bluuebunny/crossref_metadata_2025_split huggingface dataset:
Genetic analysis of developmental mechanisms in hydra: VI. cellular composition of chimera hydra
Authors: Sugiyama Tsutomu , Fujisawa Toshitaka 
Published: April 2021

ABSTRACT
The homeostatic mechanisms that maintain, constant cellular ratios in hydra tissue were studied using mutant and chimeric hydra strains.
Mutants having abnormal cellular compositions are isolated through sexual inbreeding of wild hydra, as described in previous papers of this series. Chimeric hydra are produced by making use of a strain (nf-1) which lacks interstitial cells, nerve cells and nematocytes in its tissue. Reintroduction of interstitial cells from other strains (both normal and mutant) into nf-1 leads to creation of chimeric strains having epithelial cell lineages from one strain (nf-1) and interstitial cell lineages from others.
Analyses and comparisons of the cellular compositions of all these strains revealed that the numbers of nerve or interstitial cells in the chimeras were very similar to (statistically significantly correlated with) those in their interstitial cell donors. Since chimeras and their interstitial cell donors share the same interstitial cell lineages, this suggests that interstitial cells or their derivatives (nerves and nematocytes) play major roles in determining the nerve and interstitial cell levels in the hydra tissue. It is suggested that some form of homeostatic feedback mechanisms are probably involved in regulating the levels of these cell types.
Mechanisms of cellular adhesion: IV. role of serum glycoproteins in fibroblast spreading on glass
Authors: Thom David , Powell Andrew J. , Rees David A. 
Published: April 2021

ABSTRACT
We have investigated the exogenous factors required for the transition from the round shape of suspended fibroblasts to the characteristic spread shape on serum-coated glass. Following the evidence of others that the transition is facilitated by adsorbed component(s) related to CIG/LETS (cold-insoluble globulin/large external transformation-sensitive) proteins, we have isolated 2 such preparations from chick serum. Their influence has been investigated on fibroblast adhesion, spreading and growth and they have been characterized by gel electrophoresis, immunological cross-reactivity, amino acid and carbohydrate residue analysis, sedimentation velocity behaviour and circular dichroism spectroscopy. The preparations have molecular weights of 225/215000 and 140000 Daltons respectively and are closely similar in composition and secondary structure. The 225/215000 Dalton doublet is probably a product of limited proteolysis which almost certainly occurred in the avian circulation.
For cells seeded on glass precoated in different ways and in different supplemented media we could detect no change in the extent of attachment but there were profound influences on cell shape following this initial adhesion. We confirm that prior adsorption of either CIG-related preparation to glass does indeed promote fibroblast spreading in the absence of other serum components and that CIG is the sole serum component with this type of activity. We now add 2 important qualifications: (i) the presence of substrate-adsorbed serum CIG is not essential for spreading when other serum components are present in the medium; and (ii) the adhesive organization shown by interference reflexion microscopy is incompletely formed unless the additional serum components are present in the medium.
We therefore conclude that 16C fibroblasts have the ability when given the stimulus of soluble serum components other than CIG, but not otherwise, to synthesize all the components necessary for the highly organized contacts with glass, including endogenous CIG/LETS proteins.
Post-fusion somatic incompatibility in plasmodia of Physarum Polycephalum
Authors: Lane E. Birgitte , Carlile Michael J. 
Published: April 2021

ABSTRACT
High-resolution autoradiography has been used to establish that during the incompatibility reaction that follows fusion between plasmodia of a ‘killer’ and a ‘sensitive’ strain of the myxo-mycete Physarum polycephalum, the nuclei of the sensitive strain are selectively damaged, enclosed in vacuoles and eliminated from the cytoplasm. This damage is visible as increased chromatin condensation and nucleolar segregation. Nuclear envelopes of both strains show blebbing, and there is an increase in the size and frequency of cytoplasmic vesicles of endoplasmic reticulum. Multiple nuclear fusions are seen between all combinations of genetically like and unlike types of nuclei throughout the course of the incompatibility reaction. After the reaction, mean nuclear diameters increase over 2–3 days to give nuclei an order of magnitude greater in volume than the controls; the population size range returns to normal in 4–5 days. Fusions between incompatible plasmodia carried out when the killer strain is at or very near to mitosis do not produce an immediate incompatibility reaction, but give plasmodia that are neutral and act as neither killers nor sensitives; these heterokaryons convert to killer phenotypes after a few days.
The mechanism of K-cell (antibodydependent) mediated cytotoxicity: III. the ultrastructure of K cell projections and their possible role in target cell killing
Authors: Glauert Audrey M. , Sanderson Colin J. 
Published: April 2021

