Biomedical subjects

T Kanno

Publications and source records attributed to T Kanno.

At least 37 records · Page 2Linked to original sources

PubMed2002

Endogenous viral sequences and their potential contribution to heritable virus resistance in plants.

Tobacco endogenous pararetroviruses (TEPRVs) represent the first virus-derived repetitive sequence family found in plants. The sequence conservation of TEPRVs and the lack of an exogenous form of the virus suggest that TEPRVs serve a beneficial function, perhaps by furnishing virus resistance via homologous sequence interactions. This hypothesis is supported by the observation that TEPRVs are methylated and negligibly transcribed. Moreover, transgenes driven by the TEPRV enhancer are silenced and methylated when introduced into tobacco, but remain active and unmethylated in non-host species devoid of sequences homologous to TEPRVs. In transgenic Arabidopsis, the TEPRV enhancer is active primarily in shoot meristems. This suggests that the virus giving rise to TEPRVs could infect germ cell precursors, a prerequisite for meiotically heritable insertions into host chromosomes. The copy number, organization and methylation of TEPRVs in tetraploid tobacco and one of its diploid ancestors, Nicotiana sylvestris, the presumed original host for the virus, have remained constant since polyploid formation. The remarkable conservation of these features in two independently evolving species further supports a role for TEPRVs in viral immunity.

Arabidopsis↗

PubMed2002

A new neuromodulatory pathway with a glial contribution mediated via A(2a) adenosine receptors.

A low concentration (10 nM) of adenosine potentiated hippocampal neuronal activity via A(2a) adenosine receptors without affecting presynaptic glutamate release or postsynaptic glutamatergic conductance. Adenosine inhibited glutamate uptake through the glial glutamate transporter, GLT-1, via A(2a) adenosine receptors. In addition, adenosine stimulated GLT-1-independent glutamate release from astrocytes, possibly in response to a rise in intracellular Ca(2+), via A(2a) adenosine receptors involving PKA activation. Those adenosine actions could lead to an increase in synaptic glutamate concentrations responsible for the potentiation of hippocampal neuronal activity. The results of the present study thus represent a novel neuromodulatory pathway with a glial contribution, bearing both inhibition of GLT-1 function and stimulation of glial glutamate release, as mediated via A(2a) adenosine receptors.

Adenosine↗

PubMed2002

Multi-slice 3D-CTA - an improvement over single slice helical CTA for cerebral aneurysms.

BACKGROUND AND OBJECTIVE: The aim of this study was to demonstrate the utility of volume rendered multi-slice helical three-dimensional CT angiography in patients with cerebral aneurysm when compared with single slice CT angiography and formal digital subtraction angiography. METHODS: A prototype Toshiba Aquilon multi-slice CT scanner was employed with the following scan conditions: voltage 135 kV; current 300 mA; slice thickness 0.8 mm; scan speed 0.75 sec/cycle; couch speed 1 mm/sec; range 50 mm from foramen magnum; scan pitch 3; three dimensional images were reconstructed using multiple image projections and integral volume rendering algorithms on a Xlink/Xtension workstation. 80 cases of multi-slice CTA for cerebral aneurysm carried out at Fujita University from January 1999 to January 2001 were reviewed. RESULTS: The advantages of multi-slice imaging are illustrated with representative cases of cerebral aneurysm - good demonstration of three dimensional anatomy, appreciation of perforators down to 1 mm in size, delineation of the vessels around the aneurysm complex, relationship between the aneurysm and skull base, information on calcification, thrombus and blebs in the wall and eleven routine views for perusal. CONCLUSION: Multi-slice CTA is a significant improvement over single slice CTA for cerebral aneurysms. It is our experience the superior and precise images produced by multi-slice technology displays anatomical information not readily available from standard DSA. Multislice 3D-CTA is relatively non-invasive and provides better and adequate detail for surgical planning. The basis of multi-slice CT angiography is described. Multi slice CTA is changing the way cerebral aneurysms are being managed nowadays. New advances in the technology of multi-slice CTA resulting in increased image resolution are outlined.

Angiography, Digital Subtraction↗

PubMed2002

Selective production of organic acids in anaerobic acid reactor by pH control.

