Biomedical subjects

N Kudo

Publications and source records attributed to N Kudo.

At least 73 records · Page 4Linked to original sources

PubMed1996

Characterization of 5'AMP-activated protein kinase activity in the heart and its role in inhibiting acetyl-CoA carboxylase during reperfusion following ischemia.

Despite the high expression of 5'AMP activated protein kinase (AMPK) in heart, the activity and function of this enzyme in heart muscle has not been characterized. We demonstrate that rat hearts have a high AMPK activity, comparable to that found in liver, which could be stimulated up to 3-fold by 5'AMP. Cardiac AMPK is also under phosphorylation control, since in vitro incubation of cardiac AMPK with protein phosphatase 2A completely abolished activity, while incubation with ATP/Mg(2+) resulted in over a 2-fold increase in activity. To investigate the function of AMPK in heart muscle, isolated working rat hearts were subjected to 30 min of global no-flow ischemia, followed by 60 min of aerobic reperfusion. AMPK activity was increased in heart at the end of reperfusion compared to aerobic controls (379 +/- 53 (n=5) vs. 139 +/- 19 (n=5) pmol x min(-1) x mg protein(-1), P<0.05, respectively). Treatment of AMPK in vitro with protein phosphatase 2A reversed this activation. Since AMPK can phosphorylate and inactivate acetyl-CoA carboxylase (ACC) in other tissues, and heart ACC has an important role in regulating fatty acid oxidation, we measured ACC activity in hearts reperfused post-ischemia. ACC activity was decreased at the end of reperfusion compared to aerobic controls (3.64 +/- 0.36 (n=9) vs. 10.93 +/- 0.60 (n=11) nmol x min(-1) x mg protein(-1), respectively, P<0.05). A significant negative correlation (r= -0.78) was observed between AMPK activity and ACC activity measured in aerobic and reperfused ischemic hearts. Low ACC activity could be reversed if ACC was extracted from hearts in the absence of phosphatase inhibitors, suggesting that phosphorylation of ACC decreased enzyme activity. This suggests that following ischemia AMPK is phosphorylated and activated (possibly by an AMPK kinase). AMPK then phosphorylates and inactivates ACC. The resultant decrease in malonyl-CoA levels could explain the acceleration of fatty acid oxidation that is observed during reperfusion of ischemic hearts.

AMP-Activated Protein Kinases↗

PubMed1996

Biphasic effect of cadmium ions on the secretion of leukotriene B4 in rabbit alveolar macrophages.

One major role of alveolar macrophages is the production of eicosanoids, which modulate immune and inflammatory processes in the lung. In this study, the effects were investigated of cadmium ions on the secretion of leukotriene (LT)B4 and prostaglandin (PG)E2, predominant products of lipoxygenase and cyclooxygenase, respectively. Cd2+ had an inhibitory effect on the secretion of LTB4 and PGE2 in response to A23187 stimulation at concentrations > 3 x 10(-5)M. This effect can be explained by the inhibition of arachidonic acid (20:4) liberation from membrane phospholipids by Cd2+, because Cd2+ inhibits both [3H] arachidonic acid (20:4) liberation from [3H]20:4-prelabeled macrophages and the cytosolic phospholipase A2 activity. At concentrations < 3 x 10(-5)M, Cd2+ had no effect on PGE2 secretion but showed an augmentation of LTB4 secretion. In vitro study using macrophage lysate showed enhanced LTB4 synthesis from arachidonic acid by Cd2+, which could be responsible for the augmentation of LTB4 secretion in cells. These results indicate that Cd2+ may increase inflammation by increasing LTB4 production in lung.

Analysis of Variance↗

PubMed1996

The treatment of chronic hemodialysis vascular access by directional atherectomy.

