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PubMed1991

Drosophila as a model system for molecular analysis of tumorigenesis.

In Drosophila, homozygous mutations in a series of genes can cause the appearance of tissue-specific tumors. These tumors occur either during embryonic or larval development. The majority of the identified genes give rise to larval tumors that affect either the presumptive adult optic centers of the brain, the imaginal discs, the hematopoietic organs, or the germ cells. These genes act as recessive determinants of neoplasia and have been designated as tumor-suppressor genes. They are normally required for the regulation of cell proliferation and cell differentiation during development. Among these genes, the lethal(2)giant larvae (l(2)gl) has been best studied. Homozygous mutations in l(2)gl produce malignant tumors in the brain hemispheres and the imaginal discs. The l(2)gl gene has been cloned, introduced back into the genome of l(2)gl-deficient animals, and shown to restore normal development. The nucleotide sequence of the l(2)gl gene has been determined, as well as the sequence of its transcripts. Anti-l(2)gl antibodies recognize a protein of about 130 kDa that corresponds to the major product of l(2)gl transcripts. Analysis of the spatial distribution of l(2)gl transcripts and proteins revealed a first phase of intensive expression during embryogenesis and a second weaker phase during the larval to pupal transition period. As revealed by mosaic experiments, the critical period of l(2)gl expression for preventing tumorigenesis takes place during early embryogenesis. During this period, the l(2)gl protein is ubiquitously expressed in all cells and tissues, while during late embryogenesis expression becomes gradually restricted to the midgut epithelium and the axon projections of the ventral nervous system that show no phenotypic alteration in the mutant animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2005

Expression of 'segmentation' genes during larval and juvenile development in the polychaetes Capitella sp. I and H. elegans.

Polychaete annelids and arthropods are both segmented protostome invertebrates. To investigate whether the segmented body plan of these two phyla share a common molecular ground pattern, we report the developmental expression of orthologues of the arthropod segment polarity genes engrailed (en), hedgehog (hh), and wingless (wg/Wnt1) in larval and juvenile stages of the polychaete annelid Capitella sp. I and en in a second polychaete, Hydroides elegans. Temporally, neither Wnt1 nor hh are detected in the segmented region of the larval body until after morphological segmentation is apparent. Expression of CapI-Wnt1 is limited to a ring of ectoderm marking the future anus during larval segmentation. CapI-hh is expressed in a ring of the hindgut internal to that of CapI-Wnt1, as well as in a subset of ventral nerve cord neurons, anterior gut tissue, and mesoderm. In both H. elegans and Capitella sp. I, en is expressed in a spatially and temporally dynamic manner in segmentally iterated structures as well as a population of cells that migrate internally from ectoderm to mesoderm, possibly representing a population of ecto-mesodermal precursors. Significantly, the expression patterns we report for wg, en, and hh orthologues in Capitella sp. I and for en in larval development of H. elegans are not comparable to the highly conserved ectodermal segment polarity pattern observed in arthropods at any life history stage, consistent with distinct origins of segmentation between annelids and arthropods.

Amino Acid Sequence↗
PubMed1986

Mutations of the Drosophila myosin heavy-chain gene: effects on transcription, myosin accumulation, and muscle function.

Mutations of the myosin heavy-chain (MHC) gene of Drosophila melanogaster were identified among a group of dominant flightless and recessive lethal mutants (map position 2-52, 36A8-B1,2). One mutation is a 0.1-kilobase deletion in the 5' region of the MHC gene and reduces MHC protein in the leg and thoracic muscles of heterozygotes to levels found in 36AC haploids. Three mutations are insertions of 8-to 10-kilobase DNA elements within the MHC gene and produce truncated MHC transcripts. Heterozygotes of these insertional mutations possess levels of MHC intermediate between those of haploids and diploids. An additional mutation has no gross alteration of the MHC gene or its RNA transcripts. Although leg and larval muscles function normally in each mutant heterozygote, indirect flight muscles are defective and possess disorganized myofibrils. Homozygous mutants die during embryonic or larval development and display abnormal muscle function prior to death. These findings provide direct genetic evidence that the MHC gene at 36B (2L) is essential for both larval and adult muscle development and function. The results are consistent with the previous molecular evidence that Drosophila, unlike other organisms, has only a single muscle MHC gene per haploid genome. Quantitative expression of both copies of the MHC gene is required for function of indirect flight muscle, whereas expression of a single MHC gene is sufficient for function of larval muscles and adult tubular muscles.

