Quantification of macrophage aggregates in the liver of Mugil cephalus.

Macrophages are involved in the recycling, storage and detoxification of cellular debris/waste products and exogenous substances their presence is quite normal. An accumulation of these cells, however, can be the sign of an alteration. A quantification of the surface area occupied by macrophage aggregates (1.3 to 21.5%) in Mugil cephalus suggests a possible environmental stress for the specimens examined.

Maturation of mosquito spermatozoa during their transit throughout the male and female reproductive systems.

The testes, seminal vesicles and spermathecae of 22 species of mosquitoes belonging to the genera Aedes, Anopheles, Culex, Mansonia and Toxorhynchites are investigated under the electron microscope. Modifications of the acrosome and sperm wall occur during the transit of the spermatozoon from the lower region of the testes to the spermathecae throughout the seminal vesicles. The origin and fate of the cell coat and the possible roles of somatic cell layers both in the testes and the seminal vesicles are discussed.

Spermatogenesis in mosquitoes (Diptera: Culicidae).

An ultrastructural study of spermatogenesis has been carried out on 18 species of mosquitoes of the Anophelinae, Culicinae and Toxorhynchitinae sub-families. In this spermatogenesis, which follows a classical way, primordial cells, primary and secondary spermatogonia, as well as primary and secondary spermatocysts are considered. We have identified 9 stages of development all along the spermiogenesis. This process ends up with the formation of a needle-like spermatozoon showing head and tail regions. After a treatment with tannic acid, the protofilaments of the axoneme of Culex tigripes are counted. For the first time we have carried out a complete study of spermatogenesis in mosquitoes.

Extracellular and intracellular rickettsia-like microorganisms in gonads of mosquitoes.

The mosquitoes Culex tigripes, C. decens and C. quinquefasciatus have been investigated by electron microscopy. An intracytoplasmic rickettsia-like microorganism is present in ovaries and testes of the three species. An extracellular form of a rickettsia-like microorganism is described in the testis of C. tigripes in which it sometimes appears in great number. The extra- and intracellular forms present ultrastructural differences. The possibility they represent two different morphotypes of the same microorganism or simply two different types is discussed. They both disappear after treatment with tetracycline. This is believed to be the first electron microscope description of extracellular rickettsia-like cells in mosquitoes.

Podophyllotoxin-induced modifications of the nuclear envelope.

In spermatids of Culex tigripes (Culicidae) the manchette is composed of numerous expansion-bearing microtubules which surround the nucleus. Under the action of podophyllotoxin, in zones where manchette microtubules are absent, the nuclear envelope bulges and forms abnormal extranuclear vesicles. We hypothesize that this newly recognized capacity of podophyllotoxin is due to its action on microtubule-membrane relationships.

Process of nuclear envelope reduction in spermiogenesis of a mosquito, Culex tigripes.

When the Culex tigripes spermatid begins to elongate, the nucleus exhibits on its surface invaginations of the nuclear envelope. These invaginations have a uniform diameter of 0.3 microns. They separate from the envelope of the nucleus and form spherical intranuclear vesicles. In the old spermatids these vesicles are imprisoned in the condensed chromatin. The spermatozoon also possesses these vesicles which are then ovoid in shape. This process of vesiculation permits the diminution of the surface of the nucleus when it decreases in volume during spermiogenesis.

Endosymbiotic relationship between a rickettsia-like microorganism and the male germ-cells of Culex tigripes.

The male mosquitoes of the species Culex tigripes possess endosymbionts localized in the cytoplasm of the germ-cells. The somatic cells of the testis do not exhibit this particularity. The spermatogonia, spermatocytes and spermatids all possess a few symbionts. They are eliminated in the residual body at the end of spermiogenesis when the spermatozoon matures. They are absent from the seminal vesicles. A few spermatocytes and spermatids show a proliferation of the endosymbionts. This seems to be associated with an abnormal spermiogenesis. These symbionts are comparable to the Wolbachia described in two other species of mosquitoes: Culex pipiens and Aedes scutellaris.

Polarity of microtubular structures in manchette-like formations: possible role of the "11th filament".

Bundles of microtubular structures appear in the cytoplasm of spermatids of the African frog Dicroglossus occipitalis. They are observed in the vicinity of axonemes. Natural tubulin polymerization leads to the formation of hooks on microtubular structures. They can be related to experimentally induced tubulin hooks. The direction of curvature of the hooks allows us to define the polarity of the bundles. This is opposite to the polarity of axonemal microtubules: Bundles and axonemes are antiparallel. Under colchicine action, arch-like microtubular structures are shown to open in the same direction as they lock. This enables us to characterize their opening and locking site: It corresponds to the place of the "11th filament" described in microtubular structures such axonemes. The "11th filament" is thus demonstrated to be the most susceptible to natural opening and to the action of colchicine in microtubular structures.

