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.     

Leaf alkaloids of Rauwolfia vomitoria

Nineteen indole alkaloids were isolated from Ghanaian Rauwolfia vomitoria leaves. The alkaloids comprised E-seco indole, sarpagan, picrinine, akuammiline, heteroyohimbine, oxindole, yohimbine and indolenine types. The biosynthetic relationship of the alkaloids is discussed.     

Stem alkaloids of Rauwolfia vomitoria

22 indole alkaloids were isolated from the stem bark of Nigerian Rauwolfia vomitoria and 20 characterized. The alkaloids comprised E-seco heteroyohimbine, sarpagan, dihydroindole, yohimbine and heteroyohimbine types. The biosynthetic relationship of the alkaloids is discussed.     

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.     

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.     

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.     

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.     

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.     

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.     

Simultaneous chemical and electrical stimulation of labellar taste hairs of the blowfly Calliphora vicina

When recording from the tip of insect taste hairs, responses to chemical stimulation may be influenced by electrical currents, such as the preamplifier's input bias current. The effect of electrical currents on firing frequency of the salt receptor cell to KCl and NaCl stimulation was determined in labellar ‘aboral’ and ‘adoral’ taste hairs of the blowfly Calliphora vicina. Negative currents always decreased spike frequency, whereas positive currents either increased it, or did not change it significantly. Spike frequency changed less than 1% per 5 × 10^?11 A.A consistent picture of the electrophysiology of blowfly taste hairs is given. It includes a distal pore, present in the dendrite-free lumen of the hair. It abandons the concept of a generator current that transmits excitation from the distal, chemoreceptive part of the taste cell dendrite to the action potential generator in or near the taste cell body. The experimental results are interpreted on the basis of this picture. It is concluded that the ‘electrophoretic effect’ of the electrical current is very small. Thus, the measured effect should mainly be due to a ‘direct effect’ of electrical current on electrically excitable structures in the salt receptor cell, particularly in its dendrite.     

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.     

The effect of digging on development of adult characters in blowflies Calliphora erythrocephala

Digging delays expansion after emergence of adult Calliphora. If flies are kept digging for 12 to 14 hr they lose the capacity to expand and, if they are then reared for 10 days, do not develop the normal adult corpus allatum, ovaries, and cuticle. In particular, ultrastructural examination of the resilin tendon of the pleurotergal muscle shows that development is arrested at a stage similar to that in the late pharate adult but the resilin is not cross-linked. It is suggested that bursicon release is irreversibly inhibited in flies that fail to expand normally.     

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.     

Virus DNA replication and protein synthesis in Amsacta moorei entomopoxvirus-infected Estigmene acrea cells

Amsacta moorei entomopoxvirus DNA synthesis was detected in Estigmene acrea cells by [³H]thymidine incorporation 12 hr after virus inoculation. Hybridization of ³²P-labeled Amsacta entomopoxvirus DNA to the DNA from virus-infected cells indicated that viral-specific DNA synthesis was initiated between 6 and 12 hr after virus inoculation. A rapid increase in the rate of virus DNA synthesis was detected from 12 to 24 hr after virus inoculation. Amsacta entomopoxvirus protein biosynthesis in E. acrea cells was studied by [su35S]methionine incorporation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Extracellular virus and virus-containing occlusion bodies were first detected in virus-infected cell cultures 18 hr after virus inoculation. Thirty-seven virus structural proteins, ranging in molecular weight from 13,000 to 208,000 were detected in both occluded and nonoccluded forms of the virus. The biosynthesis of virus structural proteins increased rapidly from 18 to 34 hr after infection. A major viral-induced protein corresponding in molecular weight to viral occlusion body protein (110,000) was detected approximately 24 hr after virus inoculation.     

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.     

