bluuebunny/crossref_metadata_2025_split huggingface dataset:
The conversion of ATP to IMP by muscle surface enzymes
Authors: Dunkley C. R. , Manery J. F. , Dryden E. E. 
Published: February 2005

AbstractThese experiments showed that an isolated muscle bundle could be used to study, simultaneously, ion transport and the activity of surface enzymes. Frog muscles were carefully dissected and incubated for four hours in Ringer's solution containing a tris buffer and 3 mM ATP; at various times samples of the medium were chromatographed and analysed spectrophotometrically for nucleotide content. Samples of the final medium were analysed for inorganic phoshpate and for ammonia. The results demonstrated the conversion of adenosine triphosphate to inosine monophosphate, via adenosine diphosphate and adenosine monophosphate. Under the conditions of the experiment IMP was detected on chromatograms within 20 minutes of incubation; at the end of four hours the media had concentrations of 2.3 mM IMP, 4.4 mM inorganic phosphate and 2.6 mM ammonia, showing a stoichiometric relation among the products formed. There was convincing evidence that the enzymes involved (ATPase, adenylate kinase and AMP deaminase) must be situated close to or on the muscle surface. No effect of ouabain (1 μM) on the activity of the ATPase, adenylate kinase or deaminase could be found in these experiments, but the drug inhibited Na and K recovery from a Na‐loaded, K‐depleted state.
Amino acid incorporation by cleaving nucleate and non‐nucleate egg‐fragments of Arbacia punctulata
Authors: Rinaldi Robert A. 
Published: February 2005

AbstractTritium labeled alanine and leucine are incorporated into activated non‐nucleate and nucleate egg‐fragments of Arbacia. Labeling is similar in both non‐nucleate and nucleate fragments, and the pattern is network‐like. There may be slight amino acid incorporation by asters, prespindles, or mitotic apparatus in early cleavages of the activated fragment, but it is not above incorporation by the cytoplasm. In some samples it is not significantly above “background.” It is concluded that these organelles do not necessarily depend on new synthesis of proteins during early cleavage stages. The role of those proteins synthesized during the first precleavage stage is unknown.
Erythrocyte membrane sulfhydryl groups and cation permeability
Authors: Sutherland Robert M. , Rothstein Aser , Weed Robert I. 
Published: February 2005

AbstractReaction of the slowly penetrating organic mercurial compound parachloromercuribenzene sulfonate (PCMBS) with intact erythrocytes has been characterized. Addition of concentrations of PCMBS which result in binding within the interior of the membrane of more than 1.9 × 10−18 moles/cell produces alterations in Na+ and K+ permeability, but does not affect choline permeability. However, the increased cation permeability is observed only after a lag period of over two hours. After ten hours, a spontaneous slow “recovery” to normal rates of K+ leakage occurs at 25°C but not at 2°C. Subsequent to the effects on cation balance, increasing degrees of hemolysis occur, interpreted as colloid osmotic lysis. The relationships between the binding of the agent and its effects are as follows: a small, rapid initial uptake does not affect cation permeability; the subsequent slower uptake is associated with increased leakage of K+ and Na+; and the recovery at 25°C is associated with desorption of about half of the PCMBS due to competition by soluble thiol substances released into the medium from the cells. Desorption and “recovery” can be mimicked at any time by addition of small amounts of protein in the medium. The half of the PCMBS that cannot be desorbed is assumed to be bound by the hemoglobin inside the cell. The sulfhydryl groups involved in control of cation permeability constitute only a fraction of the total within the membrane (4–18%). They are located within the interior of the membrane separated from the medium and from the interior of the cell by diffusion barriers to PCMBS.
Regeneration of sialic acid on the surface of chinese hamster cells in culture. II. Incorporation of radioactivity from glucosamine‐l‐14C
Authors: Kraemer Paul M. 
Published: February 2005

