bluuebunny/crossref_metadata_2025 huggingface dataset:
Microelectrode analysis of light responses in the brain of the cricket (Gryllus domesticus)
Authors: Dingle Hugh , Fox Stephen S.
Published: February 2005

Electrical activity in response to light stimuli was recorded from the brain of the cricket (Gryllus domesticus) using stainless steel microelectrodes. Four basic types of elements were observed as follows: (1) units which registered ambient light intensity by frequency of firing as well as responding with transient changes in rate to stepwise increases or decreases in intensity; (2) units which fired at a higher frequency in dark than in light; (3) units which fired continuously at low level in light and responded with a transient high frequency burst to light off; and (4) units which responded with a brief burst to on and off, but tended to be “on‐dominant” or “off‐dominant.” Also observed were synchronized spikes in mushroom body responding primarily to light off, but also on occasion to light on, and often accompanied by single unit responses. The units registering intensity are probably homologous with units showing similar properties recorded from the visual systems of several other arthropods and usually referred to as “sustaining units.” On‐off, off, and dark units are also known from other forms. The mushroom body light responses were similar to synchronized spikes recorded in cockroach mushroom body following antennal stimulation.
Regeneration of sialic acid on the surface of Chinese hamster cells in culture. I. General characteristics of the replacement process
Authors: Kraemer Paul M.
Published: February 2005

Treatment of cultured CHO cells with neuraminidase reduced the mean surface sialic acid density to less than 10% of pretreatment values. Upon return to culture the mean density returned to pretreatment values within 12‐‐16 hours. During the period of surface sialic acid deficiency, no effect on cell volume, cell division, or attachment and spreading of cells on glass could be discerned. Surface sialic acid regeneration occurred at the same rate in suspension and monolayer cultures. Cells treated with neuraminidase, then with 10 mM thymidine or 6 μg/ml actinomycin D, ceased division yet replaced their surface sialic acid at the usual rate. By contrast puromycin (50 μg/ml), while stopping cell division, caused rapid inhibition of the regeneration process. Puromycin did not prevent cells untreated with neuraminidase from maintaining their control amount of surface sialic acid per cell.
Effect of temperature on the activity of ribonuclease from Tetrahymena pyriformis
Authors: Lazarus Lawrence H. , Scherbaum Otto H.
Published: February 2005

Intracellular ribonuclease from the ciliate Tetrahymena pyriformis GL was purified 10‐fold. After preheating for 20 minutes at 100°C of the ribonuclease preparation 80% of its activity was lost. Preheating under the same conditions, however, in the presence of RNA, did not affect the enzyme activity. Between 0°C and 41°C the apparent activation energy was 15,600 cal per deg. per mole.
Difference between medullary and cortical thymic lymphocytes of the pig in their response to phytohemagglutinin
Authors: Weber W. T.
Published: February 2005

Pig thymus tissue was cultured with organ culture techniques in the presence and absence of phytohemagglutinin in the culture medium. Morphologic and autoradiographic observations indicate that in the pig, lymphocytes capable of responding to phytohemagglutinin are located predominantly in the medulla of the thymus.
Immunogenetic analysis of microsomal and non‐microsomal lipoproteins from normal and malignannt mouse tissues for histocompatibility‐2 (H‐2) antigens
Authors: Palm Joy , Manson L. A.
Published: February 2005

The H‐2 antigenic properties of lipoprotein fractions from malignant (L‐5178Y leukemia) and normal (spleen, thymus, liver, kidney) mouse tissues have been studied by serological and immunological tests, and the results compared to the previously described activities of these fractions in homograft‐sensitization tests. Although, in general, the relative activities in the different assays parallel each other some notable exceptions were found. The non‐microsomal lipoproteins from leukemic tissue, inactive in homograft‐sensitization tests, did elicit H‐2 antibody. Also, the liver microsomal lipoproteins, which are inactive in homograft‐sensitization tests in amounts 400 × the minimal effective doses of spleen preparations, exhibited, in in vitro agglutinin‐inhibition tests, approximately one‐fourth the H‐2 activity of the latter. Other findings of note include the high antibody‐eliciting potency of the spleen and leukemia microsomal lipoproteins (15 μg protein was sufficient to initiate primary immunization and 1 μg protein to cause an anamnestic response); and the quantitive identity of H‐2 antigen activity of the microsomal lipoproteins from spleen and thymus.
Isolation and karyological characteristics of seven hybrids between somatic mouse cells in vitro
Authors: Yoshida Michihiro C. , Ephrussi Boris
Published: February 2005

