Search PubMed⌕ Search

Biomedical subjects

T Araki

Publications and source records attributed to T Araki.

At least 127 records · Page 7Linked to original sources
PubMed2000

A model of photoinhibition related to mRNA instability in ethylene production by a recombinant cyanobacterium.

Photoinhibition mechanism is studied for ethylene production by a recombinant cyanobacterium. The kinetic pattern of the production is similar to that of substrate inhibition in enzyme reactions, whereas the photoinhibition is believed not to be substrate-related, but to originate from the enzyme for ethylene formation. In a proposed model, the inhibition is attributed to the process of enzyme synthesis, where light-dependent mRNA decomposition affects enzyme concentration. A mathematical formula derived accordingly for light dependence of ethylene production rate gives the same form as a well-known equation of substrate inhibition. The model also predicts ethylene production under dark condition, which has been observed experimentally.

Animals↗
PubMed2000

Targeted expression of baculovirus p35 caspase inhibitor in oligodendrocytes protects mice against autoimmune-mediated demyelination.

The mechanisms underlying oligodendrocyte (OLG) loss and the precise roles played by OLG death in human demyelinating diseases such as multiple sclerosis (MS), and in the rodent model of MS, experimental autoimmune encephalomyelitis (EAE), remain to be elucidated. To clarify the involvement of OLG death in EAE, we have generated transgenic mice that express the baculovirus anti-apoptotic protein p35 in OLGs through the Cre-loxP system. OLGs from cre/p35 transgenic mice were resistant to tumor necrosis factor-alpha-, anti-Fas antibody- and interferon-gamma-induced cell death. cre/p35 transgenic mice were resistant to EAE induction by immunization with the myelin oligodendrocyte glycoprotein. The numbers of infiltrating T cells and macrophages/microglia in the EAE lesions were significantly reduced, as were the numbers of apoptotic OLGs expressing the activated form of caspase-3. Thus, inhibition of apoptosis in OLGs by p35 expression alleviated the severity of the neurological manifestations observed in autoimmune demyelinating diseases.

Animals↗
PubMed2000

Ninjurin2, a novel homophilic adhesion molecule, is expressed in mature sensory and enteric neurons and promotes neurite outgrowth.

A large number of cell adhesion molecules mediate cell-to-cell and cell-to-extracellular matrix interaction during development, differentiation and regeneration of the peripheral nervous system. Here, we report the identification of a novel cell surface adhesion molecule, ninjurin2 (for nerve injury induced protein 2). Ninjurin2 is a homolog of a homophilic cellular adhesion molecule, ninjurin1, that was previously isolated as a gene induced in Schwann cells after nerve injury. Ninjurin1 and 2 share conserved hydrophobic regions for their transmembrane domains; however, they do not contain comparable adhesion motifs nor do they interact with each other. In the peripheral nervous system, ninjurin2 is expressed constitutively in mature sensory and enteric neurons but not in glial cells or in autonomic ganglia. Ninjurin2 is upregulated in Schwann cells surrounding the distal segment of injured nerve with a time course similar to that of ninjurin1, neural CAM, and L1. Ninjurin2 promotes neurite outgrowth from primary cultured dorsal root ganglion neurons, presumably via homophilic cellular interactions. Ninjurin2 is also highly expressed in hematopoietic and lymphatic tissues. Finally, the ninjurin2 gene is located on human chromosome 12p13 in which several disorders of unknown etiology have been mapped, including inflammatory bowel disease and acrocallosal syndrome.

Animals↗
PubMed2000

Novel gene fusion of COX6C at 8q22-23 to HMGIC at 12q15 in a uterine leiomyoma.

