Spermatozoa and Spermatogenesis in the Ribbon Worm Asteronemertes gibsoni (Hoplonemertea, Oerstediidae), a Symbiont of Sea Stars.

In the phylum Nemertea, the class Hoplonemertea (former Enopla) comprises the largest number of studied species with complex spermatozoa. Asteronemertes gibsoni Chernyshev, 1991, a nemertean species having a symbiotic relationship with sea stars, is characterized by complex filiform spermatozoa. Here, spermatogenesis and spermatozoon structure in A.

Microscopic anatomy of gonadal area in the deep-sea clam Calyptogena pacifica (Bivalvia: Vesicomyidae) with emphasis on somatic cells.

Somatic cells in the gonadal area of male and female deep-sea clams, Calyptogena pacifica, were examined using light and transmission electron microscopy. Acini both at the pre-spawning stage and at the stage of active spermatogenesis were observed to be simultaneously present in sections through a male gonad. Oocytes of various degrees of maturity were simultaneously present in female acini.

Ultrastructural aspects of spermatogenesis in Calyptogena pacifica Dall 1891 (Vesicomyidae; Bivalvia).

The process of spermatogenesis and spermatozoon morphology was characterized from a deep-sea bivalve, Calyptogena pacifica (Vesicomyidae, Pliocardiinae), a member of the superfamily Glossoidea, using light and electron microscopy. Spermatogenesis in C. pacifica is generally similar to that in shallow-water bivalves but, the development of spermatogenic cells in this species has also some distinguishing features.

Integrated assessment of the acclimation capacity of the marine bivalve Crenomytilus grayanus under naturally highly contaminated conditions: Subcellular distribution of trace metals and structural alterations of nephrocytes.

The aim of our work was to assess whether the cellular processes in the nephrocytes of the long-lived mussel Crenomytilus grayanus tend to acclimation or destruction under trace metal contamination. Mussels were collected from three sites in the north-western Pacific Ocean: reference site, upwelling site, and a site highly contaminated with trace metals. Concentration, subcellular distribution of trace metals (Cd, Cu, Zn, and Pb) in the mussel kidneys, and ultrastructural alterations of the nephrocytes were studied.

Spermatozoa ultrastructure of two basal pilidiophoran nemerteans, Hubrechtella juliae and Sonnenemertes cantelli (Nemertea, Pilidiophora).

Nemertea is a phylum of worms with a simple internal morphology; nemerteans' spermatozoon morphology can be used for their classification and phylogenetic analyses. The aim of the present study was to describe spermatozoa of the nemerteans Hubrechtella juliae and Sonnenemertes cantelli from the basal groups of the class Pilidiophora at the ultrastructure level. Both species have primitive ('compact-head' sensu Stricker and Folsom, 1998) spermatozoa with ovoid head and five mitochondria in the midpiece, but differ in the structure of acrosomal complex: in Hubrechtella juliae, the single lens-shaped acrosomal vesicle contains an area of moderate electron density not enclosed by a separate membrane; in Sonnenemertes cantelli, the acrosome shows a unique morphology and contains a few electron-dense vesicles with irregular shapes and positions and one more electron-lucent elongated vesicle.

Autophagy in nutrient storage cells of the Pacific oyster, Crassostrea gigas.

In oysters, nutrients are stored in a special type of cells referred to as vesicular-connective tissue cells (VCT-cells). These cells accumulate and provide nutrient to satisfy various needs of the organism, including gametogenesis. During the annual reproductive cycle, VCT-cells pass through a series of changes in their morphology associated with nutrients mobilization for developing germ cells.

Peripheral sensory neurons govern development of the nervous system in bivalve larvae.

Recent findings regarding early lophotrochozoan development have altered the conventional model of neurogenesis and revealed that peripheral sensory elements play a key role in the initial organization of the larval nervous system. Here, we describe the main neurogenetic events in bivalve mollusks in comparison with other Lophotrochozoa, emphasizing a novel role for early neurons in establishing larval nervous systems and speculating about the morphogenetic function of the apical organ. We demonstrate that during bivalve development, peripheral sensory neurons utilizing various transmitters differentiate before the apical organ emerges.

Macroautophagy is involved in residual bodies formation during spermatogenesis in sea urchins, Strongylocentrotus intermedius.

An ultrastructural study of developing spermatids in sea urchins, Strongylocentrotus intermedius, showed that macroautophagy is involved in formation of residual bodies and removal of excessive cytoplasm by spermatids during spermatogenesis in this species. During late stages of spermatogenesis spermatids sequester excessive cytoplasm into vesicles, surrounded by a double membrane. Subsequently, these vesicles fused to one another into larger vacuoles, up to 1.

Morphology of nutrient storage cells in the gonadal area of the Pacific oyster, Crassostrea gigas (Thunberg, 1793).

Successful gametogenesis in invertebrates is tightly associated with functioning of specific nutrient-storing cells. In oysters, cells of vesicular connective tissue (VCT-cells), also referred to as storage cells, which form a meshwork around gonadal acini, are the major population of cells that accumulate and provide nutrients for developing gametes. During the annual reproductive cycle, populations of developing germ cells and VCT-cells demonstrate the inversely proportional size dynamics: the larger the acini, the smaller the VCT-cells.

