Biomedical subjects

K Mizuno

Publications and source records attributed to K Mizuno.

At least 19 recordsLinked to original sources

PubMed1992

Proteolytic activation of a single-chain precursor of hepatocyte growth factor by extracellular serine-protease.

Hepatocyte growth factor (HGF) is biosynthesized as a single-chain precursor (pro-HGF) and is proteolytically processed to a two-chain mature form. When MRC-5 fibroblasts were pulse-radiolabeled under serum-free conditions, pro-HGF was the predominant molecular form of HGF in the culture medium. CHO cells transfected with an expression plasmid containing a full-size human HGF cDNA produced pro-HGF when these cells were cultured in serum-free medium. These findings suggest that HGF is secreted as a pro-form, which is then converted to a two-chain form by extracellular protease. Single-chain HGF exhibited mitogenic activity on cultured hepatocytes, with a potency similar to that of mature HGF, but this activity was remarkably inhibited by leupeptin. We postulate that inactive pro-HGF is converted to an active two-chain form by a leupeptin-sensitive serine-protease expressed by hepatocytes. Neither plasminogen activators nor plasmin showed any processing activity of pro-HGF in vitro.

Animals↗

PubMed1992

[A case of insulinoma with frequent hypoglycemic attacks not showing evident hyperinsulinemia].

Confirmation of inappropriate hyperinsulinemia is an indispensable requisite for the diagnosis of insulinoma. We report here a case of insulinoma without evident hyperinsulinemia at an early stage. The patient, a 49-year-old woman, had been admitted to our hospital for the evaluation of frequent hypoglycemic attacks. At that time, plasma immunoreactive insulin (IRI) after an overnight fast ranged from 7 to 16 microU/ml. The ratio of IRI/fasting blood sugar (FBS) (Fajans index; normal range, below 0.3) was always between 0.13 and 0.28 even at hypoglycemic states. In addition, because computed tomography and arteriography of the abdomen failed to settle the diagnosis of insulinoma, the patient was discharged and followed up at our outpatient clinic for 2 years. She was admitted to our hospital at 51 years of age for the re-evaluation of hypoglycemic attacks. Laboratory examinations revealed high fasting plasma levels of IRI ranging from 20 to 29 microU/ml. Fajans index also increased to 0.47-0.89. Celiac arteriography was able to confirm the existence of insulinoma. We suggest that insulinoma should be considered in the presence of unexplained hypoglycemic attacks even when there is no evident hyperinsulinemia.

Blood Glucose↗

PubMed1992

A silencer-like cis element for the testis-specific phosphoglycerate-kinase-2-encoding gene.

Phosphoglycerate kinase (PGK), a glycolytic enzyme, possesses two isozymes: somatic-type PGK-1 and testis-specific PGK-2, encoded by distinct genes. Tissue-specific expression of the two PGK-encoding genes (Pgk) seems to be transcriptionally controlled, since tissue distribution of the mRNAs coincides well with that of the proteins. In the present study, we determined the cis-acting DNA elements that regulate the transcription of mouse Pgk-2. A transient expression assay of DNAs having various portions of the Pgk-2 upstream region linked to the chloramphenicol acetyltransferase (CAT)-encoding gene (cat) was performed using mouse cell lines that exclusively express Pgk-1. A substantial increase in cat expression was observed when the region between nucleotides (nt) -1404 and -685, relative to the most distal transcription start point at nt +1, was lost. This cis-acting region appeared to function as a silencer, since it repressed cat expression independently of either orientation to or distance from the Pgk-2 promoter. Moreover, the cis element inhibited Pgk-2 transcription with no effect on Pgk-1 transcription in a cell-free system using nuclear extracts of rat liver. These results suggest that a silencer-like negative cis element is responsible, at least partly, for tissue-specific transcription of Pgk-2.

Animals↗

PubMed1992

Estrogen modulates Ca(2+)-independent lipid-stimulated kinase in the rabbit corpus luteum of pseudopregnancy. Identification of luteal estrogen-modulated lipid-stimulated kinase as protein kinase C delta.

