A model for strain amplification in the actin cytoskeleton of osteocytes due to fluid drag on pericellular matrix

A model is presented that provides a resolution to a fundamental paradox in bone physiology, namely, that the strains applied to whole bone (i.e., tissue level strains) are much smaller (0.04-0.3 percent) than the strains (1-10 percent) that are necessary to cause bone signaling in deformed cell cultures (Rubin and Lanyon, J. Bone Joint Surg. 66A (1984) 397-410; Fritton et al., J. Biomech. 33 (2000) 317-325). The effect of fluid drag forces on the pericellular matrix (PM), its coupling to the intracellular actin cytoskeleton (IAC) and the strain amplification that results from this coupling are examined for the first time. The model leads to two predictions, which could fundamentally change existing views. First, for the loading range 1-20MPa and frequency range 1-20Hz, it is, indeed, possible to produce cellular level strains in bone that are up to 100 fold greater than normal tissue level strains (0.04-0.3 percent). Thus, the strain in the cell process membrane due to the loading can be of the same order as the in vitro strains measured in cell culture studies where intracellular biochemical responses are observed for cells on stretched elastic substrates. Second, it demonstrates that in any cellular system, where cells are subject to fluid flow and tethered to more rigid supporting structures, the tensile forces on the cell due to the drag forces on the tethering fibers may be many times greater than the fluid shear force on the cell membrane.

Developmental effects of dietary phytoestrogens in Sprague-Dawley rats and interactions of genistein and daidzein with rat estrogen receptors alpha and beta in vitro

Estrogenic isoflavones, such as genistein and daidzein, are present in virtually all natural-ingredient rodent diets that use soy as a source of protein. Since these compounds are endocrine-active, it is important to determine whether the amounts present in rodent diets are sufficient to affect sexual development. The present study consisted of in vitro and in vivo parts. In the in vitro portion, human hepatoma cells were transfected with either rat estrogen receptor (ER) alpha or beta plus an estrogen-responsive luciferase reporter gene. Genistein and daidzein were complete agonists at both ERs, genistein being more potent than daidzein, and both compounds were more potent at ER beta than ER alpha. In combined studies with estradiol, genistein exerted additive effects with estradiol in vitro. In the in vivo portion of the study, groups of six pregnant Sprague-Dawley females were fed one of the following four diets, and the pups were maintained on the same diets until puberty: (1) a natural-ingredient, open-formula rodent diet (NIH-07) containing 16 mg genistein and 14 mg daidzein per 100 g of feed; (2) a soy- and alfalfa-free diet (SAFD) in which casein and corn oil were substituted for soy and alfalfa meal and soy oil, respectively, that contained no detectable isoflavones; (3) SAFD containing 0.02% genistein (GE.02); or (4) SAFD containing 0.1% genistein (GE.1). In the GE.1 group, effects of dietary genistein included a decreased rate of body-weight gain, a markedly increased (2.3-fold) uterine/body weight (U/BW) ratio on postnatal day (pnd) 21, a significant acceleration of puberty among females, and a marginal decrease in the ventral prostate weight on postnatal day (pnd) 56. However, developmental differences among the groups fed SAFD, GE.02, or NIH-07 were small and suggested minimal effects of phytoestrogens at normal dietary levels. In particular, on pnd 21, the U/BW ratio of the GE.02 and NIH-07 groups did not differ significantly from that of the SAFD group. Only one statistically significant difference was detected between groups fed SAFD and NIH-07: the anogenital distance (AGD) of female neonates on pnd 1 whose dams were fed NIH-07 was 12% larger than that of neonates whose dams were fed SAFD. The results suggest that normal amounts of phytoestrogens in natural-ingredient rodent diets may affect one developmental parameter, the female AGD, and that higher doses can affect several other parameters in both males and females. Based on these findings, we do not suggest replacing soy- and alfalfa-based rodent diets with phytoestrogen-free diets in most developmental toxicology studies. However, phytoestrogen-free diets are recommended for endocrine toxicology studies at low doses, to determine whether interactive effects may occur between dietary phytoestrogens and man-made chemicals.

