Cytotoxicity of low pH dentin-bonding agents in a dentin barrier test in vitro

The reaction of three-dimensional cultures of pulp-derived cells in a dentin barrier test was recorded after exposure to All-Bond 2, Prime & Bond NT, Syntac SC, Syntac Classic, and Prompt L-Pop. The materials were applied on bovine dentin disks in a perfusion chamber, and the experiments were performed with (0.3 ml/h, 2 ml/h) and without perfusion of the pulpal part of the chamber. The cell reaction was recorded (MTT assay) and related to noncytotoxic controls. Bonding agents with low pH did not show any cytotoxicity. Syntac Classic decreased the cell activities to 38% to 72%, depending on different experimental conditions, and was more cytotoxic than Syntac SC. Perfusion (2 ml/h) reduced the cytotoxicity for Syntac Classic and increased cell activities from 52% to 72%. Because low pH bonding agents did not show toxic reactions in this dentin barrier test, pulp damage caused by the tested substance is unlikely if a dentin layer protects the pulp.

Receptor for advanced glycation end products plays a more important role in cellular survival than in neurite outgrowth during retinoic acid-induced differentiation of neuroblastoma cells

The receptor for advanced glycation end products (RAGE), a member of the immunoglobulin superfamily, is known to interact with amphoterin. This interaction has been proposed to play a role in neurite outgrowth and process elongation during neurodifferentiation. However, there is as yet no direct evidence of the relevance of this pathway to neurodifferentiation under physiological conditions. In this study we have investigated a possible role of RAGE and amphoterin in the retinoic acid-induced differentiation of neuroblastoma cells. The functional inactivation of RAGE by dominant negative and antisense strategies showed that RAGE is not required for process outgrowth or differentiation, although overexpression of RAGE accelerates the elongation of neuritic processes. Using the antisense strategy, amphoterin was shown to be essential for process outgrowth and differentiation, suggesting that amphoterin may interact with other molecules to exert its effect in this context. Interestingly, the survival of the neuroblastoma cells treated with retinoic acid was partly dependent on the expression of RAGE, and inhibition of RAGE function partially blocked the increase in anti-apoptotic protein Bcl-2 following retinoic acid treatment. Based on these results we propose that a combination therapy using RAGE blockers and retinoic acid may prove as a useful approach for chemotherapy for the treatment of neuroblastoma.

The EGF/ErbB receptor family and apoptosis

The ErbB receptor family can activate a multitude of cell signaling pathways that involve many aspects of cellular function. The four members of the ErbB receptor family interact with diverse ligands and substrates, as well as with each other through cell surface heterodimerization. The sum of these diverse interactions is a signaling network that is complex but also finely regulated. Among the cellular functions influenced by ErbB signaling is cell survival. ErbB receptor signaling has been demonstrated to interact with all of the major mechanisms of cell death signaling in a manner that promotes cell survival. Survival factors such as Ras, PI3-K, Akt, and Bcl-x/-2 all have been shown to be activated by ErbB signaling (Fig. 5). ErbB abrogation of apoptotic signals has been shown to play an important role during embryonic tissue development, in normal adult tissue maintenance (e.g. mammary tissue, wound healing), and also in tumor development and progression. Although the majority of studies suggest that ErbB receptor family members are mediators of cell survival, there have been occasional reports suggesting that ErbB receptors can induce cell death under selected experimental conditions. While this apparent discrepancy remains unresolved, in many of these reports, cell death may be the result of anoikis in response to changes in the cytoskeleton associated with hyperstimulation of ErbB signaling. The notion that ErbB receptor family members function to promote cell survival is not a recent observation. However, how this family functions to prevent apoptosis is an area that only recently has been considered. The understanding of ErbB receptor signaling as it relates to the avoidance of apoptosis had profound implications for the treatment of solid tumors originating in multiple tissues, as well as for the treatment of neurodegenerative disease. Further elucidation of the complex relationships between ErbB receptor signaling networks and the apoptotic machinery is certain to yield biologically important and potentially life-saving information.

