Chemical, physical, and biological attributes in soils affected by deposition of iron ore tailings from the Fundão Dam failure

Monitoring degraded areas is essential for evaluation of the quality of the rehabilitation process. In this study, we evaluate how the physical and chemical characteristics of the mixture of iron ore tailings with the soil have affected the soil microbial biomass and activity in areas along the Gualaxo do Norte River after the Fundão Dam disaster. Composite soil samples were collected from areas that were impacted (I) and not impacted (NI) by the tailings. The following attributes were evaluated: chemical element content; soil density, porosity, and texture; microbial biomass carbon; basal respiration; and enzyme activity and density of microbial groups (bacteria, actinobacteria, fungi, arbuscular mycorrhizae, phosphate solubilizers, cellulolytic microorganisms, nitrifiers, ammonifiers, and diazotrophs). According to result, the deposition of tailings increased the pH and the soil available P, Cr, Fe, and Mn content and reduced organic matter. The physical and biological attributes were negatively affected, with increases in the silt content and density of the soil, and reduction in macroporosity and in the microbial biomass and activity of the soil (respiration and enzymes) in the impacted area. However, the impacted areas exhibited greater densities of some microbial groups (cellulolytic microorganisms, nitrifiers, and diazotrophic bacteria). Modifications in the organic matter and silt content are the main attributes associated with deposition of the tailings that affected soil microbial biomass and microbial activity. This may affect erosive conditions and the functionality of the ecosystem, indicating an imbalance in this environment. In contrast, the higher density of some microbial groups in the impacted areas show the high rehabilitation potential of these areas.

Environmental drivers of shifts on microbial traits in sites disturbed by a large-scale tailing dam collapse

This study aimed to assess the most affected traits related to microbial ecophysiology and activity and investigate its relationships with environmental drivers in mine tailings spilled from the Fundão dam at disturbed sites across Gualaxo do Norte river, Minas Gerais, Brazil. The mine tailings are characterized by increased pH value, silt percentage, and bulk density, while clay percentage, organic carbon (C_org), total nitrogen (Nt), and moisture contents are reduced. Microbial biomass, enzymatic activities (arylsulfatase, β-1,4-glucosidase, acid and alkaline phosphatases), and the total microbial activity potential (FDA hydrolysis) were generally lower in tailings compared to undisturbed reference soil (Und). Enzyme-based indexes (GMea, WMean, and IBRv2) showed microbial communities with significantly lower degradative efficacy in the tailings than Und in all sites (R² ≥ 0.94, p < 0.001). Non-metric multidimensional scaling and distance-based redundancy analysis revealed that microbial communities exhibited significant differentiation (R² adjusted = 0.73, p = 0.0001) between mine tailings and Und over the different studied sites, which was strongly influenced by changes on physicochemical properties (pH, C_org and Nt contents, the predominance of small-sized particles of silt, and bulk density) and the presence of Se, Cr, Fe, and Ni, even at low concentrations. Our study suggests that the physicochemical properties and the presence of low bioavailable concentrations of heavy metals in dam tailings promote shifts on microbial communities through reductions in the C storage and biogeochemical cycling of nutrients by these communities compared to those in undisturbed reference soils surrounding and, therefore, has negative implications for the ecosystem functioning.

Head-to-head comparison of dipyridamole, dobutamine and pacing stress echocardiography for the detection of myocardial ischemia in an animal model of coronary artery stenosis

