Biomedical subjects

R Kobayashi

Publications and source records attributed to R Kobayashi.

At least 19 recordsLinked to original sources

PubMed2006

Upregulation of p27 and its inhibition of CDK2/cyclin E activity following DNA damage by a novel platinum agent are dependent on the expression of p21.

The cisplatin analogue 1R,2R-diaminocyclohexane(trans-diacetato)(dichloro)platinum(IV) (DAP) is a DNA-damaging agent that will be entering clinical trials for its potent cytotoxic effects against cisplatin-resistant tumour cells. This cytotoxicity may reside in its ability to selectively activate G1-phase checkpoint response by inhibiting CDKs via the p53/p21 pathway. We have now evaluated the role of another CDK inhibitor p27 as a contributor to DAP-mediated inhibition of G1-phase CDK2 activity. Our studies in ovarian A2780 tumour cells demonstrate that p27 levels induced by DAP are comparable to or greater than those seen for p21. The induction of p27 is not through a transcriptional mechanism, but rather is due to a four-fold increase in protein stabilisation through a mechanism dependent on p21. Moreover, DAP-induced p21 promoted the selective increase of p27 in the CDK2 complex, but not in CDK4 complex, and this selective increase contributed to inhibition of the CDK2 kinase activity. The inhibited complex contained either p27 or p21, but not both, with the relative levels of cyclin E associated with p27 and p21 indicating that about 25% of the inhibition of CDK2 activity was due to p27 and 75% due to p21. This study provides the first evidence that p27 upregulation is directly attributable to activation of the p53/p21 pathway by a DNA-damaging agent, and promulgates p53/p21/p27 axis as a significant component of checkpoint response.

Antineoplastic Agents↗

PubMed2006

TCL1 shows a regulated expression pattern in chronic lymphocytic leukemia that correlates with molecular subtypes and proliferative state.

Expression of the human oncogene TCL1 in transgenic mice produces B-cell tumors that resemble chronic lymphocytic leukemia (CLL) suggesting its role in B-cell tumorigenesis. To clarify the expression pattern and regulation of TCL1 in CLL, we assessed 213 primary tumors by immunohistochemistry (IHC), flow-cytometry and/or Western blot, using a new monoclonal antibody. TCL1 protein was detectable in the majority of CLL (90% by IHC) but showed marked variations across cases with virtual absence in approximately 10% of tumors. Higher TCL1 levels correlated with markers of the 'pre-germinal center' CLL subtype including unmutated VH status (P=0.005), ZAP70 expression (P=0.007), and presence of chromosome 11q22-23 deletions (P=0.04). Intratumoral heterogeneity in TCL1 levels was also prominent and explained in part by markedly lower TCL1 expression in proliferating tumor cells. In vitro exposure of CLL cells to interleukin-4 (but not other growth factors) produced progressive and irreversible decrease in TCL1 protein levels in association with the onset of proliferation. TCL1 expression patterns in CLL are complex and highly dynamic and appear to reflect both the histogenetic subtypes of the disease and the growth parameters of individual tumors. The observed regulation pattern suggests that TCL1 may exert its effects predominantly in the unmutated/ZAP70-positive tumor subset.

Animals↗

PubMed2006

ABRF ESRG 2005 study: identification of seven modified amino acids by Edman sequencing.

Identification of modified amino acids can be a challenging part for Edman degradation sequence analysis, largely because they are not included among the commonly used phenylthiohydantion amino acid standards. Yet many can have unique retention times and can be assigned by an experienced researcher or through the use of a guide showing their typical chromatography characteristics. The Edman Sequencing Research Group (ESRG) 2005 study is a continuation of the 2004 study, in which the participating laboratories were provided a synthetic peptide and asked to identify the modified amino acids present in the sequence. The study sample provided an opportunity to sequence a peptide containing a variety of modified amino acids and note their retention times relative to the common amino acids. It also allowed the ESRG to compile the chromatographic properties and intensities from multiple instruments and tabulate an average elution position for these modified amino acids on commonly used instruments. Participating laboratories were given 2000 pmoles of a synthetic peptide, 18 amino acids long, containing the following modified amino acids: dimethyl- and trimethyl-lysine, 3-methyl-histidine, N-carbamyl-lysine, cystine, N-methyl-alanine, and isoaspartic acid. The modified amino acids were interspersed with standard amino acids to help in the assessment of initial and repetitive yields. In addition to filling in an assignment sheet, which included retention times and peak areas, participants were asked to provide specific details about the parameters used for the sequencing run. References for some of the modified amino acid elution characteristics were provided and the participants had the option of viewing a list of the modified amino acids present in the peptide at the ESRG Web site. The ABRF ESRG 2005 sample is the seventeenth in a series of studies designed to aid laboratories in evaluating their abilities to obtain and interpret amino acid sequence data.

