Biomedical subjects

Yukio Kato

Publications and source records attributed to Yukio Kato.

At least 91 records · Page 5Linked to original sources

PubMed2003

Prolactin gene expression in the mouse nipple.

In this study, we attempted to examine the presence of prolactin (PRL) messenger ribonucleic acid (mRNA) and protein in the mouse nipple and mammary gland in pregnancy and lactation. PRL-like substances were found by immunohistochemistry using an antibody against the mouse PRL (mPRL) in the sebaceous gland cells of the nipple during late pregnancy and lactation, and the cistern of alveoli in mammary glands during lactation. Western blot analysis of proteins extracted from the nipple and the mammary gland showed immunoreactive bands corresponding to molecular weights of approximate 16 kDa and 32 kDa, respectively. The expression of mRNA for mPRL in the nipple and mammary gland during late pregnancy and lactation was demonstrated by reverse transcription-polymerase chain reaction (RT-PCR), Southern blotting, and nucleotide sequence analyses. These results suggest that mPRL mRNA and its translation product are synthesized in the mouse nipple.

Animals↗

PubMed2003

Potential cholestatic activity of various therapeutic agents assessed by bile canalicular membrane vesicles isolated from rats and humans.

The active transport of solutes mediated by the bile salt export pump (BSEP/ABCB11) and multidrug resistance associated protein-2 (MRP2/ABCC2) are thought to involve bile acid-dependent and -independent bile formation, respectively. To evaluate the potential of therapeutic agents as inhibitors of such transporters on bile canalicular membranes, we examined the inhibition of the primary active transport of typical substrates by 15 drugs, clinically known to cause cholestasis in canalicular membrane vesicles. The inhibition by most of the compounds in rat canalicular membrane vesicles (CMVs) was minimal or observed at much higher concentrations than obtained in clinical situations. However, cloxacillin, cyclosporin A and midecamycin inhibited BSEP, and cyclosporin A and midecamycin inhibited MRP2 with an inhibition constant close to the clinical concentration. By comparing the inhibition potential between rat and human CMVs, the inhibition of BSEP- and MRP2-mediated transport by midecamycin and cyclosporin A was relatively similar whereas the inhibitory effect on BSEP-mediated transport by cloxacillin and glibenclamide was more marked in humans than in rats. These results suggest that the majority of cholestasis-inducing drugs have a minimal inhibitory effect on rat BSEP and MRP2 although species differences in inhibitory potential should be considered, especially in the case of BSEP.

Journal Article↗

PubMed2003

Function of uptake transporters for taurocholate and estradiol 17beta-D-glucuronide in cryopreserved human hepatocytes.

The uptake properties of taurocholate (TC) and estradiol 17beta-D-glucuronide (E(2)17betaG) were examined in freshly isolated and cryopreserved human hepatocytes to discover if active transport is retained in cryopreserved human hepatocytes. Firstly, the uptake of TC and E(2)17betaG was measured before and after cryopreservation. The uptake of TC was found to be Na(+)-dependent both in fresh and cryopreserved hepatocytes. The uptake activity in cryopreserved hepatocytes was found to range from 10 to 200% of that observed in freshly isolated cells. A kinetic analysis was performed to evaluate the transport activity of TC and E(2)17betaG and revealed that the Michaelis constant (K(m)) for these compounds in cryopreserved human hepatocytes was 2-8 and 3-18 microM, respectively. This was within the range of K(m) values previously found in human Na(+)-taurocholate cotransporting polypeptides (NTCP) and organic anion transporting polypeptides (OATP) 2 and 8, respectively. The kinetic analyses also showed that the species difference between human and rat hepatocytes was more marked for the maximal uptake rate (V(max)) (>22 and >22 times higher for TC and E(2)17betaG in rats than in humans, respectively) than that for K(m) (2-12 and 0.7-4 times higher, respectively), compared with earlier data we obtained in primary cultured rat hepatocytes. Hence, we conclude that cryopreserved human hepatocytes, at least in part, retain their transporter functions and, therefore, can be a useful experimental system for examining the mechanism of the hepatic uptake of drugs.

Journal Article↗

PubMed2003

Involvement of multiple transport systems in the disposition of an active metabolite of a prodrug-type new quinolone antibiotic, prulifloxacin.

