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Biomedical subjects

K Okano

Publications and source records attributed to K Okano.

At least 199 records · Page 11Linked to original sources
PubMed1988

Two pharmacologically distinct receptors mediate two postsynaptic potential (PSP) components in the afferent synapse of the Plotosus eletroreceptor.

In the Plotosus electroreceptor, strong brief excitatory pulses to the ampulla induced bi-phasic postsynaptic potential (PSP), externally recorded in the afferent nerves, a fast PSP during the pulse and a later slow PSP. Both PSPs increased in size on increasing stimulus intensity, with a lower saturation level for the slow PSP. Time to peak for the fast PSP gradedly decreased to below 10 ms on stronger stimuli, while in contrast that for the slow PSP increased to over 100 ms. The two PSPs were also readily distinguished pharmacologically. Some Glu antagonists, kynurenic acid and gamma-DGG, suppressed the slow PSP, but had little effect on the fast PSP. The suppression was dose-dependent and reversible over the entire range of input-output relations. In addition, L-aspartate at 100-300 microM markedly prolonged the slow PSP, but had little effect on the fast PSP. These results indicate two distinct populations of postsynaptic receptors: one for the slow PSP pharmacologically corresponding to a Glu receptor, and the other for the fast PSP of still unknown property. The two PSPs, though discriminated under specified stimulus conditions, seem to be involved also in the synaptic responses of longer duration in general.

Action Potentials↗
PubMed1988

Induction of achromosomal cleavage by hydroxyurea in starfish embryo and the reversal by a combination of deoxyadenosine and deoxycytidine: possible involvement of salvage pathway for deoxynucleoside triphosphate biosynthesis in the presence of hydroxyurea.

Effects of hydroxyurea, an inhibitor of ribonucleotide reductase, on cleavage of starfish embryos were studied. In the presence of 1 mM hydroxyurea, fertilized eggs of the starfish, Asterina pectinifera, cleaved up to the 256-cell stage and decomposed before blastulation. Before the 16-cell stage, each blastomere contained a normal nucleus or chromosomes with mitotic apparatus. The cleavage after the 16-cell stage was slow compared to the control embryos, and not all blastomeres contained a nucleus or normal chromosomes. During the fifth cell division (between 16-cell- and 32-cell-stage embryos), chromatin mass unassociated with the mitotic apparatus remained near the cleavage furrow. When hydroxyurea was removed before the 16-cell stage, the embryos developed to normal bipinnalia larvae via normal blastulae. However, the embryos were disintegrated before blastulation when hydroxyurea was removed after the 32-cell stage. DNA synthesis was normally observed before the 16-cell stage but not after the 16-cell stage, but dNTP contents in the embryos remained low throughout development in the presence of hydroxyurea. The achromosomal cleavage observed in the presence of hydroxyurea was reversed by the combination of extracellular dAR and dCR. Therefore, it is assumed that the synthesis of dNTPs required for DNA synthesis in the presence of hydroxyurea occurs via the salvage pathway using deoxynucleosides (dNR) (dNR to dNTP via dNMP and dNDP).

Animals↗
PubMed1988

Structural characterization of recombinant human interferon-gammas derived from two different mammalian cells.

Recombinant human interferon-gammas (rHuIFN-gamma s) were obtained from two different mammalian cells (mouse C127 cells and Chinese hamster ovary, CHO, cells) cultured in a microcarrier culture system. Both rHuIFN-gamma s were purified using sequential chromatographies for their comparison of structural properties. The peptide maps of HuIFN-gamma s digested with V8 protease and Western blot analysis demonstrated that C127 cells yielded mainly about 25kDa component and CHO cells produced about 25kDa and about 20kDa components. By the identification of glycosylated peptides, it was suggested that 20kDa and 25kDa components are glycosylated at one and at two sites, respectively. C-terminal amino acid sequence analysis indicated that both rHuIFN-gamma s consisted of at least six different species lacking 2 to 16 amino acid residues from C-terminus, so that C-termini of both rHuIFN-gamma s were slightly different from each other. Amino acid sequence and composition analyses of N-terminal peptides demonstrated that N-termini of both rHuIFN-gamma s were blocked and were supposed to be identical with that of natural HuIFN-gamma. These results suggested that different molecular heterogeneities of rHuIFN-gamma s resulted from the difference of post-translational modifications of host cells.

Amino Acid Sequence↗
PubMed1988

Neuronal activity in cortical motor areas related to ipsilateral, contralateral, and bilateral digit movements of the monkey.

