Search PubMed⌕ Search

Biomedical subjects

Masatoshi Tanaka

Publications and source records attributed to Masatoshi Tanaka.

At least 19 recordsLinked to original sources
PubMed2006

Effect of MK-801 and ketamine on hydroxyl radical generation in the posterior cingulate and retrosplenial cortex of free-moving mice, as determined by in vivo microdialysis.

This study investigated the effect of MK-801 and ketamine, N-methyl-D-aspartate (NMDA) receptor antagonists which can induce schizophrenic symptoms and have neurotoxicity in human and animals, on hydroxyl radical (*OH) generation in the posterior cingulate and retrosplenial (PC/RS) cortex of free-moving mice using the salicylic acid trapping technique. MK-801 (0.6 mg/kg) or ketamine (50 mg/kg) acute administration significantly increased *OH levels in mouse PC/RS cortex. The basal *OH levels after MK-801 and ketamine administrations for 7 consecutive days were significantly increased compared with the naive basal levels. MK-801 (0.6 mg/kg) or ketamine (50 mg/kg) challenge after chronic administration further significantly increased dialysate levels of *OH. Our study also found that the release of *OH was secondary to stereotyped behavior, and the intensity of stereotyped behavior induced by MK-801 was more than that induced by ketamine. The results suggested that NMDA receptor antagonists participate in the generation of *OH in the PC/RS cortex of mouse, and oxidative stress, derived from the formation of free radicals, might play an important role in the pathophysiology of these two models of schizophrenia.

Animals↗
PubMed2006

In vitro synergistic effects of double combinations of beta-lactams and azithromycin against clinical isolates of Neisseria gonorrhoeae.

In Japan, Neisseria gonorrhoeae, a sexually transmitted pathogen, has recently shown significant resistance to various antimicrobial agents. In this study, a checkerboard method was utilized to investigate the in vitro activities of cefixime (CFIX), cefteram (CFTM), or amoxicillin (AMPC) in combination with azithromycin (AZM) against 25 clinical isolates of N. gonorrhoeae. Synergy, defined as a fractional inhibitory concentration (FIC) index of less than or equal to 0.50, was observed in 32% of isolates with CFIX+AZM, 12% of isolates with CFTM+AZM, and 4% of isolates with AMPC+AZM. Moreover, partial synergy, defined as an FIC index of greater than 0.50 and less than 1, was observed in 44% of isolates with CFIX+AZM, 68% of isolates with CFTM+AZM, and 52% of isolates with AMPC+AZM. In particular, as a result of the combination of CFIX and AZM, for all isolates, significant reductions were observed in the median CFIX minimum inhibitory concentration (MIC; from 0.25 to 0.008 microg/ml; P < 0.0001) and the median AZM MIC (from 0.12 to 0.03 microg/ml; P < 0.0001). However, antagonism, defined as an FIC index of greater than 1, was observed in only 4% of the isolates with both CFIX+AZM and CFTM+AZM, while it was seen in 12% of the isolates with AMPC+AZM. To our knowledge, this is the first study to demonstrate that the in vitro activity of CFIX against N. gonorrhoeae can be significantly enhanced in combination with AZM.

Amoxicillin↗
PubMed2006

A decrease in AFP level related to administration of interferon in patients with chronic hepatitis C and a high level of AFP.

