PubMed Health⌕ Search

Biomedical subjects

M Ichikawa

Publications and source records attributed to M Ichikawa.

At least 19 recordsLinked to original sources
PubMed1992

The differential staining patterns of two lectins in the accessory olfactory bulb of the rat.

We examined the binding sites of Bandeiraea simplicifolia lectin I (BSL-I) and Vicia villosa agglutinin (VVA) which bind to the vomeronasal nerve of the rat. BSL-I stained the whole vomeronasal nerve and glomerular layers. VVA strongly stained the posterior 2/3, but weakly stained the anterior 1/3 of the glomerular layer. These results indicate that the glomeruli of the rat AOB have two subdivisions revealed by lectin histochemistry using BSL-I and VVA.

Animals↗
PubMed1992

Existence of two pathways for the endocytosis of epidermal growth factor by rat liver: phenylarsine oxide-sensitive and -insensitive pathways.

The effect of phenylarsine oxide (PAO) on the internalization rate of epidermal growth factor (EGF) was investigated using perfused rat liver and isolated rat hepatocytes. In perfused liver, a tracer concentration of 125I-EGF alone or with excess unlabeled EGF (20 nM) was perfused and the internalization rate constants (kint) were measured. In the absence of PAO, kint values did not differ significantly for either dose condition. However, with the addition of PAO to the perfusate, the kint value dropped to 4% of that of the control at the low concentration of EGF, while dropping to only 40% of that of the control at the high concentration of EGF. These results suggest the existence of a PAO-insensitive internalization pathway having a kint value comparable with that of the other pathway. Similar EGF concentration-dependent inhibition of 125I-EGF internalization caused by PAO was ascertained using isolated rat hepatocytes. PAO also decreased the cellular ATP content in isolated hepatocytes. However, when we lowered the cellular ATP content with rotenone, the cell-surface binding and internalization of EGF were comparable with the control levels. We concluded that there exist dual pathways for the internalization of EGF and that excess doses of EGF lead to EGF internalization not only through a PAO-sensitive pathway but also through a PAO-insensitive pathway, whereas at a tracer dose of EGF, the internalization occurs mainly via the PAO-sensitive pathway.

Adenosine Triphosphate↗
PubMed1992

Ultrastructural characterization of gonadotropin-releasing hormone (GnRH)-immunoreactive terminal nerve cells in the dwarf gourami.

Recently we have been studying gonadotropin-releasing hormone (GnRH) cells of the terminal nerve (TN) in the dwarf gourami, which may serve as a good model system for the study of neuromodulator functions. Here we report on the ultrastructural characterization of TN-GnRH cells using postembedding immunoelectron microscopy. The GnRH immunoreactivities could be demonstrated on dense-cored vesicles (DCVs) in cell bodies, fibers and varicosities. However, we could find no evidence of GnRH-immunoreactive synapses which are characterized by active zones. This may suggest that GnRH is released non-synaptically from DCV-containing fiber varicosities and that it exerts its modulatory action on GnRH receptors located on nearby as well as distant target neurons.

Animals↗
PubMed1992

A novel pathway for phosphorylated oligosaccharide biosynthesis. Identification of an oligosaccharide-specific phosphate methyltransferase in dictyostelium discoideum.

The N-linked oligosaccharides on three lysosomal enzymes in Dictyostelium discoideum were found to contain mannose 6-phosphomethyl residues. We have identified and partially characterized a novel S-adenosylmethionine-dependent methyltransferase that is probably responsible for the synthesis of this unusual diester from Man-6-P. The enzyme selectively methylates the phosphate group of Man-6-P (Km 4.3 mM). Glucose-6-P and fructose-1-P are relatively poor acceptors; however, the enzyme is inactive against a broad array of other phosphorylated compounds. Using model di-, tri-, and pentasaccharide acceptors that include portions of the three different branches of high mannose-type oligosaccharides, we found that the enzyme prefers terminal alpha 1----2-linked Man-6-P residues (Km 0.15-1.25 mM) found on the known phosphorylated branches. The enzyme is membrane bound, has a neutral pH optimum and cofractionates on sucrose gradients with GlcNAc-1-P transferase, which resembles its mammalian counterpart, and is, presumably, the first enzyme in the phosphorylation pathway. Based on the substrate specificity and colocalization with GlcNAc-1-P transferase, the phosphate methyltransferase is likely to be responsible for the generation of mannose-6-phosphomethyldiester on Dictyostelium oligosaccharides.

