New ventilation design criteria for energy sustainability and indoor air quality in a post Covid-19 scenario

The Covid-19 outbreak raised great attention to the importance of indoor air quality in buildings. Even if the Covid-19 epidemic is nearing an end, all stakeholders agree that increasing outside air flow rates is beneficial for decreasing the likelihood of contagion, lowering the risk of future pandemics, and enhancing the general safety of the interior environment. Indeed, diverse concerns raised about whether the ventilation standards in place are still adequate. In this context, this research intends to assess the suitability of current ventilation standards in addressing the current pandemic scenario and to offer novel criteria and guidelines for the design and operation of HVAC systems, as well as useful guidance for the creation of future ventilation standards in a post-Covid-19 scenario. To that end, a comprehensive analysis of the ANSI/ASHRAE 62.1 is carried out, with an emphasis on its effectiveness in reducing the risk of infection. Furthermore, the efficacy of various ventilation strategies in reducing the likelihood of contagion has been investigated. Finally, because building ventilation is inextricably linked to energy consumption, the energy and economic implications of the proposed enhancements have been assessed. To carry out the described analysis, a novel method was developed that combines Building Energy Modelling (BEM) and virus contagion risk assessment. The analyses conducted produced interesting insights and criteria for ventilation system design and operation, as well as recommendations for the development of future standards.

Systems Biology-Driven Hypotheses Tested In Vivo: The Need to Advancing Molecular Imaging Tools

Processing and interpretation of biological images may provide invaluable insights on complex, living systems because images capture the overall dynamics as a "whole." Therefore, "extraction" of key, quantitative morphological parameters could be, at least in principle, helpful in building a reliable systems biology approach in understanding living objects. Molecular imaging tools for system biology models have attained widespread usage in modern experimental laboratories. Here, we provide an overview on advances in the computational technology and different instrumentations focused on molecular image processing and analysis. Quantitative data analysis through various open source software and algorithmic protocols will provide a novel approach for modeling the experimental research program. Besides this, we also highlight the predictable future trends regarding methods for automatically analyzing biological data. Such tools will be very useful to understand the detailed biological and mathematical expressions under in-silico system biology processes with modeling properties.

Evaluation of an accident and emergency teleconsultation service for north-east Scotland

We evaluated an accident and emergency teleconsultation service provided to 14 community hospitals in north-east Scotland. Each community hospital was equipped with a videoconferencing system and a document camera to allow transmission of radiographs. The network used 384 kbit/s ISDN connections. A total of 1392 teleconsultations were recorded during a 12-month study period. Seventy-seven per cent of patients ( n = 1072) were managed locally and 23% ( n = 320) were transferred to Aberdeen. The majority (95%) of teleconsultations were conducted on weekdays, and 90% of these occurred between the hours of 09:00 and 16:00. The mean delay in contacting a doctor was 9 min and the mean consultation time was 10 min. The majority of patients were suffering from fractures or suspected fractures of the limbs. Radiograph transmission was used in 75% of all teleconsultations. A high degree of satisfaction was recorded by all users of the service.

Paradoxical E-cadherin increase in 5FU-resistant colon cancer is unaffected during mesenchymal-epithelial reversion induced by γ-secretase inhibition

AIM

Presenilin-1 (PS1), the main component of γ-secretase activity support a key role during Epithelial-Mesenchymal Transition (EMT) and chemoresistance acquisition by triggering a complex sequence of molecular events, including E-cadherin down-regulation. However, we hypothesize that EMT and chemoresistance should be deemed separate processes in HCT-8 colon cancer cells.

MAIN METHODS

HCT-8 and HCT-8FUres invasion was evaluated by trans-well assay. uPA activity was detected by zymography. Prostaglandin E2 levels were quantified using an ELISA kit. E-cadherin FL and CTF2, PS1, Notch1, Cyclin D1, COX2, SNAI1 and α-SMA expression were determined using Western blot technique. β-Catenin localization was observed by confocal microscopy. Cell apoptosis was evaluated by cytofluorimetric assay, and measurement of caspase-3 and cl-PARP. γ-Secretase activity was inhibited by DAPT, a γ-secretase inhibitor.

