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Biomedical subjects

Kazuhiro Nakamura

Publications and source records attributed to Kazuhiro Nakamura.

At least 19 recordsLinked to original sources

Deletion of neurosecretory proteins GL and GM drives dual anti-obesity effects via appetite suppression and enhanced energy expenditure.

Obesity results from an imbalance between energy intake and expenditure and is regulated by hypothalamic neuropeptide systems. The neurosecretory proteins GL (NPGL) and GM (NPGM) are expressed in the hypothalamus and promote feeding in gain-of-function studies; however, their endogenous physiological roles remain unclear. Here, we show that mice lacking both NPGL and NPGM display a lean phenotype driven by reduced food intake and increased energy expenditure. This anti-obesity phenotype is associated with increased expression of anorexigenic pro-opiomelanocortin in the hypothalamus and enhanced thermogenic activity in brown adipose tissue, marked by elevated uncoupling protein 1. Consistent with these findings, suppression of NPGL/NPGM signaling reduces feeding and alters sympathetic nerve activity. In addition, genome-wide association analysis identifies an obesity-associated variant near the human NPGM locus, suggesting relevance to human energy balance. Together, these findings identify NPGL and NPGM as endogenous regulators of energy homeostasis with potential relevance to obesity.

Animals↗

IL-4Ralpha polymorphism in regulation of IL-4 synthesis by T cells: implication in susceptibility to a subset of murine lupus.

To thoroughly understand the role of IL-4 in the pathogenesis of systemic lupus erythematosus (SLE), a prototypic antibody-mediated systemic autoimmune disease, we examined the potential of in vitro IL-4 production by anti-CD3 mAb-stimulated splenic T cells in SLE model of NZB, BXSB and related mouse strains. Unexpectedly, both SLE-prone NZB and BXSB mice had a limited potential to produce IL-4, while disease-free NZW mice had a high potential. Levels in (NZB x NZW) F1 and (NZW x BXSB) F1 were in between. Genome-wide search for quantitative trait loci (QTL) controlling this variation identified a single significant QTL in the vicinity of IL-4Ralpha gene on chromosome 7. Sequence analysis of IL-4Ralpha cDNA revealed that there are 17 nucleotide substitutions resulting in eight amino acid changes between NZB and NZW strains. BXSB showed the identical sequence, as did NZB. Thus, it was suggested that the NZW-type polymorphism controls a high potential and the NZB/BXSB-type polymorphism controls a low potential for IL-4 production by T cells. Linkage studies using NZW x (NZW x BXSB) F1 male and (NZB x NZW) F1 x NZW female back-cross mice revealed that the BXSB/NZB-type IL-4Ralpha polymorphism significantly linked to BXSB, but not to (NZB x NZW) F1 lupus. Thus, the low IL-4-producing phenotype appears to predispose to SLE in BXSB, but not NZB-related strains, suggesting that the role of IL-4 in the pathogenesis may differ between certain subsets of SLE, even if they show similar disease phenotypes.

Animals↗

Measurement of lysophospholipase D/autotaxin activity in human serum samples.

OBJECTIVES: Lysophospholipase D (lysoPLD)/autotaxin regulates the blood levels of lysophosphatidic acid (LPA), and we designed a serum lysoPLD assay for use in clinical laboratory testing. DESIGN AND METHODS: LysoPLD activity was assessed based on the amount of choline released with lysophosphatidylcholine as the substrate. RESULTS AND CONCLUSIONS: It was confirmed that the lysoPLD assay can be applied to clinical laboratory testing. The serum lysoPLD activity in healthy female subjects was significantly higher than that in the male subjects.

Clinical Laboratory Techniques↗

Requirement of tryptophan hydroxylase during development for maturation of sensorimotor gating.

