Biomedical subjects

Takashi Yamada

Publications and source records attributed to Takashi Yamada.

At least 37 records · Page 2Linked to original sources

PubMed2005

Effects of reduced glycogen on structure and in vitro function of rat sarcoplasmic reticulum Ca2+-ATPase.

The aim of this study was to examine the effects of reduced glycogen concentration on sarcoplasmic reticulum (SR) Ca(2+)-ATPase activity in rat fast-twitch muscles. In the first experiment, the gastrocnemius (GAS) muscle from one leg was removed, followed by starvation for 24-72 h, after which the remaining GAS was removed. Intra-animal comparisons revealed that starvation caused a 25% reduction (P<0.05) in the glycogen concentration but no change in SR Ca(2+)-ATPase activity in the GAS. In the second experiment, the SR was purified from a mixture of the GAS and vastus lateralis muscles. In half of the samples obtained from each animal, glycogen was extracted from the SR by treatment with glucoamylase. Treatment resulted in a 94.1 and 70.2% decrease (P<0.01) in glycogen and glycogen phosphorylase, respectively, and a 41.5% increase (P<0.05) in a fluorescein isothiocyanate (FITC) binding to SR Ca(2+)-ATPase. On the other hand, SR Ca(2+)-ATPase activity and the affinity of the enzyme for ATP were unaltered. These results do not implicate depletion of muscle glycogen as a contributor to impaired SR Ca(2+)-ATPase activity as measured in vitro. Therefore, it is concluded that muscle glycogen does not influence exercise tolerance and work productivity in working muscles by modulating the structure of protein involved in Ca(2+) sequestering. Furthermore, it is suggested that the FITC binding assay may be inappropriate as a method for examining the mechanisms for the altered activity of SR Ca(2+)-ATPase.

Animals↗

PubMed2005

Amino acid ester salt recognition by ferrocene-based ditopic receptor bearing oligoethylene glycol with pendant bipy subunits: CV, UV-vis and ESR studies.

The novel ferrocene-based ditopic receptor 1 was synthesized. This receptor bears two oligoethylene glycol arms with pendant 2,2'-bipyridine unit at the identical cyclopentadienyl rings, Cu(I) cation binds to 1 to form the 1 : 1 complex (1.Cu(I)) with the cavity consisting of polyether, and the resulting complex acts as a receptor for amino acid ester salts to give the ditopic complex (1.Cu(I).AAOMe-HCl). The 1H NMR spectrum of 1.Cu(I).LeuOMe-HCl exhibits strong broadening at the bipyridine region, and the ESR spectrum of the same sample gives the signals assigned as Cu(II) species. With these data, the binding of 1.Cu(I) towards AAOMe.HCl leads to the conformational change, and the Cu(I) complex is simultaneously oxidized to the Cu(II) complex.

Amino Acids↗

PubMed2005

Immunization with a gene encoding granulocyte-macrophage colony-stimulating factor inserted with a single helper T-cell epitope of an intracellular bacterium induces a specific T-cell subset and protective immunity.

We evaluated here the effect of immunization with a gene encoding granulocyte-macrophage colony-stimulating factor (GM-CSF) inserted with a helper T cell (Th) epitope, listeriolysin O (LLO) 215-226 derived from Listeria monocytogenes on induction of a specific Th by gene gun bombardment. Immunization of C3H/He mice with pGM215m plasmid encoding murine GM-CSF inserted with LLO 215-226 Th epitope gave the epitope-specific proliferative responses of CD4(+) T lymphocytes. In addition, specific interferon-gamma production from the splenocytes was observed. Concomitantly, pGM215m-immunized mice showed significant protective immunity against lethal listerial challenge. These results suggest that immunization of a gene for GM-CSF inserted with a Th epitope is useful for eliciting a specific Th subset in vivo.

Animals↗

PubMed2005

Genetic rearrangements on the Chlorovirus genome that switch between hyaluronan synthesis and chitin synthesis.

