Impact of 4D-Flow CMR Parameters on Functional Evaluation of Fontan Circulation

We sought to evaluate the potential clinical role of 4D-flow cardiac magnetic resonance (CMR)-derived energetics and flow parameters in a cohort of patients' post-Fontan palliation. In patients with Fontan circulation who underwent 4D-Flow CMR, streamlines distribution was evaluated, as well a 4D-flow CMR-derived energetics parameters as kinetic energy (KE) and energy loss (EL) normalized by volume. EL/KE index as a marker of flow efficiency was also calculated. Cardiopulmonary exercise test (CPET) was also performed in a subgroup of patients. The population study included 55 patients (mean age 22 ± 11 years). The analysis of the streamlines revealed a preferential distribution of the right superior vena cava flow for the right pulmonary artery (62.5 ± 35.4%) and a mild preferential flow for the left pulmonary artery (52.3 ± 40.6%) of the inferior vena cave-pulmonary arteries (IVC-PA) conduit. Patients with heart failure (HF) presented lower IVC/PA-conduit flow (0.75 ± 0.5 vs 1.3 ± 0.5 l/min/m2, p = 0.004) and a higher mean flow-jet angle of the IVC-PA conduit (39.2 ± 22.8 vs 15.2 ± 8.9, p < 0.001) than the remaining patients. EL/KE index correlates inversely with VO2/kg/min: R: - 0.45, p = 0.01 peak, minute ventilation (VE) R: - 0.466, p < 0.01, maximal voluntary ventilation: R:0.44, p = 0.001 and positively with the physiological dead space to the tidal volume ratio (VD/VT) peak: R: 0.58, p < 0.01. From our data, lower blood flow in IVC/PA conduit and eccentric flow was associated with HF whereas higher EL/KE index was associated with reduced functional capacity and impaired lung function. Larger studies are needed to confirm our results and to further improve the prognostic role of the 4D-Flow CMR in this challenging population.

Relationships between plasma cytokine balance and cardiac magnetic resonance imaging in long-term post-COVID follow-up: a cross-sectional preliminary study

Background

COVID-19 infection can lead to a constellation of long-lasting post-infectious sequelae, including myocardial dysfunction, whose outcome is strongly affected by a fine-tuned balance between pro- and anti-inflammatory systemic immune responses. Plasma cytokines are key mediators of this immunological balance. In this preliminary study we evaluated the cross-sectional association between the circulating levels of the main pro- and anti-inflammatory cytokines and cardiac magnetic resonance (CMR) abnormalities.

Methods

71 subjects (59% female, mean age 52±14) with previous diagnosis of COVID-19 infection were enrolled at our institution for MULTICOVID protocol, comprehensive of CMR and biomarkers assessment performed &gt;3 months and &lt;1 year following the first negative swab test. CMR protocols consisted of conventional sequences (cine, T2-weighted imaging, and late gadolinium enhancement [LGE]) and quantitative mapping sequences (T1, T2, and extracellular volume [ECV] mapping). Plasma levels of cytokines TNF-α, IL-1β, IL-1α, IFN-α2, IL-6, IL-8, IL-13, IL-10, IL-17A, IL-18, IP-10, MIG and MCP-1 were quantified by Multiplex Immunoassays on the Luminex technology platform. Soluble cardiologic and biochemical biomarkers were measured by routine laboratory analysis.

Results

After a median of 9 (IQR 6–11) months following negative swab, CMR was normal in 48 subjects, while in 23 (32%) it revealed tissue characterization abnormalities (myocardial late enhancement and/or edema). By multivariate regression analysis (adjusted for age, sex, vaccination, severity degrees of the initial COVID disease, presence of comorbidities, smoke, time interval between COVID diagnosis and CMR assessment) the cytokine ratio TNF-α/(IL-10+IL-13) was independently associated (OR=2.89, 95% CI 1.19–7.04, p=0.02) with CMR abnormalities. Interestingly, the cumulative pro-/anti-inflammatory cytokine ratio (IL-1β+TNF-α+IFN-α2+IL-6+IL-17A+IL-8)/(IL-10+IL-13) showed a positive (OR=1.70, 95% CI: 1.04–2.75) and significant (p=0.03) association with CMR imaging aspects. Also, the ratio IFN-α2/(IL-10+IL-13), although without achieving a complete statistical significance (p=0.09), was associated positively with CMR findings.

Conclusions

The preliminary results of this cross-sectional study suggest that the systemic inflammatory environment, long-lasting unbalanced towards a prevalent cytokine-driven pro-inflammatory condition following COVID infection, could affect the development of CMR-detectable myocardial edema and fibrosis in long-term post-COVID subjects.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): Tuscany Region

P-447 Enhancing oxygen availability in the dynamic culture of bovine ovarian cortical tissue improves the yield of secondary follicles

Study question

Does enhancing oxygen availability during dynamic in vitro culture of bovine ovarian cortical tissue (BOCT) improve follicle growth and health?

Summary answer

Enhancing oxygen availability during dynamic in vitro culture of BOCT in perifusion bioreactors (PB) does improve follicle health and yield to secondary follicles

What is known already

Oxygen availability has been demonstrated to represent a key factor in follicle health and growth during in vitro culture of bovine and human ovarian cortical tissue (HOCT) under static culture conditions. Disruption of solutes gradients and application of physiological fluid mechanical stress, through in vitro dynamic culture of HOCT in a newly designed perifusion bioreactor have been shown to further enhance follicle growth and health. As it shows striking similarities with human, bovine folliculogenesis is considered a valuable model to study follicle growth in vitro

Study design, size, duration

Bovine ovaries from animals aged 8-24 months were collected at slaughterhouse. In each experiment (n = 3), BOCT strips from the same ovary were cultured for 6 days in perifusion bioreactors (PB, dynamic culture) and conventional dishes (CD, static culture). Culture outcome in static culture was analysed and compared to two bioreactor configurations in which medium oxygenation was kept low by using a standard tube reservoir (StPB) or was enhanced by using a gas-permeable dish reservoir (PB+O2).

Participants/materials, setting, methods

Slices of BOCT 0.5mm thick were cut with a tissue slicer and chopped into 1x1mm strips. In each experiment, fresh (D0) and cultured tissue (groups of ten strips) were analyzed. Follicle stages and health were assessed by histology (hematoxylin-eosin staining). Follicle viability was estimated by labelling with live-dead far-red and propidium iodide followed by clearing before analysis at the confocal laser scanning microscope.

