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[
Methods Cell Biol,
1995]
In this chapter we review methods that have been developed for working with the amoeboid sperm of nematodes. Although the sperm from a number of species have been examined, we confine our discussion to the free-living Caenorhabditis elegans and the pig parasite Ascaris suum. Each of these experimental systems offers the investigator certain strengths and weaknesses, and the type of contemplated experiment determines which is most suitable. Ascaris sperm are more easily obtainable in large quantity and are, therefore, more suited for biochemical studies. Furthermore, the Ascaris sperm is much larger than its C. elegans counterpart, allowing easier light microscopic analyses. The superb genetics and ease in obtaining DNA clones containing desired gene sequences make C. elegans the system of choice for genetic and molecular biological studies. Much evidence indicates that the sperm of these two systems share important similarities, and data obtained in one are frequently applicable to the other. Consequently, although the rest of this volume concerns principally C. elegans, we feel this chapter requires discussion of both C. elegans and Ascaris sperm because much of understanding of amoeboid sperm cell biology has, in fact, been obtained from Ascaris.
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The nematode cuticle, like the endo- and exo-skeletons of other animals, is much more than just an inert structure against which muscles can act during locomotion. The cuticle performs complex roles in organismal physiology, protection from the environment, nutrition and excretion. Cuticle composition and structure reflects this complexity. In this chapter we review briefly the ultrastructure of the cuticle and examine the biochemistry and genetics of the components of nematode cuticles. We also discuss the cuticle as a dynamic structure, both over the lifetime of the nematode (through the moults) and on shorter timescales.
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[
Methods Cell Biol,
1995]
Behavioral plasticity is the ability of organisms to modify their behavior over time, based on their experience, and is thus critical to the survival of any organism in a changing environment. It allows organisms to adapt to new surroundings and to take better advantage of novel situational variables they may encounter. It is therefore an extremely important ability, and it has attracted much research attention in innumberable organisms and across several disciplines. Much of the research on plasticity has been characterized by an attempt to integrate information and expertise from a number of these different disciplines within selected invertebrate organisms. Researchers from a variety of fields, including psychology, physiology, biochemistry, genetics, neurobiology, and molecular biology, have been uniting in an effort to investigate "simple system" in which these approaches are being combined and focused on the general goal of elucidating the cellular, molecular, and genetic basis of behavioral plasticity. These simple system approaches have led to considerable progress in our understanding of the mechanisms underlying adaptive behaviors. The general strategy of such approaches is to try to identify the genes, molecules, channels, ion currents, cells, and neural circuits underlying some form of plasticity and then determine the precise nature of their respective roles in producing behavior...
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[
WormBook,
2007]
Heterorhabditis bacteriophora is an entomopathogenic nematode (EPN) mutually associated with the enteric bacterium, Photorhabdus luminescens, used globally for the biological control of insects. Much of the previous research concerning H. bacteriophora has dealt with applied aspects related to biological control. However, H. bacteriophora is an excellent model to investigate fundamental processes such as parasitism and mutualism in addition to its comparative value to Caenorhabditis elegans. In June 2005, H. bacteriophora was targeted by NHGRI for a high quality genome sequence. This chapter summarizes the biology of H. bacteriophora in common and distinct from C. elegans, as well as the status of the genome project.
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[
1999]
Caenorhabditis elegans is a free-living soil nematode that is commonly used as a biological model. Recently, much work has been done using the nematode as a toxicological model as well. Much of the work involving C. elegans has been performed in aquatic media, since it lives in the interstitial water of soil. However, testing in soil would be expected to more accurately reproduce the organism's normal environment and may take into consideration other factors not available in an aquatic test, i.e., toxicant availability effects due to sorption, various chemical interactions, etc. This study used a modification of a previous experimental protocol to determine 24h LC50 values for Cu in a Cecil series soil mixture, and examined the use of CuCl2 as a reference toxicant for soil toxicity testing with C. elegans. Three different methods of determining percent lethality were used, each dependent on how the number of worms missing after the recovery process was used in the lethality calculations. Only tests having >/= 80% worm recovery and >/= 90% control survival were used in determining the LC50S, by Probit analysis. The replicate LC50 values generated a control chart for each method of calculating percent lethality. The coefficient of variation (CV) for each of the three methods was </= 14%. The control charts and the protocol outlined in this study are intended to be used to assess test organism health and to monitor precision of future soil toxicity tests with C.
