Androgen receptor mRNA expression in Xenopus laevis CNS: Sexual dimorphism and regulation in laryngeal motor nucleus

Using Northern analysis, in situ hybridization, and nuclease protection assays, the expression and regulation of androgen receptor messenger RNA (AR mRNA) was examined in the CNS of juvenile Xenopus laevis. Only one of the AR mRNA isoforms expressed in X. laevis is transcribed in the CNS as shown by Northern blot analysis. Nuclease protection assays demonstrate that the expression of AR mRNA is higher in the brain stem than in the telencephalon and diencephalon. Although expression of AR mRNA is widespread throughout the CNS, cells of cranial nerve nucleus IX-X (N. IX-X) and spinal cord display the highest in situ hybridization signals in their cytoplasm. Double labeling using horseradish peroxidase and digoxigenin labeled AR probes reveals that laryngeal and anterior spinal cord motor neurons express AR mRNA. More cells express AR mRNA in N. IX-X of males than of females. The number of AR expressing cells in N. IX-X decreases following gonadectomy in both sexes, and dihydrotestosterone (DHT) treatment for 1 month reverses this effect. Increased expression of AR mRNA in the brain of DHT treated animals is also apparent in nuclease protection assays. Sex differences in number of AR expressing cells and hormone regulation of AR mRNA expression in motor nuclei may influence neuromuscular systems devoted to sexually differentiated behaviors. © 1996 John Wiley & Sons, Inc.     

Rice Resistance to Brown Spot Mediated by Nitrogen and Potassium

This study was undertaken to investigate the effects of both nitrogen (N) and potassium (K) rates on rice resistance to brown spot, caused by the fungus Bipolaris oryzae. Rice plants (cultivar ‘Metica 1’) were grown in soil corrected with 0, 25, 50, 75 and 100 mg of N / kg (as NH₄NO₃) of soil as well as with 25, 50, 75, 125 and 150 mg of K / kg (as KCl) of soil. Thirty‐three‐day‐old plants were inoculated with a suspension of Bipolaris oryzae conidia and the incubation period (IP), number of lesions (NL) per cm² of leaf area and disease severity was evaluated. Disease severity was scored at 24, 48, 72, 96, 120 and 144 h after inoculation and data were used to obtain the area under brown spot progress curve (AUBSPC). Soil plant analysis development (SPAD) index, plant dry weight and concentration of N and K in leaf tissues were also determined for both non‐inoculated (NI) and inoculated (IN) plants. Concentration of N in leaf tissue increased as the N rates in the soil increased. Concentration of K in leaf tissue increased sharply as the K rates in the soil increased for both NI and IN plants. Concentration of K in leaf tissue was not affected by N rates. The IP increased as the N rates increased, but was somewhat less impacted by increasing K rates. The NL decreased as the N rates increased. The NL dramatically declined at the highest K rates. The AUBSPC dramatically declined as the N and K rates in the soil increased. SPAD index values increased as the N and K rates in the soil increased for both NI and IN plants. Plant dry weight increased as the N and K rates in the soil increased for both NI and IN plants. Results from this study suggest that combining high N and K rates may contribute to reducing the intensity of brown spot in rice while improving plant development.     

Plant patch structure modifies parasitoid assemblage richness of a specialist herbivore

1. The spatial structure of plant patches has been shown to affect host–parasitoid interactions, but its influence on parasitoid diversity remains largely ignored. Here we tested the prediction that parasitoid species richness of the specialist leafminer Liriomyza commelinae increases in larger and less isolated patches of its host plant Commelina erecta. We also explored whether parasitoid abundance and body size affected the occurrence of parasitoid species in local assemblages. 2. A total of 893 naturally established C. erecta patches were sampled on 18 sites around Córdoba city (Argentina). Also, two experiments were performed by creating patches differing in the number of plants and the distance from a parasitoid source. For these tests, plants were infected with the miner in the laboratory prior to placement in the field. 3. Plant patch size, independently of host abundance, positively affected the number of parasitoid species in both survey observations and experimental data. However, plant patch isolation did not influence parasitoid species richness. 4. The probability of finding rare parasitoid species increased with patch size, whereas occupation of isolated patches was independent of dispersal abilities (body size) of parasitoid species. 5. Overall, the results highlight the importance of considering spatial aspects such as the size of plant patches in the study of parasitoid communities.     

Successful lateral transfer requires codon usage compatibility between foreign genes and recipient genomes

We present evidence supporting the notion that codon usage (CU) compatibility between foreign genes and recipient genomes is an important prerequisite to assess the selective advantage of imported functions, and therefore to increase the fixation probability of horizontal gene transfer (HGT) events. This contrasts with the current tendency in research to predict recent HGTs in prokaryotes by assuming that acquired genes generally display poor CU. By looking at the CU level (poor, typical, or rich) exhibited by putative xenologs still resembling their original CU, we found that most alien genes predominantly present typical CU immediately upon introgression, thereby suggesting that the role of CU amelioration in HGT has been overemphasized. In our strategy, we first scanned a representative set of 103 complete prokaryotic genomes for all pairs of candidate xenologs (exported/imported genes) displaying similar CU. We applied additional filtering criteria, including phylogenetic validations, to enhance the reliability of our predictions. Our approach makes no assumptions about the CU of foreign genes being typical or atypical within the recipient genome, thus providing a novel unbiased framework to study the evolutionary dynamics of HGT.     