KEY FINDINGS

Chemoresistant HCT-8 underwent EMT that can be efficiently reversed by inhibiting PS1 activity, leading thus to a normalization of mostly of the pivotal features showed by the invasive cancer phenotype. Indeed, we observed decreased SNAI1 and Notch 1 activation, altogether with reduced E-cadherin cleavage. Concomitantly, resistant HCT-8 invasiveness was almost completely abolished. However, such reversion was not followed by any increase in apoptotic rate, not by changes in E-cadherin levels. Indeed, despite HCT-8FUres underwent an undeniable EMT, full-length E-cadherin levels were found remarkably higher than those observed in wild HCT-8.

SIGNIFICANCE

High E-cadherin concentration in presence of enhanced γ-secretase activity is incontestably a paradoxically result, highlighting that E-cadherin loss is not a pre-requisite for EMT. Additionally, EMT and chemoresistance acquisition in HCT-8 should be considered as distinct processes.

Multiwalled carbon nanotube buckypaper induces cell cycle arrest and apoptosis in human leukemia cell lines through modulation of AKT and MAPK signaling pathways

MWCNT buckypaper (BP) shows physico-chemical and mechanical properties that make it potentially useful as a substrate in nano-bio interface research including in tissue engineering. When used as a scaffold material, BP comes into contact with host cells and surrounding tissues; therefore it is critical to determine its biocompatibility and interaction with living systems. The aim of this study was to investigate BP effects on cell growth, apoptosis and reactive oxygen species (ROS) production in three human leukemia cell lines HL-60, U-937 and K-562. BP was able to induce both the reduction of cell proliferation, associated with an arrest in G0/G1 phase of cell cycle and the increase of apoptosis in leukemic cell lines, thus exerting both cytostatic and cytotoxic effects. The growth inhibitory effect was likely mediated by the decrease of cyclins D, E, A, B1 levels and CDK4 expression; meanwhile, the apoptotic effect, not mediated by ROS production, was presumably due to the combined action of the survival and pro-apoptotic AKT and MAPK signal transduction pathways. These results raised the issue of biocompatibility of MWCNT BP for the creation of carbon nanotubes based scaffolds to utilize as prostheses in tissue engineering.

Melatonin down-regulates MDM2 gene expression and enhances p53 acetylation in MCF-7 cells

Compelling evidence demonstrated that melatonin increases p53 activity in cancer cells. p53 undergoes acetylation to be stabilized and activated for driving cells destined for apoptosis/growth inhibition. Over-expression of p300 induces p53 acetylation, leading to cell growth arrest by increasing p21 expression. In turn, p53 activation is mainly regulated in the nucleus by MDM2. MDM2 also acts as E3 ubiquitin ligase, promoting the proteasome-dependent p53 degradation. MDM2 entry into the nucleus is finely tuned by two different modulations: the ribosomal protein L11, acts by sequestering MDM2 in the cytosol, whereas the PI3K-AkT-dependent MDM2 phosphorylation is mandatory for MDM2 translocation across the nuclear membrane. In addition, MDM2-dependent targeting of p53 is regulated in a nonlinear fashion by MDM2/MDMX interplay. Melatonin induces both cell growth inhibition and apoptosis in MCF7 breast cancer cells. We previously reported that this effect is associated with reduced MDM2 levels and increased p53 activity. Herein, we demonstrated that melatonin drastically down-regulates MDM2 gene expression and inhibits MDM2 shuttling into the nucleus, given that melatonin increases L11 and inhibits Akt-PI3K-dependent MDM2 phosphorylation. Melatonin induces a 3-fold increase in both MDMX and p300 levels, decreasing simultaneously Sirt1, a specific inhibitor of p300 activity. Consequently, melatonin-treated cells display significantly higher values of both p53 and acetylated p53. Thus, a 15-fold increase in p21 levels was observed in melatonin-treated cancer cells. Our results provide evidence that melatonin enhances p53 acetylation by modulating the MDM2/MDMX/p300 pathway, disclosing new insights for understanding its anticancer effect.

