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Results Probl Cell Differ,
1992]
Nematodes were first used to study embryogenesis more than 100 years ago, and this in part led to the concepts of cell-autonomous differentiation and localized cytoplasmic determinants. More recently, the techniques of genetics, experimental and descriptive embryology, and molecular biology have been combined to study the development of the small, free-living nematode Caenorhabditis elegans (Brenner 1974, 1988. This chapter focuses on embryonic development and is intended as a general overview of C. elegans embryogenesis, illustrating the experimental techniques available for this organism and the conclusions that can be drawn. Excellent reviews on postembryonic development (i.e. after hatching) in C. elegans and most other aspects of the worm's development, genetics and biology can be found in Wood (1988a). This book includes extensive appendices detailing techniques and anatomy and includes phenotypic descriptions of all mutants known at the time of publication. Other reviews of C. elegans embryogenesis can be found in Kemphues (1989), Wood (1988b), Schierenberg (1989) and Strome (1989).
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Review of Biological Research in Aging,
1990]
The last few years have marked a transition for aging research in Caenorhabditis elegans. Several new lines of work have appeared, most notable of which is the derivation of long-lived strains obtained both from naturally occurring variation and by mutation. The loss of several workers in the field due to retirement or movement to other areas of research as well as the increasingly competitive nature of funding for fundamental, nonclinical research in aging had led to the loss of several labs that in the past have been among the most productive in the field. Other areas of research with C. elegans have continued to advance, and the physical map of the nematode is more than 95% complete. The background material for studying C. elegans has also become much more accessible as a result of the publication of a book detailing much of the nonaging background material for C. elegans [Wood, 1988].
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Metabolites,
2021]
Prostaglandins comprise a family of lipid signaling molecules derived from polyunsaturated fatty acids and are involved in a wide array of biological processes, including fertilization. Prostaglandin-endoperoxide synthase (a.k.a. cyclooxygenase or Cox) initiates prostaglandin synthesis from 20-carbon polyunsaturated fatty acids, such as arachidonic acid. Oocytes of Caenorhabditis elegans (C. elegans) have been shown to secrete sperm-guidance cues prostaglandins, independent of Cox enzymes. Both prostaglandin synthesis and signal transduction in C. elegans are environmentally modulated pathways that regulate sperm guidance to the fertilization site. Environmental factors such as food triggers insulin and TGF-B secretion and their levels regulate tissue-specific prostaglandin synthesis in C. elegans. This novel PG pathway is abundant in mouse and human ovarian follicular fluid, where their functions, mechanism of synthesis and pathways remain to be established. Given the importance of prostaglandins in reproductive processes, a better understanding of how diets and other environmental factors influence their synthesis and function may lead to new strategies towards improving fertility in mammals.
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Methods Cell Biol,
1995]
Caenorhabditis elegans is in all likelihood the first metazoan animal whose entire genome will be determined. In addition, a very detailed description of the animal's morphology, development, and physiology is available (see elsewhere in this book, and Wood, 1988). Thus, the complete phenotype and genotype of an animal will be known. What is not known is how genotype determines phenotype; to study this, one needs to establish connections between genome sequence and phenotypes. Much has been done by classic or forward genetics: mutagenesis experiments have identified loci involved in a specific trait. Many of these loci have already been defined at the molecular level, and the genome sequence will certainly aid in the identification of many more. The opposite approach, reverse genetics, becomes naturally more important when more of the genome sequence is determined: Given the sequence of a gene of which nothing else is know, how can the function of that gene be determined? Reverse genetics is more than targeted inactivation. One can study a gene's function by several approaches...|
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Comp Biochem Physiol C Toxicol Pharmacol,
2002]
Oxygen is essential for most life forms, but it is also inherently toxic due to its biotransformation into reactive oxygen species (ROS). In fact, the development of many animal and plant pathological conditions, as well as natural aging, is associated with excessive ROS production and/or decreased antioxidant capacity. However, a number of animal species are able to tolerate, under natural conditions, situations posing a large potential for oxidative stress. Situations range from anoxia in fish, frogs and turtles, to severe hypoxia in organs of freeze-tolerant snakes, frogs and insect larvae, or diving seals and turtles, and mild hypoxia in organs of dehydrated frogs and toads or estivating snails. All situations are reminiscent of ischemia/reperfusion events that are highly damaging to most mammals and birds. This article reviews the responses of anoxia/hypoxia-tolerant animals when subjected to environmental and metabolic stresses leading to oxygen limitation. Abrupt changes in metabolic rate in ground squirrels arousing from hibernation, as well as snails arousing from estivation, may also set up a condition of increased ROS formation. Comparing the responses from these diverse animals, certain patterns emerge. The most commonly observed response is an enhancement of the antioxidant defense. The increase in the baseline activity of key antioxidant enzymes, as well as ''secondary'' enzymatic defenses, and/or glutathione levels in preparation for a putative oxidative stressful situation arising from tissue reoxygenation seem to be the preferred evolutionary adaptation. Increasing the overall antioxidant capacity during anoxia/hypoxia is of relevance for species such as garter snakes (Thamnophis sirtalis parietalis) and wood fogs (Rana sylvatica), while diving freshwater turtles (Trachemys scripta elegans) appear to rely mainly upon high constitutive activities of antioxidant enzymes to deal with oxidative stress arising during tissue reoxygenation. The possibility that some animal species might control post-anoxic ROS generation cannot be excluded.