The metabolism of the insecticide carbaryl (1-naphthyl N-methylcarbamate) by fat body of the blowfly larva Calliphora erythrocephala

1. Carbaryl is metabolized more rapidly by fat body of the blowfly larva than by gut, muscle, cuticle or haemolymph. 2. Metabolism of carbaryl by the fat body is affected by the age of the larva, the pH of the incubation medium, and the concentration of magnesium chloride in the incubation medium. 3. Chloramphenicol, 2,4-dinitrophenol and 5-dimethylamino-6-nitro-1,3-benzodioxole (a carbaryl synergist) inhibit carbaryl metabolism by the fat body. 4. Subcellular fractionation of the fat body indicates that the pellet sedimenting at 30000g is the most reactive with carbaryl. 5. Probable metabolites of carbaryl formed by the fat body include the 4- and 5-hydroxy derivatives, and, possibly, the N-hydroxymethyl and 5,6-dihydrodihydroxy derivatives.     

Salivary gland development in the blowfly,Calliphora erythrocephala

The salivary gland of adult Calliphora erythrocephala is a tubular structure composed of secretory, reabsorptive, and duct regions. Development of these structures has been followed during the six days of larval and ten days of pupal growth. Two small groups of imaginal cells located at the junction between larval gland and duct give rise to the adult gland. These presumptive adult cells divide during all larval stages and appear to be functional components of the larval gland. Shortly after pupation, the larval gland breaks down and the imaginal cells proliferate rapidly, forming sequentially the duct, reabsorptive and secretory regions. Proliferating regions of the developing gland are frequently encrusted with haemocytes. As it elongates the gland establishes intimate contacts first with the basement membrane of the degenerating larval gland, later with an epithelial layer surrounding the main dorsal tracheal trunks, and then with the gut. Cell division continues until about five days after pupation, bu t the gland is unable to secrete fluid in response to 5-hydroxytryptamine stimulation until two hours after the adult fly emerges. The Golgi complex appears to be involved in forming the highly folded membranes of the canaliculi in the secretory region. Presumptive adult salivary gland cells appear to increase in number logarithmically from the time of hatching of the larva until five days after pupation. This contrasts with the development of classical imaginal discs, in which cell division ceases prior to pupation.     

On the landing response of the blowfly,Calliphora erythrocephala

The dependence of the landing response on the direction of moving stimuli (periodic gratings, single or double stripes) was studied in blowflies, Calliphora erythrocephala, of both sexes. Directions of motion eliciting maximally strong responses (preference direction) vary with the eye region stimulated: they are distributed radially from a common origin forming a flow-field. This origin lies at the intersection of the eye equators with the median plane of the animal. By changing its body posture relative to the direction of flight, the fly may align the pole of this flow field-with its direction of flight thus maximizing signal flow for the landing approach. Sex-specific differences were found for dorsal eye regions in which the shift of preference directions from vertical to obliquely inclined directions of motion (against the median plane) could only be determined for male flies.     

The effect of chromosomal polytenization on the rates of RNA synthesis and decay in the salivary glands of the blowfly, Calliphora erythrocephala

The rates of total RNA synthesis and accumulation have been measured in the polytenic salivary gland cells of the blowfly, Calliphora erythrocephala, by three methods: (1) injecting larvae with [2-³H]adenosine and determining its flow into the cellular ATP pool and RNA, (2) measuring the increase in glandular RNA optically, and (3) measuring the rate of flow of ATP out of the cellular pool. The size of the steady-state pool of rapidly turning over RNA and its half-life, were calculated from these kinetic data and, also, by an independent measurement of the steady-state content of nuclear RNA. These parameters were compared at a number of developmental stages which differed in degree of chromosomal polytenization. The results indicate that these polytenic cells synthesize RNA at a rate approximately 10³ times those of other diploid eukaryotic cells. This rate is independent of the increase in chromosomal polyteny that accompanies larval development. Approximately 67% of the newly synthesized salivary gland RNA is an unstable component with an average first-order half-life of 20–25 min. The remainder is a long-lived species with an estimated average first-order half-life of about 30 hr.     

Hormonal control of resilin deposition in the blowfly, Calliphora erythrocephala

The deposition of the resilin tendon in the blowfly Calliphora erythrocephala was investigated in normal and in various experimental conditions. The results showed that the weight of the protein resilin that is deposited is controlled by diet as well as by the hormone secreted by the medial neurosecretory cells.Endocrinologically abnormal Calliphora adults deposited a tendon with normal ultrastructure but showed signs of premature ageing while Calliphora fed on a sugar diet deposited a tendon with abnormal ultrastructure.     

Synthesis and turnover of hdRNA and mRNA in the salivary gland of the blowfly Calliphora erythrocephala.

We have measured the absolute molar rates of synthesis, accumulation, and turnover of blowfly salivary gland heterodisperse RNA. Twelve- and 84-hr-stage third-instar Calliphora erythrocephala larvae were injected with [³H]adenosine, and its flow into glandular ATP, heterodisperse RNA, and polyadenylated RNA was each quantitated over a 360-min time course. The results of these experiments indicate that at least 80% of the newly synthesized heterodisperse RNA mass is a >28 S nuclear species whose average first-order half-life is approximately 20 min. The remaining 20% of the heterodisperse RNA has a 6–28 S size distribution, accumulates in the cytoplasm, and is associated with functional polysomes. The average first-order half-life of this more stable species is 20–25 hr. In addition, we have independently quantitated by optical methods the developmental change in the content of polysome-associated mRNA. The mRNA in these studies also has an average first-order half-life of 25 hr and accounts for 25–55% of the mRNA mass predicted by the incorporation-kinetic analysis of the pulse-labeled heterodisperse RNA. Despite the increased polyteny of the older stage glands, the rates of synthesis and accumulation of each of the individual heterodisperse RNA classes are the same at the 12- and 84-hr stages. Collectively, these results demonstrate that salivary gland functional specialization results from the accumulation of long-lived mRNA and not from changes in the overall rate of mRNA synthesis.     