The selective production of organic acids by anaerobic acidogenesis with pH control was examined using a chemostat culture. The results showed that the product spectrum in the acid reactor strongly depended on the culture pH. Under acidic and neutral conditions, the main products were butyric acid, while acetic and propionic acids were the main products under the basic condition. This phenomenon was reversible between the acidic and basic conditions, and was not affected by the dilution rate. The change in the main products was caused by the change in the dominant microbial populations, from butyric acid-producing bacteria to propionic acid-producing bacteria in the acid reactor due to the pH shift. The control of culture pH was considered to be a useful way for controlling the product spectrum in the anaerobic acid reactor.

Acetic Acid↗

PubMed2002

Comparison of a new system (Compactdry SCD) with conventional methods for quantitative urine cultures.

AIMS: Compactdry SCD, a new quantitative, ready-to-use and self-diffusible dry medium sheet urine culture system, was compared with conventional methods to evaluate the results of quantitative urine cultures. METHODS & RESULTS: Compactdry SCD was tested on 25 urine specimens, and results compared with those of traditional culture methods. The results from Compactdry SCD analysis correlated well with those from the standard plate count (SPC) method. In fact, the correlation was stronger than that dipslide systems and SPC. Even low-count bacteriuria (< 103 cfu ml(-1) and mixed bacteriuria were detected by Compactdry SCD. CONCLUSIONS: The Compactdry SCD system provides results comparable to those obtained by SPC: simple interpretation, ease of use, long-term storage and good sensitivity. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report suggesting that the Compactdry SCD system has many advantages over traditional quantitative urine culture methods and that it is both appropriate and practical for clinical use.

Bacteria↗

PubMed2002

Surgical clipping of basilar aneurysms: relationship between the different approaches and the surgical corridors.

BACKGROUND: Surgical clipping for basilar artery aneurysm (BAA) is a technically demanding procedure due to the depth of the surgical field and the presence of vital perforating arteries in the vicinity. The incorporation of various modifications in the conventional approaches has expanded the surgical armamentarium in dealing with these difficult lesions. METHODS AND FINDINGS: 87 patients of BAA were operated at our center, out of which in 48 patients, a pterional transsylvian approach was used. In 12 patients, this approach had to be extended to incorporate the anterior temporal approach in 6 cases, transzygomatic subtemporal approach in 2 cases and transcavernous approach in 4 cases. The surgical indications for the additional approaches and the relationships between the surgical corridors gained by their inclusion were studied. The use of neuroendoscopy facilitated adequate clipping in one case of high BAA without the incorporation of bone drilling, thus opening new surgical corridors. INTERPRETATION: The variable situation of the BAA makes it mandatory for the surgeon to be prepared to simultaneously work through multiple surgical corridors. Neuroendoscopic-assisted microneurosurgery occasionally utilizes a narrow surgical corridor to facilitate BAA clipping using the conventional approaches and eliminates the need to gain access using additional surgical corridors.

Basilar Artery↗

PubMed2002

Successful obliteration of a ruptured partially thrombosed giant m1 fusiform aneurysm with coil embolization at distal m1 after extracranial-intracranial bypass.

Proximal occlusion or trapping combined with EC-IC bypass is usually employed as a definite treatment for a giant fusiform aneurysm in cases where it is impossible to apply clips and do vascular reconstruction. Endovascular treatment is very important as an alternative or combined technique if direct surgery is impossible. The authors report a young male who presented with a 2 nd episode of intracranial bleeding in basal ganglion and subarachnoid hemorrhage with mild right hemiparesis. His 3D-CT scan revealed left ruptured partially thrombosed giant M1 fusiform aneurysm and left unruptured C3 saccular aneurysm. He underwent STA-MCA bypass with attempted M1 reconstruction and a week later attempted total occlusion of the M1 aneurysm with coils. But only a ruptured point at the distal M1 was occluded which, however, resulted in temporary mild right hemiparesis and aphasia. A month later when he was supposed to have his 2 nd coiling procedure his angiogram demonstrated spontaneous and complete obliteration of both the M1 and C3 aneurysms without any new neurological deficit, so no further endovascular procedure was attempted. The discussion is based on this case and previous reports regarding difficult giant M1 fusiform aneurysms, its treatment and spontaneous thrombosis of aneurysmal sac after bypass and distal occlusion. Conclusions are drawn that 1) spontaneous thrombosis of M1 and C3 aneurysms should be the result of hemodynamic alteration in both aneurysms due to a lower flow velocity induced by distal bypass and distal occlusion of M1, 2) combined distal bypass and endovascular obliteration of the aneurysmal sac with coils is a good alternative if vascular reconstruction is difficult or impossible.

