Physiology of red and white blood cells

Blood consists of formed elements (red blood cells, white blood cells and platelets) and plasma. Red blood cells (erythrocytes) account for 99.9% of cells. Their principal function is the transport of oxygen from the lungs to respiring tissues and carbon dioxide from tissues back to the lungs. This is achieved through the presence of haemoglobin, a conjugated metallo-protein. The affinity of haemoglobin for oxygen changes with a number of circumstances. At the partial pressure of oxygen (PO₂) in the alveoli (13 kPa) the binding of each oxygen molecule increases the affinity of haemoglobin, so aiding uptake of oxygen. At the low PO₂ in tissues, affinity is reduced, allowing the haemoglobin to offload more oxygen. This sigmoidal relationship is shifted to the right by a fall in pH or an increase in 2,3-diphosphoglycerate concentration or temperature. The role of white blood cells (leucocytes) is to defend the body against invading pathogens. Leucocytes are far less common than erythrocytes, although their numbers increase dramatically during an infection. Divided into granulocytes (neutrophils, eosinophils and basophils) and agranulocytes (monocytes and lymphocytes), leucocytes can recognize foreign material and either engulf cells or secrete membrane-disrupting chemicals that can destroy the organism. Lymphocytes play an important role in the immune response to disease, monitoring the internal environment and producing antibodies against pathogens.     

Ginkgo biloba Extract (EGb 761) Pretreatment Limits Free Radical Oxidative Stress in Patients Undergoing Coronary Bypass Surgery

A growing body of evidence supports the trigger role of free radicals in the delayed functional and metabolic myocardial recovery following cardiopulmonary bypass (CPB) in humans, thus opening the field to specific therapies. This clinical study was designed to evaluate, in 15 patients undergoing aortic valve replacement, whether the extent of CPB- and reperfusion-induced lipid peroxidation, ascorbate depletion, tissue necrosis, and cardiac dysfunction is reduced by orally administered EGb 761, a Ginkgo biloba extract withpotent in vitro antiradical properties. Patients received either EGb 761 (Tanakan, 320 mg/day, n = 8) or a matching placebo (n = 7) for 5 days before surgical intervention. Plasma samples were obtained from the peripheral circulation and the coronary sinus at crucial stages of the operation (i.e., before incision, during ischemia, and within the first 30 minutes post-unclamping), and up to 8 days postoperatively. Upon aortic unclamping, EGb 761 inhibited the transcardiac release of thiobarbituric acid species (p ` 0.05), as assessed by high-performance liquid chromatography, and attenuated the early (5–10 minute) decrease in dimethylsulfoxide/ascorbyl free radical levels, an electron spin resonance index of the plasma ascorbate pool (p ` 0.05). EGb 761 also significantly reduced the more delayed leakage of myoglobin (p = 0.007) and had an almost significant effect on ventricular myosin leakage (p = 0.053, 6 days postoperatively). The clinical outcome of recovery of treated patients was improved, but not significantly, compared with untreated patients. Our results demonstrate the usefulness of adjuvant EGb 761 therapy in limiting oxidative stress in cardiovascular surgery and suggest the possible role of highly bioavailable terpene constituents of the drug.     

Resorbierbare Stents im infrainguinalen Gefäßabschnitt

Peripheral stents aim to support revascularization procedures for intravascular stenoses by mechanically preventing vessel recoil and counteracting the pathophysiological process of luminal renarrowing triggered by procedural injury to the vessel wall. Despite improvements in stenting techniques and concomitant medication, repeated intervention due to target lesion restenosis is necessary in a significant percentage of patients. The permanent presence of an artificial implant plays a prominent role in the discussion of the mechanisms causing in-stent restenosis. Permanent metallic implants pose the risk of a continuous interaction between a non-absorbable stent and surrounding tissue, leading to physical irritation, long-term endothelial dysfunction, or chronic inflammatory reactions. In addition, there is a risk of stent fracture due to external mechanical forces. To overcome these shortcomings, stenting technology has moved towards the development of temporary implants composed of biocompatible materials which mechanically support the vessel during the period of high risk for recoil, and then completely degrade in the long-term. This removes a potential trigger for late restenosis.     

Correlation dimension analysis of the artificial circulation

Artificial circulation has been analyzed by decomposing it into parts. However, the sum of the decomposed parts is not equal to the whole system, especially in nonlinear dynamic systems such as biological systems. To evaluate prosthetic circulation as an entity, not as decomposed parts, nonlinear mathematical analytic techniques, including fractal dimension analyzing theory, were used. Two pneumatically actuated ventricular assist devices were implanted as biventricular bypasses (BVB) in chronic animal experiments using four healthy adult goats. For comparison between natural and prosthetic circulation in the same experimental animals, the BVB-type complete prosthetic circulation model with ventricular fibrillation was adopted. All hemodynamic parameters with natural and prosthetic circulation were recorded under awake conditions and calculated by a personal computer system. By the use of nonlinear mathematical techniques, time-series data of the hemodynamics were embedded into the phase space, and correlation dimension analysis was performed to evaluate the reconstructed attractor. Our results suggest that the correlation dimension of the arterial blood pressure does not linearly increase according to the increase of the embedding dimension, even during artificial circulation, suggesting those are the fractal time series data. Dimensional analysis of the hemodynamics revealed that lower dimensional fractal dynamics were observed during prosthetic circulation. Fractal time series data are suggested to have robustness and error resistance. Thus, our results suggest that the circulatory regulatory system with the artificial heart may have these desirable characteristics. Accepted: July 14, 1995     

Patient safety unit for a hot-film anemometer,used for blood-velocity determination in humans

An inexpensive patient safety unit for a constant temperature hot-film anemometer is described. Both the so-called ‘electrical hazard’ and the thermal risk, which is special for the anemometer, have been eliminated.     

Arterial Stiffness in Renal Transplant Recipients: 5-Year Follow-up

BackgroundChronic kidney disease is a risk factor for cardiovascular diseases. After renal transplant, some traditional and chronic kidney disease–specific risk factors vanish, but new risk factors emerge. This retrospective study aimed to define the long-term impact of renal transplant and diabetes mellitus on arterial stiffness, evaluated by measuring pulse wave velocity (PWV) and augmentation index (AI) and on myocardial perfusion, evaluated by subendocardial viability ratio (SEVR).MethodsPWV, AI, and SEVR were evaluated noninvasively by applanation tonometry using SphygmoCor in the first 4 weeks after kidney transplant and 4 to 5 years thereafter.ResultsA total of 48 graft recipients (18 women, 30 men; mean ± standard deviation age, 47.9 ± 11.8 years) were included. The follow-up period was 57.4 ± 8.0 months. PWV did not change significantly during the follow-up period (9.1 ± 1.8m/s and 8.7 ± 1.8m/s, respectively; P = .137). In the subgroup of patients without diabetes mellitus, we observed a trend of PWV reduction, whereas in the subgroup of patients with diabetes we observed the trend of PWV increase. The duration of smoking before transplant correlated significantly with PWV (P = .012). AI in the whole group increased significantly during the study period (from 18.3% ±10.3% to 25.9% ±9.4%; P < .01) as well as SEVR (from 134.9 ± 23.1 to 155.4 ± 28.6; P = .001).ConclusionsPWV, reflecting the central vessel stiffness, did not change significantly in the whole group during the follow-up period. The AI, which indicates systemic stiffness, increased significantly within 5 years after transplant, indicating the progression of vascular processes of elastic and muscular arteries. Significant increases in the SEVR values in both diabetics and nondiabetics indicate the long-term favorable effect of kidney transplant on myocardial perfusion.