Histochemistry and ultrastructure of the metacercarial cyst of Bolbogonotylus corkumi (Trematoda: Cryptogonimidae).

Histochemical and ultrastructural studies were conducted on the metacercarial cyst of the cryptogonimid trematode Bolbogonotylus corkumi from the muscle tissue of fantail darters Etheostoma flabellare. The metacercarial cyst consisted of an outer host capsule and an inner parasite cyst. The host capsule was composed of an outer region of fibroblasts, collagen, macrophages, and unidentified cells, and an inner region containing degenerating cells. The parasite cyst was thin, homogenous, and noncellular in nature. The host capsule stained strongly for connective tissue and proteins and moderately for lipids, nucleic acids, nonspecific esterase activity, and acid and alkaline phosphatase activities. The parasite cyst stained intensely for acid mucopolysaccharides and moderately for acid phosphatase activity. A thick glycocalyx occurred between the parasite cyst and metacercarial tegument.     

The histochemistry of Stellantchasmus falcatus Onji and Nishio, 1915 (Trematoda: Heterophyidae) metacercarial cyst in the mullet Mugil cephalus L. and histopathological alterations in the host†

The metacercarial cyst of the heterophyid trematode Stellantchasmus falcatus in the striated muscles of the mullet Mugil cephalus consists of three layers. Histochemical studies have indicated that these layers are chemically distinct. The acellular inner layer is comprised of complex carbohydrate polyanions rich in acidic groups while the medial cellular layer is comprised of a neutral mucopolysaccharide including a moeity of carbohydrate poiyanions. These two layers are believed to be of parasite origin. The outer layer is cellular and is of host origin. It is the most chemically complex and is believed to include one or more of the following: mucopolysaccharides, glycolipids and phospholipids. In addition, the carbohydrate moeity associated with the mucopolysaccharides and/or glycolipids is in the form of sulphated carbohydrate polyanions with undissociated carboxyls as well as acidic groups. The presence of the parasite results in the necrotic degeneration of the host's myofibers situated in the proximity of the parasite. Large fat cells fill the spaces vacated by necrotic muscle cells and many blood cells occur along the periphery of the parasite.     

The pathogenicity, localization, and cyst structure of echinostomatid metacercariae (Trematoda) infecting the kidneys of the frogs Rana clamitans and Rana pipiens

Light and scanning electron microscopy were used to examine the localization and pathogenicity of echinostomatid metacercariae infecting the kidneys of leopard frogs, Rana pipiens, and green frogs, Rana clamitans. Cysts occurred predominantly in the ventrolateral renal cortex, and at least some were confined to the lumen of the Bowman's capsules. Each vermiform metacercarial body was enclosed by a spherical cyst wall that had a uniform thickness. The wall was composed of a homogeneous material containing basic and keratinlike proteins, with sulfated acid mucopolysaccharides on the outer surface. Most cysts were enclosed by a fibrous capsule of host origin, or were surrounded by an inflammatory focus. Fibrosis was always focal, but its degree varied between individual hosts and between different cysts within the same host. Some heavily encapsulated cysts were darkened and contained disintegrating worms. In heavily infected kidneys, confluence of fibrotic or inflammatory foci resulted in the displacement of functional renal tissue. These data suggest that infection by echinostomatids may impair renal function and that the host's response affects parasite viability.     

Placentation in the garter snake, Thamnophis sirtalis

The structure and polysaccharide constitution of the jelly capsule of the egg of Rana pipiens is described. Microscopic examination of the jelly capsule revealed the presence of five discrete jelly layers that differed clearly in their response to selected cytochemical tests. These layers were classified as M1-through M5 from the inner to the outermost layer. A sixth layer occasionally could be observed between M3 and M4. All layers contain neutral mucopolysaccharides. In addition layers M1 and M3 contain sulphated mucopolysaccharides, M2 and M4 contain non-sulphated acid mucopolysaccharides, and layer M5 contains both sulphated and non-sulphated acid mucopolysaccharides. M2 may also contain a small quantity of sulphated mucopolysaccharides. The layer that occasionally appears between M3 and M4 is probably an area in which free acidic groups are in higher concentration than in adjacent areas rather than being a discrete jelly layer. Neither hyaluronic acid nor sialic acid was localized by the methods employed. The possible significance of some of these constituents is discussed.     

