Connectivity of Caribbean coral populations: complementary insights from empirical and modelled gene flow

Understanding patterns of connectivity among populations of marine organisms is essential for the development of realistic, spatially explicit models of population dynamics. Two approaches, empirical genetic patterns and oceanographic dispersal modelling, have been used to estimate levels of evolutionary connectivity among marine populations but rarely have their potentially complementary insights been combined. Here, a spatially realistic Lagrangian model of larval dispersal and a theoretical genetic model are integrated with the most extensive study of gene flow in a Caribbean marine organism. The 871 genets collected from 26 sites spread over the wider Caribbean subsampled 45.8% of the 1900 potential unique genets in the model. At a coarse scale, significant consensus between modelled estimates of genetic structure and empirical genetic data for populations of the reef-building coral Montastraea annularis is observed. However, modelled and empirical data differ in their estimates of connectivity among northern Mesoamerican reefs indicating that processes other than dispersal may dominate here. Further, the geographic location and porosity of the previously described east-west barrier to gene flow in the Caribbean is refined. A multi-prong approach, integrating genetic data and spatially realistic models of larval dispersal and genetic projection, provides complementary insights into the processes underpinning population connectivity in marine invertebrates on evolutionary timescales.     

Brugia malayi: whole genome amplification for genomic characterization of filarial parasites

Genetic characterization of field isolates and clinical specimens of filarial nematodes is often limited by a shortage of DNA; therefore, we evaluated a multiple displacement amplification (MDA) based whole genome amplification method. The quality of amplified DNA was examined by conventional PCR, real-time PCR, and DNA hybridization. MDA of 5.0 ng of adult Brugia malayi DNA and one-fifteenth of the DNA isolated from a single microfilaria resulted in 6.3 and 4.2 μg of amplified DNA, respectively. Amplified DNA was equivalent to native genomic DNA for hybridization to B. malayi BAC library clones or to an oligonucleotide microarray with approximately 18,000 filarial DNA sequences. MDA is useful for whole genome amplification of filarial DNA from very small amounts of starting material. This technology will permit detailed studies of genetic diversity that were not previously feasible.     

Cardiopulmonary resuscitation in the mouse.

We sought to develop a model of cardiac arrest and resuscitation on mice that would be comparable to that of large mammals and would allow for more fundamental investigations on cardiopulmonary arrest and cardiac resuscitation. A model of cardiopulmonary resuscitation previously developed by our group on rats was adapted to anesthetized, mechanically ventilated adult male Institute of Cancer Research mice that weighed 46 +/- 3 g. The trachea was intubated through the mouth, and end-tidal PCO(2) (PET(CO(2))) was measured with a microcapnometer. Catheters were advanced into the aorta and into the right atrium, and coronary perfusion pressure (CPP) was computed. A 1.5-mA alternating current was delivered to the right ventricular endocardium, which produced ventricular fibrillation or a pulseless rhythm. Precordial compression was begun 4 min later. Ten sequential studies were performed, during which five animals were successfully resuscitated and five failed resuscitation efforts. Successful resuscitation was contingent on the restoration of threshold levels of CPP and PET(CO(2)) during chest compression. As in rats, swine, and human patients, threshold levels of mean aortic pressure, CPP, and PET(CO(2)) were critical determinates of resuscitability in this murine model of threshold level of cardiac arrest and resuscitation.     

Morphogenesis of bacteriophage lambda deletion mutants. II. Escherichia coli mutants which prevent maturation of short genomes.

We have isolated mutants of Escherichia coli which severely reduce the growth of bacteriophage lambda carrying the b221 deletion. Some of the bacterial strains also cause a moderate reduction in the growth of wild-type phage. In the mutant hosts tested, the growth of λb221 is restored by chromosomal alterations producing a non-specific increase in genome length. Thus the defect in growth can be attributed to the physical size of the genome, rather than a genetic effect of the b221 deletion. Our experiments show that the failure to grow results from a block to head morphogenesis and that growth can be restored by mutations in at least two phage head genes. In the accompanying paper we have shown that even in the normal bacterium, the process of packing and cutting the λb221 genome is perturbed as a result of its small size. The block to morphogenesis in the bacterial mutant we have studied most extensively appears to result from an enhancement of the same effect. The experiments described support the hypothesis that there is host participation in the cutting of encapsulated lambda DNA, although it is not yet clear if this involves the direct participation of a host gene product.     

Plaque Assay for Polyoma Virus on Primary Mouse Kidney Cell Cultures

A plaque assay for polyoma virus using primary baby mouse kidney cells is reported.