Directional atherectomy (DA) was developed as a new therapeutic modality for coronary artery disease. For the past 3 years, we have applied DA intervention to vascular access failure with either poor blood flow rate or high venous pressure. DA intervention was performed on 27 lesions of 16 hemodialyzed patients. A reduction of stenosis to less than 20% of that before treatment was judged a technical success, and the rate of technical success was 84%. All patients showed adequate blood flow rates after DA intervention, indicating initial success. Although restenotic events occurred frequently, repeated DA interventions could be performed successfully. The patency rate at 1 month after DA intervention was 100%, at 3 months 93%, at 6 months 92% and at 12 months 75%. The short-term patency rate of DA was more satisfactory than the results of percutaneous transluminal angioplasty as reported by several investigators. Regarding the site of stenosis, restenotic events were relatively fewer in the lesions occurring at the native vein compared to those at graft-venous anastomotic sites. Eccentric-type stenosis was also associated with fewer restenotic events than circumferential-type stenosis. These results suggest that eccentric-type stenosis at the native vein is the most suitable lesion for the application of DA intervention in terms of long-term patency. As no severe complications occurred after DA intervention, this would appear to be a useful therapeutic modality for the correction of vascular access failure.

Aged↗

PubMed1996

Role of stearoyl-CoA desaturase in the modification of acyl composition of hepatic phosphatidylcholine by peroxisome proliferators.

The relative contribution of stearoyl-CoA desaturase and 1-acylglycerophosphocholine (1-acyl-GPC) acyltransferase, which are induced by peroxisome proliferators, to the increase in the proportion of oleic acid in C-2 position of phosphatidylcholine (PtdCho) in the liver of rats was investigated. Rats were administered either 4-chlorophenoxyisobutyric acid (clofibric acid), 2,2'-(decamethylenedithio)-di-ethanol (tiadenol) or perfluorooctanoic acid in varying doses. With administration of these peroxisome proliferators, the proportion of oleic acid in C-2 position of PtdCho in hepatic microsomes was increased in commensurate with the increase in activities of stearoyl-CoA desaturase and 1-acyl-GPC acyltransferase. Multiple regression analysis revealed that although there is a high correlation among the three parameters examined, the partial correlation between the proportion of oleic acid in the C-2 position and the activity of stearoyl-CoA desaturase is significantly higher than that between the proportion of oleic acid in the C-2 position and the activity of 1-acyl-GPC acyltransferase. The contribution of stearoyl-CoA desaturase to the increase in the proportion of oleic acid in the C-2 position thus appears greater than that of 1-acyl-GPC acyltransferase.

1-Acylglycerophosphocholine O-Acyltransferase↗

PubMed1996

Discovery of mammalian hosts to Gnathostoma nipponicum larvae and prevalence of the larvae in rodents and insectivores.

From September 1993 to November 1995, to clarify the natural infection of Gnathostoma nipponicum (G.n.) larvae in small wild mammals, a total of 313 animals consisted of three species of rodents and two species of insectivores, collected from an endemic area of this nematode in Aomori Prefecture, were investigated. Two species, Rattus norvegicus (R.n.) and Chimarrogale himalayica (C.h.) were infected with G.n. larvae, and the infection rate was extremely high with 27.2% and 72.7% in the former and latter. The infected animals harbored the larvae of 2-10 (mean: 6.0) in R.N. and 2-40 (10.6) in C.h., and a total of 273 larvae was recovered. The all larvae (18) from R.n. and the vast majority of the larvae (216/255: 82.4%) from C.h. were recovered from the musculature, and many encapsulated larvae were found in these portions of C.h. Taxonomically, all the larvae were identified as the advance third-stage larvae (AdL3) of G.n. The body length was 1,056-2,110 microns, and was larger than those of the naturally-infected AdL3 reported from cold-blooded animals. No morphological alterations or death of the larva was observed. From these results, it would seem that R.n. and C.h. are highly susceptible to G.n. larvae, and has very suitable characteristics as the hosts. Furthermore, a hypothesis is advanced that these mammals serves as the plausible paratenic hosts in the life cycle of G.n. This report is the first record of R.n. (Rodentia) and C.h. (Insectivora) naturally-infected with AdL3 of G.n.

Animals↗

PubMed1996

Manifestation of subclinical diabetes insipidus due to pituitary tumor during pregnancy.

