bluuebunny/crossref_metadata_2025_split huggingface dataset:
Attempts to produce in vitro the reaction of immunologically competent cells of C57BL/6 origin to Balb/c embryo fibroblasts
Authors: Koldovský P. , Turano A. , Fadda G. 
Published: February 2005

AbstractSpleen or lymph node cells of C57BL/6 origin or both were mixed with subcellular material from Balb/c tissue for several hours at 37°C. The subcellular material was then washed out (by repeated centrifugation) with PBS and the immune cells were placed either in diffusion chambers in the peritoneal cavity of Swiss mice or in Petri dishes with C57BL/6 embryo cell monolayer (feeder layer) and incubated in a thermostat at an atmosphere of 5% CO2. After 4 to 5 days these cells were added to target Balb/c embryo cells in Petri dishes. The first control was done by sensitiziing the cells with syngeneic material, the second control by adding the immune cells to syngeneic target embryo cells. The sensitized cells mixed with allogeneic embryo cells produced a positive reaction in the form of agglutination around the target cells and destruction of these cells. In controls the immune cells were seldom found and were randomly distributed.
Internal perfusion of crayfish giant axons: Action of tannic acid, DDT, and tea
Authors: Shrager Peter G. , Macey Robert I. , Strickholm Alfred 
Published: February 2005

AbstractCrayfish giant axons remain viable following internal perfusion with a mixture of fluoride and citrate salts. The relative favorability of various internal anions, and the dependence of resting and action potentials on internal cations are both similar to results on internally perfused squid axons. TEA widens the falling phase of the spike only from inside the axon, while DDT is active from either side of the membrane. Records of impedance changes show that effects of TEA and DDT on components of ionic conductances are similar to those found in other axons by voltage clamp measurements.Tannic acid perfused internally at a concentration of the order of 10 μM produces spontaneous activity, and a progressive increase in spike width. After 30 minutes, action potentials are “cardiac” type and are up to several minutes in duration. Records of impedance changes, and data from rapid changes in external ionic concentrations, suggest that the plateau phase of the spike is due to a maintained increase in sodium conductance. Since tannic acid is capable of crosslinking proteins and “rigidifying” protein monolayers, it is suggested that its effects on the axon may be the result of an interference with a conformational change in a membrane protein or protein‐phospholipid complex during excitation.
The effect of serum components on sterol biosynthesis in L cells
Authors: Rothblat George H. 
Published: February 2005

AbstractL cells were cultivated in test medium which contained 14C‐sodium acetate, and the amount of labeled digitonin‐precipitable sterol was assayed in medium and cells. Increasing concentrations of whole serum in the medium had two effects: depressed cellular synthesis and enhanced release of synthesized sterol from the cells. In experiments with delipidized serum containing unesterified cholesterol, cellular sterol synthesis decreased as free cholesterol concentration in the medium increased. In other experiments using medium containing increasing lecithin concentration and no exogenous sterol, the concentration of lecithin markedly influenced the distribution of synthesized sterol between the cells and the medium which then directly influenced the amount of sterol synthesized. These experiments indicate that cell sterol synthesis is regulated by internal levels of free sterol. This, in turn, is a function of cellular sterol flux which is regulated by the concentration and composition of serum lipoprotein in the medium.
RNA in the periphery of rapidly proliferating mouse lymphoid cells
Authors: Bennett M. , Mayhew E. , Weiss L. 
Published: February 2005

