bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cell separation by velocity sedimentation of postnatal mouse cerebellum
Authors: Barkley David S. , Rakic Ljiljana L. , Chaffee Jonathan K. , Wong Dona L. 
Published: February 2005

AbstractTrypsinized cells of newborn mouse cerebellum have been separated by velocity sedimentation at unit gravity in shallow gradients of Ficoll. The two main technical difficulties were formation of gels around the dissociated cells and clumping of cells before and during the sedimentation procedure. These were solved by adding DNase to the dissociation medium and with holding serum, respectively. Proliferating cells of the external granular layer separated according to size differences in the cell generation cycle. Identification of Purkinje or other early‐forming neurons was made by labeling them with 3H‐thymidine on their birthdays. Many of the fractions contain viable cells capable of aggregating in culture.
Flow microfluorometric studies of lectin binding to mammalian cells. I. general features
Authors: Kraemer Paul M. , Tobey Robert A. , Van Dilla Marvin A. 
Published: February 2005

AbstractFlow microfluorometry has been used to quantitate cell‐surface binding of fluorescein‐conjugated lectins. Frequency distributions of total surface binding of Concanavalin A per cell were prepared for a variety of cultured cell populations, including established cell lines, virus‐transformed lines and non‐transformed parental lines. In the case of growing Chinese hamster cells (line CHO), much of the variability of Con A binding per cell could be related to variability of cell size. Experiments with cells synchronized by mitotic selection indicated that the modal surface density of binding sites was almost constant throughout the cell cycle. However, as indicated by inhibition of binding with α‐methyl mannopyranoside and by the effect of trypsin, the sites on each cell were heterogeneous in chemical structure and/or exposure. Agglutinability of virus‐transformed cell lines or trypsin‐treated parental lines was demonstrated but could not be correlated closely with binding.
Colony formation by chicken hematopoietic cells and virus‐induced myeloblasts
Authors: Dodge W. H. , Moscovici C. 
Published: February 2005

AbstractLeukemic myeloblasts and cells derived from normal chick hematopoietic tissue produced colonies in soft agar. Colonies produced by leukemic myeloblasts differed from normal chick tissue in their morphological characteristics, in the greater initial number of cells required for colony formation and in their decreased dependence on conditioned medium for development. The colony forming cells for both types were enriched when allowed to grow for several days in liquid growth medium.In soft agar, myeloblasts differentiated into more mature granulocytic cells and macrophages. These differentiated cells accumulated between one and two weeks after seeding. When tested for release of avian myeloblastosis virus (AMV), 6 out of 18 colonies were releasing AMV at one week whereas 3 out of 39 were releasing AMV at two weeks. Five two week old colonies which were negative for AMV were producing myeloblastosis associated viruses (MAVs). Normal colony forming cells were present in leukemic buffy coat and although colonies made by these cells contained MAVs, no AMV could be detected.The data obtained with normal avian tissues were similar to those obtained by others with mammalian hematopoietic tissue. Colony formation by normal hematopoietic tissues was strictly dependent on factors present in conditioned medium. Tissues producing colonies included bone marrow, yolk sac, spleen and peripheral leukocytes. Colonies were not obtained from thymus and bursa. Furthermore, the colony origin did not appear to be erythroid in nature.
Colony formation in agar by murine plasmacytoma cells: Potentiation by hemopoietic cells and serum
Authors: Metcalf D. 
Published: February 2005

AbstractClonal growth in semisolid agar medium was obtained using cells from 19 of 25 transplanted murine plasmacytomas when the medium was supplemented by whole mouse blood or washed red cells. With different tumors cloning efficiency ranged from 0.01% to 21.6%. With two exceptions, mouse blood did not potentiate colony formation in agar by cells from transplantable myelomonocytic, myeloid, and lymphoid leukemias, reticulum cell sarcomas and fibrosarcomas. The clonal growth of some plasmacytomas was also potentiated by syngeneic thymic, spleen or bone marrow cells. Plasmacytoma colony growth was not stimulated by normal mouse serum but serum from mice injected with endotoxin or polymerised flagellin stimulated colony growth by some plasmacytomas. The active serum factor was not the colony stimulating factor (CSF) and its appearance after antigenic stimulation was not T cell‐dependent. Preimmunised mice failed tq respond to antigenic stimulation. Whole body irradiation did not induce a rise in the capacity of serum to stimulate colony formation by plasmacytoma cells.
Isolation and characterization of revertant cell lines. II. Growth control of a polyploid revertant line derived from SV40‐transformed 3T3 mouse cells
Authors: Pollack Robert , Vogel Arthur 
Published: February 2005

