Anterior determinants in embryos of Chironomus samoensis: characterization by rescue bioassay

Development ◽  
1988 ◽  
Vol 104 (1) ◽  
pp. 61-75 ◽  
Author(s):  
A. Elbetieha ◽  
K. Kalthoff
Keyword(s):  
Xenopus Oocytes ◽  
Normal Development ◽  
Posterior Pole ◽  
Mirror Image ◽  
Maximum Efficiency ◽  
Phylogenetic Distance ◽  
Anterior Pole ◽  
Polyadenylated Rna ◽  
Pyrimidine Bases ◽  
Blastoderm Stage

Embryos of Chironomus samoensis are programmed, by anterior u.v. irradiation, to form the abnormal body pattern ‘double abdomen’. Most double abdomen embryos show a mirror-image duplication of abdominal segments in the absence of cephalic or thoracic segments. Such embryos can be ‘rescued’, i.e. restored to normal development, by microinjection of cytoplasm or RNA from unirradiated donor embryos. Most of the rescued embryos look completely normal and many of them hatch spontaneously. The rescuing activity decreases from the anterior to the posterior pole in the donor cytoplasm and must be delivered near the anterior pole of the recipient for maximum efficiency. Rescuing activity is present in total RNA extracted from whole, unirradiated embryos. Upon fractionation, the activity is associated with poly(A)+ RNA, with LiCl precipitate depleted of RNA smaller than 250 nucleotides (nt) and with a sucrose gradient fraction depleted of RNA larger than 500 nt. Corresponding fractions of RNA from Xenopus oocytes have no rescuing activity. The activity of Chironomus RNA is sensitive to u.v. irradiation with low fluence affecting less than 2% of the pyrimidine bases. Rescuing activity is present in cytoplasm until the blastoderm stage but disappears earlier from poly(A)+ RNA. Rescuing activity is also present, and localized, in cytoplasm of embryos from two related dipterans, Smittia sp. and Drosophila melanogaster, although the extent of rescue observed in Chironomus decreases with the phylogenetic distance between donor and recipient. The results of these and previous experiments indicate that dipteran embryos contain localized RNP particles acting as anterior determinants. In Chironomus, the activity of these particles seems to depend on the integrity of polyadenylated RNA of about 250 to 500 nt length.

Instability of the anteroposterior axis in spontaneous double abdomen (sda), a genetic variant of Chironomus samoensis (Diptera, Chironomidae)

Development ◽  
1987 ◽  
Vol 101 (3) ◽  
pp. 591-603 ◽  
Author(s):  
K.L. Kuhn ◽  
J. Percy ◽  
M. Laurel ◽  
K. Kalthoff
Keyword(s):  
Genetic Variant ◽  
Laboratory Strain ◽  
Posterior Pole ◽  
Mirror Image ◽  
Anterior Pole ◽  
Spontaneous Formation ◽  
Pole Cells ◽  
Anterior Segments ◽  
Egg Polarity

We have isolated a laboratory strain of Chironomus samoensis in which determination of the anteroposterior egg polarity is disturbed. Most conspicuous is the spontaneous formation of ‘double abdomen’ embryos where head and thorax are replaced by a mirror image of the abdomen. Such double abdomens are found in about half of the egg clusters in this strain, which we call the spontaneous double abdomen (sda) strain as opposed to the normal (N) strain. Also observed in the sda strain, although less frequently, are ‘double cephalon’ embryos showing a mirror-image duplication of cephalic segments in the absence of thorax and abdomen. Moreover, embryos from the sda strain tend to form cells at the anterior pole resembling the pole cells at the posterior pole. Reciprocal crossings between the sda and the N strain indicate that the sda trait is inherited maternally. Spontaneous double abdomen formation is correlated with signs of disturbed egg architecture, including extruded yolk and detached cells. Double cephalons can also be generated by centrifuging embryos from the N strain, whereas centrifugation of sda embryos produces mostly double abdomens. Double abdomen formation can be induced experimentally by anterior u.v. irradiation of embryos from either strain. The sda trait and u.v. irradiation act in a synergistic fashion. The data suggest that the sda trait may be caused by one or more genomic mutations interfering indirectly with the activity of anterior determinants, i.e. cytoplasmic RNP particles necessary for the development of anterior segments. The sda defects may be ascribed to alterations in cytoskeletal components involved in anchoring anterior determinants and segregating them into anterior blastoderm cells.

