bluuebunny/crossref_metadata_2025 huggingface dataset:
Three‐dimensional structure of the bronchial microcirculation in sheep
Authors: Schraufnagel Dean E. , Pearse David B. , Mitzner Wayne A. , Wagner Elizabeth M.
Published: February 2005

Background: The bronchial circulation affects both pulmonary vascular and airway activity. Fundamental to understanding the role of the bronchial microcirculation in health and disease is understanding its anatomy. This study sought to identify specific structural elements that might contribute to the drop that occurs between the systemic blood pressure of the bronchial artery and the low pressure of the pulmonary bed into which the bronchial circulation flows and to better describe the connections of the bronchial and pulmonary circulations. METHODS: To do this, the lungs of five sheep were cast by injecting a resin through bronchial and pulmonary arteries. After taking samples for light microscopy, the tissue was digested and the casts were viewed with a scanning electron microscope. RESULTS: Casts of extrapulmonary bronchial arteries were structurally similar to other systemic arteries. Tortuous ones spiraled around bronchi and large blood vessels. Intrapulmonary bronchial arteries, about 100–300 μm in diameter, had sharp branching and deep focal constrictions with great rugosity that completely shut off the flow of the resin. These vessels correspond to the Sperrarterien described by von Hayek (and could cause the resistance associated with the pressure drop). Vasa vasorum ran in the walls of intrapulmonary pulmonary arteries for a variable distance before they entered the lumens of the pulmonary arteries. The smallest blood vessel found that was supplied with vasa vasorum was a bronchial artery 42 μm in diameter. Capillary‐like networks with large luminal diameters were found on the pleural surface. CONCLUSIONS: Scanning electron microscopy of microvasular casts provides a fresh description of the bronchial circulation, further delineates the communications of these two circulations, and may structurally account for some pressure drop between the bronchial and pulmonary circulations. © 1995 Wiley‐Liss, Inc.
Maternal pineal gland participates in prepubertal rats' ovarian oocyte development
Authors: Fernandez B. , Diaz E. , Colmenero M. D. , Diaz B.
Published: February 2005

Background: Sexual maturation is a very complex phenomenom that it is mediated by the ontogeny of the hypothalamus‐pituitarygonadal axis during intrauterine life. The maternal pineal gland can affect fetal development because the main pineal hormone, melatonin, crosses the placental barrier. We found that melatonin treatment during gestation in the rat produced delayed sexual maturation of the female offspring. The present work was undertaken to study the maturational stage of oocytes of prepubertal female rats when their mothers were either pinealectomized (PIN‐X) or treated with melatonin (MEL) during pregnancy.

Methods: Three groups of female Wistar rats were used: control, PIN‐X, and those treated (250 μg/100 g body weight) with melatonin throughout pregnancy. Ovaries of 25–30‐ and 34‐day‐old female offspring were studied during the prepubertal phase. Morphometric studies of semithin sections (1 μm) of the ovaries were performed. Oocyte, nuclear, and nucleolar volumes were calculated by a computer‐assisted program (M.I.P.) in an image analyzer Kontron. Regularity of the structures was determined by the frequency distributions of circular and regular form factors.

Results: Cytometric study of oocyte structure showed a frequency distribution of regular and circular form factors, with a high degree of regularity very close to unit. Cellular and nuclear volumes of follicular oocytes showed a transitory increase at 30 days of age in control rats. In the offspring of MEL‐treated mother rats, a pattern of oocyte development showed significantly lower nuclear and nucleolar volumes at 30 days of age than at the other time points and significantly lower cellular volume at 34 days of age than at 25 days of age. In the offspring of PIN‐X mother rats, no significant differences in oocyte cellular volumes were observed throughout prepubertal development, but we observed a significantly higher nuclear volume at 25 days of age and a significantly lower nucleolar volume at 30 days of age.

Conclusions: These findings show that the maternal pineal gland participates in cellular and nuclear volumes of prepubertal oocyte development. Melatonin treatment during pregnancy resulted in a redirected postnatal oocyte development. © 1995 Wiley‐Liss, Inc.
Mode of action of straight chain hydrocarbons on primary chemoreceptors of the blowfly, Phormia regina
Authors: Steinhardt Richard A. , Morita Hiromichi , Hodgson Edward S.
Published: February 2005

The fundamental actions of straight‐chain hydrocarbons on the three known primary chemoreceptor cell types of the blowfly, Phormia regina, were studied in quantitative terms. Lower alcohols and long‐chain amines act in two stages: first a reversible inhibition, and then injury, of the salt, water, and sugar receptors in the labellar sensilla. The primary effects on salt and water receptors resemble hydrocarbon narcosis of nerve. Effects on sugar receptors, when analyzed kinetically, superficially resemble competitive inhibition. Other evidence, however, indicates that a non‐specific effect on sugar receptor sites is more likely. The electrophysiological results from labellar chemoreceptors indicate that the previously reported hydrocarbon behavioral rejection thresholds are best explained by the inhibition of the sugar receptors. This conclusion is strengthened by further electrophysiological and behavioral tests on tarsal chemoreceptors.
The Influence of neurohumoral transmitter substances on protoplasmic streaming in the myxomycete Physarella oblonga
Authors: Hoitink A. W. J. H. , Van Dijk Gě
Published: February 2005

The authors studied the influence of adrenaline‐like substances and acetylcholine on the protoplasmic streaming in Physarella oblonga, investigating the effect on the duration of the rhythmic period. Adrenaline and noradrenaline proved to cause a shortening, whereas acetylcholine appeared to be capable of causing an extension of the period duration.

