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Biomedical subjects

K Iwata

Publications and source records attributed to K Iwata.

At least 397 records · Page 22Linked to original sources
PubMed1983

Rabbit pulmonary angiotensin-converting enzyme: the NH2-terminal fragment with enzymatic activity and its formation from the native enzyme by NH4OH treatment.

The NH2-terminal sequence of 22 residues of rabbit lung angiotensin-converting enzyme has been determined as (NH2)Thr-Leu-Asp-Pro-Gly-Leu-Leu-Pro-Gly-Asp-Phe-Ala -Ala-Asp-Asn-Ala-Gly-Ala-Arg-Leu-Phe-Ala-. In the course of purification of the enzyme for structural analysis a protein of Mr = 82,000 with angiotensin-converting activity was separated from the major fraction containing the native enzyme (Mr = 140,000). This low-molecular-weight enzyme catalyzed the hydrolysis of the synthetic substrate Hip-His-Leu at a rate 23% of that with the native enzyme, and exhibited a similar Km value as well as behaviors towards various effectors of angiotensin-converting enzyme. Edman degradation of both the native and the 82K enzymes revealed that they contain identical amino acid sequences from the NH2-termini. This result and those of peptide mapping and carbohydrate and amino acid analyses indicate that the 82K enzyme is a fragment derived from the NH2-terminal portion of the native enzyme, and hence contains its catalytic site. Evidence has been obtained indicating that the active fragment was formed from the native enzyme during its elution from the antibody-affinity column with NH4OH: on treatment of the native enzyme (140K Mr) with 1 N NH4OH at room temperature, a cleavage occurred and two proteins with Mr = 82K and Mr = 62K were obtained. The 82K Mr fragment was found to be enzymatically active and to contain the same NH2-terminal sequence as the native enzyme. The other fragment (62K Mr) was devoid of the activity and was shown to derive from the COOH-terminal portion of the native enzyme by the peptide mapping and terminal analyses. Cleavage of a peptide bond with NH4OH is unusual and appears to be specific for the native angiotensin-converting enzyme from rabbit lung.

Amino Acids↗
PubMed1983

Animal model of megaureter.

A rabbit model with a megaureter was produced by the partial obstruction of the ureter. The resultant dilatation obtained after the chronic obstruction (more than 100 days) was approximately 4 times greater than the normal ureteral diameter.

Animals↗
PubMed1983

Effects of electrical constants on conduction velocity of action potentials measured with unidimensional latency-topography in frog skeletal muscle fibers.

Conduction velocity (CV) of an action potential recorded from a single muscle fiber of the frog was measured with a new method, unidimensional latency-topography, and electrical membrane constants were determined for the same muscle fiber. CV = 1.96 +/- 0.27 m/sec (n = 52) at about 20 degrees C. Temperature coefficient of CV: Q10 = 2.0. Electrical membrane constants in the same muscle fibers (n = 52): lambda = 3.25 +/- 0.83 mm, tau = 33.4 +/- 14.3 msec, Cm = 6.09 +/- 2.13 mu F/cm2, D = 129.4 +/- 28.9 micron (mean +/- S.D.). The CV decreased linearly with increment of time constant, tau, and membrane capacity per unit area, Cm. The space constant, lambda, and the fiber diameter of the muscle fiber, D, did not correlate with CV. It was concluded that the T-system, which contributes largely to membrane capacity, has a great influence on the CV.

Action Potentials↗
PubMed1983

Unusual sensitivity to bleomycin and joint resistance to 9-beta-D-arabinofuranosyladenine and 1-beta-D-arabinofuranosylcytosine of mouse FM3A cell mutants with altered ribonucleotide reductase and thymidylate synthase.

