bluuebunny/crossref_metadata_2025 huggingface dataset:
Macrotubules induced by halothane: in vitro assembly
Authors: Hinkley Robert E.
Published: April 2021

The formation of macrotubules by the volatile anaesthetic halothane was investigated in vitro using microtubule-enriched fractions of crayfish nerve cords. Sequential studies showed that macro tubules assemble from helical ribbons of 18 –20 laterally associated microtubule protofilaments which fold upon themselves to form intact macrotubules averaging 48 nm in diameter. The initial rate of macrotubule assembly is dependent on the concentration of halothane employed and is stimulated by calcium. Glycerol pretreatment blocked macrotubule formation by halothane and caused preformed macrotubules to reassemble rapidly into typical microtubules. These experiments show that microtubules and macrotubules require different conditions for assembly and support the contention that macrotubule formation by halothane is due to a direct interaction between the anaesthetic molecule and the microtubule subunit.
IgG receptors on foetal chick yolk sac
Authors: Linden Carol D. , Roth Thomas F.
Published: April 2021

In the chicken, maternal IgG is deposited in the oocyte yolk and subsequently transported intact by the foetal chick yolk sac into the chick circulation. Such transport appears to require a specific membrane-localized IgG receptor.

Using the assay of 125I-yolk IgG binding, we have investigated the existence and properties of such receptors in yolk sac tissue disks. We find that: (1) There are specific 125I-IgG binding sites on yolk sac tissue; (2) specific yolk 125I-IgG binding has a distinct pH optimum at pH 6·0–6·3; (3) the apparent equilibrium dissociation constant of specific 125I-IgG binding is 2·3×10−6 M; and (4) heterologous proteins compete less efficiently than yolk IgG for 125I-IgG binding.
Intercellular bridges between follicle cells and oocyte during the differentiation of follicular epithelium in Lacerta sicula Raf
Authors: Andreuccetti P. , Taddei C. , Filosa S.
Published: April 2021

Intercellular bridges first appear during lizard oogenesis when follicles are rather small (150 pm in diameter); at this stage they form connecting links between the oocyte and follicle cells, which have not yet differentiated into pyriform cells. Later on, when the follicles have become larger (1 mm) and the follicular epithelium appears constituted by 3 types of cells (small, intermediate and pyriform cells) they form connecting links between the oocyte and both intermediate and pyriform cells. The establishment of intercellular bridges between pyriform cells and the oocyte precedes the complete differentiation of the former, which excludes the possibility that the fusion between pyriform cells and oocyte occurs only after these cells are completely differentiated.

In still larger follicles (up to 2 mm in diameter), during the degeneration of the pyriform cells, the occurrence, inside the bridges, of mitochondria and other cytoplasmic material suggests that these cells at the end of their function transfer their contents into the oocyte.
Cell motility in fibroblast aggregates
Authors: Armstrong Margaret T. , Armstrong Peter B.
Published: April 2021

The stable arrangements of cells in tissues and organs require that most tissue cells, whatever their inherent abilities for active pseudopod-directed locomotion, remain confined to the boundaries of their parent tissues and organs for the lifetime of the organism. Contact inhibition of motility represents a potential mechanism for immobilizing cells in tissues and thus in promoting positional stability. In order to assess the effectiveness of contact inhibition in immobilizing cells in 3-dimensional tissue-like masses, spherical aggregates of chick heart, sclera and skin fibroblasts were fused with tritiated thymidine-labelled aggregates of the identical cell type. After being placed in contact, the 2 aggregates cohere and broaden the area of mutual contact to form a single aggregate with a planar interface between the two. Mobility of cells was detected by the migration of labelled cells across the interface and into the unlabelled aggregate. Based on measurements of distances moved in day-old aggregate pairs, it was found that fibroblasts moved up to 17 cell diameters and up to 36 % as far in solid tissue masses as in monolayer culture under optimal conditions for directed migration.
Genetic analysis of developmental mechanisms in hydra: VI. cellular composition of chimera hydra
Authors: Sugiyama Tsutomu , Fujisawa Toshitaka
Published: April 2021

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.
Phosphatases and differentiation of the golgi apparatus
Authors: Dauwalder Marianne , Whaley W. G. , Kephart Joyce E.
Published: April 2021

Cytochemical techniques for the electron microscopic localization of inosine diphosphatase, thiamine pyrophosphatase, and acid phosphatase have been applied to the developing root tip of Zea mays. Following formaldehyde fixation the Golgi apparatus of most of the cells showed reaction specificity for IDPase and TPPase. Following glutaraldehyde fixation marked localization of IDPase reactivity in the Golgi apparatus was limited to the root cap, the epidermis, and the phloem. A parallelism was apparent between the sequential morphological development of the apparatus for the secretion of a polysaccharide product, the fairly direct incorporation of tritiated glucose into the apparatus to become a component of this product and the development of the enzyme reactivity.

