Continuously fluctuating selection reveals fine granularity of adaptation.

Temporally fluctuating environmental conditions are a ubiquitous feature of natural habitats. Yet, how finely natural populations adaptively track fluctuating selection pressures via shifts in standing genetic variation is unknown1,2. Here we generated genome-wide allele frequency data every 1-2 generations from a genetically diverse population of Drosophila melanogaster in extensively replicated field mesocosms from late June to mid-December (a period of approximately 12 total generations). Adaptation throughout the fundamental ecological phases of population expansion, peak density and collapse was underpinned by extremely rapid, parallel changes in genomic variation across replicates. Yet, the dominant direction of selection fluctuated repeatedly, even within each of these ecological phases. Comparing patterns of change in allele frequency to an independent dataset procured from the same experimental system demonstrated that the targets of selection are predictable across years. In concert, our results reveal a fitness relevance of standing variation that is likely to be masked by inference approaches based on static population sampling or insufficiently resolved time-series data. We propose that such fine-scaled, temporally fluctuating selection may be an important force contributing to the maintenance of functional genetic variation in natural populations and an important stochastic force impacting genome-wide patterns of diversity at linked neutral sites, akin to genetic draft.

Continuously fluctuating selection reveals extreme granularity and parallelism of adaptive tracking.

Temporally fluctuating environmental conditions are a ubiquitous feature of natural habitats. Yet, how finely natural populations adaptively track fluctuating selection pressures via shifts in standing genetic variation is unknown. We generated high-frequency, genome-wide allele frequency data from a genetically diverse population of Drosophila melanogaster in extensively replicated field mesocosms from late June to mid-December, a period of ∼12 generations. Adaptation throughout the fundamental ecological phases of population expansion, peak density, and collapse was underpinned by extremely rapid, parallel changes in genomic variation across replicates. Yet, the dominant direction of selection fluctuated repeatedly, even within each of these ecological phases. Comparing patterns of allele frequency change to an independent dataset procured from the same experimental system demonstrated that the targets of selection are predictable across years. In concert, our results reveal fitness-relevance of standing variation that is likely to be masked by inference approaches based on static population sampling, or insufficiently resolved time-series data. We propose such fine-scaled temporally fluctuating selection may be an important force maintaining functional genetic variation in natural populations and an important stochastic force affecting levels of standing genetic variation genome-wide.

Enhanced external counter pulsation: the Howard County experience in the first 18 patients.

Enhanced external counter pulsation is a noninvasive therapy that uses sequentially inflated pneumatic cuffs on the lower extremities to enhance coronary artery diastolic flow and decrease left ventricular afterload. We studied its effect on 18 patients with persistent angina despite maximal medical, surgical and catheter-based interventions. After enhanced external counter pulsation all subjects improved their functional class. Treatment with enhanced external counter pulsation improved functional class significantly from baseline 3.1 +/- 0.6 to 1.6 +/- 0.5 (p < .001). These results are consistent with the national experience. Growing physician awareness, recent Medicare approval status, and subsequent reimbursement will hopefully increase the use of this therapy.

Cat scratch encephalopathy.

Cat scratch disease is usually a self-limited illness associated with tender lymph nodes, fever, malaise, and fatigue. Lymphadenopathy usually resolves spontaneously within three to four months. Cat scratch disease can be atypical as indicated by the presentation of our patient.

Bird fanciers' lung: a case report.

The clinical course of a case of bird fanciers' lung is described along with the considerations that are important in the management of this form of hypersensitivity pneumonitis. Diagnostic parameters, therapeutic considerations, and environmental issues are discussed in the context of the current literature.

Skin cancer detection and prevention: a community program promoting sun safe behaviors.

New cases of skin cancer will be diagnosed over one million times in the United States in 1999. Basal and squamous cell types can cause significant cosmetic morbidity. Malignant melanoma can cause serious morbidity and mortality. Thus, early detection and prevention efforts are crucial for all skin cancers. Studies have identified genetic, hereditary, and environmental factors associated with increased risk of developing skin cancer. In this article, the incidence and risk factors are reviewed. The Howard County Skin Cancer Awareness Project, established in 1996, is presented as a community based program that aims to increase public awareness about the prevention and early detection of skin cancer. Future directions are also addressed.

Persistent isolation of an unusual Pseudomonas species from a phenolic disinfectant system.

A well-characterized unusual Pseudomonas species contaminated the piped disinfectant system of a newly-opened laminar air flow intensive care facility. This organism was frequently isolated (10(4)-10(6) cfu/ml) from phenolic diluted 1:256 in the system, and could also be recovered (0.01-0.2 cfu/ml) from undiluted phenolic. During the 20-month period when this unusual Pseudomonas was present, none of the severely compromised, granulocytopenic oncology patients treated in the intensive care facility were either colonized or infected with this Pseudomonas sp. Eradication of the organism from the system proved difficult and was accomplished by removing a contaminated reservoir of diluted phenolic disinfectant followed by transient cleansing of the system with very high concentrations (84,000 ppm) of chlorine. This experience demonstrates that phenolics should be added to the list of disinfectants which can harbor Pseudomonas spp. in the clinical setting.