Mutations in the Drosophila gene bullwinkle cause the formation of abnormal eggshell structures and bicaudal embryos

Development ◽  
1995 ◽  
Vol 121 (9) ◽  
pp. 3023-3033 ◽  
Author(s):  
K.R. Rittenhouse ◽  
C.A. Berg
Keyword(s):  
Cell Migration ◽  
Cell Fate ◽  
Germ Line ◽  
Follicle Cell ◽  
Posterior Pole ◽  
Mirror Image ◽  
Follicle Cells ◽  
Anterior Pole ◽  
Posterior Group ◽  
General Transport

Subcellular localization of gene products and cell migration are both critical for pattern formation during development. The bullwinkle gene is required in Drosophila for disparate aspects of these processes. In females mutant at the bullwinkle locus, the follicle cells that synthesize the dorsal eggshell filaments do not migrate properly, creating short, broad structures. Mosaic analyses demonstrate that wild-type BULLWINKLE function is required in the germ line for these migrations. Since the mRNA for gurken, the putative ligand that signals dorsal follicle cell fate, is correctly localized in bullwinkle mutants, we conclude that our bullwinkle alleles do not affect the dorsoventral polarity of the oocyte and thus must be affecting the follicle cell migrations in some other way. In addition, the embryos that develop from bullwinkle mothers are bicaudal. A KINESIN:beta-GALACTOSIDASE fusion protein is correctly localized to the posterior pole of bullwinkle oocytes during stage 9. Thus, the microtubule structure of the oocyte and general transport along it do not appear to be disrupted prior to cytoplasmic streaming. Unlike other bicaudal mutants, oskar mRNA is localized correctly to the posterior pole of the oocyte at stage 10. By early embryogenesis, however, some oskar mRNA is mislocalized to the anterior pole. Consistent with the mislocalization of oskar mRNA, a fraction of the VASA protein and nanos mRNA are also mislocalized to the anterior pole of bullwinkle embryos. Mislocalization of nanos mRNA to the anterior is dependent on functional VASA protein. Although the mirror-image segmentation defects appear to result from the action of the posterior group genes, germ cells are not formed at the anterior pole. The bicaudal phenotype is also germ-line dependent for bullwinkle. We suspect that BULLWINKLE interacts with the cytoskeleton and extracellular matrix and is necessary for gene product localization and cell migration during oogenesis after stage 10a.

Anterior Movement of the Crystalline Lens in the Process of Accommodation in Children

2007 ◽  
Vol 17 (4) ◽  
pp. 515-520 ◽  
Author(s):  
B.J. Kaluzny
Keyword(s):  
Refractive Error ◽  
Axial Length ◽  
Crystalline Lens ◽  
Posterior Pole ◽  
Anterior Pole ◽  
Forward Movement ◽  
Ophthalmic Examination ◽  
Lens Thickness ◽  
Lens Position ◽  
Refractive Status

Purpose To investigate changes of crystalline lens position during accommodation in children with emmetropia, myopia, and hyperopia. Methods A total of 188 children (372 eyes) from 4 to 19 years old (mean age 11.3±4.43) with cycloplegic refractive error within a range +9.00 D to −9.00 D were enrolled. After a general ophthalmic examination, ultrasound biometry was performed, with the eye at a maximal accommodative effort. Cycloplegia was induced by triple installation of 1% tropicamide drops and 30 minutes later the biometric examination was repeated. Results In emmetropic eyes in the process of accommodation, the anterior pole of the crystalline lens moved forward by 0.144±0.14 mm (p ≤ 0.001); the position of the posterior pole did not change. In myopic eyes, the anterior pole moved forward by 0.071±0.13 mm (p≤0.001) and the posterior pole moved backward by 0.039±0.10 mm (p=0.003). In hyperopic eyes, the whole lens translocated anteriorly: anterior pole moved forward by 0.242±0.16 mm (p≤ 0.001) and posterior pole moved forward by 0.036±0.09 mm (p≤0.001). Differences among emmetropia, myopia, and hyperopia were statistically significant. Forward movement of the posterior pole correlated with a low axial length of the eye, and also with plus refractive error and with a smaller accommodative increase of lens thickness. Conclusions In children, accommodative changes of the crystalline lens position depend on refractive status.

