PubMed · 14119600
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
H SELYE. 1964. CALCIPHYLAXIS.. https://pubmed.ncbi.nlm.nih.gov/14119600/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
We examined the effect of magnetic force on differentiation of cultured human osteoblasts. Magnetic microparticles (MPs) were introduced into the cytoplasm of a human osteoblast cell line and the cells were cultured in a magnetic field (MF) in group MP-MF. Three groups of controls were used: cells without MPs were cultured out of MF (group C), cells without MPs were cultured in MF (group MF), and cells with MPs were cultured out of MF (group MP). The cells in group MP-MF became larger and were elongated along the axis of the magnetic poles. Appearance of alkaline phosphatase (AlPase) activity, formation of bone nodules, and calcium deposition were accelerated depending on the intensity of the magnetic field. It takes longer culture in the other three groups to exhibit these changes. Core-binding factor A1 (Cbfa1: transcription factor for osteoblast differentiation) and osteocalcin (a bone-matrix protein involved in controlling osteogenesis) were expressed earlier or stronger in group MP-MF than the other groups. Then we compared phosphorylation of mitogen-activated protein kinase (MAPK) between group MP-MF and group C. Phosphorylation of p38(MAPK) (p38) was increased in group MP-MF, while total p38 as well as total and phosphorylated forms of MAPK/ERK 1/2 and SAPK/JNK were not changed between the two groups. When a p38 inhibitor, SB 203580, was added to the culture medium in group C, AlPase activity, formation of bone nodules, and calcium deposits were completely inhibited. On the other hand, they were inhibited only partially by a MAPK/ERK 1/2 inhibitor, U-0126. Based on these results, it is concluded that (1) osteoblast differentiation is accelerated by a magnetic force, (2) this acceleration is mainly attributed to the activation of p38 phosphorylation, and (3) the stimulus induced by a magnetic field offers a new approach to osteoblast differentiation.
Cooperativity between pepsin and crystallization of calcium carbonate in distilled water was studied. The results show that vaterite was formed under the influence of pepsin and the crystalline product was a composite of vaterite and pepsin. The component of this material was similar to that of nacre. At the same time, the crystallization of calcium carbonate had also an important effect on the secondary structure of the pepsin. The secondary structure of the pepsin was characterized through FT-IR technology. The result indicated that the pure pepsin is composed of 24.38% alpha-helices, 29.91% beta-sheets, 39.32% beta-turns and 6.49% random structures and the pepsin in the CaCO(3)-pepsin solution is composed of 2.09% alpha-helices, 93.304% beta-sheets, 4.592% beta-turns and 0.006% random structure. During the crystallization of the calcium carbonate from the pepsin solution, the secondary structure of the pepsin transformed. These results showed that there was cooperativity between the crystallization of vaterite and the pepsin. The cooperative mechanism is discussed.
Emiliania huxleyi and Gephyrocapsa oceanica are the predominant coccolithophorid species that produce blooms in the ocean and affect the global environment. These species are capable of carbon fixation by both photosynthesis for organic matter production and by intracellular calcification for coccolith production. Both processes were strongly affected by the nutrient status in a laboratory culture. The coccolith production was stimulated by the addition of a high concentration of sodium bicarbonate and by the depletion of phosphate. Interestingly, when the calcification was stimulated, the increase in cell number during algal growth was greatly suppressed and then the cell volume increased. When the growth rate was increased under nutrient-sufficient conditions, the cells became very small in size and most of them bore few or no coccoliths. The data from laboratory experiments show that the cell growth and calcification proceeded apparently independently at different phases. We, therefore, assume that the coccolithophorid blooms in the ocean might be separated into two phases; firstly, the increase in cell population might be triggered by an adequate supply of nutrients to enhance algal growth and then the calcification might subsequently be stimulated when the nutrients become depleted by substantial algal growth.