Engineered Aptamers to Probe Molecular Interactions on the Cell Surface.

Significant progress has been made in understanding the nature of molecular interactions on the cell membrane. To decipher such interactions, molecular scaffolds can be engineered as a tool to modulate these events as they occur on the cell membrane. To guarantee reliability, scaffolds that function as modulators of cell membrane events must be coupled to a targeting moiety with superior chemical versatility. In this regard, nucleic acid aptamers are a suitable class of targeting moieties. Aptamers are inherently chemical in nature, allowing extensive site-specific chemical modification to engineer sensing molecules. Aptamers can be easily selected using a simple laboratory-based in vitro evolution method enabling the design and development of aptamer-based functional molecular scaffolds against wide range of cell surface molecules. This article reviews the application of aptamers as monitors and modulators of molecular interactions on the mammalian cell surface with the aim of increasing our understanding of cell-surface receptor response to external stimuli. The information gained from these types of studies could eventually prove useful in engineering improved medical diagnostics and therapeutics.

Exploring at the molecular level the effects of blood and blood-insulin cardioplegias used during open-heart surgeries on myocardial prevention.

AIM: The aim of this study was to measure the changes in the levels of soluble adhesion molecules involved in acute inflammation during ischemia-reperfusion in adults who underwent open-heart surgery using blood and blood-insulin cardioplegia and to examine the differences in tissue damage at the molecular level as a consequence of insulin's effect on myocardial energy metabolism. METHODS: Non diabetic 36 patients were enrolled. Blood cardioplegia was used at all cases; insulin and glucose were added at the study group. Blood samples were taken from the coronary sinus and the radial artery before cross-clamp (T1), at 1st (T2) and 30th(T3) minutes after reperfusion. Soluble intercellular adhesion molecules-1 (sICAM-1), soluble vascular adhesion molecules-1 (sVCAM-1), soluble platelet/endothelial cells adhesion marker-1 (sPECAM-1) and serum lactate levels were measured in these samples. Cardiac enzymes (CK-MB, troponin, and myoglobin) were measured at postoperative 1th, 8th and 16th hours. The total duration of mechanical ventilatory support during postoperative period, and the number of days in the intensive care unit and hospital were recorded. RESULTS: No significant differences were observed in sVCAM-1 levels in blood taken from the radial artery at T1, T2 and T3 in either group. There were significant increases between T1 and T3 and between T2 and T3 in samples obtained form the coronary sinus (P=0.000 and P=0.003, respectively). Significant increases in sPECAM-1 in samples obtained from both sites between T2 and T3 in both groups (P=0.000) were observed. These differences were similar in both groups. Troponin levels at 8th and 16th hours in the blood-insulin cardioplegia group were higher than the blood cardioplegia group (P=0.003 and P=0.032, respectively). CONCLUSION: Supplementation of blood cardioplegia with insulin did not yield a significant improvement in adhesion molecules. Therefore, superiority of one cardioplegia over the other in delivering myocardial protection during open-heart surgery has not been shown.

Use of tunnelled catheters in haematological malignancy patients with neutropenia.

This prospective study analysed 83 patients (age 45 +/- 17 years) with haematological neoplasms, implanted with 93 tunnelled catheters, who were neutropenic or developed neutropenia during treatment. Catheters were implanted in the right (n = 82) or left (n = 11) jugular vein by the same surgical team using the same technique. They remained in place for 124 +/- 88 days: 29% were removed due to infection; 18% due to treatment termination and 2% due to mechanical problems. Seventeen patients died with catheters in place. At 30, 60, 90, 120 and 200 days mean catheter duration rates were 82%, 75%, 65%, 60% and 35%, respectively, and freedom from catheter removal due to infection was 92%, 88%, 80%, 77% and 67%, respectively. Patient diagnosis and history of previous catheter infection did not increase catheter infection risk, but patients undergoing stem cell transplantation had an increased infection risk. Tunnelled catheters can be used in high-risk patients with neutropenia. Systemic infections can be managed in most patients without catheter removal.

Insulin-blood cardioplegia decreases matrix metalloproteinase activity in ischaemia-reperfusion injury during coronary artery bypass surgery.

Reperfusion of myocardium during coronary bypass activates matrix metalloproteinases (MMPs) with changes occurring in the levels of tissue inhibitors of metalloproteinases (TIMPs) in the myocardium. This study investigated the effects of insulin-blood cardioplegia on MMP activity and TIMP levels during reperfusion. Non-diabetic patients undergoing coronary artery bypass graft with cardiopulmonary bypass were randomized into a control group (n = 12) or an insulin group (n = 12). Blood cardioplegia was used for both groups; insulin and glucose were added to the insulin group. Blood samples were obtained from the coronary sinus just before aortic cross clamping and after 1 and 30 min of reperfusion. Plasma proenzyme MMPs (proMMP-2 and -9) and TIMPs (TIMP-1 and TIMP-2) levels were measured. There were no differences between groups for MMP-2 and TIMP-2 levels. However, insulin diminished proMMP-9 activation, although some still occurred. TIMP-1 consumption lessened during reperfusion which, we conclude, was as a result of the diminished MMP activation. This is the first open heart surgery study in which diminished MMP activation was achieved via a metabolic change.