Translational control of oskar generates short OSK, the isoform that induces pole plasma assembly

Development ◽  
1995 ◽  
Vol 121 (11) ◽  
pp. 3723-3732 ◽  
Author(s):  
F.H. Markussen ◽  
A.M. Michon ◽  
W. Breitwieser ◽  
A. Ephrussi
Keyword(s):  
Positive Feedback ◽  
Translational Control ◽  
Feedback Mechanism ◽  
Posterior Pole ◽  
Start Codon ◽  
Anterior Pole ◽  
Wild Type ◽  
Alternative Start Codon ◽  
Positive Feedback Mechanism ◽  
Pole Plasm

At the posterior pole of the Drosophila oocyte, oskar induces a tightly localized assembly of pole plasm. This spatial restriction of oskar activity has been thought to be achieved by the localization of oskar mRNA, since mislocalization of the RNA to the anterior induces anterior pole plasm. However, ectopic pole plasm does not form in mutant ovaries where oskar mRNA is not localized, suggesting that the unlocalized mRNA is inactive. As a first step towards understanding how oskar activity is restricted to the posterior pole, we analyzed oskar translation in wild type and mutants. We show that the targeting of oskar activity to the posterior pole involves two steps of spatial restriction, cytoskeleton-dependent localization of the mRNA and localization-dependent translation. Furthermore, our experiments demonstrate that two isoforms of Oskar protein are produced by alternative start codon usage. The short isoform, which is translated from the second in-frame AUG of the mRNA, has full oskar activity. Finally, we show that when oskar RNA is localized, accumulation of Oskar protein requires the functions of vasa and tudor, as well as oskar itself, suggesting a positive feedback mechanism in the induction of pole plasm by oskar.

scholarly journals Embryonic Development of Eye Lens in Mosquito fish Gambusia affinis (Baird and Girard, 1853)

2007 ◽  
Vol 4 (4) ◽  
pp. 505-511
Author(s):  
Baghdad Science Journal
Keyword(s):  
Embryonic Development ◽  
Posterior Pole ◽  
Equatorial Region ◽  
Gambusia Affinis ◽  
Eye Lens ◽  
Anterior Pole ◽  
Posterior Edge ◽  
Terrestrial Vertebrates ◽  
Mosquito Fish ◽  
Lens Vesicle

The embryonic development of the Mosquito fish(Gambusia affinis) eye lens was investigated using light microscopy .The results indicated that the embryonic development of the lens does not correspond to that of the non spherical lenses of terrestrial vertebrates .This study showed that a very small cavity in the lens vesicle appears during development ,but it differs from that of the mammalian lens. The most important aspect in this study is that ,the posterior edge of the simple cuboidal epithelium which covers the anterior half of the surface of the lens is situated well beyond the equatorial region of the lens .As a result , the germinal and transitional zones became closer to the posterior pole rather than the anterior pole of the lens. This might be an important factor in causing the lens to be spherical rather than being biconvex.

scholarly journals A mRNA localized to the vegetal cortex of Xenopus oocytes encodes a protein with a nanos-like zinc finger domain