In vitro hybridization of seven pairs of genetically different murine cell has been demonstrated by the use of karyological markers, and pure cultures of these hybrids have been isolated. All somatic hybrids showed a progressive loss of chromosomes during this proliferation in vitro.
Density gradient centrifugation of hemopoietic colony‐forming cells
Authors: Turner R. W. A. , Siminovitch L. , McCulloch E. A. , Till J. E.
Published: February 2005

Buoyant density distributions of hemopoietic colony‐forming units (CFU) from normal mouse marrow were determined by equilibrium density gradient centrifugation in bovine serum albumin (BSA) gradients. The distributions were compared with those obtained for the total population of nucleated cells from normal mouse marrow. The buoyant density distribution for CFU was found to differ from the density distribution for the total nucleated cell population, and the portion of the total cell population with densities much less than the mean value was found to contain up to a 30‐fold greater proportion of CFU than an uncentrifuged control. These results provide a preliminary approach to the purification and characterization of normal hemopoietic colony‐forming stem cells.
Tissue compatibility in regenerating explants from the colonial marine hydroid Hydractinia echinata (Flem.)
Authors: Toth Steven E.
Published: February 2005

Artificially maintained colonies of the colonial marine hydroid Hydractinia echinata are endogenously limited in lateral growth and usually develop in a circular pattern with a closed periderm. Further lateral growth consists of free stolons. Preliminary studies of tissue compatibility in regenerating explants indicate that fusion generally fails to occur if the opposing explants are of differing sex, from different individuals of the same sex, or if peripheral explant contact occurs after free stolons have begun to form. Of the three aforementioned causes of fusion failure, the most important factor appears to be the timing of peripheral explant contact. If regenerating explants contact each other before the endogenous circular growth pattern is achieved, fusion will occur regardless of sex and/or individuality. Incompatibility between explants from the same individual may be because of periderm development inhibition in some instances. However, the failure of free stolon fusion between explants from the same individual suggests the development of “temporal specificity” once the endogenous limit of lateral growth is achieved.
Characteristics of an adenosine triphosphatase in erythrocyte membranes stimulated by 2,4‐dinitrophenol
Authors: Laris Philip C. , Letchworth Peter E.
Published: February 2005

Studies were made of the stimulation by 2,4‐dinitrophenol (DNP) of an adenosine triphosphatase (ATPase) in stromata of human erythrocytes. Activation by 2,4‐dinitrophenol occurs in the range 10−5 to 10−3 M and was seen in whole cells, ghosts reconstituted with Mg and ATP, and in osmotic ghosts prepared at a low ratio of cells to water. Phloretin and phloridzin also activated the DNP sensitive system but inhibited it at higher concentrations. DNP increased the Km and Vmax values of the enzyme equally. The DNP sensitive and Na+ + K+ sensitive enzymes of the stromata were compared. The activities of the two ATPases are additive, require the presence of Mg++ and require that the substrate be located at the inner surface of the membrane. The two enzymes differ in their substrate specificity, in their sensitivity to inhibition by ouabain and phloretin and in their sensitivity to some factor in hemolysates. The possible roles of this system in the erythrocyte were discussed.
Observations on acid phosphatase in Mayorella palestinensis
Authors: Lasman M.
Published: February 2005

Acid phosphatase activity has been studied in the ameba Mayorella palestinensis. Optimum activity of the enzyme was found to be at a pH of 3.2. The enzyme is inhibited by fluoride ion, but is not sensitive to Mg++.

