bluuebunny/crossref_metadata_2025 huggingface dataset:
Dna density in mitotic and meiotic metaphase chromosomes of plants and animals
Authors: Bennett M. D. , Heslop-Harrison J. S. , Smith J. B. , Ward J. P.
Published: April 2021

Studies of chromosome disposition at metaphase using serial thin-sectioning and threedimensional reconstruction techniques have produced accurate estimates of the total volume of chromosomes per cell in 15 plant and two animal species. Comparing this character with the 4C DNA amount showed no indication of systematic differences in DNA density between either organisms with widely different (>200-fold) C values or different groups or organisms. For example, there was no significant difference between the density of DNA in somatic metaphase chromosomes of man (0·141 pg/ μm3) and its mean in 14 angiosperm plant species (0·182pg/ μm3), or between four dicotyledons (0·180 pg/ μm3) and 10 monocotyledons (0–182pg//tm3). However, evidence was found showing that DNA density can vary significantly within a species. Thus, although the total chromosome volume per cell was closely correlated (r>0·97) with 4C DNA amount in somatic and meiotic cells, the density of DNA in metaphase chromosomes was significantly lower in meiocytes (0·131 pg/ μm3) than in somatic metaphase cells (0·179pg/ μm3).
Actin in xenopus yolk platelets: A peculiar and debated presence
Authors: Colombo Roberto
Published: April 2021

Our previous work showed that Xenopus yolk platelets exhibited, when reacted with actin antibodies or fluorescent DNase 1, a shiny halo of fluorescence, which revealed an external actin cover around the platelets themselves. This structure was named the ‘actin-shell’. Now we have demonstrated the actin-containing coat of Xenopus yolk platelets by agglutination tests, using anti-Xenopus-muscle-actin rabbit serum, and by indirect immunofluorescence microscopy, when the platelets reacted with antibodies directed against DNase 1. We chose these procedures to minimize the difficulties of the techniques used previously and to confirm the data obtained.
Involvement of the n-terminal polypeptide of vimentin in the formation of intermediate filaments
Authors: Traub Peter , Vorgias Constantin E.
Published: April 2021

The potential to form intermediate filaments of a 54 × 103 molecular weight (Mr) polypeptide derived from vimentin by cleavage by the intermediate filament-specific, Ca2+-activated proteinase was investigated. Under physiological conditions of assembly, the breakdown product did not form intermediate filaments. Electron microscopy revealed short, rod-like structures similar to those described by Geisler et al. for a 38 × 103Mr, α-helical core particle derived from desmin. Since the specific, Ca2+ -activated proteinase degrades vimentin preferentially from its N terminus, this result suggests the involvement of the basic, N-terminal polypeptide of vimentin in the assembly of intermediate filaments. This was supported by the observation that arginine inhibits the formation of intermediate filaments from intact vimentin. Whereas lysine had very little effect on the assembly process, guanidinium hydrochloride was effective at the same concentration as arginine. On the basis of these findings, an affinity chromatography method for the identification and isolation of intermediate filament subunit proteins was developed. Beside vimentin, desmin, the 68 × 103Mr neurofilament triplet protein, the glial fibrillary acidic protein and cytokeratins also bound to arginine methylester Sepharose 4B in a salt-stable manner and could be eluted with arginine. The 145 × 103Mrneurofilament triplet protein exhibited reduced binding activity, whereas the 210 × 103Mr subunit did not bind to the affinity matrix. Among the degradation products of vimentin produced by the specific, Ca2*-activated proteinase, only those with molecular weights higher than 40 ×103 bound to arginine methylester Sepharose 4B. The same applied to the high molecular weight degradation products of desmin with a proteinase-resistant 37 × 103Mr, polypeptide as the major component. The results suggest that arginine residues of the non-α-helical, N-terminal polypeptides of intermediate filament subunit proteins play an important role in filament assembly.
Cyclic cytoplasmic activity of nonnucleate egg fragments of Xenopus controls the morphology of injected sperms
Authors: Sakai Masao , Shinagawa Atsunori
Published: April 2021

Triton X-100-treated sperms were injected into non-nucleate egg fragments of Xenopus laevis to determine whether the structure of the injected sperm nucleus is affected by the cyclic activity of the cytoplasm.

Swollen vesicular nuclei were very frequently observed when the sperms were injected and incubated during the ‘rounding-up’ phase of the recipient fragment, whereas no such structures were found when they were incubated during the ‘relaxing’ phase.
Morphological and temporal sequence of meiotic prophase development at puberty in the male mouse
Authors: Goetz P. , Chandley Ann C. , Speed R. M.
Published: April 2021

