bluuebunny/crossref_metadata_2025_split huggingface dataset:
Increase of latent HMG‐COA reductase activity with increasing density of cell cultures
Authors: Chen Harry W. 
Published: February 2005

AbstractThe total (active plus latent) activity of HMG‐CoA reductase declined linearly with increasing cell density in cultures of three lines of mammalian cells. The active form disappeared almost entirely under this condition, while the latent (presumably phosphorylated) form increased to some extent. The disappearance of active HMG‐CoA reductase with concomitant increase in the proportion of latent HMG‐CoA reductase was correlated with the decline in cellular multiplication and sterol synthesis. These results suggest that interconversion of HMG‐CoA reductase between active and inactive forms through phospho‐rylation‐dephosphorylation can be associated with changes in the rate of cellular proliferation in cell cultures. However, the decreased rate of sterol synthesis followed more closely the slower disappearance of the total HMG‐CoA reductase activity than the rapid decrease of the active form of the reductase alone. Therefore, changes in the rate of cellular proliferation can affect the interconversion of HMG‐CoA reductase between active and inactive forms through reversible phosphorylation. However, phosphorylation of the enzyme to the inactive form appears not to be the mechanism by which the sterol synthetic rate is regulated in confluent cell cultures. Rather, the amount of total HMG‐CoA reductase determines the rate of sterol synthesis.
Two populations of acid hydrolase‐containing particles in rat epididymis
Authors: Mayorga Luis , Bertini Francisco 
Published: February 2005

AbstractTwo populations of acid hydrolase‐containing particles were distinguished in homogenates of rat epididymis. One of them was rich in acid phosphatase activity, equilibrated at density 1.17 in a sucrose gradient, and it sedimented between 12,000g 2.5 min and 43,000g 60 min (light particles). The other was poor in acid phosphphatase activity and rich in N‐acetyl‐β‐D‐glucosaminidase, arylsulphatase, and β‐glucuronidase activity, equilibrated at density 1.20 in a sucrose gradient and it sedimented between 400g 2.5 min and 12,000g 2.5 min (heavy particles). 131I‐albumin (RISA) injected into the lumen of the cauda was partially recovered in subcellular particles of homogenates of this region. These particles, incubated at pH 5, were able to digest the engulfed RISA. The subcellular distribution of RISA‐containing particles and RISA‐digesting particles was similar to that of the heavy hydrolase‐containing particles. This suggests that these latter are engaged, at least in part, in heterophagic processes.
Efficient differentiation of proadipocyte stem cells on nonadherent surfaces: Evidence for differentiation without DNA synthesis
Authors: Yun Kankatsu , Hoerl Bryan J. , Scott Robert E. 
Published: February 2005

AbstractThe differentiation of low density BALB/3T3 T proadipocytes that are cultured in standard tissue culture flasks can be induced by heparinized medium containing human plasma. It has been shown that under these conditions, cells first growth‐arrest at a distinct state in the G1 phase of the cell cycle, designated GD, and thereafter differentiate within 8 to 12 days. In this paper, we report that the kinetics of proadipocyte differentiation can be significantly accelerated by culture of cells in differentiation‐promoting medium on non‐adherent surfaces, such as agarose‐coated plates or bacteriological Petri dishes. Data also show that in a nonadherent microenvironment extensive differentiation can occur in the absence of DNA synthesis. This was established most convincingly by the demonstration that placement of mitotic cells in heparinized medium containing human plasma and hydroxyurea on agarose‐coated Petri dishes induced 70–80% of the cells to GD arrest and differentiate without traversing the S phase of the cell cycle. It is concluded that under appropriate microenvironmental conditions metabolic events that occur solely in the late M or early G1 phase of the cell cycle can mediate the integrated control of proadipocyte proliferation and differentiation.
Proliferative kinetics and differentiation of murine blast cell colonies in culture: Evidence for variable G0 periods and constant doubling rates of early pluripotent hemopoietic progenitors
Authors: Suda Tohio , Suda Junko , Ogawa Makio 
Published: February 2005