Microenvironment promotes tumor cell reprogramming in human breast cancer cell lines

The microenvironment drives mammary gland development and function, and may influence significantly both malignant behavior and cell growth of mammary cancer cells. By restoring context, and forcing cells to properly interpret native signals from the microenvironment, the cancer cell aberrant behavior can be quelled, and organization re-established. In order to restore functional and morphological differentiation, human mammary MCF-7 and MDA-MB-231 cancer cells were allowed to grow in a culture medium filled with a 10% of the albumen (EW, Egg White) from unfertilized chicken egg. That unique microenvironment behaves akin a 3D culture and induces MCF-7 cells to produce acini and branching duct-like structures, distinctive of mammary gland differentiation. EW-treated MDA-MB-231 cells developed buds of acini and duct-like structures. Both MCF-7 and MDA-MB-231 cells produced β-casein, a key milk component. Furthermore, E-cadherin expression was reactivated in MDA-MB-231 cells, as a consequence of the increased cdh1 expression; meanwhile β-catenin – a key cytoskeleton component – was displaced behind the inner cell membrane. Such modification hinders the epithelial-mesenchymal transition in MDA-MB-231 cells. This differentiating pathway is supported by the contemporary down-regulation of canonical pluripotency markers (Klf4, Nanog). Given that egg-conditioned medium behaves as a 3D-medium, it is likely that cancer phenotype reversion could be ascribed to the changed interactions between cells and their microenvironment.

Shape in migration: quantitative image analysis of migrating chemoresistant HCT-8 colon cancer cells

Unsuccessful cytotoxic anticancer treatments may contribute to tumor morphologic instability and consequent tissue invasion, promoting the selection of a more malignant phenotype. Indeed, morphological changes have been demonstrated to be more pronounced in strongly vs. weakly metastatic cells. By means of normalized bending energy, we have previously quantitatively defined the link between cell shape modifications and the acquisition of a more malignant phenotype by 5-FU-resistant colon cancer cells (HCT-8FUres). Such changes were significantly correlated with an increase in motility speed. Herein, we propose a method to quantitatively analyze the shape of wild and chemoresistant HCT-8 migration front cells during wound healing assay. We evaluated the reliability of parameters (area/perimeter ratio [A/p], circularity, roundness, fractal dimension, and solidity) in describing the biological behavior of the two cell lines, enabling hence in distinguishing the chemoresistant line from the other one. We found solidity index the parameter that better described the difference between chemoresistant and wild cells. Moreover, solidity is able to capture the differences between chemoresistant and wild cells at each time point of the migration process. Indeed, motility speed was found to be inversely correlated with solidity, a quantitative index of cell deformability. Deformability is an outstanding hallmark of the process leading to metastatic spread; consequently, solidity may be considered a marker of acquired metastatic property.

Nicotine increases survival in human colon cancer cells treated with chemotherapeutic drugs

Cigarette smoking is implicated in the development of colon cancer. Furthermore, nicotine increases cell proliferation and inhibits apoptosis through α7-nicotinic acetylcholine receptor (α7-nAChR) activation in human colon carcinoma cells. An open issue is whether nicotine interfere with colorectal cancer pharmacological treatment, by inhibiting drug-mediated apoptosis. To assess this hypothesis, we evaluated nicotine effect on Caco-2 and HCT-8 colon cancer cells, treated with 5-Fluorouracil (5-FU) and Camptothecin (CPT), chemotherapeutics commonly utilized as adjuvant treatment of colon cancer. Nicotine decreased anti-proliferative and pro-apoptotic effects exerted by chemotherapeutics on both cell lines. These effects partially reverted by exposure to α-bungarotoxin (α-BTX), an inhibitor of α7-nAChR. Nicotine addition to Caco-2 and HCT-8, treated with 5-FU or CPT, decreased the cleavage of substrate of caspase 3 and 7, poly-ADP-ribose polymerase (PARP). Moreover, P-ERK/ERK ratio was modified by nicotine addition to 5-FU and CPT treated cells in an opposite manner. However, when co-administrating PD98059, an ERK phosphorylation inhibitor, an increased apoptosis was observed. In Caco-2 and HCT-8 nicotine reverted 5-FU and CPT apoptotic effects through AKT phosphorylation, as demonstrated by apoptotic increase in presence of LY294002, an AKT phosphorylation inhibitor. Nicotine interfered with colorectal cancer pharmacological treatment in vitro by inhibiting apoptosis induced by chemotherapeutic drugs. Nicotine anti-apoptotic effects were exerted through ERK and AKT pathway activation.

