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Biomedical subjects

T Kikuchi

Publications and source records attributed to T Kikuchi.

At least 235 records · Page 13Linked to original sources
PubMed1998

Diminished kidney function and nephrocalcinosis in rats fed a magnesium-deficient diet.

The effect of a magnesium-deficient diet on kidney function was studied in young male rats. The rats were fed a purified diet with a magnesium content of either 20.5 (control diet) or 2.6 mmol/kg (magnesium-deficient diet) for 21 d. In rats fed the magnesium-deficient diet, kidney wet and dry weights were significantly increased, and calcium and phosphorus concentrations in the kidney were significantly higher than in rats fed the control diet. Upon histological examination, an increase in the mesangial matrix of the glomeruli and injury to the brush border of the proximal tubules were observed in rats fed the magnesium-deficient diet. Also, a deposition of calcium was observed in the tubules of the corticomedullary junction and medulla of these rats. Total protein and albumin concentrations in serum were significantly decreased in rats fed the magnesium-deficient diet. Urinary albumin excretion was significantly higher, and N-acetyl-beta-D-glucosaminidase activity in the urine was significantly increased in rats fed the magnesium-deficient diet. These findings indicate diminished glomerular and proximal tubular functions. We suggest that a magnesium-deficient diet not only induces nephrocalcinosis, but it also diminishes kidney function.

Acetylglucosaminidase↗
PubMed1998

[Effect of presentation time and background size on texture segregation].

We investigated the effect of presentation time and background size on texture segregation in a large visual field. In Experiment 1, participants were asked to detect a target texture embedded in a large background texture. Texture displays were presented for 68 ms, 119 ms or 221 ms. In Experiment 2, background texture size was made smaller than that in Experiment 1, and the presentation time was 119 ms. The detection rate for the target increased as the presentation time increased. Upright Ts in tilted Ts and tilted Ts in upright Ts were segregated easily in central area, but the detection rate decreased in the periphery area for all the presentation times studied. Upright Ts in Ls and Ls in upright Ts were detected better in the periphery than in the central area on 119 ms condition of Experiment 1. On the other hand, there was no difference in detection rate between the central area and the periphery with smaller backgrounds on Experiment 2. Discriminability for Ts and Ls was not determined only by the retinal position, but it was also affected by distribution of participants' attention in their visual fields.

Adult↗
PubMed1998

[Sick sinus syndrome after chemotherapy for malignant lymphoma with right atrial tumor at initial presentation].

A 56-year-old man was admitted complaining of throat discomfort and dyspnea. He was given a diagnosis of diffuse large B-cell lymphoma on the basis of findings from tumor biopsy specimens of his left pharynx. MRI tomograms and ultrasonic cardiograms revealed a right atrial tumor causing tricuspid stenosis. Although chemotherapy rendered the cardiac tumor indistinct on MRI and UCG images, gallium-67 scintigraphy still demonstrated abnormal cardiac uptake. After 6 courses of CHOP therapy, sick sinus syndrome with syncope suddenly developed in the patient. A cardiac pacemaker was immediately implanted, and radiotherapy was started. The patient's sinus rhythm returned to normal shortly afterward, and the gallium-67 uptake eventually disappeared. In this case gallium-67 scintigraphy was the only diagnostic procedure capable of detecting evidence of residual disease.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1998

[Chemical research on stilbenes from Veratrum macckii Reg].

OBJECTIVE: To study the components in rhizome of Veratrum macckii. METHODS: Column chromatography and preparative thin layer chromatography with silica gel were employed for the isolation and purification of constituents. The structures were elucidated by IR, MS and 1H-NMR analysis. RESULTS: Two compounds were obtained and elucidated as resveratrol and 2,3',4,5'-tetrahydroxystilbene. CONCLUSION: The two compounds were separated from V. macckii for the first time.

Drugs, Chinese Herbal↗
PubMed1998

[Hypoplastic myelodysplastic syndrome progressing to acute myelocytic leukemia (M2) after treatment with G-CSF and immunosuppressants].