AbstractSeveral investigators have described hemopoietic colonies expressing multilineage differentiation in culture. We recently identified a class of murine hemopoletic progenitors which form blast cell colonies with very high replating efficiencies. In order to clarify further the relationship between progenitors for blast cell colonies and progenitors for the multilineage hemopoietic colonies in culture, we carried out analyses of kinetic and differentiation properties of murine blast cell colonies. Serial observations of the development of blast cell colonies into multilineage (and single lineage) colonies in cultures of spleen cells obtained from 5‐fluorouracil (5‐FU)‐treated mice confirmed the transitional nature of the murine blast cell colonies. The data also suggested that the early pluripotent progenitors are in G0 for variable periods, and that when triggered into cell cycle, they proliferate at relatively constant doubling rates during the early stages of differentiation. The notion that some of the pluripotent progenitors are in G0 was also supported by long‐term thymidine suicide studies in which spleen cells were exposed to 3H‐thymidine with high specific activity for 5 days in culture, washed, and assayed for surviving progenitors. Comparison of replating abilities of day‐7 and day‐16 blast cell colonies from normal as well as 5‐FU‐treated mice indicated that some of the day‐7 blast cell colonies are derived from maturer populations of progenitors which are sensitive to 5‐FU. In contrast, progenitors for the day‐16 blast cell colonies are dormant in cell cycle and were not affected by 5‐FU treatment. Previously we reported that progenitors for day‐16 blast cell colonies have a significant capacity for self‐renewal. These observations suggest the hypothesis that the capability for self‐renewal is accompanied by long periods of G0, and that once commitment to differentiation takes place, then active cell division occurs.
A quantitative analysis of the aging of human glial cells in culture
Authors: Pontén Jan , Stein Wilfred D. , Shall Sydney 
Published: February 2005

AbstractThe kinetics of aging of normal human diploid brain cells in culture have been determined using the miniclone technique in which cells are cloned in the presence of a large number of other cells. The miniclone technique records the behaviour of every viable cell in the sample, not merely those cells capable of forming visible clones. This technique permits the direct measurement of the reproductive potential of individual cells growing in buik culture and of the dispersion of the sizes of colonies generated by dividing cells. The fraction of cells that are able to divide declines smoothly and continuously from the beginning of in vitro cultures of human glial cells. There is a broad distribution of colony sizes; even at the earliest passages there are significant numbers of small colonies. With increasing age of the culture there is a shift in the distribution, so that fewer large colonies and more small colonies occur. The distribution of intermitotic times is almost identical in young and middle‐aged cultures. Our data seem to exclude quite positively any description in terms of a catastrophe or any abrupt change in the population. On the contrary, the decline in reproductive potential may be described adequately either as a linear change with time, or as predicted by the mortality theory of Shall and Stein (1979), in which the single constant, gamma, describes the change in reproductive potential over the entire lifetime.
Glycosaminoglycans synthesized by cultured bovine corneal endothelial cells
Authors: Robinson Julie , Gospodarowicz Denis 
Published: February 2005

AbstractBovine corneal endothelial (BCE) cells seeded and grown on plastic dishes were labeled with 35S‐sulfate or 3H‐glucosamine for 48 h at various phases of growth of the cultures. Newly synthesized proteoglycans were isolated from the culture medium and from the extracellular matrix (ECM) produced by the BCE cells, and the glycosaminoglycan (GAG) component of the proteoglycans was analyzed. Cells actively proliferating on plastic surfaces secreted an ECM that contained heparan sulfate as the major 35S‐labeled GAG (86%) and dermatan sulfate as a minor component (13%). Upon reaching confluence, the BCE cells incorporated 35S‐labeled chondroitin sulfate (20%), as well as heparan sulfate (66%) and dermatan sulfate (14%), into the ECM. Seven‐day postconfluent cells incorporated newly synthesized heparan sulfate and dermatan sulfate into the matrix in approximately equal proportions. Dermatan sulfate was the main 35S‐labeled GAG (60–65%) in the medium of both confluent and postconfluent cultures. 35S‐Labeled chondroitin sulfate (20–25%) and heparan sulfate (15%) were also secreted into the culture medium. The type of GAG incorporated into newly synthesized ECM was affected when BCE cells were seeded onto ECM‐coated dishes instead of plastic. BCE cells actively proliferating on ECM‐coated dishes incorporated newly synthesized heparan sulfate and dermatan sulfate into the ECM in a ratio that was very similar to the ratio of these GAGs in the underlying ECM. Addition of mitogens such as fibroblast growth factor (FGF) to the culture medium altered the type of GAG synthesized and incorporated into the ECM by BCE cells seeded onto ECM‐coated dishes if the cells were actively growing, but had no effect on postconfluent cultures.
Teratocarcinoma cells exhibit growth cooperativity in vitro
Authors: Isacke Clare M. , Jane Deller M. 
Published: February 2005

