EXTERNAL MORPHOLOGY AND PIGMENTATION OF THE VAQUITA, PHOCOENA SINUS (CETACEA: MAMMALIA)

The vaquita, Phocoena sinus , is a porpoise in the family Phocoenidae that lives only in the Gulf of California. The external appearance of P. sinus was unknown until 13 fresh specimens were recently examined. The most obvious morphological feature distinguishing P. sinus from its two congeners is the proportionately higher dorsal fin. The most striking features of the pigmentation pattern are the large black eye patches and the black upper and lower lip patches. In both areas, the pigmentation contrasts sharply with the surrounding light gray coloration. The total lengths of the specimens ranged from 70.3 cm (a neonate) to 143.5 cm (an adult female).     

Chromosome deletion [46,XX,del(20)(q11)] in agnogenic myeloid metaplasia

Summary A woman in the fourth year of agnogenic myeloid metaplasia was found to have partial deletion of the long arm of chromosome 20 [46,XX, del(20)(q11)] in mitoses of presumably immature myeloid cells from unstimulated cultures of peripheral blood and bone marrow. Cytogenetic studies of peripheral blood lymphocytes showed a normal female karyotype.     

B cells regulate murine gammaherpesvirus 68 latency

The dynamics of the establishment of, and reactivation from, gammaherpesviruses latency has not been quantitatively analyzed in the natural host. Gammaherpesvirus 68 (gammaHV68) is a murine gammaherpesvirus genetically related to primate gammaherpesviruses that establishes a latent infection in infected mice. We used limiting dilution reactivation (frequency of cells reactivating gammaHV68 in vitro) and limiting dilution PCR (frequency of cells carrying gammaHV68 genome) assays to compare gammaHV68 latency in normal (C57BL/6) and B-cell-deficient (MuMT) mice. After intraperitoneal (i.p.) inoculation, latent gammaHV68 was detected in the spleen, bone marrow, and peritoneal cells. Both B-cell-deficient and C57BL/6 mice established latent infection in peritoneal cells after either i.p. or intranasal (i.n.) inoculation. In contrast, establishment of splenic latency was less efficient in B-cell-deficient than in C57BL/6 mice after i.n. inoculation. Analysis of reactivation efficiency (reactivation frequency compared to frequency of cells carrying gammaHV68 genome) revealed that (i) regardless of route or mouse strain, splenic cells reactivated gammaHV68 less efficiently than peritoneal cells, (ii) the frequency of cells carrying gammaHV68 genome was generally comparable over the course of infection between C57BL/6 and B-cell-deficient mice, (iii) between 28 and 250 days after infection, cells from B-cell-deficient mice reactivated gammaHV68 10- to 100-fold more efficiently than cells from C57BL/6 mice, (iv) at 7 weeks postinfection, B-cell-deficient mice had more genome-positive peritoneal cells than C57BL/6 mice, and (v) mixing cells (ratio of 3 to 1) that reactivated inefficiently with cells that reactivated efficiently did not significantly decrease reactivation efficiency. Consistent with a failure to normally regulate chronic gammaHV68 infection, the majority of infected B-cell-deficient mice died between 100 and 200 days postinfection. We conclude that (i) B cells are not required for establishment of gammaHV68 latency, (ii) there are organ-specific differences in the efficiency of gammaHV68 reactivation, (iii) B cells play a crucial role in regulating reactivation of gammaHV68 from latency, and (iv) B cells are important for controlling chronic gammaHV68 infection.     

Phospho-NHE3 forms membrane patches and interacts with beta-actin to sense and maintain constant direction during cell migration

The Na(+)/H(+) exchanger NHE3 colocalizes with beta-actin at the leading edge of directionally migrating cells. Using human osteosarcoma cells (SaOS-2), rat osteoblasts (calvaria), and human embryonic kidney (HEK) cells, we identified a novel role for NHE3 via beta-actin in anode and cathode directed motility, during electrotaxis. NHE3 knockdown by RNAi revealed that NHE3 expression is required to achieve constant directionality and polarity in migrating cells. Phosphorylated NHE3 (pNHE3) and beta-actin complex formation was impaired by the NHE3 inhibitor S3226 (IC50 0.02 µM). Fluorescence cross-correlation spectroscopy (FCCS) revealed that the molecular interactions between NHE3 and beta-actin in membrane protrusions increased 1.7-fold in the presence of a directional cue and decreased 3.3-fold in the presence of cytochalasin D. Data from flow cytometric analysis showed that membrane potential of cells (V_mem) decreases in directionally migrating, NHE3-deficient osteoblasts and osteosarcoma cells whereas only V_mem of wild type osteoblasts is affected during directional migration. These findings suggest that pNHE3 has a mechanical function via beta-actin that is dependent on its physiological activity and V_mem. Furthermore, phosphatidylinositol 3,4,5-trisphosphate (PIP3) levels increase while PIP2 remains stable when cells have persistent directionality. Both PI3 kinase (PI3K) and Akt expression levels change proportionally to NHE3 levels. Interestingly, however, the content of pNHE3 level does not change when PI3K/Akt is inhibited. Therefore, we conclude that NHE3 can act as a direction sensor for cells and that NHE3 phosphorylation in persistent directional cell migration does not involve PI3K/Akt during electrotaxis.     

Genetic consequences of trumpeter swan (Cygnus buccinator) reintroductions

Relocation programs are often initiated to restore threatened species to previously occupied portions of their range. A primary challenge of restoration efforts is to translocate individuals in a way that prevents loss of genetic diversity and decreases differentiation relative to source populations—a challenge that becomes increasingly difficult when remnant populations of the species are already genetically depauperate. Trumpeter swans were previously extirpated in the entire eastern half of their range. Physical translocations of birds over the last 70 years have restored the species to portions of its historical range. Despite the long history of management, there has been little monitoring of the genetic outcomes of these restoration attempts. We assessed the consequences of this reintroduction program by comparing patterns of genetic variation at 17 microsatellite loci across four restoration flocks (three wild-released, one captive) and their source populations. We found that a wild-released population established from a single source displayed a trend toward reduced genetic diversity relative to and significant genetic differentiation from its source population, though small founder population effects may also explain this pattern. Wild-released flocks restored from multiple populations maintained source levels of genetic variation and lacked significant differentiation from at least one of their sources. Further, the flock originating from a single source revealed significantly lower levels of genetic variation than those established from multiple sources. The distribution of genetic variation in the captive flock was similar to its source. While the case of trumpeter swans provides evidence that restorations from multiple versus single source populations may better preserve natural levels of genetic diversity, more studies are needed to understand the general applicability of this management strategy.