The immediate induction of extensive cell fusion by Ca2+ addition in Dictyostelium discoideum

1986 ◽  
Vol 64 (12) ◽  
pp. 1281-1287 ◽  
Author(s):  
David R. McConachie ◽  
Danton H. O'Day
Keyword(s):  
Dictyostelium Discoideum ◽  
Cell Fusion ◽  
Cell Population ◽  
Giant Cells ◽  
Binucleate Cells ◽  
Large Numbers ◽  
Synchronous Cell ◽  
Extensive Cell ◽  
Chloride Salts

In mated cultures (NC4 × V12) of Dictyostelium discoideum containing 1.0 mM CaCl2, cell fusion generates large numbers of binucleate cells which develop into zygote giant cells. In the absence of Ca2+, binucleate formation does not occur. When 1.0 mM CaCl2 is added to Ca2+-deficient cultures at 18 h, 50% of the cells fuse within 45 min producing large multinucleate syncytia. Small, presumptive gametes appear in Ca2+-deficient cultures and reach a peak of about 20% of the cell population by 10 h, but they maintain this plateau and do not fuse. Upon the addition of CaCl2, the presumptive gametes immediately fuse, producing binucleate cells which develop rapidly into morphologically distinct giant cells. Cell fusion continues, resulting in the formation of extremely large (40–80 μm diameter) multinucleate syncytia by 45 min. The induction of this extensive, synchronous cell fusion does not occur in the presence of other chloride salts and EGTA inhibits it, revealing that Ca+ is the regulatory ion.

Zygote giant cell differentiation in Dictyostelium discoideum: biochemical markers of specific stages of sexual development

1992 ◽  
Vol 70 (10-11) ◽  
pp. 1200-1208 ◽  
Author(s):  
Darren D. Browning ◽  
Keith E. Lewis ◽  
Danton H. O'Day
Keyword(s):  
Alkaline Phosphatase ◽  
Cell Differentiation ◽  
Giant Cell ◽  
Dictyostelium Discoideum ◽  
Cell Fusion ◽  
Sexual Development ◽  
Giant Cells ◽  
Second Phase ◽  
Developmental Phase ◽  
Calcium Dependent

Sexual development in Dictyostelium discoideum has many unique features making it an attractive eukaryotic model system for the study of biomembrane fusion and intercellular communication. The work presented here provides primary biochemical evidence for two distinct phases during early sexual development that appear to be defined by calcium-dependent gamete cell fusion. In addition, we introduce a novel procedure for the enrichment of zygote giant cells and use this method to define certain wheat-germ agglutinin binding glycoproteins which are specifically located in zygote giant cells and others which are markers for surrounding amoebae in the second phase of development. In addition, a G protein which is present in high amounts early in development is unique to giant cells in the second phase, suggesting a role in phagocytosis. Finally, alkaline phosphatase activity was found to mark the first phase of sexual development, suggesting a role in cell fusion. This contrasts with the patterns of α-mannosidase and β-glucosidase activity that increase late in the second developmental phase, where they likely function in endocyte digestion during the cytophagic period. The developmental significance of these findings is discussed.Key words: zygote giant cell differentiation, Ca2+, glycoproteins, GTP-binding proteins, alkaline phosphatase, glycosidase, cell fusion.

Macrocyst development in Dictyostelium discoideum. III. Cell-fusion inducing factor secreted by giant cells

1983 ◽  
Vol 62 (1) ◽  
pp. 237-248
Author(s):  
Y. Saga ◽  
K. Yanagisawa
Keyword(s):  
Dictyostelium Discoideum ◽  
Cell Fusion ◽  
Actinomycin D ◽  
External Medium ◽  
Giant Cells ◽  
Culture Conditions ◽  
Sexual Cycle ◽  
Opposite Mating Type ◽  
Fusion Products ◽  
Type Strains

A factor was discovered that markedly enhances the degree of fusion activity between cells of the opposite mating-type strains, MI1 and NC4, in the sexual cycle of Dictyostelium discoideum. This factor, designated cell-fusion inducing factor (CFIF), was detected initially in supernatants taken from 24 h dark-grown mixed cultures of HM1 and NC4 cells, and subsequently shown to be secreted by giant cells - the fusion products of HM1 and NC4 cells. HM1 cells, cultured in the dark at appropriate temperature, normally acquire fusion-competence specific to NC4 cells. The addition of CFIF to such dark-grown HM1 cultures results in a marked increase in their fusion-competence. In addition, when CFIF is added to light-grown HM1 cultures, in which cells normally do not acquire the ability to fuse with NC4 cells, fusion-competence is induced. The fusion-competence of NC4 cells is unaffected by CFIF, being quite high under the culture conditions used here. Experiments, using actinomycin D, daunomycin and cycloheximide showed that the secretion of CFIF from giant cells requires synthesis of RNA and protein. Possibly, cell fusion triggers production of CFIF, which is rapidly released into the external medium.

