Search PubMed⌕ Search

Biomedical subjects

S Honma

Publications and source records attributed to S Honma.

At least 19 recordsLinked to original sources
PubMed2001

Furanodictine A and B: amino sugar analogues produced by cellular slime mold Dictyostelium discoideum showing neuronal differentiation activity.

We investigated the constituents of Dictyostelium discoideum to clarify the diversity of secondary metabolites of Dictyostelium cellular slime molds and to explore biologically active substances that could be useful in the development of novel drugs. From a methanol extract of the multicellular fruit body of D. discoideum, we isolated two novel amino sugar analogues, furanodictine A (1) and B (2). They are the first 3,6-anhydrosugars to be isolated from natural sources. Their relative structures were elucidated by spectral means, and the absolute configurations were confirmed by asymmetric syntheses of 1 and 2. These furanodictines potently induce neuronal differentiation of rat pheochromocytoma (PC-12) cells.

Amino Sugars↗
PubMed2001

Quantitative analysis of synaptic contacts made between functionally identified oralis neurons and trigeminal motoneurons in cats.

A previous study revealed that rostrodorsomedial oralis (Vo.r) neurons synapsing on trigeminal motoneurons use GABA and/or glycine as neurotransmitters. To determine the number and spatial distribution of contacts, injections of biotinamide and horseradish peroxidase were made into a Vo.r neuron and an alpha-motoneuron in the jaw-closing (JC) and jaw-opening (JO) motor nucleus, respectively, in 39 cats. All Vo.r neurons responded to low-threshold mechanical stimulation of the oral tissues. Single Vo.r neurons terminating in the JC nucleus (Vo.r-dl neurons; n = 5) issued, on average, 10 times more boutons than Vo.r neurons terminating in the JO nucleus (Vo.r-vm neurons; n = 5; 4437 vs 445). The Vo.r-dl neuron-JC alpha-motoneuron pairs (n = 4) made contacts on either the soma-dendritic compartment or dendrites, and the Vo.r-vm neuron-JO motoneuron pairs (n = 2) made contacts on dendrites, with a range of two to seven contacts. In five of the six pairs, individual or groups of two to three terminals contacted different dendritic branches of a postsynaptic cell. The Vo.r-dl neurons innervated a greater number of counter-stained motoneuronal somata than did the Vo.r-vm neurons (216 vs 26). Total number of contacts per Vo.r neuron was higher for the Vo.r-dl than Vo.r-vm neurons (786 vs 72). The present study demonstrates that axonal branches of Vo.r neurons are divided into two types with different innervation domains on the postsynaptic neuron and that they are highly divergent. The overall effect exerted by these neurons is predicted to be much greater within the JC than JO motoneuron pool.

Action Potentials↗
PubMed2001

Circadian pattern, light responsiveness and localization of rPer1 and rPer2 gene expression in the rat retina.

Circadian expression, light-responsiveness and localization of clock genes, rPer1 and rPer2, were examined in the rat retina under constant darkness. A significant circadian variation was detected in rPer2 transcript levels with a peak at ZT14, but not in the rPer1. A light pulse given after constant darkness of 3 days increased both rPer1 and rPer2 expression phase-dependently, while rPer1 was induced at more times than rPer2. A major site of these gene expression within the retina was the inner nuclear layer. These findings indicate that rPer1 and rPer2 genes play different roles in the generation and regulation of circadian rhythms in the retina from those in the suprachiasmatic nucleus.

Animals↗
PubMed2001

Clock gene expressions in the suprachiasmatic nucleus and other areas of the brain during rhythm splitting in CS mice.

The CS mouse is a mutant strain which displays spontaneous splitting in the circadian locomotor rhythm under continuous darkness. To clarify whether the rhythm splitting occurs in the suprachiasmatic nucleus (SCN) where the mammalian circadian clock is located, the circadian rhythmicities of mammalian clock genes, mPer1, mBMAL1 and mClock, were examined in the SCN and cerebral cortex during rhythm splitting. The circadian profiles of the clock genes during rhythm splitting were essentially the same as those observed under unsplit conditions. However, the mPer1 gene expression throughout the day was bimodal in the piriform and cingulate cortices, peaking in correspondence with two split components of behavioral rhythm. These results indicate that the circadian profiles of three clock gene expressions in the SCN are not consistent with the overt circadian locomotor rhythm, suggesting that the site of rhythm splitting is somewhere outside the SCN, or alternatively different subregions or other clock genes in the SCN are involved in rhythm splitting.

