Beyond Affymetrix arrays: expanding the set of known hybridization isotherms and observing pre-wash signal intensities

Microarray hybridization studies have attributed the nonlinearity of hybridization isotherms to probe saturation and post-hybridization washing. Both processes are thought to distort ‘true’ target abundance because immobilized probes are saturated with excess target and stringent washing removes loosely bound targets. Yet the paucity of studies aimed at understanding hybridization and dissociation makes it difficult to align physicochemical theory to microarray results. To fill the void, we first examined hybridization isotherms generated on different microarray platforms using a ribosomal RNA target and then investigated hybridization signals at equilibrium and after stringent wash. Hybridization signal at equilibrium was achieved by treating the microarray with isopropanol, which prevents nucleic acids from dissolving into solution. Our results suggest that (i) the shape of hybridization isotherms varied by microarray platform with some being hyperbolic or linear, and others following a power-law; (ii) at equilibrium, fluorescent signal of different probes hybridized to the same target were not similar even with excess of target and (iii) the amount of target removed by stringent washing depended upon the hybridization time, the probe sequence and the presence/absence of nonspecific targets. Possible physicochemical interpretations of the results and future studies are discussed.

p-Nitrophenol and glutathione response in medaka (Oryzias latipes) exposed to MX, a drinking water carcinogen

When chlorine is introduced into public drinking water for disinfection, it can react with organic compounds in surface waters to form toxic by-products such as 3-chloro-4-(dichloromethyl)-5-hydroxy-2[5H]-furanone (MX). We investigated the effect of exposure to MX on cytochrome P450 2E1 (CYP2E1)-like activity and total glutathione (GSH) in the liver of the small fish model, medaka (Oryzias latipes). The multi-site carcinogen methylazoxymethanol acetate (MAMAc) was the positive control compound. Both medaka liver microsome preparations and S-9 fractions catalyzed the hydroxylation of p-nitrophenol (PNP), suggesting CYP2E1-like activity in the medaka. Male medaka exposed for 96 h to the CYP2E1 inducers ethanol and acetone under fasted conditions showed significant increases in PNP-hydroxylation activity. Furthermore, total reduced hepatic GSH was reduced in fish fasted for 96 h, indicating that normal feeding is a factor in maintaining xenobiotic defenses. Exposure to MX and MAMAc induced significant increases in hepatic CYP2E1-like activity, however MX exposure did not alter hepatic GSH levels. These data strengthen the role of the medaka as a suitable species for examining cytochrome P450 and GSH detoxification processes and the role these systems play in chemical carcinogenesis.

Does heparin pretreatment affect the haemostatic system during and after cardiopulmonary bypass?

In this clinical pilot study, the influence of heparin pretreatment on the haemostatic system during and after cardiopulmonary bypass (CPB) was investigated. Thirteen patients scheduled for elective coronary artery bypass grafting (CABG) were divided into two groups: heparin pretreated (HP, n = 6) and non-heparin pretreated (NHP, n = 7). Blood samples were taken for measurements of plasma antithrombin-III (AT-III) activity, plasma heparin levels, activated clotting time with (HACT) and without (ACT) heparinase, whole blood platelet function, platelet count, thrombin-antithrombin-III complexes and D-dimer levels. Also, the mediastinal blood loss within the initial 20 h after surgery, and the blood transfusion requirements were monitored. The mean duration of the heparin pretreatment was 55 h (range 24-161 h). There was no significant difference in plasma AT-III activity and platelet count between the groups. Before and after CPB, the platelet responsiveness was better in the NHP group (p < 0.05). The HACT was prolonged in the NHP group during and after CPB compared to baseline values (p < 0.05), whereas, in the HP group, no significant changes were found. Plasma heparin levels and ACT values suggested adequate anticoagulation during CPB. However, the extent of thrombin inhibition and fibrinolysis increased with time on CPB, but did not differ between the two groups. Twenty hours after surgery, the thrombin inhibition showed to be significantly higher in the NHP group. Furthermore, mediastinal blood loss showed a tendency to be lower in the HP group (p = 0.08). However, there was no difference in blood transfusion requirements between the groups. These data suggest that short-term heparin pretreatment affects the perioperative platelet responsiveness and attenuates the consumption of coagulation factors.

