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Biomedical subjects

Y Takagi

Publications and source records attributed to Y Takagi.

At least 217 records · Page 12Linked to original sources
PubMed1997

Identification of elongin C sequences required for interaction with the von Hippel-Lindau tumor suppressor protein.

Elongin C is a 112-amino acid protein that is found in mammalian cells as a positive regulatory subunit of heterotrimeric RNA polymerase II elongation factor Elongin (SIII) and as a component of a multiprotein complex containing the von Hippel-Lindau (VHL) tumor suppressor protein. As a subunit of the Elongin complex, Elongin C interacts directly with the transcriptionally active Elongin A subunit and potently induces its elongation activity; in addition, Elongin C interacts with the ubiquitin-like Elongin B subunit, which regulates the interaction of Elongin C with Elongin A. As a component of the VHL complex, Elongin C interacts directly with both Elongin B and the VHL protein. Binding of the VHL protein to Elongin C was found to prevent Elongin C from interacting with and activating Elongin A in vitro, leading to the proposal that one function of the VHL protein may be to regulate RNA polymerase II elongation by negatively regulating the Elongin complex. In this report, we identify Elongin C sequences required for its interaction with the VHL protein. We previously demonstrated that the ability of Elongin C to bind and activate Elongin A is sensitive to mutations in the C-terminal half of Elongin C, as well as to mutations in an N-terminal Elongin C region needed for formation of the Elongin BC complex. Here we show that interaction of Elongin C with the VHL tumor suppressor protein depends strongly on sequences in the C terminus of Elongin C but is independent of the N-terminal Elongin C region required for binding to Elongin B and for binding and activation of Elongin A. Taken together, our results are consistent with the proposal that the VHL protein negatively regulates Elongin C activation of the Elongin complex by sterically blocking the interaction of C-terminal Elongin C sequences with Elongin A. In addition, our finding that only a subset of Elongin C sequences required for its interaction with Elongin A are critical for binding to VHL may offer the opportunity to develop reagents that selectively interfere with Elongin and VHL function.

Amino Acid Sequence↗
PubMed1997

Multiple transcripts for rat nucleoside diphosphate kinase alpha isoform are structurally categorized into two groups that exhibit cell-specific expression and distinct translation potential.

Rat nucleoside diphosphate (NDP) kinase is composed of two isoforms (alpha and beta) encoded by independent genes. The mRNAs are expressed ubiquitously; however, the level of expression is tissue-dependent and is also up- or down-regulated under certain conditions, including growth stimulation, differentiation, and tumor metastasis. To address the regulatory mechanisms of gene expression for the rat NDP kinase major isoform alpha (an nm23-H2/PuF homologue), we identified the transcription initiation sites in detail by RNase protection and 5'-rapid amplification of DNA ends and located the core promoter region by chloramphenicol acetyltransferase assay. The transcripts, initiated from an extraordinarily wide range of sites, were categorized into two groups; one transcribed from an upstream region was spliced in the untranslated region (group 1), whereas the other initiated in the downstream region was not (group 2). RNase protection demonstrated that the group 1 mRNA was the dominant form present in all tissues except heart and skeletal muscle. In situ hybridization revealed cell-specific expression of these mRNA species. Furthermore, they differed in the translational efficiency (the group 2 alpha > beta > the group 1 alpha). These findings suggest that the regulation of the NDP kinase expression at both transcriptional and posttranscriptional steps could be fundamentally governed by the selection of transcription initiation sites.

Animals↗
PubMed1997

Meshwork arrangement of mitochondria-rich, Na+,K+-ATPase-rich cells in the saccular epithelium of rainbow trout (Oncorhynchus mykiss) inner ear.

