Exploring the link between serum peroxides and angiogenesis in a bi-ethnic population from South Africa: the SAfrEIC study.

BACKGROUND: Reactive oxygen species (ROS) play a fundamental role in angiogenesis, and in turn, angiogenic growth factors also affect ROS. Angiogenesis and ROS are intricately involved in vascular deterioration. Since black populations are known to have elevated oxidative stress and hypertension, we determined whether relationships exist between angiogenic growth factors and serum peroxides in Africans and Caucasians and evaluated the relationships with cardiovascular measurements. METHODS: We measured vascular endothelial growth factor-A (VEGF), angiopoietin 2 (Ang-2), and serum peroxides in Africans (N = 262) and Caucasians (N = 364) aged 20 to 70 years. RESULTS: Africans displayed higher blood pressure, serum peroxide levels, VEGF, and Ang-2 (all P ≤ .002) than similarly aged Caucasians (P = .44). In multivariable adjusted analyses, Ang-2 was independently associated with serum peroxides in African men (R² = 0.31; ß = 0.21; P = .014) and women (R² = 0.09; ß = 0.22; P = .025); and VEGF with serum peroxides in African men (R² = 0.12; ß = 0.24; P = .014), with no statistically significant associations in Caucasians. Cardiovascular measurements did not associate with serum peroxides or angiogenic factors in any subgroup. CONCLUSIONS: Significant independent relationships exist between angiogenic growth factors and serum peroxides only in Africans who also displayed an unfavorable cardiovascular profile when compared with Caucasians. These results suggest that interplay between ROS and angiogenesis occur in African individuals that may form part of the mechanisms involved in vascular deterioration.

Arterial stiffness, ambulatory blood pressure and low-grade albuminuria in non-diabetic African and Caucasian men: the SABPA study.

Recent evidence suggests that low-grade urinary albumin excretion is a marker of early general attenuation of vascular function, but studies are limited to Caucasian population groups. We compared low-grade urinary albumin excretion (<3.5 mg mmol(-1) or 30 µg mg(-1)) between non-diabetic African (aged, 41.7 years; n=70) and Caucasian (aged, 44.6 years; n=91) men and ethnic-specific associations thereof with arterial stiffness and ambulatory blood pressure. The albumin-to-creatinine ratio (ACR) was determined from an 8 h overnight urine collection. We recorded ambulatory blood pressure over 24 h during a typical workday and the carotid-dorsalis pedis pulse wave velocity measured the next morning after a controlled overnight stay. ACR was higher in Africans compared with Caucasians (P < 0.001), also after adjusting for 24 h systolic blood pressure, diastolic blood pressure and hypertension prevalence (P < 0.001) or when grouped by similar 24 h mean arterial pressures (P < 0.01 for all categories). Daytime (P=0.002) and night time (P < 0.001) systolic and daytime (P < 0.001) and night time (P < 0.001) diastolic blood pressures were higher in Africans compared with Caucasians, but no differences existed for daytime and night time pulse pressure and pulse wave velocity. In African men only, after adjustment for covariates, night time systolic blood pressure (ß=0.347; P=0.003), diastolic blood pressure (ß=0.298; P=0.010) and mean arterial pressure (ß=0.331; P=0.004) correlated positively with ACR. In addition, daytime (ß=0.265; P=0.032) and night time (ß=0.258; P=0.038) pulse pressure as well as pulse wave velocity (ß=0.271; P=0.032) correlated positively with ACR. In conclusion, arterial stiffness and ambulatory blood pressure are already associated with low-grade albuminuria in non-diabetic African men with normal kidney function.

Comparison of central pressure estimates obtained from SphygmoCor, Omron HEM-9000AI and carotid applanation tonometry.

BACKGROUND: The Omron HEM-9000AI is the first automated tonometer to provide an estimate of central SBP (cSBP), which is considered to be more predictive of cardiovascular events than brachial pressure. However, considerable differences between the cSBP estimate of Omron and that of SphygmoCor have been reported, but not explained. This study assesses the sources of differences between both cSBP estimates and provides a handle on which estimate is closest to reality. METHOD: For this purpose, aortic cSBP derived from calibrated carotid SBP was used as device- and algorithm-independent reference. Radial, brachial and carotid applanation tonometry were performed in 143 black South Africans, aged 39-91 years. Each individual was measured with an Omron HEM-9000AI and a SphygmoCor. RESULTS: When using both devices as advocated by their manufacturers, the corresponding cSBP estimates correlated strongly (r = 0.99, P < 0.001), but the Omron estimate was 18.8 (4.3) mmHg higher than the SphygmoCor estimate. Aortic SBP was in between both estimates: 11.7 (5.5) mmHg lower than cSBP-Omron and 7.1 (5.0) mmHg higher than cSBP-SphygmoCor. Alternative calibration of the radial SphygmoCor-curves with radial instead of brachial pressures yielded a cSBP that was 3.0 (4.2) mmHg lower than aortic SBP. The shape of the recorded pressure waves was similar in both devices: less than 5% of the observed cSBP difference was caused by differences in wave shape. CONCLUSION: The results from this study demonstrate that the considerable difference between the central pressure estimates of Omron HEM-9000AI and SphygmoCor is due to algorithm differences, and suggest that the overestimation by Omron HEM-9000AI is larger than the underestimation by SphygmoCor.

