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PubMed1975

Present progress towards the laboratory colonization of African Simuliidae (Diptera).

The laboratory colonization of African simuliids would facilitate critical work on many aspects of their biology and onchocerciasis vectors could be studied away from natural breeding-sites. In addition to a review of the literature of past achievements in this field, the authors' own studies are described: these centred on the Simulium damnosum and S. neavei complexes because they include vectors of human onchocerciasis. Other species studied included vectors of Onchocerca gutturosa and avian Haematozoa. Techniques for collecting the various developmental stages of African simuliids are discussed. Adult simuliids may be kept singly in small containers, or together in larger vessels, and fed on sugar-solutions, fruits or flowers. Only two members of the S. damnosum complex (one not yet identified) and one S. bovis complex species are so far known to mate in captivity. Many African simuliids have been blood-fed in captivity from sources including blood-soaked filter paper, birds, rabbits, man and the McMahon feeding apparatus, but results have been inconsistent and a few species have rarely taken blood. Blood/sugar mixtures have given better results, but in most cases normal oogenesis has not subsequently occurred. Some African simuliids lay eggs when kept in tubes, while others do so if placed in water and/or after decapitation. Although some females either fail to oviposit or retain many eggs, others lay a large number, but usually not all develop. The eggs of one species have been temporarily stored at low temperatures, but required protection from fungal attack. Larval development requires adequate water-flow and correct hydro-chemical conditions. Various rearing techniques are described. An apparatus in which the conditions of the water may be regulated has recently been modified for use with the S. damnosum complex and three members of the complex have been reared successfully so far. The Kibwezi form of the S. damnosum complex has been successfully induced to complete every stage of its life-cycle in the laboratory. The reduction of wastage throughout the life-cycle is now being attempted.

Africa↗
PubMed1998

Surveillance studies of Orthopodomyia signifera with comparisons to Aedes sierrensis.

The oviposition behaviors of Orthopodomyia signifera and Aedes sierrensis were examined with ovitraps and larval surveys during a five-year field study in northern California. Ovipositional periodicity was found to be an important factor affecting the segregation of the species into tree holes that were temporarily (Ae. sierrensis only) or permanently (both species) filled with water. Orthopodomyia signifera females also used cues associated with the permanence of the habitat when selecting oviposition sites. The distributions of the eggs of each species along horizontal and vertical transects did not indicate that interspecific competition affected oviposition site selection. The data indicate that temporal partitioning of larval development may reduce interspecific competition. Ovitraps were determined to be more sensitive tools for surveillance of Or. signifera than larval surveys, CO2-baited Fay traps and CDC light traps.

Animals↗
PubMed1997

InsP3 receptor is essential for growth and differentiation but not for vision in Drosophila.

Phospholipase C (PLC) is the focal point for two major signal transduction pathways: one initiated by G protein-coupled receptors and the other by tyrosine kinase receptors. Active PLC hydrolyzes phosphatidylinositol bisphosphate (PIP2) into the two second messengers inositol 1,4,5-trisphosphate (InsP3) and diacyl glycerol (DAG). DAG activates protein kinase C, and InsP3 mobilizes calcium from intracellular stores via the InsP3 receptor. Changes in [Ca2+]i regulate the function of a wide range of target proteins, including ion channels, kinases, phosphatases, proteases, and transcription factors (Berridge, 1993). In the mouse, there are three InsP3R genes, and type 1 InsP3R mutants display ataxia and epileptic seizures (Matsumoto et al., 1996). In Drosophila, only one InsP3 receptor (InsP3R) gene is known, and it is expressed ubiquitously throughout development (Hasan and Rosbash, 1992; Yoshikawa et al., 1992; Raghu and Hasan, 1995). Here, we characterize Drosophila InsP3R mutants and demonstrate that the InsP3R is essential for embryonic and larval development. Interestingly, maternal InsP3R mRNA is sufficient for progression through the embryonic stages, but larval organs show asynchronous and defective cell divisions, and imaginal discs arrest early and fail to differentiate. We also generated adult mosaic animals and demonstrate that phototransduction, a model PLC pathway thought to require InsP3R, does not require InsP3R for signaling.

Animals↗
PubMed2004

Cellular localisation of insulin-like growth factor binding protein-2 (IGFBP-2) during development of the marine fish, Sparus aurata.

