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Biomedical subjects

K Tanaka

Publications and source records attributed to K Tanaka.

At least 19 recordsLinked to original sources
PubMed1992

Impaired tetramer assembly of variant medium-chain acyl-coenzyme A dehydrogenase with a glutamate or aspartate substitution for lysine 304 causing instability of the protein.

Ninety percent of variant medium-chain acyl-CoA dehydrogenase (MCAD) alleles in patients with MCAD deficiency carry a 985 A-->G transition which causes glutamate substitution for lysine 329 in precursor (p) MCAD (K-304 in mature MCAD). We have used site-directed mutagenesis to produce three variant cDNAs encoding variant pMCAD with glutamate (Kp329E2), aspartate (Kp329D), or arginine (Kp329R) substitution for Kp329. We carried out in vitro expression of cDNAs, and incubated the translation products with isolated rat liver mitochondria. Kp329E was imported into mitochondria and processed into the mature subunit as efficiently as wild-type. Gel filtration analysis of the mitochondria revealed that at 10 min after import, markedly more K304E eluted as a monomer than did wild-type, and the amount of K304E tetramer formed was distinctly less than wild-type at any point up to 60 min after import, indicating that the assembly of K304E is defective. After further incubation, K304E decayed more rapidly than did wild-type, indicating a reduced stability. In similar studies, K304R behaved like the wild-type, while K304D closely resembled K304E, indicating that the presence of a basic residue at 304 is essential for tetramer formation and intramitochondrial stability of mature MCAD.

Acyl-CoA Dehydrogenase↗
PubMed1992

The prognostic value of cytogenetic analyses in patients with acute nonlymphocytic leukemia treated with the same intensive chemotherapy.

BACKGROUND: Some specific chromosome abnormalities for the leukemias have been proven to be associated with the prognosis of acute nonlymphocytic leukemia (ANLL). However, most of these reports included patients treated with different protocols. Therefore, some bias has been involved in the evaluation of the prognostic factors in such reports. METHODS: The authors studied the morphologic, cytogenetic, and clinical features of 136 patients (86 males and 50 females) with de novo ANLL treated with the same protocol of intensive induction chemotherapy using multivariate analyses. RESULTS: Chromosome abnormalities were detected in 62.5% of the patients. The overall complete remission (CR) rate of disease was 85.5% in these patients. More than 90% of the patients with t(8;21) and pseudodiploid abnormalities achieved experienced CR. However, CR rates in the patients with abnormalities of chromosome 5 or 7 were 50%. With multivariate analyses by the type of karyotypic abnormality, CR duration and survival time of the patients with t(8;21) were longer than those of patients with normal karyotype and abnormalities of chromosome 5 or 7. Abnormalities of chromosome 5 or 7 and hyperdiploid were associated with poor prognosis. Older age and lower platelet counts also were factors contributing to shorter survival times. With the analysis with French-American-British (FAB) classification, only hypoplastic leukemia was a poor prognostic factor. CONCLUSIONS: These data suggest that cytogenetic analyses plays an important role in estimating the prognosis of patients treated with intensive induction chemotherapy.

Adolescent↗
PubMed1992

Ornithine decarboxylase is degraded by the 26S proteasome without ubiquitination.

Ornithine decarboxylase (ODC), a key enzyme in polyamine biosynthesis, is the most rapidly turned over mammalian enzyme. We have shown that its degradation is accelerated by ODC antizyme, an inhibitory protein induced by polyamines. This is a new type of enzyme regulation and may be a model for selective protein degradation. Here we report the identification of the protease responsible for ODC degradation. Using a cell-free degradation system, we demonstrate that immunodepletion of proteasomes from cell extracts causes almost complete loss of ATP- and antizyme-dependent degradation of ODC. In addition, purified 26S proteasome complex, but not the 20S proteasome, catalyses ODC degradation in the absence of ubiquitin. These results strongly suggest that the 26S proteasome, widely viewed as specific for ubiquitin-conjugated proteins, is the main enzyme responsible for ODC degradation. The 26S proteasome may therefore have a second role in ubiquitin-independent proteolysis.

Adenosine Triphosphate↗
PubMed1992

Columns for visual features of objects in monkey inferotemporal cortex.

