Junctional Surface Research Articles

Chemovoltaic effect for renewable liquid and vapor fuels on semiconductor surfaces.

The chemovoltaic effect - generation of electronic excitation by exergonic redox reactions - has been observed on metallic surfaces of Schottky junctions and is proving to be pivotal in explaining in detail the momentum conservation relations of chemically active collisions. As shown in this work, it can hold keys for direct chemical energy harvesting by semiconductor solar cells. To study the possibilities of chemovoltaic energy conversion by semiconductors, we have modeled and designed an 'electrolyte-free fuel cell' formed by a GaAs diode that can host electrochemical fuel oxidation and oxidant reduction reactions on its conduction and valence bands and as a result convert renewable chemical energy (as well as light) into electricity. The experimental results show that exposing the surface of a suitably designed solar cell to methanol liquid or vapor in the presence of oxygen or hydrogen peroxide leads to the generation of electrical power.

Intraoperative application of optical coherence tomography for lung tumor.

On-site instant determination of benign or malignant tumors for deciding the types of resection is crucial during pulmonary surgery. We designed a portable spectral-domain optical coherence tomography (SD-OCT) system to do real-time scanning intraoperatively for the distinction of fresh tumor specimens in the lung. A total of 12 ex vivo lung specimens from six patients were enrolled. Three patients were diagnosed with invasive adenocarcinoma (IA), while the others were benign. After OCT-imaged reconstruction, we compared the qualitative morphology of OCT and histology among malignant, benign, and normal tissues. In addition, through analysis of the quantitative data, a discrete difference in optical attenuation coefficients around the junctional surface was shown by our data processing. This study demonstrated a feasible OCT-assisted resection guide by a rapid on-site tumor diagnosis. The results indicate that future deep learning of OCT-captured image systems able to improve diagnostic and therapeutic efficiency is warranted.

Stimulation of soluble guanylate cyclase diminishes intrauterine growth restriction in a rat model of placental ischemia.

Placental ischemia in preeclampsia (PE) results in hypertension and intrauterine growth restriction (IUGR). Stimulation of soluble guanylate cyclase (sGC) reduces blood pressure in the clinically relevant reduced uterine perfusion pressure (RUPP) rat model of PE, implicating involvement in RUPP-induced hypertension. However, the contribution of sGC in the development of IUGR in PE is not known. Thus, this study demonstrated the efficacy of Riociguat, an sGC stimulator, in IUGR reversion in the RUPP rat model of PE, and tested the hypothesis that improvement in fetal weight occurs in association with improvement in placental perfusion, placental morphology, and placental nutrient transport protein expression. Sham or RUPP surgery was performed at gestational day 14 (G14) with administration of vehicle (Sham or RUPP) or the sGC stimulator (Riociguat, 10 mg/kg/day sc; sGC-treated) until G20. Fetal weight was reduced (P = 0.004) at G20 in RUPP but not in sGC-treated RUPP compared with Sham, the control group. At G20, uterine artery resistance index (UARI) was increased (P = 0.010) in RUPP, indicating poor placental perfusion; proportional junctional zone surface area was elevated (P = 0.035), indicating impaired placental development. These effects were ameliorated in sGC-treated RUPP. Placental protein expression of nutrient transporter heart fatty acid-binding protein (hFABP) was increased (P = 0.008) in RUPP but not in sGC-treated RUPP, suggesting a compensatory mechanism to maintain normal neurodevelopment. Yet, UARI (P < 0.001), proportional junctional zone surface area (P = 0.013), and placental hFABP protein expression (P = 0.008) were increased in sGC-treated Sham, suggesting a potential adverse effect of Riociguat. Collectively, these results suggest sGC contributes to IUGR in PE.

