Suppressed Egg Production Research Articles

Aspirin Inhibition of Prostaglandin Synthesis Impairs Mosquito Egg Development.

Several endocrine signals mediate mosquito egg development, including 20-hydroxyecdysone (20E). This study reports on prostaglandin E2 (PGE2) as an additional, but core, mediator of oogenesis in a human disease-vectoring mosquito, Aedes albopictus. Injection of aspirin (an inhibitor of cyclooxygenase (COX)) after blood-feeding (BF) inhibited oogenesis by preventing nurse cell dumping into a growing oocyte. The inhibitory effect was rescued by PGE2 addition. PGE2 was found to be rich in nurse cells and follicular epithelium after BF. RNA interference (RNAi) treatments of PG biosynthetic genes, including PLA2 and two COX-like peroxidases, prevented egg development. Interestingly, 20E treatment significantly increased the expressions of PG biosynthetic genes, while the RNAi of Shade (which is a 20E biosynthetic gene) expression prevented inducible expressions after BF. Furthermore, RNAi treatments of PGE2 receptor genes suppressed egg production, even under PGE2. These results suggest that a signaling pathway of BF-20E-PGE2 is required for early vitellogenesis in the mosquito.

Bone quality and composition are influenced by egg production, layer line, and oestradiol-17ß in laying hens

ABSTRACT Keel bone fractures are a serious animal welfare problem in laying hens. The aim of the current study was to assess the influence of egg production, oestradiol-17ß, and selection for high laying performance on bone quality. Hens of two layer lines differing in laying performance (WLA: 320 eggs per year, G11: 200 eggs per year) were allocated to four treatment groups. Group S received a deslorelin acetate implant that suppressed egg production. Group E received an implant with the sexual steroid oestradiol-17ß. Group SE received both implants and group C did not receive any implant. In the 63rd week of age, composition and characteristics of the tibiotarsi were assessed using histological analysis, three-point bending test, thermogravimetric analysis, infrared spectroscopy, and two-dimensional X-ray diffraction, respectively. Non-egg-laying hens showed a higher total bone area and a higher relative amount of cortical bone compared to egg-laying hens. Hens of layer line G11 showed a higher relative amount of medullary bone and a higher degree of mineralization of the cortical bone compared to hens of layer line WLA. These differences in bone composition may explain different susceptibility to keel bone fractures in non-egg-laying compared to egg-laying hens as well as in hens of layer lines differing in laying performance. The effect of exogenous oestradiol-17ß on bone parameters varied between the layer lines indicating a genetic influence on bone physiology and the way it can be modulated by hormone substitution.

Schistosomicidal evaluation of synthesized bromo and nitro chalcone derivatives

Chalcones are compounds associated to several biological activities. The modification of chemical structures is one of the most widely used tool in the pharmaceutical industry to obtain new drugs. In this study, we synthetized chalcones with nitro and bromo substituents in different positions in the aromatic rings. NMR spectroscopy was used for characterization. Simultaneously, a conformational study of the compounds was carried out employing theoretical calculations. Furthermore, the schistosomicidal in vitro effect of bromo and nitro chalcone substituents on adult Schistosoma mansoni was investigated. The results showed that most chalcones have a conformational preference for s-cis geometry, which is favored by the conjugative effect of electronic delocalization. However, chalcones with ortho substituents dissipate greater stabilization of s-trans conformations, possibly for favoring surfaces with weak interactions such as Van der Waals. In addition, a significant effect of chalcones on female and male S. mansoni was observed. All samples evaluated reduced the motor activity of worms, caused mortality in male and female worms, and resulted in morphological alterations in a concentration- dependent manner (25–200 μg/mL) in a period of 6–24 h of incubation. Additionally, chalcones influenced the separation of couple worms and suppressed egg production at sublethal concentrations. Our results demonstrated that chalcones present potential to be used as schistosomicidal drugs, contributing to the clarification of the relation between the molecule conformation and the associated biological effects.

The Role of Egg Production in the Etiology of Keel Bone Damage in Laying Hens.

