Fission-fusion Process Research Articles

Characteristics of lump-kink and their fission-fusion interactions, rogue, and breather wave solutions for a (3+1)-dimensional generalized shallow water equation

In this study, lump and two classes of interaction, multi-stripe, and breather wave solutions for the (3+1)-dimensional generalized shallow water equation are presented via the Hirota bilinear method. Interaction solutions are found between one-lump and one-stripe, and one-lump and two-stripes solutions by combining a quadratic function and an exponential function, and a quadratic function and a hyperbolic cosine or double exponential functions, respectively. Dynamical behaviours of some obtained valid solutions are presented through some graphs. The physical interpretation of fission-fusion dynamics is also explained graphically through lump-kink interaction solutions. During the fission-fusion interaction process, it is seen that stripe solitons split into a stripe and a lump soliton, and then the lump and stripe solitons fuse together. During this process, a rogue wave is found between one lump and twin stripes soliton at Furthermore, multi-stripe and breather wave solutions are investigated by choosing the appropriate functions and the values for the free parameters. The multi-stripe waves are found to be nonsingular and rectangular hyperbolic shaped. On the other hand, breather waves are found to be periodic, which can evolve periodically along a straight line in the xy-plane. The produced wave solutions might be helpful to understand the propagation behaviour of waves in shallow water.

Adaptation of mitochondrial network dynamics and velocity of mitochondrial movement to chronic stress present in fibroblasts derived from patients with sporadic form of Alzheimer's disease.

Alzheimer's disease (AD) is one of the most common neurodegenerative diseases. Only 10% of all cases are familial form, the remaining 90% are sporadic form with unknown genetic background. The etiology of sporadic AD is still not fully understood. Pathogenesis and pathobiology of this disease are limited due to the limited number of experimental models. We used primary culture of fibroblasts derived from patients diagnosed with sporadic form of AD for investigation of dynamic properties of mitochondria, including fission-fusion process and localization of mitochondria within the cell. We observed differences in mitochondrial network organization with decreased mitochondrial transport velocity, and a drop in the frequency of fusion-fission events. These studies show how mitochondrial dynamics adapt to the conditions of long-term mitochondrial stress that prevails in cells of sporadic form of AD.

Concentration dependent supramolecular interconversions of triptycene-based cubic, prismatic, and tetrahedral structures.

The quantitative, single step, self-assembly of a shape-persistent, three-dimensional C3v-symmetric, triptycene-based tris-terpyridinyl ligand initially gives a platonic-based cubic architecture, which was unequivocally characterized by 1D and 2D NMR spectroscopy, mass spectrometry, and single crystal X-ray structural analysis. The unique metal-ligand binding properties of the Cd2+ analogue of this construct give rise to a concentration-dependent dynamic equilibrium between cube, prism, and tetrahedron-shaped architectures. Dilution transforms this cube into two identical tetrahedra through a stable prism-shaped intermediate; increasing the concentration reverses the process.

Zdhhc13-dependent Drp1 S-palmitoylation impacts brain bioenergetics, anxiety, coordination and motor skills

Protein S-palmitoylation is a reversible post-translational modification mediated by palmitoyl acyltransferase enzymes, a group of Zn2+-finger DHHC-domain-containing proteins (ZDHHC). Here, for the first time, we show that Zdhhc13 plays a key role in anxiety-related behaviors and motor function, as well as brain bioenergetics, in a mouse model (luc) carrying a spontaneous Zdhhc13 recessive mutation. At 3 m of age, mutant mice displayed increased sensorimotor gating, anxiety, hypoactivity, and decreased motor coordination, compared to littermate controls. Loss of Zdhhc13 in cortex and cerebellum from 3- and 24 m old hetero- and homozygous male mutant mice resulted in lower levels of Drp1 S-palmitoylation accompanied by altered mitochondrial dynamics, increased glycolysis, glutaminolysis and lactic acidosis, and neurotransmitter imbalances. Employing in vivo and in vitro models, we identified that Zdhhc13-dependent Drp1 S-palmitoylation, which acting alone or in concert, enables the normal occurrence of the fission-fusion process. In vitro and in vivo direct Zdhhc13-Drp1 protein interaction was observed, confirming Drp1 as a substrate of Zdhhc13. Abnormal fission-fusion processes result in disrupted mitochondria morphology and distribution affecting not only mitochondrial ATP output but neurotransmission and integrity of synaptic structures in the brain, setting the basis for the behavioral abnormalities described in the Zdhhc13-deficient mice.

