Elisa Bigliardi

Cell biology and invasion of the microsporidia.

Microsporidia are amitochondrial eukaryotic obligate intracellular parasites. They are reported to infect every animal group from protists to vertebrates, including humans. Microsporidia are of interest as opportunistic pathogens in humans and for certain characteristics which raise questions about their evolution and phylogenetic position. This review describes the basic biology and invasion mechanisms of microsporidian species infecting humans.

Multiple symbiosis in the leafhopper Scaphoideus titanus (Hemiptera: Cicadellidae): details of transovarial transmission of Cardinium sp. and yeast-like endosymbionts.

Scaphoideus titanus is the insect vector of flavescence dorée (FD), a yellow disease of grapevines. Observations on adult females and nymphs of S. titanus showed that this insect is associated with a complex microbial community. Ultrastructural analysis showed that the fat body, salivary glands and ovary of the insect harbour microorganisms showing the brush-like structure typically observed in the genus Cardinium. In particular, it has been shown that these symbiotic bacteria are present both in the follicular cells and in the eggs. In addition, cells resembling bacteriocytes, harbouring numerous Cardinium symbionts in the cytoplasm, were observed in the apical portion of the ovary in adult females. These cells are likely responsible for bacterial transmission to the ovary. Optical microscopy showed that the fat body harbours an enormous population of yeast-like symbionts (YLSs). Ultrastructural observations showed that these symbionts are enclosed within specialized cells of the fat body and are also present in the ovary, where they are found in both the follicular cells and the eggs. There is thus evidence that both Cardinium and the YLSs are transovarially transmitted to the offspring. To our knowledge, S. titanus is the sole insect known to transmit two different kinds of symbionts to the eggs, a prokaryote and an eukaryote. Gene sequence analysis and in situ hybridization led to the identification of YLSs as members of the class Sordariomycetes (=Pyrenomycetes). Finally, ultrastructural observation of the midgut content revealed the presence, in both adult females and nymphs, of a complex microbial community, which include a phytoplasma-like microorganism, likely the agent of FD.

Microsporidian Spore Wall: Ultrastructural Findings on Encephalitozoon hellem Exospore

A study of the spore wall of Encephalitozoon hellem was performed on thin sections, freeze‐fracture, and deep‐etched samples to obtain information on spore wall organization and composition. Our observations demonstrate that the spore wall is formed by an inner 30–35 nm electron‐lucent endospore and an outer 25–30 nm electron‐dense exospore. The exospore is a complex of three layers: an outer spiny layer, an electron‐lucent intermediate lamina and an inner fibrous layer. Freeze‐fracture and deep‐etching techniques reveal that the intermediate lamina and the inner fibrous layer result from the different spatial disposition of the same 4‐nm thick fibrils. In thin sections the endospore reveals a scattered electron‐dense material that appears in the form of trabecular structures when analyzed in deep‐etched samples. The presence of chitin in the exospore is discussed.

The spermatozoon of arthropoda XIII. The cell surface

In this paper the authors observe that the limiting membrane of the insect spermatozoon is asymmetrical. There is a “unit membrane” of the classical type, displaying an intense phosphatase activity, on the outer surface of which is a glycoprotein coat occurring in three structural patterns exhibiting progressive structural complexity. In Ceratitis and Drosophila (“fruit-fly model”), this coat is very thin and apparently amorphous; in Ctenocephalus (“flea” model), it is thicker and composed of transverse fibres; in Pezotettix and Aiolopus (the “locust” model), the coat is very thick and made up of short filaments or rodlets which are usually oriented normal to the sperm surface and grouped in tetrads with a rhomboidal arrangement.

Studies on the fine structure of the dorsal vessel of arthropods

SummaryThe heart of Aiolopus strepens (Insecta, Orthoptera) consists of a cylinder of circular muscle fibers between two sheaths of connective tissue. The muscle fibers are of the usual type found in arthropod “afibrillar” muscles, with 12 secondary filaments around each primary one. The T-system ends against the middle zone of the sarcomere forming typical dyads and triads, and a particular type of triad consisting of two elements of the T-system and one cisterna of endoplasmic reticulum. The two perimuscular layers (outer and inner) contain fibers of collagenous and elastic type embedded in a polysaccharide matrix. The collagen period is 600 Å. Amoebocytes are scattered in the inner layer of connective tissue lining the lumen of the heart.

