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Biomedical subjects

D L Lee

Publications and source records attributed to D L Lee.

At least 73 records · Page 4Linked to original sources
PubMed1987

A freeze-fracture study of muscle fibres infected with Trichinella spiralis.

The muscle fibres of mice containing the infective-stage larvae of the nematode Trichinella spiralis have been studied by means of the freeze-fracturing technique. The larva lies in what appears to be a fluid-filled cavity within the cytoplasm of an altered muscle fibre. There is no membrane separating the cytoplasm of the nurse cell from the cavity surrounding the larva which is therefore truly intracellular, unlike many parasites that reside within a membrane-lined parasitophorous vacuole within the host cell. This altered muscle fibre, known as a nurse cell, lacks myofilaments but does contain extensive cisternae of endoplasmic reticulum; membrane-bound vesicles are budded off from the endoplasmic reticulum and traverse the cytoplasm towards the cavity containing the nematode where they apparently pass into the cavity. It is suggested that the contents of these vesicles are used to sustain the nematode. Attention is drawn to the similarity to giant cells that have been induced by the plant-parasitic nematode Meloidogyne in the roots of host plants and which sustain the nematode. The conversion of the muscle fibre into a nurse cell is probably brought about by the presence of a metabolic sink, the larval nematode, within the cell. This take-over of the control of a metazoan cell by another metazoan organism is most unusual and warrants further study.

Animals↗
PubMed1987

The effect of Trichostrongylus tenuis on the caecal mucosa of young, old and anthelmintic-treated wild red grouse, Lagopus lagopus scoticus.

The caecal mucosa of wild young and adult grouse infected naturally with Trichostrongylus tenuis was examined by means of scanning electron microscopy and compared with adult grouse which had been treated with an anthelmintic. The caecal mucosa of young red grouse with low worm burdens possessed longitudinal plicae and exhibited little damage. The caeca from adult grouse, most of which carried high worm burdens, showed a localized depression of plicae and atrophy and cell disruption in areas of nematode aggregation. Caeca from adult birds treated with an anthelmintic showed a similar caecal structure to lightly infected caeca from young birds. It is concluded that the normal functioning of the caeca is probably affected by heavy infections of T. tenuis.

Animals↗
PubMed1986

A freeze-fracture study of the body wall of adult, in utero larvae and infective-stage larvae of Trichinella (Nematoda).

The surface layers of the cuticle, the hypodermal membranes and the muscle membranes of the adult, the in utero larvae and the infective-stage larvae of the nematode Trichinella spiralis have been studied by means of the freeze-fracturing technique. The surface of the cuticle of both adults and larvae fractures in ways different from membranes of internal cells. The surface coat on top of the epicuticle is probably the layer that changes antigenically. Reticulate ridges, with associated particles, on the E face of the outer hypodermal membrane of the adult are probably sites of attachment of the hypodermis to the cuticle. Longitudinally arranged ridges, with associated particles, of the outer hypodermal membrane are probably points of attachment to the cuticle in the in utero and infective larvae. Rectilinear arrays of particles are present on the P face of the inner hypodermal membrane and the P face of the muscle membrane adjacent to the hypodermis of adults and larvae and probably play a role in adhesion of the muscle membrane to the hypodermis. Particle-free areas of membrane lie external to the Z bundles of the muscle cell and are similar to the sites of attachment of Z lines in insect muscles.

Animals↗
PubMed1985

A freeze-fracture study of the digestive tract of the parasitic nematode Trichinella.

Freeze-fracture preparations of the esophagus and intestine of larvae and adults of the nematode Trichinella spiralis illustrate the distribution of intramembranous particles in membranes of a number of cell types, and several specializations were found. Esophageal glands are prominently linked by gap junctions, but gap junctions were not found between intestinal cells. Muscle cells of the esophagus have rectilinear arrays of particles, thought to be points of adherence of the muscles to the esophageal epithelium. Clusters of particles are associated with these arrays and particle-free areas (probably Z bodies) also occur. Intestinal cells have small particles in their microvilli, large particles in the cells' apical membranes, and intermediate size particles, similar to membranes of other cells, in the lateral and basal membranes. Apical smooth septate junctions and tricellular junctions occur between intestinal cells.

Animals↗
PubMed1985

Circulating prolactin concentrations in chickens infected with Eimeria tenella.

