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Biomedical subjects

K Takada

Publications and source records attributed to K Takada.

At least 73 records · Page 4Linked to original sources
PubMed2001

Epidermal changes caused by chronic low-dose UV irradiation induce wrinkle formation in hairless mouse.

To investigate the effects of chronic low-dose UV irradiation on the skin, hairless mice were irradiated with a 1/3 minimal erythemal dose (MED) of UV. We examined the relationship between visible changes and skin damage in the dermis and epidermis. Hairless mice were irradiated with UVB (20 mJ/cm2) and UVA (14 J/cm2) three times a week for 10 weeks, followed by a 24-week non-irradiation period. Visible fine wrinkling was present after 4 weeks of irradiation, and the wrinkling progressively worsened throughout the period of irradiation. The wrinkles remained after irradiation was discontinued. In dermal components, no significant histological changes in the collagen fibers and elastic fibers were found, and the amount of hydroxyproline was also not changed. Thus, in the epidermis, there was a significant increase in the number of stratum corneum layers and the terminal-differentiation marker, filaggrin, positive cells. The intensity of staining for the differentiation marker, keratin 1, was reduced. These changes were accompanied by wrinkle formation, and remained after discontinuance of irradiation. These findings suggested that chronic low-dose UV irradiation induces structural and quantitative changes in the epidermis as a result of keratinization impairment, and that this damage in the epidermis is an important causative factor in wrinkle formation.

Animals↗
PubMed2001

Diabetes attenuates the minimum anaesthetic concentration (MAC) and MAC-blocking adrenergic response reducing actions of clonidine in rats.

BACKGROUND: It is well known that clonidine, an alpha2 agonist, reduces anaesthetic requirement and attenuates haemodynamic responses against noxious stimuli. However, the diabetic state is known to affect several functions of alpha2 adrenoceptors. We investigated the effects of streptozotocin (STZ)-induced diabetes mellitus (DM) on these beneficial actions of clonidine in halothane-anaesthetized rats. METHODS: The rats were randomly assigned to one of three groups: diabetes (n=24, induced by 50 mg x kg(-1) IV STZ), diabetes treated with insulin (n=24), or control (n=24). We evaluated the effects of clonidine on minimum anaesthetic concentration (MAC) and minimum concentration of halothane needed to suppress cardiovascular responses evoked by a noxious stimulus (MAC-blocking adrenergic responses: MAC-BAR) in each group. MAC and MAC-BAR of halothane were determined by the tail clamp method. MAC-BAR was defined as the MAC which attenuated haemodynamic responses within 10% following the tail clamp. RESULTS: The diabetic state decreased MAC of halothane by approximately 10%, while MAC-BAR of halothane had been little affected. In the diabetes group, MAC reducing action of clonidine (30 and 100 microg x kg(-1), IV) was completely abolished and MAC-BAR reducing action of clonidine was partially reduced (30 but not 100 microg x kg(-1), IV). Insulin treatment preserved these actions of clonidine. CONCLUSION: It is suggested that the diabetic state attenuates the beneficial actions of clonidine and that insulin treatment of diabetes preserves these actions of clonidine.

Adrenergic alpha-Agonists↗
PubMed2001

Changes in the masticatory jaw movement following orthodontic traction of an impacted and transposed upper canine and occlusal adjustment.

In a 10-year-old female with an impacted and completely transposed upper left canine, posterior temporal muscle activity and jaw movement during mastication were examined before and after orthodontic traction of the canine, alignment of teeth, and occlusal adjustment of the canine. After the orthodontic treatment, but before the occlusal adjustment, esthetic improvement in the static occlusion was achieved. The posterior temporal muscle on the non-chewing side exhibited earlier bursts in the electromyography. Jaw movement trajectory of the jaw-closing phase at a level close to the maximum intercuspation position was more to the medial side on the frontal view, and the jaw-closing velocity in the lateral direction was slower during left-sided chewing. Following occlusal adjustment of the transposed canine, however, the muscle activity and jaw movement patterns were improved to normal patterns. We suggest that it might be advisable to perform occlusal adjustment at an early stage during the retention period in such cases.

Journal Article↗
PubMed2001

Changes in masticatory jaw movement and muscle activity following surgical orthodontic treatment of an adult skeletal Class III case.

