Depsidone constituents from the quintaria group of Nephroma species

A new lichen depsidone was isolated, in the form of its triacetate derivative from the acetylated extracts of Nephroma antarcticum and has been demonstrated to be hypoconstictic acid-triacetate. Two related depsidones, hypostictic acid hyposalazinic acid, were isolated from N. australe.     

Site-specific integration of an F'' lac pro factor in the region of the replication origin (oriC) of E. coli

Summary An episome, F 128, which carries approximately 8x10⁴ base pairs of chromosomal DNA homologous to the lac pro region of the E. coli chromosome, has been found to integrate into the oriC region of the chromosome in a site specific reaction. While the event appears to be recA-dependent, no homology between the episome and this region of the chromosome was detected. The Hfr strains formed result from the integration of intact F 128 molecules. The structure of the Hfr strains generated has been determined and their transfer properties analyzed.     

Homology between the invertible deoxyribonucleic acid sequence that controls flagellar-phase variation in Salmonella sp. and deoxyribonucleic acid sequences in other organisms.

The invertible deoxyribonucleic acid (DNA) segment cloned from Salmonella sp. was radioactively labeled and used as a probe to search for homologous sequences by Southern hybridization. Only one copy of the invertible segment could be found on the Salmonella sp. genome. Partial sequence homology with the invertible region was detected in bacteriophage Mu and P1 DNA by low-stringency hybridization. Under these conditions, no homology was detected with Escherichia coli DNA. A strain of Salmonella sp. defective in phase variation carrying the vH2- allele was also analyzed by DNA-DNA hybridization. The results show that there is sequence divergence between diphasic and vH2- strains within the invertible sequence.     

Hydrogen peroxide causes the fatal injury to human fibroblasts exposed to oxygen radicals

Oxygen radicals are suspected as being a cause of the cellular damage that occurs at sites of inflammation. The phagocytic cells that accumulate in areas of inflammation produce superoxide, hydrogen peroxide, hydroxyl radical, and probably singlet oxygen in the extracellular fluid. The mechanism by which these oxygen molecules kill cells is unknown. To determine which of the oxygen species is responsible for the cellular killing, we exposed human fibroblasts in culture to oxygen radicals generated by the enzymatic action of xanthine oxidase upon acetaldehyde. Using the amount of chromium-51 released from labeled fibroblasts as an index of cellular death, we found that cells were protected only by interventions that reduce hydrogen peroxide concentration. Agents that inactivate superoxide, hydroxyl radical, and singlet oxygen were ineffective in limiting oxygen radical-induced cellular death.     

Restricted randomization designs in clinical trials.

Though therapeutic clinical trials are often categorized as using either "randomization" or "historical controls" as a basis for treatment evaluation, pure random assignment of treatments is rarely employed. Instead various restricted randomization designs are used. The restrictions include the balancing of treatment assignments over time and the stratification of the assignment with regard to covariates that may affect response. Restricted randomization designs for clinical trials differ from those of other experimental areas because patients arrive sequentially and a balanced design cannot be ensured. The major restricted randomization designs and arguments concerning the proper role of stratification are reviewed here. The effect of randomization restrictions on the validity of significance tests is discussed.     

