Search PubMed⌕ Search

Biomedical subjects

F Ito

Publications and source records attributed to F Ito.

At least 217 records · Page 12Linked to original sources
PubMed1985

Enzyme replacement with liposomes containing beta-galactosidase from Charonia lumpas in murine globoid cell leukodystrophy (twitcher).

Enzyme replacement with liposomes containing beta-galactosidase obtained from charonia lumpas was carried out in murine globoid cell leukodystrophy (GLD). Charonia lumpas beta-galactosidase was able to hydrolyze galactocerebroside trapped into liposomes prepared from lecithin, cholesterol and sulfatide (molar ratio; 7:2:1). Liposomes containing charonia lumpas beta-galactosidase were successfully incorporated into the mouse tissues. 3H-galactocerebroside labeled liposomes were also incorporated into mouse liver, spleen and other tissues. The accumulation rate of 3H-galactocerebroside into twithcer mice liver and spleen was almost 40 to 100 times higher than those of controls and degraded to 70 to 80% of accumulated radioactivity of 3H-galactocerebroside by single injection of liposomes containing charonia lumpas beta-galactosidase. Results suggest that exogeneous enzyme trapped in liposomes can be useful for the correction of accumulated compound.

Animals↗
PubMed1985

Reversal of the static component of spindle potential by imposed depolarizing current in the frog muscle spindle.

The static component of the spindle potential provoked during stretch of isolated muscle spindles of the frog was reversed during the application of depolarizing currents ranging from 0.2 to 5 nA in normal Ringer solution and also in Na+-free Ringer solution. In the same range of current intensities, spontaneous rhythmic hyperpolarizations due to [Ca2+]i-activated GK, an attenuation of membrane impedance, and an anomalous decrease in amplitude of the afferent spikes were observed. All 4 phenomena were abolished by K+ channel blockers (10 mM CsCl, 1-2 mM 4-aminopyridine (4-AP), or 20 mM tetraethylammonium chloride (TEA], Ca2+ channel blockers (5-10 mM CoCl2, MnCl2, 1-2 mM CdCl2 or 0.5 mM verapamil) or 0.1 mM quinine. The amplitude of the static component of the spindle potential was markedly increased at threshold concentration of the K+ channel blockers (5 mM CsCl, 0.1-0.5 mM 4-AP or 5-10 mM TEA), but the component disappeared at that of the Ca2+ channel blockers. The rhythmic hyperpolarizations are associated with the spindle potential, except for its dynamic component, which often triggers a hyperpolarizing deflection. We suggest that both the static component of the spindle potential and rhythmic hyperpolarizations are due to GK(Ca) in the intracapsular axon, either along the terminal or at the branching nodes, or both; and that the receptor potential contributes to, but is not the same as, the spindle potential.

Animals↗
PubMed1985

Ultrastructural changes of the sensory nerve terminals in frog muscle spindle during dynamic stretch.

The sensory ending of the frog muscle spindle consists of bulbous swellings interconnected by thin, tube-like axonal branches. This study was made to determine if the bulb or thin tube regions are deformed to the same degree during dynamic stretch, by comparing spindles prepared in the relaxed and stretched states. Isolated muscle spindles were rapidly frozen, either in a completely relaxed state or at the end of dynamic stretch to 130% of the in situ length. Longitudinal sections for ultra-high-voltage electron microscopy revealed that dynamic stretch caused a decrease of 61.7% in bulb diameter, an increase of 88% in bulb length and an increase of 34.6% in bulb volume. The cross-sectional areas of the nonmyelinated terminals in the reticular and compact zones measured in electron micrographs decreased by 79.2% in the bulb region and 66.7% in the tube region during dynamic stretch.

Animals↗
PubMed1985

[A phase II study of oral VP-16 in primary lung cancer].

A clinical trial of a new semi-synthetic podophyllotoxin, VP-16, was undertaken in patients with primary lung cancer; 56 of the 81 evaluable patients had small cell carcinoma, 9 adenocarcinoma, 8 epidermoid carcinoma, 7 large cell carcinoma, and 1 adenosquamous carcinoma. A dose of 200 mg/body/day orally for 5 consecutive days was administered every 3 to 4 weeks. Partial response (PR) was attained in 19 out of 81 (23%) and PR + MR was 35 out of 81 (43%). PR and minor response (MR) were seen as follows; small cell carcinoma, 17 PR (30%), 13 MR; epidermoid carcinoma, 2 PR (25%), 1 MR; adenocarcinoma, 1 MR; adenosquamous carcinoma, 1 MR. The dose-limiting factor was leukopenia, while thrombocytopenia was experienced in 2 cases. Clinical toxicities noted were anorexia, nausea, vomiting, stomatitis, diarrhea and alopecia, but these were well tolerated in all cases. The result indicated that VP-16 has considerable efficacy in small cell carcinoma and epidermoid carcinoma of the lung and hence its usefulness in combination chemotherapy was suggested.