Animals↗
PubMed1993

Developmental analysis of two sex-determining genes, M and F, in the housefly, Musca domestica.

In the housefly, Musca domestica, a single dominant factor, M, determines maleness. Animals hemi-or heterozygous for M are males, whereas those without M develop as females. In certain strains, however, both sexes are homozygous for M, and an epistatic dominant factor, FD, dictates female development. The requirement for these factors was analyzed by producing, with mitotic recombination, mosaic animals consisting of genetically male and female cells. Removal of FD from an M/M;FD/+ cell at any time of larval development, even in the last larval instar, resulted in sex-reversal, i.e., in the development of a male clone in an otherwise female fly. In contrast, when M was removed from M/+ cells, the resulting clones remained male despite their female genotype, even when the removal of M happened at embryonic stages. The occurrence of spontaneous gynandromorphs, however, shows that the loss of M in individual nuclei prior to blastoderm formation causes the affected cells to adopt the female pathway. These results are consistent with the hypothesis that M is the primary sex-determining signal which sets the state of activity of the key gene F at around the blastoderm stage. Parallels and differences to the sex-determining system of Drosophila are discussed.

Animals↗
PubMed1984

In vitro reprogramming of the photoperiodic clock in an insect brain-retrocerebral complex.

Pupal diapause in the tobacco hornworm Manduca sexta is a photoperiodically induced event expressed by the absence of release of the cerebral peptide prothoracicotropic hormone. A short-day photoperiod (light-dark, 12:12) during larval development programs the brain to forego the release of prothoracicotropic hormone in the pupal stage. Prothoracicotropic hormone release can occur in the pupae and diapause can be averted if developing larvae experience an intervening long-day photoperiod (light-dark, 16:8) for 3 days early in the last larval instar. Implanted brains from larvae that received such long-day stimulation can reverse the diapause commitment of short-day-reared diapause-destined larvae, thus overriding the diapause program of the recipient. A system was established that demonstrated that this photoperiodic reprogramming of the insect's brain occurs in vitro. Brain-retrocerebral complexes from day 1 instar larvae were cultured in vitro for 3 days under long-day conditions. The effect of this non-diapause photoperiod on the diapause program of these brain-retrocerebral complexes was assessed by assaying the effect of the brains from these cultures on the incidence of non-diapause development in diapause-destined larval hosts. Brains that received a long-day photoperiod reversed the pupal diapause program of the recipient larvae, whereas brains that received a short-day photoperiod were ineffective. Therefore, the larval brain-retrocerebral complex of this insect is capable of photoperiodic light reception in vitro, in that it can sense the number of light-dark cycles to which it is exposed, store this environmental input, and express the information 9 days later at another stage of development. These findings demonstrate that the photoperiodic clock of an animal can be reprogrammed by a light-dark cycle in vitro.

Animals↗
PubMedDate not supplied

Evolution and development of gastropod larval shell morphology: experimental evidence for mechanical defense and repair.

