Differences of microvascular endothelium in the bovine corpus luterum of pregnancy and the corpus luteum of the estrous cycle

Summary— The purpose of the present study was to investigate potential modulations of endothelial cells of the bovine corpus luteum (CL) during pregnancy. Luteal endothelia of pregnant and non-pregnant cows were isolated and purity of cultures was verified by flow cytometric quantification of three independent endothelial markers (von Willebrand factor, angiotensin converting enzyme, Bandeiraea simplicifolia agglutinin I ligands). Different cellular parameters including light and electron microscopical investigation of morphology and growth characteristics as well as quantification of cellular lectin binding sites were compared. Extensive heterogeneity between luteal endothelial cells in pregnant and non-pregnant animals could be demonstrated, reflected in functional attributes like angiogenic activity, ultrastructural characteristics and the quantitative expression of cellular carbohydrates. Two different morphological types of cells (‘cobblestone growth pattern’ and ‘arcuate growth pattern’) were isolated from the CL of pregnancy as well as from the cyclic CL. Spontaneous angiogenic activities, including cellular migration in band-like structures and formation of ring-like structures, were observed in endothelial cells isolated from the CL of pregnant cows exclusively. This strongly suggests that microvascular luteal endothelium of pregnant animals, in contrast to the one of non-pregnant animals, is able to produce quantitatively and/or qualitatively specific angiogenesis factor(s). Heterogeneity between luteal endothelial cells in the pregnant and non-pregnant animal could also be demonstrated by quantification of lectin (Bandeiraea simplicifolia agglutinin I, concanavalin A, Dolichos biflorus agglutinin, Ulex europaeus agglutinin I, wheat germ agglutinin) binding sites: quantitative expression of specific endothelial cell surface carbohydrates could be correlated to be status of pregnancy, thus emphasizing the actual need of quantification of lectin binding.     

Ultrastructural study of the epithelial mucous cells in lizards (Lacertilia)

Summary An ultrastructural study of the mucous cells of the intestinal epithelium of four lacertilian species (Lacerta lepida, Lacerta hispanica, Psammodromus algirus and Acanthodactylus erythrurus) is here reported. Two types of mucous cells have been found in these species: common mucous cells and granular mucous cells. Immature and mature forms of both types have been observed. The common mucous cells or typical goblet cells have the same characteristics in all four species. The granules of the granular mucous cells of the two species of Lacerta are similar but differ from those of the other two species.     

Characterization of bovine immortalized luteal endothelial cells: action of cytokines on production and content of arachidonic acid metabolites

Background  

The interactions between luteal, vascular endothelial, immune cells and its products: steroids, peptide hormones, prostaglandins (PGs), growth factors and cytokines play a pivotal role in the regulation of corpus luteum (CL) function. Luteal endothelial cells undergo many dynamic morphological changes and their action is regulated by cytokines. The aims are: (1) to establish in vitro model for bovine luteal endothelial cells examination; (2) to study the effect of cytokines: tumor necrosis factor alpha (TNFalpha) and interferon gamma (IFNgamma) on cell viability, leukotrienes (LTs) and PG synthases, and endothelin-1 (EDN-1) mRNA, protein expression and their secretion in bovine immortalized luteal endothelial (EnCL-1) cells.     

Neurosecretion in the basommatophoran snail Bulinus truncatus (Gastropoda,Pulmonata)

Summary The neurosecretory system of the freshwater snail Bulinus truncatus was investigated. With the Alcian blue-Alcian yellow (AB/AY) staining method at least 10 different types of neurosecretory cells (NSC) were distinguished in the ganglia of the central nervous system. The differences in staining properties of the NSC — with AB/AY the cells take on different shades of green and yellow — are borne out at the ultrastructural level: the NSC types contain different types of neurosecretory elementary granules.The neurosecretory system of B. truncatus is compared to that of Lymnaea stagnalis, the species which has received the most attention among the pulmonates. It appears from the comparison that the systems of both species show many similarities, although some differences are also apparent.     

On the Organization and Affinities of the Amoeba,Pompholyxophrys punicea Archer,Based on Ultrastructural Examination of Individual Cells from Wild Material1

The genus Pompholyxophrys includes amoebae which have a spherical body, fine radiating pseudopodia, and a layer of adhering siliceous “perles.” These organisms are normally regarded as a type of heliozoon. Ultrastructural examination of P. punicea reveals that those characters associated with well characterized heliozoa, such as microtubular axonemes and extrusomes, are lacking. The species has much in common with nucleariid filose amoebae with which it, and the related genus Pinaciophora, are regarded as having affinities. The species P. punicea is rare, and this study was made possible by the application of techniques developed for the ultrastructural examination of single cells. The assessment of protistan diversity and interrelationships relies heavily on the use of ultrastructural characters. Although techniques that are based on the examination of a small number of individual cells have limitations, they do allow rare organisms to be included in the re-evaluation of protistan systematics.     