It is known that there is a very high incidence of hepatocellular carcinoma (HCC) among patients with type C chronic hepatitis and cirrhosis, and alpha -fetoprotein (AFP) has been widely used as a diagnostic marker for HCC. However, there are some patients showing continuous high AFP values but no evidence of HCC, and some studies have defined such patients as a high-risk group for HCC. In vitro study has shown that interferon (IFN) inhibits cell proliferation and enhances apoptosis as well as specific cytotoxic T lymphocytes against HCC, resulting in direct anticancer actions. In this study, we investigated the effect of IFN on AFP changes in chronic hepatitis C patients. Of 40 patients with chronic hepatitis C in whom diagnostic imaging confirmed the absence of HCC, 24 patients showed high pretreatment AFP values (high AFP group: AFP level > 10 ng/dl; mean +/- SD, 46.3 +/- 41.5 ng/dl) and 16 showed low pretreatment AFP values (low AFP group: pretreatment AFP level < or = 10 ng/dl; mean +/- SD, 5.3 +/- 2.2 ng/dl). Pretreatment clinical parameters were statistically evaluated in relation to the AFP value. In the high AFP group, the platelet count, albumin level, and prothrombin (%) were significantly lower (P = 0.047, P = 0.0002, and P = 0.044, respectively), suggesting that AFP value increases with advancing liver disease. Subsequently 27 patients were administered IFN (IFN group), and the remaining 13 patients were administered Stronger Neo-minophagen C (SNMC), a glycyrrhizin preparation (SNMC group), as a control group receiving liver-protective therapy. Alanine aminotransferase was reduced in both the IFN and the SNMC group (mean, 132.56 to 60.07 mg/ml [P < 0001] and 147.85 to 56.23 mg/ml [P = 0.0240], respectively). AFP was significantly reduced in the IFN group (mean, 30.03 to 12.65 ng/ml; P = 0.0034), but there was no significant change in AFP in the SNMC group (mean, 29.70 to 39.17 ng/ml). AFP is useful for diagnosing HCC; however, some patients show a persistently high AFP level in the absence of HCC, and these patients have been described as a high-risk group for HCC. In this study, we found that IFN therapy but not SNMC universally reduced the AFP baseline. Since AFP is a significant predictor for HCC, therapeutic strategies for hepatitis C, e.g., long-term low-dose IFN treatment, may reduce hepatocarcinogenesis.

Aged↗
PubMed2006

Clinical outcomes and learning curve of a laparoscopic adrenalectomy in 103 consecutive cases at a single institute.

OBJECTIVE: We examined the clinical outcomes and the learning curve for a laparoscopic adrenalectomy (LA) in 103 consecutive cases performed by three surgeons at our institute, according to the type of adrenal disorder. PATIENTS AND METHODS: One hundred and three patients with adrenal tumors, including 38 cases of primary aldosteronism, 33 cases of Cushing syndrome (including preclinical Cushing syndrome), 15 cases of pheochromocytoma, and nine cases of non-functioning adenoma were evaluated, while focusing on the approaches, intraoperative and postoperative data, and the learning curve of LA, according the type of adrenal disorder. RESULTS: There was no significant difference in the operation time, estimated blood loss, incidence of conversion to open surgery and blood transfusion, or postoperative recovery among the patients treated by LA for aldosteronoma, Cushing adenoma, pheochromocytoma, and non-functioning adenoma. In the cases of aldosteronoma and Cushing adenoma, the learning curve for the operation time and blood loss in each operator tended to decrease as the number of operations increased. On the other hand, in the cases treated by LA for pheochromocytoma, no trends in either the operation time or blood loss were observed. However, there has been neither any conversion to open surgery nor blood transfusion in cases treated by LA since 1998 (our 42nd case), even after the changes in the operators. CONCLUSIONS: Our results clearly indicate that LA is becoming safer than before, probably due to improvements in the technique, education, and training of surgeons, in addition to the increased number of cases now treated by LA.

Adrenal Gland Neoplasms↗
PubMed2006

Clinical features of hepatitis C virus-related hepatocellular carcinoma and their association with alpha-fetoprotein and protein induced by vitamin K absence or antagonist-II.

PURPOSE: We investigated the differences in clinical features between alpha-fetoprotein (AFP)-predominant hepatocellular carcinoma (HCC) and protein induced by vitamin K absence or antagonist-II (PIVKA-II)-predominant HCC, especially regarding host factors thought to contribute to hepatocarcinogenesis in chronic hepatitis C virus (HCV) infection. METHODS: HCV-related HCC patients (n=306) were divided into four groups according to median AFP (48.1 ng/ml) and PIVKA-II (60 mAU/ml). Host factors, tumor factors, survival, and risk factors affecting survival were compared. RESULTS: Aspartate aminotransferase (AST; IU/L), alanine aminotransferase (ALT; IU/L), and platelet count (x 10(4)/ml) were, respectively, 81, 67, and 8.2 in AFP-predominant HCC (group A; n=66) vs. 50, 42, and 11.4 in PIVKA-II-predominant HCC (group P; n=52). Tumor sizes (mm) in groups A and P were 20 and 37, respectively. Significant differences were evident. Survival was identical between the two groups. Factors affecting survival were total bilirubin, portal tumor thrombus and number of nodule in group A, and albumin and tumor distribution in group P. CONCLUSIONS: PIVKA-II-predominant HCC had a milder hepatitis and a better-preserved platelet count compared with AFP-predominant HCC. Considering the strong relation between hepatocarcinogenesis and hepatic inflammation with chronic HCV infection, these differences indicate that hepatocarcinogenic mechanisms in PIVKA-II-predominant HCC may differ from those in AFP-predominant HCC.

