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Volume 15 (1990)
- Issue 6 Pages 323-
- Issue 5 Pages 237-
- Issue 4 Pages 175-
- Issue 3 Pages 127-
- Issue 2 Pages 73-
- Issue 1 Pages 1-
Volume 15, Issue 2
Displaying 1-8 of 8 articles from this issue
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M. Teresa Serrano, Eduardo Angulo, Miguel A. Sevillano, Jesus Moya1990 Volume 15 Issue 2 Pages 73-77
Published: 1990
Released on J-STAGE: March 27, 2006
JOURNAL FREE ACCESSThe nephridium muscular layer of the sipunculan Phascolosoma granulatum consists of longitudinal cells oriented in parallel to the nephridial network and of circular cells. These cells are filled with myofilaments and cell organelles, such as mitochondria, nucleus, and sarcoplasmic reticulum; the organelles are located in the peripheral regions of the cells. The thick myofilaments appear to have cross striations at intervals of 14 nm, typical of paramyosin filaments.
According to our ultrastructural observations, there are three kinds of thick myofilaments in these cells. The mean diameters are respectively about 28, 42, and 58 nm. The cells can be divided into three types according to the kinds of myofilaments they contain. One type contains all three kinds of myofilaments; the second contains the 28 and 42 nm myofilaments; and the third contains only the 28 nm myofilaments. The fine structure of the cell organelles appears the same in all three types.View full abstractDownload PDF (1224K) -
Yasuko Watanabe, Masami Taniguchi, Nobuko Fukamachi, Megumi Sakuma, Bo ...1990 Volume 15 Issue 2 Pages 79-84
Published: 1990
Released on J-STAGE: March 27, 2006
JOURNAL FREE ACCESSFormation of platelet-producing megakaryocytes, the cytoplasm of which showed the terminal stage of cell maturation, heavy granulation and platelet-fields delineated with demarcation membranes, was observed in a short-term culture system, using megakaryocyte-enriched bone marrow cell suspension. Approximately 6-8% of the megakaryocytes changed to the platelet-producing megakaryocytes during 12-hour incubation. In the presence of inhibitors of energy metabolism, formation of the platelet-producing megakaryocytes was inhibited, suggesting that the process is dependent on energy producing systems. Ganglioside GD1a increased both the number of total megakaryocytes and the ratio of the platelet-producing megakaryocytes to total megakaryocytes, while GM1 did not influence the number of total megakaryocytes, but increased the ratio. Gangliosides GM2, GM3 and GD1b showed little effect on either the number of total megakaryocytes or the ratio. The results suggest that ganglioside GD1a stimulates at least two steps of megakaryocyte maturation, the change of megakaryocytic progenitors to megakaryocytes and the subsequent maturation of megakaryocytes to the platelet-producing megakaryocytes, while GM1 stimulates only the latter step of the maturation.View full abstractDownload PDF (895K) -
Itaru Moro, Kazuo Komiyama, Takashi Iwase, Zina Moldoveanu, Jiri Meste ...1990 Volume 15 Issue 2 Pages 85-91
Published: 1990
Released on J-STAGE: March 27, 2006
JOURNAL FREE ACCESSThe cytoplasmic affinity of polymeric IgA for secretory component (SC) and the expression of joining (J) chain were examined in pokeweed mitogen (PWM)-stimulated human peripheral blood lymphocytes (PBL) to determine, on the ultrastructural level, the polymerization sites of human IgA. SC-binding was found in 5.7% of transformed PBL on day 7 of culture; SC-binding was observed in a high proportion of IgA-producing cells. A low proportion of IgM-producing cells also bound to SC, while there was virtually no SC-binding by IgG-producing cells. A high proportion of IgA- and IgM-producing cells expressed intracellular J chain, while approximately half of the IgG-producing cells were positive for J chain.