Directed evolution of subtilisin E in Bacillus subtilis to enhance total activity in aqueous dimethylformamide

Sequential rounds of error-prone PCR to introduce random mutations and screening of the resultant mutant libraries have been used to enhance the total catalytic activity of subtilisin E significantly in a non-natural environment, aqueous dimethylformamide (DMF). Seven DNA substitutions coding for three new amino acid substitutions were identified in a mutant isolated after two additional generations of directed evolution carried out on 10M subtilisin E, previously "evolved' to increase its specific activity in DMF. A Bacillus subtilis-Escherichia coli shuttle vector was developed in order to increase the size of the mutant library that could be established in B.subtilis and the stringency of the screening process was increased to reflect total as well as specific activity. This directed evolution approach has been extremely effective for improving enzyme activity in a non-natural environment: the resulting-evolved 13M subtilisin exhibits specific catalytic efficiency towards the hydrolysis of a peptide substrate succinyl-Ala-Ala-Pro-Phe-p-nitroanilide in 60% DMF solution that is three times that of the parent 10M and 471 times that of wild type subtilisin E. The total activity of the 13M culture supernatant is enhanced 16-fold over that of the parent 10M.

Room-temperature antiferromagnetic memory resistor

The bistability of ordered spin states in ferromagnets provides the basis for magnetic memory functionality. The latest generation of magnetic random access memories rely on an efficient approach in which magnetic fields are replaced by electrical means for writing and reading the information in ferromagnets. This concept may eventually reduce the sensitivity of ferromagnets to magnetic field perturbations to being a weakness for data retention and the ferromagnetic stray fields to an obstacle for high-density memory integration. Here we report a room-temperature bistable antiferromagnetic (AFM) memory that produces negligible stray fields and is insensitive to strong magnetic fields. We use a resistor made of a FeRh AFM, which orders ferromagnetically roughly 100 K above room temperature, and therefore allows us to set different collective directions for the Fe moments by applied magnetic field. On cooling to room temperature, AFM order sets in with the direction of the AFM moments predetermined by the field and moment direction in the high-temperature ferromagnetic state. For electrical reading, we use an AFM analogue of the anisotropic magnetoresistance. Our microscopic theory modelling confirms that this archetypical spintronic effect, discovered more than 150 years ago in ferromagnets, is also present in AFMs. Our work demonstrates the feasibility of fabricating room-temperature spintronic memories with AFMs, which in turn expands the base of available magnetic materials for devices with properties that cannot be achieved with ferromagnets.

Cryopreserved human amniotic membrane for ocular surface reconstruction

BACKGROUND

Amniotic membrane transplantation is used for the reconstruction of the ocular surface in the context of, for example, corneal ulcers or conjunctival scarring. The mechanisms by which preserved amniotic membrane grafts promote reepithelialization are unknown. As a first step the viability and proliferative capacity of amnion cells following cryopreservation of membranes in glycerol is investigated.

METHODS

Fresh and cryopreserved (in 50% glycerol) amniotic membranes were investigated histologically and by vital stains. Following enzymatic digestion, amniotic cells were stained for viability and cultured in DMEM+10% FBS. In addition, explant cultures were established from fresh and cryopreserved membranes.

RESULTS

Histological examination showed no significant morphological alteration following cryopreservation. While fresh membranes contained predominantly vital cells, no such cells were detected following cryopreservation. Also, cells removed enzymatically from cryopreserved membranes were not viable and did not grow in culture. While both epithelial and fibroblastic cells grew from fresh membranes, no growth was seen from cryopreserved membranes.

CONCLUSION

The results suggest that the technique for preservation which is most widely used for ophthalmological amniotic membrane transplantation significantly impairs viability and proliferative capacity. This supports the clinical finding that neither immunological reactions nor signs of ingrowth of amniotic cells are observed in patients. Furthermore amniotic membrane grafts seem to function primarily as matrix and not by virtue of transplanted functional cells.

Direct regeneration of cathode materials from spent lithium iron phosphate batteries using a solid phase sintering method

A direct regeneration of cathode materials from spent LiFePO₄ batteries using a solid phase sintering method has been proposed in this article.

Adenovirus-mediated p14(ARF) gene transfer in human mesothelioma cells

BACKGROUND

The p14(ARF) protein encoded by the INK4a/ARF locus promotes degradation of the MDM2 protein and thus prevents the MDM2-mediated inhibition of p53. Homozygous deletion of the INK4a/ARF locus is common in human mesothelioma and may result in the loss of p14(ARF) and the inactivation of p53. We designed this study to evaluate the biologic and potential therapeutic roles of p14(ARF) expression in mesothelioma cells.

