Nitric oxide supplementation alleviates ammonium toxicity in the submerged macrophyte Hydrilla verticillata (L.f.) Royle.

The likely protective effects of nitric oxide (NO) against ammonium toxicity were investigated in the submerged macrophyte Hydrilla verticillata. The plants were subjected to ammonium stress (3mM ammonium chloride) in the presence of sodium nitroprusside (SNP, 10 µM), an NO donor. Treatment with SNP significantly increased the NO content and partially reversed the ammonium-induced negative effects, including membrane damage and the decrease in levels of chlorophyll, malondialdehyde, glutathione and ascorbic acid. Further, SNP application increased the catalytic activities of ascorbate peroxidase, superoxide dismutase, guaiacol peroxidase, catalase and glutathione S-transferase, but decreased that of NADH-oxidase. Histochemical staining showed that SNP application caused a significant decrease in the levels of superoxides and hydrogen peroxide. In contrast, application of other breakdown products of SNP (10 µM sodium ferrocyanide, 10 µM sodium nitrite and 10 µM sodium nitrate) failed to show any protective effect. The results suggest that the increased intracellular NO, resulting from SNP application, improved the antioxidant capacity of H. verticillata plants in coping with ammonium-induced oxidative stress.

Modificación de un método para colinesterasa plasmática empleando la reducción del ferricianuro como indicador / Modification in the method for serum cholinesterase in ferricyanide reduction how indicatory

Se describe la modificación de un método para la cuantificación de colinesterasa plasmática mediante monitoreo continuo empleando ferricianuro como indicador. La tiocolina liberada de la propioniltiocolina reduce el ferricianuro a ferrocianuro y la disminición de absorbancia a 405 nm es proporcional a la actividad de la enzima. Las precisiones día a día para muestras con valores de colinesterasa bajos y altos mostraron coeficientes de variación de 3,2 y 1,2 por ciento y en un mismo día de 1,1 y 0,52 por ciento respectivamente. La bilirrubina no presenta una interferencia importante y cada 50mg/dL de hemoglobina producen una interferencia de -4 por ciento. El reactivo de ferricianuro almacenado en botella ámbar es estable por al menos 3 meses a temperatura ambiente y 6 meses a 4-8 §C. Al comparar los resultados con un método que emplea la reacción de Ellman se obtuvo una ecuación de regresión lineal de Y = 1,22 (X) - 732, con un coeficiente de correlación (r) de 0,988 y una desviación estándar sobre la línea de regresión (Sy/x) de 378 U/L. (Rev Cost Cienc Med 1999; 20(1,2): 17-27) PALABRAS CLAVE: Colinesterasa sérica, organofosfatos, carbamatos, pesticidas, métodos colorimétrico, toxicología

A duodenal mucosal abnormality in the reduction of Fe(III) in patients with genetic haemochromatosis.

BACKGROUND: Previous in vitro studies have shown that the uptake of Fe(III) by freshly isolated duodenal mucosal biopsy specimens is increased in patients with genetic haemochromatosis. Moreover, in the mouse it has recently been found that reduction of Fe(III) to Fe(II) is a prerequisite for iron uptake by the proximal intestine. AIMS/METHODS: This study used the in vitro technique to investigate the rates of reduction and uptake of 59Fe(III) by duodenal mucosal biopsy specimens obtained at endoscopy from treated and untreated patients with genetic haemochromatosis. RESULTS: The rate of reduction of iron in the medium was proportional to the incubation time and was not caused by the release of reducing factors from the tissue fragments. Ferrozine, a specific Fe(II) chelator and ferricyanide, a non-permeable oxidising agent, inhibited uptake of 59Fe showing that reduction of Fe(III) precedes uptake. The rates (all values given as pmol/mg/min) of reduction (152 (49) v 92 (23)) and uptake (8.3 (4.0) v 3.6 (1.3), mean (SD)), were significantly increased in biopsy specimens from the untreated group (n = 6) compared with those from 10 control subjects (p < 0.04). Furthermore, the reduction and uptake rates were still increased in five patients in whom iron stores were normal after venesection treatment. CONCLUSIONS: These results show that there is a persistent abnormality in the reduction and uptake of iron by the intestine in genetic haemochromatosis.

