Biomedical subjects

M Torii

Publications and source records attributed to M Torii.

At least 55 records · Page 3Linked to original sources

PubMed1996

Membrane knobs of unfixed Plasmodium falciparum infected erythrocytes: new findings as revealed by atomic force microscopy and surface potential spectroscopy.

Cerebral malaria, a severe complication of malaria, is caused by the obstruction of cerebral microvessels by Plasmodium falciparum-infected erythrocytes. Such cells adhere to endothelial cells by means of "knobs" induced on the red cell membrane by the parasites. When atomic force microscopy was used to investigate the structure of the knobs of unfixed infected red cells, each knob was found to consist of two distinct subunits, knob components that have never been seen in chemically fixed knobs examined by conventional transmission electron microscopy. Surface potential spectroscopy revealed that the knobs have a positive charge (+20 mV), whereas the remainder of the red cell plasma membrane is negatively charged. Since endothelial plasma membranes have a negative charge, the charge difference between knobs and endothelium may play a significant role in cytoadherence between the two cell types. The subunit structure of the knobs may be a steric necessity to align adherence molecules so that they can exert their effect. This study shows that the atomic force microscope has great potential for examination of cells in their native state; in combination with surface potential spectroscopy, it may uncover fundamental processes and mechanisms in cell function.

Animals↗

PubMed1996

Effect of prewarming in the cold season on thermoregulatory responses during exercise.

OBJECTIVE: To assess whether thermoregulation in the cold season can be affected by prewarming before exercise. METHODS: Four healthy non-athletic unacclimatised males were exercised to the same degree in summer and winter on a bicycle ergometer without prewarming (experiment 1) and after prewarming by sitting for 30 min in a room at 30 degrees C (experiment 2). During exercise, sweat production and rectal and skin temperatures were measured continuously. RESULTS: There was seasonal variation in sweating capacity and sensitivity and in heat storage during exercise without prewarming (experiment 1). After the subjects were warmed before exercise, there was no such seasonal variation in their sweat rates during exercise at 30 degrees C and 40 degrees C (experiment 2). In both cases, the sweat rate and skin temperature were dependent on the environmental temperature, and the sweat rate and core temperature were dependent on the workload. In the cold season, sweating sensitivity and evaporative cooling response could be enhanced by thermal stimulation. There was no seasonal difference in the relation between evaporative heat loss and metabolic rate in the two thermal conditions. These values did not differ significantly between winter after prewarming and summer (P > 0.05), neither did heat storage and metabolic heat production at various workloads (P > 0.05). CONCLUSIONS: There is adaptation of the thermoregulatory mechanisms during temperature acclimatisation. Body warming enhances not only the heat dissipating activity of the thermoregulatory centre but also the induction of peripheral sweat gland activity. Seasonal change of sweat rate in exercising men can be eliminated through a different type of acclimatisation by prewarming in the cold season.

Acclimatization↗

PubMed1996

Roles of cell-autonomous mechanisms for differential expression of region-specific transcription factors in neuroepithelial cells.

Although a number of genes have been found to have restricted expression domains in the embryonic forebrain and midbrain, it remains largely unknown how the expression of these genes is regulated at the cellular level. In this study, we explored the mechanisms for the differential expression of region-specific transcription factors in neuroepithelial cells by using both primary and immortalized neuroepithelial cells from the rat brain at embryonic day 11.5. We found that differential expression patterns of Pax-3, Pax-5, Pax-6, Dlx-1, Dlx-2, Emx2, Otx1 and Dbx observed in vivo were maintained even when the cells were isolated and cultured in vitro, free from environmental influences. Furthermore, in response to Sonic hedgehog, which is a major inductive signal from the environment for regional specification, neuroepithelial cells that maintain distinct regional identities expressed different sets of ventral-specific genes including Islet-1, Nkx-2.1 and Nkx-2.2. These results suggest that certain cell-autonomous mechanisms play important roles in regulating both environmental signal-dependent and -independent expression of region-specific genes. Thus, we propose that use of the in vitro culture systems we describe in this study facilitates the understanding of regulatory mechanisms of region-specific genes in neuroepithelial cells.