ABSTRACT
The cytotoxic interaction between lymphoid K cells from normal rat spleen and antibody-coated P815 mastocytoma cells has been studied in conditions under which the number of cytolytic events occurring at the time of observation was at a maximum.
Electron micrographs of material fixed during the first 15 min after contact between the target and effector cells had been initiated by centrifugation showed that the K cells produce long projections which push deeply into the P815 cells, causing infoldings of the plasma membrane and distortion of the nucleus. The plasma membranes of the effector and target cells, and the nuclear membrane, remain intact. Subsequently the target cells undergo violent cytoplasmic blebbing (zeiosis) which is the first stage of cell lysis.
The evidence for the hypothesis that projections from lymphoid K cells develop as a result of contact between receptors on the K cell surface and antibody bound to the target cell, and that the projections are involved in the cytotoxic mechanism is discussed.
Production and fate of erythroid cells in anaemic Xenopus Laevis
Authors: Chegini N. , Aleporou V. , Bell G. , Hilder V. A. , Maclean N. 
Published: April 2021

ABSTRACT
Adult Xenopus laevis, rendered anaemic by phenylhydrazine injection, have been studied during the recovery from such anaemia. Electron microscopy of liver and spleen sections indicates that both of these organs are active in the phagocytosis and destruction of the old damaged red blood cells. May-Grunwald and Giemsa staining of liver and spleen cells following anaemia has been used to show that erythropoiesis also occurs in both liver and spleen, and this has been confirmed by electron-microscope studies of these organs.
Cell counting and radiolabelling of the new population of circulating erythroid cells in the period following phenylhydrazine injection suggests that a sudden release of basophilic erythroblasts from liver and spleen is followed by mitosis of this new cell population in circulation, and that no further release of erythroid cells from these organs is likely until complete recovery has occurred.
Fractionation of human liver mitochondria: Enzymic and morphological characterization of the inner and outer membranes as compared to RAT liver mitochondria
Authors: Benga Gheorghe , Hodarnau Adriana , Tilinca Rozalia , Porutiu Dorin , Dancea Silvia , Pop Victor , Wrigglesworth John 
Published: April 2021

ABSTRACT
The fractionation of human liver mitochondria into inner membrane, outer membrane and matrix material is reported. Compared with rat, human liver mitochondria are more fragile. Fractionation can be achieved in only 2 steps, a digitonin treatment for removal of the outer membrane and centrifugation of the inner membrane plus matrix particles through a linear sucrose gradient resulting in purified inner membranes and matrix.
The quantitative measurement of electrolyte elements in nuclei of maturing erythrocytes of chick embryo using electron-probe X-ray microanalysis
Authors: Jones R. Theresa , Johnson R. T. , Gupta B. L. , Hall T. A. 
Published: April 2021

ABSTRACT
Na, K and Cl measurements have been made on frozen sections of chick red blood cells throughout embryonic development, using electron-probe microanalysis. There is an apparent fluctuation in the levels of these elements during maturation, although the Na/K ratio remains fairly constant. The nuclear Na concentration resembles that of the cytoplasm, rather than that of the medium, at all stages. Inhibitor studies indicate that when cytoplasmic Na, K and Cl levels are altered, their corresponding nuclear levels are similarly affected. Additionally, the measurements in nuclei isolated in anhydrous media from lyophilized cells have shown arte-factual accumulation of high Na, K, Ca and Mg.
Studies of membrane fusion: IV. fusion of hela cells with sendai virus
Authors: Knutton S. 
Published: April 2021