A 34-year-old woman was admitted to our hospital because of pancytopenia. She had been given a diagnosis of idiopathic thrombocytopenic purpura during her first pregnancy about 7 years earlier. The patient received a diagnosis of severe aplastic anemia (AA) and was treated with methylprednisolone, cyclosporin A, and granulocyte colony-stimulating factor (G-CSF), but no hematological improvement was observed. Six months later, myeloblasts appeared in the patient's peripheral blood, and she was given a diagnosis of acute myelocytic leukemia AML (FAB : M2). No chromosomal abnormalities were found. As some dyshematopoietic features had been observed in the bone marrow when the patient was first given a diagnosis of AA, it is conceivable that she already had hypoplastic myelodysplastic syndrome (MDS) then. She was treated according to the JALSG-AML92 protocol and achieved complete remission (CR). In this case, the long-term administration of G-CSF may have played an important role in the transformation of MDS into AML. It may be difficult to strictly distinguish AA from hypoplastic MDS with slight dysplastic features, as in this case, because we have no established criteria. Recently the incidence of MDS/AML in AA patients undergoing G-CSF treatment has become a concern. We should be careful about ruling out hypoplastic MDS when diagnosing a condition as AA, especially when therapy includes G-CSF. The patient is still in CR 26 months after intensive combination chemotherapy.

Adult↗
PubMed1997

Molecular cloning of acid alpha-glucosidase cDNA of Japanese quail (Coturnix coturnix japonica) and the lack of its mRNA in acid maltase deficient quails.

Acid alpha-glucosidase (GAA) hydrolyzes alpha-1, 4 and alpha-1, 6 glucosidic linkages of oligosaccharides and degrades glycogen in the lysosomes. The full-length GAA I cDNA, pQAM8, was isolated from a cDNA library derived from Japanese quail liver. The cDNA is 3569 base pairs long and has an open reading frame capable of coding 932 amino acids. The deduced amino acid sequence shares 52% identity with human GAA. Transfection of expression vector pETAM8 into COS-7 cells or acid maltase deficient (AMD) quail embryonic fibroblasts increased the level of GAA 20-50-fold. Compared to normal quail, the levels of GAA I mRNA were significantly reduced in the muscle, liver, heart, and brain of AMD quails, suggesting the GAA deficiency in AMD quail is due to a lack of GAA I mRNA. A second GAA II cDNA was identified after probing the cDNA library from the ovarian large follicles of quails with a PCR product derived from cultured quail skin fibroblasts. This clone having 3.1 kb insert, has GAA activity as well (3 to 10 fold increase). This cDNA, designated GAA II, predicted an 873 amino acid polypeptide showing 63% identity to human GAA and 51% identity to the GAA I. The RT-PCR analysis demonstrated that GAA II mRNAs were barely detectable in normal tissues, while they were enhanced to higher levels in AMD tissues. These results suggest that GAA II expression is up-regulated at the transcription levels, and quail GAA gene redundancy performs the same function of satisfying GAA demand at the two different phases represented by normal and AMD.

Amino Acid Sequence↗
PubMed1997

Arrestin and phosducin are expressed in a small number of brain cells.

Retinal photoreceptor rods and pinealocytes contain well-characterized proteins such as arrestin and phosducin whose expression is highly restricted to these cell types. Transgenic mice having a LacZ gene under the control of an arrestin promoter expressed beta-galactosidase (beta-Gal) in the photoreceptor rods and pinealocytes. In addition, it was expressed in very small numbers of discrete cells in the habenular commissura, amygdala, ventral tegmental area and superior colliculus of the brain. Immunocytochemical studies with antibody probes revealed that high level of arrestin and phosducin were also found in the same cell types. Furthermore melatonin was found in those cells of the habenula commissura. The results indicate that novel cell types are present in the brain tissues. Since high levels of arrestin and phosducin expression are generally restricted to photoreceptor rod cells and pinealocytes, these data suggest that certain brain cells may have functions similar to pinealocytes.

Animals↗
PubMed1997

Differentiation and transforming growth factor-beta receptor down-regulation by collagen-alpha2beta1 integrin interaction is mediated by focal adhesion kinase and its downstream signals in murine osteoblastic cells.

