Diabetic muscle infarction: An unusual cause of acute limb pain in patients on maintenance hemodialysis

Diabetic muscle infarction is underdiagnosed complication occurring in dialysis patients with advanced diabetes mellitus. Atherosclerotic vascular disease and long-standing diabetes are risk factors for this painful condition. Most common presenting symptom is localized pain in the affected limb. We present here a case of muscle infarction occurring in a diabetic patient on maintenance hemodialysis (HD). Our patient had low-grade fever and pain in right thigh which restricted his movements for one month. His pain worsened during and post-HD. External examination of right lower limb was normal except for tenderness in the right thigh region. Laboratory examination showed leukocytosis with normal serum creatine phosphokinase levels. Magnetic resonance imaging of the thigh was suggestive of muscle infarction. Patient was treated with bed rest, analgesics, antiplatelets and blood transfusion. HD prescription was changed to sustained low-efficiency dialysis with reduced ultrafiltration. Gradually, in a week, his fever and pain subsided and he was able to walk on his own. Thus, it is important to identify this clinical condition early in the course of illness to further prevent its progression.

Human-Induced Pluripotent Stem-Cell-Derived Smooth Muscle Cells Increase Angiogenesis to Treat Hindlimb Ischemia

Induced pluripotent stem cells (iPSC) represent an innovative, somatic cell-derived, easily obtained and renewable stem cell source without considerable ethical issues. iPSC and their derived cells may have enhanced therapeutic and translational potential compared with other stem cells. We previously showed that human iPSC-derived smooth muscle cells (hiPSC-SMC) promote angiogenesis and wound healing. Accordingly, we hypothesized that hiPSC-SMC may be a novel treatment for human patients with chronic limb-threatening ischemia who have no standard options for therapy. We determined the angiogenic potential of hiPSC-SMC in a murine hindlimb ischemia model. hiPSC-SMC were injected intramuscularly into nude mice after creation of hindlimb ischemia. Functional outcomes and perfusion were measured using standardized scores, laser Doppler imaging, microCT, histology and immunofluorescence. Functional outcomes and blood flow were improved in hiPSC-SMC-treated mice compared with controls (Tarlov score, p < 0.05; Faber score, p < 0.05; flow, p = 0.054). hiPSC-SMC-treated mice showed fewer gastrocnemius fibers (p < 0.0001), increased fiber area (p < 0.0001), and enhanced capillary density (p < 0.01); microCT showed more arterioles (<96 μm). hiPSC-SMC treatment was associated with fewer numbers of macrophages, decreased numbers of M1-type (p < 0.05) and increased numbers of M2-type macrophages (p < 0.0001). Vascular endothelial growth factor (VEGF) expression in ischemic limbs was significantly elevated with hiPSC-SMC treatment (p < 0.05), and inhibition of VEGFR-2 with SU5416 was associated with fewer capillaries in hiPSC-SMC-treated limbs (p < 0.0001). hiPSC-SMC promote VEGF-mediated angiogenesis, leading to improved hindlimb ischemia. Stem cell therapy using iPSC-derived cells may represent a novel and potentially translatable therapy for limb-threatening ischemia.

Anti-oxidant ebselen delays microvascular thrombus formation in the rat cremaster muscle by inhibiting platelet P-selectin expression

Ebselen, a seleno-organic compound showing glutathione peroxidase-like activity, has potent anti-inflammatory and anti-oxidant effects. Since selenium deficiency is thought to be associated with an increased incidence of vascular thrombosis, we studied the effect of ebselen on blood cell aggregate formation and vessel occlusion in vivo. In individual microvessels of rat cremaster muscle preparations, photochemically induced thrombus formation was analyzed in detail using intravital fluorescence microscopy. In ebselen-pretreated animals (30mg/kg ip), venular thrombus formation was significantly delayed (50% vessel occlusion: 535±34s; initial stasis: 872±82s; complete occlusion: 908±87s) as compared to vehicle-treated controls (416±42; 612±49; 647±51). Moreover, ebselen significantly prolonged the kinetics of arteriolar thrombus formation and even completely prevented blood cell aggregate and thrombus formation in 88.9% of all arterioles studied (p<0.05 vs controls:37.5%). Anti-thrombotic properties of ebselen could also be observed in a model of ferric chloride-induced microvascular thrombosis, with a low dose (5mg/kg ip) being as effective as a high dose pretreatment (30mg/kg ip). As assessed by flow cytometry of platelet P-selectin immunfluorescence, whole blood isolated from ebselen-treated animals revealed a significantly lower fraction of P-selectin expressing platelets when compared with that of DMSO-treated controls. In addition, oxidant stress-induced upregulation of P-selectin on isolated platelets was found dose-dependently inhibited by increasing concentrations of ebselen (10-100µM). Moreover, ebselen dose-dependently inhibited H2O2-induced platelet-leukocyte aggregate formation in whole blood in vitro, suggesting that the anti-thrombotic effect of ebselen is achieved by attenuation of P-selectin dependent platelet-leukocyte aggregation. Thus, ebselen represents preventive and therapeutic value for disorders with increased risk for oxidant stress-associated thrombotic events.

Human cord blood endothelial progenitors promote post-ischemic angiogenesis in immunocompetent mouse model

BACKGROUND

Human cord blood (CB) endothelial colony forming cells (ECFCs) are endowed with high vascular regenerative ability in immunodeficient mice, but their immunogenicity and susceptibility to rejection in immunocompetent models has yet to be explored.

METHODS

We injected CB ECFCs in non-immuno-suppressed C57BL/6J mice after having induced the hindlimb ischemia and we investigated their contribution to the recovery from the ischemic injury. Human ECFCs (hECFCs) were administered by intramuscular injection and hindlimb blood perfusion was measured by laser Doppler analysis at 7-day intervals for 28days after treatment. Mice were sacrificed after 7 and 28days and immunohistochemistry for specific human (CD31) and mouse (von Willebrand factor) endothelial antigens was carried out. Before euthanasia, blood samples to assess cytokines and angiogenic growth factor levels were collected.

RESULTS

Mice injected with hECFCs showed a prompter and greater recovery of blood flow than controls. Several endothelial cells of human origin were detected at day7 after injection and their number declined progressively. Likewise, a progressive increase of mouse-derived vascular structures were observed, paralleled by the amplified endogenous production of various soluble mediators of angiogenesis, including Vascular Endothelial Growth Factor and Fibroblast Growth Factor.

