bluuebunny/crossref_metadata_2025_split huggingface dataset:
Further ultrastructural observations on polysaccharide localization in plant cells
Authors: Pickett-Heaps J. D. 
Published: April 2021

ABSTRACT
Standard periodic acid/Schiff (PAS) techniques have not shown the existence of aldehyde groups in sections of glutaraldehyde-fixed, Araldite-embedded root-tip tissue; peroxidation of such sections resulted in a typical PAS staining pattern. Permanganate-fixed root tips also gave a weak PAS reaction which was intensified by prior peroxidation of the sections. At the ultrastructural level, silver hexamine was used to detect aldehyde groups produced in poly saccharide by permanganate and/or periodate oxidation. Golgi vesicles and slime material in root-cap cells always reacted strongly; the cell wall proper was less reactive. A marked increase in the stainability of the vesicles was evident, the further removed they were from Golgi bodies. This also occurred in root epidermal cells. In both these types of cells, smallersized vesicles and/or the contents of reticulate Golgi cisternae showed evidence of histochemical staining. In meristematic root tip cells, vesicles closely apposed to Golgi bodies did not stain convincingly, though cell walls stained readily. During cell-plate formation, however, both smaller (possibly Golgi) and larger vesicles (phragmoplasts) stained strongly. The walls of permanganate-fixed sieve-tube cells also stained quite strongly, but callose did not unless the tissue block had been treated with periodate before being embedded. In glutaraldehyde-fixed xylem cells, older wall thickenings reacted very strongly even when the sections had been blocked with iodoacetate and bisulphite (which rendered the rest of the section unreactive). If similar sections of younger xylem cells were peroxidized after such blocking reactions, the primary cell wall and the wall thickenings stained, as did many of the Golgi vesicles. The results are related to other experimental observations, both ultrastructural and histochemical, on plant cells.
Spermatogenesis and the structure of the mature sperm in Nucella Lapillus (L)
Authors: Walker Muriel , Macgregor H. C. 
Published: April 2021

ABSTRACT
The testis of Nucella consists of numerous tubules, all directed inwards and joining to form a common testicular duct. In a single tubule the spermatogonia lie round the periphery. Mature sperm line the lumen of the tubule. Cells in the same stage of spermatogenesis are grouped together and all members of a group pass through spermatogenesis in phase.
Staining with fast green before and after treatment with Van Slyke reagent indicates a change from lysine-rich to arginine-rich histone in the maturing spermatid.
Sperm of Nucella are motile throughout their length. The sperm are thread-like and about 80 μ long. The head is Feulgen-positive and about 40 μ long. The mid-piece lies behind the head and is about 8 μ long. The flagellum runs from the front end of the head to the tip of the tail; in the head it is completely surrounded by the nucleus.
The spermatogonia contain two centrioles situated near the nucleus and a conspicuous Golgi complex. There are synaptinemal complexes in spermatocyte nuclei in the synapsis stage. In the early spermatid the centriole pushes a tube through the nucleus. This tube is lined by nuclear membrane and is occupied by the anterior portion of the flagellar shaft. The nucleus elongates and the nucleoprotein condenses into strands arranged helically along the long axis of the nucleus. These strands fuse to form lamellae, which disappear in the mature sperm. Mitochondria aggregate at the base of the early spermatid nucleus and form a loose spiral around the flagellar shaft. The outer mitochondrial membranes fuse. The mid-piece of the mature sperm consists of a large tubular mitochondrion enclosing a portion of the flagellar shaft. At the early spermatid stage a pro-acrosomal granule is formed from a large Golgi complex. From this the acrosome develops; it consists of a cone and an acrosome granule. There are two sets of microtubules associated with the acrosome, one lying within the cone, the other outside the cone and separated from it by a ‘ragged membrane’. The microtubules of the outer set extend backwards along the head for two-thirds of its length. The centriole which gives rise to the flagellar shaft lies at the anterior end of the head and is separated from the acrosome by a thin layer of nucleoprotein and a double layer of nuclear envelope. There is no second centriole or derivative thereof in the mature sperm. In the tail groups of coiled fibres are associated with each pair of the peripheral flagellar fibrils.
Studies on the motility of the heliozoa I. the locomotion of Actinosphaerium Eichhorni and Actinophrys Sp
Authors: Watters C. 
Published: April 2021