Adult↗

PubMed2001

Role of glial glutamate transporters in the facilitatory action of FK960 on hippocampal neurotransmission.

We found previously that N-(4-acetyl-1-piperazinyl)-p-fluorobenzamide monohydrate (FK960) facilitated hippocampal neurotransmission in the dentate gyrus of rat hippocampal slices. The present study was conducted to understand the mechanism underlying the facilitatory action of FK960. The facilitation was inhibited by H-89, an inhibitor of cAMP-dependent protein kinase (PKA), but it was not affected by cycloheximide, a protein synthesis blocker. In cultured rat hippocampal neurons, the drug had no effect on either spontaneous miniature excitatory postsynaptic currents or whole-cell membrane currents evoked by glutamate, kainate, or NMDA, suggesting that the facilitatory action of FK960 is not caused by increasing presynaptic transmitter release or excitatory postsynaptic conductances. FK960 inhibited responses of the glial glutamate transporter, GLT-1, expressed in Xenopus oocytes, and a similar effect was found with cultured rat astrocytes. The FK960 action was inhibited in the presence of H-89. The results of the present study thus suggest that FK960 facilitates hippocampal neurotransmission by inhibiting GLT-1 glial glutamate reuptake via a PKA pathway, thereby increasing synaptic glutamate concentrations.

Amino Acid Transport System X-AG↗

PubMed2001

The protective action of nefiracetam against electrophysiological and metabolic damage in the hippocampus after deprivation of glucose and oxygen.

The present study examined the effect of nefiracetam on ischemic brain damage by monitoring population spikes (PSs) in the dentate gyrus of guinea pig hippocampal slices; assaying high-energy phosphates (ATP and CrP) in guinea pig hippocampal slices; and monitoring whole-cell membrane-currents and intracellular Ca(2+) levels in cultured hippocampal neurons. Twenty-minute ischemic insult to slices, i.e., deprivation of glucose and oxygen from artificial cerebrospinal fluid, abolished PSs. As compared with only 35% recovery of the PS amplitude for control, PS amplitude reversed to 65% of basal levels 40 min after returning normal conditions by treatment with nefiracetam (0.01 microM). Ischemic insult reduced the levels of adenosine triphosphate (ATP) and creatine phosphate (CrP) in slices, and when returned to normal conditions, recovering to 70 and 85% of basal values, respectively, 30 min after returning normal conditions. Nefiracetam (0.01 microM) facilitated the recovery of ATP and CrP, reaching 110 and 140% of basal values, respectively. Nefiracetam inhibited N-methyl-D-aspartate (NMDA)-evoked currents to 35% of basal amplitudes. Likewise, nefiracetam (0.01 microM) inhibited intracellular Ca(2+) rise through NMDA receptor channels to 30% of basal levels. The results of the present study, thus, suggest that nefiracetam has the potential to protect against ischemic brain damage, possibly in part by preventing from accumulation of intracellular calcium through NMDA receptor channels.

Adenosine Diphosphate↗

PubMed2001

Virulence of swine vesicular disease virus is determined at two amino acids in capsid protein VP1 and 2A protease.

