bluuebunny/crossref_metadata_2025 huggingface dataset:
Stylar peroxidase and incompatibility reactions in Petunia hybrida
Authors: Carraro Luisa , Lombardo Giuliana , Gerola F. M.
Published: April 2021

Self-, cross- and non-pollinated styles of Petunia hybrida were treated with 3-3’-diamino-benzidine for the ultrastructural localization of peroxidase activity. Wall peroxidases were absent in cross-pollinated styles, but they were detectable as an osmiophilic deposit on the cell walls of the outer portion of the transmitting tissue in self- and non-pollinated styles. The cell layer showing peroxidase activity was thicker in the self-pollinated styles than in the non-pollinated ones. In accordance with current hypotheses on the mechanism involved in pollen incompatibility process, it is suggested : (1) that wall peroxidases present in the cells of the outer portion of the transmitting tissue are involved in the gametophytic self-incompatibility of Petunia ; (2) that self-pollination causes an increase in the number of cells involved in the rejection process; (3) that non-pollinated styles, which are characterized by the presence of cell wall peroxidases in the outer portion of the transmitting tissue, are ‘prepared’ to a certain extent for the rejection of incompatible pollen tubes. The removal of peroxidase activity thus seems to be an important step in the compatible pollination process.
Homotypic pair formation during conjugation in Tetrahymena thermophila
Authors: Kitamura Akio , Sugai Toshiro , Kitamura Yasuko
Published: April 2021

In the ciliate Tetrahymena thermophila, conjugation has been believed to occur only between cells of different mating types. We found the formation of homotypic pairs during normal conjugation by using micronuclear morphological markers. Homotypic pairs formed preferentially during the first 10 min following the first pair formation and comprised about half of the pairs. These results suggest the involvement of mating-type non-specific adhesion of cells in the initial step of conjugation. Homotypic pairs apparently persist for at least 30 min and then separate into single cells. Homotypic pairs are also formed when conjugant pairs re-form after mechanical separation of heterotypic pairs. Five kinds of glycosidases, three kinds of proteases and phospholipase C showed no effect on either the formation of homotypic pairs or their separation. The relation between the mating-type substances and the molecules responsible for mating-type nonspecific adhesion of cells is discussed.
Cell surface glycoproteins change during gastrulation in Pleurodeles waltlh
Authors: Riou Jean-François , Darribère Thierry , Boucaut Jean-Claude
Published: April 2021

Identification of the cell surface glycoproteins is an essential requirement for elucidating the mechanisms that mediate intercellular adhesion and cell migration in gastrulating amphibian embryos. In our experiments the glycoproteins present at the surface of isolated cells at blastula and gastrula stages were labelled with 3H-labelled sodium borohydride. The procedure included the oxidation of either galactosyl and, or,.’V-acetylgalactosaminyl residues with galactose oxidase or sialic acid with sodium metaperiodate. The tritiated components were analysed by two-dimensional gel electrophoresis. On the surface of isolated embryonic cells, 23 glycoproteins have been identified. The most important observation was the labelling of 15 new glycoproteins during gastrulation. At the late blastula stage, eight glycoproteins containing galactosyl or N-acetyl-galactosaminyl residues are labelled, while 23 are labelled at the late gastrula stage. In other experiments, glycoproteins labelled by [3H] fucose or [3H] mannose or precipitated by concanavalin A(ConA)-, or wheat-germ agglutinin (WGA)-Sepharose were studied by two-dimensional gel electrophoresis in order to provide supplementary data on the synthesis and lectin-binding properties of major cell surface glycoproteins. It appears that approximately 100 different glycoproteins are revealed by these methods. Among them, 13 have been identified as major cell surface glycoproteins, 12 being labelled by [3H]mannose, four by [3H]fucose, 10 bearing an affinity for ConA and five for WGA. These 13 glycoproteins are synthesized throughout gastrulation without qualitative variation.
Biochemical aspects of bupivacaine-induced acute muscle degradation
Authors: Ishiura Shoichi , Nonaka Ikuya , Sugita Hideo
Published: April 2021

A single injection of a local anaesthetic, bupivacaine, into the soleus muscle of adult rat has a severe mytoxic effect, i.e. rapid dissolution of myofilaments and degradation of myofibrillar proteins shortly after injection. Increased lysosomal enzymes were observed in homogenates of affected muscle. The activity of potent proteolytic enzyme, cathepsins B and L (assayed against a new synthetic substrate succinyl-Tyr-Met-naphthylamide), gradually increased and reached a plateau value that was 11-fold greater than the control 48 h after bupivacaine injection. The chronological change in the activity of cathepsins B and L was reflected in the myofibrillar protein pattern in bupivacaine-treated muscle. To determine whether the increase in lysosomal peptide hydrolases is due to activation of muscle lysosomes or not, mononuclear cells were separated from both injected and control muscles. The activity of cathepsins B and L in the lysate from injured muscle was 180-fold higher than the control. Affinity-purified antibody was used to study the intracellular localization of cathepsin B by immunohistochemical procedures. The results were consistent with the biochemical observation that the main source of cathepsin B in muscle homogenates was infiltrated mononuclear cells. Therefore, we conclude that the increased lysosomal enzymes may be derived mainly from mononuclear cells (macrophages), not from muscle lysosomes, in bupivacaine-induced acute muscle degeneration.
Gland cells in Hydra: Cell cycle kinetics and development
Authors: Schmidt Tobias , David Charles N.
Published: April 2021

