bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cell agglutination mediated by concanavalin a and the dynamic state of the cell surface
Authors: Inoue M. 
Published: April 2021

ABSTRACT
The binding of 131I-labelled concanavalin A (131I-Con A) to the cell surface has been studied in Ehrlich ascites tumour cells (EATC) and beef erythrocytes under various conditions. The binding of concanavalin A (Con A) to the cell surface was very specific and the available binding sites were saturated within a few minutes. The amount of 131I-Con A bound to EATC was 4·14 × 107 molecules/cell at 37 °C and 2·12 × 107 molecules/cell at o °C. Under these conditions, cell agglutination was observed only at 37 °C and not at o °C. However, the binding sites measured at o °C were also effective for agglutination at 37 °C. Beef erythrocytes were agglutinated by Con A only after treatment of cells with papain. The number of binding sites for Con A on the cell surface was decreased by this treatment to about half the number present on untreated cells. Various reagents such as colchicine, monoiodoacetic acid, dinitrophenol, rotenone, sodium azide and carboxyl cyanide-m-fluorophenylhydrazone (FCCP) had no effect on Con A-mediated cell agglutination. In contrast, periodate treatment produced a remarkable decrease in the agglutinability of cells. From these data, it is concluded that the cell agglutination induced by Con A was due to the topographical distribution of the surface receptors for the lectin, and not the result of energy-dependent or microtubule-dependent reaction processes. The number and the state of Con A receptors on the cell surface were in a dynamic condition, their conformation, orientation, and/or topographical distribution changing under different conditions.
Cell wall formation by soybean callus protoplasts
Authors: Hanke D. E. , Northcote D. H. 
Published: April 2021

ABSTRACT
Protoplasts isolated from soybean (Glycine max (L.) Merr.) callus and cultured for 40 h developed a wall which could be seen on plasmolysis. They changed shape, producing buds, and became osmotically stable. Analysis after feeding radioactive glucose showed that the regenerated wall was devoid of pectin which was in the medium. Budding occurs because of the loss of pectin and the observations assist understanding of wall expansion and growth in normal plant cells. The complete molecule of weakly acidic pectinic acid was secreted, precluding the possibility of its assembly in the wall.
Incorporation of [3H]uridine and [3H]thymidine during the phase of nucleolar multiplication in Xenopus laevis oogenesis: A high-resolution autoradiographic study
Authors: Gansen P. Van , Schram A. 
Published: April 2021

ABSTRACT
The nucleoli of the premeiotic, pachytene andyoung diplotene(A, B, C, upto 100μm diameter) oocytes are heavily labelled after 7 h of [3H]uridine incorporation, which is in good agreement with the hypothesis that nucleolar multiplication occurs throughout all these early stages of oogenesis. The total labelling of the nucleolar, nuclear and cytoplasmic volumes has been calculated from the uridine high-resolution autoradiograms and the estimated amounts are discussed. The chromatin of several premeiotic oocytes and the cap of all the pachytene oocytes are strongly labelled after 7 h of [3H]thymidine incorporation. We did not find any thymidine incorporation in the young A, B or C diplotene oocytes.
Furrow formation on a piece of cortex transplanted to the cleavage plane of the newt egg
Authors: Sawai Tsuyoshi 
Published: April 2021

ABSTRACT
As part of an investigation of cleavage furrow formation in the egg of the urodele, Cynops pyrrhogaster, transplantation of the cortex was tried. A piece of the cortex with as little cytoplasm and yolk as possible, derived from various stages, was transplanted to the cleavage plane of another egg, using a fine glass needle.
Concerning the position on which grafting was carried out when transplantation was made to the future site of the host furrow, the cleavage furrow of the host travelled across the graft. When the site of transplantation was on the already formed furrow, the result was positive at the animal half, but negative at the vegetal hah. With regard to the graft itself, transplantation was successful regardless of the stage and of the position on the egg from which the graft was taken.
In grafts of the cortex of Xenopus egg on to Cynops eggs, only one successful result was obtained in about twenty trials.
The transition from tadpole to frog haemoglobin during natural amphibian metamorphosis: i. protein synthesis by peripheral blood cells in vitro
Authors: Benbassat J. 
Published: April 2021

