bluuebunny/crossref_metadata_2025_split huggingface dataset:
The haemoglobins of healthy and anaemic Xenopus laevis
Authors: Maclean N. , Jurd R. D. 
Published: April 2021

ABSTRACT
The haemoglobins of Xenopus laevis have been studied by carboxymethyl-cellulose column chromatography and by polyacrylamide gel disk electrophoresis. In Xenopus tadpoles, 2 haemoglobins are found (Xenopuj-HbF1 and Aer/opiiS-HbF2). Both haemoglobins persist throughout tadpole life: Aenopur-HbF1 is the main tadpole haemoglobin; Xenopus-HbF2 is present in rather smaller amounts. The proportion of Xenopus-HbF 1 to Xenopus-HbF2 increases as the tadpoles age. Almost all the tadpole haemoglobin disappears soon after metamorphosis, although traces persist throughout adult life. Two adult haemoglobins occur in Xenopus: they first appear during the later tadpole stages. Xenoput-HbA1 comprises the majority of the adult haemoglobin. Between one-twentieth and one-tenth of the adult haemoglobin consists of Xenopus- HbA2, which is not a polymer of Xenopus-HbA1.
Immunoglobulins respectively specific to pooled -Xenopus-HbF1 and Xenopus-HbF2, and to pooled Aeno/wr-HbA1 and Aenopui-HbA2 were raised. Samples of these antibodies were conjugated with fluorescein isothiocyanate.
Adult Xenopus were made anaemic by bleeding or by injection of phenylhydrazine. Fourteen days after the induction of anaemia it was found, using both chromatographic and electrophoretic techniques, that most anaemic toads had started to resynthesize Aenopur-HbF1. In some animals up to 11 % of the haemoglobin present was found to be Xenopus-FLbF1 and precipitin lines were obtained when the pooled haemoglobins from these animals were tested with a specific anti-Xenopnr-HbF immunoglobulin. During recovery from anaemia greatly enhanced amounts of Aenopur-HbA2 (up to 58 % of the total haemoglobin) were present in the blood. The amounts of tadpole haemoglobins present in such recovering toads were not noticeably greater than in healthy animals. Between 42 and 120 days after the induction of anaemia the haemoglobin profile of the toads regained normality.
Blood cell smears were made from anaemic toads which were known to possess abnormal amounts of Xenopus-HbF1 14 days after the induction of anaemia. The smears were treated with specific anti--Xenopus-HbF immunoglobulin conjugated with fluorescein isothiocyanate. Although up to 11 % of the haemoglobin present in the animals was Xenopus -HbF1, the number of fluorescing cells was no greater than in similarly treated smears from healthy control adults possessing less than 1 % Xenopus -HbFl.
It is concluded that during anaemia Xenopus starts to resynthesize one of its tadpole haemoglobins. This resynthesis occurs in many or most of the circulating red cells, and is not confined to a small population of cells. During recovery from anaemia enhanced quantities of Xenopus- HbA2 are made.
Development and deployment of cilia, basal bodies, and other microtubular organelles in the cortex of the ciliate Nassula
Authors: Tucker J. B. 
Published: April 2021

ABSTRACT
The basal bodies contain more internal structures than those described for other organisms. For example, they possess 2 different and separate cartwheel structures. In cilia the 2 central tubules terminate proximally in a different fashion. Three types of cilia have been distinguished. Each type possesses a different array of rootlet fibres. During binary fisión one type develops 1 h before all the others while the ciliary shafts, but not the basal bodies, of a second type are being resorbed. These are later reformed when a third variety of cilia develop. Some new basal bodies and cilia are formed at least 30 min before they can be detected using silver staining. Studies of basal body morphogenesis based on this technique are pertinent to the separation of closely adjacent mature basal bodies rather than to their development. The arrangement and spacing of new basal bodies may be partly defined by their rootlet fibres which interconnect basal bodies before they attain their final positions in the cortex. Overlapping microtubules linking basal bodies apparently slide against each other during the final stages of basal body deployment. Heat shocks often inhibit the attachment of new basal bodies to the pellicle but ciliary and rootlet fibres assemble and grow out from the usual sites on these abnormally positioned basal bodies.
The pellicle is highly impermeable to water and the fine structure of its innermost layer resembles that of the waterproofing epicuticle of some insects. A cuff of this pellicular material forms around the distal end of each new basal body and then seals it to the undersurface of the pellicle. The outer wall of the pellicular chamber so formed breaks down when the ciliary shaft is assembled. This ‘cytoplasm-lock ‘mechanism may ensure that there is no marked change in the permeability of the pellicle when it is penetrated by outgrowing cilia.
A new type of ciliary membranelie is described. Some of its modified cilia possess flanges attached to their outer fibres. These cilia may have a sensory role. Membranelle basal bodies are linked by fibres exhibiting a non-repeating polarized banding pattern which may be involved in defining the arrangement and spacing of these basal bodies.
A ring of microfilaments encircles the narrow duct joining the contractile vacuole to its outlet pore. This ring may act as a sphincter and be involved in the control of water discharge. During binary fission contractile vacuole pores migrate posteriorly. They are apparently pulled by strands of microtubules and microfilaments attached at one end to a pore and anchored at the the other to more posteriorly situated basal bodies.
Ultrastructure of pseudocilia in Tetraspora lubrica (roth) ag
Authors: Lembi Carole A. , Walne Patricia L. 
Published: April 2021

