3D bioprinting of collagen to rebuild components of the human heart.

Collagen is the primary component of the extracellular matrix in the human body. It has proved challenging to fabricate collagen scaffolds capable of replicating the structure and function of tissues and organs. We present a method to 3D-bioprint collagen using freeform reversible embedding of suspended hydrogels (FRESH) to engineer components of the human heart at various scales, from capillaries to the full organ. Control of pH-driven gelation provides 20-micrometer filament resolution, a porous microstructure that enables rapid cellular infiltration and microvascularization, and mechanical strength for fabrication and perfusion of multiscale vasculature and tri-leaflet valves. We found that FRESH 3D-bioprinted hearts accurately reproduce patient-specific anatomical structure as determined by micro-computed tomography. Cardiac ventricles printed with human cardiomyocytes showed synchronized contractions, directional action potential propagation, and wall thickening up to 14% during peak systole.

Endoscopic transnasal cryo-assisted removal of an orbital cavernous hemangioma: a technical note.

The cryoprobe device is commonly used by orbital surgeons for the extraction of intraorbital lesions. Cryoprobes provide a safe mechanism to manipulate fluid-filled tumors. Such lesions can present in locations in which intraoperative neurosurgical assistance is essential. The authors describe a technique whereby removal of an orbital hemangioma was facilitated by the aid of an endoscopic, transnasal cryoprobe while standard microsurgical dissection was performed concurrently via a transconjunctival approach.

Cardiac ischaemia and rhythm disturbances during elective colonoscopy.

BACKGROUND: The number of colonoscopic procedures continues to rise rapidly. With widespread adoption of colonoscopy based bowel screening programmes, this rising trend is set to continue. AIMS: This study aimed to identify whether elective colonoscopy could provoke cardiac rhythm disturbances and/or myocardial ischaemia, as evidenced by 12 lead Holter ECG recordings and troponin I (cTnI) changes. MATERIALS AND METHODS: Patients were stratified into three groups based on the presence of cardiac disease or cardiovascular risk factors. They underwent real time 12 lead Holter monitoring before, during and after colonoscopy. Bloods were taken for pre- and post-procedure cTnI estimation. RESULTS: Holter ECG recordings of the three groups showed a high incidence of new but silent ischaemic and arrhythmic ECG changes during the colonoscopy in patients with documented but stable heart disease and to a lesser extent in those patients with one or more risk factors for heart disease. Three patients had high cTnI concentrations both before and after colonoscopy. Two patients with known heart disease died within 30 days of colonoscopy. CONCLUSIONS: This study demonstrates for the first time the occurrence of potentially clinically significant ST-T wave changes and rhythm disturbances during elective colonoscopy in patients with known heart disease and to a lesser extent in those patients with a known cardiovascular risk profile.

Non-invasive assessment of saphenous vein graft patency in asymptomatic patients.

The development and progression of atherosclerotic disease in saphenous vein grafts (SVGs) following coronary artery bypass surgery (CABG) are often without symptoms. Four-slice CT is a non-invasive imaging technique reliable for assessing SVG patency. This study utilised CT to assess temporal progression of patency in asymptomatic patients. A four-slice CT scanner was used employing standard techniques. Analysis of the reconstructed images was performed offline by two experienced operators blinded to patient details. The primary aim was vein graft patency. 130 asymptomatic subjects were studied. The mean time from CABG was 7.3 years (range, 15 days to 21 years 9 months; standard deviation (SD), 4.4 years). 294 of the 305 SVGs were suitable for assessment of patency. The overall occlusion rate for assessable grafts was 23.5%. Occlusion rates for grafts <1 year old was 12.5% (2/16), 20.7% (42/203) for grafts 1-10 years old, and 33.3% (25/75) for grafts >10 years old. In conclusion, significant occlusion of SVGs occurs early after CABG in asymptomatic patients. Four-slice CT has the potential for the non-invasive assessment of individuals after surgery.

Improved growth factor directed vascularization into fibrin constructs through inclusion of additional extracellular molecules.

