Piece Of Membrane Research Articles

On CH 4 decomposition during separation from H 2 mixtures with thin Pd membranes

The influence of high CH 4 concentrations (8–31%) on the H 2 permeation through a 2 μm thick Pd membrane was investigated between 473 and 823 K at 100 kPa pressure difference at the maximum H 2 extraction limit, with the retentate H 2 concentration always staying above 50%. The permeate flux was slightly higher in CH 4/H 2 mixtures than in equimolar N 2/H 2 mixtures. This is attributed to decomposition of CH 4 on the Pd surface as indicated by trace amounts of C 2H 6. At 723 K and below H 2 permeation remained stable during 6 h experiments in CH 4/H 2 mixtures, whereas it gradually decreased with time above that threshold. TPO, SEM and XRD revealed several types of carbon forming on the surface of membrane pieces during exposure to pure CH 4. Following CH 4 treatment below 723 K two types of carbon deposits were found, which are designated as carbidic carbon and disordered carbon aggregates. Carbonaceous filaments were observed after CH 4 exposure above 723 K and graphite platelets after treatment at 823 K. Furthermore, metastable Pd 0.9C 0.1 and/or Pd 0.85C 0.15 phases were detected after CH 4 treatment at 573, 623, and 773 K. Carbidization of the membrane was most severe at 623 K, but the carbides could be readily decomposed by heat treatment in N 2 between 623 and 723 K. Mechanisms for deactivation of the Pd membrane during separation of CH 4/H 2 mixtures at elevated temperatures are discussed.

Microstructure and glycosaminoglycan ratio of canine cornea after reconstructive transplantation with glycerin‐preserved porcine amniotic membranes

Although amniotic membranes of canine, feline, and equine species have some advantages as corneal transplantation material in many canine ocular diseases, their softness, thinness, and low availability can pose problems. As an alternative, the more abundant porcine amniotic membranes may be used. This paper describes the use of glycerin-preserved porcine amniotic membranes in corneal transplantation in eight normal dogs. A 0.4-mm deep recipient bed in the axial cornea of the OS of all dogs was created using an 8-mm Barron radial vacuum trephine. The recipient bed was then filled with amnion, and the entire cornea was covered with another piece of the glycerin-preserved membrane. The ocular signs evaluated were corneal opacity and corneal vascularization. The dogs were euthanized on days 5, 10, 20, or 40 after surgery, and samples were collected to evaluate corneal thickness, parenchymal cell number, mean collagen fibril diameter, collagen fibril content and the glycosaminoglycan (GAG) ratio. Corneal opacity was observed immediately after surgery. Restoration of corneal transparency, regression of corneal vascularization, and visualization of the pupil and iris were noted on day 40. The clinical observations were supported histologically by regained corneal thickness, parenchymal cell number, mean collagen fibril diameter, collagen fibril content, and GAG ratio, suggesting that this technique may be a novel method for the treatment of ocular surface disorders.

Phorbol 12-Myristate 13-Acetate-dependent Protein Kinase Cδ-Tyr311 Phosphorylation in Cardiomyocyte Caveolae

Protein kinase Cdelta (PKCdelta) activation is generally attributed to lipid cofactor-dependent allosteric activation mechanisms at membranes. However, recent studies indicate that PKCdelta also is dynamically regulated through tyrosine phosphorylation in H(2)O(2)- and phorbol 12-myristate 13-acetate (PMA)-treated cardiomyocytes. H(2)O(2) activates Src and related Src-family kinases (SFKs), which function as dual PKCdelta-Tyr(311) and -Tyr(332) kinases in vitro and contribute to H(2)O(2)-dependent PKCdelta-Tyr(311)/Tyr(332) phosphorylation in cardiomyocytes and in mouse embryo fibroblasts. H(2)O(2)-dependent PKCdelta-Tyr(311)/Tyr(332) phosphorylation is defective in SYF cells (deficient in SFKs) and restored by Src re-expression. PMA also promotes PKCdelta-Tyr(311) phosphorylation, but this is not associated with SFK activation or PKCdelta-Tyr(332) phosphorylation. Rather, PMA increases PKCdelta-Tyr(311) phosphorylation by delivering PKCdelta to SFK-enriched caveolae. Cyclodextrin treatment disrupts caveolae and blocks PMA-dependent PKCdelta-Tyr(311) phosphorylation, without blocking H(2)O(2)-dependent PKCdelta-Tyr(311) phosphorylation. The enzyme that acts as a PKCdelta-Tyr(311) kinase without increasing PKCdelta phosphorylation at Tyr(332) in PMA-treated cardiomyocytes is uncertain. Although in vitro kinase assays implicate c-Abl as a selective PKCdelta-Tyr(311) kinase, PMA-dependent PKCdelta-Tyr(311) phosphorylation persists in cardiomyocytes treated with the c-Abl inhibitor ST1571 and c-Abl is not detected in caveolae; these results effectively exclude a c-Abl-dependent process. Finally, we show that 1,2-dioleoyl-sn-glycerol mimics the effect of PMA to drive PKCdelta to caveolae and increase PKCdelta-Tyr(311) phosphorylation, whereas G protein-coupled receptor agonists such as norepinephrine and endothelin-1 do not. These results suggest that norepinephrine and endothelin-1 increase 1,2-dioleoyl-sn-glycerol accumulation and activate PKCdelta exclusively in non-caveolae membranes. Collectively, these results identify stimulus-specific PKCdelta localization and tyrosine phosphorylation mechanisms that could be targeted for therapeutic advantage.

