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Biomedical subjects

K Okamoto

Publications and source records attributed to K Okamoto.

At least 37 records · Page 2Linked to original sources
PubMed2005

High-resolution magnetic resonance of the extracranial facial nerve and parotid duct: demonstration of the branches of the intraparotid facial nerve and its relation to parotid tumours by MRI with a surface coil.

AIM: To investigate the usefulness of high-resolution MR imaging in the evaluation of the extracranial facial nerve, compared with surgical findings. MATERIALS AND METHODS: Thirteen patients with benign parotid tumours were studied on a 1.5-T MR system with a 3 in circular surface coil. High-resolution T1-weighted spin-echo, T2-weighted fast spin-echo, and three-dimensional gradient-recalled acquisition in the steady state (GRASS) images were obtained in the axial planes. Oblique reformatted images were generated. Tumours, parotid ducts and facial nerves were identified on these images. The relationship of the tumours to the facial nerves was confirmed at surgery. RESULTS: Facial nerves appeared as linear structures of low intensity on all pulse sequences. The main trunks and cervicofacial and temporofacial divisions of the facial nerves were identified in 100%, 84.1% and 53.8% of GRASS images, respectively. Parotid ducts appeared as structures of low intensity on T1-weighted (66.6%) and GRASS images (81.8%), and as structures of very high intensity on T2-weighted images (91.7%). The relationships of the tumours to the facial nerves were correctly diagnosed in 11 (91.7%) of 12 cases. CONCLUSION: High-resolution MR imaging depicts the extracranial facial nerve and the parotid duct, and is useful for preoperative evaluation of parotid gland tumours.

Adult↗
PubMed2005

The role of peripheral 5HT2A and 5HT1A receptors on the orofacial formalin test in rats with persistent temporomandibular joint inflammation.

The role of peripheral serotonin (5HT) 2A and 5HT1A receptors on the orofacial nocifensive behavioral activities evoked by the injection of formalin into the masseter muscle was evaluated in the rats with persistent temporomandibular joint (TMJ) inflammation evoked by Complete Freund's Adjuvant (CFA). The orofacial nocifensive behavioral activities evoked by the injection of formalin into masseter muscle were significantly enhanced at 1 day (CFA day 1 group) or 7 days (CFA day 7 group) during TMJ inflammation. Pretreatment with local administration of 5HT2A receptor antagonist, ketanserin (0.01, 0.1 mg/rat) into the masseter muscle or systemic administration of ketanserin via i.p. injection (1 mg/kg) reduced the orofacial nocifensive behavioral activities of the late phase evoked by formalin injection into masseter muscle on the side of TMJ inflammation (CFA day 7 group). However, local (0.001-0.1 mg/rat) or systemic (1 mg/kg) administration of 5HT1A receptor antagonist, propranolol, into masseter muscle did not produce the antinociceptive effect in CFA day 7 group. Moreover, local administration of ketanserin (0.1 mg) or propranolol (0.1 mg) into masseter muscle did not inhibit nocifensive orofacial behavior in rats without TMJ inflammation. These data suggest that persistent TMJ inflammation causes the elevation of the orofacial nocifensive behavior, and peripheral 5HT2A receptors play an important role in mediating the deep craniofacial tissue nociception in rats with TMJ inflammation.

Animals↗
PubMed2005

Central serotonin 3 receptors play an important role in the modulation of nociceptive neural activity of trigeminal subnucleus caudalis and nocifensive orofacial behavior in rats with persistent temporomandibular joint inflammation.