The structural diversity of gastropod veliger larvae offers an instructive counterpoint to the view of larval forms as conservative archetypes. Larval structure, function, and development are fine-tuned for survival in the plankton. Accordingly, the study of larval adaptation provides an important perspective for evolutionary-developmental biology as an integrated science. Patterns of breakage and repair in the field, as well as patterns of breakage in arranged encounters with zooplankton under laboratory conditions, are two powerful sources of data on the adaptive significance of morphological and microsculptural features of the gastropod larval shell. Shells of the planktonic veliger larvae of the caenogastropod Nassarius paupertus [GOULD] preserve multiple repaired breaks, attributed to unsuccessful zooplankton predators. In culture, larvae isolated from concentrated zooplankton samples rapidly repaired broken apertural margins and restored the "ideal" apertural form, in which an elaborate projection or "beak" covers the head of the swimming veliger. When individuals with repaired apertures were reintroduced to a concentrated mixture of potential zooplankton predators, the repaired margins were rapidly chipped and broken back. The projecting beak of the larval shell is the first line of mechanical defense, covering the larval head and mouth and potentially the most vulnerable part of the shell to breakage. Patterns of mechanical failure show that spiral ridges do reinforce the beak and retard breakage. The capacity for rapid shell repair and regeneration, and the evolution of features that resist or retard mechanical damage, may play a more prominent role than previously thought in enhancing the ability of larvae to survive in the plankton.

Animals↗
PubMed2004

Developmental constraint on gene duplicability in fruit flies and nematodes.

A previous study in nematodes suggested that developmental constraint reduces the duplicability of genes involved in early development. Recent large-scale gene expression studies of fly development enabled us to conduct a more detailed study of this issue. We found that the average duplicability of genes involved in embryonic development is indeed lower than that of genes involved in larval development but not significantly lower than that of genes involved in later stages of development. Moreover, in both flies and nematodes genes with multiple expression peaks do not seem to have a lower duplicability than do genes with a single expression peak. Thus, although developmental constraint does appear to reduce gene duplicability, the effect seems weak or at best moderate.

Animals↗
PubMed1986

The development and mortality of the non-infective free-living stages of Ostertagia ostertagi in the field and in laboratory culture.

A deterministic model of the population biology of the non-infective free-living phase of Ostertagia ostertagi is described and tested. A comparison of field and laboratory studies indicates that the pre-infective larvae of O. ostertagi spend about twice as long in this phase in the field as in laboratory culture (13 days and 7 days respectively at 15 degrees C), and that the subsequent transition (i.e. second moult) to the infective phase also proceeds at a much slower rate (about 10 times less at 15 degrees C) in the field. Because of this discrepancy, estimates of model parameters are based entirely on measurements from field studies. A two-parameter model of pre-infective development in the field is derived. It describes egg and larval development as a direct non-linear function of air temperature. We also show that the mortality of the eggs and pre-infective larvae increases with temperature (although this relationship probably also subsumes a dependence on faecal moisture content). The model is shown to be a good mimic of the population dynamics of the non-infective free-living phase when tested against an independent data set, and is the basis of a larger model of the epidemiology of ostertagiasis.

Aging↗
PubMed1989

Characterization of the bis(5'-nucleosidyl) tetraphosphate pyrophosphohydrolase from encysted embryos of the brine shrimp Artemia.

The P1P4-bis(5'-nucleosidyl) tetraphosphate asymmetrical-pyrophosphohydrolase from encysted embryos of the brine shrimp Artemia has been purified over 11,000-fold to homogeneity. Anion-exchange chromatography resolves two major species with very similar properties. The enzyme is a single polypeptide of Mr 17,600 and is maximally active at pH 8.4 and 2 mM-Mg2+. It is inhibited by Ca2+ (IC50 = 0.9 mM with 2 mM-Mg2+) but not by Zn2+ ions. It preferentially hydrolyses P1P4-bis(5'-nucleosidyl) tetraphosphates, e.g. P1P4-bis(5'-adenosyl) tetraphosphate (Ap4A) (kcat. = 12.7 s-1; Km = 33 microM) and P1P4-bis(5'-guanosyl) tetraphosphate (Gp4G) (kcat. = 6.2 s-1; Km = 5 microM). With adenosine 5'-P1-tetraphospho-P4-5"'-guanosine (Ap4G) as substrate, there is a 4.5-fold preference for AMP and GTP as products and biphasic reaction kinetics are observed giving Km values of 4.7 microM and 34 microM, and corresponding rate constants of 6.5 s-1 and 11.9 s-1. The net rate constant for Ap4G hydrolysis is 7.6 s-1. The enzyme will also hydrolyse nucleotides with more than four phosphate groups, e.g. Ap5G, Ap6A and Gp5G are hydrolysed at 25%, 18% and 10% of the rate of Ap4A respectively. An NTP is always one of the products. Ap2A and Gp2G are not hydrolysed, while Ap3A and Gp3G are very poor substrates. When the enzyme is partially purified from embryos and larvae at different stages of development by sedimentation through a sucrose density gradient, its activity increases 3-fold during the first 12 h of pre-emergence development. This is followed by a slow decline during subsequent larval development. The similarity of this enzyme to other asymmetrical-pyrophosphohydrolases suggests that it did not evolve specifically to degrade the large yolk platelet store of Gp4G which is found in Artemia embryos, but that it probably serves the same general function in bis(5'-nucleosidyl) oligophosphate metabolism as in other cells.

