Leógenes Horácio Pereira

Are there interactions between schistosomes and intestinal nematodes

A survey for intestinal parasites was carried out in a homogenous rice cultivation area, in which people had equal opportunities of acquiring the local endemic helminthiases, including schistosomiasis mansoni. The numbers of Schistosoma mansoni eggs excreted in faeces were counted. Infections with S. mansoni, Ascaris lumbricoides, ancylostomes and Trichuris trichiura were not randomly distributed, but were correlated, depending on the species of worms present. The S. mansoni egg counts were positively correlated with ancylostome infection but inversely correlated with A. lumbricoides and T. trichiura. Patients with schistosomiasis associated with 2 other helminth infections excreted more S. mansoni eggs than the patients with S. mansoni plus only one other helminth infection.

Oogram studies in mice infected with Schistosoma mansoni and treated with dexamethasone

Mice infected with about 90 cercariae of Schistosoma mansoni (LE strain) were treated during five consecutive days with dexamethasone (50 mg/Kg, subcutaneously), starting on the 42nd day of infection. Groups of five mice were then daily sacrificed from the first day after onset of treatment until the first day after. The perfusion of the portal system was performed and a piece of the intestine was processed for qualitative and quantitative oograms. This treatment carries to larger numbers of eggs in the tissues of treated mice, when compared with untreated groups. No changes were observed in the kinetics of oviposition, as all stages of viable eggs were observed in the tissues of treated and control mice. These data reinforce the hypothesis of a partial blockade of the egg excretion in immunosuppressed mice.

Activity of 9-acridanone-hydrazone drugs detected at the pre-postural phase, in the experimental schistosomiasis mansoni

The compound Ro-15.5458/000, derivative in the class of 9-acridanone-hydrazones, was found to be effective against Schistosoma mansoni in mice, killing almost all the skin schistosomules (24 hr after infection), when administered at the dose of 100 mg/kg. In experiments carried out with Cebus monkeys, the drug was shown to be fully effective at 25 mg/kg, 7 days after infection. These data, associated with the good results obtained earlier at the post-postural phase of schistosomiasis, allow the inference that this promising compound may be important in the set of antischistosomal drugs, depending on further toxicological and clinical tests.

Levantamento malacológico da Bacia Hidrográfica do Lago Soledade, Ouro Branco, (Minas Gerais, Brasil)

A malacological survey was carried out at the Soledade Lake, in Ouro Branco, State of Minas Gerais, for the period 1986-1991. A total amount of 46,579 mollusks was collected, and among them seven species corresponding to five families could be found, as follows: 39,176 specimens of Biomphalaria tenagophila; 1,296 B. glabrata; 7 Drepanotrema cimex; 2,527 Physa sp; 417 Lymnaea sp; 92 Pomacea hastrum, and 3,064 specimens of Melanoides tuberculata (Melanniidae = Thiaridae) were collected from March/1990 onwards. Four specimens of B. tenagophila were found to be positive for Schistosoma mansoni.A malacological survey was carried out at the Soledade Lake, in Ouro Branco, State of Minas Gerais, for the period 1986-1991. A total amount of 46,579 mollusks was collected, and among them seven species corresponding to five families could be found, as follows: 39,176 specimens of Biomphalaria tenagophila; 1,296 B. glabrata; 7 Drepanotrema cimex; 2,527 Physa sp; 417 Lymnaea sp; 92 Pomacea hastrum, and 3,064 specimens of Melanoides tuberculata (Melanniidae=Thiaridae) were collected from March/1990 onwards. Four specimens of B. tenagophila were found to be positive for Schistosoma mansoni.Em estudo malacologico realizado na Bacia Hidrografica do Lago Soledade, Ouro Branco, MG, no periodo de setembro de 1986 a marco de 1991, foram coletados 46.579 moluscos, representados por 07 especies de 05 familias. Foram coletados 39.176 exemplares de Biomphalaria tenagophila, 1.296 de B. glabrata, sete exemplares de Drepanotrema cimex, 2.527 de Physa sp, 417 de Lymnaea sp, 92 de Pomacea haustrum e, a partir de marco/1990, 3.064 exemplares de Melanoides tuberculata (Melanniidae = Thiaridae). Dos moluscos que apresentaram positividade para diversas larvas de trematodeos, quatro exemplares de B. tenagophila estavam positivos para S. mansoni.

