Eimeria crotalviridis sp. n. from Prairie Rattlesnakes, Crotalus viridis viridis, in New Mexico with Data on Excystation of Sporozoites and Ultrastructure of the Oocyst Wall

SYNOPSIS Oocysts of Eimeria crotalviridis sp. n. are described from prairie rattlesnakes, Crotalus viridis viridis in New Mexico on the basis of light and electron microscopy and in vitro excystation of sporozoites. Sporulated oocysts of E. crotalviridis are elliptical, 26.4 × 22.3 (23–29 × 20–24) μm with ovoid sporocysts 11.7 × 8.1 (11–13 × 7–9) μm. A micropyle, micropyle cap and polar bodies are absent, but oocyst and sporocyst residua and Stieda and substieda bodies are present. Excysted sporozoites are 12.4 × 2.8 (11–13 × 2–3) μm and have 1 large posterior refractile body and a nucleus with a prominent nucleolus. Ultrastructurally, the oocyst wall has 2 layers, a thick, electron-dense, highly sculptured outer layer composed of a fine granular matrix and a thin, granular, osmiophilic inner layer, separated from the outer layer by at least one unit membrane. These layers are 441 (353–510) and 21.6 (19–29) nm thick, respectively. Within 15 min after exposure to a trypsin-sodium taurocholate fluid, sporozoites of E. crotalviridis excysted from 5-month-old sporocysts.     

Comparative morphology of the carpel in the Liliaceae: Helonieae

Most Helonieae have only slight septal indentations between the three carpels: in Xerophyllum deep septal clefts extend centripetally and completely enclosed, narrow septal pockets occur in Metanarthecium . Other unique generic features are found: tepallary-staminal nectarial glands in Heloniopsis , zygomorphy in Chionographis , and dioecism in Chamaelirium . The carpels are biovulate in Chionographis; there are two to several ovules per carpel in Xerophyllum; 8–12 ovules occur in the carpel of Chamaelirium; and numerous bitegmic ovules are borne in many longitudinal rows on enlarged placentae in Helonias, Heloniopsis, Metanarthecium , and Ypsilandra . Except for Metanarthecium , this last-named group of genera displays a near ring composed of 'accessory' placental bundles and a compound septal bundle (with normally oriented xylem and phloem) in cross-section at the inner edge of each septum. Ventral bundles occur in the other four genera.     

Artificial Infections of Pneumocystis carinii in the SCID Mouse and their Use in the In Vivo Evaluation of Antipneumocystis Drugs

A model for the in vivo evaluation of antipneumocystis drugs has been developed in SCID mice infected intratracheally with cryopreserved mouse-derived Pneumocystis carinii. The development of a highly reproducible fatal P. carinii pneumonia occured within 10 weeks (mean survival time ± SEM = 72.2 ± 1.2 days). Continuous administration of dexamethasone (2 mg/liter in the drinking water) exacerbated the rate of onset of severe P. carinii pneumonia (mean survival time ± SEM = 63 ± 1.3 days) in SCID mice. The number of cysts per g of lung homogenate (homogenate counts) were maximal with an inoculum of 20,000 cysts at 6 weeks post infection. Homogenate counts correlated with infection scores (graded assessments of immunofluorescent cysts on lung impression smears) suggesting that infection scoring accurately and rapidly reflects the severity of P. carinii pneumonia in SCID mice. These studies led to the development of a drug screening protocol in which Pneumocystis-free female SCID mice (20–25 g) were started on dexamethasone 7 days prior to IT inoculation with a single dose of 20,000 cysts. Drugs were evaluated either for: a) prophylaxis (continuously from day 1 post infection) or b) treatment (from day 21 post infection) until day 42 post infection, when all mice were killed and infection scores determined. Co-trimoxazole (at 250 mg sulfamethoxazole + 50 mg trimethoprim/kg/day) given in the drinking water was found to be highly effective in both the prophylaxis and treatment of mouse P. carinii pneumonia. Co-trimoxazole remained very effective in the prophylaxis P. carinii pneumonia in the SCID mouse at 125 mg sulfamethoxazole + 25 mg trimethoprim/kg/day p.o. and showed some enhancement of efficacy over sulfamethoxazole alone at 125 mg/kg/day p.o., suggesting limited synergy between sulfamethoxazole and trimethoprim. The results presented provide confirmation of the usefulness and predictability of the model.     

Leaf miner assemblies: effects of plant succession and grazing management

Abstract. 1. Changes in leaf-miner assemblies during 4 years of secondary succession, under different controlled sheep-grazing treatments, are described and compared to the miner fauna of older grazed grassland nearby.
2. Multivariate analyses were used in conjunction with examination of individual common species to assess the independent effects of time, grazing treatment, plant species composition and architecture on the leaf-miner assemblies.
3. Leaf-miner species composition was strongly related to plant species composition, but was modified by plant structure under different grazing treatments. There was a strong successional trend in miner assemblies, even when the effects of changes in plant composition had been taken into account. Conversely, local variation in miner species composition generally reflected foodplant distribution alone.
4. Grazed treatments had fewer mines than controls, but there were also species specializing in grazed areas, despite the abundance of their foodplants elsewhere. There was a weak indication that miner species in grazed treatments were more likely to fluctuate in abundance than those in controls.
5. The results are discussed in relation to the assembly of grassland insect communities during succession, and the use of 'indicator groups' in management for nature conservation.     