AbstractMalignant PC13 embryonal carcinoma (EC) cells differentiate in vitro in response to retinoic acid, giving rise to a population of benign endoderm‐like cells (END), termed PC13 END. PC13 EC and PC13 END cells exhibit growth cooperatively in co‐culture, whereby the EC cells stimulate END cell proliferation and the END cells can support EC cell multiplication. The EC cells' stimulatory effect operates via soluble, diffusible factors which are also active on a range of fibroblast cell lines. END cells support the multiplication of EC cells plated at low density, via a multifactorial mechanism. Contact‐dependent effects can operate in the absence of END cell metabolic activity, while contact‐independent effects require the continuous presence of live END cells. It was observed that there was a variation in the ability of fibroblast cell lines to act as EC cell feeders. Similar interactive events may be important during the in vivo proliferation and differentiation of teratocarcinoma cells and their embryonic counterparts.
Hormonal regulation of discrete portions of the cell cycle: Commitment to DNA synthesis is commitment to cellular division
Authors: Wharton Walker 
Published: February 2005

AbstractDensity‐arrested human fibroblasts were stimulated to traverse G0/G1 and initiate DNA synthesis by the addition of medium containing either serum or a combination of platelet‐derived growth factor and platelet‐poor plasma. Medium containing a combination of epidermal growth factor and high concentrations of insulin also stimulated DNA synthesis in platelet factor‐treated quiescent cells. Platelet factor was required only to initiate proliferation. Epidermal growth factor and insulin then allowed G1 traverse and commitment to DNA synthesis. Cells could complete S, G2, and M in unsupplemented medium lacking peptide growth factors.
In vitro demonstration of deleterious effect of steel mutation on spermatogenesis in mice
Authors: Nishimune Yoshitake , Haneji Tatsuji , Maekawa Mamiko , Kitamura Yukihiko 
Published: February 2005

AbstractThe effect of the steel mutation on spermatogenesis was investigated by using organ culture. Cultured cryptorchid testes from C57BL/6− +/+ mice showed an effective differentiation of type A spermatogonia in response to an increased concentration of bovine serum. In contrast, the cryptorchid testes from C57BL/6 – S/d/ + mice showed only limited differentiation of type A spermatogonia even in the highest concentration of serum tested. The type A spermatogonia of mutant mice showed the normal mitotic response but did not differentiate further. The findings reported here are the first in vitro demonstration of the deleterious effects of the steel mutation on testicular germ cell differentiation and suggest that the effect of the steel mutation is expressed in Sertoli cells, the only supporting element in seminiferous tubules, or germ cells themselves.
In situ oxygen consumption rates of cells in V‐79 multicellular spheroids during growth
Authors: Freyer J. P. , Tustanoff E. , Franko A. J. , Sutherland R. M. 
Published: February 2005

AbstractThe rate of consumption of oxygen by V‐79 cells in multicellular spheroids was measured as a function of the spheroid diameter. In situ consumption was equal to that of exponentially growing cells for spheroids less than 200 μm in diameter. The rate of oxygen consumption decreased for cells in spheroids between 200 and 400 μm diameter to a value one‐fourth the initial, then remained constant with further spheroid growth. Comparison of consumption rates for spheroid‐derived cells before and after dissociation from the spheroid structure indicated that the spheroid microenvironment accounted for only 20% of the change in oxygen consumption rate. Cell‐cell contact, cell packing, and cell volume were not critical parameters. Plateau‐phase cells had a fivefold lower rate of oxygen consumption than exponential cells, and it is postulated that the spheroid quiescent cell population accounts for a large part of the intrinsic alteration in oxygen consumption of cells in spheroids. Some other mechanism must be involved in the regulation of cellular oxygen consumption in V‐79 spheroids to account for the remainder of the reduction observed in this system.
Selection of mouse macrophage‐like sublines that differ in leukemogenic potential and characterization
Authors: Kasukabe Takashi , Honma Yoshio , Hozumi Motoo 
Published: February 2005