METHODS AND RESULTS

We constructed Adp14, an adenoviral vector carrying human p14(ARF) complementary DNA, and used it to transfect human mesothelioma cell lines H28, H513, H2052, and MSTO-211H. Overexpression of p14(ARF) led to increased amounts of p53 and the p21(WAF) proteins and dephosphorylation of the retinoblastoma protein. The growth rate of mesothelioma cells was inhibited markedly by infection with Adp14 compared with mock infection or infection with a control adenovirus vector, AdCtrl. Overexpression of p14(ARF) induced G(1)-phase cell cycle arrest and apoptotic cell death. Cytotoxicity assays showed that Adp14 had a statistically significantly (P =.002) greater effect on colon cancer (HCT116) cell lines containing two copies of the wild-type p53 gene than on p53-null cells, suggesting that functional p53 is a critical determinant of p14(ARF)-mediated cytotoxicity.

CONCLUSIONS

The transfection of p14(ARF) into mesothelioma cells led to the overexpression of p14(ARF), which resulted in G(1)-phase arrest and apoptotic cell death. These results suggest that this gene therapy-based approach may be of use in the treatment of mesothelioma.

Interface control of bulk ferroelectric polarization

The control of material interfaces at the atomic level has led to novel interfacial properties and functionalities. In particular, the study of polar discontinuities at interfaces between complex oxides lies at the frontier of modern condensed matter research. Here we employ a combination of experimental measurements and theoretical calculations to demonstrate the control of a bulk property, namely ferroelectric polarization, of a heteroepitaxial bilayer by precise atomic-scale interface engineering. More specifically, the control is achieved by exploiting the interfacial valence mismatch to influence the electrostatic potential step across the interface, which manifests itself as the biased-voltage in ferroelectric hysteresis loops and determines the ferroelectric state. A broad study of diverse systems comprising different ferroelectrics and conducting perovskite underlayers extends the generality of this phenomenon.

Boson Sampling with 20 Input Photons and a 60-Mode Interferometer in a 10^{14}-Dimensional Hilbert Space

Quantum computing experiments are moving into a new realm of increasing size and complexity, with the short-term goal of demonstrating an advantage over classical computers. Boson sampling is a promising platform for such a goal; however, the number of detected single photons is up to five so far, limiting these small-scale implementations to a proof-of-principle stage. Here, we develop solid-state sources of highly efficient, pure, and indistinguishable single photons and 3D integration of ultralow-loss optical circuits. We perform experiments with 20 pure single photons fed into a 60-mode interferometer. In the output, we detect up to 14 photons and sample over Hilbert spaces with a size up to 3.7×10^{14}, over 10 orders of magnitude larger than all previous experiments, which for the first time enters into a genuine sampling regime where it becomes impossible to exhaust all possible output combinations. The results are validated against distinguishable samplers and uniform samplers with a confidence level of 99.9%.

Computation, prediction, and experimental tests of fitness for bacteriophage T7 mutants with permuted genomes

We created a simulation based on experimental data from bacteriophage T7 that computes the developmental cycle of the wild-type phage and also of mutants that have an altered genome order. We used the simulation to compute the fitness of more than 10(5) mutants. We tested these computations by constructing and experimentally characterizing T7 mutants in which we repositioned gene 1, coding for T7 RNA polymerase. Computed protein synthesis rates for ectopic gene 1 strains were in moderate agreement with observed rates. Computed phage-doubling rates were close to observations for two of four strains, but significantly overestimated those of the other two. Computations indicate that the genome organization of wild-type T7 is nearly optimal for growth: only 2.8% of random genome permutations were computed to grow faster, the highest 31% faster, than wild type. Specific discrepancies between computations and observations suggest that a better understanding of the translation efficiency of individual mRNAs and the functions of qualitatively "nonessential" genes will be needed to improve the T7 simulation. In silico representations of biological systems can serve to assess and advance our understanding of the underlying biology. Iteration between computation, prediction, and observation should increase the rate at which biological hypotheses are formulated and tested.