ABSTRACT
The flagella-like, but immobile, pseudocilia of the unicellular green alga, Tetraspora lubrica, have been characterized ultrastructurally and compared with the true flagella of the motile green alga, Chlamydomonas. The basal body and transitional regions of the 2 organelle systems are basically similar. Most of the marked differences occur in the pseudocilium proper, and a few important dissimilarities are found in the cytoplasmic portions of the apparatus. The major differences are: (1)4 instead of 2 proximal striated fibres in the pseudociliary apparatus; (2) a proximal-to-distal progressive decrease in subfibre number from 9 doublet fibres to a solitary fibre in the pseudocilium proper; (3) loss of interconnexions among the subfibres in the pseudocilium proper and a concomitant disorientation of those subfibres; (4) absence of major arms (dynein) on the A subfibre of peripheral doublets; (5) absence of the central pair of fibres. These and other differences are discussed with regard to their possible roles in loss of motility. Additional ultrastructural details - interconnexions between cytoplasmic microtubules and basal body subfibres of pseudocilia and flagella - are described and discussed in terms of their possible roles in the regulation of flagellar movement in motile organisms.
Sialic acid and cell aggregation
Authors: Mcquiddy P. , Lilien J. 
Published: April 2021

ABSTRACT
Chick embryo neural retina cells from 7-, 10- and 14-day embryos and muscle cells from 9-day embryos, dissociated mechanically or with trypsin, reaggregate at the same initial rate whether treated before and during aggregation with active or inactive N-acetyl neuraminidase. JV-acetyl neuraminidase treatment also has no effect on the size or number of aggregates formed over 24 or 48 h of aggregation. It was also found that the amount of trypsin used to dissociate the tissue into single cells alters the initial rate of aggregation but has no effect on the size or number of aggregates formed over a 24-h period.
Distribution of hyaluronate and hyaluronate receptors in the adult lung
Authors: Green Shawn J. , Tarone Guido , Underhill Charles B. 
Published: April 2021

ABSTRACT
In the present study, we have examined the distribution of both hyaluronate receptors and hyaluronate in adult hamster lung. The receptor for hyaluronate is a transmembrane glycoprotein of Mr 85 000 that interacts with actin filaments and is thought to mediate many of the effects that hyaluronate has on cell behaviour, such as cell-to-cell adhesion and migration. It was localized histochemically with a monoclonal antibody, designated as K-3, which specifically binds to the receptor. Hyaluronate was detected by a biotinylated form of cartilage proteoglycan, which binds with high affinity and specificity to hyaluronate. At the light-microscopic level, both hyaluronate and its receptor were present on the basolateral surfaces of bronchial and bronchiolar epithelium, suggesting that these two components interact with each other. This interaction may be important for maintaining the attachment of the epithelium to the basement membrane. In addition, hyaluronate was present in the adventitial regions of large pulmonary blood vessels. Receptors for hyaluronate were also evident on the surfaces of pulmonary macrophages, as demonstrated by the fact that K-3 immunoreactive cells coincided with cells positive for non-specific esterase, a characteristic feature of macrophages. The receptors on pulmonary macrophages probably mediate the effects that hyaluronate has on these cells with respect to cell-to-cell adhesion and migration.
G-proteins in mammalian gametes: An immunocytochemical study
Authors: Garty Nira B. , Galiani Dalia , Aharonheim Ami , Ho Yee-Kin , Phillips David M. , Dekel Nava , Salomon Yoram 
Published: April 2021

