Biomedical subjects
Publications and source records attributed to J Oikarinen.
An assay procedure for the determination of protein disulphide isomerase activity is presented. The method is based on the reactivation of randomly cross-linked RNAase, the extent of RNAase reactivation being determined from the degradation of radioactively labelled RNA. The method is rapid and sensitive and allows one to test a large number of samples simultaneously.
The labelling of the subunits of prolyl 4-hydroxylase tetramers was studied in freshly isolated chick-embryo tendon cells and in chick-embryo tissues. In the former both the alpha- and beta-subunits of the tetramer were labelled during a 4 h labelling and 2 h chase period, although the radioactivity in the beta-subunit was much lower than in the alpha-subunit. The corresponding subunits of the enzyme from 12-day chick-embryo cartilaginous bone and heart were labelled in 7 h, again the beta-subunit much less than the alpha-subunit, the ratio of radioactivity in the beta-subunit to that in the alpha-subunit (beta/alpha-radioactivity) being 0.20 and 0.32 respectively. The beta/alpha-radioactivity then increased almost linearily with time between 7 and 24 h, by 9.5-fold in the cartilaginous bone and 3-fold in the heart, and beta/alpha-radioactivity values above 1.0 were reached. The free beta-subunit-size protein (the beta'-protein), which is also present in cells, had been labelled quite heavily by 7 h. The beta/alpha-radioactivity at 7h, determined in four tissues with different ratios of prolyl hydroxylase tetramers to total immunoreactive protein (tetramer percentage), was low in tissues with a high tetramer percentage. It is thus proposed that only a minor fraction of the beta'-protein must be processed to the tetrameric beta-subunit and utilized in the synthesis of the prolyl 4-hydroxylase tetramers.
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The calvarial mRNA species of chick embryos were translated in the rabbit reticulocyte-lysate cell-free translation system. The amount of procollagen type-I mRNA species was determined by digestion with bacterial collagenase and by fluorography of the cell-free translation products. Administration of cortisol resulted in a specific decrease in the cellular concentration of translatable procollagen type-I mRNA species in the calvaria of developing chick embryos. There was a lag period of up to 12 h before the response, which was dose-dependent. The data suggest that the decrease in amounts of procollagen mRNA species is the main reason for the lower amount of tissue collagen after topical or systemic administration of glucocorticoids, although other factors may contribute to the response.
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Decalcified bone matrix was prepared from cortical bones of rats premedicated with I) Diphenylhydantoin (DPH), II) DPH + Vitamin D3, III) Vitamin D3 or IV) no premedication for 10 days. In the donor animals, DPH lowered the serum calcium level, caused a weight loss of 10 per cent, and stopped the growth of the long bones. Vitamin D3 supplementation normalized the serum calcium concentration but had no effect on the other parameters. Vitamin D3 alone caused hypertrophy of the growth cartilage, while the bone growth and structure was normal. The bone inductive capacity of decalcified bone matrix was highest in the DPH group, and the DPH + D3 group also showed significantly higher values than the D3, and control groups. The results of the present study show that the bone inductive capacity of the decalcified bone matrix is independent of Vitamin D3 metabolism.
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Experimental fibular defects in 16 rats were filled with an acid decalcified homogenous bone matrix (bone inductive material). Autogenous bone grafts in corresponding defects in the other legs of the same rats served as controls. After 3 months, 11 of the 16 defects filled with bone inductive material healed with bony union, but only 4 of the 16 defects treated with autogenous bone grafts had healed. The results suggest that bone inductive material can repair bone defects are too large to be healed by autogenous bone grafts.
The bone defect repairing capacities of autogenous cancellous bone (ACB), decalcified bone (DB), autodigested "low-antigenic" bone matrix (LBM) and preserved bone (PB) were tested in experimental defects in rabbit scapulae. The healing of the defects was most effective with ACB transplants as judged by roentgenologic and microscopic studies. The DB and LBM transplants caused states of healing comparable to each other, and the PB transplants showed the least satisfactory results in this experiment. The ACB, DB and LBM transplants caused bone induction, which resulted in the formation of new bone, subsequent resorption of the transplanted material and rapid reshaping of the callus. The PB transplants caused no bone induction; only some growth of callus on the edges of the defect was observed and pieces of the transplanted material were seen as late as 10 weeks after the operation as dead particles encapsulated by fibrous tissue. The infiltrations of inflammatory cells around the PB transplants indicated a considerable host versus graft reaction whereas this reaction was less with the other materials tested.
The effects of allogeneic decalcified bone matrix (DBM) on the formation of bone between the spinous processes of the rabbit vertebrae was compared with the effects of allogenic deep-frozen cortical bone (AFB). Autologous cancellous bone (ACB) chips were used for a control substance. Healing was estimated by gross anatomical roentgenologic and microscopic methods one, two, four and six months after the operation. The ACB and DBM transplants gave comparable results. A stable bony bridge was formed at one month, and this was seen to strengthen during the follow-up time. Both transplanting materials were accepted by the host without foreign body reactions. Inflammatory cell accumulations and sequesterated particles were not seen in any of the specimens with ACB and DBM transplants. The DBM induced new bone formation and the transplanted material was resorbed within two months after the operation. The AFB transplants did not induce the new bone formation, but the implanted fragments in contact with the host bone were surrounded by the callus, which produced a bony bridge but only as late as four months after the operation. After six months, the bridging was incomplete and sequestered bone particles were still seen in some of the specimens. The AFB transplants were slowly resorbed and accumulations of inflammatory cells were present at least six months postoperation. The results indicate that in rabbits, decalcified bone matrix is a better substitute for autologous bone than the allogeneic deep-frozen cortical bone.