This paper describes unusual sensitivity to bleomycin; resistance to aphidicolin, 9-beta-D-arabinofuranosyladenine, 1-beta-D-arabinofuranosylcytosine, and hydroxyurea; and a mutator phenotype as common phenotypes of two classes of previously reported mouse FM3A cell mutants with distinct biochemical defects. One class of mutants, selected for aphidicolin resistance, contains altered ribonucleotide reductase desensitized to deoxyadenosine triphosphate, a negative allosteric effector, and the other class contains temperature-sensitive thymidylate synthase. Abnormal levels of deoxyribonucleoside triphosphate pools, especially those of deoxyadenosine triphosphate, were the common biochemical trait for both classes of mutants. The aphidicolin-resistant thymidylate synthase mutants, isolated independently of aphidicolin resistance, showed reduced levels of thymidylate synthase and increased levels of ribonucleotide reductase. Bleomycin was more lethal to both classes of mutants than to wild-type cells, as determined by colony-forming ability. It also caused more marked scissions of DNA in the ribonucleotide reductase mutant cells than in the wildtype cells as analyzed by sedimentation on an alkaline sucrose gradient. Thus, the activity or level of ribonucleotide reductase seems to be one factor determining the bleomycin sensitivity of cells by potentiating the capacity of bleomycin to cleave DNA strands.

Animals↗
PubMed1983

[HBs antigen-positive adult type liver cancer in a child with sustained remission induced by infusion of antineoplastic agents into the hepatic artery].

A 9-year-old boy with non-resectable hepatocellular carcinoma was treated with irradiation and intra-hepatic arterial infusion of antitumor agents. His blood was positive for hepatitis B surface antigen (HBs Ag), but negative for hepatitis B e antigen (HBe Ag). Maternal transmission was suspected, because his mother's blood was positive for HBs Ag and his grand mother died from hepatic cirrhosis. The patient received a total dose of 4000 rad in 30 fractions. A chemotherapy cycle consisted of 5-FU (6 mg/M2/day, given continuously), EX (300 mg/M2, given on 1st, 3rd, 5th, 7th, and 9th week), VCR (1.5 mg/M2, on 2nd, 4th, 6th, 8th, and 10th week), and ADM (30 mg/M2, on 13th and 16th week). Since 6 months after the initiation of the chemotherapy, alpha-fetoprotein has become negative (less than or equal to 100n g/ml), and now, 2 years and 11 months after the diagnosis was settled, the patient remains a disease free state. His blood continues to be positive for HBs Ag.

Antineoplastic Agents↗
PubMed1983

Significance of test for antibody-coated bacteria in biliary tract infection.

To detect a biliary tract infection, antibody-coated bacteria (ACB) in bile and duodenal juice was examined in 146 specimens from 111 patients by direct immunofluorescent antibody technique (FA test). One hundred and forty one of these specimens were also cultured and the results were compared with those of FA test. Organisms were isolated in 77 specimens from 59 patients. Thirty nine (from 31 cases) in these 77 specimens showed ACB. Result of FA test was related to clinical findings such as fever and leucocytosis, but was not to upper abdominal pain, jaundice, liver function test abnormality and the presence of gallstones. Isolates were mainly gram negative rods in ACB positive group (77%). Classification of immunoglobulin of ACB indicated a predominance of IgG and IgA classes over IgM class.

Adult↗
PubMed1983

Incidence of hepatitis A virus infection among Japanese volunteers staying in developing countries.

Incidence of hepatitis A virus infection was studied serologically in 260 adult males and females sent for volunteer service to developing countries from Japan. Among 225 initially seronegative subjects, 29 (12.9%) were seropositive to hepatitis A virus at their return from two year's overseas service. Seroconversion occurred in none of 39 subjects who received two doses or more of prophylactic administration of human immunoglobulin. There were clinical records of acute non-B hepatitis in 10 subjects among 29 who seroconverted to hepatitis A virus, while in 6 among 231 who did not seroconvert.

Adult↗
PubMed1982

Molecular and catalytic properties of rabbit testicular dipeptidyl carboxypeptidase.

Rabbit testicular dipeptidyl carboxypeptidase activity was purified by a procedure exploiting its affinity for N-alpha-[1-(S)-carboxy-3-phenylpropyl]-L-lysyl-L-proline. The molecular, catalytic, and immunological properties of the testicular enzyme are presented and compared with the corresponding properties of pulmonary angiotensin-converting enzyme. Although catalytically similar and immunologically related to pulmonary dipeptidyl carboxypeptidase, the testicular enzyme has a molecular weight (100,000) which is lower by a factor of about one-third and differs in its NH2 and COOH termini. Furthermore, we present evidence that the testicular enzyme is not a post-translation product of the pulmonary type enzyme. These data suggest that testicular and pulmonary dipeptidyl carboxypeptidase are two distinct proteins which are catalytically similar and immunologically closely related.

Amino Acids↗