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Biomedical subjects

E Miyamoto

Publications and source records attributed to E Miyamoto.

At least 73 records · Page 4Linked to original sources
PubMed1999

Preparation and drug retention of biodegradable chitosan gel beads.

Chitosan (CS) gel beads containing drug could be prepared in amino acid solutions of pH about 9, despite the requirement for a pH above 12 for gelation in water. This phenomenon was observed not only in amino acid solutions but also in solutions of compounds having amino groups. A solute concentration of more than 10% was required for preparation of gel beads at pH 9. Gelation of the CS beads required about 25 to 40 min, depending on the species of amino acid. Lidocaine hydrochloride (LC) as a model drug was retained in the beads to about 20 to 35% of the theoretical total amount, despite being a water-soluble drug. The release of LC from the CS gel beads was prolonged. The release pattern was not affected by the species of amino acid or CS, or the preparation time.

Biocompatible Materials↗
PubMed1999

Current studies on a working model of CaM kinase II in hippocampal long-term potentiation and memory.

There have been recent advances in understanding the molecular basis of the long-term potentiation (LTP) of synaptic transmission in the hippocampus. This review documents current views on mechanisms underlying LTP induction, from activation of the NMDA receptor to stimulation of Ca2+/calmodulin-dependent protein kinase II (CaM kinase II). We will focus in particular on recent findings of how CaM kinase II encodes the frequency of synaptic usage and serves as a molecular memory switch at the synapse. Furthermore, a role for CaM kinase II in spatial learning and memory is demonstrated by recent studies using transgenic mice.

Animals↗
PubMed1999

Mitogen-activated protein kinase activation and regulation of cyclooxygenase 2 expression by platelet-activating factor and hCG in human endometrial adenocarcinoma cell line HEC-1B.

The activation of mitogen-activated protein kinase (MAP kinase) and the regulation of cyclooxygenase 2 (COX-2) were investigated in the human endometrial adenocarcinoma cell line HEC-1B by treatment with platelet-activating factor (PAF) and hCG. Pre-treatment of the cells with both oestradiol and medroxyprogesterone acetate was required for MAP kinase activation and COX-2 expression to respond to PAF and hCG. PAF-induced MAP kinase activation was sensitive to MAP kinase kinase (MEK) inhibitor, PD098059, and phosphatidylinositol-3-OH kinase (PI3K) inhibitor, wortmannin. In contrast, hCG-induced MAP kinase activation was sensitive to PD098059 and protein kinase A inhibitor, H-89, but not to wortmannin. PAF-induced COX-2 expression was insensitive to PD098059 but sensitive to wortmannin, whereas hCG-induced COX-2 expression was sensitive to PD098059 and H-89 but insensitive to wortmannin. 8-(4-chlorophenylthio)-cAMP, a potent cAMP analogue, induced activation of MAP kinase and expression of COX-2. These results indicate that MAP kinase is activated with PAF and hCG in HEC-1B cells. In addition, COX-2 expression is stimulated through the MAP kinase activation pathway with hCG and the wortmannin sensitive pathway with PAF in HEC-1B cells. These results also imply that protein kinase A remains upstream of hCG-induced activation of MAP kinase in HEC-1B cells.

Adenocarcinoma↗
PubMed1999

Coinfection of visceral leishmaniasis and Mycobacterium in a patient with acquired immunodeficiency syndrome.

We report a case of coinfection of visceral leishmaniasis and Mycobacterium avium-intracellulare in the same lesions in the small bowel and bone marrow of a 33-year-old man with acquired immunodeficiency syndrome who complained of abdominal pain and chronic diarrhea. The duodenal mucosa and bone marrow biopsy specimens showed numerous foamy macrophages packed with two forms of microorganisms that were identified histologically and ultrastructurally as Leishmania and Mycobacterium species. Visceral leishmaniasis is rarely suspected in patients residing in nonendemic countries including the United States. It should be included in the differential diagnosis for opportunistic infection in patients with acquired immunodeficiency syndrome. An appropriate travel history is important. To our knowledge, this is the first reported case showing coinfection of visceral leishmaniasis and Mycobacterium avium-intracelluulare in the same lesion in a patient with acquired immunodeficiency syndrome.

AIDS-Related Opportunistic Infections↗
PubMed1998

Serine/threonine phosphatase activity of calcineurin is inhibited by sodium orthovanadate and dithiothreitol reverses the inhibitory effect.

Orthovanadate is known to be an inhibitor of protein tyrosine phosphatases. However, we found that it inhibited calcineurin which has the activity of a serine/threonine protein phosphatase, using casein phosphorylated by cyclic AMP-dependent protein kinase as a substrate. Orthovanadate inhibits the Mn2+-activated activity of purified calcineurin to 20%; this is not the case without Mn2+. Furthermore, 10 mM dithiothreitol (DTT) reversed the inhibitory effects of orthovanadate. Orthovanadate showed the same inhibitory effect for calcineurin activity in homogenates as for the purified enzyme; the inhibitory effect was reversed by DTT. These results indicate that orthovanadate inhibits not only protein tyrosine phosphatases as reported, but also serine/threonine phosphatase activity of calcineurin.

