Conservation of regulatory elements between two species of Drosophila

Background  

One of the important goals in the post-genomic era is to determine the regulatory elements within the non-coding DNA of a given organism's genome. The identification of functional cis-regulatory modules has proven difficult since the component factor binding sites are small and the rules governing their arrangement are poorly understood. However, the genomes of suitably diverged species help to predict regulatory elements based on the generally accepted assumption that conserved blocks of genomic sequence are likely to be functional. To judge the efficacy of strategies that prefilter by sequence conservation it is important to know to what extent the converse assumption holds, namely that functional elements common to both species will fall within these conserved blocks. The recently completed sequence of a second Drosophila species provides an opportunity to test this assumption for one of the experimentally best studied regulatory networks in multicellular organisms, the body patterning of the fly embryo.     

Structure of the auditory system of the weta Hemideina crassidens (Blanchard, 1851) (Orthoptera,Ensifera, Gryllacridoidea,Stenopelmatidae)

Summary This study of the ultrastructure of the auditory sensilla of the New Zealand weta, Hemideina crassidens, is the first such study on a member of the orthopteran Superfamily Gryllacridoidea. Ultrastructure of the auditory sensilla is similar in all of the tibial mechanosensory organs, here called subgenual organ, intermediate organ and crista acoustica by analogy with comparable structures in Tettigoniidae.Distal to each sensory soma is a dendrite containing multiple ciliary rootlets that fuse into a single ciliary root. This splits into nine root processes that pass around the outside of the proximal basal body and then rejoin at the level of the distal basal body, distal to which the dendrite has a modified ciliary structure with a circlet of nine peripheral paired tubes and rods as it passes through the proximal extracellular space. It is then enclosed by a zone of scolopale cell cytoplasm before expanding into a dilatation within the distal extracellular space. In some sensilla this space is partially occluded by electron dense material which is part of the scolopale cell. Distal to the dilatation the cilium shrinks and ends surrounded by the scolopale cap.Accessory cells consist of glia enwrapping the sensory neuron in the region of its soma, the scolopale cell surrounding the ciliary portion of the dendrite, and the attachment cell surrounding the scolopale cell and scolopale cap and connected to them by desmosomes. The attachment cells are filled with microtubules in differing densities and orientations. Lamellae are present in the acellular matrix surrounding the attachment cells. Banded fibres, presumably of collagen, are also present in the matrix.     

Structure of cephalic abnormalities in Drosophila melanogaster (Diptera: Drosophilidae)

Scanning and transmission electron microscopy were utilized in studying the cephalic abnormalities of the tu-h strain of Drosophila melanogaster. Abnormalities, appearing as protuberances (growths) of different shapes and sizes, were observed only on or in close proximity to receptor cites. Compound eyes of some flies, besides having such protuberances, either had modified corneal lenses or were absent altogether. Cuticles of the growths were thinner than that of the normal surrounding layer. The epidermal cells associated with setae on the growths or underlying modified corneal lenses remained undifferntiated. Both setae and growths lacked innervation. The receptor portions (retinular sensory cells and secondary pigment cells) of the abnormal compound eye, where the dioptric portions were replaced by protuberances or remained undifferentiated, were unaffected by the mutation. Nuclei of several cells, including oenocytes and fat bodies, close to or underlying epidermal cells of abnormalities, were large and contained compact nucleoli without nucleonemas. Viruslike particles were observed in several nuclei of growth cells. It was concluded from the present study that the alterations induced by the mutation can be only a localized phenomenon restricted to at least several cephalic epidermal cells and/or their derivatives.     

