Suppressor and reactive lymphocytes in radiation leukemia virus (RadLV)-induced leukemogenesis

Summary Suppressor cells capable of enhancing tumor growth in vivo and of abrogating a potential anti-tumor immunity in vitro are generated in C57BL/6 mice inoculated with the high-leukemogenic A-RadLV. Mice inoculated with low-leukemogenic D-RadLV do not develop suppressor cells but contain anti-tumor reactive lymphocytes that can inhibit in vivo tumor growth. Cyclophosphamide (CyF) treatment of mice inoculated with A-RadLV hampered suppressor cell function and rendered the animals' lymphocytes responsive to A-RadLV induced tumor cells in vitro. Administration of CyF also reduced leukemia incidence in mice inoculated with A-RadLV, but had no effect on leukemia induction by D-RadLV in irradiated mice. It is suggested that the high leukemogenic activity of A-RadLV depends on the virus' ability to recruit CyF-sensitive suppressor cells early in latency and that tumor progression in mice inoculated with D-RadLV is arrested due to the host immune response.     

Kinship and sociality in coastal river otters: are they related?

Previous studies of coastal river otters (Lontra canadensis)in Prince William Sound, Alaska, USA, documented atypical socialorganization for mammals. Social groups were composed largelyof males, but some males remained solitary year-round and mostfemales were asocial. Because, in carnivores, groups are usuallycomposed of highly related individuals but group living alsoprovides advantages unrelated to kinship, we concurrently evaluatedthe role of relatedness and ecological benefits in socialityamong coastal river otters. By using DNA microsatellite analysisand radiotelemetry, we were able to reject the hypothesis thatsocial groups of otters were kin based. In addition, we foundno indication of kin avoidance, as would be expected from lowdispersal and high local competition. Sociality conferred noreproductive benefits or costs to otters; number of offspringand number of relatives in the population did not differ betweensocial and solitary animals. Solitary males were not older orlarger than were social males, and there was no relation betweenmale size and number of offspring, indicating that sexual selectiondid not mask a potential relation between sociality and reproductivesuccess. Among coastal river otters in this region, socialitycould be explained by the benefits obtained from cooperativeforaging on high-quality schooling pelagic fishes. Such benefitsdid not require association with kin, resulting in no selectionpressure for kin-based groups. The prediction that the degreeof sociality in the population will fluctuate relative to theabundance of schooling pelagic fishes merits further investigation.     

Quadrupedal locomotor performance in two species of arboreal squirrels: predicting energy savings of gliding

Gliding allows mammals to exploit canopy habitats of old-growth forests possibly as a means to save energy. To assess costs of quadrupedal locomotion for a gliding arboreal mammal, we used open-flow respirometry and a variable-speed treadmill to measure oxygen consumption and to calculate cost of transport, excess exercise oxygen consumption, and excess post-exercise oxygen consumption for nine northern flying squirrels (Glaucomys sabrinus) and four fox squirrels (Sciurus niger). Our results indicate that oxygen consumption during exercise by flying squirrels was 1.26–1.65 times higher than predicted based on body mass, and exponentially increased with velocity (from 0.84 ± 0.03 ml O₂ kg⁻¹ s⁻¹ at 0.40 m s⁻¹ to 1.55 ± 0.03 ml O₂ kg⁻¹ s⁻¹ at 0.67 m s⁻¹). Also, cost of transport in flying squirrels increased with velocity, although excess exercise oxygen consumption and excess post-exercise oxygen consumption did not. In contrast, oxygen consumption during exercise for fox squirrels was similar to predicted, varying from 0.51 (±0.02) ml O₂ kg⁻¹ s⁻¹ at 0.63 m s⁻¹ to 0.54 (±0.03) ml O₂ kg⁻¹ s⁻¹ at 1.25 m s⁻¹. In addition, the cost of transport for fox squirrels decreased with velocity, while excess exercise oxygen consumption and excess post-exercise oxygen consumption did not. Collectively, these observations suggest that unlike fox squirrels, flying squirrels are poorly adapted to prolonged bouts of quadrupedal locomotion. The evolution of skeletal adaptations to climbing, leaping, and landing and the development of a gliding membrane likely has increased the cost of quadrupedal locomotion by >50% while resulting in energy savings during gliding and reduction in travel time between foraging patches.     

