bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pulsed DC electric fields couple to natural NAD(P)H oscillations in HT-1080 fibrosarcoma cells
Authors: Rosenspire Allen J. , Kindzelskii Andrei L. , Petty Howard R. 
Published: April 2021

ABSTRACT
Previously, we have demonstrated that NAD(P)H levels in neutrophils and macrophages are oscillatory. We have also found that weak ultra low frequency AC or pulsed DC electric fields can resonate with, and increase the amplitude of, NAD(P)H oscillations in these cells. For these cells, increased NAD(P)H amplitudes directly signal changes in behavior in the absence of cytokines or chemotactic factors. Here, we have studied the effect of pulsed DC electric fields on HT-1080 fibrosarcoma cells. As in neutrophils and macrophages, NAD(P)H levels oscillate. We find that weak (∼10−5 V/m), but properly phased DC (pulsed) electric fields, resonate with NAD(P)H oscillations in polarized and migratory, but not spherical, HT-1080 cells. In this instance, electric field resonance signals an increase in HT-1080 pericellular proteolytic activity. Electric field resonance also triggers an immediate increase in the production of reactive oxygen metabolites. Under resonance conditions, we find evidence of DNA damage in HT-1080 cells in as little as 5 minutes. Thus the ability of external electric fields to effect cell function and physiology by acting on NAD(P)H oscillations is not restricted to cells of the hematopoietic lineage, but may be a universal property of many, if not all polarized and migratory eukaryotic cells.
Superactivation of integrin αvβ3 by low antagonist concentrations
Authors: Legler Daniel F. , Wiedle Guido , Ross F. Patrick , Imhof Beat A. 
Published: April 2021

ABSTRACT
Integrins are implicated in cell adhesion, migration and homeostasis. An important feature is their ability to adopt different affinity states that can be regulated by a variety of intra- and extracellular factors. To study affinity modulation of the integrin ectodomain by extracellular factors, we produced a soluble recombinant form of mouse integrin αvβ3 in a mammalian expression system and isolated it to purity. We show that the two transmembrane truncated integrin subunits stably associate to form a functional receptor, soluble recombinant αvβ3. The affinity of this receptor for its ligands vitronectin, fibronectin and fibrinogen can be modulated by the divalent cations magnesium, calcium and manganese. Most importantly, we found that a cyclic RGD-peptide has a biphasic effect on rsαvβ3 and native purified αvβ3, with an antagonistic phase at high concentrations, and an agonistic phase at low concentrations. This integrin superactivation by low antagonist concentrations is shown in binding of srαvβ3 to immobilized ligands by ELISA, and in adhesion of cells that express the chimaeric integrin ligand KISS31 to immobilized rsαvβ3 and native purified αvβ3. Our results indicate that low concentrations of the ligand mimetic cyclo-RGD can result in superactivation of the extracellular domain of integrin αvβ3 to a comparable level as activation by manganese.
Phosphatidylinositol 3-kinase mediates integrin-dependent NF-κB and MAPK activation through separate signaling pathways
Authors: Reyes-Reyes Merit , Mora Nancy , Zentella Alejandro , Rosales Carlos 
Published: April 2021

ABSTRACT
Integrin-mediated signals play an important but poorly understood role in regulating many leukocyte functions. In monocytes and monocytic leukemia cells, β1 integrin-mediated adhesion results in a strong induction of immediate-early genes that are important in inflammation. To investigate the signaling pathways from integrins in monocytic cells, THP-1 cells were stimulated via β1 integrins by binding to fibronectin and by crosslinking the integrins with specific monoclonal antibodies. The involvement of MAPK and PI 3-K on nuclear factor kB (NF-κB) activation was then analyzed. We found that integrins activated both NF-κ B and MAPK in a PI 3-K-dependent manner, as wortmannin and LY294002 blocked these responses. However, the specific MEK inhibitor PD98059 did not prevent integrin-mediated NF-kB activation. In contrast, a dominant negative mutant of Rac completely prevented NF-κ B activation, but it did not affect MAPK activation. These results indicate that integrin signaling to NF-κ B is not mediated by the MAPK pathway, but rather by the small GTPase Rac. In addition, a dominant negative form of Rho augmented NF-κ B activation and blocked MAPK activation, implying that these two pathways are in competition with each other. These data suggest that integrins activate different signaling pathways in monocytic cells. One uses PI 3-K and Rac to activate NF-κ B, while the other uses PI 3-K, MEK, and MAPK to activate other nuclear factors, such as Elk-1.
feh-1 and apl-1, the Caenorhabditis elegansorthologues of mammalian Fe65 and β-amyloid precursor protein genes, are involved in the same pathway that controls nematode pharyngeal pumping
Authors: Zambrano Nicola , Bimonte Marida , Arbucci Salvatore , Gianni Davide , Russo Tommaso , Bazzicalupo Paolo 
Published: April 2021

