bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interphase action of vinblastine and vincristine: Differences in their lethal action through the mitotic cycle of cultured mammalian cells
Authors: Madoc‐Jones H. , Mauro F. 
Published: February 2005

AbstractVinblastine and vincristine, agents which cause arrest of cells in mitosis, have been examined for their effect on the survival of synchonously growing HeLa and Chinese hamster cells. At concentrations higher than those sufficient to induce mitotic arrest, both agents were found to exert a differential lethal action depending upon the position of the cells in interphase. Cells exposed for a short time (3 hours) to 0.3 μg/ml of vinblastine are more sensitive in S and in late G1 than those in other parts of G1 or in G2. Cells exposed to vincristine (0.1 μ/ml) show only the S phase sensitivity. These difference reflect variations in the survival curves for the two drugs in different phases of the cycle. Cells exposed for a short time to lethal doses of either agent during the S phase proceed at a normal rate to mitosis where they are then arrested irreversibly. In addition, vinblastine causes an immediate interphase death by lysis of cells treated in late G1.
Effects of divalent cations on adhesiveness of rat polymorphonuclear neutrophils In vitro
Authors: Garvin James E. 
Published: February 2005

AbstractCell preparations rich in polymorphonuclear neutrophils (PMN) were obtained from peritoneal exudates of rats without the use of any anticoagulant. The adhesiveness of these PMN to glass bead columns coated with rat serum were studied quantitatively using suspending solutions free of added serum protein. A dependence of the PMN adhesiveness upon divalent cations was demonstrated. Added singly Mg2+, Ni2+, Zn2+, Co2+, Mn2+, Cu2+, or Cd2+ were found to be effective whereas Ca2+, Sr2+ and Ba2+ were ineffective. A possible auxilliary role for Ca2+ when added with Mg2+ is suggested by the data. The ineffectiveness of the ions Ca2+, Sr2+ and Ba2+ was shown by use of an ion electrode not to be due to the unavailability of the ionized species. Procedures are described for obtaining highly reproducible results with the Orion Divalent Cation Electrode. The ineffectiveness of the ions Ca2+, Sr2+ and Ba2+ were also shown not to be due to action as general protoplasmic poisons. The effective ions are distinguished from the ineffective ones by characteristic ranges of ionic radii, coordination number, second ionization potentials, electronegativities and affinity constants. Removal of components of complement from the cells by washing in 0.05 M EDTA, and heating all serum used for 30 minutes at 56°C had no significant effect on the adhesiveness of the PMN. A role for complement, therefore appears largely excluded.
The self renewal probability of hemopoietic stem cells
Authors: Vogel Helmut , Niewisch Helgard , Matioli Gastone 
Published: February 2005

AbstractThe probability of a colony which originated as a single stem cell to become extinct due to differentiation of all of its stem cells in any generation is closely connected to stem cell self renewal probability p. p can be determined from the coefficient of variation of the colony numbers received by reinjecting single colonies of the same age. Whole spleens containing a known average colony number can also be used with advantage for this purpose. The results of both procedures indicate a stem cell self renewal probability p =0.62 ± 0.04, which does not change significantly between the sixth and the fourteenth day of colony development, and an extinction probability ω = 0.63 ± 0.12.
Decreased neutrophils and megakaryocytes in anemic mice of genotype W/Wv
Authors: Chervenick Paul A. , Boggs Dane R. 
Published: February 2005

AbstractThe concentration of neutrophils and megakaryocytes was determined in the marrow of anemic mice of genotype W/Wv and their normal (+/+) litter mates. In all groups studied, the humerus of W/Wv mice contained significantly less neutrophils and megakaryocytes than did normal animals. Blood neutrophil concentration was less in all groups of W/Wv mice but in only one group which was the youngest group studied, did this value differ significantly from normal.The blood and marrow neutrophil response to endotoxin was similar in W/Wv and “+/+” animals. This suggests that the neutrophilic system of W/Wv mice responds to this stimulus in a relatively normal manner, much as their erythroid system responds to hypoxia, and androgens.
Cell electrophoretic mobility and cationic flux
Authors: Weiss Leonard , Levinson Charles 
Published: February 2005