Animals↗

PubMed1996

Cerebral cysticercosis manifesting as hydrocephalus--case report.

A 70-year-old female presented with gait disturbance and dementia. Cerebrospinal fluid examination revealed mild aseptic meningitis. Magnetic resonance images showed multiple cystic lesions and mural nodules in some of the cysts in the cerebral parenchyma. Metrizamide computed tomography clearly demonstrated multiple intracisternal cysts. Some cysts were surgically excised and a ventriculoperitoneal shunt was implaced. Postoperatively, her gait disturbance and dementia disappeared. Histological examination revealed cysticercosis with viable larva. Ten months after the initial surgery, she presented with right hemiparesis due to enlargement of the remaining cysts in the left frontal lobe. These cysts were removed. Postoperative neurological examination showed slight right hemiparesis. We recommend ventriculoperitoneal shunting for hydrocephalus due to cisternal cysticercosis and praziquantel administration for parenchymal lesions.

Aged↗

PubMed1995

Naloxone and initial estrogen action to induce lordosis in ovariectomized rats: the effect of a cut between the septum and preoptic area.

The effects of intra-third-ventricular (ITV) injection of naloxone (NLX), an opioid receptor antagonist, on lordosis behavior were studied in ovariectomized female rats given a horizontal half-circle cut located just above the anterior commissure (ARD) and subcutaneously (s.c.) treated with estradiol benzoate (EB) and progesterone (Prog). In ARD-sham control animals, lordosis quotient (LQ) was 78.8 +/- 4.2% (SE,n = 8). LQ (48.3 +/- 7.2%, SE, n = 8) in the ARD-sham rats significantly decreased with the ITV injection of NLX at the time of s.c. EB-priming. In contrast, lordosis reflex in the ARD-operated animals was maximally facilitated (sham versus ARD, P < 0.01). LQ in the ARD-operated rats did not decrease with the ITV injection of NLX at the s.c. EB-priming. The present results suggest that the opioidergic systems modulate an initial phase of estrogen action to induce lordosis and play a part in neural input from the forebrain structures to regulate female sexual receptivity.

Animals↗

PubMed1995

The fatty acids of each lipid fraction and their use in providing energy source of the plerocercoid of Spirometra erinacei.

The fatty acid concentration of each lipid fraction of plerocercoids of Spirometra erinacei and the host snake serum was investigated. The major fatty acids of phospholipid of the plerocercoids were C18:1, C18:0 and C16:0, and those of the host snake serum were C16:0, C18:1 and C18:0, in order of amount in both cases. The changes of the fatty acid composition of phospholipid of the plerocercoids when they were incubated in physiological saline at 18 degrees C and at 37 degrees C for 24 h were investigated in both cases. Polyunsaturated fatty acids increased at 18 degrees C, and saturated fatty acids increased at 37 degrees C. Michaelis constants (Km) of beta-hydroxyacyl-CoA dehydrogenase (HAD), NADH: ubiquinone oxidoreductase (complex I) (NADH: ferricyanide reaction) and complex I (NADH: ubiquinone reaction) for NADH were 20.6, 50 and 13.3 microM, respectively. The ATP production in mitochondria of the plerocercoids was accelerated by adding ADP and inhibited by adding such electron transport system inhibitors as rotenone, antimycin A and sodium cyanide. These results suggested that the fatty acids in the plerocercoids played an important role in regulating the fluidity of membrane by changing the composition in membrane lipid corresponding with the change of temperature circumstance. The NADH reduced by HAD might be accepted by the complex I in the electron transport system, and thus the parasites were capable of ATP production in a classical pathway of the oxidative phosphorylation system.

Adenosine Triphosphate↗

PubMed1995

Adhesion of Plasmodium falciparum-infected erythrocytes to human cells and secretion of cytokines (IL-1-beta, IL-1RA, IL-6, IL-8, IL-10, TGF beta, TNF alpha, G-CSF, GM-CSF.