The multigenic family of mammalian Fe65s encodes three highly similar proteins with the same modular organisation: a WW domain and two phosphotyrosine-binding domains. The PTB2 domain of these proteins binds to the cytosolic domains of the Alzheimer's β-amyloid precursor protein APP and related proteins APLP1 and APLP2, generating a highly redundant system that is hard to dissect by reverse genetics. By searching potential Fe65-like genes in the nematode Caenorhabditis elegans, we identified a single gene, feh-1 (Fe65 homolog-1), encoding a protein with a high sequence similarity to mammalian Fe65s. FEH-1 is also functionally related to mammalian orthologues;in fact its PTB2 domain binds to APL-1, the product of the C. elegansorthologue of APP. Staining with specific antibodies show that the neuromuscular structures of the pharynx are the sites in which FEH-1 is present at highest levels. Expression studies with reporters indicate that the feh-1 gene is also expressed by a subset of the worm neurons.
We generated and isolated a deletion allele of feh-1, and the corresponding homozygous mutants arrest as late embryos or as L1 larvae,demonstrating for the first time an essential role for a Fe65-like gene in vivo. The pharynx of homozygous larvae does not contract and the worms cannot feed. Analysis of pharyngeal pumping in heterozygous worms and in feh-1 RNA-interfered worms indicates that dosage of feh-1function affects the rate of pharyngeal contraction in C. elegans. Interference with apl-1 double-stranded RNA showed a similar effect on pharyngeal pumping, suggesting that FEH-1 and APL-1 are involved in the same pathway. The non-redundant system of the nematode will prove useful for studying the basic biology of the Fe65-APP interaction and the molecular events regulated by this evolutionarily conserved system of interacting proteins.
Light saturation of growth and photosynthesis of the shade plant Marchantia Polymorpha
Authors: Mache R. , Loiseaux S. 
Published: April 2021

ABSTRACT
The growth rate of the shade plant Marchantia was at its maximum for a low illumination, 2–3 × 103 lx, and was inhibited by an excess of light.
Photosynthesis by intact thalli and by isolated chloroplasts of Marchantia was saturated by a light intensity of 2–3 × 103 lx. These isolated chloroplasts were able to carry on satisfactory rates of photosynthesis, up to 35 μM CO 2 /h/mg chlorophyll.
The Hill reaction and photosystem II were also saturated by the same light intensities, demonstrating that the factor limiting the light saturation of photosynthesis is located in the chloroplast. The structure of chloroplasts was strongly modified by an excess of light, small grana and fret membranes being replaced by continuous grana.
Panoramic views of cells in tissue culture using an orbiting chamber
Authors: Hlinka J. , Sanders F. K. 
Published: April 2021

ABSTRACT
A new method has been developed for observing single, or small groups, of cells at an angle that can be varied from 0 to 360 °. A better understanding can thus be achieved of cell/cell and cell/substrate interactions during locomotion, adhesion and, especially, emperipolesis and phagocytosis.
Erythropoiesis in the newt, Triturus Cristatus laur. : I. identification of the ‘erythroid precursor cell’
Authors: Grasso J. A. 
Published: April 2021