AbstractThe net negativity of the surfaces of Ehrlich ascites cells was reduced by treating them with either neuraminidase or ribonuclease. Neither enzyme treatment affected the Na+ or K+ content of the cells, before or after cooling at 4°C. Experiments with K42 revealed a reduction (9.5 to 17%) in unidirectional K+‐fluxes following incubation with neuraminidase, but no change after ribonuclease‐treatment. Our data suggest that surface anionic sites associated with RNA and sialic acid moieties are not of major quantitative importance in regulating either intracellular Na+ and K+ concentrations, or unidirectional transmembrane K+‐flux. Our results do not enable us to determine whether ion‐binding to anionic sites at the electro‐kinetic surface is not an essential prerequisite to transmembrane movement, or whether it is essential, but occurs through the 40% of cell surface net negativity which is unaffected by ribonuclease‐ and neuraminidase‐treatment.
Formation and properties of thin‐walled phospholipid vesicles
Authors: Reeves John P. , Dowben Robert M. 
Published: February 2005

AbstractLarge numbers of thin‐walled vesicles, 0.5 to 10 μ in diameter, can be formed by permitting a thinly spread layer of hydrated phospholipids to swell slowly in distilled water or an aqueous solution of nonelectrolytes. Electron micrographs and phospholipid analyses indicate that the walls consist of a single or a few bilayers. The vesicles can be centrifuged and resuspended in another medium, making them a useful system for studying permeability. The osmolarity of the solution in the interior of the vesicles can be estimated by immersion refractometry. The osmolarity of the internal aqueous phase is linearly related to the osmolarity of the external medium.
Phenylalanine hydroxylase activity in mammalian cells
Authors: Tourian Ara , Goddard Judy , Puck Theodore T. 
Published: February 2005

AbstractSurvey of twelve mouse tissues revealed the presence of appreciable phenylalanine hydroxylase activity in the pancreas and kidney as well as the liver but in no other of the tissues tested. Single cell suspensions of mouse liver were prepared by use of tetraphenylboron. The enzyme activity of such suspensions was much more stable than that of liver extracts, and permitted determination of the Michaelis‐Menten constant, the pseudo‐first order reaction velocity constant on a cell‐number basis, and the temperature coefficient and apparent activation energy of the enzyme activity. Possible applications of these methods to problems in cellular biology have been indicated.
A comparative study of the role of mitochondria and the sarcoplasmic reticulum in the uptake and release of Ca++ by the rat diaphragm
Authors: Carafoli Ernesto , Patriarca Pierluigi , Rossi Carlo Stefano 
Published: February 2005

AbstractThe respective importance of mitochondria and of sarcoplasmic reticulum in the uptake and maintenance of Ca++ by the isolated rat diaphragm has been compared. Diaphragms were incubated at 30° in conditions optimal for Ca++ uptake either by isolated mitochondria or by sarcoplasmic reticulum: more Ca++ was taken up from the “mitochondrial” medium. For maximal uptake, Pi and Mg++ were necessary; substitution of NaCl and KC1 with sucrose had no effect on the uptake. The uptake was markedly inhibited by uncouplers of oxidative phosphorylation, by respiratory inhibitors, and by lowering the temperature of the incubation medium to 0°; it was not affected by oligomycin, aurovertin, DCCD, nor by inhibitors of Ca++ transport in the isolated sarcoplasmic reticulum (ergotamine, ergobasinine, caffeine). The lack of effect of caffeine was not due to lack of penetration into the muscle. Permeability barriers for ergotamine and ergobasinine could not be excluded. The maintenance of Ca++ by the diaphragm was optimal in a medium contaming Pi and Mg++. Uncoupling agents and respiratory inhibitors accelerated the rate and extent of release of Ca++ by the diaphragm. Lowering the temperature of the incubation medium to 0°, or addition of oligomycin, aurovertin, DCCD, had no effect on the release. The release of Ca++ was also unaffected by ergotamine, ergobasinine, caffeine. The results suggest a role for mitochondria in the uptake and maintenance of Ca++ by the isolated diaphragm.
Purification and ultrastructural properties of the calcium accumulating membranes in isolated sarcoplasmic reticulum preparations from skeletal muscle
Authors: Greaser M. L. , Cassens R. G. , Hoekstra W. G. , Briskey E. J. 
Published: February 2005