CONCLUSIONS

Overall, our findings are consistent with the hypothesis that human ECFCs might expand the endogenous vascular repair potential of recipients and support their possible HLA-independent unconventional use.

Protective effects of thymoquinone and alpha-tocopherol on the sciatic nerve and femoral muscle due to lower limb ischemia-reperfusion injury

OBJECTIVE

Thymoquinone (TQ) is an antioxidant and anti-apoptotic substance found in the Nigella sativa plant. Alpha-tocopherol (α-TP) is a potent antioxidant. We aimed to determine whether or not TQ and TP have a protective effect against lower limb ischemia-reperfusion (IR) injury of muscle and the sciatic nerve.

MATERIALS AND METHODS

A single dose of TQ 25 mg/kg was given intraperitoneally to the TQ group, a single dose of α-TP 200 mg/kg was given intraperitoneally to the α-TP group. IR was performed for 45 minutes after the drugs' applications.

RESULTS

While serum levels of malondialdehyde (MDA) and interleukin-6 (IL-6) of the IR group were significantly higher than those of the TQ plus α-TP, TQ and α-TP groups (p<0.001, p<0.001, p=0.008, respectively) and IL-6 (all p<0.001), the reduced glutathione (GSH) level of the IR group was lower than that of the other three groups. While neuronal nitric oxide synthase activity of nerve tissues of the IR group was significantly lower than that of the TQ plus α-TP group, the muscle tissue caspase-3 activity was higher than that of the TQ plus α-TP group.

CONCLUSIONS

Administration of TQ plus α-TP may strongly protect muscle and nerve tissues against IR injury via their synergistic effects.

Atypical MRI features in soft-tissue arteriovenous malformation: a novel imaging appearance with radiologic-pathologic correlation

BACKGROUND

The absence of a discrete mass, surrounding signal abnormality and solid enhancement are imaging features that have traditionally been used to differentiate soft-tissue arteriovenous malformations from vascular tumors on MRI. We have observed that these findings are not uncommon in arteriovenous malformations, which may lead to misdiagnosis or inappropriate treatment.

OBJECTIVE

To estimate the frequency of atypical MRI features in soft-tissue arteriovenous malformations and assess their relationship to lesion size, location, tissue type involved and vascular architecture.

MATERIALS AND METHODS

Medical records, MRI and histopathology were reviewed in consecutive patients with soft-tissue arteriovenous malformations in a multidisciplinary vascular anomalies clinic. Arteriovenous malformations were divided into those with and without atypical MRI findings (perilesional T2 signal abnormality, enhancement and/or a soft-tissue mass). Lesion location, size, tissue involved and vascular architecture were also compared between groups. Tissue stains were reviewed in available biopsy or resection specimens to assess relationships between MRI findings and histopathology.

RESULTS

Thirty patients with treatment-naïve arteriovenous malformations were included. Fifteen lesions demonstrated atypical MRI. There was no difference in age, gender, lesion size or involved body part between the groups. However, more than half of the atypical lesions demonstrated multicompartmental involvement, and tiny intralesional flow voids were more common in atypical arteriovenous malformations. Histopathology also differed in atypical cases, showing densely packed endothelial cells with connective tissue architectural distortion and edema.

CONCLUSION

Arteriovenous malformations may exhibit features of a vascular tumor on MRI, particularly when multicompartmental and/or containing tiny internal vessels. These features are important to consider in suspected fast-flow vascular malformations and may have implications with respect to their treatment.

Multispectral opto-acoustic tomography of exercised muscle oxygenation

Unlike near-infrared spectroscopy, multispectral opto-acoustic tomography (MSOT) has the potential to offer high-resolution imaging assessment of hemodynamics and blood saturation levels in muscle. However motion artifacts impede the real-time applications of the technique. We developed fast-MSOT with motion tracking that reduces motion artifacts. We used this algorithm to follow blood oxygenation level changes associated with muscle exercise in the muscle and the skin of healthy volunteers.

[The clinical pathological characteristics and follow-up of 4 cases of immune-mediated necrotizing myopathy]

OBJECTIVE

To characterize the clinical, electrophysiology and neuropathological features of 4 cases with immune-mediated necrotizing myopathy (IMNM).

METHODS

We retrospectively analyzed the clinical, electrophysiology, neuropathological characteristics of 4 IMNM patients with muscular and skin biopsy in our department during 4 years (from January 2011 to January 2014).

RESULTS

Among these 4 patients, 2 were men and 2 were women (aged 37 to 58 years) with disease duration ranging from 1 month to 60 months. Two patients were with acute onset and 2 with chronic onset. All 4 patients had proximal muscle weakness with three patients with cervical flexor muscle weakness and one with respiratory muscles weakness and noninvasive ventilator assisted respiration. One patient had interstitial lung disease. The anti-signal recognition particle antibodies were strong positive in all 4 patients. Muscle biopsy showed group necrotizing and regenerating fibers in one patient and few scattered necrotizing and regenerating fibers in the other 3 patients. Both muscle fiber hypertrophy and muscle fiber atrophy together with proliferation of connective tissue on endomysium could be viewed in all 4 patients. However, very few inflammatory cells were detectable in patients. One patient was treated with corticosteroids and the other three were treated with combination of corticosteroids and immunosuppressant drugs.

CONCLUSIONS

IMNM is characterized by heterogeneity at disease onset, severity and iInvolvement of muscles with, however, similary pathological changes including the presence of numerous necrotic and regenerating fibers with little or none inflammation. Corticosteroid and/or immunosuppressant is effective for patients.

Macromolecule extravasation-xenograft size matters: a systematic study using probe-based confocal laser endomicroscopy (pCLE)

PURPOSE

Profound changes of the vasculature in tumors critically impact drug delivery and therapy response. We aimed at developing a procedure to monitor morphological and functional parameters of the vasculature in subcutaneous xenograft models commonly applied for therapy testing by using probe-based confocal laser endomicroscopy.

PROCEDURES

By monitoring various normal and diseased tissues, we established an experimental and analytical set-up to systematically analyze tracer extravasation from the microvasculature. Application of the approach in two xenograft models (HCT-116 and SW620) was realized consecutively throughout tumor growth.

