Biomedical subjects

T Totsuka

Publications and source records attributed to T Totsuka.

At least 37 records · Page 2Linked to original sources

PubMed1998

Pathological changes in levels of three small stress proteins, alphaB crystallin, HSP 27 and p20, in the hindlimb muscles of dy mouse.

Using three different analyses, we investigated the levels of the three small stress proteins alphaB crystallin, HSP 27 and p20 in the slow-twitch soleus muscle and fast-twitch tibialis anterior muscle of normal and dy mice. All of these analyses (immunoassay, Western blot and immunohistochemistry) showed markedly increased levels of these stress proteins in fast-twitch type muscle (tibialis anterior muscle) of dy mouse. In contrast, the levels of alphaB crystallin, HSP 27 and p20 of dy mouse were reduced in slow-twitch type muscle (soleus muscle). Manipulation of this protective response may reduce injury and may have potential therapeutic application in congenital muscular dystrophy (CMD), which possesses a deficiency of laminin-alpha2 chain in muscle fiber basement similar to dy mouse.

Animals↗

PubMed1998

Muscular dystrophy: centronucleation may reflect a compensatory activation of defective myonuclei.

Muscular dystrophy has long been believed to be characterized by degeneration and abortive regeneration of muscle fibers (the muscle degeneration theory), but unfortunately its pathogenesis is still unclear and an effective treatment has yet to be developed. As a challenge to the theory, we have proposed an alternative muscle-defective-growth theory and a further bone muscle growth imbalance hypothesis supposing possible defects in bone-growth-dependent muscle growth based on our findings in hereditary dystrophic dy mice (C57BL/6J dy/dy). This review presents some new insights into the pathogenesis of the disease along with our hypothesis, focusing on the physiological meaning of centronucleation, one of the major pathological changes commonly observed in dystrophic muscles of man and experimental animals.

Animals↗

PubMed1998

Differential adaptations of insulin-like growth factor-I, basic fibroblast growth factor, and leukemia inhibitory factor in the plantaris muscle of rats by mechanical overloading: an immunohistochemical study.

We investigated changes in several growth factors in the rat plantaris muscle produced by mechanical overloading by ablation of synergists using immunohistochemistry. At 1 and 3 days post surgery, the insulin-like growth factor-I (IGF-I) level was slightly increased in the cytosol and markedly increased in the invading cells of the extracellular space. Thereafter, the IGF-I immunoreactivity evoked by overloading rapidly decreased to the normal level. The level of leukemia inhibitory factor (LIF), which was not shown to change at 1 day post surgery, was increased in the cytosol at 3, 5, 7 and 10 days and at 2 weeks. Basic fibroblast growth factor (bFGF) immunoreactivity did not change during the entire period of overloading (1 day-3 weeks post surgery). These results indicate that the elevations of the levels of IGF-I and LIF show differential time course in the plantaris muscle subjected to functional overload. Furthermore, bFGF appears not to be related to the compensatory hypertrophy produced by overloading.

Adaptation, Physiological↗

PubMed1998

Hypoglycemic and hypotensive effects of 6-cyclohexyl-2'-O-methyl-adenosine, an adenosine A1 receptor agonist, in spontaneously hypertensive rat complicated with hyperglycemia.