TCam-2 seminoma cells exposed to egg-derived microenvironment modify their shape, adhesive pattern and migratory behaviour: a molecular and morphometric analysis

Seminoma is one of the most common Testicular Germ Cell Tumours that originates during embryonic development due to an alteration of the local niche that in turn results in a delayed or blocked differentiation of Primordial Germ Cells. The block of differentiation is actually a common way to develop cancer disease as postulated by the "embryonic rest theory of cancer". In agreement with this theory different studies have demonstrated that embryonic cues display the capacity of reprogramming aggressive cancer cells towards a less aggressive phenotype. Herein we investigate the ability of a culture medium added with 10% egg albumen (EW, Egg White) to modulate seminoma cell phenotype and behaviour, by ensuring a proper set of morphogenetic signals. We chose to use the TCam-2 seminoma cell line that has been established as the only available cell line, obtained from a primary testicular seminoma. EW is able to: 1) modify TCam-2 cell spreading rate and cell-substrate adhesion without affecting proliferation and survival indexes; 2) modulate TCam-2 actin distribution pattern increasing cortical localization of actin filaments; 3) increase TCam-2 cell-cell junction capability; 4) decrease both chemo-sensitive and collective TCam-2 migratory behaviour. According to these observations morphometric fractal analysis revealed the ability of EW to increase Circularity and Solidity parameters and, consequently, to decrease Fractal dimension. Prompted by these observations we hypothesize that EW treatment could rescue, at least in part, the neoplastic-metastatic behaviour of seminoma cells.

Theoretical aspects of Systems Biology

The natural world consists of hierarchical levels of complexity that range from subatomic particles and molecules to ecosystems and beyond. This implies that, in order to explain the features and behavior of a whole system, a theory might be required that would operate at the corresponding hierarchical level, i.e. where self-organization processes take place. In the past, biological research has focused on questions that could be answered by a reductionist program of genetics. The organism (and its development) was considered an epiphenomenona of its genes. However, a profound rethinking of the biological paradigm is now underway and it is likely that such a process will lead to a conceptual revolution emerging from the ashes of reductionism. This revolution implies the search for general principles on which a cogent theory of biology might rely. Because much of the logic of living systems is located at higher levels, it is imperative to focus on them. Indeed, both evolution and physiology work on these levels. Thus, by no means Systems Biology could be considered a 'simple' 'gradual' extension of Molecular Biology.

Minor injuries telemedicine

A minor injuries telemedicine network in Grampian connects 14 accident and emergency departments in community hospitals to a teaching hospital department. In a six-month study, 407 new telemedicine consultations met the inclusion criteria. Rates of transfer for treatment to the base hospital were used as an outcome measure. Fourteen out of a total of 19 members of medical staff gave telemedical advice. They were mainly middle-grade accident and emergency doctors. Transfer rates were 16-48% (median 29%) across staff. The rates did not seem to be affected by the base doctor's seniority, but were a reflection of that doctor's experience of and confidence in using videoconferencing equipment for clinical purposes. Transfer rates decreased as experience increased. Training for doctors undertaking the provision of specialist advice should include the clinical practicalities of making remote diagnoses.

