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Biomedical subjects

W Rudin

Publications and source records attributed to W Rudin.

At least 37 records · Page 2Linked to original sources
PubMed1992

Nematode surface coats: actively evading immunity.

The classical view of nematode parasites depicts their surface as the epicuticle, the outermost layer of a thick extracellular cuticle. However, many stages and species of nematode have been found to bear an electron-dense cuter envelope distinct from and distal to the epicuticle itself. In this review, Mark Blaxter and colleagues summarize some wide-ranging studies in both free-living and parasitic nematodes, and suggest that, in many cases, it is the surface coat rather than the cuticle that displays dynamic properties thought to be involved in immune evasion by parasites.

Journal Article↗
PubMed1992

Lectin binding to secretory structures, the cuticle and the surface coat of Toxocara canis infective larvae.

Toxocara canis infective larvae are known to produce abundant glycosylated molecules which may be found associated with the surface or secreted into their environment. Using a range of fluorescein-conjugated and gold-conjugated lectins, the localization of particular carbohydrates was defined on the surface of live parasites, and internally at the ultrastructural level. Surface exposure of N-acetyl galactosamine and N-acetyl glucosamine was deduced by binding of FITC-conjugated Helix pomatia (HPA) and wheat-germ agglutinins (WGA). These sugars appear to be associated with a densely staining surface coat as conventional immuno-electron microscopy procedures dissipate this coat and reveal no surface binding site for these lectins. However, by using cryo-immuno-electron microscopical (C-IEM) techniques, the surface coat is retained and can be shown to bind WGA. The fluorescent lectins also revealed strong WGA binding to the secretory and amphidial pores, while the buccal opening and the cuticular alae bound HPA. Corresponding results were obtained at the ultra-structural level. Thus, HPA bound to the electron-dense area of the cuticle, areas of local cuticular thickening such as the alae and buccal labia, as well as to the oesophageal lumen. WGA also bound to the thickened cuticle of the alae and the buccal opening, but showed no reaction to either the electron-dense layer of the cuticle or the oesophageal lumen. Unlike HPA, WGA did bind specifically to the secretory column contents and the electron-dense regions of the lips associated with the chemosensory amphids. The compartmentalization of the sugars N-acetyl galactosamine and N-acetyl glucosamine, their sources and routes of surface expression and the possible association with the TES glycoprotein antigens are discussed.

Acetylgalactosamine↗
PubMed1992

The role of the mosquito peritrophic membrane in bloodmeal digestion and infectivity of Plasmodium species.

Secretion and luminal formation of the peritrophic membrane (PM) were induced in female Anopheles stephensi and Aedes aegypti by feeding the mosquitoes on a warmed suspension of latex particles in Ringer's solution. The PM in A. stephensi was produced from apical secretion vesicles stored in the midgut epithelial cells and secreted into the lumen during feeding. In A. aegypti, the PM was formed de novo. When the latex feeding was followed 24 hr later by a meal of lyophilized pig blood, the 2 mosquito species exhibited very different modifications to their PM structure; in A. stephensi no PM was formed around the blood meal, whereas de novo synthesis of the PM in A. aegypti continued during the blood meal, with the resulting PM greatly thickened compared to the normal feeding. This artificial induction of PM formation was used as the basis to study the role of the PM in blood meal digestion and in infectivity of mosquitoes by the appropriate species of Plasmodium. The feeding of a latex suspension alone had no stimulatory effect on the 2 major midgut proteases, trypsin and aminopeptidase, in either species. After a blood meal alone, proteases rose to maximum activity at 30 hr and 24 hr after feeding in A. stephensi and A. aegypti, respectively. After double feeding, protease activities in both species were almost identical to those in blood-fed mosquitoes. Neither the absence of a PM (in A. stephensi) nor the presence of a thickened PM (in A. aegypti), therefore, has any effect on the ability of mosquitoes to digest a blood meal. Malaria infectivity, measured by oocyst counts, also was compared after normal and double feeding using infective blood meals. Infectivity of A. stephensi by Plasmodium berghei was unaffected by the presence or absence of the PM. The thickened PM produced by double feeding in A. aegypti caused a reduction of midgut infectivity by Plasmodium gallinaceum. These results suggest that the PM may act as a partial, but not an absolute, barrier to invasion of the midgut by the ookinete.