Functional interactions between herpes simplex virus pUL51, pUL7 and gE reveal cell-specific mechanisms for epithelial cell-to-cell spread

Herpes simplex virus spread between epithelial cells is mediated by virus tegument and envelope protein complexes including gE/gI and pUL51/pUL7. pUL51 interacts with both pUL7 and gE/gI in infected cells. We show that amino acids 30–90 of pUL51 mediate interaction with pUL7. We also show that deletion of amino acids 167–244 of pUL51, or ablation of pUL7 expression both result in failure of gE to concentrate at junctional surfaces of Vero cells. We also tested the hypothesis that gE and pUL51 function on the same pathway for cell-to-cell spread by analyzing the phenotype of a double gE/UL51 mutant. In HaCaT cells, pUL51 and gE function on the same spread pathway, whereas in Vero cells they function on different pathways. Deletion of the gE gene strongly enhanced virus release to the medium in Vero cells, suggesting that the gE-dependent spread pathway may compete with virion release to the medium.

Assessing the airtightness performance of container houses in relation to its effect on energy efficiency

This study examines the airtightness performance of four types of commonly-used container houses (CHs) and its impact on their energy efficiency. One of the CHs was treated by sealing all junctions inside the container envelope. The airtightness levels of unsealed and sealed CHs were measured by using the fan pressurization method. The interior surfaces of building envelope were scanned by thermal imaging in order to locate the areas suffering from air leakages and thermal failures. The annual energy consumptions of unsealed and sealed CHs for their heating were predicted by energy simulation analyses. The unsealed CHs have poor airtightness features while performing in Energy Rating B category. The junctions of those houses, especially where wall, slab and roof panels come together and the edges of the openings also suffer from air leakages, thermal bridges and condensation. Sealing the interior surfaces of junctions and edges improves the airtightness level considerably while heat loss and condensation problems at the junctions still continue. An 81% improvement in airtightness performance of the CH Type B provided a reduction of 9.3% in annual energy demand which is not enough to step up its Energy Rating category. The results indicate that airtight jointing is needed at junctions while the use of thermal breaks at junction details has vital importance to eliminate thermal failures and to improve energy efficiency performance of CHs. The combined use of Blower Test Method and Infrared Thermography is useful for non-destructive assessment of airtightness features of building envelopes.

Three-State Microwave Tunable Resonator Integrating Several Active Elements on Silicon Technology in a Global Design

This letter addresses a discrete tunable resonator with three different states controlled by a single dc source. The passive components are designed together with the active elements, and both are integrated into a silicon substrate. This method of codesign offers great flexibility in doped area sizing and positioning, allowing for easy management of novel three-state resonators based on two different doped areas (or two different surfaces of semiconductor junctions). The largest area switches from the reverse state (OFF state) to the forward state (ON1 state), with a lower bias voltage than that of the smallest area (ON2 state). This concept offers some new degrees of freedom in the design of tunable microwave devices, showcased in this letter by a demonstrator that can operate at three different resonant frequencies. Good agreement was obtained between simulations and measurements in the three states. Insertion losses are lower than 1.6 dB and the same for the different states.

Molecular Regulation of Sprouting Angiogenesis.

The term angiogenesis arose in the 18th century. Several studies over the next 100 years laid the groundwork for initial studies performed by the Folkman laboratory, which were at first met with some opposition. Once overcome, the angiogenesis field has flourished due to studies on tumor angiogenesis and various developmental models that can be genetically manipulated, including mice and zebrafish. In addition, new discoveries have been aided by the ability to isolate primary endothelial cells, which has allowed dissection of various steps within angiogenesis. This review will summarize the molecular events that control angiogenesis downstream of biochemical factors such as growth factors, cytokines, chemokines, hypoxia-inducible factors (HIFs), and lipids. These and other stimuli have been linked to regulation of junctional molecules and cell surface receptors. In addition, the contribution of cytoskeletal elements and regulatory proteins has revealed an intricate role for mobilization of actin, microtubules, and intermediate filaments in response to cues that activate the endothelium. Activating stimuli also affect various focal adhesion proteins, scaffold proteins, intracellular kinases, and second messengers. Finally, metalloproteinases, which facilitate matrix degradation and the formation of new blood vessels, are discussed, along with our knowledge of crosstalk between the various subclasses of these molecules throughout the text. Compr Physiol 8:153-235, 2018.

