Colloidal-gold immunocytochemical localization of osteopontin in avian eggshell gland and eggshell.

During mineralization of the avian eggshell, there is a sequential and orderly deposition of both matrix and mineral phases. Therefore, the eggshell is an excellent model for studying matrix-mineral relationships and the regulation of mineralization. Osteopontin, as an inhibitor of crystal growth, potently influences the formation of calcium phosphate and calcium carbonate biominerals. The purpose of this study was to characterize matrix-mineral relationships, specifically for osteopontin, in the avian eggshell using high-resolution transmission (TEM) and scanning (SEM) electron microscopy to gain insight into how calcite crystal growth is structured and compartmentalized during eggshell mineralization. Osteopontin was localized at the ultrastructural level by colloidal-gold immunocytochemistry. In EDTA-decalcified eggshell, an extensive matrix network was observed by TEM and SEM throughout all regions and included interconnected fibrous sheets, irregularly shaped aggregates, vesicular structures, protein films, and isolated protein fibers. Osteopontin was associated with protein sheets in the highly mineralized palisades region; some of these features defined boundaries that compartmentalized different eggshell structural units. In fractured and undecalcified eggshell, osteopontin was immunolocalized on the {104} crystallographic faces of calcite-its natural cleavage plane. The specific occlusion of osteopontin into calcite during mineralization may influence eggshell structure to modify its fracture resistance.     

The fine structure of the cysticercoid of Hymenolepis diminuta. III. The scolex.

Transmission electron microscopy of the scolex of the 8-day-old Hymenolepis diminuta cysticercoid demonstrates its resemblance to the scolex of the adult. A syncytial tegument composed of external and internal layers is connected by cytoplasmic extensions. Fully developed microtriches are present. Furthermore, a basement membrane, muscle layers, and medullary region containing flame cells, nerve tissue, and other cell bodies are observed. Of particular interest is the presence of discrete sensory endings whose function is discussed.     

Ootaxonomy and eggshell ultrastructure of Phlebotomus sandflies

The eggshell structure of four sandfly species: Phlebotomus perniciosus Newstead, P.perfiliewi Parrot, P.papatasi Scopoli and P.duboscqi Neveu-Lemaire, was examined by scanning and transmission electron microscopy (SEM and TEM). At the TEM level, the eggshell appears to have a homogeneous vitelline envelope and a thick chorion. At SEM level, the eggshell of all species is characterized by the outer chorion forming a series of fifteen to twenty longitudinal sinuous ridges, cross-linked in places to form a pattern of polygons, each line of the chorion consisting of columns arranged in a palisade. The aeropyle region of the egg is described for the first time in phlebotomine sandflies. Specific characters of the eggshell topography are described for distinguishing between these and other species of Phlebotomus.     

Serotonin stimulates protein phosphorylation in the cestode Hymenolepis diminuta.

1. Serotonin stimulated the incorporation of 32P from [gamma-32P] ATP into crude membrane preparations (P2) of Hymenolepis diminuta in a dose-dependent manner (EC50 of approximately 0.79 microM). 2. This response was seen with several serotonin agonists, and was inhibited by several serotonin antagonists, which were identical to the previously described activation and inhibition of serotonin-sensitive adenylate cyclase. 3. Cyclic AMP produced a dose-dependent stimulation of 32P incorporation into the P2 fraction, with an EC50 of approximately 2.51 microM. 4. The targets for the serotonin stimulated incorporation of 32P were found to be in trypsin-labile proteins with Mr's of 134,000, 110,000, 82,000, 80,000 and 31,000.     

Galactose utilization by the rat tapeworm, Hymenolepis diminuta.

1. Hymenolepis diminuta incorporated label from 14C-galactose into glycogen, but the sugar would not support net glycogen synthesis. Glucose stimulated the incorporation of label from 14C-galactose into glycogen, while glycerol did not. 2. During incubations in galactose, large internal pools of galactose and galactose 1-P accumulated, while the concentration of glucose 6-phosphate remained unchanged. 3. In vitro culture experiments indicated that galactose would not support worm growth. Therefore, while galactose can be metabolized to a limited extent, it cannot substitute for glucose as a nutrient source.     

Hymenolepis diminuta: immunogenicity of the strobilate worm

Mice were immunized against challenge with Hymenolepis diminuta by feeding cysticercoids or by surgically implanting into the duodenum strobilate worms of different ages. Young worms stimulate stronger immunity than older ones, although the latter presents the host with a greater amount of strobilar tissue per unit time. An increase in the number of immunizing worms is associated with an increase in the level of protection. It is concluded that the development of functional immunity against H. diminuta in mice has both quantitative and qualitative antigenic requirements; it is influenced by worm age and is independent of worm mass.     

Intestinal contractions and migration behaviour in Hymenolepis diminuta.

The aim of this study was to determine if intestinal contractions were important in the migration behaviour of the rat tapeworm Hymenolepis diminuta. The objectives were to investigate the intestinal motility responses of the host to a meal which initiates worm migration, and the worms' responses to an artificial peristaltic contraction. A 1 g glucose meal elicited a significant orad migration by H. diminuta in the small intestine of the rat host when compared to water-fed controls (P less than 0.05). The glucose meal also significantly increased the transit rate, and thus, frequency of intestinal contractions in the small intestine of the rat, when compared to water-fed controls (P less than 0.05). Application of a circumintestinal ligature (6.3 g) (simulating an intestinal peristaltic contraction) resulted in significant worm migration when the ligature was applied in regions containing the worm's strobila as compared to controls where loose ligatures were tied in regions containing the strobila, or to controls where tight ligatures were tied ahead of the worm's strobila. These results suggest that H. diminuta migrates in an orad direction in response to the mechanical pressure produced by intestinal contractions induced by host feeding. It is concluded that contractions of the small intestine are an important cue in the migration behaviour of this cestode.