Molecular characterization and phylogenetic relationships of a protein with potential oxygen-binding capabilities in the grasshopper embryo. A hemocyanin in insects?

Arthropodan hemocyanins, prophenoloxidases (PPOs), and insect hexamerins form a superfamily of hemolymph proteins that we propose to call the AHPH superfamily. The evolutionary and functional relationships of these proteins are illuminated by a new embryonic hemolymph protein (EHP) that is expressed during early stages of development in the grasshopper embryo. EHP is a 78-kDa soluble protein present initially in the yolk sac content, and later in the embryonic hemolymph. Protein purification and peptide sequencing were used to identify an embryonic cDNA clone coding for EHP. In situ hybridization identifies hemocytes as EHP-expressing cells. As deduced from the cDNA clone, EHP is a secreted protein with two potential glycosylation sites. Sequence analysis defines EHP as a member of the AHPH superfamily. Phylogenetic analyses with all the currently available AHPH proteins, including EHP, were performed to ascertain the evolutionary history of this protein superfamily. We used both the entire protein sequence and each of the three domains present in the AHPH proteins. The phylogenies inferred for each of the domains suggest a mosaic evolution of these protein modules. Phylogenetic and multivariate analyses consistently group EHP with crustacean hemocyanins and, less closely, with insect hexamerins, relative to cheliceratan hemocyanins and PPOs. The grasshopper protein rigorously preserves the residues involved in oxygen binding, oligomerization, and allosteric regulation of the oxygen transport proteins. Although insects were thought not to have hemocyanins, we propose that EHP functions as an oxygen transport or storage protein during embryonic development.      

Wolbachia infection frequencies in insects: evidence of a global equilibrium?

Wolbachia are a group of cytoplasmically inherited bacteria that cause reproduction alterations in arthropods, including parthenogenesis, reproductive incompatibility, feminization of genetic males and male killing. Previous general surveys of insects in Panama and Britain found Wolbachia to be common, occurring in 16-22% of species. Here, using similar polymerase chain reaction methods, we report that 19.3% of a sample of temperate North American insects are infected with Wolbachia, a frequency strikingly similar to frequencies found in two other studies in widely separated locales. The results may indicate a widespread equilibrium of Wolbachia infection frequencies in insects whose maintenance remains to be explained. Alternatively, Wolbachia may be increasing in global insect communities. Within each of the three geographic regions surveyed, Hymenoptera are more frequently infected with A group Wolbachia and Lepidoptera more frequently infected with B group Wolbachia.     

The search for the missing link: a relic plastid in Perkinsus?

Perkinsus marinus (Phylum Perkinsozoa) is a protozoan parasite that has devastated natural and farmed oyster populations in the USA, significantly affecting the shellfish industry and the estuarine environment. The other two genera in the phylum, Parvilucifera and Rastrimonas, are parasites of microeukaryotes. The Perkinsozoa occupies a key position at the base of the dinoflagellate branch, close to its divergence from the Apicomplexa, a clade that includes parasitic protista, many harbouring a relic plastid. Thus, as a taxon that has also evolved toward parasitism, the Perkinsozoa has attracted the attention of biologists interested in the evolution of this organelle, both in its ultrastructure and the conservation, loss or transfer of its genes. A review of the recent literature reveals mounting evidence in support of the presence of a relic plastid in P. marinus, including the presence of multimembrane structures, characteristic metabolic pathways and proteins with a bipartite N-terminal extension. Further, these findings raise intriguing questions regarding the potential functions and unique adaptation of the putative plastid and/or plastid genes in the Perkinsozoa. In this review we analyse the above-mentioned evidence and evaluate the potential future directions and expected benefits of addressing such questions. Given the rapidly expanding molecular/genetic resources and methodological toolbox for Perkinsus spp., these organisms should complement the currently established models for investigating plastid evolution within the Chromalveolata.     

Prostaglandins E and F2α in the house cricket and other insects

Prostaglandin E (PGE₁ and PGE₂) and prostaglandin F_2α (PGF_2α) are widely distributed in insects belonging to seven species representing six orders. Whole body concentrations range from 0.2 to 16 pg/mg protein. PGE and PGF_2α are found in muscle but are not abundant in testicular tissue. In the house cricket, Acheta domesticus (L.), high prostaglandin levels in the testes and the female spermatheca are reduced in the presence of the prostaglandin synthesis inhibitors aspirin, acetaminophen and indomethacin. An interaction of the prostaglandins with cyclic GMP and cyclic AMP in cricket tissues was not observed using these inhibitors. The house cricket appears to be a model for studying prostaglandin function in insects.     