Developmental effects of the major ions found in a groundwater sample on sexual cultures of Dictyostelium discoideum

1988 ◽  
Vol 34 (3) ◽  
pp. 207-211 ◽  
Author(s):  
Michael A. Lydan ◽  
Danton H. O'Day
Keyword(s):  
Dictyostelium Discoideum ◽  
Cell Fusion ◽  
Major Ions ◽  
Giant Cells ◽  
Mixed Mating ◽  
Proteose Peptone ◽  
Liquid Culture Medium ◽  
Developmental Age ◽  
Combined Action ◽  
Sexual Cultures

Addition of 25 ppm magnesium, 40 ppm nitrate, 140 ppm sulphate, and 170 ppm chloride to mixed mating type cultures of Dictyostelium discoideum was found to both markedly increase the peak number and cause an earlier developmental age of appearance of binucleate and zygote giant cells over similar cultures made without the ions. Peak cell fusion values were enhanced by about 20% in ion-supplemented cultures. Developmental kinetics in separate cultures made with each component ion showed that the enhancement of cell type percentages and total cell fusion required the combined action of at least two of the ions. Lactose (0.1 %) – proteose peptone no. 3 (0.1%) liquid culture medium supplemented with the above ions yields a medium which maximizes cell fusion, facilitating its study during sexual development in D. discoideum.

scholarly journals ON THE ROLE OF THE RESPONSE OF THE CELL MEMBRANE IN DETERMINING VIRUS VIRULENCE

1966 ◽  
Vol 124 (3) ◽  
pp. 501-520 ◽  
Author(s):  
Kathryn V. Holmes ◽  
Purnell W. Choppin
Keyword(s):  
Cell Membrane ◽  
Cell Fusion ◽  
Cell Formation ◽  
Time Lapse ◽  
Giant Cells ◽  
Virus Multiplication ◽  
Monkey Kidney ◽  
Kidney Cells ◽  
F Cells ◽  
Extensive Cell

The simian myxovirus SV5 multiplies in a continuous line of baby hamster kidney (BHK21-F) cells causing extensive cell fusion, followed by cell death. After inoculation of 15 PFU/cell, the latent period was 7 hr, the doubling time approximately 60 min, and the yield 7 PFU per cell. Giant cell formation began about 6 hr after infection and rapidly progressed to the formation by 14 to 18 hr of a single syncytium which disintegrated by 24 to 36 hr. In contrast, SV5 multiplies in primary rhesus monkey kidney cells for long periods of time producing high yields of virus with little cytopathic effect. High multiplicities of SV5 induced cell fusion in BHK21-F cells within 1 hr in the absence of virus multiplication but had no visible effect on monkey kidney cells. Time-lapse photomicrography has demonstrated that giant cells form by fusion of infected cells, and that some polykaryocytes divide. During aberrant division of polykaryocytes giant nuclei are formed from the nuclear material of several parent nuclei. The cytoplasmic development of viral antigens as demonstrated by immunofluorescence is similar in BHK21-F and monkey kidney cells. Synthesis of cellular DNA, RNA, and protein in monkey kidney cells is not shut off by SV5-infection, and in BHK21-F cells synthesis of these macromolecules is not inhibited until after extensive cell fusion has occurred 12 to 15 hr after infection. Persistently infected BHK21-F and monkey kidney cells have been serially carried through 11 and 28 cell passages, respectively. The results suggest that whether SV5 acts as a moderate virus, as in monkey kidney cells, or a virulent virus, as in BHK21-F cells, depends on the response of the cell membrane to the virus.

