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PubMed1997

Methylation of genomes and genes at the invertebrate-vertebrate boundary.

Patterns of DNA methylation in animal genomes are known to vary from an apparent absence of modified bases, via methylation of a minor fraction of the genome, to genome-wide methylation. Representative genomes from 10 invertebrate phyla comprise predominantly nonmethylated DNA and (usually but not always) a minor fraction of methylated DNA. In contrast, all 27 vertebrate genomes that have been examined display genome-wide methylation. Our studies of chordate genomes suggest that the transition from fractional to global methylation occurred close to the origin of vertebrates, as amphioxus has a typically invertebrate methylation pattern whereas primitive vertebrates (hagfish and lamprey) have patterns that are typical of vertebrates. Surprisingly, methylation of genes preceded this transition, as many invertebrate genes have turned out to be heavily methylated. Methylation does not preferentially affect genes whose expression is highly regulated, as several housekeeping genes are found in the heavily methylated fraction whereas several genes expressed in a tissue-specific manner are in the nonmethylated fraction.

Animals↗

PubMed1990

A myofibrillar protein of insect muscle related to vertebrate titin connects Z band and A band: purification and molecular characterization of invertebrate mini-titin.

We show that myofibrils of insect flight and leg muscle contain a doublet of polypeptides with apparent molecular weights of 700K (K = 10(3) Mr) (Hmp I) and 600K (Hmp II), respectively. In Locusta migratoria high ionic strength extraction solubilizes only Hmp II, which is readily purified in native form. It probably reflects a proteolytic derivative of the non-extractable Hmp I. On the basis of its viscosity radius and sedimentation coefficient, Hmp II has a molecular weight of 600K and seems to consist of a single polypeptide chain. The highly asymmetric structure of the molecule is confirmed by rotary shadowing. The flexible rods have a uniform diameter of 3-4 nm and an average length of 260 nm. Polyclonal antibodies show cross-reactivity between Hmp II and its putative precursor Hmp I. We discuss the similarities and differences between the larger titin I/titin II of vertebrate sarcomeric muscle and the smaller Hmp I/Hmp II of invertebrate muscle and conclude that the latter may reflect a mini-titin. In line with the smaller length, immunoelectron microscopy locates the insect mini-titin to the I band and a very short portion of the A band only, while vertebrate titin is known to connect the Z band to the M band. Mini-titin has also been purified from several other insects including Drosophila. Immunofluorescence microscopy on frozen sections shows that mini-titin is present in the sarcomeric muscles of various species from different invertebrate phyla. These include Annelida, Nematomorpha, Plathelmintha, Nemertea and Nematoda like Ascaris lumbricoides and Caenorhabditis elegans. This wide-spread occurrence of invertebrate mini-titin is confirmed by immunoblotting experiments.

Animals↗

PubMed1994

Role of the invertebrate electrogenic 2Na+/1H+ antiporter in monovalent and divalent cation transport.

In recent years, an electrogenic 2Na+/1H+ antiporter has been identified in a variety of invertebrate epithelial brush-border membranes of gut, kidney and gill tissues. The antiporter differs significantly in its physiological properties from the electroneutral 1Na+/1H+ antiporter proposed for vertebrate cells. In all invertebrate cells examined, the antiporter displayed a 2:1 transport stoichiometry, responded to an induced transmembrane potential and exhibited a high binding affinity for the divalent cation Ca2+, which acted as a competitive inhibitor of Na+ transport. A monoclonal antibody specific for the crustacean electrogenic antiporter inhibited 2Na+/1H+ exchange, but was without effect on Na(+)-dependent D-glucose transport. Immunoreactivity was localized at hepatopancreatic brush-border and vacuolar membranes, antennal gland coelomosac podocytes and posterior gill epithelial cells-all locations were published reports described unique cation exchange kinetics. Significant fractions of Ca2+ transport into invertebrate cells across brush-border membranes occurred by an electrogenic, amiloride-sensitive exchange process, probably by the 2Na+/1H+ antiporter, and this transport was markedly inhibited by exogenous zinc and cadmium. A recently identified electroneutral, amiloride-sensitive, hepatopancreatic epithelial basolateral Na+/H+ antiporter was uninfluenced by the brush-border monoclonal antibody, exhibited an apparent 1:1 transport stoichiometry and possessed a minimal divalent cation specificity. Calcium transport at this epithelial pole occurred by the combination of a Ca2+/Na+ antiporter, an ATP-dependent Ca(2+)-ATPase and a verapamil-sensitive calcium channel. These crustacean brush-border and basolateral transporters may play significant roles in calcification and heavy metal detoxification.