AbstractThe murine macrophage‐like cell line (Mm‐1), which is nonleukemogenic to syngeneic SL mice, was originally derived from spontaneously differentiated cells of a clonal line of mouse myeloid leukemia cells (M1). In the present experiment, variant cell lines with a high (Mm‐A), moderate (Mm‐P), and little or no (Mm‐Sl and Mm‐S2) leukemogenic potential were obtained from the Mm‐1 cells. The mean survival times of syngeneic SL mice inoculated i.p. with 5 × 106 Mm‐A and Mm‐P cells were 17 and 33 days, respectively, whereas almost all the mice inoculated with Mm‐S1 or Mm‐S2 cells survived for more than 90 days. These variant cell lines did not lose their macrophage‐like characteristics in vitro. These variant cell lines phagocytized latex beads and sensitized sheep erythrocytes, produced lysozyme, and adhered to culture dishes. The four variant cell lines showed no significant difference in porliferation rates in vitro in liquid medium containing 10% calf serum, but Mm‐A cells could grow both in soft agar medium in the absence of ascitic fluid containing colony‐stimulating factor (CSF) and in liquid medium containing 1% serum, whereas Mm‐P cells could grow in the liquid medium but not in soft agar medium without ascitic fluid, and Mm‐S1 and Mm‐S2 cells could not grow in either medium. The ratio of the nuclear area to the cell area (NCR) of Mm‐A cells was a high (51%) but those of Mm‐Sl and Mm‐S2 cells were low (40–41%), and that of Mm‐P cells was intermediate (44%). The leukemogenicity of Mm‐1 cell lines was roughly correlated with their NCR. The possibility that interactions between Mm‐1 variant cells and host immune cells might be involved in the mechanisms of their different leukemogenicities was not supported by results on the in vitro susceptibilities of Mm‐1 variant cells to the cytostatic actions by normal macrophages and spleen cells and on leukemogenicities of the Mm‐1 variant cells in athymic nude mice. A possible method of control of the leukemogenicity of Mm‐1 variant cells is discussed.
Cultured mouse marrow cell lines: Interactions between fibroblastoid cells and monocytes
Authors: Zipori Dov , Friedman Aharon , Tamir Merana , Silverberg David , Malik Zvi 
Published: February 2005

AbstractContinuous cell lines were derived from primary cultures of adherent bone marrow cells from SJL/J, BALB/c, C3H/eb, RF, and nude‐ICR mice. All these lines readily assumed a pure fibroblastoid appearance with the exception of the BALB/c line (MBA‐14), which retained both fibroblastoid and monocytoid cells. This particular line could promote the proliferation of myeloid progenitors (CFU‐C) in short‐term bone‐marrow cultures. The two cell types that composed the MBA‐14 cell line were successfully isolated and grown separately; the monocytes as the 14M and 14M1 cell lines and the fibroblastoid cells as the 14F clones. The latter were found to be preadipocytes and accumulated fat in the absence of added hydrocortisone, in medium supplemented with fetal calf serum. Growth of the monocyte lines (14M and 14M1) was dependent upon the mononuclear phagocyte stimulator CSF‐1. In the parent MBA‐14 cell line the growth of monocytes seemed to depend upon stimulating factor(s) produced by the fibroblastoid cells. The 14M1 monocytes were able to process and degrade antigen as efficiently as primary macrophages. Furthermore, processed antigen produced by 14M1 cells evoked proliferative response by antigen‐primed lymph‐node cells. In addition to these immunological functions the 14M1 cells were capable of modulating the colony‐stimulating activity and degree of adipogenesis exhibited by the fibroblastoid cells. These interactions between monocytes and fibroblastoid cells may constitute part of the mechanism controlling the activity of the hematopoietic microenvironment.
Dependence of HL‐60 myeloid cell differentiation on continuous and split retinoic acid exposures: Precommitment memory associated with altered nuclear structure
Authors: Yen Andrew , Reece Sara L. , Albright Kevin L. 
Published: February 2005

AbstractThe cell differentiation of HL‐60 human leukemic promyelocytes along the myeloid pathway due to various continuous and distributed exposures to retinoic acid was studied. HL‐60 myeloid differentiation was a continuously driven process; significant terminal cell differentiation occurred only after a minimum exposure to inducer of two division cycles. Cells so committed to differentiation retained a heritable, finite memory of differentiation commitment over a further division cycle. Prior to becoming committed, cells acquired precommitment memory of exposure to inducer. Precommitment memory abbreviated the subsequent exposure to inducer needed for commitment to differentiation. Precommitment memory was semistable. It was heritable, but was lost after four division cycles. The acquisition and loss of precommitment memory correlated with alterations in nuclear architecture detected by narrow angle light scatter using flow cytometry. The altered nuclear architecture first occurred before any overt cell differentiation or growth arrest. It was thus an early event in the induced program of terminal cell differentiation. Alterations in relative abundances of cytoplasmic proteins also occurred prior to overt cell differentiation or growth arrest. One of these was a 17 kdalton, anionic, probably Ca2+ binding, protein. Retinoic acid thus induced early cellular changes, including cytoplasmic and nuclear alterations, within one cell cycle when cell differentiation was not yet apparent.
Anion requirement and effect of anion transport inhibitors on the response of vero cells to diphtheria toxin and modeccin
Authors: Sandvig Kirsten , Olsnes Sjur 
Published: February 2005