ABSTRACT
The presence of transductory GTP(G)-regulatory proteins in mammalian gametes has been examined by indirect fluorescence immunocytochemistry. Using rabbit antisera to bovine rod /β γ-transducin (RAβγT), bovine rod holotransducin (AS–1), bovine rod α-transducin (RAαT), synthetic bovine rod α-transducin C-terminal decapeptide (AS–6), bovine brain α39Gο (RAα39), and two mouse monoclonal antibodies raised against frog retinal trans-ducin (4A), and rat brain β-tubulin, we demonstrated the presence of corresponding immunoreactive material in both rat oocytes and bovine ejaculated sperm. Immunostaining in the oocyte was evenly distributed on the oolemma, excluding the cell cytoplasm and zona pellucida. Immunoreactive material was also present in the cumulus cells that encapsulate the oocyte. In contrast, the immunofluorescence corresponding to transductory G–proteins was confined in sperm to functionally defined regions in the head and tail, in a manner specific for each antibody. While RA/β γT, AS-1 and RAα39 all stained the entire acrosome, AS–6 and RAαT stained only the acrosomal tip. Monoclonal antibody 4A stained the midpiece exclusively and anti-rat β-tubulin (a structural G–protein) stained the full length of the sperm tail. The existence of several G-protein types in mammalian gametes suggests their possible involvement in the regulation of various effector systems, in a manner reminiscent of somatic cells. The unique situation in sperm, where different G–proteins show distinct and specific patterns of distribution, further suggests their association with various effector systems in discrete functional domains.
Dna repair and transcriptional activity in genes
Authors: Bohr Vilhelm A. 
Published: April 2021

Recent findings on the genomic heterogeneity of mammalian DNA repair have disclosed new features about molecular aspects of the repair processes and have also raised new interesting questions to help direct our research. The studies on preferential DNA repair in active genes demonstrate that there are variations in the repair processes corresponding to different parts of the genome and we are now attempting to study how these processes are regulated or controlled. In this commentary, it seems pertinent to discuss an important aspect of the preferential DNA repair mechanisms, the potential relationship between the DNA repair efficiency, the local chromatin structure and the transcriptional activity for a specific mammalian gene.
Most of the available results on DNA repair in specific genomic sequences are based on a technique to measure damage and repair after ultraviolet (u.v.) irradiation using quantitative hybridization (Bohr et al. 1985; Bohr & Okumoto, 1988) and have been reviewed recently (Bohr et al. 1987). The initial findings were that the essential, active gene dihydrofolate reductase (DHFR) was preferentially repaired in hamster and human cells (Bohr et. al. 1985; Mellon et al. 1986), and some results have been outlined in Table 1. The fine structure of DNA repair in and around the DHFR gene in CHO cells has been examined, and it was found that the preferential DNA repair was confined to a genomic region of about 60–80 kilobases. This region has been called a DNA repair domain and its size corresponds well with described higher order structures or loops in chromatin (Bohr et al. 1986). However, further studies are needed to clarify whether DNA repair is regulated within such loops in chromatin.
Visualization of the cytoplasmic Ca2+ gradient in Fucus serratus rhizoids: Correlation with cell ultrastructure and polarity
Authors: Brownlee Colin , Pulsford Ann L. 
Published: April 2021

ABSTRACT
Fura-2 has been used with digital image analysis to visualize and quantify the cytoplasmic Ca2+ gradient in rhizoid cells of Fucus serratus. Ca2+ was higher at the growing rhizoid tip in about 50-60% of cells studied to date. Considerable variation in the pattern of the Ca2+ gradient has been found. Verapamil reduced but did not abolish the Ca2+ gradient. Nifedipine had no effect on Ca2+ distribution during the experimental period. Removing Ca2+ from the growth medium permeabilized the plasmalemma and allowed fura-2 to efflux from the cytoplasmic compartment, permitting an assessment of the degree of sequestration of the dye into vacuoles and vesicles. Comparisons of ratio images with electron micrographs suggested that lower Ca2+ levels were associated with the nuclear region, but there was no direct correlation between Ca2+ levels and vesicle distribution in healthy cells. The role of localized differences in Ca2+ distribution in the control of polarity is discussed.
The prometaphase configuration and chromosome order in early mitosis
Authors: Chaly Nathalie , Brown David L. 
Published: April 2021