ABSTRACT
Analysis of ciné records indicates that the locomotion of Actinosphaerium eichhorni and Actinophrys sp. includes a definite rolling motion, in addition to evident horizontal and vertical displacements. Such movements could be correlated with significant changes in the lengths of supportive axopods, but not with axopodial rowing or sliding movements. The data also do not support a model of locomotion based simply on those systematic shifts in the cell’s centre of gravity that would be caused by sequential collapse of supportive axopods. Although active bending of attached axopods cannot be discounted, locomotion would seem to result from forces generated between the cytosome and substratum by attached axopods undergoing changes in length. The observations suggest, moreover, that axopodial retraction is more important than elongation in the generation of motive force.
It is proposed that the relative magnitude of each locomotory component is determined by the dimensional parameters of the particular species. As a consequence, changes in axopodial length can account for both the ‘rolling’ and ‘gliding’ behaviour reported in the literature.
Incorporation of [3H]Thymidine in mouse spleen
Authors: Pelc S. R. 
Published: April 2021

ABSTRACT
Mice were given 4 injections of [3H]thymidine at 2-hourly intervals and killed at times varying from 1 h to 12 days after the last injection. Autoradiographs of spleen, oesophagus and heart were prepared by the stripping-film technique and exposed for 21, 189 and 367 days.
Groups of lymphoid cells surrounding trabeculae were heavily labelled, the decline in grain count suggesting division of these cells within 24 h. The appearance of large numbers of labelled nucleated cells in venules suggests that cells leave the spleen through the lining of the venules. The cells in germinal centres were preponderantly weakly labelled and spread into the white pulp after 2 days. It is suggested that the weak labelling indicates turnover of DNA rather than pre-mitotic synthesis. Megacaryocytes were unlabelled 1 h after a single injection of [3H]thymidine, nearly all being labelled from 1 to 8 days after the last of 4 injections. The grain count declined steadily with increasing interval between injection and fixation.
Occurrence, molecular structure, and induced formation of the ‘stromacentre’ in plastids
Authors: Gunning B. E. S. , Steer M. W. , Cochrane M. P. 
Published: April 2021

ABSTRACT
The ‘stromacentre’ is a fibrillar spherulite found in plastids of aldehyde osmium-tetroxide fixed leaves of species in the genus Avena. Fibrils, each up to 0·2 μ. × 80–90 A, are associated in bundles, sometimes in hexagonal close packing, and the bundles in turn are aggregated in the spherulite. Individual bundles, or structures resembling them, occur in the plastid stroma in some other plants. In Avena, the stromacentre develops along with the internal membrane system of the plastids. Its staining reactions suggest absence of nucleic acid, and that it is proteinaceous. It is probably present in all mature Avena plastids.
Stromacentre fibrils have been negatively stained. They consist of linearly aggregated particles. In side view these measure about 85–90 Å square, though the outline of the particles varies according to the orientation of the fibril. Particle outlines and staining patterns within particles are illustrated in photographically reinforced images. Micrographs interpreted as illustrating disaggregation into free particles are presented. These free particles are indistinguishable from numerous others in the preparations, and these in turn are thought to be Fraction I protein molecules.
A process somewhat similar to stromacentre formation occurs in etioplasts and chloroplasts in Phaseolus leaves that have been dehydrated by plasmolysis, by wilting, or by high-speed centrifugation. These aggregates are not quite the same as the Avena stromacentre, but negative staining shows that they too are composed of units that are about the same size as Fraction I protein molecules.
The hypothesis that the stromacentre fibrils consist of linearly aggregated Fraction I protein molecules is discussed.
Synchronous pollen mitosis and the formation of the generative cell in massulate orchids
Authors: Heslop-Harrison J. 
Published: April 2021

