bluuebunny/crossref_metadata_2025_split huggingface dataset:
Human hair growth in vitro
Authors: Philpott Michael P. , Green Martin R. , Kealey Terence 
Published: April 2021

ABSTRACT
We report for the first time the successful maintenance and growth of human hair follicles in vitro. Human anagen hair follicles were isolated by microdissection from human scalp skin. Isolation of the hair follicles was achieved by cutting the follicle at the dermo-subcutaneous fat interface using a scalpel blade. Intact hair follicles were then removed from the fat using watchmakers’ forceps.
Isolated hair follicles maintained free-floating in supplemented Williams E medium in individual wells of 24-well multiwell plates showed a significant increase in length over 4 days. The increase in length was seen to be attributed to the production of a keratinised hair shaft, and was not associated with the loss of hair follicle morphology. [methyl-3H]thymidine autoradiography confirmed that in vitro the in vivo pattern of DNA synthesis was maintained; furthermore, [35S]methionine labelling of keratins showed that their patterns of synthesis did not change with maintenance.
The importance of this model to hair follicle biology is further demonstrated by the observations that TGF-βl has a negative growth-regulatory effect on hair follicles in vitro and that EGF mimics the in vivo depilatory effects that have been reported in sheep and mice.
Mitochondrial growth and DNA synthesis occur in the absence of nuclear DNA replication in fission yeast
Authors: Sazer Shelley , Sherwood Steven W. 
Published: April 2021

ABSTRACT
Cell growth and division require the doubling of cellular constituents followed by their equal distribution to the two daughter cells. Within a growing population, the ratio of mitochondrial to cellular volume is maintained, as is the number of mitochondrial genomes per cell. The mechanisms responsible for coordinating nuclear and mitochondrial DNA synthesis, and for balancing increases in cell and mitochondrial size are not well understood. In studies of the fission yeast Schizosaccharomyces pombe we quantified cellular and mitochondrial DNA content by both Southern blot analysis and flow cytometry of cells stained with a variety of DNA-binding fluorochromes, which we show are able to detect nuclear and mitochondrial DNA with different efficiencies. In the conditional cell division cycle mutant cdclO, which is unable to initiate nuclear DNA synthesis, we found that there was an increase in the mitochondrial DNA content in the absence of nuclear DNA replication. This demonstrates that mitochondrial and nuclear DNA synthesis are not obligately linked. We also show that mitochondrial DNA replication is not required for the increase in mitochondrial size that occurs as cells elongate, although this results in a decrease in the ratio of mitochondrial DNA to mitochondrial volume.
Identification of a 40×103Mr centromere-associated protein in cultured mammalian cells
Authors: Balczon Ron , Accavitti Mary Ann , Brinkley B. R. 
Published: April 2021

ABSTRACT
Monoclonal antibodies were raised against a complex of proteins that was purified following the crosslinking of tubulin to the centromeres of CHO chromosomes using Lomant’s reagent. One of the clones, hybridoma 32–9, produced antibodies that reacted with a 40×103Mr protein present in the crosslinked complex. Furthermore, immunoblot analysis demonstrated that the 40×103Mr antigen was present in various mammalian cell types from several different species. Indirect immunofluorescence using the antibody produced by clone 32–9 demonstrated that the 40 × 103Mr antigen was associated with both spindle and cytoplasmic microtubules. Ln addition, centromere/kinetochore staining was detected in metaphase-arrested cells, while staining of prekinetochores in interphase nuclei was not observed. Unlike microtubule-associated pro teins and microtubule-dependent ATPases, the 40 ×103 Mr protein did not copurify with microtubules when tubules were assembled from cellular homogenates using taxol and either GTP or GTP and AMP-PNP. Instead, the 40×103Mr protein remained associated with the insoluble cellular material. The 40×103Mr antigen could be released from the insoluble pelleted material by extraction with 1M NaCl. Once solubilized, the 40×103Mr protein was able to copurify with microtubules in assembly assays in vitro. This monoclonal antibody should serve as a valuable probe for studies of centromere/kinetochore structure and function.
Hydrostatic pressure influences histone mRNA
Authors: Symington Alison L. , Zimmerman Selma , Stein Janet , Stein Gary , Zimmerman Arthur M. 
Published: April 2021

