Studies on energy transformation in the freshwater snail Pila globosa

The effects of eleven chosen feeding levels ranging from 0 to 198 mg damp dry (plant) Ceratophyllum/g live snail/day on the absorption, conversion and metabolism of the snail Pila globosa (of 1 -9 g body weight) have been studied. Absorption rates increased from 3-0 to 21-0 mg dry food/g live snail/day in snails fed 3-4-28-8 mg dry food/g live snail/day. In these snails, absorption efficiency decreased from 87.5 to 73.0%. Conversion rates increased from 0-3 mg/g/day for snails receiving 23-4 mg/g/day to 2-7 mg/g/day for those fed maximum amounts, and the efficiency (K₂) also increased from 1-9% to 130%. When compared to other gastropods, Pila globosa appears to be a poor convertor. During 30 days' starvation, the test individuals lost 4.4 mg dry body substance/g/day i.e. the maintenance cost was 14-7 cal/g live snail/day. The SDA increased by four times for those feeding on maximum rations in comparison to those receiving about 5 mg/g/day, i.e. the energy cost for converting food was increased four times.     

Biological control of Salvinia by the snail Pila globosa Swainson

The recent spread of Salvinia molesta , a free floating weed in tropical and sub-tropical regions has attracted attention the world over. In India, many states face serious problems on account of Salvinia infestation. Several methods of controlling the weed have been tried, but with limited success. Biological control by snails, especially Pila globosa , a common tropical snail found in Kerala and other parts of India is suggested. It was found to feed voraciously on Salvinia , but not on paddy which forms a major crop in Kerala and other parts of India. The snail has efficient adaptations for a tropical environment in aquatic, semi-aquatic and even terrestrial habitats and its flesh is edible. Further studies on the performance of the snails in the field are, however, required.     

Storage excretion in the Indian apple snail,Pila globosa (Swainson), during aestivation

Uric acid accumulates in several tissues of the Indian apple snail, P. globosa, during aestivation. This accumulation is particularly high in the foot muscle and reproductive organs. Since the kidney, a tiny organ in the snail, has only a limited capacity to store uric acid, extrarenal tissues are used as storage depots of uric acid during aestivation. It is suggested that the aestivating snail, faced with a cleidoic situation, resorts to storage excretion, a phenomenon well documented in insects.     

Effects of feeding level and body size on food utilization of the freshwater snail Pila globosa

Food supply caused an increase in the overall energy budget of all size groups of Pila globosa. Feeding rate increased from 3.4 to 28.7, 2.0 to 19.1 and 0.2 to 7.2 mg/g/day in young, intermediate and old snails respectively. The corresponding increase in body weight (growth rate) ranged from 1.3 to 2.7, 0.5 to 1.5 and 0.4 to 0.5 mg/g/day. When compared with the other two groups, maximum values were recorded for young P. globosa, i.e. an increase in size (ageing) caused a decrease in the energy budget. Data obtained for the maintenance, optimum and maximum feeding rates for the young P. globosa were 12.0, 22.0 and 28.8 mg/g/day. The corresponding values for the intermediate and old snails were 7.4, 14.0 and 19.0 mg/g/day and 4.1, 5.6 and 7.2 mg/g/day. With the increase in body weight, a progressive reduction in the slope of the regression lines was noticed in the body weight-conversion rate relationship.Paper presented in the first Indian Conference on Ecology and Environmental Sciences, University of Rajasthan, Jaipur (1980).     

Excretion, accumulation and site of synthesis of urea in the snail Pila globosa during active and dormant periods.

The pattern of urea excretion in active and dormant phases of the amphibious Indian apple snail, Pila globosa, as well as the possible site and mechanism of urea synthesis in this animal have been studied. 1. Urea may be synthesized in the hepatopancreas of this snail and excreted through the nephridia with the nephridial fluid during the active period of the animals life. In dormant snails, this metabolic excretory waste accumulates in its various organs and body fluids. 2. The possibility of the presence of an ornithine cycle for the synthesis of urea in the hepatopancreas is indicated in this snail.     