Rabbit corpora lutea were tested for the presence of phosphorylative responses sensitive to estrogen. Luteal Ca(2+)-independent lipid-stimulated kinase activity was detected by phosphorylation of the endogenous substrate, p76. Estrogen treatment, by way of estradiol-17 beta implant, increased levels of the lipid-stimulated phosphoprotein 2-3-fold throughout pseudopregnancy. Midpseudopregnant rabbit luteal extracts were further evaluated to determine the identity of the lipid-stimulated kinase. Results of low pH-activated phosphorylation were consistent with the identification of p76 as an autophosphorylated member of the protein kinase C (PKC) family. Partial purification of the luteal lipid-stimulated kinase was performed using sequential DEAE-cellulose/hydroxylapatite chromatographies and using gel filtration. Western immunoblot with type-specific anti-PKC delta antiserum showed coelution of kinase p76 activity with immunoreactive PKC delta. Immunoblot analysis confirmed that luteal levels of PKC delta were increased by estrogen treatment.

Animals↗

PubMed1992

Studies on antidiabetic agents. 11. Novel thiazolidinedione derivatives as potent hypoglycemic and hypolipidemic agents.

In the course of further chemical modification of the novel antidiabetic pioglitazone (AD-4833, U-72,107), a series of 5-[4-(2- or 4-azolylalkoxy)benzyl- or -benzylidene]-2,4-thiazolidinediones was prepared and evaluated for hypoglycemic and hypolipidemic activities in insulin-resistant, genetically obese, and diabetic KKA(y) mice. Replacement of the 2-pyridyl moiety of pioglitazone by a 2- or 4-oxazolyl or a 2- or 4-thiazolyl moiety greatly enhanced in vivo potency. The corresponding 5-benzylidene-type compounds, in which a methine was used as a linker between the benzene ring and the thiazolidinedione ring, also had potent biological activity. Among the compounds synthesized, 5-[4-[2-(5-methyl-2-phenyl-4-oxazolyl)ethoxy]benzyl]-2,4- thiazolidinedione (18) exhibited the most potent activity, more than 100 times that of pioglitazone. The synthesis and structure-activity relationships for this novel series of derivatives are detailed.

Animals↗

PubMed1992

Direct effect of basic fibroblast growth factor on gene transcription in a cell-free system.

Recent findings on the translocation of intact fibroblast growth factor (FGF) into the cell nucleus suggest that it functions directly in nuclear events. We examined the effect of human basic FGF (bFGF) on gene transcription in a cell-free system. When mouse genes encoding phosphoglycerate kinases 1 and 2 (Pgk-1 and Pgk-2) were transcribed by using nuclear extracts of Ehrlich ascites tumor cells, FGF affected transcription in different ways: in the presence of bFGF, transcription of the Pgk-1 gene was inhibited, whereas that of the Pgk-2 gene was enhanced. When viral genes were tested, transcription of the adenovirus major late DNA was slightly stimulated but that of the adenovirus early E1A DNA or the human immunodeficiency virus DNA was not changed by the addition of bFGF. Moreover, the presence of a distinct 5' upstream region of the Pgk-2 gene, which includes a negative cis-acting element, was required for transcription stimulation by bFGF. These results suggest that bFGF can regulate transcription directly in the nucleus in a gene-specific manner.

Adenovirus Early Proteins↗

PubMed1992

Antihypertensive and hormonal activity of MK 954 in spontaneously hypertensive rats.

MK 954 (DuP 753), a recently developed angiotensin II (Ang II) receptor antagonist, was administered orally for 2 weeks to spontaneously hypertensive (SHR) and Wistar-Kyoto rats (WKY). Whereas the basal levels of plasma Ang II were lower in SHR than in WKY, treatment with MK 954 markedly reduced blood pressure in SHR but not in WKY. Plasma renin activity, Ang I and Ang II were increased, while plasma aldosterone was decreased in both strains. These results no only indicate therapeutic efficacy of this agent in the chronic treatment of human hypertension, but also support the idea that the renin-angiotensin system plays an important role in the control of blood pressure in SHR.

Angiotensin I↗

PubMed1992

Expression of c-met proto-oncogene in COS cells induces the signal transducing high-affinity receptor for hepatocyte growth factor.

By transfection of the expression plasmid containing a human c-met cDNA into COS-7 cells, high-affinity binding sites specific for HGF with a Kd value of 30 pM were newly detected. Furthermore, only in the c-met transfected COS-7 cells, but not in the control COS-7 cells, DNA synthesis was markedly induced in response to HGF. Thus, transient expression of exogenous c-met cDNA resulted in the appearance of high-affinity receptor for HGF and conversion of the normally non-responsive COS-7 cells into the HGF-responsive cells. These results provide evidence for identifying the c-met product as a signal transducing high-affinity receptor for HGF.