Main results and the role of chance

Overall, 2417 follicles were analyzed (histology, 1476; viability, 941). At day 0 most follicles were primordial (primordial, 88.7%; primary, 10.6%; secondary, 0.7%), and had good quality (grade 1-2, 92.2%; grade 3, 7.8%), and high viability (91.8%). At day 6, follicle growth and health in StPB was superior than in CD (StPB vs CD - staging: primordial, 6.8 vs 16.3, P &lt; 0.01; primary, 70.7 vs 74.1, NS; secondary, 22.5 vs 9.6%, P &lt; 0.01; grading: grade 1 + 2, 71.4 vs 44.8, P &lt; 0.01; grade 3, 28.6 vs 55.2%, P &lt; 0.01). Dynamic culture in StPB better-preserved follicle viability compared to static culture in CD (StPB vs CD: 77.75 vs 64.9%, P &lt; 0.01). Enhancing oxygen availability during dynamic culture increased follicle progression and viability (PB+O2 vs StPB - staging: primordial, 5.1 vs 6.8, NS; primary, 65.4 vs 70.7, NS; secondary, 29.5 vs 22.5%, P &lt; 0.05; viability - 92 vs 77.75, P &lt; 0.01). Overall, the obtained results demonstrate that i) disruption of stagnant layers of medium and application of shear stress to BOCT through dynamic culture improves follicle activation, growth and health; ii) enhancing oxygen availability by means of a gas-permeable medium reservoir further increases follicle progression and viability.

Limitations, reasons for caution

Although the bovine is considered a reliable model for human folliculogenesis, the study should be validated on human ovarian tissue.

Wider implications of the findings

A limiting step in the in vitro production of mature oocytes starting from primordial follicles is the low yield of secondary follicles after organ culture. The adoption of a newly designed dynamic bioreactor and modulation of oxygen availability could represent a valuable tool for multistep in vitro folliculogenesis.

Trial registration number

none

P-446 Influence of strip thickness and FSH supplementation on follicle growth in the in vitro culture of strips of bovine ovarian cortical tissue in gas-permeable dishes

Study question

Do tissue thickness and FSH supplementation affect follicle growth and health in the vitro culture of bovine ovarian cortical strips (BOCS) in gas-permeable dishes?

Summary answer

Culture of 0.5mm thin BOCS with 5ng/ml FSH does improve follicle health and yield to secondary follicles compared with 1mm thick BOCS

What is known already

Oxygen availability inside tissue has been demonstrated to represent a key factor in follicle health and growth during in vitro culture of bovine and human ovarian cortical strips (HOCS). Although, strip thickness can limit nutrients and gases diffusion in and out of the innermost tissue zone, the presence of the outer medulla in thick strips could positively affect follicle growth. The role of FSH on the progression of primordial to secondary follicles in ovarian organ culture is still debated.

Study design, size, duration

Bovine ovaries from animals aged 8-24 months were collected at a slaughterhouse. In each experiment (n = 3), BOCS of varying thickness collected from the same ovary were cultured with or without FSH in gas-permeable dishes for 10 and 15 days.

Participants/materials, setting, methods

Slices either 0.5mm or 1mm thick were cut with a tissue-slicer and were chopped into 1x1mm2 strips. BOCS were cultured for 10 or 15 days at the same tissue/medium volume ratio (groups of either five 1mm strips or ten 0.5mm strips in 5ml medium) with 0, 1, or 5ng/ml FSH. Follicle stages were assessed by histology. Follicle viability was estimated by labeling with live-dead far red and propidium iodide at the confocal laser scanning microscope.

Main results and the role of chance

Overall, 2314 follicles were analyzed (histology, 998; viability, 1316). At day 0 most follicles were primordial (primordial, 89.4%; primary, 8.7%; secondary, 1.9%), and had a high viability (94.69%). The best follicle growth and viability was observed in 0.5mm thin BOCS cultured with 5ng/ml FSH. In particular, when compared to 1mm thick BOCS cultured with 5ng/ml FSH, 0.5mm thin BOCS cultured with 5ng/ml FSH showed a higher and significant proportion of secondary follicles at day 10 (0.5 vs 1mm, % secondary follicles: 26.5 vs 10, P &lt; 0.05) and a significantly higher proportion of viable follicles at day 15 (0.5 vs 1mm, % viable follicles: 89.4 vs 60.7, P &lt; 0.01).

These results demonstrate that smaller BOCS thickness and 5ng/ml FSH supplementation significantly improve the growth and health of secondary follicles.

Limitations, reasons for caution

Although the bovine is considered a reliable model for human folliculogenesis, the study should be validated on human ovarian tissue.

Wider implications of the findings

A limiting step in the production of mature oocytes starting from primordial follicles is the low yield to secondary follicles at the end of organ culture. Given the similarities between bovine and human folliculogenesis, the best culture conditions herein identified could contribute to the refinement of human in vitro folliculogenesis.

Trial registration number

Not applicable

Polystyrene nanoparticles may affect cell mitosis and compromise early embryo development in mammals

A great interest surrounds the development of nanoparticles (NPs) for biomedical applications such as drug delivery and cancer therapy. However, the interplay between nanoscale materials and biological systems and the associated hazards have not been completely clarified yet. In this study, bovine oviductal epithelial cells (BOECs) and embryos were used as in vitro models to investigate whether cell mitosis and early mammalian embryo development could be affected by the exposure to polystyrene (PS) nanoparticles. Analysis of the karyotype performed on BOECs exposed to PS-NPs did not show chromosomal anomalies compared to the control, although more tetraploid metaphase plates were observed in the former. In vitro fertilization experiments designed to understand whether exposure to PS-NPs could affect pre-implantation development showed that incubation with PS-NPs decreased 8-cell embryo and blastocyst rate in dose-dependent fashion. The quality of the blastocysts in terms of mean cell percent blastomeres with fragmented DNA was the same in exposed blastocysts compared to controls. These results show that the exposure to PS-NPs may impair development. In turn, this may affect the rate of mitosis in embryos and yield a lower developmental competence to reach the blastocyst stage. This suggests that release in the environment and the subsequent accumulation of PS-NPs into living organisms should be carefully monitored to prevent cytotoxic effects that may compromise their reproduction rates.

Contribution of the Lung to the Genesis of Cheyne-Stokes Respiration in Heart Failure: Plant Gain Beyond Chemoreflex Gain and Circulation Time

Background

The contribution of the lung or the plant gain (PG; ie, change in blood gases per unit change in ventilation) to Cheyne‐Stokes respiration (CSR) in heart failure has only been hypothesized by mathematical models, but never been directly evaluated.

Methods and Results

Twenty patients with systolic heart failure (age, 72.4±6.4 years; left ventricular ejection fraction, 31.5±5.8%), 10 with relevant CSR (24‐hour apnea‐hypopnea index [AHI] ≥10 events/h) and 10 without (AHI <10 events/h) at 24‐hour cardiorespiratory monitoring underwent evaluation of chemoreflex gain (CG) to hypoxia (CGO2) and hypercapnia (CGCO2) by rebreathing technique, lung‐to‐finger circulation time, and PG assessment through a visual system. PG test was feasible and reproducible (intraclass correlation coefficient, 0.98; 95% CI, 0.91–0.99); the best‐fitting curve to express the PG was a hyperbola (R²≥0.98). Patients with CSR showed increased PG, CGCO2 (but not CGO2), and lung‐to‐finger circulation time, compared with patients without CSR (all P<0.05). PG was the only predictor of the daytime AHI (R=0.56, P=0.01) and together with the CGCO2 also predicted the nighttime AHI (R=0.81, P=0.0003) and the 24‐hour AHI (R=0.71, P=0.001). Lung‐to‐finger circulation time was the only predictor of CSR cycle length (R=0.82, P=0.00006).