Social stability in times of change: effects of group fusion and water depth on sociality in a globally invasive fish

Many animals form dynamic societies in which the fission and fusion of subgroups occurs on a regular basis. Such societies are intriguing, because it is unclear whether stable dominance relationships that form within subgroups are retained upon fusion with other subgroups, and what the implications of rank instability may be at higher levels of ecological organization. Additionally, little is known about how environmental change affects the fission–fusion process, even though environments often fluctuate and are predicted to become increasingly variable, in part due to climate change. Here we investigated the social organization, levels of conflict and stability of dominance relationships during group fusion in a globally invasive fish, the eastern mosquitofish, Gambusia holbrooki . To assess the effect of environmental variation, we conducted group fusion experiments at high and low water depths, to simulate normal and drought conditions, and recorded dominance interactions during prefusion, early fusion and late fusion stages. Individuals formed size-based hierarchies within prefusion groups, although the relationship between size and dominance varied with group fusion. Levels of conflict were affected by group fusion and water depth, with higher levels of conflict after fusion and at low depth. Rank relationships in early and late fusion groups were stable and unaffected by water depth. Finally, there was no evidence of coat-tail effects, as familiarity with the alpha dominant in postfusion groups did not lead to a significant increase in subordinate dominance rank. All in all, these results provide key experimental evidence that environmental change in terms of water level is unlikely to impact social organization or rank stability in response to group fusion in this species. More generally, they indicate that sociality in fission–fusion societies may be relatively robust to changes in both social and environmental contexts.

Wnt-5a Ligand Modulates Mitochondrial Fission-Fusion in Rat Hippocampal Neurons

The Wnt signaling pathway plays an important role in developmental processes, including embryonic patterning, cell specification, and cell polarity. Wnt components participate in the development of the central nervous system, and growing evidence indicates that this pathway also regulates the function of the adult nervous system. In this study, we report that Wnt-5a, a noncanonical Wnt ligand, is a potent activator of mitochondrial dynamics and induces acute fission and fusion events in the mitochondria of rat hippocampal neurons. The effect of Wnt-5a was inhibited in the presence of sFRP, a Wnt scavenger. Similarly, the canonical Wnt-3a ligand had no effect on mitochondrial fission-fusion events, suggesting that this effect is specific for Wnt-5a alone. We also show that the Wnt-5a effects on mitochondrial dynamics occur with an increase in both intracellular and mitochondrial calcium (Ca(2+)), which was correlated with an increased phosphorylation of Drp1(Ser-616) and a decrease of Ser-637 phosphorylation, both indicators of mitochondrial dynamics. Electron microscope analysis of hippocampal tissues in the CA1 region showed an increase in the number of mitochondria present in the postsynaptic region, and this finding correlated with a change in mitochondrial morphology. We conclude that Wnt-5a/Ca(2+) signaling regulates the mitochondrial fission-fusion process in hippocampal neurons, a feature that might help to further understand the role of Wnt-related pathologies, including neurodegenerative diseases associated with mitochondrial dysfunction, and represents a potentially important link between impaired metabolic function and degenerative disorders.

Herd composition, kinship and fission–fusion social dynamics among wild giraffe

AbstractA variety of social systems have evolved as a consequence of competition and cooperation among individuals. Giraffe (Giraffa camelopardalissp.) societies are an anomaly because the dearth of long‐term data has produced two polar perspectives: a loose amalgamation of non‐bonded individuals that sometimes coalesce into a herd and a structured social system with a fission–fusion process modifying herd composition within a community. We analysed 34 years of data collected from a population ofThornicroft's giraffe (G. c. thornicrofti,Lydekker 1911) residing inSouthLuangwa,Zambia, to establish the nature of giraffe society. Our sample consisted of 52 individually recognized animals. We found that giraffe herd composition is based upon long‐term social associations that often reflect kinship, with close relatives significantly more likely than non‐relatives to establish herds. Mother/offspring dyads had the strongest associations, which persisted for years. Giraffe live in a complex society characterized by marked flexibility in herd size, with about 25% of the variance in herd composition owing to kinship and sex. We suggest that giraffe herds share many characteristics of fission–fusion social systems and propose that sophisticated communication systems are a crucial component regulating subgroup dynamics.