ABSTRACT
Phenylhydrazine injection in salamanders (Triturus sp.) produces a complete loss of all erythrocytes and haemoglobin but does not result in an immediate erythropoietic response. Splenectomized newts survive absence of the erythron most readily. At 11–14 days after injection, the peripheral blood contains numerous, primitive cells which exhibit large, leptochromatic nuclei, wide variation in cytoplasmic basophilia, and variation in cell size. These cells constitute a spectrum of cells collectively called ‘erythroid precursor cells’ (EPC) which terminate in the formation of basophilic erythroblasts. Earlier cell forms (at 11 days) contain few cytoplasmic ribosomes and few organelles but the ribosome concentration gradually increases, as does a fibrillogranular precipitate presumed to be associated with haemoglobin synthesis. Metabolically, these cells are engaged in proliferation, RNA, haem, and protein synthesis. Erythroid precursor cells, which comprise 50–60% of the total blood cell population at 11–14 days, are replaced by basophilic erythroblasts at 15–18 days. The morphological and metabolic properties of these cells are compatible with their role in red blood cell formation. However, their similarity to mammalian marrow ‘transitional’ cells and the occurrence of similar cells in association with macrophages suggest possible differentiative potencies along several cell lines. While little is known about the origin of erythroid precursor cells, preliminary experiments suggest that they may be derived from circulating lymphocytes.
Ultrastructural and cytochemical features of mammalian skeletal muscle fibres following denervation
Authors: Gauthier Geraldine F. , Dunn Rosemary A. 
Published: April 2021

ABSTRACT
After denervation, the usual cytochemical criteria for identifying fibre types in mammalian skeletal muscle are lost, and thus ultrastructural analysis becomes essential. The width of the Z-line is a valuable criterion for the identification of fibre types in normal muscle, and the differences in width remain apparent even after denervation. In the red portion of the normal rat semitendinosus muscle, there is a mixture of red, intermediate and white fibres. The red fibre has the highest mitochondrial content and the widest Z-line, whereas the white fibre has the lowest mitochondrial content and the narrowest Z-line (about half as wide as that of the red fibre). The intermediate fibre is intermediate in both characteristics. At 14 days after denervation, there is a shift toward a more homogeneous population of fibres, which are rich in mitochondria, but which have an ultrastructural appearance distinct from that of normal fibres. Most of the fibres resemble normal red or intermediate fibres, but lack the characteristic subsarcolemmal aggregations of mitochondria. There are also some fibres which exhibit severe myofibrillar disruption. These have narrow Z-lines, and are therefore classified as white fibres. This suggests that there is a preferential alteration of white fibres, and that their degradation may be responsible for the apparent increase in the proportion of red or intermediate fibres at this stage of denervation. In these disrupted fibres the sarcoplasmic membrane systems lose their usual organization, and triads become aligned parallel to the longitudinal axis of the myofibrils. All fibres, therefore, are, to some extent, altered by denervation, though the changes differ according to the type of fibre.
In normal fibres, ribosomes are sparse, but following denervation they are abundant, particularly at the periphery. This is a general response to removal of the nerve supply, and does not appear to be related to fibre type; but it is more apparent in red and intermediate fibres, which possess an extensive superficial sarcoplasm. Conspicuous aggregations of large mitochondria normally occur in the subsarcolemmal region of these fibres, but after denervation, there are, instead, massive accumulations of free ribosomes and a few cisternae of roughsurfaced endoplasmic reticulum. Our observations suggest, moreover, that this concentration of protein-synthetic machinery corresponds to a spread in the sensitivity to acetylcholine along the surface of the fibres.
Abolition by myosin and heavy meromyosin of the inhibitory effect of smooth-muscle actomyosin antibodies on cell aggregation In Vitro
Authors: Kemp R. B. , Jones B. M. , Gröschel-Stewart U. 
Published: April 2021

ABSTRACT
The ability of anti-chicken smooth-muscle actomyosin γ-globulins (anti-GAM) to inhibit the aggregation of dissociated cells from the skeletal muscle and liver of chick embryos was abolished by pretreatment of the anti-GAM with either myosin or heavy meromyosin (HMM). When the same cells were treated with HMM at a concentration of 1 mg per 2×10’ cells/ml Eagle’s MEM they aggregated as readily as untreated cells.
The negative electrophoretic mobility of the embryonic chick fibroblastic cells was significantly reduced by the globulin fraction of anti-GAM but not of HMM-treated anti-GAM or non-immunized rabbit serum. Anti-chicken striated muscle actomyosin γ-globulins slightly reduced negative mobility but HMM had no effect.
The experiments show that the inhibitory effect on cell aggregation of anti-GAM preparations is produced by the anti-myosin antibodies. They also provide support for the theory that a surface-localized myosin-like protein has a regulatory function in cell adhesion.
The mammalian intervertebral disk: Fibrous structures of the whale nucleus pulposus
Authors: Ludowieg J. J. , Parker J. 
Published: April 2021