The spatial localisation of insulin-like growth-factor-binding protein-2 (IGFBP-2) and its mRNA was investigated during larval and post-larval developmental stages of the gilthead seabream ( Sparus aurata) by immunohistochemistry and in situ hybridisation with specific antisera and riboprobes. During larval development, immunoreactivity was found in skin, muscle, gills, pharynx, intestine, liver and olfactory epithelium. After metamorphosis, immunoreactivity was found in the oesophageal epithelium (the strongest reaction) and in red skeletal muscle, heart muscle, the thymus and the epithelium of renal tubules. In the adult, immunostaining with IGFBP-2 antibody was also found in the saccus vasculosus, ovary and testis. IGFBP-2 mRNA was detected by in situ hybridisation mainly in the intestine, skeletal musculature and ovary. These results show that IGFBP-2 protein and mRNA are expressed in a variety of seabream tissues, suggesting that IGFBP-2 regulates the actions of IGFs on these tissues during development and growth.

Animals↗
PubMed2000

[Effect of plumular axis-cutted cotton on growth and development of cotton bollworm].

The method of plumular axis cutting was used to induce the resistance of cotton plants to cotton bollworms(Heliothis armigera). The bollworm was cultured in the laboratory, and the effect of induced cotton on the duration of larval development and weights of larvae and pupae was studied. In the treatments of infection and control, the lengths of larval period were delayed by 3 days and 0.5 days, the weights of larvae were decreased by 19.60% and 11.45%, and the pupae weights were decreased by 10.81% and 6.54%, respectively. After the 8 days old larvae were reared with induced cotton leaves for 3 days, the infected and uninfected cutted plants resulted in a decrease of the relative growth rates of larvae by 22.9% and 17.2% respectively, and in a decrease of the relative feeding rates by 26.1% and 21.4% respectively. It is suggested that plumular axis cutting could induce the resistance of cotton plants to bollworm, and influence the growth and development speed of bollworms through retarding their feeding and digestion. Combining with the treatment of Pseudomona gladioli D-2251 strain could obviously increase the insect-resistance of cotton plants.

Animals↗
PubMed2003

Expression profiling of homeobox genes in silk gland development in the mulberry silkworm Bombyx mori.

The homeobox (Hox) genes constitute an evolutionarily conserved family encoding transcription factors which play major roles in segmental identity and organ specification, across species. The expression patterns of three Hox genes, Antennapedia (Antp), Ultrabithorax (Ubx) and even-skipped (eve) were analyzed during silk gland development in Bombyx mori. Antp followed a middle silk gland (MSG) restricted pattern of expression, whereas Ubx was specifically expressed in the posterior silk gland (PSG) during embryonic and larval developmental stages. Eve protein, on the other hand, was expressed in both MSG and PSG. We have also identified and characterized a novel Pax-like mRNA that is expressed exclusively in the PSGs during embryonic and larval development. The expression of Antp, Ubx and Pax-like reached maximum levels in the fifth larval intermoult and no expression was detected during the intervening moults. The region-specific expression of certain Hox genes appears to be responsible for the specification of silk gland compartments, whereas other Hox genes may play a global role in controlling the expression of genes encoding silk proteins.

Animals↗
PubMed2006

Neuronal leucine-rich repeat 6 (XlNLRR-6) is required for late lens and retina development in Xenopus laevis.

Leucine-rich repeat proteins expressed in the developing vertebrate nervous system comprise a complex, multifamily group, and little is known of their developmental function in vivo. We have identified a novel member of this group in Xenopus laevis, XlNLRR-6, and through sequence and phylogenetic analysis, have placed it within a defined family of vertebrate neuronal leucine-rich repeat proteins (NLRR). XlNLRR-6 is expressed in the developing nervous system and tissues of the eye beginning at the neural plate stage, and expression continues throughout embryonic and larval development. Using antisense morpholino oligonucleotide (MO) -mediated knockdown of XlNLRR-6, we demonstrate that this protein is critical for development of the lens, retina, and cornea. Reciprocal transplantation of presumptive lens ectoderm between MO-treated and untreated embryos demonstrate that XlNLRR-6 plays autonomous roles in the development of both the lens and retina. These findings represent the first in vivo functional analysis of an NLRR family protein and establish a role for this protein during late differentiation of tissues in the developing eye.

Amino Acid Sequence↗
PubMed2000

The ontogeny of kin recognition in tadpoles of the toad Bufo melanostictus (Anura; bufonidae).

