Biomedical subjects

M Taketani

Publications and source records attributed to M Taketani.

7 recordsLinked to original sources

PubMed2000

Origins and distribution of cholinergically induced beta rhythms in hippocampal slices.

Regional variations and substrates of high-frequency rhythmic activity induced by cholinergic stimulation were studied in hippocampal slices with 64-electrode recording arrays. (1) Carbachol triggered beta waves (17.6 +/- 5.7 Hz) in pyramidal regions of 75% of the slices. (2) The waves had phase shifts across the cell body layers and were substantially larger in the apical dendrites than in cell body layers or basal dendrites. (3) Continuous, two-dimensional current source density analyses indicated apical sinks associated with basal sources, lasting approximately 10 msec, followed by apical sources and basal sinks, lasting approximately 20 msec, in a repeating pattern with a period in the range of 15-25 Hz. (4) Carbachol-induced beta waves in the hippocampus were accompanied by 40 Hz (gamma) oscillations in deep layers of the entorhinal cortex. (5) Cholinergically elicited beta and gamma rhythms were eliminated by antagonists of either AMPA or GABA receptors. Benzodiazepines markedly enhanced beta activity and sometimes introduced a distinct gamma frequency peak. (6) Twenty Hertz activity after orthodromic activation of field CA3 was distributed in the same manner as carbachol-induced beta waves and was generated by a current source in the apical dendrites of CA3. This source was eliminated by high concentrations of GABA(A) receptor blockers. It is concluded that cholinergically driven beta rhythms arise independently in hippocampal subfields from oscillatory circuits involving (1) bursts of pyramidal cell discharges, (2) activation of a subset of feedback interneurons that project apically, and (3) production of a GABA(A)-mediated hyperpolarization in the outer portions of the apical dendrites of pyramidal neurons.

Acetylcholine↗

PubMed1999

A new planar multielectrode array for extracellular recording: application to hippocampal acute slice.

The present paper describes a new planar multielectrode array (the MED probe) and its electronics (the MED system) which perform electrophysiological studies on acute hippocampal slices. The MED probe has 64 planar microelectrodes, is covered with a non-toxic, uniform insulation layer, and is further coated with polyethylenimine and serum. The MED probe is shown to be appropriate for both stimulation and recording. In particular, multi-channel recordings of field EPSPs obtained by stimulating with a pair of planar microelectrodes were established for rat hippocampal acute slices. The recordings were stable for 6 h. Finally a spatial distribution of long-term potentiation was studied using the MED system.

Animals↗

PubMed1999

Characterization of esterases involved in the stereoselective hydrolysis of ester-type prodrugs of propranolol in rat liver and plasma.

An inhibition study showed that the stereoselective hydrolysis of butyryl propranolol (butyryl PL) in rat liver microsomes and plasma involves carboxylesterase. The hydrolysis of (S)-butyryl PL in plasma was specifically inhibited by eserine and bis-nitrophenyl phosphate (BNPP), compared to the (R)-isomer, despite the non-stereoselective hydrolysis of butyryl PL in plasma. In addition, inhibition of hydroloysis by eserine and BNPP showed little stereoselectivity for butyryl PL in liver, although liver microsomes showed an (S)-preferential hydrolysis for butyryl PL (R/S ratio of Vmax/Km: 2.1 +/- 0.2). The hydrolysis of butyryl PL was not inhibited by a polyclonal antibody against a high affinity carboxylesterase (hydrolase A, RH1). Moreover, the high Km value and the high IC50 for phenylmethylsulfonyl fluoride (PMSF) against the hydrolysis of butyryl PL in rat liver microsomes suggest that a low affinity carboxylesterase (perhaps hydrolase B) might be involved in this hydrolysis in rat liver.

Adrenergic beta-Antagonists↗

PubMed1999

Pancreatic Schwannoma: report of a case.