The number of J chain-positive cells exceeded the number of SC-binding cells among transformed PBL on day 7 of culture. Immunoelectron microscopic study of the sites of SC-binding, and of IgA and J chain expression, revealed that polymerization of human IgA and the addition of J chain occur in the perinuclear space and endoplasmic reticulum, prior to immunoglobulin secretion.View full abstractDownload PDF (1715K) -
Kazuhiro Ishii1990 Volume 15 Issue 2 Pages 93-97
Published: 1990
Released on J-STAGE: March 27, 2006
JOURNAL FREE ACCESSThymidine auxotrophs (B3T) of rat nerve-like cells (B103) were isolated. B103 cells were preincubated in a thymidine medium and mutagenized with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Afterward, cells were incubated in a medium supplemented with dialyzed fetal calf serum and then treated with 5-fluorodeoxyuridine for 24 h. Next, cells were grown in a thymidine medium for twenty days. Thymidine auxothrophs were thus obtained and one clone of them was designated B3T cells. The modal number of chromosomes in B3T cells was 85. Growth tests revealed the following interesting facts: (1) The medium containing pyrazofurin and uridine could not support the growth of B3T cells, but the addition of thymidine to such a medium enabled cells to grow. (2) Even deoxyuridine supported the growth of B3T cells when added to the medium of pyrazofurin and uridine. These findings suggest that the catalytic ability of thymidylate synthetase in B3T cells may have decreased, probably due to the decreased affinity of the enzyme molecules to the substrate (dUMP), and that thymidine kinase activity was high enough to support the growth of B3T cells. B3T cells have maintained the ability to differentiate and extend neurites in response to dibutyryl-cyclic AMP as also demonstrated in wild cells (B103). B3T cells will be available for genetical and molecular biological studies of neuronal cells.View full abstractDownload PDF (1039K) -
Tetsuaki Osafune, Jerome A. Schiff, Eiji Hase1990 Volume 15 Issue 2 Pages 99-105
Published: 1990
Released on J-STAGE: March 27, 2006
JOURNAL FREE ACCESSThe light-harvesting chlorophyll a/b complex (LHCP II) of Euglena gracilis contains a 26.5- kDa polypeptide. This polypeptide is low or undetectable in wild-type cells grown in darkness or in dark-grown resting wild-type cells exposed to 7 ft-c of light (the threshold for chloroplast development). On exposure of dark-grown resting cells or cells at 7 ft-c to a normal intensity for development (80 ft-c), the 26.5-kDa apoprotein is rapidly formed. Using a highly specific antibody to the 26.5-kDa apoprotein, little reaction can be detected in electron micrographs of dark-grown resting cells or the same cells at 7 ft-c, as determined by deposition of protein A-gold. However, in the same cells after exposure to 80 ft-c of light, gold deposition over the Golgi apparatus as well as the thylakoids of the plastids can be seen. No deposition is seen if preimmune serum is substituted for immune serum.View full abstractDownload PDF (4782K) -
Takeshi Inoue, Yasuo Nakaoka1990 Volume 15 Issue 2 Pages 107-112
Published: 1990
Released on J-STAGE: March 27, 2006
JOURNAL FREE ACCESSA transient depolarization was recorded in response to the cooling of a deciliated Paramecium. The amplitude of the depolarization was almost proportional to the cooling rate. Therefore, the cells are sensitive to the rate of temperature change. The input resistance of the membrane transiently increased during the cooling. When constant current was applied to shift the resting membranepotential to a negative or positive level, the initial depolarization in response to cooling decreased, and the following hyperpolarization during cooling reversed to a gradual depolarization during a positive shift. The potential at which the reversal occurred was independent of K+ concentration and was slightly dependent on Ca2+ concentration (10 mV/log[Ca2+]0). The amplitude of the initial depolarization decreased with the increase in K+ and was not affected by Ca2+. These results are discussed in terms of changes in membraneconductances in response to cooling.View full abstractDownload PDF (385K) -
Youtarou Higashi, Kenichi P. Takahashi, Toshiko Uchimoto, Seiji Morisa ...1990 Volume 15 Issue 2 Pages 113-116
Published: 1990
Released on J-STAGE: March 27, 2006
JOURNAL FREE ACCESSS1 proteins (A, B, C and D) are a group of nuclear proteins, isolated bylowering pH to 4.9 of the reaction supernatant of hepatocyte nuclei that had been mildly digested with DNase I. Protein B, apparently ubiquitous in vertebrate cells, was prepared from rat liver and used to immunizea rabbit. The raised antiserum specifically reacted with SI proteins; it reacted not only with protein B, but also with C and D. Immunoblotting demonstrated that these proteins occurred exclusively in the nucleus, being absent in the cytosol, microsome and mitochondrial fractions. Indirect immunofluorescence of liver tissue sections confirmed their nuclear localization, and further showed that the antibody selectively stained extranucleolar regions of the cell nucleus. These findings suggest that the anti-Si antibody is specific to SI proteins and may be useful for their structural and functional studies.View full abstractDownload PDF (684K) -
Yasushi Fukui, Akitsugu Yamamoto, Takahiro Kyoden, Keitaro Kato, Yutak ...1990 Volume 15 Issue 2 Pages 117-125
Published: 1990
Released on J-STAGE: March 27, 2006
JOURNAL FREE ACCESSWe investigated ultrastructural localization of dipeptidyl peptidase IV (DPP IV) [EC3.4.14 5] in rat liver cells quantitatively by post embedding protein A-gold technique. In the hepatocyte, DPP IV was mainly localized on the bile canalicular surface and the lysosomal membranes, but were scarcely detectable on the sinusoid-lateral surface. A small number of DPPIV was also detected in the trans region of the Golgi apparatus, suggesting that this part may play important roles in intracellular transport or recycling of this enzyme. In the endothelial cell, DPPIV existed on the whole surface of the plasma membraneand the lysosomes. In the Kupffer cell DPPIV was mainly localized in lysosomes and a few were detected on the plasma membrane.View full abstractDownload PDF (3262K)
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