AbstractSarcoplasmic reticulum fragments, prepared from skeletal muscle homogenates, were found to consist of two major types when examined after negative staining. One type possessed 90 Å subunits and was thought to be of mitochondrial origin. The other had 35 Å subunits and ws presumably derived from the sarcoplasmic reticulum. Only the latter type accumulated visible calcium oxalate deposits inside the vesicle when they were exposed to a medium containing ATP, MgCl2, K2C2O4 and CaCl2. The calcium oxalate loaded vesicles were strikingly angular in shape and did not have tails. The calcium oxalate loaded vesicles had identical membrane subunit arrangement to inactive companion membranes and nonincubated controls; this suggested that the membrane subunits were not the critical structural requirement for calcium transport. A method was described whereby the calcium accumulating membranes could be purified 3‐ to 4‐fold on the basis of the best previously used preparation procedures.
Physical separation of hemopoietic stem cells from cells forming colonies in culture
Authors: Worton R. G. , McCulloch E. A. , Till J. E. 
Published: February 2005

AbstractMouse bone marrow cells in suspension were separated into a number of fractions on the basis of cell density by equilibrium density gradient centrifugation, or on the basis of cell size by velocity sedimentation. After each type of separation, the cells from the various fractions were assayed for their ability to form macroscopic spleen colonies in irradiated recipient mice, and for their ability to form colonies in a cell culture system. The results from either separation technique demonstrate that cells in some fractions formed more colonies in vivo than in the culture system, while cells in other fractions formed more colonies in culture than in the spleen. The results of control experiments indicate that this separation of the two types of colony‐forming cells was not an artifact of the separation procedures. From these experiments it was concluded that the population of cells which form colonies in culture under the conditions used is not identical to the population of cells detected by the spleen colony assay.
Viability of human diploid cells as a function of in vitro age
Authors: Merz George S. , Ross John D. 
Published: February 2005

AbstractThe fraction of cell capable of division was determined for (1) population of the human diploid cell strains, WI38 after different numbers of subcultivations in vitro and (2) a single population of WI38 cells at intervals throughout its entire in vitro lifespan. In both cases the percentage of cells capable of division decreased with increasing age in tissue culture. The rate and the magnitude of the decrease is sufficient to account for the limited in vitro lifespan reported by other investigators. Furthermore, the decrease in the fraction of cells capable of division in similar in some respects of senescence among human populations.
Permeability and photoxidative damage of membrane enzymes
Authors: Duncan C. J. , Bowler K. 
Published: February 2005

AbstractThe pattern of photodynamic damage of pig erythrocyte and rat brain microsomal ATPases and erythrocyte acetylcholinesterases has been studied, using rose bengal as photosensitizer. Of these enzymes the Na+‐K+‐Mg2+‐ATPase, believed to be associated with active transport, is very much more sensitive to damage than are the Mg2+‐ATPase and the erythrocyte acetylcholinesterase. Earlier photoxidative studies of the haemolysis of erythrocytes have shown that ion movements occur in two phases which are dependent on the duration of exposure to light and it is suggested that these are correlated with the differential sensitivity of these membrane enzymes.The ATPases of the brain microsomal preparation were more sensitive to photodynamic damage during preincubation at 0°C, i.e. in the absence of substrate. Raising the preincubation temperature to 37°C protected both enzymes, the inactivation of the Na+‐K+‐Mg2+‐ATPase being markedly reduced. The presence of substrate during pre‐incubation at 0°C also protects both enzymes, especially the Mg2+‐ATPase. These interacting effects of temperature and substrate are compared with the known different temperature sensitivities of these two enzymes.
A melanin‐dispersing effect of cyclic adenosine monophosphate on Fundulus melanophores
Authors: Novales R. R. , Fujii R. 
Published: February 2005