AbstractCultured Chinese hamster cells incorporated radioactivity from glucosamine‐1‐14C into surface sialic acid and into trypsin‐removable material distinct from the surface sialoglycans. Cells prelabeled with glucosamine‐1‐14C and then transferred to medium containing unlabeled glucosamine progressively lost counts to the medium for many hours. Such chase experiments suggested a more rapid turnover of trypsinremovable material than of surface‐bound sialic acid. Further studies of the regeneration of surface sialic acid showed that the actinomycin D‐resistant portion of the process involved emergence of an intracellular precursor onto the cell surface. An earlier portion of the process was inhibited by actinomycin D, and at least three steps were inhibited by puromycin or cycloheximide.
Comparison of the requirements for ribonucleic acid synthesis with the requirements for deoxyribonucleic acid synthesis in animal tissues
Authors: Furth J. J. , Rosenberg Martin , Ho Patricia L. 
Published: February 2005

AbstractRibonucleic acid polymerase and deoxyribonucleic acid polymerase have been partially purified from bovine lymphosarcoma, lymph node, and thymus. An examination of the deoxyribonucleic acid requirements of the two enzymes indicates that “native” deoxyribonucleic acid is the preferred template for ribonucleic acid synthesis; heat‐denatured deoxyribonucleic acid is considerably less active. The primer requirements for deoxyribonucleic acid synthesis differ: “native” deoxyribonucleic acid is usually inactive, while denatured deoxyribonucleic acid is active. The two enzymes also differ in pH optima and in their requirements for metal cofactors.
Effects of inhibitors of RNA and protein synthesis on activation of glyconeogenesis in Tetrahymena
Authors: Levy Michael R. 
Published: February 2005

AbstractThe effects of actinomycin D, puromycin, and p‐fluorophenylalanine on the activation of glyconeogenesis in Tetrahymena were studied.The extent of activation of glyconeogenesis in cultures containing inhibitor was as great as or greater than in the controls, as was the uptake of tracer levels of acetate into glycogen. These increases occurred despite a partial or complete inhibition of synthesis of isocitrate lyase, a glyconeogenic enzyme in Tetrahymena. Washed cells from these cultures could convert tracer or substrate levels of acetate to glycogen at enhanced rates. When glyconeogenesis was activated in starved cells in the presence of inhibitor, there was a negligible increase in the amount of isocitrate lyase, but a significant increase in the rate of glyconeogenesis. The data indicate that glyconeogenesis in Tetrahymena can be activated in the absence of enzyme synthesis.
Growth of the L‐cell in galactose medium
Authors: Baugh Clarence L. , Fitzgerald Joan M. , Tytell Alfred A. 
Published: February 2005

AbstractThe failure of the L‐cell to grow in a medium containing galactose as the sole carbohydrate was found to be directly related to the initial pH of the medium. Excellent growth of L‐M cultures in Eagle's minimum essential medium containing galactose instead of glucose was obtained by adjusting the medium to pH 6.2–6.8.
Ribonucleic acid within the cellular peripheral zone and the binding of calcium to ionogenic sites
Authors: Weiss L. , Mayhew E. 
Published: February 2005

AbstractRibonuclease was shown to reduce the electrophoretic mobility of a line of cultured mammalian cells (RPMI no. 41), and Ehrlich ascites tumour cells. No reduction was detected in the case of human, mouse or embryonic chick erythrocytes. These data, taken with the various controls, support the hypothesis that RNA is a structural component of the peripheries of two types of cells, but not of erythrocytes from three species.Calcium‐binding was studied in RPMI no. 41 cells, Ehrlich ascites tumour cells, and human and mouse eryhrocytes, by measurement of reduction in cellular electrophoretic mobility in suspending solutions containing various concentrations of calcium chloride. The effect of treating cells with neuraminidase and/or ribonuclease on calcium‐binding was also studied. The results suggest that less calcium binds to the carboxyl groups of peripheral sialic acids than to the phosphates of peripheral, structural RNA. However, calcium apparently binds most avidly to as yet unidentified anionic sites.
Clonal repopulation in reticular tissues of x‐irradiated mice: Effect of dose and of limb‐shielding
Authors: Nowell Peter C. , Cole Leonard J. 
Published: February 2005