AbstractRNA in the peripheries of various populations of lymph node cells (LNC) has been evaluated by measuring the electrophoretic mobilities of cells, before and after treatment with active or inactivated ribonucleases. Three different populations of LNC were studied: (1) “resting” normal age control LNC; (2) “syngeneic” LNC from irradiated (C3H × C57BL)F1 or C3H mice four to six days following transplantation of syngeneic spleen cells; such cells were progeny of lymphopoietic progenitor cells of the spleen; and (3) “allogeneic” LNC from irradiated (C3H × C57BL)F1 mice four to six days after grafting C3H (parental) spleen cells; such cells were progeny of lymphopoietic progenitor cells, but also alloantigen‐sensitive cells of the spleen which proliferate in response to the host's alloantigens (a “graft‐versus‐host” immunological reaction). Whereas the normal LNC had no detectable peripheral RNA, the allogeneic and syngeneic LNC did, i.e., ribonuclease reduced their mean electrophoretic mobilities by 13.6 and 9.2 per cent, respectively. Since both allogeneic and syngeneic LNC had peripheral RNA, no specific correlation could be made with immunological activity. 3H‐uridine and 14C‐thymidine incorporation into lymph nodes was greatest in allogeneic, intermediate in syngeneic and least in age control lymph nodes, indicating a “population shift” in the spleen cell chimeras toward relatively immature, rapidly proliferating cells, which had a relatively high rate of RNA synthesis. Thus, rapidly proliferating lymphoid cells do have RNA in their peripheries, but its relation to specific immunological function has yet to be ascertained.
Serum‐dependent depression of alkaline phosphatase in HeLa cells
Authors: Herz Fritz , Kaplan Eugene , Sevdalian David A. 
Published: February 2005

AbstractReduction in alkaline phosphatase activity was observed when HeLa S3 cells were grown in Puck's medium containing high concentrations of human serum. This effect was not seen with the enzyme of Chang liver 8A cells. The induction of increased alkaline phosphatase in HeLa S3 by prednisolone or by osmolality changes was not prevented by serum. The concentration of serum in the culture medium had no influence on acid phosphatase activity.
The dependence of pacemaker discharge of Aplysia neurons upon Na+ and Ca++
Authors: Carpenter David , Gunn Rufus 
Published: February 2005

AbstractIn total absence of Na+ some identified neurons of Aplysia, after a period of silence, resume pacemaker discharge in the normal pattern with normal action potentials, while other identified neurons remain silent. In absence of Ca++ all pacemaker neurons increase spontaneous discharge and develop abnormal bursting patterns. Those neurons which discharge spontaneously in Na+ free solutions show much less dependence on Na+ and much greater dependence on Ca++ for action potentials initiated by electrical stimulation than do those neurons which do not fire spontaneously in absence of Na+. In absence of both Na+ and Ca++ all neurons become inexcitable, but much more rapidly at higher temperatures.
The use of pronase in tissue culture: A comparison with trypsin
Authors: Foley John F. , Aftonomos Byron 
Published: February 2005

AbstractPronase is a proteolytic enzyme recently introduced as an effective dispersing agent of tissue culture cells. We have found it to be a most rapid and complete dispersing agent for primary fibroblastic cell lines and clearly superior to trypsin. On the other hand, with certain continuous epithelial cell lines its completeness of dispersion is inferior to that of trypsin necessitating study of each cell line individually with both enzymes to select the most advantageous one.
Extracellular concentrating of proteins in the cecropia moth follicle
Authors: Anderson Lucy M. , Telfer William H. 
Published: February 2005

AbstractYolk proteins, derived from the blood, are incorporated into the oocytes of insects and certain vertebrates by pinocytosis, but reach the oocyte surface only after penetrating the surrounding follicular epithelium via intercellular channels. In an investigation of the events occurring in these intrafollicular spaces, the dense extracellular material present between the follicle cells and in the oocyte's brush border was extracted from vitellogenic cecropia moth follicles by soaking in physiological saline. Quantitative immunochemical determination of several eluted blood proteins revealed that these components had been more concentrated in the extracellular spaces than in the blood. The average concentration factors were 2.5 for the predominant yolk protein, vitellogenin, and 4.5 for the carotenoid protein.Since injected foreign proteins were also accumulated in the spaces, the concentrating mechanism seemed to act on all available proteins. However, in vitro inhibition of yolk formation with dinitrophenol resulted in a selective increase in the amount of extracellular vitellogenin in follicles which had been previously exposed to a medium low in this protein, suggesting accumulation of a factor with a specific affinity for it. Furthermore under certain conditions vitellogenin was more readily released from the concentrate than was the carotenoid protein. These results indicate that, despite apparent lack of discrimination in the binding of blood proteins in the spaces, extracellular interactions may contribute to the selectivity known to occur during vitellogenesis.
Lipid composition of heteroploid cells in culture: Effects of prednisolone
Authors: Dell'Orco Robert T. , Melnykovych George 
Published: February 2005