The proliferative capacity of gland cells in Hydra attenuata was investigated. The results indicate that both gland cell proliferation and interstitial cell differentiation to gland cells contribute to the maintenance of the whole population. On the basis of [3H]thymidine incorporation and nuclear DNA measurements, gland cells consist of at least three different populations. One population consists of rapidly proliferating cells with a cell cycle of about 72 h. These cells are distributed throughout the body column. In the lower gastric region there is a population of non-cycling cells in G2 while in the upper gastric region there is a population of noncycling cells in G1. About half the G1 population becomes a new antigen, SEC 1, which is typical of mucus cells.
Change in the rate of CO2 production in synchronous cultures of the fission yeast Schizosaccharomyces pombe: A periodic cell cycle event that persists after the DNA-division cycle has been blocked
Authors: Novak B. , Mitchison J. M.
Published: April 2021

CO2 production has been followed by manometry in synchronous and asynchronous cultures of Schizosaccharomyces pombe prepared by elutriation from the same initial culture. The rate of production follows a linear pattern in synchronous cultures with a rate change once per cycle at the time of cell division. This pattern is most clearly shown in oscillations of the difference between values of the second differential (acceleration) for the synchronous and asynchronous cultures. The association between the rate change and the time of division is maintained during growth speeded up in rich medium and slowed down in poor medium and at lower temperature. It is also maintained after a shift-up in temperature. Results with wee mutants suggest that the association is with the S period rather than division itself. The rate and acceleration of CO2 production are approximately proportional to cell size (protein content) in asynchronous cultures.

When synchronous cultures of the temperature-sensitive mutants CdC 2.33 and CdC 2.33 wee 1.6 are shifted up to the restrictive temperature, the DNA-division cycle is blocked. The oscillatory pattern of CO2 production, however, continues for one to two cycles until the acceleration reaches a constant value, after which the oscillations are undetectable. This point is reached later in the double mutant and there is a phase difference in the oscillations compared to those in the single mutant. With both blocked mutants the ‘free-running’ oscillations are about 15 % shorter than the normal cycle time. There are well-known examples of such oscillations in eggs but they are rare in growing systems.
Cytoskeletons from a mutant of Dictyostelium discoideum with flattened cells*
Authors: Claviez M. , Brink M. , Gerisch G.
Published: April 2021

Development of a mutant of Dictyostelium discoideum, HG403, is described whose cells spread strongly on a substratum. Although the mutant cells were less clearly polarized into the front and rear ends, and usually less extensively elongated than wild-type cells, their aggregation pattern was only slightly less regular. Cells of the mutant responded well to cyclic AMP by chemotaxis, although their capability of stabilizing cell shape and maintaining dominance of a single moving front appeared to be reduced. Mutant HG403 proved to be ideal for the preparation of cytoskeletons in which the organization of the microtubular system, the network of filaments between them, the dense texture of the microfilament network at the periphery of the cells, as well as the bundling of microfilaments in spike-like extensions, could be observed.
Development of microtubule capping structures in ciliated epithelial cells
Authors: Portman R. W. , Lecluyse E. L. , Dentler W. L.
Published: April 2021

Although capping structures are present at the tips of microtubules in both growing cilia and mature cilia, previous work has not determined the time of cap formation. The results reported here reveal that the large caps of mature palate cilia appear in cilia with lengths as short as 1·75 μm. In the growing palate cilium, a diskshaped plate is formed at the tip during the first gm of growth. As the cilium elongates to 1·5–2·0μm, a small plate forms underneath the disk-shaped plate that gives an asymmetrical appearance to the whole cap structure. The structure of the cap is complete in cilia longer than 2·0 μm. The hair-like structures that form the extraciliary crown appear on the membrane at the ciliary tip at the same time as the mature cap is forming. The formation of a cap structure is discussed in relation to microtubule assembly during ciliogenesis.
Periodic cell cycle changes in the rate of CO2 production in the fission yeast Schizosaccharomyces pombe persist after a block to protein synthesis
Authors: Novak B. , Mitchison J. M.
Published: April 2021

