Biomedical subjects

Takashi Nakagawa

Publications and source records attributed to Takashi Nakagawa.

At least 19 recordsLinked to original sources

PubMed2026

Epidermal NAD+ deficiency induces IL-36-mediated skin inflammation and acanthosis.

Nicotinamide adenine dinucleotide (NAD+) is essential for cellular metabolism, DNA repair, and stress responses. NAD+ is synthesized from nicotinamide, nicotinic acid (collectively termed niacin), and tryptophan. In humans, deficiencies in these nutrients result in pellagra, marked by dermatitis, diarrhea, and dementia. The dermatitis associated with pellagra typically manifests as photodermatosis in sun-exposed areas. This study examined the effects of NAD+ deficiency on skin homeostasis using epidermis-specific Nampt-conditional KO (Nampt-cKO) mice. These mice displayed substantial NAD+ depletion, reduced poly(ADP-ribose) polymerase (PARP) activity, and increased DNA damage. Consequently, Nampt-cKO mice developed spontaneous skin inflammation and epidermal hyperplasia. RNA-seq and IHC analyses demonstrated increased IL-36 cytokine expression, suggesting that DNA repair-related genomic stress triggers keratinocyte-driven IL-36 production, which promotes inflammation. Furthermore, reduced COL17A1 expression and elevated thymic stromal lymphopoietin (TSLP) levels were observed. NAD+ repletion by transdermal supplementation of nicotinamide mononucleotide (NMN) suppressed the rise of IL-36 levels and skin inflammation. These findings underscore the importance of Nampt-mediated NAD+ metabolism for epidermal stability and indicate that NAD+ depletion may contribute to IL-36-mediated skin inflammation, offering insights for therapeutic strategies in inflammatory skin disorders.

Animals↗

PubMed2006

A new index of the autonomic nervous balance and its clinical usefulness; a power law 1/f like scale of a spectral analysis of the heart rate variability.

OBJECTIVE: This study was undertaken to develop a new autonomic scoring scale distinct from the conventional sympathetic or parasympathetic parameters cardiac autonomic response. METHODS: The parameters were obtained from a log-log scale of frequency (f ) vs. power spectral (P) amplitude of heart rate variability (HRV). A gradient value in which the graph decreases towards a high frequencies on the X-axis, while showing an absolute value beta itself based on the formula 'P = f (-beta)' was newly named the 'Balance index' by implying a balanced state in the living body. The index was categorized into four bands based on the appearance of the whole frequency ranges (T-Balance Index). Therefore, we compared the responses of the following groups: the patient test group (Group PT), the normal test group (Group NT), and the normal non-test group (group NN). RESULTS: Significant differences in parameters were observed among the three groups. In addition, the difference between the 'High-side Balance Index' and the 'Low-side Balance Index' was 0.75 +/- 0.12 vs. 0.07 +/- 0.04 (p < 0.005) for groups NT vs. PT. This novel analyzing method was useful for evaluating the subtle changes in a living body to regulate the living-power (strength of vitality). Moreover, the difference between the 'T-Balance Index' and 'SV-Balance Index' was 0.18 +/- 0.12 vs. -0.21 +/- 0.15 (p < 0.01) for groups NT vs. PT. CONCLUSIONS: One application of new parameters 'Balance Index' is its ability to evaluate the vital or emotional functions of unconscious patients in a critical condition undergoing a sense challenge test. This method assists in improving our ability to measure the early stage of conscious recovery with greater accuracy by using our novel analysis method for performing senses challenge test, with the aid of media such as music.

Adolescent↗

PubMed2006

Mitochondrial membrane permeability transition and cell death.

