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Biomedical subjects

N Ishii

Publications and source records attributed to N Ishii.

At least 19 recordsLinked to original sources
PubMed2006

Widely tunable soliton frequency shifting of few-cycle laser pulses.

Photonic-crystal fibers are employed to demonstrate widely tunable frequency down-conversion of unamplified 6-fs Ti:sapphire laser pulses through the soliton self-frequency shift induced by the Raman effect. Wavelength shifts as large as 500 nm are achieved for input few-cycle pulses with broadband spectra centered at approximately 820 nm. The central wavelength of the redshifted output of a photonic-crystal fiber is smoothly tuned from the low-frequency edge in the spectrum of the 6-fs Ti:sapphire laser pulse up to 1.35 microm by varying the input energy in the fundamental mode of the fiber.

Journal Article↗
PubMed2006

Effects of temperature gradient correction of carbon dioxide absorbent on carbon dioxide absorption.

BACKGROUND: The effects of temperature gradients in CO(2) absorbents on water content and CO(2) absorption are not clear. We constructed a novel temperature gradient correction (TGC) canister, and investigated the effects of temperature gradient correction on the water content and longevity (time to exhaustion) of CO(2) absorbent using a simulated anaesthesia circuit. METHODS: Experiments were divided into two groups according to the type of canister used: the TGC canister (n=6) or the conventional canister (n=6). One kilogram of fresh CO(2) absorbent was placed into the canister. The anaesthetic ventilator was connected to a 3 litre bag and 300 ml min(-1) of CO(2) was introduced. Oxygen (500 ml min(-1)) was used as fresh gas. The anaesthetic ventilator was set at a ventilatory frequency of 12 bpm, and tidal volume was adjusted to 700 ml. RESULTS: Before the experiment, the water content of the fresh CO(2) absorbent in the conventional canister and TGC canister was 16.1 (0.9)% and 15.7 (1.1)%, respectively. After the experiment, the water content of CO(2) absorbent near the upper outer rim of the canister increased to 32.4 (0.7)% in the conventional canister, but increased to only 20.6 (1.3)% in the TGC canister (P<0.01). The longevity of CO(2) absorbent in the conventional canister and TGC canister was 434 (9) min and 563 (13) min (P<0.01). CONCLUSIONS: Temperature gradient correction prevented a local excessive increase in water content and improved the longevity of CO(2) absorbent.

Absorption↗
PubMed2006

Diffraction-arrested soliton self-frequency shift of few-cycle laser pulses in a photonic-crystal fiber.

The balance between diffraction and index-step guiding in photonic-crystal fibers is controlled by modifying the fiber structure, leading to different wavelength dependences of the effective mode area and providing a mechanism to control nonlinear-optical phenomena. In optical fibers with a steep profile, the guided mode of the light field tends to become much less compact with an increase in radiation wavelength, slowing down the Raman-induced soliton self-frequency shift of an ultrashort laser pulse. A reduction of the soliton self-frequency shift is demonstrated for input laser pulses.

Journal Article↗
PubMed2006

Parametric amplification of few-cycle carrier-envelope phase-stable pulses at 2.1 microm.

We demonstrate an optical parametric chirped-pulse amplifier producing infrared 20 fs (3-optical-cycle) pulses with a stable carrier-envelope phase. The amplifier is seeded with self-phase-stabilized pulses obtained by optical rectification of the output of an ultrabroadband Ti:sapphire oscillator. Energies of -80 microJ with a well-suppressed background of parametric superfluorescence and up to 400 microJ with a superfluorescence background are obtained from a two-stage parametric amplifier based on periodically poled LiNbO3 and LiTaO3 crystals. The parametric amplifier is pumped by an optically synchronized 1 kHz, 30 ps, 1053 nm Nd:YLF amplifier seeded by the same Ti:sapphire oscillator.

Journal Article↗
PubMed2006

A novel neuroprotective compound FR901459 with dual inhibition of calcineurin and cyclophilins.

Brain ischemia leads to severe damage in the form of delayed neuronal cell death. In our study, we show that the marked neuroprotection of the new immunosuppressant FR901495 in forebrain ischemia is due not only to inhibition of calcineurin, but also to protection against mitochondrial damage caused by mitochondrial permeability transition pore formation through cyclophilin D, one of the prolyl cis/trans isomerase family members. These findings shed light on the clinical application and development of new drugs for the treatment of ischemic damage in the brain as well as in the heart and liver.