Natural degenerating mitochondria in ovarian follicles of a cyprinodontidae fish, Epiplatys spilargyreus (teleost).

This study examines the evolution of mitochondria in the follicular cells during the development of the ovarian follicle in the teleostean fish Epiplatys spilargyreus. The mitochondria are few in number until the end of previtellogenesis; their matrix is dense, and their cristae are well developed. They proliferate during vitellogenesis and then are modified by deterioration of their matrix. Multilamellar structures are organized in the vacuolized mitochondria. During postvitellogenesis, these modifications become more advanced. The mitochondria degenerate, leaving vacuoles that contain heterogeneous structures, which will be released into the intercellular spaces. At the end of these mitochondrial transformations, the follicular cells degenerate. They release the elements which will participate in forming the secondary envelope.

Demonstration of the orientation of the Cestodes spermatozoon illustrated by the ultrastructural study of spermiogenesis and the spermatozoon of a Cyclophyllidea: Thysaniezia ovilla, Rivolta, 1874.

Spermiogenesis in Thysaniezia ovilla begins with the appearance of a differentiation zone equipped with peripheral microtubules, surrounded by arched membranes and containing two parallel centrioles surrounded by electron dense granular material. One of the centrioles aborts, the other gives rise to a flagellum which quickly grows in the cytoplasmic extension in which the nucleus migrates and protein granules form. During the nuclear migration crested-like bodies appear among the peripheral microtubules in the differentiation zone. The Th. ovilla spermatozoon is filiform. One of its extremities, which we show to be anterior, exhibits two helicoidal crested-like bodies, surrounded by electron dense material resembling an acrosome. Cortical microtubules run along almost the whole length of the spermatozoon. The cytoplasm has no mitochondria and contains protein granules. The axoneme is of the 9 + '1' pattern. It stops before reaching the posterior extremity of the gamete. The nucleus is wrapped round the axoneme, in the middle region of the spermatozoon. It generally stops before reaching the posterior extremity of the flagellum. This study has enabled us to describe precisely the orientation of the spermatozoon of cestodes in general.

Morphogenesis of the secondary envelope of the oocyte in a teleostean fish of the family Cyprinodontidae: Aphyosemion splendopleure.

The follicular epithelium of the oocyte in Aphyosemion splendopleure is made up of prismatic cells in which the density of the cytoplasm is variable. At the end of vitellogenesis the follicular cells show polarity. The rough endoplasmic reticulum is localized in the cytoplasm situated between the nucleus and the basal lamina. This reticulum splits up into vesicles limited by a membrane covered with ribosomes. At the beginning of postvitellogenesis the Golgi apparatus produces numerous secretion granules in the cytoplasmic region contiguous to the surface of the oocyte. These Golgi elements, together with amorphous material whose origin we have not been able to define, form the secondary envelope of the egg. This envelope is made up of two layers: an inner layer formed by an agglomeration with a membranous aspect and a superficial layer made up of tubular elements. The superficial layer forms an ornamentation clearly shown up by scanning electron microscopy.

Evidence for nucleating microtubules in microtubular associations and for an opening polarity under colchicine action.

Bundles of microtubular structures appear in the cytoplasm of germinal cells of the African frog Dicroglossus occipitalis. They are made of several associated microtubules. Every bundle contains one normal singlet and numerous arch-shaped microtubular structures growing in all directions from the singlet wall. The walls of these microtubules are shown to contain 10 to 13 protofilaments. Attempts made with colchicine point out their susceptibility to this antimitotic drug. The formation and opening of these microtubular structures give evidence of complex organization.

The flagellar apparatus of spermatozoa in fish. Ultrastructure and evolution.

Chondrichthyes possess an evolved type of spermatozoa. Their flagellar apparatus is characterized by the presence of flagellar roots which form the axis of the midpiece, and the existence of one or two lateral elements associated with the axoneme. Osteichthyes, mainly teleosteans, show a great diversity of spermatic forms. The primitive spermatozoon with a 9 + 2 pattern flagellum is common. The primitive spermatozoon has evolved along different lines. The spermatic diversity which results from this is mainly evident in the structure of the flagellar apparatus. In the animal kingdom the primitive spermatozoon with a 9 + 2 pattern flagellum, present in primitive metazoa, is retained in phyla where external fertilization is maintained. The main evolutionary tendencies--elongation, aflagellarity or biflagellarity--are generally connected with the acquisition of internal fertilization. These evolutionary tendencies are found in teleosteans. It is not possible to link aflagellarity or biflagellarity of the gamete in certain fishes to this method of fertilization. Only the elongation of the spermatozoon is connected, in certain cases, with internal fertilization, but this cannot be taken as general.

Reinvestigation of spermatic flagella structure: the teleostean Cyprinodontidae.