Mitochondria are important organelles for energy production, Ca2+ homeostasis, and cell death. In recent years, the role of the mitochondria in both apoptotic and necrotic cell death has received much attention. In apoptotic and necrotic death, an increase of mitochondrial membrane permeability is considered to be one of the key events, although the detailed mechanism remains to be elucidated. The mitochondrial membrane permeability transition (MPT) is a Ca2+-dependent increase in the permeability of the mitochondrial membrane that leads to loss of Deltapsi, mitochondrial swelling, and rupture of the outer mitochondrial membrane. The MPT is thought to occur after the opening of a channel, which is termed the permeability transition pore (PTP) and putatively consists of the voltage-dependent anion channel (VDAC), the adenine nucleotide translocator (ANT), cyclophilin D (Cyp D: a mitochondrial peptidyl prolyl-cis, trans-isomerase), and other molecule(s). Our studies of mice lacking Cyp D have revealed that it is essential for occurrence of the MPT and that the Cyp D-dependent MPT regulates some forms of necrotic cell death, but not apoptotic death. We have also shown that two anti-apoptotic proteins, Bcl-2 and Bcl-x(L), block the MPT by directly inhibition of VDAC activity. Here we summarize a role of the MPT in cell death.

Animals↗

PubMed2006

Photometric recording of transmembrane potential in outer hair cells.

Cochlear outer hair cells (OHCs) are polarized epithelial cells that have mechanoelectrical transduction channels within their apical stereocilia and produce electromotile force along their lateral wall. Phase shifts, or time delays, in the transmembrane voltage occurring at different axial locations along the cell may contribute to our understanding of how these cells operate at auditory frequencies. We developed a method to optically measure the phase of the OHC transmembrane potential using the voltage-sensitive dye (VSD) di-8-ANEPPS. The exit aperture of a fibre-optic light source was driven in two dimensions so that a 24 microm spot of excitation light could be positioned along the length of the OHC. We used the whole-cell patch-clamp technique in the current-clamp mode to stimulate the OHC at the base. The photometric response and the voltage response were monitored with a photodetector and patch-clamp amplifier, respectively. The photometric response was used to measure the regional changes in the membrane potential in response to maintained (dc) and sinusoidal (ac) current stimuli applied at the base of the cell. We used a neutral density filter to lower the excitation light intensity and reduce phototoxicity. A sensitive detector and lock-in amplifier were used to measure the small ac VSD signal. This permitted measurements of the ac photometric response below the noise floor of the static fluorescence. The amplitude and phase components of the photometric response were recorded for stimuli up to 800 Hz. VSD data at 400-800 Hz show the presence of a small phase delay between the stimulus voltage at the base of the cell and the local membrane potential measured along the lateral wall. Results are consistent with the hypothesis that OHCs exhibit inhomogeneous membrane potentials that vary with position in analogy with the voltage in nerve axons.

Animals↗

PubMed2006

Bilirubin potentiates inhibitory synaptic transmission in lateral superior olive neurons of the rat.

Bilirubin is a well-known neurotoxin that can result in multiple neurologic deficits. Previous studies have suggested that bilirubin affects aspects of synaptic transmission; however the acute effects of bilirubin on synaptic transmission have not been examined in real-time. In this study, using whole-cell voltage-clamp recordings, we observed the effect of bilirubin on inhibitory postsynaptic currents (IPSC) in postnatal 13-15-day-old neurons dissociated from lateral superior olive nuclei (LSO), one of the brainstem auditory nucleus that are highly vulnerable to bilirubin. The results showed that 10(-5)M bilirubin increased the frequency of spontaneous IPSC without causing change in their amplitudes or in the response to bath applied glycine, suggesting a presynaptic locus for the action. In the presence of tetrodotoxin, the frequency of miniature IPSC was also potentiated by 10(-5)M bilirubin. The facilitation by bilirubin was concentration dependent and increased with an increase in exposure time. Bicuculline only partially reduced the action of bilirubin. The action of bilirubin was observed in extracellular Ca(2+)-free ([Ca(2+)](o) free) solution but was fully occluded by pretreatment with BAPTA-AM in [Ca(2+)](o) free solution. Thus, in LSO neurons, bilirubin facilitates inhibitory synaptic transmission, in a manner independent of voltage-activated Na(+) and Ca(2+) channels but dependent on presynaptic [Ca(2+)](i). The increase of inhibitory synaptic transmission in response to acute bilirubin is a novel effect of bilirubin on the central nervous system and may have implications for neurotoxicity and the impairment of auditory transduction seen in hyperbilirubinemia.