This case report examines the masticatory jaw movements and electromyograph (EMG) recordings of anterior and posterior temporal and masseter muscles before and after surgical orthodontic treatment in an adult patient with incisor crossbite and skeletal Class III jaw base relationship. The prescribed treatment resulted in a good occlusion and skeletal and dental Class I relationship. The chopping type jaw movement pattern during gum chewing was transformed to more of a grinding motion after treatment. But this motion was not as broad as is normally seen. This observation is indicative of the difficulties associated with improving the masticatory jaw movements in an adult patient to a completely normal pattern even after retention. In this patient, the high frequency of silent periods on the EMG that were observed in the early intercuspal phase before treatment were decreased to normal low levels after treatment. A similar decrease was also seen in the mean duration of the chewing cycle. We conjecture that this patient unsuccessfully attempted to compensate for the silent periods by increasing the period of his chewing cycle.

Journal Article↗
PubMed2001

Unexpected and variable phenotypes in a family with JAK3 deficiency.

Mutations of the Janus kinase 3 (JAK3) have been previously described to cause an autosomal recessive variant of severe combined immunodeficiency (SCID) usually characterized by the near absence of T and NK cells, but preserved numbers of B lymphocytes (T-B+SCID). We now report a family whose JAK3 mutations are associated with the persistence of circulating T cells, resulting in previously undescribed clinical presentations, ranging from a nearly unaffected 18-year-old subject to an 8-year-old sibling with a severe lymphoproliferative disorder. Both siblings were found to be compound heterozygotes for the same deleterious JAK3 mutations: an A96G initiation start site mutation, resulting in a dysfunctional, truncated protein product and a G2775(+3)C mutation in the splice donor site sequence of intron 18, resulting in a splicing defect and a predicted premature stop. These mutations were compatible with minimal amounts of functional JAK3 expression, leading to defective cytokine-dependent signaling. Activated T cells in these patients failed to express Fas ligand (FasL) in response to IL-2, which may explain the accumulation of T cells with an activated phenotype and a skewed T cell receptor (TcR) Vbeta family distribution. We speculate that residual JAK3 activity accounted for the maturation of thymocytes, but was insufficient to sustain IL-2-mediated homeostasis of peripheral T cells via Fas/FasL interactions. These data demonstrate that the clinical spectrum of JAK3 deficiency is quite broad and includes immunodeficient patients with accumulation of activated T cells, and indicate an essential role for JAK3 in the homeostasis of peripheral T cells in humans.

Adolescent↗
PubMed2001

Obesity, body fat distribution and coronary atherosclerosis among Japanese men and women.

OBJECTIVE: To investigate the relation of the obesity and body-fat distribution with angiographically defined coronary atherosclerosis. DESIGN: Cross-sectional study in a clinical setting. SUBJECTS: Three hundred and twenty men (median age, 59 y) and 212 women (median age, 67 y) who underwent coronary angiography for suspected or known coronary heart disease at 5 cardiology departments between September 1996 and August 1997. Patients with disease duration >1 y were excluded. MEASUREMENTS: The body mass index (BMI) and the waist to hip circumference ratio (WHR) were used as main exposure variables, and either the presence of significant coronary stenosis or the Gensini's score (> or =10 vs<10) as an outcome variable, in a sex-specific multiple logistic regression analysis controlling for age, hospital, and other coronary risk factors. RESULTS: Among male patients, BMI was progressively higher with an increasing number of vessels involved (P trend=0.05); the adjusted odds ratios for the presence of significant stenosis across quartiles of BMI were 1.0 (reference), 1.1, 1.9 and 2.5 (P trend=0.02), and the positive association was more pronounced for younger patients. Among females, however, such associations were not evident. Employing the Gensini's score as an outcome gave similar results. WHR was not significantly associated with either outcome regardless of sex. CONCLUSION: These results suggested that BMI was predictive of coronary stenosis among male patients, but not among female patients. Unlike most previous studies, this study failed to detect a positive association with WHR.

Adipose Tissue↗
PubMed2001

Evaluation of diagonal earlobe crease as a marker of coronary artery disease: the use of this sign in pre-operative assessment.

