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Biomedical subjects

K Sakai

Publications and source records attributed to K Sakai.

At least 163 records · Page 9Linked to original sources
PubMed2000

Reduction of ischemic brain injury by topical application of insulin-like growth factor-I after transient middle cerebral artery occlusion in rats.

In order to examine the effect of insulin-like growth factor-1 (IGF-1) on ischemic brain injury, IGF-1 was applied topically on the surface of reperfused rat brain after 60 min of transient middle cerebral artery occlusion (MCAO). In contrast to the cases treated with vehicle, the infarct area was greatly reduced at 24 h of reperfusion by treatment with IGF-1. Terminal deoxynucleotidyl transferase mediated dUTP-biotin in situ nick labeling (TUNEL) staining and immunoreactivity for glycogen synthase kinase 3beta (GSK3beta) were also markedly reduced in the brains with IGF-1 treatment. The present results suggest that the treatment with IGF-1 significantly ameliorates brain injury after transient focal brain ischemia associated with the reduction of TUNEL and GSK3beta stainings.

Administration, Topical↗
PubMed2000

cDNA cloning of an alternative splicing variant of protein kinase C delta (PKC deltaIII), a new truncated form of PKCdelta, in rats.

Recently, an alternative splicing variant of mouse protein kinase C delta (PKC deltaII, GenBank Accession No. AB011812) has been reported which has a 78 bp (26 amino acid) insertion at the caspase-3 recognition sequence in the V3 region of PKC delta (PKC deltaI). We isolated a cDNA encoding a new variant of PKC delta (PKC deltaIII, AF219629), which has a 83 bp insertion at the same site in the V3 region, by RT-PCR using rat testis RNA as a template. In rats, the 83 bp insertion causes inframe termination, and rat PKC deltaIII protein is expressed as a truncated form, having only the regulatory domain without a catalytic domain. Genomic DNA analysis revealed that the difference between mouse PKC deltaII and rat PKC deltaIII is derived from the different sequence at the 5'-splicing donor sites. To investigate the potential functions of the truncated form of PKC delta, rat PKC deltaIII fused to green fluorescent protein (GFP) was expressed in CHO-K1 cells. PKC deltaIII-GFP was localized in the cytoplasm with dot-like accumulation and highly expressed on the plasma membrane, whereas PKC deltaI-GFP is localized homogeneously throughout the cytoplasm, including the nucleoplasm. Stimulation by phorbol ester caused weak translocation of deltaIII-GFP from the cytosol to the plasma membrane. These results suggest that PKC deltaIII may show a dominant negative effect against PKC deltaI, and that the modulation of signal transduction by alternative splicing variant may play a crucial role in the physiological and/or pathological conditions, and the pathogenesis of disease.

Alternative Splicing↗
PubMed2000

A preliminary outcome analysis of the Patterns of Care Study in Japan for esophageal cancer patients with special reference to age: non surgery group.

BACKGROUND: The Patterns of Care Study (PCS) was imported to Japan from the United States in July 1996. A preliminary outcome analysis of the PCS for esophageal cancer patients in Japan was made with special reference to age, because the elderly population is rapidly increasing in Japan. PATIENTS AND METHODS: From July 1996 to February 1998, external PCS audits were performed for 37 institutions nationwide and detailed information of 561 esophageal cancer patients treated during the period 1992-1994 was collected by using the fifth PCS data format developed in the United States. This format was provided courtesy of the American College of Radiology. For this study, patients who had not undergone surgery (n = 336) were selected. The patients were classified into three age groups: < 65 years old (n = 119), between 65 and 74 years (n = 93), and 75 years or older (n =123). Cox's proportional hazards model was used for the statistical analysis, with survival, acute/subacute complication and late complication of grade 3 or more based on RTOG criteria, as the endpoints. RESULTS: Significant prognostic factors for the entire non-surgery group were Karnofsky Performance Status (KPS) (p = 0.0007), stage (p = 0.0001), and external irradiation dose (p = 0.0001). For the younger group, KPS (p = 0.0004), stage (p = 0.0197), and utilization of brachytherapy (p = 0.0010) were significant, while for the intermediate age group it was KPS (p = 0. 0027), history of pulmonary disease (p = 0.0339), stage (p = 0.0001), and external dose (p = 0.0001), and for the elderly group, stage (p = 0.0001) and external irradiation dose (p = 0.0224) were significant. Significant risk factors for complications for the entire group were stage (p = 0.0411), external dose (p = 0.0163), and stratification of institution (academic vs. nonacademic) (p = 0. 0114). Significant risk factors for the younger group were history of pulmonary disease (p = 0.0495) and external dose (p = 0.0037), and the other age groups showed no significant risk factors. CONCLUSION: Age was not a significant prognostic or risk factor for esophageal cancer patients in the non-surgery group treated with radiation therapy. Therefore, radiation therapy represented an important treatment modality for the elderly as well as for the younger esophageal cancer patients. External dose was a treatment-related prognostic factor for the elderly as well as for the intermediate age group.