Microscopic origin of the giant ferroelectric polarization in tetragonal-like BiFeO(3)

We report direct experimental evidence for a room-temperature, ∼130  μC/cm(2) ferroelectric polarization from the tetragonal-like BiFeO(3) phase. The physical origin of this remarkable enhancement of ferroelectric polarization has been investigated by a combination of x-ray absorption spectroscopy, scanning transmission electron microscopy, and first principles calculations. A large strain-induced Fe-ion displacement relative to the oxygen octahedra, combined with the contribution of Bi 6s lone pair electrons, is the mechanism driving the large ferroelectric polarization in this tetragonal-like phase.

Genistein modulates immune responses and increases host resistance to B16F10 tumor in adult female B6C3F1 mice

The isoflavone genistein (4,7,4'-trihydroxyisoflavone) is a phytoestrogen found in high levels in soy products that has been associated with decreased incidences of breast and prostate cancers. The potential effects of genistein on the immune system were evaluated in adult female B6C3F1 mice. Groups of mice were exposed to vehicle or genistein by gavage for 28 d. The doses of genistein used were 2, 6 and 20 mg/kg body. Consistent with the chemopreventive effect of genistein, exposure to this compound significantly increased host resistance to B16F10 tumor as reflected by a decrease in the number of lung tumor nodules after tumor cell injection at the middle and high dose levels. Inhibition of B16F10 tumor formation was not due to a direct effect of serum genistein and/or its metabolites on the proliferation of B16F10 tumor cells. When innate and acquired immune responses were evaluated, a dose-related increase of cytotoxic T-cell activity was observed in genistein-treated mice with significant changes observed at the middle and high dose levels. Furthermore, in vitro interleukin (IL)-2-stimulated natural killer (NK) cell activity was significantly enhanced in the high genistein dose group, although the basal NK cell activity was not affected. Although no affect on the mixed lymphocyte responses and anti-CD3 antibody-mediated splenocyte proliferation was observed, exposure to genistein significantly increased basal splenocyte proliferation. Exposure to genistein did not alter the activity of the mononuclear phagocyte system and the cytotoxic/cytostatic function of thioglycollate-recruited peritoneal cells on B16F10 tumor cells. Finally, exposure to genistein did not produce biologically meaningful changes in spleen immunoglobulin (Ig)M and IgG antibody-forming cell responses. In conclusion, genistein enhanced host resistance as evaluated in the B16F10 tumor model, which may be related to the increases in the activities of cytotoxic T cells and NK cells.

Tunable atomic spin-orbit coupling synthesized with a modulating gradient magnetic field

We report the observation of synthesized spin-orbit coupling (SOC) for ultracold spin-1 ⁸⁷Rb atoms. Different from earlier experiments where a one dimensional (1D) atomic SOC of pseudo-spin-1/2 is synthesized with Raman laser fields, the scheme we demonstrate employs a gradient magnetic field (GMF) and ground-state atoms, thus is immune to atomic spontaneous emission. The strength of SOC we realize can be tuned by changing the modulation amplitude of the GMF, and the effect of the SOC is confirmed through the studies of: 1) the collective dipole oscillation of an atomic condensate in a harmonic trap after the synthesized SOC is abruptly turned on; and 2) the minimum energy state at a finite adiabatically adjusted momentum when SOC strength is slowly ramped up. The condensate coherence is found to remain very good after driven by modulating GMFs. Our scheme presents an alternative means for studying interacting many-body systems with synthesized SOC.

Stochastic vs. deterministic modeling of intracellular viral kinetics

Within its host cell, a complex coupling of transcription, translation, genome replication, assembly, and virus release processes determines the growth rate of a virus. Mathematical models that account for these processes can provide insights into the understanding as to how the overall growth cycle depends on its constituent reactions. Deterministic models based on ordinary differential equations can capture essential relationships among virus constituents. However, an infection may be initiated by a single virus particle that delivers its genome, a single molecule of DNA or RNA, to its host cell. Under such conditions, a stochastic model that allows for inherent fluctuations in the levels of viral constituents may yield qualitatively different behavior. To compare modeling approaches, we developed a simple model of the intracellular kinetics of a generic virus, which could be implemented deterministically or stochastically. The model accounted for reactions that synthesized and depleted viral nucleic acids and structural proteins. Linear stability analysis of the deterministic model showed the existence of two nodes, one stable and one unstable. Individual stochastic simulation runs could access and remain at the unstable node. In addition, deterministic and averaged stochastic simulations yielded different transient kinetics and different steady-state levels of viral components, particularly for low multiplicities of infection (MOI), where few virus particles initiate the infection. Furthermore, a bimodal population distribution of viral components was observed for low MOI stochastic simulations. The existence of a low-level infected subpopulation of cells, which could act as a viral reservoir, suggested a potential mechanism of viral persistence.