ARNTL Transcription Factors↗
PubMed2001

Continuous measurement of targeted promoter activity by a secreted bioluminescence reporter, Vargula hilgendorfii luciferase.

The promoter activity of growth hormone (GH) was continuously monitored in rat pituitary adenoma cells (GH3) by a secreted bioluminescence reporter, Vargula hilgendorfii (Vh) luciferase. The sensitivity of the reporter was approximately 60-times higher than that of the firefly luciferase. GH3 cells were transfected with a plasmid containing a DNA sequence of the GH promoter (1.8 kb) and a full length of the Vh luciferase cDNA. Using the stable transformants, the Vh luciferase activity was monitored in the plate culture through the bioluminescence of Vh luciferase secreted into the culture medium. The reporter activity was well correlated with GH mRNA as well as GH when the GH promoter activity was activated by thyroid hormone. To develop a continuous monitoring system of the promoter, the reporter activity was sequentially measured in the perfusion system. When the promoter activity of the stable transformants was suppressed by a transcription inhibitor, the reporter activity and GH in the perfusate were simultaneously decreased. The Vh luciferase reporter is a sensitive and convenient tool for continuous and prolonged measurement of promoter activity in living cell culture systems.

Animals↗
PubMed2001

Sensitive detection and differentiation of Sapporo virus, a member of the family Caliciviridae, by standard and booster nested polymerase chain reaction.

Norwalk virus and Sapporo virus (SV) were approved as type species of the genus Norwalk-like viruses and the genus Sapporo-like viruses, respectively, in the family Caliciviridae. Nested polymerase chain reaction (PCR), using newly designed primers in the RNA-dependent RNA polymerase region, was developed to detect and differentiate viruses in the three genetic groups of SV based on the relative size of the PCR products obtained. In addition, a booster nested PCR that performs nested PCR in a single tube was introduced to reduce the chance of contamination during the procedure of standard nested PCR. The specificity of the newly developed PCR was confirmed by testing 77 stool specimens and 16 tissue culture fluids derived from growth of unrelated viruses. The sensitivity of the nested PCR was compared with the conventional PCR using Sapp35/Sapp36 primer pair by testing the three cDNA clones obtained from viruses in the SV/SV82, the SV/London92, and the SV/Parkville virus, respectively. This assay can detect SV in a more sensitive way than the conventional PCR and Southern hybridization. Sensitive and suitable methods to detect and differentiate SV are required to obtain accurate epidemiological data on these viruses and the standard and booster nested PCR should be a very useful tool for this purpose.

Caliciviridae↗
PubMed2001

Quantitative ultrastructure of slowly adapting lingual afferent terminals in the principal and oral nuclei in the cat.

Previous studies provide evidence that a structure/function correlation exists in the cytoarchitectonically different zones of the trigeminal sensory nuclei. To extend this relationship, we examined the ultrastructural features of trigeminal primary afferent neurons in the cat dorsal principal nucleus (Vpd) and the rostrodorsomedial oral nucleus (Vo.r) using intra-axonal labeling with horseradish peroxidase and morphometric analyses. All labeled boutons contained round synaptic vesicles. Eighty-two percent of the boutons in the Vo.r and 99% of the boutons in the Vpd were presynaptic to nonprimary dendrites. The remaining boutons in the Vo.r were presynaptic to somata (8%) or primary dendrites (10%). The average number of postsynaptic profiles per labeled bouton did not differ in the Vpd and Vo.r. Most labeled boutons in the two nuclei were postsynaptic to unlabeled axon terminals with pleomorphic vesicles (p-ending). The number of p-endings per labeled bouton was higher in the Vpd than Vo.r A morphometric analysis indicated that labeled bouton volume and apposed surface area were larger in the Vpd than Vo.r while active zone area and vesicle number did not differ. All these parameters were larger than those of p-endings in each nucleus. In both labeled boutons and p-endings, the parameters were positively correlated with bouton size. These results suggest that sensory information conveyed through trigeminal afferents is more strongly controlled at the level of the first synapse by presynaptic mechanisms in the Vpd than in the Vo.r, while the efficacy of transmission at primary afferent synapses does not differ.

Animals↗
PubMed2001

Quantitative ultrastructure of synapses on functionally identified primary afferent neurons in the cat trigeminal mesencephalic nucleus.