ABSTRACT
Exposure of HeLa S3 cells to high hydrostatic pressure (6.89 ×103 to 6.89 ×104 kPa: 1000 to 10000lbfin-2) reduced core and H1 histone mRNA levels as determined by hybridization to specific histone DNA probes. At 4.14×104kPa for 10 min core histone and H1 histone mRNA levels were reduced 32–38% and 56%, respectively. At 30 min post-decompression core mRNA levels returned to atmospheric control levels while H1 histone mRNA levels continued to be suppressed. Levels of macromolecular synthesis were monitored under hydrostatic pressure with radioactive precursors of RNA, DNA and protein. Macromolecular synthesis was shown to be suppressed in a dose-dependent manner with increasing magnitude and duration of pressure. To determine the influence of pressure on histone mRNA stability, actinomycin D (10 μg ml-1) was used to block RNA synthesis. Relative amounts of H4 and H1 mRNA were determined at atmospheric pressure and following treatment with actinomycin D (10μgml1), pressure (4.14×104kPa) and a combination of pressure and actinomycin D. This study shows that a synthesis component and a stability component are involved in the pressure-induced reduction of core histone mRNA. At 4.14×104kPa for 15 min, there was a 42% reduction in core histone mRNA of which approximately one third was due a suppression of transcription and two thirds to a loss of mRNA stability. The pressure-induced reduction in histone mRNA is attributed to the instability of endogenous histone mRNA and a reduction in transcription/processing of new histone mRNA.
Human hepatocellular carcinoma cell lines exhibit multidrug resistance unrelated to Mdr1 gene expression
Authors: Shen D.-W. , Lu Yuan-G. , Chin Khew-V. , Pastan I. , Gottesman M. M. 
Published: April 2021

ABSTRACT
Multidrug resistance of human cancer cells may result from expression of P-glycoprotein, the product of the MDR1 gene, acting as an energy-dependent drug efflux pump. However, direct evidence that expression of the MDR1 gene contributes to the multidrug resistance of human liver carcinomas has not been established. In this study, we tested five cell lines derived from human hepatocellular carcinomas for sensitivity to a variety of drugs used widely as anticancer agents: these included vinblastine, doxorubicin, actinomycin D, mitomycin C, 5-fluorouracil, 6-mercaptopurine, melphalan, methotrexate, cj’s-pla- tinum and etoposide (VP-16). All five hepatoma cell lines were resistant at different levels to these chemicals compared to human KB cells. Although it has been demonstrated that resistance to vinblastine, colchicine, doxorubicin and actinomycin D in human multidrug-resistant cells is associated with overexpression of P-glycoprotein, very little expression of P-glycoprotein was found in these human hepatoma cells. Neither verapamil nor quinidine, inhibitors of the drug efflux pump, were able to overcome multidrug resistance in hepatoma cells. These results indicate that the multidrug resistance phenotype in human hepatocellular carcinoma cells cannot be attributed to expression of the MDR1 gene, but that novel mechanisms may account for the resistance of these cancer cells.
Immunological identification of a new 14×103Mr membrane-bound protein in Torpedo electric organ
Authors: Morel Nicolas , Brochier Guy , Synguelakis Monique , Salle Gildas Le Gal La 
Published: April 2021

ABSTRACT
A series of monoclonal antibodies binding to different epitopes shared by a 14×103Mr membrane-bound polypeptide has been obtained. By indirect immunofluorescence, it was shown that the 14×103Mr antigen is present in various cell types in Torpedo electric organ and muscle, especially fibroblasts, capillary endothelial cells, axonal cuff cells and, to a lesser extent, Schwann cells. At the electron-microscope level, after immunogold labelling, the antigen was found associated with the external surface of the plasma membrane of these cells, with the exception of the axonal cuff cells where part of the labelling was intracellular. The possible biological role of this 14×103Mr protein is unknown but preliminary experiments suggest that this antigen has affinity for other Torpedo electric organ membrane proteins.
Induction of cell processes by local force
Authors: Margolis L. B. , Popov S. V. 
Published: April 2021