The authors present and discuss critically the possibility that the adrenergic and cholinergic transmitter substances, which influence the visceral (mechano‐) effectors in the higher animal organism often antagonistically, may also affect an elementary “functional” effector system responsible for protoplasmic streaming, and that in so doing they have comparable effects.

The results of experiments with eserine, acetylcholine and a mixture of these two substances render it probable that an acetylcholine esterase and acetylcholine occur in the plasmodium.

The mean normal value of the period duration was, calculated from 976 measurements and expressed in seconds: 284.183 ± 1.486 (S.E. of the mean). The average duration of the progressive and the regressive phase was found to be almost the same.
Ascorbic acid metabolism and glycolysis in the polymorphonuclear leucocyte of the guinea pig
Authors: Elliott C. George , Smith M. Doreen
Published: February 2005

Exudate leucocytes lost approximately 30% of their original intracellular ascorbic acid content during two hour incubation in glucose medium. The same loss was observed for cells containing initially both high and low levels of ascorbic acid. High concentrations of ascorbic acid in the incubation medium depressed lactic acid production and increased oxygen uptake by the cells. Iodoacetate and fluoride at low concentrations decreased ascorbic acid loss from cells during incubation; at high concentrations they increased loss. Ascorbic acid uptake from the medium was inhibited by iodoacetate but stimulated by fluoride.
Growth dynamics of an amphibian tissue
Authors: Reddan John R. , Rothstein Howard
Published: February 2005

By the “labeled mitoses” method of Quastler and Sherman and others, the cell cycle of the germinative zone cells of the bullfrog lens epithelium has been characterized. It has been shown that this cycle lasts approximately 83 days with the DNA synthetic phase enduring 100 hours and G2, 11 hours. G1 occupies over 90% of the total time. the duration of mitosis itself has not been precisely determined. the length of the synthetic phase was corroborated by double labeling with c14 and h3‐thymidine.

When the temperature is raised by 6°c, from 24° to 30° the cycle is compressed by 40%.

When the nongerminative, central cells of bullfrog lens epithelium are activated (stimulated to undergo DNA synthesis and mitosis) by injury or through in vitro culture, the length of the cycle also appears to decrease. in the in vitro experiments the generation time, as judged by the period elapsing between two successive bursts of DNA synthesis involving the same cells, amounts to 177–190 hours at 24°c. by raising the temperature to 30°c the time from injury or isolation until the appearance of the first wave of mitosis is reduced by 20%.
Transport of sugars into human red blood cell ghosts
Authors: Lacko L.
Published: February 2005

It has been found that human red cell ghosts react differently in the presence of various sugars in the medium. The stability of spheric ghosts is preserved in solutions of sugars entering red cells by means of the common carrier. In media of other sugars the ghosts' shapes change to shrunken, crenated forms and between the microscope slides to discoid ones. Under the conditions employed it was further observed that the incubation of fructose‐ or rhamnose‐containing ghosts in solutions of sugars sharing the carriers led to an equilibration of sugars between the medium and the ghosts. The impermeability of ghosts for sugars not sharing the carriers was supported by the finding that fructose could be washed out to a much less extent than glucose. These results suggest that sugars without affinity to the carriers may move in the erythrocyte membrane through nonspecific sites (pores, channels).
Hemoglobin functions in the blood of Bufo marinus
Authors: Hall F. G.
Published: February 2005

The effects of three physical‐chemical factors, temperature, hydrogen ion concentration, and partial pressure of oxygen, on the respiratory functions of blood of the toad (Bufo marinus) have been studied.

Measurements of oxygen affinity of hemoglobin in whole blood were measured tonometrically by a method devised for small quantities of blood. At pH 7.40 and 25°C blood was found to be 50% saturated with oxygen at a partial pressure of 44 mm Hg of oxygen. The Bohr effect was measured at various temperatures and found to be about one‐half that found for mammalian blood. Carbon dioxide content of toad blood changes only slightly in the oxygenated and reduced states. Thus the “Haldane” effect parallels the small Bohr effect. Toad blood was found to have average hematocrit values of 37% for erythrocytes and average hemoglobin values of 11 gm/100 ml per cubic millimeter of blood. The respiratory functions of the blood of the toad conform to the pattern of respiratory mechanisms available for gas exchange between the environment and tissues of the organism.
Contraction of protoplasm. II. Theory: Anodal vs. Cathodal in relation to calcium
Authors: Jahn Theodore L.
Published: February 2005

It has been known for over 100 years that when the protoplasm of protozoan cells respond to electrical stimulation by contraction, contraction always starts at the anodal end (e.g., Spirostomum, Jones, Jahn and Fonseca, 1965). It also is known that the cell membrane of protozoa does not have a self‐propagating depolarizing action potential of the type found in axons and muscle cells.

If we assume that contraction of the cytoplasmic protein is caused by an increased association of calcium with the protein, as known for muscle, these antithetical facts can easily be explained. Another necessary assumption is that all of the anionic sites on the protein have associated counterions, in accordance with the theories of Debye‐Hückel, Ling, and Eisenman.