Abstract3T3 mouse fibroblasts in 10% calf serum cease to increase in number at confluence. SV40‐transformed 3T3 cells lose their sensitivity to this growth control and so are able to reach multilayered cell densities. We previously described a polyploid revertant line F1SV101, isolated from a SV40‐transformed cell, that has a low maximum cell density (Pollack et al., '68), despite the continued presence in this revertant of SV40‐specific DNA, RNA and Tantigen. We have examined the mechanism by which the revertant maintains a low saturation density, and find that at confluence the revertant and 3T3 are both reduced in mitotic index, fraction of cells synthesizing DNA, and rate of DNA synthesis. The transformed cell does not respond to confluence. None of the lines sheds intact cells into the medium at confluence.
The effects of inhibitors of RNA and DNA synthesis on protein synthesis and polysome levels in mouse L‐cells
Authors: Craig Nessly 
Published: February 2005

AbstractMetabolic inhibitors of RNA synthesis, such as actinomycin D and MPB (2‐mercapto‐1‐(β‐4‐pyridethyl) benzimidazole) have often been used to test the possibility that transcription is required for some cellular process or to measure the „half‐life”︁ of messenger RNA (mRNA). The basic assumption of this work has been that the primary effect of these inhibitors is on transcription alone, and that any effect on translation is secondary to the inhibition of mRNA synthesis. This assumption has been tested by examining the effects of these inhibitors at different doses on various parameters of the transcriptional and translation processes in mouse L‐cells in culture, i.e., the rates of RNA, DNA, and protein synthesis; the level and size of cytoplasmic polysomes; the rates of polypeptide elongation and termination, and the role of peptide chain initiation in protein synthesis. The results indicate that the basic assumption is not correct since these inhibitors affect protein synthesis by inhibiting the rate of initiation and not the level of mRNA. Another implication of the experiments is that the average mRNA in L‐cells has a half‐life of at least one cell generation (16–18 hours), and that earlier values from experiments using actinomycin are underestimates. Cordycepin (3′‐deoxyadenosine) which inhibits the production of ribosomal and messenger RNA also affects protein synthesis at the level of initiation. In contrast, two inhibitors of DNA synthesis (hydroxyurea and cytosine arabinoside) inhibit protein synthesis and the level of polysomes by some other mechanism.
Calcium‐dependent stimulation by a phorbol ester (PMA) of thymic lymphoblast DNA synthesis and proliferation
Authors: Whitfield J. F. , Macmanus J. P. , Gillan D. J. 
Published: February 2005

AbstractPMA (phorbol myristate acetate, i.e., 12‐0‐tetradecanoyl‐phorbol‐13‐acetate) a tumor‐promoting ester from croton oil, at its most effective concentration of 0.05 μg per milliliter, rapidly (within one hour) induces a large fraction of the lymphoblasts in suspended thymic lymphocyte populations to start making DNA, and these stimulated cells later progress into mitosis. This stimulatory PMA action is probably mediated by calcium because it disappears when calcium is omitted from the medium, and PMA strikingly increases the sensitivity of the lymphoblasts to calcium's stimulatory action.
Pyridine nucleotide metabolism in mammalian cells in culture
Authors: Hillyard David , Rechsteiner M. C. , Olivera Baldomero M. 
Published: February 2005

