Biochemical effects of thiabendazole and cambendazole on Hymenolepis diminuta (Cestoda) in vivo

An investigation of the chemotherapeutic and biochemical effects of two benzimidazole anthelmintics, thiabendazole (TBZ) and cambendazole (CBZ), on Hymenolepis diminuta in experimentally infected rats is reported. Thiabendazole was active against H. diminuta at a relatively high dosage. A single oral dose of TBZ at 250 mg/kg body weight on day 15 of infection eliminated 100% of the tapeworms as determined at necropsy 5 days after treatment. The chemotherapeutic actions of TBZ on H. diminuta were accompanied by marked changes in worm weight and chemical composition. Tapeworms recovered from rats that had received a therapeutically effective dose of TBZ 24 hr earlier were significantly smaller and contained much less glycogen (as a percent of the wet weight) than worms from unmedicated controls. Protein concentrations increased in TBZ-treated worms and at a rate sufficient to offset the decline in glycogen concentration. Glycogen/protein ratios in TBZ-treated worms were significantly lower than the corresponding control values. Cambendazole proved to be five times more potent than TBZ against H. diminuta and produced the same basic changes in worm weight and chemical composition within 18 hr of treatment of the host. Administration of a single oral dose of TBZ or CBZ to the host produced in H. diminuta another change, the onset of which coincided with, or preceded, the gross alterations in worm weight and chemical composition. That change, observed in in vitro studies carried out 14 hr after treatment, revealed that tapeworms from drug-treated rats absorbed and metabolized much smaller quantities of exogenous glucose than did the controls, and the ability of the worm to accumulate glucose against a concentration difference was significantly depressed.     

Structure-activity relationships of benzothiazole and benzimidazole anthelmintics: a molecular modeling approach to in vivo drug efficacy

An investigation of the biochemical effects of an anthelmintic, tioxidazole (TIOX, methyl 6-[n-propoxy]benzothiazole-2-carbamate), on Hymenolepis diminuta in experimentally infected rats is reported. The chemotherapeutic actions of TIOX on H. diminuta in vivo were accompanied by marked changes in worm weight and chemical composition. Tapeworms recovered from rats that had received a therapeutically effective dose of TIOX 24 hr earlier were significantly smaller and contained much less glycogen (as a percentage of the wet weight) than worms from untreated controls. In TIOX-treated worms, protein concentrations rose at a rate sufficient to offset the decline in glycogen concentration. Glycogen/protein ratios in TIOX-treated worms were considerably lower than the corresponding control-values. Differences in the absolute amounts of glycogen and protein between control and drug-treated worms were even more pronounced. Administration of a subcurative dose of TIOX to the rat produced in H. diminuta another change, the onset of which preceded the gross alterations in worm weight and chemical composition. In vitro studies, carried out 18 hr after treatment, revealed that TIOX-treated worms absorbed and metabolized much smaller quantities of exogenous glucose than did the controls and that the ability of the worm to accumulate glucose against a concentration difference was significantly depressed. A mode of action common to the structurally related benzothiazole and benzimidazole anthelmintics is indicated by the similarity of their biochemical and physiological effects on the tapeworms and their time course of action when administered to rats infected with H. diminuta. Molecular modeling revealed that the benzothiazole and benzimidazole anthelminitics are congruent electronically and structurally. In vivo drug efficacy depends upon the magnitude of the molecular dipole moment and the percentage of polar surface area. Within the benzimidazole series, structural and electronic congruence is found between the 2-thiazolyl and 2-methyl carbamate groups, suggesting that these groups behave similarly in transport to, and binding at, the active site. Finally, anthelmintics that have the 5' substituents twisted out-of-plane were more active than those anthelminitics with 5' substituents in-plane. All of these factors implicate a highly polar, L-shaped cleft to which the anthelmintics bind at the active site.     