The role of central serotonin 3 receptors on neural activities recorded from superficial laminae of trigeminal subnucleus caudalis/upper cervical spinal cord junction region was investigated using rats with (Complete Freund's Adjuvant day 7 group) or without (non-Complete Freund's Adjuvant group) persistent temporomandibular joint inflammation evoked by Complete Freund's Adjuvant for 7 days. We identified two types of units, Deep-wide dynamic range units and Skin-wide dynamic range units from extracellular recordings. Deep-wide dynamic range units have mechanoreceptive fields in the deep craniofacial tissues including masseter muscle but do not have cutaneous mechanoreceptive fields. Deep-wide dynamic range unit discharges evoked by the formalin injection into masseter muscle were significantly enhanced in the late phase in Complete Freund's Adjuvant day 7 group. Discharges of Skin-wide dynamic range units evoked by the noxious pinch stimulation to facial skin in Complete Freund's Adjuvant day 7 group were significantly enhanced compared with those in non-Complete Freund's Adjuvant group. Topical administration of central serotonin 3 receptor antagonist, tropisetron, onto trigeminal subnucleus caudalis/upper cervical spinal cord junction region significantly reduced both formalin-evoked Deep-wide dynamic range unit and pinch-evoked Skin-wide dynamic range unit discharges in non-Complete Freund's Adjuvant and Complete Freund's Adjuvant day 7 groups significantly. The inhibitory effects of tropisetron on pinch-evoked Skin-wide dynamic range unit discharges were prolonged in Complete Freund's Adjuvant day 7 group compared with those in non-Complete Freund's Adjuvant group. The role of central serotonin 3 receptors in trigeminal subnucleus caudalis/upper cervical spinal cord junction region was also tested by orofacial formalin test in Complete Freund's Adjuvant day 7 group. Intracisternal administration of tropisetron decreased the orofacial nocifensive behavior in the late phase evoked by the injection of formalin into the masseter muscle. These results suggest that central serotonin 3 receptors in trigeminal subnucleus caudalis/upper cervical spinal cord junction region are involved in mediating pronociceptive effects in both superficial and deep craniofacial tissues nociception during persistent temporomandibular joint inflammation.

Action Potentials↗
PubMed2005

Sensitization of osteosarcoma cells to death receptor-mediated apoptosis by HDAC inhibitors through downregulation of cellular FLIP.

Fas-mediated apoptosis plays an important role in elimination of tumor cells in vivo, but some tumor-derived cells are resistant to this mechanism. Here, we show that treatment with the histone deacetylase (HDAC) inhibitor FR901228 renders Fas-resistant osteosarcoma cell lines sensitive to Fas-mediated apoptosis by downregulating expression of cellular FLIP (cellular FLICE-inhibitory protein), an inhibitor of Fas-mediated activation of caspase-8. Moreover, sensitization to Fas-mediated apoptosis was also induced in Fas-resistant osteosarcoma cells by suppressing FLIP expression using FLIP-specific RNA interference. HDAC inhibitors including FR901228 were shown to induce downregulation of cellular FLIP through inhibiting generation of FLIP mRNA, rather than stimulating degradation at either protein or mRNA level, and the inhibition was independent of de novo protein synthesis. These results clearly indicate that some tumor cells exhibit a phenotype resistant to death receptor-mediated apoptosis by expressing cellular FLIP, and that HDAC inhibitors sensitize such resistant tumor cells by directly downregulating cellular FLIP mRNA.

Antibiotics, Antineoplastic↗
PubMed2005

A novel diagnostic method for evaluation of vascular lesions in the digestive tract using infrared fluorescence endoscopy.