To compare the sensitivity of dipyridamole, dobutamine and pacing stress echocardiography for the detection of myocardial ischemia we produced a physiologically significant stenosis in the left circumflex artery of 14 open-chest dogs (range: 50 to 89% reduction in luminal diameter). In each study, dobutamine (5 to 40 microg kg(-1) min(-1) in 3-min stages) and pacing (20 bpm increments, each 2 min, up to 260 bpm) were performed randomly, and then followed by dipyridamole (up to 0.84 mg/kg over 10 min). The positivity of stress echocardiography tests was quantitatively determined by a significant (P<0.05) reduction of or failure to increase absolute and percent systolic wall thickening in the stenotic artery supplied wall, as compared to the opposite wall (areas related to the left anterior descending artery). Systolic and diastolic frozen images were analyzed off-line by two blinded observers in the control and stress conditions. The results showed that 1) the sensitivity of dobutamine, dipyridamole and pacing stress tests was 57, 57 and 36%, respectively; 2) in animals with positive tests, the mean percent change of wall thickening in left ventricular ischemic segments was larger in the pacing (-19 +/- 11%) and dipyridamole (-18 +/- 16%) tests as compared to dobutamine (-9 +/- 6%) (P = 0.05), but a similar mean reduction of wall thickening was observed when this variable was normalized to a control left ventricular segment (area related to the left anterior descending artery) (pacing: -16 +/- 7%; dipyridamole: -25 +/- 16%; dobutamine: -26 +/- 10%; not significant), and 3) a significant correlation was observed between magnitude of coronary stenosis and left ventricular segmental dysfunction induced by ischemia in dogs submitted to positive stress tests. We conclude that the dobutamine and dipyridamole stress tests showed identical sensitivities for the detection of myocardial ischemia in this one-vessel disease animal model with a wide range of left circumflex artery stenosis. The pacing stress test was less sensitive, but the difference was not statistically significant. The magnitude of segmental left ventricular dysfunction induced by ischemia was similar in all stress tests evaluated.

Immunophenotype of normal and leukemic bone marrow B-precursors in a Brazilian population. A comparative analysis by quantitative fluorescence cytometry

The distinction between normal and leukemic bone marrow (BM) B-precursors is essential for the diagnosis and treatment monitoring of acute lymphoblastic leukemia (ALL). In order to evaluate the potential use of quantitative fluorescence cytometry (QFC) for this distinction, we studied 21 normal individuals and 40 patients with CD10+ ALL. We characterized the age-related changes of the CD10, CD19, TdT, CD34 and CD79a densities in normal and leukemic BM. Compared to normal adults, the B-precursors from normal children expressed significantly lower values of CD34-specific antibody binding capacity (SABC) (median value of 86.6 vs 160.2 arbitrary units (a.u.) in children and adults, respectively). No significant age-related difference was observed in the expression of the other markers in the normal BM, or in any of the markers in the leukemic BM. Based on the literature, we set the cut-off value for the normal CD10 expression at 45 x 10(3) a.u. for both age groups. For the remaining markers we established the cut-off values based on the minimum-maximum values in the normal BM in each age group. The expression of CD10 was higher than the cut-off in 30 ALL cases and in 18 of them there was a concomitant aberrant expression of other markers. In 9 of the 10 CD10+ ALL with normal CD10 SABC values, the expression of at least one other marker was aberrant. In conclusion, the distinction between normal and leukemic cells by QFC was possible in 38/40 CD10+ ALL cases.

[Surgical treatment of dysphagia lusória]

Two cases of this anomaly, in women (26 and 49 years old), with symptoms of short duration (4 and 3 months) of dysphagia, regurgitation and esophagitis, without loss of weight, are presented. In both, the final diagnosis was made by mean of thoracic aortogram. Esophagoscopy realized only in the first patient, demonstrated the pulsatile esophageal compression. The first patient was operated on through a right cervical incision, made in the anterior border of the sternomastoid muscle. In the second, a partial sternotomy, combined with a right supraclavicular prolongation, was used. In both, the anomalous artery was taken from the aorta and behind the esophagus, and anastomosed to the right common carotid artery. The dysphagia disappeared in the second case, but persisted attenuated, in the first one. Manometric studies realized in the 3rd and 18th months postoperatively demonstrated an aperistaltic segment of the esophagus (between 4 and 7 cm from the superior sphincter).