Adenocarcinoma↗
PubMed1984

Suppression of placental alkaline phosphatase biosynthesis by tunicamycin.

Placental alkaline phosphatase activity and immunoreactivity were inhibited in a parallel fashion in choriocarcinoma cells by tunicamycin, a protein glycosylation inhibitor. Tunicamycin suppressed placental alkaline phosphatase biosynthesis in addition to inhibiting protein glycosylation in general. An anti-placental alkaline phosphatase-precipitable polypeptide of 58,000 daltons was formed in the presence of this antibiotic. The 58,000-dalton polypeptide had a degradation rate similar to that of the glycosylated phosphatase monomer from control cultures. Tunicamycin suppressed placental alkaline phosphatase mRNA activity leading to the observed decrease in biosynthesis.

Alkaline Phosphatase↗
PubMed1984

Effects of dantrolene and methylxanthines on the sensory nerve terminal of the frog muscle spindle.

The application of 1.5-4 microM dantrolene decreased the threshold and the current sensitivity of the rhythmic hyperpolarizations that occur during depolarization of the sensory nerve terminal in the frog muscle spindle. The higher concentration provoked spontaneous rhythmic changes even without depolarization. Methylxanthines (5 mM caffeine, theophylline or pentylene-tetrazole) increased the threshold and the sensitivity. Electron microscopic observations of the dantrolene-treated spindles revealed numerous electron-dense deposits associated with the cytoplasmic membrane of the sensory terminals and with mitochondrial membranes. The deposits were found to contain K+ and Ca2+ by energy dispersive X-ray microanalysis. Electron-dense deposits containing Ca2+ were usually observed in the inner capsular space and in the mitochondria of the sensory terminals perfused by normal or high Ca2+ Ringer solutions. They were reduced in number following incubation with methylxanthines. The amplitudes of afferent spikes and the spindle potential were increased by methylxanthines in much the same way as by K+ channel blockers, suggesting that GK of the terminal membrane may be reduced by methylxanthines. We suggest that methylxanthines may modulate the terminal responses both as a K+ channel blocker and by enhancing the release of Ca2+ from a storage site, perhaps in the inner capsular space, whereas dantrolene has the opposite effect.

Animals↗
PubMed1984

Induction of placental alkaline phosphatase biosynthesis by sodium butyrate.

Placental alkaline phosphatase activity was induced in choriocarcinoma cells by sodium butyrate. Butyrate stimulated de novo synthesis of the enzyme and the increase in phosphatase activity could be completely accounted for by the increase in phosphatase protein: the increases in placental alkaline phosphatase immunoactivity and placental alkaline phosphatase biosynthesis as measured by incorporation of the radioactive precursors, L-[35S]methionine, [3H]mannose, and [3H] glucosamine were similar to the increase in phosphatase activity. Sodium butyrate increased the rates of placental alkaline phosphatase biosynthesis but had no effect on the rate of placental alkaline phosphatase degradation or processing. Both control and butyrate-induced cells contained polypeptides of 61,500 and 64,500 apparent molecular weights that were identified as the precursor and fully processed forms of the placental alkaline phosphatase monomer, respectively. Further, processing of the 61,500-dalton polypeptide to the 64,500-dalton polypeptide involved the incorporation of additional glucosamine and N-acetylneuraminic acid moieties. Gel electrophoresis of anti-placental alkaline phosphatase-precipitable polypeptides from an in vitro protein-synthesizing system directed by RNA isolated from control or butyrate-induced cells demonstrated that sodium butyrate induced the synthesis of placental alkaline phosphatase mRNA. Our data indicate that sodium butyrate induces the specific transcription of the placental alkaline phosphatase gene.

Alkaline Phosphatase↗
PubMed1984

Role of retinoic acid in maturation of fetal liver cells in vitro.