Aged↗
PubMed2005

Analysis of mutations within multiple genes associated with resistance in a clinical isolate of Neisseria gonorrhoeae with reduced ceftriaxone susceptibility that shows a multidrug-resistant phenotype.

A Neisseria gonorrhoeae strain with a reduced susceptibility to ceftriaxone (minimum inhibitory concentration (MIC) = 0.5 microg/mL) was isolated among 398 clinical isolates obtained from 2000-2001 in Fukuoka City, Japan. The N. gonorrhoeae strain was negative for penicillinase production but it showed multidrug resistance against penicillin (MIC = 8 microg/mL), tetracycline (MIC = 4 microg/mL), azithromycin (MIC = 0.5 microg/mL) and ciprofloxacin (MIC = 16 microg/mL). The molecular mechanisms of the multidrug-resistant phenotype in this strain were analysed. Polymerase chain reaction and direct DNA sequencing were performed to identify mutations within the penA, ponA, mtrR, penB, gyrA and parC genes of the gonococcal strain, which thus explain the multidrug-resistant phenotype. The N. gonorrhoeae strain contained a significantly different sequence of the penA gene from that of the ceftriaxone-susceptible strains. Some regions of the transpeptidase domain within this penA gene were closely similar to those found in other Neisseria species such as Neisseria subflava, Neisseria flavescens or Neisseria perflava/sicca. This strain also included a ponA mutation that is associated with high-level resistance to penicillin, mtrR mutations that mediate overexpression of the MtrCDE efflux pump responsible for resistance to hydrophobic agents such as azithromycin, and penB mutations that reduce porin permeability to hydrophilic agents such as tetracycline. Moreover, this strain contained gyrA and parC mutations that confer high-level resistance to ciprofloxacin. These results indicate the emergence of a N. gonorrhoeae strain with reduced susceptibility to ceftriaxone, which also showed a multidrug-resistant phenotype that can be explained by the presence of multiple loci mutations associated with antibiotic resistance.

Amino Acid Sequence↗
PubMed2005

Effect of acute and chronic MK-801 administration on extracellular glutamate and ascorbic acid release in the prefrontal cortex of freely moving mice on line with open-field behavior.

The present study was designed to investigate the effects of acute and chronic administration of MK-801 (0.6 mg/kg), a noncompetitive NMDA-receptor antagonist on extracellular glutamate (Glu) and ascorbic acid (AA) release in the prefrontal cortex (PFC) of freely moving mice using in vivo microdialysis with open-field behavior. In line with earlier studies, acute administration of MK-801 induced an increase of Glu in the PFC. We also observed single MK-801 treatment increased AA release in the PFC. In addition, our results indicated that the basal AA levels in the PFC after MK-801 administration for 7 consecutive days were significantly decreased, and basal Glu levels also had a decreased tendency. After chronic administration (0.6 mg/kg, 7 days), MK-801 (0.6 mg/kg) challenge significantly decreased dialysate levels of AA and Glu. Our study also found that both acute and chronic administration of MK-801 induced hyperactivity in mice, but the intensity of acute administration was more than that of chronic administration. Furthermore, in all acute treatment mice, individual changes in Glu dialysate concentrations and the numbers of locomotion were positively correlated. In conclusion, this study may provide new evidence that a single MK-801 administration induces increases of dialysate AA and Glu concentrations in the PFC of freely moving mice, which are opposite to those induced by repeated MK-801 administration, with an unknown mechanism. Our results suggested that redox-response might play an important role in the model of schizophrenic symptoms induced by MK-801.

Animals↗
PubMed2005

Nicotine regulates DARPP-32 (dopamine- and cAMP-regulated phosphoprotein of 32 kDa) phosphorylation at multiple sites in neostriatal neurons.