Animals↗
PubMed2006

Search for novel gene markers of traumatic brain injury by time differential microarray analysis.

Neuronal and glial cell death caused by axonal injury sometimes contributes to whole brain pathology after traumatic brain injury (TBI). We show that neuroprotection by 2 types of immunosuppressants, cyclosporin A (CsA) and tacrolimus (FK506), in a cryogenic brain injury model results from inhibition of calcineurin and protection from mitochondrial damage caused by formation of a mitochondrial permeability transition pore induced by cyclophilin D (CyPD), one of the prolyl cis/trans isomerase family members. We evaluated why CsA is neuroprotective by microarray analysis of gene expression in the cryogenic brain injury rat model. Analyses of expression patterns demonstrated that expression of over 14,000 genes changed between the groups with and without CsA treatment, and about 350 genes among them were extracted showing a significant difference. We learned that the differential expression of several gene targets showed specific patterns in a time-dependent manner. These results may help elucidate the mechanisms of neuronal cell death after TBI and the neuroprotective effects of CsA after TBI.

Animals↗
PubMed2005

Nonlinear-optical spectral transformation of few-cycle laser pulses in photonic-crystal fibers.

Photonic-crystal fibers with special dispersion profiles are shown to provide a high efficiency of spectral transformation of chirped sub-6-fs Ti:sapphire laser pulses. With the wavelength of zero group-velocity dispersion of the fiber lying within the broad spectrum of the input few-cycle pulse, the output spectra feature well-resolved spectral peaks, indicative of soliton self-frequency shift, four-wave mixing, and Cherenkov emission of dispersive waves. We demonstrate that up to 3% of radiation energy at the output of the fiber can be confined within a spectrally isolated soliton peak centered at , which is ideally suited as a seed for Nd:YAG- and ytterbium-based laser devices.

Journal Article↗
PubMed2005

Multimillijoule chirped parametric amplification of few-cycle pulses.

The concept of optical parametric chirped-pulse amplification is applied to attain pulses with energies up to 8 mJ and a bandwidth of more than 100 THz. Stretched broadband seed pulses from a Ti:sapphire oscillator are amplified in a multistage noncollinear type I phase-matched beta-barium borate parametric amplifier by use of an independent picosecond laser with lock-to-clock repetition rate synchronization. Partial compression of amplified pulses is demonstrated down to a 10-fs duration with a down-chirped pulse stretcher and a nearly lossless compressor comprising bulk material and positive-dispersion chirped mirrors.

Journal Article↗
PubMed2005

The role of stress in ageing: research on the nematode, Caenorhabditis elegans.

The nematode Caenorhabditis elegans has proven a robust genetic model for studies of aging and the roles of stress. In this review we focus on the genetics of select long-lived and short-lived mutants of C. elegans that have proven useful in revealing the relationships that exist between oxidative stress and life span. The former are known to be controlled by an insulin/insulin-like signaling pathway, while the latter are affected by mitochondrial functions.

Aging↗
PubMed2004

Potential impact of orthotic gait exercise on natural killer cell activities in thoracic level of spinal cord-injured patients.

STUDY DESIGN: Prospective before-after trial. OBJECTIVE: To examine the changes of natural killer (NK) cell activity in response to orthotic gait exercise in thoracic level of spinal cord-injured (SCI) patients. SETTING: National Rehabilitation Center for Persons with Disabilities, Japan. METHODS: In all, 10 thoracic level of SCI patients (ranging Th5-Th12), who experienced orthotic gait training, participated in this study. NK cell activity at an effector:target (E/T) ratio (20:1) was examined in a sample of peripheral blood taken before and just after orthotic gait exercise for 20 min. On a separate day, to evaluate the physical intensity of the orthotic gait exercise, cardiorespiratory responses at rest and during exercise were measured. RESULTS: The resting value of the NK cell activity in our SCI patients was remarkably lower than that in normal subjects reported in previous studies. The NK cell activity was significantly increased through a 20 min orthotic gait exercise (pre versus post; 12.7+/-5.28 versus 17.76+/-6.71, P<0.05). The steady-state value of oxygen (VO2) and heart rate (HR) were 18.13+/-3.92 ml/kg and 142.53+/-19.84 b/min, respectively. It was noteworthy that a patient who showed decrement of NK cell activity in response to exercise had the highest level of injury (Th5), and showed the higher energy cost of orthotic gait. CONCLUSION: These findings suggested that the orthotic gait exercise has the potential to enhance the immune function for SCI persons, although patients with a higher level of SCI may have some difficulties. SPONSORSHIP: Mitsui Sumitomo Insurance Welfare Foundation