Intravenous infusions of nitroprusside, dobutamine, and nitroglycerin are compatible.

It is now customary practice to couple separately metered infusions via a manifold to a common catheter that enters the patient. Nitroprusside, however, is considered incompatible with all other medications. Critically ill patients who require multiple infusions of vasoactive and inotropic medications would benefit if physicians had additional information regarding compatibility of nitroprusside with other commonly used infusions. Utilizing high-performance liquid chromatography, the authors investigated the physical and chemical compatibility of nitroprusside, dobutamine, and nitroglycerin in solutions of 5% dextrose or 0.9% NaCl at clinically relevant concentrations. All drugs were present within the guidelines of the U.S. Pharmacopeia (+/- 10%) over 24 h in NaCl, but nitroglycerin degraded over 24 h when the three drugs were mixed in dextrose. We recommend diluting these medicines in NaCl when mixtures of them would exist for greater than 4 h.

Model reference adaptive control with constraints for postoperative blood pressure management.

This paper presents an approach for adaptive control of blood pressure using sodium nitroprusside. A modified stochastic model reference adaptive control algorithm with a time varying reference model is developed and used for this purpose. An automatic adjustment of the reference model is proposed in order to optimize the performance of the closed loop system while meeting clinical constraints imposed on the infusion rate and the mean arterial pressure. Extensive computer simulations show the robustness of the proposed controller in the presence of relatively high noise levels, over the full range of plant parameters and for large parameter variations.

Decay of nitroprusside. II: In vivo.

Clinical experience suggests that nitroprusside (SNP) concentrations decay more rapidly in vivo than in vitro. Plasma concentrations of SNP were measured therefore in 20 patients at the end of an infusion, with mean arterial pressure (MAP) and cyanide (HCN) concentrations. Plasma SNP concentrations (20-243 micrograms litre-1; mean = 123.5 micrograms litre-1), were related to infusion rate (r = 0.66, P less than 0.001), and declined rapidly to a mean (SD) of 7.7 (4.5) micrograms litre-1 in 15 min. The decay of SNP correlated closely with the increase in arterial pressure (mean MAP vs log mean plasma SNP concentrations: r = -0.993, P less than 0.001), and was probably biphasic: mean (SD) T1/2 alpha = 0.89 (0.62) min, T1/2 beta = 14.3 (12) min. Mean plasma HCN and mean plasma SNP concentrations decreased together (r = 0.955, P less than 0.001), thus confirming that in vivo decomposition of the drug is the source of HCN.

Real-time expert-system-based fuzzy control of mean arterial pressure in pigs with sodium nitroprusside infusion.

This paper deals with real-time fuzzy control of mean arterial pressure (MAP) in pigs by regulating the infusion rate of the vasodilator drug, sodium nitroprusside (SNP). The fuzzy controller was based on the parallel firing mode of a general-purpose Fuzzy LOgic Production System shell, FLOPS [2,3,16,20]. One of the major advantages of this fuzzy control drug delivery system over other existing automatic drug delivery systems is that the fuzzy control system may be designed by using experts' knowledge and experience without any explicit mathematical models involved. Mean arterial pressure in pigs was controlled satisfactorily in real-time by the fuzzy control system. It comes to the conclusion that it may be feasible to employ this fuzzy controller in the management of mean arterial pressure of patients clinically. Also, various applications of the fuzzy controller may exist in industry and in biomedical engineering.

[Sympatho-adrenergic reactions during drug-induced hypotension. A comparative study on probands]. / Sympatho-adrenerge Reaktionen bei medikamentös induzierter Hypotension. Eine vergleichende Studie an Probanden.