Macrocyst development in Dictyostelium discoideum. II. Mating-type-specific cell fusion and acquisition of fusion-competence

1983 ◽  
Vol 60 (1) ◽  
pp. 157-168
Author(s):  
Y. Saga ◽  
H. Okada ◽  
K. Yanagisawa
Keyword(s):  
Dictyostelium Discoideum ◽  
Cell Fusion ◽  
Mating Type ◽  
Cell Formation ◽  
Giant Cells ◽  
Specific Cell ◽  
Restrictive Temperature ◽  
Opposite Mating Type ◽  
Multinucleated Cells ◽  
Giant Cell Formation

The early events of macrocyst development in Dictyostelium discoideum have been investigated using a new culturing system. When cells of opposite mating-types, HM1 and NC4, are cultured together at the appropriate temperature in the dark, giant cells appear, ingest the surrounding amoebae, and develop into macrocysts. Although these giant cells have been assumed to be the products of the fusion of opposite mating-type cells, no experimental evidence to prove this assumption has been obtained using such mixed-culture systems. In order to avoid the complexities involved in mixed-culturing, we have developed a new system involving the separate culture, and later mixing, of opposite mating-type cells. This has enabled us to obtain direct evidence that giant cells are produced by fusion between opposite mating-type cells. Cell fusion occurs immediately after mixing and is completed within 30 min. As a number of cells fuse simultaneously, giant cells produced by this method are very large multinucleated cells, and not binucleated zygotes. Using this system we also discovered the following facts related to giant cell formation: (1) cells can acquire their fusion competence without the presence of cells of the opposite mating-type; (2) only HM1 cells require darkness to acquire their fusion competence; (3) the restrictive temperature, 25 degrees C, inhibits the induction of fusion competence in HM1 cells, but not in NC4 cells.

Pronuclear migration, swelling, and fusion during sexual development in Dictyostelium discoideum

1987 ◽  
Vol 33 (12) ◽  
pp. 1046-1049 ◽  
Author(s):  
David R. McConachie ◽  
Danton H. O'Day
Keyword(s):  
Dictyostelium Discoideum ◽  
Mating Type ◽  
Sexual Development ◽  
Significant Relationship ◽  
Giant Cells ◽  
Mixed Mating ◽  
Binucleate Cells ◽  
Ultrastructural Studies

In mixed mating type cultures (strains NC4 × V12) of Dictyostelium discoideum, gametes fuse to produce binucleate cells which differentiate into zygote giant cells. As pronuclei move together their volumes increase dramatically. Measurements of pronuclear volumes revealed that there is a direct, linear, and statistically significant relationship between pronuclear size and proximity. Juxtaposition of the swollen pronuclei is followed by their fusion. Ultrastructural studies indicate that pronuclear fusion involves intact pronuclear envelopes.

Phagocytic specificity during sexual development in Dictyostelium discoideum

1986 ◽  
Vol 32 (2) ◽  
pp. 79-82 ◽  
Author(s):  
Keith E. Lewis ◽  
Danton H. O'Day
Keyword(s):  
Dictyostelium Discoideum ◽  
Concanavalin A ◽  
Sexual Development ◽  
Wheat Germ ◽  
Giant Cells ◽  
Inhibitory Effect ◽  
Sexual Cycle ◽  
Type I ◽  
Further Development ◽  
Type Receptor

During the sexual cycle of Dictyostelium discoideum, zygote giant cells develop and serve as foci for further development by chemoattracting and cannibalizing hundreds of local amoebae. Previous work has shown that the phagocytic process bears similarities to and differences from asexual endocytosis. In the present study, sexual phagocytosis in D. discoideum was found to be species and developmental stage specific. It was inhibited selectively by glucose and concanavalin A. Although a partial, inhibitory effect of mannose on phagocytosis was not statistically significant, alpha-methylmannosamine, like alpha-methyl-glucose, significantly restored the phagocytic competence of giant cells treated with concanavalin A. Other sugars (N-acetyl glucosamine, N-acetylgalactosamine, and galactose) and lectins (wheat germ agglutinin, Ulex europus type I, and Ricinis communis agglutinin type I) had no significant effect on sexual phagocytosis. Together these data indicate that a glucose-type receptor is involved in selective uptake of D. discoideum amoebae by giant cells.

The origin of multiple mating types in mushrooms

1993 ◽  
Vol 104 (2) ◽  
pp. 227-230
Author(s):  
U. Kues ◽  
L.A. Casselton
Keyword(s):  
Mating Type ◽  
Multiple Mating ◽  
Mating Types ◽  
Mating Partner ◽  
Binucleate Cells ◽  
Large Numbers ◽  
Mating Type Genes ◽  
And Function ◽  
Developmental Switch ◽  
Sterile Mycelium

