Search results for "Multicellular organism"

Aging in Sponges

2003

The sponges (phylum Porifera) are the lowest and phylogenetically oldest, still extant phylum of Metazoa [1, 2]. These animals are considered as the evolutionary earliest living relicts of the successful transition from the (perhaps) unicellular to the multicellular state [2]. Evidence has been presented by molecular phylogenetic analysis that sponges share a common ancestor with the other metazoan phyla, the hypothetical Urmetazoa [2, 3].

2001

Symbioses between unicellular and multicellular organisms have contributed significantly to the evolution of life on Earth. As exemplified by several studies of bacterium-insect symbioses, modern genomic techniques are providing exciting new information about the molecular basis and the biological roles of these complex relationships, revealing for instance that symbionts have lost many genes for functions that are provided by the host, but that they can provide amino acids that the host cannot synthesize.

Exosome basic mechanisms

2020

Abstract Cell-cell communication plays a key role in maintaining homeostasis in multicellular organism. Cells communicate each other not only via the canonical pathways (cytokines, neurotransmitters, direct contact, ECM-mediated interactions or hormones) but also releasing extracellular vesicles that can reach different regions of the organism acting as a new “endocrine signalling mechanism”. Among extracellular vesicles, exosomes are emerging as efficient players to modulate target cells phenotype through the delivery to compliant receiving cells of a multitude of molecules such as mRNAs, microRNAs, long non-coding RNAs, DNA, lipids, metabolites and proteins. A deeper understanding of thei…

Routes to cell death in animal and plant kingdoms: from classic apoptosis to alternative ways to die—a review

2018

Programmed cell death is fundamental for multicellular organisms either in animal or plant kingdom. Classic apoptosis, which represents the best studied form of cell death, is dependent on caspase protease activity in animals. These proteases are not present in plants, where caspase-like activities, including metacaspases, are involved in the execution of plant cell death. Beyond apoptosis, various non-apoptotic forms of cell death also exist, including autophagy, necroptosis, pyroptosis, and ferroptosis. These types of cell death can be activated independently of apoptosis and sometimes occur when apoptosis is inhibited. Non-apoptotic forms of cell death are best characterized in animals, …

Molecular phylogeny of Metazoa (animals): monophyletic origin.

1995

The phylogenetic relationships within the kingdom Animalia (Metazoa) have long been questioned. Focusing on the lowest eukaryotic multicellular organisms, the metazoan phylum Porifera (sponges), it remained unsolved if they evolved multicellularity independently from a separate protist lineage (polyphyly of animals) of derived from the same protist group as the other animal phyla (monophyly). After having analyzed genes typical for multicellularity (adhesion molecules/receptors and a nuclear receptor), we present evidence that Porifera should be placed in the kingdom Animalia. We therefore suggest a monophyletic origin for all animals.

Synchronization of Bioelectric Oscillations in Networks of Nonexcitable Cells: From Single-Cell to Multicellular States.

2019

Biological networks use collective oscillations for information processing tasks. In particular, oscillatory membrane potentials have been observed in nonexcitable cells and bacterial communities where specific ion channel proteins contribute to the bioelectric coordination of large populations. We aim at describing theoretically the oscillatory spatiotemporal patterns that emerge at the multicellular level from the single-cell bioelectric dynamics. To this end, we focus on two key questions: (i) What single-cell properties are relevant to multicellular behavior? (ii) What properties defined at the multicellular level can allow an external control of the bioelectric dynamics? In particular,…

Polarity and bioelectrical patterning in a linear chain of non-excitable cells

2020

Abstract Polarity in multicellular systems is influenced by bioelectrical signals because electric potentials can act as spatio-temporal patterns for other biochemical processes that eventually emerge as long-lasting biological outcomes. We study the role of the electric potential in establishing head-tail polarity for the case of a chain of non-excitable cells. This biophysical model incorporates both single-cell (membrane ion channels) and multicellular (intercellular gap junctions) characteristics. The results are presented in the form of a bioelectrical phase space that complements traditional biochemical approaches and provides qualitative insights for the case of anterior/posterior po…

Oxygen Consumption and Oxygen Diffusion Properties of Multicellular Spheroids from two Different Cell Lines

1984

Multicellular spheroids are an in vitro tissue model in which the cells are supplied by diffusion of oxygen and substrates from the environmental growth medium (Sutherland et al., 1971). Since these substances are consumed when diffusing to the spheroid center, their concentration should decrease continuously towards the inner parts of the spheroids. Therefore, the location of the cells within the spheroid is an important determinant of the efficiency of the O2 and nutrient supply. The restriction of the O2 availability in the inner part of the spheroids may influence the metabolic and cell cycle state, and may even cause cell death, indicated by central necrosis in larger spheroids. Also, …

Size-Dependent Oxygenation and Energy Status in Multicellular Tumor Spheroids

1990

Multicellular tumor spheroids show numerous analogies to tumor microregions in vivo, such as the development of central necrosis at a certain spheroid size (for reviews see: Mueller-Klieser, 1987; Sutherland, 1988). The histological structure of the cell aggregates suggests that diffusion limitation of oxygen or nutrients in spheroids may cause cell death in the innermost parts of the spheroids. However, measurements with oxygen-sensitive microelectrodes are indicative of necrosis arising in the presence of relatively high oxygen tension (PO2) values, as they were found in normal tissue (Carlsson and Acker, 1985; Mueller-Klieser et al., 1986). Although still controversial in literature, rec…

The Role of Autophagy and Apoptosis During Embryo Development

2015

Programmed cell death (PCD) and cell survival are two sides of the same coin. Autopha‐ gy and apoptosis are crucial processes during embryo development of Invertebrates and Vertebrates organisms, as they are necessary for the formation of a new organism, start‐ ing from a fertilized egg. Fertilization triggers cell remodeling from each gamete to a toti‐ potent zygote. During embryogenesis, the cells undergo various processes, thus allowing the transformation of the embryo into an adult organism. In particular, cells require the appropriate tools to suddenly modify their morphology and protein content in order to respond to intrinsic and external stimuli. Autophagy and apoptosis are involved…