Comparison of an in vitro method and an in vivo method of Giardia excystation.

An in vitro method and an in vivo method of excystation were compared to determine the most useful method for the retrieval of Giardia duodenalis isolates. Cysts from 11 Giardia strains were used. In vitro excystation produced motile trophozoites in 16 sets, while in vivo excystation produced trophozoites in all of the 21 comparative sets of excystations. Few cultures were lost because of contamination by either method (17% of in vitro-derived trophozoites versus 23% of in vivo-derived trophozoites; P greater than 0.05). Both methods demonstrated comparable isolate retrieval rates (15% of in vitro-derived trophozoites adapting to culture compared with 29% of in vivo-derived trophozoites; P greater than 0.05), although analysis of the strains retrieved showed that two isolates were retrieved from in vitro excystation alone, compared with four from in vivo excystation. Analysis that included results of extra in vivo cultures showed that a total of nine isolates were retrieved by using this type of excystation. Despite the disadvantages of cost and labor, in vivo excystation appears to be more useful than in vitro excystation for isolate retrieval at the present time.     

Biogeographical history of cuckoo‐shrikes (Aves: Passeriformes): transoceanic colonization of Africa from Australo‐Papua

Aim Cuckoo‐shrikes and allies (Campephagidae) form a radiation of birds widely distributed in the Indo‐Pacific and Africa. Recent studies on the group have been hampered by poor taxon sampling, causing inferences about systematics and biogeography to be rather speculative. With improved taxon sampling and analyses within an explicit spatiotemporal framework, we elucidate biogeographical patterns of dispersal and diversification within this diverse clade of passerine birds. Location Africa, Asia, Australo‐Papua, the Pacific, the Philippines and Wallacea. Methods We use model‐based phylogenetic methods (Mr Bayes and garli ) to construct a phylogenetic hypothesis of the core Campephagidae (Campephagidae with the exclusion of Pericrocotus). The phylogeny is used to assess the biogeographical history of the group with a newly developed Bayesian approach to dispersal–vicariance analysis (Bayes‐diva) . We also made use of a partitioned beast analysis, with several calibration points taken from island ages, passerine mitochondrial substitution rates and secondary calibration points for passerine birds, to assess the timing of diversification and dispersal. Results We present a robust molecular phylogeny that includes all genera and 84% of the species within the core Campephagidae. Furthermore, we estimate divergence dates and ancestral area relationships. We demonstrate that Campephagidae originated in Australo‐Papua with a single lineage (Pericrocotus) dispersing to Asia early. Later, there was further extensive transoceanic dispersal from Australo‐Papua to Africa involving lineages within the core Campephagidae radiation. Main conclusions The phylogenetic relationships, along with the results of the ancestral area analysis and the timing of dispersal events, support a transoceanic dispersal scenario from Australo‐Papua to Africa by the core Campephagidae. The sister group to core Campephagidae, Pericrocotus, dispersed to mainland Asia in the late Oligocene. Asia remained uncolonized by the core Campephagidae until the Pliocene. Transoceanic dispersal is by no means an unknown phenomenon, but our results represent a convincing case of colonization over a significant water gap of thousands of kilometres from Australo‐Papua to Africa.     

Phosphorus-31 nuclear magnetic resonance of ethidium complexes with ribonucleic acid model systems and phenylalanine-accepting transfer ribonucleic acid

The temperature dependence of the 31P NMR spectra of the ethidium complexes with poly(A) X oligo(U) and the 31P spectra of phenylalanine tRNA (yeast) in various molar ratios of ethidium ion (Et) are presented. In the poly(A) X oligo(U) X Et complex, a new peak about 2.0 ppm downfield from the double-helix peak appears. We have assigned this peak to phosphates perturbed by ethidium. The chemical shift of this peak is consistent with the intercalation mode of binding and provides additional support for our hypothesis that 31P shifts are sensitive probes of phosphate ester conformations. The main effect of ethidium on the 31P spectra of tRNAPhe is the broadening of several of the scattered signals. These scattered signals are associated with phosphates involved in tertiary interactions. We propose that these broadened signals arise from phosphates near the Et binding site.     

Immunoblot patterns of Giardia duodenalis isolates from different hosts and geographical locations

Eighteen isolates of Giardia duodenalis from animal and human sources were studied for protein differences by polyacrylamide gel electrophoresis and for antigenic differences by immunoblot analysis. The polyacrylamide gels showed that whilst the isolates were for the most part homogeneous in their protein banding patterns, some isolates did show some differences. The immunoblot analysis yielded many bands, including prominent bands of 32 and 66 kilodaltons. Five of the six isolates that showed differences in protein banding pattern also showed differences in antigenic reactivity. Our findings suggest that differences can be seen with the use of immunoblotting and that this technique is a tool that may be useful for isolate differentiation when used in conjunction with other techniques.     

The Alchemy of Charity: Of Class and Buddhism in Northern Thailand

This essay focuses on a form of unidirectional giving current in Theravada Buddhism: the institution of merit making as practiced in northern Thailand. Many scholars have noted its centrality in village religious practices but have failed to locate it within the broader context of class stratification. As a result, the prevailing paradigm of merit making misrepresents the character of the recipients, the donors, and their mutual interaction. This essay argues that cross-class, unidirectional forms of giving such as charity may be important in mediating hegemony and resistance in complex societies.     

Long-term propagation of distinct hematopoietic differentiation programs in vivo

Heterogeneity in the differentiation behavior of hematopoietic stem cells is well documented but poorly understood. To investigate this question at a clonal level, we isolated a subpopulation of adult mouse bone marrow that is highly enriched for multilineage in vivo repopulating cells and transplanted these as single cells, or their short-term clonal progeny generated in vitro, into 352 recipients. Of the mice, 93 showed a donor-derived contribution to the circulating white blood cells for at least 4 months in one of four distinct patterns. Serial transplantation experiments indicated that two of the patterns were associated with extensive self-renewal of the original cell transplanted. However, within 4 days in vitro, the repopulation patterns subsequently obtained in vivo shifted in a clone-specific fashion to those with less myeloid contribution. Thus, primitive hematopoietic cells can maintain distinct repopulation properties upon serial transplantation in vivo, although these properties can also alter rapidly in vitro.