Having multiple mating types greatly improves the chances of meeting a compatible mating partner, particularly in an organism like the mushroom that has no sexual differentiation and no mechanism for signalling to a likely mate. Having several thousands of mating types, as some mushrooms do, is, however, remarkable - and even more remarkable is the fact that individuals only recognise that they have met a compatible mate after their cells have fused. How are such large numbers of mating types generated and what is the nature of the intracellular interaction that distinguishes self from non- self? Answers to these fascinating questions come from cloning some of the mating type genes of the ink cap mushroom Coprinus cinereus. A successful mating in Coprinus triggers a major switch in cell type, the conversion of a sterile mycelium with uninucleate cells (monokaryon) to a fertile mycelium with binucleate cells (dikaryon) which differentiates the characteristic fruit bodies. The mating type genes that regulate this developmental switch map to two multiallelic loci designated A and B and these must both carry different alleles for full mating compatibility. A and B independently regulate different steps in the developmental switch, making it possible to study just one component of the system and work in our laboratory has concentrated on understanding the structure and function of the A genes. It is estimated that some 160 different A mating types exist in nature, any two of which can together trigger the A-regulated part of sexual development. The first clue to how such large numbers are generated came from classical genetic analysis, which identified two functionally redundant A loci, (alpha) and beta. Functional redundancy is, indeed, the key to multiple A mating types and, as seen in Fig.1, molecular cloning has identified many more genes than was possible by recombination analysis.

scholarly journals THE RELEVANCE OF NUTRITIONAL STATUS AND HISTOPATHOLOGICAL FINDINGS ON THE INFECTIOUS PROCESS OF BALB/C MICE INOCULATED WITH Lacazia loboi

2015 ◽  
Vol 57 (5) ◽  
pp. 421-426 ◽  
Author(s):  
Adriana Sierra Assencio Almeida BARBOSA ◽  
Suzana Madeira DIÓRIO ◽  
Silvia Cristina Barboza PEDRINI ◽  
Adauto José Ferreira NUNES ◽  
Andréa de Faria Fernandes BELONE ◽  
...  
Keyword(s):  
Great Influence ◽  
Giant Cells ◽  
The Body ◽  
Histopathological Analysis ◽  
Restricted Diet ◽  
Regular Diet ◽  
Protein Calorie Malnutrition ◽  
Large Numbers ◽  
Lacazia Loboi ◽  
Lacazia Loboï

SUMMARY The aim of this study was to evaluate the effects of the protein-calorie malnutrition in BALB/c isogenic mice infected with Lacazia loboi, employing nutritional and histopathological parameters. Four groups were composed: G1: inoculated with restricted diet, G2: not inoculated with restricted diet, G3: inoculated with regular diet, G4: not inoculated with regular diet. Once malnutrition had been imposed, the animals were inoculated intradermally in the footpad and after four months, were sacrificed for the excision of the footpad, liver and spleen. The infection did not exert great influence on the body weight of the mice. The weight of the liver and spleen showed reduction in the undernourished groups when compared to the nourished groups. The macroscopic lesions, viability index and total number of fungi found in the footpads of the infected mice were increased in G3 when compared to G1. Regarding the histopathological analysis of the footpad, a global cellularity increase in the composition of the granuloma was observed in G3 when compared to G1, with large numbers of macrophages and multinucleated giant cells, discrete numbers of lymphocytes were present in G3 and an increase was observed in G1. The results suggest that there is considerable interaction between Jorge Lobo's disease and nutrition.

scholarly journals A Stochastic Model for Virus Growth in a Cell Population

2014 ◽  
Vol 51 (3) ◽  
pp. 599-612 ◽  
Author(s):  
J. E. Björnberg ◽  
T. Britton ◽  
E. I. Broman ◽  
E. Natan
Keyword(s):  
Stochastic Model ◽  
Host Cell ◽  
Cell Population ◽  
Branching Process ◽  
Virus Population ◽  
Virus Growth ◽  
Optimal Balance ◽  
Large Numbers ◽  
A Cell

In this work we introduce a stochastic model for the spread of a virus in a cell population where the virus has two ways of spreading: either by allowing its host cell to live and duplicate, or by multiplying in large numbers within the host cell, causing the host cell to burst and thereby let the virus enter new uninfected cells. The model is a kind of interacting Markov branching process. We focus in particular on the probability that the virus population survives and how this depends on a certain parameter λ which quantifies the ‘aggressiveness’ of the virus. Our main goal is to determine the optimal balance between aggressive growth and long-term success. Our analysis shows that the optimal strategy of the virus (in terms of survival) is obtained when the virus has no effect on the host cell's life cycle, corresponding to λ = 0. This is in agreement with experimental data about real viruses.

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