The ontogeny of kin recognition and influence of social environment on the development of kin recognition behaviour was experimentally investigated in tadpoles of Bufo melanostictus that lived in aggregations and showed low larval dispersion. Embryos and tadpoles of the toad were reared as (i) kin only, (ii) with kin and non-kin (separated by a mesh screen), and (iii) in isolation. They were tested for the ability to discriminate between (i) familiar siblings and unfamiliar non-siblings, (ii) familiar siblings and familiar non-siblings and, (iii) unfamiliar siblings and unfamiliar non-siblings. All tadpoles were fed on boiled spinach before conducting trials. Preference of test tadpoles to associate near the end compartments whether empty or containing members of specific stimulus groups was assessed using a rectangular choice tank. When tested in tanks with empty end compartments, the test tadpoles showed random distribution and thus no bias for the apparatus or the procedure. In the presence of kin/non-kin in the end compartments a significantly greater number of test tadpoles spent the majority of the time near familiar or unfamiliar kin rather than near familiar or unfamiliar non-kin. Kin discrimination ability persisted throughout larval development. Familiarity with siblings is not required for discriminating kin from non-kin, and kin discrimination ability is not modified following exposure to non-kin. Also, involvement of dietary cues is unlikely to be the prime mechanism of kin recognition in B. melanostictus unlike in some other anurans.

Animals↗
PubMed2003

A first infection of Galba truncatula with Fasciola hepatica modifies the prevalence of a subsequent infection and cercarial production in the F1 generation.

Snails from two populations highly susceptible to Fasciola hepatica and their F1 generations were subjected to individual bimiracidial exposures to determine if changes noted in infection parameters were due to an effect imposed on the snail by the parasite, or to some other effect such as the food used for the snails. Apart from the higher survival of unexposed parents at day 30 post exposure (p.e.) and their higher shell heights at day 45 p.e., the differences between the survival rates of exposed parents, prevalences of infections, and shell sizes were not significant. In the F1 snails born to previously infected parents, the prevalences of F. hepatica infection and cercarial production were significantly lower than those noted for the F1 born to unexposed parents. The survival of these snails and their shell growth did not show any significant variation. The F1 snails born to previously exposed snails would have developed a partial resistance against F. hepatica and this process would probably be maximal in the first 2 weeks of larval development inside the snail.

Animals↗
PubMed1989

Intraovular development and moulting of Toxocara pteropodis.

Observations of Toxocara pteropodis eggs removed from an adult worm and embryonated in 0.05 M-sulphuric acid showed the first moult to occur on the sixth day followed by the second moult over days 8-11, as indicated by the finding of a transient, loose, double-layered sheath over the definitive cuticle. Infectivity to mice first developed on day 11, reached a maximum at 36 days and then waned over the next 6 months. Details of larval development are described and the significance of loose sheaths on larvae recovered from tissues is discussed.

Animals↗
PubMed1994

Anthelmintic resistance.

Anthelmintic resistance is widespread in nematode parasites of sheep, goats and horses. Resistance is also developing in nematode parasites of cattle and has been detected in pig parasites. Benzimidazole, levamisole/morantel and ivermectin resistances occur in nematodes of sheep and goats and closantel resistance has been found in Haemonchus contortus. Anthelmintic resistance is likely to develop wherever anthelmintics are frequently used and be detected if it is investigated. Worm count or egg count reduction after treatment are useful for the detection of all types of anthelmintic resistances. More economical, faster and more sensitive in vitro assays for the detection of anthelmintic resistance have been developed. Some, such as the egg hatch assay are specific for a particular class of anthelmintic, whilst others such as larval development assays can be used with most anthelmintics. Improvements in our understanding of the biochemistry and molecular genetics of anthelmintic actions should lead to the development of more sensitive assays for the detection of anthelmintic resistance in individual nematodes. Levamisole/morantel resistance appears to be associated with alterations in cholinergic receptors in resistant nematodes. Ivermectin appears to act by binding to a glutamate receptor of a membrane chloride channel. This receptor has been expressed in vitro so that further studies of the interaction of ivermectin with this receptor and its possible alteration in ivermectin resistance will be feasible. Benzimidazole resistance in nematodes and fungi appears to be associated with an alteration in beta-tubulin genes which reduces or abolishes the high affinity binding of benzimidazoles for tubulin in these organisms. This knowledge can be exploited for DNA probes for benzimidazole resistance/susceptibility in individual organisms.

Animals↗
PubMed2004

Positive autoregulation of the Myocyte enhancer factor-2 myogenic control gene during somatic muscle development in Drosophila.

