[RNA-Synthesis in telotrophic meroistic ovarioles of dysdercus intermedius DIST. (heteroptera, pyrrhoc.)]

Nurse cell-oocyte interaction in the telotrophic ovarioles of an insect, Rhodnius prolixus

Microinjection of intracellular tracers fluorescein, Procion Yellow, Lucifer Yellow and horseradish peroxidase unequivocally showed the syncytial structure of the tropharium and its interaction with the oocytes. The tropharium tip is a separate isolated compartment. Finger-like nurse cell projections comprising the syncytial tropharium interact via gap junctions along their abutting membranes and also via large cytoplasmic continuities at the central trophic core. The trophic cords connecting the tropharium to oocyte vary in diameter relative to oocyte stage. Continuity of the tropharium with the oocytes is lost at approximately 1000 micron oocyte length and the severed cords then regress from the oocyte to the tropharium base. Variation in cord diameters and timing of cord closure may account for the highly regulated sequential oocyte growth.

Insect egg cortex isolated by microsurgery: Specific protein pattern and uridine incorporation

Egg cortex material (ECM) containing the oolemma and adherent periplasm has been isolated from an insect egg by means of micromanipulation. Analysis of proteins by SDS-PAAG-electrophoresis demonstrated striking differences between the protein banding patterns of ECM and of whole eggs. ECM and whole eggs also differ clearly with respect to³H-uridine uptake; the ECM contains RNA labeled during the previtellogenetic period of oogenesis (probably in the germarium) but, in contrast to the central parts of the oocyte, is largely void of label taken up during the last stages of oogenesis.

Development and cellular differentiation of an insect telotrophic ovary (Rhodnius prolixus)

Differentiation events accompanying the larval-adult ovarian transformation in Rhodnius prolixus can be divided into three phases: proliferative phase (unfed to 3 days post-feed or DPF), early differentiation phase (9-15 DPF) and late differentiation phase (16 DPF to moult at 21 DPF). Ovarioles remain morphologically larval until feeding initiates development. The unfed ovariole contains germ cells surrounding a central trophic core region with the 'germarial lumen' occupying the basal region of the tropharium immediately above the pre-follicular tissue. Mitosis of germ cells during the proliferative phase results in a progressive increase in tropharial size with no differentiation of tissues. Regional specialization within the ovariole marks the beginning of the early differentiation phase. A zone of oocytes is established at the base of the tropharium with nuclei containing synaptonemal complexes and condensing chromosomes. Nurse cell differentiation is characterized by nucleolar elaboration and nucleo-cytoplasmic transport, the cytoplasm becoming rich in ribosomes. Autoradiographic results suggest that functional nurse cell-oocyte divergence occurs concurrently with morphological divergence. Pre-follicular tissue is divided into apical and basal zones with apical zone differentiation occurring during early and late differentiation phases.

Amatoxins, phallotoxins, phallolysin, and antamanide: the biologically active components of poisonous Amanita mushrooms

This review gives a comprehensive account of the molecular toxicology of the bicyclic peptides obtained from the poisonous mushrooms of the genus Amanita. The discussion of the biochemical events will be preceded by a consideration of the chemistry of the toxic peptides. The structural features essential for biological activities of both the amatoxins and the phallotoxins will be discussed, also including the most important analytical data. Similar consideration will be given to antamanide, a cyclic peptide, which counteracts phalloidin. In addition, the phallolysins, three cytolytic proteins from Amanita phalloides will be discussed. The report on the biological activity of the amatoxins will deal with the sensitivity of the different RNA-polymerases towards the toxins and with their action on various cell types. Consideration will also be given to systems in which alpha-amanitin was used and can be used as a molecular tool; in the past, many investigators used the inhibitor in molecular biology, genetics, and even in physiological research. As for the phallotoxins, discussion of the affinity of these toxins for actin is provied. Further discussion attempts to understand the course of intoxication by filling in the gap between the first molecular event, formation of microfilaments, and the various lesions in hepatocytes during the intoxication.

Separation of isolated cell nuclei of tissues of the meal moth, Ephestia kuehniella Z. by metrizamide density gradient centrifugation

The behaviour of isolated cell nuclei of different tissues in the mediterranean meal moth has been studied in metrizamide density gradients to find whether differences exist in the bouyant density between nuclei derived from different specialized tissues. The different nuclei studied have buoyant densities ranging form 1.228-1.295 g/cm3 in metrizamide density gradients and clear differences exist between different populations of nuclei. The different buoyant densities make it possible to separate isolated nuclei from a heterogeneous population of nuclei according to their characteristic densities. This has been tested by the separation of silk gland nuclei from follicle cell nuclei by the density centrifugation method. The degree of polyploidy of the nuclei is not correlated to a decrease or increase of the buoyant density, which suggests that different amounts of nuclear proteins, ribonucleoproteins or RNA are responsible for the differences determined. These tissue-specific differences of the nuclear densities might be correlated to different transcriptional activities. In addition to this, the isopycnic sedimentation technique in metrizamide density gradient provides a method to purify nuclei very carefully without any visible alteration of their morphology and integrity.

Autoradiography ofCoelopa frigida (Diptera) embryos, after labeling with3H-uridine during various phases of oogenesis

The distribution of tritiated (³H) uridine or its derivatives in embryos of the kelp flyCoelopa frigida is analyzed by autoradiography. The radioactive label is introduced into the growing oocyte, after injectio into females at different time periods post eclosion. The majority of the label remains in the cytoplasm for the entire embryonic development and is presumably incorporated into stable RNA. Only when the precursor is injected toward the final stages of oogenesis, can presence of label be detected in the nuclei, for a short time period during the blastodern stage. Since no preferential location in nucleoli is found, it appears possible that labeled cytidine could have been derived from the original precursor which would be available for incorporation into DNA.