ABSTRACT
Striated fibres showing a beaded appearance in the electron microscope were prepared from the insoluble collagen residue of foetal nucleus pulposus. The assembling and stability of the beaded fibres are controlled to a significant degree by electrostatic forces. In acid solutions (pH 2·0) the organization of the structures is preserved. Analytical data on the preparations show the presence of proteoglycans containing chondroitin sulphate and keratan sulphate, as well as collagen.
Contractile filamentous material in the pillar cells of fish gills
Authors: Bettex-Galland M. , Hughes G. M. 
Published: April 2021

ABSTRACT
The secondary lamellae of the gill filaments are the sites of gas exchange in fish gills. They are mainly composed of 2 epithelial sheets joined together by pillar cells. These cells are characterized by collagen columns contained in infoldings of the cell membrane and oriented perpendicular to the epithelial sheets. The gill is the first organ to which the blood flows from the heart and within the secondary lamellae it flows through channels between the pillar cells.
The presence in the pillar cells of fine cytoplasmic filaments situated parallel to the collagen columns has now been observed in many fishes and the hypothesis has been advanced that they constitute a contractile system.
This paper describes how gill filaments were treated in a way similar to that used for other non-muscular cells in order to demonstrate in situ the presence of contractile proteins of the actomyosin type. Gill filaments were extracted in glycerol-containing solutions of low ionic strength, and then incubated with and without ATP. After incubation with ATP examination in the electron microscope showed that in the vicinity of the collagen columns, the pillar cells contain clusters of disordered thin filaments intermingled with spindle-shaped needles. This structure is characteristic of muscle actomyosin, as well as actomyosin-like proteins extracted from cells of non-muscular origin and fixed in a contracted state. It is deduced that the thin cytoplasmic filaments surrounding the collagen columns consist of an actomyosin-like con-tractile protein. On incubation of extracted gill filaments without ATP, the expected negativeresult was obtained, i.e. the filaments retain their orientation parallel to the columns. The function of the contractile filaments within the pillar cells is discussed in relation to the control of blood flow through the secondary lamellae and the reduction of pressure drop during the flow of blood across the gills of fish.
Factors determining the site of synthesis of poliovirus proteins: The early attachment of virus particles to endoplasmic membranes
Authors: Fenwick M. L. , Wall Margaret J. 
Published: April 2021

ABSTRACT
Cytoplasmic extracts of HeLa cells made 1 to 2 h after infection with radioactive poliovirus contained 150-s virus particles and 130-s, perhaps partially disrupted, particles. The latter were resistant to RNase but sensitive to dodecylsulphate. Both particles were associated with fast sedimenting material from which they could be released by deoxycholate, but not by EDTA. In isopyenic gradients of sucrose in D2O the labelled particles formed a sharp band coincident with membrane-bound ribosomes at a density of 1·23 g cm”3. It is suggested that attachment of virus particles to endoplasmic reticulum may be an early stage in the infectious cycle, determining the site of subsequent steps.
The inhibition of cellular protein synthesis that develops during infection affects membrane-bound as well as free polysomes and therefore does not determine the membrane-association of viral protein synthesis.
Some aspects of remyelination after demyelination produced by the intraneural injection of lysophosphatidyl choline
Authors: Hall Susan M. 
Published: April 2021

