UV-induced interstrand cross-linking of d(GT)n.d(CA)n is facilitated by a structural transition

Photochemical alterations following ultraviolet irradiation of the alternating copolymer d(GT)n.d(CA)n were studied. We found that in solution conditions which produced circular dichroism spectra compatible with B-form or A-form DNA, no interstrand cross-linking or photoproduct formation could be demonstrated. Zimmer et al. (Zimmer, C., Tymen, S., Marck, C., and Guschlbaumer, W. (1982) Nucleic Acids Res. 10, 1081-1091) and Vorlickova et al. (Vorlickova, M., Kypr, J., Sotkrova, S., Sponar, J. (1982) Nucleic Acids Res. 10, 1071-1080) have reported a number of solution conditions which produce a structural transition of this polymer characterized by a negative deviation of the circular dichroism spectrum in the region of 280 nm. The nature of this transition has not yet been elucidated. Following ultraviolet irradiation of d(GT)n.d(CA)n under two conditions which produce this transition (manganese solution or ethanol plus trace salts solution) we found ultraviolet dose-dependent interstrand cross-linking as well as dose-dependent formation of thymine-containing photoproduct. Interstrand cross-linking is demonstrated by two criteria: increase in polymer size as detected by alkaline agarose gel electrophoresis, and generation of intermediate density material in alkaline cesium sulfate isopycnic gradients. The thymine-containing photo-product was demonstrated by thin layer chromatography of acid hydrolysates of the polymer. The photo-product is at least partially photoreversible. These findings suggest that the geometry of the alternative conformation is such that pyrimidines from different strands are closely approximated, allowing for photodimerization.     

Influence of broth dilution on the disruption of Escherichia coli

Summary The effect of cell concentration (5 to 150 g/L wet wt after broth dilution) on homogenizer disruption efficiency and homogenate viscosity is reported for E. coli. Broth dilution increases homogenizer efficiency and decreases feed and homogenate viscosity. However, this increase in disruption efficiency is not sufficient to warrant dilution of the broth prior to homogenization. The optimal feed concentration is the maximum possible that does not lead to practical handling difficulties due to high viscosity.     

Steinernema diaprepesi n. sp. (Rhabditida: Steinernematidae), a Parasite of the Citrus Root Weevil Diaprepes abbreviatus (L) (Coleoptera: Curculionidae)

A nematode collected from Diaprepes abbreviatus is identified and described as a new species, Steinernema diaprepesi n. sp. The new species is closely related to S. feltiae, S. glaseri, and S. oregonense and can be distinguished from these species by the following characteristics: Males: Spicule averaging 79 (71-90) µm and spicule shape; D% (distance from anterior end to excretory pore/ esophagus length × 100) about 80; the ratio SW (spicule length/anal body width) about 1.8. Females: Vulva with short, double- flapped epiptygma; tail terminus usually with 5 papillae-like structures. Infective juveniles: Body averaging 1,002 (880-1,133) µm, EP (distance from anterior end to excretory pore) = 74 (66-83) µm; tail length = 83 (65-91) µm, and E% (EP/tail length × 100) = 89.6 (78-114). Lateral field pattern variable, the formula for the arrangement of ridges from head to tail is: 2, 6, 7, 8, 4, 2. The portion with eight ridges is the longest. This new species can be differentiated further from three closest species (S. feltiae, S. glaseri, and S. oregonense) by characteristic sequences of their ITS regions, including sequence lengths, ratios of similarity, composition, and differences in base characters in sequence alignment.     

Lipid-Based Nanocarriers via Nose-to-Brain Pathway for Central Nervous System Disorders

Neurochemical Research - Neurodegenerative disorders are distinguished by the gradual deterioration of the nervous system’s structure and function due to oxidative stress, mitochondrial...     

Oncogenic Notch Promotes Long-Range Regulatory Interactions within Hyperconnected 3D Cliques

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Monitoring in vivo changes in lung microstructure with ³He MRI in Sendai virus-infected mice

Recently, a Sendai virus (SeV) model of chronic obstructive lung disease has demonstrated an innate immune response in mouse airways that exhibits similarities to the chronic airway inflammation in human chronic obstructive pulmonary disease (COPD) and asthma, but the effect on distal lung parenchyma has not been investigated. The aim of our study is to image the time course and regional distribution of mouse lung microstructural changes in vivo after SeV infection. (1)H and (3)He diffusion magnetic resonance imaging (MRI) were successfully performed on five groups of C57BL/6J mice. (1)H MR images provided precise anatomical localization and lung volume measurements. (3)He lung morphometry was implemented to image and quantify mouse lung geometric microstructural parameters at different time points after SeV infection. (1)H MR images detected the SeV-induced pulmonary inflammation in vivo; spatially resolved maps of acinar airway radius R, alveolar depth h, and mean linear intercept Lm were generated from (3)He diffusion images. The morphometric parameters R and Lm in the infected group were indistinguishable from PBS-treated mice at day 21, increased slightly at day 49, and were increased with statistical significance at day 77 (p = 0.02). Increases in R and Lm of infected mice imply that there is a modest increase in alveolar duct radius distal to airway inflammation, particularly in the lung periphery, indicating airspace enlargement after virus infection. Our results indicate that (3)He lung morphometry has good sensitivity in quantifying small microstructural changes in the mouse lung and that the Sendai mouse model has the potential to be a valid murine model of COPD.     

A novel pollen-specific α-tubulin in sunflower: structure and characterization

We describe here a new -tubulin isoform from sunflower we named -tubulin. -tubulin is the most divergent higher-plant -tubulin described so far, having an unusual deletion in the H1/B2 loop and a glutamine-rich C-terminus. We constructed a three-dimensional model and discuss its implications. Using specific antibodies, we show that -tubulin expression is restricted to the male gametophyte. -tubulin mRNA represents 90% of -tubulin mRNA and a small percentage of total pollen mRNA. Among the plants tested, -tubulin was only detected in sunflower and in Cosmos. Since both plants are Asteraceae, we propose that -tubulin is specific to this family. Our results suggest that -tubulin can inhibit tubulin assembly in pollen. This hypothesis is reinforced by the fact that -tubulin is found in a complex with -tubulin in mature sunflower pollen.     

ARSENIC CHEMISTRY AND REMEDIATION IN HAWAIIAN SOILS

Past use of arsenical pesticides has resulted in elevated levels of arsenic (As) in some Hawaiian soils. Total As concentrations of 20–100 mg/kg are not uncommon, and can exceed 900 mg/kg in some lands formerly planted with sugarcane. With high contents of amorphous aluminosilicates and iron oxides in many Hawaii's volcanic ash-derived Andisols, a high proportion (25–30%) of soil As was associated with either these mineral phases or with organic matter. Less than 1% of the total As was water soluble or exchangeable. Furthermore, the soils can sorb As strongly: the addition of 1000 mg/kg as As (+5) resulted in only between 0.03 and 0.30 mg/L As in soil solution. In contrast, soils having more crystalline minerals (e.g., Oxisols) sorb less As and thus often contain less As. Phosphate fertilization increases As bioaccessibility, whereas the addition of Fe(OH)₃ decreases it. Brake fern (Pteris vittata L.) can be used to remove some soil As. Concentrations of As in fronds varied on average from 60 mg/kg when grown on a low-As Oxisol to 350 mg/kg when grown on a high-As Andisol. Ratios of leaf As to CaCl₂-extractable soil As were 12 and 222 for the Oxisol and Andisol, respectively.