Studies on some kinetic parameters of aminotransferases in tissues of the snail, Pila globosa (Swainson) during malathion intoxication

The aspartate and alanine aminotransferases in the tissues of the snail, Pila globosa showed high catalytic potentials (low Km and high Vmax) during malathion exposure in vivo. In vitro addition of different concentrations of malathion did not influence aminotransferase activity. The results are discussed in relation to the regulative influence of the intracellular environment of the cell.     

Functional significance of AMP deaminase and adenosine deaminase in the aestivating freshwater snail, Pila globosa (swainson): possible neuroendocrine involvement

The functional significance of AMP deaminase and adenosine deaminase has been studied in hepatopancreas of active, aestivated and ganglionic extracts-administered snails. The activity levels of both enzymes decreased in aestivating snails. Active snails injected with ganglionic extracts of aestivated snails also showed decreased activity. Contrastingly, the hepatopancreas of aestivated snails when treated with ganglionic extracts of active snails showed increased specific activities of both enzymes. The decrease or increase in the specific activities varied with different ganglionic extracts and the significance of the same is discussed.     

Purification, Spectroscopic Characterization and o-Diphenoloxidase Activity of Hemocyanin from a Freshwater Gastropod: Pila globosa

Hemocyanins are multi-subunit oxygen carrier proteins, found in select species of arthropoda and mollusca. Here, we have purified native hemocyanin from Pila globosa, a freshwater gastropod, verified using mass spectrometry and determined its molecular weight, secondary structure and the spectral properties, using Ultraviolet/visible, Fourier transform infra-red and Circular dichroism spectroscopy. Our results reveal the oligomeric and glycosylated nature of the protein, comprising of 400 kDa subunits, organized predominantly into a thermo-stable, alpha-helical conformation. Further, biochemical assays confirm catecholoxidase-like activity in hemocyanin, which has been used to develop a first-generation optical sensor, for the detection of phenols.     

N-glycolylneuraminic acid deficiency in humans

Classic studies suggested that the common mammalian sialic acid N-glycolylneuraminic acid (Neu5Gc) is an oncofetal antigen in humans, being immunogenic in adult humans and yet apparently expressed in human fetuses and tumors. We and others have recently found that the human deficiency of Neu5Gc can be explained by an inactivating mutation in the gene encoding CMP-N-acetylneuraminic acid hydroxylase. Thus, Neu5Gc is not an oncofetal antigen in the classical sense, and other explanations must be found for the observed expression pattern. This review provides an update on this matter, and considers a variety of other old and new questions that arise from it.     

A single step purification of a sialic acid binding lectin (AchatininH) from Achatina fulica snail

A sialic acid binding lectin, Achatinin_H, was purified in single step from the hemolymph of the land snail, Achatina fulica, by the affinity chromatography on sheep submaxillary mucin coupled to Sepharose 4B. The yield of the lectin was found to be 3 mg from 100 ml of hemolymph. The homogeneity of the lectin was established by alkaline gel electrophoresis, immunodiffusion, immunoelectrophoresis and analytical isoelectrophoresis. The molecular weight of the native protein was 242000, having identical subunits of Mr 15000. The lectin agglutinated rabbit erythrocytes in the presence of Ca^2–. The inhibition study clearly suggests that the binding site of the lectin recognizes sialic acid as the immunodominant sugar. This was further confirmed by the observation that there was a marked decrease of agglutinating activity of the lectin with neuraminidase treated rabbit erythrocytes and asialofetuin was unable to inhibit the activity of Achatinin_H. Among the inhibitors used the glycoconjugate containing 2-6 linkages of N-acetylneuraminic acid with subterminal galactopyranose or 2-acetamido-2-deoxy-galactopyranose residue was found to be better inhibitor than that containing 23 linkages of N-acetyl neuraminic acid. Besides that sialoglycoprotein containing both N and O type of glycosidic linkages plays an important role in binding with the lectin. Fetuin was found to be the best inhibitor.     