AbstractThe biosynthesis of pyridine nucleotides has been examined in a number of mammalian cell lines in culture. In all lines examined, nicotinamide is incorporated by a biochemical pathway distinct from the Preiss‐Handler pathway for nicotinic acid.In at least the human cell line D98/AH2, there is no detectable endogenous synthesis of the pyridine ring from tryptophan. Although most cell lines examined (hamster BHK 21/13, mouse L929 and human D98/AH2) use either nicotinic acid or nicotinamide as a precursor for DPN and TPN, two mouse cell lines, 3T3‐4E and LM CIID, are unable to utilize nicotinic acid as a source of the pyridine ring.If nicotinic acid is present in the medium, substantial amounts of intracellular desamido DPN accumulate suggesting that the last step (desamido DPN→DPN) is limiting in the Preiss‐Handler pathway. With nicotinamide, the only compound which accumulates in substantial amounts apart from DPN and TPN is nicotinamide ribose; there is no detectable NMN. The results of pulse‐labeling experiments suggest that nicotinamide ribose may be an intermediate in the nicotinamide pathway.Following growth of D98/AH2 cells in high concentrations of niacin, biosynthesis of DPN from nicotinamide was completely inhibited for at least six hours. The converse experiment revealed no inhibition of niacin incorporation. This observation suggests that a niacin pathway intermediate, which present evidence indicates is desamido‐DPN. can inhibit nicotinamide utilization.Newly synthesized DPN turns over with a half‐life of two hours in azaserine‐treated D98/AH2 cells. In the absence of azaserine, the nicotinamide moiety of newly synthesized DPN is lost from D98/AH2 cells to the medium with a half‐life of eight hours. About 80% of the nicotinamide is lost to medium as nicotinamide ribose.
Isolation and characterization of revertant cell lines. III. Isolation of density‐revertants of SV40‐transformed 3T3 cells using colchicine
Authors: Vogel A. , Risser R. , Pollack R. 
Published: February 2005

AbstractTreatment of the SV40 transformed 3T3 cell line SV101 with colchicine permits the isolation of polyploid revertant sublines Which have lower saturation densities than SV101. These low saturation density lines have also reverted to a high serum requirement for growth, and are unable to form colonies in methocel. Normal SV40 has been recovered from these revertants.3T3 cells are more resistant to colchicine than SV3T3 cells at all cell densities. Colchicine revertants do not display a 3T3‐like resistance to colchicine at low density, but do survive colchicine at confluent cell densities, presumably due to their increased contact inhibition.
On the kinetics of erythroid cell differentiation in fetal mice. III. DNA and hemoglobin measurements of individual erythroblasts during gestation
Authors: Steiner Rudolf 
Published: February 2005

AbstractMicrospectrophotometric absorption measurements were used to determine the hemoglobin content of erythroid cells derived from the yolk sac during gestation of fetal C3H mice, from day 9 to day 15. Using the DNA content as a marker for the mitotic state between 2C and 4C phase, five successive cell generations and their mean hemoglobin contents were distinguished: 12 pg (pg, picogram = 10−12 gm). 22.2 pg, 37 pg, 50 pg and 56 pg. In the final state, nucleated erythrocytes contained 98 ± 22 pg hemoglobin.Erythroid cells derived from the liver were measured on day 15 of fetal gestation. The hemoglobin content of proerythroblasts was below 0.3 pg. The two cell generations in the basophilic state had 0.6 pg and 1.7 pg respectively. Polychromatic erythroblasts yielded a hemoglobin content of 5.1 pg in the first cell generation and 7.5 pg in the second one. Orthochromatic erythroblasts contained 8 pg, reticulocytes 12 pg and mature erythrocytes 28 ± 7 pg hemoglobin.Calculations based on these data suggest that the rate of total hemoglobin synthesis is similar in both yolk sac and liver erythropoiesis. The difference between the final hemoglobin content in nucleated erythrocytes of yolk sac origin and that in hepatic erythrocytes can be explained by the different cell generation times.
Uridine uptake and its intracellular phosphorylation during the cell cycle
Authors: Stambrook Peter J. , Ebert James D. , Sisken Jesse E. 
Published: February 2005

AbstractThe rate of 5‐3H uridine uptake into Chinese hamster V79 cells and the rate of its incorporation into RNA increase tenfold during the cell cycle. Both reactions exhibit the same apparent Km(1.7 × 10−5 M). Chromatography of acid‐soluble material from cells incubated with 5‐3H uridine (0.25 μM) at different times of the cell cycle revealed that intracellular uridine was rapidly phosphorylated at all times, even though cells in late S and G2 take up roughly ten times as much uridine as cells in G1. Uridine kinase activity in synchronized cells increases about two and one‐half‐fold during the same time period, and in exponentially growing cells is not saturated until the external uridine concentration is raised above 200 μM. It is concluded that the change in uridine kinase activity during the cell cycle is not responsible for the tenfold increase in the rate of uridine transport, and that these two processes are independently regulated.
Tetrodotoxin‐sensitive and ‐insensitive action potentials, in myotubes
Authors: Land B. R. , Sastre A. , Podleski T. R. 
Published: February 2005

