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Biomedical subjects

K Kaji

Publications and source records attributed to K Kaji.

At least 91 records · Page 5Linked to original sources
PubMed1992

Effect of Harderian gland-derived growth factor on the growth of cornea stromal cells.

To investigate the physiological role of Harderian gland-derived growth factor (HGDGF), the effects of HGDGF and various other growth factors on the growth of cultured guinea pig cornea stromal cells were examined. HGDGF increased the incorporation of [3H]thymidine to 150% of the control (5% fetal calf serum). The combination of HGDGF with fibroblast growth factors (FGFs) or platelet-derived growth factor enhanced the cell growth over that of either growth factor alone, increasing the incorporation of [3H]thymidine to 180 and 190% of the control, respectively. The combination of HGDGF with transforming growth factor (TGF-beta) decreased the growth to 60% of the control, and epidermal growth factor had no effect on the activity of HGDGF. The growth-stimulating activity of HGDGF was inhibited by suramin in a different manner from that of FGFs. These findings suggest that HGDGF binds a specific cell-surface receptor and plays a role in the repair of injured parts of the cornea and in the maintenance of the cornea stromal cells.

Animals↗
PubMed1992

Annual changes of testis size, seminiferous tubules and plasma testosterone concentration of wild Sika deer (Cervus nippon yesoensis Heude, 1884) in Hokkaido.

Testis size, seminiferous tubules and plasma testosterone concentrations showed conspicuous annual changes in Sika deer of Hokkaido, Japan. The onset of the spermatogenic process occurred in July or August. Spermatogenic activity had already reached its height in late October, at the beginning of the rutting season, and had begun to decline in late December. Spermatogenesis had stopped in February or March. Plasma testosterone concentrations showed very high levels in late October and early November, but was almost at the basal level in February, March, June and December. The wide individual variation of the plasma levels in October suggest pulsatile secretions of testosterone.

Animals↗
PubMed1992

[Function, molecular structure and gene expression regulation of Platelet-derived growth factor].

Platelet-derived growth factor (PDGF) is a cationic glycoprotein of approximately 30 kDa, composed of two subunits. These subunit chains are termed A (18 kDa) and B (12-14 kDa) with high homology of the peptide sequences, including 8 cysteine residues at identical positions. Three isoforms of PDGF, AA, BB homodimers and AB heterodimer are distributed in the different tissues and cell lines suggesting that these isoforms have different functions. Two types of PDGF receptors alpha, and beta with Mr of 160-180 kDa are seen on the cell surface. PDGFR alpha can bind to both A and B subunits of the PDGD, while PDGFR beta, only B subunit. PDGF (AA) combines alpha alpha, PDGF (AB) makes dimers of alpha alpha and alpha beta, and PDGF (BB) can make three types of dimers, alpha alpha, alpha beta, and beta beta. These dimeric PDGFRs are active forms and phosphorylate its own domain and other neighbor specific proteins. The substrates of the receptor kinase are phospholipase C-gamma, GTPase activating protein (GAP), serine/threonine kinase Raf-1 and others. These molecules are thought to transfer information of the PDGFs on its receptors to the nucleus.

Amino Acid Sequence↗
PubMed1991

A new human male diploid cell strain, TIG-7: its age-related changes and comparison with a matched female TIG-1 cell strain.

A new human diploid cell strain, TIG-7, which has the male karyotype, was established and characterized. Isozyme and histocompatibility typing of the cell strain was performed. The average in vitro life span of the cells is 73 population doublings. Changes in cell volume, doubling time, saturation density, the efficiency of cell attachment, plating efficiency, and relative DNA content were examined during in vitro cellular aging. Hydrocortisone slightly prolongs the life span of the cell strain when the hormone is administered to the cultures during middle passages. The age-related changes in the parameters of TIG-7 are not appreciably different from those of the previously established TIG-1 cell strain. These results show that this cell strain is useful for research on cellular aging; further profit is anticipated from research using a combination of these two sexually different cell strains.

Cell Line↗
PubMed1991

Heterogeneous responses of human endothelial cells to tumor necrosis factor with respect to growth inhibition.

The response of human arterial endothelial cells (ECs) to tumor necrosis factor (TNF) was compared to that of venous ECs. It was found that arterial ECs were more susceptible to TNF induced inhibition of growth and colony formation by TNF than venous ECs. In addition, synergistic effect of TNF with Interferon-gamma (IFN-gamma) was more evident in arterial ECs. Little difference, however, was identified in the characteristics of TNF receptors between arterial and venous ECs; the dissociation constant (Kd) was 0.35 nM and the number of receptors/cell was approximately 5,000. This indicates that different susceptibility of ECs to TNF is not due to these characters of TNF receptors. In conclusion, ECs are heterogeneous in the responsiveness to TNF depending on the sites of origins.

Animals↗
PubMed1991

[Serum-free culture--a theoretical note].