Metabolic and cardiovascular effects of 6-cyclohexyl-2'-O-methyl-adenosine (SDZ WAG 994), a selective and orally-active adenosine A1 receptor agonist, were examined in spontaneously hypertensive rats (SHR) with hyperglycemia (SHR-DM). This model was made by the administration of streptozotocin (STZ; 60 mg/kg s.c.) to SHR 2 days after their birth. The serum glucose concentration and systolic/mean blood pressures (MBP) in 18-22-week-old rats were 14.7 +/- 0.8 mmol/1 and 153 +/- 3/124 +/- 3 mmHg in SHR-DM, 13.7 +/- 0.3 mmol/1 and 123 +/- 3/96 +/- 4 mmHg in normotensive with STZ (WKY-DM), 10.3 +/- 0.3 mmol/1 and 165 +/- 1/136 +/- 3 mmHg in non-treated (without STZ) SHR, and 10.0 +/- 0.3 mmol/1 and 115 +/- 3/90 +/- 4 mmHg in non-treated WKY, SDZ WAG 994 at 0.1 mg/kg p.o. lowered the serum glucose concentration, blood pressure and heart rate in SHR-DM. The effects were associated with the decrease in free fatty acid (FFA), triglyceride (TG), phospholipid (PL) and total cholesterol (TC) in serum of both SHR-DM and WKY-DM. On the contrary, the hypoglycemic effect was not found in WKY-DM, although the hypotensive effect was still observed. These data suggest that the risk factors for metabolic and cardiovascular complications in diabetes are reduced by SDZ WAG 994 through activation of adenosine A1 receptors in adipocyte.

Adenosine↗

PubMed1998

The dual identities of mammalian tRNA(Sec) for SerRS and selenocysteine synthase.

Se is an essential trace element and is found as a selenocysteine in the active site of Se-enzymes, such as glutathione peroxidase. tRNASec is first aminoacylated with serine by Ser RS and further is converted to selenocysteyl-tRNA by selenocysteine synthase. Mammalian selenocysteine tRNA has dual identities with Ser RS and selenocysteine synthase. Key identity elements for selenocysteine synthase are the long 9 bp AA- and long 6 bp D-stems. Major serine tRNA was converted to a mutant with a 9 bp AA-stem and 6 bp D-stem, instead of a 7 bp AA-stem and 3 bp D-stem. This mutant was active for selenylation as well as serylation. The relative kinetic parameter (Vmax/Km) of the mutant was 0.052 of the value (1.00) of wild-type Sec tRNA. This low value suggests that there is an unknown fine base specific for selenocysteine synthase. For serylation, mutant having 12 bp and wild type tRNASec having 13 bp of the total length of AA- + T-stems were active but the mutants having 11 or 14 bp were inactive. This shows that SerRS measures the distance between the discrimination base and long extra arm for recognition of tRNASer.

Animals↗

PubMed1998

Recycling of acetylcholine following impulse transmission in rat muscle revealed in the presence of neostigmine.

1. The recycling process of acetylcholine (ACh) following impulse transmission was studied in terms of muscle potentials evoked by repetitive stimulation in the presence of neostigmine. 2. Wistar rats were anaesthetized with urethane and muscle potentials were recorded with concentric electrodes from their exposed medial gastrocnemius muscles before and after the injection of neostigmine. 3. All potentials before neostigmine treatment were similar in amplitude. A set of 10 stimuli was given at 0.5 Hz 6-8 min after drug administration. The first potential was as large as that before it. The second potential was greatly depressed. Thereafter, potentials gradually recovered. 4. Two sets of 10 stimuli were delivered at a 1 min interval (i.e. with a 40 s rest period between them). The second potential was not depressed so severely in the second set as in the first set. The same procedure was repeated in some rats and the aforementioned phenomenon was noted. When two sets of 10 stimuli were given at an interval of 2 min or more, the second potential was equally depressed in the both sets of stimuli. 5. The recycling of ACh following impulse transmission in the junctional region was revealed in terms of muscle potentials in the presence of neostigmine. This process was activated due to repetitive stimulation. Moreover, the activated state seemed to be maintained for a while after the cessation of stimuli. These results suggest the possible existence of a neural mechanism that can exert an influence on the recycling of ACh following impulse transmission beyond a short period of time.

Acetylcholine↗

PubMed1998

Developmental changes of impulse transmission in rat gastrocnemius muscles revealed by neostigmine.