Amino Acid Sequence↗

PubMed2005

Signal propagation and failure in one-dimensional FitzHugh-Nagumo equations with periodic stimuli.

We analyze the effect of additive periodic stimuli in one-dimensional FitzHugh-Nagumo equations in an excitable regime. With a suitable stimulus interval, the suppression of the pulse propagation occurs in some parameter regime. This propagation failure comes from the formation of the "death spot" where successive pulses annihilate. In the parameter regime where the solitary pulse cannot propagate in space stably, however, periodic stimuli cause a propagation of envelope of a traveling pulse under a "resonance" condition, i.e., the pulse at the leading edge disappears successively, however, an envelope is formed and propagates with keeping its shape.

Journal Article↗

PubMed2005

Therapy-related myelodysplastic syndrome in childhood: a retrospective study of 36 patients in Japan.

We report here a retrospective analysis of 36 children with therapy-related myelodysplastic syndrome (t-MDS) diagnosed between 1990 and 1999 in Japan. Their median age was 7.7 years and the median latency period for the development of t-MDS was 38.5 months. The primary tumors were hematologic in 15 of the cases and nonhematologic in 21. Chromosomal abnormalities were detected in 32/34(94%) patients: abnormalities of chromosomes 5and/or 7 in 41% and notably, 11q23 abnormalities in 31%. The prognosis of children with t-MDS was very poor as compared to children with primary MDS (5 year survival: 16% versus 54%, p<0.0001).

Adolescent↗

PubMed2005

Significance of eosinophilia after stem cell transplantation as a possible prognostic marker for favorable outcome.

Although eosinophilia after stem cell transplantation (SCT) has been addressed in recent reports, the significance of eosinophilia in disease outcome after SCT has not been well studied. In this study, we investigate the frequency of eosinophilia after SCT to determine its prognostic value. The subjects were 113 patients with malignant or nonmalignant diseases who underwent SCT treatment. In these patients, eosinophilia was detected in 44 cases (38.9%), on average 67.5 days after transplantation, and the mean maximum absolute eosinophil count was 840.5 x 10(6)/l. To study the basis of eosinophilia after SCT, various serum cytokine levels during SCT in patients both with and without eosinophilia were analyzed. Statistical analysis indicated that the overall patient survival rates improved in those with eosinophilia compared to those without eosinophilia (88.7 vs 43.0%, P=0.0034). In particular, in patients with malignant diseases, those with eosinophilia showed a higher event-free survival (81.1 vs 44.6%, P=0.0025) and a lower relapse rate (16.0 vs 43.0%, P=0.0287) than those without eosinophilia. In conclusion, we propose that eosinophilia after SCT could be a useful prognostic marker for determining favorable outcomes in patients with malignant diseases. The reasons for this good prognosis in SCT patients with eosinophilia are discussed.

Adolescent↗

PubMed2005

Progression and prognosis in pure autonomic failure (PAF): comparison with multiple system atrophy.

OBJECTIVE: To clarify the progression of autonomic symptoms and functional deterioration in pure autonomic failure (PAF), particularly in comparison with multiple system atrophy (MSA). METHODS: The investigation involved eight patients with PAF (M/F = 7/1; mean age at onset, 57 years) and 22 with probable MSA matched for age at onset (M/F = 14/8; onset 56 years). Subjects were followed up for neurological symptoms, activities of daily living, and autonomic function for more than seven years. Autonomic functional tests were carried out. RESULTS: In PAF, fainting or sudomotor dysfunction occurred first, followed by constipation and syncope. Urinary dysfunction developed late, and respiratory dysfunction was not evident. This clinical course contrasted sharply with that in MSA, where early urinary dysfunction usually proceeded to sudomotor dysfunction or orthostatic hypotension (p = 0.004), followed by respiratory dysfunction (p = 0.0004). Results of pharmacological tests also distinguished PAF from MSA. Progression and prognosis in patients with PAF did not worsen, unlike the steady progressive autonomic dysfunction in MSA (p < 0.0001, p < 0.0001, p = 0.0009, and p = 0.003, for progression to modified Rankin scale grade III, IV, V, and death, respectively). CONCLUSIONS: The time course and pattern of progression of autonomic failure differed significantly between PAF and MSA. Patients with PAF had slower functional deterioration and a better prognosis.

Activities of Daily Living↗

PubMed2004

Umbilical cord blood stem cell transplantation from unrelated HLA-matched donor in an infant with severe congenital neutropenia.

