Schistosoma mansoni: praziquantel-induced changes to the female reproductive system.

The long-term in vivo effects of a single subcurative dose (200 mg/kg body wt of mouse) of praziquantel on the ultrastructure of the female reproductive system of Schistosoma mansoni were investigated. Morphological changes in the structure of both the vitelline gland and the ovary were apparent within 24 hr post-treatment, and lead to a partial or complete regression of both organ systems. Associated with this regression was a cessation of egg production. In surviving, paired females, irrespective of the initial severity of the drug-induced damage, both the vitelline gland and the ovary completely redeveloped and lead eventually to a resumption of egg production. In contrast, in unpaired, previously mature females the reproductive system also regressed but did not redevelop. In these cases, although the initial changes in the reproductive system were the result of drug action, the long-term regressive changes were due to discontinued male stimulation.

Biomphalaria glabrata: changes in calcium reserves following parasitism by larval Schistosoma mansoni.

Larval Schistosoma mansoni have been shown to induce morphological changes to the internal calcium reserves (in particular the calcareous inclusions in Type A calcium cells and to the inner, nacreous layer of the shell) of Biomphalaria glabrata within 48 h of miracidial penetration. Control experiments have shown that these changes were not due to either the experimental procedures used, mechanical damage or to starvation effects. The effects were, however, analogous to experimentally induced acidosis, suggesting that the rapidly transforming miracidium-sporocyst quickly induces changes in the host's metabolism, presumably by the production and release of CO2 and waste metabolites into the haemolymph.

Schistosoma mansoni: structural damage and tegumental repair after in vivo treatment with praziquantel.

The long-term, in vivo effects of a single, subcurative dose (200 mg/kg body weight of mouse) of praziquantel on the structure of adult Schistosoma mansoni and on the process and speed of tegumental repair are described. In both male and female worms praziquantel caused often extensive damage to the tegument, in the form of surface blebbings, swellings and lesions, and vacuolization and disruption of the subtegumental tissues. Repair of the drug-induced tegumental damage occurred slowly with partial and, more rarely, complete repair only being seen after 65 days post-treatment (p.t.), although signs of damage were still observed, particularly in male worms, at 100 days p.t. In contrast, repair of damage to the subtegumental/parenchymal tissues including the tegumental perikarya occurred relatively quickly, with the majority of worms examined appearing normal by 8-12 days p.t. The possible role(s) of the host immune response in relation to the speed of tegumental repair in vivo is discussed.

Structural and metabolic changes in femaleSchistosoma mansoni following male stimulation.

Pairing of males and females from single-sex infections results in the multiplication and differentiation of undifferentiated cells of the vitelline lobule culminating in the production of mature vitelline cells involved in egg shell formation. These changes are accompanied by increases in the rate of uptake of tyrosine, thymidine, and an increased accumulation of calcium.

Schistosoma mansoni: male stimulation and DNA synthesis by the female.

Unisexual females, (80-100 days post-infection) were cultured in vitro and exposed to mature male worms from either mixed or single-sex infections. A comparison was made of the uptake of [3H]thymidine (used as a marker for DNA synthesis) by isolated unisexual females or by those females exposed to males derived from either mixed or unisexual infections during in vitro culture. All males were observed to be paired with females by approximately 18 h post-culture. At 24 h post-culture females paired with males from mixed infections had an elevated uptake of [3H]thymidine compared to females that had not paired and uptake was also significantly different (P less than or equal to 0.001) from females exposed to males from unisexual infections. By 48 h there was no significant difference between uptake in females paired with either type of male. The frequency of uptake in the paired females was approximately double that in unstimulated females while non-paired females in the presence of males had an increase of between 35 and 45%. In a second experiment the effect of depriving a mature egg-laying female of the paired male was investigated. These females had a continual decrease in uptake of [3H]thymidine compared to mature females maintained with male partners. The uptake of [3H]thymidine was used as a marker for DNA synthesis and the effect of the male worm on DNA synthesis in the unisexual female is discussed in view of the above results.

Schistosoma mansoni: ultrastructure of adults from mice treated with oxamniquine.

The in vivo effects of a single oral dose (50 mg/kg) of oxamniquine on the ultrastructure of Schistosoma mansoni were investigated. In male worms, severe disruption of the tegument and gastrodermis took place, and extensive extracellular spaces developed between the cells of the internal tissues. Elimination of the damaged worms was associated with complete tegumental breakdown and encapsulation by host cells. A small proportion of females showed similar drug-induced changes and were also eliminated. In the residual females, no drug-induced morphological damage was observed even after a second dose of oxamniquine. However, these females became much reduced in size, and regression of the organs of the reproductive system took place. It is suggested that such regressive changes resulted from discontinued male stimulation rather than the direct effect of oxamniquine.

Schistosoma mansoni: electron probe X-ray microanalysis of the elemental composition of the tegument and subtegumental tissues of adult worms.