The correct sequence of meiotic prophase development in the male mouse has been established by the use of pubertal males. The first wave of spermatogenesis at this time provides a unique opportunity to study progressive meiotic development in a direct way. Air-dried and micro-spread analyses have been carried out. Temporal and morphological progression at this time is entirely consistent with that occurring in the later waves of meiosis of the adult male. Morphological detail shows delayed pairing of the X and Y chromosomes relative to the autosomes. The longest XY synaptonemal complex is seen in early pachytene cells, occupying up to 72% of the length of the Y and 22% of the length of the X axis. By late pachytene, end-to-end pairing in the XY bivalent is established, the autosomal axes remaining fully paired. Desynapsis of the autosomes commences at early diplotene. A ‘diffuse’ diplotene stage in the male, comparable to the dictyate stage of the female, could not be found. Marked lengthening of the XY and autosomal axes did, however, occur through the diplotene stage.
The apical structure in Perophora annectens (tunicate) spermatozoa: Fine structure, differentiation and possible role in fertilization*
Authors: Fukumoto Makoto
Published: April 2021

The apical structure in Perophora annectens spermatozoa is approximately 4 μm in length and it is helically coiled. Its major component is a striated structure, which may be analogous to a perforatorium. The plasmalemma enclosing the anterior quarter of the apical structure is covered by extracellular materials, the anterior ornaments.

During spermiogenesis, the apical structure is first recognized as a small blister of the plasmalemma at the apex of the young spermatid. It develops into a conical protrusion and then into a fingerlike process (approximately 1 μm in length). This process is transformed into an elongated process (approximately 4 μm in length) with electron-dense material in its core. Finally, the elongated process is helically coiled to form an apical structure in which electron-dense material forms dense striations.

Vesicles (50–70nm in diameter), presumably derived from the Golgi apparatus, have been recognized in the blisters of younger spermatids, and can be followed through to the finger-like process. In the finger-like process these vesicles are transformed into smaller vesicles (20–30 nm in diameter), which probably fuse with the anterior plasmalemma of the finger-like process. This suggests that chorion lysin(s) is associated with the anterior membrane enclosing the apical structure in these spermatozoa.
An analysis of in vivo cell migration during teleost fin morphogenesis
Authors: Wood Andrew , Thorogood Peter
Published: April 2021

In the teleost embryo the pectoral fin bud initially displays an apical ectodermal ridge along its entire distal margin. The ridge subsequently becomes transformed into an apical fold as the distal ectodermal epithelium grows and folds to enclose an extracellular space between the apposed basal surfaces of the epithelium. Collagen fibrils up to 2μm in diameter, termed ‘actinotrichia’, are deposited along the proximo-distal axis in two (dorsal and ventral) arrays. The actinotrichia are aligned parallel to one another with a regular spacing along the greater part of their length. Mesenchymal cells migrating distally from the base of the fin bud encounter the dorsal and ventral arrays of actinotrichia and move between them apparently using the fibrils as a substratum. The entire structure is transparent and, using the killifish Aphyosemion scheeli, we have investigated the migration of the mesenchymal cells between 135 and 220 h of development, using Nomarski interference contrast microscopy and time-lapse video recording. The number of cellular processes per cell increased significantly during the period of observation. These processes could be graded according to their diameters. Processes of diameter greater than 2 μm were not usually aligned along actinotrichia and arose at any aspect of the cell body. In contrast, processes with diameters less than 2 μm appeared to be confined to the distal aspects of the migrating cells and showed an increasing tendency to become aligned as development progressed. Time-lapse video recordings revealed that such aligned processes move faster (mean speed 17·98(±2·25) μm/h) than non-aligned processes (mean speed 4·66(±0·67) μm/h). Whole cell translocation was generally slower than rates of process movement: the lowest mean value (1 ·52(±0·36) μm/h) was recorded between 135 and 160h of development rising to a maximum mean rate (4·72(±0·42) μm/h) between 195 and 220h; the period of the fastest rate of cell translocation correlated with maximum process alignment along actinotrichia. Thin 1 μm plastic sections revealed that, generally, aligned processes were in close association with the surface of the actinotrichial fibrils and not the spaces between them.
Distribution of concanavalin a binding carbohydrates during mating in Chlamydomonas
Authors: Millikin Blake E. , Weiss Richard L.
Published: April 2021

Cell surface carbohydrates, detected by fluorescein isothiocyanate/concanavalin A (F1TC-ConA), were identified at four locations on gametes of Chlamydomonas reinhardtii. (1) The cell wall: uniform labelling with FITC-ConA was observed; a substantial number of sites were localized in the sodium dodecyl sulphate-insoluble inner wall, which contains the flagellar collars. (2) The periplasm-, a crescent-shaped area was visualized with FITC-ConA and localized by ferritin-ConA. We were able to recover autolytic activity on a ConA affinity column from the mating medium of wild-type cells after the release of these periplasmic sites. The cell-wall-less mutant CW15 displays no periplasmic sites and demonstrates a corresponding inability to release autolytic activity after mating for 60 min. A model for wall lysis is presented, which considers the involvement of these sites in the lytic process. (3) The mating structure: during mating a small fluorescent plaque-like site was observed on cells at a location corresponding to the carbohydrate-like zone of the mating type minus mating structure and may indicate the involvement of ConA binding material in gametic cell fusion. (4) Secreted products: following cell fusion zygotes begin to secrete ConA positive material at about . After 24 h a ConA positive zygote wall and pellicle appear.
Effect of cell–substrate interaction time and shearing force on adhesion of L1210 cells to collagen and glass
Authors: Kowalczyńska Hanna M. , Nowak Małgorzata
Published: April 2021

The early adhesive interaction of living cells with substrates was examined. L1210 cells were allowed to interact with collagen or glass in serum-containing medium (time of cell–substrate interaction, tint, under stationary conditions, was within 2–2 5 min) or in serum-free medium (tintwas 58–1 5 min). The relative number A of cells adhering under stationary conditions, and remaining adherent to the substrate despite experiencing a shearing force F, was determined.