AbstractThe anion requirement for toxic action of diphtheria toxin and modeccin was studied. In Cl−‐free Hepes buffer made isotonic with mannitol, cells were insensitive to diphtheria toxin and modeccin. Just 2 mM NaCl was sufficient to obtain full toxic activity of modeccin, whereas 140 mM NaCl was required for maximal intoxication with diphtheria toxin. Br− could substitute for Cl−. NO3−, I− and ClO3− were less efficient than Cl−, whereas SO42− and SCN− were unable to replace Cl−. Cl− deprivation both reduced the ability of cells to bind diphtheria toxin and prevented bound toxin from intoxicating the cells. The binding of modeccin was not reduced. SITS (4‐acetamide‐4′‐isothio‐cyano‐stilbene‐2,2′‐disulfonic acid), an inhibitor of Cl− entry, protected against diphtheria toxin and modeccin, indicating that Cl− transport is required for intoxication.
An increase in adenylate cyclase activity precedes DNA synthesis in cultured vascular smooth muscle cells
Authors: Franks D. J. , Plamondon J. , Hamet P. 
Published: February 2005

AbstractAdenylate cyclase activity in cultured rat aortic vascular smooth muscle cells showed a linear correlation with the rate of DNA synthesis. When smooth muscle cells were rendered quiescent by shifting them from a serum‐supplemented medium to a medium containing low concentrations of plasma, the cells could be stimulated to proliferate by the addition of serum or by addition of a crude preparation of platelet‐derived growth factor. DNA synthesis began at 16 hours and was maximal at 24 hours. Prior to synthesis of DNA there was an increase in adenylate cyclase activity with a peak at 12 hours. Adenylate cyclase activity returned to basal level before DNA synthesis began. The increase in adenylate cyclase activity was not blocked by cycloheximide. Adenylate cycase activity could also be increased by incubating vascular smooth muscle cells with cholera toxin; however, the time course and magnitude of this increase was different from that caused by growth stimulants. Cholera toxin caused a slight increase in DNA synthesis at 16 hours, but was also cytotoxic to smooth muscle cells. An increase in adenylate cyclase activity may be a prerequisite for the progression from G1 to S.
Regulation of pyruvate kinase expression and growth in P‐815 mastocytoma cells. II. Potential role of prostaglandins
Authors: Ngo Julie‐Lani , Orlando Robert A. , Ibsen Kenneth H. 
Published: February 2005

AbstractP‐815 mastocytoma cells increase the level of pyruvate kinase (PK) expression in response to chloroform‐methanol extracts of conditioned media, butyrate, and dibutyryl cyclic AMP ( but2cAMP) plus theophylline. The butyrate effect is indomethacin sensitive, suggesting a prstaglandin (PG) is the active signaling factor. Moreover, the chloroform‐methanol extracts contain PGE2 and PGF2α and additions of the latter enhance PK activity. PGE2α alone has little or no effect but acts synergistically with PGF2. These data show that PGF2α can regulate PK levels. On the other hand, other factors may also be active, since the endogeneous and the but2cAMP plus theophylline effects are indomethacin insensitive. Most of the factors that increase PK activity also inhibit cellular growth; however, regulation of PK expression can be uncoupled from growth inhibition.
Transaminase inhibitors block glycolysis and G1 to S phase progression in chick embryo fibroblasts: Reversal by α‐keto acids
Authors: Groelke John , Amos Harold 
Published: February 2005

AbstractTwo transaminase inhibitors, aminooxyacetate and cycloserine, inhibited the initiation of insulin‐stimulated DNA synthesis in chick embryo fibroblasts. This inhibition was overcome when pyruvate (4 mM), oxaloacetate (4 mM), or α‐ketobutyrate (10 mM) was included in the culture medium with hormone and inhibitor. Aminooxyacetate also inhibited lactate production in insulin treated cultures in the absence of added α‐keto acid.