Acid phosphatase, generally accepted as a lysosomal marker, was found in association with the Golgi apparatus in only a few cell types near the apex of the root. The localization was usually in a single cisterna at the face of the apparatus toward which the production of secretory vesicles builds up and associated regions of what may be smooth endoplasmic reticulum. Since the cell types involved were limited regions of the cap and epidermis and some initial cells, no functional correlates of the reactivity were apparent. Despite the presence of this lysosomal marker, no structures clearly identifiable as ‘lysosomes ‘were found and the lack of reaction specificity in the vacuoles did not allow them to be so defined.
Division and dna synthesis in the kinetoplast of Crithidia Fasciculata
Authors: Anderson W. , Hill G. C.
Published: April 2021

In Critliidia fascicuJata division of the kinetoplast occurs prior to karyokinesis. Kinetoplast division involves the lateral replication of the nucleoid, and the subsequent constriction and ‘pinching off’ of the nucleoid and mitochondrial components. Two subunits are produced.

DNA synthesis in the kinetoplast and the nucleus is overlapping but asynchronous. Experiments for short labelling times indicate that the kinetoplast S period either precedes, succeeds or is simultaneous with the nuclear period of DNA synthesis. The kinetoplast divides in a manner in which some radioactivity is transmitted to each unit.
Compartimentage des activités enzymatiques dans le spermatozoïde de certains mollusques gastéropodes: I. localisation des déshydrogenases
Authors: Personne P. , Anderson W.
Published: April 2021

Les activités succinate tétrazolium réductasique et NADH2 tétrazolium réductasique one été mises én évidence á l’aide de la cytochimie ultrastructurale dans les spermatozoides de quelques Gastériopodes Pulmonés, Testacelle et Escatgot. Ces activités enzymatiques se localisent dans un espace fort restreint du derivd mitochondrial, l’hélice secondaire, qui correspond ácequi subsists de la matrice des mitochondries originelles. La ‘métamorphose’ mitochondriale a abouti á uneségregation des activites déshydrogénasiques dans une portion spécialisée du dérivé mitochondrial, le compartiment matriciel.

By electron-microscope cytochemistry, succinate- and NADH2-tetrazolium reductase activities have been demonstrated in spermatozoa of the pulmonate gastropods, Testacella and Helix. Enzyme reaction product is restricted to the mitochondrial compartment named the secondary helix; this compartment is derived from the matrix of typical mitochondria. ‘Mitochondrial metamorphosis’ during spermiogenesis accomplishes the segregation of dehydrogenases to this matrical compartment.
Changes in thrombocyte ultra-structure during clot retraction*
Authors: Shepro D. , Belamarich F. A. , Merk F. B. , Chao F. C.
Published: April 2021

The contraction of the entire thrombocyte appears to be a primary factor in the retracting mechanism of dogfish (Musteltis canis) in vitro blood clots. Microtubules probably account for the condensation and lobation of the nucleus, and the impetus for cytoplasmic contraction appears to be dependent upon the grouping of microfibres of dimensions difficult to measure. These microfibres show a striking resemblance to materials stored within adjacent vesicles. A second type of fibre (60 A in diameter) extends from the bases of pseudopods into the adjacent matrix. There also appears to be partial engulfment of an extracellular amorphous material by the plasma membrane. The ultrastructure of the thrombocyte during clot retraction shows some striking similarities to the mammalian platelet under similar conditions, and leads one to believe a phylogenetic relationship exists between these haemostatic cells.
Non-nucleolar transcription complexes of rat liver as revealed by spreading isolated nuclei
Authors: Harper Francis , Puvion-Dutilleul Francine
Published: April 2021