The elementary composition [Na, Mg, P, S, Cl, K, Ca and Fe] of the tegument, tegumental spines, and subtegumental tissues of adult male and female Schistosoma mansoni have been determined by electron probe X-ray microanalysis of unfixed, freeze-dried cryosections. Statistical analysis of the results suggests that there are distinct differences in the elemental composition of the tissues both between and within individual male and female worms, and between male and female worms in general. In particular, there were significant variations in the elemental contents of the tissues between individual male and female worms, which may reflect differences in the physiology and/or metabolic state of the worms. Significant differences in the elemental composition of the various tissues examined within individual worms were also found. In general, in both male and female worms, there were significantly higher elemental levels in the tegument, as opposed to the subtegumental tissues. The elemental composition of the tegumental spines in both male and female worms differed from that of the tegumental cytoplasm, although the differences in the elemental composition between spines from male and female worms reflected the differences in the elemental content between the teguments themselves. Differences in the elemental composition of the tissues between male and female worms were also found, with the female tegument containing significantly higher elemental levels (with the exception of Cl) than the male tegument. In particular, the tegument of female worms contained higher levels of calcium and, in relatively small areas, isolated calcium-containing granules. This higher tegumental calcium level in female worms may reflect a higher calcium demand by sexually mature female worms due to the presence, within the mature vitelline cells, of calcium-containing corpuscles and the production of large numbers of eggs.

Schistosoma mansoni: DNA synthesis in males and females from mixed and single-sex infections.

The pattern of DNA synthesis in male and female Schistosoma mansoni from mixed and single-sex infections in mice has been determined biochemically and autoradiographically using the incorporation of [3H]-thymidine as a specific marker of DNA synthesis. During early development (up to 35 days post-infection (p.i.] adult males and females from mixed infections had a comparable specific activity of DNA. In males, from 35 days p.i. onwards, the specific activity of DNA decreased rapidly to become significantly different from that observed in females. In single-sex infections DNA synthesis in females was depressed compared to that observed in males from single-sex infections and was also significantly different (P less than or equal to 0.01) from DNA synthesis in females from mixed infections. There was no significant difference in DNA synthesis between males from single or mixed infections. DNA synthesis in both sexes was found to be sensitive to hydroxyurea treatment, the inhibition in sexually mature females being approximately 75% and in males approximately 45%. Autoradiography using both light microscope and electron microscope techniques revealed that the testes and ovary had labelled cells. In male schistosomes the only other labelled cells were small undifferentiated cells found scattered through the tissues. In females the vitelline gland had large numbers of densely labelled nuclei within Stage 1 vitelline cells, as well as numerous small undifferentiated cells.

Schistosoma mansoni: an in vivo study of drug-induced autophagy in the gastrodermis.

The effects of Astiban, Lucanthone, Hycanthone and Niridazole on autophagic activities in the gastrodermis of Schistosoma mansoni were determined in vivo, using different dosage levels and dosage times. With Astiban, high levels of autophagy were observed in the gastrodermis 2 hours after an injection of the drug into the mouse, and this response had declined by 20 hours, marking a recovery by the parasite from the drug. Hycanthone and Lucanthone produced an autophagic response several days after the onset of treatment, and no recovery was observed in the morphology of the gastrodermis after the drug was discontinued. The effects of Niridazole on the gastrodermis were to produce the most dramatic ultrastructural changes after high doses and over several days of treatment. With all the drugs examined, gastrodermal autophagy was characterized by the formation of vacuoles containing cell components, lipid droplets and sometimes hydrolytic enzyme reaction product. The autophagic vacuoles appeared to be formed by the sequestration of cytoplasmic material by the basal membrane infoldings, and the transfer of enzymes into the vacuole from within the limiting membrane. The residues from intracellular digestion appeared to be emptied into the caecal lumen.

An ultrastructural study of the effect of parasitism by larval Schistosoma mansoni on the calcium reserves of the host, Biomphalaria glabrata.

The tissues of Biomphalaria glabrata contain three types of calcium cells which can be differentiated by their location and the size and number of their contained corpuscles. X-ray analysis has confirmed the presence of calcium and magnesium in the corpuscles. Molluscs containing the larval stages of Schistosoma mansoni at 40 days post infection show disintegration of the calcareous corpuscles in Type-A calcium cells and erosion of the inner surface of the shell.

Schistosoma mansoni: changes in elemental composition in relation to the age and sexual status of the worms.