We report here a 6-month-old boy with severe congenital neutropenia (SCN) successfully treated by cord blood stem cell transplantation (CBSCT) from an unrelated donor. He had recurrent life-threatening respiratory infection due to severe neutropenia that was refractory to recombinant human granulocyte colony-stimulating factor (rhG-CSF). Because he had no HLA-matched sibling and no time to wait for unrelated donor, he received HLA-matched unrelated CBSCT as determined by DNA typing. A total of 6.4 x 10(7) CB nucleated cells/kg was infused after conditioning with busulfan/horse antihuman thymocyte serum/cyclophosphamide. No GVHD developed under the treatment with cyclosporin A and methyl prednisolone. The neutrophil count reached 0.5 x 10(9)/l on day 14, reticulocyte 1% on day 13 and platelet count over 50 x 10(9)/l on day 31. We conclude that unrelated CBSCT can be an indication for some cases of SCN, who have recurrent life-threatening infections and are refractory to rhG-CSF, and have no HLA-matched sibling.

Busulfan↗

PubMed2004

Hyponatremia and syndrome of inappropriate antidiuretic hormone secretion complicating stem cell transplantation.

Hyponatremia is a common electrolyte disorder in hospitalized patients. Although there are a few case reports of hyponatremia following stem cell transplantation (SCT), no reports concerning the incidence are currently available. We describe the occurrence of hyponatremia and the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) following SCT. In a single center analysis of 140 patients, hyponatremia and SIADH were observed in 40 and 11.4% of patients, respectively, following SCT. Risk factors for SIADH included young age, transplantation from an HLA-mismatched or unrelated donor, cord blood transplantation, and graft-versus-host disease prophylaxis with methyl prednisolone. Multivariate analysis revealed that transplantation from an HLA-mismatched donor and performance of SCT in a child below 4 years of age were risk factors for SIADH. For patients who underwent SCT from an HLA-mismatched or unrelated donor, those with SIADH showed a significantly higher overall survival rate (90.9 vs 40.2%) and event-free survival rate (77.8 vs 33.8%) compared to those without SIADH. Overall, our data show that hyponatremia and SIADH are relatively common complications following SCT, especially in children below 4 years of age and after SCT from an HLA-mismatched donor.

Adolescent↗

PubMed2004

[Thoracoscopically resected cystic mediastinal hemangioma; report of a case].

An asymptomatic 66-year-old female was admitted because of an abnormal shadow on chest X-ray. Computed tomography (CT) revealed that a well-marginated round mass with low density, about 3 cm in diameter, was located in the right anterior superior mediastinum. The border was partially enhanced at contrast material-enhanced CT. Magnetic resonance imaging (MRI) [T 2-weighted] showed the lesion as a high intensity tumor. We performed thoracoscopic surgery and resected the easy-bleeding tumor completely. The tumor was dark red in color and contained old blood. The histopathological diagnosis was hemangioma. There was no recurrence for 3 years. Hemangiomas should be considered in the differential diagnosis of well-marginated masses. Thoracoscopic surgery is the very useful methods to resect the mediastinal hemangioma.

Aged↗

PubMed2004

[Thoracoscopically diagnosed multicentric Castleman disease; report of a case].

A 57-year-old female was admitted because of chest and back pain. Computed tomography (CT) revealed that many well-marginated lymph nodes were located in mediastinum and abdominal para-aortic area, especially in the right lower mediastinum. These lymph nodes were enhanced at contrast material-enhanced CT. We performed thoracoscopic surgery. The histopathologic diagnosis was multicentric Castleman disease (MCD). MCD should be considered in the differential diagnosis of multiple lymph nodes swelling with hyper globulinemia. Thoracoscopic surgery is the useful method to resect the lymph nodes and diagnose MCD.

Adult↗

PubMed2003

MRI in methotrexate-related leukoencephalopathy: Disseminated necrotising leukoencephalopathy in comparison with mild leukoencephalopathy.

We report two fatal cases of methotrexate (MTX)-induced disseminated necrotising leukoencephalopathy (DNL) in which MRI was repeated from the onset. Initial T2-weighted images showed multiple areas of high signal, mainly in deep cerebral white matter, which on follow-up, spread and coalesced to involve the entire white matter. Small irregular low-signal foci on T2-weighted images were seen within the high-signal lesions. Multiple areas of contrast enhancement corresponded to these low-signal foci. The condition of both patients deteriorated and they died. We compared their MRI findings with those of seven patients with mild MTX-related leukoencephalopathy, six of whom were asymptomatic; one had transient neurological symptoms. They showed no contrast enhancement, but rather mild-to-moderate diffuse high signal in deep white matter, which later disappeared. These findings suggest that multiple low-signal foci on T2-weighted images with contrast enhancement may be characteristic of DNL, and that contrast-enhanced imaging is useful to differentiate this condition from mild leukoencephalopathy.

