Biomedical subjects

Y Fujii

Publications and source records attributed to Y Fujii.

At least 901 records · Page 50Linked to original sources

PubMed1989

Dissociation of various biological activities of Clostridium perfringens alpha toxin by chemical modification.

The effect of N-acetylimidazole, tetranitromethane, maleic anhydride and N-ethylmaleimide on various biological activities of Clostridium perfringens alpha (alpha)-toxin was investigated. Treatment of the toxin with N-acetylimidazole, tetranitromethane or maleic anhydride resulted in significant reduction of lethal, hemolytic and platelet-aggregating activities and phospholipase C activity (EY activity), as measured by increased turbidity in egg yolk emulsions. However, EY activity was more resistant to these reagents than lethal, hemolytic or aggregating activities. Phospholipase C activity (PN activity) as measured by hydrolysis of p-nitrophenylphosphorylcholine was retained after treatment with N-acetylimidazole, tetranitromethane or maleic anhydride. The activities of the toxin were not inactivated by treatment with N-ethylmaleimide. These data suggest that alpha-toxin contains multiple sites for biological activities of the toxin.

Animals↗

PubMed1989

The protease and gag gene products of the human immunodeficiency virus: authentic cleavage and post-translational modification in an insect cell expression system.

Three recombinant baculoviruses which are capable of expressing human immunodeficiency virus (HIV) protease, p55gag, and both products simultaneously in insect cell culture have been constructed. Upon co-infection of cells with the protease and p55gag-expressing viruses, authentic processing of the gag precursor is observed to take place. This processing could be reproduced in vitro using mixtures of cellular lysates containing the expressed proteins. When expressed alone, uncleaved p55gag precursor appears to form retroviral core-like particles within the cytoplasm of infected cells. Metabolic labeling studies of the baculovirus-expressed gag products have demonstrated that p17 is myristylated at its amino terminus, and that p24 is phosphorylated. In these respects, the insect cell system is evidently capable of carrying out post-translational processing resembling that which occurs in authentic HIV-1 replication.

Acylation↗

PubMed1989

Effects of human PTH-related peptide and human PTH on cyclic AMP production and cytosolic free calcium in an osteoblastic cell clone.

Recently, human parathyroid hormone-related peptide (hPTHrP) has been purified and its amino acid sequence determined. Within the amino-terminal 13 residues of hPTHrP, 8 amino acids were found homologous between hPTHrP and human PTH (hPTH). This peptide was reported to stimulate cyclic AMP (cAMP) production in osteoblastic cell lines (UMR106 and ROS17/2.8). However, whether or not this peptide affects another second messenger, i.e., cytosolic free calcium ([Ca2+]i), in osteoblasts has not yet been determined. Therefore, in the present study, we examined the effects of synthetic amino-terminal fragments of hPTHrP (Tyr40hPTHrP1-40 and hPTHrP1-34) on intracellular cAMP production and [Ca2+]i in an osteoblastic cell line (MC3T3-E1) and compared them with those of hPTH1-34. Human PTHrP1-34, Tyr40hPTHrP1-40 and hPTH1-34 stimulated cAMP production in an equipotent manner at concentrations ranging from 2.5 x 10(-10) to 1.3 x 10(-6) M. Human PTH1-34 at concentrations from 2.5 x 10(-7) to 1.3 x 10(-6) M significantly (P less than 0.05) increased [Ca2+]i, but hPTHrP1-34 and Tyr40hPTHrP1-40 at the same concentrations did not. These results suggest a different receptor-mediated mechanism for [Ca2+]i increase between hPTHrP and hPTH, although these two peptides appear to share the same receptor site(s) which is coupled to the cAMP system in MC3T3-E1.

Animals↗

PubMed1989

Quantitative computed tomography of lumbar vertebrae in Japanese patients with osteoporosis.

Vertebral trabecular bone mineral density of both healthy Japanese subjects and Japanese patients with osteoporosis was measured by quantitative computed tomography (QCT) technique. The age-related reduction rate in vertebral trabecular bone mineral density of control females averaged 1.1% per year, from age 20 to 80, with an accelerated loss demonstrated after age 40. In the male controls, trabecular bone mineral density declined by an average of 0.9% per year. These values were found to be similar to the University of California at San Francisco (UCSF) QCT data (US Caucasians: 1.2% for female, 0.72% for male). Therefore, it appears that age-related rates of trabecular bone loss in the lumbar vertebrae may be similar for both Japanese and Caucasians. However, when compared to average values in UCSF QCT data of comparable age and sex, the mean values in Japanese appear to be approximately 10-20 mg/cm3 lower than Caucasian counterparts. All female patients with osteoporosis as evidenced by atraumatic vertebral fracture had QCT values below 50 mg/cm3. It is suggested that the Japanese may have lower trabecular bone mineral density than Caucasians but may also have a lower threshold for fracture of the vertebrae. Further studies are needed to establish the possible racial differences in vertebral trabecular bone mineral density, and to determine whether these possible disparities are related to genetic differences, or to differences in body size, dietary intake, physical activity or other lifestyle/environmental factors.