CO2 production has been followed by manometry in synchronous and asynchronous control cultures of Schizosaccharomyces pombeprepared by elutriation from the same initial culture. Earlier results showed a periodic change in the rate of production, which took place once per cell cycle. These changes were most clearly shown as oscillations in the difference between values of the second differential (acceleration) for the synchronous and asynchronous cultures. This paper shows that the oscillations continue for atleast three cycles in the presence of cycloheximide (with and without chloramphenicol). Protein synthesis is virtually absent and there is no cell division. The control of this metabolic oscillation is therefore not directly dependent on translation. The period of the oscillation under these conditions is about 60 % of the normal cycle time.
Incompatibility in Populus: Structural and cytochemical characteristics of the receptive stigmas of Populus alba and P. nigra
Authors: Villar M. , Gaget M. , Said C. , Knox R. B. , Dumas C.
Published: April 2021

Structural and cytochemical characteristics of stigmas of Populus alba (section Leuce) and P. nigra (section Aigeiros) have been studied to provide an understanding of the cell biology of the interspecific incompatibility reactions between these two species. In addition to specific morphological characteristics, stigma surfaces differ in the presence of an exudate studied by ultrastructural and stigma print techniques. P. nigra shows features of a dry-type stigma covered by a pellicle, whereas P. alba has a copious exudate typical of a wet-type stigma that contains unsaturated lipids.
Signal-Induced Reorganization Of The Microtubular Cytoskeleton In The Ciliated Protozoon Euplotes Octocarinatus
Authors: Jerka-Dziadosz Maria , Dosche Christine , Kuhlmann Hans-Werner , Heckmann Klaus
Published: April 2021

A predator-released substance induces the freshwater ciliate Euplotes octocarinatus to undergo, within a few hours, a drastic change in cell form that makes engulfment by the predator more difficult or even impossible. During this transformation, the outline of the cell changes from ovoid to circular and the size increases considerably. The cells cease dividing while they transform, but later continue divisional morphogenesis and maintain the circular form for many cell generations if the concentration of the predator factor is maintained

The microtubular cytoskeleton of Euplotes was studied by transmission electron microscopy of cells from which the cytoplasm had been extracted by mild treatment with Triton X-100. This procedure increased the visibility of microtubules, especially single microtubules located in the endoplasm. In transformed cells, a considerable increase in number of microtubular triads on the dorsal and ventral surfaces and the appearance of extra single microtubules between the dorsal triads was observed. However, certain interconnected groupings of microtubules located on the dorsal surface were greatly diminished after transformation. Intracytoplasmic microtubules were also more abundant in the enlarged cells than in the untreated ovoid ones. The spacing and general pattern of microtubules, however, appears to be the same in untreated and treated cells.

We conclude from these observations that the transformation of Euplotes cells from their typical ovoid form into the enlarged circular form is accompanied by the mobilization and utilization of microtubules already present in subcortical regions and an assembly of new microtubules needed for support of the expanding cell cortex.
Distribution of an endogenous β-galactoside-specific lectin during foetal and neonatal rabbit development
Authors: Catt James W. , Harrison F. Lynne , Carleton J. Susan
Published: April 2021

The tissue concentration of an endogenous β-galactoside-specific lectin is developmentally regulated in rabbit tissues during foetal and neonatal development. Immunoassay data and localization studies both indicate that the lectin is particularly associated with late embryonic and early postnatal development. No lectin could be detected in embryos prior to 21 days of gestation, whereas many tissues showed an increase in lectin around the time of birth. It is likely that in most tissues the high concentrations of lectin are largely due to increased synthesis by fibroblasts, which are particularly abundant and active in connective tissue during the extensive tissue reorganization taking place at this time. The lectin appears to be synthesized by other differentiated cell types also, notably myoblasts, alveolar cells and erythroblasts. The peak of lectin concentration seen in foetal liver probably reflects lectin associated with foetal erythropoiesis. The rabbit lectin has a low specific activity but its tissue concentration is correspondingly higher than lectin concentrations in other mammals. This conservation of total lectin activity suggests a fundamental role for the lectin dependent upon its saccharide binding activity. This and other indirect evidence suggests that these lectins are involved in the synthesis, secretion or organization of extracellular matrix components.
General electromagnetic theory of total internal reflection fluorescence: the quantitative basis for mapping cell-substratum topography
Authors: Gingell D. , Heavens O. S. , Mellor J. S.
Published: April 2021

Total internal reflection fluorescence (TIRF) has recently been used to look at the contacts made between cells and a glass surface on which they are spread. Our method utilizes the fluorescence of a water-soluble dye that acts as an extracellular aqueous volume marker. Fluorescence is stimulated by the short-range electric field near the glass surface that exists under conditions of total internal reflection. Since fluorescence is normally generated beneath a spread cell and not beyond it, the fluorescence of the image is related to the size of the cell-glass water gap. The images obtained are remarkable for their detail, contrast and the absence of confusing granularity due to cytoplasmic heterogeneity, which is commonly seen in interference reflection (IRM) images.

