Search PubMed⌕ Search

Biomedical subjects

Tsutomu Nakada

Publications and source records attributed to Tsutomu Nakada.

15 recordsLinked to original sources
PubMed2025

Loss and Gain of Aqp10 Paralogs With Broad Solute Selectivity in Anguillid Eels.

Aquaporin (Aqp) 10 is a member of the aquaglyceriporin family, which transports small, uncharged solutes in addition to water. Although the solute selectivity of aquaglyceroporins varies, the mechanism of solute selectivity has not yet been fully elucidated. The common ancestor of ray-finned fish possessed two paralogous genes for aquaporin 10, aqp10.1 and aqp10.2, which produce Aqps with different solute selectivities. Most teleosts possess one or more ohnologs derived from aqp10.1 and aqp10.2; however, the common ancestor of Anguilliformes species lost all aqp10.1-derived ohnologs. Anguilliformes species, except Anguilla species, have one aqp10.2b, but recent tandem duplications in the European eel have generated three aqp10.2b paralogs (aqp10.2b1-aqp10.2b3), whose activities remain ambiguous. In this study, we found that the four sites forming the aromatic/arginine (ar/R) selectivity filter in European eel Aqp10.2b1 were identical to those in Aqp10.2b of other species. However, the Y residue at position 3 was replaced with G in the ar/R selectivity filter of Aqp10.2b2 and b3. When expressed in Xenopus oocytes, Aqp10.2b2 and b3 showed higher permeability to urea and boric acid than Aqp10.2b1, indicating that Aqp10.2b2 and b3 acquired broad solute selectivity similar to that of Aqp10.1, which was lost in the ancestral Anguilliformes species. Urea and boric acid permeabilities of Aqp10.2b1 increased when the Y residue at position 3 of the ar/R selectivity filter was replaced with G. Overall, our results outline the history of the loss and gain of Aqp10 paralogs with broad solute selectivity in anguillid eels.

Animals↗
PubMed2003

Molecular cloning and characteristics of a novel zinc finger protein and its splice variant whose transcripts are expressed during spermatogenesis.

Testicular zinc finger protein (TZF) has a zinc finger motif of the Cys2-His2 type and its transcript is expressed predominantly in mouse spermatogenic cells. Using the fragment of TZF as a probe, we isolated the alternative splice variant form (TZF-L) from mouse testis cDNA library. Analysis of the open reading frame of each cDNA indicated that TZF and TZF-L were polypeptides of 942 and 2025 amino acid residues, respectively, and the N-terminal 902 amino acids of TZF-L were identical to those of TZF. The C-terminal region of TZF-L had more a zinc finger motif of the Cys2-His2 type and poly-Glu and poly-Pro regions. The mouse TZF/TZF-L gene spanned >20 kb and consisted of 11 exons. RT-PCR analysis of the expression level of mRNAs for mouse TZF and TZF-L showed that both transcripts are highly expressed in testis and moderately in kidney and ovary. Elevated expression of both transcripts during testicular development in mice was restricted to spermatocytes at the pachytene stage of meiotic prophase. Fusion proteins with GFP also demonstrated the nuclear localization of TZF and TZF-L. These experiments suggest that TZF and TZF-L may act to control the gene activity during spermatogenesis.

Alternative Splicing↗
PubMed2003

Enhanced expression of B7.2 (CD86) by percutaneous sensitization with house dust mite antigen.

House dust mite antigen is a well-known allergen in the pathogenesis of atopic dermatitis (AD), a chronic relapsing inflammatory skin disease. We evaluated the AD model mice sensitized with house dust mite antigen and observed a Th2-dominant immune response. In this experiment, BALB/c mice were sensitized percutaneously with house dust mite antigen three times with 7 days interval after skin barrier disruption. A remarkable infiltration of polymorphonuclear granulocytes and monocytes in the cutis was observed in mice treated with this antigen, high serum IgE levels and IL-4 mRNA expression in local lymph node cells was also observed. CD19(+) B cell numbers overturned to CD4(+) helper T cells. In these mice, there was significant increase of B7.2 (CD86) expression on CD19(+) B cells. These results indicate that house dust mite antigen sensitizes BALB/c mice and skews their Th1/Th2 balance toward Th2.

