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Morphine coupling to invertebrate immunocyte nitric oxide release is dependent on intracellular calcium transients.

Morphine significantly stimulated invertebrate immunocyte intracellular calcium level increases in a concentration-dependent manner in cells preloaded with Fura 2/AM. Morphine's action was blocked by prior exposure of the cells to the opiate receptor antagonist naloxone. Various opioid peptides did not exhibit this ability, indicating a morphine-mu 3 mediated process. In comparing the sequence of events concerning morphine's action in stimulating both [Ca2+]i and NO production in these cells, we found that the first event precedes the second by 42 +/- 7 s. The opiate stimulation of [Ca2+]i- was attenuated in cells leached of calcium. strongly suggesting that intracellular calcium levels regulate cNOS activity in invertebrate immunocytes.

Animals↗

Organization of the gene for an invertebrate mitochondrial creatine kinase: comparisons with genes of higher forms and correlation of exon boundaries with functional domains.

Two major gene duplication events are thought to have taken place in the evolution of creatine kinases (CK) in the vertebrates - (1) the formation of distinct mitochondrial (MiCK) and cytoplasmic forms from the primordial gene and (2) subsequent formation of the sarcomeric (sar-) and ubiquitous (ubi-) isoforms of octameric MiCK and muscle (M) and brain (B) isoforms of dimeric, cytoplasmic CK. The genes of these two CK clades reflect a distant divergence as sar- and ubiMiCK genes consistently have nine protein-coding exons while M- and B-CK genes have seven protein-coding exons; these genes share only one common exon. CKs are also widely distributed in the invertebrates and it has recently been shown that MiCKs evolved well before the divergence of the major metazoan groups. In the present communication, we report the structure and topology of the gene for MiCK from the protostome marine worm Chaetopterus variopedatus. The protein-coding region of the gene for this primitive MiCK spans over 10 kb and consists of eight exons, the last five (E4-E8) have identical boundaries to the corresponding exons of sar- and ubiMiCK genes. Exon-3 of the C. variopedatus MiCK gene consists of the corresponding E3 and E4 of the vertebrate MiCKs with no intervening intron. E1 is longer and E2 is shorter in the polychaete MiCK gene than the counterpart sarcomeric and ubiquitous genes. The insertion of the intron in C. variopedatus E3 creating the two exons as well as the rearrangement of the intron between E1 and E2 must have occurred prior to or coincident with the duplication event creating the two vertebrate mitochondrial isoforms. Sarcomeric and ubiMiCKs display substantial differences from their invertebrate MiCK counterparts in properties relating to octamer stability and membrane binding. The evolutionary changes in gene topology may be a component of this functional progression.

Amino Acid Sequence↗

The invertebrate growth factor/CECR1 subfamily of adenosine deaminase proteins.

Adenosine deaminase (ADA) catalyzes the hydrolysis of adenosine to inosine. Its lack determines severe combined immunodeficiency in mammals, possibly due to accumulation of extracellular adenosine, which induces apoptosis in lymphocytes (Franco et al., 1998). Thus, presence of normal levels of ADA leads to normal growth and proliferation of lymphocytes. Several vertebrate and microbial ADA amino-acid sequences are known, with substantial similarity to each other. On the other hand, there are invertebrate growth factors as well as a candidate gene for the human cat eye syndrome (CECR1) (Riazi et al., 2000. Genomics 64, 277-285), which share substantial similarity to each other, and also to ADA. In this study, we report the expression and ADA enzymatic activity of a cDNA from the salivary glands of Lutzomyia longipalpis, a blood-sucking insect, with substantial similarity to insect growth factors and to human CECR1. We also demonstrate the existence of a subfamily of the adenosine deaminase family characterized by their unique amino-terminal region. Both Drosophila melanogaster and humans have both types of adenosine deaminases. Results indicate that these invertebrate proteins previously annotated as growth factors, as well as the human CECR1 gene product, may exert their actions through adenosine depletion. The different roles played by each type of adenosine deaminase in humans and Drosophila remains to be fully investigated.

Adenosine↗

An aryl hydrocarbon receptor (AHR) homologue from the soft-shell clam, Mya arenaria: evidence that invertebrate AHR homologues lack 2,3,7,8-tetrachlorodibenzo-p-dioxin and beta-naphthoflavone binding.

