bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ultrastructural localization of cationic proteins in cytoplasmic granules of chicken and rabbit polymorphonuclear leukocytes
Authors: Macrae Edith K. , Spitznagel J. K. 
Published: April 2021

ABSTRACT
Cytoplasmic granules known to contain cationic arginine-rich proteins can be identified by the ammoniacal silver reaction (ASR) which provides a cytochemical marker detectable under the electron microscope. Only the large rod-shaped granules of the chicken polymorphonuclear leukocytes (heterophils) and the large spherical azurophilic granules of the rabbit neutrophilic polymorphonuclear leukocytes show the ASR product as a discrete particulate electron-dense deposit. The other smaller granules are devoid of reaction product, as are membranes and mitochondria. The intracellular localization of the ASR product on the large granules coincides with the ASR product localization on the same isolated granule populations, when the ammoniacal silver reaction is applied to these granules after their separation by sucrose-density gradients. The cationic proteins may have intraleukocytic bacteriolytic properties, since ASR product, presumably indicating cationic protein from discharged granules, appears to surround ingested bacteria within cytoplasmic phagosomes.
Phase-contrast and electron-microscopic observations on a membranous complex in primary spermatocytes of the mouse
Authors: Pleshkewych A. , Levine L. 
Published: April 2021

ABSTRACT
A prominent cytoplasmic inclusion present in living mouse primary spermatocytes has been observed by both light and electron microscopy. It began to form at prometaphase and continued to increase in thickness and length as the cells developed. By metaphase it was a distinct sausage-shaped boundary that enclosed a portion of the cytoplasm between the spindle and the cell membrane. At the end of metaphase, the inclusion reached its maximum length. At telophase, it was divided between the daughter secondaries. The inclusion persisted as a circular contour in the interphase secondary spermatocyte.
Electron microscopy of the same cultured cells that were previously observed with light microscopy revealed that the inclusion was a distinctive formation of membranes. It consisted of agranular cisternae and vesicles, and was therefore a membranous complex. Many of the smaller vesicles in the membranous complex resembled those found in the spindle. The cisternae in the membranous complex were identical to the cisternal endoplasmic reticulum of interphase primary spermatocytes. Neverthless, the organization of vesicles and cisternae into the membranous complex was unique for the primaries in division stages, since such an organization was not present in their interphase stages.
Extraocular muscle degeneration and regeneration after exposure of rats to incandescent radiant energy
Authors: O’steen W. K. , Shear C. R. , Anderson K. V. 
Published: April 2021

ABSTRACT
Exposure of albino rats to incandescent radiant energy for a short period of time in an elevated environmental temperature (39 °C) causes degenerative changes in the extraocular muscles. The muscle fibres regenerate and the muscles reorganize if the animals are returned to room lighting and temperature. Extraocular muscles (EOMs) were damaged first near their insertion on the eyeball. All EOMs of both eyes were affected, but the degeneration did not extend the entire length of the muscle. The peripheral fibres of each muscle-were damaged before the more central fibres. Mitochondria were swollen and often contained dense bodies. Numerous vesicular profiles, possibly from the sarcotubular system, were present. Myofibrils of the more severely damaged fibres lacked typical Z-disk structures, and I-bands had disappeared by 24 h after the exposure period, a degenerative pattern which seems to be unique for this method of EOM damage.
EOM degeneration appeared to be dependent on the interaction between thermal and radiant energy on the orbital contents. However, EOMs were only rarely and very slightly affected when rats were exposed to elevated temperature in the absence of incandescent radiant energy. When an opaque, black, ocular occluder was placed over one eye and the contralateral eye was left unoccluded, EOMs and retinas of occluded eyes were undamaged, while those tissues were severely damaged in unoccluded eyes. Therefore, the most critical single variable in inducing EOM degeneration appears to be exposure to radiant energy.
Some evidence for replication transcription coupling in Physarum polycephalum
Authors: Fouquet H. , Böhme R. , Wick R. , Sauer H. W. , Scheller K. 
Published: April 2021

