The relative importance of the oligosaccharide units in human chorionic gonadotropin (CG) for LH/CG receptor activation in rat Leydig cells and mouse Leydig tumor cells.

The biological properties of deglycosylated human chorionic gonadotropin (DhCG), obtained by hydrogen fluoride treatment (HF-DhCG) of intact hCG or by oligonucleotide-directed mutagenesis (CHO-DhCG), and that of their fully glycosylated counterparts, were tested in terms of cAMP and steroid production in rat Leydig cells and in mouse Leydig tumor cells (MA-10 cells). In both cell types, HF-DhCG and CHO-DhCG possessed comparable biological activities. The maximum for DhCG-induced cAMP production was approximately 12% of that of intact hCG when tested in rat Leydig cells, and only 2% when tested in MA-10 cells. DhCG possessed significant steroidogenic activity in both cell types. In MA-10 cells the maximum for DhCG-induced steroidogenesis was 30-50% of that of intact hCG, while in rat Leydig cells DhCG and hCG induced similar steroidogenic maxima. Based on its ED50, DhCG possessed 10-17% of the steroidogenic potency of intact hCG in rat Leydig cells, while in MA-10 cells DhCG was only 2-fold less potent than hCG. When accurate hormone-receptor binding data are absent, the intrinsic receptor-stimulating activity of a ligand can still be estimated at full receptor occupancy, provided that over the whole dose range the biological response is proportional to receptor stimulation. The present data show that in transfected MA-10(P+29) cells which over-express rat phosphodiesterase, the hormone-induced stimulation of cAMP and steroid production is directly coupled to receptor activation up to maximal occupation of the LH/CG receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

Inorganic phosphors as new luminescent labels for immunocytochemistry and time-resolved microscopy.

A new strongly luminescent marker consisting of inorganic crystals is described for time-resolved microscopy. These crystals, known as phosphors, show delayed luminescence, unlike prompt fluorescent labels such as FITC, TRITC and phycobiliproteins, and are therefore potentially suitable for time-resolved microscopy. The luminescence of these phosphors is strong and non-fading in comparison to FITC/TRITC, and not significantly influenced by pH or temperature. The phosphor yttriumoxisulfide activated with europium emits maximally at 620 nm with a typical half life-time of approximately 700 musec, upon excitation with near ultraviolet light (360 nm). Phosphors for immunocytochemical staining were made by ball milling and were stabilized in suspension with polycarboxylic acids. Proteins such as avidin, protein A or immunoglobulins were allowed to adsorb to the surface of the phosphors. The immunocytochemical properties of the conjugates were evaluated in a model system of latex beads with defined surface antigens and in a cellular system containing fixed human lymphocytes or erythrocytes. Specific cytochemical staining was observed in suspension as well as on glass slides. A specially constructed time-resolved microscope was used to suppress the fast decaying fluorescence, thereby permitting visualization of the specific, slowly decaying luminescence of the phosphor label without the necessity of integration. Finally, the use of multiple phosphors with different kinetic and spectral characteristics for multiparameter studies is indicated.

On the mechanism of gallium accumulation in tumours. Isolation of N-hydroxypeptides.

With the use of A SEP-PAK Alumina N cartridge, peptide fractions containing the hydroxamate moiety have been isolated from tumour-tissue homogenate. It is therefore postulated that N-hydroxypeptides might play a role in the accumulation of gallium-67 in tumours. The biodistribution of several 67Ga-labelled hydroxamate peptide fractions is determined. Although their biodistribution differs from that of 67Ga-citrate no enhancement in tumour accumulation is observed indicating that they do not act like tumour-specific siderophores.

Synthesis and biodistribution of [18F]-5-fluorocytosine.

[18F]-5-fluorocytosine was prepared by reaction of [18F]-acetylhypofluorite with cytosine in acetic acid and was isolated in an overall radiochemical yield of 20%. Tissue distribution studies in sarcoma-bearing rats indicated in vivo stability, limited tissue uptake and rapid urinary excretion.