Chondroid bone arises from mesenchymal stem cells in organ culture of mandibular condyles

Mandibular condyles of fetal mice 19 to 20 days in utero comprising clean cartilage and its perichondrium were cultured for up to 14 days, and their capacity to develop osteoid and to mineralize in vitro was examined. After 3 days in culture the cartilage of the mandibular condyle appeared to have lost its inherent structural characteristics, including its various cell layers: chondroprogenitor, chondroblastic, and hypertrophic cells. At that time interval no chondroblasts could be seen; instead, most of the cartilage consisted of hypertrophic chondrocytes. By that time, the surrounding perichondrium, which contains pluripotential mesenchymal stem cells, revealed the first signs of extracellular matrix enclosing type I collagen, bone alkaline phosphatase, osteonection, fibronectin, and bone sialoprotein as demonstrated by immunofluorescent techniques. Electron microscopic examinations of the newly formed matrix revealed foci of mineralization within and along collagen fibers as is normally observed during bone development. The composition of the latter mineral deposits resembled calcium pyrophosphate crystals. Following 14 days in culture larger portions of the condyle revealed signs of osseous matrix, yet the tissue reacted positively for type II collagen. Hence, the condylar cartilage, a genuine representative of secondary-type cartilage, elaborated in vitro a unique type of bone that would be most appropriately defined as chondroid bone. Biochemical assays indicated that the de novo formation of chondroid bone was correlated with changes in alkaline phosphatase activity and 45Ca incorporation. The findings of the present study imply that mesenchymal stem cells that ordinarily differentiate into cartilage possess the capacity to differentiate into osteogenic cells and form chondroid bone.     

Acute and long-term proteome changes induced by oxidative stress in the developing brain

The developing mammalian brain experiences a period of rapid growth during which various otherwise innocuous environmental factors cause widespread apoptotic neuronal death. To gain insight into developmental events influenced by a premature exposure to high oxygen levels and identify proteins engaged in neurodegenerative and reparative processes, we analyzed mouse brain proteome changes at P7, P14 and P35 caused by an exposure to hyperoxia at P6. Changes detected in the brain proteome suggested that hyperoxia leads to oxidative stress and apoptotic neuronal death. These changes were consistent with results of histological and biochemical evaluation of the brains, which revealed widespread apoptotic neuronal death and increased levels of protein carbonyls. Furthermore, we detected changes in proteins involved in synaptic function, cell proliferation and formation of neuronal connections, suggesting interference of oxidative stress with these developmental events. These effects are age-dependent, as they did not occur in mice subjected to hyperoxia in adolescence.     

The sub-ice algal community in the Chukchi sea: large- and small-scale patterns of abundance based on images from a remotely operated vehicle

We examined the sub-ice algal community in the Chukchi Sea during June 1998 using a remotely operated vehicle (ROV). Ice algae were observed on the under-ice surface at all ten stations (from 70°29′N to 72°26′N; 162°00′W to 153°56′W) and varied in abundance and distribution from small aggregations limited to depressions in the ice to nets, curtains and strands of Melosira. There was no relationship between percent cover of sub-ice algae and physical factors at the kilometer scale, but at the scale of individual ice floes the percent cover of sub-ice algae was positively correlated with distance from the floe edge and negatively correlated with snow depth. A significant positive relationship between the concentration of sediment pigments and percent cover of sub-ice could indicate a coupling between ice algal and benthic systems. Pieces of ice algae that appeared to be Melosira were observed on the seafloor to a depth of over 100 m and cells or spores of obligate ice algal taxa were collected from sediments from 44-m to 1,000-m deep. The large biomass of sub-ice algae observed at many stations in the Chukchi Sea and the presence of ice algae on the seafloor indicates that the distribution and abundance of sub-ice algae needs to be understood if we are to evaluate the role of ice algae in the Arctic marine ecosystem.     

