bluuebunny/crossref_metadata_2025_split huggingface dataset:
The calcium‐mediated promotion of mitotic activity in rat thymocyte populations by growth hormone, neurohormones, parathyroid hormone and prolactin
Authors: Whitfield J. F. , Perris A. D. , Youdale T. 
Published: February 2005

AbstractGrowth hormone, oxytocin, parathyroid hormone, prolactin and lysine vasopressin strongly stimulate mitotic activity in rat thymocyte populations maintained in vitro. These hormones have no mitotic effect on cells maintained in calcium‐free medium. It is concluded that they stimulate mitosis only indirectly by sensitising the mitotically competent segment of a thymocyte population to the action of calcium. The stimulatory action of calcium itself is opposed by low concentrations of the mucopolysaccharide chondroitin sulphate. However, the inhibitory action of chondroitin sulphate can be overcome by growth hormone.A possible common mechanism of action of these hormones on mitotically competent cells is discussed.
Evidence from studies of birefringence of structure across the dimple region of red cells
Authors: Shrivastav B. B. , Burton A. C. 
Published: February 2005

AbstractAnalysis of the equilibrium of the normal biconcave human red cell, in terms of its tension and a pressure inside, suggests a force of attraction between the opposite membranes at the dimple regions. The analogous attraction that causes rouleaux formation is mediated by long‐chain molecules. Single cells hanging on edge between polarizer and analyser, almost “crossed,” were photographed at different angles to the axis of the polarizer. Enlarged prints were scanned by a photometer. For single cells the records showed non‐significant fluctuations of intensity, but mean values for 32 cells showed a very significant sinusoidal variation with angle, as predicted by theory for birefringence in the cell at the dimple region. For the rim region, the averaged data showed no variation with angle. In cells moderately osmotically swollen, birefringence in the centre of the dimple region was absent, but persisted close to the inside of the membranes. The latter disappeared in cells further swollen to a biconvex shape. The data is interpreted as indicating oriented chains of molecules across the interior of the cell at the dimple region. The behaviour on swelling was what had been seen in a model with nylon fibres oriented between the charged plates of a condenser, in which the variation of attractive force with distance was adequate to explain the equilibrium of the red cell membrane.
Incorporation of H3‐uridine and the isolation and characterization of RNA from squid axon
Authors: Fischer S. , Gariglio P. , Tarifeño E. 
Published: February 2005

AbstractH3‐Uridine microinjected in the giant axons of the squid is incorporated in a TCA insoluble material. There is no difference between stimulated and resting axons as to the amount incorporated.The amount incorporated is increased if the stimulation precedes the microinjection of the tracer.RNA was purified and characterized from the axoplasm, axon sheaths and from a purified membrane preparation obtained from squid retinal nerve.
Early alterations in amino acid pools and protein synthesis of diploid fibroblasts stimulated to synthesize DNA by addition of serum
Authors: Wiebel F. , Baserga R. 
Published: February 2005

AbstractDiploid human fibroblasts in culture (WI 38) were allowed to reach a stationary phase and were then stimulated to reenter DNA synthesis and cell division by addition of serum to the culture medium. The rate of protein synthesis increased during the first hours after addition of serum reaching at three hours a plateau value that continued for at least 24 hours after serum addition. Inhibition of protein synthesis during the early hours after serum addition abolished the stimulation of DNA synthesis occurring 20 to 28 hours later.Increased protein synthesis was preceded by a rapid decrease in the intracellular pool size of most amino acids. These changes were independent of concomitant protein synthesis. They suggest that serum exerts an immediate effect on the function of the cell membrane.
Differentiation of a cell line of myeloid leukemia
Authors: Ichikawa Yasuo 
Published: February 2005