Effect of Cultured Dermal Substitute Composed of Collagen Sponge Seeded with Fibroblasts in Simultaneous Skin Graft Overlay

An artificial dermal substitute composed of a xenogenous collagen sponge has been widely used to create a dermal component in a full-thickness skin wound. However, one of the disadvantages in using the dermal substitute is that it requires a 2-stage surgical procedure for final wound closure. In order to close the wound much more rapidly, another type of dermal substitute which enables a simultaneous skin graft overlay is needed. In the present study, we investigated the effect of a collagen sponge seeded with isogenic fibroblasts on a simultaneously overlaid skin graft in a rat model. Normal dermal fibroblasts of SD rat were seeded and cultured on a collagen sponge composed of cross-linked porcine type I collagen. Full-thickness skin wounds were created on the dorsum of SD rats. The collagen sponges with or without fibroblasts were placed in the wounds, then covered simultaneously with split-thickness skin graft (STSG) . At 1 week and 4 weeks after grafting, overlaid STSG survival, TGF-β1 level, wound contraction, final re-epithelization and histology of the grafts were studied. The overlaid STSG survived moderately but the seeded fibroblasts did not enhance the STSG survival rate. Also, there were no significant differences in wound contraction and in the final wound epithelization between the collagen sponge seeded with and without fibroblasts. Both collagen sponges with and without fibroblasts developed neo-dermal structure without any specific immunological reaction. However, the fibroblast-seeded collagen sponge grafts showed significant re-epithelization along the junctional surface between the collagen sponge and the STSG by out-growing of the hair follicle cells. This epithelization seemed to result in formation of epithelial inclusion cysts in the neo-dermis. It was suggested that the seeded fibroblasts strongly induced such an epithelial outgrowth. The cultured collagen sponge may have beneficial effect on re-epithelization in a certain type of simultaneous skin graft overlay such as meshed STSG. 原 著

Endothelial Mechanosignaling: Does One Sensor Fit All?

Significance: Forces are important in the cardiovascular system, acting as regulators of vascular physiology and pathology. Residing at the blood vessel interface, cells (endothelial cell, EC) are constantly exposed to vascular forces, including shear stress. Shear stress is the frictional force exerted by blood flow, and its patterns differ based on vessel geometry and type. These patterns range from uniform laminar flow to nonuniform disturbed flow. Although ECs sense and differentially respond to flow patterns unique to their microenvironment, the mechanisms underlying endothelial mechanosensing remain incompletely understood. Recent Advances: A large body of work suggests that ECs possess many mechanosensors that decorate their apical, junctional, and basal surfaces. These potential mechanosensors sense blood flow, translating physical force into biochemical signaling events. Critical Issues: Understanding the mechanisms by which proposed mechanosensors sense and respond to shear stress requires an integrative approach. It is also critical to understand the role of these mechanosensors not only during embryonic development but also in the different vascular beds in the adult. Possible cross talk and integration of mechanosensing via the various mechanosensors remain a challenge. Future Directions: Determination of the hierarchy of endothelial mechanosensors is critical for future work, as is determination of the extent to which mechanosensors work together to achieve force-dependent signaling. The role and primary sensors of shear stress during development also remain an open question. Finally, integrative approaches must be used to determine absolute mechanosensory function of potential mechanosensors. Antioxid. Redox Signal. 25, 373–388.

Taper junction failure in large-diameter metal-on-metal bearings

ObjectivesAn ongoing prospective study to investigate failing metal-on-metal hip prostheses was commenced at our centre in 2008. We report on the results of the analysis of the first consecutive 126 failed mated total hip prostheses from a single manufacturer.MethodsAnalysis was carried out using highly accurate coordinate measuring to calculate volumetric and linear rates of the articular bearing surfaces and also the surfaces of the taper junctions. The relationship between taper wear rates and a number of variables, including bearing diameter and orientation of the acetabular component, was investigated.ResultsThe measured rates of wear and distribution of material loss from the taper surfaces appeared to show that the primary factor leading to taper failure is the increased lever arm acting on this junction in contemporary large-diameter metal-on-metal hip replacements.ConclusionsOur analysis suggests that varus stems, laterally engaging taper systems and larger head diameters all contribute to taper failure.

