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D Kerboeuf

Publications and source records attributed to D Kerboeuf.

At least 55 records · Page 3Linked to original sources
PubMed1990

A Ca2+ influx associated with exocytosis is specifically abolished in a Paramecium exocytotic mutant.

A Paramecium possesses secretory organelles called trichocysts which are docked beneath the plasma membrane awaiting an external stimulus that triggers their exocytosis. Membrane fusion is the sole event provoked by the stimulation and can therefore be studied per se. Using 3 microM aminoethyl dextran (AED; Plattner, H., H. Matt, H.Kersken, B. Haake, and R. Stürz, 1984. Exp. Cell Res. 151:6-13) as a vital secretagogue, we analyzed the movements of calcium (Ca2+) during the discharge of trichocysts. We showed that (a) external Ca2+, at least at 3 X 10(-7) M, is necessary for AED to induce exocytosis; (b) a dramatic and transient influx of Ca2+ as measured from 45Ca uptake is induced by AED; (c) this influx is independent of the well-characterized voltage-operated Ca2+ channels of the ciliary membranes since it persists in a mutant devoid of these channels; and (d) this influx is specifically abolished in one of the mutants unable to undergo exocytosis, nd12. We propose that the Ca2+ influx induced by AED reflects an increase in membrane permeability through the opening of novel Ca2+ channel or the activation of other Ca2+ transport mechanism in the plasma membrane. The resulting rise in cytosolic Ca2+ concentration would in turn induce membrane fusion. The mutation nd12 would affect a gene product involved in the control of plasma membrane permeability to Ca2+, specifically related to membrane fusion.

Animals↗
PubMed1988

Trichostrongylus colubriformis: effects on villi and crypts along the whole small intestine in infected rabbits.

In control and Trichostrongylus colubriformis-infected rabbits histological samples were taken from the small intestine at 25-cm intervals from the pylorus. Length of villi, surface of glands of Lieberkühn, and number of epithelial cells per unit length were measured with a digitized table. Two zones were so delimited along the parasitized mucosa: in the proximal part of the gut, both shortened villi and dilated crypts were found; in the distal region of the intestine, which was also the area with the lowest density of parasites, dilatation of crypts was associated with an increase in the size of villi. In both regions, the size of enterocytes was unchanged. Correlation coefficients calculated between worm burdens and relative variation in length of villi were significant and negative. Conversely, the same coefficients were significant and positive between worm burdens and surface of crypts. The possibility of local and general actions of Trichostrongylus colubriformis on both villi and crypts is evoked to explain the changes in the two zones. The functional importance of the hypertrophy in the distal region is still to be investigated during a T. colubriformis infection.

Animals↗
PubMed1986

Winter survival of third stage Trichostrongylus colubriformis larvae: effects on infectivity and fecundity of adult worms.

Two groups of six lambs were fed with grass cut from two plots which had been contaminated by spreading Trichostrongylus colubriformis larvae. One plot received larvae in December, the other in April. The post mortem examination results showed that the infectivity of overwintering larvae was significantly higher than that of fresh larvae. An inverse relationship was demonstrated between infectivity of larvae and egg production of adult worms developed from these larvae. The results are compared with those obtained under laboratory conditions.

Animals↗
PubMed1986

Population dynamics of Trichostrongylus colubriformis in sheep following anthelmintic treatment.

Three groups of five, three-and-a-half to four-month-old lambs were put to graze on three plots contaminated by Trichostrongylus colubriformis. One group (control) was free of parasites, while the other two were infected just before turning out with 3 X 700 third stage larvae. Depending on whether or not the lambs were treated with 50 mg kg-1 thiabendazole nine days after the first infection, the worm burden and the egg output increased or decreased during the grazing period when compared with the control group. In tracer animals put to graze on the same plots afterwards, it was found that the smaller the number of eggs excreted by the first lambs, the higher were the worm burdens of the tracer lambs.

Animals↗
PubMed1985

The effect of host density on the establishment and fecundity of Heligmosomoides polygyrus.

The effect of mouse population density on the establishment, survival and fecundity of single cohorts of Heligmosomoides polygyrus was investigated. No significant relationship was found between host population density and the worm burden at post mortem. But, lower host population densities were associated with higher parasite fecundities and with higher overall mean daily faecal output. The results might be explained by a decrease in male hormone secretion or digestive disturbances associated with lower ingesta in the higher host population densities. Effects resulting from changes in immunological responses might also exist.

