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As primary-care providers have become increasingly adept at recognizing patients with lung disease, and pulse oximetry has simplified the detection of hypoxemia, the use of long-term oxygen therapy for adults [...]

Abstract Genotyping of 11 microsatellites in 432 offspring from 28 families of the hermaphroditic, freshwater snail Bulinus forskalii detected 10 de novo mutant alleles. This gave an estimated mutation rate of 1.1 × 10-3 per locus per gamete per generation. There was a trend towards repeat length expansion and, unlike most studies, multi-step mutations predominated, suggesting that the microsatellite mutation process does not conform to a strict stepwise mutation model. Interestingly, the ten mutant alleles appear to have arisen from only six independent germline mutation events within the microsatellite array, with seven of them residing in three mutational clusters. Our results extend observations of clustered microsatellite mutations to another taxonomic group and type of mating system, self-fertile gastropods, and provide compelling evidence of premeiotic germline mutations, a phenomenon that could greatly impact upon our understanding of mutation dynamics but which has received little attention.

Freshwater snails of the genus Biomphalaria, Preston 1910, are the most important and widely distributed intermediate hosts of Schistosoma mansoni, the blood fluke responsible for human intestinal schistosomiasis, in Africa and the Neotropics. S. mansoniis thought to have been imported repeatedly into the Americas during the last 500 years with the African slave trade. Surprisingly, considering that the New and Old World separated 95–106 million years (Myr) ago, the disease rapidly became established due to the presence of endemic susceptible hosts. Reconstructing the phylogenetic relationships within Biomphalariamay provide insights into the successful intercontinental spread of S. mansoni. Parsimony and distance analyses of mitochondrial and nuclear sequences show African taxa to be monophyletic and Neotropical speciesparaphyletic, with Biomphalaria glabrataforming a separate clade from other Neotropical Biomphalaria, and ancestral to the African taxa. A west to east trans–Atlantic dispersal of a B. glabrata–like taxon, possibly as recently as the Plio–Pleistocene (1.8–3.6 Myr ago) according to a general mitochondrial clock, would fit these observations. Vicariance or an African origin for B. glabratafollowed by multiple introductions to South America over the past 500 years with the African slave trade seem unlikely explanations. Knowledge of the phylogenetic relationships among important intermediate host species may prove useful in furthering control measures which exploit genetic differences in susceptibility to parasites, and in elucidating the evolution of schistosome resistance.

Restriction analysis had revealed only Mus domesticusmtDNA in house mouse populations in northern Denmark, Sweden, and Finland, where the nuclear genomes are Mus musculus.The goals of the present study were to (1) test the proposal that these Scandinavian musculusmice arose by a series of founder and island-hopping events from one or a few populations near the domesticus-musculushybrid zone on the East Holstein Peninsula of northern Germany and (2) see whether more than the two types of domesticusmtDNA detected by restriction analysis existed among these musculuspopulations. Sequences of the 1-kilobase mtDNA segment encompassing the entire control region and the flanking tRNAs were gathered from 217 domesticusand musculusmice. Included were 104 mice from 12 localities across a 120-km transect of the Holstein hybrid and adjacent zones, 56 animals from 12 localities in the musculusrange of Scandinavia, 56 domesticusmice representing 46 localities in Europe, North Africa, the Middle East, and the Americas, and one musculusmouse from Czechoslovakia. Save for the Czech mouse, all individuals had domesticusmtDNA, a total of 56 types being resolved and 10 of these being found among the Holstein mice. Electrophoresis of proteins encoded by nuclear loci along with assessment of external morphology and of skeletal, cranial, and dental traits revealed a transition from domesticusto musculusnuclear genomes over a distance of about 20-40 km in East Holstein. Of the 216 mtDNAs, 149 fall into a clade of 17 types characterized by the addition of an 11-bp direct repeat; included are all Swedish, Finnish, and northern Danish mtDNAs as well as 82 from the Holstein transect. Support for the previously proposed migration pathway from the European mainland to Scandinavia came from finding that on the domesticusside of the hybrid zone in Holstein a high proportion of mice carry the types of mtDNA found in the mice with musculusnuclear genomes. Sequencing revealed 11 different mtDNAs in the +11-bp clade among musculusmice, one of these being widespread, seven others being confined to single localities, and one Danish collecting locality yielding five types. The mitochondrial diversity uncovered among these mice leads to a reexamination of some aspects of the original model, notably with respect to the number of founding females, the possible role of selection, and the possibility of an accelerated rate of mtDNA evolution. This study also showed that for the mouse control region the transition/transversion ratio is significantly lower than for the human control region and that small length mutations occur about as frequently as transversions during mouse control region evolution.

Six microsatellite loci were isolated and characterized in Bulinus globosus, a freshwater snail with a wide distribution throughout sub-Saharan Africa. Bulinus globosus is an intermediate host of Schistosoma haematobium, the causative agent of human urinary schistosomiasis. Microsatellites were tested using 32 snails from four populations collected from Pemba and Unguja islands of Zanzibar. The microsatellite loci displayed relatively low levels of variation, with between two and five alleles per locus. FST estimates indicate that gene flow is low, as has previously been suggested for other species of Bulinus.