Conclusions

PG is a powerful contributor of CSR and should be evaluated together with the CG and circulation time to individualize treatments aimed at stabilizing breathing in heart failure.

Respiratory Training Late After Fontan Intervention: Impact on Cardiorespiratory Performance

Fontan palliation allows patients with "single ventricle" circulation to reach adulthood with an acceptable quality of life, although exercise tolerance is significantly reduced. To assess whether controlled respiratory training (CRT) increases cardiorespiratory performance. 16 Adolescent Fontan patients (age 17. 5 ± 3.8 years) were enrolled. Patients were divided into CRT group (n = 10) and control group (C group, n = 6). Maximal cardiopulmonary test (CPT) was repeated at the end of CRT in the CRT group and after an average time of 3 months in the C group. In the CRT group a CPT endurance was also performed before and after CRT. In the CRT group there was a significant improvement in cardiovascular and respiratory response to exercise after CRT. Actually, after accounting for baseline values, the CRT group had decreased breathing respiratory reserve (- 15, 95% CI -22.3 to - 8.0, p = 0.001) and increased RR peak (+ 4.8, 95% CI 0.7-8.9, p = 0.03), VE peak (+ 13.7, 95% CI 5.6-21.7, p = 0.004), VO₂ of predicted (+ 8.5, 95% CI 0.1-17.0, p = 0.05), VO₂ peak (+ 4.3, 95% CI 0.3 to 8.2, p = 0.04), and VO₂ workslope (+ 1.7, 95% CI 0.3-3.1, p = 0.02) as compared to the control group. Moreover, exercise endurance time increased from 8.45 to 17.7 min (p = 0.01). CRT improves cardiorespiratory performance in post-Fontan patients leading to a better aerobic capacity.

Comparative Analysis of Metabolism of Medium-and Plasma Perfused Primary Pig Hepatocytes Cultured around a 3-D Membrane Network

Culture media are frequently used in the evaluation of metabolical functions of hepatocytes in hybrid liver support systems (hLSS). However, media compositions differ substantially from those of plasma. Therefore, our study was designed to investigate whether current in vitro studies with medium are suitable to assess the metabolical competence of hLSS-cultures during clinical application as well as to explore whether the cell nutrition with medium provides a suitable modus operandi for stand by cultivation. Paired bioreactor cultures were perfused with either Williams’ Medium E (MPB) or human plasma (PPB). About 6x108 primary pig hepatocytes (>97% viability) were cultured in three laboratory scale bioreactors designed according to Gerlach's bioreactor-concept. Different perfusion protocols were initiated after a standardised period allowing for cell attachment and reorganisation in aggregates. Whereas patterns of enzyme release were similar in both protocols the metabolical behaviour was different between MPB (anabolic state) and PPB (catabolic state). Furthermore, compared to MPB the lidocaine-MEGX-tests for PPB demonstrated lower MEGX-concentrations and a different reaction pattern. We conclude that the nutrition of hepatocytes with medium during the stand by period itself might influence the cell function and subsequently the efficacy of the hLSS-treatment during clinical application. (Int J Artif Organs 2000; 23: 104–10)

The Effect of Catabolite Concentration on the Viability and Functions of Isolated Rat Hepatocytes

The treatment of patients with hepatic failure by means of hybrid liver support devices using primary xenogeneic hepatocytes is currently hindered by the rapid loss of cell metabolic functions. Similarly to what happens with other mammalian cells, accumulation of catabolites in the neighborhood of cultured hepatocytes might significantly affect their viability and functions. In this paper, we investigated the effects of high concentrations of catabolites, such as ammonia and lactic acid, on the viability and functions of rat hepatocytes cultured on collagen coated Petri dishes. The effects on hepatocyte functions were established with respect to their ability to synthesize urea and to eliminate ammonia. Indeed, high catabolite concentrations effected both hepatocyte viability and functions. The number of viable hepatocytes decreased with increasing ammonia concentrations in the culture medium. High ammonia concentrations had also both an inhibitory and a toxic effect on hepatocyte functions. In fact, the hepatocytes synthesized urea and eliminated ammonia at rates that decreased with increasing ammonia concentrations. Similarly, high lactic acid concentrations were toxic to the cells and also inhibited their synthetic functions.

Mass Transfer Limitations to the Performance of Membrane Bioartificial Liver Support Devices

A number of membrane bioartificial devices have been proposed for liver support. However, their design does not yet ensure the successful treatment of acute liver insufficiency. In this paper, the Author reviews the limitations of the mass transport phenomena to the performance of a membrane bioartificial liver support device. First of all the requirements that an optimal membrane bioartificial liver support device has to meet for the therapy to be effective are presented. On these grounds, the issues that are still to be addressed to optimize the performance of such devices are discussed: particular attention is devoted to the mass transport phenomena in each region of the membrane bioartificial device. Finally, the main transport features of the membrane bioartificial liver support devices proposed so far are illustrated and examined.

The Effect of Oxygen Transport Resistances on the Viability and Functions of Isolated Rat Hepatocytes

The treatment of fulminant hepatic failure with a bioartificial liver support device relies on the possibility of replacing the detoxification and synthetic functions of the injured liver for as long as needed for patient recovery. In spite of progress in cell culture techniques, the effective use of isolated hepatocytes in liver support devices is currently hampered by a lack of information on the metabolic factors limiting long term hepatocyte culture. In this paper, we report our investigation on the effects of oxygen transport resistances on the viability and functions of isolated rat hepatocytes cultured on collagen coated Petri dishes. Detoxification and synthetic functions of the hepatocytes were studied with respect to ammonia and phenolsulphonphthalein elimination and urea synthesis. Lower resistances to oxygen transport favored hepatocyte survival. The isolated hepatocytes synthesized urea at rates that decreased as the resistance to oxygen transport increased. The rate at which urea was synthesized also decreased during the culture. Neither PSP, nor ammonia elimination rate was greatly affected by increasing oxygen transport resistances and remained rather constant up to a week of culture.

Importance of the Kinetic Characterization of Liver Cell Metabolic Reactions to the Design of Hybrid Liver Support Devices

Hybrid liver support devices (HLSDs) developed for the treatment of fulminant hepatic failure often perform well on a laboratory scale but rapidly lose their metabolic functions, or are not therapeutically effective, on a clinical scale. This suggests that the procedures adopted so far for the design of HLSDs are susceptible to improvement. In this paper, we discuss how essential a reliable and thorough kinetic characterization of the liver cell metabolic reactions is to the design of a clinically effective membrane HLSD. The features of the bioreactors used for the kinetic characterization of liver cell reactions are presented and discussed on the basis of the multifactorial nature of such reactions. The relevance of kinetics to the design of a membrane HLSD is also discussed with respect to the effect of the kinetics of oxygen consumption on the performance of the device.