BACKGROUND: Electrolyte composition of the teleost fish inner ear endolymph is characterized by a high potassium concentration. From the ultrastructural characteristics, the mitochondria-rich cells (MRCs) in the inner ear epithelium are suggested to regulate the ionic composition of the endolymph. METHODS: In the present study, the ultrastructure of MRCs in the saccular epithelium of the rainbow trout (Onchorhynchus mykiss) was studied, and the immunocytochemical detection of Na+,K+-ATPase, the key enzyme of the ion-transport, in the saccular epithelium was conducted. Electrolyte composition of the saccular endolymph was also determined. RESULTS: Electron-microscopic observations revealed that MRCs located at the periphery of the sensory macula have numerous elongated mitochondria and a well-developed tubular system. Immunocytochemical detection of Na+,K+-ATPase on paraffin sections showed that immunoreactive (ir-) cells were distributed specifically around the sensory macula. Judging from their shape, size, and localization, the Na+,K+-ATPase ir-cells corresponded to the MRCs. The whole-mount immunocytochemistry using Na+,K+-ATPase as a marker for the MRC revealed that MRCs were connected with one another by extended cellular processes, and thus forming a dense meshwork structure around the macula. In the endolymph, potassium levels were 13 times higher than those in plasma, chloride levels were slightly higher whereas sodium, calcium, magnesium, and phosphate levels were lower. CONCLUSIONS: Thus, the saccular MRCs abundant in Na+,K+-ATPase are distributed around the sensory macula forming a dense meshwork structure, with the suggested function to regulate the electrolyte composition of the saccular endolymph.

Animals↗
PubMed1997

Identification of pig primordial germ cells by immunocytochemistry and lectin binding.

Monoclonal antibodies anti-SSEA-1 and EMA-1, and the lectins DBA and LTA, bound to the surface of large, round cells randomly distributed in the 26-day pig genital ridge. Other antibodies, SSEA-3, SSEA-4, TRA-1-60, and TRA-1-81, did not react with any cells in the pig genital ridge. SSEA-1-positive cells displayed pseudopods and appeared to migrate from the dorsal mesentery of the hindgut (18-day) to the primordium of the gonad (day 23) and entered the genital ridge by 26 days. The number of SSEA-1-positive cells associated with the dorsal mesentery and genital ridge markedly increased from the 18-day to the 26-day pig embryo. It was concluded that the SSEA-1-positive cells were primordial germ cells (PGCs). Using these markers and alkaline phosphatase histochemistry, pig PGCs derived from the 26-day genital ridge showed no proliferation when grown in STO co-culture in the presence of human LIF, bFGF and SCF.

Animals↗
PubMed1997

Cortisol inhibits glycosaminoglycan synthesis in cultured rainbow trout cartilage.

In vitro actions of corticosteroids (cortisol, 11-deoxycortisol, cortisone, and corticosterone) as well as interaction between cortisol and triiodothyronine (T3) or recombinant human insulin-like growth factor-I (rhIGF-I) on cartilage glycosaminoglycan (GAG) synthesis in rainbow trout (Oncorhynchus mykiss) were examined. Uptake of [35S]sulfate by isolated branchial cartilage was measured as a marker for GAG synthesis. In vitro exposure of cartilage to cortisol at concentrations of 10, 100, and 1000 nM for 6 days dose-dependently inhibited sulfate uptake, while exposure to 0.1 and 1 nM cortisol had no effect. Corticosterone and 11-deoxycortisol at concentrations of 10 and 100 nM inhibited sulfate uptake slightly but not dose-dependently. Cortisone (1, 10, and 100 nM) had no effect. When cortisol (1, 10, and 100 nM) and T3 (0.075 and 0.75 nM) were simultaneously added to the culture, the T3-induced sulfate uptake was dose-dependently reduced by the presence of 10 and 100 nM cortisol. When cortisol (1, 10, and 100 nM) and rhIGF-I (0.1 and 1 nM) were added together, the sulfate uptake induced by 0.1 nM rhIGF-I was only slightly inhibited by 100 nM cortisol, but 1 nM rhIGF-I completely masked the inhibitory effect of cortisol. These data suggest that GAG synthesis in the rainbow trout cartilage is controlled by multiple interactions among stimulative hormones, such as T3 and IGF-I, and inhibitory hormones, such as cortisol.

Adrenal Cortex Hormones↗
PubMed1997

Improvement of oxygen metabolic reserve after extracranial-intracranial bypass surgery in patients with severe haemodynamic insufficiency.

