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Biomedical subjects

K Nagai

Publications and source records attributed to K Nagai.

At least 19 recordsLinked to original sources
PubMed1992

Circadian variation of [3H]dopamine handling in adrenal chromaffin cells of mice.

Circadian variation of exogenous [3H]dopamine handling by adrenal chromaffin cells was examined using mice habituated to 08.00-20.00 h light cycle. Experiments were carried out at 00.00, 06.00, 12.00 and 18.00 h. [3H]Dopamine-derived radioactivity reached a peak at 2 min then decreased rapidly except at 18.00 h, when no particular peak was observed at 2 min but at 30 min in both intact and denervated adrenals. In intact adrenals, the 2-min peak at 06.00 h was suppressed by corticosterone while in denervated adrenals the 2-min peak remained. The present result indicates that quick turnover of [3H]dopamine was suppressed by a steroid surge at about 2 h before light to dark alteration. Normal innervation is necessary for corticosterone-induced suppression.

Adrenal Glands↗
PubMed1992

Association of oriC region of Escherichia coli chromosome with outer membrane: effects of culture condition.

We isolated complexes containing oriC region DNA and outer membrane, named origin complex heavy and origin complex light, from the cells of Escherichia coli cultured in media with poor or rich of nutrients, and found the different nature of association between origin DNA and outer membrane. The ratio of origin complex light to origin complex heavy prepared from the cells cultured in rich media was lower than that of those from minimal medium culture. Outer membrane preparations from the cells grown in nutritious media had high abilities of association with origin complex light in the presence of magnesium. These results indicated that the number of binding sites on outer membrane with origin region DNA increase, or the binding between outer membrane and origin region DNA become more rigid, when cells grow faster and DNA replication initiate more frequently in a nutritious medium.

Binding Sites↗
PubMed1992

Effect of orbital enucleation on glucose homeostasis and morphology of the suprachiasmatic nucleus.

In rats there is a direct neural connection called the retinohypothalamic tract (RHT) from retinal ganglion cells to the ventrolateral part of the suprachiasmatic nucleus (SCN), which has neurons containing vasoactive intestinal polypeptide (VIP)-like substance. Previously, we observed that bilateral orbital enucleation (blinding) caused temporary suppression of the hyperglycemic response to intracranial injection of 2-deoxy-D-glucose (2DG) from week 4 to 6 after blinding. Moreover, bilateral lesions of the SCN had a similar effect. From these findings, we supposed that the neurons responsible for the hyperglycemic response to 2DG were present in the SCN, that after blinding these neurons temporarily lost their activity, and that this functional change was reflected in the morphology of the SCN. To investigate this possibility, we examined the morphological changes of the SCN by Nissl staining and immunohistochemical studies with anti-VIP and anti-peptide histidine isoleucine (PHI) antibodies in blinded rats, and the relationship between these morphological changes and the hyperglycemic response to 2DG. After surgical blinding, we observed following changes. (1) The optic chiasm became thinner. (2) The SCN became displaced rostrally. (3) The density of neurons in the middle to caudal part of the SCN, where the retinal ganglion cells projected, decreased markedly without change in cell number during the period when the hyperglycemic response to intracranial injection of 2DG was temporarily suppressed after blinding. The first and second changes seemed to reflect reduction of fibers and axon terminals of retinal ganglion cells and their innervation, respectively. As the third change was parallel with suppression of the hyperglycemic response to 2DG injection, it may reflect functional change of the neurons in the SCN that are responsible for the hyperglycemia due to 2DG.

Animals↗
PubMed1992

Slope of the end-systolic pressure-volume relation derived from single beat analysis is not always sensitive to positive inotropic stimuli in humans.