Global scale variation in the salinity sensitivity of riverine macroinvertebrates: eastern Australia, France, Israel and South Africa

Salinity is a key abiotic property of inland waters; it has a major influence on biotic communities and is affected by many natural and anthropogenic processes. Salinity of inland waters tends to increase with aridity, and biota of inland waters may have evolved greater salt tolerance in more arid regions. Here we compare the sensitivity of stream macroinvertebrate species to salinity from a relatively wet region in France (Lorraine and Brittany) to that in three relatively arid regions eastern Australia (Victoria, Queensland and Tasmania), South Africa (south-east of the Eastern Cape Province) and Israel using the identical experimental method in all locations. The species whose salinity tolerance was tested, were somewhat more salt tolerant in eastern Australia and South Africa than France, with those in Israel being intermediate. However, by far the greatest source of variation in species sensitivity was between taxonomic groups (Order and Class) and not between the regions. We used a bayesian statistical model to estimate the species sensitivity distributions (SSDs) for salinity in eastern Australia and France adjusting for the assemblages of species in these regions. The assemblage in France was slightly more salinity sensitive than that in eastern Australia. We therefore suggest that regional salinity sensitivity is therefore likely to depend most on the taxonomic composition of respective macroinvertebrate assemblages. On this basis it would be possible to screen rivers globally for risk from salinisation.     

Myosin VI is required for structural integrity of the apical surface of sensory hair cells in zebrafish

Unconventional myosins have been associated with hearing loss in humans, mice, and zebrafish. Mutations in myosin VI cause both recessive and dominant forms of nonsyndromic deafness in humans and deafness in Snell's waltzer mice associated with abnormal fusion of hair cell stereocilia. Although myosin VI has been implicated in diverse cellular processes such as vesicle trafficking and epithelial morphogenesis, the role of this protein in the sensory hair cells remains unclear. To investigate the function of myosin VI in zebrafish, we cloned and examined the expression pattern of myosin VI, which is duplicated in the zebrafish genome. One duplicate, myo6a, is expressed in a ubiquitous pattern during early development and at later stages, and is highly expressed in the brain, gut, and kidney. myo6b, on the other hand, is predominantly expressed in the sensory epithelium of the ear and lateral line at all developmental stages examined. Both molecules have different splice variants expressed in these tissues. Using a candidate gene approach, we show that myo6b is satellite, a gene responsible for auditory/vestibular defects in zebrafish larvae. Examination of hair cells in satellite mutants revealed that stereociliary bundles are irregular and disorganized. At the ultrastructural level, we observed that the apical surface of satellite mutant hair cells abnormally protrudes above the epithelium and the membrane near the base of the stereocilia is raised. At later stages, stereocilia fused together. We conclude that zebrafish myo6b is required for maintaining the integrity of the apical surface of hair cells, suggesting a conserved role for myosin VI in regulation of actin-based interactions with the plasma membrane.     

Identification and characterization of a novel powdery mildew resistance gene <Emphasis Type="Italic">PmG3M</Emphasis> derived from wild emmer wheat, <Emphasis Type="Italic">Triticum dicoccoides</Emphasis>

Powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt) is one of the most important wheat diseases worldwide. Wild emmer wheat, Triticum turgidum ssp. dicoccoides, the tetraploid ancestor (AABB) of domesticated bread and durum wheat, harbors many important alleles for resistance to various diseases, including powdery mildew. In the current study, two tetraploid wheat mapping populations, derived from a cross between durum wheat (cv. Langdon) and wild emmer wheat (accession G-305-3M), were used to identify and map a novel powdery mildew resistance gene. Wild emmer accession G-305-3M was resistant to all 47 Bgt isolates tested, from Israel and Switzerland. Segregation ratios of F₂ progenies and F₆ recombinant inbred line (RIL) mapping populations, in their reactions to inoculation with Bgt, revealed a Mendelian pattern (3:1 and 1:1, respectively), indicating the role of a single dominant gene derived from T. dicoccoides accession G-305-3M. This gene, temporarily designated PmG3M, was mapped on chromosome 6BL and physically assigned to chromosome deletion bin 6BL-0.70-1.00. The F₂ mapping population was used to construct a genetic map of the PmG3M gene region consisted of six simple sequence repeats (SSR), 11 resistance gene analog (RGA), and two target region amplification polymorphism (TRAP) markers. A second map, constructed based on the F₆ RIL population, using a set of skeleton SSR markers, confirmed the order of loci and distances obtained for the F₂ population. The discovery and mapping of this novel powdery mildew resistance gene emphasize the importance of the wild emmer wheat gene pool as a source for crop improvement.     

Immunoaffinity purification of monoclonal antibodies: In search of an elution buffer of general applicability

Summary Of a number of elution buffers tested, 4MgCl2 in 25% ethylene glycol was the most eficient for recovering active monoclonal antibodies from immunoaffinity columns. This solution may be useful as a general purpose eluant for monoclonal antibody purification.