A Possible Extra-Ovarian Site for Synthesis of Lipovitellin During Vitellogenesis in Artemia sp. (Crustacea; Anostraca)

Summary

Lipovitellin samples, extracted from yolk platelets of cysts, were applied to SDS-PAGE. A female specific antiserum was raised against the high molecular weight apoprotein lipovitellin alpha-1 (LV-α1) of the lipovitellin complex. This anti-LV-α1 was used in the peroxidase-anti-peroxidase staining method with frontal paraffin sections (of 4μm) of whole embedded Artemia. Females were studied during a complete vitellogenic cycle. The presence of exogenous yolk precursors in the fat storage cells of the thoracopods of female Artemia was demonstrated. The amount of the female specific yolk polypeptides and the number of positively stained cells changes during the vitellogenic cycle. In vitro experiments with ³⁵S-radiolabelled methionine show the synthesis of lipovitellin-like substances in the fat storage cells of vitellogenic females.     

Osmotic lysis of corpora cardiaca using distilled water reveals the presence of partially processed peptides and peptide fragments

Abstract. A simple, single-step aqueous extraction method has been developed to study the neuropeptide content of small neuroendocrine organs. Perifusion of these tissues with deionized water causes osmotic bursting of the cells and release of their content into the surrounding fluid. The neuropeptides are immediately retained from the perifusion fluid using disposable C18 cartridges. After one separation step and mass spectrometry, it was possible to identify a large number of known neuropeptides from the corpora cardiaca of Locusta migratoria (L). Also present in the extract were a number of neuropeptide fragments and two incompletely processed peptides. Using this method, a 959Da peptide present in the corpora cardiaca was sequenced de novo . The full sequence, deduced using Collision Induced Dissociation Tandem Mass Spectrometry (CID MS/MS), is Ser-Pro-Leu-Asp-Ala-His-His-Leu-Ala. This nonapeptide is predicted from the gene encoding the ion transport peptide precursor and from the gene encoding the ion transport-like peptide precursor. In both cases, this nonapeptide, which was named ion transport peptide-copeptide, is flanked by the signal sequence at the N -terminus and a dibasic cleavage site (Lys-Arg) at the C -terminus. This structural feature is common to many physiologically important locust preproneuropeptides and indicates that this copeptide might have a physiological function, but this is not yet known.     

Comparative developmental physiology and molecular cytology of the polytrophic ovarian follicles of the blowfly Sarcophaga bullata and the fruitfly Drosophila melanogaster

1. The ovarian follicles of Sarcophaga and Drosophila consist of one oocyte and 15 nurse cells, the whole being surrounded by follicle cells. Although oocyte and nurse cells are genetically identical sibling cells, and although they are interconnected by cytoplasmic bridges, their physiology is very different. 2. The DNA content of the oocyte nucleus (germinal vesicle) never exceeds 4C, while values of polyploidisation up to 1024C have been measured in the nurse cells, this being dependent on their position within a follicle. 3. The nurse cell nuclei very actively synthesize RNA, while the germinal vesicle is almost completely inactive in this respect. 4. It has been possible to visualise the major cytoskeletal elements in the different ovarian cell types. Cellular markers of polarity and dorsoventral asymmetry have been described. 5. Electrophysiological measurements have been performed to find out whether or not the self-electrophoresis principle may be involved in polarised transport between nurse cells and oocyte. 6. Most of the vitellogenin is synthesized by the fat body but some follicle cells also synthesize small amounts. 7. The role of 20-OH ecdysone in the induction of vitellogenin synthesis in the fat body, as well as the presence of met-enkephalin like immunoreactivity in the gonads is well established in both species. Not so clear is the exact role of juvenile hormones and the nature of brain factors controlling ovarian development. 8. Drosophila has the advantage of its well documented genetics while the larger species Sarcophaga is preferable for the study of (electro-) physiological and cell biological mechanisms.