The aryl hydrocarbon receptor (AHR) mediates numerous toxic effects following exposure of vertebrate animals to certain aromatic environmental contaminants, including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). To investigate possible effects of TCDD on invertebrates, a cDNA encoding an AHR homologue was cloned from the soft-shell clam, Mya arenaria. The predicted amino acid sequence contains regions characteristic of vertebrate AHRs: basic helix-loop-helix (bHLH) and PER-ARNT-SIM (PAS) domains and a glutamine-rich region. Phylogenetic analysis shows that the clam AHR sequence groups within the AHR subfamily of the bHLH-PAS family, in a clade containing AHR homologues from Drosophila melanogaster and Caenorhabditis elegans. AHR mRNA expression was detected in all tissue types tested: adductor muscle, digestive gland, foot, gill, gonad, mantle, and siphon. The in vitro-expressed clam AHR exhibited sequence-specific interactions with a mammalian xenobiotic response element (XRE). Velocity sedimentation analysis using either in vitro-expressed clam AHR or clam cytosolic proteins showed that this AHR homologue binds neither [(3)H]TCDD nor [(3)H]beta-naphthoflavone (BNF). Similarly, in vitro-expressed D. melanogaster and C. elegans AHR homologues lacked specific binding of these compounds. Thus, the absence of specific, high-affinity binding of the prototypical AHR ligands TCDD and BNF, is a property shared by known invertebrate AHR homologues, distinguishing them from vertebrate AHRs. Comparative studies of phylogenetically diverse organisms may help identify an endogenous ligand(s) and the physiological role(s) for this protein.

Amino Acid Sequence↗

Maternal transfer of strain-specific immunity in an invertebrate.

The most celebrated component of the vertebrate immune system is the acquired response in which memory cells established during primary infection enhance the proliferation of antibodies during secondary infection. Additionally, the strength of vertebrate acquired immune responses varies dramatically depending on the infecting pathogen species or on the pathogen genotype within species. Because invertebrates lack the T-cell receptors and Major Histocompatibility Complex (MHC) molecules that mediate vertebrate adaptive immune responses, they are thought to lack adaptive immunity and be relatively unspecific in their interactions with pathogens. With only innate immunity, invertebrate hosts are believed to be nai;ve at each new encounter with pathogens. Nevertheless, some forms of facultative immunity appear to be important in insects; some individuals have enhanced immunity due to population density, and some social insects benefit when their nest-mates have been exposed to a pathogen or pathogen mimic (; see for a predation example.) Here we provide evidence for acquired strain-specific immunity in the crustacean Daphnia magna infected with the pathogenic bacteria Pasteuria ramosa. Specifically, the fitness of hosts was enhanced when challenged with a bacterial strain their mother had experienced relative to cases when mother and offspring were challenged with different strains.

Animals↗

Simultaneous measurements of oxygen consumption and ammonia-N excretion in embryos and larvae of marine invertebrates.

The quantification of oxygen consumption and ammonia-N excretion rates is essential in determining energy requirements for development of larval invertebrates. In larval energetics, there is a need for accurate and uncomplicated techniques to quantify metabolic rates. A method for simultaneous measurements of oxygen and ammonia-N concentrations is presented. It employs sealed respirometric chambers (ca. 30 ml) in which embryos and larvae are incubated. Analysis is carried out in end-point samples by Winkler's titration and indophenol-blue for oxygen and ammonia-N, respectively. Water is sampled into volume-calibrated glass syringes and oxygen consumption and ammonia-N excretion rates were determined by the difference between experimental and control (no animals) units. The method was successfully used to measure metabolic rates in embryo and larval stages of the shrimp Farfantepenaeus paulensis and in veliger of the mussel Perna perna. The accuracy denoted by the coefficient of variation is comparable to previous results on larval metabolic rates. A biomass: volume (microg ml(-1)) is proposed to extend its application to further species of marine invertebrates. The method is simple to operate, involves non-expensive material and is portable enough for field work. A substantial number of replicates can be analyzed at the same time and O:N ratio, an indicator of the catabolized substrate, can be calculated.