ABSTRACT
The transition from larval to adult haemoglobin during natural metamorphosis of Rana catesbeiana tadpoles was studied by polyacrylamide gel electrophoresis of either untreated or reduced and alkylated haemolysates in 8 M urea. The capacity of the peripheral red cells to synthesize haemoglobin in vitro declined in the course of the development of tadpoles prior to metamorphosis. The beginning of the metamorphosis climax, characterized by emergence of the front legs, was associated with an abrupt increase in the capacity of the circulating cells to synthesize haemoglobin. The protein synthesized at this stage consisted mainly of frog haemoglobin and of smaller amounts of tadpole haemoglobin.
The observed changes in haemoglobin synthesis during metamorphosis are compatible either with the appearance of a new cell line synthesizing adult haemoglobin, or with the renewed proliferation of the tadpole erythroid cell line which eventually produces cells capable of synthesis of frog haemoglobin.
The chloroplast nucleoid inOchromonas danica: I. three-dimensional morphology in light and dark-grown cells
Authors: Gibbs Sarah P. , Cheng D. , Slankis T. 
Published: April 2021

ABSTRACTThe 3-dimensional structure of the plastid nucleoid was determined from serial sections of the plastid of dark-grown, greening, and light-grown cells of Ochromonas danica. In light-grown and greening cells, the chloroplast nucleoid forms a continuous cord or ring which closely follows the rim of each lateral lobe of the chloroplast and is continuous across the top and bottom of the bridge connecting the 2 chloroplast lobes. The nucleoid always lies just inside the chloroplast girdle bands where they loop around the rim of the plastid. It was demonstrated by electron-microscopic autoradiography of greening cells labelled with [3H]-thymidine that all the plastid DNA is localized in this peripheral ring-shaped nucleoid. In the proplastid of dark-grown cells, the nucleoid also forms a ring-shaped structure lying just inside the single girdle thylakoid, although frequent irregularities, such as gaps, are present. It is postulated that the girdle bands determine the shape of the chloroplast nucleoid, possibly by having specific attachment sites for the plastid DNA molecules. A survey of the literature shows that a peripheral ring-shaped chloroplast nucleoid is a characteristic feature of the 5 classes of algae whose chloroplasts possess girdle bands, namely the Raphidophyceae, Chrysophyceae, Bacillariophyceae, Xanthophyceae, and Phaeophyceae, and has never been observed in plants whose plastids lack girdle bands.
Ontogeny of hamster haemoglobins determined by isoelectric focusing in polyacrylamide gel
Authors: Boussios Thalia , Bertles J.F. 
Published: April 2021

ABSTRACTHaemoglobin ontogeny in an inbred strain of the golden hamster was determined from 12 days in gestation to adulthood. Haemoglobins, separated by isoelectric focusing in poly-acrylamide gel in a linear pH gradient (7·0 to 8·0), were quantified by optical density scanning (420 nm) of the unstained gels. Three species (adult haemoglobins) increase in proportion, one (15% at 12 days gestation) becomes dominant (85% in adults), and two (nearly absent at 12 days gestation) increase and exist as minor species in adults. Two species (foetal haemoglobins) decrease rapidly, one (37% at 12 days gestation) to trace levels, the other (24% at 12 days gestation) to a persistent 3% in adults.Isoelectric-focused haemoglobins were eluted individually and re-identified by isoelectric focusing, disk-gel electrophoresis, and vertical gel electrophoresis. Gel exclusion studies ruled out the possibility that any one haemoglobin species is a polymer of another.Haemoglobin proportions determined by the technique used here, isoelectric focusing, are very reproducible, both from sample to sample and from hamster to hamster of any specific age. The presence of a foetal haemoglobin fraction persisting at significant levels into adulthood suggests that this small laboratory animal is a suitable model for studies on foetal haemoglobin synthesis.
Electron-microscopic mapping of at-rich regions and of E. Coli RNA polymerase-binding sites on the circular kinetoplast DNA of Trypanosoma Cruzi
Authors: Brack Christine , Delain Etienne 
Published: April 2021

