Haemostatic and fibrinolytic factors in men with a small abdominal aortic aneurysm.

BACKGROUND: : The presence of an abdominal aortic aneurysm (AAA) independently predicts cardiovascular disease (CVD) and its complications. Levels of plasma markers of fibrin turnover are raised in men with a large AAA (at least 5.5 cm) and predict CVD risk in healthy subjects. This study examined fibrin turnover in men with a small AAA. METHODS: : Seventy-five men with a small AAA (30-55 mm) were compared with 90 controls matched for age, sex and race. Haemostatic and fibrinolytic parameters were assessed. RESULTS: : Men with a small AAA had higher mean levels of fibrinogen (2.92 versus 2.59 g/l; P = 0.019), thrombin-antithrombin (TAT) complex (4.57 versus 1.89 ng/ml; P < 0.001), prothrombin F1 + 2 (1.13 versus 0.82 ng/ml; P = 0.004) and D-dimer (346.7 versus 120.2 ng/ml; P < 0.001). All markers correlated with maximum aortic diameter determined by ultrasonography. On multivariable regression the association between presence of an AAA and fibrinogen, TAT complex, prothrombin F1 + 2 and D-dimer levels remained significant after adjustment for confounding influences. CONCLUSION: : Fibrin turnover was increased in these men with a small AAA, independently of concomitant CVD, conventional risk factors and inflammatory markers. Enhanced fibrin turnover may contribute to the risk of cardiac complications in this group.

Cyclooxygenase-2 expression and its association with increased angiogenesis in human abdominal aortic aneurysms.

Although the mechanism whereby non-steroidal anti-inflammatory drugs may reduce abdominal aortic aneurysm (AAA) development is unknown, one potential route is via inhibition of the cyclooxygenase (COX) enzyme. Despite the fact that evidence from animal models suggests a role for the COX-2 isoform in promotion of AAA development, only very limited data exist on COX-2 expression in human AAAs. Semiquantitative immunohistochemistry for COX-2 was performed on a series of formalin-fixed, paraffin-embedded human AAAs (n = 49). Associated clinicopathological data, including the degree of inflammatory cell infiltration and neorevascularization, were obtained. COX-2 protein was detected in 46 of 49 (94%) human AAAs. Expression of COX-2 protein varied widely between AAAs. COX-2 protein localized to cells in the inflammatory infiltrate with a morphology characteristic of macrophages. COX-2 expression increased with the extent of inflammatory cell infiltration (P < 0.001) and with the degree of AAA neorevascularization (P < 0.001). Logistic regression analysis identified neorevascularization (P < 0.001) as the only significant independent predictor of COX-2 positivity in human AAAs. COX-2 protein is present at increased levels in the majority of human AAAs and is expressed by mononuclear cells in the inflammatory cell infiltrate. Promotion of angiogenesis by COX-2 may play a role in AAA development.

Fibrinolytic risk factor clustering and insulin resistance in healthy male relatives of men with intermittent claudication.

BACKGROUND: Raised fibrinolytic factors predict cardiovascular risk in healthy subjects. The aim of this study was to measure fibrinolytic factors and insulin resistance in healthy male first-degree relatives of men with intermittent claudication younger than 65 years. METHODS: The study compared 165 healthy first-degree relatives with 165 age-, sex- and race-matched control subjects free from a personal or family history of premature cardiovascular disease. Primary outcome measures were plasminogen activator inhibitor 1 (PAI-1), tissue plasminogen activator (tPA) and D-dimer levels. Insulin resistance was estimated by Homeostasis Model Assessment. Clinical and biochemical risk factors were measured and subjects genotyped for the PAI-1 4G/5G polymorphism. RESULTS: First-degree relatives had significantly higher mean PAI-1 (10.23 versus 7.85 ng/ml; P = 0.024), tPA (9.98 versus 8.29 ng/ml; P < 0.001) and D-dimer levels (56.6 versus 46.1 ng/ml; P = 0.004). They also had significantly higher insulin resistance (1.85 versus 1.53; P < 0.001) and clustered multiple atherogenic risk factors. On multivariate analysis the association between both tPA and D-dimer levels and relative status was independent of other variables. CONCLUSION: Raised levels of PAI-1, tPA, D-dimer and estimated insulin resistance were present in the healthy male first-degree relatives of men with intermittent claudication. These data support the hypothesis of fibrinolytic risk factor clustering in this high-risk population.