ABSTRACT
The morphology of remyelination following demyelination induced by the intraneural injection of lysophosphatidyl choline, LPC, has been examined in the mouse sciatic nerve, at periods up to 240 days post-injection. It was found that, in many fibres, the process resembled primary myelinogenesis. There was a moderate Schwann cell proliferation; those Schwann cells not involved in remyelination remained closely associated with the remyelinating Schwann cell/axon unit, within a common basal lamina tube. Numerous small axons, considered to be sprouts from the remyelinating axon, were observed lying in contact with the ‘supernumerary Schwann cells’.
In a small population of fibres, however, atypical morphological features were consistently seen: (i) multiple mesaxons, indicating probable remyelination by tunication; (ii) paranodal reorganization in the junctional zone; (iii) the formation of internodal ‘pseudonodes’, which subsequently underwent transition into incisures of Schmidt-Lanterman.
These structures are discussed in terms of the re-establishment of the Schwann cell/axon relationship.
Electron-microscopic observations on the macronuclear development of Stylonychia Mytilus and Tetrahymena Pyriformis (Ciliophora-Protozoa)
Authors: Murti K. G. 
Published: April 2021

ABSTRACT
This report describes an ultrastructural investigation of macronuclear development follow-ing conjugation in Stylonycltia mytilus (a spirotrichous ciliate) and Tetrahymena pyriformis (a holotrichous ciliate).
In S. mytilus, polytene chromosomes are formed in the young macronucleus (macronuclear Anlage). They are subsequently broken between the bands by ‘membranous’ partitions; the assembly of the membranes appears to be concomitant with the formation of the polytene chromosomes. The membranes in the Anlage appear to originate from fibrous material seen in the early Anlage. This fibrous material in the earlier stages is seen concentrated at several points along the border of the inner nuclear membrane. In the later stages it is seen in the interior of the Anlage, outlining the developing polytene chromosomes. As the chromosomes reach the maximum degree of polyteny, the fibrous material condenses to acquire a mem-branous appearance and extends into the interband regions. The Anlage throughout this period shows a progressive increase in size.
Subsequently, the membranes enclose individually each band plus portions of the 2 adjacent interband regions of the polytene chromosomes to form a large number of vesicles. After vesicle formation the Anlage shrinks, and the chromatin inside the vesicles shows degradative changes. Finally, the vesicles disappear, the membrane degradation products appear at the nuclear membrane, and the Anlage now contains nucleoli. The Anlage increases its DNA content by multiple roundsof replication to become a mature macronucleus. The ultra-structural changes observed in the Anlage support the idea of genetic diminution (i.e. extensive DNA synthesis, elimination of many DNA nucleotide sequences, and amplification of the remaining DNA nucleotide sequences in a second period of DNA synthesis) proposed earlier on the basis of cytochemical, biochemical, and limited electron-microscope studies.
In T. pyriformis, the macronuclear development differs substantially from that of Stylonychia. Features such as the formation and degradation of polytene chromosomes are absent in the macronuclear development of Tetrahymena; the young macronucleus in this cell becomes a mature macronucleus by progressive increment in size and chromatin content with no apparent genetic diminution. These observations agree with cytochemical studies on the macronuclear development of Tetrahymena.
Timing of the first cleavage division of haploid mouse eggs, and the duration of its component stages
Authors: Kaufman M. H. 
Published: April 2021

ABSTRACT
Mouse eggs were activated by treatment with hyaluronidase which removed the follicle cells, followed by culture in vitro, and examined at the first cleavage mitosis. Second polar body extrusion usually occurred and haploid parthenogenesis was initiated. Air-dried chromosome preparations were made between 11 and 15·5 h after activation. Out of the 308 eggs examined 74 had already progressed to the 2-cell stage; the remaining 234 at the 1-cell stage were examined in detail. All chromosome preparations of the first cleavage mitosis were classified into groups corresponding with the stages of prometaphase, metaphase (early or ‘pre-chromatid’, ‘chromatid’ and ‘late chromatid’) and anaphase.
An indirect estimate was made of the duration of the first cleavage mitosis and of its com-ponent stages from the incidence of stages observed at different time intervals after activation. Similar eggs were also observed at 37 °C by time-lapse cine-photography and the interval between the disappearance of the pronucleus to the beginning of telophase of the first cleavage division was determined. The results of timing studies on the haploid eggs were compared with results obtained from similar observations on the first cleavage division of fertilized eggs which would of course normally be diploid.
Artificially activated eggs with2 pronuclei, resulting from second polar body suppression, were also examined, and serial chromosome preparations during mitosis showed that the 2 pronuclear chromosome groups unite on the first cleavage spindle and divide to give a hetero-zygous diploid 2-cell embryo.