Effect of host feeding and available glucose on glycogen synthase and phosphorylase activities in Hymenolepis diminuta and Vampirolepis microstoma

The influences of host feeding and the availability of glucose in vitro on the activities of glycogen synthase and glycogen phosphorylase in Hymenolepis diminuta and in Vampirolepis microstoma were studied. The worms were recovered from hosts that had been fed ad libitum, starved for 24 hr, or starved 24 hr and then refed for 1 hr immediately prior to worm recovery. The ratios of active to inactive glycogen synthase and phosphorylase were correlated with the host feeding regimen prior to recovery. Glycogen synthase in H. diminuta was predominately in the inactive D form in worms from both fed and fasted hosts. One hour after refeeding, up to 80% of the synthase was in the active I form. Phosphorylase in H. diminuta was predominantly in the active a form in worms from fed and fasted hosts, but activity of this enzyme was suppressed in worms from refed hosts. When H. diminuta from fasted hosts was incubated in a balanced salt solution containing 40 mM glucose, glycogen synthase I increased, and phosphorylase a decreased. Glycogen synthase in V. microstoma was predominantly in the inactive D form in worms from both the fed and fasted hosts, but the proportion in the active I form increased to over half the total synthase by 1 hr of host refeeding. The proportion of glycogen phosphorylase a was high in worms from fed hosts and decreased, but not dramatically, in worms from fasted hosts. The results suggested that the worms had access to another source of glucose, probably from the host bile, and we measured a low but significant concentration of carbohydrate in the gall bladder bile of mice.(ABSTRACT TRUNCATED AT 250 WORDS)     

Hymenolepis diminuta: ultrastructural abnormalities in worms from C57 mice

Ultrastructural studies, including stereological analyses of micrographs, have been made of five-worm primary infections of Hymenolepis diminuta from C57 mice to determine whether the immune destrobilation/rejection process was accompanied by significant changes in the fine structure of the scolex tegument. Destrobilation/rejection of worms occurred from Days 9-12 after infection. For the first 5 days after infection, the scolex tegument showed no detectable differences in ultrastructure compared with that of "control" worms from either Wistar rats or immunosuppressed C57 mice. By Day 6, large lipid deposits were observed in the tegument and associated musculature of worms from untreated C57 mice. Further, worms recovered from Days 6-8 after infection also showed increased activity of the Golgi apparatus, GER, and mitochondria of the tegument, resulting in increased numbers of discoidal secretory bodies. Concomitant with destrobilation/rejection from Day 9 was a drop in the number of secretory bodies, an increase in autophagic activity throughout the tegument, and a blistering of the tegument surface plasma membrane. The possible functional significance of the results is discussed in relation to host immunity.     

Biochemical effects of fenbensazole on Hymenolepis diminuta in vivo

An investigation of the chemotherapeutic and biochemical effects of a new broad-spectrum anthelmintic, fenbendazole, (FBZ, methyl 5-[phenylthio]-benzimadazole-2-carbamate), on Hymenolepis diminuta in experimentally infected rats is reported. FBZ proved to be highly active against H. diminuta; a single oral dose of 12.5, 25 and 50 mg/kg body wt. on day 15 of infection eliminated 77, 100 and 88% of the tapeworms respectively as determined at necropsy 24 h after treatment. The chemotherapeutic actions of FBZ on H. diminuta in vivo were accompanied by marked changes in worm wt. and chemical composition. Tapeworms recovered from rats that had received a therapeutically effective dose of FBZ 18 h earlier were significantly smaller and contained much less glycogen (as a percent of the fresh wt.) than worms from unmedicated controls. Protein concentrations rose in FBZ-treated worms, but more slowly than the rate of decline in glycogen concentration. Glycogen/protein ratios in FBZ-treated worms were considerably lower than the corresponding control values. Differences in the absolute amounts of glycogen and protein between control and drug-treated worms were even more profound. Administration of a single oral dose of FBZ (14 mg/kg) to the rat produced in H. diminuta another change, the onset of which coincided with, or preceded, the gross alterations in worm wt. and chemical composition. In vitro studies, carried out 16 h after treatment, revealed that FBZ-treated worms absorbed and metabolized much smaller quantities of exogenous glucose than did the controls, and the ability to the worm to accumulate glucose against a concentration difference was significantly depressed.     