Fine structure of the gametes and spermiogenesis in Spiophanes uschakowi (Annelida: Spionidae) from the Sea of Japan, with comments on fertilization biology in broadcast-spawning spionids.

Spiophanes uschakowi is a common polychaete living in tubes in sandy sediments in shallow waters of the Sea of Japan. Females and males release their gametes into the water where fertilization and holopelagic, planktotrophic larval development occur. In females, oogenesis is intraovarian: vitellogenesis occurs when the oocytes grow in paired ovaries attached to genital blood vessels in fertile segments.

Nervous system development in the Pacific oyster, (Mollusca: Bivalvia).

Background: Bivalves comprise a large, highly diverse taxon of invertebrate species. Developmental studies of neurogenesis among species of Bivalvia are limited. Due to a lack of neurogenesis information, it is difficult to infer a ground pattern for Bivalvia.

Microautophagy in nutritive phagocytes of sea urchins.

Two types of cells were observed in germinative epithelium of male and female sea urchins: germ cells and somatic accessory cells; the latter referred to as nutritive phagocytes. At the onset of gametogenesis, nutritive phagocytes accumulate nutrients and greatly increase in their size. As gametogenesis progresses, the accumulated nutrients are transferred from nutritive phagocytes into developing gametes, and size of the nutritive phagocytes decreases.

Spermatogenesis and spermatozoa ultrastructure of two Dipolydora species (Annelida: Spionidae) from the Sea of Japan.

Spermatogenesis and the structure of the spermatozoa of two spionid polychaetes Dipolydora bidentata and Dipolydora carunculata are described by light and transmission electron microscopy. Both species are gonochoristic borers in shells of various molluscs. Proliferation of spermatogonia occurs in paired testes regularly arranged in fertile segments, and the rest of spermatogenesis occurs in the coelomic cavity.

Comparative ultrastructural study of spermatozoa in some oyster species from the Asian-Pacific Coast.

Sperm organization in the oysters Crassostrea gigas, Crassostrea nippona, Crassostrea cf. rivularis and Saccostrea cf. mordax inhabiting Asian Pacific coast was studied.

MicroRNA-mediated drug resistance in breast cancer.

Chemoresistance is one of the major hurdles to overcome for the successful treatment of breast cancer. At present, there are several mechanisms proposed to explain drug resistance to chemotherapeutic agents, including decreased intracellular drug concentrations, mediated by drug transporters and metabolic enzymes; impaired cellular responses that affect cell cycle arrest, apoptosis, and DNA repair; the induction of signaling pathways that promote the progression of cancer cell populations; perturbations in DNA methylation and histone modifications; and alterations in the availability of drug targets. Both genetic and epigenetic theories have been put forward to explain the mechanisms of drug resistance.

Morphology of spermatogenic and accessory cells in the mussel Modiolus kurilensis under environmental pollution.

A comparative light- and electron microscopic study of the male gonads of the bivalve mollusk Modiolus kurilensis from the reference and polluted sites in Amursky Bay (Sea of Japan) was conducted. Testicular acini in the mussels from the reference site had well-ordered structure (vertical spermatogenic columns located among the accessory cells bodies) whereas in the testes of the mollusks from the polluted site, the accessory and spermatogenic cell populations were disarranged. Mussels from the polluted station had about 26% of spermatogenic cells with marginal localization of nuclear chromatin, swollen outer nuclear membrane and heavily vacuolated cytoplasm and about 8% of spermatozoa with transformed or destructed acrosome; in mussels from the reference station, these values were close to zero.

Role of DNA hypomethylation in the development of the resistance to doxorubicin in human MCF-7 breast adenocarcinoma cells.

The resistance of cancer cells to chemotherapeutic agents is a major clinical problem and an important cause of treatment failure in cancer. Mechanisms that have developed to guard cancer cells against anti-cancer drugs are major barriers to successful anti-cancer therapy. Therefore, the identification of novel mechanisms of cellular resistance holds the promise of leading to better treatments for cancer patients.

The adaptor protein SH2D1A regulates signaling through CD150 (SLAM) in B cells.

The CD150 receptor is expressed on activated T and B lymphocytes, dendritic cells, and monocytes. A TxYxxV/I motif in the CD150 cytoplasmic tail can bind different SH2-containing molecules, including tyrosine and inositol phosphatases, Src family kinases, and adaptor molecules. To analyze CD150-initiated signal transduction pathways, we used DT40 B-cell sublines deficient in these molecules.

Selective resorption in nutritive phagocytes of the sea urchin Anthocidaris crassispina.

Phagocytic resorption during spermatogenesis was studied in the sea urchin Anthocidaris crassispina. Nutritive phagocytes in gonad absorbed both waste sperm cells and residual bodies discarded from maturing spermatids, and these materials were subsequently compartmented in heterophagosomes. Based on 180 heterophagosomes examined by transmission electron microscopy, over 99% of heterophagosomes contained either residual bodies or sperm cells only.

Sublethal effects of phenol on spermatogenesis in sea urchins (Anthocidaris crassispina).

Adult sea urchins, Anthocidaris crassispina, were exposed to 0.1 and 10 mgL(-1) phenol for 4 weeks. Abnormal sperm development was clearly evident in phenol-treated sea urchins, although no mortality was found throughout the exposure period.