At early stages of the mammalian visual cortex, neurons with similar stimulus selectivities are vertically arrayed through the thickness of the cortical sheet and clustered in patches or bands across the surface. This organization, referred to as a 'column', has been found with respect to one-dimensional stimulus parameters such as orientation of stimulus contours, eye dominance of visual inputs, and direction of stimulus motion. It is unclear, however, whether information with extremely high dimensions, such as visual shape, is organized in a similar columnar fashion or in a different manner in the brain. Here we report that the anterior inferotemporal area of the monkey cortex, the final station of the visual cortical stream crucial for object recognition, consists of columns, each containing cells responsive to similar visual features of objects.

Animals↗
PubMed1992

[Altered responses of heart rate, renal sodium handling and plasma growth hormone to clonidine in type II diabetic patients].

The aim of the present study is to explore whether the renal and cardiovascular response to clonidine in type II diabetic patients is different from that in control subjects, and to clarify the role of central alpha 2-receptor in the regulation of cardiovascular response and sodium handling in type II diabetes mellitus (DM). Thirty-five diabetic inpatients aged 30-71 years (54.1 +/- 9.7) and ten control subjects (N) were enrolled in this study after their fasting plasma glucose had been improved. To evaluate the peripheral sympathetic nerve activity, 24-hour urinary catecholamine was measured, and pulse rate (PR) responses to a 30-second standing test was determined. On another day, blood pressure (BP), PR, plasma norepinephrine (PNE), cyclic AMP (p-cAMP), renin activity (PRA), aldosterone (PAC) and growth hormone (p-GH) were measured at 0, 30, 60, 90, 120, 150, 180 minutes following the oral administration of clonidine (150 micrograms). Type II DM were classified as DM with hyper-response (DM-HR, n = 12) when their PR decreased after clonidine more than that of N, and if not, they were classified as DM with normal response (DM-NR, n = 23). Urinary catecholamine excretions in type II DM were within the normal range. BP, PNE and p-cAMP were markedly decreased with clonidine in similar fashion in DM-NR, DM-HR and N. The percent changes of PNE were correlated positively with the changes of p-cAMP in both N and DM-NR (r = 0.660 and 0.449, respectively), but not in DM-HR. No significant difference in the changes of p-GH (delta p-GH) and integral of GH (the area under the curve) following clonidine administration was observed in the three groups. The decrease in PR was correlated with neither delta p-GH (N: r = 0.082, DM-NR: r = -0.400, DM-HR: r = 0.242) or integral of GH (N: r = 0.191, DM-NR: r = 0.382, DM-HR: r = 0.162). The fractional excretion of sodium (FENa) decreased in N (p < 0.01), increased in DM-NR (p < 0.05) and did not change in DM-HR. The changes of FENa were not correlated with those of PRA and PAC.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1992

A new bioabsorbable material for rat vascular cuff anatomosis: establishment for the long-term orthotopic liver transplantation model.

Rat vascular anastomosis was performed using a newly synthesized bioabsorbable material (LA-GA copolymer) cuffs and the ordinary polyethylene cuffs. The LA-GA copolymer cuff which anastomosed the portal vein and the inferior vena cava were patent and developed no collateral veins even after 6 months, keeping the transplanted liver normal. By contrast, the polyethylene cuff anastomosed portal vein was completely occluded and the collateral veins were highly developed, with the transplanted liver showing the fatty degeneration of hepatocytes and numerous regenerative nodules. It is concluded that the LA-GA copolymer cuff is a suitable material for the short and long term study of rat orthotopic liver transplantation.

Absorption↗
PubMed1992

Purification and initial characterization of the proteasome from the higher plant Spinacia oleracea.