Using the chick chorioallantoic membrane assay (CAM) and a novel histological technique, we investigated the ability of blood vessels to directly invade fibrin-based scaffolds. In our initial experiments utilizing vascular endothelial growth factor (VEGF(165)), we found no direct invasion. Instead, the fibrin was completely degraded and replaced with highly vascularized new tissue. Addition of fibroblast growth factor-2 (FGF-2), bone morphogenic protein-2 (BMP-2), or platelet-derived growth factor-BB (PDGF-BB) to the fibrin construct also did not result in construct vascularization. Because natural and regenerating tissues exhibit complex extracellular matrices (ECMs), we hypothesized that a more complex scaffold may improve blood vessel invasion. Addition of fibronectin, hyaluronic acid, and collagen type I within 20 mg/mL fibrin constructs resulted in no significant improvement. However, the same additive concentrations within 10 mg/mL fibrin constructs resulted in dramatic improvements, specifically with hyaluronic acid. Overall, we believe that these results indicate the importance of structural and functional cues of not only in the initial scaffold but also as the construct is degraded and remodeled. Furthermore, the CAM assay may represent a useful model for understanding ECM interactions as well as for screening and designing tissue-engineered scaffolds.

One year results of the Middlesbrough early revascularisation to limit infarction (MERLIN) trial.

OBJECTIVE: To report one year results of the MERLIN (Middlesbrough early revascularisation to limit infarction) trial, a prospective randomised trial comparing the strategy of coronary angiography and urgent revascularisation with conservative treatment in patients with failed fibrinolysis complicating ST segment elevation myocardial infarction (STEMI). The 30 day results have recently been published. At the planning stage of the trial, it was determined that follow up of trial patients would continue annually to three years to determine whether late benefit occurred. SUBJECTS: 307 patients who received a fibrinolytic for STEMI but failed to reperfuse early according to previously described ECG criteria and did not develop cardiogenic shock. METHODS: Patients were randomly assigned to receive either emergency coronary angiography with a view to proceeding to urgent revascularisation (rescue percutaneous coronary intervention (rPCI) arm) or continued medical treatment (conservative arm). The primary end point was all cause mortality at 30 days. The secondary end points included the composite end point of death, reinfarction, stroke, unplanned revascularisation, or heart failure at 30 days. The same end points were evaluated at one year and these results are presented. RESULTS: All cause mortality at one year was similar in the conservative arm and the rPCI arm (13.0% v 14.4%, p = 0.7, risk difference (RD) -1.4%, 95% confidence interval (CI) -9.3 to 6.4). The incidence of the composite secondary end point of death, reinfarction, stroke, unplanned revascularisation, or heart failure was significantly higher in the conservative arm (57.8% v 43.1%, p = 0.01, RD 14.7%, 95% CI 3.5% to 25.5%). This was driven almost exclusively by a significantly higher incidence of subsequent unplanned revascularisation in the conservative arm (29.9% v 12.4%, p < 0.001, RD 17.5%, 95% CI 8.5% to 26.4%). Reinfarction and clinical heart failure were numerically, but not statistically, more common in the conservative arm (14.3% v 10.5%, p = 0.3, RD 3.8%, 95% CI -3.7 to 11.4, and 31.2% v 26.1%, p = 0.3, RD 5.0%, 95% CI -5.1 to 15.1). There was a strong trend towards fewer strokes in the conservative arm (1.3% v 5.2%, p = 0.06, RD -3.9%, 95% CI -8.9 to 0.06). CONCLUSION: At one year of follow up, there was no survival advantage in the rPCI arm compared with the conservative arm. The incidence of the composite secondary end point was significantly lower in the rPCI arm, but this was driven almost entirely by a highly significant reduction in the incidence of further revascularisation.

Cadmium uptake in rat hepatocytes in relation to speciation and to complexation with metallothionein and albumin.