Development ◽  
1993 ◽  
Vol 117 (1) ◽  
pp. 377-386 ◽  
Author(s):  
L. Mosquera ◽  
C. Forristall ◽  
Y. Zhou ◽  
M.L. King
Keyword(s):  
Cell Fate ◽  
Zinc Finger ◽  
Regional Differences ◽  
Xenopus Oocytes ◽  
Rna Binding ◽  
Protein Product ◽  
Posterior Pole ◽  
Cortical Region ◽  
Zinc Finger Domain ◽  
Vegetal Cortex

mRNAs concentrated in specific regions of the oocyte have been found to encode determinants that specify cell fate. We show that an intermediate filament fraction isolated from Xenopus stage VI oocytes specifically contains, in addition to Vg1 RNA, a new localized mRNA, Xcat-2. Like Vg1, Xcat-2 is found in the vegetal cortical region, is inherited by the vegetal blasomeres during development, and is degraded very early in development. Sequence analysis suggests that Xcat-2 encodes a protein that belongs to the CCHC RNA-binding family of zinc finger proteins. Interestingly, the closest known relative to Xcat-2 in this family is nanos, an RNA localized to the posterior pole of the Drosophila oocyte whose protein product suppresses the translation of the transcription factor hunchback. The localized and maternally restricted expression of Xcat-2 RNA suggests a role for its protein in setting up regional differences in gene expression that occur early in development.

Spermiogenesis in the Nine-Banded Armadillo

1973 ◽  
Vol 31 ◽  
pp. 632-633
Author(s):  
Frank J. Weaker
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Apparatus ◽  
Smooth Endoplasmic Reticulum ◽  
Posterior Pole ◽  
Seminiferous Tubules ◽  
Anterior Pole ◽  
Chromatoid Body ◽  
Acrosome Formation

The testes of mature armadillos were fixed by either perfusion or immersion. The morphology of the seminiferous tubules and the process of spermiogenesis were studied.The developing spermatids are generally oval in shape and contain a centrally placed nucleus. A well-developed Golgi apparatus, scattered mitochondria, centrioles, smooth endoplasmic reticulum, and a chromatoid body are observed within the cytoplasm. Granules formed within the Golgi appear to coalesce to form the acrosomal granule, which is enclosed within a vesicle (Fi,g. 1). The acrosome adheres to the nucleus at the anterior pole of the developing spermatid. The acrosome vesicle collapses and extends over the anterior two-thirds of the nucleus (Fig. 2). As this vesicle expands, the Golgi continues to release granules into the vesicle. Concomitant with acrosome formation, the centrioles and chromatoid body migrate to the posterior pole of the developing cell.

Asymmetric distribution of metals in the Xenopus laevis oocyte: a synchrotron X-ray fluorescence microprobe study

2007 ◽  
Vol 85 (5) ◽  
pp. 537-542 ◽  
Author(s):  
Bogdan Florin Gh. Popescu ◽  
Zachery R. Belak ◽  
Konstantin Ignatyev ◽  
Nick Ovsenek ◽  
Helen Nichol
Keyword(s):  
Xenopus Oocytes ◽  
Normal Development ◽  
Asymmetric Distribution ◽  
Xenopus Laevis Oocyte ◽  
Animal Pole ◽  
X Ray ◽  
Iron Copper ◽  
Copper And Zinc ◽  
Cellular Specialization ◽  
Asymmetrically Distributed

The asymmetric distribution of many components of the Xenopus oocyte, including RNA, proteins, and pigment, provides a framework for cellular specialization during development. During maturation, Xenopus oocytes also acquire metals needed for development, but apart from zinc, little is known about their distribution. Synchrotron X-ray fluorescence microprobe was used to map iron, copper, and zinc and the metalloid selenium in a whole oocyte. Iron, zinc, and copper were asymmetrically distributed in the cytoplasm, while selenium and copper were more abundant in the nucleus. A zone of high copper and zinc was seen in the animal pole cytoplasm. Iron was also concentrated in the animal pole but did not colocalize with zinc, copper, or pigment accumulations. This asymmetry of metal deposition may be important for normal development. Synchrotron X-ray fluorescence microprobe will be a useful tool to examine how metals accumulate and redistribute during fertilization and embryonic development.