The proteasome (multicatalytic protease complex), a high molecular weight protein complex, has been purified from spinach leaves by successive chromatography on DEAE-cellulose, Bio-Gel A-1.5m, DEAE-TOYOPEARL 650C, and DEAE-5PW. The molecular mass was estimated to be 850 kDa by gel filtration. Polyacrylamide gel electrophoresis of the proteasome gave a single protein band under nondenaturing conditions and at least 10 bands in the range of 21-32 kDa in the presence of sodium dodecyl sulfate. By electron microscopy after negative staining with uranyl acetate, the proteasome from spinach appeared as symmetrical ring-shaped particles. The substrate specificity of proteasomes indicates that they contain at least three types of activity, namely, chymotrypsin-like, Staphylococcus aureus V8 protease-like, and trypsin-like activities. The former two activities were enhanced by poly-L-lysine or sodium dodecyl sulfate. Moreover, we examined the immunological reactivities of proteasomes from various eukaryotes. As a result, cross-immunoreactivities of some subunits were observed. These properties of the proteasome are similar to those of proteasomes isolated from various other eukaryotic sources.

Amino Acid Sequence↗
PubMed1992

Iodothyronine 5-deiodinase in rat posterior pituitary.

We first describe the presence of iodothyronine 5-deiodinase (5D) in the neural lobe of rat pituitary. 6-n-Propyl-2-thiouracil (PTU), a specific inhibitor of type-I deiodinase, had no effect, showing that 5D in neurohypophysis is of type-III isozyme, which is specific for 5-deiodination and has been found only in the brain, placenta and skin. The presence of 5D (type-III) together with our previous report of 5'-deiodinase (type-I in euthyroidism and type-II in hypothyroidism) shows that the isozymes of deiodinases in the neurohypophysis are quite similar to those in the brain. These data suggest a previously unrecognized role of thyroid hormone in posterior pituitary physiology.

Animals↗
PubMed1992

FAD-dependent regulation of transcription, translation, post-translational processing, and post-processing stability of various mitochondrial acyl-CoA dehydrogenases and of electron transfer flavoprotein and the site of holoenzyme formation.

The most prominent biochemical consequence of riboflavin deficiency in rats is a drastic decrease in various acyl-CoA dehydrogenase activities, especially that of short chain and isovaleryl-CoA dehydrogenase (IVD). As a result, oxidation of fatty acids and leucine is severely inhibited. We studied the effects of FAD at various stages of acyl-CoA dehydrogenase biogenesis. Immunoblot revealed severe losses of various acyl-CoA dehydrogenases and electron transfer flavoprotein in riboflavin-deficient rat liver mitochondria. The decreases in IVD and short chain acyl-CoA dehydrogenase were particularly severe, reaching values of 17 and 34% of controls, respectively. With the exception of IVD, the rate of in vitro transcription of the respective genes and the amounts of mRNAs of these flavoproteins in tissues increased 3-8.5-fold over controls. The amount of IVD mRNA and its transcription rate remained unchanged, suggesting that IVD expression is regulated separately from other acyl-CoA dehydrogenases. When riboflavin was depleted, in vitro translation of acyl-CoA dehydrogenase and electron transfer flavoprotein alpha-subunit mRNAs was moderately inhibited. Translation of non-flavoproteins was also inhibited. The stability of precursor acyl-CoA dehydrogenases and their mitochondrial import/processing were unaffected. However, mature acyl-CoA dehydrogenases degraded markedly faster in deficient mitochondria than in controls. Regardless of whether precursors were translated under riboflavin-depleted or riboflavin replete conditions, mature acyl-CoA dehydrogenases survived well when imported into normal mitochondria but degraded faster when imported into deficient mitochondria. These findings indicate that FAD ligand binds to mature acyl-CoA dehydrogenase inside the mitochondria.

Acyl-CoA Dehydrogenases↗
PubMed1992

Regulation of gene expression of proteasomes (multi-protease complexes) during growth and differentiation of human hematopoietic cells.

