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PubMed1983

The role of vitamin D in the medullary bone formation in egg-laying Japanese quail and in immature male chicks treated with sex hormones.

The effect of vitamin D3 on medullary bone formation was investigated in egg-laying Japanese quail and in immature male chicks treated with sex hormones. When laying quail were fed a vitamin D-deficient diet for 16 days, their eggshell weights and egg production rate were markedly reduced in a time-dependent manner with a significant decrease in plasma calcium and 25-hydroxyvitamin D3 levels. The calcium content of the medullary bone of femurs decreased markedly with the progress of vitamin D deficiency, whereas that of the cortical bone remained unchanged. Quantitative histological examination also showed that the area of the mineralized portion of medullary bone in quail that were fed the vitamin D-deficient diet markedly decreased compared with that in the control laying quail, whereas the total area of the mineralized and unmineralized portions of medullary bone in the bone marrow cavity increased moderately. Daily administration of vitamin D3 (0.75 microgram/day) to the vitamin D-deficient quail increased the mineralization of medullary bone as early as day 4. Daily administration of both estradiol (0.3 mg/day) and testosterone (0.9 mg/day) for 3 weeks to immature male chicks induced an apparent hypercalcemia and matrix formation of medullary bone, regardless of the vitamin D status of the chicks. Mineralization of medullary bone was observed only when vitamin D3 was administered together with the sex hormones. These results suggest that vitamin D3 is directly involved in the mineralization of medullary bone in birds.

Animals↗
PubMed1982

Inductive specificity of mineralized bone matrix in ectopic osteoclast differentiation.

The present report describes the first in a series of studies designed to identify the factor or factors responsible for eliciting osteoclast differentiation. Particles of mineralized and demineralized bone, hydroxyapatite (HA), and eggshell were grafted onto the chorioallantoic membranes (CAMs) of chick embryos. After 3 of 6 days, portions of CAMs with associated grafts were harvested, processed for light and electron microscopy, and examined for the presence of multinucleated giant cells with the morphological characteristics of osteoclasts. Light microscopic examination revealed that, within only 3 days, many particles of mineralized materials had become surrounded or engulfed by multinucleated giant cells. Ultrastructurally, all such cells possessed a vacuolated and mitochondria-enriched cytoplasm, but they differed in the nature of the contacts formed at the cell-particle interface. With eggshell, the cells developed filopodia but lacked clear zones and ruffled membranes. With HA, clear zones were evident but cytoplasmic extensions and membrane ruffling were absent. Implants of mineralized bone, however, elicited the formation of giant cells with prominent clear zones and ruffling of the plasma membrane like that observed in bonafide osteoclasts. In contrast, grafts of demineralized bone did not evoke giant cell formation but rather recruited two cell types morphologically akin to either fibroblasts or macrophages. We conclude that the factor(s) responsible for osteoclast differentiation resides specifically within bone matrix and is intimately associated with the mineral phase. Further, in response to such a factor(s), osteoclast differentiation can occur ectopically, outside of the developing vertebrate body.

Allantois↗
PubMed1989

Transgenic regulation of moth chorion gene promoters in Drosophila: tissue, temporal, and quantitative control of four bidirectional promoters.

Bidirectional chorion gene promoter regions from three silkmoth species, Bombyx mori, Antheraea pernyi, or Antheraea polyphemus (members of two different moth families), were tested for their ability to transcriptionally activate a bacterial marker gene (chloramphenicol acetyltransferase) in transformant Drosophila. Relatively short 5' flanking DNA fragments (272-367 bp) of chorion gene pairs are sufficient to confer a high degree of tissue and choriogenic stage specificity of expression to the marker gene. Thus, significant conservation of molecular interactions controlling transcription during choriogenesis is observed between the distantly related orders, Lepidoptera and Diptera. However, quantitative and fine temporal regulation in the Drosophila host does not fully parallel the in situ regulation in moths, indicating that some regulatory protein-DNA interactions have diversified in the approximately 250 million years since the last common ancestor of these insect groups. Limited in vitro mutagenesis of a B. mori promoter DNA has shown that a central 189-bp region includes elements sufficient for the qualitative specificity of chorion-specific expression. The same experiments have shown that a previously identified essential element, centered on the TCACGT hexamer, is not sufficient for chorion-specific expression: an additional essential element or elements are found farther upstream, within a 112-bp DNA region. Comparisons of silkmoth and Drosophila chorion gene promoter sequences have identified some candidates for cis-acting elements involved in the developmental regulation of chorion gene expression.