Adult↗

PubMed1989

The effects of human parathyroid hormone-related peptide on cytosolic free calcium and cAMP production in opossum kidney cell.

The effects of three synthetic amino-terminal fragments of human parathyroid hormone-related peptide (hPTHrP) on cytosolic free calcium ([Ca2+]i) mobilization and intracellular cAMP production were investigated and compared with those of human PTH(1-34) in opossum kidney (OK) cells. The mean basal [Ca2+]i in OK cells was 115 +/- 7.8 nM (mean +/- SE, n = 30). Human PTHrP(1-34), [40Tyr]hPTHrP(1-40) and hPTH(1-34) significantly (P less than 0.01) raised [Ca2+]i to 149 +/- 3, 150 +/- 5 and 148 +/- 6% of the basal value, respectively (mean +/- SE, n = 3). These three peptides showed similar dose dependency at concentrations between 10(-10) and 10(-7) M. These increases appeared to be, in part, due to mobilization from intracellular calcium stores. On the other hand, these three peptides also stimulated intracellular cAMP production in an equipotent manner in OK cells. However, both 10(-3) M dibutyryl cAMP and 10(-5) M forskolin failed to cause an increase in [Ca2+]i. Furthermore, [40Tyr]hPTHrP(3-40) neither affected the intracellular cAMP content significantly nor caused an increase in [Ca2+]i. These results indicate that hPTHrP mimics PTH by activating a dual second messenger system ([Ca2+]i and cAMP) in OK cells, and that [Ca2+]i stimulation by hPTHrP and hPTH is independent of cAMP production. Additionally, N-terminal amino acid position 1 to 2 of hPTHrP appears to play a crucial role in both [Ca2+]i stimulation and cAMP production.

1-Methyl-3-isobutylxanthine↗

PubMed1989

Diagnosis of peripapillary carcinoma: endoscopic findings.

During the period 1982-1988, 8 patients were admitted with peripapillary carcinoma. Pancreatico-duodenectomy (PD) was successfully carried out on 7 occasions but only 3 patients are alive today. Early diagnosis of this disease is therefore mandatory. Endoscopic sphincterotomy is particularly useful for the diagnosis of the non-exposed type of carcinoma in the peripapillary region.

Aged↗

PubMed1989

Effect of dopamine on parathyroid hormone release during surgery.

There is much evidence that dopamine (DA) may play an important role in modulating parathyroid gland function. DA stimulates parathyroid hormone (PTH) secretion in cattle, which increases ionized calcium, but is without such effect on humans under normal physiological conditions. Ionized calcium plays a major role in muscle contraction including myocardial contractility. Therefore, we studied the PTH response to infusion of DA (4 micrograms/kg/min) under pathophysiological states during two different types of surgery; gastrectomy with halothane anesthetics and open heart surgery with high-dose fentanyl anesthetics. There was no change in PTH concentration, as measured by radioimmunoassay, in patients undergoing gastrectomy, although infusion of DA in these patients was effective in lowering the prolactin levels. However, plasma PTH concentration significantly increased where DA was applied (4 micrograms/kg/min) in patients undergoing open heart surgery. These results suggest that DA may stimulate PTH secretion by an indirect mechanism in humans under pathophysiological states, although details of the mechanism are unknown, and that there is the possibility that DA would indirectly regulate the levels of electrolytes such as ionized calcium and phosphate in patients undergoing open heart surgery mediated by elevation of PTH.

Calcium↗

PubMed1989

Purification and characterization of chitinase produced by Streptomyces erythraeus.

A chitinase was purified from the culture filtrate of Streptomyces erythraeus (SE). The enzyme (SE chitinase) has a molecular weight of 30,000 and pI 3.7, and shows optimal activity at pH 5.0 with an optimal ionic strength of less than 0.2 M NaCl. SE chitinase could hydrolyze chitin and its derivatives, but could not hydrolyze cell walls of Micrococcus lysodeikticus. The substrate specificity of SE chitinase was compared with those of hen egg white (HEW) and SE lysozymes. The binding mode of the chitinase to substrates was investigated using chitooligosaccharides and their derivatives. The results showed that the binding mode of SE chitinase to the substrate is similar to that of HEW and SE lysozymes.