The ultrastructure of the symbionts ofRhizocarpon geographicum,Parmelia conspersa andUmbilicaria pustulata growing under dryness conditions

Summary The dryness-induced ultrastructural changes of both myco- and phycobiont of three lichen species (R. geographicum, P. conspersa, andU. pustulata) have been studied over three months and half, period of time. During this time other ecological factors, such as rock substratum, temperature, light and gas interchange were unaltered compared to the natural conditions. A large number of ultrastructural changes were observed in the mycobiont as well as in the phycobiont (Trebouxia) and often, cells showed a highly disorganized morphology. The most important ultrastructural modifications were: 1. pyrenoglobuli of the algae were peripheral, 2. new and unknown structures were observed in the phycobionts of bothR. geographicum andU. pustulata as well as in the mycobiont of the latter species.     

A new type of 3‐D peripheral ultrastructure in Glaucocystis (Glaucocystales,Glaucophyta) as revealed by ultra‐high voltage electron microscopy

The coccoid glaucophyte genus Glaucocystis is characterized by having a thick cell wall, which has to date prohibited examination of the native ultrastructural features of the protoplast periphery. Recently, however, the three‐dimensional (3‐D) ultrastructure of the protoplast periphery was revealed in two divergent Glaucocystis species, with the world's most powerful ultra‐high voltage electron microscope (UHVEM). The two species exhibit morphological diversity in terms of their 3‐D ultrastructural features. However, these two types do not seem to encompass actual ultrastructural diversity in the genetically diverse genus Glaucocystis. Here, we report a new type of peripheral 3‐D ultrastructure resolved in “G. incrassata” SAG 229‐2 cells by 3‐D modeling based on UHVEM tomography using high‐pressure freezing and freeze‐substitution fixation. The plasma membrane and underlying flattened vesicles in “G. incrassata” SAG 229‐2 exhibited grooves at intervals of 200–600 nm, and the flattened vesicles often overlapped one another at the protoplast periphery. This 3‐D ultrastructure differs from those of the two types previously reported in other species of Glaucocystis. The possibility of classification of Glaucocystis species based on the 3‐D ultrastructure of the protoplast periphery is discussed.     

Destruction of Pigments and Ultrastructural Changes in Cyanobacteria during Photodamage

Sequential stages of pigment degradation and ultrastructural changes were examined in cyanobacteria Anabaena variabilis ATCC 29413, Synechococcus sp. PCC 6301 (Anacystis nidulans) and S. elongatus B-267 during irradiation of cell suspensions with high-intensity light. Early manifestations of photooxidative destruction were evident as profound changes in ultrastructure of thylakoids; in A. variabilis these changes appeared even before bleaching of pigments. Concomitant to these alterations, the cytoplasmic matrix turned homogenous and the nucleoid was subject to degradation, while ultrastructural changes of cytoplasmic membrane and cell walls became evident in some species. In A. variabilis these changes were related to a subsequent autolysis of cells. Synechococcus strains demonstrated comparatively high resistance to irradiation. The experimental data were compared with previously described behavior of the same species of cyanobacteria cultured under photooxidative conditions. This comparison revealed principal similarity and species-specific features in the destructive changes of thylakoids and other cell components of cyanobacterial cells.     

Influence of nitrogen stress on Isochrysis galbana strain U4, a candidate for biodiesel production

