Electron microscopic study of the cyst of the sarcosporidian, Sarcocystis ovifelis

Cysts of S. ovifelis, examined from the sheep oesophagus muscles have been shown to be covered by a cyst wall made of a primary and a secondary envelopes. Within the cyst, three morphologically different cell types are distinguished: metrocytes, merozoites, and interstitial cells. The latter have been first discovered for the genus Sarcocystis, in addition to earlier literature evidence of their availability in cysts of the genus Frenkelia.     

Cytochemical study of the cyst stages of the sarcosporidian, Sarcocystis ovifelis

Cysts and cyst stages (merozoites) of Sarcocystis ovifelis were studied using methods of light microscope cytochemistry for detecting nucleic acids, proteins, polysaccharids, lipids and phosphatases, the latter substances being examined with negative results. DNA has been localized in the zoites whereas high contents of RNA and amylopectin were seen in cytoplasm. Tannofilic protein was detected evenly distributed both in the nucleus and cytoplasm.     

Oxidation-reduction enzymes in the cyst stages of the sarcosporidian, Sarcocystis ovifelis

Using methods of light microscope cytochemistry, the availability of oxidative enzymes were examined in the cyst stages (merozoites) of Sarcocystis ovifelis. Enzymes of glycolysis, Krebs' cycle and pentose--phosphate way of oxidation were detected suggesting a mixed character of merozoite's oxidative metabolism. A weak activity of glutamate dehydrogenase (an enzyme involved in protein metabolism) was shown in merozoites in addition to the absence of beta-hydroxybutyrate dehydrogenase (an enzyme of lipid metabolism).     

Electron microscopic study of the division processes in cysts of the sarcosporidian, Sarcocystis, ovifelis

The metrocyte stage in the cysts of S. ovifelis has been found to divide not by endodyogeny, but by a different mode, not yet completely understood. The nucleus of the dividing metrocyte displays no nuclear envelope, the cytoplasm is full of large vacuoles. During the metrocyte division, some kind of nucleoplasm spreading occurs over the cytoplasm and between the large vacuoles, thus making any morphological limits between the cytoplasm and the nucleus invisible. The cytokinesis is accomplished due to the deep invaginations of the metrocyte pellicle. The metrocyte division first gives rise to a large multicellular (4--6) body lying in the peripheral zone of the cyst. The very impossibility of endodyogenetic division in the metrocyte stage may be due to its vaery peculiar morphofunctional organization, much different from what is characteristic of any asexual penetrative stage (= zoite) of Apicomplexa. The progeny of a metrocyte are interstitial cells which eventually, through the number of generations, evolve towards the metrozoite stage. Step by step, the interstitial cells aquire polarity due to the establishment of a conoid, rhoptries and micronnemes on the anterior pole, the pellicle becoming more rigid thus making, together with subpellicular microtubules, the cytoskeleton of the parasite. The study performed enables us to conclude that it is interstitial cells of advanced generations that divide by endodogeny. Merozoites being homologous to gamonts of other coccidia undergo no asexual division at all.     

The kinetics of specific serum antibodies in sheep infested with sheep bot larvae]

The kinetics of specific antibodies of the blood serum of sheep experimentally infested with 80, 160 and 1000 specimens of Oestrus ovis larvae was examined. The affinity pure serum IgG and the immunoferment analysis (ELISA) were used for qualitative estimation of specific antibodies. It has been shown that the level of specific antibodies correlates with the larval biomass and is connected with ontogenesis of this parasite. The younger animals, which were infested for the first time, are characterized by more intensive production of specific IgG than adult reinfested ones. The ways of immunity response formation in animals infested with Oestrus ovis larvae are considered.     

Sarcocystis arieticanis and other Sarcocystis species in sheep in the United States

Histological sections of tongues, esophagi, and diaphragms from 512 adult ewes from the northwest United States and Texas were examined for Sarcocystis spp. Sarcocysts were found in sections of 82.1% of 504 tongues, 44.4% of 478 esophagi, and 51.7% of 89 diaphragms. Sarcocystis tenella was the predominant species and was found in 430 (84.0%) sheep; S. arieticanis was found in 18 (3.5%) sheep. The mean number of S. tenella sarcocysts in tissue sections was approximately 10 times higher than that of S. arieticanis. The identification of S. arieticanis was confirmed by ultrastructural studies and by transmission to dogs. Macroscopic sarcocysts of S. gigantea were also found but were not quantitated in all sheep; sarcocysts of S. medusiformis were not observed.     

