Coherent optical OFDM: theory and design

Coherent optical OFDM (CO-OFDM) has recently been proposed and the proof-of-concept transmission experiments have shown its extreme robustness against chromatic dispersion and polarization mode dispersion. In this paper, we first review the theoretical fundamentals for CO-OFDM and its channel model in a 2x2 MIMO-OFDM representation. We then present various design choices for CO-OFDM systems and perform the nonlinearity analysis for RF-to-optical up-converter. We also show the receiver-based digital signal processing to mitigate self-phase-modulation (SPM) and Gordon-Mollenauer phase noise, which is equivalent to the midspan phase conjugation.

Factor analysis in the Genetics of Asthma International Network family study identifies five major quantitative asthma phenotypes

BACKGROUND

Asthma is a clinically heterogeneous disease caused by a complex interaction between genetic susceptibility and diverse environmental factors. In common with other complex diseases the lack of a standardized scheme to evaluate the phenotypic variability poses challenges in identifying the contribution of genes and environments to disease expression.

OBJECTIVE

To determine the minimum number of sets of features required to characterize subjects with asthma which will be useful in identifying important genetic and environmental contributors. Methods Probands aged 7-35 years with physician diagnosed asthma and symptomatic siblings were identified in 1022 nuclear families from 11 centres in six countries forming the Genetics of Asthma International Network. Factor analysis was used to identify distinct phenotypes from questionnaire, clinical, and laboratory data, including baseline pulmonary function, allergen skin prick test (SPT).

RESULTS

Five distinct factors were identified:(1) baseline pulmonary function measures [forced expiratory volume in 1 s (FEV(1)) and forced vital capacity (FVC)], (2) specific allergen sensitization by SPT, (3) self-reported allergies, (4) symptoms characteristic of rhinitis and (5) symptoms characteristic of asthma. Replication in symptomatic siblings was consistent with shared genetic and/or environmental effects, and was robust across age groups, gender, and centres. Cronbach's alpha ranged from 0.719 to 0.983 suggesting acceptable internal scale consistencies. Derived scales were correlated with serum IgE, methacholine PC(20), age and asthma severity (interrupted sleep). IgE correlated with all three atopy-related factors, the strongest with the SPT factor whereas severity only correlated with baseline lung function, and with symptoms characteristic of rhinitis and of asthma.

CONCLUSION

In children and adolescents with established asthma, five distinct sets of correlated patient characteristics appear to represent important aspects of the disease. Factor scores as quantitative traits may be better phenotypes in epidemiological and genetic analyses than those categories derived from the presence or absence of combinations of +ve SPTs and/or elevated IgE.

Circulating FGF-21 levels in normal subjects and in newly diagnose patients with Type 2 diabetes mellitus

Fibroplast growth factor (FGF-21) is a recently discovered metabolic regulator. Its pathophysiologic role in humans remains unknown. In this study, we have investigated whether or not plasma FGF-21 level was different in patients with type 2 diabetes mellitus (T2DM) and non-diabetic controls. We also assessed associations between plasma FGF-21 body composition and several metabolic parameters. Fasting FGF-21 levels were significantly increased in patients with T2DM compared with controls (1.82+/-0.65 VS. 1.53+/-0.60 microg/L, P<0.05). In T2DM patients, fasting plasma FGF-21 correlate negatively with fasting blood glucose ( R= -0.31, P<0.05). Multiple regression analysis showed that FBG, plasma insulin and HOMA (IS) were independent influencing plasma FGF-21 levels. The present work suggests a potential role for FGF-21 in the pathogenesis of insulin resistance and T2DM.

