Heart attacks, heart rate, and gel electrodes: the invention of ambulatory cardiology

Ambulatory cardiology began in 1959 in a department of pathology to answer a question raised at the autopsy table: are high heart rates in apparently healthy individuals a risk factor for developing coronary artery disease? This question led to the development of a miniature monitor and a new kind of electrode, which enabled clinicians to measure EKG signals during activity and over prolonged periods of time. These electrodes are now used universally for diagnosis and for monitoring the heart during a myriad of different activities and circumstances. The story of the development of the monitor and electrodes illustrates the ways in which ideas and discovery lead to applications and advances in medicine.     

Analysis of cedar pollen time series: no evidence of low-dimensional chaotic behavior

Much of the current interest in pollen time series analysis is motivated by the possibility that pollen series arise from low-dimensional chaotic systems. If this is the case, short-range prediction using nonlinear modeling is justified and would produce high-quality forecasts that could be useful in providing pollen alerts to allergy sufferers. To date, contradictory reports about the characterization of the dynamics of pollen series can be found in the literature. Pollen series have been alternatively described as featuring and not featuring deterministic chaotic behavior. We showed that the choice of test for detection of deterministic chaos in pollen series is difficult because pollen series exhibit power spectra. This is a characteristic that is also produced by colored noise series, which mimic deterministic chaos in most tests. We proposed to apply the Ikeguchi–Aihara test to properly detect the presence of deterministic chaos in pollen series. We examined the dynamics of cedar (Cryptomeria japonica) hourly pollen series by means of the Ikeguchi–Aihara test and concluded that these pollen series cannot be described as low-dimensional deterministic chaos. Therefore, the application of low-dimensional chaotic deterministic models to the prediction of short-range pollen concentration will not result in high-accuracy pollen forecasts even though these models may provide useful forecasts for certain applications. We believe that our conclusion can be generalized to pollen series from other wind-pollinated plant species, as wind speed, the forcing parameter of the pollen emission and transport, is best described as a nondeterministic series that originates in the high dimensionality of the atmosphere.     

Mitotic Recombination in Yeast: Isolation and Characterization of Mutants with Enhanced Spontaneous Mitotic Gene Conversion Rates

Semi-dominant mutants displaying greatly elevated (up to 200-fold above control) levels of spontaneous mitotic recombination have been isolated in a disomic haploid strain of yeast heteroallelic at the arg4 locus. They are designated by the symbol MIC. The mutants variously exhibit associated sensitivity to UV and ionizing radiation and to methyl methanesulfonate, enhanced UV-induced mitotic recombination, and enhanced spontaneous forward mutation rates. Possible enzyme defects and involvement in repair and editing of DNA are discussed. The mutants are expected to simplify the analysis of recombination pathways in yeast.     

Ecology and Physics of Bacterial Chemotaxis in the Ocean

Summary: Intuitively, it may seem that from the perspective of an individual bacterium the ocean is a vast, dilute, and largely homogeneous environment. Microbial oceanographers have typically considered the ocean from this point of view. In reality, marine bacteria inhabit a chemical seascape that is highly heterogeneous down to the microscale, owing to ubiquitous nutrient patches, plumes, and gradients. Exudation and excretion of dissolved matter by larger organisms, lysis events, particles, animal surfaces, and fluxes from the sediment-water interface all contribute to create strong and pervasive heterogeneity, where chemotaxis may provide a significant fitness advantage to bacteria. The dynamic nature of the ocean imposes strong selective pressures on bacterial foraging strategies, and many marine bacteria indeed display adaptations that characterize their chemotactic motility as “high performance” compared to that of enteric model organisms. Fast swimming speeds, strongly directional responses, and effective turning and steering strategies ensure that marine bacteria can successfully use chemotaxis to very rapidly respond to chemical gradients in the ocean. These fast responses are advantageous in a broad range of ecological processes, including attaching to particles, exploiting particle plumes, retaining position close to phytoplankton cells, colonizing host animals, and hovering at a preferred height above the sediment-water interface. At larger scales, these responses can impact ocean biogeochemistry by increasing the rates of chemical transformation, influencing the flux of sinking material, and potentially altering the balance of biomass incorporation versus respiration. This review highlights the physical and ecological processes underpinning bacterial motility and chemotaxis in the ocean, describes the current state of knowledge of chemotaxis in marine bacteria, and summarizes our understanding of how these microscale dynamics scale up to affect ecosystem-scale processes in the sea.     

Growth and age determination of the tropical Australian cubozoan Chiropsalmus sp.

Chiropsalmus sp. medusae collected in this study ranged from 3 to 71 mm diagonal bell width and displayed growth best described by the following equation size (mm) = 74.9 × exp (−exp(0.041 (time since metamorphosis (day) −35.6674))). Growth rates of up to 7 mm week⁻¹ increase in diagonal bell width are theoretically possible, with animals able to reach sexual maturity in approximately 70 days. Correlation of the number of rings on the statoliths with the predicted age of the individual from the field produced a relationship that indicates the growth rings are laid down daily and as such could be used to infer age of the medusae. Over the 1998–1999 season, there were four influxes of juvenile cohorts, each occurring approximately 14 days after a major rainfall event.