bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inverse correlation between neutrophil microtuble numbers and enhanced random migration
Authors: Rich A. M. , Hoffstein S. T. 
Published: April 2021

ABSTRACT
The random migration of neutrophils under agarose as measured by the number of cells leaving the well, is enhanced when the pH or the osmolality of the medium is reduced or when microtubule agents are used. Concentrations of colchicine above 5 × 10−7 M increased the number of cells migrating and decreased the mean number of centriolar microtubules in a dosedependent fashion from 16 to 4 per 4 μm2 at 10−5 M. The distance that colchicine-treated neutrophils migrated from the well was not different from the control. Lowering the pH from 7·4 to 6·o also increased random migration and decreased pericentriolar microtubules from a mean of 16 to a mean of 10. At pH 6· 0, both the number of cells that migrated and the distance the cells forming the leading edge travelled from the well were increased. Since peripheral microtubules may play a greater role in cell migration than centriolar ones, we examined the numerical density of microtubules in the peripheral cytoplasm. Lowering the medium pH reduced the mean number of microtubules per 10 μ m ;3; from 6 to 2. Colchicine reduced microtubules in the same area to 1. At the low pH, colchicine reduced even further the numbers of both centriole-associated and peripheral microtubules but the migration pattern was the same as that seen at pH 6-0 without colchicine. Lowering medium osmolality from 280 to 230 m-osmol increased random migration but did not affect microtubule numbers. The addition of colchicine to this system decreased microtubule numbers and increased migration even further. Conditions that enhanced neutrophil migration also affected cell shape. Whereas cells at pH 7-4 were generally fan-shaped with a broad, smooth leading edge, cells at pH 6’0 with or without colchicine were long and narrow. Neutrophils at pH 7·4 but 230 m-osmol had a scalloped ege, which often appeared thickened. This too was not altered by colchicine. The morphology of cells treated with colchicine was similar to controls except for the more frequent presence of long retraction fibres. Each of these treatments thus appears to act on a different aspect of the cell’s locomotory apparatus. The mechanisms by which colchicine and lowered pH enhance migration may partially overlap since both significantly decrease peripheral microtubules. The data suggest that microtubules play a constraining role within the cell, limiting the ability of the cell to move and change direction.
Inhibition of cell division by interferon: Changes in cell cycle characteristics and in morphology of ehrlich ascites tumour cells in culture
Authors: Richard L. , Panniers V. , Clemens Michael J. 
Published: April 2021

ABSTRACT
The rate of division of Ehrlich ascites tumour cells in culture is inhibited by mouse interferon. A 75 % reduction in cell number is achieved after 3 days and this effect is species specific. The growth inhibition is associated with a marked increase in modal cell volume and with extensive changes in cellular morphology. The cells also become more resistant to detachment from the substratum by mild trypsin treatment.
Analysis of the duration of specific phases of the cell cycle indicates prolongation of mitosis (by 150 %), G2 (by 44 %) and S-phase (by too %), but a slight shortening of G1, as a result of interferon treatment. There is also a dramatic rise in the proportion of cells in culture which contain 2 or more nuclei. As a result of these changes, together with the increase in cell size, the mean cellular contents of protein, RNA and DNA are considerably elevated.
There is a small but significant increase in 3′5′ cyclic AMP (cAMP) content of Ehrlich cells after exposure to interferon, and exogenous cAMP or its analogues cause morphological changes similar to those elicited by interferon. However, many of the other effects of the latter are not mimicked by the cyclic nucleotide, suggesting that cAMP is only involved in part of the complex pattern of responses of cells to interferon which result in inhibition of growth and division.
Effects of disuse on growing and adult chick skeletal muscle
Authors: Shear Charles R. 
Published: April 2021

