Showing papers in "Journal of Parasitology in 1976"

A simple monophasic medium for axenic culture of hemoflagellates.

Abstract: An inexpensive, easily prepared monophasic medium which supports continuous culture of Leishmania donovani (approximately 4 X 10(7) cells/ml/day 5) and L. tarentolae (approximately 3.5 X 10(7) cells/ml/day 5) promastigotes has been developed. This medium, designated HO-MEM, is a modified Eagle's minimal essential medium with Spinner's salts and 10% fetal calf serum. Epimastigotes of Trypanosoma cruzi, Costa Rica strain, also grew well in HO-MEM (approximately 2 X 10(7) cells/ml/day 5) but cells of the Corpus Christi strain grew poorly in the medium. The initial inoculum for all of the above culture systems was 3 X 10(5) cells which means that there was approximately 100-fold increase in cell number within 5 days of culture. Average doubling time for L. donovani in HO-MEM during log growth phase was 10 to 12 hr; this shortened to 9.25 hr at mid-log growth (day 2). The optimal pH range for L. donovani was 7.2 to 7.4 and optimal culture temperatures were 25 to 26 C. A change was seen in the average size distribution of L. donovani promastigotes during the growth cycle with smaller cells predominating each succeding day of culture. HO-MEM is a good medium for transformation of L. donovani amastigotes to promastigotes (60 to 80% in 48 hr).

Zoospores of the Oyster Pathogen, Dermocystidium marinum. I. Fine Structure of the Conoid and Other Sporozoan-Like Organelles

Abstract: An apical complex comparable to that found in the Sporozoa is described from zoospores of Dermocystidium marlnum Mackin, Owen, and Collier, a pathogen of the American oyster (Crassostrea oirginica Gmelin) . The complex consists of a conoid, polar ring, up to 39 subplasmalemmal microtubules, rhoptries, and micronemes. Micropores and a subpellicular membrane equivalent were also found. Acid phosphatase activity was found in cistemae of the endoplasmic reticulum, inclusion bodies, and vesicles within the conoid lumen. No polysaccharides were detected in the rhoptries and micronemes using the Thiery method. Observations indicate that D. marinum is a protozoan in the subphylum Apicomplexa and is most closely related to the coccidian Sporozoasida Leuckart. Since the initial description by Gustafson et al. (1954), nwnerous authors have noted that coccidians, gregarincs, Sarcocystis sp ., Besnoitia sp., and Frenkelia sp. all have, in one or more cell stages iJ1 the li£e cycle, a hollow, cone-like structure at Lhe antedor end of the cell. This organelle, termed a conoid, consists of tubular subunits, spirally arranged to form a truncated hollow cone 0.08 μ.m to 0.4 μ.m in diameter at the anterior end and 0.2 μ.m to 0.53 μ.m at the posterior end ( Scholtyseck, 1973). Anterior to the conoid are 2 (possibly 3: Porchet-Hennere, 1975) preconoidal rings consisting of elecb·on-dense granular material connected to the conoid by a canopy of elecb·on-dense material which has an opening at the extreme anterior end. A ring of electrondense material, the polar ring, encircles the conoid. The ring is an anterior elaboration of the two closely opposed unit membranes (''subpellicular membrane\") which lie slightly under the plasmalcmma. Two or more flaskshaped, membrane-bound sacs of electrondense material converge on the conoid, the neck of each \"flask\" lying within the conoid Ju.men. These sbuctw·es, termed rhoptries or paired organelles, are believed to contain lytic enzymes which aid the organism in host cell penetration. Scattered throughout the anterior 1⁄2 or 11.i of the cell are the micronemes which are cord-like, membrane-bound sacs of electron-dense material. Some workers have suggested the rhopbi es and micronemes are Received for publication 26 January 1976. • Contribution No. 786, Virginia Institute of Maline Science, Gloucester Point, Virg inia 23062. 959 one functional system, possibly the latter giving rise to the former (Vivier and Petitprez, 1972) . Attached to and radiating from the polar ring are generally 22 to 24 microtubules which lie beneath the \"subpellicular membrane\" and extend most of the distance toward the cell posterior. In most of the organisms with conoids are also found 1 to 9 invaginations of the plasmalemma, the micropores. These specialized stmctures often have a collar of electron-dense mate1ial around the distal part of the invaginatiou and another outer cylindrical collar fonncd by infolding of the \"subpellicular membrane.\" The latter is discontinuous at the proximal end of the invagi.nation. Collectively the conoid, polar ring, subpellicular microtubles, micronemes, and rhoptries have been termed the apical complex (Levine, 1973). The consistency with which the complex has been observed in Protozoa that appear to be related for other reasons, has led to the consb.uction of the subphylum Apicomplexa Levine 1970, which includes the piroplasms, gregarines, and coccidians. The latter group includes sp ecies of Toxoplasma, Sarcocystis, Besnoit ia, Plasmodium, Frenkelia, Eirneria, and Isospora. In this paper it is shown that the oyster pathogen, Dermocystidium marinum, also has the organelles described above and thus has affinities with the Apicomplexa. There are numerous suggestions in the literature as to the affinities of the pathogen, ranging through such diverse groups as the Rhinosporidiaceae 960 THE JOURNAL OF PARASITOLOGY, VOL. 62, NO. 6, DECEMBER 1976 of the Endomycctales (Mackin, 1962), Sy11chytriaceae of the Chytricliales (Mackin and BoswolJ, 1956), Labyrinthulia ( Mackin and Ray, 1966), Ascomycctes (Mackin, 1951), lJaplosporida (Sprague, 1954) , and EntomophtJ1oralcs (F. K. Sparrow, Jr. in Ray, 1954). Mackin and Ray ( 1066) have renamed the organism Labyrinthomyxa marina thus considering it to be allied to the Labyrinthulia. Their decision resulted from observations of gliding cells with labyrinlhulid \"tracks,\" plasmoclia, and vegetative division figures similar to those of Labyrinthomyxa sauvageatii (Dul,osct1 1921). Perkins ( 1974) did not find any laby1inthulid characteristics in the oyster pathogen, except an unusual kinetosome granule, and e»'Presscd the opinion that D. marinu.m could not, at that time, be related to any k11own group