AbstractChromosome studies in irradiated mice have indicated that following high sublethal whole‐body exposure regeneration of the reticular tissues occurs in a clonal fashion. With increasing doses, from 100 to 700 rads, these organs appeared to be repopulated from fewer and fewer surviving stem cells. In a few instances at the highest dose, the progeny of the same cell apparently differentiated to marrow cells at one site and to lymphoid cells in others, suggestive evidence of a totipotent hematopoietic stem cell in the adult mouse.Chromosome studies in mice receiving 900 rads with one limb shielded have indicated repopulation of the thymus and other reticular tissues by undamaged cells from the shielded marrow. Such marrow‐derived cells, perhaps by restoring immunological competence or by non‐immunological contact inhibition, could account for the known effect or limb shielding in reducing the incidence of radiation‐induced thymic lymphomas.
Distribution in tissue homogenates, and the nature of the linkage of injected proteins to subcellular particles
Authors: Bertini Francisco , Mego John L. , McQueen J. Donald 
Published: February 2005

AbstractIntravenously injected labeled proteins were recovered mostly in particulate fractions of rat liver homogenate. Distribution showed changes depending on the time elapsed from the injection. 131I‐albumin undergoes an intraparticulate hydrolysis which shows the highest activity in the gradient fractions associated with the highest level of acid phosphatase. The labeled albumin‐bearing particles separated at 27,000 g × 10 minutes released their radioactive protein at the same rate as acid phosphatase appeared in the medium, under the effect of such agents as distilled water, salts, homogenization, sonication and pH changes. The substitution of sucrose for distilled water or salts showed that the particles behave as an osmotic system as do lysosomes. These experiments prove that secondary lysosomes involved in the hydrolysis of foreign proteins, whose existence was shown by other authors only at the histochemical level, may survive the distrupting action of conventional homogenization and maintain many properties characteristic of primary lysosomes in addition to the ability of hydrolysing “in vitro” the engulfed material.
Cyclic changes in the alcohol‐soluble carbohydrates in synchronized Tetrahymena. I. Fractionation
Authors: Whitson G. L. , Green J. G. , Francis A. A. , Willis D. D. 
Published: February 2005

AbstractFifteen alcohol‐soluble carbohydrates have been isolated from logphase cultures of Tetrahymena. Preliminary results obtained by parallel chromatography of impure extracts indicate that some of the soluble components were 2‐D‐deoxyribose, ribose, mannose, fructose, arabinose, xylose, and glucose. Another elution gradient with extracts from cells washed several times, indicates that maltose and glucose were the only identifiable components as compared with 18 known standards. Differences were observed in the alcohol‐soluble carbohydrate content in log‐phase versus stationary‐phase cells. For example, it is clearly indicated that component 13 is missing in stationary‐phase cells while component 15 is missing in log‐phase cells. Fifteen alcohol‐soluble carbohydrates have been chromatographed from synchronized cells. All of these compounds show cyclic variation in relation to cell division. Component 13 accumulates in cells blocked in morphogenesis and decreases as oral development proceeds in synchronized cells.
Control of polytenic replication in dipteran larvae. I. Increased number of cycles in a mutant strain of Drosophila melanogaster
Authors: Rodman Toby C. 
Published: February 2005

AbstractPrevious studies have demonstrated that a consistent maximum number of polytenic replication cycles occurs in the salivary gland nuclei of a wild‐type strain of D. melanogaster. Since that number is achieved within the larval period, the DNA synthesis of the prepupal period is believed to be that of propagation of the final cycle. Photometric determinations have been made, in this study, of the salivary gland nuclei of larvae and prepupae of the tu‐h strain in which the larval period has been extended as a consequence of delay or failure of pupation. The DNA values indicate that a higher maximum number of polytenic replications is achieved in such nuclei. It is inferred, thereby, that initiation of polytenic replication is a function of the larval state and, since it is terminated by the intervention of metamorphosis, a hormonal dependence is suggested.
Control of polytenic replication in dipteran larvae. II. Effect of growth temperature
Authors: Rodman Toby C. 
Published: February 2005

AbstractA comparison has been made, by Feulgen photometry, of the polytene nuclei of the salivary glands of a wild‐type strain of Drosophila melanogaster grown at 17°C and 25°C, respectively. Despite the fact that the time period of the larval stage was more than doubled at the lower temperature, the DNA values were the same in magnitude and similar in distribution of replication classes at each of the stages studied. The data have been interpreted as indicating that, so long as the larval state prevails, initiation of polytenic replication occurs upon completion of the previous cycle.
Orthophosphate flux across the membrane of Tetrahymena pyriformis W
Authors: Pruett Patricia O. , Conner Robert L. , Pruett John R. 
Published: February 2005

