bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lipid components of sarcotubular membranes
Authors: Sanslone W. R. , Bertrand H. A. , Yu B. P. , Masoro E. J. 
Published: February 2005

AbstractThe lipid composition of a highly purified preparation of rat skeletal muscle sarcoplasmic reticulum was studied. These membranes contain per mg of protein 0.50 ± 0.02 μmoles of phosphatidylcholine, 0.13 ± 0.02 μmoles of phosphatidylethanolamine and 0.07 ± 0.02 μmoles ofphosphatidylinositol. These three components account for 97.3% of total lipid phosphorus. Unlike other mammalian membranes so far studied, this preparation contains neither sphingomyelin nor phosphatidylserine. Neural lipids were also measured and it is concluded that neither cholesterol nor other neutral lipids are components of the membranes studied. The results of this study indicate therefore that the lipid profile of sarcotubular membranes is relatively simple compared with most other membranes.
Lanthanum‐Induced alterations in cellular electrolytes and membrane potential in ehrlich ascites tumor cells
Authors: Levinson Charles , Mikiten Terry M. , Smith Thomas C. 
Published: February 2005

AbstractWe have investigated the effect of varying La+3 concentrations (0.01 mM to 2.0 mM) on membrane potential and electrolyte composition of Ehrlich ascites tumor cells. La+3 concentrations less than 0.02 mM had no effect. Above 0.02 mM, La+3 induced concentration‐dependent loss of electrolytes and water from the cells. At 1.0 mM the effect was maximal and resulted in an 87% reduction in cellular K+, 79% in Cl− and 21% in Na+ within 4.8 minutes. The Na+ loss occurred even in the face of an electrochemical potential gradient favoring Na+ entry. La+3 increased the recorded values of membrane potential; the magnitude of the effect was related to the external La+3 concentration, and was maximal at 1.0 mM. Studies using 140La showed that La+3 binds rapidly to the cell surface and does not enter the cells. The amount of La+3 bound to the cells was related to the external La+3 concentration by a sigmoidal curve and was maximal at about 1.0 mM. The bound La+3 could not be displaced by either added La+3 or Ca+2. Agents known to effect the integrity of the cell membrane, such as phospholipase C, neuraminidase, pronase and Hg+2 were tested for their ability to displace bound La+3. Only pronase displaced bound La+3, indicating that La+3 associates with cell protein. It is hypothesized that La+3 rapidly interacts with membrane protein causing alterations in membrane permeability and capacity to actively transport ions.
Hemopoietic inductive environment necessary for an early stage in differentiation of thymic immune cells: Effect of antilymphocytic serum
Authors: Bennett Michael 
Published: February 2005

AbstractTreatment of adult mice with rabbit anti‐mouse thymocyte serum decreased the number and frequency of alloantigen‐sensitive units responsible for graft‐versus‐host reactions and prolonged the survival of skin allografts. Whereas alloantigen‐sensitive units were suppressed directly in vitro, they were not apparently suppressed directly in vivo since the fall‐off of their numbers and/or function did not occur during the first day after serum injection. Treatment of prospective recipients of thymus cell grafts impaired the production of alloantigen‐sensitive units by transplanted primitive progenitors. Differentiation with proliferation of alloantigen‐sensitive units was less affected.Similarly, treatment of prospective recipients of thymus cell grafts with antilymphocytic serum impaired the production of specific inducer cells responsive to sheep erythrocytes by transplanted more primitive cells, presumably antigenreactive cells. Production of new precursors of anti‐sheep erythrocyte hemolytic plaque‐forming cells by transplanted bone marrow was not affected. Thus, antilymphocytic serum impairs the generation of immunocompetent cells of thymic origin by altering a hemopoietic inductive environment necessary for an early stage in differentiation.
Effects of anthramycin and actinomycin on RNA synthesis patterns in L1210 cells
Authors: Kann Herbert E. , Kohn Kurt W. 
Published: February 2005