Amino Acids↗

PubMed1989

Translocation t(12;16)(q13;p11) in myxoid liposarcoma of a child and implication of the human int-1 gene in tumorigenesis.

Cytogenetic and gene analyses were performed in a child with myxoid liposarcoma (MLS). A reciprocal chromosome translocation t(12;16)(q13;p11) was found in the tumor cells. This result, combined with the previous reports of a similar translocation in adult MLS strongly suggests that this translocation may be a characteristic cytogenetic marker in MLS. The human int-1 gene has been reported to be located close to the 12q13 breakpoint associated with MLS. Therefore, we examined the rearrangement of the human int-1 gene by Southern blotting analysis. When genomic DNAs from the tumor cells were digested with KpnI, EcoRI and BamHI, no difference was seen compared to peripheral blood leukocytes (PBL) DNAs from a normal individual. However, with HindIII digestion there appeared a 3.1 kb fragment in tumor cell DNA as compared to a 2.8 kb fragment in DNAs prepared from normal PBL and the patient's PBL. These findings suggest that the int-1 gene may be implicated in tumorigenesis of MLS with t(12;16)(q13;p11).

Adolescent↗

PubMed1989

Contraction of the rat isolated aorta caused by Clostridium perfringens alpha toxin (phospholipase C): evidence for the involvement of arachidonic acid metabolism.

1. Alpha toxin produced by Clostridium perfringens contracted the rat isolated aorta and stimulated release of arachidonic acid in the tissue. 2. Quinacrine did not inhibit contraction caused by the toxin. 3. Indomethacin blocked contraction caused by the toxin in a dose-dependent manner and markedly increased levels of arachidonic acid released by the toxin. 4. The toxin-induced contraction was blocked by the thromboxane synthetase inhibitor OKY-046 and the thromboxane A2 (TXA2) antagonist ONO-3708. 5. The toxin stimulated production of TXB2 and this was blocked by pretreatment with either indomethacin or OKY-046. 6. Toxin-induced contraction was diminished by pretreating aorta with collagenase or by rubbing the intimal surface to remove the endothelium. 7. These data suggest that the contractile response to the toxin is associated with stimulation of TXA2 production from arachidonic acid released by the toxin in the endothelial cells of the aorta.

Animals↗

PubMed1989

Chromosomal beta-lactamase of Klebsiella oxytoca, a new class A enzyme that hydrolyzes broad-spectrum beta-lactam antibiotics.

The chromosomally encoded beta-lactamase gene of Klebsiella oxytoca E23004, a strain resistant to cefoperazone and aztreonam, was cloned and expressed in Escherichia coli HB101. The molecular mass and pI of this enzyme were 28 kilodaltons and 7.4, respectively. Although the beta-lactamase of K. oxytoca hydrolyzed many cephalosporins, including broad-spectrum drugs, the nucleotide sequence and deduced amino acid sequence lacked homology with chromosomal class C beta-lactamase genes (ampC) of E. coli or Citrobacter freundii. Rather, about 45% nucleotide sequence homology and 40% deduced amino acid sequence homology were observed between the K. oxytoca beta-lactamase and TEM-1, a class A beta-lactamase which does not efficiently hydrolyze cephalosporins. Values of Km, relative Vmax, and relative Vmax/Km for the K. oxytoca beta-lactamase indicated that the enzyme is a penicillinase but that it can hydrolyze cefoperazone effectively and other broad-spectrum cephems weakly. Hence, the chromosomal beta-lactamase of K. oxytoca E23004 belongs to class A but differences in its amino acid sequence provide a broader spectrum of activity.

Ampicillin↗

PubMed1989

Renal potassium adaptation: role of the Na+-K+ pump in rat cortical collecting tubules.

