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R Houin

Publications and source records attributed to R Houin.

At least 37 records · Page 2Linked to original sources
PubMed1995

Covalent cross-linking of liver collagen by pyridinoline increases in the course of experimental alveolar echinococcosis.

We report that covalent cross-linking of collagen molecules by pyridinoline increases significantly in liver in a murine model of alveolar echinococcosis. The highest amount of pyridinoline per collagen molecule (up to 3.5 fold the control values) is found in liver parasitic lesions. It is also increased, but to a far lesser extent, at distance from the fibrotic areas, in macroscopically normal zones of the liver, suggesting that the increase in mature collagen cross-linking occurring in the fibrogenesis due to Echinococcus multilocularis infection involves the whole liver. The comparison of these data with those we have obtained in another parasitic disease, murine schistosomiasis leading to a milder liver fibrosis, largely reversible following chemotherapy, supports a relationship between the liver pyridinoline level and the severity of liver fibrosis. Pyridinoline could be a tissular marker of chronic liver fibrosis in parasitic diseases.

Amino Acids↗
PubMed1995

[Importance of drug carriers in the treatment of visceral leishmaniasis].

Visceral leishmaniasis is caused by hemoflagellate protozoa which are obligatory parasites of the mononuclear phagocyte system. Leishmaniasis causes high morbidity and mortality worldwide. The treatment of choice remains pentavalent antimonials, but high toxicity and failures have been reported. An alternative to conventional treatment is delivery anti-leishmania agents using colloidal carrier systems. Carriers improve drug activity against intracellular disease involving the mononuclear phagocyte system. The principle of drug delivery by carrier systems has been applied successfully for anticancer drugs. Recently complete remission of polyresistant visceral leishmaniasis was obtained by injection of liposomal amphotericin B. At present, no colloidal drug carrier for antimony derivatives is available, but pentamidine can be linked experimentally to methacrylate polymer nano-particles. Drug-loaded nanoparticles have been shown to be effective against amastigote leishmania both in vitro and in vivo. Another colloidal system of major interest for drug delivery, the liposome has already been loaded with amphotericin B and used for human therapy. The concept of particulate drug carriers opens the way for new chemotherapeutic approaches in the field of parasitology.

Amphotericin B↗
PubMed1994

Action of pentamidine-bound nanoparticles against Leishmania on an in vivo model.

The efficiency of antileishmanial agents may be enhanced by improving their bioavailability with a colloidal drug carrier. We have investigated the action of free pentamidine, compared with pentamidine bound to polymethacrylate nanoparticles, in a rodent model. BALB/c mice were infected, via the tail vein, with 4 x 10(7) L. major (MON 74) promastigotes. Twelve days after infection, seven groups of mice were treated respectively with methylglucamine antimoniate (Glucantime) 5.56 mg/kg i.p. x 5 d., pentamidine bound nanoparticles (100 microM), unloaded polymethacrylate nanoparticles, unloaded nanoparticles associated with free pentamidine (100 microM) 0.1 ml i.v. x 3 d and free pentamidine isethionate (2.28 mg/kg and 0.17 mg/kg i.v. x 3 d.). Twenty-one days post infection, the mice were sacrificed and the Leishmania load in the liver calculated from the number of amastigotes/500 liver cells and total liver weight in treated and untreated mice. Results demonstrated a 77% amastigote reduction in the group treated with targeted pentamidine relative to the control group. The ratio free pentamidine/bound-pentamidine was approx. 12.

Animals↗
PubMed1993

Detection of Echinococcus multilocularis DNA in fox faeces using DNA amplification.

In order to identify Echinococcus multilocularis DNA in fox faeces for epidemiological purposes, we have developed a new method to prepare DNA suitable for PCR amplification. DNA isolation from fox excrement was performed according to a novel procedure involving lysis in KOH, phenol-chloroform extraction and a purification step on a matrix (Prep-A-Gene). The target sequence for amplification was the E. multilocularis U1 snRNA gene. PCR products were indistinguishable for 32 different E. multilocularis isolates and no signal was observed after ethidium bromide staining with DNAs from other tapeworm species, including E. granulosus. The sensitivity of amplification was monitored by the addition of E. multilocularis DNA or eggs to faeces free of E. multilocularis and was estimated to be 1 egg per 4 g of faeces. PCR products were blotted onto nylon membranes and hybridized with an internal oligonucleotide probe in order to confirm the results. Twenty nine faecal samples from foxes shot in Franche-Comté (East France) were tested. Out of 10 samples from foxes in which no E. multilocularis adult worms could be observed after necropsy, 7 were PCR positive, showing that the PCR test is more sensitive than microscopical examination. Out of 19 samples from foxes harbouring E. multilocularis adult worms, 18 were PCR positive. The remaining PCR-negative sample could be due either to the misidentification of the species of adult worm (E. granulosus and E. multilocularis), or to DNA variation between different isolates of E. multilocularis. Further work in the field should be initiated in order to confirm these results.