RESULTS

The incidence of dilated vessels increased with xenograft size in both models while macromolecule extravasation and tracer accumulation in the tumor tissue, respectively, was significantly reduced throughout growth. The development of dilated/ultradilated vessels correlated with tracer extravasation only in the HCT-116 but not the SW620 model. The underlying mechanisms are still ambiguous and discussed.

CONCLUSIONS

Our findings clearly indicate that both xenograft type and size matter for drug delivery and therapy testing.

[Diabetic muscle infarction]

BACKGROUND

Diabetic muscle infarction is a rare complication of diabetes mellitus that typically presents in the thigh; microvascular abnormalities may play a role.

CASE DESCRIPTION

A 32-year-old female presented at the outpatient clinic with a painful, swollen thigh. She had suffered from type 1 diabetes for 22 years. The patient was admitted to the nephrology ward for further evaluation. Deep-venous thrombosis and abscess were excluded with echography. After additional investigations - MRI and a biopsy of skin, muscle and fascia - the diagnosis diabetic muscle infarction was made. The patient was treated with bed rest and analgesics. With hindsight, the muscle biopsy was not actually required in reaching a diagnosis.

CONCLUSION

The diagnosis 'diabetic muscle infarction' is made on the basis of clinical presentation in combination with MRI findings. The treatment consists of bed rest and analgesics.

Nitric oxide synthesis is increased in cybrid cells with m.3243A>G mutation

Nitric oxide (NO) is a free radical and a signaling molecule in several pathways, produced by nitric oxide synthase (NOS) from the conversion of l-arginine to citrulline. Supplementation of l-arginine has been used to treat MELAS (mitochondrial encephalopathy with lactic acidosis and stroke like syndrome), a mitochondrial disease caused by the m.3243A>G mutation. Low levels of serum arginine and endothelium dysfunction have been reported in MELAS and this treatment may increase NO in endothelial cells and promote vasodilation, decreasing cerebral ischemia and strokes. Although clinical benefits have been reported, little is known about NO synthesis in MELAS. In this study we found that osteosarcoma derived cybrid cells with high levels of m.3243A>G had increased nitrite, an NO metabolite, and increased intracellular NO, demonstrated by an NO fluorescent probe (DAF-FM). Muscle vessels from patients with the same mutation had increased staining in NADPH diaphorase, suggestive of increased NOS. These results indicate increased production of NO in cells harboring the m.3243A>G, however no nitrated protein was detected by Western blotting. Further studies are necessary to clarify the exact mechanisms of l-arginine effect to determine the appropriate clinical use of this drug therapy.

Treatment with a nitric oxide-donating NSAID alleviates functional muscle ischemia in the mouse model of Duchenne muscular dystrophy

In patients with Duchenne muscular dystrophy (DMD) and the standard mdx mouse model of DMD, dystrophin deficiency causes loss of neuronal nitric oxide synthase (nNOSμ) from the sarcolemma, producing functional ischemia when the muscles are exercised. We asked if functional muscle ischemia would be eliminated and normal blood flow regulation restored by treatment with an exogenous nitric oxide (NO)-donating drug. Beginning at 8 weeks of age, mdx mice were fed a standard diet supplemented with 1% soybean oil alone or in combination with a low (15 mg/kg) or high (45 mg/kg) dose of HCT 1026, a NO-donating nonsteroidal anti-inflammatory agent which has previously been shown to slow disease progression in the mdx model. After 1 month of treatment, vasoconstrictor responses to intra-arterial norepinephrine (NE) were compared in resting and contracting hindlimbs. In untreated mdx mice, the usual effect of muscle contraction to attenuate NE-mediated vasoconstriction was impaired, resulting in functional ischemia: NE evoked similar decreases in femoral blood flow velocity and femoral vascular conductance (FVC) in the contracting compared to resting hindlimbs (ΔFVC contraction/ΔFVC rest = 0.88±0.03). NE-induced functional ischemia was unaffected by low dose HCT 1026 (ΔFVC ratio = 0.92±0.04; P>0.05 vs untreated), but was alleviated by the high dose of the drug (ΔFVC ratio = 0.22±0.03; P<0.05 vs untreated or low dose). The beneficial effect of high dose HCT 1026 was maintained with treatment up to 3 months. The effect of the NO-donating drug HCT 1026 to normalize blood flow regulation in contracting mdx mouse hindlimb muscles suggests a putative novel treatment for DMD. Further translational research is warranted.

The role of endothelial cells in myofiber differentiation and the vascularization and innervation of bioengineered muscle tissue in vivo

Musculoskeletal disorders are a major cause of disability and effective treatments are currently lacking. Tissue engineering affords the possibility of new therapies utilizing cells and biomaterials for the recovery of muscle volume and function. A major consideration in skeletal muscle engineering is the integration of a functional vasculature within the regenerating tissue. In this study we employed fluorescent cell labels to track the location and differentiation of co-cultured cells in vivo and in vitro. We first utilized a co-culture of fluorescently labeled endothelial cells (ECs) and muscle progenitor cells (MPCs) to investigate the ability of ECs to enhance muscle tissue formation and vascularization in an in vivo model of bioengineered muscle. Scaffolds that had been seeded with both MPCs and ECs showed significantly greater vascularization, tissue formation and enhanced innervation as compared to scaffolds seeded with MPCs alone. Subsequently, we performed in vitro experiments using a 3-cell type system (ECs, MPCs, and pericytes (PCs)) to demonstrate the utility of fluorescent cell labeling for monitoring cell growth and differentiation. The growth and differentiation of individual cell types was determined using live cell fluorescent microscopy demonstrating the utility of fluorescent labels to monitor tissue organization in real time.

Noninvasive monitoring of treatment response in a rabbit cyanide toxicity model reveals differences in brain and muscle metabolism

Noninvasive near infrared spectroscopy measurements were performed to monitor cyanide (CN) poisoning and recovery in the brain region and in foreleg muscle simultaneously, and the effects of a novel CN antidote, sulfanegen sodium, on tissue hemoglobin oxygenation changes were compared using a sub-lethal rabbit model. The results demonstrated that the brain region is more susceptible to CN poisoning and slower in endogenous CN detoxification following exposure than peripheral muscles. However, sulfanegen sodium rapidly reversed CN toxicity, with brain region effects reversing more quickly than muscle. In vivo monitoring of multiple organs may provide important clinical information regarding the extent of CN toxicity and subsequent recovery, and facilitate antidote drug development.