The myocyte enhancer factor-2 (MEF2) transcription factor plays a central role in the activation and maintenance of muscle gene expression in fruit flies and vertebrates. The mechanism of action and downstream target genes of MEF2 have been defined in considerable detail, but relatively little is known about the mechanisms that regulate MEF2 expression during muscle development. Here we demonstrate that MEF2 maintains its own expression in all differentiated muscle cell types during late embryonic and larval development in Drosophila by binding a conserved MEF2 site in a muscle-specific regulatory enhancer. Ectopic expression of Mef2 is sufficient to directly activate this enhancer in some, but not all, non-muscle cells. Furthermore, activation of the Mef2 enhancer normally in muscle cells and ectopically in non-muscle cells is dependent upon the integrity of the MEF2 binding site. These findings suggest an evolutionarily conserved mechanism whereby MEF2 can stabilize the muscle phenotype by sustaining its own expression through a myogenic autoregulatory loop.

Animals↗
PubMed1988

The vectoral role of several blackfly species (Diptera: Simuliidae) in relation to human onchocerciasis in the Sierra Parima and Upper Orinoco regions of Venezuela.

Experimental and natural infections with Onchocerca volvulus were studied in several anthropophilic blackfly species present in the endemic area of the Upper Orinoco region of Venezuela. When fed on four different Yanomami volunteers in the Sierra Parima, the total infection rate was 31.4% for Simulium guianense in comparison with 7.5% for S. limbatum. The proportion of ingested microfilariae that entered the thorax during the first 24 hours and completed development to the infective stage was also much lower in the latter than in the former species. There was no larval development of O. volvulus in S. antillarum, but one female harboured in its head six infective larvae of a zoonotic filaria. When S. oyapokense s.l. was fed on an infected volunteer in the Upper Orinoco most flies ingested few microfilariae, and further development reached only the L1 stage. Natural infection and infectivity rates for S. guianense in two localities of the Sierra Parima were 0.2-4.0% and 1.3-10.2%, respectively, more than 50% of the L3 larvae being in the head. The corresponding data for S. oyapockense s.l. in the Upper Orinoco were 0.1-0.5%, although the only L3 larva found did not correspond to O. volvulus. It is suggested that S. guianense is the main vector of onchocerciasis in the Sierra Parima and that S. limbatum could play a secondary role. Simulium oyapockense s.l. replaces them in the Upper Orinoco and may maintain a degree of transmission, but its epidemiological importance remains to be assessed.

Animals↗
PubMed1999

The role of wingless in the development of multibranched crustacean limbs.

Arthropods are the most diverse and speciose group of organisms on earth. A key feature in their successful radiation is the ease with which various appendages become readily adapted to new functions in novel environments. Arthropod limbs differ radically in form and function, from unbranched walking legs to multibranched swimming paddles. To uncover the developmental and genetic mechanisms underlying this diversification in form, we ask whether a three-signal model of limb growth based on Drosophila experiments is used in the development of arthropod limbs with variant shape. We cloned a Wnt-1 ortholog (Tlwnt-1) from Triops longicaudatus, a basal crustacean with a multibranched limb. We examined the mRNA in situ hybridization pattern during larval development to determine whether changes in wg expression are correlated with innovation in limb form. During larval growth and segmentation Tlwnt-1 is expressed in a segmentally reiterated pattern in the trunk. Unexpectedly, this pattern is restricted to the ventral portion of the epidermis. During early limb formation the single continuous stripe of Tlwnt-1 expression in each segment becomes ventrolaterally restricted into a series of shorter stripes. Some but not all of these shorter stripes correspond to what becomes the ventral side of a developing limb branch. We conclude that the Drosophila model of limb development cannot explain all types of arthropod proximodistal outgrowths, and that the multibranched limb of Triops develops from an early reorganization of the ventral body wall. In Triops, Tlwnt-1 plays a semiconservative role similar to that played by Drosophila wingless in segmentation and limb formation, and morphological innovation in limb form arises in part through an early modulation in the expression of the Tlwnt-1 gene.

Amino Acid Sequence↗
PubMed1997

Development of bombesin-like and histamine-like innervation in the bullfrog (Rana catesbeiana) central nervous system.

