Spermatozoon ultrastructure of Thysanotaenia congolensis (Cyclophyllidea, Anoplocephalidae, Inermicapsiferinae): phylogenetic implications

The mature spermatozoon of Thysanotaenia congolensis, an intestinal parasite of black rat Rattus rattus from Cape Verde, is described by means of transmission electron microscopy. The ultrastructural organization of the sperm cell of T. congolensis follows Levron et al.'s type VII of the Eucestoda. It corresponds to a uniflagellate spermatozoon that presents crested bodies, periaxonemal sheath and intracytoplasmic walls, spiralled cortical microtubules and nucleus spiralled around the axoneme. These characteristics are also present in the spermatozoa of other inermicapsiferines and differ from the characters found in species belonging to the remaining subfamilies of anoplocephalids, namely Anoplocephalinae, Linstowiinae and Thysanosomatinae. Several authors consider the family Anoplocephalidae as a polyphyletic group, and its relationships with the Davaineidae are a matter of controversy. The phylogenetic implications of spermatological ultrastructural features present in inermicapsiferines and in the remaining anoplocephalids are discussed, and the available data on anoplocephalids are compared to similar results in davaineids in order to contribute to a better knowledge of relationships between these cyclophyllidean families

Ultrastructure of spermiogenesis and the spermatozoon in cyclophyllidean cestodes

Podeu consultar el llibre complet a: http://hdl.handle.net/2445/67430The usefulness of the ultrastructural characters of spermiogenesis and of the spermatozoon in the interpretation of relationships in the Platyhelminthes has been widely demonstrated. The present paper provides a review and an update on the ultrastructural knowledge on spermiogenesis and on the spermatozoon in cyclophyllidean cestodes. For each family of cyclophyllideans the pattern of spermiogenesis and the type of sperm cell is provided. Moreover, the most interesting characteristics of both spermiogenesis and the spermatozoon are compiled and illustrated for each family. Finally, new spermatological data on some species of the Anoplocephalidae and the Taeniidae are provided

Heavy metal accumulation by intestinal helminths of vertebrates

Podeu consultar el llibre complet a: http://hdl.handle.net/2445/32393The relevancy of parasites as potential indicators of environmental quality has been increasing over the last years, mostly due to the variety of ways in which they respond to anthropogenic pollution. The use of fish parasites as bioindicators of heavy metal pollution in aquatic ecosystems has been widely studied. However, little information concerning terrestrial habitats is presently available. In fact, in the last two decades several studies have been performed worldwide in different habitats and/or conditions (theoretically both in polluted and unpolluted terrestrial ecosystems, but mainly in aquatic ecosystems) in order to investigate heavy metal pollution using parasitological models. Different groups of vertebrates (mainly fish, mammals and birds) and several parasitological models have been tested involving acanthocephalans mostly, but also cestodes and nematodes. It is not the aim of this chapter to do a complete revision of the available data concerning this subject. Instead, we emphasize some general aspects and compile a mini-review of the work performed in this field by our research group. The results obtained until now allow confirming several parasitic models as promising bioindicator systems to evaluate environmental cadmium and mainly lead pollution in terrestrial non-urban habitats, as it was already demonstrated for aquatic ecosystems. The present knowledge also allows confirming that parasites can reveal environmental impact. Environmental parasitology is an interdisciplinary field, which needs simultaneous expertise from toxicology, environmental chemistry and parasitology. Furthermore, environmental parasitology should be taken into account in order to increase the efficiency of environmental monitoring programs

Recent advances in pharmaceutical sciences VII

The E-book series Recent Advances in Pharmaceutical Sciences reports research contributions from different areas of the multidisciplinary field of Pharmaceutical Sciences. This seventh volume consists of nine chapters, mainly dealing with the fields of botany, physiology, food science, biochemistry & molecular biology, plant physiology, microbiology, parasitology, pharmacology, and medicinal chemistry

Mechanical properties obtained by nanoindentation of sintered zircon-glass matrix composites