Cell Line↗

PubMed1992

Angioscopic evaluation of coronary-artery thrombi in acute coronary syndromes.

BACKGROUND: Disruption of an atherosclerotic plaque in a coronary artery followed by the formation of a thrombus is believed to be the cause of both unstable angina and acute myocardial infarction. Although thrombolytic therapy is efficacious in patients with acute myocardial infarction, for unknown reasons it is far less effective in patients with unstable angina. We postulated that there might be differences in the composition of the coronary-artery thrombi in unstable angina and acute myocardial infarction. METHODS: To investigate the appearance of coronary-artery thrombi, we performed percutaneous transluminal coronary angioscopy in 15 patients with unstable angina and 16 with acute myocardial infarction. Angioscopy was performed within 48 hours after an episode of pain at rest in the patients with unstable angina and within 8 hours of onset in those with acute myocardial infarction. RESULTS: Angioscopy revealed coronary thrombi in all but two patients (one in each group). Of the 29 patients with thrombi, those with unstable angina were frequently observed to have grayish-white thrombi (10 of 14, 71 percent), but none were seen in the 15 patients with acute myocardial infarction (P less than 0.01). By contrast, reddish thrombi were observed in all 15 patients with acute myocardial infarction who had thrombi, but in only 4 of the 14 patients with unstable angina and thrombi (P less than 0.01). As assessed by coronary angiography, occlusive thrombi occurred frequently in patients with acute myocardial infarction (13 of 16 patients) but were not seen in any of the 15 patients with unstable angina (P less than 0.01). CONCLUSIONS: Coronary-artery thrombi play an important part in the pathogenesis of unstable angina and acute myocardial infarction. However, the appearance of the thrombi is different in the two conditions, possibly reflecting differences in the composition of age of the thrombi or the presence or absence of blood flow in the artery. This difference may account for the contrasting results of thrombolytic therapy.

Angina Pectoris↗

PubMed1992

Purification and characterization of protein kinase C epsilon from rabbit brain.

Protein kinase C epsilon was chromatographically purified from rabbit brain to electrophoretic homogeneity. We identified the enzyme as the epsilon species of novel-type protein kinase C (nPKC epsilon), originally discovered and defined by cDNA cloning [Ohno, S., et al. (1988) Cell 53, 731-741], on the basis of the following observations: (i) the enzyme reacts specifically with an antipeptidic antiserum to nPKC epsilon but not with antisera to any of the other molecular species of PKC thus far known; (ii) it exhibits enzymatic behavior essentially identical to that of a recombinant nPKC epsilon purified from transfected COS cells [Konno, Y., et al. (1989) J. Biochem. 106, 673-678] and distinct from that of conventional PKC (alpha, beta I/II, and gamma) in its dependence on magnesium concentration and cofactors such as phospholipids, calcium, and phorbol ester; and (iii) it has an apparent molecular weight of 95.7K +/- 0.4K on SDS-PAGE, significantly greater than the other conventional and novel PKCs thus far identified. Notably, calcium exhibits a complex effect, both positive and negative, on the kinase activity of epsilon depending on the kind of substrate and the coexisting phospholipid, calling for a modification of the current notion that epsilon is a kinase unresponsive to calcium. The amount of epsilon species in the brain was estimated to be comparable to that of each conventional species, indicating that epsilon stands as one of the major PKC family members in brain. Furthermore, the enzyme shows a broader substrate spectrum than conventional PKC when examined with endogenous substrates, implying that it may cover a wider or different range of physiological functions.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

PubMed1992

Time course of hepatitis A virus antibody titer after active and passive immunization.

To investigate the antibody titer necessary to prevent hepatitis A virus infection, either 15 or 7.5 mg/kg of immune serum globulin was injected into 10 antihepatitis A virus negative volunteers and their serum antihepatitis A virus titers were observed for 28 wk. In addition, antibody titers were observed for 96 wk in a phase 1 clinical trial of a hepatitis A vaccine. The two studies were then compared to assess the immunogenicity of the vaccine and the persistence of the antibody. Serum-neutralizing antibody titers that were greater than or equal to 4 (considered as positive) persisted for 18 wk and 14 wk after the injection of 15 and 7.5 mg/kg of globulin, respectively. Hepatitis A virus vaccine recipients showed adequate neutralizing antibody titers, with the groups receiving 1, 0.5 and 0.25 micrograms/dose showing titers of 4(5.5), 4(4.7) and 4(4), respectively, at 18 mo after the third inoculation. These findings suggested that effective blood antibody titers were likely to be retained in the 1.0 micrograms or 0.5 micrograms/dose groups for at least several years. Moreover, the serum antihepatitis A virus titers demonstrated by a modified radioimmunoassay changed in parallel with the neutralizing antibody titers in the volunteers injected with globulin.

