Developmental changes in Hymenolepis citelli and Hymenolepis diminuta during patency

Stem cell frequency, wet weight, proglottid number, and egg production were measured in Hymenolepis citelli at specific intervals between 20 and 120 days postinfection in an effort to correlate changes in stem cell frequency to other developmental parameters. Considerable variability was seen in wet weight and proglottid number, but differences did not seem to reflect any relation between these parameters and stem cell frequency. Significant differences were observed in egg production at specific postinfection periods. These appeared to correspond to changes seen in stem cell frequency during patency. Similar changes in egg production which also correspond to measured changes in stem cell frequency were recorded for Hymenolepis diminuta. Differences were also seen in number of eggs contained within gravid proglottids at various times postinfection for both species.     

Intestinal contractions and migration behaviour in Hymenolepis diminuta.

The aim of this study was to determine if intestinal contractions were important in the migration behaviour of the rat tapeworm Hymenolepis diminuta. The objectives were to investigate the intestinal motility responses of the host to a meal which initiates worm migration, and the worms' responses to an artificial peristaltic contraction. A 1 g glucose meal elicited a significant orad migration by H. diminuta in the small intestine of the rat host when compared to water-fed controls (P less than 0.05). The glucose meal also significantly increased the transit rate, and thus, frequency of intestinal contractions in the small intestine of the rat, when compared to water-fed controls (P less than 0.05). Application of a circumintestinal ligature (6.3 g) (simulating an intestinal peristaltic contraction) resulted in significant worm migration when the ligature was applied in regions containing the worm's strobila as compared to controls where loose ligatures were tied in regions containing the strobila, or to controls where tight ligatures were tied ahead of the worm's strobila. These results suggest that H. diminuta migrates in an orad direction in response to the mechanical pressure produced by intestinal contractions induced by host feeding. It is concluded that contractions of the small intestine are an important cue in the migration behaviour of this cestode.     

Molecular cloning and characterization of Rab6 gene in duck.

Rab (ras-like in rat brain) proteins are small GTP-binding proteins that belong to largest subfamily in the small G protein, which are important for molecular modulation of membrane in the vesicular trafficking pathways. We have cloned and sequenced full length cDNA of Rab6 gene in duck. The cDNA sequence consists of 761 nucleotides and contains a complete open reading frame (ORF) of 627 nucleotides; the putative protein includes 208 amino acids. The CDS of duck Rab6 gene shares 86.1-90.0% homology with house mouse, silurana tropicalis, dog, human and orangutan, which indicates the Rab6 gene is high evolutional conservation in above animals.     

The architecture of the eggshell of Hymenolepis diminuta.

Lethbridge R. C. 1976. The architecture of the eggshell of Hymenolepis diminuta. International Journal for Parasitology6: 87–90. Scanning and transmission electron microscopy demonstrated that the eggshell of H. diminuta consisted of an inner continuous band from which arose an outer zone of finger-like projections with rounded tips. These tips were revealed as globule-like units lacking a regular spatial distribution but entirely covering the eggshell's surface. The appearance of these structures suggested that the shell constituents may have been deposited in an initially plastic state and possible methods of attaining the final architecture of the hardened eggshell have been discussed on the basis of this hypothesis.     

Genetic characterization of three strains of Hymenolepis diminuta at 39 enzyme loci

The technique of allozyme electrophoresis was applied to three strains of Hymenolepis diminuta to distinguish between three hypotheses [(1) multiple species, (2) genetically distinct founder stocks and (3) response to differential selection among similar stocks] proposed to account for metabolic differences among strains. There was no evidence from the 39 enzyme loci established that the three strains represented more than one species. In the absence of knowledge of the population structure of H. diminuta in the wild, electrophoretic data herein could not distinguish between the latter hypotheses. Nevertheless, all three strains were distinguishable on electrophoretic profiles and allelic similarities between strains question the view of their proposed origins.     

Molecular cloning and characterization of a thioredoxin gene from Echinococcus granulosus.

The insert of a clone from a lambdagt11 Echinococcus granulosus (Platyhelminth, Cestoda) protoscolex cDNA library, showed an open reading frame whose deduced protein sequence presents a high homology with all described thioredoxins (TRX). The TRX active site (Trp-Cys-Gly-Pro-Cys) is completely conserved. With a monospecific antibody, selected from a total anti-protoscolex sera by the isolated clone, a 12 kDa polypeptide was immunoprecipitated from a protoscolex total protein extract. Furthermore, an antiserum raised against a recombinant EgTRX also recognizes a 12 kDa band in these extracts. The recombinant protein presents TRX activity, using the insulin reduction assay. Finally, a TRX activity was characterized in protoscolex extracts. In all organisms where TRXs were studied, they participate in a cascade of redox exchanges, contributing to the maintaining of cell homeostasis. Considering that the parasitic flatworm E. granulosus is probably submitted to an important oxidative stress due to host defences, EgTRX protein could be involved in the survival strategies of this parasite.