Current-in-plane Tunneling Measurement through Patterned Contacts on Top Surfaces of Magnetic Tunnel Junctions

This study reports an alternative method for measuring the magnetoresistance of unpatterned magnetic tunnel junctions similar to the current-in-plane tunneling (CIPT) method. Instead of using microprobes, a series of point contacts with different spacings are coated on the top surface of the junctions and R-H loops at various spacings are then measured by the usual four-point probe method. The values of magnetoresistance and resistance-area products can be obtained by fitting the measured data to the CIPT theoretical model. The test results of two types of junctions were highly similar to those obtained from standard CIPT tools. The proposed method may help to accelerate the process for evaluating the quality of magnetic tunnel junctions when commercial CIPT tools are not accessible.

Bcl-2 Breaks Up Cell-Cell Junctions

Expression of Bcl-2 is stimulated by estrogen, and estrogen-responsive human tumors often have increased Bcl-2 levels. Li et al. examined the effect of overexpression of Bcl-2 on MCF-7 breast carcinoma cells and Madin-Darby canine kidney (MDCK) cells, a polarized epithelial cell line, and observed loss of cell-cell junctions and redistribution of proteins that were associated with E-cadherin-containing junctions in wild-type cells. E-cadherin, like Bcl-2, is regulated by estrogen; however, no consensus estrogen-responsive elements appear to exist in the promoter, so the regulation may be indirect. E-cadherin-containing junctions include tight junctions, gap junctions, and desmosomes. In MCF-7 cells overexpressing Bcl-2, proteins--which in wild-type cells were associated with the cell-cell junctions--were redistributed either to the cytosol or, for ZO-1, to the cytosol and the nucleus. ZO-1 is known to interact with ZONAB (ZO-1-associated nucleic acid binding protein), which stimulates expression of the epidermal growth factor receptor gene ErbB2, and indeed ErbB2 protein was increased in the Bcl-2-overexpressing cells. Upon estrogen withdrawal, wild-type MCF-7 cells dissociated from each other and became motile and also exhibited increased cell death. In contrast, the MCF-7 cells overexpressing Bcl-2 required prolonged withdrawal of estrogen in order to observe decreased Bcl-2 expression in subpopulations of cells that also formed cell-cell junctions and exhibited membrane association of the junctional proteins and cell surface expression of E-cadherin. In MDCK cells overexpressing Bcl-2, the junctional proteins were also redistributed to the cytosol; however, ZO-1 colocalized with Bcl-2 instead of appearing in the nucleus as in the MCF-7 cells. Disruption of tight junctions in the MDCK and MCF-7 cells overexpressing Bcl-2 was confirmed by a decrease in transepithelial cell resistance. Increased expression of Bcl-2 may contribute to cancer invasiveness through its role in regulating cell-cell contact, as well as contribute to the proliferation of cancer cells through its ability to inhibit apoptosis.L. Li, J. Backer, A. S. K. Wong, E. L. Schwanke, B. F. Stewart, M. Pasdar, Bcl-2 expression decreases cadherin-mediated cell-cell adhesion. J. Cell Sci. 116, 3687-3700 (2003). [Abstract] [Full Text]