50000 oocysts of Eimeria tenella were inoculated into three-week-old cockerels and the effect of the infection (coccidiosis) on circulating concentrations of glucose, prolactin, sodium, potassium and haematocrit was determined. At day 5 of infection haematocrit was reduced and glucose was increased. From day 7 onwards prolactin concentration was elevated in infected birds compared with control and pair-fed birds. Plasma electrolytes were unchanged. It appears likely that loss of water resulting in osmotic changes during infection is the major reason for the observed changes in prolactin concentration in infected cockerels.

Animals↗
PubMed1984

A freeze-fracture study of the surface of the infective-stage larva of the nematode Trichinella.

The surface layers of the cuticle of the infective, first-stage larva of the nematodes Trichinella spiralis and T. spiralis var. pseudospiralis have been studied by means of the freeze-fracturing technique. No obvious differences between the two nematodes were found. A double-layered structure covers the cuticle. Its outermost layer consists of particles embedded in an amorphous matrix; its inner layer is composed of a sheet of fine filaments which may be composed of globular subunits. This unique double layered structure is not like a normal cell membrane in structure. The surface of the cuticle beneath it is relatively smooth except for impressions from the inner surface of the double-layered structure. The cuticle surface did not fracture in the manner of a cell membrane.

Animals↗
PubMed1983

The use of plasma etching to reveal the internal structure of Nippostrongylus brasiliensis (Nematoda).

Plasma etching has been used to strip away the cortical layers of the cuticle of adult Nippostrongylus brasiliensis to reveal the struts, with their supporting fibres, which are found in the fluid-filled middle layer of the cuticle, and the basal fibre layers. The etched specimens were studied by means of scanning electron microscopy. The results support earlier work, obtained by transmission electron microscopy, on the cuticle of this nematode. Plasma etching has been shown to have potential in studying the structure of nematodes.

Animals↗
PubMed1983

Nematodirus battus: structure of the body wall of the adult.

Males of Nematodirus battus have a body wall composed of a longitudinally ridged cuticle made up of 8 layers, a hypodermis and a layer of longitudinal muscle cells which are divided into 4 sectors by the hypodermal cords. There is a characteristic cephalic inflation of the cuticle in both sexes. The structure of the body wall in the anterior half of the female is similar to that of the male. In the posterior half of the female the cuticle is not ridged and has 7 layers; the longitudinal muscles are reduced in number and the lateral hypodermal cords increasingly extend dorsally and ventrally along the length of the posterior part of the nematode and come to occupy most of the lateral sectors of the body. The possible significance of these modifications in the structure of the female nematode are discussed.

Animals↗
PubMed1982

Inhibition of acetylcholinesterase secretion from Nippostrongylus brasiliensis by benzimidazole anthelmintics.

Treatment of rats infected with Nippostrongylus brasiliensis with a single, oral therapeutic dose of the anthelmintic benzimidazole carbamates oxfendazole or mebendazole resulted, 24 hr later, in a marked reduction (60-90%) in the secretion of a low molecular weight acetylcholinesterase from the parasites when they were incubated in vitro. This effect coincided with the expulsion of parasites from the host as a result of the therapy. When parasites were incubated in vitro with 0.1 mM oxfendazole, mebendazole, flubendazole, parbendazole, cambendazole or thiabendazole a similar effect was observed; with oxfendazole and mebendazole the effect was apparent within 1 hr and lasted for at least 4 hr after removal to fresh, drug-free medium. Whether treated in the host or in vitro the reduction in secretion was balanced by an equivalent rise in acetylcholinesterase activity within the parasites. It is suggested that the inhibition of protein secretion may be a specific manifestation of a general effect of these compounds on microtubule function.

Acetylcholinesterase↗
PubMed1982

A new soluble antigen preparation of Toxoplasma gondii and its use in serological diagnosis.