We here develop a rigorous electromagnetic theory of total internal reflection in layered structures appropriate for cell contacts and apply it to quantitative TIRF. We show that: (1) TIRF, unlike IRM, can report cell-glass gaps in a way that is practically independent of the detailed physical properties of the cell; (2) TIRF is also far more sensitive than IRM for measuring cellglass water gaps up to ≈100 nm. These striking results explain the image quality seen by TIRF. As the initial step towards verifying our theory we show that measurement of the fluorescence stimulated by total internal reflection at a simple glass-water interface matches theoretical predictions.
Biochemical and ultrastructural data on Tetrahymena pyriformis treated with copper and cadmium
Authors: Piccinni E. , Irato P. , Coppellotti O. , Guidolin L.
Published: April 2021

The addition of copper (10 μgml−1) or cadmium (5 μgml−1) to the medium is well tolerated by Tetrahymena pyriformis GL. Both metals are accumulated by cells, cadmium to a greater extent than copper. The growth rate is not affected and from the micrographs it is evident that the ultrastructure is not altered by the treatments. After 3 days of culture the macronucleus contains dense masses of chromatin and numerous nucleolar fusion bodies. Granules, cytolysomes and many food vacuoles are present in both control and treated cells. Cadmium induces the formation of a chelating protein; the amino acid analyses and the ultraviolet spectrum indicate that it is similar to the metallothionein isolated by higher organisms.

The molecular weight of native protein is about 27 000. After treatment by sulphitolysis or oxidation we obtained a peak of molecular weight at about 6000.

The treatment with copper does not appear to induce metallothioneins or other chelatins. The high tolerance of Tetrahymena towards cadmium is believed to be due to the formation of a Cd-Zn metallothionein.

The different chelating proteins induced by copper and cadmium in other groups of Protozoa and the different detoxification mechanisms present in these organisms are discussed.
Hydrostatic pressure in epidermal cells is dependent on ca-mediated contractions
Authors: Strohmeier Renate , Bereiter-Hahn Jürgen
Published: April 2021

Volume/osmotic pressure relationships were compared in Xenopus epidermal cells treated with the calcium antagonist lanthanum and in control cells. In lanthanum-treated cells the volume was found to be proportional to the reciprocal of the osmotic pressure in the hypotonic range, but not in the control cells. This difference is interpreted as being caused by contractions of the actomyosin system in control cells, which require external calcium. On the basis of the different slopes of the measurements under these two conditions the contractile force of the cells in isotonic conditions was calculated to be 0-96× 105 Nm-2.

The observation that in hypotonic media the cell body is enlarged in the direction of movement provides evidence that the cell body/lamella transition region is the part of the cell that contracts most during locomotion.

By analysing cell speed in media with varying osmotic pressures, the relationship between internal pressure and cell locomotion was revealed.
Development of macrociliary cells in Beroë II. Formation of macrocilia
Authors: Tamm Sidney L. , Tamm Signhild
Published: April 2021

Two patterns of macrociliary growth occur in Beroë. Early differentiation described previously (Tamm & Tamm, 1988) leads to the first pattern of ciliogenesis. A tuft of 10–20 single cilia initially grows out from basal bodies that have migrated to the cell surface and are axially aligned. Ciliary membranes then begin to fuse along their length, except at the base, resulting in thicker groups of cilia on each cell. Progressive fusion of ciliary membranes, together with addition and elongation of new axonemes, finally results in mature macrocilia, 5 μm thick and 40 μm long, enclosed by a single membrane distally. The second pattern of ciliogenesis begins with the simultaneous appearance of several hundred ciliary buds on the apical surface. The short cilia possess individual membranes with bulbous tips, and are not axially aligned. Subsequent elongation is accompanied by progressive fusion of neighbouring ciliary membranes, except at the base, leading to flat-topped ‘stumps’ surrounded by a single membrane distally. Further elongation then proceeds asymmetrically within each stump. Axonemes on the aboral side of the macrocilium stop elongating, while those towards the oral side increase progressively in height, resulting in a slanted profile. Basal feet and central-pair microtubules are now uniformly aligned. Unequal elongation of axonemes on the oral and aboral sides of the macrocilium continues until the macrocilium resembles a lobster’s claw, with a long slender shaft projecting from a broad base. Finally, the polarity of unequal growth reverses: the shorter axonemes on the aboral side elongate and almost catch up with the longer ones on the opposite side, resulting in a mature macrocilium of uniform diameter. The unusual membrane architecture of the macro-cilium is thus a consequence of selective fusion of the distal regions of originally separate ciliary membranes. The polarized, asymmetrical growth of axonemes on the two sides of the macrocilium illustrates a remarkable control of microtubule elongation at the subcellular level.
Fertilization in ascidians: Apical processes and gamete fusion in Ciona intestinalis spermatozoa
Authors: Fukumoto Makoto
Published: April 2021

This paper describes the fine structure of the spermatozoan apex and its morphological changes during the process of fertilization in Ciona intestinalis.

At the apex of the head an acrosome is present in the form of a flattened vesicle containing moderately electron-dense material with an electron-dense plate in its centre. Contiguous to the acrosome, an apical substance is located in the anterior-most tip of the sperm head.