Effects of rapid antigen degradation and VEE glycoprotein specificity on immune responses induced by a VEE replicon vaccine

Genetic vaccines are engineered to produce immunogens de novo in the cells of the host for stimulation of a protective immune response. In some of these systems, antigens engineered for rapid degradation have produced an enhanced cellular immune response by more efficient entry into pathways for processing and presentation of MHC class I peptides. VEE replicon particles (VRP), single cycle vaccine vectors derived from Venezuelan equine encephalitis virus (VEE), are examined here for the effect of an increased rate of immunogen degradation on VRP vaccine efficacy. VRP expressing the matrix capsid (MA/CA) portion of SIV Gag were altered to promote rapid degradation of MA/CA by various linkages to co-translated ubiquitin or by destabilizing mutations and were used to immunize BALB/c mice for quantitation of anti-MA/CA cellular and humoral immune responses. Rapid degradation by the N-end rule correlated with a dampened immune response relative to unmodified MA/CA when the VRP carried a glycoprotein spike from an attenuated strain of VEE. In contrast, statistically equivalent numbers of IFNgamma(+)T-cells resulted when VRP expressing unstable MA/CA were packaged with the wild-type VEE glycoproteins. These results suggest that the cell types targeted in vivo by VRP carrying mutant or wild type glycoprotein spikes are functionally different, and are consistent with previous findings suggesting that wild-type VEE glycoproteins preferentially target professional antigen presenting cells that use peptides generated from the degraded antigen for direct presentation on MHC.

Endothelin-1 inhibits outward potassium currents in mouse outer sulcus cells

The outer sulcus cells are epithelial cells covering the luminal side of spiral sulcus of cochlea. It has been suggested that outer sulcus cells contribute to cation absorption from the lumen of the cochlea. We investigated the electrical properties and the effects of endothelin-1 (ET-1) on the outward potassium currents in mouse outer sulcus cells using a whole-cell patch clamp technique. The cell capacitance was 3.16+/-0.66 pF (n =35) and the resting membrane potential was -98.4+/-1.6 mV (n=6) in extracellular fluid bath solution. The outward K+ currents were activated by depolarizing pulses more positive than -60 mV, and was sensitive to TEA (10 mM). Tail current analysis revealed that it was primarily K+ selective. Application of ET-1 caused a decrease of outward potassium currents within seconds, whereas treatment with BQ123, a competitive inhibitor of the ET type-A receptor, counteracted the inhibitory effect of ET-1. These results suggest that ET-1 inhibits outward potassium currents through the activation of ET type-A receptor. ET-1 may play an important role in maintaining the ionic homeostasis of endolymph.

NF-kappaB activation as a key mechanism in ethanol-induced disruption of the F-actin cytoskeleton and monolayer barrier integrity in intestinal epithelium

Intestinal barrier disruption has been implicated in several intestinal and systemic disorders including alcoholic liver disease (ALD). Using monolayers of intestinal (Caco-2) cells, we showed that ethanol (EtOH) disrupts the barrier integrity via destabilization of the cytoskeleton. Because proinflammatory conditions are associated with activation of NF-kappa B (NF-kappaB), we hypothesized that EtOH induces disruption of cytoskeletal assembly and barrier integrity by activating NF-kappaB. Parental cells were pretreated with pharmacological modulators of NF-kappaB. Other cells were stably transfected with a dominant negative mutant for the NF-kappaB inhibitor, I-kappaBalpha. Monolayers of each cell type were exposed to EtOH and we then monitored monolayer barrier integrity (permeability); cytoskeletal stability and molecular dynamics (confocal microscopy and immunoblotting); intracellular levels of the I-kappaBalpha (immunoblotting); subcellular distribution and activity of NF-kappaB (immunoblotting and sensitive ELISA); and intracellular alterations in the 43kDa protein of the actin cytoskeleton, polymerized F-actin, and monomeric G-actin (SDS-PAGE fractionation). EtOH caused destabilizing alterations, including I-kappaBalpha degradation, NF-kappaB nuclear translocation, NF-kappaB subunit (p50 and p65) activation, actin disassembly (upward arrow G-, downward arrow F-), actin cytoskeleton instability, and barrier disruption. Inhibitors of NF-kappaB and stabilizers of I-kappaBalpha (e.g., MG-132, lactacystin, etc) prevented NF-kappaB activation while protecting against EtOH-induced injury. In transfected I-kappaBalpha mutant clones, stabilization of I-kappaBalpha to inactivate NF-kappaB protected against all measures of EtOH-induced injury. Our data support several novel mechanisms where NF-kappaB can affect the molecular dynamics of the F-actin cytoskeleton and intestinal barrier integrity under conditions of EtOH injury. (1) EtOH induces disruption of the F-actin cytoskeleton and of intestinal barrier integrity, in part, through I-kappaBalpha degradation and NF-kappaB activation; (2) The mechanism underlying this pathophysiological effect of the NF-kappaB appears to involve instability of the assembly of the subunit components of actin network.