Adolescent↗

PubMed2003

Onset age and severity of motor impairment are associated with reduction of myocardial 123I-MIBG uptake in Parkinson's disease.

OBJECTIVES: To elucidate the factors associated with severity of cardiac sympathetic nerve involvement in idiopathic Parkinson's disease (PD). METHODS: (123)I-metaiodobenzylguanidine uptake was examined in 88 patients with PD. The ratio of the uptake in the heart (H) to that in the mediastinum (M) (the H/M ratio) was calculated and correlated with age at onset, age at examination, and disease severity and duration. Twenty five healthy people were also examined as a control. RESULTS: There was a mild but significant negative correlation between H/M ratio and age at onset (early, r = -0.33, p = 0.002; delayed, r = -0.34, p = 0.001) and between Hoehn and Yahr (H-Y) stage (early, r = -0.30, p = 0.006; delayed, r = -0.32, p = 0.003). There was no significant correlation between disease duration and H/M ratio. When patients with PD were classified into four subgroups on the basis of age at onset (> 62 or < 62 years) and disease severity (H-Y > III or H-Y < or = II), the median H/M ratio of the older and more severe group was significantly lower than that of the younger and less severe group (p = 0.005). CONCLUSION: This study suggests that late onset, high severity PD is associated with myocardial sympathetic dysfunction.

3-Iodobenzylguanidine↗

PubMed2003

Sequential constriction of upper airway and vocal cords in sleep apnoea of multiple system atrophy: low field magnetic resonance fluoroscopic study.

Low field magnetic resonance fluoroscopy was used to clarify temporal and spatial features of airway obstruction in sleep apnoea syndrome (SAS) in multiple system atrophy (MSA), as well as in obstructive SAS (OSAS). 20 patients with OSAS with severe obesity (mean (SD) age 66 (10) years; 16 men, 4 women) and 6 patients with SAS related to probable MSA (60 (9) years; 4 men, 2 women) were studied. In the OSAS group, body mass index, apnoea index, and desaturation index were significantly higher than in the MSA group. In OSAS, simultaneous obstruction extended from the retropalatal pharynx to the retroglossal during sleep on low field magnetic resonance fluoroscopy. In MSA, obstruction of upper airway followed a similar distribution, but obstruction of vocal cords followed upper airway obstruction. In contrast to OSAS, sequentially acting neural mechanisms are suspected in SAS with MSA.

Aged↗

PubMed2002

Antitumor activity of a phenoxazine compound, 2-amino-4,4alpha-dihydro-4alpha,7-dimethyl-3H-phenoxazine-3-one against human B cell and T cell lymphoblastoid cell lines: induction of mixed types of cell death, apoptosis, and necrosis.

PURPOSE: We studied the antitumor activity of 2-amino-4,4alpha-dihydro-4alpha,7-dimethyl-3H-phenoxazine-3-one (Phx), which was synthesized by the reactions of 2-amino-5-methylphenol with bovine hemoglobin, on human B cell lymphoblastoid cell lines, P3HR-1 and Raji derived from African Burkitt's lymphoma, and the human T cell lymphoblastoid cell line Molt-4. We also studied whether Phx might cause apoptosis and necrosis in these cells. METHODS: We evaluated cell viability and apoptosis and necrosis of the cells in the presence of Phx, by using agarose gel electrophoresis, flow cytometry, and fluorescence microscopy. RESULTS: Phx suppressed the viability of P3HR-1, Raji, and Molt-4 cells, though the suppression patterns were different, i.e., Phx suppressed the viability of P3HR-1, Raji, and Molt-4 cells at higher concentrations, while the drug enhanced the viability of Raji cells, but not those of P3HR-1 and Molt-4 cells at lower concentrations. To investigate which type of cell death - apoptosis or necrosis - is induced by Phx, induction of DNA ladder, phosphatidylserine externalization, and propidium iodide-permeable cells were examined in Phx-treated cells. Although Phx did not induce DNA ladder formation, it induced the phosphatidylserine externalization and propidium iodide-permeable cells, suggesting that Phx caused a mixed type of cell death, both apoptosis and necrosis. The population of early stage apoptotic cells was dominant in Raji cells, and that of the late stage apoptotic/necrotic cells was dominant in Molt-4 cells after 72-h treatment with Phx. The population of the early stage apoptotic cells and the late stage apoptotic/necrotic cells was almost equal in P3HR-1 cells in the presence of Phx, though the population of both types of cells increased with time. The nuclear morphological analysis of Phx-treated Raji, P3HR-1, and Molt-4 cells also showed that Phx induces apoptosis. CONCLUSIONS: The present results suggest that Phx shows antitumor activity against human B cell-derived and T cell-derived lymphoblastoid cell lines, in vitro, causing apoptosis and necrosis.