Animals↗
PubMed2006

Microstructure and chemical composition of giant avian eggshells.

The microstructure and composition of the layers of two giant avian eggshells were investigated using a combination of scanning electron microscopy, electron probe microanalyses, and X-ray absorption near-edge structure spectroscopy (XANES). The two species have some similarities and differences in their microstructure and composition; the composition is not homogeneous throughout the eggshell thickness. XANES studies show that sulfur is associated with amino acids in the inner organic membranes, whereas in the mineralised layers the sulfur is mainly associated with sulfated polysaccharides. These results are similar to those obtained on chicken eggshells, and confirm the active role of sulfated acidic polysaccharides in biomineralisation processes of carbonate skeletons.

Animals↗
PubMed2005

Heavy-metal concentrations in female laying great tits (Parus major) and their clutches.

Egg laying may be an additional excretory pathway for heavy metals available to laying female birds. In this study, we examined the relationships between tissue concentrations (both internal organs and feathers) of 10 breeding female great tits (Parus major) and the concentrations in their eggs. We also investigated differences in metal concentrations (Ag, Al, As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Zn) among eggs as a result of the laying order of the eggs. Heavy-metal concentrations in internal tissues were highest in bone (Cr, Ni, Pb, Zn), kidney (Cd), liver (Cu), blood (Al, As, Co, Hg), and intestine (Ag, Mn). In the egg contents, relatively high concentrations of the essential elements Cr, Co, Cu, Mn, Ni, and Zn were found. In eggshells, concentrations of Ag, Al, As, Co, Cr, and Ni were high compared with internal tissue concentrations. Metal concentrations in the egg contents and eggshells were poorly correlated with metal concentrations in internal tissues and feathers; significant positive correlations were found only for cadmium and lead. We found few significant differences in metal concentrations among eggs, and none were according to the laying order of the eggs. The egg volume tended to decrease significantly as egg laying progressed. Our results seem to suggest that no special sampling strategies (e.g., sampling the first egg or pooling eggs from one clutch) are required for most metals.

Animals↗
PubMed2006

Bioreactors for tissue engineering.

Bioreactors are essential in tissue engineering, not only because they provide an in vitro environment mimicking in vivo conditions for the growth of tissue substitutes, but also because they enable systematic studies of the responses of living tissues to various mechanical and biochemical cues. The basic principles of bioreactor design are reviewed, the bioreactors commonly used for the tissue engineering of cartilage, bone and cardiovascular systems are assessed in terms of their performance and usefulness. Several novel bioreactor types are also reviewed.

Animals↗
PubMed1990

The major structural proteins of cod (Gadus morhua) eggshells and protein crosslinking during teleost egg hardening.

The highly hydrophobic protein aggregate which constitutes the fish eggshell has for the first time been quantitatively solubilized. This study shows that the nonactivated eggshell from cod is composed primarily of only three protein monomers, designated alpha (74 kDa) beta (54 kDa) and gamma (47 kDa). Protein extraction studies of the eggshells before and after egg activation demonstrate that egg hardening is accompanied by a 10-fold decline in total protein solubility, which is due to nonextraction of the alpha, beta, and gamma chains. When present during the egg activation process monodansylcadaverine (MDC-a fluorescent lysine analog) inhibits eggshell hardening and at the same time becomes covalently incorporated into the eggshell. This MDC incorporation is calcium-dependent and suggests the induction of a perivitelline transglutaminase activity after egg activation. (Transglutaminases catalyze the formation of an amide bond (isopeptide bond) between the gamma-carbonyl group of glutamine and the epsilon-amino group of lysine with release of ammonia. Crosslinks between proteins are generated when the two amino acid residues are located on different proteins.) Protein solubilization studies and NaDodSO4 gel analysis of the eggshell proteins from eggs subjected to 5 mM MDC during egg activation, reveal that when eggshell hardening is blocked by MDC, the three main eggshell proteins remain extractable even after egg activation. Simultaneously we observed a covalent incorporation of MDC into the gamma protein.

Amino Acids↗