Receptor turnover and the action of 5-hydroxytryptamine on the salivary glands of the blowfly Calliphora erythrocephala, the housefly Musca domestica and frog skin epithelium

1. Continual stimulation of frog skin epithelium and the salivary glands of the insects Calliphora and Musca with 5-hydroxytryptamine (5-HT) leads to desensitisation, i.e. the tissue fails to respond to the application of further 5-HT. 2. Incubation of desensitised frog skin and Musca salivary glands with either N-acetyl neuraminic acid or inositol partially restored the 5-HT responses whilst incubation with a combination of N-acetyl neuraminic acid and inositol gave additive effects on the recovery of the 5-HT responses. 3. Incubation of desensitised salivary glands of Calliphora with inositol totally restored the 5-HT response whilst incubation with N-acetyl neuraminic acid had no effect. 4. It is concluded that desensitisation involves depletion of secondary messenger from the tissues coupled with receptor degradation and that considerable differences exist in the turnover of 5-HT receptors, the receptors in Musca salivary glands being highly labile, those in Calliphora salivary glands highly stable and those of frog skin epithelium being intermediate in their stability.     

Extracellular ribosomes during metamorphosis in the blowfly Calliphora erythrocephala

During metamorphosis of the blowfly Calliphora erythrocephala extracellular ribosomes, in the form of monosomes, appear in the body fluid. The total number of ribosomes, i.e. intracellular and extracellular, remains approximately constant during this period, whereas the proportion of extracellular ribosomes first rises, plateaus, and then declines in a manner suggesting that their appearance is a result of larval tissue breakdown.     

Cholinergic neurons in the lamina ganglionaris of the blowfly Calliphora erythrocephala

Summary The distribution of putative cholinergic neurons in the lamina of the blowfly Calliphora erythrocephala was studied by immunocytochemical and histochemical methods. Three different antibodies directed against the AChsynthesizing enzyme, choline acetyltransferase (ChAT), revealed a cholinergic population of fibres running parallel to the laminar cartridges, which have branch-like structures at the distal lamina border. Cell bodies in the chiasma next to the lamina border were also labelled by the anti-ChAT antibodies. Monopolar cell bodies in the nuclear layer were faintly labelled. The distribution of the acetylcholine hydrolyzing enzyme, acetylcholine esterase (AChE), was revealed by histochemical staining and was similar to the ChAT immunocytochemistry. The arrangement of ChAT positive fibres in transverse and longitudinal sections and the distribution of AChE stained fibres indicate that the amacrine cells of the lamina are cholinergic cells.We dedicate this work to Prof. F. Zettler who passed away in fall 1988: K.-H. Datum, I. Rambold     

Production of specific-protein secretion granules by fat body cells of the blowfly,Calliphora erythrocephala

Summary During the first four days of the imaginai stage the fat cells of ovariectomized females of Calliphora develop a protein synthetic apparatus, and produce dense bodies (lysosomes) as do the fat cells of normal females, but apparently they cannot synthesize the protein secretion granules that characterize the productive phase of the fat cells of normal females and that we believe to represent vitellogenin. Injection of ovariectomized females with -ecdysone restored the ability of the fat cells to produce the secretion granules. It is suggested that the ovary gives off a factor which induces the production of the protein secretion granules by the fat cells, and that the factor from the ovary can be substituted by -ecdysone. This, we believe, is the first ultrastructural evidence for an effect of the ovary and of -ecdysone on the synthesis of specific protein.We are grateful to the Carlsberg Foundation and to the Danish Science Research Council for generous grants, and to the latter for placing an electron microscope at our disposal. It is a pleasure to thank Dr. Gareth Griffiths for valuable advice as to the preservation of the fat body tissue. We also thank Mrs. Lotte Bakhoj and Mrs. Elsebeth Lund for skilful technical assistance1896–1976     

In vitro synthesis of peritrophic membranes of the blowfly, Calliphora erythrocephala.

Tyrode solution containing added glutamine and Leloup's medium 1 has been used as a basic medium for the in vitro culture of the so-called proventriculus of adult Calliphora erythrocephala to elucidate some of the factors controlling the synthesis of peritrophic membranes (PM) in vitro. The formation rate was chosen as a quantitative criterion for the evaluation of the modifications of the incubation media.After systematic variation of osmolarity, pH, and temperature optimal formation rates were obtained in media with an osmolarity of 320 to 360 mOsmol, a pH of 6·8, and an incubation temperature of 27°C. Under these conditions the average rate of formation was in the modified Tyrode solution 3·0±1·1 mm PM/hr, and in Leloup's medium 3·6±0·8 mm PM/hr. In the modified Tyrode solution the formation of PM was complete after 5 to 7 hr, whereas in Leloup's medium it continued up to 24 hr. The addition of β-ecdysone caused an increase of the formation rate of PM to 4·5 to 5·5 mm PM/hr.The results obtained led to the hypothesis that an osmotically regulated enzyme system could be the limiting factor of the formation rate of peritrophic membranes, i.e. a system which could regulate the internal osmolarity of the formative cells by the interconversion of a bulk polymer and its monomer which are needed for the synthesis of PM.