Biomedical subjects

T Amano

Publications and source records attributed to T Amano.

At least 55 records · Page 3Linked to original sources

PubMed2001

Excitation of rat striatal large neurons by dopamine and/or glutamate released from nerve terminals via presynaptic nicotinic receptor (A4beta2 type) stimulation.

Previous in vivo experiments using rats anesthetized with chloral hydrate have revealed that nicotine applied iontophoretically increased firing of striatal neurons receiving excitatory dopaminergic input from the substantia nigra, and nicotine-induced firing was inhibited by domperidone, a dopamine D2 antagonist. The results suggest that nicotine increases release of dopamine from the terminals of dopaminergic neurons. Therefore, we performed the present patch clamp study using slice and acutely dissociated preparations of the rat striatum to elucidate the mechanisms underlying the nicotine-induced excitation of striatal neurons. Application of nicotine (100 microM) to large striatal neurons in slice preparations did not produce any effect on the resting membrane potential, but did increase the frequency of miniature postsynaptic potentials (mpps) and action potentials in all 15 neurons tested. The nicotine-induced increase in mpps and action potentials were inhibited during simultaneous application of domperidone; L-glutamic acid diethyl ester hydrochloride, a non-selective glutamate receptor antagonist; and/or dihydro-beta-erythroidine, a central nicotinic acetylcholine receptor (alpha4beta2 type) antagonist. Postsynaptic current was not induced by nicotine applied by U-tube in 96% of acutely dissociated striatal neurons. The present findings suggest that nicotine mainly acts on the presynaptic nicotinic receptors in the nerve terminals to release neurotransmitters such as dopamine and/or glutamate, thereby activating the striatal large neurons.

Action Potentials↗

PubMed2001

Cloning and nucleotide sequence of the mycodextranase gene from Streptomyces sp. J-13-3.

Mycodextranase (EC 3.2.1.61) is an alpha-glucanase that cleaves alpha-1,4-bonds of alternating alpha-1,3- and alpha-1,4-linked D-glucan (nigeran). The gene encoding mycodextranase from Streptomyces sp. J-13-3 was cloned by hybridization with a degenerate oligonucleotide probe from the amino-terminal amino acid sequence of the enzyme and its nucleotide structure was analyzed. The open reading frame consisted of 1,803 base pairs encoding a signal peptide of 60 amino acids and a mature protein of 540 amino acids with a calculated molecular weight of 56,078. The deduced amino acid sequence showed weak similality to a chitinase homolog from Streptomyces lividans and a chitinase from Xanthomonas sp.

Amino Acid Sequence↗

PubMed2001

Full-term development of enucleated mouse oocytes fused with embryonic stem cells from different cell lines.

The developmental potential of enucleated mouse oocytes receiving embryonic stem cells from ten lines with either the same or different genetic backgrounds using the cell fusion method was examined in vitro and in vivo. The development of nuclear-transferred oocytes into blastocysts was high (34-88%). However, there was no clear correlation between development into blastocysts after nuclear transfer and the chimaera formation rate of embryonic stem cells. The development into live young was low (1-3%) in all cell lines and 14 of 19 young died shortly after birth. Most of the live young had morphological abnormalities. Of the five remaining mice, two died at days 23 and 30 after birth, but the other three mice are still active at days 359 (mouse 1) and 338 (mice 4 and 5) after birth, with normal fertility. However, the reasons for the abnormalities and postnatal death of embryonic stem cell-derived mice are unknown.

Animals↗

PubMed2001

Tumoral calcinosis in the upper cervical spine causing progressive radiculomyelopathy--case report.

A 54-year-old woman with chronic renal failure presented with tumoral calcinosis manifesting as progressive radiculomyelopathy. Magnetic resonance imaging revealed a spinal epidural mass in the C-2 to C-4 levels. The clinical and radiological findings suggested malignant tumor. Resection of the lesion was performed with total C-2 laminectomy and C-3 and C-4 laminoplasty. The symptoms totally disappeared after surgery. The histological diagnosis was tumoral calcinosis. Tumoral calcinosis is a rare tumoral calcium pyrophosphate dihydrate crystal deposition disease which presents as periarticular soft tissue calcification. Tumoral calcinosis should be considered in patients with a mass lesion involving the upper cervical spine and associated with metabolic abnormalities. Surgical excision is the treatment of choice, because this is completely curative without known recurrence.