A new method of solubilizing Toxoplasma gondii in 5% saponin and 5% octyl glucoside in combination (S-Ag) is described. When analysed by IEP, seven antigens could be detected. Four of these antigens (Ag 1, 2, 3 and 12) were shown by 125I-iodination to be of membrane origin. The remaining three (Ag 4, 5 and 6) were shown to be of intracellular origin and comprise the antigenic profile of more conventional preparations used in serodiagnosis. The S-Ag preparation was tested by ELISA (S-ELISA) in parallel with a freeze-thaw preparation containing only Ag 4, 5 and 6 (FT-ELISA), against the IgG-IFAT. The regression of the FT-ELISA against the IgG-IFAT was poor and there was a high incidence (28.9%) of false negative results. A second order polynomial provided a better fit and this predicted FT negative results on sera with IgG-IFAT titres lower than 1:1024. From this titre upwards, the test was specific but insensitive. The S-ELISA was more specific (5.6% false negatives) and more sensitive; polynomial terms could not provide a better fit. The improvement in the test using the S-Ag is considered to be due to the additional membrane antigens. The possible role of this solubilized antigen in future serodiagnosis is discussed.

Animals↗
PubMed1981

Changes in the acetylcholinesterase activity of the nematode Nippostrongylus brasiliensis following treatment with benzimidazoles in vivo.

Acetylcholinesterase (acetylcholine hydrolase, EC 3.1.1.7) activities of Nippostrongylus brasiliensis were measured following treatment of the hosts with oxfendazole and mebendazole. Drug treatment of N. Brasiliensis caused large, sustained increases in enzyme activity in male and female worms which coincided with the expulsion of the nematodes from the small intestine of the host. It is suggested that the increases in acetylcholinesterase activity may be due to an inhibition by the benzimidazole carbamates of the secretion of enzyme to the exterior of the worms which, in turn, leads to expulsion through failure of the so-called "chemical holdfast".

Acetylcholinesterase↗
PubMed1981

Changes in the level of acetylcholinesterase of nematospiroides dubius and Trichostrongylus colubriformis following paralysis by levamisole in vivo.

Acetylcholinesterase (acetylcholine acetylhydrolase; EC 3.1.1.7) levels of Nematospiroides dubius from laboratory mice and Trichostrongylus colubriformis from lambs have been measured. The anthelmintic levamisole (leavo isomer of 2,3,5,6-tetrahydro-6-phenylimidazo-(2,1b)-thiazole (Tetramizole)) did not affect the level of acetylcholinesterase in N. dubius in vivo but caused a reduction in the level of the enzyme in T. colubriformis following paralysis in vivo. The effect of levamisole on acetylcholinesterase in the nematodes is explained in terms of the differing roles of the enzyme in these two species.

Acetylcholinesterase↗
PubMed1980

The structure of the intestine of Nematodirus battus and changes during the course of an infection in lambs.

The structure of the intestine of adult Nematodirus battus is described. It is similar to the intestine of some other trichostrongyles but with a few minor differences. Changes in the structure of the intestinal cells are described in N. battus taken from lambs during the later stages of an infection (days 20 to 32) with 60000 infected larvae. The most noticeable changes were a decrease in the amounts of glycogen and smooth endoplasmic reticulum, a reduction in the numbers of secretory-type granules and the appearance of vacuoles within the cells. Some of these vacuoles contained small crystals, and crystals, some of them large, were also found in the intestinal lumen. These changes, with the exception of the appearance of the crystals, are similar to changes described for Nippostrongylus brasiliensis affected by the immune response of the rat host, and it is concluded that the changes in N. battus could have been initiated by an immune response to this nematode in the lamb. Lambs given 2000 larvae of N. battus do not reject the nematodes in 32 days, and no changes were observed in the structure of these nematodes.

Animals↗
PubMed1980

Nematodirus battus: scanning electron microscope studies of the duodenal mucosa of infected lambs.

Lambs given 60 000 third-stage larvae of Nematodirus battus were killed on days 16, 20 22, 24 and 32 of the infection and the duodenal mucosa was examined by scanning electron microscopy (SEM). On day 16 of the infection the villi were long and finger-like and, although goblet cells were visible, the surface of the villi was not extensively folded, as is the surface of villi of uninfected control animals. By day 20 of the infection the villi had been reduced to flattened, plate-like structures or had formed low, irregular-shaped ridges. On this day of the infection the nematodes appeared to be enclosed by mucus-like material. As the infection progressed the intestinal damage was repaired, so that, by day 24 of the infection, the surface of the intestine was covered by short, smooth, finger-like projections and, by day 32 of the infection, the morphology of the intestine was somewhat similar to that of the control lamb. The possible role of villus atrophy and of mucus in the rejection of N. battus from the intestine is discussed.

Animals↗