Prulifloxacin is a prodrug-type new quinolone. The purpose of this study is to clarify the mechanism of biliary excretion and brain distribution of its active metabolite, UFX. UFX was efficiently excreted into the bile in rats, with its concentration in the bile being 30-60 times higher than that in plasma. The in vivo disposition study revealed that multidrug resistance-associated protein 2 (MRP2) was involved in the biliary excretion of glucuronide metabolite, but not of the unchanged UFX. A transport study using a P-glycoprotein (P-gp) overexpressing cell line, LLC-GA5-COL150, showed that UFX was a substrate of P-gp. Nevertheless, the biliary clearance (CLbile) of UFX in P-gp-gene-deficient mice was not different from that in the normal mice, although the concentration in the liver was slightly higher than that in the normal mice. These observations suggest that multiple transport systems are involved in the biliary excretion of UFX, with minor contribution of P-gp. The distribution of UFX in the rat brain was quite low, and its tissue to plasma concentration ratio (Kp) in the brain was much less than the unity and was increased by cyclosporin A. The Kp in the brain of mdr1a/1b(-/-) mice was higher than that in the normal mice, suggesting that efflux by P-gp played a major role in the limited brain distribution of UFX.

Journal Article↗

PubMed2003

Primary cutaneous diffuse large B cell lymphoma: a clinically aggressive case.

An 80-year-old woman was diagnosed with primary cutaneous B cell lymphoma. She had multifocal cutaneous tumors, but no nodal lymphadenopathy or bone marrow involvement. Histopathological examination of a biopsy specimen showed diffuse large B cell lymphoma without a bcl-2 expression. Complete resolution of hypercalcemia and disappearance of tumors were achieved with CHOP therapy, but a rapidly progressive skin lesion was observed soon after the completion of the therapy. The clinical manifestation of primary cutaneous diffuse large B cell lymphoma is diverse and the treatment strategy is not entirely clarified. This case represents another example of this rare lymphoma.

Aged↗

PubMed2003

[Systemic infection of Aspergillus flavus in a patient with acute lymphoblastic leukemia].

A 57-year-old woman with acute lymphoblastic leukemia (ALL) developed an antibiotics-resistant fever after remission induction therapy. Chest X-ray and computed tomography scan revealed multiple consolidations and cavities. Successively, numerous subcutaneous nodules and a thyroid mass emerged. Aspergillus flavus (A. flavus) was cultured from both sites. Despite the patient's granulocyte recovery, the fever persisted and multiorgan function deteriorated rapidly. However, she was successfully treated with intensive supportive therapy including continuous hemodialysis and filtration. Prolonged use of amphoterin B and itraconazole failed to cure her aspergillosis, but the illness remained indolent thereafter.

Amphotericin B↗

PubMed2002

Toxicological implications of hepatobiliary transporters.

Recent progress in molecular biological research has revealed that many types of transporters are expressed in the liver. Such xenobiotic transporters have a wide range of substrate specificity, which allows them to act as a barrier to protect the body from potentially harmful xenobiotics. Most of them mediate active transport of the substrates, leading to concentrative uptake and excretion into the hepatocytes and bile. Transport properties such as these may play a role in the toxicity of certain types of substrates. For example, anticancer agents such as methotrexate and irinotecan are efficiently excreted into the bile and such excretion has been suggested to account for their toxic gastrointestinal side-effects. A similar hypothesis has also been proposed for NSAIDs. Considering their tissue-specific expression, these transporters also appear to be a promising target for the delivery of small molecules, while simultaneously minimizing their side-effects. For example, transporters involved in the oral absorption, hepatic uptake, and biliary excretion of pravastatin, an HMG-CoA reductase inhibitor, ensure its enterohepatic circulation giving it an important pharmacokinetic advantage since its pharmacological target is the liver. Of the major ACE inhibitors currently available, temocaprilat is a substrate of hepatic transporters. Since the major elimination route for other ACE inhibitors is via urinary excretion, their plasma concentrations exhibit a high degree of inter-patient variability over a wide range of renal function whereas the concentrations of temocaprilat exhibit a much lower degree of inter-patient variability due to its elimination into the bile. Thus, the hepatobiliary transporters are involved in some aspects of toxicology and, therefore, a rational strategy for regulating the recognition by such transporters may be required for optimum drug design. This presentation will discuss the possible role of hepatic transporters from a toxicological point of view.