Calcinosis↗

PubMed2001

Primary neurotransmitters and regulatory substances onto vestibular nucleus neurons.

This review article focused on the primary neurotransmitters involved in transmission from the otolith to the vestibular nucleus (VN), especially in relation to the neurotransmission to the VN neurons (gravity-sensitive neurons) activated by tilt stimulation. The medial vestibular nucleus (MVN) neurons were classified in 8 types (alpha-theta) according to the patterns in response to the clockwise and counterclockwise tilt-stimulations. The tilt-induced firing was inhibited by GDEE (a non-selective glutamate receptor antagonist) and/or atropine (a muscarinic receptor antagonist). Thus, glutamate and/or acetylcholine may serve as the primary neurotransmitters. This conclusion is supported by the previous findings that glutamate exists in the vestibular nerve and is released from the nerve besides the presence of glutamate receptor subtypes in the VN. In addition, acetylcholine induced atropine-reversible firing of MVN neurons, and the enzymes involved in acetylcholine synthesis/metabolism are also found in the VN. Furthermore, serotonin was found to inhibit the MVN neuronal activities via the 5-HT1A receptors. As such, the 5-HT1A agonist, tandospirone, may be effective in preventing and/or treating motion sickness and/or space sickness.

Acetylcholine↗

PubMed2001

A brief review of Dr F Gotoh's contribution to neuroscience: research in the field of cerebral blood flow and stroke.

Professor Emeritus Fumio Gotoh began and continues his remarkable career in medicine at Keio University. Since his graduation from medical school there in 1951, Dr. Gotoh has devoted himself to neurology, especially in the enigmatic field of stroke science. He is most renown for his groundbreaking research and leadership in the study of cerebral blood flow and metabolism. Beginning with his doctoral thesis paper in 1959 entitled "Effects of blood pressure on cerebral circulation," our article briefly delineates how Prof. Gotoh has paved the path for current and future discoveries in modern medicine. Although wholly difficult to sum up Dr. Gotoh's extensive career in such a short article, we have attempted to chronologically list and furthermore to describe his numerous works. Herein we describe his expansion to the international arena with his contributions at Wayne State University as well as his novel cerebral blood gas monitoring techniques now used in modified fashion throughout the world. From his CO2-based investigations in animals to his study of the autonomic nervous system's role in human cerebrovascular control, we remark on Dr. Gotoh's accomplishments without the use of functional imaging. Yet despite the basic science theme of his research, he has always kept them clinically correlated to entities such as Cheyne-Stokes phenomenon and Shy-Drager syndrome. Prof. Gotoh has been asked to head some of the most influential stroke societies and was the second president of the International Stroke Society. In conjunction with leading authorities, he developed a quantifiable, evidence-based stroke scale which was introduced in the International Journal of Stroke in 2001. Today despite his retirement, Dr. Gotoh continues his work in cerebral blood flow and metabolism.

Cerebrovascular Circulation↗

PubMed2001

An essential role of histone deacetylases in postembryonic organ transformations in Xenopus laevis.

Amphibian metamorphosis is the result of thyroid hormone (TH)-induced organ transformations including de novo morphogenesis, tissue remodeling and resorption through programmed cell death (apoptosis). All changes during metamorphosis are presumed to be mediated through gene regulation cascades initiated by TH. Numerous studies have implicated important roles of chromatin remodeling in transcriptional regulation. In particular, several lines of evidence support the view that histone acetylation is associated with transcriptional activation and histone deacetylation leads to gene repression. Here we address the physiological roles of histone deacetylases during vertebrate postembryonic development by using amphibian metamorphosis as a model. We first demonstrate that Xenopus laevis Rpd3 (a histone deacetylase) and Sin3 (a corepressor associated to Rpd3) are expressed in premetamorphic and metamorphic tadpole tissues, suggesting their involvement in these postembryonic processes. To test this possibility, we use a histone deacetylase inhibitor, trichostatin A, to block histone deacetylases and examine the development of the tadpoles. Our results indicate both natural and T3-induced metamorphosis are blocked by the inhibitor. We further show that this drug inhibits metamorphosis in different tissues, whether they involve de novo development or resorption through apoptosis, and that it functions in a stage-dependent but organ-autonomous manner. The data thus support an important role of histone deacetylases in the gene regulation cascades induced by T3 during metamorphosis.