On the basis of known ionic electrical mobilities it can be predicted for cells with non‐excitable membranes that calcium (1) is removed from both the inside and the outside of the membrane at the cathodal end and is added to both sides at the anodal end, (2) is added to cytoplasmic protein throughout the cell, but is added more rapidly at the anodal end, and (3) is made available for addition to cytoplasmic protein at the cathodal end, as it is released from the membrane. In a cell with an excitable membrane the above will be true, and furthermore (4) the action current will release larger quantities of calcium than those resulting directly from the stimulus. For these reasons it is predictable that in cells with a non‐excitable membrane, contraction should start at the anodal end, whereas in cells with excitable membranes, it should start at the cathodal end, and that is exactly what occurs.
Malignant transformation in Vitro of chinese hamster embryonic fibroblasts with the Schmidt‐Ruppin strain of Rous sarcoma virus and karyological analysis of this process
Authors: Hložánek Ivo , Donner Ludvík , Svoboda Jan
Published: February 2005

Using a method of cocultivation of embryonic Chinese hamster cells (CHEF) with Rous sarcoma cells and infection of CHEF by RSV‐SR, it was possible to obtain malignant transformation of hamster cells. The morphologically altered cells became apparent within 15–36 days.

In the cells transformed by cocultivation, the genome of RSV was determined by the method of contact of the transformed cell and the chicken cell in vivo; the malignant character of the transformed cells was demonstrated by transfer to a homologous newborn host. Repeated attempts to detect virus production in transformed Chinese hamster cells failed.

Prior to malignant transformation and in early transformed cultures the diploid stem‐line was maintained. A slight decrease in the proportion of diploid cells in transformed cultures was revealed in some experiments and is discussed. Prolonged cultivation of these cells, as also of control fibroblasts, shifts the stem‐line to the hyperdiploid or hypotetraploid region.

The mechanism of malignant transformation by RSV is discussed with regard to the action of the viral genome and alteration of the genetic make‐up of the cell by the virus.
Phosphate transport in fertilized sea urchin eggs. I. Kinetic aspects
Authors: Chambers Edward L. , Whiteley Arthur H.
Published: February 2005

Properties of the fully developed phosphate transport system in the fertilized egg of the sea urchin, Strongylocentrotus purpuratus, were investigated. The rates of phosphate transport at concentrations of external phosphate of 1 to 44 μM, both in the absence and in the presence of 100 μM arsenate, exhibit typical saturation kinetics. At sea water concentrations of 2 μM phosphate, the rate of uptake is about 2 × 10−9 μm/egg/minute at 15°C. Arsenate is a competitive inhibitor of phosphate transport, fully and immediately reversible in its effects, yielding Ki values ranging from 10.5 to 14.1 × 10−6 M in comparison to the corresponding apparent KM (Michaelis‐Menten) constants for phosphate of 5.6 to 7.5 × 10−6 M (pH 8.0, 15°C).

The rate of arsenate uptake in a phosphate deficient medium amounts to 2.8 to 2.9 × 10−10 μm arsenate/egg/minute at an arsenate concentration of 2.9 to 10.2 μM arsenate (HAsO4−−), which is 9.5 and 5.6% of the rate of phosphate uptake at corresponding phosphate concentrations.

Arsenate has essentially the same developmental effects at initial concentrations of 5–10 μM and 100 μM arsenate, namely no observable effects for exposure periods of 7.5 hours, although longer periods result in blockage of development at the early blastula stage.

Outward flux of phosphate ions cannot be demonstrated by washing prelabelled eggs with sea water containing low or high concentrations of phosphate, even when phosphorylation has been blocked by exposing the eggs to a metabolic inhibitor.

Phosphate uptake rates measured in the pH range from 5.0 to 10.0 reveal a sharp optimum at pH 8.8–8.9. Reference to the apparent pK' values of the phosphoric acid system indicate that the entering species is the HPO4−− ion. The effects on rates of phosphate uptake of exposure to sea water at pH values between 7 and 10 for 30 minute periods are fully reversible, but at lower pH values, reversal is delayed, and is only partial.

Sodium molybdate (0.01 M), sodium pyrophosphate (1.5 × 10−4 M), and adenosine triphosphate (1–5 × 10−4 M) for exposure periods ranging from 40 to 180 minutes did not significantly affect phosphate uptake. Omission of Ca++ ion from artificial sea water is without effect on phosphate uptake but the absence of both Ca++ and Mg++ results in profound and irreversible depression of both phosphate uptake and development.

The data of this and the following paper are consistent with the conclusion that the transport of phosphate involves a surface located carrier.

The apparent secondary and tertiary ionization constants of phosphoric acid in sea water (ionic strength = 0.6885) were measured, resulting in a value for pK′2 = 6.14 and for pK′3 = 10.99, at 15°C and phosphate at infinite dilution.
Phosphate transport in fertilized sea urchin eggs. II. Effects of metabolic inhibitors and studies on differentiation
Authors: Whiteley Arthur H. , Chambers Edward L.
Published: February 2005

Metabolic inhibitors were applied after the transport system was fully developed in concentrations sufficient to block cleavage. 0.5–1.0 × 10−4 M cyanide and anaerobiosis caused from negligible to moderate (40%) inhibition of phosphate uptake. The inhibition occurred late in the breeding season, and the inhibitory action of cyanide on uptake was associated with irreversible developmental effects. Azide (3 × 10−3 M) did not inhibit uptake when the chamber method was used, but the aliquot and Hopkins' tube methods gave considerable inhibition. Purified preparations of 2,4‐dinitrophenol (1 × 10−4 M) did not inhibit uptake. Sodium iodoacetate (up to 0.05 M) and phlorizin (0.005 M) exerted no effect.