Theoretical and experimental study on PMD-supported transmission using polarization diversity in coherent optical OFDM systems

In this paper, we conduct theoretical and experimental study on the PMD-supported transmission with coherent optical orthogonal frequency-division multiplexing (CO-OFDM). We first present the model for the optical fiber communication channel in the presence of the polarization effects. It shows that the optical fiber channel model can be treated as a special kind of multiple-input multiple-output (MIMO) model, namely, a two-input two-output (TITO) model which is intrinsically represented by a two-element Jones vector familiar to the optical communications community. The detailed discussions on various coherent optical MIMO-OFDM (CO-MIMO-OFDM) models are presented. Furthermore, we show the first experiment of polarization-diversity detection in CO-OFDM systems. In particular, a CO-OFDM signal at 10.7 Gb/s is successfully recovered after 900 ps differential-group-delay (DGD) and 1000-km transmission through SSMF fiber without optical dispersion compensation. The transmission experiment with higher-order PMD further confirms the immunity of the CO-OFDM signal to PMD in the transmission fiber. The nonlinearity performance of PMD-supported transmission is also reported. For the first time, nonlinear phase noise mitigation based on receiver digital signal processing is experimentally demonstrated for CO-OFDM transmission.

Relation of cognitive activity to risk of developing Alzheimer disease

BACKGROUND

Frequent cognitive activity in old age has been associated with reduced risk of Alzheimer disease (AD), but the basis of the association is uncertain.

METHODS

More than 700 old people underwent annual clinical evaluations for up to 5 years. At baseline, they rated current and past frequency of cognitive activity with the current activity measure administered annually thereafter. Those who died underwent a uniform postmortem examination of the brain. Amyloid burden, density of tangles, and presence of Lewy bodies were assessed in eight brain regions and the number of chronic cerebral infarctions was noted.

RESULTS

During follow-up, 90 people developed AD. More frequent participation in cognitive activity was associated with reduced incidence of AD (HR = 0.58; 95% CI: 0.44, 0.77); a cognitively inactive person (score = 2.2, 10th percentile) was 2.6 times more likely to develop AD than a cognitively active person (score = 4.0, 90th percentile). The association remained after controlling for past cognitive activity, lifespan socioeconomic status, current social and physical activity, and low baseline cognitive function. Frequent cognitive activity was also associated with reduced incidence of mild cognitive impairment and less rapid decline in cognitive function. Among 102 persons who died and had a brain autopsy, neither global nor regionally specific measures of neuropathology were related to level of cognitive activity before the study, at study onset, or during the course of the study.

CONCLUSION

Level of cognitively stimulating activity in old age is related to risk of developing dementia.