Animals↗

PubMed2001

[Brain stem hemorrhage associated with venous angioma: report of two cases].

The incidence of hemorrhage associated with venous angioma has been considered to be rare. We here report two cases of brain stem venous angioma which also showed brain stem hemorrhage. Case 1; a 15-year-old female had experienced weakness in the left upper extremity 8 months prior to admission. She developed dysfunction of the left cranial nerves, and magnetic resonance imaging (MRI) showed a huge enlarging hematoma in the pons. Cerebral angiography showed venous angioma penetrating through the pons. Evacuation of the hematoma was performed through the fourth ventricle and many small vessels were found in the hematoma. Although all symptoms were partially resolved after the operation, a re-hemorrhage occurred 1 month after the operation. Case 2; a 50-year-old man had suddenly developed headache and vertigo several days prior to admission. Computed tomography (CT) and MRI showed a small hematoma in the lesion with venous angioma adjacent to the hematoma. All symptoms gradually resolved with conservative therapy.

Adolescent↗

PubMed2001

In vitro prevention of cell-mediated xeno-graft rejection via the Fas/FasL-pathway in CrmA-transducted porcine kidney cells.

Cell-mediated cytotoxicity may be involved in delayed and/or chronic xenograft rejection in which apoptosis is induced in the grafted cells via the Fas/Fas-ligand (FasL) and perforin/granzyme pathways. One barrier to the potential use of xeonogenic grafts for humans may be Fas/FasL-mediated apoptosis, which would be blocked by the gene expression of cytokine response modifier A (CrmA), a cowpox virus gene product. The purpose of this study is to explore whether crmA is an effective candidate gene for inhibiting apoptosis in an in vitro model of xenograft rejection, using Fas-expressing non-primate cells cultured with a soluble recombinant human FasL (sFasL). A recombinant adenovirus vector expressing CrmA (AxCALNLCrmA) was successfully generated with a Cre-mediated switching system. PK15 cells, derived from a porcine kidney and infected with AxCALNLCrmA and/or AxCANCre at a multiplicity of infection (MOI) ranging from 0.1 to 100, were cultured with human sFasL derived from KFL74.18, a human FasL-overexpressed cell line. The gene-expression level of the PK15 cells was confirmed by CrmA-immune staining. Approximately 70% of the control PK15 cells showed induced apoptosis when cultured with sFasL. In contrast, the apoptosis was dramatically reduced in crmA-gene-transduced PK15 cells. The inhibitory effect of apoptosis increased with an increase in the infection dose of AxCANCre. In addition, the activity of caspases 3 and 8 was significantly inhibited in the crmA-transduced cells. These results indicate that CrmA is an effective gene product for inhibiting Fas/FasL-mediated apoptosis, which suggests the potential therapeutic use of its gene transduction to protect against graft damage due to delayed and/or chronic xenograft rejection.

Animals↗

PubMed2001

[Primary thalamic hemorrhage penetrating to the lateral ventricle in an infant with abnormal protein S(protein S-Tokushima)].

We experienced a 3 months infant with thalamic hemorrhage penetrating to lateral ventricle with abnormal Protein S. Although the coagulation factor and fibrinogenolysis factors were evaluated, there were no remarkable abnormal laboratory data except for slightly decline of Protein S. The DNA analysis was performed for Protein S, and a missense mutation(A to G transmission) was found, which was resulting in Lys-155 to Glu. The total Protein S antigen was normal level, but co-factor activity for activated Protein C was declined. That mutation is named Protein S-Tokushima, and the patient who has abnormal Protein S tends to suffer recurrent coagulopathy. In our patient, it was interesting that any thrombotic disease had not occurred, but cerebral hemorrhage had occurred.

Cerebral Hemorrhage↗

PubMed2001

[A case of septic shock due to ileal conduit obstruction].

