A puzzling population-genetic phenomenon widely reported in allozyme
surveys of marine bivalves is the occurrence of heterozygote deficits
relative to Hardy-Weinberg expectations. Possible explanations for this
pattern are categorized with respect to whether the effects should be
confined to protein-level assays or are genomically pervasive and expected
to be registered in both protein- and DNA-level assays. Anonymous nuclear
DNA markers from the American oyster were employed to reexamine the
phenomenon. In assays based on the polymerase chain reaction (PCR), two
DNA-level processes were encountered that can lead to artifactual genotypic
scorings: (a) differential amplification of alleles at a target locus and
(b) amplification from multiple paralogous loci. We describe symptoms of
these complications and prescribe methods that should generally help to
ameliorate them. When artifactual scorings at two anonymous DNA loci in the
American oyster were corrected, Hardy-Weinberg deviations registered in
preliminary population assays decreased to nonsignificant values.
Implications of these findings for the heterozygote-deficit phenomenon in
marine bivalves, and for the general development and use of PCR-based
assays, are discussed.
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The distribution of Na+ pump sites (Na+-K+-ATPase) in the secretory epithelium of the avian salt gland was demonstrated by freeze-dry autoradiographic analysis of [(3)H] ouabain binding sites. Kinetic studies indicated that near saturation of tissue binding sites occurred when slices of salt glands from salt-stressed ducks were exposed to 2.2 μM ouabain (containing 5 μCi/ml [(3)H]ouabain) for 90 min. Washing with label-free Ringer's solution for 90 min extracted only 10% of the inhibitor, an amount which corresponded to ouabain present in the tissue spaces labeled by [(14)C]insulin. Increasing the KCl concentration of the incubation medium reduced the rate of ouabain binding but not the maximal amount bound. In contrast to the low level of ouabain binding to salt glands of ducks maintained on a freshwater regimen, exposure to a salt water diet led to a more than threefold increase in binding within 9-11 days. This increase paralleled the similar increment in Na+-K+-ATPase activity described previously. [(3)H]ouabain binding sites were localized autoradiographically to the folded basolateral plasma membrane of the principal secretory cells. The luminal surfaces of these cells were unlabeled. Mitotically active peripheral cells were also unlabeled. The cell-specific pattern of [(3)H]ouabain binding to principal secretory cells and the membrane-specific localization of binding sites to the nonluminal surfaces of these cells were identical to the distribution of Na+-K+-ATPase as reflected by the cytochemical localization of ouabain-sensitive and K+-dependent nitrophenyl phosphatase activity. The relationship between the nonluminal localization of Na+-K+-ATPase and the possible role of the enzyme n NaCl secretion is considered in the light of physiological data on electrolyte transport in salt glands and other secretory epithelia. 相似文献
Pathogens carried by ticks pose a threat to both human and animal health across the world. Typically associated with rural landscapes, ticks appear to adapt well to life in urban recreational areas. Although Dermacentor reticulatus is commonly found across Europe, data on the prevalence of pathogens in this tick species, in an urban environment, are very limited. PCR was used to examine 368 D. reticulatus individuals collected in the Zwierzyniecki Forest Nature Reserve in Bia?ystok, Poland. In total, 10.3% of ticks were infected, with Babesia spp. (9.2%), Anaplasma phagocytophilum (0.8%) and Borrelia burgdorferi sensu lato (0.3%). Rickettsia spp., Bartonella spp., and Coxiella burnetii were not detected. Sequence analysis for Babesia-positive samples identified 79.4% of them as Babesia canis, 8.8% as Babesia microti, 5.9% as Babesia spp., 2.9% as Babesia venatorum, and 2.9% as Babesia vogeli. Results obtained in this study indicate that D. reticulatus ticks found within the urban premises of the study area are infected with at least three pathogens and therefore are an important factor in public health risk for tick-borne diseases.
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