Vascular development during distraction osteogenesis proceeds by sequential intramuscular arteriogenesis followed by intraosteal angiogenesis

Vascular formation is intimately associated with bone formation during distraction osteogenesis (DO). While prior studies on this association have focused on vascular formation locally within the regenerate, we hypothesized that this vascular formation, as well as the resulting osteogenesis, relies heavily on the response of the vascular network in surrounding muscular compartments. To test this hypothesis, the spatiotemporal sequence of vascular formation was assessed in both muscular and osseous compartments in a murine model of DO and was compared to the progression of osteogenesis. Micro-computed tomography (μCT) scans were performed sequentially, before and after demineralization, on specimens containing contrast-enhanced vascular casts. Image registration and subtraction procedures were developed to examine the co-related, spatiotemporal patterns of vascular and osseous tissue formation. Immunohistochemistry was used to assess the contributory roles of arteriogenesis (formation of large vessels) and angiogenesis (formation of small vessels) to overall vessel formation. Mean vessel thickness showed an increasing trend during the period of active distraction (p=0.068), whereas vessel volume showed maximal increases during the consolidation period (p=0.009). The volume of mineralized tissue in the regenerate increased over time (p<0.039), was correlated with vessel volume (r=0.59; p=0.025), and occurred primarily during consolidation. Immunohistological data suggested that: 1) the period of active distraction was characterized primarily by arteriogenesis in the surrounding muscle; 2) during consolidation, angiogenesis predominated in the intraosteal region; and 3) vessel formation proceeded from the surrounding muscle into the regenerate. These data show that formation of vascular tissue occurs in both muscular and osseous compartments during DO and that periods of intense osteogenesis are concurrent with those of angiogenesis. The results further suggest the presence of morphogenetic factors that coordinate the development of vascular tissues from the intramuscular compartment into the regions of osseous regeneration.

The effect of hyperbaric oxygen in crush injuries and skeletal muscle-compartment syndromes

Crush injuries represent a spectrum of injury to body parts as result of trauma. Presentations vary from minor contusions to limb-threatening damage. Typically, the injury involves multiple tissues, from skin and subcutaneous, to muscle and tendons, to bone and joints. In their most severe presentations, predictable complications--including osteomyelitis, non-union of fractures, amputations and failed flaps--occur in approximately 50 percent of the cases with standard of practice surgical and medical interventions. Skeletal muscle-compartment syndrome (SMCS) is another consequence of trauma, but in this situation the target tissues are muscles and nerve. Edema and/or bleeding within the confines of the fascial envelope can increase the pressure within the skeletal muscle-compartment. When the tissue fluid pressure within the compartment exceeds the capillary perfusion pressure to the muscles and nerves in the compartment, these tissues are rendered ischemic and manifest the signs and symptoms of SMCS. The SMCS, especially in its incipient stages before a fasciotomy is required, is a therapeutic challenge since no means to arrest its progression exist other than hyperbaric oxygen (HBO2). Unfortunately, HBO2 is woefully neglected as an adjunct for managing crush injury and SMCS. Strong arguments exist for its use based on evidenced-based information and how HBO2 mitigates the pathology of these conditions.

Endothelial dysfunction in type 2 diabetes

The mechanisms responsible for the accelerated atherosclerosis observed in type 2 diabetes are not fully understood. One of the earliest events in the development of atherosclerosis is endothelial dysfunction, namely, a reduction in nitric oxide (NO) synthesis or its bioavailability within the peri-endothelial environment, where it is responsible for maintenance of vascular tissue integrity. The clinical evaluation of this pathway is hampered by the fact that in vivo NO cannot be directly measured; however, exploiting a novel, complex and elegant experimental setup, McVeigh and co-workers (Diabetologia 1992;35:771-776) were the first to document that NO bioavailability in type 2 diabetic patients is indeed reduced. In this edition of 'Then and now' that paper is reappraised not only for its originality, but also for the broad and extensive evaluation of the vascular functions explored, the complete clinical characterisation of patients enrolled and for the fact that all the major findings were subsequently replicated.

Therapeutic effect of fucoidan-stimulated endothelial colony-forming cells in peripheral ischemia

BACKGROUND

Fucoidan, an antithrombotic polysaccharide, can induce endothelial colony-forming cells (ECFC) to adopt an angiogenic phenotype in vitro.

OBJECTIVES

We evaluated the effect of fucoidan on vasculogenesis induced by ECFC in vivo.

METHODS

We used a murine hindlimb ischemia model to probe the synergic role of fucoidan-treatment and ECFC infusion during tissue repair.

RESULTS

We found that exposure of ECFC to fucoidan prior to their intravenous injection improved residual muscle blood flow and increased collateral vessel formation. Necrosis of ischemic tissue was significantly reduced on day 14, to 12.1% of the gastronecmius cross-sectional surface area compared with 40.1% in animals injected with untreated-ECFC. ECFC stimulation with fucoidan caused a rapid increase in cell adhesion to activated endothelium in flow conditions, and enhanced transendothelial extravasation. Fucoidan-stimulated ECFC were resistant to shear stresses of up to 21 dyn cm(-2). Direct binding assays showed strong interaction of fucoidan with displaceable binding sites on the ECFC membrane. Bolus intramuscular administration of fucoidan 1 day after surgery reduces rhabdomyolysis. Mice injected with fucoidan (15 mg kg(-1)) had significantly lower mean serum creatine phosphokinase (CPK) activity than control animals. This CPK reduction was correlated with muscle preservation against necrosis (P < 0.001).

CONCLUSIONS

Fucoidan greatly increases ECFC-mediated angiogenesis in vivo. Its angiogenic effect would be due in part to its transportation to the ischemic site and its release after displacement by proteoglycans present in the extracellular matrix. The use of ECFC and fucoidan together, will be an efficient angiogenesis strategy to provide therapeutic neovascularization.

