Biomedical subjects

Nobuyuki Kai

Publications and source records attributed to Nobuyuki Kai.

8 recordsLinked to original sources

PubMed2006

Decline of striatal dopamine release in parkin-deficient mice shown by ex vivo autoradiography.

Parkin is the causal gene of autosomal recessive juvenile parkinsonism (AR-JP). Dopamine (DA) metabolism has been linked to Parkinson's disease (PD). To understand the pathogenesis of AR-JP, we generated parkin-deficient mice to assess the status of DA signaling pathway and examine DA release and DA receptor by ex vivo autoradiography. Ex vivo autoradiography using [11C]raclopride showed a clear decrease in endogenous DA release after methamphetamine challenge in parkin-deficient mice. Furthermore, parkin deficiency was associated with considerable upregulation of DA (D1 and D2) receptor binding in vivo in the striatum and increased DA levels in the midbrain. Our results suggest that dopaminergic neurons could behave abnormally before neuronal death.

3,4-Dihydroxyphenylacetic Acid↗

PubMed2006

Altered gene expression in the subdivisions of the amygdala of Fyn-deficient mice as revealed by laser capture microdissection and mKIAA cDNA array analysis.

Fyn-tyrosine-kinase-deficient mice exhibit increased fearfulness and display enhanced excitability in the amygdala. To gain insight into the molecular changes associated with the increased excitability of the amygdala, we used a newly developed cDNA array system comprising mouse KIAA cDNA clones to identify novel genes differentially expressed in the amygdala of fyn(-/-) and fyn(+/-) mice following administration of N-methyl-D-aspartate (NMDA). Laser capture microdissection in combination with PCR-based cDNA amplification allowed us to analyze gene expression in each amygdalar subdivision. The statistical significance of the differential expressions was tested by one-way analysis of variance (ANOVA) by the false discovery rate controlling approach. Among the 805 mKIAA cDNA clones tested, only the expression level of mKIAA1577 (Zinc finger SWIM domain containing protein 6; gene name, Zswim6) showed statistically significant change in regard to the genotype and amygdalar subdivision. Namely, only the lowered expression of mKIAA1577 in the central nucleus of fyn(-/-) mice 1 h after NMDA administration (2.1-fold lower relative to fyn(+/-) mice) was statistically significant. In situ hybridization analysis confirmed the downregulation of the mRNA in the central nucleus of the fyn(-/-) mice 1 h after NMDA administration (3.2-fold lower relative to fyn(+/-) mice). The NMDA-induced change in gene expression was partially blocked by the NMDA antagonist D-AP-5. These results suggest that Fyn deficiency was responsible for the NMDA-induced downregulation of a specific gene in the amygdalar central nucleus.

2-Amino-5-phosphonovalerate↗

PubMed2006

Predictives regarding outcome after transurethral resection for prostatic adenoma associated with detrusor underactivity.

OBJECTIVES: To elucidate the predictive factors regarding the treatment outcomes after transurethral resection of the prostate for symptomatic benign prostatic enlargement with detrusor underactivity. METHODS: A retrospective study was conducted in 190 patients with detrusor underactivity of 1397 men who had undergone transurethral resection of the prostate. All patients had completed the International Prostate Symptom Score and quality-of-life (QOL) questionnaires and had undergone a full urodynamic analysis before surgery. The outcomes were assessed at 3 and 12 months postoperatively using the International Prostate Symptom Score, QOL score, and peak urinary flow rate. The association between the baseline variables and improvement in the outcome variables was analyzed statistically. RESULTS: Preoperative urodynamic abnormalities included bladder outlet obstruction in 58.9% and detrusor overactivity (DO) in 32.1%. Multivariate analysis suggested that the initial level of storage symptoms, as well as the QOL score, were predictive of an improvement in the QOL. Postoperative improvement in symptoms and QOL was consistently influenced by the presence of DO before surgery. The baseline degree of bladder outlet obstruction, as well as patient age, consistently influenced the improvement in the peak urinary flow rate. CONCLUSIONS: In selected patients with benign prostatic enlargement associated with detrusor underactivity, greater baseline storage symptom scores and the presence of DO were negative predictive factors for QOL improvement. Baseline DO was also predictive of poorer improvement in the subjective symptoms after transurethral resection of the prostate. A greater degree of baseline bladder outlet obstruction positively predicted for postoperative peak urinary flow rate improvement, and patient age predicted negatively for it.

Aged↗

PubMed2006

Lower urinary tract dysfunction in type 1 familial amyloidotic polyneuropathy in Kumamoto, Japan.

OBJECTIVE: To evaluate lower urinary tract dysfunction of type 1 familial amyloidotic polyneuropathy (FAP) patients in Kumamoto, Japan. METHODS: Lower urinary tract symptoms were evaluated in FAP patients. Urodynamic studies were evaluated in FAP patients as compared to those in control subjects. The location and distribution of amyloid deposits were evaluated in the urinary bladder in an autopsy case. RESULTS: In lower urinary symptoms, 86%, 19% and 38% patients showed difficulty in urination, urinary frequency and urinary incontinence. In detrusor function during filling cystometry, 14% patients showed detrusor overactivity. Moreover, 43% patients showed low compliance bladder, 62% and 38% patients showed normal and reduced bladder sensation, respectively. First desire to void (FDV), strong desire to void (SDV) and post-voided residual urine (PVR) were increased in FAP patients as compared to those in control subjects. In the urethral pressure profilometry, 71%, 10% and 19% patients showed incompetent, normal functional and overactive urethral closure mechanism, respectively. Maximum urethral pressure (MUP), maximum urethral closure pressure (MUCP) and functional profile length (FPL) were decreased in FAP patients compared to those in control subjects. CONCLUSION: Autonomic, somatic nerve systems and bladder detrusor musculature might be impaired in lower urinary tract of type 1 FAP patients in Kumamoto, Japan.

