Studies on fresh water snails, specific intermediate hosts for schistosomiasis 1--isolation of total lipids from native and irradiated snails

Total lipids were isolated from native and irradiated Biomphalaria alexandrina snails, specific intermediate hosts for Schistosoma mansoni.     

Selected enzymatic activities in fresh water snails, specific intermediate host for human schistosomiasis

The activities of aspartate aminotransferase (AST) (EC.2.6.1.1.) I, alanine aminotransferase (ALT) (EC.2.6.1.2) II and lactate dehydrogenase (LD) (EC.1.1.1.27) III have been measured in tissue homogenate and in haemolymph of Biomphalaria alexandrina snails, the specific intermediate host for the human parasitic disease schistosomiasis due to Schistosoma mansoni.     

Activity of some hydrolytic enzymes in tissue homogenates and haemolymph of fresh water snails, intermediate hosts in schistosomiasis.

The activities of 5-nucleotidase (Ec.3.1.3.5), alkaline phosphatase (Ec.3.1.3.1), glucose-6-phosphatase (Ec.3.1.3.9), and ribonuclease (Ec.3.1.13) had been measured in tissue homogenate and in haemolymph of Biomphalaria alexandrina, the specific intermediate host for the parasitic disease schistosomiasis, induced by the parasite Schistosoma mansoni.     

The suitability of several aquatic snails as intermediate hosts for Angiostrongylus cantonensis.

Sixteen species of aquatic snails of four families were tested by quantitative technique under standardized conditions for their suitability as intermediate hosts for Angiostrongylus cantonensis. These species were the planorbid snails Biomphalaria glabrata, Biomphalaria alexandrina, Planorbis planorbis, Planorbis intermixtus, Bulinus truncatus, Bulinus contortus, Bulinus africanus, Bulinus tropicus and Helisoma sp.; the lymnaeid snails Lymnaea natalensis, Lymnaea tomentosa, Lymnaea stagnalis, and Stagnicola elodes; the physid snail Physa acuta (an Egyptian and a German strain) and the ampullariid snails Marisa cornuarietis and Lanistes carinatus. All these snail species proved to be susceptible to infection with A. cantonensis, and first stage larvae reached the infective third stage in all of them. However, the rate and intensity of infection varied with different species. B. glabrata was the most susceptible snail species with a 100% infection rate and an average percentage recovery of third stage larvae of 26.1. This was followed by S. elodes and B. africanus, with a 100% infection rate and an average percentage recovery of third stage larvae of 15.6 and 14.6 respectively. The rest of snail species proved to be less susceptible. For comparative evaluation of the suitability of the various snail species as intermediate hosts of A. cantonensis a "Capacity Index" was determined. This index should provide a useful method for the evaluation of the suitability of various snails as intermediate hosts of nematode parasites under standardized conditions in the laboratory.     

Isolation and characterization of a ribonuclease from human leukemic blood cells specific for ribonucleic acid of ribonucleic acid-deoxyribonucleic acid hybrid molecules.

A ribonuclease that specifically hydrolyzes RNA in RNA. DNA hybrids has been purified more than 100-fold from human acute leukemic white blood cells. The molecular weight of this enzyme has been estimated as 80,000 by glycerol gradient centrifugation. It requires Mg-2plus for activity and is inhibited by N-ethylmaleimide. The optimum activity is observed at pH 8 (37 DEGREES). It is a heat-labile protein, t 1/2 at 50 degrees being 2 min. Among the substrates examined, (A)n X (dT)m, (I)n X (DC)m, and PHIX-174 DNA X RNA were hydrolyzed efficiently. (U)n X (dA)m showed a slight substrate activity, while (c) n X (dG) m and (G)n X (dC)m were not significantly hydrolyzed. The enzyme is an endonuclease and does not require RNA ends in the substrate molecule. It is capable of converting more than 95% of the RNA portions in hybrid substrates into acid-soluble products which are mono- and oligonucleotides terminated in 3'-OH and 5'-phosphate.