Some features of the regulation of the free amino acids in adult Calliphora erythrocephala

The amounts of nearly every amino acid in Calliphora remain unchanged inspite of stress. Thus the free amino acid pool is regulated. The amounts of free amino acid in the haemolymph account for only a small part of the total free amino acid in a fly and therefore most free amino acid is located and regulated intracellularly. A comparison of the rates of conversion and turnover of glycine-C¹⁴ in flies fed protein and sugar and in flies fed sugar alone indicates that in the absence of a dietary source of amino acid, not only is the rate of total turnover appreciably lower but the rates of conversion to other amino acids also change. With a dietary source of amino acid, the rates of incorporation into protein account for only a part of the total turnover of each amino acid. With a sufficiency of amino acid, substantial amounts are probably used as an energy source.     

The relationship between age,acclimatization temperature,and heat death point in adult Calliphora erythrocephala

The heat resistance of adult Calliphora erythrocephala declines after eclosion and its rate of loss is dependent upon the temperature at which the adult is maintained. At 29°C the decline was complete in 5 days; at 24, 19, and 15°C it was complete in 10 days; at 10°C it was complete in 30 days; and at 5°C it was not complete even after 73 days. Physiological acclimatization in the adult stage was only observed at temperatures above 32°C, when an increase in heat resistance was superimposed upon the age-dependent decline.     

Effects of ecdysone on the in vivo growth of wing disks of Calliphora erythrocephala

The normal growth of wing disks is compared with the growth of disks from larvae surgically deprived of ring glands at 5 or 6 days and later unable to form a puparium. During the third instar, the growth of wing disks is constant. It seems to slow down after puparium formation. Twelve days after the ablation of the ring gland, the volume of the wing disks is no different from the volume of the wing disks for 6-day-old larvae. Ecdysone is needed for the growth of imaginal wing disks but the ecdysone peak does not accelerate growth.     

Increase in acid phosphatase activity in the fat body during larval and pharate pupal development in Calliphora erythrocephala

Biochemical evidence was obtained for an increase in acid phosphatase activity in the larval fat body of Calliphora erythrocephala during larval and pharate pupal instars. This observation is in conflict with published data indicating a decreasing enzyme activity in late third stage larvae. Centrifugation and filtration studies showed that the pH of the homogenisation medium has a strong influence on the solubilisation of acid phosphatase and its distribution in homogenate components. Differences in biochemical techniques including the pH value may explain the discrepancy between the published results and the present findings.The observed increase in acid phosphatase activity is related to the activity of the lysosomal system in the period immediately preceding pupal-adult apolysis.     

Effects of Weismann ring gland on RNA synthesis in imaginal wing disks of Calliphora erythrocephala

Imaginal wing disks of Calliphora erythrocephala have been studied in normal animals and in permanent larvae surgically deprived of the ring gland. By the end of larval life, uridine incorporation in the nuclear RNA and the ribosomal RNA increases for a brief period. This phenomenon does not occur in permanent larvae. A quantitative study suggests that renewal of a part of the ribosomal RNA might precede wing evagination.     

Membrane potential of the corpus cardiacum neurosecretory cells of the blowfly, Calliphora erythrocephala

The corpus cardiacum neurosecretory cells (c.n.c.) of Calliphora are unipolar cells with slender projections (axonal length: 50 to 110 μ; diameter: 0·25 to 1·75 μ).The cell body, where production of neurosecretory material occurs, is electrically inexcitable (resting potential about 36 mV, inside negative), whereas the axon—responsible for controlled neurohormone release—is excitable. Spike potentials with a duration of 3 to 7 msec occur in volleys the number and duration of which are supposed to determine the amount of secretion released. Electrical activity may be stimulated via the brain. Resting and action potentials are compared with recordings from other cell types of the blowfly.     

Threshold and receptor reserve in the action of 5-hydroxytryptamine on the salivary glands of Calliphora erythrocephala

The interrelationships of 5-HT receptors and the increased fluid secretion by isolated salivary glands of Calliphora have been studied using pharmacological techniques. Removal of the 5-OH group (tryptamine) or displacement to position 6 (6-HT) results in a decrease in potency but no change in intrinsic activity of the hormone whereas altering the ethyl amine side chain (5-OH tryptophan) results in a decrease in both potency and intrinsic activity. Removal of the 5-OH group and alteration of the side chain (gramine and tryptophan) results in a total loss of activity. Gramine and tryptophan behave as competitive antagonists of 5-HT.Prostaglandin E₁ (PGE₁) was found to be a non-competitive inhibitor of 5-OH tryptophan and theophylline whereas the response to 5-HT and cyclic AMP was only slightly diminished indicating a ‘receptor reserve’ for 5-HT.Saturating concentrations of gramine and tryptophan potentiate theophylline revealing a ‘threshold’ for the mediation of the response. It is concluded that 5-HT derivatives are capable of producing graded effects on adenyl cyclase both above and below the range of enzyme activity which evokes graded changes in fluid secretion.     