Amphibians rely exclusively on behavioral thermoregulation to maintain body temperature within species- and developmental stage-specific critical limits. Several members of the bombesin family of peptides and histamine are included in a class of neurochemicals that have potent thermoregulatory effects in ectothermic and endothermic vertebrate species and may be involved in behavioral thermoregulation in amphibians. Because amphibians respond to environmental temperature cues differently in larval versus adult animals, we used immunocytochemistry to study developmental changes in bombesin-like (BN) and histamine-like (HA) innervation in the bullfrog brain and spinal cord. Neurons and fibers that were BN-immunoreactive and HA-immunoreactive were present in the earliest stage tadpoles examined (Gosner stage 29); BN-immunoreactive perikarya were found only in the preoptic area, posterior thalamic nucleus and in the rostroventral tegmentum of the mesencephalon. In the preoptic area, dramatic changes were observed in the number and staining intensity of BN-ir somata; neuronal labelling was greatest in tadpoles undergoing tail resorption (i.e. metamorphic climax) and was nearly absent in adults. Neurons immunoreactive to BN in the ventral mesencephalon also were developmental stage-dependent; limb-bud growth stage tadpoles had the largest numbers of labelled neurons, whereas in the adults, labelled cells were rarely visible in this area. The highest density of fibers was in the medial septum, lateral amygdala, and the optic tectum. Fewer fibers were observed within the dorsal and ventral hypothalamus, the pineal gland, and all the thalamic nuclei. Perikarya immunoreactive to HA were localized in the dorsal infundibular nucleus of the hypothalamus. Immunoreactivity was present in all developmental stages examined, and the numbers of labelled cells increased throughout metamorphosis to a maximum in adult brains. Fibers were found in the medial septum, medial amygdala, preoptic area, thalamus, pineal gland, hypothalamus and optic tectum. These results show that BN- and HA-immunoreactivities are established early in larval development, but their phenotypes are differentially expressed during larval and adult growth stages. This pattern suggests that reorganization of BN-like and HA-like neural circuitry may occur during metamorphosis and may be involved in the reported developmental changes in amphibian thermoregulation. In addition, BN-like peptides and HA may modulate other related mechanisms of amphibian thermoregulation and behaviour, such as thermal acclimation, circadian shifts in temperature selection and feeding. To what extent they are involved in amphibian thermoregulation remains to be investigated.

Acclimatization↗
PubMed2003

Expression of 5-HT2B and 5-HT2C receptor genes is associated with proliferative regions of Xenopus developing brain and eye.

Here we clone the Xenopus 5-HT2B receptor cDNA and describe its spatio-temporal mRNA expression within the developing larval brain and visual system. Expression of the 5-HT2B transcripts is compared to that of 5-HT2C as well as proliferation and neurogenic markers. In developing brain and retina, 5-HT2B and 2C mRNAs are mainly expressed in proliferative regions. We suggest that these receptors may play a role in the larval secondary neurogenesis by mediating mitogenic effects of serotonin.

Animals↗
PubMed1983

Qualitative and quantitative measures of plasticity during the normal development of the Rana pipiens retinotectal projection.

We have examined the following aspects of retinal development in the frog, Rana pipiens: (1) the overall pattern of cell addition to the retina; (2) the relative rate of retinal ganglion cell (RGC) accretion; and (3) the changes in RGC density during larval development. In addition, we have studied the development of the retinal projection onto the tectum by means of the anterograde transport of horseradish peroxidase (HRP) and measurements of the volume of tectal neuropil at several larval stages and in postmetamorphic frogs. We find that the addition of new cells to the retina of Rana pipiens larva is restricted to the ciliary margin and that this addition is concentric at all larval stages. Additionally, the morphometric measures of retinal and tectal growth, along with the HRP histochemistry, indicate that the retinal projection exhibits considerable plasticity during normal development. The plasticity we observe in normal development may explain why the retinotectal projection can compensate its area and volume in experimental paradigms that effect drastic changes in innervation density.

Animals↗
PubMed1982

Spinal cord development in anuran larvae: I. Primary and secondary neurons.

The spinal cord of the bullfrog (Rana catesbeiana) tadpole contains primary neurons, born during embryonic stages, and secondary neurons born for the most part during larval stages. Electrophysiological and anatomical characteristics of these two categories of neurons were examined during larval development to trace the development of secondary neurons and to determine whether primary neurons persist into adult life or are replaced by secondary neurons. Five classes of primary neuron were identified on the basis of their distinctive locations, morphologies, cytoplasmic melanin content, and presence at the earliest larval stages examined: primary motoneurons, Rohon-Beard cells, commissural cells, dorsal marginal cells, and anterolateral marginal cells. Secondary neurons of the lateral motor column and dorsal root ganglia underwent extensive developmental changes during larval life manifested both in anatomical studies with horseradish peroxidase and electrophysiological experiments on the isolated spinal cord. Primary motoneurons that innervate the tadpole tail were not found in the adult, although those innervating thoracic musculature persisted, as did at least some primary neurons projecting to other spinal segments or brainstem. Primary neurons are thus replaced or maintained through metamorphosis depending on their class and location.

Animals↗