AbstractTreatment of Fundulus melanophores with adenosine 3′,5′‐monophosphate (cyclic AMP) is followed by reversible melanin dispersion in these cells. Adenosine 3′‐monophosphate and adenosine 5′‐monophosphate both have a similar, but weaker dispersing action. In addition, adenosine 5′‐monophosphate also has a melanin aggregating effect. These results are interpreted to mean that nerve transmitters may act by controlling the level of cyclic AMP within the Fundulus melanophore.
Colony‐forming cells in organ cultures of embryonal liver
Authors: Latsinik Nataly V. , Luria Elen A. , Friedenstein Alexander J. , Samoylina Nina L. , Chertkov Iosiph L. 
Published: February 2005

AbstractLivers from 17‐ to 20‐day CBA mouse embryos were maintained for three weeks in organ culture. During this period, hematopoiesis continued; morphologically recognizable cells were identified until day 24 and hematopoietic cells with colony forming ability were present until day 23. The method appears to hold promise for studies of hematopoietic differentiation in vitro.
Further studies on the biological properties of friend virus‐induced leukemic cells differentiating along the erythrocytic pathway
Authors: Rossi Giovanni B. , Friend Charlotte 
Published: February 2005

AbstractWhen Friend virus‐induced leukemic cell lines were injected into irradiated hosts after the second radiation dose, the colony‐forming unit (CFU) in the recipient spleens per 104 cells was found to be 7‐fold higher than the CFU obtained when the second radiation dose had been given shortly after the inoculation of the cells. Serial passage of the cells from the spleen colonies to irradiated hosts resulted in a marked increase of the CFU value, indicating that this cell population was capable of both self‐replication and erythroid differentiation. The “f” fraction, which indicates the percentage of the inoculated cells that reach the spleen in the irradiated recipients, was found to be approximately 15%. If the highest CFU value obtained from serial colony‐to‐colony passages is corrected by this factor, a final cloning efficiency of about 18% is demonstrated.Neither induced plethora nor the administration of erythropoietin (1 u/mouse/for 2 days) appeared to affect the spleen colony‐forming ability of the leukemic cells.Erythroid differentiation is not detectable in the transplantable subcutaneous tumors which were used to initiate the tissue culture lines and which also are capable of inducing erythroid spleen clones in irradiated recipients. This lends support to the theory of the influence of “microenvironmental factors” on the fate of stem cells with potential for differentiation.
Selection of synchronous Chlorella cells by centrifugation to equilibrium in aqueous ficoll
Authors: Hopkins H. A. , Sitz T. O. , Schmidt R. R. 
Published: February 2005

AbstractSynchronous daughter cells of Chlorella pyrenoidosa can be selected, on the basis of their unique density, from cultures growing in continuous light by centrifugation to equilibrium in aqueous Ficoll. The degree of synchrony, as judged from cell release data, is equivalent to or better than that obtained by intermittent‐illumination procedures.
The molecular biology of reovirus
Authors: Joklik Wolfgang K. 
Published: February 2005

AbstractThe genome of reoviruses consists of ten discrete segments of double‐stranded RNA. The molecular weight of three of these, the L segments, is about 2.7 × 106; of another three, the M segments, about 1.4 × 106; and of the remaining four, the S segments, 0.6–0.8 × 106. In addition, reovirions contain about 2,000 molecules of oligonucleotide from 2 to 20 nucleotides long, most of which are very rich in ademine.The protein capsid of reovirions, which consists of an inner core and 92 outer shell capsomeres, is composed of seven species of polypeptides which also fall into three size classes. The size of six of these polypeptides is such that each accounts for the entire information content of one of the genome RNA segments.Reovirus messenger RNA molecules are transcripts of all ten genome RNA segments. Transcription proceeds not only in vivo in the infected cell, but can also take place in vitro. It is then catalyzed by reovirus cores, the polypeptide composition of which is strikingly similar to that of E. coli DNA‐dependent RNA polymerase. Transcription both in vitro and in vivo is entirely asymmetric and is conservative with respect to template.The patterns of transcription of the several reovirus genome RNA segments have been determined both in vitro and in vivo and the pattern of translation has been analyzed under in vivo conditions. The results suggest that transcription and especially translation are regulated within infected cells.
Influence of exogenous ions on the events of maturation in Rana pipiens oocytes
Authors: Ecker R. E. , Dennis Smith L. 
Published: February 2005

