Steroid Producing Cells during Ovarian Differentiation of the Tilapia, Sarotherodon niloticus

In order to examine the initial appearance and development of the steroid producing cells (SPCs) during the process of ovarian differentiation, histology and ultrastructure of tilapia ( Sarotherodon niloticus ) ovaries were investigated from 10 to 50 days after hatching. In gonads of fry at 23–26 days after hatching, initial ovarian differentiation was confirmed by the differentiation of stromal aggregations in the proximal and distal region of the gonad on the side facing the lateral wall. This represents the initial formation of the ovarian cavity. At the same time as ovarian differentiation, a few large cells appeared initially in the vicinity of blood vessels. They have some of the ultrastructural features characteristic of SPCs such as a moderate number of mitochondria with tubular cristae, a large amount of smooth endoplasmic reticulum and many free ribosomes. Based on these ultrastructural criteria, together with the present finding that these cells further differentiated into the typical SPCs at older stages, these cells were identified as SPCs. Thereafter, by 30–50 days, SPCs increased gradually in number in the area enclosing the blood vessels of ovaries. The increase in SPCs coincided with the development of germ cells, including the multiplication of oogonia and the transformation from oogonia to oocytes.     

The Ontogeny of Thymic Myoid Cells in the Chicken

The ontogeny of thymic myoid cells in the chick was studied electron microscopically and immunohistochemically. An anticreatine kinase antibody which reacts specifically to skeletal muscle cells was used. This antibody reacts only to myoid cells in the thymus. Myoid cells were found in the medulla or in the interlobular region, though the number of the myoid cells was small. Immunohistochemically, myoid cells were detected on the 18th day of incubation. Mature myoid cells showed clear cross striations after immunohistochemical staining around the time of hatching. Electron microscopically, myoid cells were detectable on the 19th day of incubation. The discrepancy between immunohistochemical and electron microscopical detection may be due to the low number of myoid cells.     

Territory and group living in the polygynandrous Alpine Accentor Prunella collaris

The spacing system of Alpine Accentors Prunella collaris was studied on the summit of Mt. Norikura in central Japan for five breeding seasons. This species lived in groups (mean 7.2 individuals), sharing large areas of their individual home ranges within which all activities occurred. Membership of a group was closed and stable within a breeding season. The group home ranges overlapped little with each other, and antagonistic behaviour, including communal defence, was observed at the boundaries. Each female established an exclusive area around her own nest which she defended against other females (but not males) within the shared home range, but her activities (feeding, singing and mating) were observed over the whole of the group home range. Members of the same group moved around and fed together within the home range during the prebreeding season, but individual birds tended to become more solitary as the breeding season progressed. These results suggest that the primary breeding unit of Alpine Accentors is a group consisting of five to ten members who share a group territory which contains all the resources necessary for living and breeding, but this species is not a typical social one in which all members move around together within their group territory.     

Density Dependent Change of Myristoylated Proteins in C3H10T1/2 Fibroblasts and Their Transformants

We have examined the pattern of protein myristoylation in C3H10T1/2 fibroblasts during cell growth. During the growing phase of 10T1/2 cells, several proteins were radiolabelled with [³H]myristate, and among them proteins with molecular masses of 22, 35, a doublet of 42–45 and 67 kDa were labelled predominantly. The extent of myristoylation in each of these proteins changed with cell density. The amount of radioactivity incorporated into the 22 kDa protein in 10T1/2 cells decreased with increasing cell density and remained at a low level during the stationary phase. In contrast, the incorporation into the 67 kDa protein increased parallel to cell density. The density-dependent change of myristoylation was not observed in any of the transformants of 10T1/2 cells thus far examined. The 67 kDa protein was identified as MARCKS (myristoylated alanine-rich C kinase substrate) by immunoprecipitation with an anti-MARCKS antibody. By Western blot analysis, we found that the amount of MARCKS in 10T1/2 cells increased significantly analogous with cell density. Therefore, it is possible that MARCKS and the 22 kDa protein play a role in contact-mediated cell signalling in 10T1/2 cells, but the mechanism is lost in transformed cells. © 1997 John Wiley & Sons, Ltd.     

Evaluating the relationship between basin‐scale fish species richness and ecologically relevant flow characteristics in rivers worldwide

1. River flow alterations due to climate change and increasing water usage affect freshwater biodiversity including fish species richness. Here, we statistically explored the relationships of fish species richness to 14 ecologically relevant flow metrics as well as basin area and latitude in 72 rivers worldwide. 2. The statistical models best supported by the data included three variables with positive coefficients (mean river discharge, basin area and the maximum proportion of no‐flooding period) and three variables with negative coefficients (latitude, coefficients of variation in the frequency of low flow and the Julian date of annual minimum flow). 3. The model outputs have provided the first empirical indication that specific low‐ and high‐flow characteristics may be important in explaining variations in basin‐scale fish species richness. Our findings can be useful in identifying high‐risk basins for conservation of fish species diversity. 4. The results not only support the adoption of mean discharge as a predictor, but also suggest the importance of basin area in predicting basin‐scale fish species richness around the world.     

Transplanted interleukin-4--secreting mesenchymal stromal cells show extended survival and increased bone mineral density in the murine femur

Background

Mesenchymal stromal cell (MSC)–based therapy has great potential to modulate chronic inflammation and enhance tissue regeneration. Crosstalk between MSC-lineage cells and polarized macrophages is critical for bone formation and remodeling in inflammatory bone diseases. However, the translational application of this interaction is limited by the short-term viability of MSCs after cell transplantation.