An electron nuclear double resonance investigation of redox-induced electronic structural change at CuA2+ in cytochrome c oxidase

We measured an electronic change at cysteine ligand(s) of the CuA2+ center brought on by reduction of other metal centers within cytochrome c oxidase, notably cytochrome a. This change specifically manifested itself as a modification in magnetic hyperfine coupling to the beta-protons of the beta-carbons adjacent to the cysteine sulfur in the CuA2+ coordination sphere. The electron nuclear double resonance ENDOR signals of these beta-protons had previously been assigned through study of selectively deuterated yeast oxidase. In the present study the ENDOR signals of the CuA2+ center were compared from the following forms of oxidase: resting (a3+.CuA2+.a3+3.CuB2+); mixed valence, 2-electron-reduced CO-ligated oxidase (a3+.CuA2+.a2+3CO.CuB+), and a more completely reduced mixed-valence CO-ligated oxidase. In agreement with previous studies on 3-electron-reduced oxidase, the latter more completely reduced oxidase showed cytochrome a preferentially reduced with respect to CuA, implying that the majority of paramagnetic CuA2+ centers had reduced cytochrome a partners. The ENDOR-resolved splitting of the beta-proton hyperfine features substantially decreased in going from the first two more oxidized forms to the more fully reduced latter form. Thus, the electronic structure of the CuA2+ center specifically monitored by hyperfine couplings to cysteine protons changed in response to a reductive event elsewhere in the protein. This structural change may correlate with the anticooperative redox interaction recently reported between cytochrome a and CuA.

Radioimmunoassay of the serum free beta-subunit of human chorionic gonadotropin in trophoblastic disease

We developed a RIA specific for the free beta hCG employing anti-beta hCG monoclonal antibody 1D12. This RIA was highly sensitive to free beta hCG; the minimum detectable concentration was 0.4 ng/ml. alpha hCG, LH, beta LH, and FSH had little effect in the assay; the cross-reactivity of hCG was about 4%. Using this RIA, we measured serum free beta hCG concentrations in 38 normal pregnant women and 72 untreated patients with 3 types of trophoblastic disease: hydatidiform mole (n = 15), invasive mole (n = 29), and choriocarcinoma (n = 28). All of these samples were simultaneously assayed for hCG by RIA. In normal pregnant women, serum hCG changed as pregnancy progressed, but serum free beta hCG was not detected at any time. In contrast, serum free beta hCG was measurable in the majority of patients with trophoblastic disease. Strong correlations were found between the concentration of free beta hCG and that of hCG in each type of trophoblastic diseases. The mean free beta hCG to hCG ratio was lowest for hydatidiform mole and highest for choriocarcinoma, and the difference between the ratios in these 2 groups was statistically significant. Serial measurements in 7 patients with trophoblastic disease failed to reveal remarkable changes in the free beta hCG to hCG ratio throughout their clinical course. We conclude that the production of free beta hCG increases with the immaturity of the trophoblastic cell, and the degree of differentiation of trophoblastic cells may be reflected by the free beta hCG to hCG ratio.

[The study of drug sensitivity on newly established three choriocarcinoma cell lines]

After serial transplantation in nude mice, we had established three new human choriocarcinoma cell lines (NaUCC-1,2 and 3). These three cell lines and BeWo were examined for sensitivity to Act-D, MTX and the combined agents (Act-D + MTX) 3H-Act-D uptake and 3H-MTX uptake, and were compared for each treatment. NaUCC-1 showed low sensitivity to MTX (p less than 0.05), but showed high sensitivity to Act-D (p less than 0.05). BeWo showed low sensitivity to Act-D (p less than 0.05). In examining sensitivity to the combined agents (Act-D+ MTX), the sensitivity of NaUCC-2 to Act-D was decreased (p less than 0.05) by MTX added at the same time. In the 3H-Act-D uptake experiment, NaUCC-1 did uptake a relatively larger amount of 3H-Act-D (p less than 0.01) and BeWo a smaller amount of it (p less than 0.05). In the 3H-MTX uptake experiment, NaUCC-1 did uptake a relatively smaller amount of 3H-MTX (p less than 0.05), but NaUCC-2 uptook a larger amount of it (p less than 0.005). NaUCC-1 established from the patient in whom tumor cells were resistant to treatment, had a low response to MTX. NaUCC-2 was established from the patient in whom it was found that MTX inhibits the Act-D effect on tumor cells. In the study of combined agents in NaUCC-2, the growth inhibition effect of Act-D was suppressed by the MTX added.