Rho Kinase-Mediated Reduction in Cardiac Capillary Endothelial Cell Dimensions, In Situ, Against Flow.

OBJECTIVE: We previously showed that ischemia, induced by interrupting vascular flow, reduced cardiac capillary caliber. This was accomplished by a reduction in endothelial cell dimensions which was sensitive to Rho kinase (ROK) inhibition and stabilization of the actin cytoskeleton. Here, we investigated whether similar changes in endothelial cells, in situ, could be elicited in the presence of flow through the capillary bed. METHODS: Langendorffs perfused rat hearts were subjected to vasoactive agents, ischemia, and reperfusion. Luminal and abluminal perimeters of capillary cross-sections and their areas were measured from electron micrographs to monitor changes in endothelial cell dimensions. RESULTS: Histamine (100 microM) reduced capillary endothelial cell dimensions, in situ, without endothelial injury. While cross-sectional areas of endothelial cells were not altered by histamine, all other parameters measured were significantly reduced in comparison to controls. These changes were pre- vented by ROK inhibition. CONCLUSIONS: Cardiac capillary endothelial cells, in situ, are able to change shape against continuous flow. One hundred (100) microM histamine induces morphometric changes in these endothelial cells, in situ, without cell damage. These cell-shape changes require ROK and mimic those observed following myocardial ischemia. Targeting the actomyosin contractile system may be useful in ameliorating effects of ischemia on the myocardium

A Rho-associated kinase mitigates reperfusion-induced change in the shape of cardiac capillary endothelial cells in situ.

OBJECTIVE: We have previously demonstrated that ischaemia and reperfusion of the myocardium alter capillary dimensions and endothelial cell shape and that these changes are likely to be effected by the actomyosin contractile system in endothelial cells. Rho GTPases are involved in the regulation of cytoskeletal re-organization and in cell contraction. Rho-associated kinase regulates the sensitivity of myosin light chain to Ca(2+) in smooth muscle but not in cardiac or skeletal muscle myocytes. This study investigated the role of Rho-associated kinase in endothelial cell shape change induced by cardiac ischaemia and reperfusion. The role of Rho proteins in endothelial cell shape change in situ in the myocardial capillary bed has to date not been investigated. METHODS: Ischaemia and reperfusion were induced in Langendorff perfused rat hearts at constant flow. Electron microscopy and immunofluorescence studies localized the beta Rho-associated kinase isotype in capillary endothelial cells. Whole capillary and luminal cross-section areas, luminal and abluminal membrane lengths were measured to monitor changes in cell dimensions. We used a ROCK inhibitor, Y-27632, to investigate the role of this protein in endothelial cell shape change. RESULTS: ROCK1 localized primarily to intracellular membranes in endothelial cells. Morphometric analysis and a study of capillary lumen resin casts demonstrated that inhibition of the activity of this kinase with Y-27632 ablated the change in shape of endothelial cells induced by ischaemia and reperfusion. CONCLUSION: These results suggest that ROCK1 is involved in cardiac capillary endothelial cell shape change in situ and that targeting the contractile system in this way may be useful in ameliorating reperfusion injury.

Oxidative stress and cardiac microvascular structure in ischemia and reperfusion: the protective effect of antioxidant vitamins.

Reperfusion of the ischemic myocardium results in structural changes in the capillary bed, which may contribute to decreased microcirculatory flow ("no reflow"). This study was designed to correlate the endothelial cell shape changes with both oxidative stress and lipid peroxidation and to evaluate the beneficial potential of Trolox (a hydrophilic analogue of alpha-tocopherol) and ascorbic acid. Isolated buffer-perfused rat hearts were made ischemic for 45 min and then reperfused with 100 microM Trolox and/or 100 microM ascorbic acid. Morphological changes were quantified by measuring capillary cross-sectional areas. Increased myocardial content of oxidized glutathione and its release into the coronary effluent were used as indices of oxidative stress. Myocardial MDA, an end product of lipid peroxidation, was also measured. Luminal membrane blebs and capillary "constriction" in the ischemic groups occurred when there was no change in either glutathione status or MDA concentrations. Reperfusion altered the redox state of the heart sufficiently to induce lipid peroxidation. It also induced endothelial cell swelling and a reduction in luminal area. Ascorbic acid was a more effective antioxidant than Trolox as it significantly reduced both oxidative stress and ultrastructural injury. The combined antioxidant treatment returned both the stress ratio and the capillary measurements to control values. We conclude that endothelial cell swelling correlates with the degree of oxidative stress and that antioxidant vitamins reduce membrane damage by preventing lipid peroxidation.