Potential of bovine herpesvirus 4 as a gene delivery vector

A cloning system was developed for construction of BHV-4 recombinants and recombinant virus BHV-4EGFPDeltaTK containing an enhanced green fluorescent protein (EGFP) gene was constructed. The host range of BHV-4EGFPDeltaTK was characterized in vitro. When cell lines from various species and tissues were infected, most of the non-bovine cell lines exhibited neither cytopathic effect (CPE) nor supported viral replication, but EGFP expression was clearly observed. Next, embryonic stem cells were infected and induced to either non-specific or neural differentiation to determine whether they could survive and differentiate after BHV-4EGFPDeltaTK infection. Embryonic stem cells were infected successfully, as indicated by EGFP expression prior to differentiation, and EGFP expression could be detected in many differentiated cells. No CPE was noted. Therefore, BHV-4EGFPDeltaTK infection caused neither cell death nor interfered with non-specific or neural differentiation of embryonic stem cells. Finally, to assess the capability of BHV-4EGFPDeltaTK to infect post-mitotic neurons, cultures from brains of 2-weeks old mice were infected. No death of neuronal cells due to infection was observed and EGFP expression persisted for at least 15 days. Several biological characteristics of BHV-4 demonstrated previously make it a good candidate for a gene delivery vector. These include: little or no pathogenicity, unlikely oncogenicity, ability to establish persistent infection, and capability of herpesviruses to accommodate large amounts of foreign genetic material. These findings add the ability to infect several cell types coming from different animal species, usually without CPE, lack of interference with differentiation, and ability to maintain transgene expression in both undifferentiated and differentiated cells.

Activating transcription factor 1 and CREB are important for cell survival during early mouse development

Activating transcription factor 1 (ATF1), CREB, and the cyclic AMP (cAMP) response element modulatory protein (CREM), which constitute a subfamily of the basic leucine zipper transcription factors, activate gene expression by binding as homo- or heterodimers to the cAMP response element in regulatory regions of target genes. To investigate the function of ATF1 in vivo, we inactivated the corresponding gene by homologous recombination. In contrast to CREB-deficient mice, which suffer from perinatal lethality, mice lacking ATF1 do not exhibit any discernible phenotypic abnormalities. Since ATF1 and CREB but not CREM are strongly coexpressed during early mouse development, we generated mice deficient for both CREB and ATF1. ATF1(-/-) CREB(-/-) embryos die before implantation due to developmental arrest. ATF1(+/-) CREB(-/-) embryos display a phenotype of embryonic lethality around embryonic day 9.5 due to massive apoptosis. These results indicate that CREB and ATF1 act in concert to mediate signals essential for maintaining cell viability during early embryonic development.

Functional proteomics using chromophore-assisted laser inactivation

Proteins are the molecules that fulfil most cellular functions and represent over 90% of drug targets in the market. Chromophore-assisted laser inactivation (CALI) provides a timely and locally restricted protein inactivation and has proven to specifically destroy protein function using dye-coupled ligands and laser irradiation. CALI involves the generation of short-lived radicals thus limiting the radius of covalent modifications to spatially restricted sites on the target molecule. A transient functional inactivation occurs if the radicals modify amino acids of the target protein that are responsible for function. Here we show specific inactivation of several protein targets, that are members of relevant signal transduction pathways. For each of these targets, simple and high throughput screening-scaleable assays have been developed, making it possible to quantify the observed inactivation. Activities of target proteins have been addressed in cell-free as well as cell-based assays employing human primary and tumor-derived cell lines. In all cases, at least 50% inactivation was achieved. The data presented here demonstrate that CALI is a highly versatile tool for validating disease relevant targets at the protein level. This approach also takes into account post-translational modifications like phosphorylation, glycosylation or acylation, thereby enlarging its applicability for many different types of targets.