Miller’s technique was applied to isolated nuclei of rat liver. Both the usual nucleolar and non-nucleolar transcription complexes were visualized. In addition, an unusual type of putative non-ribosomal transcription unit was revealed. It was characterized by a high density of the lateral ribonucleoprotein (RNP) fibrils. Although these particular units exhibited a regular increase of fibril lengths, the length of the transcript-covered deoxyribonucleoprotein (DNP) fibres and the morphological aspect of the RNP fibrils distinguished them from the nucleolar ‘Christmas-tree’ -like figures. The linear and granular configuration of the transcripts and the absence of terminal knobs made them similar to non-nucleolar nascent RNP fibrils.
High-voltage electron microscopy reveals new components in the axonemes and centroplast of the centrohelidian Raphidiophrys ambigua
Authors: Riedek Conly L.
Published: April 2021

A high-voltage electron microscope was used to study the structure of the centroplast and axonemes in the ccntrohclidian Heliozoan Raphidiophrys ambigua. In Raphidiophrys the microtubules (Mrs) of each axonemc are arranged so that they describe the apices of an array of hexagonally shaped prisms and all axonemes originate from a centroplast located near the centre of the cell. The centroplast was found to consist of 3 components: (1) a tripartite central disk, (2) a sphere of electron-opaque material, approximately 0·75μm in diameter, which immediately surrounds the central disk, and (3) a slightly less electron-opaque centroplast shell, approximately 2–3 μm in diameter, which consists primarily of hitherto undcscribed components associated with the proximal 1–2μm of each axonemal base. The new axonemal components described in this study include: (1) a 20-nm rod positioned in the centre of each hexagonal prism of Mts comprising the axonemal pattern, and (2) an electron-opaque linkage material which connects each Mt of the axonemal pattern to its 4 nearest neighbours. Both of these structures are associated with the base of each axoneme within the centroplast shell, both form crossbridges with axonemal Mts, and both terminate at the periphery of the centroplast shell once the complete axonemal Mt pattern is established. It is suggested that these structures are involved in forming and maintaining the Mt pattern seen in the axopodia of Raphidiophrys.
Characterization of a cv-1 cell cycle ii. the role of cell-substrate attachment
Authors: Gershey Edward L. , D’Alisa Rose M.
Published: April 2021

The availability of synchronous cultures of untransformed CV-1 cells has allowed analysis of the role of cell-substrate attachment in cell cycle progression as well as the ability of serum and SV40 infection to override the requirement for cell-substrate attachment. Attachment to a solid substrate is required for progression through G1. Prevention of attachment results in cell cycle arrest 30 min after cytokinesis. Serum is required for attachment, but increasing the serum concentration from 2 to 20% does not enhance cell attachment, nor obviate its need for cell cycle progression. SV40 infection does not overcome the requirement of serum for attachment nor the need of attachment for normal cycling.
Inhibition of fibronectin-mediated adhesion of hamster fibroblasts to substratum: effects of tunicamycin and some cell surface modifying reagents
Authors: Butters Terry D. , Devalia Vinod , Aplin John D. , Hughes R. Colin
Published: April 2021

Using baby hamster kidney (BHK) fibroblasts we have studied the effect of tunicamycin, a specific inhibitor of protein glycosylation, on the ability of trypsinized cells to attach and spread onto fibronectin. Tunicamycin inhibited mannose incorporation into total acid-precipitable glycoproteins by at least 95 % while glucosamine and leucine incorporation were less or hardly inhibited. Hydrolysis and analysis of [3H]glucosamine-labelled glycoproteins showed that radioactivity incorporated into cells exposed to tunicamycin was present predominantly as galactosamine, presumably present in O-glycosidically linked glycan chains whose assembly is insensitive to the drug.

Treated cells exhibit reduced amounts of surface-associated fibronectin and adhere relatively poorly to plastic or collagen surfaces pre-coated with plasma or BHK cell-derived fibronectins at the minimum concentrations required to induce nearly quantitative attachment and spreading of untreated cells. Drug-treated cells do adhere and spread into a bipolar configuration on surfaces saturated with fibronectin. Cells treated with tunicamycin and then grown in the absence of the drug revert to a more normal behaviour, indicating that under certain conditions the effects of the drug are reversible.

