Involvement of BMP-2, TGF-ß2 and TGF-ß3 Signaling in Initial and Early Stages of Heterotopic Ossification in a rat Experimental Model

This study focused on the localization and expression of bone morphogenetic protein 2 (BMP-2) and different  isoforms of transforming growth factor s (TGF-s1, TGF-s2 and TGF-s3) in the initial and early stages  of heterotopic ossification (HO) employing an animal model mimicking the situation after total hip arthroplasty  (THA). Bone growth was induced in rats using s-tricalcium phosphate implants immersed either in  osteoinductive rhBMP-2 solution or in saline and implanted at the site where the HO is usually expected  to develop after THA. Implants were removed at 3 or 21 days after the operation and handled according to  stereology principles. mRNA expression and protein staining of growth factors in different types of tissues  was determined by in situ hybridization and immunohistochemistry, respectively. After three days, TGF-s3 content in the undifferentiated mesenchymal-like cells in the rhBMP-2 treated  implants was, as assessed by immunohistochemistry, 49.6% higher compared to the saline treated group  (p=0.024). This was also supported by in situ hybridization of mRNA of TGF-s3, which showed stronger  expression in rhBMP-2 treated group. Immunohistochemical investigation showed that after 21 days the  connective tissue in the rhBMP-2 treated implants contained more TGF-s1, TGF-s2 and TGF-s3, compared  to BMP-2 and osteoblasts contained significantly (27.2%) more TGF-s3 compared to TGF-s1 (p=0.045). In  the formed HO the proportion of the TGF-s2 and TGF-s3 producing bone tissue was increased by 32.1% and  47.8% respectively, compared to the TGF-s1 producing bone tissue (p=0.007 and p=0.006) and although  this difference was not so clear at mRNA level, this suggests that TGF-s2 and TGF-s3 signaling seem to play  an important role during initial and early stages of HO formation.

Nutrition of the intervertebral disc: solute transport and metabolism.

The metabolism of the canine nucleus pulposus was investigated at different oxygen tensions. It was found that even at high oxygen tensions the metabolism is mainly anaerobic, only approximately 1.5% of the glucose being converted to carbon dioxide. The concentration dependence of oxygen consumption is limited to very low oxygen tensions. Values of oxygen consumption and lactic acid production were used to calculate the concentration profiles of these substances within the nucleus pulposus, using a diffusion theory. The predicted concentration profiles were compared with the experimental measurements of concentration at various positions in the disc. The good agreement in these values found in the nucleus confirms that the main mechanism of metabolite transport is diffusion, and the main route of nutrient supply into the nucleus is via the endplate

Iron Deficiency in Cyanobacteria Causes Monomerization of Photosystem I Trimers and Reduces the Capacity for State Transitions and the Effective Absorption Cross Section of Photosystem I in Vivo

The induction of the isiA (CP43′) protein in iron-stressed cyanobacteria is accompanied by the formation of a ring of 18 CP43′ proteins around the photosystem I (PSI) trimer and is thought to increase the absorption cross section of PSI within the CP43′-PSI supercomplex. In contrast to these in vitro studies, our in vivo measurements failed to demonstrate any increase of the PSI absorption cross section in two strains (Synechococcus sp. PCC 7942 and Synechocystis sp. PCC 6803) of iron-stressed cells. We report that iron-stressed cells exhibited a reduced capacity for state transitions and limited dark reduction of the plastoquinone pool, which accounts for the increase in PSII-related 685 nm chlorophyll fluorescence under iron deficiency. This was accompanied by lower abundance of the NADP-dehydrogenase complex and the PSI-associated subunit PsaL, as well as a reduced amount of phosphatidylglycerol. Nondenaturating polyacrylamide gel electrophoresis separation of the chlorophyll-protein complexes indicated that the monomeric form of PSI is favored over the trimeric form of PSI under iron stress. Thus, we demonstrate that the induction of CP43′ does not increase the PSI functional absorption cross section of whole cells in vivo, but rather, induces monomerization of PSI trimers and reduces the capacity for state transitions. We discuss the role of CP43′ as an effective energy quencher to photoprotect PSII and PSI under unfavorable environmental conditions in cyanobacteria in vivo