Biomedical subjects

Jun Sasaki

Publications and source records attributed to Jun Sasaki.

At least 55 records · Page 3Linked to original sources

PubMed2003

Functional analysis of the stem-loop structures at the 5' end of the Aichi virus genome.

Aichi virus is a member of the family Picornaviridae. Computer-assisted secondary structure prediction suggested the formation of three stem-loop structures (SL-A, SL-B, and SL-C from the 5' end) within the 5'-end 120 nucleotides of the genome. We have already shown that the most 5'-end stem-loop, SL-A, is critical for viral RNA replication. Here, using an infectious cDNA clone and a replicon harboring a luciferase gene, we revealed that formation of SL-B and SL-C on the positive strand is essential for viral RNA replication. In addition, the specific nucleotide sequence of the loop segment of SL-B was also shown to be critical for viral RNA replication. Mutations of the upper and lower stems of SL-C that do not disrupt the base-pairings hardly affected RNA replication, but decreased the yields of viable viruses significantly compared with for the wild-type. This suggests that SL-C plays a role at some step besides RNA replication during virus infection.

5' Untranslated Regions↗

PubMed2003

Natural mutations of apolipoprotein A-I impairing activation of lecithin:cholesterol acyltransferase.

Five natural mutations of apolipoprotein A-I (apoA-I), apoA-I(A95D), apoA-I(Y100H), apoA-I(E110K), apoA-I(V156E) and apoA-I(H162Q), were studied for their ability to activate lecithin:cholesterol acyltransferase (LCAT). Mutants apoA-I(E110K), apoA-I(V156E) and apoA-I(H162Q) had an impaired ability to activate LCAT. Combined with data on other apoA-I mutants this finding is consistent with the idea that the central region between amino acids 110 and 160 is likely to be the "active site" of apoA-I involved in the interaction with LCAT and that a specific sequence of apoA-I is required for activation of the enzyme.

Amino Acid Sequence↗

PubMed2003

Association of cholesteryl ester transfer protein activity and TaqIB polymorphism with lipoprotein variations in Japanese subjects.

Cholesteryl ester transfer protein (CETP) facilitates the transfer of cholesteryl ester from high-density lipoprotein (HDL) to apolipoprotein (apo)B-containing lipoproteins, whereby it potentially regulates steady-state concentrations of HDL-cholesterol (HDL-C), as well as low-density lipoprotein-cholesterol (LDL-C). We performed a multicenter trial to assess the association of CETP activity with plasma lipoprotein levels in 591 Japanese subjects. Women had significantly higher CETP activity (15%) and mass (24%) compared to men. For both genders CETP activity was negatively correlated with HDL-C and HDL(2)-C, but positively correlated with LDL-C. B2 allele frequency in TaqIB polymorphism was 40%, with no gender difference. TaqIB genotypes were significantly associated with CETP activity and HDL-C level (both P <.001). B1B1 had the highest CETP activity and the lowest HDL-C concentrations, whereas B2B2 had the lowest CETP activity and the highest HDL-C concentrations. However, no statistically significant differences in triglycerides (TG) or LDL-C were observed across TaqIB genotypes. Multivariate analysis revealed that determinants of HDL-C were age, gender, body mass index (BMI), smoking, alcohol intake, exercise, CETP activity, and TG, and for LDL-C were BMI, age, and CETP. These data demonstrate that CETP activity is a significant determinant of HDL-C and LDL-C levels and that TaqIB CETP gene polymorphism affects CETP activity and HDL-C level in Japanese population examined.

Adult↗

PubMed2003

Utility of the dried blood on filter paper as a source of cytokine mRNA for the analysis of immunoreactions in Plasmodium yoelii infection.

We examined the utility of dried blood on filter paper for the source of cytokine messenger RNA (mRNA). Total RNA was isolated from the dried blood of mice infected with Plasmodium yoelii, and cDNA was amplified by reverse transcription-polymerase chain reaction (RT-PCR). As a reference, we extracted total RNA from peripheral blood collected at the same time as the preparation for dried blood. There was no difference in cytokine mRNA expression between the two sources; the dried blood on filter paper and the peripheral blood. Th1 cells, Th2 cells, and monocytes/macrophages derived cytokine mRNAs in the dried blood from infected mice were detected, and the increase of some of the cytokines mRNAs after infection was also observed. These results suggested that the dried blood on filter paper is satisfactory RNA source for immunological examination in field-based studies.