ABSTRACT
A method of applying local mechanical force to the plasma membrane of mouse embryo fibroblasts is described. The force is generated by local treatment of cells with an alternating current (a.c.) electrical field. The phenomenon of cell process formation under the action of this force was investigated. Inhibitors of actin polymerization did not prevent generation of processes in the electrical field. At the early stages of cell spreading, the processes could be induced at any part of the cell membrane. After cell polarization was completed, protrusions could beformed at the active edge of the cell, but not at its stable edge. Pre-existing protrusions (but not retraction fibers) could be elongated by the external force. The results of these experiments demonstrate that different areas of the cell membrane differ in their ability to form processes under the action of a membrane-applied force. The significance of these data to the structure of the cortical layer is discussed.
Analysis of the distribution of the INCENPs throughout mitosis reveals the existence of a pathway of structural changes in the chromosomes during metaphase and early events in cleavage furrow formation
Authors: Earnshaw William C. , Cooke Carol A. 
Published: April 2021

ABSTRACT
The INCENPs are two polypeptides of 135 ×103 and 150×103 Mr that enter mitosis as tightly bound chromosomal proteins, but subsequently leave the chromosomes altogether and become associated with the central spindle and cell cortex at the contractile ring. In the experiments reported here we have used confocal microscopy and immunoelectron microscopy to provide a detailed picture of the intracellular location of these proteins during mitosis. The experiments have not only revealed a number of new details concerning the properties of the INCENPs in mitosis, but have revealed a number of novel aspects of the mitotic process itself. The first of these is the existence of a sequential pathway of structural changes in the chromosomes that occurs during metaphase. This pathway is revealed by the existence of four distinct INCENP staining patterns in mitotic cells. In ‘early’ and ‘early/mid’ metaphase, the INCENPs gradually become concentrated at the centromeres, forming a ring at the center of the metaphase plate. During *mid/late’ metaphase they exit from the chromosomes, so that by late metaphase they are found solely in streaks that traverse the plate parallel to the spindle axis. The streaks probably correspond to INCENPs closely associated with microtubule bundles, perhaps as part of the stem body material. Examination of transverse optical sections of the spindle interzone during early anaphase reveals an unexpectedly high degree of order. The INCENP antigens are localized on fibers that are organized into a hollow ring 8 μm in diameter and ∼4μm beneath the cell cortex. Measurement of cellular dimensions in the confocal microscope reveals that the maximum diameter of early anaphase cells lies across the spindle equator, so that when the cleavage furrow forms, it does so around the maximum circumference of the cell. During anaphase, a subpopulation of the INCENP antigen becomes localized to the cortex where the furrow will subsequently form. This occurs prior to any other evidence of furrowing. Thus, binding of the INCENPs to this region may represent an early step in furrow formation. Together, these results suggest that the INCENPs may represent a new class of ‘chromosomal passenger’ proteins that are carried to the spindle equator by the chromosomes and subsequently perform a cytoskeletal role following their release from the chromosomes at the metaphase:anaphase transition.
Derangement of microtubule arrays in interphase and mitotic PtK2 cells treated with deuterium oxide (heavy water)
Authors: Lamprecht Jan , Schroeter Dieter , Paweletz Neidhard 
Published: April 2021

ABSTRACT
The extent and pattern of the rearrangements of microtubule arrays in interphase and mitotic PtK2 cells treated with deuterium oxide (2H2O) were evaluated using light, immunofluorescence and electron microscopy.
Combined labelling with anti-tubulin antibodies and staining with a DNA-specific fluorochrome revealed that 2H2O influences the reassembly of the cytoplasmic microtubule complex (CMTC) of interphase cells after depolymerization of microtubules (MTs) with nocodazole. In cells entering mitosis in the presence of 75% 2H2O the conversion of the CMTC into the mitotic spindle was affected, resulting in a retardation of the prophase/prometaphase transition. (Pro)metaphase cells did not assemble a regular mitotic spindle and the metaphase/anaphase transition was blocked. Immunofluorescence and ultrastructural studies suggest that separation of centrosomes, nucleation of MTs around centrosomes, organization of MTs into the mitotic spindle, as well as the ultrastructure and positioning of the mitotic poles, are affected in deuterated PtK2 cells. In comparison with control cells, a significantly higher proportion of multipolar divisions was found after stimulation of proliferation in the presence of 25-50% 2H2O or during recovery after a long-term exposure to 75% 2H2O.
On the basis of these results we discuss the mechanism of the antimitotic action of deuterium oxide and suggest that, apart from perturbation of MT polymerization, it could also encompass disturbances in MT reorganization, most probably by impairment of the microtubule-organizing centres (MTOC).
Factors influencing perpendicular elongation of embryonic frog muscle cells in a small applied electric field
Authors: McCaig C. D. , Dover P. J. 
Published: April 2021

