Brugia pahangi: Feeding and nutrient uptake in vitro and in vivo

Incubation in vitro of adult Brugia pahangi in an apparatus which permitted the separate exposure of the anterior, middle, or posterior region of the worms to medium-containing radioactively labeled d-glucose, l-leucine, and adenosine has provided evidence that these materials are taken up in physiologically significant amounts by a transcuticular route. No evidence for an oral ingestion of materials has been obtained from worms in vitro, but in vivo an oral uptake of Trypan blue has been demonstrated. The ultrastructure and cytochemical staining reactions for nonspecific esterase, acid phosphatase (EC-3.1.3.2), and leucine naphthylamidase of the gut and body wall are described.     

Body wall of juvenile and adult Gastromermis boophthorae (Nematoda: Mermithidae): Ultrastructure and nutritional role

During the life cycle of the mermithid nematode Gastromermis boophthorae the main components of the body wall, namely the cuticle, hypodermis and somatic musculature, undergo radical changes in structure and relative proportions. In the non-feeding, free-living stages the cuticle is a well-defined, multilayered structure which lies upon a generally thin hypodermis; the somatic musculature has the extensive and highly organised appearance typical of motile nematodes. In parasitic juveniles the body wall has a completely different structure which is adapted for the suggested purpose of nutrient uptake from the host insect's haemocoelomic fluid; the cuticle is characteristically thin and rather diffuse, the underlying hypodermis becomes very extensive and metabolically active, and there is a corresponding reduction in the proportion of somatic musculature. The sub-cuticular surface of the enlarged hypodermis has a microvillous configuration and has associated alkaline phosphatase activity.     

The amino acid sequence of the peptide moiety of the pseudomurein from Methanobacterium thermoautotrophicum

The amino acid sequence of the peptide subunits of the peptide moiety of the sacculus polymer (pseudomurein) of Methanobacterium thermoautotrophicum was elucidated by analysing overlapping peptides obtained from partial acid hydrolysates of isolated sacculi. It is suggested that the peptide subunits are attached to glycan strands via one of their glutamyl residues. Another glutamyl residue may crosslink two adjacent peptide subunits to form a dimer. The calculated molar ratios of the amino acids and the percentages of the N-or C-terminal amino acid residues of the supposed dimers are compatible with those actually found in the sacculus polymer.     

Ultrastructure of cell wall and thylakoid membranes of the thermophilic cyanobacterium Synechococcus lividus under the influence of temperature shifts

The ultrastructure of the cell wall and the thylakoid membranes of the thermophilic cyanobacterium Synechococcus lividus was studied by freezefracture electron microscopy after temperature shifts. Different fracture faces of the outer, the cytoplasmic and the thylakoid membranes were demonstrated when the preparation-temperature was in the range of the optimal growth temperature at 52°C or after fixation at 52°C. In the outer membrane of the cell wall two fracture faces with holes and 7.5 nm intramembrane particles were detected. On both the outer (EF) and inner (PF) leaflet of the cytoplasmic membrane randomly distributed particles were demonstrated. The particle density on the PF-face was approx. three times that of the EF-face. The EF-face of the thylakoid membrane exposed rows of particles with an average diameter of 10 nm. The spacing between the particle rows was 35–50 nm. This regular particle arrangement on the EF-face was demonstrated only in a few cases. Mostly the intramembrane particles were distributed randomly on the thylakoid fracture faces. The particle density of thylakoids with a random distribution was approx. in the same range both on the EF-and PF-face. The EF-particles fall into four groups of 9,10,11, and 12.5 nm. The main particle class was the 10 nm class. The PF-face exposed smaller particles with two maxima at 8.5–9 nm and 10 nm. When Synechococcus lividus OH-53s was chilled to temperatures below 30–35°C before the freeze-etch preparation a phase transition took place after the temperature shift. On the fracture faces of the thylakoid and cytoplasmic membranes particle depleted areas occurred. The size of the areas were different in both membranes and dependent on the velocity of cooling. Contrary to Synechococcus lividus OH-53s in the mesophilic Synechococcus strain 6910 the phase transition point was 15°C. The lower phase transition point may be due to a higher content of unsaturated fatty acids.Dedicated to Prof. D. Peters (Hamburg) on the occasion of the 65th anniversary of his birthday     

Stereological investigation on the increase in surface area due to the microtriches of the hydatid cyst in different organs and in different hosts

Bortoletti G. and Diaz G. 1978. Stereological investigation on the increase in surface area due to the microtriches of the hydatid cyst in different organs and in different hosts. International Journal for Parasitology8: 433–436. The increase in surface area of the germinal membrane due to the microtriches has been morphometrically investigated in Echinococcus granulosus cysts developed in three different intermediate hosts. The results, achieved by Stereological methods, indicate that the development of the microtriches: (a) is more or less homogeneous all over the germinal membrane of the cysts; (b) is greater in human than in pig and sheep cysts; (c) is also greater in lung than in liver cysts within the same host and it is not related to the fertility or sterility of the parasite.     