Vasorelaxant effect of iloprost on isolated human internal mammary artery.

In this study, vasodilator effect of iloprost on KCl-induced contraction in human internal mammary artery (IMA) was studied and compared with other vasodilators papaverin and diltiazem. Ring segments of IMA were studied in organ baths for measurement of isometric tension. After the tissues has reached their baseline tension, precontraction was induced by 100 mm KCl and cumulative concentration-relaxation was measured by the application of iloprost (10(-9)-10(-6) m), papaverine (10(-5)-10(-4) m), diltiazem (10(-9)-10(-4) m) or ethanol; a solvent for iloprost; alone. The maximal relaxation of IMA segments to iloprost was 13.5 +/- 2.2%. Iloprost caused significantly limited relaxation when compared with papaverin (106.0 +/- 2.9%) and diltiazem (93.6 +/- 2.5%) (P < 0.001). Papaverin produced the greatest maximal relaxation to KCl-induced contraction of IMA. The potency of iloprost (-log EC(50) = 6.59 +/- 0.19) was significantly higher than those of papaverine (-log EC(50) = 4.21 +/- 0.11) and diltiazem (-log EC(50) = 5.63 +/- 0.06) (P < 0.001). In addition, -log EC(50) of diltiazem was significantly greater than papaverin (P < 0.001). Iloprost appears to be more potent than those of papaverine and diltiazem but it was inefficient in maximal inhibition on KCl-induced contraction. Iloprost may have little benefit in KCl-related vasoconstriction on human IMA segments.

Fresh homografts obtained through a national organ-sharing programme for repair of congenital heart disease.

Homografts have been used in congenital cardiac surgery for over 30 years. We utilized the resources of a national organ-sharing programme to obtain fresh homografts and report their use in correcting cardiac pathologies in 20 children between March 2001 and May 2003. In 16 patients, a valved conduit was used to form a connection between the pulmonary ventricle and the pulmonary artery. In three patients, a non-valved aortic conduit was used to form an extra-cardiac Fontan circulation and in one patient, non-valved pulmonary and aortic conduits were used to repair an infected aortic aneurysm. Three patients died following surgery. Survivors were followed up using echocardiography between 2 and 24 months post-surgery. Results demonstrate that, with the help of a national organ-sharing programme, the use of fresh homograft conduits is feasible in a paediatric patient population with reasonable waiting times.

The effects of heparin coated circuits on pulmonary injury. A clinical study.

AIM: Heparin-coated circuits have dramatic effects on the coagulation cascade, but their role on complement activation has not been clearly defined. In this clinical study the effect of heparin-coated circuits on static lung compliance and pulmonary vascular resistance is described. METHODS: Thirty patients were randomly divided into two groups: with either a heparin-coated circuit or an identical but non-coated circuit control group. In the heparin-coated group, all the blood contacting surfaces were treated with immobilized heparin (Duraflo II.) RESULTS: Early postoperative pulmonary function is determined with measurements of static lung compliance, pulmonary vascular resistance and arterial blood gases. Static lung compliance was significantly better in the heparin coated (HC) group in the early postoperative period (p=0.001). Pulmonary vascular resistance was significantly lower in the heparin-coated (HC) group in the early postoperative period (p=0.001). CONCLUSION: We believe that the method of heparin binding may play a role in its diminished effect on complement activation, but the general augmentation of the circuit's biocompatibility may explain its beneficial effect on pulmonary vascular resistance and static lung compliance.

Low dose systemic thrombolytic therapy for treatment of deep venous thrombosis.

BACKGROUND: Thrombolytic therapy is still not used widely for treatment of deep vein thrombosis despite its known efficacy. This reluctance to use it stems from worries about its hemorrhagic complications. METHODS: In a 4-year period 97 patients with deep vein thrombosis diagnosed by duplex study were enrolled into the study. Fifty patients received streptokinase as a bolus of 250,000 units followed by 100,000 units/hr with a maximum of 4,000,000 units and 47 patients received anticoagulation with heparin. RESULTS: Minor hemorrhagic complications occurred in 2 patients (4%) in the thrombolytic therapy group. An improvement in the control duplex study was observed in 56% of the patients in the thrombolytic therapy group compared to 5% in the heparin group (p=0.000). The patients treated within 4 days of onset of symptoms had significantly higher success rates compared to those treated later (p=0.000). Higher success rates were obtained for those with either femoral vein or more distal venous thrombosis compared to those with iliac vein and vena cava thrombosis (p=0.007). These results show that systemic low dose streptokinase achieves significantly higher recanalization rates compared to heparin alone. CONCLUSIONS: Hemorrhagic complications at these dose levels are within acceptable ranges. Low dose streptokinase regimen could be beneficial in patients who present within 4 days of femoral or more distal venous thrombosis.