AbstractFull‐grown ovarian oocytes removed from non‐hormone‐treated Rana pipiens females exhibit a low level of protein synthesis, the rate of which is dependent upon the ionic environment. The highest rates of protein synthesis in these oocytes are obtained in media containing either a divalent cation (Ca++ or Mg++) or high levels of K+. The dependence of protein synthesis on ionic environment persists through about the first 18‐24 hours of maturation (at 18°C). Normal maturation of oocytes in vitro also has specific ionic requirements for the first 24 hours. In this case, the process requires high ionic strength (T/2 = 1.0‐1.2) and divalent cations. The kinetics of K+ exchange suggest that K+ exists in the ovarian oocyte in two compartments; one in equilibrium with the exogenous medium and freely exchangeable; the other in equilibrium with the exogenous medium and freely exchangeable; the other in equilibrium with the first internal compartment and only very slowly exchangeable. The slowly exchangeable (bound) compartment contains about 95% of all endogenous K+. In hormone stimulated oocytes, the kinetics of K+ exchange are essentially the same. Oocyte adaptation to ionic environment is discussed as a possible regulatory mechanism during maturation.
Studies on the mechanism of hormonal stimulation of zinc uptake in human cell cultures: Hormone‐cell interactions and characteristics of zinc accumulation
Authors: Cox Rody P. , Ruckenstein Adriana 
Published: February 2005

AbstractAdrenal steroid hormones with glucocorticoid activity increase the uptake of Zn++ in HeLa cell cultures. On the basis of the level of Zn++ accumulation induced, steroid hormones can be classified into four groups: (a) optimal inducers (e.g., hydrocortisone and prednisolone); (b) suboptimal inducers (e.g., aldosterone and corticosterone); (c) anti‐inducers (e.g., progesterone and 17 α‐methyl testosterone) which competitively inhibit induction by optimal inducers; and (d) non‐inducers (e.g., cortisone and pregnenolone) which neither induce nor inhibit the steroid‐mediated increase in Zn++ uptake. The ability of an anti‐inducer to block the effects of optimal inducers is not the result of inhibition of steroid uptake or an effect on general protein synthesis. Optimal inducers do not increase adenyl cyclase activity of HeLa cells nor can the hormone effects on Zn++ uptake be reproduced by 3'‐5' cyclic AMP. The prednisolone‐induced enhancement of Zn++ uptake is gradually lost over two or three days following removal of the hormone. Uptake of Zn++ by HeLa cells is not altered by a decrease of sodium concentration in the medium nor by changes in medium osmolarity. The uptake mechanism is not affected by subjecting intact cells to proteolytic enzymes; however, if cells are disrupted the hormone‐mediated increase in Zn++ accumulation is lost. The Zn++ taken up by HeLa cells in the presence or absence of hormone is primarily cytoplasmic in localization and appears to be distributed in a multicompartmental system.
Stimulation by epinephrine of adenyl cyclase activity, cyclic AMP formation, DNA synthesis and cell proliferation in populations of rat thymic lymphocytes
Authors: MacManus J. P. , Whitfield J. F. , Youdale T. 
Published: February 2005

AbstractDuring the first ten minutes after the beginning of a continuous exposure of rat thymocyte populations (maintained in vitro) to epinephrine, there is an increase in the cellular concentration of cyclic AMP. The hormone also increases the activity of a crude preparation of the thymocyte's cyclic AMP‐forming enzyme, adenyl cyclase. Between 30 and 45 minutes after the beginning of exposure to epinephrine, an additional part of the cell population begins to synthesize deoxyribonucleic acid (DNA). These changes are finally followed two to four hours later by an increase of the flow of cells into mitosis.Since cyclic AMP itself is known to stimulate both the initiation of DNA synthesis and thymocyte proliferation, and since the mitogenic action of epinephrine is shown to be potentiated by caffeine and inhibited by imidazole, it is concluded that the mitogenic action of this hormone is mediated by the cyclic nucleotide.