Chlorella viruses or chloroviruses form polysaccharide fibers on the cell wall of host Chlorella cells after infection. Such polysaccharides are either hyaluronan synthesized by virus-encoded hyaluronan synthase (HAS) or chitin synthesized by viral chitin synthase (CHS). Some chloroviruses synthesize both hyaluronan (HA) and chitin simultaneously. To understand the relationship between "HA-synthesizing" and "chitin-synthesizing" viruses, we characterized the CVK2 genomic regions, one flanking chs and the other corresponding to PBCV-1 has and found that on CVK2 DNA, a single ORF (PBCV-1 A330R) was replaced with a 5 kbp region containing chs, ugdh2 (the second gene for UDP-glucose dehydrogenase) and two other ORFs, and that has was replaced with another chs gene. In some chloroviruses, ugdh was lost. These results suggest that chlorovirus types changed from "has viruses" to "chs viruses" or from "chs viruses" to "has viruses" by exchanging the genes.

Base Sequence↗

PubMed2005

Distinct conformation-mediated functions of an active site loop in the catalytic reactions of NAD-dependent D-lactate dehydrogenase and formate dehydrogenase.

The three-dimensional structures of NAD-dependent D-lactate dehydrogenase (D-LDH) and formate dehydrogenase (FDH), which resemble each other, imply that the two enzymes commonly employ certain main chain atoms, which are located on corresponding loop structures in the active sites of the two enzymes, for their respective catalytic functions. These active site loops adopt different conformations in the two enzymes, a difference likely attributable to hydrogen bonds with Asn97 and Glu141, which are also located at equivalent positions in D-LDH and FDH, respectively. X-ray crystallography at 2.4-A resolution revealed that replacement of Asn97 with Asp did not markedly change the overall protein structure but markedly perturbed the conformation of the active site loop in Lactobacillus pentosus D-LDH. The Asn97-->Asp mutant D-LDH exhibited virtually the same k(cat), but about 70-fold higher K(M) value for pyruvate than the wild-type enzyme. For Paracoccus sp. 12-A FDH, in contrast, replacement of Glu141 with Gln and Asn induced only 5.5- and 4.3-fold increases in the K(M) value, but 110 and 590-fold decreases in the k(cat) values for formate, respectively. Furthermore, these mutant FDHs, particularly the Glu141-->Asn enzyme, exhibited markedly enhanced catalytic activity for glyoxylate reduction, indicating that FDH is converted to a 2-hydroxy-acid dehydrogenase on the replacement of Glu141. These results indicate that the active site loops play different roles in the catalytic reactions of D-LDH and FDH, stabilization of substrate binding and promotion of hydrogen transfer, respectively, and that Asn97 and Glu141, which stabilize suitable loop conformations, are essential elements for proper loop functioning.

Amino Acid Sequence↗

PubMed2005

Magnetic resonance image findings of placental lake: report of two cases.

Two cases with a large cystic mass within the placenta are reported. By ultrasonography, it was found that both women had a subchorionic hypoechoic lesion (11.0 x 4.8 x 4.0 cm and 6.6 x 3.7 x 2.2 cm, respectively) at 24 and 35 weeks of gestation, respectively. In both cases, turbulent blood flow generated by a pulsatile jet flow (pulse rate; 40 to 60 beats per minute) into the cystic lesion seen on real-time imaging and lesions being low intensity on T1-weighted and isointensity on T2-weighted magnetic resonance image suggested that they contained fresh maternal blood. In both cases, the sonolucency of the lesions did not change until cesarean deliveries of females, both of whom were small-for-gestational-age infants (1940 g at 37 weeks and 2195 g at 37 weeks, respectively). Biochemical analysis of the fluid in the cystic lesion sampled during the cesarean section in the latter case confirmed that the fluid had originated from the maternal blood. These lesions histologically corresponded to large avillous areas surrounded by normal villi. Thus, a huge placental lake was diagnosed in both cases.

Adult↗

PubMed2005

Studies on intramolecular hydrogen bonding between the pyridine nitrogen and the amide hydrogen of the peptide: synthesis and conformational analysis of tripeptides containing novel amino acids with a pyridine ring.

