Ellen Thomsen

The neurosecretory system of the adult Calliphora erythrocephala

SummaryIn continuation of previous light microscopical investigations using darkfield microscopy of the living cells and sections stained with paraldehyde-fuchsin, an electron microscopical study of the medial neurosecretory cells (m.n.c.) of virgin females of Calliphora has been performed. The neurosecretory material consists of elementary granules corresponding in quantity to the amount of secretory material found by the two other methods in flies of the same age and kept on the same diet. The majority of the cells (m.n.c. I) contain granules measuring c. 2000–3000 Å, while fewer cells (m.n.c. II) show a smaller granular diameter (c. 1000–1500 Å). Due to the Tyndall effect the elementary granules are visible when using darkfield microscopy.The granules were seen to be pinched off from the Golgi complexes. These are numerous and well-developed, except in the less active m.n.c. I of the six days old sugar-flies. The reticulum and mitochondria are described. “Axoplasmic channels” were observed in the m.n.c. I, probably corresponding to structures found by Wigglesworth (1959 and 1960) in other insect neurons with another technique.The fine structure of the “giant neurons” and the “vacuolated cells” has been studied, the observations supporting the conclusions of M. Thomsen in a light microscopical study (1965). Lacunae in the ramifying glia are interpreted as belonging to the “glial lacunar system” described by Wigglesworth (1960).

Fine structure of the fat body of the female of Calliphora erythrocephala during the first egg-maturation cycle

SummaryDuring the first egg-maturation period (6 days at 25° C) the adult fat body of the female of Calliphora goes through sequential changes correlated with the development of the oocytes.The first two days represent a growth and differentiation phase. Free ribosomes and rough endoplasmic reticulum (RER) gradually increase in quantity. Golgi complexes consisting of clusters of vesicles and vacuoles appear to bud off from cisternae of the RER. Dense bodies possibly arise by sequestration from Golgi complexes. Content of acid phosphatase shows the dense bodies to be lysosomes. Many contain crystalloids.Glycogen is first seen as a network, in which gamma-elements appear; later alpha-particles occur. Lipid droplets are abundant. Lipid droplets break down where they border upon glycogen.In four-day old females the fat body is in a phase of production. Golgi complexes concentrate protein secretion granules believed to represent yolk protein.Then follows a phase of regression characterized by the formation of cytosegresomes and by an accumulation of lipid. In mature females a remodeling of the fat cell begins, evidenced by a renewed formation of free ribosomes, RER, and probably dense bodies resembling those of the one-day old female.

Fine structure of the corpus allatum of the female blow-fly Calliphora erythrocephala

SummaryAn electron microscopical study of the corpus allatum (CA) of the adult female Calliphora was undertaken.The cells have a very irregular shape. Light and dark cells are found. Mitochondria occur in great numbers. Microtubules are frequently observed. Free ribosomes are plenty, but rough-surfaced reticulum is scarce. Golgi complexes are not very conspicuous. Axons, mostly containing neurosecretory granules, are frequently found between the cells.The active corpus allatum is remarkable by the numerous lipid droplets and the abundance of tubular agranular reticulum. The reticulum sometimes forms aggregates from which vacuoles are budded off. The vacuoles lose their membrane, at the same time becoming slightly electron opaque, thus being transformed into lipid droplets.It is tentatively postulated that the hormone (or a precursor) is synthesized in the tubules of the agranular reticulum, collected in the vacuoles, and, when the membrane disintegrates, it is dissolved in lipid. The lipid droplets are thought to be released into the haemolymph through the surface of the gland or via intercellular channels.The inactive corpus allatum of the six days old sugar fed flies is small and more or less shrunken. The agranular reticulum is poorly developed, vacuoles are small, and lipid droplets few. The reticulum tends to form whorls, which eventually may possibly be transformed into myelin figures.

