Moisture susceptibility of high and low compaction dry process crumb rubber modified asphalt mixtures

The field performance of dry process crumb rubber-modified (CRM) asphalt mixtures has been reported to be inconsistent with stripping and premature cracking on the surfacing. One of the concerns is that, because achieving field compaction of CRM material is difficult due to the inherent resilient nature of the rubber particle, nonuniform field compaction may lead to a deficient bond between rubber and bitumen. To assess the influence of compaction, a series of CRM and control mixtures was produced and compacted at two levels: 4% (low, optimum laboratory compaction) and 8% (high, field experience) air void content. The long-term durability, in regard to moisture susceptibility of the mixtures, was assessed by conducting repeated moisture conditioning cycles. Mechanical properties (stiffness, fatigue, and resistance to permanent deformation) were determined in the Nottingham Asphalt Tester. Results indicated that compared with conventional mixtures, the CRM mixtures, regardless of compaction effort, are more susceptible to moisture with the degree of susceptibility primarily depending on the amount of rubber in the mixture, rather than the difference in compaction. This behavior is different from that of conventional mixtures in which, as expected, poorly compacted mixtures were found to be more susceptible to moisture than were well-compacted mixtures

Synergistic interaction of a protease and protease inhibitors from Russell's viper (Vipera russelli) venom

Synergistic interaction of a protease and protease inhibitors from Russell's viper (Vipera russelli) venom. Toxicon28, 65–74, 1990.—An acidic proteolytic enzyme, RVVX, was purified from Vipera russelli venom by successive chromatography on CM-Sephadex C-25, DEAE-cellulose and Sephadex G-100 columns. RVVX is a glycoprotein with a mol. wt of 79,000. It exhibited caseinolytic and factor X activating properties. Two trypsin inhibitors, TI-I and TI-II, were purified from V. russelli venom in a single step by CM-Sephadex C-25 column chromatography. The trypsin inhibitors interacted with the proteolytic enzyme RVVX. TI-I inhibited only the factor X activating property of RVVX while TI-II inhibited both, the caseinolytic and also factor X activating properties of RVVX. The edema inducing activity of RVVX increased markedly in the presence of non-edema inducing doses of TI-I and TI-II. RVVX, TI-I and TI-II were non-lethal in mice. The combination of RVVX and TI-II demonstrated enhanced toxicity

Isolation and characterization of an endogenous inhibitor of phospholipase A(2) from Indian cobra (Naja naja naja) venom

A PLA(2)-inhibitor has been purified from Indian cobra (Naja naja naja) venom by the combination of ion-exchange and gel-filtration chromatography. The inhibitor, NN-I-3 was a peptide with mol.wt 6500 and has a fluorescence emission maxima cn 340 nm. NN-I-3 specifically inhibited the enzyme activity of the three acidic PLA? from the same venom. The inhibition of NN-I-2d-PLA(2) and NN-I-2e-PLA(2) by NN-I-3 was of mixed type and NN-I-2c-PLA(2) was of uncompetitive type, Neither the inhibitor nor the individual mixtures of acidic PLA(2) with the inhibitor (1:1 w/w or 1:2 mol:mol) were lethal to mice when injected intraperitoneally in doses up to 10 mgkg(-l) body weight. (C) 1998 Elsevier Science Ltd. All rights reserved

Purification and characterization of a neurotoxic phospholipase A2 from Indian cobra (Naja naja naja) venom

Snake venoms contain multimolecular forms of phospholipase A2 which are diverse with respect to their pharmacological properties. A neurotoxic PLA2 from Naja naja naja venom has been purified in two steps. (1) The whole venom was fractionated on CM-Sephadex C-25 column; 4.6% of the total PLA2 activity recovered was found in the NN-V fraction. (2) The NN-Vb-PLA2 fraction was purified to homogeneity by gel filtration of fraction NN-V on Sephadex G-50. It is a basic protein with a mol. wt between 10,500 and 11,000, and is more toxic than other basic PLA2s purified from Naja naja naja venom. The LD50 Of NN-Vb-PLA2 is 0.27 mg/kg body wt. It induced neurotoxic symptoms in experimental mice and is devoid of myotoxic, anticoagulant and edema-inducing activities

Identification, isolation and purification of neurotoxic phospholipases A2 from Vipera russelli venom using polyclonal antibodies

All the neurotoxic phospholipases A2 present in whole Vipera russelli venom were precipitated selectively from other non-neurotoxic phospholipases A2 and non-phospholipases A2 fractions using antibodies (anti PL-V Ig) raised against one of the purified neurotoxic phospholipases A2 (VRV PL-V). These neurotoxins were identified and isolated in their homogeneous form by chromatographic and electrophoretic methods. The present report of selective isolation and purification of all the neurotoxic phospholipases A2 of V. russelli venom is first of its kind