ABSTRACT
The mechanism controlling the perpendicular elongation of embryonic muscle cells exposed to a small applied electric field has been studied using a pharmacological approach. Inhibition of the inositol phosphate second messenger system, of calcium entry and of microfilament polymerisation all prevented perpendicular elongation. A model involving strengthened adhesion asymmetrically along the cathodal-facing side of round myoblasts and incorporating the above requirements is proposed to explain electric field-induced perpendicular differentiation.
Some asymmetry of organelles is described also, with ribosomes, yolk granules and actin filaments all predominantly found on the anodal side of myoblasts.
Neural crest cell locomotion induced by antibodies to β1 integrins A tool for studying the roles of substratum molecular avidity and density in migration
Authors: Duband Jean-Loup , Dufour Sylvie , Yamada Susan S. , Yamada Kenneth M. , Thiery Jean Paul 
Published: April 2021

ABSTRACT
Migration of neural crest cells depends on direct, transient interactions between fibronectin molecules and their corresponding Arg-Gly-Asp integrin receptors. We have previously suggested that the moderate-avidity interaction between integrin receptors and fibronectin may be critical for the transient association of the cells with their substratum. In order to test this hypothesis, we have examined the in vitro locomotory behavior of neural crest cells on substrata of differing apparent avidities for integrin receptors. As substrata, we used a variety of monoclonal and polyclonal antibodies to the integrin β subunit that were characterized for their respective relative apparent avidities for the receptor. Neural crest cells were able to migrate on these antibodies and exhibited an organization of substratumadhesion sites and of cytoskeletal elements virtually identical to that observed on fibronectin, indicating that they can at least partially mimic the migrationpromoting activity of fibronectin. However, the number of migrating cells as well as their morphology and their speed of locomotion varied significantly with both the concentration of the antibody substratum and its relative avidity for the receptor. Thus, on high-avidity monoclonal antibodies and on polyclonal divalent antibodies at high concentrations only a limited number of cells escaped from the neural tube, and the rate of their migration was reduced compared to that on fibronectin (23±5/μh−1versus 65±10/μh−1). In addition, cells were unusually flattened and cohesive. Time-lapse videomicroscopy revealed that, on high-avidity substrata, neural crest cells were able to extend cell processes that adhered to the substratum, but showed a dramatically reduced capability of breaking pre-existing substratum contacts. In contrast, the same antibodies at low concentrations produced neural crest cell migration at rates very similar to those on fibronectin at the same concentrations. Low-avidity monoclonal antibodies and polyclonal monovalent antibodies at all concentrations tested permitted extensive migration of neural crest cells, which exhibited the same morphology and locomotory behavior as on fibronectin. These results indicate that both the avidity of receptors for the substratum and the number of receptors bound to the substratum are critical in regulating the locomotory behavior of neural crest cells in vitro, and therefore might help to regulate the directionality of migration and final localization pattern of neural crest cells in vivo.
Localization of soluble and insoluble fractions of hydroxyproline-rich glycoproteins during maize kernel development
Authors: Fritz Sue E. , Hood Kendall R. , Hood Elizabeth E. 
Published: April 2021

ABSTRACT
Monoclonal antibodies have been developed against PC-1 protein, the major hydroxyproline-rich glycoprotein (HRGP) from maize pericarp, and have been used as probes in an indirect alkaline phosphatase antibody assay to localize this protein in tissue of three maize varieties. Kernels were sampled several days after pollination (d.a.p.). HRGPs were assayed by reacting antibodies with tissue prints of kernels and embedded tissue samples. Tissue prints show that soluble HRGPs are present in small quantities even at early stages of kernel development The greatest accumulation of PC-1 in the pericarp is at the top of the kernel. As the kernels mature, HRGPs begin to accumulate in the developing embryo. Total HRGPs in embedded tissue begin to accumulate at 10 d.a.p. and increase quite dramatically at 20-30 d.a.p. Popcorn kernels lose antigenic reactivity at 40 d.a.p., while sweet corn kernels continue to show strong reactivity.
A new direct-viewing chemotaxis chamber
Authors: Zicha Daniel , Dunn Graham A. , Brown Alastair F. 
Published: April 2021

