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J Hosoi

Publications and source records attributed to J Hosoi.

At least 55 records · Page 3Linked to original sources
PubMed1986

Induction of anchorage-independent growth of JB6 mouse epidermal cells by 1 alpha,25-dihydroxyvitamin D3.

1 alpha,25-Dihydroxyvitamin D3 [1 alpha,25(OH)2D3], a hormonally active form of vitamin D3, was shown previously to enhance chemically induced transformation of BALB 3T3 cells and Syrian hamster embryo cells. This report demonstrates that 1 alpha,25(OH)2D3, like phorbol ester tumor promoters, induces anchorage-independent growth of mouse JB6 epidermal cells. When plated on agar plates containing 1 alpha,25(OH)2D3 at concentrations higher than 0.05 ng/ml or 0.12 nM, JB6 cells formed colonies on the surface of agar plates dose dependently. This anchorage-independent growth was further confirmed by stimulation of DNA synthesis after liquefying the agar layer with NaI. A phorbol-ester resistant variant of JB6 cells was also resistant to 1 alpha,25(OH)2D3 in terms of induction of anchorage independency. Induction of anchorage-independent growth was specific for 1 alpha,25(OH)2D3: other derivatives of vitamin D3 also induced colony formation on agar plates but only at a higher concentration (500 ng/ml) and to much less extent than did 1 alpha,25(OH)2D3. JB6 cells were found to contain a receptor specific for 1 alpha,25(OH)2D3 with a Kd of 55.7 pM and Nmax of 102.5 fmol/mg protein, suggesting a receptor-mediated mechanism of the induction. The clone that was resistant to 1 alpha,25(OH)2D3 also contained the receptor. DNA-cellulose chromatography showed that a 1 alpha,25(OH)2D3-receptor complex interacted with DNA. In contrast to 1 alpha,25(OH)2D3, retinoic acid did not induce anchorage-independent growth of JB6 cells, but it inhibited the induction by 1 alpha,25(OH)2D3 when applied with it.

Animals↗
PubMed1985

Regulation of melanin synthesis of B16 mouse melanoma cells by 1 alpha, 25-dihydroxyvitamin D3 and retinoic acid.

Melanin synthesis of B16 mouse melanoma cells was found to be stimulated dose and time dependently by 1 alpha,25-dihydroxyvitamin D3 [1 alpha,25(OH)2D3], the hormonal form of vitamin D3. The stimulation of melanogenesis resulted from an increase in the activity of tyrosinase, a key enzyme in melanin synthesis. The minimum dose required for this stimulation was as low as 0.05 ng/ml, or 0.12 nM, a physiological level of plasma 1 alpha,25(OH)2D3. The stimulation by 1 alpha,25(OH)2D3 was specific; other derivatives of vitamin D3 caused no stimulation at a concentration of 500 ng/ml. When the cells were plated on agar plates, the proportion of dark or black colonies was not increased by the exposure to 1 alpha,25(OH)2D3. Furthermore, this compound did not induce melanin synthesis of an amelanotic variant. Thus, its stimulatory effect seemed to be due to stimulation of melanin synthesis of melanotic cells, rather than to conversion of amelanotic clones to melanotic ones. 1 alpha,25(OH)2D3 did not induce intracellular cyclic adenosine 3':5'-monophosphate, while cholera toxin induced cyclic adenosine 3':5'-monophosphate and stimulated melanin synthesis and tyrosinase activity much more than did 1 alpha,25(OH)2D3, suggesting that 1 alpha,25(OH)2D3 stimulates melanin synthesis by a cyclic adenosine 3':5'-monophosphate-independent mechanism. B16 melanoma cells contained specific receptors for 1 alpha,25(OH)2D3. Scatchard plot analysis revealed two types of receptor; the high-affinity receptor had a Kd of 18.3 pM and an Nmax of 10.6 fmol/mg of protein. The specificity of receptor binding was demonstrated by studies showing that, for 50% displacement of 1 alpha,alpha,25(OH)2D3 binding, other derivatives were required at 500 times higher concentrations or more. In contrast to 1 alpha,25(OH)2D3, retinoic acid inhibited melanin synthesis and tyrosinase activity of B16 melanoma cells dose and time dependently. On simultaneous treatment, 1 alpha,25(OH)2D3 and retinoic acid caused mutual interference, and a balance between their respective stimulating and inhibitory effects was obtained at a molar ratio of 10:1; i.e., with 10 nM 1 alpha,25(OH)2D3 and 1 nM retinoic acid.

Animals↗
PubMed1984

Viscometric and electron microscopic analysis of effects of griseofulvin and its derivatives on in vitro polymerization of microtubule proteins and depolymerization of microtubules.

