Marrow stroma-derived osteogenic clonal cell lines: Putative stages in osteoblastic differentiation

This report documents characterization of five osteogenic cell subpopulations of bone marrow stroma. The clonally derived cell lines were isolated from the parental line MBA-15 known to express osteoblastic-associated features in vitro and to form bone in vivo. The latter, presumably “arrested” at a particular stage along the osteogenic lineage, are useful models to study the processes involved in the differentiation of bone forming cells. The clones differ in their morphology, proliferation rate, quantities and distribution of extracellular matrix proteins, levels of alkaline phosphatase activity and activation of adenylate cyclase by parathyroid hormone and/or prostaglandin E. These properties have been retained during prolonged growth and subculturing through many passages. MBA-15.4 is a presumptive preosteoblast with a fibroblast-like appearance; it proliferates rapidly, synthesizes equal amounts of collagen and noncollagenous proteins, and produces constitutively low levels of alkaline phosphatase. This clone has PGE₂-stimulated adenylate cyclase activity and a very low constitutive response to PTH. On the other hand, MBA-15.6 has a large polygonal morphology with limited proliferative potential, synthesizes twice as much noncollagenous proteins as collagen, has high alkaline phosphatase activity, and responds strongly to PTH. The characteristics of the other clones place them between these two categories. The effects of 10^?7 M dexamethasone or 10^?12–10^?8 M 1,25 dihydroxyvitamin D₃ on growth and differentiation further strengthen the variance between these clones. The different in vitro characteristics of the various clones were directly reflected in their bone formation ability in vivo. When transplanted under the renal capsule, MBA-15.33 formed a thick fibrous tissue, MBA-15.4 formed small foci of bone, and MBA-15.6 formed massive woven bone at the same period of time. © 1993 Wiley-Liss, Inc.     

Molecular and morphological evidence for conspecificity of two common Indo-Pacific species of Palythoa (Cnidaria: Anthozoa)

Most studies characterize metacommunities based on a single snapshot of the spatial structure, which may be inadequate for taxa with high migratory behavior (e.g., fish). Here, we applied elements of metacommunity structure to examine variations in the spatial distributions of stream fishes over time and to explore possible structuring mechanisms. Although the major environmental gradients influencing species distributions remained largely the same in time, the best-fit pattern of metacommunity structure varied according to sampling occasion and whether or not we included non-native species in the analyses. Quasi-Clementsian and Clementsian structures were the predominant best-fit structures, indicating the importance of species turnover among sites and the existence of more or less discrete community boundaries. The environmental gradient most correlated with metacommunity structure was defined by altitude, area of artificial ponds in the catchment, and dissolved oxygen content. Our results suggest that the best-fit metacommunity structure of the native species can change in time in this catchment due to seasonal changes in distribution patterns. However, the distribution of non-native species throughout the landscape homogenizes the temporal variability in metacommunity structure of native species. Further studies are necessary from other regions to examine best-fit metacommunity structures of stream fishes within relatively short environmental gradients.     

Differential recruitment of benthic communities on neighboring artificial and natural reefs

Shedding light on the ability of benthic artificial reef (AR) communities to resemble those of a natural reef (NR) is of great importance if we are to harness ARs as tools for rehabilitation and restoration of degraded marine habitats. Studying recruitment processes to experimental settlement plates attached to ARs and NRs reveal the factors that shape community structure at the two reef types, and determine the ability of an AR to support communities similar to those found in adjacent natural habitats. In this study, conducted in Eilat (Red Sea), we used settlement plates to test the hypothesis that differences in benthic communities between ARs and NRs are derived from differential recruitment processes. A monitoring period of 18 months revealed great differences in the recruitment of corals and other benthic communities between the studied ARs and adjacent NRs. The ARs were either made of PVC or metal and 10-17 years old when the study commenced. The recruitment of soft corals reflected the species assemblage found in the area, consisting mainly of the family Nephtheidae and Xeniidae, species, while that of stony corals was mostly determined by the life history traits of the recruited taxa, e.g., the opportunistic nature of the family Pocilloporidae. Benthic organisms, mainly filter feeders like bryozoans, bivalves, sponges and tunicates, were more abundant at the ARs than at the NRs, mainly on the underside of the plates. We suggest that this differential recruitment resulted from a synergistic effect of abiotic and biotic factors, including current regime, sedimentation load and larval settlement preferences, which subsequently differentiated the composition of the benthic communities at the ARs and NRs. Thus, in order to construct an AR for restoration purposes, it must offer similar structural features to those found in the natural surrounding, leading to recruitment of local taxa. However, if the AR and NR will differ structurally, the composition of recruits will also differ and eventually the communities at the two reef types will become distinct, hereby increasing the species diversity in the area.     