Cadmium (Cd) uptake has been studied in primary cultures of rat hepatocytes focusing on the impact of inorganic and organic speciation. Uptake time-course studies over a 60-min exposure to 0.3 microM (109)Cd revealed a zero-time uptake and a slower process of accumulation which proceeds within minutes. (109)Cd uptake showed saturation kinetics (K(m) = 3.5 +/- 0.8 microM), and was highly sensitive to inhibition by Zn and Hg. There was no evidence for sensitivity to the external pH nor for any preferential transport of the free cation Cd(2+) over CdCl(n) (2-n) chloro-complexes. According to the assumption that only inorganic metal species are available, metal uptake decreased upon albumin (BSA) addition to the exposure media. In contrast, higher levels of (109)Cd accumulation were obtained under optimal conditions for Cd complexation by MT. Comparison among uptake data obtained under inorganic and organic conditions revealed that Cd-MT would be taken up 0.4 times as rapidly as Cd(inorg). We conclude that uptake of Cd in rat hepatocytes involves specific transport mechanism(s) subjected to Zn or Hg interactions. Uptake of inorganic Cd is not proportional to the levels of free Cd(2+) and does not involve the divalent cation transporter DCT1 nor the co-transporter Fe(2+)-H(+) NRAMP2. We found Cd-MT but not Cd-BSA to be available for the liver cells, and have estimated a binding affinity four orders of magnitude higher for Cd complexation with MT compared to BSA; MT may have a significant role in Cd delivery to the liver.

[The effect of growth/differentiation factor-5 (GDF-5) on genotype and phenotype in human adult mesenchymal stem cells]. / Effekt von Growth/Differentiation Factor-5 (GDF-5) auf Genotyp und Phänotyp humaner adulter mesenchymaler Stammzellen.

AIM: To evaluate the effects of GDF-5 on genotype and phenotype of human mesenchymal stem cells (hMSC). HYPOTHESIS: GDF-5 leads to up-regulation of the Type I-collagen (Col) gene without altering bone marker genes or alkaline phosphatase activity. METHODS: To test our hypothesis hMSC were treated with rmGDF-5. Using quantitative real-time PCR we analyzed mRNA for Col, Runx2 and Osterix (Osx). Furthermore, we analyzed alkaline phosphatase activity (ALP) as a phenotypical bone marker. ANOVA and post hoc statistical analyses were used to determine differences among treatments (p < 0.05). RESULTS: HMSC showed a biphasic response in both Col and Runx2 after rmGDF-5. Initial up-regulation was followed by a significant down-regulation below controls. Interestingly, the controls presented with changes for Col and Runx2 over time. There was no Osx expression in either treated hMSC or controls. No significant differences could be detected in ALP. CONCLUSION: Increased expression of Col and Runx2 might indicate differentiation towards both osteoblast and fibroblast lineage. However, no Osx expression and no change in ALP support the assumption that rmGDF-5 does not lead to an osteoblast phenotype in hMSC. Our in vitro studies confirm a possible therapeutic benefit of GDF-5 in the treatment of tendon and ligament injuries and tissue engineering approaches. Further research is necessary to prove its clinical value.

Early and late reactions following the use of iopamidol 340, iomeprol 350 and iodixanol 320 in cardiac catheterization.

GOAL: To investigate the incidence of early (< 24 hours) and late (> 24 hours to 7 days) reactions to 3 contrast agents commonly used in cardiac catheterization. METHODS AND RESULTS: A total of 2,108 patients undergoing cardiac catheterization in a Regional Cardiothoracic Unit were randomly assigned to receive 1 of 3 commonly used contrast agents in a prospective, double-blind study. The contrast agents were iopamidol 340 (Niopam ), a nonionic monomer; iomeprol 350 (Iomeron ), a nonionic dimer; and iodixanol 320 (Visipaque ), a nonionic dimer. The main outcome measures were the incidence of early (< 24 hours) reactions following catheterization and the incidence of late (24 hours to 7 days) reactions. Early reactions, excluding patients with heat on left ventriculography as the sole symptom, were relatively common (7.4%), but there was no significant difference between the 3 agents (p = 0.35). Late skin reactions, excluding reactions solely at the site of the arterial puncture and continuations of early urticarial reactions, were also relatively common (5.4%), but the incidence differed between the 3 agents. Such reactions occurred in 2.7% of those receiving iopamidol 340 (Niopam ), 3.5% of those receiving iomeprol 350 (Iomeron ) and 10.4% of those receiving iodixanol 320 (Visipaque ) (p < 0.01). CONCLUSION: The incidence of early adverse reactions is similar with these 3 contrast agents. However, late skin reactions are significantly more common with iodixanol 320 (Visipaque ) than with the other 2 agents. Although such reactions were rarely troublesome, patients should be advised accordingly.