Ultrastructural Localization of Monoclonal IgG Antibodies for Antigenic Sites of Eimeria tenella Oocysts,Sporocysts, and Sporozoites1

Monoclonal IgG antibodies against sporozoites of Eimeria tenella were obtained from the ascites fluid of BALB/c mice. Oocysts, sporocysts, and sporozoites were exposed to medium 199, normal ascites fluid, or monoclonal antibodies 1A, 9D, 3D3II, or 2G8f. Specimens were then incubated with ferritin-conjugated goat anti-mouse IgG antibody. Ferritin was uniformly distributed over the surface of sporozoites exposed to 1A, 9D, or 3D3II; ferritin was localized in patches on sporozoites exposed to 2G8f. A uniform layer of ferritin was present on the inner layer of oocyst walls and on the Stieda body and outer surface of sporocysts exposed to 1A, 9D or 3D3II. In specimens treated with 2G8f, ferritin was present on the inner layer of the oocyst wall and the Stieda body, but not on the sporocyst wall. No ferritin was found on specimens exposed to medium 199 or normal ascites fluid. Monoclonal antibodies 1A, 9D, and 3D3II, but not 2G8f, caused complement-mediated lysis of sporozoites. These findings indicate that oocysts, sporocysts, and sporozoites of E. tenella contain common antigens specific for each monoclonal antibody tested.     

Ultrastructural Study of Plasmodium knowlesi Antigen Used in Vaccination of Rhesus Monkeys*

SYNOPSIS. Material from various steps obtained in the French pressure cell technic of preparing antigen from Plasmodium knowlesi-infected red cells, was examined by electron microscopy. A positively charged colloidal iron solution was used to differentiate between membranes of host red cells and parasites. Red cell membranes take the stain, whereas parasite membranes do not. This antigen which has been used previously to protect monkeys against P. knowlesi appears to consist almost entirely of membrane-bounded vesicles. Some of these vesicles contain a fine granular material, whereas others appear empty. The antigen failed to stain with the positively charged iron solution, which suggests that it is free of contamination by host cell membrane.     

Fine Structure of Differentiating Oocysts and Mature Sporozoites of Haemoproteus metchnikovi in its Intermediate Host Chrysops callidus*

The fine structure of the sporogonic stages of Haemoproteus metchnikovi has been investigated by electron microscopy. Young oocysts are found beneath the basement membrane of midgut epithelial cells. These eventually protrude outward into the haemocoel space and are surrounded by a distinct oocyst capsule. Sporozoite formation begins with a subcapsular vacuolation. Evagination of the oocyst cytoplasm occurs in regions of membrane thickenings and 100–200 sporozoites are formed about a single sporoblastoid body. Remnants of the ookinete pellicle can be observed in maturing oocysts and always are found in the residual body. The fine structure of the mature sporozoite is essentially similar to that which has been described for other haemosporidia and a spherical body is described in association with the mitochondrion of the sporozoite. The sporogonic stages of H. metchnikovi have features common to the sporogonic stages of Plasmodium and Leucocytozoon that are not held in common by the latter 2 genera, including pattern of sporozoite formation and number of sporozoites formed, the presence of a cytostome and of “crystalloid” in the sporozoite.     

Comparative morphology of the carpel in the Liliaceae: Tofieldieae

The Tofieldieae consist of Narlhecium, Nietneria, Pleea , and Tofieldia. Although the three carpels of the pistil are generally coherent, their bases are separate for a short distance in some species of Tofieldia and in Pleea , where a septal nectary seems to be differentiated. These two genera are also alike in the extension of the chalaza as a filiform hook. The sutures are open at flowering only in some species of Tofieldia. Nietneria is distinguished by its inferior ovary and the alternate structure of the pistil. No raphide idioblasts were found in the carpels of any species.     

Horizontal gene transfer: sustaining pathogenicity and optimizing host–pathogen interactions

Successful host–pathogen interactions require the presence, maintenance and expression of gene cassettes called 'pathogenicity islands' (PAIs) and 'metabolic islands' (MAIs) in the respective pathogen. The products of these genes confer on the pathogen the means to recognize their host(s) and to efficiently evade host defences in order to colonize, propagate within the host and eventually disseminate from the host. Virulence effectors secreted by type III and type IV secretion systems, among others, play vital roles in sustaining pathogenicity and optimizing host–pathogen interactions. Complete genome sequences of plant pathogenic bacteria have revealed the presence of PAIs and MAIs. The genes of these islands possess mosaic structures with regions displaying differences in nucleotide composition and codon usage in relation to adjacent genome structures, features that are highly suggestive of their acquisition from a foreign donor. These donors can be other bacteria, as well as lower members of the Archaea and Eukarya. Genes that have moved from the domains Archaea and Eukarya to the domain Bacteria are true cases of horizontal gene transfer. They represent interdomain genetic transfer. Genetic exchange between distinct members of the domain Bacteria, however, represents lateral gene transfer, an intradomain event. Both horizontal and lateral gene transfer events have been used to facilitate survival fitness of the pathogen.