Studies on the biology of Culiseta longiareolata (Macquart) (Diptera: Culicidae)

1981 ◽  
Vol 71 (1) ◽  
pp. 71-79 ◽  
Author(s):  
R. Van Pletzen ◽  
T. C. De K. Van Der Linde
Keyword(s):  
South Africa ◽  
Sucrose Solution ◽  
Survival Rates ◽  
Posterior Pole ◽  
Cotton Wool ◽  
Anterior Pole ◽  
Mating Activity ◽  
Adult Females ◽  
Laboratory Populations ◽  
Culiseta Longiareolata

AbstractThe dark-scaled form of Culiseta longiareolata (Macq.) was found near Bloemfontein in South Africa. Breeding took place in various kinds of flooded pools, small containers and drinking troughs. It was multivoltine and overwintered as hibernating second-, third- and fourthinstar larvae and adult females. Laboratory colonisation was easily accomplished. Adults were maintained alive at 23°C and 70% relative humidity, and survival rates were high for 40–50 days. Starved females fed readily on blood from pigeons at night or on a 3:1 mixture of human blood and 10% sucrose solution from cotton-wool pads. Mating swarms were not observed in the field, but swarming activity occurred in laboratory populations provided with simulated dawn and dusk conditions. The fact that mating activity could be readily induced at any time was taken to show that it is not governed by a rigid endogenous rhythm. Egg-rafts varied in shape from round to oblong. Oviposition was invariably nocturnal. Some substance, probably emitted by bacteria, served as an oviposition attractant. The anterior pole of each egg lacks an exochorion and is hydrophilic. The posterior pole bears a lipid droplet. The exochorion is sculptured, the sculpturing consisting of bosses connected to one another by bridges constituting the outlines of a series of pores. The exochorial pattern varies in different regions of the egg. Pupation and emergence occurred mainly at night, and there was an approximately normal sex ratio.

scholarly journals Memoirs: The Embryonic Development of Trichogramma evanescens, Westw., Monembryonic Egg Parasite of Donacia Simplex, Fab

1917 ◽  
Vol s2-62 (246) ◽  
pp. 149-187
Author(s):  
J. BRONTÉ GATENBY
Keyword(s):  
Germ Cells ◽  
Nuclear Division ◽  
Single Case ◽  
Dorsal Surface ◽  
Posterior Pole ◽  
The Body ◽  
Egg Mass ◽  
Trichogramma Evanescens ◽  
Polar Bodies ◽  
Blastoderm Stage

(1) Trichogramma evanescens lays its eggs on the egg mass of a beetle, Donacia simplex, a single parasite emerging from one host's egg. (2) The ovum has a large germ cell determinant at its posterior pole, and in segmentation the determinant is divided among the large cells at the posterior pole, which are the germ cells. (3) In the single case found there were two polar bodies. (4) The blastula is fairly normal except for the curious arrangement of the chromatin in the somatic nuclei. (5) Many nucleoli are cast out into the centre of the egg, where they collect till from twenty-five to fifty are present; the mass is then extruded on the periphery of the egg. (6) As the blastoderm grows it broadens without lengthening up to the stage where the germ layers begin to form. (7) About thirty-five nuclei sink inwards from the dorsal surface of the embryo to form endoderm. (8) From the blastoderm stage to that of the gastrula no nuclear division appears to take place. (9) Shortly after the formation of the endoderm amitosis may be found, and from this onwards the number of nuclei increases. (10) The mesoderm seems to be formed from peripheral nuclei, which sink in sporadically; no somites can be made out, nor does any segmental method of formation of the mesoderm occur. (11) The nervous system, stomodæum, and probably proctodæum, are normally formed. (12) The germ cells lie in a pocket formed be several somatic cells, which embrace them. (13) Ordinary mouth parts, tracheæ, heart, and œsophageal valve are wanting; the head has two horn-like mandibular processes, which may assist in scooping forwards the food. (14) The larva does not feed on the food little by little, defecating as it eats; instead, it begins by swallowing all the yolk at once, so that its body becomes enormously distended and stretched. (15) Metameric external segmentation is absent, the body and head being continuous and sac-like.

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