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At least 973 records · Page 54Linked to original sources
PubMed1999

Some aspects of nitrogen metabolism in Biomphalaria alexandrina snails treated with selenium.

The toxicity of selenium on Biomphalaria alexandrina snails, intermediate host for Schistosoma mansoni, was traced by studying its effect on the protein profile, free amino acids (FAA) and some urea cycle enzymes, namely, ornithine aminotransferase, argininosuccinate synthetase and arginase in hepatopancreas of snails. The results revealed that treatment with 15 ppm selenium dioxide (SeO2) caused an elevation in the protein content and a variation in the percentage and number of the different polypeptides as obtained by gel electrophoresis, and a remarkable reduction in all FAA except arginine alanine and threonine. On the other hand, the activity of ornithine, aminotransferase was elevated whereas that of arginase was reduced. The study is a trial to focus some metabolic disorders caused by SeO2 on the physiological status of these intermediate host snails, which may greatly control parasite-host association and thus the life-cycle of the parasite within its respective host may be somewhat disturbed.

Animals↗
PubMed1999

Factors affecting adoptive transfer of resistance to Schistosoma mansoni in the snail intermediate host, Biomphalaria glabrata.

We examined potential variables affecting adoptive transfer of resistance to Schistosoma mansoni in Biomphalaria glabrata implanted with amebocyte-producing organs (APOs) from resistant snails. Transplants of 7 tissues other than the APO (heart, kidney, mantle, albumin gland, brain, digestive gland, and gonad) did not transfer resistance, suggesting a unique property of this structure. Only APOs from donors previously exposed to miracidia transferred resistance, although whether this is evidence for a priming effect or merely the elimination of susceptible donors is not known. Variability in the donor and in the implant itself apparently was unimportant, inasmuch as implants from small or large snails or from 2 separate donors all conferred similar levels of resistance. Recipients of APOs from 2 additional resistant strains of B. glabrata, 10-R2 and Salvador, also displayed resistance. However, no resistance was transferred by APOs from schistosome-refractory B. obstructa. Histological examination of implants removed from recipients that either did or did not show transferred resistance revealed no differences in mitotic activity. Furthermore, implanted APOs from B. obstructa displayed no mitotic activity. Finally, reexposure of snails with transferred resistance to a large dose of miracidia caused infection in 70%, suggesting that either transferred resistance is transitory or it can be overwhelmed.

Adoptive Transfer↗
PubMed2000

Sublethal concentration of Ambrosia maritima(Damsissa) affecting compatibility of Biomphalaria alexandrina snails to infection with Schistosoma mansoni through disturbing the glycolytic pathway.

High glycolytic flux as an emergency pathway for generating ATP was recorded as the most important metabolic pathway required for the success of Biomphalaria-Schistosome sporocyst interaction. Effect of LC25 of dry powdered Ambrosia maritima (Damsissa) as plant molluscicide on hexokinase (HK), pyruvate kinase(PK), glucose phosphate isomerase(GPI) was tested. It resulted in a significant inhibition of the three investigated enzymes. Treatment of snails with LC10 concentrations of A. maritima reduced considerably the infection rate of Biomphalaria alexandrina with Schistosoma mansoni to be 34% compared to an infection rate of 80% in control non-treated snails. Longer prepatent period and remarkable decrease in cercarial production was also recorded in snails treated with the sublethal concentrations of this molluscicide.

Animals↗
PubMed1975

Seasonal population densities of snails transmitting urinary and intestinal schistosomiasis in Lusaka, Zambia.

The two molluscan intermediate hosts of S. haematobium schistosomiasis: Bulinus africanus and Bulinus globosus, were found most commonly in habitats that retained water for a substantial part of the year rather than in temporary rain-filled pools. Biomphalaria pfeifferi which transmits S. mansoni were found principally in streams and impoundments like dams but scarce in rivers. In a permanent habitat, the peak density of snails was between the warm, dry months of August and September while in a temporary habitat B. (Physopsis) sp. were most abundant towards the end of the rainy season in March and April. The influence of rainfall and the prevailing the temperature on the fluctuations in the density of snails populations is considered. Further, the low infection rate in snails found in the field is discussed in relation to the critical effect of temperature on this feature. The problem of increasing migration of rural inhabitants to the peri-urban areas and the possible escalation of prevalence rates is considered in relation to the control measures that may be instituted in view of the substantial body of base-line data now available to effect focal control.

