Urea reduces the thermal stability of polyanion-treated chromatin

High-resolution localization of hyaluronic acid in the golden hamster oocyte-cumulus complex by use of a hyaluronidase-gold complex

The distribution of hyaluronic acid in the oocyte-cumulus complexes collected from the oviduct ampulla of superovulated hamsters was revealed by use of hyaluronidase coupled to colloidal gold. On thin sections of Lowicryl-embedded oocyte-cumulus complexes, gold particles were associated specifically with interconnecting fibrillar materials that make up the cumulus matrix. Inside the cumulus cells, gold particles were found over the cisternal membrane of the rough endoplasmic reticulum, in the contents of lysosomes and multivesicular bodies, and over Golgi vesicles of some cumulus cells. A high concentration of gold labeling was observed over the peripheral condensed chromatin and perinucleolar components in the nucleus. The cell surface of the cumulus cells also appeared to be labeled. Gold particles, however, were absent over the mitochondria and lipid vacuoles. In the oocytes, labeling was found to be associated mainly with rough endoplasmic reticulum and arrays of lamellar structures; cortical granules, mitochondria, and coated vesicles were essentially devoid of gold particles. Gold particles were also seen along the plasma membrane of the oocytes and within the perivitelline space. The zona pellucida was not labeled by hyaluronidase-gold. Different control experiments confirmed the specificity of the labeling. Digestion of thin sections with hyaluronidase prior to incubation with hyaluronidase-gold abolished the initial reaction, whereas treatment of thin sections with chondroitinase did not prevent labeling of oocyte-cumulus complexes by hyaluronidase-gold. Although the function of hyaluronic acid in the oocyte-cumulus complex at the time of ovulation and fertilization is not known, the high concentration of this particular compound in the cumulus matrix and the cumulus cells and its specific locations in the perivitelline space and in the superovulated oocytes implicate the significance of its presence and warrant future investigations.

Heparin-sepharose as a tool in the subcellular fractionation of a polyamine-rich organ (rat ventral prostate)

Heparin-sepharose forms complexes with putrescine, spermidine, and spermine and indirect measurements of its affinity for polyamines gives values similar to those obtained with free heparin. A direct measurement of the binding of heparin-sepharose to spermine gives an apparent dissociation constant (Kd) of 1.5 X 10(-6)M spermine. Unlike free heparin, heparin-sepharose does not cause either disruption of the nuclei or more sutble modifications able to modify their sedimentation behavior. The heparin-sepharose polyamine complex formed by the addition of heparin-sepharose to the homogenate can easily be removed and the homogenate can be processed according to normal schedules. Heparin-sepharose is able to sequester 85% of the exchangeable spermine present in the homogenate of rat ventral prostate. The distribution of the marker enzyme galactosyltransferase (Golgi apparatus) on a sucrose density gradient was followed to assess the usefulness of heparin-sepharose in minimizing the aggregation of cellular organelles brought about by polyamines.