Single beat estimation of the slope of the end-systolic pressure-volume relation assumes symmetric left ventricular pressure increase and decay and requires extrapolation of peak isovolumic developed pressure (Pmax) from the left ventricular pressure curve of an ejection contraction. To test the sensitivity of this slope to positive inotropic stimuli, biplane cineangiocardiography and simultaneous high-fidelity left ventricular pressure measurements were performed in 50 patients with heart disease. The end-systolic pressure-volume relations were assessed under baseline conditions and during norepinephrine infusion (n = 19) or after postextrasystolic potentiation (n = 24), or both (n = 7). Norepinephrine did not change left ventricular end-systolic volume despite significant elevations of end-systolic pressure. Postextrasystolic potentiation significantly decreased end-systolic volume in association with an unaltered left ventricular end-systolic pressure. The potentiation significantly decreased the pressure half-time of contraction, an index of the speed of the left ventricular pressure increase, while it increased the pressure half-time of relaxation, an index of the speed of the pressure decline, indicating asymmetric pressure increase and decay. The slope of the end-systolic pressure-volume relation increased from 3.3 to 4.4 mm Hg/ml/m2 (p less than 0.001) during norepinephrine infusion. In contrast, despite an augmented contractility, the slope decreased significantly from 3.2 to 2.4 mm Hg/ml/m2 (p less than 0.0001) after the potentiation. The slope showed a high correlation with Pmax (r = 0.86, p less than 0.0001, n = 107). Thus, the slope of the end-systolic pressure-volume relation derived from single beat analysis is not always sensitive to inotropic interventions.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Immobilized ferredoxins for affinity chromatography of ferredoxin-dependent enzymes.

An immobilized ferredoxin more stable than the conventional immobilized spinach ferrodoxin was prepared by reacting CNBr-Sepharose with ferredoxins isolated from barley and Synechococcus vulcanus, a thermophilic blue-green alga. The dissociation constants of immobilized ferredoxin from spinach, barley and S. vulcanus for spinach ferredoxin-NADP reductase were 0.922, 2.505 and 5.209 microM, respectively, whereas those for barley ferredoxin-NADP reductase were 1.159, 0.579 and 2.851 microM, respectively. The order of stability was S. vulcanus greater than barley greater than spinach. The immobilized ferredoxin was applied to the simultaneous detection of ferredoxin-dependent enzymes in spinach chloroplasts. Over 20 polypeptides were detected. Synechococcus ferredoxin could also be immobilized on a Toyopearl gel and repeatedly used in an automated high-performance liquid chromatographic system.

Chemical Phenomena↗
PubMed1992

Structure and antitumor activity of a branched (1----3)-beta-D-glucan from the alkaline extract of Amanita muscaria.

A beta-(1----6)-branched (1----3)-beta-D-glucan(AM-ASN) was isolated from the alkaline extract of the fruiting bodies of Amanita muscaria. AM-ASN had [alpha]D - 11 degrees in 0.5 M sodium hydroxide. Its estimated molecular weight was 95,000 in this alkaline solution and 260,000 in a neutral solution. The branches in the glucan were primarily single, (1----6)-linked D-glucopyranosyl groups, two for every seven residues in the (1----3)-linked main chain. AM-ASN exhibited significant antitumor activity against Sarcoma 180 in mice, and a mixture of AM-ASN with mitomycin C was more effective against the tumor than mitomycin C only.

Amanita↗
PubMed1992

Photodestruction of fluorophores and optimum conditions for trace DNA detection by automated DNA sequencer.

Although automated DNA sequencers are becoming popular, their sensitivity in detecting DNA bands is still around 10(-17) mole/band. The sensitivity of a system depends on the laser power, labeling fluorophore, and the fluorescence-collecting yield. The emission and photodestruction cross-sections of the fluorophores are critical in optimizing the irradiated laser power and the migration speeds of DNA fragments to achieve high sensitivity. We investigated photodestruction cross-sections of various fluorophores to optimize the irradiation laser power. In addition, we used a cylindrical lens system to improve the fluorescence-collecting yield of a DNA sequencer using side entry laser irradiation. Fluoresceine isothiocyanate (FITC) commonly used in fluorescence studies, is very photo-destructive, the cross-section of the destruction being about 3.8 x 10(-20) cm2 in buffer solution while that of Texas Red is 1.5 x 10(-21) cm2. When the time for DNA fragments to transit through the irradiated region is 11 s, the optimum laser powers are 0.9 mW, with an Ar laser (488 nm) for FITC-DNA, and 18 mW, with an He-Ne laser (594 nm) for Texas Red DNA. We have developed a DNA sequencer, with a cylindrical lens system which improves the fluorescence-collecting efficiency by a factor of 4, and an He-Ne laser (5 mW). Although the sequencer uses a slab gel, an ultra-high sensitivity of 5 x 10(-20) mole/band (S/N-4) was achieved under optimized conditions.