This study was undertaken to compare the influence of different regimens for induced hypotension down to Power a limit of 80 mmHg (systolic) on sympatho-adrenergic responses in 10 volunteers. Volunteers were investigated in five batteries of tests using glyceryl trinitrate (10 micrograms/kg BW/min), sodium nitroprusside (10 micrograms/kg BW/min maximal dosage), nifedipine (0.35 micrograms/kg BW/min) and urapidil (bolus injections of 25, 25 and 50 mg, followed by an infusion of 180 ml/h) and placebo. Catecholamines in plasma were detected by HPLC/ECD within a period of 1 h of hypotension and 1 h of recovery at 11 measuring points. Using sodium nitroprusside and glyceryl trinitrate, a significant hypotension was achieved. Urapidil was less potent. No hypotension was observed during or after treatment with nifedipine. Heart rate increased during treatment with sodium nitroprusside and glyceryl trinitrate. Sodium nitroprusside, glyceryl trinitrate and urapidil caused significant rises in noradrenaline levels. With nifedipine, noradrenaline increased within the normal range. Adrenaline left the normal range only during urapidil treatment. MAP, HR, and levels of noradrenaline and adrenaline returned to the initial values 5 min after discontinuation of the sodium nitroprusside infusion. After treatment with glyceryl trinitrate and urapidil, MAP was still low even 60 min after discontinuation of treatment. Urapidil caused marked increases in noradrenaline and adrenaline, which persisted even into the recovery phase. With regard to clinical management and sympatho-adrenergic responses, sodium nitroprusside is the most useful of these compounds for the reduction of hypotension. Having similar potency and active metabolites, glyceryl trinitrate has a longer duration of action.(ABSTRACT TRUNCATED AT 250 WORDS)

Repeated hypotension induced by nitroprusside and haemorrhage in sheep: effects on vasopressin release and recovery of arterial blood pressure.

The arginine vasopressin (AVP) release in response to repeated hypotension caused by intravenous (i.v.) infusion of sodium nitroprusside (SNP) or haemorrhage was studied in conscious euhydrated sheep. Parallel determinations of renal excretion and plasma concentration of AVP were made in experiments involving two consecutive 10-min i.v. infusions of SNP (about 35 micrograms kg-1 min-1) with a 3-h interval between and repeated the next day. The AVP response to the second SNP administration was significantly reduced, but partial recovery was observed in response to the initial infusion the next day. Maximal fall in mean arterial blood pressure (MABP) and its recovery pattern did not differ in response to any of the four SNP infusions. In contrast, impaired recovery of the MABP together with markedly reduced AVP response was seen as a consequence of a hypotensive haemorrhage repeated after 3 h, but not when the interval between haemorrhages was extended to 24 h. The haemorrhage-induced increase in plasma renin activity was not affected by variations in the interval between experiments. It is concluded that the massive AVP liberation normally seen as an effect of acute isovolaemic hypotension becomes markedly reduced upon a renewed fall in the MABP occurring within 3 h. An iteration of hypotensive haemorrhage accentuates this fatigue of the hormonal response, which may contribute to the impaired recovery of the MABP.

[The effect of urapidil and sodium nitroprusside on intrapulmonary right-left shunt and arterial oxygenation in the treatment of hypertension following coronary surgery]. / Der Einfluss von Urapidil und Natriumnitroprussid auf den intrapulmonalen Rechts-links-Shunt und die arterielle Oxygenation bei der Behandlung der Hypertonie nach koronarchirurgischen Eingriffen.

20 patients who developed arterial hypertension following coronary artery bypass grafting were randomly treated with either sodium nitroprusside (SNP) or urapidil. Both drugs led to a significant decrease in blood pressure. A significant tachycardia was noted only in the SNP-group. A decrease in peripheral and pulmonary vascular resistance was seen in both groups. Following application of SNP, alveolarterial oxygen difference and venous admixture increased significantly, whereas PaO2 showed a significant decrease. Three patients had to be taken out of the SNP group because of an increase of venous admixture. Alveoloarterial oxygen difference and venous admixture showed no significant changes following application of urapidil.

Automated control of postoperative hypertension: a prospective, randomized multicenter study.

Hypertension after a cardiac operation is a frequent phenomenon. Complications resulting from this include bleeding, disruption of vascular suture lines, subendocardial ischemia, and possible cerebrovascular accidents. Treatment with sodium nitroprusside has become accepted practice to prevent these complications. To improve control of arterial blood pressure, a closed-loop system for sodium nitroprusside administration was developed. A prospective, randomized multicenter study was carried out postoperatively in 180 cardiac surgical patients to evaluate the performance of this system compared with manual control of infusion. Adherence of mean arterial blood pressure to +/- 10% of the target blood pressure occurred 85% of the time with the automatic system and 61% of the time with manual regulation (p less than 0.0001). With the automatic system, there was less hypertension (9% versus 22%; p less than 0.0001) and hypotension (6% versus 22%; p less than 0.0001). The superior control of hypertension was achieved more rapidly with less requirement for nurse regulation of infusion rate. The superior control of blood pressure resulted in less chest tube drainage in the automatic mode (720 mL versus 840 mL; p less than 0.05).