HIGH AFFINITY CHOLINE UPTAKE: IONIC AND ENERGY REQUIREMENTS

Abstract— High affinity choline uptake into rat hippocampal synaptosomes was examined at 37°C when various ions were deleted from normal Kreb's-Ringer media. When sodium chloride was replaced by sucrose, lithium chloride, cesium chloride or rubidium chloride, choline uptake was markedly reduced. When the sodium concentrations of the Kreb's media were gradually reduced to zero, the uptake was gradually reduced in parallel. A kinetic analysis performed at low and normal sodium concentrations revealed changes in K_m and V^max values. When several non-chloride sodium salts were utilized, the uptake was reduced in all cases suggesting also a chloride-dependence in addition to the sodium-dependence. Omission of calcium chloride or magnesium sulfate from the media did not alter uptake. Sodium-dependent choline uptake was examined over a range of potassium concentrations (0–35 DIM). It was found that uptake was maximal between potassium concentrations of 0.35–4.8 mm but was reduced at both lower and higher potassium concentrations. The kinetics of uptake were examined under varying potassium concentrations, and at low potassium, only a change in V_max was observed while at high potassium concentrations, there were changes in both K^m and V^max values. Preincubation and incubation of synaptosomes with 0.1 m -ouabain, 0.1 mm -2,4-dinitrophenol and 1 mm -KCN caused a reduction in sodium-dependent uptake. When dextrose was omitted from the preincubation and incubation media there was also a reduction in sodium-dependent uptake. By contrast, the sodium-independent uptake was unaffected by the metabolic inhibitors or omission of dextrose, and had a very low Q₁₀. When various incubation temperatures were utilized in uptake experiments, the Q¹⁰ for the interval 37-27°C was 2.7 and the activation energy was 22.7 kcal/mol. Slightly different ionic dependences were observed when animals pretreated with pentobarbital of oentylenetetrazol were utilized as the source of synaptosomes.     

Cholesterol ester hydrolase in human red blood cells.

1. Cholesterol ester hydrolytic activity (sterol-ester hydrolase EC 3.1.1.13) was detected in human red blood cells. Enzyme activity appeared confined to the cell membrane and was most marked in washed preparations of red cell ghosts. 2. Hydrolytic activity was stimulated by the anti-oxidants D-alpha-tocopherol and butylated hydroxytoluene. Marked inhibition was produced by erythrocyte hemolysate, sodium taurocholate, and Triton X-100. 3. Optimal pH for the reaction was 5.4--5.7. 4. Because red cell cholesterol is all unesterified, it is speculated that the hydrolase serves to maintain the erythrocyte membrane free of esterified cholesterol.     

Global biogeography of warning coloration in the butterfly Danaus chrysippus

Warning coloration provides a textbook example of natural selection, but the frequent observation of polymorphism in aposematic species presents an evolutionary puzzle. We investigated biogeography and polymorphism of warning patterns in the widespread butterfly Danaus chrysippus using records from citizen science (n = 5467), museums (n = 8864) and fieldwork (n = 2586). We find that polymorphism in three traits controlled by known mendelian loci is extensive. Broad allele frequency clines, hundreds of kilometres wide, suggest a balance between long-range dispersal and predation of unfamiliar morphs. Mismatched clines for the white hindwing and forewing tip in East Africa are consistent with a previous finding that the black wingtip allele has spread recently in the region through hitchhiking with a heritable endosymbiont. Light/dark background coloration shows more extensive polymorphism. The darker genotype is more common in cooler regions, possibly reflecting a trade-off between thermoregulation and predator warning. Overall, our findings show how studying local adaptation at the global scale provides a more complete picture of the evolutionary forces involved.     

An ecological niche model to predict the geographic distribution of Haemagogus janthinomys,Dyar, 1921 a yellow fever and Mayaro virus vector,in South America

Yellow fever virus (YFV) has a long history of impacting human health in South America. Mayaro virus (MAYV) is an emerging arbovirus of public health concern in the Neotropics and its full impact is yet unknown. Both YFV and MAYV are primarily maintained via a sylvatic transmission cycle but can be opportunistically transmitted to humans by the bites of infected forest dwelling Haemagogus janthinomys Dyar, 1921. To better understand the potential risk of YFV and MAYV transmission to humans, a more detailed understanding of this vector species’ distribution is critical. This study compiled a comprehensive database of 177 unique Hg. janthinomys collection sites retrieved from the published literature, digitized museum specimens and publicly accessible mosquito surveillance data. Covariate analysis was performed to optimize a selection of environmental (topographic and bioclimatic) variables associated with predicting habitat suitability, and species distributions modelled across South America using a maximum entropy (MaxEnt) approach. Our results indicate that suitable habitat for Hg. janthinomys can be found across forested regions of South America including the Atlantic forests and interior Amazon.