Familial antithrombin-III deficiency during cardiopulmonary bypass: a case report

The serine protease inhibitor antithrombin-III (AT-III) is the principal in vivo inhibitor of blood coagulation, inactivating mainly thrombin, but also other serine proteases. Binding of AT-III to heparin dramatically increases its inhibitory effect. AT-III deficiency during cardiopulmonary bypass (CPB) can lead to insufficient anticoagulation which cannot be treated by higher doses of heparin. A 60-year-old male with familial AT-III deficiency was admitted to our hospital for coronary artery bypass surgery and aortic valve replacement. Four days before the operation, acenocoumarol was stopped and anti-Xa nadroparincalcium (Fraxiparine) was started. AT-III activity at that time was 56%. Two hours before the operation, a single dose of 4500 IU AT-III concentrate was administered. Heparinization was performed with 400 IU/kg of porcine mucosal heparin, increasing the activated coagulation time (ACT) from a baseline of 115 to 549 s. AT-III activity at that time was above 100% and the plasma D-dimer concentration was 230 ng/l. ACTs during CPB remained above 999 s, whereas the AT-III activity dropped to 54% and the D-dimer increased up to 500 ng/l at the end of CPB. CPB was terminated uneventfully. Heparin was reversed with 3 mg/kg protamine chloride, decreasing the ACT to 155 s. In the intensive care unit (ICU), the patientreceived prophylactic Fraxiparine and 1500 IU AT-III, increasing the AT-III activity to 84%. Postoperatively, there was continued blood loss, which necessitated the administration of whole blood and eventually re-exploration. The case presented illustrates an uneventful treatment of a patient with a hereditary AT-III deficiency undergoing CPB. In spite of an uneventful treatment with AT-III pre-CPB, administration of prophylactic AT-III concentrate after surgery should be considered with caution, as this might increase the postoperative morbidity.

[Aortocoronary bypass surgery; at least 6 months follow-up required for assessment of postoperative course]

OBJECTIVE

To determine how the mortality and morbidity after aortocoronary bypass surgery during the hospital stay correspond with those in the first 6 months after the operation.

DESIGN

Prospective and retrospective.

METHOD

Data of 563 patients undergoing isolated myocardial revascularization in 1998 in the Academic Hospital Nijmegen, the Netherlands, were collected on mortality and morbidity 180 days after the operation. The Parsonnet score was used to assess the operative risk of the patients.

RESULTS

The patient group consisted of 422 males and 141 females, with a mean age of 64.3 years. The median Parsonnet score was 6 (range: 0-50). The mean hospital stay was 7.9 days (SD: 9.4). The hospital mortality was 3.9% (22/563). The follow-up was 100%. During the follow-up 11 patients died, 10 from cardiac causes. Six months postoperatively the mortality was 5.9% (22/563). The Kaplan-Meier curve of the survival probability rate showed a persistent decrease, mainly in the higher risk patients. Non-fatal cardiovascular events were registered in 9.6% of the surviving patients (51/530).

CONCLUSION

The hospital mortality and morbidity after aortocoronary bypass surgery were considerably lower than the total postoperative mortality and morbidity during the first 6 months after the operation. For assessment of the postoperative course, systematic follow-up over 6 months is necessary.

[Partial left ventriculectomy (Batista procedure) for the treatment of terminal heart failure after rejection for heart transplantation]

A woman aged 64 was severely handicapped by dyspnoea due to 'terminal heart failure' resulting from idiopathic dilated cardiomyopathy. The mitral valve was seriously insufficient; the coronary vessels were normal. The patient was not eligible for heart transplantation. Partial left ventriculectomy by Batista's method was performed and the mitral valve replaced by an artificial one. The left ventricular ejection fraction increased from 0.12 before the operation to 0.35 postoperatively and to 0.43 two years later. Patient was then capable of normal exercise (New York Heart Association (NYHA): class I-II). In the Netherlands partial left ventriculectomy is the last surgical option for patients rejected for heart transplantation.

The use of neuromuscular blocking agents in noncardiac surgery after dynamic cardiomyoplasty

Dynamic cardiomyoplasty is a surgical treatment to improve cardiac performance in patients with end-stage heart failure by wrapping the latissimus dorsi muscle around the heart. The use of skeletal muscle raises concerns about the safety of neuromuscular blocking agents used during general anaesthesia in noncardiac surgery in patients after cardiomyoplasty. We describe the administration of rocuronium to a patient undergoing carotid endarterectomy 18 months after cardiomyoplasty. No clinically relevant effects on haemodynamics were observed. We conclude that the use of nondepolarising neuromuscular blocking agents for noncardiac surgery in patients after cardiomyoplasty does not compromise cardiac performance in a clinically relevant way, although the time between the cardiomyoplasty procedure and the use of nondepolarising neuromuscular blocking agents remains a concern.