Association of petrochemical exposure with spontaneous abortion

OBJECTIVES

To assess the association between petrochemical exposure and spontaneous abortion, a retrospective epidemiological study in a large petrochemical complex in Beijing, China was conducted.

METHODS

Plant employment records identified 3105 women who were married, were 20-44 years of age, and had never smoked. Of those, 3070 women (98.8%) reported at least one pregnancy. From this group, 2853 (93%) of the women participated in the study. According to their plant employment record, about 57% of these women workers reported occupational exposure to petrochemicals during the first trimester of their pregnancy. Trained interviewers administered a standardised questionnaire to this group of women and their husbands, collecting information on reproductive history, pregnancy outcomes, employment history, occupational exposure, smoking habits, alcohol consumption, indoor air pollution, and demographic variables. The results from the womens' first pregnancies were analysed.

RESULTS

There was a significantly increased risk of spontaneous abortion for women working in all of the production plants with frequent exposure to petrochemicals (8.8%; range of 5.8%-9.8%) compared with those working in nonchemical plants (2.2%; range of 0.0%-7.1%). Also, when a comparison was made between exposed and non-exposed groups within each plant, exposure to petrochemicals was consistently associated with an increased risk of spontaneous abortion. The overall odds ratio (OR) was 2.7 (95% confidence interval (95% CI) 1.8 to 3.9) after adjusting for potential confounders. When the analysis was performed with the exposure information obtained from the women' interview responses for (self reported) exposures, the estimated OR for spontaneous abortions was 2.9 (95% CI 2.0 to 4.0). The analysis was repeated by excluding those 452 women who provided inconsistent reports between recalled exposure and work history, and a comparable risk of spontaneous abortion (OR 2.9; 95% CI 2.0 to 4.4) was found. In analyses for exposure to specific chemicals, an increased risk of spontaneous abortion was found with exposure to most chemicals, and the results for benzene (OR 2.5; 95% CI 1.7 to 3.7), gasoline (OR 1.8; 95% CI 1.1 to 2.9), and hydrogen sulphide (OR 2.3; 95% CI 1.2 to 4.4) were significant.

CONCLUSION

An increased risk of spontaneous abortion was found associated with the exposure to petrochemicals, including benzene, gasoline, and hydrogen sulphide.

Parental bias of Ki-ras oncogenes detected in lung tumors from mouse hybrids

A mouse strain with low lung tumor susceptibility (C3H) and a strain with high lung tumor susceptibility (A/J) were reciprocally crossed to produce C3A and AC3 F1 hybrid mice. Ki-ras oncogenes were detected in spontaneous and chemically induced lung tumors obtained from the C3A and AC3 mice. To further explore the genetics of the Ki-ras gene in mouse lung tumor susceptibility, the parental origin of Ki-ras oncogenes detected in lung tumors from the F1 hybrids was determined by a strategy based on a 37-base-pair deletion in the second intron of the A/J Ki-ras allele. Ki-ras oncogenes were derived from the A/J parent in 38 of 40 tumors obtained from C3A mice and 30 of 30 tumors from AC3 mice. The observation that the activated oncogene in hybrids originates from the susceptible parent suggests that the Ki-ras gene is directly linked to mouse lung tumor susceptibility. This finding may have implications for pulmonary adenocarcinoma development in humans, since Ki-ras oncogenes are detected in 35% of this human tumor type.