Adenocarcinoma↗
PubMed2000

Proline accumulation by mutation or disruption of the proline oxidase gene improves resistance to freezing and desiccation stresses in Saccharomyces cerevisiae.

We examined the role of intracellular proline under freezing and desiccation stress conditions in Saccharomyces cerevisiae. When cultured in liquid minimal medium, the proline-nonutilizing mutant containing the put1 mutation (proline oxidase-deficient) produced more intracellular proline, and increased the cell survival rate as compared to the wild-type strain after freezing and desiccation. We also constructed two PUT1 gene disruptants. PUT1-disrupted mutants in minimal medium supplemented with external proline at 0.1% accumulated higher proline levels than those of the control strains (17-22-fold). These disruptants also had a 2-5-fold increase in cell viability compared to the control strains after freezing and desiccation stresses. These results indicate that proline has a stress-protective function in yeast.

Adaptation, Physiological↗
PubMed2000

Malignant transformation and EGFR activation of immortalized mouse liver epithelial cells caused by HBV enhancer-X from a human hepatocellular carcinoma.

We have previously observed that all human hepatocellular carcinomas (HCCs) from HBV carriers examined had the integrated X region. In this study, HBV DNA was isolated from an integration site in one HCC that had a single, very small integrated viral DNA including the X region, but it had no expression of X gene as poly(A)RNA. It was found that HBV DNA was present between alphoid repetitive sequences, and it included Enhancer and X regions, encompassing the adr sequence from 910 to 1811. Nucleotides for 8 amino acids at the 3' end, a stop codon of X gene and a poly(A) signal downstream of X gene were lost by integration, and nucleotides for 7 amino acids and a stop codon were substituted by a connected alphoid sequence. When this cloned HBV DNA was transfected with an expression vector to an immortalized mouse liver epithelial cell line, MLE-10, malignant transformation occurred. Transformants having expressed poly(A)RNA of the X gene showed anchorage-independent growth in soft agar and tumor formation in the subcutis of nude mice. The mRNA level of EGFR was found to be remarkably enhanced in X-transformed cells, in contrast with the absence of this mRNA in parental and ras-transformed MLE-10. Our data provide evidence that the Enhancer-X region alone is the key contributor to the malignant change of pre-malignant liver cells in HBV carriers through activation of some specific genes, such as EGFR.

Amino Acid Sequence↗
PubMed2000

Loss of bag-1 immunoreactivity in rat brain after transient middle cerebral artery occlusion.

Although bag-1 is a strong apoptosis repressor protein, its functions in normal or injured brains are not fully understood. In the present study, we investigated expression of bag-1 protein in rat brain after transient middle cerebral artery (MCA) occlusion, and compared the results with that of terminal deoxynucleotidyl transferase-mediated dUTP-biotin end labeling (TUNEL). Immunohistochemical analysis revealed that neuronal, choroid plexus, and ependymal cells were positively stained in the sham control brain. After 90 min of transient MCA occlusion, immunoreactivity for bag-1 progressively decreased from 3 to 48 h in the nuclei of neurons. Western blot analysis revealed that immunoreactive bag-1 was markedly decreased in the nuclear fraction. In contrast, cytosolic and mitochondrial fractions showed no or only slight change after the ischemia. TUNEL positive cells appeared at 48 h after the reperfusion, which was preceded by loss of bag-1 immunoreactivity. The present results suggest that bag-1 plays some roles in normal neuronal function, and its loss may be involved in neuronal cell death after ischemia.