Animals↗

PubMed2003

Aichi virus leader protein is involved in viral RNA replication and encapsidation.

Aichi virus, a member of the family Picornaviridae, encodes a leader (L) protein of 170 amino acids (aa). The Aichi virus L protein exhibits no significant sequence homology to those of other picornaviruses. In this study, we investigated the function of the Aichi virus L protein in virus growth. In vitro translation and cleavage assays indicated that the L protein has no autocatalytic activity and is not involved in polyprotein cleavage. The L-VP0 junction was cleaved by 3C proteinase. Immunoblot analysis showed that the L protein is stably present in infected cells. Characterization of various L mutants derived from an infectious cDNA clone revealed that deletion of 93 aa of the center part (aa 43 to 135), 50 aa of the N-terminal part (aa 4 to 53), or 90 aa of the C-terminal part (aa 74 to 163) abolished viral RNA replication. A mutant (Delta114-163) in which 50 aa of the C-terminal part (aa 114 to 163) were deleted exhibited efficient RNA replication and translation abilities, but the virus yield was 4 log orders lower than that of the wild type. Sedimentation analysis of viral particles generated in mutant Delta114-163 RNA-transfected cells showed that the mutant has a severe defect in the formation of mature virions, but not in that of empty capsids. Thus, the data obtained in this study indicate that the Aichi virus L protein is involved in both viral RNA replication and encapsidation.

Animals↗

PubMed2003

The 5'-end sequence of the genome of Aichi virus, a picornavirus, contains an element critical for viral RNA encapsidation.

Picornavirus positive-strand RNAs are selectively encapsidated despite the coexistence of viral negative-strand RNAs and cellular RNAs in infected cells. However, the precise mechanism of the RNA encapsidation process in picornaviruses remains unclear. Here we report the first identification of an RNA element critical for encapsidation in picornaviruses. The 5' end of the genome of Aichi virus, a member of the family Picornaviridae, folds into three stem-loop structures (SL-A, SL-B, and SL-C, from the most 5' end). In the previous study, we constructed a mutant, termed mut6, by exchanging the seven-nucleotide stretches of the middle part of the stem in SL-A with each other to maintain the base pairings of the stem. mut6 exhibited efficient RNA replication and translation but formed no plaques. The present study showed that in cells transfected with mut6 RNA, empty capsids were accumulated, but few virions containing RNA were formed. This means that mut6 has a severe defect in RNA encapsidation. Site-directed mutational analysis indicated that as the mutated region was narrowed, the encapsidation was improved. As a result, the mutation of the 7 bp of the middle part of the stem in SL-A was required for abolishing the plaque-forming ability. Thus, the 5'-end sequence of the Aichi virus genome was shown to play an important role in encapsidation.

5' Untranslated Regions↗

PubMed2003

Sustained reduction of serum cholesterol in low-dose 6-year simvastatin treatment with minimum side effects in 51,321 Japanese hypercholesterolemic patients.

The Japan Lipid Intervention Trial (J-LIT) study, a nationwide cohort study utilizing the clinical practice of general physicians, was designed to clarify the relationship between the incidence of coronary heart disease and serum lipid concentrations during simvastatin therapy, as well as the safety of the therapy, in a large number of Japanese hypercholesterolemic patients. All the enrolled patients were treated with simvastatin. The current study analyzed the lipid lowering effect and safety of the low-dose simvastatin therapy used in the J-LIT study. Open-labeled simvastatin was given to 51,321 patients at an initial dose of mostly 5 mg/day. After 6 months of the treatment, the average serum total cholesterol (TC) and low density lipoprotein-cholesterol concentrations in all the patients followed up were reduced by 18.3% and 26.0%, respectively, and that of high density lipoprotein-cholesterol increased 2.3% on average. These concentrations were well maintained throughout the 6-year treatment period. A minority of patients (1.4%) unexpectedly had a remarkable reduction in TC concentration by more than 40%. Hyper-responders, even to low-dose statin, were found for the first time in this large-scale and long-term investigation. Overall adverse drug reactions occurred in 3.3% of subjects during the 6-year treatment, the major events being hepatic and musculoskeletal disorders, of which the incidence was less than 1%. Low-dose simvastatin therapy of 5 mg/day effectively controlled the serum TC concentration by reducing it by approximately 20% on average in hypercholesterolemic Japanese patients, a reduction that corresponds to the effect of simvastatin 20 mg/day in Western studies. In addition, the low incidence of drug-related adverse events in this study may be also related to the low dosage of simvastatin.