We describe a case of diabetes insipidus (DI) due to a pituitary tumor in a 33-year-old pregnant woman who developed a sudden onset of polyuria (over 8 l/day) and polydipsia at 30 weeks of gestation. Her plasma concentration of vasopressin (AVP) was low compared with high serum osmolality (298 mOsm/kg), and her urine output was well controlled by treatment with desmopressin acetate (DDAVP). Cranial magnetic resonance imaging (MRI) demonstrated a 1.8 x 1.2-cm pituitary tumor, but she did not have any disturbance in the release of anterior pituitary hormones. The serum concentration of cystine aminopeptidase (CAP) was within the normal range for a woman at 34 weeks of gestation. After an uncomplicated delivery of a healthy girl, her polyuria gradually resolved. The size of the pituitary tumor gradually decreased in parallel to a reduction in her urine output, but a silent hemorrhage was detected in her pituitary gland 4 weeks after the delivery. Although pregnancy is sometimes associated with central DI, the occurrence of DI due to pituitary tumor under pregnancy is rare. The basal AVP recovered to within the normal range, but the low response of AVP secretion to high osmolality persisted. In this case, pregnancy may affect the manifestation of subclinical DI. This case may therefore enhance our understanding of the mechanisms of DI during pregnancy.

Adenoma↗

PubMed1995

Platelet-activating factor and its structural analogues in the earthworm Eisenia foetida.

The earthworm Eisenia foetida was shown to contain large amounts of ether-containing phospholipids such as alkylacylglycerophosphocholine (61.3% of choline glycerophospholipids) and alkenylacylglycerophosphoethanolamine (66.0% of ethanolamine glycerophospholipids). We also found a substantial amount of ether-containing PAF-like lipid in this animal, its level being increased after the animal is injured. We showed evidence that this PAF-like lipid consists of PAF and PAF analogues containing short chain fatty acids other than acetic acid. Notably, a propionic acid-containing species but not PAF itself, is the most predominant species in this animal. We also confirmed that the earthworms contain enzyme activities involved in the synthesis of PAF and short chain fatty acid-containing PAF analogues. Interestingly, the acetyltransferase activity in earthworms is resistant to high concentrations of the substrate lysophospholipid. Thus, both the structure of the PAF-like lipid and the properties of the enzymes involved in the PAF-like lipid metabolism in the earthworms are somewhat different from those in mammalian tissues.

Acetyltransferases↗

PubMed1995

High rates of fatty acid oxidation during reperfusion of ischemic hearts are associated with a decrease in malonyl-CoA levels due to an increase in 5'-AMP-activated protein kinase inhibition of acetyl-CoA carboxylase.

We determined whether high fatty acid oxidation rates during aerobic reperfusion of ischemic hearts could be explained by a decrease in malonyl-CoA levels, which would relieve inhibition of carnitine palmitoyl-transferase 1, the rate-limiting enzyme involved in mitochondrial uptake of fatty acids. Isolated working rat hearts perfused with 1.2 mM palmitate were subjected to 30 min of global ischemia, followed by 60 min of aerobic reperfusion. Fatty acid oxidation rates during reperfusion were 136% higher than rates seen in aerobically perfused control hearts, despite the fact that cardiac work recovered to only 16% of pre-ischemic values. Neither the activity of carnitine palmitoyltransferase 1, or the IC50 value of malonyl-CoA for carnitine palmitoyl-transferase 1 were altered in mitochondria isolated from aerobic, ischemic, or reperfused ischemic hearts. Levels of malonyl-CoA were extremely low at the end of reperfusion compared to levels seen in aerobic controls, as was the activity of acetyl-CoA carboxylase, the enzyme which produces malonyl-CoA. The activity of 5'-AMP-activated protein kinase, which has been shown to phosphorylate and inactivate acetyl-CoA carboxylase in other tissues, was significantly increased at the end of ischemia, and remained elevated throughout reperfusion. These results suggest that accumulation of 5'-AMP during ischemia results in an activation of AMP-activated protein kinase, which phosphorylates and inactivates ACC during reperfusion. The subsequent decrease in malonyl-CoA levels wil result in accelerated fatty acid oxidation rates during reperfusion of ischemic hearts.

AMP-Activated Protein Kinases↗

PubMed1995

Coenzyme A-dependent cleavage of membrane phospholipids in several rat tissues: ATP-independent acyl-CoA synthesis and the generation of lysophospholipids.