ABSTRACT
The Sendai virus-induced fusion of HeLa cells has been studied by freeze-fracture electron microscopy. Freeze-fracture observations confirm previous scanning electron-microscope studies (1977) and show that at 4 °C virus particles bind to the cell surface and that cell agglutination results from the crosslinking by virus particles of microvilli on adjacent cells. Incubation at 37 °C initiates a change in viral envelope structure and fusion of ‘altered’ virus particles with the cell plasma membrane. Fusion of a virus particle with two crosslinked cells is probably the membrane fusion event which initiates cell-cell fusion; fusion is completed as a result of virally induced cell swelling. Lateral diffusion of viral envelope components following viruscell fusion and, in some instances, an aggregation of plasma membrane intramembrane particles occurs in swollen cells. These observations show that the mechanisms of viral envelope-cell and probably cell-cell fusion are the same as have been reported for erythrocytes. Although endocytosis of intact virus particles does occur, the specialized cell-mediated mechanism for fusion of the viral envelope with the cell plasma membrane suggests that this, and not viropexis, is the mechanism of Sendai virus infection.
Motility of the Limulus blood cell
Authors: Armstrong Peter B. 
Published: April 2021

ABSTRACT
The sole cell type (the amoebocyte) found in the coelomic fluid of the horseshoe crab, Limulus polyphenrus can be stimulated to become motile by extravasation or trauma. Motility was studied using time-lapse microcinematography and direct microscopic examination of cells in tissue culture and in gill leaflets isolated from young animals. Phase-contrast and Nomarski differential-interference contrast optics were employed. Both in culture and in the gills, motile cells showed 2 interconvertible morphological types: the contracted cell, which was compact and rounded and had a relatively small area of contact with the substratum, and a flattened form with a larger area of contact. In both morphological types, motility involved the protrusion of hyaline pseudopods followed by flow of granular endoplasm forward in the pseudopod. Cellular motility in vivo (in the gill leaflet) was morphologically identical to that displayed in tissue culture. In culture, motility was unaffected by the nature of the substratum: cells were indistinguishable on fluid (paraffin oil) or solid (glass) substrata or on hydrophobic (paraffin oil, siliconized glass) or hydrophilic (clean glass) surfaces. Cells migrated and spread on agar surfaces. Cell motility was unaffected by high concentrations (100 μg/ml) of the microtubuledepolymerizing agent colcemid and was abolished by cytochalasin B at 1 μg/ml.
Production of nerveless Hydra Attenuata by hydroxyurea treatments
Authors: Sacks Peter G. , Davis Lowell E. 
Published: April 2021

ABSTRACT
Hydroxyurea was used to produce hydra with varying nerve cell densities including a new type of nerveless animal. Hydra attenuata were treated with 10−2 M hydroxyurea. By 23 days after treatment, 2 populations of animals are in culture. Both have a decrease in nerve cells. The first is a normal-coloured feeding animal (HU-R) and is recovering while the second is a pale non-feeding animal (HU-P). HU-P animals resemble nerveless animals in their lack of behavioural responses but they contain about 2% nerve cells. Upon hand feeding, some HU-P animals will recover but most will produce nerveless buds. Nerveless hydra produced by hydroxyurea resemble nerveless animals produced by other techniques, in their behavioural, morphological and developmental properties.
Normal animals, as cultured and in regeneration experiments, show a compact tentacle number distribution pattern with a small variance. Nerveless animals show broad tentacle distribution patterns with increased means and variances. It is suggested that a normal tentacle number regulatory mechanism is lacking or diminished in nerveless animals. This defect is correlated with hypostomal circumference and with nerve cells.
Inhibition of movement of triton-demembranated sea-urchin sperm flagella by Mg2+, ATP1-, ADP AND P1
Authors: Okuno Makoto , Brokaw C. J. 
Published: April 2021

ABSTRACT
Three distinct patterns of inhibition of MgATP2−-activated flagellar motility have been found by measuring the motility of Triton-demembranated sea-urchin spermatozoa beating with their heads attached to a glass surface.
Inhibition of beat frequency by the reaction products, ADP and Pb is competitive with the normal substrate, MgATP2−, and the inhibitory effects are similar to a reduction in MgATP2− concentration.
Inhibition of beat frequency by ATP4- is competitive with MgATP2−, but is accompanied by an inhibition of bending, as measured by the angle between the straight regions on either side of a bend, which is not seen when MgATP2− concentration is reduced.
Inhibition of beat frequency by Mg2+ is not competitive with MgATP2−, and is accompanied by an increase in bend angle, so that there is no change in the rate of sliding between flagellar tubules.
These differences suggest unexpected complexity of dynein ATPase action in flagella.
The beat frequencies of both swimming and attached spermatozoa show a linear double reciprocal dependence on MgATP2− concentration, with identical slopes. The calculated sliding velocities between tubules also give linear relationships, but the slopes are different, suggesting that beat frequency may be the more fundamental dependent variable in this system.
Granulocyte adhesion to endothelium in culture
Authors: Pearson Jeremy D. , Carleton J. Susan , Beesley Julian E. , Hutchings Amanda , Gordon John L. 
Published: April 2021