Tissue oxygenation and microvascular hemodynamics in experimental arterial gas embolism

Microvascular hemodynamic responses to arterial gas embolism (AGE) and local oxygen tensions (PO2) have never been evaluated in vivo using intravital microscopy. A system was implemented to study AGE in real time using brightfield and phosphorescence microscopy as well as laser-induced microvessel occlusion. Bubble dynamics, microhemodynamics and oxygenation were studied following AGE in 61 microvessels and 41 interstitial spaces from 19 anesthetized rats. AGE was induced by direct air injection into the femoral artery ipsilateral to the studied cremaster muscle. Bubble-induced vaso-occlusion was investigated, and microvascular blood flow redistribution were associated with changes in intravascular and interstitial PO2. Microvascular blood flow as well as intravascular and tissue PO2 decreased after microvascular occlusion following microembolism. However, certain areas did not become fully hypoxic since redistribution of blood allowed oxygen to be supplied by nearby microvessels with blood (or plasma) flow or tissue gas diffusion. A linear correlation between interstitial and intravascular PO2 was found during baseline and after AGE. Because some microvessels remain flowing even after AGE, our observations suggest that intravascular therapeutic agents administered during severe AGE may reach microvascular networks and provide additional oxygenation to tissue areas where blood flow is compromised due to occlusion of some microvessels.

A Comparison Between the Vascular Responses to Adrenaline and Noradrenaline in Individual Skeletal Muscles of the Cat

The effects of intra-arterially and intravenously administered adrenaline and noradrenaline on the venous outflow from individual muscles in the hind limbs of cats under chloralose anaesthesia were studied. The various responses to these amines were shown to depend on the dose administered, the route of injection, the general arterial blood pressure and the vasomotor tone in the muscle. They did not vary with the type of muscle studied. When the vasomotor tone was high, intra-arterially administered adrenaline caused vasodilatation, vasoconstriction or a compound response according to the dose administered. Intra-arterially administered noradrenaline caused only vasoconstriction. However, both intravenously administered adrenaline and noradrenaline in small doses caused vasodilatation in skeletal muscles, the former being the more potent. That this effect depended on intact nervous connections was confirmed in cross-circulation experiments in which the muscle of one cat was perfused entirely by blood from a donor cat. When the vasomotor tone in the muscle was low, either naturally or as a result of acute denervation, it was difficult to produce any dilatation with adrenaline, and noradrenaline always caused vasoconstriction. Under these conditions, the increase in blood flow produced by the intravenous administration of the amines was shown, by means of a blood pressure stabiliser, to be a passive effect caused by the rise in blood pressure forcing more blood through the muscles.

Intraoperative evaluation of revascularization effect on ischemic muscle hemodynamics using near-infrared diffuse optical spectroscopies

Arterial revascularization in patients with peripheral arterial disease (PAD) reestablishes large arterial blood supply to the ischemic muscles in lower extremities via bypass grafts or percutaneous transluminal angioplasty (PTA). Currently no gold standard is available for assessment of revascularization effects in lower extremity muscles. This study tests a novel near-infrared diffuse correlation spectroscopy flow-oximeter for monitoring of blood flow and oxygenation changes in medial gastrocnemius (calf) muscles during arterial revascularization. Twelve limbs with PAD undergoing revascularization were measured using a sterilized fiber-optic probe taped on top of the calf muscle. The optical measurement demonstrated sensitivity to dynamic physiological events, such as arterial clamping/releasing during bypass graft and balloon inflation/deflation during PTA. Significant elevations in calf muscle blood flow were observed after revascularization in patients with bypass graft (+48.1 ± 17.5%) and patients with PTA (+43.2 ± 11.0%), whereas acute post-revascularization effects in muscle oxygenation were not evident. The decoupling of flow and oxygenation after revascularization emphasizes the need for simultaneous measurement of both parameters. The acute elevations/improvements in calf muscle blood flow were associated with significant improvements in symptoms and functions. In total, the investigation corroborates potential of the optical methods for objectively assessing the success of arterial revascularization.

Multifractal and lacunarity analysis of microvascular morphology and remodeling

OBJECTIVE

Classical measures of vessel morphology, including diameter and density, are employed to study microvasculature in endothelial membrane labeled mice. These measurements prove sufficient for some studies; however, they are less well suited for quantifying changes in microcirculatory networks lacking hierarchical structure. We demonstrate that automated multifractal analysis and lacunarity may be used with classical methods to quantify microvascular morphology.

METHODS

Using multifractal analysis and lacunarity, we present an automated extraction tool with a processing pipeline to characterize 2D representations of 3D microvasculature. We apply our analysis on four tissues and the hyaloid vasculature during remodeling.

RESULTS

We found that the vessel networks analyzed have multifractal geometries and that kidney microvasculature has the largest fractal dimension and the lowest lacunarity compared to microvasculature networks in the cortex, skin, and thigh muscle. Also, we found that, during hyaloid remodeling, there were differences in multifractal spectra reflecting the functional transition from a space filling vasculature which nurtures the lens to a less dense vasculature as it regresses, permitting unobstructed vision.

CONCLUSION

Multifractal analysis and lacunarity are valuable additions to classical measures of vascular morphology and will have utility in future studies of normal, developing, and pathological tissues.

Nitric oxide and the cardiovascular system: cell activation, vascular reactivity and genetic variant

Nitric oxide (NO), primarily identified as an endothelium-derived relaxing factor, is a free radical that signals different biological processes. The identification of NO synthase (NOS) isoforms and the subsequent characterization of the mechanisms of cell activation of the enzymes permitted the partial understanding of both the physiological interactions and of the mechanisms of the diseases in which NO is involved. Mainly expressed in the vascular endothelium, the endothelial NOS isoform (eNOS) plays an important role in the regulation of vascular reactivity and in the development and progression of atherosclerosis. The purpose of this review is to contextualize the reader about the eNOS structure and its mechanisms of cell activation. In view of the advances in molecular biology, we will also address the known mechanisms of gene expression regulation and the role of variants on the genetic code of eNOS associated with cardiovascular phenotypes. Although the importance of NO as an atheroprotective molecule is recognized, our focus will be the review of the literature on NO and its participation in the modulation of the muscle vasodilatation phenotype.