A spheroid-based 3-D culture model for pancreatic cancer drug testing, using the acid phosphatase assay

Current therapy for pancreatic cancer is multimodal, involving surgery and chemotherapy. However, development of pancreatic cancer therapies requires a thorough evaluation of drug efficacy in vitro before animal testing and subsequent clinical trials. Compared to two-dimensional culture of cell monolayer, three-dimensional (3-D) models more closely mimic native tissues, since the tumor microenvironment established in 3-D models often plays a significant role in cancer progression and cellular responses to the drugs. Accumulating evidence has highlighted the benefits of 3-D in vitro models of various cancers. In the present study, we have developed a spheroid-based, 3-D culture of pancreatic cancer cell lines MIAPaCa-2 and PANC-1 for pancreatic drug testing, using the acid phosphatase assay. Drug efficacy testing showed that spheroids had much higher drug resistance than monolayers. This model, which is characteristically reproducible and easy and offers rapid handling, is the preferred choice for filling the gap between monolayer cell cultures and in vivo models in the process of drug development and testing for pancreatic cancer.

Androgen receptor expression in the testes and epididymides of prenatal and postnatal Sprague-Dawley rats

The androgen receptor (AR) plays a critical role in sexual differentiation and in the virilization of the male reproductive system. A clear understanding of AR expression at the early stages of sexual development will help elucidate the sensitivity of perinatal animals to endocrine modulation by external agents, such as some environmental chemicals. Immunohistochemistry was used in this study to localize the AR in the differentiating testis and epididymis of Sprague-Dawley rats starting from gestation day 15 until postnatal day 21. Positive AR staining was found on gestation day 15 in the mesenchymal as well as in the epithelial cells in the mesonephros. Weak staining was also observed in a small number of interstitial cells in the primordial testis at this age. The fetal interstitial and peritubular myoid cells showed positive AR immunoreactivity early in development, but the Sertoli cells did not overtly express the receptors until postnatal day 5. The intensity of staining and number of AR-positive cells in the testis and epididymis increased over time. The epithelium in the mesonephros-derived tissues, including rete testis and epididymis, appeared to exhibit a higher capacity to express AR than the rest of the testicular tissue. The results demonstrate that AR expression in the primordial male reproductive system is highly specific to time and cell type and modify previous understanding on the timing of AR expression in the testicular tissue. Since AR-positive cells at various developmental stages may be potential sites of interaction with chemicals that adversely affect sexual differentiation, improved understanding of AR ontogeny will help in investigating the effects of AR-reactive agents, such as environmental antiandrogens, with respect to specific windows of sensitivity.

Observation of spinor dynamics in optically trapped 87Rb Bose-Einstein condensates

We measure spin mixing of F=1 and F=2 spinor condensates of 87Rb atoms confined in an optical trap. We determine the spin mixing time to be typically less than 600 ms and observe spin population oscillations. The equilibrium spin configuration in the F=1 manifold is measured for different magnetic fields and found to show ferromagnetic behavior for low field gradients. An F=2 condensate is created by microwave excitation from the F=1 manifold, and this spin-2 condensate is observed to decay exponentially with time constant 250 ms. Despite the short lifetime in the F=2 manifold, spin mixing of the condensate is observed within 50 ms.

Transplacental and lactational transfer of p,p'-DDE in Sprague-Dawley rats

p,p'-DDE (hereafter DDE), a persistent metabolite of p,p'-DDT, is a widespread environmental contaminant that can induce antiandrogenic developmental effects in rats. Quantitative measurements of the transfer of DDE from pregnant or lactating dams to the fetus or suckling neonate were performed, and physiologically based pharmacokinetic (PBPK) models for the transplacental and lactational transfer of DDE were developed. Pregnant Sprague-Dawley rats were dosed by gavage in corn oil with either 10 or 100 mg DDE per kg body wt per day from Gestation Day (gd) 14 to 18. DDE was analyzed in several maternal tissues as well as in fetal and neonatal tissues from gd 15 to Postnatal Day (pnd) 21. Fetal DDE concentrations were about threefold lower than corresponding placental concentrations. By adopting a cross-fostering design, the contributions of transplacental and lactational transfer were compared. In the pup liver, where DDE was detectable in the 100 mg/kg groups on pnd 10, the lactationally exposed group had DDE concentrations about 50 times higher than those of the in utero only exposure group; the lactation only exposure groups had DDE tissue dose profiles very similar to those of the in utero plus lactation exposure groups, indicating that the lactational route is far more important than the in utero route quantitatively. The PBPK models postulated initial absorption of DDE into both the blood circulation and lymphatic system with the primary storage sites being maternal and neonatal adipose tissues. Mobilization of DDE from its storage sites is postulated to occur via its association with mobilized fatty acids and lipoproteins. The results provide an overall framework for evaluating the tissue dosimetry of DDE and for understanding how maternal exposure to DDE could affect perinatal sexual development in utero or in the early postnatal period.