To identify the genetic determinants of virulence for swine vesicular disease virus, a panel of recombinant and site-directed mutant viruses were constructed from cDNA clones of a virulent J1'73 strain and an avirulent H/3'76 strain. Initial studies mapped the genetic determinants of virulence to either or both of the two sites at nucleotide (nt) 2842, encoding VP1-132, and nt 3355, encoding 2A-20. To determine their relative importance with regard to virulence, viruses mutated at either of these two sites from the avirulent to the virulent genotype and vice versa were tested in pigs. Viruses, mutated at nt 2842 to the virulent genotype (vSVLS104MJ1) or mutated at nt 3355 to the virulent genotype (vSVLS201MJ1), slightly recovered virulence but were very weak compared with viruses with site-directed mutations at both sites (vSVLS104/201MJ1). On the other hand, viruses, mutated at nt 2842 to the avirulent genotype (vSVLS104M00) or mutated at nt 3355 to the avirulent genotype (vSVLS201M00), did not have attenuated virulence. Sequence analysis of viruses recovered from inoculated pigs revealed that reversion at nt 3355 to the virulent genotype occurred in pigs which had been inoculated with vSVLS201M00. These results suggested that both amino acids determined the virulent phenotype, but that the 2A-20 site might be the major determinant for virulence.

Animals↗

PubMed2001

Preservation of neurotrophin expression in microglia that migrate into the gerbil's brain across the blood-brain barrier.

Microglia isolated from a mixed glial culture drawn from neonatal Mongolian gerbils were demonstrated to produce high amounts of brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF). The gerbil microglia retained the capability to migrate into the brain parenchyma after intra-arterial injection. We found that exogenously migrated microglia retained their BDNF and GDNF productive ability and expressed large amounts of BDNF and GDNF in damaged brain areas which suggests microglia's role as a protectant of damaged neurons. Since peripherally injected microglia exhibit specific affinity for areas of neural damage within the brain, we suggest that microglia are possible tools for cell therapy of brain damage.

Animals↗

PubMed2001

Roles of long chain fatty acids and carnitine in mitochondrial membrane permeability transition.

Palmitoyl-CoA (Pal-CoA) lowered the respiratory control ratio (RCR), and induced mitochondrial membrane permeability transition (MPT) and cytochrome c (Cyt. c) release from isolated rat liver mitochondria. L-Carnitine suppressed the Pal-CoA-induced dysfunction, MPT, and Cyt. c release of isolated mitochondria. This suppression was inhibited by cephaloridine, an inhibitor of carnitine uptake into mitochondria. Cyclosporin A (CsA), an inhibitor of MPT, and BSA also suppressed the Pal-CoA-induced MPT. In the presence of inorganic phosphate (P(i)), Ca2+-induced MPT was suppressed by BSA, L-carnitine, and chlorpromazine, an inhibitor of phospholipase A2. In the presence of a low concentration of Ca2+, 3,3',5-triiodothyronine, long chain fatty acids, salicylic acid, and diclofenac induced MPT by a mechanism that was suppressed by BSA, L-carnitine, or chlorpromazine. During the incubation of mitochondria on ice, their respiratory competence decreased; L-carnitine and BSA also prevented this decrease. Mitochondrial depolarization in pheochromocytoma PC12 cells was induced by either serum deprivation or arachidonic acid by a mechanism that was suppressed by acetyl-L-carnitine. These results indicate that some MPTs may be regulated by fatty acid metabolism and that the Pal-CoA-induced MPT plays an important role in the induction of apoptosis.

Animals↗

PubMed2001

Phorbol ester impairs electrical excitation of rat pancreatic beta-cells through PKC-independent activation of KATP channels.