[Vasodilator therapy utilizing nitroprusside and nitroglycerin after coronary artery surgery].

The hemodynamic effects of combined therapy utilizing sodium nitroprusside (SNP) and nitroglycerin (TNG) were compared with those of TNG therapy in patients who underwent coronary artery bypass grafting (CABG). Of 58 patients who received catecholamine infusion to maintain hemodynamics after CABG, 17 had perioperative myocardial infarction (PMI (+) cases) and the other 41 had not PMI (PMI (-) cases). 26 of 41 patients (PMI (-) cases) received nitroglycerin therapy (NTG group) and the other 15 patients received combined therapy (SNP + NTG group). 11 of 17 patients (PMI (+) cases) received NTG therapy and the other 6 patients received combined therapy. The hemodynamic valuables, which were studied, were as follows; cardiac index, stroke volume index, left ventricular stroke work index, systemic vascular resistance index, pulmonary vascular resistance index, and deep core temperature. SNP + TNG group revealed significantly lower systemic vascular resistance index and pulmonary vascular resistance index than TNG group in PMI (-) cases. In PMI (+) cases, SNP + TNG group revealed significantly higher cardiac index, stroke volume index, left ventricular stroke work index, and significantly lower pulmonary vascular resistance index than TNG group. These findings demonstrate that combined therapy can obtain more secure vasodilation than TNG therapy.

Alteration of intracranial pressure, cerebral blood flow, autoregulation and carbondioxide-reactivity by hypotensive agents in baboons with intracranial hypertension.

Intracranial pressure (ICP) was recorded by epidural transducer and cisterna magna catheter, and regional cerebral blood flow (rCBF) using the intraarterial Xenon 133-technique were measured in baboons with normal and during increased ICP provoked by an inflatable balloon positioned subdurally. Arterial blood pressure was altered by controlled infusion of Sodium-nitroprusside (SNP), Nitroglycerine (NG) or Trimetaphan (TMP) with the aim of reducing blood pressure by about 20%. During exflated balloon SNP provoked an increase of ICP which was more prominent than with NG and TMP. During increased ICP (due to inflation of the balloon) again SNP led to a higher further increase of ICP than both NG and TMP. rCBF rose during the state of normal ICP when SNP was infused. This was not observed with infusion of NG or TMP. When ICP was increased again by inflation of the balloon all 3 substances reduced rCBF, indicating damage to the autoregulation. CO2-reactivity as measured by induced hyperventilation with reduction of arterial CO2-tension was affected by all 3 substances thus indicating impairment of vasoconstriction during increase of ICP and simultaneous decrease of blood pressure. However, this impairment of physiological vasoconstriction was more prominent with SNP than with NG and TMP. The results indicate that all 3 substances should be used with care to reduce blood pressure during surgery or under intensive care condition, particularly in patients with increased ICP.

Automatic control of arterial pressure after cardiac surgery. Evaluation of a microcomputer-based control system using glyceryl trinitrate and sodium nitroprusside.

Arterial hypertension after cardiac surgery is common and is associated with increased morbidity. Glyceryl trinitrate may be a more suitable agent for control of hypertension than sodium nitroprusside. We have developed a closed-loop system for the Atari 1040ST microcomputer to control arterial pressure by the simultaneous infusion of two vasodilators under computer control. Use of this system with glyceryl trinitrate and sodium nitroprusside in 24 patients who required vasodilators after cardiopulmonary bypass, revealed that hypertension was controlled by glyceryl trinitrate alone in 14 of the patients and 10 required supplementary sodium nitroprusside. The results suggest that glyceryl trinitrate is a suitable agent for control of hypertension after cardiac surgery in the majority of patients. They also show that a sizeable minority required additional sodium nitroprusside, and that an automated 'dual pump' system is a satisfactory method of administering two vasodilators in this way.