The structure and composition of the cyst wall of the metacercaria of Cloacitrema narrabeenensis (Howell & Bearup, 1967) (Digenea: Philophthalmidae).

The mstacercarial cyst of Cloacitrema narrabeenensis which is formed in the open is composed of four layers: an outermost layer of acid mucopolysaccharide, a layer of protein which is presumed to be tanned, a layer of neutral mucopolysaccharide and an innermost layer of keratinized protein. The two layers which together form the outer cyst wall can be split off by slight pressure from the two remaining layers which together form the inner cyst wall. In the centre of the ventral side of the inner cyst wall, the keratinized layer is incomplete and this ventral plug region is composed of neutral mucopolysaccharide. The cyst wall is therefore very similar to that of Fasciola hepatica, the main difference being that the order of the two layers of the outer cyst is reversed. General evolutionary and functional relationships of metacercarial cysts are discussed.     

The fine structure of the phoront of Gymnodinioides pacifica, a ciliated protozoan (Ciliophora, Apostomatida) from euphausiids of the Northeastern Pacific

Phoretic stages of the exuviotrophic apostome Gymnodinioides pacifica were examined using transmission and scanning electron microscopy (TEM and SEM). TEM revealed that the mature cyst wall possesses 2 or 3 layers differing by the presence or absence of the third inner layer. This inner layer may represent a different form of the middle wall material. The inner cyst layer is approximately 0.15 microm thick and has striations with a periodicity of approximately 19 nm. The middle cyst layer has a variable thickness and the outer dense layer is approximately 0.1 microm thick. The 3 layered cyst wall had a thickness of 0.3-0.7 microm and averaged 0.5 microm. Advanced phoront stages were enclosed by fully formed cyst walls or by cyst walls thinned to approximately 0.1 microm, as the phoronts prepared to excyst prior to host ecdysis. Additionally, we report the fine structure of the rosette, trichocysts, nuclei, food plaquettes, oral fiber, and other cytoplasmic inclusions. SEM revealed an outer cyst wall layer connected to the secreted peduncle material, which was observed to extend over a wide (15 microm) area on the host setae. Cysts were usually attached at their posterior ends or, less frequently, along their side.     

Histochemical and ultrastructural studies on the metacercarial cyst of Echinostoma revolutum (Trematoda).

Histochemical and ultrastructural studies were made on the metacercarial cyst of Echinostoma revolutum obtained from the kidney of experimentally infected Physa and Lymnaea snails. Ultrastructural studies revealed three cyst walls, an outer, middle and inner. The outer wall was more electron-dense than the middle, and contained coarser granules than those found in the middle layer. The inner wall was lamellated and contained membranous whorls. Collagenous fibers presumably of host origin surrounded the outer cyst wall. The outer and middle cyst walls stained identically with all histochemical procedures used. These walls contained acid mucopolysaccharides and glycoprotein, whereas the inner cyst wall contained glycoprotein. All cyst walls stained positively with a variety of protein stains.     

The fine structure of secretion in Hyalophysa chattoni: formation of the attachment peduncle and the chitinous phoretic cyst wall.

The settling tomite stage of the apostome Hyalophysa chattoni secretes a phoretic cyst wall composed of chitin, mucopolysaccharides, and protein. Within 1 1/2 h after settling, an electron-dense proteinaceous cyst layer (the outer layer) is formed from secretions originating at the base of the kineties and from the thick pellicular layer between the kineties. The inner cyst layer, composed primarily of chitin (acidic and neutral polysaccharides are also present), is secreted across the entire cell surface. Cyst wall formation is completed within 6 h. The fine structure of endocyst secretion resembles stages in the secretion of chitin by fungi, yeasts, and arthropods. A proteinaceous attachment peduncle is secreted to anchor the cell to a shrimp host and is formed by the release of electrondense dense secretory bodies from the cell's ventral surface.     