ABSTRACT
In orchd species forming microspores in aggregates, the pollen mitotic division occurs synchronously in all cells of each massula, as do the earlier meiotic divisions. The synchroneity can be traced to the persistence of cytoplasmic connexions between the cells, from the meiotic prophiase until pollen maturation. The mitosis giving the generative nucleus is asymmetrical, and the spindle is truncated at one side, where the microtubules converge towards an amorphuos polar structure lying against the spore wall. The cell plate formed after pollen mitosis is hemispherical, and its curved growth is related to a radial spread of the microtubules of the phragmoplast after the telophase of the division. The plate itself, and the wall derived from it, is identifiable as callose by its fluorescence properties. In the later development of the gametophyte, growth of the callose wall continues until the originally hemispherical generative cell becomes separated from the spore wall. The cell then assumes a spherical shape and moves to the vicinity of the vegetative nucleus, where it remains freely suspended, bathed in the cytoplasm of the vegetative cell but insulated from it by the completely ensheathing callose wall.
Genetic analysis of developmental mechanisms in Hydra: IV. characterization of a nematocystdeficient strain
Authors: Fujisawa Toshitaka , Sugiyama Tsutomu 
Published: April 2021

ABSTRACT
The authors have previously found that mutant hydra strains showing various types of developmental defects can be isolated through sexual inbreeding of wild hydra. One such defective strain, called nem-4, contains virtually no stenoteles, one of the four types of nematocysts present in hydra, in its tentacles. However, stenoteles are present at a normal level in the body column of this strain, and they are turned over also at a normal rate.
Grafting experiments between the head region of nem-4 hydra and the body column of wild type hydra (and vice versa) showed that wild type stenotele nematocytes can move into nem-4 tentacles but that nem-4 stenotele nematocytes can not move into the wild type tentacles. These observations suggest that the stenotele nematocytes are produced normally by differentiation from the interstitial cells in the body column of nem-4 hydra, but that they are somehow prevented from migrating into the tentacles in this strain.
A technique for the freeze-fracture of tissue culture
Authors: Prescott Lise , Brightman Milton W. 
Published: April 2021

ABSTRACT
Cultures of rat cerebellum grown on glass coverslips coated first with collodion and then collagen are fixed in glutaraldehyde to which ruthenium red has been added. After fixation, the collodion comes off the glass coverslips and the 3 layers: collodion-collagen-culture are handled as one piece. Following immersion in glycerol, selected areas are cut from the piece; the excised areas are a little smaller than those of the specimen carriers used in a Balzers apparatus. The ruthenium red, which stains all cells and processes, is a good indicator of specimen thickness. The explant which consists of several cell layers is redder than the peripheral monolayer of outgrowth. The square areas cut from either the explant or the outgrowth can be matched in thickness according to their shade of red. In frozen specimens, the red colour distinguishes the culture layer from the collodion-collagen support under it and from the white frost on top. During fracturing, the appearance of pink flakes on the edge of the knife indicates that the culture layer has been cleaved. The growth of cells on collodion-collagen and the fracture of the cultures with a knife, eliminate the restrictions inherent in the use of frozen ‘metallic sandwiches’.
Effects of pronase and concanavalin a upon the freeze-etch morphology of cell membranes of intact human erythrocytes
Authors: Wise Gary E. , Shienvold Frances L. , Rubin Robert W. 
Published: April 2021

ABSTRACT
Freeze-etch studies reveal that mild pronase treatment with subsequent incubation in con-canavalin A induces aggregation of intramembranous particles (IMP) in intact human erythrocytes. This alteration in particle distribution is accompanied by a change in the distribution of the Con A molecules such that they also become clustered on the extracellular etch face. If divalent succinyl Con A is used after pronase instead of tetravalent Con A the IMPs still become clustered. Pronase only, Con A only, or succinyl Con A only does not cause the IMPs to become aggregated. Most surprising is the finding that pronase followed by Con A causes partial haemolysis of the cells whereas pronase only, Con A only, or pronase + succinyl Con A do not cause this haemoglobin loss. These perturbations of the erythrocyte plasma membrane appear to be a result of the pronase +Con A exerting a transmembrane effect on the spectrin. This conclusion is supported by sodium dodecylsulphate polyacrylamide gel electrophoresis of material crosslinked with dimethyl adipimidate dihydrochloride, which indicates that spectrin is more susceptible to being cross-linked after pronase + Con A; i.e. the spectrin is probably aggregated by the enzyme and lectin incubation.
Analysis of the penetrable space within the nucleus
Authors: Burgoyne Leigh A. , Skinner Jennifer D. , Marshall Alistair 
Published: April 2021