Animals↗

PubMed2006

Intractable otitis media with eosinophils: Importance of diagnosis and validity of treatment for hearing preservation.

This study investigated hearing levels in cases of intractable otitis media with eosinophils and validated the treatment strategy. Medical charts were reviewed retrospectively. The diagnosis was made when the proportion of eosinophils in middle ear secretions exceeded 10%. Twelve patients were identified and treated with an antihistaminergic agent, leukotriene receptor antagonist and topical steroid. The air-bone conductance gap decreased significantly with the relief of subjective symptoms. Bone conduction hearing levels at 4 and 8 kHz were higher than at lower frequencies. There was a significant correlation between subjective symptom duration and bone conduction hearing level at 8 kHz, which diminished with treatment. Compared with suppurative otitis, active otitis with eosinophilia damages high-tone sensory hearing in a time-dependent manner, and antiallergic treatment prevents progression of the high-tone sensory hearing loss. We emphasize the importance of diagnosis and the validity of treatment for intractable otitis media with eosinophils.

Adult↗

PubMed2006

Squamous cell carcinoma of the external auditory canal and middle ear: an operation combined with preoperative chemoradiotherapy and a free surgical margin.

OBJECTIVE: Treatment outcomes for squamous cell carcinoma of the temporal bone were evaluated regarding stage, therapeutic strategy, and prognostic factors. STUDY DESIGN: Retrospective case review. SETTING: University hospital and outpatient clinic. PATIENTS: Twenty-five patients with primary squamous cell carcinoma of the external auditory canal and middle ear. INTERVENTION: Preoperative chemoradiotherapy and radiotherapy were used in 7 of 12 patients. Lateral temporal bone resection was performed for the lesions not beyond the tympanic membrane. Subtotal temporal bone resection was chosen for lesions extending to the middle ear cavity when there was no invasion to the pyramidal apex, carotid canal, or dura or metastasis. Others were conservatively treated by chemoradiotherapy. When the performance status was poor or an agreement regarding the operation could not be reached, the treatment was modified. MAIN OUTCOME MEASURE: Estimated survival rates. RESULTS: The 3-year estimated survival for T1 and T2 lesions was 100%. The 5-year estimated survival for T3 and T4 lesions was 80% and 35%, respectively. The 5-year estimated survival improved up to 75% for T4 tumors with operation and 16% for those without operation after 47 months. The tumor-free surgical margin is significantly related to patient survival in T3 and T4 lesions. Multivariate analysis predicted that concomitant chronic otitis media and positive lymph nodes were significantly associated with poorer survival. CONCLUSION: The tumor-free surgical margin was important to survival. When T4 lesions did not involve the pyramidal apex, carotid canal, dura, or any lymph nodes, the surgical intervention improved the estimated survival rate to a level as good as T3 lesions.

Adult↗

PubMed2005

GABA-induced response in spiral ganglion cells acutely isolated from guinea pig cochlea.

The physiological and pharmacological properties of gamma-aminobutyric acid (GABA)-induced responses were investigated in acutely isolated spiral ganglion cells (SGCs) of guinea pig by using either a nystatin-perforated patch recording configuration or a conventional whole-cell patch recording mode combined with rapid drug application. GABA and GABA(A) subtype receptor agonist, muscimol, induced inward currents in a concentration-dependent manner in 74% of all cells. The current-voltage relationship for the GABA response indicated the GABA-induced current in SGCs is carried by Cl-. Bicuculline (BIC), strychnine (STR), and picrotoxin (PTX) suppressed the GABA response in a concentration-dependent manner. BIC and STR, and PTX blocked the GABA response in a competitive manner and in a non-competitive manner, respectively. For inorganic antagonists, Cd2+ and Ni2+ also inhibited the GABA response. On the other hand, Zn2+ failed to suppress the GABA response in SGCs. An antibiotic, benzylpenicillin, suppressed the GABA response. The GABA response was augmented by both a barbiturate derivative, pentobarbital (PB), and a benzodiazepine derivative, diazepam. The results suggest clearly that the physiological and pharmacological characteristics of GABA(A) receptor on acutely isolated guinea pig SGCs are quite similar to the common GABA(A) receptor found in other sensory ganglion cells.