The Fine Structure of Secretion in Hyalophysa chattoni: Formation of the Attachment Peduncle and the Chitinous Phoretic Cyst Wall

ABSTRACT. The settling tomite stage of the apostome Hyalophysa chattoni secretes a phoretic cyst wall composed of chitin, mucopolysaccharides, and protein. Within 1 1/2 h after settling, an electron-dense proteinaceous cyst layer (the outer layer) is formed from secretions originating at the base of the kineties and from the thick pellicular layer between the kineties. The inner cyst layer, composed primarily of chitin (acidic and neutral polysaccharides are also present), is secreted across the entire cell surface. Cyst wall formation is completed within 6 h. The fine structure of endocyst secretion resembles stages in the secretion of chitin by fungi, yeasts, and arthropods. A proteinaceous attachment peduncle is secreted to anchor the cell to a shrimp host and is formed by the release of electron-dense secretory bodies from the cell's ventral surface.     

In vivo and in vitro excystation of Zygocotyle lunata (Trematoda) metacercariae and histochemical observations on the cyst.

Encysted metacercariae of Zygocotyle lunata (Trematoda) excyst within 2 hr postexposure in the lower ileum of the domestic chick. Optimal in vitro excystation of this species occurs following pretreatment of the cyst for 15 min in 1% acidified pepsin, treatment in 0.02 M sodium dithionite (a reductant) for 1 to 2 min and then 2 hr treatment in an excystation medium containing 1% sodium glycocholate plus 1% trypsin in Earle's BSS adjusted to pH 8.8 with tris and maintained at 41 C. The cyst of this species is a dome-shaped hemisphere containing an inner and outer wall. The outer wall contains mainly acid mucopolysaccharides, whereas the inner wall is mainly proteinaceous. The cyst contains a ventral lid which only was visualized during excystation.     

Histochemical characteristics of spermatophore layers of Scylla serrata (Forskal) (Decapoda: Portunidae)

The spermatophores of S. serrata are protected by an outer thick chitinous layer and an inner thin non-chitinous one. Both layers are rich in acid mucopolysaccharides containing sulphated (outer layer) and carboxylic groups (inner layer). The proteins of the two layers show much tryptophan, but lack tyrosyl, sulfhydryl and disulphide groups. No phenols or phenol oxidases could be detected histochemically in either layer, suggesting the absence of phenolic tanning in the spermatophore. The physical properties, as revealed from treatment with acids and alkali, indicate the resistant nature of the outer layer; the inner layer easily shrinks or disrupts under such treatment. The outer layer, though resistant, is readily permeable to low molecular weight dye substances employed in permeability experiments. The mechanism of sperm release is recorded and discussed. It is suggested that, in S. serrata, the dehiscence of spermatophore may be caused by imbibing of low molecular weight substances by the sperm mass substances of the spermatophore while the latter is inside the spermatheca.     

The fine structure of the boundary tissue of the seminiferous tubule of the camel (Camelus dromedarius)

An ultrastructural study of the boundary tissue of the seminiferous tubule of the camel reveals that it consists of three lamellae; inner fibrous, inner cellular and outer cellular. The inner lamella is subdivided into two homogeneous layers enclosing a third one that contains collagenous fibres and fine filaments. The inner cellular lamella consists of several layers of myoid cells; each layer is separated from the adjacent layer by homogeneous material and varying amounts of collagen. The outer cellular lamella consists predominantly of fibrocytes together with some fibroblasts and scattered collagen.     