Life cycle of Sarcocystis tenella in sheep and dog

For Sarcocystis tenella, the second microscopic sarcocyst in sheep, the dog was shown to act as final host shedding sporocysts measuring 13.75-15.8 (14.8 +/- 0.8) X 9.7-10.8 (10.1 +/- 0.4) micron after a prepatent period of 8-13 days. The clinical signs and the course of experimental infections in sheep were most similar to S. ovicanis. After high doses of sporocysts sheep had temperatures up to 42 degrees C, anaemia, and paresis; they finally died from haemorrhagic diathesis. The development of S. tenella in sheep was studied and it resulted in microscopic cysts in the musculature that measured 300-650 X 20-50 micron. They showed hair-like delicate protrusions of the cyst wall measuring 6-8 X less than 0.5 micron, by which S. tenella could be clearly differentiated from S. ovicanis from day 60 p.i. onwards. The decreasing number of S. tenella through degeneration of cysts is suggested to be a self-cleaning process.     

Antigens of Amblyomma americanum ticks recognized by repeatedly infested sheep

Sera were taken from 3 sheep that had been infested 5 times with Amblyomma americanum and that exhibited manifestations of humoral depression to homologous antigens and anti-tick resistance. Proteins extracted from the intestine or salivary glands of unfed ticks or salivary glands from partially (3-day) fed ticks were analyzed by polyacrylamide gel electrophoresis (PAGE) and sodium dodecyl sulfate-PAGE. Antigens recognized by the sheep in the same materials before and after each infestation were analyzed by western blots. The sheep responded to 44 antigens. Nine to 23 antigens were recognized by the preinfestation sera and the sera of 2 gnotobiotic sheep. Four antigens (34,000, 36,500, 38,000, and 115,000 MW) were revealed conspicuously by the serum of the first infestation but very weakly or not at all by the sera of the third infestation onward. Two antigens (35,500 and 29,000 MW) from fed salivary glands were revealed only by sera taken after manifestations of resistance had appeared. These antigens may be responsible for anti-tick protection. The 29,900 MW antigen was present also in salivary extracts of Boophilus microplus.     

Manifestations of immunity in sheep repeatedly infested with Amblyomma americanum ticks

Three sheep were infested 4 times with 100 Amblyomma americanum tick pairs and kept indoors until the natural termination of the infestations. Characteristics of the tick populations that show efficiency of feeding, fertility, and offspring development, and ELISA antibodies to tick salivary gland extracts were studied at each infestation. On average, female ticks fed on tick-naive sheep detached at 12.1 +/- 0.2 (mean +/- standard error) days, weighed 492 +/- 16.8 mg, engorged 40.7 mg per day, and 35% survived to detachment during the first infestation. During the fourth infestation, they detached at 17.3 +/- 0.8 days, weighed 321 +/- 14.4 mg, engorged 18.8 mg per day on average, and 23% survived to detachment. On average, oviposition of female ticks fed on tick-naive sheep started at 11.8 +/- 0.6 days of detachment, the egg mass weighed 236 +/- 13.2 mg, 43% of the female weight turned into eggs, and 89% of the ticks that detached survived to oviposition during the first infestation. During the fourth infestation, oviposition started at 15.1 +/- 0.5 days, the eggs weighed 103 +/- 9.9 mg, 13% of the tick weight became eggs, and 67% of the ticks survived to oviposition. On average, eclosion started at 35.4 +/- 0.9 days of oviposition and 83% of the egg batches hatched in the first infestation. During the fourth infestation, eclosion started on day 34.9 +/- 0.7, and 47% of the egg batches hatched. Anti-tick resistance was expressed as an inhibition of feeding, fertility, and offspring development.(ABSTRACT TRUNCATED AT 250 WORDS)     