Dissociation of enzymatic activity from toxic properties of the most basic phospholipase A2 from Vipera russelli snake venom by guanidination of lysine residues

The most basic phospholipase A(2) VRV-PL-VIIIa purified from Russell's viper venom is a toxic enzyme. It induced neurotoxicity, myotoxicity, and oedema and was lethal to mice at 5.3 mu g/g body weight. It also inhibited the coagulation of the human plasma. The epsilon-amino groups of lysine residues of the toxic enzyme VRV-PL-VIIIa were guanidinated with o-methylisourea. Guanidination of the enzyme did not alter the enzymatic activity markedly. The guanidinated enzyme became non-lethal in doses up to 16 mu g/g body weight, and failed to elicit neurotoxic symptoms in experimental animals and oedema in the foot pads of mice. Also, its myotoxic and anticoagulant potencies were decreased significantly

Purification and characterization of three acidic, cytotoxic phospholipases A(2) from Indian cobra (Naja naja naja) venom

Three acidic phospholipases A(2) (NN-I-2c-PLA(2), NN-I-2d-PLA(2) and NN-I-2e-PLA(2)) were purified by successive chromatography of Indian cobra (Naja naja naja) venom on CM-Sephadex C-25, Sephadex G-50 and QAE-Sephadex A-25 columns. They have molecular weights of 13 000-14 500 by sodium dodecyl sulphatepolyacrylamide gel electrophoresis. They showed tryptophan specific fluorescence emission spectra (similar to 345 nm). All the three phospholipases A(2) were enzymatically highly active with specific activities 9-17 mu mol min(-1) mg(-1) They were non-lethal to mice when injected intraperitoneally in doses up to 10 mg kg(-1) body weight. They induced edema in mouse foot pads and were cytotoxic to Ehrlich ascites tumour cells. They did not exhibit direct haemolytic and anticoagulant activities. (C) 1998 Elsevier Science Ltd. All rights reserved

Effects of chemical modification on enzymatic and toxicological properties of phospholipases A2 from Naja naja naja and Vipera russelli snake venoms

The effects of chemical modification with 4-NN-dimethyl amino azo benzene-4'-isothiocyanate on various biological activities of phospholipases A2, NN-XIII-PLA2 from Naja naja naja and VRV-PL-VIIIa from Vipera russelli snake venoms were investigated. Modification of the enzymes resulted in significant reduction of lethal, hemolytic, anticoagulant and enzymatic activities. The K(m) value of the modified enzymes was increased. The modified enzymes failed to induce edema in the foot pads of mice and were non-lethal up to 16 mg/kg body weight. However, considerable myotoxicity was retained, suggesting that the toxins have multiple sites for biological activities. The aggregated form obtained from modified NN-XIII-PLA2 exhibited decreased enzymatic activity and increased toxicity compared to the modified monomer. This aggregated form did not show pyrophosphatase/phosphomonoesterase activity in contrast to the aggregated form obtained from the native NN-XIII-PLA2 molecule

Comparative characterization of two toxic phospholipases A2 from Indian cobra (Naja naja naja) venom

Indian cobra venom contains many phospholipase A2 (PLA2) toxins. In the present study two toxic PLA2s have been purified from the Indian cobra (Naja naja naja) venom by column chromatography. The NN-XIa-and NN-XIb-PLA2s have mol. wts between 10,700 and 15,000. The NN-XIa-PLA2 induces myotoxic effects, oedema and neurotoxicity in mice and has an i.p. LD50 of 8.5 mg/kg body weight. The NN-XIa-PLA2 is also cytotoxic to Ehrlich ascites tumour cells. The other PLA2, NN-XIb, in contrast has an i.p. LD, of 0.22 mg/kg body weight, and it induces acute neurotoxicity. The NN-XIb-PLA2 is devoid of the other biological activities which are exhibited by NN-XIa-PLA2

Effects of chlorpromazine on the enzymatic and toxic properties of the most basic phospholipase A2 fromVipera russelli snake venom

The effect of chlorpromazine on various biological activities of phospholipase A(2) VRV-PL-VIIIa from Vipera russelli snake venom was investigated. The drug inhibited the in vitro phospholipase A(2) activity of the enzyme by 55%. The ID50 was found to be 1.15 mu M. Increasing substrate concentration relieved the inhibition of phospholipase A(2) activity by the drug indicating probable interaction with the substrate. The drug totally quenched the fluorescence intensity of the enzyme. Chlorpromazine increased the LD(50) Of the enzyme by 1.6 fold. The drug also inhibited hemolytic and anticoagulant potencies but failed to inhibit edema inducing activity and myotoxicity of the enzyme