Fine Structure of Oocyst Transformation and the Sporozoites of Leucocytozoon dubreuili*

SYNOPSIS. The sporogonic stages of Leucocytozoon dubreuili in the midgut and salivary glands of the simuliid vectors was studied by electron microscopy. Young uninucleate oocysts have a pellicle that initially resembles that of the ookinetc. Numerous electron-dense bodies and microtubules in the peripheral cytoplasm may be involved in the formation of the cyst wall. The dense bodies appear to give rise to the amorphous material of the wall. The tubules which run circumferentially beneath the oocyst's boundary probably serve as a skeletal support for the cell surface during deposition of the wall material. A subcapsular “space” which provides area for expansion of the developing sporozoites is formed in early multinucleate oocysts. The subcapsular “space” appears to be formed through a condensation of the peripheral cytoplasm, resulting in an osmotic gradient across the oocyst's limiting membrane. Consequently water diffuses out, creating a fluid-filled space. Sporozoite formation begins with localized thickenings on the oocyst's limiting membrane. Subsequent extension of the thickened regions into the subcapsular “space” marks the onset of sporozoite budding. The process is highly synchronized, and culminates with the production of up to 150 sporozoites about the sporoblastoid body. The structure of sporozoites from mature oocysts and of the salivary glands of the vector is basically similar, although salivary gland sporozoites are more elongate and have numerous electron-dense micronemes. The paired rhoptries in the latter sporozoites are more elongate and uniformly electron-dense than in oocyst sporozoites.     

Hyphal walls of isolated lichen fungi

The hyphal walls of three mycobionts, isolated from the lichens Xanthoria parietina, Tornabenia intricata and Sarcogyne sp. were investigated by two techniques: microautoradiography of fungal colonies exposed to radioactive carbohydrate precursors; and binding, in vivo, of fluorescein conjugated lectins to hyphal walls of such colonies.N-[³H] acetylglucosamine was readily incorporated into tips, young hyphal walls and septa of the three mycobionts and the free-living fungus Trichoderma viride, but not into Phytophthora citrophthora, indicating that chitin is a major component of the mycobionts' hyphal walls. All three mycobionts, but neither of the free-living fungi, incorporated [³H] mannose and [³H] mannitol into their hyphal walls.Fluorescein-conjugated wheat germ agglutinin was bound to the hyphal walls of the three mycobionts and T. viride, but not to the walls of P. citrophthora; the binding pattern was similar to the grain pattern obtained in autoradiographs after short N-[³H] acetylglucosamine labelling. As wheat germ agglutinin binds specifically to chitin oligomers, the lectin binding tests further confirmed that chitin is a mycobiont hyphal wall component.Binding characteristics of several fluorescein-conjugated lectins to the three mycobionts indicated that this technique can yield useful information concerning the chemical composition of hyphal wall surfaces.List of abbreviations FITC fluorescein isothiocyanate - WGA wheat germ agglutinin - TCA trichloroacetic acid - PNA peanut agglutinin - LA lotus agglutinin - Glc NAc N-acetylglucosamine - ConA concanavalin A - SBA soybean agglutinin - WBA waxbean agglutinin Part of an M.Sc. thesis submitted by A. Braun to the Department of Botany, Tel Aviv University.     

Some Ultrastructural Changes Induced in Resistant and Susceptible Soybean Roots Following Infection by Rotylenchulus reniformis

A developmental electron microscopic study of the parasitism of Rolylenchulus reniforrnis in resistant ''Peking'' and susceptible ''Lee'' soybeans was made during a 21-day period under controlled conditions. Within 2 days of inoculation, the nematode had penetrated the cortical cells to the endodermis where it inserted its stylet, secreted and initiated syncytial formation and cell hypertrophy. Syncytia primarily involved pericycle tissues and, to a lesser extent, xylem parenchyma and endodermis. When identifiable, the cell into which the nematode stylet was inserted to initiate syncytial development was endodermal. Susceptible tissues exhibited two basic phases of development during this infection period: (i) an initial phase represented by partial cell wail lysis and separation; and (ii) an anabolic phase, characterized by organelle proliferation and development accompanied by secondary wall deposits, which provided nutrition for sessile female development. The resistant or hypersensitive reaction (HR) lacked the anabolic phase found in the susceptible reaction, and was characterized by an extension and usually accelerated type of Iysis found in the first phase of the syncytial development. The HR was usually very evident 4 days after inoculation, and could be identified by an almost complete lysis of the cell walls and cytoplasm. The possibility that the initial cell of the developing syncytium or "prosyncyte" may influence a susceptible or resistant reaction is discussed. Successive stages of cell wall dissolution and the deposition of secondary cell walls are described.     

Light and electron microscopical study of Nosema eurytremae

A nuclear-polyhedrosis virus (NPV) of the silkworm, Bombyx mori, which forms an icosahedral inclusion body, was transmitted to larvae of the rice stem borer, Chilo suppressalis. Serial passages of Bombyx NPV in the alternate host by injecting the supernatant of diseased hemolymph produced inclusion bodies with cuboidal and other shapes that differed from the original shape formed in Bombyx. These different shapes increased with times of passages, and after the twelfth passage, only cuboidal inclusion bodies were formed. The icosahedral inclusion bodies in B. mori and the cuboidal inclusion bodies in C. suppressalis occluded singly enveloped virions of the same size (350 × 75 nm), but the cuboidal inclusion bodies contained only a few virions and a large number of membraneous spherical structures. The formation process of the cuboidal inclusion body differed from that of the icosahedral. At first, irregularly branched inclusion bodies containing “vacant” spaces appeared in the infected nuclei. The bodies grew larger with the deposition of protein in the spaces between the branches, and this was accompanied with the occlusion of a large number of membraneous structures formed in the vicinity of the inclusion bodies, which became cuboidal in shape.