Purification of native survival of motor neurons complexes and identification of Gemin6 as a novel component

The survival of motor neurons (SMN) protein, the product of the gene responsible for the motor neuron degenerative disease spinal muscular atrophy (SMA), is part of a large macromolecular complex. The SMN complex is localized in both the cytoplasm and the nucleus and contains SMN, Gemin2, Gemin3, Gemin4, Gemin5, and a few not yet identified proteins. The SMN complex plays a key role in the biogenesis of spliceosomal small nuclear ribonucleoproteins (snRNPs) and other ribonucleoprotein particles. As a step toward the complete characterization of the components of the SMN complex, we generated stable cell lines that express FLAG-tagged SMN or Gemin2 under the control of a tetracycline-inducible promoter. Native SMN complexes of identical protein composition to those isolated by immunoprecipitation with anti-SMN antibodies were purified by affinity chromatography from extracts of both cell lines. Here we report the identification by mass spectrometry of a novel protein component of the SMN complex termed Gemin6. Co-immunoprecipitation, immunolocalization, and in vitro binding experiments demonstrate that Gemin6 is a component of the SMN complex that localizes to gems and interacts with several Sm proteins of the spliceosomal snRNPs.

BRCA1 transcriptionally regulates damaged DNA binding protein (DDB2) in the DNA repair response following UV-irradiation

The p53 and BRCA1 tumor suppressors are involved in repair processes and may cooperate to transactivate certain genes, including p21WAF/CIP1 and GADD45. We find that the Xeroderma Pigmentosum Complementation group E (XPE) mutated Damaged-DNA binding protein p48 (DDB2) is upregulated by BRCA1 in a p53-dependent manner following UVC, Adriamycin, or Cisplatin exposure. BRCA1 enhances p53 binding to the DDB2 promoter in vivo as well as p53-dependent transactivation of DDB2 promoter-reporter constructs through a classical p53 DNA responsive element. Antisense abrogation of BRCA1 expression abrogates upregulation of DDB2 after UVC or cisplatin exposure. Using a host cell reactivation assay, DNA repair activity is more significantly restored by introduction of BRCA1 into wt as compared to DDB2-deficient cells. Furthermore disappearance of the photoproducts cyclobutane pyrimidine dimer (CPD) and 6-4 photoproduct (6-4PP) was delayed by antisense abrogation of BRCA1 expression in UV-exposed human cells. Thus the DNA repair function of BRCA1 may be attributed in part to p53-dependent transcriptional induction of DDB2. Loss of BRCA1-dependent DDB2 repair function may contribute to cancer susceptibility and cellular sensitivity to DNA damage.

Transitional B lymphocyte subsets operate as distinct checkpoints in murine splenic B cell development

Signaling through the Ag receptor is required for peripheral B lymphocyte maturation and maintenance. Defects in components of the B cell receptor (BCR) signalosome result in developmental blocks at the transition from immature (heat-stable Ag (HSA)(high)) to mature (HSA(low)) B cells. Recent studies have subdivided the immature, or transitional, splenic B cells into two subsets, transitional 1 (T1) and transitional 2 (T2) cells. T1 and T2 cells express distinct surface markers and are located in distinct anatomic locations. In this report, we evaluated the BCR signaling capacity of T1 and T2 B cell subsets. In response to BCR engagement, T2 cells rapidly entered cell cycle and resisted cell death. In contrast, T1 cells did not proliferate and instead died after BCR stimulation. Correlating with these results, T2 cells robustly induced expression of the cell cycle regulator cyclin D2 and the antiapoptotic factors A1/Bfl-1 and Bcl-x(L) and exhibited activation of Akt. In contrast, T1 cells failed to up-regulate these markers. BCR stimulation of T2 cells also led to down-regulation of CD21 and CD24 (HSA) expression, resulting in a mature B cell phenotype. In addition, T2 cells from Bruton's tyrosine kinase-deficient Xid mice failed to generate these proliferative and survival responses, suggesting a requirement for the BCR signalosome specifically at the T2 stage. Taken together, these data clearly demonstrate that T2 immature B cells comprise a discrete developmental subset that mediates BCR-dependent proliferative, prosurvival, and differentiation signals. Their distinct BCR-dependent responses suggest unique roles for T1 vs T2 cells in peripheral B cell selection.