Quantitative X-ray projection microscopy: phase-contrast and multi-spectral imaging.

We outline a new approach to X-ray projection microscopy in a scanning electron microscope (SEM), which exploits phase contrast to boost the quality and information content of images. These developments have been made possible by the combination of a high-brightness field-emission gun (FEG)-based SEM, direct detection CCD technology and new phase retrieval algorithms. Using this approach we have been able to obtain spatial resolution of < 0.2 micro m and have demonstrated novel features such as: (i) phase-contrast enhanced visibility of high spatial frequency image features (e.g. edges and boundaries) over a wide energy range; (ii) energy-resolved imaging to simultaneously produce multiple quasi-monochromatic images using broad-band polychromatic illumination; (iii) easy implementation of microtomography; (iv) rapid and robust phase/amplitude-retrieval algorithms to enable new real-time and quantitative modes of microscopic imaging. These algorithms can also be applied successfully to recover object-plane information from intermediate-field images, unlocking the potentially greater contrast and resolution of the intermediate-field regime. Widespread applications are envisaged for fields such as materials science, biological and biomedical research and microelectronics device inspection. Some illustrative examples are presented. The quantitative methods described here are also very relevant to projection microscopy using other sources of radiation, such as visible light and electrons.

Pharmacological salvage of a combined distal bypass and free flap with catheter-directed thrombolysis.

With recent improvements in microvascular techniques, the use of combined distal bypass and free-flap transfer has been advocated for salvaging the critically ischaemic limb in extreme conditions. Distal bypass, however, carries an inherent risk of graft failure due to thrombosis, and this may threaten the viability of the free flap and, indeed, the lower limb. We present the case of a 66-year-old man with acute-on-chronic ischaemia of his left leg and rectus abdominis free flap. Despite a prolonged ischaemic time of 72 h, both were successfully salvaged using catheter-directed recombinant tissue plasminogen activator. This is previously unreported in the literature.

False aneurysm of the peroneal artery: an unusual complication of femoro-peroneal bypass grafting.

Non-traumatic false aneurysm formation involving the native crural vessels is rare. We present the case of a false aneurysm of the native peroneal artery, which complicated femoro-peroneal bypass grafting. It seemed most likely to be of an infective aetiology, arising as a consequence of contiguous methicillin resistant Staphylococcus aureus wound infection. This was previously unreported in the literature. Successful management was achieved by primary suture, local wound debridement, excision of the distal graft and replacement with an interposition vein graft through uninfected tissue planes.

Myosin heavy chain expression and plasticity: role of myoblast diversity.

Muscle fibers exhibit a limited capacity to alter their myosin heavy chain expression in response to various stimuli. Recent results pertinent to this observation are discussed, and a hypothetical scheme is presented whereby the contribution of myonuclei from distinct populations of myogenic precursors may account for this limited adaptive range.

Endovascular repair of an inflammatory abdominal aortic aneurysm complicated by aortoduodenal fistulation with an unusual presentation.

Aortoenteric fistulation (AEF) is a well-documented late complication of open abdominal aortic aneurysm (AAA) repair, occurring in between 0.4% and 4% of cases. In the absence of an anastomosis, AEF is likely to be rare after endovascular aneurysm repair (EVAR) and has only recently been described in the literature as a result of mechanical stent failure or migration. We present the case of a 61-year-old man who underwent EVAR for an AAA with a "nonspecific" periaortic inflammatory mass. Six months postoperatively, an AEF developed, presenting with metastatic sepsis followed by septic infective thromboembolization to his right leg, and amputation was necessary. His stent was well positioned and mechanically intact. We emphasize the need for vigilance about the risk of AEF when adopting an endovascular approach to repair the AAA with a nonspecific periaortic inflammatory mass and highlight the need for awareness about the unusual septic manifestations of AEF.

