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[
1980]
The use of nematodes as models to study aging is currently attracting wide interest among developmental biologists. The trend is clearly indicated by the large numbers of recent papers on nematode aging cited in these volumes. Because of the rapidly expanding interest in free-living nematodes, a large amount of data has accumulated on all aspects of the biology of these organisms. Certainly there is no other group of multicellular organisms about which so much is known. The question arises, Why the nematode and not another small metazoan chosen as a model? This question was considered in detail in other reviews, and only the principal advantages need be summarized here. Briefly, these include a short life span (about 25 days for Caenorhabditis briggsae), small size, ease of maintainance in axenic or monoxenic culture, the relatively small number of cells that are differentiated into nervous, digestive, reproductive, and muscular systems, and, most important, the rapidly expanding body of information which is now available on the genetics, nutrition, development, and physiology of several species of free-living nematodes. Another critical question often asked by biomedical researchers is the relevance of nematode aging to human senescence. As knowledge of molecular biology grew it rapidly became apparent that certain basic cellular processes proceed along similar paths of all living things. This chapter refers to a number of observations related to the biology and physiology of nematode aging that appear to parallel events associated with mammalian aging.
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[
Nematologica,
1971]
Caenorhabditis briggsae was used as a model to study aging of a metazoan under gnotobiotic conditions. At higher temperatures nematodes were shorter-lived and had a shorter generation time. Nematodes moved more slowly as they aged. Physiologic aging was marked by a decreased ability to withstand osmotic stress, a possible increase in the body's internal solute concentration, and increased sensitivity to formaldehyde. These results suggest that the ability to osmoregulate and the permeability of the body wall are altered during senescence. The interchordal hypodermis, as well as the chordal hypodermis, contained fairly abundant structures having biosynthetic activity. During aging mitochondria of the hypodermis degenerated, some areas of the thin hypodermal band thickened and lysosome-like bodies formed in the interchordal hypodermis. Changes in osmoregulatory and excretory mechanisms are probably associated with deterioration of hypodermis organelles.
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Advances in the Biosciences,
1987]
Data supporting the use of nematodes as a preliminary screen for pharmaceuticals effective in retarding certain degenerative events associated with mammalian aging is presented. Among the criteria are 1. certain indices of cellular aging in nematodes are relevant to mammals; 2. the nematode system produces results in weeks as compared to one to two years for laboratory rats; and 3. the overall cost of nematode research is but a fraction of that required for mammalian studies with similar goals.
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[
Annual Review of Phytopathology,
1984]
It has long been recognized that free-living nematodes utilize specific recognition mechanisms for finding their hosts or prey in the soil. One of the earliest observations described the attraction of the plant parasitic nematode Meloidogyne incognita to tomato roots grown in sterile petri plates. If nematodes were unable to detect signals emanating from a food source, food finding would be a random, inefficient process. Such is not the case. The general consensus, based on experimental evidence and the morphologic configuration of purported sensory structures located in the cephalic region, is that in nematodes the primary food-finding mechanisms are governed by chemotactic factors emanating from the host or prey. Other stimuli, such as thermal, vibratory, or tactile stimuli, are believed to play a minor role, if any, in food-finding behavior. Once the nematode reaches the potential food source, it faces further barriers before it can commence feeding. For plant nematodes this includes recognition of an area of the root susceptible to attack. For bacteriophagous nematodes, recognizing certain species of bacteria as good food sources is vital, for these nematodes will not grow and reproduce on all bacteria. Molecular recognition of "good" and "bad" bacteria undoubtedly come into play, but here again definitive data are lacking. A larger body of information has accrued concerning the way nematophagous fungi attract and attack their prey. In this association, the role of the chemoattractant is reversed; chemotactic factors given off by the fungus lure the nematode to its death. This review considers the possible molecular mechanisms involved in this relation. Mating is another activity in which the perception of chemotactic factors is critical: specifically, detection of female sex pheromone by the male. The mechanisms of this detection appear to include specific binding of the pheromone by the male, sensory recognition, and an effector response. Progress and
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[
Curr Opin Cell Biol,
2011]
Cell invasion through basement membrane (BM) is a specialized cellular behavior critical to many normal developmental events, immune surveillance, and cancer metastasis. A highly dynamic process, cell invasion involves a complex interplay between cell-intrinsic elements that promote the invasive phenotype, and cell-cell and cell-BM interactions that regulate the timing and targeting of BM transmigration. The intricate nature of these interactions has made it challenging to study cell invasion in vivo and model in vitro. Anchor cell invasion in Caenorhabditis elegans is emerging as an important experimental paradigm for comprehensive analysis of BM invasion, revealing the gene networks that specify invasive behavior and the interactions that occur at the cell-BM interface.