The scientific interest in the physical interaction of Plasmodium falciparum-infected erythrocytes with host cells stems from the suggestion that excessive binding in the microvasculature leads to severe malaria. The authors studied, therefore, two parasites for their ability to adhere to normal human cells and to induce cytokine production, one parasite lacking a binding capacity (DD2) and one which adhered to CD36+ transfected CHO cells (MCAMP). The MCAMP parasites readily bound to platelets and erythrocytes and to monocytes, polymorphonuclear granulocytes and EBV-transformed B cells as seen by light and electron microscopy. Platelets were frequently attached in large numbers to the infected erythrocyte surface and groups of infected erythrocytes were sometimes held together by several platelets. Nine out of 17 cytokines tested were found to be secreted into the culture supernatants after 35 h of co-cultures containing monocytes or unfractionated peripheral blood mononuclear cells (PBMC) and parasites (IL-1RA, IL-6, IL-8, IL-10, TGF beta, TNF alpha, G-CSF, IL-1-beta, and GM-CSF). Three additional cytokines were also present in low levels (< 200 pg/ml, IL-2, IL-4, IFN gamma) in the culture supernatants after incubation of the cells for 4 days. TNF alpha, IL-RA, and IL-8 were secreted from polymorphonuclear granulocytes, LGLs and T cells. Platelets and, to a lesser degree, monocytes and T cells secreted large amounts of TGF beta (10-30 ng/ml). Cytokines may participate in the pathogenesis but also the suppression of immune responses seen during acute malarial infections.

Animals↗

PubMed1995

Comparative study on free radical injury in the endothelium of SHR and WKY aorta.

1. Using 13 week old SHR and WKY rats, aortic endothelial injury was examined after tert-butylhydroperoxide (t-BOOH) perfusion. 2. ESR analysis revealed a hydroxyl radical adducts in the perfusate after t-BOOH perfusion. 3. After t-BOOH perfusion, endothelial changes such as cauliflower-like blebs and crater-like holes were frequently observed in the SHR aorta, but rarely seen in the WKY aorta. 4. X-ray spectra revealed the cerium perhydroxide deposition on the surface of endothelial cells of the SHR aorta. 5. These findings indicate that free radical injury is much more intense in the endothelial cells of SHR than in those in WKY.

Animals↗

PubMed1995

Murine complement reduces infectivity of Plasmodium yoelii to mosquitoes.

The alternative pathway of complement in the mouse serum significantly reduced, but did not eliminate, the infectivity of Plasmodium yoelii to Anopheles stephensi. The reduction of the infectivity is mainly due to the inability of the zygote to transform into the ookinete in the mosquito midgut.

Animals↗

PubMed1995

Thermoregulation of exercising men in the morning rise and evening fall phases of internal temperature.

The purpose of this study was to compare the thermoregulatory responses during exercise in the morning rise (0900 h) and evening fall phases (2000 h) in circadian variation of body temperature. Five healthy volunteers performed bicycle exercises at 30% and 60% of maximal aerobic power (VO2max) at 26 degrees C with a relative humidity of 50%. Whole-body sweat rate (SR), rectal (Tre), mean skin (Tsk) and mean body (Tb) temperature, pulmonary ventilation (VE), oxygen uptake (VO2), and carbon dioxide output (VCO2) and heart rate (HR) were measured during the experimental period. SR during exercise at 30% VO2max was significantly higher at 2000 h than at 0900 h. However, the circadian variation of SR during exercise was not observed at 60% VO2max. At the two experimental times, there were also no significant differences in VO2, VCO2, VE and Tsk in both workloads. In HR, Tb and Tre circadian effects were demonstrated as well as in workload levels. As Tb was plotted against SR during exercise, positive correlations were observed. The data showed that there was a parallel shift in the SR to Tb relationship during exercise in the morning and evening. This rightward shift indicated that there was an increased Tb threshold for the onset of sweating in the evening. Resting Tb at 2000 h was significantly higher when compared with Tb at 0900 h. The present results suggest that the circadian influence on the thermoregulatory response to exercise may be evident only at low workloads.