Phosphoinositide 3-kinases in the gut: a link between inflammation and cancer?

Carcinoma of the gastrointestinal tract is the most common internal malignancy affecting men and women in Western countries. Chronic intestinal inflammation, especially of the colon, is also a Western disease and correlates with a significantly increased risk of developing cancer. This has suggested that the immune processes involved in both conditions might share some common pathways. Indeed, there is increasing evidence that phosphatidylinositol 3-kinases (PI 3-kinases) are involved in both the pathogenesis of colorectal carcinoma and intestinal inflammation. Here, we discuss this rapidly progressing area of research, presenting evidence for a pivotal role of PI 3-kinase(s) in intestinal pathophysiology.     

Is it enemy-free space? The evidence for terrestrial insects and freshwater arthropods

Abstract.

• 1 Enemy-free space (EFS) was defined by Jeffries & Lawton (1984) as ‘ways of living that reduce or eliminate a species’ vulnerability to one or more species of natural enemies’. EFS has emerged in the literature as a significant niche-moulding factor. However, the lack of consistency among the empirical studies as to how EFS should be defined, and what hypotheses should be tested in order to evaluate its relative importance, prompted us to review the literature and to propose a working definition that results in a general set of testable hypotheses.
• 2 To test the relative importance of EFS in structuring the communities of organisms, we propose a set of three falsifiable null hypotheses that must be tested sequentially and rejected. Ho1: The fitness of the organism in an original habit (e.g. on an original host plant) in the presence of natural enemies is equal to the fitness of the organism in that habit in the absence of natural enemies. Acceptance of the alternative hypothesis that the fitness of the organism in the presence of natural enemies is less than in the absence of natural enemies is necessary to demonstrate the importance of natural enemies. Ho2: The fitness of the organism in an alternative habit with natural enemies is equal to the fitness of the organism in the original habit with natural enemies. Acceptance of the alternative hypothesis that the fitness of the organism in the alternative habit with natural enemies is greater than that in the original habit with natural enemies is necessary to demonstrate that the alternative habit provides EFS. Ho3: The fitness of the organism in an alternative habit without natural enemies equals the fitness of the organism in the original habit without natural enemies. Acceptance of the alternative hypothesis that the fitness of the organism in an alternative habit without natural enemies is less than in the original habit without natural enemies is necessary to demonstrate the relative importance of EFS compared with other co-occurring niche-moulding factors such as competition or host nutritional quality.
• 3 We searched the literature and evaluated fifty-three references (nineteen references to seventeen different terrestrial systems and thirty-four references to twenty-four different freshwater systems) to test our hypotheses.
• 4 Of the forty-one systems examined, nineteen (46%) tested only for differences in vulnerability of the prey or host species between EFS and non-EFS options (our Ho2); sixteen (39%) tested for the importance of natural enemies and the effectiveness of the alternative habit in providing EFS (our Ho1 and Ho2); and only ten systems (24%) tested for Ho1, Ho2 and the relative importance of EFS in the system as measured by fitness (our Ho3).
• 5 Of the systems that tested for EFS, sixteen of nineteen (84%), thirteen of sixteen (81%) and seven of ten (70%) showed evidence in support of the existence of EFS according to hypothesis Ho2 only, hypotheses Ho1 and Ho2, and our three working hypotheses, respectively.
• 6 These results indicate that very few studies have actually tested for the existence of EFS. Nevertheless, results from this limited number of natural systems suggest that EFS may be important in moulding the niches of arthropods. Because of the large number of claims for EFS in systems where none of the basic hypotheses were investigated, we suggest that authors test for EFS experimentally, be judicious in selecting articles to cite in support of EFS, and exert care in attributing it as a selective force in the evolution of arthropods in specific systems.

     

Innate immunity: the missing link in neuroprotection and neurodegeneration?

Innate immunity was previously thought to be a nonspecific immunological programme that was engaged by peripheral organs to maintain homeostasis after stress and injury. Emerging evidence indicates that this highly organized response also takes place in the central nervous system. Through the recognition of neuronal fingerprints, the long-term induction of the innate immune response and its transition to an adaptive form might be central to the pathophysiology and aetiology of neurodegenerative disorders. Paradoxically, this response also protects neurons by favouring remyelination and trophic support afforded by glial cells.     

Weight loss and regain in obese individuals: a link with adipose tissue metabolism indices?