Germination and outgrowth of Bacillus subtilis and Bacillus licheniformis spores in the gastrointestinal tract of pigs

To determine if orally ingested Bacillus spores used as probiotics or direct-fed microbial feed additives germinate and the vegetative cells grow in the gastrointestinal (GI) tract. Three independent experiments were done to determine if spores of Bacillus licheniformis and Bacillus subtilis germinate and grow in the GI tract of pigs. After a 2 weeks spore-feeding period, spores were detected in all segments of the GI tract. The lowest number of spores was found in the stomach, increasing in the small intestine to approx. 55% of the dietary inclusion. When spores were withdrawn from the feed, faecal excretion of spores reflected the dietary inclusion, but decreased gradually to the background level after 1 week. By containing spores in short, sealed pieces of dialysis membrane that were orally administered to the pigs, both the number of spores and vegetative cells could be determined by flow cytometry. Spores accounted for 72% of the total counts after 4-6 h in the stomach and proximal part of the small intestine. After 24 h, spores constituted only 12% of the total counts in the stomach, caecum, and mid-colon. Less spores and more vegetative cells were detected after 24 h, but total counts increased only 2.14-fold compared to time zero. The experiments showed that 70-90% of dietary-supplemented Bacillus spores germinate in the proximal part of the pig GI tract, and that only limited outgrowth of the vegetative cell population occurs. The two Bacillus strains can temporarily remain in the GI system, but will be unable to permanently colonize the GI tract. A substantial population of growing vegetative cells in the GI tract is not a prerequisite for the mode of action of Bacillus feed additives and probiotics.

A microfilter utilizing a polyethersulfone porous membrane with nanopores

We present a novel microfilter system used for the selective separation of solutes of molecular sizes 1–2 nm. The microfilter system consists of two layers of micro chambers made of PDMS and one piece of porous membrane made of polyethersulfone (PES) using the wet-phase inversion method. The PES membrane at the center of the two micro chambers acts as a barrier to molecules larger than its pores. A novel method of bonding the PES membrane to PDMS surface was developed in the device fabrication, whereby diffusion in the microfilter was theoretically derived and applied in the filtering evaluation. The filtering capacity of this microfilter for molecules of molecular sizes from 0.3 nm to 6.6 nm was evaluated using solution samples of sodium chloride (NaCl) and fluorescein isothiocyanate (FITC) dextrans with molecular weights of 4k, 20k and 70k, respectively. The filtering experiments indicated that the optimal membrane used for the device was P2S2. This microfilter system with optimal PES membrane was believed to be capable of selective separation at a molecular size barrier of 1–2 nm and also believed to have the potential for use in portable hemodialysis systems.

Probing Individual Proteins in Unsupported Membranes

Abstract Proteins in biologic membranes perform a large variety of essential functions. The fact that about one third of all genes code for membrane proteins, and that the majority of drugs target these proteins, attest to that fact. However, until now, proteins have been studied under artificial conditions, such as after being crystallized, frozen, or adsorbed to a substrate. Rui Pedro Gonçalves, Guillaume Agnus, Pierre Sens, Christine Houssin, Bernard Bartenlian, and Simon Scheuring have devised a novel setup with the atomic force microscope (AFM) to allow proteins to be probed while they are in unsupported membranes. Their method is similar in principle to methods where a small area of a membrane is sampled, such as when a piece of membrane is examined by patch clamping. The difference is that instead of attaching a membrane to the end of a pipette, it is spread across a piece of perforated Si(001).