ABSTRACT
The effects of long-term muscle inactivity, throughout post-hatching development, have been examined. Continuous immobilization of the chicken posterior latissimus dorsi (PLD) muscle from the first hour after hatching for varying periods up to 330 days, resulted in a significantly greater decrease in myofibre size (40―64 % less than control) than occurred when adult muscles were immobilized for similar periods (20―40 % less than control). The myofibre atrophy resulting from long-term immobilization of adult muscle is reversible, after removal of the plaster cast. In contrast, the myofibres immobilized immediately after hatching, for similar periods of time, were unable to recover once the casts were removed. On the basis of myofibre cross-sectional area, 2 populations of cells were seen in muscles immobilized during postnatal development: small myofibres of 0·5―200 µm2 and larger myofibres of 500―800 µm2. The distribution of fibre cross-sectional area within immobilized adult muscles was similar to controls, suggesting a uniform response (i.e. atrophy) by all of the myofibres within the muscle. Immobilization in both newly hatched and adult PLD muscles did not appear to alter the pattern of motor endplate distribution within the muscle. Small, multiple motor endplates were observed associated with immobilized and control myofibres near their terminal ends. This finding suggests that the embryonic pattern of myofibre innervation is not entirely lost from all the fibres during postnatal development.
Repair of strand breaks in superhelical dna of ataxia telangiectasia lymphoblastoid cells
Authors: Lavin M. F. , Davidson M. 
Published: April 2021

ABSTRACT
A number of different assay methods have been used to study repair of strand breaks in DNA after exposure of cells to ionizing radiation. Use of these methods indicates that fibroblasts from patients with ataxia telangiectasia (AT), a multiform genetic disease exhibiting high sensitivity to ionizing radiation, have a normal ability to repair strand breaks in DNA. All of these methods determine the extent of breakage of DNA and the resealing of these breaks but do not provide information on restoration of DNA configuration in the nucleus.
In this report we have used a sensitive technique to investigate restoration of the 3-dimensional structure of DNA in AT lymphoblastoid cells after exposure to ionizing radiation. This technique provides a means of lysing cells using a high concentration of salt and a non-ionic detergent, giving rise to structures called nucleoids which contain nuclear RNA and DNA, are depleted in protein, and sediment in a manner characteristic of supercoiled DNA. We have shown that the degree of supercoiling is the same in control and AT lymphoblastoid cells using sedimentation in the presence of ethidium bromide. The extent of breakage after exposure of cells to y-radiation, and the rate of repair of these breaks are similar in both cell types. Rate of repair of strand breaks is dose dependent and the restructured rapidly sedimenting complex behaves similarly, on sucrose gradients containing ethidium bromide, to that extracted from unirradiated cells.
Dna synthesis and mitosis in fused cells: I. hela homokaryons
Authors: Johnson R. T. , Harris H. 
Published: April 2021

ABSTRACT
When HeLa cells growing in asynchronous culture are fused together by inactivated Sendai virus, synchrony of DNA synthesis and mitosis is rapidly imposed in the resultant multinucleate cells, even though the single cells which fuse to form these multinucleate cells are at different stages of the cell cycle. Some measure of nuclear co-ordination can already be observed within a few hours of cell fusion, and maximal synchrony is achieved within 2 days. By the end of the second day after fusion, asynchronous DNA synthesis or mitosis is rare. In binucleate cells this high order of synchrony is maintained for at least 5 days, but in cells containing greater numbers of nuclei some loss of synchrony begins to appear after the third day. The results indicate that the ability of the multinucleate cell to co-ordinate nuclear events is not impaired by the use of virus to facilitate cell fusion.
Dna synthesis and mitosis in fused cells: II. hela-chick erythrocyte heterokaryons
Authors: Johnson R. T. , Harris H. 
Published: April 2021

ABSTRACT
When chick erythrocyte nuclei are introduced into the cytoplasm of HeLa cells they resume the synthesis of DNA. The reactivated nuclei synthesize DNA in a highly co-ordinated manner and essentially in synchrony with the HeLa nuclei. Asynchronous DNA synthesis is rare. The erythrocyte nuclei in the HeLa cytoplasm respond to the signals which regulate DNA synthesis in the same way as the HeLa nuclei; and they do not, for at least 2 days after cell fusion, interfere in any way with the synthesis of DNA in the HeLa nuclei.
Dna synthesis and mitosis in fused cells: III. HeLa-Ehrlich heterokaryons
Authors: Johnson R. T. , Harris H. 
Published: April 2021