Animals↗
PubMed1992

Block of synapse formation between cerebral cortical neurons by a protein kinase inhibitor.

Synchronized Ca2+ transients in cultured hippocampal neurons reflect the pattern of underlying electrical activity. Here we demonstrate a similar synchronization of cerebral cortical neurons in culture, and show that this functional coupling is correlated to the appearance of morphologically identified synapses using electron microscopy. During screening of a series of drugs for inhibition of in vitro synaptogenesis, the continuous presence of a protein kinase inhibitor (K-252b) in the culture medium was found to block the synchronous firing and to decrease significantly the number of morphologically identifiable synapses. Since K-252b does not permeate the cell membrane, the results strongly suggest that phosphorylation of cell surface protein(s) by a K-252b sensitive-protein kinase is an essential process in synapse formation.

Animals↗
PubMed1992

Steroid saponins from Polygonatum kingianum.

Four new steroid saponins, kingianosides A-D, were isolated from the rhizome of Polygonatum kingianum, together with two known steroid saponins. On the basis of chemical and spectral evidence, the structures of kingianosides A-D were established as gentrogenin 3-O-beta-D-glucopyranosyl (1-->4)-beta-D-galactopyranoside, gentrogenin 3-O-beta-D-glucopyranosyl(1-->4)-beta-D-fucopyranoside, 26-O-beta-D-glucopyranosyl-22-hydroxy-25(R)-furost-5-en-12-on-3 beta, 22-diol 3-O-beta-D-glucopyranosyl(1-->4)-beta-D-galactopyranoside and 26-O-beta-D-glucopyranosyl-22-hydroxy-25(R)-furost-5-en-12-on-3 beta,22-diol 3-O-beta-D-glucopyranosyl(1-->4)-beta-D-fucopyranoside, respectively.

Carbohydrate Sequence↗
PubMed1992

Bandeiraea simplicifolia lectin I and Vicia villosa agglutinin bind specifically to the vomeronasal axons in the accessory olfactory bulb of the rat.

The binding of 21 lectins to the accessory olfactory bulb (AOB) of the rat was examined by histochemistry. Two lectins [Bandeiraea simplicifolia lectin I (BSL-I) and Vicia villosa agglutinin (VVA)] bound specifically to the vomeronasal (VN) axons in the AOB. Seven lectins (Datura stramonium lectin, Erythrina cristagalli lectin, Lycoperisicon esculentum lectin, Ricinus communis agglutinin I, soybean agglutinin, Solanum tuberosum lectin, and Ulex europaeus agglutinin) bound to both VN axons in AOB and olfactory axons in the main olfactory bulb. BSL-I and VVA are useful as the marker of VN axons. This selective binding of lectins indicates the presence of specific glycoconjugates on the surface of VN axons.

Animals↗
PubMed1992

'Albumin-mediated transport phenomenon' observed for ligands with high membrane permeability. Effect of the unstirred water layer in the Disse's space of rat liver.

In this paper, we offer experimental evidence of the rate-limiting diffusion of ligands through the unstirred water layer (UWL) as an explanation for the so-called albumin-mediated transport phenomenon. The relative membrane permeability of various ligands was first evaluated using isolated rat hepatocytes. Then, the effect of albumin on the uptake of ligands of a wide range of membrane permeabilities was examined using the perfused rat liver. The results were similar to those expected from the UWL model: ligands with high membrane permeability (warfarin, diazepam and taurocholate) clearly exhibited albumin-mediated transport, those with medium membrane permeability (tolbutamide and salicylate) showed less albumin-mediated transport, and ligand with low membrane permeability (cefodizime) did not show albumin-mediated transport. These results were explained by simulation studies of two separate cases based on the UWL model; one assuming the rapid equilibrium of ligand binding with albumin, and the other considering the slow dissociation of ligands from albumin. In light of these findings, we suggest that the rate-limiting diffusion through the UWL plays an important role in the so-called albumin-mediated transport phenomenon.

Animals↗
PubMed1992

Hepatitis E virus: cDNA cloning and expression.