Use of Biotin Derivatives to Probe Conformational Changes in Proteins

Sulfosuccinimidyl-6-(biotinamido) hexanoate and derivatives thereof covalently bind to the epsilon-amino group of lysine residues. Our observation that access of the biotin derivative to specific lysine residues depends on conformational properties of the entire polypeptide chain prompted us to investigate whether differential biotinylation patterns of a protein can be used as indicators for conformational changes. Bovine serum albumin is a soluble protein with characteristic unfolding kinetics upon exposure to high temperature. First, we show that biotinylation patterns of proteins are highly reproducible. Second, we demonstrate by mass spectrometry and tandem mass spectrometry that unfolding of the protein correlates with the accessibility of the biotin derivative to specific lysine residues. We have applied this experimental strategy to the analysis of a cell-surface protein, viz. the human band 3 anion exchanger of erythrocytes infected with the malaria parasite Plasmodium falciparum. We found that Lys(826) in a highly flexible loop can be biotinylated in non-infected (but not infected) erythrocytes, confirming earlier observations (Winograd, E., and Sherman, I. W. (2004) Mol. Biochem. Parasitol. 138, 83-87) based on epitope-specific monoclonal antibodies suggesting that this region undergoes a conformational change upon infection.

Convenient synthesis of CeO 2 nanotubes

A simple and facile route was used in the fabrication of CeO 2 nanotubes within anodic alumina membrane. A piece of membrane was first immersed into Ce(NO 3) 3 aqueous solution under ambient conditions. After dried at 50 °C and thermally calcined at 150 °C and 550 °C, CeO 2 nanotubes can be easily synthesized. The characterization with electron microscopy and X-ray diffraction indicated that CeO 2 nanotubes were composed of tiny well-crystalline CeO 2 nanoparticles.

Removal of anionic reactive dyes from water using anion exchange membranes as adsorbers

Two commercial anion exchange membranes, strong basic (SB6407) and weak basic (DE81), were evaluated for the removal of anionic reactive dyes, Cibacron blue 3GA (three sulfonic acid groups per dye molecule) and Cibacron red 3BA (four sulfonic acid groups per dye molecule), from water in this study. The adsorption isotherm results show that the Langmuir maximum adsorption capacities of Cibacron blue 3GA (31.5 mg/cm 3 for SB6407 and 25.5 mg/cm 3 for DE81) were greater than those of Cibacron red 3BA (24.5 mg/cm 3 for SB6407 and 18.5 mg/cm 3 for DE81). For each reactive dye, the capacity for SB6407 was higher than DE81 based on the same membrane volume. However, consideration of the number of ion exchange sites interacting with a dye molecule indicates that the DE81 results are close to the theoretical values while the SB6407 membrane had some unused binding sites. In addition, Cibacron red 3BA demonstrated faster and stronger binding with both anion exchange membranes than Cibacron blue 3GA. Both dyes could bind with strong basic SB6407 more quickly and stronger. In the batch desorption process, different desorption solutions were tested and the mixtures of salt, acid, or base in methanol solution (e.g. 1 N KSCN in 60% methanol or 1 N HCl in 60% methanol) achieved better performance. Finally, in the flow process with one piece of anion exchange membrane (initial dye concentration of 0.05 g/L), SB6407 was found superior to DE81 in dye recovery and both membranes retained their original uptake capacities over three cycles of adsorption, washing, and desorption.

Antler regeneration: a dependent process of stem tissue primed via interaction with its enveloping skin