Animals↗
PubMed2001

Embryonic development of the freshwater snail Biomphalaria glabrata under microgravity conditions (STS-89 mission).

The embryonic development of the fresh-water snail Biomphalaria glabrata was examined under microgravity-conditions and compared with the ground control and standard embryos, putting special emphasis on the shell formation. The process of shell formation may be particularly sensitive to the change of gravitational forces. The project aimed at determining whether the processes of mineralization during the formation of the exoskeleton in the growing snail embryo take place normally under microgravity conditions. Twenty-four adult individuals of the tropical freshwater snail B. glabrata were maintained 9 days in the Closed Equilibrated Biological Aquatic System (CEBAS Minimodule) on Space Shuttle flight STS-89. The animals produced spawning packs throughout the duration of the mission so that embryos of all developmental stages were achieved. The embryos developed slightly slower in the CEBAS than under standard conditions, and in older embryos a decreased mineralization of the shell was detected. These phenomena, however, were observed in the flight module as well as in the ground control specimens and was not an effect caused by the microgravity conditions. Embryos of B. glabrata showed a correct morphogenesis under microgravity, no teratological effects were noticed, and the shell formation proceeded normally.

Animals↗
PubMed1976

Studies on resistance in snails. 3. Tissue reactions to Echinostoma lindoense sporocysts in sensitized and resensitized Biomphalaria glabrata.

The resistance of Biomphalaria glabrata snails that have been sensitized by various levels of irradiated or nonirradiated Echinostoma lindoense miracidia increased after a second challenge infection with nonirradiated miracidia of the same species. This was demonstrated by increased suppression of migrating capacity of invading sporocysts, an accelerated host tissue reaction, and a greater tendency of snail amebocytes to flatten while attacking the parasite. Three methods of elimination of invading sporocysts were observed: (1) encapsulation by amebocytes followed by destruction of the sporocysts; (2) expulsion of the sporocyst through the host epithelium after its encapsulation in the subepithelial tissues; (3) blockade of the parasite's entry into subepithelial tissues by a localized amebocyte aggregation. The basic mechanism of host snail response to a single or a repeated challenge infection appears to be similar, though an anamnestic reaction is evident in the accelerated response following a second challenge exposure.

Animals↗
PubMed2004

Compatibility of Biomphalaria alexandrina snails to infection with Schistosoma mansoni after exposure to sublethal concentrations of Myrrh.

The effect of exposing B. alexandrina to sub-lethal dose (LC10 & LC20) of Myrrh, on its susceptibility to infection with S. mansoni miracidia were determined. Starting three weeks post miracidial exposure, cercarial shedding was monitored. No shedding of cercariae were observed from snails treated with LC20. In snails treated with LC10, longer prepatent cercarial and shorter cercarial production periods than those of control group were recorded. The number of infected snails and of shedding cercariae were decreased. The study revealed that sublethal values of myrrh decreased the compatibility of B. alexandrina to S. mansoni infection thus playing an important role in the control of schistosomiasis.

Animals↗
PubMed2004

Toxicological effect and biochemical alterations induced by different fractions of Euphorbia royleana latex in freshwater harmful vector snail Lymnaea acuminata.