Aedes↗
PubMed1991

Surface coat synthesis and turnover from epimastigote to bloodstream forms of Trypanosoma brucei.

Monoclonal antibodies to metacyclic surface coat glycoproteins of Trypanosoma brucei brucei STIB 247LG were produced for a study of the synthesis of metacyclic variable surface glycoproteins (VSGs) within the salivary gland of Glossina morsitans morsitans, and of the first exchange of the surface glycoproteins after infection in mice. Immunofluorescence antibody tests and protein A-gold labelling revealed that the VSGs are continuously integrated into the whole surface of the trypanosome while it is still attached to the gland epithelium. A pool of 8 antibodies recognized about 50% of the metacyclic forms present in the saliva of an infected tsetse fly, which confirmed the heterogeneity of the metacyclic VSG-generation. The labelling experiments showed that the integration of the first VSG-generation into the surface of bloodstream forms takes place in the same way as in the metacyclics. This process started on day 3 after infection and was finished on day 6.

Animals↗
PubMed1991

The fate of Plasmodium gallinaceum in Anopheles stephensi Liston and possible barriers to transmission.

Plasmodium gallinaceum develops up to the ookinete stage in the non-compatible mosquito, Anopheles stephensi, this development occurring over the same time period and with the same success as in the compatible vector, Aedes aegypti. The slower digestive rate in An. stephensi, smaller blood-meal and lower enzyme activity than in Aedes, and an acceleration of the formation of the peritrophic membrane (PM) do not inhibit the development of the parasite. However, the ookinetes are not able to penetrate the midgut epithelium. The role of blood, vector and parasite in establishing a parasite infection in the mosquito are all considered. In particular, the role of vector-parasite recognition mechanisms in determining vector-parasite specificity are discussed.

Aedes↗
PubMed1990

Development and interactions of Trypanosoma rangeli in and with the reduviid bug Rhodnius prolixus.

Two strains of Trypanosoma rangeli and three strains of Rhodnius prolixus were used in various combinations to transmit the trypanosomes via the reduviid bug. A persisting infection in the midgut lumen posterior to the stomach resulted in all 2,500 bugs being third and fourth instars. Infectious, metacyclic forms developed exclusively in the salivary glands; forms excreted with bug feces were noninfectious to mice. The midgut epithelium was the main barrier to transmission of the parasite. In only 2%-5% of the infected bugs was it penetrated, and no correlation with any parameter tested could be found. The trypanosomes passed through the gut epithelium by an intracellular route; they were contained in a parasitophorous vacuole. The salivary glands of R. prolixus were found to be infected whenever the hemolymph was infected, after a successful penetration of the gut epithelium, or after injection of T. rangeli. On the other hand, hemolymph infections in Triatoma infestans were eliminated within a few days, and the salivary glands of this bug were never invaded. Pathogenic effects of T. rangeli on R. prolixus could be seen in midgut epithelial cells by a loss of cytoplasm and in muscle and salivary gland cells by very high parasite densities. However, as the penetration rate of the gut is low, T. rangeli is not likely to prove to be efficient in natural control of R. prolixus.

Animals↗
PubMed1990

Comparison of the cuticular structure of parasitic nematodes recognized by immunocytochemical and lectin binding studies.

The cuticle structure of some nematode species was studied by immunogold and lectin-gold techniques. The gold labelling made it possible to distinguish the cuticle layers by the distribution and/or the density of the marker. On the other hand, no labelling pattern was found which led to a clear grouping of the layers into larger 'zones', since there were no subunits consisting of more than one layer which reacted in a characteristic way as compared to the rest of the cuticle. The outer surface of the epicuticle of parasitic adult worms turned out to be highly inert; it did not react with any of the antibodies or lectins tested. The cuticle of parasitic nematodes seems to function as a protection against the host's defense mechanisms rather than as an interaction site. An immunogenic component on the surface was only found in infective larvae. All antibodies and lectins showed a preferential binding to the electron dense layers and fibrous structures (HPL/GalNAc, WGA/GlcNAc) or to the amorphous ground-substance (Con A/Glc, RCA I/Gal).