Seasonal variation in carbohydrate and lipid metabolism of yellow perch (Perca flavescens) chronically exposed to metals in the field.

The effects of heavy metals on growth, intermediary metabolism and enzyme activities were investigated in yellow perch (Perca flavescens), sampled in summer and fall from lakes situated along a contamination gradient of Cd, Zn and Cu in the mining region of Rouyn-Noranda, Québec. An exposure-dependent decrease in condition factor was observed in both seasons. Liver glycogen and triglyceride reserves were higher in summer than in fall in fish from the reference lake, while the seasonal pattern was different in fish from the contaminated lakes. Plasma free fatty acids (FFA) levels were also influenced by season and contamination. Activities of malic enzyme (ME) and glucose 6-phosphate dehydrogenase (G6PDH) in the liver were higher in the summer than in the fall in reference lakes whereas no seasonal variations were detected in fish from contaminated lakes. Activities of pyruvate kinase (PyK), aspartate transaminase (AST), phosphoenolpyruvate carboxykinase (PEPCK) and malate dehydrogenase (MDH), were higher in fish from contaminated lakes in fall but not in summer. Chronic exposure of yellow perch to sublethal levels of heavy metals impairs growth and alters the seasonal cycling of liver glycogen and triglycerides as well as the activities of metabolic enzymes.

Cadmium accumulation and metallothionein synthesis in freshwater bivalves (Pyganodon grandis): relative influence of the metal exposure gradient versus limnological variability.

The relative influence of limnological confounding factors on cadmium (Cd) bioaccumulation and metallothionein (MT) synthesis was quantified in natural populations of freshwater bivalves (Pyganodon grandis) living in lakes along a Cd concentration gradient. During the ice-free period, we measured 15 environmental variables in the water compartment and determined total concentrations of Cd and MT in the gills of bivalves at 37 littoral stations in 20 lakes distributed across the mining area of Rouyn-Noranda in northwestern Quebec. A multiple linear regression model including pH (+), dissolved Ca concentrations (-) and free Cd2+ concentrations at the sediment-water interface (+) explained 74% of the variability in Cd concentrations in the bivalve gills. Dissolved Ca (-) and free Cd2+ (+) together explained 62% of the variation in MT concentrations in the bivalve gills. Partial linear regression analyses indicated that the limnological factors' pure and shared effects together accounted for 48 and 45% of the total variation in Cd and MT concentrations in the gills, respectively. A lake selection procedure that could be applied in monitoring programs is proposed to minimise the relative influence of these confounding variables.

Thiosulfate enhances silver uptake by a green alga: role of anion transporters in metal uptake.

Short-term (< 1 h) silver uptake by the green alga Chlamydomonas reinhardtii was measured in the laboratory in defined inorganic media in the presence or absence of ligands (chloride and thiosulfate). In contradiction to the free-ion model of metal uptake, silver accumulation by the alga proved to be sensitive to the choice of ligand used to buffer the free silver concentration. For a low fixed free Ag+ concentration of 10 nM, silver uptake in the presence of thiosulfate (0.11 microM) was 2x greater than in the presence of chloride (4 mM). When sulfate was removed from the exposure medium (i.e., 81 microM-->0 microM), silver uptake in the presence of thiosulfate was even more markedly enhanced (more than 4x greater than in the presence of chloride). Varying the sulfate concentration in the exposure medium only affected silver uptake if thiosulfate was present. We conclude that silver-thiosulfate complexes are transported across the plasma membrane via sulfate/thiosulfate transport systems and that sulfate acts as a competitive inhibitor of this uptake mechanism.

Geochemical changes in sulfidic mine tailings stored under a shallow water cover.