Electrophoretic studies on three enzymes from Sarcocystis species in sheep

Summary Thin-layer starch gel electrophoresis was used to distinguish isoenzymic differences between three species of Sarcocystis from sheep, Sarcocystis tenella, S. gigantea and S. medusiformis. Three enzymes, NADP dependent glutamate dehydrogenase, phosphoglucomutase and 6-phosphogluconate dehydrogenase showed distinctive enzyme banding patterns for the three species. ac]19800301     

Effect of developing Sarcocystis muris tissue cysts on ultrastructural change of murine muscle fibers

A study was made of the influence exerted by developing sarcocysts of Sarcocystis muris on the ultrastructural organization of muscle fibres, both harbouring the sarcocysts (HSM) and sarcocyst-free (SFM), from skeletal muscles of experimentally infected mice. Muscle fibres of non-infected mice of the same age served as a control. Mice were sacrificed 6 months following feeding S. muris oocysts (or sporocysts). The developing sarcocysts seriously destroyed HSM: their myofilaments were no hold in register, cross-bridges almost entirely disappeared, M-lines and Z-disks looked as broken structures. The majority of actin myofilaments were arranged along myosin myofilaments as discrete units. The host cell sarcoplasm was packed with numerous vacuoles of different form and size. Compared to muscle fibres in the control, SFM of infected mice also displayed an obvious ultrastructural alteration. On the periphery of SFM, some destroyed sarcomeres with swollen myofilaments were noticed whose cross-bridges were totally lacking. In other extreme areas myosin and actin myofilaments were disintegrated into thin straightened filaments 2.0-2.5 nm in diameter. It is supposed that HSM and SFM of the infected mice may experience different kinds of influence on the part of the developing intracellular parasite (sarcocyst). And it dos not seem unlikely that various biologically active substances, produced by the parasite, may be vesicle transported to SFN through the endomysium space.     

Histological and ultrastructural analysis of cryopreserved sheep preantral follicles

The aim of this study was to verify the histological and ultrastructural characteristics of sheep preantral follicles after exposure of ovarian tissue to cryopreservation in glycerol (GLY), ethylene glycol (EG), propanediol (PROH) or dimethyl sulfoxide (DMSO) in order to determine the optimum method to store sheep ovarian tissue for later experimental or clinical use. Each ovarian pair from five mixed-breed ewes was divided into 17 fragments. One (control) fragment was immediately fixed for routine histological and ultrastructural studies and the remaining (test) fragments were randomly distributed in cryotubes, equilibrated at 20 degrees C/20 min in 1.8 mL of minimal essential medium (MEM) containing 1.5 or 3 M GLY, EG, PROH or DMSO and then either fixed for morphological studies to determine their possible toxic effect or frozen/thawed and then fixed to test the effect of cryopreservation on preantral follicles. Histological analysis showed that, compared to control fragments, all cryoprotectants at both concentrations significantly reduced the percentage of normal preantral follicles in ovarian fragments prior to or after cryopreservation. PROH 3.0 M appeared to exert a more toxic effect (P<0.05) than the other cryoprotectants in noncryopreserved tissues. After freezing/thawing, the highest (P<0.05) percentages of lightmicroscopical normal preantral follicles were observed in ovarian fragments cryopreserved in EG (1.5 and 3 M) or DMSO (1.5 M). However, transmission electronic microscopical (TEM) examination showed that only the DMSO-cryopreserved preantral follicles had normal ultrastructure. The data suggest that sheep preantral follicles should be cryopreserved with 1.5 M DMSO for later clinical or experimental application.     

白粉菌侵染对小麦叶片显微及超微结构的影响白粉菌侵染对小麦叶片显微及超微结构的影响

通过半薄及超薄切片,比较了正常和受白粉菌感染的小麦叶片细胞的显微及超微结构的差异。观察结果发现(1)受感染小麦叶肉细胞的细胞壁上局部沉积大量团状电子致密颗粒;(2)叶绿体形状由原来的椭圆形转变成圆形,叶绿体膜破裂,类囊体膨大,基粒片层排列疏松,同时,叶绿体内嗜锇性颗粒数量增加;(3)线粒体膜解体,内含物分散到了细胞质中