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Summary Biochemical and immunological studies of the membrane cytoskeleton were carried out using the entodiniomorphid ciliated protozoa: Entodinium bursa, Eudiplodinium maggii, Epidinium caudatum and Polyplastron multivesiculatum. Immunological cross-reactions within the four ciliates show significant labelling of proteins with the same or different molecular weights among species. Antigenic homologies among cytoskeletal proteins with variable MW suggest that Ophryoscolecidae have maintained both a similar architectural organization and a cytoskeletal function while diversifying the MW of many cytoskeletal proteins. A comparative study of the antigenic relationships points away from an evolutionary lineage from simplest (the ancestral Entodinium) to more complex (the intermediate Eudiplodinium and the more advanced Epidinium and then Polyplastron), and also the linear evolution based on the increasing complexity of the cytoalimentary system. It suggests a bushy evolution by radiation from unknown ancestral forms. This is supported by sequencing of the different entodiniomorphid ribosomal RNAs.

Summary We have previously reported biochemical evidence suggesting that a 58 Kd protein (p 58) is a major constituent of the membrane skeleton of the ciliated protozoan Entodinium bursa . In this study, monoclonal antibodies were produced in order to determine the distribution of p 58 in the four entodiniomorphids Entodinium bursa, Eudiplodinium maggii, Epidinium caudatum and Polyplastron multivesiculatum . Two clones, 78-116-4 and 76-12-7, were selected from a set of hybridomas obtained using either p 58 or whole proteins from cytoskeletal preparations of Eudiplodinium maggii as immunogens. Specificity tests by Western blot analysis indicate that MABs 78-116-4 and 76-12-7 both recognize p 58 in Entodinium bursa and protein ranging from 59 to 62 Kd in the three other species examined. Immunocytochemical evidence is presented which confirms that 78-116-4 and 76-12-7 antigens are located in the membrane skeleton. This suggests that the latter may represent homologous proteins implicated in the maintenance of a consistent pattern of cortical organization in the entodiniomorphid ciliates.

The microsporidian Encephalitozoon cuniculi is an obligate intracellular parasite that can cause opportunistic infections in AIDS patients. Spore invasion of host cells involves extrusion of a polar tube. After immunocytochemical identification of several polar tube proteins (PTPs) in E. cuniculi, a major PTP was isolated from two-dimensional gels and two peptide fragments were sequenced. The complete nucleotide sequence of the corresponding gene was obtained using a combination of PCR amplification and cloning techniques. The gene exists as a single copy per haploid genome and encodes an acidic proline-rich protein, with a deduced molecular mass of 37 kDa, that contains four tandemly arranged 26-amino-acid repeats. An N-terminal region of 22 residues represents a cleaved signal peptide, probably involved in the targeting of the PTP. No similarity with known proteins has been found. The protein was expressed in Escherichia coli, purified and injected into mice. The antisera reacted specifically with the polar tube in indirect immunofluorescence assays and electron microscope immunocytochemistry. Further identification of conserved and variable PTP structural motifs should be useful for diagnostic purposes and new therapeutic strategies.

Chick and Quail eggs were treated for 30 seconds, before incubation, with diluted aqueous suspension of commercial DDT. During the early stages of development, the germ cell population of treated embryos increases progressively and is only slightly lower than the control one. For each stage, the difference between the number of germ cells in controls and embryos contaminated by DDT, is not statistically significant. To exert its sterilizing effect on the germ cells, DDT must be administered before the beginning of incubation. At a later stage, when the gonocytes have colonized the gonads, the germ deficit becomes significant.

1) An ultrastructural and optical examination of the "in utero" development of the stomach in Rabbit embryos, demonstrates that the epithelium increases by"vacuolisation". The intraepithelial vacuoles, formed by a secretory process, secondarily open into the gastric cavity, whence the constitution of primary villi. Then the mesenchyme buds chorionic evaginations under the epithelial crests and transforms the primary into secondary villi. As the villi grow longer the epithelium loses its pseudostratified structure in order to become simply unistratified. At the same time, the four types of gastric cells progressively accomplish their differentiation into parietal, mucous, peptic cells and surface epithelium. 2) The presumptive gastric area of a ten-day-old Rabbit embryo corresponds to the lower third of the entomesoblastic part of the embryonic pharynx, posteriorly amputated at the umbilical edge. This presumptive area, grafted in the Chick embryo, differentiates into characteristic gastric tissue. Finally the stomach is explanted ("in vitro" and"in ovo") at different stages of ontogenesis. Up to the thirteenth day it degenerates in culture but grows and accomplishes its morphogenesis as a graft. From the fifteenth day, the cultured and grafted stomach differentiates on both morphogenetic and cytochemical planes.

The epithelio-mesenchymal relations during the gastric organogenesis of the rabbit foetus The experimental study of the epithelio-mesenchymal relations during the gastric organogenesis shows the following facts: Completely deprived of mesenchyme, the cultured or grafted isolated epithelium cannot develop. On the other hand the mesenchyme free of epithelium can survive and differentiate its muscular layer. Isolated after the 18th day, it possesses sufficient autonomy to form chorionic villi when covered only by vitelline membrane. The epithelium and the mesenchyme, dissociated by treatment with trypsin, then reassociated in culture (with or without subsequent grafting), develop identically to those of untreated controls. From the 19th day the mesenchyme shows a polarity and only the zone normally adjacent to the epithelium can form chorionic villi. The heterochronic associations of gastric epithelium and mesenchyme demonstrate the existence of two types of mesenchymal inductors: (a) a primary inductor, responsible for the epithelial morphogenesis, elaborated early in embryonic life (10th day); it acts till about the 21st day. (b) A secondary inductor, produced at a later time (15th day), provokes the epithelial cytodifferentiation; its activity is still strong at the 23rd day. These experiments again show the early competence of the epithelium to react to the two mesenchymal inductors. The presumptive gastric endoderm of the 10-day-old rabbit foetus has a developmental potential such that it can respond as well to the stimuli elaborated by a young mesenchyme as to those of an older mesenchyme.