Adult Fat Body Research Articles

Pteridines in the Fat Body of a Mutant of Drosophila melanogaster

A mutant, white-mottled orange, which deposits less than wild-type amounts of drosopterins in the eyes, has been found in Drosophila melanogaster. Variations in other pteridines were also observed. The mutant accumulates and later loses drosopterins in the abdominal fat body of adults.

Photoperiodic Responses of Two Latitudinally Diverse Groups of Anopheles freeborni (Diptera: Culicidae)1

A California strain (37°N) and a Washington strain (47°N) of Anopheles freeborni Aitken were compared for their responses to photoperiod. A sharp 1-hr difference (critical photoperiod) in response of adult female fat body was demonstrated. This critical photoperiod was 9–10 hr for the California strain, 11–12 hr for the Washington strain. These latitudinal differences in response seem explainable on the basis of expected seasonal temperatures. Ovary length was also noted to respond to photoperiod, but no consistent relationship was seen in willingness of females to take a blood meal. Both larvae and adults respond to day length.

Lipid release and transport in insects

1. 1. When isolated fat body of the silkmoth. cockroach or grasshopper was incubated with [ carboxy- 14 C] palmitate, the 14C-labeled fatty acid was rapidly incorporated into the neutral lipids of the fat body. When this “prelabeled fat body” was reincubated with insect hemolymph, a rapid release of 14C-labeled diglyceride took place from the fat body into the hemolymph, whereas no significant release of triglyceride occurred. 2. 2. This diglyceride release was specific for insect hemolymph. No significant release of diglyceride occurred into a solution of bovine serum albumin, egg albumin or rat plasma. In contrast, free fatty acid was released not only into the insect hemolymph but also into synthetic media. 3. 3. Diglyceride release was markedly inhibited by cyanide, 2,4-dinitrophenol azide, whereas the release of free fatty acid was accelerated by these chemicals. 4. 4. The greatest rate of release of diglyceride was observed from adult silkmoth fat body, and the lowest from diapausing pupal fat body. 5. 5. Electrophoretic analysis of the hemolymph showed that the diglyceride released into the hemolymph was complexed to one of the hemolymph proteins. This diglyceride-protein complex seems to be the most likely form by which long-chain fatty acids are transported in the insects studied.

Haemocytes and the metamorphosing tissues in Sarcophaga bullata, Drosophila melanogaster, and other cyclorrhaphous Diptera

Changes occurring in the haemocytes during metamorphosis in Sarcophaga bullata, Drosophila melanogaster, and other Diptera Cyclorrhapha are considered. Phases in the formation of the familiar ‘spherules’ are described in detail for Sarcophaga: the granular haemocytes, in the late larval and pre-pupal stages, undergo nuclear division to form multi-nucleate haemocyte masses; these send out extensive cytoplasmic processes, which become attached to pieces of larval tissues; subsequent retraction of the processes and ingestion of the larval fragments by the multi-nucleate haemocytes results in the formation of the spherules. Haemocytes were found attacking only tissue-fragments. Cytoplasmic filaments from the spherules are, at later stages, closely associated with the developing adult tissues, particularly hypodermis and tracheal epithelium, eye ommatidia, and developing flight muscles. The spherules, at least in the appendages, do not appear to circulate; they occupy specific locations and their contents are digested and utilized in situ. Their later phases may represent the adipohaemocytes of other authors. Late in the pupal stage the spherules would appear to contribute material towards connective tissue formation by adjacent cells. It is thought possible that food transfer may be direct by way of the cytoplasmic filaments and not indirect by way of the haemolymph. Many of the multi-nucleate haemocytes, depleted of their inclusions, persist into the adult, where some are found fragmenting. Others may become the multi-nucleate adult fat body cells, but further evidence for this is required. It is suggested that the larval fat body cells, as with the spherules, remain stationary during pupation and that cells of specific areas contribute specific materials to particular developing tissues. The various plasmatocytes are present throughout pupation, some passing through motile and inclusion laden phases, and many reverting to their larval appearance after emergence. Certain of the ‘oenocytoid’ homologies are questioned in connexion with cuticle darkening. Preliminary results in Drosophila suggest that in general the haemocyte picture parallels that of other Cyclorrhapha, with typical spherules and spindle-shaped plasmatocytes present in the pupal stage.

A Study of Ovarial Development and Its Relation to Adult Nutrition in the Blowfly Protophormia Terrae-Novae (R.D.)

ABSTRACT A method has been developed for obtaining 200-300 flies daily from a culture of Protophormia terrae-novae reared on whale-meat. Normal growth changes in adults have been described, and five stages in ovarial development have been defined. Experimental conditions affecting ovarial growth in adults have been investigated and a satisfactory routine method for examining the effect of adult nutrition on ovarial growth has been devised. Precautions were taken against bacterial contamination of food although non-sterile conditions were used. Ovarial development was not related to relative humidity, if above 55 % R.H., nor to the weight of the adults at emergence. Evidence has been given for the conversion of food material from pupal to adult fat body and for the transfer of material from fat body to ovaries at yolk formation. Healthy adult females can be maintained on a diet of sucrose and water. Addition to the diet of protein or amino-acids produces only slight enlargement of the ovaries. Yolk formation only occurs if the diet is further supplemented by accessory factors, or substances required only in small amount. Ovarial maturation requires considerable amounts of protein, though not more than 0-4 mg. per fly is needed and food solutions must be concentrated. The accessory factors have not been identified but are known to be resistant to slow boiling and are dialysable. Certain mineral salts and B vitamins are thought to be involved. Tryptophane is an essential part of the amino-acid mixture. Protein hydrolysates or equivalent amino-acid mixtures can be substituted for the whole protein but are less effective. The proportions of amino-acids present are very critical, particularly when the amino-acids are in a free state. The aminoacid mixtures have no toxic effect and the presence of some D-isomers do not inhibit growth, although some D-isomers cannot be used by the flies for growth. A chemically defined diet similar to that used for Drosophila did not promote ovarial growth in Protophormia. A mixture containing ten B vitamins, ribose nucleic acid and mineral salts and cholesterol contained some effective accessory substances but lacked some unidentified factor required for yolk formation. The missing factor was not vitamin B12. Penicillin had no significant effect on ovarial growth whether used in minute or in antibiotic concentration.

THE FUNCTION OF THE CORPUS ALLATUM IN MUSCOID DIPTERA

1. Evidence from extirpation and transplantation experiments suggests that the ring gland of Lucilia sericata and Sarcophaga securifera produces a hormone concerned with normal development. Its action can be seen in the larva where it results in puparium formation, and in the adult fly first in the changes which occur during the breakdown of the larval fat body cells and subsequently in the changes undergone by the adult fat body cells, the oenocytes, and the development of the ovaries. 2. These last two activities may be under the influence of a hormone (probably different from that influencing development), whose action seems to be on the general metabolic activity of the fly. The oenocytes undergo marked changes after extirpation of the ring gland. If these are concerned with some general metabolic function, as seems likely, the action may be primarily on them and the effects on fat body cells may be altered by implanting a ring gland into the abdomen of a fly, after extirpation of the ring gland, but this has no visible effect on oenocytes or on ovarian development. 3. Castration of adult female Lucilia sericata results in hypertrophy of the cells of the corpus allatum. No effect is produced in the male Lucilia sericata or in either sex in Sarcophaga securifera. 4. Destruction of the innervation of the ring gland of Sarcophaga securifera results in slight hypertrophy of the corpus allatum cells, and of their nuclei. The physiological significance of this hypertrophy is not yet known.