The magnetoresistance of La 2Ϫx Sr x CuO 4 single crystals has been studied extensively over a wide composition range ͑0.07рxр0.28͒ using current parallel ͑in plane͒ and perpendicular ͑out of plane͒ to the CuO 2 plane. In the underdoped superconducting phase (xϳ0.10͒, the in-plane magnetoconductivity above T c is well described as fluctuation conductivity but only with the Aslamasov-Larkin term. The negligibly small MakiThompson contribution is suggestive of anisotropic Cooper pairing. We find a pronounced negative and isotropic out-of-plane magnetoresistance at low temperatures in this composition range. In the optimally doped to the overdoped superconducting phases ͑0.15рxр0.20͒, a substantial normal-state component is observed in the in-plane magnetoresistance. The classical Kohler's rule appears to break down for the normal-state magnetoresistance, which supports the involvement of two distinct scattering rates tr and H . In the out-of-plane magnetoresistance, we find an unconventional scaling ⌬ c / c ϰ(H/ a ) 2 for HЌJ and (H/T) 2 for HʈJ. In contrast to these anomalous behaviors, we find that Kohler's rule holds for both the in-plane and the out-ofplane transverse magnetoresistance in the overdoped normal metal region, implying a conventional anisotropic three-dimensional transport. These findings provide further evidence for the unconventional normal-state transport in the samples which exhibit high-T c superconductivity.

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A sensitive radioimmunoassay measuring serum medroxyprogesterone acetate (MPA) has been developed in order to measure and correlate serum MPA concentrations and ovarian function in women following im administration of deop-MPA (DMPA), employing goat anti-MPA-3-(O-carboxymethyl) oxime-bovine serum albumin and MPA-3-(O-carboxymethyl) imino-125I-iodohistamine. In the 3 women studied, im injection of 150 mg of DMPA yielded brief initial serum MPA concentrations ranging from 1.5 to 3 ng/ml for a few days. Serum MPA concentrations gradually declined and remained relatively constant at about 1 ng/ml for 2 to 3 months, declined gradually thereafter reaching 0.2 ng/ml during the 6th month and became undetectable (less than 0.02 ng/ml) about 7-1/2 to 9 months following administration. Serum estradiol remained at early to midfollicular phase levels for 4 to 6 months after DMPA injection and rose to preovulatory levels when serum MPA levels fell below 0.5 to 0.25 ng/ml. Ovulation, however, as evidenced by serum progesterone concentrations did not occur, apparently due to suppression of the LH peak by positive feedback inhibition. Prolonged inhibition of cyclic ovarian function following DMPA injection is caused by slow MPA absorption and persists until serum MPA levels have decreased below 0.1 ng/ml or become undetectable about 7 to 9 months after DMPA administration.