Animals↗
PubMed1993

[In vitro study of leishmanicidal agents with drug carriers].

Antileishmanial chemotherapy is hampered by the location of parasites within lysosomal vacuoles of the macrophages which restricts the bioavailability of many potential antileishmanial compounds. In this study, the effectiveness of pentamidine targeted to the infected cells by a linkage to a colloidal drug carrier, methacrylate polymer nanoparticles was explored. In the same way, polyisoalkylcyanoacrylate nanospheres which have, in vitro, trypanolytic properties were also tested. The study was performed in an in vitro model using Leishmania major amastigote stages within the U 937 human monohistiocytic cell line. The antileishmanial activities of unloaded or pentamidine-loaded nanoparticles were compared to those of the free drugs. The 50% effective concentration of targeted pentamidine was 0.10 microgram/ml, while it was up to 2.7 micrograms/ml with the free drug after a 24-hour incubation time. The pentamidine-bound nanoparticles proved to be 25 times more active than the free drug. Unloaded polyisoalkylcyanoacrylate nanoparticles destroyed intracellular amastigote stages (50% EC = 15 micrograms/ml) but at a level close to the cytotoxic concentration.

Cell Line↗
PubMed1992

Effects of cyclosporin A on the course of murine alveolar echinococcosis and on specific cellular and humoral immune responses against Echinococcus multilocularis.

The effects of cyclosporin A (CsA) on Echinococcus multilocularis (E. multilocularis) metacestode growth, and on the specific immune responses of the hosts, were examined in AKR mice. Mice were intra-peritoneally infected with a metacestode homogenate. CsA (40 mg kg(-1) day(-1)) was injected subcutaneously from the 45th day after infection (Group 1), and from the day before infection (Group 2) until the day of autopsy (days 125 and 80, respectively). Results showed that unlike ths situation with some other helminthiases, CsA had no antiparasitic effect, although it lengthened the maturation time of protoscoleces in Group 1. The parasitic burden, unmodified in Group 1, was significantly enhanced in Group 2. This enhancement was associated with a decrease in antibody levels, whereas the delayed-type hypersensitivity was decreased in the two groups. These results confirm the role of cellular immunity in controlling the first stages of the larval development of E. multilocularis and indicate the necessity for a careful follow-up of any recurrence of alveolar echinococcosis in patients treated with CsA after liver transplantation.

Animals↗
PubMed1992

[Detection of the eggs of Echinococcus multilocularis Leuckart, 1863, in the feces of the fox (Vulpes vulpes Linnaeus, 1758) by the polymerase chain reaction].

The polymerase chain reaction (PCR) was applied to the identification of eggs of Echinococcus multilocularis in faeces from foxes. The test was positive in three of six faeces samples from foxes which were harbouring adult worms, and in one of four samples from foxes in which no adult E. multilocularis was found in the intestines. These initial results show that it is possible to use PCR to identify E. multilocularis eggs in faeces. PCR can be used to complement examination of intestinal contents, showing that the distribution of eggs in faeces is uneven. The sensitivity of the test was estimated to be 50 eggs in 5 g of faeces. Further work is needed to confirm these initial results before the test can be used more widely.

Animals↗
PubMed1992

[Alveolar echinococcosis in China: current data].

Very few information about alveolar echinococcosis in China is available outside the country. The aim of the authors is to give some precisions about the human cases and the infection in the natural animal hosts. It occurs in 3 distinct foci which comprise poor and remote rural areas. Approximately, 420 cases of human disease have been detected, and the most intense focus is Ningxia province in central China. In all areas, the adult tapeworm is frequently found in V. vulpes, V. corsac, and in the domestic dog. The intermediate hosts differ from an area to the others. Their infection rate is high in the central and the northern foci. More researches are needed for improving our knowledge about the epidemiology of the disease. But the actual major requirement is to apply control measures as health education and medical information.