BACKGROUND: Phorbol 12-myristate 13-acetate (PMA) is often used as an activating phorbol ester of protein kinase C (PKC) to investigate the roles of the kinase in cellular functions. Accumulating lines of evidence indicate that in addition to activating PKC, PMA also produces some regulatory effects in a PKC-independent manner. In this study, we investigated the non-PKC effects of PMA on electrical excitability of rat pancreatic beta-cells by using patch-clamp techniques. RESULTS: In current-clamp recording, PMA (80 nM) reversibly inhibited 15 mM glucose-induced action potential spikes superimposed on a slow membrane depolarization and this inhibition can not be prevented by pre-treatment of the cell with a specific PKC inhibitor, bisindolylmaleimide (BIM, 1 microM). In the presence of a subthreshold concentration (5.5 mM) of glucose, PMA hyperpolarized beta-cells in a concentration-dependent manner (0.8-240 nM), even in the presence of BIM. Based on cell-attached single channel recordings, PMA increased ATP-sensitive K+ channel (KATP) activity. Based on inside-out patch-clamp recordings, PMA had little effect on KATP activity if no ATP was in the bath, while PMA restored KATP activity that was suppressed by 10 microM ATP in the bath. In voltage-clamp recording, PMA enhanced tolbutamide-sensitive membrane currents elicited by repetitive ramp pulses from -90 to -50 mV in a concentration-dependent manner, and this potentiation could not be prevented by pre-treatment of cell with BIM. 4alpha-phorbol 12,13-didecanoate (4alpha-PDD), a non-PKC-activating phorbol ester, mimicked the effect of PMA on both current-clamp and voltage-clamp recording configurations. With either 5.5 or 16.6 mM glucose in the extracellular solution, PMA (80 nM) increased insulin secretion from rat islets. However, in islets pretreated with BIM (1 microM), PMA did not increase, but rather reduced insulin secretion. CONCLUSION: In rat pancreatic beta-cells, PMA modulates insulin secretion through a mixed mechanism: increases insulin secretion by activation of PKC, and meanwhile decrease insulin secretion by impairing beta-cell excitability in a PKC-independent manner. The enhancement of KATP activity by reducing sensitivity of KATP to ATP seems to underlie the PMA-induced impairment of beta-cells electrical excitation in response to glucose stimulation.

ATP-Binding Cassette Transporters↗

PubMed2001

Selective cholinergic denervation inhibits expression of long-term potentiation in the adult but not infant rat hippocampus.

The present study assessed the role of the cholinergic systems on the expression of perforant path long-term potentiation (LTP) in rat hippocampal slices from the infant and adult brain. To denervate the cholinergic systems, 192 IgG--saporin was injected into the lateral ventricle of the infant (2-weeks-old) and adult (6-weeks-old) rat brain. There, choline acetyltransferase-immunoreactive fibers were barely detectable 2 weeks and 2 months after injection for both the groups. For the infant rats, perforant path LTP was not affected by selective cholinergic denervation; the probability of LTP development was 0.83 (five out of six slices) and 0.78 (seven out of nine slices) at 2 weeks and 2 months later in 192 IgG--saporin-treated slices, as compared with 0.83 at each period in control saline-treated slices. In contrast, the expression of the LTP was blocked by selective cholinergic denervation for the adult rats; the probability of LTP development was 0 (zero out of 10 slices) and 0.38 (three out of eight slices) at 2 weeks and 2 months later in 192 IgG--saporin-treated slices, as compared with 0.8 (eight out of 10 slices) and 0.83 (five out of six slices) at each period in control saline-treated slices. The results of the present study thus suggest that the cholinergic systems play a crucial role in the expression of LTP in the adult brain and that the denervated systems in the infant brain could be compensated by the sprouting of non-cholinergic fibers.

Age Factors↗

PubMed2001

Tributyltin interacts with mitochondria and induces cytochrome c release.

Although triorganotins are potent inducers of apoptosis in various cell types, the critical targets of these compounds and the mechanisms by which they lead to cell death remain to be elucidated. There are two major pathways by which apoptotic cell death occurs: one is triggered by a cytokine mediator and the other is by a mitochondrion-dependent mechanism. To elucidate the mechanism of triorganotin-induced apoptosis, we studied the effect of tributyltin on mitochondrial function. We found that moderately low doses of tributyltin decrease mitochondrial membrane potential and induce cytochrome c release by a mechanism inhibited by cyclosporine A and bongkrekic acid. Tributyltin-induced cytochrome c release is also prevented by dithiols such as dithiothreitol and 2,3-dimercaptopropanol but not by monothiols such as GSH, N-acetyl-L-cysteine, L-cysteine and 2-mercaptoethanol. Further studies with phenylarsine oxide agarose revealed that tributyltin interacts with the adenine nucleotide translocator, a functional constituent of the mitochondrial permeability transition pore, which is selectively inhibited by dithiothreitol. These results suggest that, at low doses, tributyltin interacts selectively with critical thiol residues in the adenine nucleotide translocator and opens the permeability transition pore, thereby decreasing membrane potential and releasing cytochrome c from mitochondria, a series of events consistent with established mechanistic models of apoptosis.