Though a number of studies have reported the presence of synapses on neurons in the trigeminal mesencephalic nucleus (Vmes), there have been no quantitative studies of either the density of innervation, or the ultrastructure, of the synapses on single, physiologically identified neurons in this nucleus. In this study we recorded from single neurons in the Vmes, identified them as being either muscle spindle afferents (MS) or periodontal ligament mechanoreceptor afferents (PL), and then labeled the neurons by intra-axonal injection of horseradish peroxidase (HRP). The material was first processed to reveal the HRP activity, following which ultrathin sections through the labeled somata were cut and examined under the electron microscope. Complete serial reconstructions were made through the soma of one MS neuron and one PL neuron, and the contacts on the neurons reconstructed. Boutons were found on the soma, spines, appendages and the axon hillock and the initial segment of the axon. The numbers of boutons terminating on the two neurons were 198 (PL) and 424 (MS), giving a packing density of 4.4 and 10.7 boutons respectively (i.e., number of boutons/100 micron 2 of the postsynaptic membrane). Boutons could be separated into two types on the basis of their vesicles: those containing clear, round vesicles (i.e., S-type) and those containing a mixture of round, oval and flattened vesicles (P-type). Ninety-five (PL neuron) and 99% (MS neuron) of terminals on the two neurons were P-type. All the S-type boutons and 80% of the P-type boutons formed asymmetric synaptic contacts while 10% of the P-type boutons made symmetric contacts. Quantitative measurements of the P-type boutons on the labeled neurons, in which the data of MS and PL neurons were pooled, revealed that bouton volume was highly correlated with bouton surface area, active zone number, total active zone area, vesicle number, and mitochondrial volume. However, comparing the quantitative measurements of the P-type boutons with those of previously reported vibrissa afferent terminals and their associated axon terminals revealed that all the parameters were smaller for the P-type boutons (on Vmes neurons) than those of the vibrissa afferent terminals but similar to those of axon terminals presynaptic to the vibrissa afferents. Taken together, our results emphasize the wide scope for synaptic interactions in the Vmes and suggest that it may be more fruitful to view the Vmes as an integrating center.

Action Potentials↗
PubMed2001

Quantitative trait locus analysis of abnormal circadian period in CS mice.

CS mice show a free-running period (tau) longer than 24 h and rhythm splitting in constant darkness (DD). These features in behavioral circadian rhythms are distinctive as compared with other inbred strains of mice, which exhibit robust free-running rhythms with T shorter than 24 h. To identify the genes affecting tau, quantitative trait locus (QTL) analysis was initially conducted by using 289 F2 mice derived from a cross between CS and C57BL/6J strain. A suggestive QTL (LOD = 3.71) with CS allele increasing tau was detected on the distal region of Chromosome (Chr) 19. Next, using 192 F2 mice from a cross between CS and MSM strain, the presence of the QTL on Chr 19 was examined, and we confirmed the QTL at the genome-wide significant level (LOD = 4.61 with 10.4% of the total variance explained). This QTL was named long free-running period (Lfp). Three other suggestive QTLs (LOD = 3.24-4.28) were mapped to the midportion of Chr 12 in (CSxC57BL/6J)F2 mice, and to the proximal and middle region of Chr 19 in (CSxMSM)F2 mice, respectively, of which, CS alleles for two QTLs on Chr 19 have the effect of lengthening tau. None of these QTLs were mapped to the chromosomal regions of previously described QTLs for tau and known clock genes (Clock, mPer1, Bmal1, mCrv1, mCry2, mTim, and Csnk1e).

Animals↗
PubMed2001

Regional pacemakers composed of multiple oscillator neurons in the rat suprachiasmatic nucleus.

Regional specificities of the dorsal and ventral regions of the suprachiasmatic nucleus (SCN) were examined to elucidate the structure of multioscillator circadian organization. The circadian rhythms of arginine vasopressin (AVP) and vasoactive intestinal polypeptide (VIP) release, and of electrical activity of individual neurons were measured in an organotypic, static slice culture of the SCN obtained from neonatal rats. Five days after the start of culture, robust circadian rhythms were detected in AVP release with a peak located consistently at the middle of the original light phase, while the 24 h profiles of VIP release were either arrhythmic or rhythmic. In the latter case, a phase delay of 5-7 h was observed in the circadian peak from the AVP rhythm. Multi-channel, extracellular recording revealed that 51 (76.1%) out of 67 firing neurons, examined in the SCN, showed circadian rhythms in their firing rate. The percentage of rhythmic neurons was significantly larger in the dorsal (86.8%) than in the ventral (62.1%) region of the SCN, where the AVP and VIP containing neurons predominate, respectively. Twenty-seven percent of the firing rhythms were almost antiphasic from the majority of rhythms. There was no regional specificity in the distribution of the antiphasic rhythm. These findings, that the dorsal and ventral regions of the SCN both contain circadian pacemakers with different properties that regulate the AVP and VIP release separately, is probably due to differences in the number and, hence, the coupling strength of oscillating neurons.