Fine Structure of Marteilia sydneyi sp. n.: Haplosporidan Pathogen of Australian Oysters

Abstract: A new species of oyster pathogen, Marteilia sydneyi, from Australian oysters, Crassostrea commercialis, is described incorporating light and electron microscope observations. The pathogen is a haplosporidan which exists as a plasmodium in the oyster hepatopancreas. Upon sporulation, 8 to 16 uninucleate sporangial primordia are internally cleaved (endogenously budded) from each plasmodium; thus conversion to a sporangiosorus occurs. Each sporangium enlarges and internally cleaves into 2 or 3 spore primordia each of which, in turn, internally cleaves into 3 uninucleate sporoplasms of graded sizes, the largest containing the smaller 2 in a vacuole and the intermediate-sized one containing the smallest in a vacuole. The spore wall is continuous without an orifice or operculum. Wolf (1972) recorded the presence of a haplosporidan in Sydney Rock oysters (Crassostrea commercialis Iredale and Roughley) from Moreton Bay, Queensland, Australia, in which he noted spores in the hepatopancreas. In subsequent papers Grizel et al. (1974) and Mix and Sprague (1974) noted its close similarity to Marteilia refringens Grizel, Comps, Bonami, Cousserans, Duthoit, and LePennec, a pathogen of Ostrea edulis Linne in French estuaries. Grizel et al. (1974) suggested that M. refringens is one of the lower fungi; however, Perkins (1976) noted haplosporidan characteristics in the form of haplosporosomes and in the mechanism of spore formation from sporangia. The organism has, therefore, been placed in the Class Haplosporea. The present paper shows that the pathogen of C. commercialis is a haplosporidan and is in the same genus as the pathogen of Ostrea edulis, popularly known as the agent of Aber disease (Alderman, 1974). The pathogen has been found only in subtropical and tropical regions of the eastern Received for publication 14 October 1975. *Contribution No. 744, Virginia Institute of Marine Science, Gloucester Point, Virginia 23062. Australian coast, not in the colder waters south of Richmond River in Australia. The other species of Crassostrea, C. echinata Quoy and Gaimard, from the eastern coast of Australia is also parasitized by a species of Marteilia probably identical to the one described herein (Wolf, unpublished). MATERIALS AND METHODS Blocks of hepatopancreas, 1 to 4 mm8 in size, were obtained from Moreton Bay, Queensland oysters (C. commercialis) and fixed in 6% glutaraldehyde for 5 to 7 days during transit from Australia to the U.S.A. Subsequent treatment has been described (Perkins, 1976). Light micrographs were obtained from histological slides of oysters fixed in Davidson's fluid and stained with Harris' hematoxylin and eosin. Conclusions concerning spore structure were based on electron microscope observations of serial sections through 2 spores as well as observations of individual sections. Serial sections were mounted on a Formvar substrate on Mason and Morton slot (2 X 1 mm) discs.