Vitellogenin and vitellin from the blowfly Calliphora vicina: Occurrence, purification and antigenic characterization

Abstract The occurrence and purification of vitellogenin and vitellin from Calliphora vicina Rob.-Dev. (= C. erythrocephala (Meig.)) are described together with the preparation of specific anti-vitellogenin antibodies. C. vicina vitellogenin and vitellin were purified from ovaries and eggs respectively; both proteins contain two polypeptide subunits identical to the dominating polypeptides in the growing oocytes. The polypeptides show molecular weights of 52,000 and 48,500 respectively, and are associated with carbohydrate and lipid. Polypeptides of similar size could be identified in haemolymph from yolk-depositing females, but were absent in ovariectomized females. The anti-bodies specifically precipitated the vitellogenin polypeptides from fat body homogenates of females depositing yolk or from the purified vitellogenin. Therefore, these antibodies were judged suitable for use in a study on the ultrastructural localization of vitellogenin in fat body cells ( Thomsen et al. , 1980).

Über das Thermopräferendum der Larven einiger Fliegenarten

Zusammenfassung1.Zur Bestimmung des Thermopräferendums (der Vorzugstemperatur) von Fliegenlarven wurde eine abgeänderte Temperaturorgel konstruiert, worin sich die Larven in einem Medium (Mist) frei bewegen können, und in welcher ein Temperaturgefälle von etwa 9–50° erzielt wurde. Dabei wurde gleichzeitig dafür gesorgt, daß der Wassergehalt im ganzen Bereich des Versuchskastens im Laufe des Versuches nicht wesentlich geändert wurde.2.Larven von Musca domestica zeigten in diesem Apparat ein deutliches Thermopräferendum, das aber mit dem Alter der Larven in gesetzmäßiger Weise variiert. In der Hauptsache haben die jungen Larven (im Freßstadium) ein hoch gelegenes Thermopräferendum (zwischen 30 und 37°), die verpuppungsreifen Larven dagegen ein tief gelegenes (unter 15°). Wenn die Versuchstiere einer bei etwa 25° gehaltenen Zucht entstammen, bei welcher Temperatur die Larvenperiode 6 Tage dauert, ist jeder Lebenstag (Larventag) durch eine sehr charakteristische Verteilungskurve gekennzeichnet, so daß man auch umgekehrt von dem Aussehen einer solchen Kurve auf das Alter der verwendeten Larven (auch im Einzelversuch) Rückschlüsse ziehen kann (vgl. Abb. 4–15).3.Durch sogenannte „biologische Kontrollversuche“ (S. 362) konnten wir zeigen, daß außer Temperaturdifferenzen auch eine während des Versuches eintretende dauernde Änderung einer gewissen Zone des Mistes für die Konzentrierung der Larven mitverantwortlich ist. Diese Änderung, die ohne Zweifel chemischer Art ist, macht sich jedoch nur bei Larven am 2. Lebenstage deutlich bemerkbar. Wir müssen demnach schließen, daß die Musca-Larven außer Thermotaxis auch Chemotaxis zeigen, und daß sie neben einem stark ausgeprägten Thermopräferendum ein schwächeres Chemopräferendum aufweisen.4.Die Lage des Thermopräferendums bei den Larven von Musca domestica entspricht durchaus den Temperaturen, die in dem natürlichen Habitat dieser Larven, d. h. in der larvenhaltigen Zone eines gärenden Misthaufens, herrschen (Abb. 1). Auch die Umstimmung der verpuppungsreifen Larven stimmt mit dem Benehmen der freien Larven im Dunghaufen sehr schön überein. Wir schließen daraus, daß die lokale Verteilung und die Bewegungen der Larven unter natürlichen Bedingungen ebenfalls vorwiegend von ihrem Thermopräferendum und in geringerem Grade von Chemotaxis (und Chemopräferendum) bestimmt werden. Daneben mögen auch negative Phototaxis, Hygrotaxis und Thigmotaxis eine gewisse Rolle spielen.5.Zum Vergleich wurden Larven dreier Arten von Stomoxydinen herangezogen. Bei den Larven von Stomoxys calcitrans, die gewöhnlich in misthaltiger Streu von Kälberboxen bei Temperaturen von 20–30° leben, liegt das Thermopräferendum innerhalb einer Zone von 23–30° (wahrscheinlich zwischen 23 und 26°). Bei Larven von Haematobia stimulans, die in Kuhfladen leben, aber nur im Frühling und Herbst auftreten, liegt das Thermopräferendum recht tief, nämlich zwischen 15 und 26° (wahrscheinlich 19 und 23°). Larven von Lyperosia irritans, die sich ebenfalls in Kuhfladen entwickeln, aber nur im Hochsommer vorkommen, haben ein entschieden höheres Thermopräferendum, nämlich zwischen 27 und 33°. Nur bei dieser Art gibt es Anzeichen dafür, daß die verpuppungsreifen Larven ein tieferes Thermopräferendum besitzen, doch konnte dies wegen der Spärlichkeit des Materiales vorläufig nicht bewiesen werden. Bei allen drei Arten von Stomoxydinen sehen wir also, ähnlich wie bei Stubenfliegenlarven, eine schöne Übereinstimmung zwischen der Lage des Thermopräferendums im Versuch und den vorherrschenden Temperaturen in der natürlichen Umwelt der Larven.

