Laboratory assessment of the molluscicidal and cercaricidal activities of the Egyptian weed, Solanum nigrum L

The molluscicidal properties of Solanum nigrum L. were tested against three Egyptian snail species (Biomphalaria alexandrina, Bulinus truncatus and Lymnaea natalensis), each an intermediate host of parasites causing human schistosomiasis or fascioliasis. The plant was collected in two regions within Egypt: Fayium and Giza. Snails were exposed for 24 and 48 h, to the dry powdered fruits and leaves or to crude water extracts of the powders, and mortality was recorded. The water extract of the leaves collected in Fayium (FLWE) had the highest molluscicidal activity, with median lethal concentrations (LC50) of 18.6 mg/litre for Bi. alexandrina, 14.5 mg/litre for Bu. truncatus and 17.7 mg/litre for L. natalensis. When Bi. alexandrina infected with Schistosoma mansoni were exposed to FLWE (20 or 25 mg/litre), they shed significantly fewer cercariae than unexposed snails (P < 0.02). The cercaricidal properties of FLWE were directly tested against S. haematobium, S. mansoni and Fasciola gigantica cercariae and a time-concentration relationship was observed; the concentrations needed to kill all cercariae (LC100) within 30 min of exposure were 30 mg/litre for both S. haematobium and S. mansoni and 40 mg/litre for F. gigantica.     

Seasonal variation in molluscicidal activity of Solanum nigrum L

Solanum nigrum L. leaves and fruits were shown to have molluscicidal activities against snails transmitting schistosomiasis and fascioliasis. In the present study, their molluscicidal activity against adult Biomphalaria alexandrina snails was assessed to determine whether plants collected at various seasons would have different degrees of toxicity. Leaves and fruits of three S. nigrum varieties were collected from Faiyoum and/or Giza during the four seasons. Leaves collected in autumn had the highest effect (LC50-35.4) followed by spring (LC50 = 44.36), summer (LC50 = 46.7) and winter (LC50 = 100.4). Toxicity of plant extracts was also affected by other seasonal dependent factors. These are the duration of plant exposure to direct sunlight and the size of the fruits. S. nigrum (black fruits) was more toxic (LC50 = 18.1) than the other two types, S. nigrum v. vellosum (yellow fruits) (LC50 = 38.9) and S. nigrum v. juidaicum (red fruits) (LC50 = 34.7).     

Invasion of the Nile Valley in Egypt by a hybrid of Biomphalaria glabrata and Biomphalaria alexandrina, snail vectors of Schistosoma mansoni

Two years (1996-1997) of systematic survey showed that a hybrid of Biomphalaria glabrata and Biomphalaria alexandrina has invaded the irrigation and drainage systems in the Nile Delta and the Valley nor the of El-Menya. However, the infestation of water courses by and the population density of this snail were variable in various localities. The infestation rate ranged between 7.1% in El-Fayoum Governorate and 52.6% in El-Dakahliya Governorate and the snail density from 2 snails/site to 69.7 snails/site in the same governorates, respectively. Comparing the survey results of the two study years in the sampling sites indicated that the hybrid snail has relatively increased in population density than B. alexandrina. The hybrid snail of B. glabrata and B. alexandrina was found alone in some sites, but was mostly associated with B. alexandrina. The results showed also that both Biomphalaria have almost the same major physicochemical requirements. However, the hybrid snails and B. alexandrina were found differently associated with aquatic snails and plants. The hybrid snail was found naturally infected with S. mansoni thus giving indication that it is presently participating in schistosomiasis mansoni transmission in Egypt.     

Increased neopterin in patients with chronic and acute coronary syndromes

The effect of aprotinin on Schistosoma mansoni miracidial penetration process, by its direct topical application on Biomphalaria alexandrina snails, was studied The snails were exposed to S. mansoni miracidial suspension which was mixed with aprotinin at concentrations ranging from 0.02 to 20 Kallikrein inactivator units (KIU)/ml of applied solution. Results showed that aprotinin had marked inhibitory effect on miracidial penetration of the snails. The concentration that resulted in 50% inhibition of the miracidial penetration into B. alexandrina snails (LD50) was 2.4 KIU/ml while (LD96) was 20 KIU/ml of the applied solution. Thus, aprotinin may be one of the important methods in the control of schistosomiasis.     

