Increased Expression of miR-146a in Valvular Tissue From Patients With Aortic Valve Stenosis

miR-146a has been implicated in the regulation of the immune response as well as in inflammatory process of atherosclerosis. In the present study, we have investigated the expression of miR-146a and its targets, TLR4 a IRAK1, in aortic valve stenosis. A total of 58 patients with aortic stenosis (non- and atherosclerotic; tissue obtained during standard aortic valve replacement) were enrolled. The relative expression of mir-146a was higher in valvular tissue from patients with atherosclerosis compared to those without atherosclerosis (p = 0.01). Number of the IRAK1 and TLR4 transcripts did not differ between the investigated groups. There was a trend toward elevation of miR-146a expression in context of inflammatory infiltrate observed in the valvular tissue from patients with atherosclerosis (p = 0.06). In conclusion, in line with the acknowledged role of miR-146a in atherosclerotic inflammation, our data suggest it may be extended to the specific location of aortic valves in aortic stenosis.

Electrospun vascular grafts fabricated from poly(L-lactide-co-ε-caprolactone) used as a bypass for the rabbit carotid artery

The study involved the electrospinning of the copolymer poly(L-lactide-co-ε-caprolactone) (PLCL) into tubular grafts. The subsequent material characterization, including micro-computed tomography analysis, revealed a level of porosity of around 70%, with pore sizes of 9.34 ± 0.19 μm and fiber diameters of 5.58 ± 0.10 μm. Unlike fibrous polycaprolactone, the electrospun PLCL copolymer promoted fibroblast and endothelial cell adhesion and proliferation in vitro. Moreover, the regeneration of the vessel wall was detected following implantation and, after six months, the endothelialization of the lumen and the infiltration of arranged smooth muscle cells producing collagen was observed. However, the degradation rate was found to be accelerated in the rabbit animal model. The study was conducted under conditions that reflected the clinical requirements-the prostheses were sutured in the end-to-side fashion and the long-term end point of prosthesis healing was assessed. The regeneration of the vessel wall in terms of endothelialization, smooth cell infiltration and the presence of collagen fibers was observed after six months in vivo. A part of the grafts failed due to the rapid degradation rate of the PLCL copolymer.

Failure of sternal wires depends on the number of turns and plastic deformation: combined experimental and computational approach

OBJECTIVES

The number of turns at the end of a wire closure is not described or discussed in any cardiosurgical guidelines. The hands-on experience of the surgeon plays a significant role. The aim of this work was to clarify the relationship between the number of turns of the suture and the resulting strength of the sternal fixation.

METHODS

The study was performed in 2 independent steps. The first step was a finite element simulation, where the stress and strain distribution of the sternal fixation was observed. The second step included the experimental set-up and the statistical evaluation of the results.

RESULTS

Our study showed that the failure force rose linearly as the number of turns increased. The lowest average measured force was 370 N (3 turns); the highest was 430 N (7 turns). The failure modes were either untwisting of the wires or rupture of the closure, which is controlled by the number of turns. As the number of turns increases, superficial cracks can occur.

CONCLUSIONS

Based on our results, the 5-turn option is the best solution for the closure. The failure force is still double the value reported in the literature, so there is a high safety margin for failure. The failure mode is untwisting; hence, no unexpected fracture can occur, and there is still an elastic core in the cross-section of the wire.

Efficiency of riboflavin and ultraviolet light treatment against high levels of biofilm-derived Staphylococcus epidermidis in buffy coat platelet concentrates

BACKGROUND AND OBJECTIVES

Staphylococcus epidermidis forms surface-attached aggregates (biofilms) in platelet concentrates (PCs), which are linked to missed detection during PC screening. This study was aimed at evaluating the efficacy of riboflavin-UV treatment to inactivate S. epidermidis biofilms in buffy coat (BC) PCs.