Dissection of the ascending aorta due to metastatic carcinoma.

The association of aortic dissection with a malignancy is a rare finding and previous reports are usually those of primary aortic sarcomas. In this report we present a case with typical ascending aorta dissection associated with metastatic carcinoma originating from the lungs. The metastatic infiltration of the vasovasorum of the aorta by carcinoma cells may have caused aortic dissection by decreasing medial strength and integrity. This is a mechanism of aortic dissection that we have not encountered in previous reports.

The effect of adjuvant chemotherapy on osteoarticular allografts.

Two hundred lower extremity osteoarticular allografts (in 200 patients) performed for aggressive or malignant bone tumors between 1976 and 1997 included 124 grafts of the distal femur, 46 of the proximal tibia, and 30 of the proximal femur. Seventy-four patients did not receive chemotherapy, and 126 received either adjuvant or neoadjuvant therapy. The diagnoses, mean ages, and length of followup were different for the two groups because most of the patients in the chemotherapy group had osteosarcoma, whereas the largest number in the control group had chondrosarcoma or parosteal osteosarcoma. The extent of the surgery was essentially the same for both patient groups, as is reflected by a low recurrence rate (7% for the control and 6% for the chemotherapy group). A statistical comparison of the various parameters showed that the infection, fracture, and amputation rates were the same, but the nonunion rate was markedly increased in the patients who received chemotherapy (32% versus 12%). Cox regression and Kaplan-Meier studies showed that chemotherapy had a significant effect on outcome, with the success rates for the two groups being quite different (72% versus 56%). The results for the distal femur showed a greater effect than for either the proximal tibia or the proximal femur. Analysis of these data suggest the distal femur is perhaps the most prone to healing problems, possibly based in part on the extent of the surgery. A final study supports the concept that the results improved in later years, suggesting a modification or application of the drugs used, better selection of patients, and improvements in surgical technique.

Chylous ascites due to constrictive pericarditis.

Chylous ascites due to constrictive pericarditis is an extremely rare clinical entity, possibly caused by the augmented lymph production and high impedance to lymph drainage due to central venous hypertension. The authors describe a patient with chylous ascites caused by constrictive pericarditis in the absence of lymphatic obstruction. Cardiac catheterization is essential for the confirmation of accurate diagnosis of constrictive pericarditis. Magnetic resonance imaging of the heart is also very helpful in the diagnosis. The patient was symptom free and his ascites and edema completely resolved after pericardiectomy.

Experimental model for allograft incorporation and allograft fracture repair.

This study describes a rat model of allograft osteotomy healing. An intercalary skeletal defect was created in adult Lewis rats by resecting a 2-cm segment of the femur in the diaphysis, including the periosteum and the cuff of muscle layers. The skeletal defects were replaced with fresh-frozen devascularized intercalary allografts from Sprague-Dawley rats. A transverse osteotomy was made in the middle of the allograft. The osteotomized segments were stabilized with an intramedullary threaded Kirschner wire, which allowed immediate ambulation. Radiographic and histological examination at 4 and 8 weeks revealed a characteristic healing process at three different interfaces. Radiographically, the distal metaphyseal host-donor junction healed faster than the proximal diaphyseal host-donor interface. The osteotomy site did not have evidence of an intramembranous or endochondral repair process. This model can serve as a baseline for assessing allograft incorporation and fracture repair.

Ligation of patent ductus arterious by the method of video-assisted thoracoscopic surgery and our other VATS experiences.

In April and May 1996, two cases of PDA ligation were performed firstly in Turkey by the method of video assisted thoracoscopic surgery (VATS) in Dokuz Eylül Medical Faculty, Thoracic and Cardiovascular Surgery Department. There was not any complication in these patients in the postoperative period and they were discharged on the second day in symptom-free condition by the detection of closed ductus in their echocardiographic examination. Between February 1993 and October 1996, a total of 46 patients have undergone interventional application by VATS. While in six of these patients the procedure could not be manipulated because of massive pleural fibrosis, there was no mortality or morbidity among the patients, and they were discharged on average on the second day. The ratio of complications, such as bleeding, air leak, arrhythmia and empyema are so low in these operations, and hospital stay, with return to work time are shorter than with the open technique.

The effect of coronary artery bypass surgery on brain perfusion.