Adhesion and Function of Rat Liver Cells Adherent to Silk Fibroin/Collagen Blend Films

Collagen is often used in bioartificial livers as a biomimetic coating to promote liver cell adhesion and differentiation. Animal proteins are expensive and expose the host to risks of cross-species infection due to contamination with prions. Silk fibroin (SF) is a biocompatible protein produced by Bombyx mori silk worms and possibly an alternative to collagen. We prepared SF-collagen blend films with different SF content adherent to the bottom of standard tissue culture dishes, and characterized their surface morphology by SEM, their wettability and examined them for their capacity to support rat liver cell adhesion and metabolism. Cell metabolism was characterized by estimating the rate at which cells eliminated ammonia and synthesized urea for up to 48h of culture. SF-containing films were smooth, clear and more wettable than collagen. Cells readily adhered, formed junctions and small size aggregates on all films. As many cells adhered on SF as on collagen films. Cell adhesion to high collagen content blend films could not be reliably estimated because cells dwelt in the large cavities in the film. The effect of SF on cell metabolism differed with the investigated metabolic pathway. However, cells on SF-containing films eliminated ammonia and synthesized urea at rates generally comparable to, for urea synthesis at times higher than, that of cells on collagen. These results suggest that silk fibroin is a suitable substratum for liver cell attachment and culture, and a potential alternative to collagen as a biomimetic coating.

Feasibility of Continuous CO2 Removal with Hydrophilic Membranes at Low Blood Flow Rates

In the conventional treatment of acute respiratory distress syndrome (ARDS), high O2 concentrations and mechanical ventilation may damage the lung tissue. Extracorporeal membrane oxygenation limits damage, provides the needed O2 supply and improves survival of ARDS neonates, but not of adults. Hydrophilic membranes used in hemodialysis are more non-thrombogenic and biocompatible than those used in blood oxygenation, but their O2 transport capacity is not as high. In recent years, CO2 removal at low blood flow rates combined with apneic oxygenation and low frequency ventilation has proved promising in the treatment of ARDS. This approach makes O2 supply across ECMO membranes unnecessary; it also makes hydrophilic membranes candidates for extracorporeal CO2 removal to minimize anticoagulation and immune system activation. This paper reports on the in vitro capacity of hydrophilic polysulphone membranes to remove CO2 from carbonated pig blood into an oxygen-rich gas stream. Experiments were performed on clinical-size dialysis modules and their capacity to remove CO2 as a function of blood flow rate and membrane surface area was investigated. Membranes effectively removed CO2, more so at increasing blood flow rates and membrane surface areas, at rates of up to 15% of the CO2 metabolic production rate. The specific CO2 removal rate was comparable to that of blood oxygenators equipped with microporous hydrophobic membranes. It is concluded that CO2 removal from slowly flowing blood with hydrophilic membranes is feasible.

New Generation Ceramic Membranes have the Potential of Removing Endotoxins from Dialysis Water and Dialysate

Poor water properties, use of concentrated bicarbonate, and biofilm growth in pipes and storage tanks often cause dialysis water and dialysate contamination with bacteria and endotoxins. High-flux dialysis with bicarbonate may favor endotoxin transfer from the dialysate into the blood exposing patients to serious short - and long-term side effects. Ultrafiltration across hydrophobic synthetic membranes effectively removes endotoxins from dialysis water by combined filtration and adsorption. However, repeated sterilization worsens the membrane separation properties, and limits their use. Ceramic membranes are generally more resistant to harsh operating conditions than polymeric membranes, and may represent an alternative for endotoxin removal. Previously, we proved that the ceramic membranes commercially available at that time were not retentive enough to ensure production of endotoxin-free dialysis water.

In this paper, we investigated the endotoxin removal capacity of new generation commercial ceramic membranes with nominal molecular weight cut-off down to 1,000. In dead-end filtration, all investigated membranes produced water meeting, the European standards, or close to, when challenged with low endotoxin concentrations, but only one membrane type succeeded at high endotoxin concentrations. In cross-flow filtration, none produced water meeting the European standard. Moreover, sterilization and rinsing procedures altered the separation properties of two out of three membrane types.

Improved survival in limited scleroderma-related pulmonary artery hypertension

Reportedly, patients with scleroderma-related pulmonary hypertension (SSc-PAH) respond poorly to new vasoactive drugs (NVD). Forty-nine SSc-PAH patients underwent right heart catheterization (RHC) and, according to NVD availability, divided as follows: Group 1 (n = 23, from 1999 to 2004, poor availability), and Group 2 (n = 26, from 2005 to 2010, good availability). Before diagnostic RHC, NVD had been given to 30 % of the patients in Group 1, and 58 % of those in Group 2 (p = 0.049). At diagnosis, patients in Group 1 had greater heart dilatation (p < 0.01), higher mean pulmonary artery pressure (p < 0.05), lower pulmonary artery capacitance (p < 0.05), and lower carbon monoxide lung diffusing capacity (DLco, p < 0.05) than those in Group 2. At a median follow-up time of 15.5 months, DLco further decreased in Group 1 (p < 0.05), whereas cardiac index increased in Group 2 (p < 0.05). At 36 months of follow-up, 72.4 % of the patients in Group 2 were still alive as opposed to 30.4 % in Group 1 (p = 0.02). In multivariate analysis, DLco and mixed venous oxygen saturation (SvO2) were independent predictors of survival. A value of DLco <7.2 mL/mmHg/min was associated with a hazard ratio (HR) of 5.3 (p < 0.001); for SvO2 <63.8 %, the HR was 3.7 (p < 0.01).NVD have beneficial effects in patients with SSc-PAH. Both DLco and SvO2 are predictors of survival and may assist in planning treatment.

Improved survival in patients with inoperable chronic thromboembolic pulmonary hypertension

Patients with inoperable chronic thromboembolic pulmonary hypertension (Inop-CTEPH) treated with conventional therapy have a poor survival. We compare the 3-year survival between those treated with conventional therapy and those treated with conventional therapy and a combination of novel drugs. We also evaluate the clinical course. A total of 34 Inop-CTEPH consecutive patients were evaluated from 1991 to 2009 including right heart catheterization (RHC) and perfusion lung scan (PLS): 7 underwent surgical treatment while 27 were confirmed inoperable. Of these 27 patients, 12 evaluated from 1991 to 2003 (Group 1) were treated with conventional therapy and 15 evaluated from 2004 to 2009 (Group 2) were treated with conventional and novel therapies. At baseline, no group difference emerged at RHC. Based on clinical course, novel drugs and oxygen supplementation were given to patients of Group 2. Seven of these who had worse clinical course repeated RHC and four of them also PLS during therapy. Those without repeat RHC had baseline pulmonary artery mean pressure and brain natriuretic peptide (NT-proBNP) lower and mixed venous saturation (SvO2) and exercise test higher (p = 0.022, 0.015, 0.044 and 0.003, respectively). During therapy, those with repeat RHC had total pulmonary vascular resistance reduced (p = 0.012), base excess increased (p = 0.002) and significant redistribution of pulmonary blood flow at PLS. At the 3-year follow-up, survival was 86% in Group 2 and 31% in Group 1 (p = 0.031). In Inop-CTEPH patients, the clinical course may help to select drugs and the level of oxygen supply that can improve hemodynamics, gas exchange and long-term survival.