The spermatozoa that bind to and penetrate the chorion of both normal and caffeine-treated eggs have an intact acrosome and do not show an observable alteration of the plasmalemma enclosing the apex of the head. On the other hand, spermatozoa in the perivitelline space of both normal and caffeine-treated eggs lack an acrosome. Instead of an acrosome, apical processes are observed at the apex of the spermatozoa in the perivitelline space of both normal and caffeine-treated eggs. Gamete fusion seems to occur between the egg membrane and some of these apical processes at the tip of the sperm head. The apical process reported here is thought to be analogous to the acrosomal process in other marine invertebrates. The apical processes that are induced in the perivitelline space have not been previously described in ascidians.
Aggregative behaviour of embryonic chick cells in the presence of anti-bodies directed against actomyosins
Authors: Kemp R. B. , Jones B. M. , Gröschel-Stewartf U.
Published: April 2021

Skeletal muscle and liver tissue from 9-day-old chick embryos were dissociated into separate cells using 0·25 % (w/v) crude trypsin. The effect of rabbit anti-actomyosin sera on the aggregation of these cells was estimated by the gyratory shaker and turbidimetric methods. Studies were also undertaken on the ability of fluorescein isothiocyanate-labelled rabbit anti-uterine actomyosin serum (FITC-labelled anti-UAM) to stain the cell surface and on the type specificity and species specificity of rabbit anti-chicken actomyosin sera.

Antisera against chicken gizzard smooth-muscle actomyosin (anti-GAM) and against chicken pectoralis striated muscle actomyosin (anti-PAM) both gave single precipitin bands with their respective actomyosins on diffusion through agar. The antisera neither reacted with their heterologous actomyosin nor with gizzard tropomyosin; they were type-specific. Serial sections of human cervix were stained in a similar pattern with both anti-UAM and anti-GAM, showing that anti-smooth muscle actomyosin sera were not species-specific. The fibrocytes of the human umbilical cord and human platelets were stained by FITC-labelled anti-UAM serum but not by labelled anti-human PAM.

The aggregation of muscle and liver cells over a 24-h period in the presence of antisera against human or chicken PAM was not significantly different from the controls incubated on a gyratory shaker in Eagle’s minimum essential medium (MEM) containing 10% (v/v) rabbit non-immunized serum (NIS) or calf serum. However, anti-UAM and anti-GAM inhibited both the rate of aggregation of liver and muscle cells and the size of aggregates attained in 24 h. This effect could not be simulated with specific rabbit antisera against human plasma proteins.

The globulin-enriched fraction of anti-GAM markedly inhibited the aggregation of liver and muscle cells in a range of concentrations between 50 and 500 μg per 2×106 cells/ml Eagle’s MEM. In contrast, the aggregation of cells incubated with globulin-enriched anti-PAM was similar to the controls. The addition of anti-GAM globulins at 1 or 2 h to muscle cells rotated by the turbidimetric method reduced the aggregative competence of the cells over the remainder of a 4-h period.

The possibility that the inhibitory effect of anti-UAM and anti-GAM on cell aggregation is due to impurities in the antisera or to a general reaction with cell surface ATPases is discussed but, in the light of evidence, rejected in favour of a reaction between the antisera and an actomyosin of the smooth-muscle type at the cell surface.
The fine structure of Gonyaulax polyedra, a bioluminescent marine dinoflagellate
Authors: Schmitter Ruth E.
Published: April 2021

An electron-microscope study of Gonyaulax polyedra, a holophytic marine dinoflagellate which is bioluminescent, has revealed 2 structures not previously described in free-living dino flagellates: a polyvesicular body occurring at intervals along the cell’s periphery, and a large spherical body which may function in intracellular digestion. Coated vesicles were found in the nuclear-Golgi region. Chloroplast lamellae were widely and regularly spaced in portions of the chloropla8t8 at the interior of cells harvested during the light period of the culture cycle. The lamellae were closer together and not so regularly arrayed in peripherally located chloroplast branches, or in chloroplasts harvested during the dark period. Other aspects of the ultrastructure of G. polyedra are described and discussed.
The neuron types of the glomerular layer of the olfactory bulb
Authors: Pinching A. J. , Powell T. P. S.
Published: April 2021