Cell lineage analysis of the mammalian female germline

Fundamental aspects of embryonic and post-natal development, including maintenance of the mammalian female germline, are largely unknown. Here we employ a retrospective, phylogenetic-based method for reconstructing cell lineage trees utilizing somatic mutations accumulated in microsatellites, to study female germline dynamics in mice. Reconstructed cell lineage trees can be used to estimate lineage relationships between different cell types, as well as cell depth (number of cell divisions since the zygote). We show that, in the reconstructed mouse cell lineage trees, oocytes form clusters that are separate from hematopoietic and mesenchymal stem cells, both in young and old mice, indicating that these populations belong to distinct lineages. Furthermore, while cumulus cells sampled from different ovarian follicles are distinctly clustered on the reconstructed trees, oocytes from the left and right ovaries are not, suggesting a mixing of their progenitor pools. We also observed an increase in oocyte depth with mouse age, which can be explained either by depth-guided selection of oocytes for ovulation or by post-natal renewal. Overall, our study sheds light on substantial novel aspects of female germline preservation and development.     

Differential gene expression of cultured human osteoblasts.

Human cells with osteogenic capacity were studied for differential gene expression. In the first part of the study we compared gene expression of marrow stroma cells (MSC) in comparison to matured osteoblasts cultured from trabecular bone (TBC) that were analyzed by RT-PCR for series of messages. High expression was detected for PTH-r, TGFb1 and biglycan in TBC compared to MSC's. The messages for c-MYC, IL-6, IL-11, M-CSF, osteonectin, and osteocalcin were expressed at the same level in the two populations of cells. In the second part of the study, we analyzed gene expression within the MSC derived from 25 donors (2.5-49 years old) with respect to donors' age and gender. Increased message levels for M-CSF and biglycan were measured in correlation with age of the donors. Gender differences did not affect the expression of cytokines studied (IL-6, IL-11, MCSF, TGFb1). We investigated the effect of Dexamethasone treatment on MSC and monitored an increased expression of IL-11, M-CSF, biglycan, and osteocalcin messages. This study employs primary cell systems (MSC and TBC) to illustrate differential gene expression by osteoblastic cells. The expression was correlated with maturation status of the cells with respect to differences between donors.     

Does elevated pCO2 affect reef octocorals?

Increasing anthropogenic pCO₂ alters seawater chemistry, with potentially severe consequences for coral reef growth and health. Octocorals are the second most important faunistic component in many reefs, often occupying 50% or more of the available substrate. Three species of octocorals from two families were studied in Eilat (Gulf of Aqaba), comprising the zooxanthellate Ovabunda macrospiculata and Heteroxenia fuscescens (family Xeniidae), and Sarcophyton sp. (family Alcyoniidae). They were maintained under normal (8.2) and reduced (7.6 and 7.3) pH conditions for up to 5 months. Their biolological features, including protein concentration, polyp weight, density of zooxanthellae, and their chlorophyll concentration per cell, as well as polyp pulsation rate, were examined under conditions more acidic than normal, in order to test the hypothesis that rising pCO₂ would affect octocorals. The results indicate no statistically significant difference between the octocorals exposed to reduced pH values compared to the control. It is therefore suggested that the octocorals' tissue may act as a protective barrier against adverse pH conditions, thus maintaining them unharmed at high levels of pCO₂.     

Parathyroid hormone effect on cell-to-cell communication in stromal and osteoblastic cells

We characterized the formation and regulation of the gap junction in calvarial osteoblasts and in a series of subtypes from marrow stromal cells. The stromal cells included osteogenic, chondro-osteogenic, and endothelial cells. The cell coupling was measured by using fluorescence dye injected into single cells, and its migration to neighboring cells was measured. The functional coupling of cells was highly expressed by the osteoblastic cells. This process is mediated through fast changes in intracellular Ca⁺² levels. Calcium ionophore (A 23187) demonstrated an uncoupling effect on the cells. In addition, the exposure of the cells to the parathyroid hormone increased the formation of the gap junction complex; the highest level was demonstrated in the osteoblastic cells. J. Cell. Biochem. 69:81–86, 1998. © 1998 Wiley-Liss, Inc.