Routine Chest X-ray: Still Valuable for the Assessment of Left Ventricular Size and Function in the Era of Super Machines?

Objectives:

The development of technologically advanced, expensive techniques has progressively reduced the value of chest X-ray in clinical practice for the assessment of left ventricular (LV) dilatation and dysfunction. Although controversial data are reported on the role of this widely available technique in cardiac assessment, it is known that the cardio-thoracic ratio is predictive of risk of progression in the NYHA Class, hospitalization, and outcome in patients with LV dysfunction. This study aimed to evaluate the reliability of the transverse diameter of heart shadow [TDH] by chest X-ray for detecting LV dilatation and dysfunction as compared to Magnetic Resonance Imaging (MRI) performed for different clinical reasons.

Materials and Methods:

In 101 patients, TDH was measured in digital chest X-ray and LV volumes and ejection fraction (EF) by MRI, both exams performed within 2 days.

Results:

A direct correlation between TDH and end-diastolic volumes (r = .75, P<0.0001) was reported. TDH cut-off values of 14.5 mm in females identified LV end-diastolic volumes >150 mL (sensitivity: 82%, specificity: 69%); in males a cut-off value of 15.5 mm identified LV end-diastolic volumes >210 mL (sensitivity: 84%; specificity: 72%). A negative relation was found between TDH and LVEF (r = -.54, P<0.0001). The above cut-off values of TDH discriminated patients with LV systolic dysfunction – LVEF <35% (sensitivity and specificity: 67% and 57% in females; 76% and 59% in males, respectively).

Conclusions:

Chest X-ray may still be considered a reliable technique in predicting LV dilatation by the accurate measurement of TDH as compared to cardiac MRI. Technologically advanced, expensive, and less available imaging techniques should be performed on the basis of sound clinical requests.

Early subclinical increase in pulmonary water content in athletes performing sustained heavy exercise at sea level: ultrasound lung comet-tail evidence

Whether prolonged strenuous exercise performed by athletes at sea level can produce interstitial pulmonary edema is under debate. Chest sonography allows to estimate extravascular lung water, creating ultrasound lung comet-tail (ULC) artifacts. The aim of the study was to determine whether pulmonary water content increases in Ironmen (n = 31) during race at sea level and its correlation with cardiopulmonary function and systemic proinflammatory and cardiac biohumoral markers. A multiple factor analysis approach was used to determine the relations between systemic modifications and ULCs by assessing correlations among variables and groups of variables showing significant pre-post changes. All athletes were asymptomatic for cough and dyspnea at rest and after the race. Immediately after the race, a score of more than five comet tail artifacts, the threshold for a significant detection, was present in 23 athletes (74%; 16.3 ± 11.2; P < 0.01 ULC after the race vs. rest) but decreased 12 h after the end of the race (13 athletes; 42%; 6.3 ± 8.0; P < 0.01 vs. soon after the race). Multiple factor analysis showed significant correlations between ULCs and cardiac-related variables and NH(2)-terminal pro-brain natriuretic peptide. Healthy athletes developed subclinical increase in pulmonary water content immediately after an Ironman race at sea level, as shown by the increased number of ULCs related to cardiac changes occurring during exercise. Hemodynamic changes are one of several potential factors contributing to the mechanisms of ULCs.

Time course of carbon monoxide transfer factor after breath-hold diving

Breath-hold divers may experience haemoptysis during diving. Central pooling of blood as well as compression of pulmonary gas content can damage the integrity of the blood-gas barrier, resulting in alveolar hemorrhage. The single-breath carbon monoxide test (DL,CO) was used to investigate the blood-gas barrier following diving. The study population consisted of 30 divers recruited from a training course. DL,CO levels were measured before diving and at 2, 10 and 25 min after the last of a series of four dives to depths of 10, 15, 20 and 30 m. When compared to pre-diving values, DL,CO values increased significantly at 2 min following diving in all subjects except one. Thereafter values progressively decreased toward baseline at 10 and 25 min in all subjects but one, while in four divers DL,CO values decreased below baseline. The early but transient increase in DL,CO levels shortly after diving supports the persistence of capillary pooling of red blood cells following emersion. Persistence at 25 min of high DL,CO values in one subject could be attributed by lung CT to extravasation of blood into the alveoli. Early or late DL,CO values >10% below baseline values suggest the presence of pulmonary edema. The relatively high prevalence of DL,CO alterations found suggests caution on the safety of breath-hold diving activities.

Giant cystic intraventricular cerebral cavernous malformation: MRI with pathologic correlation. A case report

The purpose of this case report is to increase awareness of the spectrum of cerebral cavernous malformations (CCMs). We report the MRI findings and histological features of an uncommon case of a single giant (maximum diameter: >6 cm) cystic CCM of the left lateral ventricle occurring in a 26-year-old man who had undergone 30 Gy cranial irradiation for acute leukemia at the age of six years. Large cystic CCMs must be included in the neuroradiological differential diagnosis of intraventricular hemorrhagic cystic lesions.

Assessment of the alveolar volume when sampling exhaled gas at different expired volumes in the single breath diffusion test

BACKGROUND

Alveolar volume measured according to the American Thoracic Society-European Respiratory Society (ATS-ERS) guidelines during the single breath diffusion test can be underestimated when there is maldistribution of ventilation. Therefore, the alveolar volume calculated by taking into account the ATS-ERS guidelines was compared to the alveolar volume measured from sequentiallly collected samples of the expired volume in two groups of individuals: COPD patients and healthy individuals. The aim of this study was to investigate the effects of the maldistribution of ventilation on the real estimate of alveolar volume and to evaluate some indicators suggestive of the presence of maldistribution of ventilation.

METHODS

Thirty healthy individuals and fifty patients with moderate-severe COPD were studied. The alveolar volume was measured either according to the ATS-ERS guidelines or considering the whole expired volume subdivided into five quintiles. An index reflecting the non-uniformity of the distribution of ventilation was then derived (DeltaVA/VE).

RESULTS

Significant differences were found when comparing the two measurements and the alveolar volume by quintiles appeared to have increased progressively towards residual volume in healthy individuals and much more in COPD patients. Therefore, DeltaVA/VE resulted in an abnormal increase in COPD.

CONCLUSION

The results of our study suggest that the alveolar volume during the single breath diffusion test should be measured through the collection of a sample of expired volume which could be more representative of the overall gas composition, especially in the presence of uneven distribution of ventilation. Further studies aimed at clarifying the final effects of this way of calculating the alveolar volume on the measure of DLCO are needed. DeltaVA/VE is an index that can help assess the severity of inhomogeneity in COPD patients.