Haploinsufficiency of CDK4 prevents hepatocarcinogenesis in mice deficient in ELF, a mediator of TGF-beta signaling

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Background: The transforming growth factor-β (TGF-β) has a dual role in cancer, but in the prevention of tumorigenesis, TGF-β signaling inhibits cell cycle progression through an increase in cell cycle inhibitors and decrease in cell cycle activators. The adaptor protein embryonic liver fodrin (ELF) is crucial for normal TGF-β signaling. ELF facilitates the association and nuclear translocation of the TGF-β signaling proteins, Smad3 and Smad4. We have demonstrated that elf± mice develop hepatocellular cancers (HCC) spontaneously within 12 months. We have also shown that most human HCCs demonstrate a decreased expression of ELF. Our goal was to assess the interaction between ELF and cyclin dependent kinase 4 (CDK4), which is overexpressed in most human cancers. Methods: We compared the expression of CDK4 and ELF by immunohistochemistry and analyzed the interaction between CDK4 and ELF, in vitro by immunoprecitpitation and western blot. Finally, we assessed the development of HCC in intercrossed elf± and CDK4+/neo mice. Results: CDK4 and ELF expression are inversely correlated in HCCs from elf± mice. Furthermore, ELF interacts with CDK4 by forming a complex that includes Smad3 in COS-7 and HepG2 cells. ELF is phosphorylated upon overexpression of CDK4, revealing a possible mechanism by which CDK4 may inhibit ELF-dependent TGF-β signaling. To further assess whether the development of HCC in elf± mice is dependent upon CDK4 expression, we have intercrossed elf± and CDK4+/neo mice. At 12 months, only 17% of the elf±/CDK4+/neo mice developed HCC, compared to 40% of our historical control elf± mice. This initial data strongly suggests that haploinsufficiency of CDK4 can prevent the HCCs seen in elf± mice, and provides the genetic foundation for further exploring the benefits of specific inhibitors of CDK4 in the treatment of HCC. Conclusions: These results demonstrate the molecular interactions between ELF and CDK4, and suggest a mechanism by which CDK4 may render cells unresponsive to the growth inhibitory effects of TGF-β signaling. Furthermore, haploinsufficiency of CDK4 prevents the formation of HCC, and thus targeted-inhibition of CDK4 activity may be a logical treatment for HCC in humans.

No significant financial relationships to disclose.

Donor lymphocyte infusions from Ad-sig-TAA/ecdCD40L vector prime-TAA/ecdCD40L protein boost (VPP) vaccinated allodonors decrease tumor cell growth post allograft

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Background: Individuals of advanced chronological age exhibit an impaired immune response to vaccines. This may be due to a reduction in the ratio of antigen naïve/memory CD4 and CD8 T cells and acquisition of functional defects in activated “helper” CD4 T cells (eg diminished CD40 ligand (CD40L) expression) during the aging process. Methods: In order to circumvent this defective response to vaccines in individuals in the fifth and sixth decades of life, our laboratory has developed an adenoviral vector (Ad-sig- TAA/ecdCD40L) vaccine which is designed for the in vivo target associated antigen (TAA) loading and activation of dendritic cells (DCs), and to overcome the absence of CD40L expression in activated CD4 helper T cells in older individuals. Results: The subcutaneous (sc) injection of this vector leads to the release of a fusion protein composed of a TAA linked to the extracellular domain (ecd) of the CD40 ligand (CD40L), which binds to the CD40 receptor on DCs, activates the DCs, and leads to the presentation of TAA fragments on Class I MHC. Two sc injections of the TAA/ecdCD40L protein as a booster following the sc administration of the Ad-sig-TAA/ecdCD40L vector (VPP) expands the magnitude of the cellular and humoral immune response induced by the vector in 18 month old aged mice as well as in younger mice. This vaccine decreased levels of negative regulatory CD4 FOXP3 T cells in tumor nodules. We administered TBI and an allogeneic stem cell transplant 7 days post sc injection of the E7 positive TC-1 cells. DLI from an Ad-sig-E7/ecdCD40L vector prime-E7/ecdCD40L protein boost vaccinated donor were injected iv 3 days post transplant, and a single E7/ecdCD40L protein boost sc vaccination one week thereafter. We found that the growth rate of the E7 positive TC-1 tumor cells post allograft was less in the vaccinated than in the control (injection of tumor cells followed in 7 days by TBI), or the animals in which the allograft recipient was vaccinated without DLI. Conclusions: Thus, the use of DLI from VPP vaccinated allodonors decreased tumor cell growth post allograft.

