Dynamic expression of Ralstonia solanacearum virulence factors and metabolism-controlling genes during plant infection.

BACKGROUND: Ralstonia solanacearum is the causal agent of bacterial wilt, a devastating plant disease responsible for serious economic losses especially on potato, tomato, and other solanaceous plant species in temperate countries. In R. solanacearum, gene expression analysis has been key to unravel many virulence determinants as well as their regulatory networks. However, most of these assays have been performed using either bacteria grown in minimal medium or in planta, after symptom onset, which occurs at late stages of colonization. Thus, little is known about the genetic program that coordinates virulence gene expression and metabolic adaptation along the different stages of plant infection by R. solanacearum. RESULTS: We performed an RNA-sequencing analysis of the transcriptome of bacteria recovered from potato apoplast and from the xylem of asymptomatic or wilted potato plants, which correspond to three different conditions (Apoplast, Early and Late xylem). Our results show dynamic expression of metabolism-controlling genes and virulence factors during parasitic growth inside the plant. Flagellar motility genes were especially up-regulated in the apoplast and twitching motility genes showed a more sustained expression in planta regardless of the condition. Xylem-induced genes included virulence genes, such as the type III secretion system (T3SS) and most of its related effectors and nitrogen utilisation genes. The upstream regulators of the T3SS were exclusively up-regulated in the apoplast, preceding the induction of their downstream targets. Finally, a large subset of genes involved in central metabolism was exclusively down-regulated in the xylem at late infection stages. CONCLUSIONS: This is the first report describing R. solanacearum dynamic transcriptional changes within the plant during infection. Our data define four main genetic programmes that define gene pathogen physiology during plant colonisation. The described expression of virulence genes, which might reflect bacterial states in different infection stages, provides key information on the R. solanacearum potato infection process.

Cardiotoxicity of environmental contaminant tributyltin involves myocyte oxidative stress and abnormal Ca2+ handling.

Tributyltin (TBT) is an organotin environmental pollutant widely used as an agricultural and wood biocide and in antifouling paints. Countries began restricting TBT use in the 2000s, but their use continues in some agroindustrial processes. We studied the acute effect of TBT on cardiac function by analyzing myocardial contractility and Ca2+ handling. Cardiac contractility was evaluated in isolated papillary muscle and whole heart upon TBT exposure. Isolated ventricular myocytes were used to measure calcium (Ca2+) transients, sarcoplasmic reticulum (SR) Ca2+ content and SR Ca2+ leak (as Ca2+ sparks). Reactive oxygen species (ROS), as superoxide anion (O2•-) was detected at intracellular and mitochondrial myocardium. TBT depressed cardiac contractility and relaxation in papillary muscle and intact whole heart. TBT increased cytosolic, mitochondrial ROS production and decreased mitochondrial membrane potential. In isolated cardiomyocytes TBT decreased both Ca2+ transients and SR Ca2+ content and increased diastolic SR Ca2+ leak. Decay of twitch and caffeine-induced Ca2+ transients were slowed by the presence of TBT. Dantrolene prevented and Tiron limited the reduction in SR Ca2+ content and transients. The environmental contaminant TBT causes cardiotoxicity within minutes, and may be considered hazardous to the mammalian heart. TBT acutely induced a negative inotropic effect in isolated papillary muscle and whole heart, increased arrhythmogenic SR Ca2+ leak leading to reduced SR Ca2+ content and reduced Ca2+ transients. TBT-induced myocardial ROS production, may destabilize the SR Ca2+ release channel RyR2 and reduce SR Ca2+ pump activity as key factors in the TBT-induced negative inotropic and lusitropic effects.

Malnutrition and brain function: experimental studies using the phenomenon of cortical spreading depression.

Depending on its intensity and duration, nutritional deficiency can disrupt the structure and function of the nervous system of humans and other mammals, with consequences more or less devastating for the whole organism, particularly in the early postnatal life, when body growth is very rapid and the need for proteins, calories and other nutrients is greatest. In this review, electrophysiological data are presented regarding the use of the phenomenon of cortical spreading depression (CSD) to study effects of malnutrition on the brain. Several conditions of clinical importance and that are known to alter brain function are shown also to influence CSD features in experimental animals. Some of these conditions, (e.g., pharmacological manipulation of neurotransmitter systems, dietary treatment with Lithium, acute hyperglycemia, hypothyroidism, aging and environmental stimulation) decrease CSD susceptibility, while other conditions increase it, as, for example, systemic reduction of extracellular chloride levels, deprivation of REM-sleep, acute hypoglycemia, treatment with diazepam, consumption of ethanol and malnutrition. Particular emphasis is laid on the effect of early environmental enrichment on CSD in normal and malnourished animals. Our results suggest that such effect is more evident in the malnourished brain, as compared to the well-nourished one. The data also show that malnutrition alters the brain responsivity to some CSD-facilitatory or inhibitory agents. The underlying mechanisms to explain the observed effects are discussed.

[Oncologic pathology at an internal medicine service]. / Patologia oncológica num serviço de medicina interna.

A retrospective survey of the patients with oncological disease admitted to our Department of Internal Medicine in 1987 was conducted to determine its prevalence and to draw a descriptive profile of these patients' admissions. The results show that oncological diseases were the second cause of hospital admissions that year (12%) only exceeded by cardiovascular diseases. About 60% of the patients had neoplasms already diagnosed elsewhere and were admitted for complications or with therapeutic purposes; in 40% of cases the disease was diagnosed in our Department. A wide variety of hematological and non-hematological tumors was found. There were some difficulties in interdisciplinary coordination in the diagnostic and therapeutic approach. More than 50% of the patients had advanced disease, limiting medical intervention to supportive measures. In about 60% of them were oriented to primary care physicians after physicians after discharged from Hospital. These results suggest the dispersion of the available resources for the diagnosis, treatment and follow-up of oncological diseases in our population. A better cancer patients' assistance in Portugal will depend on the promotion of national cancer registers as well as the improvement of cancer prevention and early detection programs, according to the directives of EEC and WHO. We also emphasize the need of investment on undergraduate and postgraduate education programs, specially for primary care physicians.