Fibronectin-mediated spreading of trypsinized BHK cells is also inhibited by pre-treatment of cells with several non-penetrating reagents reactive with cell surface amino groups, namely pyridoxal phosphate, trinitrobenzene sulphonate and fluorescein 5-isothiocyanate. Analysis of surface substitution indicates a strong correlation between the extent of amino group substitution and inability of treated cells to interact with a fibronectin lattice.

While the extent of attachment under these conditions is normal, cells pretreated with a specific non-penetrating thiol reagent, p-chloromercuribenzenesulphonate fail to attach to fibronectin-coated culture dishes in a dose-dependent fashion, indicating that a biochemical distinction can be made between the processes of attachment and spreading.

We conclude that both N-glycosidically linked carbohydrate moieties of BHK cell surface glycoproteins and primary amine groups present in surface proteins or lipid head groups play a role in interactions of cells with fibronectin, leading to the formation and maintenance of a stable well-spread morphology. Both N-linked glycans and surface sulphydryl groups appear to be required for an attachment process which precedes spreading.
Calcium requirement for the secretion of peroxidases by plant cell suspensions
Authors: Sticher Liliane , Penel Claude , Greppin Hubert
Published: April 2021

Spinach (Spinacia oleracca, L.) cells in liquid culture release peroxidases. This release is reduced by EGTA and promoted by calcium ions. In a medium deprived of calcium the rate of peroxidase release is low, but immediately after addition of 1 mM calcium there is a sudden increase of the extracellular peroxidase activity. Extracellular calcium apparently penetrates into the cultured cells rather freely and, as a consequence, the rate of peroxidase secretion by these cells is directly correlated with the concentration of calcium in the medium. Magnesium, at twice the concentration used for calcium, has no effect on the release of peroxidases. Cells treated with Na azide, Na hydrogenarsenate or fluphenazine secrete less peroxidase upon addition of calcium.
Specific rosette formation between fibroblasts and erythrocytes
Authors: Rosen Steven D. , Singer Mark S. , Glabe Charles G. , Grabel Laura B.
Published: April 2021

Fibroblast-like cells (BHK-21, Swiss 3T3, SV40 3T3, L929) will form rosettes by binding to erythrocytes of specific types. The specificity of binding varies with the cell line. Monolayer cultures of spread baby hamster kidney (BHK) cells also bind erythrocytes with the same specificity exhibited by suspended cells. Our studies have concentrated on rosette formation between trypsinized-ox (TOx) erythrocytes and BHK cells. Extensive protease treatment of the BHK cells reduces their ability to bind TOx erythrocytes in a dose- and time-dependent manner, suggesting the involvement of protein in the binding site. Simple saccharides, and glycopeptides isolated from ox erythrocyte ghosts, do not inhibit rosetting. However, neutral glycosphingolipids from ox erythrocyte ghosts inhibit BHK-TOx rosetting, whereas neutral glycosphingolipids from non-rosettirig rabbit erythrocytes have no effect on rosetting. Furthermore, incorporation of ox glycolipids into guinea-pig erythrocytes causes these non-rosetting erythrocytes to adhere to BHK cells. These experiments suggest that specific glycolipids of the ox erythrocyte act as receptors for binding sites on the cell surface of BHK cells. These cellspecific binding sites may play a role in cell-surface events involving carbohydrate recognition.
Endoplasmic reticulum membrane isolated from small-intestinal epithelial cells: enzyme and protein components
Authors: Fujita Michiya , Ohta Hidehiko , Uezato Tadayoshi
Published: April 2021

Endoplasmic reticulum membrane-rich fraction was obtained by subfractionation of the light microsomes from mouse jejunal mucosal epithelial cells. It was marked by high glucose-6-phosphatase, NADPH-cytochrome c reductase, and NADH-cytochrome c reductase activities and low Na+,K+-ATPase activity. The enrichment of Na+,K+-ATPase was 180-fold higher in the basolateral membranes than in the endoplasmic reticulum membrane-rich fraction relative to glucose-6-phosphatase. The protein peak that was phosphorylated in a Na-dependent manner was prominent in the basolateral membranes while it was a minor peak in the endoplasmic reticulum membrane-rich fraction. Under the electron microscope the fraction was seen to be composed of homogeneous small vesicles with thin smooth membranes.
Fibronectin, intercellular junctions and the sorting-out of chick embryonic tissue cells in monolayer
Authors: Nicol A. , Garrod D. R.
Published: April 2021