Cytogenetic analyses have shown that aberrations involving 12q13-15 are frequent chromosomal changes in a variety of human benign mesenchymal tumors, e.g., pleomorphic adenomas of the parotid gland, pulmonary chondroid hamartomas, lipomas, and uterine leiomyomas. Recently, the high-mobility group protein gene HMGIC was identified as the target gene affected by the 12q13-15 aberrations. Using 3' rapid amplification of cDNA ends experiments, we isolated novel ectopic sequences fused to HMGIC in a uterine leiomyoma. Cloning of the fusion cDNA identified the human cytochrome c oxidase subunit VIc (COX6C) gene on 8q22-23 as the fusion partner of HMGIC. Nucleotide sequences of the fusion transcript revealed that the first 3 exons of the HMGIC gene, encoding the 3 DNA binding domains, was fused to the exon 2 of the COX6C gene. The identification of a gene rearrangement suggests a role for HMGIC in tumorigenesis of uterine leiomyoma and suggests a possible involvement of HMGIC in mesenchymal differentiation. Genes Chromosomes Cancer 27:303-307, 2000.

Chromosomes, Human, Pair 12↗
PubMed2000

Relationship between delta-aminolevulinic acid dehydratase genotypes and heme precursors in lead workers.

BACKGROUND: The objective of this study was to investigate the relationships between genotypes of delta-aminolevulinic acid (ALA) dehydratase (ALAD) and disturbances in the heme biosynthetic pathway by lead exposure. METHODS: The subjects were 192 male lead workers and 125 control subjects. Blood lead concentrations (Pb-B), plasma ALA concentrations (ALA-P), and ALAD genotypes were determined for all subjects. In lead workers, ALAD activity, ALA in urine (ALA-U), and erythrocyte zinc protoporphyrin (ZP) were also determined. RESULTS: The frequency of ALAD2 (minor type of ALAD allele) was calculated to be 0.087 in all subjects. No significant relationship was found between ALAD2 frequency and Pb-B levels in lead workers. ALAD1 homozygotes showed significantly higher levels of ZP and ALA-P in comparison with those of ALAD2 carriers at Pb-B levels more than 20 microg/dL and 40 microg/dL, respectively. CONCLUSIONS: ALAD1 homozygotes might be more susceptible than ALAD2 carriers to disturbances in heme metabolism caused by lead exposure.

Adult↗
PubMed2000

Protective effect of riluzole on MPTP-induced depletion of dopamine and its metabolite content in mice.

The neuroprotective effects of riluzole (2-amino-6-trifluoromethoxy benzothiazole), a Na+ channel blocker with antiglutamatergic activity, MK-801, a blocker of N-methyl-D-aspartate (NMDA) receptors and monoamine oxidase (MAO) inhibitor pargyline were compared in the model of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced depletion of dopamine and its metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) levels in mice. The mice received four intraperitoneal injections of MPTP (10 mg/kg) at 1-hr intervals and then the brains were analyzed at 1, 3 and 7 days after the treatments. Dopamine and DOPAC levels were significantly decreased in the striatum from 1 day after MPTP treatments. A severe depletion in dopamine and DOPAC levels was found in the striatum 3 and 7 days after MPTP treatments. Riluzole dose-dependently antagonized the MPTP-induced decrease in dopamine and DOPAC levels in the striatum. Pargyline also protected against MPTP-induced decrease in dopamine levels in the striatum. However, this drug showed no significant change in the striatal DOPAC levels. On the other hand, MK-801 failed to protect against MPTP-induced decrease in dopamine levels in the striatum. However, MK-801 reversed the MPTP-induced decrease in DOPAC levels. These results suggest that riluzole can protect against MPTP-induced striatal dopamine and DOPAC depletion in mice. This protective effect may be caused by inactivation of voltage-dependent Na+ channels by riluzole. Furthermore, the present study suggests that the activation of NMDA receptors does not mainly contribute to MPTP-induced neurodegeneration, whereas MAO, especially MAO type B(MAO-B) plays a crucial role in MPTP-induced degeneration of the nigrostriatal dopaminergic neuronal pathway.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed2000

Incidence of neonatal hypoglycemia in large-for-gestational-age infants of dichorionic twin pregnancies.

