Hox gene colinear expression in the avian medulla oblongata is correlated with pseudorhombomeric domains

The medulla oblongata (or caudal hindbrain) is not overtly segmented, since it lacks observable interrhombomeric boundaries. However, quail-chick fate maps showed that it is formed by 5 pseudorhombomeres (r7-r11) which were empirically found to be delimited consistently at planes crossing through adjacent somites (Cambronero and Puelles, 2000). We aimed to reexamine the possible segmentation or rostrocaudal regionalisation of this brain region attending to molecular criteria. To this end, we studied the expression of Hox genes from groups 3 to 7 correlative to the differentiating nuclei of the medulla oblongata. Our results show that these genes are differentially expressed in the mature medulla oblongata, displaying instances of typical antero-posterior (3′ to 5′) Hox colinearity. The different sensory and motor columns, as well as the reticular formation, appear rostrocaudally regionalised according to spaced steps in their Hox expression pattern. The anterior limits of the respective expression domains largely fit boundaries defined between the experimental pseudorhombomeres. Therefore the medulla oblongata shows a Hox-related rostrocaudal molecular regionalisation comparable to that found among rhombomeres, and numerically consistent with the pseudorhombomere list. This suggests that medullary pseudorhombomeres share some AP patterning mechanisms with the rhombomeres present in the rostral, overtly-segmented hindbrain, irrespective of variant boundary properties.     

Dominant inhibition of lens placode formation in mice

The lens in the vertebrate eye has been shown to be critical for proper differentiation of the surrounding ocular tissues including the cornea, iris and ciliary body. In mice, previous investigators have assayed the consequences of molecular ablation of the lens. However, in these studies, lens ablation was initiated (and completed) after the cornea, retina, iris and ciliary body had initiated their differentiation programs thereby precluding analysis of the early role of the lens in fate determination of these tissues. In the present study, we have ablated the lens precursor cells of the surface ectoderm by generation of transgenic mice that express an attenuated version of diphtheria toxin (Tox176) linked to a modified Pax6 promoter that is active in the lens ectodermal precursors. In these mice, lens precursor cells fail to express Sox2, Prox1 and αA-crystallin and die before the formation of a lens placode. The Tox176 mice also showed profound alterations in the corneal differentiation program. The corneal epithelium displayed histological features of the skin, and expressed markers of skin differentiation such as Keratin 1 and 10 instead of Keratin 12, a marker of corneal epithelial differentiation. In the Tox176 mice, in the absence of the lens, extensive folding of the retina was seen. However, differentiation of the major cell types in the retina including the ganglion, amacrine, bipolar and horizontal cells was not affected. Unexpectedly, ectopic placement of the retinal pigmented epithelium was seen between the folds of the retina. Initial specification of the presumptive ciliary body and iris at the anterior margins of the retina was not altered in the Tox176 mice but their subsequent differentiation was blocked. Lacrimal and Harderian glands, which are derived from the Pax6-expressing surface ectodermal precursors, also failed to differentiate. These results suggest that, in mice, specification of the retina, ciliary body and iris occurs at the very outset of eye development and independent of the lens. In addition, our results also suggest that the lens cells of the surface ectoderm may be critical for the proper differentiation of the corneal epithelium.     

The production and transfer of spermatophores in three Asian species of Luciola fireflies

During mating, many male insects transfer sperm packaged within a spermatophore that is produced by reproductive accessory glands. While spermatophores have been documented in some North American fireflies (Coleoptera: Lampyridae), little is known concerning either production or transfer of spermatophores in the aquatic Luciola fireflies widespread throughout Asia. We investigated this process in Japanese Luciola lateralis and L. cruciata by feeding males rhodamine B, a fluorescent dye known to stain spermatophore precursors. We then mated males with virgin females, and dissected pairs at various timepoints after mating. In both of these Luciola species, spermatophores were produced by three pairs of male accessory glands and were transferred to females during the second stage of copulation. Male spermatophores were highly fluorescent, and were covered by a thin outer sheath; a narrow tube leading from an internal sperm-containing sac fit precisely into the female spermathecal duct, presumably for sperm delivery. Both L. lateralis and L. cruciata females have a spherical spermatheca as well as a highly extensible gland where spermatophore breakdown commences by 24h post-mating. Similar reproductive anatomy was observed for both sexes in Luciola ficta from Taiwan. These results suggest that nuptial gifts may play an important role in many firefly-mating systems.     