A 70-year-old man with bladder cancer received a total cystectomy and an ileal conduit 64 months before he visited our hospital with complaints of lower abdominal pain, shaking and chilliness. Bilateral hydronephrosis due to an ileal conduit obstruction were observed on the ultrasonography. Bacterial culture from blood and urine samplings revealed E. coli. Under the diagnosis of urosepsis, the administration of anti-biotics and bilateral percutaneous nephrostomy were performed. However, he suffered from septic shock and disseminated intravascular coagulation (DIC). Therefore, the treatments for DIC were done, and they were effective. The obstruction of the ileal conduit was cured spontaneously. No recurrence or metastases were found on ultrasonography and computed tomographic scan for 12 months after these treatments.

Aged↗

PubMed2001

Selective repopulation of mice liver after Fas-resistant hepatocyte transplantation.

Hepatocyte transplantation has been proposed as a potential therapeutic method to treat irreversible liver failure and inherited hepatic disorders, although transplanted cells do not easily reconstruct the liver tissue under intact conditions. This study was aimed at modulating the recipient liver conditions to promote repopulation of the liver after hepatocyte transplantation. Hepatocytes isolated from male MRL-lpr/lpr (lpr) mice with a mutation of Fas antigen were transplanted in a number of 1 x 10(6) cells in female MRL-+/+ (wild-type mice) by intrasplenic injection. An agonistic anti-Fas antibody (0.15 mg/kg) was administered intravenously 24 h after cell transplantation. We also administrated the antibody at 0.3 mg/kg 1 week after grafting and at 0.6 mg/kg 2 weeks after transplantation. The liver specimens were taken at different time intervals for histological examination. The reconstructed male lpr hepatocytes in the female wild-type mice were determined by a real-time quantitative PCR assay using the primers and probe for the sry gene. The pathologic findings of the recipient livers after treatment with anti-Fas antibody revealed a large number of apoptotic hepatocytes. The grafted lpr hepatocytes were observed to reconstruct as much as 6.9% of the recipient liver in the anti-Fas antibody-treated group 3 months after transplantation. In contrast, we observed the transplanted cells at lower than 0.1% in the nontreated livers. These findings demonstrated that repeated induction of apoptosis in recipient hepatocytes shifts the environment of the liver to a regenerative condition. This method may be useful to promote the reconstruction of transplanted hepatocytes in a recipient liver.

Animals↗

PubMed2000

Induction and alternative splicing of delta isoform of Ca(2+)/calmodulin-dependent protein kinase II during neural differentiation of P19 embryonal carcinoma cells and during brain development.

Since the expression of Ca(2+)/calmodulin-dependent protein kinase II (CaM kinase II) is regulated during brain development, the developmental change of the enzyme was investigated during the neural differentiation of murine P19 embryonal carcinoma cells. CaM kinase II activity was induced during the differentiation of P19 cells treated with retinoic acid. Expression of the enzyme was induced 2 days after the treatment and maximized at 5 days. The enzyme activity increased about approximately 8-fold. The enzyme protein was shown to differ between differentiated and undifferentiated cells. The delta isoform of CaM kinase II was found as the major isoform in P19 cells by immunoblotting and reverse transcription-polymerase chain reaction (RT-PCR). A total of four and three alternatively spliced variants of delta isoform were detected in P19 cells by RT-PCR analysis and by immunoblotting, respectively. Although multiple alternatively spliced forms have been reported, the major splice variants of delta isoform in differentiated cells were delta l and delta 9 isoforms, which were specifically detected in differentiated cells. In undifferentiated cells, the major splice variant corresponded to delta 2 isoform. These results indicated that the expression of delta isoform of CaM kinase II was induced, and the splicing pattern of the isoform changed, during neural differentiation. Cell type distinctive changes of splicing pattern of delta isoform were also observed not only during differentiation of cultured neuronal cells, but also during development of rat forebrain and cerebellum.

Alternative Splicing↗

PubMed2000

Evidence for changes in the nucleotide conformation in the active site of H(+)-ATPase as determined by pulsed EPR spectroscopy.