Trypsin adsorption by Hymenolepis diminuta (Cestoda)

Significant amounts of radioactivity were associated with Hymenolepis diminuta following incubation in 3H-trypsin. Autoradiography of worms incubated in 3H-trypsin for 30 min demonstrated that all radioactivity was associated with the worm's surface (tegument). The amount of 3H-trypsin adsorbed by the worms was not sufficient to account for the inactivation of this enzyme in the presence of intact worms. Unlabeled trypsin and poly-L-glutamate (but not poly-L-lysine) inhibited adsorption of 3H-trypsin, but were without effect on trypsin inactivation by H. diminuta. Therefore, trypsin was adsorbed by intact H. diminuta, but the process of adsorption apparently did not play any role in inactivation of the enzyme.     

Immunity to adult cestodes: basic knowledge and vaccination problems. A review.

Immunity in mammals to intestinal cestodes has been reviewed using the normal final host infected with the tapeworms Hymenolepis diminuta in rats and H. microstoma and H. nana in mice as a model. Primary infections up to a certain level continue to live as long the host, while most worms in infections with larger doses are destrobilated and expelled. It has been argued that concomitant immunity against a superimposed infection exists in rats and mice infected with H. diminuta and H. microstoma, respectively, and suggested that it also takes place in humans infected with Taenia spp. Immunity to secondary infections after expulsion of a primary infection occurs, but immunological memory is rather short-lived, although depression of worm growth occurs for at least two third of the rat's life. Serum antibodies have been shown to produce a direct precipitate on the surface of cestodes in vitro, but a direct effect of antibodies in vivo or the relationship with e.g. host effector cells, like mast cells and eosinophils, is unknown. It has been shown that peritoneal exudate cells from rats are able to kill H. diminuta in vitro. Very little is known about the mechanisms of tapeworms to counteract host immunological responses, but the tegumental glycoconjugates and discoidal secretory bodies are possible candidates. Passive transfer of immunity by mesenteric lymph node cells has only been successful using cells from H. nana egg-infected mice and has shown that only short-lived proliferating cells are responsible for transferring immunity. Vaccination procedures and problems are discussed with special reference to E. granulosus in dogs.     

The occurrence and distribution of 5-hydroxytryptamine in Hymenolepis diminuta and H. nana

The presence of 5-HT in Hymenolepis diminuta and Hymenolepis nana was detected by 2 biochemical methods and as yellow fluorescence in a histochemical method. In H. diminuta, 5-HT was found in a concentration of about 1.2 micron/g; this amount did not vary significantly in worms aged 6 to 18 days or more or in various regions of the worm. In H. nana, 5-HT was found in a concentration of about 1.8 micron/g. It was histochemically localized in H. diminuta and H. nana in a pattern similar to that of acetylcholinesterase previously described in these 2 cestodes, and it may be the opposing neuro-transmitter to acetylcholine. The lack of 5-HT in the vestigial rostellum of H. diminuta may be correlated with loss of function of this organ.     

Study of the effects of insulin on the migration of Hymenolepis diminuta in rats

The effects of insulin on worm (Hymenolepis diminuta) migration was studied. Insulin injection (20 U/kg, s.c.) significantly increased gastric acid output but did not affect the serotonin content of blood, intestinal lumen or worms. The drug produced, dose-dependently, posteriad migration of the worms in rats without pylorus-ligation but ligation of the pylorus prevented this migration. It is concluded that the hypersecretion of gastric acid induced by insulin is responsible for the posteriad migration of H. diminuta in rats.     

Schistosoma mansoni: effect of a protein-free host diet on tegument.