Adult↗
PubMed2004

Epidermolysis bullosa acquisita sera react with distinct epitopes on the NC1 and NC2 domains of type VII collagen: study using immunoblotting of domain-specific recombinant proteins and postembedding immunoelectron microscopy.

BACKGROUND: The sera of epidermolysis bullosa acquisita (EBA) react with type VII collagen, a major component of anchoring fibrils, in which the major epitopes have been considered to be present in the N-terminal noncollagenous (NC) 1 domain. OBJECTIVES: To determine whether there are also epitopes in the C-terminal NC2 domain, and to determine their ultrastructural localization. METHODS: Immunoblotting using recombinant proteins of the NC1 and NC2 domains of type VII collagen, and postembedding immunoelectron microscopy. RESULTS: Twenty of 28 EBA sera tested reacted with the NC1 domain and eight sera reacted with the NC2 domain. The sera that reacted with the NC1 domain showed immunoreactivity within the lamina densa and the sera that reacted with the NC2 domain showed immunoreactivity in the dermis 300-360 nm below the lamina densa. CONCLUSIONS: This study clearly identified the presence of epitopes in the NC2 domain, and showed that the epitope in the NC1 domain is present in the lamina densa and that the epitope in the NC2 domain is in the dermis below the lamina densa.

Collagen Type VII↗
PubMed2004

Immunolocalization of target autoantigens in IgA pemphigus.

IgA pemphigus is a rare autoimmune bullous disease characterized by IgA deposition at keratinocyte cell surfaces. Clinically and histologically, IgA pemphigus is divided into two major subtypes: subcorneal pustular dermatosis (SPD) type and intraepidermal neutrophilic IgA dermatosis (IEN) type. Using cDNA transfection and living cell immunofluorescence, we previously showed that desmocollin 1, one of the desmosomal cadherins, is the autoantigen in SPD-type IgA pemphigus, but the autoantigen in IEN type is still unclear. In the present study we investigated antigen localization by postembedding immunoelectron microscopy. We examined three sera each of SPD-type and IEN-type IgA pemphigus. In SPD-type, gold particles were observed predominantly in the extracellular spaces between keratinocytes at desmosomes, although a few particles were observed in the intracellular domain at the desmosomal attachment plaques. In IEN type, the gold particles were observed mainly in the intercellular spaces in nondesmosomal areas. These results provide evidence that the IgA in the sera of SPD-type IgA pemphigus reacts with the extracellular domain of desmocollins. In contrast, the autoantigen for IEN type may in fact not be a component of desmosomes. IEN-type IgA pemphigus may be the first member of the pemphigus group of autoimmune bullous dermatoses that reacts with a nondesmosomal transmembranous protein.

Autoantigens↗
PubMed2004

Endotoxin stimulates monocyte-endothelial cell interactions in mouse intestinal Peyer's patches and villus mucosa.

Although monocyte-endothelial cell interactions represent an initial step in controlling the recruitment of monocytes in inflamed tissues, their dynamic processes in microvessels of lymphoid (Peyer's patches) and non-lymphoid (villus) regions in gut-associated lymphoid tissue remain poorly understood. We monitored the migration of fluorescence-labelled monocytes derived from the spleen in intestinal microvessels with or without lipopolysaccharide (LPS) treatment and investigated the role of adhesion molecules, P-selectin, vascular cell adhesion molecule (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1). In control mice, there were few interactions between infused monocytes and the endothelium of intestinal microvessels. The monocyte-endothelial interactions (both rolling and adhesion) were significantly increased in intestinal microvessels of LPS-treated mice compared with those in controls. Anti-P-selectin monoclonal antibody (MoAb) significantly suppressed the LPS-induced increase in monocyte rolling in postcapillary venules of Peyer's patches and submucosal venules. Anti-VCAM-1 MoAbs significantly suppressed the LPS-induced increase in monocyte adhesion to postcapillary venules (PCVs) of Peyer's patches, submucosal venules, and villus capillaries. In contrast, anti-ICAM-1 MoAb significantly suppressed the number of adherent monocytes in PCV of Peyer's patches but not in submucosal venules or villus capillaries. These observations demonstrated that LPS treatment resulted in a significant increase in recruitment of monocytes both in microvessels of lymphoid and non-lymphoid regions and that P-selectin, VCAM-1 and ICAM-1 appeared to play important roles in LPS-induced interactions.