ABSTRACT
Unlike HeLa homokaryons and HeLa-erythrocyte heterokaryons, heterokaryons made by fusing HeLa cells with Ehrlich ascites cells do not, in general, succeed in synchronizing DNA synthesis or mitosis. Indeed, a form of antisynchrony is observed in which most of the Ehrlich nuclei synthesize DNA and most of the HeLa nuclei do not. This anomalous situation appears to be the consequence of competition between the Ehrlich nuclei and the HeLa nuclei for some factor or factors essential for DNA synthesis. In this competition the Ehrlich nuclei are overwhelmingly successful, so that synthesis of DNA in the HeLa nuclei is largely inhibited. The patterns of DNA synthesis in these heterokaryons are thus essentially determined by the proportions of the two kinds of nuclei in the cell.
Lavender, a chick melanocyte mutant with defective melanosome translocation: a possible role for 10nm filaments and microfilaments but not microtubules
Authors: Mayerson Paula L. , Brumbaugh John A. 
Published: April 2021

ABSTRACT
Lavender is a mutation of chick neural-crest-derived melanocytes showing dilute feather pigmentation. This defect, previously attributed to a lack or attenuation of dendrites, was found to be due to a defect in melanosome translocation. The mutant phenotype, of melanin-congested perikarya and pigmentless dendrites is expressed both in vivo and in vitro. Studies with colcemid and cytochalasin B suggest that the avian melanocyte resembles a dispersing amphibian melanophore in its requirement for microfilaments but not microtubules.
Ultrastructural analysis revealed a normal complement of intracellular filaments. Microtubules, however, are scarce. Intermediate (10 nm) filaments surround and are closely associated with intracellular organelles, while microfilaments interconnect all filaments and organelles. Whole-cell centrifugation at 300 g showed that 10 nm filaments stream behind and appear to attach to mobile membrane-bound organelles including the nucleus, lipid granules and mitochondria, as well as melanosomes. It is suggested that all intracellular filaments, especially microfilaments and intermediate filaments, interconnect forming a network responsible for organelle motility.
DNA replication in Chironomus polytene chromosomes during treatment with ethanol
Authors: Lönn Ulf 
Published: April 2021

ABSTRACT
DNA replication in Chironomus polytene chromosomes was investigated. The results show that during treatment with ethanol there is an accumulation of newly synthesized DNA with the size expected of replicons. These and previous results indicate that it is possible that in polytene chromosomes the termination of replication and merging of adjacent replicons is more sensitive to damage than the initiation and/or elongation steps.
Sequential alterations in the nuclear chromatin region during mitosis of the fission yeast Schizosa Ccharomyces Pombe-: Video fluorescence microscopy of synchronously growing wild-type and cold-sensitive cdc mutants by using a dna-binding fluorescent probe
Authors: Toda Takashi , Yamamoto Masayuki , Yanagida Mitsuhiro 
Published: April 2021

ABSTRACT
Video-connected fluorescence microscopy was introduced to study the yeast nuclear chromatin region. It was defined as the nuclear area where a DNA-binding fluorescent probe 4′,6-diamidino-2-phenylindole specifically bound and fluoresced. The 3-dimensional feature of the mitotic chromatin region was deduced by analysing the successive video images of a cell viewed at different angles. By investigating synchronous culture of the wild-type fission yeast Schizosaccharomyces pambe, we found sequential structural alterations in the chromatin region during mitosis. The steps found include the compaction of the chromatin region from the regular hemispherical form, the formation of a U-shaped intermediate and the rapid segregation into 2 daughter hemispherical forms. Six cs cdc mutants, apparently blocked in mitosis, were observed by fluorescence microscopy. Under the restrictive conditions their chromatin regions exhibited either hemispherical, compact, disk-like, U-shaped or partially segregated chromatin regions. Two mutants showed anomalous nuclear locations. The results of the temperature shift-up experiments of the highly reversible KM52 and KM108 strains supported the above scheme of sequential alterations in the chromatin region.
A biochemical dissection of the cardiac intercalated disk: isolation of subcellular fractions containing Fascia Adherentes and gap junctions
Authors: Colaco C. A. L. S. , Evans W. Howard 
Published: April 2021

