Larval Formation Research Articles

Anthelmintic activity of Moringa oleifera seed aqueous and ethanolic extracts against Haemonchus contortus eggs and third stage larvae

Haemonchus contortus is one of the prevalent and pathogenic ruminant parasites that has grown resistance to common anthelmintic treatment. This study evaluated the anthelmintic potential of Moringa oleifera seed ethanolic and aqueous extracts against H. contortus eggs and infective stage larvae (L3s). The efficacy of five extract concentrations (0.95, 1.95, 3.9, 7.8, and 15.6mg/mL) were tested through egg hatch assay and larval motility test. Phytochemical tests were conducted to detect the different plant secondary metabolites in the extracts. In the ovicidal assay, the ethanolic and aqueous extracts showed 95.89% and 81.72% egg hatch inhibition at 15.6mg/mL, respectively. The ovicidal activity of 15.6mg/mL ethanolic extract was comparable with that of albendazole (p>0.05). The LC50 against the eggs was recorded at 2.91 and 3.83mg/mL for ethanolic and aqueous extracts, respectively. In the larvicidal assay, the ethanolic and aqueous extracts exhibited 56.94% and 92.50% efficacy at 7.8mg/mL, respectively. The larvicidal activity of 7.8mg/mL aqueous extract was similar statistically with that of ivermectin (p>0.05). The LC50 against L3s was recorded at 6.96 and 4.12mg/mL for ethanolic and aqueous extracts, respectively. The secondary metabolites detected were tannins in ethanolic extract and saponins in aqueous extract. Both extracts inhibited larvae formation inside the eggs and rendered the L3s immobile. Therefore, M. oleifera seed extracts contained plant bioactive compounds with anthelmintic property against the eggs and L3s of H. contortus.

REPRODUCTIVE CYCLE, GAMETOGENESIS AND EMBRYONIC DEVELOPMENT OF NITIA TERETIUSCULA (BIVALIVA: UNIONIDAE), FROM THE RIVER NILE, AT SOHAG GOVERNORATE, EGYPT

The present study dealt with the description of the reproductive and gametogenic cycles and the embryonic development of the freshwater mussel Nitia teretiuscula from the River Nile. Macro and micro-anatomy showed that the present species is dioceous and gonadosomatic indices showed that the species is semiannual and had two gonadal growth periods, a short period of gonadal growth from January to March and a long period from April to August. Visceral indices revealed a reciprocal relationship with the gonadosomatic indices of both the two sexes. The recorded sex ratio of females to males was (1.5: 1). The oogenesis displayed five developmental stages; oogonia, previtellogenic oocytes, vitellogenic oocytes, late vitellogenic oocytes and mature ova. Also, spermatogenesis illustrated five developmental stages: spermatogonia, primary spermatocytes, and secondary spermatocytes, spermatids; which clustered to form sperm morula and finally metamorphosed to spermatozoa. Within the gills of females (marsupia), brooding of embryos was occurred till the formation of glochidia larvae. The unfertilized eggs were released from the gonads with distinct germinal vesicle. The fertilized eggs had two polar bodies and a fertilization cone. Successive cleavages were observed. Spiral cleavage, non-ciliated blastula and D-shaped larvae were recorded.

Maternal investment in fish oocytes and eggs: The molecular cargo and its contributions to fertility and early development