The secretory glands of <Emphasis Type="Italic">Asphodelus aestivus</Emphasis> flower

Various secretory glands are observed on Asphodelus aestivus flower, a common geophyte of Mediterranean type ecosystem. The floral nectary has the form of individual slits between the gynecium carpels (septal nectary). The septal slits extend downwards to the ascidiate zone of the carpels. The nectar is secreted by the epidermal cells of the slits, which differentiate into epithelial cells. The latter contain numerous organelles, among which endoplasmic reticulum elements and golgi bodies predominate. Nectar secretion results in an expansion of the space between the septa. The nectar becomes discharged through small holes on the ovary wall. Six closely packed stamens surround the ovary and bear numerous papillae at their basis. These papillae are actually osmophores, i.e. secretory structures responsible for the manufacture, secretion and dispersion of terpenic scent. A mucilage gland (obturator) exists between the lateral ovule and the ovary septa, giving a positive reaction with Schiff’s reagent. This gland secretes a mucoproteinaceous product to nourish the pollen tube and to facilitate its penetration into the ovary.     

Sorting of growth hormone-erythropoietin fusion proteins in rat salivary glands

Neuroendocrine and exocrine cells secrete proteins in either a constitutive manner or via the regulated secretory pathway (RSP), but the specific sorting mechanisms involved are not fully understood. After gene transfer to rat salivary glands, the transgenic model proteins human growth hormone (hGH) and erythropoietin (hEpo) are secreted primarily into saliva (RSP; exocrine) and serum (constitutive; endocrine), respectively. We hypothesized that fusion of hGH at either the C-terminus or the N-terminus of hEpo would re-direct hEpo from the bloodstream into saliva. We constructed and expressed two fusion proteins, hEpo-hGH and hGH-hEpo, using serotype 5-adenoviral vectors, and delivered them to rat submandibular glands in vivo via retroductal cannulation. Both the hEpo-hGH and hGH-hEpo fusion proteins, but not hEpo alone, were secreted primarily into saliva (p < 0.0001 and p = 0.0083, respectively). These in vivo studies demonstrate for the first time that hGH, in an N- as well as C-terminal position, influences the secretion of a constitutive pathway protein.     

Fine structure of the spermatheca and of the accessory glands in Orchesella villosa (Collembola, Hexapoda)

The spermatheca and the accessory glands of the collembolan Orchesella villosa are described for the first time. Both organs exhibit ultrastructural differences, according to the time of the intermolt in which the specimens were observed. A thick cuticular layer lines the epithelial cells of the accessory glands. In the reproductive phase, they are involved in secretory activity; a moderately dense secretion found in the apical cell region opens into the gland lumen. Cells with an extracellular cistern are intermingled with the secretory cells. These cells could be involved in fluid secretion, with the secretory product opening into the cistern which is filled with an electron-transparent material. After the reproductive phase, the gland lumen becomes filled with a dense secretion. The accessory gland secretion may play a protective role towards the eggs. The spermatheca is located between the accessory glands; its epithelium is lined by a thin cuticle forming spine-like projections into the lumen and consists of cells provided with an extracellular cistern. Secretory cells, similar to those seen in the accessory glands, are missing. Cells with a cistern could be involved in the production of a fluid secretion determining sperm unrolling and sperm motility.     