Anticholesteremic Agents↗

PubMed2003

Reduction in serum total cholesterol and risks of coronary events and cerebral infarction in Japanese men: the Kyushu Lipid Intervention Study.

Lowering serum total cholesterol is shown to decrease the risk of coronary heart disease (CHD) in Western countries,but evidence is limited regarding cerebral infarction (CI). The present study used the Kyushu Lipid Intervention Study to examine the risks of CHD events and CI in relation to reduction in serum total cholesterol. Subjects were 4,615 men aged 45-74 years with serum total cholesterol of 220 mg/dl (5.68 mmol/L) or greater who had no history of CHD events or stroke. CHD events and CI numbered 125 and 92, respectively, in a 5-year follow-up. After adjustment for potential confounding factors, the relative risks of CHD events and CI for 15% or greater reduction in total cholesterol, compared with less than 5% reduction, were 0.78 (95% confidence limit [CL]0.46-1.32) and 0.39 (95% CL 0.22-0.69), respectively. As compared with on-treatment cholesterol levels of 240 mg/dl (6.20 mmol/L)or higher, the risk of CHD events was approximately 50% lower across 3 categories below 240 mg/dl (6.20 mmol/L), and that of CI was 70%lower at 2 categories below 220 mg/dl (5.68 mmol/L). Lowering serum total cholesterol below 220 mg/dl (5.68 mmol/L) seems desirable with regard to the prevention of CI.

Aged↗

PubMed2003

Necrotic hepatitis due to Clostridium perfringens infection in newly hatched broiler chicks.

Multiple necrotic hepatitis lesions of 5 newly hatched broiler chicks in three flocks derived from two hatcheries were examined pathologically. The livers were brittle, and multiple yellowish or green foci were scattered on the surface and cut surface. The main histological finding was well demarcated multi-focal necrosis in the liver. Many Gram-positive large bacilli that reacted positively with polyclonal anti-Clostridium perfringens serum were observed in necrotic areas.

Animals↗

PubMed2002

Resonance Raman spectroscopy and quantum chemical calculations reveal structural changes in the active site of photoactive yellow protein.

Photoactive yellow protein (PYP) is a bacterial photoreceptor containing a 4-hydroxycinnamyl chromophore. Photoexcitation of PYP triggers a photocycle that involves at least two intermediate states: an early red-shifted PYP(L) intermediate and a long-lived blue-shifted PYP(M) intermediate. In this study, we have explored the active site structures of these intermediates by resonance Raman spectroscopy. Quantum chemical calculations based on a density functional theory are also performed to simulate the observed spectra. The obtained structure of the chromophore in PYP(L) has cis configuration and no hydrogen bond at the carbonyl oxygen. In PYP(M), the cis chromophore is protonated at the phenolic oxygen and forms the hydrogen bond at the carbonyl group. These results allow us to propose structural changes of the chromophore during the photocycle of PYP. The chromophore photoisomerizes from trans to cis configuration by flipping the carbonyl group to form PYP(L) with minimal perturbation of the tightly packed protein interior. Subsequent conversion to PYP(M) involves protonation on the phenolic oxygen, followed by rotation of the chromophore as a whole. This large motion of the chromophore is potentially correlated with the succeeding global conformational changes in the protein, which ultimately leads to transduction of a biological signal.

Bacterial Proteins↗

PubMed2002

Light-induced unfolding of photoactive yellow protein mutant M100L.