Animals↗

PubMed2006

Community response patterns: evaluating benthic invertebrate composition in metal-polluted streams.

Human activities are modifying the condition and character of ecosystems at a rapid rate. Because of these rapid changes, questions concerning how ecosystems and their assemblages respond to anthropogenic stressors have been of general interest. Accurate prediction of assemblage composition in ecosystems with anthropogenic degradation requires that we assess both how assemblages respond to stressors and the generality of the responses. We ask whether assemblage composition among stream sites becomes more similar after exposure to a common stressor. Using data from biological monitoring programs in the southern Rocky Mountain ecoregion of Colorado and in West Virginia, we compare benthic invertebrate similarity and assemblage composition among sites having different levels (background, low, medium, and high) of heavy-metal pollution. Invertebrate assemblages were most similar within the background metal category, and similarity was progressively lower in low, medium, and high metal categories. An analysis of the frequency of occurrence of genera within metal categories reveals taxonomic shifts that conform to expectations based on metal tolerance of benthic invertebrates. However, different metal-tolerant genera were found at different metal-impacted sites, suggesting that local abiotic and biotic processes may influence the identity of the metal-tolerant genera that become established in polluted sites. Low community similarity in the medium and high-metal categories suggests that accurate prediction of assemblage composition at impacted sites may be challenging.

Animals↗

PubMed2006

Effects of pesticides on soil invertebrates in laboratory studies: a review and analysis using species sensitivity distributions.

Species sensitivity distributions (SSD) and 5% hazardous concentrations (HC5) are distribution-based approaches for assessing environmental risks of pollutants. These methods have potential for application in pesticide risk assessments, but their applicability for assessing pesticide risks to soil invertebrate communities has not been evaluated. Using data obtained in a systematic review, the present study investigates the relevance of SSD and HC5 for predicting pesticide risks to soil invertebrates. Altogether, 1950 laboratory toxicity data were obtained, representing 250 pesticides and 67 invertebrate taxa. The majority (96%) of pesticides have toxicity data for fewer than five species. Based on a minimum of five species, the best available endpoint data (acute mortality median lethal concentration) enabled SSD and HC5 to be calculated for 11 pesticides (atrazine, carbendazim, chlorpyrifos, copper compounds, diazinon, dimethoate, gamma-hexachlorocyclohexane, lambda-cyhalothrin, parathion, pentachlorophenol, and propoxur). Arthropods and oligochaetes exhibit pronounced differences in their sensitivity to most of these pesticides. The standard test earthworm species, Eisenia fetida sensu lato, is the species that is least sensitive to insecticides based on acute mortality, whereas the standard Collembola test species, Folsomia candida, is among the most sensitive species for a broad range of toxic modes of action (biocide, fungicide, herbicide, and insecticide). These findings suggest that soil arthropods should be tested routinely in regulatory risk assessments. In addition, the data indicate that the uncertainty factor for earthworm acute mortality tests (i.e., 10) does not fully cover the range of earthworm species sensitivities and that acute mortality tests would not provide the most sensitive risk estimate for earthworms in the majority (95%) of cases.

Animals↗

PubMed2006

An evaluation of cause-effect relationships between polychlorinated biphenyl concentrations and sediment toxicity to benthic invertebrates.