The effect of a protein deficiency in the host's diet on the tegument of Schistosoma mansoni is described. Both the infected and the uninfected hamsters, fed on the diet, were stunted in growth; but the effect of the diet was more pronounced on the infected hamsters. The parasites recovered from both the liver and the mesenteric veins of animals fed on the diet from the time of infection were also retarded in growth. The tegument of both groups of parasites were reduced in height as compared with the tegument of control worms. The worms recovered from the liver of the hamsters were less adversely affected than the worms recovered from the mesenteric veins, in the sense that the tegument did not show any sign of degeneration, as was found in the latter group of parasites. In the worms from the mesenteric veins, the external plasma membrane was approximately half the thickness of the external plasma membrane of control worms. The invaginations of the external plasma membrane of experimental worms penetrated deeply into the tegument and in most instances almost reached the basal plasma membrane. Prolonged feeding of the hosts on the experimental diet resulted in the disintegration of the tegument in localised areas of the body. There was no adverse effect on adult worms of an established infection after the hosts were transferred to the protein-free diet for up to 3 wk. The ability of the tegument to regenerate after transferring the hosts from the experimental diet to normal laboratory diet (control diet) was demonstrated.     

Amino acid metabolism in the rat tapeworm, Hymenolepis diminuta

1. The amino acid metabolism of the rat tapeworm, Hymenolepis diminuta was investigated. 2. In addition to the characteristic end products of helminth metabolism, H. diminuta also forms substantial amounts of 14C-alanine during incubations in 14C-glucose. 3. Of 10 amino acids tested, only 14C-labelled asparate and, to a lesser extent alanine, generated substantial amounts of 14CO2 when incubated with H. diminuta. 4. 14C-aspartate was incorporated into both succinate and acetate, major products of the worms mitochondrial metabolism, but the rates were low when compared to the metabolism of exogenous glycogen. 5. These results suggest that amino acid metabolism in H. diminuta is very limited.     

Complement-mediated leucocyte adherence to newly excysted and 4-day-old Hymenolepis diminuta

Four-day-old and newly excysted H. diminuta were exposed in vitro (37 degrees C; 5% CO2/air atmosphere) to serum and peritoneal cells (1.7-4.4 X 10(5] obtained from rats. Four-day-old worms incubated in serum alone were lysed in titres of less than 16. In assays containing peritoneal cells, leucocytes, predominantly eosinophils and macrophages, adhered to the posterior end of the parasite in serum titre 32, but not in serum titres 64 and 128. In this region of the worms phagocytosis of microtriches by macrophages, microthrix denudation and loss of tegument were noted. Serum-mediated lysis of newly excysted cysticercoids occurred at a serum titre of 64 and leucocyte adherence and phagocytosis of microtriches occurred in serum titres 128 and 256. Attachment of peritoneal cells to worms did not occur in assays containing heat-inactivated serum and it is suggested that regional leucocyte adherence and subsequent parasite damage is complement-mediated.     

Specific cross-immunity between Hymenolepis nana and H. diminuta: immunization with heterologous and homologous light infections

The consequences of previous and concurrent infection with two related species of cestodes, Hymenolepis nana and H. diminuta, were studied in CD1 mice. A H. diminuta infection strongly affected the establishment and the survival of a secondary H. nana egg or cyst infection administered 30 days later. An infection of 20 H. nana eggs strongly protected against a 5-cyst H. diminuta challenge, whereas an infection of 10 H. nana cysts was ineffective; 20 H. nana eggs also protected against a challenge with 5 cysts of H. diminuta administered 5 days later. No effects were observed in either parasite during a concurrent infection established by administration of cysts. An H. nana egg-infection was unable to affect the establishment of a secondary H. nana cyst-infection given 1 month later; however a significant decrease in growth was found. Similar results were found when a primary H. nana egg-infection was followed 5 days later by the homologous cyst-infection. But an infection with 5 H. nana cysts was unable to protect against a homologous challenge of 5 cysts or 200 eggs. The reciprocal cross immunity between the heterologous parasites and the failure of protection of homologous challenges are discussed in relation to light infections.     

