On the Ecology and Distribution of <i>Echinococcus spp. (Cestoda: Taeniidae), and Characteristics of Their Development in the Intermediate Host. II. Comparative Studies on the Development of Larval <i>E. multilocularis Leuckart, 1863, in the Intermediate Host

This paper reports the results of a comparative study of the development of the larval Echinococcus multilocularis Leuckart, 1863), and associated tissue reaction in naturally and experimentally infected mammals representing 31 species. The histogenesis of the larval cestode was traced in detail in arvicoline rodents of several species, and interspecific differences were defined. In arvicoline rodents, the developing larva exhibited host-specific characteristics within about a month after infection was established. The tissue reaction in Microtus oeconomus was characterized by the production of a large quantity of detritus around the larva, and by the formation of a thick epithelioid zone. In one subspecies, M. oeconomus innuitus, development of the larva was retarded, and the detrital mass was often calcified; in another, M. oeconomus operarius, the detritus rarely became calcified and the larva proliferated more rapidly. In M. pennsylvanicus, the tissue reaction was minimal, and little detritus was present. The characteristics of the tissue reaction in M. montebelli placed it in an intermediate position between the aforementioned species. In Clethrionomys rutilus, a thin epithelioid zone and an outer zone of loose collagenous fibers composed the adventitial layer; exogenous budding was retarded in this vole. A minimal tissue reaction occurred in Lagurus curtatus. In Lemmus spp., larger cysts were characteristic, but areas of small-cystic proliferation were always present. Similar differences in species or subspecies of Citellus and Dicrostonyx were described. Lesions of alveolar bydatid disease in man also were studied. The invasive growth of the larval cestode in the human liver involves a process comparable to small-cystic proliferation in the natural intermediate hosts. Although the later stages of development of the larval cestode are inhibited in man, exogenous proliferation of vesicles continues for the life of the host. The lesion in man was compared with a morphologically similar formation produced by anomalous development of the larval E. granulosus in the bovine liver. The latter is distinguished by the absence of areas of small-cystic proliferation. Non-echinococcal lesions found in the tissues studied, some of which resembled foci caused by the larval E. multilocularis, were briefly discussed.

Development and Characterization of 15 Polymorphic Microsatellite Loci Isolated From Rafinesque’s Big-Eared Bat, Corynorhinus rafinesquii

We developed and characterized 15 microsatellite markers for Rafinesque’s big-eared bat, Corynorhinus rafinesquii. In a population from Tennessee, the number of alleles per locus ranged from three to 13 and observed heterozygosities were 0.35 to 0.97 per locus. These loci will provide appropriate variability for estimation of population connectivity, demographic parameters, and genetic diversity for this species of concern.

Both apolipoprotein E and A-I genes are present in a nonmammalian vertebrate and are highly expressed during embryonic development

Apolipoprotein E (apoE) is associated with several classes of plasma lipoproteins and mediates uptake of lipoproteins through its ability to interact with specific cell surface receptors. Besides its role in cardiovascular diseases, accumulating evidence has suggested that apoE could play a role in neurodegenerative diseases, such as Alzheimer disease. In vertebrates, apoA-I is the major protein of high-density lipoprotein. ApoA-I may play an important role in regulating the cholesterol content of peripheral tissues through the reverse cholesterol transport pathway. We have isolated cDNA clones that code for apoE and apoA-I from a zebrafish embryo library. Analysis of the deduced amino acid sequences showed the presence of a region enriched in basic amino acids in zebrafish apoE similar to the lipoprotein receptor-binding region of human apoE. We demonstrated by whole-mount in situ hybridization that apoE and apoA-I genes are highly expressed in the yolk syncytial layer, an extraembryonic structure implicated in embryonic and larval nutrition. ApoE transcripts were also observed in the deep cell layer during blastula stage, in numerous ectodermal derivatives after gastrulation, and after 3 days of development in a limited number of cells both in brain and in the eyes. Our data indicate that apoE can be found in a nonmammalian vertebrate and that the duplication events, from which apoE and apoA-I genes arose, occurred before the divergence of the tetrapod and teleost ancestors. Zebrafish can be used as a simple and useful model for studying the role of apolipoproteins in embryonic and larval nutrition and of apoE in brain morphogenesis and regeneration.

Impairment of axonal development and of synaptogenesis in hippocampal neurons of synapsin I-deficient mice.

Synapsin I, the most abundant of all neuronal phosphoproteins, is enriched in synaptic vesicles. It has been hypothesized to regulate synaptogenesis and neurotransmitter release from adult nerve terminals. The evidence for such roles has been highly suggestive but not compelling. To evaluate the possible involvement of synapsin I in synaptogenesis and in the function of adult synapses, we have generated synapsin I-deficient mice by homologous recombination. We report herein that outgrowth of predendritic neurites and of axons was severely retarded in the hippocampal neurons of embryonic synapsin I mutant mice. Furthermore, synapse formation was significantly delayed in these mutant neurons. These results indicate that synapsin I plays a role in regulation of axonogenesis and synaptogenesis.