This study was performed to examine whether changes in subcutaneous adipose tissue (SCAT) metabolism indices after weight loss were related to the magnitude of weight regain. Nine men and ten premenopausal women whose body mass index ranged from 30 to 42 kg/m², 35–48 years old, were studied before and after a 15-week weight loss program, as well as at a 17–22-month follow-up period. Although body composition was evaluated at all study periods, abdominal and femoral SCAT-lipoprotein lipase (LPL) and hormone-sensitive lipase (HSL) activities, and α2- and β-adrenoceptors (ARs) were measured before and after weight loss, exclusively. Although the SCAT-LPL activity did not change after weight loss in men, it tended to decrease in the femoral depot of women (p?=?0.06). SCAT-HSL activity remained unchanged after weight reduction in men, while the post-weight loss lipase activity tended to be higher in both regions of women (p?=?0.06). Although the post-weight loss number of β-ARs was higher irrespective of the fat depot (0.001?<?p?<?0.05), the number of α2-ARs was increased in the femoral (p?<?0.05), but not in the abdominal SCAT (p?=?0.08) after weight reduction, in men. Neither the α2- nor the β-AR density changed after weight reduction, in women. Abdominal SCAT-LPL activity after weight reduction was negatively related to weight regain indices, in women (?0.65?<?Rhô?<??0.75; 0.01?<?p?<?0.05). Both the post-weight loss abdominal SCAT α2-AR density and the α2-/β-AR balance were positively associated with weight regain indices, in men (0.69?<?Rhô?<?0.88; 0.01?<?p?<?0.05). These results suggest that selected SCAT metabolism indices could predict failure to weight loss maintenance, in both genders.     

Albinism and immunity: what's the link?

A small number of inherited diseases show a combination of immunological and pigmentation defects. Chediak-Higashi, Griscellis and Hermansky-Pudlak syndromes are all autosomal recessive diseases with these characteristics. Recent advances in both the identification of the genes giving rise to these diseases and the cell biology of immune cells and melanocytes have begun to reveal the molecular links between immunodeficiencies and albinism. These studies identify key proteins, such as Rab27a, which are critical for secretion of specialised granules found in melanocytes and immune cells. The granules of these cells are modified lysosomes termed 'secretory lysosomes'. These studies reveal that secretory lysosomes use specialised mechanisms of secretion, not found in other cell types, which explains the selective defects in these diseases.     

Bamboo flowers visited by insects: do insects play a role in the pollination of bamboo flowers?

Relatively little is known about pollination and other aspects of the reproductive biology of bamboos, but wind pollination is assumed to be the rule, at least in woody bamboos. Documenting the reproductive biology of woody bamboos is a complex task due to the long periods of time between flowering cycles, which range from 3 to 120 years. Insects visiting Guadua paniculata and G. inermis flowers were collected in the field. Scanning electron micrographs were taken of the visiting insects. Four species of bees, three from tribe Meliponini (Geotrigona acapulconis, Plebeia frontalis and Trigona fulviventris) and one from tribe Apini (Apis mellifera), along with a syrphid fly (Toxomerus teligera) were found visiting bamboo flowers. Some species of Hemiptera were also found feeding on the flowers, such as Neortholomus jamaicensis (Lygaeidae), or preying on the flower visitors (Apiomerus pictipes (Reduviidae)). Insects visiting bamboo inflorescences may facilitate the release of pollen grains into the air, promoting outcrossing and genetic flow among the individuals of the flowering bamboo populations.     

Creatine supplementation in health and disease: What is the evidence for long-term efficacy?

Creatine supplementation is an established ergogenic aid in sports and is now claimed to have therapeutical applications in a variety of diseases. The available literature mainly covers the short-term (one to several weeks) effects of creatine supplementation on skeletal muscle function in health and disease, which is of little help to evaluate the long-term (two or more months) potential of creatine as a drug in chronic disorders, such as neurodegenerative diseases or muscular dystrophies. Recent findings in healthy humans indicate that the beneficial effect on muscle function and muscle total creatine content may disappear when creatine is continuously ingested for more than two or three months. The mechanism for this habituation to chronic creatine exposure is poorly understood. The primary purpose of the present review article is to critically evaluate the available evidence for long-term efficacy of creatine administration and to hypothesize about ways to optimize creatine administration regimens.     

Oxidative stress and nitric oxide deficiency in the kidney: a critical link to hypertension?