We have reported that proteasomes are expressed at abnormally high levels in various hematopoietic tumor cells (Kumatori, A., Tanaka, K., Inamura, N., Sone, S., Ogura, T., Matsumoto, T., Tachikawa, T., Shin, S., and Ichihara, A. (1990) Proc. Natl. Acad. Sci. U.S.A. 87, 7071-7075). In the present study, we examined changes in the expressions of proteasomes during growth of peripheral T-lymphocytes from healthy adults and differentiation of human leukemic cell lines. Up-regulation of mRNAs encoding multiple proteasome subunits was observed during proliferation of resting T-cells induced by mitogens such as phytohemagglutinin and interleukin-2. In contrast, in vitro terminal differentiation into monocytic, granulocytic, and erythroid cells of various immature leukemic cell lines, such as HL-60 promyelocytic leukemia cells and K562 erythroleukemia cells, by various inducing agents caused rapid and marked down-regulation of proteasomes expression, independently of the cell type, direction of differentiation, or type of signal. The syntheses of proteasome subunits of 21-31 kDa and their associated components of 35-110 kDa, measured by [35S]methionine incorporation, were much higher in mitogen-activated T-cells and unstimulated HL-60 cells, which grow rapidly, than in resting and differentiated cells, indicating apparent correlations of the mRNA levels of proteasomes with their translational activities. However, immunochemically, no detectable difference in the cellular contents of proteasomes was found in these cells in induced and uninduced states for proliferation and differentiation, suggesting accelerated turnover of proteasomes in rapidly proliferating cells. Inhibition of proteasome expression by an antisense oligodeoxynucleotide for the largest proteasome subunit, C2, caused partial arrest of cell cycle progression of T-lymphocytes, suggesting that up-regulation of proteasomes is indispensable for proliferation of the cells. We also observed that the nuclear fraction of proteasomes increased in proliferating T-cells and that proteasomes moved rapidly between the nucleus and cytoplasm during differentiation of HL-60 cells.

Base Sequence↗
PubMed1992

Association of annexin V with prolactin in the rat anterior pituitary gland.

When pituitary extracts were subjected to non denaturing polyacrylamide gel electrophoresis, an unknown protein was found to associate with a proportion of the prolactin. This protein was dissociated from prolactin by sodium dodecyl sulfate. The protein was purified and sequenced. As the amino terminus was blocked, the amino acid sequences of three peptide fragments were determined. The obtained sequences of 41 amino acids were identical to partial sequences of a known protein, rat Annexin V. The molecular mass, 36 kDa, was also the same as the molecular weight of Annexin V. The existence of Annexin V mRNA in rat pituitary glands was also confirmed by polymerase chain reaction. These results show that Annexin V, a member of the calcium-dependent phospholipid binding proteins, is synthesized in the rat pituitary gland, and suggest its association with prolatin in the gland.

Animals↗
PubMed1992

Identification of osteopontin in isolated rabbit osteoclasts.

Bone remodeling is a complex process coupling bone formation and resorption. Osteoblasts, the bone-forming cells, are known to produce various bone matrix proteins and cytokines; however, little is known about protein factors produced by osteoclasts or bone-resorbing cells. A method utilizing the high affinity of osteoclasts for tissue culture dishes was developed to isolate a large number of pure osteoclasts from rabbit long bones. A cDNA library was then constructed from these isolated osteoclasts, and differential cDNA screening was performed between osteoclasts and spleen cells. Two clones representing osteoclast-specific clones, named OC-1 and OC-2, were isolated. By Northern blot analysis, OC-1 was expressed in osteoclasts and in kidneys, whereas OC-2 was specific for osteoclasts. OC-1 was found to encode osteopontin from its nucleotide sequence, and therefore, osteopontin may have other functions for osteoclastic bone resorption besides osteoclast attachment to bone.

Amino Acid Sequence↗
PubMed1992

Effects of dihydroergotoxine on central cholinergic neuronal systems and discrimination learning test in aged rats.

We evaluated changes in the cholinergic neuronal system and learning ability with aging. Choline acetyltransferase (ChAT) activity, a presynaptic index of the cholinergic system, was decreased in the cerebral cortex, hippocampus, striatum, and hypothalamus in the brain of aged rats compared with young adults. Muscarinic cholinergic binding sites (receptors, MCR), a postsynaptic index of the cholinergic system, were markedly decreased in all areas of the brain. However, intraperitoneal injection of 1 mg/kg of dihydroergotoxine (DHET) for 14 days normalized both ChAT and MCR in the cerebral cortex and hippocampus. In the striatum, ChAT was normalized, but MCR did not recover. Aged rats showed marked learning impairment in a 30-day operant type brightness discrimination learning test. Daily DHET administration restored the discrimination ability in the aged rats to nearly the young adult level. DHET had no effects on central cholinergic indices or learning test results in young adult rats. These findings suggest that learning is impaired in aged rats due to impairment in the central cholinergic neuronal system, and that DHET normalizes the decreased function in this system, restoring the learning ability.