Action Potentials↗
PubMed2001

Behavioural rhythm splitting in the CS mouse is related to clock gene expression outside the suprachiasmatic nucleus.

CS mice exhibit a spontaneous splitting in the circadian rhythm of locomotor activity under constant darkness, suggesting that they contain two weakly coupled oscillators in the circadian clock system regulating locomotor activity rhythm. In order to clarify whether the two oscillators are located in the suprachiasmatic nucleus (SCN), a site of the master circadian pacemaker in mammals, circadian rhythms in mRNA of mouse Period genes (mPer1, mPer2 and mPer3) in the SCN and cerebral cortex were examined during rhythm splitting by in situ hybridization. In the SCN, mPer1 and mPer2 showed a circadian rhythm with a single peak in both split and unsplit mice. The rhythms of mPer1 and mPer2 were slightly phase delayed during rhythm splitting in reference to the activity onset, but the phase relationship between the two rhythms was not changed. In the cerebral cortex, the expression of mPer1 and mPer2 underwent the bimodal fluctuation with peaks temporally corresponding to split activity components. The unsplit mice showed the circadian rhythms with a single peak. There was no difference in the mPer3 rhythms in either the SCN or the cerebral cortex between the split and unsplit mice. These results indicate that the circadian oscillations of mPer1, mPer2 and mPer3 in the SCN are not related to the rhythm splitting of CS mice. The split rhythms of the CS mice are suggested to be caused by uncoupling of oscillators located outside the SCN from the SCN circadian pacemaker.

Animals↗
PubMed2001

Circadian activity rhythm in methamphetamine-treated Clock mutant mice.

It is well established that the Clock gene is essential for expressing circadian activity rhythms in mammals under constant darkness. The Clock gene product is a positive component of a molecular feedback loop which is assumed to generate the circadian rhythm. On the other hand, chronic treatment of methamphetamine (MAP) induces locomotor activity rhythm in a circadian domain, which is independent of the suprachiasmatic nucleus (SCN) and is driven by a pacemaker outside the SCN. However, it is not known whether the pacemaker outside the SCN possesses a similar molecular mechanism to that in the SCN. Here we show that MAP restores locomotor activity rhythm in arrhythmic homozygous Clock mutant (Clock/Clock) mice under constant darkness. This result indicates that the Clock mutation does not affect the MAP-induced locomotor rhythm.

Animals↗
PubMed2001

Effects of light and sleep stages on heart rate variability in humans.

Effects of light intensity and sleep stages on heart rate variability (HRV) were investigated in young healthy subjects. The low-frequency (LF)/high-frequency (HF) ratio was significantly increased by exposing either to bright lights of 10 000 lx or to extreme darkness (< 0.01 lx), while HF and LF components of HRV were not changed, when compared with those under dim light (100 lx). However, LF was significantly increased at REM sleep, when compared with that at the pre-sleep wake. In contrast, HF was increased at all stages of sleep, and the LF/HF ratio was decreased at slow wave sleep during the baseline night.

Adult↗
PubMed2001

Cytochrome P450 enzymes involved in the metabolic pathway of the histamine 2 (H2)-receptor antagonist roxatidine acetate by human liver microsomes.

Roxatidine acetate hydrochloride (ROX, 2-acetoxy-N-[3-[m-(1-piperidinylmethyl)phenoxy]propyl]acetamide hydrochloride, CAS 78273-80-0), a histamine 2 (H2)-receptor antagonist, has been clinically applied for the treatment of gastritis, gastric and duodenal ulcers. There is no report on the identification of the metabolic enzyme of M-1 (2-hydroxy-N-[3-[m-(1-piperidinylmethyl)phenoxy]propyl]acetamide), the pharmacologically active metabolite, in humans. In this study, the Cytochrome P450 (CYP or P450) enzymes which participate in the metabolism of ROX were identified using human liver microsomes and S9 fractions. M-1 was converted to M-4 (3-[m-(1-piperidinyl-methyl)phenoxy]propylamine) by the enzyme reaction with the S9 but not with microsomes. M-4 was further metabolized to M-5 (3-[m-(1-piperidinylmethyl)phenoxy]propanol) by microsomes. The metabolism was inhibited by coumarin and anti-CYP2A1 serum. (3-[m-(1-piperidinylmethyl)-phenoxy]propionic acid) and M-3 (m-(1-piperidinylmethyl) phenol) formation from M-5 were inhibited by quinidine and anti-CYP2D6 serum. Moreover, M-5 was converted to M-2 and M-3 by cDNA-expressed CYP2D6. In conclusion, this study shows that microsomal enzymes do not participate in the clearance of the active metabolite M-1, CYP2A6 primarily catalyzes M-5 formation from M-4, and CYP2D6 primarily catalyzes M-2 and M-3 formation from M-5 in humans.

