Tegumental alterations in juvenile Schistosoma haematobium harboured in hamsters following artemether treatment.

We report the findings of a detailed temporal study on tegumental alterations in juvenile Schistosoma haematobium, induced by artemether, using scanning electron microscopy. Hamsters infected with S. haematobium cercariae for 28 days were treated intragastrically with a single dose of 300 mg/kg artemether. Groups of two hamsters were killed 24 h, 72 h and 7 days after treatment, and schistosomula were recovered from livers by perfusion and subsequent systematic examination of the tissue, before routinely processing for scanning electron microscopic examination. Most schistosomula collected 24 h after artemether administration showed severe tegumental damage, usually including swelling, fusion, vesiculation, peeling and collapse of enlarged sensory structures. After 72 h, tegumental damage had increased and schistosomula generally showed contraction with extensive swelling, erosion and peeling of the tegument. Seven days post-treatment, severe tegumental damage was only seen in a single male specimen with swelling of the worm body and destruction of the oral sucker. The other schistosomula showed only light to moderate damage, suggesting that schistosomula surviving the treatment began to recover. Our findings of tegumental damage following artemether treatment correlate with the efficacy of this novel antischistosomal drug in killing the juvenile stages of S. haematobium and complement recent findings with S. japonicum and S. mansoni.

Effect of combined treatment with praziquantel and artemether on Schistosoma japonicum and Schistosoma mansoni in experimentally infected animals.

Praziquantel and artemether are safe and efficacious antischistosomal drugs that act against different developmental stages of the parasite: praziquantel against adult worms and artemether against schistosomula. A combined treatment has been suggested as a strategy for transmission control. Recent laboratory experiments with rabbits with a mixed infection of Schistosoma japonicum parasites of different ages confirmed the effectiveness of a combination therapy. In the present work, we assessed the effect of a combined treatment on adult worms of S. japonicum and found significantly higher worm reduction rates than with a single dose of praziquantel. In a next step, we extended the study of the combined treatment to Schistosoma mansoni. A combined treatment with 75 mg/kg praziquantel and 150 mg/kg artemether was administered to hamsters infected with juvenile and adult S. mansoni. The two drugs, administered simultaneously or spaced by 6 h, 1, 3 or 7 days, resulted in significantly higher worm reduction rates than a single treatment with praziquantel. A combination therapy with increased doses of 100 mg/kg praziquantel and 300 mg/kg artemether showed very high worm reduction rates of 90% and above, however, some hamsters died in five different combined treatment experiments, suggesting that these drug concentrations were too high. We conclude that a combined treatment with praziquantel and artemether at the lower doses is safe and more effective than praziquantel alone, which forms a foundation for designing respective clinical trials in humans.

Histopathological changes in juvenile Schistosoma haematobium harboured in hamsters treated with artemether.

Histopathological changes in juvenile Schistosoma haematobium, caused by artemether administered to the infected hamsters, were studied. Hamsters were infected with S. haematobium cercariae, and after 28 days, a single dose of artemether (300 mg/kg) was administered intragastrically. After 24 h, 72 h and 7 days, groups of two hamsters were sacrificed, and livers were removed, fixed and processed routinely, and examined by light microscopy. After 24 h, 93% of the schistosomulae examined showed degeneration, which included swelling of the tegument, adherence of inflammatory cells to the damaged tegument, collapsed and damaged intestine, and infiltration of inflammatory cells, predominantly lymphocytes. After 72 h, the intensity of damage increased, including severe swelling of the tegument, loss of definition in the internal structures, collapse of intestine accompanied by release of pigment particles to the parenchymal tissues, and emergence of dead schistosomulae. Seven days after treatment, the number of dead schistosomulae increased, and most of them developed to an early- or late stage of dead worm granuloma. Meanwhile, 12% of the schistosomulae showed a normal appearance, which suggested that those schistosomulae that had survived the treatment were recovered to normal. The results demonstrated that artemether effectively acts against the juvenile stages of S. haematobium and confirms earlier results with S. japonicum and S. mansoni.

Carrier-mediated uptake and phloem systemy of a 350-Dalton chlorinated xenobiotic with an alpha-amino acid function.

In a previous paper we have shown that epsilon-(phenoxyalkanecarboxylyl)-L-Lys conjugates are potent inhibitors of amino acid transport systems and that it is possible to modulate the uptake inhibition by hydrophobic or hydrophilic additions in the 4-position of the aromatic ring (J.F. Chollet, C. Delétage, M. Faucher, L. Miginiac, J.L. Bonnemain [1997] Biochem Biophys Acta 1336: 331-341). In this report we demonstrate that epsilon-(2,4-dichlorophenoxyacetyl)-L-Lys (2,4D-Lys), one of the largest molecules of the series and one of the most potent inhibitors, is a highly permeant conjugate. Uptake of 2,4D-Lys by broad bean (Vicia faba) leaf discs is mediated by an active carrier system (Km1 = 0.2 mM; Vmax1 = 2.4 nmol x cm(-2) x h(-1) at pH 5.0) complemented by an important diffusive component. Among the compounds tested (neutral, basic, and acidic amino acids, auxin, glutathione, and sugars), only the aromatic amino acids clearly compete with 2,4D-Lys. The conjugate accumulates in the vein network, is exported toward the growing organs, and exhibits a distribution pattern different from that of the herbicide moiety. However, over time 2,4D-Lys progressively splits into 2,4D and lysine. Analyses by high-performance liquid chromatography and liquid scintillation spectrometry of the phloem sap collected from the castor bean system, used as a systemy test, indicate decreasing capacities of 2,4D, 2,4D-Lys, and glyphosate, respectively, to move from the epidermis cell wall to the sieve element. Our results show that it is possible to design synthesis of large-size xenobiotics (approximately 350 D) with a lipophilic pole, exhibiting high mobility within the vascular system.

