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PubMed1990

Endopolyploidy in follicle epithelial cells around the nurse chamber during oogenesis in Chrysomya putoria (Diptera, Calliphoridae).

Feulgen-DNA values and nuclear areas were evaluated microspectrophotometrically for epithelial cells of the ovarian follicle during oogenesis in Chrysomya putoria. The aim was to investigate whether polyploidization occurred in the cells surrounding the nurse chamber and/or in those around the oocyte as well as whether different DNA amounts were found regarding the cell types considered. Four DNA endoreduplicative cycles could be demonstrated for the epithelial cells regardless of their localization on the follicle, during oogenesis. A small percentage of epithelial cells reaches a 32C degree. The nuclear area, however, did not increase at the same rate in cells covering the oocyte as in those covering the nurse chamber, in some of the oogenesis stages. The meaning of endopolyploidy for these cells is discussed, considering reports on relevance of secretory activities and their maintenance in polyploid cell systems.

Animals↗
PubMed1992

Unusual organizational features of the Drosophila Gart locus are not conserved within Diptera.

The Drosophila Gart locus consists of two genes. One gene encodes three enzymes in the de novo purine nucleotide biosynthesis pathway [glycinamide ribonucleotide synthetase (GARS), aminoimidazole ribonucleotide synthetase (AIRS), and glycinamide ribonucleotide transformylase (GART)]. The second gene lies within an intron of the purine gene and encodes a cuticle protein. To investigate the evolution of the Gart locus, the Chironomus tentans homolog was cloned by screening a genomic DNA library with a polymerase chain reaction product. This study shows that the interesting structural features of this locus conserved in two distant Drosophila species are not found in the Chironomus homolog. These features include the cuticle protein gene nested within an intron and the existence of an alternative transcript to yield a monofunctional enzyme. In addition, the extremely rapid divergence of coding sequence seen for members of the tandemly duplicated AIRS domain in Drosophila is found to be much less rapid in Chironomus.

Acyltransferases↗
PubMed1992

The specificity of yolk protein uptake in cyclorrhaphan diptera is conserved through evolution.

Yolk proteins are transported from the hemolymph into the oocytes of insects during vitellogenesis by receptor-mediated endocytosis. Since other hemolymph proteins, both native and foreign, are not accumulated in the oocyte, the process of uptake is selective for yolk proteins. Peptide domains within the yolk proteins must therefore be involved in receptor recognition. With the long-term aim of identifying these domains and to open the possibility of understanding the molecular basis of receptor-mediated endocytosis of yolk proteins, we began investigating how well this mechanism has been conserved in evolution. We studied the uptake of yolk proteins from 13 different Drosophila species and five other dipteran species, namely, Calliphora erythrocephala, Sarcophaga argyrostoma, Musca domestica, Lucilia servicata, and Protophormia terrae-novae, into the ovaries of Drosophila melanogaster and Drosophila funebris. The results from these experiments showed that in all cases the foreign yolk proteins were taken up by the host ovaries, indicating that the mechanism and peptide domains of the yolk proteins involved in recognition of the receptor have been well conserved in dipteran evolution.

Animals↗
PubMed1982

The distribution of pancreatic polypeptide in the nervous system and gut of the blowfly, Calliphora vomitoria (Diptera).

The distribution of a neuropeptide, previously shown to have the same or a very similar amino acid composition as vertebrae pancreatic polypeptide (PP), has been studied in the nervous system gut of the blowfly, Calliphora vomitoria. Neurones immunoreactive to a bovine PP antiserum occur in the thoracic and abdominal ganglionic components of the central nervous system, in addition to the brain and suboesophageal ganglion. Pancreatic polypeptide appears to be relayed from its cells of origin to a neurohaemal organ in the dorsal sheath of the thoracic ganglion. PP immunoreactivity is also found in cells of the hypocerebral ganglion of the stomatogastric nervous system and in associated nerve fibres. The mid-gut contains PP-positive material in flask-shaped cells of its epithelial lining.

Animals↗
PubMed1981

Moulting hormone, juvenile hormone and the ultrastructure of the fat body of adult Sarcophaga bullata (Diptera).

In the ovoviviparous fly, Sarcophaga bullata, vitellogenesis in cyclic; a process reflected in ultrastructural changes in the fat body cells and oenocytes. At eclosion the larval fat body has not yet completely disappeared. During vitellogenesis the fat body cells are specialized for intensive protein synthesis showing a very extensive RER and numerous invaginations of the plasma membrane. These features disappear when the eggs descend into the oviducts to complete embryogenesis. The predominant feature of the oenocytes is their very prominent SER. The fat body cells of the males are never as specialized for protein synthesis as those of the females. Feeding of ecdysterone to males for 3 or more days induces a rather extensive subcellular apparatus for protein synthesis, i.e., invaginations of the plasma membrane and an extensive RER. Juvenile hormone is completely ineffective in this respect. Both ecdysterone and juvenile hormone have pronounced but different effects on the oenocytes of males.

Adipose Tissue↗
PubMed1984

Immunocytochemical mapping of gastrin/CCK-like peptides in the neuroendocrine system of the blowfly Calliphora vomitoria (Diptera).