ABSTRACT
We have examined early mitotic stages in HeLa cells, mouse 3T3 fibroblasts and mitogen-activated mouse lymphocytes by immunofluorescence labelling with anti-tubulin and anti-centromere. Chromatin organization was monitored with the DNA-specific fluorochrome Hoechst 33258. This approach has led us to identify a modified Rabi array of chromosomes and spindle microtubules early in mitosis that is distinct from that at metaphase, and which we have called ‘the prometaphase configuration’. In the configuration, chromosomes are oriented so that telomeres are clustered at the outer surface, whereas centromeres are clustered inside the configuration, at the surface of a hollow spindle. Observations on cells earlier in mitosis indicate that the configuration is presaged by the spatial relationship between chromosomes and cytoplasmic microtubules in prophase and early prometaphase. We propose a model in which the prometaphase configuration represents an important step linking prophase and metaphase, serving to translate interphase spatial and intragenomic order into order at the metaphase plate.
Incorporation of tubulin from an evolutionarily diverse source, Physarum polycephalum, into the microtubules of a mammalian cell
Authors: Prescott A. R. , Foster K. E. , Warn R. M. , Gull K. 
Published: April 2021

ABSTRACT
Physarum myxamoebal tubulin was injected into PtK2 cells to determine whether tubulin from this eukaryotic microbe could act as a reporter for microtubule growth and dynamics in a mammalian cell. The distribution of Physarum tubulin was determined by the use of a monoclonal antibody specific for Physarum tubulin and unable to detect mammalian tubulin. Physarum tubulin was incorporated into the microtubules of both interphase arrays and the mitotic spindle. Measurements of microtubule turnover kinetics were found to be similar to those of other studies in which chemically modified brain tubulin has been used. Results using this heterologous system demonstrate that tubulin from an evolutionarily diverse organism can be used as a marker for microtubule growth in mammalian cells. Furthermore, the Physarum tubulin was able to endow the injected cells with novel properties. Resistance to colchicine-induced microtubule disassembly, a characteristic of Physarum tubulin, was conferred on the injected PtK2 cells. Use of this heterologous reporter tubulin system has also revealed features of variation in microtubule dynamics both within individual cells and between cells.
Intracellular transport of the glycoprotein of VSV is inhibited by CCCP at a late stage of post-translational processing
Authors: Burkhardt Janis K. , Argon Yair 
Published: April 2021

ABSTRACT
The appearance of newly synthesized glycoprotein (G) of vesicular stomatitis virus at the surface of infected BHK cells is inhibited reversibly by treatment with carbonylcyanide m-chlorophenylhydrazone (CCCP). Under the conditions used, CCCP treatment depleted the cellular ATP levels by 40-60%, consistent with inhibition of transport at energy-requiring stages. The G protein that ac-cumulates in cells treated with CCCP is heterogeneous. Most of it is larger than the newly synthesized G protein, is acylated with palmitic acid, and is resistant to endoglycosidase H (Endo H). Most of the arrested G protein is also sensitive to digestion with neuraminidase, indicating that it has undergone at least partial sialylation. A minority of G protein accumulates under these conditions in a less-mature form, suggesting its inability to reach the mid-Golgi compartment. The oligosaccharides of this G protein are Endo-H-sensitive and seem to be partly trimmed. Whereas sialylated G protein was arrested intracellularly, fucose-labelled G protein was able to complete its transport to the cell surface, indicating that a late CCCP-sensitive step separates sialylation from fucosylation. These posttranslational modifications indicate that G protein can be transported as far as the trans-Golgi in the presence of CCCP and is not merely arrested in the endoplasmic reticulum.
Effects of vitamin a on growth and differentiation of human tracheobronchial epithelial cell cultures in serum-free medium
Authors: Chopra D. P. , Klinger M. M. , Sullivan J. K. 
Published: April 2021