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[
Methods Cell Biol,
1995]
Sequence analysis of cosmids from C. elegans and other organisms currently is best done using the random or "shotgun" strategy (Wilson et al., 1994). After shearing by sonication, DNA is used to prepare M13 subclone libraries which provide good coverage and high-quality sequence data. The subclones are assembled and the data edited using software tools developed especially for C. elegans genomic sequencing. These same tools facilitate much of the subsequent work to complete both strands of the sequence and resolve any remaining ambiguities. Analysis of the finished sequence is then accomplished using several additional computer tools including Genefinder and ACeDB. Taken together, these methods and tools provide a powerful means for genome analysis in the nematode.
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[
1982]
Much of this meeting is devoted to the study of multi-gene families and the differential expression of various members during muscle development. Structural analysis of myosin and then other muscle proteins by peptide mapping and amino acid sequencing first suggested that these isoforms are the products of different genes. The use of antibodies specific to distinct structural gene products has permitted detailed investigations of myosin structure, biosynthesis and degradation, and cellular location as muscle development proceeds. The small nematode, Caenorhabditis elegans, is a laboratory animal which offers genetic dissection and manipulation as tools in deciphering of gene regulation in terms of specific protein synthesis during muscle development. The examination of specific mutants by protein chemistry and immunochemistry has already proved a powerful comination in many fields.
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[
WormBook,
2005]
A genetic enhancer is a mutation in one gene that intensifies the phenotype caused by a mutation in another gene. The phenotype of the double mutant is much stronger than the summation of the single mutant phenotypes. The isolation of enhancers can lead to the identification of interacting genes, including genes that act redundantly with respect to each other. Examples in Caenorhabditis elegans of dominant enhancers are presented first, followed by a review of recessive enhancers of null mutations. In some of these cases, the interacting genes are related in structure and function, but in other cases, the interacting genes are nonhomologous. Recessive enhancers of non-null mutations can also be useful. A powerful advance for the identification of recessive enhancers is genome-wide screening based on RNA interference.
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[
1975]
Studies in behaviour genetics have covered a wide field: motivation, development, sensory capacities, intelligence, learning, evolution, neuromorphology and neurochemistry have all been approached using genetic techniques, and there are probably others. Whilst it is at present impossible to construct any unities one must accept that many such studies have as their common aim one of the most fundamental problems in biology: how is behavioral potential encoded in genetic terms and expressed in the course of development? The relative enormity of this problem is often matched by its inaccessibilty. It cannot be claimed that there is any agreed view of the way forward and much of the work has frankly to be opportunistic-seizing on some favourable material or a useful new analytical technique to gain a limited objective. Consequently, behaviour genetics often presents a confusing picture of numerous disjointed studies, with
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[
WormBook,
2006]
Receptor Tyrosine Kinase (RTK)/Ras GTPase/MAP kinase (MAPK) signaling pathways are used repeatedly during metazoan development to control many different biological processes. In the nematode Caenorhabditis elegans , two different RTKs ( LET-23 /EGFR and EGL-15 /FGFR) are known to stimulate LET-60 /Ras and a MAPK cascade consisting of the kinases LIN-45 /Raf, MEK-2 /MEK and MPK-1 /ERK. This Ras/MAPK cascade is required for multiple developmental events, including induction of vulval, uterine, spicule, P12 and excretory duct cell fates, control of sex myoblast migration and axon guidance, and promotion of germline meiosis. Studies in C. elegans have provided much insight into the basic framework of this RTK/Ras/MAPK signaling pathway, its regulation, how it elicits cell-type specific responses, and how it interacts with other signaling pathways such as the Wnt and Notch pathways.