Influence of Early Antihypertensive Treatment on Vascular and Cardiac Design in SHR with and without Renal Hypertension

The present study was designed to explore to what extent pressure reduction by antihypertensive therapy and pressure elevation by renal hypertension are able to affect structural vascular and cardiac changes in young spontaneously hypertensive rats (SHR). Pressure elevation in SHR was induced by means of superimposing 2 kidney, 1 clip renal hypertension (2K1C). Pressure reduction was achieved by means of the vasoselective calcium antagonist felodipine from 6 to 13 weeks of age in both clipped and unclipped SHR. Vascular structure of the skeletal muscle was assessed hemodynamically by perfusing a hindlimb preparation and left ventricular dimensions were calculated from pressure-volume relationships of isolated hearts arrested in diastole. Induction of renal hypertension in SHR resulted, besides augmentation of arterial pressure in a marked concentric left ventricular hypertrophy, i.e. elevations of wall thickness to internal radius ratio. Likewise, in renal hypertensive SHR, a structural adaptation of the skeletal muscle vascular bed occurred, reflected as elevations of minimal vascular resistance and maximal generated perfusion pressure. Antihypertensive treatment for 8 weeks with felodipine reduced and also prevented mean arterial pressure from increasing further in SHR, and in SHR with superimposed renal hypertension by approximately 15% (p < 0.001 for both). In renal hypertensive SHR, felodipine partly prevented the development of exaggerated structural changes, both in the heart and in the skeletal muscle vascular bed, as reflected by reduced wall thickness to internal radius ratio and reduced minimal vascular resistance by 22% and maximal pressure response by 10% respectively (p < 0.01 for both parameters).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of daidzein, 4-methylbenzylidene camphor or estrogen on gastrocnemius muscle of osteoporotic rats undergoing tibia healing period

The effect of daidzein (D), 4-methylbenzylidene camphor (4-MBC) or estradiol-17beta-benzoate (E(2)) on muscle of osteoporotic rats during fracture healing was studied. After performing a metaphyseal tibia osteotomy in 96 osteoporotic 5-month-old female Sprague-Dawley rats, they received daily 50 mg D, 200 mg 4-MBC or 0.4 mg E(2) per kg body weight, or soy free (SF) diet up to 36 and 72 days. Mitochondrial activity, fiber area, and capillary density were analyzed in M. gastrocnemius. Osseous callus bridging of fracture was observed in half of the rats after 36 days. By day 72, fracture was healed in most of the animals. State 3 mitochondrial respiration significantly enhanced in E(2), 4-MBC and D groups versus SF after 36 days (30, 32 and 32 vs 23 pmol O(2)/s per mg). It declined after 72 days, however, in E(2) group it was still at a higher level versus SF (25, 23 and 21 vs 20 pmol O(2)/s per mg). Size of fast oxidative glycolytic (FOG) and fast glycolytic (FG) fibers, capillary density did not differ significantly between the groups, however, at day 36 an increase in D and 4-MBC groups was detectable. FOG diameter was 64, 66, 68, and 58 microm and FG diameter was 88, 98, 95, and 89 microm in SF, D, 4-MBC, and E(2) groups. The ratio of capillaries to muscle fiber was 1.1, 1.4, 1.3, and 1.1 in SF, D, 4-MBC and E(2) groups by day 36. D and 4-MBC react similar to estrogen thereby improving oxidative cell metabolism in severe osteoporotic rats. The level of mitochondrial activity was higher, though no significant morphological differences could be shown.

Effects of chronic iron deficiency anaemia on myoglobin content, enzyme activity, and capillary density in the human skeletal muscle

The influence of chronic iron deficiency anaemia on myoglobin content, maximal enzyme activities and capillarization in the human skeletal muscle was investigated. Muscle samples from musculus vastus lateralis were screened in an Indonesian population. The causes of iron deficiency were chronic intestinal bleeding or repeated pregnancy combined with low iron intake. The maximal activities of iron-dependent and non-iron-dependent glycolytic and oxidative enzymes as well as myoglobin showed similar values in the iron-deficient group and the matched control group. The activities of the oxidative enzymes in both the iron-deficient group and the controls were lower, however, compared even to untrained Swedish subjects. The capillary density was essentially within a normal range in both groups. It is concluded that chronic iron deficiency anaemia of a moderate or severe degree, with Hb concentrations of about 80-100 g.1(-1), does not cause an impaired biochemical function of the human skeletal muscle.

Laser-Doppler flowmetry--a non-invasive and continuous method for blood flow evaluation in microvascular studies

Skin viability has during the last decades been studied by a number of different techniques. Some of these are briefly presented in this paper. One method, based on the laser-Doppler principle, makes possible continuous and noninvasive measurement of blood flow in the outermost layer (1 mm) of the skin. The basic physical principles and the properties of this flowmeter are presented. Some clinical and research applications of laser-Doppler flowmetry in a number of medical disciplines are discussed.

Capillary permeability in skeletal muscle of normal subjects

Capillary diffusion capacity (CDC) and muscle blood flow (MBF) were determined from the anterior tibial muscle in 25 normal subjects by measuring the simultaneous clearance of 133xenon and sodium131iodide. The subjects were divided into two groups: one with a mean age of 31 years and the other with a mean age of 51. The older group had a significantly lower MBF (54.6 +/- 9.0 vs. 64.2 +/- 9.5 ml/100 g/min; p less than 0.05) and a significantly greater CDC (7.6 +/- 1.2 vs. 6.1 +/- 1.3 mol/min; p less than 0.01) than the younger group. There was a significant correlation between the CDC increase and the age of the subjects (r = 0.61; p less than 0.01). Furthermore, MBF decreased with increasing age (r = 0.48; p less than 0.05). No differences were found in MBF or CDC between female and male subjects. The mechanisms of increased capillary permeability are discussed.

Leg muscle circulation by 133Xenon clearance as a predictor of cardiovascular disease in an aged population

In a 10-year cardiovascular survey of an unselected population aged 70 at entry. 133Xenon clearance was carried out in the anterior tibial muscle in both legs after maximal exercise during ischaemia in 211 men and 166 women. The maximal blood flow and the delay time (Ti) until this was achieved were measured. Using multivariate Cox's regression analyses with mortality from cardiovascular diseases (CVD) and CVD events in the eighth decade as end-points, and maximal blood flow, Ti, distal pulse abnormality and intermittent claudication as possible predictors, high Ti was found to be an independent predictor of both end-points in both sexes. In further multivariate Cox's regression analyses including other possible CVD risk markers, high Ti was of individual predictive value for excess total mortality, excess CVD mortality and excess CVD events in both sexes. It is concluded that high Ti by 133Xenon clearance at the age of 70 is a powerful predictor of future CVD events.