The activity was found to be correlated with age of culture. Two maxima have been obtained, one from cultures in the logarithmic phase, and the other during the period of maximal cell encystation. These results suggest that acid phosphatase play an important role in cell metabolism during growth and differentiation processes of this ameba.
Repolarization of striated muscle fibers by the antifatigue agent, K‐Mg‐aspartate
Authors: Henderson Edward G. , Walkenstein Sidney S.
Published: February 2005

Resting membrane potentials of isolated frog sartorius muscles were measured under a variety of conditions using intracellular glass microelectrodes. Muscle cells depolarized by the addition of 5.0 or 10.0 mM KCl to the bathing Ringer solution can be repolarized some 5 to 10 mV by the substitution of an equivalent amount of K‐aspartate for KCl in the presence of 2.0 mM Mg++. The repolarization produced by this method persists when the muscle is again placed in the initial KCl solution, thus eliminating the possibility that the hyperpolarization is due to the reduction of chloride in the bathing medium. If for some reason the resting membrane potential of the muscle fibers is considerably below (less negative than) the normal level of 92 mV reported for muscles bathed in 2.5 mM Ringer solution, the substitution of 2.5 mM K‐aspartate for the 2.5 mM KCl and the addition of 2.0 mM Mg‐aspartate to the Ringer solution will, within 15 minutes, repolarize the fiber to the normal level. Magnesium ions alone will not produce the observed repolarization nor can it be attributed to a reduction in the activity of the potassium in the Ringer solution.
Oxygen consumption in diapausing blastocysts
Authors: Gulyas Bela J. , Daniel Joseph C.
Published: February 2005

The oxygen consumption of various diapausing blastocysts from mammals having delayed implantation (mink, northern fur seal, black bear, armadillo and lactating rat) was studied with the Cartesian diver apparatus and compared with that of blastocysts from mammals where implantation is not delayed (rabbit, nonlactating rat). In general, there is a variation in the respiratory rate between species and within a species but the oxygen consumption of the delayed blastocysts was not different from the non‐delayed ones. It was concluded that the control of the delay in implantation in the animals studied, does not lie in the realm of respiratory changes.
The mechanism of ciliary movement. III. Theory of suppression of reversal by electrical potential of cilia reversed by barium ions
Authors: Jahn Theodore L.
Published: February 2005

It is well known that Paramecium (1) is cathodally galvanotactic in mixtures of sodium and calcium salts because of ciliary reversal at the cathodal end, and that (2) the cilia also may be reversed in solutions rich in monovalent cations or in barium or manganese ions, and (3) the organisms swim backward in these solutions.

It also is well known (Kamada, '31) that Paramecium in solutions of barium salts (4) is anodally galvanotactic at low electric potentials, (5) is cathodally galvanotactic at higher potentials, and (6) again becomes anodally galvanotactic if the potential is lowered, but these results have never been explained.

However, they can be explained if the membrane is assumed to act as an ion exchanger. Cilia are reversed by barium because barium replaces some of the calcium on the membrane. When a low cathodal potential is applied, the barium, because of its high electrophoretic velocity (Ba++> Ca++> Na+) is removed, thereby causing a suppression of the reversal. If the potential is increased, calcium is also removed, leaving mostly sodium on the membrane, and this causes a return of the reversal. Lowering the potential again causes a suppression of the reversal. Changes at the anodal end can be explained in a comparable manner.
Evidence implicating a membrane ATPase in the control of passive permeability of excitable cells
Authors: Bowler K. , Duncan C. J.
Published: February 2005