Deer antlers are unique mammalian appendages in that each year they are cast and fully regenerate from permanent bony protuberances, called pedicles. In a previous study, we found that there is a difference in the degree of association between pedicle bone and its enveloping skin: tight at the distal third and loose at the proximal two thirds of a pedicle stump. The distal part has been termed the "potentiated" region, and the proximal part the "dormant" region. In the present study, pedicle stumps were artificially created in yearling sika deer by cutting off the tissue distal to either the potentiated or the dormant region. A piece of impermeable membrane was then inserted into the space between the bone and the skin of each treated pedicle stump, while the control pedicles had the same surgery without membrane insertion. The results showed that the inserted membrane blocked pedicle skin participation in the process of antler regeneration. All three potentiated bony pedicle stumps regenerated skin-less antlers; whereas, one of the three dormant bony pedicle stumps failed to regenerate any antler tissue. The other two dormant stumps eventually regenerated normal antlers; however, this only occurred after loss of the inserted membrane. No antler tissue regenerated from the dormant stumps while the inserted membrane remained in place (up to 55 days). All control pedicle stumps regenerated normal antlers. Therefore, we conclude that it is the pedicle bone, but not pedicle skin, that gives rise to regenerating antlers, and that pedicle bone can acquire the potential to regenerate an antler only when it is primed via interaction with its enveloping skin.

Equilibrium Sampling of Freely Dissolved Alkylphenols into a Thin Film of 1-Octanol Supported on a Hollow Fiber Membrane

A new negligible depletion extraction procedure was proposed for equilibrium sampling of 4-tert-octylphenol (OP) and 4-nonylphenol (NP) into a thin film of 1-octanol supported on a hollow fiber membrane. This thin liquid film extraction technique was directed at the determination of (1) freely dissolved concentrations, (2) distribution coefficients to 1-octanol (D(ow)), and (3) binding to dissolved organic matter (DDOC). The sampling device was prepared by dipping pieces of polypropylene microporous hollow fiber membrane (10-mm length, 30-microm wall thickness, 240-microm inner diameter) into 1-octanol for a few seconds to impregnate the pores of the hollow fiber wall. After stirring in 100 mL of sample solution for 24 h, the sampling device was harvested and desorbed with 30 microL of methanol, of which 20 microL was injected for HPLC analysis. With the measured D(ow) of a chemical and its equilibrium concentration in the 1-octanol sampling phase (C(octanol)), the freely dissolved concentration (Cfree) was calibrated based on Cfree = C(octanol)/D(ow). Measured log Dow values of OP (4.32 +/- 0.06) and NP (4.79 +/- 0.02) were independent of the chemical concentration, only minimally affected by the environmentally relevant pH, buffering capacity, and salinity of samples, and agreed well with reported values. Log DDOC values of OP (4.89 +/- 0.43) and NP (5.14 +/- 0.37), determined in Aldrich humic acid solution, agreed with reported partition coefficients to organic carbon (log Koc) for particles in river water and effluent wastewater. Short equilibration times and high enrichment factors were obtained for both analytes due to the high surface to volume ratio of the new sampler. The technique was successfully applied to determine Cfree of OP and NP in real water samples and to study their association with humic acids and bovine albumin.

Development of a chemiluminescent immunosensor for chloramphenicol

A direct competitive chemiluminescent immunosensor system that exploits the competition between chloramphenicol (CAP) as an analyte and CAP–horseradish peroxidase conjugate as a tracer for binding to an anti-CAP antibody on a solid support was devised by installing a flow-through cell which was connected to an injector and a peristaltic pump inside a dark box, followed by positioning a photomultiplier tube as light detector in front of it. The anti-CAP antibody was immobilized onto positively charged Biodyne B membrane pieces by a dipping procedure. The operating conditions for the immunosensor were selected with respect to substrate composition (0.25, 13.3 and 0.66 mM for luminol, H 2O 2 and p-iodophenol, respectively), injection volume of the substrate solution (200 μL) and the concentrations of antibody for immobilization (0.10 mg mL −1) and tracer (0.030 mg mL −1). At these conditions, sensor response according to analyte concentration was well fitted to a linear equation when plotted in semi-logarithmic scale, with the limit of detection for CAP of 10 −8 M. By using the immunosensor, CAP measurement in the model samples prepared from five food materials was conducted.

Conducting polymer micro-tubules hosting electroactive species without guest modification

A hollow micro-tubule structure comprised of the conducting polymer, PEDOT, was manufactured by the electrochemical polymerization of EDOT into a template membrane containing 1.2 μm pores. The tubules formed were then capped with a conducting PEDOT/PSS aqueous dispersion. In order to assist in effective capping, a piece of a PC membrane containing 0.05 μm pores was attached to the capping film of the aqueous dispersion. The cap was then reinforced with PEDOT via the electrochemical polymerization of EDOT in order to make it insoluble in aqueous solutions. The cavity of this micro-cylinder structure worked as a container retaining water-soluble electroactive materials and played the role as a current collector for the electrochemical reaction of the species retained inside. In this study, K 3Fe(CN) 6 was used as the probe material stored in the cylinders. The current collector exhibited a fine current response due to the redox reaction of the interior species. These results show that guest materials can be stored in this capped cylinder structure without the problems associated with the use of organic solvents during the manufacturing processes. Moreover, the most important part of the whole process can be monitored using simple electrochemical methods.

