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Biomedical subjects

P Wenk

Publications and source records attributed to P Wenk.

At least 37 records · Page 2Linked to original sources
PubMed1986

Fecundity of Litomosoides carinii (Nematoda, Filarioidea) in vivo and in vitro.

Several parameters concerning the reproduction of Litomosoides carinii were assessed using quantitatively infected cotton rats (Sigmodon hispidus). The course of embryogenesis from the fertilization of eggs to the delivery of the first microfilariae was observed by daily autopsies during prepatency. The duration of embryogenesis in vivo could thus be determined as 18 +/- 2 days. The contents of embryos in the uteri of female worms had been examined at various intervals. At the onset of patency 7-8 weeks p.i. the females were 71 +/- 6 mm long and on average contained 308 X 10(3) embryos/female, of which 19% were pathologically altered. In the middle of patency 16-20 weeks p.i. the females had grown up to 100 +/- 11 mm in length and now contained 509 X 10(3) embryos/female, 25% of them were pathologically altered, the others were normally developed. A positive correlation between the body length of a female worm and its number of embryos in utero was evident. Additionally the percentage of pathologically altered embryos was increased with respect to the age of the worms. The calculated fecundity of a female L. carinii in vivo of around 20 X 10(3) microfilariae/female per day had been confirmed with worms maintained in vitro. Three combinations of media and serum supplements were used and their influence on embryogenesis evaluated.

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PubMed1986

T-cell dependent and T-cell independent immune response in normal and in with Litomosoides carinii infected cotton rats.

The immune responses to SRBC and LPS were examined in immunized and non-immunized inbred cotton rats at different times after an infection with Litomosoides carinii. During the infection, the T-cell dependent immune response to SRBC was significantly suppressed in non-immunized animals as compared to non infected controls. In contrast, after immunization with SRBC the antibody levels of infected animals were significantly higher in three of five events. At the onset of patency the response to SRBC was significantly depressed transiently in immunized animals. A corresponding depression could be provoked by injections of isolated microfilariae as well as by FCS in immunized animals, infected and non-infected. The level of the antibodies was dependent on the density of microfilariae in the peripheral blood. The T-cell independent response to LPS was equal in non-immunized infected animals as in controls. After immunization with LPS during prepatency and at onset of patency a distinct but commensurate reaction was observed. Only after immunization at the peak of patency, the immune response of infected animals was significantly suppressed. In general, the antibody levels to LPS were not influenced by the microfilaremia.

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PubMed1983

The distribution of the microfilariae of Onchocerca volvulus in the different body regions in relation to the attacking behaviour of Simulium damnosum s.l. in the Sudan savanna of northern Cameroon.

Densities of Onchocerca volvulus microfilariae in four volunteers with low to moderate infections were estimated at five body sites by paired skin snips. The landing of Simulium damnosum s.1. females on the body of these volunteers was recorded during 12 hours for six days. Most flies fed at the ankles (53% and 51%) and calves (28% and 27% respectively) in both the standing and sitting positions. The density of microfilariae in the skin was highest in the pelvic region (24.1 mf/mg) and relatively low in the calf (14.8 mf/mg) and ankle (1.0 mf/mg) regions. From the biting rate (females/body part) and the microfilarial density (mf/mg) a transmission index was calculated for the different body regions. This was highest for the calves showing that this part of the leg, if unclothed, accounts for the highest rate of contact (50 to 60% of total) between vector and parasite.

Animals↗
PubMed1982

Studies on acquired resistance of the cotton rat against microfilariae of Litomosoides carinii. 2. Injection of microfilariae during prepatency.

Cotton rats infected by infective third-stage larvae of Litomosoides carinii were treated at increasing time intervals by a threefold injection of living homologous microfilariae (mf) during the prepatent period. Starting with the first treatment 3, 4 or 5 weeks p.i. seven animals remained completely and two almost mf-negative (1 or 2 mf/mm3 each only once) until 16 weeks p.i. Starting 6, 7 or 8 weeks p.i. six animals developed a normal level of parasitaemia between 42 and 436 mf/mm3, two animals developed a continuous level of 1-2 mf/mm3. The number of fertile adult worms shedding great numbers of microfilariae in the pleural cavity was equal in all animals. However, in mf-negative animals the lung capillary blood showed, in the geometric mean, only 0.6% of the mf-concentration seen in mf-positive animals. The hypothesis is proposed that microfilariae accumulating primarily in the lung capillaries absorb all aggressive components specifically reacting with microfilarial antigens, i.e. neutralize the immune response against them to enable the development of the parasitaemia in the peripheral blood.

