Hymenolepis diminuta infection can initiate a nonmigratory contractile pattern of the small intestine, called the sustained spike potential (SSP). These contractions slow the movement of material along the length of the small intestine. In the absence of a tapeworm infection, the SSP can also be induced by infusion of the cyclic nucleotide, cyclic guanosine monophosphate (cGMP), into the duodenum of a rat. cGMP induces the SSP pattern of contraction in a dose-dependent fashion. The intestinal infusion of at least 200 nmol of cGMP alone is required to induce SSP. The infusion of succinate and cGMP together, effectively lowers the minimal-necessary concentration of cGMP required to induce SSP by 1 × 10 6 times. Succinate alone does not induce SSP; however, succinate acts cooperatively with cGMP, allowing the stimulation of SSP with as little as 560 fmol of cGMP. The amounts of succinate (2.4 μmol) and cGMP (560 fmol) in 0.2 ml infused in this study are the amounts reported by earlier studies to be present in 0.2 ml of H. diminuta –conditioned medium. This indicates that succinate and cGMP, 2 secretions from the tapeworm, interact with the tissues of the small intestine to activate an SSP pattern of contractility.

Methods for killing Echinococcus multilocularis eggs within stool or intestinal samples, without damaging the diagnostic value of the sample, would significantly reduce the risk of animal health providers acquiring alveolar hydatid disease. The first objective of this study was to determine whether E. multilocularis eggs located in fox intestines can survive storage at −70 C for at least 4 days. Results showed that none of 72,000 E. multilocularis eggs remained infectious to defined strains of mice under these conditions, yet, similar eggs recovered from nonfrozen carcasses stored at 4 C for the same time period were viable. The structural identities of adult worms and eggs were not significantly altered by the freezing and thawing processes. These results indicate that ultracold temperatures can be used to kill or inactivate E. multilocularis eggs, making them safe to handle when diagnosing this parasite in definitive hosts. The second objective of this study was to determine whether E. multilocularis eggs could survive freezing to −70 C if commonly used cryopreservation protocols were used. The use of the cryoprotectant solution, 5% dimethyl sulfoxide–35% saline–60% lamb serum, with a −1 C/min freezing rate was unable to prevent the eggs from being killed by freezing to −70 C. Rapid cooling by plunge freezing into liquid nitrogen was also lethal to E. multilocularis eggs. Only a few of the many potential cryopreservation protocols were tested in this study, so it is not yet possible to completely rule out the possibility of preserving these eggs at ultralow temperatures, but it does indicate that temperatures below −70 C are lethal to eggs even under favorable storage conditions.

The strobilocercus stage of the cat tapeworm Taenia taeniaeformis is surrounded by a single syncytial sheet of cytoplasm called the tegument. The outer membrane of the tegument covers both the scolex/strobila (S/S) and the bladder portions of the strobilocercus, but only the S/S region is resistant to intestinal digestion. It has been suggested that the glycocalyx, the surface-exposed glycoconjugates of the outer membrane, may serve to insulate underlying surface membrane components from digestion. In this study, we used lectin binding to test the hypothesis that the glycocalyx of the S/S is different from that of the bladder and that this may serve as the resistance mechanism of the S/S to digestion. Biotin-labeled lectins and an avidin–glucose oxidase detection system were applied to whole strobilocerci and to 1-µm epon-araldite plastic-embedded sections. Lectins bound to either both regions of the strobilocerci, to the S/S regions only, or did not bind at all. The restriction of some glycoconjugates to the glycocalyx of the S/S region only is consistent with our hypothesis.