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Biomedical subjects

Kaori Sasaki

Publications and source records attributed to Kaori Sasaki.

12 recordsLinked to original sources
PubMed2006

An allosteric activator of glucokinase impairs the interaction of glucokinase and glucokinase regulatory protein and regulates glucose metabolism.

Glucokinase (GK) plays a key role in the control of blood glucose homeostasis. We identified a small molecule GK activator, compound A, that increased the glucose affinity and maximal velocity (V(max)) of GK. Compound A augmented insulin secretion from isolated rat islets and enhanced glucose utilization in primary cultured rat hepatocytes. In rat oral glucose tolerance tests, orally administrated compound A lowered plasma glucose elevation with a concomitant increase in plasma insulin and hepatic glycogen. In liver, GK activity is acutely controlled by its association to the glucokinase regulatory protein (GKRP). In order to decipher the molecular aspects of how GK activator affects the shuttling of GK between nucleus and cytoplasm, the effect of compound A on GK-GKRP interaction was further investigated. Compound A increased the level of cytoplasmic GK in both isolated rat primary hepatocytes and the liver tissues from rats. Experiments in a cell-free system revealed that compound A interacted with glucose-bound free GK, thereby impairing the association of GK and GKRP. On the other hand, compound A did not bind to glucose-unbound GK or GKRP-associated GK. Furthermore, we found that glucose-dependent GK-GKRP interaction also required ATP. Given the combined prominent role of GK on insulin secretion and hepatic glucose metabolism where the GK-GKRP mechanism is involved, activation of GK has a new therapeutic potential in the treatment of type 2 diabetes.

Active Transport, Cell Nucleus↗
PubMed2005

Platelet mitochondrial evaluation during cytochrome c and dichloroacetate treatments of MELAS.

We hypothesized that serial changes in platelet (PLT) mitochondrial enzyme (ME) activities might correspond to the effects of medications for mitochondrial encephalomyopathy and stroke-like episodes (MELAS). Cytochrome c and sodium dichloroacetate (DCA) were given to a 7-year-old girl with MELAS who had an A3243G mitochondrial DNA mutation. The effects were evaluated with whole PLT-ME assays, developed by our group, using a microplate-reader. During cytochrome c treatment, complex II+III (II+III), complex IV (IV) and citrate synthase (CS) activities showed gradual but statistically significant decrease. II+III activity dropped below normal. II+III/CS activity was initially below normal, followed by a transient improvement, then decreased again before the appearance of central nervous system symptoms. II+III, IV, II+III/CS and IV/CS activities reached their lowest levels in association with a stroke-like episode, then increased with DCA treatment. Our results suggest that progressive mitochondrial dysfunction may occur before the stroke-like episodes in MELAS and that DCA treatment may increase mitochondrial activities. Our whole PLT-ME assay system may be useful for serially evaluating mitochondrial functions in relation to clinical symptoms.

Blood Platelets↗
PubMed2005

High bone turnover of type I collagen depends on fetal growth.

The bone metabolic processes of proliferation and differentiation in preterm and term newborns have yet to be fully elucidated. Seventy-four umbilical cord blood samples were collected from preterm and term newborns delivered at 27 to 42 gestational weeks (GWs). Carboxy-terminal propeptide of type I procollagen (PICP), pyridinoline cross-linked telopeptide domain of type I collagen (ICTP), alkaline phosphatase (ALP), and bone-specific alkaline phosphatase (BAP) were measured. Calcitonin (CT), estrogen (E2), intact parathyroid hormone, and insulin-like growth factor-I (IGF-I) were also examined in 20 or 23 randomly selected samples. We conducted cross-sectional regression analyses for bone metabolic markers, fetal growth markers including GWs, birth weight (BW), height (BH) and head circumference (HC), and bone related hormones. PICP and ICTP activities were very high, but decreased significantly with fetal growth based on GWs, BW, BH, and HC changes (GWs, BW, and BH to both PICP and ICTP, P < 0.0001; HC to ICTP, P < 0.0001; HC to PICP, P < 0.05), while BAP and ALP did not change significantly. E2 and CT both showed a significant positive correlation with Ca (P < 0.05), but neither hormone had any apparent correlation with PICP, ALP, BAP, or ICTP. These results suggest very active bone formation and resorption of type I collagen to be dependent on fetal growth and that fetal osteoblasts dominate the proliferation phase of development rather than the maturation phase. However, factors contributing to high bone turnover in the fetus remain to be elucidated.