Interaction of type I collagen (COL(I)) with alpha2beta1 integrin causes differentiation and transforming growth factor (TGF)-beta receptor down-regulation in osteoblastic cells (Takeuchi, Y., Nakayama, K., and Matsumoto, T. (1996) J. Biol. Chem. 271, 3938-3644). The TGF-beta receptor down-regulation enables cells to escape from the inhibition of differentiation by TGF-beta. To clarify how the cell-matrix interaction regulates these phenotypic changes, signaling pathways were examined in murine MC3T3-E1 cells. Attachment of cells to COL(I) stimulated tyrosine phosphorylation of focal adhesion kinase (FAK) and extracellular signal-regulated kinase (ERK), a mitogen-activated protein kinase (MAPK), and enhanced MAPK activity. Inhibition of tyrosine kinase by herbimycin A, destruction of focal adhesion by cytochalasin D, or overexpression of antisense FAK mRNA prevented the activation of ERK/MAPK and the increase in alkaline phosphatase (ALP) activity. Transient expression of a MAPK-specific phosphatase, CL100, also suppressed the elevation of ALP activity. In addition, introduction of a constitutively active MAPK kinase enhanced ALP activity in the absence of collagen production. TGF-beta receptor down-regulation was abrogated by treatments that inactivate FAK, whereas the expression of CL100 had no effect. These results demonstrate that COL(I)-alpha2beta1 integrin interaction facilitates differentiation and down-regulates TGF-beta receptors via the activation of FAK and its diverse downstream signals. These signaling pathways may play an important role in the sequential differentiation of osteoblasts during bone formation.

3T3 Cells↗
PubMed1997

Epilepsy and exacerbation of brain injury in mice lacking the glutamate transporter GLT-1.

Extracellular levels of the excitatory neurotransmitter glutamate in the nervous system are maintained by transporters that actively remove glutamate from the extracellular space. Homozygous mice deficient in GLT-1, a widely distributed astrocytic glutamate transporter, show lethal spontaneous seizures and increased susceptibility to acute cortical injury. These effects can be attributed to elevated levels of residual glutamate in the brains of these mice.

ATP-Binding Cassette Transporters↗
PubMed1997

Antagonist activity of [Thr18,gamma-methylleucine19]endothelin-1 in human endothelin receptors.

Receptor binding and antagonist properties of endothelin-1 analogues, [Thr18,gamma-methylleucine19]endothelin-1, [Thr18,Leu19]endothelin-1 and [Thr18,cyclohexylalanine19]endothelin-1, were investigated using cloned human endothelin ET(A) and ET(B) receptors expressed in Chinese hamster ovary cells. Among them, [Thr18,gamma-methylleucine19]endothelin-1 had a high affinity for endothelin ET(A) and ET(B) receptors with respective Kd values of 300 and 110 pM and had no agonist activity on the stimulation of arachidonic acid release in endothelin ET(A) and ET(B) receptor-expressing cells. [Thr18,gamma-methylleucine19]Endothelin-1 had potent antagonist activity in endothelin-1-induced arachidonic acid release in endothelin ET(A) and ET(B) receptor-expressing cells with respective pA2 values of 8.2 and 8.5. In an inositol phosphates accumulation assay, [Thr18,gamma-methylleucine19]endothelin-1 also exhibited potent antagonist activity for endothelin ET(A) and ET(B) receptors with respective pA2 values of 8.0 and 8.4. In conclusion, [Thr18,gamma-methylleucine19]endothelin-1 acts as a potent and nonselective antagonist with no agonist activity for cloned human endothelin ET(A) and ET(B) receptors.

Animals↗
PubMed1997

Sequence analysis, tissue expression and chromosomal localization of a mouse secreted superoxide dismutase gene.