The induction of lysosomal enzyme activity in the fat body of Calliphora erythrocephala: Changes in the internal environment

The activity of the lysosomal marker enzyme acid phosphatase in the larval fat body of Calliphora erythrocephala increases during development, but not at the same rate throughout the tissue. During the feeding stage, the posterior region has a higher acid phosphatase activity than the anterior region. When the larvae cease feeding on the 5th day of development, the acid phosphatase activity of the inactive anterior lobe increases rapidly in a mosaic-cell pattern. When 4-day-old feeding stage larvae are starved, this increase occurs one day earlier than normally. After the emptying of the gut, the acid phosphatase activity of all the anterior cells both in normal and in starved larvae exceeds that of those in the posterior region.Transplantation experiments indicate that the induction of acid phosphatase activity in the fat body during normal development, especially in the anterior region, is caused by a change in the internal environment when the larvae cease feeding. Both RNA and protein synthesis are involved in this induction process. Inductive factors are present in 5-day-old larvae as well as during formation of the puparium. The competence of the feeding-stage fat cells to develop high acid phosphatase activity is acquired before the actual induction takes place.     

Hormone mediated induction of acid phosphatase activity in the fat body of Calliphora erythrocephala prior to metamorphosis

At the end of the larval feeding stage of Calliphora erythrocephala, ecdysteroids are most likely to be responsible for the rapid increase in acid phosphatase activity in the fat body. This is demonstrated by the precocious induction of the enzyme by 20-hydroxyecdysone in ligatured feeding-stage larvae weighing 55–70 mg. The hormone does not influence normal protein accumulation: this is inhibited by the ligature and is not restored by injection of the hormone.     

Gravity reception in the walking fly, Calliphora erythrocephala: Tonic and modulatory influences of leg afferents on the head position

The proprioceptive gravity receptor system of the fly, Calliphora erythrocephala, is functionally organized in a manner similar to the statocyst system in vertebrates, molluscs and crustaceans. It includes one system in which excitation is modulated by the gravitational stimulus, and another which exerts a tonic excitation on the neurones of the reflex arc between the leg receptors and the neck muscles. While the modulating system for the compensatory head movement of the walking flies is located only in the forelegs and the middle legs, the tonic excitation is mediated by receptors of all legs.     

Evidence for a sugar receptor (lectin) in the peritrophic membrane of the blowfly larva, Calliphora erythrocephala Mg. (Diptera)

For the first time a sugar receptor (lectin) has been localized by electron microscopy in an invertebrate. The peritrophic membrane of the blowfly larva, Calliphora erythrocephala, is shown here to express lectins with high specificity for mannose. The lectin is restricted to the lumen side of the peritrophic membrane. The surface of the midgut epithelium is devoid of mannose-specific lectins. It is suggested that the midgut epithelium has lost these lectins during the course of evolution in favour of the peritrophic membrane which is secreted by specialized cells only at the beginning of the midgut.Peritrophic membranes and the midgut epithelium lack lectins specific for galactose. The lumen side of the peritrophic membrane of the larvae has mannose and/or glucose residues, and it is densely packed with two species of bacteria, Proteus vulgaris and P. morganii. These also have mannose-specific lectins as well as mannose residues on their pili. The existence of mannose-specific receptors and mannose residues on both, peritrophic membranes and bacteria, leads to the assumption of mutual adherence between the two surfaces.     

The cell cycle time of the haemocytes in the insect Calliphora vicina

The cell cycle time of Calliphora vicina prohaemocytes was examined using the labelled mitoses method after the administration of a pulse of H³-thymidine. The total cycle time occupied 9.1 hr, while $\text{G}{}_1\text{+}\text{1}\text{2}\text{M}$, S and $\text{G}{}_2\text{+}\text{1}\text{2}\text{M}$ occupied 1.6 hr, 2.7 hr and 4.8 hr respectively.     

The effects of precocene II on early adult development in male Locusta

Haemolymph protein synthesis and the accumulation of protein in haemolymph and accessory reproductive gland of normal adult male locusts were compared to that of males treated with precocene II. The precocene-treated insects showed a lower level of protein synthesis in both the fat body (source of haemolymph protein) and accessory reproductive gland. Topical application of juvenile hormone reversed the effects of precocene treatment. It would appear that the observed effects are the result of a reduction in juvenile hormone titre in the treated animals.     