Adult↗

PubMed1992

Evaluation of three hepatitis C virus-related antibodies C100, KCL-163, JCC. Tests for screening blood donors.

To evaluate the most effective method for detecting hepatitis C virus (HCV) carriers in a large population of blood donors, HCV-related antibodies were measured in 919 donor serum samples using three different enzyme-linked immunosorbent assays. The antibodies were C100 and KCL-163, nonstructural proteins of HCV, as well as JCC, a translation product of the presumptive HCV core gene. Fourteen (1.5%), 12 (1.3%), and 13 (1.4%) specimens were positive for anti-C100, anti-KCL-163, and anti-JCC, respectively. HCV RNA was detected by the polymerase chain reaction in seven (25.0%) of the 28 specimens that were anti-HCV-positive by at least one of the three assays. Four of the seven specimens were detected by anti-C100 screening, while the remaining three were not. All seven specimens were positive for KCL-163 and/or JCC antibodies. These findings suggest that screening for both KCL-163 and JCC antibodies may be of particular use in accurately identifying HCV-positive blood.

Adult↗

PubMed1992

Clinical evaluation of three anti-HCV ELISAs in patients with various liver diseases.

We measured antibodies to hepatitis C virus (HCV) in 380 patients with various liver diseases by three enzyme-linked immunosorbent assays (ELISAs): HCV antibody ELISA test (C100), KCL-163 (KCL) corresponding to the nonstructural protein of HCV, and JCC based on the translation product of the presumptive HCV core gene. Of 233 cases of non-A, non-B (NANB) liver disease, 63.9% were anti-C100 positive, 69.1% were anti-KCL positive, and 79.8% were anti-JCC positive. Detection of serum HCV-RNA in 213 cases of chronic NANB liver disease revealed that the concordance was 80.3% for C100, 86.4% for KCL, 94.8% for JCC, and 95.3% for all three ELISAs. Overall, 85.4% of chronic NANB cases were considered to have type C disease with HCV infection. The most reliable assays for diagnosing chronic NANB liver disease as type C appeared to be the KCL and JCC ELISAs.

Adolescent↗

PubMed1992

Differences in plasma beta-endorphin and bradykinin levels between patients with painless or with painful myocardial ischemia.

To verify whether plasma beta-endorphin and bradykinin affects the pathophysiology of myocardial ischemia and the perception of cardiac pain, 35 patients with coronary artery disease were subjected to treadmill testing and 48-hour Holter ECG monitoring to measure their pain thresholds. Patients were divided into two groups during exercise testing: group 1 (N = 19) who had ST segment depression, and group 2 (N = 16), who had chest pain. Both groups were then compared with 12 age-matched control subjects. Pain thresholds were measured after Holter ECG monitoring, and blood samples were drawn before and immediately after exercise. No statistical differences were noted between groups 1 and 2 with regard to the severity of myocardial ischemia as assessed by ST segment depression or exercise tolerance time. The frequency of the episodes of silent myocardial ischemia in group 1 was found to be significantly (p less than 0.05) higher than that in group 2. The duration of the episodes of silent myocardial ischemia in group 1 was 41.9 minutes (range 3 to 343 minutes), which was significantly (p less than 0.05) longer than that in group 2 (11.5 minutes; range 0 to 74). The pain threshold in group 1 was a statistically (p less than 0.05) higher value than that in group 2. Although the resting plasma beta-endorphin level in group 1 was not statistically significantly different from values in either group 2 or the control group, during exercise the plasma beta-endorphin levels in both group 1 and the control group were significantly (p less than 0.05) elevated in comparison with their resting levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Bradykinin↗

PubMed1992

Heart rate variability in patients with diabetes mellitus, ischemic heart disease, and congestive heart failure.