The temperature sensitivity of the ATPase enzyme systems in a muscle microsomal preparation from the crayfish, Astacus pallipes, was studied. Preincubation of the enzyme preparation in the range 33–36°C produced a marked inactivation of the ATPases; the Mg++‐dependent ATPase was very much more sensitive to this treatment than the Na+‐K+‐Mg++‐dependent ATPase. Thus, the Arrhenius μ for the inactivation of the Mg++‐dependent ATPase produced by eight minute preincubation is > 100 Kcals. These results are compared with the changes that are observed during the heat death of the whole animal, where exposure to 35°C produces a dramatic change in Na+ permeability within five minutes. Arrhenius μ for heat death is also > 100 Kcals and operates over the identical critical temperature range. It is suggested that the Mg++‐dependent ATPase controls passive permeability in these excitable cells and the results also confirm the view that Mg++ and Na+‐K+‐Mg++ ATPases are separate enzymes.
Amino acid requirements for growth of the rabbit blastocyst in vitro
Authors: Daniel Joseph C. , Krishnan R. Sivarama
Published: February 2005

Ten amino acids, namely, arginine, histidine, lysine, tryptophane, methionine, phenylalanine, leucine, valine, threonine and serine were indispensable for growth of rabbit blastocysts in vitro; others were nonessential. Of all the essential amino acids, arginine and lysine were required in relatively high concentrations, 10−2 M and 10−3 M, respectively, for optimum growth. Complete omission of the non‐essential amino acids from the medium markedly reduced blastocyst growth. Interaction between serine and glycine demonstrated a partial sparing action on serine by glycine, similar to that observed between methionine and cysteine. The amino acid composition of a culture medium capable of providing continuous and consistent growth of rabbit blastocysts in vitro is described.
Evidence for dual physiological forms of ergosterol in Saccharomyces cerevisiae
Authors: Adams B. G. , Parks L. W.
Published: February 2005

Data obtained from acid hydrolysis and extraction of yeast have demonstrated that routine saponification does not recover total sterol from the cells. This suggests the existence of a form of ergosterol resistant to saponification. Time course analyses of sterol synthesis by resting cell suspensions reveal an inverse relationship between the amounts of base labile and acid labile forms of sterol. These data give strong presumptive evidence for dual forms of ergosterol which are interconvertible according to the respiratory state of the cell.
Clonal growth of cells taken directly from adult rabbits
Authors: Ham Richard G. , Murray Louann W.
Published: February 2005

Single cell suspensions were prepared from the choroids of adult rabbit eyes using Pronase digestion, gentle pipetting and centrifugation. When diluted and inoculated into medium F12 supplemented with 5% fetal bovine serum and 10% rabbit serum, the choroid cell suspensions yielded large, healthy colonies with an average plating efficiency of about 45%. The growth in culture of a large portion of the cells from a normal non‐embryonic tissue opens new possibilities for the study of cellular differentiation in vitro.
The cytogenetic effects of mycoplasma in human leukocyte cultures
Authors: Aula Pertti , Nichols Warren W.
Published: February 2005

To evaluate the possible role of mycoplasma contamination of tissue cultures in virus induced chromosome breakage, human leukocyte cultures were inoculated with three mycoplasma strains; M. salivarium, M. hominis type 2 and M. fermentans. All three strains caused mitotic inhibition when an inoculum of approximately 106 CFU was used, the effect of M. fermentans being less severe than the one produced by the two other strains. Using a lower inoculum of 103 CFU an increase of chromosome breakage could be produced with M. salivarium when the leukocytes were cultivated for five days. No chromosome changes were seen with M. hominis type 2 and M. fermentans.

The mitotic inhibition and chromosome breaks induced by M. salivarium were discovered to be related to an arginine deficiency of the culture medium produced by the mycoplasma. This conclusion is dervied from the fact that arginine addition was able to inhibit the mitotic inhibition and the increase of chromosome breakage, and secondly, that similar changes could be produced in leukocytes grown in argining deficient medidum without mycoplasma.

