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Biomedical subjects

M Shimamura

Publications and source records attributed to M Shimamura.

At least 145 records · Page 8Linked to original sources
PubMed1985

Effects of dolichol and dolichyl phosphate on in vitro differentiation of hematopoietic progenitors.

The exogenous addition of dolichyl phosphate (Dol-P), an active form of dolichol (Dol) that carries oligosaccharide chains for protein-N-glycosylation, significantly enhanced colony formation of mouse bone marrow hematopoietic progenitors (CFU-e, BFU-e, and CFU-gm) was stimulated by erythropoietin (Epo) and colony-stimulating factor (CSF), but Dol enhanced colony formation of CFU-e only. The effects of Dol or Dol-P on these hematopoietic progenitors were fully dependent on stimulation by Epo or CSF. Other mevalonate-metabolites, such as cholesterol, coenzyme Q10, and isopentenyladenine, had no effect on hematopoietic progenitors. These studies suggest that exogenous Dol-P enhances the frequency of differentiation of hematopoietic progenitors stimulated by Epo or CSF, and there may be a diversity in cellular response of these progenitors to Dol.

Adenine↗
PubMed1985

Enkephalin-degrading dipeptidyl carboxypeptidase in guinea pig serum: its properties and action on bioactive peptides.

A dipeptidyl carboxypeptidase, which cleaved the Gly3-Phe4 bond of enkephalins, was purified from guinea pig serum 420-fold. The optimum pH of the enzyme was in the neutral range (pH 7.25), and the molecular weight was estimated to be approx. 280,000. The enzyme hydrolyzed Met- and Leu-enkephalin with Km values of 0.30 and 0.50 mM, respectively. The enzyme was inhibited by metal chelators and p-chloro-mercuribenzoate. Captopril showed high inhibitory potency, while phosphoramidon and Phe-Ala showed no effect on the enzyme activity. Therefore, the obtained enzyme can be classified as an angiotensin-converting enzyme (EC 3.4.15.1). Among the bioactive peptides examined, bradykinin and angiotensin I were hydrolyzed by the enzyme. Angiotensin III showed a stronger inhibitory effect than that of angiotensin II. Substance P, gastrin I, and secretin were also inhibitory toward the enzyme activity. On high-performance liquid chromatography analysis, Met-enkephalin-Arg6-Phe7 and Leu-enkephalin-Arg6 were cleaved sequentially at the second peptide bond of the C terminus. Thus, the dipeptidyl carboxypeptidase in guinea pig serum may play a role not only in the angiotensin-bradykinin system but also in the metabolism of circulating enkephalins and other bioactive peptides.

Animals↗
PubMed1985

In vitro IgE-secreting cells in man. I. Mitogen-independent and -dependent subpopulations.

In vitro IgE secretion by atopic and normal peripheral-blood lymphocytes was examined in culture with pokeweed mitogen or Staphylococcus aureus strain Cowan-I (StaCw) or without mitogen. IgE secreted in culture supernatants was measured with double antibody radioimmunoassay. Enumeration of IgE-secreting cells was made by a protein-A plaque assay. IgE was detected in increasing quantities in supernatants of cultured lymphocytes without mitogen up to the 12th day. IgE-plaque-forming cells were formed by the lymphocytes in large numbers on days 4-7 in cultures with mitogen. These results suggest that not only mitogen-independent but also mitogen-dependent subpopulations may exist in the IgE-secreting cells.

Antibody-Producing Cells↗
PubMed1985

Pharmacokinetics of ceftazidime in patients with renal insufficiency and in those undergoing hemodialysis.

The pharmacokinetics of ceftazidime, a new cephalosporin antibiotic, were studied in 7 healthy volunteers and 32 patients with renal insufficiency after a single 500-mg intravenous injection. The mean plasma half-life during beta-phase was 1.67 h in normal subjects and was prolonged to 15.09 h in hemodialysis patients. There were significant correlations between the elimination rate constant and the creatinine clearance, and between the beta-phase rate constant and the creatinine clearance. The mean urinary recovery during 24 h amounted to 89.6% of the dose in normal subjects and decreased with the lowering of renal function. The plasma levels during hemodialysis were lower than those between hemodialyses.

Adult↗
PubMed1985

Study on the metabolism of volatile hydrocarbons in mice--propane, n-butane, and iso-butane.

A study was conducted to establish whether volatile hydrocarbons, such as propane, n-butane and iso-butane, are metabolized in mice or not. In mice having inhaled these gases, isopropanol and acetone were yielded from propane, sec-butanol and methyl ethyl ketone from n-butane, and tert-butanol from iso-butane as the respective metabolites. In addition, liver microsomes were found to contain the enzymic system participating in these metabolisms. In vitro reactions with liver microsomes produced isopropanol from propane, sec-butanol from n-butane, and tert-butanol from iso-butane. It was assumed that hydrocarbons were first converted to (omega-1)-alcohols by microsomal enzyme system and then to corresponding ketones by alcohol dehydrogenase.

