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Short-term incubations of intact canine articular cartilage slices with prostaglandins E1 and E2 caused significant losses of hexosamine from cartilage matrix compared to controls. Chloroquine, an inhibitor of DNA primer, prevented this prostaglandin-induced hexosamine depletion. These data suggest that E-prostaglandins may degrade articular cartilage directly through DNA-dependent RNA synthesis of cathepsin-like proteases. Catabolism of articular cartilage probably involves degradation of existing matrix in addition to inhibition of synthesis.

High-spin level. s of the deformed nucleus Hf were deduced from y-ray spectroscopy, both in beam following the heavy-ion reaction 59Tb(~4N, 4ny) 9Hf and out of beam from P decay of 9Ta. The half-l. ife of 9Ta was remeasured as 4.7 + 0.7 m. Three rotational bands were assigned in Hf: & [523] ground band, up to spin 2, 2 [512], 59.1 keVbandhead, up to spin +2, . and g [642], p bandhead at 28.80 keV, up to spin~2 and tentatively up to spin -,. The 2 bandhead of the 2 [642] band is isomeric and decays with a half-life of 82+&5 ns to the ground state. The g factors in the negative parity bands were deduced from the measured angular distributions and branching ratios and compared to the predictions of the Nilsson model. Both this test and the systematics of the moments of inertia confirm the proposed assignments. The z [642] band (originating in the &~3g2 shell-model. state) is strongly perturbed. This band does not backbend although the~@ Hf core does at a lower rotational angular momentum than attained in 9Hf. The consequence of this observation for the explanation of backbending is discussed. The mixing amplitudes in the positive parity band are compared with the predictions of Pyatov's theory. NUCLEAR REACTIONS '"Tb("N 4nq) E =56-92 Mev measured Z, I (6), yy coin, T&g2 of 28.80 keV level.~Hf deduced levels, J, x, K, g, I /2S. RADIOACTIVITY~6 9Ta; measured T&j2, E&, I& 69Hf deduced levels, J, m, K. 1767 1768 I. RE ZANKA et al.surements to avoid counting of the radioactive recoils, from the Al foils, implanted into the next foil in the beam direction. The energy of the beam reaching the target was 116 MeV. Control runs were performed also at lower and higher energies to assure the optimum production of ' Ta. The duration of irradiation was 5 min. Isolation of Ta activityChemical isolation of Ta activity from the Tb target material was accomplished by a method similar to that described by Felber. ' The irradiated target was dissolved in hot 6 V HCl, and the rare earth fluorides were precipitated by using 2-3 drops of concentrated HF. The mixture was centrifuged and the supernatant solution was transferred to a separatory funnel where 3 ml of diisopropylketone was used to extract the Ta activities. This solution was then used as the source for the yand x-ray spectroscopy. The time elapsed between the end of the bombardment and the beginning of the measurement was 3-5 min. y-ray spectraThe y-ray spectra were measured by means of a Ge(Li) detector (volume 40 cm', resolution 2. 1 keV at 1332 keV) in several time intervals for