Light-activation of the PAS domain protein photoactive yellow protein (PYP) is believed to trigger a negative phototactic response in the phototropic bacterium Halorhodospira halophila. To investigate transient conformational changes of the PYP photocycle, we utilized the PYP mutant M100L that displays an increased lifetime of the putative signaling-state photointermediate PYP(M) by 3 orders of magnitude, as previously reported for the M100A mutant [Devanathan, S., Genick, U. K., Canestrelli, I. L., Meyer, T. E., Cusanovich, M. A., Getzoff, E. D., and Tollin, G. Biochemistry (1998) 37, 11563-11568]. The FTIR difference spectrum of PYP(M) and the ground state of M100L demonstrated extensive peptide-backbone structural changes as observed in the FTIR difference spectrum of the wild-type protein and PYP(M). The conformational change investigated by CD spectroscopy in the far-UV region showed reduction of the alpha-helical content by approximately 40%, indicating a considerable amount of changes in the secondary structure. The optical activity of the p-coumaric acid chromophore completely vanished upon PYP(M) in contrast to the dark state, indicating deformation of the binding pocket structure in PYP(M). The tertiary structural changes were further monitored by small-angle X-ray scattering measurements, which demonstrated a significant increase of the radius of gyration of the molecule by approximately 5% in PYP(M). These structural changes were reversed concomitantly with the chromophore anionization upon the dark state recovery. The observed changes of the quantities provided a more vivid view of the structural changes of the mutant PYP in going from PYP(M) to PYP(dark), which can be regarded as a process of folding of the secondary and the tertiary structures of the "PAS" domain structure, coupled with the p-coumaric acid chromophore deprotonation and isomerization.

Bacterial Proteins↗

PubMed2002

A randomized, double-blind trial comparing the efficacy and safety of pitavastatin versus pravastatin in patients with primary hypercholesterolemia.

Pitavastatin (p-INN) is a novel and fully synthetic 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, with a cholesterol-lowering action stronger than that of other statins currently in use. A 12-week, multi-center, randomized, double-blind, controlled study was conducted to confirm the efficacy and safety of pitavastatin compared with pravastatin, an agent for using to reduce low density lipoprotein cholesterol (LDL-C) in hypercholesterolemic patients. Patients were recruited at 43 institutes in Japan. Following more than 4 weeks run-in period, 240 patients were randomized to receive 2 mg of pitavastatin or 10 mg of pravastatin daily. At 12 weeks post-randomization, the pitavastatin group showed significantly lower LDL-C levels by -37.6% from baseline compared with -18.4% in the pravastatin group (P<0.05). Pitavastatin also significantly lowered total cholesterol (TC) by -28.2% compared with -14.0% of pravastatin (P<0.05). The LDL-C target level of <140 mg/dl was attained in 75% of the patients treated with pitavastatin, compared with 36% of those in the pravastatin group (P<0.05). Pitavastatin also significantly reduced triglycerides (TG), apo B, C-II and C-III, compared with pravastatin, and increased HDL-C, apo A-I and A-II, to the same extent of pravastatin. Safety was assessed by monitoring adverse events and measuring clinical laboratory parameters. The adverse event profile was similar for both treatment groups and neither treatment caused clinically relevant laboratory abnormalities. These results indicated that pitavastatin was more effective than pravastatin, and both drugs were well-tolerated in the treatment of hypercholesterolemia.

Adult↗

PubMed2002

Effects of fenofibrate on high-density lipoprotein particle size in patients with hyperlipidemia: a randomized, double-blind, placebo-controlled, multicenter, crossover study.