AbstractPrednisolone‐induced alterations in the content and composition of the total lipids, cholesterol, phospholipids and fatty acids were studied in HeLa S3 cells. After relatively long exposure of the cell cultures to the hormone analog (24 to 72 hours), total cell lipid content was decreased. Partial inhibition of cholesterol and phospholipid metabolism resulted in a shift in the molar ratio of these two lipid constituents. Total fatty acid content was unaffected by prednisolone but there were minor changes in the relative distribution of the individual fatty acids.The observed decrease in cholesterol turnover after addition of prednisolone was primarily due to the reduced uptake of intact cholesterol from the culture medium. This was compensated, in part, by an increased de novo synthesis of cholesterol from acetate and glucose.
Growth kinetics of hemopoietic fetal stem cells
Authors: Vogel Helmut , Hajdik Irene , Niewisch Helgard , Sultanian Ishkhan , Matioli Gastone 
Published: February 2005

AbstractFetal spleen stem cells have growth characteristics similar to those of normal adult spleen stem cells. On the contrary there is an early fetal liver stem cell population which possesses a lag time longer than that of adult stem cells. The duration of the lag time is controlled by a built‐in biological timer which seems to regulate some proliferative functions of the primitive liver stem cell.
Hemopoietic environment necessary for an early stage in differentiation of antibody‐forming cells: Effect of cortisol
Authors: Bennett Michael 
Published: February 2005

AbstractTreatment of adult mice with cortisol decreased the number and frequency of bone marrow precursors of anti‐sheep erythrocyte hemolytic plaque‐forming cells (P‐PFC) and marrow “lymphocytes.” However, the more primitive progenitors of P‐PFC in marrow were not affected. Treatment of prospective recipients of marrow grafts with cortisol impaired the generation of P‐PFC by transplanted primitive progenitor cells. Differentiation with proliferation of P‐PFC into mature PFC was less dramatically affected by cortisol. P‐PFC were not apparently suppressed directly, since the fall‐off of P‐PFC did not occur during the first day after administration of cortisol. Thus, cortisol impairs the generation of P‐PFC by altering a hemopoietic inductive environment necessary for this step in differentiation of immunocompetent cells.
An apparent discrepancy between the number of colony forming units transplanted and survival of busulphan lethally treated rats
Authors: Dunn C. D. R. , Elson L. A. 
Published: February 2005

AbstractConditions for keeping busulphan lethally treated rats alive by transplantation of bone marrow cells from syngeneic donors are described. After busulphan treatment of the donor rats with a dose which only reduces the colony forming units (CFU's) in the marrow (assayed by the spleen colony technique) to half the normal numbers, at least 100 times as many cells from these treated donors, compared to untreated rats, are required to produce an equivalent increase in survival of busulphan lethally treated recipients. In contrast, aminochlorambucil, despite producing a marked fall in bone marrow cellularity, has no effect on the number of CFU/femur, yet the marrow from these aminochlorambucil treated donors is no more effective in increasing the survival of busulphan lethally treated recipients than untreated marrow. Theories which may explain this apparent discrepancy and evidence which it affords on the mode of action of busulphan are discussed.
Defective bacteriophages
Authors: Garro Anthony J. , Marmur Julius 
Published: February 2005

AbstractNaturally occurring defective phage particles, which do not form plaques on any known host, but have a restricted host killing range, appear to be widely distributed. The defective phages are produced spontaneously but can be induced, at much higher levels, by chemical and physical agents which interfere with metabolism or structure of DNA. The defective phages discussed in this article have been divided into various categories on the basis of their structural complexity, which ranges from what appears to be phage tail components through to intact phage particles, and the source of the DNA packaged into the heads of the phage‐like particles. The evolution of the defective phages is discussed and the possibility is entertained that they may have originated from temperate phages.
Adhesion of human erythrocytes to glass: The nature of the interaction and the effect of serum and plasma
Authors: George James N. , Weed Robert I. , Reed Claude F. 
Published: February 2005