The objective of this study was to assess the effectiveness of an engineered shallow water cover in reducing the oxidation of sulfidic mine tailings and thus preventing the development of acid rock drainage. Fresh tailings were submerged under a 0.3-m water cover in experimental field cells. From 1996 to 1998, we followed the chemistry of the interstitial water near the tailings-overlying water interface using in situ dialysis, and determined pH and dissolved oxygen (DO) profiles across the tailing water interface using micro-electrodes. Penetration of DO into the tailings was limited to <7 mm, even in the presence of DO produced by benthic periphyton. Anoxia in the tailings was further demonstrated by the appearance of dissolved sigmaH2S, Fe and Mn in pore water at depths -1.5 cm below the interface. However, there was clear evidence of surface oxidation of the mine tailings at the mm scale (i.e., DO depletion, coupled with localized increases in [H+] and [SO4(2-)]). Mobilization of Cd and Zn from this surface layer was indicated by the presence of sub-surface peaks in the concentrations of these two metals in the tailings interstitial water and by a change in their solid phase partitioning from refractory to more labile fractions. In contrast, mobilization of Cu from tailings was less evident. Unlike previous reports, which suggested that submerged tailings were effectively inert, our results show alteration of the superficial layer over time.

Fine-scale tissue distribution of cadmium, inorganic mercury, and methylmercury in nymphs of the burrowing mayfly Hexagenia rigida studied by whole-body autoradiography.

The distribution of inorganic 109Cd(II), inorganic 203Hg(II), and [203Hg] methylmercury (MeHg) in nymphs of the burrowing mayfly Hexagenia rigida after exposure via water and sediments was studied. To better understand the mechanisms underlying the fate of Cd, Hg, and MeHg in this animal and to identify target organs, autoradiography of whole-body cryosections was used to obtain a detailed view of the distribution of the radiolabels. The gut and exoskeleton were the only structures labeled in nymphs exposed to Cd via water or sediments. After exposure to inorganic Hg via water, the Malpighian tubules exhibited a very high labeling, indicating that these organs may be a target for Hg toxicity. The distribution of Hg after exposure via sediments was similar, though the labeling of Malpighian tubules was less intense. Distribution of MeHg strongly differed between treatment groups. Nymphs were rather uniformly labeled after exposure via water, whereas in those exposed to MeHg in sediments, the intense labeling of all internal tissues contrasted with the very low labeling of the hemolymph, indicating that the translocation rate of the absorbed MeHg was faster in the latter group. This may be related to the complexation of MeHg by small thiol ligands in the gut as a result of the digestion process.

Cadmium uptake by Caco-2 cells: effects of Cd complexation by chloride, glutathione, and phytochelatins.

Short-term cadmium uptake by the highly differentiated TC7 clone of enterocytic-like Caco-2 cells was studied as a function of Cd speciation. For low metal concentrations and with a constant free [Cd(2+)] = 43 nM, initial uptake rates of (109)Cd increased linearly as a function of increasing concentration of chlorocomplexes (Sigma[(109)CdCl(2-n)(n)]) over the range from 0 to 250 nM. When normalized as a function of the metal concentration, the absorption rate for the chlorocomplexes was less than that estimated for uptake of the free Cd(2+) cation. Metal absorption decreased upon organic ligand addition in the exposure media, but much less than predicted from the assumption that only inorganic metal species would be transported. Under exposure conditions where the concentration of each of the inorganic species was kept constant, (109)Cd uptake increased with increasing concentrations of cadmium glutathione ((109)Cd-GSH) or phytochelatin ((109)Cd-hmPC(3)) complexes. A specific system of very high affinity but low capacity has been characterized for (109)Cd-GSH transport, whereas accumulation data increased linearly with (109)Cd-hmPC(3) up to 6 microM. Comparison among uptake data for 0.3 microM inorganic (109)Cd, (109)Cd-GSH, or (109)Cd-hmPC(3) yields the following accumulation ratios: Cd-GSH/Cd(inorg) = 0.2; Cd-hmPC(3)/Cd(inorg) = 0.5. These results clearly show that Cd(2+) is not the exclusive metal species participating in Cd absorption, though, for comparable Cd concentrations, its contribution to transport would be more important than that of other species. Cadmium bound to thiol-containing peptides may be absorbed via transport systems that differ from those involved in absorption of the inorganic metal species.