Ultrastructural immunocytochemical localization of vitellogenin in the fat body of the blowfly, Calliphora vicina Rob.-Desv. (erythrocephala Meig.) by use of the unlabeled antibody-enzyme method

SummaryThe unlabeled antibody-enzyme method was used to demonstrate ultrastructurally the specific localization of vitellogenin in the fat body of Calliphora. In control flies the binding sites to vitellogenin were localized in secretory granules situated in the Golgi complex, and in larger bodies named composite secretory granules. These composite granules appear to be formed when a part of a Golgi complex containing secretory granules and a number of small vesicles become surrounded by a common membrane. Ovariectomized flies, which apparently do not produce secretory granules, exhibited no immunocytochemical staining. Ovariectomized flies in which the administration of ecdysterone induced formation of secretory granules, also revealed specific staining on these granules. This is the first ultrastructural evidence of: (a) the specific localization of vitellogenin in secretory granules of the fat body of an insect; (b) the relationship between the presence of the ovary, and of ecdysterone, and the synthesis of vitellogenin by the fat body.

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

SummaryDuring 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 β-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 β-ecdysone. This, we believe, is the first ultrastructural evidence for an effect of the ovary and of β-ecdysone on the synthesis of specific protein.

Esterase in the cells of the hind-midgut of the Calliphora female, and its possible dependence on the medial neurosecretory cells of the brain

SummaryA characteristic distribution pattern of esterase is seen in the cells of the hind-midgut of the Calliphora female when the substrate 5-bromoindoxyl acetate is applied to the fresh tissue.The pattern consists of “granules”, “filaments” and “caps” which evidently correspond to similar elements described in Rhodnius by Wigglesworth (1958).In normal meat fed flies the development of caps on the fat droplets in the apical end of the cells, which is thought to reflect the esterase activity, follows a cycle correlated with the development of the ovaries.A clear correlation was found between the size of the fat droplet and its cap. The caps seem to lie on the droplets, not inside these.Observations suggest that granules may be transformed into filaments and filaments into caps.Some findings might perhaps be interpreted as an indication that the cap enzyme is transformed back into filament or granule in a mechanism that might be taken as a form of recycling of the enzyme.The cells of flies fed on a protein free diet only developed a low content of esterase. A similar result was seen in flies deprived of their medial neurosecretory cells even if they were given meat to eat; this indicates that the m.n.c. in some way directly or indirectly influence the development of esterase in the cells.

Esterase activity of the posterior midgut of the female blowfly, Calliphora erythrocephala.

Abstract Quantitative determinations of the esterase activity of the posterior midgut of the Calliphora female showed this part of the gut to possess considerable esterase activity. Calculated on a weight basis no significant difference could be demonstrated between the esterase activity of posterior-midguts with many big ‘caps’ from protein-flies and that of posterior midguts with few small ‘caps’ from sugar-flies.