The stichosome and its secretion granules in the mature muscle larva of Trichinella spiralis.

Abstract: The stichosome of the mature muscle larva of Trichinella spiralis consists of a single row of 45 to 55 stichocytes. Each stichocyte is about 25 mum in diameter and possesses a single nucleus. A duct leads from each stichocyte to the lumen of the esophagus. The stichocyte cytoplasm contains mitochondria, structures resembling Golgi-complexes, rough endoplasmic reticulum, and usually 1 of 2 types of secretory granules. The alpha-granule measures about 800 mn in diameter, contains a prominent inclusion, and has a granular matrix. The beta-granule is about 600 mn in diameter and is homogeneous in appearance. Both granule types are surrounded by a single membrane. Ten to thirteen stichocytes containing alpha-granules are confined to the posterior portion of the stichosome. After isopycnic centrifugation in sucrose gradient of large granule fractions obtained from cell-free homogenates, the alpha- and beta-granules show characteristic distribution patterns as revealed by the morphology of the fractions. The median equilibrium density of the alpha-granules is 1.245, while that of the beta-granules is 1.230. There is a correlation between the distribution of the granules and of antigens reacting with hyperimmune antitrichinella seruma. At least 4 unique antigens can be attributed to each of the granule types. Fractions enriched in mitochondria do not contain specific antigens. Antigens from both types of secretory granules cross react totally with those present in the excretion-secretion products of living muscle larvae. Cytoimmunochemical data show that antigens are distributed in a patchy fashion throughout the stichocyte cytoplasm. This finding is consistent with the distribution of the secretory granules in the intact stichocyte.

Boophilus microplus: passive transfer of resistance in cattle.

Abstract: Plasma from cattle highly resistant to the tick Boophilus microplus conferred some resistance to unexposed calves. In contrast plasma from hosts of low resistance had no significant effect compared with plasma from unexposed donors.

The intestinal parasites of a community of feral chimpanzees, Pan troglodytes schweinfurthii.

Abstract: Fecal specimens from 32 champanzees living in Gombe National Park, Tanzania, were examined. Six species of helminths and 2 species of ciliates were found: Probstmayris gombensis File (in press), Strongyloides fuelleborni von Linstow 1905, Necator sp., Oesophagostomum sp., Abbreviata caucasica von Linstow 1902, Trichuris sp., Troglodytella abrassarti Brumpt and Joyeux 1921, and an unidentified ciliate. None of the parasitic infections were heavy. This is the first such survey of the chimpanzee in its natural habitat.

Possible secretory function of the rhoptries of Eimeria magna during penetration of cultured cells.