The influence of polymer blend composition on the degradation of polymer/hydroxyapatite biomaterials.

The in vitro degradation of biodegradable polymer/ceramic composites was assessed in two different environments under both static and pseudodynamic conditions. The blends, consisting of polycaprolactone, poly(lactic-co-glycolic acid), and hydroxyapatite, have potential use in bone tissue engineering applications, thus it is essential to establish a standardized method of characterizing the degradation of new biomaterials. In this study, the variation in polymer blend ratio was examined to observe a change in degradation rate. The porous blends were degraded in water and serum-containing media. A previous study examined in vitro degradation in serum-free buffer. Molecular weight loss, gravimetric weight loss, pH changes and morphological changes were evaluated. The changes in porosity were observed with scanning electron microscopy and quantitatively assessed using image analysis. There was a significant difference in molecular weight loss and gravimetric weight loss between the blends after 10 weeks in vitro. Blends containing the greatest amount of poly(lactic-co-glycolic acid) degraded most rapidly.

Selective use of abciximab in coronary stenting: overall outcomes can still be equivalent to those in the EPISTENT treatment group.

BACKGROUND: The EPISTENT trial reported improved early outcomes with routine use of abciximab after coronary stenting. Increasing use of stents means that routine abciximab adds significantly to costs of percutaneous coronary intervention (PCI). This paper reports the results of a protocol encouraging restriction of abciximab therapy to high-risk patients only. METHODS: Data were collected prospectively over a 34-month period for patients undergoing PCI with stenting. In addition to those who fulfilled criteria for inclusion in the EPISTENT trial, patients treated in the setting of acute myocardial infarction (AMI) were studied. Demographic data, procedural details and early clinical outcomes were recorded. RESULTS: Of 808 patients studied, 601 fulfilled EPISTENT inclusion criteria and comprised 367 patients (45%) treated for stable angina and 234 (30%) treated for unstable or post-infarct angina. The additional 207 patients (25%) were treated during AMI. The 808 patients received a total of 981 stents. Abciximab was given in only 88 cases (10.9%). Major adverse clinical events occurred in 39 patients (4.8%). CONCLUSION: Selective use of abciximab for patients undergoing coronary stenting can be associated with outcomes equivalent to those reported for routine use, but with significant cost savings.

Reappraising the role of immediate intervention following thrombolytic recanalization in acute myocardial infarction.

Early studies indicated that after successful thrombolytic recanalization, adjunctive percutaneous transluminal coronary angioplasty (PTCA) was not appropriate, even when a significant residual stenosis was present. The aim of this study was to assess in-hospital clinical outcomes of patients with acute myocardial infarction (AMI) who underwent successful recanalization after thrombolytic therapy. The relation between repeat AMI/unstable angina and the severity of the stenosis, as well as other angiographic and clinical features was also examined. One hundred patients with AMI of <10 hours underwent coronary angiography 2 hours after receiving thrombolytic therapy. Salvage PTCA +/- stenting was performed if recanalization was unsuccessful (Thrombolysis In Myocardial Infarction [TIMI] trial grade 0 to 2), and no PTCA was undertaken if there was brisk anterograde flow (TIMI 3). Angiographic analysis was performed to assess the severity of the residual lesion, as well as the presence or absence of thrombus. Forty patients had unsuccessful recanalization, and of these, 36 underwent attempted PTCA. Of the 60 patients with TIMI 3 flow, 15 required repeat angiography and PTCA after repeat AMI (n = 13) or unstable angina (n = 2) within 5 days. Receiver-operating characteristic analysis indicated an optimum percent diameter stenosis predictor of 85% for repeat AMI/unstable angina. There was no additional relation to age, gender, time to thrombolysis, the infarct-related artery, or the presence of culprit lesion thrombus. After recanalization, a high-grade stenosis >85% is common (n = 25, 42.4%). This is associated with a 54% repeat AMI/unstable angina risk-a ninefold increase in the incidence of such events than in patients with lesions <85%. Thus, patients with narrowings >85% may benefit from early intervention rather than a conservative approach. Narrowings <85% have a 94% probability of no repeat AMI/unstable angina and do not require early intervention.