ABSTRACT
Radioactive glycogen molecules have been used as passive probes to compare cavity systems within nuclei and isolated chromatin. Isolated chromatin was found to possess a narrow range of microspaces with mean effective diameters between 4·0 and 4·5 nm (40 and 45 A) depending on shape assumptions. Intact nuclei contained a far larger class of free spaces with average diameters in the order of 11·0–15·0 nm. This clearly shows that DNase-I (diam. 4-1 nm) can penetrate and occupy a large proportion of nuclear space even though this enzyme does not readily attack the undisturbed nuclear structure. A structure which simulated the pattern of penetrability and incorporated other known properties of chromatin was used to explain this DNase-I resistance of intact nuclei in terms of an ordered, compact, local structure interspersed by much larger spaces. A system for this local packing is suggested and the functional implications of this type of organization considered.
Sulphate metabolism in the exocrine pancreas. ii. the production of sulphated macromolecules by the mouse exocrine pancreas
Authors: Berg N. B. 
Published: April 2021

ABSTRACT
The types of sulphated macromolecules produced by the exocrine pancreas were investigated. To determine whether this tissue utilized inorganic sulphate for protein production, the in-vitro behaviour of material labelled with 35S-sulphate was compared with material labelled with [3H]leucine (secretory proteins). While incubating tissue slices in the presence of cycloheximide resulted in an immediate and nearly complete inhibition of protein synthesis, a similar decrease in production of sulphated material was not observed until after 2 h of incubation in the presence of the drug. Likewise, the kinetics of pilocarpine-induced discharge of radioactive material from pancreatic slices pulse-labelled with either 3H-Leu. Or 35S-sulphate were compared. During the first 90 min of stimulation sulphated macromolecules were detected in chase medium 10–15 min prior to the appearance of [3H] labelled secretory proteins. That in-vitro behaviour of sulphated material differed from radioleucine-labelled material is indicative of the fact that the pancreas utilizes inorganic sulphate for the production of macromolecules other than secretory proteins.
Lipid and proteoglycan fractions were prepared from pancreatic tissue 4 h after intraperitoneal injection of radiosulphate. The recovery of a significant amount of radioactivity in both fractions demonstrated the ability of the pancreas to use inorganic sulphate for the production of both sulphated lipids and sulphated proteoglycans.
The possible function of sulphated macromolecules in pancreatic secretion is discussed.
Effect of ultraviolet or laser light irradiation on the growth of Micrasterias thomasiana
Authors: Nishimura M. , Ueda K. 
Published: April 2021

ABSTRACT
The effect of ultraviolet or laser light on the growth of lobes in a green alga, Micrasterias thomasiana was investigated. During plasmolysis, the cell wall and the outermost region of the cytoplasm were separately irradiated with an ultraviolet or laser microbeam. Growth of the lobes was more effectively inhibited by irradiation of the cytoplasm than of the cell wall when the dose of irradiation was weak. Growth inhibition was observed in the irradiated cytoplasm where no apparent decrease in velocity of plasma streaming was seen, which suggested that irradiation caused more damage to the mechanism of exocytosis than to the migration of secretion vesicles. Strong irradiation resulted in gelatinization of the cytoplasm. With strong doses of irradiation on both the cytoplasm and cell wall, growth was completely inhibited.
Genetic aspects of intracellular motility: cortical localization and insertion of trichocysts inParamecium tetraurelia
Authors: Aufderheide Karl J. 
Published: April 2021

ABSTRACTWild-type and selected mutants of Paramecium tetraurelia were subjected to detailed analysis of the trichocyst phenotype. The characteristics of morphology, saltatory motility, and cortical insertion of trichocysts were found to be genetically distinguishable. In mutants with defective trichocyst saltatory motility, other intracellular motility systems (i.e. mitochondrial saltatory motility, and cyclosis) appeared to be unaffected.Saltatory motility appears to be an essential intermediate step in the functional development of the trichocyst, since it serves to transport the trichocyst from its site of assembly, deep in the cytoplasm, to the cortex, where it is inserted and becomes discharge-competent. If trichocyst saltatory motility is lost, as in the mutants ndA and tam8, then trichocysts are not transported to the cortex and are therefore not inserted. However, the successful transport of a trichocyst to the cortex does not guarantee the proper insertion of that trichocyst, as in the case of the mutant am. Apparently there are independent steps involved specifically with trichocyst insertion. The gross morphology of the trichocyst appears to be independent of its saltatory motility, and to a degree, independent of cortical insertion.
Cell movement and the mechanism of invasiveness: a survey of the behaviour of some normal and malignant cells implanted into the developing chick wing bud
Authors: Tickle C. , Crawley A. , Goodman M. 
Published: April 2021