The aim of this study was to estimate standards of large-for-gestational-age (LGA) infants of twin pregnancies based on the incidence of neonatal hypoglycemia. We examined 277 dichorionic twin infants (in 201 dichorionic twin pregnancies) who were delivered weighing > or = 2,500 g at 37-41 weeks of gestation. LGA in twin pregnancies was identified when the infant deviated > by 1.5SD from the mean gestational age of this study (LGA based on the twin pregnancy standard), or when the infant deviated by >1.5 SD of the intrauterine growth curve of Japanese (LGA based the singleton pregnancy standard). Using the twin pregnancy standard, the incidence of neonatal hypoglycemia in LGA twin infants was not measurably different from that in appropriate-for-gestational-age (AGA). However, using the singleton pregnancy standard, the incidence of neonatal hypoglycemia was significantly higher than that in AGA infants. In conclusion, LGA in twin pregnancies should be studied based on the singleton pregnancy standard to assess the incidence of neonatal hypoglycemia.

Birth Weight↗
PubMed2000

First presentation of polymyositis postpartum following intrauterine fetal death.

We present a case of polymyositis (PM) following intrauterine fetal death. The first presentation of PM in the patient was during postpartum. The patient was referred to our hospital because of a fever of unknown cause 13 d after delivery of dead fetus at 32 weeks' gestation. PM was diagnosed based on the increased serum creatine phosphokinase level, typical electromyogram findings and characteristic muscle biopsy findings.

Adult↗
PubMed2000

Two-dimensional thick-slice MR digital subtraction angiography for assessment of cerebrovascular occlusive diseases.

Although spatial resolution of current MR angiography is excellent, temporal resolution has remained unsatisfactory. We evaluated clinical applicability of 2D thick-slice, contrast-enhanced subtraction MR angiography (2D-MR digital subtraction angiography) with sub-second temporal resolution in cerebrovascular occlusive diseases. Twenty-five patients with cerebrovascular occlusive diseases (8 moyamoya diseases, 10 proximal internal carotid occlusions, and 2 sinus thromboses ) were studied with a 1.5-T MR unit. The MR digital subtraction angiography (MRDSA) was performed per 0.97 s continuously just after a bolus injection of 15 ml of gadolinium chelates up to 40 s in sagittal (covering hemisphere) or coronal planes. Subtraction images were generated at a workstation. We evaluated imaging quality and hemodynamic information of MRDSA in comparison with those of routine MR imaging, non-contrast MR angiography, and X-ray intra-arterial DSA. Major cerebral arteries, all of the venous sinuses, and most tributaries were clearly visualized with 2D MRDSA. Also, pure arterial phases were obtained in all cases. The MRDSA technique demonstrated prolonged circulation in sinus thromboses, distal patent lumen of proximal occlusion, and some collateral circulation. Such hemodynamic information was comparable to that of intra-arterial DSA. Two-dimensional thick-slice MRDSA with high temporal resolution has a unique ability to demonstrate cerebral hemodynamics equivalent to that of intra-arterial DSA and may play an important role for evaluation of cerebrovascular occlusive diseases.

Adult↗
PubMed2000

Time-resolved two-dimensional thick-slice magnetic resonance digital subtraction angiography in assessing brain tumors.

The aim of this study was to evaluate clinical applicability of two-dimensional (2D) thick-slice, contrast-enhanced magnetic resonance digital subtraction angiography (MRDSA) with high temporal resolution in diagnosis of brain tumors. Forty-four patients with brain tumors including, 15 meningiomas, 8 gliomas, 6 metastatic tumors, 4 neuromas, and 2 hemangioblastomas, were studied with 2D MRDSA with frame rate approximately 1 s. Images were continuously obtained following the initiation of bolus injection of gadolinium chelates for 40 s and subtraction images were generated in a workstation. We evaluated visualization of normal cranial vessels on MRDSA and compared MRDSA and intra-arterial digital subtraction angiography (IADSA) with regard to hemodynamic information. Large cerebral arteries, all venous sinuses, and most tributaries were clearly visualized. A stain was present in hypervascular tumors including all 15 meningiomas and 2 hemangioblastomas on MRDSA. Presence of a stain demonstrated on MRDSA and that on IADSA coincided in 16 of 20 cases (Spearman rank correlation value was 0.85). The location, shape, and phase of the stain on MRDSA were similar to those on IADSA. Two-dimensional MRDSA with high temporal resolution has a unique ability to demonstrate cerebral hemodynamics, such as IADSA, and can play an important role in assessing brain tumors.