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Eur J Cell Biol,
2010]
The basement membrane (BM) is a dense, tightly cross-linked matrix that acts as physiological barrier to maintain tissue homeostasis. Studies on Caenorhabditis elegans, leucocytes diapedesis and cancer cell invasion have shown that BM transmigration is a conserved three-stage process. Firstly, invadopodia-like protrusions form at the ventral surface of invasive cells; later, one protrusion elongates that lastly drives the infiltration of cells into the underlying compartment. This review illustrates the mechanism used by invasive cancer cells to cross the BM barrier by focusing on the role of key cytoskeleton components. We also describe currently available in vitro assays to study each step of the BM transmigration program.
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[
Age,
1978]
Studies on enzyme changes during aging from rodents, nematodes and tissue culture cells have been reviewed. In the rodent and tissue culture studies, conflicting results on aging of specific enzymes have been reported from several laboratories. These works have been analyzed, with the aim of stressing the different findings and analyzing possible reasons for the discrepancies. With regard to the nematode studies, the authors suggest that the examination of the concept of general failure of protein synthesis mechanisms as a basic cause of cellular senescence requires more rigorous methods than have been utilized in previous studies.
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Matrix Biol,
2018]
Basement membranes (BMs) are thin dense sheets of extracellular matrix that surround most tissues. When the BMs of neighboring tissues come into contact, they usually slide along one another and act to separate tissues and organs into distinct compartments. However, in certain specialized regions, the BMs of neighboring tissues link, helping to bring tissues together. These BM connections can be transient, such as during tissue fusion events in development, or long-term, as with adult tissues involved with filtration, including the blood brain barrier and kidney glomerulus. The transitory nature of these connections in development and the complexity of tissue filtration systems in adults have hindered the understanding of how juxtaposed BMs fasten together. The recent identification of a BM-BM adhesion system in C. elegans, termed B-LINK (BM linkage), however, is revealing cellular and extracellular matrix components of a nascent tissue adhesion system. We discuss insights gained from studying the B-LINK tissue adhesion system in C. elegans, compare this adhesion with other BM-BM connections in Drosophila and vertebrates, and outline important future directions towards elucidating this fascinating and poorly understood mode of adhesion that joins neighboring tissues.
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Matrix Biol,
2015]
The members of the ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs) family of secreted proteins, MIG-17 and GON-1, play essential roles in Caenorhabditis elegans gonadogenesis. The genetic and molecular analyses of these proteinases uncovered novel molecular interactions regulating the basement membrane (BM) during the migration of the gonadal leader cells. MIG-17, which is localized to the gonadal BM recruits or activates fibulin-1 and type IV collagen, which then recruits nidogen, thereby inducing the remodeling of the BM that is required for directional control of leader cell migration. GON-1 acts antagonistically with fibulin-1 to regulate the levels of type IV collagen accumulation in the gonadal BM, which facilitates active migration of the leader cells. The cooperative action of MIG-17 and GON-1 represents an excellent model for understanding the mechanisms of organogenesis mediated by ADAMTS proteinases.