MATERIALS AND METHODS

Biofilm and non-biofilm cells from S. epidermidis ST-10002 and S. epidermidis AZ-66 were individually inoculated into whole blood (WB) units (~10⁶ colony-forming units (CFU)/ml) (N = 4-5). One spiked and three unspiked WB units were processed to produce a BC-PC pool. Riboflavin was added to the pool which was then split into two bags: one for UV treatment and the second was untreated. Bacterial counts were determined before and after treatment. In vitro PC quality was assessed by flow cytometry and dynamic light scattering.

RESULTS

Bacterial counts were reduced during BC-PC production from ~10⁶ CFU/ml in WB to 10³ -10⁴ CFU/ml in PCs (P < 0·0001). Riboflavin-UV treatment resulted in significantly higher reduction of S. epidermidis AZ-66 than strain ST-10002 (≥3·5 log reduction and 2·6-2·8 log reduction, respectively, P < 0·0001). Remaining bacteria post-treatment were able to proliferate in PCs. No differences in S. epidermidis inactivation were observed in PCs produced from WB inoculated with biofilm or non-biofilm cells (P > 0·05). Platelet activation was enhanced in PCs produced with WB inoculated with biofilms compared to non-biofilm cells (P < 0·05).

CONCLUSION

Riboflavin-UV treatment was similarly efficacious in PCs produced from WB inoculated with S. epidermidis biofilm or non-biofilm cells. Levels of biofilm-derived S. epidermidis ≥10³ CFU/ml were not completely inactivated; however, further testing is necessary with lower (real-life) bacterial levels.

Bacterial survival and distribution during buffy coat platelet production

BACKGROUND AND OBJECTIVES

At Canadian Blood Services, buffy coat (BC) platelet concentrates (BC-PCs) show a generally lower bacterial contamination rate than apheresis PCs. This study investigated whether the PC production method contributes to this observation.

MATERIALS AND METHODS

Whole blood (WB) inoculated with eight bacterial strains was processed using the BC method. Bacteria were enumerated throughout BC-PC production and subsequent PC storage. Endotoxin production and bacterial adhesion to PC bags were evaluated during PC storage. PC quality was monitored by CD62P expression (flow cytometry) and changes in dynamic light scattering (ThromboLUX^® ).

RESULTS

During overnight WB hold, Staphylococcus epidermidis titres remained unchanged, commercial Escherichia coli and Klebsiella pneumoniae were eliminated and the remaining organisms proliferated to high concentrations. Through BC-PC production, bacteria segregated preferentially towards the cellular fractions compared to plasma (P < 0·05). During PC storage, most bacteria adhered to the PC bags and Gram negatives produced clinically significant endotoxin levels. Changes in CD62P expression or ThromboLUX scoring did not consistently reflect bacterial contamination in BC-PCs.

CONCLUSION

WB hold during BC-PC production does not have a broad-spectrum bactericidal effect, and therefore, other factors contribute to low rates of contamination in BC-PCs.

Biofilm formation by Staphylococcus capitis strains isolated from contaminated platelet concentrates

Bacterial contamination of platelet concentrates (PCs) poses the greatest infectious risk in modern transfusion medicine despite the implementation of measures such as improved skin disinfection and first aliquot diversion. The majority of PC contaminants are commensal skin flora introduced by venipuncture at the time of blood collection. The predominant organisms are Gram-positive coagulase-negative staphylococci such as Staphylococcus capitis. This bacterium has been implicated in numerous instances of infection and sepsis, likely for its ability to form surface-associated communities of micro-organisms encased in extracellular materials, known as biofilms. In the present study, five strains of S. capitis isolated from contaminated PCs were assessed for their ability to produce extracellular polysaccharide (slime), a canonical indicator of biofilm-formation ability, on Congo red agar plates. Biofilm formation was evaluated in both glucose-enriched trypticase soy broth (TSBg) and in PCs by using a crystal violet staining assay. The chemical nature of the biofilms was evaluated by disruption assays using sodium metaperiodate and proteinase K. In addition, biofilm architecture was observed by scanning electron microscopy. The presence of the biofilm-associated icaR and icaADBC genes was also examined by PCR. While only two out of the five S. capitis strains formed biofilms in TSBg, all strains formed biofilms in PCs. The ability of strains to produce extracellular polysaccharide and their possession of wild-type ica genes were not exclusive predictors of biofilm formation in TSBg or PCs; different profiles of biofilm markers were observed among isolates. This is likely due to the proteinaceous composition of the S. capitis biofilm matrix. Interestingly, an ica-negative, non-slime-producing isolate was capable of biofilm formation in PCs. Together, these data indicate that the platelet storage environment stimulates biofilm formation in S. capitis in the absence of extracellular polysaccharide production and that multiple bacterial factors and regulatory elements are likely involved in biofilm formation in this milieu.