BACKGROUND: Fenofibrate lowers serum total cholesterol and triglyceride levels while it elevates serum high-density lipoprotein cholesterol (HDL-C) level. OBJECTIVE: The aim of this study was to investigate the effects of fenofibrate on the particle size of high-density lipoprotein (HDL). METHODS: Patients with hyperlipidemia (as defined by serum triglyceride level > or = 150 mg/dL in the fasting state) were enrolled in this randomized, double-blind, placebo-controlled, multicenter, crossover study. Fenofibrate 300 mg (corresponding to 200 mg of micronized fenofibrate) or placebo was administered orally once daily after dinner for 8 weeks, followed by crossover of the 2 drugs for an additional 8 weeks. RESULTS: Fifty hyperlipidemic patients (31 men, 19 women; mean [SD] age, 54.6 [12.7] years) were enrolled. Serum total cholesterol and triglyceride levels were significantly reduced with fenofibrate treatment compared with placebo (9.4% [P = 0.007] and 34.4% [P < 0.001], respectively), whereas HDL-C levels were significantly elevated (by 25.8% [P < 0.001]). Lipoprotein lipase (LPL) activity, LPL protein level, and hepatic triglyceride lipase activity increased by 10.5%, 13.4%, and 11.4%, respectively, with fenofibrate compared with placebo. HDL was classified into 3 groups by particle size: HDL3 <88 A; HDL2a > or = 88 A but <98 A; and HDL2b > or = 98 A. The amount of HDL3 increased significantly with fenofibrate compared with placebo (P < 0.001). Fenofibrate was well tolerated during the study. Abnormal clinical laboratory values were noted in 20 of 48 patients (41.7%), but these events were mild and not clinically significant. CONCLUSION: Taken together, these findings indicate that fenofibrate therapy increased the HDL subfraction with the smallest diameter (HDL3), which is largely responsible for withdrawing cholesterol from peripheral cells.

Adult↗

PubMed2002

Antioxidative effects of fluvastatin on superoxide anion activated by angiotensin II in human aortic smooth muscle cells.

We examined the antioxidative effects of fluvastatin, a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor (statin), on superoxide anion formation activated by angiotensin II (Ang II) in vitro. The effects of fluvastatin were also compared to simvastatin and a water-soluble analog of alpha-tocopherol, trolox. Treatment of human aortic smooth muscle cells (hASMC) with Ang II for 24 hours resulted in a 3.2 +/- 0.5-fold increase in intracellular superoxide anion formation as detected by lucigenin assay. hASMC treated with clinical concentrations of fluvastatin (0-100 nM) showed a dose-dependent decrease in Ang II-activated superoxide anion formation. The addition of similar concentrations of trolox to hASMC inhibited Ang II-activated superoxide anion formation in a dose-dependent manner. However, simvastatin at similar doses failed to inhibit Ang II-activated superoxide anion formation by hASMC. Our results indicate that in addition to its hypocholesterolemic effect, fluvastatin may have direct antioxidative effects, suggesting its possible protective effect on atherosclerotic process.

Adult↗

PubMed2002

Clinical efficacy of pitavastatin, a new 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, in patients with hyperlipidemia. Dose-finding study using the double-blind, three-group parallel comparison.

Pitavastatin (CAS 147526-32-7, NK-104), the first totally synthetic 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor discovered in Japan, was examined. Pitavastatin significantly decreased the serum levels of total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) at doses of 1 mg/day or more, and significant dose-dependence of the effect of this drug was observed within the dose range from 1 mg/day to 4 mg/day. It also significantly decreased the serum levels of triglycerides (TG) within this dose range. There was no dose-dependence of the incidence of adverse reactions to pitavastatin.

Adult↗

PubMed2002

A role of methionine 100 in facilitating PYP(M)-decay process in the photocycle of photoactive yellow protein.

PYP (photoactive yellow protein) is a photoreceptor protein, which is activated upon photo-isomerization of the p-coumaric acid chromophore and is inactivated as the chromophore is thermally back-isomerized within a second (in PYP(M)-to-PYP(dark) conversion). Here we have examined the mechanism of the rapid thermal isomerization by analyzing mutant PYPs of Met100, which was previously shown to play a major role in facilitating the reaction [Devanathan, S. et al. (1998) Biochemistry 37, 11563-11568]. The mutation to Lys, Leu, Ala, or Glu decelerated the dark state recovery by one to three orders of magnitude. By evaluating temperature-dependence of the kinetics, it was found that the retardation resulted unequivocally from elevations of activation enthalpy (DeltaH( double dagger )) but not the other parameters such as activation entropy or heat capacity changes. Another effect exerted by the mutations was an up-shift of the apparent pK(a) of the chromophore [the pK(a) of a titratable group (X) that controls the pK(a) of the chromophore] in the PYP(M)-decay process. The pK(a) up-shift and the DeltaH( double dagger ) elevation show an approximately linear correlation. We, therefore, postulate that the role of Met100 is to reduce the energy barrier of the PYP(M)-decay process by an indirect interaction through X and that the process is thereby facilitated.