Kinetics of the cercaria-schistosomulum transformation in vivo

Sitice most studies on the cercaria-schistosomulum transformation have been carried out in vitro, the authors used the inoculation ofcercariae into the peritoneal cavity of mice tofollow the steps involved in this progressive adaptation of cercarie to the vertebmte host. The main conclusions were: 1. Most cercariae reach the schistosomular stage between 90-120 min after intraperitoneal inoculation. 2. Changes usuallystart with detachment of the tail followed by loss, rupture or changes of the glycocalix. 3. After 120 min most larvae loss their tails and present water sensitivity. 4. Acetabular grands depletion usually does not occur in cercaria-shistosomulum changes in the peritoneal cavity of mice. These steps differ in some way from those described in the kinetics of the in vitro observations performed by other investigators, and is more like those described in the penetration in the skin of living vertebrates.

Kinectics of the pulmonary phase of Schistosoma mansoni in mice treated with dexamethasone

In the experimental schistosomiasis mansoni glucocorticoids cause a reduction in the worm burden when administered in the week of infection or, the longest, at the next week. In order to determinate the probable(s) site(s) of reduction of the worm burden, mice were infected with cercariae of LE strain of S. mansoni and dexamethasone was administered daily (50 mg/kg, subcutaneously) starting 1 hour before infection until the eighth day. Mice were sacrificed daily starting on the third day after infection until the ninth day, and schistosomula from lungs were collected. Six weeks after infection, the remaining mice were sacrificed and perfused for adult worm recovery. Analysis of the results showed that the non-treated mice presented larger numbers of lung larvae than the treated ones, and this difference was also found later in the worm burden in the portal system. This difference may reflect the early death of larvae in treated animals, before or after reaching the lungs.

On the finding of biomphalaria tenagophila naturally infected with Schistosoma mansoni in the State of Minas Gerais, Brazil

Natural infection in Biomphalaria tenagophila with Schistosoma mansoni was observed for the first time in a small area, in Jaboticatubas, in the State of Minas Gerais, Brazil. In view of this finding, the Authors decided to carry out some detailed investigations, since B. glabrata has been known as the vector snail of schistosomiasis in that State. B. tenagophila was found naturally infected throughout the investigation period (15 months). Strains of the snail and of the parasite were isolated four times, and then maintained at the laboratory through B. tenagophila — hamster passages. The possibilities of B. tenagophila to play a role in the epidemiology of the human disease in the State of Minas Gerais, in the future, are discussed.

Host cell adhesion to Schistosoma mansoni larvae in the peritoneal cavity of naive mice: histological and scanning electron microscopic studies

Cercariae of Schistosoma mansoni inoculated into the peritoneal cavity of naive mice induced host cell adhesion to their surface, but after 90 minutes the number of adherent cells sharply decreased. The cell detachment is progressive and simultaneous to the cercaria-schistosomule transformation. The histological study showed mainly neutrophils in close contact with the larvae. Mononuclear cells and some eosinophils were occasionally seen surrounding the adherent neutrophils. The scanning electron microscopy showed cells displaying twisted microvilli and several microplicae contacting or spreading over the larval surface, and larvae completely surrounded by clusters of cells. These results suggest that the neutrophils recognize molecules on the cercarial surface which induce their spreading.

In vivo cercaria-schistosomulum transformation: inhibitory effect of oxamniquine.

High doses of oxamniquine (given intramuscularly) produced inhibition of cercaria-schistosomulum transformation following intraperitoneal injections of cercariae into mice. Cercariae, tail-less cercarial bodies, and schistosomula were recovered from the peritoneal cavity of drug-treated mice in numbers significantly different from those recovered from untreated mice. Since untreated animals induced transformation of almost all the injected cercariae, the data suggest the compound is active during the process of host-larvae adaptation.

Desenvolvimento do Schistosoma mansoni na cavidade peritoneal de camundongos da linhagem AKR/J

Cercarias de Schistosoma mansoni, inoculadas na cavidade peritoneal de camundongos da linhagem AKR/J, conseguiram sobreviver in situ e chegar a maturidade sexual. Ao contrario da linhagem convencional (SWISS), onde as femeas que se desenvolveram no peritonio nao produziram ovos, 7,7% das femeas retiradas da cavidade peritoneal de camundongos AKR/J apresentavam ovo normal no utero. Os parasitos recuperados da cavidade peritoneal de ambas as linhagens nao apresentaram pigmento hemoglobinico, indicando que os mesmos sobrevivem na cavidade peritoneal de camundongos sem a necessidade de ingestao de hemacias. O desenvolvimento do parasito na cavidade peritoneal de camundongos AKR/J, com producao de ovos normais, reforca os dados, ja existentes na literatura, que mostram que o ciclo evolutivo do parasito pode ser completado sem a necessidade da fase pulmonar.