Animals↗
PubMed1990

Interaction of monoclonal antibodies with cuticular antigens of filarial parasites, Brugia malayi and Wuchereria bancrofti.

Monoclonal antibodies (mAbs) have been prepared against excretory-secretory-metabolic (ESM) antigens of microfilariae (mf) of Wuchereria bancrofti (WbmfESM) and against third stage larvae (L3) of Brugia malayi (BmL3), and purified from ascites fluids with ammonium sulphate. Both antibodies were of the IgM type and did not react with phosphorycholine. The mAb against BmL3 (F46) reacted in ELISA with antigens of L3 of B. malayi, B. pahangi and W. bancrofti and of adults of B. malayi. The mAb raised against wbmfESM (F32) resembled F46 in this respect, though with a lower titer towards the antigens, and in addition reacted with the ESM-antigens of mf and of L3 of W. bancrofti. F46 was able to detect L3 antigens of filarial parasites in spiked serum samples with a detection limit of 8-16 ng in absolute amount. The antibody was found to label the cuticular portion of L3 and adults of the lymphatic parasites, and not the epicuticular surface, in immunoelectron microscopic studies. The antibody recognized a 36 kDa component of the beta-mercaptoethanol extracts of B. pahangi-adults in Western blot analysis.

Animals↗
PubMed1990

Identification of an Onchocerca volvulus cDNA encoding a low-molecular-weight antigen uniquely recognized by onchocerciasis patient sera.

The primary structure of an immunodominant antigen of the filarial parasite, Onchocerca volvulus was deduced from cDNA sequence analysis. Using affinity-purified antibody from onchocerciasis patients from West Africa, we have isolated a cDNA clone from a lambda gt11 cDNA expression library derived from microfilariae-producing female O. volvulus. The open reading frame encodes 152 amino acids, and the deduced sequence predicts a Mr of 16,850 (consistent with the apparent Mr of 18,000 of the immunoprecipitated in vitro translated product). The primary translation product contains a putative signal peptide of 16 amino acids. The mRNA coding for this antigen has an estimated size of 950 nucleotides. Furthermore, immunoelectron microscopy established that the antigen encoded by this clone is present in the hypodermis, the cuticle, and in the uterus of the filarial worms. Since this antigen is recognized exclusively by sera from onchocerciasis patients, and not by other sera from patients infected by other filarial parasites, it may prove to be an especially valuable tool for improving the specific diagnosis of onchocerciasis.

Amino Acid Sequence↗
PubMed1989

Lectin-binding sites in the midgut of the mosquitoes Anopheles stephensi Liston and Aedes aegypti L. (Diptera: Culicidae).

The presence and distribution of binding sites for eight different lectins, Con A, DBA, HPL, LFA, RCA I, SBA, UEA I, and WGA, were compared in the midguts of Plasmodium gallinaceum-infected Aedes aegypti and Plasmodium berghei-infected Anopheles stephensi. Lectins with high specificity for N-acetyl-D-glucosamine (GlcNAc) exhibited high binding preference for the peritrophic membrane and microvillar glycocalyx of Ae. aegypti; the same structures were preferentially labeled by N-Acetyl-D-galactosamine (GalNAc)-specific lectins in An. stephensi. No differences could be observed in the lectin-binding patterns of the intercellular spaces or cellular organelles and structures. The Plasmodium ookinete surface did not react with any of the lectins tested. It appears that sugars are involved in vector recognition by the parasite and that the peritrophic membrane and/or glycocalyx may be crucial structures for the penetration of the gut epithelium by the ookinete.

Aedes↗
PubMed1989

Cytochemical demonstration of lectin binding-sites in the cuticle and tissues of Acanthocheilonema viteae (Filarioidea).