Animals↗
PubMed1991

Structure of the Echinococcus multilocularis U1 snRNA gene repeat.

The gene encoding U1 snRNA in Echinococcus multilocularis has been cloned and sequenced. This gene is contained within a 1300-bp sequence which is tandemly repeated in the E. multilocularis genome. E. multilocularis U1 snRNA is 50-70% homologous to U1 snRNAs of other species. E. multilocularis U1 snRNA could assume a predicted secondary structure similar to that proposed for other U1 snRNAs, and appears shorter (157 bases) than the U1 snRNAs of higher eukaryotes (163-166 bases).

Amino Acid Sequence↗
PubMed1991

[Which training for the parasitologist of tomorrow?].

The symposium "Which training for Parasitologists tomorrow" tried to define the difficulties met in this field, as well as to prospect the future. Parasitology is actually deeply changing, and its traditional approaches are frequently deserted as new methods look more favourable. The situation was first stated: applied parasitology (particularly medical) contrasts with fundamental. In the first case, there are important needs and training is expected. In the latter, many teams disappear or are included into units bearing different titles. In some fields (particularly systematic), it is no longer possible to find specialists able to secure the basis of the experiments carried out with the new tools. From such observations, the ways to train future Parasitologists, and to give to those who will use parasites as models substantial basis were prospected. An early initiation can be proposed, by choice of parasitic models to demonstrate general biological facts. Beyond, a common language must be acquired by any scientist concerned by parasitism. At the highest level, tools must not overshadow the essential. Moreover, an effort in communication is expected, to promote Parasitology. Under their Federation authority the scientific Societies are encouraged to define the needs in their areas and to organize training.

Parasitology↗
PubMed1990

Rapid technique for cryopreservation of Echinococcus multilocularis metacestodes.

Cysts of E. multilocularis were minced to prepare a crude homogenate and after addition of glycerol at a final concentration of 10%, cryopreservation was performed at a rate of 1 degree C min-1 in a controlled-rate freezer. The aliquots were subsequently stored in liquid nitrogen. All 22 isolates tested were successfully cryopreserved and their viability maintained.

Animals↗
PubMed1990

Comparison of the viability and developmental characteristics of Echinococcus multilocularis isolates from human patients in France.

Alveolar echinococcosis, due to E. multilocularis, is usually a fatal disease in patients whether treated by benzimidazolecarbamates or not. However, aborted infections have been described, suggesting the existence of strains of parasites of varying pathogenicity. These observations led us to analyse the viability of larvae in 20 patients. After observation of human lesions, the viability of metacestodes was tested by intraperitoneal infection in two intermediate host species, Meriones unguiculatus and AKR inbred mice. Parasitic development was more frequent in mice than in M. unguiculatus, but in the latter, growth was more rapid and the larval mass produced was greater. Isolates which originated from patients undergoing treatment had an abortive growth; two others were characterized by a steady, though slow, development, producing a poorly budding larva; lastly there were some which were morphologically similar with a multivesicular appearance but differing development times. These results may serve as a guide for more basic studies leading to an understanding of the problem of intraspecific variations in E. multilocularis.

Adolescent↗
PubMed1990

Cellular immunity in experimental Echinococcus multilocularis infection. I. Sequential and comparative study of specific in vivo delayed-type hypersensitivity against E. multilocularis antigens in resistant and sensitive mice.

Species- or strain-related differences in receptivity of intermediate hosts to E. multilocularis larvae could be related to differences in specific cellular immune response of the host. In order to test this hypothesis, we assessed the delayed-type hypersensitivity (DTH) to E. multilocularis antigens (EmAg) in mice of three strains differing by their sensitivity (AKR and C57BL.6) or resistance (C57BL.10) to E. multilocularis infection. DTH was determined by measuring in vivo the foot-pad response 24 h after an EmAg antigenic challenge. The level of positive response was evaluated in immunized mice; however, a typical DTH response was only observed by immunizing mice with a strong adjuvant schedule. Course of DTH in the immunized mice was shown to be somewhat different in sensitive and resistant mice. The differences were much more marked in mice infected with proliferative E. multilocularis larvae. The levels of the footpad response was significantly higher in resistant mice, although the peak of the reaction was obtained later than in sensitive mice. DTH, expressed by the foot-pad response against EmAg, remained significant for the entire period of observation in sensitive as well as in resistant mice. There was no correlation between receptivity of the murine hosts and levels of specific antibodies against EmAg. These results suggest a relationship between resistance to E. multilocularis infection and intensity and/or course of DTH in mice. The resistance could be mediated by some particularities of the in situ cellular immune response in the periparasitic granuloma.