The growth of M. salivarium was inhibited in leukocyte cultures treated with kanamycin, but the mycoplasma induced mitotic inhibition was still present, indicating that replication of mycoplasma organisms was not required for the production of arginine deficiency.
Interferon induction and utilization
Authors: Hilleman M. R.
Published: February 2005

The interferon mechanism offers the hope for moderate to high level prophylactic immunity of broad antiviral spectrum but of relatively short duration. Economic and biological considerations offer little hope for utilization of exogenous interferon as a prophylactic or therapeutic substance, unless but a small part of the total molecule be found to carry the activity. The real promise for interferon application is in the administration of suitable inducers so as to cause the body to produce and distribute its own interferon. Certain ribonucleic acids (RNA's) offer hope for high level potency as inducers without adverse effect. The condition for interferon induction by ribonucleic acids appears to be double‐ or multistrandedness and freedom from inhibitors. These can be of biologic or synthetic origin. The mechanism of action of interferon is not fully understood but appears to fit into the Jacob‐Monod model involving two phases: first, a derepression by the inducer to cause the cell to form interferon and second, a derepression by interferon to cause recipient cells to form the active substance which acts by preventing translation from viral messenger RNA. Double or multistranded RNA of viral or other origin appears to be unique to the cell and serves as the alert to it to produce interferon in phase 1. Greatest need for interferon is clearly for those diseases in which there is a multiplicity of immunologic types in excess of the numbers which could be put into a vaccine as, e.g., the common cold and enteric viruses. There might be some overall therapeutic benefit also if inducer were given early enough in infection. Special value for interferon induction might derive by administration in early life before the development of immunologic maturity, as a means for preventing infection with oncogenic or other viruses. Additionally, suitable inducers might be capable of interrupting the reinfection cycle in virus‐dependent malignancies.

The favorable outlook for interferon utilization must always be tempered with the realization that under certain as yet undiscovered situations, adverse rather than beneficial effects might result from indution of interferon. It is not impossible that in certain special circumstances, as in ordinary immunologic responses, it might be more beneficial to negate rather than to promote the effect.
Membrane potentials of human fibroblast strains in culture
Authors: Swift Michael R. , Todaro George J.
Published: February 2005

With a simple technique, the membrane electro‐physiology of mammalian fibroblasts in tissue culture can be explored with micro‐electrodes. Measured in complete, serum‐containing medium, the mean membrane potential for human diploid cell strains in between 70 and 75 millivolts.
Photoreactivation of amphibian cells in culture
Authors: Regan James D. , Cook John S. , Lee William H.
Published: February 2005

Photoreactivation of growth and DNA synthesis in UV‐irradiated cells and photoreactivating‐enzyme activity of cell‐free extracts can be demonstrated in a cell line derived from liver tissue of the African clawed toad, Xenopus laevis. This cell line, A8W2, is a favorable system for the quantitative study of photoreactivation in vertebrates.
Photo‐inhibition of cell division and growth in euglenoid flagellates
Authors: Cook J. R.
Published: February 2005

Visible light of moderate intensity causes two and perhaps three types of division inhibition in Euglena gracilis are related cells. Fluorescent light causes a general inhibition of growth and division which is temperature‐dependent. Pigmentation or complex organic media partially lifts this inhibition. A second type of inhibition, which is transient, can be caused by either fluorescent or incandescent light, and is found with an irreversibly bleached strain of Euglena grown on a limiting concentration of acetate; this inhibition could not be demonstrated in cells grown on limiting concentrations of glucose.
Production of the inducer for macrophage and granulocyte colonies by leukemic cells
Authors: Paran Michael , Ichikawa Yasuo , Sachs Leo
Published: February 2005

Cell lines from a myeloid, an erythroid, and two lymphoid leukemias, were tested for the production of the inducer required for the formation of macrophage and granulocyte colonies. It was shown that the inducer was produced by all lines except one of the lymphoid leukemias.
Thymidine as a synchronizing agent. I. Nucleic acid and protein formation in synchronous HeLa cultures treated with excess thymidine
Authors: Studzinski George P. , Lambert W. Clark
Published: February 2005