Introducing the fission–fusion reaction process: using a laser-accelerated Th beam to produce neutron-rich nuclei towards the N=126 waiting point of the r-process

We propose to produce neutron-rich nuclei in the range of the astrophysical r-process around the waiting point N=126 by fissioning a dense laser-accelerated thorium ion bunch in a thorium target (covered by a CH2 layer), where the light fission fragments of the beam fuse with the light fission fragments of the target. Via the 'hole-boring' mode of laser Radiation Pressure Acceleration using a high-intensity, short pulse laser, very efficiently bunches of 232Th with solid-state density can be generated from a Th layer, placed beneath a deuterated polyethylene foil, both forming the production target. Th ions laser-accelerated to about 7 MeV/u will pass through a thin CH2 layer placed in front of a thicker second Th foil closely behind the production target and disintegrate into light and heavy fission fragments. In addition, light ions (d,C) from the CD2 production target will be accelerated as well to about 7 MeV/u, inducing the fission process of 232Th also in the second Th layer. The laser-accelerated ion bunches with solid-state density, which are about 10^14 times more dense than classically accelerated ion bunches, allow for a high probability that generated fission products can fuse again. In contrast to classical radioactive beam facilities, where intense but low-density radioactive beams are merged with stable targets, the novel fission-fusion process draws on the fusion between neutron-rich, short-lived, light fission fragments both from beam and target. The high ion beam density may lead to a strong collective modification of the stopping power in the target, leading to significant range enhancement. Using a high-intensity laser as envisaged for the ELI-Nuclear Physics project in Bucharest (ELI-NP), estimates promise a fusion yield of about 10^3 ions per laser pulse in the mass range of A=180-190, thus enabling to approach the r-process waiting point at N=126.

Redox Reactions Induced by Nitrosative Stress Mediate Protein Misfolding and Mitochondrial Dysfunction in Neurodegenerative Diseases

Overstimulation of N-methyl-D-aspartate (NMDA)-type glutamate receptors accounts, at least in part, for excitotoxic neuronal damage, potentially contributing to a wide range of acute and chronic neurologic diseases. Neurodegenerative disorders including Alzheimer's disease (AD) and Parkinson's disease (PD), manifest deposits of misfolded or aggregated proteins, and result from synaptic injury and neuronal death. Recent studies have suggested that nitrosative stress due to generation of excessive nitric oxide (NO) can mediate excitotoxicity in part by triggering protein misfolding and aggregation, and mitochondrial fragmentation in the absence of genetic predisposition. S-Nitrosylation, or covalent reaction of NO with specific protein thiol groups, represents a convergent signal pathway contributing to NO-induced protein misfolding and aggregation, compromised dynamics of mitochondrial fission-fusion process, thus leading to neurotoxicity. Here, we review the effect of S-nitrosylation on protein function under excitotoxic conditions, and present evidence suggesting that NO contributes to protein misfolding and aggregation via S-nitrosylating protein-disulfide isomerase or the E3 ubiquitin ligase parkin, and mitochondrial fragmentation through beta-amyloid-related S-nitrosylation of dynamin-related protein-1. Moreover, we also discuss that inhibition of excessive NMDA receptor activity by memantine, an uncompetitive/fast off-rate (UFO) drug can ameliorate excessive production of NO, protein misfolding and aggregation, mitochondrial fragmentation, and neurodegeneration.

Phenolic rigid organic filler/isotactic polypropylene composites. I. Preparation

A novel phenolic rigid organic filler (KT) was melt-mixed with an isotactic polypropylene (iPP) to prepare a series of PP/KT composites, with or without maleic anhydride grafted polypropylene (MAPP) as compatilizer. The evolution of filler morphology during melt-mixing and melt-pressure processes was monitored by scanning electron microscope (SEM) and polarized optical microscope (POM). The influences of shear force, pressure time, filler content and MAPP concentration on the final filler dispersion were studied. We found that this rigid organic filler readily melted and dispersed homogenously into the iPP matrix through a fission-fusion process during the melt-mixing process. Thus a balanced dispersion, which was closely related to shear force and MAPP concentration, can be achieved. During the meltpressure process, parts of the filler particles combined gradually through a coalescence process. However, the incorporation of MAPP can effectively inhibit the tendency to coalesce and refine the filler particles sizes into nanoscale. Thus, a series of PP/KT composites with controllable filler particles size and narrow size distribution can be obtained just by adjusting process conditions and MAPP concentration. In addition, due to the in-situ formation mechanism, the filler phase possessed a typical solid true-spherical shape.