Acetic acid induced ulceration in rats is not affected by infection with Hymenolepis diminuta

Analysis of rodent models of inflammatory bowel disease, airways hyper-reactivity, diabetes, and multiple sclerosis has shown that infection with helminth parasites can significantly reduce the severity of the disease. Here, we assessed whether rats infected with the tapeworm Hymenolepis diminuta were protected from gastric ulceration induced by the serosal application of acetic acid. All rats gavaged with infective cysticercoids harbored adult worms when assessed 6 wk later, and acetic acid evoked the expected gastric ulceration. However, infection with H. diminuta did not affect the degree of gastric ulceration at either 3 or 7 days post-acetic acid application, as gauged by ulcer area or histopathology. While the data do not dismiss the possibility that infection with other helminths could be anti-ulcerogenic, they illustrate that 'helminth therapy' for inflammatory disease is likely to be both disease- and helminth-specific.     

The symbiotic microflora associated with the tegument of proteocephalidean cestodes and the intestines of their fish hosts

The indigenous symbiotic microflora associated with the tegument of proteocephalidean cestodes and the intestines of their fish hosts has been investigated in morphological and ecological aspects. The indigenous microflora associated with the cestode tegument consists of the nannobacteria population, which was present obligatorily on the surface of tegument, and the "deep microflora". The deep microflora associates with some few species of parasites only. Each individual host-parasite micro-biocenosis includes specific indigenous symbiotic microorganisms, with the differing microfloras of host intestine and parasite. Physiology, biochemistry and/or diet of hosts apparently influence on the symbiotic microflora's structure of parasites. The least bacteria abundance and diversity of their morphotypes were observed in the parasites from baby fishes. The diversity and abundance of bacteria were increased with the fish host ageing and the formation of the definitive structure of its intestine. It is an evidence of the gradual invading of the intestinal parasites (cestodes) tegument by bacterial cells. The invading is realized on the base of the microflora that was present in the food of fish host. The symbiotic microflora has specific morphological features, can regulate the homeostasis of the cestodes and fish hosts and also can maintain equilibrium of alimentary and immune interrelations in the host-parasite system.     

Scanning electron microscope studies of the mucosa of rats infected with Hymenolepis diminuta (Cestoda)

The intestinal morphology of rats given one, 10 or 100 cysticercoids of hymenolepis diminuta was examined by scanning electron microscopy. The presence of this tapeworm causes extensive villous atrophy and fusion. The most extreme changes in mucosal architecture were observed adjacent to the mature proglottides of the worm and in these areas the villi were reduced either to flattened plate-like structures or to low irregularly shaped undulations. The presence of one large H. diminuta resulted in more severe pathological damage than caused by several smaller worms. Colonization of the upper region of the ileum by long filamentous bacteria was also observed in rats infected with H. diminuta.     

Mucosal mast cell response to Hymenolepis diminuta infection in different rat strains.

Five-week-old DA male rats infected with 10 Hymenolepis diminuta cysticercoids showed significant mastocytosis 6 weeks post-infection and low persistence of worms. In F344/N rats, however, no mastocytosis and no worm loss occurred during a 6 week infection. Mucosal mast cells appear to be associated with the expulsion of H. diminuta from DA rats.     

Hymenolepis diminuta: lack of sulphate activation and sulphotransferase activity

There is no evidence that Hymenolepis diminuta can carry out sulphoconjugation reactions. Neither whole worms nor worm extracts were able to sulphate 4-methylumbelliferone. No sulphotransferase activity could be demonstrated in H. diminuta using a variety of substrates, nor was H. diminuta capable of synthesising the sulphate donor 3'-phosphoadenosine-5'-phosphosulphate from ATP and inorganic sulphate. Possible alternative sources of active sulphate in this parasite are discussed.     

Hymenolepis citelli and H. diminuta: worm burdens in homologous and heterologous infections in rats

Primary and secondary infections of Hymenolepis citelli were followed in CFHB rats. In primary infections of 6, 20, and 50 cysticercoids, over 75% of the worms administered became established and grew. Thereafter, survival depended on the intensity of the primary infection. Acquired resistance to homologous challenge infections could be stimulated in rats by prior infection with H. citelli. The growth of secondary worms decreased as the intensity of the sensitizing infection increased. The protective response waned with time in the absence of the primary worms. Cross-protective responses between H. citelli and H. diminuta occur in rats infected previously with either parasite. Retardation in the growth of secondary worms may have an immunological basis.