In this study, we examined the usefulness of the earlobe crease sign as a marker of coronary artery disease in the pre-operative assessment of patients. We were interested in evaluating this sign for use in emergency patients. We investigated 530 patients, aged > 40 years, undergoing elective surgery. If the electrocardiogram was abnormal or the patient reported symptoms suggesting coronary artery disease, further cardiac examinations were performed. Patients who demonstrated evidence of coronary artery disease in the additional investigations or had a clear history of coronary artery disease were classified as the abnormal coronary group. Other patients with no history and/or normal investigations were classified as the normal coronary group. The assessment of earlobe crease sign was performed prior to anaesthesia, and the sensitivity, specificity and positive predictive value of this sign were calculated. We found that the sensitivity and specificity was high regardless of age, except for specificity in patients > 70 years old. The data suggest that the earlobe crease sign may be a useful marker for the presence of coronary artery disease in patients undergoing emergency operations in which little or no history and investigations are available. However, more work is required to assess the use of this sign in other ethnic groups.

Adult↗
PubMed2001

Serum alpha-subunit levels in patients with pituitary adenomas.

OBJECTIVE: We investigated preoperative and postoperative serum alpha-subunit levels and the alpha-subunit response to TRH in patients with various types of pituitary tumour and correlated the data with histological findings in order to clarify the significance of alpha-subunit measurement in pituitary adenomas. PATIENTS: We examined 59 patients with pituitary tumours (22 with GH cell adenomas, 30 with clinically nonfunctioning adenomas and seven with other tumours) treated at Toranomon Hospital between 1996 and 1998. RESULTS: The basal alpha-subunit level was supranormal in six out of 22 (27%) patients with a GH cell adenoma and in nine out of 30 (30%) patients with a nonfunctioning adenoma. A paradoxical alpha-subunit response to TRH was found in seven out of 22 (32%) patients with a GH cell adenoma. These seven patients also showed a paradoxical GH response to TRH administration. In addition, paradoxical response to TRH was found in eight out of 30 (27%) patients with a clinically nonfunctioning adenoma. In contrast, patients with other types of pituitary tumour showed neither a supranormal alpha-subunit level nor a paradoxical response to TRH. The supranormal alpha-subunit level and the abnormal response to TRH were normalized in both GH cell adenoma and nonfunctioning adenoma patients after successful surgery. Immunohistochemical studies showed alpha-subunit positive cells in 51% of GH cell adenomas or nonfunctioning adenomas and there was a good concordance with the serum alpha-subunit levels in both GH cell adenoma and nonfunctioning adenoma patients. CONCLUSIONS: These findings suggest that supranormal serum alpha-subunit levels are mainly due to hypersecretion by the tumour itself, while the paradoxical alpha-subunit response to TRH is an associated phenomenon in patients with a GH cell adenoma or nonfunctioning adenoma. The alpha-subunit level and the response to TRH may be useful indicators for assessing the operative outcome, especially in nonfunctioning adenoma patients who have no other definite endocrine markers.

Adenoma↗
PubMed2001

Aggregated occurrence of sleep apnea syndrome in a family.

We experienced a family in whom sleep apnea syndrome (SAS) was recognized in six members and habitual snoring in seven members among 26 subjects of four generations. In all members with snoring, the disorder was noticed before the age of 20. Hypercapnic response study showed normal findings, and ultrafast magnetic resonance image of the upper airway revealed that the obstruction of the upper airway occurred at the velopharyngeal portion during apneic episodes in all SAS-afflicted subjects. In this family, the similar craniofacial structural abnormalities were thought to cause the aggregated occurrences of the disorders at young ages, and obesity was regarded as a contributor for the aggravated symptoms.

Adult↗
PubMed2001

A case of successful management of portosystemic shunt with autosomal dominant polycystic kidney disease by balloon-occluded retrograde transvenous obliteration and partial splenic embolization.