A hierarchy of relative cohesiveness in monolayer of four different embryonic chick tissues was determined in a previous study. The hierarchy is: corneal epithelium ≏ liver parenchyma > pigmented epithelium > limb bud mesenchyme. The purpose of this paper is to describe the correlation between these adhesive relationships and, firstly, the amount of the adhesive glycoprotein, fibronectin, associated with the cells and, secondly, the morphology of their intercellular contacts. Fluorescent antibody staining of the cells with anti-fibronectin antibody showed that limb bud mesenchyme cells, the most weakly cohesive, had much more fibronectin than the other cell types. Thus there was a negative correlation between the amount of fibro-nectin and cellular cohesiveness. Analysis of intercellular contacts by electron microscopy showed that the most strongly cohesive cell types, corneal epithelium and liver parenchyma, were also those that possessed desmosomes.
Effects of dexamethasone on antigen expression and virus production in avian sarcoma virus-transformed cells
Authors: Wainberg M.A. , Silber L.P. , Kaufman M. , Cohen S.D.
Published: April 2021

We studied the effects of dexamethasone on virus production and antigen expression in avian retrovirus-infected chick embryo fibroblast (CEF) cells. The presence of specific receptors for this hormone in both normal and infected CEF cells could only be demonstrated using cultures that were at or near confluence. Dexamethasone, while not toxic to the cells, exerted a growth-retarding influence when employed at concentrations of 10(−8) or 10(−9) M. These same concentrations of hormone were inhibitory to virus production, elaboration of plasminogen activator activity, and antigen expression as determined in a sensitized lymphocyte stimulation assay. In contrast, infected cells that had been treated with hormone displayed enhanced reactivity in a specific immunofluorescence test.
The analysis of malignancy by cell fusion IX.* Re-examination and clarification of the cytogenetic problem
Authors: Evans E. P. , Burtenshaw M. D. , Brown B. B. , Hennion R. , Harris H.
Published: April 2021

Previous experiments with crosses between malignant and diploid mouse cells had shown that the reappearance of malignancy in hybrids in which it was initially suppressed was associated in some cases with the elimination of the chromosomes 4 derived from the diploid parent cell. In others, however, this did not appear to be so. In the present study, we have re-examined the role of the diploid chromosomes 4 in the suppression of malignancy using natural polymorphisms of the centromeric heterochromatin to identify the parental origin of the chromosomes 4 in the hybrid cells. We now find that the diploid chromosomes 4 are indeed involved in the suppression of malignancy in all the tumours that we have examined, which include a carcinoma, a melanoma, a sarcoma and a lymphoma. In all crosses between these malignant tumour cells and diploid fibroblasts, there is selective pressure in vivo against the chromosomes 4 derived from the diploid cell and in favour of the chromosomes 4 derived from the malignant cell. This indicates that the chromosomes 4 in all these tumours are in some way functionally different from the chromosomes 4 of the diploid fibroblast. Reappearance of malignancy in hybrids in which it was initially suppressed may result from a reduction in the number of diploid chromosomes 4, an increase in the number of malignant chromosomes 4, or both. The gene on the diploid chromosome 4 responsible for the suppression of malignancy acts in a dose-dependent manner.
Nucleolar fusion in wheat
Authors: Jordan E. G. , Martini G. , Bennett M. D. , Flavell R. B.
Published: April 2021

Two pairs of major nucleoli form in cells of the wheat variety Chinese Spring and these frequently fuse during the cell cycle. The volume of the nucleolus formed at the organizer on chromosome iB is approximately twice the volume of the nucleolus formed at the organizer on chromosome 6B. The volumes of fused nucleoli are distributed around the additive means expected if the nucleoli of the two different sizes fused in all possible combinations. Thus nucleolar volume but not the surface area is additive on fusion.

Four nucleoli can fuse to produce nuclei with nine different nucleolar patterns. All nine were found but the frequencies of the different fusion classes were different in different genotypes. The frequencies in euploid Chinese Spring and tetrasomie 3B showed small deviations from those expected if fusion between different nucleoli occurred with equal frequency, but in the aneuploids DT 5BL and DT sAL the fusion of heterologous nucleoli from chromosome 1B and 6B organizers occurred with a much higher frequency. It is suggested that the pattern of nucleolar fusion is determined in part by the position of the organizers in the nucleus, and their positions are altered in these ditelosomic stocks.