bluuebunny/crossref_metadata_2025_split huggingface dataset:
The uptake and localization of catecholamines in chick embryo sympathetic neurons in tissue culture
Authors: England J. M. , Goldstein M. N. 
Published: April 2021

ABSTRACT
The uptake of exogenous [3H]dopamine, [3H]norepinephrine, and [3H]epinephrine by dissociated chick embryo sympathetic neurons growing in tissue culture was studied by autoradiography. The neurons, growing in a medium containing nerve growth factor, rapidly and specifically took up all three catecholamines for at least 60 days, while no uptake was observed in several other cell types, including satellite cells and chick dorsal-root ganglion cells. The uptake was dependent on the concentration of the catecholamine and the duration of the pulse and was inhibited by cocaine and several sympathomimetic amines.
Labelling was visualized only with fixatives which react with catecholamines to form waterinsoluble compounds.
Autoradiographs showed that the label was much denser over the axons than the cell bodies. The label was distributed uniformly along the axons and did not seem to be preferentially localized at the axon terminals or varicosities which contain aggregates of dense core granules. These observations indicate that a large portion of the exogenous 3[H]catecholamine is localized in an extragranular compartment and suggest that the differentiated function of the sympathetic neuronal cell membrane, which plays an important role in uptake, is retained after prolonged tissue culture.
Control of nerve cell formation from multipotent stem cells in hydra
Authors: Berking Stefan 
Published: April 2021

ABSTRACT
Feeding of starved animals provides a very short signal which determines stem cells to differentiate into nerve cells after the next mitosis. Only those stem cells become determined which are just in the middle of their S-phase at the time of feeding. Stem cells of any other stage of the cycle do not become determined. Nerve cell determination is suppressed by very low concentrations of an endogenous inhibitor. The inhibitor exerts its effect only during the first half of the S-phase, not before and not after this period. Based on these findings it is proposed that stem cells are susceptible to 2 different signals during the first half of their S-phase; one signal allows the development into nerve cells, the other prevents this development. Within this period the decision whether to become a nerve cell or not is reversible. It becomes fixed at the end of this period.
Intercellular transfer of β-glucuronidase in chimeric mice
Authors: Herrup Karl , Mullen Richard J. 
Published: April 2021

ABSTRACT
Chimeric mice were produced by aggregating 2 embryos, each of which was homozygous for a different structural allele of the enzyme β-glucuronidase. The two alleles used were Gusb, the ‘wild-type’ allele, and Gutk, an allele whose gene product shows decreased activity in all tissues as well as decreased heat stability. Staining of untreated adult chimeric livers for glucuronidase activity revealed a mosaic of high (Gusb) and low (Gusk) activity cells. The boundaries between cells of different activity were sharp and revealed no diffusion of enzyme or reaction product.
Treating sections at 73 °C before staining led to a decay of staining activity in normal (non-chimeric) Gusk/Gusk and Gusb/Gusb tissue. The rates of activity loss under the conditions used differed by 10-fold. Of the 2 genotypes in the chimera, the dark-staining, Gusb, cells decayed in a fashion similar to that of the Gusb/Gusb control. The light-staining, Gusk, cells of the chimera lost their staining in a unique fashion. Within 20 min they quickly lost a majority of their staining activity but that which remained was relatively heat stable. The second Gusb Mike phase of the decay, seen both photographically and photometrically, suggests that Gusb gene product has been transferred to cells of Gusk/GusK genotype.
The effects of egta and trypsin on the serum requirements for cell attachment to collagen
Authors: Schor Seth L. 
Published: April 2021

ABSTRACT
Cells growing on plastic or glass surfaces in vitro may be brought into suspension by proteases (e.g. trypsin) or chelating agents (e.g. EGTA). Trypsin and EGTA remove different quantities and types of molecules from cell surfaces. Previous studies have revealed that when confluent cultures of either BHK or PyBHK cells are brought into suspension by exposure to trypsin, foetal calf serum (or fibronectin) is required for cell attachment to films of denatured type I collagen, but not to 3-dimensional gels of native collagen fibres. In this communication the scrum requirements for the attachment of BHK and PyBHK cells to collagen substrata have been examined as a function of (a) the method used to prepare the cell suspension (EGTA or trypsin), and (b) cell density. Data are presented consistent with the view that cell surface-associated fibronectin is able to mediate cell attachment directly to films of denatured collagen.
Abnormal microtubule deployment during defective macronuclear division in a Paramecium mutant
Authors: Cohen J. , Beisson J. , Tucker J. B. 
Published: April 2021

