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 58,342 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Biochemical analyses and immunocytochemistry were used to examine the developmental appearance of a major approximately 66 kDa bone phosphoprotein (66 kDa BPP) in the mid-diaphyseal region of embryonic and post-natal chicken tibiae in vivo. Total protein and O-phosphoserine (Ser-P) and O-phosphothreonine (Thr-P) content of 8-, 12-, and 18-day embryonic, and 4-wk post-natal chicken tibiae were determined by amino acid analysis. Similar bone samples were carried through a wide variety of tissue-processing regimes including different protocols for fixation, decalcification, dehydration, and embedding prior to electron microscopy. For immunocytochemistry, tissue sections were incubated with a polyclonal antibody raised in rabbits against 66 kDa BPP, and the antigen was revealed by the high-resolution protein A-gold technique. Amino acid analysis, Western blotting, and immunocytochemistry all showed the presence and increasing concentration of bone phosphoprotein with advancing developmental age. Immunogold labeling was observed over osteoblasts and mineral deposits throughout the bone with the most intense reaction occurring at the mineralization front in embryonic tibiae. Electron probe X-ray microanalysis confirmed the association of 66 kDa BPP with mineral. The levels of phosphoprotein in the tissue were directly correlated with increasing degrees of mineralization. These observations are consistent with previous proposals suggesting that phosphoproteins may play a significant role in the calcification of bone matrix.
Anat Rec 1990 Sep
PMID:Developmental appearance and ultrastructural immunolocalization of a major 66 kDa phosphoprotein in embryonic and post-natal chicken bone. 224 Jun 4

Embryonic chicken osteoblasts cultured over a 30 day period were used as a model system for studying the expression of bone phosphoproteins during cellular differentiation and the possible role of these proteins in extracellular matrix mineralization. Accumulation of total phosphoprotein in the cultures, as determined by O-phosphoserine (Ser-P) and O-phosphothreonine (Thr-P) amino acid analysis, revealed a greater than 10-fold increase over the 30 day period. Total phosphoprotein synthesis, as assessed by (32P)-, (3H)-Ser-P, and (14C)-Thr-P protein labeling, showed the highest levels concurrent with initial mineral deposition within the matrix. The major phosphoprotein present in chicken bones and synthesized by the cultured osteoblasts had a molecular weight of approximately 66 kDa. This 66 kDa bone phosphoprotein (66 kDa BPP) was purified to homogeneity and was used for antibody production. Application of this antibody in Western blot analysis revealed that 66 kDa BPP was present only in protein extracts of mineralizing cultured osteoblasts and was absent in cultures of non-mineralizing chondrocytes, myoblasts, and tendon fibroblasts. The 66 kDa BPP in vitro accumulated continuously in the extracellular matrix in a manner that paralleled both phosphoprotein synthesis and total phospho-amino acid production. A comparison of the results obtained in vitro to those from developing embryonic tibiae in vivo demonstrated a similar qualitative and temporal expression of phosphoprotein and a continual accumulation of 66 kDa BPP in the matrix with advancing mineralization and developmental age. Ultrastructural immunocytochemistry using the 66 kDa BPP antibody and the protein A-gold technique revealed specific immunolabeling over electron-dense regions of mineralization in the cultures that appeared identical to the distribution of labeling observed in vivo (McKee et al.: Connect. Tissue Res., 21:21-29, 1989; Anat. Rec., 228:77-92, 1990). These results demonstrate that this major 66 kDa BPP was expressed concurrently with other differentiated osteoblast functions and suggests that it may play a role in the initiation or regulation of mineralization.
Anat Rec 1990 Sep
PMID:Expression and ultrastructural immunolocalization of a major 66 kDa phosphoprotein synthesized by chicken osteoblasts during mineralization in vitro. 224 Jun 5

Size, incidence, and volume density of atrial specific granules (ASG) in right atrial cells from five animals each of the rat (average weight 210 g), mouse (average weight 28 g), fruit-eating bat Megaloglossus woermanni (BMW; average weight 35 g), and the insect-eating bat Pipistrellus pipistrellus (BPP; average weight 6 g) have been compared via ultrastructural morphometry. In all three parameters of granule measurement, significantly higher figures were obtained in the rodents than in the bats. However, between the rat and the mouse, as also between the two species of bats, no significant differences were noted in any of the measurements. These results therefore do not support the prevalent view that the number and size of the granules decrease with increase in size of the animal species. The low content of ASG in atrial cells of the bats is probably an indication of low demand for the natriuretic hormone of the granule, because, in such animals, and particularly in flight, conservation of fluid and electrolytes is of paramount importance. This suggests that granule content is adapted to fluid and electrolyte regulation in relation to the functional capacity of the animal. We also observed ASG-like structures in endothelial cells of capillaries of bat tissue but not in rodents. The function of these granules or whether or not they represent atrial specific ones is not clear from the present study.
Anat Rec 1993 Jan
PMID:Comparative ultrastructural morphometric analysis of atrial specific granules in the bat, mouse, and rat. 841 31