Calculations of the minimal work requirement for the transport process reveal that this amounts to only a small fraction (0.24% at an external phosphate concentration of 2 μM) of the total available metabolic energy.

Exposure of eggs at five minutes after insemination (lag phase) to cyanide (5 × 10−5 M), anaerobic conditions, or azide (3 × 10−3 M) blocked the expected increase of phosphate uptake. Removal of the inhibitors led to resumption of development and the appearance of the phosphate transport system in an essentially normal pattern.

Exposure of eggs to 1.4–2.0 × 10−4 M p‐chloromercuribenzoate (p‐CMB) during the accumulation phase severely depressed phosphate uptake, but cleavage was not inhibited nor delayed; recovery from the inhibition was accelerated by 1 × 10−3 M cysteine. Exposure to p‐CMB during the lag phase blocked the appearance of the transport system; cleavage proceeded normally. After the removal of p‐CMB little reversal occurred until the addtion of 1 × 10−3 M cysteine, when the phosphate transport system developed in an essentially normal manner.

Trypsin (0.001–0.01%) neither activates the transport system in unfertilized eggs, nor inactivates it in denuded fertilized eggs by removal of surface proteins.

The data are consistent with the conclusion that (1) the phosphate transport system is newly synthesized at fertilization in energy dependent reactions, and (2) phosphate transport is a carrier mediated process not directly dependent on metabolic energy.
The Mg, Ca, EDTA and ATP dependence of Na binding by rat liver microsomes
Authors: Sanui Hisashi , Pace Nello
Published: February 2005

The role of ionic interactions in the adenosinetriphosphate (ATP) dependent Na binding by rat liver microsomes was investigated. In the concentration range of 0 to 20 mM, Mg and Ca are demonstrated to compete strongly against Na for microsome binding sites. In the presence of Ca, the nonbiological complexing agent ethylenediaminetetraacetate (EDTA) produced a marked increase in Na binding accompanied by a concomitant decrease in Ca binding. Under similar conditions ATP, which is a weaker complexing agent than EDTA, produced quantitatively smaller but qualitatively similar changes in binding. The data show that the effect of ATP on Na binding is not dependent upon the formation of a hypothetical Na binding intermediate in the hydrolysis of ATP as other investigators have postulated. Rather, the effect of ATP is demonstrated to depend upon the presence of unhydrolyzed ATP and its ability to complex divalent cations, and thereby to reduce divalent cation competition against monovalent cations for membrane binding sites.
Nucleolar RNA synthetic activity in chinese hamster cells in vitro and the effects of actinomycin D and nogalamycin
Authors: Arrighi Frances E.
Published: February 2005

RNA synthesis was studied by autoradiographic analysis using tritiated uridine incorporation in the Chinese hamster cell line Dede after a one‐minute pulse labeling period. RNA synthesis continues during all stages of interphase and mitosis except during metaphase and anaphase. Cytoplasmic RNA was apparently synthesized in the nucleus, since no grains were observed above the background level in the sample immediately following the labeling. Nucleoli synthesize their own RNA and are not reservoirs for RNA synthesized elsewhere. Both actinomycin D and nogalamycin inhibited the RNA synthetic activity of chromatin and nucleoli. However, the nucleolar synthetic activity was more susceptible to these agents than that of chromatin. Furthermore, actinomycin D was a stronger inhibitor than nogalamycin.
Some properties of alkaline phosphatase from a human cell strain and from a clonal derivative with low activity
Authors: Santachiara‐Benerecetti Silvana A. , Cesari I. , De Carli L.
Published: February 2005

A comparative study of some physico‐chemical properties of alkaline phosphatase of a human cell line, the EUE, with high level of enzyme and one of its clonal derivatives the E6D, with low activity, has been carried out.

Electrophoretic analysis reveals a multiple banding pattern within each line and qualitative differences between the two lines. The alkaline phosphatase activity of the E6D cell extracts is almost completely inhibited by 5 × 10−2 M inorganic phosphate while in the EUE the enzymic activity is reduced to one third under these conditions. The enzymes of the two lines show also a different thermostability which is not referable to extrinsic factors, as demonstrated by mixing experiments. The time course of heat inactivation at 70°C suggests molecular heterogeneity in each line, and a prevalence of a thermostable fraction in the cells with low activity and a thermolabile one in those with high enzymic levels. A rough estimate of inactivation constants does not rule out the possibility that the molecular species in the two lines are the same but in different proportions. The cytological analysis confirms the relationship between the number of small acrocentric chromosomes and alkaline phosphatase levels. The significance of the biochemical data in relation to the proposed model of a gene dosage effect is discussed.
A study of the release of phosphate and arsenate from yeast
Authors: Pauwels G. W. F. H. Borst
Published: February 2005

Under certain conditions yeast cells release previously accumulated phosphate or arsenate. This efflux occurs only when metabolism is not inhibited. There is a rough correlation between the content of orthophosphate and the rate of release.
An effect of exogenous thymidine on the cell cycle in Haplopappus gracilis
Authors: Ames Ira H. , Mitra Jyotirmay
Published: February 2005