Cause-effect sediment-quality benchmarks for the protection of benthic invertebrates are needed for polychlorinated biphenyls (PCBs) to support predictive risk assessments and retrospective evaluations of the causes of observed sediment toxicity. An in-depth evaluation of PCB aquatic toxicity and organic carbon partitioning was conducted to predict sediment effect concentrations using the equilibrium partitioning (EqP) approach. This evaluation was limited to invertebrate toxicity data, because PCBs may exert toxicity to invertebrates and fish via different toxicological mechanisms. As a result of differences in organic carbon partitioning among PCBs of differing levels of chlorination, the estimated EqP benchmarks increase with increasing degree of chlorination for various commercial and environmental PCB mixtures. Studies of spiked sediment toxicity using PCBs were reviewed, and their results generally were consistent with EqP predictions. Additionally, toxicity and benthic community data were reviewed for eight PCB-contaminated sites; these data also showed agreement with EqP predictions. None of these lines of evidence supports previously proposed, empirical sediment-quality guidelines for PCBs. Reasons for the lack of agreement between cause-effect and association-based benchmarks are discussed, and areas of future research to further refine EqP predictions for PCBs are identified.

Animals↗

PubMed2001

Acetylcholinesterase inhibition in estuarine fish and invertebrates as an indicator of organophosphorus insecticide exposure and effects.

The majority of insecticides currently in use are organophosphorus, carbamate, and synthetic pyrethroid compounds. Organophosphorus insecticides (OPs) produce toxicity by inhibiting the cholinesterase enzymes in the nervous system. Monitoring of acetylcholinesterase (AChE) inhibition has been widely used in terrestrial and freshwater aquatic systems as an indicator of OP exposure and effects. This review describes the use of AChE inhibition as a biomarker in the estuarine environment, discusses the relationship between AChE inhibition and other manifestations of OP toxicity, and highlights areas where additional research is needed. A variety of studies with estuarine fish have suggested that brain AChE inhibition levels of > 70% are associated with mortality in most species. Selected species, however, appear capable of tolerating much higher levels (> 90%) of brain inhibition. Sublethal effects on stamina have been reported for some estuarine fish in association with brain AChE inhibition levels as low as 50%. Most studies suggest, however, that these effects are observed only when brain AChE inhibition is at near-lethal levels. A number of field studies have successfully used AChE inhibition in fish as a biomarker in the estuarine environment. The use of AChE inhibition as a biomarker in estuarine invertebrates has been less well studied. Although AChE inhibition has been measured in the tissues of a variety of invertebrate species following OP exposure, the relationship between AChE inhibition and lethality is less distinct. Additional work is needed in both fish and invertebrates to better explain species-specific differences in the relationship between AChE inhibition and mortality and to investigate other physiological perturbations associated with AChE inhibition.

Animals↗

PubMed2005

Discovery and pre-clinical development of antithrombotics from hematophagous invertebrates.

Bloodfeeding (hematophagous) parasites have evolved effective means of inhibiting mammalian thrombosis, thereby facilitating the acquisition and digestion of a bloodmeal. To date, specific inhibitors of coagulation and platelet function have been identified from numerous invertebrate species, representing an impressive array of convergent functional strategies. These parasite antithrombotics, in addition to playing a critical role in the diseases caused or transmitted by bloodfeeding invertebrates, may also serve as potentially useful therapeutic agents for the treatment of a variety of conditions associated with activation of thrombosis. A number of naturally occurring anticoagulants and platelet inhibitors have been evaluated in vivo, with some currently in varying stages of preclinical and clinical development. Because of the unique specificity and potency of parasite antithrombotics, these invertebrate natural products hold great promise for improving the treatment of a variety of human illnesses, including heart disease, stroke, and cancer.

Ancylostomatoidea↗

PubMed2001

Invertebrate-Inspired sensory-motor systems and autonomous, olfactory-guided exploration.