Synchronous cultures of HeLa cells obtained by selective detachment of mitoses were treated with high concentrations of thymidine. The inhibitor was added soon after completion of cell division and rates of cell enlargement and accumulation of DNA, RNA and protein were compared for untreated and thymidine‐treated cultures at various points of the cell cycle. It was found that concentrations of thymidine which in randomly growing cultures inhibit the rate of cell division by more than 90% allowed a considerable degree of DNA synthesis and did not affect the rate of accumulation of RNA and protein, when applied to cells in the G1 phase of synchronous culture. Treated and untreated cells enlarged at the same rate throughout their life cycle. The results show that concentrations of thymidine commonly employed to produce cell synchrony do not arrest the cells at the G1‐S boundary, but allow slow progress through S in respect to DNA synthesis, and near‐normal progress towards G2 as regards RNA and protein accumulation and cell enlargement.
Effect of estradiol on splenic repopulation by endogenous and exogenous hemopoietic cells in irradiated mice
Authors: Jenkins V. K. , Upton A. C. , Odell T. T.
Published: February 2005

Estradiol treatment of irradiated mice during repopulation of their spleens by endogenous hemopoietic cells reduced the number of myelocytic colonies and increased the numbers of erythropoietic and undifferentiated colonies. The inhibitory effects of the hormone on myelopoiesis were not dependent on stimulation of erythropoiesis, since they occurred in the absence of erythropoiesis in mice made polycythemic by hypertransfusion.

Treatment of bone marrow donors with estradiol reduced the ability of their marrow cells to form spleen colonies, particularly reducing the proportion of myelopoietic colonies relative to the total number of colonies of all types. Conversely erythropoietic colonies, though reduced in absolute number, were increased in relative number. Such treatment also decreased the volume and cell content of the marrow cavity through stimulation of endosteal bone formation.

Estradiol treatment of lethally irradiated recipient mice did not detectably alter the total numbers or types of hemopoietic spleen colonies formed in these animals from transplanted marrow cells; however, without estradiol treatment, myelopoietic colonies were so few and erythropoietic colonies so numerous that the effects of the hormones may have been undetectable by the methods employed.

The sex of the donor or recipient mouse did not affect the numbers or types of colonies formed, suggesting that endogenous levels of estradiol were too low to exert effects dectectable by the methods used. However, since our mice were only 8 weeks old, the data do not exclude the possibility that older female mice, with higher levels of estradiol, would have differed from males in relative numbers of myelopoietic as compared with erythropoietic colonies.
Ribonucleic acid within the extracellular matrix during embryonic tooth formation
Authors: Slavkin H. C. , Bringas P. , Bavetta L. A.
Published: February 2005

During embryonic tooth formation, interactions between epithelial and mesenchymal cells results in the formation of a metachromatic interface or extracellular matrix. The cervical or germinative region of this epidermal organ system is populated by an increasing gradient of cellular differentiation and an extracellular matrix which is the progenitor for subsequent dentine organic matrix formation. Embryonic rabbit tooth primordia can be maintained in culture enabling kinetic studies of labeled precursor incorporation. Autoradiographs of tooth organ cultures continusly incubated with labeled uridine for periods up to eight hours, demonstrated initial cellular incorporation with subsequent transfer of 2% of the grain density to the extracellular matrix by four hours. The grain density was removed by ribonuclease treatment. No incorporation of tritiated thymidine into the matrix was observed. The incorporation of C14‐uridine during organ culture was inhibited by actinomycin D. Micrurgy was employed to isolate the extracellular matrix free of adherent cells. Electron microscopy demonstrated membrane‐bound, electron dense bodies within the matrix, presumably cytoplasmic extensions. No cells per se were observed on the isolated matrix. Several experimental criteria suggested that uridine incorporation into the extracellular matrix was regulated by epithelial and mesenchymal cells. Phenol extraction procedures of labeled cervical matrices demonstrated an ultraviolet absorption maximum at 260 μU. Both spectrophotometric determinations and orcinol assays found RNA to be 0.4–0.5% of the cervical extracellular matrix.