The effectiveness of extracranial-intracranial arterial bypass (EC-IC bypass) surgery on impaired haemodynamic status was studied in 12 patients with reduced regional cerebral perfusion pressure (rCPP) and elevated regional oxygen extraction fraction (rOEF) in the area distal to the symptomatic arterial lesion. Postoperative positron emission tomography (PET) study demonstrated a statistically significant decrease of rOEF in the operated hemispheres with disappearance of the pre-operative interhemispheric rOEF difference. Regional cerebral blood flow (rCBF) and regional cerebral oxygen metabolism (rCMRO2) were also increased in the operated hemispheres with disappearance of the pre-operative interhemispheric differences. Regional CBF/regional cerebral blood volume (rCBV) ratios of the symptomatic hemispheres were increased after surgery, but were still lower than in the contralateral hemispheres. We conclude that EC-IC bypass surgery improves impaired cerebral oxygen metabolic reserve.

Aged↗
PubMed1997

Effects of endotoxin on intestinal hemodynamics, glutamine metabolism, and function.

The purpose of this study was to investigate the intestinal hemodynamics and gut glutamine metabolism during endotoxemia, and their correlation with altered intestinal absorptive capacity and permeability. Seventeen Sprague-Dawley rats were used in the study. The endotoxin group (ENDO) received endotoxin (10 mg/kg intraperitoneally, n = 9), while the control group (CONT, n = 8) received saline injection. Twelve hours later, D-xylose (0.5 g/kg) and fluorescein isothiocyanate-dextran (FITC-dextran, 750 mg/kg) were given by oral gavage. One hour later abdominal aortic (AA) blood flow, superior mesenteric venous (SMV) flow, mean arterial pressure (MAP), central venous pressure (CVP), and SMV pressure (SMVP) were also measured. The MAP, AA, and SMV blood flow decreased (P < 0.05), while the CVP and SMVP increased (P < 0.05) in the ENDO group as compared with the CONT group. The ENDO group showed significant decreases for both intestinal glutaminase activity and net intestinal glutamine uptake (P < 0.05). The D-xylose concentration in SMV decreased significantly (P < 0.05) in the ENDO group as compared with the CONT group. However, the plasma FITC-dextran concentration showed no significant difference between the groups. Endotoxin produced a hypodynamic effect in rats 12 h after intraperitoneal administration in association with both a decreased intestinal glutamine metabolism and an absorptive capacity.

Animals↗
PubMed1997

Beneficial effects of growth hormone combined with parenteral nutrition in the management of inflammatory bowel disease: an experimental study.

BACKGROUND: Growth hormone (GH) improves net protein anabolism and stimulates wound healing. Although GH is also known to exert the trophic effect on the intestinal tract, its role in the healing of intestinal ulceration is not known. The aim of this study was to evaluate the effects of exogenous GH coinfused with parenteral nutrition (PN) in an experimental model of inflammatory bowel disease in rats. METHODS: All rats underwent central venous cannulation and were randomized to two groups after induction of small intestinal ulceration with indomethacin. Both groups received the same PN formula. In addition, the GH group (n = 10) received subcutaneous injections of human GH at a dose of 1.0 IU/kg daily for 4 days, whereas the control group (n = 10) received injections of normal saline solution. Nitrogen balance, macroscopic inflammation score, intestinal myeloperoxidase activity, DNA content, and mucosal permeability were determined for each rat. Insulin-like growth factor-I (IGF-I) mRNA was detected by reverse transcription and polymerase chain reaction. RESULTS: Administration of GH significantly improved the cumulative nitrogen balance, ameliorated the gross inflammation score, and decreased intestinal myeloperoxidase activity. Similarly, intestinal permeability was significantly decreased in the GH group as compared with the control group. GH treatment resulted in increased plasma concentration of IGF-I and IGF-I mRNA expressions in both the liver and the small intestine compared with those in the control group. CONCLUSIONS: Exogenous GH plays an important role in accelerating intestinal healing in an experimental model of small bowel ulceration in rats. The mechanisms may include the stimulated IGF-I production, which thereafter augments intestinal epithelial cell growth.