ABSTRACT
Hydroxyurea, at concentrations of 40–60 mM, selectively and effectively blocked incorporation of thymidine into DNA. Inhibition occurred within 5–10 min of application of the agent when DNA synthesis was in progress, while the onset of replication at the beginning of S-phase and DNA synthesis in G2 phase were not affected.
Uridine incorporation into TCA-precipitable material, in the presence of hydroxyurea, was significantly (up to 70%) inhibited in early S-phase of the cell cycle. Selective inhibition of RNA synthesis was confirmed for RNA separated into rRNA-rich and poly-(A)-rich RNA fractions and analysed by the 2 kinds of DNA-RNA hybridization reactions. Uridine incorporation into poly (A) RNA was also inhibited under conditions where cycloheximide prevented maturation of nascent DNA molecules in early S-phase.
We assume that chromatin which is replicating early DNA sequences may be a more competent template for transcription.
Localization of atpase activity in striated muscle and probable sources of artifact
Authors: Gillis J. M. , Page Sally G. 
Published: April 2021

ABSTRACT
An attempt has been made to localize sites of ATPase activity in stretched fibrils from glycerinated rabbit muscle by precipitating the liberated phosphate with lead ions. As a control, the distribution of lead phosphate grains precipitated by adding phosphate solutions to fibrils incubated with lead (without ATP) has been studied. In these conditions, the grains are not uniformly distributed along the fibrils, but show many of the features of the pattern of distribution that is found after the fibres have been incubated in ATP and lead. It is suggested that differential lead binding by the protein filaments, or movement of the grains, may be responsible for this non-uniform distribution, and that consequently no conclusions concerning sites of ATPase activity within the sarcomere can be drawn from the results of methods using lead precipitation.
The ultrastructure of the perineurium in two insect species, carausius morosus and periplaneta americana
Authors: Maddrell S. H. P. , Treherne J. E. 
Published: April 2021

ABSTRACT
The organization of the perineurium in two insect species (Carausius morosus and Periplaneta americana) has been examined with the electron microscope. In both species this cellular layer has been found to possess an extensive system of tortuous channels between the lateral cell walls. These channels are open at the outer margin adjacent to the fibrous connective-tissue sheath, but appear to be closed at the inner margin by regions of septate desmosomes and/or ‘ tight’ junctions. There is an increased surface area at the inner margin of the perineurial cells produced by the presence of long inwardly directed flanges. An electron-dense coat has also been identified on the cytoplasmic side of the type II perineurial cell membranes at points of contact with the underlying extracellular system and at the outer surface adjacent to the connective-tissue sheath. This organization of the perineurium is strikingly similar to that observed in a variety of fluid-secreting epithelia and its possible function in fluid transport is discussed in relation to the available evidence on the physiology of the insect central nervous system. It is suggested, contrary to some earlier suppositions, that the perineurium may not be primarily involved in the control of the extracellular sodium level and that this regulation may be effected at a deeper level in the central nervous tissues.
The activation and reactivation of peripheral lymphocytes in culture
Authors: Ling N. R. , Holt P. J. L. 
Published: April 2021

ABSTRACT
Human lymphocytes stimulated for 16 h and then cultured without stimulant showed maximal activity on days 2–3 following a stimulus of phytohaemagglutinin (PHA) and on days 3–4 following a stimulus of staphylococcal filtrate (SF). At low dosage of stimulant the response of the cells was less marked but persisted for a longer period than at high dosage. The pattern of response is discussed in relation to the mechanism of activation.
After the effect of the initial stimulus had died away cell populations which had been stimulated with SF or PHA could be restimulated with either stimulant. Their response, when stimulated this second time, was quicker than that of incubated cells from the same donor which had not been previously stimulated. Prestimulated cells were also tested in two immunospecific reactions : the reaction to tuberculin-purified protein derivative (PPD), and the mixed lymphocyte reaction. Cells which had been previously exposed to SF responded more quickly to PPD than cells not previously stimulated. Cell populations which had been previously stimulated also reacted more quickly in a mixed lymphocyte reaction. It is concluded that lymphocyte populations which have been recently stimulated not only retain their capacity to react to immunospecific mitotic stimuli but also react more quickly.
Fine-structural changes in relation to ion and water transport in the rectal papillae of the blowfly, calliphora
Authors: Berridge M. J. , Gupta B. L. 
Published: April 2021