UNLABELLED: Coronary artery bypass grafting (CABG) is one of the major treatment methods of coronary artery disease. CABG is an open-heart surgery that uses cardiopulmonary bypass (CPB). After CPB, it is well known that neurological and neuropsychological complications may occur. The purpose of this study was to evaluate brain perfusion patterns before and after CPB and to locate brain perfusion changes in patients with neurological and neuropsycological complications after CPB. METHODS: Twenty-five patients who underwent open-heart surgery (22 CABG, 3 valve replacement) and 5 patients (4 cholecystectomy, 1 periferic vascular surgery) as a control group were included in the study. The 99mTc-HMPAO injected dose was 925 MBq. Brain perfusion SPECT images were obtained 30-60 min postinjection using a dedicated triple-head brain SPECT camera. Imaging was performed 1 wk before and 4-6 wk after surgery. Technetium-99m-HMPAO brain SPECT slices were evaluated visually and semiquantitatively. RESULTS: None of the patients had severe neurologic complications. Neuropsychological deficits occurred in eight patients after CABG. Cognitive deterioration and depressive mood occurred in five patients. Disorientation, agitation and confusion periods were present in another two patients. Frontal hypoperfusion was found in these patients by visual and semiquantitative evaluations (p = 0.0277) and left parietal hypoperfusion was also present semiquantitatively (p = 0.0277). Visual hallucinations occurred in one patient. Computed tomography of these patients was normal. No perfusion abnormalities were observed in the patient with visual hallucinations and in patients without symptoms after open-heart surgery nor in the control group. Brain SPECT was repeated in two symptomatic patients 5 mo after CABG. Frontal hypoperfusion became normal, and these patients' symptoms disappeared. CONCLUSION: The results of this study indicate that regional cortical hypoperfusion may occur in patients with neuropsychological complications after CABG. Technetium-99m-HMPAO brain SPECT is a useful method to locate and determine brain perfusion changes after CABG.

Lung-volume reduction in parallel with coronary heart surgery: a case report.

For patients with severe disabling emphysema, lung-volume reduction surgery has recently been introduced as an alternative to transplantation. Performing parenchyma resection from appropriate areas can improve pulmonary functions in selected patients having severe emphysema with a flattened diaphragm. We report the case of a patient, who urgently needed coronary revascularization and was otherwise inoperable because of severe chronic obstructive pulmonary disease (COPD). We carried out lung-volume reduction surgery at the same time as the coronary bypass.

Reconstruction of the shoulder joint using an acetabular allograft. A report of two cases.

Wide resection of tumors involving the glenoid region of the scapula compromises a center of motion in the shoulder joint and can cause significant loss of function. Two patients with aggressive tumor of the scapula were treated with wide resection and reconstruction using an osteoarticular acetabular allograft. The ball and socket geometry of the newly reconstructed joint and secure reattachment of soft tissues in the allograft provided a stable shoulder joint. The functional results of the two patients were 87% and 93%, respectively according to the Musculoskeletal Tumor Society system. In a select group of patients with locally aggressive lesions of the scapula, a surgical reconstruction with an osteoarticular allograft would yield satisfactory functional and cosmetic results.

Relationship between high serum digoxin levels and toxicity.

A retrospective study of 1,269 patients on digoxin was done to determine the relationship between serum digoxin levels of 3.0 ng/ml or higher and clinical toxicity. Of 1,269 patients, 58 (4.6%) had digoxin serum levels of 3.0 ng/ml or higher. Clinical evidence of digoxin toxicity was present in only 11 of these patients and premature blood sampling accounted for the high levels in 10 other nontoxic patients. None of the patients with clinical toxicity died. The other 37 patients tolerated the high digoxin levels without exhibiting toxic effect. Low cardiac output, concomitant use of other drugs, and impaired renal function increased the serum digoxin levels in patients with and without clinical toxicity. Appropriate therapeutic digoxin level monitoring and confirmatory laboratory-clinical relationship may have important influences on these results. Additional work on further definition of "toxic" digoxin levels needs to be performed.

Cervical aortic arch. A case report.

Cervical aortic arch is a rare type of aortic arch anomaly that is presumed to result from persistence of the third aortic arch and regression of the normal fourth arch. Most of the patients with this anomaly are asymptomatic, but symptoms of dysphagia and respiratory distress due to the compression by the vascular ring have been reported. Other findings such as a supraclavicular pulsatile mass, blood pressure discrepancies between the upper limbs, and loss of femoral or opposite-upper-limb pulses with compression of the cervical mass may also be present. In this article a twenty-two-year-old woman with symptomatic cervical aortic arch is presented. The patient had a left cervical pulsatile mass and elevated blood pressure on her right upper limb and was treated surgically with reanastomosis of the aorta.