The localization of resources in a natural environment is a multifaceted problem faced by both invertebrate animals and autonomous robots. At a first approximation, locomotion through natural environments must be guided by reliable sensory information. But natural environments can be unpredictable, so from time to time, information from any one sensory modality is likely to become temporarily unreliable. Fortunately, compensating mechanisms ensure that such signals are replaced or disambiguated by information from more reliable modalities. For invertebrates and robots to rely primarily on chemical senses has advantages and pitfalls, and these are discussed. The role of turbulence, which makes tracking a single odor to its source a complex problem, is contrasted with the high-fidelity identification of stimulus quality by the invertebrate chemoreceptor and by artificial sensors.

Animals↗

PubMed2007

Marine invertebrate mitochondria and oxidative stress.

The marine environment confronts its inhabitants with a wide variety of O2 concentrations, as well as with fluctuations of small scale local O2 availability over time. This review analyzes the respiratory response of marine animal ectotherms to fluctuating environmental O2 availability in their specific habitats and reactive O2 species generation under environmental stress, with a special emphasis on temperature. Specifically we compare mitochondrial functioning and reactive O2 species formation in these animals to what is known from endothermal, mammalian species. Among the strategies employed by marine invertebrates to maintain tissue PO2 low and within tolerable margins, the possible role of mitochondrial oxyconformity to control cellular PO2 in water breathers is discussed. Mitochondrial generation of reactive O2 species in ectotherms has been shown to depend on the magnitude of the mitochondrial membrane potential and the mitochondrial H+ leak. Alternative mitochondrial oxidases are described in marine ectotherms and might add to ameliorate reactive O2 species formation. The effect of nitric oxide, which in mammals controls the reduction state of the electron transport by lowering cytochrome oxidase O2 affinity, remains to be investigated in marine invertebrates. A new concept is proposed, showing how the cross talk of reactive O2 species in metabolically low marine invertebrates could support their outstanding hypoxia tolerance under non-stressed conditions.

Animals↗

PubMed2005

Recent advances in the innate immunity of invertebrate animals.

Invertebrate animals, which lack adaptive immune systems, have developed other systems of biological host defense, so called innate immunity, that respond to common antigens on the cell surfaces of potential pathogens. During the past two decades, the molecular structures and functions of various defense components that participated in innate immune systems have been established in Arthropoda, such as, insects, the horseshoe crab, freshwater crayfish, and the protochordata ascidian. These defense molecules include phenoloxidases, clotting factors, complement factors, lectins, protease inhibitors, antimicrobial peptides, Toll receptors, and other humoral factors found mainly in hemolymph plasma and hemocytes. These components, which together compose the innate immune system, defend invertebrate from invading bacterial, fungal, and viral pathogens. This review describes the present status of our knowledge concerning such defensive molecules in invertebrates.

Animals↗

PubMed2000

Conserved roles for peptidases in the processing of invertebrate neuropeptides.

Invertebrates use a wide range of peptides as transmitters and hormones to regulate complex behaviour, physiology and development. These animals, especially those that are amenable to genetic study and are the subject of genome-sequencing projects, provide powerful model systems for understanding the functions of peptidases in controlling the bioactivity of peptides. Neprilysin, a zinc metallopeptidase and a key enzyme in the metabolism of mammalian peptides, is also implicated in the inactivation of peptides at synapses and of circulating peptide hormones in insects and nematodes. A family of neprilysin-like genes are present in the genomes of both Drosophila melanogaster and Caenorhabditis elegans; in C. elegans it seems that individual family members have evolved to take on different physiological functions, because they are expressed in a tissue-specific manner. Angiotensin I-converting enzymes (peptidyl dipeptidase A, angiotensin-converting enzyme) are another group of zinc metallopeptidases found in some invertebrates that lack angiotensin peptides. In D. melanogaster there are two functional angiotensin-converting enzymes that are essential for normal development. One of these (Acer) is expressed in the embryonic heart, whereas the second enzyme (Ance) is expressed in several tissues at different stages of the life cycle. The accumulation of Ance within secretory vesicles of some peptide-synthesizing cells suggests a role for the enzyme in the intracellular processing of insect peptides. Ance is very efficient at cleaving pairs of basic residues from the C-terminus of partly processed peptides, suggesting a novel role for the enzyme in prohormone processing. Invertebrates will continue to provide insights into the evolutionarily conserved functions of known peptidases and of those additional family members that are expected to be identified in the future from genome-sequencing projects.