Physical-chemical and biological characterization of silk fibroin-coated porous membranes for medical applications

Membranes in artificial organs and scaffolds for tissue engineering are often coated with biomimetic molecules (e.g., collagen) to improve their biocompatibility and promote primary cell adhesion and differentiation. However, animal proteins are expensive and may be contaminated with prions. Silk fibroin (SF) made by Bombyx Mori silk worms, used as a scaffold or grafted to other polymers, reportedly promotes the adhesion and growth of many human cell types. This paper describes how commercial porous membranes were physically coated with SF, and their physical-chemical properties were characterized by SEM, AFM, tensile stress analysis and dynamic contact angle measurements. The effect of the SF coating on membrane biocompatibility and resistance to bacterial colonization is also examined. The proposed technique yields SF coats of different thickness that strengthen the membranes and make their surface remarkably more wettable. The SF coat is not cytotoxic, and promotes the adhesion and proliferation of an immortalized fibroblast cell line. Similarly to collagen, SF-coated membranes also exhibit a much better resistance to the adhesion of S. epidermidis bacteria than uncoated membranes. These preliminary results suggest that SF is a feasible alternative to collagen as a biomimetic coating for 3D scaffolds for tissue engineering or bioartificial (as well as artificial) prosthesis.

Role of the chest radiograph in the preoperative assessment of the pulmonary function in patients with cirrhosis candidates to liver transplant

PURPOSE

To appraise the role of chest radiography (CXR) in the clinical assessment of pulmonary complications occurring as a result of liver disease of any cause, a standardised reading of CXR was compared both with the results of lung function studies and with the severity of liver disease in 60 consecutive patients with cirrhosis candidates to liver transplant.

MATERIALS AND METHODS

CXR were scored for signs of cardiomegaly, enlargement of central and or peripheral vessels, hyperkinetic circulatory and/or intravascular volume states, abnormally increased interstitial lung markings, and pleural effusion by three independent observers.

RESULTS

The CXR score of this complete vascular-interstitial deficiency showed a high interobserver reproducibility and was significantly increased in those patients with a more decompensated liver cirrhosis. Moreover, a larger number of CXR signs of vascular and interstitial deficiency was present in those patients who had a more severe cirrhosis (Child-Pugh class 3). Functional indices of pulmonary gas exchange and diffusing capacity were worse in patients with end-stage liver cirrhosis, and for some indices the correlation was statistically significant. The comparison between lung function and CXR score showed that on average lung function impairment was significantly less severe in patients with lower CXR scores.

CONCLUSIONS

In conclusion, the information derived from a standardised reading of CXR is valuable in the clinical assessment of the pulmonary damage induced by liver cirrhosis as it allows discrimination of classes of severity of liver disease and of lung function impairment. When integrated with physiologic measurements and, if necessary, with high resolution tomographic studies, chest radiography helps to discriminate patients with advanced liver cirrhosis and progressing towards a hepatopulmonary syndrome, who need a proper therapeutic management.

A diagnostic strategy for pulmonary embolism based on standardised pretest probability and perfusion lung scanning: a management study

Pulmonary embolism remains a challenging diagnostic problem. We developed a simple diagnostic strategy based on combination of assessment of the pretest probability with perfusion lung scan results to reduce the need for pulmonary angiography. We studied 390 consecutive patients (78% in-patients) with suspected pulmonary embolism. The pretest probability was rated low (<10%), intermediate (>10%, < or =50%), moderately high (>50%, < or =90%) or high (>90%) according to a structured clinical model. Perfusion lung scans were independently assigned to one of four categories: normal; near-normal; abnormal, suggestive of pulmonary embolism (wedge-shaped perfusion defects); abnormal, not suggestive of pulmonary embolism (perfusion defects other than wedge shaped). Pulmonary embolism was diagnosed in patients with abnormal scans suggestive of pulmonary embolism and moderately high or high pretest probability. Patients with normal or near-normal scans and those with abnormal scans not suggestive of pulmonary embolism and low pretest probability were deemed not to have pulmonary embolism. All other patients were allocated to pulmonary angiography. Patients in whom pulmonary embolism was excluded were left untreated. All patients were followed up for 1 year. Pulmonary embolism was diagnosed non-invasively in 132 patients (34%), and excluded in 191 (49%). Pulmonary angiography was required in 67 patients (17%). The prevalence of pulmonary embolism was 41% ( n=160). Patients in whom pulmonary embolism was excluded had a thrombo-embolic risk of 0.4% (95% confidence interval: 0.0%-2.8%). Our strategy permitted a non-invasive diagnosis or exclusion of pulmonary embolism in 83% of the cases (95% confidence interval: 79%-86%), and appeared to be safe.

Combined effect of oxygen and ammonia on the kinetics of ammonia elimination and oxygen consumption of adherent rat liver cells

Oxygen is essential for the survival of isolated liver cells and its concentration is known to affect their viability and function. Recent reports have also shown that ammonia is eliminated at a rate depending on its concentration and that high ammonia concentrations may be cytotoxic to rat liver cells. Nonetheless, little quantitative information on the effect of either metabolite on liver cell reaction kinetics is available although important to the design of bioreactors for bioartificial livers (BALs). In this investigation, we characterized the dependence of the rate of oxygen consumption (OCR), ammonia elimination (AER) and urea synthesis (USR) on ammonia concentration at physiological (i.e., 43 and 72 mmHg) and supra-physiological (i.e., 134 mmHg) dissolved oxygen tensions. To this purpose, isolated rat liver cells were cultured in adhesion on collagen in a continuous-flow bioreactor optimised for the kinetic characterisation of liver cell metabolic reactions. Rates of the investigated reactions generally increased with increasing ammonia concentrations. OCR and USR significantly increased with increasing dissolved oxygen tensions, particularly at high ammonia concentrations. The actual dissolved oxygen tension significantly influenced also OCR and USR dependence on ammonia concentration. The best-fit rate equations were used to show that, at the beginning of the treatment with a bioreactor packed with primary liver cells, high ammonia concentration in the blood may cause large hypoxic zones in the bioreactor as a result of its effect on OCR. This suggests that plasma (or blood) detoxification prior to entering the bioreactor might enhance BAL efficacy by preserving a large fraction of the available cell activity for longer times.

Propofol EEG burst suppression in carotid endarterectomy

BACKGROUND

The results of randomized trials indicate that carotid endarterectomy, performed with a low morbidity-mortality perioperative risk, is the best therapeutic option both for patients with high-grade symptomatic and asymptomatic stenosis. Since the main operative risk is represented by embolic or hemodynamic cerebral ischemia, it appears necessary to maintain an adequate intraoperative cerebral blood flow and to carry out a meticulous endarterectomy.

METHODS

On the basis of these considerations we prospectively studied a series of 100 consecutive patients operated on for high-grade carotid stenosis, by using a protocol based on: 1) an accurate selection of patients for surgery; 2) meticulous surgical technique without any shunt; 3) perioperative cerebral protection by barbiturate or propofol; 4) pre- and postoperative medical treatment of risk factors. All patients of our series performed preoperatively brain CT scan, transcranial Doppler, carotid duplex scanning, four vessel angiography, brain 99mTc-HMPAO SPECT. Eighty-two patients had symptomatic carotid stenosis ranged between 70 and 90%, 18 had carotid stenosis higher than 90%.