Animals↗
PubMed1998

The antibody specific for myristoylated alanine-rich C kinase substrate phosphorylated by protein kinase C: activation of protein kinase C in smooth muscle cells in human coronary arteries.

Myristoylated alanine-rich C kinase substrate (MARCKS), a major substrate for protein kinase C, is distributed in a variety of cells. It has been reported that phosphorylation of MARCKS at serines 152 and 156 according to the numbering of rat brain MARCKS can be used as an indicator for protein kinase C activation in intact cells. To detect the activation of protein kinase C in vivo, we produced a specific antibody against MARCKS phosphorylated at serines 152 and 156. We synthesized a phosphopeptide which contained phosphoserines 152 and 156 and prepared the antibody specific for this phosphopeptide. Immunoblot analysis with both purified MARCKS and the cytosol fraction from rat brain revealed that the antibody reacted only with MARCKS phosphorylated by protein kinase C. The antibody was suitable for immunoblot analysis and immunostaining with cultured human coronary artery smooth muscle cells. Phosphorylation of MARCKS was increased about eightfold by the treatment of the cells with phorbol 12-myristate 13-acetate, a protein kinase C activator. Furthermore, treatment of the cells with endothelin-1 and tumor necrosis factor alpha increased phosphorylation of MARCKS. Interestingly, phosphorylation of MARCKS was clearly observed in smooth muscle cells in atherosclerotic lesion of subjects at autopsy. These results suggest that the antibody is useful for examination of the activation of protein kinase C in vascular smooth muscle cells in vivo.

Animals↗
PubMed1998

Ig receptor binding protein 1 (alpha4) is associated with a rapamycin-sensitive signal transduction in lymphocytes through direct binding to the catalytic subunit of protein phosphatase 2A.

Rapamycin is an immunosuppressant that effectively controls various immune responses; however, its action in the signal transduction of lymphocytes has remained largely unknown. We show here that a phosphoprotein encoded by mouse alpha4 (malpha4) gene transmitting a signal through B-cell antigen receptor (BCR) is associated with the catalytic subunit of protein phosphatase 2A (PP2Ac). The middle region of alph4, consisting of 109 amino acids (94-202), associates directly with PP2Ac, irrespective of any other accessory molecule. Rapamycin treatment disrupts the association of PP2Ac/alpha4 in parallel with the inhibitory effect of lymphoid cell proliferation. The effect of rapamycin was inhibited with an excess amount of FK506 that potentially completes the binding to FKBP. Rapamycin treatment also suppresses the phosphatase activity of cells measured by in vitro phosphatase assay. Introduction of the malpha4 cDNA into Jurkat cells or the increased association of PP2Ac/alpha4 by the culture with low serum concentration confers cells with rapamycin resistance. Moreover, glutathione S-transferase (GST)-alpha4 augments the PP2A activity upon myelin basic protein (MBP) and histone in the in vitro assay. These results suggest that alpha4 acts as a positive regulator of PP2A and as a new target of rapamycin in the activation of lymphocytes.

Adaptor Proteins, Signal Transducing↗
PubMed1998

Role of MAP kinase in neurons.

Extracellular stimuli such as neurotransmitters, neurotrophins, and growth factors in the brain regulate critical cellular events, including synaptic transmission, neuronal plasticity, morphological differentiation and survival. Although many such stimuli trigger Ser/Thr-kinase and tyrosine-kinase cascades, the extracellular signal-regulated kinases, ERK1 and ERK2, prototypic members of the mitogen-activated protein (MAP) kinase family, are most attractive candidates among protein kinases that mediate morphological differentiation and promote survival in neurons. ERK1 and ERK2 are abundant in the central nervous system (CNS) and are activated during various physiological and pathological events such as brain ischemia and epilepsy. In cultured hippocampal neurons, simulation of glutamate receptors can activate ERK signaling, for which elevation of intracellular Ca2+ is required. In addition, brain-derived neurotrophic factor and growth factors also induce the ERK signaling and here, receptor-coupled tyrosine kinase activation has an association. We describe herein intracellular cascades of ERK signaling through neurotransmitters and neurotrophic factors. Putative functional implications of ERK and other MAP-kinase family members in the central nervous system are give attention.

Animals↗
PubMed1998

Precise distribution of neuronal nitric oxide synthase mRNA in the rat brain revealed by non-radioisotopic in situ hybridization.

Regional distribution of neurons expressing neuronal nitric oxide synthase mRNA in the rat brain was examined by non-radioisotopic in situ hybridization, using digoxigenin-labeled complementary RNA probes. Clustering of intensely positive neurons was observed in discrete areas including the main and accessory olfactory bulbs, the islands of Calleja, the amygdala, the paraventricular nucleus of the thalamus, several hypothalamic nuclei, the lateral geniculate nucleus, the magnocellular nucleus of the posterior commissure, the superior and inferior colliculi, the laterodorsal and pedunculopontine tegmental nuclei, the nucleus of the trapezoid body, the nucleus of the solitary tract and the cerebellum. Strongly-stained isolated neurons were scattered mainly in the cerebral cortex, the basal ganglia and the brain stem, especially the medulla reticular formation. In the hippocampus, an almost uniform distribution of moderately stained neurons was observed in the granular cell layer of the dentate gyrus and in the pyramidal cell layer of the Ammon's horn, while more intensely stained isolated neurons were scattered over the entire hippocampal region. These observations can serve as a good basis for studies on function and gene regulation of neuronal nitric oxide synthase.

