Heparin effect on in vitro nuclear maturation of bovine oocytes.

Oocytes undergo numerous biochemical and morphological changes during their development from preantral to preovulatory phases. In vitro studies have suggested several compounds that might induce oocyte maturation. Heparin is a natural component of ooplasm, follicular fluid and uterine fluid and previous studies indicated that it might act as a chromatin maturation factor in bovine oocytes. We tested this hypothesis in vitro by timing germinal vesicle breakdown (GVBD) and first polar body (PB) formation without any other natural or introduced factors that might influence the rate of oocyte maturation. We also determined if these oocytes could be fertilized. Bovine oocytes were incubated in a salt medium and TCM 199 supplemented with different concentrations of heparin for 24 h at 37.5 degrees C in a humidified atmosphere of 5% CO2. With 1.0 and 6.5 mg/ml heparin, the time of GVBD was reduced from 4.7+/-1.1 h to about 1.5 h and the time of first PB formation was reduced from 22.0+/-1.1 h to 9.0-11.0 h in salt medium. In TCM 199, only 6.5 mg/ml heparin significantly reduced the time of PB formation. In both incubation media, 1.0 and 6.5 mg/ml heparin induced GVBD, extrusion of the first PB and formation of the metaphase II nucleus. Moreover, heparin did not interfere with the fertilization of oocytes matured in TCM 199. Based on the results, we propose that heparin plays an important role in the rearrangement of the oocyte chromatin and acts as an oocyte maturation factor.

A biologically active hydrophobic T-1-conotoxin from the venom of Conus spurius.

A major, very hydrophobic peptide, sr5a, was purified from the venom duct of Conus spurius specimens collected in the Yucatan Channel, Mexico. Its amino acid sequence (IINWCCLIFYQCC; calculated monoisotopic mass assuming two disulfide bridges 1616.68 Da) was determined by automatic Edman degradation after reduction and alkylation, and confirmed by mass spectrometry (ESI monoisotopic mass, 1616.60; MALDI monoisotopic mass 1616.42 Da). The primary structure of sr5a showed the pattern that characterizes the family of the T-1-conotoxins, which belong to the T-superfamily of conotoxins. The disulfide bonds were determined by partial reduction and alkylation with N-ethylmaleimide, followed by total reduction and alkylation with 4-vinylpyridine, and automatic Edman sequencing. The connectivity of the Cys residues (I-III, II-IV) is the same as that found in the T-1-conotoxin family. When injected intracranially (2.0 nmol) into mice, peptide sr5a caused depressed behavioral activity.