Keel bone fractures and deviations belong to the most severe animal welfare problems in laying hens and are influenced by several factors such as husbandry system and genetic background. It is likely that egg production also influences keel bone health due to the high demand of calcium for the eggshell, which is, in part, taken from the skeleton. The high estrogen plasma concentration, which is linked to the high laying performance, may also affect the keel bone as sexual steroids have been shown to influence bone health. The aim of this study was to investigate the relationship between egg production, genetically determined high laying performance, estradiol-17ß concentration, and keel bone characteristics. Two hundred hens of two layer lines differing in laying performance (WLA: high performing; G11: low performing) were divided into four treatment groups: Group S received an implant containing a GnRH agonist that suppressed egg production, group E received an implant containing the sexual steroid estradiol-17ß, group SE received both implants, and group C were kept as control hens. Between the 12th and the 62nd weeks of age, the keel bone of all hens was radiographed and estradiol-17ß plasma concentration was assessed at regular intervals. Non-egg laying hens showed a lower risk of keel bone fracture and a higher radiographic density compared to egg laying hens. Exogenous estradiol-17ß was associated with a moderately higher risk of fracture within egg laying but with a lower risk of fracture and a higher radiographic density within non-egg laying hens. The high performing layer line WLA showed a significantly higher fracture risk but also a higher radiographic density compared to the low performing layer line G11. In contrast, neither the risk nor the severity of deviations were unambiguously influenced by egg production or layer line. We assume that within a layer line, there is a strong association between egg production and keel bone fractures, and, possibly, bone mineral density, but not between egg production and deviations. Moreover, our results confirm that genetic background influences fracture prevalence and indicate that the selection for high laying performance may negatively influence keel bone health.

Combining bioinformatics, cheminformatics, functional genomics and whole organism approaches for identifying epigenetic drug targets in Schistosoma mansoni

Schistosomiasis endangers the lives of greater than 200 million people every year and is predominantly controlled by a single class chemotherapy, praziquantel (PZQ). Development of PZQ replacement (to combat the threat of PZQ insensitivity/resistance arising) or combinatorial (to facilitate the killing of PZQ-insensitive juvenile schistosomes) chemotherapies would help sustain this control strategy into the future. Here, we re-categorise two families of druggable epigenetic targets in Schistosoma mansoni, the histone methyltransferases (HMTs) and the histone demethylases (HDMs). Amongst these, a S. mansoni Lysine Specific Demethylase 1 (SmLSD1, Smp_150560) homolog was selected for further analyses. Homology modelling of SmLSD1 and in silico docking of greater than four thousand putative inhibitors identified seven (L1 – L7) showing more favourable binding to the target pocket of SmLSD1 vs Homo sapiens HsLSD1; six of these seven (L1 – L6) plus three structural analogues of L7 (L8 – L10) were subsequently screened against schistosomula using the Roboworm anthelmintic discovery platform. The most active compounds (L10 - pirarubicin > L8 – danunorubicin hydrochloride) were subsequently tested against juvenile (3 wk old) and mature (7 wk old) schistosome stages and found to impede motility, suppress egg production and affect tegumental surfaces. When compared to a surrogate human cell line (HepG2), a moderate window of selectivity was observed for the most active compound L10 (selectivity indices - 11 for schistosomula, 9 for juveniles, 1.5 for adults). Finally, RNA interference of SmLSD1 recapitulated the egg-laying defect of schistosomes co-cultivated in the presence of L10 and L8. These preliminary results suggest that SmLSD1 represents an attractive new target for schistosomiasis; identification of more potent and selective SmLSD1 compounds, however, is essential. Nevertheless, the approaches described herein highlight an interdisciplinary strategy for selecting and screening novel/repositioned anti-schistosomals, which can be applied to any druggable (epigenetic) target encoded by the parasite's genome.

The Effect of Pyriproxyfen as a “Population Growth Regulator” against Aedes albopictus under Semi-Field Conditions

An insect growth regulator, pyriproxyfen, has been used for the control of a range of pest insects, including mosquitoes. Pyriproxyfen is effective in inhibiting adult emergence and sterilizing adult females. The Asian tiger mosquito, Aedes albopictus (Skuse), is an important vector of dengue and chikungunya, and is expanding its distribution throughout Europe and the Americas. In the present study, we evaluated the impact of pyriproxyfen-treated bed nets on population growth of Ae. albopictus under semi-field conditions, using 6 small microcosms. We created microcosms containing breeding sites to simulate the natural ecosystem of vector mosquito and installing miniature bed net treated with 350 mg/m2 pyriproxyfen in Experiment I and 35 mg/m2 in Experiment II. For each experiment, we also established microcosms installing untreated polyethylene net (untreated control). The installing nets were provided with artificially torn holes, to simulate damage and allow mosquitoes to penetrate. We released 100 pairs of Ae. albopictus into each microcosm, and allowed them to feed on a mouse under the bed nets at approximately 1-week intervals. In comparison with the untreated control microcosms, the number of eggs laid by the released adults in the pyriproxyfen-treated microcosms was significantly lower in both Experiment I and II. Moreover, egg hatchability was significantly suppressed and pupal mortality was increased. Our results indicate that tarsal contact with pyriproxyfen has been shown to suppress egg production and hatchability in adult females and the auto-dissemination of pyriproxyfen into larval breeding sites by adult mosquitoes, through contact with pyriproxyfen-treated polyethylene bed nets, may suppress the mosquito population density.