The study of an effect of exogenous thymidine on the mitotic cycle demonstrated that a 30 minute exposure to unlabeled and to tritiated thymidine at a concentration of 2.9 × 10−6 M was sufficient to cause a significant increase in the mitotic index of root meristem cells of Haplopappus gracilis. An analysis of the data revealed that this was due to the prolongation of metaphase rather than to an increase in the actual number of cells entering division.
K+‐stimulated phosphatase of microsomes from gastric mucosa
Authors: Forte John G. , Forte Gertrude M. , Saltman Paul
Published: February 2005

The light microsomal fraction was isolated from homogenates of rabbit and bullfrog gastric mucosa. On examination with the electron microscope, the light microsomes appear as tubular membranous structures with morphology and dimensions similar to the elements of the smooth‐surfaced endoplasmic reticulum seen in intact oxyntic cells. A K+‐stimulated, Mg++‐requiring p‐nitrophenylphosphatase has been demonstrated in the gastric microsomes. Neither Na+ nor ouabain (10−6–10−3 M) altered the K+‐stimulated phosphatase. SCN− was not very effective as an inhibitor of the gastric microsomal phosphatase, in contrast to the effect of this anion on the ATPase activity; however, the gastric phosphatase as well as the ATPase are destroyed by phospholipase C, thus showing the lipoprotein nature of these enzymes. Kinetics of the K+ activation of the microsomal phosphatase suggest that the K+‐PNPP complex is the active substrate for the enzymic reaction. Rb+, NH4 + and Cs+ will substitute to some degree for K+ as an activator of the microsomal phosphatase. It is pointed out that K+ is an essential requirement for HCl secretion in intact gastric mucosa and the replacement of K+ with Rb+, Cs+ and NH4+ is discussed. The K+‐stimulated phosphatase presented in this paper may play a role in the H+ secretion process.
The purine and pyrimidine metabolism of Tetrahymena pyriformis
Authors: Hill Donald L. , Chambers Patti
Published: February 2005

The metabolism of purines and pyrimidines by the ciliated protozoan Tetrahymena was investigated with the use of enzymatic assays and radioactive tracers. A survey of enzymes involved in purine metabolism revealed that the activities of inosine and guanosine phosphorylase (purine nucleoside: orthophosphate ribosyltransferase, E.C. 2.4.2.1) were high, but adenosine phosphorylase activity could not be demonstrated. The apparent Km for guanosine in the system catalyzing its phosphorolysis was 4.1 ± 0.6 × 10−3 M. Pyrophosphorylase activities for IMP and GMP (GMP: pyrophosphate phosphoribosyltransferase, E.C. 2.4.2.8), AMP (AMP: pyrophosphate phosphoribosyltransferase, E.C. 2.4.2.7), and 6‐mercaptopurine ribonucleotide were also found in this organism; but a number of purine and pyrimidine analogs did not function as substrates for these enzymes. The metabolism of labeled guanine and hypoxanthine by intact cells was consistent with the presence of the phosphorylases and pyrophosphorylases of purine metabolism found by enzymatic studies. Assays for adenosine kinase (ATP: adenosine 5'‐phosphotransferase, E.C. 2.7.1.20) inosine kinase, guanosine kinase, xanthine oxidase (xanthine: O2 oxidoreductase, E.C. 1.2.3.2), and GMP reductase (reduced‐NADP: GMP oxidoreductase [deaminating], E.C. 1.6.6.8) were all negative. In pyrimidine metabolism, cytidine‐deoxycytidine deaminase (cytidine aminohydrolase, E.C. 3.5.4.5), thymidine phosphorylase (thymidine: orthophosphate ribosyltransferase, E.C. 2.4.2.4), and uridine‐deoxyuridine phosphorylase (uridine: orthophosphate ribosyltransferase, E.C. 2.4.2.3) were active; but cytidine kinase, uridine kinase (ATP: uridine 5'‐phosphotransferase, E.C. 2.7.1.48), and CMP pyrophosphorylase could not be demonstrated.
Differential response of two derivatives of the BHK21 hamster cell to thymidine
Authors: Tobey R. A. , Petersen D. F. , Anderson E. C.
Published: February 2005

Attempts to synchronize the BHK21 hamster cell C‐13 and its polyoma‐transformed derivative P‐183 with excess thymidine resulted in the observation that the parent cell line could be readily synchronized but the transformed derivative could not. Differences in the growth pattern indicate that excess thymidine (10 mM) stops progress of the virus‐transformed derivative at all stages in the life cycle rather than exclusively in S. The data are suggestive but do not establish that the difference is a result of the presence of the virus genome.
Synthesis of antibody by spleen cells after exposure to kiloroentgen doses of ionizing radiation
Authors: Makinodan T. , Nettesheim Paul , Morita Toshiteru , Chadwick Carol J.
Published: February 2005

Mouse spleen cells in diffusion chambers were studied in an effort to assess the radiation survival curves of lymphoid cells during the different serological phases of immune response and to characterize morphologically and metabolically these radiation‐resistant cells. The results showed that the capacity of immunocompetent progenitor cells to proliferate and differentiate into antibody‐synthesizing cells was highly sensitive to x‐irradiation. Their fully differentiated progenies, which were made up mainly of mature plasma cells, were resistant in that they were able to synthesize antibody effectively for as long as several days after their exposure to radiation doses up to 10,000 R.

