Unimodality,symmetry and the step-state hypothesis of electrophoretic variation in natural populations

Summary The population frequency distributions of electromorphs of polymorphic loci, when ordered by electrophoretic mobility, tend strongly and significantly to be both unimodal and symmetrical. Such distributions are predicted by all step-change models and their generality in published data can be construed as supportive of the step-change hypothesis. On the other hand, unimodality and symmetry might also be due to artifactual unit perception biases that affect the interpretation and reporting of electro-phoretic data. In any case, it appears that perceived electromorphs are highly heterogeneous.This work was supported by PHS Grant RO 1 GM 21283-O1 GEN.     

Stimuli inducing gregarious colouration and behaviour in nymphs of Schistocerca gregaria

Solitarious nymphs of Schistocerca gregaria were reared under various conditions in both Jerusalem and Oxford to tease apart cues involved in behavioural and colour phase change. Treatments included rearing nymphs from the IInd or IIIrd until the final nymphal stadium in physical contact with similarly aged conspecific groups or with another locust species, Locusta migratoria migratorioides, as well as confining single nymphs in mesh cages, which were kept within crowds of S. gregaria or L. migratoria migratorioides, providing visual and olfactory but no physical contact with other locusts. In the Oxford experiments, an extra treatment was included which provided olfactory cues without visual or contact stimulation. Our results confirm that transformation from the solitarious to the gregarious phase of locusts is complex, and that different phase characteristics not only follow different time courses, but are also controlled by different suites of cues. As predicted from earlier studies, behavioural phase change was evoked by non-species-specific cues. Rearing in contact with either species was fully effective in inducing gregarious behaviour, as was the combination of the sight and smell of other locusts, but odour alone was ineffective. Colour phase change was shown to comprise two distinct elements that could be dissociated: black patterning and yellow background. The former of these could be induced as effectively by rearing S. gregaria nymphs in a crowd of L. migratoria migratorioides as by rearing with conspecifics. Sight and smell of other locusts also triggered black patterning and, unlike behavioural change, some black patterning was induced by odour cues alone. Hence, physical contact was not needed to induce gregarious black patterning. Yellow colouration, however, was only fully induced when locusts were reared in contact with conspecifics, implying the presence of a species-specific contact chemical cue.     

Use of a Florida Gulf Coast Barrier Island by Spring Trans-Gulf Migrants and the Projected Effects of Sea Level Rise on Habitat Availability

Barrier islands on the north coast of the Gulf of Mexico are an internationally important coastal resource. Each spring hundreds of thousands of Nearctic-Neotropical songbirds crossing the Gulf of Mexico during spring migration use these islands because they provide the first landfall for individuals following a trans-Gulf migratory route. The effects of climate change, particularly sea level rise, may negatively impact habitat availability for migrants on barrier islands. Our objectives were (1) to confirm the use of St. George Island, Florida by trans-Gulf migrants and (2) to determine whether forested stopover habitat will be available for migrants on St. George Island following sea level rise. We used avian transect data, geographic information systems, remote sensing, and simulation modelling to investigate the potential effects of three different sea level rise scenarios (0.28 m, 0.82 m, and 2 m) on habitat availability for trans-Gulf migrants. We found considerable use of the island by spring trans-Gulf migrants. Migrants were most abundant in areas with low elevation, high canopy height, and high coverage of forests and scrub/shrub. A substantial percentage of forest (44%) will be lost by 2100 assuming moderate sea level rise (0.82 m). Thus, as sea level rise progresses, less forests will be available for migrants during stopover. Many migratory bird species’ populations are declining, and degradation of barrier island stopover habitat may further increase the cost of migration for many individuals. To preserve this coastal resource, conservation and wise management of migratory stopover areas, especially near ecological barriers like the Gulf of Mexico, will be essential as sea levels rise.     

Biotechnology for phosphorus removal during wastewater treatment

Advanced biological wastewater treatment for the removal of phosphorus in excess of the normal metabolic requirements of activated sludge type processes has been developed as an alternative to chemical addition. Current laboratory and pilot plant investigations have confirmed that a preliminary anaerobic zone and plug-flow type configuration are necessary for good enhanced biological phosphorus removal. Nitrate in the anaerobic stage inhibits the process whereas acetate enhances phosphorus uptake. The bacteria probably responsible are of the Acinetobacter genus and the presence of stored polyphosphate within these bacteria has been demonstrated. It has also been shown that pure cultures of Acinetobacter do not necessarily take up soluble substrate as phosphate is released during the anaerobic phase, in contrast to the current proposed mechanism, and that in certain cases natural chemical precipitation could make a significant contribution towards overall phosphorus removal. Several studies of pilot and full-scale plants have been reported.     