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PubMed1982

[Suppression of parasitemia in rodent filariasis (Litomosoides carinii) by immunization with BCG and microfilaria. I. Intracutaneous inoculation of BCG].

After intracutaneous inoculation of BCG and challenge by subcutaneous injection of infective larvae of Litomosoides carinii, the parasitaemia of the filarial infection in cotton rats remains significantly lower when BCG and larvae are applied in the region of the same popliteal and ileal lymph nodes. However, when the infective larvae are directed to other regional lymph nodes (Ln cubitales and axillares), the depression of microfilaraemia is missed. The worm load (recovery rate) and the expulsion of microfilariae by the adult worms are not influenced by the BCG inoculation. Obviously BCG stimulates the lymphatic tissue unspecifically, and the infective larvae produce the first antigen contact, which is boostered by the microfilariae at the onset of patency. When the intracutaneous BCG inoculation is combined with specific antigen stimulation by simultaneous injection of blood microfilariae in the region of the same lymph nodes, the microfilaraemia of the challenge infection disappears completely or remains extremely low.

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PubMed1981

The transmission of Onchocerca tarsicola (Filarioidea: Onchocercidae) by Odagmia ornata and Prosimulium nigripes (Diptera: Simuliidae).

Onchocerca tarsicola is a subcutaneous filariid of the red deer living on the tendons of the radial-carpal and tibial-tarsal joints. Its microfilariae concentrate mainly in the external ears. The extrinsic cycle of this parasite was investigated. In a hyperendemic area wild-caught Odagmia ornata were dissected, as well as samples which had fed on a tame deer and been kept in the laboratory after the infecting blood-meal. About 3 to 5% of the flies were infected with larval stages of Onchocerca tarsicola. More than 40% of Odagmia ornata induced to feed on the ears of the deer became infected and about 30% of the flies which survived more than 18 days contained third-stage larvae. The larval development in the vector is described. Prosimulium nigripes appears to be a second natural vector of Onchocerca tarsicola. Observations concerning the potential vectors of O. flexuosa, O. tubingensis and Cutifilaria wenki living in red deer are discussed.

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PubMed1978

[Experiments in vitro with Litomosoides carinii (Nematoda: Filarioidea). I. Maintenance of adult females and microfilariae as well as release of microfilariae in different culture media (author's transl)].

Embryos of L. carinii continue intrauterine development to microfilariae and are totally released into the medium within 5--6 days when the latter (Tc 199) is changed daily and air is used as the gas phase. Oogenesis or further fertilization of eggs, however, does not occur in vitro in any of the media examined by us. One female releases 140 X 10(3) microfilaria/day on an average in vitro within 5--6 days. Mean initial numbers of 300 X 10(3) Mf/female/day are observed. Addition of equine serum inhibits microfilarial release in vitro; normal cotton rat serum prolongs survival of females while total numbers of released microfilariae or retained embryonic stages are not increased. The serum of post-patent animals does not influence the numbers of released microfilariae or their viability or survival of females. Microfilariae released in vitro in Tc 199 + 33% normal cotton rat serum survive for more than 8 days, when air is used as the gas phase and the medium is changed daily. Microfilariae isolated from the blood of patent animals survive for at most 6 days, at a 48-hourly change of medium survival does not even exceed 4 days.

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PubMed1976

[Investigations on the Filariidae of the Cervidae in Southern Germany. 4. Onchocerca garmsi Bain and Schulz-Key, 1976, a subcutaneous Filaria of red deer (Cervus elaphus)].

O. garmsi is a filaria living free in the subcutaneous tissues on the chest of red deer. The microfilarial distribution pattern in the skin of the host is studied. The convergent distribution of microfilariae of O. garmsi, O. tubingensis and O. cervicalis on the one hand and of O. tarsicola and W. rugosicauda on the other hand is discussed.

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PubMed1972

Mating, blood feeding, and oviposition of Simulium damnosum Theobald in the laboratory.

The development of suitable techniques for colonizing the vectors of human onchocerciasis in the laboratory would facilitate critical studies on many aspects of their biology. Progress towards this end, however, has until now been prevented by the fact that no African simuliid had been induced to mate in captivity. The main vector of human onchocerciasis in Africa is Simulium damnosum, which exists in a number of different forms, some but not all of which bite man. During the present investigations one form of S. damnosum, the "Kibwezi" form, was successfully induced to mate, to blood-feed, and to lay viable eggs in the laboratory. The methods described should be tested on other forms of S. damnosum, especially the anthropophilic forms responsible for the transmission of Onchocerca volvulus.

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