Substantial amounts of acyl-CoA were formed when microsomes from several rat tissues were incubated with varying concentrations of free CoA and bovine serum albumin even in the absence of ATP and Mg2+. For instance, 86 nmol of acyl-CoA was produced when microsomes (5 mg protein) were incubated with 300 microM CoA for 30 min. It was calculated that 1.8% of total fatty acyl residues were converted to acyl-CoA during the incubation. No appreciable amount of acyl-CoA was formed from free fatty acid or from boiled microsomes under the same experimental conditions. These observations indicate that acyl-CoA is formed from microsomal lipids by an enzyme activity distinct from previously known long-chain fatty acyl-CoA synthetase. The apparent Km value for CoA and Vmax were 180 microM and 20 nmol/30 min per mg protein, respectively. We found that several species of acyl-CoA such as arachidonoyl-CoA were preferentially synthesized through the reaction and that several types of phospholipids actually act as acyl donors in the formation of acyl-CoA. Phosphatidylinositol and phosphatidylcholine appear to be preferred substrates. We confirmed that lysophosphatidylinositol and lysophosphatidylcholine were generated along with the formation of acyl-CoA. It seems very likely that CoA-mediated cleavage of phospholipids/ATP-independent acyl-CoA synthesis is implicated in the metabolism of certain types of fatty acyl residues of membranous phospholipids in mammalian cells.

Acyl Coenzyme A↗

PubMed1995

Cloning and characterization of a gene involved in aerial mycelium formation in Streptomyces griseus.

A-factor (2-isocapryloyl-3R-hydroxymethyl-gamma-butyrolactone) is essentially required for aerial mycelium formation and streptomycin production in Streptomyces griseus. A DNA fragment which induced aerial mycelium formation and sporulation in an A-factor-deficient mutant strain, S. griseus HH1, was cloned from this strain on a high-copy-number plasmid. Subcloning and nucleotide sequencing revealed that one open reading frame with 218 amino acids, named AmfC, served as a multicopy suppressor of the aerial mycelium-defective phenotype of the A-factor-deficient strain. The amfC gene did not restore A-factor or streptomycin production, indicating that amfC is involved in aerial mycelium formation independently of secondary metabolic function. Disruption of the chromosomal amfC gene in the wild-type S. griseus strain caused a severe reduction in the abundance of spores but no effect on the shape or size of the spores. The infrequent sporulation of the amfC disruptant was reversed by introduction of amfC on a plasmid. The amfC-defective phenotype was also restored by the orf1590 gene but not by the amfR-amfA-amfB gene cluster. Nucleotide sequences homologous to the amfC gene were distributed in all of 12 Streptomyces species tested, including Streptomyces coelicolor A3(2). The amfC homolog of S. coelicolor A3(2) was cloned and its nucleotide sequence was determined. The AmfC products of S. griseus and S. coelicolor A3(2) showed a 60% identity in their amino acid sequences. Introduction of the amfC gene of S. coelicolor A3(2) into strain HH1 induced aerial mycelium formation and sporulation, which suggests that both play the same functional role in morphogenesis in the strains.

4-Butyrolactone↗

PubMed1995

Pulmonary dirofilariasis in a Japanese hare, Lepus brachyurus angustidens.

A case of pulmonary dirofilariasis in a Japanese hare, Lepus brachyurus angustidens captured in Aomori Prefecture, was first reported in Japan. Two dead worms recovered from the pulmonary artery and detected within an organized arterial thrombus in the lung, were identified as a male and a female young adult Dirofilaria immitis, respectively. Principal lesions in the lung were associated with pulmonary arterial degeneration and consisted of rugose and villous intimal fibrosis, endarteritis with infiltration by numerous eosinophils and mononuclear inflammatory cells, and thrombosis.

Animals↗

PubMed1995

Coenzyme A-dependent modification of fatty acyl chains of rat liver membrane phospholipids: possible involvement of ATP-independent acyl-CoA synthesis.