The lectin-gold technique was used for the ultrastructural localization of lectin binding sites on thin sections of Lowicryl K4M embedded adult females, infective larvae and SDS-2-mercaptoethanol-insoluble cuticle components of Acanthocheilonema (Dipetalonema) viteae. Helix pomatia lectin (HPL) coupled to 14 nm gold particles, was used for the demonstration of N-acetyl-D-galactosamine-containing glycoconjugates. Triticum vulgaris (wheat germ) agglutinin (WGA) coupled to 10 nm gold particles after cross-linking to BSA or ovomucoid-gold after application of unlabeled WGA, demonstrated WGA binding sites (N-acetyl-D-glucosamine). With both lectins no surface labelling of the cuticle was observed, but subcuticular layers reacted positively. HPL-gold was bound to cuticular fibers, the matrix and to the electron dense layer within the cortical zone of the cuticle of female worms. WGA-gold complexes were bound mainly to the cuticle matrix and somatic tissues. The results support the hypothesis that tissue-dwelling parasitic nematodes have reduced their surface carbohydrates perhaps as a consequence of their parasitic life.

Acetylgalactosamine↗
PubMed1989

On the effect of muscle activity on the end-plate membrane in denervated mouse muscle.

1. Mouse soleus muscles were denervated and some of them were chronically stimulated. Sixteen to twenty-one days later, the number of junctional acetylcholine receptors (AChR) and their metabolic stability were examined by measuring binding of 125I-alpha-bungarotoxin, their gating properties by analysis of acetylcholine-induced current fluctuations and the ultrastructure of the end-plate membrane by electron microscopy. 2. In agreement with other studies on inactive muscles, no effect of denervation on junctional AChR number could be resolved. However, some of the fast-gating 'adult' AChR channels had been replaced by slowly gating fetal AChRs, their half-life was lowered to 38 h and the folding of the end-plate membrane was reduced. 3. These changes were prevented in denervated but stimulated active muscles: the junctional AChR population remained homogeneously 'adult', the half-life of junctional AChRs was 13 days and folding of the end-plate membrane remained comparable to that in control muscles. 4. The significance of these results is discussed with respect to the role of muscle activity in end-plate development.

Animals↗
PubMed1988

Solubilization of epicuticular antigen from Dirofilaria immitis third-stage larvae.

The solubilization of epicuticle from third-stage (L3) Dirofilaria immitis larval cuticles was investigated. Cuticles collected after L3 had molted were incubated in 1.5% sodium dodecyl sulfate (SDS) at 37 degrees C with vigorous shaking. Solubilization of epicuticular layers was accomplished as demonstrated by electron microscopy. Diminished binding of an epicuticular specific monoclonal antibody (DIM-229) was seen when SDS-treated cuticles were compared to untreated cuticles in an indirect fluorescence antibody assay. Cuticles which were extracted further by boiling in 1.5% dithiothreitol (DTT) produced less protein than cuticles solubilized in SDS. Both extracts reacted with DIM-229 in an indirect enzyme-linked immunosorbent assay, indicating retention of antigenic reactivity of the solubilized epitope. SDS-polyacrylamide gel electrophoresis of SDS-derived antigens revealed, after silver staining, proteins from 12 to 77 kDa and only 1 band at 15 kDa for SDS-treated cuticles boiled in DTT. Western blot analyses of the extracts with DIM-229 were inconclusive.

Animals↗
PubMed1988

Differential infectivity of Plasmodium for mosquitoes.

The four human malarias - Plasmodium falciparum, P. vivax, P. ovale and P. malariaecan - canonly be transmitted by mosquitoes of the genus Anopheles, although not all species (nor all strains) of these mosquitoes are equally susceptible. Moreover, there are many other plasmodial parasites of other mammals and birds, that can infect other genera of mosquito. What determines this level of vector-parasite specificity? Malarial gametocytes, ingested by a feeding mosquito, must transform to gametes, fuse to form zygotes, and then, as ookinetes, migrate to the mosquito's midgut epithelium to develop as oocysts that release sporozoites to infect the mosquito's salivary glands. During this process, the blood- fed mosquito is developing its peritrophic membrane lining the gut. In this article, the Guthors examine these parallel processes in three sets of mosquito-parasite models, suggesting that parasite-vector specificity may depend on a balance between speed of parasite development versus speed of formation of the peritrophic membrane which can act as a barrier to ookinete migration and establishment in the midgut epithelium.