An evaluation of a telemedicine fracture review clinic

Telemedicine is being widely used in the treatment of patients with minor injuries in north-east Scotland. A telemedicine fracture review clinic has been developed. During a one-month study period there were a total of 67 review appointments and 88 new patients. Fifty individual patients were reviewed and 10 were seen on more than one occasion. The mean number of reviews for all patients was 2.3. Thirty-six patients had initially been seen by telemedicine, six of whom (17%) had to come to Aberdeen for part of their treatment. Fourteen patients reviewed by telemedicine had initially been seen in person. All patients were safely managed and normal guidelines were followed. There is scope for significant expansion of this service, since 131 patients were seen in a fracture clinic in Aberdeen who lived close to a minor injury unit with telemedicine and X-ray facilities. The majority of these patients were likely to have had injuries suitable to be followed up using telemedicine.

A role for tele-education in the centralization of accident and emergency services

We evaluated the use of tele-education to provide an induction programme for accident and emergency senior house officers (SHOs) in three remote locations, and compared their performance with that of SHOs receiving the same induction programme in the conventional manner. Both groups of doctors performed similarly in a pre-course multiple-choice question (MCQ) paper, and showed comparable improvement following the induction programme lectures. Sound quality and levels of interactivity were identified as areas for improvement in the tele-education programme. Tele-education might allow doctors based in peripheral units similar access to high-quality teaching to that enjoyed by those in larger hospitals. Further experience and evaluation are required to optimize this method of education delivery.

Community coronary units: strategies to promote pre-hospital thrombolysis

Early diagnosis and the early delivery of pre-hospital thrombolysis in cases of acute myocardial infarction (AMI) have been shown to decrease mortality. Despite strong evidence of its benefits, pre-hospital thrombolysis rates are still worryingly low. The challenge is to empower community practitioners to deliver thrombolysis. In the Grampian region there is a network of community hospitals which have been equipped with both videoconferencing and remote telemetry equipment. This allows realtime consultation with the local accident and emergency department and coronary care unit. Early trials of the system show that clinical information can be viewed in realtime, with transfer of a 12-lead electrocardiogram at 60 s intervals. This will give general practitioners unprecedented access to specialist advice. Our aim is to use a combination of teaching and decision support technology to ensure that all patients with AMI have the opportunity to access timely and appropriate prehospital thrombolysis.

Air sea rescue, telemedicine style

Historically, requests from shipping in UK coastal waters for emergency medical advice have been handled on an ad hoc basis by various accident and emergency departments on behalf of the Coastguard. A formal contract to provide this service has recently been established with the Aberdeen Royal Infirmary in Scotland and the Royal Alexandra Hospital in Portsmouth, England. A pre-contract audit showed that the involvement of medical professionals in the evacuation decision improved the quality of triage and intervention. The medical staff at both hospitals received training in giving medical advice and the level of medical knowledge that could reasonably be expected of ships crews. Providing advice to commercial airlines developed from the maritime service. In association with a private company, staff at the Aberdeen Royal Infirmary have developed procedures to support cabin crew and medical professionals on board (initial figures suggest that a medical professional is present on about 45% of flights). At present, although there are insufficient data to draw any firm conclusions, it appears that up to two-thirds of diversions could be avoided using this service.

Can paediatric radiographs be accurately interpreted using an inter-hospital telemedicine system?

Children make up a significant proportion of attendances at accident and emergency departments but there is little published information about the use of telemedicine for viewing paediatric radiographs in the emergency setting. The radiographs and case-notes of 30 children were randomly selected from attendances at an accident and emergency department and were then transmitted over a telemedicine link equipped with a document camera. The doctor recorded the diagnosis and proposed management, along with the confidence in diagnosis and satisfaction with the image. This process was repeated using hardcopy radiographs and a standard viewing box. Five accident and emergency specialists took part in the study; there were in total 300 radiograph viewings. There was one missed fracture out of 75 positive radiographs viewed by telemedicine compared with no missed fractures on direct inspection of the film. Thirteen radiographs viewed over the telemedicine link were thought to be positive or suspicious of injury when the formal report was of no bony injury. The sensitivity of fracture diagnosis using telemedicine was 98.6% compared with 100% on direct inspection of the film, and specificities were 82.6% and 86.6%, respectively. Our study suggests that telemedicine can be used to aid diagnosis and make management decisions in children with minor trauma.