Membrane biophysics

Membrane biophysics

In vivo and in vitro degradation of a novel bioactive guided tissue regeneration membrane

The aim of this study was to assess degradation of a novel bioactive guided tissue regeneration (GTR) membrane and to quantify the concurrent tissue responses. Pieces of membrane composed of poly- l-lactide, poly- d,l-lactide, trimethylenecarbonate and polyglycolide were dipped into an N-methyl-2-pyrroline (NMP) solution and implanted in the mandibles of 10 sheep. The animals were sacrificed at 6–104 weeks. Parallel in vitro degradation was analysed by measuring the inherent viscosity, water absorption and remaining mass. One of the 2 in vitro sets of membranes was prehandled with NMP. At 6–26 weeks in vivo, the gradually more degraded implants were surrounded by a fibrous network. At 52 and 104 weeks, the implants and fibrous networks were non-detectable. Foreign body granulomatous reactions were not observed. In vitro, the mass of the NMP-exposed membranes diminished linearly over the 2-year period down to 10%, while the non-NMP-exposed membrane maintained all their mass for the first 16 weeks. The membranes without NMP had absorbed significantly less water at weeks 4 and 8 than the other group. The inherent viscosity decreased relatively uniformly in the in vitro groups. In conclusion, the in vivo degradation was complete in 12 months with only mild histologic responses; the degradation in vitro may be slower. NMP accelerates the degradation.

CDK Phosphorylation Inhibits the DNA-binding and ATP-hydrolysis Activities of the Drosophila Origin Recognition Complex

Faithful propagation of eukaryotic chromosomes usually requires that no DNA segment be replicated more than once during one cell cycle. Cyclin-dependent kinases (Cdks) are critical for the re-replication controls that inhibit the activities of components of the pre-replication complexes (pre-RCs) following origin activation. The origin recognition complex (ORC) initiates the assembly of pre-RCs at origins of replication and Cdk phosphorylation of ORC is important for the prevention of re-initiation. Here we show that Drosophila melanogaster ORC (DmORC) is phosphorylated in vivo and is a substrate for Cdks in vitro. Cdk phosphorylation of DmORC subunits DmOrc1p and DmOrc2p inhibits the intrinsic ATPase activity of DmORC without affecting ATP binding to DmOrc1p. Moreover, Cdk phosphorylation inhibits the ATP-dependent DNA-binding activity of DmORC in vitro, thus identifying a novel determinant for DmORC-DNA interaction. DmORC is a substrate for both Cdk2 x cyclin E and Cdk1 x cyclin B in vitro. Such phosphorylation of DmORC by Cdk2 x cyclin E, but not by Cdk1 x cyclin B, requires an "RXL" motif in DmOrc1p. We also identify casein kinase 2 (CK2) as a kinase activity in embryonic extracts targeting DmORC for modification. CK2 phosphorylation does not affect ATP hydrolysis by DmORC but modulates the ATP-dependent DNA-binding activity of DmORC. These results suggest molecular mechanisms by which Cdks may inhibit ORC function as part of re-replication control and show that DmORC activity may be modulated in response to phosphorylation by multiple kinases.

Segmental mandibular reconstruction by elasticity distraction osteogenesis associated with guided bone regeneration

To accelerate distraction osteogenesis by utilizing guided bone regeneration technique, and to improve the automatic process of canine segmental mandibular reconstruction by elasticity distraction osteogenesis using shape memory metal alloy distractor. Adult hybrid canines were used. Osteotomy was performed to remove a bone segment of 2.5-4.0 cm in one side of the mandible. Mandibular fixation devices and shape memory metal alloy distractor were secured according to the principles of bi-focal distraction technique. A piece of ePTFE membrane was sutured to cover the buccal side of bone defect and osteotomy gap of transport disc, where the periosteum was peeled for exposing mandible in operation. Then the incisions were totally closed. The canines were sacrificed 3 months later to harvest the mandibles for morphological observation and measurement of bone density and intensity. The shape memory metal alloy distractor performed distraction osteogenesis automatically and reconstructed the mandibles with bone defect. A regenerated bone segment of 1.5-2.0 cm was formed in the compression region between transport disc and contralateral mandibular end. The new bone in both of distraction and compression regions had similar height and thickness with normal mandible. Moreover the new bone density and intensity were rather satisfied. Membrane guided bone regeneration can avoid bone synthesis commonly caused by cicatrization of soft tissue in the bone defect, and accelerate ossification and maturation of new generated bone.

