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Biomedical subjects

Y Fujimoto

Publications and source records attributed to Y Fujimoto.

At least 253 records · Page 14Linked to original sources
PubMed1994

Structure-specific inhibition of lysosomal cholesterol transport in macrophages by various steroids.

Cultured mouse peritoneal macrophages effectively take up and metabolize liposomes containing phosphatidylserine and cholesterol, resulting in massive accumulation of cholesteryl esters and triacylglycerols in their cytoplasm (Nishikawa, K., Arai, H. and Inoue, K. (1990) J. Biol. Chem. 265, 5226-5231). With this system, various steroid derivatives were assessed as to their ability to inhibit the cholesteryl ester formation from endocytosed cholesterol in macrophages. Among the steroids tested, one group of steroids having an oxo group at the C17 or C20 position, such as androstenedione, dehydroisoandrosterone, progesterone and pregnenolone, completely inhibited cholesteryl ester formation at 10 microM. Another group of steroids having a hydroxy group at the C17 position, such as testosterone and androstenediol, had a lesser effect; complete inhibition of cholesteryl ester formation was achieved with 100 microM or more. The mechanism underlying the inhibition by the former class of steroids was further studied. These steroids did not block the uptake or lysosomal hydrolysis of liposomes, nor esterification of fatty acyl chains into triacylglycerols. Moreover, dehydroisoandrosterone and pregnenolone, both of which possess a hydroxy group at the C3 position, had essentially no effect on 25-hydroxycholesterol-stimulated esterification of endogenous cellular cholesterol. On the other hand, androstenedione and progesterone, which possess an oxo group at the C3 position, had a mild inhibitory effect on the esterification of endogenous cholesterol. Upon incubation with a steroid having an oxo group at the C17 or C20 position, free cholesterol taken up by macrophages was accumulated in phagolysosomes, as judged from cytochemical study with filipin-cholesterol staining. These results indicate that a series of structurally-related steroids characterized by the presence of an oxo group at the C17 or C20 position inhibit cholesteryl ester formation in macrophages through blocking the intracellular transport of endocytosed cholesterol from lysosomes to endoplasmic reticulum.

Animals↗
PubMed1994

An in-frame deletion of codon 298 of the NADH-cytochrome b5 reductase gene results in hereditary methemoglobinemia type II (generalized type). A functional implication for the role of the COOH-terminal region of the enzyme.

The nucleotide sequence was determined for the gene of NADH-cytochrome b5 reductase of a patient of type II hereditary methemoglobinemia found in Yokohama, Japan. An in-frame deletion of 3 base pairs corresponding to codon 298 (TTC) was identified in the patient. The patient was homozygous for the mutation as shown by hybridization experiments using allele-specific oligonucleotides. The mutation causes deletion of Phe-298, which is the third to the COOH-terminal residue, indicating that in this mutant enzyme the sequence of this region has changed from -Cys-Phe-Val-Phe-COOH to -Cys-Val-Phe-COOH. The mutant enzyme, whose Phe-298 was deleted (F298 delta), was prepared by means of a bacterial expression system and site-directed mutagenesis. The kcat/Km value (NADH) of the enzyme was 5.7 s-1 M-1, which corresponds to 0.4% of that of the wild type. Moreover, the enzyme was much less thermostable than the wild type. To examine further the role of the COOH-terminal portion of the enzyme, various mutant enzymes were also prepared and characterized. The enzymatic properties of F298L, F300L, and F298L/F300L were essentially the same as that of the wild type. The kinetic properties of F298A, and F300A were not greatly affected, but the stability of the enzymes was somewhat impaired. Since Val-299 is naturally Ala in steer enzyme, no specific residues in the carboxyl-terminal region (298-300) are essential to the enzyme function. The instability of the F298/F300A double mutant indicates that the hydrophobicity of the carboxyl-terminal region of the enzyme might be important to maintain the conformation of the enzyme. high impairment of the activity of the F298 delta, F298stop, and F300stop mutants might be caused by the loss of the residue(s) in the carboxyl-terminal portion. These results indicate that the hydrophobicity, but not the specific amino acid residues, of the carboxyl-terminal portion of the enzyme is important for the stability of the enzyme.

