bluuebunny/crossref_metadata_2025_split huggingface dataset:
Colloidal iron hydroxide‐binding to the surfaces of chick embryo fibroblasts transformed by wild‐type and a temperature‐sensitive mutant of Rous sarcoma virus
Authors: Subjeck J. R. , Weiss L. , Warren L. 
Published: February 2005

AbstractThe densities of colloidal iron hydroxide (CIH) particles binding to the surfaces of chick embryo fibroblasts were determined before and after transformation with wild type Rous sarcoma virus and a temperature sensitive (ts) mutant of this virus. On the basis of in vitro behavior, cells transformed by the ts virus manifest a malignant phenotype at 36°C (permissive temperature) and appear normal at 41°C (non‐permissive temperature). At the permissive temperatures there is a significant increase in CIH particle‐binding to spaces of cell surface between microvilli on the wild type and ts transformed cells. At the non‐permissive temperature this significant increase in binding is only observed on the wild type transformant, while the density found on the ts transformant is not significantly different from the untransformed state. Therefore, in vitro characteristics of normalcy and malignancy are reflected in changes in the CIH binding properties of the cell surface spaces between microvilli.The CIH densities observed on the microvilli are significantly different from the density on the spaces between them for each of the classes of cells studied at either temperature. The microvilli are found to bind a lower density of particles in five of the six cases. No correlations between microvilli particle density and transformation to in vitro malignant characteristics were observed.
Electron microbeam analysis of calcium distribution in the ciliated protozoan, Spirostomum ambiguum
Authors: Osborn Dustan , Hamilton T. C. 
Published: February 2005

AbstractElectron microprobe analyses of calcium distribution in the ciliated protozoan, Spirostomum ambiguum, indicated several calcium rich sites. One site was an endoplasmic distribution of calcium coincident with phosphorus which corroborates previous findings of hydroxyapatite deposits within Spirostomum. These apatite deposits were distributed throughout the endoplasm, but not within the nuclei or the contractile vacuole. Calcium was also detected within the cortical region. Cortical calcium was in greater concentration in the anterior portion of the organism and decreased towards the posterior end (region containing the contractile vacuole). Phosphorus and potassium were also detected as gradients from the anterior end, whereas magnesium was detected in the same density throughout the cortical region. Line scans of cortical regions suggested (1) distributions of calcium within mitochondria and/or vesicles, and (2) calcium associated with bundles of microfilaments.
Hormonal regulation of initiation of DNA synthesis and of differentiated function in Y‐1 adrenal cortical cells
Authors: Gill Gordon N. , Weidman E. Russell 
Published: February 2005

AbstractACTH, 8‐Br‐cAMP, and serum deprivation arrested Y‐1 functional mouse adrenal tumor cells in the G1 phase of the cell cycle. Though ACTH and 8‐Br‐cAMP treated cells were larger with increased macromolecular synthetic rates compared to cells arrested in G1 by serum removal, a similar 8‐ to 10‐hour lag to initiation of DNA synthesis was observed after either ACTH or 8‐Br‐cAMP removal or after serum addition. After the 8‐ to 10‐hour lag period, cells entered S phase exponentially. ACTH or 8‐Br‐cAMP opposed serum induced DNA synthesis initiation only when added prior to S. Once commitment to DNA synthesis occurred, ACTH or 8‐Br‐cAMP addition did not inhibit DNA synthesis although 8‐Br‐cAMP induced a secondary block in G2. Though ACTH and 8‐Br‐cAMP inhibited serum induced initiation of DNA synthesis and did not affect serum induced cellular hypertrophy, both substances increased the steroidogenic capacity of the cell. ACTH and 8‐Br‐cAMP thus appear to specifically oppose the stimulatory effects of serum on initiation of DNA synthesis while inducing the differentiated function of the cell.
Control of normal differentiation of myeloid leukemic cells. XII. Isolation of normal myeloid colony‐forming cells from bone marrow and the sequence of differentiation to mature granulocytes in normal and D+ myeloid leukemic cells
Authors: Lotem Joseph , Sachs Leo 
Published: February 2005