Griseofulvin and its sixteen derivatives were investigated by viscometry to examine their effects on in vitro polymerization and aggregation of microtubule proteins and depolymerization of microtubules. Of these compounds, eight pairs of enantiomers were compared in their activities. Electron microscopic studies were performed in several samples. The results indicate that in the C ring moiety of griseofulvin derivatives natural (+)-griseofulvin structure is essential to show their functions on microtubule proteins and microtubules.

Animals↗
PubMed1983

Study of negatively stained images of Sendai virus nucleocapsids using minimum-dose system.

Using minimum-dose system and optical diffraction, effects of electron irradiation on negatively stained images of trypsin-straightened nucleocapsids of Sendai virus were semiquantitatively compared for uranyl-acetate (UA) and phosphotungstic acid (PTA). The results confirmed the superiority of UA in display of fine structures and showed that both UA- and PTA-stained images tended to turn from a one-sided to a two-sided image during irradiation, the general contrast of the picture increased in the UA-stained images but not in the PTA-stained ones, and furthermore the electron doses for the richest information were 18 000 to 30 000 e-/nm2 for UA, but 1000 e-/nm2 for PTA, under the condition used. The optical diffraction patterns of the UA-stained nucleocapsids, its analysis by the superposition method, and rotational harmonics of end-on views of nucleocapsids, together indicated that the most probable arrangement of subunits was 13 per turn of a helix with 5-nm periodicity. This helix also had an arrangement of subunits parallel to the axis. The occurrence of 2.5 nm periodicity was probably produced by an arrangement of a UA-penetrable concave substructure of the subunit.

Capsid↗
PubMed1983

Regulation of terminal differentiation of cultured mouse epidermal cells by 1 alpha,25-dihydroxyvitamin D3.

Terminal differentiation of mouse epidermal cells in primary culture was found to be regulated by 1 alpha,25-dihydroxyvitamin D3 (1 alpha,25(OH)2D3), the hormonal form of vitamin D3 produced by sequential hydroxylations in the liver and kidney. Epidermal differentiation was stimulated dose dependently by 1 alpha,25(OH)2D3 at concentrations of 0.12 nM or more. In the presence of the vitamin, stratified foci increased in number and size and contiguous foci coalesced. Basal cells in the treated cultures decreased sharply and underwent differentiation into squamous and enucleated cells which sloughed off into the medium during cultivation. The size and density of the cells became larger and lighter during the course of differentiation. 1 alpha,25(OH)2D3 markedly stimulated formation of a cornified envelope, a structure with chemically stable cross-links formed beneath the plasma membrane. Of several derivatives of vitamin D3 examined, 1 alpha,25(OH)2D3 was the most potent in inducing epidermal differentiation. Stimulation of epidermal differentiation was also observed in low calcium medium. DNA synthesis was inhibited dose dependently by 1 alpha,25(OH)2D3. A specific receptor for 1 alpha,25(OH)2D3 was found in the cytosol fraction of the epidermal cells. Scatchard plot analysis revealed that the receptor has an apparent dissociation constant (Kd value) of 54 pM and maximum binding value (Nmax) of 43 fmol/mg protein. The specificity of the receptor was demonstrated by analog competition in the following order: 1 alpha,25(OH)2D3 much greater than 25-hydroxyvitamin D3 greater than 1 alpha-hydroxyvitamin D3 greater than 24R,25-dihydroxyvitamin D3.

Animals↗
PubMed1982

Three-dimensional structure of the crystalloid in the microbody of Kloeckera sp.: composite crystal model.

Electron microscopic investigations using the cryosectioning technique, together with electron diffraction, optical diffraction, and computer simulation, were carried out for the determination of the intrinsic structure of the crystalloid in the microbody of Kloeckera sp. The lattice images seen in the cryosections could be changed from one to another by tilting the specimen at an appropriate angle, the images obtained being well consistent with those obtained by computer simulation. The electron diffraction patterns also agreed with those obtained by optical diffraction. The results demonstrated that the crystalloid was composed of two different types of particles, large and small ones, arranged alternately and making up the composite crystal of rock salt structure. Large particles seemed to consist of alcohol oxidase molecules, while the small particles were presumably made up of catalase molecules.

Bacteria↗
PubMed1981

Measurement of partial specific thickness (net thickness) of critical-point-dried cultured fibroblast by energy analysis.

The relative specimen thickness obtained with an energy analyser is one of the most important parameters in electron microscopy. It has been made clear that this parameter can be applied not only to inorganic specimens, but also to organic and biological specimens. Moreover, the partial specific thickness of a critical-point-dried cultured fibroblast, that is, a net thickness converted in terms of Epon, was calculated from the relative specimen thickness. The partial specific thickness of each domain of the critical-point-dried cultured fibroblast is: CC 0.05 microns, PE 0.14 microns, ED 0.32 microns and PN 0.54 microns. As a result, it is suggested that 27% of the volume of this specimen consists of biological materials.

Cells, Cultured↗