Adolescent↗
PubMed1994

The capacity of the malate-aspartate shuttle differs between periportal and perivenous hepatocytes from rats.

The capacity of the malate-aspartate shuttle was evaluated in periportal (PP-H) and perivenous subfraction of rat hepatocytes (PV-H). The rate of glutamine production from alanine was 34-fold higher in PV-H than in PP-H. Statistically significant differences between PP-H and PV-H were found for the activities of lactate dehydrogenase and pyruvate kinase but not for the activities of NAD(+)-malate dehydrogenase, aspartate aminotransferase, and mitochondrial alanine aminotransferase. The rate of glucose production from sorbitol and the rate of ethanol utilization were higher in PP-H than in PV-H. In the presence of phenazine methosulfate (PMS), the increments in these rates were significantly greater in PV-H than in PP-H. The capacity of malate-aspartate shuttle in the presence of alanine was significantly higher in PP-H than in PV-H but in the presence of asparagine was similar in PP-H and PV-H. The results suggest that the capacity of malate-aspartate shuttle distributes heterogeneously along liver lobules with the dominance in periportal zone and that the difference of the capacity may result from the difference in the transport of aspartate across the mitochondrial membrane.

Alanine↗
PubMed1994

Alterations of tumor suppressor genes and allelic losses in human hepatocellular carcinomas in China.

Aflatoxin B1 has been suggested as a causative agent for a G to T mutation at codon 249 in the p53 gene in human hepatocellular carcinomas (HCC) from southern Africa and Qidong in China. The objective of the present work was to test the hypothesis that exposure to aflatoxin B1 either alone or coincident with other environmental carcinogens might be associated with allelic losses occurring during development of human hepatocarcinogenesis in China. The HCCs were obtained from two different areas in China: Qidong, where exposure to hepatitis B virus (HBV) and aflatoxin B1 is high; and Beijing, where exposure to HBV is high but that of aflatoxin B1 is low. We analyzed the tumors for mutations in the p53 gene and loss of heterozygosity for the p53, Rb, and APC genes and at marker loci on chromosomes 4, 13, and 16. Frequencies of mutation, loss, and aberration (mutation and loss) of the p53 gene in 25 HCCs from Qidong were 60, 58, and 80%, respectively. The frequencies in 9 HCCs from Beijing were 56, 57, and 78%. However, the frequency of a G to T transversion at codon 249 in HCCs from Qidong and Beijing were 52 and 0%, respectively. These data indicate that mutation and/or loss of heterozygosity in the p53 gene, independent of the 249 mutation, play a critical role in the development of hepatitis B virus-associated HCCs in China. Loss of the Rb and APC genes was observed in 44 and 7% of HCCs from Qidong, respectively. Allelic losses on chromosome 4 and especially on chromosome 16 were frequent in HCCs from Qidong but were not observed in HCCs from Beijing, while loss of heterozygosity on chromosome 13 occurred at similar frequency in both Qidong and Beijing. These results show a distinct difference in the pattern of allelic losses between HCCs in Qidong and Beijing and suggest that aflatoxin B1 and/or other environmental carcinogens may contribute to this difference.

Base Sequence↗
PubMed1994

Nonkallikrein arginine endopeptidase in the human submaxillary gland: purification and characterization of the enzyme.

The two major species of arginine endopeptidase present in the soluble fraction of human submaxillary gland are glandular kallikrein and another enzyme tentatively named nonkallikrein arginine endopeptidase. In this study, we purified the latter enzyme to homogeneity and examined its catalytic properties. The newly found enzyme was clearly distinguishable from human tissue kallikrein in its molecular nature, action toward various synthetic substrates, and kinin-generated activity. The specificity of the action of the enzyme was further investigated using various basic amino acid-containing peptides as model substrates. HPLC analysis of peptide fragments produced, followed by their amino acid analysis, revealed that the enzyme preferentially hydrolyzed the Arg-Arg or Arg-Lys bonds in dynorphins A 1-10, 1-9, and 1-8, beta-neoendorphin, adenorphin, and neurotensin.

Amino Acid Sequence↗
PubMed1994

Importance of cytotoxic T lymphocytes in the rejection of transplanted hepatocellular carcinoma.