Adult↗

PubMed1995

Marginal adaptability and fit of ceramic milled inlays.

The authors investigated the marginal adaptation and internal fit of ceramic inlay made by a ceramic milling system. The study's results indicated that the mean marginal and internal gap size of the ceramic inlay restorations was less than 100 microns, making the fit clinically acceptable.

Computer-Aided Design↗

PubMed1995

Decreased superoxide dismutase activity and increased superoxide anion production in cardiac hypertrophy of spontaneously hypertensive rats.

In order to investigate SHR hypertrophied heart myocardial vulnerability, superoxide dismutase, a potent scavenger of superoxide anion, was examined in myocardium of SHR and WKY in relation to aging, as well as under doxorubicin (DOX)-induced cardiomyopathy. Superoxide anion production due to doxorubicin administration was also examined histochemically. Superoxide dismutase (SOD), either as Mn-SOD in mitochondria or as CuZn-SOD in cytoplasm, was found to be lower in aged SHR hypertrophied heart than in age-matched WKY heart. Under DOX-induced cardiomyopathy, SOD activity was significantly lower in SHR hypertrophied heart than either control SHR or treated WKY myocardium. Superoxide anion generation, examined morphologically as formazan deposits, was much more intense in SHR myocardium and some degenerative changes were found such formazan-containing cells. These results clearly indicate that the myocardial vulnerability of SHR hypertrophied heart might be a result of a lowered free radical scavenge ability.

Aging↗

PubMed1995

Relationship between particle size of barium glass filler and water sorption of light-cured composite resin.

The reaction of barium glass filler with water was determined by investigation of the effects of the particle size of barium glass filler on the water sorption rate and the mechanical properties of composite resin. Barium glass and quartz were milled to obtain powders with different average particle sizes. These powders were silanized and used as inorganic filler in composite resin. Photoactivated base monomer was loaded at 65% (w/w) with these fillers to prepare the composite resin paste. The water sorption of barium glass filled resin was always more than that of quartz filled resin. The amount of sorbed water obtained by barium glass filled resin increased as the particle size decreased. The particle size of the quartz filler did not affect the water sorption. The flexural strength of barium filled resin decreased after water immersion more than that of the quartz filled resin as the particle size decreased. These results suggest that the water durability of barium glass is low and the surface of barium glass filler is damaged by water. Water would be retained in the interface between the barium glass filler and the matrix resin.

Absorption↗

PubMed1995

Antibacterial effect of composite incorporating Triclosan against Streptococcus mutans.

It has been shown that composite incorporating the antibacterial agent Triclosan (Irgasan DP 300, which is sparingly soluble in water, inhibited in vitro plaque formation by Streptococcus mutans, although the release of the agent was much less than the minimum inhibitory concentration for the bacterium. In this study, the inhibitory effect of the composite incorporating 1% Triclosan against growth and adherence of S. mutans was investigated. S. mutans was inoculated on the surface of a specimen made of control or Triclosan-incorporated composite and the number of bacteria was compared after 3, 6, 12 and 24 hr of incubation. The adherence of S. mutans to the control and experimental composite, with or without saliva treatment, was also examined by scanning electron microscopy. The composite incorporating Triclosan demonstrated significant inhibition of growth of S. mutans after 6, 12 and 24 hr of incubation. Adherence of S. mutans to the Triclosan-incorporated composite was less compared with control for both non-treated and saliva-treated specimens. It is concluded that the antiplaque effect of composite incorporating Triclosan depends upon its ability to inhibit bacterial growth and adherence, and Triclosan-incorporated composite is able to exhibit the antibacterial activity even after being treated with saliva.

Anti-Infective Agents, Local↗

PubMed1995

Additional heat-curing of light-cured composite resin for inlay restoration.