Animals↗

PubMed2000

Comparative aspects of invertebrate neuropeptides.

1. We searched for bioactive peptides, most of which were considered to be neuropeptides, in various animals of several phyla. These peptides were compared with each other and with peptides identified by many other investigators. Consequently, we found that structures of neuropeptides are generally conserved in each phylum. 2. We also found some exceptional interesting aspects. First, there are a number of peptide groups whose members are distributed among several phyla. Second, there are many structural similarities between molluscan and annelidan peptides as if molluscs and annelids were the animals in a phylum. Third, certain toxic peptides of invertebrates are closely related to vertebrate neuropeptides. 3. In addition to the above phylogenetic aspects, we found some other interesting aspects. A wide structural variety of members of a peptide group is generally found in invertebrate species. Invertebrate muscles seem to be generally regulated not only by some or several classical non-peptidic neuromediators but also by various peptidic neuromediators. Peptides containing a D-amino acid residue are not rare.

Amino Acid Sequence↗

PubMed1992

Mechanisms of amplification, deactivation, and noise reduction in invertebrate photoreceptors.

In this review we have discussed the problem of deactivation at both the rhodopsin and G protein levels. Of particular interest is the novel observation that rhodopsin deactivation can be modulated by light. This modulation is likely to play an important role in light adaptation by reducing the gain of transduction. One interesting possibility is that this modulation involves the phosphorylation of an arrestin-like molecule, but this remains to be tested. One of the experimental advantages of Limulus photoreceptors is the large size of the single photon responses and the fact that even single G proteins produce a detectable response. This made possible the observation that nonhydrolyzable GTP analogues produce discrete transient events rather than the step-like events that would be predicted by previous models. This observation led us to a new view of how enzyme deactivation is coupled to GTP hydrolysis on G protein. According to this view, enzymes are activated by G protein, but can be deactivated by processes that are not dependent on G protein or the hydrolysis of GTP. We have conducted several types of experiments, including some on the vertebrate rod system, that strongly support this hypothesis. A second major theme of this review is transduction noise. The available biochemical evidence suggests that both G protein and G protein-activated enzymes are likely to become spontaneously active and generate undesirable noise. Our measurements indicate, however, that this noise is orders of magnitude smaller than would be predicted by simple models, suggesting that special mechanisms must exist for suppressing this noise. We have proposed a specific mechanism by which enzymes regulated allosterically by multiple subunits could act as coincidence detectors to reduce transduction noise. Finally, there is the fundamental question of which second messengers have a direct role in invertebrate phototransduction. After Fesenko et al. (1985) showed that the light-dependent conductance in vertebrate rods was modulated by cGMP and not by Ca2+, there was rapid progress in understanding the vertebrate photoreceptor transduction mechanism. Now that it has been established that invertebrate light-dependent channels are regulated by cGMP and not by Ca2+, we can expect rapid progress in understanding invertebrate phototransduction. A key question that needs to be answered is whether the InsP3-Ca2+ pathway somehow triggers changes in cGMP or whether there is an altogether different pathway by which cGMP metabolizing enzymes are affected by light.

Adaptation, Physiological↗

PubMedDate not supplied

Relationships between specialized cells, capillaries and intermediary cytofibrillary elements. Xth Note. Biological evolution of the emonctory subsystem and stereotype in invertebrates.

