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PubMed1985

Use of nifedipine to decrease ischemic-reperfusion injury in the surgical setting.

This report summarizes studies that provided a basis for a randomized clinical trial of nifedipine in cold hyperkalemic cardioplegic solution. Data from normothermic, isolated working rabbit heart studies demonstrated that presence of micromolar concentrations of nifedipine in the perfusate during continuous low flow or nifedipine used as bolus washouts during global ischemia prevented increases in systolic and diastolic stiffness, which could be related to dose and prevention of intracellular accumulation of calcium. Other studies in open-chest dogs in whom regional ischemia was produced showed that nifedipine was superior to sodium nitroprusside when infused during the ischemic and reperfusion intervals with respect to preservation of hemodynamic variables and reduction of myocardial injury. Further, data from cardiopulmonary bypass experiments in dogs conducted at myocardial temperatures of 37, 28, 18 and 12 degrees C with 1, 2 and 3 hours of global ischemia all demonstrated significant efficacy. To date, the randomized clinical trial has shown a small reduction in the incidence of low cardiac output syndrome in high-risk patients. Those receiving nifedipine had improved hemodynamic variables. No patient in the treated group had myocardial injury in the postoperative interval shown by radionuclide pyrophosphate scan. The conclusions from this trial are that nifedipine was efficacious when included in a cold hyperkalemic cardioplegic solution. The responses observed, however, appear to be dose-, vehicle- and species-dependent.

Animals↗
PubMed1989

Frequency and significance of complete atrioventricular block after coronary artery bypass grafting.

Three hundred forty-eight consecutive patients were evaluated during 1985 and 1986 for the development of complete atrioventricular (AV) block after coronary artery bypass grafting. Cold (4 degrees) asanguineous potassium cardioplegia with temperature monitoring was used uniformly. AV block developed in 56 instances (16%). In 32 patients (group 1) the block was transient (less than 6 hours) and in 24 it was persistent (group 2). Left main coronary artery stenosis in conjunction with total obstruction of a dominant right coronary artery occurred more commonly in patients manifesting AV block (18 of 56, 32%) than in those without it (35 of 292, 12%) (p less than 0.05). Complete occlusion of a dominant right coronary artery was observed with equal frequency in patients with and without AV block. The presence of an ungraftable right coronary artery, however, was significantly more frequent in the AV block group: 16 of 37 (47%) vs 6 of 194 (3%) (p less than 0.01). Endarterectomy of the right coronary artery was performed in 8 of 24 patients (33%) with persistent AV block versus none in the patients with transient AV block (n = 32) or normal sinus rhythm postoperatively (n = 292) (p less than 0.0001). Persistent AV block (greater than 6 hours) was associated with myocardial infarction in 6 patients (25%) (p less than 0.05) and with low cardiac output in 18 patients (75%) (p less than 0.0001). In conclusion, AV block after myocardial revascularization was frequently associated with the presence of multivessel coronary disease and an ungraftable dominant right coronary artery. Persistent (greater than 6 hours) AV block was correlated with both perioperative myocardial infarction and low cardiac output.

Aged↗
PubMed1976

Recurrent nephrolithiasis: natural history and effect of phosphate therapy. A double-blind controlled study.

In a double-blind controlled clinical study, 71 patients with recurrent calcium oxalate stones were divided into three treatment groups: those who received potassium acid phosphate, those who received an inert placebo, and those who received a low calcium diet only. Follow-up periods averaged 2.9 years. Although the mean urinary calcium level of the patients who received phosphate was reduced 33 per cent, their renal stone disease did not diminish. Mean urinary phosphorus increased 88 per cent with phosphate treatment but did not correlate with the decrease in urinary calcium, or with treatment success. The data did not suggest that phosphorus and its metabolites retard calcium oxalate crystallization in urine. No evidence appeared for an association of hypercalciuria with severe stone disease, or with a specific clinical or chemical response to phosphate therapy. Patients whose urinary calcium level fell more than 25 percent when dietary calcium was reduced may have excessive gastrointestinal calcium absorption, which appears to be associated with improved chemical response to phosphate therapy.

Adult↗
PubMed1985

Calcofluor and ink-potassium hydroxide preparations for identifying fungi.