Adult↗

PubMed2006

Mass screening for prostate cancer in patients with end-stage renal disease: a comparative study.

OBJECTIVE: To determine the usefulness of prostate-specific antigen (PSA) screening for prostate cancer in patients with end-stage renal disease (ESRD), as although serum PSA is effective in the early detection of this cancer in the general population, there are few reports of its utility in patients with ESRD. PATIENTS AND METHODS: Blood samples were obtained for PSA screening from April 2002 to September 2003; 1250 men with ESRD aged >50 years were compared with 1007 healthy control men aged >55 years, all in Kumamoto Prefecture, Japan. All men with a serum PSA level of >4.0 ng/mL were categorized as PSA-positive and were further assessed, including a prostate biopsy. RESULTS: There was a statistically significantly greater increase in PSA level with age in the ESRD group than in the healthy controls. The rate of cancer detection among men with a PSA level of >10 ng/mL was significantly higher in patients with ESRD than in healthy controls. Thirteen patients with ESRD and five healthy control men were finally diagnosed with prostate cancer. CONCLUSION: The serum PSA level was slightly higher and the incidence of prostate cancer at higher PSA levels appeared to be greater in men with ESRD than in healthy controls. The findings of this large study suggest that PSA screening is useful for the diagnosis of prostate cancer in these patients.

Aged↗

PubMed2005

Subthalamic neurons coordinate basal ganglia function through differential neural pathways.

The subthalamic nucleus (STN) is a key component of basal ganglia circuitry that mediates a variety of motor functions. The STN neurons send glutamatergic projections to the output structures of basal ganglia, including the substantia nigra pars reticulata (SNr) and the entopeduncular nucleus, and also innervate the globus pallidus (GP). However, the mechanism by which the STN regulates motor functions in the neural circuitry is not fully understood. Here we performed conditional ablation of the STN neurons by using immunotoxin-mediated cell targeting. We then analyzed dopamine (DA)-mediated motor behavior and firing activity of the SNr and GP neurons. Ablation of the STN neurons increased spontaneous movement and reduced hyperactivity in response to DA stimulation. Ablation of these neurons modulated the pattern and rate of spontaneous firing of the SNr neurons, although it did not substantially affect spontaneous firing of the GP neurons. The ablation attenuated DA-induced suppression of the firing rate of the SNr neurons and inhibited DA-induced elevation of the rate of the GP neurons. In addition, pharmacological blockade of GP activation in response to DA stimulation inhibited the suppression of SNr activity and the resultant motor activation. These results suggest that the STN neurons suppress spontaneous behavior through their direct projection to the output neurons and that, in response to DA, they contribute to expression of behavior by acting on the output neurons mainly through the GP-mediated pathways. We conclude that the STN coordinates motor behavior through differential neural pathways depending on the state of DA transmission.

Action Potentials↗

PubMed2003

Aberrant responses to acoustic stimuli in mice deficient for neural recognition molecule NB-2.

NB-2, a member of the contactin subgroup in the immunoglobulin superfamily, is expressed specifically in the postnatal nervous system, reaching a maximum level at 3 weeks postnatal. NB-2 displays neurite outgrowth-promoting activity in vitro. To assess its function in the nervous system, we generated mutant mice in which a part of the NB-2 gene was ablated and replaced with the tau-LacZ gene. The general appearance of NB-2-deficient mice and their gross anatomical features were normal. The LacZ expression patterns in heterozygous mice revealed that NB-2 is preferentially expressed in the central auditory pathways. In the audiogenic seizure test, NB-2-deficient mice exhibited a lower incidence of wild running, but a higher mortality rate than the wild-type littermates. c-Fos immunohistochemistry demonstrated that neural excitability induced by the audiogenic seizure test in the NB-2-deficient mice was prominently attenuated in both the dorsal and external cortices of the inferior colliculus, where enhanced neural excitability was observed in the wild-type mice. In response to pure-tone stimulation after priming, NB-2-deficient mice exhibited a diffuse and low level of c-Fos expression in the central nucleus of the inferior colliculus, which was distinctly different from the band-like c-Fos expression corresponding to the tonotopic map in the wild-type littermates. Taken together, these results suggest that a lack of NB-2 causes impairment of the neuronal activity in the auditory system.

Acoustic Stimulation↗

PubMed2002

Altered tone-induced Fos expression in the mouse inferior colliculus after early exposure to intense noise.

Mice become highly susceptible to audiogenic seizures (AGS) after being exposed to intense, high-frequency noise during a critical period of early life (priming). To determine the critical site for AGS priming in the auditory brainstem, animals in the experimental group were primed at 21 days, and the tone-induced Fos immunoreactivity was examined 1, 7, and 14 days after priming as an index of excitability of neurons. Enhanced Fos immunoreactivity was observed in the inferior colliculus (IC) of the primed mice 7 and 14 days after priming as compared to that of non-primed mice and attenuated Fos expression was observed 1 day after priming. No significant elevation of Fos expression was observed in the cochlear nucleus and the deep layer of the superior colliculus of either type of mice. These results strongly suggest that the IC is the target site of AGS priming.

Acoustic Stimulation↗