There is growing evidence that oxidative stress contributes to hypertension. Oxidative stress can precede the development of hypertension. In almost all models of hypertension, there is oxidative stress that, if corrected, lowers BP, whereas creation of oxidative stress in normal animals can cause hypertension. There is overexpression of the p22(phox) and Nox-1 components of NADPH oxidase and reduced expression of extracellular superoxide dismutase (EC-SOD) in the kidneys of ANG II-infused rodents, whereas there is overexpression of p47(phox) and gp91(phox) and reduced expression of intracellular SOD with salt loading. Several mechanisms have been identified that can make oxidative stress self-sustaining. Reactive oxygen species (ROS) can enhance afferent arteriolar tone and reactivity both indirectly via potentiation of tubuloglomerular feedback and directly by microvascular mechanisms that diminish endothelium-derived relaxation factor/nitric oxide responses, generate a cyclooxygenase-2-dependent endothelial-derived contracting factor that activates thromboxane-prostanoid receptors, and enhance vascular smooth muscle cells reactivity. ROS can diminish the efficiency with which the kidney uses O(2) for Na(+) transport and thereby diminish the P(O(2)) within the kidney cortex. This may place a break on further ROS generation yet could further enhance vasculopathy and hypertension. There is a tight relationship between oxidative stress in the kidney and the development and maintenance of hypertension.     

Bone and cartilage in osteoarthritis: is what's best for one good or bad for the other?

The interest in the relationship between articular cartilage and the structural and functional properties of peri-articular bone relates to the intimate contact that exists between these tissues in joints that are susceptible to the development of osteoarthritis (OA). The demonstration in several animal models that osteoporosis and decreased bone tissue modulus leads to an increased propensity for the development of post-traumatic OA is paradoxical in light of the extensive epidemiological literature indicating that individuals with high systemic bone mass, assessed by bone mineral density, are at increased risk for OA. These observations underscore the need for further studies to define the pathophysiological mechanisms involved in the interaction between subchondral bone and articular cartilage and for applying this information to the development of therapeutic interventions to improve the outcomes in patients with OA.     

AMPK: a link between metabolism and reproduction?

5'AMP-activated protein kinase (AMPK) is a serine/threonine kinase that acts as a fuel gauge in regulating energy metabolism. It restores cellular ATP levels by switching on catabolic pathways and switching off anabolic pathways. Some evidence indicates that AMPK could be also implicated in reproductive functions such as granulosa cell steroidogenesis and nuclear oocyte maturation in several species. Some metabolic hormones such as leptin, resistin, adiponectin (three adipokines) and ghrelin may in part act through the AMPK signaling. These hormones are also involved in the control of the reproductive functions at the hypothalamus-pituitary-gonadal axis level in both male and female. Thus, AMPK could be one of the signaling pathways controlling the interactions between energy balance and reproduction. The reproductive system is tightly coupled with energy balance, and thereby metabolic abnormalities can lead to the development of some physiopathological situations such as the polycystic ovary syndrome (PCOS). Women with PCOS show altered fertility mostly associated with metabolic disorders such as insulin-resistance, hyperinsulinemia and/or dyslipidemia. Metformin, an insulin-sensitizer, is used for the treatment of women with PCOS. It restores subnormal fertility and energy balance. Recent studies show that AMPK is involved in the mechanism of action of metformin. Thus, it may be a therapeutic target. However, further investigations are necessary to elucidate the functions of AMPK in both metabolic and reproductive tissues.     

Myzostomida: a link between trochozoans and flatworms?

Myzostomids are obligate symbiotic invertebrates associated with echinoderms with a fossil record that extends to the Ordovician period. Due to their long history as host-specific symbionts, myzostomids have acquired a unique anatomy that obscures their phylogenetic affinities to other metazoans: they are incompletely segmented, parenchymous, acoelomate organisms with chaetae and a trochophore larva. Today, they are most often classified within annelids either as an aberrant family of polychaetes or as a separate class. We inferred the phylogenetic position of the Myzostomida by analysing the DNA sequences of two slowly evolving nuclear genes: the small subunit ribosomal RNA and elongation factor-1alpha. All our analyses congruently indicated that myzostomids are not annelids but suggested instead that they are more closely related to flatworms than to any trochozoan taxon. These results, together with recent analyses of the myzostomidan ultrastructure, have significant implications for understanding the evolution of metazoan body plans, as major characters (segmentation, coeloms, chaetae and trochophore larvae) might have been independently lost or gained in different animal phyla.     

Ribonucleotide reductases: the link between an RNA and a DNA world?

The structures of a class III ribonucleotide reductase (RNR) and pyruvate formate lyase exhibit striking homology within their active site domains with respect to each other and to the previously published structure of a class I RNR. The common structures and the common complex-radical-based chemistry of these systems, as well as of the class II RNRs, suggest that RNRs evolved by divergent evolution and provide an essential link between the RNA and DNA world.