Animals↗
PubMed2000

Changes of free fatty acids and acyl-CoAs in rat brain hippocampal slice with tetraethylammonium-induced long-term potentiation.

We investigated the role of acyl-CoAs during induction and maintenance of long-term potentiation in rat brain hippocampus. Changes of acyl-CoA and free fatty acids (FFA) in hippocampus were measured during tetraethylammonium (TEA)-induced LTP. Results indicated that concentrations of acyl-CoAs and FFAs in slices were changed during TEA-induced LTP and 16:0-CoA and 18:0-CoA were increased in the early phase of stimulation, whereas free fatty acids in this phase were rather decreased. The increase of 20:4-CoA was delayed more than saturated acyl-CoAs. To examine the role of acyl-CoA in LTP of evoked transmitter release, we measured the glutamate release from hippocampal slice with the addition of acyl-CoA using glutamate electrode. Acyl-CoA (16:0-, 18:1-, and 20:4-CoA) could enhance glutamate release in hippocampal slice. It is suggested that saturated acyl-CoAs may play a functional role in the early phase of LTP.

Acyl Coenzyme A↗
PubMed2000

The clinical significance of tumor-associated antigen RCAS1 expression in the normal, hyperplastic, and malignant uterine endometrium.

OBJECTIVE: A tumor-associated antigen, RCAS1, is recognized by 22-1-1 monoclonal antibody. It was found in carcinomas derived from the uterus and ovary and was especially strongly expressed in invasive cancers. A previous investigation showed the RCAS1 expression to be correlated with a poor prognosis in uterine cervical adenocarcinoma. In this study, we examined whether the expression of RCAS1 is associated with the progression of the uterine endometrial neoplasms. METHODS: The expression of RCAS1 was evaluated by an immunohistochemical analysis. The tissue specimens used in this study included 46 cases of normal uterine endometrium, 40 cases of hyperplasia, and 121 cases of adenocarcinoma. The relationship between RCAS1 expression and several clinicopathological variables (clinical stage, histology, grade, myometrial invasion, lymph-vascular space invasion, and lymph node metastasis) was also assessed in endometrial adenocarcinoma. RESULTS: RCAS1 was positive in 26% of the normal uterine endometrium specimens (12 of 46 total cases), in 32% of the hyperplasia specimens (13 of 40 total cases), and in 68% of the adenocarcinoma specimens (83 of 121 total cases). As a result, the expression of RCAS1 was statistically higher in adenocarcinoma than in the normal and hyperplastic endometrium (P < 0.0001). RCAS1 was statistically detected more frequently in grade 3 than in grade 1 or 2 (P < 0.05); however, there was no correlation between the antigen expression and the clinical stage, myometrial invasion, lymph-vascular space invasion, or lymph node metastasis. CONCLUSION: RCAS1 expression might thus be associated with the malignant transformation and poor differentiation observed in uterine endometrial adenocarcinoma.

Adenocarcinoma↗
PubMed2000

Mitral valve replacement and subsequent composite graft replacement of the aortic root for infantile Marfan syndrome.

The cardiovascular lesions commonly seen in Marfan syndrome can frequently be the primary cause of premature death. Cardiac lesions involving both the mitral valve and the aortic root are commonly observed among patients diagnosed during early infancy, as so-called infantile Marfan syndrome. Since the lesions tend to progress rapidly with the end results of high morbidity and mortality, the majority of patients require surgical intervention at a young age. However, patients who undergo surgical intervention for both lesions during the first decade of life have been rarely reported in literature. In this report, we present a case of a 9-year-old boy who underwent aortic root replacement with a composite graft at 3.5 years after a prior prosthetic valve replacement of the mitral valve. Although the immediate result was satisfactory, the long-term result remains to be seen.