AbstractA cell line was established in vitro from a spontaneous myeloid leukemia of SL strain mice. This cell line was cytologically identified as myeloblast, and its normal differentiation appeared to be completely blocked in mass culture. When the line cells were seeded in soft agar with a conditioned medium from normal cells, either macrophages or neutrophil granulocytes appeared from a single clone. The rate of formation of colonies containing differentiated cells always increased with an increase in the concentration of conditioned medium. The conditioned medium from this line cell was not as effective as was that from normal cells in inducing differentiation.
Migration and proliferation of diploid human fibroblasts following “wounding” of confluent monolayers
Authors: Raff E. C. , Houck J. C. 
Published: February 2005

AbstractSix diploid human fibroblast strains were grown in confluent monolayers. Holes were scraped in these monolayers and the number of cells proliferating into these “wounds” with time were determined. The migration and mitotic aspects of the proliferation of fibroblasts into these wounds were analyzed separately.Small amounts of undialysed or dialysed serum were essential for cell division but not migration. Saline extracts of skin could not substitute for serum in the medium. Neither zinc nor cupric ion at tolerable concentrations (10−5M) increased the rate of cell proliferation.Normal human fibroblasts did not immediately start to divide from confluency into the “wound” space. Their generation time was about 32–39 hours. Fibroblasts from patients with cystic fibrosis began to divide almost immediately into the “wounded” area. Their generation time was about 48 to 56 hours.
Photolysis in a culture medium for Tetrahymena pyriformis
Authors: Lee Donald 
Published: February 2005

AbstractConsiderable variability has been found in the yield of cells in batch cultures of Tetrahymena pyriformis grown axenically in 1% tryptone/0.05% yeast extract. This variability has been traced to the photolysis by visible light of the flavin mononucleotide and thiamine components of yeast extract.
Density dependent inhibition of cell growth in cultures of primary and established lines of cells
Authors: Oren Rachel , Kohn Alexander 
Published: February 2005

AbstractThe effect of cell crowding on DNA synthesis (incorporation of 3HTdR and 32PO4) was studied by an improved method in monolayers of secondary cells and established cell lines, either normal or transformed by viruses or carcinogens. The method was based mainly on pulse labeling of cultures of cells a few hours after their seeding in equal numbers onto areas of different size in identical dishes, a condition which ensured equal physiological conditions and different degrees of crowding of cells.DNA synthesis was hardly inhibited in crowded monolayers of secondary chick, mouse and hamster embryo cells. The incorporation of radioactive thymidine and phosphate into DNA of cell lines such as BHK 21, 3T3/SV40 and L929 was strongly inhibited. An SV40‐transformed line of hamster kidney cells (HKT7) synthetized DNA equally well in sparse as in crowded monolayers. In lines of human amnion (FL) and BHK 21 cells which were more extensively studied the degree of inhibition of DNA synthesis was inversely proportional to their density.Autoradiography after 3HTdR pulse‐labeling indicated that the same proportion of cell nuclei were labeled in sparse and in crowded cultures. The extent of labeling (number of grains per nucleus) was lower in crowded cultures of those cells that also showed inhibition of incorporation of this label as measured by scintillation. The inhibition is thus expressed in retardation of DNA synthesis in cells in S phase rather than arresting it in a larger percentage of cells.
Divalent cation activation of flagellar ATP‐phosphohydrolase from bull sperm
Authors: Young L. G. , Nelson L. 
Published: February 2005

AbstractThe apparently inconsistent reports on flagellar ATPase properties may be resolved by elimination of adenylate kinase from the system. Removal of the adenylate kinase from alkaline M/2 KCl extracts of bull sperm flagella yields a spermosin‐ATPase which liberates only the terminal phosphate of ATP. In any case spermosin is preferentially activated by calcium. However, combination of spermosin with flactin (e.g., by addition of digitonin and MgCl2 to the extraction medium) produces an ATPase much more highly activated by magnesium. But flactospermosin has so far resisted purification from its adenylate kinase contaminant. In divalent cation activation, pH optima and nature of ATP hydrolysis, the flagellar contractile protein system closely parallels the muscle system.
Contraction of protoplasm. III. Cinematographic analysis of the contraction of some heterotrichs
Authors: Jones Alick R. , Jahn Theodore L. , Fonseca James R. 
Published: February 2005