Laboratory evaluation was made to assess the molluscicidal activity of different fractions of Euphorbia royleana (Family- Euphorbiaceae) latex obtained through sephadex gel column against freshwater snail Lymnaea (Radix) acuminata Lamarack. This snail is the vector of liver fluke, Fasciola hepatica Linnaeus and Fasciola gigantica Cobbold, which causes endemic fascioliasis in cattle and livestock. The toxic effect of the different fractions was time dependent and fifth fraction obtained through benzene: ethyl acetate (5:5) had maximum molluscicidal activity against Lymnaea acuminata. There was a significant negative correlation between LC values and exposure periods thus increase in exposure time, the LC50 value of V fraction of Euphorbia royleana latex was decreased from 14.28 mg/l (24 hr) to 9.28 mg/l (96 hr) against Lymnaea acuminata. After exposure to sub-lethal concentrations of this fraction there were significant time and dose dependent alterations observed in pyruvate, lactate levels, ALAT, AAT, AChE and cytochrome oxidase enzyme activities in different body tissues of Lymnaea acuminata. It is proposed that the fifth fraction of E. royleana latex can be used as a molluscicide for controlling the harmful snail population from aquatic ecosystem without any harm due to their reversible toxic action.

Animals↗
PubMed2005

Appearance of morphological novelty in a hybrid zone between two species of land snail.

On the small oceanic island of Chichijima, two endemic species of land snails, Mandarina mandarina and M. chichijimana, have discrete distributions separated by a hybrid zone. This study investigates the potential of hybridization as a source of morphological novelty in these snails. Mandarina mandarina possesses a shell with a higher whorl expansion rate and a smaller protoconch than M. chichijimana, relative to shell size. The number of whorls and shell size of M. mandarina do not differ from those of M. chichijimana, because the effect of higher expansion rate on number of whorls and size of the former is compensated for by its smaller protoconch. The whorl expansion rate and protoconch diameter of the individuals from the hybrid populations are intermediate or typical of either of the two species, and their average values show clinal changes along the hybrid zone. However, the hybrid populations include exceptionally high shells with many whorls and flat shells with few whorls, which are never found in the pure populations of either species. In addition, gradual increases in variance in shell height and number of whorls were found from the edges to the center of the hybrid zone. A combination of low expansion rate (typical of M. chichijimana) and a small protoconch (typical of M. mandarina) produces a shell with an extremely large number of whorls because of the geometry of shell coiling. However, the combination of high expansion rate and a large protoconch produces a shell with an extremely small number of whorls. Because of the correlation between the number of whorls and shell height, shells with an exceptional number of whorls possess an extraordinarily high or flat spire. Hybrids can inherit a mosaic of characters that, as they play out during growth, lead to novel adult morphologies. These findings emphasize the importance of hybridization as a source of morphological variation and evolutionary novelty in land snails.

Analysis of Variance↗
PubMed2006

Molluscicidal effect of fenitrothion and anilofos on Lymnaea natalensis and Biomphalaria alexandrina snails and on the free larval stages of Schistosoma mansoni.

Psticides; fenitrothion and anilofos (aniloguard) were testd as molluscicides against Lymnaea natalensis and Biomplhalaria alexandrina. The LC10 & LC90 of fenitrothion was 0.12 & 0.21 ppm for L. nalalensis and 0.17 & .26 ppm for B. alexandrina, respectively. The LC50 & LC90 anilofos was 2.61 & 6.47 ppm for Lymnaea and 3.07 & 8.6 ppm for Biomphalaria. The effect of sublethal concentrations (LC0, LC5 & C10) of Feni-rothion on B. alexandrina growth rate, eggs hatchability and on free larval stages of Schistosonma mansoni (miracidia & cerca-riae) were studied. The results obtained showed that sublethal concentrations of fenitrothion caused reduction in growth rate of B. alexandrina and reduction in the hatchibility of snails eggs. The mortality rates of miracidia and cercariae were elevated by increasing both the concentrations of fenitrothion and the time of exposure. The results showed that fenitrothion was more toxic to the free larval stages of S. mansoni than to their snails. The results showed a significant reduction in total protein of treated snails when compared with controls in haemolymph while there was an increase of protein contents of the tissue. The AlkP enzyme activity was slightly increased in the haemolymph of experimental groups than the control and in the tissues the values were significantly higher when compared with control. ALT enzyme activity in haemolymph of experimental groups was higher than controls while its activity in tissue was lower. AST enzyme activity was higher in haemolymph and tissue of experimental groups than in controls.