Acid Anhydride Hydrolases↗
PubMed1994

DNA polymerase alpha-primase complex from the silk glands of the non-mulberry silkworm Philosamia ricini.

The DNA content in the silk glands of the non-mulberry silkworm Philosamia ricini increases continuously during the fourth and fifth instars of larval development indicating high levels of DNA replication in this terminally differentiated tissue. Concomitantly, the DNA polymerase alpha activity also increases in the middle and the posterior silk glands during development, reaching maximal levels in the middle of the fifth larval instar. A comparable level of DNA polymerase delta/epsilon was also observed in this highly replicative tissue. The DNA polymerase alpha-primase complex from the silk glands of P. ricini has been purified to homogeneity by conventional column chromatography as well as by immunoaffinity techniques. The molecular mass of the native enzyme is 560 kDa and the enzyme comprises six non-identical subunits. The identity of the enzyme as DNA polymerase alpha has been established by its sensitivity to inhibitors such as aphidicolin, N-ethylmaleimide, butylphenyl-dGTP, butylanilino-dATP and antibodies to polymerase alpha. The enzyme possesses primase activity capable of initiating DNA synthesis on single-stranded DNA templates. The tight association of polymerase and primase activities at a constant ratio of 6:1 is observed through all the purification steps. The 180 kDa subunit harbours the polymerase activity, while the primase activity is associated with the 45 kDa subunit.

Animals↗
PubMed1997

Genetic and environmental responses to temperature of Drosophila melanogaster from a latitudinal cline.

Field-collected Drosophila melanogaster from 19 populations in Eastern Australia were measured for body size traits, and the measurements were compared with similar ones on flies from the same populations reared under standard laboratory conditions. Wild caught flies were smaller, and latitudinal trends in size were greater. Reduced size was caused by fewer cells in the wing, and the steeper cline by greater variation in cell area. The reduction in size in field-collected flies may therefore have been caused by reduced nutrition, and the steeper cline may have been caused by an environmental response to latitudinal variation in temperature. No evidence was found for evolution of size traits in response to laboratory culture. The magnitude of phenotypic plasticity in response to temperature of development time, body size, cell size and cell number was examined for six of the populations, to test for latitudinal variation in plasticity. All characters were plastic in response to temperature. Total development time showed no significant latitudinal variation in plasticity, although larval development time showed a marginally significant effect, with most latitudinal variation at intermediate rearing temperatures. Neither thorax length nor wing size and its cellular components showed significant latitudinal variation in plasticity.

Adaptation, Physiological↗
PubMed1989

Effect of cocaine in tissues on the development rate of Boettcherisca peregrina (Diptera: Sarcophagidae).

