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PubMed1987

Antifilarials and their mode of action.

Diethylcarbamazine and suramin are the drugs of choice for the control of lymphatic filariasis and onchocerciasis respectively. Benzimidazoles, ivermectin, furapyrimidone, and isothiocyanates and their derivatives emerge as compounds of potential clinical interest as antifilarials. Diethylcarbamazine is predominantly a microfilaricide affecting the neuromuscular system of the parasites and promotes cellular cytotoxicity mediated by immune factors. Suramin is macrofilaricidal, has a narrow therapeutic index and damages the intestinal epithelium of the worms. Benzimidazoles bind to tubulins and inhibit their assembly to microtubules. Ivermectin is an extremely potent microfilaricide in onchocerciasis; it augments immune responses and impairs the neuromuscular function of the parasites, leading to paralysis. Isothiocyanates and their derivatives are both microfilaricidal and macrofilaricidal and affect the energy metabolism of the parasites. Although the precise mode of action of antifilarial drugs is not established, information is available on the responses listed above and also on the effects of the drugs on the carbohydrate and folate metabolism of the parasites.

Animals↗
PubMed1987

Dynamics of the filarial surface.

The surface of the filarial worm consists of an extracellular cuticle which overlies the outer plasma membrane of the hypodermis. The cuticle is permeable to a wide range of molecules of low molecular weight, and L-amino acid and D-glucose uptake occurs transcuticularly by active transport and diffusion in physiologically significant amounts. Transport mechanisms are associated with the plasma membrane of the hypodermis, and the cuticle may be considered an 'unstirred layer' distal to the transport loci. The outermost layer of the cuticle, or epicuticle, consists of a lipid bilayer which differs from a typical plasma membrane. There is no conclusive evidence for turnover of the epicuticular materials between the larval moults and in the adult stage. It is proposed that the filarial surface does not show the dynamic properties associated with the surface membranes of parasitic cestodes and trematodes.

Animals↗
PubMed1987

Characterization of the filarial genome.

Filarial parasites are just beginning to be studied at the genetic level. The potential of recombinant DNA technology for identifying parasite genes that are important in the pathogenesis of filarial disease or for the survival of the parasite is enormous. Work in several laboratories has already identified genes which encode ribosomal RNAs, as well as highly repeated DNA sequences that can be used as diagnostic probes. In addition, new methods to separate chromosomes will allow the physical mapping of parasite genes without the requirement for classical genetic analysis, which would be difficult in filariids.

Animals↗
PubMed1986

The incidence of Filaria as an aetiological factor for testicular hydrocele.

Five hundred cases of hydrocele of the tunica vaginalis testis (TVT) have been studied in detail in order to ascertain their aetiology. In 43 per cent of cases hydrocele was found to be definitely due to filariasis, in 14 per cent it was highly likely that filariasis was responsible and in 16 per cent filariasis was suspected to be the aetiological factor. The remaining 27 per cent of cases were found to be non-filarial.

Adult↗
PubMed1989

Surface characterization of the cuticle of Dirofilaria immitis.

The surface reactivity of the dog heartworm (D. immitis) was evaluated by comprehensive contact angle measurements and a platelet retention test. Contact angle data yielded calculated surface energy terms very similar to those previously reported for intact vascular endothelium. The platelet test revealed the native worm surface to be nonreactive, retaining fewer platelets than glass or worms whose surfaces had been modified by extraction with acid and high salt solutions. The cuticular morphology of the heartworm was studied with both light and electron microscopy, the latter coupled with ferritin-conjugated double-layer immunolabeling to reveal adsorbed host protein on the cuticle surfaces. Multiple attenuated internal reflection (MAIR) IR spectroscopy confirmed the general composition of this surface layer to be glycoproteinaceous. Morphological and histochemical studies confirmed and extended previous descriptions of nematode cuticle, adding ultrastructural detail on cortical, medial, and basal layers. A trilaminar membrane, apparently corresponding to a mammalian cell membrane (plasmalemma), constituted the external cortical layer as observed in high magnifications. The existence of a glycocalyx of varying thickness was demonstrated in ruthenium red-stained sections. MAIR IR spectra showed this glycoproteinaceous film to appear, in fully hydrated samples, as a loose biological gel. Ferritin-antibody conjugate labeling confirmed the presence of adsorbed dog albumin, dog immunoglobulin class G (IgG) and dog complement fraction 3 (C3) in the cuticular surface layer. It is likely, therefore, that D. immitis heartworms demonstrate long-term thromboresistance at least in part due to their passive low-surface-energy overcoating with host proteins.

Animals↗