Simplifying the internal iliac artery aneurysm.

Isolated aneurysms of the internal iliac (hypogastric) artery are a rare variant of aorto-iliac aneurysm disease, with an incidence at around 0.04% of all aorto-iliac aneurysms. Because of their location deep within the pelvis, they may present late and are often large. The incidence of rupture is high and may be up to 38% at initial presentation; furthermore, this has been reported to carry a 58% mortality rate. As such the early and aggressive management of isolated internal iliac artery aneurysms (IIAAs) is mandatory to avoid the high morbidity and mortality associated with rupture. This article includes a literature review regarding IIAAs and outlines the current surgical and endovascular management options for this most rare and technically challenging of aneurysms.

Myotubes originating from single fast and slow satellite cells display similar patterns of AChE expression.

Slow- and fast-contracting skeletal muscles of both rats and mice display significant differences in their patterns of acetylcholinesterase (AChE) expression. Although neural influences are known to account for a large proportion of these differences, intrinsic variations between fast and slow myogenic precursor cells have been implicated. In the present study, we have capitalized on the use of Immorto transgenic mice to obtain single myogenic precursor cells isolated from either slow or fast muscle fibers and determined whether these cells generated myotubes that produced distinct patterns of AChE expression as observed in vivo between slow and fast muscles. These two myotube populations displayed similar cell-associated and secreted AChE enzyme activity as well as comparable levels of AChE transcripts. Both myotube populations also expressed nearly identical molecular form profiles. By contrast, AChE activity and transcript levels were approximately two- and fivefold greater in fast skeletal muscles compared with slow ones. Together, these findings indicate that differences in AChE expression between fast and slow muscles are not due to inherent differences in myogenic precursor cells, thereby suggesting that other factors, such as innervation, play a predominant role in establishing the distinct patterns of AChE expression in these muscle types.

Physiological characteristics of identified motor units in the mouse extensor digitorum longus muscle: an in vitro approach.

Physiological, histochemical, and morphometric properties of fast-twitch single motor units were studied in mouse extensor digitorum longus muscles in an in vitro ventral root-nerve-muscle preparation. Single motor units were functionally isolated by microdissection of the ventral root, and the glycogen depletion technique was used to demonstrate the component muscle fibers. Monoclonal antibodies were used to identify their myosin heavy chain composition. The technique allows one to correlate physiological characteristics of single motor units with fiber type but is less useful for morphological assessment of motor unit size as a result of failure to deplete glycogen from all fibers of motor units containing fibers with high oxidative capacity.

Regulation of myosin heavy chain expression in adult rat hindlimb muscles during short-term paralysis: comparison of denervation and tetrodotoxin-induced neural inactivation.

The extent to which myosin profiles within adult fast and slow muscles are altered by short-term paralysis remains equivocal. We used an array of specific antibodies to identify adult and developmental MHC isoforms within EDL and soleus muscle fibers, and show a marked multiple expression of MHCs with a general shift towards slower and more energy efficient MHC profiles after 2 weeks of denervation or TTX nerve conduction block. Paralysis also induced marked expression of an embryonic MHC within most EDL cell types, and a subtle, paralysis-sensitive, expression of alpha-cardiac MHC within specific EDL and soleus extrafusal fibers. Comparison of treatment groups also permitted assessment of the relative influence of neural activity versus trophic factors on these isoforms, and confirmed activity as a major, but not sole, regulator of MHC expression.

Ciliary neurotrophic factor: regulation of acetylcholinesterase in skeletal muscle and distribution of messenger RNA encoding its receptor in synaptic versus extrasynaptic compartments.

