Retinal fractals and acute lacunar stroke

This study aimed to determine whether retinal fractal dimension, a quantitative measure of microvascular branching complexity and density, is associated with lacunar stroke. A total of 392 patients presenting with acute ischemic stroke had retinal fractal dimension measured from digital photographs, and lacunar infarct ascertained from brain imaging. After adjusting for age, gender, and vascular risk factors, higher retinal fractal dimension (highest vs lowest quartile and per standard deviation increase) was independently and positively associated with lacunar stroke (odds ratio [OR], 4.27; 95% confidence interval [CI], 1.49–12.17 and OR, 1.85; 95% CI, 1.20–2.84, respectively). Increased retinal microvascular complexity and density is associated with lacunar stroke. ANN NEUROL 2010;68:107–111     

Cloning and characterization of DNA polymerase η from Trypanosoma cruzi: Roles for translesion bypass of oxidative damage

We report the cloning and characterization of the DNA polymerase η gene from Trypanosoma cruzi (TcPolη), the causative agent of Chagas disease. This protein, which can bypass cyclobutane pyrimidine dimers, contains motifs that are conserved between Y family polymerases. In vitro assays showed that the recombinant protein is capable of synthesizing DNA in undamaged primer‐templates. Intriguingly, T. cruzi overexpressing TcPolη does not increase its resistance to UV‐light (with or without caffeine) or cisplatin, despite the ability of the protein to enhance UV resistance in a RAD30 mutant of Saccharomyces cerevisiae. Parasites overexpressing TcPolη are also unable to restore growth after treatment with zeocin or gamma irradiation. T. cruzi overexpressing TcPolη are more resistant to treatment with hydrogen peroxide (H₂O₂) compared to nontransfected cells. The observed H₂O₂ resistance could be associated with its ability to bypass 8‐oxoguanine lesions in vitro. The results presented here suggest that TcPolη is able to bypass UV and oxidative lesions. However the overexpression of the gene only interferes in response to oxidative lesions, possibly due to the presence of these lesions during the S phase. Environ. Mol. Mutagen. 2009. © 2009 Wiley‐Liss, Inc.     

Seizures in the Jamaica cohort study of sickle cell disease

Although there is some evidence that epilepsy is more common in Sickle Cell Disease (SCD), we sought to establish the incidence rates, risk factors for and specific types of seizures in a SCD cohort followed from birth, and how seizure occurrence affects morbidity and mortality . We examined all records of persons in the Jamaica cohort Study of Sickle Cell Disease (JSSCD) clinically identified as having experienced a seizure during their lifetime. At first presentation, seizures were classified as Febrile Convulsion, Acute Symptomatic Seizure or Single Unprovoked Seizure. The seizure classification was revised to include Epilepsy if seizures recurred. Thirty‐eight persons in the JSSCD (N = 543) were identified with seizures. The 5‐year cumulative incidence of febrile convulsions was 2·2%. The incidence rate of epilepsy (all genotypes) was 100/100 000 person‐years, 139/100 000 for the SS genotype. Despite limited availability of diagnostic investigations, clinical seizures were associated with increased all‐cause mortality. Male gender (Odds Ratio [OR]: 4·0[95% confidence interval [CI]; 1·03–20·0]) and dactylitis in childhood (OR: 17·4 [95% CI; 4·82–62·85]) were associated with increased risk of developing epilepsy. Epilepsy in persons with SCD is 2–3 times more common than in non‐sickle populations and is associated with increased all‐cause mortality in all sickle cell genotypes.     

Effects of Technical-Grade Active Ingredient vs. Commercial Formulation of Seven Pesticides in the Presence or Absence of UV Radiation on Survival of Green Frog Tadpoles

Commercial formulations of pesticides contain both active and other ingredients. In some instances, the other ingredients have detrimental effects on nontarget species. Other factors such as UV radiation and predator cues have been shown to modify the toxicity of pesticides. In a laboratory study we compared the effects of technical-grade active ingredients to commercial formulations of seven common pesticides in the presence or absence of UV radiation on the survival of Rana clamitans (green frog) tadpoles over 96 h. We found a significant difference in the survival of tadpoles in technical-grade active ingredients versus commercial formulations in all of the pesticides tested. We also found that either the presence or the absence of UV radiation affected the survival of tadpoles in five of the seven pesticides tested. These results suggest that there is a need to test the effects of both active ingredients and commercial formulations of pesticides and, also, to include relevant abiotic factors like UV radiation treatments in the testing of pesticides because they can have a dramatic impact on the toxicity of some chemicals.     

Propulsion of African trypanosomes is driven by bihelical waves with alternating chirality separated by kinks

Trypanosoma brucei, a parasitic protist with a single flagellum, is the causative agent of African sleeping sickness. Propulsion of T. brucei was long believed to be by a drill-like, helical motion. Using millisecond differential interference-contrast microscopy and analyzing image sequences of cultured procyclic-form and bloodstream-form parasites, as well as bloodstream-form cells in infected mouse blood, we find that, instead, motility of T. brucei is by the propagation of kinks, separating left-handed and right-handed helical waves. Kink-driven motility, previously encountered in prokaryotes, permits T. brucei a helical propagation mechanism while avoiding the large viscous drag associated with a net rotation of the broad end of its tapering body. Our study demonstrates that millisecond differential interference-contrast microscopy can be a useful tool for uncovering important short-time features of microorganism locomotion.