AbstractAnthramycin and actinomycin D, two different types of DNA‐binding antibiotics, were compared for their effects on RNA synthesis in suspension cultures of mouse leukemia L1210 cells. RNA was labeled with radioactive uridine and selective effects on the synthesis of different classes of RNA were studied by sucrose gradient sedimentation of RNA purified from whole cells or from nucleolar and nucleoplasmic fractions.Two major differences were noted. (1) Whereas actinomycin produced two phases in the inhibition of uridine incorporation, the rapid phase being complete within a few minutes, anthramycin produced only a slow progressive inhibition. (2) Whereas actinomycin selectively inhibits nucleolar 45s RNA synthesis, anthramycin inhibits this RNA equally to the inhibition of the same size RNA in the nucleoplasm.Both antibiotics caused a shift towards lower molecular weight (slower sedimentation) in the distribution of nucleoplasmic RNA molecules synthesized in the presence of drug. When the two antibiotics were compared at concentrations producing equal extents of inhibition of nucleoplasmic RNA synthesis, anthryamycin produced the greater shift. The shift in sedimentation anthramycin produced the greater shift. The shift in sedimentation was not due to a slowing of RNA chain growth rate, since the change in sedimentation persisted when uridine incorporation time was increased so as to compensate for the reduction in RNA synthesis rate.The selective inhibition of nucleolar RNA synthesis by actinomycin could be due to possible differences in the properties of the different RNA polymerases, or to differences in the initiation rates for transcription. The absence of selectivity in the case of anthramycin might be related to the near irreversibility of its binding to DNA. The shift towards lower molecular weight of the RNA synthesized is compatible with (but does not constitute strong evidence for) premature termination of RNA chains.
Density distribution and cation composition of red blood cells in newborn puppies
Authors: Lee Ping , Miles P. R. 
Published: February 2005

AbstractThe density distribution and cation composition of red blood cells from newborn puppies have been studied. The density distribution of red cells from a newborn puppy in a bovine serum albumin density gradient resembles a normal distribution with a peak density at a region less than that found for adult dog red cells. In two weeks the whole distribution shifts toward a more dense region, and a second cell peak appears so that the distribution becomes bimodal. This second cell peak is smaller than the original peak, and it appears at a region of lower density. In nine weeks the distribution becomes a normal one again, but the peak density corresponds to the peak density of the second cell peak which first appeared at two weeks. Evidence has been obtained to show that fetal red cells are located in the more dense cell peak and neonatal cells are in the less dense second peak. These results were obtained by labeling fetal cells with Cr51 and neonatal cells with Fe59. The analysis of the cation content of these cells shows that fetal cells contain more K and Na and have a higher K/Na ratio than adult red cells. Furthermore, neonatal cells contain considerably less cation and hemoglobin than do fetal cells. From a study of the cation and hemoglobin content of red cells appearing in various density fractions it is concluded that fetal cells lose K and Na during the first two weeks after birth. Thus, the change in the density disribution of the erythrocytes is thought to be due to two factors: (1) An increase in the density of fetal cells due to the loss of K and Na and, hence, water during the first two weeks after birth, and (2) the entry of less dense neonatal cells into the circulation.
Properties and cellular distribution of cyclic AMP‐dependent protein kinase from thymus
Authors: Klein Monroe I. , Makman Maynard H. 
Published: February 2005

AbstractA protein kinase that catalyzes the phosphorylation of histone was partially purified from rat thymus, and the rate of histone phosphorylation was stimulated three‐ to fourfold by 1 × 10−6 M adenosine 3′,5′‐monophosphate (cyclic AMP). Thymic protein kinase was more active than the enzyme from spleen. Histone fractions f1, f2a, f2b, and f3 were all capable of serving as phosphate acceptors for the thymic protein kinase, and the rate of phosphorylation of each fraction was stimulated by cyclic AMP. The ability of various 3′,5′‐mononucleotides to stimulate protein kinase activity was compared. Inosine 3′,5′‐monophosphate (cyclic IMP) was the most effective substitute for cyclic AMP.The cellular distribution of cyclic AMP‐dependent protein kinase and adenylate cyclase activities in the thymus was determined. Cyclic AMP‐dependent protein kinase activity is present in both small thymocytes and residual thymic tissue. The specific activity of protein kinase from residual tissue, both for basal and cyclic AMP‐stimulated enzyme, was greater than that of enzyme from small thymocytes. In contrast to this, adenylate cyclase activity is predominately localized in the thymocytes.
Fibrinogen inhibits red cell adhesion to glass
Authors: George James N. 
Published: February 2005