Artemether administered together with haemin damages schistosomes in vitro.

We conducted experiments in vitro to assess the effect of artemether in combination with haemin on adult Schistosoma japonicum, S. mansoni and S. haematobium. When schistosomes were maintained in a medium containing artemether at concentrations of 20 micrograms/mL or less for 72 h, no apparent effect on the schistosomes was seen. When the medium contained 50 or 100 micrograms/mL haemin as well as artemether, the schistosomes showed decreased motor activity 2-24 h after exposure, which was followed by the staining of the whole worm body a reddish-yellow colour, dilatation of the intestine, and extensive vesiculation of the tegument. Some of the schistosomes died 24 h after exposure, and almost all died within 48-72 h. When schistosomes were exposed to the same concentrations of haemin alone, they were stained a light yellow colour but there was no apparent effect on their survival. Our findings suggest that artemether interacts with haemin to exert a toxic effect on the worms, which might be of importance in the further elucidation of the mechanism of action of artemether on schistosomes.

Tegumental changes in 21-day-old Schistosoma mansoni harboured in mice treated with artemether.

Alterations in the tegument of 21-day-old Schistosoma mansoni, caused by artemether administered to the infected mice, were studied using scanning electron microscopy (SEM). Mice were infected with S. mansoni cercariae, and after 21 days a single dose of artemether (400 mg/kg) was administered intragastrically. After 24, 72 h and 7 days groups of three mice were killed and the schistosomules collected by perfusion, fixed and processed routinely, and examined by SEM. After 24 h, all male and female worms examined showed alterations in the tegument, characterised by swelling, vesiculation and fusion of tegumental ridges; peeling, erosion and collapse of damaged tegumental surface, and also destruction of the oral sucker and acetabulum. After 72 h, severe damage to the tegument was seen, usually including extensive peeling, swelling and vesiculation, and host leukocytes were adhered to the damaged surface. Some worms were surrounded by clusters of host leukocytes or had even disintegrated. Seven days after treatment, some schistosomules still showed severe tegumental damage, but in some cases the damage was less than at earlier times, which suggested that those schistosomules that had survived were beginning to recover. The ability of artemether to cause severe damage to the tegument correlates with its high efficacy in killing 21-day-old schistosomules.

Preventive effect of artemether in experimental animals infected with Schistosoma mansoni.

The effect of artemether, an antimalarial drug developed from the plant Artemisia annua, has been tested against the larval stages of Schistosoma mansoni covering the time from skin penetration to the early adult liver-stage. The results show that the experimental animals used (hamster and mice) do not develop schistosomiasis mansoni if treated with artemether during the first month after infection. The parasite was found to be especially susceptible between the 3rd and 4th week after infection, resulting in worm reductions of 75.3-82.0% compared to non-treated controls. This level was boosted to 97.2-100% when the animals were subjected to various schedules of repeated treatment. Almost complete protection was also reached in parallel experiments with repeated infections carried out to mirror more closely the real situation of trickle infection.

[Mechanical circular colorectal anastomosis using a transanal approach. Apropos of a series of 51 cases]. / Les anastomoses mécaniques circulaires colo-rectales par voie trans-anale. A propos d'une série de 51 cas.

Automatic circular suture forceps offer new technical possibilities for the confection of colorectal anastomosis. A retrospective study was conducted in 51 patients, representing a homogeneous group of anastomoses performed by the same surgeon using the same operative technique and with routine review by barium enema examination on the 8 th postoperative day. Technical difficulties during operation were encountered in 10 patients (19.6%) requiring supplementary sutures in 3 cases and protective colostomies in 3 others. Review examinations revealed anastomotic dehiscence in 7 cases (13.7%), only 3 (5.9%) of these radiologic fistulae provoking clinical manifestations, and only one of these (1.9%) necessitating recovery operation. Perfect compliance with conditions of use of the mechanical forceps and a minute technique identical to those of manual sutures produced excellent early result with circular mechanical suturing using EEA forceps when compared with manual suturing methods. This was particularly true in Goligher's series in which there were 51% of radiologic fistulae. Under certain difficult conditions, the use of EEA forceps simplifies performance of a colorectal anastomosis, mechanical anastomosis using the circular forceps constituting an undeniable technical progress in colorectal surgery with conservation of anal sphincter.