BACKGROUND AND STUDY AIMS: We have developed an infrared fluorescence endoscope to evaluate gastrointestinal vascular lesions. Infrared endoscopy (IRE) after intravenous administration of indocyanine green (ICG) is used at present to examine vascular lesions such as esophageal varices. However, no previous study has compared the sensitivity of infrared fluorescence endoscopy (IRFE) with that of IRE. In this study, we compared the usefulness of IRFE and IRE. PATIENTS AND METHODS: For IRFE we used an infrared endoscope equipped with excitation and barrier filters and an intensified charge-coupled device camera. In preliminary experiments, the observable tissue depth was assessed by wrapping increasing numbers of layers of commercially available pork around a syringe containing a uniform concentration of ICG or by changing the concentration of ICG in a syringe covered by a piece of pork of uniform thickness. In the clinical part of the study, ICG was administered intravenously at different concentrations to patients with esophageal varices and the resulting infrared fluorescent images were evaluated. RESULTS: The preliminary experiments revealed that the depth of tissue that could be visualized was significantly greater in IRFE than it was in IRE (11.2 mm in IRFE vs. approximately 3.2 mm in IRE). Clear infrared fluorescence was obtained by IRFE at lower concentrations of ICG than the concentrations required to obtain clear images using IRE. In the clinical part of the study, clear infrared fluorescence was observed in a region where esophageal varices had been detected by conventional endoscopy when ICG was administered in doses of 0.005 mg/kg to 0.01 mg/kg, which was lower than the doses used in IRE. CONCLUSIONS: Compared with conventional IRE, IRFE facilitated the observation of deeper layers, and esophageal varices were observed by IRFE following the intravenous administration of a markedly reduced dose of ICG. IRFE, in combining the characteristics of reflected infrared light and fluorescence, may be a useful novel procedure in the diagnosis of vascular lesions in the gastrointestinal tract.

Aged↗
PubMed2004

Adult-onset leukoencephalopathy with vanishing white matter with a missense mutation in EIF2B5.

We report of a woman aged 52 years born to consanguineous parents and seeking treatment for progressive dementia and delusion. Neurologic examination revealed dementia and emotional instability, indifference, and confabulation. There was also mild spasticity of the bilateral lower limbs. MRI revealed diffuse white matter hyperintensity on T2-weighted images accompanied by hypointense areas on fluid-attenuated inversion recovery images. A homozygous missense mutation was identified in EIF2B5.

Adult↗
PubMed2004

Efferent connections of "posterodorsal" auditory area in the rat cortex: implications for auditory spatial processing.

We examined efferent connections of the cortical auditory field that receives thalamic afferents specifically from the suprageniculate nucleus (SG) and the dorsal division (MGD) of the medial geniculate body (MG) in the rat [Neuroscience 117 (2003) 1003]. The examined cortical region was adjacent to the caudodorsal border (4.8-7.0 mm posterior to bregma) of the primary auditory area (area Te1) and exhibited relatively late auditory response and high best frequency, compared with the caudal end of area Te1. On the basis of the location and auditory response property, the cortical region is considered identical to "posterodorsal" auditory area (PD). Injections of biocytin in PD revealed characteristic projections, which terminated in cortical areas and subcortical structures that play pivotal roles in directed attention and space processing. The most noticeable cortical terminal field appeared as dense plexuses of axons in area Oc2M, the posterior parietal cortex. Small terminal fields were scattered in area frontal cortex, area 2 that comprises the frontal eye field. The subcortical terminal fields were observed in the pontine nucleus, the nucleus of the brachium inferior colliculus, and the intermediate and deep layers of the superior colliculus. Corticostriatal projections targeted two discrete regions of the caudate putamen: the top of the middle part and the caudal end. It is noteworthy that the inferior colliculus and amygdala virtually received no projection. Corticothalamic projections terminated in the MGD, the SG, the ventral zone of the ventral division of the MG, the ventral margin of the lateral posterior nucleus (LP), and the caudodorsal part of the posterior thalamic nuclear group (Po). Large terminals were found in the MGD, SG, LP and Po besides small terminals, the major component of labeling. The results suggest that PD is an auditory area that plays an important role in spatial processing linked to directed attention and motor function. The results extend to the rat findings from nonhuman primates suggesting the existence of a posterodorsal processing stream for auditory spatial perception.

Acoustic Stimulation↗
PubMed2004

Early prediction of infection after craniotomy for brain tumours.