AbstractStudies of human erythrocyte adhesion to glass have demonstrated consistently greater adhesion with serum‐containing media than with a comparable concentration of plasma. This serum‐plasma difference is explained by the adhesion‐inhibiting property of plasma fibrinogen. The fibrinogen effect is probably mediated through its firm binding to glass, since no adsorption onto the red cell surface could be demonstrated.The ability of more red cells to adhere to a foreign surface after plasma coagulation (the formation of serum from plasma) may be significant in the red cell surface interactions necessary for the formation of a fibrin‐red cell thrombus.
The multiple hemoglobins of the chick embryo
Authors: Fraser Ronald , Horton Bennett , Dupourque Daniel , Chernoff Amoz 
Published: February 2005

AbstractTwo embryonic hemoglobins are found in chick erythrocytes during early development by column chromatography on DEAE‐cellulose and by electrophoresis on starch gel and gelatinized cellulose acetate. Beginning during the sixth day of incubation these are replaced by three different hemoglobins. Following hatching, chicks lose the most alkaline component, so that in the adult two hemoglobins are again found. Chromatographic fractionation on phosphonic acid cellulose also revealed an increase in the number of hemoglobins present in chicks during their development. We report the presence of at least 11 hemoglobins whose relative concentrations rise and fall during chick ontogeny. Failure to recognize the multiplicity of chicken hemoglobins is believed to be the major source of the confusion regarding this subject in the present literature.
Effect of X‐irradiation of one partner on hybrid frequency in fusions between Chinese hamster cells
Authors: Harris Morgan 
Published: February 2005

AbstractSublines derived from V79 and B150 Chinese hamster cells lack hypoxanthine‐guanine phosphoribosyltransferase (HGPRT) and thymidine kinase (TK) respectively. When these strains are cultivated together without virus treatment in HAT medium, hybrid colonies with normal enzymic patterns arise in high frequency. The ratio of proliferating hybrid colonies to the minority cell inoculum in mixed cultures is approximately 1/1000. This observation has been used to examine the effect of x‐irradiation pretreatment of one cell type on the frequency of hybrid formation in mixed cultures. B150 cells (TK‐) were irradiated in monolayer cultures at dose levels of 200–4000r (180 KV, 15 ma). After trypsinization, the irradiated cells were mixed with unirradiated V79 cells (subline 129, HGPRT‐) and cultivated in HAT medium. The per cent decline in hybrid frequency as a function of x‐irradiation was compared to the relative decline in viability of x‐irradiated B150 cells when assayed in cultures alone. These curves diverged markedly, with the frequency of proliferating hybrids decreasing much less rapidly with radiation dose than survival of B150 cells. By contrast, when B150 cells were subjected to acute heat shock for graded intervals and subsequently mixed with untreated V79–129 cells, both viability of B150 cells and hybrid formation declined at the same rate. Our results suggest that lethally irradiated cells can still fuse with normal cells, and may contribute functional chromosomes to the hybrid karyotype. At limiting doses of x‐irradiation this technique may be useful as a means for induced segregation of marker chromosomes.
Lanthanum‐induced alterations of cellular electrolytes in Ehrlich ascites tumor cells: A new view
Authors: Levinson Charles , Smith Thomas C. , Mikiten Terry M. 
Published: February 2005