The following was found for cells adherent to collagen and glass, both in the presence and absence of serum in the medium. The number A increases with the value of tint and tends to reach a plateau. The plateau value depends on adhesion conditions (presence or absence of serum).When adhesion occurred in serum-containing medium (F ≃ 0·1 × 10−l3 N), function A(tint) increased up to 15 min. The plateau values were in the ratio of 2: 1 for cells adherent to collagen and glass, respectively.When adhesion took place in serum-free medium, the function A(tint) increased within the first 20 or 130 s for cells adhering to glass or collagen, respectively. The value of A(tint) increased up to the effective interaction time, teff int, i.e. the time after which a plateau was reached at 100% adhesion. This meant that after tint≥teff int all cells were in adhesion with glass and collagen despite the application of the greatest shearing force, F= 2 × 10−9 N. The values of teff int for cells adherent to collagen and glass were in the ratio of 6:1, respectively.The value of A decreases with the value of F for cells adherent to substrate in the absence of serum when tint< teff int. The function A(F) for cells adherent to collagen and glass in the presence of serum, but not in the absence of serum, can be described by the equation: , where a and c = constant > 0. The values of a were in the ratio of 2: 1 for cells adherent to collagen and glass, respectively.The Brownian motion of cells interacting with both substrates in the absence of serum ceased. The times during which cell motion persisted for cells interacting with collagen and glass, respectively, were in the ratio of 2·5: 1.
Roles of calcium in aggregation of rat ascites hepatoma cells by cell surface-associated adhesive factor
Authors: Kurano Shinya , Ishida Mitsugu , Ishimaru Yasuji
Published: April 2021

Our previous studies have shown that a cell surface-associated adhesive factor (AF), separated from rat ascites hepatoma AH136B cells of a differentiated type and highly purified by chromatography, induces not only aggregation of dissociated AH136B cells or rat ascites hepatoma AH 109 A cells of an undifferentiated type but also adhesiveness characterized by the development of junctional complexes; the AF-induced aggregation of the cells was Ca2+-dependent.

Further analysis of the roles of Ca2+ in cell aggregation was performed using AH109A cells (present as single cells in vivo). (1) AF clearly enhanced 45 Ca uptake by the cells; (2) calmodulin was isolated from the cells; (3) calmodulin inhibitor, W-7 (iV-(6-amino-hexyl)-5-chloro-l-naphthalenesulphonamide), strongly inhibited aggregation of the cells; (4) W-7 also inhibited the clustering or capping of AF-binding sites on the cell surface; (5) binding of 125 I-labelled AF to the cells was independent of Ca2+ concentration; (6) binding of 125 I-labelled AF to AF-conjugated beads was not observed, independently of the presence of Ca2+. These findings suggest that Ca2+ and Ca2+-activated calmodulin may play a key role in the process of aggregation of the cells by controlling the microfilament components and that Ca2+ may not be involved either in the interactions between AF and its cellular receptor or in linkages of AF molecules.
Effect Of Altered Oligosaccharide Structure On The Cell Surface Number, Distribution And Turnover Of The High Molecular Weight Acidic Glycoproteins Of CHO Cells
Authors: Fitzgerald L. A. , Denny J. B. , Baumbach G. A. , Ketcham C. M. , Roberts R. M.
Published: April 2021

The influence of altered carbohydrate structure on the surface number, distribution and turnover of plasma membrane glycoproteins has been studied in Chinese hamster ovary (CHO) cells by comparing three lines that are resistant to the cytotoxic effects of wheat germ agglutinin (WGA) with parental CHO cells. The glycoproteins investigated were members of a group of high molecular weight acidic glycoproteins (HMWAG). On parental cells these represent the major surface components that become labelled by lactoperoxidase-catalysed iodination. They are the only plasma membrane glycoproteins that bind WGA. The mutant lines also possess iodinatable surface polypeptides of high molecular weight, but these were less acidic and electrophoretically less diffuse than those from parental cells. These polypeptides in general did not bind [l25I]WGA when two dimensional polyacrylamide gels were overlaid with iodinated lectin. Mutant cells treated with fluorescein-conjugated WGA showed low surface fluorescence. However, the nuclear envelope and a small region in the perinuclear zone fluoresced strongly. Together, these results confirm that the surface glycoproteins of mutant cells had altered carbohydrate structure. Mouse antiserum prepared against the HMWAG, however, bound equally effectively to the mutant lines as to the parental lines. Indirect immunofluorescence experiments showed that the HMWAG had a fairly uniform distribution over the surface, and that internalization induced by second antibody occurred at a similar rate and in a similar manner in all lines, including the mutants. Electron microscopic observations using immunoperoxidase procedures confirmed the similarities in glycoprotein distribution on mutant and parental cells. Two mouse monoclonal antibodies raised against the HMWAG also revealed no difference in the number or topography of surface glycoproteins. Finally, the half-lives of several HMWAG in a parental and a mutant line (15B) maintained on low-serum medium were compared by means of a 121I /1311 double-label technique. Half-lives of HMWAG from the former averaged 12 h and from the latter 11 h. It is concluded that the lack of complex termini on oligosaccharides of this particular group of CHO plasma membrane glycoproteins has no effect on their number, distribution or turnover.
Ultrastructure Of The Flagellar Roots In Chlamydomonas Gametes
Authors: Weiss Richard L.
Published: April 2021