Impairment of baroreflex control of the sinoatrial node after cardiac operations with extracorporeal circulation in man

The sensitivity of the baroreceptor reflex to transient hypertension was determined in 13 patients before (control) and after (72 hours) open cardiac operations with extracorporeal circulation (ECC). In all patients early postoperative values were appreciably decreased (p less than 0.01) as compared to the preoperative values. This decrease suggested severe impairment of baroreflex control of the sinoatrial node. These changes were not correlated with concurrent alterations in heart rate or systemic arterial, left atrial, or right atrial pressures. In addition, respiratory sinus node arrhythmia was absent in all subjects. In four patients, subsequent studies 4, 8, 10, and 12 months, respectively, after the operation revealed good recovery of baroreflex sensitivity and respiratory influences on beat-to-beat variation. No similar effects were observed in two patients studied before and after cardiac operations without ECC. It is possible that direct trauma to the nervous supply of the sinoatrial node is a major factor in that reversible dysfunction; in fact, in three patients evidence was obtained that while sinoatrial node responses were impaired, the reflex control of the atrioventricular region remained unaltered. These findings point to further impairment of the fine control of heart rate imposed by the conditions of cardiac operations with ECC in patients with previously curtailed cardiac reserve.

Intraoperative measurement of the orifice area in patients with mitral valve stenosis

This study was carried out in ten patients in order to compare results of mitral valve area evaluated by a new intraoperative technique and those provided by conventional hemodynamic methods. The results obtained correlated very well (r = 0.95) with values calculated by the Gorlin formula. Paired data checking were closer than 0.3 cm2 in all but one of patients with moderately severe mitral stenosis. It is concluded that the method for intraoperative measurement of the mitral valve area is simple, safe and reliable.

Change in liver blood flow and blood content in dogs during direct and reflex alteration of hepatic sympathetic nerve activity

A mean decrease of 60% in liver blood volume was recorded by a plethysmographic technique during electrical stimulation of the hepatic nerves in anesthetized, vagotomized dogs. A decrease in pressure in the vascularly isolated carotid sinus to 40 mm Hg, from a mean control of 144 mm Hg, decreased liver blood volume by a mean of 16%; arterial blood pressure increased by a mean of 77 mm Hg. Carotid sinus hypotension was accompanied by respective mean increases of 16% and 1.4% in hepatic arterial and portal venous blood flows, and of 45% and 22% in arterial and portal resistances. Increase in sinus pressure to 240 mm Hg increased liver blood volume by a mean of 20%; arterial blood pressure decreased by 90 mm Hg. Sinus hypertension was accompanied by respective mean decreased of 10% and 1.5% in hepatic arterial and portal venous blood flows, and of 44% and 18% in arterial and portal resistances. Interruption of afferent vagal traffic from cardiopulmonary receptors was maximally effective in decreasing liver blood volume at a carotid sinus pressure of 40 mm Hg and was ineffective at carotid sinus pressures greater than 160 mm Hg. Combined withdrawal of carotid and cardiopulmonary vasomotor inhibition decreased liver blood volume by 42%; of this 37% was due to the cardiopulmonary and 63% to the carotid baroreflex. The study showed the canine liver to function as a blood reservoir by active mobilization of a portion of its blood volume.

Blood reservoir function of dog spleen, liver, and intestine

The reflex decrease in blood volume of the spleen, the liver, and the intestine of vagotomized dogs was measured by plethysmographic techniques during bilateral carotid occlusion and moderate and severe hemorrhage. The volume of blood mobilized from each organ during carotid occlusion and moderate hemorrhage was from 6 to 30% of their respective blood volumes and from 55 to 81% during severe hemorrhage. In each experimental situation the spleen exhibited the greatest ability to release blood and the intestine, the least. During moderate hemorrhage (9 ml/kg) the spleen yielded a volume equal to 35% of the blood lost, the liver 14% and the intestine 7%. Comparable figures for severe hemorrhage were 26, 13, and 5%, respectively. This order of ranking the component regions of the splanchnic circulation with regard to function as a blood reservoir may be specific for the dog.