Animals↗
PubMed1997

Lock method using sodium hydroxide solution to clear occluded central venous access devices.

Occlusion of central venous access devices (CVADs) is not an uncommon problem duringlong-term parenteral nutrition. A number of techniques have been developed to deal with obstructed CVADs. This study investigated the effectiveness of the sodium hydroxide (NaOH) lock method for gradual CVAD occlusion. When a progressively declining flow was noticed, 0.1 N NaOH solution was injected into the CVAD and locked. Nineteen CVAD occlusions in 11 home parenteral nutrition patients were treated Sixteen of 19 trials cleared the occlusions, whereas 3 of 19 failed. One of the failures was due to a mechanical occlusion and the other two were able to be restored by using ethanol. There were no significant complications. The benefits of this method are: (1) a shorter treatment time and a lower dose than NaOH infusion therapy, (2) it does not require hospital admission and (3) it does not result in bursting of the catheter.

Journal Article↗
PubMed1997

Evaluation of a trans configuration for the apoptosis-inducing activity of ceramide.

The requirement of a trans double bond for the biological action of ceramide was assessed by comparing the apoptosis-inducing activity of various ceramide analogs. The cis isomer and an acetylene type derivative of sphingosine were chemically synthesized, and the 2-amino moiety was acylated with hexanoic acid. These cell-permeable ceramide derivatives were compared with N-hexanoyl sphingosine (C6-Cer) or N-hexanoyl dihydrosphingosine (C6-DH-Cer) in their activity to induce apoptosis of HL60. Either the cis isomer of C6-Cer (C6-cis-Cer) or a triple bond derivative (C6-TRP-Cer) induced apoptosis when assessed by fluorescence microscopy of the morphological changes and electrophoretic analysis of DNA C6-TRP-Cer yielded the highest percentage of apoptotic cells corresponding to three times that was induced by C6-Cer. C6-cis-Cer also showed stronger activity than C6-Cer. The minimum amounts of C6-TRP-Cer and C6-cis derivative required to induce apoptosis were 0.1 and 0.5 microM, respectively, while 1 microM C6-Cer was required to exhibit the activity. C6-DH-Cer showed very low but significant activity above 10 microM. N-acetyl-sphingosine (C2-Cer) induced more apoptotic cells than C6-Cer, and C2-TRP-Cer was much more potent than C2-Cer. These observations suggest that the trans configuration of ceramide is not necessarily essential for the activity to induce apoptosis. In addition, distinctive activity of C6- or C2-TRP-Cer suggests that this ceramide analog might be useful for developing a new type of antitumor drug.

Apoptosis↗
PubMed1997

Molecular cloning, characterization and expression of cDNA encoding phosphoserine aminotransferase involved in phosphorylated pathway of serine biosynthesis from spinach.

Phosphoserine aminotransferase (PSA) catalyzes the conversion of phosphohydroxypyruvate to phosphoserine in the phosphorylated pathway of serine biosynthesis. A cDNA clone encoding PSA was isolated from the cDNA library of spinach (Spinacia oleracea L.) green leaves. Determination of the nucleotide sequence revealed the presence of an open reading frame encoding 430 amino acids, exhibiting 38-50% homology with the amino acid sequences of bacterial, yeast and animal PSA. It contains an N-terminal extension of ca. 60 amino acids in addition to the sequences from other organisms. The general features of plastidic transit peptide are observed in this N-terminal sequence, suggesting the plastid localization of the PSA protein encoded by this cDNA. The bacterial expression of the cDNA could functionally rescue the auxotrophy of serine in the serC- mutant, Escherichia coli KL282. The enzymatic activity of PSA was demonstrated in vitro in the extracts of E. coli over-expressing the cDNA. Southern blot analysis indicated the presence of a couple of related genes (Psa) in the spinach genome. RNA blot hybridization suggested the preferential expression of the Psa gene in the roots of green seedlings and in the suspension cells cultured under a dark condition.