Ammonia↗

The common properties of neurogenesis in the adult brain: from invertebrates to vertebrates.

Until recently, it was believed that adult brains were unable to generate any new neurons. However, it is now commonly known that stem cells remain in the adult central nervous system and that adult vertebrates as well as adult invertebrates are currently adding new neurons in some specialized structures of their central nervous system. In vertebrates, the subventricular zone and the dentate gyrus of the hippocampus are the sites of neuronal precursor proliferation. In some insects, persistent neurogenesis occurs in the mushroom bodies, which are brain structures involved in learning and memory and considered as functional analogues of the hippocampus. In both vertebrates and invertebrates, secondary neurogenesis (including neuroblast proliferation and neuron differentiation) appears to be regulated by hormones, transmitters, growth factors and environmental cues. The functional implications of adult neurogenesis have not yet been clearly demonstrated and comparative study of the various model systems could contribute to better understand this phenomenon. Here, we review and discuss the common characteristics of adult neurogenesis in the various animal models studied so far.

Animals↗

Comparison of fatty acid composition in major lipid classes of the dominant benthic invertebrates of the Yenisei river.

The composition and content of fatty acids (FAs) in total lipids, triacylglycerols (TAG) and polar lipids (PL) in dominant groups of benthic invertebrates: gammarids (Gammaridae, Amphipoda), chironomid larvae (Chironomidae, Diptera), caddisfly larvae (Trichoptera) and mayfly larvae (Ephemeroptera) were studied in the Yenisei river. For the first time data on the FA composition of species belonging to Trichoptera (Insecta) are presented. The groups of aquatic insect larvae and gammarids weakly differed in total content of essential polyunsaturated fatty acids (PUFAs). Hence, the strong invasion of gammarids which occurred in the last decades in the Yenisei river should not result in a decrease in potential yield of essential PUFA in the ecosystem and corresponding decrease in food resource quality for fish in respect to PUFA content. Significant differences in biomarker FAs in TAG were found which correlated to specific food sources. Different levels of long-chain PUFA in PL of the invertebrates are discussed in relation to the genetic ability of particular taxa to form these FAs.

Analysis of Variance↗

Copper toxicity to larval stages of three marine invertebrates and copper complexation capacity in San Diego Bay, California.

Temporal and spatial measurements of the toxicity (EC50), chemical speciation, and complexation capacity (Cu-CC) of copper in waters from San Diego Bay suggest control of the Cu-CC over copper bioavailability. While spatial distributions of total copper (CuT) indicate an increase in concentration from the mouth toward the head of San Diego Bay, the distribution of aqueous free copper ion (Cu(II)aq) shows the opposite trend. This suggests that the bioavailability of copper to organisms decreases toward the head of the bay, and is corroborated by the increase in the amount of copper needed to reach an EC50, observed for larval stages of three marine invertebrates (Mediterranean mussel, Mytilus galloprovincialis, sand dollar, Dendraster excentricus, and purple sea urchin, Strongylocentrotus purpuratus), and by the increase in Cu-CC heading into the head of the bay. The amount of Cu(II)aq required to produce a 50% reduction in normal larval development (referred to here as pCuTox,) of the mussel, the most sensitive of the three marine invertebrates, was generally at or above approximately 1 x 10(-11) mol L(-1) equivalents of Cu (i.e., pCuTox approximately 11 = -(log [Cu(II)aq])). These results suggest that the copper complexation capacity in San Diego Bay controls copper toxicity by keeping the concentration of Cu(II)aq at nontoxic levels.

Animals↗

Alpha-actinin in different invertebrate muscle cell types of Drosophila melanogaster, the earthworm Eisenia foetida, and the snail Helix aspersa.

