Tolerância ao alumínio em genótipos de cereais de inverno sob cultivo hidropônico e campo

The objective of this work was to determine the root growth capacity of 75 genotypes of small graine cereals in hydroponic culture under different aluminum concentrations, and to assess the relationship betwen the level of tolerance/sensitivity in hydroponic solution and the resistance/susceptibility index in the field. Barley, triticale, rye, wheat and Aegilops tauschii were evaluated in hydroponics, with Al3+ concentrations that varied between 0.5 (barley), 2 and 6 (triticale), 6 and 10 (rye) and 2 mg L-1 (wheat and Ae. tauschii). The experiments' designs were completely randomized. In the field trial, the same genotypes were assessed, except for Ae. tauschii, in soil with pH 4.4 and 4.85 adjusted to 1/2 and 1/4 of the SMP index. A score scale ranging from 0.5 (highly resistant) to 5 (highly susceptible) was used. A strong relationship between aluminum tolerance in hydroponics and resistance to blight in the field was observed. Cereals selection in hydroponic medium can be considered an efficient tool to support breeding programs for this characteristic.O objetivo deste trabalho foi determinar a capacidade de crescimento radicular de 75 genótipos de cereais de inverno em cultivo hidropônico, em diferentes concentrações de alumínio, avaliar a relação entre o grau de tolerância/sensibilidade, em solução hidropônica, e a resistência/suscetibilidade ao crestamento em campo. Os cereais cevada, triticale, centeio, trigo e Aegilops tauschii foram avaliados em hidroponia, com concentrações de Al3+ que variaram entre 0,5 (cevada), 2 e 6 (triticale), 6 e 10 (centeio) e 2 mg L-1 (trigo e Ae. tauschii). Os delineamentos experimentais foram inteiramente casualizados. Em campo, foram avaliados os mesmos genótipos, exceto Ae. tauschii, em solo com pH 4,4 e 4,85, corrigido a 1/2 e 1/4 do índice SMP. Utilizou-se uma escala de notas com variação de escores de 0,5 (altamente resistente) a 5 (altamente suscetível). Foi observada elevada relação entre a tolerância ao alumínio em hidroponia e a resistência ao crestamento em campo. A seleção de cereais em meio hidropônico pode ser considerada eficiente como ferramenta de apoio aos programas de melhoramento genético para essa característica

From a static to a dynamic concept of risk: the circadian epidemiology of cardiovascular events

A growing body of evidence substantiates that the occurrence of cardiovascular events in unevenly distributed in time, especially during the 24 h. These temporal patterns are indicative of temporal variation in the (1) pathophysiological mechanisms that trigger cardiovascular events and (2) physiological status of the cardiovascular system, which combine to give rise to 24 h and other periodicities in the susceptibility to disease. The classic assumption of epidemiologic studies is constancy (or homeostasis) in one's risk to disease during the 24 h, as well as other, time domains. However, we propose a new concept, that of chronorisk since it takes into account the temporal variability in the pathophysiological mechanisms and their reciprocal temporal interactions that lead to day-night and other time-dependent patterns in cardiovascular events. This chronobiological approach, which is expected to contribute new insight into the prognostic and therapeutic assessment of cardiovascular events, is worthy of broader application in cardiovascular and other fields of medicine and warrants further investigation

Seasonal variation in the occurrence of epistaxis

Several diseases have well-defined circadian or seasonal patterns. For example, in the United States, about 50% more acute myocardial infarctions occur during the winter than during the summer, whereas no seasonal variation is found in warmer regions. We conducted a prospective study in 1366 consecutive patients with epistaxis (mean [±SD] age 53 ± 22 years) who were seen in the emergency department of the St. Anna Hospital, in Ferrara, Italy, from January 1, 1992, to December 31, 1998. The total number of patients admitted each month, as well as the number of men, women, normotensive patients, and hypertensive patients were recorded, and rhythms analysis was performed by partial Fourier series. A significant annual rhythm, usually with a peak in January, was found in the total group of patients and in each subgroup (P<0.001 for all comparisons). There is no certain explanation for our findings. Dry air due to room heating could damage the prominent, thin-walled blood vessels responsible for epistaxis. In addition, the greater prevalence of upper respiratory infections during the winter is also likely to contribute to direct damage of the nasal mucosa

Oxidative stress in essential hypertension

A major cause for endothelial dysfunction in essential hypertension is decreased availability of nitric oxide (NO). Impairment in NO bioavailability is likely to be the consequence of multiple mechanisms affecting NO synthesis as well as NO breakdown. An alteration in the redox balance in endothelial cells leads to increased superoxide anion production and oxidative stress. This in turn not only exerts negative effects on vascular tone, but is also able to activate important mechanisms (such as platelet activity, leukocyte adhesion, vascular smooth muscle cell proliferation and expression of adhesion molecules) with an established central role in the pathogenesis of hypertensive target organ damage. As a consequence, a drug therapy able to restore NO availability in essential hypertensive patients would probably exert additional benefits, as compared to blood pressure lowering per se, in terms of prevention of target organ damage and improved prognosis of these patients. Unfortunately, as of today only the antagonists of the renin-angiotensin system and the calcium-channel blockers have shown some ability in this respect, whereas no longitudinal intervention study has been undertaken, so far, to prove that the restoration of NO bioavailability through an antihypertensive treatment may confer additional prognostic advantage to essential hypertensive patients

Circadian rhythmicity in the occurrence of spontaneous acute dissection and rupture of thoracic aorta

A circadian rhythm is observed for the first time in the occurrence of spontaneous acute dissection and rupture of thoracic aorta

Circadian rhythmicity in the occurrence of spontaneous acute dissection and rupture of thoracic aorta

A circadian rhythm is observed for the first time in the occurrence of spontaneous acute dissection and rupture of thoracic aorta

Relationships of the circadian rhythms of thrombotic, ischemic, hemorrhagic, and arrhythmic events to blood pressure rhythms

Convincing evidence has recently accumulated that several unfavorable cardiovascular events show a well defined pattern in their occurrence throughout the day. Myocardial angina and infarction, sudden cardiac death, arrhythmias, fatal pulmonary thromboembolism, and ischemic and hemorrhagic cerebrovascular accidents occur more frequently in the morning, after awaking, until noon. Diurnal variations in multiple biologic functions, such as assumption of an upright posture associated with increased platelet aggregability, changes in blood clotting, fibrinolysis, and vascular tone and resistance, may be potentially active triggering factors. Moreover, variations in sympathetic tone, catecholamine secretion, and blood pressure have to be considered. The role of triggering factors and their relationships with blood pressure patterns is discussed in view of an optimized pharmacologic treatment