Aorta, Thoracic↗
PubMed2000

Solitary myofibromatosis of the skull.

We present a case of solitary infantile myofibromatosis of the skull in a 3-month-old boy. A right parietal subcutaneous lump was found at birth, and it increased in size over the ensuing 3 months. Surgery was performed, and a diagnosis of myofibromatosis was confirmed histopathologically. Solitary myofibromatosis of the skull is extremely rare. The radiographical, CT, and MR appearances, as well as histopathological findings, are described in this article.

Humans↗
PubMed2000

Diffusion-weighted echo-planar MR imaging in differential diagnosis of brain tumors and tumor-like conditions.

We assess diffusion-weighted MR images in the differential diagnosis of intracranial brain tumors and tumor-like conditions. Heavily diffusion-weighted (b = 1100 or 1200 s/mm2) axial images were obtained with single-shot echo-planar technique in 93 patients with pathologically confirmed various intracranial tumors and tumor-like conditions with diffusion gradient perpendicular to the images. We compared signal intensity of the lesions with those of gray and white matter, and cerebrospinal fluid (CSF). In 29 cases (31.1%) the lesions were isointense to gray and/or white matter. However, 5 cases (5.4%) showed extremely increased signal intensity: two epidermoid cysts; two chordomas; and one brain abscess. The entire portion of a tumor was markedly hyperintense in 10 cases (10.8%): four malignant lymphomas; four medulloblastomas; one germinoma; and one pineoblastoma. A CSF-like hypointense signal was seen in many cystic tumors, and cystic or necrotic portions of tumors. A neurosarcoid granulation was the only solid lesion showing characteristically a hypointense signal like CSF. The combination of markedly hyperintense and hypointense signals was seen generally in hemorrhagic tumors. Diffusion-weighted echo-planar MR imaging is useful in the differential diagnosis of brain tumors and tumor-like conditions, and suggests specific histological diagnosis in some cases.

Adolescent↗
PubMed2000

Expression of p57(KIP2) potently blocks the growth of human astrocytomas and induces cell senescence.

Astrocytic tumors frequently exhibit defects in the expression or activity of proteins that control cell-cycle progression. Inhibition of kinase activity associated with cyclin/cyclin-dependent kinase co-complexes by cyclin-dependent kinase inhibitors is an important mechanism by which the effects of growth signals are down-regulated. We undertook the present study to determine the role of p57(KIP2) (p57) in human astrocytomas. We demonstrate here that whereas p57 is expressed in fetal brain tissue, specimens of astrocytomas of varying grade and permanent astrocytoma cell lines do not express p57, and do not contain mutations of the p57 gene by multiplex-heteroduplex analysis. However, the inducible expression of p57 in three well-characterized human astrocytoma cell lines (U343 MG-A, U87 MG, and U373 MG) using the tetracycline repressor system leads to a potent proliferative block in G(1) as determined by growth curve and flow cytometric analyses. After the induction of p57, retinoblastoma protein, p107, and E2F-1 levels diminish, and retinoblastoma protein is shifted to a hypophosphorylated form. Morphologically, p57-induced astrocytoma cells became large and flat with an expanded cytoplasm. The inducible expression of p57 leads to the accumulation of senescence-associated beta-galactosidase marker within all astrocytoma cell lines such that approximately 75% of cells were positive at 1 week after induction. Induction of p57 in U373 astrocytoma cells generated a small population of cells ( approximately 15%) that were nonviable, contained discrete nuclear fragments on Hoechst 33258 staining, and demonstrated ultrastructural features characteristic of apoptosis. Examination of bax and poly-(ADP ribose) polymerase levels showed no change in bax, but decreased expression of poly-(ADP ribose) polymerase after p57 induction in all astrocytoma cell lines. These data demonstrate that the proliferative block imposed by p57 on human astrocytoma cells results in changes in the expression of a number of cell cycle regulatory factors, cell morphology, and a strong stimulus to cell senescence.