Induction of hepatic aromatase by p,p'-DDE in adult male rats

1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (p,p'-DDE, DDE) is a stable metabolite of the pesticide DDT and a persistent environmental pollutant. Earlier reports have demonstrated that DDE is an endocrine-active compound capable of affecting early-stage sexual differentiation in male rats. Experiments based on receptor binding affinity and receptor-mediated transcriptional activation have identified DDE as an androgen receptor antagonist. Other effects of DDE include modulation of the expression and activity of cytochrome P450 (CYP) enzymes, some of which function as steroid hydroxylases, and elevation of serum estrogen levels in treated male rats. These effects suggest the possibility of DDE-caused induction of aromatase, a member of CYP family that catalyzes the conversion of C19 steroids to estrogens. The present study was conducted to determine whether hepatic aromatase was responsive to DDE treatment. We found that hepatic aromatase protein in adult male rats was greatly increased after seven daily oral treatments of DDE at a dosage of 100 mg/kg wt. per day. This induction was seen in both immunoblot and immunohistochemistry of liver tissue sections. Distribution of the aromatase in the liver corresponded to the distribution of hypertrophic hepatocytes in the tissue. Furthermore, we found a large increase in hepatic microsomal aromatase activity in DDE-treated animals, although the difference in serum 17beta-estradiol concentrations between treated animals and controls was not statistically significant. However, an in vitro experiment using primary culture of rat hepatocytes did not show a change in aromatase level after DDE treatment at four concentrations ranging from 0 to 5x10(-6) M for 24 h. Meanwhile, CYP 2B1 induction, a known DDE effect in primary rat hepatocyte culture, was seen in those cells. This study supports the notion that induction of aromatase by DDE is a contributory factor to its reproductive developmental effects.

Amplification and spread of viruses in a growing plaque

The two-dimensional propagation of viruses through a "lawn" of receptive hosts, commonly called plaque growth, reflects the dynamics of interactions between viruses and host cells. Here we treat the amplification of viruses during plaque growth as a reaction-diffusion system, where interactions among the virus, uninfected host cells, and virus-producing host-virus complexes are accounted for using rates of viral adsorption to and desorption from the host-cell surface, rates of reproduction and release of progeny viruses by lysis of the host, and by the coupling of these reactions with diffusion of free virus within the agar support. Numerical solution of the system shows the development of a traveling wave of reproducing viruses, where the velocity of the wave is governed by the kinetic and diffusion parameters. The model has been applied to predict the propagation velocity of a bacteriophage plaque. Different mechanisms may account for the dependence of this velocity on the host density during early stages of a growing plaque. The model provides a means to explore how changes in the virus-host interactions may be manifest in a growing plaque.

Microfluidic co-culture platform for investigating osteocyte-osteoclast signalling during fluid shear stress mechanostimulation

Bone cells exist in a complex environment where they are constantly exposed to numerous dynamic biochemical and mechanical stimuli. These stimuli regulate bone cells that are involved in various bone disorders, such as osteoporosis. Knowledge of how these stimuli affect bone cells have been utilised to develop various treatments, such as pharmaceuticals, hormone therapy, and exercise. To investigate the role that bone loading has on these disorders in vitro, bone cell mechanotransduction studies are typically performed using parallel plate flow chambers (PPFC). However, these chambers do not allow for dynamic cellular interactions among different cell populations to be investigated. We present a microfluidic approach that exposes different cell populations, which are located at physiologically relevant distances within adjacent channels, to different levels of fluid shear stress, and promotes cell-cell communication between the different channels. We employed this microfluidic system to assess mechanically regulated osteocyte-osteoclast communication. Osteoclast precursors (RAW264.7 cells) responded to cytokine gradients (e.g., RANKL, OPG, PGE-2) developed by both mechanically stimulated (fOCY) and unstimulated (nOCY) osteocyte-like MLO-Y4 cells simultaneously. Specifically, we observed increased osteoclast precursor cell densities and osteoclast differentiation towards nOCY. We also used this system to show an increased mechanoresponse of osteocytes when in co-culture with osteoclasts. We envision broad applicability of the presented approach for microfluidic perfusion co-culture of multiple cell types in the presence of fluid flow stimulation, and as a tool to investigate osteocyte mechanotransduction, as well as bone metastasis extravasation. This system could also be applied to any multi-cell population cross-talk studies that are typically performed using PPFCs (e.g. endothelial cells, smooth muscle cells, and fibroblasts).