Abstract: Ultrastructure of the penetration of Eimeria magna sporozoites into embryonic bovine trachea cells demonstrated that the host cell membrane was not broken during entry of the parasite. This membrane did, however, undergo alterations characterized by blebbing of vesicles, thickening, and eventual disorganization once penetration was completed. Concurrent with the entrance of the parasite into the cell, and the subsequent membrane alterations, was the appearance of empty membrane saccules, probably rhoptries, in the apical region of the sporozoite. It was proposed that rhoptry secretions aided penetration by changing cell surface characteristics which produced an eventual breakdown of the invaginated protion of the host cell membrane.

Development of the large American liver fluke, Fascioloides magna, in white-tailed deer, cattle, and sheep.

Abstract: The comparative development of Fascioloides magna in white-tailed deer, cattle and sheep has been studied. Flukes were recovered from 72% of 32 deer administered 40 to 500 metacercariae, from 82% of 11 cattle administered 10 to 500 metacercariae, and from 53% of 15 sheep administered 8 to 200 metacercariae. The percentage recovery of the flukes administered as metacercariae was 4.1% of 6,130 in deer, 5.7% of 2,510 in cattle, and 4.7% of 1,213 in sheep. Flukes were recovered only from livers of infected deer, while in cattle, 1 fluke was also found in the lungs of each of 2 animals. In sheep, all but 10 flukes were recovered from the livers; 6 were found in the lungs and 4 in the abdominal cavities. The black iron porphyrin pigment associated with F. magna infection was found to be most widespread in cattle and sheep, but was also a pathognomonic feature in deer. Growth of the fluke was similar in all 3 host species tested, but eggs were passed only from deer, the normal definitive host. In cattle, the eggs were retained in the liver, and F. magna was lethal to sheep before its own maturity was attained. In cattle and deer, flukes matured approximately 7 months after exposure, but immature migrating flukes were found 12 months after infection and apparently can remain in this retarded state for an undetermined period of time.

Ultrastructure of Pharyngostomoides procyonis Harkema 1942 (Diplostomatidae). I. Observations on the male reproductive system.

Abstract: Spermatogonia, nutritive cells, and developmental stages of spermatids were observed with the electron microscope. Spermatogonia are near the surface of the testis and contain large nuclei and comparatively little cytoplasm. Nutritive or supporting cells are associated with the spermatogonia. Early spermatids are characterized by a circle of mitochondria around the nucleus. Late spermatids have 2 parallel free flagella separated by a cytoplasmic process, and a nucleus containing electron-dense strands of chromatin arranged in coils or concentric layers. Mature sperm have 2 flagella enclosed by cytoplasm. Their nuclei contain dense, fibrillar chromatin. A microtubule-organizing center (MTOC) found between basal bodies of spermatids is described. Descriptions are presented of the seminal reservoir, seminal vesicle, and the sperm found in those organs.

Arabinosyl nucleosides inhibit Toxoplasma gondii and allow the selection of resistant mutants.

Abstract: Adenine arabinoside, which inhibits the synthesis of DNA by intracellular Toxoplasma gondii, is more inhibitory to the parasite than it is to cultured human fibroblast host cells. A single-step mutant of T. gondii that is 50-fold more resistant to adenine arabinoside was isolated after mutagenesis with N-methyl-N'-nitro-N-nitrosoguanidine. Cytosine arabinoside is notably more inhibitory to cultured human cells than it is to T. gondii. Thus in infected cells treated with cytosine arabinoside and labeled with 3H-deoxyuridine nearly all of the label is specifically incorporated into the intracellular T. gondii.

The fine structure of Schistosoma mansoni sperm (Trematoda: Digenea).

Abstract: The sperm of the blood fluke Schistosoma mansoni consist of a bulbous head 8 by 2 mum, with a rounded anterior tip and tapering posterior region, followed by a relatively short flagellum ca. 20 mum long. Electron microscopic observations revealed that these sperm are devoid of an acrosome, while a few undifferentiated mitochondria accumulate at the anterior part of the head. The nucleus appears dense, except for some electron-lucent patches. The flagellum starts at the basal body, posterior and slightly lateral to the nucleus, and the axial complex is of the 9 + 0 type. A layer of microtubules runs longitudinally, just beneath the plasmalemma, from the anterior part of the head to the initial part of the flagellum, where they overlap with the axial complex. It is suggested that this relatively rudimentary type of the S. mansoni sperm is probably related to the low activity required for fertilization.