The conformation of di- and triphosphate nucleosides in the active site of ATPsynthase (H(+)-ATPase) from thermophilic Bacillus PS3 (TF1) and their interaction with Mg(2+)/Mn(2+) cations have been investigated using EPR, ESEEM, and HYSCORE spectroscopies. For a ternary complex formed by a stoichiometric mixture of TF1, Mn(2+), and ADP, the ESEEM and HYSCORE data reveal a (31)P hyperfine interaction with Mn(2+) (|A((31)P)| approximately 5.20 MHz), significantly larger than that measured for the complex formed by Mn(2+) and ADP in solution (|A((31)P)| approximately 4.50 MHz). The Q-band EPR spectrum of the Mn.TF1.ADP complex indicates that the Mn(2+) binds in a slightly distorted environment with |D| approximately 180 x 10(-4) cm(-1) and |E| approximately 50 x 10(-4) cm(-1). The increased hyperfine coupling with (31)P in the presence of TF1 reflects the specific interaction between the central Mn(2+) and the ADP beta-phosphate, illustrating the role of the enzyme active site in positioning the phosphate chain of the substrate for efficient catalysis. Results with the ternary Mn.TF1.ATP and Mn.TF1.AMP-PNP complexes are interpreted in a similar way with two hyperfine couplings being resolved for each complex (|A((31)P(beta))| approximately 4.60 MHz and |A((31)P(gamma))| approximately 5.90 MHz with ATP, and |A((31)P(beta))| approximately 4.20 MHz and |A((31)P(gamma))| approximately 5.40 MHz with AMP-PNP). In these complexes, the increased hyperfine coupling with (31)P(gamma) compared with (31)P(beta) reflects the smaller Mn.P distance with the gamma-phosphate compared with the beta-phosphate as found in the crystal structure of the analogous enzyme from mitochondria [3.53 vs 3.70 A (Abrahams, J. P., Leslie, A. G. W., Lutter, R., and Walker, J. E. (1994) Nature 370, 621-628)] and the different binding modes of the two phosphate groups. The ESEEM and HYSCORE data of a complex formed with Mn(2+), ATP, and the isolated beta subunit show that the (31)P hyperfine coupling is close to that measured in the absence of the protein, indicating a poorly structured nucleotide site in the isolated beta subunit in the presence of ATP. The inhibition data obtained for TF1 incubated in the presence of Mg(2+), ADP, Al(NO(3))(3), and NaF indicate the formation of the inhibited complex with the transition state analogue namely Mg.TF1.ADP.AlF(x) with the equilibrium dissociation constant K(D) = 350 microM and rate constant k = 0.02 min(-1). The ESEEM and HYSCORE data obtained for an inhibited TF1 sample, Mn.TF1.ADP.AlF(x), confirm the formation of the transition state analogue with distinct spectroscopic footprints that can be assigned to Mn.(19)F and Mn.(27)Al hyperfine interactions. The (31)P(beta) hyperfine coupling that is measured in the inhibited complex with the transition state analogue (|A((31)P(beta))| approximately 5.10 MHz) is intermediate between those measured in the presence of ADP and ATP and suggests an increase in the bond between Mn and the P(beta) from ADP upon formation of the transition state.

Bacillus↗

PubMed2000

Inverse regulation of F1-ATPase activity by a mutation at the regulatory region on the gamma subunit of chloroplast ATP synthase.

Chloroplast ATP synthase is a thiol-modulated enzyme whose DeltamuH(+)-linked activation is strongly influenced by reduction and the formation of a disulphide bridge between Cys(199) and Cys(205) on the gamma subunit. In solubilized chloroplast coupling factor 1 (CF(1)), reduction of the disulphide bond elicits the latent ATP-hydrolysing activity. To assess the regulatory importance of the amino acid residues around these cysteine residues, we focused on the three negatively charged residues Glu(210)-Asp-Glu(212) close to the two cysteine residues and also on the following region from Leu(213) to Ile(230), and investigated the modulation of ATPase activity by chloroplast thioredoxins. The mutant gamma subunits were reconstituted with the alpha and beta subunits from F(1) of the thermophilic bacterium Bacillus PS3; the active ATPase complexes obtained were purified by gel-filtration chromatography. The complex formed with a mutant gamma subunit in which Glu(210) to Glu(212) had been deleted was inactivated rather than activated by reduction of the disulphide bridge by reduced thioredoxin, indicating inverse regulation. This complex was insensitive to the inhibitory CF(1)-epsilon subunit when the mutant gamma subunit was oxidized. In contrast, the deletion of Glu(212) to Ile(230) converted the complex from a modulated state into a highly active state.