AbstractWe have shown previously that Ehrlich ascites tumor cells maintained at room temperature under an oxygen atmosphere lose Na+, K+ and Cl− isosmotically when exposed to La+++ (0.1 to 1.0 mM). Concomitant with these changes there is an increase in the recorded membrane potential (increasing intracellular negativity). The present studies further characterize the effect of La+++ on electrolyte distribution. Ehrlich ascites tumor cells were maintained at 0.5° C to permit Na+ gain and K+ loss. The addition of 1 mM La+++ to low temperature cells induces rapid loss of Na+, K+ and Cl−. This net loss of cellular electrolytes occurs even in cells depleted of ATP content using 2‐deoxyglucose (5 mM) and rotenone (10−6 M). Analysis of the appearance of tracer 22Na in the environment of cells preloaded with the radioisotope shows that La+++‐induced changes in membrane permeability or in active ion transport mechanisms are not responsible for the dramatic loss of electrolytes from experimental cells. The electrolyte loss occurs only when the cells are resuspended mechanically during the washing procedure used to prepare the cells for electrolyte determination.We conclude that the results of La+++ interaction with Ehrlich ascites tumor cells are twofold. As we have previously reported, La+++ stabilizes and causes a hyperpolarization of the membrane potential. Secondly, La+++ predisposes the cell membrane to become highly permeable when subjected to mechanical stress.
Nuclear magnetic resonance relaxation time and self‐diffusion coefficient measurements of water in frog ovarian eggs (Rana pipiens)
Authors: Mild Kjell Hansson , James Thomas L. , Gillen Kenneth T. 
Published: February 2005

AbstractSelf‐diffusion coefficient measurements of water in untreated ovarian eggs of Rana pipiens using nuclear magnetic resonance indicate that cytoplasmic water has reduced translational mobility compared with pure water. Using a simple two‐state model, we find that ∼67% is “relatively immobile.” Consideration of the nuclear magnetic resonance spin‐lattice and spin‐spin relaxation times indicates that the decreased mobility can largely be ascribed to hydration. Our value for the self‐diffusion coefficient (6.8 × 10−6 cm2/sec) is lower than those reported by other investigators using isotopic water exchange techniques on frog eggs chemically treated to remove the membrane. However, the results reported here are in agreement with unpublished data on untreated frog eggs implying that chemical treatment has modified the cytoplasm in some manner.
Activation of a ribonuclease on dispersion of rat liver to a single cell suspension and incubation of the cells at 37°
Authors: Kumar B. Vijaya , Bhargava P. M. 
Published: February 2005

AbstractIncubation of rat liver parenchymal cell suspensions at 37° results in degradation, to acid‐soluble material, of 15% of cellular RNA at 30 minutes and 40% at three hours, beyond which there is little, if any, further degradation. The RNA which remains in the acid‐insoluble form in the cells up to 30 minutes appears to exist largely in the native state. However, after 30 minutes, the acidinsoluble RNA of the cells is found to be partially depolym‐erised. These observations suggest the activation of an intracellular nuclease on dispersion of the liver tissue to a single cell suspension and incubation at 37°. This nuclease appears to be responsible also for the degradation, reported earlier, of exogenous RNA taken up by the cells. Activation of the nuclease is not due to depletion of pool of ATP or of other ribonucleotides from the cells, during either dispersion of the tissue or incubation at 37°. Incubation of the cells at 28°, or of liver slices at 37°, does not lead to any significant degradation to acid‐soluble material, or to partial depolymerisation, of RNA. Analysis of RNA obtained from cells incubated at 37° for various periods showed that chromatography on methylated albumin‐kiesulguhr (MAK) and Sephadex columns is not suitable for detecting partial depolymerisation of cellular RNA; RNA shown to be partially depolymerised by analysis on sucrose density gradient, in an analytical ultracentrifuge, and on a cellulose column, gave the normal pattern in MAK or Sephadex runs.
Contraction of protoplasm. IV. Cinematographic analysis of unfertilized sea urchin eggs stimulated with continuous direct current
Authors: Perkins Donald L. , Jahn Theodore L. 
Published: February 2005

AbstractThe response of unfertilized sea urchin eggs stimulated with continuous D.C. was studied using cinematographic techniques. As reported by previous workers, the initiation of the response was anodal in polarity and followed a typical strength‐duration curve. However, the anodal response may be swelling and/or contraction, depending on the amplitude of the applied stimulus, i.e., the magnitude of the contraction is directly related to the applied stimulus and is a graded response. It is suggested that the phenomena of anodal swelling and anodal contraction represent a continuum of responses based on ion exchange.
Physical separation of colony stimulating cells from in vitro colony forming cells in hemopoietic tissue
Authors: Moore M. A. S. , Williams N. 
Published: February 2005