Animals↗
PubMed1990

Cellular immunity in experimental Echinococcus multilocularis infection. II. Sequential and comparative phenotypic study of the periparasitic mononuclear cells in resistant and sensitive mice.

Cellular immune responses have been shown to be associated with differential evolutions of E. multilocularis infection in intermediate hosts. A relationship between course of delayed-type hypersensitivity (DTH) against parasitic antigens and receptivity of murine strains has been demonstrated recently. The aim of this study was to correlate resistance and sensitivity to E. multilocularis infection with the phenotypic patterns of cells within the periparasitic granuloma. Evolution of the ratios, macrophages/T lymphocyte and Ly1/Ly2 T lymphocytes, was associated with the receptivity of the strains. Persistence of numerous L3T4 + T lymphocytes and low numbers of macrophages and Ly2 + T lymphocytes were observed in the 'resistant' C57BL.10 mice. Comparison of the results with course of the DTH against E. multilocularis antigens showed that the particular phenotypic pattern observed in resistant mice was associated with a particular profile of DTH after infection. These results and similar observations in human alveolar echinococcosis suggest that cell composition of the periparasitic granuloma might be of crucial importance in controlling the spontaneous development of E. multilocularis larvae in the intermediate host.

Animals↗
PubMed1990

[Cryptosporidiosis in children: epidemics and sporadic cases].

From April 16 1987 through May 16 1987, during an outbreak of gastroenteritis, stool specimens were obtained from 53 children aged 18 to 36 months among the 90 children attending an on-site day-care center for the staff of a large teaching hospital in the Paris urban area (59%). Oocysts of Cryptosporidium were found in 11 specimens (21%) using an auramine staining technique. Children with diarrhea were more likely to have stools containing Cryptosporidium (p less than 0.01). Subsequently, a prospective study was carried out in the same day care center from July 1987 through January 1988. Among the 103 episodes of diarrhea observed during the study period, there were five cases of cryptosporidiosis (5%). In all these cases, diarrhea was moderate and resolved within ten days. Furthermore, among 148 hospitalized children aged 2 months to 10 years, 2 (1.4%) had positive stool specimens for Cryptosporidium and significant failure to thrive. Thus, Cryptosporidium is a common cause of diarrhea in immunocompetent children, especially in child group settings. Further studies are needed to determine the prevalence and spectrum of the clinical patterns of this parasitic disease.

Child Day Care Centers↗
PubMed1989

[Viability of new valvular homografts. Myth or reality?].

Use in cardiac surgery of aortic homografts as a valvular substitute is old and was specially developed in France by F. Fontan. In fact, these first allografts were non-viable and the results, in aortic position, were not better than current bioprosthesis. Renewed interest is related to the important notion of "viability" allowed by an immediate procurement (organ donors), preparation in nutrient medium RPMI with low doses of antibiotics and final storage at -196 degrees C (cryopreservation). We have reviewed our initial experience concerning 32 implanted homografts in children either in reconstruction of the right ventricular outflow tract (in many forms of congenital heart disease) or in aortic position. No mortality was observed. The only failure was due to an initial sizing mistake leading to an aortic valve replacement at 13 months. No late deterioration (mean follow-up: 12.5 months) was detected by echocardiography. These results seem to confirm other larger series (as O'Brien's, Brisbane, Australia). Biologic, histological and immunological assessments of "viable" homografts are discussed. The limits of the technique are reported.

Adolescent↗
PubMed1988

[Cross-reactivity between parasitic antigens and T lymphocyte surface antigens: a possible host-escape mechanism for Echinococcus multilocularis].

We report an immunocytochemical analysis of E. m. protoscolices obtained in 2 strains of mice (AKR, Balb c) which were experimentally infected. Sections of hepatic and peritoneal lesions and spreading of protoscolices from peritoneal vesicles were analyzed. Five monoclonal antibodies, specific of murine T lymphocyte populations, produced an intense and regular staining of the anterior area of the protoscolices. This immunostaining has not yet been explained; it could bear witness to particular mode of parasite protection against host immunological responses.

Animals↗