A Survey of the Postpartum Reproductive Performance of Dairy Cows with Fertility Problems in Southern Iceland

The purpose of this survey was to evaluate the reproductive performance of dairy cows on problem farms in southern Iceland. In all 229 cows on 6 farms were studied. The animals were examined clinically by rectal palpation, once a month. Blood samples were taken 2–5 and 7–10 weeks after calving. The blood samples were analysed for the contents of glucose, urea, inorganic phosphate, calcium and magnesium. Milk samples for progesterone profiles were taken, by the farmer, every 4th day from day 10 postpartum until first oestrus. Because of this sampling method, 128 cows had no rise in progesterone levels, when milk sampling was stopped. These 128 animals were excluded from the study. The results are based on 101 animals. There was a large variation between cows in postpartum reproductive performance. In the total material 1st ovulation occurred later than reported in many other countries. Fifty percent of the cows had ovulated 35 days after calving and 90 percent 70 days after calving. The first luteal phase was short in about 60 % of the cows. The progesterone values assayed from those short cycles were lower than the values assayed from the following cycle. First artificial insemination (ai) was on the average 77 days postpartum (pp). The conception rate to first service was 49 %. Of 100 milk samples taken at the time of ai, 20 had high progesterone value. This indicates a high frequency of luteal phase inseminations. Clinical ketosis was diagnosed in 35 cows. Of these, 31 had a low glucose value. Cows with clinical ketosis ovulated, on the average, later than other animals and 24 ovulated later than 40 days pp. The results indicated that the fertility problems of these cows studied were late ovulations, low conception rate, probably in part, due to luteal phase inseminations, and a high frequency of ketosis which could be caused by low quality feedstuff.     

Spinach plastocyanin: Comparison of reduced and oxidized forms by natural abundance carbon-13 nuclear magnetic resonance spectroscopy

Differences between the reduced Cu(I) and oxidized Cu(II) forms of spinach plastocyanin were investigated by natural abundance carbon-13 nuclear magnetic resonance spectroscopy at 67.9 MHz using proton noise decoupling. The spectra confirm that histidines 38 and 91 are copper ligands and demonstrate that coordination is by the N^o1 of both imidazole rings. Spectra of reduced plastocyanin yielded 128 separately resolved carbon resonances. Upon oxidation, 16 of these were observed to disappear; yet there was little change in the positions or intensities of other peaks. Those peaks which disappear are assigned to carbons near the metal. The protein evidently does not undergo a substantial change in conformation upon change of redox state.     

The functional morphology of the english sparrow cecum

As birds do not have a urinary bladder, the kidneys and lower gastrointestinal tract must function in concert to maintain fluid and electrolyte homeostasis. In birds, urine is conveyed to the cloaca, and moved by reverse peristalsis into the colon and digestive ceca. Digestive ceca have been well studied for non-passerine birds and have been shown to absorb substrates and water. The ceca of passerine birds have been suggested to be non-functional because of their small size. The present study was undertaken to examine the morphology and cytochemistry of the small ceca of the English sparrow (Passer domesticus). Three-dimensional reconstruction of the ceca from serially sectioned tissue showed these organs to have a central channel with a large number of side channels. Electron micrographs indicated that all of the channels are lined by epithelial cells with a very dense microvillus brush border as well as a region densely packed with mitochondria just below the brush border. Specific staining for Na(+), K(+)-ATPase indicated the enzyme to be localized to the brush border. Quantification of Na(+), K(+)-ATPase activity showed it to be comparable to the coprodeum of domestic fowl. The data suggest that the small ceca of passerine birds may function in fluid and electrolyte homeostasis.     

Maintenance of ancestral complexity and non-metazoan genes in two basal cnidarians

Cnidarians are among the simplest extant animals; however EST analyses reveal that they have a remarkably high level of genetic complexity. In this article, we show that the full diversity of metazoan signaling pathways is represented in this phylum, as are antagonists previously known only in chordates. Many of the cnidarian ESTs match genes previously known only in non-animal kingdoms. At least some of these represent ancient genes lost by all bilaterians examined so far, rather than genes gained by recent lateral gene transfer.     

Animal evolution: the enigmatic phylum placozoa revisited

A recent report of high levels of genetic variation between strains of Trichoplax adhaerens challenges the traditional view that the phylum Placozoa comprises only one species. At the morphological level, placozoans are amongst the simplest extant animals, but molecular evidence suggests that they may have more complex origins.