An Electron Microscopical Study of the Interaction of Monoclonal Antibodies with Gametes of the Malarial Parasite Plasmodium gallinaceum1

Anti-malarial gamete antibodies prevent the fertilization of gametes in the mosquito midgut and prevent transmission of malaria. Recently, hybridoma cell lines secreting monoclonal antibodies (10G3 and 11C7) against gametes of the malarial parasite have been developed. These antibodies act synergistically to mediate 80–90% suppression of the infectivity of gametocytes, although neither monoclonal antibody alone has a significant effect on gametocyte infectivity. We performed immuno-electron microscopy to characterize the interactions of these monoclonal antibodies with gametes of Plasmodium gallinaceum. Male gametes exposed to either 10G3 or 11C7 agglutinated into loose clusters, while those exposed to a mixture of 10G3 and 11C7 agglutinated into long, rope-like bundles. This difference appears to be related to the distribution of the antibodies on the surface of the gametes. When 10G3 or 11C7 labeled with a ferritin-conjugated anti-mouse Ig were used singly, the ferritin particles were distributed in focal areas over the surface of the parasites. By contrast, when the male gametes were exposed to a mixture of 10G3 and 11C7, the ferritin particles were distributed over their entire surface. Female gametes reacted similarly to these antibodies. These observations indicate that combinations of antibody specificities that reduce fertilization efficiency coat the entire surface of the gametes. On the other hand, focal interactions resulting from a single antibody are unable to block fertilization.     

Postfertilization Poly(A) · Protein Complex Formation on Sea Urchin Maternal Messenger RNA

A two-fold increase in polyadenylate [poly(A)] content occurs between fertilization and the two-cell stage in sea urchin zygotes. In this report the role of this cytoplasmic polyadenylation process in the provision of binding sites for poly(A)-associated proteins during early development of Lytechinus pictus is evaluated. Protein-associated poly(A) sequences, from ribonuclease-treated, post-mitochondrial supernatants of various developmental stages, were collected by nitrocellulose filtration and quantified by ³H-poly(U) complex formation. The proportion of protein-associated poly(A) rose from about 27% to about 60% of the total poly(A), on a nucleotide basis, during the period between fertilization and the eight-cell stage. However, the actual increase in number of poly(A) sequences associated with protein was more extensive, about 2.5-fold, since protein-associated poly(A) sequences average about 45 nucleotides longer than free poly(A). The protein-associated poly(A) of eggs and zygotes is found in two types of protease-sensitive complexes which sediment at 8–12 S and 15–20 S. The 8–12 S complex appears to be selectively increased in amount following fertilization. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the poly(A) protein complex fraction indicates the presence of 87,000 and 130,000 molecular weight polypeptides in both eggs and zygotes. It is concluded that quantitative, but not qualitative, alterations in the proportion of protein-associated poly(A) accompanies post-fertilization cytoplasmic polyadenylation in sea urchin zygotes. The attachment of specific proteins to the 3'terminus of maternal RNAs may be involved in their subsequent activities during early embryogenesis.     

Consideration of Proprioception and Neuromuscular Integration in Crustacean Locomotion

Recent work on sensory, motor and behavioral aspects of walkingin a variety of decapod Crustacea is discussed and compared.In these studies there has been considerable emphasis on modificationsof the motor program by variations imposed experimentally totest its capabilities and by naturally occurring variationsin environmental conditions which challenge the integrated system.The roles of sensory structures in signalling such changes arediscussed as well as the integrative capabilities of neuromuscularsystems in adaptive responses.     

Phylogeny, ontogeny and adaptive radiation in the superfamily Tydeoidea (Acari: Actinedida), with a reappraisal of morphological characters

The Tydeoidea as a whole (Tydeidae, Iolinidae and Ereynetidae) are analysed cladistically for the first time, based on a critical reappraisal of morphological characters. In addition to the chaetotaxy, solenidiotaxy and poroidotaxy, the following characters are considered: form of dehiscence line; number of eyes; presence of a posterior trichobothrium; number of discs on genital acetabula; breadth of cis‐acetabulal area; sexual dimorphism (indicative of true mating); segmentation of legs and palps; presence and structure of ereynetal organ; shape of chelicerae and tarsus I; and number of calyptostases. Special attention is paid to a comparative study of the segmentation and chaetotaxy of the palp within the superfamily, as well as to the presence of prodorsal eye‐spots, variations of the posterior sensilla and the segmentation of femur IV during ontogeny. Three types of phylogenetic analyses are employed: phenetic, cladistic and ontogenetic. The phenetic approach reveals that the current classification relies heavily on overall similarity between taxa, especially in adults, supplemented by ontogenetic peculiarities, such as the calyptostatic nymphs of Speleognathinae. The cladistic analyses lead to a reorganization of the Tydeoidea into four families. The Meyerellidae, characterized by the presence of three prodorsal eye‐spots, include the Meyerellinae and Triophtydeinae, while the Tydeidae are restricted to Australotydeinae, Pretydeinae and Tydeinae. The remaining two families, lolinidae and Ereynetidae, form the informal group Procurvata, characterized by the procurved dehiscence line. The family lolinidae is enlarged to encompass the subfamilies Tydaeolinae, Pronematinae and Iolininae. The Ereynetidae, characterized by the ereynetal organ and double genital discs, include the Ereynetinae (senior synonym of Pseudotydeinae, transferred from the Tydeidae), Lawrencarinae and Speleognathinae. Minor discrepancies were found between the results for immatures and adults. These can be explained by ontogenetic trajectories that are not parallel and undergo a spectacular expansion into the character space as they extend. Within the Tydeoidea, diversification and adaptation have occurred through acceleration, with adult adaptations extending into earlier stases. Heterostasy is only expressed in the Speleognathinae, in which the nymphs are all calyptostatic. The monophyly of the Tydeoidea remains questionable, since the Meyerellidae might constitute a separate group, more closely related to the Eupodoidea. The Meyerellidae aside, the tydeoid mites seem to have originated from a group of free‐living forms that colonized the soil and related habitats and underwent an early radiation, giving rise to three major lineages: the Tydeidae, Iolinidae and Ereynetidae. The Tydeidae are characterized by a low evolutionary rate combined with a high diversification indicative of a secondary adaptive radiation within the Tydeoidea. In contrast, the Iolinidae are characterized by a high evolutionary rate combined to a low diversification. The third lineage, the Ereynetidae, is highly diverse, showing high rates of evolution and speciation, linked to the adoption of endoparasitic habits. Different hypotheses to explain the success and diversification in Tydeidae and Ereynetidae are examined.