Changes in public order after the opening of a medically supervised safer injecting facility for illicit injection drug users

Background

North America''s first medically supervised safer injecting facility for illicit injection drug users was opened in Vancouver on Sept. 22, 2003. Although similar facilities exist in a number of European cities and in Sydney, Australia, no standardized evaluations of their impact have been presented in the scientific literature.

Methods

Using a standardized prospective data collection protocol, we measured injection-related public order problems during the 6 weeks before and the 12 weeks after the opening of the safer injecting facility in Vancouver. We measured changes in the number of drug users injecting in public, publicly discarded syringes and injection-related litter. We used Poisson log-linear regression models to evaluate changes in these public order indicators while considering potential confounding variables such as police presence and rainfall.

Results

In stratified linear regression models, the 12-week period after the facility''s opening was independently associated with reductions in the number of drug users injecting in public (p < 0.001), publicly discarded syringes (p < 0.001) and injection-related litter (p < 0.001). The predicted mean daily number of drug users injecting in public was 4.3 (95% confidence interval [CI] 3.5–5.4) during the period before the facility''s opening and 2.4 (95% CI 1.9–3.0) after the opening; the corresponding predicted mean daily numbers of publicly discarded syringes were 11.5 (95% CI 10.0–13.2) and 5.4 (95% CI 4.7–6.2). Externally compiled statistics from the city of Vancouver on the number of syringes discarded in outdoor safe disposal boxes were consistent with our findings.

Interpretation

The opening of the safer injecting facility was independently associated with improvements in several measures of public order, including reduced public injection drug use and public syringe disposal.Many cities are experiencing epidemics of bloodborne diseases as a result of illicit injection drug use,^1,2,3 and drug overdoses have become a leading cause of death in many urban areas.^4,5,6 Public drug use also plagues many inner city neighbourhoods, and the unsafe disposal of syringes in these settings is a major community concern.^{7,8,9,10,11,12,13}In over 2 dozen European cities and, more recently, in Sydney, Australia, medically supervised safer injecting facilities, where injection drug users (IDUs) can inject previously obtained illicit drugs under the supervision of medical staff, have been established in an effort to reduce the community and public health impacts of illicit drug use.¹⁴ Inside these facilities IDUs are typically provided with sterile injecting equipment, emergency care in the event of overdose, as well as primary care services and referral to addiction treatment.^13,15 Although anecdotal reports have suggested that such sites may improve public order,¹² reduce the number of deaths from overdose¹⁶ and improve access to care,¹⁷ no standardized evaluations of their impact are available in the scientific literature.¹⁸On Sept. 22, 2003, health officials in Vancouver opened a government-sanctioned safer injecting facility as pilot project. The facility, the first in North America, is centrally located in Vancouver''s Downtown Eastside, which is the most impoverished urban neighbourhood in Canada and home to well-documented overdose and HIV epidemics among the estimated 5000 IDUs who reside there.^19,20 Federal approval for the 3-year project was granted on the condition that the health and social impacts of the facility be rigorously evaluated. Although evaluation of the facility''s impact on certain outcomes (e.g., HIV incidence) is ongoing and will take several years, it is now possible to examine the impacts of the site on public order. Therefore, we conducted this study to test the hypothesis that changes in improperly discarded syringes and public drug use would be observed after the opening of the safer injecting facility.     

Progressive iron accumulation induces a biphasic change in the glutathione content of neuroblastoma cells

Glutathione (GSH) constitutes the single most important antioxidant in neurons, whereas iron causes oxidative stress that leads to cell damage and death. Although GSH and iron produce opposite effects on redox cell status, no mechanistic relationships between iron and GSH metabolism are known. In this work, we evaluated in SH-SY5Y neuroblastoma cells the effects of iron accumulation on intracellular GSH metabolism. After 2 d exposure to increasing concentrations of iron, cells underwent concentration-dependent iron accumulation and a biphasic change in intracellular GSH levels. Increasing iron from 1 to 5 microM resulted in a marked increase in intracellular oxidative stress and increased GSH levels. Increased GSH levels were due to increased synthesis. Further increases in iron concentration led to significant reduction in both reduced (GSH) and total (GSH + (2 x GSSG)) glutathione. Cell exposure to high iron concentrations (20-80 microM) was associated with a marked decrease in the GSH/GSSG molar ratio and the GSH half-cell reduction potential. Moreover, increasing iron from 40 to 80 microM resulted in loss of cell viability. Iron loading did not change GSH reductase activity but induced significant increases in GSH peroxidase and GSH transferase activities. The changes in GSH homeostasis reported here recapitulate several of those observed in Parkinson's disease substantia nigra. These results support a model by which progressive iron accumulation leads to a progressive decrease in GSH content and cell reduction potential, which finally results in impaired cell integrity.