Biomedical subjects

Toshihiko Shimizu

Publications and source records attributed to Toshihiko Shimizu.

9 recordsLinked to original sources

PubMed2006

Altered levels of serotonin in lymphoblasts derived from migraine patients.

We previously reported that dysfunctions in the autonomic nervous systems of patients with migraines occur not only in the brain, but throughout the whole body. Serotonin and neuropeptides are also known to have important roles in the pathophysiology of migraine. With this background in mind, we analyzed human lymphoblast cell lines from migraine with aura (MwA) patients to investigate the pathophysiology of migraine. The characteristics of these lymphoblasts and the involvement of the lymphoblasts in serotonin metabolism were examined. The lymphoblasts expressed serotonin receptors as well as some enzymes related to serotonin metabolism. The serotonin level in the MwA lymphoblasts was higher than that in the control cells. However, serotonin uptake into the lymphoblasts in MwA patients was similar to that in the control subjects. These findings suggest that lymphoblasts in MwA patients have altered levels of serotonin metabolism. Moreover, we propose that this lymphoblast cell system could serve as a novel modality for migraine research.

5-Hydroxytryptophan↗

PubMed2006

Interferometric autocorrelation of an attosecond pulse train in the single-cycle regime.

We report on the direct observation of the phase locking of the attosecond pulse train (APT) via interferometric autocorrelation in the extreme ultraviolet region. APT is formed with Fourier synthesis of high-order harmonic fields of a femtosecond laser pulse. Time-of-flight mass spectra of N+, resulting from the Coulomb explosion of N2 absorbing two photons of APT, efficiently yield correlated signals of APT. The measured autocorrelation trace exhibits that the duration of the pulse should be only 1.3 periods of the extreme ultraviolet carrier frequency. A few interference fringes within the short pulse duration clearly show two types of symmetry, which ensure the phase locking between pulses in APT.

Journal Article↗

PubMed2006

Conclusive evidence of an attosecond pulse train observed with the mode-resolved autocorrelation technique.

We report on the direct observation of an attosecond pulse train with a mode-resolved autocorrelation technique. The chirp among the three harmonic fields is specified by analyzing two-photon above-threshold ionization spectra of electrons, resulting in a pulse duration that should be shorter than 450 as, which is, to our knowledge, the first determination of the chirp in the attosecond pulse train with an autocorrelation technique. These results will open the way to full characterization of an attosecond pulse train with its envelope.

Journal Article↗

PubMed2006

Plasma 5-hydroxytryptamine (5-HT) in migraine during an attack-free period.

OBJECTIVE: We measured the plasma 5-HT, 5-hydroxytryptophan (5-HTP), and tryptophan levels in controls, migraine patients with aura (MWA), and migraine patients without aura (MWoA) during an attack-free period. BACKGROUND: Serotonin (5-hydroxytryptamine, 5-HT) has been implicated in the pathophysiology of migraine. The precise relationship between 5-HT and migraine, however, remains unclear. METHODS: Blood samples in controls, MWA, and MWoA patients during an attack-free period were collected from brachial arteries and analyzed using HPLC. RESULTS: The plasma tryptophan and 5-HTP levels were not significantly different between the controls and migraine patients (either MWA or MWoA). However, the plasma 5-HT level in the MWA patients was significantly lower than that in the controls and MWoA patients. CONCLUSIONS: The present data suggest that reduced levels of 5-HT in MWA may result from either a dysfunction in the enzymes involved in serotonin biosynthesis or a dysfunction in 5-HT release or uptake from platelets and lymphocytes. These findings indicate the existence of a serotonin metabolism dysfunction in MWA patients that may differ from the state of serotonin metabolism in MWoA patients.

5-Hydroxytryptophan↗

PubMed2005

Most peptide-containing sensory neurons lack proteins for exocytotic release and vesicular transport of glutamate.