No significant financial relationships to disclose.

Chronic distress and incidence of mild cognitive impairment

OBJECTIVE

Mild cognitive impairment (MCI) is associated with increased morbidity and mortality but its development is not well understood. Here we test the hypothesis that chronic psychological distress is associated with increased incidence of MCI in old age.

METHODS

Participants are older persons from two cohort studies with uniform annual clinical evaluations which included detailed cognitive testing and clinical classification of MCI. We excluded persons with dementia or MCI at baseline; follow-up data were available on 1,256 persons without cognitive impairment (95% of those eligible). At baseline, they completed a six-item measure of neuroticism (mean = 15.6, SD = 6.6), an indicator of the tendency to experience psychological distress.

RESULTS

During up to 12 years of follow-up, 482 persons (38%) developed MCI. Risk of MCI increased by about 2% for each one unit increase on the distress scale (relative risk [RR] = 1.02; 95% CI: 1.01, 1.04), with the association slightly stronger in men than women. Overall, a distress-prone person (score = 24, 90th percentile) was about 40% more likely to develop MCI than someone not prone to distress (score = 8, 10th percentile). Adjustment for depressive symptomatology at baseline did not substantially change results (RR = 1.02; 95% CI: 1.00, 1.03). Depressive symptoms were also related to risk of MCI but not after controlling for distress score. In mixed-effects models, higher distress score was associated with lower level of function in multiple cognitive domains at baseline and more rapid cognitive decline, especially in episodic memory.

CONCLUSION

Among older persons without manifest cognitive impairment, higher level of chronic psychological distress is associated with increased incidence of mild cognitive impairment.

Disruption of transforming growth factor-beta signaling through beta-spectrin ELF leads to hepatocellular cancer through cyclin D1 activation

Transforming growth factor-beta (TGF-beta) signaling members, TGF-beta receptor type II (TBRII), Smad2, Smad4 and Smad adaptor, embryonic liver fodrin (ELF), are prominent tumor suppressors in gastrointestinal cancers. Here, we show that 40% of elf(+/-) mice spontaneously develop hepatocellular cancer (HCC) with markedly increased cyclin D1, cyclin-dependent kinase 4 (Cdk4), c-Myc and MDM2 expression. Reduced ELF but not TBRII, or Smad4 was observed in 8 of 9 human HCCs (P<0.017). ELF and TBRII are also markedly decreased in human HCC cell lines SNU-398 and SNU-475. Restoration of ELF and TBRII in SNU-398 cells markedly decreases cyclin D1 as well as hyperphosphorylated-retinoblastoma (hyperphosphorylated-pRb). Thus, we show that TGF-beta signaling and Smad adaptor ELF suppress human hepatocarcinogenesis, potentially through cyclin D1 deregulation. Loss of ELF could serve as a primary event in progression toward a fully transformed phenotype and could hold promise for new therapeutic approaches in human HCCs.

Systematic errors and susceptibility to noise of four methods for calculating anatomical dead space from the CO 2 expirogram

BACKGROUND

Anatomical dead space is usually measured using the Fowler equal area method. Alternative methods include the Hatch, Cumming, and Bowes methods, in which first, second, and third order polynomials, respectively, fitted to an expired CO2 volume vs expired volume curve, intercept the x-axis at the anatomical dead space. This study assessed systematic errors and susceptibility to noise of the Fowler, Hatch, Cumming, and Bowes dead spaces calculated over 40-80% of the CO2 expirogram.

METHODS

Simulated CO2 expirograms with 220 ml anatomical dead space and varying alveolar plateau slopes were generated digitally and zero-mean Gaussian noise added. CO2 expirograms were recorded in 10 anaesthetized human subjects. Anatomical dead space was calculated by the Fowler, Hatch, Cumming, and Bowes methods.