Ultrastructure of early stages of Rozella allomycis (Cryptomycota) infection of its host, Allomyces macrogynus (Blastocladiomycota)

This study reconstructs early stages of Rozella allomycis endoparasitic infection of its host, Allomyces macrogynus. Young thalli of A. macrogynus were inoculated with suspensions of R. allomycis zoospores and allowed to develop for 120 h. Infected thalli at intervals were fixed for electron microscopy and observed. Zoospores were attracted to host thalli, encysted on their surfaces, and penetrated their walls with an infection tube. The parasite cyst discharged its protoplast through an infection tube, which invaginated the host plasma membrane. The host plasma membrane then surrounded the parasite protoplast and formed a compartment confining it inside host cytoplasm. The earliest host-parasite interface within host cytoplasm consisted of two membranes, the outer layer the host plasma membrane and the inner layer the parasite plasma membrane. At first a wide space separated the two membranes and no material was observed within this space. Later, as the endoparasite thallus expanded within the compartment, the two membranes became closely appressed. As the endoparasite thallus continued to enlarge, the interface developed into three membrane layers. Thus, host plasma membrane surrounded the parasite protoplast initially without the parasite having to pierce the host plasma membrane for entry. Significantly, host-derived membrane was at the interface throughout development.     

Structure and composition of the metacercarial cyst wall of Sphaeridiotrema globulus (Trematoda)

1986. Structure and composition of the metacercarial cyst wall of Sphaeridiotrema globulus (Trematoda). International Journal for Parasitology 16: 647–653. Histochemical and structural observations were made on the metacercarial cyst wall of Sphaeridiotrema globulus, obtained from naturally infected Goniobasis virginica (Pleuroceridae) snails. The cyst wall of S. globulus is a thin, glistening, transparent structure that thickens as the metacercaria ages. The cysts occur singly beneath the shell of the snail host or linked together in sheets, pyramids and other three dimensional forms. Light and electron microscopic examination of the cyst wall reveals an inner, middle and outer layer, each of which may vary in thickness. Adjacent cysts are linked by their outer layers. The chemical composition of these layers, elucidated through histochemistry, is described.     

High-resolution electron microscopic evidence for the filamentous structure of the cyst wall in Giardia muris and Giardia duodenalis

High-resolution morphological studies of the cyst wall of Giardia spp. were performed using low-voltage scanning electron microscopy (LVSEM) and transmission electron microscopy (TEM). The cyst wall was composed of membranous and filamentous layers. The membranous layer consisted of an inner and an outer cyst membrane separated by a thin layer of cytoplasm. The filamentous layer contained individual filaments that ranged from 7 to 20 nm in diameter when measured by LVSEM, formed a dense meshwork with branches or interconnections, and were occasionally arranged on the surface in whorled patterns. Cysts of Giardia muris from mice, Giardia duodenalis from dogs, pigs, voles, beavers, muskrats, and humans, and Giardia psittaci from a bird (parakeet), possessed an essentially identical wall composed of filaments. Inducement of excystation in viable Giardia cysts produced a dramatic increase in the interfilament spacing over an entire cyst, but none was observed in heat-killed or chemically fixed control cysts. These results demonstrated that the cyst wall of Giardia spp. was composed of a complex arrangement of filaments, presumably formed during the process of encystment.     

A histochemical study of the secretory gland cells of Cercaria shikokuensis and their role during development from cercaria to metacercaria.

The roles of secretory glands during the developmental process from an immature cercaria to a metacercaria in Cercaria shikokuensis were studied. Four types of secretory cells were identified in this species. On maturation of the cercaria in redia, the products of ventral gland cells and mucoid gland cells formed a thick surface coat on the mature cercaria, and the products of cephalic gland cells also formed a thin cover on the surface coat. In the process leading to the formation of a metacercaria, the surface coat constituted the outer layer of the cyst, mucoid gland cells secreted mucous substances inside the wall, and then cystogenous gland cells discharged their products to the inner wall. The cyst wall was composed of four layers, and it was thought that the outermost surface layer helped the cyst wall to adhere to the matrix and the intermediate layers helped to put together outer and inner walls.     