Administration, Cutaneous↗
PubMed2003

Dorsolateral prefrontal lobe activation declines significantly with age--functional NIRS study.

Dorsolateral prefrontal cortex (DLPF) activation in response to cognitive paradigms engaging working memory was quantitatively evaluated using functional near infrared spectroscopy (fNIRS) in cognitively normal individuals across the age spectrum (20-90 years; 8 females, 52 males). DLPF activation score (DAS) demonstrated a significant decline (r(2) = -0561, p < 0.05) as a function of age. The study indicates that blood flow response associated with DLPF activation declines as a function of age in cognitively normal individuals and that fNIRS can be used as a convenient, portable tool for assessing such activation.

Adult↗
PubMed2003

Free convection schema defines the shape of the human brain: brain and self-organization.

As a fundamental rule of nature, the shape of a functioning organ should never be considered accidental. Since the principal rules for a self-organizing neural network are not sufficient for determining the shape and anatomic features of the brain, these must be governed by other rules. Ontogeny of the global shape of the brain is guided by radial glial fibers. The rules defining the growth pattern of radial glial fibers, therefore, should be the rules for a self-organization for the shape of the brain. In this work, the overall shape and structural anatomic detail of the human brain was successfully simulated utilizing self-organization rules of heat convection represented by Boussinesq partial differential equations. The result suggests that radial glial fibers may grow in Markovian fashion, guided by gaseous substrates moving miniature distances according to a convection schema. The result also holds implication that the shape of the brain has specific physical meaning in the creation of a virtual sphere, which in turn ensures equivalence of columns within the entire cortex, the well-known vital fundamental of brain organization.

Brain↗
PubMed2003

Clinical experience on 3.0 T systems in Niigata, 1996 to 2002.

High-field human magnetic resonance imaging (MRI) systems developed over the recent years have contributed significantly to the field of functional MRI and multinuclear spectroscopy. As more experience is gained, it has become apparent that high-field systems, especially those at 3.0 T, possess significant advantages in the clinical setting over conventional MRI systems. High-field MRI is promising as an all-in-one system for both structural and functional assessments. This review summarizes the exciting features of clinical imaging based on our cumulative 6-year experience on various 3.0 T systems.

Brain Mapping↗
PubMed2003

Cortical reorganization in patients with subcortical hemiparesis: neural mechanisms of functional recovery and prognostic implication.

OBJECT: A systematic investigation on cortical reorganization in patients with hemiparesis of a subcortical origin, with special emphasis on functional correlates, was conducted using functional magnetic resonance (fMR) imaging performed on a 3-tesla system specifically optimized for fMR imaging investigation. METHODS: The study group included 46 patients with hemiparesis (25 with right and 21 with left hemiparesis) and 30 age-matched healthy volunteers as controls. All study participants were originally right handed. The characteristics of the lesion were putaminal hemorrhage in 19 patients, thalamic hemorrhage in 10 patients, and striatocapsular bland infarction in 17 patients. Functional recovery in subcortical hemiparesis showed two distinct phases of the recovery process involving entirely different neural mechanisms. Phase I is characterized by the process of recovery and/or reorganization of the primary system. Successful recovery of this system is typically reached within 1 month after stroke onset. Its clinical correlate is a rapid recovery course and significant recovery of function within 1 month of stroke onset. Failure of recovery of the primary system shifts the recovery process to Phase II, during which reorganization involving the ipsilateral pathway takes place. The clinical correlate of Phase II is a slow recovery course with variable functional outcome. CONCLUSIONS: Effective functional organization of the ipsilateral pathway, as identified by linked activation of the ipsilateral primary sensorimotor cortex and contralateral anterior lobe of the cerebellum, is correlated with a good prognostic outcome for patients in the slow recovery group. A high degree of connectivity between supplementary motor areas, bilaterally, appears to influence functional recovery adversely.