Viral hepatitis E is endemic, frequently provoking epidemic outbreaks in many developing countries. We have attempted to clone the viral genome and to develop an antibody assay system. A lambda gt11 cDNA library was constructed from the bile juice containing putative causative viruses and was immunoscreened by the antisera obtained from patients and monkeys infected with hepatitis E. Three virus-specific clones were isolated and were revealed to overlap one another in sequence, with 1,459 nucleotides in total length. These clones direct the synthesis of polypeptides probably having common immunological epitope(s). Immunoplaque assay revealed the occurrence of antibodies against this epitope in the sera from experimental monkeys with the convalescent phase and from patients of Myanmar, Nepal and India. The data indicate that the cDNA fragments are useful for immunodiagnosis of hepatitis E.

Amino Acid Sequence↗
PubMed1992

An improved cryofixation method: cryoquenching of small tissue blocks during microwave irradiation.

The metal contact method of rapid freezing is greatly improved by irradiating the specimen with microwaves at 2.45 GHz for a short period of time (50 ms), while pushing the specimen onto the surface of the copper block cooled by liquid N2. The microwave irradiation, together with two technical improvements (a light-mass plunger and a recently developed beta-gel shock absorber) for preventing bounce, produces a good freezing zone for squid retina, with high reproducibility for each experimental trial, extending from the contact surface to a depth of about 15 microns, which is comparable to the depth obtained by the metal contact method using liquid He in the absence of microwave irradiation. A good freezing zone was also experimentally demonstrated in specimens of rat liver and heart muscle. Microwave irradiation does not have appreciable effects on the ultrastructure of squid retina. The mechanism underlying the improvement in the rapid freezing under the microwave irradiation is discussed.

Animals↗
PubMed1992

Renal nerves contribute to salt-induced hypertension in sinoaortic-denervated uninephrectomized rabbits.

The objective of this study was to investigate the role of the renal nerves in the pathogenesis of salt-induced hypertension in sinoaortic-denervated uninephrectomized rabbits. Twelve rabbits were divided into two groups. Sinoaortic-denervated uninephrectomized rabbits with intact renal nerves (sham group: n = 6) and without renal nerves (RDN group; n = 6). In both groups, 2 days of 154 meq/l NaCl loading was followed by 10 days of 1,700 meq/l NaCl loading. We administered 154 meq/l or 1,700 meq/l NaCl intravenously at every 8 h. Serial changes in mean arterial pressure (MAP) and heart rate (HR) were recorded using a microcomputer system. We chronologically measured hematocrit, serum osmolality, serum sodium, potassium, and chloride concentration, serum creatinine, plasma renin activity, plasma aldosterone, plasma norepinephrine, plasma arginine vasopressin, and plasma atrial natriuretic peptide. Urine volume and body weight were recorded every day, as were urinary concentrations of sodium, potassium, and chloride. The basal value of MAP in the sham group was significantly higher than that in the RDN group (on day -2, 111 +/- 1 mmHg for sham, 99 +/- 2 for RDN, P less than 0.001). Hypertonic saline loading induced an elevation of blood pressure in the sham group (126 +/- 2 mmHg on day 4, 127 +/- 2 on day 7, 124 +/- 4 on day 10). There were no significant changes in the response to salt loading in the RDN group. In the sham group, the retention of sodium was significant compared with that in the RDN group on day 5, and this difference was maintained until the end of the experiments.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Alexithymia and depression in families with alcoholics.

Alexithymia and depression in family members of alcoholics were examined among 48 families. Results were as follows: (1) The prevalence of alexithymia was 47.9% (23 cases), whereas that of depression was only 6.3% (3 cases); (2) no significant correlation between alexithymia and depression was noted; (3) expressiveness and conflict were significantly lower in families with alcoholics than in healthy families without alcoholics, although families with alcoholics do have strong conflicts. The results suggest the possibility that half of them forcefully suppress their conflicts, unconsciously deny the existence of alcoholics, and finally manifest secondary alexithymia.

Adult↗
PubMed1992

Effects of antihypertensive agents on arterial baroreceptor reflexes in conscious rats.