We describe a patient with autosomal dominant polycystic kidney disease who was successfully managed for severe abdominal distension, impaired liver function and a portosystemic shunt by interventional therapies. The patient's intra-hepatic portal vein was compressed and narrowed by multiple liver cysts, which resulted in a decrease of the portal blood flow and portal hypertension due to a huge gastro-renal shunt These haemodynamic changes were assumed to contribute to insufficient protein synthesis in the liver. Therefore, we first repeatedly performed minocycline hydrochloride instillations to treat the multiple liver cysts. Then, we conducted a partial splenic embolization to prevent elevation of the portal vein pressure prior to balloon-occluded retrograde transvenous obliteration which was performed to increase the portal blood flow. The portal blood flow markedly increased, and protein synthesis in the liver also recovered and the clinical symptoms improved. The patient has been monitored for more than two years up to the present and her liver function parameters have remained within the normal range. Renal insufficiency is known to be a major prognostic factor in autosomal dominant polycystic kidney disease. In some cases, however, liver involvement with multiple cysts may result in a fatal outcome. In such cases, interventional therapies, as provided to this patient, should be considered.

Cysts↗
PubMed2001

Complete 3-D reconstruction of dental cast shape using perceptual grouping.

To achieve the complete three-dimensional (3-D) data retrieval of the shape of dentition, dental casts were measured from four directions; occlusal, right, left, and labial sides using a line laser scanner. Reconstruction of the entire shape, including undercuts and tooth crowding area, was attempted by applying a perceptual grouping algorithm, which is one of pattern-recognition theories. In the data measured from occlusal, right and left sides, the rows of measurements were parallel to the frontal plane, and three-directionally combined data (3-DC data) was accomplished by affine transformation. While, in the labial side, transformation to the frontal plane was done since rows of the measured data were parallel to the sagittal plane. To combine the labial data with the 3-DC data and reconstruct the complete image, rearrangement of the order of the data in the file was attempted by applying the perceptual grouping. That is, the minimum total length of data combining was examined by considering the factor of proximity and continuity between the data. The most appropriate order of data combining and recognition of islands were accomplished. Using a computer graphic (CG) with a wire-frame model, complicated regions such as anterior segments showing tooth crowding and undercut area were found to be successfully reconstructed without any data defects. The accuracy of reconstruction was ascertained by comparing the characteristic distances between apexes of molars in the reconstructed model with the real cast. The difference was within 0.3 mm, and present method for dental cast reconstruction is considered to be satisfactory for the present purpose such as orthodontics.

Dental Casting Technique↗
PubMed2001

Effect of transjugular intrahepatic portosystemic shunt formation on portal hypertensive gastropathy and gastric circulation.

OBJECTIVES: The aim of this study was to investigate the effect of a transjugular intrahepatic portosystemic shunt (TIPS) on portal hypertensive gastropathy (PHG) and gastric hemodynamics. METHODS: A total of 16 patients with cirrhosis and portal hypertensive gastropathy were prospectively studied. Of these, 12 patients underwent TIPS for esophageal varices and four for refractory ascites. Gastric mucosal blood flow (GMBF) was assessed by laser Doppler flowmeter, and total blood flow (TBF) in submucosa and mucosa by near-infrared endoscopy. Portal venous pressure was obtained by a transducer during the TIPS procedure. The severity of portal hypertensive gastropathy was classified as none, mild, or severe. The examinations were performed before and 2 wk after the procedure. RESULTS: TIPS significantly reduced portal venous pressure. PHG improved in all four patients with severe PHG and in five of 12 patients with mild PHG after treatment. Gastric mucosal blood flow increased from 49.0 to 55.6 ml/min/100 g after TIPS. In contrast, TBF decreased from 0.35/s to 0.27/s after treatment. Liver function tests showed no significant changes before and after the procedure. CONCLUSIONS: It is considered that TIPS may have a beneficial effect on PHG at least for a short time. The mechanism by which PHG improves may be closely related to the improvement of the injured gastric perfusion in cirrhotic patients with PHG.

Esophageal and Gastric Varices↗
PubMed2001

Differential regulation of Epstein-Barr virus (EBV) latent gene expression in Burkitt lymphoma cells infected with a recombinant EBV strain.