AbstractThe contraction of Stentor and Blepharisma, in response to mechanical and electrical stimulation and of Spirostomum in response to mechanical stimulation is described. All three species respond to electrical stimulation by contraction of the cytoplasm, beginning at the anodal end regardless of orientation of the animal. The differences in contractile ability and shapes during contraction are discussed in relation to body form and microanatomy. Stentor and Spirostomum also respond to mechanical stimulation. Dropping a weight on the slide causes contraction of the whole body of Spirostomum, but not of Stentor. Stimulation of the oral region of Stentor by means of a vibrating needle causes a contraction of the entire body, but this sensitivity is limited to the oral region. Blepharisma does not respond to mechanical stimulation. Spirostomum and Stentor undergo rapid spontaneous contractions, but Blepharisma does not contract spontaneously.
Contraction of protoplasm. IV. Cinematographic analysis of the contraction of some peritrichs
Authors: Jones Alick R. , Jahn Theodore L. , Fonseca James R. 
Published: February 2005

AbstractThe contraction and relaxation of Vorticella difficilis, V. campanula and Carchesium sp. were studied by high speed cinematography. In Vorticella it was shown that coiling of the stalk usually started near the zooid and spread downwards; the point of initiation bore no relation to the position of the stimulating electrodes. Contraction took about 5 msec to complete, and the fully contracted animals were 29 ± 3.9% of their original lengths. The zooids were 66 ± 5.0% and the stalks 14 ± 6.0% of their original lengths (V. difficilis). The shortening of the stalk was mostly in the form of coiling. Measurement of the myoneme length demonstrated that its real shortening was less than 10%. Thus the contraction is virtually isometric, producing a helical deformation of the stalk. As the stalk contracts it takes the form of a steeply pitched helix. This change in shape should produce rotational forces on the zooid (torque). Physical models of similar proportions produced about 1.5 revolutions of torque for similar changes in pitch. However during contraction no turning of the zooid was detected, though rotation did occur after the completion of contraction.In Carchesium the contraction is not so isometric, the myoneme apparently shortening by 20%. While the coiled shape of the contracted Vorticella stalk can be explained by its acentric structures, the stalk of Carchesium is much more symmetrical in cross‐section, demonstrating that a high acentricity is not necessary for helical coiling. In all three species there seems to be some separation of the control of zooid and stalk contraction.
Enzyme kinetics in mammalian cells. II. Simultaneous determination of rate constants for the first three steps of galactose metabolism in red cells
Authors: Hill Helene Z. , Puck Theodore T. 
Published: February 2005

AbstractThe method for simultaneous measurement of the first two sequential enzymes of galactose metabolism of red cells has been extended to include the third step of the chain, epimerization of uridine diphosphogalactose to uridine diphosphoglucose. The method is rapid and precise and is applicable to a variety of genetic‐biochemical problems.
An improved chemically defined culture medium for strain L mouse cells based on growth responses to graded levels of nutrients including iron and zinc ions
Authors: Higuchi Kiyoshi 
Published: February 2005

AbstractNutritional factors were evaluated for effects on growth of mouse fibroblast cells in suspension in a chemically defined medium. Quantitative requirements for each of the essential amino acids, choline, inorganic phosphate, iron, and zinc were established. An improved chemically defined medium was formulated on the basis of the findings yielding populations of L cells in excess of 5 × 106 per ml without nutrient replenishment. When spent medium was replaced periodically, yields approaching 30 × 106 cells per ml were attained. The efficiency of utilization of most amino acids in the new medium appears to be 2‐ to 3‐fold better than results reported by others.
Nitrogen metabolism during synchronous growth of chlorella. II. Free‐, peptide‐, and protein‐amino acid distribution
Authors: Hare Theodore A. , Schmidt Robert R. 
Published: February 2005