Effect of low frequency, low amplitude magnetic fields on the permeability of cationic liposomes entrapping carbonic anhydrase: II. No evidence for surface enzyme involvement

Observations recently reported by our group indicate that combined 7 Hz sinusoidal (B(acpeak) = 50 mu T) and parallel static (B(dc) = 50 mu T) magnetic fields can induce a significant increase in diffusion rate of substrate across carbonic anhydrase (CA)-loaded liposomes (DPPC:Chol:SA). A direct involvement of charges of stearylamine (SA) on the lipid membrane surface was also demonstrated. Kinetic studies showed that CA was mainly entrapped in liposomes at 5:3:2 molar ratio, although a small amount (17%) of enzyme was also located on the external surface of these cationic liposomes. In this paper we report steady state kinetic studies on this latter CA after ELF-EMFs exposure. No difference in the apparent K(m) between exposed and sham samples was observed. On the contrary the apparent V(max) was increased by approximately a factor of 2 after field exposure. In spite of the proteolytic digestion of this external CA, a significant increase of enzymatic activity, as a function of increase in the diffusion rate of substrate across the lipid bilayer, was observed in the exposed samples. Based on these results, a conformational change induced by the field on the CA located on the external surface of 5:3:2 liposomes is excluded as an explanation for our previous observations, supporting the primary role of bilayer SA in the interaction with ELF. A model of ELF interaction, based on the Larmor precession theory, explaining the physical phenomenon induced on the dipole of SA has been developed.

Evaluation of tilting disc valves after fatigue life testing: preliminary results within a comparison program

A fatigue life test, by accelerating the beat rate, simulates several years of virtual life of a prosthetic heart valve in a short period of time. The correlation between the in vivo life of a valve and in vitro testing expectations is as yet not well established, but reproducible test conditions yield precious information about wear and failure. The paper reports a qualitative analysis of mechanical valve wear as part of a comparison program designed to investigate the significance of fatigue testing with the ultimate aim of defining standard guidelines for these type of tests. Two tilting disc valves (29 mm) were subjected to 16 years of fatigue life simulated by means of a Rowan Ash fatigue tester (accelerated rate of 1,200 bpm). Fatigue-induced effects on valve disc and ring surfaces were observed under a monitor microscope to identify wear sites and patterns. A high speed cinematographic system was used to investigate the mechanisms responsible for the wear (wear modes). Valve closure was inspected at a 6,000 frame/s rate. Because of disc rotation during the tilting movement, the points of contact between disc and ring are distributed all around the disc edge but focally on the ring. On both sides of the disc, the surfaces present ring-like concentric grooves. After 16 years of fatigue life the valves showed neither severe wear nor alteration of their fluidodynamic behavior in the pulsatile flow test.

Approaching comparability and results of pulsatile flow in vitro testing of prosthetic heart valves

The testing of prosthetic heart valves under pulsatile conditions is still a subject for debate among researchers and competent standardization bodies. The laboratory of Biomedical Engineering, of the Istituto Superiore di Sanità in Rome, has reproduced the current inter-laboratory situation with several test apparatuses, focusing on the definition of significant measurement parameters and procedures to obtain reasonably comparable data. The laboratory is also equipped with a Laser Doppler Anemometer (LDA) and a High-Speed Cinematographic system (HSC). A 29 mm tilting disc valve model, was mounted in the aortic position. Under tightly controlled system conditions the analyses performed on two pulse duplicators (PDs) may be deemed consistent for the valve model tested. Useful results, on the same valve specimen, are reported concerning velocity profiles and turbulent shear stress values (TSS). Furthermore valve motion on the Sheffield PD was monitored during the closing phase, and related cinematic data reported. The applied methodologies can provide relevant data to support surgeon decision making.