The presence and distribution of alpha-actinin has been studied in several invertebrate muscle cell types. These comprised transversely striated muscle (flight muscle) from the fruit fly Drosophila melanogaster, transversely striated muscle (heart muscle) from the snail Helix aspersa, obliquely striated muscle (body wall muscle) from the earthworm Eisenia foetida, smooth muscle (retractor muscle) from H. aspersa, and smooth muscle (outer muscular layer of the pseudoheart) from E. foetida. The study was carried by means of Western blot analysis, ELISA, and immunohistochemical electron microscopy, using anti alpha-actinin antibody. Immunoreaction for a protein with the same molecular weight as that of mammalian alpha-actinin was detected in all muscle types studied, although the amount and intensity of immunoreaction varied among them. In the insect muscle, immunolabelling was found along the whole Z-line. In both the transversely striated muscle from the snail and the obliquely striated muscle from the earthworm, immunolabelling did not occupy the whole Z-line but showed discontinuous, orderly arranged patches along the Z-line course. In the two smooth muscles studied (snail and earthworm), immunolabelling was limited to small patches which did not show an apparently ordered distribution. Since it is assumed that alpha-actinin is located at the anchorage sites for actin filaments, present observations suggest that, only in the Drosophila muscle, actin filaments are parallelly arranged in all their course, whereas in the other invertebrate muscles studied these filaments converge on discontinuously distributed anchorage sites.

Actin Cytoskeleton↗

Importance of predator diet cues in responses of larval wood frogs to fish and invertebrate predators.

We examined the effects of predator diet on the antipredator responses of larval woodfrogs (Rana sylvatica). We found that tadpoles showed stronger responses to fish (Perca flavescens) that were fed tadpoles than those fed invertebrates. Similarly, we found that tadpoles responded more strongly to larval dragonflies (Anax spp.) fed tadpoles than to dragonflies fed invertebrates. The overall intensity of response of tadpoles to fish was much stronger than that to dragonflies. Predator diet effects are not ubiquitous in predator-prey systems. We discuss possible reasons why predator diet effects are seen in some, but not all, predator-prey systems.

Animals↗

Cadmium toxicity for terrestrial invertebrates: taking soil parameters affecting bioavailability into account.

Acute and chronic ecotoxicity tests with cadmium were conducted with the earthworm Eisenia fetida, the potworm Enchytraeus albidus and the springtail Folsomia candida. To assess the influence of the soil type on cadmium bioavailability, these tests were carried out in a standard artificial soil, in a sandy and a loamy field soil. It was not possible to evaluate the influence of soil parameters on the bioavailability on the basis of the experiments that were conducted in only three different soil types, therefore, literature data were also included. However, even in the same standard artificial soils, toxicity data in the literature for Eisenia fetida and Folsomia candida varied considerably. Consequently, no models could be developed that allow a normalization of the ecotoxicity of cadmium to parameters controlling bioavailability. In contrast to zinc, effect concentrations of cadmium for terrestrial invertebrates were always much higher than background concentrations. As the effect of aging on the bioavailability of cadmium was never taken into account, because toxicity experiments were always carried out in freshly spiked soilds, these effect concentrations may even be regarded as conservative. Furthermore, the zinc-cadmium ratio in soils is usually so high that the risk of zinc ecotoxicity for terrestrial invertebrates will usually be much greater in comparison to cadmium ecotoxicity.

Animals↗

Innate defence: evidence for memory in invertebrate immunity.

Acquired immunity in vertebrates is characterized by immunological memory and specificity, whereas the innate defence systems of invertebrates are assumed to have no specific memory. Here we use a model system of a copepod, which is a minute crustacean, and a parasitic tapeworm to show that the success of reinfection depends on the antigenic resemblance between the consecutively encountered parasites. This finding indicates that an invertebrate defence system may be capable of specific memory.

Animals↗

Fc receptor-independent phagocytosis by mouse macrophages of erythrocytes sensitized with a lectin from a marine invertebrate.

A lactose-specific lectin present in the haemolymph of the colonial ascidian Botrylloides leachii was tested for its ability to act as an opsonin for the phagocytosis of erythrocytes by mouse macrophages. Sensitization of sheep or mouse erythrocytes with one agglutinating dose of the invertebrate agglutinin enhanced significantly the clearance of these cells from the circulation of mice, as did treatment with specific antibody. By measuring the adhesion and phagocytosis of 51Cr-labelled erythrocytes by monolayers of macrophages in vitro, it was shown that the B. leachii agglutinin was highly opsonic, promoting the ingestion of erythrocytes by the macrophages with an initial efficiency similar to that of specific antibody. The adherence and ingestion of antibody-coated erythrocytes was severely inhibited by blocking Fc receptors on the macrophages with soluble immune complexes, whereas the binding and ingestion of lectin-coated erythrocytes was unaffected by this treatment. The results demonstrate that invertebrate lectins can act as efficient opsonins for the uptake of particles by vertebrate phagocytes and that it is not necessary for particles to bind to Fc receptors for phagocytosis to be induced.