ABSTRACTA survey of the behaviour of a variety of normal and malignant tumours and cells has been carried out to gain insights into the mechanisms of tumour invasiveness. The tumours and cells were implanted into the developing chick wing bud, which is a loose mesenchyme bounded by ectoderm. The distribution of the grafted cells was examined histologically after one or two days. The special feature of this assay is that the behaviour of cells is tested in a 3-dimensi0nal tissue. Cells from 3 different carcinomas, mouse lung tumour, rat bladder tumour and human breast tumour did not invade the mesenchyme, whereas trophoblast, sarcoma 180, cultured hamster fibroblasts (BHK, PyBHK, Nil 8, HSV Nil 8) and neuroblastoma cells did. Cells from embryonic pigmented retina and heart ventricle were non-invasive. These results suggest that cell movement may not be a common feature of all invasive tumours.The cells that did move into the mesenchyme appeared to do so by various mechanisms. Lack of contact inhibition of movement, although probably involved in the invasiveness of sarcoma 18o cells, does not appear to be necessary for invasion: cells that have been shown to exhibit contact inhibition of movement (BHK and PyBHK) also invade. Both normal and transformed cells (BHK and PyBHK; Nil 8 and HSV Nil 8) moved into the mesenchyme. Other invading cells, such as trophoblast, neuroblastoma and to a small extent, HSV Nil 8 cells, destroy the adjacent host tissue and this may be important in the invasiveness of these cells.The patterns of invasion and interactions with the host tissue were varied. Trophoblast and the fibroblasts were often elongated along the basement membrane at the ectoderm/mesen-chyme border and also closely apposed to the endothelial linings of blood vessels. Sarcoma 180 and neuroblastoma cells clustered around nerves. The embryonic tissues and neuroblastoma cells were often associated with blood vessels. These results are discussed in relation to tumour invasion.A striking finding was that the carcinoma cells were frequently found positioned within the wing ectoderm on the basement membrane. This affinity of carcinoma cells for the epithelium rather than the mesenchyme leads to a reappraisal of the mechanisms involved in the invasiveness of carcinomas.
Ruthenium red-positive surface layer, extracellular filamentous material and intercellular junctions in hybrids between tumour and normal cells: abundant gap junctions correlate with density-dependent inhibition of growth
Authors: Stamatoglou S. C. , Marshall C. J. 
Published: April 2021

ABSTRACT
The cell surface and intercellular junctions of transformed and non-transformed hybrid cells, obtained from fusion of murine mammary adenocarcinoma cells (TA3B) and normal rat embryo fibroblasts (REF), were compared with those of the parental cells, using ruthenium red (RR) staining of cells fixed in situ. An RR-positive layer of variable thickness was found on the surface of all cell types. Measurements of the thickness of this layer on the free surface of the cell cultures demonstrated a significant difference between transformed and non-transformed cells. The thickness distribution of the RR layer was similar on the surface of REF and nontransformed hybrid cells, but there was significant variation among all the transformed cell lines.
Extracellular filamentous RR-positive material, usually in direct contact with the cell surface, was present in confluent cultures of REF and non-transformed hybrid cells, but was absent in the transformed cell lines.
Gap junctions were few in both parental cell lines and rare or absent in transformed hybrids; a large increase in number and size of gap junctions was found in non-transformed hybrids. Abundance of long gap junctions was correlated with density-dependent inhibition of growth, since non-transformed hybrids grew in single layers whereas both normal and tumour parental cell types, and transformed hybrids grew in multilayers. Tight junctions were frequently encountered in TA3B and transformed hybrid cells but were not seen in REF cells and only occasionally seen in non-transformed hybrids. Intermediate-type junctions occurred in all cells, but desmosomes were found only rarely in TA3B cells and never in the other cell types.