AbstractAn enriched population of early myeloid cells has been obtained from normal mouse bone marrow by injection of mice with sodium caseinate and the removal of cells with C3 (EAC) rosettes by Ficoll‐Hypaque density centrifugation. This enriched population had no EAC or Fc (EA) rosettes and contained 87% early myeloid cells stained for myeloperoxidase and/or AS‐D‐chloroacetate esterase, 7% cells in later stages (ring forms) of myeloid differentiation and 6% unstained cells, 2% of which were small lymphocytes. After seeding in agar with the macrophage and granulocyte inducer MGI, the enriched population showed a cloning efficiency of 14% when removed from the animal and of 24% after one day in mass culture. Both the enriched and the unfractionated bone marrow cells gave the same proportion of macrophage and granulocyte colonies.The normal early myeloid cells were induced to differentiate by MGI in mass culture in liquid medium to mature granulocytes and macrophages. The sequence of granulocyte differentiation was the formation of EA and EAC rosettes followed by the synthesis and secretion of lysozyme and morphological differentiation to mature cells. D+ myeloid leukemic cells with no EA or EAC rosettes had a similar morphology to normal early myeloid cells and showed the same sequence of differentiation. The induction of EA and EAC rosettes occurred at the same time in both the normal and D+ leukemic cells, but lysozyme synthesis and the formation of mature granulocytes was induced later in the leukemic than in the normal cells. The results indicate that selection for non‐rosette‐forming normal early myeloid cells also selected for myeloid colony forming cells, that these normal early myeloid cells can form colonies with differentiation to macrophages and granulocytes, that normal and D+ myeloid leukemic cells have a similar sequence of differentiation and that the normal cells had a greater sensitivity for the formation of mature cells by MGI.
The effect of TLCK on transcription and its role in modifying cell growth
Authors: Noonan Norine E. , Noonan Kenneth D. 
Published: February 2005

AbstractThe synthetic protease inhibitor N‐tosyl‐L‐lysine‐chloromethyl ketone (TLCK) acts to inhibit transcription when added to cell lines growing in vitro. This inhibition of transcription is most pronounced in transformed cells where TLCK is very toxic at concentrations as low as 25 μg/ml of culure medium. Non‐transformed cells are more resistant to the effect of TLCK, requiring ten times more TLCK to produce a comparable inhibition of transcription. The effect of this protease inhibitor on transcription can be prevented by preincubation of the cells in reduced glutathione or cysteine; however, the cells can not be rescued from the effect of TLCK even if glutathione or cysteine are added to the culture medium within five minutes of the addition of TLCK.
Phagocytosis by rabbit polymorphonuclear leukocytes: The effect of albumin and polyamino acids on latex uptake
Authors: Deierkauf Frans A. , Beukers Harm , Deierkauf Martha , Riemersma Jelle C. 
Published: February 2005

AbstractAlbumin in low concentrations (0.001–0.01 weight percent) was found to be an effective inhibitor of phagocytosis of polystyrene latex beads by rabbit polymorphonuclear leukocytes. Polyglutamic acid proved to be an inhibitor of latex uptake at even lower concentrations. Polylysine stimulates phagocytosis, maximal stimulation occurring at 0.002% polylysine. These findings are discussed with reference to the surface properties of latex particles and leukocytes, and particularly with reference to electrostatic interactions in phagocytosis.
Membrane transport by macrophages in suspension and adherent to glass
Authors: Pofit Joseph F. , Strauss Phyllis R. 
Published: February 2005

AbstractWe have compared membrane transport of lysine and adenosine by rabbit lung macrophages in suspension and adherent to glass cover slips. The rapid sampling techniques employed permitted measurements to be made over intervals as short as 10 seconds. Suspended cells transported both nutrients at a faster rate, although the Km values for the two transport systems remained unchanged. Colchicine, cytochalasin B and adenosine did not interfere with the enhancement.
Pyruvate carboxylase and phosphoenolpyruvate carboxykinase in cultured human fibroblasts
Authors: Raghunathan Rengachari , Russell James D. , Arinze Ifeanyi J. 
Published: February 2005