The effects of antihypertensive treatment with four currently used agents (trichlormethiazide, atenolol, nicardipine, and enalapril) on the arterial baroreceptor reflex control of renal sympathetic nerve activity and heart rate were investigated in 45 conscious spontaneously hypertensive rats and 37 age-matched Wistar-Kyoto rats. Antihypertensive agents were administered for 2 weeks beginning at 8 weeks of age to treat and prevent the development of hypertension. Blood pressure was reduced to a similar level (-13 +/- 3 mm Hg, p < 0.05) by each antihypertensive agent. Blood pressure, heart rate, and renal sympathetic nerve activity were recorded in the conscious state during phenylephrine and nitroglycerin ramp infusion. The gain in the baroreceptor reflex was determined from the maximum slope of logistic function curves. Untreated spontaneously hypertensive rats exhibited decreased sensitivity of reflex control of renal sympathetic nerve activity and heart rate (-1.78 +/- 0.07% of control/mm Hg and -2.16 +/- 0.05 beats per minute/mm Hg, respectively) compared with untreated Wistar-Kyoto rats (-3.62 +/- 0.18% of control/mm Hg, p < 0.01, and -3.46 +/- 0.11 beats per minute/mm Hg, p < 0.05, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Subcellular localization of xanthine oxidase in rat hepatocytes: high-resolution immunoelectron microscopic study combined with biochemical analysis.

Xanthine oxidase (XO), a molybdo-flavoprotein enzyme involved in purine degradation, was localized immunocytochemically in rat hepatocytes by high-resolution immunoelectron microscopy. XO was isolated from rat liver and a 150 KD polypeptide was purified. Antibodies were raised in rabbits. Small pieces of fresh liver were quickly frozen by contact with a copper block pre-cooled with liquid helium and were freeze-substituted with either 2.5% OsO4 or 0.2% glutaraldehyde in acetone. They were then warmed and embedded in Epon-Araldite or Araldite 6005. Resin sections were treated by indirect immunostaining using anti-rat liver XO antibody and protein A-gold. The labeling pattern was clearly over the cytosol and not on cell organelles. A few gold particles were found over the mitochondrial matrix, but not over the endoplasmic reticulum, Golgi apparatus, lysosomes, or peroxisomes, including their crystalloid core. These results are consistent with those of the biochemical assay of XO in this study. The significance of the occasional immunolabeling of the mitochondrial matrix remains obscure, since biochemical determinations in this study indicate no XO activity in the mitochondrial fraction.

Animals↗
PubMed1992

Synthesis of dibenzoylmethane derivatives and inhibition of mutagenicity in Salmonella typhimurium.

Twenty dibenzoylmethanes with methyl, methoxy, bromo, chloro, or fluoro substitution on either one or both benzene rings were synthesized and assayed for inhibition of the mutagenicity of 2-nitrofluorene in S. typhimurium TA98. 2,2-Dimethoxy, 3,3-dimethoxy and 3,3,4,4-tetramethoxydibenzoylmethane was as active as dibenzoylmethane. None of the halogen-substituted dibenzoylmethanes were active. These results demonstrate that dibenzoylmethanes can inhibit the mutagenicity of 2-nitrofluorene, and that modifications made on the benzene rings of dibenzoylmethane cannot enhance the antimutagenicity of this parent compound.

Antimutagenic Agents↗
PubMed1992

Thyroid papillary adenocarcinoma in a woman with Peutz-Jeghers syndrome.

We present a rare case of Peutz-Jeghers(P-J) syndrome in a 29-year-old woman who developed adenocarcinoma of the thyroid and polyps in the gastrointestinal tract. Polyps removed from the stomach, colon and ileum showed features typical of hamartomas. Histological examination indicated that the tumor resected from the right lobe of the thyroid was a papillary adenocarcinoma. This appears to be the first precise report of a P-J syndrome associated with thyroid carcinoma. This case adds an example of predisposition of P-J syndrome to extra-intestinal malignancy and indicates the importance of long-term observation of malignancy.

Adenocarcinoma, Papillary↗
PubMed1992

Abscess within a glioblastoma multiforme--case report.

A rare case of abscess within a glioblastoma with an unusual presentation occurred in a 46-year-old female who developed right hemiparesis and seizure. Computed tomography and magnetic resonance imaging demonstrated hemorrhage which mimicked hemorrhagic infarction. However, the lesions developed ring enhancement. Aspiration showed one to be an abscess, which collapsed by drainage but later re-expanded. The mass was removed, and histological examination revealed glioblastoma.

Brain Abscess↗