We used multiple-labeling immunohistochemistry and confocal microscopy to examine co-expression of immunoreactivity for vesicular glutamate transporters (VGluTs), synaptic vesicle proteins, and soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins in peptide-containing sensory neurons of guinea pigs, mice, and toads. Axon terminals in the superficial layers of the dorsal horn of the spinal cord with immunoreactivity (IR) for both substance P (SP) and calcitonin gene-related peptide (CGRP) lacked IR for synaptosome-associated protein of 25 kDa (SNAP-25), syntaxin, synaptotagmin, synaptophysin, and synapsin, although adjacent varicosities without neuropeptides had IR for these synaptic proteins. Similarly, peptide-containing axon terminals in the superficial dorsal horn lacked IR for VGluT1 and VGluT2, despite the presence of VGluT2-IR in nearby nonpeptide varicosities. VGluT3-IR was sparse in the dorsal horn of the mouse spinal cord and was not present in peptide-containing axons. Most peripheral terminals of sensory neurons with both SP-IR and CGRP-IR in the skin, viscera, and autonomic ganglia of guinea pigs and mice also lacked IR for synaptic vesicle proteins, SNARE proteins, VGluT1, and VGluT2. In dorsal root ganglia from guinea pigs and mice, most small neurons with IR for both SP and CGRP lacked IR for SNAP-25, VGluT1, and VGluT2. Thus, proteins considered essential for vesicular uptake and exocytotic release of glutamate are not expressed at detectable levels by most sensory neurons containing SP and CGRP in rodents and toads. These data raise the possibility that most peptide-containing sensory neurons may not normally release glutamate as a transmitter.

Amino Acid Transport Systems, Acidic↗

PubMed2005

[Structure and function of nociceptive neuronal receptors].

It has been well known that pain is caused by nociceptive stimulation such as protons (i.e. acidic solutions), heat and capsaicin, a pungent ingredient of chilli peppers. For a long period, the signal transduction mechanism of pain activated by these nociceptive stimuli has not been clarified. Recent advance, especially the identification of TRPV1 receptor (for which capsaicin, protons and heat are ligands), P2X and P2Y receptor (for which ATP is a ligand) and acid sensing ion channel made a remarkable progress in understanding the mechanism of nociceptive neurons. This article reviews the structures and functions of nociceptive neuronal system particularly in TRPV1 receptor, P2X and P2Y receptors.

Humans↗

PubMed2005

[Diagnostic imaging of headache].

The diagnosis of headache is based on the subjective symptom, and it is generally classified into the primary headaches, which have intracranially no abnormality, and the secondary headaches, which have organic abnormality. Neuroimaging examinations, computed tomography (CT) scan, and magnetic resonance imaging (MRI) are useful for differential diagnosis and can perform to rule out vascular malformation, brain tumor, and other pathologies, and to confirm the diagnosis. There are cases of the secondary headaches resembling the primary headaches and patients complaint of pain by complex of them, in those cases, it is necessary to perform more detailed neuroimaging(three dimensional MRA, helical CT and so on). These neuroimaging could contribute to make diagnosis and treatments for the patients.

Cerebrovascular Disorders↗

PubMed2003

Time-resolved Auger decay in CsBr using high harmonics.

The temperature-dependent decay dynamics of innershell holes in CsBr was measured by using high harmonics. The measured lifetime was as short as 1.5 ps at 340 K due to increasing the Auger-allowed final state density in the Urbach exciton tail, whereas it is 1.1 ns at 10 K, determined by radiative recombination. The temperature-dependent Auger lifetime extrapolated to a high temperature corresponds to the fully energy-allowed Auger decay. In the model to be presented, this yields an interatomic Auger decay lifetime of 2.4+3.8/-1.5 fs, in line with a theoretical calculation for NaF.

Journal Article↗

PubMed2002

Interleukin-1 receptor immunoreactivity in sympathetic vascular and non-vascular neurons in guinea-pig coeliac ganglion.

Immunoreactivity (IR) for the interleukin-1 receptor type I (IL1RI) was examined in sympathetic neurons in guinea-pig coeliac ganglion using multiple-labelling immunofluorescence. IL1RI-IR was present in 8% of sympathetic neurons in untreated preparations. The proportion of neurons with IL1RI-IR increased significantly after incubation in interleukin-6 (200 ng/ml) for 2-4 h (16-26% neurons), or after incubation for 4 h without cytokine (16%), with interleukin-1beta (IL1beta, 200 ng/ml; 18%) or tumour necrosis factor-alpha (200 ng/ml; 16%). This increase occurred predominantly in neuropeptide Y-IR, vasoconstrictor neurons. IL1RI-IR also was present in varicose axons, some of which projected from the gut, and in vascular smooth muscle cells and endothelium. These potential binding sites for the proinflammatory cytokine, IL1beta, on vasoconstrictor neurons and blood vessels may modulate sympathetic regulation of intestinal blood flow in inflammatory conditions.

Animals↗