As a result of these studies, a method with a high recovery yield was devised for obtaining a highly purified preparation of dispersed monospecific antibody‐synthesizing cells. This was done by simply exposing primed spleen cells to 10,000 R at the end of the log phase of response and harvesting the culture several days later.
Studies on carcinogenesis by avian sarcoma viruses. VI. Differential multiplication of uninfected and of converted cells in response to insulin
Authors: Temin Howard M.
Published: February 2005

Insulin can replace the factor(s) in calf serum whose amount is limiting for multiplication in cell culture of chicken embryo fibroblasts and of chicken embryo fibroblasts infected and converted by avian sarcoma virus. In serum‐free, insulin‐containing medium, converted cells multiply more than do uninfected cells. It appears, therefore, that the increased multiplication in cell culture of converted cells as compared with uninfected cells results from a decreased requirement by the converted cells for an insulin‐like activity found in serum.
RNA synthesis in synchronously growing populations of HeLa S3 cells. II. Rate of synthesis of individual RNA fractions
Authors: Pfeiffer S. E.
Published: February 2005

The rates of synthesis of various species of RNA were examined in synchronously growing HeLa cells as a function of stage in the cell generation cycle. The synthesis of each RNA species examined occurs throughout interphase, but undergoes a two‐fold increase in rate during early S which is dependent on the duplication of DNA; blocking the initiation of DNA synthesis also blocks the acceleration of RNA synthesis. To explain the data, a model is discussed in which the acceleration of RNA synthesis during early S is regulated by the number of active cistrons present; thus, as the genome is duplicated, more template is available for transcription, and the rate of RNA synthesis increases. Some implications of the model, and experimental evidence bearing on them, are also discussed.
Factors influencing hematopoietic spleen colony formation in irradiated mice. V. Effect of foreign plasma upon colony forming cell kinetics
Authors: Boggs D. R. , Marsh J. C. , Chervenick P. A. , Cartwright G. E. , Wintrobe M. M.
Published: February 2005

Foreign plasma injection induces a profound and somewhat complex change in the size and location of the colony forming unit (CFU) cell compartment. Injection of foreign plasma before irradiation induces an increase in CFU cells as judged by endogenous colonies as well as by a modification of the endogenous method which excludes spleen colony formation from in situ spleen cells. However, the enlargement does not take place in the most populous CFU cell areas, the spleen and marrow. The concentration and/or total number of CFU cells in spleen and marrow was not increased by plasma injection whether judged by the number of transplantable cells or by the number of migrating endogenous cells.

These studies emphasize the complexity of this cellular system and suggest that the use of but one type of stem cell assay may yield results which do not reflect changes within the total compartment. Evidence for cell damage in vitro as a factor influencing results in studies involving transplantation was searched for but was not forthcoming.
The stimulation of tumor cell growth by a substance produced by normal and tumor cells
Authors: Ichikawa Yasuo , Paran Michael , Sachs Leo
Published: February 2005

It has been shown that a dialyzable substance produced by normal and tumor cells can stimulate the growth of a myeloid, erythroid, and two lymphoid leukemias, and a sarcoma. The growth stimulation of the tumor cells was observed as an increase in cloning efficiency and number of cells per colony. Rat granulocytes stimulated the growth of mouse tumor cells as efficiently as a variety of mouse cells. The stimulating substance was found in conditioned medium, and it was produced by all the normal and tumor cells tested.
Isolation of nuclei from mature peritoneal granulocytes
Authors: Lipke Herbert , Hester Ralph , Groff William , Petrali John
Published: February 2005

Nuclei from mature neutrophil granulocytes were prepared from peritonal exudates of goats. Fluorescein mercuric acetate was required to stabilize the nuclei and fix nucleoproteins. Following differential centrifugation and detergent treatment, electron microscopy showed the interlobar region to be free of cytoplasmic tabs. All of the DNA of the cell was recovered in the nucleus and 71% of the RNA. The DNA : RNA was 6 : 1 in the intact cells, and 9 : 1 in the isolated nuclei. Protein:DNA was 11 : 1 and 4 : 1 for cells and nuclei, respectively. Representative fractions of histones and tryptophan‐rich acidic proteins were prepared with (asp + glu) : (lys + arg + hist) values averaging 0.7 and 1.4 respectively. Histones accounted for 30% of the nuclear proteins while the residual proteins contained the bulk of the cystinyl residues. Granulocytes were characterized by high glycine titers, from 8 to 18% of the nuclear proteins, and 70% of the total free amino acids of the cell.
Recovery of cells in vitro from the effects of hypoxia and hyperoxia
Authors: Shaw David H. , Pace Donald M.
Published: February 2005

The cytotoxic effect of high, as well as low, oxygen tension of proliferation and metabolism of Low line cells in culture is reversible even after several days of exposure provided the cells are returned to 95% air + 5% CO2 environment. This suggests that the activity of certain mechanisms within the cells may have been altered or in other ways inhibited by the abnormal environments but are quite rapidly regenerated once the adverse condition is removed. The cells tolerate a low O2 exposure for at least 20 days while continuous exposure to high O2 atmosphere results in degeneration and death after 7–10 days. Both glucose utilization and lactic acid production are elevated in cultures exposed to either low or high O2 tensions, although they are markedly higher in the latter condition. When cell so exposed are returned to an air + 5% CO2 atmosphere, rate of glucose uptake and lactic acid formation soon approaches that found in control cultures.
Differences between exogenous and endogenous hemopoietic spleen colonies
Authors: Jenkins V. K. , Upton A. C. , Odell T. T.
Published: February 2005

Histologic examination of the spleens in RFM/Un mice killed 6 to 9 days after 350 to 800 R whole‐body x‐irradiation revealed hemopoietic colonies, the numbers of which decreased exponentially with increasing radiation dose. In such animals, myelocytic colonies were the predominant type on the sixth to the eighth day. However, they decreased in number with time, being fewer than erythropoietic colonies by the ninth day after irradiation. In C57BL mice, erythropoietic colonies were relatively more numerous, markedly predominating on both the eighth and the thirteenth days.