AbstractThe study of long‐term cultures of myogenic cells has proven that electrical excitability develops only after the development of electrical coupling between the cells. That is, neither surface contact in itself nor coupling in itself is sufficient to cause excitability to develop in these cells. Following the formation of multinucleated myotubes, several different types of electrical responses develop. Some of the action potentials are sodium‐dependent and are blocked by tetrodotoxin (TTX). Others are dependent upon sodium and possibly calcium and they are not blocked by TTX. Furthermore, these two types of responses may exist in a myotube at the same time. Under some circumstances the kinetics of the two systems are sufficiently different to result in action potentials that have two peaks. Under these conditions the first peak is always of shorter duration and it is always blocked by TTX.
Induction of lysosomal enzymes in contact inhibited 3T3 cells
Authors: Horvat A. , Ács G. 
Published: February 2005

AbstractThe pattern of changing activities of three lysosomal enzymes, N‐acetyl‐β‐D‐glucosaminidase, aryl sulfatase, and DNase II, and that of DNA polymerase was followed in homogenates of 3T3 cells during the logarithmic phase of growth and in stationary cultures. The change in activities of the polymerase and the lysosomal enzymes is antiparallel. DNA polymerase exhibits highest activity in growing cultures, and shows a three‐fold decline of the specific activity in stationary cultures. The lysosomal enzymes show a very marked increase in their specific activity after density saturation is reached, which can be prevented by the addition of cycloheximide. Colcemid added to logarithmically growing cultures also causes an increase in the specific activities of lysosomal enzymes.
The subcellular distribution of lysosomal hydrolases in the Harding‐Passey melanoma
Authors: Mufson R. Allan 
Published: February 2005

AbstractDifferential centrifugation of homogenates of Harding‐Passey melanoma demonstrated that aryl sulfatase A and β‐glucuronidase sediment with particles (i.e., lysosomes) distinct from those particles bearing tyrosinase (i.e., melanosomes). The sedimentation curves for the lysosomal enzymes and tyrosinase, however, demonstrated that an adequate separation of these particle types could not be obtained by differential centrifugation. Isopycnic density gradient centrifugation was used to obtain the necessary resolution. The results of the density gradient studies demonstrated that lysosomes and melanosomes could be separated by this technique, as judged by enzyme distribution among the fractions recovered from the gradients and from electron microscopic examination of the melanosome fractions. It was further evident that the purified and washed melanosomes contained significant amounts of both acid hydrolase activities. Indeed 24% to 27% of the total acid hydrolase activities recovered from the density gradients were associated with the melanosome fractions. The acid hydrolases associated with the melanosomes could not be solubilized by treatment with 0.1% (v/v) Triton X‐100, nor by exposure to hypo‐osmotic shock. The melanoma lysosomes, however, did release most of both their hydrolase activities into soluble form after treatment with the same percentage of detergent. The lysosomes were, however, very resistant to rupture by exposure to hypo‐osmotic conditions.
Glycolytic enzyme activity in developing red and white muscle
Authors: Dalrymple R. H. , Cassens R. G. , Kastenschmidt L. L. 
Published: February 2005

AbstractThe activities of the constant proportion enzymes of the Embden‐Meyerhof chain (triose phosphate isomerase (TIM), glyceraldehyde‐3‐phosphate dehydrogenase (GAPDH), phosphoglycerate kinase (PGK), phosphoglycerate mutase (PGM) and enolase (ENOL)), and the activity of lactic dehydrogenase (LDH) were studied in developing red (trapezius) and white (longissimus) muscles of the pig from a fetal stage to 24 weeks postnatal. Both muscles were differentiated by two weeks postnatal in the sense that they had reached the adult level of enzyme activity. Enzyme activities were two‐ to three‐fold greater in the longissimus than in the trapezius. Enzyme activity ratios based on GAPDH were not consistent in the fetal and day 1 samples but were consistent during later stages of growth. Ratios of enzyme activity based on activity at 105 days gestation revealed that TIM, PGK and PGM are grouped and follow the same pattern, but GAPDH and ENOL are quite different from each other and from the pattern shown by TIM, PGK and PGM. The constant proportion concept in developing muscle is therefore questioned.
Effect of tolbutamide on the metabolism of Tetrahymena
Authors: Blum J. J. , Connett R. J. , Porter Pamela 
Published: February 2005