Several recent studies have shown that the ciliary neurotrophic factor exerts myotrophic effects in addition to its well-characterized neurotrophic actions on various neuronal populations. Since expression of acetylcholinesterase in skeletal muscle has been shown to be regulated by putative yet unknown nerve-derived trophic factors, we tested the hypothesis that the ciliary neurotrophic factor is a neurotrophic agent capable of influencing expression of acetylcholinesterase in adult rat skeletal muscle in vivo. To this end, we first determined the impact of daily ciliary neurotrophic factor administration on expression of acetylcholinesterase in both intact and denervated rat soleus muscles. The results of our experiments indicate that although chronic administration of ciliary neurotrophic factor partially counteracted the atrophic response of soleus muscles to surgical denervation, thus confirming its myotrophic effects, it failed to either increase acetylcholinesterase expression in intact muscles or prevent the decrease normally occurring in seven-day denervated muscles. In fact, acetylcholinesterase messenger RNA and enzyme levels were further reduced by ciliary neurotrophic factor treatment in denervated muscles without significant modifications in the pattern of acetylcholinesterase molecular forms. Conversely, transcript levels of the epsilon subunit of the acetylcholine receptor in intact and denervated soleus muscles treated with the ciliary neurotrophic factor were similar to those observed in their respective counterparts from vehicle-treated animals. In addition, we also determined whether transcripts encoding the receptor for the ciliary neurotrophic factor selectively accumulate in junctional domains of rat skeletal muscle fibres. In contrast to the preferential localization of transcripts encoding acetylcholinesterase and the epsilon subunit of the acetylcholine receptor within the postsynaptic sarcoplasm, messenger RNAs for the ciliary neurotrophic factor receptor appeared homogeneously distributed between junctional and extra-junctional compartments of both diaphragm and extensor digitorum longus muscle fibres, with no compelling evidence for a selective accumulation within the postsynaptic sarcoplasm. These data show that the ciliary neurotrophic factor exerts an inhibitory influence on expression of acetylcholinesterase in muscle fibres. Furthermore, the lack of an effect on expression of the epsilon acetylcholine receptor transcripts indicates that treatment with ciliary neurotrophic factor does not lead to general adaptations in the expression of all synaptic proteins. Given the distribution of transcripts encoding the ciliary neurotrophic factor receptor along multinucleated muscle fibres, we propose a model whereby the ciliary neurotrophic factor, or a related unknown molecule that also utilizes the receptor for the ciliary neurotrophic factor, contributes to the maintenance of low levels of enzyme activity in extrajunctional regions of muscle fibres by acting as a repressor of acetylcholinesterase expression that functions directly or indirectly via a pretranslational regulatory mechanism. Accordingly, these results further highlight the complexity of the regulatory mechanisms presiding over acetylcholinesterase expression in vivo.

Phenotype of adult mouse muscle myoblasts reflects their fiber type of origin.

Phenotypic diversity among mature skeletal muscle fibers originates from muscle progenitor cells, primary and secondary myoblasts, each of which is intrinsically committed to express a characteristic complement of developmentally regulated myosin heavy chain genes when differentiated. Similarly, postnatal muscle myoblasts, the satellite cells nestling beneath basement membranes of mature skeletal muscle fibers, have been shown to exhibit diversity, related to whether the muscle in which they reside is of a slow, fast or superfast type. Here we analyzed this association in more detail, evaluating the myosin heavy chain gene expression in immature muscle fibers (myotubes) formed in vitro from satellite cells extracted from isolated, living, single muscle-fibers of mature murine muscle. We identified a population of satellite cells that form myotubes expressing type I (slow) myosin heavy chain and found this population to be preferentially associated with individual slow muscle-fibers. These results not only confirm diversity among mammalian satellite cells, but also demonstrate that the phenotype of satellite cells is indicative of the type of fiber from which they derive.

Culturing satellite cells from living single muscle fiber explants.

Conventional methods for isolating myogenic (satellite) cells are inadequate when only small quantities of muscle, the tissue in which satellite cells reside, are available. We have developed a tissue culture system that reliably permits isolation of intact, living, single muscle fibers with associated satellite cells from predominantly fast and slow muscles of rat and mouse; maintenance of the isolated fibers in vitro; dissociation, proliferation, and differentiation of satellite cells from each fiber; and removal of the fiber from culture for analysis.