AbstractThe levels of free‐, peptide‐, and protein‐amino acids were measured during the synchronous growth and division cycle of a thermophilic strain of Chlorella pyrenoidosa. Most of the protein amino acids exhibited little periodism (as % of total cellular‐N); however, the free‐ and peptide‐amino acids showed a variety of dramatic changes in level during the cell cycle.Fractionation of the acid‐soluble peptides by Sephadex gel‐filtration showed that an average of only 2.8% of the peptide amino acids were associated with peptides of high molecular weight (> 5000), while approximately 75% of the peptide amino acids were components of low molecular weight peptides (< 700). The low molecular weight peptides were predominately made up of relatively few amino acids (i.e., alanine, glutamate, lysine, glycine and arginine accounted for approximately 92% of the low molecular weight peptide amino acids).Several experiments revealed that nucleotide‐peptides do not contribute significantly to the pool of acid‐soluble peptides during the cell cycle of this organism.
Tracer kinetic analysis of incorporation of glucose and adenine by yeast cells
Authors: Burns Victor W. F. 
Published: February 2005

AbstractA kinetic model of adenine and glucose incorporation into log phase yeast cells has been developed, and experimental tests of certain predictions of the model validate it. The cellular pool of purine nucleotides is 6 × 10−3 μmoles per 107 cells, the turnover time of this pool is 21.8 minutes, and the rate of incorporation into nucleic acids is 4.86 × 10−2 μmoles per hour per 107 cells. Corresponding figures for glucose are given. The model should be useful in other kinetic studies and the method of applying it is explained.
Characterization of RNA molecules restricted to the nucleus in mouse L‐cells
Authors: Shearer Ruth W. , McCarthy Brian J. 
Published: February 2005

AbstractRNA molecules which are restricted to the nucleus in mouse L‐cells were characterized by the technique of RNA/DNA hybridization. Competition of cytoplasmic RNA with labeled nuclear RNA of various sizes revealed that the RNA restricted to the cell nucleus is heterogeneous in size. Competition for sites on fractions of mouse DNA of various base compositions indicated that this unstable RNA is also heterogeneous in base composition. Fractionation of nuclei into three subfractions failed to separate the uniquely nuclear RNA from the precursors of cytoplasmic RNA. The significance of the selective transport of RNA from the nucleus to the cytoplasm and its importance in the control of gene activity in eucaryotic cells is discussed.
Density distribution analysis of In vivo and In vitro colony forming cells in bone marrow
Authors: Haskill J. S. , McNeill T. A. , Moore M. A. S. 
Published: February 2005

AbstractThe technique of buoyant density separation in gradients of Bovine Serum Albumin has been used to separate hemopoietic cell populations in mouse bone marrow that form in vivo spleen colonies and in vitro colonies of granulocytes and macrophages in an agar culture system. The density distribution profiles showed a number of reproducible density subpopulations of both in vivo and in vitro colony forming cells (C.F.C.'s). The mean density of in vitro C.F.C.'s exceeded that of the in vivo but overlap of the density profiles of the two populations was evident. Density‐related differences in seeding efficiency of in vivo C.F.C.'s were observed.Freund's adjuvant treatment increased marrow and spleen in vitro C.F.C. populations. Marrow density profiles obtained three and seven days after adjuvant showed a progressive increase in in vitro C.F.C.'s in a restricted density region with no associated elevation of in vivo activity.The antimitotic agent, vinblastine, revealed differences in mitotic activity between the two cell populations, reducing the in vitro C.F.C. population to .07% and the in vivo to 5% of normal in 24 hours. Density separation of vinblastine‐treated marrow produced density regions devoid of in vitro activity but containing in vivo in vivo C.F.C.'s which, upon transfer to irradiated recipients, regenerated both in vivo and in vitro density distribution profiles.
Membranes of animal cells. V. Biosynthesis of the surface membrane during the cell cycle
Authors: Gerner E. W. , Glick M. C. , Warren L. 
Published: February 2005