The larvicidal activity of solvent extracts of three medicinal plants against third instar larvae of Chrysomyia albiceps

Four solvent extracts of each of Lemongrass (Symbopogon citratus), Santonica (Artemisia cinae) and Pomegranate (Punica granatum) were tested against the 3rd instar larvae of Chrysomyia albiceps. The pomegranate extracts showed the larvicidal activity with LC50 ranging between 25 ppm (acetone extract) and 280 ppm (chloroform extract). The Santonica showed larvicidal activity with LC50 ranging between 48 ppm (ethanol extract) and 380 ppm (acetone extract). The Lemongrass showed activity with LC50 ranging between 135 ppm (ethanol extract) and 570 ppm (chloroform extract). So, the most effective action in accordance to LC50 were the acetone extract of pomegranate, followed by ethanol extract of Santonica and lastly ethanol extract of Lemongrass. The slope functions of these three extracts were 4.6, 2.8 and 8.22 respectively. The shift to insect control by plant extracts pave the way to a somewhat healthy environment.     

Laboratory evaluation of molluscicidal activity of extracts from Cotula cinerea (L) and Quercus lusitania var. infectoria galls (Oliv.)

In this work, we have studied the molluscicidal activity of different extracts obtained from Cotula cinerea and Quercus lusitania var. infectoria galls. The hydroalcoholic extract of Cotula cinerea, acetonic extract and gallotanin of Quercus infectoria galls have presented high activity against Bulinus truncatus. The hydroalcoholic extract of Cotula cinerea was fractionated by chromatography on silica gel column. We have isolated two very active fractions at concentrations respectively of 52.5 and 27.5 ppm.     

Intraarterial infusion of anti-cancer agents. (A suitable technic introducing a polyethylene tube, with angiographic visualization, through the deep femoral artery directly into the artery in the abdomen selected for injection, using two kinds of guidewires) (author''s transl)

The authors have infected 127 B. glabrata by 2 miracidia of S. mansoni, either on the Same day, or introducing a second miracidium after 3, 7 and 16 days. 1 All the groups of planorbid snails had a low percentage of positivity (31 to 41 %). 2 The first cercarial emissions, in the 4 groups were scattered in the time, the delay being in correlation with the second infection. 3 In the snails reinfected after 3 and 7 days occured the highest emissions, those with the simultaneous double infection or second infection delayed to 16 days, had the lesser emissions. 4 An interval cycle of about 3 weeks was discovered for the highest emissions. All those phenomena are probably due to competition between the sporocysts born from both miracidia. Moreover, evident reduction of the fecundity in the positive snails were shown only after the beginning of the cercarial emissions, while a normal, or even increased fecundity was established in the prepatent period of the infected snails.     

Reducing perineal trauma: implications of flexion and extension of the fetal head during birth

Among the determinant factors in the resistance and susceptibility of Biomphalaria to Schistosoma mansoni, hemocytes play an important role. Aiming at studying S. mansoni/Biomphalaria interactions related to hemocytes, the first step is certainly connected with the standardization of this cell population in uninfected Biomphalaria. In this way, quantification of this cell population in hemolymph, as well as its phagocitary capacity, have been determined for the first time. Furthermore, using susceptible and resistant strains of B. glabrata and B. tenagophila, the hemocytegram and phagocytary capacity of hemocytes after infection with S. mansoni were determined too. Resistant and susceptible strains of B. glabrata (BA and BH, respectively), as well as resistant and susceptible strains of B. tenagophila (TAIM and CF, respectively) were infected with 10 miracidia of the LE and SJ strains of S. mansoni, respectively. These infected snails and respective uninfected controls were assessed in relation to the number of circulating hemocytes and alteration in the phagocytary capacity, by using Zymozan and MTT. Reading was taken by means of a spectrophotometer at 5 hours and 1, 2, 5, 10, 20 and 30 days after infection. The results showed a decrease in population of the circulating phagocytary cells, 5 hours after infection. One day post-infection, the circulating cells of the susceptible snails showed an increased metabolic activity, but the same event could not be observed in the resistant strains. In the subsequent observation periods, significant differences among the strains studied could not be observed until the end of the experiment.     