RESULTS

In this series there have been one postoperative death due to myocardial infarction and one major stroke.

CONCLUSIONS

We think that this protocol can significantly minimize risks of endarterectomy and probably maximize the benefits of surgery, also in patients with asymptomatic high-grade carotid stenosis.

Relationship between extent of pulmonary emphysema by high-resolution computed tomography and lung elastic recoil in patients with chronic obstructive pulmonary disease

We investigated the relationship between the extent of pulmonary emphysema, assessed by quantitative high-resolution computed tomography (HRCT), and lung mechanics in 24 patients with chronic obstructive pulmonary disease (COPD). The extent of emphysema was quantified as the relative lung area with CT numbers < -950 Hounsfield Units (HU). Patients with COPD had severe airflow obstruction (FEV(1) 35 +/- 15% pred) and severe reduction of CO diffusion constant (DCO/VA 37 +/- 19% pred). Maximal static elastic recoil pressure (Pst(max)) averaged 54 +/- 24% predicted, and the exponential constant K of pressure-volume curves was 258 +/- 116% predicted. Relative lung area with CT numbers < -950 HU averaged 21 +/- 11% (range 1 to 38%). It showed a highly significant negative correlation with DCO/VA (r = -0.84, p < 0.0001), a weak correlation with FEV(1)% predicted, and no correlation with either Pst(max) or constant K. A significant relationship was found between the natural logarithm of K and the full width at half maximum of the frequency distribution of CT numbers, taken as an index of the heterogeneity of lung density (r = 0.68, p < 0.0005). We conclude that currently used methods of assessing the extent of emphysema by HRCT closely reflect the reduction of CO diffusion constant, but cannot predict the elastic properties of the lung tissue.

Morphology and metabolism of hepatocytes cultured in Petri dishes on films and in non-woven fabrics of hyaluronic acid esters

Polymers of hyaluronic acid (Hyal) esters exhibit good tissue compatibility and are available in various geometrical configurations. These properties can be exploited for the design of innovative bioartificial liver support devices (BALSDs) using primary hepatocytes. In this paper, we report a preliminary investigation of the polymer feasibility of the ethyl and the benzyl Hyal ester in the form of films and non-woven fabrics for the in vitro culture of primary rat hepatocytes. Cell function was evaluated daily in Petri dishes with respect to the rate of ammonia elimination (AER) and urea synthesis (USR). Cells cultured in non-woven fabrics of the ethyl ester of Hyal (HYAFF7nw) exhibited an initial AER about 32% lower and synthesised urea 33% faster than that of cells on collagen films. After a week in culture, cells on collagen films retained only a minor fraction of their initial rates. Cells cultured in non-woven fabrics of HYAFF7nw retained about 62 and 44% of their initial AER and USR, respectively, and exhibited an AER approximately equal to and a USR 3.6 times greater than those of cells adherent to collagen. These results suggest that non-woven fabrics of HYAFF7nw are promising substrata for hepatocyte culture in BALSDs.

Characterization of the distribution of matter in hybrid liver support devices where cells are cultured in a 3-D membrane network or on flat substrata

Bioreactors for liver assist tested on small animal models are generally scaled-up to treat humans by increasing their size to host a given liver cell mass. In this process, liver cell function in different culture devices is often established based on the metabolite concentration difference between the bioreactor inlet and outlet irrespective of how matter distributes in the bioreactor. In this paper, we report our investigation aimed at establishing whether bioreactor design and operating conditions influence the distribution of matter in two bioreactors proposed for liver assist. We investigated a clinical-scale bioreactor where liver cells are cultured around a three-dimensional network of hollow fiber membranes and a laboratory-scale bioreactor with cells adherent on collagen-coated flat substrata. The distribution of matter was characterized under different operating modes and conditions in terms of the bioreactor residence time distribution evaluated by means of tracer experiments and modeled as a cascade of N stirred tanks with the same volume. Under conditions recommended by the manufacturers, matter distributed uniformly in the clinical-scale bioreactor as a result of the intense backmixing (N=1) whereas axial mixing was negligible in the laboratory-scale bioreactor (N=8). Switching from recycle to single-pass operation definitely reduced axial mixing in the clinical-scale bioreactor (N=2). Increasing feed flow rate significantly enhanced axial mixing in the laboratory-scale bioreactor (N=4). The effects of design, operating mode and conditions on matter distribution in bioreactors for liver cell culture suggest that characterization of the distribution of matter is a necessary step in the scale-up of bioreactors for liver assist and when function of liver cells cultured in different bioreactors is evaluated and compared.

Membranes for endotoxin removal from dialysate: considerations on feasibility of commercial ceramic membranes

As the quality of water in dialysis fluid varies considerably, dialysate is often contaminated by large amounts of bacteria and endotoxins. Membrane properties and operating pressures are acknowledged to give high-flux dialysis with bicarbonate the bacteriological potential to favor passage of endotoxin fragments from the dialysate into the blood stream. Therefore, a sterile dialysate will have to become a standard. Ultrafiltration across hydrophobic synthetic membranes was shown to remove endotoxins (and their fragments) from dialysis water by the combined effect of filtration and adsorption. However, each module can be used for a limited time only. Ceramic membranes may represent an alternative to polymeric membranes for endotoxin removal. In this article, we tested the capacity of different commercial ceramic membranes with nominal molecular weight cut-off down to 1,000 to retain endotoxins from Ps. aeruginosa. The tested membranes did not generally produce dialysate meeting the Association for the Advancement of Medical Instrumentation standard. When using aluminum-containing membranes, we detected aluminum leaking into the dialysate that could possibly be transported into the blood stream.

Treatment of symptomatic intracranial arachnoid cysts by stereotactic cyst-ventricular shunting

BACKGROUND

The optimal treatment of symptomatic intracranial arachnoid cysts is controversial and different surgical approaches have been described. The aim of the treatment is to reduce the intracystic pressure. To accomplish this goal, many techniques have been proposed, each with specific limitations or failures.

METHODS

Nine patients with symptomatic arachnoid cysts were treated by stereotactic cyst-ventricular shunting. One patient with suprasellar arachnoid cyst showed signs related to intracranial pressure, the remaining 8 patients complained of headache and/or drug-resistant epilepsy. All the intracranial cysts were supratentorial. The surgical procedure was performed under general anesthesia in 6 cases and local anesthesia in 3 cases. The CRW Stereotactic System (Radionics) was used. The acquisition of both target points (cyst and ventricle) was always realized by means of CT scan slices. A right precoronal burr hole was made and a silicon catheter was stereotactically inserted into the lateral ventricle. Another burr hole was subsequently performed close to the cyst; a silicon catheter was placed in the middle of the cavity in the shortest intracerebral crossing. Then both catheters were connected to a subcutaneous burr hole Ommaya reservoir.