Matching between theoretical and experimental data for ELF ion transport effects

In recent years, several studies have been focused on the problem of nonthermal interaction between extremely low-frequency (ELF) electromagnetic fields and cell environment at membrane level. In the paper, to analyse the dynamic effects of weak static and harmonic fields on charged particles, some new considerations have been developed, based on the Lorentz model. The authors have reached a suitable formulation so that the data processing has led expressly to the evaluation of ionic-velocity components against magnetic-field amplitudes and frequencies, as well as a viscosity parameter. Even through a direct and rough comparison, the results of the authors' investigation have demonstrated an interesting agreement with some experimental data relative to ionic fluxes through cell membranes. Indeed, by means of an algorithm based on the techniques of the inversion theory, the author's have found definite values of the viscosity parameter for which the expected resonant behaviours (amplitude and frequency windows) fit existing experiments well. It seems worthy of interest that such viscosity values fall within a consistent, narrow range of low amplitude.

In vitro evaluation of prosthetic heart valves: towards comparable testing

The Laboratory of Biomedical Engineering (of the National Health Institute, technical body of the Italian Health Service) performs in vitro testing of prosthetic heart valves for mechanical characteristics of materials, fatigue life, and fluidodynamic performance. Testing of materials is directed towards the physicomechanical characterization of the structural components of the valves, e.g. elasticity and resistance to stress of biological tissues and stents. Long-term fatigue life tests are conducted by means of systems which make valves beat at more than 1200 cycles/min. These tests are preceded and followed by geometrical characterization and by steady flow testing in order to obtain information about stenosis and leakage. Special attention is devoted to pulsatile flow testing which is performed on two pulse duplicators: the Dynatek system and the system developed by the University of Sheffield. The same valve was tested with these systems according to their different possible set-ups within the general requirements established by ISO-DIS 5840. This paper presents significant measurements, taking into account their dependence on the systems adopted. Results show (a) the difficulties in comparing test results because of different operating conditions, and (b) the systems' sensitivity with regards to some parameters which affect measurements under comparable set-up conditions (FDA Interlaboratory Comparison Testing Protocol).

Prosthetic heart valve evaluation in vitro: critical aspects of data comparability

The technology of heart valve substitution has considerably improved in the last few years, but its reliability after implantation is still not good enough, hence the need to study new valve design and improve quality testing. Different pulse duplicators are used for heart valve testing, but the results depend very much on the system adopted and the measurement protocol. Tests on two pulse duplicators currently used at the Biomedical Engineering Laboratory at the Istituto Superiore di Sanità, Rome, are reported here. The most significant parameters for valve evaluation were measured following each system's own protocol. Attention was focused on vascular load tuning when setting up the system and on the relationship between drive unit flow waveform and valve regurgitation and energy loss measurements. Standardization criteria must be defined in order to ensure the reliable comparability of in vitro testing results.

Effects of culture media on murine hybridomas: definition of optimal conditions for hybridoma viability, cellular proliferation, and antibody production

Different cell culture media were compared for their ability to support and promote the growth of stable hybridoma cell lines derived from three commonly used parental murine myelomas. Supplemented Dulbecco's modified Eagle's media (DMEM) and RPMI 1640 media were studied. The DMEM-based media were found to support greater numbers of cells for longer time periods than were the RPMI 1640-based media. Aminopterin supplemented medium was shown to be significantly less effective in supporting hybridoma reproduction and viability than medium without aminopterin. Antibody levels were directly related to cell concentration and viability regardless of the medium used for the hybridoma culture. An optimally formulated DMEM-based medium is suggested as the medium of choice for hybridoma propagation and maintenance.

Enhancing the establishment efficiency of hybridoma cells. Use of irradiated human diploid fibroblast feeder layers

Eight different cell feeder layers and 2 conditioned media were compared for their ability to increase the establishment efficiency of newly formed hybridoma cells. Enhancement was noted particularly with all 3 irradiated human lung diploid fibroblasts which were tested. Hybridomas established in the presence of the feeder layers were found to be stable upon propagation even in the absence of the feeder cells. MRC-5 diploid fibroblasts are suggested as the hybridoma feeder layer cell of choice due to this cell's ease of culture and handling.