Animals↗

PubMed2002

Dec1 and Dec2 are regulators of the mammalian molecular clock.

The circadian rhythms in mammals are regulated by a pacemaker located in the suprachiasmatic nucleus of the hypothalamus. Four clock-gene families have been found to be involved in a transcription-translation feedback loop that generates the circadian rhythm at the intracellular level. The proteins Clock and Bmal1 form a heterodimer which activates the transcription of the Per gene from the E-box elements in its promoter region. Protein products of Per act together with Cry proteins to inhibit Per transcription, thus closing the autoregulatory feedback loop. We found that Dec1 and Dec2, basic helix-loop-helix transcription factors, repressed Clock/Bmal1-induced transactivation of the mouse Per1 promoter through direct protein-protein interactions with Bmal1 and/or competition for E-box elements. Dec1 and Dec2 are expressed in the suprachiasmic nucleus in a circadian fashion, with a peak in the subjective day. A brief light pulse induced Dec1 but not Dec2 expression in the suprachiasmic nucleus in a phase-dependent manner. Dec1 and Dec2 are regulators of the mammalian molecular clock, and form a fifth clock-gene family.

ARNTL Transcription Factors↗

PubMed2002

Basic helix-loop-helix protein DEC1 promotes chondrocyte differentiation at the early and terminal stages.

The mRNA level of basic helix-loop-helix transcription factor DEC1 (BHLHB2)/Stra13/Sharp2 was up-regulated during chondrocyte differentiation in cultures of ATDC5 cells and growth plate chondrocytes, and in growth plate cartilage in vivo. Forced expression of DEC1 in ATDC5 cells induced chondrogenic differentiation, and insulin increased this effect of DEC1 overexpression. Parathyroid hormone (PTH) and PTH-related peptide (PTHrP) suppressed DEC1 expression and the differentiation of ATDC5 cells, but DEC1 overexpression antagonized this inhibitory action of PTH/PTHrP. Transforming growth factor-beta or bone morphogenetic protein-2, as well as insulin, induced DEC1 expression in ATDC5 cultures where it induced chondrogenic differentiation. In pellet cultures of bone marrow mesenchymal stem cells exposed to transforming growth factor-beta and insulin, DEC1 was induced at the earliest stage of chondrocyte differentiation and also at the hypertrophic stage. Overexpression of DEC1 in the mesenchymal cells induced the mRNA expressions of type II collagen, Indian hedgehog, and Runx2, as well as cartilage matrix accumulation; overexpression of DEC1 in growth plate chondrocytes at the prehypertrophic stage increased the mRNA levels of Indian hedgehog, Runx2, and type X collagen, and also increased alkaline phosphatase activity and mineralization. To our knowledge, DEC1 is the first transcription factor that can promote both chondrogenic differentiation and terminal differentiation.

Alkaline Phosphatase↗

PubMed2002

Effects of overexpression of membrane-bound transferrin-like protein (MTf) on chondrogenic differentiation in Vitro.

Membrane-bound transferrin-like protein (MTf) is expressed in parallel with the expression of cartilage-characteristic genes during differentiation of chondrocytes, and the MTf level is much higher in cartilage than in other tissues. To investigate the role of MTf in cartilage, we examined the effects of growth factors on MTf expression in mouse prechondrogenic ATDC5 cells and the effect of MTf overexpression on differentiation of ATDC5 and mouse pluripotent mesenchymal C3H10T1/2 cells. In ATDC5 cultures, bone morphogenetic protein-2 and transforming growth factor-beta as well as insulin induced MTf mRNA expression when these peptides induced chondrogenic differentiation. Forced expression of rabbit MTf in ATDC5 cells induced aggrecan, type II collagen, matrilin-1, type X collagen mRNAs, and cell-shape changes from fibroblastic cells to spherical chondrocytes. Accordingly, the synthesis and accumulation of proteoglycans were higher in MTf-expressing cultures than in control cultures. These effects of MTf overexpression correlated with the MTf protein level on the cell surface and decreased in the presence of anti-MTf antibody. However, the aggrecan mRNA level in the ATDC5 cells overexpressing MTf was lower than that in wild type ATDC5 cells exposed to 10 microg/ml insulin. MTf overexpression in C3H10T1/2 cells also induced aggrecan and/or type II collagen mRNA but not the spherical phenotype. These findings suggest that the expression of MTf on the cell surface facilitates the differentiation of prechondrogenic cells, although MTf overexpression alone seems to be insufficient to commit pluripotent mesenchymal cells to the chondrocyte lineage.