ABSTRACT
The fine structure of the epithelial cells of the rectal papillae in the blowfly, Calliphora erythrocephala Meig., has been investigated to elucidate the possible mechanism of reabsorption of water and ions from the rectal lumen. To observe the variations in the structure of the epithelium in response to the absorptive processes the material was taken (a) from flies at the various stages of their first oviposition cycle, and (b) from freshly emerged imagoes starved for 2 days and injected into the rectum with solutions of various tonicities. It has been found that the complex system of intercellular spaces, formed by a prolific infolding of the lateral plasma membrane of the cells, shows a direct response to the conditions of supposedly maximal and minimal transport of fluid. These spaces are (a) grossly distended in the flies injected with hypotonic media, (b) highly dilated under normal conditions, and (c) completely collapsed in fasting and starved flies. These observations have been discussed in the light of the available theories to explain the mechanism of water transport in biological tissues. It is proposed that the structural design of the rectal papillae favours the application of double-membrane theory to explain the reabsorption of water against osmotic gradients as a consequence of an active transport of solutes into enclosed spaces.
Studies on plasma membranes: IV. the ultrastructural localization and content of sialic acid in plasma membranes isolated from rat liver and hepatoma
Authors: Benedetti E. L. , Emmelot P. 
Published: April 2021

ABSTRACT
Plasma membranes were isolated from rat liver and a transplanted rat hepatoma of the hepato-cellular type. After glutaraldehyde fixation the membranes were treated with colloidal iron hydroxide (CIH) at pH 1·7, which was found to react specifically with the neuraminidase-sensitive sialic acid of the liver membranes. The CIH-reactive, neuraminidase-sensitive sialic acid, comprising 70 % of the membrane-bound sialic acid, was exclusively located in the outer leaflet of the liver membranes as shown by the rather regular distribution of electron-dense CIH granules. This granular, asymmetric type of staining was also observed in the hepatoma membranes, which contained some 50% more sialic acid than did the liver membranes. In addition, the hepatoma membranes showed an intense and uniform staining by CIH of short segments of both membrane leaflets; the latter type of staining was but little impaired by neuraminidase pre-treatment. None of the junctional complexes of the liver membranes was stained by CIH. Tight junctions were very rarely observed in the hepatoma membrane preparations, and the desmosomes and intermediate junctions of these membranes not infrequently exhibited a loosened appearance exposing CIH-reactive neuraminidase-sensitive sialic acid at their opposite plates. This aspect could be induced in the desmosomes and intermediate junctions, but not in the tight junctions, by pre-treatment of the liver membranes with the chelating agent ethylenediaminetetra-acetate.
The structure of the macromolecular units on the cell walls of Bacillus polymyxa
Authors: Finch J. T. , Klug A. , Nermut M.V. 
Published: April 2021

ABSTRACT
Electron micrographs of negatively stained preparations of cell walls of Bacillus polymyxa have been investigated by optical diffraction and optical filtering techniques. Images of single layers of the cell wall, from which the ‘ noise’ has been filtered optically, show hollow, square-shaped morphological units arranged on a square lattice of side 100 A. Single-layer images showing the same pattern have been filtered from moir6 patterns arising from two overlapping single layers. The morphological units are composed of four smaller subunits. The optical diffraction patterns from regions of two overlapping layers show extra reflexions which are attributed to multiple electron scattering.
Polyploidy and nuclear fusion in the fat body of Rhodnius (hemiptera)
Authors: Wigglesworth V. B. 
Published: April 2021

ABSTRACT
The diploid number in Rhodnius is 22 in both sexes. At hatching the fat-body cells are tetraploid, with a few octoploid. This polyploidy is presumed to arise by endomitosis in the egg. In the fully nourished insect this state persists throughout life; and occasional 16n and 32n nuclei occur. Whether these arise by endomitosis or by nuclear fusion has not been established.
In extreme starvation (e.g. 8 months from the time of moulting in the 4th-stage larva at 26 °C) polyploidy increases greatly. This results from nuclear fusion in interphase. The evidence is as follows: All intermediate stages in fusion can be observed.Polyploidy develops many months after growth and mitosis have been arrested. (iii) It occurs mainly in those regions where the food reserves first become exhausted. (iv) When these starved insects are fed the polyploid cells divide and chromosome counts include 12n, 20n, 24n, etc., as well as the regular series 4n, 8n, 16n, 32n, etc. Contiguous nuclei which have not fused in interphase often amalgamate their chromosomes to form a single plate and spindle at metaphase and likewise produce more highly polyploid daughter cells. The high incidence of nuclear fusion in Rhodnius is ascribed to the low rate of metabolism which permits prolonged survival in the starving insect.
Light- and electron microscope studies on the spleen of the newtTriturus cristatus:The fine structure of erythropoietic cells
Authors: Tooze J. , Davies H. G. 
Published: April 2021