Developing rats between 5 and 44 days of age as well as rats about 2 months old were anesthetized with urethane. Spontaneous activities and muscle potentials to sciatic stimuli were recorded from their exposed medial gastrocnemius muscles using concentric electrodes. Neostigmine of 0.12-0.40 mg/kg was injected into the contralateral muscles. Regardless of age, spontaneous activities were not observed and muscle potentials were evoked by single stimuli primarily in a biphasic wave (main component) before the drug treatment. Developmental differences were revealed in the presence of the drug. 1) Spontaneous activities were detected only in single spikes around postnatal 10 days. Single or double spikes were often found in rats of about two weeks. Burst discharges such as seen in adult rats were observed immediately before weaning. 2) In rats of 2 weeks or so, one or more components were observed obscurely following the main component of muscle potentials, which appeared definitely at the preweaning period. 3) When double shocks with the interval of 2 sec were delivered in the presence of the drug, the second potential was greatly depressed in rats older than two weeks as well as in adult rats. The potential was only slightly reduced in rats around 10 days. Thus, an adult pattern as to impulse transmission was observed immediately before weaning. These alterations would, at least in part, reflect the maturation of acetylcholine receptors at neuromuscular junctions.

Action Potentials↗

PubMed1997

Facilitation of apoptosis by cyclosporins A and H, but not FK506 in mouse bronchial eosinophils.

This study was undertaken to clarify whether or not binding to cyclophilin is a prerequisite for cyclosporin A-induced modulation of apoptotic cell death in eosinophils. Eosinophils were isolated from bronchoalveolar lavage fluid of mice challenged with inhaled allergen after sensitization. Apoptosis was determined by analysing the DNA content. At 72 h, 99% of the cells had died without addition of cytokines, whereas 55-60% of the cells survived in the presence of 10 U/ml recombinant murine interleukin 5 or recombinant murine granulocyte macrophage-colony stimulation factor (GM-CSF). Apoptotic cell death at 72 h in the presence of 10 U/ml interleukin 5 was increased by addition of cyclosporin H, an analogue of cyclosporin A without cyclophilin binding activity, in a concentration-dependent (0.3 to 3 microM) manner. The increase in apoptosis elicited by cyclosporin A and cyclosporin H took place also in the presence of 10 U/ml GM-CSF but to a lesser extent. There was a significant augmentation of apoptosis in eosinophils cultured in the presence of each cytokine for 72 h or longer. Tacrolimus (FK506) failed to augment apoptotic cell death. Thus, it is unlikely that binding of cyclosporin A to cyclophilin accounts for the increased apoptosis induced by cyclosporin A and its analogue in eosinophils. The increase in apoptosis induced by cyclosporin A, but not FK506, in activated eosinophils from the airways may be attributed to the anti-asthmatic effects of cyclosporin A.

Animals↗

PubMed1996

Inhibitory effect of fluvastatin at doses insufficient to lower serum lipids on the catheter-induced thickening of intima in rabbit femoral artery.

The anti-atherosclerotic effect of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors at doses insufficient to lower serum cholesterol was investigated in rabbit femoral artery denuded by balloon catheter. Fluvastatin and pravastatin were given orally at doses of 4 and 8 mg/kg per day, respectively, for 2 weeks after the catheterization. There was little change in serum cholesterol, triglyceride and phospholipid by chronic treatment with the drugs. The cross-sectional area of the intima, expressed as relative values to media (I/M ratio), was increased by the catheterization, showing intimal thickening in the denuded arteries. The I/M ratio was reduced by fluvastatin but not pravastatin: 0.327 +/- 0.060 for control, 0.116 +/- 0.035 for 4 mg/kg fluvastatin, 0.088 +/- 0.027 for 8 mg/kg fluvastatin and 0.22 +/- 0.069 for 8 mg/kg pravastatin. Fluvastatin (8 mg/kg)-induced effect on the I/M ratio, was prevented by the combined administration with 40 mg/kg per day mevalonate, a metabolite in the HMG-CoA reductase pathway. These results suggest that fluvastatin inhibits intimal thickening after catheterization-induced injury through percutaneous transluminal coronary angioplasty (PTCA) and that the inhibition is presumably attributed to reduced migration and proliferation of smooth muscle cells but not secondarily to a lowering of serum lipid.

Animals↗

PubMed1996

Augmentation of apoptosis in bronchial exuded rat eosinophils by cyclosporin A.