The study of 7 genera and 15 species of teleostean fishes belonging to the family Cyprinodontidae shows a similar morphology of mobile spermatozoa and a wide diversity of structure of the spermatic flagellum. The flagellar membrane has one, two, or three lateral expansions depending on the species. Peripheral doublets of axonema show only the external arm, except for two species that completely lack them. Intratubular differentiations (ITD) are present in A or B tubules of peripheral doublets as in central tubules of some species, whereas others are totally devoid of them. The ITD can affect all doublets or preferentially doublets 1, 5, and 6. These variations may be due to neutral mutations.

[Giant mitochondria in the A cells of the pancreas of a lizard: Varanus niloticus]. / Mitochondries géantes dans les cellules A du pancréas d'un varan: Varanus niloticus.

Pancreatic A cells of the lizard Varanus niloticus are characterized by the presence of two types of mitochondria: (a) normal, small mitochondria (about 0.4 X 1 micron), and (b) giant mitochondria, measuring up to 9 micron in length and 1 micron in diameter. Giant mitochondria show various shapes. Their matrix is filled with tubules, filaments, and dense granules. Transverse sections of tubules are polygonal in shape and about 20 nm in diameter. They are grouped in bundles. The filaments, about 9-10 nm in diameter, are arranged in parallel layers crossing each other at a 57 degree angle. In a closely related species, Varanus exanthematicus, pancreatic A cells do not show these peculiar features.

The aflagellate spermatozoon of Diplozoon (Platyhelminthes: Monogenea: Polyopisthocotylea): a demonstrative case of relationship between sperm ultrastructure and biology of reproduction.

Diplozoon is known to display an exceptional biology of reproduction: the hermaphroditic adults are permanently fused together and their genital ducts communicate. In contrast to all other polyopisthocotylean monogeneans in which the spermatozoa show an homogeneous biflagellate structure, the spermatozoon of Diplozoon is aflagellate. It is filiform, and composed of a cytoplasmic region and a nuclear region. The cytoplasmic region exhibits mitochondria, a well-developed smooth endoplasmic reticulum, and up to 450 longitudinal singlet microtubules. The microtubules show links between them; seen in cross section, they are arranged as rows or polygons. The spermatozoon nuclear region contains the nucleus surrounded by cortical longitudinal microtubules. The spermiogenesis shows no zone of differentiation, a typical structure found in all other parasitic Platyhelminthes. Diplozoon is the first case of aflagellate spermatozoon found in the parasitic Platyhelminthes. The atypical sperm structure is not linked with phylogeny, but is well correlated with the atypical biology of reproduction.

[Crystallization of reptile hemoglobin during its digestion in a pentastomide]. / Cristallisation de l'hémoglobine d'un reptile au cours de sa digestion chez un pentastomide.

The hemoglobin of the lizard Tarentola annularis has been studied within erythrocytes being digested in the gut of a parasitic pentastomide, Raillietiella sp. The hemoglobin is crystallized in the form of bundles comprised of numerous tubules (up to 2000). These tubules are simple or complex. Simple tubules are 50 nm in diameter; their wall is made up of two electron-opaque rings, separated by a clear ring. Complex tubules are up to 100 nm in diameter and show as many as 13 concentric walls. High magnification of transverse sections of simple tubules show 96 granules; each opaque ring is made up of 48 granules. Human hemoglobin is known to crystallize as 18-nm tubules, the wall of which is made up of six molecules; comparison of these data with our observations indicates that transverse sections of tubules of crystallized lizard hemoglobin should contain 24 molecules. Thus, each molecule of crystallized lizard hemoglobin consists of four granules; these granules may be considered as globin molecules. Erythrocytes in fresh lizard blood do not show crystallized hemoglobin; however, in blood treated with sodium bisulfite, they show tubules similar to that found in the parasite.

Microtubules and macrotubules in fish meiosis.

During meiosis in the male of a cyprinodontid fish, Aphyosemion splendopleure, and during the organization of the spindle of division, the spindle is made of two types of tubules: microtubules (20-25 nm) and macrotubules (30-50 nm). The macrotubules are associated only with the polar region of the meiotic apparatus and are located outside the spindle of microtubules. At the end of meiosis, the spindle microtubules depolymerize whereas the macrotubules remain. One can find them throughout the entire process of spermiogenesis; later, they disappear only at the end of spermatid maturation. We have studied four populations from Cameroon, three of them with macrotubules.

Alterations of endocrine pancreas B cells in a sahelian reptile (Varanus exanthematicus) during starvation.

During the long starvation period (November to June) of the lizard (Varanus exanthematicus), pancreatic B cells undergo profound modification. The degeneration of beta granules observed in electron microscopy appears correlated with the diminution of the immunoreactive insulin-like content of the pancreas. The analogy between the phenomena observed here and those reported in animals treated with alloxan is discussed.