AbstractTetrahymena pyriformis W suspended in a buffered glucose solution accumulated orthophosphate [32P] from the external solution at a measurable rate. The uptake of orthophosphate by the organisms was linear with respect to time when corrections were made to account for a constant efflux observed during the one hour time course of the experiments. Such corrections were based on the measured lowering of the relative specific activity of the suspension medium and led to the derivation of the expressions for the influx and efflux coefficients. The derived expressions for the coefficients are based solely upon the isotopic measurements and by means of these equations it is possible to describe the observed net inward flux of orthophosphate in quantitative terms. The dependence of the uptake of orthophosphate on the external concentration of orthophosphate followed Michaelis‐Menten kinetics, and the temperature coefficient (18–28°) of 1.7 for the process fell into the range normally associated with a chemical reaction. The kinetic pattern, per se, does not distinguish a membrane transport mechanism from metabolic incorporation of Pi. Deviations from the expected pattern of uptake were observed at low temperatures.
The effect of pH on the propagation of the diploid cell WI‐38 in galactose medium
Authors: Baugh Clarence L. , Lecher Robert W. , Tytell Alfred A. 
Published: February 2005

AbstractThe pH range for optimal growth of WI‐38 in Eagle's minimum essential medium varies with the carbohydrate utilized. Growth with glucose occurred only in the pH range 6.8–7.4. Glucose‐free galactose supported growth only if the pH of the medium was adjusted to 6.4–6.8. Supplementing the galactose medium with pyruvate extended the pH range for growth to 7.4. The addition of 0.01% glucose to the galactose medium increased growth at pH 7.0–7.4, reduced growth at pH 6.8, and completely inhibited growth at pH 6.6. This toxic effect of glucose under conditions impairing glycolysis was considered to be a contributing factor to the post‐confluent growth rate decline associated with “contact inhibition.”
Role of RNA synthesis in DNA replication of synchronized populations of cultured mammalian cells
Authors: Fujiwara Yoshisada 
Published: February 2005

AbstractUsing the harvesting method of synchronizing L cells, the relationship of RNA synthesis of DNA replication was studied by the use of selective inhibitors of RNA synthesis such as actinomycin D and chromomycin succinate. The synthesis of the early replicating DNA fraction is a process sensitive to the inhibition of RNA synthesis during the G1 period.The synthesis of early replicating DNA was inhibited by chromomycin succinate without affecting the initation of DNA synthesis. However, actinomycin D inhibited the synthesis of early replicating DNA and prevented the initiation of DNA synthesis in 50% of the synchronized cells. However, it was found that the continued synthesis of RNA during the S period is not essential for the synthesis of late replicating DNA.In addition to this specific response of DNA synthesis to the inhibitors of RNA synthesis, another function of early and late replicating DNA was determined relative to the cell viability. Cells synthesizing early replicating DNA were killed more efficiently by chromomycin than at other stages of the cell cycle. This indicates that the early replicating DNA unit plays a more important role in cell reproduction than the late replicating DNA unit.
Factors influencing hematopoietic spleen colony formation in irradiated mice. IV. The effect of erythropoietic stimuli
Authors: Marsh John C. , Boggs Dane R. , Chervenick Paul A. , Cartwright George E. , Wintrobe Maxwell M. 
Published: February 2005