ABSTRACT
Differentiating epithelial cell cultures from human tracheobronchial epithelium have been propagated in serum-free medium. The major objective of this study was to examine the trophic effects of vitamin A on cell multiplication and morphology of the tracheal cell cultures. The cellular responses were analyzed in terms of growth kinetics, morphological and ultrastructural alterations and secretion of glycoconjugates. Cell cultures in control medium exhibited characteristics of epithelial cells including microvilli on cell surfaces, desmosomes between cells, and numerous secretory vesicles in the cytoplasm. Vitamin A at 10−6 M and 10−7 M inhibited cell replication and enhanced the secretion of [3H]glucosamine-labeled glycoconjugates. Further, vitamin A increased the production of plasma membrane vesicles and acquisition by the cells of a highly secretory ultrastructure. This in vitro model of human epithelial cells will be important in the investigation of various aspects of growth and differentiation.
Saccharide expression on wounded endothelial cell monolayers in vitro
Authors: Ball R. Y. , Stoddart R. W. , Jones C. J. P. , Mitchinson M. J. 
Published: April 2021

ABSTRACT
Monolayer cultures of porcine aortic endothelial cells were used as a model of the endothelium of large arteries. Linear wounds were produced in such cultures by scraping and the subsequent sequence of events in nearby cells was analysed. The earliest detectable event was cellular spreading at the margins of the wounds (2h) followed by cell migration (starting at 6–8 h) and cell proliferation in regions adjacent to the wound (16 h and later). Cell spreading was associated with the appearance of saccharides selectively at the spreading margins of the cells, which bound the lectins, ConA, LCA and PSA, and were sensitive to a-mannosidase. Terminal a-mannosyl residues were therefore present.
The appearance of these saccharides suggests a mechanism by which monocytes might adhere to and/or migrate through the endothelium of vessels at sites of cellular response to injury.
Morphometric analysis of isolated Zea mays sperm
Authors: Wagner Vincent T. , Dumas Christian , Mogensen H. Lloyd 
Published: April 2021

ABSTRACT
Recently developed techniques for the isolation of sex cells of flowering plants represent an important first step toward eventual detailed cytological and biochemical analyses and experimental manipulations of higher plant gametes that was not previously possible. In the present investigation we have analysed a population of isolated viable male gametes from the standpoint of qualitative and quantitative ultrastructure in order to elucidate the process of double fertilization in angiosperms. The vast majority of the Zea mays sperm cells were found to be structurally intact spherical cells. Morphometric analysis of 400 isolated sperm cells indicates that the average cell is 7·66 μm in diameter, has volume and surface areas of 235·3 μm3 and 184·3 μm2, respectively, and contains a variously shaped, often curved nucleus, which occupies 38·5% of the cell volume. Other cell constituents and their relative volumes (expressed as percent ages of the protoplasm) included in the analysis are: vacuoles, 9·3%; endoplasmic lamellae, 5·9%; mitochondria, 3·5%; osmiophilic bodies, 1·2%; Golgi complex, 0·6%; and hyaloplasm (background cytoplasm), 41·1%. No plastids or microtubules were observed in the hybrid line used.
Two types of nuclei were found, i.e. heterochromatic and non-heterochromatic. Although statistical analysis of cell components shows some significant differences between cells of the two nuclear types, we do not believe that they represent the two sperms of a pair within pollen grains, since they do not occur in a 1:1 ratio. It is more likely that the variability within the sperm population is the result of slightly different developmental states at the time of anther dehiscence.
Expression of a cell surface antigen in Dictyostelium discoideum in relation to the cell cycle
Authors: Krefft Marianne , Weijer Corneeis J. 
Published: April 2021

ABSTRACT
We have previously shown binding of a monoclonal antibody MUD 9 to the cell surface of Dictyostelium discoideum amoebae and slug cells. In the slug stage the prestalk region was predominantly labelled, while vegetative amoebae showed a great heterogeneity in binding. In the present paper it is shown that the heterogeneous label of vegetative amoebae is due to differences in MUD 9 binding by cells in different cell cycle phases. Cells were synchronized by dilution from stationary phase and the level of MUD 9 binding was determined. Synchrony was determined by investigating increase in cell number and changes in the volume distribution of the cells, and by estimating the number of cells in S phase by monitoring bromodeoxyuridine (BUdR) incorporation. Simultaneously the amount of MUD 9 binding was determined by quantitative microscopy and flow cytometry. The amount of MUD 9 label varies during the cell cycle. The highest amount of label is found on cells early in the cell cycle, i.e. S-phase. These results support the finding that the developmental fate of Dictyostelium discoideum cells depends among other things on the cell cycle position of the cells at the moment of starvation.