Biocontrol potential of native Trichoderma isolates against root-knot nematodes in West African vegetable production systems

Seventeen isolates of the free-living soil fungus Trichoderma spp., collected from Meloidogyne spp. infested vegetable fields and infected roots in Benin, were screened for their rhizosphere competence and antagonistic potential against root-knot nematodes, Meloidogyne incognita , in greenhouse pot experiments on tomato. The five isolates expressing greatest reproductive ability and nematode suppression in pots were further assessed in a typical double-cropping system of tomato and carrot in the field in Benin. All seventeen isolates were re-isolated from both soil and roots at eight weeks after application, with no apparent crop growth penalty. In pots, a number of isolates provided significant nematode control compared with untreated controls. Field assessment demonstrated significant inhibition of nematode reproduction, suppression of root galling and an increase of tomato yield compared with the non-fungal control treatments. Trichoderma asperellum T-16 suppressed second stage juvenile (J 2 ) densities in roots by up to 80%; Trichoderma brevicompactum T-3 suppressed egg production by as much as 86%. Tomato yields were improved by over 30% following the application of these biocontrol agents, especially T. asperellum T-16. Although no significant effects were observed on carrot galling and yield, soil J 2 densities were suppressed in treated plots, by as much as 94% ( T. asperellum T-12), compared with the non-fungal controls. This study provides the first information on the potential of West-African Trichoderma spp. isolates for use against root-knot nematodes in vegetable production systems. The results are highly encouraging, demonstrating their strong potential as an alternative and complementary crop protection component. ► West African Trichoderma spp. isolates significantly suppressed root-knot nematodes. ► Trichoderma spp. isolates persisted in soil for at least eight weeks after application. ► Tomato yield was improved by 30% following Trichoderma application in field. ► Soil nematode densities were suppressed by up to 94% in follow-on carrot crops. ► The most effective Trichoderma spp. isolates were sourced from nematode egg masses.

Irradiation of <I>Anastrepha ludens</I> (Diptera: Tephritidae) Revisited: Optimizing Sterility Induction

Irradiation doses currently applied to sterilize Mexican fruit flies, Anastrepha ludens (Loew) (Diptera: Tephritidae), for release under the sterile insect technique eradication campaign in Mexico, were reviewed in an effort to increase sterile male performance in the field. A dose maximizing sterility induction into wild populations was sought by balancing somatic fitness with genetic sterility. Doses of 40, 60, and 80 Gy induced 95% or more sterility in all males, which in turn induced similar degrees of sterility into a cohort of wild flies in the laboratory. However, a low dose of 40 Gy was sufficient to completely suppress egg production in females. Similarly, a mild carryover of genetic damage might have been transferred to the F1 progeny of males irradiated at 40 Gy crossed with fertile wild females. Our results suggest that the 80-Gy dose currently applied in Mexico can be lowered substantially without jeopardizing program goals. This view could be strengthened by comparing performance of males irradiated at different doses under more natural settings. In general, we discuss the value of determining irradiation doses for pest species where females are more radiosensitive than males, by selecting the dose that causes 100% sterility in females.

Facultative sperm storage in response to nutritional status in a female insect.

We investigated sperm storage by females of a predatory bug, Nabis rugosus, before and after hibernation and with regard to nutritional status. In the field, females had more sperm available before than after hibernation. Food-deprived females maintained fewer sperm than fed females before but not after hibernation. However, after hibernation food-deprived females suppressed egg production rather than decreasing sperm-storage efficiency. Because mated females did not exhibit increased overwinter survival relative to virgin females there is a low likelihood of direct benefits in the form of ejaculate-derived nutrients. If nutrition-dependent sperm storage by females is widespread in the animal kingdom, our findings may have important implications for the understanding of postcopulatory sexual selection and the evolution of food gifts.

Low oviposition stimuli reduce egg production in the pollen beetle Meligethes aeneus

Abstract. Gravid female pollen beetles, Meligethes aeneus (F.) (Coleoptera: Nitidulidae), were exposed at different intervals to oviposition sites that varied in acceptability.The egg load of dissected individuals which had been deprived of oviposition sites was not greater than individuals which had been frequently exposed to oviposition sites.However, the egg load of individuals which had been exposed to highly acceptable host plants was greater than those exposed to a host plant of low acceptability.Over the experimental period the total number of eggs which an individual produced was lower for those that were either deprived of an oviposition site or frequently exposed to a low‐quality host plant.There was no evidence of either increased oviposition probability or clutch size as the period since the last oviposition increased.It is concluded that low host quality and low host encounter rate reduce the egg production of M.aeneus. It is further concluded that the suppressed egg production reduces the accumulation of eggs, so that physiological motivation for the insect to oviposit is not increased.If low oviposition site quality acts to reduce oogenesis, as found here, then the probability of egg deposition on low‐quality species may not increase over time and the effect of antixenotic resistance may be enhanced.