Certain species of fatty acyl chains of microsomal lipids from rat hepatocytes underwent desaturation when the microsomal fraction was incubated with CoA and NADH. For instance, 18:0, 18:2(n-6), and 20:3(n-6) incorporated into membrane lipids were gradually converted to 18:1(n-9), 18:3(n-6), and 20:4(n-6), respectively. Further, 20:5(n-3) and 18:3(n-6) were metabolized to 22:5(n-3) and 20:4(n-6) respectively, through chain elongation or chain elongation plus subsequent desaturation when malonyl-CoA was present. In contrast to esterified fatty acids, negligible change was observed for fre fatty acids under the same experimental conditions. It is apparent that ATP-independent acyl-CoA synthesis is implicated in such enzymatic modification of fatty acyl chains. The presence of either gel-filtered cytosol or bovine serum albumin markedly potentiated the reaction. However, the addition of ATP and Mg2+ did not accelerate the overall reaction induced in the presence of CoA alone. These results suggest that the pathway of CoA-dependent/ATP-independent modification of fatty acyl chains is sufficiently active to account for the desaturation and chain elongation of fatty acids esterified in membrane lipids, especially phospholipids, of living cells.

Acyl Coenzyme A↗

PubMed1994

Development of spinal reflex pathways from muscle afferents to motoneurones in chick embryos devoid of descending inputs.

1. The synaptic connections of reflex pathways between hindlimb muscle afferents and motoneurones were investigated in chicken embryos. Descending inputs to the lumbar spinal cord were eliminated by removing two to four segments of the thoracic spinal cord at embryonic day 2 (E2; gap operation). Intracellular recordings from motoneurones innervating the lateral gastrocnemius (LG) muscle were performed in isolated spinal cord preparations of normal and gap-operated embryos at E14-E15. 2. In both normal and gap-operated embryos, homonymous and synergistic muscle nerve stimulation evoked EPSPs in LG motoneurones at a short and fixed latency, suggesting that they were evoked monosynaptically. EPSPs from synergistic muscle afferents were much smaller than those from homonymous muscle afferents. The volleys from the antagonistic muscle nerve evoked IPSPs at a longer central latency than found for EPSPs in both embryos. 3. The maximal amplitudes of homonymous and synergistic EPSPs in gap-operated embryos were 1.3 and 1.7 times, respectively, larger than in normal embryos. Homonymous EPSPs were observed in all LG motoneurones examined, but synergistic EPSPs were more common in gap-operated than in normal embryos. 4. Antagonistic IPSPs were more common in motoneurones of gap-operated embryos than in those of normal embryos. Homonymous and synergistic muscle nerve stimulation also elicited IPSPs in LG motoneurones in both normal and gap-operated embryos. IPSPs evoked both by homonymous and by synergistic muscle nerve stimulation were more common in gap-operated than in normal embryos. 5. The spatial pattern of reflex pathways from hindlimb muscle afferents to motoneurones in chick embryos devoid of both supraspinal and long propriospinal inputs to the lumbar spinal cord is similar to that in normal embryos. However, both mono- and polysynaptic connections in these pathways are enhanced by the blockade of descending projections.

Animals↗

PubMed1994

Mercuric chloride induces the production of leukotriene B4 by rabbit alveolar macrophages.

The effects of HgCl2 on the production of leukotriene B4 (LTB4) by rabbit alveolar macrophages were investigated. Alveolar macrophages synthesized only a small amount of LTB4 when incubated in Hanks' balanced salt solution (HBSS) in the absence of stimuli or chemical reagents (0.2 +/- 0.1 ng/10(6) cells). The amount of LTB4 synthesized was greatly enhanced when macrophages were incubated with 5 x 10(-6) M HgCl2 (5.3 +/- 0.2 ng/10(6) cells). Increases in levels of free arachidonic acid (20:4), a precursor of eicosanoids, were also observed on treatment of [3H]20:4-labeled cells with HgCl2 in a concentration-dependent manner. We confirmed that [3H]20:4 was mainly liberated from the alkenyl subclass of ethanolamine glycerophospholipids (EGP). Degradation of alkenyl-EGP was also observed when HgCl2 and [3H]20:4-labeled lipids were incubated in HBSS, resulting in an increase in the level of [3H]20:4-labeled lysoEGP. When a microsomal fraction prepared from macrophages was added to the same mixture, [3H]20:4 was liberated from [3H]20:4-containing lysoEGP. These results suggest that the alkenyl linkage of EGP was degraded in the presence of HgCl2 with resultant formation of lysoEGP which was subsequently hydrolyzed by lysophospholipase. As a consequence, the level of free 20:4 in and the rate of production of LTB4 by alveolar macrophages were elevated.

