Immunolocalization of HSP 70-related proteins constitutively expressed during Xenopus laevis oogenesis and development

Using immunocytochemical and biochemical methods, we analyzed the localization of HSP 70-related proteins constitutively expressed during oogenesis and embryogenesis in the amphibian Xenopus laevis. Our results provided evidence for a regional localization in oocytes. In embryos, the regional distribution observed in oocytes was found to be maintained from fertilization up to late blastula. It is noteworthy that, at the beginning of gastrulation, nuclear transfer of such proteins had already occurred by the time of internalization in the involuting marginal zone (IMZ), whereas cells of the vegetal area exhibited only a perinuclear localization of these proteins. These results suggest that HSP 70-related proteins might be involved in the control of the process of cellular internalization.

Comparison between in vivo and in vitro heat-induced changes in amphibian lampbrush chromosomes

At normal breeding temperature (20 degrees C), amphibian lampbrush chromosomes are characterized by the presence of lateral loops which are related to the transcriptional process. Heat treatment induces changes in these loops, but the nature and timing of these modifications depend on hyperthermic stress conditions. Indeed, our data demonstrate that, at the same high temperature (34 degrees C), lampbrush chromosome modifications induced by in vivo and in vitro gradual heat treatments are different from those induced by in vitro heat shock. In vivo and in vitro heat treatments lead to progressive disorganization of landmark loops, whereas in vitro heat shock results in chromosome condensation. The progressive adaptation of lampbrush chromosome structure in response to gradual heat stress is considered and discussed.

Chromosomes of amphibian oocytes as a model for gene expression: significance of lampbrush loops

Amphibian lampbrush chromosome loops exhibit morphological variability in their RNP matrix. The biological significance of such variability remains unknown. In order to approach this problem, the structural organization of each RNP matrix type was analyzed in relation to transcriptional and post-transcriptional processes. First, autoradiographic and transcription inhibition studies in conjunction with macromolecular spread analysis revealed a particular transcription pattern in the most typical loops, i.e. the globular loops. This pattern was characterized by asynchronous variations in RNA synthesis in the different transcription units present in a given loop. Second, morphological and experimental studies provided evidence that the typical morphologies of different RNP matrices were interconvertible and that the differences between the different RNP matrices resulted from various degrees of tightness in packaging of transcription products. In particular, analysis of thermic-shock-induced changes in the structure of lampbrush chromosomes enabled us to visualize the progressive disorganization of dense RNP matrices into globular, granular and normal matrices. Furthermore, these studies suggested that changes in post-transcriptional processes might play a determining role in the specific morphology of the loops. In particular, the kinetics of each of these different processes, related to one another and/or proteins specific to one or another of these processes, might determine the morphological appearance of the loops. The immunological approach revealed that specific nuclear proteins might therefore interfere with each of these processes. Third, the problem of a possible relationship between the specific morphologies of lateral loops and the expression of particular DNA sequences was approached at the molecular level.

Effects of in vivo heat treatment on lampbrush chromosome structure in amphibian oocytes

When Pleurodeles (Amphibian, Urodele) females were subjected to high temperatures (32-35 degrees C) for varying periods of time (45 min to 7 days), lampbrush chromosome structure underwent striking modifications. These changes included a numerical reduction in normal loops and progressive disorganization of RNP matrices of various loops. The degree of such disorganization was a function of the intensity and duration of the stress. These modifications were completely reversible when females or oocytes were returned to a normal breeding temperature (20 degrees C). Results are discussed in comparison with previous studies on morphological changes induced by heat shock in lampbrush chromosomes carried out in vitro.

[Protein composition of the hemolymph of Biomphalaria glabrata (Mollusca, Gastropoda). Influence of the method of sampling and relation to the protein composition of different organs]

The blood composition of B. glabrata is analyzed by electrophoresis. Its proteic composition differs in relation with the blood sampling method. Most of the supplementary fractions also have been found in the gut, some proteins possibly come from the hepatopancreas, whereas others could have their origin in the albumen gland. The sampling method must be selected according to these observations.

[Host-parasite relation between Carcinus mediterraneus and Sacculina carcini; immunochemical analysis and demonstration of antisacculin precipitin]

The hemolymph from both healthy and parasitised Carcinus mediterraneus are immunochemically analysed. The study confirms the presence in the blood of the infested Crab of a supplementary fraction which was already observed by electrophorsis. Moreover, some infested Crabs develop an anti sacculin precipitin reaction, not visible on healthy animals. The relations between these proteic fractions are discussed.

[Protein composition of hemolymph from the crabs Carcinus mediterraneus Czerniavsky, healthy or parasitized by Sacculina carcini Thompson]

The proteic composition of haemolymph from C. mediterraneus varies during the intermoult cycle. Some proteic fractions are occasionally absent in post-ecdysis. At each intermoult stage, parasitized Crabs have generally the same protein pattern as healthy ones, but the presence of the observed fractions is not constant. Compared healthy Crabs, the sacculinized animals show a surnumerary proteic fraction. With very short delay, the injection of ecdysterone puts the proteic composition of haemolymph from sacculinized Crabs in order, this composition becomes comparable to that from healthy individuals.