Larvae of the flesh fly, Boettcherisca peregrina (Robineau-Desvoidy), were reared on the tissue of rabbits to study the effects of cocaine and benzoylecognine on development rates. The rabbits were given 35, 69, and 137 mg of cocaine through cardiac puncture. From hours 30 to 70, larvae developed more rapidly on tissue containing cocaine, benzoylecognine, or both, from rabbits injected with 69 and 137 mg of cocaine than on tissue from rabbits injected with 35 mg of cocaine or no cocaine. Total development times required for pupation and adult eclosion were shortened correspondingly. Differences observed in the rate of development were sufficient to alter postmortem interval estimates based on larval development in decomposing human tissues by up to 24 h.

Animals↗
PubMed2003

Pallial origin of mitral cells in the olfactory bulbs of Xenopus.

We used two developmental transcription factors, x-Eomes (T-box family) and x-Lhx5 (LIM-homeodomain family), to follow the origin and development of the olfactory bulbs in Xenopus. During embryonic and larval development, x-Eomes and x-Lhx5 were expressed in highly similar patterns, in the lateral and latero-ventral wall of the pallium. In adults, both markers were strongly and specifically expressed in mitral cells, i.e., in the projection neurons of the main and accessory olfactory bulbs. These results demonstrate the pallial origin of the olfactory projecting cells in Xenopus. Combined with previous results suggesting a subpallial origin for olfactory interneurons, these findings emphasize the dual origin of different neuronal populations in the bulbs of anamniotes, and suggest that this organization is a shared feature of tetrapods.

Animals↗
PubMed2002

The Caenorhabditis elegans histone hairpin-binding protein is required for core histone gene expression and is essential for embryonic and postembryonic cell division.

As in all metazoans, the replication-dependent histone genes of Caenorhabditis elegans lack introns and contain a short hairpin structure in the 3' untranslated region. This hairpin structure is a key element for post-transcriptional regulation of histone gene expression and determines mRNA 3' end formation, nuclear export, translation and mRNA decay. All these steps contribute to the S-phase-specific expression of the replication-dependent histone genes. The hairpin structure is the binding site for histone hairpin-binding protein that is required for hairpin-dependent regulation. Here, we demonstrate that the C. elegans histone hairpin-binding protein gene is transcribed in dividing cells during embryogenesis and postembryonic development. Depletion of histone hairpin-binding protein (HBP) function in early embryos using RNA-mediated interference leads to an embryonic-lethal phenotype brought about by defects in chromosome condensation. A similar phenotype was obtained by depleting histones H3 and H4 in early embryos, indicating that the defects in hairpin-binding protein-depleted embryos are caused by reduced histone biosynthesis. We have confirmed this by showing that HBP depletion reduces histone gene expression. Depletion of HBP during postembryonic development also results in defects in cell division during late larval development. In addition, we have observed defects in the specification of vulval cell fate in animals depleted for histone H3 and H4, which indicates that histone proteins are required for cell fate regulation during vulval development.

3' Untranslated Regions↗
PubMed2005

Relative abundance of tree hole-breeding mosquitoes in Boone County, Missouri, USA, with emphasis on the vector potential of Aedes triseriatus for canine heartworm, Dirofilaria immitis (Spirurida: Filariidae).

Aedes (Protomacleaya) triseriatus currently shares its habitat in the USA with the introduced species Aedes (Finlaya) japonicus and Aedes (Stegomyia) albopictus. In the late 1980s, before the introduction of these 2 species, Ae. triseriatus was the dominant tree hole- and artificial container-breeding mosquito in central Missouri. Aedes triseriatus represented 89% of the mosquito immatures collected from water-filled tree holes and artificial containers at 3 forested field sites in central Missouri, from May to October, 1986 to 1988. Laboratory-reared female Ae. triseriatus were able to support larval development of Dirofilaria immitis (canine heartworm) to the infective 3rd larval stage. A blood meal from a microfilaremic Collie-mix dog was sufficient to infect adult female mosquitoes, indicating that Ae. triseriatus is a possible vector of canine heartworm in central Missouri. Confirmation of the vector status of this species depends on the yet-to-be observed transmission of D. immitis by Ae. triseriatus in the field, possibly by experimental infection of dogs by wild-caught mosquitoes. Defining the role of this species in epizootic outbreaks could contribute toward accurate risk assessment as the abundance of Ae. triseriatus increases and decreases in response to the success of Ae. albopictus, Ae. japonicus, or other introduced container-breeding mosquitoes.