ABSTRACT
We previously described a model system for studying the adherence of granulocytes to cultured endothelium, and have now investigated the effects of other blood components on granulocyte adhesion in this system. Red cells enhanced adhesion, whereas blood platelets decreased adhesion, and further experiments suggested that endothelial cells secrete a pro-adhesive factor, particularly if incubated with plasma. We have also investigated the effects of several drugs, and attempted to localize their sites of action. Flavonoid drugs increased adhesion by an effect at the endothelial cell surface, whereas agents that increase cyclic AMP levels, including several prostaglandins, stimulated adhesion mainly by their effects on granulocytes. The effects of some agents on granulocyte adhesion to endothelium were not paralleled by their effects on adhesion to serum-coated glass. We conclude that granulocyte-endothelial interaction is a complex process, with each cell type responding to the other or to factors produced by it, and that data derived solely from studies of granulocyte adhesion to inert substrata will not always reflect granulocyte-endothelial interaction in vivo.
Developmental mechanisms in heterospory: Cytochemical demonstration of spore-wall enzymes associated with p-lectins, polysaccharides and lipids in water ferns
Authors: Pettitt J.M. 
Published: April 2021

ABSTRACT
Cytochcmical methods arc used to examine the distribution and localization of acid phos phatase, non-specific cstcrasc, ribonuclcasc and peroxidase activity in the walls of the spores of the hctcrosporous Marsilcaccac before and during germination. In the quiescent spore, the principal activity is associated with the pcrinc layer of the wall and the intine, with some acti vity in the outer, gelatinous wall layer, but none in the cxine. The microsporcs of Marsilea and Pilularia have non-specific cstcrasc activity concentrated in the intinc in the immediate vicinity of the germinal site; that is, above the position of the future male gamctangia. The enzymes are not leached from the wall during hydration of the spores, although ribonucleasc is redistributed during imbibition with a high concentration of activity remaining in or around the germinal site.
The wall enzymes occur together with PAS-reactive and acidic carbohydrates, lipids, and in the microspore pcrine, β-lcctins. Following the enzyme pattern, the β-lectins are found to be concentrated in the region of the germinal site. β-lcctin activity is absent from the mcgaspore wall. Acidic carbohydrates are confined to the gelatinous wall layer and this layer also binds con canavalin A. In contrast to what has been found for other plant cells, the spore-wall β-lcctins arc not water-labile; the activity is not significantly diminished after hydration. This surprising stability suggests that these molecules, together with the enzymes, may be retained in position in the wall by the waterproof overlay of lipid.
From the evidence of preliminary developmental studies, it appears that the enzymes as sociated with the pcrine layer of the wall originate in the sporophytic tapctal pcriplasmodium and inclusion of the activity is concurrent with wall differentiation, while the activity associated with the intinc is derived from the gametophytc. It is possible, however, in the megasporc at least, that the distribution of the activity may to some extent be influenced by a system of exine channels which communicates between the two domains of the wall during sporogenesis.
No definite information is obtained concerning the utility of the enzymes and associated molecules in the life of the spore. Acting separately or in co-operation, their role could con ceivably be connected with one or more of four processes; wall differentiation, gametophyte nutrition, gametophyte protection or reproduction. Each of these possibilities is discussed.
Origin and spatial distribution of maternal messenger rna during oogenesis of an insect, Oncopeltus fasciatus
Authors: Capco David G. , Jeffery William R. 
Published: April 2021