Usually the cells are cultured in serum-supplemented media. Since serum is a highly complex, largely undefined fluid, it is difficult to study the interactions of mitogens and cells in a carefully controlled fashion. Serum-free culture methods must be important for escape the complexity of classical serum-containing culture methods. In this short note, I tried to introduce the theoretical field of serum-free culture, mainly emphasizing the importance of growth factors.

Animals↗
PubMed1990

Role of protein kinase C in the inhibition by fibroblast growth factor of apoptosis in serum-depleted endothelial cells.

Apoptosis in vascular endothelial cells is suppressed by fibroblast growth factor (FGF)1. In order to investigate the signal transduction system that regulates endothelial apoptosis, we studied the effects of several mitogenic factors. Apoptosis occurred in human vascular endothelial cells under serum-free conditions, and FGF inhibited apoptosis without a requirement of any cooperative factors, as distinct from the mitogenic response. Other mitogenic agents, such as epidermal growth factor, transferrin, transforming growth factor beta, and interleukin 1 etc., with the exception of dexamethasone, had no such inhibitory effects. The effect of FGF was mimicked by a phorbol ester and was prevented by an inhibitor of protein kinase C. The results suggest that the FGF and protein kinase C are important in endothelial apoptosis.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1990

Purification and identification of a growth factor produced by Paramecium tetraurelia.

We previously reported that the jumyo mutant of a cilate protozoan Paramecium tetraurelia excretes into the medium a factor which promotes its own cell division. Here, the factor was purified to electrophoretic homogeneity through a series of liquid chromatographic procedures. This substance is a protein with a molecular weight of 17,000 which at concentrations of 1 X 10(-9) M (17 ng/ml) or more results in the recovery of the cell division rate of the jumyo mutant to the level of the wild type. The factor is therefore considered to be a growth factor and was named Paramecium growth factor (ParGF). This is the first report of direct proof for the production of a growth factor in an organism other than vertebrates.

Animals↗
PubMed1990

Apoptosis of vascular endothelial cells by fibroblast growth factor deprivation.

Survival and proliferation of many types of vascular endothelial cells are influenced by fibroblast growth factor (FGF)1. Removal of FGF from the medium of human umbilical vein endothelial cells (HUVEC) in culture resulted in death of the cells. Here we show that the death caused by deprivation of FGF is active death or apoptosis, and the process of apoptosis can be inhibited by cycloheximide, an inhibitor of protein synthesis. The present study shows apoptosis occurs in endothelial cells in culture. The process of active death of vascular endothelial cells is inhibited by growth factor. This mechanism may be important for the regulation of vascular organization through the degeneration of vessels.

Animals↗
PubMed1990

Growth-inhibiting effect of tumor necrosis factor on human umbilical vein endothelial cells is enhanced with advancing age in vitro.

We have examined the effects of in vitro aging on the growth capacity of human umbilical vein endothelial cells (HUVECs) under the influence of tumor necrosis factor (TNF) with or without interferon-gamma (IFN-gamma). The growth and colony-forming abilities of control cells were impaired with advancing age in vitro, especially at later stages (more than 70-80% of life span completed). It was found that treatment with TNF inhibited growth and colony-forming efficiency at any in vitro age. The effects of TNF were shown to increase with increasing in vitro age, as reflected by a more pronounced increase in doubling times, a decrease in saturation density, and a reduction in colony-forming efficiency. However, the characteristics of TNF receptors, including the dissociation constant, and the number of TNF-binding sites per cell-surface area remained rather constant. The effect of TNF was augmented by IFN-gamma at a dose that alone affected growth and colony formation only slightly. The augmentation by IFN-gamma was also found to depend on in vitro age; the synergy with TNF in the deterioration of colony-forming ability was observed only in "aged" cells. These results suggest that the intrinsic responsiveness of HUVECs to growth-inhibiting factors, as well as to growth-stimulating factors, changes during aging in vitro.

Aging↗
PubMed1990

Tumor necrosis factor reduces lifespan of human endothelial cells in vitro.

Tumor necrosis factor (TNF) is known to regulate the proliferation and function of vascular endothelial cells (ECs). We have examined the effects of TNF on the growth and aging of human ECs of different origins and compared them with those in human normal diploid fibroblasts. The results obtained were as follows: (1) TNF reduces the growth rate and in vitro life span of ECs in both dose- and treatment length-dependent fashions; (2) ECs are significantly more sensitive to TNF than fibroblasts; and (3) the life span shortening effect of TNF on ECs increases as a function of in vitro cell age. These results suggest that the aging of ECs is modified by TNF exposure.

Cell Division↗
PubMed1989

Purification and characterization of a growth factor from guinea pig harderian gland.