Chromatography, High Pressure Liquid↗
PubMed2001

Multiple oscillators in the suprachiasmatic nucleus.

The suprachiasmatic nucleus (SCN) of the hypothalamus is the site of the pacemaker that controls circadian rhythms of a variety of physiological functions. Data strongly indicate the majority of the SCN neurons express self-sustaining oscillations that can be detected as rhythms in the spontaneous firing of individual neurons. The period of single SCN neurons in a dissociated cell culture is dispersed in a wide range (from 20h to 28h in rats), but that of the locomotor rhythm is close to 24h, suggesting individual oscillators are coupled to generate an averaged circadian period in the nucleus. Electrical coupling via gap junctions, glial regulation, calcium spikes, ephaptic interactions. extracellular ion flux, and diffusible substances have been discussed as possible mechanisms that mediate the interneuronal rhythm synchrony. Recently, GABA (gamma-aminobutyric acid), a major neurotransmitter in the SCN, was reported to regulate cellular communication and to synchronize rhythms through GABA(A) receptors. At present, subsequent intracellular processes that are able to reset the genetic loop of oscillations are unknown. There may be diverse mechanisms for integrating the multiple circadian oscillators in the SCN. This article reviews the knowledge about the various circadian oscillations intrinsic to the SCN, with particular focus on the intercellular signaling of coupled oscillators.

Animals↗
PubMed2001

Effect of rotavirus vaccine on Sapporo virus gastroenteritis in Finnish infants.

BACKGROUND: Sapporo-like viruses (SLVs) occur worldwide, but there is limited information about the SLV-associated gastroenteritis outside Japan. METHODS: Stool specimens from 1,432 episodes of gastroenteritis that occurred in children between 2 months and 2 years of age during a rotavirus vaccine trial (776 episodes in placebo-vaccinated and 656 in rotavirus-vaccinated infants) were examined for SLVs using a reverse transcription-PCR assay. The reverse transcription-PCR took advantage of new primers specific for Sapporo virus genetic clusters I, II and III; SV/SV82 (SV/Sapporo virus 82); SV/Lond92 (SV/ London 92); and SV/PV (Parkville virus). RESULTS: SLVs were detected in association with 132 (9.2%) of all episodes; in 80 (5.6%) episodes SLV was the only gastroenteritis virus detected. The epidemic season of SLVs peaked from March to May concurrently with rotaviruses and astroviruses and overlapping withNorwalk-like viruses. Clinically SLV gastroenteritis was characterized by a mild diarrheal disease, being sharply different from the Norwalk-like virus-associated "winter vomiting disease." Rotavirus vaccination did not have any effect on the number of SLV episodes, but the intensity and duration of SLV-associated diarrhea were reduced in rotavirus-vaccinated children compared with placebo-vaccinated children (P = 0.0008). CONCLUSIONS: SLVs are common causative agents of acute gastroenteritis in young Finnish children. SLV disease is characterized by diarrhea, which is usually mild but can be severe. By an unknown mechanism rotavirus vaccine seems to reduce the severity of SLV-associated diarrhea.

Caliciviridae Infections↗
PubMed2001

Clinical severity of Norwalk virus and Sapporo virus gastroenteritis in children in Hokkaido, Japan.

OBJECTIVE: To clarify the clinical significance and etiologic impact of Norwalk virus (NV) and Sapporo virus (SV) in viral gastroenteritis in Japanese children. STUDY DESIGN: Two outbreaks each of NV gastroenteritis and SV gastroenteritis occurring in an infant home in Sapporo, Japan, as well as 95 hospitalized children with acute gastroenteritis were retrospectively evaluated using a 0- to 20-point clinical severity scoring system. RESULTS: The mean severity scores for NV and SV gastroenteritis outbreaks were 7.9 and 5.2, respectively, as compared with 8.4 for rotavirus A gastroenteritis that occurred in the same infant home. Among 95 hospitalized children with acute gastroenteritis, rotavirus A was detected in 47% followed by NV in 18%. SV was not found. CONCLUSION: Our data indicate that NV can cause severe gastroenteritis and is an important etiologic agent in hospitalized cases, whereas SV causes mild gastroenteritis in Japanese children.

Acute Disease↗