The neurons of the glomerular layer of the rat olfactory bulb have been studied using Nissl staining and Golgi-Kopsch impregnation in light microscopy to define the size, shape and morphological features of individual cell somata, dendrites and axons; these have been correlated with electron-microscopic material in which fine-structural characteristics were also noted for each cell type, particularly synaptic specializations. Three neuron types are described: the external tufted and periglomerular cells of classical microscopy, and additional, superficial short-axon cells; a description of the glomerular arborizations of the mitral and deep tufted cells is also included. The tufted and mitral cells show large, non-spiny glomerular dendritic arborizations, having terminal varicosities, the external tufted cells being more limited in their branching than the deeper cells. External tufted cells have large somata and abundant cytoplasm containing stacks of Nissl material; their main dendrites are characterized by pale cytoplasm and a regular array of neurotubules. Reciprocal dendro-dendritic and somato-dendritic synapses are commonly found, the tufted/mitral cells containing spherical vesicles and contacting by means of asymmetrical membrane thickenings; the other profile involved is a gemmule containing large flattened vesicles and associated with a symmetrical thickening. The periglomerular cells are smaller, with a spiny glomerular arborization, as well as some other dendrites; all the dendrites of these cells tend to be of irregular outline. They have a dark nucleus and very little somatic cytoplasm; somatic and dendritic appendages are common and often contain large flattened vesicles. Synapses oriented from the dendritic shaft or gemmule also show such vesicles, invariably associated with symmetrical thickenings. The superficial short-axon cells are characterized by the entirely periglomerular distribution of their dendrites, which are varicose and rarely branch. Of intermediate soma dimensions, but containing dispersed Nissl material, these cells and their stem dendrites show no regions that can be designated as presynaptic.

Features of axon initial segments, axo-somatic and axo-dendritic synapses are also described for each cell, as well as some unusual glial relationships. Reasons are adduced for relating the superficial short-axon cell to the axon terminal type containing small flattened vesicles, as well as for considering that the external tufted and periglomerular cells show the same synaptic specializations at their axon terminals as at their dendritic and somatic synapses. The cells of the glomerular layer are compared with those of the deeper layers of the bulb and atypical synaptic specializations discussed; some physiological implications of these findings are considered.
The neuropil of the periglomerular region of the olfactory bulb
Authors: Pinching A. J. , Powell T. P. S.
Published: April 2021

The periglomerular region of the olfactory bulb, apart from containing the somata and stem dendrites of the cells contributing to the glomeruli, is the sole region of distribution of the periglomerular cell thin dendrites and the short-axon cell dendrites. It is also the major site of termination of all axons to the glomerular layer except the olfactory axons — i.e. tufted cell collaterals, periglomerular cell and short-axon cell axons and centrifugal fibres. Its characteristic neuropil has been studied with the electron microscope to define the cells of origin of the types of neuronal process and their synaptic relationships. Three types of axon terminals have been found: those with spherical, large flattened and small flattened vesicles, which are deduced to derive from tufted cell collaterals or centrifugal fibres, periglomerular cell and short axon-cell axons respectively; those with spherical vesicles are consistently associated with asymmetrical membrane thickenings and those with either type of flattened vesicles with symmetrical thickenings. The thin periglomerular cell dendrites are very irregular and often have a somewhat dense cytoplasm, rich in ribosomes; they may become extended into very attenuated glia-like sheets that surround the mitral or tufted cell stem dendrites, from which they may receive synaptic contacts. Such dendrites also receive some synapses from all 3 types of axon in the periglomerular region. The short-axon cell dendrites are thick and varicose and show no sign of synaptic specialization oriented from them; they have few spines but receive many asymmetrical-type synapses on their shafts. Both axon terminal types synapsing with symmetrical thickenings are also found on the shafts. The evidence obtained from the study of normal material is summarized and the various cellular roles considered. In the light of observations on the olfactory bulb, it is suggested that dendrites may be divided into 2 major classes: those that only receive synapses (Class A) and those that make synaptic contacts as well as receiving them (Class B). Further comparisons with the deep layers of the bulb and physiological implications are discussed.
Cell migration in wool follicles of sheep
Authors: Chapman R. E.
Published: April 2021

The migration of cells in wool follicles was studied by autoradiography of skin biopsies taken at half-day intervals from 2 to 5 days after intradermal injections of tritiated thymidine in 8 Corriedale sheep on different planes of nutrition. Cell migration rates were not the same in all follicles. Therefore, the shortest and longest times for cells to migrate to defined levels in the follicles were determined. Cells of the inner root sheath moved up the proximal part of some follicles ahead of contemporaneously formed cells in the fibre. Subsequently, cells in the fibre reached the level where the fibre attained its definitive form in about 2·5–4 days. Cell migration also occurred in the outer root sheath, and sloughing of both outer and inner root sheath cells was observed. In the distal half of the follicles, cells of the root sheaths and of the fibre migrated at similar rates, which suggested that the inner root sheath and fibre were carried through the upper part of the follicle by migrating cells of the outer root sheath.

Cell migration times were about 0·5 day less in fat sheep on large and moderate food intakes than in lean sheep on restricted intakes.
Effects of synthetic polycations on leucine incorporation, lactate dehydrogenase release, and morphology of human umbilical vein endothelial cells
Authors: Morgan David M. L. , Clover Julie , Pearson Jeremy D.
Published: April 2021