Fischer rats became resistant to syngeneic hepatocellular carcinoma (FAA-HTC1) cells on repeated sensitization with mitomycin C-treated FAA-HTC1 cells. In contrast, FAA-HTC1 cells injected into the liver killed normal control Fischer rats within 2 months. Histopathological studies revealed massive accumulation of mononuclear cells in the tumor tissues of sensitized rats that rejected syngeneic FAA-HTC1 cells, whereas very few mononuclear cells were found in the tumor tissues of control rats. Cell populations infiltrating the tumor tissues were identified by flow cytometric analysis. Mononuclear cells found within the regressing tumors of the sensitized rats were identified as mostly T cells, and two-thirds of these T cells were CD8-positive. Compared with the activity in control rats, the killer activity of mononuclear cells infiltrating tumors was significantly increased in the sensitized rats 7 days after tumor inoculation. Depletion of CD8(+) T cells significantly reduced the cytotoxicity of mononuclear cells infiltrating tumors obtained from sensitized rats. In contrast, depletion of CD16(+) cells reduced the cytotoxicity of mononuclear cells infiltrating tumors obtained from both control and sensitized rats. Furthermore, the CD16(+) cell-depleted fraction of mononuclear cells infiltrating tumors showed significant cytotoxicity against FAA-HTC1 cells, but failed to show cytotoxicity against other syngeneic tumor cells or allogeneic hepatoma cells.

Animals↗
PubMed1994

Effect of 13-hydroperoxy-9,11-octadecadienoic acid (13-HPODE) on arachidonic acid metabolism in rabbit platelets.

1. The effect of 13-hydroperoxy-9,11-octadecadienoic acid (13-HPODE) on the formation of thromboxane (TX) B2, 12-hydroxy-5,8,10-heptadecatrienoic acid (HHT) and 12-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE) from exogenous arachidonic acid in washed rabbit platelets was examined. 2. 13-HPODE inhibited TXB2 and HHT formation without affecting 12-HETE production. 3. 13-Hydroxy-9,11-octadecadienoic acid which was produced rapidly from 13-HPODE, did not suppress the formation of TXB2 and HHT, indicating the requirement of the hydroperoxy moiety for the inhibitory effect of 13-HPODE on TXB2 and HHT formation. 4. Experiments utilizing mannitol and dimethyl sulfoxide (hydroxy radical scavengers) revealed that the action of 13-HPODE is not due to hydroxy radicals which are expected to be formed from 13-HPODE. 5. These results suggest that 13-HPODE is a selective inhibitor of platelet cyclo-oxygenase and may have functional effects within platelets.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1994

Sex pheromones in marine polychaetes: steroids from ripe Nereis succinea.

A number of neutral marine steroids such as desmosterol, campesterol, brassicasterol, gorgosterol, and other trace steroids were isolated from the coelomic fluid of ripe Nereis succinea and checked for biological activity as sex pheromones on swarming specimens of Platynereis dumerilii and Nereis succinea. No significant influence of synthetic gorgosterol or a natural extract of gorgosterol or the other identified steroids on the swarming behavior was observed.

Animals↗
PubMed1994

Inhibition of 15-hydroxy prostaglandin dehydrogenase activity in rabbit gastric antral mucosa by 13-hydroperoxyoctadecadienoic acid.

The effect of 13-hydroperoxyoctadecadienoic acid (13-HPODE), a hydroperoxy adduct of linoleic acid (LA), on the activities of prostaglandin (PG) synthesizing and catabolizing enzymes in rabbit gastric antral mucosa was examined. 13-HPODE had no effect on the synthesis of PGE2, PGF2 alpha and PGD2 from exogenous arachidonic acid in the microsomal fraction of the gastric mucosa at concentrations ranging from 5-20 microM. On the other hand, at 1-10 microM, it inhibited the activity of 15-hydroxy PG dehydrogenase (PGDH), which catalyzes the initial step of catabolism of PGs, in a dose-dependent manner. The concentration required for 50% inhibition was approximately 1 microM. Experiments utilizing LA, 13-hydroperoxyoctadecadienoic acid and Fe2+ indicated the requirement of the hydroperoxy moiety for the inhibitory effect of 13-HPODE on the PGDH activity. These results suggest that 13-HPODE has the potential to increase the levels of biologically active PGs in gastric mucosa by preventing their inactivation and may have functional effects within the stomach.