Homology between the recessus lateralis and cephalic sensory canals, with the proposition of additional synapomorphies for the Clupeiformes and the Clupeoidei

The recessus lateralis , a complex structure in the otic region of the skull that is probably associated with detection and analysis of small vibrational pressures and displacements, is widely recognized as a synapomorphy of the Clupeiformes. The Clupeiformes includes the Denticipitoidei, with one living species, Denticeps clupeoides , and the Clupeoidei, with about 360 living species commonly known as herrings and anchovies. Comparisons between details of the recessus lateralis of the Clupeoidei and Denticipitoidei, and the sensory cephalic canals of other teleosts, lead to hypotheses of a series of transformations of the cephalic sensory canals . Treating that complex as a single binary 'presence vs. absence' character as was traditional practice obscures important phylogenetically informative variation. Specific synapomorphies in that system exist for the Clupeiformes and the Clupeoidei. Hypothesized synapomorphies in the recessus lateralis for the Clupeiformes are the presence of a dilated internal temporal sensory canal in the pterotic, a postorbital branch of the supraorbital sensory canal located in a bony groove in the lateral wing of the frontal, and the terminal portions of preopercular and infraorbital sensory canals closely positioned. Hypothesized synapomorphies for the Clupeoidei are the presence of a postorbital branch of the supraorbital sensory canal located deep within the body of the lateral wing of the frontal, with the distal portion of that branch totally internal on the cranium, and the expanded distal portion of the postorbital branch of the supraorbital sensory canal. The homology of the sinus temporalis of Clupeoidei, and of the dermosphenotic of both Denticeps and the Clupeoidei, with those of other teleosts is also considered.  © 2004 The Linnean Society of London, Zoological Journal of the Linnean Society , 2004, 141 , 257–270.     

Relationships between otolith microstructure, otolith growth, somatic growth and ontogenetic transitions in two cohorts of windowpane

Otolith increments in larval and juvenile windowpane Scophthalmus aquosus can provide an estimate of daily age for spring-spawned individuals held under summer conditions. Otolith increments for spring- and autumn-spawned individuals occurred at intervals >1 day under winter conditions. A significant decrease in the slope of the linear relationship between otolith size and somatic size at 40 mm L_S coincided with significant habitat, morphological and behavioural transitions. In smaller, field-captured windowpane belonging to spring- and autumn-spawned cohorts, the formation of accessory growth centres coincided with a transitional settlement period and the completion of eye migration (c. 8–20 mm L_S). Back-calculated growth rate estimates for spring-spawned windowpane were significantly faster than those for autumn-spawned windowpane and these differences could produce differential rates of survival for the two cohorts during the first year of life.     

Ultrastructural organization of the anal organs in the anal capsule of Craterostigmus tasmanianus Pocock, 1902 (Chilopoda, Craterostigmomorpha)

We describe the ultrastructural organization of the anal organs of Craterostigmus tasmanianus, which are located on the ventral side of the bivalvular anal capsule. Each part of the capsule bears four pore fields with several anal pores. The pores lead into a pore canal, which is surrounded by the single-layered epithelium of the anal organs. Each anal organ is composed of four different cell types: transporting cells of the main epithelium, junctional cells, isolated epidermal glands, and the cells forming the pore canal. The transporting cells exhibit infoldings of the outer cell membranes, forming a basal labyrinth and a poorly developed apical complex. The cells are covered by a specialized cuticle with a widened subcuticular layer. Only the cuticle of the main epithelium is covered by a mucous layer, secreted by the epidermal glands. The ultrastructural organization of the anal organ is comparable to the coxal and anal organs of other pleurostigmophoran Chilopoda. It is likely that the coxal and anal organs of the Pleurostigmophora are homologous, due to their identical ultrastructural organization. Differences concerning the location on the trunk of Pleurostigmophora are not sufficient to reject a hypothesis of homology. Anal organs are found not only in Craterostigmomorpha, but also in most adult Geophilomorpha, and in larvae and most adults of Lithobiomorpha. The anal organs of C. tasmanianus are thought to play an important role in the uptake of atmospheric water. J. Morphol.