Nicotinic acetylcholine receptors (nAChRs) regulate dopaminergic signaling in the striatum by modulating the release of neurotransmitters. We have recently reported that nicotine stimulates the release of dopamine via alpha4beta2(*) nAChRs and/or alpha7 nAChRs, leading to the regulation of DARPP-32 at Thr34, the site involved in regulation of protein phosphatase-1 (PP-1). In this study, we investigated the regulation of DARPP-32 phosphorylation at its other sites, Thr75 [cyclin-dependent kinase-5 (Cdk5) site], Ser97 (CK2 site), and Ser130 (CK1 site), that serve to modulate Thr34 phosphorylation and dephosphorylation. In neostriatal slices, nicotine (100 microM) increased phosphorylation of DARPP-32 at Ser97 and Ser130 at an early time point (30 s) and decreased phosphorylation of DARPP-32 at Thr75 at a late time point (3 min). The increase in Ser97 and Ser130 phosphorylation was mediated through the release of dopamine via activation of alpha4beta2(*) nAChRs and alpha7 nAChRs and the subsequent activation of dopamine D1 and D2 receptors. The decrease in Thr75 phosphorylation was mediated through the release of dopamine via activation of alpha4beta2(*) nAChRs and the subsequent activation of dopamine D1 receptors. These various actions of nicotine on modulatory sites of phosphorylation would be predicted to result in a synergistic increase in the state of phosphorylation of DARPP-32 at Thr34 and thus would contribute to increased dopamine D1 receptor/DARPP-32 Thr34/PP-1 signaling.

Animals↗
PubMed2005

Glutamate regulation of DARPP-32 phosphorylation in neostriatal neurons involves activation of multiple signaling cascades.

Dopamine- and cAMP-regulated phosphoprotein of 32 kDa (DARPP-32) plays a central role in medium spiny neurons in the neostriatum in the integration of various neurotransmitter signaling pathways. In its Thr-34-phosphorylated form, it acts as a potent protein phosphatase-1 inhibitor, and, in its Thr-75-phosphorylated form, it acts as a cAMP-dependent kinase inhibitor. Here, we investigated glutamate-dependent signaling cascades in mouse neostriatal slices by analyzing the phosphorylation of DARPP-32 at Thr-34 and Thr-75. Treatment with glutamate (5 mM) caused a complex change in DARPP-32 Thr-34 phosphorylation. An initial rapid increase in Thr-34 phosphorylation was NMDA/alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/metabotropic glutamate-5 receptor-dependent and was mediated through activation of a neuronal nitric oxide synthase/nitric oxide/cGMP/cGMP-dependent kinase signaling cascade. A subsequent decrease in phosphorylation was attributable to activation of an NMDA/AMPA receptor/Ca2+/protein phosphatase-2B signaling cascade. This decrease was followed by rephosphorylation via a pathway involving metabotropic glutamate-5 receptor/phospholipase C and extracellular receptor kinase signaling cascade. Treatment with glutamate initially decreased Thr-75 phosphorylation through activation of NMDA/AMPA receptor/Ca2+/protein phosphatase-2A signaling. Thereafter, glutamate slowly increased Thr-75 phosphorylation through activation of metabotropic glutamate-1 receptor/phospholipase C signaling. Our analysis of DARPP-32 phosphorylation in the neostriatum revealed that glutamate activates at least five different signaling cascades with different time dependencies, resulting in complex regulation of protein kinase and protein phosphatase activities.

Animals↗
PubMed2005

A side effect of neuraminidase inhibitor in a patient with liver cirrhosis.

Neuraminidase inhibitors have been widely used in Japan since 2001, and several side-effects of their use have been reported. However, erythema toxicum has rarely been described as a side-effect of these drugs in patients with liver function disorder. Here, we report a case of generalized rash after treatment with the neuraminidase inhibitors zanamivir and oseltamivir administered prophylactically to prevent influenza infection in two patients with hepatoma associated with liver cirrhosis.

Acetamides↗
PubMed2005

Incidence of adrenal involvement and assessing adrenal function in patients with renal cell carcinoma: is ipsilateral adrenalectomy indispensable during radical nephrectomy?