Autoanalysis↗
PubMed1992

ATPase activity of SopA, a protein essential for active partitioning of F plasmid.

The sopA, B, C genes of the F plasmid play an essential role in plasmid partitioning during cell division in Escherichia coli. In this paper, the products of the sopA and sopB genes were isolated and their biochemical activities studied. [alpha-32P]ATP was cross-linked to the SopA protein by UV irradiation; this cross-linking was observed only in the presence of magnesium ion, and was competitively inhibited in the presence of non-radioactive ATP, ADP and dATP, but not other NTPs or dNTPs. In contrast, no ATP binding activity was detected for the SopB protein. The SopA protein showed a modest magnesium ion-dependent ATPase activity and this activity was stimulated in the presence of DNA. The ATPase activity in the presence of DNA was further stimulated by addition of the SopB protein. However, the SopB protein alone failed to stimulate the ATPase activity.

Adenosine Triphosphatases↗
PubMed1992

Accumulation of 99mTc-HM-PAO in photon deficient areas in bone scan of bone metastasis from hepatocellular carcinoma.

To evaluate bone metastasis from hepatocellular carcinoma (HCC), both bone and 99mTc-HM-PAO scintigraphies were performed in six patients with clinically and pathologically confirmed HCC. Two patients had a bone scintigram which revealed abnormal accumulation in the skull base, pelvic bone and thoracic spine. The 99mTc-HM-PAO scans of both these patients also showed abnormal accumulation in the same sites. The bone scintigrams in one patient revealed not only abnormal accumulation in the ribs but also photon deficient areas in the sternum, thoracic spine and femur, while 99mTc-HM-PAO scans showed abnormal accumulation in all these sites. In three patients, bone scintigraphy revealed photon deficient areas in the ribs, pelvic bone and femur, and their 99mTc-HM-PAO scintigrams showed abnormal accumulation in the same sites. Thus, it was shown that, in the detection of bone metastasis from HCC by means of bone scintigraphy, it was necessary to pay attention to hot and cold lesions, and that a combination study with 99mTc-phosphorous compounds and 99mTc-HM-PAO was useful in evaluating these lesions.

Aged↗
PubMed1992

A case of rheumatoid arthritis associated with silent thyroiditis.

A 41-year-old female with rheumatoid arthritis had nontender enlarged thyroid gland. Thyroid function tests revealed increased concentrations of serum free T3 (FT3, 10.8 pmol/L) and free T4 (FT4, 31.1 pmol/L) with suppressed concentration of thyrotropin (TSH, lower than 0.1 mU/L) and low 24-hour thyroidal radioactive iodine uptake (1.6%). Serum thyrotropin receptor antibody (TRAb) was negative (0%) and she had positive anti-thyroglobulin and anti-microsomal antibodies. A diagnosis of silent thyroiditis was made based on laboratory findings. Serum concentrations of FT3 and FT4 normalized one month later without treatment. The causal relationship between the two diseases is discussed.

Adult↗
PubMed1992

Endothelin-3 modification of dopamine release in anaesthetised rat striatum; an in vivo microdialysis study.