For the first time tripeptides, Z-AA(1)-Xaa-AA(3)-OMe (AA(1) and AA(3) = Gly or Aib, Xaa = 2Pmg and 2Pyg) were prepared containing alpha-methyl-alpha-(2-pyridyl)glycine (2Pmg) and alpha-(2-pyridyl)glycine (2Pyg) by solid-phase Ugi reaction. These results clearly indicate that for the preparation of tripeptides containing an amino acid with a pyridine ring, the solid-phase Ugi reaction is very useful.NMR analysis clarified that 2Pmg-containing tripeptides adopt a unique conformation with an intramolecular hydrogen bond between 2Pmg-NH and the pyridine nitrogen. However, in the case of Z-Gly-2Pyg-Gly-OMe, the intramolecular hydrogen bonding between 2Pyg-NH and the pyridine nitrogen was not observed, whereas Z-Aib-2Pyg-Aib-OMe adopts a unique conformation with an intramolecular hydrogen bond between 2Pyg-NH and a pyridine nitrogen. Conformational analysis of the tripeptides, Z-AA(1)-Xaa-AA(3)-OMe (AA(1), AA(3) = Gly or Aib, Xaa = alpha,alpha-di(2-pyridyl)glycine (2Dpy), alpha-phenyl-alpha-(2-pyridyl)glycine (2Ppg), 2Pmg and 2Pyg), clarified that when an alpha,alpha-disubstituted glycine with a 2-pyridyl group at an alpha-carbon atom is introduced into any peptide, an intramolecular hydrogen bond between a pyridine nitrogen and an amide proton is formed and conformational mobility of the peptide backbone is restricted.

Amides↗

PubMed2005

Changes in antithrombin activity and platelet counts in the late stage of twin and triplet pregnancies.

It is possible that women with triplet pregnancies are more likely to exhibit pregnancy-induced antithrombin deficiency, gestational thrombocytopenia, and perinatal elevation in serum aspartate aminotransferase (AST) than women with twin pregnancies. We retrospectively reviewed changes in antithrombin activity, platelet count, and blood chemistry in 23 twin and seven triplet pregnancies in which the mothers received antenatal care and gave birth in our hospital during 1999 and 2001. Both antithrombin activity and platelet counts gradually decreased until delivery, then promptly increased after delivery in both twin and triplet pregnancies. A significantly larger number of women developed gestational thrombocytopenia of < 100 x 10 (9)/L (43% [three of seven] versus 4.3% [one of 23]; p < 0.01) and pregnancy-induced antithrombin deficiency of < 60% of normal activity (57% [four of seven] versus 17% [four of 23]; p < 0.05) in triplet than in twin pregnancies. Eight women with pregnancy-induced antithrombin deficiency, including three women with gestational thrombocytopenia, were significantly more likely to develop perinatal elevations of AST, lactate dehydrogenase, serum creatinine, fibrin/fibrinogen degradation products, and D-dimer than were those without pregnancy-induced antithrombin deficiency. These findings suggest that women with triplet pregnancies are at an increased risk of the HELLP syndrome and acute fatty liver of pregnancy compared with women with twin pregnancies.

Adult↗

PubMed2005

Effects of theanine, r-glutamylethylamide, on neurotransmitter release and its relationship with glutamic acid neurotransmission.

t Theanine, r-glutamylethylamide, is one of the major amino acid components in green tea and many researchers have compared theanine's effects with glutamic acid because the chemical structure is similar. In the previous study, we demonstrated that theanine can pass brain-blood barrier and may play as an agonist or an antagonist of some receptors. In this study, we investigated the effects of theanine on neurotransmitter release in the rat brain striatum by in vivo brain microdialysis and examined whether theanine affected glutamate transporters by comparing it with a glutamate transporter blocker, L-trans-Pyrrolidine-2,4-dicarboxylic acid (L-trans-2,4-PDC). Because we investigated whether the effects of theanine is similar to L-trans-2,4-PDC on the brain neurotransmission, we measured dopamine release and some amino acids release which are known as excitatory or inhibitory neurotransmitters from neurons by theanine or L-trans-2,4-PDC perfusion into the rat brain striatum. L-trans-2,4-PDC or theanine perfusion into the brain striatum caused dopamine release from dopaminergic neurons. In addition, L-trans-2,4-PDC perfusion increased glutamic acid, aspartic acid and, whereas theanine perfusion prevented aspartic acid release and increased glycine release. These results suggested that the mechanism of dopamine release caused by theanine is different from glutamate transporter blockers or glutamic acid. Further, L-trans-2,4-PDC cause excitatory neurotransmission, whereas theanine may inhibit excitatory neurotransmission and cause inhibitory neurotransmission via glycine receptors.