Animals↗

PubMed2005

Cyclophilin D-dependent mitochondrial permeability transition regulates some necrotic but not apoptotic cell death.

Mitochondria play an important role in energy production, Ca2+ homeostasis and cell death. In recent years, the role of the mitochondria in apoptotic and necrotic cell death has attracted much attention. In apoptosis and necrosis, the mitochondrial permeability transition (mPT), which leads to disruption of the mitochondrial membranes and mitochondrial dysfunction, is considered to be one of the key events, although its exact role in cell death remains elusive. We therefore created mice lacking cyclophilin D (CypD), a protein considered to be involved in the mPT, to analyse its role in cell death. CypD-deficient mice were developmentally normal and showed no apparent anomalies, but CypD-deficient mitochondria did not undergo the cyclosporin A-sensitive mPT. CypD-deficient cells died normally in response to various apoptotic stimuli, but showed resistance to necrotic cell death induced by reactive oxygen species and Ca2+ overload. In addition, CypD-deficient mice showed a high level of resistance to ischaemia/reperfusion-induced cardiac injury. Our results indicate that the CypD-dependent mPT regulates some forms of necrotic death, but not apoptotic death.

Animals↗

PubMed2005

Clinical features of patients with GJB2 (connexin 26) mutations: severity of hearing loss is correlated with genotypes and protein expression patterns.

Mutations in the GJB2 (connexin 26, Cx26) gene are the major cause of nonsyndromic hearing impairment in many populations. Genetic testing offers opportunities to determine the cause of deafness and predict the course of hearing, enabling the prognostication of language development. In the current study, we compared severity of hearing impairment in 60 patients associated with biallelic GJB2 mutations and assessed the correlation of genotypes and phenotypes. Within a spectrum of GJB2 mutations found in the Japanese population, the phenotype of the most prevalent mutation, 235delC, was found to show more severe hearing impairment than that of V37I, which is the second most frequent mutation. The results of the present study, taken together with phenotypes caused by other types of mutations, support the general rule that phenotypes caused by the truncating GJB2 mutations are more severe than those caused by missense mutations. The present in vitro study further confirmed that differences in phenotypes could be explained by the protein expression pattern.

Adolescent↗

PubMed2005

Sonochemical preparation of composite nanoparticles of Au/gamma-Fe2O3 and magnetic separation of glutathione.

We prepared Au/gamma-Fe2O3 composite nanoparticles by sonochemically reducing Au(III) ions employing no stabilizer in the aqueous solution to form stable Au nanoparticles and allowing them to attach onto the surface of gamma-Fe2O3 particles with an average size of 21 nm. Size of the formed Au nanoparticle depended on the initial concentration of Au(III) ions. The number of the Au nanoparticles, supported on each gamma-Fe2O3 particle was controlled by changing the relative amounts of Au(III) ions and gamma-Fe2O3 particles. The composite nanoparticles exhibited a high affinity with glutathione, a tripeptide with mercapto group so that separation and manipulation of glutathione in aqueous solutions could be performed by application of external magnetic field. Because the surfaces of the Au nanoparticles were not shielded by any stabilizers, or naked, sonochemically prepared Au/gamma-Fe2O3 composite nanoparticles seemed to show stronger affinity to the glutathione than those by the radiochemical method.

Benzamides↗

PubMed2005

Structural analysis of sonochemically prepared Au/Pd nanoparticles dispersed in porous silica matrix.