Acylation↗

PubMed1993

Reproductive risk in mating between two translocation carriers: case report and review of the literature.

We conducted a study to determine the reproductive risk in a couple who were translocation carriers. This couple, who carried balanced reciprocal translocations, experienced habitual abortions. The wife had a karyotype of 46,XX,t(7;13)(p15.3;q12.3) and the husband of 46,XY,t(1;7)(p11.1;p11.1). Chromosome study of their fourth abortus demonstrated a chimera consisting of two cell lines with a 46,XY and a 46,XX,t(1;7)(p11.1;p11.1)pat, -13, + der(7)t(7;13)(p15.3;q12.3)mat, karyotype. A review of the literature indicates that the risk of having unbalanced live offspring or of spontaneous abortion/stillborns is similar in couples in whom both were translocation carriers and in couples in whom one individual was a translocation carrier. The apparent lack of increased reproductive failure may result from the selective disadvantage of aneusomic gametes at fertilization or very early spontaneous abortions of unbalanced conceptuses.

Abortion, Habitual↗

PubMed1993

Acute conduction block in vitro following exposure to antiganglioside sera.

We studied the role of antiganglioside antibodies in the pathogenesis of autoimmune neuropathies using an in vitro preparation of a rat sciatic nerve. Human and rabbit sera with high titers of the antibodies were applied to a restricted segment of the sciatic nerve mounted in a recording chamber, and the compound nerve action potentials of the myelinated and unmyelinated fibers were observed. Myelinated fiber conduction became blocked at the segment within a few hours, whereas the unmyelinated fiber conduction remained unchanged. These results suggest that antiganglioside sera directly produce an acute conduction block only in myelinated nerve fibers and that this in vitro model is useful for studying the ionic mechanism by which the acute conduction block occurs.

Action Potentials↗

PubMed1993

Development of descending fibers to the rat embryonic spinal cord.

Onset and development of descending pathways to the rat embryonic spinal cord was examined by the use of retrograde transport of horseradish peroxidase (HRP). HRP was injected in the lower thoracic segments of the spinal cord of embryos ranging in age from embryonic day (E)14.5 to E20.5. A small number of labelled cells were found in the brain stem nuclei on E14.5: they were located in medullary as well as pontine reticular formation, lateral vestibular nucleus and interstitial nucleus of the medial longitudinal fasciculus. By E15.5 labelled cells were observed in the reticular formation of the caudal part of the medulla oblongata, medullary raphe nuclei, locus coeruleus, subcoeruleus nucleus, Barrington's nucleus and central gray of the midbrain. Cells in the red nucleus and in the nucleus of the solitary tract were labelled by E 16.5 and E17.5, respectively. Thereafter, labelled cells were first found in a few other nuclei: the gracile nucleus on E19.5 and the paraventricular nucleus on E20.5. The present study demonstrated that all the major supraspinal inputs except corticospinal fibers project to the lower thoracic spinal cord by E20.5.

Animals↗

PubMed1992

Resetting from low threshold afferents of N-methyl-D-aspartate-induced locomotor rhythm in the isolated spinal cord-hindlimb preparation from newborn rats.

In this study we have investigated the effects of low threshold afferent stimulation on the centrally generated locomotor rhythm in an isolated spinal cord-hindlimb preparation from newborn (0-3 days old) rats. Locomotor activity was induced by bath application of N-methyl-D-aspartate (NMDA). Stimulation of low threshold afferents (below 2 times threshold (x T) for the incoming volley) in L2 and L3, but not L4 and L5 dorsal roots resets the ongoing rhythm. This is due to an abrupt excitation of the L2 and L3 ventral root bursts and an inhibition of the L5 ventral root burst on the ipsilateral side followed by reciprocal effects on the contralateral side. Similar effects were seen after stimulation of the quadriceps nerve with weak intensity (below 1.8 x T). We conclude that low threshold muscle afferents, possible group I afferents, have access to central pattern generators early in postnatal life and suggest that these findings may give an important opening in ontogenetic studies of how neural networks are assembled.

Afferent Pathways↗