RFM/Un mice injected with nonirradiated syngeneic bone marrow cells within 24 hours after 750 R developed colonies, predominantly of erythropoietic and undifferentiated types, the numbers of which were proportional to the numbers of marrow cells injected. The number of colonies formed from exogenous marrow cells increased slightly between the sixth and ninth days after inoculation, possibly because of a greater likelihood of counting them due to an increase in their size.
Thymidine as a synchronizing agent. II. Partial recovery of HeLa cells from unbalanced growth
Authors: Lambert W. Clark , Studzinski George P.
Published: February 2005

Randomly growing cultures of HeLa‐S3 cells were subjected to synchronizing treatment with excess thymidine. Unbalanced growth occurred during the thymidine treatment, but the abnormal cellular composition was found to revert to control levels so that at the time of the first mitosis following a 12–24 hour treatment with the inhibitor the cellular DNA, RNA and protein content and cell size were close to control values. However, an alkaline deoxyribonuclease which attacks denatured DNA was still found to be significantly elevated at this time. The results argue against the use of thymidine as a synchrony producing agent.
Macromolecular synthesis, differentiation and cell division in Tetrahymena pyriformis mating type I variety 1
Authors: Gavin Ray H. , Frankel Joseph
Published: February 2005

In Tetrahymena pyriformis, mating type I, variety 1, cycloheximide rapidly and completely inhibited incorporation of 14C‐L‐leucine into protein. Actinomycin D (25 μg per ml) inhibited incorporation of 14C‐uracil into cold‐TCA‐insoluble material, after a 5–10 minute lag. Frequently a subsequent decline in the amount of radioactivity was observed. Protein synthesis continued in actinomycintreated cultures for a variable time after cessation of RNA synthesis.

Oral development was affected by cycloheximide virtually immediately, and by actinomycin D after a 10–15 minute lag. Cells affected by either drug before the onset of oral membranelle formation were permanently arrested in the stomatogenic field phase. Cells affected in the early and middle stages of membranelle formation completed development of membranelles, but did not invariably complete cell division. Cycloheximide, when added at the beginning of membranelle formation, brought about arrest or resorption of membranelles after they were completed. Actinomycin did not elicit resorption, but sometimes brought about blockage during cell division. Cells affected by either drug after membranelles were fully formed (and cell division was just beginning) completed oral development, nuclear divisions, and cell division. These results suggest that concurrent RNA and protein synthesis are essential for the initiation but not for the completion of membranelle differentiation. The results also suggest that a specific messenger RNA(s) with a very short half‐life is required for the synthesis of proteins involved in the initiation of membranelle differentiation.
The effect of polyamines on cell culture cells
Authors: Higgins M. Louise , Tillman M. Constance , Rupp James P. , Leach Franklin R.
Published: February 2005

Growth of KB cells was inhibited by both spermine and spermidine, but the inhibition is reduced in conditioned medium. The amount of spermine required for 50% inhibition of plating varied according to the type of serum used with medium 199 (calf, fetal bovine, and horse; 0.55, 0.9, and 24 μg/ml respectively). The spermine oxidase activity of the three sera was calf > horse > fetal bovine, which is not the same ordering as was obtained for the inhibition. When the concentration of sera in the media was varied, the inhibition decreased as calf and fetal bovine sera concentration increased, whereas, with horse serum, an increase in serum concentration increased the inhibition. The opposite effects of increasing concentrations of the sera on the inhibition suggest that at least two factors are involved in the inhibition. A scheme which involves three factors (spermine oxidase, another enzyme and its activator) is postulated to account for the inhibitions and reversals observed. Spermine oxidase alone cannot account for the action of polyamine on cells.
Reversible inhibition of ribosomal RNA synthesis in HeLa by lucanthone (Miracil D) with continued synthesis of DNA‐like RNA
Authors: Bases Robert , Mendez Frances
Published: February 2005

Ribosomal RNA synthesis was selectively inhibited in HeLa cells by lucanthone, a clinically useful schistosomicide which shares many of the properties of Actinomycin D. Synthesis of DNA‐like RNA continued during complete inhibition of ribosomal RNA synthesis. Under these conditions newly synthesized DNA‐like RNA accumulated normally in polyribosomes of the cell cytoplasm; most of it appeared to be messenger RNA. DNA synthesis was partially inhibited by lucanthone but protein synthesis was undisturbed. Synthesis of ribosomal RNA promptly resumed after removal of lucanthone and cell survival was not affected if exposures to the drug were limited to two hours.
The kinetics of DNA methylation in cultures of a mouse adrenal cell line
Authors: Kappler John W.
Published: February 2005