The distribution of gastrin/CCK-like immunoreactive material has been studied in the retrocerebral complex of Calliphora. The material reacts with antisera specific for the common COOH terminus of gastrin and CCK but not with N-terminal antisera. The three thoracic ganglia and the fused abdominal ganglia each contain a specific number of symmetrically arranged immunoreactive cells both dorsally and ventrally in pairs on either side of the midline in a sagittal plane. The neuropil of these ganglia also contains a considerable amount of immunoreactive fibres and droplets. Reconstructed axonal pathways suggest that some of the nerve fibres have their origins within the brain and/or the suboesophageal ganglion. Immunoreactive material may also be seen apparently leaving the thoracic ganglion posteriorly via the abdominal nerves, and there is strong evidence of a neurohaemal organ within the dorsal sheath in the region of the metathoracic and abdominal ganglia. There appears to be a direct correlation between the content of peptidergic material of cells and fibres and the age and diet of the flies. The corpus cardiacum contains COOH-terminal specific gastrin/CCK-like material within the intrinsic cells and in the neuropil. It is present also in the cardiac-recurrent nerve entering the corpus cardiacum anteriorly and in the nerves leaving the gland dorsoposteriorly, the aortic or cardiac nerves. It is not observed, however, in the nerves leaving the corpus cardiacum ventroposteriorly, the so-called oesophageal, gastric or crop-duct nerves. The corpus allatum and the hypocerebral ganglion do not contain immunoreactive material of this type. Gastrin/CCK-like and secretin-like immunoreactive materials appear to co-exist in the cells of the corpus cardiacum and co-existence of gastrin/CCK-like and pancreatic polypeptide-like substances occurs within certain cells of the thoracic ganglion.

Animals↗
PubMed1981

Twisted rhabdomeres in the compound eye of a tipulid fly (Diptera).

The individual rhabdomeres of the outer retinular cells (R 1-6) in the tipulid fly, Ptilogyna, twist about their long axes. Proximally, the rhabdoms become partitioned off by processes from the retinular cells, so that the basal region of each rhabdomere is enclosed in a "pocket" formed by its own cell (Fig. 2). This organisation of the rhabdom enables each rhabdomere to twist while supported within its own retinular cell, and while the cell itself maintains its orientation with respect to the entire ommatidium. Theory predicts that the rhabdomeral twisting should significantly reduce the polarisation sensitivity of R 1-6, but have little effect on the efficiency with which unpolarized light is absorbed.

Animals↗
PubMed1976

Digestive enzyme secretion in Stomoxys calcitrans (diptera: muscidae).

Enzyme assays and morphological and histological studies show that the opaque zone midgut cells of the hematophagous fly Stomoxys calcitrans are responsible for the production of proteolytic digestive enzymes and that these are secreted into the gut lumen via membrane bound vesicles (MBV). The secretory cycle can be summarized as follows: initially the rough endoplasmic reticulum is stacked and the apices of the cells are packed with MBV. This is followed by a period of release characterized first by cytoplasmic extrusions containing high densities of MBV, then by microvesiculation of the microvilli combined with a progressive distribution of rough endoplasmic reticulum and lightening of the cellular cytoplasm. Glycogen appears in the cells at this stage and is gradually lost as the rough endoplasmic reticulum becomes stacked once more and the numbers of MBV build up again. The cycle which occurs regularly and synchronously in the cells of the zone repeats itself many times up to the completion of digestion of the blood meal. The secretory cycle is discussed with reference to activity in other secretory tissues.

Animals↗
PubMed1978

The ultrastructure of the non-neurosecretory components in the brain of the midge, Chironomus riparious Mg. (diptera: nematocera).

The ultrastruct of the neural sheath, glial cells and neurons in the brain of the neoimaginal male Chironomus riparius is described. The neural sheath comprises a neural lamella and underlying perineurium. The neural lamella consists of an amorphous matrix in which fine fibrils occur. The perineurium is composed of two cell types forming a continuous layer around the brain. The subjacent cortical layer, composed of the cell bodies of neurons and glial cells, varies considerably in thickness and surrounds the centrally located neuropiles. Three types of glial cells are distinguished on the basis of their positions and appearances. Five types of neurons are described which differ in size and relative frequency of organelles. Four types of axons, including those of neurosecretory cells, are distinguished by their size and content.

Animals↗
PubMed1978

An ultrastructural study of the larval integument of the midge, Chironomus riparius Meigen (diptera: chironomidae).

The larval integument of the midge, Chironomus riparius Mg., is unusually thin although it conforms with the normal insect pattern. The cuticle of the post-cephalic segments is about 3 micrometer thick and overlies an epidermis which has an irregular basal plasma membrane resulting in spaces occurring between it and the basement membrane. The ventral tubuli have a similar epidermis but the cuticle is somewhat thinner. The anal papillae have the thinnest cuticular covering with a uniquely folded epicuticle of variable thickness, and their epidermis has the characteristics of a transporting epithelium. No evidence of pore canals could be found in the cuticle of any part except the head capsule which has a remarkably smooth epicuticle and a distinct layer which may represent the exocuticle. There are no spaces between the basement membrane and basal plasma membrane of the epidermis in the head. Ultrastructural evidence would suggest that gaseous exchange can occur across most of the post-cephalic integument.