Animals↗

The effect of a transmembrane amino acid on etomidate sensitivity of an invertebrate GABA receptor.

1. The gamma-aminobutyric acid (GABA)-modulatory and GABA-mimetic actions of etomidate at mammalian GABA(A) receptors are favoured by beta2- or beta3- versus beta1-subunit containing receptors, a selectivity which resides with a single transmembrane amino acid (beta2 N290, beta3 N289, beta1 S290). Here, we have utilized the Xenopus laevis oocyte expression system in conjunction with the two-point voltage clamp technique to determine the influence of the equivalent amino acid (M314) on the actions of this anaesthetic at an etomidate-insensitive invertebrate GABA receptor (Rdl) of Drosophila melanogaster. 2. Complementary RNA-injected oocytes expressing the wild type Rdl GABA receptor and voltage-clamped at -60 mV responded to bath applied GABA with a concentration-dependent inward current response and a calculated EC50 for GABA of 20+/-0.4 microM. Receptors in which the transmembrane methionine residue (M314) had been exchanged for an asparagine (RdlM314N) or a serine (RdlM314S) also exhibited a concentration-dependent inward current response to GABA, but in both cases with a reduced EC50 of 4.8+/-0.2 microM. 3. Utilizing the appropriate GABA EC10, etomidate (300 microM) had little effect on the agonist-evoked current of the wild type Rdl receptor. By contrast, at RdlM314N receptors, etomidate produced a clear concentration-dependent enhancement of GABA-evoked currents with a calculated EC50 of 64+/-3 microM and an Emax of 68+/-2% (of the maximum response to GABA). 4. The actions of etomidate at RdlM314N receptors exhibited an enantioselectivity common to that found for mammalian receptors, with 100 microM R-(+)-etomidate and S-(-)-etomidate enhancing the current induced by GABA (EC10) to 52+/-6% and 12+/-1% of the GABA maximum respectively. 5. The effects of this mutation were selective for etomidate as the GABA-modulatory actions of 1 mM pentobarbitone at wild type Rdl (49+/-4% of the GABA maximum) and RdlM314N receptors (53+/-2% of the GABA maximum) were similar. Additionally, the modest potentiation of GABA produced by the anaesthetic neurosteroid 5alpha-pregnan-3alpha-ol-20-one (Rdl = 25+/-4% of the GABA maximum) was not altered by this mutation (RdlM314N = 18+/-3% of the GABA maximum). 6. Etomidate acting at beta1 (S290)-containing mammalian GABA(A) receptors is known to produce only a modest GABA-modulatory effect. Similarly, etomidate acting at RdlM314S receptors produced an enhancement of GABA but the magnitude of the effect was reduced compared to RdlM314N receptors. 7. Etomidate acting at human alpha6beta3gamma2L receptors is known to produce a large enhancement of GABA-evoked currents and at higher concentrations this anaesthetic directly activates the GABA(A) receptor complex. Mutation of the human beta3 subunit asparagine to methionine (beta3 N289M found in the equivalent position in Rdl completely inhibited both the GABA-modulatory and GABA-mimetic action of etomidate (10-300 microM) acting at alpha6beta3 N289Mgamma2L receptors. 8. It was concluded that, although invertebrate and mammalian proteins exhibit limited sequence homology, allosteric modification of their function by etomidate can be influenced in a complementary manner by a single amino acid substitution. The results are discussed in relation to whether this amino acid contributes to the anaesthetic binding site, or is essential for transduction. Furthermore, this study provides a clear example of the specificity of anaesthetic action.

Allosteric Regulation↗

The activities of pyruvate carboxylase, phosphoenolpyruvate carboxylase and fructose diphosphatase in muscles from vertebrates and invertebrates.