Using a reverse transcriptase polymerase chain reaction (RT-PCR), a complement DNA encoding secreted superoxide dismutase (s-SOD) of a mouse kidney has been isolated and the nucleotide sequence was determined. The deduced amino acid sequence of mouse s-SOD cDNA shares 79% identity with the rat seminal SOD sequence and 61% identity with the human SOD3 sequence. Northern blot analysis showed that mouse s-SOD is intensely expressed in the kidney and lung tissues and detectable in other tested tissues, including the brain. The mouse s-SOD gene was assigned to chromosome 5 using fluorescence in situ hybridization analysis and PCR analysis of mouse/hamster hybrid cells.

Amino Acid Sequence↗
PubMed1997

Finite one-dimensional spin systems as models of biopolymers.

New models are proposed for describing various properties of biopolymers, especially those of proteins and nucleic acids. Each model is constituted of a set of spins arranged on a chain, and each pair of spins produces an interaction. We examine the transitions of these spin systems between the ground state and the disordered state. It is found that the transitions of the present spin systems demonstrate various properties in response to values of the so-called interaction energy. If we define interaction energy parameters with no so-called frustration, the system exhibits two-state transitions, similar to the folding-unfolding transition of small proteins. The addition of frustrations to the model produces effects similar to those of mutations in proteins. On the other hand, if the interactions between two spins attenuate as a function of their separation along the chain, the transition of the system has characteristics similar to those of nucleic acids. Thus, the present spin systems can offer a unified view of the folding-unfolding transition of biopolymers in terms of differences in the pairwise interactions between spins. Based on our models, we propose a condition for two-state transition behavior for proteins.

Journal Article↗
PubMed1997

Protective effect of a novel free radical scavenger, OPC-14117, on wobbler mouse motor neuron disease.

A possible protective effect of a novel free radical scavenger, OPC-14117, on the progressive motor neuron death in wobbler mice was examined. Clinical parameters such as mortality, body weight, motor activity as a rolling number of circular cage, and forelimb muscle power as grasping on a rolling column, an angle of slipping down from slope, and hanging ability on a flat plate were compared every 4 weeks from 4 to 36 weeks of age among mice groups treated with vehicle or daily oral administration of OPC-14117 of 10 or 30 mg/kg body weight. The treatment with OPC-14117 dose dependently improved the clinical parameters such as mortality, motor activity, and forelimb weakness. Pathological analysis showed that a diffuse neurogenic change in the forelimb muscle was improved at 36 weeks of age in the drug treated mice with a marked preservation of motor neurons in the spinal cord. Treatment of the mice with the drug reduced age-dependent increase of lipid peroxides in the spinal cord in vivo, and a supplement of the drug to the homogenate of spinal cord in vitro ameliorated the formations of lipid peroxides generated by an exogenous addition of ascorbate or xanthine/xanthine oxidase. These results suggest that OPC-14117 has a protective effect on the motor neuron death probably as a free radical scavenger, resulting in an improvement of clinical symptoms in wobbler mice.

Aldehydes↗
PubMed1997

Evaluation of learning and memory dysfunction and histological findings in rats with chronic stage contusion and diffuse axonal injury.

We previously reported a modified fluid percussion device capable of consistently producing experimental cortical contusion (CC) and diffuse axonal injury (DAI) in separate groups of rats by lateral and midline fluid percussion, respectively. The purpose of the present study was to compare the differences in learning acquisition and memory retention impairments between these two types of injured rats in the chronic stage using the Morris water maze technique. We also compared the histological differences between these two different types of traumatic brain injury. The results showed a statistically significant difference in learning acquisition impairment between the sham and CC rats and also between the sham and DAI rats. However, a significant difference in memory retention impairment was observed only between the sham and DAI rats. Histologically, the neuronal cell loss of CA3 pyramidal cells in the hippocampus was observed on the ipsilateral side in the CC and bilaterally in DAI. The neuronal cell loss was seen in bilateral entorhinal cortex layer II in DAI, but it was not seen in CC. From these results, we speculate that the marked cell loss in the hippocampus CA3 region in both CC and DAI rats was related to the impairment of spatial learning acquisition. The marked cell loss in entorhinal cortex layer II in DAI rats may be one of the important factors in the impairment of spatial memory retention.