Animals↗
PubMed1976

A structural study of the anal papillae of the midge Chironomus riparius Meigen (Diptera: Chironomidae).

Larvae of the midge, Chironomus riparius Mg., have four anal papillae arranged as two pairs, one dorsal to and the other ventral to the anus. Structural study with light and electron microscopes has revealed that their integument consists of a thin cuticle overlaying a thick, syncytial epidermis which is specialised to facilitate ion transport. There is a distinct neck or collar region at the junction of each papilla with the rest of the body wall. Although in many respects these structures resemble those in mosquitoes, there are both morphological and physiological features which suggest that differences exist in the means by which ion exchange with the environment is controlled and effected in the two families.

Animals↗
PubMed1977

Ultrastructure of the myocardial cell and its membrane systems in the adult fly Calliphora erythrocephala (insecta: diptera).

Calliphora erythrocephala has cross-striated cardiac muscle cells with A, I and Z-bands. The diameters of the myosin and actin filaments are 200-250 A and 85 A respectively and the length of the myosin filaments (A-band) is approximately 1.5 micron. Usually 8-10 actin filaments surround each myosin filament. The myocardial cells show a well-developed membrane system and interior couplings. A perforated sheet of SR envelopes the myofibrils at the A-band, dilates into flattened cisternae at both A-I band levels before it merges into a three-dimensional net-work between the actin filaments of the I-bands and between the dense bodies of the discontinuous Z-discs. The T-system consists of broad flattened tubules running between the myofibrils at the A-I band levels forming dyads with the SR-cisternae. Longitudinal connections between the transverse (T-) tubules often occur. It is suggested that this well-developed SR may be an adaptation to facilitate a rapid contraction/relaxation frequency by an effective Ca2+ uptake.

Actins↗
PubMed1980

Localisation of pancreatic polypeptide (PP)-like immunoreactive material in neurones of the brain of the blowfly, Calliphora erythrocephala (Diptera).

The brain of the blowfly, Calliphora erythrocephala, has been studied by means of the peroxidase-antiperoxidase immunocytochemical method, with the use of antibodies to bovine pancreatic polypeptide (BPP). A number of immunoreactive neurones have been localised, some corresponding to neurones previously identified tentatively as neurosecretory. This finding is further evidence that biologically active peptides, previously considered to be "vertebrates", also exist in invertebrates. It also supports the concept of their evolutionary origin in nervous tissue.

Animals↗
PubMed1980

Ca++-induced structural changes in photoreceptor microvilli of Diptera.

When the compound eyes of the fly Lucilia are fixed for electron microscopy with glutaraldehyde in common buffer solutions, artefactual whorls are liable to be formed from the photoreceptor microvilli. The whorls result from two factors: (i) a prolonged time interval prior to osmication, such as the "overnight" primary fixation or wash at 4 degrees C commonly used in studies of compound eyes; (ii) as little as 1-2 mM Ca++ in the primary fixative and wash solutions. Osmication after short (1h) glutaraldehyde fixation at 4 degrees C, or omission of Ca++ and addition of 2 mM EGTA, prevent whorl-formation. In the tipulid fly Ptilogyna, similar artefacts are produced, but are confined to the distal zone of the microvilli that sheds during turnover.

Animals↗
PubMed1981

Fine structure of the ommatidia and the occurrence of rhabdomeric twist in the dorsal eye of male Bibio marci (Diptera, Nematocera, Bibionidae).

The ommatidia in the dorsal eye of male Bibio marci (March flies) are comprised of eight retinula cells (R 1--8). In the distal region, the open rhabdomeres of retinula cells 1--6 are arranged in a symmetrically circular pattern with their microvilli directed radially. Immediately beneath the crystalline cone, cell 7 forms a rhabdomere that is about 1 micrometer long and lies in the center of the circle formed by the rhabdomeres of cells 1--6. For the remaining length of an ommatidium it is replaced by the rhabdomere of retinula cell 8. The cell body of this retinula cell almost encloses its own rhabdomere by forming a deep invagination. Consequently, no ommatidial cavity is present. In the left eye rhabdomeres R 3, 5 and 6 first twist clockwise along their longitudinal axes, while rhabdomeres R 1, 2, 4 and 8 twist counterclockwise. Opposite twisting is observed in the right eye. The twist rate varies along the length of the rhabdomeres. In a middle region of 60 micrometers, within which the direction of twist does not change, the maximal twist rates are approximately 2 degrees--5 degrees/micrometers in R 1--6 and even higher in R 8. In a proximal region, the direction of twist is reversed, but the initial orientation of the microvilli not reestablished. Both the cross-sectional shape of the rhabdomeres and their geometric arrangement in the retinula change along with the twisting. It is substantiated that the rhabdomeric twist is not due to artifactual deformation.

Animals↗