ABSTRACTThe stages of erythrocyte maturation were identified in spleen smears stained with May-Grünwald-Giemsa. The fine structure of sectioned cells from about the basophilic erythroblast stage onwards was investigated in the electron microscope and serial 1-μ sections were examined by microspectrophotometry to ascertain haemoglobin content. The nuclei of basophilic erythro-blasts contain large and small blocks of chromatin as well as light-staining zones of unknown composition and ill-defined structure: the nuclear sap contains numerous interchromatin granules, about 400 Å in diameter. During maturation the small blocks of chromatin aggregate and the nuclear light-staining zones tend to disappear, as do the interchromatin granules. Storage lysosomes occur in the basophilic and early polychromatic erythroblasts and during subsequent maturation these lysosomes are probably involved in the degradation of mito-chondria. The changes in distribution of ribosomes in cells at the later stages of maturation have been investigated by counting the numbers of single ribosomes and polysomes seen in electron micrographs. During erythropoiesis the ratio of the amount of fibrillar material to the amount of granular material in the nucleolus increases; in the mature erythrocyte the nucleolus consists almost exclusively of fine fibrillar material.
A localized region of basal body proliferation in growing cells of Dileptus visscheri (ciliata, gymnostomata)
Authors: Kink J. 
Published: April 2021

ABSTRACT
In the ciliate Dileptus organisms are completely organized at the time of excystation. They grow intensively, increasing in volume several times, before they reach the trophic cell size. The growth includes both the somatic part of the body as well as the oral parts, consisting of the cytostomal field and the ventral band of the proboscis. From the time of excystation, during the growth of the cell, the oral apparatus is able to capture and ingest food. Growth of an oral apparatus while functioning has not previously been reported in ciliates.
The proliferation of new oral kinetosomes in the growing oral apparatus occurs only in the cytostomal field. There is no proliferation of ciliature in the oral kineties of the growing proboscis. In those regions of the somatic kineties bordering the cytostomal field an extensive proliferation of somatic ciliature takes place. The zone of proliferation common to the oral and somatic ciliature supplies new kinetosomes for the elongating proboscis, the growing oral apparatus and the growth of the rest of the body.
The mode of proliferation of the oral kinetosomes differs from that of the somatic kinetosomes. The oral kinetosomes form randomly in large numbers, appearing similar to an anarchic field such as is found in other ciliates. The somatic kinetosomes always arise singly and in a defined position in relation to the mature kinetosome.
The proliferation of basal bodies in a defined area in Dileptus suggests the existence of a growth zone localized around the cytostomal field.
Salivary epithelial cells in primary culture: Characterization of their growth and functional properties
Authors: Wigley Caroline B. , Franks L. M. 
Published: April 2021

ABSTRACT
Mouse submandibular salivary gland cells were grown in primary explant culture. After an initial period of degeneration within the explant, surviving epithelial cells proliferated rapidly and duct-like structures recolonized the explant. Autoradiographic studies showed that a peak of DNA synthesis occurred after 4 days in vitro and that proliferation was enhanced by insulin and hydrocortisone. These cells retained specialized secretory function (protease activity) for at least 2 weeks in vitro. This enzyme is a differentiated product of granular tubule cells in vivo. Between 6 and 10 days, explants attached to the substrate. An outgrowth developed, consisting largely of ultrastructurally identifiable epithelial cells which formed pseudoglandular structures in the monolayer. Epithelium survived for over 6 months in primary culture but could not be serially transferred. Secondary cultures were rapidly overgrown by mesenchymal cells.
Macronuclear division with and without microtubules in Tetrahymena
Authors: Williams N. E. , Williams R. Jaeckel 
Published: April 2021