Animals↗
PubMed2003

Calcineurin and cyclophilin D are differential targets of neuroprotection by immunosuppressants CsA and FK506 in ischemic brain damage.

The search for an effective treatment for global ischemia following cardiac arrest has proved to be very difficult. However, studies by Uchino et al. show that the immunosuppressant cyclosporin A (CsA), when administered in such a way that the drug can bypass the blood brain barrier (BBB), dramatically reduces ischemic damage in rat forebrain preparations. An alternative immunosuppressant, FK506, is apparently less efficacious. Both CsA and FK506 are specific inhibitors of immunophilins, (CsA inhibits cyclophilins, FK506 inhibits FKBPs), and of calcineurin, a type 2B Ser/Thr phosphatase that is abundant in the central nervous system. The superiority of CsA may be partly attributable to its selective amelioration of mitochondrial damage, as assayed in vivo and in vitro. Our results suggest that pathways involving calcineurin and cyclophilins, particularly mitochondrial cyclophilin D, play pivotal roles in the development of ischemic brain damage. The present findings may inform the search for new drugs in the treatment of global ischemic damage to the brain, and in other organs.

Animals↗
PubMed2003

Ecological effects of various toxic agents on the aquatic microcosm in comparison with acute ionizing radiation.

The purpose of this study was an evaluation of the effect levels of various toxic agents compared with acute doses of ionizing radiation for the experimental model ecosystem, i.e., microcosm mimicking aquatic microbial communities. For this purpose, the authors used the microcosm consisting of populations of the flagellate alga Euglena gracilis as a producer, the ciliate protozoan Tetrahymena thermophila as a consumer and the bacterium Escherichia coli as a decomposer. Effects of aluminum and copper on the microcosm were investigated in this study, while effects of gamma-rays, ultraviolet radiation, acidification, manganese, nickel and gadolinium were reported in previous studies. The microcosm could detect not only the direct effects of these agents but also the community-level effects due to the interspecies interactions or the interactions between organisms and toxic agents. The authors evaluated doses or concentrations of each toxic agent which had the following effects on the microcosm: (1) no effects; (2) recognizable effects, i.e., decrease or increase in the cell densities of at least one species; (3) severe effects, i.e., extinction of one or two species; and (4) destructive effects, i.e., extinction of all species. The resulting effects data will contribute to an ecological risk assessment of the toxic agents compared with acute doses of ionizing radiation.

Animals↗
PubMed2003

Responses to serotonin (5HT) in isolated corpus cavernosum penis of rabbit.

This study was aimed at determining serotonin (5-hydroxytryptamine: 5HT) receptor subtypes participating in 5HT-induced response in the isolated corpus cavernosum penis (CCP) of rabbits. 5HT contracted the CCP in a concentration-dependent manner. Both WAY100635 (5HT(1A) antagonist) and LY53857 (5HT(2) antagonist) concentration-dependently suppressed the 5HT-induced contraction. The suppression of the 5HT-induced contraction by ketanserin (5HT(2A) antagonist) was weaker than that by LY53857. LY278584 (5HT(3) antagonist) did not affect the 5HT-induced contraction. SDZ205557 (5HT(4) antagonist) showed a tendency to potentiate the 5HT-induced contraction. The above results suggest that 5HT(1A) and 5HT(2) receptor subtypes partially participate in the contractile response to 5HT in rabbit CCP, and the potentiation by SDZ205557 of the 5HT-induced contraction implies the existence of dual contractile and relaxing responses to 5HT via 5HT(1) and 5HT(2), and 5HT(4) receptors, respectively. The relaxing response to 5HT(4) receptor stimulation may be masked by 5HT-induced contraction.

4-Aminobenzoic Acid↗