Dynamic changes in the microcirculation of diabetics as related to diabetic microangiopathy

Reversible abnormalities of many vascular beds have been observed in early diabetes, before irreversible structural changes of diabetic microangiopathy became apparent. In the bulbar conjenctiva and in the kidney the changes are associated with vascular dysfunction and may be due to autonomic neuropathy. The role of autoregulation in these vascular beds is not clear. In the limb muscles and in the retina the functional abnormality in early diabetes and in those with only mild retinopathy is increased blood flow. This increase in blood flow is probably the result of autoregulatory adaptation to hypoxia induced by 2,3 diphosphoglycerate deficiency. Lactic acid accumulation may also contribute. Breakdown of the autoregulation in the retina results in the development of diabetic retinopathy. The late stages of retinopathy, new vessel formation, are an attempt at revascularisation of areas of capillary non-perfusion.

Metabolic effects of beta-adrenoceptor blockade on skeletal muscle at rest and during exercise

beta-Adrenoceptor antagonists influence the metabolic responses in man at rest and during exercise. Impaired working capacity and muscular fatigue have been reported in patients on beta-blockers and this could be due to an altered substrate supply to the muscles. The results from several studies show that the main effect of beta-blockade on metabolism is decreased lipolysis, with less fat available to the muscles. This results in an increased carbohydrate demand to maintain an unchanged aerobic metabolism, and liver and muscle glycogen stores are more rapidly depleted. beta-blockade also results in decreased lactate release from the muscles, probably due to a membrane effect and/or changed perfusion. It is concluded that beta-blockade a) decreases fat metabolism in the muscle, which secondarily increases the use of carbohydrates during exercise, resulting in earlier hypoglycaemia and/or depletion of muscle glycogen with reduction of the working capacity, b) impairs lactate transport from the muscle but does not cause lactate accumulation within the muscle which could be responsible for muscular fatigue.

beta-Adrenoceptor blockade and exercise: effects on endurance and physical training

beta-adrenoceptor antagonists influence almost all haemodynamic and metabolic actions in the body. High levels of sympathetic stimulation accompany aerobic exercise and it is known that beta-blockade results in a decreased working capacity. Furthermore it has also been questioned whether beta-blockade inhibits the normal response to physical training. Although adrenergic mechanisms are involved in muscle and liver glycogen breakdown, beta-blockade does not seem to reduce glycogen utilisation during exercise. Both selective and non-selective beta-blockade inhibit lipolysis and result in less free fatty acids being available for muscle utilisation. Surgical and chemical sympathectomy in animals has been shown to inhibit the responses to physical training but results are now available showing that beta-adrenergic blockade does not prevent the effect of physical conditioning in patients treated with propranolol. It is concluded that beta-blockade during prolonged exercise a) does not reduce oxygen uptake by the working muscles b) decreases fat metabolism, which secondarily increases the use of carbohydrates, resulting in earlier hypoglycaemia and/or depletion of muscle glycogen with reduction in working capacity c) does not inhibit central and peripheral adaptation to physical conditioning.

Metabolism in ischemic muscles before and after treatment with glucose-insulin-potassium infusion

Arteriosclerosis, arterial thrombosis and emboli in the lower extremities of man result in metabolic disorders in the muscles due to a deficit between oxygen required and oxygen made available. Furthermore, diminished perfusion pressure results in diminished exchange of substrates and electrolytes across the capillary walls. In the muscle cells there is a depression of glycolytic enzyme function and a stimulation of lipid activity, resulting in accumulation of free fatty acids and acidosis within the cells. In order to increase R.Q. in the muscles in question, infusion of glucose-insulin-potassium were installed via a catheter introduced into the superior vena cava for 3 days. Following this, muscle samples showed significant increase of carbohydrate metabolism as compared to lipid metabolism and nearly normalization of intracellular content of free fatty acids. This was accompanied by improvement of the clinical condition of the patients and loss of pain in the extremities affected.

Coupling between dietary changes, reduced body weight, muscle fibre size and improved glucose tolerance in middle-aged men with impaired glucose tolerance

Fourteen middle-aged med with impaired glucose tolerance were studied prior to and 6 months after exchange of simple carbohydrates for complex carbohydrates rich in fibers and saturated for polyunsaturated fats in their diet when exchangeable. Body weight was reduced by 6.4 kg (p less than 0.001). Physical work capacity was unchanged. Fasting blood glucose and insulin were lowered (p less than 0.001) at 6 months and so were the values during an OGTT at 120 min. Both serum triglyceride and cholesterol concentrations were reduced (p less than 0.01) by the changes diet, the most marked reduction being found in the VLDL fraction. HDL levels increased by 21% (p less than 0.01). Enzyme activities in gastrocnemius muscle specimens were subnormal and uninfluenced by changed dietary habits. The number of capillaries per fiber was normal throughout, but as muscle fiber size was reduced in relation to the decreased body weight, the number of capillaries/mm2 increased during the dieting period. It is suggested that the observed improvement in insulin sensitivity and glucose tolerance after a dietary period with weight reduction is related to and partly explained by shorter diffusing distances in weight-bearing muscles.

Ultrastructure of the microvessels in skeletal muscle in a case of systemic capillary leak syndrome

The microvessels of skeletal muscle were examined electron microscopically in a case of systemic capillary leak syndrome (SCLS). One biopsy was taken in a free interval of the disease and one about 6 hours after the onset of an attack with hypovolemia. The microvascular endothelium exhibited a large number of multivesicular bodies, especially in the specimen obtained during an attack. Possibly this indicates a high heterophagic activity of the endothelium. A blebbing of the luminal surface of arteriolar endothelium was observed in the attack specimen. Since a complement activation seemed to occur during attacks, the blebbing is tentatively interpreted as a sign of a complement-mediated injury to the endothelium, leading to a breakdown of the endothelial barrier. This mechanism might explain the dramatic increase of microvascular permeability to plasma proteins during an attack of SCLS. The findings did not indicate that the increase might depend on some disturbance of the transendothelial vesicular transport function, nor could any openings of endothelial junctions, as in inflammation, be demonstrated. Regionally the periendothelial basal lamina appeared thickened, a finding which seems common in angiopathies of different kinds.