ABSTRACT
Partial alkaline denaturation of the circular kinetoplast DNA (kDNA) of Trypanosoma cruzi has shown the existence of 4 small, well-defined AT-rich regions with an average size of about 200 base pairs. They are almost equally distributed, separated by approximately 90 degrees on the circular molecule. All minicircles, whether free or linked in networks, have the same denaturation pattern and, therefore, seem to contain the same information. The long linear molecules present in low amounts in the kDNA samples do not show the same denaturation pattern. Partial denaturation of molecules in larger associations indicates that the circular units may be linked to each other by one strand only.
kDNA can be transcribed in vitro by the RNA polymerase of E. coli. RNA polymerase-kDNA complexes have been studied in the electron microscope. By spreading the DNA-protein complexes by adhesion to positively charged carbon films and dark-field observation, it was possible to show the existence of 4 specific binding sites of the E. coli RNA polymerase on the kDNA circles. Comparing the position of the polymerase-binding sites and the AT-rich melted zones, it is suggested that a correlation exists between the two.
As had been shown in earlier work, the replication of circular kDNA can be blocked by treating the trypanosomes with the trypanocidal drug Berenil. The comparison of the relative position of the Berenil-blocked replication forks with the position of the 4 denaturation loops shows that the DNA replication is stopped at these AT-rich regions. Since there is evidence that Berenil binds preferentially to AT-rich DNA and seems to be involved in inhibition of DNA replication, the following hypothetical model can be proposed. The replication of the circular kDNA molecules is discontinuous and involves the synthesis of RNA primers; when Berenil is bound to the AT-rich regions, synthesis of new RNA primers is inhibited and replication is blocked at these points, leading to the accumulation of replicating intermediates with defined branch lengths.
The synaptinemal complex in Rhoeo spathacea
Authors: McQuade H. A. , Wells B. 
Published: April 2021

ABSTRACT
The synaptinemal complex in meiocytes of Rhoco spathacea is described.
Unpaired zygotene chromosomes do not exhibit well defined axial cores under the ordinary fixations of electron microscopy and appear diffuse. However, the axial core is defined by ethanolic phosphotungstic acid (PTA) although it docs not respond to uranyl-EDTA-lead. Thus the core appears to contain histone but not RNA and presents a condition which is modified later in pairing when lateral elements of the synaptinemal complex respond positively to both tests.
The total number of attachments of synaptinemal complexes to the nuclear envelope was determined in several nuclei from serial sections. Eleven of the twelve possible attachments were found in one nucleus. It thus seems certain that all must be so attached. In the same manner all chromosomes can be seen to have an attachment to a chromocentre.
Chromocentres are often very large and compound in that two kinds of heterochromatin can be distinguished. These states of chromatin within the chromocentre are considered to be a function of the degree of condensation.
Segments of synaptinemal complexes are distributed randomly through sections of pachytene nuclei and long uncoiled segments of complexes are frequently found in or near the centres of median nuclear sections. Synaptinemal complexes are also found in chromocentres.
Our findings suggest that on completion of pairing, which begins distally, homologous chromosomes in Rhoeo are paired throughout their entire lengths, rather than in small terminal segments only.
The quantitative requirements of human diploid cells (Strain MRC-5) for amino acids, vitamins and serum
Authors: Lambert Kathleen , Pirt S. J. 
Published: April 2021

ABSTRACT
The uptakes of all essential amino acids, vitamins (except riboflavin), glucose and serum during growth of human diploid cells (MRC-5) were determined. The amino acid uptakes varied considerably with the conditions of culture. The glucose requirement is several times greater than that for mouse LS or human HeLa cells. These analytical results were used to modify the medium so as to ensure that an excess of all defined medium constituents was present and pH was not limiting during study of the scrum requirement. It was then found that maximum cell populations were directly proportional to the serum concentration. Hence the growth was limited by the supply of an unknown growth factor in serum. The scrum growth factor was not replaced by a mixture of over 60 vitamins, co-enzymcs, hormones and other organic and inorganic compounds considered to be possible growth factors, although this mixture did not lower the growth rate and somewhat (22 %) increased the yield from the serum growth factor. The unit of scrum growth factor is precisely defined in terms of the amount in a standard batch of calf scrum. This standard contains 10 units/ml whereas the other batch of serum used contained only 5 units/ml.
Haemoglobin synthesis in fused cells
Authors: Davis T. J. , Harris H. 
Published: April 2021