RESULTS

The Fowler, Hatch, Cumming, and Bowes methods displayed systematic biases of -1.8%, 13.2%, 2.4%, and -1.3%, respectively, at a normalized simulated alveolar plateau slope of 1.6 litre(-1). At a noise level of 0.0066 vol/vol, the standard deviations of recovered simulated dead spaces were 70.6, 1.8, 2.4, and 3.7 ml, respectively. The Hatch, Cumming, and Bowes methods applied to human expirograms differed significantly from that of Fowler by 13, -4, and -11 ml, respectively. In the human study, the Hatch and Cumming methods yielded the lowest intra-individual dead space variability.

CONCLUSIONS

The Fowler method shows greatest susceptibility to measurement noise and the Hatch method exhibits the largest systematic error. The Cumming method, which exhibits both low bias and low noise susceptibility, is preferred for estimating anatomical dead space from CO2 expirograms.

Lower Extremity Motor Function and Disability in Mild Cognitive Impairment

Recent findings suggest that lower extremity motor dysfunction may be a feature of mild cognitive impairment (MCI), but little is known about the nature and significance of lower extremity motor dysfunction in MCI. The aim of this study was to examine the extent to which MCI is associated with impaired gait, balance, and strength and to examine the relation of lower extremity function to disability among persons with MCI in the Rush Memory and Aging Project, a clinical-pathologic study of common chronic conditions of old age. In a series of analyses adjusted for age, sex, and education, individuals with MCI exhibited more impaired gait and balance than individuals without cognitive impairment. Because vascular factors can contribute to lower extremity motor dysfunction, the authors repeated the initial analyses including terms for vascular risk factors and vascular disease, and the associations between MCI and lower extremity motor dysfunction persisted. Moreover, among those with MCI, impairments in gait and balance were associated with an increased likelihood of disability. These findings suggest that lower extremity motor dysfunction is common and contributes to disability in MCI, but lower extremity motor dysfunction in MCI does not appear to be explained by the vascular factors examined in this study.

The effect of different platelet-rich plasma concentrations on proliferation and differentiation of human periodontal ligament cells in vitro

OBJECTIVES

The use of platelets and platelet products has become increasingly popular clinically as a means of accelerating endosseous wound healing. It is likely that growth factors released by activated platelets at the site of injury play a role in periodontal regeneration by regulating cellular activity. The purpose of this study was to evaluate the biological effects of platelet-rich plasma (PRP) on human periodontal ligament cells (hPDLCs) in vitro.

MATERIALS AND METHODS

Primary cultures of hPDLCs were obtained from healthy premolars. PRP was isolated by two-step centrifugation. Two main growth factors present in the thrombin-activated PRP (platelet-derived growth factor [PDGF-AB] and transforming growth factor-beta1 [TGF-beta1]) were evaluated using ELISA assay. Activated PRP or the combination of recombined human TGF-beta1 (rhTGF-beta1) and PDGF-AB (rhPDGF-AB) were added to hPDLCs in different concentrations to assess cell proliferation and osteogenic differentiation.

RESULTS

PRP contained high levels of TGF-beta1 and PDGF-AB. Cell attachment, proliferation and ALP activity were enhanced by addition of PRP or rhTGF-beta1 and rhPDGF-AB combination to the cell cultures, while the stimulatory potency of PRP was much greater than the latter. These stimulatory effects presented in a dose-dependant manner, it seemed that PRP with 50~100 ng/ml TGF-beta1 was an ideal concentration.

CONCLUSIONS

PRP can enhance hPDLC adhesion, proliferation and induce the differentiation of hPDLC into mineralized tissue formation cell; thereby contribute to the main processes of periodontal tissue regeneration. For economical and biological reasons, PRP has more clinical beneficial than analogous growth factors.