[Mechanical complications due to ischemic damage after an acute myocardial infarct]

Three patients, two women aged 61 and 60 years and one man aged 78 years, who had sustained a myocardial infarction shortly before, developed acute dyspnoea, shock and (or) chest pain, and a holosystolic souffle. They suffered from rupture of the interventricular septum, acute mitral valve incompetence due to rupture of the papillary muscles, and rupture of the free wall of the ventricle, and died in spite of attempts at surgical repair. In these relatively infrequent mechanical complications of myocardial infarction the interval between the initial myocardial infarction and the onset of dyspnoea or profound shock is characteristic. With the current thrombolytic therapy and beta-blockade, reduction of the mechanical complications of myocardial infarction is possible, in particular of rupture of the free wall of the ventricle.

[Initial Groningen experiences with dynamic cardiomyoplasty]

Four patients, one woman and three men aged 48, 62, 49, en 54 years respectively, were subjected to cardiomyoplasty because of medically refractory heart failure secondary to ischaemic or idiopathic dilating cardiomyopathy. The operation and the training period were uncomplicated. In one patient symptoms of heart failure did not improve; the other patients experienced substantial relief of symptoms. However, all three died suddenly within one year after the operation, probably due to ventricular arrhythmias. Cardiomyoplasty may deserve a place in the treatment of heart failure, provided sudden death can be better prevented. Possibly, treatment with an implantable cardioverter-defibrillator might be useful.

[Successful heart transplantation in long-term ventilated patients]

Cardiac transplantation was carried out in three men, aged 50, 34 and 36 years with severe chronic heart failure. They did not completely meet the Dutch criteria, notably with respect to absence of contraindications and the requirement of thorough screening. The treatment was successful.

Congenital quadricuspid aortic valve

Two patients with a quadricuspid aortic valve are described, one of them with concomitant juxtaposed coronary orifices facing the right hand facing sinus. The etiology and incidence of this congenital anomaly will be discussed.

Growth of the hypoplastic aortic arch after simple coarctation resection and end-to-end anastomosis

Surgical treatment of a hypoplastic aortic arch associated with an aortic coarctation is controversial. The controversy concerns the claimed need to surgically enlarge the diameter of the hypoplastic arch, in addition to resection and end-to-end anastomosis. The purpose of this prospective study is to determine the fate of the hypoplastic aortic arch after resection of the aortic coarctation and end-to-end anastomosis. Between July 1, 1988, and January 1, 1990, 15 consecutive infants less than 3 months of age with an aortic coarctation were evaluated echocardiographically. A Z-value was calculated, being the number of standard deviations the aortic arch differs from the expected value, derived from a control group. Eight of these 15 infants had a hypoplastic aortic arch with a mean Z-value of -7.14 +/- 1.39. The other seven infants had a "normal" aortic arch with a mean Z-value of -1.85 +/- 1.08. All 15 infants underwent simple coarctation resection and end-to-end anastomosis. Six months after operation the mean Z-value increased significantly in those with a hypoplastic arch to -1.08 +/- 0.69 (p less than 0.0001) and in those with a "normal" aortic arch to 0.106 +/- 0.99 (p = 0.004). No infant died in our series (0%; CL 0% to 12%) and a recoarctation developed once (12.5%; CL 2% to 36%). Therefore we believe that simple resection and end-to-end anastomosis is the operation of choice for aortic coarctation associated with a hypoplastic aortic arch despite the presence of a ventricular septal defect and that enlargement of the hypoplastic aortic arch is not necessary.

Repair of aortic coarctation in infants

Fifty-three consecutive infants younger than 2 years underwent coarctation repair. A recoarctation occurred in 11 infants (21%). To determine variables associated with recoarctation, we entered preoperative and operative data into a multivariate stepwise logistic regression analysis. Patient weight was an incremental risk factor for recoarctation instead of age, in contrast to previously published studies. Furthermore, the residual gradient after the operation was a strong incremental risk factor. This risk factor was even more significant when expressed as a ratio of the systolic arm pressure, which takes background hemodynamics into account. Because weight is a more significant risk factor than age, we conclude that deferring operation is indicated only when the infant gains weight. Furthermore, a residual gradient is more important in the hemodynamic setting of a lower systolic arm pressure.

Long-term results of 44 cross-over bypasses

Forty-four patients with an unilateral iliac obstruction were treated with a cross-over bypass. The ASPI at rest in the recipient leg was 0.53 +/- 0.16 pre-operatively and had increased to 0.82 +/- 0.13 3 months after operation (p less than 0.001). One patient died within 30 days of operation and in another graft thrombosis occurred within this period. In 2 patients above-knee amputation had to be performed owing to graft failure. During the follow-up period (3 months to 10 years) 9 patients died and 8 late graft failures (30 days) occurred without limb loss. The cumulative patency rate amounted to 73.7% after 5 years. A significant steal effect could not be demonstrated. The cross-over bypass is a procedure justified in unilateral iliac occlusion in high- and moderate risk patients with intermittent claudication and pain at rest or gangrene.