AbstractTolbutamide partially inhibited the growth but increased the glycogen content of Tetrahymena pyriformis in logarithmically growing cultures. Tolbutamide slightly increased 14CO2 production from [1‐14C] and [6‐14HC] glucose and [2‐14C] pyruvate, but had little effect on the oxidation of [1‐14C] acetate when any of these substrates were added to the proteose‐peptone medium in which the cells had been grown. Measurement of 14CO2 production from [1‐14C] and [2‐I4C]‐glyoxylate showed that this substrate was primarily oxidized via the glyoxylate cycle, with little if any oxidation occurring via the peroxisomal glyoxylate oxidase. Addition of tolbutamide inhibited the glyoxylate cycle as indicated by a marked reduction in label appearing in CO2 and in glycogen from labeled acetate. In control cells, addition of acetate strongly inhibited the oxidation of [2‐14C]‐pyruvate whereas addition of pyruvate had little effect on the oxidation of [1‐14C]‐acetate. Acetate was more effective than pyruvate in preventing the growth inhibitory and glycogen‐increasing effects of tolbutamide. The data suggest that one effect of tolbutamide may be to interfere with the transfer of isocitrate and acetyl CoA across mitochondrial membranes.
Properties of protein polymers as substratum for cell growth in vitro
Authors: Macieira‐Coelho A. , Berumen L. , Avrameas S. 
Published: February 2005

AbstractThe behavior of two established cell lines was found to vary when subcultivated on protein polymers covered with either negatively or positively charged substances. Results indicate that the influence on cell behavior is conditioned by the charge rather than by structural differences or degree of attachment of the substances to the polymer. Furthermore, the substratum seems to have just a physical effect at the cell membrane without any direct influence on cell metabolism.Cells were also seeded on a calf serum polymer and it was found that serum loses its properties on cultivated cells when used as substratum.
Potassium content of single human red cells measured with an electron probe
Authors: Gary Kirk R. , Crenshaw Miles A. , Tosteson D. C. 
Published: February 2005

AbstractThe potassium content of single human red cells was measured with an electron probe. Cells were placed on beryllium discs and coated with a thin layer of dibutyl pthalate to prevent loss of cellular contents. Samples were stable under the electron beam during analysis for more than 15 minutes and could be stored for long periods of time. Primary standards were prepared by loading red cells with varying known amounts of potassium in order to circumvent the corrections for absorption. The X‐ray intensity was found to be directly proportional to the potassium content of the cells.
Effects of lymphocytes from the thymus and lymph nodes on differentiation of hemopoietic spleen colonies in irradiated mice
Authors: Basford Nancy L. , Goodman Joan W. 
Published: February 2005

AbstractHemopoietic colonies were counted macroscopically and microscopically in spleens of hybrid mice seven or eight days after they had been irradiated and given parental bone marrow in donor‐host combinations exhibiting poor growth. Colonies counted microscopically were classified as to differentiation pathway. Lymphocytes from the thymus or lymph nodes were injected into some recipients at several different dosages and lymphocyte: bone marrow (L:B) ratios. In confirmation of earlier work it was found that thymocytes increased the number and size of colonies in recipients of marrow. A shift of differentiation toward granulopoiesis was also seen when thymocytes were given, although erythropoietic colonies were still the most frequently seen type except at very high L:B ratios. Lymph node lymphocytes shifted the pattern more markedly toward granulopoiesis, even at low L:B ratios. When lymphocytes from either source were given without marrow, only a few colonies could be found in recipients, and if differentiated they were almost exclusively granulopoietic. Irradiation (900 R) of lymphocyte donors reversed the shift so that a normal pattern of differentiation, like that resulting from marrow alone, was seen; irradiated lymphocytes were nonetheless capable of augmenting the size and total number of hemopoietic colonies.