Deficits in sensorimotor gating, a function to focus on the most salient stimulus, could lead to a breakdown of cognitive integrity, and could reflect the "flooding" by sensory overload and cognitive fragmentation seen in schizophrenia. Sensorimotor gating emerges at infancy, and matures during childhood. The mechanisms that underlie its development are largely unclear. Here, we screened the mouse genome, and found that tryptophan hydroxylase (TPH) is implicated in the maturation of sensorimotor gating. TPH, an enzyme involved in the biosynthesis of serotonin, proved to be required only during the weaning period for maturation of sensorimotor gating, but was dispensable for its emergence. Proper serotonin levels during development underlie the mature functional architecture for sensorimotor gating via appropriate actin polymerization. Thus, maintaining proper serotonin levels during childhood may be important for mature sensorimotor gating in adulthood.

Acoustic Stimulation↗

Central efferent pathways mediating skin cooling-evoked sympathetic thermogenesis in brown adipose tissue.

Control of thermoregulatory effectors by the autonomic nervous system is a critical component of rapid cold-defense responses, which are triggered by thermal information from the skin. However, the central autonomic mechanism driving thermoregulatory effector responses to skin thermal signals remains to be determined. Here, we examined the involvement of several autonomic brain regions in sympathetic thermogenic responses in brown adipose tissue (BAT) to skin cooling in urethane-chloralose-anesthetized rats by monitoring thermogenic [BAT sympathetic nerve activity (SNA) and BAT temperature], metabolic (expired CO(2)), and cardiovascular (arterial pressure and heart rate) parameters. Acute skin cooling, which did not reduce either rectal (core) or brain temperature, evoked increases in BAT SNA, BAT temperature, expired CO(2), and heart rate. Skin cooling-evoked thermogenic, metabolic, and heart rate responses were inhibited by bilateral microinjections of bicuculline (GABA(A) receptor antagonist) into the preoptic area (POA), by bilateral microinjections of muscimol (GABA(A) receptor agonist) into the dorsomedial hypothalamic nucleus (DMH), or by microinjection of muscimol, glycine, 8-OH-DPAT (5-HT(1A) receptor agonist), or kynurenate (nonselective antagonist for ionotropic excitatory amino acid receptors) into the rostral raphe pallidus nucleus (rRPa) but not by bilateral muscimol injections into the lateral/dorsolateral part or ventrolateral part of the caudal periaqueductal gray. These results implicate the POA, DMH, and rRPa in the central efferent pathways for thermogenic, metabolic, and cardiac responses to skin cooling, and suggest that these pathways can be modulated by serotonergic inputs to the medullary raphe.

Adipose Tissue, Brown↗

Genetic dissection of the effects of stimulatory and inhibitory IgG Fc receptors on murine lupus.

Immune complex (IC)-mediated tissue inflammation is controlled by stimulatory and inhibitory IgG Fc receptors (FcgammaRs). Systemic lupus erythematosus is a prototype of IC-mediated autoimmune disease; thus, imbalance of these two types of FcgammaRs is probably involved in pathogenesis. However, how and to what extent each FcgammaR contributes to the disease remains unclear. In lupus-prone BXSB mice, while stimulatory FcgammaRs are intact, inhibitory FcgammaRIIB expression is impaired because of promoter region polymorphism. To dissect roles of stimulatory and inhibitory FcgammaRs, we established two gene-manipulated BXSB strains: one deficient in stimulatory FcgammaRs (BXSB.gamma(-/-)) and the other carrying wild-type Fcgr2b (BXSB.IIB(B6/B6)). The disease features were markedly suppressed in both mutant strains. Despite intact renal function, however, BXSB.gamma(-/-) had IC deposition in glomeruli associated with high-serum IgG anti-DNA Ab levels, in contrast to BXSB.IIB(B6/B6), which showed intact renal pathology and anti-DNA levels. Lymphocytes in BXSB.gamma(-/-) were activated, as in wild-type BXSB, but not in BXSB.IIB(B6/B6). Our results strongly suggest that both types of FcgammaRs in BXSB mice are differently involved in the process of disease progression, in which, while stimulatory FcgammaRs play roles in effecter phase of IC-mediated tissue inflammation, the BXSB-type impaired FcgammaRIIB promotes spontaneous activation of self-reactive lymphocytes and associated production of large amounts of autoantibodies and ICs.