Symbionts in the oocytes of Blattella germanica (L.) (Dictyoptera : Blattellidae): Their mode of transmission

Abstract In Blattodea, the transmission of symbionts from one generation to the next is of transovarial type. The symbionts in Blattella germanica (L.) (Dictyoptera : Blattellidae) reach the ovary inside bacteriocytes in the 5-day-old nymphal instar, and are located among the ovarioles. Between the 11th and 17th day, the symbionts leave the bacteriocytes, cross the ovariole sheath, the tunica propria, and the follicular epithelium, and reach the space between the latter and the oocyte. In 17-day-old nymphs, the symbionts are in contact with the microvilli of the oocyte, remaining in this position until the end of the vitellogenic phase, when the microvillar border is progressively reduced. At this stage, the symbionts are actively phagocytosed by the oocyte before chorion formation.

The morphogenesis of vertebrate perforatorium.

The perforatorium morphogenesis in birds and mammals spermatid evolution is described. In all cases studied by us, the perforatorium morphogenesis begins with an assembly of actin, demonstrated by HMM decoration and immunostaining with AA antibodies, which initiates with the classical nucleation granule of invertebrates, the actomere, in birds, or in an ample perinuclear area in mammals. The role played by the subacrosomal actin during spermiogenesis is discussed.

Interleukin-1 in reproductive strategies

SUMMARY Evolutionary studies on different classes of vertebrates could help clarify the role of cytokines in acceptance of the embryo by the maternal tissues. This review focuses on the cytokine interleukin‐1 (IL‐1) and reports on its presence in the female reproductive tract of species with different reproductive strategies, that is, viviparity, oviparity, and ovuliparity. Unlike oviparity and viviparity, ovuliparity does not involve any contact between paternal‐derived fetal antigens and maternal tissues, because eggs are released unfertilized in the external environment. Therefore, we consider ovuliparity a natural negative control for mechanisms of materno‐fetal immunotolerance. The goal of this review is to discuss the role of the IL‐1 system in the acquisition of the ability to retain the embryo in the female genital tract during the transition from ovuliparity to viviparity.

The interleukin 1 (IL-1) system in the uteroplacental complex of a cartilaginous fish, the smoothhound shark, Mustelus canis

Cartilaginous fish are the oldest extant jawed vertebrates and the oldest line to have placentae. Their pivotal evolutionary position makes them attractive models to investigate the mechanisms involved in the maternal-fetal interaction. This study describes the tissue expression of the cytokine interlukin-1 (IL-1) α, IL-1 β and its specific membrane receptor, IL-1 receptor type I (IL-1R tI) in a placental cartilaginous fish, the smoothhound shark, Mustelus canis. The presence of this cytokine has been reported in many mammalian placentae, as well as in the placenta of a squamate reptile and this study extends these observations to the cartilaginous fishes. The uteroplacental complex in M. canis consists of a yolk sac modified into a functional yolk sac placenta and complimentary uterine attachment sites. Immunohistochemistry for IL-1 α, IL-1 β and the receptor reveals leucocytes of both the mother and fetus to be positive, as well as the apical aspect of paraplacental cells and the apical vesicles in the umbilical cord epithelium. Yolk sac endoderm is also positive with all the stains while the ectoderm is positive only for IL-1 α. Immunoreactivity in the uterine epithelium was obtained for IL-1 α and the receptor. The egg envelope is always negative.In light of the recent finding of IL-1 β gene in a cartilaginous fish and of the high level of conservation of proteins implicated in IL-1 action, our data suggest that IL-1 system is a key mediator of the materno-fetal interaction since the oldest extant placental vertebrates.

Gap junctions between Sertoli cells in the infertile human testis.

Freeze-fracture of Bertoli cell junctions of infertile human testis revealed the presence of atypical gap junctions intercalated among the particle rows of the occluding junctions.