Calcofluor and ink-potassium hydroxide preparations identified Fusarium solani, Aspergillus fumigatus, and Candida albicans, the three most common ocular fungal pathogens, in scrapings, biopsy specimens, and tissue sections of corneal mycotic infections in rabbits. These stains also identified fungal organisms in specimens from four human patients with keratomycoses. Neither procedure requires more than a few minutes to perform or extensive training or experience to interpret. The specimen stained with calcofluor can be examined immediately, but may not identify all fungi. The more sensitive ink-potassium hydroxide preparation should be examined after 18 to 24 hours, and is less likely to provide false-positive results than the calcofluor method.

Animals↗
PubMed1983

A method for concentration of nucleoside triphosphates by coprecipitation with calcium fluoride.

A method for concentration of nucleoside triphosphates (NTP) is described. NTPs are quantitatively coprecipitated from the solution with calcium fluoride. The precipitate is separated by filtration through a membrane filter and NTPs are dissolved from the filter by immersing it in 0.5 N H2SO4. With this method also nucleoside diphosphates can be efficiently concentrated, but the method does not work with nucleoside monophosphates or cyclic AMP.

Adenosine Monophosphate↗
PubMed1984

Protein adsorbents intended for use in aqueous two-phase systems.

Preparation of adsorbents with high partition coefficients in polyethylene glycol-dextran and polyethylene glycol-phosphate systems is described. These adsorbents may be used to carry to carry proteins away from the insoluble cell fragments generated during cell disruption. By chromatographic elution, proteins may be selectively desorbed in a reduced volume.

Adsorption↗
PubMed1984

A simple micromethod for rapid kinetic analyses of yeast enzymes in situ.

A simple approach for rapid assay of enzymes in large numbers of samples of whole cells of yeast is described. The technique involves treatment of yeast cells with toluene dissolved in ethanol (1:4, v/v; TE), rendering them selectively permeable to small molecules, while letting the enzymes remain intracellular and catalytically active but accessible to exogenously added assay reagents. The permeated cell preparations permit rapid assay of nitrate reductase activity in situ [P. V. Choudary and G. Ramananda Rao (1976) Current Sci. 45, 324-327]. Investigation of enzyme kinetic parameters such as pH optima, temperature dependence, and substrate saturation, which involves several samples and needs to be investigated very rapidly and accurately, is greatly facilitated by permeated cells prepared from a very small culture of cells, eliminating the need for elaborate preparations of cell extracts. By using permeabilized cell preparations, the need to supplement the reaction mixture with expensive cofactors can also be obviated to a large extent. Further, the enzyme activity displays a broader range of tolerance in situ to variations in reaction conditions compared to that in vitro. Permeabilized cell preparations thus seem to present the enzymes in the form of relatively less disintegrated functional complexes, making them a valuable tool in biochemical and cell biological investigations, and facilitate the correlation of in vitro data with the in vivo phenomena more confidently.

Candida↗
PubMed1985

Matrix modifiers in graphite furnace atomic absorption analysis of trace lithium in biological fluids.

The use of KH2PO4/NH4NO3 as matrix modifier eliminates severe interference effects on the atomic absorption analysis of lithium in biological fluids. This enables determination of trace lithium in microliter size samples with absolute sensitivity (0.0044 absorbance) of 2 pg. There is no requirement for standard additions experiments to correct for interferences in specific matrices such as serum and saliva. The biological half-life of trace lithium was 16.9 +/- 2.8 h. Saliva lithium is a good estimate of serum level; the two are highly correlated (r = 0.97) and saliva level is about three times serum.

Adult↗
PubMed1988

Assay of cholesterol 7 alpha-hydroxylase activity in rat hepatocytes in primary monolayer culture.

A sensitive and precise method is described to assay cholesterol 7 alpha-hydroxylase activity in homogenates of rat hepatocytes cultured in monolayers for up to 76 h. The assay is based on measurement of the amount of radioactive cholesterol converted into 7 alpha-[14C]-hydroxycholesterol. Since no subcellular fractionation was applied to measure enzyme activity, this method is rapid and can be performed with cell protein, corresponding to as little as 1 to 2 million hepatocytes. Optimal assay conditions were determined and the reproducibility of this cholesterol 7 alpha-hydroxylase determination was established. Exogenous cholesterol (105 microM), solubilized in Tween 80, was added to saturate the enzyme, giving an apparent Km of 56 microM. Under these conditions, 70% of the cholesterol present in the homogenates is directly accessible to the cholesterol 7 alpha-hydroxylase. The detection limit of the assay was found to be about 10 pmol per incubation. A time course of the cholesterol 7 alpha-hydroxylase activity in cultured hepatocytes revealed that after an initial loss of approximately 60% of the activity as compared with 287 pmol/h/mg for freshly isolated cells, the enzyme activity was increased to the initial level in hepatocytes cultured for 52 h. This result and the finding that the cholesterol 7 alpha-hydroxylase activity was diminished by 94% after a 24-h incubation with 5 microM cycloheximide suggest that the enzyme activity is associated with de novo protein synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Sulfate composition of glycosaminoglycans determined by infrared spectroscopy.