1. Single cell activity was studied in the precentral (PCM), premotor (PM), and supplementary (SMA) motor cortex of the monkey to compare magnitudes of activity changes in relation to ipsilateral, contralateral, and bilateral digit movements. 2. Three Japanese monkeys were trained to press a small key with the right or left hand, or with both hands, in accordance with visual instruction signals given 2.6-5.4 s before a visual movement-trigger signal. Great care was taken to train the animal to use only the required part of the limb. As a result of extensive training, electromyographic (EMG) studies revealed that muscle activities before the key press were limited to the digit and hand muscles of the limb instructed to move. No overt increase or decrease in activity was detectable in the proximal limb or body muscles in relation to the key-press movements or instructions. 3. Even though the movement was thus limited to distal forelimb, distinct ipsilateral relationships were observed in 8.2% of the task-related PCM neurons. They changed their activity before ipsilateral and bilateral (but not before contralateral) key press. 4. A majority of the neurons recorded from the digit area of PCM (mostly limited to the anterior bank of the central sulcus) exhibited a contralateral relationship; namely the activity increased or decreased before the onset of the contralateral and bilateral key-press movements. In most of them, the magnitudes of the activity changes before the contralateral and bilateral movements were similar. 5. In proximal limb and trunk areas of PCM and also in the somatosensory cortex, no neurons were found to exhibit distinct relations to any of the key-press movements. 6. In both SMA and PM, a number of neurons exhibited relationships of the type never or only rarely observed in the primary motor cortex. Thirty-seven percent of SMA and 62% of PM neurons exhibited premovement activity changes before all of the key-press movements. The movement-specific type of activity was observed in 28% of SMA and 16% of PM neurons. In these neurons, the activity changes were observed in relation to only one of the right or left key-press movements or exclusively in relation to the bilateral key press. Neuronal activity resembling the majority of the PCM neurons (contralateral type) was observed in 31% of SMA and 13% of PM neurons. 7. Instruction-induced changes in activity were more often found in the secondary than in the primary motor area.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1988

Decreased T-colony formation by lymphocytes from patients with focal glomerular sclerosis.

The T-colony-forming capacity was examined in 13 normal subjects and 8 patients with biopsy-proven focal glomerular sclerosis (FGS). Fifteen patients with chronic mesangial proliferative glomerulonephritis (CGN) without renal insufficiency were studied as a disease control. The two main assays used were the counting of T colonies formed by the patients' lymphocytes, and the measurement of T-colony-forming activity in conditioned medium from cultures of patients' lymphocytes. The levels of T-colony-forming cells (TCFC) and T-colony-stimulating factor (TCSF) were decreased in patients with FGS compared with those in normal controls and lower in FGS patients with the nephrotic syndrome (NS) than in those without NS. In contrast, these parameters in CGN patients with or without NS did not differ from normal subjects. TCSF activity for TCFC in both normal individuals and FGS patients was removed from media conditioned by phytohemagglutinin (PHA)-stimulated peripheral blood lymphocytes (PHA-LCM) with interleukin-2 (IL-2) receptor bearing cultured T cells. These in vitro findings suggest that IL-2 is the essential factor contained in PHA-LCM. Thus, depressed TCFC in FGS patients with NS may result in part from impaired generation of TCSF by lymphocytes.

Absorption↗
PubMed1988

Purification and characterization of human placental aminopeptidase A.

Human placental aminopeptidase A (AAP) was purified 3,900-fold from human placenta and characterized. The enzyme was solubilized from membrane fractions with Triton X-100, then subjected to trypsin digestion, zinc sulfate fractionation, chromatographies with DE-52, Sephacryl S-300, and hydroxylapatite, affinity chromatography with Bestatin-Sepharose 4B, and finally immunoaffinity chromatography with the antibody against microsomal leucine aminopeptidase (LAP). Aminopeptidase A was completely separated from leucine aminopeptidase by the immunoaffinity chromatography. The apparent relative molecular mass (Mr) of the enzyme was estimated to be 280,000 by gel filtration. The purified enzyme was most active at pH 7.1 with L-aspartyl-beta-naphthylamide (L-Asp-NA) as substrate; the Km value for this substrate was 4.0 mmol/l in the presence of Ca2+. Human placental aminopeptidase A was markedly activated by alkaline earth metals (Ca2+, Sr2+, Ba2+), but strongly inhibited by metal chelating agents such as EDTA and o-phenanthroline. The highest activity was observed with L-glutamyl-beta-naphthylamide, while only minimal hydrolysis was found with some neutral and basic amino acid beta-naphthylamides.

Aminopeptidases↗
PubMed1988

Constitutive long-term production and characterization of recombinant human interferon-gammas from two different mammalian cells.

Two expression plasmids (pSVIFN gamma/BPV97 and pSVIFN gamma/AdDHFR) for constitutive production of human interferon-gamma (HuIFN-gamma) were constructed and introduced into the two different mammalian cell lines, mouse C127 cells and Chinese hamster ovary (CHO) cells. Genetically engineered C127 and CHO cells grew on microcarriers having high productivity of HuIFN-gammas for at least six months. Isoelectric focusing patterns and molecular weight analyses suggest that C127- and CHO-HuIFN-gammas are glycoproteins and that both HuIFN-gammas have different molecular structures. The development of a microcarrier culture system for genetically engineered mammalian cells has enabled us to prepare glycosylated HuIFN-gammas on a large scale.

Animals↗
PubMed1988

Production of C3 nephritic factor by cultured lymphocytes derived from a patient with partial lipodystrophy.