Localisation of sulfakinin neuronal pathways in the blowfly Calliphora vomitoria

The distribution of neurones immunoreactive to antisera raised against the undecapeptide C-terminal fragment of drosulfakinin II (DrmSKII), Asp-Gln-Phe-Asp-Asp-Tyr(SO₃H)-Gly-His-Met-Arg-Phe-NH₂, has been studied in the blowfly Calliphora vomitoria. Antisera were preabsorbed with combinations of the parent antigen, the tetrapeptide Phe-Met-Arg-Phe-NH₂ and cholecystokinin, the vertebrate sulfated octapeptide (CCK-8), Asp-Tyr(SO₃H)-Met-Gly-Trp-Met-Asp-Phe-NH₂, in order to ensure specificity for the sulfakinin peptides of C. vomitoria (the nonapeptide callisulfakinin I is identical to drosulfakinin I and callisulfakinin II differs from DrmSK II only by the presence of -Glu³-Glu⁴- in place of -Asp³-Asp⁴-). Only four pairs of sulfakinin-immunoreactive neurones have been visualised in the entire nervous system. These occur in the brain: two pairs of cells situated medially in the caudo-dorsal region close to the roots of the ocellar nerve and two other pairs at the same level but positioned more laterally. Despite the small number of sulfakinin-immunoreactive cells, there are extensive projections to many areas of neuropile in the brain and the thoracic ganglion. The pathway of the medial sulfakinin cells extends into each of the three thoracic ganglia and a metameric arrangement of sulfakinin neuronal projections is also seen in the abdominal ganglia. Neither the dorsal neural sheath of the thoracic ganglion, nor the abdominal nerves contain sulfakinin-immunoreactive material. These observations suggest that the sulfakinins of the blowfly function as neurotransmitters or neuromodulators. They do not appear to have a direct role in gut physiology, as has been shown by in vitro bioassays for the sulfakinins of orthopterans and blattodeans. In addition to the neurones that display specific sulfakinin immunoreactivity, other cells within the brain and thoracic ganglion are immunoreactive to cholecystokinin/gastrin antisera. There are, therefore, at least two types of dipteran neuropeptides with amino acid sequences that are similar to the vertebrate molecules cholecystokinin and gastrin.     

Blood protein synthesis in pupae of the silkmoth, Hyalophora cecropia

The blood proteins of pupae of Hyalophora cecropia were studied by acrylamide gel electrophoresis. Analyses of fractions separated on Sephadex G-75 columns revealed that a series of low molecular weight proteins previously reported to be absent in diapausing pupae are a normal component of diapausing pupal blood. Incorporation of isotopically labelled leucine into blood protein bands of injured pupae, perfused pupae, and perfused isolated pupal abdomens (lacking a midgut) revealed that each of these three preparations could synthesize all of the low molecular weight protein bands, with maximal incorporation in the perfused whole pupae.     

Muscle fiber type-dependent differences in the regulation of protein synthesis

This study examined fiber type-dependent differences in the regulation of protein synthesis in individual muscle fibers found within the same whole muscle. Specifically, the in vivo SUrface SEnsing of Translation (SUnSET) methodology was used to measure protein synthesis in type 1, 2A, 2X and 2B fibers of the mouse plantaris muscle, in response to food deprivation (FD), and mechanical overload induced by synergist ablation (SA). The results show that 48 h of FD induced a greater decrease in protein synthesis in type 2X and 2B fibers compared to type 1 and 2A fibers. Type 2X and 2B fibers also had the largest FD-induced decrease in total S6 protein and Ser(240/244) S6 phosphorylation, respectively. Moreover, only type 2X and 2B fibers displayed a FD-induced decrease in cross-sectional area (CSA). Ten days of SA also induced fiber type-dependent responses, with type 2B fibers having the smallest SA-induced increases in protein synthesis, CSA and Ser(240/244) S6 phosphorylation, but the largest increase in total S6 protein. Embryonic myosin heavy chain (MHC(Emb)) positive fibers were also found in SA muscles and the protein synthesis rates, levels of S6 Ser(240/244) phosphorylation, and total S6 protein content, were 3.6-, 6.1- and 2.9-fold greater than that found in fibers from control muscles, respectively. Overall, these results reveal differential responses in the regulation of protein synthesis and fiber size between fiber types found within the same whole muscle. Moreover, these findings demonstrate that changes found at the whole muscle level do not necessarily reflect changes in individual fiber types.