AbstractStudies of normal human erythrocyte adhesiveness to glass have demonstrated quantitative and qualitative differences between cell‐glass and cell‐cell contact interaction. Identifiable charged groups on the red cell surface were of minor importance in the adhesive process and it is postulated that direct cell‐glass contact attraction involves nonpolar regions of the red cell surface. However, erythrocyte adhesion to glass in the presence of serum and plasma is affected by electrostatic forces. At least two critical factors are present in serum and plasma: a heat‐stable factor(s) diminishing adhesion and a heat‐labile factor(s) promoting cell‐glass interaction. A postulate is presented concerning the role of soluble fibrin monomer complexes in promoting cell adhesion to glass.
The absence of electrically demonstrable polarizing factors in Hydra
Authors: Macklin Martin 
Published: February 2005

AbstractVarious investigators have shown that in the marine hydroids, Tubularia, Obelia, Eudendrium, and Pennaria, regeneration and polarity is affected by an electrical field applied parallel to the regenerate. Using electrical currents up to the physiological limits for Hydra, no relation between electrical current and regeneration rate or polarity could be demonstrated. This is in spite of the fact that adult Hydra are normally electrically polarized with the distal end approximately–18 mV relative to the proximal end of the animal. When the electrophoretic mobility and isoelectric point of cells from distal, central and proximal thirds of Hydra were measured, a significant difference was found between cells of the two cell layers but not between cells of the three body thirds. These results are discussed in relation to Hydra growth factors described by various other authors.
The density distribution of thymus, thoracic duct and spleen lymphocytes
Authors: Shortman Ken 
Published: February 2005

AbstractEquilibrium density gradient centrifugation in isotonic gradients of albumin may be used as an analytical tool to reveal features of cell populations not apparent from morphological or size distribution studies. All lymphocyte sources studied gave a complex distribution pattern consisting of many distinct peaks and shoulders.The thymus contains proportionally more dense lymphocytes than spleen or thoracic duct. The spleen of neonatally thymectomised animals contains proportionally more light lymphocytes than the spleen of normal animals. This suggests density may effect a separation between dense “thymus‐derived” and light “bone‐marrow‐derived” lymphocytes.Normal animals give variation in lymphocyte density distribution profiles from one animal to another. Part of this variation and part of the complexity is attributed to corticosteroid mediated stress effects on the lymphocytes. Corticosteroid injection increases the number of peaks seen in thymus density distribution profiles. Adrenalectomised animals give more reproducible and simpler profiles, although several distinct density peaks remain.Large lymphocytes are in general less dense than small lymphocytes, probably because of the increased ratio of light cytoplasm to dense nucleus. However, there exists a small proportion of dense, large lymphocytes and light, small lymphocytes. Each given size of lymphocyte showed heterogeneity in its density distribution, in both normal and adrenalectomised animals.The technique should be useful in a detailed study of the diversity of lymphocytes, of their differentiation and their precise immunological function.
Cytotoxic effects of thiopyrimidines
Authors: Lozzio Carmen B. , Wigler Paul W. 
Published: February 2005

AbstractThe cytotoxic action of 2‐thiouracil, 2‐thiocytosine, 2‐thiouridine and 4‐thiouridine was studied in cultures of a clone of Chinese hamster cells with a generation time of 16 hours (S — 8 hours, G2 — 2 hours, and G1 plus M — 6 hours). The cells were synchronized at metaphase by the method of reversal of colcemid inhibition and cell survival was measured by their colony‐forming ability.The four analogs induced cytotoxic effects which increased with the concentration of the chemical and the length of the exposure time. Exposure to 4 × 10−4 M 2‐thiocytosine, 2‐thiouridine or 4‐thiouridine for a period of 20 hours reduced cell survival to less than 10% of the controls. The other analog (2‐thiouracil) was less effective when tested at similar concentrations and time of exposure and decreased the survival to only 35% of the controls.Short periods of treatment (one hour) produced little effect at concentrations of 4 × 10−5M, and affected the survival of cells differently when 4 × 10−4 M were administered at different stages of the cell cycle. Two peaks of maximum sensitivity, one at late G1 and the other at G2 were observed. These peaks correspond to the peaks of maximum RNA synthesis described for synchronized mammalian cells. Therefore, it is likely that the cytotoxic effects of thiopyrimidine analogs are related to interference with RNA synthesis.
Sex chromatin and X chromosome replication patterns and incidence of sex chromatin in canine cell cultures
Authors: Brown Robert C. , Cole K. W. 
Published: February 2005