Anhydrous sodium sulfate (Na2SO4) was analyzed at varying concentrations by infrared (ir) spectroscopy. A standard curve was obtained from a linear plot of sulfate (SO2-(4] concentration vs the weight of the ir band area of S = O stretching. Standard chondroitin 4-sulfate, chondroitin 6-sulfate, heparan sulfate, heparin, keratan sulfates, and various dermatan sulfates isolated from human and rat skins were also studied by ir spectroscopy. The spectrum of every glycosaminoglycan (GAG) displayed an ir band around 1230 cm-1 which originated from S = O stretching of sulfate esters. Therefore, the weight of the latter band was employed to quantify sulfate, by using the standard curve indicated above. Sulfate was also estimated quantitatively by the gelatin/BaCl2 method of K.S. Dodgson and R.G. Price (Biochem. J. 1962, 84, 106-110). The sulfate composition determined by ir spectroscopy ranged from 8.5 to 22.1% (w/w), and agreed closely with the values obtained chemically. In the ir spectroscopy method, sulfate was determined using the polymer forms of the GAGs. After analysis, these heteropolysaccharides were recovered unaffected in a yield greater than 95%. The data show that the infrared spectroscopy technique, in addition to being sensitive and reliable, is much more economical than the chemical procedures currently employed to quantify GAG sulfate.

Bromides↗
PubMed1989

Effect of cold cardioplegic solution and hypothermia on response to acetylcholine in perfused epicardial coronary artery of pig.

The effect of cold cardioplegic solution and hypothermia on the response to acetylcholine, a major postganglionic neurotransmitter of the parasympathetic nervous system, was studied using perfused epicardial coronary arteries of pigs. Cold crystalloid cardioplegic solution (5 degrees C) and hypothermia including topical cooling with slushed ice significantly augmented the coronary flow reduction by acetylcholine at one and two hours after rewarming. Cold Krebs-Henseleit solution (5 degrees C) with hypothermia showed similar effects. However, cardioplegic solution at 37 degrees C did not affect the responsiveness. The coronary flow reduction induced by potassium chloride (60 mmol/L) did not change even after the administration of cold cardioplegic solution (5 degrees C) or cold Krebs-Henseleit solution (5 degrees C), indicating that cooling did not necessarily augment the coronary contractile response generally. It is concluded that cooling and subsequent rewarming can potentiate the contractile response of the coronary artery of the pig to acetylcholine. This suggests that cold cardioplegic solution with hypothermia can promote intraoperative coronary spasm upon activation of the parasympathetic nervous system.

Acetylcholine↗
PubMed1990

Preservation of myocardial function and biochemistry after blood and oxygenated crystalloid cardioplegia during cardiac arrest.

We compared the ability of blood cardioplegia and oxygenated crystalloid cardioplegic solutions to maintain regional left ventricle contractility and adenosine triphosphate levels after cardiopulmonary bypass. Ten baboons were subjected to 90-minute cardiopulmonary bypass conducted at 28 degrees C. Hemodynamic measurements were made before and after the bypass procedure, and biopsies for high-energy phosphate determinations were performed at different time intervals during and after bypass. The results showed improved maintenance of myocardial contractility (measured with the regional end-systolic pressure-length relationship) with the oxygenated crystalloid solution. Expressed as a percentage of values before bypass, contractility after bypass averaged 81.69% +/- 4.81% and 80.47% +/- 10.05%, respectively, after 10 and 20 minutes using the oxygenated crystalloid cardioplegia. For blood cardioplegia, the corresponding values were 71.9% +/- 8.73% and 64.99% +/- 8.60% (mean +/- standard error of the mean). The 10- and 20-minute postbypass values between the two groups differed significantly (t test, Welch modification: p = 0.0464 and p = 0.0342). Myocardial adenosine triphosphate level was higher immediately after induction of cardiac arrest when blood cardioplegia was used (blood cardioplegia, 6.82 mol.g wet wt-1; crystalloid cardioplegia, 4.95 mol.g wet wt-1; p = 0.0314), but values subsequently equalized.