RESULTS

All patients tolerated the procedure well and the preoperative clinical signs progressively disappeared or improved. The CT scan at 1, 3, 6 and over 12 months showed progressive reduction in size of the cysts. No clinical recurrence was found at the follow-up (14-73 months).

CONCLUSIONS

The successful outcome of the above cases suggests that, in carefully selected symptomatic intracranial arachnoid cysts, stereotactic cyst-ventricular shunting is likely to prove an effective operative method.

Comparative analysis of metabolism of medium- and plasma perfused primary pig hepatocytes cultured around a 3-D membrane network

Culture media are frequently used in the evaluation of metabolical functions of hepatocytes in hybrid liver support systems (hLSS). However, media compositions differ substantially from those of plasma. Therefore, our study was designed to investigate whether current in vitro studies with medium are suitable to assess the metabolical competence of hLSS-cultures during clinical application as well as to explore whether the cell nutrition with medium provides a suitable modus operandi for stand by cultivation. Paired bioreactor cultures were perfused with either Williams' Medium E (MPB) or human plasma (PPB). About 6x108 primary pig hepatocytes (>97% viability) were cultured in three laboratory scale bioreactors designed according to Gerlach's bioreactor-concept. Different perfusion protocols were initiated after a standardised period allowing for cell attachment and reorganisation in aggregates. Whereas patterns of enzyme release were similar in both protocols the metabolical behaviour was different between MPB (anabolic state) and PPB (catabolic state). Furthermore, compared to MPB the lidocaine-MEGX-tests for PPB demonstrated lower MEGX-concentrations and a different reaction pattern. We conclude that the nutrition of hepatocytes with medium during the stand by period itself might influence the cell function and subsequently the efficacy of the hLSS-treatment during clinical application.

The effect of surface roughness of microporous membranes on the kinetics of oxygen consumption and ammonia elimination by adherent hepatocytes

In membrane hybrid liver support devices (HLSDs) using isolated hepatocytes where oxygen is transported only by diffusion to the cells, about 15-40% of the cell mass is likely to be in direct contact with the semipermeable membranes used as immunoselective barriers: quantitative effects of membrane surface properties on the kinetics of hepatocyte metabolic reactions may also affect HLSD performance. In this paper, we report our investigation of the effects of surface morphology of two microporous commercial membranes on the kinetics of oxygen consumption and ammonia elimination by primary hepatocytes in adhesion culture. Isolated rat hepatocytes were cultured on polypropylene microporous membranes with different surface roughness and pore size in a continuous-flow bioreactor whose fluid dynamics was optimized for the kinetic characterization of liver cell metabolic reactions. Collagen-coated membranes were used as the reference substratum. Hepatocyte adhesion was not significantly affected by membrane surface morphology. The rates of the investigated reactions increased with ammonia concentration according to saturation kinetics: the values of kinetic parameters Vmax and K(M) increased as cells were cultured on the membrane with the greatest membrane surface roughness and pore size. For the reaction of oxygen consumption, Vmax increased from 0.066 to 0.1 pmol h(-1) per cell as surface roughness increased from 70 to 370 nm. For the kinetics of ammonia elimination. K(M) increased from 0.23 to 0.32 mM and Vmax increased from 1.49 to 1.79 pmol h(-1) per cell with membrane surface roughness increasing from 70 to 370 nm. Cells cultured on collagen-coated membranes consistently yielded the highest reaction rates. The Vmax values of 0.18 and 2.84 pmol h(-1) per cell for oxygen consumption and ammonia elimination, respectively, suggest that cell functions are also affected by the chemical nature of the substratum.

Cerebrovascular reactivity before and after carotid endarterectomy

BACKGROUND

The hemodynamic relevance of internal carotid artery (ICA) stenosis often does not correlate with anatomic features, as angiographically defined. The cerebrovascular reactivity (CVR) has been advocated as a means of defining the cerebral hemodynamic impairment.

METHODS

We assessed the results of pre- and postoperative CVR evaluation, using the CO2 transcranial doppler method, in 25 patients with high-grade ICA stenosis. The patients with history of stroke, evidence of cerebral CT infarction or symptoms from the contralateral circulation or the brain stem were excluded to avoid the effects of cerebral infarction on the hemodynamic studies. Statistical analysis was used to evaluate the CVR changes after carotid endarterectomy.

RESULTS

Preoperative evaluation showed that CVR was generally well correlated with the degree of ICA stenosis and concomitant contralateral carotid steno-occlusion. Before endarterectomy the mean CVR value was 66.5% (moderately reduced). After surgery the overall mean value of CVR was 84.1% (normal), with a statistically significant improvement.

CONCLUSION

The results of this study suggest that the CVR evaluation allows one to obtain hemodynamic information of clinical interest in the patients with ICA stenosis and that carotid endarterectomy is effective to restore the CVR in patients with cerebral hemodynamic impairment.

Congenital absence of the internal carotid artery

We report three cases of congenital absence of an internal carotid artery (ICA), diagnosed incidentally by digital subtraction angiography. The analysis of the cases is based on the classification of segmental ICA agenesis proposed by Lasjaunias and Berenstein. Usually the patients with this rare vascular anomaly are asymptomatic; some may have symptoms related to cerebrovascular insufficiency, compression by enlarged intracranial collateral vessels, or complications associated with cerebral aneurysms. Diagnosis of congenital absence of ICA is made by skull base computed tomography (CT) scan, CT and magnetic resonance angiography, and conventional or digital subtraction angiography.

Technique for the kinetic characterization of the metabolic reactions of hepatocytes in adhesion culture

In this paper, we report on the development of a technique for the kinetic characterization of the metabolic reactions of liver cells in adhesion culture. The technique is based on the use of a continuous-flow bioreactor which is designed and operated in such a way as to ensure a uniform distribution of metabolite at the cell site: hence, the metabolite concentration at the surface of cells cultured in adhesion at the bottom of the bioreactor equals that in the stream leaving the bioreactor. Under steady conditions, the rate of a given cell reaction is directly estimated from the metabolite concentration difference in the streams entering and leaving the bioreactor and can be correctly related to the actual concentration at the cell surface. Such a technique was used for a preliminary investigation of the kinetics of ammonia elimination, urea synthesis, and phenolsulfonphthalein (PSP) elimination by primary rat hepatocytes cultured in adhesion on collagen, with respect to ammonia and PSP concentration, respectively. The rate at which the hepatocytes eliminated ammonia increased with increasing ammonia concentrations according to a Michaelis-Menten kinetics. The hepatocytes synthesized urea also in the absence of ammonia in the medium: as ammonia concentration increased, the cells synthesized urea at a rate that increased according to a saturation kinetics. In the concentration range investigated, the hepatocytes eliminated PSP at a rate that increased linearly with the actual PSP concentration in the medium. Such kinetic information can be coupled to the mechanism of metabolite transport in a hybrid liver support device to yield an effective device design for the treatment of acute liver failure.