Structure and composition of the Bacillus anthracis capsule

Avakyan, A. A. (Academy of Medical Sciences, Moscow, USSR), L. N. Katz, K. N. Levina, and I. B. Pavlova. Structure and composition of the Bacillus anthracis capsule. J. Bacteriol. 90:1082-1095. 1965.-Observations by various methods of light microscopy (phase contrast, dark-field, and fluorescence) revealed the complex structure of the Bacillus anthracis capsule, which changes regularly during the growth cycle of the culture. Special cytological methods of staining the capsule made it possible to study its fine structure, which is not revealed by negative staining with India ink. For example, the capsule shows a membranelike outline, fine transverse lines, and interruptions and transverse septa traversing the entire capsule. By using cytochemical methods, it was found that the capsule has a stratified structure and that the various layers of the capsule differ as to the value of the isoelectric point, metachromatic ability, sensitivity to various enzymes, and, consequently, chemical composition. It was thus shown that the membranelike outline of the capsule consists of peptides and neutral mucopolysaccharides. The middle part of the capsule consists of a complex of substances of both polysaccharide and protein nature, and the inner part consists of acid mucopolysaccharides. Observation of the capsular forms of B. anthracis by means of an electron microscope revealed differences in the osmiophilia and submicroscopic structure of the membranelike outline and the middle and inner parts of the capsule. Immunochemical studies conducted by the fluorescent-antibody method revealed localization of antigens in different parts of the capsule, and made it possible to differentiate the capsular antigens according to their serum-staining ability and according of their relations to enzymes, i.e., their chemical composition. This paper concerns the possibility of studying the fine structure of bacterial capsules in fixed preparations, and the differences and similarities of the antigens of the capsule and cell wall of B. anthracis and of the related species, B. megaterium.     

Heart structure of some deep-sea fish (Teleostei: Macrouridae)

The hearts of 29 species of macrourid teleosts were examined in this study. For the one species for which a length range was available ( Coryphaenoides (C.) rupestris ), the heart weight as a percentage of body weight was 0·059. This is similar to values for relatively inactive fish. The atrial myocardium was reduced and had only a sparse trabecular network. In some species it was surrounded by a highly developed epicardium, but in others there was interstitial connective tissue in the myocardium that may serve to strengthen this chamber. The ventricle was entirely spongy, and all species lacked an outer compact layer of myocardium and associated coronary vasculature. All the ventricles were sac-like in form. The bulbus arteriosus was highly complex, and in its proximal portion there was an endothelially-lined, inner tube surrounded by a spongy network of blood-filled spaces, outside which was an outer compact layer of smooth muscle and elastica. These features of the bulbus may prevent backflow of blood after ventricular systole. The endothelial cells lining the bulbus were usually PAS-positive and in some species contained acid mucopolysaccharides.     

Metacercarial cyst formation in vitro of Echinostoma paraensei

Cercariae of Echinostoma paraensei Lie and Basch 1968 encysted normally in the presence of Biomphalaria glabrata embryo (Bge) cells in culture, partially in culture conditioned medium, and not at all in fresh culture medium alone. At the ultrastructural level the cyst is composed of 2 well defined regions. The outer cyst wall (OCW) is particulate to fibrous in nature, formed from secretory granules released from the cercarial tegument. Membranous scrolls or rodlets secreted from the subtegumental cystogenous gland cells are then added to this layer, forming the inner cyst wall (ICW). After 24 hr the cultured cyst is enclosed by a thin cellular capsule similar to that found around cysts in the snail host. The capsule also contains collagen fibers, not found elsewhere in Bge cell cultures.     

Light and transmission electron microscopical studies and amino acid analysis of the metacercarial cyst of Zygocotyle lunata (Trematoda).

Light microscopical studies indicated that the cyst of Zygocotyle lunata consists of outer, inner and ventral cyst walls. Transmission electron microscopical studies showed that the outer cyst and the ventral cyst each consist of two layers. The inner cyst is lamellated and contains a specialized ventral region designated the ventral lid. Amino acid analysis of cyst walls showed only trace amounts of cysteine, indicating that disulphide bonds are not used to stabilize the inner cyst of Z. lunata.