The production of fertile eggs with the capacity to develop into larvae and subsequently into marketable fish is centrally important to the aquaculture industry. This entails not only the programmed production of large numbers of eggs, but also high quality eggs with the potential to support normal development and high survival of offspring to juvenile and later stages of development and growth. Numerous studies highlight the maternal contributions to the development of embryos, including transcripts that regulate cell division and determine oocyte polarity, pattern development during early and late embryonic stages and the transition from maternal to zygotic gene expression and translation. Since most fish embryos develop independently within an enclosed egg envelope, they rely on compounds deposited within the oocytes during their various stages of development. In addition to regulatory nucleic acids (maternal DNA and RNA), these include proteins and other compounds that contribute to the structure and function of the egg envelope and the bulk molecular cargo that will be used as a source of cellular energy and structural components for formation of embryos and larvae. These latter components notably include yolk lipids and proteins deposited during oocyte growth and water acquired at the same time and during cytoplasmic maturation. In this review we highlight recent advances made in revealing the transcripts deposited within the oocyte that contribute to the structural and morphological development of the embryo, and to the regulation of gene expression and translation during oocyte development. Significant advances have been made in revealing the molecular mechanisms of lipid accumulation and metabolism within the oocyte, the intricacies of yolk protein formation via endocytosis of multiple yolk precursor proteins by multiple oocyte receptors, and the complex machinery supporting massive accumulation of water by maturing oocytes of many species. Additionally, many advances have been made in our understanding of the endocrine regulation of all of these processes during oogenesis. We provide here an overview of recent advances in our knowledge on these various aspects of oogenesis and identify several gaps in our knowledge for future studies.

A method for collecting eggs of Pseudocapillaria tomentosa (Nematoda: Capillariidae) from zebrafish Danio rerio and efficacy of heat and chlorine for killing the nematode's eggs.

Pseudocapillaria tomentosa is a common pathogen of zebrafish (Danio rerio) in research facilities. We developed a method to collect and concentrate the nematode eggs using a modified sugar centrifugation method and documented their normal development. Embryonating stages with blastomere formation followed by elongation of the embryo prior to larva formation cumulated in developed larvae inside the eggs and hatching after 5-10day. We then evaluated the efficacy of heat and chlorine to kill them based on a larva development assay. Eggs were exposed to 40, 50, 60°C for 30min and 1h. Chlorine treatment was performed at 100, 250, 500, 1000, 3000 and 6000ppm for 10min. Samples exposed to 40°C for 30min or 1h showed incidences of larvated eggs similar to controls. In contrast, no larvation occurred with eggs exposed to either 50 or 60°C for 30min or 1h. Remarkably, in repeated assays, samples exposed to low doses of chlorine (100, 250, 500 and 1000ppm for 10min) showed significantly higher incidence of larvation than controls. Eggs treated with 3000ppm for 10min did not develop larvae, and no eggs were found after 6000ppm treatment.

Sperm Affects Head Sensory Neuron in Temperature Tolerance of Caenorhabditis elegans.

Tolerance to environmental temperature change is essential for the survival and proliferation of animals. The process is controlled by various body tissues, but the orchestration of activity within the tissue network has not been elucidated in detail. Here, we show that sperm affects the activity of temperature-sensing neurons (ASJ) that control cold tolerance in Caenorhabditis elegans. Genetic impairment of sperm caused abnormal cold tolerance, which was unexpectedly restored by impairment of temperature signaling in ASJ neurons. Calcium imaging revealed that ASJ neuronal activity in response to temperature was decreased in sperm mutant gsp-4 with impaired protein phosphatase 1 and rescued by expressing gsp-4 in sperm. Genetic analysis revealed a feedback network in which ASJ neuronal activity regulates the intestine through insulin and a steroid hormone, which then affects sperm and, in turn, controls ASJ neuronal activity. Thus, we propose that feedback between sperm and a sensory neuron mediating temperature tolerance.

The gene expression and the activity of enzyme synthesis of trehalose during development of Ascaris suum (Nematoda) eggs

The activity of trehalose-6-phosphate synthase (TPS) and trehalose-6-phosphate phosphatase (TPP) and their mRNA expression was determined in Ascaris suum eggs developing from a zygote to invasive larvae in an in vitro culture. The stages of nematode embryonic development, i.e. cleavage, gastrulation and formation of larvae, were always accompanied by an increase in TPS activity. An increase in TPP activity, the second enzyme of the analysed pathway, followed in subsequent developmental stages. Key changes in trehalose metabolism were observed in the tadpole stage. The development of moving larvae was accompanied by the highest mRNA expression and activity level of TPP, which converts metabolic intermediate T6P to trehalose. The trehalose synthesis enzymes activity was positively correlated with their mRNA expression. For three genes: tps1, tps2 (TPS coding) and tpp (TPP coding) there was very strong and statistically significant correlation with the activity of a specific enzyme. The Pearson’s coefficient was r = 0.903714 (p < 0.001) for tps1 gene, r = 0.803012 ( < 0.01) for tps2 and r = 0.856244 (p < 0.01) for tpp over development time.