Naturally occurring cationic proteins secreted by human granulocytes have pro-inflammatory effects including induction of increased vascular permeability and oedema, which are likely to be mediated by damage to vascular endothelium. Synthetic cationic polyamino acids have been shown to exert similar inflammatory effects in vivo. We have therefore used a range of synthetic polycationic amino acids to investigate the characteristics required to cause endothelial cell damage, assessed by in vitro inhibition of leucine incorporation into macromolecules by human umbilical vein endothelial cells (HUVEC) in culture. Exposure of HUVEC to 20 nM–2 μM cationic polypeptides of similar Mr(av) (≈40000) in the presence of 20% serum produced a dose-dependent inhibition of [3H] leucine incorporation by polymers of ornithine, arginine or lysine. Similar results were obtained using [3H]thymidine. Neutral or anionic polypeptides of similar Mr were without effect. The molar potency of polylysines increased over the range Mr 40000–120000, while polylysines of Mr(av; <25 000 had no effect. In the absence of serum, inhibition occurred more rapidly and at lower doses. Inhibition of leucine and thymidine incorporation was time-dependent, e.g. exposure to 800 nM-polylysine, Mr (av) 90 000, led to progressively increasing inhibition that was complete after 24 h exposure, and was irreversible. The effects of polycations could not be blocked by pretreatment of the cells with polyanions. Precoating of the culture surface with polylysines had no effect on leucine incorporation by HUVEC or their subsequent response to polylysines in solution. Exposure to the peptide Arg-Gly-Asp-Ser inhibited incorporation by 30% but did not increase susceptibility to polylysine. The extent of inhibition of radiolabel incorporation was correlated with changes in cell morphology and release of a cytoplasmic enzyme (1actate dehydrogenase). We conclude that cationic proteins can exert significant, essentially irreversible, cytotoxic effects on endothelium, the magnitude of which depends on the density of cationic residues interacting with the cell and the time of exposure to the polycation. The use of synthetic amino acid polymers in such a model system provides a means of investigating the characteristics of cationic polypeptides that affect endothelial cells and the nature of the responses induced.
Immunochemical and immunocytochemical identification of a myosin heavy chain polypeptide in Nicotiana pollen tubes
Authors: Tang Xlaojing , Hepler Peter K. , Scordilis Stylianos P.
Published: April 2021

A myosin heavy chain polypeptide has been identified and localized in Nicotiana pollen tubes using monoclonal anti-myosin antibodies. The epitopes of these antibodies were found to reside on the myosin heavy chain head and rod portion and were, therefore, designated anti-S-1 (myosin S-l) and anti-LMM (light meromyosin). On Western blots of the total soluble pollen tube proteins, both anti-S-1 and anti-LMM label a polypeptide of approximately 175 000Mr. Immunofluorescence microscopy shows that both antibodies yield numerous fluorescent spots throughout the whole length of the tube, often with an enrichment in the tube tip. These fluorescent spots are thought to represent vesicles and/or organelles in the pollen tubes. In addition to this common pattern, anti-S-1 stains both the generative cell and the vegetative nuclear envelope. The different staining patterns of the nucleus between anti-S-1 and anti-LMM may be caused by some organization and/or anchorage state of the myosin molecules on the nuclear surface that differs from those on the vesicles and/or organelles.
Activation of the hprt gene on the inactive X chromosome in transformed diploid female Chinese hamster cells
Authors: Grant Stephen G. , Worton Ronald G.
Published: April 2021

Treatment with 5-azacytidine, a potent inhibitor of DNA methylation, was used to induce activation of the selectable hprt gene on the inactive X chromosome in a diploid female Chinese hamster cell line. The transformed, stably diploid cell line F3B was selected in media containing the lethal purine analogue 6-thioguanine, to generate a phenotypically HPRT− mutant, F3BT1, of presumed genotype hprt − /hprt-+), where (+) represents the presumably wild-type allele on the inactive X chromosome. Treatment of F3BT1 with 5-azacytidine resulted in phenotypic reversion to HPRT + at a frequency greater than 10−3. Similar treatment of 6-thioguanine-resistant control lines derived from male cells, or from CHO (which has no inactive X chromosome), had no effect on the frequency of phenotypic reversion, indicating that activation of the hprt-+) allele, rather than reversion of the hprt− is responsible. This conclusion is substantiated by documentation of the low mutagenic capacity of 5-azacytidine in this system. Proof that the hprt-+) allele can be activated by 5-azacytidine treatment was obtained in somatic cell hybrids in which hprt gene products from the active and inactive X chromosomes could be distinguished by isoelectric focusing. Our results demonstrate that X-linked gene activation associated with generalized DNA demethylation occurs with high frequency in transformed diploid Chinese hamster cells.
Anionic site behavior in Leishmania and its role in the parasite—macrophage interaction
Authors: Saraiva E. M. B. , Vannier-Santos M. A. , Silva-Filho F. C. , Souza W. De
Published: April 2021