Use of allogenous bone graft and osteosynthetic stabilization in treatment of massive post-sternotomy defects

Thoracic stabilization using transverse plate fixation represents a modern and safe method of sternal dehiscence treatment. However, it still remains difficult to apply in cases of massive loss of bone tissue of the chest wall. An unsatisfactory stability of thorax often results in severe respiratory insufficiency, and also affects healing of soft tissue closure while increasing the risk of development of chronic fistulas and other dehiscences. In the reported case, we opted for a unique treatment of massive post-sternotomy defect using an allogenous bone graft of calva. Transverse titanium plates were applied to achieve stabilization of bone grafts and chest wall.

Serratia marcescens strains implicated in adverse transfusion reactions form biofilms in platelet concentrates and demonstrate reduced detection by automated culture

BACKGROUND AND OBJECTIVES

Serratia marcescens is a gram-negative bacterium that has been implicated in adverse transfusion reactions associated with contaminated platelet concentrates. The aim of this study was to investigate whether the ability of S. marcescens to form surface-attached aggregates (biofilms) could account for contaminated platelet units being missed during screening by the BacT/ALERT automated culture system.

MATERIALS AND METHODS

Seven S. marcescens strains, including biofilm-positive and biofilm-negative control strains and five isolates recovered from contaminated platelet concentrates, were grown in enriched Luria-Bertani medium and in platelets. Biofilm formation was examined by staining assay, dislodging experiments and scanning electron microscopy. Clinical strains were also analysed for their ability to evade detection by the BacT/ALERT system.

RESULTS

All strains exhibited similar growth in medium and platelets. While only the biofilm-positive control strain formed biofilms in medium, this strain and three clinical isolates associated with transfusion reactions formed biofilms in platelet concentrates. The other two clinical strains, which had been captured during platelet screening by BacT/ALERT, failed to form biofilms in platelets. Biofilm-forming clinical isolates were approximately three times (P<0·05) more likely to be missed by BacT/ALERT screening than biofilm-negative strains.

CONCLUSION

S. marcescens strains associated with transfusion reactions form biofilms under platelet storage conditions, and initial biofilm formation correlates with missed detection of contaminated platelet concentrates by the BacT/ALERT system.

PEGylation prevents bacteria-induced platelet activation and biofilm formation in platelet concentrates

Bacterial contamination of platelet concentrates represents the greatest post-transfusion infectious risk. Biofilm formation in this environment resulting from platelet-bacteria interactions can lead to non-uniform contaminant distribution and thus missed detection. As formation of platelet-bacteria aggregates is largely based on receptor-ligand interactions, we examined whether shielding these events would result in reduced biofilm formation by contaminant bacteria. We introduced methoxypoly(ethylene glycol) to covalently modify the platelet surface using a process termed 'PEGylation'. In the first study of its kind, we demonstrate that PEGylated platelet concentrates inoculated with Staphylococcus epidermidis display a significant reduction in bacterial binding and biofilm formation.

Negative pressure therapy as a treatment modality for surgical site infection in cardiac surgery

BACKGROUND

Negative pressure therapy (NPT), primarily introduced for the treatment of pressure ulcers or chronic debilitating wounds, has recently emerged as a novel treatment strategy in the field of cardiac surgery, providing superior results to the conventional therapeutic strategies.