Bcl-2 Breaks Up Cell-Cell Junctions

Expression of Bcl-2 is stimulated by estrogen, and estrogen-responsive human tumors often have increased Bcl-2 levels. Li et al. examined the effect of overexpression of Bcl-2 on MCF-7 breast carcinoma cells and Madin-Darby canine kidney (MDCK) cells, a polarized epithelial cell line, and observed loss of cell-cell junctions and redistribution of proteins that were associated with E-cadherin-containing junctions in wild-type cells. E-cadherin, like Bcl-2, is regulated by estrogen; however, no consensus estrogen-responsive elements appear to exist in the promoter, so the regulation may be indirect. E-cadherin-containing junctions include tight junctions, gap junctions, and desmosomes. In MCF-7 cells overexpressing Bcl-2, proteins--which in wild-type cells were associated with the cell-cell junctions--were redistributed either to the cytosol or, for ZO-1, to the cytosol and the nucleus. ZO-1 is known to interact with ZONAB (ZO-1-associated nucleic acid binding protein), which stimulates expression of the epidermal growth factor receptor gene ErbB2 , and indeed ErbB2 protein was increased in the Bcl-2-overexpressing cells. Upon estrogen withdrawal, wild-type MCF-7 cells dissociated from each other and became motile and also exhibited increased cell death. In contrast, the MCF-7 cells overexpressing Bcl-2 required prolonged withdrawal of estrogen in order to observe decreased Bcl-2 expression in subpopulations of cells that also formed cell-cell junctions and exhibited membrane association of the junctional proteins and cell surface expression of E-cadherin. In MDCK cells overexpressing Bcl-2, the junctional proteins were also redistributed to the cytosol; however, ZO-1 colocalized with Bcl-2 instead of appearing in the nucleus as in the MCF-7 cells. Disruption of tight junctions in the MDCK and MCF-7 cells overexpressing Bcl-2 was confirmed by a decrease in transepithelial cell resistance. Increased expression of Bcl-2 may contribute to cancer invasiveness through its role in regulating cell-cell contact, as well as contribute to the proliferation of cancer cells through its ability to inhibit apoptosis. L. Li, J. Backer, A. S. K. Wong, E. L. Schwanke, B. F. Stewart, M. Pasdar, Bcl-2 expression decreases cadherin-mediated cell-cell adhesion. J. Cell Sci. 116 , 3687-3700 (2003). [Abstract] [Full Text]

Targeted recycling of PECAM from endothelial surface-connected compartments during diapedesis.

Leukocytes enter sites of inflammation by squeezing through the borders between endothelial cells that line postcapillary venules at that site. This rapid process, called transendothelial migration (TEM) or diapedesis, is completed within 90 s after a leukocyte arrests on the endothelial surface. In this time, the leukocyte moves in ameboid fashion across the endothelial borders, which remain tightly apposed to it during transit. It is not known how the endothelial cell changes its borders rapidly and reversibly to accommodate the migrating leukocyte. Here we show that there is a membrane network just below the plasmalemma at the cell borders that is connected at intervals to the junctional surface. PECAM-1, an integral membrane protein with an essential role in TEM, is found in this compartment and constitutively recycles evenly along endothelial cell borders. During TEM, however, recycling PECAM is targeted to segments of the junction across which monocytes are in the act of migration. In addition, blockade of TEM with antibodies against PECAM specifically blocks the recruitment of this membrane to the zones of leukocyte migration, without affecting the constitutive membrane trafficking.

Type 3 ryanodine receptors of skeletal muscle are segregated in a parajunctional position.

A key event in skeletal muscle activation is the rapid release of Ca(2+) from the sarcoplasmic reticulum (SR), the Ca(2+) storage organelle in the muscle cell. The surface membrane/transverse tubules and the SR form functional units (calcium release units containing one or two couplons or junctions), where the voltage-sensing dihydropyridine receptor of the surface membrane interacts with the SR Ca(2+) release channel [ryanodine receptor (RyR)] and depolarization of the cell membrane is converted into Ca(2+) release from the SR. Although RyR1 is the most important isoform in skeletal muscle, some muscles also express high levels of RyR3, an isoform with a wide tissue distribution. The cytoplasmic domains of RyRs are visible in the electron microscope as periodically disposed feet. We find that, in muscles containing only RyR1, feet are exclusively located over the junctional SR surface facing the surface membrane/transverse tubule. In muscles containing RyR1 as well as RyR3, additional feet are located in lateral parajunctional regions immediately adjacent to junctional SR. Biochemical content of RyR3 and content of parajunctional feet are highly correlated in different muscles and the disposition of parajunctional versus junctional feet are notably different. On the basis of these two observations, we postulate that RyR3s are restricted to the parajunctional region, and thus their activation must be indirect and derivative during excitation-contraction coupling.