Early experiences with a porcine hepatocyte-based bioartificial liver in acute hepatic failure patients

Orthotopic liver transplantation (OLT) is the only effective therapeutic modality in severe acute hepatic failure (AHF). The scarcity of organs for transplantation leads to an urgent necessity for temporary liver support treatments in AHF patients. A hepatocyte-based bioartificial liver (BAL) is under investigation with the main purpose to serve as bridging treatment until a liver becomes available for OLT, or to promote spontaneous liver regeneration. We developed a novel radial-flow bioreactor (RFB) for three-dimensional, high-density hepatocyte culture and an integrated pumping apparatus in which, after plasmapheresis, the patient's plasma is recirculated through the hepatocyte-filled RFB. Two hundred thirty grams of freshly isolated porcine hepatocytes were loaded into the RFB for clinical liver support treatment. The BAL system was used 8 times in supporting 7 AHF patients in grade III-IV coma, all waiting for an urgent OLT Three patients with no history of previous liver diseases were affected by fulminant hepatic failure (FHF) due to hepatitis B virus, 3 by primary non-function (PNF) of the transplanted liver, and one by AHF due to previous abdominal trauma and liver surgery. Six out of 7 patients underwent OLT following BAL treatment(s), which lasted 6-24 hours. All patients tolerated the procedures well, as shown by an improvement in the level of encephalopathy, a decrease in serum ammonia, transaminases and an amelioration of the prothrombin time, with full neurological recovery after OLT Our initial clinical experience confirms the safety of this BAL configuration and suggests its clinical efficacy as a temporary liver support system in AHF patients.

The snail superfamily of zinc-finger transcription factors

The Snail superfamily of zinc-finger transcription factors is involved in processes that imply pronounced cell movements, both during embryonic development and in the acquisition of invasive and migratory properties during tumour progression. Different family members have also been implicated in the signalling cascade that confers left right identity, as well as in the formation of appendages, neural differentiation, cell division and cell survival.

[Synthetic peptides -- analogs of biologically active fragment of the differentiation factor from HL-60 cells show radioprotective and adaptogenic activities]

It was shown that the addition of synthetic six-membered peptide (HLDF-6) and its Tyr-analog (HLDF-Y) to cultural medium significantly increased the survival of cells HL-60, treated by cold shock. The prophylactic administration of HDLF-Y (1 mg/kg, 4 hours prior to applied actions) decreased the response of hypothalamushypophysis-adrenal glands system and sympathicoadrenal system of rat males on supercooling and also increased the resistance of mouse males to supercooling and X-irradiation. In the experiences with females HDLF-Y did not show the similar biological activity.

Neuronal survival following remote adenovirus gene delivery

OBJECT

Virus-mediated central nervous system gene delivery is a promising means of treating traumatized tissue or degenerative diseases. In the present study, the authors examined gene expression and neuronal survival in the spinal cord after sciatic nerve administration of an adenovirus vector expressing a LacZ reporter gene.

METHODS

The time course of adenovirus gene expression, DNA fragmentation, and neuronal density were quantified in rat lumbar spinal cord by staining for beta-galactosidase (beta-Gal), terminal deoxynucleotidyl transferase, and cresyl violet after microinjection of either saline or the reporter virus into rat sciatic nerve. The expression of beta-Gal following remote vector delivery peaked at 7 days and declined thereafter but was not accompanied by neuronal cell death, as measured by DNA fragmentation. No significant difference in spinal motor neuron density was detected between virus-treated and control rats at any time point examined. Although the spinal cords removed from rats treated with cyclosporine prior to adenovirus injection contained substantially more neurons staining for beta-Gal at 7 days (67% of total neurons), the decay in the number of stained neurons was not paralleled by a decline in motor neuron density.

CONCLUSIONS

The authors conclude that remote gene expression is suppressed by a noncytolytic process.

A comparison of type I collagen, fibronectin, and vitronectin in supporting adhesion of mechanically strained osteoblasts