These results are interpreted to indicate that RNA is a component of the metachromatic extracellular matrix during epithelio‐mensenchymal interactions associated with tooth formation. The functional significance of these observations is premature at this time.
Increased resistance of immature red cells of rat and dog to osmotic lysis
Authors: Sacher G. A. , Miller M.
Published: February 2005

Mature male rats were injected with radioiron, which labeled immature red cells that were in the stage of hemoglobin synthesis at the time. Washed cells were subjected to lysis by hypotonic saline at 14 intervals ranging from 1 to 85 hours after 59Fe injection. Lysis curves were determined colorimetrically (for the whole population) and by scintillation counting of 59Fe gamma rays (for the labeled population). Newly labeled rat red cells are much more resistant than mature erythrocytes. The mature curve of osmotic resistance is acquired about 67 hours after injection. The delivery of labeled cells continues for more than 36 hours, so the maturation of osmotic properties of a typical rat red cell takes about 30 hours from entry into the circulation. Washed dog cells behave in similar fashion but delivery continues for three days and the mature lysis curve does not appear until five days after labeling, so that maturation takes about two days. Preincubation of cells is requisite for the appearance of osmotic resistance, but the basis of the incubation effect is not yet known.
Stimulation of mitotic activity and the initiation of deoxyribonucleic acid synthesis in populations of rat thymic lymphocytes by magnesium
Authors: Whitfield J. F. , Perris A. D. , Rixon R. H.
Published: February 2005

The progression of rat thynocytes (maintained in vitro) into mitosis is profoundly affected by the level of magnesium in the medium. Increasing the extracellular MgC12 concentration from 0 to 1.0 mM does not affect mitotic activity, but a further increase to 1.2 and 2.5 mM rapidly and strongly stimulates the flow of cells into mitosis. The level of extracellular magnesium also governs the mitogenic effectiveness of calcium ions. The mitogenic action of magnesium stems from an ability to stimulate the initiation of deoxyribonucleic acid synthesis.
Attempts to produce in vitro the reaction of immunologically competent cells of C57BL/6 origin to Balb/c embryo fibroblasts
Authors: Koldovský P. , Turano A. , Fadda G.
Published: February 2005

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

Crayfish giant axons remain viable following internal perfusion with a mixture of fluoride and citrate salts. The relative favorability of various internal anions, and the dependence of resting and action potentials on internal cations are both similar to results on internally perfused squid axons. TEA widens the falling phase of the spike only from inside the axon, while DDT is active from either side of the membrane. Records of impedance changes show that effects of TEA and DDT on components of ionic conductances are similar to those found in other axons by voltage clamp measurements.

Tannic acid perfused internally at a concentration of the order of 10 μM produces spontaneous activity, and a progressive increase in spike width. After 30 minutes, action potentials are “cardiac” type and are up to several minutes in duration. Records of impedance changes, and data from rapid changes in external ionic concentrations, suggest that the plateau phase of the spike is due to a maintained increase in sodium conductance. Since tannic acid is capable of crosslinking proteins and “rigidifying” protein monolayers, it is suggested that its effects on the axon may be the result of an interference with a conformational change in a membrane protein or protein‐phospholipid complex during excitation.
The effect of serum components on sterol biosynthesis in L cells
Authors: Rothblat George H.
Published: February 2005

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

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

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

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

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

Yolk proteins, derived from the blood, are incorporated into the oocytes of insects and certain vertebrates by pinocytosis, but reach the oocyte surface only after penetrating the surrounding follicular epithelium via intercellular channels. In an investigation of the events occurring in these intrafollicular spaces, the dense extracellular material present between the follicle cells and in the oocyte's brush border was extracted from vitellogenic cecropia moth follicles by soaking in physiological saline. Quantitative immunochemical determination of several eluted blood proteins revealed that these components had been more concentrated in the extracellular spaces than in the blood. The average concentration factors were 2.5 for the predominant yolk protein, vitellogenin, and 4.5 for the carotenoid protein.