Independent replication of the ribosomal RNA genes in the polytrophic-meroistic ovaries of Calliphora erythrocephala, Drosophila hydei, and Sarcophaga barbata

By filter saturation hybridizations the ribosomal (r)DNA contents of the ovaries Calliphora erythrocephala, Drosophila hydei, and Sarcophaga barbata have been measured in comparison to the rDNA percentages of their diploid brains. The measurements of the ovarian rDNA have been carried out on ovaries where the nurse cells in the distal egg chamber of the ovarioles had reached their highest ploidy level. The diploid rDNA content of each of the respective species was chosen as a 100% standard and the rDNA amounts of the ovaries were related to this 100% level. The results show that the ovaries of C. erythrocephala contain 135% rDNA whereas the rDNA contents in the ovaries of D. hydei and S. barbata are only 51% and 47%, respectively. Measurements carried out on isolated nuclei of the nurse cells and follicle cells in D. hydei show that both have a reduced rDNA content in comparison to the brains (45% and 70%, respectively). The data are discussed in relation to the problem of an rDNA amplification in the germ cells and an rDNA underreplication in polyploid nuclei.

[Development of prospective diapause-germs (Bombyx mori L.)in vitro without dormancy : III. Their competence and interference inLYS-media, without extraembryonic storage material]

In a foreign protein medium (LTS), naked prospective diapause-germs have a tendency to develop into fully segmented germ bands (stage of dormancy): however, deposition of chorion, serosa or yolk will stimulate themvia the medium to pass through organogenesis without delay (non-dormancy =Nd). The question remained if a germ from a non-diapausing egg would stimulate the uninterrupted development of such a test-germ (Tk). Using 2 different or 2 to 3 equal germs as well asTk alone (control) in hanging drops, experimental evidence was obtained permitting conclusions not only as to the competence and sensitivity of the embryonic reaction system, but also as to factors of the extraembryonicNd-action systems in eggs with and without predetermined diapause regulatory mechanism. 1. Control explants (1 prospective diapause-Tk inLYS) have aNd-level of 10% (= average ofNd-rates in operative stages). This difference from former controls (0%Nd) can be explained by the longer operative procedure in the cups when several test-germs were used. Seven minutes after opening an egg one can reckon on aNd-stimulationvia LYS medium from egg-residues in the operation cup. While transfering the test-germs, yolk-derived substances related to theNd-stimulation can be brought into the hanging drop. The difference betweenNd-controls and the results ofNd-stimulation have to be statistically significant. 2. In experiments with two different germs in LYS-droplets no influence of a non-diapause germ (polyvoltine) on a prospective diapause germ (univoltine) could be noted. Accordingly, the naturally prospectiveNd-germs, have a tendency to develop to dormant germs only, as do the 2Tk and 1Tk controls. In combination with artificially prospectiveNd-germs (univoltine, HCl-treated) no stimulation of the test germ occcurs; nor after explantation with an older germ-band or a young embryo. 3. Combination with two prospective diapause germs of equal age in a drop, having the same minor contamination ofNd-factors in the operation-cup, will result in a threefold increase of theNd-level as compared to the 1Tk-controls. The competence of the embryonic reaction system ranges from a coatlike germ-anlage to a germ with thoracic segmentation. In the dish-like germ-anlage at diapause onsetin ovo maximalNd-rate (70%) is foundin vitro, i.e. highest sensibility towardsNd-stimulatory factors. Also at this operative stage, bothTk of a drop, most frequently developed beyond the dormancy stage. 4. Experiments with three prospective diapause germs of equal age in a drop, having the same minor contamination ofNd-factors in the operation-cup, show a sevenfold increase of theNd-level as compared to controls, showing an almost similar stage-range in competence and stage-specificity in sensibility. The increase of theNd-stimulation rate in relation with the number of test germs in the drop corresponds to a morphogenetic crowding-effect, the influence of the test germs on each other being called "interference". 5. Experiments with LYS-media which was slightly contaminated with bacteria and then refiltered had a 42%Nd-level in the 1Tk experiments. This significant difference from the 10% control level can be related to a sensitivity increasing factor or to aNd-stimulating "masterkey"-effect of the bacterial products in addition to the yolk factors already present. The 65%Nd-level in the 2Tk experiments clearly indicates "interference". 6. Interference was also shown inexperiments with artificially prospective non-diapause germ of the same age. Test-germs isolated immediately after the HCl-treatment had a very highNd-rate (78% in 2Tk and 100% in 3Tk). Interference also occurred in germ-bands that were removed at a later stage, i.e.in ovo prior to organogenesis (2Tk, 60%Nd-rate instead of 1Tk, 20%Nd-rate). Consequently, interference may be caused by a factor promoting an overall increase of tissue activity. 7. Critical evaluation of the methods and discussion of the resultsin vitro permit the following conclusions as to the developmentin ovo. Up to organogenesis, the continuous development of the germ-anlage (non-dormancy), is stimulated by an extra-embryonic system. In particular, the yolk-cell system contains factors, without which all germ-bands (including nondiapausal eggs fromBombyx and presumably other insect eggs) can only pass autonomously through the already programmed and/or determined gastrulation and segmentation. In pre-determined egg-diapause, an extra-embryonic dormancy regulatory mechanism inactivates thisNd-action system. Maternal hormonal depots may influence the continuous stimulation of cell division and the information-transfer for the programming of organogenesis. The activation of enzyme-systems inNd-stimulation can be imitatedin vitro by bacterial contamination and by interference from test germs of the same age, and may be appear as increased sensibility of the test germs.