Early development of the blue mussel Mytilus edulis (Linnaeus, 1758) cultured in potassium-fortified inland saline water

The low potassium concentration in inland saline water (ISW) restrains the normal development of cultured marine organisms, and thus, possesses challenges for the development of ISW aquaculture. Therefore, assessing the effects of potassium fortification in ISW on the performance of cultured marine species is an important step to determine the feasibility of their culture in ISW. The aim of this research was to investigate the effects of potassium fortification in ISW on the performance of early life stages of the blue mussel Mytilus edulis including fertilised eggs, trochophore, veliger and pediveliger larvae. These stages were reared in five different levels of potassium-fortified ISW, namely 20, 40, 60, 80 and 100% of potassium levels equivalent to the potassium level in ocean water (OW) and two controls namely, ISW at 27ppt (ISW27) and OW at 25ppt (OW25). The results showed that the higher levels of potassium in ISW, particularly with 100% K+ fortification (ISW100K+), invariably improved the survival and size, and reduced the developmental stage interval and deformities of blue mussel larvae. Deformities, such as faulty cell cleavage, abnormal formation of trochophore larvae, protruding mantle in veliger larvae, and indented shell margin in veliger and in pediveliger, were observed when reared in any ISW. However, rearing in ISW did not result in any deformities in settlement larvae. The number of deformities was reduced at higher K+ fortification levels, and there were no deformities in pediveliger larvae reared in ISW100K+ and in OW. These results showed that K+ fortification in ISW improves the performance of the rearing of the larval stages of the blue mussel. Statement of relevanceThis study is the first attempt to culture larval stages of blue mussel Mytilus edulis in potassium-fortified inland saline water. The results have shown that that the larval development is feasible only if ISW is fortified with K+. By initiating larval culture in inland saline water, we expect better results will be reflected by adult stages.

Winter Aconite (Eranthis hyemalis) Lectin as a cytotoxic effector in the lifecycle of Caenorhabditis elegans.

The lectin found in the tubers of the Winter Aconite (Eranthis hyemalis) plant is an N-acetyl-D-galactosamine specific Type II Ribosome Inactivating Protein (RIP); Type II RIPs have shown anti-cancer properties, and hence have potential as therapeutic agents. Here we present a modified protocol for the extraction and purification of the E. hyemalis lectin (EHL) using affinity chromatography. De novo amino acid sequencing of EHL confirms its classification as a Type II Ribosome Inactivating Protein. The biocidal properties of EHL have been investigated against the nematode Caenorhabditis elegans. Arrested first stage larvae treated with EHL have shown some direct mortality, with surviving larvae subsequently showing a range of phenotypes including food avoidance, reduced fecundity, developmental delay and constitutive dauer larvae formation. Both inappropriate dauer larvae development and failure to locate to bacterial food source are consistent with the disruption of chemosensory function and the ablation of amphid neurons. Further investigation indicates that mutations that disrupt normal amphid formation can block the EHL-induced dauer larvae formation. In combination, these phenotypes indicate that EHL is cytotoxic and suggest a cell specific activity against the amphid neurons of C. elegans.

Integration of carbohydrate metabolism and redox state controls dauer larva formation in Caenorhabditis elegans.