Bimetallic Au/Pd nanoparticles supported on a silica matrix were prepared by an ultrasonic technique. The samples heat-treated at 100, 200, 300 and 400 degrees C were examined with techniques of XRD (X-ray diffraction), TEM and XAS (X-ray absorption spectrometry) for studying correlation between their structure and the catalytic activity of hydrogenation of cyclohexene. Even after the heat treatment at 400 degrees C, the particles were smaller than 20 nm and well dispersed in the matrix without agglomeration nor sintering. Results of the XRD, TEM and XAS indicated that the as-prepared particles have a core/shell structure of Au/Pd and transform into a random alloy at 300 degrees C. The catalysis seemed to be deactivated by alloying.

Journal Article↗

PubMed2004

The effect of cyclin D1 overexpression in human head and neck cancer cells.

Overexpression of cyclin D1 in head and neck cancer has been suggested to be a poor prognostic factor. To understand the role of cyclin D1 expression in head and neck cancer, we overexpressed cyclin D1 in TU182 (a cell line derived from pharyngeal cancer) using a retroviral vector. Stable transfectants were isolated by neomycin (G418) selection. Compared to the parental and control-vector transfected cells, the cyclin D1 transfected cells revealed a decrease of the G1/G0 population and resulted in continuous proliferation under low serum conditions. Proliferation assays revealed an increase in resistance to cisplatin in cyclin D1 overexpressing cells. These observation suggest that deregulation of cyclin D1 may reduce growth factor requirements and contribute to the resistance to some chemotherapeutic agents among head and neck cancer patients.

Antineoplastic Agents↗

PubMed2004

Effects of the angiotensin-I converting enzyme inhibitor perindopril on tumor growth and angiogenesis in head and neck squamous cell carcinoma cells.

PURPOSE: Recently, it has been reported that angiotensin-I converting enzyme (ACE) inhibitors have anticancer activity. In particular, the ACE inhibitor, perindopril, significantly inhibits tumor growth and angiogenesis in hepatocellular carcinoma cells along with suppression of the VEGF level. However, the mechanisms of suppression of the VEGF level are still unclear, and there are no previous reports on this subject related to head and neck squamous cell carcinoma (HNSCC). In some previous studies, angiotensin II, which is produced from angiotensin I by ACE, directly stimulates VEGF expression. METHODS: In the present study, we focused upon angiotensin II, and investigated the effect of perindopril on VEGF expression, angiogenesis, and tumor development of HNSCC with in vitro and in vivo studies. RESULTS: In the in vitro cell proliferation assays, there was no significant difference between the perindopril-treated group and the control group. However, the perindoprilat-treated group showed a significant reduction in mRNA expression of VEGF and inhibited the induction activity of the VEGF promoter in comparison to the control group. Perindoprilat treatment also significantly suppressed angiotensin II production in vitro. In the in vivo studies, perindopril had a significant inhibitory effect on tumor growth, and reduced blood vessel formation surrounding the tumors. CONCLUSIONS: Our findings suggest that perindopril has no direct cytotoxicity against tumor cells, but has a potential to inhibit tumor growth due to suppression of VEGF-induced angiogenesis in vivo. Angiotensin II might have an important role in carcinogenesis, and the antiangiogenic activity of perindopril is at least partly mediated by angiotensin II inhibition. The ACE inhibitor perindopril has clinical potential as a useful antitumor agent.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed2004

A computer image processing system for quantification of zebrafish behavior.