Journal Article↗
PubMed1988

The cross-reactive immune response between infective larvae and adult worms of Acanthocheilonema (Dipetalonema) viteae is dominated by phosphorylcholine.

The immune response of BALB/c mice against living L3 or adult extract of Acanthocheilonema viteae induces three antibody populations, namely antibodies which cross-react between the two forms of A. viteae, and either (i) do, or (ii) do not express specificity for phosphorylcholine (PC), and (iii) antibodies which do not cross-react between the two stages. In the anti-L3 serum, almost all cross-reactive antibodies to adult antigen are PC specific and of the IgM isotype, apart from a minor non-PC-reactive IgE response. On the other hand, the cross-reactive antibodies in the anti-adult serum are not PC reactive and of the IgG3 isotype. The non-cross-reactive antibodies in the two sera were predominantly IgM and IgG2/IgG1 for the anti-L3 and anti-adult respectively. Immunofluorescence and immunocytochemical studies on third-stage larvae and female worms revealed that antigens expressing PC determinants were mainly found on certain internal structures, whereas the cuticles of adults and the outer cuticle part of L3 are PC negative. Topographical analyses revealed distinct differences in labelling patterns by the two antisera, in the different areas. Thus the cross-reactive and non-cross-reactive antibodies induced by BALB/c mice to the two stages of A. viteae are different in nature. Since the antibody response induced by the L3 form and cross-reactive to the adult form is directed towards an ubiquitous antigen, namely PC, which is not present on cuticula of either the L3 or adult worms, this response may not contribute to protection against the parasite.

Animals↗
PubMed1988

Development of Trypanosoma congolense, T vivax and T brucei in the skin reaction induced in goats by infected Glossina morsitans centralis: a light and electron microscopical study.

The development and distribution of Trypanosoma congolense, T vivax and T brucei in the skin of goats was examined after the animals were bitten by infected Glossina morsitans centralis. Following the tsetse bite, the trypanosomes in the skin multiplied, reaching maximum numbers when the skin reaction (chancre) of the host attained its maximum size. In goats infected with T vivax and T brucei, trypanosomes were observed circulating in the blood before the peak of the chancre, while in T congolense-infected goats microscopically detectable parasites were found in blood only during the decline of the chancre. In contrast to T vivax, large numbers of T congolense and T brucei parasites were found in the skin following tsetse-transmitted infection. Ultrastructural differences were observed in T congolense and T brucei indicating an intracutaneous transformation from metacyclic to blood stream forms. T congolense forms in the skin reactions had a well developed secretory reticulum, small mitochondria and lacked large lipid inclusions compared to metacyclic and blood stream forms. The intracutaneous forms of T brucei had smaller mitochondria, the glycosomes were of more uniform size and the rough endoplasmic reticulum was less developed than in metacyclic or blood stream forms.

Animals↗
PubMed1987

Immunoelectron microscopic demonstration of pancreatic polypeptide in midgut epithelium of hematophagous dipterans.

Midguts of mosquitoes, Aedes aegypti and Anopheles stephensi, and of the tsetse fly, Glossina morsitans morsitans, as well as guinea pig pancreas, were prepared for electron microscopy by using low-temperature embedding in Lowicryl K4M. Rabbit antiserum to bovine pancreatic polypeptide (PP) crossreacted with secretory granules of pancreatic PP-producing cells and of the clear cells in mosquito gut. Rabbit antiserum to human somatostatin crossreacted with the control tissue, guinea pig pancreas D-cells, but not with the mosquito clear cells. None of the antisera used showed a distinct reaction with the endocrine-like cells of tsetse fly midgut. Positive reactions were revealed by gold as electron-dense marker. The gold particles were coated with protein A-gold or goat antibodies to rabbit immunoglobulin.

Aedes↗