Biomarkers↗
PubMed2005

Crystallization and preliminary crystallographic analysis of the N-terminal domain of PriA from Escherichia coli.

PriA, a DEXH-type DNA helicase, binds specifically to the 3' end of DNA through its N-terminal domain, and is a candidate sensor protein that recognizes arrested DNA replication forks in bacteria. We crystallized an N-terminal fragment of PriA in the absence and the presence of oligonucleotides to elucidate the structural basis for the specific recognition of the 3' terminus of DNA.

Adenosine Triphosphatases↗
PubMed2005

Chorea and Broca aphasia induced by diabetic ketoacidosis in a type 1 diabetic patient diagnosed as Moyamoya disease.

We here report one case of hemichorea and Broca aphasia occurred with diabetic ketoacidosis. A 20-year-old woman with type 1 diabetes mellitus had experienced diabetic ketoacidosis fourth time after the onset of diabetes. At the third ketoacidotic episode, the patient was admitted to our hospital for the first time to show hemichorea of the left extremities. Brain computed tomography (CT) demonstrated a high-density area in the right caudate head and low-density area in the right putamen. Magnetic resonance angiography (MRA) demonstrated a stenosis at the root of the bilateral middle and anterior cerebral arteries. The hemichorea disappeared within 3 days. At the fourth ketoacidotic episode, not hemichorea but unconsciousness was there for 2 days even after ketoacidosis disappeared. After the unconscious state, Broca aphasia was demonstrated for 15 days. The cerebral angiography showed a finding compatible to Moyamoya disease. These findings support that chorea and Broca aphasia induced by diabetic ketoacidosis was developed in addition to blood vessel abnormalities such as Moyamoya disease. We suggest that poorly controlled diabetic patients with hemichorea should undergo cerebral angiography.

Adult↗
PubMed2005

Effect of ACTH therapy for epileptic spasms without hypsarrhythmia.

PURPOSE: We analyzed the short- and long-term effects of adrenocorticotropic hormone (ACTH) therapy for patients with epileptic spasms (ESs) who did not meet the criteria of West syndrome (WS). METHODS: The subjects were 30 patients, including 13 boys and 17 girls, who had received ACTH therapy between 1970 and 2003. We excluded patients with WS, but included those with a history of WS who no longer showed hypsarrhythmia at the period of ACTH therapy. The age at onset of ESs and at ACTH therapy ranged from 2 to 82 months with a median of 18 months, and from 11 to 86 months with a median of 29 months, respectively. RESULTS: Excellent and poor responses were obtained in 19 (63%) and 11 (37%) patients, respectively, as a short-term effect. Although the patients could be subclassified into five subgroups according to the previous reports, no difference was seen in short- term response to ACTH. Among 17 of the 19 patients with excellent short-term outcomes and a follow-up of >1 year after the ACTH therapy, eight patients have continued to be seizure free (29%; excellent long-term effect), whereas the remaining nine patients had a recurrence of seizures (complex partial seizures, four; generalized tonic seizures, three; ESs, two) at 9 months to 198 months (median, 49 months) after ACTH therapy. In addition, nine of the 17 patients demonstrated a localized frontal EEG focus after the ACTH therapy, although most of these had previously shown diffuse epileptic EEG abnormality. CONCLUSIONS: ACTH therapy is worth trying for patients with resistant ESs, even without features of WS. However, the long-term effect is uncertain because recurrences of various types of seizures, including focal, were frequently observed.

Adolescent↗
PubMed2004

Rhodium-catalyzed intramolecular hydroacylation of 5- and 6-alkynals: convenient synthesis of alpha-alkylidenecycloalkanones and cycloalkenones.