ABSTRACT
The tam 8mutant of Paramecium tetraureliais a representative of a class of mutants characterized by abnormal nuclear divisions during binary fission and the failure of trichocysts to attach to the plasma membrane. Compared with wild-type organisms the following abnormalities occur in tam 8individuals. (1) The spherical interphase macronucleus is not positioned near the oral apparatus; it is randomly located in the cytoplasm of interfission organisms. (2) The macronucleus does not migrate towards the anterior dorsal cortex as its division starts, nor is it dorsally and subcortically positioned as it elongates. (3) Elongating macronuclei exhibit variable and irregular shapes. (4) This elongation is delayed and reduced. (5) Longitudinally oriented microtubules assemble in the nucleoplasm of dividing macronuclei but their spatial deployment is abnormal. (6) Unequal segregation of micronuclei between daughter organisms occurs during binary fission. The abnormal arrangement of nucleoplasmic microtubules provides support for the proposal that a microtubule sliding mechanism is involved during the elongation of dividing macronuclei. The extent to which macronuclear division may be controlled by the cell cortex is considered in relation to the pleiotropic effects of the tam 8mutation.
Ability of a cell-surface protein produced by fibroblasts to modify tissue affinity behaviour of cardiac myocytes
Authors: Armstrong Peter B. 
Published: April 2021

ABSTRACT
When fragments of 2 diasimilar embryonic tissues are placed in contact in organ culture, cells of one fragment migrate over the surface of the second to envelop it. Holtfreter proposed that this behaviour was in response to ‘tissue affinities’. He proposed that these also play important roles in the control of morphogenetic cell movement during development. The present study demonstrates that the heart fibroblast, present as a minority cell type in heart ventricle, can modify the affinity behaviour of heart tissue. The fibroblast effect appears to be mediated by a factor that can be extracted from living fibroblast monolayers by 1 M urea. The factor is a cell-surface protein since it is absent in monolayers which had been treated with trypsin prior to extraction.
Timing of nuclear division cycle in Neurospora Crassa
Authors: Martegani E. , Tomè F. , Trezzp F. 
Published: April 2021

ABSTRACT
The timing of the nuclear division cycle in Neurospora crassa was studied by inhibiting DNA synthesis with hydroxyurea added to exponentially growing cultures at concentrations that do not inhibit cytoplasmic growth. After the addition of hydroxyurea only the nuclei that have passed the .S’-phase divide, and therefore by counting the increase in the average number of nuclei per hypha, the stage in the cycle in which completion of S phase occurred was determined in different nutritional conditions of exponential growth. The stage at which DNA replication terminates is different in different conditions of exponential growth; however, when the length of Gt+ M phases is calculated a constancy of these phases is shown. Our data indicate that in N. crassa the coordination between cytoplasmic growth and the nuclear division cycle is achieved mainly through a growth-rate-dependent expansion of the G, phase, according to a sizer-plus-timer model of control of the nuclear division cycle.
Fibroblast adhesion on collagen substrata in the presence and absence of plasma fibronectin
Authors: Grinnell Frederick , Bennett Marylyn Hoy 
Published: April 2021