Lipid accumulation has been investigated in numerous microalgal species to assess their potential with respect to biodiesel production. The present work determines the effect of nitrogen stress on physiological and ultrastructural changes in Isochrysis galbana U4. This study is unique in showing the correlations between growth, lipid production, pigmentation and ultrastructural changes in Isochrysis cells undergoing nitrogen starvation. The continuation of algal growth after the complete depletion of external nitrogen was shown to be supported by internal nitrogen stores, possibly in the pyrenoid. Cell growth ceased and lipid accumulation was initiated after the internal store of nitrogen had become exhausted. The depletion of intracellular nitrogen reservoirs to critical thresholds initiated the onset of the stationary phase, a decline in chlorophyll content and the initiation of lipid and carotenoid accumulation. The most notable ultrastructural changes, upon nitrogen stress, were the accumulation of plastidial and cytoplasmic lipid bodies and the dismantling of the chloroplast. The size of the pyrenoid when external nitrogen became depleted was found to decrease significantly, up to four‐fold. This was attributed to the remobilization of nitrogen from Rubisco. The level of expression of heterochromatin was found to increase when cells were nitrogen starved. This is thought to favor long‐term dormancy in this species because aging cells have been noted to recover rapidly when returned to conditions favorable for growth. The observations of this study are consistent with the hypothesis that the responses of Isochrysis cells to nitrogen starvation are regulated by the internal reserves of nitrogen, and the depletion of these reserves is an important trigger for lipid accumulation in this species. The findings of this study also indicate that Isochrysis galbana U4 is a promising candidate for biodiesel lipid production.     

Haemoglobin producing cells in freshwater snails

Summary One of the cell types occurring in the connective tissue of gastropods and bivalves is thepore cell. Cells of this type have a characteristic morphology in that their plasmamembrane has many invaginations bridged by cytoplasmic tongues. In the well developed granular endoplasmic reticulum and in these invaginations fine granular material, sometimes arranged in crystalline patterns, is present. InLymnaea stagnalis this material has been identified as haemocyanin on a morphological basis. Histochemical and ultrastructural results on pore cells of 2 snail species(Biomphalaria glabrata, Planorbarius corneus) having haemoglobin in their blood indicate that the pore cells in these species synthesize haemoglobin. Possible other functions of pore cells are briefly discussed.     

Taxonomic studies on the Chlorarachniophyta. II. Generic delimitation of the chlorarachniophytes and description of Gymnochlora stellata gen. et sp. nov. and Lotharella gen. nov.

A new chlorarachniophytan alga, Gymnochlora stellata Ishida et Y. Hara gen. et sp. nov., has been isolated from Anae Island in Guam. It is a green, star-shaped, unicellular, amoeboid organism with several filopodia that do not form a reticulopodial network. Neither zoospores nor walled coccoid cells have been observed throughout the life cycle. The chloroplast ultrastructure is similar to those of described species; however, the pyrenoid matrix, which is invaded by many tubular structures originating from the inner membrane of the chloroplast envelope, is unique. A classification system is proposed for the Chlorarachniophyta. In this system, the ultrastructural features of the pyrenoid and the location of the nucleomorph in the periplastidial compartment are used as generic criteria, while the morphological features of the vegetative cells and life cycle patterns are used for species criteria. The described species, except for Cryptochlora perforans Calderon-Saenz et Schnetter, are also reassessed under the new system, and consequent nomenclatural requirements for the genus Chlorarachnion are dealt with in this paper. The taxonomic rank of a previously described species, Chlorarachnion globosum Ishida et Y. Hara, is elevated and Lotharella globosa (Ishida et Y. Hara) Ishida et Y. Hara gen. nov. et comb. nov. is proposed.     

Peptidergic cells in the mammalian pineal gland. Morphological indications for a paracrine regulation of the pinealocyte

Several neuropeptides are present in the mammalian pineal gland. Most of these peptides, eg neuropeptide Y, vasoactive intestinal peptide, and peptide histidine isoleucine, are located in nerve fibres innervating the gland. In some mammalian species, neuropeptides are also found in cells scattered in the pineal parenchyma. In the rat, bipolar cells immunoreactive for somatostatin are present, just as cells containing mRNA encoding somatostatin can be detected in the gland by in situ hybridisation. In the pineal gland of the European hamster, many cells are immunoreactive for enkephalin. Ultrastructural cytochemical analysis of these cells reveals a pinealocyte morphology. Processes from the opioidergic pinealocytes terminate in the parenchyma between the non-immunoreactive pinealocytes. Some of the processes contain small clear and large dense core vesicles and end in club shaped swellings which make synapse-like contacts with other pinealocytes. The ultrastructural morphology suggests that the opioidergic cells exert a paracrine regulation on other pinealocytes.     

Antimicrobial effects of Cellvibrio on blue-green algae

Summary The culture fluids from two Cellvibrio strains, in the stationary phase of growth, are shown to contain heat-resistant, low molecular weight substances with antibiotic-like effects on blue-green algae. Morphological changes and lysis of cells were observed in various species of blue-green algae; ultrastructural changes were noted in the cell walls of growing vegetative cells of Anabaena inaequalis. The viability of resting cells, including heterocysts and akinetes was not affected.     