Amino Acid Sequence↗
PubMed1997

Induction of nitric oxide synthase in rat intestine by interleukin-1alpha may explain diarrhea associated with zinc deficiency.

Synthesis of inducible nitric oxide synthase (iNOS) in the intestine may result in local tissue damage. We investigated whether a challenge with interleukin-1alpha could give rise to intestinal iNOS expression and diarrhea in rats of differing zinc status. Weaning male rats were fed a zinc-deficient (ZD) diet (2 mg zinc/kg) for 4 wk to induce zinc deficiency or a zinc-supplemented diet [50.8 mg zinc/kg; controls, including pair-fed (PF ) and ad libitum (AL) consumption groups], and then subcutaneously injected with interleukin-1alpha (2 x 10(7) units/kg body wt). Without the interleukin-1alpha challenge, ZD rats had significantly lower plasma zinc concentration than the other groups. Intestinal metallothionein-1 mRNA abundance was lower in ZD rats than in AL rats. iNOS was expressed in the intestine of ZD rats but not in the others. None of the rats experienced diarrhea during the feeding period. Interleukin-1alpha led to a reduction in plasma zinc concentration, enhancement in intestinal metallothionein-1 mRNA levels, and expression of the intestinal iNOS gene in all groups. However, the abundance of iNOS mRNA was significantly higher in ZD rats than in the other groups. The presence of iNOS protein was demonstrated by immunohistochemical staining in the intestine of ZD rats that had been treated with interleukin-1alpha 12 h earlier. In addition, diarrhea occurred in most of the ZD rats and some of the PF rats but not in AL rats after interleukin-1alpha treatment. We conclude that ZD rats respond to interleukin-1alpha challenge more severely than controls, reflected by a more marked and prolonged iNOS expression and a greater incidence of diarrhea.

Animals↗
PubMed1997

Predictability of extracranial/intracranial bypass function: a retrospective study of patients with occlusive cerebrovascular disease.

OBJECTIVE: When the efficacy of extracranial/intracranial bypass surgery is discussed, can we include the patients with extensive collateral circulation through the bypass and those with poor collateral circulation in the same group? The bypass function should be determined not by the patency of the bypass but by the extent of collateral circulation through the bypass. We retrospectively analyzed our patients to determine whether the extent of bypass flow can be predicted from the results of preoperative studies. METHODS: In 51 hemispheres of 44 consecutive patients who underwent extracranial/intracranial bypass surgery, correlation between the extent of bypass flow and the preoperative results of angiographic and stimulated cerebral blood flow studies were investigated. RESULTS: The bypass function is highly predictable with the aid of preoperative studies. In 11 hemispheres that showed both retrograde spontaneous circulation via leptomeningeal anastomoses and decreased reactivity to acetazolamide of cerebral blood flow in an area distal to the arterial lesion, collateral circulation through the bypass developed well and reactivity to acetazolamide improved. In all of 13 hemispheres that showed normal reactivity to acetazolamide, the bypass was patent but the collateral circulation did not develop well. In only 4 of 24 hemispheres with spontaneous antegrade circulation distal to the lesion was there satisfactory collateral circulation through the bypass. CONCLUSION: Our results indicate that improvement of the hemodynamic status by bypass surgery should be expected only in patients with both spontaneously developed leptomeningeal anastomoses and decreased reactivity to acetazolamide.

Acetazolamide↗
PubMed1997

Bilateral chromophobe cell renal carcinoma in tuberous sclerosis complex.

We report on a patient with tuberous sclerosis complex and polycystic kidney disease who developed bilateral chromophobe cell renal carcinoma. We discuss the tuberous sclerosis complex, associated bilateral renal cell carcinoma, polycystic kidney disease and chromophobe cell renal carcinoma; a recently established subtype with a rather favorable prognosis. In a patient with tuberous sclerosis complex and multiple space-occupying lesions, a diagnosis of angiomyolipoma should be considered first but bilateral and/or multifocal renal cell carcinoma is a likely diagnosis.

Adult↗