Under adverse conditions, Caenorhabditis elegans enters a diapause stage called the dauer larva. External cues signal the nuclear hormone receptor DAF-12, the activity of which is regulated by its ligands: dafachronic acids (DAs). DAs are synthesized from cholesterol, with the last synthesis step requiring NADPH, and their absence stimulates dauer formation. Here we show that NADPH levels determine dauer formation in a regulatory mechanism involving key carbohydrate and redox metabolic enzymes. Elevated trehalose biosynthesis diverts glucose-6-phosphate from the pentose phosphate pathway, which is the major source of cellular NADPH. This enhances dauer formation due to the decrease in the DA level. Moreover, DAF-12, in cooperation with DAF-16/FoxO, induces negative feedback of DA synthesis via activation of the trehalose-producing enzymes TPS-1/2 and inhibition of the NADPH-producing enzyme IDH-1. Thus, the dauer developmental decision is controlled by integration of the metabolic flux of carbohydrates and cellular redox potential.

Cell Differentiation in a Bacillus thuringiensis Population during Planktonic Growth, Biofilm Formation, and Host Infection.

ABSTRACTBacillus thuringiensis (Bt) is armed to complete a full cycle in its insect host. During infection, virulence factors are expressed under the control of the quorum sensor PlcR to kill the host. After the host’s death, the quorum sensor NprR controls a necrotrophic lifestyle, allowing the vegetative cells to use the insect cadaver as a bioincubator and to survive. Only a part of the Bt population sporulates in the insect cadaver, and the precise composition of the whole population and its evolution over time are unknown. Using fluorescent reporters to record gene expression at the single-cell level, we have determined the differentiation course of a Bt population and explored the lineage existing among virulent, necrotrophic, and sporulating cells. The dynamics of cell differentiation were monitored during growth in homogenized medium, biofilm formation, and colonization of insect larvae. We demonstrated that in the insect host and in planktonic culture in rich medium, the virulence, necrotrophism, and sporulation regulators are successively activated in the same cell. In contrast, in biofilms, activation of PlcR is dispensable for NprR activation and we observed a greater heterogeneity than under the other two growth conditions. We also showed that sporulating cells arise almost exclusively from necrotrophic cells. In biofilm and in the insect cadaver, we identified an as-yet-uncharacterized category of cells that do not express any of the reporters used. Overall, we showed that PlcR, NprR, and Spo0A act as interconnected integrators to allow finely tuned adaptation of the pathogen to its environment.

The evolution of plasticity of dauer larva developmental arrest in the nematode Caenorhabditis elegans.

Organisms can end up in unfavourable conditions and to survive this they have evolved various strategies. Some organisms, including nematodes, survive unfavourable conditions by undergoing developmental arrest. The model nematode Caenorhabditis elegans has a developmental choice between two larval forms, and it chooses to develop into the arrested dauer larva form in unfavourable conditions (specifically, a lack of food and high population density, indicated by the concentration of a pheromone). Wild C. elegans isolates vary extensively in their dauer larva arrest phenotypes, and this prompts the question of what selective pressures maintain such phenotypic diversity? To investigate this we grew C. elegans in four different environments, consisting of different combinations of cues that can induce dauer larva development: two combinations of food concentration (high and low) in the presence or absence of a dauer larva-inducing pheromone. Five generations of artificial selection of dauer larvae resulted in an overall increase in dauer larva formation in most selection regimes. The presence of pheromone in the environment selected for twice the number of dauer larvae, compared with environments not containing pheromone. Further, only a high food concentration environment containing pheromone increased the plasticity of dauer larva formation. These evolutionary responses also affected the timing of the worms’ reproduction. Overall, these results give an insight into the environments that can select for different plasticities of C. elegans dauer larva arrest phenotypes, suggesting that different combinations of environmental cues can select for the diversity of phenotypically plastic responses seen in C. elegans.