Adenosine Triphosphate↗

PubMed2000

Requirement for matrix metalloproteinase stromelysin-3 in cell migration and apoptosis during tissue remodeling in Xenopus laevis.

The matrix metalloproteinase (MMP) stromelysin-3 (ST3) was originally discovered as a gene whose expression was associated with human breast cancer carcinomas and with apoptosis during organogenesis and tissue remodeling. It has been shown previously, in our studies as well as those by others, that ST3 mRNA is highly upregulated during apoptotic tissue remodeling during Xenopus laevis metamorphosis. Using a function-blocking antibody against the catalytic domain of Xenopus ST3, we demonstrate here that ST3 protein is specifically expressed in the cells adjacent to the remodeling extracellular matrix (ECM) that lies beneath the apoptotic larval intestinal epithelium in X. laevis in vivo, and during thyroid hormone-induced intestinal remodeling in organ cultures. More importantly, addition of this antibody, but not the preimmune antiserum or unrelated antibodies, to the medium of intestinal organ cultures leads to an inhibition of thyroid hormone-induced ECM remodeling, apoptosis of the larval epithelium, and the invasion of the adult intestinal primodia into the connective tissue, a process critical for adult epithelial morphogenesis. On the other hand, the antibody has little effect on adult epithelial cell proliferation. Furthermore, a known MMP inhibitor can also inhibit epithelial transformation in vitro. These results indicate that ST3 is required for cell fate determination and cell migration during morphogenesis, most likely through ECM remodeling.

Animals↗

PubMed2000

Compensatory vasoconstrictor effects of sodium pentobarbital on the hindquarters of conscious normotensive control and lumbar-sympathectomized Wistar rats.

The aim of this study was to compare the vasoconstrictor effect of sodium pentobarbital on the hindquarter resistance of intact control Wistar rats with the effect on lumbar-sympathectomized rats. For this purpose, mean arterial pressure (MAP) and hindquarter (supplied terminal aorta) flow (HQF) were simultaneously measured in these conscious rats with an arterial in dwelling cannula and electromagnetic flow probe implanted around the terminal aorta. Hindquarter resistance (HQR) was calculated as MAP divided by HQF. In the intact control conscious rats, subsequent pentobarbital anesthesia (30 mg/kg, i.v.) caused an increase in HQR (+43.5 +/- 7.4%, mean +/- S.E.M.) and a decrease in MAP (-17.0 +/- 3.2%). After pentobarbital anesthesia, subsequent ganglionic blockade with hexamethonium bromide (C6; 25 mg, i.v.) induced a significant decrease in HQR (-30.9 +/- 3.0%) with a further lowering of MAP (-20.9 +/- 1.6%). However, in rats not anesthetized with sodium pentobarbital, C6 alone induced almost no change in HQR (-3.4 +/- 5.3%), even when MAP was lowered (-24.2 +/- 2.5%). In the lumbar-sympathectomized rats, pentobarbital anesthesia produced almost no change in HQR (-11.7 +/- 4.4%), although MAP decreased significantly (-24.3 +/- 2.2%). These findings suggest that: (1) sodium pentobarbital anesthesia newly generates a compensatory vasoconstrictor tone in the hindquarters acting against the depressor effect, and (2) the vasocompensator tone is controlled by the efferent fibers, including those in the lumbar sympathetic nerves.

Anesthesia↗

PubMed2000

Activation by nicotine of striatal neurons receiving excitatory input from the substantia nigra via dopamine release.

An electrophysiological study was performed to elucidate the role of nicotinic receptors in the striatal neurons in chloral hydrate-anesthetized rats. The effects of microiontophoretic application of nicotine and other drugs were examined on the caudate nucleus (CN) neurons activated monosynaptically by stimulation of the substantia nigra pars compacta (SN). Application of nicotine facilitated spontaneous firing. The nicotine-induced firing of the CN neurons was inhibited by concomitant application of domperidone or hexamethonium. These findings suggested that nicotine enhances dopamine release from the SN-derived dopaminergic nerve terminals by activating the neurons via D2 receptors.

Action Potentials↗