The behavior of cationized ferritin (CF) binding sites on the surface of Leishmania mexicana amazonensis (amastigotes, infective and non-infective promastigotes) and their participation in the interaction with macrophages were evaluated. Glutaraldehyde-fixed parasites treated with CF present a uniform labelling over the whole cell surface. However, living parasites displayed CF patches and caps. Capping was usually seen towards the anterior (flagellated) portion of the cells, where shedding phenomena took place. These processes were inhibited by sodium azide but not by low temperature (4°C). CF treatment of non-infective promastigotes led to an increase in their uptake by macrophages, whereas the uptake of amastigotes or infective promastigotes was not significantly altered. The effect of CF on the parasite surface charge was analyzed by whole-cell microelectrophoresis. The mean electrophoretic mobility (EPM) of non-infective promastigotes was decreased by 26%, while once again the other parasite forms were not significantly affected. Transmission electron microscopy of mouse peritoneal macrophage cultures, fixed after interaction with CF-labelled parasites, revealed that both amastigotes and infective promastigotes quickly removed bound CF. Therefore CF was seen neither in parasite-macrophage attachment areas nor in parasitophorous vacuoles. On the contrary, non-infective promastigote-macrophage attachment areas were remarkably large and preferentially comprised CF-labelled membranes. These results strongly suggest an important participation of cell surface anionic sites in the L. mexicana amazonensis-macrophage interaction.
The effect of antisense RNA to fibronectin on the malignancy of hybrids between melanoma cells and normal fibroblasts
Authors: Steel Diana M. , Harris Henry
Published: April 2021

An expression vector containing a cDNA complementary to 1·3 kb of the 5’ coding sequences of the fibronectin gene in the antisense orientation with respect to its promoter was introduced by electroporation into hybrids between melanoma cells and normal fibroblasts in which malignancy was suppressed. Immunofluorescence analysis of clones transfected with the antisense cDNA showed a dramatic decrease in the amount of fibronectin on the cell surface compared to that seen on the surface of the untransfected hybrid cells or of cells transfected with fibronectin cDNA in the sense orientation or with the expression vector alone. Four out of five clones transfected with the antisense cDNA were highly tumorigenic, whereas transfectants containing either the sense fibronectin construct or the expression vector alone remained non-tumori-genic. These results suggest that antisense RNA to fibronectin may be able to abrogate the suppression of malignancy imposed on the hybrid cells by the fibroblast parent.
Fine–structural aspects of bromodeoxyuridine incorporation in sister chromatid differentiation and replication banding
Authors: Jack Elspeth M. , Harrison Christine J. , White Gavin R. M. , Ockey Charles H. , Allen Terence D.
Published: April 2021

The structure of harlequin-stained chromosomes following substitution with low levels of 5-bromodeoxyuridine (BrdUrd) over two cell cycles and high levels over the last part of one cycle (replication banding) was studied in Chinese hamster ovary (CHO) cells. By using correlative light (LM) and scanning electron microscopy (SEM), it was shown that the effects of both the ultraviolet light (u.v.) and hot SSC treatment steps of the harlequin staining procedure were necessary to obtain sister-chromatid differentiation (SCD) or replication banding, u.v. treatment alone resulted in dark Giemsa staining of both chromatids with SEM morphology of short compact protuberances and an overall flattened smooth appearance in both the unsubstituted and BrdUrd-substituted chromatids, a morphology essentially similar to that of untreated chromosomes. SSC alone on the other hand resulted in dark-staining chromatids with an SEM morphology of raised, 100sely packed 100ps of fibres in both types of chromatids, u.v. and SSC treatment together resulted in dtfferentiation, with dark-staining unifilarly (TB) chromatids in the LM corresponding to raised 100sely packed 100ps in the SEM and pale bifilarly (BB) chromatids corresponding to the smooth compact flattened SEM appearance. Where the BrdUrd-substituted strand became the template (BT), or when the nascent strand TB contained high levels of BrdUrd substitution in replication banding, the chromatid stained pale and showed the compact smooth appearance in the SEM. The Giemsa staining ability and ultra- structural morphology of harlequin staining is discussed with respect to putative DNA loss and also in terms of preferential protein–protein, protein–DNA cross-linkage in BrdUrd-containing DNA. These changes are also compared with the ultrastructural morphology observed after other banding methods, where deterioration of protein and DNA-protein interaction resulting in aggregation of chromatin fibres appears to be the major mechanism.
Myosin associated with the surfaces of organelles, vegetative nuclei and generative cells in angiosperm pollen grains and tubes
Authors: Heslop-harrison J. , Heslop-harrison Y.
Published: April 2021

Myosin, detected by immunofluorescence using an antibody to bovine skeletal and smooth muscle myosin, has been localised on individual identifiable organelles from the grasses Alopecurus praten-sis and Secale cereale, and on the surfaces of vegetative nuclei and generative cells from pollen and pollen tubes of Hyacinthus orientalis and Hel-leborus foetidus. Taken in conjunction with recent evidence showing that the growing pollen tube contains an actin cytoskeleton consisting of numerous mainly longitudinally oriented microfilament bundles, and that isolated pollen-tube organelles show ATP-dependent movement along the actin bundles of the giant cells of the characeous algae, this finding suggests that an actomyosin motility system is present in pollen tubes, and indicates that the movements of the different classes of inclusions are driven by interaction of the surface myosin with the actin fibrils at the zones of contact.