, an indicator of hydrogen bond strength. W4 and W6 increase in frequency with increase in hydrogen bond strength and the frequency variation is particularly large for W6. On the other hand, another indole ring vibration, W3, observed around 1550 cm−1, changes in frequency as a function of the torsional angle, χ2,1, of the C-2C-3C-βC-α linkage. As the absolute value of χ2,1 becomes larger and the C-α atom moves away from the C-2 atom, the W3 frequency increases. In the Raman spectra of proteins excited with visible radiation, the W3 band is usually strong and can be used as a conformational marker, whereas the W4 band is very weak and the W6 band is overlapped by strog scattering due to C–H bending vibrations of aliphatic side-chains. In UV resonance Raman spectra, however, all these Raman bands are enhanced and may provide key information on the hydrogen bonding and conformation of tryptophan side-chains.

Activation of endogenous c-fos proto-oncogene expression by human T-cell leukemia virus type I-encoded p40tax protein in the human T-cell line, Jurkat.

Abstract: We examined the ability of the trans-acting factor p40tax of human T-cell leukemia virus type I (HTLV-I), which is thought to be a crucial molecule in T-cell transformation by HTLV-I, to activate expression of a set of endogenous cellular genes related to T-cell proliferation. For this purpose we established a subclone (JPX-9) of Jurkat cells that was stably transfected with an expression plasmid containing the p40tax gene, whose expression is definitely dependent on heavy-metal ions. Expression of the interleukin-2 receptor alpha chain in JPX-9 cells was induced in response to the induction of p40tax expression, as has been demonstrated by others in transient transfection experiments with Jurkat cells. In addition, we found that significant enhancement of expression of the nuclear proto-oncogene c-fos was closely associated with expression of p40tax. Continous enhancement in the level of c-fos mRNA was observed in the presence of p40tax. In contrast, mRNA levels of other nuclear proto-oncogenes (c-myc, c-myb, and c-jun) were not appreciably effected by the expression of p40tax. These results suggest that (i) in addition to the interleukin-2-interleukin-2 receptor system, cellular genes such as c-fos, which regulate normal T-cell growth, are also activated directly or indirectly by p40tax and (ii) p40tax-induced modulation of gene expression plays a crucial role in T-cell transformation by HTLV-I.

Immunolocalization of aromatase, 17α-hydroxylase and side-chain-cleavage cytochromes P-450 in the human ovary

Abstract: Immunohistochemical localization of cholesterol side-chain-cleavage, 17 alpha-hydroxylase and aromtase cytochromes P-450 was performed in 35 morphologically normal human premenopausal ovaries by using specific antibodies against the enzymes. In well-developed ovarian follicles in the late stages of follicular growth, immunoreactivity of P-450AROM was only seen in granulosa cells while P-450(17 alpha) and P-450SCC activity was confined to theca interna cells, confirming that follicular oestrogen is produced in granulosa cells by the aromatization of androgens derived from the theca interna cells. In the corpus luteum, this functional differentiation is maintained, since immunoreactivity of P-450AROM was exclusively present in luteinized granulosa cells while that of P-450(17 alpha) was present in luteinized theca calls. Immunoreactivity of P-450SCC was present in both types of cells in the corpus luteum.

Normally close microvalve and micropump fabricated on a silicon wafer

Abstract: A normally closed microvalve and micropump were fabricated on a silicon wafer by micromachining techniques. Normally closed microvalve has a silicon diaphragm and a small piezoelectric actuator to drive it. The controllable gas flow rate is from 0.1 ml/min to 85 ml/min at a gas pressure of 0.75 kgf/cm/sup 2/. The micropump is a diaphragm-type pump which consists of two polysilicon one-way valves and a diaphragm driven by a small piezoelectric actuator. The maximum pumping flow rate and pressure are 20 mu l/min and 780 mmH/sub 2/O/cm/sup 2/, respectively. >

Stratum corneum hydration and amino acid content in xerotic skin.

Abstract: The relationship between clinical severity, the hydration state of the skin surface as assessed by a conductance with a 3.5 MHz high frequency impedance meter, and the amino acid content of the stratum corneum (SC) of six patients with ichthyosis vulgaris and 30 elderly persons with varying degrees of xerosis was investigated. With an increase in the severity of xerosis the SC showed a decrease in hydration and in its extractable amino acid content. There was a significant correlation between the hydration state and amino acid content of the SC. Although there was a significant correlation between the amino acid content of the lower leg SC and that of the forearm SC in the same subject, the former was generally lower, corresponding to the greater incidence of xerosis on the lower leg. These results suggest that a decreased amount of amino acids may be the result of low profilaggrin biosynthesis in the epidermis and that this is involved in the pathogenesis of these xerotic skin conditions. Clinical improvement of the xerosis following treatment with a urea-containing cream was not accompanied by any significant change in the amino acid content of the SC.

Recombinant human tumor necrosis factor alpha suppresses autoimmune diabetes in nonobese diabetic mice.

Abstract: We previously reported that administration of a streptococcal preparation (OK-432) inhibited insulitis and development of autoimmune diabetes in nonobese diabetic (NOD) mice and BB rats as animals models of insulin-dependent diabetes mellitus. In this study, we screened various cytokines that could be induced by OK-432 in vivo, for their preventive effect against diabetes in NOD mice. Among recombinant mouse IFN gamma, human IL1 alpha, human IL2, mouse granulocyte-macrophage colony-stimulating factor and human TNF alpha, only human TNF alpha suppressed insulitis and significantly (P less than 0.001) inhibited development of diabetes. NOD mice were the lowest producers of the mRNA of TNF and serum TNF on stimulation with OK-432 or with IFN gamma plus LPS, compared with C57BL/6, C3H/He, and Balb/c mice. The results imply a role for low productivity of TNF in the pathogenesis of autoimmune diabetes in NOD mice.

