Basic proteins I and II (BP-I and BP-II) isolated from Trimeresurus flavoviridis venom, which are classified into a group of lysine-49-phospholipases A2 (Lys-49-PLA2), exhibited only limited lipolytic activity for the mixed micelles of various phospholipids. Based on the finding that BP-II elicits a strong contraction of guinea pig ileum due to the release of arachidonic acid, BP-II together with BP-I has been tested for their interaction with artificial phospholipid bilayer membranes. The dye leakage experiments indicated that BP-II interacts strongly with liposomes of beta-arachidonoyl-gamma-stearoyl-L-alpha-phosphatidylcholine. The perturbation of liposomes was observed only in the Ca(2+)-containing buffer, and as demonstrated by HPLC analyses, accompanied by the release of arachidonic acid. The concentration of Ca2+ which gave a half maximal activity of BP-II was 3.0 x 10(-4) M, suggesting that the affinity of BP-II for Ca2+ is more than 10 times stronger than that of BP-II without liposomes. These observations clearly show that Lys-49-PLA2 of BP-II is the enzyme responsible for the hydrolysis of membrane phospholipids and that Ca2+ is essential for such enzymatic activity. The interaction of BP-I with liposomes was much weaker than BP-II BP-I and BP-II share a common sequence except for Asp-67 (BP-I) and Asn-67 (BP-II) in the aligned sequences. This implies that the amino acid at position 67 of Lys-49-PLA2s is the residue required for discriminatory recognition of phospholipid membranes.

Animals↗

PubMedDate not supplied

[Peripheral nervous system in limited systemic sclerosis].

OBJECTIVES: PNS is involved in Systemic Sclerosis (SSc) since the earliest phases. Our aim is to perform an ultrastructural study on skin PNS fibers in SSc. METHODS: Skin biopsies were taken from forearms of 8 patients affected by limited SSc (lSSc) and 3 controls and processed for transmission electron microscopy (TEM). The semithin sections (2 mm) were observed at light microscope and optical fields were chosen for ultrathin sections (1 mm) preparation and TEM examination. RESULTS: In lSSc skin, in the semithin sections, damaged areas are close to apparently spared areas. At TEM, in early lSSc patients, signs of inflammation and damaged microvessels are visible in derma. PNS fibers are no damaged. In advanced lSSc, fibrosis prevails on inflammation, and slight ultrastructural alterations of PNS fibers are evident in papillar derma. CONCLUSIONS: PNS lesions are different in severity in lSSc according to the disease duration, resulting more severe in advanced than in early phase.

Biopsy↗

PubMedDate not supplied

[Retrobulbar neuritis in a worker exposed to styrene].

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Adult↗