Aged↗
PubMed2002

EZ-tracing: a new ready-to-use algorithm for magnetic resonance tractography.

A new algorithm for tractography based on diffusion tensor analysis (DTA) is presented. This method, called EZ-tracing, is based on a new algorithm for analyzing DTA data, lambda chart analysis (LCA), and effectively overcomes the main shortcomings of previous methods for tractography. EZ-tracing is written in MATLAB scripting language (MathWorks, Natick, MA, USA) and can be implemented on any of the common operating systems, such as Microsoft Windows, UNIX, and LINUX. The program is available in public at coe@bri.niigata-u.ac.jp.

Adult↗
PubMed2002

Effect of mild hypothermia on energy state recovery following transient forebrain ischemia in the gerbil.

A transient (lasting for 15 min) bilateral carotid artery occlusion model was created by using male Mongolian gerbils ( n=20, weight 50-60 g). The animals were divided into a group with mild hypothermia (34 degrees C, n=10) and a normothermic group (37 degrees C, n=10). High-energy phosphate metabolism (ATP, PCr, Pi) and intracellular pH were sequentially measured using (31)P-MRS during ischemia and after reperfusion for 1 week. The same animals were also subjected to a histopathological evaluation. During ischemia, there were no statistically significant differences between the two groups in the quantities of the metabolites. However, after reperfusion the rate of metabolic recovery by the mildly hypothermic (MH) group was significantly higher (by 10-20%) than the normothermic (NT) group. The intracellular pH decreased about 0.4 in both groups after ischemia; and after reperfusion the intracellular pH of the MH group returned to baseline levels faster than in the NT group. One week after ischemia, energy metabolism gradually decreased about 10-20% in both groups. In the histopathological evaluation, pyramidal cell damage in the hippocampus was 33% on average in the MH group and 79% in the NT group. The neuronal damage to the cerebral cortex was 26% in the MH group and 61% in the NT group. Astrocyte reactivity in the hippocampus and cerebral cortex was 2.9% and 1.1% in the MH group and 9.7% and 5.2% in the NT group. The results of this experiment indicate that the protective effect of mild hypothermia is due to the high recovery rate of ATP and PCr and the prevention of a secondary decline in high phosphate energy.

Adenosine Triphosphate↗
PubMed2002

Fast and precise independent component analysis for high field fMRI time series tailored using prior information on spatiotemporal structure.

Independent component analysis (ICA) has been shown as a promising tool for the analysis of functional magnetic resonance imaging (fMRI) time series. Each of these studies, however, used a general-purpose algorithm for performing ICA and the computational efficiency and accuracy of elicited neuronal activations have not been discussed in much detail. We have previously proposed a direct search method for improving computational efficiency. The method, which is based on independent component-cross correlation-sequential epoch (ICS) analysis, utilizes a form of the fixed-point ICA algorithm and considerably reduces the time required for extracting desired components. At the same time, it is shown that the accuracy of detecting physiologically meaningful components is much improved by tailoring the contrast function used in the algorithm. In this study, further improvement was made to this direct search method by integrating an optimal contrast function. Functional resolution of activation maps could be controlled with a suitable selection of the contrast function derived from prior knowledge of the spatial patterns of physiologically desired components. A simple skewness-weighted contrast function was verified to extract sufficiently precise activation maps from the fMRI time series acquired using a 3.0 Tesla MRI system.

Adolescent↗
PubMed2002

Effect of orally administered Hochu-ekki-to, a Japanese herbal medicine, on contact hypersensitivity caused by repeated application of antigen.