Identification of differentially expressed nucleolar TGF-beta1 target (DENTT) in human lung cancer cells that is a new member of the TSPY/SET/NAP-1 superfamily

The transforming growth factor-beta1 (TGF-beta1) responsive epithelial non-small-cell lung cancer (NSCLC) cell line NCI-H727 was used to identify potential target genes involved in TGF-beta1-mediated responses. Comparative cDNA expression patterns between cells treated with TGF-beta1 and those treated with vehicle were generated by differential mRNA display. One 496-bp fragment, differentially increased threefold by TGF-beta1 and hybridizing to a 2.7-kb mRNA species in NCI-H727 cells by Northern analysis, revealed no significant match to any known gene sequence. The mRNA transcript of this novel gene that we named differentially expressed nucleolar TGF-beta1 target (DENTT) is expressed in several normal human tissues, with the highest level of expression in brain. Human brain cDNA library screening and 5' rapid amplification of cDNA ends yielded full-length DENTT cDNA containing an 1899-bp open reading frame encoding a predicted 633-amino-acid protein with four potential nuclear localization signals (NLSs) and two coiled-coil regions. DENTT contains a conserved 191-residue domain that shows significant identity to, and defines, the TSPY/TSPY-like/SET/NAP-1 superfamily. Enhanced green fluorescent protein (EGFP)-tagged full-length DENTT transfected into COS-7 cells showed nucleolar and cytoplasmic localization. Transfection of EGFP-tagged DENTT NLS deletion constructs lacking the bipartite NLS-1 were excluded from the nucleolus. While NLS-1 is necessary for nucleolar localization of DENTT, it is not sufficient for sole nucleolar localization. Our data show that DENTT mRNA induction by TGF-beta1 correlates with induction of TGF-beta1 mRNA, induction of extracellular matrix gene expression, and inhibition of colony formation in soft agarose in TGF-beta1 responsive NSCLC cells when exposed to TGF-beta1. TGF-beta1 does not induce DENTT mRNA expression in TGF-beta1 nonresponsive NSCLC cells. Our data suggest that this novel TGF-beta1 target gene has distinct domains for direction to different subnuclear locations.

Prostaglandin E2 and vasoactive intestinal peptide increase vascular endothelial cell growth factor mRNAs in lung cancer cells

The effects of prostaglandin E2 (PGE2) and vasoactive intestinal peptide (VIP) on vascular endothelial cell growth factor (VEGF) mRNAs were investigated using lung cancer cells. By RT-PCR, VEGF(121), VEGF(165), and VEGF(189), but not VEGF(206) isoforms were detected in all lung cancer cell lines and biopsy specimens examined. By Northern blot, VEGF mRNA was detected in all small cell lung cancer (SCLC) and non-SCLC (NSCLC) cell lines examined. PGE2, VIP and forskolin caused increased VEGF expression in a time- and concentration-dependent manner using NSCLC cell line NCI-H157. Approximately 1 microM PGE2, 0.1 microM VIP and 50 microM forskolin caused cAMP elevation, 64-, 33- and 128-fold, respectively, using NCI-H157 cells after 5 min. The increase in cAMP caused by PGE(2) and VIP was reversed by somatostatin (SST). Also 1 microM PGE2, 0.1 microM VIP and 50 microM forskolin increased the VEGF mRNA 2.0-, 1.5- and 2.3-fold, respectively, after 4 h. The increase in VEGF mRNA caused by PGE2, VIP and forskolin was inhibited by H-89, a protein kinase A inhibitor. A VIP receptor antagonist, VIPhybrid, inhibited the increase in cAMP and VEGF mRNA caused by VIP. By ELISA, VEGF was detected in the conditioned media exposed to the lung cancer cell lines. These results suggest that VEGF synthesis in and secretion from lung cancer cells can be regulated by agents, which cause adenylyl cyclase activation.