Host choice by larval parasites: a study of Biomphalaria glabrata snails and Schistosoma mansoni miracidia related to host size

Within snail/trematode associations the age/size of the host at infection has consequences with regard to miracidial infection success, further intramolluscan parasite development and reproduction, and the host response, mainly in terms of growth and reproductive effort. Taking into account these differences, we were interested in determining whether miracidia could discriminate and make a choice between snails of different sizes. Using the Schistosoma mansoni/Biomphalaria glabrata system, we compared data on the snail infection rate and the mother sporocyst abundance among three size classes of snails (juvenile, subadult, and adult) exposed separately or together to the parasite larvae. When exposed individually, juvenile snails (3-5 mm) had significantly higher prevalence and abundance values than did subadult snails, followed by adult snails. In contrast, when snails of the three size classes were exposed together in heterogeneous size groups the prevalence and abundance values were always significantly higher for subadult snails of the 7- to 9-mm class than for juvenile and adult snails. A host choice experiment confirmed that significantly more miracidia were attracted by subadult snails, suggesting that the parasite has been selected for specific locating and recognition mechanisms increasing the infection rate of subadult snails when the latter have been exposed in a heterogeneous size group. Selective forces that may be responsible for such a preferential infectivity of the parasite vis-à-vis particular host age/size class are discussed in relation to host resources and host responses.     

Selective interference with granulocyte function induced by Echinostoma paraensei (Trematoda) larvae in Biomphalaria glabrata (Mollusca)

Various trematode larvae can interfere with the host snail's resistance to the same or unrelated trematode species, chiefly, it appears by interference with the function of the host's granulocytes. In Biomphalaria glabrata infected with the trematodes, Echinostoma paraensei, granulocytes lose their ability to encapsulate the larvae of trematodes to which the hosts were previously resistant. However, the granulocytes in these snails retain their ability to encapsulate injected latex spheres, or larvae of the metastrongyle nematode, Angiostrongylus malaysiensis, and to phagocytose epidermal plates cast off by miracidia of the trematode, Schistosoma mansoni. Cellular infiltration in injured preputial tissue of the snail also was not suppressed by the presence of E. paraensei larvae. Interference with the granulocyte function in B. glabrata induced by E. paraensei infection therefore appears to be a selective phenomenon.     

Nicotine dependence among Norwegian smokers and possible consequences for preventive actions]

Plant-derived acaricides, extracted from various botanical species, and commercially available phytochemicals were evaluated for biological activity against immature Ixodes scapularis (Say) using the disposable pipet method. In addition, residual activity of the plant extracts was determined. Of the 13 plant extracts tested, 9 exhibited biological activity with Alaska yellow cedar, Chamaecyparis nootkatensis (D. Don) Spach., being the most effective against the nymphal ticks (LC50 = 0.151% wt:vol) and eastern red cedar, Juniperus virginiana L., showing the greatest activity against larval ticks (LC50 = .001% wt:vol). The commercially available products were significantly less active than the plant extracts we prepared, but some commercial compounds did exhibit limited activity. Only the Alaska yellow cedar exhibited any residual activity that lasted 21 d after treatment.     

Effects of snail-conditioned water from Biomphalaria glabrata on hatching of Echinostoma caproni miracidia

In vitro studies were done on Echinostoma caproni eggs with fully developed miracidia to determine the effects of snail-conditioned water (SCW) from Biomphalaria glabrata on miracidial hatching in the light. Observations were made on miracidial hatching at 4, 8, 12, 16, 20, and 24 h in multiwell chambers in the presence of SCW (experimentals) versus controls in artificial spring water (ASW). The number of hatched eggs was significantly greater (Student's t-test, P<0.05) in SCW at all times as compared with those maintained in ASW. Significantly greater hatching was also obtained when snails were maintained in intact or perforated dialysis sacs in multiwell chambers as compared with sacs without snails. Agar plugs impregnated with SCW or the hydrophilic fraction of SCW that had been extracted in chloroform-methanol (2:1) did not influence significant hatching. However, the lipophilic fraction of the SCW extract caused significant hatching. Substances in SCW significantly increase hatching of E. caproni miracidia, but details on what these compounds are remain obscure.     