We used an adhesion assay for cells cultured under high dynamic strain to measure human osteoblast-like HOS cell adherence to immobilized type I collagen, fibronectin, and vitronectin. These conditions were designed to model the increased forces present at unstable fractures or loose joint prostheses. At a constant, low protein-coating density (1000 molecules/microm2) and 20% cyclic strain for 24 h, type I collagen, fibronectin, and vitronectin supported 24.6 +/- 2%, 16.7 +/- 3%, and 1.1 +/- 1% adherence, respectively, which paralleled the relative number of integrin-binding sites in each protein. Thus, when the number of available binding sites was limited, strain resistance was proportional to the number of integrin-ligand interactions. In contrast, at high protein-coating densities (> or = 2,500 molecules/microm2), vitronectin supported greater adherence (45.7 +/- 2%) when compared with type I collagen (37 +/- 2%) or fibronectin (34.8 +/- 2%) and directed constitutive expression of osteopontin (OPN), which suggested that there exist discrete signals on vitronectin receptor occupancy that promoted cell adherence and survival under strain. Integrin-mediated binding was necessary for resistance to strain, as evidenced by the low levels of strain resistance observed when cells were adherent in a nonintegrin-dependent manner. These findings support the utilization of at least two distinct mechanisms (i.e., tensegrity and integrin-mediated signal transduction) by HOS cells to remain adherent and viable on exposure to mechanical forces.

Methotrexate exacerbates tumor progression in a murine model of chronic myeloid leukemia

Expression of drug-resistant forms of dihydrofolate reductase (DHFR) in hematopoietic cells confers substantial resistance of animals to antifolate administration. In this study, we tested whether the chemoprotection conferred by expression of the tyrosine-22 variant DHFR could be used for more effective therapy of the 32Dp210 murine model of chronic myeloid leukemia (CML). 32Dp210 tumor cells were found to be sensitive to methotrexate (MTX) in vitro, whereas cells expressing the tyrosine-22 DHFR gene were protected from MTX at up to micromolar concentrations. MTX administered at low dose (2 mg/kg/day) did not protect normal C3H-He/J mice from 32Dp210 tumor infused intravenously, with drug toxicity limiting the administration of higher doses. Animals engrafted with transgenic tyrosine-22 DHFR marrow were protected from greater MTX doses (up to 6 mg/kg/day). However, the increased doses of MTX afforded by drug-resistance gene expression surprisingly resulted in decreased survival of the transplanted tumor-bearing animals, with increased levels of tumor detected in peripheral blood. This apparent exacerbation of tumor progression by MTX was not observed in DHFR transgenic mice in which all cells and tissues contain the drug-resistance gene. This suggests that increased tumor progression in MTX-administered animals resulted from MTX sensitivity of a nonhematopoietic host component, thus allowing tumor expansion. We conclude that MTX exacerbates tumor progression in the 32Dp210 model of CML, and that based on this model alternate DHFR inhibitors combined with drug-resistant DHFR or other chemotherapeutic agent/drug-resistance gene combinations may be required for the application of drug-resistance gene expression to the treatment of CML.

Evaluation of human sperm function after repeated freezing and thawing

Sperm storage via freezing has been useful for men who have difficulty masturbating during assisted reproductive technology (ART) programs and before impotency caused by chemotherapy, vasectomy, and other procedures. Studies were undertaken to evaluate the extent of cryoinjury to sperm after repeated freezing and thawing. The results showed that normozoospermic and oligozoospermic sperm survived after 3 repeated freeze-thaw cycles. The inclusion of seminal plasma did not seem to protect human sperm during freezing and thawing. There were no significant differences in recovery percentages for motile, vital, and morphologically normal sperm between slow and rapid freezing methods in thaws 1, 2, and 3 of normozoospermic and oligozoospermic unwashed (u), washed (w), and washed + seminal plasma (ws) samples. However, there were significant percentage drops in the recovery of motile and vital sperm between each thaw (ie, first to second thaw, and second to third thaw) using both slow and rapid freezing for u, w, and ws samples (P < .01). There were also no significant differences in percentage recovery of motile, vital, and morphologically normal sperm between u, w, and ws samples during thaws 1 to 3 in the normozoospermic and oligozoospermic groups. Sperm were capable of fertilizing hamster oocytes microinjected with single sperms after 3 freeze-thaw cycles as evidenced by the formation of 2 distinct pronuclei and 2 polar bodies in 22.2% and 17.2% of normozoospermic and oligozoospermic samples, respectively. The numbers of normal vital motile sperm after 3 serial freeze-thaw cycles are adequate for bringing about fertilization via intracytoplasmic sperm injection in ART programs. Thus, leftover washed sperm in laboratories that perform in vitro fertilization can be frozen, thawed, and refrozen several times without loss of the sperms' ability to fertilize. This approach has tremendous benefits for men who have difficulty producing sperm and for those with low and declining sperm counts.