Animals↗
PubMed1994

Intraoperative adjustable suture surgery for bilateral superior oblique palsy.

BACKGROUND: The modified Harada-Ito procedure has been reported to be an effective treatment for correction of cyclotorsion in bilateral superior oblique palsy. However, there are no reports regarding its use in intraoperative adjustable suture surgery. METHODS: The authors performed a retrospective study of 12 patients with traumatic bilateral superior oblique palsy who were classified as having either symmetric or asymmetric palsy according to the symmetry of the alternate hyperdeviation on side gazes. Cyclotorsion and vertical and horizontal deviation in the nine diagnostic positions were measured preoperatively and postoperatively. RESULTS: Of the 12 patients, 6 were determined to have symmetric palsy and 6 asymmetric palsy. Intraoperative adjustable suture surgery with the modified Harada-Ito procedure was performed bilaterally in the six patients with symmetric palsy and unilaterally in those with asymmetric palsy. The median measured value of extorsion in the primary position was reduced from 14.5 degrees to 2.5 degrees in patients with symmetric palsy and from 9.5 degrees to 2.0 degrees in those with asymmetric palsy. In downgaze, some degree of residual extorsion remained, and there was no significant change in esodeviation after surgery. In five patients with symmetric palsy and in all of those with asymmetric palsy, normal single binocular vision in the primary position but did not that in downgaze was restored after surgery. CONCLUSION: Intraoperative adjustable suture surgery is an effective treatment in correcting torsion, but may not be as effective for esodeviation in downgaze.

Adult↗
PubMed1994

Dietary NaCl restriction deteriorates oral glucose tolerance in hypertensive patients with impairment of glucose tolerance.

This study investigated whether the change of glycemic response to oral glucose loading with an increase of dietary NaCl intake is different between salt-sensitive and salt-resistant groups, or whether it is related to glucose tolerance on a low NaCl diet independent of salt sensitivity. The plasma glucose and insulin response to 75 g oral glucose intake was assessed on low (34 mmol/day) and high (342 mmol/day) NaCl diets in 31 patients with essential hypertension, and the area under the curve for both variables (AUCglu and AUCins) was calculated. The data on the high NaCl diet were corrected for change in hematocrit. The percentage change in systolic, diastolic, and mean blood pressure between the two diets was defined as the salt sensitivity index (SSI) for systolic blood pressure (SSISBP), diastolic blood pressure (SSIDBP), and mean blood pressure (SSIMBP), respectively. The mean values of both AUCglu and AUCins decreased significantly with increase of NaCl intake; however, there was no significant correlation between SSI (SSISBP, SSIDBP, or SSIMBP) and the percentage changes in AUCglu and AUCins. Meanwhile, the percentage changes in AUCglu and AUCins significantly correlated with the respective values of AUCglu and AUCins on the low NaCl diet. These results suggest that extreme NaCl restriction may deteriorate glucose metabolism in hypertensive patients, especially in those with diabetes mellitus or impaired glucose tolerance.

Adult↗
PubMed1994

p53 gene mutation in hepatocellular carcinoma induced by 2-amino-3-methylimidazo[4,5-f]quinoline in nonhuman primates.

2-Amino-3-methylimidazo[4,5-f]quinoline (IQ) is one of several heterocyclic amines formed during the cooking of proteinaceous foods. IQ is a potent carcinogen in rodent bioassays and causes a high incidence of hepatocellular carcinomas in nonhuman primates. We examined 20 hepatocellular carcinomas (HCCs) from nonhuman primates for mutations of the p53 gene using polymerase chain reaction-single strand conformational polymorphism analysis. Mutations in the p53 gene were detected in 4 of 20 HCCs (20%) with 3 showing G-to-T transversions and one a G-to-A transition. Three of these mutations were observed in codons 175 and 248 that are known mutational hot spots in human cancers. These data indicate that part of the IQ-induced HCCs in nonhuman primates may involve inactivation of the p53 gene and suggest that IQ and possibly other heterocyclic amines may participate in human carcinogenesis by a similar mechanism.