The cytoskeleton of Chlamydomonas reinhardtii gametes has been studied by electron microscopy. The microtubular system, consisting of four flagellar roots inserted into the basal apparatus, is shown to include two daughter basal bodies and two striated fibres, newly described in this report. One new fibre associates with the 3-over-l root and is similar to its counterpart, the striated fibre of the 2-membcr root. These similar root fibres connect each daughter basal body to the V-shaped microtubular root pair. The other new striated fibre joins the daughter basal body to both flagellar roots and is similar to the proximal striated fibre. In mt+ gametes, the conventional root microtubules make direct contact with the doublet zone of the non-activated mating structure. During activation, doublet zone microfilaments associate with the daughter basal body and the finely striated fibre of the 3-over-l root. These observations suggest that the cytoskeleton acts as a scaffolding for membrane extension by the mt+ mating structure microfilaments.
Nucleolar Nomenclature
Authors: Jordan E. G.
Published: April 2021

At the 8th European Nucleolar Workshop, which was organized by M. Bouteille and colleagues at Banyuls-sur-mer in June 1983, a discussion was held on nucleolar nomenclature. The terms that are italicized in the following report were agreed upon. The short descriptions following each term were written to convey the consensus of opinion that emerged. After the discussion a report was displayed for approval. The following account is the approved, amended report of the meeting, incorporating a few minor points made in later comments.
The Major 67 000 Molecular Weight Protein Of The Clam Oocyte Nuclear Envelope Is Lamin-Like
Authors: Maul Gerd G. , Baglia Frank A. , Newmeyer Donald D. , Ohlsson-Wilhelm Betsy M.
Published: April 2021

Nuclear envelopes of somatic cells have at least two different major proteins in the 60—70(×103) molecular weight range (1amins A(C) and B) that seem to be involved in chromatin attachment. In contrast, nuclear envelopes from clam germinal vesicles have only a single major protein of the same size class (∽67×103Mr) and have no chromatin attached to them. The data presented in this report show that this 67×103μ, clam protein shares a variety of physical properties with lamins A(C) and B, derived from rat liver nuclei. These properties include similar size, although different isoelectric points; phosphorylated forms; strong tendencies to cross-link by disulphide bonds; presence of carbohydrates, demonstrated by direct incorporation of mannose and labelling with borohydride; and shared epitopes, demonstrated using both monoclonal and polyclonal antibodies. Taken together, these observations identify the clam 67× 10Mr protein, the major structural protein of a nuclear envelope that lacks attached chromatin, as being lamin-like and demonstrate that it is more closely related to lamin A(C) than to lamin B.
Chemoattractant-mediated changes in cytoskeletal actin of cellular slime moulds
Authors: Mcrobbie S. J. , Newell P. C.
Published: April 2021

We report changes in actin associated with the Triton-insoluble cytoskeleton following chemotactic stimulation in five species of cellular slime moatd, Dictyostelium discoideum, D. mucoroitSes, D. purpureurn, D. lacteum and Polysphondylium violaceum. Stimulation of amoebae with the chemoattractant specific for each species elicits at rapid increase in cytoskeletal actin content with a peak at 5 s, probably corresponding to pseudopodium formation. Subsequent changes consist of a second discrete peak of actin accumulation and, in at least two species, D. discoideum and P. vtolaceum, a third peak. We correlate these later changes in actin content with the changes in amoebal shape that have been reported to be a consequence of chemotactic stimulation.

We have also investigated species variation in actin content and find D. purpureum to have a remarkably low cytoskeletal actin content in comparison to other species.

Whole cell and cytoskeletal actin levels during the first 12 h of D. discoideum development have also been analysed. While little change is found in total protein content, whole cell actin shows an abrupt decline during aggregation and this is accompanied by an increase in cytoskeletal actin, amounting to 100% over 0—12h of development.