Genetic ablation of phosphatidylinositol transfer protein function in murine embryonic stem cells

Phosphatidylinositol transfer proteins (PITPs) regulate the interface between signal transduction, membrane-trafficking, and lipid metabolic pathways in eukaryotic cells. The best characterized mammalian PITPs are PITP alpha and PITP beta, two highly homologous proteins that are encoded by distinct genes. Insights into PITP alpha and PITP beta function in mammalian systems have been gleaned exclusively from cell-free or permeabilized cell reconstitution and resolution studies. Herein, we report for the first time the use of genetic approaches to directly address the physiological functions of PITP alpha and PITP beta in murine cells. Contrary to expectations, we find that ablation of PITP alpha function in murine cells fails to compromise growth and has no significant consequence for bulk phospholipid metabolism. Moreover, the data show that PITP alpha does not play an obvious role in any of the cellular activities where it has been reconstituted as an essential stimulatory factor. These activities include protein trafficking through the constitutive secretory pathway, endocytic pathway function, biogenesis of mast cell dense core secretory granules, and the agonist-induced fusion of dense core secretory granules to the mast cell plasma membrane. Finally, the data demonstrate that PITP alpha-deficient cells not only retain their responsiveness to bulk growth factor stimulation but also retain their pluripotency. In contrast, we were unable to evict both PITP beta alleles from murine cells and show that PITP beta deficiency results in catastrophic failure early in murine embryonic development. We suggest that PITP beta is an essential housekeeping PITP in murine cells, whereas PITP alpha plays a far more specialized function in mammals than that indicated by in vitro systems that show PITP dependence.

Impairment of immunological memory in the absence of MHC despite survival of memory T cells

The mechanisms by which immunological memory is maintained after infection or vaccination are still a matter of debate. Long-term survival of memory T cells does not require major histocompatibility complex (MHC) contact. We show here that compared with memory CD4+ T cells that maintain contact with MHC class II, memory CD4+ T cells deprived of MHC class II contact show distinct functional defects upon antigen re-encounter. Thus, in contrast to their survival, maintenance of the typical quality of memory T cells crucially depends on MHC-derived signals.

Quantitative analysis of gap-junctional intercellular communication in precision-cut mouse liver slices

Direct intercellular communication through gap junction channels is involved in the maintenance of tissue homeostasis and suppression of carcinogenesis. Gap-junctional communication is often altered in tumor cells but it can also be modulated in response to tumor promotors or inflammatory signals. In order to evaluate the effect of nongenotoxic compounds, suggested to be involved in tumor promotion, on gap junctional intercellular communication in the liver, we have developed a direct dye transfer method. The fluorescent dye Alexa Fluor 488 was iontophoretically injected into hepatocytes of freshly prepared, precision-cut mouse liver slices (250 microm). The area of dye spreading was monitored and quantified by microscopy. Comparison of dye spreading in connexin-32-deficient versus wild-type liver revealed a 96% decrease in connexin-32-deficient tissue. Induction of an acute phase response in connexin-32-deficient mice by intraperitoneal injection of lipopolysaccharide increased dye coupling by 33%, probably due to upregulation of connexin-26-containing gap junction channels.

Anatomical correlations of intrinsic axon repair after partial optic nerve crush in rats

About 15% of retinal ganglion cells survive diffuse axonal injury of the optic nerve in adult rats. Following initial blindness, discrimination of visual stimuli in behavioral tests recovers within three weeks. To investigate the mechanisms promoting this functional recovery the axonal transport and the neurofilaments were studied. Intraocularly applied MiniRuby is transported until the place of crush and accumulated in enlarged axon terminals. Three weeks after lesion the anterograde transport of MiniRuby recovers distal to the place of crush. At the same point in time the retrograde transport of surviving retinal ganglion cells is restored which was visualized by horseradish peroxidase injected into the superior colliculus. The heavy neurofilament was stained immunohistochemically and analyzed statistically up to three weeks after optic nerve crush. The stained filaments in the axon fibers of retinal ganglion cells appear wavelike and/or fragmented up to day 8, but first signs of heavy neurofilament restitution in the fibers of the optic nerve are seen at day 12 after axonal injury. Because these results cannot be explained by longlasting axon regeneration, the present results provide convincing evidence for intrinsic axon repair soon after diffuse axonal injury that correlates in time with recovery of vision.