We present herein a case of solitary schwannoma of the pancreas and also review 26 previously reported cases from the English and Japanese literature. Primary schwannoma of the pancreas is a rare tumor. A 50-year-old female was discovered to have a large mass in the upper abdomen on ultrasonography. An examination by computed tomography (CT) scan, magnetic resonance imaging (MRI), and ultrasonography revealed a solid and cystic tumor in the left upper quadrant of the abdomen. A distal pancreatectomy with a splenectomy was performed to remove this tumor. A microscopic examination identified the tumor to be situated in the pancreas while it was composed of cells that originated from Schwann cells. Only 26 cases of pancreatic schwannoma have previously been reported in the English and Japanese literature. We describe in detail the characteristic findings based on image analyses, including CT scan, MRI, ultrasonography, and angiography, in these 26 cases.

Diagnostic Imaging↗

PubMed1999

In vitro identification of the human cytochrome P-450 enzymes involved in the N-demethylation of azelastine.

Azelastine hydrochloride [4-[(4-chlorophenyl)methyl]-2-(hexahydro-1-methyl-1H-azepin-4yl )-1-(2 H)-phthalazinone monohydrochloride], is a long-acting antiallergic and antiasthmatic drug. The human cytochrome P-450 (CYP) isoform responsible for azelastine N-demethylation, the major metabolic pathway for azelastine, has been examined. Eadie-Hofstee plots of azelastine N-demethylation in human liver microsomes were biphasic. In microsomes from baculovirus-infected insect cells, recombinant CYP3A4, 2D6, 1A2, and 2C19 exhibited high azelastine N-demethylase activity. The K(m) values of the recombinant CYP2D6 (3.75 microM) and CYP3A4 (43.7 microM) were relatively close to that of high-affinity (14.1 microM) and low-affinity (54.7 microM) components in human liver microsomes, respectively. Azelastine N-demethylase activity was inhibited only by the anti-CYP3A antibody, in contrast to antibodies for CYP1A, 2D6, and 2C. In addition, desmethylazelastine formation was significantly inhibited by ketoconazole and troleandomycin but only weakly by omeprazole, sulfaphenazole, and furafylline. These observations suggested that the N-demethylation of azelastine is most extensively catalyzed by the CYP2D6 and 3A4 isoforms in humans.

Baculoviridae↗

PubMed1996

Distinct memory circuits composing the hippocampal region.

The very different anatomical designs of the adjacent circuitries of the cortico-hippocampal pathway, along with their somewhat different synaptic plasticity mechanisms, suggest a nearly serial pathway of distinct memory circuits each contributing its own specialized processing operation to overall hippocampal function. Modeling and formal theoretical analysis of the prominent anatomical design features of particular circuits (piriform/entorhinal cortex; hippocampal field CA3; hippocampal field CA1) are found to identify potential emergent function not readily arrived at in the absence of these formal models, and yet which once derived can be seen potentially to confer unique capabilities to an integrated hippocampal mechanism for processing memories during behavior.

Animals↗

PubMed1995

Role of conserved amino acid residues in the complementarity determining regions on hapten-antibody interaction of anti-(4-hydroxy-3-nitrophenyl) acetyl antibodies.

Monoclonal antibodies (mAbs) specific to (4-hydroxy-3-nitrophenyl)acetyl (NP) were prepared at various times after immunization and the amino acid sequences of VH and V lambda 1 in these mAbs were deduced from cDNA nucleotide sequences. Replacements due to somatic mutation were not found in day 7 mAbs but were found in those of days 14, 84 and 294. The affinity of day 7 mAbs to NP-glycine(NP-Gly) was in the order of 10(4) M-1 and it increased about 8000-fold with time after immunization. The extrinsic circular dichroism (CD) spectrum of the NP-epsilon-aminocaproic acid (NP-Cap)/Ab complex was unique for each mAb, although the spectra were grouped into two types, which tended to shift from one type to another with time, suggesting a variation in the micro-environments around NP-Cap in the combining sites. All these data indicate that the structure of the combining site was altered by somatic mutation; however, the fine-specificity measured by cross-reactivity with hapten analogues did not change significantly with time. We examined the amino acid residues in CDRs responsible for recognition of NP-haptens by comparing the amino acid sequences of anti-NP mAbs. Analyses revealed the presence of several conserved amino acid residues in CDRs of VH and V lambda 1, such as Tyr-32H, and Tyr-60H, in addition to a core segment involving Arg-50H.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