An unique specificity of a sialic acid binding lectin AchatininH, from the hemolymph of Achatina fulica snail

A sialic acid-binding lectin, AchatininH, from the hemolymph of Achatina fulica snail is found to be highly specific for 9-0-acetyl sialic acid. The binding specificity of AchatininH distinguishes it from other known sialic-acid specific lectins which usually show a broader range of specificity for sialic acid. It is even better than crab lectin which shows specificity for both 4- and 9-0-acetylated derivatives of sialic acid. This limited specificity of AchatininH appear to account for the fact that it agglutinates only rabbit, rat and guinea pig erythrocytes which contain 9-0-acetylated sialic acid but not horse (mainly contain 4-0-acetylated sialic acid), human, monkey, sheep, goat and chicken erythrocytes which contain either N-acetyl or N-glycolyl neuraminic acid but no 0-acetylated derivatives. This finding was further supported by the potent inhibition of hemagglutination by free 9-0-acetylated neuraminic acid and by several glyco shingolipids of human origin having 0-acetylated sialic acid.     

N-glycolylneuraminic acid as a carbohydrate cancer biomarker

One of the forms of aberrant glycosylation in human tumors is the expression of N-glycolylneuraminic acid (Neu5Gc). The only known enzyme to biosynthesize Neu5Gc in mammals, cytidine-5′-monophosphate-N-acetylneuraminic acid (CMAH), appears to be genetically inactivated in humans. Regardless, low levels of Neu5Gc have been detected in healthy humans. Therefore, it is proposed that the presence of Neu5Gc in humans is from dietary acquisition, such as red meat. Notably, detection of elevated Neu5Gc levels has been repeatedly found in cancer tissues, cells and serum samples, thereby Neu5Gc-containing antigens may be exploited as a class of cancer biomarkers. Here we review the findings to date on using Neu5Gc-containing tumor glycoconjugates as a class of cancer biomarkers for cancer detection, surveillance, prognosis and therapeutic targets. We review the evidence that supports an emerging hypothesis of de novo Neu5Gc biosynthesis in human cancer cells as a source of Neu5Gc in human tumors, generated under certain metabolic conditions.     

Specificity of the sialic acid-binding lectin from the snail Cepaea hortensis.

The specificity of the sialic acid-binding lectin from the snail Cepaea hortensis, purified by affinity chromatography on fetuin-Sepharose, was studied by hemagglutination inhibition assay applying 32 sialic acid derivatives and 14 glycoproteins. 2-alpha-Methyl-9-O-acetyl-NeuAc was the most potent inhibitor, followed closely by 2-alpha-methyl-NeuAc and 2-alpha-benzyl-NeuAc. An axially orientated carboxyl group is a prerequisite for maximal lectin-sugar binding. Neither size nor polarity of the alpha-anomeric substituent significantly influenced inhibition potency. An intact sialic acid N-acetyl group is essential for optimal lectin-sugar interaction. The trihydroxypropyl side chain also is of great importance. However, a bulky hydrophobic substituent at the side chain like a 9-O-tosyl residue did not decrease binding to the lectin. The lectin did not distinguish between NeuAc alpha 2----3Gal beta 1----4Glc and NeuAc alpha 2----6Gal beta 1----4Glc. Among other sugars tested, only N-acetylglucosamine showed inhibition, although 50-fold less. The most potent glycoprotein inhibitors were those carrying O-chains only or preferentially, as ovine submaxillary mucin, bovine submaxillary mucin, and glycophorin A. Tamm-Horsfall protein was an exception being a strong inhibitor, although carrying only N-chains. Asialoglycoproteins were inactive. Glycoproteins containing the NeuAc alpha 2----3Gal sequence inhibited the lectin as well as those with NeuAc alpha 2----6GalNAc. From the results a model of the lectin's binding site for sialic acid is suggested.