AbstractA variety of erythropoietic stimuli influenced the number of endogenous spleen colonies in irradiated mice and the number of transplantable colony forming cells in the spleen and marrow of unirradiated mice.Bleeding was the most effective stimulus. Bleeding before irradiation resulted in a 30‐fold increase in endogenous spleen colonies and in increases in spleen weight, spleen iron and iododeoxyuridine uptake and volume of packed red cells ten days after irradiation. Bleeding unirradiated mice produced a 10‐fold increase in the number of transplantable colony forming cells in the spleen and a slight decrease in the total number in the humerus. Bleeding before irradiation resulted in a significant reduction in 30‐day post irradiation deaths, an effect abolished by splenectomy. Plasma from bled mice induced an increase in endogenous colonies when injected before irradiation into normal mice.Injection of erythropoietin, testosterone or testosterone plus cobalt induced effects which were, in general, qualitatively similar to those of bleeding, although they were less effective quantitatively. Except for a slight effect induced by ten injections of erythropoietin, post‐irradiation stimulation in normal mice proved ineffective. Erythropoietin increased colony numbers and spleen iron uptake when given after irradiation to hypertransfused mice.The results of these studies do not support the concept that the colony forming cell and the erythropoietin sensitive cell are separate entities.
Properties of a hybrid between lines sensitive and insensitive to contact inhibition of cell division
Authors: Weiss Mary C. , Todaro George J. , Green Howard 
Published: February 2005

AbstractHybrid cell lines have been prepared between 3T3, a line highly sensitive to contact inhibition of division, and cl 1‐D, an L cell derivative which is not sensitive. A number of hybrid clones isolated were found to be quite sensitive, indicating that in this respect the 3T3 behavior is the more fully expressed in the hybrid. On serial subculture, the hybrid lines gave rise to variants less sensitive to contact inhibition.
Deficient Fe59 and I125 deoxyuridine uptake by lympho‐hemopoietic cell transplants engaged in homograft reactions
Authors: Davis William E. , Schofield Raymond , Cole Leonard J. 
Published: February 2005

AbstractErythropoietic activity of spleen cell grafts was measured (Fe59 uptake) in X‐irradiated recipient mice under conditions in which these grafts were engaged in homograft reactions against allogeneic target cells or in graft‐versus‐host reactions. Such Fe59 incorporation was greatly reduced at 7 to 10 days after graft implantation relative to that of control grafts. This reduced erythropoiesis did not occur when the spleen cell graft was immunologically incompetent. Transplantation of bone marrow‐lymph node cell mixtures also resulted in a relative decline in Fe59 uptake, but only when minimal numbers (105 to 106) of marrow cells were injected. The incorporation of I125 UdR in the spleen of irradiated recipients was used to assess cellular proliferation. Incorporation of this label was reduced when measured 7–10 days after implantation of the lympho‐hemopoietic cell graft, but reached a peak at five days—the latter indicating stimulated lymphopoiesis. These data are consistent with the concept of depletion of a pluripotent stem cell pool (limited in size under these experimental conditions) due to excessive and concurrent functional demands for erythropoiesis and lymphopoiesis. An alternative explanation would involve cytotoxic effects on hemopoietic elements present in the milieu of the immunologic reaction.
The rhythm of mating in Paramecium aurelia, syngen 3
Authors: Karakashian Marlene W. 
Published: February 2005

AbstractThe periodic mating behavior of some stocks of Paramecium aurelia, syngen 3, exhibits features typical of circadian rhythms. In the most extensively studied stock (37p), rhythmicity persists at least four days in continuous darkness, but disappears rapidly in continuous illumination (200 foot‐candles). The period of the free‐running rhythm is 22.2 hours, and relatively insensitive to ambient temperature. Cycles of illumination and temperature can regulate the mating rhythm. Changes in illumination at specified times in the circadian cycle will induce shifts in the phase of the rhythm. Stock differences with respect to the persistence of the rhythm and the environmental control of its phase have been observed.
Monocyte kinetics: Observations after pulse labeling
Authors: Whitelaw D. M. , Bell M. F. , Batho H. F. 
Published: February 2005

AbstractBecause monocytes and their precursors cannot be recognized with certainty in tissues, an approach to the study of monocyte kinetics was made through examination of the peripheral blood. Injection of a single pulse of tritiated thymidine into rats resulted in the appearance of labeled monocytes identified as circulating peroxidase‐positive mononuclear cells. The increase in the percent of labeled cells and in the mean grain count per cell followed a course described by a mathematical model with a generation time of 21 hours and a DNA synthesis time of 12.5 hours. The generation and synthesis times appear to be very uniform for the monocyte so that the phasing of cells represented by the uptake of label could be followed for more than two generations, a property not shared by neutrophils or lymphocytes. Monocytes appear in the circulation within eight hours of DNA synthesis.