Animals↗

PubMed2005

Autologous blood transfusion in patients with placenta previa.

BACKGROUND: Several studies have shown that autologous blood storage during pregnancy is relatively safe for mother and fetus. However, the need for reappraisal of autologous blood transfusion in obstetric patients has been proposed. METHODS: We retrospectively reviewed the cases of placenta previa and low-lying placenta among pregnancies at our hospital during an 18-year period, 1985-2002. The utility of autologous blood transfusion program, which started in 1994 for those with placental positional disorders, was evaluated. RESULTS: Of the pregnancies reviewed, there were 158 cases (1.9%) of placenta previa or low-lying placenta. The number of patients transfused with homologous blood decreased from 27.6% (21/76) in the period before implementation of the autologous blood transfusion program to 8.5% (7/82) after its implementation in 1994. In the latter time period, 39.0% (32/82) of patients with placenta previa and low-lying placenta were phlebotomized and had blood stored. Of those, 71.9% (23/32) were reinfused where one patient (3.1%) needed homologous blood as well. The volume of collected blood per phlebotomy was 367 +/- 65 ml, the total volume of collected blood per patient was 803 +/- 350 ml, and the total of estimated blood loss per patient was 1326 +/- 873 ml. The volume of reinfused blood per patient was 578 +/- 326 ml. CONCLUSIONS: The program of autologous blood collection and transfusion in patients with placenta previa resulted in a decrease in homologous blood transfusion. In our program, we recommend starting blood collection and storage at 32 weeks' gestation and phlebotomize 400 ml per week to reach a volume of stored blood of 1200-1500 ml.

Adult↗

PubMed2005

Evaluation of the ESPLINE INFLUENZA A&B-N Kit for the diagnosis of avian and swine influenza.

The ESPLINE INFLUENZA A&B-N kit was evaluated for its applicability to the rapid diagnosis of influenza in chickens and pigs. The kit specifically detected viral antigens in tracheal swabs and tissue homogenates of the trachea, liver, spleen, and colon of chickens inoculated with a highly pathogenic avian influenza virus strain, A/chicken/Yamaguchi/7/04 (H5N1), at 48 hr post-inoculation (p.i.) as well as in the tracheal and cloacal swabs and tissue homogenates of dead chickens. For those infected with a low pathogenic strain, A/chicken/aq-Y-55/01 (H9N2), antigens were detected only in the samples from tracheal swabs and organs 1-4 days p.i. The kit also detected viral antigens in the nasal swabs of miniature pigs infected with swine and avian influenza viruses. The kit was found to be sensitive and specific enough for the rapid diagnosis of infections of influenza A virus in chickens and pigs.

Animals↗

PubMed2005

Late restenosis of the balloon-dilated site: serial angiographic observations beyond 7 years.

BACKGROUND: The present retrospective study was performed to assess the long-term (>7 years) fate of stabilized balloon-dilated sites. METHODS AND RESULTS: Between February and April 1986, 171 patients underwent successful percutaneous balloon angioplasty. Early restenosis (<1 year) occurred in 53%, but repeat balloon angioplasty stabilized the balloon-dilated site. The early period was defined as 6 months, late years as 3-5 years and long-term years as 7-12 years. Angiographic evaluation at both early year or late year periods (mean = 4.7 years) and long-term (mean = 10.4 years) periods following stabilization was available in 71 patients (94 lesions) with mean age of 61.7+/-8.5 years. Of the 71 patients 69.6% were male. Restenosis occurring after 1 year was defined as late restenosis. The mean diameter stenosis changed from 6 months (50.3+/-12.4%) to late-period (44.2 +/-13.2%; p < 0.05) and long-term period (50.3+/-16.1%; p < 0.001); but the reference vessel diameter did not change significantly. Late restenosis occurred in 28% (3-5 years) and 33% (7-12 years) of 94 lesions, and 13.8% of lesion required repeat target lesion revascularization. During this period, 5.3% of patients (5 lesions) underwent revascularization for new proximal or distal lesions. CONCLUSIONS: Decrease of luminal diameter during the early 6 months, was followed by regression after stabilization of the balloon-dilated site up to 5 years, but luminal re-narrowing occurs again over 7 years after balloon angioplasty.