A novel intramolecular hydroacylation of 5- and 6-alkynals leading to alpha-alkylidenecycloalkanones was accomplished by using cationic a rhodium(I)/BINAP complex. For all cyclizations described, a single (E)-olefin isomer was obtained. At elevated temperature, hydroacylation and double bond migration of 5- and 6-alkynals proceeded in a one-pot reaction to give cycloalkenones. An intramolecular hydroacylation of a 7-alkynal was unsuccessful. This method represents an attractive new route to highly functionalized alpha-alkylidenecycloalkanones and cycloalkenones.

Acylation↗
PubMed2003

Continuous culture of novel mitochondrial cells lacking nuclei.

We isolated stable cell lines, designated as mitochondrial cells, from cybrids obtained by fusing mitochondria-less HeLa cells with platelets from patients with Leigh syndrome, a subtype of mitochondrial encephalomyopathy. The cells contain a pathogenic point mutation, T9176C, in the mitochondrial DNA. Hematoxylin-eosin staining, confocal fluorescent microscopy and flow cytometry in fixed or living cells showed that the majority of these mitochondrial cells lack nuclear DNA and nuclei, but contain active mitochondria. Despite the absence of nuclear DNA, these cells can be continuously generated in culture. Therefore, it is likely that they arise from the minority of cells which possess a nucleus.

Journal Article↗
PubMed2002

The subtypes of muscarinic receptors for neurogenic bladder contraction in rats.

We evaluated in vivo functional selectivity profiles for muscarinic M(2) and M(3) subtypes of four muscarinic antagonists: Compound A (a novel muscarinic receptor antagonist with M(2)-sparing antagonistic activity), darifenacin, (a muscarinic M(3) receptor antagonist); methoctramine (a muscarinic M(2) receptor antagonist) and tolterodine (a nonselective muscarinic receptor antagonist), and compared the inhibition potency on distention-induced bladder contraction in rats. In an in vivo functional study, Compound A (0.03-10 mg/kg, i.v.) showed antimuscarinic activity with high selectivity for M(3) (salivation) over M(2) (bradycardia) (>100-fold). Darifenacin (0.01-0.3 mg/kg, i.v.) showed only slight selectivity for M(3) over M(2) (3.7-fold). Methoctramine (0.003-1 mg/kg, i.v.) showed the reverse selectivity profile (0.077-fold). Tolterodine (0.003-0.3 mg/kg, i.v.) showed less selectivity (1.2-fold). Compound A at M(3) inhibitory doses (0.1 and 0.3 mg/kg, i.v.) showed inhibition in a distention-induced neurogenic bladder contraction model, and its maximal inhibitory effects were about 60% at an even higher dose (3 mg/kg). Methoctramine at M(2) inhibitory doses (0.03 and 0.1 mg/kg, i.v.) did not significantly affect distention-induced bladder contraction. When tolterodine and darifenacin caused inhibition of distention-induced bladder contraction, its maximal inhibitory effects were similar to that of Compound A. Therefore, these findings suggest that Compound A would be an excellent pharmacological tool to give a better understanding of which subtypes of muscarinic receptors act in bladder function so far, and muscarinic M(3), but not M(2), receptors mainly mediate the cholinergic component of distention-induced bladder contraction.

Animals↗
PubMed2002

Constituents of holothuroidea, 12. Isolation and structure of glucocerebrosides from the sea cucumber Holothuria pervicax.

Ten glucocerebrosides, HPC-3-A-HPC-3-J, have been isolated from their obtained parent glucocerebroside molecular species HPC-3, together with other glucocerebroside molecular species HPC-1 and HPC-2, from the less polar lipid fraction of a chloroform/methanol extract of the sea cucumber Holothuria pervicax. The structures of these glucocerebrosides have been determined on the basis of chemical and spectroscopic evidence. Reversed-phase HPLC, including a recycling system, was effective in isolating these glucocerebrosides, revealing a very close resemblance in structure, though the problem due to regio-isomers remains.

Animals↗
PubMed2002

[Heart block].

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Animals↗