ABSTRACT
When primitive erythroid cells from 5-day-old chick embryos are exposed to inactivated Sendai virus they do not undergo haemolysis but fuse with other cells by the normal process of cytoplasmic coalescence. In this way cells actively engaged in the synthesis of haemoglobin may be fused with others that are not. In heterokaryons formed by the fusion of such erythroid cells with cells from established mouse or hamster lines, haemoglobin synthesis initially continues at a high level, but then declines and ceases altogether within a period of about 60 h. This decline affects the synthesis of both haem and globin and reflects the activity of a specific regulatory mechanism, for under these conditions other chick proteins continue to be synthesized. The haemoglobin synthesized in the heterokaryons is entirely chick, and not mouse or hamster, haemoglobin.
Calcium regulation of the contractile state of isolated mammalian fibroblast cytoplasm
Authors: Izzard C. S. , Izzard Sally L. 
Published: April 2021

ABSTRACT
Calcium-dependent contractions have been induced in fresh, naked cytoplasm of L-929 fibroblasts using physiological solutions (rigor, relaxing and contracting) similar to those designed to control the contractile state of vertebrate striated muscle. Free access of solutions to the cytoplasm was achieved by popping and stripping the plasma membrane from cells using 7-10 strokes of a Dounce homogenizer. Contracting solution (free Ca2+ 7 ×10−5 M; with added MgATP) applied locally from a micropipette to cells popped in rigor (free Ca2+ &lt; 10−8 M) or relaxing (free Ca2+ &lt; 10−8M; with added MgATP) solutions induced symmetrical contractions of unstretched cytoplasm and directional shortening of stretched cytoplasm. The contractions produced 12–18 % shortenings and were complete in 1·38. The cytoplasm could be cycled repeatedly through the contracted state from the relaxed state.
Exogenous MgATP was required for the Ca2+-dependent contractions. At low free Ca2+ concentrations (&lt; 10−8 M), MgATP had a marked plasticizing effect on the cytoplasm. Thus cytoplasm prepared in relaxing solution was less cohesive and more easily deformed than cytoplasm prepared in rigor solution. When induced to contract, relaxed cytoplasm showed a loss of plasticity. Using this criterion, the threshold concentration of free Ca2+ for contraction was determined to lie between 7 × 10−8 and 5 ×10−7 M.
Autoradiography of soluble [2-14C]thymidine derivatives during meiosis and microsporogenesis in Lilium anthers
Authors: Heslop-Harrison J. , Mackenzie A. 
Published: April 2021

Abstract
A dry autoradiographic method suitable for locating soluble tracers has been used to follow the fate of [2-14C]thymidine supplied to detached buds and inflorescences of Lilium henryi and a related cultivar. During the interval from the archesporial phase until pachytene, the derivative (or derivatives) reaching the anther loculi moved freely into the meiocytes. Subsequently, the tracer was excluded from the mother cells until the dissolution of the tetrads. The young spores readily took up tracer in the thecal fluid upon their release, and yielded strongly localized autoradiographs. These observations are interpreted as indicating that access of materials to the meiocytes is related to the formation of cytoplasmic links between mother cells in the early meiotic prophase, and the later severance of these links through the growth of the isolating callose wall which comes to invest the tetrads. Judged from the tracer retained in preparations extracted with trichloroacetic acid, thymidine incorporation occurs mostly in the premeiotic and early leptotene period, although there is some slight evidence of incorporation later in prophase. In the tapetal cells, incorporation occurred in most of the stages tested, but there was no indication of a transfer of labelled materials from tapetum to spores in the post-meiotic period.
The fibrillar flight muscles of giant water-bugs: An electronmicroscope study
Authors: Ashhurst Doreen E. 
Published: April 2021