OBJECTIVE: To determine the value of ipsilateral adrenalectomy with radical nephrectomy, by investigating the clinical aspects of adrenal involvement and adrenocortical function in patients with renal cell carcinoma (RCC). PATIENTS AND METHODS: The demographic, clinical and pathological data of adrenal involvement were reviewed in 247 patients with RCC. To evaluate adrenocortical function, 14 patients (adrenalectomy in eight, adrenal-sparing in six) had a rapid adrenocorticotropic hormone (ACTH) stimulation test before and 2 weeks after surgery. RESULTS: There was adrenal involvement with RCC in seven of the 247 (2.8%) patients (a solitary adrenal metastatic tumour in four and direct extension into the adrenal gland in three). All adrenal involvement was detectable on abdominal computed tomography before surgery, and these patients had a large primary renal tumour of > pT2 and/or distant metastasis. Plasma cortisol levels declined significantly more in response to the rapid ACTH stimulation test in those treated by adrenalectomy than in those with spared adrenal glands at 2 weeks after surgery (P < 0.05), while there was no significant difference between the groups before surgery. CONCLUSIONS: These results suggest that unconditional ipsilateral adrenalectomy with radical nephrectomy for RCC should be avoidable, and thus preserve the reserve of adrenocortical function, as preoperative imaging, especially thin-slice multidetector helical computed tomography, can detect adrenal involvement with RCC in most cases. Unilateral adrenalectomy might cause an irreversible impairment of the reserve of adrenocortical function.

Adrenal Gland Neoplasms↗
PubMed2004

Antimicrobial resistance of Neisseria gonorrhoeae in Japan, 1993-2002: continuous increasing of ciprofloxacin-resistant isolates.

Susceptibility testing was conducted on 1357 isolates of Neisseria gonorrhoeae isolated from 1993 through 2002 in Japan to assess the antimicrobial resistance. Selected isolates were characterised by auxotype and analysis was done for mutations within the quinolone resistance-determining region (QRDR) in the gyrA and parC genes, which confer fluoroquinolone resistance to the organism. Isolates with ciprofloxacin resistance increased significantly from 6.6% (1993-1994) to 73.5% (2002). The proportion of plasmid-mediated penicillin-resistant isolates (PPNG) decreased significantly from 7.9% (1993-1994) to 0.9% (2002). The percentage of chromosomal-mediated resistance to penicillin decreased from 27.4% in 2000 to 12.0% in 2001 but increased to 28.9% in 2002. The proportion of isolates with any type of resistance to tetracycline decreased from 24.7% in 2000 to 13.9% in 2001 and then increased to 22.3% in 2002. The proportion of prototrophic isolates significantly decreased from 84.4% in 1992-1993 to 7.7% in 2001, while that of the proline-requiring isolates significantly increased from 4.4% in 1992-1993 and 80.8% in 1998. The proline-requiring isolates were less susceptible to ciprofloxacin than the prototrophic or arginine-requiring isolates. Of 87 isolates resistant to ciprofloxacin, 2 (2.3%) contained five amino acid substitutions within the GyrA and ParC proteins, 76 (87.4%) contained three or four amino acid substitutions and 9 (10.3%) contained one or two amino acid substitutions.

Amino Acid Substitution↗
PubMed2004

Changes in health habits of female shift workers.

This paper examines the effects of shift work on the lifestyles of female factory workers. As an indicator of healthy lifestyle habits, we used a scoring system (referred to below as the 'health score') based on Lester Breslow's health habits. The 'health score' of the women was higher than that of the men, but the shift workers' score was lower than that of the non-shift workers (p<0.01). In addition, the score of workers who had changed from non-shift work to double-shift work was remarkably low (p<0.01). These results suggest that, while the female shift workers manage to maintain relatively healthy lifestyles in comparison with the males, they have more difficulty maintaining these habits than do female workers who do not perform shift work. It can be concluded that, in addition to heightening women's consciousness of their own health, surrounding entities such as the work environment, the home, and the community in general need to pay due care to Japan's female shift workers.

Adult↗
PubMed2004

[Effects of exposure to occupational hand-arm vibration on maintenance of postural balance].