AbstractThe activities of pyruvate carboxylase and phosphoenolpyruvate carboxykinase were measured in cultured human fibroblasts. Considerable variation was observed in strains derived from different individuals. The activities of both enzymes throughout the culture cycle were measured in two strains. In these strains the specific activities of the enzymes increased during log phase and remained constant during the stationary phase. However, one cell strain exhibited a high activity of pyruvate carboxylase which remained unchanged throughout the culture cycle, suggesting that this enzyme may be regulated differently in different strains of cultured human cells. Familial studies suggest that the observed variations in pyruvate carboxylase activity may be due to a genetic polymorphism.
Protein metabolism during growth of vero cells
Authors: Lee Gloria T‐Y. , Engelhardt Dean L. 
Published: February 2005

AbstractProtein synthesis and degradation were studied throughout a growth cycle of Vero cells. The rate of protein synthesis, measured as the rate of amino acid incorporation, reached a maximum at the mid‐exponential phase and declined to 10–30% of the maximum in the stationary phase. The rate of protein degradation, measured as the release of radioactive amino acids from uniformly labelled cellular proteins, did not vary in the growth cycle. The amount of protein per cell, measured by an isotopic method, remained constant when normalized to account for the variation in the proportion of actively dividing cells in the cell population during the growth cycle. Cellular protein was determined using this method since it was found that the chemical determination of the amount of protein in the monolayer was not accurate during the early stage of the growth cycle. This was due to a significant amount of serum protein adsorbed to the cells. In this study we were able to show that, in Vero cells, protein synthetic activity is correlated with the rate of cell division, and variations in the rate of synthesis alone are sufficient to meet the changing requirements for cellular protein in a growth cycle.
Decreased in vivo and in vitro colony stimulating activity responses to bacterial lipopolysaccharide in C3H/HeJ mice
Authors: Russo Momtchilo , Lutton John D. 
Published: February 2005

AbstractMice of the C3H/HeJ strain exhibit low inflammatory and immunological responses to certain bacterial lipopolysaccharide (LPS) preparations. Lymphocytes from C3H/HeJ mice also show defective LPS‐induced mitogenesis. We tested the colony stimulating activity (CSA) response of C3H/HeJ mice. As controls we used mice of the congenic C3HeB/FeJ strain, which are good responders to LPS. Serum was obtained three hours after intravenous administration of LPS. Serum CSA was determined in agar cultures of bone marrow cells from AKR mice. The serum CSA response of C3H/HeJ to 10 μg LPS was approximately 8‐fold lower than that of control C3HeB/FeJ mice. In contrast, both strains showed similar serum CSA‐induced by Poly I:poly C. Peritoneal macrophage cultures were also incubated with 0.1–10.0 μg LPS and culture media assayed for CSA. The response of C3H/HeJ macrophages was about 6‐fold lower than that of macrophages obtained from the control mice. The results show that the lower responsiveness of C3H/HeJ mice to LPS also extends to the production of CSA. The in vitro findings indicate that the postulated defect in the LPS receptor of B lymphocytes may also be present on macrophages.
Time of replication of genes responsible for a temperature‐sensitive function in a cell cycle‐specific ts mutant from a hamster cell line
Authors: Chang Helena L. , Baserga Renato 
Published: February 2005

AbstractA method involving short pulses of 5‐bromodeoxyuridine (brUdRib) followed by irraidation with 313 nm light was used to locate the time of replication of certain genes during the cell cycle of two cell lines, AF8 and AL106. AF8, a temperature‐sensitive mutant of BHK21/13 cells, grows at 33°C but not at 39.5°C. AL106, a hybrid clone of tsAF8 and SV‐40 transformed Lesch‐Nyhan fibroblasts (LNSV), which retains all hamster chromosomes and one human chromosome (No. 3), has the ability to grow at 39.5°C. AF8 and AL106 cells synchronized at the G1‐S boundary were released from their block and pulsed with brUdRib for 2‐hour periods during the S phase. The cells were subsequently irradiated with 313 nm light. Colony‐forming efficiency and revertants frequency were studied. Incorporation of brUdRib during the early S phase (0–4 hours from the begining of S), decreased the colony‐forming efficiency of AL106 cells both at 33°C and 39.5°C, and also of AF8 cells at 33°C. No AF8 colonies grew at the nonpermissive temperature regardless of the treatment. Thus the time of replication of genes responsible for colony‐forming ability was the same in tsAF8 at the permissive temperature and in AL106 at both temperatures. The time of replication of the genes responsible for the ts function in AF8 cells was located by determining the revertants frequency in synchronized AF8 cells pulsed with brUdRib and irradiated during 1‐ to 2‐hour periods of the S phase. Back‐mutants were scored by counting the number of clones capable of growing at 39.5°C (nonpermissive for AF8 cells). The highest frequency of induced back‐mutations occurred in synchronized AF8 cells pulsed with brUdRib (and irradiated) between two to four hours from the begining of the S phase. Exposure to brUdRib during other periods of the S phase or during G1 had no effect on the reversion rate.This method can be used to locate the time of replication (in S) of ts genes in other temperature‐sensitive mutants or of other specific genes in other conditional mutants.
Steroid hormone receptors and the differentiation of myeloid leukemic cells
Authors: Krystosek Alphonse , Sachs Leo 
Published: February 2005