Aggrecans↗

PubMed2002

Identification of functional hypoxia response elements in the promoter region of the DEC1 and DEC2 genes.

Adaptation to hypoxia is a crucial process both physiologically (i.e. in chondrocytes) and pathologically (i.e. in tumor cells). Previous studies have shown that DEC1, a basic helix-loop-helix transcription factor, is induced by hypoxia in glioma cells (Ivanova, A. V., Ivanov, S. V., Danilkovitch-Miagkova, A., and Lerman, M. I. (2001) J. Biol. Chem. 276, 15306-15315). In the present study, we found that hypoxia or CoCl(2) enhanced the mRNA expression of DEC2, as well as DEC1, within 24 h in chondrogenic ATDC5, 293T, and HeLa cells. In luciferase assays, the regions between -524 and -401 in the DEC1 promoter, and between -863 and -258 in the DEC2 promoter, were responsible for the hypoxia- or hypoxia-inducible factor-1alpha (HIF-1alpha)-induced transcription. In these regions, we identified functional hypoxia response elements (HREs) that bound to HIF-1alpha and HIF-1beta. In addition to an HIF-1 binding site consensus sequence, the DEC1 HRE had cAMP response element-like and CACAG sequences, which were also involved in the transcription activation in response to HIF-1alpha. Although the DEC2 HRE did not have a cAMP response element-like or CACAG sequence, it showed a higher affinity for HIF-1 than did the DEC1 HRE. Because DEC1 and DEC2 are directly inducible by HIF-1, these transcription factors may be crucial for the adaptation to hypoxia.

Aryl Hydrocarbon Receptor Nuclear Translocator↗

PubMed2002

pH-dependent receptor/ligand dissociation as a determining factor for intracellular sorting of ligands for epidermal growth factor receptors in rat hepatocytes.

Both epidermal growth factor (EGF) and transforming growth factor-alpha (TGF alpha) bind to EGF receptors and TGF alpha has been reported to be more potent than EGF as far as many biological effects are concerned. One possible reason for this is thought to be the difference in their dissociation from the receptors in intracellular acidic compartments, which may affect the final pathway (lysosomal degradation or recycling to cell-surface) of endocytosed ligands. This study was aimed at clarifying the relationship between intracellular dissociation from the receptors and the fate of the endocytosed ligands. First, (125)I-human EGF (hEGF), mouse EGF (mEGF), or human TGF alpha (hTGF alpha) was prebound to cell-surface receptors or intracellularly preloaded, followed by further incubation at 37 degrees C in primary cultured rat hepatocytes. In these experiments, the magnitude of the dissociation rate constant (k(off)) of each ligand at pH 6.0, which is similar to that inside early endosomes, was found to be in the following order: hTGF alpha>mEGF>hEGF. The recycled portion of endocytosed ligands was also in the order: hTGF alpha>mEGF>hEGF. Digitonin treatment of preloaded cells revealed that the intracellular dissociation of hTGF alpha was more rapid than that of hEGF. Moreover, several histidine-inserted or -deleted hEGF mutants were prebound to rat liver sinusoidal membrane vesicle, followed by further incubation at 37 degrees C. The dissociation rate of histidine-deleted hEGF mutants was less rapid than that of hEGF itself. These results suggested that efficient dissociation in the earlier intracellular compartment leads the endocytosed ligands to be recycled to the cell surface whereas late dissociation results in intracellular degradation in hepatocytes. Thus, one possible strategy to improve their stability in the circulation may be a change in intracellular ligand/receptor dissociation with a minimal effect on the affinity for receptors on the cell-surface and histidine residues may partly contribute to the pH-sensitive dissociation.