Abstract
The fibrillar flight muscles of several species of tropical water-bugs of the family Belosto-matidae have been examined in the electron microscope. The myofibrils are very similar to those of the other fibrillar flight muscles which have been studied. The membrane systems, however, display features which appear to be peculiar to this family. The sarcoplasmic reticulum can be divided into three parts : a series of interconnecting vesicles surrounding the Z-lines, randomly scattered small vesicles around the myofibrils, and flattened cisternae which lie along the transverse tubular system, and form the dyads. These three components of the sarcoplasmic reticulum do not appear to be interconnected. The cisternae of the dyads contain an electron-dense substance. The narrow tubules of the transverse tubular system or T-system penetrate deep into the fibre from the cell mémbrane. They follow a course roughly perpendicular to the myofibrils at the level of the M-lines. The dyads are scattered along their length, and may not be near a myofibril. Another system of very large vesicles is found in the muscle fibres, interspersed among the mitochondria. These vesicles usually appear to be empty; their nature and function are not at present known. Numerous mitochondria are present among the myofibrils.
The peculiarities of the water-bug fibrillar flight muscle are discussed in relation to the flight muscles of other insects and the physiological properties of fibrillar flight muscle.
Invertebrate gap junctions
Authors: Flower N. E. 
Published: April 2021

ABSTRACT
Both glycerol and glutaraldehyde, the two most commonly used chemical aids in freeze-fracture studies, have been shown individually to affect the structure of certain membranes as observed in freeze-fracture replicas. The present investigation studied the effect of glycerol on the gap junctions found in a number of tissues from several invertebrate phyla. Glycerol was shown, in some of these tissues, to affect both the spatial arrangement of the particles within the membrane and their fracturing properties if the tissue had not been prefixed with glutaraldehyde. It is suggested that the effect of glycerol on invertebrate gap junctions may be of diagnostic use in enabling them to be separated into a number, or spectrum, of types.
Previously B-type gap junctions have been reported only in Arthropoda. This study has extended knowledge of their occurrence into the phyla Coelenterata, Platyhelminthes and Annelida. The B-type gap junctions appear consistently to have a 12-nm particle separation, which is larger than the 10-nm separation found in vertebrate and molluscan A-type gap junctions.
Gene transfer by means of cell fusion : I. statistical mapping of the human X-chromosome by analysis of radiation-induced gene segregation
Authors: Goss S. J. , Harris H. 
Published: April 2021

ABSTRACT
Hybrid cells were obtained by virus-induced fusion of hamster cells with irradiated human cells. The analysis of such hybrids permits a study of the effects of lethal doses of radiation on human cells and provides a method of sub-chromosomal genetic mapping that is independent of karyological analysis. Radiation-induced chromosome exchanges are shown to be extremely localized, and a map of 4 X-linked genes is presented.
Experimental results on mammalian cells growing In Vitro in deuterated medium for neutron-scattering studies
Authors: Murphy J. , Desaive C. , Giaretti W. , Kendall F. , Nicolini C. 
Published: April 2021

ABSTRACT
SV-40 virus-transformed human diploid fibroblasts (2RA) were grown in a monolayer on plastic Petri dishes in an aqueous medium deuterated to different concentrations of deuterium oxide: 10, 20, 30, up to 60%. The cells must be acclimatized to concentrations higher than 20% D2O by stepping them from a lower initial concentration during their exponential growth. The increase of cell doubling time with increasing deuterium concentrations seems to correlate, at least at 20% D2O, with an initial period of suspended cell growth (lag-phase), and is qualitatively similar to that previously reported for Escherichia coli.
Influence of the time in culture on cellular and neuronal properties of neuroblastoma X glioma hybrid cells
Authors: Heumann R. , Valet G. , Maison D. , Kemper J. , Reiser G. , Hamprecht B. 
Published: April 2021

ABSTRACT
The stability of a clonal mouse neuroblastoma × rat glioma hybrid cell line was examined. Cell volume and cellular content of DNA and protein were measured as functions of the passage number. They decreased with the number of serial subcultivations. Cellular volume was linearly related to cellular DNA and protein. Thus, measurements of cell volume can be used to monitor the loss of DNA from hybrid cells. After about 60 passages a stable population of hybrid cells arose, as judged by the constancy of cellular volume and by the decreased coefficient of variation of the cell volume distribution. A mathematical model for the kinetics of the simultaneous loss of cellular volume, DNA and protein is introduced. Several neuronal properties were investigated. The specific activity of the neurotransmitter enzyme choline acetyltransferase decreased by more than 50 % during 56 passages. After 70 subcultivations, the hybrid cells were still capable of extending processes, action potentials could still be elicited electrically or by iontophoretic application of acetylcholine, and the cells still responded to prostaglandin E1 as they do at low passage number.