The paper points out the importance of homeostasis as the most general system of the organism (Ist order system) and the 2nd order subsystem which composes it, discussing the relations between them and the biological evolution of the emonctory subsystem in protists and invertebrates. The emonctory structures, functions and stereotype and their component parts are studied in protists, spongia, coelenterata and coelomata: lower worms, annelids, their hyponeurian descendents (arthropods, molluses) and epineurian descedents echinoderms and protochordates (Stomochordata, Tunicata, Cephalochordata). The structure, functions and stereotypes of protonephridia and metanephridia and of substitutive (vicarious) emonctory organs (nephrocytes and peritoneal cells) are studied in coelomatic invertebrates. Their evolution appears to be directioned to localize within the limits of the emonctory subsystem. During their evolution, some nephridial functions are performed by the vicarious emonctory organs. The evolution of the subsystem in invertebrates appears to be based on stable characters and their relationships with variable features.

Animals↗

PubMed1979

Gas-liquid chromatographics determination of Bayer 73 in fish, aquatic invertebrates, mud, and water.

A gas-liquid chromatographic (GLC) method is described for determining residues of Bayer 73 (2-aminoethanol salt of 2',5-dichloro-4'-nitrosalicylanilide) in fish muscle, aquatic invertebrates, mud, and water by analyzing for 2-chloro-4-nitroaniline (CNA), a hydrolysis product of Bayer 73. Bayer 73 residues are extracted from fish muscle tissue, invertebrates, and mud with acetone-formic acid (98+2), and partitioned from water samples with chloroform. After sample cleanup by solvent and acid-base partitioning, the concentrated extract is hydrolyzed with 2N NaOH and H2O2 for 10 min at 95 degrees C. The CNA is then partitioned into hexane-ethyl ether (7+3) and determined by electron capture GLC. Average recoveries were 88% for fish, 82% for invertebrates, 82% for mud, and 98% for water at 3 or more fortification levels.

Animals↗

PubMed1980

[Determination of the degree of ribosomal genes conservativity in some invertebrate species].

DNA-RNA hybridization was used to determine the degree of similarity of ribosomal genes in some invertebrate species. The degree of similarity of the nucleotide sequences of the ribosomal genes in various classes of Echinodermata appeared to be the same as in different invertebrate types. The base sequence mismatch in hybrid rRNA-DNA molecules did not exceed 10%, even when species from different invertebrate types were compared. The results obtained suggest that the changes in common rRNA structures occurred at a very low rate in the course of a long time period (more than 600 million years).

Animals↗

PubMed1994

On being a parasite in an invertebrate host: a short survival course.

Many parasites develop in invertebrate hosts that possess internal defense systems (IDS) that vigorously defined self-integrity. Invertebrates apparently do not produce a large diversity of finely tuned immunorecognition molecules but rather rely on recognition of patterns. As a consequence, requirements for immune evasion are likely to be fundamentally different in such hosts. Although parasites of invertebrates certainly employ diverse tactics to evade host IDS, this review focuses on parasite-mediated interference with the structural and functional integrity of host hemocytes and argues that this is a common strategy of immune evasion. Parasites mediating such effects on host hemocytes are termed suppressors. In some cases, interference is mediated by mutualistic symbionts carried by the suppressors. Hemocytes from infected hosts exhibit diminished adherence to substrates, impaired spreading ability, and reduced ability to participate in phagocytosis or encapsulation reactions. As a result of the action of suppressors, the host's vulnerability to opportunistic parasites is increased, a phenomenon termed acquired susceptibility. A strategy of interference is therefore risky, particularly for suppressors with relatively long development times. As a result, suppressors may provoke either a partial generalized interference or a selective interference with host IDS function, actively contribute to protection of the host to discourage growth of opportunists (termed parasite-mediated internal defense), or induce compensatory host responses that protect the host but that do not jeopardize their own development. Some parasites consistently colonize previously infected hosts and seem to be specialized opportunists.

Animals↗