Molecular and Structural Characterization of Barley Vernalization Genes

Vernalization, the requirement of a period of low temperature to induce transition from the vegetative to reproductive state, is an evolutionarily and economically important trait in the Triticeae. The genetic basis of vernalization in cultivated barley (Hordeum vulgare subsp. vulgare) can be defined using the two-locus VRN-H1/VRN-H2 model. We analyzed the allelic characteristics of HvBM5A, the candidate gene for VRN-H1, from ten cultivated barley accessions and one wild progenitor accession (subsp. spontaneum), representing the three barley growth habits – winter, facultative, and spring. We present multiple lines of evidence, including sequence, linkage map location, and expression, that support HvBM5A being VRN-H1. While the predicted polypeptides from different growth habits are identical, spring accessions contain a deletion in the first intron of HvBM5A that may be important for regulation. While spring HvBM5A alleles are typified by the intron-localized deletion, in some cases, the promoter may also determine the allele type. The presence/absence of the tightly linked ZCCT-H gene family members on chromosome 4H perfectly correlates with growth habit and we conclude that one of the three ZCCT-H genes is VRN-H2. The VRN-H2 locus is present in winter genotypes and deleted from the facultative and spring genotypes analyzed in this study, suggesting the facultative growth habit (cold tolerant, vernalization unresponsive) is a result of deletion of the VRN-H2 locus and presence of a winter HvBM5A allele. All reported barley vernalization QTLs can be explained by the two-locus VRN-H1/VRN-H2 model based on the presence/absence of VRN-H2 and a winter vs. spring HvBM5A allele. Electronic Supplementary Material Electronic Supplementary material is available for this article at and accessible for authorised users.     

Lipopolysaccharide-induced injury is more pronounced in fetal transgenic ErbB4-deleted lungs

Pulmonary ErbB4 deletion leads to a delay in fetal lung development, alveolar simplification, and lung function disturbances in adult mice. We generated a model of intrauterine infection in ErbB4 transgenic mice to study the additive effects of antenatal LPS administration and ErbB4 deletion during fetal lung development. Pregnant mice were treated intra-amniotically with an LPS dose of 4 μg at E17 of gestation. Lungs were analyzed 24 h later. A significant influx of inflammatory cells was seen in all LPS-treated lungs. In heterozygote control lungs, LPS treatment resulted in a delay of lung morphogenesis characterized by a significant increase in the fraction of mesenchyme, a decrease in gas exchange area, and disorganization of elastic fibers. Surfactant protein (Sftp)b and Sftpc were upregulated, but mRNA of Sftpb and Sftpc was downregulated compared with non-LPS-treated controls. The mRNA of Sftpa1 and Sftpd was upregulated. In ErbB4-deleted lungs, the LPS effects were more pronounced, resulting in a further delay in morphological development, a more pronounced inflammation in the parenchyma, and a significant higher increase in all Sftp. The effect on Sftpb and Sftpc mRNA was somewhat different, resulting in a significant increase. These results imply a major role of ErbB4 in LPS-induced signaling in structural and functional lung development.     

Quaternary structure of the Mr 46,000 mannose 6-phosphate specific receptor: effect of ligand, pH, and receptor concentration on the equilibrium between dimeric and tetrameric receptor forms

The Mr 46,000 mannose 6-phosphate specific receptor exists in solution as a mixture of noncovalently associated dimeric and tetrameric forms. The two quaternary forms were separated by sucrose density centrifugation, and their composition was assessed by cross-linking with bifunctional reagents followed by SDS-polyacrylamide gel electrophoresis. The dependence of equilibrium between the dimeric and tetrameric forms on pH, receptor concentration, and presence of mannose 6-phosphate was studied. The formation of tetrameric forms is favored by pH values around 7, high receptor concentration, and presence of mannose 6-phosphate ligand. Tetrameric forms bind stronger at pH 7 to phosphomannan-Sepharose 4B than dimeric forms. Both quaternary forms dissociate at the same pH from a mannose 6-phosphate affinity matrix. When starting with dimeric or tetrameric forms, the equilibrium between dimeric and tetrameric forms is reached at pH 7.5 and 4 degrees C after 6-8 days. The presence of 5 mM mannose 6-phosphate shifts the equilibrium toward tetrameric forms. At pH 4.5 and 4 degrees C, the association of dimeric to tetrameric forms is negligible, while tetrameric forms dissociate to dimeric forms within 12 h. The results demonstrate that oligomerization is an intrinsic property of MPR-46 that is affected by ligand binding, pH, and receptor concentration.