The tropical zebrafish (Danio rerio) has frequently been used for investigating developmental biology. Here, we developed a computer image processing system for quantifying zebrafish behavior. We could acquire an image of zebrafish freely moving in an aquarium using a CCD camera through a graphic I/O board. To acquire the image of moving zebrafish in real time, we required high spatial (256 x 256 pixels) and temporal (10 frames/s) resolution. Such a high speed of data analysis was accomplished using a skipping search method. By using a small aquarium, trackings of newborn zebrafish could be traced. The velocity of adult zebrafish (7.2 cm/s) was far faster than that of newborn zebrafish (1.8 cm/s). Furthermore, by separation of occluded images of two fish, we could acquire images of the two zebrafish. They behaved as in a school in which one fish chased the other. The chasing was defined by the distance, angle and approach of the two fishes. The chasing ratio of pairs of zebrafish was 37%, whereas those of pairs of different fish were significantly reduced to less than 20%. The present image processing system is a very useful tool for quantitatively scoring the schooling behavior of multiple fish.

Animals↗

PubMed2003

Unusual reactions of N-allylic difluoroenamines under thermal conditions.

N-Allylic difluoroenamines exhibited unusual behaviors under thermal conditions; N-allyl difluoroenamines in refluxing xylene afforded not only aza-Claisen rearrangement products, but also 2-azabicyclo[2.1.1]hexanes, whose formation could be explained via intramolecular [2+2]-cycloaddition, whilst N-prenyl difluoroenamine underwent an ene reaction to give the pyrrolidine as a sole product.

Journal Article↗

PubMed2003

Comparison of LNS-AmB, a novel low-dose formulation of amphotericin B with lipid nano-sphere (LNS), with commercial lipid-based formulations.

Three lipid-based delivery systems (AmBisome, Amphocil, and Abelcet) for amphotericin B (AmB) have been marketed to overcome the disadvantages associated with the clinical use of AmB. However, to show their efficacy, they need to be administered at higher doses than the conventional dosage form, Fungizone. In this study, we compared LNS-AmB, our new low-dose therapeutic system for AmB using lipid nano-sphere (LNS), with these commercial formulations in terms of their pharmacokinetics and efficacy. The plasma AmB levels yielded by LNS-AmB after intravenous administration to rats were much higher than those yielded by Amphocil or Abelcet, and similar to those yielded by AmBisome, but in dogs LNS-AmB yielded plasma AmB concentrations about three times higher than did AmBisome. In a carrageenin-induced pleurisy model in rats, LNS-AmB yielded AmB levels in the pleural exudate over 20 times those yielded by Amphocil or Abelcet, and similar to those yielded by AmBisome. From these pharmacokinetic results, it is clear that Amphocil and Abelcet are based on a quite distinct drug-delivery concept from LNS-AmB. In a rat model of localized candidiasis, LNS-AmB significantly inhibited the growth of Candida albicans in the pouch, whereas AmBisome did not, even though the AmB concentrations in the pouch were similar. This difference in antifungal activity between LNS-AmB and AmBisome was also found in vitro. That is, the antifungal activity of LNS-AmB against C. albicans was similar to that of Fungizone and dimethyl sulfoxide-solubilized AmB, while AmBisome showed weaker antifungal activity than did other formulations. Based on these results, the release of AmB from AmBisome was judged to be slow and slight. In a mouse model of systemic candidiasis, LNS-AmB (1.0mg/kg) was much more effective than AmBisome (8.0mg/kg) or Fungizone (1.0mg/kg). These results suggest that LNS-AmB maintained the potent activity of AmB against fungal cells even though the AmB was incorporated into LNS particles. We conclude that LNS-AmB may offer an improved therapeutic profile at lower doses than Fungizone and commercial lipid-based formulations.

Amphotericin B↗

PubMed2003

Mg-promoted double silylation of trifluoroacetimidoyl chlorides. A new entry to the fluorinated dianion equivalents.

[reaction: see text] A Mg(0)/Me(3)SiCl system was found to be effective for the preparation of a novel fluorinated dianion equivalent. A one-pot reaction sequence involving reductive C-F and C-Cl bond cleavage reactions of trifluoroacetimidoyl chlorides afforded bis-silylated difluoroenamines. Subsequent carbon-carbon bond-forming reactions of the bis(silyl)enamines with two kinds of electrophiles gave a variety of difluorinated imines.

Journal Article↗