These results are discussed in the Light of a possible changing role for actin during the course of development, from being involved in the dynamic events of chemotaxis to assuming a more structural role in the multicellular aggregate.
Ectodermal fragments from normal frog gastrulae condition substrata to support normal and hybrid mesodermal cell migration in vitro
Authors: Nakatsuji Norio , Johnson Kurt E.
Published: April 2021

Using time-lapse cinemicrography and scanning electron microscopy, we have shown that normal Rana embryos and gastrulating hybrid embryos have extracellular fibrils on the inner surface of the ectodermal layer. These fibrils are absent prior to gastrulation and appear in increasing numbers during gastrulation. They can also be deposited in vitro where they condition substrata in such a way that normal presumptive mesodermal cells placed on them show extensive attachment and unoriented cell movement. These fibrils are also present in some arrested hybrid embryos, but in reduced numbers, or are lacking in other arrested hybrid embryos. Explanted ectodermal fragments from arrested hybrid embryos fail both to condition culture substrata by the deposition of fibrils and to promote cell attachment and translocation. In contrast, ectodermal fragments from normal embryos can condition culture substrata so as to promote moderate cell attachment and, for one particular gamete combination, even cell translocation of presumptive mesodermal cells taken from arrested hybrid embryos. These results provide new evidence to support the hypothesis that extracellular fibrils represent a system that promotes mesodermal cell migration in amphibian embryos. Differences in the fibrillar system in urodele and anuran embryos are discussed in relation to fundamental differences in the mode of mesodermal cell migration in these two classes of Amphibia.
Membrane-substrate contact under the spermatozoon of Caenorhabditis elegans, a crawling cell that lacks filamentous actin
Authors: Roberts Thomas M. , Streitmatter Gloria
Published: April 2021

Caenorhabditis elegans spermatozoa use a single, persistent pseudopod to crawl at about 20μm/min but, unlike other types of crawling cells, sperm lack both filamentous actin and myosin. Interference reflection microscopy has revealed that sperm form broad grey areas of contact, analogous to the close contacts that have been described underneath other crawling eukaryotic cells, between their pseudopods and their substrate. Individual sperm change the size, shape and pattern of their substrate attachments as they crawl but we found no correlation between the extent of underside of the cell in contact with the substrate and the velocity of locomotion. Two predominant attachment patterns were observed: (1) a single broad contact extending from the front of the pseudopod nearly to the rear of the cell; and (2) two separate contact sites, one under the front of the pseudopod and one under the cell body. Occasionally, under cells exhibiting the second type of attachment pattern, portions of the anterior contact separated and remained stationary relative to the substrate while the cell moved forward. This observation, as well as the continuous change in shape of the contact areas, suggests that sperm continually form new contacts near the tip of the pseudopod and release these contacts backwards. In extreme cases, sperm were able to crawl with only the front of the pseudopod in contact with the substrate. Therefore, we propose that sperm locomotion depends on the interaction of several key events (traction, propulsion, membrane insertion) occurring at the leading edge of the pseudopod.
Ultrastructural morphometry of gap junctions during differentiation of stratified squamous epithelium
Authors: White F. H. , Thompson D. A. , Gohari K.
Published: April 2021

The presence of gap junctions in stratified epithelia has now been extensively documented, but there have been few attempts to quantify them. In the present report, samples of hamster cheek pouch mucosa were processed for electron microscopy and electron micrographs from defined basal, spinous and granular layers were obtained. Using a combination of direct measurement and stereological intersection counting techniques, the relative surface areas of peripheral gap junctions (i.e. those in direct contact with the epithelial plasma membrane) and annular gap junctions (i.e. those present as complete, approximately circular profiles within the epithelial cell cytoplasm) were determined. Following estimation of the plasma membrane surface area of ‘average’ epithelial cells from each of the defined strata, relative values were transformed into absolute data. Data from peripheral and annular junctions were pooled to provide an estimate of total gap junctional area.

Relative surface area estimates were similar for peripheral, annular and total gap junctions, in that values were invariably highest in the spinous layer and lowest in the granular layer. Absolute data indicate that there is more than a threefold increase in the area of membrane differentiated into gap junctions in the average spinous cell when compared with the average basal cell. Values for total gap-junctional areas in the average granular cell are reduced somewhat with respect to the average spinous cell and this is effected by a decrease in the area of peripheral gap junctions. We conclude that there is synthesis of gap junctions between basal and spinous cells, which is followed by evidence of degradation between spinous and granular cells. The magnitude of the estimates of area is comparable to those obtained from other stratified and non-stratified epithelia and it would thus appear that gap junctions may play a significant role in cellular control processes in all viable epithelial strata.
Lanthanum staining of neurotubules in axons from cockroach ganglia
Authors: Lane Nancy J. , Treherne J. E.
Published: April 2021

The axoplasm of the neurons of Penplaneta amencana contains numerous neurotubules which are morphologically similar to the microtubules found in non-nervous tissues after sectioning or negative staining. In cross-sections of fixed material such tubules usually appear as electron-dense circles containing a less dense core and surrounded by a non-opaque ‘clear zone’. However, when cockroach ganglia are fixed and incubated in lanthanum hydroxide, the lanthanum is taken up intracellularly by the axoplasm of certain of the neurons and in these is found to stain the entire core of the neurotubules, as well as the clear zone. At least part of the wall of the tubules remains unstained and appears as a ring of non-opaque subunits against an electron-dense, lanthanum-stained background. Since lanthanum staining, under the conditions used here, is sometimes considered to demonstrate the presence of acid muco polysacchandes, its uptake by the neurotubules may indicate that they contain carbohydrate as well as the protein that is generally considered to form part of the microtubular wall. Alter natively, the lanthanum could indicate the location of other anionic molecules, possibly under going extra- or intratubular translocation. The extent to which neurotubules could mediate movements of relatively small water-soluble ions and molecules is considered in relation to their diffusion through the polyamon matrix represented by the core of the tubules.
The origin of flimmer inSaprolegnia, Dictyuchus, synuraandCryptomonas
Authors: Heath I. B. , Greenwood A. D. , Griffiths H.B.
Published: April 2021