Endothelin-3 (ET-3), a member of the vasoconstrictive peptide family, has recently been recognized as a neuropeptide. We used brain microdialysis and on-line HPLC to examine the effect of ET-3 on the basal outflow of monoamines and their metabolites in the ketamine-anaesthetised rat striatum in vivo. Although intrastriatal infusion of ET-3 (40 pmol/rat) did not change basal dopamine (DA) release, after perfusion of DA releasing agent (5 x 10(-5) M ouabain or 120 mM KCl), ET-3 could increase the DA level. Further, these effects of ET-3 were attenuated by calcium-free Ringer. These data indicated that ET-3 may act by modifying the exocytosis from the striatum of rat brain to enhance DA release after depolarization induced by an agent such as KCl or ouabain.

Amines↗
PubMed1992

Light enhances sympathetic and suppresses vagal outflows and lesions including the suprachiasmatic nucleus eliminate these changes in rats.

Neurons in the suprachiasmatic nucleus (SCN) are suggested to be involved in the mechanism of glucose homeostasis. This mechanism was examined by studies on the effect of illumination on the activity of autonomic efferents to the adrenals, pancreas and liver. Exposure of one eye of anesthetized rats to light enhanced the efferent activity of the adrenal nerve and suppressed that of vagal pancreatic and hepatic nerves. No change in efferent activities of these nerves was observed on light-stimulation of rats with lesions that included the bilateral SCN. These findings indicate that light signals modulate visceral functions including metabolic processes through the retinohypothalamic tract probably via the SCN to autonomic efferent pathways innervating visceral organs.

Adrenal Glands↗
PubMed1992

Chromosome 11 rearrangement at band 11q21 in a patient with essential thrombocythemia.

A case of essential thrombocythemia with a partial deletion of the long arm of chromosome 11, del(11)(q21) as a sole chromosomal anomaly is reported. Rearrangement of chromosome 11 at band 11q21 has been reported in six patients with chronic myeloproliferative disorders: four with post-polycythemic myelofibrosis, one with myelofibrosis with myeloid metaplasia, and one with Ph+ chronic myeloid leukemia in blastic phase. Except for the last patient, all patients had been treated with 32P and/or an alkylating agent prior to cytogenetic examination. This is the first report of the 11q21 abnormality in essential thrombocythemia seen at diagnosis.

Adult↗
PubMed1992

Endogenous inhibitors of human placental prostaglandin dehydrogenase.

The presence of endogenous inhibitors of NAD(+)-dependent 15-hydroxyprostaglandin dehydrogenase (PGDH) has been indicated by increasing total activity after the initial purification step of PGDH in human placenta. Based on this observation, we tried to characterize and analyze endogenous inhibitors of PGDH in human placenta in this study. The inhibitors were extracted from the supernatant by precipitation at pH 5.2 and partially purified by acetone precipitation and by thin layer chromatography. The inhibitors were stable to heating at 100 degrees C for 10 min, and to trypsin digestion. The pattern of inhibition was competitive with regard to PGE2 and uncompetitive with regard to NAD at pH 8.0. The Ki value for PGE2 was 18.9 microM. Analysis by gas chromatography and mass spectrometry indicated that the inhibitors consisted of fatty acids which were palmitic, stearic, oleic and linoleic acids. Myristic, palmitic and stearic acids were confirmed to exert an inhibitory action on PGDH and showed a competitive inhibition pattern. Stearic acid was less potent in inhibition than other fatty acids. These findings suggest that intracellular fatty acids may play a unique role in the control of PGDH activity.

Binding, Competitive↗
PubMed1992

Effects of saturated fatty acids on prostaglandin E 9-keto-reductase.

We examined the effects of three saturated fatty acids (myristic acid 14:0, palmitic acid 16:0, and stearic acid 18:0) on prostaglandin E 9-ketoreductase (PGE-9-KR, EC 1.1.1.189), which catalyzes the conversion of prostaglandin E2 (PGE2) into prostaglandin F2 alpha (PGF2 alpha). Palmitic acid inhibited PGE-9-KR activity dose-dependently, whereas the other two fatty acids had no effect. In spite of the structural similarity of these fatty acids, our findings suggest that, of the three, only palmitic acid has an inhibitory effect on PGE-9-KR.

Catalysis↗