A polymerase chain reaction assay for detecting snails infected with bilharzia parasites (Schistosoma mansoni) from very early prepatency

In the present study, we adapted a polymerase chain reaction (PCR) assay, previously shown by us to be very sensitive for detecting cercariae in water, for the sensitive detection of Schistosoma mansoni DNA in infected snails from early prepatency. Polymerase chain reaction primers were designed based on the 121-basepair highly repeated sequence we previously identified in the genome of S. mansoni. The DNA was prepared from the snails by a simple alkaline extraction procedure, and the PCR assay enabled a clear differentiation between infected and normal snails. Infected snails were detected as early as one day after penetration of a single miracidium. The high sensitivity of the test enabled identification of a single infected snail even when its DNA was pooled with material from up to 99 uninfected snails, thus demonstrating the possibility of mass diagnosis in pools of snails. The assay has the potential for large-scale determination of prepatent infection prevalence in snails, thus offering new possibilities for the evaluation of schistosomiasis transmission and for schistosomiasis control, as discussed.     

Release of proteins and polysaccharides from the albumen gland of the freshwater snail Helisoma duryi: effect of cAMP and brain extracts

The albumen gland is a compound tubular exocrine gland found in the female reproductive tract of freshwater pulmonate snails such as Helisoma duryi. It secretes a perivitelline fluid, composed of protein and polysaccharide complexes, and coats each fertilized egg. A 288-kDa native glycoprotein, composed of several 66-kDa subunits, was identified in soluble extracts of albumen gland. Forskolin stimulates the release of secretory granules, containing both proteins and polysaccharides, from the cytoplasm of the glandular cells. An acid extract of the central nervous system or the adenosine-3', 5'-cyclic monophosphate (cAMP) analogue 8-bromo cAMP, stimulates protein secretion from the gland. Pretreatment of the albumen gland with cAMP antagonist (Rp isomer of cAMP) inhibits the stimulatory effect of a brain extract. Digestion of brain extract with proteolytic enzymes abolishes its activity, suggesting the factor from the brain is peptidergic. The neuroactive agents serotonin, Phe-Met-Arg-Phe-amide, Tyr-Gly-Gly-Phe-Met-Arg-Phe-amide, small cardioactive peptide B, and caudodorsal cell hormone were also tested for potential secretion-promoting ability. Brain extracts were partially purified with a Sep-Pak C18 reverse-phase cartridge and indicate the peptide is relatively hydrophobic. These results suggest that a brain peptide promotes the secretion of perivitelline fluid, and this is mediated by the adenylate cyclase/cAMP signal transduction pathway.     

Recombinant expression and localization of Schistosoma mansoni cathepsin L1 support its role in the degradation of host hemoglobin

Cysteine proteinases expressed by schistosomes appear to play key roles in the digestion of host hemoglobin, the principal source of amino acid nutrients utilized by these parasites. We have shown previously that the predominant cysteine proteinase activity in soluble extracts and excretory/secretory (ES) products of adults of Schistosoma mansoni and S. japonicum is cathepsin L-like in its substrate specificity. However, biochemical analysis of the cathepsin L activity in extracts and ES products of schistosomes has been complicated by the presence of at least two distinct forms of schistosome cathepsin L, termed SmCL1 and SmCL2. We now report the purification and enzyme characteristics of active, recombinant SmCL1 which was obtained by transforming Saccharomyces cerevisiae with an expression plasmid encoding the preproenzyme of SmCL1. Recombinant SmCL1 was secreted by the transformed yeast into the culture media from which it was purified by gel filtration and ion-exchange chromatography. The purified enzyme exhibited substrate specificity against synthetic peptidyl substrates (e.g., Boc-Val-Leu-Lys-NHMec and Z-Phe-Arg-NHMec; kcat/Km = 17.25 and 6.24 mM-1 s-1, respectively) and against gelatin and hemoglobin, characteristic of cathepsin L. Immunoblot analysis using antiserum raised against recombinant SmCL1 demonstrated that native SmCL1 of 33 kDa was present in ES products and soluble extracts of S. mansoni. Using this antiserum and thin tissue sections, we localized the native SmCL1 to the gastrodermis and to the tegument of adult schistosomes. Recombinant SmCL1 was capable of degrading human hemoglobin at pH 4.0 to 4.5 but not higher, suggesting that denaturation of hemoglobin by low pH, as found in the cecum of the adult schistosome, may be necessary for its catalysis by cathepsin L and other gut-associated proteinases. Together, these results support a role for SmCL1 in the degradation of host hemoglobin within the gut of the schistosome.     