ABSTRACT
We have used scanning electron microscopy and transmission electron microscopy to compare the initial adhesion of baby hamster kidney (BHK) cells and early passage human skin fibroblasts on glass, dried collagen, and hydrated collagen substrata. On glass or dried collagen substrata, BHK cell spreading required fibronectin and the cells were extensively flattened, with broad lamellipodia. In marked contrast, BHK cell spreading on hydrated collagen substrata did not require fibronectin and the cell bodies tended to be rounded, with one or several large filipodia. These filipodia generally penetrated into collagen lattice where they interwove with the collagen fibrils. Proteolysis of the collagen was not evident. In the presence of fibronectin, the morphology of BHK cell spreading on hydrated collagen substrata was similar, except that there was an increase in the number of cells that spread with lamellipodia that did not penetrate the collagen lattice. Human fibroblasts also demonstrated marked differences in cell spreading on glass or dried collagen compared to hydrated collagen substrata. Spreading was characterized by lamellipodia on glass or dried collagen but by multiple filipodia on hydrated collagen. In the latter case, the filipodia penetrated just beneath the surface of the collagen lattice. Added fibronectin was not required for spreading of human fibroblasts on any of the substrata and the presence of added fibronectin had no effect on cell morphology. Finally, the human fibroblasts were observed to form adhesion plaques in some cases where the fibroblasts made close contacts with individual collagen fibrils. The results are discussed in terms of connective tissue organization.
Recovery of sliding ability in arm depleted flagellar axonemes after recombination with extracted dynein I
Authors: Yano Y. , Miki-Noumura T. 
Published: April 2021

ABSTRACT
We compared sliding velocity between outer doublet tubules in demembranated axonemes of sea-urchin (Pseudocentrotus depressus) sperm flagella with that of arm-depleted axonemes recombined with extracted dynein 1.
The outer arm-depleted axonemes after extraction with 0·5 M NaCl had a velocity of 6·9 ± 1·0 μm/s, while the intact axonemes had a velocity of 14·3 ± 1·5 μm/s in the presence of 1 mM ATP and 2 μg/ml trypsin at 25 °C. The sliding velocity was closely related to the number of remaining outer arms following the NaCl-extraction process. When the outer arm-depleted axonemes were recombined with dynein 1, the sliding velocity increased to 11·3 ± 1·3μm/s. Electron microscopy confirmed the recovery of 94 % of outer arms in the axonemes.
After extraction with Tris-EDTA solution for 10 min, the axonemes lost their sliding ability completely, even in the presence of ATP and trypsin. Such axonemes lacked most of both inner and outer arms, although sometimes the basal segment of the arms appeared to remain. When the exogenous dynein 1 fraction extracted from other axonemes was added, the axonemes could extrude tubules, and both types of arms reappeared clearly and distinctly in the axonemes. The recombined axonemes with one-fold stoichiometric excess of dynein 1 recovered 58 % of the total number of arms and had a velocity of 7·4 ± 1·6 μm/s. Those with 2-fold stoichiometric excess had a velocity of 11·0 ± 1·5 μm/s, up to 82% of the arms in these axonemes being restored.
These results indicated that the exogenous dynein 1 fraction derived from the outer arms restored sliding ability to arm-depleted axonemes, recombining with the outer doublet tubules as inner and outer arms, and that the sliding velocity had a close relationship to the total number of arms in the axonemes, irrespective of their being inner or outer arms.
Effect of vinblastine and cytochalasin B on the cytoskeletal domains in 3T3 cells
Authors: Temmink J. H. M. , Spiele H. 
Published: April 2021

ABSTRACTNormal 3T3 cells were exposed to vinblastine and cytochalasin B in an atttempt to correlate the morphological changes of the cell surface as seen in the scanning electron microscope with ultrastructural changes of the cytoskeletal elements as seen in critical-point-dried cells in the transmission electron microscope. Special attention was given to the changes in the cytoplasmic domains distinguished in a previous paper. Cytochalasin B primarily affects the ultrastructure of the cytocortical domain by inducing the formation of condensation foci in the cytoplasmic material. Vinblastine not only induces the depolymerization of microtubules and the perinuclear concentration of intermediate filaments, but it also causes the disappearance of stress fibres from the cortical cytoplasm and the widening of the cytocortex at the expense of the endoplasmic domain. These results support the hypothesis that the differentiation in ultrastructural domains is dependent on the spreading of the cells and their adhesion to substrate.* Present address: Agricultural University, Department of Toxicology, De Dreijen 12, 6703 BC Wageningen, The Netherlands.
Cytology and growth characteristics of human tumour astrocytes transformed by Rous sarcoma virus
Authors: Macintyre E. H. , Grimes R. A. , Vatter A. E. 
Published: April 2021