Animals↗
PubMed2006

Effect of the plant Cupressus macro-carpa (Cupressacea) on some haematolo-gical and biochemical parameters of Biomphalaria alexandrina snails.

The dry powder of the plant aereal part; Cupressus macro-carpa (Cupressacea) was tested against Biomphalaria alexandrina. LC50 & LC90 values were 59.5 & 98.8 ppm, respec-tively. Exposure of B. alexandrina to sublethal concentrations (LC0, LC10 & LC25) of C. macrocarpa for three weeks signi-ficantly decreased the number of circulating hemocytes. The magnitude of reduction was increased with increasing of the tested concentration. The main type of cell in the hemolymph of B. alexandrina was the granulocyte (71.8%), followed by large round cells or hyalinocytes (19.0%) and small round cells or undifferentiate cells (9.2%). The percentage of different hemocyte categories was changed in treated snails. In snails maintained at LC25, showed significantly higher percentages of small round cells than controls, 56.2% & 9.2% respectively. Maintainence of B. alexandrina in sublethal concentrations for three weeks significantly reduced protein & hemoglobin content in the hemolymph. Reduction in enzyme activities occurred in the hemolymph and tissues of treated snails. The enzymes were pyruvate kinase (PK), lactat dehydrogenase (LDH), hexokinase (HK) and phosphoenol pyruvate carboxy kinase (PEPCK) which are very important in metabolism of the protein and carbohydrate. The infectivity of Schistosoma mansoni miracidia was greatly reduced by exposure to the sublethal concentrations (LC0, LC10 & LC25) of Cupressus. Infection rate of B. alexandrina reached to 54.5%, 37.5% & 16.7%, respectively compared to control (81.25%). Duration of cercarial shedding and the total periodic cercarial production/snail showed significant reduction while the parasite incubation period was significantly longer (p<0.05).

Animals↗
PubMed1991

Inhibition of lactate dehydrogenase isoenzyme associated with anaerobic respiration in schistosomiasis intermediate host snails.

Lactate dehydrogenase isoenzyme (LD5) which is associated with anaerobic respiration was inhibited to a certain degree in Biomphalaria alexandrina snails, the intermediate host for Schistosoma mansoni. Urea and thiourea were used as inhibitors. The effect of LD5 inhibition on the mortality rate of infected Biomphalaria alexandrina snails and on the susceptibility of the snails to the trematode infection was also studied.

Anaerobiosis↗
PubMed1991

Ecdysteroids as regulators of host and parasite interactions: a study of interrelationships between Schistosoma mansoni and the host snail, Biomphalaria glabrata.

Ecdysteroids have been detected in trematode parasites and in several species of gastropod snails. The potential role of these and other hormones as regulators of host/parasite interactions is discussed. This study considers the role of ecdysteroids in the host parasite interactions between Schistosoma mansoni and Biomphalaria glabrata interactions. beta-Ecdysterone was found to be effective in stimulating host location activities in S. mansoni miracidia and in enhancing growth and egg production in B. glabrata. However, plant extracts rich in phytoecdysteroids were not attractive to miracidia and did not affect growth and egg production in snails. The potential role of ecysteroids in the process of parasitism and snail physiological processes is discussed. Plants rich in phytoecdysteroids do not appear to be of value in process which may interfere with the host parasite interactions in schistosomes.

Animals↗
PubMed1990

[Inventory of fresh water snails in Mayotte, Comoro Islands].

No trematodosis is known at the present time in Mayotte despite the close historical relationships between the Mayotte Archipelago and the neighbouring island of Madagascar, which is heavily infested. It is noteworthy that no intermediate host has been described in previous studies in Mayotte. An inventory of fresh water snails was performed from 1985 to 1988, in 53 experimental stations during the rainy and the dry seasons: 3,940 snails of eight different species were collected and further identified. The sole occurrence of Lymnaea natalensis constitutes a new record in Mayotte where there are now 14 different species of fresh water snails. According to the role of Lymnaea natalensis as a vector of Fasciola gigantica, particularly in Madagascar, the veterinary control of cattle importation into Mayotte is of great interest.