ABSTRACT
A new form of chamber for studying chemotaxis, similar in principle to the Zigmond chamber, allows the behaviour of the cells in a linear concentration gradient to be observed directly. The chamber was developed mainly for studying chemotaxis in fibroblasts using interferometric microscopy and the main design criteria were that it should have better optical characteristics, a higher dimensional precision and better long-term stability than the Zigmond chamber. It is made entirely from glass by grinding a blind circular well centrally in the counting platform of a Helber bacteria counting chamber. This procedure leaves an annular ‘bridge’, approximately 1 mm wide, between the new inner circular well and the original outer annular well. This bridge fulfils the same function as the linear bridge of the Zigmond chamber but the preciseconstruction of the counting chamber ensures that a gap of 20/nn between bridge and coverslip can be accurately and repeatedly achieved when the chamber is assembled. It is envisaged that the improved optical clarity, dimensional accuracy and long-term stability of the new chamber will be advantageous in other applications, particularly in studies requiring critical microscopy or a precise knowledge of the gradient and in studies of cells, such as fibroblasts, that move much more slowly than neutrophils.
Isolation and ultrastructural analysis of microfibrillar structures from foetal bovine elastic tissues: Relative abundance and supramolecular architecture of type VI collagen assemblies and fibrillin
Authors: Kielty Cay M. , Cummings Christine , Whittaker Stephen P. , Worth C. Adrian Shuttle , Grant Michael E. 
Published: April 2021

ABSTRACT
Extensive intact assemblies of matrix macromolecules have been solubilized from foetal calf skin, nuchal ligament and aorta by a new procedure that includes bacterial collagenase digestion under nonreducing, non-denaturing conditions and gel filtration chromatography. Type VI collagen was identified as the major microfibrillar element of these tissues by SDS-PAGE analysis and Western blotting. Rotary shadowing electron microscopy of these preparations revealed by far the most abundant and extensive arrays of intact collagen VI microfibrils isolated to date. The distinct microfibrillar species, fibrillin, which was identified on the basis of its periodicity and morphology, was also solubilized in abundance by this protocol. Analysis of these complex polymers has generated new information on their supramolecular architecture and relative abundance in these tissues. The protocol also demonstrates that the release of intact collagen VI microfibrils from these tissues is largely dependent on the removal of the major collagen fibrils.
On Unicellular Plants and Animals
Authors: Siebold C. Th. v. 
Published: April 2021

ABSTRACT
Respecting the motions, which have been frequently noticed in unicellular Algæ, Nägeli observes very truly (p. 19), that they present nothing of a spontaneous or animal character, since they arise, not in the contraction or expansion of the membrane, excited by an external or internal irritant, but proceed singly from the vegetative processes of absorption and excretion of fluid, and the formation and solution of solid matters. Of the four categories of these plant-motions distinguished by Nägeli, we are here interested only in the third and fourth, since it is precisely those which have been confounded with animal movements.
Die Pelanzenzelle, Der Innere Bau Und Das Leben Der Gewachse, &c.
Authors: Schacht Hermann 
Published: April 2021

ABSTRACT
This work, for which the author has recently received a decoration from the King of Prussia, was briefly alluded to in a former part, and we here take occasion to lay a somewhat extended account of it before our readers. Dr. Schacht’s book is one that has attracted great notice, and will have considerable influence on the progress of the microscopic examination of vegetable structure, but this will not be so much the result of originality of the matter contained in it as of the method pursued in the investigations and in the exposition of them. In fact there are few new points, and the merits of the work rest chiefly upon the industry and directness with which the author has worked over the whole field of vegetable anatomy under the point of view laid down in his title, that of comparison of the tissues in the various classes, not merely by simple inspection, but by parallel series of observations on development, assisted by the systematic application of reagents for the determination of the chemical characters. The mode of operation pursued is thus described in the Introduction (p. 7).