Bacterial Proteins↗

PubMed2002

Large scale cohort study of the relationship between serum cholesterol concentration and coronary events with low-dose simvastatin therapy in Japanese patients with hypercholesterolemia.

Hyperlipidemia is a well-established risk factor for primary coronary heart disease (CHD). Although simvastatin is known to lower serum lipid concentrations, the protective effect of such lipid-lowering therapy against primary CHD has not been established in Japanese patients with hypercholesterolemia. The Japan Lipid Intervention Trial was a 6-year, nationwide cohort study of 47,294 patients treated with open-labeled simvastatin (5-10 mg/day) and monitored by physicians under standard clinical conditions. The aim of the study was to determine the relationship between the occurrence of CHD and the serum lipid concentrations during low-dose simvastatin treatment. Simvastatin reduced serum concentrations of total cholesterol (TC), low-density lipoprotein- cholesterol (LDL-C) and triglyceride (TG), by 18.4%, 26.8% and 16.1% on average, respectively, during the treatment period. The risk of coronary events was higher when the average TC concentration was > or =240 mg/dl and the average LDL-C concentration was > or =160 mg/dl. The incidence of coronary events increased in the patients with TG concentration > or =300 mg/dl compared with patients with TG concentration <150 mg/dl. The high-density lipoprotein cholesterol (HDL-C) inversely correlated with the risk of coronary events. The J-curve association was observed between average TC or LDL-C concentrations and total mortality. Malignancy was the most prevalent cause of death. The health of patients should be monitored closely when there is a remarkable decrease in TC and LDL-C concentrations with low-dose statin. A reasonable strategy to prevent coronary events in Japanese hypercholesterolemic patients without prior CHD under low-dose statin treatment might be regulating the serum lipid concentrations to at least <240 mg/dl for TC, <160 mg/dl for LDL-C, <300 mg/dl for TG, and >40 mg/dl for HDL-C.

Adult↗

PubMed2002

Large scale cohort study of the relationship between serum cholesterol concentration and coronary events with low-dose simvastatin therapy in Japanese patients with hypercholesterolemia and coronary heart disease: secondary prevention cohort study of the Japan Lipid Intervention Trial (J-LIT).

Hyperlipidemia is primarily implicated in the progression of coronary heart disease (CHD) and its treatment is essential for patients with a history of CHD. Statins such as simvastatin, the lipid-lowering agents, are well-known for their ability to normalize patient's serum lipid levels. The Japan Lipid Intervention Trial study of simvastatin is the first nationwide investigation of the relationship between serum lipid levels and the development of CHD in Japanese patients with hypercholesterolemia. Of 5,127 patients, exclusively with a history of documented CHD at enrollment, 4,673 were treated with open-labeled simvastatin at an initial dose of 5-10 mg/day and were monitored for 6 years. The risk of coronary events tended to be higher in patients with a serum total cholesterol (TC) > or =240 mg/dl compared with total cholesterol <240 mg/dl. The concentration of low-density lipoprotein cholesterol (LDL-C) positively correlated and that of high-density lipoprotein cholesterol (HDL-C) inversely correlated with the risk of CHD. Each 10 mg/dl decrease in LDL-C and each 10 mg/dl increase in HDL-C concentration reduced the risk of CHD by 8.0% (95% confidence interval 3.8-12.0) and 28.3% (95% CI 13.9-40.3), respectively. A reasonable therapeutic strategy to reduce CHD progression in patients with prior CHD under low-dose statin treatment might be regulating the serum LDL-C concentration to at least <120 mg/dl and HDL-C >40 mg/dl, respectively.

Adult↗