Adolescent↗
PubMed2000

Simultaneous display of MRA and MPR in detecting vascular compression for trigeminal neuralgia or hemifacial spasm: comparison with oblique sagittal views of MRI.

A new technique, simultaneous display of magnetic resonance angiography (MRA) and multiplanar reconstruction (MPR), was performed by a workstation to identify the involved vessels in patients with trigeminal neuralgia (TN) or hemifacial spasm (HFS), and the results were compared with those of oblique sagittal MRI technique. Twelve patients with either HFS or TN were prospectively assessed by simultaneous display of MRA and MPR, and oblique sagittal techniques, to point out the neurovascular compression and to identify the involved vessels. Three-dimensional (3D) time-of-flight (TOF) spoiled gradient-echo (SPGR) images were acquired to create MRA and MPR. Oblique sagittal views were also created and displayed on films. A total of 15 vessels in 12 patients were identified as compressing vessels during surgery. Simultaneous display of MRA and MPR technique pointed out the presence of vessels at and/or around root entry/exit zone (REZ) in all 12 patients, but proper identification by the name of the individual vessel was correct in 13 of 15 cases. However, oblique sagittal technique indicated the presence of vessels at and/or around REZ in 11 patients, but only 8 of 14 vessels were correctly identified. Our new method, simultaneous display of MRA-MPR, facilitated correct identification of the involved vessels compared with the oblique sagittal view method.

Hemifacial Spasm↗
PubMed2000

Severity of hyperemesis gravidarum correlates with serum levels of reverse T3.

To investigate the possible physiological relevance of extra-thyroidal production of reverse T3 (rT3) in hyperemesis gravidarum, measurements of serum rT3, free T3 (FT3), free T4, (FT4), and nonesterified fatty acids (NEFA) were correlated with weight loss of hyperemetic women. All the thyroid hormones, NEFAs and weight loss were significantly higher in hyperemesis gravidarum than in control subjects, and also higher than in those with milder symptoms of morning sickness (p < 0.05). Elevations of FT3, FT4 and NEFAs correlated with the extent of weight loss, the latter taken as the index of the severity of hyperemesis gravidarum (p < 0.05). Only rT3 correlated with both weight loss and the rate of lipolysis, as reflected by elevations of NEFAs (p < 0.05). The data are consistent with a shift from T3 to rT3 as products of 5'-monodeiodination of thyroxine in hyperemesis gravidarum. Because reverse T3 is physiologically inactive a control mechanism may be postulated wherein T3 production is minimized, thereby reducing weight loss and lipolysis in patients with hyperemesis gravidarum.

Fatty Acids, Nonesterified↗
PubMed2000

Sequential changes of cholinergic and dopaminergic receptors in brains after 6-hydroxydopamine lesions of the medial forebrain bundle in rats.