The endoplasmic reticulum of Saprolegnia, Dictyuchus, Synura and Cryptomonas may contain tubules less than 20 nm in diameter. In Saprolegnia these tubules have a maximum length of 1·6μm, a wall of a single layer of colchicine-resistant, osmiophilic subunits, and a tapering end-piece. Flimmer hairs (flagellar hairs) are morphologically similar and are attached to the flagellum sheath by a tapering end-piece. It is suggested that Flimmer hairs are produced in cisternae of the endoplasmic reticulum of the above organisms. Cryptomonas bears 2 rows of Flimmer hairs on one flagellum and a single row of shorter ones on the other.
The effect of inhalational anaesthetics on the microtubular system in Actinosphaerium nucleofilum
Authors: Allison A. C. , Hulands G. H. , Nunn J. F. , Kitching J. A. , Macdonald A. C.
Published: April 2021

Six different anaesthetic agents were found to cause reversible collapse of the axopods of Actinosphaerium nucleofilum. The effect occurred at concentrations proportional to those required to anaesthetize man. Electron microscopy showed dispersal of the microtubular system and disaggregation of the microtubules of the axonemes, and expanded microtubules without interlinkage were seen in the related heliozoon Actinophrys sol under treatment with halothane. In both genera there was a rapid reassembly during the recovery period. Diethyl ether, an inhalational anaesthetic with a particularly large molecule, was ineffective except at relatively very high concentrations, and with this agent cytolysis often occurred with little or no shortening of axopods.
Some physiological and morphological effects of polylysine on Amoeba proteus
Authors: Sanders E. J. , Bell L. G. E.
Published: April 2021

The effect of polylysine on pinocytosis and the cell surface of Amoeba proteus was investigated. The intensity of the pinocytotic response was evaluated by a channel counting method, and the surface was examined by means of transmission and scanning electron microscopy.

Cells treated with polylysine and then immersed in a protein pinocytosis inducer showed a higher intensity of channel formation during the initial stages of the cycle than cells not pre- treated. This was considered to be an additive effect of the protein and the polymer, since the latter alone was demonstrated to induce pinocytosis. No influence of molecular weight of the basic polymer on this reaction could be demonstrated.

As well as normal pinocytotic channels electron micrographs revealed the presence of fine channels, 20–50 nm in width, in the cytoplasm as a result of polylysine treatment. The polymer was visualized as dense surface aggregates, about 25·0 nm in diameter, associated with the extracellular material. This deposit was not seen on Amoeba dubia, which lacked a well-developed extracellular covering, and micro-channels failed to develop in this case. It has been demonstrated that when polylysine and a protein pinocytosis inducer were applied to the cell sequentially both compounds occupied the same channels. In view of the lack of effect of metabolic inhibitors on the formation of channels by polylysine it was concluded that this phenomenon is distinct from pinocytosis. It is proposed that this kind of channel formation can be explained in terms of the bridging of areas of membrane by the polymer–polysaccharide complex.
Heterochromatin, the synaptonemal complex and crossing over
Authors: Stack Stephen M.
Published: April 2021

A combined light- and electron-microscopic examination of chromosomes from two angiospermous plants, Plantago ovata and Lycopersicon esculentum, and a mammal, Mus musculus, was performed. From this investigation three observations have been made that may be relevant to the observed lack of crossing over in heterochromatin. (1) Differential staining indicates that heterochromatin represents a smaller fraction of the length of pachytene chromosomes than it represents in the length of mitotic metaphase chromosomes. Since the synaptonemal complex (SC) runs throughout the length of these pachytene chromosomes, it is under-represented in heterochromatin. Considering the evidence for a rough correlation between the length of SC and the amount of crossing over, this could result in less crossing over in heterochromatin than expected on the basis of its length in mitotic metaphase chromosomes. (2) Electron microscopy indicates that, unlike the SC in euchromatin, the SC in heterochromatin is densely ensheathed in highly compact chromatin. If crossing over occurs in the SC or even in the surrounding chromatin, the compaction of the chromatin may prevent the penetration of enzymes needed in recombination. (3) Finally, a difference in the structure of SCs in euchromatin versus heterochromatin was observed that could be associated with the lack of crossing over in heterochromatin.
Effects of sulphydryl reagents on the structure of dehistonized metaphase chromosomes
Authors: Jeppesen Peter , Morten Helen
Published: April 2021

