Bone mineral content measured by DEXA scan in preterm neonates receiving total parentral nutrition with and without phosphorus supplementation.

Intravenous phosphorus preparation was not available in Egypt till recently. So we aimed to prove the positive effect of adding intravenous phosphorus to total parentral nutrition (TPN) on calcium (Ca) and phosphorus (PO4) metabolism ofpreterm neonates by measuring bone mineral content (BMC) using DEXA scan. A case-control study was conducted in NICU of Obstetric and Gynecology Hospital of Ain Shams University which is a tertiary care unit in Cairo. Thirty preterm infants were prospectively enrolled in the study divided into 2 groups; 15 preterm infants received TPN with phosphorus supplementation (group 1) and 15 preterm received TPN without phosphorus supplementation (group 2). Serum Ca, PO4 and alkaline phosphatase (ALP) assay were done together with urinary calcium/creatinine (Ca/Cr) ratio, abdominal ultrasound and DEXA scan. There were no significant difference regarding serum Ca and PO4 between group 1 and 2. Yet there were highly significant increase in serum ALP and urinary Ca/Cr ratio in group 2 compared to group 1 (p = 0.001). Also group 1 had significantly higher BMC compared to group 2 even with TPN duration less than 15 days (p = 0.001). BMC was significantly positively correlated with G.A and B.W in both groups and was significantly negatively correlated with serum ALP in group 2 and with urinary calcium/creatinine ratio in group 1. Duration of TPN as short as 2 weeks can affect negatively the BMC as documented by DEXA scan in preterm infants receiving TPN without phosphorus supplementation.

Effect of cerastobin, a thrombinlike enzyme from Cerastes vipera (Egyptian sand snake) venom, on human platelets.

Cerastobin, a thrombinlike enzyme with arginine esterase activity, was purified from crude Cerastes vipera (Egyptian Sahara snake) venom. Unlike thrombinlike enzymes isolated from other snake venoms, cerastobin had a potent platelet aggregatory effect. The activation of human platelets was not related to adenosine diphosphate release and/or prostaglandin synthesis. Cerastobin showed a proteolytic activity towards protein constituents of the platelets' cytoskeleton. It hydrolyzed actin, actin-binding protein, and P235. This may explain at least a part of the aggregatory mechanism(s) of cerastobin. Electron microscopic studies of the stimulated platelets revealed changes in their morphology, including the appearance of pseudopodia, dilatation of the canalicular system with the formation of peripheral balloons, and centralization of the platelet organelles. Some inhibitors of the esteratic activity of cerastobin also inhibited its ability to aggregate platelets.

Characterization of cerastobin, a thrombin-like enzyme from the venom of Cerastes vipera (Sahara sand viper).

Cerastobin, a thrombin-like enzyme, was isolated from the venom of Cerastes vipera (Sahara sand viper) in homogeneous form. Cerastobin had a molecular weight of 38,000 with 348 amino acid residues. It had an isoelectric point of 7.7 (a pH optimum of 7.9 and a temperature optimum of 45 degrees C). Cerastobin hydrolyzed arginine-containing synthetic substrates such as TAME, BAME, and BAEE, but BAPNA was not hydrolyzed. Cerastobin had thrombin-like activity, producing fibrin from fibrinogen and also hydrolyzing chromogenic substrates for thrombin such as 2AcOH.H-D-CHG-But-Arg-pNA (CBS 34.47) and H-D-Phe-Pip-Arg-pNA (S-2238). It showed kallikrein-like activity and hydrolyzed kallikrein substrates 2AcOH.H-D-Phe-Gly-Arg-pNA (CBS 33.27) and H-D-Pro-Phe-Arg-pNA (S-2302). It produced bradykinin from bradykininogen, as uterus contraction was observed. A serine inhibitor, DFP, exerted a pronounced inhibitory effect, suggesting that cerastobin is a serine-type protease. The sequence of 37 residues from the amino-terminal end was investigated. The amino-terminal amino acid was valine as it is in most other thrombin-like enzymes. The amino acid sequence of cerastobin was similar to that of thrombin in some residues and had some homology with that of kallikrein. However, cerastobin showed a high degree of homology to thrombin-like enzymes isolated from various snake venoms. Factor X was partially degraded by cerastobin. It was also found that antithrombin III was degraded by the enzyme. The alpha and beta chains of fibrin monomer were preferentially hydrolyzed by cerastobin, but the gamma chain was quite resistant.