The purpose of this study was to evaluate the effect of heat application after light curing on some physical properties of composite resin for dental inlay. Specimens each were additionally dry heat-cured at various temperatures for 15 min after initial light curing, and other specimens were not heat-cured as a control. Fracture toughness, bending strength, bending elastic modulus, coefficient of thermal expansion, hygroscopic expansion, microhardness, water absorption and solubility were determined. Fracture toughness, bending strength and bending elastic modulus were significantly higher when heated at 80-120 degrees C than the control. The coefficient of thermal expansion, hygroscopic expansion, microhardness and solubility were significantly improved than those of the control when heated, while water absorption was not significantly altered by dry heat-curing. These results indicate that the physical properties of composite resin, except water absorption, were improved significantly when heated after initial cure.

Absorption↗

PubMed1995

Maximal sweating rate in humans.

We reviewed the literature concerning the maximal sweating rate (SRmax) during heat acclimatization, walking in desert heat and marathon running, and analyzed it from the viewpoint of sex, age, level of maximal oxygen uptake, and experimental conditions, i.e., ambient temperature, relative humidity, work intensity, work type, working duration, seasonal factors and the techniques of heat acclimatization. Exercise simulation, walking, running or bicycling, to induce the SRmax was conducted in a hot climatic chamber or in the desert. The SRmaxs due to marathon running were 1,000 to 1,200 g.h-1 in the cold season and 1,500 to 2,000 g.h-1 in the hot season. After several days of heat acclimatization, sweating capacity in the exercise simulation reached a maximum rate, over 2,000 g.h-1. There was a sexual difference in the SRmax, and the sweating capacity in the female was less than that in the male. Thus, the maximal sweating capacity in human was observed by prolonged moderate muscular exercise under thermal stress and internal and/or external heat loads.

Acclimatization↗

PubMed1994

Hepatotrophic activity in mouse serum infected with plerocercoids of Spirometra erinacei.

To investigate the mechanism by which liver weight increases during plerocercoid infections as well as the possible existence of a hepatocyte-growth-factor (HGF)-like substance in the serum of mice infected with Spirometra erinacei plerocercoids, liver DNA synthesis was measured in vivo and in vitro. Infection with S. erinacei plerocercoids significantly stimulated DNA synthesis in mouse parenchymal hepatocytes prior to the increase in liver weight, at least partly by stimulating the induction of the salvage pathways of pyrimidine biosynthesis. Furthermore, infected mouse serum directly stimulated DNA synthesis in cultured mouse parenchymal hepatocytes. These results suggest that an HGF-like substance is present in the serum of mice infected with S. erinacei plerocercoids.

Animals↗

PubMed1994

The effects of intraventricular injection of beta-endorphin on initial estrogen action to induce lordosis behavior.

Ovariectomized female rats subcutaneously (SC) injected or intracerebrally implanted with estradiol benzoate (EB), and given progesterone SC were used as experimental animals to assess the effects of the beta-endorphin (beta-EP) neuronal system on lordosis behavior. In intraventricular (IV) injection of beta-EP at the onset of sc EB priming, the lordosis behavior was significantly (p < 0.001) facilitated. In contrast, the lordosis behavior was significantly (p < 0.001) inhibited by IV injection of naloxone, an opioid receptor antagonist. beta-EP facilitation of lordosis was observed exclusively within the initial stage of estrogen action. The behavior was significantly (p < 0.001) facilitated by IV injection of beta-EP given with an intracerebral implantation of crystalline EB into the septal-preoptic regions. However, the lordosis behavior was significantly (p < 0.001) inhibited by beta-EP when EB was implanted into the ventromedial hypothalamus. Animals receiving EB implants into the mesencephalic reticular formation were not affected by beta-EP. The present study suggests that the beta-EP neuronal system stimulates sexual receptivity through an action on the central nervous system in relation to the site of estrogen-initial activation to induce the lordosis reflex. The sites of beta-EP action may be the estrogen receptive septal-preoptic and hypothalamic regions; the former for facilitatory effect and the latter for inhibitory effect.

Animals↗