Mississippian Chiefdoms and the Fission-Fusion Process

AbstractIn the American Southeast, the simple-complex chiefdom cycle is the predominant model of sociopolítical development applied to the Precolumbian ranked societies known as Mississippian. In this paper, mound-center settlement patterns in the South Appalachian area are reviewed. Most of these distributions fail to conform to the hierarchy of centers predicted by the simple-complex chiefdom model. Contrary to the model, an absence of primary-secondary center hierarchies implies that extension of regional administrative control was not the primary determinant of mound-center distributions. A review of ethnohistorical sources suggests that another sociopolitical mechanism, the fission-fusion process, created the majority of mound-center settlement patterns through the aggregation or dispersal of basic political units. The fission-fusion process was the product of efforts by factional leaders to resolve the conflicting values of autonomy and security. Unlike the simple-complex chiefdom dichotomy, the fission-fusion model encompasses a greater diversity of Mississippian political forms and provides an alternative explanation for changes in mound center size, complexity, and location.

Chromosome evolution in kangaroos (Marsupialia: Macropodidae): cross species chromosome painting between the tammar wallaby and rock wallaby spp. with the 2n = 22 ancestral macropodid karyotype.

Marsupial mammals show extraordinary karyotype stability, with 2n = 14 considered ancestral. However, macropodid marsupials (kangaroos and wallabies) exhibit a considerable variety of karyotypes, with a hypothesised ancestral karyotype of 2n = 22. Speciation and karyotypic diversity in rock wallabies (Petrogale) is exceptional. We used cross species chromosome painting to examine the chromosome evolution between the tammar wallaby (2n = 16) and three 2n = 22 rock wallaby species groups with the putative ancestral karyotype. Hybridization of chromosome paints prepared from flow sorted chromosomes of the tammar wallaby to Petrogale spp., showed that this ancestral karyotype is largely conserved among 2n = 22 rock wallaby species, and confirmed the identity of ancestral chromosomes which fused to produce the bi-armed chromosomes of the 2n = 16 tammar wallaby. These results illustrate the fission-fusion process of karyotype evolution characteristic of the kangaroo group.

Fluorescent recovery after photobleaching (FRAP) of a fluorescent transferrin internalized in the late transferrin endocytic compartment of living A431 cells: Theory

In previous works, other authors characterized a compartment (LCT) of A431 carcinoma cells in which markers of transferrin endocytose had accumulated during a long chase period. This compartment, was essentially formed by large stationary vacuoles. A few small vesicles budded from these vacuoles, rapidly saltated along microtubules and eventually fused with other vacuoles, causing an intracellular transport of the marker bound to the limiting membrane (M. De Brabander, R. Nuygens, H. Geerts, C.R. Hopkins, Cell. Mot. Cytoskel. 9 (1988) 30). In the present paper, we derived the fluorescence recovery after photobleaching (FRAP) of a fluorescent marker of LCT. We assumed that the rate of the intracellular transport of the marker was controlled by the fission–fusion process between vesicles and vacuoles. We showed that the concentration of a bleached fluorescent marker was a decreasing exponential function of the time elapsed from the beginning of the recovery phase. The rate constant of this exponential was equal to the product of the vesicle surface by the number of vesicles which fused with a unit of vacuole surface during one second. If a fraction of the marker spontaneously reactivated itself with a much higher rate constant of reaction than the rate constant of the transport process, the fractional FRAP of the marker was the sum of the fractional FRAP of both processes occurring separately. In a companion paper (F. Azizi, P. Wahl, Biochim. Biophys. Acta 1327 (1997) 75–88), our FRAP experiments will be described and analysed with the mathematical expressions derived in the present paper.