A multichannel FES system for the restoration of motor functions in high spinal cord injury patients: a respiration-controlled system for multijoint upper extremity

Abstract: A multichannel functional electrical stimulation (FES) system for the restoration of quadriplegic upper extremity function is described. The system is composed of a personal computer, peripheral electronic circuits, CRT display and respiratory sensors for volitional control by the patient, and percutaneous electrodes. In this system, versatile volitional control is realized by controlling the memory allocation of the stored stimulation data by voluntary respiratory signals, and sophisticated fine control of the fingers, wrists, and elbow is realized by creating multichannel stimulation data from recorded myoelectric activities of normal subjects during movements of the upper limb. >

Expert systems for image processing: knowledge-based composition of image analysis processes

Abstract: Recently several expert systems for image processing were proposed to facilitate the development of image analysis processes. They use the knowledge about image processing techniques to compose complex image analysis processes from primitive image processing operators. In this paper, we classify them into the following four categories and discuss their objectives, knowledge representation, reasoning methods, and future problems: (1) consultation system for image processing, (2) knowledge-based program composition system, (3) rule-based design system for image segmentation algorithms, and (4) goal-directed image segmentation system. In the latter half of the paper, we emphasize the importance of image analysis strategies in realizing effective image analysis: analysis using the pyramid (multi-resolution) data structure, combination of edge-based and region-based analyses, and so on. We propose two methods of representing image analysis strategies: one from a software engineering viewpoint and the other from a knowledge representation viewpoint. Several examples are given to demonstrate the effectiveness of these methods.

Effects of Submental Electrical Stimulation during Sleep on Upper Airway Patency in Patients with Obstructive Sleep Apnea

Abstract: We examined the effects of percutaneous electrical stimulation of the genioglossus in six patients with obstructive sleep apnea syndrome (OSAS) during sleep and investigated the possible applicability of this procedure as a treatment of OSAS. Six patients with OSAS were polysomnographically studied in the supine position during all-night sessions with and without electrical stimulation of the genioglossus. Using an apnea demand-type stimulator that we developed, electrical pulses of 0.5 ms (repetition rate, 50 Hz) and 15 to 40 V were delivered through bipolar electrodes (10 mm in diameter) attached to the skin of the submental region when apnea lasted more than 5 s, and was stopped immediately after breathing resumed or after 10 s at the longest. With submental stimulation, the apnea index, apnea time/total sleep time, longest apnea duration, and the number of times per hour that oxygen saturation dropped below 85% decreased significantly compared with those on control nights. The lowest arterial oxygen saturation and the duration of sleep stages III and IV increased significantly. The stimulation employed did not cause arousal, and it did not affect blood pressure or heart rate significantly. These findings show that submental stimulation decreases the incidence of apnea episodes and promotes deeper sleep without accompanying serious side effects, suggesting that the apnea demand-type stimulator may be a noninvasive and effective treatment for OSAS.

Screening for gastric cancer.

Abstract: Mass screening for gastric cancer in Japan has been conducted nationwide since 1960. The total number of examinees in 1985 amounted to 5,161,876 and 6,240 cases (0.12%) of gastric cancer were detected. Approximately half of these cases were early stage cancers. According to the studies of mass gastric screening in the Miyagi Prefecture, Japan, the sensitivity of the screening test by the indirect x-ray method was 82.4%, and the specificity was 77.2%. The positive predictive value was 1.78%. Recently, mortality from gastric cancer has been decreasing in Japan. Many studies have been carried out to investigate the relationship between the decreasing trend of mortality from cancer of the stomach and the effectiveness of mass gastric screening. From these studies and from time trend analyses of incidence and death rates, case-control studies, nonexperimental cohort studies, etc., it is believed that mass screening for gastric cancer is effective in reducing the death rate from cancer at this site.

Observation of coherent synchrotron radiation.

Abstract: Coherent effects in synchrotron radiation (SR) have been observed for the first time from 180-MeV short electron bunches of 2.4 mm using the Tohoku 300-MeV Linac. The intensity of the coherent SR was about ${10}^{5}$ times as strong as that of incoherent SR in the wavelengths of 0.4--2.2 mm. This enhancement factor corresponds to the number of electrons in a bunch. The SR intensity showed a quadratic dependence on the electron beam current. The radiation was mainly polarized in the orbital plane. The possibility of induced rf in a vacuum chamber was excluded experimentally.

High‐Temperature Passive Oxidation of Chemically Vapor Deposited Silicon Carbide

Abstract: The oxidation behavior of chemically vapor deposited (CVD) SiC at high temperature was investigated using a thermogravimetric technique in the temperatures range of 1823 to 1948 K. The specimens were prepared by chemical vapor deposition using SiCl4, C3H8, and H2 as source gases. The oxidation behavior of the CVD-SiC indicated “passive” oxidation and a two-step parabolic oxidation kinetics over the entire temperature range. The crystallization of the SiO2 film formed may have caused this two-step parabolic behavior. The parabolic oxidation rate constant (Kp) varied with the square root of the oxygen partial pressure (P1/2O2). The activation energy for the oxidation was determined to be 345 and 387 kJ · mol−1. These values suggest that the diffusion process of the oxygen ion which passes through the SiO2 film is rate-controlling.