AbstractReceptors for the steroid hormone dexamethasone have been analyzed in clones of myeloid leukemic cells which differ in their ability to be induced by dexamethasone to form C3 and Fc rosettes, to synthesize and secrete lysozyme and form macrophages. The receptor dependent nuclear binding of (3H)‐dexamethasone has been measured in intact cells. As found with other glucocorticoid receptors, saturation of nuclear binding occurred at 4 × 10−8 M (3H)‐dexamethasone. The specificity of the receptors for only certain steroids was shown by the competition of nuclear binding by prednisolone, progesterone and testosterone, but not by the inactive steroid androstenedione. Nuclear bound hormone‐receptor complexes were released from the nucleus by treatment with deoxyribonuclease, indicating that the complexes were associated with DNA‐containing structures.The amount of nuclear binding of receptors was similar in all clones examined, including those which could not be induced for rosette, lysozyme or macrophages. The non‐responding clones were also similar to the responding clones in the kinetics of binding, hormone concentration dependence of binding and association with DNA‐containing structures. The results indicate that the non‐responding clones of myeloid leukemic cells did not have detectable defects in the number, nuclear transport, or association with DNA of their steroid receptors.
Intracellular protein degradation in growing, in density‐inhibited, and in serum‐restricted fibroblast cultures
Authors: Hendil Klavs B. 
Published: February 2005

AbstractExponentially growing Balb/3T3 mouse fibroblasts contain protein populations with slow and fast turnover. These two stability classes were labelled selectively with 3H‐leucine. The intracellular degradation of the proteins was then followed as the release into the medium of radioactive leucine.The degradation rate of both stability classes of protein is increased by about 55% in cultures whose growth is inhibited by high cell density. Serum‐deprivation, which also halts cell growth, accelerates protein breakdown to a smaller extent, the increase for relatively stable and unstable proteins being 30% and 13%, respectively.The density‐dependent increase in protein breakdown is also found in BHK21 cells but not in chick fibroblasts. Protein degradation in Balb/3T3 cells transformed by simian virus 40 is affected by serum‐deprivation but not by cell density.The proteins which are relatively stable during growth were shown to become less stable in density‐inhibited or serum‐deprived cultures, and vice versa.Cycloheximide inhibits protein degradation to a variable extent. Dibutyryl adenosine‐3′,5′‐cyclic monophosphate has no effect on the protein degradation under the conditions investigated here.
Coexpression of mutant and wild type protein kinase in lymphoma cells resistant to dibutyryl cyclic AMP
Authors: Lemaire Irma , Coffino Philip 
Published: February 2005

AbstractA mutant clone resistnat to dibutyryl cyclic AMP was isolated from S49 mouse lymphoma cells. The mutant expressed a form of cyclic AMP‐dependent protein kinase distinguishable from wild type kinase by its decreased sensitivity to activation by cyclic AMP and its increased thermal lability. Hybrids formed between mutant and wild type cells were resistant to dibutyryl cyclic AMP and expresed both mutant and wild type activities in about equal amount. The parent mutant cells also appeared to express wild type kinase activity, but at a lower level. We conclude that wild type S49 cells have and expression two identical alleles for the regulatory subunit of protein kinase, one of which has undergone mutation in the mutant cells.
On the regulation of DNA synthesis in a line of adrenocortical tumor cells: Effect of serum, adrenocorticotropin and pituitary factors
Authors: Armelin Mari C. S. , Gambarini Angelo G. , Armelin Hugo A. 
Published: February 2005

