Scanning Microscopy


Effects of ionizing radiation on the structure and size-distribution of newly synthesized proteoglycan aggregates are studied in-vitro. Chondrocytes, isolated from embryonic chick sterna, are cultured for 7 days in a tri-dimensional agarose system. Single radiation doses of 10, 20 and 50 Gy are given before starting the culture. Digestion of the artificial agarose matrix liberates the newly synthesized proteoglycans. Spreading with cytochrome C allows electron microscopic investigations of the individual, newly synthesized molecules.

The structure of aggregates synthesized by control and irradiated chondrocytes is comparable. However, radiation causes alterations in the size-distributions of the aggregate-populations. For the control cultures, an average aggregate contains 27 aggrecans per aggregate. 34 pro mille of the molecules contain more than 100 aggrecans per aggregate. Irradiation with 10 Gy doesn't cause alterations. With radiation doses of 20 and 50 Gy, an average molecule contains 20 aggrecans. Only about 9 pro mille of the aggregates contain more than 100 aggrecans. Stimulation of lysosomal activity after irradiation could explain the observed alterations.

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