The effect of cyclosporin A on apoptosis in eosinophils was examined to clarify the inhibitory mechanisms of cyclosporin A on allergen-induced eosinophilia in the airway. Eosinophils in bronchoalveolar lavage fluid from sensitized rats after inhaling an allergen were used. More than 50% of the eosinophils that died spontaneously by apoptosis within 24 hour incubation in RPMI 1640 medium contained 10% fetal calf serum. The addition of cyclosporin A or dexamethasone significantly enhanced the eosinophils apoptosis at concentrations of more than 0.1 microM. Apoptosis in eosinophils was considerably suppressed in the presence of culture supernatant of activated splenocytes as a source of various cytokines. Even in the presence of culture supernatant of activated splenocytes, cyclosporin A or dexamethasone facilitated apoptosis in eosinophils. These results suggest that apoptotic death of activated eosinophils is augmented with cyclosporin A and that accelerated apoptosis in eosinophils of the airway may account for the inhibitory effect of cyclosporin A on eosinophilia.

Animals↗

PubMed1996

The individual and combined effects of ozone and simulated acid rain on growth, gas exchange rate and water-use efficiency of Pinus armandi Franch.

The seedlings of Pinus armandi Franch. were exposed to ozone (O(3)) at 300 ppb for 8 h a day, 6 days a week, and simulated acid rain of pH 3.0 or 2.3, 6 times a week, alone or in combination, for 14 weeks from 15 June to 20 September 1993. The control seedlings were exposed to charcoal-filtered air and simulated rain of pH 6.8 during the same period. Significant interactive effects of O(3) and simulated acid rain on whole plant net photosynthetic rate were observed, but not on other determined parameters. The exposure of the seedlings to O(3) caused the reductions in the dry weight growth, root dry weight relative to the whole plant dry weight, net photosynthetic rate, transpiration rate in light, water-use efficiency and root respiration activity, and increases in shoot/root ratio, and leaf dry weight relative to the whole plant dry weight without an appearance of acute visible foliar injury, but did not affect the dark respiration rate and transpiration rate in the darkness. The decreased net photosynthetic rate was considered to be the major cause for the growth reduction of the seedlings exposed to O(3). On the other hand, the exposure of the seedlings to simulated acid rain reduced the net photosynthetic rate per unit chlorophyll a + b content, but did not induce the significant change in other determined parameters.

Journal Article↗

PubMed1996

Inhibitory effect of fluvastatin, an HMG-CoA reductase inhibitor, on the expression of adhesion molecules on human monocyte cell line.

The effect of fluvastatin, an HMG-CoA reductase inhibitor, was investigated on the adhesive interaction between U937 cells, the human monocyte cell line, and human umbilical vein endothelial cells (HUVEC), focusing on the expression of adhesion molecules. U937 treated with fluvastatin lowered the capacity for binding to HUVEC. Fluvastatin at 0.1 microM or more inhibited the expression of lymphocyte function associated antigen-1 (LFA-1) on U937 and intercellular adhesion molecule-1 (ICAM-1) on U937. The expression of ICAM-1 on HUVEC was not inhibited by fluvastatin. The inhibitory effects of fluvastatin on the expression of adhesion molecules on U937 were completely reversed by the addition of mevalonate. Because fluvastatin did not affect the expression of other cell surface markers, CD4 and CD71, the inhibitory effects of fluvastatin on adhesion molecule expression could not be attributed to the non-specific suppression of the cell. It is conceivable that cellular interaction between monocytes and endothelial cells is inhibited by fluvastatin, mediated via reducing the expression of adhesion molecules, particularly in the side of monocyte.

Cell Adhesion Molecules↗

PubMed1996

Inhibitory effects of fluvastatin, a new HMG-CoA reductase inhibitor, on the increase in vascular ACE activity in cholesterol-fed rabbits.