Animals↗
PubMed1990

The effect of Schistosoma haematobium infection on the growth and fecundity of three sympatric species of bulinid snails.

Three species of bulinid snails were monitored to determine the effect of infection with 2 sympatric strains of Schistosoma haematobium on longevity, growth, and reproductive output, from the onset of cercarial production until death. Bulinus senegalensis was least affected by infection, with total fecundity reduced by less than 34%. Infected Bulinus truncatus showed an acceleration in growth accompanied by a 63% reduction in fecundity, although the majority of snails continued to oviposit at a low level. The longest-lived snails in this study, Bulinus globosus, showed decreased growth and survival when infected. In addition a significant proportion of infected individuals of this species failed to oviposit, and those that retained some reproductive capacity produced fewer embryos than controls. Total fecundity of B. globosus was reduced almost 90% by infection with S. haematobium, yet long-term monitoring of individuals showed that reproductive activity recovered when parasite productivity was low. Results from this and similar studies indicate that the time of infection by a trematode in relation to reproductive maturity of the molluscan host is important in determining the subsequent effects on host growth and fecundity.

Animals↗
PubMed1990

On the effects of ivermectin on freshwater snails of medical and veterinary importance.

Ivermectin is lethal to Bulinus (Physopsis) globosus, Biomphalaria pfeifferi, and Lymnaea natalensis at concentrations of 0.08 micrograms/ml and above. Studies show that these snails will not recover from a 24 h exposure to 2.00 micrograms/ml of Ivermectin in the laboratory at 28 +/- 2 degrees C. A time dependent toxicity to snails was recorded and an exposure of adult snails to sub lethal concentrations significantly reduced the number of eggs laid (r = -0.08, t = 2.64, P less than 0.05).

Animals↗
PubMed1989

Defensive behaviour in the pond snail, Lymnaea stagnalis: the whole body withdrawal associated with exsanguination.

The freshwater snail L. stagnalis is known to be able to respond to a strong, noxious stimulus with a full retraction of the foot and head into the shell accompanied with expelling the blood through the hemal pore. We have found that this behavioural response, besides graded local retractions, can be triggered by mild tactile stimulation provided that the stimulus is repeated several times. Only a complete exsanguination could be obtained, indicating that it is an all-or-none defensive behaviour. In an electrophysiological investigation of isolated brain, a number of similarities were found between this all-or-none behaviour and the so-called input 3 to central neurons, as described by Benjamin and Winlow. These include ability to be selectively activated by high calcium solutions, and blocked by keeping the snails in a spoiled water. Injection of snails with naloxone (0.5-2.0/micrograms/g) or ergotamine (0.4/microgram/g) blocked selectively the whole body withdrawal induced by tactile stimulation, but not that induced by injection of a high calcium saline or acetylcholine solution, indicating that enkephalinergic and/or dopaminergic mechanosensory neurons might be involved. The consideration of available data has led to a working hypothesis that the activity of input 3 might be the neurophysiological correlate of the high threshold all-or-none whole body withdrawal associated with exsanguination.

Animals↗
PubMed1987

The effect of seasonal temperature and experimental illumination on reproductive rate in the snail Biomphalaria glabrata.

1. Reproduction in the snail Biomphalaria glabrata, a vector of Schistosoma mansoni, was measured by egg production and other parameters such as number of clutches, eggs per clutch and egg hatching, under laboratory conditions. 2. Reproductive rates were highest in terms of total number of eggs, clutches and hatching under constant illumination, followed by conditions similar to the natural rhythm of illumination. The greatest reduction in reproduction occurred in constant darkness. In summary, reproductive rate was dependent on both the intensity of absolute illumination and the schedule of illumination exposure. 3. Seasonal variation in reproductive rate appeared to vary inversely with local temperature in Belo Horizonte, situated in a tropical zone (latitude 20 S) owing probably to a temperature preference of 20 to 25 degrees C by the snail. The highest reproductive rates occurred in winter, except for the parameter eggs per clutch which was maximal in autumn. Snail reproduction appeared to be most reduced during summer. There was no linear correlation between reproductive rate and temperature.

Animals↗