Animals↗

PubMed2002

Change in the composition of the microflora on vacuum-packaged beef during chiller storage.

Five fresh beefcut samples were divided into 10 pieces, respectively, vacuum-packaged and stored at 2 degrees C for up to 6 weeks. The average pH values of five pieces from five beef samples were 5.62 +/- 0.04 at the start of storage and 5.12 +/- 0.07 after 6 weeks of storage. The pieces were homogenized, diluted and cultivated at weekly intervals on glucose-blood-liver (BL), de Man Rogosa and Sharpe (MRS) and trypticase soya (TS) agars at 7 degrees C for 10-14 days. From plates with 30-300 colonies, or the highest number if below 30, 15 colonies were randomly picked from each of the three media used for each beef sample. Based on morphologies, SDS-PAGE whole-cell protein profiles and physio-chemical characteristics, a total of 1493 strains isolated were identified as Brochothrix thermosphacta (64), Carnobacterium divergens (79), Carnobacterium piscicola (27), Lactobacillus algidus (637), Lactobacillus sp. (4), Lactococcus piscium (270), Leuconostoc gelidum (375), Acinetobacter (3), Aeromonas (1), Bacillus (10), Corynebacterium (3), Enterobacteriaceae (1), Pseudomonas (13) or Psychrobacter (6). A wider range of organisms was isolated from TS (13 organisms) and BL (7) agars than from MRS agar (3). Leuc. gelidum, Lc. piscium and L. algidas increased in numbers during the first 3 weeks of storage from about 5 x 10(3) cfu/g to the level of about 10(8) cfu/g and persisted at this level thereafter. C. divergens and C. piscicola were inconsistently detected, but seemed to persist at the relatively low level of about 5 x 10(7) cfu/g during the last 3 weeks of storage. B. thermosphacta increased to the level of about 7 x 10(5) cfu/g during the first 2 weeks of storage, but was not detected thereafter. Remaining organisms were detected sporadically at levels of <3.5 x 10(2) cfu/g during the first 2 weeks of storage.

Agar↗

PubMed2002

Preferential expression of ADP-ribosylation factor gene in the chick embryonic gonads.

cDNA cloning from chick embryonic gonads subtracted from tissues of the brain, heart, liver, gizzard, mesonephros and skeletal muscle was performed to identify genes with expression unique to embryonic gonads. Several cDNA clones encoding characterized as well as many uncharacterized genes were obtained. ADP-ribosylation factor (ARF) of these identified genes was preferentially expressed in the chick embryonic ovary and testis as revealed by reverse transcription-polymerase chain reaction analysis. Expression of the ARF was evaluated through embryonic development, but no difference in the transcript (relative to glyceraldehyde-3-phosphate dehydrogenase transcript) was observed between the left and right ovaries, and between the ovary and testis. In addition, the ARF transcript was detected in the gonads on embryonic days 5 to 21. These findings indicate that the ARF is constantly, but preferentially expressed in the embryonic gonads during development.

ADP-Ribosylation Factors↗

PubMed2002

Structural basis for acidic-cluster-dileucine sorting-signal recognition by VHS domains.

Specific sorting signals direct transmembrane proteins to the compartments of the endosomal-lysosomal system. Acidic-cluster-dileucine signals present within the cytoplasmic tails of sorting receptors, such as the cation-independent and cation-dependent mannose-6-phosphate receptors, are recognized by the GGA (Golgi-localized, gamma-ear-containing, ADP-ribosylation-factor-binding) proteins. The VHS (Vps27p, Hrs and STAM) domains of the GGA proteins are responsible for the highly specific recognition of these acidic-cluster-dileucine signals. Here we report the structures of the VHS domain of human GGA3 complexed with signals from both mannose-6-phosphate receptors. The signals bind in an extended conformation to helices 6 and 8 of the VHS domain. The structures highlight an Asp residue separated by two residues from a dileucine sequence as critical recognition elements. The side chains of the Asp-X-X-Leu-Leu sequence interact with subsites consisting of one electropositive and two shallow hydrophobic pockets, respectively. The rigid spatial alignment of the three binding subsites leads to high specificity.