To evaluate the mechanism of renal potassium adaptation we explored several facets of Na+-K+-ATPase function during K loading in rat cortical collecting tubule (CCT). Urinary K excretion increased within the 1st day after initiation of dietary loading to a level matching intake, indicating the early onset of K adaptation. CCT Na+-K+-ATPase activity after 1 and 2 days on the high-K diet was not different from that observed in control animals, whereas it increased to threefold base line after 7 days. Similarly, the specific binding of ouabain was unchanged by 2 days of high-K diet, but was increased on the 7th day. In contrast, there was an early increase in Rb uptake that persisted throughout the period of observation. Acute (60 min) KCl infusion into control rats led to a significant increase in Rb uptake, whereas Na+-K+-ATPase hydrolytic activity remained unchanged. In the isolated perfused kidney, increasing perfusate K led to an increase in CCT Rb uptake similar to that observed in vivo, again without altering the hydrolytic activity of the enzyme. We conclude that K adaptation is an early event developing rapidly after initiation of dietary change. In its early phase the Na+-K+ pump responds by increasing K-transport rate to accommodate the acute homeostatic need; when the requirement for increased K secretion is sustained, a different adaptive pattern emerges characterized by an increase in the number of pumps. The adaptive response to an acute K load appears to be an intrinsic property of the pump independent of hormonal influences.

Acclimatization↗

PubMed1989

Direct Na+-K+ pump stimulation by K+ in cortical collecting tubules: a mechanism for early renal K+ adaptation.

To evaluate the mechanism of increased Na+-K+ pump turnover rate that characterizes the early cortical collecting tubule (CCT) response to K+ loading [Y. Fujii, S. K. Mujais, and A. I. Katz. Am. J. Physiol. 256 (Renal Fluid Electrolyte Physiol. 25): F279-F284, 1989.], we measured ouabain-sensitive 86Rb+ uptake in microdissected rat CCT exposed acutely to elevated ambient K+ in vivo and in vitro. Tubules preincubated in 10 mM K+ had higher 86Rb+ uptake than when preincubated in 5 mM K+ (25.9 +/- 1.2 vs. 18.9 +/- 0.7 pmol.mm-1.min-1, P less than 0.001). KCl infusion (5 mumol.100 g-1.min-1 x 60 min) increased 86Rb+ uptake from 19.2 +/- 1.0 to 31.2 +/- 1.4 pmol.mm-1.min-1, P less than 0.001; the increment was preserved in tubules subsequently treated with monensin or nystatin in vitro, suggesting that pump stimulation was not mediated by increased cell Na+. This conclusion was confirmed in separate experiments in which the effect of K+ on 86Rb+ uptake was not altered by concurrent preincubation with amiloride. Studies with CCT from isolated perfused kidneys and from adrenalectomized animals revealed that stimulation of 86Rb+ uptake by a K+ load occurs rapidly (less than or equal to 5 min) and is independent of hormonal factors. Increased external K+ produces a rapid rise in K+-transporting capacity (turnover rate) of the Na+-K+ pump in CCT. This phenomenon probably represents a direct effect on K+ on the pump and is an important component of the early renal response to increased K+ secretory load.

Animals↗

PubMed1989

Radioimmunoassay for erythrocyte acidic GSH S-transferase.

We have developed a RIA for erythrocyte acid glutathione S-transferase (GST), which is immunologically identical to major GSTs from other blood cell components, and measured its serum concentrations in various hematological disorders. In some patients with paroxysmal nocturnal hemoglobinuria, chronic myelomonocytic leukemia, chronic myelocytic leukemia, polycythemia vera and myelofibrosis, the concentrations were high. Very high levels were found in 2 of 3 patients with acute lymphocytic leukemia, while acute myelocytic leukemia exhibited a modest increment. No or little increase was seen in aplastic anemia and myelodysplastic syndrome except chronic myelomonocytic leukemia. It is suggested that the measurement of serum acidic GST may be of use as a clinical marker of increased destruction and/or overproduction of blood cells.

Erythrocytes↗

PubMed1989

Effects of dopamine on immunoreactive growth hormone-releasing factor and somatostatin secretion from rat hypothalamic slices perifused in vitro.

The effects of dopamine (DA) on the release of GRF and somatostatin (SRIF) from the hypothalami of adult male rats were examined in an in vitro perifusion system using horizontal hypothalamic slices, 400 micron thick, including the median eminence and arcuate nuclei. When hypothalamic slices from five animals were perfused in a chamber with artificial cerebrospinal fluid (ACSF) at a flow rate of 100 microliters/min under a gaseous phase of 95% O2 and 5% CO2 at 37 C, rat (r) GRF- and SRIF-like immunoreactivities (-LI) were constantly detected in 30-min perifusates at least until 240 min of perifusion, and during the perifusion with 60 mM K+, the concentrations of rGRF-LI and SRIF-LI were increased 2.1 and 3.2 times, respectively, over basal values. Under the perifusion with ACSF containing normal goat gamma-globulin, the addition of 10(-8) M DA resulted in a significant increase in SRIF-LI from 8.2 +/- 0.3 to 14.3 +/- 1.5 pg/hypothalamus.30 min, but conversely, it caused a slight but significant decrease in rGRF-LI from 4.5 +/- 0.9 to 2.0 +/- 0.3 pg/hypothalamus.30 min. On the other hand, 10(-8) and 10(-6) M DA significantly stimulated rGRF-LI release from hypothalamic slices perifused with ACSF containing anti-SRIF goat gamma-globulin. These findings suggest that DA is a secretagogue for both SRIF and rGRF in the hypothalamus, but the rGRF-stimulating effect of DA is masked unless the action of endogenous SRIF is attenuated.