Mutual pheromonal inhibition among queens in polygyne colonies of the fire ant Solenopsis invicta

Decrease in individual reproductive output with increasing numbers of reproductives is a general feature of social insect colonies. The previously described negative relationship between the fecundity of individual queens and number of resident queens in polygyne (multiple-queen) colonies of the fire ant Solenopsis invicta appears to result from mutual pheromonal inhibition. In an experimental test for the presence of fecundity reducing pheromones, corpses of functional (egg-laying) queens were found to effectively inhibit the fecundity of functional queens, suggesting that queen-produced pheromones suppress egg production in such queens. Evidence concerning a possible mechanism mediating this inhibition was also obtained. Treatment of queens with methoprene, a juvenile hormone (JH) analog, increased ovary development, suggesting that fecundity in functional queens may be mediated by the level of endogenous JH. These findings are consistent with the occurrence of mutual pheromonal inhibition among queens achieved by suppression of endogenous JH titers.

Synthesis and biological activity of a series of diaryl-substituted .alpha.-cyano-.beta.-hydroxypropenamides, a new class of anthelmintic agents

A series of alpha-cyano-beta-hydroxypropenamides was prepared and tested for anthelmintic activity. alpha-Cyano-beta-hydroxy-N-[4- (trifluoromethyl)phenyl]-3-[4-(trifluoromethyl)phenyl]propenamide (1) showed good activity against the nematode Nematospirodes dubius in a mixed parasite infection in mice; several of the analogues were also effective against the cestode Hymenolepis nana. In sheep trials, 1 caused 100% reduction of the hematophagous nematode Haemonchus contortus after a single dose of 20 mg/kg but did not show satisfactory control of Trichostrongylus colubriformis or Ostertagia circumcincta. Against the liver fluke Fasciola hepatica, 1 suppressed egg production but only temporarily, suggesting that the adult flukes were not eliminated. Mechanism of action studies on 1 using Ascaris mitochondria showed it to be an uncoupler of oxidative phosphorylation.

Lead-Induced Egg Production Decrease in Leghorn and Japanese Quail Hens

A study was conducted to compare the response of chicken hens and Japanese quail hens to various levels of dietary lead as plumbus acetate. Egg production was decreased significantly in quail receiving 1 mg lead/kg of diet from day of hatch, and 10 mg lead/kg diet was required to suppress egg production when the metal was given to the quail hens after they had reached sexual maturity. In chicken hens given lead after they had attained approximately 80% hen-day production, a comparable decline in egg production was seen in hens consuming at least 200 mg lead/kg of diet. Total plasma calcium in quail hens was reduced significantly by 10 mg lead/kg of diet, but total plasma calcium in chicken hens was not reduced with levels of less than 200 mg lead/kg of diet. There was no correlation between blood calcium level and decreased egg production in chicken hens consuming dietary lead at levels less than 200 mg/kg diet, suggesting that lead influences egg production in birds through mechanisms that may not be dependent entirely upon calcium metabolism. Removal of lead from the diets of quail was associated with significant increases in egg production and total plasma calcium, but removal of lead from the diets of chicken hens did hot cause any increase in total plasma calcium or increase egg production in treated hens. However, hens consuming the highest level of dietary lead (400 mg/kg) did increase significantly their rate of egg production, but this was attributed to recovery from a lead-induced molt. Results from this study indicated that the Japanese quail hen was more sensitive to the reproductive inhibitory effects of lead than the chicken hen.

Schistosoma mansoni in the baboon (Papio anubis): parasitological responses of Kenyan baboons to different exposures of a local parasite strain.

The course of infection with a local strain of Schistosoma mansoni was investigated in Kenyan baboons (Papio anubis). A single exposure to 5000 cercariae per baboon (cpb) killed five 4-8 kg baboons; a sixth survived the full 30-week post-exposure period, with suppressed egg production after week 11. Lower doses were not lethal. A single exposure to 1000 cpb gave satisfactory adult worm recoveries, high and steady faecal egg excretion, and a high tissue egg recovery, predominantly from the large intestine. A similar but less consistent picture was obtained with a single exposure to 200 cpb. Baboons receiving 5 monthly exposures of 200 cpb (1000 cpb total) showed some evidence of the development of protective immunity. Three animals showed patterns resembling those for 200 and 1000 cpb. The other 3 had suppressed egg production (faecal and tissue) indicating, perhaps, some immunological process. They also had an abnormally high percentage of eggs in the liver.