Studies on the development and chemotherapy of larvae of Parascaris equorum (Nematoda: Ascaridoidea) in experimentally and naturally infected foals.

Abstract: Experimentally induced infections of Parascaris equorum in worm-free pony foals required 14 to 17 days for migration of the larvae through the liver and lungs, and 79 to 110 days to become gametogenically functional. Treatment of experimentally infected or naturally exposed foals during the parenteral phase of development, using levamisole at 8 mg/kg, a mixture of levamisole at 8 mg/kg plus piperazine at 88 mg base equivalent/kg, or dl-tetramisole at 10 mg/kg, was quite efficacious in (1) reducing the number of P. equorum larvae recovered from the small intestines of the foals at necropsy, or (2)delaying the appearance of ascarid eggs in the feces of treated foals beyond the time period observed for the untreated foals. Three formulations of dichlorvos at doses of 10, 20, 30, or 40 mg/kg, and 2 formulations of trichlorfon at 20 or 40 mg/kg, were not effective when treatment was given on or before the 14th day after infective eggs were administered. Treatment with a gel formulation of dichlorvos at 20 mg/kg 17 to 28 days after experimental infection was 100% effective in removing ascarid larvae from the small intestines of poly foals.

Habitat and reproductive behavior of Trichinella spiralis.

Abstract: The normal niche of Trichinella spiralis adults was found to be in the epithelial layer of the mucosa of the small intestine of its host. Most worms were found in the epithelium at the base of the villi and in the glandular crypts. Copulation and insemination occurred between 30 and 32 hr postinfection, all although these acts were never observed, it was concluded that copulation and insemination took place in the epithelial layer of the mucosa. A majority of the adults were found to be completely embedded in the epithelium during the deposition of the motile larvae. Motile larvae were deposited in this location and from there migrated through the stroma to venules and lymphatic vessels. Male T. spiralis were found to be capable of inseminating at least 4 females.

Ultrastructure of interlamellar Henneguya exilis in the channel catfish.

Abstract: Ultrastructural aspects of interlamellar Henneguya exilis infections in channel catfish are reported. The plasmodium wall of this form differs from that of other species in that it is composed of two outer unit membranes which give rise to a zone of numerous pinocytic canals. Single-membraned canals appeared to be a stable feature of the wall while double-membraned canals are interpreted as those actively carrying out pinocytosis. Evidence suggests that host cellular cytoplasm as well as interstitial material is taken in by plasmodia. Plasmodium wall integrity, aggregation of parasite ectoplasmic components, numbers of pinocytic canals, and number of mitochondria proximal to the wall vary among different plasmodium profiles and may be related to plasmodium maturity. The parasite causes extensive hyperplasia of basal cells, which in turn replaces most other cell types found in noninfected gill filaments. Cytoarchitectural differences between basal cells of noninfected filaments and basal cells adjacent to plasmodia include significantly shorter microfilament bundles in the latter.

Studies on resistance in snails. 7. Evidence of interference with the defense reaction in Biomphalaria glabrata by trematode larvae.

Abstract: Echinostoma lindoense sporocysts that develop from irradiated miracidia normally are destroyed by amebocyte capsules in the ventricle of Biomphalaria glabrata within 10 days postexposure. The survival period of these ventricular sporocysts was considerably longer in snails that also harbored normal sporocysts of E. lindoense, Paryphostomum segregatum, or Schistosoma mansoni. Protection of irradiated E. lindoense sporocysts by the same of different trematode species is presumed to be the result of an active process by which normal sporocysts interfere with capsule formation and protect themselves and other trematode larvae from encapsulation. Homologous protection was stronger than heterologous.

The Ornithodoros (Alectorobius) capensis group (Acarina: Ixodoidea: Argasidae) of the palearctic and oriental regions. O. (A.) maritimus: identity, marine bird hosts, virus infections, and distribution in western Europe and northwestern Africa.