Animals↗
PubMed1998

Hindlimb suspension induces the expression of multiple myosin heavy chain isoforms in single fibres of the rat soleus muscle.

To examine the expression patterns of myosin heavy chain (MHC) isoforms in single fibres of the soleus muscle following weightlessness, 10-week-old male Wistar rats were subjected to hindlimb suspension for 4 weeks. Hindlimb suspension resulted in reduced body weight and absolute and relative mass of the soleus muscle compared with controls (P < 0.01). A total of 975, 892 and 1098 single fibres from pre-suspended controls, age-matched controls and suspension groups, respectively, were subjected to MHC analyses using SDS-PAGE. Single fibres containing only MHC I decreased (87.9 vs. 67.9%, P < 0.05) and single fibres containing only MHC IIa disappeared after hindlimb suspension. On the contrary, single fibres containing multiple type II MHC isoforms were observed as follows: 10.1% single fibres contained MHCs IIa and IId; 14.1% contained MHCs I, IIa and IId; and some (1.4%) expressed the MHC IIb isoform with MHCs IIa and IId. The relative content (%) of each MHC isoform in MHC hybrid single fibres was calculated using densitometer scanning. The MHCs IIa and IId hybrid single fibres contained the same amount of MHC IIa (51.3 +/- 6.3%) and MHC IId (48.7 +/- 6.3%). In the MHCs I, IIa and IId hybrid single fibres, the percentage of MHC IIa was distributed in a wide range (approximately 80%), whereas the percentage of MHC IId was a relatively low range (approximately 40%), and the relative content of MHC I was inversely correlated with that of MHC IIa and MHC IId, respectively. The fibre type composition of suspended soleus muscle, analysed by histochemical myosin ATPase staining, was changed, with a decrease in the percentage of type I fibres and an increase in that of type IIA fibres. Our results indicate that hindlimb suspension induces multiple type II MHC expression in the soleus single fibres and suggest that the single fibres containing multiple type II MHC isoforms should be classified into type IIA.

Adenosine Triphosphatases↗
PubMed1998

Propofol inhibits ketamine-induced c-fos expression in the rat posterior cingulate cortex.

UNLABELLED: Ketamine, a noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist, has psychotomimetic activity. NMDA receptor antagonists cause morphological damage in the posterior cingulate cortex, which may be the brain region responsible for their psychotomimetic effects. Benzodiazepines are effective in preventing these effects through gamma-aminobutyric acid A (GABA(A)) receptor activation. We investigated the effect of propofol, which has both GABAA receptor-activating and NMDA receptor-suppressing activity, on ketamine-induced c-fos expression in the rat posterior cingulate cortex. Propofol or vehicle was continuously infused IV. Fifteen minutes later, 100 mg/kg ketamine or isotonic sodium chloride solution was injected intraperitoneally. Two hours later, brain sections were prepared, and c-fos expression was detected using immunohistochemical methods. Propofol significantly inhibited ketamine-induced c-fos expression in the posterior cingulate cortex. Propofol itself did not induce c-fos expression in this brain region. We conclude that propofol may be able to inhibit ketamine-induced psychotomimetic activity and neuronal damage. IMPLICATIONS: In the present study, we demonstrated that the clinically relevant dose of propofol significantly inhibited ketamine-induced c-fos expression in the rat posterior cingulate cortex. This finding implies that propofol may inhibit ketamine-induced psychotomimetic activity and neuronal damage.

Anesthetics, Dissociative↗
PubMed1998

Histiocytic sarcoma of the spleen associated with hypoalbuminemia, hypo gamma-globulinemia and thrombocytopenia as a possibly unique clinical entity--report of three cases.

We report three patients with histiocytic sarcoma of the spleen associated with severe hypoalbuminemia, hypo gamma-globulinemia and thrombocytopenia. After the clinical diagnosis of splenic tumor of unknown origin was made, all three patients underwent splenectomy. The histiocytic origin of the tumor was confirmed histopathologically and immunohistochemically using a panel of antibodies. In contrast to malignant histiocytosis (MH), which typically reveals severe generalized clinical manifestations and a rapidly fatal course caused by the disseminated proliferation of neoplastic histiocytes, these patients were asymptomatic or showed only mild clinical symptoms for a long period of time until the recurrence was detected by which time the tumor cells had already spread to other organs. All three cases were characteristically associated with hypoalbuminemia, hypo gamma-globulinemia and thrombocytopenia, which returned to normal after splenectomy. Splenic histiocytic sarcoma with the features described here may represent a unique clinical entity, distinct from MH.

Adult↗