Regulation of the biosynthesis of alpha-fetoprotein and albumin was studied in a temperature-sensitive fetal rat hepatocyte line (RLA209-15) which exhibits a differentiated phenotype when grown at 40 degrees C. Retinoic acid inhibited alpha-fetoprotein production but increased albumin production. This retinoid also changed the proportion of three forms of alpha-fetoprotein; the biosynthesis of the 73,000- and 69,000-dalton variants, which are indistinguishable from authentic rat alpha-fetoprotein, was inhibited and an additional 65,000-dalton variant was induced. It has previously been shown that alpha-fetoprotein production decreases during maturation whereas albumin production increases. Our data suggest that retinoic acid induces maturation of fetal liver cells in vitro. Further, the 65,000-dalton alpha-fetoprotein variant may be characteristic of liver maturation.

Animals↗
PubMed1984

5-Bromo-2'-deoxyuridine induces placental alkaline phosphatase biosynthesis in cultured choriocarcinoma cells.

5-Bromo-2'-deoxyuridine (BrdUrd) stimulated the biosynthesis and hence increased the activity of placental alkaline phosphatase in choriocarcinoma cells. While BrdUrd had no effect on the rate of degradation or processing of placental alkaline phosphatase, it increased the rate of phosphatase synthesis. The stimulation of enzyme activity could be completely accounted for by the increase in alkaline phosphatase protein. Both control and BrdUrd-induced cells contained polypeptides of 61,500 and 64,500 Da, identified as the precursor and fully processed forms of placental alkaline phosphatase monomer. The half-life of this enzyme monomer in both control and BrdUrd-treated cells was estimated to be 36 h. BrdUrd induced a specific increase in the placental alkaline phosphatase mRNA leading to the observed enhancement of biosynthesis. The continued rise in alkaline phosphatase biosynthesis in BrdUrd-induced cells following BrdUrd removal indicated that this analog acted by incorporation into DNA.

Alkaline Phosphatase↗
PubMed1984

Transmembrane delivery of polypeptide hormones bypassing the intrinsic cell surface receptors: a conjugate of insulin with alpha 2-macroglobulin (alpha 2M) recognizing both insulin and alpha 2M receptors and its biological activity in relation to endocytic pathways.

125I-labeled insulin has been cross-linked to alpha 2-macroglobulin (alpha 2M) via a disulfide bond. The resulting insulin-alpha 2M conjugate carried 2.2 insulin moieties per mole of alpha 2M and was able to deliver insulin into rat hepatoma cells H35 and HTC. The insulin delivery was mediated predominantly through alpha 2M receptors and 2 h after binding it was found in the lyposomal fractions in the form of conjugate. When the conjugate was applied to rat hepatoma cells it stimulated activity of tyrosine aminotransferase (TAT) with a potency one-half that of native insulin. Hepatoma cells which were treated with conjugate in the presence of bacitracin were also stimulated for TAT activity. Since bacitracin completely inhibited the alpha 2M binding to its receptors, but inhibited conjugate binding by only 80%, this stimulation must have resulted from the remaining binding of conjugate. These results indicate that the insulin-alpha 2M conjugate was biologically active if it bound to insulin receptors, but that the conjugate bound and internalized through alpha 2M receptors did not act as a mediator for TAT activation. Our results using Percoll density gradients indicate a difference in intracellular processing between insulin, alpha 2M and the conjugate. Mechanisms of action of the conjugate are discussed in relation to the receptor-mediated endocytic pathways.

Animals↗
PubMed1984

Transmembrane delivery of polypeptide growth factors bypassing the intrinsic cell surface receptors: synthesis and biological activity of a conjugate of epidermal growth factor with alpha 2-macroglobulin.

Epidermal growth factor (EGF) was derivatized at the amino terminus with N-succinimidyl 3-(2-pyridyldithio)propionate and then cross-linked to the cysteinyl residues of alpha 2-macroglobulin (alpha 2M) via disulfide bonds. The EGF-alpha 2M conjugate delivered EGF into dense lysosomal fractions through binding to alpha 2M receptors in a variant of mouse Swiss/3T3 fibroblasts, NR-6, which are deficient in EGF receptors. The conjugate stimulated DNA synthesis in Swiss/3T3 cells, but it did not stimulate DNA synthesis in NR-6 cells. This differential stimulation was due to the conjugate's binding to EGF receptors since bacitracin, which completely inhibits [125I]alpha 2M binding to its receptors, inhibited conjugate binding by approximately 80%. Thus, EGF bound to and internalized through alpha 2M receptors does not function as a mediator for DNA stimulation. The mechanisms of action of the conjugate are discussed in relation to the role of receptor-mediated endocytic pathways.

Animals↗