ABSTRACT
Human tumour astrocytes (118MG) were exposed in vitro to the Engelbreth-Holm strain of Rous sarcoma virus at a multiplicity of infection of one. Morphological transformation of the cells in 60-mm plates was complete in 9-11 weeks after viral exposure. The transformed cells (EH-118MG) grew as a monolayer, upon which nests of rounded cells developed. From these nests, rounded cells shed into the medium and in turn on seeding formed a monolayer and repeated the cycle. The transformed cells contained the viral group-specific antigen in the cytoplasm, and produced Rous sarcomas in chickens. No complete virus was demonstrated in the mammalian cells. Electron micrographs of the parent 118MG and transformed EH-118MG cells gave further details of the structure of cytoplasmic protrusions which were formed in some of the free EH-1 18MG but not in the 118MG cells. Their nature is completely unknown.
Isopropyl N-phenylcarbamate affects spindle microtubule orientation in dividing endosperm cells of Haemanthus katherinae baker
Authors: Hepler P. K. , Jackson W. T. 
Published: April 2021

ABSTRACT
The mitotic inhibitor isopropyl N-phenylcarbamate (IPC) effects changes in the ultrastructure of the dividing endosperm cells of Haemanthus katherinae. In cells treated with 10 p.p.m. IPC for 0·5–2 h the microtubules lose their parallel alignment and become oriented in radial arrays. These radial arrays are interpreted as micropoles of the spindle apparatus and are thought to be the focal points for the chromosomes as they aggregate into micronuclei. Thus, IPC has a markedly different effect on the structure of the spindle apparatus than colchicine, which is observed at concentrations of 50 p.p.m. for 1 h to destroy the microtubules in Haemanthus. The structure of the microtubules appears unaffected by IPC since those from control and treated cells are similar in diameter (22 nm), in degree of staining, and in sensitivity to the fixation. In addition, the chromosomes and cytoplasmic components such as mitochondria, plastids, dictyosomes, elements of the endoplasmic reticulum, and ribosomes are not structurally modified by treatment with IPC.
Regulation of mitosis: II. interaction of isopropyl N-phenyl-carbamate and melatonin
Authors: Jackson W.T. 
Published: April 2021

ABSTRACT
Earlier studies on the effects of the herbicide isopropyl N-phenylcarbamate (IPC) on mitosis revealed blocked metaphases, multinucleate cells, giant nuclei and an increase in number of partly contracted chromosomes. It was assumed that IPC, like colchicine, was causing these effects by disruption of the spindle apparatus by destroying the spindle microtubules. The animal hormone melatonin causes an increase in birefringence of the mitotic spindle in animal cells, presumably by increasing the number of microtubules. We have studied the effects of IPC, melatonin, and combinations of the two on mitosis in dividing endosperm cells of the African blood lily (Haemanthus katherinae Baker) in vivo by phase-contrast and polarization microscopy. Both qualitative and quantitative data are presented. Interpretation of these results has been aided materially by a time-lapse cinemicrographic analysis of dividing cells subjected to 1 and 10 p.p.m. IPC (unpublished) and by an accompanying fine-structural analysis of untreated and IPC-treated cells. Mitosis was disrupted by 0·01–10 p.p.m. IPC, the severity of the effect depending on both concentration and stage of mitosis of the cell at the time of treatment. Concentrations of IPC that caused cessation of chromosome movement also caused loss of birefringence of the mitotic spindle. Melatonin increased birefringence of the mitotic spindle in these plant cells and partly nullified the adverse effects of IPC. The results of this study demonstrate that the herbicide IPC, under our conditions, causes disruption of mitosis and loss of birefringence of the spindle. And it has been established that an animal hormone is capable of increasing the birefringence, and presumably the number of microtubules, of the mitotic spindle in dividing endosperm cells of a higher plant. Although melatonin is capable of partly nullifying the effects of IPC, a competitive antagonism is not postulated.
Differentiation of Dictyostelium discoideum mutant cells in a shaken suspension culture and the effect of cyclic AMP
Authors: Abe K. , Saga Y. , Okada H. , Yanagisawa K. 
Published: April 2021