Aged↗

PubMed2005

Microbial synthesis of hyaluronan and chitin: New approaches.

Hyaluronan (HA) is an important structural element in the vitreous humor of the eye, synovial fluid, and skin of vertebrates. Moreover, HA interacts with proteins such as CD44, RHAMM, and fibrinogen, thereby influencing many natural processes such as angiogenesis, cancer, cell motility, wound healing, and cell adhesion. Reflecting such a variety of functions, HA has attracted attention from a wide range of application fields such as medicine (including surgery), cosmetics, and health foods. Traditionally HA was extracted from rooster combs, but nowadays is produced by the fermentation of streptococci. At present, quality issues such as purity and molecular weight distribution, rather than quantity, have been the focus of strain and process development in HA production. To meet ever-increasing public demand, novel systems that can yield sufficient amounts of high-quality of HA and related materials are required.

Chitin↗

PubMed2005

Production of hydroxycitric acid by microorganisms.

Hydroxycitric acid (HCA) is a major acid component of the tropical plants Garcinia cambogia and Hibiscus subdariffa. (2S,3S)-HCA from G. cambogia was shown to be a potent inhibitor of ATP citrate lyase (EC4.1.3.8), which catalyzes the extramitochondrial cleavage of citrate to oxaloacetate and acetyl-CoA. (2S,3R)-HCA from H. subdariffa inhibits alpha-amylase and alpha-glucosidase, leading to reduction of carbohydrate metabolism. The availability of HCA is limited by the restricted habitat of the plants as well as the difficulty of stereoselective organic synthesis. Hence, we screened microorganisms producing HCA to find an alternative source of optically pure bulk HCA. Two strains, Streptomyces sp. U121 and Bacillus megaterium G45C, were screened by HPLC analysis. Particular metabolites were purified from their culture broths and compared with authentic HCA from plants. NMR studies indicated that the products are identical to Hibiscus-type HCA. This is the first report showing isolation of microorganisms producing HCA.

Bacillus megaterium↗

PubMed2005

Correlation between the pituitary size and function in patients with asthenia.

To explore the relationship between pituitary morphology and function, we performed mid-sagittal MRI and endocrinological evaluation in 38 patients with asthenia. Six patients were diagnosed as having complete empty sella (ES) and 16 patients partial empty sella (PES). BMI, blood pressure, serum Na, ACTH, cortisol, TSH and T(4) were lower in ES group and PES group than in the group with normal pituitary size. Age in the patients with ES was oldest. Multiple regression analysis revealed that serum cortisol level was independently correlated with the size of the pituitary (beta = 0.586, p = 0.0069). Other variables, including age, BMI, blood pressure, serum Na, ACTH, TSH and T(4), were not correlated with the pituitary size when multivariate analysis was employed. In conclusion, there is a close relationship between the reduction of size of pituitary gland and the degree of adrenocortical dysfunction in asthenic patients. It is suggested that the pituitary-adrenal axis is especially vulnerable in empty sella syndrome, and therefore, meticulous evaluation of the hypophysial adrenal axis is recommended in subjects with reduced pituitary size even in elderly population.

Adrenal Insufficiency↗

PubMed2005

Development, progression, and regression of microalbuminuria in Japanese patients with type 2 diabetes under tight glycemic and blood pressure control: the Kashiwa study.