NEW TAXONOMIC CRITERIA IN CLASSIFICATION OF CHLOROCOCCUM SPECIES. II. PYRENOID FINE STRUCTURE2

The pyrenoids of 18 Chlorococcum species (including 3 now transferred to Tetracystis) have been investigated at the ultrastructural level. Three categories of pyrenoids were observed, including pyrenoids with unfragmented perforate starch plates in 11 species; those with many separate fragmented starch plates in 6 species; and those with hemispherical starch plates in 1 species. Pyrenoids were further distinguishable on the basis of the number of thylakoid disks or tubules which penetrate the ground substance. Stability and diversity of pyrenoid fine structure as a taxonomic criterion at the specific level have been demonstrated.     

Ultrastructural study of spermatogenesis in silver salmon Oncorhynchus kisutch and cherry salmon O. masou (Salmonidae, Teleostei)

Spermatogenesis in silver salmon Oncorhynchus kisutch and cherry salmon O. masou was studied by transmission electron microscopy. The spermatogenic cells of both species have been shown to have no considerable differences in their dimensional and ultrastructural parameters. The characteristic peculiarity of spermatogonia was the presence of a germ determinant substance, which is the cytoplasmic marker of sex line cells. The primary and secondary spermatocytes, as well as early spermatids, were arranged in gonads as cell clusters at the same stage of development. In spermiogenesis, the regular appearance of the electron-lucent vesicle was observed, which forms a structural complex with the apical condensation of the nuclear membrane. This complex is morphologically similar to the not-yet-formed spermatid acrosomes in many Metazoa and is referred to by the authors as an acrosome-like structure (AS). At the final stage of spermiogenesis, the disappearance of an AS allows one to considering it to be a temporarily existing structure that recapitulates the ancestral morphotype of salmonid sperm. Spermatozoa of the both species are typical, primitive, acrosome-lacking cells, which are characteristic of many representatives of Teleostei that have external insemination.     

Inside an enigma: do mitochondria contribute to cell death in Drosophila?

Mitochondria have been shown to play an important role in cell death in mammalian cells. However, the importance of mitochondria in Drosophila apoptosis is still under investigation. Many proteins involved in the regulation of apoptosis in mammals act at mitochondria or are released from mitochondria, resulting in caspase activation. In addition, these organelles undergo significant ultrastructural changes during apoptosis. This review highlights similarities and differences in the roles of mitochondria and mitochondrial factors in apoptosis between Drosophila and mammals. In Drosophila, many key regulators of apoptosis also appear to localize to this organelle, which also undergoes ultrastructural changes during apoptosis. Although many of the proteins important for the control of apoptosis in mammalian cells are conserved in Drosophila, the role that mitochondria play in apoptosis in this model system remains an area of controversy and active research.     

A scanning electron microscopic study of the luteo-follicular complex

Summary As observed by SEM, the repair of an ovulated mammalian follicle is accompanied by a sequence of morphogenetic processes. In the initial phase, a mass of cells and coagulated fluids forms at the site of rupture. Shortly thereafter, connective cells, recruited from the adjacent and subjacent connective tissue stroma begin to proliferate and to migrate over this mass such that in the rabbit, the entire site of disruption is covered by a layer of connective cells by approximately 2 days following ovulation. Coincident with the migration of the connective tissue, superficial cells from undisturbed lateral and basal areas of an ovulated follicle also proliferate and begin to migrate over the newly established connective tissue matrix. By approximately 4 days following ovulation in the rabbit, the surface of an ovulated follicle is repopulated by elements of the superficial epithelium. The formation of the underlying corpus luteum (corpora luted) involves characteristic morphological changes as granulosa cells transform into steroid secreting luteal cells. The luteal cells become organized into cords of cells which usually surround capillary vessels. When examined by SEM, the smooth-surfaced endoplasmic reticulum of the luteal cell is quite apparent and is observed to form a three-dimension network of anastomosing tubules which are continuous with the nuclear membrane. Variations in the appearance of the surface of the ovary which directly overlies corpora lutea were observed when the mouse, rat and rabbit were compared. The regression of corpora lutea involves the infiltration of the luteal mass by connective tissue and both degeneration and vacuolization of the luteal cells. The regressing corpus luteum is a honey-comb-like structure in which each space is occupied by a degenerating luteal cell.This work was supported by grants from the National Institutes of Health, Public Health Service (to J.V.B., no. HD-04274), and from Consiglio Nationale delle Ricerche (C.N.R., contracts nos. CT 76.01288.04 and CT 77.01921.4)