Annexin A5↗

PubMed2002

Impact of additional pleurodesis in video-assisted thoracoscopic bullectomy for primary spontaneous pneumothorax.

BACKGROUND: Bullectomy for primary spontaneous pneumothorax has been associated with high postoperative recurrence rates when video-assisted thoracoscopic surgery (VATS) has been used rather than thoracotomy. The aim of this study was to evaluate the efficacy and identify the disadvantages, if any, of adding pleurodesis to VATS bullectomy to prevent recurrent pneumothorax. METHODS: Fifty-three patients who underwent VATS bullectomy with additional pleurodesis for pneumothorax after November 1996 and 50 who underwent VATS bullectomy alone before October 1996 were compared retrospectively in terms of intraoperative factors and postoperative chest pain, pulmonary function, and pneumothorax recurrent rates. Pleurodesis was achieved by electrocauterizing the upper surface of the parietal pleura in a patchy fashion. RESULTS: There were no significant differences between the additional pleurodesis group and the bullectomy alone group in terms of age, sex, operating time, intraoperative bleeding, number of resected bullae, duration of chest drainage, or volume of fluid drained. Postoperative chest pain and pulmonary function were also similar in both groups. A recurrent pneumothorax occurred in one patient (1.9%) in the additional pleurodesis group; this recurrence rate was significantly lower than that for the bullectomy alone group (eight patients, 16%; p = 0.029). Although the mean postoperative follow-up period was considerably shorter in the additional pleurodesis group (38 months [range, 26-49]) than in the bullectomy alone group (63 months [range, 50-72] ), eight (89%) of all nine recurrences occurred within 26 months of surgery-i.e., within the minimum follow-up period for the additional pleurodesis group. CONCLUSIONS: Pleurodesis is a minimally invasive technique that is effective in preventing postoperative recurrences of pneumothorax when added to VATS bullectomy. Additional pleurodesis has no disadvantages vs bullectomy alone in terms of worsening postoperative chest pain or pulmonary function.

Adult↗

PubMed2002

Nerve sheath myxoma of the tongue in a child.

Nerve sheath myxoma (NSM) is a benign peripheral nervous system tumour that rarely occurs in the oral cavity. Among 17 cases of oral NSM described in the literature (average patient age 33 years), only two, including the present case, have been reported in children. The present case occurring in an 8-year-old boy was therefore extremely rare. Histopathologically, the tumour was found as multinodules under the mucosal epithelium, and was composed of spindle- or stellate-shaped cells with a myxoid background that stained with alcian blue and toluidine blue. Immunohistochemically, the tumour cells were strongly positive for S-100 beta protein and neuron-specific enolase. These results suggested that the tumour originated from Schwann cells.

Child↗

PubMed2001

Differential regulatory mechanism of Ca2+/calmodulin-dependent protein kinase kinase isoforms.

We have previously demonstrated that the alpha isoform of Ca(2+)/calmodulin-dependent protein kinase kinase (CaM-KKalpha) is strictly regulated by an autoinhibitory mechanism and activated by the binding of Ca(2+)/CaM [Tokumitsu, H., Muramatsu, M., Ikura, M., and Kobayashi, R. (2000) J. Biol. Chem. 275, 20090-20095]. In this study, we find that rat brain extract contains Ca(2+)/CaM-independent CaM-KK activity. This result is consistent with an enhanced Ca(2+)/CaM-independent activity (60-70% of total activity) observed with the recombinant CaM-KKbeta isoform. By using various truncation mutants of CaM-KKbeta, we have identified a region of 23 amino acids (residues 129-151) located at the N-terminus of the catalytic domain as an important regulatory element of the autonomous activity. A CaM-KKbeta deletion mutant of this domain shows a significant increase of Ca(2+)/CaM dependency for the CaM-KK activity as well as for the autophosphorylation activity. The activities of CaM-KKalpha and CaM-KKbeta chimera, in which autoinhibitory sequences were replaced by each other, were completely dependent on Ca(2+)/CaM, suggesting that the autoinhibitory regions of CaM-KKalpha and CaM-KKbeta are functional. These results establish for the first time that residues 129-151 of CaM-KKbeta participate in the release of the autoinhibitory domain from its catalytic core, resulting in generation of autonomous activity.

Amino Acid Sequence↗