Adenosine Triphosphate↗
PubMed1992

Initial experience with low-potassium cold blood cardioplegia: a clinical comparative study.

This study presents the results of bypass grafting in 96 patients operated on for triple-vessel coronary artery disease between May 1988 and September 1990. In the first 54 patients a cold crystalloid solution was employed, and in the 42 more recent patients cold blood low-potassium cardioplegia was employed. There were no differences in postoperative cardiac index or left ventricular stroke work index. Yet, in patients with impaired prebypass left ventricular stroke work index, postbypass left ventricular performance correlated negatively with duration of aortic cross-clamping in the cold crystalloid group (r = -0.441, p = 0.045). In contrast, no correlation was found in the cold blood low-potassium group (r = 0.125, p = 0.587). The incidence of myocardial infarction, need for inotropic support, and need for intraaortic balloon counterpulsation were similar among the groups. Release of the myocardial isoenzyme creatine kinase-MB from 12 to 30 hours after operation was significantly less in the low-potassium blood cardioplegia group. The use of low-potassium blood cardioplegia resulted in a marked reduction in the operative administration of fluids (1,527 +/- 87 versus 3,511 +/- 148 mL; p less than 0.001). In conclusion, low-potassium cold blood cardioplegia is a simple and effective method of myocardial protection. The fact that left ventricular stroke work index recovery was not dependent on the duration of aortic occlusion and that release of the MB isoenzyme of creatine kinase was reduced in the low-potassium blood cardioplegia group implies better myocardial protection.

Adult↗
PubMed1993

Effects of pressure and duration of hyperkalemic infusions on endothelial function.

Infusions of crystalloid hyperkalemic cardioplegic solutions (CHCSs) are known to impair endothelium-dependent coronary relaxation. This impairment might also be influenced by high perfusion pressure and duration of CHCS infusion. To verify this hypothesis, we designed experiments to study the influence of pressure and duration of CHCS infusion as modulating factors in CHCS-related endothelial impairment. Isolated hearts of Sprague-Dawley rats were studied in a Langendorff apparatus for coronary endothelial function. Hearts (n = 6) were exposed to four different CHCSs containing 12, 24, 40, or 100 mmol/L of potassium chloride (KCl). Endothelial and smooth muscle functions were respectively tested by infusion of 5-hydroxytryptamine (1 x 10(-6) mol/L) and sodium nitroprusside (1 x 10(-5) mol/L) before and after CHCS perfusion. In group I (n = 24), 37 degrees C CHCSs were perfused at 80 cm H2O of pressure for 30 minutes. In group II (n = 24), the same CHCSs were perfused at 160 cm H2O for 30 minutes. In group III (n = 18), CHCSs containing 24, 40, and 100 mmol/L of KCl were infused at 160 cm H2O for 10 minutes. In all groups, response to sodium nitroprusside was unaltered by CHCS infusion, indicating that smooth muscle function was preserved. However, in group II, 5-hydroxytryptamine-induced vasodilation was significantly impaired in hearts perfused with CHCS containing 24 mmol/L of KCl or more, suggesting endothelial damage. This study demonstrates that, in addition to KCl concentration, pressure and duration of infusion are two major determinants in CHCS-mediated endothelial damage.

Animals↗
PubMed1993

Lidocaine cardioplegia for prevention of reperfusion ventricular fibrillation.

Lidocaine addition to crystalloid cardioplegic solution for prevention of reperfusion ventricular fibrillation after the release of the aortic cross-clamp was studied in 50 patients undergoing coronary artery bypass grafting and in 30 patients undergoing mitral or aortic valve replacement. Twenty-six of the patients undergoing coronary artery bypass grafting received lidocaine, 100 mg/L of cardioplegia, whereas a control group of 24 patients received cardioplegia without lidocaine. In the group undergoing valve replacement, 14 patients received lidocaine cardioplegia and 16 patients served as control. In the coronary artery bypass grafting group, lidocaine cardioplegia reduced significantly the incidence of reperfusion ventricular fibrillation from 100% to 42%. In the valve group, lidocaine cardioplegia also reduced significantly the incidence of reperfusion ventricular fibrillation from 93% to 42%. In both groups, lidocaine cardioplegia decreased the number of direct-current countershocks required to defibrillate the heart, with no significant increase in the incidence of high-grade atrioventricular block.

Cardioplegic Solutions↗