Multinucleate cells in thymus of C3H mice

Summary Multinucleate epithelial cells occur in the thymus of C3H mice. They are poorly differentiated and scarce, but are more numerous in the medulla than in the cortex. Their increase in number with age is particularly significant between the first and the third months especially for cells with a large number of nuclei, and may be related to thymic involution.Viral particles of type C, similar to those described in murine leukemias, are found in mono- and multinucleate medullary epithelial cells.Research supported by grant 10.013 of the Fonds de la Recherche Fondamentale Collective (Brussels)     

Formation of multinucleate zoospores inPhytophthora infestans (Mont.) De Bary (Oomycetes,Pythiaceae)

Summary Zoospore formation in sporangia ofPhytophthora infestans, the causal agent of potatoes downy mildew disease, was influenced by reduction of oxygen tension, by application of a respiratory poison (KCN), and by an inhibitor of cytokinesis (cytochalasine B). As demonstrated by different methods of light microscopy, in all three cases the percentage of morphologically abnormal, multinucleate, multiflagellate cells increased. High concentrations of KCN caused a complete inhibition of zoospore formation. These effects are interpreted as disorders of the process of cytokinesis during zoosporogenesis.     

Ultrastructure of spermiogenesis in the American alligator,Alligator mississippiensis (Reptilia,Crocodylia, Alligatoridae)

Testicular samples were collected to describe the ultrastructure of spermiogenisis in Alligator mississipiensis (American Alligator). Spermiogenesis commences with an acrosome vesicle forming from Golgi transport vesicles. An acrosome granule forms during vesicle contact with the nucleus, and remains posterior until mid to late elongation when it diffuses uniformly throughout the acrosomal lumen. The nucleus has uniform diffuse chromatin with small indices of heterochromatin, and the condensation of DNA is granular. The subacrosome space develops early, enlarges during elongation, and accumulates a thick layer of dark staining granules. Once the acrosome has completed its development, the nucleus of the early elongating spermatid becomes associated with the cell membrane flattening the acrosome vesicle on the apical surface of the nucleus, which aids in the migration of the acrosomal shoulders laterally. One endonuclear canal is present where the perforatorium resides. A prominent longitudinal manchette is associated with the nuclei of late elongating spermatids, and less numerous circular microtubules are observed close to the acrosome complex. The microtubule doublets of the midpiece axoneme are surrounded by a layer of dense staining granular material. The mitochondria of the midpiece abut the proximal centriole resulting in a very short neck region, and possess tubular cristae internally and concentric layers of cristae superficially. A fibrous sheath surrounds only the axoneme of the principal piece. Characters not previously described during spermiogenesis in any other amniote are observed and include (1) an endoplasmic reticulum cap during early acrosome development, (2) a concentric ring of endoplasmic reticulum around the nucleus of early to middle elongating spermatids, (3) a band of endoplasmic reticulum around the acrosome complex of late developing elongate spermatids, and (4) midpiece mitochondria that have both tubular and concentric layers of cristae. J. Morphol., 2010. © 2010 Wiley‐Liss, Inc.     

Fad104, a positive regulator of adipogenesis, negatively regulates osteoblast differentiation

Fad104 (factor for adipocyte differentiation 104) is a novel gene expressed temporarily in the early stages of adipocyte differentiation. Previously, we showed that fad104 promotes adipocyte differentiation in mouse 3T3-L1 cells and mouse embryonic fibroblasts (MEFs). Furthermore, we reported that implanted wild-type MEFs could develop into adipocytes, whereas fad104-deficient MEFs could not. Interestingly, bone-like tissues were only observed in the implants derived from fad104-deficient MEFs. This result implies that fad104 is involved in osteoblast differentiation. However, the functions of fad104 during osteogenesis are unknown. In this paper, we show that fad104 negatively regulates osteoblast differentiation. During the differentiation process, the level of fad104 expression decreased. Deletion of fad104 facilitated osteoblast differentiation in MEFs, and elevated the level of runx2, a master regulator of osteoblast differentiation. Disruption of fad104 suppressed BMP-2-mediated adipocyte differentiation in MEFs. In conclusion, we demonstrate that fad104 reciprocally regulates differentiation of adipocytes and osteoblast; functions as a positive regulator in adipocyte differentiation and as a negative regulator in osteoblast differentiation.     

Alterations in the testis of hormone sensitive lipase-deficient mice is associated with decreased sperm counts, sperm motility, and fertility

Hormone-sensitive lipase (HSL, Lipe, E.C.3.1.1.3) functions as a triglyceride and cholesteryl esterase, supplying fatty acids, and cholesterol to cells. Gene-targeted HSL-deficient (HSL(-/-)) mice reveal abnormal spermatids and are infertile at 24 weeks after birth. The purpose of this study was to follow the evolution of spermatid abnormalities as HSL(-/-) mice age, characterize sperm motility in older HSL(-/-) mice, and determine if mice expressing a human testicular HSL transgene (HSL(-/-)ttg) produce normal motile sperm. In situ hybridization indicated that HSL is expressed exclusively in steps 5-16 spermatids, but not in Sertoli cells. In HSL(-/-) mice, abnormalities were evident in step 16 spermatids at 5 weeks after birth, with defects progressively increasing in spermatids with age. The defects included multinucleation of spermatids, abnormal shapes and a reduction of elongating spermatids. In older HSL(-/-) mice, sperm counts appeared reduced by 42%, but this value was lower because samples were compromised by the presence of small degenerating germ cells in addition to sperm, both of which appeared of similar size and density. Sperm motility was dramatically reduced with only 11% classified as motile in HSL(-/-) mice compared to 76-78% of sperm in wild-type and HSL(-/-)ttg mice. Sperm morphology, counts, and motility were normal in HSL(-/-)ttg mice, as was their fertility. Collectively, the data indicate that HSL deficiency results in abnormal spermatid development with defects arising at 5 weeks of age and progressively increasing at later ages. HSL(-/-) mice also show a dramatic reduction in sperm counts and motility and are infertile.     

Spermiogenesis in the Australian cockatiel Nymphicus hollandicus

Information on the ultrastructure of parrot spermatids and spermatozoa is limited to only four species with no comprehensive study of spermiogenesis conducted within the order Psittaciformes. The present study was undertaken to describe the development of the cockatiel spermatid using electron microscopy. Four phases of spermatid maturation were documented on the basis of nuclear morphology, development of the acrosome, perforatorium, and axial filament. These phases included 1) round nuclei, 2) irregular nuclei, 3) elongated nuclei with granular chromatin, and 4) elongated nuclei with homogenous chromatin. While development of the cockatiel spermatid was comparable to that of other domestic avian species, we have noted the hollow nature of some chromatin granules, an abnormal formation of the axoneme, the absence of the fibrous sheath around the axoneme of the principal piece, and the absence of an annulus. J. Morphol. , 2012. © 2012 Wiley Periodicals, Inc.