AbstractY‐1 adrenal cells responded to serum step down by a several fold decrease in DNA synthesis. Serum starved cells resumed DNA synthesis upon serum step up. ACTH and cAMP inhibited DNA synthesis both at low and high serum concentrations, a fact previously known. Pituitary, brain and liver crude extracts stimulated DNA synthesis in serum starved cells. Purified pituitary factors preparations contained two activities: one specific for Y‐1 cells and another active with both fibroblasts and Y‐1 cells. The kinetics of restimulation of DNA synthesis by serum and pituitary factors was studied. DNA synthesis restimulation occurred after a lag of 11 hours. This lag did not vary irrespective of the type of stimulator or its concentration. Cells entered S phase continuously at a rate which increased with increasing concentrations of the stimulator. Cells became refractory to the inhibitory action of ACTH five hours before entering S phase. The implications of these data to the understanding of cell growth control are considered.
Fatty acid and glucose oxidation by cultured rat heart cells
Authors: Rosenthal Miriam D. , Warshaw Joseph B. 
Published: February 2005

AbstractMonolayer cultures of fetal rat myocardial cells can be utilized to examine substrate preferences and interactions. The specific activity of glucose oxidation by myocardial cell cultures was high in sparse cultures but decreased with increased cell density. In contrast, palmitate oxidation was independent of initial cell density. Palmitate inhibited glucose oxidation by 50% in rat heart cultures. Glucose had only a slight sparing effect on palmitate oxidation. This suggests that fetal and newborn rat myocardial cells in culture preferentially oxidize palmitate similar to adult heart. The sparing effect of palmitate on glucose oxidation is accounted for by inhibition of the glycolytic‐aerobic pathway and not by inhibition of the pentose phosphate pathway. Data on oxidation of 14C‐pyruvate specifically labelled suggest that palmitate or a product of its oxidation such as acetyl‐CoA may be acting directly to inhibit the pyruvate dehydrogenase complex. Palmitate oxidation per mg of cell protein was constant from 15 days gestational age to 2 days postnatal age. The observed differences between cultured cells and the intact heart may relate to decreased aerobic metabolism in monolayer cell culture and suggest that the increase in fatty acid oxidation observed in vivo is controlled by the oxygen environment of the cell. These studies show that heart cells in monolayer culture can be utilized to obtain metabolic information similar to an adult organ perfusion model.
The stability of tyrosine aminotransferase and other proteins in enucleated rat hepatoma tissue culture cells
Authors: Gopalakrishanan T. V. , Brad Thompson E. 
Published: February 2005

AbstractThe role of the nucleus in bringing about the induction of tyrosine aminotransferase (TAT) by glucocorticosteroid hormone and its deinduction upon steroid removal has been studied in enucleated rat hepatoma tissue culture cells (FU5–5). Both processes require the presence of the nucleus. However, cytoplasts from preinduced cells show an intial rapid decline in enzyme activity immediately after enucleation followed by maintenance of a constant level of activity. This initial decline in enzyme activity can be partially prevented by trypan blue, an inhibitor of lysosomal activity. This suggests that the early fall in enzyme activity could be due to an increase in the level of lysosomal activity immediately after enucleation. The subsequent constant level of activity seems due to maintenance rather than synthesis and degradation since it is not affected by cycloheximide. The absence of degradation applies to other kinds of proteins in enucleated FU5–5 cells and enucleated mouse fibroblast L cells. Thsese experiments suggest that some kind of labile RNA or protein dependent on the presence of the nucleus is required for the degradation of all classes of proteins in diferent kinds of cells.
Alteration of membrane electrical activity in rat myocardial cells following selective laser microbeam irradiation
Authors: Kitzes Margarita , Twiggs Gary , Berns Michael W. 
Published: February 2005

AbstractLaser microirradiation of neonatal rat (1 to 2‐day‐old) ventricular cells in tissue culture results in overt changes in contractility. The intracellular study of their ongoing electrical activity prior to, during, and after laser microirradiation demonstrates that definite membrane alteration occurs concomitantly with induced contractile responses. Although all ventricular cells are depolarized by laser microirradiation, the ultimate response elicited seems to differ according to the type of myocardial cell impaled. Typical fibrillation potentials were induced mainly in pacemaker cells.