Cell adhesion and the actin cytoskeleton of the enveloping layer in the zebrafish embryo during epiboly

As the zebrafish embryo undergoes gastrulation and epiboly, the cells of the enveloping layer (EVL) expand, covering the entire yolk cell. During the epiboly process, the EVL cells move as a coherent layer, remaining tightly attached to each other and to the underlying yolk syncytial layer (YSL). In view of the central role of the actin cytoskeleton, in both cell motility and cell-cell adhesion, we have labeled these cells in situ with fluorescent phalloidin and anti-actin antibodies. We show that, throughout their migration, the EVL cells retain a conspicuous cortical actin cytoskeletal belt coinciding with cell surface cadherins. At the margins approaching the YSL, the EVL cells extend, from their apicolateral domains, actin-rich filopodial protrusions devoid of detectable cadherin. We have studied the role of the actin cytoskeleton in the maintenance of EVL cohesion during epiboly. Cytochalasin treatment of embryos induces EVL dissociation accompanied by general detachment of the rest of the embryonic cells. In the dissociating EVL cells, the cortical actin belt undergoes fragmentation with the formation of actin aggregates; cadherins, on the other hand, remain evenly distributed at the junctional cell surface. Removal of Ca2+ by ethyleneglycolbis (amino-ethyl-ether)-tetraacetic acid (EGTA) treatment also induces cell dissociation without visible disruption of the cortical actin belt. The protein kinase inhibitor (1-isoquinolinylsulfonyl)-2-methyl-piperazine dihydrochloride (H-7), which blocks acto-myosin contractility and disrupts actin cables in cultured cells, also potentiates cytochalasin-induced dissociation and promotes the projection of numerous actin-rich lamellipodial extensions. The fact that EVL cells produce microspike-like structures towards the YSL and are capable of lamellipodial activity lend further support to the suggestion (R.W. Keller and J.P. Trinkaus. 1987. Dev. Biol. 120: 12-24) that the EVL cells are not passively mobilized on the expanding YSL but actively participate in epiboly.

Developmental expression of ZO-1 antigen in the mouse blood–brain barrier

Tight junction biogenesis during blood–brain barrier development (BBB) in mesencephalon microvessels of mouse embryos of day 9, foetuses of day 15 and 19 and new-born (2-day-old) mice was examined by light and electron microscopy, using monoclonal antibodies recognizing the tight junction peripheral membrane protein ZO-1. A faint spot-like staining began to be recognizable under the light microscope in day 15 vessels in which the endothelial cells showed isolated fusion points between the external plasmamembrane leaflets under the electron microscope. A stronger labelling was present in microvessels of day 19 foetuses and new-born animals when the endothelial tight junction appeared completely differentiated. In the immunogold study, gold particles were seen scattered throughout the cytoplasm of endothelial cells of day 15 foetuses. In day 19 foetuses and in the new-born mice, gold particles were located only at the cytoplasmic surfaces of the tight junctions. The results indicate that the ZO-1 protein is a specific molecular marker in the developing brain endothelial tight junctions and that its expression takes place parallel to BBB morphofunctional maturation.

Changes in the distribution of peanut agglutinin (PNA) binding molecules during muscle reinnervation following nerve crush injury.