ABSTRACT
In order to investigate the origin and spatial distribution of maternal mRNA during oogenesis, in situ hybridization with [3H]-poly(U) was utilized for the detection of poly(A)-containing RNA [poly(A) + RNA] in histological sections of Oncopeltus fasciatus ovaries. In the germarium poly(A) + RNA was found to accumulate in the trophocyte cytoplasm concomitant with the maturation of these cells. Poly(A) + RNA was also detected in the trophic cores and nutritive tubes suggesting that these channels participate in the transport of trophocyte-derived mRNA to the oocytes. Although large amounts of poly(A) + RNA were also detected in the cytoplasm of the follicle cells, particularly during late vitellogenesis when pseudopod-like processes projected into the ooplasm, no evidence was obtained for the transport of poly(A) + RNA from these processes to the oocytes. The content of poly(A) + RNA in the oocyte cytoplasm continually increased during oogenesis. In stage 2–4 oocytes poly(A) + RNA accumulation occurred in the apparent absence of transcriptional activity in the germinal vesicle nuclei suggesting that most maternal mRNA molecules synthesized during early oogenesis are of trophocyte origin. Poly(A) + RNA also continued to accumulate after chorion formation, when the nutritive tubes are no longer active in RNA transport. This implies that other sources of maternal mRNA may exist during late oogenesis. The distribution of poly(A) + RNA molecules in the oocyte cytoplasm appeared to be uniform throughout oogenesis with one exception. During late vitellogenesis poly(A) + RNA activity was significantly enhanced in the anterior and posterior periplasmic cytoplasms relative to the lateral periplasm and the endoplasm. After chorion formation these variations disappeared. The results suggest that maternal mRNA molecules arise from at least 2 sources during oogenesis. During late vitellogenesis these molecules appear to be subject to differential localization in the polar perimeters of the oocyte cytoplasm.
An electron-microscopic study of the starch-containing plastids in the fern Todea barbara
Authors: Smith H. M. , Smith D. S. 
Published: April 2021

ABSTRACT
Gametophytes of Todea barbara grown in vitro have two types of starch-containing plastids. The first type are chloroplasts having well-developed grana regions connected by intervening membranes and little deposition of starch. The other type are amyloplasts usually containing abundant starch deposits and stacks of membranes which resemble the grana of the chloroplast but are not connected. Even when little starch is present, the latter type has very few internal membranes.
Membrane spacing and gross organization of the mature plastid of both types suggests similar morphological development. However, when and where in this development known physiological differences arise is not yet known.
On the question of nervous syncytia: Lack of axon fusion in two insect sensory nerves
Authors: Steinbrecht R. A. 
Published: April 2021

ABSTRACT
Electron micrographs of insect antennal nerves reveal that 98 % of the nerve fibres are below 0·5 μ in diameter and are packed in bundles of naked axons without individual glia sheaths (average fibre calibre: 0·3 μ in Bombyx, 0·12 μ in Rhodnius). Re-examination of earlier light-microscopic fibre countings, which led to the hypothesis of axon fusion in insect sensory nerves, is now necessary. In the two nerves studied, each antennal sense cell is individually connected with the brain by its own axon. The results are compared with other cases of proposed axon fusion (e.g. giant fibre systems) and the physiological consequences are discussed.
Ultrastructural changes in pig hepatocytes during the transitional period from late foetal to early neonatal life
Authors: Bischoff M. B. , Richter W. R. , Stein R. J. 
Published: April 2021

ABSTRACT
A light- and electron-microscopic study of pig hepatocytes from late prenatal to early neonatal animals shows changes which reflect an increasing rate of synthetic activity. The granular endoplasmic reticulum (ER) in the prenatal pig hepatocyte is situated along the periphery of the cytoplasm and in the region immediately surrounding the nucleus. Mitochondria are most abundant in the area adjacent to the nucleus, while the Golgi complex is generally located in the region of the bile canaliculus. The remaining portion of the hepatocyte is occupied with glycogen. A few hours after birth the hepatocyte increases about twofold in size with the nucleus shifting from a peripheral to a more centrally located position. The glycogen decreases quickly coincident with a rapid increase in the amount of granular ER and the dispersion of the mitochondria throughout the cell. The Golgi complex becomes distended and numerous vesicles appear in its immediate vicinity containing a moderately dense material. Numerous peribiliary inclusions appear during the second postnatal day. These structural changes are an indication of the increased synthetic activity occurring within the hepatocytes of rapidly developing animals.