Animals↗

The function of the frontal lobe in neonates for response to a prosodic voice.

We examined how neonates responded at the brain level to an element of acoustic stimulation using near-infrared spectroscopy (NIRS). Twenty full-term, healthy neonates were included in the study. The neonates were tested in their cribs while they slept in a silent room. First, two probe holders were placed on the left and right sides of the forehead over the eyebrows using double-sided adhesive tape. Then the neonates were exposed to the auditory stimuli from an external auditory speaker. The stimuli, readings of the first scene of "Little Red Riding Hood," were made with a digital voice. The stimuli consisted of two conditions: variably pitched speech (variable speech: VS) and monotonous flat-pitched speech (monotonous speech: MS). The analyses focused on changes in O(2)Hb because O(2)Hb is the most sensitive indicator of changes in cerebral blood flow in NIRS measurement. The O(2)Hb level promptly increased at the beginning of the VS condition, and then returned to baseline again, while O(2)Hb did not show any changes during the MS condition. Differences between baseline-stimulation relative values were used to perform a 2 (condition)x2 (recording site)x2 (gender) analysis of variance. The results show that VS (M=0.45, S.D.=1.33) produced a greater increase of oxygenated blood to the frontal area of the brain area than MS (M=-0.19, S.D.=1.28). Neonates' brain activation patterns suggest that they can discriminate differences in the prosodic patterns of utterances.

Acoustic Stimulation↗

Late developmental stage-specific role of tryptophan hydroxylase 1 in brain serotonin levels.

Serotonin [5-hydroxytryptamine (5-HT)] is a major therapeutic target of psychiatric disorders. Tryptophan hydroxylase (TPH) catalyzes the rate-limiting reaction in the biosynthesis of 5-HT. Two isoforms (TPH1 and TPH2) having tryptophan hydroxylating activity were identified. Association studies have revealed possible TPH1 involvement in psychiatric conditions and behavioral traits. However, TPH1 mRNA was reported to be mainly expressed in the pineal gland and the periphery and to be barely detected in the brain. Therefore, contribution of TPH1 to brain 5-HT levels is not known, and the mechanisms how TPH1 possibly contributes to the pathogenesis of psychiatric disorders are not understood. Here, we show an unexpected role of TPH1 in the developing brain. We found that TPH1 is expressed preferentially during the late developmental stage in the mouse brain. TPH1 showed higher affinity to tryptophan and stronger enzyme activity than TPH2 in a condition reflecting that of the developing brainstem. Low 5-HT contents in the raphe nucleus were seen during development in New Zealand white (NZW) and SWR mice having common functional polymorphisms in the TPH1 gene. However, the 5-HT contents in these mice were not reduced in adulthood. In adult NZW and SWR mice, depression-related behavior was observed. Considering an involvement of developmental brain disturbance in psychiatric disorders, TPH1 may act specifically on development of 5-HT neurons, and thereby influence behavior later in life.

Animals↗

PB1 domain-dependent signaling complex is required for extracellular signal-regulated kinase 5 activation.

MEKK2, MEK5, and extracellular signal-regulated kinase 5 (ERK5) are members of a three-kinase cascade for the activation of ERK5. MEK5 is the only MAP2K to express a PB1 domain, and we have shown that it heterodimerizes with the PB1 domain of MEKK2. Here we demonstrate the MEK5 PB1 domain is a scaffold that also binds ERK5, functionally forming a MEKK2-MEK5-ERK5 complex. Reconstitution assays and CFP/YFP imaging (fluorescence resonance energy transfer [FRET]) measuring YFP-MEKK2/CFP-MEK5 and CFP-MEK5/YFP-ERK5 interactions define distinct MEK5 PB1 domain binding sites for MEKK2 and ERK5, with a C-terminal extension of the PB1 domain contributing to ERK5 binding. Stimulus-dependent CFP/YFP FRET in combination with mutational analysis was used to define MEK5 PB1 domain residues critical for the interaction of MEKK2/MEK5 and MEK5/ERK5 required for activation of the ERK5 pathway in living cells. Fusion of the MEK5 PB1 domain to the N terminus of MEK1 confers ERK5 regulation by a MAP2K normally regulating only ERK1/2. The MEK5 PB1 domain confers stringent MAP3K regulation of ERK5 relative to more promiscuous MAP3K control of ERK1/2, JNK, and p38.

