Leucocyte behaviour in controlled ischaemia of the calves

Multiple skeletal muscle mitochondrial DNA deletions in patients with unilateral peripheral arterial disease

Peripheral arterial disease (PAD) is associated with metabolic derangements and accumulation of the common 4977 bp mitochondrial DNA (mtDNA) deletion mutation. The current study was undertaken to test the hypothesis that PAD is associated with multiple mtDNA deletions. Gastrocnemius biopsies were obtained from nine patients with unilateral PAD. DNA extracted from the biopsies was analyzed for mtDNA deletions using a primer- shift PCR strategy. Multiple primers and strict, prospective criteria were used to identify deletions. PAD was associated with multiple mtDNA deletions (average of 8.2 distinct deletions in muscle from the hemodynamically affected limb). mtDNA injury was present in both the worse- and less-affected limbs of the unilateral PAD patients, and the estimated degree of mtDNA injury was strongly correlated in the two limbs on an intra-subject basis. The 4977 bp deletion was frequently identified, but was not always the deletion of highest frequency in individual samples. The estimated relative frequency of the 4977 bp deletion was correlated with the overall mtDNA injury in the biopsies. In summary, PAD is associated with mtDNA injury as reflected by multiple deletion mutations. As the mutations are not limited to the ischemic limb in unilateral patients, they are unlikely to contribute to the pathophysiology of claudication.

Examination of a rheological profile for blood using micropore filters

Various techniques have been used to assess the flow properties of blood and blood cells in a range of clinical situations. Filtration through microfilters offers a single technique for measuring the flow properties of all cellular components of blood in one experiment but depends on an assumed ability to recognize cells that make up <10% of leucocytes. The remaining leucocytes, labelled fast leucocytes, were previously presumed to be lymphocytes and granulocytes. This study confirmed the identities of these fast leucocytes as those of lymphocytes and granulocytes in undiluted blood. The transit time for lymphocytes (1.2 s) and granulocytes (1.6 s) is close to that recorded for fast leucocytes (1.7 s). The resistance of each type of blood cell to flow through 5 microm filters was defined in this study as the product of the concentration of that cell in blood and its transit time through a pore in the filter. The total resistance to flow of healthy blood through the filter is 4.46 x 10(7) s/ml and is attributed to plasma (2.7%), red cells (25.9%), fast leucocytes (25.3%) and slow leucocytes (46.1%). In a cohort of 21 men with peripheral arterial disease the total resistance was increased to 7.82 x 10(7) s/ml and attributed to plasma (1.5%), red cells (14.5%), fast leucocytes (21.0%) and slow leucocytes (63.00%). This analysis therefore provides a single test for assessing the flow properties of all the cellular components of blood and plasma.

Neutrophils may contribute to the morbidity and mortality of claudicants

Peripheral arterial occlusive disease is a common cause of morbidity in middle-aged men; 5 per cent of those aged over 50 years suffer from intermittent claudication. While claudication itself is not fatal, claudicants have a mortality rate approximately three times that of non-claudicating men of the same age, mainly from cardiovascular disease. This review examines the evidence for involvement of the neutrophil in this increased mortality and describes the possible pathogenesis. It also discusses how treatment of claudication may modify neutrophil behaviour, reducing subsequent mortality and morbidity rates.

Role of the leucocyte in the pathogenesis of vascular disease

The leucocyte plays a key role in the local and systemic tissue injury that results from peripheral arterial disease and chronic venous insufficiency. Despite the apparent dissimilarities between limb ischaemia and chronic venous ulceration, in both diseases macrovascular abnormalities lead to microvascular leucocyte trapping and activation. Activated leucocytes adhere to and damage adjacent endothelium by expressing adhesion molecules and releasing harmful moieties such as proteases and free radicals. Subsequent loss of endothelial integrity and the migration of activated leucocytes outwith the circulation leads to destruction of surrounding tissue. Leucocytes and their products are also involved in the systemic manifestations of ischaemia such as multiple organ failure and coagulopathy. An overview of leucocyte biology as it pertains to peripheral arterial and venous disease is presented. The opportunities for novel therapeutic interventions based on a better understanding of this biology are also discussed.

Use of pentoxifylline as an inhibitor of free radical generation in peripheral vascular disease. Results of a double-blind placebo-controlled study

The effects of an infusion of pentoxifylline 1 g as an inhibitor of free radical generation have been determined in a double-blind placebo-controlled study. Leucocyte-derived free radical generation (by the superoxide dismutase-inhibitable reduction of ferricytochrome), the release of reactive oxygen metabolites (as plasma oxidant activity), unfractionated leucocyte and erythrocyte filterability rates (using a constant-flow positive-pressure system), plasma viscosity, and plasma fibrinogen concentration have been measured in two matched groups of 10 patients with Stage II peripheral vascular disease, before and after treatment. Transcutaneous oxygen pressure (PtcO2) during treadmill exercise to stress leg circulation was also measured. Leucocyte-derived free radicals were generated during peripheral ischaemia. Pentoxifylline inhibited their generation, blocked the release of reactive oxygen metabolites, and reduced impairment of the filterability rate of unfractionated leucocytes. The improvements were accompanied by significant shortening of the half-time of recovery of transcutaneous oxygen pressure, indicating that ischaemic damage had been contained.

Leucocyte rheology in controlled coronary ischaemia

Since no studies have been carried out on the exact origin of the alterations in white blood cell rheology during the early stages of controlled ischaemia in coronary arterial disease, a model was set up using a cycle ergometer test (with a 25 watts increase every 2 minutes). Blood samples were taken (before and after exercise and again 8 minutes later at recovery) from 18 patients with stable angina pectoris and a group of 22 matched controls. The filterability (through 5 micrometer diameter pore filters) of the polymorphonuclear leucocyte sub-population (separated by density gradient), the monocyte and lymphocyte sub-fractions (separated by adhesion to Petri dishes) as well as leucocyte activation (observed under a light microscope) were monitored. Our results showed that the total leucocyte count in patients and controls rose after exercise and was accompanied by a differential shift from the polymorphonuclear to the lymphocyte cells. The polymorphonuclear filterability rate increased significantly in patients when compared to their basal values at rest, and to the controls after exercise (+ 19.58%; P less than 0.002 vs basal values at rest; + 18.72%; P less than 0.002 vs controls). This increase persisted throughout the recovery period (+ 19.86%; P less than 0.002 vs basal values; and + 23.52% P less than 0.001 vs controls), indicating that a reduced polymorphonuclear leucocyte filterability can be associated with the first signs of ischaemia.