Epstein-Barr virus (EBV)-negative Burkitt lymphomas (BLs) can be infected in vitro with prototype EBV strains to study how the virus may affect the phenotype of tumor cells. Studies thus far have concentrated on the use of transforming B95-8 and nontransforming P3HR1 strains. Immunological and phenotypic differences between the sublines infected with these two strains were reported. The majority of these differences, if not all, can be attributed to the lack of EBNA-2 coding sequences in the P3HR1 strain. The recent development of a selectable Akata strain has opened up new possibilities for infecting epithelial and T cells as well. We infected five EBV-negative BL lines with the recombinant Akata virus. Our results indicate that the infected cell lines BL28, Ramos, and DG75 express EBNA-1, EBNA-2, and LMP1, the viral proteins associated with type III latency, and use both YUK and QUK splices. In contrast, two EBV-negative variants of Akata and Mutu when reinfected displayed restricted type I latency and expressed only EBNA-1. All clones of infected Mutu cells used the QUK splice exclusively. The usage of Qp was observed in a majority of Akata clones. Some Akata clones, however, were found to have double promoter usage (Qp and C/Wp) but at 4 months after infection did not express EBNA-2. The results demonstrate differential regulation of EBV latency in BLs with the same recombinant viral strain and suggest that the choice of latency type may be cell dependent. The restricted latency observed for infected Akata and Mutu cells indicates that a BL may opt for type I latency in the absence of immune pressure as well.

Burkitt Lymphoma↗
PubMed2001

Role of bcl-2 in Epstein-Barr virus-induced malignant conversion of Burkitt's lymphoma cell line Akata.

We have demonstrated that Epstein-Barr virus (EBV) confers enhanced growth capability in soft agarose, tumorigenesis in the SCID mouse, and resistance to apoptosis in the Burkitt's lymphoma cell line Akata. Subsequently, we have shown that EBV-encoded small RNAs (EBERs) are responsible for these phenotypes. We constantly observed the upregulation of bcl-2 oncoprotein expression upon EBV infection and expression of EBERs. To test whether these phenotypes were due to the upregulation of bcl-2 expression, we introduced bcl-2 into EBV-negative Akata cells at various levels encompassing the range at which EBV-positive cells expressed it. As cells expressed bcl-2 at higher levels, they became more capable of growing in soft agarose and became resistant to apoptosis. However, clones expressing bcl-2 at a higher level than EBV-positive Akata cells were negative in the tumorigenesis assay in the SCID mouse. On the other hand, introduction of bax into EBV-positive Akata cells reduced the resistance to apoptosis; however, it failed to reduce the growth capability in soft agarose. These data indicate that EBV targets not only bcl-2, but also an unknown pathway(s) to enhance the oncogenic potential of Akata cells.

Animals↗
PubMed2001

Electron microscopic study of persistent dengue virus infection: analysis using a cell line persistently infected with Dengue-2 virus.

We investigated persistent infection of Epstein-Barr virus (EBV)-transformed lymphoblastoid cells with dengue virus using a transmission electron microscope. Most of the infected cells kept an intact morphology with only a few virus particles in the cytoplasm, but without any indication of active viral replication. Some cells were apoptotic and a few dengue virus particles were present in these apoptotic cells. Raji cells acutely infected with dengue-2 virus showed degenerative morphology. There were membranous tubular structures and many virus particles around and within the infected cells. Approximately 95% of the cells were dengue viral antigen positive in the persistently infected EBV-transformed cell line. It is likely that persistent infection is maintained mainly by the division of infected cells without cytopathic effect by dengue-2 virus.

Antigens, Viral↗
PubMed2001

Kinematic modeling of jaw-closing movement during food breakage.

It has been demonstrated that the vertical jaw movement trajectories during gum-chewing can be explained by jerk-cost minimization. However, it is uncertain whether the masticatory jaw movement in space can be predicted by the minimum-jerk model. The aims of the present study were to develop minimum-jerk models that would explain 3D masticatory jaw movements with different hardnesses of foods, and to evaluate if the models can predict the movements accurately. The 3D masticatory jaw movement during food breakage was formulated for two types of test foods. The coefficients of determination (R2) between the measured and model-based values ranged from 0.846 to 0.882. Differences were found in the kinematic parameters between the test foods. The results suggest that the models predict the 3D jaw movements during food breakage and are effective in differentiating among the kinematic features of masticatory jaw movements that are peculiar to the mechanical properties of foodstuffs.

Adult↗