1. The effects of fluvastatin, a new 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, on the vascular angiotensin converting enzyme (ACE) activity in hyperlipidaemic rabbits were compared with those of enalapril, an ACE inhibitor. 2. Rabbits were fed a 1.5% cholesterol containing diet or normal diet for 16 weeks and treated with either fluvastatin or enalapril in the diet at the respective doses of 2 and 10 mg kg-1 day-1. The total cholesterol, triglyceride and phospholipid levels in serum were significantly increased in rabbits fed the high cholesterol diet. Treatment with fluvastatin but not enalapril resulted in a decrease in serum lipids. 3. The vascular ACE activities assessed via the cleavage rate from synthetic substrate in the aortic arches and upper thoracic aortae were increased by 8 to 10 times when the rabbits were made hyperlipidaemic. Fluvastatin as well as enalapril significantly lowered the tissue ACE in the aortae. 4. The ACE activities in serum did not alter in hyperlipidaemic rabbits either in the presence or absence of fluvastatin. The serum ACE activity was lowered by enalapril. 5. The lipid peroxide in serum as well as the plaque area in the thoracic aorta was significantly increased in the cholesterol diet-fed rabbits. Treatment with fluvastatin or enalapril reduced both serum lipid peroxide and plaque formation. The relaxant responses to acetylcoholine (ACh) were significantly suppressed in the cholesterol-fed rabbits. Treatment with fluvastatin or enalapril significantly reversed the suppression of ACh-induced relaxation. 6. It seems that the reduction of vascular ACE is not coupled to lipids and ACE activity in serum, but rather to lipid peroxidation. Thus, the decrease in vascular ACE activity by fluvastatin as well as the lipid-lowering effect may reduce the risk of atherosclerosis progression in the vasculature.

Animals↗

PubMed1996

Increased activity of vascular ACE related to atherosclerotic lesions in hyperlipidemic rabbits.

The relationship between vascular angiotensin-converting enzyme (ACE) activity in the aorta and atherosclerotic lesions was investigated in rabbits fed two atherogenic diets, 0.5 and 1.5% cholesterol, for 17 wk. Tissue ACE activity was assessed by the cleavage rate of hippuric acid from a synthetic substrate. Total cholesterol, triglycerides, and phospholipids in the serum were significantly increased by the diet. Vascular ACE activity in the femoral artery, abdominal aorta, and aortic arch was significantly increased (2-5 times) by the atherogenic diet in a high-cholesterol-related manner compared with the rabbits fed a normal diet. The increase was associated with vascular heterogeneity of regions. There was a significant correlation between plaque area and vascular ACE activity in the aortic arch isolated from rabbits fed the higher (1.5%)-cholesterol diet. Contractile responses of the femoral artery to angiotensin I and II in the atherogenic diet-fed rabbits did not differ from those in animals fed the normal diet. It is conceivable that increased ACE in the vascular walls is involved in hyperlipidemia-induced atherogenesis, presumably through production of growth or stimulating factor(s) contributing to plaque formation.

Animals↗

PubMed1995

Selenocysteylation in eukaryotes necessitates the uniquely long aminoacyl acceptor stem of selenocysteine tRNA(Sec).

Selenocysteine synthesis is achieved on a specific tRNA, tRNA(Sec), which is first charged with serine to yield seryl-tRNA(Sec). Eukaryotic tRNA(Sec) exhibits an aminoacyl acceptor stem with a unique length of 9 base pairs. Within this stem, two base pairs, G5a.U67b and U6.U67, drew our attention, whose non-Watson-Crick status is maintained in the course of evolution either through U6.U67 base conservation or base covariation at G5a.U67b. Single or double point mutations were performed, which modified the identity of either or both of the base pairs. Serylation by seryl-tRNA synthetase was unaffected by substitutions at either G5a.U67b or U6.U67. Instead, and quite surprisingly, changing G5a.U67b and U6.U67 to G5a-C67b/U6.G67 or G5a-C67b/C6-G67 gave rise to a tRNA(Sec) mutant exhibiting a gain of function in serylation. This finding sheds light on the negative influence born by a few base pairs in the acceptor stem of tRNA(Sec) on its serylation abilities. The tRNA(Sec) capacities to support selenocysteylation were next examined with regard to a possible role played by the two non-Watson-Crick base pairs and the unique length of the acceptor stem. It first emerges from our study that tRNA(Sec) transcribed in vitro is able to support selenocysteylation. Second, none of the point mutations engineered at G5a.U67b and/or U6.U67 significantly modified the selenocysteylation level. In contrast, reduction of the acceptor stem length to 8 base pairs led tRNA(Sec) to lose its ability to efficiently support selenocysteylation. Thus, our study provides strong evidence that the length of the acceptor stem is of prime importance for the serine to selenocysteine conversion step.