Dehistonized metaphase chromosomes lose their apparent axial organization (the ‘scaffold’) and sediment more slowly following exposure to β-mercaptoethanol (BME). We have subsequently treated BME chromosomes with reagents that oxidize protein sulphydryls to disulphides, and found that if calcium is also present during the oxidation an apparently similar axial structure is restored following dehistonization, as seen by microscopic examination. In general, however, we do not find that oxidation restores the higher sedimentation rate of dehistonized control chromosomes. Analysis of residual core protein in dehistonized chromosomes by sodium dodecyl sulphate/polyacrylamide gel electrophoresis fails to detect any differences in polypeptide composition related to the state of oxidation or to the presence or absence of visible axial organization. Combining our results with those of other workers, we conclude that the axial structure evident in dehistonized metaphase chromosomes is maintained, at least partially, by inter-protein cross-linking, although in vivo this may not be via simple disulphide bridges. Additional factors, which we have not yet characterized, but which possibly include heavy metal ions, appear to be involved in the axial organization existing in vivo.
Monoclonal antibody to a 43 000 M
r surface protein of a human leukaemia cell line (thp-1) crossreacts with the fibroblast intermediate filament protein vimentin
Authors: Herrmann Harald , Aberer Werner , Majdic Otto , Schuler Gerold , Wiche Gerhard
Published: April 2021

Monoclonal antibodies were produced against surface antigens of live cells from a human acute monocytic leukaemia cell line (THP-1). One clone, VIC-C2, when assayed by immunofluor-sscence microscopy, brightly stained the surface of THP-1 cells and the cytoplasm of Langerhans cells, fibroblasts and melanocytes in sections of human skin. The immunoreactive cytoplasmic structures were filamentous and resembled intermediate filaments. By double immunofluorescence microscopy using VIC-C2 and polyclonal antibodies to vimentin, the VIC-C2 antigen was shown to be located on intermediate filaments of cultured fibroblasts and to follow these filaments during various drug-induced rearrangements. As demonstrated by immunoprecipitation, antibody gel overlay and immunoblotting of two-dimensional polyacrylamide gels, VIC-C2 recognized two different antigens in extracts of THP-1 cells: one of Mr = 43000 and pl = 7, the other of Mr = 57000. In extracts from various cultured fibroblast cells only the 57 000Mr antigen was detected. This 57000AL protein was identified as vimentin by immunoblotting of rat glioma C6 cytoskeletons on two-dimensional gels. When vimentin was digested with chymotrypsin, only fragments containing parts of both helical rod pieces and the connecting non-helical spacer-region were strongly antigenic, whereas the helical rods alone were only weakly crossreactive. Moreover, immunoprecipitation revealed that VIC-C2 preferentially reacted with native compared to denatured vimentin.
Electron probe x-ray microanalysis of the effects of Bacillus thuringiensis var Kurstaki crystal protein insecticide on ions in an electrogenic k+-Transporting epithelium of the larval midgut in the lepidopteran, Manduca sexta, in vitro
Authors: Gupta Brij L. , Dow Julian A. T. , Hall Theodore A. , Harvey William R.
Published: April 2021

An alkaline hydrolysate of Bacillus thuringiensis var kurstaki HD 1 (Btk) parasporal crystals was administered at 25 μgml-1 (f.c.) to isolated, short-circuited, midguts of tobacco homworm (Manduca sexta) larvae. The short-circuit current (s.c.c.), a precise measure of K+ active transport, was inhibited by 78% in 10 min in Btft-treated midguts as compared to controls. The elemental concentrations of K, together with Na, Mg, P, S, Cl and Ca, as well as the water content, were determined by electron probe X-ray microanalysis (EPXMA) in the muscle cells, columnar cells and goblet cells, as well as in the extracellular goblet cavity and the bathing media. The average K concentration in the goblet cell cavity was 129mmol/kg wet wt in control midguts but only 37 mmol/kg wet wt in fitA-treated midguts. The elemental concentrations, including that of K, in other cell compartments were much less affected by Btk, but a rise in total cell calcium is suggested. It has been previously suggested that in vivo Btk acts specifically on limited regions of the apical membrane of the midgut epithelial cells. The simplest interpretation of the EPXMA results would be that initially Btk interacts specifically with the goblet cell apical membrane, which bounds the goblet cavity and contains the K+ pump responsible for the s.c.c. and high transepithelial potential difference (p.d.). Such interaction results in a rapid disruption of K+ transport across the goblet cell apical membrane, leading to dissipation of the K+ gradient and loss of p.d. The histopathological changes previously reported by other workers would then be a consequence of K+ pump inhibition causing changes in the intracellular pH, Ca2+ etc. Some possible molecular bases for these specific interactions between Btk and cell membrane are discussed.
Isolation and partial characterization of Urechis caupo egg envelopes
Authors: Cross Nicholas L. , Slezynger T. C. , Holland Linda Z.
Published: April 2021