ABSTRACT
In Dictyostelium discoideum, 16 mutants in which cells differentiate into spores and stalk cells without normal morphogenesis were isolated. AU these mutants are rapidly developing and capable of differentiating in a shaken suspension of phosphate buffer. The developmental kinetics of specific activities of enzymes in one of the mutants, HTY1851, cultured in the suspension was compared with that in the parental strain, X2, developed on a solid surface. Most of the enzyme activities appeared much earlier and the peaks of the activities were lower in HTY1851 than X2, but the order of appearance of the activities was the same in both the strains cultured under the conditions described above. These results suggest that the biochemical steps in the development of the mutant in a shaken suspension are essentially the same as those of the parental strain X2 on a solid surface. It was also found that addition of cyclic AMP (2·5 × 10−5 M to 1 × 10−4 M) to the mutant cell suspension 6–8 h after the initiation of development induced an increase in the number of spores and the specific activities of some enzymes to values twice as high as those of an untreated control.
Contact-induced spreading in cultures of corneal epithelial cells
Authors: Brown R. M. , Middleton C. A. 
Published: April 2021

ABSTRACTThe behaviour of dissociated chick-embryo corneal epithelial cells in primary culture was investigated. These cells colliding in subconfluent culture formed long-lasting adhesions with each other and the cells accumulated into islands and sheets of cells. The contacts that developed between the cells were not necessarily permanent since cells often broke away from islands they had previously joined.Corneal epithelial cells in islands or sheets were extensively spread on the substratum, lacked blebs and, if marginally positioned, displayed a leading lamella from a part of their margin not in contact with other cells. In contrast, isolated cells, lacking contacts with other cells, exhibited a range of different morphologies. They could either be extensively spread with a well-defined leading lamella, or they could be only poorly spread and bleb vigorously. Alternatively, they could have a morphology intermediate between these two extremes. An individual isolated cell could, at different times, adopt any of these varying morphologies. Within 30 min of making contact with an island of cells, an isolated cell, if poorly or partially spread, changed its morphology to become indistinguishable from the well-spread cells or the island it had joined. Well-spread isolated cells did not show similar changes in response to contact. Measurements of the area of substratum occupied (spread area) by the cells showed that, on average, the individual cells in 2-cell islands had larger spread areas than did isolated cells.These observations suggest that isolated corneal epithelial cells, when poorly or partially spread, exhibit contact-induced spreading. Since isolated cells may spread extensively, cell contact is not an absolute pre-requisite for spreading, but such contact apparently induces and stabilizes the well-spread morphology more transiently displayed by isolated cells.
Acid phosphatase localization in PAS-bodies ofGonyaulax
Authors: Schmitter Ruth E. , Jurkiewicz Antoni J. 
Published: April 2021

ABSTRACTPeriodic acid-Schiff staining, acid phosphatase localization, and yellow autofluorescence have been correlated with the PAS-body of Gonyaulax polyedra for the first time. PAS- staining and acid phosphatase activity are both correlated with the PAS-body of Gonyaulax tamarensis. These results suggest that the PAS-body of these marine dinoflagellate algae functions in subcellular digestion.
Cytoskeleton-related structures in Tetrahymena thermophila: Microfilaments at the apical and division-furrow rings
Authors: Jerka-Dziadosz Maria 
Published: April 2021

ABSTRACT
A ring consisting of microfilaments was found in the apical region of Tetrahymena thermophila wild-type strain B and janus mutant. This ring, about 0·4 μm wide and 0·2 μm thick, is located at the bases of the anterior, non-ciliated basal bodies of the apical ciliary couplets. The apical ring is made of fine filaments showing a banded pattern, the distance between bands depending on the fixation procedure and ranging from 50–200 nm. The bands are made of small beads fastened to the filaments. The microfilaments of the apical ring are attached to the’ bases of the basal bodies. No connection with the cell membrane was found.
In dividing cells in the incipient furrow region a filamentous band originates from the epiplasmic fibrogranular meshwork. This contractile ring is about 0·4 μm wide and 0·8 μm thick. It is formed by circumferentially aligned microfibrils. During constriction the contractile ring remains associated with the epiplasmic layer, which in turn adheres to the inner alveolar membrane. The microfilaments of both the apical and the division-furrow rings have diameters ranging from about 3·8–7·1 nm.