Enzymatic basis for the lack of oxamniquine activity in Schistosoma haematobium infections

The notion that oxamniquine is active against Schistosoma mansoni but inactive against S. haematobium was confirmed using in vitro cultures of adult worms. Since oxamniquine and hycanthone have been shown to become effective upon activation by a schistosome enzyme, enzymatic tests were carried out to detect possible differences between the enzyme of S. mansoni and that of S. haematobium. It was found that the S. mansoni enzyme could activate hycanthone and, to a lesser extent, oxamniquine. The S. haematobium enzyme, on the other hand, was capable of activating hycanthone but virtually incapable of activating oxamniquine. It is concluded that the different activity of oxamniquine in the two species is due to differences in the drug-activating enzyme.     

Circadian periodic response of Phaseolus vulgaris l. to 2,4-dichlorophenoxyacetic acid

The susceptibility of bean plants, Phaseolus vulgaris L., cv. Executive, to 2,4-dichlorophentoxyacetic acid (2,4-D) appeared to depend upon the time of application. Oscillations in response to 2,4-D were evident in plants subjected to conditions of alternating light and dark spans, continuous illumination or darkness. The fresh and dry weight of plant material was generally less when 2,4-D was applied to plants near the later portions of the light span.     

A note on multidimensional models of neutral mutation

Previous studies using radioactive miracidia have shown that a number of non-host snails and bivalves, interposed as 'decoys' in linear test channels, may interfere with the capacity of Fasciola hepatica miracidia to infect Lymnaea truncatula. Applying similar experimental principles, the role of several other potential interferents have been analysed in the present study. Daphnia pulex (Cladocera) and larvae of Corethra sp. (Diptera) exercised significant interfering effects by protecting 'target' snails from infection. Evidence suggested that this effect was a result of their normal predatory behaviour. Other organisms including Herpobdella testacea and Helobdella stagnalis (Hirudinea), Acellus aquaticus (Isopoda), Planaria lugubris (Turbellaria) and L. truncatula egg clusters failed to interfere with miracidial host-finding. Nor did P. lugubris and L. truncatula 'conditioned water' interfere with the capacity of the miracidia to infect their host snail.     

Pairing of Schistosoma mansoni males in infected Syrian hamsters

Pairing of male schistosomes in the liver of infected hamsters was recorded with Egyptians S. mansoni strain. The homospecific male pairs never carried each other in the gynaecophoric duct, but they being closed in either central or hepatic veins. Other perfused males and females en copula showed normal mating behaviour. The paired males were more or less in the same size. The random sexed miracidia used resulted in obtaining 1:2.1 female/male ratio. It is concluded that the random increase of male schistosomes may create the male pairing behaviour. Also, the migration of female against the blood stream to the mesenteric plexus of the host and the failure of male to catch them may lead to this homosexual pairing. The black haemozoin-like substance seen in mature females was also observed in the pairing males and this probably reflects the effect of scarcity or migration of females to the mesenteric plexus.     

Detection of antiviral and antitumoral fractions of Chenopodium amaranticolor leaf extract

Based on the fact that Chenopodium amaranticolor extracts showed inhibitory activity against tobacco mosaic virus (TMV) and Ehrlich tumour (EA), tests were carried out to investigate whether the antiviral and antitumoral activity were caused by the same compounds. When the extract was purified by CM Sephadex C-25 column, after precipitation with 90% ammonium sulphate, twenty active fractions against TMV and two pools of fractions active against EA were obtained. Only one fraction with high absorbance values at 260 and 280 nm was able to inhibit both TMV and EA. When the extract was purified by Bio Gel P-60 column two active fractions against TMV and EA were obtained, suggesting that they were contained in the 0.01 M fraction of the CM Sephadex column. It is suggested that C. amaranticolor leaf extract contained at least two protein-like substances manifesting antiviral and antitumoral activity.