ABSTRACT
In view of our limited knowledge of the biochemical composition of intercellular junctions, a method was developed for the preparation from rats and mice of plasma membranes containing cardiac intercalated disks. When these membranes were extracted with detergents, e.g. N-lauryl sarcosinate or deoxycholate, the detergent-insoluble material contained structures derived mainly from fascia adherentes junctions, but a few gap junctions and maculae adherentes were also present. When the detergent extraction was carried out at an alkaline pH, the maculae adherentes junctions were dissolved. Fractionation of the detergentinsoluble extract on a sucrose gradient yielded a fraction containing fascia adherentes junction of density 1.20–1.26 g/cm*. Gap junctions banded at a lower density, 1.16–1.20 g/cm3. Polyacrylamide gel electrophoresis showed that the major polypeptide bands in the fascia adherentes-enriched fraction were of molecular weights 134000, 108000, 62–64000, 58000, 47000 and 43000. Although fractions with the gap junctions were contaminated by fascia adherentes junctions, the major polypeptides were calculated by subtraction to be of mol. wt 37000, 26000 and 19000. Two glycoproteins corresponding to minor polypeptides visualized by Coomassie Blue staining were present in the fascia adherentes fraction. Comparison of the fasci aadherentes-enriched fraction with a Z-disc fraction prepared from rabbit hearts indicated a different morphology and polypeptide composition.
Stability ratio of red blood cells: Its dependence on temperature and its relationship to the erythrocyte sedimentation rate
Authors: Sewchand Lionel S. 
Published: April 2021

ABSTRACT
The theory of the coagulation of particles in laminar shear flow was applied in a study of the aggregation of red blood cells. The theory predicts that in a system of initially dispersed particles the total particle concentration would decay (because of aggregation) logarithmically with time with the decay rate, depending on the adhesiveness of the particles. The applicability of this theory was tested at 4 different shear rates (G = 5.0 s-1, 12.6 s-1, 15.7 s-1 and 23.3 s-1) for normal red blood cells in plasma. At every shear rate it was found that an equilibrium condition was approached after 10–20 min, suggesting that the equation is valid only during the first 10–20 min of the aggregation process. Having established the time period over which the theory is valid, values for the stability ratio of red blood cells were computed. The stability ratio, which is essentially a measure of the adhesiveness of the cells, is defined as the ratio of the number of effective collisions (collisions resulting in adhesion) to the total number of collisions.
A very simple shearing technique was used. The suspension of red blood cells was placed in a small weighing bottle and the shearing force was provided by a small magnetic stirring rod, whose rotational frequency could be controlled. The mixing chamber was clamped in a small water bath, which in turn rested on a heated magnetic stirrer. Samples for microscopic viewing and counting were prepared by transferring a very small volume of the suspension onto a microscope slide and preserving it by placing an identical slide on top.
The stability ratio (α) was found to have a negative linear relationship with shear rate (regression line α = 0.02640 — 0.00084 G, r = 0.94) and extrapolation to a = o suggests that a minimum shear rate of ∼ 32 s-1 is required to prevent re-aggregation of the red blood cells. For 10 healthy men and women the stability ratio, calculated at a shear rate of 12.6 s−l, was found to be 0.0129 ±0.0009 (S.E.M.).
The stability ratio was also found to be temperature-dependent. It increased linearly with temperature from 4 °C to 41 °C and then decreased at higher temperatures, becoming zero at a temperature of 52 °C.
Results obtained from a group of patients with high erythrocyte sedimentation rate (e.s.r.) were combined with those from normal, healthy subjects and a positive linear relationship between α, and e.s.r. was obtained. This finding suggests that the stability ratio might be a valuable measurement in comparing red blood cells in disease with normal red blood cells.
Effects of 5-bromo-2′-deoxyuridine on friend erythroleukaemia cells : II. oxidative metabolism and enzyme content of whole cells and isolated mitochondria
Authors: Walter Robert J. 
Published: April 2021