Reliably predicting infection soon after craniotomies would prevent infection and reduce treatment costs and hospitalization expenses. Therefore we analysed potential risk factors and blood count data after craniotomies for brain tumours in order to predict infection as soon as possible after surgery. We analysed 139 patients who underwent craniotomies for brain tumours from January 1997 to December 2001, and divided them into four categories (Types A to D) according to the following: increase in their white blood counts (WBCs) from Day 0 to Day 1, maximum WBC between Day 0 and Day 2, and maximum c-reactive protein (CRP) between Day 0 and Day 4 after surgery. We evaluated potential risk factors and the blood count data for infections via logistic regression analysis. Type D patients had a significantly higher rate of infection (p = 0.0123) than the other Types, while Type B patients had the lowest rate among the four groups (p = 0.0006). When Type A patients suffered CSF leakages, they had a significantly higher possibility of meningitis (p < 0.0001) or scalp infection (p = 0.012). In those Type A or D patients who were male, more than 70 years old, and suffered from metastases from primary lung cancer lesions, the possibility of pneumonia was significantly higher (p = 0.0178). In conclusion, we are able to predict infection within four days after craniotomies for brain tumours according to standard blood count data and certain risk factors. This possibility allows for improved care and better clinical outcomes in patients that undergo craniotomies for brain tumours.

Adolescent↗
PubMed2004

Streptococcus mutans strains harboring collagen-binding adhesin.

A previously unidentified 120-kDa protein was detected in Streptococcus mutans strain Z1 and was involved in the cold-agglutination of the strain. We have identified the gene, designated cnm, as being involved in the agglutination of strain Z1 following random mutagenesis. The amino acid sequence of the deduced Cnm protein exhibited high similarity to those of collagen-binding adhesins from staphylococci and other organisms. To confirm whether the protein is involved in collagen-binding, we cloned a cnm gene fragment, overexpressed it in E.coli, and prepared crude extracts. The extracts containing recombinant protein exhibited binding to immobilized collagen and laminin but not to fibronectin. Compared with the parental strain Z1, the cold-agglutination-negative mutant 05A02 exhibited reduced binding to collagen and laminin but retained that to fibronectin. This gene was detected in some strains of S. mutans. Therefore, the cnm gene encoded a new strain-specific member of the collagen-binding adhesin family.

Adhesins, Bacterial↗
PubMed2003

Diffusion-weighted MRI of haemangioblastomas and other cerebellar tumours.

We examined the signal intensity on diffusion-weighted imaging and the apparent diffusion coefficients (ADC) relative to normal cerebellum of the solid portions of 10 cerebellar haemangioblastomas and 12 other cerebellar tumours: three metastases, three medulloblastomas, three malignant lymphomas, an atypical teratoid rhabdoid tumour, an ependymoma and a subependymoma. The tumours were confirmed histopathologically except for one metastasis with pathological diagnosis of the primary lesion. In nine of the haemangioblatomas, the solid and contrast-enhancing portions gave low signal on DWI, but this was not seen in the other tumours. The ADC was increased in haemangioblastomas. These findings may indicate rich vascular spaces of the haemangioblastomas. DWI may be useful for distinguishing haemangioblastomas from other enhancing cerebellar tumours.

Adult↗
PubMed2003

Distribution of intracellular and extracellular water molecules in developing rat's midbrain: comparison with fraction of multicomponent T(2) relaxation time and morphological findings from electron microscopic imaging.

OBJECTIVE: In the present study, we examined the behavior and state of water molecules in immature and mature rat brains by measuring the components of magnetic resonance (MR) water proton transverse relaxation time ( T(2)). We also performed morphological examination of immature and mature rat brains using electron microscopy (EM). We then compared the fraction of T(2) component and the EM findings. METHODS: Midbrains of male Wistar rats were examined at various time points ranging from 4 h to 12 weeks after birth. T(2) was measured by MR, and the ratios of intra- to extracellular spaces were determined by EM in each stage. RESULTS: T(2) consisted of two components: fast T(2) (<100 ms), and slow T(2) (>100 ms). During maturation, values of fast T(2) decreased dramatically, but slow T(2) remained constant. However, the fraction accounted for by slow T(2) decreased from 59% to 9% during maturation. Morphological examination showed that the extracellular space fraction of the midbrain decreased from 49% to 5% during maturation. Thus, morphological change correlated well with changes in slow T(2); in other words, multicomponent T(2) results showed a close correlation with tissue compartmentalization. CONCLUSION: MR relaxation times obtained by means of multicomponent analysis can thus be used to measure intra- and extracellular space fractions.