Increased viability of transplanted hepatocytes when hepatocytes are co-encapsulated with bone marrow stem cells using a novel method

This study is to investigate the viability of hepatocytes when transplanted into Wistar rats using co-encapsulated hepatocytes and bone marrow stem cells. Hepatocytes and bone marrow stem cells, isolated from Wistar rats, are co-encapsulated using either the standard single-step method or a novel two-step cell encapsulation method (www.artcell.mcgill.ca). After intraperitoneal transplantation into Wistar rats, the histology, fate of recovered microcapsules and viability of encapsulated hepatocytes are studied. When prepared using the standard method, there is excellent viability but only for up to 3 weeks. After this, there is extensive fibrous coating and severe fibrous adhesion and no microcapsules can be recovered. On the other hand, using the new two-step encapsulation method, the viability of the encapsulated hepatocytes can be followed for more than 4 months after transplantation. Even up to 4 months, there is significantly less host reaction when using the two-step encapsulation method and 50% of the microcapsules can be recovered. Co-encapsulated with bone marrow stem cells resulted in further increase in viability of the hepatocytes when followed up to 4 months after transplantation. This new approach may improve the potential feasibility of using co-encapsulation of hepatocytes and bone marrow stem cells in bio-artificial liver support for the treatment of liver failure, especially for acute liver failure.

Low sex steroid environment affects survival and steroid secretion of ovarian tumour cells in primary cultures

Ovarian epithelial tumours are considered to be endocrine related. The effects of an environment with low levels of the steroid hormones 17 beta-estradiol, testosterone or progesterone on cell survival and steroid secretion were studied in primary cell cultures derived from 25 patients suffering from epithelial ovarian tumours. Tumour cells cultured in 17 beta-estradiol and testosterone showed a reduced cell survival (-10.3 +/- 2.3% and -15.6 +/- 2.7% minimum survival respectively). This reduction was inversely proportional to hormone concentrations within the range studied. No similar effect was observed in the progesterone cultures. It was found that 17 beta-estradiol was secreted from the primary cell cultures and, interestingly, the amount of 17 beta-estradiol secreted increased with increasing levels of 17 beta-estradiol in the environment. Neither progesterone nor testosterone production was observed in any of the cultures studied. It is believed that 17 beta-estradiol has an antiapoptotic effect on ovarian surface epithelial (OSE) cells. Reduction of 17 beta-estradiol in the environment may inhibit this effect, resulting in reduced cell survival. The ability of ovarian epithelial tumour cells to secrete 17 beta-estradiol suggests that epithelial ovarian tumours play an active role in altering their own hormonal environment, promoting tumour progression.

Ultrasound-induced physiological changes in cultured cells of Petunia hybrida

Petunia hybrida cell suspension cultures were exposed to ultrasonic standing wave fields at 2.43 MHz for 40 min with mean sound pressures (within homogenous sound fields) varying from 0 (control) to ca. 1.1 MPa. Mean (+/- s.d.; n =6-9) cell viability was reduced to 87+/-10% at 0.6 MPa and to 59 +/- 23% at 1.1 MPa, compared to an initial control value of 92 +/- 6% (P <0.05). Mean (n = 3) cell alkaline phosphatase concentration increased linearly with sound pressure from a control value of 0.006+/-0.001 to 0.02+/-0.01 Sigma-Units microg(-1) protein at 1.1 MPa (P<0.05). Similarly, mean cell catalase activity increased from a control value of 0.020 +/- 0.003 to 0.026 +/- 0.008 arbitrary units at 1.1 MPa. In contrast, mean cellular lactate dehydrogenase concentration was unchanged. These observations indicate that cellular repair processes associated with increased alkaline phosphatase activity might be triggered by physical cell damage caused by ultrasound. The observed increase in catalase activity suggests increasing production of free radicals and other sonochemicals, which warrants further study. The absence of changes in lactate dehydrogenase indicates that there was no major damage to respiratory pathways or to overall cellular integrity.