Eggs of Urechis caupo are surrounded by a≃0·9 μm thick egg envelope and, attached to that, a peripheral jelly layer about 3 μm thick. Before fertilization, the sperm undergoes the acrosome reaction and binds to the egg envelope. As part of a study of the induction of the acrosome reaction and sperm binding in Urechis, we have developed a method to prepare an egg envelope fraction by differential centrifugation. The isolation procedure removes much of the jelly layer, but does not alter the fine structure of the envelope. When a sperm contacts an isolated envelope, it undergoes a normal acrosome reaction and binds to the envelope’s outer face. Electrophoresis of the envelope fraction on sodium dodecyl sulphate (SDS)/polyacrylamide gels revealed six major components stained by Coomassie Blue, of which four are stained by the periodic acid-Schiff reagents (PAS). To measure the degree of enrichment of the envelope fraction, envelopes were isolated from eggs that had been externally radio-iodinated; the specific activity of the envelope fraction was 17 ± 3 times greater than that of intact eggs. The amino acid composition of the envelope fraction is dominated by Gly (19 mole%), Asx (11%), Thr (11%), Ser (8%), Ala (8%) and Glx (8%). The sugars fucose, xylose, mannose, galactose, glucose, jV-acetylglucosamine and N-acetylgalactosamine were detected by gas-liquid chromatography. We also investigated whether the egg envelope changes at fertilization. No change was detected in the electrophoretic 125I pattern of externally radio-iodinated eggs, and the envelope fractions prepared from unfertilized and fertilized eggs produced the same Coomassie Blue pattern on SDS/polyacrylamide. gels.
Inhibition of cell spreading on the band of extracellular fibres in early chick and quail embryos
Authors: Andries L. , Vanroelen Ch. , Hoof J. Van , Vakaet L.
Published: April 2021

The ventral surface of the upper layer shows a band of extracellular fibrils around the anterior and lateral border of tfieareapellucida during gastrulation of the chick embryo. Using scanning electron microscopy, we found that this disposition is correlated with the motility of the middle-layer cells of gastrulating chick and quail embryos. Outside the fibrous band, single middle-layer cells and a sheet of mesoblast cells were spread out and possessed lamellae. Single cells on the fibrous band did not form lamellae. The same cell behaviour was obtained with the expiants of deep layer on the fibrous band. The fibrous band is assumed to operate as a barrier that inhibits cell motility during gastrulation.
Morphological response of cultured cells to Naegleria amoeba cytopathogenic material
Authors: Dunnebacke T.H. , Schuster F.L.
Published: April 2021

Naegleria amoebae contain cytopathogenic material (NACM). The morphological response of cultured cells to this material follows a number of characteristics in common with those resulting from infectious agents. The cytopathologic changes varied depending on the strain of the cultured cells. Among those from 17 different vertebrate sources, both primary and continuous cell lines, some were destroyed completely by dilutions of NACM up to 10(−8) while others appeared unaffected by NACM at any concentration. The response had no apparent relationship to species, organ source, or passage level of the cells. The reaction was typified by a long latent period (4-10 days) during which the number of cells in the culture increased up to 10-fold, followed abruptly by a short period (less than 24 h) during which all of the cells were destroyed. The latent period was prolonged when the culture conditions were adverse, or when the amount of NACM in the inoculum was minimal. A high multiplicity of NACM in the inoculum lysed the entire culture, while dilutions near the end-point caused generalized or only focal changes of rounded cytopathic cells. The cytopathic effect could be maintained in cultured cells by serial passage, such that the total activity greatly exceeded what could be attributed to the original inoculum. These findings are consistent with the concept that NACM has properties of an infectious agent and that its quantity is enhanced and spread through the culture by cell-to-cell contact and by cell division.
Extraction model of the longitudinal flagellum of Ceratium tripos (dinoflagellida): Reactivation of flagellar retraction
Authors: Maruyama Tadashi
Published: April 2021

The mechanism of retraction of the longitudinal flagellum of Ceratium tripos was studied by making extracted models of the flagellum. Non-detergent models extracted in low ionic strength medium containing 1 M-glucose, 10mM-EDTA and 50mM-Tris. HCl buffer (pH8·0), retracted when Ca2+, Mg2+, Ba, Sr2+, Mn2+ or Cd2+ was applied locally with a glass capillary. A demembranated model of the flagellum was made with an extraction medium containing 0·8-TO M-glucoβe, 20mM-Tris-acetate (pH7·8), 2mM-EGTA, 5–7mM-MgS04, 0·l M-potassium glutamate and 0·l% Triton X-100. The model required a concentration of Mg2+ of a few mmol/1 for successful reactivation of both retraction and undulation, and about 0·l M-potassium glutamate (or sodium glutamate) for reactivation of undulation. Neither type of motion of the models could be reactivated above 35 °C. Ca2+ induced the retraction at pCa 5·5 or less. In addition to Ca2+, Mn2+, Ba2+, Sr2+ and Cd2+ also induced retraction but Mg2+, La3+ or Tb3+ did not. Although ATP was required for undulation, it was not required for retraction. Co-incubation with hexokinase to remove contaminating ATP did not suppress the retraction. The potent ATPase inhibitor, orthovanadate, inhibited undulation at 10μM but did not inhibit retraction even at 2mM. SH blockers, N- ethylmaleimide and dithio-bis-nitrobenzoic acid strongly suppressed undulation but had no effect on retraction. Calmodulin inhibitors, trifluoperazine and chlorpromazine, also had no effect on retraction. These data indicate that undulation is generated by a 9+2 microtubular axoneme using energy released by hydrolysis of ATP and that retraction can be induced by Ca2+ without a requirement for ATP.