Acylation↗

PubMed1995

In vivo responsiveness of thyroid glands to TSH in normal and novel 'growth-retarded' mice: transient elevation in normal mice and impairment in 'growth-retarded' mice.

The in vivo responsiveness of thyroid glands to TSH at various ages in novel 'growth-retarded' (grt/grt) mice derived from Snell's dwarf (DW/J) mice and in their normal counterparts were analysed by determining serum T4 concentrations before and after the administration of exogenous TSH. The serum T4 concentration in normal mice increased in response to TSH at 2, 4 and 12 weeks of age but not at 1 week of age. A transient augmentation of such thyroidal responsiveness to TSH was apparent in normal mice at 2 weeks of age, when the serum T4 level exhibits a peak and the pubertal growth of mice starts. In contrast to normal mice, at any age examined from 2 to 12 weeks after birth, exogenous TSH did not influence serum T4 concentrations in the grt/grt mice at all. On the other hand, serum TSH concentrations in young grt/grt mice were highly elevated compared with those in normal mice and they were normalized by a 2-3 week's treatment with T3. Morphological studies demonstrated degenerated thyroid glands in the grt/grt mice. These results suggest that the severe hypothyroidism and consequent growth retardation in growth-retarded mice are due to impairment of the thyroid glands of the mutant mice in producing and/or secreting thyroid hormones in response to TSH.

Aging↗

PubMed1994

A factor protecting mammalian [75Se]SeCys-tRNA is different from EF-1 alpha.

In Escherichia coli, an elongation factor (EF-Tu-like) specific to SeCys-tRNA, SELB, has been identified; however, a mammalian counterpart of SELB has not been reported to date. We searched for and found this factor in bovine liver extracts using the assay of [75Se]SeCys-tRNA protecting activity against alkaline hydrolysis (SePF activity). We found SePF activity in the protein extracts of the precipitate (microsomal fraction) collected at 150,000 x g from bovine liver. The proteins were separated by Sephacryl S-300 chromatography, and the SePF and EF-1 alpha activities were found in the same fraction, indicating that SePF and EF-1 alpha have the same molecular mass (approximately 50 kDa). We then chromatographed this active fraction using CM-Sephadex C-25 columns. The SePF activity was eluted after the peak of EF-1 alpha activity. This result indicated that this SePF activity was not dependent on EF-1 alpha. In addition to performing these two chromatographies, we investigated pure EF-1 alpha from Bombyx mori but could not detect any SePF activity in B. mori EF-1 alpha. Thus we showed that the SePF activity in bovine liver differs from that of EF-1 alpha in eukaryotes. Therefore the factor protecting [75Se]SeCys-tRNA in bovine liver is not EF-1 alpha and must be a SELB-like factor.

Animals↗

PubMed1994

Expression of high activity of ornithine decarboxylase and occurrence of unusual chromophobic cells in anterior pituitary gland of a novel growth-retarded strain of mice, grm/grm.

Extremely high activity of ornithine decarboxylase (ODC) was detected in the pituitary gland of growth-retarded mice, grm/grm at 2 months after birth. The elevated enzyme activity gradually decreased to the control level in 14 months after birth. In the pituitary gland of the growth-retarded mice, unusual chromophobic cells were also present from the early stages after birth. The chromophobic cells showed conspicuous proliferations and resulted in a distinct hyperplasia of the tissue after 4 months after birth. These findings suggest that ODC is correlated to the progressive transformation of pituitary cells into the chromophobic cells.

Animals↗