Apoptosis↗
PubMed2000

Reactions of direct LDL-cholesterol assays with pure LDL fraction and IDL: comparison of three homogeneous methods.

According to the definition of the Lipid Research Clinic's protocol, low-density lipoprotein (LDL) refers to the lipoprotein of density (d)=1.006-1.063 g/ml which contains another atherogenic lipoprotein, IDL (d=1.006-1.019 g/ml). Because metabolic properties are largely different between LDL and IDL, LDL is now defined as the lipoprotein of d=1.019-1.063 g/ml. Recently direct LDL-cholesterol assay kits using novel surfactants (the homogeneous methods) have become commercially available and widely used in Japan. The aim of this study is to examine how three direct LDL-cholesterol assay kits, LDL-EX, Choletest-LDL and Determinor-L LDL, react with pure LDL (d=1. 019-1.063 g/ml) and IDL (1.006-1.019 g/ml) fractions isolated by ultracentrifugation. Thirty-one healthy subjects and one type III dysbetalipoproteinemic patient were enrolled in this study. All homogeneous methods highly correlated with LDL-cholesterol (r=0.95-0. 98), although the values for LDL-EX were closer to the values for ultracentrifugation than were those of the other two methods (95 vs. 86-87%, P<0.0001). Cross-reactivity with IDL was 31, 47 and 64% for LDL-EX, Choletest-LDL, and Determinor-L LDL, respectively. Similar results were obtained in the IDL from a type III dysbetalipoproteinemic patient. These results suggest that LDL-cholesterol measured by LDL-EX better reflects pure LDL fraction with weaker cross-reaction with IDL than other homogeneous methods.

Cholesterol↗
PubMed2000

Mode of action of sesame lignans in protecting low-density lipoprotein against oxidative damage in vitro.

We investigated the antioxidant properties of sesaminol, a major component of sesame oil, on the oxidative modification of human low-density lipoprotein (LDL) in vitro. Sesaminol inhibited the Cu2+-induced lipid peroxidation in LDL in a concentration-dependent manner with an IC50 36.0 +/- 10.0 nM. Sesaminol was a more effective scavenger than either alpha-tocopherol or probucol in reducing the peroxyl radicals derived from 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH) in aqueous solution. In addition, as determined by the secondary products of lipid peroxidation identified by using immunochemical methods, sesaminol completely inhibited the formation of 4-hydroxy-nonenal (4-HNE)- and malondialdehyde (MDA)-adducts in a concentration-dependent manner. Probucol and alpha-tocopherol at the same concentration exhibited a lesser inhibitory effect. Our findings suggest that sesaminol is a potentially effective antioxidant that can protect LDL against the oxidation.

Antioxidants↗
PubMed2000

Nonlinear piezoelectricity in PZT ceramics for generating ultrasonic phase conjugate waves

We have succeeded in the generation of acoustic phase conjugate waves with nonlinear PZT piezoelectric ceramics and applied them to ultrasonic imaging systems. Our aim is to make a phase conjugator with 100% efficiency. For this purpose, it is important to clarify the mechanism of acoustic phase conjugation through nonlinear piezoelectricity. The process is explained by the parametric interaction via the third-order nonlinear piezoelectricity between the incident acoustic wave at angular frequency omega and the pump electric field at 2 omega. We solved the coupling equations including the third-ordered nonlinear piezoelectricity and theoretically derived the amplitude efficiency of the acoustic phase conjugation. We compared the efficiencies between the theoretical and experimental values for PZT ceramics with eight different compositions. Pb[(Zn1/3Nb2/3)(1 - x)Tix]O3 (X = 0.09, PZNT91/9) piezoelectric single crystals have been investigated for high-performance ultrasonic transducer application, because these have large piezoelectric constants, high electrical-mechanical coupling factors and high dielectric constants. We found that they have third-order nonlinear piezoelectric constants much larger than PZT and are hopeful that the material as a phase conjugator has over 100% efficiency.

Journal Article↗