Since injected foreign proteins were also accumulated in the spaces, the concentrating mechanism seemed to act on all available proteins. However, in vitro inhibition of yolk formation with dinitrophenol resulted in a selective increase in the amount of extracellular vitellogenin in follicles which had been previously exposed to a medium low in this protein, suggesting accumulation of a factor with a specific affinity for it. Furthermore under certain conditions vitellogenin was more readily released from the concentrate than was the carotenoid protein. These results indicate that, despite apparent lack of discrimination in the binding of blood proteins in the spaces, extracellular interactions may contribute to the selectivity known to occur during vitellogenesis.
Lipid composition of heteroploid cells in culture: Effects of prednisolone
Authors: Dell'Orco Robert T. , Melnykovych George
Published: February 2005

Prednisolone‐induced alterations in the content and composition of the total lipids, cholesterol, phospholipids and fatty acids were studied in HeLa S3 cells. After relatively long exposure of the cell cultures to the hormone analog (24 to 72 hours), total cell lipid content was decreased. Partial inhibition of cholesterol and phospholipid metabolism resulted in a shift in the molar ratio of these two lipid constituents. Total fatty acid content was unaffected by prednisolone but there were minor changes in the relative distribution of the individual fatty acids.

The observed decrease in cholesterol turnover after addition of prednisolone was primarily due to the reduced uptake of intact cholesterol from the culture medium. This was compensated, in part, by an increased de novo synthesis of cholesterol from acetate and glucose.
Growth kinetics of hemopoietic fetal stem cells
Authors: Vogel Helmut , Hajdik Irene , Niewisch Helgard , Sultanian Ishkhan , Matioli Gastone
Published: February 2005

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

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

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

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

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

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

Equilibrium density gradient centrifugation in isotonic gradients of albumin may be used as an analytical tool to reveal features of cell populations not apparent from morphological or size distribution studies. All lymphocyte sources studied gave a complex distribution pattern consisting of many distinct peaks and shoulders.

The thymus contains proportionally more dense lymphocytes than spleen or thoracic duct. The spleen of neonatally thymectomised animals contains proportionally more light lymphocytes than the spleen of normal animals. This suggests density may effect a separation between dense “thymus‐derived” and light “bone‐marrow‐derived” lymphocytes.

Normal animals give variation in lymphocyte density distribution profiles from one animal to another. Part of this variation and part of the complexity is attributed to corticosteroid mediated stress effects on the lymphocytes. Corticosteroid injection increases the number of peaks seen in thymus density distribution profiles. Adrenalectomised animals give more reproducible and simpler profiles, although several distinct density peaks remain.

Large lymphocytes are in general less dense than small lymphocytes, probably because of the increased ratio of light cytoplasm to dense nucleus. However, there exists a small proportion of dense, large lymphocytes and light, small lymphocytes. Each given size of lymphocyte showed heterogeneity in its density distribution, in both normal and adrenalectomised animals.

The technique should be useful in a detailed study of the diversity of lymphocytes, of their differentiation and their precise immunological function.
Cytotoxic effects of thiopyrimidines
Authors: Lozzio Carmen B. , Wigler Paul W.
Published: February 2005

The cytotoxic action of 2‐thiouracil, 2‐thiocytosine, 2‐thiouridine and 4‐thiouridine was studied in cultures of a clone of Chinese hamster cells with a generation time of 16 hours (S — 8 hours, G2 — 2 hours, and G1 plus M — 6 hours). The cells were synchronized at metaphase by the method of reversal of colcemid inhibition and cell survival was measured by their colony‐forming ability.

The four analogs induced cytotoxic effects which increased with the concentration of the chemical and the length of the exposure time. Exposure to 4 × 10−4 M 2‐thiocytosine, 2‐thiouridine or 4‐thiouridine for a period of 20 hours reduced cell survival to less than 10% of the controls. The other analog (2‐thiouracil) was less effective when tested at similar concentrations and time of exposure and decreased the survival to only 35% of the controls.

Short periods of treatment (one hour) produced little effect at concentrations of 4 × 10−5M, and affected the survival of cells differently when 4 × 10−4 M were administered at different stages of the cell cycle. Two peaks of maximum sensitivity, one at late G1 and the other at G2 were observed. These peaks correspond to the peaks of maximum RNA synthesis described for synchronized mammalian cells. Therefore, it is likely that the cytotoxic effects of thiopyrimidine analogs are related to interference with RNA synthesis.