A polypeptide growth factor, Harderian gland-derived growth factor (HGDGF), has been purified approximately 43,000-fold from guinea pig Harderian gland by column chromatography on TSK gel DEAE-5PW, blue-Sepharose CL-6B, and Superose 12. The yield was approximately 10%. The Superose 12 fraction was further purified by Aquapore BU-300 reversed-phase chromatography to apparent homogeneity. HGDGF was eluted from TSK gel DEAE-5PW at 0.20-0.35 M NaCl, with a linear gradient of 0.15-0.80 M NaCl and at 2.20 M NaCl from blue-Sepharose CL-6B. The activity of HGDGF toward human embryonic cells (TIG-3) was quantitated, [3H]thymidine incorporation for 48 h being stimulated in a linear and dose-dependent manner. Purified HGDGF has a molecular weight of approximately 13,000, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and molecular sieve column chromatography. HGDGF is labile to treatment with SH reagents or acetic acid. Both trypsin digestion and boiling decrease the activity of HGDGF. Its pI is 5.1. HGDGF stimulates the multiplication of TIG-3 cells but has no effect on human endothelial cells K2T1 or A2T2 which require fibroblast growth factor for growth. HGDGF appears to differ from other growth factors, suggesting that it is a previously undescribed growth factor.

Animals↗
PubMed1989

Association of increased intracellular free Ca2+ by platelet-derived growth factor with mitogenesis but not with proteoglycan synthesis in chondrocytes--effect of suramin.

The effects of platelet-derived growth factor (PDGF) on the intracellular free Ca2+ concentration [( Ca2+]i) in chondrocytes were studied with a fluorescent Ca2+ indicator, fura 2, and compared with the effects of PDGF on mitogenesis and proteoglycan synthesis. PDGF evoked phasic and then tonic increase in [Ca2+]i dose-dependently in quiescent cultures of chondrocytes, and it also stimulated both DNA and proteoglycan syntheses dose-dependently similar to somatomedins. Suramin, which inhibits the interaction of PDGF with its receptors, caused dose-dependent inhibition of both the PDGF-evoked increase in [Ca2+]i and stimulation of DNA synthesis by PDGF. However, suramin rather enhanced the proteoglycan synthesis induced by PDGF without affecting the basal level of proteoglycan synthesis directly. These results suggest that [Ca2+]i may be an important signal for the action of PDGF on cell proliferation in chondrocytes, and that the initial signal for proteoglycan synthesis is different from that for DNA synthesis induced by PDGF after the activation of PDGF receptor.

Animals↗
PubMed1989

Identification of a gene that shortens clonal life span of Paramecium tetraurelia.

We have isolated a Paramecium tetraurelia mutant that divides slowly in daily reisolation cultures and repeats short clonal life spans after successive autogamies. Here we show, using breeding analysis, that a recessive mutation is responsible for the low fission rate and that this low rate is closely related to the short clonal life span. We conclude that a single pleiotropic gene controls these traits and have named it jumyo. In an attempt to further characterize the jumyo mutant, we have revealed that it has a culture life span similar to that of the wild-type cells and that, when mass cultured, it can divide as rapidly as wild-type cells. There was strong evidence that the mutant cells excreted into culture medium some substance that promotes their cell division. These findings may not only present supporting evidence for the hypothesis that the cellular life span is genetically programmed but also give a material basis for the study of the controlling mechanism of cell division in relation to the clonal life span.

Animals↗
PubMed1988

Cytotoxicities of a linoleic acid hydroperoxide and its related aliphatic aldehydes toward cultured human umbilical vein endothelial cells.

An assay method for the quantification of the cytotoxicities of various agents toward cultured human endothelial cells was developed using Earle's solution as an incubation medium. By this method, the cytotoxicities of a linoleic acid hydroperoxide (LOOH) and its related aliphatic aldehydes toward human umbilical vein endothelial cells were investigated. Saturated aldehydes, pentanal, hexanal and 9-oxononanoic acid, are nontoxic; alpha, beta-unsaturated aldehydes, 2-hexenal, 2-heptenal, 2-octenal and 2-nonenal, are toxic only at high concentrations; LOOH and alpha, beta-unsaturated aldehydes with a hydroxy group or an additional double bond, 4-hydroxy-2-nonenal, 2,4-nonadienal and 2,4-decadienal, are highly toxic. In particular, 2,4-decadienal, whose 50% lethal concentration is 9 microM, is the most injurious. The cytotoxicities of LOOH and its related aldehydes were found to be much reduced in growth medium containing serum, growth factors, heparin, amino acids and vitamins.

Aldehydes↗
PubMed1988

Effects of serum from human subjects of various ages on proliferation of human lung and skin fibroblasts.

We carried out a study to determine whether serum from old human subjects inhibited cell proliferation. The results showed that serum from old subjects of either sex did not greatly inhibit the proliferation of human fetal lung fibroblast TIG-1 cells, even when serum from subjects in their 80s was used. The same results were obtained when the effects of serum on cell proliferation were examined up to a serum concentration of 50%. It was also found that serum from old subjects did not inhibit proliferation of human skin fibroblasts from a young adult to any greater degree than serum from young adult subjects, and that serum from young adult subjects did not stimulate proliferation of skin fibroblasts from an elderly donor to any greater degree than serum from old subjects.

Adolescent↗