In order to determine the relationship between exposure to hand-arm vibration through the use of vibration tools and dysfunction in the maintenance of postural balance, 106 male forestry workers were examined by stabilometry for deflection in the center of gravity and in the air conduction hearing levels. A questionnaire survey was also conducted among the workers in order to obtain details regarding their age, the types of tools used by them, and the duration for which they had used a chain saw. The vibration acceleration of a chain saw has been limited to a level of 3 G or less since 1976 in accordance with the notification from the Japanese Forestry Agency and the Ministry of Labor. In fact, chain saws with significantly reduced vibration acceleration in comparison with those used before 1976 have been available. Therefore, in 2000, we conducted a test on forestry workers who were divided into two groups-workers who had used a chain saw for 25 years or more (25-yr-or-more group) and workers who had used a chain saw for 24 yr or less (24-yr-or-less group). Compared to the 24-yr-or-less group, the 25-yr-or-more group exhibited significantly higher levels of average deflection in the center of gravity, expressed as the enveloped (aENV) and rectangular (aREC) areas, and in the hearing levels at 500, 1000, 2000, 4000 and 8000 Hz. For the aENV, the correlation coefficients revealed significant relationships between the hearing levels at 4,000 Hz, the duration of use of a chain saw, and age. Since the duration of use of a chain saw exhibited a significant relationship with age, it was necessary to eliminate the effect of age on the aENV. Subsequently, we divided all the workers into age groups spanning ten years each (from 20 to 70 yr) and compared the aENV among the same age groups in both the 25-yr-or-more and the 24-yr-or-less groups. The averages of the aENV for each age group were higher in the 25-yr-or-more group than in the 24-yr-or-less group. In particular, a significant difference was observed in the group of workers in their 40s. Moreover, the average of aENV value was significantly higher in the 25-yr-pr-more group than in the 24-yr-or-less group among the workers between 46 and 68 yr, with their ages being congruent in both groups. While investigating the impact on the workers who had used chain saws, it might be difficult to examine the effect of occupational vibration independent of the noise load. Nevertheless, this study suggests the possibility that a decrease in the maintenance of postural balance has a stronger relationship with exposure to thumping vibration in the past than with the age factor.

Adult↗
PubMed2004

Effect of shift work on mental state of factory workers.

This paper examines the effects of shift work on the mental state of factory workers. As an indicator of the workers' mental condition, the authors used a scoring system (referred to below as the 'depression tendency score') based on the SRQ-D investigative report. The depression tendency score of the men was higher among the shift worker group than among the regular day worker group (p < 0.01). The depression tendency score of the male back-to-back shift workers was higher than that of the male regular day workers among skilled workers (p < 0.05). Among the women, no notable difference in depression tendency score was observed between the regular day worker group and the shift worker group. However, the depression tendency score of the female two-shift workers was higher than that of the female regular day workers among skilled workers (p < 0.05). We conclude that the mental health of men is easily affected by back-to-back shift work and that of women is affected by two-shift work because of the difference in modern societal/home role between man and woman.

Adult↗
PubMed2003

Surgical outcome of laparoscopic radical prostatectomy: summary of early multiinstitutional experience in Japan.

BACKGROUND: Because laparoscopic radical prostatectomy requires significant laparoscopic expertise, it needs to be evaluated critically before being accepted as a standard therapeutic option for localized prostate cancer. METHODS: A total of 148 men diagnosed as having clinically resectable prostate cancer underwent laparoscopic radical prostatectomy at seven different institutions in Japan. Early biochemical and oncological outcomes were investigated. RESULTS: Policies underlying the selection of laparoscopic radical prostatectomy did not appear to be consistent among the participating institutions. Pathologically organ-confined disease was found in 64.0% of the patients who had undergone neoadjuvant therapy and in 77.2% of those who had not. Positive surgical margins were found in 36.0% and 34.1%, respectively, of the specimens. The most common site was the apex, which accounted for 77.8% of positive margins in patients who had undergone neoadjuvant therapy and 50.0% in those who had not. Seven patients have experienced biochemical failure at a median follow-up of 9.0 months. No clinical progression has been reported. CONCLUSIONS: Continuing improvements in each step of laparoscopic radical prostatectomy, especially apical dissection, should be sought as we pursue the goal of still better oncological outcomes. A systematic approach and therapeutic guidelines should help to reduce the learning curve for competent performance of this procedure.

Aged↗