AbstractKB cells grown in suspension culture were synchronized by using a double thymidine block. At various times throughout the life cycle aliquots of cells were pulsed with 14C‐L‐leucine, 14C‐D‐glucosamine and 14C‐choline for one hour periods. Surface membranes, cell particulates and soluble proteins were isolated and their 14C specific activities were determined. It was found that there was a marked increase in the rate of incorporation into surface membrane just after division. The pattern of incorporation was the same for all three isotopic precursors. The rate of incorporation of isotopic precursors into soluble proteins was constant throughout the cycle. Some increase in rate of incorporation of isotope into the particulate fraction was observed during division.
Thymidine as synchronizing agent. III. Persistence of cell cycle patterns of phosphatase activities and elevation of nuclease activity during inhibition of dna synthesis
Authors: Churchill Judy Rae , Studzinski George P. 
Published: February 2005

AbstractSynchronous cultures of HeLa cells were obtained by selective detachment of cells in mitosis and fluctuations in enzyme activity were followed during the subsequent cell cycle. The enzymes measured were alkaline and acid phosphatases and a nuclease active on denatured DNA at alkaline pH (alkaline DNase). Each of these enzymes showed a different pattern of activity in the cell cycle, but a temporal relationship to the DNA synthetic phase was apparent in each case. Treatment of the cultures at the beginning of the cell cycle with 15 mM thymidine did not alter the subsequent pattern of fluctuations in activity of alkaline phosphatase or of acid phosphatase, although DNA synthesis was fully inhibited by this treatment. This indicates that the pattern of activity of some enzymes is not linked to DNA replication. On the other hand, the pattern of fluctuations in the activity of alkaline DNase was abolished by thymidine treatment, and elevation of the activity of this enzyme was observed. These results suggest complex and variable relationships between phases of the cell cycle and enzyme activity, and show that inhibition of DNA synthesis is not a suitable procedure for induction of culture synchrony if enzyme activities are to be studied.
Effects of phenethyl alcohol on transport reactions, nucleotide pools and macromolecular synthesis in novikoff rat hepatoma cells growing in suspension culture
Authors: Plagemann Peter G. W. 
Published: February 2005

AbstractAt cytostatic concentrations, phenethyl alcohol has immediate and reversible effects on multiple metabolic processes of Novikoff rat hepatoma cells growing in suspension culture. These include an inhibition of the transport of various low molecular weight substances into the cell, an inhibition of DNA and protein synthesis and the processing of ribosomal RNA, and a degradation of ribosomal RNA. All effects might be explained as resulting from an interaction of the chemical with cellular membranes. Phenethyl alcohol does not have an immediate effect on RNA synthesis per se. The immediate failure of phenethyl alcohol‐treated cells to incorporate uridine from the medium into RNA is due to an inhibition of the uridine transport reaction.
Synthesis by a clonal line of rat glial cells of a protein unique to the nervous system
Authors: Pfeiffer S. E. , Herschman H. R. , Lightbody J. , Sato G. 
Published: February 2005

AbstractThe synthesis of a protein unique to the nervous system, the “S100‐protein,” has been studied in a clonal line of rat glial cells. It has been shown that these cells do not begin to accumulate “S100‐protein” until the cultures enter a phase of density‐dependent inhibition of cell proliferation. Further experiments indicate that the regulation of “S100‐protein” accumulation resides at least in part in an interaction involving the cell surface.
Variation in the latency of acid phosphatase and ribonuclease throughout the growth cycle of Tetrahymena pyriformis
Authors: Lee Donald 
Published: February 2005

AbstractThe latency of both acid phosphatase and ribonuclease was studied throughout the growth cycle of the ciliate protozoan Tetrahymena pyriformis and was found to be remarkably low in cells in the logarithmic phase of growth. The latency increased progressively throughout the log phase until it reached a maximum just after the cells had entered the stationary phase.The specific activity of acid phosphatase remained constant throughout the whole of the growth cycle while that of ribonuclease decreased as the cells began to leave log phase.The possibility is discussed that all rapidly dividing cells have a high proportion of their acid hydrolases outside the lysosomes and that these free hydrolases may have a function in cell division.