OBJECTIVE: The goal of this study was to know the fate of albuminuria in Japanese patients with type 2 diabetes under tight blood pressure and glycemic control. RESEARCH DESIGN AND METHODS: Patients having normoalbuminuria (urinary albumin excretion <30 mg/g creatinine, n = 179) or microalbuminuria (albumin excretion 30-299 mg/g creatinine, n = 94) at baseline have been followed up for 8 years: ratio of men to women was 160/113, the mean age was 58 years, pretreatment HbA(1c) (A1C) was 8.8%, and blood pressure was 136/76 mmHg. A1C <6.5% and blood pressure <130/80 mmHg were targeted, and the A1C of 6.5 +/- 0.7% (mean +/- SD) and blood pressure of 127 +/- 11/72 +/- 6 mmHg have been maintained during the 8 years. Development of microalbuminuria or macroalbuminuria (albumin excretion > or =300 mg/g creatinine) in initially normoalbuminuric patients and progression to macroalbuminuria or regression to normoalbuminuria in initially microalbuminuric patients were assessed at year 8. RESULTS: Development occurred in 27 (15%) of the normoalbuminuric patients and progression and regression in 16 (17%) and 20 (21%), respectively, of the microalbuminuric patients. Significant independent relationships existed between development and higher achieved mean systolic blood pressure (SBP) and regression and lower achieved mean SBP. In the patients with achieved mean SBP <120 mmHg, development was 3%, progression was 11%, and regression was 44% during 8 years. Prediction for nephropathy by blood pressure and glycemia alone was limited. Nevertheless, albumin excretion at year 8 was positively correlated with achieved mean SBP and baseline albuminuria. CONCLUSIONS: Development and progression were low and regression was high with SBP of 120 mmHg, provided A1C was maintained at 6.5%.

Aged↗

PubMed2005

[Placement of an ultraflex nitinol stent for severe tracheobronchial obstruction in a case of relapsing polychondritis].

A 59-year-old man, who had been treated for bronchial asthma since 2000, was hospitalized with high fever and productive cough in November 2003. Chest radiography on admission showed consolidations in both lower lung fields, and computed tomography demonstrated anteroposterior narrowing of both main bronchi. A physical examination revealed deformity of auricular cartilage and saddle nose, and we diagnosed him relapsing polychondritis (RP). When he was readmitted 4 months later because of severe tracheobronchial stenosis and respiratory failure he required mechanical ventilation, but it was difficult to wean him from the ventilator. Self-expandable metallic stents were placed in the left main bronchus and the trachea. After the procedure, he was successfully weared from mechanical ventilation. Since airway complications of RP can be fatal, stent implantation should be considered in the management of RP with airway manifestations.

Alloys↗

PubMed2004

Embryo loss pattern is predominant in miscarriages with normal chromosome karyotype among women with repeated miscarriage.

OBJECTIVE: The aim of this study was to assess pregnancy loss patterns in women with repeated miscarriage (RM), according to fetal chromosome karyotypes and aetiologies of RM. METHODS: In this cohort study, 168 fetal chromosome karyotypes of miscarriages were investigated. The pregnancy loss patterns were compared between 75 miscarriages from RM women who had a history of two or more consecutive miscarriages and 93 miscarriages from control women whose previous pregnancies ended in live births without a history of RM. By serial ultrasonography, embryo loss (EL) was defined as miscarriage before fetal heat movement was identified and fetal loss (FL) as miscarriage after fetal heat movement was identified. The EL rate was calculated as EL/(EL+FL). RESULTS: The EL rate (66.7%) in miscarriages with normal karyotypes among RM women (n=42) was higher (P<0.05) than that (45.7%) in controls (n=46), while the EL rate (30.3%) in miscarriages with abnormal karyotypes among RM women (n=33) did not differ from that (25.5%) in the controls (n=47). The EL rate (71.4%) in miscarriages with normal karyotypes among unexplained RM women (n=21) was much higher (P<0.05) than that in the controls. CONCLUSIONS: By evaluating fetal karyotypes, we demonstrated for the first time that EL was predominant in miscarriages with normal karyotype among RM women.

Abortion, Habitual↗