ADP-Ribosylation Factors↗

PubMed2002

Prominent expression of transforming growth factor beta2 gene in the chicken embryonic gonad as revealed by suppressive subtraction cloning.

cDNA cloning from chicken embryonic gonad subtracted from tissues of the brain, heart, liver, gizzard, mesonephros, and muscle was performed to identify growth factor genes with expression unique to embryonic ovary and testis. We obtained several cDNA clones encoding known and many unknown genes. We found for the first time that the transforming growth factor beta2 (TGF-beta2) is preferentially expressed in the chicken embryonic ovary and testis. cDNA subtraction cloning with respect to the selective expression of TGF-beta2 in the ovary and testis was further analyzed by reverse transcription-polymerase chain reaction analyses of other embryonic tissues. The ontogeny of TGF-beta2 was evaluated in chicken embryonic ovary and testis. In both testis and ovary, the levels of TGF-beta2 transcripts were high during the early period of embryonic development (E7), gradually decreased until the late embryonic days (E14--E17), and then slightly increased at the last embryonic day (E21). There was no difference in the TGF-beta2 transcripts per RNA between the left and the right ovaries. TGF-beta2 may have a critical role in the regulation of the development of chicken ovarian and testicular germ cells during the embryonic period.

Animals↗

PubMed2002

Comparative inhibitory effects of different compounds on rat oatpl (slc21a1)- and Oatp2 (Slc21a5)-mediated transport.

PURPOSE: The purpose of the present study is to examine the selectivity of various inhibitors towards the rat organic anion transporting polypeptides 1 (Oatp1: gene symbol Slc21a1) and 2 (Oatp2: Slc21a5). METHODS: The inhibitory effects of 20 compounds on the Oatpl-mediated transport of estradiol 17beta-D-glucuronide and on the Oatp2-mediated transport of digoxin were examined in cDNA-transfected LLC-PK1cells. RESULTS: Among the compounds examined in this study, nonsteroidal anti-inflammatory drugs, deoxycorticosterone. and quinidine preferentially inhibited Oatpl. whereas digoxin, quinine, and rifampicin preferentially inhibited Oatp2 at low concentrations. On the other hand, propionic acid, re-ketoglutarate and p-aminohippurate showed no inhibitory effects on either transporter up to a concentration of 1,000 microM. The Ki values of ibuprofen and quinidine were estimated to be 19 and 13 times lower for Oatpl compared with Oatp2, whereas the values for rifampicin, quinine, and digoxin were 13, 20, and 100< times lower for Oatp2 compared with Oatpl. CONCLUSIONS: At low concentrations, some of the tested inhibitors exert selective inhibition of either Oatpl- or Oatp2-mediated substrate transport. These selective inhibitors may be used at appropriate concentrations to estimate the maximum contribution of Oatp1 or Oatp2 to the total substrate uptake into rat hepatocytes.

Algorithms↗

PubMed2002

Reduced gastrointestinal toxicity following inhibition of the biliary excretion of irinotecan and its metabolites by probenecid in rats.

PURPOSE: To ameliorate the late-onset of severe gastrointestinal toxicity provoked by irinotecan (CPT-11), which may be related to the biliary excretion of CPT-11 and/or its metabolites. METHODS: Effects of probenecid, an inhibitor of MRP2/ABCC2, on the biliary excretion and mucosal intestinal tissue concentration of CPT-11 and its metabolites were examined in rats. CPT-11-induced late-onset gastrointestinal toxicity was also evaluated. RESULTS: Coadministration of probenecid reduced the biliary excretion of CPT-11, an active metabolite (SN-38) and its glucuronide by half with a concomitant increase in their plasma concentration. When the dose of CPT-11, in the presence of probenecid, was set at half that in its absence, the plasma SN-38 concentration was maintained at the same level as the control, whereas the mucosal intestinal tissue concentration of SN-38 was reduced. Under this condition, CPT-11-induced watery diarrhea, changes in intestinal marker enzymes and body weight reduction were much less in the probenecid-treated group, although the degree of bone marrow suppression was almost the same as that in the control. CONCLUSIONS: Coadministration of probenecid with a reduced dose of CPT-11 potently reduces both SN-38 exposure and CPT-11-induced late-onset toxicity in gastrointestinal tissues, possibly by inhibiting the biliary excretion of CPT-11 and/or its metabolites.

Animals↗