This study was undertaken to determine the effect of zircon content and firing temperature on the hardness and indentation modulus of zircon–glass composites obtained by sintering. A standard non-devitrified borosilicate glass (SRM 717a) powder and an industrial micrometric zircon powder were used to prepare mixtures with a zircon volume/solids volume between 0 and 0.63, by the wet method. The values of these mechanical properties were determined by nanoindentation and related to the most important microstructural characteristics of the composites, such as porosity, zircon volume fraction, glass volume fraction, and average zircon grain size. Composite mechanical performance was interpreted and determined by statistically analysing the results of a large number of indentations using two maximum loads. An empirical model was developed that describes the effect of these microstructural characteristics on composite hardness and modulus of indentation. Composites of high hardness (11.3 ± 2.5 GPa) and low porosity (ε = 0.07) were obtained at 1100 °C from a mixture with a zircon volume/solids volume of 0.43

Phylogenetic triangulation: Using predator-prey-parasite interactions to infer population history from partial genetic information

Phylogeographic studies, which infer population history and dispersal movements from intra-specific spatial genetic variation, require expensive and time-consuming analyses that are not always feasible, especially in the case of rare or endangered species. On the other hand, comparative phylogeography of species involved in close biotic interactions may show congruent patterns depending on the specificity of the relationship. Consequently, the phylogeography of a parasite that needs two hosts to complete its life cycle should reflect population history traits of both hosts. Population movements evidenced by the parasite's phylogeography that are not reflected in the phylogeography of one of these hosts may thus be attributed to the other host. Using the wild rabbit (Oryctolagus cuniculus) and a parasitic tapeworm (Taenia pisiformis) as an example, we propose comparing the phylogeography of easily available organisms such as game species and their specific heteroxenous parasites to infer population movements of definitive host/predator species, independently of performing genetic analyses on the latter. This may be an interesting approach for indirectly studying the history of species whose phylogeography is difficult to analyse directly

Non-isothermal sintering of powdered vitrified composites. A kinetic model

This report sets out the results obtained on studying the sintering process of glass–zircon composites, analysing the microstructural changes that developed on modifying zircon content. The sintering of composites with moderate zircon contents only developed via particle rearrangement by viscous flow. In contrast, at high zircon contents, the zircon solution–reprecipitation process was also required. A kinetic model was developed and validated that describes the effect of the heating rate and zircon volume fraction on the composite degree of non-isothermal sintering progress associated with particle rearrangement by viscous flow

Sinter-crystallisation kinetics of a SiO2–Al2O3–CaO–MgO–SrO glass-ceramic glaze

This paper examines the microstructural development and kinetics of the sintering and crystallisation processes of a SiO2–Al2O3–RO (R = Ca, Mg, Sr) glass-ceramic glaze. Crystallisation and sintering kinetics were studied by DTA and HSM, respectively, at different heating rates. The kinetic parameters of crystallisation were determined by the usual methods (Kissinger, Kissinger-Akahira-Sunose, Ozawa and Augis-Bennet methods), and the Johnson–Mehl–Avrami–Kolmogorov (JMAK) model, with an Avrami index of n = 3, characteristic of the surface crystallisation of very fine glass particles, was found to describe crystallisation kinetics very well. Sintering could also be described by the JMAK model, but with n < 1. Assuming the effect of temperature on the sintering rate to be the same as that of this variable on the inverse of glass matrix viscosity, a model was developed, based on the JMAK model, which only required a single fitting parameter. As the heating rate increased, the degree of overlap between the sintering and crystallisation processes was verified to decrease

Densification of irregular polydispersed glass particles described as a complex relaxation process

The sintering of compacts of irregular non-crystallising glass particles was studied by isothermal and constantrate heating experiments in a hot stage microscope. The resulting data fitted very well to kinetic equations developed in this study, in which sintering is assumed to be a complex relaxation process, described by the Kohlrausch–Williams–Watts (KWW) relaxation function. The effect of compact pressing pressure, heating rate, and particle size distribution on the sintering curve was determined. It was generally verified that the effect of temperature on the sintering rate could be described by the effect of temperature on the inverse of glass viscosity. For industrial particle size distributions, that the pre-exponential factor of the process rate constant (or inverse of relaxation time) increased with pressing pressure and decreased with the inverse of particle mean radius. For abnormally wide particle distributions a combination of KWW functions were required