Mass balance of heavy metal uptake by encapsulated cultures ofKlebsiella aerogenes

Dialysis was employed as a method of speciating heavy metals in cultures of an extracellular polymer forming strain ofKlebsiella aerogenes. A noncapsulated strain of the same bacterium was used as a control, and a mass balance of copper, cadmium, cobalt, nickel, and manganese in batch culture at pH 4.5 and pH 6.8 and in continuous culture at pH 6.8 was constructed. Copper and cadmium were accumulated by the cell during rapid proliferation whereas all 5 metals were bound nonspecifically by extracellular polymer produced during stationary phase and at low dilution rates. The presence of extracellular polymer appeared to inhibit cellular uptake of nickel. At the lower pH, metal uptake was considerably reduced. The results are discussed in the context of metal removal in the activated sludge process of waste water treatment.     

The evolutionary dynamics of the lion Panthera leo revealed by host and viral population genomics

The lion Panthera leo is one of the world's most charismatic carnivores and is one of Africa's key predators. Here, we used a large dataset from 357 lions comprehending 1.13 megabases of sequence data and genotypes from 22 microsatellite loci to characterize its recent evolutionary history. Patterns of molecular genetic variation in multiple maternal (mtDNA), paternal (Y-chromosome), and biparental nuclear (nDNA) genetic markers were compared with patterns of sequence and subtype variation of the lion feline immunodeficiency virus (FIV(Ple)), a lentivirus analogous to human immunodeficiency virus (HIV). In spite of the ability of lions to disperse long distances, patterns of lion genetic diversity suggest substantial population subdivision (mtDNA Phi(ST) = 0.92; nDNA F(ST) = 0.18), and reduced gene flow, which, along with large differences in sero-prevalence of six distinct FIV(Ple) subtypes among lion populations, refute the hypothesis that African lions consist of a single panmictic population. Our results suggest that extant lion populations derive from several Pleistocene refugia in East and Southern Africa ( approximately 324,000-169,000 years ago), which expanded during the Late Pleistocene ( approximately 100,000 years ago) into Central and North Africa and into Asia. During the Pleistocene/Holocene transition ( approximately 14,000-7,000 years), another expansion occurred from southern refugia northwards towards East Africa, causing population interbreeding. In particular, lion and FIV(Ple) variation affirms that the large, well-studied lion population occupying the greater Serengeti Ecosystem is derived from three distinct populations that admixed recently.     

Nodular pulmonary amyloidosis.

An elderly man had a 10-year history of multiple pulmonary nodules that he had refused to have investigated. He died of a ruptured abdominal aortic aneurysm. At autopsy the nodules were shown to consist of amyloid. There was no evidence of systemic amyloidosis.     

Formation of Adeno-Associated Virus Circular Genomes Is Differentially Regulated by Adenovirus E4 ORF6 and E2a Gene Expression

A central feature of the adeno-associated virus (AAV) latent life cycle is persistence in the form of both integrated and episomal genomes. However, the molecular processes associated with episomal long-term persistence of AAV genomes are only poorly understood. To investigate these mechanisms, we have utilized a recombinant AAV (rAAV) shuttle vector to identify circular AAV intermediates from transduced HeLa cells and primary fibroblasts. The unique structural features exhibited by these transduction intermediates included circularized monomer and dimer virus genomes in a head-to-tail array, with associated specific base pair alterations in the 5′ viral D sequence. In HeLa cells, the abundance and stability of AAV circular intermediates were augmented by adenovirus expressing the E2a gene product. In the absence of E2a, adenovirus expressing the E4 open reading frame 6 gene product decreased the abundance of AAV circular intermediates, favoring instead the linear replication form monomer (Rf_m) and dimer (Rf_d) structures. In summary, the formation of AAV circular intermediates appears to represent a new pathway for AAV genome conversion, which is consistent with the head-to-tail concatemerization associated with latent-phase persistence of rAAV. A better understanding of this pathway may increase the utility of rAAV vectors for gene therapy.