Amino Acid Sequence↗

Excision of juvenile pilocytic astrocytoma of the midbrain after radiotherapy.

A 13-year-old girl presented with consciousness disturbance, right hemiparesis, and impairment of hearing, swallowing, and ocular movements. A magnetic resonance image demonstrated marked hydrocephalus due to a large cystic tumor (40 x 40 x 30 mm) in the midbrain. Emergency ventricular drainage and stereotactic cyst puncture dramatically improved her condition. Since her family did not agree to surgery on the brain stem, radiotherapy was performed after ventriculoperitoneal shunting. Conventional radiotherapy of 50.4 Gy was temporarily effective, and the growth of the tumor was stabilized until approximately 8 months later when regrowth was noticed. At this stage, with the consent of her family, the tumor was removed via an infratentorial supracerebellar approach. The pathological diagnosis was juvenile pilocytic astrocytoma. The postoperative course was uneventful. No recurrence has been observed during the follow-up period of more than 6 years. This case study shows that initial excision may be appropriate for some low-grade focal lesions in the midbrain when the histological diagnosis and consent have been obtained.

Adolescent↗

[Two cases of laryngoplasty performed under a general anesthesia applied using a laryngeal mask for the treatment of unilateral vocal cord paralysis].

In general, laryngoplasty for unilateral vocal cord paralysis is performed under local anesthesia because the patient's voice must be heard and the movement of the vocal cords visualized during the endoscopic procedure to ensure good results. We encountered two cases who could not endure a long operation under local anesthesia and the insertion of an endoscope because of their age and gag reflex. We thus performed a combined lateral cricoarytenoid muscle pull (LCA-pull) and a type I thyroplasty under general anesthesia applied using a laryngeal mask. Although the patients could not phonate during the operation, the laryngeal mask allowed the vocal cords to be observed. Both patients achieved in maximal phonation time over 13 seconds, and the postoperative mean flow rates improved to under 110 mL/s. The postoperative period perturbation quotient and amplitude perturbation quotient also improved to within the normal limits.

Aged, 80 and over↗

[General anesthesia for thyroplasty employing voice test].

BACKGROUND: We reported an anesthetic technique for thyroplasty employing voice test. Thyroplasty is performed to improve voice quality in patients with unilateral vocal cord paralysis. Correct displacement of the vocal cord is assessed by asking the patient to phonate. At this point all patients should have recovered from general anesthesia and cooperate to phonation, facilitating correct displacement of the vocal cords. METHODS: Anesthesia was induced with i.v. pentazocine 15-30 mg and continuous propofol infusion 10 mg x kg(-1) x hr(-1). The patients received propofol infusion 4-6 mg x kg(-1) x hr(-1) with spontaneous ventilation. At the point of correct displacement of the vocal cords, we stopped propofol infusion and all the patients woke up immediately and cooperated. After determining the voice propofol was given at a rate of 4-6 mg x kg(-1) x hr(-1). RESULTS: The average times of surgery and anesthesia were 98 +/- 23 min and 139 +/- 22 min, respectively. At the point of correct displacement of the vocal cords, the average time from the end of propofol infusion until awakening with good quality of recovery was 313 +/- 93 sec. No patients complained of pain during or after CONCLUSIONS: This anesthetic technique provided both optimal operating conditions and patient comfort without serious complications.

Aged↗

In vivo function of Rnd2 in the development of neocortical pyramidal neurons.