Animals↗
PubMed1997

Aripiprazole, a novel antipsychotic drug, inhibits quinpirole-evoked GTPase activity but does not up-regulate dopamine D2 receptor following repeated treatment in the rat striatum.

Aripiprazole, a quinolinone derivative, is a new dopaminergic agent which has been recently developed and demonstrated to be clinically useful as an antipsychotic drug with reduced extrapyramidal motor side effects. Here, we found that aripiprazole competed [3H]spiperone binding with a 100-fold higher affinity than [3H]SCH23390 binding, and inhibited the quinpirole-induced facilitation of high-affinity GTPase activity in rat striatal membranes. The effects of chronic administration of aripiprazole and haloperidol on dopamine D2 receptor binding and mRNA level in rat striata were examined by a [3H]spiperone binding assay and a ribonuclease protection assay. Haloperidol induced a significant rise in Bmax of [3H]spiperone binding at 1 mg/kg and in the level of dopamine D2L receptor mRNA at 4 mg/kg. A high dose of aripiprazole (100 mg/kg) only tended to increase the Bmax of [3H]spiperone binding non-significantly, and had no effect on the level of dopamine D2L receptor mRNA. These results indicated that aripiprazole had an antagonistic activity to dopamine D2 receptors with a high affinity, but that the potency of aripiprazole to up-regulate dopamine D2 receptors in the striatum was much smaller than that of haloperidol. This small up-regulation may be related to the ability to aripiprazole to act without side effects including tardive dyskinesia.

Animals↗
PubMed1997

Carcinogenicity test of 50 Hz sinusoidal magnetic fields in rats.

Male and female F344 rats, 48 per exposure group, were sham exposed (Group A) or exposed to 0.5 (Group B) and 5 mT (Group C) magnetic fields for two years. Animals were exposed from 5-109 weeks of age in SPF conditions according to the OECD test guideline No. 451. Average exposure was 22.6 hr/day. No significant differences in body weight and food consumption were observed between the sham and exposed groups. At the end of the exposure period, survival rates of the male rats were 73, 83, and 79%, and those of the females, 77, 79, and 75% for Groups A, B, and C, respectively, with no significant differences between groups. Differential counts of leukocytes were measured at the 52nd, 78th, and 104th weeks of exposure and no significant differences were observed between the exposure groups. All survivors were euthanized on schedule, and all the organs and tissues suspected of tumoral lesions were examined histopathologically. Incidences of mononuclear cell leukemia in the male and the female rats were 5, 4, 4 and 8, 6, 7 for Groups A, B and C, respectively; incidences of malignant lymphoma in the female rats were 0, 1 and 1. Neither significant increases nor acceleration of incidence of leukemia were observed. Incidences of brain and intracranial tumors did not increase in the exposed groups. Incidences of both benign and malignant neoplasms showed no significant difference between the exposed and sham exposed groups with one exception: fibroma of the subcutis in the male rats, which was considered not to be a statistically significant when evaluated with respect to the historical control data in our laboratory.

Animals↗
PubMed1997

Type-II collagen gene expression is transiently upregulated in experimentally induced degeneration of rabbit intervertebral disc.

To clarify phenotypic alterations of intervertebral disc cells during the repair process, we cloned partial type-II collagen cDNA from rabbits and analyzed the level of expression of type-II collagen mRNA in disc degeneration. An animal model was created by surgical denucleation of rabbit intervertebral discs through an extraperitoneal approach. Eight animals each from an experimental and a control group were killed at 2, 4, 8, or 16 weeks postoperatively, and the disc samples were used for this study. Round chondrocyte-like cells that filled the herniated space showed intense signal of type-II collagen mRNA and significant pericellular immunostaining of type-II collagen but no clear staining of type-I collagen. Northern blot analysis revealed that the expression of type-II collagen mRNA of the repair disc cells was transiently increased at 4 weeks postoperatively. The cells were able to change their morphology in response to mechanical stimulation by surgical denucleation and to induce a significant increase in the gene expression of type-II collagen at an early phase of disc degeneration. The present results indicate the transient enhancement of repair activity in the degenerative process of injured fibrocartilage.

Animals↗