AbstractIn order to provide evidence as to whether sex chromatin (SC) of interphase cells is equivalent to the late replicating X chromosome in female mammalian cells, time‐lapse cinephotometric and autoradiographic methods were used to give precise data for comparison of the DNA replication patterns of SC with that of each of the X chromosomes throughout the S period. Canine kidney epithelial cells were selected because they have distinct large metacentric X chromosomes and typical SC. Time‐lapse cinephotometry was used to avoid possible alteration of DNA synthesis by chemical cell synchronization agents. Determination of the incidence of SC during the stages of the cell life cycle of proliferating cells of the same origin was performed in order hopefully to clarify conflicting reports on the subject. Our results clearly show that time and intensity of the SC replication throughout S period is like that of the late replicating X chromosome and unlike that of the early replicating X chromosome. The incidence of SC in proliferating cells in culture was found to vary with the stage of the cell life cycle, increasing with increasing postmitotic interval — least in G1, greater in S, and greatest in G2. The SC incidence increased strikingly from G1 to S and a less marked increase was observed between S and G2.
Modification of cell surface antigenicity as a function of culture conditions
Authors: Pfeiffer S. E. , Herschman H. R. , Lightbody J. E. , Sato G. , Levine L. 
Published: February 2005

AbstractAdaptation of monolayer cultures of a clonal line of rat glial cells to suspension culture resulted in the nearly complete loss of certain surface antigens. This change in surface antigenicity was paralleled by the loss of the ability of the cells to accumulate in vitro a protein specific to the nervous system (“S100‐protein”). In contrast, when glial cells were co‐cultivated in monolayer culture with another cell line apparently lacking these surface antigens, the number of these antigens was markedly increased. The possibility of a causal relationship between the changes in the surface antigenicity and the expression of differentiated function is considered.
Inhibition of cellular adhesiveness by sulfhydryl blocking agents
Authors: Grinnell Frederick , Srere Paul A. 
Published: February 2005

AbstractRat hepatoma cells rapidly adhered to the polystyrene surfaces of culture bottles. The adhesiveness of the cells was inhibited by sulfhydryl blocking reagents including mercurials, arsenicals, and alkylating agents. Inhibition was prevented, and in some cases reversed, by the addition of dithiothreitol to the adhesive medium. The current model explaining cellular adhesion is discussed in the light of these observations.
Surface charge and cell volume of synchronized mouse lymphoblasts (L5178‐Y)
Authors: Shank Brenda Buckhold , Burki H. John 
Published: February 2005

AbstractCellular electrophoretic mobility, and therefore, surface charge/ unit area, was found to be constant throughout the cell cycle of synchronized L5178‐Y mouse lymphoblasts, remaining at – 1.21 μ sec−1 V−1 cm. Measured cell volumes of these synchronized cells increased linearly over the cell cycle and at mitosis each cell divided into two cells, each cell having half of the parent volume. An hypothesis is presented which explains the presence of a mobility peak at mitosis in cells which normally are grown attaching to a glass surface on the basis of differential morphological changes during mitosis; cells such as the L5178‐Ys, which do not attach to glass normally, do not undergo such morphological changes at mitosis and, therefore, would not demonstrate a mobility peak at that time.
Influence of culture pH on photo‐inhibition of division in Euglena gracilis
Authors: Cook J. R. 
Published: February 2005

AbstractIn the dark, growth rates of Euglena gracilis were independent of culture pH between the limits of three to eight. Visible light of moderate intensity inhibited growth rates, with the degree of inhibition being markedly pH dependent. The most severe inhibition was observed at pH 4 to 5, with little or no inhibition at pH 3 or above pH 6.8 at the light intensity used (400 foot‐candles).