Mathematical study on gradient formation of cetyltrimethylammonium bromide in centrifugal precipitation chromatography

Centrifugal precipitation chromatography (CPC) is a separation system that mainly employs a moving concentration gradient of precipitating agent along a channel. Solutes of interest undergo repetitive precipitation‐dissolution, and fractionate at different locations, and finally elute out from the channel according to their solubility in the precipitant solution. In the practical apparatus, two channels are formed by inserting a piece of dialysis membrane between a pair of disks with mutually mirror‐imaged spiral grooves. A sample is injected into one channel and the precipitant solution is fed into another one. When the precipitant travels across the membrane to the sample channel, its concentration gradient is formed. Gradient profile of precipitant inside the sample channel is crucial to the success of CPC; therefore, it is worthwhile to investigate the formation of the precipitant concentration gradient. In this paper, an established mathematical model used to explain the steady‐state gradient formation of ammonium sulfate, (NH4)2SO4, in CPC was adopted for studying the gradient formation of cationic surfactant cetyltrimethylammonium bromide (CTAB). Its concentration, velocity and pressure profile obtained from the model are discussed.

Regulation of the Proapoptotic ARTS Protein by Ubiquitin-mediatedDegradation

ARTS is a mitochondrial protein that promotes apoptosis induced by a variety of proapoptotic stimulators. ARTS induces apoptosis, at least in part, through binding to and antagonizing IAPs (inhibitors of apoptosis proteins). As a result of ARTS binding to IAPs, caspase inhibition is removed and apoptosis can be executed. Here we show that high cellular levels of ARTS protein sensitize cells toward apoptosis. Accordingly, in healthy cells ARTS levels are kept low through constant ubiquitin-mediated degradation. Upon proapoptotic stimuli, the ubiquitination process is inhibited, resulting in increased levels of ARTS. Increased ARTS in turn leads to a decrease of Bcl-2 and Bcl-xL protein levels, cytochrome c release from mitochondria and apoptosis.

Experimental analyses of the function of the proepicardium using a new microsurgical procedure to induce loss‐of‐proepicardial‐function in chick embryos

The proepicardium (PE) is a primarily extracardiac progenitor cell population that colonizes the embryonic heart and delivers the epicardium, the subepicardial and intramyocardial fibroblasts, and the coronary vessels. Recent data show that PE-derived cells additionally play important regulatory roles in myocardial development and possibly in the normal morphogenesis of the heart. Developmental Dynamics 233, 2005. Research on the latter topics profits from the fact that loss-of-PE-function can be experimentally induced in chick embryos. So far, two microsurgical techniques were used to produce such embryos: (1) blocking of PE cell transfer with pieces of the eggshell membrane, and (2) mechanical excision of PE. Both of these techniques, however, have their shortcomings. We have searched, therefore, for new techniques to eliminate the PE. Here, we show that loss-of-PE-function can be induced by photoablation of the PE. Chick embryos were treated in ovo by means of a window in the eggshell at Hamburger and Hamilton (HH) stage 16 (iday 3). The pericardial coelom was opened, and the PE was externally stained with a 1% solution of Rose Bengal by means of a micropipette. Photoactivation of the dye was accomplished by illumination of the operation field with visible light. Examination on postoperative day 1 (iday 4, HH stages 19/20) disclosed complete removal of PE in every experimental embryo. On iday 9 (HH stages 33/34), the survival rate of experimental embryos was 35.7% (15 of 42). Development of the PE-derivatives was compromised in the heart of every survivor. The abnormalities encompassed hydro- or hemopericardium, epicardium-free areas with aneurysmatic outward bulging of the ventricular wall, thin myocardium, defects of the coronary vasculature, and abnormal tissue bridges between the ventricles and the pericardial wall. Our results show that photoablation of the PE is a powerful technique to induce long-lasting loss-of-PE-function in chick embryos. We have additionally obtained new data that suggest that the embryonic epicardium may make important contributions to the passive mechanics of the developing heart.