Animals↗
PubMed1985

Winter survival of trichostrongyle larvae: a study using tracer lambs.

Six groups of tracer lambs grazed from April to August on a pasture ungrazed since the previous November. A gradual decrease was observed in the worm burdens until July when a marked increase both in the number of worms and in egg counts was recorded. Haemonchus species were solely responsible for this sudden increase and it seems most likely that infection originated from larvae of the previous year rather than from overwintering eggs. Survival of Haemonchus species larvae in soil is suggested.

Animals↗
PubMed1985

Study of gastro-intestinal strongylosis in a sheep flock on permanent pasture 2. Sheep parasitism in 1978-1979.

The epidemiological study carried out in 1977 in the Limousin region of France was continued for the next two years. Eighty-five lambs were slaughtered at the rate of five animals every weeks: sixty were slaughtered from May 1978 to March 1979 and twenty-five from May to September 1979. Total parasite counts and coprological examinations were carried out. In spring the infestation of the lambs was early and heavy, and revealed that certain free-living stages can survive in low temperatures. The pattern of development of the parasites differed according to the year. It was concluded that control programmes based on theoretical patterns of evolution of the parasite will need profound study of climatic variations. Three species were found most frequently: Ostertagia circumcincta, Nematodirus spp. and Trichostrongylus colubriformis. Haemonchus contortus, exceptionally numerous in 1977, did not return to its normal level until 1979. A significant correlation was demonstrated between the number of eggs per gram of faeces and the number of female adult parasites. Thus the usefulness of coprological examinations in the diagnosis of ovine digestive strongylosis was proven. In spite of relatively high parasitism, no significant difference was found over the two years between the weight gains of regularly treated and untreated lambs.

Animals↗
PubMed1985

Trichostrongylus colubriformis: relationship between ageing of infective larvae, infectivity and egg production by adult female worms.

Relationships between egg production and infectivity were studied with infective larvae of Trichostrongylus colubriformis which had been stored for up to 22 weeks at 24 degrees C. After different storage times, larvae were administered to lambs and the number of parasites which reached the adult stage was counted five weeks after infection. Egg production was estimated for the same batches of animals by performing a quantitative coproscopic examination from the third week of infection onwards. Infectivity was maximum and constant during the first six weeks of storage and then decreased regularly from the 9th week to the end of the experiment. However, the number of eggs produced per female worm was constant during the first 6 weeks then doubled and remained constant from the 9th to the 22nd week of storage.

Aging↗
PubMed1984

Heligmosomoides polygyrus: time of anthelmintic treatment and infection parameters in mice exposed to increasing doses of larvae.

Mice were multiply infected with increasing doses of Heligmosomoides polygyrus larvae. On Day 9 or on Day 30 after the beginning of infections, an anthelmintic treatment was administered and its effect on reinfections and egg production was studied. The time of treatment was found to be an important factor, since early treatment produced marked resistance to subsequent infection, whereas a similar effect was not observed for the late treatment. Most immunity appeared after a lag time of about 3 weeks following treatment. Mice placed in direct contact with high doses of larvae had massive infections, and large quantities of worm eggs were recovered in the faeces. After larval doses were no longer given, there was a decrease of the worm burden in both treated and untreated animals. Studies of egg laying showed that the increased resistance induced by the treatment was also responsible for a reduced egg production. The relationship between fertility of H. polygyrus females and the size of young parasite populations was positive, but was negative for older populations. The slope of the regression line of this relationship was steeper in treated than in untreated mice. Egg production by a female worm was depressed to a certain extent by the resistance reactions of the host, but did not decrease below a threshold value of 100 eggs per female per day.

Animals↗
PubMed1984

A new method for culture of larvae used in diagnosis of ruminant gastrointestinal strongylosis: comparison with fecal cultures.

A study was carried out in order to compare two techniques for culture of strongyle larvae: the usual fecal culture and a new one where eggs were extracted from feces and larvae were grown in a more defined medium (agar plate fortified with Earle's medium and yeast extract). The efficiency of "on-agar" cultures was better than that of the fecal cultures with a difference of 26% for Trichostrongylus colubriformis and 32% for Ostertagia circumcincta. The variability observed between the number of larvae collected from each culture was low (8% on average) in comparison with that of fecal cultures (15% on average) thus demonstrating a better reproducibility. On the other hand growth of the larvae was similar to that obtained in fecal medium. This new technique avoids the difficulty of controlling the conditions found in fecal cultures (particularly moisture) and could become a more accurate method for diagnosis than the conventional methods. A morphometric study of infective larvae derived from the two methods of culture was carried out. Despite the more defined conditions of development in the "on-agar" cultures, it was not possible to obtain sufficiently homogeneous populations with regard to their measurements so as to distinguish larvae merely with the help of these criteria.