Alcohol Oxidoreductases↗
PubMed1985

Partial purification of two distinct enkephalin-degrading aminopeptidases from human cerebrospinal fluid.

In human cerebrospinal fluid, aminopeptidase, dipeptidyl aminopeptidase, dipeptidyl carboxypeptidase, and carboxypeptidase which were capable of hydrolyzing enkephalins were detected. Among these enzymes, two distinct aminopeptidase, designated C-AP1 and C-AP2, were partially purified. These enzymes were not purified thoroughly, but the characteristics of C-AP2 were similar to those of an aminopeptidase purified from monkey brain. But the inhibitory activity of amastatin on C-AP2 was stronger, and that of substance P was negligible. On the other hand, characteristics of C-Ap1 were extremely differ from those of C-AP2 or an aminopeptidase purified from monkey brain. C-AP1 had an optimum pH more in the acidic range (the highest at pH 6.0) and was not inhibited by any of the protease inhibitor tested including bestatin and amastatin.

Aminopeptidases↗
PubMed1984

Reductive cleavage of Xaa-proline peptide bonds by mild alkaline borohydride treatment employed to release O-glycosidically linked carbohydrate units of glycoproteins.

During the deglycosylation reaction of fish egg polysialoglycoproteins under the conditions of 1 M NaBH4 in 0.1 M NaOH at 37 degrees C for 48 h, a marked loss of the glycine content has been encountered, besides the serine and threonine residues to which the carbohydrate units are linked. The chemical basis behind this phenomenon has been elucidated by amino acid analysis first of the major glycopeptides (carbohydrate-(O)Thr-Gly-Pro-Ser) derived from desialylated polysialoglycoproteins and subsequently six proline-containing peptides before and after treatment under similar conditions. It has thus been established that -Xaa-Pro- sequences are remarkably susceptible to reductive cleavage under such mild aqueous conditions. In view of the finding that the reductive cleavage of insulin B-chain, which contains a single proline residue adjacent and C-terminal to a threonine residue, led to about 80% loss of the threonine residue, deglycosylation with alkaline borohydride reagents warrants a special comment. The decreased amounts of serine or threonine residues cannot be related simply to the degree of glycosylation of these residues. The above results are therefore discussed in the relation to other work.

Amino Acids↗
PubMed1984

Role of joint afferents in relation to the initiation of forelimb stepping in thalamic cats.

To analyze the roles of joint afferents in relation to initiation of forelimb stepping in thalamic cats, we recorded the unit spikes of the cervical dorsal roots, stimulated the joint afferents, and applied local anesthesia to the joint capsule. Almost all of the joint afferents of the shoulder, elbow, wrist and finger adapted slowly and exhibited alternating firing during forelimb stepping. About 45% of the afferents of each joint showed firings as the limb moved from forward to backward. About 44% of the afferents exhibited discharges as the limb moved from backward to forward. The remaining afferents showed firings as the limb moved in both directions. The application of local anesthesia to joints of the shoulder, elbow or wrist resulted in a marked reduction of forelimb stepping. Forelimb stepping was evoked by electric stimulation of the joint capsule, when excitabilities of flexor motoneurons were increased due to muscle stretching. Impulses originating in the joint afferents of the forelimb entered the spinal cord and ascended to the dorsolateral funiculus of the cervical cord, since forelimb stepping was abolished after bilateral transection of this part. Our results indicate that joint afferents may play an important role in the initiation of forelimb stepping in thalamic cats walking on a motor-driven treadmill.

Afferent Pathways↗
PubMed1984

Purification and characterization of an enkephalin-degrading aminopeptidase from guinea pig serum.

An enkephalin-degrading aminopeptidase using Leu-enkephalin as a substrate was purified about 4100-fold from guinea pig serum. The purified preparation was apparently homogenous, showing one band on polyacrylamide gel electrophoresis. The molecular weight of the enzyme was approx. 92 000. The aminopeptidase had a pH optimum of 7.0 with Km values of 0.12 mM and 0.18 mM for Leu- and Met-enkephalin, respectively. The enzyme hydrolyzed neutral, basic and aromatic amino acid beta-naphthylamides, but did not the acidic one. The enzyme was inhibited strongly by metal-chelating agents, bestatin and amastatin and weakly by puromycin. Among several biologically active peptides, angiotensin III and substance P strongly inhibited the enzyme.

Animals↗
PubMed1984

Fish egg polysialoglycoproteins: structures of new sialooligosaccharide chains isolated from the eggs of Oncorhynchus keta (Walbaum). Fucose-containing units with oligosialyl groups.