Animals↗

PubMed2001

Physicochemical and immunological characterization of hepatitis B virus envelope particles exclusively consisting of the entire L (pre-S1 + pre-S2 + S) protein.

The hepatitis B virus (HBV) envelope (env) protein is composed of three regions; the 108- or 119-residue pre-S1 region involved in the direct interaction with hepatocytes, the 55-residue pre-S2 region associated with the polymerized albumin-mediated interaction, and the major 226-residue S protein region. Thus, to improve the immunogenic potency of conventional HB vaccines, development of a new vaccine containing the entire pre-S1 region in addition to pre-S2 and S is desired. We previously reported the efficient production of the HBV env L (pre-S1 + pre-S2 + S) protein in the recombinant yeast cells [J Biol Chem 267 (1992) 1953]. In this study, the HBV env L protein produced as nano-particles in yeast has been purified and characterized. By equilibrium sedimentation, an average molecular weight of L particle was estimated to be approximately 6.4 x 10(6), indicating that about 110 molecules of L proteins are assembled into an L particle. By atomic force microscopy in a moist atmosphere, the L particles were observed as large spherical particles with a diameter of 50-500 nm. The L particles were stable on short-time heating at a high temperature and long-time storage at a low temperature but rather unstable on repeated freezing and thawing and treatment with dithiothreitol. When immunized in mice, L particles elicited efficiently and simultaneously the anti-S, anti-pre-S2, and anti-pre-S1 antibodies. The ED(50) values in mice for the anti-S and anti-pre-S2 antibodies were similar to those elicited by the M (pre-S2 + S) particles. Furthermore, the anti-pre-S1 rabbit antibodies were found to recognize various segments of the pre-S1 region, including the pre-S1 (21-47) segment. These results show the high ability of L particles to induce all antibodies against HBV env proteins, hence promising the future application of L particles for the next generation HB vaccine.

Animals↗

PubMed2001

Tryptophan glycoconjugate as a novel marker of renal function.

PURPOSE: Neither serum creatinine concentration nor creatinine clearance assess renal function accurately. Serum creatinine concentration is affected by muscle mass, and the creatinine clearance overestimates the glomerular filtration rate because of tubular secretion of creatinine. The present study was designed to determine whether serum concentrations of 2-(alpha-mannopyranosyl)-L-tryptophan (MPT), a tryptophan glycoconjugate, can be used as a marker of renal function. METHODS: Clearances of MPT and of inulin were compared in normal rats and in rats with cisplatin-induced acute renal failure. We also compared the clearances of MPT and of creatinine with inulin clearance in 25 patients with chronic renal disease. Serum concentrations of MPT and creatinine as a function of MPT clearance were determined in 108 patients with chronic renal disease. RESULTS: There was strong linear correlation between clearances of MPT and inulin in rats (r = 0.97) and humans (r = 0.87), indicating that renal handling of MPT is similar to that of inulin. In humans, linear regression analyses indicated that MPT was a better indicator of inulin clearance than was creatinine clearance. At the same level of renal function, serum creatinine concentrations tended to be lower in patients with less muscle mass (as indicated by a urinary creatinine excretion <1,000 mg in 24 hours) than in those who excreted >1,000 mg in 24 hours, whereas serum MPT concentrations were not affected by creatinine excretion. CONCLUSION: MPT clearance can replace inulin clearance in the clinical setting. The serum MPT concentration is an accurate measure of renal function even in patients with diminished muscle mass, and thus is a better indicator of renal function than is the serum creatinine concentration.

Acute Kidney Injury↗

PubMed2001

Treatment of unruptured intracranial aneurysms--a clinicopathological correlation.

OBJECT: Brain check-up is very important for detecting the incidence and prevalence of aneurysms in the population and to get the definite strategy for the treatment of intracranial aneurysms. METHODS: This is a retrospective study of 116 aneurysms detected by brain check-up between 1998-1999 which were treated either by clipping or endovascular coiling. In some cases the aneurysmal wall was resected for histopathological examination and compared with five normal autopsy cases. CONCLUSIONS: Direct surgery is the primary option for a patient with an aneurysm in the anterior circulation especially in young patients. Intravascular therapy is suitable for aneurysms in the posterior circulation and in intracavernous site.

Aged↗