The present study examined the in vivo role of Rnd2, a Rho family small GTPase, in brain development. Rnd2 was expressed by radially migrating cells, which primarily develop to pyramidal neurons, during their stay in the subventricular zone of embryonic cerebral cortex and hippocampus. Exogenous expression of wild-type and a constitutively active Rnd2, but not a negative mutant of Rnd2, in radially migrating cells by in utero electroporation disturbed their morphology and migration to upper layers. These results indicate that Rnd2 functions in vivo as a regulator of the migration and morphological changes associated with the development of pyramidal neurons.

Amino Acid Sequence↗

Pyramidal neurons of upper cortical layers generated by NEX-positive progenitor cells in the subventricular zone.

The generation of pyramidal neurons in the mammalian neocortex has been attributed to proliferating progenitor cells within the ventricular zone (VZ). Recently, the subventricular zone (SVZ) has been recognized as a possible source of migratory neurons in brain slice preparations, but the relevance of these observations for the developing neocortex in vivo remains to be defined. Here, we demonstrate that a subset of progenitor cells within the SVZ of the mouse neocortex can be molecularly defined by Cre recombinase expression under control of the NEX/Math2 locus, a neuronal basic helix-loop-helix gene that by itself is dispensable for cortical development. NEX-positive progenitors are generated by VZ cells, move into the SVZ, and undergo multiple asymmetrical and symmetrical cell divisions that produce a fraction of the neurons in the upper cortical layers. Our data suggest that NEX-positive progenitors within the SVZ are committed to a glutamatergic neuronal fate and have evolved to expand the number of cortical output neurons that is characteristic for the mammalian forebrain.

Animals↗

Correlation of aggression with serum IgM level in autoimmune-prone NZB mice.

Neurological symptoms are often found in patients with systemic lupus erythematosus, an autoimmune disease. We found an enhanced aggression in young autoimmune-prone NZB mice before expression of autoimmune hemolytic anemia, which was accompanied by an increase in neural activity in the accessory olfactory bulb. The performance of aggressive behavior was correlated with serum IgM level. These results indicate that IgM class autoantibodies could be implicated in brain dysfunction without apparent pathological changes of autoimmune disease.

Aggression↗

Platelet release of beta-thromboglobulin and platelet factor 4 and serotonin in plasma samples.

OBJECTIVES: Platelet release of alpha granule-derived CXC chemokines and dense granule-derived serotonin in plasma samples was evaluated. METHODS: Concentrations of the CXC chemokines beta-TG and PF4 were assayed by an enzyme immunoassay; serotonin was measured by an HPLC method. RESULTS: Beta-TG and PF4 were more easily released than serotonin by in vitro procedures. Use of the anti-platelet cocktail CTAD and preservation of the samples at 4 degrees C were necessary to accurately measure beta-TG and PF4, but not serotonin. CONCLUSIONS: Assaying serotonin may be useful for assessing platelet activation in vivo as a laboratory test because of facile preparation of plasma samples.

Adenosine↗

129Xe spectra from the heads of rats with and without ligation of the external carotid and pterygopalatine arteries.

After rats inhaled hyperpolarized (129)Xe gas, in vivo spectra from their heads revealed a dominant peak around 195 ppm, another easily resolvable peak near 189 ppm, a broad peak around 210 ppm, and two minor peaks around 198 ppm and 192 ppm. However, the source of each peak remains controversial. To further study the origin of each peak, we compared spectra obtained from the heads of normal rats with spectra taken from the heads of rats that had undergone ligation of the external carotid (ECA) and pterygopalatine (PPA) arteries, the major feeding vessels of nonbrain tissue in the rat head. The amplitude of the peak at around 189 ppm was greatly reduced in the ECA/PPA-ligated rats, while the peak around 195 ppm persisted. We conclude that the signal that originates from the rat brain after inhalation of (129)Xe gas is overwhelmingly dominated by the single resonance at 195 ppm.

Administration, Inhalation↗