ABSTRACT
The effects of cold shocks (0 °C) and colchicine (4 mg/ml) on macronuclear microtubules and macronuclear division have been investigated in Tetrahymena. Macronuclear division was affected by both treatments, but loss of microtubules occurred only in the presence of colchicine.
When colchicine was applied immediately prior to macronuclear elongation, the nuclei underwent a partial elongation without microtubules, but were unable to constrict and separate into daughter nuclei. Such nuclei were cut in two by the advancing cytoplasmic fission furrow. When colchicine was applied to macronuclei in the fully elongated state, they maintained their elongation in the absence of microtubules, and were subsequently separated into daughter nuclei by the cytoplasmic furrow. It is suggested that macronuclear microtubules, most probably the membrane-associated microtubules, are required for the terminal stages of nuclear elongation and separation. However, the considerable macronuclear elongation which takes place in the absence of microtubules serves to focus attention on molecular mechanisms of force production which must reside elsewhere in the macronucleus.
Early events during substrate adhesion of normal and virus-transformed mouse fibroblasts
Authors: Mapstone T. B. , Culp L. A. 
Published: April 2021

ABSTRACT
The relationship between attachment of Balb/c 3T3 cells and their SV40 transformants to glass or plastic substrates and deposition of substrate-attached material (SAM – proteoglycans implicated in substrate adhesion) has been examined very early after inoculation of cells subcultured with ethylenebis (oxyethylenenitrilo) tetra-acetic acid (EGTA). The metabolic inhibitors cycloheximide and colchicine minimally affected the kinetics or short-term stability of attachment of cells or deposition of SAM. SAM deposition on to the substrate began immediately after inoculation of cells and was maximal prior to the highest cell attachment level (30–40 min after inoculation). At 4 °C, there was no attachment of cells to the substrate and no deposition of leucine- or glucosamine-radiolabelled SAM on to the substrate. 3T3 cells deposited SAM to a maximal level earlier during the attachment process than SV4O-transformed cells. SVT2 cells deposited much smaller amounts of SAM (measured on a per-cell basis) to 3T3 SAM-coated substrates during attachment processes, whereas 3T3 cells and concanavalin A (con A) revertant variants of SVT2 cells, which have regained density-dependent inhibition of growth, deposited identical amounts of SAM (per-cell) on untreated or SAM-coated substrates. Serial attachment experiments with SVT2 cells indicated that all SVT2 cells reduced their deposition amounts on SAM-coated substrates, rather than there being an ability of a small proportion of cells to attach preferentially to SAM-coated substrates while being unable to deposit SAM themselves. The data are consistent with the presence of a sizeable pool of SAM-like proteoglycans being present on the surface of EGTA-removed cells whose deposition may be a requirement for, but may not necessarily be sufficient for, stable adhesion of cells to the substrate.
Stationary phase and the cell cycle of Dictyostelium discoideum in liquid nutrient medium
Authors: Soll D. R. , Yarger J. , Mirick M. 
Published: April 2021

ABSTRACT
Cells of the axenic strain of the cellular slime mould Dictyostelium discoideum, Ax-3, multiply in the liquid nutrient medium HL-5 with a doubling time of 12 h. When the cell concentration reaches approximately 1 ×107 per ml the rate of cell multiplication begins decreasing and after 20—30 h reaches zero, at a stationary phase cell concentration of 2 to 2 5 ×107 cells per ml. The intercept of the extrapolated log phase and stationary phase plots has arbitrarily been considered the onset of the stationary phase. We have found that after cells have been in stationary phase for 24– 32 h, mean cell volume increases by 25 %, average dry weight by 37 %, and average protein content by 24 %. These values are close to the expected values for a cell population which is blocked at a point late in the cell cycle. Stationary phase cells also contain 25 % more nuclear DNA than log phase cells, indicating that the population of cells at stationary phase is blocked after the DNA replication phase. Finally, when stationary phase cells are washed free of stationary phase medium and reinoculated into fresh medium, they reinitiate cell division synchronously. In the light of the demonstrated relationship between stationary phase and the cell cycle, a possible role for the growth inhibitor produced at stationary phase is considered.