Action of ethanolic extract from aerial parts of Tagetes patula L. (Asteraceae) on hatchability and embryogenesis of Rhipicephalus sanguineus eggs (Acari: Ixodidae)

Rhipicephalus sanguineus (Latreille, 1806) presents medical importance, being the principal vector of Rickettsia conorii, the causative agent of Botonous fever, occurring in various regions of Europe and Africa. In the Americas, has been reported as a vector of Rickettsia rickettsii, the causative agent of Mountain Spotted Fever. It presents veterinary importance because is responsible by the transmission of zoonosis like babesiosis, ehrlichiosis, hepatozoonosis and others. The resistance that these ticks show to some of the active principles used in acaricides has risen wildly. In other hand, the use of herbal medicines has been outstanding recently. Among the advantages of phytotherapics that justify their use are synergistic effects of its components and easy degradation in the environment. In this scenario, Tagetes patula L. (Asteraceae) appears as a species with great biocide potential. The phytochemical investigation of T. patula has resulted in the isolation of several chemical constituents such as benzofurans, carotenoids, flavonoids and thiophenes. This study aimed to test the effect of the ethanolic extract obtained from aerial parts of T. patula against eggs of R. sanguineus by Egg hatchability test and to verify, for the first time, the action of this sample on ovary cells of engorged females submitted to the Adult Immersion Test. The extract was very effective, inhibiting egg hatching in 96.98% (±0.025) with LD50=6.312mg/mL (4.064–8.497mg/mL). Microscopic analysis of the structure of the ovaries showed significant morphological changes in the structure of oocytes II–V and pedicel cells, interfering directly in its normal embryogenesis, impairing or impeding the formation of healthy larvae, breaking the life cycle of this ticks in the beginning. Despite the difficulty to control adult populations of ticks, these findings are important and provide an alternative to disrupt development on the environment.

Highly polygenic variation in environmental perception determines dauer larvae formation in growing populations of Caenorhabditis elegans.

BackgroundDetermining how complex traits are genetically controlled is a requirement if we are to predict how they evolve and how they might respond to selection. This requires understanding how distinct, and often more simple, life history traits interact and change in response to environmental conditions. In order to begin addressing such issues, we have been analyzing the formation of the developmentally arrested dauer larvae of Caenorhabditis elegans under different conditions.ResultsWe find that 18 of 22 previously identified quantitative trait loci (QTLs) affecting dauer larvae formation in growing populations, assayed by determining the number of dauer larvae present at food patch exhaustion, can be recovered under various environmental conditions. We also show that food patch size affects both the ability to detect QTLs and estimates of effect size, and demonstrate that an allele of nath-10 affects dauer larvae formation in growing populations. To investigate the component traits that affect dauer larvae formation in growing populations we map, using the same introgression lines, QTLs that affect dauer larvae formation in response to defined amounts of pheromone. This identifies 36 QTLs, again demonstrating the highly polygenic nature of the genetic variation underlying dauer larvae formation.ConclusionsThese data indicate that QTLs affecting the number of dauer larvae at food exhaustion in growing populations of C. elegans are highly reproducible, and that nearly all can be explained by variation affecting dauer larvae formation in response to defined amounts of pheromone. This suggests that most variation in dauer larvae formation in growing populations is a consequence of variation in the perception of the food and pheromone environment (i.e. chemosensory variation) and in the integration of these cues.

The embryonic development of the cnidarian Hydractinia echinata.

With the rapid increase of the quantity of molecular data, many animals joined the ranks of the so-called 'emerging models' of Evo-Devo. One of the necessary steps in converting an emerging model into an established one is gaining comprehensive knowledge of its normal embryonic development. The marine colonial hydrozoan Hydractinia echinata - an excellent model for research on stem cells, metamorphosis, and allorecognition - has been studied for decades. Yet knowledge of its embryonic development remains fragmentary and incomplete. Here we provide a detailed account of H. echinata embryonic development using in vivo observations, histology, immunohistochemistry, and electron microscopy. Furthermore, we propose a model describing the cellular basis of the morphogenetic movements occurring during development and also reveal a functional link between canonical Wnt signaling and regional differences in the morphology of the embryo. Hydractinia embryogenesis is an example of the diversity and plasticity of hydrozoan development where multiple routes lead to the same result - the formation of a normal planula larva.

Diverse and potentially manipulative signalling with ascarosides in the model nematode C. elegans.