AbstractHemopoietic colony formation in agar occurred spontaneously in mass cultures of marrow cells obtained from a number of species (guinea pig, rat, lamb, rabbit, pig, calf, human and Rhesus monkey). This contrasted with the observation that colony formation by mouse bone marrow exhibited an absolute requirement for an exogenous source of a colony stimulating factor. Analysis of spontaneous colony formation in Rhesus monkey marrow cultures revealed the presence of a cell type in hemopoietic tissue, capable of elaborating colony stimulating factor when used to condition media or as feeder layers. Equilibrium density gradient centrifugation separated colony stimulating cells from in vitro colony forming cells in monkey bone marrow. Separation studies on spleen, blood and marrow characterized the stimulating cells as of intermediate density, depleted or absent in fractions enriched for cells of the granulocytic series and localized in regions containing lymphocytes and monocytes. Adherence column separation of peripheral blood leukocytes showed the stimulating cells to be actively adherent, unlike the majority of lymphocytes, and combined adherence column and density separation indicated that stimulating cells were present in hemopoietic tissue within the population of adherent lymphocytes or monocytes.
The effect of cyclic AMP and cytochalasin B on tissue cultured melanophores of Xenopus laevis
Authors: Lyerla Timothy A. , Novales Ronald R. 
Published: February 2005

AbstractThe effects of cytochalasin B or low concentrations of adenosine 3′,5′‐monophosphate (cyclic AMP) were tested on melanophores in hanging drop preparations of neural fold explants from Xenopus laevis embryos in Barths' solution. After one week in culture, the melanophores were punctate in this medium. Cyclic AMP at 5 mM consistently caused reversible morphological transformation of these cells to the stellate state, whether they were situated within an epithelial outgrowth or isolated on the surface of the coverglass. Only the isolated melanophores consistently responded to 1 mM cyclic AMP. Cytochalasin B at 1–10 μg/ml caused aggregation of melanin granules in stellate cells, but left long, narrow cell branches containing some melanosomes. Its effect was at least partially reversible and appeared to be dose dependent. At 1% concentration, dimethyl sulfoxide caused melanin dispersion.
A cell line which is temperature‐sensitive for cytokinesis
Authors: Smith B. J. , Wigglesworth N. M. 
Published: February 2005

AbstractWe have isolated several cell lines which are temperature‐sensitive for growth. One of these appears to be temperature‐sensitive for cytokinesis. It was isolated from a Syrian hamster cell line by selecting cells which were not killed by 1 μg/ml cytosine arabinoside at 39° but which grew normally at 31°. It shows an increased proportion of binucleate cells when shifted to the non‐permissive temperature and time‐lapse photomicroscopy shows that a high proportion of attempted mitoses fail at 39°, apparently at the stage of cytokinesis. The cells which have failed to complete mitosis reattach to the plate and have two normal‐size nuclei but otherwise behave normally.
Fluctuations of Feulgen‐ and diphenylamine‐DNA in peripheral leukocytes,
Authors: Fontaine Julia C. , Swartz Frank J. 
Published: February 2005

AbstractThe circulating leukocyte is usually considered a mature, differentiated cell which does not normally divide. Cytophotometry of human and mouse leukocyte nuclei, however, reveals significant fluctuations in amounts of Feulgen‐DNA in all leukocytes at various times of the day. When analyzed for DNA content by the diphenylamine method, the same samples demonstrate variations closely correlated with those obtained by cytophotometry. Although these data may be interpreted as suggesting, among other things, the presence of metabolic DNA, a preliminary radioautographic study of the uptake of tritiated thymidine in mouse leukocytes failed to demonstrate evidence of DNA synthesis in the entire population of cells. In this study only 6–7% of the total leukocyte population was labelled over a 24‐hour period. This discrepancy, when considered in light of other uncertainties concerning the Feulgen and diphenylamine reactions, has led to reservations over the ability of either reaction to reflect the true amount of DNA in cells at all times. Rather, we consider it more likely that both procedures reveal similar incomplete fractions of leukocyte DNA at various times of the day, and that the magnitude of this fraction is, perhaps, determined by cyclic influences acting on such parameters as nuclear volume and degree of packing of the nucleohistones.