We studied sequential changes in muscarinic cholinergic receptors, high-affinity choline uptake sites and dopamine D2 receptors in the brain after 6-hydroxydopamine lesions of the medial forebrain bundle in rats. The animals were unilaterally lesioned in the medial forebrain bundle and the brains were analyzed at 1, 2, 4 and 8 weeks postlesion. [3H]Quinuclidinylbenzilate (QNB), [3H]hemicholinum-3 (HC-3) and [3H]raclopride were used to label muscarinic cholinergic receptors, high-affinity choline uptake sites and dopamine D2 receptors, respectively. The degeneration of nigrostriatal pathway produced a transient decrease in [3H]QNB binding in the parietal cortex of both ipsilateral and contralateral sides at 2 and 8 weeks postlesion. [3H]QNB binding also showed a mild but insignificant decrease in the ipsilateral striatum throughout the postlesion periods. No significant change was observed in the substantia nigra (SN) of both ipsilateral and contralateral sides throughout the postlesion periods. In contrast, [3H]HC-3 binding showed no significant change in the parietal cortex of both ipsilateral and contralateral sides during the postlesion. However, [3H]HC-3 binding was upregulated in the ipsilateral dorsolateral striatum throughout the postlesion periods. The ventromedial striatum also showed a significant increase in [3H]HC-3 binding at 1 week and 2 weeks postlesion. On the other hand, no significant change in [3H]raclopride binding was found in the parietal cortex of both ipsilateral and contralateral sides during the postlesion. [3H]Raclopride binding showed a conspicuous increase in the ipsilateral striatum (35-52% of the sham-operated values in the lateral part and 39-54% in the medial part) throughout the postlesion periods. In the contralateral side, a mild increase in [3H]raclopride binding was also found in the striatum (10-15% of the sham-operated values in the lateral part and 22% in the medial part) after lesioning. However, a significant decline in [3H]raclopride binding was observed in the ipsilateral SN and ventral tegmental area during the postlesion. The present study indicates that 6-hydroxydopamine injection of medial forebrain bundle in rats can cause functional changes in high-affinity choline uptake site in the striatum, as compared with muscarinic cholinergic receptors. Furthermore, our studies demonstrate an upregulation in dopamine D2 receptors in the striatum and a decrease in the receptors in the SN and ventral tegmental area after the 6-hydroxydopamine injection. Thus, these findings provide further support for neurodegeneration of the nigrostriatal pathway that occurs in Parkinson's disease.

Animals↗
PubMed2000

Relation between serum uric acid and plasma adenosine levels in twin pregnancies.

OBJECTIVE: To examine the relationship between plasma adenosine and serum uric acid levels in women with singleton and twin pregnancies. METHODS: We sampled maternal arterial blood and measured serum uric acid and plasma adenosine levels in 22 singleton pregnancies and nine twin pregnancies at 33 to 38 weeks' gestation. RESULTS: The average plasma adenosine levels were 0.31 +/- 0.12 micromol/L in the singleton pregnancy group and 0.45 +/- 0.09 micromol/L in the twin pregnancy group (P <.001). The mean serum uric acid level in women with twin pregnancy was 5.7 +/- 0.44 mg/dL which was higher than that in the singleton pregnant women (4.4 +/- 0.69 mg/dL, P <.001). Positive correlations were found between serum uric acid and plasma adenosine levels in both the singleton (r(2) = 0.54, P <.001) and the twin pregnancy groups (r(2) = 0.65, P =.009). Moreover, there was also a significant correlation between serum uric acid and plasma adenosine levels overall (r(2) = 0.66, P <.001). CONCLUSION: Our results suggest that higher adenosine levels are a contributing source of hyperuricemia in twin pregnancies.

Adenosine↗
PubMed2000

Small bowel obstruction in early pregnancy treated by jejunotomy and total parenteral nutrition.

BACKGROUND: Small bowel obstruction in early pregnancy increases maternal and fetal morbidity and mortality and might be diagnosed mistakenly as hyperemesis gravidrum. Prompt diagnosis and therapy is essential. CASE: A 29-year-old primigravida was admitted at 13 weeks' gestation with small bowel obstruction. After jejunotomy, total parenteral nutrition was given until oral intake was resumed completely 1 month after surgery. She was discharged with no complications and the rest of her pregnancy and delivery were uneventful. CONCLUSION: Small bowel obstruction in early pregnancy should be diagnosed expeditiously and can be treated with jejunotomy and total parenteral nutrition.

Adult↗
PubMed2000

A putative chemoattractant receptor, C5L2, is expressed in granulocyte and immature dendritic cells, but not in mature dendritic cells.

Leukocyte chemoattractants are involved in the inflammatory response act via G protein-coupled receptors. We report the cloning of a novel human gene encoding the putative orphan receptor, C5L2, belonging to a subfamily of C3a, C5a and formyl Met-Leu-Ph receptors that are related to the chemokine receptor family. C5L2 transcript levels were abundant in granulocytes and immature dendritic cells but not in mature dendritic cells. We speculate that this receptor may regulate the activation of immature dendritic cells and play a role in the chemoattraction of leukocytes to inflammatory regions.

Amino Acid Sequence↗