ABSTRACT
Untreated or bromodeoxyuridine (BrdUrd)-treated Friend erythroleukaemia (EL) cells from 15- and 72-h cultures were harvested and the mitochondria were isolated by homogenization and differential centrifugation. Aliquots of the original cell suspensions or the final mitochondrial suspensions were either fixed for electron microscopy, assayed for enzyme activities, or introduced into a i-ml Clarke oxygen electrode chamber. Whole BrdUrd-treated cells exhibited notable morphological alterations (see accompanying paper) but no effect was observed on whole-cell respiration. Morphologically, isolated mitochondria exhibited a highly condensed matrix and a greatly expanded outer compartment. Functionally, these mitochondria oxidized a variety of substrates at high state-3 (ADP-stimulated) rates (60–210 ng atoms O/min per mg protein) and displayed adequate respiratory control and ADP/O ratios. In the mitochondria isolated from BrdUrd-treated EL cells (both 15- and 72-h cultures), the state-3 oxygen consumption rates, respiratory control ratios, and ADP/O ratios generally decreased compared to their matched controls. These functional deficiencies coincided with in situ increases in the volume of the mitochondrial compartment and conspicuous (30–100%) increases in the specific and total activities of several mitochondrial enzymes. In addition, the mitochondria isolated from the 72-h group (treated and untreated) displayed immediate alterations when BrdUrd was added to the electrode chamber. Oxygen consumption rates dropped, respiratory control ratios changed moderately, and ADP/O ratios increased. BrdUrd may act both as an inhibitor of oxidative phosphorylation and perhaps as a sink for some of the high energy phosphate that is being generated. Thus, BrdUrd may exert its inhibitory effect on cell differentiation by interfering with mitochondrial function.
Identification of a microfilament-enriched, motile domain in amoeboflagellates of Physarum Polycephalum
Authors: Pagh Kathryn , Adelman Mark r. 
Published: April 2021

ABSTRACT
A distinctive, transient cytoplasmic domain was identified in haploid cells of Physarum polycephalum that are transforming from amoebae into flagellate swimming cells. As revealed by light microscopy, this region, termed the ridge, is a flattened cytoplasmic extension that displays a specific form of motility, characterized by undulations that propagate rapidly down its long axis. The ridge was further examined by scanning electron microscopy of whole cells, and by transmission electron microscopy of serial sections and negative stain preparations of amoeboflagellate cytoskeletons. We identified three distinct components possibly related to ridge motility: a short flagellum closely associated with the ridge surface, an array of micro-tubules that is part of a complex microtubular apparatus and a network of filaments that forms a well-defined laminar core within the ridge.
Labelling studies with heavy meromyosin subfragment 1 (S-1) indicated that a major portion of the filament network is actin. Peripheral microfilaments appeared to have a uniform orientation in that arrowheads pointed towards the cell body. Other ordered filament arrangements were apparent with a modified extraction protocol using phalloidin. Similar microfilament organization has been reported in motile regions of other systems, such as the lamellipodia of tissue culture cells. However, the ridge can be distinguished from such other motile regions in that it forms independently of contact with a substratum and is only present in a specific region of amoeboflagellates. Moreover, the ridge appears at a specific time during the course of the transformation.
The ridge constitutes a new system for studying the structural basis of cell motility. The arrangements of actin- and microtubule-containing ridge components suggest several testable hypotheses concerning their involvement in cytoskeletal or motile functions.
The course of the acrosome reaction in guinea-pig sperm
Authors: Green D. P. L. 
Published: April 2021

ABSTRACT
The acrosome reaction in guinea-pig sperm is accompanied by a marked cavitation of the acrosomal contenta. Two divergent views are held as to whether this cavitation precedes or follows the membrane fusion that occurs in the reaction. To distinguish between these 2 views cavitation was induced in media containing a colloid, either Ficoll 70 or inulin, either by inducing a normal acrosome reaction using the calcium ionophore A2 3187 or by using the detergent Triton X100. Both Ficoll 70 and inulin, when incorporated into media of normal osmolality, were able to suppress various features of the cavitation. Complete retention of acrosomal shape was achieved in sperm treated with detergent in 30% (w/v) Ficoll 70 solution despite the absence of the limiting acrosomal and plasma membranes. This evidence supports the suggestion that the cause of the cavitation is a colloid osmotic pressure within the acrosomal matrix. This in turn supports one of the 2 proposed mechanisms for the temporal sequence of events occurring in the acrosome reaction.