BackgroundAnimals use environmental information to make developmental decisions to maximise their fitness. The nematode Caenorhabditis elegans measures its environment to decide between arresting development as dauer larvae or continuing to grow and reproduce. Worms are thought to use ascarosides as signals of population density and this signalling is thought to be a species-wide honest signal. We compared recently wild C. elegans lines’ dauer larva arrest when presented with the same ascaroside signals and in different food environments.ResultsWe find that the hitherto canonical dauer larva response does not hold among these lines. Ascaroside molecules can, depending on the food environment, both promote and repress dauer larva formation. Further, these recently wild C. elegans lines also produce ascaroside mixtures that induce a wide diversity of dauer larva formation responses. We further find that the lines differ in the quantity and ratios of ascaroside molecules that they release. Some of the dauer larva formation responses are consistent with dishonest signalling.ConclusionsTogether, the results suggest that the idea that dauer larva formation is an honestly-signalled C. elegans-wide effect does not hold. Rather, the results suggest that ascaroside-based signalling is a public broadcast information system, but where the correct interpretation of that information depends on the worms’ context, and is a system open to dishonest signalling.

Host insulin stimulates Echinococcus multilocularisinsulin signalling pathways and larval development

BackgroundThe metacestode of the tapeworm Echinococcus multilocularis is the causative agent of alveolar echinococcosis, a lethal zoonosis. Infections are initiated through establishment of parasite larvae within the intermediate host’s liver, where high concentrations of insulin are present, followed by tumour-like growth of the metacestode in host organs. The molecular mechanisms determining the organ tropism of E. multilocularis or the influences of host hormones on parasite proliferation are poorly understood.ResultsUsing in vitro cultivation systems for parasite larvae we show that physiological concentrations (10 nM) of human insulin significantly stimulate the formation of metacestode larvae from parasite stem cells and promote asexual growth of the metacestode. Addition of human insulin to parasite larvae led to increased glucose uptake and enhanced phosphorylation of Echinococcus insulin signalling components, including an insulin receptor-like kinase, EmIR1, for which we demonstrate predominant expression in the parasite’s glycogen storage cells. We also characterized a second insulin receptor family member, EmIR2, and demonstrated interaction of its ligand binding domain with human insulin in the yeast two-hybrid system. Addition of an insulin receptor inhibitor resulted in metacestode killing, prevented metacestode development from parasite stem cells, and impaired the activation of insulin signalling pathways through host insulin.ConclusionsOur data indicate that host insulin acts as a stimulant for parasite development within the host liver and that E. multilocularis senses the host hormone through an evolutionarily conserved insulin signalling pathway. Hormonal host-parasite cross-communication, facilitated by the relatively close phylogenetic relationship between E. multilocularis and its mammalian hosts, thus appears to be important in the pathology of alveolar echinococcosis. This contributes to a closer understanding of organ tropism and parasite persistence in larval cestode infections. Furthermore, our data show that Echinococcus insulin signalling pathways are promising targets for the development of novel drugs.

Taurine drinking attenuates the burden of intestinal adult worms and muscle larvae in mice with Trichinella spiralis infection

The parasitic nematode Trichinella spiralis can cause trichinellosis, which leads to pathological processes in the intestine and muscle. The intestinal invasion determines the development, subsequent course, and consequences of the disease. Gastrointestinal nematode infection, including with T. spiralis, is accompanied by a rapid and reversible expansion of mucosal mast cell and goblet cell in the intestinal epithelium, which play important roles in the host immune response to parasite and worm expulsion from the intestine. Taurine and its derivatives have anti-infection and anti-inflammatory properties. We investigated whether taurine supplementation in mice could influence the development and pathological processes of infection with T. spiralis. Supplementing 1% taurine in drinking water in mice infected with T. spiralis could alleviate the burden of intestinal adult worms on days 7 and 10 postinfection (all p < 0.01) and the formation of infective muscle larvae in striated muscle during T. spiralis infection (p < 0.01). As compared with T. spiralis infection alone, taurine treatment increased the number of goblet cells on days 7, 10, and 15 (p < 0.01 and p < 0.05) and alleviated intestinal mucosal mast cell hyperplasia on days 10 and 15 (all p < 0.01). So taurine supplementation in drinking water increased infection-induced intestinal goblet cell hyperplasia and ameliorated mucosal mastocytosis. Thus, taurine can ameliorate the pathological processes of trichinellosis and may be of great value for the treatment and prevention of infection with T. spiralis and other gastrointestinal nematodes.