Animals↗
PubMed2003

A case of germinoma in the septum pellucidum manifesting as amnesia and hemiparesis.

BACKGROUND: We report a rare case of germinoma mainly located in the septum pellucidum. CASE DESCRIPTION: A 19-year-old man presented with germinoma located in the septum pellucidum manifesting as amnesia and right hemiparesis. Magnetic resonance imaging demonstrated a heterogeneously enhanced mass in the septum pellucidum and abnormal T2-weighted signals in the left basal ganglia. An anterior transcallosal approach was performed to remove the mass in the septum pellucidum. The histological diagnosis was germinoma. Radiotherapy and chemotherapy were given. He was discharged with slight amnesia and right hemipareis. INTERPRETATION: Intracranial germinoma can arise from the septum pellucidum.

Adult↗
PubMed2003

Simultaneous detection of mutations associated with resistance to macrolides and quinolones in Campylobacter jejuni and C. coli using a PCR-line probe assay.

Quinolone and macrolide resistance of Campylobacter jejuni and Campylobacter coli mainly depend on a mutation in gyrA and in 23S rDNA, respectively. In order to detect quinolone and/or macrolide resistant C. jejuni and C. coli strains, a macrolide and quinolone line probe assay (MQ-LiPA) was developed and 42 C. jejuni and C. coli strains were tested to evaluate the efficiency of the assay. Profiles of the mutations in 23S rDNA and in gyrA characterized by MQ-LiPA agreed with resistance to macrolides and quinolones. MQ-LiPA is a rapid and simple method for simultaneous detection of quinolone and macrolide resistance of C. jejuni and C. coli. We could also discriminate between C. jejuni and C. coli using probes for detection of gyrA mutations in MQ-LiPA.

Campylobacter coli↗
PubMed2003

Attempts to separate female Ascaris suum antigen and to investigate its partial characterization.

The location and separation of Ascaris suum antigen for serological testing was investigated. The antigenic constituent was rich in the ovary of the adult worm and was obtained by dialysis with 50% ammonium sulphate saturated solution. Sodium dodecyl sulphate polyacrylamide gel electrophoresis and immunoblotting analysis demonstrated that the heat labile antigenic preparation showed one major and seven faint bands. The major band seemed also to be a glycoprotein. The sera from pigs with/without hepatic milk spot showed relatively high precipitation titres, while, those from the specific pathogen free pigs manifested low titres.

Animals↗
PubMed2003

Localization of a non-melanoma skin cancer susceptibility region within the major histocompatibility complex by association analysis using microsatellite markers.

The major histocompatibility complex (MHC) is known to have a role in the development of non-melanoma skin cancer (NMSC), although the genes and mechanisms involved have yet to be determined. To identify the susceptibility locus for NMSC within the MHC, we used a collection of well-defined polymorphic microsatellite markers from the Human leucocyte antigen (HLA) region for an association analysis of 150 cases with NMSC and 200 healthy controls selected from the Busselton population in Western Australia. High-resolution mapping was undertaken using a total of 40 highly polymorphic markers located at regular intervals across the HLA region (3.6Mb). Polymerase chain reaction (PCR) analysis was initially performed on pooled DNA markers to detect those markers that showed different allele profiles. Statistically significant differences in allelic frequencies (differentiating alleles) were found between cases and controls at three polymorphic microsatellite loci within a 470-kb genomic susceptibility region ranging between 6 kb centromeric of the HLA-B gene and intron 5 of the DDR gene. Interestingly, this genome region corresponded completely with the psoriasis-susceptibility locus. The three differentiating alleles and another four markers outside the susceptibility region were then PCR tested by individual genotyping of cases and controls. The newly identified susceptibility locus for NMSC within the MHC was found to be significantly different between the cases and controls by comparisons of allele frequencies at the three differentiating loci estimated from DNA pools and then confirmed by individual genotyping. This is the first study using high density microsatellite markers to localize a NMSC susceptibility region within the human genome.

Australia↗