Aedes↗
PubMed1991

Effect of heroin in decomposing tissues on the development rate of Boettcherisca peregrina (Diptera, Sarcophagidae) and implications of this effect on estimation of postmortem intervals using arthropod development patterns.

Larvae of the flesh fly Boettcherisca peregrina (Robineau-Desvoidy) were reared on the tissues of rabbits to study the effects of heroin on the development rates of this species. The rabbits were given 6, 12, 18, and 24 mg of heroin by cardiac puncture. From Hours 18 to 96, larvae feeding on tissues containing heroin (as morphine) developed more rapidly than those feeding on tissues from the control. The time required for pupation was significantly greater for colonies fed on tissues from heroin-dosed rabbits than for the control colony. The differences observed in the rates of development were sufficient to alter postmortem interval estimates based on larval development by up to 29 h and estimates based on pupal development by 18 to 38 h.

Animals↗
PubMed1982

Developmental stages of Dirofilaria immitis in the dog.

Thirty-six Beagles were inoculated with 3rd-stage infective Dirofilaria immitis larvae to determine when 3rd and 4th molts occurred, how long each stage of development persisted in muscle and skin, and the patterns of larval migration from the infection site to the heart. From 22% to 84% of these larvae were recovered when the dogs were euthanatized and necropsied (mean recovery 45%). Larvae were recovered only from the skin and muscle during the first 58 days. The 5th-stage immature adults were first recovered from the heart in dogs killed on postinoculation day (PID) 70. Migration to the heart was essentially completed in dogs killed on PID 120, although 1 immature adult was recovered from subcutaneous tissues of each dog killed on PID 140 and 142. Starting and completion days of molting periods were recorded along with body lengths of male and female worms from the 3rd, 4th, and 5th stages. Microfilariae were first recovered from the peripheral blood in dogs killed on PID 190. Optimal time for drug evaluation against a particular stage of larval development is as follows: 3rd-stage larvae, PID 0 to 2; 4th-stage larvae, PID 15 to 50; and 5th-stage or immature adults, PID 65 to 120.

Animals↗
PubMed2002

Steroid regulation of midgut cell death during Drosophila development.

Steroid hormones trigger dynamic tissue changes during animal development by activating cell proliferation, cell differentiation, and cell death. Here we characterize steroid regulation of changes in midgut structure during the onset of Drosophila metamorphosis. Following an increase in the steroid 20-hydroxyecdysone (ecdysone) at the end of larval development, future adult midgut epithelium is formed, and the larval midgut is rapidly destroyed. Mutations in the steroid-regulated genes BR-C and E93 differentially impact larval midgut cell death but do not affect the formation of adult midgut epithelia. In contrast, mutations in the ecdysone-regulated E74A and E74B genes do not appear to perturb midgut development during metamorphosis. Larval midgut cells possess vacuoles that contain cellular organelles, indicating that these cells die by autophagy. While mutations in the BR-C, E74, and E93 genes do not impact DNA degradation during this cell death, mutations in BR-C inhibit destruction of larval midgut structures, including the proventriculus and gastric caeca, and E93 mutants exhibit decreased formation of autophagic vacuoles. Dying midguts express the rpr, hid, ark, dronc, and crq cell death genes, suggesting that the core cell death machinery is involved in larval midgut cell death. The transcription of rpr, hid, and crq are altered in BR-C mutants, and E93 mutants possess altered transcription of the caspase dronc, providing a mechanism for the disruption of midgut cell death in these mutant animals. These studies indicate that ecdysone triggers a two-step hierarchy composed of steroid-induced regulatory genes and apoptosis genes that, in turn, regulate the autophagic death of midgut cells during development.

Animals↗