Ultrastructural and morphometric comparison of retinal and myocardial capillaries following acute ischaemia.

The recovery of any tissue following a period of ischaemia is dependent on a patent microvasculature to restore blood flow. In the ischaemic myocardium, a reduction in capillary cross-sectional dimensions occurs, which is likely to contribute to "no-reflow" injury. Clinical and experimental evidence indicates that the retina is able to tolerate moderate periods of ischaemia without significant loss of function. The aim of the present study is to test the hypothesis that, as an end-arterial system, the retina possesses compensatory processes to maintain a functional microcirculation following acute ischaemia. Thirty minutes of no-flow global ischaemia was induced in isolated hearts of Wistar rats without reperfusion. The retina was also made ischaemic for 30 min using two experimental models: microsphere embolization and anoxic superfusion. Changes in capillary dimensions were assessed by ultrastructural morphometry. Following 30 min of myocardial ischaemia capillaries appeared swollen with a significant reduction in total capillary and luminal cross-sectional area. By contrast, ischaemic retinal capillaries showed minimal morphological changes and no significant alteration in dimensions. We have demonstrated notable differences in the response of retinal and myocardial microvessels to acute ischaemia. It is likely that the maintenance of capillary patency following short periods ischaemia in the retina is part of an adaptive mechanism to protect visual function.

Changes in the actin cytoskeleton of cardiac capillary endothelial cells during ischaemia and reperfusion: the effect of phalloidin on cell shape.

A reduction in capillary dimensions has been demonstrated in postischaemic reperfusion in the heart. The aim of this study was to demonstrate that in ischaemia and ischaemia followed by reperfusion, the change in shape of the constituent endothelial cells can be inhibited by phalloidin which stabilises the actin microfilament system. Isolated, perfused rat hearts were made globally ischaemic both with and without reperfusion and in the presence or absence of phalloidin. Changes in ischaemic endothelial cell dimensions were quantified by measuring whole capillary and luminal cross-sectional areas, abluminal and luminal membrane lengths. The distribution of beta-actin within the endothelial cells was determined by immunocytochemistry. In control hearts, beta-actin is distributed throughout the endothelium with a slight increase towards the luminal membrane. In ischaemia, this was more marked and other patterns of actin distribution were also observed. After reperfusion, a 'double ring' of actin could be distinguished. With phalloidin, the actin staining was more regular and the ring pattern was not observed. Morphometry showed that phalloidin was more effective in reducing endothelial cell shape change after reperfusion than after ischaemia alone. We conclude that endothelial cell shape change on reperfusion can be modified by agents which target the contractile proteins.

Nuclear differentiation in the filamentous caulonema of the moss Funaria hygrometrica.

Nuclei from different cell types in plants and animals show many features of differentiation; they differ in shape, volume, structure, ultrastructure and in the distribution of nuclear components. Using the filamentous caulonema of the moss Funaria hygrometrica Hedw. this study records the changes in cytoplasmic organization alongside the reorganization of the interphase nucleus, Events taking place in the meristematic cells at or near the lip of the advancing caulonemal filaments (e.g. acquisition of polarity, tip growth, nuclear and cell division, side branch initiation] are associated with haploid nuclei (1C DXA amount 0.5 pg) that are spherical or slightly oval, with no blocks of condensed chromatin, and a large central nucleolus with a large granular component. Maturation of the caulonemal cells involves wall thickening and pigmentation concomitant with suspension of elongate plastids in linear arrays along endoplasmic strands. Many cells become highly polarized with the majority of the organelles at their apical ends. These eytoplasmic changes are associated with endoreduplication of the genome to about 8C, endoreduplication occurs by amplification of the 1C genome to give nuclei with IC-SC DNA amounts. There is no evidence of differential amplification of the genome. The amplification in the copy number of ribosomal RNA genes is associated with the heterochromatinisation of the genes within the nucleolus. At the same time the nucleolus reduces in volume owing to a diminution of the granular component and all components of the nucleolus become spatial separate. There is an increased nuclear volume associated with endoreduplication and the nucleus elongates causing an increase in the surface area of the nuclear envelope. These major nuclear reorganizations are associated with a stable distribution of the 'D' polypeptide involved in pre-mRNA splicing. Scrutiny of published data suggests that similar differentiation events might be encountered commonly in other organisms. The changing nuclear morphology probably reflects the changing activity of the nucleus and the cell. It might be that nuclear reorganization changes the balance of genes or gene products and the spatial distribution of the component pans to enable the new nuclear functions. These results suggest that nuclear differentiation is a fundamental feature of cell differentiation.