C3 nephritic factor (C3 NeF) has been found mainly in the sera of patients with membranoproliferative glomerulonephritis (MPGN) and partial lipodystrophy (PLD). We examined whether peripheral blood mononuclear cells (PBMC) from a patient with PLD could produce C3 NeF. We investigated the in vitro immunoglobulin synthesis of PBMC with mitogen. We further studied the C3bBb stabilizing activity and undertook agglutination assays of the IgG obtained from the culture supernatants. The patient IgG was able to agglutinate only EAC4b3bBb cells and none of the other intermediate cells. We this demonstrated that C3 NeF could be produced in vitro by PBMC derived from a patient with PLD.

Child↗
PubMed1987

Source of elevated serum mitochondrial creatine kinase activity in patients with malignancy.

Mitochondrial creatine kinase (CK-mit) is increased in cancer tissues of the digestive tract. There is no difference in molecular weight, electrophoretic and kinetic properties between the isoenzymes extracted from the tumor and those from the adjacent normal tissues. High non-CK-M/total CK activity ratios in some sera from cancer patients probably reflect leakage of CK-mit from the tumor tissues.

Adult↗
PubMed1987

Neuronal activities in the primate motor fields of the agranular frontal cortex preceding visually triggered and self-paced movement.

Single cell activity was examined in the three motor fields of the monkey frontal cortex with the aim of comparing the neuronal activity preceding movements triggered by a visual signal to that preceding nontriggered (self-paced) movements. The following findings emerged from this study. 1. Neuronal activity changes were observed at two different phases in relation to the movement onset; the short-lead type observed within 480 ms prior to the movement onset and the long-lead type, beginning earlier (typically 1 to 2 s). 2. Neurons in both the supplementary motor area (SMA) and premotor area (PM) exhibited the short-lead activity changes prior to the triggered and self-paced movement. Their magnitudes were similar in 63% of SMA and in 36% of PM neurons, whether the movement was triggered or self-paced. 3. SMA neurons, as a whole, were not less active before the triggered than self-paced movement. 4. On the other hand, as many as 92 PM neurons (61%) were related exclusively or peferentially to the triggered movement. 5. The majority of precentral motor cortex (MC) neurons exhibited similar activity changes before the two modes of movement initiation. 6. The long lead type of activity changes were observed mainly prior to the self-paced and much less frequently before the triggered movement. They were particularly abundant among SMA neurons. These results do not support the simple dichotomy hypothesis that SMA primarily takes part in self-paced movement and PM is only involved in visually triggered movement. However, PM neurons show relatively more prominent responses to the visual trigger signal and SMA neurons are intimately related to a long-lasting process leading to initiation of the self-paced movement.

Animals↗
PubMed1987

[13C]methacetin breath test for evaluation of liver damage.

Methacetin undergoes rapid O-dealkylation by hepatic microsomal enzyme systems, and the resultant CO2 is present in the expired air. The rate of O-dealkylation of methacetin was assessed by the [13C]methacetin breath test in seven healthy volunteers and 30 patients with histologically proven chronic liver diseases. The 30-min recovery of orally administered [13C]methacetin as 13CO2 in the exhaled air was significantly reduced in patients with chronic aggressive hepatitis and in those with liver cirrhosis but not in patients with chronic persistent hepatitis or healthy controls. Patients with either advanced cirrhosis or hepatocellular carcinoma showed significantly lower values than those with well-compensated cirrhosis. The levels in two patients with late primary biliary cirrhosis were reduced. These results show that the severity of liver damage can be effectively evaluated by [13C]methacetin breath test. In addition, this test is simple, safe, and time efficient.

Acetamides↗
PubMed1987

Molecular cloning of complementary DNA for human medullasin: an inflammatory serine protease in bone marrow cells.

Medullasin, an inflammatory serine protease in bone marrow cells, modifies the functions of natural killer cells, monocytes, and granulocytes. We have cloned a medullasin cDNA from a human acute promyelocytic cell (ML3) cDNA library using oligonucleotide probes synthesized from the information of N-terminal amino acid sequence of natural medullasin. The cDNA contained a long open reading frame encoding 237 amino acid residues beginning from the second amino acid of natural meduallasin. The deduced amino acid sequence of medullasin shows a typical serine protease structure, with 41% homology with pig elastase 1.

Amino Acid Sequence↗
PubMed1986

Incipient germ cell tumor in Sertoli-cell-only syndrome testis, accompanied with retroperitoneal teratocarcinoma and widespread metastases.

Incipient germ cell tumor in Sertoli-cell-only syndrome testis was examined in an autopsy case of retroperitoneal teratocarcinoma with widespread metastases. Although both testes of a 28-year-old man had clinically been small and free from tumor mass to palpation, histopathological examinations revealed a malignancy in the right testis with the appearance of Sertoli-cell-only syndrome. The left testis showed solely the histology of Sertoli-cell-only syndrome. The testicular malignancy consisted of undifferentiated, atypical germ cells mainly confined within approximately one-tenth of seminiferous tubules, and only one small cartilage nodule. Some tubules showed intratubular growth pattern suggestive of seminoma. A few syncytiotrophoblast-like giant cells occurred in the tubules. These findings seem to furnish substantial evidence to the concept that atypical germ cells are the origin of testicular germ cell tumors of different types.

Adult↗