A series of acidic oligosaccharide alditols having different neutral core oligosaccharides were isolated from salmon egg polysialoglycoproteins by alkali-borohydride treatment followed by anion-exchange chromatography and Iatrobead chromatography. Their structures were determined by methylation analysis, molecular secondary ion mass spectrometry of underivatized oligosaccharides, and enzymatic desialylation. The molecular secondary ion mass spectra of intact sialooligosaccharides exhibit pronounced quasi-molecular-ion peaks, (M + H)+, (M + Na)+, (M + 2Na - H)+, and/or (M + K)+, as well as some diagnostic sequence ion peaks. Of a number of oligosaccharide alditols, the following are novel: Fuc alpha 1 leads to 3GalNAc beta l1 leads to 3Gal beta 1 leads to 4Gal beta 1 leads to 3[(leads to 8NeuGc alpha 2)n leads to 6]GalNAcol (n = 1-6). The proton nuclear magnetic resonance spectra of these oligosaccharides are also reported and discussed.

Animals↗
PubMed1984

Purification and characterization of two distinct dipeptidyl aminopeptidases in soluble fraction from monkey brain and their action on enkephalins.

Two distinct dipeptidyl aminopeptidases, which were designated DPP-A and DPP-B, were purified from soluble fraction of monkey brain using Leu-enkephalin as the substrate. The enzymes were purified 187 and 136 fold, respectively. Both enzymes showed the optimum pH in neutral range. Their molecular weights were almost equal and were estimated to be about 100,000. Their Km values with Leu-enkephalin as the substrate were 5.6 X 10(-5) and 1.1 X 10(-5) M, respectively. Among synthesized substrates, the highest affinity of the enzymes was toward arginyl-arginine beta-naphthylamide with the Km values of 6.25 X 10(-5) and 6.41 X 10(-5) M, respectively. Both enzyme activities were inhibited by the metal-chelators DFP and PCMB. Two hundred fifty microM arphamenine A inhibited DPP-A and -B with inhibition of 36.6% and 44.1%, respectively. Beta-endorphin, ACTH, and glucagon inhibited only DPP-B, while beta-lipotropin and angiotensin II inhibited both DPP-A and -B when Leu-enkephalin was used as the substrate.

Animals↗
PubMed1984

Inhibition of a membrane-bound enkephalin-degrading aminopeptidase by bestatin analogs.

A variety of bestatin analogs were examined as potent inhibitors of a membrane-bound enkephalin-degrading aminopeptidase that was purified from monkey brain. Bestatinyl amino acid derivatives showed strong inhibition of this enzyme. The most effective was bestatin-L-Arg X AcOH, with a Ki value of 0.21 X 10(-8) M with Leu-enkephalin as substrate. It exhibited competitive kinetics and was about 100-fold more potent than bestatin. This compound seems to be useful for pharmacological and other studies.

Aminopeptidases↗
PubMed1984

[Seminal vesicle cyst associated with contralateral renal agenesis: a case report].

A 37-year-old man was hospitalized for a more extensive examination of azoospermia. A seminal vesiculogram demonstrated a cystic lesion of the right seminal vesicle, but failed to show the left seminal vesicle because of intrascrotal adhesion caused by previous orchidopexy. A transrectal ultrasonogram and CT-scan revealed a large cystic mass in the retrovesical region. At urethrocystoscopy, the left half of the trigone and left ureteral orifice were absent, and the verumontanum increased in size. Bilateral testicular biopsies demonstrated a small type of the seminiferous tubule showing a thickening of the basement membrane and low spermatogenesis. The cystic mass was examined by transabdominal needle aspiration under the guidance of supurapubic ultrasound. Microscopic examination of the cystic fluid obtained revealed a few immobile spermatozoa. The patient was not subjected to any surgical intervention.

Adult↗
PubMed1984

[Studies on an oral calcium loading test in upper urinary tract stone formers].

An oral calcium loading test was performed on 55 patients with upper urinary tract stones to find absorptive or renal hypercalciuria. The mean urinary calcium excretion level of this patient group was significantly greater than that of a control group of 10 patients without abnormal upper urinary tract. Idiopathic hypercalciuria defined as more than 250 mg per day in males and more than 200 mg per day in females was observed in 13 patients; 4 patients with absorptive hypercalciuria, 6 patients with renal hypercalciuria and 3 patients of origin-unknown hypercalciuria. Five of the 6 patients with renal hypercalciuria had recurrent and/or multiple urolithiasis. From these results, this test was considered to be useful in the discrimination between absorptive and renal hypercalciuria.

Administration, Oral↗
PubMed1983

Enkephalin degrading enzymes in cerebrospinal fluid.

Enkephalins were rapidly degraded by specific enzyme systems in vivo. In cerebrospinal fluid (CSF), however, it has been undefined whether these enzyme systems existed. Our experiments showed enkephalins were hydrolyzed by the enzymatic activity in both CSF of human and monkey. The results by the thin layer chromatography and the high performance liquid chromatography revealed the reaction products of CSF and enkephalin were tyrosine, tyrosyl-glycine and tyrosyl-glycyl-glycine. Therefore, the enzymes in CSF were considered to be an aminopeptidase, a dipeptidyl aminopeptidase and a dipeptidyl carboxypeptidase. Our results suggest that in the assay of enkephalin in CSF, the effects of these enzymes should be considered.

Cerebrospinal Fluid↗