Direct measurements of the methylation of newly‐synthesized DNA were made in cultures of a clonal mouse adrenal cortex cell line, Y129OS3, by (1) following the incorporation of radioactivity from methionine‐(methyl)‐C14 into a segment of DNA which had been density‐labeled with bromouracil and (2) labeling DNA cytosine with C14‐deoxycytidine and then following the appearance of radioactivity in DNA 5‐methylcytosine. The results establish that during exponential growth the DNA of this cell line is methylated entirely within a few minutes of its synthesis. Using the second technique described above accurate, sensitive measurements of DNA methylation levels can be made by comparing radioactivity in 5‐methylcytosine to radioactivity in cytosine plus 5‐methylcytosine. In this cell line 5‐methylcytosine accounts for 4.3 ± 0.2% of the DNA cytosine. Some apparent contradictions between these results and those of other workers are discussed.
Flattening, movement and control of division of epithelial‐like cells
Authors: Castor Laroy N.
Published: February 2005

The kinetics of cell division and movement in four epithelial‐like cell lines, grown in continuously perfused culture medium, were studied by time‐lapse cinemicrography. One line exhibited “contact regulation of cell division,” so that the rate of mitosis per cell decreased steadily as population density increased. In the other three lines mitosis was not controlled as a function of population density until the cells became very crowded. An explanation for this difference was sought in terms of the hypothesis that the rate of division depends on the area of the cell membrane.

Cells of the contact‐regulated line flattened uniformly on the substrate. Their motility was restrained by adhesion between their borders. As they crowded together, contact inhibition of cell overlap caused a steady decrease in average surface area per cell. All three of the non‐controlled lines also had contact inhibition of overlap. Cells of two of them flattened on the substrate; but these cells had little mutual adhesion and were highly motile, so that they continually changed their shapes. The areas of their cell membranes were therefore not subject to a restraint that could control the rate of division. Cells of the fourth line remained rounded or only slightly flattened during culture growth, so that no change in cell membrane area occurred that could change the rate of division.
Strain‐specific mitotic inhibition in large mononucleate amoebae
Authors: Jeon K. W. , Lorch I. J.
Published: February 2005

A strain‐specific antimitotic substance is present in large mononucleate amoebae. It inhibits mitosis when injected into amoebae of heterologous strains. The antimitotic substance has been isolated from homogenized cells, and some of its properties have been studied. The results obtained show that the active factor is a protein(s) of molecular weight between 200,000 and one million. The activity of this substance differs from other known antimitotic agents in that its action is strain‐specific.
Stimulation of DNA synthesis in cultures of mouse embryo fibroblast‐like cells
Authors: Vasiliev Ju. M. , Gelfand I. M. , Guelstein V. I. , Fetisova E. K.
Published: February 2005

Stimulation of the DNA synthesis and mitoses in stationary cultures of mouse embryo fibroblast‐like cells was induced by various agents such as ribonuclease, digitonin, fresh medium and commercial preparations of hyaluronidases. Time sequence of stimulation was similar in experiments with all these agents. Cells were activated to enter S phase from GI phase. The rise of the number of DNA‐synthesizing cells was preceded by a latent period of about 8–12 hours with the maximal number of DNA‐synthesizing cells being observed at 16–24 hours. Mitotic wave was observed after the wave of DNA synthesis. Stimulation of DNA synthesis and mitosis was not preceded by any significant decrease of an average cell density in the culture. The progeny of activated cells had no greater chance than other cells to be activated again when stimulation was repeated.

It is concluded that similar proliferative reactions can be induced in stationary cultures by a variety of diverse agents. Possible role of cell surface changes in the induction of these reactions is discussed.
Induction of fatty acid synthesis in cultured mammalian cells: Effects of cycloheximide and x‐rays
Authors: Raff R. A.
Published: February 2005

It was found that L cells deprived of exogenous fatty acids responded adaptively by increased synthesis of fatty acids. This adaptive increase was found to be sensitive to cycloheximide presented at the time of removal of exogenous lipids, but was not sensitive to cycloheximide added six hours after removal of lipids. It was concluded that the adaptive increase in fatty acid synthesis represents a case of enzyme induction. The effect of x‐rays on this process was studied. It was found that induction was inhibited to a greater extent than total protein synthesis. Factors of potential importance to such an effect are discussed.
An analysis of the recovery of Tetrahymena from effects of cycloheximide
Authors: Frankel Joseph
Published: February 2005

When cycloheximide (0.2 μg per ml) was added to synchronized cultures of Tetrahymena pyriformis GL‐C, the initial rate of incorporation of 14C‐leucine was reduced to about 20% of the rate observed in control cells. After one hour, the rate increased fairly abruptly to about 60% of the control rate. The cells in cycloheximide underwent synchronous division about three hours after addition of cycloheximide. A second addition of cycloheximide had little effect on either the rate of incorporation or on the time of cell division in the drug. The medium in which cells had recovered brought about full inhibition of 14C‐leucine incorporation in fresh cells, indicating that recovery was not accompanied by appreciable degradation of the cycloheximide. It was therefore concluded that during recovery the cells were either adapting to the cycloheximide or excluding it. The recovery process shows some specificity, since cells which had recovered from cycloheximide, and had become insensitive to a second dose of this drug, still retained full sensitivity to another drug, colchicine. Conversely, cells recovering in colchicine became insensitive to fresh colchicine but remained sensitive to cycloheximide.