1. The activities of pyruvate carboxylase, phosphoenolpyruvate carboxylase and fructose diphosphatase in crude homogenates of vertebrate and invertebrate muscles are reported. 2. Pyruvate carboxylase activity was present in all insect flight muscles that were investigated: in homogenates of bumble-bee flight muscle the activity was inhibited by ADP and activated by acetyl-CoA, and it was distributed mainly in the mitochondrial fraction. This is the first demonstration of pyruvate carboxylase activity in muscle. However, the activity appears to be restricted to insect flight muscle, since it was not found in other invertebrate or vertebrate muscles. 3. Since the three enzymes were never found together in the same muscle, it is concluded that these enzymes cannot provide a pathway for the synthesis of glycogen from lactate or pyruvate in muscle. Other roles for these enzymes in muscle are suggested. In particular, pyruvate carboxylase may be present in insect flight muscle for the provision of oxaloacetate to support the large increase in activity of the tricarboxylic acid cycle which occurs when an insect takes flight.

Acetyl Coenzyme A↗

The contents of adenine nucleotides, phosphagens and some glycolytic intermediates in resting muscles from vertebrates and invertebrates.

The lowest contents of ATP and the lowest ATP/AMP concentration ratios are observed in the molluscan muscles that have very low rates of energy expenditure during contraction. The highest contents of ATP are observed in the extremely aerobic insect flight muscle and the extremely anaerobic pectoral muscle of the pheasant and domestic fowl. In general, the lowest ATP/AMP concentration ratios are observed for muscle in which the variation in the rate of energy utilization is small (e.g. some molluscan muscles, heart muscle); the highest ratios are observed in muscles in which this variation is large (lobster abdominal muscle, pheasant pectoral muscle, some insect flight muscles). This finding is consistent with the proposed role of AMP and the adenylate kinase reaction in the regulation of glycolysis. However, in the flight muscle of the honey-bee the ATP/AMP ratio is very low, so that glycolysis may be regulated by factors other than the variation in AMP concentration. The variation in the contents of arginine phosphate in muscle from the invertebrates is much larger than the variation in creatine phosphate in muscle from the vertebrates. The contents of hexose monophosphates and pyruvate are, in general, higher in the muscles of vertebrates than in those of the invertebrates. The contents of phosphoenolpyruvate are similar in all the muscles investigated, except for the honey-bee in which it is about 4-10-fold higher. The mass-action ratios for the reactions catalysed by phosphoglucoisomerase and adenylate kinase are very similar to the equilibrium constants for these reactions. Further, the variation in the mass-action ratios between muscles is small. It is concluded that these enzymes catalyse reactions close to equilibrium. However, the mass-action ratios for the reactions catalysed by phosphofructokinase and pyruvate kinase are much smaller than the equilibrium constants. The variation in the ratios between different muscles is large. It is concluded that these enzymes catalyse nonequilibrium reactions. Since the variation in the mass-action ratios for the reactions catalysed by the phosphagen kinases (i.e. creatine and arginine phosphokinases) is small, it is suggested that these reactions are close to equilibrium.

Adenine Nucleotides↗

Limulus alpha 2-macroglobulin. First evidence in an invertebrate for a protein containing an internal thiol ester bond.

Intra-chain thiol ester bonds are present in a limited number of proteins. The thiol ester class of proteins includes vertebrate alpha 2-macroglobulin and the complement proteins C3 and C4. We report here the first instance of a thiol ester protein from an invertebrate, the alpha 2-macroglobulin proteinase-inhibitor homologue present in the plasma of the American horseshoe crab Limulus polyphemus. Our evidence is of three kinds: (1) the proteinase-binding activity of Limulus alpha 2-macroglobulin is inactivated by the low-molecular-mass primary amine methylamine; (2) the native protein is subject to autolytic fragmentation during mild thermal denaturation, yielding fragments of approx. 125 kDa and 55 kDa, whereas the methylamine-treated protein is stable under these conditions of thermal treatment; (3) new thiol groups are generated rapidly during reaction of the protein with trypsin. The demonstration of the thiol ester bond in a protein from an ancient invertebrate provides evolutionary evidence for the importance of this bond in the function of plasma forms of the alpha 2-macroglobulin-like proteinase inhibitors.

Animals↗