Changes during development in the elemental contents (Ca, P, K, Mg and S) of male and female Schistosoma mansoni from both mixed and single sex infections have been measured for the first time. In mixed infections, there is a significant difference between the calcium content of male and female worms; female worms having between 2 and 3 times more calcium. In mature female worms from mixed infections, after an initial rise in the calcium content corresponding to the time when vitelline development occurs, the amount of calcium ranged from 0.36 to 0.65 mg/g dry wt, whereas the amounts in similarly aged male worms ranged between 0.19 and 0.32 mg/g dry wt. While the type of infection does not affect the calcium content of male worms, a significant difference in the calcium levels in female worms from mixed and single sex infections was found. The amount of calcium in females from single sex infections ranged from 0.21 to 0.39 mg/g dry wt and this is considerably less than the levels recorded in females from mixed infections. This difference in calcium content between mixed and single sex infections can be related to the differences in degree of development of the vitelline gland in the two types of female worm. The amounts of phosphorus, potassium, magnesium and sulphur in both male and female worms from both single and mixed infections are similar, although females from mixed infections contained slightly more phosphorus than either females from single sex infections or either type of male worm.

Schistosoma mansoni: dose-related tegumental surface changes after in vivo treatment with praziquantel.

The in vivo effects of a range of concentrations of praziquantel (10, 25, 50, 100, 200 and 500 mg/kg body weight of mouse) on the tegumental surface of adult Schistosoma mansoni were studied using scanning electron microscopy. Worms were recovered from mice at 1 and 4 h post-treatment. In general, irrespective of the dose level, male worms exhibited more pronounced and extensive surface alterations which included surface bleeding, swellings, wrinkling and constrictions and surface lesions, particularly on the spined tubercles. In male worms, in particular, the number of worms exhibiting damage and the amount of tegumental surface damage depended, mainly, on the concentration of praziquantel, although, at any given dose level, the extent of the damage increased with time post-treatment.

Schistosoma mansoni: the effects of a subcurative dose of praziquantel on the ultrastructure of worms in vivo.

The in vivo effects of a subcutaneously-administered subcurative dose (200 mg/kg body weight of mouse) of praziquantel on the structure of Schistosoma mansoni was investigated. Worms were collected at varying times post-treatment and processed for both SEM and TEM examination. Praziquantel caused extensive structural changes to both male and female worms within 15 min of treatment although variations in the amount of drug-induced damaged was observed between male and female worms. In female worms although some tegumental vacuolation was observed within 15 min, the major structural change was an often extensive vacuolisation of the subtegumental tissues followed by varying degrees of structural disruption to the subtegumental and gastrodermal musculature. In male worms the initial effects were a vacuolisation of parts of the dorsal tegument and loss of tegumental cytoplasm due to the pinching off of evaginations of the outer surface. With increasing time post-treatment there was an increase in the amount of tegumental damage, particularly in male worms, with total disruption of parts of the outer surface occurring. Also in male worms there was an increase in the amounts of vacuolisation of the parenchymal tissues and in the degree of structural damage to the musculature. In those female worms where subtegumental damage was not extensive changes in the structure of the differentiating vitelline cells were noted.

Schistosoma mansoni: the survival and reproductive status of mature infections in mice treated with oxamniquine.

A single oral dose of 50 mg/kg of oxamniquine administered to mice with mature infections of Schistosoma mansoni gave rise to a hepatic shift and almost total elimination of the male worms. Regression of the reproductive system and a conspicuous reduction in size took place in the residual females which eventually resembled sexually immature adults. A second dose of oxamniquine had no apparent effect on these females within a period of 28 days following this treatment and it is suggested that this change in reproductive status is the result of discontinued male stimulation.

A comparative study of the vitelline cell in Schistosoma mansoni, S. haematobium, S. japonicum and S. mattheei.

A comparison is given of the ultrastructure of the vitelline cell in Schistosoma mansoni, S. haematobium, S. japonicum and S. mattheei. Four stages in development of the vitelline cell have been categorized as follows: Stage 1, the undifferentiated cell; Stage 2, the developing cell showing the beginning of synthetic activity; Stage 3, the developing cell showing active protein synthesis; Stage 4, the fully mature vitelline cell. These stages in development have been defined morphologically and Stages 1, 2 and 3 are very similar in all 4 species. Lipid is present in the Stage 4 cells of all species but appears earlier at Stage 3 in S. haematobium and S. mattheei. There are several differences as to the intercellular inclusions of the Stage 4 cells, the most marked of these being the absence of calcareous corpuscles from S. japonicum as compared with the other 3 species.

Schistosoma mansoni: the presence and ultrastructure of vitelline cells in adult males.

The presence of vitelline cells in male Schistosoma mansoni from both mixed ans single sex infections in mice is described. Ultrastructurally these vitelline cells resemble the mature, Stage 4 cells from normal female worms. As yet no developing vitelline cells (Stages 1 to 3) have been found. The cells do not appear to form complete lobules as in the female.

The demonstration of calcium in the axonal granules of the peripheral nervous system of male Schistosoma mansoni by X-ray microanalysis.

A conspicuous feature of freeze-dried cryosections of male Schistosoma mansoni is the presence of groups of electron-dense granules. X-ray analysis in the TEM of these granules shows them, in comparison with the adjacent cytoplasm, to contain significantly greater amounts of sodium and calcium. In glutaraldehyde-fixed material, these granules have been correlated with the membrane-bounded, electron-dense granules found within the axons of the peripheral nervous system.