Agar↗
PubMed1983

The control of parasitic gastroenteritis of grazing cattle in Normandy, France using the morantel sustained release bolus.

The efficacy of the morantel sustained release bolus in controlling parasitic gastroenteritis in 153 first-season grazing cattle was assessed in three separate field trials conducted in Normandy, France. In each trial, comparisons were made on weight gain performance and parasitology data (faecal worm egg counts, herbage larval counts and- in two of the trials- worm counts from principal animals sacrificed at the end of the grazing season) when bolus treatment was given either at spring turnout or in mid-season in order to determine the optimum time for bolus administration. Cattle were allocated into three groups, each group maintained on a separate but equivalent paddock constructed from the division of a larger pasture. A morantel sustained release bolus was administered to one group of animals at the time of turnout and to a second group of animals in midsummer. The third group of animals in each trial remained nontreated. The effect of the treatment on the contamination of pasture, and parasite levels and weight gain of the principal trial animals was assessed. Similar results were observed in all three trials. Faecal worm egg counts were reduced during the first part of the grazing season in animals receiving the bolus at turnout compared with mid-season treated animals where egg counts followed a pattern similar to the controls until bolus treatment at which time counts abruptly dropped to a low level. Likewise, levels of infective larvae on pastures grazed by control and mid-season treated animals followed similar patterns, increasing to a high level in late summer, while larval levels on pastures grazed by early-season treated animals remained at low levels throughout most of the season. Serum pepsinogen levels, worm counts and weight gain reflected the results from faecal worm egg and herbage larval counts indicating that early-season treatment with the bolus provided the most efficient treatment time for controlling parasitic gastroenteritis throughout the grazing season. The overall mean weight gain advantage of the early-season bolus-treated animals over the controls was 37.2 kg (P less than 0.01) while the advantage of the mid-season treated animals over controls was 13.7 kg.

Animals↗
PubMed1982

Egg output of Heligmosomoides polygyrus (Nematospiroides dubius) in mice infected once only.

Three experiments were carried out with the aim of knowing variations in egg production of Heligmosomoides polygyrus female worms in mice infected once only. The first experiment allowed definition of egg production cycle. A steep decrease in number of eggs laid was shown when worms had been implanted for more than 40 days. The cause of this decrease was investigated in the second experiment and in particular a possible elimination of a part of worm population was tested. Results showed that during 114 days at least the size of this population was stable. Therefore the decrease in egg production was rather to be put in relation with an ageing process of worms or as host's reaction. Results of the third experiment showed effect of the size of worm population on the individual fecundity of one female: the larger number of worms became the smaller was the fecundity. The main consequence of this reduction was a stabilization of total number of eggs laid by the whole parasite population beyond a certain number of worms (about 200 H. polygyrus adult stages).

Animals↗
PubMed1982

Egg output of Heligmosomoides polygyrus (Nematospiroides dubius) in mice given multiple infections of constant or increasing size.

The effect of repeated infections on the development of gastrointestinal strongyle and on their fecundity was studied using Heligmosomoides polygyrus as an experimental model. Two experiments were carried out: animals were dosed with constant numbers of larvae in the first experiment and with increasing numbers of parasites in the second. Results allowed us to determine the effects of the conditions of infection on the settlement of parasite populations and on their fecundity. Our observations showed that with repeated and increasing infections, the percentage of worms which developed following each ingestion of larvae diminished as the number of ingested larvae increased. When infections stopped the worm burden sharply decreased. The kinetics of egg excretion was comparable to that observed in the case of single infection. Fluctuations of egg excretion were to a large extent related to the variations in size of the worm burden. Finally, the individual fecundity of worms did not seem to fall below a certain value. In these experiments the number of eggs layed per female and per day never fell below 100.

Animals↗
PubMed1981

Coccidia parasitism increases resistance of mice to subcutaneous inoculation with Salmonella abortus ovis.

Resistance of outbred mice to subcutaneous challenge with S. abortus ovis was increased when previously or simultaneously parasitized with Eimeria Falciformis. This was measured by mortality rates and levels of splenic infection induced by Salmonella in parasitized and control NMRI or CD-1 (CR) mice. No effect was observed when E. falciformis was inoculated after S. abortus ovis.

Animals↗