[Dynamics organ blood flow in rats in postnatal ontogenesis]

In the 4-, 13-, 30-, and 65- 90-day-old Wistar rats the voluminous blood flow rate was measured in liver, kidney, small intestine wall, and in the predominantly white gracilis muscle of femur. A LAKK-01 laser-Doppler flowmeter and its cutaneous (for kidney) and needle (for other organs) probes were used; they provided estimation of blood flow (per organ mass unit) to the tissue depth of about 1 mm. It has been found that the blood flow rates (per organ mass unit fall in liver, intestine, and even more in muscle, whereas increase in kidney, particularly for the first month of life. Calculations show that in adult rats as compared with the 4-day-old pups (with their mass exceeding 22 times) the blood flow to muscle, liver, intestine, and kidney should rise 14, 17, 18 and 43 times, respectively.

The respiratory responses to the combined activation of the muscle metaboreflex and the ventilatory chemoreflex

The excessive hyperventilation seen during exercise in chronic heart failure (CHF) contributes to the limited exercise capacity in this condition. The hyperactivation of reflexes originating, independently, from muscle (ergoreflex) and from chemoreceptors (chemoreflex) has been suggested to play an important part in the mediation of the CHF ventilatory abnormalities. In this study we aimed to assess the ventilatory responses to the combined activation of the muscle ergoreflex and the ventilatory chemoreflex, achieved by post-exercise circulatory occlusion (PECO) and euoxic hypercapnia (end-tidal PCO(2) = 7 mmHg above normal), respectively.Three healthy women and three healthy men (29.33 +/- 1.28 yrs; mean +/- SD) undertook four trials, in random order, separated from each other by 30 min of rest: 2 min of isometric handgrip exercise followed by 2 min of PECO with hypercapnia, 2 min of isometric handgrip exercise followed by 2 min of PECO while breathing room air, 4 min of rest with hypercapnia and 4 min of rest while breathing room air.Ventilation (V(E)) was significantly elevated by the ventilatory chemoreflex and it was further elevated by 5.13+/-0.83 L/min (P<0.05) when the muscle ergoreflex was superimposed upon it. The response to the combination of these stimuli was significantly greater than the sum of the responses to the two stimuli when given independently (P<0.05).The results indicate that the interaction between the two reflexes has an additional stimulatory effect on ventilation and consequently could be involved in the limited exercise capacity in CHF.

Interferon-gamma limits Th1 lymphocyte adhesion to inflamed endothelium: a nitric oxide regulatory feedback mechanism

CD4(+) T helper (Th1 and Th2) cell localization to a site of inflammation is important for the development, maintenance and regulation of an immune response. The factors that regulate Th1 and Th2 cell recruitment into tissue are not fully understood. The aim of the present study was to examine the effect of different cytokine microenvironments on the recruitment of Th1 and Th2 lymphocytes into tissue. Fluorescently labelled Th1 or Th2 lymphocyte-endothelial interactions were observed via intravital microscopy of the cytokine-treated cremaster muscle. Our results show that TNF-alpha alone is sufficient to maximally recruit Th1 cells. Surprisingly, treatment with TNF-alpha + IFN-gamma significantly decreased Th1 adhesion and emigration in comparison to TNF-alpha treatment alone. The decreased adhesion of Th1 cells in response to TNF-alpha + IFN-gamma reflected a decreased ability to bind to ICAM-1 and was iNOS-dependent. This phenomenon was not observed with Th2 cells. These results suggest that IFN-gamma may play a key immunomodulatory role in the recruitment of different T lymphocyte subsets. Indeed, blockade of IFN-gamma or iNOS function during the Th1-mediated contact hypersensitivity response resulted in an acceleration and exacerbation of the late-phase inflammatory response.

From scrawny to brawny: the quest for neomusculogenesis; smart surfaces and scaffolds for muscle tissue engineering

The successful generation of functional muscle tissues requires both an in-depth knowledge of muscle tissue physiology and advanced engineering practices. The inherent contractile functionality of muscle is a result of its high-level cellular and matrix organization over a multitude of length scales. While there have been many attempts to produce artificial muscle, a method to fabricate a highly organized construct, comprised of multiple cell types and capable of delivering contractile strengths similar to that of native smooth, skeletal or cardiac muscle has remained elusive. This is largely due to a lack of control over phenotype and spatial organization of cells. This paper covers state-of-the-art approaches to generating both 2D and 3D substrates that provide some form of higher level organization or multiple biochemical, mechanical or electrical cues to cells in order to successfully manipulate their behavior, in a manner that is conducive to the production of contractile muscle tissue. These so-called 'smart surfaces' and 'smart scaffolds' represent vital steps towards surface-engineered substrates for the engineering of muscle tissues, showing confidently that cellular behavior can be effectively and reproducibly manipulated through the design of the physical, chemical and electrical properties of the substrates on which cells are grown. However, many challenges remain to be overcome prior to reaching the ultimate goal of fully functional 3D vascularized engineered muscle.

[The Zung's autoscale for depression as predictor of sensorial and autonomic alterations to pain]

Clinical and experimental evidence support a relationship between susceptibility to chronic pain and a subjacent depression. Nevertheless, it's not clear if the currently available clinical evaluation instruments for depression allow for linking both disorders. Thus, we evaluated a Zung's autoscale for depression and its different categories: affective, physiological, motor and psychological, as possible predictors of sensorial and autonomic alterations and vulnerability to clinical chronic pain. In 32 healthy controls and 11 subjects with minor depression and free of treatment, ischemic pain was first induced by applying a tourniquet on the dominant arm, and then followed by paresthesias during the reperfusion of arm as the tourniquet is released. Ischemic muscular pain, post-ischemic paresthesias and associated cardiovascular responses were recorded throughout the experimental procedure. The affective category's score was correlated linearly in individual form with the greatest number of variables and it was adjusted to a model of multiple regressions that almost explained the variance in 100% with a contribution of the sensorial and autonomic variables of a 70% and 30%, respectively. In addition, the affective category was 50% greater in subjects with persistent clinical pain. The Zung's index and the other categories had a smaller number of individual linear correlations and models of multiple correlations that only explained between 30-70% of the variance, with a more predominant contribution of the autonomic variables (20-50%), especially in the psychological category. This suggests that the affective category predicts cutaneous-muscular sensorial alterations with greater effectiveness than the Zung's total index.