PATIENTS AND METHODS

From November 2004 to October 2005, 25 patients underwent NPT (negative pressure therapy). Four patients (16%) were treated for extensive leg-wound infections, 10 (40%) were treated for superficial sternal wound infections and 11 (44%) for deep sternal wound infections. The median age was 67.9 years (range 48 to 79) and the median BMI was 34.2 kg/m2 (range 28 to 41). Because of wound infection complications, 11 patients (44%) were re-admitted to the department. In 13 patients (52%), NPT was employed after the failure of the conventional treatment strategy.

RESULTS

All 25 patients were successfully healed. In-hospital mortality was 0% and 30-day survival was 100%. The overall length of hospitalization reached 36.4 days (range 11 to 62). The median number of dressing changes was 4.9 (range 3 to 9). The median NPT treatment time until the surgical closure was 9.7 days (range 6 to 24 days). In 17 patients (68%), the excessive residual sternal defect required a local advancement flap transfer. One patient (4%) with a chronic wire-related fistula was re-admitted 6 months after NPT therapy.

CONCLUSION

NPT therapy can be considered as an effective treatment strategy associated with a low risk of procedure failure and wound infection recurrence, particularly in the management of sternal wound infection after cardiac surgery.

[Measurement of impedance of hepatic tissue transformed by pathological process. A preliminary communication]

Intrahepatic impedance was measured using a special electrode in 44 patients, 38 of whom identified abnormalities of the hepatic parenchyma. Impedance values were compared with ultrasound findings and with the histological results of needle biopsy. Impedance was relatively unaffected in the presence of cirrhosis (n = 7) or chronic hepatitis (n = 5). It was markedly decreased in the presence of cysts (n = 4) and of hepatocarcinoma (n = 4). Values were variable in secondary carcinoma of the liver (n = 16). This preliminary study suggests that the measurement of intrahepatic impedance could contribute to the etiological diagnosis of hepatic tumour lesions.

Effect of peroral administration of isosorbide dinitrate on portal pressure and blood flow in patients with cirrhosis of the liver

The effect of slow-release isosorbide dinitrate, given orally four times daily for 14 days, on the portal circulation was studied in 10 patients with liver cirrhosis and oesophageal varices. Mean arterial pressure and heart rate were not influenced significantly by isosorbide dinitrate. Statistically significant dilation of the portal vein by 11.9% and an increase in blood flow velocity by 35.4% and in portal blood flow rate by 54.3% were observed at the end of therapy. The average wedged hepatic vein pressure was 32.9 mmHg before therapy and after therapy it was decreased to 60.5%. The slight decrease observed in free hepatic vein pressure was not statistically significant. Before treatment the portohepatic gradient was four times above normal and after therapy it fell to 9.5 mmHg. The results indicate that, in patients with portal hypertension, an improvement in haemodynamics can be achieved by the use of isosorbide dinitrate. This improvement may lead to the prevention of bleeding from oesophageal varices.

Microstructure of dairy foods. 2. Milk products based on fat

Cold-stage scanning electron microscopy and transmission electron microscopy of replicas of freeze-fractured samples have been suggested as the electron microscopic techniques best suited to study the microstructure of milk products based on fat. New developments in other techniques such as fixation of fat with imidazole-buffered osmium tetroxide and embedding in a resin also have been mentioned. Microstructure of various forms of cream, ice cream, cream cheese, cream cheese spread, and butter, established by the techniques mentioned, has been reviewed with respect to the specific properties of each of the fat-based milk products.

Improved recovery of fecal coliforms from the Ottawa River by membrane filters in the presence of food debris

In the absence of food debris, Sartorius and Millipore HA filters recovered substantially fewer fecal coliforms from Ottawa River water than did Millipore HC. On addition of a small quantity of sterile blended carrot to water samples, recovery by the poorer filters equalled that on Millipore HC. Scanning electron microscopy revealed bacteria sheltered in crevices formed by carrot fibres and thus protected from the normal stresses of exposure. Addition of carrot debris (e.g., 0.03 g carrot to 100 mL of sample) thus provides a convenient and inexpensive means of reducing variations in fecal coliform recovery between brands of membrane filters.