Effects of ecdysteroids on RNA synthesis of fat body cells in Calliphora vicina

Ecdysone and ecdysterone induce the synthesis of RNA in fat body cells and isolated nuclei from Calliphora larvae. The inducibility of RNA synthesis is correlated to specific development stages. The fat body cells and the isolated nuclei differ in their response to the two ecdysteroids, ecdysterone giving rise to better responses. The greatest part of the induced RNA represents ribosomal RNA but also new species of nonribosomal RNA are transcribed under the influence of ecdysterone.     

Muscle growth and protein synthesis in the puparia of Calliphora vomitoria

The effects of cycloheximide on the development of the dorsal longitudinal flight muscle of 3- to 5-day-old puparia of Calliphora vomitoria have been investigated. One μg of cycloheximide injected into the puparia reduced the incorporation of ¹⁴C phenylalanine and lysine into protein to 5 and 8 per cent of their normal levels. The cycloheximide was found to have produced its maximum effect within 2 hr of its injection and increasing the concentration did not further depress the amount of amino acid incorporation. The sixth dorsal longitudinal muscles continued to increase in length after the injection of cycloheximide and the elongation of the muscle fibres was accompanied by an increase in protein content in normal and cycloheximide-treated animals. An injection of colchicine (which is believed to disrupt microtubules) immediately halted muscle growth. Electron microscopy of the muscle fibre revealed that fibres from cycloheximide-treated animals contained myofilaments, although there were some differences in myofilament structure between normal and treated animals. The formation of the muscle fibres in the absence of protein synthesis is discussed.     

The tracheal supply and muscle metabolism during muscle growth in the puparium of Calliphora vomitoria

Thirty hours after puparium formation in Calliphora, the larval tracheal system is replaced by an air-filled pupal system. This is characterized initially by many tufts of tracheae and coiled tracheoles lying in the blood. Between the third and fourth day, the sixth dorsal longitudinal flight muscles are practically without attached tracheae and their longitudinal growth can partially occur when oxygen uptake is inhibited with potassium cyanide. Sodium iodoacetate prevents muscle growth. After the fifth day of development the pupal tracheoles spread out over the surface of the developing adult muscles. Between the seventh and ninth day, longitudinal growth and increases in the diameter of the myofibrils are halted by cyanide and iodoacetate. Some longitudinal growth and an increase in the total protein content of the muscles can occur in 1% oxygen. Air filling of the adult tracheae takes place 2–3 hr before the emergence of the adult and is accompanied by an increase in oxygen consumption of the thorax. The metabolism and growth of the muscles is discussed with respect to their changing oxygen supply.     

Isolation and characterization of the haemocytes of Calliphora vicina on density gradients of Ficoll

Discontinuous gradients of Ficoll have been used in an equilibrium density analysis of the haemocytes of Calliphora vicina. Using histochemical criteria, it was shown that the acid phosphatase-containing haemocytes decreased in mean density during larval life. Enzymatic analysis, and an analysis of the density distribution of labelled haemocytes at various times after an injection of [H³]-thymidine, provided evidence that a dense, replicating population of cells had been separated from a non-replicating acid phosphatase-containing population. The latter gained increasing amounts of the lysosomal enzymes acid phosphatase and protease as they aged.     

The effect of diet on activity in male Calliphora vicina blowflies

ABSTRACT. The effect of diet on the activity of male Calliphora vicina R.D. (Diptera, Calliphoridae) was studied. Protein–fed males (PF) were significantly more active than males fed only on sugar and water (NPF); as a consequence they ingested more sugar. The phenomenon was probably due to PF insects spending more time in flight than NPF, as no significant differences were found between the wingbeat frequencies and flight speeds of tethered flies of the two treatments. Protein ingestion also had a physiological effect, as PF flies had heavier thoraces than NPF flies with increased titres of protein.     

Structural and functional aspects of sense organs on the maxillary palps of Calliphora vicina

The maxillary palps of the blowfly Calliphora vicina Robineau-Desvoidy are shown to bear, in addition to long mechanoreceptive hairs, small sensilla basiconica ccontaining three neurons. The electrical responses obtained with a simple qualitative olfactometer indicate an olfactory function. The palpal sensilla showed high sensitivity to cycloheptanon, whereas the antennal organs were more strongly stimulated by heptylalcohol, which indicates the presence of carrion receptors.