Aging↗
PubMed1992

Deficiency of fibrinolytic enzyme activities in the serum of patients with Alzheimer-type dementia.

Previously we reported that there is a kallikrein deficiency in the cerebral tissue of patients with Alzheimer-type dementia. The present study was performed to investigate protease changes in the serum of these patients. The results showed that the kallikrein activity was normal, but that the activities of plasmin and urokinase were significantly low. The present findings indicate a derangement in the clotting and fibrinolytic systems in Alzheimer patients.

Aged↗
PubMed1992

Inversion of chromosome 16 and bone marrow eosinophilia in a myelomonocytic transformation of chronic myeloid leukemia.

We report a case of chronic myeloid leukemia (CML) in myelomonocytic transformation associated with bone marrow (BM) eosinophilia. At diagnosis, all BM cells showed a Ph chromosome. At the time of blastic phase, more than 50% of Ph+ cells had a pericentric inversion of chromosome 16, inv(16)(p13q22). This case confirms that blastic transformation of CML can involve any committed progenitor, and myelomonocytic leukemia with BM eosinophilia is specifically associated with rearrangement of chromosome 16 at band p13 and q22.

Blast Crisis↗
PubMed1992

Genetic changes of both p53 alleles associated with the conversion from colorectal adenoma to early carcinoma in familial adenomatous polyposis and non-familial adenomatous polyposis patients.

Mutation and loss of heterozygosity (LOH) in the p53 gene were analyzed in 274 colorectal tumors of 4 histopathological grades. Among 160 tumors from 40 familial adenomatous polyposis patients, none of 58 adenomas with moderate dysplasia had p53 mutations, whereas 8% (3 of 37) of severe adenomas, 15% (6 of 40) of intramucosal carcinomas, and 40% (10 of 25) of invasive carcinomas had p53 mutations. Only 3% (1 of 33) of severe adenomas showed both mutation and LOH, while 25% (6 of 24) of intramucosal carcinomas and 40% (10 of 25) of invasive carcinomas had both mutation and LOH. All intramucosal and invasive carcinomas that had mutations lost the other allele of the p53 gene. In 114 tumors from 86 non-familial adenomatous polyposis patients, similar results were obtained; no adenoma showed both mutation and LOH, but both alterations occurred in intramucosal and invasive carcinoma. As regards specificity in 56 mutations detected in the present study, the frequently affected codons were codons 175, 238, 245, 248, 273, and 282, 4 of these amino acids being arginine, and 72% (39 of 54) of all mutations were GC to AT transition. Although expression into p53 polyadenylated RNA was high in every invasive carcinoma irrespective of the presence of mutation or LOH, there was a correlation between mutation and protein level; immunostaining of p53 protein was negative in almost all adenomas, but it was positive in 86% of invasive carcinomas exhibiting p53 mutation. These data suggest that genetic changes on both alleles of the p53 gene through mutation and LOH, which result in abnormal protein accumulation, are involved in the conversion of adenoma to early carcinoma. Also, carcinoma cells with p53 mutations existing within adenoma tissues are detectable by immunostaining, even in formalin-fixed, paraffin-embedded specimens.

Adenoma↗
PubMed1992

Loss of heterozygosity at D3S2 locus of short arm of chromosome 3 in chronic myelogenous leukemia.

Loss of heterozygosity (LOH) on the short arm of chromosome 3 was studied in four patients with chronic myelogenous leukemia (CML). The bcr gene rearrangement-negative spleen cells and a B-cell line were used as normal tissue controls. Five probes showing restriction fragment length polymorphisms (RFLP) and a variable number of tandem repeats on chromosome 3 were used. DNA patterns in Southern blotting were compared between normal cells and leukemic cells. One of the four patients had LOH at the D3S2 locus mapped to 3p14.3-3p21.3. The LOH was detected in the blastic phase, but not in the chronic phase. This patient showed normal chromosomes 3 in the blastic phase. These data suggest the possibility of the existence of LOH in CML, occurring as a secondary event in the blastic phase, and which might have been induced by submicroscopic deletion or somatic recombination.

Blotting, Southern↗