Animals↗

PubMed1989

Parathyroid hormone-related protein and interleukin-1 alpha synergistically stimulate bone resorption in vitro and increase the serum calcium concentration in mice in vivo.

To elucidate the mechanism of humoral hypercalcemia elicited by human esophageal carcinoma cells (EC-GI), which constitutively produced interleukin-1 alpha (IL-1 alpha) and PTH-like factor, the effects of IL-1 alpha and PTH-related protein (PTH-rP) on bone resorption in vitro and on serum calcium concentrations in vivo were investigated. Nude mice transplanted with EC-GI cells invariably developed hypercalcemia, although their urinary cAMP excretion remained within the normal range. IL-1 alpha or PTH-rP-(1-34) stimulated 45Ca release from prelabeled fetal mouse forearm bones in a concentration-dependent manner, and when combined, IL-1 alpha and PTH-rP-(1-34) synergistically stimulated bone resorption in vitro. Injection of PTH-rP-(1-34) into mice three times a day for 2 days increased the serum calcium concentration in a dose-dependent manner. Continuous infusion of IL-1 alpha occasionally increased the serum calcium concentration. Simultaneous administration of IL-1 alpha at rates of 1-2.7 micrograms/day and PTH-rP-(1-34) at doses of 15-30 micrograms/day synergistically increased the serum calcium concentration in vivo. These findings suggest that PTH-rP and IL-1 alpha produced by the tumor cells were synergistically responsible for the humoral hypercalcemia observed in both the original patient and the tumor-bearing nude mice, and that at least two bone-resorbing factors [PTH-rP and another nonadenylate cyclase-stimulating bone-resorbing factor(s)] are active in patients with malignancy-associated hypercalcemia, in whom nephrogenous cAMP excretion is neither increased nor decreased.

Animals↗

PubMed1989

Synthesis of entadamide A and entadamide B isolated from Entada phaseoloides and their inhibitory effects on 5-lipoxygenase.

Two new sulfur-containing amides, entadamide A (1) and entadamide B (2), isolated from the seeds of Entada phaseoloides, were synthesized by the addition reaction of methanethiol to propiolic acid (5) followed by condensation with ethanolamine by the use of dicyclohexylcarbadiimide. These compounds inhibited the 5-lipoxygenase activity of RBL-1 cells at 10(-4) g/ml. This finding suggests that entadamides A and B may be examples of a new type of antiinflammatory drug.

Acrylamides↗

PubMed1989

Effect of taurine administration on serum lipid and biliary lipid composition in man.

The effect of oral administration of taurine (3.2 g/day, 2 weeks) on the metabolism of lipids and bile acids was studied with healthy humans. Four male subjects were fed taurine. Another five male subjects were administered 1 g of cholesterol daily for two weeks and, at intervals of two weeks, cholesterol and taurine simultaneously. Serum lipoprotein and duodenal bile were analyzed. Oral administration of taurine resulted in the increase of taurine-conjugated bile acids. However, neither serum lipid nor biliary lipid composition was altered. Addition of taurine with cholesterol administration showed elevation of both the serum low density lipoprotein cholesterol level and the lithogenic index in bile. The ratio of glycine-to taurine-conjugated bile acids was changed from 4.1 to 0.63. The ratio of cholic acid/chenodeoxycholic acid was augmented from 0.57 to 0.81. The percentage of taurocholic acid, taurochenodexycholic acid and taurodeoxycholic acid were increased about 4-fold, 2.5-fold and 3-fold, respectively. Our results suggested that taurine administration alone did not influence the serum lipid level although taurine-conjugated bile acids were increased. The taurine intake would increase serum low density lipoprotein cholesterol and biliary cholesterol levels when excessive cholesterol is administered simultaneously.

Administration, Oral↗