The effects of oral administration of Hochu-ekki-to (HET; bu-zhong-yi-qi-tang in Chinese), a traditional Japanese and Chinese herbal medicine, on chronic contact hypersensitivity were investigated. HET suppressed ear swelling due to chronic contact hypersensitivity caused by repeated application of 2,4,6-trinitro-1-chlorobenzene (TNCB). HET significantly suppressed not only increases in hapten-specific immunoglobulin E (IgE) and IgG1 titer due to repeated application of TNCB, but also total IgE and IgG1 concentration in the serum. Interleukin 4 (IL-4) level in inflamed ear tissue was significantly increased by repeated application of TNCB, and this increase in IL-4 level in the ear was significantly suppressed by oral administration of HET. Interferon gamma (IFN-gamma), IL-2, IL-5, IL-10 and IL-12 levels are not changed as much as IL4 by TNCB and HET did not alter these cytokines as much as IL-4. These results suggest that oral administration of HET suppresses chronic contact hypersensitivity, and it can be assumed that the suppression of serum Ig E and Ig G1 and IL-4 in inflamed ear.

Administration, Oral↗
PubMed2002

Effect of ninjin-youei-to on Th1/Th2 type cytokine production in different mouse strains.

Ninjin-youei-to (NYT; ren-shen-yang-rong-tang in Chinese) is a traditional herbal formula, which is widely used in Japan, Korea and China to modulate physiological immunity. The effects of oral administration of NYT on cytokine production from splenocytes were investigated in both C57BL/6 and BALB/c mice in which Th1 and Th2 were dominant, respectively. Splenocytes from C57BL/6 and BALB/c mice, which took NYT orally forfour weeks, were cultured with anti-mouse CD3 mAb, and the supernatant was examined for cytokine production using enzyme-linked immunosorbent assay (ELISA). Administration of NYT to C57BL/6 mice, increased the production of interleukin-4 (IL-4) significantly, and slightly decreased interferon-y (IFN-gamma) production from splenocytes. In contrast, the same treatment significantly increased IFN-gamma secretion from splenocytes of BALB/c mice. No remarkable changes of IL-12 production from splenocytes were observed in either strain of mice. These results suggest that oral administration of NYT ameliorates the excessive inclination of Th1 and Th2 type cytokine production, and NYT may provide a beneficial effects for the treatment of diseases caused by a skewed Th1-Th2 balance in the immune system.

Animals↗
PubMed2002

[Diffusion tensor analysis: principles and applications].

Diffusion tensor analysis represents a versatile yet powerful application of magnetic resonance imaging (MRI). Early applications of diffusion weighted imaging(DWI), especially those related to ischemic brain disease were quickly overshadowed by more advanced applications of DTA, namely, those dealing with anisotropy analysis. Considering the array of possibilities, from neuronal tract tracing to neuronal density imaging, DTA is rapidly becoming an indispensable tool not only in neuroscience but also in clinical investigations of the brain.

Brain↗
PubMed2002

Criteria for normalcy of cavities observed within the adult hippocampus: high-resolution magnetic resonance imaging study on a 3.0-T system.

BACKGROUND AND PURPOSE: Cavities occasionally found within the hippocampus during routine clinical magnetic resonance imaging (MRI) studies are believed to be a normal variant reflecting fluid collection within the vestigial hippocampal sulcus. However, the lack of systematic studies defining objective criteria for such cavities has hampered further assessment of potential abnormalities within the hippocampus. This study assessed the detailed characteristics of hippocampal cavities in normal subjects using a new high-resolution MRI technique in an attempt to define objective criteria of normalcy. METHODS: A new high-resolution imaging technique, T2-reversed MRI on a high-field (3.0-T) system was used to image the hippocampus in 74 normal volunteers in 3 age groups (28 young, 24 middle, and 22 senior). RESULTS: Residual cavities in the vestigial hippocampal sulcus were resolved as single, crescent-shaped structures along the deep aspect of the vestigial hippocampal sulcus. The size of the cavities did not vary with age and never exceeded 1 mm in width and 3 mm in length. The frequency of detection, however, increased with age (21.4% [5/28] in the young, 25.0% [6/24] in the middle, and 36.4 [8/22] in the senior age group). CONCLUSION: The study established clear objective criteria for normal cavities within the hippocampus. These cavities likely represent physiological fluid collection within the vestigial hippocampal sulcus. Any cavity that does not meet these defined criteria should be considered potentially abnormal.

Adult↗