Genetic mapping of variation in dauer larvae development in growing populations of Caenorhabditis elegans.

In the nematode Caenorhabditis elegans, the appropriate induction of dauer larvae development within growing populations is likely to be a primary determinant of genotypic fitness. The underlying genetic architecture of natural genetic variation in dauer formation has, however, not been thoroughly investigated. Here, we report extensive natural genetic variation in dauer larvae development within growing populations across multiple wild isolates. Moreover, bin mapping of introgression lines (ILs) derived from the genetically divergent isolates N2 and CB4856 reveals 10 quantitative trait loci (QTLs) affecting dauer formation. Comparison of individual ILs to N2 identifies an additional eight QTLs, and sequential IL analysis reveals six more QTLs. Our results also show that a behavioural, laboratory-derived, mutation controlled by the neuropeptide Y receptor homolog npr-1 can affect dauer larvae development in growing populations. These findings illustrate the complex genetic architecture of variation in dauer larvae formation in C. elegans and may help to understand how the control of variation in dauer larvae development has evolved.

Effect of Temperature on Embryonation of Ascaris suum Eggs in an Environmental Chamber

The influence of temperature on the development and embryonation of Ascaris suum eggs was studied using coarse sand medium in an environmental chamber with 50% humidity. The time required for development and embryonation of eggs was examined under 3 different temperature conditions, 5℃, 25℃, and 35℃. A. suum eggs did not develop over 1 month at the temperature of 5℃. However, other temperature conditions, 25℃ and 35℃, induced egg development to the 8-cell-stage at days 5-6 after incubation. All eggs examined developed to the 8-cell stage at day 6 after incubation in the sand medium at 25℃. The higher temperature, 35℃, slightly accelerated the A. suum egg development compared to 25℃, and the development to the 8-cell stage occurred within day 5 after incubation. The formation of larvae in A. suum eggs at temperatures of 35℃ and 25℃ appeared at days 17 and 19 after incubation, respectively. These findings show that 35℃ condition shortens the time for the development of A. suum eggs to the 8-cell-stage in comparison to 25℃, and suggest the possibility of accelerated transmission of this parasite, resulting from global warming and ecosystem changes.

Manipulation of in vivo iron levels can alter resistance to oxidative stress without affecting ageing in the nematode C. elegans

Iron-catalyzed generation of free radicals leads to molecular damage in vivo, and has been proposed to contribute to organismal ageing. Here we investigate the role of free iron in ageing in the nematode Caenorhabditis elegans. Media supplementation with Fe(III) increased free iron levels in vivo, as detected by continuous-wave electron paramagnetic resonance spectroscopy and elevated expression of the iron-sensitive reporter transgene pftn-1::gfp. Increased free iron levels caused elevated levels of protein oxidation and hypersensitivity to tert-butyl hydroperoxide (t-BOOH) given 9mM Fe(III) or greater, but 15mM Fe(III) or greater was required to reduce lifespan. Treatment with either an iron chelator (deferoxamine) or over-expression of ftn-1, encoding the iron sequestering protein ferritin, increased resistance to t-BOOH and, in the latter case, reduced protein oxidation, but did not increase lifespan. Expression of ftn-1 is greatly increased in long-lived daf-2 insulin/IGF-1 receptor mutants. In this context, deletion of ftn-1 decreased t-BOOH resistance, but enhanced both daf-2 mutant longevity and constitutive dauer larva formation, suggesting an effect of ferritin on signaling. These results show that high levels of iron can increase molecular damage and reduce lifespan, but overall suggest that iron levels within the normal physiological range do not promote ageing in C. elegans.