Effect of calcium on proteolytic activity and conformation of hemorrhagic toxin I from five pace snake (Agkistrodon acutus) venom

AaHI, a proteolytic hemorrhagic toxin from A. acutus venom, contains one g-atom Zn per mole protein and 2 g-atoms Ca per mole protein. AaHI is activated by calcium and slightly inhibited by zinc. When treated with EDTA, AaHI is completely inactivated. When dialyzed against 1,10-O-phenanthroline, 50-80% of the metal content and activities are lost, while 90% of the hemorrhagic and proteolytic activities are retained when dialyzed against 1,10-O-phenanthroline containing 5mM Ca2+. The results suggest that calcium is essential for the hemorrhagic and proteolytic activities. The circular dichroism spectra show that calcium may play an important role in maintaining a proper structure for AaHI. The function of zinc is not clear.

Electron microscopy of G-banded human mitotic chromosomes

Trypsin-treated human metaphase chromosomes stained with Giemsa and uranyl acetate showed clear, reproducible band structures under the transmission electron microscope (TEM). The banding pattern observed with TEM corresponded very closely to the G-band pattern visualized by light microscopy. The TEM images were used for karyotype analyses. Trypsin-treated chromosomes stained with uranyl acetate alone also showed clear G-bands under TEM. Shadow casting in addition to uranyl acetate staining revealed more structural detail of the chromosomes. Chromosome fibers, 200 A-300 A in diameter, were observed in the interband regions. Most chromosomes showed the major G-bands under the higher TEM magnification without any trypsin treatment.

Recent advances in anther culture of Hevea brasiliensis (Muell.-Arg.)

The yield of pollen embryoids from cultured Hevea anthers was increased 4 fold by optimizing the proportion of ammonium nitrate to potassium nitrate in the dedifferentiation medium. For optimal differentiation of pollen embryoids, kinetin, 2,4-D and α-naphtalene acetic acid are required. Anther culture for 50 days on the dedifferentiation medium is a prerequisite for the selective development of calli and embryoids from microspores.The determination of chromosome numbers in embryoids, plantlets and regenerated trees reveals that they originate from (poly)haploid pollen grains (n=2x=18). Aneuploid, triploid (3x=27) and tetraploid (4x=36) cells were encountered in increasing frequencies as the embryoids and plants developed. A few haploid cells with 9 chromosomes were consistently observed. Buds from shoots with mixoploid chromosome numbers can be grafted and the change in the chromosome constitution of the developing new shoots followed.

Purification and partial characterization of hyaluronidase from five pace snake (Agkistrodon acutus) venom

A hyaluronidase (EC 3.2.1. 35) was isolated and purified from Agkistrodon acutus venom. The purification procedure included CM-Sephadex C-50 chromatography, gel-filtration on Sephadex G-75 and CM-Sephadex C-25 chromatography. The purified preparation of the enzyme was homogeneous on polyacrylamide gel electrophoresis at pH 4.3, a 45-fold purification being obtained. The hyaluronidase was a glycoprotein (positive PAS staining) with a molecular weight of 33,000 and a pI of 10.3. No hemorrhagic activity was found. The hyaluronidase had an optimum pH of 3.5-5.0 and an optimum temperature of 37 degrees C. It was heat sensitive, was more stable in the acidic than in the neutral region, and lost its activity in the alkaline region. Fe2+, Cu2+ and heparin inhibited the venom hyaluronidase. The Km value for hyaluronic acid was 6.2 X 10(-3) mg/ml.