Abstract: In 1967, Vermeil and Marguet described Ornithodoros coniceps maritimus from larvae reared from larvae taken from marine birds on Dumet Island (Atlantic Ocean), Basse Bretagne, France. We collected O. (A.) coniceps Canestrini, 1890, from the type locality (Venice, Italy) and determined that the taxons coniceps and maritimus each require full species status. We selected a lectotype and paralectotypes for the taxon maritimus from the original Dumet Island material. The larva of maritimus is redescribed and the nymph, male, and female are described for the first time. Collection data are recorded from Dumet and other islands off France, Aegimures Islands off Tunisia, Puffin Island off northern Wales, and Great Saltee Island off Ireland. This tick infests nesting colonies of the common tern, roseate tern, sandwich tern, herring gull (northern and Mediterranean races), common cormorant, shag, razorbill, common murre, black-legged kittiwake, and probably other marine birds nesting nearby. Adults and nymphs (tentatively identified as maritimus but lacking associated larvae for full confirmation) were taken near nests of the little egret in Lake Tunis, Tunisia. Soldado virus was isolated from Puffin Island tick samples and a Soldado-like virus from Great Saltee Island tick samples. An experimental study of West Nile virus in the Tunisian tick population is reviewed. The birds species associated with maritimus in each collecting locality, and their nesting and resting habits and migration patterns in relation to tick and arbovirus survival and distribution, will be reported in the following paper in this series.

Studies on resistance in snails. 3. Tissue reactions to Echinostoma lindoense sporocysts in sensitized and resensitized Biomphalaria glabrata.

Abstract: The resistance of Biomphalaria glabrata snails that have been sensitized by various levels of irradiated or nonirradiated Echinostoma lindoense miracidia increased after a second challenge infection with nonirradiated miracidia of the same species. This was demonstrated by increased suppression of migrating capacity of invading sporocysts, an accelerated host tissue reaction, and a greater tendency of snail amebocytes to flatten while attacking the parasite. Three methods of elimination of invading sporocysts were observed: (1) encapsulation by amebocytes followed by destruction of the sporocysts; (2) expulsion of the sporocyst through the host epithelium after its encapsulation in the subepithelial tissues; (3) blockade of the parasite's entry into subepithelial tissues by a localized amebocyte aggregation. The basic mechanism of host snail response to a single or a repeated challenge infection appears to be similar, though an anamnestic reaction is evident in the accelerated response following a second challenge exposure.

Winter ecology of ectoparasites collected from hibernating Myotis velifer (Allen) in southwestern Oklahoma (Chiroptera: Vespertilionidae.

Abstract: During the winter of 1971-72, Trichobius major, T, corynorhini, Mydopsylla collinsi, Macronyssus crosbyi, M. unidens, Paraspinturnix globosus, Spinturnix carloshoffmani, Ornithodoros sp., Albeckia senase, Nycteriglyphus sp. A, and Olabidocarpus sp. were quantitatively collected from hibernating Myotis velifer, Plecotus townsendii, and Pipistrellus subflavus. Significantly greater numbers of S. carloshoffmani and M. crosbyi were found on female M. velifer, while greater numbers of P. globosus were found on males. With the exception of T. major and P. globosus which were radomly distributed, all ectoparasites exhibited a contagious distribution on M. velifer. Only T. major and S. carloshoffmani had a 1:1 sex ratio, the remaining species had significantly fewer males. M. unidens, M. crosbyi, and N. species A were positively associated, while M. collinsi was negatively associated with both Macronyssus; the remaining species were not signficantly associated. With the exception of T. major and P. globosus, ectoparasite densities decreased during the winter.

The eosinophilic response of the rat to infection with Taenia taeniaeformis.