The prognosis of patients with heart disease and prediction of sudden cardiac death can be assessed through heart rate variability, an indirect measure of abnormal autonomic control. The authors have evaluated the heart rate variability by 24-hour ambulatory electrocardiographic monitoring in 25 diabetic patients, 19 ischemic heart disease patients, 18 congestive heart failure patients, and 10 normal subjects. Thirteen diabetic patients had autonomic neuropathy and 12 patients did not. Heart rate variability index (mean SD) in patients with diabetes mellitus, ischemic heart disease, and congestive heart failure was significantly lower (34.5 +/- 12.6 ms, 43.7 +/- 15.4 ms, and 34.6 +/- 15.8 ms vs 65.6 +/- 16.7 ms, p less than 0.05) than that of normal subjects. Mean SD was significantly lower in patients with autonomic neuropathy as compared to patients without autonomic neuropathy (26.4 +/- 6.5 ms vs 44.2 +/- 11.0 ms, p less than 0.05) mean SD as compared to survivors: 49 +/- 7 ms in patients with mild ischemic heart disease, 48 +/- 15 ms in patients with severe ischemic heart disease, and 23 +/- 7 ms in patients who died. Similarly, the mean SD in 4 congestive heart failure patients who died was lower significantly (p less than 0.05) than in those who survived (19.0 +/- 5.6 ms vs 40.0 +/- 14.5 ms). Among congestive heart failure patients, clinical improvement by therapy was associated with a significant increase in mean SD. When the mean SD of 30 ms was used as the cutoff point for detection of autonomic dysfunction or patient death, specificity exceeded 90% and sensitivity was 75%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1992

Losartan, a specific angiotensin II receptor antagonist, increases angiotensin I and angiotensin II release from isolated rat hind legs: evidence for locally regulated renin-angiotensin system in vascular tissue.

The effect of Losartan (10(-9) to 10(-6) M) on angiotensins I and II release was examined in isolated hind legs perfused with Krebs-Ringer solution from normal and bilaterally nephrectomized rats. Losartan increased dramatically both angiotensins I (Ang I) and II (Ang II) release in a dose-dependent fashion; the maximal percent increment in Ang I and Ang II release evoked by Losartan (10(-6) M) was about +380% and +160%, respectively, in normal rat hind legs. In nephrectomized animals, Losartan elicited a marked increase in both peptides dose-dependently. There was a highly positive correlation between the released amounts of Ang I and that of Ang II altered by Losartan in either normal (r = 0.954) or nephrectomized rats (r = 0.923). These results not only confirm the existence of a functional renin-angiotensin system in vascular tissues, but also suggest that the system is regulated by locally generated Ang II.

Angiotensin I↗

PubMed1992

Effects of losartan, a nonpeptide angiotensin II receptor antagonist, on cardiac hypertrophy and the tissue angiotensin II content in spontaneously hypertensive rats.

Losartan, a recently developed nonpeptide angiotensin II (Ang II) receptor antagonist, was administered orally to 10-week-old spontaneously hypertensive rats (SHR) for 2 weeks. Cardiac weight and tissue Ang II, as well as plasma renin activity (PRA) and Ang II, were determined. Treatment with Losartan (10 mg/kg per day) lowered blood pressure markedly. Losartan reduced significantly the left ventricular weight by 11% compared with control rats. The left ventricular Ang II content was lowered by Losartan (18.6 +/- 0.9 pg/tissue; 21.9 +/- 0.9 pg/tissue, control, p less than 0.05), whereas PRA and plasma Ang II concentration were increased by the treatment. With the control and Losartan-treated animals, there was a significant positive correlation between the left ventricular weight and the tissue Ang II content (r = 0.563, p less than 0.05). These results provide evidence that cardiac tissue Ang II, rather than circulating Ang II, plays an important role in the pathophysiology of left ventricular hypertrophy of this animal model of human hypertension.

Analysis of Variance↗

PubMed1992

Hypotensive activity of TCV-116, a newly developed angiotensin II receptor antagonist, in spontaneously hypertensive rats.

TCV-116, a recently developed angiotensin II (Ang II) receptor antagonist, was administered orally (1 mg/kg per day) to 10-week-old spontaneously hypertensive rats (SHR) for 2 weeks. Blood pressure and plasma components of the renin-angiotensin-aldosterone system were determined in these rats. TCV-116 produced a marked reduction in blood pressure without altering heart rate. Whereas plasma renin concentration (PRC), angiotensin I (Ang I) and angiotensin II (Ang II) all were significantly increased, plasma aldosterone was decreased by approximately 70% compared with control animals. These results not only indicate therapeutic efficacy of this agent in the chronic treatment of human hypertension, but support also the concept that the renin-angiotensin system plays an important role in the control of blood pressure in this animal model of human essential hypertension.

Angiotensin Receptor Antagonists↗