Animals↗
PubMed1994

Induction of the conversion of xanthine dehydrogenase to oxidase in rabbit liver by Cu2+,Zn2+ and selenium ions.

Effects of Cu2+,Zn2+,Fe2+ and selenium ions on the conversion of xanthine dehydrogenase to oxidase in rabbit liver were examined. Under basal conditions, xanthine oxidase activity represented only 16% of the total xanthine oxidase plus dehydrogenase activity. Cu2+ (2-10 microM), Zn2+ (5-30 microM) and selenium ions (5-100 microM) brought about the conversion of xanthine dehydrogenase to oxidase in a dose-dependent manner. The concentrations of Cu2+,Zn2+ and selenium ions required for increasing xanthine oxidase activity by 50% was approximately 4, 10 and 20 microM, respectively. On the other hand, Fe2+ had no effect on the conversion of the enzyme up to 100 microM. These results suggest that Cu2+,Zn2+ and selenium ions have the potential to modulate the conversion of xanthine dehydrogenase to oxidase in rabbit liver.

Allopurinol↗
PubMed1994

Antiestrogenic effects of danazol on rabbit uterus.

To examine antiestrogenic effects of danazol through the receptor system and to clarify its direct effects on the endometrium in vivo, we applied danazol jelly directly into the rabbit uterine cavity and measured uterine estrogen, progesterone and androgen receptors (ER, PR and AR, respectively). Danazol significantly reduced ER, PR and AR (p < 0.05). Treatment with receptor-blocking agents (RU 486 and oxendolone) showed that the decrease in the ER level showed a closer association with that in PR than with AR. These results indicate that danazol directly administered into the uterine cavity is absorbed by the endometrial tissue and exerts its antiestrogenic effects possibly through PR in the cells.

Animals↗
PubMed1994

Non-stereoselective formation of 3 alpha,7 alpha,12 alpha,24-tetrahydroxy-5 beta-cholestan-26-oic acid during cholic acid biosynthesis.

Incubation of (25RS)-, (25R)- and (25S)-3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholestan-26-oic acid (THCA, 6, 6a, 6b) and (24E)-3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholest-24-en-26-oic acid (7) with rat liver mitochondria gave all four stereoisomers (9a,9b,9c,9d) of 3 alpha,7 alpha,12 alpha,24-Tetrahydroxy-5 beta-cholestan-26-oic acid (TeHCA). The corresponding 27-nor analogs (10,11) were also converted non-stereoselectively to a 1:1 mixture of the epimeric 24-hydroxy compounds (12).

Animals↗
PubMed1994

Characteristics of ventricular premature contractions and their clinical course.

One hundred patients with frequent (> 1,000 beats/day) ventricular premature contractions (VPCs) were followed for 4 years. All of the patients, except those with non-cardiac death (n = 8), were classified into 3 groups based on their outcome. Group A consisted of 29 patients with idiopathic VPCs who survived the study period. Group B consisted of 49 patients with underlying diseases who survived the study period. Group C consisted of 14 patients who suffered cardiac death. There was no significant difference in the daily number of VPCs. However, groups B and C had more patients with Lown grade 4a or 4b VPCs than group A. The mean coupling interval was significantly longer in group C than in group A, and the standard deviation of the coupling interval was significantly larger in group C than in group A. Forty patients underwent serial Holter monitorings to assess changes in the number of VPCs. VPCs spontaneously decreased in 13 patients, while the other 27 patients continued to have frequent VPCs. Most of these 13 patients were classified as Lown grade 2. The results suggest that in patients with frequent VPCs, longer and more varied coupling intervals may predict a poor prognosis, and Lown grade 2 may predict a spontaneous regression.

Adult↗
PubMed1994

Total syntheses of (2S)-antafumicins A and B.

To clarify the absolute configurations of antafumicins A and B, which are antifungal substances from Aspergillus niger NH-401, the total synthesis of (2S)-antafumicins was accomplished by starting from (S)-malic acid in 12 steps. Based upon the physicochemical data of the synthetic samples, the absolute configurations of naturally occurring antafumicins A and B were determined as (2R,4S)- and (2R,4R)-4-(3-acetyl-2,6-dihydroxyphenyl)-2-methoxy-4-butanolide, respectively.

4-Butyrolactone↗