Abstract: Rats were dosed with eggs of Taenia taeniaeformis and hematologic parameters were measured throughout the course of primary infection. There was no evidence of anemia but differential leukocyte counts revealed distinct and reproducible patterns of white blood cell changes. A lymphocytosis developed at the end of the 1st and 5th weeks postinfection (p.i.). Neutrophil counts peaked 8 days p.i., although at that time there was no marked neutrophilic infiltration of the tissues. Eosinophil counts began to rise during the 2nd week p.i., and reached a peak during the 3rd week, followed by a decline and then another peak during the 5th week p.i. Eosinophilic infiltration of the tissues was remarkable during the period of peripheral eosinophilia. A wide zone of eosinophils surrounded the developing larvae at 22 days p.i. and persisted in some cases for a further 2 weeks. Eosinophils remained in lesser numbers in the connective tissue capsule throughout the infection, often in association with plasma cells. After oral challenge with 1,000 eggs infected rats showed brisk secondary eosinophilic responses 3 to 7 days later but other hematologic parameters were unaffected. Average peripheral eosinophil counts at 3 and 4 days post-challenge were significantly higher than those in unchallenged controls (P less than 0.05 and P less than 0.01, respectively). There was no detectable increase in eosinophilic infiltration of small intestinal tissues in challenged rats. These results are discussed in relation to current understanding of the mechanisms of eosinophil chemotaxis in vitro and the possible causes of local eosinophil accumulation in parasitic infections in vivo.

Hatching of Schistosoma mansoni eggs and observations on motility of miracidia.

Abstract: Eggs of Schistosoma mansoni were obtained from livers of mice and hatching was observed under varying conditions of light and ionic composition of the medium. Hatching occurred equally well in light and in darkness. Eggs also hatched readily in 1- to 50-m OsM solutions of urea, sucrose, sodium chloride, and glycerol, but hatching was inhibited at higher concentrations unless the eggs were left in solutions for long periods of time. Hatching readily occurred in deionized water, but the emerged miracidia did not swim longer than 5 to 10 min unless Na+ was added. Histochemistry of the egg showed DNA-positive egg granules and a polysaccharide-positive vacuole matrix. Acid mucopolysaccharides were stained in the vacuolar matrix and in the anterior sac of the miracidium. Longitudinal alignment of constituents of the egg shell is suggested by the predominance of longitudinal rents in the shell at hatching. A mechanism of hatching involving an osmotic stimulus is proposed.

Scanning electron microscopy of the integumental surfaces of Schistosoma haematobium.

Abstract: The integumental surfaces of critical point dried S. haematobium were studied by scanning electron microscopy at 34 to 8,000 magnifications. There are marked differences between the surface structures of male and female as well as from one part of the same parasite to another. The surface of the male schistosome is moderately rough while that of the female is relatively smooth. SEM reveals certain basic features such as spines in the oral sucker and the acetabulum of both sexes which may facilitate rasping and/or attachment of the parasite for residence in the bloodstream of the definitive host. The lining of the gynecophoral canal is roughened by minute spines. The presence of a gynecophoral fold may enhance anchorage of the female in the grasp of the male. The significance of visualization of surface features by SEM as a means for differentiating species is not yet known.

Resistance to Boophilus microplus (Canestrini) in genetically different types of calves in early life.

Abstract: Tick resistance and blood composition were studied in British (1/2 Shorthorn x 1/2 Hereford) and zebu (1/2 Brahman x 1/2 British) calves from birth to 33 days of age in a tropical grazing area in which B. microplus is endemic. Calves of the 2 breeds were either naturally infested or were, in addition, artificially infested with 5,000 larvae at 2 and 9 days of age. Total numbers of mature female ticks carried from either type of infestation were significantly lower (P less than 0.01) on zebu than on British calves. In the artificially infested calves of both breeds, the total number of ticks maturing between 20 to 26 days of age was significantly higher (P less than 0.01) than the number maturing between 27 to 33 days of age emphasizing that a major component of resistance is acquired. However, in the naturally infested calves, breed differences in the numbers of ticks maturing during these 2 periods suggested the presence of genetic differences in innate resistance. Within breeds, total tick numbers carried during the study were negatively correlated with calf weight gain and with the concentrations of serum albumin, total protein, and cholesterol.