Peanut agglutinin (PNA) staining during muscle reinnervation following a crushing injury of the sciatic nerve was performed in reference to the neural profiles immunolabeled with the PGP 9.5 antibody. PNA staining in the normal controls exhibited dots, granules, or lines along the length of the nerve fibers in the nerve trunk, but was faint or absent in the motor endplate. At seven days post-crush, PNA staining was detected around the vacuolated neural structures in the disorganized nerve trunk, but was still faint or absent in the motor endplate. At twenty-one days post-crush, when PGP 9.5-positive regenerating axons appeared in most of the motor endplates, PNA staining, either faint or strong, followed the pathway of the nerve fibers delineated by PGP 9.5-like immunoreactivity. During reinnervation to the motor endplates, PNA staining displayed signs of remodeling in the nerve trunk, such as marked variations in density and profile in the nerve fiber-associated dots or patches; it increased in intensity in the connective tissue covering the area of the motor endplate, as well as in the junctional myofiber surface. The structures recognizable by PNA coincided with components of the connective tissue such as collagen fibers and capillaries. Results suggest that: 1) the expression of PNA-binding molecules is dependent on the state of innervation, and 2) the spatiotemporal relationship between neural profiles and PNA staining provides sequences of axonal extension and subsequent nerve terminal maturation during regeneration in the motor endplate.

Integration properties of bone substitute materials. Experimental studies on animals

In order to avoid the potential risks of disease transmission in allograft surgery, numerous substitute materials have been described. As the biological response to implant materials is different, we undertook the following study to assess type and amount of bone ingrowth in CaP-ceramics. 105 cylindrical bone defects with a diameter of 5.4 mm were created surgically in the femoral condyles of 53 skeletal mature NZW rabbits. The defects were filled with crushed coralline hydroxyapatite (HA) implants (n = 21), synthetically produced hydroxyapatite (n = 21) and surface-modified alpha-Tricalciumphosphate (TCP) grains (n = 21). 21 defects were left empty and other drill holes were filled with rabbit cancellous bone cylinders (n = 21) after 3 months of cryopreservation at -78 degrees C without sterilization. Following observation periods of 2, 4, 6, 8, 12, 26 and 52 weeks the femoral condyles were harvested for histological evaluation and quantitative analysis of bone ingrowth. Woven bone formation at implant periphery can be observed in all substances as early as 2 weeks postoperatively. At 4-week-intervals cryopreserved allografts show new bone apposition on surfaces of necrotic trabeculae and graft-host junctions by a predominantly osteoblastic reaction at the periphery of all cylinders, while in HA- and TCP-grains early bone formation in the center of drill holes is detectable as well. There is a direct contact between HA-/TCP-particles and newly formed bone without fibrous tissue formation at the implant surfaces. Central new bone formation in rabbit allografts can be observed after 6 to 8 weeks together with a secondary osteoclastic resorption of necrotic transplant trabeculae. The result of this remodeling process is a complete degradation of transplant cylinders with reorganization of vital trabeculae oriented in a mature pattern after 12 to 26 weeks. In contrast the HA- and TCP-implants did not show any signs of resorption.

Retinal pigment epithelium cell culture on thin biodegradable poly(DL-lactic-co-glycolic acid) films

Thin films of 50 : 50 and 75 : 25 poly(DL-lactic-co-glycolic acid) (PLGA) were manufactured with a controlled thickness of less than 10 μm. The effect of PLGA copolymer ratio on in vitro cell attachment, proliferation, morphology, and tight junction formation was evaluated using a human D407 retinal pigment epithelium (RPE) cell line. Almost complete cell attachment was achieved on both PLGA films after 8 h of cell seeding, which was comparable to that on tissue culture polystyrene (TCPS) controls. The initial cell seeding density affected attachment, and the optimal value for 50: 50 PLGA was 25 000 cells cm-2. After 7 days of in vitro culture, cell density on 50 : 50 and 75 : 25 PLGA films increased 45 and 40 folds, respectively, and a 34-fold increase was observed on TCPS. The RPE cells cultured on PLGA films at confluence had a characteristic cobblestone morphology. Confluent RPE cells also developed normal tight junctions in vitro which were concentrated mainly at the apical surfaces of cell-cell junctions. These results demonstrated that thin biodegradable PLGA films can provide suitable substrates for human RPE cell culture, and may serve as temporary carriers for subretinal implantation of organized sheets of RPE.